Multilayer sheets and multilayer electronic devices

Abstract

The multilayer sheet according to the embodiment includes an elastic layer and an adhesive layer disposed on the elastic layer. The multilayer sheet has a storage modulus measured at 20°C of 10 MPa to 1000 MPa. Such a multilayer sheet is characterized by its resistance to peeling from the surface of an object to which it is attached, its lack of interlayer separation, and its resistance to external impact, even when subjected to repeated bending or rolling over a wide temperature range.

Description

[Technical Field]

[0001] [Cross-reference with related applications] This application claims priority to Korean Patent Application No. 10-2022-0091016, filed on 22 July 2022, and the contents of said patent document are incorporated in their entirety into this invention for reference.

[0002] The concrete example relates to a multilayer sheet applicable for protection of displays and other devices, and a multilayer electronic device including the same. [Background technology]

[0003] As mobile devices such as cell phones, smartphones, and tablets, as well as information processing terminals such as ATMs and kiosks, become more diverse, surface protection sheets are being used in a variety of ways. Furthermore, with the emergence of various display devices such as foldable, flexible, and rollable types, there is a demand for surface hardness to suppress scratches, as well as sufficient durability against repeated folding and rolling. Naturally, when applied to display screens, optical properties are also required. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Korean Registered Patent No. 10-1798759 [Patent Document 2] Korean Registered Patent No. 10-1810422 [Overview of the project] [Problems that the invention aims to solve]

[0005] The objective of this embodiment is to provide a multilayer sheet that exhibits characteristics such as suppressed peeling from the surface to which it is attached despite repeated bending and rolling over a wide temperature range, no interlayer separation occurring, and strong resistance to external impacts.

Means for Solving the Problem

[0006] The multilayer sheet according to an embodiment of the present specification includes an elastic layer and an adhesive layer disposed on the elastic layer.

[0007] The storage modulus of the multilayer sheet measured at 20°C is 10 MPa or more and 2000 MPa or less.

[0008] The RSM value of the multilayer sheet measured at 20°C according to the following formula (1) may be 1 or more and 200 or less.

[0009] [Formula (1)] RSM = SM / SM B

[0010] In the formula (1), the SM E is the storage modulus value of the elastic layer.

[0011] The SM B is the storage modulus value of the adhesive layer.

[0012] The absolute value of the value obtained by subtracting the storage modulus value measured at 60°C from the storage modulus value measured at 20°C of the multilayer sheet may be 1000 MPa or less.

[0013] The absolute value of the value obtained by subtracting the storage modulus value measured at 20°C from the storage modulus value measured at -40°C of the multilayer sheet may be 1500 MPa or less.

[0014] The storage modulus of the elastic layer measured at 20°C may be 10 MPa or more and 3000 MPa or less.

[0015] The storage modulus of the adhesive layer measured at 20°C may be 1 MPa or more and 50 MPa or less.

[0016] The adhesive strength after curing of the adhesive layer may be 2 N / inch or more.

[0017] The adhesive strength per unit thickness (1 μm) after curing of the adhesive layer may be 0.8 N / inch or more.

[0018] The multilayer electronic device according to another embodiment of the present specification includes the multilayer sheet and a light-emitting functional layer disposed under the multilayer sheet.

Effects of the Invention

[0019] Examples of the multilayer sheet and the like are characterized in that peeling from the surface of the adhesion target is suppressed even under repeated bending or rolling within a wide temperature range, separation between layers does not occur, and they are resistant to external impacts.

Brief Description of the Drawings

[0020] [Figure 1] It is a conceptual diagram for explaining a multilayer sheet according to an embodiment of the present specification. [Figure 2] It is a conceptual diagram for explaining a multilayer sheet according to another embodiment of the present specification. [Figure 3] It is a conceptual diagram for explaining a multilayer sheet according to still another embodiment of the present specification. [Figure 4] It is a conceptual diagram for explaining a multilayer sheet according to still another embodiment of the present specification. [Figure 5] It is a conceptual diagram for explaining a multilayer electronic device according to still another embodiment of the present specification. [Figure 6] It is a graph showing measured values of storage modulus according to temperature for each of the examples and comparative examples. [Figure 7] It is a graph showing measured values of storage modulus according to temperature for each of the examples and comparative examples. [Figure 8] It is a graph showing measured values of storage modulus according to temperature for each of the examples and comparative examples. [Figure 9] It is a graph showing measured values of storage modulus according to temperature for each of the examples and comparative examples. [Figure 10] It is a graph showing measured values of storage modulus according to temperature for each of the examples and comparative examples. [Figure 11] This graph shows the measured storage modulus at different temperatures for each example and comparative example. [Figure 12] This graph shows the measured storage modulus at different temperatures for each example and comparative example. [Best Mode for Carrying Out the Invention]

[0021] The following describes the embodiments in detail so that they can be easily implemented by a person with ordinary skill in the technical field to which the embodiments belong. However, the embodiments can be realized in various different forms and are not limited to the embodiments described herein.

[0022] Terms of degree used herein, such as “about” and “substantially,” are used in the sense of the numerical value or close to the numerical value when tolerances for manufacture and material inherent to the meaning referred to are presented, and are used to prevent unscrupulous infringers from unfairly exploiting disclosures that refer to precise or absolute numerical values ​​to aid in understanding the specific examples.

[0023] Throughout this specification, the term “these combinations” as used in any expression in Markush form means one or more mixtures or combinations selected from the group of components described in the Markush form, and includes one or more of those components.

[0024] Throughout this specification, the phrase "A and / or B" means "A, B, or A and B."

[0025] Throughout this specification, terms such as “First,” “Second,” or “A,” “B” are used to distinguish the same term from one another unless otherwise specified.

[0026] In this specification, the meaning of B being located on A means that B may be located on A, or another layer may be located between them while B is located on A, and is not limited to B being located in contact with the surface of A.

[0027] In this specification, unless otherwise specified, singular expressions are interpreted to include singular or plural, as interpreted in the context.

[0028] The resins described herein are interpreted to include the resins themselves and compounds derived from those resins. Exemplarily, the polyester resins described herein mean polyester resins and derivatives of polyester resins.

[0029] In this specification, if the adhesive layer is a curable adhesive layer, the storage modulus value of the adhesive layer corresponds to the value measured from the cured adhesive layer.

[0030] In this specification, when the adhesive layer contained in a multilayer sheet is a curable adhesive layer, the storage modulus value of the multilayer sheet corresponds to the value measured from the multilayer sheet after the adhesive layer within the multilayer sheet has been cured.

[0031] The inventors of the embodiment controlled the storage modulus value of a multilayer sheet having an elastic layer and an adhesive layer. As a result, the inventors experimentally confirmed that when the multilayer sheet is attached to a flexible object such as a flexible display, the multilayer sheet does not lift off the surface of the object even when the object is repeatedly bent or rolled, and can stably protect the object, thus completing the embodiment.

[0032] The following provides a detailed explanation of specific examples.

[0033] Figure 1 is a conceptual diagram illustrating the structure of a multilayer sheet in a cross-sectional view in an example. The multilayer sheet in the example will be described in more detail with reference to Figure 1.

[0034] The multilayer sheet 100 in the embodiment includes an elastic layer 10 and an adhesive layer 20 disposed on the elastic layer 10.

[0035] Multilayer sheet The multilayer sheet 100 has a storage modulus of 10 MPa to 2000 MPa, measured at 20°C.

[0036] In this embodiment, the storage modulus of the multilayer sheet 100 at different measurement temperatures can be controlled to stay within a range predetermined in the embodiment. In such a case, the difference in modulus between the flexible display, which has a relatively high storage modulus value, and the multilayer sheet 100 can be reduced. Through this, the peeling of the multilayer sheet 100 attached to the display from the display surface due to repeated bending can be effectively suppressed. In addition, the display can be stably protected from external impacts.

[0037] The storage modulus of the multilayer sheet 100 at different measurement temperatures is measured in accordance with ASTM D4065. Specifically, a viscoelasticity measuring device is used to measure the storage modulus of the multilayer sheet 100 at different measurement temperatures by applying a heating rate of 5°C / min in the temperature range of -50°C to 100°C.

[0038] For example, the storage modulus can be measured using the Hitachi DMA7100 model.

[0039] The multilayer sheet 100 may have a storage modulus of 10 MPa or more and 2000 MPa or less, measured at 20°C. The storage modulus value may be 20 MPa or more. The storage modulus value may be 50 MPa or more. The storage modulus value may be 100 MPa or more. The storage modulus value may be 200 MPa or more. The storage modulus value may be 300 MPa or more. The storage modulus value may be 1800 MPa or less. The storage modulus value may be 1500 MPa or less. The storage modulus value may be 1200 MPa or less. The storage modulus value may be 1000 MPa or less. When such a multilayer sheet is attached to a flexible display, it can adhere stably to the display surface despite the repeated bending of the display.

[0040] The multilayer sheet 100 may have a storage modulus of 20 MPa or more and 2500 MPa or less, measured at 0°C. The storage modulus value may be 30 MPa or more. The storage modulus value may be 40 MPa or more. The storage modulus value may be 100 MPa or more. The storage modulus value may be 200 MPa or more. The storage modulus value may be 350 MPa or more. The storage modulus value may be 2000 MPa or less. The storage modulus value may be 1500 MPa or less. The storage modulus value may be 1000 MPa or less. The storage modulus value may be 700 MPa or less.

[0041] The multilayer sheet 100 may have a storage modulus of 30 MPa or more and 3000 MPa or less, measured at -20°C. The storage modulus value may be 50 MPa or more. The storage modulus value may be 100 MPa or more. The storage modulus value may be 200 MPa or more. The storage modulus value may be 300 MPa or more. The storage modulus value may be 400 MPa or more. The storage modulus value may be 2500 MPa or less. The storage modulus value may be 2000 MPa or less. The storage modulus value may be 1500 MPa or less. The storage modulus value may be 1000 MPa or less. The storage modulus value may be 700 MPa or less.

