Multilayer sheet and multilayer electronic device

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 TO RELATED APPLICATIONS This application claims priority to Korean Patent Application No. 10-2022-0091016, filed on July 22, 2022, the contents of which are incorporated herein by reference in their entirety.

[0002] Embodiments relate to a multi-layer sheet applicable for protecting displays and the like, and a multi-layer electronic device including the same. [Background technology]

[0003] Surface protection sheets are being used in a variety of applications as mobile devices such as mobile phones, smartphones, and tablets, and information processing terminals such as ATMs and kiosks, become more diverse. Furthermore, with the emergence of various display devices, such as foldable, flexible, and rollable, surface hardness is required to prevent scratches on the surface, as well as durability sufficient to withstand repeated folding and rolling. Furthermore, when applied to display screens, optical properties are of course also required. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Korean Patent No. 10-1798759 [Patent Document 2] Korean Patent No. 10-1810422 Summary of the Invention [Problem to be solved by the invention]

[0005] The purpose of the embodiment is to provide a multilayer sheet that is resistant to peeling from the surface of the object to which it is attached, does not cause interlayer separation, and is resistant to external impacts despite repeated bending and rolling over a wide temperature range. [Means for solving the problem]

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

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

[0008] The multilayer sheet may have an RSM value of 1 or more and 200 or less, measured at 20° C. and calculated using the following formula 1:

[0009] [Formula 1] RSM=SM E / SM B

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

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

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

[0013] The multilayer sheet may have an absolute value of the difference between the storage modulus measured at -40°C and the storage modulus measured at 20°C of 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 adhesive layer may have a storage modulus measured at 20° C. of 1 MPa or more and 50 MPa or less.

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

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

[0018] A multi-layer electronic device according to another embodiment of the present disclosure includes the multi-layer sheet and a light-emitting functional layer disposed below the multi-layer sheet. [Effects of the Invention]

[0019] The multilayer sheet of the embodiment is characterized by being resistant to peeling from the surface of the object to which it is attached, preventing separation between layers despite repeated bending and rolling over a wide temperature range, and being resistant to external impacts. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a conceptual diagram illustrating a multilayer sheet according to an example of the present specification. [Figure 2] FIG. 2 is a conceptual diagram illustrating a multilayer sheet according to another example of the present specification. [Figure 3] FIG. 10 is a conceptual diagram illustrating a multilayer sheet according to yet another example of the present specification. [Figure 4] FIG. 10 is a conceptual diagram illustrating a multilayer sheet according to yet another example of the present specification. [Figure 5] FIG. 10 is a conceptual diagram illustrating a multilayer electronic device according to yet another embodiment of the present specification. [Figure 6] 1 is a graph showing measured values of storage modulus according to temperature for Examples and Comparative Examples. [Figure 7] 1 is a graph showing measured values of storage modulus according to temperature for Examples and Comparative Examples. [Figure 8] 1 is a graph showing measured values of storage modulus according to temperature for Examples and Comparative Examples. [Figure 9] 1 is a graph showing measured values of storage modulus according to temperature for Examples and Comparative Examples. [Figure 10] 1 is a graph showing measured values of storage modulus according to temperature for Examples and Comparative Examples. [Figure 11] 1 is a graph showing measured values of storage modulus according to temperature for Examples and Comparative Examples. [Figure 12] 1 is a graph showing measured values of storage modulus according to temperature for Examples and Comparative Examples. BEST MODE FOR CARRYING OUT THE INVENTION

[0021] Although the present invention will be described in detail below so that those skilled in the art can easily implement the present invention, it should be understood that the present invention may be embodied in many different forms and is not limited to the embodiments set forth herein.

[0022] As used herein, terms of degree such as "about," "substantially," etc., when given the tolerances of manufacturing and materials inherent in the referred meaning, are used in the sense of a numerical value or close to that numerical value, and are used to prevent unscrupulous infringers from unfairly exploiting disclosures in which precise or absolute numerical values are mentioned to aid in the understanding of embodiments.

[0023] Throughout this specification, the term "combinations thereof" contained in a Markush form phrase means a mixture or combination of one or more selected from the group of elements set forth in the Markush form phrase, and means including one or more selected from the group of elements.

[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 identical terms from one another unless otherwise specified.

[0026] In this specification, the term "B is located on A" means that B can be located on A or B can be located on A with another layer located therebetween, and is not to be interpreted as being limited to B being located in contact with the surface of A.

[0027] In this specification, unless otherwise specified, the singular expression is to be construed as including the singular or plural as the context requires.

[0028] The resins described herein are understood to include the resin itself and compounds derived from the resin. Illustratively, the polyester resins described herein refer to polyester resins and polyester resin derivatives.

[0029] In this specification, when 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 included in the multilayer sheet is a curable adhesive layer, the storage modulus value of the multilayer sheet corresponds to a value measured from the multilayer sheet after curing the adhesive layer in the multilayer sheet.

[0031] The inventors of the embodiment controlled the storage modulus value of the multilayer sheet having an elastic layer and an adhesive layer, and 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 if the object is repeatedly bent or rolled, and can stably protect the object, thereby completing the embodiment.

[0032] The specific examples will be described below.

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

[0034] The multilayer sheet 100 of 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 measured at 20°C of 10 MPa or more and 2000 MPa or less.

