Sealing material sheet for self-luminous display body or direct backlight, self-luminous display body, and direct backlight

Abstract

To provide "a sealing material sheet for a self-luminous display body or a direct backlight" that is a heat shrinkable sealing material sheet having high heat resistance enough to withstand service under extremely high temperature environment, which has extremely excellent moldability.SOLUTION: There is provided a sealing material sheet 1 for a self-luminous display body or a direct backlight in which an olefinic resin is used as a base resin, a melting point is 45°C or higher and 60°C or lower, melt viscosity at a shear rate of 2.43×10 sec-1 in the entire layer of a resin sheet, which is measured at a temperature of 120°C, is 2.0×103 Pa s or more and 9.0×103 Pa s or less, and 0.1 mass% or more and 1.2 mass% or less of a crosslinking agent is contained in the resin component.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an encapsulant sheet for a self-luminous display or a direct backlight, a self-luminous display, and a direct backlight. [Background technology]

[0002] As a next-generation display device, the development of self-luminous display devices, typified by micro LED televisions, is progressing. In such self-luminous display devices, an encapsulant sheet for protecting the light-emitting elements is laminated on the surface of the light-emitting surface side of a surface light source device, such as an LED module, which is configured by mounting light-emitting elements, such as LED elements, on a wiring board (see Patent Document 1). In parallel with the development of these self-luminous display devices, the development of encapsulant sheets that are highly suitable for self-luminous display devices or direct backlights is also progressing (see Patent Document 2).

[0003] Here, the "encapsulant sheet for a self-luminous display or a direct backlight" disclosed in Patent Document 2 is a resin sheet made of a thermoplastic resin, and in order to emphasize the viscosity of the base resin during heat press processing, the melt viscosity at a temperature of 120°C is set to 5.0 × 10 3 poise or more 1.0×10 5 It is optimized for a limited high viscosity range of less than 1 poise, which allows it to achieve a high level of both molding properties during heat press processing and suppression of resin overflow due to excessive flow.

[0004] However, in some cases where a display device configured with a self-luminous display or a direct backlight is used in a vehicle exposed to direct sunlight, for example, the ambient temperature rises during use, and the heat generated by the display itself increases as the brightness increases, causing the temperature inside the housing to reach approximately 90°C. In order to use the encapsulant sheet made of the thermoplastic resin disclosed in Patent Document 2 in such an environment, it is conceivable to use a resin with an even higher melting point and viscosity as the base resin.

[0005] However, with such thermoplastic encapsulant sheets that use high-melting-point, high-viscosity resins as the base resin, a new problem has come to be recognized: when they are integrated into self-luminous displays, etc., problems arise in molding, such as the generation of minute air bubbles at the interface between the encapsulant sheet and the electronic device. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-155737 [Patent Document 2] Patent No. 6760542 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide an "encapsulant sheet for a self-luminous display or a direct backlight" that has high heat resistance that can withstand use in particularly high-temperature environments and also has extremely excellent molding properties. [Means for solving the problem]

[0008] The present inventors have found that the above-mentioned problems can be solved by using a thermally crosslinkable resin as a base resin for an "encapsulant sheet for a self-luminous display or a direct backlight" and by limiting the viscosity of the base resin to a specific range unique to the use of "a self-luminous display or a direct backlight" that differs from conventional methods, and have thus completed the present invention. Specifically, the present invention provides the following.

[0009] (1) An encapsulant sheet for a self-luminous display or a direct backlight, which uses an olefin resin as the base resin, has a melting point of 45°C or higher and 60°C or lower, and has a shear rate of 2.43 x 10 sec across the entire resin sheet when measured at a temperature of 120°C.-1 The melt viscosity at 2.0 × 10 3 Pa·s or more 9.0×10 3 The encapsulant sheet has a crosslinking agent content of 0.1% by mass or more and 1.2% by mass or less in the resin component.

[0010] According to the encapsulant sheet of (1), it is possible to obtain an "encapsulant sheet for a self-luminous display or a direct backlight" which is a thermally crosslinked encapsulant sheet having high heat resistance that can withstand use in particularly high-temperature environments and which also has extremely excellent molding properties.

[0011] (2) A self-luminous display comprising the encapsulant sheet described in (1), a display surface panel, and a light-emitting module in which a plurality of light-emitting elements are mounted on a wiring board, wherein the encapsulant sheet covers the light-emitting elements and the wiring board and is laminated on the light-emitting module, and the display surface panel is laminated on the encapsulant sheet.

[0012] According to the self-luminous display element (2), it is possible to enjoy the advantageous effects of the "sealant sheet" (1) described above, and obtain a self-luminous display element that exhibits particularly excellent durability when used in a high-temperature environment.

[0013] (3) The self-luminous display according to (3), wherein the gel fraction of the sealing material sheet is 50% or more and 90% or less.

[0014] According to the self-luminous display element (3), the above-mentioned advantageous effects of the self-luminous display element (2) can be enjoyed and the high heat resistance that can withstand use in particularly high temperature environments can be more stably exhibited, thereby making it possible to obtain a self-luminous display element that exhibits particularly excellent durability when used in high temperature environments.

[0015] (4) A self-luminous display body according to (2) or (3), wherein the light-emitting elements are LED elements, the width and depth of each of the LED elements are 300 μm or less, the height is 200 μm or less, and the spacing between the LED elements is 0.03 mm or more and 100 mm or less.

[0016] The self-luminous display body (4) is an embodiment in which the self-luminous display body (2) or (3) is applied to various high-definition LED display devices, such as a "dot matrix display device" in which a large number of LED elements (LED chips) are directly mounted on a substrate using a chip-on-board method. This allows for the production of a high-definition LED display device that enjoys the above-mentioned advantageous effects of the self-luminous display body (2) or (3) and has high heat resistance that can withstand use in particularly high-temperature environments, thereby demonstrating excellent durability in high-temperature environments.

[0017] (5) A self-luminous display body as described in (2) or (3), in which the light-emitting element is an LED element, the LED element having an LED light-emitting chip and a resin cover covering the LED light-emitting chip, the width and depth of the LED element are both 50 μm or less, the height is 10 μm or less, and the arrangement spacing of each of the LED elements is 0.005 mm or more and 5 mm or less.

[0018] The self-luminous display (5) is an embodiment in which the self-luminous display (2) or (3) is applied to various ultra-high definition LED display devices, such as "micro LED TVs," which are expected to be next-generation video display devices. This allows for the production of ultra-high definition LED display devices that enjoy the above-mentioned advantageous effects of the self-luminous display (2) or (3) and have high heat resistance that can withstand use in particularly high temperature environments, thereby demonstrating excellent durability in high temperature environments.