[0042] The multilayer sheet 100 may have a storage modulus of 50 MPa or more and 4000 MPa or less, measured at -40°C. The storage modulus value may be 100 MPa or more. The storage modulus value may be 200 MPa or more. The storage modulus value may be 300 MPa or more. The storage modulus value may be 400 MPa or more. The storage modulus value may be 500 MPa or more. The storage modulus value may be 3500 MPa or less. The storage modulus value may be 3000 MPa or less. The storage modulus value may be 2500 MPa or less. The storage modulus value may be 2000 MPa or less. The storage modulus value may be 1500 MPa or less. The storage modulus value may be 1000 MPa or less. The storage modulus value may be 600 MPa or less.

[0043] The multilayer sheet 100 may have a storage modulus of 5 MPa or more and 2000 MPa or less, measured at 40°C. The storage modulus value may be 10 MPa or more. The storage modulus value may be 20 MPa or more. The storage modulus value may be 50 MPa or more. The storage modulus value may be 100 MPa or more. The storage modulus value may be 150 MPa or more. The storage modulus value may be 1500 MPa or less. The storage modulus value may be 1200 MPa or less. The storage modulus value may be 1000 MPa or less. The storage modulus value may be 800 MPa or less. The storage modulus value may be 700 MPa or less.

[0044] The multilayer sheet 100 may have a storage modulus of 3 MPa or more and 800 MPa or less, measured at 60°C. The storage modulus value may be 10 MPa or more. The storage modulus value may be 20 MPa or more. The storage modulus value may be 50 MPa or more. The storage modulus value may be 80 MPa or more. The storage modulus value may be 100 MPa or more. The storage modulus value may be 600 MPa or less. The storage modulus value may be 400 MPa or less. The storage modulus value may be 300 MPa or less.

[0045] The multilayer sheet 100 may have a storage modulus of 1 MPa or more and 500 MPa or less, measured at 80°C. The storage modulus value may be 5 MPa or more. The storage modulus value may be 10 MPa or more. The storage modulus value may be 30 MPa or more. The storage modulus value may be 50 MPa or more. The storage modulus value may be 400 MPa or less. The storage modulus value may be 300 MPa or less. The storage modulus value may be 250 MPa or less. The storage modulus value may be 200 MPa or less.

[0046] In such cases, the multilayer sheet can be stably adhered to the flexible display over a wide temperature range.

[0047] The absolute value obtained by subtracting the storage modulus value of the multilayer sheet 100 measured at 40°C from the storage modulus value of the multilayer sheet 100 measured at 20°C may be 700 MPa or less. The absolute value may be 500 MPa or less. The absolute value may be 300 MPa or less. The absolute value may be 100 MPa or less. The absolute value may be 50 MPa or less. The absolute value may be 20 MPa or less. The absolute value may be 10 MPa or less. The absolute value may be 1 MPa or more.

[0048] The absolute value obtained by subtracting the storage modulus value of the multilayer sheet 100 measured at 60°C from the storage modulus value of the multilayer sheet 100 measured at 20°C may be 1000 MPa or less. The absolute value may be 700 MPa or less. The absolute value may be 500 MPa or less. The absolute value may be 300 MPa or less. The absolute value may be 100 MPa or less. The absolute value may be 50 MPa or less. The absolute value may be 30 MPa or less. The absolute value may be 15 MPa or less. The absolute value may be 1 MPa or more.

[0049] The absolute value obtained by subtracting the storage modulus value of the multilayer sheet 100 measured at 80°C from the storage modulus value of the multilayer sheet 100 measured at 20°C may be 1000 MPa or less. The absolute value may be 700 MPa or less. The absolute value may be 500 MPa or less. The absolute value may be 300 MPa or less. The absolute value may be 100 MPa or less. The absolute value may be 50 MPa or less. The absolute value may be 30 MPa or less. The absolute value may be 1 MPa or more.

[0050] In such cases, it is possible to effectively suppress the phenomenon of the multilayer sheet lifting due to temperature rise.

[0051] The absolute value obtained by subtracting the storage modulus value of the multilayer sheet 100 measured at 20°C from the storage modulus value of the multilayer sheet 100 measured at 0°C may be 500 MPa or less. The absolute value may be 400 MPa or less. The absolute value may be 300 MPa or less. The absolute value may be 200 MPa or less. The absolute value may be 100 MPa or less. The absolute value may be 50 MPa or less. The absolute value may be 30 MPa or less. The absolute value may be 1 MPa or more.

[0052] The absolute value obtained by subtracting the storage modulus value of the multilayer sheet 100 measured at 20°C from the storage modulus value of the multilayer sheet 100 measured at -20°C may be 1000 MPa or less. The absolute value may be 800 MPa or less. The absolute value may be 600 MPa or less. The absolute value may be 500 MPa or less. The absolute value may be 300 MPa or less. The absolute value may be 200 MPa or less. The absolute value may be 100 MPa or less. The absolute value may be 50 MPa or less. The absolute value may be 1 MPa or more.

[0053] The absolute value obtained by subtracting the storage modulus value of the multilayer sheet 100 measured at 20°C from the storage modulus value of the multilayer sheet 100 measured at -40°C may be 1500 MPa or less. The absolute value may be 1200 MPa or less. The absolute value may be 1000 MPa or less. The absolute value may be 700 MPa or less. The absolute value may be 500 MPa or less. The absolute value may be 200 MPa or less. The absolute value may be 100 MPa or less. The absolute value may be 50 MPa or less. The absolute value may be 30 MPa or less. The absolute value may be 20 MPa or less. The absolute value may be 1 MPa or more.

[0054] In such cases, a decrease in temperature reduces the bending characteristics of the multilayer sheet, effectively suppressing the delamination of the multilayer sheet from the display.

[0055] The multilayer sheet 100 may have an RSM value of 1 or more and 200 or less, as measured at 20°C using the following formula 1.

[0056] [Formula 1] RSM=SM E / SM B

[0057] In the above formula 1, the SM E This is the storage modulus value of the elastic layer.

[0058] Said SM B This is the storage modulus value of the adhesive layer.

[0059] In this embodiment, the RSM value of the multilayer sheet 100 can be controlled to a range predetermined in the embodiment. Through this, the difference in mechanical properties between layers within the multilayer sheet 100 can be adjusted, effectively suppressing not only delamination of the multilayer sheet from the surface to which it is attached, but also delamination between layers within the multilayer sheet.

[0060] The explanation of how to measure the storage modulus of the elastic layer 10 and the adhesive layer 20 will be omitted as it will be redundant with what has been described above.

[0061] The multilayer sheet 100 may have an RSM value of 1 or more and 200 or less measured at 20°C. The RSM value may be 3 or more. The RSM value may be 5 or more. The RSM value may be 10 or more. The RSM value may be 15 or more. The RSM value may be 20 or more. The RSM value may be 180 or less. The RSM value may be 150 or less. The RSM value may be 120 or less. The RSM value may be 100 or less. The RSM value may be 80 or less.

[0062] The multilayer sheet 100 may have an RSM value of 5 or more and 400 or less measured at 40°C. The RSM value may be 10 or more. The RSM value may be 20 or more. The RSM value may be 30 or more. The RSM value may be 45 or more. The RSM value may be 55 or more. The RSM value may be 350 or less. The RSM value may be 300 or less. The RSM value may be 250 or less. The RSM value may be 220 or less. The RSM value may be 200 or less.

[0063] The multilayer sheet 100 may have an RSM value of 0.1 or more and 100 or less measured at 0°C. The RSM value may be 1 or more. The RSM value may be 3 or more. The RSM value may be 5 or more. The RSM value may be 10 or more. The RSM value may be 80 or less. The RSM value may be 65 or less. The RSM value may be 50 or less.

[0064] The multilayer sheet 100 may have an RSM value of 0.5 or more and 75 or less measured at -20°C. The RSM value may be 1 or more. The RSM value may be 3 or more. The RSM value may be 5 or more. The RSM value may be 7 or more. The RSM value may be 60 or less. The RSM value may be 50 or less. The RSM value may be 40 or less.

[0065] The multilayer sheet 100 may have an RSM value of 0.7 or more and 60 or less measured at -40°C. The RSM value may be 1 or more. The RSM value may be 3.5 or more. The RSM value may be 5.5 or more. The RSM value may be 7.5 or more. The RSM value may be 50 or less. The RSM value may be 30 or less. The RSM value may be 20 or less.

[0066] In such cases, the difference in modulus between the adhesive layer and the elastic layer, or between the adhesive layer and the display, can effectively suppress the delamination of the adhesive layer.

[0067] The adhesive strength of the multilayer sheet 100 may be 2 N / inch or more.

[0068] The embodiment allows for control of the adhesive strength of the multilayer sheet 100. Such a multilayer sheet 100 can exhibit stable adhesion even when applied to displays that are repeatedly bent or rolled.

[0069] The adhesive strength of the multilayer sheet 100 is measured after the adhesive layer 20 has cured. The adhesive strength of the multilayer sheet 100 is measured using an Advanced Force Gauge in a 180° peel test, with a peeling speed of 300 mm / min and a glass plate as the adherend.

[0070] For example, the Advanced Force Gauge can be the AFG50 model from Mecmesin, and the adherend can be the NA32G model from Avanstrate.

[0071] The adhesive strength of the multilayer sheet 100 may be 2 N / inch or more. The adhesive strength may be 3 N / inch or more. The adhesive strength may be 5 N / inch or more. The adhesive strength may be 8 N / inch or more. The adhesive strength may be 10 N / inch or more. The adhesive strength may be 25 N / inch or less. The adhesive strength may be 23 N / inch or less. The adhesive strength may be 20 N / inch or less. The adhesive strength may be 18 N / inch or less. In such cases, the adhesion of the multilayer sheet can be further improved.

[0072] The thickness of the multilayer sheet 100 may be 10 μm or more. The thickness may be 15 μm or more. The thickness may be 20 μm or more. The thickness may be 30 μm or more. The thickness may be 1000 μm or less. The thickness may be 800 μm or less. The thickness may be 500 μm or less. The thickness may be 300 μm or less. The thickness may be 200 μm or less. The thickness may be 100 μm or less. The thickness may be 50 μm or less. The thickness may be 10 μm or more. In such cases, the multilayer sheet can reliably protect the object to be protected, such as a display, from external impacts.

[0073] Figure 2 is a conceptual diagram illustrating a multilayer sheet according to another embodiment of this specification. The concrete example will be described in further detail with reference to Figure 2.

