Resin sheets, optoelectronic devices, and electronic equipment

Abstract

The present invention provides a resin sheet that can suppress ion migration even when optoelectronic semiconductor elements are mounted at high density or miniaturized, and that exhibits excellent embedding and adhesion properties, as well as optoelectronic semiconductor devices and electronic devices using the same. [Solution] A resin sheet 30 for forming an insulating layer 3 on a substrate 1 on which multiple optical semiconductor elements 2 are mounted, wherein the chlorine elution amount of the resin sheet 30 is 500 ppm or less, the coefficient of linear expansion of the cured resin sheet 30 at -50 to 50°C is 20 to 250 ppm / °C, the storage modulus of the resin sheet 30 at 60°C (G'60) is 100 kPa to 100 MPa, and the content of the flow modifier in the resin sheet 30 is 0.3 to 30 mass% relative to the resin sheet 30.

Description

[Technical Field]

[0001] This disclosure relates to resin sheets, as well as to optoelectronic devices and electronic equipment. [Background technology]

[0002] In thin displays for smartphones, tablets, and personal computers, the development of display technologies using optoelectronic semiconductor elements such as organic EL elements, quantum dot light-emitting elements, and micro-LED elements is being actively pursued. For these technologies to become widespread, technologies that enhance long-term reliability are essential, and methods to improve reliability through the use of resin materials to protect various elements have been proposed. Patent Document 1 proposes a sheet-like encapsulant comprising an encapsulant resin layer containing a polyolefin polymer and a specific amount of a tackifier of a specific type, wherein the water vapor permeability and electrical conductivity are within a specific range. According to the encapsulant described in the same document, it has excellent moisture barrier properties and can suppress migration due to dendrite precipitation. Patent Document 2 discloses a curable resin composition that contains a polymer resin with a glass transition temperature of 20°C or lower and a weight-average molecular weight of 10,000 or more, an epoxy resin, and carbon black, and does not contain inorganic fillers, and yields a cured product with excellent light-shielding properties (transmittance of less than 0.5% in the visible light band). According to the same document, it is possible to provide a curable resin composition that has sufficient light-shielding properties and excellent dispersibility and sedimentation suppression of carbon black. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-168378 [Patent Document 2] Japanese Patent Publication No. 2022-22562 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] With the growing need for lighter, thinner, and smaller displays, various elements such as organic EL, quantum dots, and micro-LEDs are becoming more densely packed, and wiring circuits, wiring widths, and wiring spacing are becoming narrower. As a result of the increased density of elements, the gaps between elements are becoming smaller, and the problem of dielectric breakdown due to ion migration between elements is becoming more serious than ever before. In addition, because the area of ​​the same material on the substrate becomes smaller due to the reduction in element size and the narrowing of the gaps between elements, there is a problem that resin materials are more prone to peeling than before. Furthermore, the problem of poor embedding in recesses due to uneven surfaces is becoming more serious than before.

[0005] This disclosure has been made in view of the above-mentioned problems, and aims to provide a resin sheet for forming an insulating layer on a substrate on which multiple optical semiconductor elements are mounted, which can suppress ion migration and has excellent embedding and adhesion properties, even when the size of the optical semiconductor elements is reduced or the optical semiconductor elements are mounted at high density, as well as an optical semiconductor device and an electronic device. [Means for solving the problem]

[0006] As a result of diligent research by the inventors, we have found that the above problems can be solved by the resin composition shown below, and have completed the present invention described in [1] to [6] below. [1]: A resin sheet for forming an insulating layer on a substrate on which multiple optical semiconductor elements are mounted, wherein the amount of chlorine eluted when 10 g of the resin sheet is immersed in 90 g of purified water at 90°C for 24 hours is 500 ppm or less, the coefficient of linear expansion of the cured product obtained by heat-treating the resin sheet at 150°C for 120 minutes is 20 to 250 ppm / °C at -50 to 50°C, the storage modulus of elasticity (G'60) at 60°C obtained by dynamic viscoelasticity measurement of the resin sheet is 100 kPa to 100 MPa, and the resin sheet contains a flow regulator, wherein the content of the flow regulator is 0.3 to 30% by mass relative to 100% by mass of the solid content of the resin sheet. [2]: The resin sheet according to [1], wherein the flow regulator is a hydrogenated hydrocarbon resin. [3]: The resin sheet according to [1] or [2], wherein the softening temperature of the flow regulator is 70 to 140°C. [4]: A resin sheet described in any of [1] to [3], having an optical density of 4 or higher. [5]: A resin sheet as described in any of [1] to [3], having a reflectance of 70% or more. [6]: The resin sheet according to any one of [1] to [3], wherein the cured product obtained by heat-treating the resin sheet at 150°C for 120 minutes has a total light transmittance in the visible light band of 80% or more and a refractive index of 1.47 to 1.56. [7]: A resin sheet according to any one of [1] to [6], containing a resin (A) with a weight-average molecular weight of 10,000 or more, wherein resin (A) contains a (meth)acrylic resin. [8]: The resin sheet may contain a thermal polymerization initiator (B) and a silane coupling agent (C), as described in any of [1] to [7]. [9]: A resin sheet as described in any of [1] to [8], having a sulfur content of 1000 ppm or less.

