Multilayer sheet and multilayer electronic device

Abstract

Examples of the present invention provide multilayer sheets, multilayer electronic devices, etc. The multilayer sheet includes: a transparent film having a total light transmittance of 85% or more according to ISO 13468; a coating disposed on one side of the transparent film; and an adhesive layer disposed on the other side of the transparent film; the thickness of the adhesive layer after curing is less than twice the thickness of the coating. The multilayer sheets and multilayer electronic devices of the present invention do not peel off from the substrate even during repeated folding or rolling, and due to their excellent surface hardness, they exhibit excellent scratch resistance, dent resistance, etc. The multilayer sheets can be used as cover sheets for displays and offer excellent utilization for multilayer electronic devices.

Description

Technical Field

[0001] Examples of the present invention relate to multilayer sheets that can be used to protect displays and the like, and multilayer electronic devices including the same. Background Technology

[0002] With the diversification of mobile devices such as mobile phones, smartphones, and tablets, as well as information processing terminals such as ATMs and kiosks, surface protectors are widely used. Furthermore, the advent of various display devices, including foldable, flexible, and rollable types, has created a demand for surface hardness that inhibits surface scratches, while also requiring sufficient durability to withstand repeated folding and rolling. In addition, when applied to display screens, optical properties are naturally required.

[0003] As related prior art, there are Korean patents 10-1798759 and 10-1810422, etc. Summary of the Invention

[0004] The problem the invention aims to solve

[0005] The purpose of this invention is to provide multilayer wafers and multilayer electronic devices. These multilayer wafers offer excellent utilization in applications such as protecting displays.

[0006] means for solving problems

[0007] To achieve the above objectives, the multilayer sheet according to an embodiment of the present invention comprises: a transparent film having a total luminous transmittance of 85% or more according to ISO 13468; a coating disposed on one side of the transparent film; and an adhesive layer disposed on the other side of the transparent film; wherein the thickness of the adhesive layer after curing is less than twice the thickness of the coating.

[0008] The adhesive force per unit thickness (1 μm) of the adhesive layer can be above 80 gf / inch.

[0009] The storage modulus of the laminate with the coating on the transparent film is called SMm, and the storage modulus of the adhesive layer is called SMa. At 0°C, the difference between SMa and SMm can be less than 2450 MPa.

[0010] The energy storage modulus of the adhesive layer can be above 0.1 MPa at 60°C.

[0011] The laminate consists of the transparent film and the coating.

[0012] The storage modulus of the laminate is referred to as SMm, and the storage modulus of the adhesive layer is referred to as SMa. At 60°C, the difference between SMa and SMm can be below 2200 MPa.

[0013] The adhesive layer can have an adhesive force of more than 200 gf / inch after curing.

[0014] The thickness of the adhesive layer after curing can be greater than 1 μm.

[0015] The adhesive layer may include a silicone-based adhesive layer or a precursor layer thereof.

[0016] The combined thickness of the coating and the adhesive layer can be less than 30 μm.

[0017] The adhesive layer can be a layer cured from silicone adhesives and silicone MQ resin.

[0018] To achieve the above objectives, a multilayer electronic device according to another embodiment of the present invention includes: a multilayer wafer; and a light-emitting functional layer disposed on the lower portion of the multilayer wafer, wherein the multilayer wafer is a multilayer wafer according to an embodiment of the present invention.

[0019] The effects of the invention

[0020] The multilayer sheets and multilayer electronic devices exemplified by this invention do not delamination from the substrate even during repeated folding or winding, and due to their excellent surface hardness, they exhibit excellent scratch resistance, dent resistance, and other properties. These multilayer sheets can be used as cover sheets for displays and offer excellent utilization for multilayer electronic devices. Attached Figure Description

[0021] Figure 1 This is a conceptual diagram illustrating the structure of a multilayer sheet according to an embodiment of the present invention using cross-section.

[0022] Figure 2 This is a conceptual diagram illustrating the structure of a multilayer sheet according to another embodiment of the present invention, using cross-section.

[0023] Figure 3 This is a conceptual diagram illustrating the structure of a multilayer electronic device according to another embodiment of the present invention, using cross-section.

[0024] Figure 4 This is a conceptual diagram illustrating the structure of a multilayer electronic device according to another embodiment of the present invention, using cross-section.

[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] 40: Release film

[0031] 42: Elastic layer

[0032] 150: Light-emitting functional layer

[0033] 200: Multilayer electronic device 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 embodied in many different forms and is not limited to the embodiments described in this specification. Throughout the specification, similar reference numerals are used for similar portions.

[0035] In this specification, unless otherwise stated to the contrary, the phrase “comprising” of one component means that other components may also be included, without excluding other components.

[0036] In this specification, when a component is "connected" to another component, this includes not only the case of "direct connection" but also the case of "connecting with another component placed in between".

[0037] In this specification, B being located on A means that B is located on A in direct contact with A or that B is located on A if there are other configurations between B and A, and cannot be limited to the interpretation that B is in contact with the surface of A.

[0038] The terms "up" and "down" are relative and are described in this specification based on the accompanying drawings, but are not limited thereto.

[0039] In this specification, the term "combination of them" included in the Markush form of expression means a mixture or combination of one or more of the multiple structural elements described in the Markush form of expression, and means including one or more of the multiple structural elements described above.

[0040] In this specification, the reference to "A and / or B" means "A or B, or A and B".

[0041] In this specification, unless otherwise specified, the terms “first,” “second,” or “A,” “B,” etc., are used to distinguish the same terms.

[0042] In this specification, unless otherwise specified, the singular includes the singular or plural as the context suggests.

[0043] In this specification, the storage modulus was measured according to ASTM D4065 on a Hitachi DMA7100 model within the range of -50°C to 100°C. A heating rate of 5°C / min was used as the baseline.

[0044] In this specification, in-plane retardation (Ro) is a parameter defined by the product of the anisotropy of the refractive index of two orthogonal axes in the plane of the measured object (film or sheet, hereinafter referred to as film) (Δnxy = |nx - ny|) and the thickness (d) (Δnxy × d). It is a standard for representing optical isotropy or anisotropy. Furthermore, the minimum in-plane retardation value (Romin) refers to the lowest measured value of in-plane retardation (Ro) when measured at multiple locations within the plane of the film.