[0019] (6) A direct-type backlight comprising an encapsulant sheet according to (1) or (2) and a light-emitting module in which a plurality of light-emitting elements are mounted on a wiring board, wherein the encapsulant sheet covers the light-emitting elements and the wiring board and is laminated on the light-emitting module.

[0020] According to the direct-type backlight (6), by enjoying the above-mentioned advantageous effects of the "sealant sheet" (1) or (2) and having high heat resistance that can withstand use in particularly high-temperature environments, it is possible to obtain a direct-type backlight that exhibits particularly excellent durability when used in high-temperature environments.

[0021] (7) A liquid crystal display comprising the direct-type backlight according to (6), a diffusion plate, and a display surface panel, wherein the diffusion plate is laminated on the sealing material sheet constituting the direct-type backlight.

[0022] The liquid crystal display (7) is an embodiment of the present invention as a liquid crystal display using the direct-type backlight (6) as a surface light source device, which provides the above-mentioned effects of the direct-type backlight (6) and provides a liquid crystal display that exhibits particularly excellent durability when used in a high-temperature environment. [Effects of the Invention]

[0023] According to the present invention, it is possible to obtain a thermally crosslinked encapsulant sheet that has high heat resistance that can withstand use in particularly high-temperature environments, and that also has extremely excellent molding properties, such as an "encapsulant sheet for a self-luminous display or a direct-type backlight," a "self-luminous display," a "direct-type backlight," and a "liquid crystal display." [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a plan view and a partially enlarged plan view of the image display surface of a self-luminous display (micro LED display device) constructed using the "encapsulant sheet for a self-luminous display or a direct backlight" of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a cross section of the AA portion of FIG. [Figure 3] FIG. 2 is a perspective view of an LED element constituting the self-luminous display (micro LED display device) of FIG. [Figure 4] FIG. 1 is a perspective view schematically illustrating an example of the configuration of a display device (liquid crystal display) using a direct backlight configured using the “encapsulant sheet for a self-luminous display or a direct backlight” of the present invention. [Figure 5] FIG. 1 is a partially enlarged cross-sectional view of the periphery of a mounting area of ​​one LED element in a display device (liquid crystal display) using a direct-type backlight of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] <Self-luminous display> In this specification, the term "self-luminous display" refers to an information display device that displays visual information such as text, images, and video, and is configured to include a display surface panel and a surface light source device consisting of a light-emitting module in which a large number of tiny light-emitting elements (such as LED elements) are mounted on a wiring board. The information display device can display various visual information such as text, images, and videos on the display surface panel by selectively blinking the light-emitting elements (such as LED elements) using a light-emission control means. Specific examples of "self-luminous display devices" include "dot matrix display devices" in which a large number of LED elements (LED chips) are directly mounted on a board using a chip-on-board method, and the above-mentioned "micro LED television."

[0026] Furthermore, in this specification, the term "micro LED display device" collectively refers to a self-luminous display device, such as a "dot matrix display device" or a "micro LED television," in which "micro-sized LED elements" or "ultra-small-sized LED elements" are arranged in a matrix with a pitch of approximately 0.005 mm to 5 mm. In this specification, a "micro-sized LED element" refers to an LED element whose width (W) and depth (D) are both greater than 50 μm and less than 300 μm, and whose height (H) is greater than 10 μm and less than 200 μm. Similarly, a "ultra-small-sized LED element" refers to an LED element whose width (W) and depth (D) are both less than 50 μm and whose height (H) is less than 10 μm (see Figure 3). Note that when an LED element includes an LED light-emitting chip and a resin cover covering it, the size of the LED element refers to the overall size of the light-emitting element, including the resin cover.

[0027] Hereinafter, the present invention will be described in detail, taking as an example an embodiment in which the "self-luminous display body" of the present invention is implemented as a "micro LED display device" as a preferred example of an embodiment of the present invention. However, the technical scope of the present invention is not limited to the embodiment as a "micro LED display device." The present invention is not limited to only "micro LED display devices," but is a technology that can be applied to "self-luminous display bodies" in general as defined above.

[0028] Fig. 1 is a front view of a micro LED display device 100, which is an example of an embodiment of a self-luminous display device of the present invention, and a partially enlarged view (100A) thereof. Fig. 2 is a cross-sectional view showing a cross section of part AA in Fig. 1, and is a drawing provided for explaining the layer structure of the micro LED display device 100 shown in Fig. 1. As shown in Figs. 1 and 2, this micro LED display device 100 includes an LED module 30 in which a large number of LED elements 10 are mounted on a wiring substrate 20 and function as a surface light source device, and a display surface panel 2.

[0029] [LED module] The LED module 30 is a light-emitting module in the micro LED display device 100. As shown in Fig. 2, in the LED module 30, the LED elements 10 are mounted on the wiring portion 22 of the wiring substrate 20 via a solder layer 23 in a conductive manner. In the LED module 30, the light emission of each LED element 10 is individually controlled by a light-emission control means (not shown) such as an IC chip substrate that is separately bonded.

[0030] In the LED module 30, an encapsulant sheet 1 is laminated on the mounting surface of the LED elements 10 in a manner that covers the LED elements 10. In the micro LED display device 100, the "encapsulant sheet for a self-luminous display or a direct backlight" of the present invention is used as this encapsulant sheet 1. Details of the "encapsulant sheet for a self-luminous display or a direct backlight" of the present invention will be described separately later.

[0031] Furthermore, in the micro LED display device 100, a display surface panel 2 such as various optical films and transparent protective glass is further laminated on the outer surface side of the sealing material sheet 1 (the display surface side of the micro LED display device 100).

[0032] (wiring board) The support substrate 21 constituting the wiring board 20 in the LED module 30 can be a conventionally known hard glass epoxy substrate used as a substrate for electronic circuits. Alternatively, the support substrate 21 can be a flexible resin film such as polyethylene terephthalate, polyimide, or polyethylene naphthalate, making the wiring board 20 a flexible substrate. In either case, the wiring portion 22 can be formed from a metal such as copper or any other conductive material.

[0033] (LED element) The LED element 10 is a light-emitting element that utilizes light emission from a PN junction where a P-type semiconductor and an N-type semiconductor are joined. Two types of LED elements have been proposed: one with a P-type electrode and an N-type electrode on the top and bottom surfaces of the element, and another with both a P-type and an N-type electrode on one side of the element. LED elements of either structure can be used as the light-emitting element of the micro LED display device 100. As an example, the LED element disclosed in Japanese Patent Laid-Open Publication No. 2006-339551 as a "chip-type electronic component" can be preferably used in the "self-luminous display" of the present invention. The LED element disclosed in this publication is said to have dimensions of approximately 25 μm x 15 μm x 2.5 μm (width x depth x height) (corresponding to the "ultra-small LED element" of the present invention).