[0036] In the embodiment, the storage modulus of the multilayer sheet 100 at each measurement temperature may be controlled within a preset range. In this case, the difference in modulus between the multilayer sheet 100 and a flexible display having a relatively high storage modulus value may be reduced. This effectively prevents the multilayer sheet 100 attached to the display from peeling off from the display surface due to repeated bending. In addition, the display may be stably protected from external impact.

[0037] The storage modulus of the multilayer sheet 100 at each measurement temperature is measured in accordance with ASTM D 4065. Specifically, the storage modulus of the multilayer sheet 100 at each measurement temperature is measured using a viscoelasticity measuring device at a temperature range of -50°C to 100°C at a heating rate of 5°C / min.

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

[0039] The multilayer sheet 100 may have a storage modulus measured at 20°C of 10 MPa or more and 2000 MPa or less. 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 attached to a flexible display, such a multilayer sheet may be stably attached to the display surface despite repeated bending of the display.

[0040] The multilayer sheet 100 may have a storage modulus measured at 0°C of 20 MPa or more and 2500 MPa or less. 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 measured at -20°C of 30 MPa or more and 3000 MPa or less. 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 measured at -40°C of 50 MPa or more and 4000 MPa or less. 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 measured at 40°C of 5 MPa or more and 2000 MPa or less. 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 measured at 60°C of 3 MPa or more and 800 MPa or less. 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 measured at 80°C of 1 MPa or more and 500 MPa or less. 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 a case, the multilayer sheet can be stably attached to the flexible display over a wide temperature range.

[0047] The absolute value of the difference between the storage modulus value of the multilayer sheet 100 measured at 20°C and the storage modulus value of the multilayer sheet 100 measured at 40°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 of the difference between the storage modulus value of the multilayer sheet 100 measured at 20°C and the storage modulus value of the multilayer sheet 100 measured at 60°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 of the storage modulus value of the multilayer sheet 100 measured at 20°C minus the storage modulus value of the multilayer sheet 100 measured at 80°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 a case, the occurrence of the lifting phenomenon of the multilayer sheet due to a temperature rise can be effectively suppressed.

[0051] The absolute value of the storage modulus value of the multilayer sheet 100 measured at 0°C minus the storage modulus value of the multilayer sheet 100 measured at 20°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 of the difference between the storage modulus value of the multilayer sheet 100 measured at -20°C and 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 of the storage modulus value of the multilayer sheet 100 measured at -40°C minus the storage modulus value of the multilayer sheet 100 measured at 20°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 a case, the bending characteristics of the multilayer sheet are reduced as the temperature is lowered, and peeling of the multilayer sheet from the display can be effectively prevented.

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

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

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

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

[0059] In some embodiments, the RSM value of the multilayer sheet 100 can be controlled within a predetermined range, thereby adjusting the difference in mechanical properties between layers within the multilayer sheet 100, thereby effectively suppressing not only peeling of the multilayer sheet from the surface of the attachment target, but also delamination within the multilayer sheet.

[0060] The description of the method for measuring the storage modulus of the elastic layer 10 and the adhesive layer 20 is omitted because it is the same as that 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 a case, peeling of the adhesive layer due to a difference in modulus between the adhesive layer and the elastic layer, or between the adhesive layer and the display, can be effectively prevented.

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

[0068] In the embodiment, the adhesive strength of the multilayer sheet 100 can be controlled. Such a multilayer sheet 100 can exhibit stable adhesive strength even when applied to a display that is repeatedly bent or rolled.

[0069] The adhesive strength of the multilayer sheet 100 is measured after curing the adhesive layer 20. The adhesive strength of the multilayer sheet 100 is measured by a 180° peel test using an advanced force gauge, with a peel speed of 300 mm / min and a glass plate as the adherend.

[0070] For example, the Advanced Force Gauge may be an AFG50 model manufactured by Mecmesin, and the adherend may be an NA32G model manufactured by 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 adhesiveness 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 stably protect an object to be protected, such as a display, from external impact.

[0073] 2 is a conceptual diagram illustrating a multilayer sheet according to another embodiment of the present specification. An embodiment will be described in more detail with reference to FIG.

[0074] The multilayer sheet 100 can include an adhesive layer 20 disposed on the elastic layer 10 and an adhesive layer 20 disposed 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 disposed as the outermost layer on the one side and another side. A multilayer sheet having such a structure is suitable for use as an adhesive film for a display.

[0076] 3 is a conceptual diagram illustrating a multilayer sheet according to yet another embodiment of the present specification. An embodiment will be described in more detail with reference to FIG.

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

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

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

[0080] The transparent layer 30 may serve 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 may be the outermost surface exposed to the outside.

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

[0083] 4 is a conceptual diagram illustrating a multilayer sheet according to yet another embodiment of the present specification. An embodiment will be described in more detail with reference to FIG.

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

[0085] The release film 50 may be disposed in contact with the upper surface of the adhesive layer 20. The release film 50 may be disposed 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 a base layer for the release layer 51 .

[0087] The release film 50 can include a release layer 51 disposed on the adhesive layer 20 and a release substrate layer 52 disposed on the release layer 51 .

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

[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.