[0045] In this specification, the thickness direction retardation (Rth) is a parameter defined as the average of the phase differences obtained by multiplying the two birefringences, Δnxz (=|nx-nz|) and Δnyz (=|ny-nz|), respectively, by the film thickness (d) when viewed from a cross-section along the film thickness direction. Furthermore, the aforementioned maximum thickness direction retardation (Rthmax) refers to the maximum measured value when the thickness direction retardation (Rth) is measured at multiple locations within the plane of the film.

[0046] In this specification, the text and / or numbers listed together with the compound name refer to the abbreviation of the compound name.

[0047] In this specification, for ease of explanation, the relative size, thickness, etc. of the components shown in the accompanying drawings may be exaggerated.

[0048] The multilayer film, which is an example of the present invention, will be described in more detail below.

[0049] Figure 1 This is a conceptual diagram illustrating the structure of a multilayer sheet according to an example of the present invention, using cross-section. Figure 2 This is a conceptual diagram illustrating the structure of a multilayer sheet according to another embodiment of the present invention, using cross-section. (See also...) Figure 1 and 2 The multilayer wafers of the embodiments of the present invention will be described in more detail below.

[0050] To achieve the above objectives, a multilayer sheet 100 according to an embodiment of the example includes: a transparent film 20; a coating layer 10 disposed on one side of the transparent film; and an adhesive layer 30 disposed on the other side of the transparent film.

[0051] A release film layer 40 may also be provided below the aforementioned adhesive layer.

[0052] An elastic layer (not shown) may also be provided below the aforementioned 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 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 99% or less. However, it is not limited to this if the transmittance is sufficient to serve as a support layer for 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 below 3. For example, the yellow index can be below 3, below 2.8, below 2.2, below 1.0, below 0.8, or below 0.5. 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. Within the above range, when the multilayer film is applied to the front of the display, the possibility of rainbow spots occurring depending on the viewing angle can be minimized.

[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 value of the transparent film 20 can be 0 nm, or, in order to balance optical performance and mechanical and physical performance, the lower limit of the in-plane phase difference (Ro) can be set to 10 nm or more, 30 nm or more, or 50 nm or more.

[0062] The phase difference (Rth) in the thickness direction of the transparent film 20 can be above 4000 nm, below 5000 nm, or above 5500 nm.

[0063] The maximum thickness direction phase difference (Rthmax) of the transparent film 20 can be above 6000 nm, for example, above 6500 nm, above 7500 nm, above 8000 nm, or above 8500 nm.

[0064] The ratio (Rth / Ro) of the thickness direction phase difference (Rth) to the in-plane phase difference (Ro) of the transparent film 20 can be greater than 10, 15, or 20. The smaller the in-plane phase difference (Ro) and the larger the thickness direction phase difference (Rth), the better it is to prevent the occurrence of rainbow spots. Therefore, the ratio (Rth / Ro) of the two values ​​should preferably be kept relatively large.

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

[0066] The transparent film possessing the properties described above exhibits enhanced crystallization due to its large molecular orientation, thereby achieving a suitable level of mechanical and physical properties and effectively suppressing the occurrence of rainbow spots. The aforementioned 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 the transparent film 20 can be 15 kgf / mm. 2 That's all. Specifically, the tensile strength mentioned above can be 18 kgf / mm². 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 or lower.

[0070] The compressive strength of the transparent film 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, a polyimide film can be used.

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

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

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

[0076] The aforementioned polyester film may include polyester resin.

[0077] The aforementioned polyester resin can be a homopolymer resin or copolymer resin formed by the condensation of dicarboxylic acid and diol. Furthermore, the aforementioned polyester resin can be a blend resin containing both homopolymer resin and copolymer resin.

[0078] Examples of the aforementioned dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylicacid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, diphenylcarboxylic acid, diphenoxyethane dicarboxylic acid, diphenylsulfone carboxylic acid, anthracenedicarboxylic acid, 1,3-cyclopentane dicarboxylic acid, and 1,3-cyclohexane dicarboxylic acid. (The list of carboxylic acids is missing from the original text.) 1,4-cyclohexanedicarboxylicacid, hexahydro terephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethyl succinicacid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid, 2-methyladipate trimethyladipate, pimelic acid, azelaic acid, sebacic acid, subericacid, dodecanedicarboxylic acid, etc.

[0079] In addition, examples of the aforementioned diols include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexane dimethanol, 1,4-cyclohexane dimethanol, 1,10-decanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis(4-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone.

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

[0081] When the transparent film 20 is a polyester film, the polyester film may contain polyester resin, specifically, it may contain about 85% by weight or more PET resin, more specifically, it may contain 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 contain other polyester resins. Specifically, the polyester film may also contain about 15% by weight or less polyethylene naphthalate (PEN) resin. More specifically, the polyester film may also contain about 0.1% by weight to 10% by weight, or about 0.1% by weight to 5% by weight of PEN resin.

[0082] Based on the above composition, polyester films can improve crystallinity and mechanical and physical properties such as tensile strength through manufacturing processes such as heating and stretching.

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

[0084] The filler described above can be at least one selected from the group consisting of barium sulfate, silicon dioxide, and calcium carbonate. The transparent film 20, by including the filler, improves roughness and curlability, and enhances traveling performance and scratch reduction during film manufacturing.

[0085] The particle size of the filler can be from 0.01 μm to 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% by weight to 3% by weight. For example, based on the total weight of the transparent film 20, the content of the filler can be from 0.05% by weight to 2.5% by weight, 0.1% by weight to 2% by weight, or 0.2% by weight to 1.7% by weight, but is not limited thereto.

[0087] The thickness of the aforementioned 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, or it 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. When the thickness is within these ranges, sufficient mechanical and physical properties and excellent optical properties can be obtained.

[0088] The manufacturing method of the transparent film follows the conventional transparent film manufacturing method.

[0089] For example, a polyester film can be prepared by including the following steps: (1) obtaining an unstretched film by extruding a composition containing polyester resin; (2) stretching the unstretched film in the length and width directions; and (3) heat-fixing the stretched film.