[0034] The LED element 10 used in the LED module 30 includes at least an LED light-emitting chip 11. It may also include a resin cover 12 covering the LED chip 11. When the LED element 10 includes the resin cover 12, the resin cover 12 is made of an organic insulating material such as epoxy resin, silicone resin, or polyimide resin. Among these, epoxy resin is particularly preferred. The resin cover 12 made of epoxy resin not only protects the LED light-emitting chip 11 from physical impact but also suppresses total reflection of light into the semiconductor that constitutes the LED chip 11 due to the difference in refractive index between the semiconductor and air, thereby enhancing the luminous efficiency of the LED element 10. The "encapsulant sheet for a self-luminous display or direct-type backlight" (encapsulant sheet 1) of the present invention is made of an olefin-based resin that has excellent adhesion to epoxy resin, as described below. Therefore, it is particularly suitable as an encapsulant sheet to be mounted on a micro LED display device 100 configured using LED elements 10 with resin covers 12 made of epoxy resin.

[0035] In the LED module 30, "micro-sized LED elements" can be preferably used. In this case, the spacing between the "micro-sized LED elements" is preferably 0.03 mm or more and 100 mm or less. This mounting mode of the "micro-sized LED elements" is also the standard mounting mode of LED elements in "dot matrix display devices."

[0036] Furthermore, when using "ultra-small LED elements" in the LED module 30, the spacing between these "ultra-small LED elements" is preferably 0.005 mm or more and 5 mm or less. This mounting mode of the "ultra-small LED elements" is also the standard mounting mode of LED elements in "micro LED TVs."

[0037] There are no particular limitations on the overall size of the LED module 30. However, a diagonal length of 50 inches to 200 inches is preferred from the standpoint of cost performance. However, a light-emitting surface of a micro LED display device (self-luminous display) can also be configured by tiling multiple LED modules 30 in a matrix on the same plane. Such a display device formed by combining multiple LED modules by tiling is also naturally included in the technical scope of the present invention. For example, a large micro LED display device with a large screen diagonal length of 600 inches can be configured by joining 100 x 100 LED modules 30, each with a diagonal length of 6 inches, vertically and horizontally.

[0038] [Method of manufacturing a self-luminous display] The micro LED display device 100, which is an example of an embodiment of the self-luminous display of the present invention, can be obtained by laminating an LED module 30 for the self-luminous display, an encapsulant sheet 1, and other optical components arranged as needed into a laminate, and then integrating the laminate by heat pressing, and then laminating and integrating the display surface panel 2 onto the laminate by adhesive bonding or the like. Note that the "integrating the laminate by heat pressing" can be achieved by various known methods, such as roll lamination or vacuum lamination.

[0039] In the above manufacturing method, the encapsulant sheet 1 is laminated in a manner that exhibits sufficient molding properties in the "step of integrating the laminated body by heat pressing" to adequately cover the LED elements, and at the same time, crosslinking of the uncrosslinked encapsulant sheet 1 is also sufficiently progressed in parallel with the heat pressing, thereby making the micro LED display device 100 a self-luminous display body with extremely high heat resistance. Note that a self-luminous display body can also be manufactured by a manufacturing method in which a "heating step (curing step) for sufficiently progressing crosslinking of the encapsulant sheet" is performed after the heat pressing, as a separate step from the "step of integrating the laminated body by heat pressing".

[0040] In the method for manufacturing the self-luminous display of the present invention, the heating conditions (heating time, heating temperature, etc.) in the above-mentioned heat pressing process or the above-mentioned heating step (curing step) are appropriately optimized so that the gel fraction of the encapsulant sheet 1 is 50% or more and 90% or less, preferably 60% or more and 80% or less.

[0041] <Direct-type backlight> In this specification, a "direct backlight" is a light source unit that can be used as a light source for a direct backlight type liquid crystal display, and is a surface light source device that illuminates a display surface panel such as a liquid crystal display panel from the back side of the liquid crystal display. A direct backlight type "liquid crystal display" comprises a display surface panel such as a liquid crystal display panel and a backlight that illuminates the display surface panel from the back side (see Figure 4).

[0042] An example of the "direct type backlight" of the present invention is a direct type backlight 200 shown in Fig. 5. The direct type backlight 200 is a light-emitting module in which a plurality of LED elements 10 are mounted on a wiring board 20, and an "encapsulant sheet for a self-luminous display or a direct type backlight (encapsulant sheet 1)" of the present invention is laminated in a manner that covers the LED elements 10 and the wiring board 20. Furthermore, in the direct type backlight 200, an optical member such as a diffusion plate 3 may be further laminated on the LED elements 10 via the encapsulant sheet 1.

[0043] 5, in a wiring board 20 constituting a direct type backlight 200, a wiring section 22 is usually formed on a support substrate 21 via an adhesive layer 24. An insulating protective film 25 is formed on the support substrate 21 and the wiring section 22, and a reflective layer 26 made of a white resin or the like is further laminated on the insulating protective film 25. In addition, an LED element 10 consisting of an LED light-emitting chip 11 and a light-diffusing lens 13 is mounted on the wiring section 22 via a solder layer 23 in a conductive manner.

[0044] [Manufacturing method for direct type backlights] A direct-type backlight 200, which is one embodiment of the direct-type backlight of the present invention, can also be manufactured by laminating each component, including the encapsulant sheet 1, into a laminate and integrating this laminate by heat pressing. It is preferable to bond some of the laminated members with an adhesive before the heat pressing, if necessary. By sufficiently promoting crosslinking of the encapsulant sheet 1 (uncrosslinked encapsulant sheet 1) during the heat pressing, a direct-type backlight 200 with extremely high heat resistance can be obtained. In the manufacture of the direct-type backlight 200, a direct-type backlight can also be manufactured by providing a separate heating step (curing step) for crosslinking after the heat pressing, thereby sufficiently promoting crosslinking of the encapsulant sheet 1.

[0045] [Liquid crystal display] An example of the "liquid crystal display" of the present invention is a liquid crystal display 300 shown in Fig. 4. The liquid crystal display 300 includes a display surface panel 2 such as a liquid crystal display panel, and a direct-type backlight 200 as a surface light source device that illuminates the display surface panel 2 from the back side, with a diffuser plate 3 disposed between the direct-type backlight 200 and the display surface panel 2. In the direct-type backlight 200, the "encapsulant sheet (encapsulant sheet 1) for a self-luminous display or a direct-type backlight" of the present invention is laminated in a manner that covers the LED elements 10 and the wiring board 20, and the diffuser plate 3 is laminated on the encapsulant sheet 1.