[0090] Elastic layer In this embodiment, the elastic layer 10 may have a storage modulus value controlled according to the measurement temperature, thereby imparting excellent bending properties to the multilayer sheet over a wide temperature range and stably protecting the display.

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

[0092] The elastic layer 10 may have a storage modulus value measured at 20°C of 10 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 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 1200 MPa or less.

[0093] The elastic layer 10 may have a storage modulus value measured at 40°C of 10 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 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.

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

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

[0096] The elastic layer 10 may have a storage modulus value of 30 MPa or more measured at 0°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 2200 MPa or less. 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. The storage modulus value may be 800 MPa or less.

[0097] The elastic layer 10 may have a storage modulus value of 50 MPa or more measured at -20°C. 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 200 MPa or more. The storage modulus value may be 300 MPa or more. The storage modulus value may be 350 MPa or more. The storage modulus value may be 400 MPa or more. The storage modulus value may be 2400 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 1200 MPa or less. The storage modulus value may be 1000 MPa or less. The storage modulus value may be 800 MPa or less.

[0098] The elastic layer 10 may have a storage modulus value of 80 MPa or more measured at -40°C. 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 500 MPa or more. The storage modulus value may be 2600 MPa or less. The storage modulus value may be 2300 MPa or less. The storage modulus value may be 2000 MPa or less. The storage modulus value may be 1700 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. The storage modulus value may be 850 MPa or less.

[0099] In such cases, the elastic layer can be useful in enabling the multilayer sheet to have stable bending properties over a wide temperature range.

[0100] The absolute value of the difference between the storage modulus value of elastic layer 10 measured at 20°C and the storage modulus value of elastic layer 10 measured at 40°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 of the 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 of the 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 of elastic layer 10 measured at 0°C and the storage modulus value of 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 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 of elastic layer 10 measured at -20°C and the storage modulus value of 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 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 value obtained by subtracting the storage modulus value of elastic layer 10 measured at 20°C from the storage modulus value of elastic layer 10 measured at -40°C 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 this 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 has a resistance of 2,500 kJ / m 2 The impact strength can be 3,500 kJ / m or more. 2 The impact strength may be 4,500 kJ / m or more. 2 The impact strength may be 5,000 kJ / m or more. 2 The impact strength may be 10,000 kJ / m or more. 2The elastic layer having such characteristics can absorb external shocks well, but is not easily broken or damaged.

[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 absorb the impact transmitted to the object to be protected.

[0109] Impact strength and absorbed energy are 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, 88% or more, 90% or more, or 99.99% or less.

[0112] An elastic layer having such characteristics can have optical properties suitable for use as a protective layer for a display.

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

[0114] The yellowness may be measured using a Color meter ultra scanpro manufactured by Hunterlab in the YI E313 (D65 / 10) mode.

[0115] The elastic layer 10 may have a yellowness index of 2 or less after being exposed to ultraviolet light having a wavelength of 280 to 360 nm at an output of 3.0 W for 72 hours, minus the yellowness index before exposure. The elastic layer 10 may have a yellowness index of 1 or less after being exposed to ultraviolet light having a wavelength of 280 to 360 nm at an output of 3.0 W for 72 hours, minus the yellowness index before exposure. The elastic layer 10 may have a yellowness index of 0.1 or more after being exposed to ultraviolet light having a wavelength of 280 to 360 nm at an output of 3.0 W for 72 hours, minus the yellowness index before exposure. An elastic layer having these characteristics may 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 substantially free of cloudy appearance. The area where cloudy appearance is observed may be less than 1% of the total area of the elastic film. Here, the total area is based on the total area of the film applied to the product. Cloudy appearance may be objectively evaluated through haze measurement, and a haze measurement value of more than 1% may be considered to be cloudy. The degree of cloudiness may be adjusted by controlling the degree of gelation and molecular weight distribution of the resin used to manufacture the elastic layer.

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

[0118] The polyether block amide may be, for example, Pebax®, Pebax® Rnew® from ARKEMA, or VESTAMID® E from EVONIK.

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

[0120] The amide residues may be 50 wt % or more, or 60 wt % or more, based on the total polymer content of the elastic film. The amide residues may be 80 wt % or less, or 70 wt % or less, based on the total polymer content of the elastic film. When a polymer having these characteristics is used in the elastic film, an elastic film with even better mechanical properties can be provided.

[0121] The elastic layer 10 may include elastic polyamide (long chain polyamide). Exemplary elastic polyamides may be Rilsan (registered trademark), Rilsamid (registered trademark), or the like, manufactured by Arkema.

[0122] The elastic layer 10 may comprise thermoplastic polyurethane (TPU), a copolymer of polyurethane blocks (PU) and polyether blocks (PE), also called polyetherurethane.

[0123] The elastic layer 10 may include a copolyetherester (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 properties to the multilayer sheet.

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

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

[0127] The explanation of the resin will be omitted as it overlaps with the above content.

[0128] The method for forming the resin composition for elastic layer into the shape of the elastic layer can be any method that is applicable to the production of a film, and for example, a melt extrusion method may be applied.

[0129] When the resin composition for the elastic layer is melt-extruded to form an elastic sheet, the melt-extrusion temperature may be 200 to 300° C. When melt-extrusion is performed within this temperature range, the properties of the resin itself are not damaged, and fluidity is imparted to the resin composition, allowing it to be smoothly formed into a sheet.