[10] : An optoelectronic semiconductor device having a substrate on which a plurality of optoelectronic semiconductor elements are mounted, and an insulating layer formed on the substrate, wherein the insulating layer is a cured resin sheet according to any of [1] to [9].

[11] : An electronic device having the optoelectronic device described in

[10] . [Effects of the Invention]

[0007] According to this disclosure, a resin sheet for forming an insulating layer on a substrate on which multiple optical semiconductor elements are mounted can suppress ion migration even when the size of the optical semiconductor elements is reduced or the optical semiconductor elements are mounted at high density, and the present invention provides a resin sheet, optical semiconductor device, and electronic device with excellent embedding and adhesion properties. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic top view of the main components of the mounting substrate for a micro-LED display device. [Figure 2]Cross-sectional view taken along the line II-II of FIG. 1. [Figure 3] Schematic cross-sectional view of a main part of a mounting substrate of a micro-LED display device according to a modified example. [Figure 4] Schematic cross-sectional view of a main part of a mounting substrate of a micro-LED display device according to another modified example. [Figure 5] Schematic cross-sectional view showing an example of a laminated sheet. [Figure 6] Schematic cross-sectional view for explaining a manufacturing process of a mounting substrate. [Figure 7] Schematic cross-sectional view for explaining the structure of a test substrate.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, an example of an embodiment to which the present disclosure is applied will be described. The present disclosure includes modified examples implemented within a range not changing the gist of the present disclosure. Numerical values specified using "~" in this specification include the numerical values described before and after as the minimum value and the maximum value. "(Meth)acrylic acid" means acrylic acid and / or methacrylic acid, and "(meth)acryloyl" means acryloyl and / or methacryloyl. In addition, various components appearing in this specification can be used alone or in combination of two or more unless otherwise noted. When two or more are used in combination, the content thereof uses the total value. In addition, the numerical values specified in this specification are values obtained by the method of [Examples] described later.

[0010] 1. Optical Semiconductor Device and Electronic Device The optical semiconductor device according to the present embodiment has an optical semiconductor element mounting substrate on which optical semiconductor elements such as quantum dot light-emitting elements, organic EL elements, and micro-LED elements are mounted. Hereinafter, an example in which the optical semiconductor device of the present embodiment is applied to a micro-LED display device will be described. FIG. 1 shows an example of a schematic top view of a main part of a micro-LED element mounting substrate (hereinafter, also referred to as a micro-LED substrate). As shown in the figure, on a substrate 1, a plurality of micro-LEDs 2 are arranged in an array in the X direction and in the Y direction orthogonal to the X direction. The Z direction in the figure is the thickness direction of the substrate 1.

[0011] The micro LED 2 is a fine LED element (chip) with a thickness of, for example, 100 μm or less, and includes a red (R) element, a green (G) element, a blue (B) element, and the like. The substrate 1 has, for example, a thin film transistor (TFT) for driving the micro LED 2, an interlayer insulating layer, an electrode for connecting the TFT and the micro LED 2, wiring, and a protective layer for protecting the electrode and the like on a base substrate. Examples of the base substrate include glass, plastic (for example, acrylic, urethane, polycarbonate, epoxy, polyimide, or polyethylene terephthalate), paper, cloth, aluminum, and ceramic.

[0012] FIG. 2 shows a cross-sectional view of the cut portion II-II of FIG. 1. As shown in the figure, an insulating layer 3 is formed in the gap between the micro LEDs 2 on the substrate 1. The insulating layer 3 functions as a sealing layer and plays a role of fixing the micro LED 2 to prevent detachment. The insulating layer 3 can take various coating forms. For example, in addition to the configuration shown in FIG. 2, as shown in FIG. 3, the insulating layer 3 covers the gap and the upper surface of the micro LED, and seals the micro LED 2; as shown in FIG. 4, the insulating layer 3 forms a partition wall higher than the height of the micro LED 2. The insulating layer 3 is a cured product of the resin sheet (hereinafter also referred to as the present resin sheet) of the present disclosure, and is obtained by curing the present resin sheet.

[0013] 2. Resin Sheet The present resin sheet satisfies the following (i) to (iv). (i) When 10 g of the resin sheet is immersed in 90 g of purified water at 90° C. for 24 hours, the chlorine elution amount eluted is 500 ppm or less. (ii) The linear expansion coefficient of the cured product obtained by heat-treating the resin sheet at 150° C. for 120 minutes at -50 to 50° C. is 20 to 250 ppm / ° C. (iii) The storage elastic modulus (G'60) at 60° C. obtained by dynamic viscoelasticity measurement of the resin sheet is 100 kPa to 100 MPa. (iv) The resin sheet contains a flow regulator, and the content of the flow regulator is 0.3 to 30% by mass based on 100% by mass of the resin sheet. In this specification, "cured product" refers to a state in which the curing treatment has progressed sufficiently and further treatment will not substantially advance the crosslinking reaction. This resin sheet is either uncured or partially cured (so-called B-stage) in which the curing treatment has progressed.

[0014] The resin sheet may be single-layered or multi-layered. The resin sheet is formed from a resin composition. In the case of multi-layered sheets, it is sufficient that the resin sheet satisfies (i) to (iv) above, and each layer does not need to satisfy (i) to (iv). However, it is preferable that the bottom layer of the resin sheet, which is placed on the substrate side, satisfies (i) to (iv), and it is more preferable that each layer satisfies (i) to (iv).