[0046] <Sealant sheet for self-luminous displays or direct backlights> The "encapsulant sheet for self-luminous displays or direct-type backlights (hereinafter also simply referred to as "encapsulant sheet")" of the present invention is a resin sheet that can be preferably used as an encapsulant sheet for covering and laminating a large number of tiny LED elements mounted as light-emitting elements in various "self-luminous displays" or "direct-type backlights" on the wiring board of a surface light source device such as an LED module or direct-type backlight, in order to protect the LED elements from mainly physical impact.

[0047] The "encapsulant sheet" of the present invention can be particularly preferably used for "micro LED display devices" that use "micro-sized LED elements" as light-emitting elements, among various "self-luminous display devices" or "direct backlights." A high-definition "dot matrix display device" can be constructed by directly mounting "micro-sized LED elements" on a wiring board using a chip-on-board method, and the "encapsulant sheet" of the present invention can be particularly preferably used as an encapsulant sheet for this "dot matrix display device," among various "self-luminous display devices."

[0048] Furthermore, the "encapsulant sheet" of the present invention can be preferably used in "micro LED display devices" that use, as light-emitting elements, "ultra-small LED elements" that are even smaller in size than the above-mentioned "micro LED elements" among various "self-luminous display devices" or "direct backlights." By mounting "micro LED elements" on a wiring board, it is possible to construct a "micro LED television," which is expected to become the mainstream of next-generation televisions. The "encapsulant sheet" of the present invention can be preferably used as an encapsulant sheet for this "micro LED television," among various "self-luminous display devices."

[0049] Furthermore, the "encapsulant sheet" of the present invention can be used as an encapsulant sheet to cover and laminate a large number of tiny LED elements in various "micro LED display devices" or various "liquid crystal display devices" equipped with "direct backlights," thereby providing the "micro LED display devices" or "liquid crystal display devices" with exceptional heat resistance that can withstand use in harsh high-temperature environments of around 90°C, for example, when installed inside an automobile, while also adequately protecting the LED elements.

[0050] The "encapsulant sheet" of the present invention, which has the above-described advantages over conventional "encapsulant sheets for self-luminous displays or direct backlights," is a sheet-like member obtained by forming a film from an encapsulant composition (details of this "encapsulant composition" will be described separately below) containing an olefin-based resin as a base resin. After film formation, this "encapsulant sheet" is a resin sheet in an uncrosslinked state having a gel fraction of 0% to 10%, more preferably 0%, in the stage of a standalone sheet product before integration (modularization) into a "self-luminous display" or the like. In this specification, unless otherwise specified, the "encapsulant sheet" of the present invention refers to a resin sheet in an uncrosslinked state in the stage of a standalone product before integration (modularization) into a self-luminous display after film formation.

[0051] However, the "encapsulant sheet" of the present invention is a thermally crosslinkable resin sheet that is expected to undergo crosslinking during any process performed after film formation, up to the time when the sheet is integrated with other components such as an LED module to form a self-luminous display or a direct-type backlight. Therefore, as will be described in detail later, the "encapsulant sheet" contains a predetermined amount of crosslinking agent, specifically, a ratio of 0.1% by mass to 1.2% by mass of the resin component. Details of the type and content of the crosslinking agent will be described separately below in the explanation of the encapsulant composition.

[0052] Furthermore, the "encapsulant sheet" of the present invention preferably has a gel fraction of 50% or more and 90% or less, and more preferably 60% or more and 80% or less, after crosslinking has progressed in the stage of a finished product such as a self-luminous display device or a direct-type backlight.

[0053] Here, the term "gel fraction (%)" in this specification refers to a value obtained by placing 1.0 g of an encapsulant sheet in a resin mesh, extracting it with xylene at 110°C for 12 hours, removing it from the resin mesh, drying it, and weighing it. The weights before and after extraction were compared to determine the percentage (mass %) of residual insoluble matter. A gel fraction of 0% means that the residual insoluble matter is essentially zero, and the crosslinking reaction has not substantially started. More specifically, a "gel fraction of 0%" means that the residual insoluble matter is completely absent, or that the mass % of the residual insoluble matter measured using a precision balance is less than 0.05 mass %. The residual insoluble matter does not include pigment components other than the resin component. If the residual insoluble matter is found to contain impurities other than the resin component in the above test, the content of these impurities in the resin component can be separately measured in advance to calculate the "gel fraction (%)" that should be obtained for the residual insoluble matter derived from the resin component excluding these impurities.

[0054] The "encapsulant sheet" of the present invention has a melting point of 45°C or higher and 60°C or lower, more preferably 50°C or higher and 55°C or lower. Because the "encapsulant sheet" of the present invention is made of a thermally crosslinkable resin, it can have sufficient heat resistance even when using such a low-melting-point resin that has excellent moldability. In this specification, the melting point of the encapsulant sheet refers to the melting peak temperature measured by differential scanning calorimetry (DSC) after the encapsulant sheet is formed into a sheet by a molding method such as extrusion melt molding from an encapsulant composition containing a resin component and other additives, i.e., at a post-film, uncrosslinked stage.

[0055] Furthermore, the "encapsulant sheet" of the present invention has a shear rate of 2.43 × 10 sec in the entire resin sheet layer measured at a temperature of 120°C. -1 The melt viscosity at 2.0 x 10 3 Pa·s or more 9.0×10 3 The melt viscosity is preferably 3.0×10 Pa·s or less. 3 Pa·s or more 8.0×10 3 Pa·s or less, more preferably 3.0×103 Pa·s or more 4.0×10 3 Pa s or less, and most preferably 3.2 × 10 3 Pa·s or more 3.4×10 3 The melt viscosity is not more than Pa·s. In this specification, the melt viscosity is measured by a method in accordance with JIS K7199.

[0056] The above "melt viscosity" is 2.0 x 10 3 By setting the viscosity at Pa·s or higher, in the production of an "encapsulant sheet" using a thermally crosslinkable resin, resin overflow due to excessive flow during heat press processing and poor light emission due to lateral stress on the LED elements can be sufficiently suppressed, and the uniformity of the film thickness of the encapsulant sheet in which crosslinking has progressed after the heat press processing can be well maintained. In a self-luminous display such as the micro LED display device 100, the encapsulant sheet laminated on the light-emitting surface side of the LED elements requires particularly uniform film thickness. This is because even a slight difference in film thickness between the center and the edge of this encapsulant sheet causes the encapsulant sheet to become lenticular, which can have an unintended and undesirable effect on the display quality of the micro LED display device.

[0057] On the other hand, assuming that a thermal crosslinking resin is used as the base resin, the above "melt viscosity" is set to 9.0 x 10 3 By keeping the melt viscosity at 4.0×10 Pa·s or less, it is possible to achieve both high heat resistance and molding properties during hot press processing of the encapsulant sheet. 3 By limiting the viscosity to a low range of Pa·s or less, it is possible to improve molding properties while maintaining heat resistance, thereby achieving a higher level of both heat resistance and molding properties.