[0074] The multilayer sheet 100 may include an adhesive layer 20 placed on the elastic layer 10 and an adhesive layer 20 placed below the elastic layer 10. A multilayer sheet having such a structure can be used as an adhesive film.

[0075] The multilayer sheet 100 may include one side and another side. In the multilayer sheet 100, an adhesive layer 20 may be arranged as the outermost layer on both the one-side and the other-side. A multilayer sheet having such a structure is suitable for use as an adhesive film for displays.

[0076] Figure 3 is a conceptual diagram illustrating a multilayer sheet according to yet another embodiment of this specification. Specific examples will be described in further detail with reference to Figure 3.

[0077] The multilayer sheet 100 may include a transparent layer 30 placed on an adhesive layer 20, and a coating layer 40 placed on the transparent layer 30.

[0078] The transparent layer 30 may be placed in contact with the adhesive layer 20. The transparent layer 30 may also be placed on the adhesive layer 20 without being in contact with it.

[0079] The coating layer 40 may be placed in contact with the transparent layer 30. The coating layer 40 may be placed on the transparent layer 30 without being in contact with it.

[0080] The transparent layer 30 can be used as a base layer for the coating layer 40.

[0081] The lower surface of the coating layer 40 faces the transparent layer 30, and the upper surface of the coating layer 40 is the outermost surface exposed to the outside.

[0082] The coating layer 40 may be a curable coating layer.

[0083] Figure 4 is a conceptual diagram illustrating a multilayer sheet according to yet another embodiment of this specification. Specific examples will be described in further detail with reference to Figure 4.

[0084] The multilayer sheet 100 may further include a release film 50 on the adhesive layer 20.

[0085] The release film 50 may be placed in contact with the upper surface of the adhesive layer 20. Alternatively, the release film 50 may be placed on the adhesive layer 20 via another layer located between the lower surface of the release film 50 and the upper surface of the adhesive layer 20.

[0086] The release substrate layer 52 can be used as the base layer for the release layer 51.

[0087] The release film 50 may include a release layer 51 placed on the adhesive layer 20, and a release substrate layer 52 placed on the release layer 51.

[0088] The release layer 51 may be a cured layer of a silicone resin composition containing fluorine groups. Specifically, the release layer 51 may be a cured layer of a release coating liquid containing an organopolysiloxane containing fluorine groups and an organopolysiloxane containing alkenyl groups.

[0089] The release substrate layer 52 is not limited as long as it is one that is commonly used in the field of substrate films. For example, the release substrate layer 52 may be a polyethylene terephthalate film or the like.

[0090] elastic layer In practice, the elastic layer 10 can have a storage modulus value controlled according to the measurement temperature. Through this, excellent bending characteristics can be imparted to the multilayer sheet over a wide temperature range, and the display can be stably protected.

[0091] The method for measuring the storage modulus value of the elastic layer 10 at different temperatures is the same as the method for measuring the storage modulus value of the multilayer sheet at different temperatures described above.

[0092] The elastic layer 10 may have a storage modulus value of 10 MPa or higher, measured at 20°C. The storage modulus value may be 50 MPa or higher. The storage modulus value may be 100 MPa or higher. The storage modulus value may be 200 MPa or higher. The storage modulus value may be 300 MPa or higher. The storage modulus value may be 3000 MPa or lower. The storage modulus value may be 2500 MPa or lower. The storage modulus value may be 2000 MPa or lower. The storage modulus value may be 1500 MPa or lower. The storage modulus value may be 1200 MPa or lower.

[0093] The elastic layer 10 may have a storage modulus value of 10 MPa or higher, measured at 40°C. The storage modulus value may be 50 MPa or higher. The storage modulus value may be 100 MPa or higher. The storage modulus value may be 200 MPa or higher. The storage modulus value may be 1200 MPa or lower. The storage modulus value may be 1000 MPa or lower. The storage modulus value may be 800 MPa or lower. The storage modulus value may be 700 MPa or lower.

[0094] The elastic layer 10 may have a storage modulus value of 10 MPa or higher, measured at 60°C. The storage modulus value may be 50 MPa or higher. The storage modulus value may be 100 MPa or higher. The storage modulus value may be 700 MPa or lower. The storage modulus value may be 500 MPa or lower. The storage modulus value may be 300 MPa or lower.

[0095] The elastic layer 10 may have a storage modulus value of 10 MPa or higher, measured at 80°C. The storage modulus value may be 20 MPa or higher. The storage modulus value may be 50 MPa or higher. The storage modulus value may be 70 MPa or higher. The storage modulus value may be 500 MPa or lower. The storage modulus value may be 350 MPa or lower. The storage modulus value may be 200 MPa or lower. The storage modulus value may be 170 MPa or lower.

[0096] The elastic layer 10 may have a storage modulus value of 30 MPa or higher, measured at 0°C. The storage modulus value may be 50 MPa or higher. The storage modulus value may be 100 MPa or higher. The storage modulus value may be 200 MPa or higher. The storage modulus value may be 300 MPa or higher. The storage modulus value may be 2200 MPa or lower. The storage modulus value may be 1800 MPa or lower. The storage modulus value may be 1500 MPa or lower. The storage modulus value may be 1200 MPa or lower. The storage modulus value may be 1000 MPa or lower. The storage modulus value may be 800 MPa or lower.

[0097] The elastic layer 10 may have a storage modulus value of 50 MPa or higher, measured at -20°C. The storage modulus value may be 100 MPa or higher. The storage modulus value may be 150 MPa or higher. The storage modulus value may be 200 MPa or higher. The storage modulus value may be 300 MPa or higher. The storage modulus value may be 350 MPa or higher. The storage modulus value may be 400 MPa or higher. The storage modulus value may be 2400 MPa or lower. The storage modulus value may be 2000 MPa or lower. The storage modulus value may be 1500 MPa or lower. The storage modulus value may be 1200 MPa or lower. The storage modulus value may be 1000 MPa or lower. The storage modulus value may be 800 MPa or lower.

[0098] The elastic layer 10 may have a storage modulus value of 80 MPa or higher, measured at -40°C. The storage modulus value may be 200 MPa or higher. The storage modulus value may be 350 MPa or higher. The storage modulus value may be 500 MPa or higher. The storage modulus value may be 2600 MPa or lower. The storage modulus value may be 2300 MPa or lower. The storage modulus value may be 2000 MPa or lower. The storage modulus value may be 1700 MPa or lower. The storage modulus value may be 1500 MPa or lower. The storage modulus value may be 1200 MPa or lower. The storage modulus value may be 1000 MPa or lower. The storage modulus value may be 850 MPa or lower.

[0099] In such cases, the elastic layer can help impart stable bending properties to the multilayer sheet over a wide temperature range.

[0100] The absolute value obtained by subtracting the storage modulus value of the elastic layer 10 measured at 40°C from the storage modulus value of the elastic layer 10 measured at 20°C may be 1000 MPa or less. The absolute value may be 850 MPa or less. The absolute value may be 550 MPa or less. The absolute value may be 450 MPa or less. The absolute value may be 300 MPa or less. The absolute value may be 200 MPa or less. The absolute value may be 0.1 MPa or more.

[0101] The absolute value obtained by subtracting the storage modulus value of the elastic layer 10 measured at 60°C from the storage modulus value of the elastic layer 10 measured at 20°C may be 2000 MPa or less. The absolute value may be 1800 MPa or less. The absolute value may be 1500 MPa or less. The absolute value may be 1300 MPa or less. The absolute value may be 1000 MPa or less. The absolute value may be 800 MPa or less. The absolute value may be 500 MPa or less. The absolute value may be 300 MPa or less. The absolute value may be 1 MPa or more.

[0102] The absolute value obtained by subtracting the storage modulus value of the elastic layer 10 measured at 80°C from the storage modulus value of the elastic layer 10 measured at 20°C may be 2000 MPa or less. The absolute value may be 1800 MPa or less. The absolute value may be 1500 MPa or less. The absolute value may be 1300 MPa or less. The absolute value may be 1000 MPa or less. The absolute value may be 800 MPa or less. The absolute value may be 500 MPa or less. The absolute value may be 350 MPa or less. The absolute value may be 1 MPa or more.

[0103] The absolute value of the difference between the storage modulus value measured at 20°C and the storage modulus value measured at 0°C of the elastic layer 10 may be 1000 MPa or less. The absolute value may be 850 MPa or less. The absolute value may be 550 MPa or less. The absolute value may be 350 MPa or less. The absolute value may be 180 MPa or less. The absolute value may be 1 MPa or more.

[0104] The absolute value of the difference between the storage modulus value measured at 20°C and the storage modulus value measured at -20°C of the elastic layer 10 may be 1000 MPa or less. The absolute value may be 850 MPa or less. The absolute value may be 550 MPa or less. The absolute value may be 350 MPa or less. The absolute value may be 180 MPa or less. The absolute value may be 1 MPa or more.

[0105] The absolute value of the difference between the storage modulus value measured at 20°C and the storage modulus value measured at -40°C of the elastic layer 10 may be 1200 MPa or less. The absolute value may be 1000 MPa or less. The absolute value may be 800 MPa or less. The absolute value may be 600 MPa or less. The absolute value may be 500 MPa or less. The absolute value may be 400 MPa or less. The absolute value may be 1 MPa or more.

[0106] In such a case, the display can be stably protected over a wide temperature range, and excessive fluctuations in the bending characteristics of the elastic layer can be suppressed.

[0107] The elastic layer 10 can have an impact strength of 2,500 kJ / m 2 or more. The impact strength may be 3,500 kJ / m 2 or more. The impact strength may be 4,500 kJ / m 2 or more. The impact strength may be 5,000 kJ / m 2 or more. The impact strength may be 10,000 kJ / m 2The following may also apply: An elastic layer having such characteristics can absorb external impacts well, but is not easily damaged or broken.

[0108] The elastic layer 10 may have an absorption energy of 1.4 J or more. The absorption energy may be 1.5 J or more. The absorption energy may be 1.6 J or more. The absorption energy may be 2.0 J or less. An elastic layer having such characteristics can effectively mitigate the impact transmitted to the protected object.