[0015] By using this resin sheet that satisfies all of the above conditions (i) to (iv), it becomes possible to suppress ion migration even when miniaturizing micro-LED elements or mounting micro-LEDs at high density, and it also offers excellent embedding and adhesion properties.

[0016] A flow modifier is a compound that maintains fluidity during the pressing process of resin sheets while suppressing fluidity after embedding and curing. The flow modifier is a resin. The flow modifier is a resin with a Mw of less than 10,000, and is distinguished from resin (A), described later, by its Mw.

[0017] By including 0.3 to 30% by mass of a fluidity regulator per 100% by mass of the resin sheet, the fluidity of the resin sheet is improved during the pressing process in which the resin sheet is applied to electronic components, effectively enhancing its embedding ability. As a result, it becomes possible to reduce the pressure conditions in the pressing process. This is because the fluidity regulator reduces the viscoelasticity of the resin sheet at high temperatures, causing the sheet to soften even with relatively weak heating, thus enabling embedding at low pressure. Furthermore, the addition of a flow modifier increases the viscoelasticity from low to room temperature, thereby suppressing the flow of the resin sheet after embedding and curing. This prevents deformation of the coated insulating layer, resulting in improved retention of the insulating layer and enabling more secure fixing of electronic components. In addition, the addition of a flow modifier effectively suppresses ion migration. The flow modifier is suitable for coating uneven surfaces with electronic components and is particularly suitable for micro-LEDs where miniaturization and high density are required.

[0018] The insulating layer 3 may have functions other than insulation. Specific examples include light diffusion prevention, light shielding, shielding, light leakage prevention, water vapor barrier properties, wavelength conversion, light reflectivity, high refractive index, low refractive index, heat dissipation, and sealing properties.

[0019] This resin sheet offers excellent productivity because it can form an insulating layer on an array of optical semiconductor elements on a substrate in a single application. In addition to single-application coating, this resin sheet may also be used for partial coating. For example, it may be used to seal between R, G, and B element units.

[0020] As the density of micro-LEDs 2 increases, short circuits in the electrodes and wiring formed on the substrate 1 become more likely, leading to serious malfunctions in electronic equipment. By forming an insulating layer using this resin sheet, short circuits in the electrodes and wiring formed on the substrate 1 can be effectively suppressed. The main reason for this is that this resin sheet satisfies (iv) and (i) above, that is, it contains 0.3 to 30% by mass of the flow regulator relative to the resin sheet, and the chlorine elution amount is 500 ppm or less, which effectively suppresses the phenomenon of metals such as copper used as electrodes and wiring formed on the substrate detaching and ionizing, and suppresses ion migration to other electrodes and wiring. The chlorine elution amount is preferably 400 ppm or less, more preferably 300 ppm or less, and even more preferably 200 ppm or less. The lower limit of the chlorine elution amount is not limited, but it is preferable to contain as little chlorine as possible, and the closer to 0 ppm, the better. Here, "chlorine" refers to chloride ions.

[0021] The amount of chlorine eluted can be measured using known methods such as ion chromatography (IC) or ICP-MS. The amount of chlorine eluted in this disclosure is the value measured by the method described in the examples below. To reduce the amount of chlorine eluted, it is effective to suppress the chlorine content of the resin composition that forms the resin sheet. Specifically, it is preferable to select a reagent grade that does not contain chlorine derived from impurities as a compounding component, or to avoid using chlorine-containing compounds during synthesis. If it is unavoidable to use a chlorine-containing compound during the synthesis of raw materials, it is effective to repeatedly purify the resulting compound or to increase the weight-average molecular weight of the resin used as a binder component. For example, when an epoxy compound is synthesized using a chlorine-containing compound, chlorine may remain as an impurity in the epoxy compound. Therefore, it is preferable to avoid using such epoxy compounds or to reduce their content.

[0022] Furthermore, the amount of chlorine leached from the insulating layer 3, which is the cured product of this resin sheet, may be higher than the amount of chlorine leached from the resin sheet itself. The main reason for this is chlorine migration from materials in contact with the insulating layer 3. For example, chlorine may migrate to the insulating layer 3 when a substrate containing a small amount of chlorine is used as the substrate 1, when a paper phenol substrate containing chlorine in the bleaching agent is used, or when a chlorine-containing compound is used as a component of the protective film (not shown). While it is not essential that the amount of chlorine leached from the insulating layer 3 satisfies the above (i), it is preferable that the insulating layer 3 also satisfies the above (i).

[0023] As the density of micro-LEDs 2 increases, a high degree of conformability of the insulating layer 3 to the uneven shape is required, making the insulating layer 3 prone to peeling. In addition, gaps tend to form between the insulating layer and the adherend at the corners of the uneven areas. This resin sheet provides an insulating layer 3 with excellent embedding properties, adhesion, insulation, and storage stability. The reason for the excellent embedding properties is thought to be mainly because this resin sheet satisfies (iv) and (iii) above, allowing for uniform pressure to be diffused across the resin sheet during the heating press process in which the resin sheet is embedded in the gaps between the optical semiconductor elements, thereby promoting deformation that conforms to the uneven shape. The reason for the excellent adhesion is thought to be that by using a resin sheet that satisfies (ii) to (iv) above, the fluidity can be appropriately increased, preventing the formation of gaps due to poor embedding at the corners of the micro-LEDs 2. The reason for the excellent insulating properties is thought to be that (i) above suppresses the ionization of metals in electrodes and wiring such as substrate 1, while (ii) and (iv) above effectively suppress the movement of metal ions in insulating layer 3, and furthermore, by combining these with (iii) above, an insulating layer with excellent adhesion and storage stability and high reliability is obtained.