[0058] Measured at a temperature of 120°C, shear rate 2.43 x 10 sec -1The melt viscosity at a desired value can be obtained by, for example, selecting the polyolefin that is the base resin of the resin sheet or a material other than the base resin contained in the encapsulant composition. Considerations for selecting a polyolefin include, for example, the molecular structure, molecular weight, and density of the polyolefin. The "melt viscosity" value can be adjusted by, for example, the type and number of polymerizations of the olefin, the length of the linear chain portion, the number and length of branched portions, and the type, number, and length of side chain portions, as the molecular structure of the polyolefin. Specifically, increasing the length of the linear chain portion tends to decrease the "melt viscosity" value, while decreasing the length of the linear chain portion tends to increase the "melt viscosity" value. Increasing the number of branched portions tends to decrease the "melt viscosity" value, while decreasing the number of branched portions tends to increase the "melt viscosity" value. Introducing polar groups into the side chain portion tends to increase the "melt viscosity" value. Increasing the molecular weight of the polyolefin tends to increase the "melt viscosity" value, while decreasing the molecular weight of the polyolefin tends to decrease the "melt viscosity" value. Increasing the density of the polyolefin tends to increase the "melt viscosity" value, while decreasing the density of the polyolefin tends to decrease the "melt viscosity" value. Examples of adjustments using materials other than the base resin contained in the encapsulant composition include adding a resin with a "melt viscosity" different from that of the base resin, or adding an inorganic component such as a filler.

[0059] Conventionally, the MFR value, which has been widely adopted as an index of the fluidity of encapsulant sheets, is measured at 190°C when measured in accordance with JIS K6922. However, this temperature is dissociated from the temperature at which encapsulant sheets for self-luminous displays actually melt during heat press processing. The reason for this is presumably that MFR is an evaluation of flowability under static load, and is an index assuming a low viscosity liquid. As an index for controlling the fluidity of resin during heat press processing, as mentioned above, the shear modulus at a temperature of 120°C, i.e., a shear rate of 2.43 × 10 sec measured at a temperature of 120°C, is used. -1By using the melt viscosity at 1000 kJ / cm2 as an index for optimizing the physical properties of an encapsulant sheet for a self-luminous display, it is possible to obtain an index for more effective and precise resin selection that is more suited to the actual use of the encapsulant sheet.

[0060] The melt viscosity is a measurement of the viscosity when melted. The "encapsulant sheet" of the present invention is not subjected to heat pressing at a temperature significantly higher than 120°C in order to prevent crosslinking from progressing during film formation, but is subjected to heat pressing at a temperature close to 120°C. On the other hand, polyolefins have a certain viscosity at temperatures around 120°C. Since the "encapsulant sheet" of the present invention is required to fill the gaps between micro-sized LED elements, it is important to pay attention to the viscosity of the encapsulant sheet.

[0061] The melt mass flow rate (MFR) of the "encapsulant sheet" is preferably 10.0 g / 10 min or more and 40.0 g / 10 min or less, more preferably 10.0 g / 10 min or more and 30.0 g / 10 min or less, and most preferably 10.0 g / 10 min or more and 25.0 g / 10 min or less. By setting the MFR of the "encapsulant sheet" to 10.0 g / 10 min or more, an encapsulant sheet with excellent molding properties can be obtained. Furthermore, by setting the MFR to 40.0 g / 10 min or less, the encapsulant sheet after crosslinking can maintain a high level of film thickness uniformity after hot press processing for integration into a self-luminous display device or the like.

[0062] In this specification, the "MFR" of an encapsulant sheet refers to the value measured at a stage after the completion of sheet formation of an encapsulant sheet obtained by forming an encapsulant composition containing a resin component and other additives into a sheet by a molding method such as extrusion melt molding, i.e., the MFR of the encapsulant sheet in an uncrosslinked state after film formation, in accordance with JIS K 7210, under conditions of 190°C and a load of 2.16 kg. Note that, with regard to the MFR when the encapsulant sheet is a multilayer film, the measured value obtained by measuring by the above-mentioned treatment while the encapsulant sheet is in a multilayer state in which all layers are laminated together is taken as the MFR value of the multilayer encapsulant sheet.

[0063] When the encapsulant sheet is a multilayer film, it is more preferable that each layer has a different MFR within a range that satisfies the essential constituent requirements of the present invention, and in this case, it is preferable that the layer with a higher MFR is disposed on the outermost layer side as a skin layer. Even when the encapsulant sheet of the present invention is a single-layer encapsulant sheet, it has sufficiently preferable transparency, heat resistance, and appropriate flexibility, but by disposing a layer with a relatively high MFR as the outermost layer in this way, it is possible to further improve adhesion and molding properties as a thermally crosslinkable encapsulant sheet while maintaining the above-mentioned preferable transparency and heat resistance.

[0064] The thickness of the "encapsulant sheet" of the present invention may be 3 μm or more and 1000 μm or less, and preferably 3 μm or more and 600 μm or less. A thickness of 1000 μm or less allows the "encapsulant sheet" of the present invention to exhibit sufficient molding properties. Specifically, during heat pressing with the LED elements covered, the resin constituting the encapsulant sheet can sufficiently fit into the irregularities on the LED module surface, achieving good gap-free lamination. Therefore, for example, if the LED elements are arranged so as to occupy half the area of ​​the surface covered by the encapsulant sheet, the "encapsulant sheet" of the present invention can adequately protect the LED elements from impact after integration into a self-luminous display or direct backlight by using an "encapsulant sheet" having a thickness of about half the height of the LED elements. On the other hand, the lower limit of the thickness of the "encapsulant sheet" is usually considered to be at least 3 μm or more in order to maintain the homogeneity of the film, but for example, if the LED element to be covered is a "very small-sized LED element" with a height of 6 μm or less, an extremely thin "encapsulant sheet" with a thickness of 3 μm can be used to cover it. However, if the LED element to be covered is a "micro-sized LED element" with a height of 10 μm or more, the thickness of the "encapsulant sheet" is preferably 5 μm or more.

[0065] The encapsulant sheet of the present invention may be a single-layer film, or may be a multilayer film composed of a core layer and skin layers disposed on both sides of the core layer. For example, in an encapsulant sheet that is a multilayer film composed of three or more layers, the thickness of the outermost layer is preferably 30 μm or more and 120 μm or less, and the thickness ratio of the intermediate layer composed of all layers other than the outermost layer to the outermost layer (outermost layer:intermediate layer:outermost layer) is preferably in the range of 1:3:1 to 1:8:1. This allows the encapsulant sheet as a whole to maintain desirable heat resistance while exhibiting desirable molding properties in the outermost layer.