[0090] In the above preparation method, the unstretched film is manufactured by extruding, preheating, stretching, and heat-setting the raw resin. Furthermore, the extrusion can be carried out at temperatures ranging from 230°C to 300°C or from 250°C to 280°C.

[0091] Before stretching, the unstretched film is preheated at a specified temperature. 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. Within these ranges, the flexibility beneficial to the stretching of the unstretched film is ensured, while effectively preventing breakage during stretching.

[0092] The aforementioned stretching is performed in a biaxial stretching manner. For example, it can be performed using a simultaneous biaxial stretching method or a successive biaxial stretching method, stretching along two axes: the width direction (lateral direction (TD)) and the length direction (mechanical direction, MD). Preferably, a sequential biaxial stretching method can be used, in which stretching is performed first in one direction and then in a direction perpendicular to that direction.

[0093] The aforementioned stretch ratio in the length direction ranges from 2.0 to 5.0, more specifically, from 2.8 to 3.5. Furthermore, the aforementioned stretch ratio in the width direction ranges from 2.0 to 5.0, more specifically, from 2.9 to 3.7. Preferably, the stretch ratio in the length direction (d1) and the stretch ratio in the width direction (d2) are similar; specifically, the ratio (d2 / d1) of the stretch ratio in the length direction (d2) to the stretch ratio in the width direction (d1) can be 0.5 to 1.0, 0.7 to 1.0, or 0.9 to 1.0. The aforementioned stretch ratios (d1, d2) are the ratio of the length after stretching when the length before stretching is set to 1.0. Furthermore, the aforementioned stretching speed can be from 6.5 m / min to 8.5 m / min, but is not particularly limited.

[0094] The stretched sheet described above can be heat-fixed at 150°C to 250°C, more specifically, at 160°C to 230°C. The heat-fixing process can last from 5 seconds to 1 minute, more specifically, from 10 seconds to 45 seconds.

[0095] After heat curing begins, the membrane may relax in the length and / or width directions, at which point the temperature range can be from 150°C to 250°C.

[0096] Coating 10

[0097] The coating 10 is disposed on one side of the transparent film 20.

[0098] The lower surface of coating 10 may be opposite to transparent film 20, and the upper surface of coating 10, as a multilayer sheet surface, may be the outermost exposed surface.

[0099] The lower surface of coating 10 can be in direct contact with transparent film 20, or an additional layer can be bonded to transparent film 20 as a medium.

[0100] The coating 10 can directly contact one side of the transparent film 20.

[0101] Coating 10 can improve the mechanical and physical properties and / or optical and physical properties of the transparent film 20.

[0102] The coating 10 may include at least one coating material selected from organic components, inorganic components, and organic-inorganic composite components.

[0103] The coating material may include organic resins. Specifically, the organic resin may be a curable resin or an adhesive resin.

[0104] Coating 10 can be a curable coating.

[0105] The coating 10 may include one or more of the following cured products selected from polyurethane acrylate compounds, acrylic ester compounds, acrylate compounds, and epoxy acrylate compounds.

[0106] The coating 10 may contain polyurethane acrylate compounds, acrylate compounds, or cured products thereof.

[0107] The coating 10 may contain polyurethane acrylate compounds, acrylate compounds, acrylate compounds, or cured products thereof.

[0108] The aforementioned polyurethane acrylate compounds contain urethane bonds as repeating units and may have multiple functional groups.

[0109] The aforementioned polyurethane acrylate compounds can be compounds in which the end of an urethane compound formed by the reaction of a diisocyanate compound and a polyol is replaced by an acrylate group.

[0110] For example, the aforementioned diisocyanate compound may comprise 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 aforementioned 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 based on the aforementioned acrylate group may be carried out by an acrylate compound having a functional group capable of reacting with an isocyanate group (-NCO). For example, an acrylate compound having hydroxyl, amino, etc., may be used; hydroxyalkyl acrylates or amino acrylates having 2 to 10 carbon atoms may be used.

[0111] The aforementioned polyurethane acrylate compounds may contain 2 to 15 functional groups.

[0112] Examples of the aforementioned polyurethane acrylate compounds may include, but are not limited to, bifunctional polyurethane acrylate oligomers with a weight-average molecular weight of 1,400 to 25,000, trifunctional polyurethane acrylate oligomers with a weight-average molecular weight of 1,700 to 16,000, tetrafunctional polyurethane acrylate oligomers with a weight-average molecular weight of 500 to 2,000, hexafunctional polyurethane acrylate oligomers with a weight-average molecular weight of 818 to 2,600, nonfunctional polyurethane acrylate oligomers with a weight-average molecular weight of 2,500 to 5,500, decafunctional polyurethane acrylate oligomers with a weight-average molecular weight of 3,200 to 3,900, and quintuplet polyurethane acrylate oligomers with a weight-average molecular weight of 2,300 to 20,000.

[0113] The glass transition temperature (Tg) of the above-mentioned polyurethane acrylate compounds can be -80℃ to 100℃, -80℃ to 90℃, -80℃ to 80℃, -80℃ to 70℃, -80℃ to 60℃, -70℃ to 100℃, -70℃ to 90℃, -70℃ to 80℃, -70℃ to 70℃, -70℃ to 60℃, -60℃ to 100℃, -60℃ to 90℃, -60℃ to 80℃, -60℃ to 70℃, -60℃ to 60℃, -50℃ to 100℃, -50℃ to 90℃, -50℃ to 80℃, -50℃ to 70℃, or -50℃ to 60℃.

[0114] The aforementioned acrylate compounds may be at least one selected from the group consisting of substituted or unsubstituted acrylates and substituted or unsubstituted methacrylates. The aforementioned acrylate compounds may include 1 to 10 functional groups.

[0115] Examples of the aforementioned acrylate compounds may include, but are not limited to, trimethylolpropane triacrylate (TMPTA), trimethylol propane ethoxylated triacrylate (TMPEOTA), glyceryl propoxy tricrylate (GPTA), pentaerythritol tetraacrylate (PETA), and dipentaerythritol hexaacrylate (DPHA).