[0109] Impact strength and absorbed energy shall be measured in accordance with JIS K 7160.

[0110] The elastic layer 10 may have a haze value of 3% or less. The haze value may be 2% or less. The haze value may be 1.5% or less. The haze value may be 1.2% or less. The haze value may be 0.01% or more. The haze value may be 0.1% or more.

[0111] The elastic layer 10 may have a visible light transmittance of 85% or more. The transmittance may be 88% or more. The transmittance may be 90% or more. The transmittance may be 99.99% or less.

[0112] An elastic layer possessing these characteristics can have optical properties that make it suitable for application as a protective layer for displays.

[0113] The elastic layer 10 may have a yellowness index (YI) of 1 or less.

[0114] The yellowness may be a value measured using the Color Meter Ultra ScanPro manufactured by Hunterlab, in YI E313 (D65 / 10) mode.

[0115] The elastic layer 10 may have a yellowness value of 2 or less obtained by subtracting the yellowness value before exposure from the yellowness value after exposure to ultraviolet light with a wavelength of 280 to 360 nm at an output of 3.0 W for 72 hours. The elastic layer 10 may have a yellowness value of 1 or less obtained by subtracting the yellowness value before exposure from the yellowness value after exposure to ultraviolet light with a wavelength of 280 to 360 nm at an output of 3.0 W for 72 hours. The elastic layer 10 may have a yellowness value of 0.1 or more obtained by subtracting the yellowness value before exposure from the yellowness value after exposure to ultraviolet light with a wavelength of 280 to 360 nm at an output of 3.0 W for 72 hours. An elastic layer having such characteristics can have excellent ultraviolet resistance, with little or no yellowing of the coating layer even when exposed to ultraviolet light.

[0116] The elastic layer 10 may be one in which cloudiness is not substantially observed. The area in which cloudiness is substantially observed in the elastic film may be less than 1% of the total area. In this case, the total area is based on the total area of ​​the film applied to the product. Cloudiness can be objectified through haze measurement, and if the measured haze value is greater than 1%, it can be treated as cloudiness being perceived. The degree of cloudiness can be adjusted by controlling the degree of gelation and molecular weight distribution of the resin applied to the manufacture of the elastic layer.

[0117] The elastic layer 10 may contain a polyether block amide (PEBA). The polyether block amide comprises two phases: a rigid polyamide region and a flexible polyether region. The polyamide region has a melting point of about 80°C or higher, specifically about 130 to 180°C, and can constitute a hard region with a substantially crystalline phase. The polyether region has a glass transition temperature of about -40°C or lower, specifically in a low temperature range of -80 to -40°C, and can constitute a substantially amorphous flexible region.

[0118] The aforementioned polyether block amide may, for example, be Pebax®, Pebax® Rnew®, or VESTAMID® E, manufactured by Arkema.

[0119] The elastic layer 10 may contain a polymer having amide residues as repeating units. The elastic layer 10 may be a plastic film containing a polymer having amide residues as repeating units. The elastic layer 10 may be an elastomer film containing a polymer having amide residues as repeating units.

[0120] The amide residue may be 50% by weight or more, or 60% by weight or more, based on the total amount of polymer contained in the elastic film. The amide residue may be 80% by weight or less, or 70% by weight or less, based on the total amount of polymer contained in the elastic film. When a polymer having such characteristics is applied to the elastic film, an elastic film with even better mechanical properties can be provided.

[0121] The elastic layer 10 may include an elastic polyamide (long chain polyamide). The elastic polyamide may, for example, be Rilsan® or Rilsamid® from Arkema.

[0122] The elastic layer 10 may include thermoplastic polyurethane (TPU), that is, a copolymer of polyurethane block (PU) and polyether block (PE), also known as polyether urethane.

[0123] The elastic layer 10 may contain a polyether ester copolymer (COPE).

[0124] The thickness of the elastic layer 10 may be 500 μm or less. The thickness may be 300 μm or less. The thickness may be 200 μm or less. The thickness may be 100 μm or less. The thickness may be 80 μm or less. The thickness may be 1 μm or more. The thickness may be 5 μm or more. The thickness may be 10 μm or more. In such cases, the elastic layer can impart excellent impact resistance and bending characteristics to the multilayer sheet.

[0125] The elastic layer 10 can be formed using a resin composition for elastic layers.

[0126] The resin composition for the elastic layer may contain a polymer containing an amide residue as a repeating unit. The resin composition for the elastic layer may contain an elastic polyamide. The resin composition for the elastic layer may contain a thermoplastic polyurethane. The resin composition for the elastic layer may contain a polyether ester copolymer (COPE).

[0127] The explanation of the aforementioned resin will be omitted as it will be redundant with the previous explanation.

[0128] The method for forming the resin composition for the elastic layer into the shape of the elastic layer can be any method applicable to the manufacture of films, and a melt extrusion method may be applied as an example.

[0129] When a resin composition for an elastic layer is melt-extruded to form an elastic sheet, the melt-extrusion temperature may be 200 to 300°C. Performing melt-extrusion within this temperature range allows for smooth molding into a sheet without damaging the properties of the resin itself, while also imparting fluidity to the resin composition.

[0130] To adjust the thickness of the elastic layer 10, the manufactured elastic layer can be passed through a roller. If necessary, an elastic layer protective film can be laminated above and below the elastic layer to form a laminate, and then the laminate can be passed through a roller.

[0131] adhesive layer In one concrete example, the storage modulus value of the adhesive layer 20 can be controlled according to the measurement temperature, thereby reducing the difference in modulus characteristics between the adhesive layer 20 and the elastic layer 10 within the multilayer sheet 100 over a wide temperature range. Through this, it is possible to suppress the peeling of the adhesive layer 20 from the elastic layer 10 during repeated bending processes. At the same time, it is possible to suppress the peeling of the multilayer sheet 100 from the flexible display due to the difference in bending characteristics between the flexible display and the adhesive layer 20.

[0132] The method for measuring the storage modulus of the adhesive layer 20 at different temperatures is the same as the method for measuring the storage modulus of the multilayer sheet at different temperatures described above.

[0133] The adhesive layer 20 may have a storage modulus value of 1 MPa or higher, measured at 20°C. The storage modulus value may be 5 MPa or higher. The storage modulus value may be 7 MPa or higher. The storage modulus value may be 100 MPa or lower. The storage modulus value may be 80 MPa or lower. The storage modulus value may be 50 MPa or lower. The storage modulus value may be 20 MPa or lower.

[0134] The adhesive layer 20 may have a storage modulus value of 0.1 MPa or higher, measured at 40°C. The storage modulus value may be 0.5 MPa or higher. The storage modulus value may be 1 MPa or higher. The storage modulus value may be 2 MPa or higher. The storage modulus value may be 30 MPa or lower. The storage modulus value may be 20 MPa or lower. The storage modulus value may be 10 MPa or lower.

[0135] The adhesive layer 20 may have a storage modulus value of 0.01 MPa or higher, measured at 60°C. The storage modulus value may also be 0.05 MPa or higher. The storage modulus value may also be 0.1 MPa or higher. The storage modulus value may also be 5 MPa or lower.

[0136] The adhesive layer 20 may have a storage modulus value of 0.001 MPa or higher, measured at 80°C. The storage modulus value may also be 0.003 MPa or higher. The storage modulus value may also be 0.01 MPa or lower.

[0137] The adhesive layer 20 may have a storage modulus value of 5 MPa or higher, measured at 0°C. The storage modulus value may be 10 MPa or higher. The storage modulus value may be 20 MPa or higher. The storage modulus value may be 25 MPa or higher. The storage modulus value may be 200 MPa or lower. The storage modulus value may be 180 MPa or lower. The storage modulus value may be 150 MPa or lower. The storage modulus value may be 120 MPa or lower. The storage modulus value may be 100 MPa or lower. The storage modulus value may be 80 MPa or lower. The storage modulus value may be 50 MPa or lower.

[0138] The adhesive layer 20 may have a storage modulus value of 10 MPa or higher, measured at -20°C. The storage modulus value may be 20 MPa or higher. The storage modulus value may be 30 MPa or higher. The storage modulus value may be 200 MPa or lower. The storage modulus value may be 180 MPa or lower. The storage modulus value may be 150 MPa or lower. The storage modulus value may be 120 MPa or lower. The storage modulus value may be 100 MPa or lower. The storage modulus value may be 80 MPa or lower.

[0139] The adhesive layer 20 may have a storage modulus value of 20 MPa or higher, measured at -40°C. The storage modulus value may be 30 MPa or higher. The storage modulus value may be 40 MPa or higher. The storage modulus value may be 50 MPa or higher. The storage modulus value may be 300 MPa or lower. The storage modulus value may be 250 MPa or lower. The storage modulus value may be 200 MPa or lower. The storage modulus value may be 170 MPa or lower. The storage modulus value may be 150 MPa or lower. The storage modulus value may be 120 MPa or lower. The storage modulus value may be 100 MPa or lower.

[0140] The adhesive layer 20 may be a curable adhesive layer.

[0141] The adhesive layer 20 may have a storage modulus value of 1 MPa or higher after curing, measured at 20°C. The storage modulus value may be 5 MPa or higher. The storage modulus value may be 7 MPa or higher. The storage modulus value may be 100 MPa or lower. The storage modulus value may be 80 MPa or lower. The storage modulus value may be 50 MPa or lower. The storage modulus value may be 20 MPa or lower.

[0142] The adhesive layer 20 may have a storage modulus value of 0.1 MPa or higher after curing, measured at 40°C. The storage modulus value may be 0.5 MPa or higher. The storage modulus value may be 1 MPa or higher. The storage modulus value may be 2 MPa or higher. The storage modulus value may be 30 MPa or lower. The storage modulus value may be 20 MPa or lower. The storage modulus value may be 10 MPa or lower.

[0143] The adhesive layer 20 may have a storage modulus value of 0.01 MPa or higher after curing, measured at 60°C. The storage modulus value may be 0.05 MPa or higher. The storage modulus value may be 0.1 MPa or higher. The storage modulus value may be 5 MPa or lower.

[0144] The adhesive layer 20 may have a storage modulus value of 0.001 MPa or higher after curing, measured at 80°C. The storage modulus value may also be 0.003 MPa or higher. The storage modulus value may also be 0.01 MPa or lower.