[0130] The manufactured elastic layer can be passed through rollers to adjust the thickness of the elastic layer 10. If necessary, protective films for the elastic layer can be laminated on the top and bottom of the elastic layer to form a laminate, and then the laminate can be passed through the rollers.

[0131] adhesive layer In the embodiment, the storage modulus value of the adhesive layer 20 at each measurement temperature can be controlled to reduce the difference in modulus characteristics between the adhesive layer 20 and the elastic layer 10 in the multilayer sheet 100 over a wide temperature range. This can prevent the adhesive layer 20 from peeling from the elastic layer 10 during repeated bending. At the same time, it can prevent the multilayer sheet 100 from peeling from the 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 measured at 20°C of 1 MPa or more. The storage modulus value may be 5 MPa or more. The storage modulus value may be 7 MPa or more. The storage modulus value may be 100 MPa or less. The storage modulus value may be 80 MPa or less. The storage modulus value may be 50 MPa or less. The storage modulus value may be 20 MPa or less.

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

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

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

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

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

[0139] The adhesive layer 20 may have a storage modulus value of 20 MPa or more measured at -40°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 50 MPa or more. 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. The storage modulus value may be 170 MPa or less. The storage modulus value may be 150 MPa or less. The storage modulus value may be 120 MPa or less. The storage modulus value may be 100 MPa or less.

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

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

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

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

[0144] After curing, adhesive layer 20 may have a storage modulus value measured at 80°C of 0.001 MPa or more, 0.003 MPa or more, or 0.01 MPa or less.

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

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

[0147] After curing, adhesive layer 20 may have a storage modulus value measured at -40°C of 20 MPa or more. 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 50 MPa or more. 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. The storage modulus value may be 170 MPa or less. The storage modulus value may be 150 MPa or less. The storage modulus value may be 120 MPa or less. The storage modulus value may be 100 MPa or less.

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

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

[0151] The method for measuring the adhesive strength of the adhesive layer 20 will be omitted here because it overlaps with the method for measuring the adhesive strength of the multilayer sheet described above.

[0152] The adhesive layer 20 may have a total light transmittance (light transmittance) in accordance with ISO 13468 of 85% or more. 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 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 yellow index (YI) of the adhesive layer 20 may be 3 or less. The yellow index may be 2.8 or less. The yellow index may be 2.2 or less. The yellow index may be 1.0 or less. The yellow index may be 0.8 or less. The yellow index may be 0.5 or less. The yellow index may be greater than 0.

[0155] Such adhesive layers have excellent optical properties and are therefore 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 more specifically, a silicone adhesive layer. The silicone adhesive layer can provide an adhesive layer with high light transmittance, heat resistance, weather resistance, and the like. In particular, the adhesive layer of the embodiment described below has strong adhesive strength even at a thin thickness, thereby further improving the physical properties of the multilayer sheet compared to existing optically clear adhesives (OCAs) such as acrylic adhesive layers.

[0157] The adhesive layer 20 may have a high adhesive strength.

[0158] In order for the multilayer sheet to maintain its physical properties even after repeated bending or folding, the performance of not only the transparent layer and coating layer 40 but also the adhesive layer that secures them and prevents delamination must be improved. The inventors were able to achieve this improved performance by applying a silicone-based adhesive layer.

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

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

[0161] The silicone adhesive may be a commercially available silicone adhesive that can be used for optical purposes. 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 KR-100, KR-101-10, and KR-130 from Shin-Etsu Chemical, DOWSIL SH 4280 from Dow, and SilGrip PSA 510 from Momentive Performance Materials.

[0163] Examples of the addition reaction type silicone adhesive that may be used include Shin-Etsu Chemical's KR-3700, KR-3701, X-40-3237, X-40-3240, and X-40-3291-1; Dow's DOWSIL SD4580, DOWSIL 4584, DOWSIL 4585, and DOWSIL 4587L; and Momentive Performance Materials' SilGrip TSR1512 and TSR1516.

[0164] As for the silicone adhesive, it may be advantageous in terms of process convenience to use an addition reaction type silicone adhesive.

[0165] In some embodiments, a silicone MQ resin may be further included to improve the adhesive strength of the silicone adhesive layer. Silicon MQ resin is a polymer of cage-like oligosiloxanes represented by the general formula RnSiXmOy, which has at least two methyl groups in the siloxane skeleton. In the general formula, R may be an alkyl group having 1 to 5 carbon atoms, and contains at least two 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 each integers from 2 to 200. Specifically, R1R2X3SiO 1 / 2 M units (mono-terminated siloxane units) represented by the formula, and SiO 4 / 2The weight average molecular weight may be 2000 to 8000 g / mol. If the silicone MQ resin is applied to the adhesive layer, the adhesive strength can be further improved, and in particular the initial adhesive strength can be improved.

[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 a ratio, the adhesive layer can have excellent adhesive strength even at a very thin thickness.

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

[0168] The catalyst may be a platinum catalyst. For example, a product such as Shin-Etsu Chemical's CATPL-50T may be used. The catalyst shortens the curing time, so that an adhesive layer can be efficiently formed without substantially damaging the substrate, even when a transparent film or substrate having 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 a catalyst, based on 100 parts by weight of the silicone adhesive. In such cases, the catalyst can effectively promote the curing reaction within the composition.