[0116] The weight-average molecular weight of the aforementioned acrylate compounds can be 500 to 6000, 500 to 5000, 500 to 4000, 1000 to 6000, 1000 to 5000, 1000 to 4000, 1500 to 6000, 1500 to 5000, or 1500 to 4000. The acrylate equivalent of the aforementioned 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.

[0117] The aforementioned acrylate compounds may contain 1 to 10 functional groups. Examples of such acrylate compounds may include monofunctional acrylate oligomers with a weight-average molecular weight of 100 to 300, difunctional 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.

[0118] The aforementioned epoxy acrylate compounds may contain 1 to 10 functional groups. Examples of such epoxy acrylate compounds may 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 aforementioned epoxy acrylate (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.

[0119] Based on the total weight of coating 10, the content of the aforementioned organic resin may be 30 to 100% by weight, 40 to 90% by weight, or 50 to 80% by weight.

[0120] The coating 10 may optionally include a filler.

[0121] The filler described above can be, for example, inorganic particles. Examples of fillers include silica, barium sulfate, zinc oxide, or aluminum oxide. The particle diameter of the filler can be from 1 nm to 100 nm. Specifically, the particle diameter of the filler can be from 5 nm to 50 nm, or from 10 nm to 30 nm. The filler can include inorganic fillers with different particle size distributions. For example, the filler can 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 content of the filler 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 content of the filler can be 50% by weight or less, 45% by weight or less, or 40% by weight or less. Preferably, the coating 10 may not contain inorganic fillers such as silica. In this case, for example, the adhesion between the transparent film 20 and the coating 10 having the above composition can be improved.

[0122] The coating 10 may also contain a photoinitiator or its reactants. The photoinitiator may participate in the process of curing the aforementioned resin, etc., into a coating.

[0123] Examples of the aforementioned photoinitiators may include 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, and methylbenzoyl carboxylate. Formate, 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, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide Photoinitiators include, but are not limited to, oxides, etc. Furthermore, commercially available products may include Irgacure 184, Irgacure 500, Irgacure 651, Irgacure 369, Irgacure 907, Darocur 1173, Darocur MBF, Irgacure 819, Darocur TPO, Irgacure 907, Esacure KIP100F, etc. The above photoinitiators can be used alone or in combination of two or more different photoinitiators.

[0124] The coating 10 may also include functions such as anti-glare, anti-fouling, and anti-static properties.

[0125] Coating 10 may also include an antifouling agent. For example, coating 10 may include a fluorinated compound. The aforementioned fluorinated compound can provide antifouling functionality. Specifically, the aforementioned fluorinated compound may be an acrylate compound having a perfluoroalkyl group, such as perfluorohexylethyl acrylate, but is not limited to this.

[0126] The coating 10 may also include an antistatic agent. The antistatic agent may include an ionic surfactant. For example, the ionic surfactant may include ammonium salts or quaternary alkylammonium salts, and the ammonium salts and quaternary alkylammonium salts may include halides of chlorides, bromides, etc.

[0127] The coating 10 may also include additives such as surfactants, ultraviolet (UV) absorbers, UV stabilizers, anti-yellowing agents, leveling agents, or color-improving dyes. For example, the surfactants may be fluoroacrylates, fluorinated surfactants, or silicone surfactants having one or two functionalities. These surfactants may be included in the coating 10 in a dispersed or crosslinked form. Furthermore, the UV absorbers may include benzophenone compounds, benzotriazole compounds, or triazine compounds, and the UV 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 entire coating, the content of the additives may be from 0.01% by weight to 10% by weight, but is not limited to this.

[0128] The coating 10 may consist of a single layer or two or more layers.

[0129] The coating 10 is formed by a single layer, which increases the surface durability of the multilayer sheet and also serves to prevent fingerprints or contamination.

[0130] The thickness of coating 10 can be 2μm or more, 3μm or more, 5μm or more, or 10μm, and can be less than 50μm, 30μm or less, 20μm or less, or 10μm or less. When it has this thickness, it can be used with a thin thickness while providing the multilayer sheet with a suitable level of surface hardness and other durability, and can also maintain the overall flexibility of the multilayer sheet.

[0131] Coating 10 can be formed by coating preparation methods.

[0132] The method for preparing a coating may include the steps of applying a coating preparation composition and then curing it.

[0133] The composition for coating preparation may include at least one of organic resin compositions, inorganic resin compositions, and organic-inorganic composite compositions.

[0134] The composition for coating preparation may include at least one of acrylate compounds, siloxane compounds, or silsesquioxane compounds. Additionally, it may include inorganic particles.

[0135] Specific examples of compositions for coating preparation may include polyurethane acrylate compounds, acrylate compounds, and fluorinated compounds.

[0136] In addition, the composition for coating preparation may also include, as needed, photoinitiators, antifouling additives, antistatic agents, other additives and / or organic solvents.

[0137] Organic solvents can include: 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, diethyl ethylene glycol monoethyl ether, diethyl ethylene glycol monopropyl ether, diethyl ethylene glycol monobutyl ether, and diethylene glycol-2-ethylhexyl ether; aromatic solvents, such as benzene, toluene, and xylene; etc., which can be used alone or in combination.

[0138] The content of the aforementioned organic solvent can be adjusted in various ways without reducing the physical properties of the coating, and is not particularly limited. Based on the solid component included in the composition for preparing the coating, the weight ratio of solid component to organic solvent is approximately 1:1 to 250. When the aforementioned organic solvent is within the aforementioned range, suitable flowability and coating properties can be achieved.

[0139] The above-mentioned coating preparation composition may include 10% to 30% by weight of organic resin, 0.1% to 5% by weight of photoinitiator, 0.01% to 2% by weight of antifouling additive, 0.1% to 10% by weight of antistatic agent, and the remainder of organic solvent.

[0140] Based on the above composition, the mechanical properties of the coating, as well as its antifouling and antistatic properties, can be improved simultaneously.

[0141] The coating composition can be applied to a transparent film using conventional coating methods and then cured. Coating methods can include rod coating, knife coating, roller coating, blade coating, die coating, gravure coating, comma coating, slot die coating, lip die coating, or solution casting, etc.