[0024] The coefficient of linear expansion of the cured product at -50 to 50°C is preferably 40 to 200 ppm / °C, more preferably 60 to 150 ppm / °C, and even more preferably 70 to 130 ppm / °C. The storage modulus (G'60) of the resin sheet at 60°C is preferably 500 kPa to 50 MPa, and more preferably 1000 kPa to 10 MPa.

[0025] The loss tangent (tanδ60) at 60°C obtained by dynamic viscoelasticity measurement of the resin sheet is preferably 0.6 to 1.9, more preferably 0.7 to 1.6, and even more preferably 0.9 to 1.3. By setting tanδ60 to 0.6 to 1.9, the pressure applied to the resin sheet during the pressing process is appropriately transmitted, resulting in better embedding properties. Tanδ60 is the ratio of the loss modulus / storage modulus at 60°C obtained by dynamic viscoelasticity measurement in the torsional mode at a frequency of 10 Hz and a temperature of -50 to 150°C, and can be measured by the method described in the examples below.

[0026] The content of the flow regulator is 0.3% by mass or more based on 100% by mass of the resin sheet, with a preferred lower limit of 0.4% by mass, more preferred of 0.5% by mass, even more preferred of 0.8% by mass, 1.2% by mass, and even more preferred of 3% by mass. The preferred upper limit of the content is 30% by mass, more preferred of 28% by mass, even more preferred of 26% by mass, 24% by mass, 22% by mass, and even more preferred of 19% by mass.

[0027] The sulfur content of this resin sheet is preferably 1,000 ppm or less. By limiting the sulfur content to 1,000 ppm or less, short circuits of electrodes and wiring formed on the substrate 1 can be more effectively suppressed. The main reason for this is thought to be that sulfidation reactions with metal ions such as silver can be suppressed, the phenomenon of metals such as copper in the electrodes and wiring formed on the substrate detaching and ionizing can be effectively suppressed, and ion migration to other electrodes and wiring can be suppressed. In addition, adhesion is improved. The sulfur content is more preferably 500 ppm or less, and even more preferably 300 ppm or less. There is no lower limit to the sulfur content of the resin sheet, but it is preferable to be as close to 0 ppm as possible. The sulfur content can be measured using known methods such as ion chromatography (IC) or ICP mass spectrometry (ICP-MS).

[0028] The gel fraction of the cured resin sheet is preferably 45-98%, more preferably 50-95%, and even more preferably 60-92%. In addition to (i) to (iv) above, by further setting the gel fraction to 45-98% in this resin sheet, the flow of metal ions such as silver and copper is more effectively suppressed, resulting in superior migration properties and adhesion.

[0029] This resin sheet may be composed of multiple layers having different functions. For example, examples of resin sheets include any combination of a white layer exhibiting light reflectivity / a black layer exhibiting light shielding, a high refractive index layer exhibiting high refractive index / a black layer exhibiting light shielding, a high refractive index layer exhibiting high refractive index / a wavelength conversion layer, and a heat dissipation layer / a high refractive index layer.

[0030] The resin sheet can be manufactured by known methods. For example, it can be formed by coating a liquid resin composition, which is prepared by adding an arbitrary solvent to the components constituting the resin sheet to adjust its viscosity. The film thickness of the resin sheet can be appropriately selected depending on the application and the height of the optoelectronic semiconductor device. The thickness of the resin sheet is usually about 1 to 300 μm. The lower limit of the thickness is more preferably 3 μm, even more preferably 5 μm, and even more preferably 10 μm. The upper limit of the thickness is more preferably 150 μm, even more preferably 100 μm, and even more preferably 50 μm. The components of the resin sheet (resin composition) will be described below.

[0031] As described above, this resin sheet contains a flow regulator and further contains a curable component. From the viewpoint of film-forming properties and handling ease of the resin sheet, and from the viewpoint of obtaining a resin sheet that satisfies (ii) and (iii) above, it is preferable to include a resin (A) with a weight-average molecular weight (Mw) of 10,000 or more. Resin (A) preferably contains a curable resin. Oligomers and / or monomers may be used as the curable component. Furthermore, a flow regulator is included from the viewpoint of improving the embedding properties of the resin sheet during the manufacturing process and the reliability of the insulating layer, which is a cured product formed from the resin sheet. From the viewpoint of improving the adhesion of the insulating layer, which is a cured product of the resin sheet, to the adherend, it is preferable to include a thermal polymerization initiator (B) and / or a silane coupling agent (C), and the combined use of a thermal polymerization initiator (B) and a silane coupling agent (C) is more preferable. Resin (A) may also contain a resin that functions as a dispersant for dispersing inorganic fillers and / or colorants.