[0170] The silicone adhesive composition may further include a solvent. The solvent dilutes the silicone adhesive composition and imparts fluidity to the composition, thereby improving workability, such as coating. The solvent also helps form a relatively thin adhesive layer with excellent overall physical properties. For example, toluene may be used as the solvent, but any solvent may be used as long as it does not impair the physical properties of the silicone adhesive composition.

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

[0172] The silicone adhesive composition can be applied onto the elastic layer 10 to form the silicone-based curable adhesive layer 20. The silicone adhesive composition can be applied to one side of a separate substrate film (not shown) and then laminated onto the elastic layer 10. However, depending on the process order, drying and curing can be performed immediately after application or in separate processes. The silicone adhesive composition is coated to form a thin layer, and this layer can be included in the adhesive layer before being dried and completely cured by heat or light. This dried layer of silicone adhesive composition before curing is referred to as a 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 precursor layer and the adhesive layer can be disposed so that their surfaces are in direct contact with each other, and the adhesive layer 20 can be formed by thermal curing at 90 to 130°C for 1 to 5 minutes.

[0174] The adhesive layer 20 can contain repeating units derived from a silicone adhesive and repeating units derived from a silicone MQ resin. The adhesive layer 20 can 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 the repeating units derived from the silicone MQ resin, based on 100 parts by weight of the repeating units derived from the silicone adhesive. The adhesive layer 20 can 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 the repeating units derived from the silicone MQ resin, based on 100 parts by weight of the repeating units derived from the silicone adhesive. In such cases, the adhesive layer can have a thin thickness while still achieving 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 a catalyst per 100 parts by weight of the repeating units derived from the silicone adhesive and the repeating units derived from the 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 a catalyst per 100 parts by weight of the repeating units derived from the silicone adhesive and the repeating units derived from the silicone MQ resin. In this case, 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 greater. The thickness may be 1.8 μm or greater. The thickness may be 2 μm or greater. The thickness may be 2.5 μm or greater. The thickness may be 3 μm or greater. The thickness may be 3.5 μm or greater. 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, excellent adhesive effects can be obtained.

[0177] Other layers transparent layer The transparent layer 30 can serve 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 thereto as long as it is applicable to the support layer of a cover film for a display.

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

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

[0181] The transparent layer 30 may have excellent retardation properties. The transparent layer 30 may have an in-plane retardation of 600 nm or less, 500 nm or less, 400 nm or less, 300 nm or less, or 200 nm or less. The transparent layer 30 may have an in-plane retardation of 0 nm or more, 10 nm or more, 30 nm or more, or 50 nm or more. In this case, when the multilayer sheet is applied to the front portion of a display, the possibility of rainbow irregularities 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 retardation of 200 nm or less or 150 nm or less. Specifically, the minimum in-plane retardation 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 thickness direction retardation 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 thickness direction retardation (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 thickness direction retardation to in-plane retardation of 10 or more, 15 or more, or 20 or more. A smaller in-plane retardation and a larger thickness direction retardation are more advantageous in preventing rainbow irregularities, so it is preferable to maintain a large ratio between the two values.

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

[0186] The transparent layer having the above-described characteristics has a high degree of molecular orientation and promotes crystallization, thereby providing mechanical properties at an appropriate level or higher. Furthermore, the transparent layer can effectively suppress the possibility of rainbow irregularities.

[0187] The retardation is based on a value measured from a transparent layer having a thickness of 40 μm to 50 μm.

[0188] The transparent layer 30 has a tensile strength of 15 kgf / mm 2 The tensile strength may be 18 kgf / mm or more. 2 Over 20kgf / mm 2 Above, 21kgf / mm 2 or more, or 22kgf / mm 2 It may be more than that.

[0189] The transparent layer 30 may have an elongation of 15% or more. The elongation may 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 more. The modulus may be 3 GPa or more, 3.5 GPa or more, 3.8 GPa or more, or 4.0 GPa or more. The modulus may be 10 GPa or less, or 8 GPa or less.

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

[0192] As the transparent layer 30, a polyester film, a polyimide film, a polyamide film, or a polyimide-amide film may be applied.

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

[0194] The polyester resin may be a homopolymer resin or a copolymer resin obtained by polycondensation of a dicarboxylic acid and a diol, or a blend resin obtained by mixing the homopolymer resins or the copolymer resins.

[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, diphenylsulfonecarboxylic 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 having excellent crystallinity, and may contain, for example, polyethylene terephthalate (PET) resin as the main component.

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

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

[0200] The polyester film having such a composition can have improved mechanical properties such as tensile strength due to an increase in crystallinity during the manufacturing process, which involves heating and stretching.

[0201] The transparent layer 30 may further contain a filler in addition to the polyester-based 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, which can improve winding properties. Furthermore, the running properties and scratch prevention effects during film production can be improved.

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

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

[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 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, more specifically, 20 μm to 95 μm, or 25 μm to 85 μm. A transparent layer having such a thickness can achieve excellent optical properties along with sufficient mechanical properties.