[0142] The composition used to prepare the coated layer can be subjected to drying and curing processes sequentially or simultaneously.

[0143] The drying process described above is the removal of organic solvents from the composition used to prepare the coated layer. The drying can be carried out at temperatures ranging from 40°C to 100°C, preferably from 40°C to 80°C, 50°C to 100°C, or 50°C to 80°C, for about 1 minute to 20 minutes, preferably from about 1 minute to 10 minutes, or 1 minute to 5 minutes.

[0144] The above-described curing process involves inducing a chemical reaction in the coating preparation composition to form a film. Depending on the resin or other materials used in the coating preparation composition, appropriate photocuring and / or thermal curing methods can be applied.

[0145] Adhesive layer 30

[0146] The adhesive layer 30 is disposed on the other side of the transparent film 20.

[0147] The upper surface of the adhesive layer 30 is opposite to the transparent film 20, and can be in direct contact with the transparent film 20, or the additional layer can be used as a medium to bond with the transparent film 20.

[0148] The upper surface of the adhesive layer 30 can directly contact the other surface of the transparent film 20.

[0149] The lower surface of the adhesive layer 30 may be exposed to the outside or opposite to one surface of the release film 40.

[0150] The lower surface of the adhesive layer 30 can be bonded to the release film through other layers, such as the elastic layer, as a medium.

[0151] The lower surface of the adhesive layer 30 can be directly bonded to the light-emitting functional layer 150 (see [link to adhesive layer]) using other layers such as the elastic layer as a medium, or without such a medium. Figure 3 and Figure 4 ) to be joined together to be used as part of a multilayer electronic device.

[0152] The adhesive layer 30 can be an optically transparent adhesive layer.

[0153] The adhesive layer 30 can be an acrylic adhesive layer, a urethane adhesive layer, or a silicone adhesive layer; specifically, a silicone adhesive layer can be used. Using a silicone adhesive layer provides an adhesive layer with high light transmittance, heat resistance, weather resistance, and other properties. In particular, the adhesive layer in the embodiments described later exhibits strong adhesion even at thin thicknesses, further improving the physical properties of the multilayer sheet compared to existing optically clear adhesives (OCAs) such as acrylic adhesive layers.

[0154] The adhesive layer 30 can be applied with high adhesion.

[0155] To maintain the physical properties of multilayer sheets even under repeated bending or folding, it is necessary to improve not only the transparent film or coating, but also the performance of the adhesive layer used to hold them in place and inhibit delamination. The inventors achieved this improved performance by applying a silicone-based adhesive layer.

[0156] Silicone adhesive layers can be obtained by applying an silicone adhesive composition followed by drying and / or curing.

[0157] Silicone adhesive compositions may include silicone adhesives, catalysts, and solvents.

[0158] In an example, to improve the adhesion of the silicone adhesive layer, an organosilicon MQ resin may also be included. The organosilicon MQ resin is a polymer of cage-like oligosiloxanes (cage-like oligosiloxanes) represented by the general formula RnSiXmOy, having two or more methyl groups on the siloxane backbone. 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 between 2 and 200. Specifically, it may include a polymer composed of R1R2X3SiOy. 1 / 2 The M-units (mono-terminated siloxane units) and those made of SiO2 4 / 2 The Q unit represents tetra-terminated siloxane units. 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 the initial adhesion.

[0159] Commercially available silicone adhesives suitable for optical applications can be used. Specifically, peroxide-curing silicone adhesives and addition-reactive silicone adhesives can be used.

[0160] Examples of peroxide-curable silicone adhesives include Shin-Etsu Chemicals' KR-100, KR-101-10, KR-130, Dow Chemical's DOWSIL SH 4280, Momentive Advanced Materials Ltd's SilGrip PSA510, and equivalent products.

[0161] Examples of addition-reaction silicone adhesives include KR-3700, KR-3701, X-40-3237, X-40-3240, and X-40-3291-1 from Shin-Yue Chemical Co., Ltd.; DOWSIL SD4580, DOWSIL 4584, DOWSIL 4585, and DOWSIL 4587L from Dow Chemical Co., Ltd.; SilGrip TSR1512 and TSR1516 from Momentive Advanced Materials Co., Ltd.; and equivalent products.

[0162] Using addition-reaction silicone adhesives offers advantages in terms of process convenience.

[0163] Silicone MQ resins can be used in conjunction with silicone adhesives to enhance adhesion. Examples of silicone MQ resins include Shin-Etsu Chemical Co., Ltd.'s X-92-128 and X-41-3003; Momentive Advanced Materials Ltd.'s SilGrip SR545 and SilGrip SR1000; and equivalent products.

[0164] The catalyst can be a platinum catalyst, for example, CAT-PL-50T or equivalent products from Shin-Etsu Chemical Co., Ltd. Even when using transparent films or substrates that are relatively fragile to heat due to shortened curing time, the above-mentioned catalyst can effectively form an adhesive layer without causing substantial damage to the substrate.

[0165] Solvents such as toluene can be used, but their use is unrestricted as long as it does not degrade the performance of the silicone adhesive layer.

[0166] The silicone adhesive composition, based on 100 parts by weight of silicone adhesive, 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. The silicone adhesive composition, based on 100 parts by weight of silicone adhesive, 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 above-mentioned silicone adhesive and silicone MQ resin are applied simultaneously in these ratios, excellent adhesion can be achieved even with a relatively thin thickness.

[0167] The silicone adhesive composition, based on 100 parts by weight of silicone adhesive, may contain 0.5 to 2 parts by weight, or 0.8 to 1.5 parts by weight, of a catalyst. The catalyst can effectively form an adhesive layer from the silicone adhesive composition by promoting curing.

[0168] The silicone adhesive composition may also contain a solvent, which can dilute the silicone adhesive composition or impart fluidity, making operations such as coating advantageous and contributing to the formation of a relatively thin adhesive layer with excellent overall physical properties. Toluene can be used as an example solvent, but its use is unrestricted and can be limited to the extent that it does not degrade the physical properties of the silicone adhesive composition.

[0169] For example, the above-described 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.