[0032] 2-1. Flow regulators The softening point of the fluidity regulator can be designed as appropriate, but from the viewpoint of appropriately adjusting the fluidity in the aforementioned pressing process, it is preferable to have a softening point of 150°C or lower, and from the viewpoint of suppressing the fluidity of the sheet after embedding and curing, it is preferable to have a softening point of 65°C or higher. The upper limit of the softening point is more preferably 140°C, and even more preferably 130°C. The lower limit of the softening point is more preferably 70°C, and even more preferably 80°C.

[0033] The flow modifier is preferably a hydrocarbon resin without unsaturated bonds, and if it has unsaturated bonds, hydrogenation treatment is preferred. That is, in the case of a hydrocarbon resin with unsaturated bonds, a hydrogenated hydrocarbon resin is preferred, and a hydrogenated aromatic hydrocarbon resin is more preferred. Weather resistance can be improved by having no or reduced unsaturated bonds in the flow modifier. Furthermore, durability can be increased by improving the cohesive force of the insulating layer.

[0034] From the viewpoint of maintaining close contact with the substrate immediately after embedding, preventing deformation of the insulating layer after coating, preventing bleeding during storage of the resin sheet, and avoiding excessive fluidity during embedding, the flow regulator preferably has an acid value and / or a hydroxyl value, and more preferably has both an acid value and a hydroxyl value. The acid value of the flow regulator is preferably 0.5 to 400 mg KOH / g, and the hydroxyl value of the flow regulator is preferably 0.5 to 80 mg KOH / g. The upper limit of the acid value is more preferably 380 mg KOH / , even more preferably 360 mg KOH / , and even more preferably 300 mg KOH / . The lower limit of the acid value is more preferably 0.8 mg KOH / , even more preferably 1 mg KOH / , and even more preferably 1.5 mg KOH / . The upper limit of the hydroxyl value is more preferably 70 mg KOH / , even more preferably 60 mg KOH / , and even more preferably 50 mg KOH / . The lower limit of the hydroxyl value is more preferably 0.8 mg KOH / , even more preferably 1.2 mg KOH / , and even more preferably 2 mg KOH / . It is preferable that the flow regulator does not contain amines.

[0035] At room temperature, the flow regulator interacts with the resin through hydrogen bonding, thus suppressing the molecular motion of resin (A), as described later. Furthermore, this interaction with resin (A) restricts the free movement of the flow regulator itself, making bleeding less likely. On the other hand, during heating, the hydrogen bonds between resin (A) and the flow regulator are broken, and the flow regulator functions as a freely moving "flow component." At this time, the effect of suppressing the movement of resin (A) weakens, improving overall fluidity. Moreover, the flow regulator acts like a lubricant, aiding in the dispersion of resin (A) and promoting its uniform flow. If the flow regulator possesses both acid and hydroxyl values, a gradient occurs in the rate at which hydrogen bonds are broken, preventing the resin (A) from flowing too rapidly and allowing it to proceed in a controlled manner. Therefore, the resin spreads more uniformly during the embedding process, achieving a good embedding state. Furthermore, immediately after embedding this resin sheet into electronic components, the adhesion between the resin (A) and the embedded object is insufficient, making it prone to delamination. In addition, because the resin (A) is distorted by the embedding process, stress is generated that tries to return it to its original shape. However, because the flow modifier has an acid value, a hydrogen bond network is formed, and this stress can suppress deformation. Moreover, because the flow modifier has an acid value, it also has the effect of maintaining adhesion to the substrate immediately after embedding. In this way, delamination of the resin sheet during heat dissipation and curing after the embedding process can be prevented, and the occurrence of embedding defects can be suppressed.

[0036] The flow regulator can be one or more of the conventionally known types. Specifically, examples include rosin and its derivatives (e.g., hydrogenated rosin, disproportionated rosin, polymerized rosin, acrylic acid modified rosin, fumaric acid modified rosin, maleic acid modified rosin, and esterified rosins of these rosins such as alcohol, glycerin, and pentaerythritol), terpene resins and their derivatives (e.g., terpene resins derived from α-pinene and β-pinene, terpene phenol resins, aromatic modified terpene resins, hydrogenated terpene resins), petroleum resins and their derivatives (aliphatic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins, alicyclic petroleum resins), coumarone-indene resins, phenol resins, styrene resins and their derivatives (e.g., styrene oligomers, copolymers of styrene and α-methylstyrene), etc. Among these, rosin and its derivatives, petroleum resins, and styrene resins with a softening temperature in the range of 70 to 140°C can be suitably used. From the viewpoint of improving weather resistance, hydrogenated hydrocarbon resins are preferred as flow regulators, and hydrogenated aromatic hydrocarbon resins are more preferred.

[0037] The flow regulator is preferably solid at room temperature. The flow regulator that is solid at room temperature is not particularly limited, but examples include rosin resin, rosin ester resin, terpene phenol resin, terpene resin, coumarone resin, petroleum resin, etc.