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

[0207] The transparent layer may be produced by a method including the steps of: (1) extruding a composition containing a polyester resin to obtain an unstretched film; (2) stretching the unstretched film in the longitudinal and transverse directions; and (3) heat-setting the stretched film.

[0208] In the above-mentioned production method, the unstretched film is produced by extruding a raw material resin, followed by preheating, stretching, and heat setting. The extrusion may be carried out at a temperature of 230 to 300°C, or 250 to 280°C.

[0209] The unstretched film is preheated at a certain temperature before stretching. The preheating temperature range can be determined within a range of Tg+5°C to Tg+50°C, based on the glass transition temperature (Tg) of the polyester resin, and also within a range of 70°C to 90°C. When the preheating temperature is within this range, the flexibility of the unstretched film that allows it to be easily stretched can be ensured, and at the same time, breakage during stretching can be effectively prevented.

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

[0211] The longitudinal stretch ratio may be 2.0 to 5.0 times, more specifically 2.8 to 3.5 times. The widthwise stretch ratio may be 2.0 to 5.0 times, more specifically 2.9 to 3.7 times. Preferably, the longitudinal stretch ratio (d1) and the widthwise stretch ratio (d2) are substantially the same. Specifically, the ratio (d2 / d1) of the longitudinal stretch ratio (d2) to the widthwise stretch ratio (d1) may be 0.5 to 1.0, 0.7 to 1.0, or 0.9 to 1.0. The stretch ratios (d1, d2) are the ratios of the length after stretching when the length before stretching is 1.0. The stretching speed may be 6.5 m / min to 8.5 m / min, but is not particularly limited.

[0212] The stretched sheet may be heat-set at 150° C. to 250° C., more specifically, 160° C. to 230° C. The heat-setting may be performed for 5 seconds to 1 minute, more specifically, for 10 seconds to 45 seconds.

[0213] After the heat setting is initiated, the film may be relaxed in the longitudinal and / or transverse directions, at a temperature ranging from 150°C to 250°C.

[0214] Coating layer The coating layer 40 can include at least one coating material selected from the group consisting of an organic component, an inorganic component, and an organic-inorganic composite component.

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

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

[0217] The coating layer 40 may include at least one compound selected from the group consisting of a urethane acrylate-based compound, an acrylic ester-based compound, an acrylate-based compound, and an epoxy acrylate-based compound, or a cured product of the compound.

[0218] The urethane acrylate compound contains a urethane bond as a repeating unit and may have a plurality of functional groups.

[0219] The urethane acrylate compound may be a urethane compound formed by reacting a diisocyanate compound with a polyol, the terminal of which is substituted with an acrylate group.

[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 hydroxy groups (-OH) and having 4 to 12 carbon atoms, or an aromatic polyol compound having 6 to 20 carbon atoms. The terminal substitution with an acrylate group may be carried out using an acrylate compound having a functional group capable of reacting with an isocyanate group (-NCO). For example, an acrylate compound having a hydroxy group, an amine group, or the like may be used, or a hydroxyalkyl acrylate or aminoalkyl acrylate having 2 to 10 carbon atoms may be used.

[0222] The urethane acrylate compound may contain 2 to 15 functional groups.

[0223] Examples of urethane acrylate compounds include, but are not limited to, difunctional urethane acrylate oligomers having a weight average molecular weight of 1,400 to 25,000, trifunctional urethane acrylate oligomers having a weight average molecular weight of 1,700 to 16,000, tetrafunctional urethane acrylate oligomers having a weight average molecular weight of 500 to 2,000, hexafunctional urethane acrylate oligomers having a weight average molecular weight of 818 to 2,600, nonafunctional urethane acrylate oligomers having a weight average molecular weight of 2,500 to 5,500, 10-functional urethane acrylate oligomers having a weight average molecular weight of 3,200 to 3,900, and 15-functional urethane acrylate oligomers having a weight average molecular weight of 2,300 to 20,000.

[0224] The glass transition temperature (Tg) of the urethane acrylate compound 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, and may contain 1 to 10 functional groups.

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

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

[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] The acrylate compound can contain 1 to 10 functional groups. Examples of the acrylate compound include a monofunctional acrylate oligomer having a weight-average molecular weight of 100 to 300, a bifunctional acrylate oligomer having a weight-average molecular weight of 250 to 2000, and an epoxy acrylate oligomer having 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, monofunctional epoxy acrylate oligomers having a weight-average molecular weight of 100 to 300, difunctional epoxy acrylate oligomers having a weight-average molecular weight of 250 to 2000, and tetrafunctional epoxy acrylate oligomers having 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% by weight to 100% by weight, 40% by weight to 90% by weight, or 50% by weight to 80% by weight based on the total weight of the coating layer 40.

[0232] The coating layer 40 may not contain an inorganic filler such as silica, in which case the adhesive strength between the transparent film layer and the coating layer 40 having the above-mentioned composition can be improved.

[0233] The coating layer 40 may optionally further include a filler.

[0234] The filler may be, for example, inorganic particles, such as silica, barium sulfate, zinc oxide, or alumina.

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

[0236] The filler may include inorganic fillers having different particle size distributions, such as a first inorganic filler having a D50 of 20 nm to 35 nm and a second inorganic filler having a D50 of 40 nm to 130 nm.