[0170] The silicone adhesive composition can be coated onto the other side of the transparent film 20 to form a silicone-based adhesive layer. Alternatively, the silicone adhesive composition can be coated onto one side of another base film (not shown) and then lamination onto the other side 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 forms a thin layer through coating and can be contained within the adhesive layer in a state prior to complete curing by heat or light after drying. The dried layer of the silicone adhesive composition prior to such curing is referred to as the precursor of the silicone-based adhesive layer.

[0171] The precursor layer can be heat- or light-cured to form the adhesive layer 30. Exemplarily, the precursor layer and the surface to be bonded can be configured to be in direct contact and heat-cured at 90°C to 130°C for 1 to 5 minutes to form the adhesive layer.

[0172] The adhesive layer 30 may comprise 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 comprise 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 comprise 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 at a relatively thin thickness, excellent optical properties and adhesion strength exceeding the required level can be obtained.

[0173] To ensure stable bending and winding properties, the storage modulus of the adhesive layer 30 preferably has a value within a specified range. In particular, considering the various usage environments of display components and the heat generated by the device, it is preferable to have a modulus, adhesive force, etc., that can ensure the adhesive layer performs stable functions within the temperature variation range of the device surface.

[0174] The storage modulus of the adhesive layer 30 at -40°C can be below 100 MPa, below 90 MPa, or below 80 MPa. The storage modulus of the adhesive layer 30 at -40°C can be above 0.1 MPa.

[0175] The storage modulus of the adhesive layer 30 at -20°C can be below 100 MPa, below 90 MPa, or below 80 MPa. The storage modulus of the adhesive layer 30 at -20°C can be above 0.1 MPa.

[0176] The storage modulus of the adhesive layer 30 at 0°C can be below 70 MPa, below 55 MPa, or below 45 MPa. The storage modulus of the adhesive layer 30 at 0°C can be above 0.1 MPa.

[0177] The storage modulus of the adhesive layer 30 at 20°C can be below 50 MPa, below 35 MPa, or below 25 MPa. The storage modulus of the adhesive layer 30 at 20°C can be above 0.1 MPa.

[0178] The storage modulus of the adhesive layer 30 at 40°C can be below 20 MPa, below 15 MPa, or below 5 MPa. The storage modulus of the adhesive layer 30 at 40°C can be above 0.1 MPa.

[0179] The storage modulus of the adhesive layer 30 at 60°C can be below 10 MPa, below 5 MPa, or below 3 MPa. The storage modulus of the adhesive layer 30 at 60°C can be above 0.1 MPa.

[0180] The adhesive strength of adhesive layer 30 can be above 200 gf / inch. This adhesive strength refers to the adhesive strength after the adhesive layer has cured, and the specific evaluation method is shown in the experimental examples described later.

[0181] 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.

[0182] The adhesive strength 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 strength 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 strength per unit thickness is beneficial for obtaining a sufficient adhesive layer with a thinner thickness. The adhesive strength per unit thickness as described above can vary depending on the type and thickness of the applicable adhesive layer, based on the cured thickness.

[0183] The thickness of the adhesive layer 30 can be greater than 1 μm.

[0184] The thickness of the adhesive layer 30 can be greater than 1 μm, or greater than 1.5 μm, greater than 1.8 μm, greater than 2 μm, greater than 2.5 μm, greater than 3 μm, or greater than 3.5 μm. The thickness of the adhesive layer 30 can be less than 20 μm, less than 10 μm, less than 8 μm, or less than 7 μm.

[0185] The adhesive layer 30 has excellent optical properties.

[0186] 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 may be 85% or more. For example, the transmittance may be 88% or more, 89% or more, or less than 99%.

[0187] 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%.

[0188] 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. In addition, the yellow index can be greater than 0.

[0189] The adhesive layer 30 has excellent optical properties and strong adhesion, which helps to prevent delamination in environments with repeated bending or winding.

[0190] Multilayer film 100

[0191] Since the multilayer sheet 100 is repeatedly bent and folded in its laminated state, the possibility of peeling or other defects at the interface between the transparent film 20 and the adhesive layer 30 should be minimized. For this purpose, the aforementioned adhesive layer can be used, or the difference in storage modulus can be limited.

[0192] When the storage modulus of the laminate on which the coating 20 is disposed on the transparent film 10 is referred to as SMm, and the storage modulus of the adhesive layer 30 is referred to as SMa, the difference between SMm and SMa is preferably within a specified range. This difference can be expressed as a positive number after subtracting the smaller value from the larger value. SMm can be greater than the value of SMa, but is not limited to this.

[0193] At -40℃, the difference between SMm and SMa can be below 2600MPa, below 2500MPa, or below 2400MPa. At -40℃, the difference between SMm and SMa can be above 1200MPa.

[0194] At -20℃, the difference between SMm and SMa can be below 2500MPa, below 2400MPa, or below 2300MPa. At -20℃, the difference between SMm and SMa can be above 1200MPa.

[0195] At 0℃, the difference between SMm and SMa can be below 2450MPa, below 2350MPa, or below 2200MPa. At 0℃, the difference between SMm and SMa can be above 1200MPa.

[0196] At 20℃, the difference between SMm and SMa can be below 2300MPa, below 2200MPa, or below 2100MPa. At 20℃, the difference between SMm and SMa can be above 1200MPa.

[0197] At 40℃, the difference between SMm and SMa can be below 2300MPa, below 2200MPa, or below 2100MPa. At 40℃, the difference between SMm and SMa can be above 1200MPa.

[0198] At 60℃, the difference between SMm and SMa can be below 2200MPa, below 2100MPa, or below 2000MPa. At 60℃, the difference between SMm and SMa can be above 1200MPa.

[0199] When this feature is present, delamination between the laminate and the adhesive layer can be minimized.

[0200] Multilayer film 30 has excellent optical properties.

[0201] According to ISO 13468, the total light transmittance of the multilayer film 30 can be above 85%, above 88%, above 91%, and below 99%.

[0202] The haze of the multilayer film 30 can be below 3%, below 2%, below 1.5%, below 0.85%, or below 0.8%.

[0203] The yellow index (YI) of the multilayer film 30 can be below 3. For example, the yellow index can be below 3, below 2.8, below 2.2, below 1.0, below 0.8, or below 0.5. Furthermore, the yellow index can be greater than 0.