[0145] The adhesive layer 20 may have a storage modulus value of 5 MPa or higher after curing, measured at 0°C. The storage modulus value may be 10 MPa or higher. The storage modulus value may be 20 MPa or higher. The storage modulus value may be 25 MPa or higher. The storage modulus value may be 200 MPa or lower. The storage modulus value may be 180 MPa or lower. The storage modulus value may be 150 MPa or lower. The storage modulus value may be 120 MPa or lower. The storage modulus value may be 100 MPa or lower. The storage modulus value may be 80 MPa or lower. The storage modulus value may be 50 MPa or lower.

[0146] The adhesive layer 20 may have a storage modulus value of 10 MPa or higher after curing, measured at -20°C. The storage modulus value may be 20 MPa or higher. The storage modulus value may be 30 MPa or higher. The storage modulus value may be 200 MPa or lower. The storage modulus value may be 180 MPa or lower. The storage modulus value may be 150 MPa or lower. The storage modulus value may be 120 MPa or lower. The storage modulus value may be 100 MPa or lower. The storage modulus value may be 80 MPa or lower.

[0147] The adhesive layer 20 may have a storage modulus value of 20 MPa or higher after curing, measured at -40°C. The storage modulus value may be 30 MPa or higher. The storage modulus value may be 40 MPa or higher. The storage modulus value may be 50 MPa or higher. The storage modulus value may be 300 MPa or lower. The storage modulus value may be 250 MPa or lower. The storage modulus value may be 200 MPa or lower. The storage modulus value may be 170 MPa or lower. The storage modulus value may be 150 MPa or lower. The storage modulus value may be 120 MPa or lower. The storage modulus value may be 100 MPa or lower.

[0148] In such cases, controlling the bending characteristics of the adhesive layer can further improve the peel resistance of the multilayer sheet.

[0149] The adhesive strength of the adhesive layer 20 after curing may be 2 N / inch or more. The adhesive strength may be 2.5 N / inch or more. The adhesive strength may be 3 N / inch or more. The adhesive strength may be 3.5 N / inch or more. The adhesive strength may be 4 N / inch or more. The adhesive strength may be 4.5 N / inch or more. The adhesive strength may be 5 N / inch or more. The adhesive strength may be 5.5 N / inch or more. The adhesive strength may be 25 N / inch or less. The adhesive strength may be 22 N / inch or less. The adhesive strength may be 20 N / inch or more. The adhesive strength may be 18 N / inch or more. The adhesive strength may be 15 N / inch or more. The adhesive strength may be 12 N / inch or more. The adhesive strength may be 10 N / inch or more. In such cases, excellent adhesive strength can be imparted to the multilayer sheet.

[0150] The adhesive strength per unit thickness (1 μm) of the cured adhesive layer 20 may be 0.8 N / inch or more. The adhesive strength per unit thickness (1 μm) of the cured adhesive layer 20 may be 0.9 N / inch or more. The adhesive strength per unit thickness (1 μm) of the cured adhesive layer 20 may be 1 N / inch or more. The adhesive strength per unit thickness (1 μm) of the cured adhesive layer 20 may be 1.2 N / inch or more. The adhesive strength per unit thickness (1 μm) of the cured adhesive layer 20 may be 1.5 N / inch or more. The adhesive strength per unit thickness (1 μm) of the cured adhesive layer 20 may be 1.8 N / inch or more. The adhesive strength per unit thickness (1 μm) of the cured adhesive layer 20 may be 2 N / inch or more. The adhesive strength per unit thickness (1 μm) of the cured adhesive layer 20 may be 2.3 N / inch or more. The adhesive strength per unit thickness (1 μm) of the cured adhesive layer 20 may be 2.5 N / inch or more. The adhesive strength per unit thickness (1 μm) of the cured adhesive layer 20 may be 3.5 N / inch or less. The adhesive strength per unit thickness (1 μm) of the cured adhesive layer 20 may be 3.2 N / inch or less. The adhesive strength per unit thickness (1 μm) of the cured adhesive layer 20 may be 3.0 N / inch or less. In such cases, a relatively thin adhesive layer can be applied, which can contribute to imparting excellent bending characteristics to the multilayer film.

[0151] The explanation of how to measure the adhesive strength of the adhesive layer 20 will be omitted as it will overlap with the explanation of how to measure the adhesive strength of the multilayer sheet described above.

[0152] The adhesive layer 20 may have a total light transmittance (light transmittance) of 85% or more in accordance with ISO 13468. The light transmittance may be 88% or more. The light transmittance may be 89% or more. The light transmittance may be 99% or less.

[0153] The haze of the adhesive layer 20 may be 3% or less. The haze may be 2% or less. The haze may be 1.5% or less. The haze may be 1% or less. The haze may be greater than 0%.

[0154] The yellowness index (YI) of the adhesive layer 20 may be 3 or less. The yellowness index may be 2.8 or less. The yellowness index may be 2.2 or less. The yellowness index may be 1.0 or less. The yellowness index may be 0.8 or less. The yellowness index may be 0.5 or less. The yellowness index may be greater than 0.

[0155] Such adhesive layers have excellent optical properties, making them suitable for application in the field of displays.

[0156] The adhesive layer 20 may be an acrylic adhesive layer, a urethane adhesive layer, or a silicone adhesive layer, and specifically, a silicone adhesive layer may be used. By using a silicone adhesive layer, it is possible to provide an adhesive layer that has high light transmittance as well as heat resistance and weather resistance. In particular, the adhesive layer in the embodiment described later has strong adhesive strength even at a thin thickness, so it can further improve the physical properties of the multilayer sheet compared to existing OCA (optically clear adhesive) such as an acrylic adhesive layer.

[0157] The adhesive layer 20 may be one that has high adhesive strength.

[0158] In order for the physical properties of a multilayer sheet to be maintained well even with repeated bending or folding, not only the transparent layer and coating layer 40, but also the performance of the adhesive layer that fixes them and suppresses the occurrence of delamination must be improved. The inventors were able to obtain such improved performance by applying a silicone-based adhesive layer.

[0159] A silicone-based adhesive layer can be obtained by applying a silicone adhesive composition and then drying and / or curing it.

[0160] The silicone adhesive composition may contain a silicone adhesive, a catalyst, and a solvent.

[0161] The silicone adhesive can be a commercially available silicone adhesive suitable for optical applications. Specifically, a peroxide-curing silicone adhesive or an addition-reaction silicone adhesive may be used.

[0162] Examples of peroxide-curing silicone adhesives that may be used include Shin-Etsu Chemical's KR-100, KR-101-10, KR-130, Dow's DOWSIL SH 4280, and Momentive Performance Materials' SilGrip PSA 510.

[0163] Addition-reaction silicone adhesives may include, for example, Shin-Etsu Chemical's KR-3700, KR-3701, X-40-3237, X-40-3240, X-40-3291-1; Dow's DOWSIL SD4580, DOWSIL 4584, DOWSIL 4585, DOWSIL 4587L; and Momentive Performance Materials' SilGrip TSR1512, TSR1516.

[0164] In terms of process convenience, using an addition-reaction type silicone adhesive may be advantageous.

[0165] An example of this is that the silicone MQ resin may be further included to improve the adhesive strength of the silicone adhesive layer. Here, the silicone MQ resin is a polymer among cage-like oligosiloxanes represented by the general formula RnSiXmOy, having at least two methyl groups in its siloxane skeleton. In the general formula, R may be an alkyl group having 1 to 5 carbon atoms, and at least two of these are included as methyl groups. In the general formula, X is hydrogen, a hydroxyl group, a chloride group, 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, R1R2X3SiO 1 / 2 M units (mono-terminated siloxane units) and SiO are represented by these units. 4 / 2It may contain Q units (tetra-terminated siloxane units) represented by . The weight-average molecular weight may be 2000 to 8000 g / mol. Applying silicon MQ resin to the adhesive layer can further improve adhesive strength, and in particular, improve initial adhesive strength.

[0166] The silicone adhesive composition may contain 5 parts by weight or more, 8 parts by weight or more, 10 parts by weight or more, or 20 parts by weight or more of silicone MQ resin, based on 100 parts by weight of silicone adhesive. The silicone adhesive composition may contain 70 parts by weight or less, 60 parts by weight or less, or 50 parts by weight or less of silicone MQ resin, based on 100 parts by weight of silicone adhesive. When the silicone adhesive and the silicone MQ resin are applied together in such ratios, the adhesive layer can have excellent adhesive strength even at a very thin thickness.

[0167] Examples of silicon MQ resins that may be used include Shin-Etsu Chemical's X-92-128 and X-41-3003; and Momentive Performance Materials' SilGrip SR545 and SilGrip SR1000.

[0168] A platinum catalyst may be used as the catalyst. For example, a product such as Shin-Etsu Chemical's CATPL-50T may be used. By shortening the curing time, the catalyst can efficiently form an adhesive layer without substantially damaging the substrate, even when a transparent film or substrate with relatively heat-sensitive properties is applied.

[0169] The silicone adhesive composition may contain 0.5 to 2 parts by weight, or 0.8 to 1.5 parts by weight, of catalyst based on 100 parts by weight of silicone adhesive. In such cases, the catalyst can effectively promote the curing reaction within the composition.

[0170] The silicone adhesive composition may further contain a solvent. The solvent can dilute the silicone adhesive composition and impart fluidity to the composition, thereby improving workability, such as for coating. It also helps to form a relatively thin adhesive layer with good overall physical properties. Toluene may be used as an example of the solvent, but it is not limited to any solvent that does not impair the physical properties of the silicone adhesive composition.

[0171] For example, the silicone adhesive composition may contain 20-45% by weight of silicone adhesive, 2-25% by weight of silicone MQ resin, 0.2-0.5% by weight of catalyst, and 50-70% by weight of solvent.

[0172] A silicone adhesive composition can be applied onto an elastic layer 10 to form a silicone-based curable adhesive layer 20. The silicone adhesive composition may be applied to one surface of a separate substrate film (not shown) and then laminated onto the elastic layer 10. However, depending on the order of the process, drying and curing may be performed immediately after application or in a separate process. The silicone adhesive composition may be coated to form a thin layer, and this layer may be included in the adhesive layer before it dries and is completely cured by heat or light. This dried layer of the silicone adhesive composition before curing is referred to as the precursor layer of the silicone-based curable adhesive layer.