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

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

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

[0240] Examples of photoinitiators include, but are not limited to, 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, 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. Commercially available products include Irgacure 184, Irgacure 500, Irgacure 651, Irgacure 369, Irgacure 907, Darocur 1173, Darocur MBF, Irgacure 819, Darocur TPO, Irgacure 907, Esacure KIP 100F, etc. The photoinitiators may be used alone or in combination of two or more different types.

[0241] The coating layer 40 may further include an antifouling agent. The coating layer 40 may include a fluoro-based compound as the antifouling agent. The fluoro-based compound can perform an antifouling function. Specifically, the fluoro-based compound may be an acrylate-based compound having a perfluoro-based alkyl group, and a specific example thereof may be, but is not limited to, perfluorohexylethyl acrylate.

[0242] The coating layer 40 may further include an antistatic agent. The antistatic agent may include an ionic surfactant. For example, the ionic surfactant may include an ammonium salt or a quaternary alkyl ammonium salt, and the ammonium salt and the quaternary alkyl ammonium salt may include a halide such as a chloride or a bromide.

[0243] The coating layer 40 may further include additives such as a surfactant, a UV absorber, a UV stabilizer, a yellowing inhibitor, a leveling agent, or a dye for improving color. For example, the surfactant may be a mono- or di-functional fluorine-based acrylate, a fluorine-based surfactant, or a silicone-based surfactant. The surfactant may be dispersed or crosslinked within the coating layer 40. Examples of the UV absorber include benzophenone-based compounds, benzotriazole-based compounds, and triazine-based compounds, and examples of the UV stabilizer include tetramethylpiperidine. The content of these additives may be adjusted in various amounts within a range that does not deteriorate the physical properties of the coating layer 40. For example, the content of the additives may be 0.01 to 10 wt % based on the total weight of the 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 is formed as a single layer, which increases the surface durability of the multi-layer sheet and simultaneously provides anti-fingerprint or anti-stain functions.

[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, or may be 50 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. When the coating layer has such a thickness, it can provide the multilayer sheet with durability such as surface hardness at an appropriate level or more, while maintaining the overall flexibility of the multilayer sheet, even when applied at a thin thickness.

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

[0248] The method for producing a coating layer may include a step of coating a composition for producing a coating layer and then curing the composition.

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

[0250] The composition for producing a coating layer may include at least one of an acrylate compound, a siloxane compound, and a silsesquioxane compound, and may further include inorganic particles.

[0251] Specific examples of the composition for preparing the coating layer may include a urethane acrylate-based compound, an acrylic ester-based compound, and a fluoro-based compound.

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

[0253] Examples of organic solvents that can be used alone or in combination include alcohol solvents such as methanol, ethanol, isopropyl alcohol, and butanol; alkoxy alcohol solvents such as 2-methoxyethanol, 2-ethoxyethanol, and 1-methoxy-2-propanol; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl propyl ketone, and cyclohexanone; ether solvents such as propylene glycol monopropyl ether, propylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethyl 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.

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

[0255] The composition for preparing the coating layer may contain 10 to 30 wt % of an organic resin, 0.1 to 5 wt % of a photoinitiator, 0.01 to 2 wt % of an antifouling additive, 0.1 to 10 wt % of an antistatic agent, and the remaining amount of an organic solvent.

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

[0257] The composition for preparing the coating layer can be applied to a transparent film by a conventional coating method, such as 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 composition for producing a coating layer may be subjected to drying and curing steps sequentially or simultaneously.

[0259] Drying is a process for removing the organic solvent from the applied coating layer production composition. Drying may be performed 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 minute to 20 minutes, preferably 1 minute to 10 minutes, or 1 minute to 5 minutes.

[0260] Curing is a process of inducing a chemical reaction in the composition for preparing a coating layer to form a coating film. Depending on the resin used in the composition for preparing a coating layer, an appropriate photocuring and / or thermal curing method may be used.

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

[0262] The substrate layer can be disposed on adhesive layer 20 in contact with it. If another layer is disposed between the substrate layer and adhesive layer 20, the substrate layer can be disposed on adhesive layer 20 without contacting it.

[0263] The material of the substrate layer is not limited as long as it is a resin 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, the substrate layer may be any one of polyester film, polyimide film, and polyether block amide film. The polyester film may be a polyethylene terephthalate (PET) film.

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

[0265] Multilayer sheet manufacturing method A method for manufacturing a multilayer sheet according to yet another embodiment of the present 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 the elastic layer may include a step of applying a silicone adhesive composition on the elastic layer and drying the composition to form a precursor layer, and the step of laminating an adhesive layer on the 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 a pre-formed elastic layer on the adhesive layer.

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

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

[0270] The explanation of the method for forming each layer is omitted here since it overlaps with the above description.

[0271] multilayer electronic device 5 is a conceptual diagram illustrating a multilayer electronic device according to yet another embodiment of the present disclosure. An embodiment will be described with reference to FIG.

[0272] A multi-layer electronic device 200 according to yet another embodiment of the present disclosure includes a multi-layer sheet 100 and a light-emitting functional layer 150 disposed below the multi-layer sheet 100 .

[0273] The multi-layer sheet 100 may be applied as a cover layer of a multi-layer electronic device 200 .