[0038] Examples of flow regulators include Arakawa Chemical Co., Ltd.'s "Alcon P-90, P-100, P-115, P-125, P-140, M-90, M-100, M-115, M-135, Pencel A, A7, C, D-125, D-135, D-160, KK, Super Ester L, A-18, A-75, A-100, A-115, A-125, Pine Crystal KR-85, KR-612, KR-614, KE-100, KE-311, PE-590, KE-359, KE-604, KR-120, KR-140, D-6011, KE-615-3, KM-1500, KR-50M, Ester Gum AA-G, AA-L, AA-V, 105, AT" Examples include "YS Resin PX1250, 1150, 1000, 800, 1150N, 300N, YS Polystar U130, 115, YS Polystar T160, 145, 130, 115, 100, YS Polystar S145, YS Polystar G160, 125, YS Polystar N125, YS Polystar K140, 125, YS Polystar TH130, YS Polystar UH115, Clearon P150, 135, 125, 115, 105, 85, Clearon M125, 115, 105, Clearon K100, 4100, YS Resin TO125, 115, 105, 85, and YS Resin SX100" manufactured by Yasuhara Chemical Co., Ltd.

[0039] 2-2. Resin (A) Resin (A) is a resin with an Mw of 10,000 or more. Including resin (A) with an Mw of 10,000 or more can improve the film-forming properties of the resin sheet. Furthermore, by using a portion of resin (A) as a dispersant for inorganic fillers containing inorganic pigments or organic fillers containing organic pigments, the uniform dispersion of inorganic fillers containing inorganic pigments or organic fillers containing organic pigments within the resin sheet can be improved. The upper limit of Mw for resin (A) is preferably 1,000,000, more preferably 500,000, even more preferably 300,000, and even more preferably 200,000. The lower limit of Mw for resin (A) is more preferably 13,000, even more preferably 20,000, and even more preferably 30,000.

[0040] Resin (A) is preferably a thermosetting resin, a photocurable resin, and / or a thermoplastic resin. From the viewpoint of improving the reliability of the resin sheet, such as storage stability and embedding properties, it is preferable that resin (A) contains a thermosetting resin. The thermosetting resin may be a self-crosslinking resin or a resin that reacts with a thermal polymerization initiator (B) and / or a crosslinking agent to form a crosslinked structure. The content of resin (A) is preferably 40 to 98% by mass, preferably 45 to 97% by mass, and more preferably 50 to 96% by mass, per 100% by mass of the resin sheet. If there are two or more types of resin (A), this is the total content.

[0041] Resin (A) is used in one or more forms. Specific examples include (meth)acrylic resin, maleic acid resin, polybutadiene resin, polyester resin, condensation-type polyester resin, addition-type polyester resin, melamine resin, polyurethane resin and polyurethane urea resin (urethane-based resins), epoxy resin, polycarbonate resin, oxetane resin, phenoxy resin, polyimide resin, polyamide-imide resin, alkyd resin, amino resin, polylactic acid resin, oxazoline resin, benzoxazine resin, silicone resin, and fluororesin. From the viewpoint of improving conformability to uneven shapes, it is preferable to include at least one of (meth)acrylic resin, urethane-based resin, polycarbonate resin, and polyamide resin. Among these, (meth)acrylic resin (α) is more preferable from the viewpoint of adhesion to the adherend and zipping properties.

[0042] Resin (A) may be a thermoplastic resin, a photocurable resin, or a thermosetting resin, but from the viewpoint of obtaining a highly reliable insulating layer 3, it is preferable that it has one or more functional groups that can be used for polymerization / crosslinking reactions by heat or light. The functional groups may be appropriately selected depending on the reactivity with other resins (A) or with the thermal polymerization initiator (B) and crosslinking agent described later, and self-crosslinkable functional groups may also be used. Examples of functional groups include hydroxyl groups, carboxyl groups, amino groups, epoxy groups, oxetanyl groups, oxazoline groups, oxazine groups, aziridine groups, thiol groups, isocyanate groups, blocked isocyanate groups, silanol groups, (meth)acryloyl groups, N-vinyl groups, vinyl ether groups, allyl groups, and unsaturated carboxylic acid groups. Radical polymerizable functional groups such as (meth)acryloyl groups, N-vinyl groups, vinyl ether groups, allyl groups, and unsaturated carboxyl groups are preferred, and (meth)acryloyl groups are more preferred from the viewpoint of storage stability.

[0043] The resin (A) preferably contains a thermosetting resin from the viewpoint of providing a highly reliable insulating layer with excellent adhesion and storage stability. The thermosetting resin is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and may also be 100% by mass, based on 100% by mass of resin (A).

[0044] Resin (A) preferably contains a thermosetting resin having a reactive functional group that forms a crosslinked structure by a thermal polymerization initiator (B), and more preferably has a reactive functional group that reacts with the functional group of the crosslinking agent by the thermal polymerization initiator (B) to form a crosslinked structure. The functional group that can be used in the thermal polymerization reaction of the thermal polymerization initiator (B) preferably has one or more of the following: (meth)acryloyl group, N-vinyl group, vinyl ether group, allyl group, or unsaturated carboxyl group, and among these, the (meth)acryloyl group is more preferred.