[0173] The precursor layer can be cured by heat or light to form the adhesive layer 20. For example, the surface to be bonded to the precursor layer can be placed in direct contact with the surface to be bonded, and the adhesive layer 20 can be formed by heat curing at 90 to 130°C for 1 to 5 minutes.

[0174] The adhesive layer 20 may contain repeating units derived from silicone adhesive and repeating units derived from silicone MQ resin. Based on 100 parts by weight of repeating units derived from silicone adhesive, the adhesive layer 20 may contain 5 parts by weight or more, 8 parts by weight or more, 10 parts by weight or more, 20 parts by weight or more, 30 parts by weight or more, or 40 parts by weight or more of repeating units derived from silicone MQ resin. Based on 100 parts by weight of repeating units derived from silicone adhesive, the adhesive layer 20 may contain 90 parts by weight or less, 80 parts by weight or less, 70 parts by weight or less, or 60 parts by weight or less of repeating units derived from silicone MQ resin. In such cases, the adhesive layer can have a thin thickness while still obtaining excellent optical properties and adhesive strength.

[0175] The adhesive layer 20 may contain 0.1 parts by weight or more, 0.2 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more of catalyst per 100 parts by weight of repeating units derived from silicone adhesive and repeating units derived from silicone MQ resin. The adhesive layer 20 may contain 5 parts by weight or less, 4 parts by weight or less, 3 parts by weight or less, or 2 parts by weight or less of catalyst per 100 parts by weight of repeating units derived from silicone adhesive and repeating units derived from silicone MQ resin. In such cases, the efficiency of the curing process for the precursor layer can be effectively improved.

[0176] The thickness of the adhesive layer 20 may be greater than 1 μm. The thickness may be 1.5 μm or more. The thickness may be 1.8 μm or more. The thickness may be 2 μm or more. The thickness may be 2.5 μm or more. The thickness may be 3 μm or more. The thickness may be 3.5 μm or more. The thickness may be 20 μm or less. The thickness may be 10 μm or less. The thickness may be 8 μm or less. The thickness may be 7 μm or less. In such cases, an excellent adhesive effect can be obtained.

[0177] Other layers transparent layer The transparent layer 30 can be used as a base layer for the coating layer 40.

[0178] The transparent layer 30 may have a total light transmittance (light transmittance) of 85% or more in accordance with ISO 13468. The light transmittance may be 88% or more, or 89% or more, and 99% or less. However, the light transmittance is not limited to this, as long as it is within an acceptable range for use as a support layer for the cover film of the display.

[0179] The haze of the transparent layer 30 may be 3% or less. The haze may also be 2% or less, 1.5% or less, or 1% or less. The haze may also be greater than 0%. In such cases, the multilayer sheet can be made more transparent.

[0180] The yellowness index (YI) of the transparent layer 30 may be 3 or less. For example, the transmitted yellowness index may 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. The transmitted yellowness index may also be greater than 0.

[0181] The transparent layer 30 can have excellent retardation characteristics. The in-plane retardation of the transparent layer 30 may be 600 nm or less, 500 nm or less, 400 nm or less, 300 nm or less, or 200 nm or less. The in-plane retardation of the transparent layer 30 may be 0 nm or more, 10 nm or more, 30 nm or more, or 50 nm or more. In such cases, when the multilayer sheet is applied to the front of the display, the possibility of unevenness due to the viewing angle can be effectively reduced, and the transparent layer can have stable mechanical properties.

[0182] The transparent layer 30 may have a minimum in-plane phase difference of 200 nm or less or 150 nm or less. Specifically, the minimum in-plane phase difference may be 120 nm or less, 100 nm or less, 85 nm or less, 75 nm or less, or 65 nm or less.

[0183] The transparent layer 30 may have a phase difference in the thickness direction of 4,000 nm or more, 5,000 nm or more, or 5,500 nm or more. The transparent layer 30 may have a maximum phase difference in the thickness direction (Rthmax) of 6,000 nm or more, 6,500 nm or more, 7,500 nm or more, 8,000 nm or more, or 8,500 nm or more.

[0184] The transparent layer 30 may have a ratio of the phase difference in the thickness direction to the in-plane phase difference of 10 or more, 15 or more, or 20 or more. Since a smaller in-plane phase difference and a larger phase difference in the thickness direction are advantageous in preventing the occurrence of unevenness, it is desirable to maintain a large ratio between the two values.

[0185] The transparent layer 30 may have a ratio of the phase difference in the maximum thickness direction to the minimum in-plane phase difference of 30 or more, 40 or more, 50 or more, or 60 or more.

[0186] The transparent layer having the above-described properties has a high degree of molecular orientation, and crystallization is promoted, allowing it to possess mechanical properties above an appropriate level. Furthermore, the transparent layer can effectively suppress the possibility of the occurrence of variegation.

[0187] The aforementioned phase difference is based on values ​​measured from a transparent layer with a thickness of 40 μm to 50 μm.

[0188] The transparent layer 30 has a tensile strength of 15 kgf / mm². 2 The above may be true. 2 Above 20 kgf / mm 2 Above, 21kgf / mm 2 or more, or 22 kgf / mm² 2 That's fine too.

[0189] The transparent layer 30 may have an elongation of 15% or more. The elongation may also be 16% or more, 17% or more, or 17.5% or more.

[0190] The modulus of the transparent layer 30 may be 2.5 GPa or higher. The modulus may also be 3 GPa or higher, 3.5 GPa or higher, 3.8 GPa or higher, or 4.0 GPa or higher. The modulus may also be 10 GPa or lower, or 8 GPa or lower.

[0191] The compressive strength of the transparent layer 30 may be 0.4 kgf / μm or more. The compressive strength may also be 0.45 kgf / μm or more, or 0.46 kgf / μm or more.

[0192] A polyester film, polyimide film, polyamide film, or polyimidoamide film may be used as the transparent layer 30.

[0193] The transparent layer 30 may be a polyester film. The polyester film may contain a polyester resin.

[0194] The polyester resin may be a monopolymer resin or copolymer resin obtained by polycondensation of a dicarboxylic acid and a diol. The polyester resin may also be a blended resin obtained by mixing the monopolymer resin or copolymer resin.

[0195] Examples of dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfoncarboxylic acid, anthracenedicarboxylic 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-methyladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, sebacic acid, suberic acid, and dodecanedicarboxylic acid.

[0196] Examples of diols include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, decamethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis(4-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone.

[0197] Preferably, the polyester resin may be an aromatic polyester resin with excellent crystallinity, for example, polyethylene terephthalate (PET) resin can be the main component.

[0198] If the transparent layer 30 is a polyester film, the transparent layer 30 may contain 85% or more by weight, 90% or more by weight, 95% or more by weight, or 99% or more by weight of polyester resin.

[0199] The polyester film may further contain other polyester resins in addition to PET resin. Specifically, the polyester film may further contain polyethylene naphthalate (PEN) resin in an amount of approximately 15% by weight or less. More specifically, the polyester film may further contain PEN resin in an amount of approximately 0.1% to 10% by weight, or approximately 0.1% to 5% by weight.

[0200] Polyester films having such a composition can increase their degree of crystallinity during the manufacturing process, including heating and stretching, which can improve their mechanical properties such as tensile strength.

[0201] The transparent layer 30 may further contain fillers in addition to the polyester resin.

[0202] The filler may be one or more selected from the group consisting of barium sulfate, silica, and calcium carbonate. By including the filler, the transparent layer 30 has controlled roughness characteristics and can improve winding performance. It can also improve the running performance and scratch resistance during film production.

[0203] The particle size of the filler may be 0.01 μm or more and less than 1.0 μm. The particle size of the filler may be 0.05 μm to 0.9 μm, or 0.1 μm to 0.8 μm, but is not limited to these.

[0204] The filler may be present in an amount of 0.01 to 3% by weight based on the total weight of the transparent layer 30. The filler may also be present in an amount of 0.05 to 2.5% by weight, 0.1 to 2% by weight, or 0.2 to 1.7% by weight based on the total weight of the transparent layer 30, but is not limited to these amounts.

[0205] The thickness of the transparent layer 30 may 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, or 75 μm or more, and may also be 500 μm or less, 400 μm or less, 300 μm or less, 200 μm or less, 120 μm or less, 95 μm or less, or 85 μm or less. Specifically, the thickness of the transparent layer 30 may be 15 μm to 120 μm, and more specifically, 20 μm to 95 μm, or 25 μm to 85 μm. A transparent layer having such a thickness can obtain excellent optical properties along with sufficient mechanical properties.

[0206] As the transparent layer 30, products such as SKC's commercially available SH33 / 34, SH37 / 38, TF110, V7610, V5400, V7611, TU94, TU63A, and TOF50 can be used, but are not limited to these.

[0207] The method for producing the transparent layer follows the usual method for producing films. For example, a polyester film may be produced by a method comprising: (1) extruding a composition containing a polyester resin to obtain an unstretched film; (2) stretching the unstretched film in the longitudinal and width directions; and (3) heat-setting the stretched film.

[0208] In the above manufacturing method, the unstretched film is produced by extruding the raw resin, followed by preheating, stretching, and heat setting. Extrusion may be carried out at temperatures of 230°C to 300°C, or 250°C to 280°C.

[0209] The unstretched film is preheated to a certain temperature before stretching. The preheating temperature range can be determined to satisfy the range of Tg+5°C to Tg+50°C, based on the glass transition temperature (Tg) of the polyester resin, and simultaneously satisfy the range of 70°C to 90°C. When the temperature is within this range, the unstretched film can be made flexible enough to be easily stretched, while at the same time effectively preventing breakage during stretching.

[0210] Stretching is carried out by biaxial stretching, and may be performed in two axes, the width direction (tenter direction, TD) and the longitudinal direction (machine direction, MD), for example, through simultaneous biaxial stretching or sequential biaxial stretching. Preferably, sequential biaxial stretching may be performed, in which the material is first stretched in one direction and then stretched in a direction perpendicular to that direction.