[0066] Furthermore, the "encapsulant sheet" of the present invention can be made into a "black encapsulant sheet" having a black color by forming a film using a resin composition containing a black colorant as the "encapsulant composition." For example, by using such a "black encapsulant sheet" in a self-luminous display device comprising a light-shielding layer, it is possible to improve the contrast by reducing reflected light from the wiring substrate side and prevent the light from mixing between adjacent LED elements, thereby improving the display quality. In addition, it is also possible to simplify the layer structure of the self-luminous display device, contributing to improved productivity (see JP 2022-103204 A). Details of additives such as colorants used when the "encapsulant sheet" of the present invention is made into a "black encapsulant sheet" will be described separately below in the explanation of the encapsulant composition. In addition, "black" in this specification refers to a color in which the CIE color coordinates measured in accordance with JIS Z 8701-1999 using a C light source and a viewing angle of 2 degrees are -1.0≦a * ≦2.5 and -1.0≦b * ≦15.0, L * For values, 0≦L * This refers to a color tone in the range of ≦50.

[0067] Furthermore, the "encapsulant sheet" of the present invention can be formed into a "light-diffusing encapsulant sheet" that diffuses light emitted from an LED element by using a resin composition containing a light-diffusing agent as the "encapsulant composition" and forming a film from the resin composition. When the "encapsulant sheet" has a multilayer structure, the diffusing agent may be contained in only some of the layers. For example, by using such a "light-diffusing encapsulant sheet" in a direct backlight, the distance between the wiring board and the LED element, which was previously ensured by a spacer, can be ensured by this "light-diffusing encapsulant sheet." This eliminates the need for a diffusion plate, enabling a thinner direct backlight to be achieved (see JP 2021-9807 A). Details of additives such as colorants used when the encapsulant sheet of the present invention is made into a "light-diffusing encapsulant sheet" will be described separately below in the description of the encapsulant composition.

[0068] [Encapsulant composition] The encapsulant composition used in producing the encapsulant sheet of the present invention (hereinafter also simply referred to as "encapsulant composition") is a thermally crosslinkable resin composition containing a low-density olefin-based resin (preferably a polyethylene-based resin) as a base resin and a crosslinking agent as an essential component. In this specification, the term "base resin" refers to the resin with the largest content ratio among the resin components of a resin composition containing the base resin. When a mixed resin is made of the same type of resin but with different densities (for example, multiple polyethylenes each with a different density), the entire mixed resin is referred to as the base resin.

[0069] (base resin) The base resin of the encapsulant composition forming the encapsulant sheet of the present invention has a melting point of 45°C or higher and 60°C or lower, and has a shear rate of 2.43 x 10 sec measured at a temperature of 120°C. -1 The melt viscosity at 2.0 x 10 3 Pa·s or more 9.0×10 3A wide variety of olefin resins can be selected as long as they have a modulus within the Pa·s range. Among these, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), metallocene linear low-density polyethylene (M-LLDPE), and various polyethylene resins are preferably used.

[0070] Furthermore, among the various polyethylenes mentioned above, linear low-density polyethylene (LLDPE) has a narrow crystallinity distribution and uniform crystal size, so not only are there no large crystals, but the crystallinity itself is low, resulting in excellent transparency when processed into a sheet as an encapsulant sheet. Therefore, when an encapsulant sheet made of an encapsulant composition containing this as a base resin is placed on the light-receiving surface side of a solar cell element in a self-luminous display, it can better prevent a decrease in power generation efficiency due to attenuation of light incident on the solar cell element.

[0071] The density of the olefin resin used as the base resin of the encapsulant composition is 0.875 g / cm 3 More than 0.900g / cm 3 Preferably, it is 0.880 g / cm or less. 3 More than 0.890g / cm 3 The density of the base resin of the encapsulant composition is more preferably 0.875 g / cm or less. 3 By setting the density to 0.900 g / cm or more, the heat resistance of the sealing material sheet can be stably improved to a sufficient level. 3 By setting the thickness to the following range, the adhesion of the encapsulant sheet to the wiring board or the like can be maintained at a sufficiently preferable level.

[0072] Furthermore, the term "polyethylene resin" as used herein includes not only ordinary polyethylene obtained by polymerizing ethylene, but also resins obtained by polymerizing compounds having ethylenically unsaturated bonds such as α-olefins, resins obtained by copolymerizing a plurality of different compounds having ethylenically unsaturated bonds, and modified resins obtained by grafting other chemical species onto these resins.

[0073] Among these, a "silane copolymer obtained by copolymerizing an α-olefin and an ethylenically unsaturated silane compound as a comonomer" can be preferably used as part of the base resin of the encapsulant composition. By using such a resin, sufficient adhesive strength can be obtained between the encapsulant sheet and other laminate members such as a glass protective substrate or a solar cell element.

[0074] The content of the ethylenically unsaturated silane compound in the copolymer of an α-olefin and an ethylenically unsaturated silane compound is, for example, preferably 0.001% by mass or more and 15% by mass or less, more preferably 0.01% by mass or more and 5% by mass or less, and most preferably 0.05% by mass or more and 2% by mass or less, based on the total mass of the copolymer.

[0075] (Crosslinking agent) The crosslinking agent used in the encapsulant composition preferably has a one-hour half-life temperature of 120° C. or higher and 145° C. or lower, which allows the encapsulant composition according to the present invention to be a composition that can be melt-extruded at a temperature range of 110° C. or lower.

[0076] Specific examples of preferred crosslinking agents that satisfy the above conditions include peroxyketals such as n-butyl 4,4-di(t-butylperoxy)valerate, ethyl 3,3-di(t-butylperoxy)butyrate, and 2,2-di(t-butylperoxy)butane, and dialkyl peroxides such as di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-di(t-peroxy)hexyne-3, which can be preferably used as crosslinking agents to be added to the sealing material composition.

[0077] The content of the crosslinking agent in the encapsulant composition may be from 0.2% by mass to 1.2% by mass, and more preferably from 0.4% by mass to 0.8% by mass, relative to the base resin in the encapsulant composition. By setting the content of the crosslinking agent within the above range, the "encapsulant sheet" of the present invention can be provided with excellent heat resistance. As described above, the encapsulant sheet of the present invention is formed into a film without causing substantial crosslinking, and it is expected that the content of the crosslinking agent in the encapsulant sheet at the sheet stage after film formation will be in the range of from 0.1% by mass to 1.2% by mass.

[0078] (Crosslinking aid) The encapsulant composition preferably contains a cross-linking aid that is a polyfunctional monomer having a carbon-carbon double bond and / or an epoxy group, more preferably a polyfunctional monomer whose functional group is an allyl group, a (meth)acrylate group, or a vinyl group. This promotes an appropriate cross-linking reaction, thereby improving the heat resistance of the encapsulant sheet to a high level. In addition, the cross-linking aid reduces the crystallinity of the base resin, such as linear low-density polyethylene, that forms the encapsulant sheet, thereby maintaining transparency. This not only improves heat resistance, but also makes the transparency of the encapsulant sheet even more excellent.