[0045] The acid value of resin (A) is preferably 1 to 50 mgKOH / g, more preferably 3 to 30 mgKOH / g, and even more preferably 5 to 20 mgKOH / g. Setting the acid value of resin (A) to 1 mgKOH / g or higher optimizes the crosslinking density with the crosslinking agent while maintaining good intermolecular forces with the adherend, improving light resistance, adhesion, and zipping properties. Setting the acid value of resin (A) to 50 mgKOH / g or lower maintains good intermolecular forces with the adherend and allows for appropriate adjustment of the residual amount of carboxyl groups after the crosslinking reaction, which promotes yellowing of resin (A). This improves light resistance, adhesion, and zipping properties. The acid value was measured by the method described in the examples below. Examples of suitable thermosetting resin (A) include the aforementioned resins having carboxyl groups and / or hydroxyl groups. When there are multiple types of resin (A), it is preferable that the total acid value of the resins (A) used has the above-mentioned acid value. The same applies to the hydroxyl value.

[0046] The hydroxyl value of resin (A) is preferably 1 to 45 mgKOH / g, more preferably 2 to 35 mgKOH / g, and even more preferably 3 to 25 mgKOH / g. By setting the hydroxyl value of resin (A) to 1 mgKOH / g or higher, the intermolecular forces with the adherend are maintained well while optimizing the crosslinking density with the crosslinking agent, improving heat resistance, fluidity during the embedding process, and zipping properties. By setting the hydroxyl value of resin (A) to 45 mgKOH / g or lower, the intermolecular forces with the adherend are maintained well, and the amount of residual hydroxyl groups after the crosslinking reaction that promotes yellowing of resin (A) can be appropriately adjusted. As a result, heat resistance and zipping properties are improved. The hydroxyl value was measured by the method described in the examples below. Examples of suitable thermosetting resin (A) include the aforementioned resin having hydroxyl groups.

[0047] When resin (A) contains carboxyl groups and hydroxyl groups, the sum of the acid value and hydroxyl value is preferably 1 to 30 mgKOH / g, more preferably 2 to 25 mgKOH / g, and even more preferably 3 to 18 mgKOH / g. By setting the sum of the acid value and hydroxyl value of resin (A) to 1 mgKOH / g or more, the crosslinking density with the crosslinking agent is optimized while maintaining good intermolecular forces with the adherend, improving heat resistance, light resistance, adhesion, fluidity during the embedding process, and zipping properties. By setting the sum of the acid value and hydroxyl value of resin (A) to 30 mgKOH / g or less, the storage stability of resin (A) is maintained well, and the residual amount of carboxyl groups and hydroxyl groups after the crosslinking reaction, which promotes yellowing of resin (A), can be appropriately adjusted. As a result, light resistance, adhesion, heat resistance, and zipping properties are improved. The acid value and hydroxyl value were measured by the method described in the examples below. Examples of suitable thermosetting resins (A) include the aforementioned resins having carboxyl groups and hydroxyl groups.

[0048] The (meth)acrylic resin (α) is preferably an acrylic copolymer obtained by copolymerizing monomers containing (meth)acrylic acid ester monomers. A suitable example of the (meth)acrylic acid ester monomer is alkyl (meth)acrylic acid ester monomer. When introducing functional groups that can be used in polymerization / crosslinking reactions, a (meth)acrylic copolymer obtained by copolymerizing a functional group-containing monomer with a (meth)acrylic acid ester monomer is preferred.

[0049] (Meth)acrylate alkyl ester monomers are compounds obtained by esterifying (meth)acrylic acid and introducing an alkyl group or cycloalkyl group, where the alkyl group or cycloalkyl group may be a linear, branched, or cyclic saturated aliphatic hydrocarbon group. The saturated aliphatic hydrocarbon group is preferably a saturated aliphatic hydrocarbon group having 1 to 20 carbon atoms, more preferably a saturated aliphatic hydrocarbon group having 1 to 12 carbon atoms, and even more preferably a saturated aliphatic hydrocarbon group having 1 to 4 carbon atoms. Specific examples include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, s-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, nonyl methacrylate, isononyl methacrylate, and methyl methacrylate. Examples include decyl, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, 4-n-butylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, etc. Among these, methyl (meth)acrylate, n-butyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate are particularly preferred from the viewpoint of compatibility with the thermal polymerization initiator (B), and methyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate are more preferred.

[0050] From the viewpoint of adhesion, the amount of structural units derived from alkyl ester monomers of (meth)acrylate is preferably 1 to 100% by mass, more preferably 30 to 97% by mass, even more preferably 50 to 95% by mass, and particularly preferably 80 to 93% by mass, relative to 100% by mass of (meth)acrylic resin (α). From the viewpoint of storage stability, the amount of structural units derived from alkyl methacrylate monomers is preferably 50 to 100% by mass, more preferably 60 to 98% by mass, and even more preferably 70 to 97% by mass, relative to 100% by mass of (meth)acrylic resin (α).

[0051] The (meth)acrylic resin (α) preferably has one or more functional groups that can be used in polymerization / crosslinking reactions by heat or light. The functional groups can be appropriately selected based on their reactivity with other (meth)acrylic resins (α) or with the thermal polymerization initiator (B) and crosslinking agent described later, and may be self-crosslinkable functional groups. Examples of functional groups include the aforementioned functional groups (hydroxyl group, carboxyl group, amino group, epoxy group, oxetanyl group, oxazoline group, oxazine group, aziridine group, thiol group, isocyanate group, blocked isocyanate group, silanol group, (meth)acryloyl group, N-vinyl group, vinyl ether group, allyl group, unsaturated carboxylic acid group, etc.). Examples of radical polymerizable functional groups include (meth)acryloyl group, N-vinyl group, vinyl ether group, allyl group, and unsaturated carboxyl group. Among these, the (meth)acryloyl group is more preferred from the viewpoint of storage stability.