[0204] The multilayer sheet 30 has a relatively thin thickness. Specifically, the sum of the thicknesses of the transparent film 10, the coating 20, and the adhesive layer 30 can be 30 μm or more, 40 μm or more, 50 μm or more, 60 μm or more, 70 μm or more, or 80 μm or more, or less than 200 μm or less than 150 μm.

[0205] The cured thickness of the adhesive layer 30 can be less than twice the thickness of the coating 20. The cured thickness of the adhesive layer 30 can be less than 1.8 times, 1.5 times, 1.3 times, 1.1 times, or 1.0 times the thickness of the coating 20. The cured thickness of the adhesive layer 30 can be more than 0.1 times or more than 0.2 times the thickness of the coating 20. By using a relatively thin adhesive layer, the thickness of the part other than the transparent film 10, which provides support in the multilayer sheet 30, becomes relatively thin, thereby providing a multilayer sheet with a relatively thin overall thickness.

[0206] The sum of the thicknesses of coating 20 and adhesive layer 30 can be less than 30 μm, less than 25 μm, less than 20 μm, less than 15 μm, or less than 12 μm. The sum of the thicknesses of coating 20 and adhesive layer 30 can be greater than 2 μm.

[0207] Furthermore, the multilayer sheet 100 has an adhesive layer 30 that is thinner than the transparent film 10. During bending or winding, interlayer delamination or damage to the transparent film can easily occur near the interface between the transparent film and the adhesive layer. In this embodiment, to address this problem, the adhesive layer is configured to be thin and have strong adhesive force. Moreover, even when using the same resin, the adhesive force may vary depending on the thickness of the adhesive layer; therefore, the thickness ratio of the transparent film to the adhesive layer preferably has the following characteristics. Specifically, the thickness of the transparent film can be 8 to 60 times, or 8 to 40 times, the unit thickness (1 μm) of the adhesive layer.

[0208] The multilayer sheet 100 may further include a release film 40 disposed beneath the other side of the adhesive layer 30. The release film 40 may be configured to be in direct contact with the other side of the adhesive layer 30. Alternatively, the release film 40 may be disposed beneath the other side of the adhesive layer 30 by using other layers as a medium between it and the other side of the adhesive layer 30.

[0209] Release films can be made of polyethylene terephthalate (PET) films, but are not limited to these.

[0210] The multilayer sheet 30 uses an adhesive layer 30 with strong adhesion and relatively thin thickness, thereby providing a thin multilayer sheet that can substantially suppress interlayer delamination even when repeatedly bent, folded, rolled, etc.

[0211] Multilayer electronic devices 200

[0212] Figure 3 This is a conceptual diagram illustrating the structure of a multilayer electronic device based on another example, using a cross-sectional view. Figure 4 This is a conceptual diagram illustrating the structure of a multilayer electronic device based on another example, using a cross-sectional view. (See reference...) Figure 3 and Figure 4 , for details, the multilayer electronic device 200.

[0213] The multilayer electronic device 200 includes: a multilayer sheet 100; and a light-emitting functional layer 15 disposed under the multilayer sheet 100.

[0214] The multilayer film 100 can be used as a cover layer for the multilayer electronic device 200.

[0215] For example, the multilayer electronic device 200 can be a display device, which can be a large-area display device, a foldable display device, a bendable display device, or a flexible display device. Alternatively, it can be a bendable mobile communication device (e.g., a mobile phone) or a bendable laptop computer.

[0216] The light-emitting functional layer 150 includes a light-emitting layer (not shown).

[0217] The light-emitting layer includes elements that emit light according to a signal in a display device. Exemplarily, the light-emitting layer may include: a signal transmission layer for transmitting an external electrical signal to a color display layer; a color display layer disposed on the signal transmission layer and displaying color according to the provided signal; and an encapsulation layer for protecting the color display layer. The signal transmission layer may include a thin-film transistor (TFT), and exemplaryly, low-temperature polysilicon (LTPS), amorphous silicon (a-Si TFT), or oxide thin-film transistor (Oxide TFT) technologies may be used, but is not limited thereto. The encapsulation layer may use thin-film encapsulation (TFE), but is not limited thereto.

[0218] The light-emitting layer can be disposed on the support layer. The support layer can be a layer with insulating and heat-resistant properties, for example, a polyimide film, a glass layer, a polyester film (PET film), etc.

[0219] The light-emitting functional layer may also include a sensor layer. The sensor layer can include touch sensors, etc.

[0220] The light-emitting functional layer may also include a polarizing layer. The polarizing layer may be disposed on the light-emitting layer or on the sensor layer.

[0221] 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.

[0222] 1. Preparation of adhesive composition

[0223] KR-3700 from Shin-Etsu Chemical Co., Ltd. was prepared as the silicone adhesive; X-92-128 from Shin-Etsu Chemical Co., Ltd. was prepared as the silicone MQ resin; CAT-PL-50T from Shin-Etsu Chemical Co., Ltd., a platinum-based catalyst, was prepared as the catalyst; and toluene was prepared as the solvent. The adhesive layer composition was mixed in the amounts shown in Table 1 below and then applied.

[0224] 2. Formation of the adhesive layer and physical performance evaluation of the cured adhesive layer

[0225] To achieve the thickness shown in Table 1 after curing, a precursor layer was obtained by printing and coating onto a PET film (manufactured by SKC, NRF grade) and then drying. Drying and curing were carried out at 90°C for 5 minutes.

[0226] In the adhesion test, the adhesion was measured in T-Peel form using the COMETECH QC-M1F UTM model, with a peeling speed of 300 mm / min.

[0227] Table 1

[0228]

[0229] *The content is based on 100 parts by weight of silicone adhesive.

[0230] **This refers to the adhesive force measured at the corresponding adhesive layer thickness.

[0231] *** is the value obtained by dividing the adhesive force measured at the corresponding adhesive layer thickness by the thickness, expressed as adhesive force per unit thickness of 1 μm or gf / (inch·μm).