[0211] The elongation ratio in the longitudinal direction may be 2.0 to 5.0 times, more specifically 2.8 to 3.5 times. The elongation ratio in the width direction may be 2.0 to 5.0 times, more specifically 2.9 to 3.7 times. Preferably, the elongation ratio in the longitudinal direction (d1) and the elongation ratio in the width direction (d2) are approximately the same, and specifically, the ratio of the elongation ratio in the longitudinal direction (d2) to the elongation ratio in the width direction (d1) (d2 / d1) may be 0.5 to 1.0, 0.7 to 1.0, or 0.9 to 1.0. The elongation ratios (d1, d2) represent the length after elongation, with the length before elongation being 1.0. The elongation speed may be 6.5 m / min to 8.5 m / min, but is not particularly limited.

[0212] 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 carried out for 5 seconds to 1 minute, more specifically at 10 seconds to 45 seconds.

[0213] After heat setting is initiated, the film may relax in the longitudinal and / or widthwise directions, and the temperature range at this time may be 150°C to 250°C.

[0214] coating layer The coating layer 40 may contain at least one coating material selected from organic components, inorganic components, and organic-inorganic composite components.

[0215] The coating material may include an organic resin. Specifically, the organic resin may be a curable resin or a binder resin.

[0216] The coating layer 40 may be a curable coating layer.

[0217] The coating layer 40 may contain at least one compound from among urethane acrylate compounds, acrylic ester compounds, acrylate compounds, and epoxy acrylate compounds, or a cured product of said compound.

[0218] Urethane acrylate compounds contain urethane bonds as repeating units and can have multiple functional groups.

[0219] The urethane acrylate compound may be a urethane compound formed by the reaction of a diisocyanate compound and a polyol, in which the terminal ends of the compound are substituted with acrylate groups.

[0220] The diisocyanate compound may include at least one of a linear, branched, or cyclic aliphatic diisocyanate compound having 4 to 12 carbon atoms, and an aromatic diisocyanate compound having 6 to 20 carbon atoms.

[0221] The polyol may be a linear, branched, or cyclic aliphatic polyol compound containing 2 to 4 hydroxyl groups (-OH) and having 4 to 12 carbon atoms, or an aromatic polyol compound having 6 to 20 carbon atoms. The terminal substitution with the acrylate group can be carried out by an acrylate compound having a functional group that can react with an isocyanate group (-NCO). For example, an acrylate compound having a hydroxyl group, an amine group, etc., may be used, or a hydroxyalkyl acrylate or aminoalkyl acrylate having 2 to 10 carbon atoms may be used.

[0222] Urethane acrylate compounds can contain 2 to 15 functional groups.

[0223] Examples of urethane acrylate compounds include, but are not limited to, difunctional urethane acrylate oligomers with a weight-average molecular weight of 1400 to 25000, trifunctional urethane acrylate oligomers with a weight-average molecular weight of 1700 to 16000, tetrafunctional urethane acrylate oligomers with a weight-average molecular weight of 500 to 2000, hexafunctional urethane acrylate oligomers with a weight-average molecular weight of 818 to 2600, nnahfunctional urethane acrylate oligomers with a weight-average molecular weight of 2500 to 5500, decahfunctional urethane acrylate oligomers with a weight-average molecular weight of 3200 to 3900, and decahtofunctional urethane acrylate oligomers with a weight-average molecular weight of 2300 to 20000.

[0224] The glass transition temperature (Tg) of urethane acrylate compounds may be -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.

[0225] The acrylic ester compound may be one or more selected from the group consisting of substituted or unsubstituted acrylates and substituted or unsubstituted methacrylates. The acrylic ester compound may contain 1 to 10 functional groups.

[0226] Examples of acrylic ester compounds include, but are not limited to, trimethylolpropane triacrylate (TMPTA), trimethylolpropane ethoxytriacrylate (TMPEOTA), glycerol propoxylated triacrylate (GPTA), pentaerythritol tetraacrylate (PETA), and dipentaerythritol hexaacrylate (DPHA).

[0227] The weight-average molecular weight of the acrylic ester compound may be 500-6,000, 500-5,000, 500-4,000, 1,000-6,000, 1,000-5,000, 1,000-4,000, 1,500-6,000, 1,500-5,000, or 1,500-4,000.

[0228] The acrylate equivalent of the acrylic ester compound may be 50 g / eq to 300 g / eq, 50 g / eq to 200 g / eq, or 50 g / eq to 150 g / eq.

[0229] Acrylate compounds can contain 1 to 10 functional groups. Examples of such acrylate compounds 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.

[0230] The epoxy acrylate compound may contain 1 to 10 functional groups. Examples of the epoxy acrylate compound include, but are not limited to, a monofunctional epoxy acrylate oligomer with a weight-average molecular weight of 100 to 300, a bifunctional epoxy acrylate oligomer with a weight-average molecular weight of 250 to 2000, or a tetrafunctional epoxy acrylate oligomer with a weight-average molecular weight of 1000 to 3000. The epoxy equivalent of the epoxy acrylate compound may be 50 g / eq to 300 g / eq, 50 g / eq to 200 g / eq, or 50 g / eq to 150 g / eq.

[0231] The content of the organic resin may be 30% to 100% by weight, 40% to 90% by weight, or 50% to 80% by weight, based on the total weight of the coating layer 40.

[0232] The coating layer 40 does not need to contain inorganic fillers such as silica. In this case, the bonding strength between the transparent film layer and the coating layer 40 having the above-described composition can be improved.

[0233] The coating layer 40 may selectively further contain fillers.

[0234] The filler may be, for example, inorganic particles. Examples of the filler include silica, barium sulfate, zinc oxide, or alumina.

[0235] The particle size of the filler may be 1 nm to 100 nm. The particle size of the filler may also be 5 nm to 50 nm, or 10 nm to 30 nm.

[0236] The filler may include inorganic fillers having different particle size distributions. 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.

[0237] The filler content may be 25% by weight or more, 30% by weight or more, or 35% by weight or more, based on the total weight of the coating layer 40. Alternatively, the filler content may be 50% by weight or less, 45% by weight or less, or 40% by weight or less, based on the total weight of the coating layer 40.

[0238] In such cases, the mechanical properties of the filler can be improved.

[0239] The coating layer 40 may further contain a photoinitiator or a reactant thereof. The photoinitiator, etc., can initiate the curing reaction of the coating layer 40.

[0240] Examples of photoinitiators include, but are not limited to, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, methylbenzoyl 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, or bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. Other commercially available products include Irgacure 184, Irgacure 500, Irgacure 651, Irgacure 369, Irgacure 907, Darocur 1173, Darocur MBF, Irgacure 819, Darocur TPO, Irgacure 907, and Esacure KIP 100F. The photoinitiators may be used individually or in mixtures of two or more different types.

[0241] The coating layer 40 may further contain an antifouling agent. The coating layer 40 may contain a fluoro compound as an antifouling agent. The fluoro compound can perform an antifouling function. Specifically, the fluoro compound may be an acrylate compound having a perfluoroalkyl group, and a specific example is perfluorohexylethyl acrylate, but is not limited thereto.

[0242] The coating layer 40 may further contain an antistatic agent. The antistatic agent may include an ionic surfactant. For example, the ionic surfactant may include an ammonium salt or a quaternary alkylammonium salt, and the ammonium salt and quaternary alkylammonium salt may include halides such as chlorides and bromides.

[0243] The coating layer 40 may further contain additives such as surfactants, UV absorbers, UV stabilizers, anti-yellowing agents, leveling agents, or dyes for improving hue values. For example, the surfactant may be a 1-2 functional fluorinated acrylate, a fluorinated surfactant, or a silicone surfactant. The surfactant may be contained in a form dispersed or crosslinked within the coating layer 40. Examples of UV absorbers include benzophenone compounds, benzotriazole compounds, or triazine compounds, and examples of UV stabilizers include tetramethyl piperidine. The content of these additives can be varied within a range that does not degrade the physical properties of the coating layer 40. For example, the content of the additives may be 0.01 to 10% by weight based on the entire coating layer 40, but is not limited thereto.

[0244] The coating layer 40 may consist of a single layer or two or more layers.

[0245] The coating layer 40, formed as a single layer, increases the surface durability of the multilayer sheet while simultaneously providing fingerprint-resistant or anti-fouling functionality.

[0246] The thickness of the coating layer 40 may be 2 μm or more, 3 μm or more, 5 μm or more, or 7 μm or more, and may also be 50 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. With such thicknesses, even when applied at a thin thickness, it is possible to impart durability such as surface hardness to the multilayer sheet at an appropriate level or higher, while also maintaining the overall flexibility of the multilayer sheet.

[0247] The coating layer 40 can be formed by a method for manufacturing the coating layer.

[0248] A method for manufacturing a coating layer may include the step of coating with a coating layer manufacturing composition and then curing it.

[0249] The composition for manufacturing the coating layer may include at least one of an organic resin composition, an inorganic resin composition, and an organic-inorganic composite composition.

[0250] The composition for manufacturing the coating layer may contain at least one of acrylate compounds, siloxane compounds, and silsesquioxane compounds. It may also further contain inorganic particles.

[0251] The composition for manufacturing the coating layer may, as specific examples, include urethane acrylate compounds, acrylic ester compounds, and fluoro compounds.

[0252] Furthermore, the composition for manufacturing the coating layer may further contain, as necessary, a photoinitiator, an antifouling additive, an antistatic agent, other additives, and / or an organic solvent.

[0253] Organic solvents that can be used include alcoholic solvents such as methanol, ethanol, isopropyl alcohol, and butanol; alkoxy alcoholic solvents such as 2-methoxyethanol, 2-ethoxyethanol, and 1-methoxy-2-propanol; ketoneic solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, and cyclohexanone; etheric 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 glycol monoethyl ether, diethyl glycol monopropyl ether, diethyl glycol monobutyl ether, and diethylene glycol-2-ethylhexyl ether; and aromatic solvents such as benzene, toluene, and xylene; which can be used alone or in combination.

[0254] The content of the organic solvent is not particularly limited, as it can be adjusted in various ways within a range that does not degrade the physical properties of the coating layer. However, it may be included such that the weight ratio of solids to organic solvent is approximately 1:1 to 250, based on the solids content of the components contained in the coating layer manufacturing composition. When the organic solvent is within this range, it can have appropriate fluidity and coatability.