[0079] Specific examples of crosslinking aids that can be used in the encapsulant composition include polyallyl compounds such as triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fumarate, and diallyl maleate; poly(meth)acryloxy compounds such as trimethylolpropane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, and 1,9-nonanediol diacrylate; and epoxy compounds containing a double bond and an epoxy group, such as glycidyl methacrylate, 4-hydroxybutyl acrylate glycidyl ether, and 1,6-hexanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, and trimethylolpropane polyglycidyl ether, each of which contains two or more epoxy groups. These may be used alone or in combination. Among the above cross-linking aids, TAIC is particularly preferred because it has good compatibility with linear low-density polyethylene, reduces crystallinity by cross-linking, maintains transparency, and is likely to exhibit a significant effect of imparting flexibility at low temperatures. The content of the cross-linking aid in the encapsulant composition is preferably 0.01% by mass or more and 3% by mass or less, more preferably 0.05% by mass or more and 2.0% by mass or less, relative to the base resin in the encapsulant composition.

[0080] [Other additives] The encapsulant composition may further contain other components. For example, hindered amine light stabilizers (HALS), ultraviolet absorbers, heat stabilizers, adhesion improvers, nucleating agents, dispersants, leveling agents, plasticizers, defoamers, flame retardants, and various other fillers may be added as appropriate. The content ratio of these additives varies depending on the particle shape, density, etc., but is preferably within the range of 0.001% by mass to 60% by mass of each additive in the encapsulant composition. The inclusion of these additives can impart stable mechanical strength over a long period of time and prevent yellowing, cracking, and other problems to the encapsulant composition.

[0081] (black colorant) When the "encapsulant sheet" of the present invention is a "black encapsulant sheet," the black colorant used to impart an appropriate color to the resin sheet is preferably a pigment-based material. For example, carbon black, which is commonly used as a black pigment, is one example of a preferred pigment. When coloring for display applications, black is often achieved by combining multiple dyes. In this case, however, uneven pressure during adhesive lamination can easily cause color unevenness. Furthermore, since dye-based materials are prone to dye degradation (fading), pigment-based materials are also preferred from the standpoint of heat resistance. However, if it is necessary to reduce the transmittance of a specific wavelength in order to expand the color tone range, an appropriate amount of dye can be used.

[0082] When carbon black is used as the black pigment, the content of carbon black in the resin component of the "black encapsulant sheet" may be adjusted appropriately within a range of 0.0001% by mass to 50% by mass, depending on the thickness of the "black encapsulant sheet" and the required color. When the thickness of the "black encapsulant sheet" exceeds 500 μm, the required black color can be expressed by setting the content of carbon black to 0.0001% by mass or more. When the thickness of the "black encapsulant sheet" is 10 μm or less, the content of carbon black may be adjusted within a range of 10% by mass to 50% by mass. By setting the content of carbon black within the above range, stable coloring with sufficiently little unevenness can be achieved.

[0083] When the "encapsulant sheet" of the present invention is to be a "black encapsulant sheet," it is more preferable to add a dispersant to the "encapsulant composition." Various metal soaps can be used as the dispersant. Furthermore, in addition to metal soaps, a low content of polyethylene wax or the like can also be used as the dispersant. Specific examples of preferred dispersants include lithium stearate, magnesium stearate, calcium stearate, barium stearate, zinc stearate, calcium laurate, barium laurate, zinc laurate, calcium ricinoleate, barium ricinoleate, zinc ricinoleate, and zinc octoate. Among these, calcium stearate, zinc stearate, zinc laurate, and the like are preferred from the viewpoint of the melting point of the resin. In particular, calcium stearate, which is often contained in ordinary polyethylene-based resins, can be preferably used as the dispersant because it does not deteriorate compatibility.

[0084] Furthermore, when the "encapsulant sheet" of the present invention is intended to be a "black encapsulant sheet," the combination with an antioxidant is also important in order to promote good dispersion of the black pigment, and it is preferable to add a phenolic or phosphorus-based antioxidant in a proportion of 200 ppm or more and 800 ppm or less to the resin component of the encapsulant composition.

[0085] (light diffusing agent) When the "encapsulant sheet" of the present invention is made into a "light-diffusing encapsulant sheet," the light diffusing agent used is not particularly limited as long as it can diffuse light from an LED element, but it is preferable that the light diffusing agent has a refractive index of 1.4 or more and 2.2 or less. Such a refractive index can be measured by the Becke method, minimum deviation method, deviation angle analysis, mode line method, ellipsometry, Abbe method, etc. Furthermore, it is preferable that the refractive index of the light diffusing agent has a predetermined refractive index difference from the base resin constituting the "encapsulant sheet." Specifically, this refractive index difference is preferably 0.03 or more, and more preferably 0.05 or more.

[0086] The light diffusing agent may be an organic material or an inorganic material. Specific examples of organic light diffusing agents include synthetic resins such as polymethyl methacrylate (PMMA) resin particles, melamine resin particles, silicone resin particles, styrene resin, polyurethane resin, polyester resin, fluorine-based resin, and copolymers thereof. These may be used alone or in combination of two or more. Specific examples of inorganic light diffusing agents include TiO2, SiO2, Al2O3, silicon, zirconia, glass, smectite, kaolinite, and the like. These may also be used alone or in combination of two or more.

[0087] From the viewpoint of dispersibility in the resin, the shape of the light diffusing agent is preferably particulate, and in this case, the average primary particle size (D50) of the light diffusing agent is preferably 0.1 μm or more and 50 μm or less, and more preferably 1 μm or more and 20 μm or less.

[0088] Furthermore, the content of the light diffusing agent in the "encapsulant composition" is preferably 0.1% by mass or more and 50% by mass or less. By setting the content of the light diffusing agent within this range, it is possible to reliably diffuse the light emitted from the LED element and also to prevent the light diffusing agent from becoming difficult to disperse and forming clumps. Note that when the "encapsulant sheet" has a multilayer structure, the content of the light diffusing agent refers to the proportion of the light diffusing agent in the layer containing the light diffusing agent.