[0274] The explanation of the multilayer sheet 100 is omitted here since it overlaps with the above content.

[0275] The multi-layer electronic device 200 may be, for example, a display device, such as a large-area display device, a foldable display device, a bendable display device, or a flexible display device, or may 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 signals in a display device. The light-emitting layer may include, for example, a signal transmission layer that transmits an external electrical signal to a color-emitting layer, a color-emitting layer disposed on the signal transmission layer and emitting color in response to the applied signal, and an encapsulation layer that protects the color-emitting layer. The signal transmission layer may include a thin film transistor (TFT), for example, but not limited to, LTPS, a-Si TFT, or oxide TFT. The encapsulation layer may include, but is not limited to, TFE (Thin Film Encapsulation).

[0278] The light-emitting layer may be disposed on a support layer (not shown). The support layer may be a layer having insulating and heat-resistant properties, such as a polyimide film, a glass layer, or a PET film.

[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 disposed on the light-emitting layer or on the sensor layer.

[0281] Specific examples will be described in more detail below.

[0282] Manufacturing example: Manufacturing of multi-layer sheets Examples: Elastic layers were manufactured using Arkema's PEBA resin products for 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 manufacture the elastic layer. The product names of the PEBA resins used to manufacture the elastic layers for each example and the thicknesses of the elastic layers are listed in Table 1 below.

[0283] Adhesive layers were formed on both sides of the elastic layer. Specifically, a silicone adhesive composition was applied to both sides of the elastic layer, and then dried and cured to form adhesive layers. The drying and curing were carried out at a temperature of 90°C for 5 minutes.

[0284] The silicone adhesive composition used contained 29.851 wt% of Shin-Etsu KR-3700 model silicone adhesive, 7.164 wt% of Shin-Etsu X-92-128 model silicone MQ resin, 0.299 wt% of Shin-Etsu CAT-PL-50T model platinum catalyst, and 62.686 wt% of toluene.

[0285] The adhesive layers formed on both sides of the elastic layer had the same thickness. The thicknesses of the adhesive layers applied in each example are shown in Table 1 and FIGS. 6 to 11.

[0286] Comparative Example 1: The silicone adhesive composition used 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 by temperature The modulus of each example and comparative example was measured using dynamic mechanical analysis (DMA). Specifically, the storage modulus of each example and comparative example sample was measured using Hitachi's DMA7100 model in the range of -50°C to 100°C. The heating rate was 5°C / min.

[0288] The measurement results at each measurement temperature for each example and comparative example are shown in Tables 1 and 2 below and in FIGS. 6 to 12.

[0289] Evaluation example: Measurement of RSM value by temperature SM according to the temperature of the elastic layer and adhesive layer applied to the multilayer sheets of Examples 2, 8, 14, 20, 26 and 32 E Value and SM B The values were measured using a Hitachi DMA7100 model. The measurement temperature range was set to -50°C to 100°C, and the heating rate was 5°C / min. SM values at -40°C, -20°C, 0°C, 20°C, and 40°C were measured. E Value and SM B The values were measured, and the RSM values were calculated from the values.

[0290] SM by measurement temperature for each example E Value, SM B The values and RSM values are listed in Tables 3 and 4 below.

[0291] Evaluation example: Measurement of adhesive strength according to adhesive layer thickness For each preparation example, the silicone adhesive composition used in the examples was die-coated onto a PET film (SKC NRF grade), 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 used for each preparation example is shown in Table 3 below.

[0292] The adhesive strength of the adhesive layer formed for each manufacturing example was then measured. The adhesive strength was measured in T-Peel format using COMETECH's QC-M1F UTM model, and the peeling speed was 300 mm / min.

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

[0294] [Table 1]

[0295] [Table 2]

[0296] [Table 3]

[0297] [Table 4]

[0298] [Table 5]

[0299] Although the preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using 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 multi-layer sheets 10 Elastic layer 20 Adhesive layer 30 transparent layer 40 coating layers 50 Release film 51 Release layer 52 Release base material layer 150 Light-emitting functional layer 200 Multilayer electronic devices

Claims

1. an elastic layer; and an adhesive layer disposed on the elastic layer; A multilayer sheet having a storage modulus measured at 20°C of 10 MPa or more and 2000 MPa or less.

2. 2. The multilayer sheet according to claim 1, wherein the RSM value measured at 20°C according to the following formula 1 is 1 or more and 200 or less. [Formula 1] RSM=SM Ｅ / SM Ｂ (In the above formula 1, Said S.M. Ｅ is the storage modulus value of the elastic layer, Said S.M. Ｂ is the storage modulus value of the adhesive layer.

3. 2. The multilayer sheet according to claim 1, wherein the absolute value of the difference between the storage modulus measured at 20°C and the storage modulus measured at 60°C is 1000 MPa or less.

4. 2. The multilayer sheet according to claim 1, wherein the absolute value of the difference between the storage modulus measured at -40°C and the storage modulus measured at 20°C is 1500 MPa or less.

5. 2. The multilayer sheet according to claim 1, wherein the storage modulus of the elastic layer measured at 20°C is 10 MPa or more and 3000 MPa or less.

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

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

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

9. The multilayer sheet according to claim 1; a light-emitting functional layer disposed beneath the multilayer sheet.

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