[0255] The aforementioned coating layer manufacturing composition 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 the remainder of an organic solvent.

[0256] When the above composition is followed, both the mechanical properties and the antifouling and antistatic properties of the coating layer can be improved.

[0257] The coating layer manufacturing composition can be applied to a transparent film using a conventional coating method and then cured. Applicable coating methods include bar coating, knife coating, roll coating, blade coating, die coating, microgravure coating, comma coating, slot die coating, lip coating, or solution casting.

[0258] The applied coating layer composition may undergo drying and curing steps sequentially or simultaneously.

[0259] Drying is the process of removing organic solvents from the coated coating layer manufacturing composition. Drying may be carried out at a temperature of 40°C to 100°C, preferably 40°C to 80°C, 50°C to 100°C, or 50°C to 80°C, for about 1 to 20 minutes, preferably 1 to 10 minutes, or 1 to 5 minutes.

[0260] Curing is the process of inducing a chemical reaction in the coating layer manufacturing composition to form a coating film. Depending on the resin and other components applied to the coating layer manufacturing composition, an appropriate photocuring and / or thermocuring method may be used.

[0261] Base material layer The multilayer sheet 100 may further include a substrate layer (not shown) placed on the adhesive layer 20.

[0262] The base layer may be placed on the adhesive layer 20 in contact with it. If another layer is placed between the base layer and the adhesive layer 20, the base layer may be placed on the adhesive layer 20 without contacting it.

[0263] The material of the substrate layer is not limited as long as it is a resin that can be commonly used in the field of substrate films. For example, the substrate layer may include at least one of polyester resin, polyimide resin, and polyether block amide resin. In particular, one of polyester film, polyimide film, and polyether block amide film can be used as the substrate layer. The polyester film may be a polyethylene terephthalate (PET) film.

[0264] The multilayer sheet 100 may contain two or more base material layers. In such cases, the multilayer sheet 100 may have a structure in which base material layers and adhesive layers 20 are alternately laminated.

[0265] Manufacturing method for multilayer sheets A method for manufacturing a multilayer sheet according to yet another embodiment of this specification may include the steps of providing an elastic layer and laminating an adhesive layer on the elastic layer.

[0266] The step of laminating an adhesive layer on an elastic layer may include a step of applying and drying a silicone adhesive composition on the elastic layer to form a precursor layer. The step of laminating an adhesive layer on an elastic layer may further include a step of curing the precursor layer to form the adhesive layer.

[0267] When the multilayer sheet includes two or more adhesive layers and has a structure in which elastic layers and adhesive layers are alternately laminated, the method for manufacturing the multilayer sheet may further include a step of laminating an elastic layer previously provided on the adhesive layer.

[0268] The method for manufacturing the multilayer sheet may further include, if necessary, a step of disposing a transparent layer on the adhesive layer, and may further include a step of forming a coating layer on the transparent layer.

[0269] The method for manufacturing the multilayer sheet may further include, if necessary, a step of disposing a release film on the adhesive layer.

[0270] The description of the method for forming each layer is omitted because it overlaps with the foregoing content.

[0271] multilayer electronic device FIG. 5 is a conceptual diagram for explaining a multilayer electronic device according to still another embodiment of the present specification. An embodiment will be described with reference to FIG. 5.

[0272] A multilayer electronic device 200 according to still another embodiment of the present specification includes a multilayer sheet 100 and a light-emitting functional layer 150 disposed under the multilayer sheet  100.

[0273] The multilayer sheet 100 can be applied as a cover layer of the multilayer electronic device 200.

[0274] The description of the multilayer sheet 100 is omitted because it overlaps with the foregoing content.

[0275] The multilayer electronic device 200 may be, exemplary, a display device, and may be, exemplary, a large-area display device, a foldable display device, a bendable display device, or a flexible display device. It may also be a bendable mobile communication device (e.g., a mobile phone) or a bendable notebook computer.

[0276] The light-emitting functional layer 150 includes a light-emitting layer (not shown).

[0277] The light-emitting layer includes elements that emit light in response to a signal in a display device. The light-emitting layer may, for example, include a signal transmission layer that transmits an external electrical signal to a color-generating layer, a color-generating layer disposed on the signal transmission layer and color-generating in response to the given signal, and a sealing layer that protects the color-generating layer. The signal transmission layer may include thin-film transistors (TFTs), and may, but is not limited to, LTPS, a-SiTFTs, or oxide TFTs. The sealing layer may, but is not limited to, TFE (Thin Film Encapsulation).

[0278] The light-emitting layer may be placed on a support layer (not shown). The support layer may be a layer having insulating and heat-resistant properties, and examples may include a polyimide film, a glass layer, a PET film, and the like.

[0279] The light-emitting functional layer 150 may further include a sensor layer (not shown). A touch sensor or the like may be applied as the sensor layer.

[0280] The light-emitting functional layer 150 may further include a polarizing layer (not shown). The polarizing layer may be placed on the light-emitting layer or on the sensor layer.

[0281] The following provides a more detailed explanation of specific examples.

[0282] Manufacturing example: Manufacturing of multilayer sheets Examples: Elastic layers were manufactured using Arkema's PEBA resin products in each example. Specifically, the PEBA resin was placed in an extruder, melt-kneaded at approximately 220°C, and then extruded as a single layer to produce the elastic layer. The product names of the PEBA resins used in the manufacture of the elastic layer in each example and the thickness of the elastic layer are listed in Table 1 below.

[0283] An adhesive layer was formed on one and the other surface of the manufactured elastic layer. Specifically, a silicone-based adhesive composition was applied to one and the other surface of the elastic layer, and then dried and cured to form the adhesive layer. Drying and curing were carried out at a temperature of 90°C for 5 minutes.

[0284] The silicone-based adhesive composition used was one containing 29.851% by weight of Shin-Etsu's KR-3700 model as a silicone adhesive, 7.164% by weight of Shin-Etsu's X-92-128 model as a silicone MQ resin, 0.299% by weight of Shin-Etsu's CAT-PL-50T model as a platinum catalyst, and 62.686% by weight of toluene.

[0285] The thickness of the adhesive layer formed on one and the other surface of the elastic layer was applied identically to each other. The thickness of the adhesive layer applied in each example is shown in Table 1 and Figures 6 to 11 below.

[0286] Comparative Example 1: The silicone-based adhesive composition applied in the example was dried and cured to form an adhesive layer with a thickness of 10 μm.

[0287] Evaluation example: Measurement of storage modulus value with respect to temperature The modulus was measured for each example and comparative example via Dynamic Mechanical Analysis (DMA). Specifically, the storage modulus of samples from each example and comparative example was measured using a Hitachi DMA7100 model in the range of -50°C to 100°C. A heating rate of 5°C / min was applied.

[0288] The measurement results for each measurement temperature for the examples and comparative examples are shown in Tables 1 and 2 and Figures 6 to 12 below.

[0289] Evaluation Example: Measurement of RSM Value by Temperature SM by Temperature of Elastic Layer and Adhesive Layer Applied to Multilayer Sheets of Examples 2, 8, 14, 20, 26 and 32 E Value and SM B The values of SM and SM were measured through the DMA7100 model of HITACHI. The measurement temperature range was set from -50°C to 100°C, and the heating rate was applied at 5°C / min. The SM E Value and SM B values were measured, and the RSM value was calculated from the said values.

[0290] SM by Measurement Temperature for Each Example E Value, SM B Value and RSM value are described in Table 3 and Table 4 below.

[0291] Evaluation Example: Measurement of Adhesive Strength by Thickness of Adhesive Layer The silicon adhesive composition applied to the said examples was die-coated on a PET film (NRF grade manufactured by SKC) for each production example, and then dried and cured to obtain an adhesive layer. Drying and curing were performed at a temperature of 90°C for 5 minutes. The thickness of the adhesive layer applied for each production example is described in Table 3 below.

[0292] Thereafter, the adhesive strength of the adhesive layer formed for each production example was measured. The adhesive strength was measured in T-Peel format using the QC-M1F UTM model of COMETECH, and the peeling rate was applied at 300 mm / min.

[0293] The values of the adhesive strength measured for each production example are shown in Table 5 below.

[0294] [Table 1]

[0295] [Table 2]

[0296] [Table 3]

[0297] [Table 4]

[0298] [Table 5]

[0299] Although preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto. Various modifications and improvements by those skilled in the art, utilizing the basic concepts of the embodiments defined in the appended claims, also fall within the scope of the present invention. [Explanation of Symbols]

[0300] 100 multilayer sheets 10 Elastic layer 20 Adhesive layer 30 transparent layer 40 Coating layer 50 Release film 51 Release layer 52 Release base material layer 150 Light-emitting functional layer 200 Multilayer electronic devices

Claims

1. The elastic layer and the adhesive layer placed on the elastic layer are included. The storage modulus of the elastic layer measured at 20°C is 10 MPa or more and 3000 MPa or less. The RSM value calculated using the following formula 1 at 20°C is between 1 and 200. The absolute value obtained by subtracting the storage modulus value measured at 60°C from the storage modulus value measured at 20°C is 1000 MPa or less. The absolute value obtained by subtracting the storage modulus value measured at 20°C from the storage modulus value measured at -40°C is 1500 MPa or less. A multilayer sheet having a storage modulus of 10 MPa to 2000 MPa, measured at 20°C. [Formula 1] RSM=SM E / SM B (In the above formula 1, The SM E is the storage modulus value of the elastic layer, The aforementioned SM B is the storage modulus value of the adhesive layer.

2. The multilayer sheet according to claim 1, wherein the storage modulus of the adhesive layer measured at 20°C is 1 MPa or more and 50 MPa or less.

3. The multilayer sheet according to claim 1, wherein the adhesive strength of the adhesive layer after curing is 2 N / inch or more.

4. The multilayer sheet according to claim 1, wherein the adhesive strength per unit thickness (1 μm) of the adhesive layer after curing is 0.8 N / inch or more.

5. A multilayer sheet according to claim 1, A multilayer electronic device comprising a light-emitting functional layer disposed beneath the multilayer sheet.

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