[0089] <Method of manufacturing encapsulant sheet> The encapsulant sheet of the present invention can be produced by a method of melt-molding the "encapsulant composition" described in detail above. The encapsulant composition can be melt-molded by known molding methods, specifically, various molding methods such as injection molding, extrusion molding, blow molding, compression molding, and rotational molding. The lower limit of the molding temperature during molding may be a temperature above the melting point of the encapsulant composition. The upper limit of the molding temperature may be a temperature at which crosslinking does not start during film formation, depending on the one-minute half-life temperature of the crosslinking agent used, i.e., a temperature at which the gel fraction of the encapsulant composition can be maintained at 10% or less, preferably 0%. [Example]

[0090] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0091] <Production of encapsulant sheets for self-luminous displays> Each example and comparative example was produced using an encapsulant composition having the composition shown in Table 1 below. A linear low-density polyethylene resin (LLDPE) was used as the base resin (however, for each example and comparative example, a resin with a different molecular weight was used as needed), and Luperox TBEC (manufactured by Arkema Yoshitomi Co., Ltd.) was used as the crosslinking agent. The one-hour half-life temperature of this crosslinking agent is 121°C.

[0092] [Table 1]

[0093] <Evaluation example 1: Heat resistance> To evaluate heat resistance, a "heat creep test" was conducted using the method described below. In the "heat creep test," a 5 cm x 7.5 cm piece of the encapsulant sheet of the example or comparative example was first placed on a glass plate, and a 5 cm x 7.5 cm glass plate was then placed on top of it. A vacuum lamination process was then performed using a vacuum laminator for solar cell module manufacturing under conditions of a temperature of 150°C, a vacuuming time of 5 minutes, a press holding time of 10 minutes, and an upper chamber pressure of 50 KPa to prepare a "heat resistance evaluation sample." The large-sized glass was then placed vertically and left at 100°C for 168 hours. The distance traveled (mm) of the 5 cm x 7.5 cm glass plate after leaving the sample was measured, and the heat resistance of the "encapsulant sheet" of the present invention was evaluated based on the "evaluation criteria" described below. The evaluation results are shown in Table 2. (Evaluation criteria) A: 0 mm or more and less than 0.5 mm B: 0.5mm or more and less than 5mm C: 5mm or more

[0094] <Evaluation example 2: Molding properties> To evaluate heat resistance, a molding test was conducted using the following method. In the molding test, an LED module was prepared, in which micro-sized LED elements measuring 25 μm wide, 15 μm deep, and 2.5 μm high were arranged at 2 mm intervals on the surface of a 200 × 300 mm glass epoxy wiring substrate. A 300 μm-thick encapsulant sheet from any of the Examples and Comparative Examples was laminated on the LED element-mounted surface of the module. A 50 μm-thick ethylene tetrafluoroethylene (ETFE) film corona-treated on one side was then laminated on top of the encapsulant sheet as a surface protection film. The encapsulant sheet was then vacuum-laminated using a vacuum laminator for solar cell module manufacturing at a temperature of 150°C, a vacuuming time of 5 minutes, a press hold time of 10 minutes, and an upper chamber pressure of 50 kPa to produce a molding property test module. Each test module was then visually observed, and the molding property of the encapsulant sheet of the present invention was evaluated based on the following evaluation criteria. The evaluation results are shown in Table 2. (Evaluation criteria) A: The encapsulant sheet perfectly conforms to the unevenness of the LED element placement surface. No voids were observed. B: 2mm 2 Up to three bubbles were observed. C: 2mm 2 More than three bubbles within the area were observed, or a part of the encapsulant sheet did not completely conform to the unevenness of the facing surface on which the LED element was placed, resulting in the formation of a defective lamination area (void) near the LED element.

[0095] <Gel fraction of encapsulant sheet> A 1.0 g test piece was taken as a sample from each of the encapsulant sheets constituting the above-mentioned "heat resistance evaluation sample," and the gel fraction of each encapsulant sheet was measured by the "gel fraction measurement method" described in detail above. The measurement results are shown in Table 2.

[0096] <Melting point of encapsulant sheet> The melting point of each encapsulant sheet in an uncrosslinked state after film formation was measured by differential scanning calorimetry (DSC). The measurement results are shown in Table 2.

[0097] <Melt viscosity of encapsulant sheet> The shear rate of each encapsulant sheet in an uncrosslinked state after film formation was 2.43 × 10 sec -1 The "melt viscosity at room temperature" was measured in accordance with JIS K7199 using a Toyo Seiki Co., Ltd. Capillograph 1-B with a set temperature of 120°C, D=1 mm, and L / D=10. The measurement results are shown in Table 2.

[0098] [Table 2]

[0099] From Table 2, it can be seen that the "encapsulant sheet" of the present invention has sufficient molding properties for finely textured surfaces and also has high heat resistance that enables it to withstand use in particularly high-temperature environments. [Explanation of symbols]

[0100] 1. Encapsulating material sheet 2 Display panel 3 Diffuser 10 LED elements 11 LED light-emitting chips 12 Resin cover 13 Light diffusion lens 20 Wiring board 21 Support substrate 22 Wiring section 23 Solder layer 24 Adhesive layer 25 Insulating protective film 26 Reflective layer 30 LED modules 100, 100A, 100B Micro LED display device (self-luminous display) 200 Direct Backlight 300 LCD display (direct backlight type)

Claims

1. An encapsulant sheet for a self-luminous display or a direct backlight, The base resin is an olefin-based resin. The melting point is 45°C or higher and 60°C or lower, Shear rate of 2.43 x 10 sec in all layers of the resin sheet measured at a temperature of 120 ° C. －１ The melt viscosity at ３ Pa・s or more 9.0×10 ３ Pa s or less, The resin component contains a crosslinking agent in an amount of 0.1% by mass or more and 1.2% by mass or less. Sealing material sheet.

2. The sealing material sheet according to claim 1; A display panel; a light-emitting module in which a plurality of light-emitting elements are mounted on a wiring substrate; the sealing material sheet covers the light-emitting element and the wiring board and is laminated on the light-emitting module, The display panel is laminated on the sealing material sheet. Self-luminous display.

3. The gel fraction of the sealing material sheet is 50% or more and 90% or less.

3. The self-luminous display according to claim 2.

4. The light-emitting element is an LED element, The width and depth of the LED element are both greater than 50 μm and not greater than 300 μm, and the height is not greater than 200 μm, The arrangement interval between the LED elements is 0.03 mm or more and 100 mm or less.

4. The self-luminous display according to claim 2 or 3.

5. The light-emitting element is an LED element, The width and depth of the LED element are both 50 μm or less, and the height is 10 μm or less, The arrangement interval between the LED elements is 0.005 mm or more and 5 mm or less.

4. The self-luminous display according to claim 2 or 3.

6. The sealing material sheet according to claim 1; a light-emitting module in which a plurality of light-emitting elements are mounted on a wiring substrate; the sealing material sheet covers the light-emitting element and the wiring board and is laminated on the light-emitting module; Direct type backlight.

7. The direct type backlight according to claim 6 ; A diffusion plate; a display surface panel; the diffusion plate is laminated on the sealing material sheet that constitutes the direct-type backlight; liquid crystal display.

Images