[0232] Referring to Table 1 above, the adhesive strength generally showed an increasing trend when the thickness of the adhesive layer increased. When comparing at the same thickness, except for 1 μm, the adhesive layer used in Preparation Example 2 was the best overall. However, Preparation Examples 1 and 3 also showed excellent adhesive strength with changes in thickness.

[0233] The adhesive force per unit thickness was observed and confirmed. Overall, the adhesive force showed an increasing trend with increasing thickness. However, even when using the same composition, the rate of increase showed a decreasing trend.

[0234] It was confirmed that an adhesive layer with sufficient adhesion at a relatively thin thickness could be obtained.

[0235] 3. Preparation of multilayer wafers

[0236] Obtain NRF grade PET films of various thicknesses manufactured by SKC for use as transparent films.

[0237] For the coating, the coating preparation composition having the composition shown in Table 2 below was applied to one side of the transparent film using a stamping method. The film was then heat-treated at 60°C for 3 minutes to dry the solvent, and cured by irradiation with 1J UV light to form a coating with a thickness of approximately 5μm.

[0238] Table 2

[0239]

[0240] For the sample applying the adhesive layer, the adhesive composition was applied to the other side of the transparent film of the laminate (a coating is formed on one side of the transparent film) in the same manner as described above, and dried to form a precursor layer. After curing, the adhesive layer was formed. The above composition used in Composition Preparation Example 2. The specific layer structures and thicknesses of each layer are shown in Table 3 below.

[0241] 4. Evaluation of the physical properties of multilayer wafers

[0242] (1) Optical properties and color

[0243] Optical properties and color were measured. The average visible light transmittance of the film samples was measured according to ISO 13468 standard using a haze meter (NDH-5000W, Nippon Denko Co., Ltd.), and the haze was measured according to ISO 14782 standard. The yellowness index (YI) of the samples was measured according to ASTM-E313 standard using a spectrophotometer (UltraScan PRO, Hunter Associates Laboratory, USA) with a D65 light source at 10°. The results are shown in Table 4 below.

[0244] Light transmittance of 85% or higher is indicated by ○, and light transmittance of 91% or higher is indicated by ◎.

[0245] Use △ to represent haze levels below 1%, ○ to represent haze levels below 0.85%, and ◎ to represent haze levels below 0.8%.

[0246] Use △ to represent YI values ​​greater than 0.8, ○ to represent values ​​less than 0.8, and ◎ to represent values ​​less than 0.5.

[0247] (2) Thickness measurement

[0248] The thickness of each layer was measured using an F-20 instrument from Filmetrics, USA, according to the manufacturer's manual. Measurements at 3 to 5 points on the sample were verified, and their average value was used as the thickness.

[0249] (3) Evaluation of folding durability

[0250] In the multilayer film embodiment, folding durability was assessed by bonding it to a 35μm thick elastic layer (SKC manufactured using a single-layer extruded film made from PEBA 72R grade resin by Arkema, France) and conducting a dynamic folding test. After 200,000 dynamic bending cycles at a radius of curvature of 2mm and a bending time of 2 seconds per cycle at room temperature (approximately 20°C), the presence of cracks was confirmed. Cracks were visually inspected for appearance. No cracks were observed in the sample multilayer films of the embodiment, and therefore, they were rated as good.

[0251] Table 3

[0252]

[0253]

[0254] (4) Measurement of modulus

[0255] Modulus was measured using a Dynamic Mechanical Analysis (DMA) system. A Hitachi DMA7100 was used to measure the storage modulus of the samples within the range of -50°C to 100°C. The heating rate was 5°C / min.

[0256] The measurement results for each temperature are shown in Table 4.

[0257] Table 4

[0258]

[0259] Referring to Tables 3 and 4 above, it is confirmed that the samples of the embodiments generally possess excellent optical properties and excellent folding durability. Although the samples of the embodiments are thin, they have strong adhesive force, and can well bond multilayer films with modulus differences within an appropriate range over a wide temperature range, thereby substantially suppressing peeling even under repeated folding and other conditions.

[0260] The preferred embodiments of the present invention have been described in detail above, but the scope of the claims of the present invention is not limited thereto. Various modifications and improvements implemented by those skilled in the art using the basic concepts of the present invention as defined in the claims are also within the scope of the claims of the present invention.

Claims

1. A multilayer sheet, characterized in that, include: A transparent film, wherein the total light transmittance of the transparent film is 85% or higher according to ISO 13468. A coating, the coating being disposed on one side of the transparent film, and An adhesive layer disposed beneath the other side of the transparent film; The adhesive layer is a layer of cured silicone adhesive and silicone MQ resin. The organosilicon MQ resin is a polymer of cage-type oligomeric siloxanes having two or more methyl groups on the siloxane backbone. Based on 100 parts by weight of the aforementioned silicone adhesive, the content of the silicone MQ resin is 10 parts by weight or more and 70 parts by weight or less. The thickness of the transparent film is 25 μm to 85 μm. The thickness of the cured adhesive layer is less than twice the thickness of the coating. The thickness of the adhesive layer after curing is greater than 1 μm. The adhesive layer has an adhesive force of over 200 gf / inch after curing. The adhesive force per unit thickness of the adhesive layer is above 80 gf / inch. The thickness per unit is 1 μm. The multilayer sheet serves as a cover layer for multilayer electronic devices.

2. The multilayer sheet according to claim 1, characterized in that, The storage modulus of the laminate with the coating disposed on the transparent film is referred to as SMm. The storage modulus of the adhesive layer is referred to as SMa. At 0°C, the difference between SMa and SMm is less than 2450 MPa.

3. The multilayer sheet according to claim 1, characterized in that, The storage modulus of the adhesive layer is above 0.1 MPa at 60°C.

4. The multilayer sheet according to claim 1, characterized in that, The laminate consists of the transparent film and the coating. The storage modulus of the stack is referred to as SMm. The storage modulus of the adhesive layer is referred to as SMa. At 60°C, the difference between SMa and SMm is less than 2200 MPa.

5. The multilayer sheet according to claim 1, characterized in that, The combined thickness of the coating and the adhesive layer is less than 30 μm.

6. A multilayer electronic device, characterized in that, include: The multilayer sheet according to claim 1, and A light-emitting functional layer is disposed on the underside of the multilayer wafer.

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