[0052] Functional group-containing monomers are monomers that have functional groups, including alkyl (meth)acrylate ester monomers and monomers that do not fall under the category of alkyl (meth)acrylate ester monomers. Specific examples of these include carboxyl group-containing monomers, hydroxyl group-containing monomers, epoxy group-containing monomers, and amino group-containing monomers. By including functional group-containing monomers, the cohesive strength of the (meth)acrylic resin (α) is improved, resulting in a tough resin composition. In particular, it is preferable to include carboxyl group-containing monomers or hydroxyl group-containing monomers.

[0053] Examples of carboxyl group-containing monomers include (meth)acrylic acid, β-carboxyethyl (meth)acrylate, p-carboxybenzyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, citraconic acid, and isocrotonic acid. Among these, (meth)acrylic acid is preferred from the viewpoint of adhesion, and methacrylic acid is more preferred.

[0054] Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. Among these, 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate are preferred from the viewpoint of adhesion, and 2-hydroxyethyl methacrylate is more preferred.

[0055] Examples of amino group-containing monomers include monoalkylamino esters of (meth)acrylates such as monomethylaminoethyl (meth)acrylate, monoethylaminoethyl (meth)acrylate, monomethylaminopropyl (meth)acrylate, and monoethylaminopropyl (meth)acrylate.

[0056] Hydroxyl group-containing monomers and carboxyl group-containing monomers are also used for the purpose of introducing unsaturated bonds such as (meth)acryloyl groups into (meth)acrylic resin (α). For example, it is preferable to use a hydroxyl group-containing monomer such as 2-hydroxyethyl (meth)acrylate to obtain a (meth)acrylic copolymer having hydroxyl groups, and then react at least a portion of these hydroxyl groups with a monomer having an isocyanate group and an unsaturated bond such as a (meth)acryloyl group to introduce an unsaturated bond such as a (meth)acryloyl group into (meth)acrylic resin (α). In this case, for the reasons mentioned above, it is preferable that resin (A) retains hydroxyl groups. Alternatively, it is preferable to obtain a (meth)acrylic copolymer having carboxyl groups using a carboxyl group-containing monomer such as (meth)acrylic acid, and to react at least a portion of these carboxyl groups with the epoxy group of a monomer having an epoxy group and an unsaturated bond such as a (meth)acryloyl group to introduce an unsaturated bond such as a (meth)acryloyl group into the (meth)acrylic resin (α). In this case, for the reasons mentioned above, it is preferable that the resin (A) retains carboxyl groups.

[0057] Examples of monomers having an epoxy group and an unsaturated bond such as a (meth)acryloyl group include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and 6-methyl-3,4-epoxycyclohexylmethyl (meth)acrylate. Among these, glycidyl (meth)acrylate is preferred from the viewpoint of reactivity. It is preferable that the number of epoxy groups in the monomer having an epoxy group and an unsaturated bond such as a (meth)acryloyl group be one or less per molecule. Examples of monomers having an isocyanate group and an unsaturated bond such as a (meth)acryloyl group include curene MOI and AOI (manufactured by Resonaq).

[0058] With respect to 100% by mass of (meth)acrylic resin (α), the total amount of structural units derived from hydroxyl group-containing monomers is preferably 0.1 to 20% by mass, more preferably 1 to 10% by mass, and even more preferably 1 to 5% by mass. By setting it to 0.1 to 20% by mass, adhesion can be improved. The amount of constituent units derived from epoxy group-containing monomers is preferably 0.1 to 7% by mass, more preferably 0.3 to 5% by mass, and even more preferably 0.5 to 3% by mass, relative to 100% by mass of (meth)acrylic resin (α). By setting it to 0.1 to 7% by mass, adhesion can be improved and the amount of chlorine elution can be suitably adjusted. The amount of constituent units derived from carboxyl group-containing monomers is preferably 0.1 to 15% by mass, more preferably 0.5 to 10% by mass, and even more preferably 1 to 5% by mass, relative to 100% by mass of (meth)acrylic resin (α). Adhesion can be improved by setting it to 0.1 to 15% by mass.

[0059] When the (meth)acrylic resin (α) has a carboxyl group, the acid value of the (meth)acrylic resin (α) is preferably 1 to 50 mg KOH / g, more preferably 3 to 40 mg KOH / g, even more preferably 5 to 20 mg KOH / g, and particularly preferably 7 to 15 mg KOH / g. Setting the acid value of the (meth)acrylic resin (α) to 1 to 50 mg KOH / g improves adhesion. The acid value in this disclosure was measured by the method described in the examples below. When (meth)acrylic resin(α) has hydroxyl groups, the hydroxyl value of (meth)acrylic resin(α) is preferably 1 to 50 mg KOH / g, more preferably 3 to 40 mg KOH / g, even more preferably 5 to 20 mg KOH / g, and particularly preferably 7 to 15 mg KOH / g. Adhesion is improved by setting the hydroxyl value of (meth)acrylic resin (α) to 1-50 mgKOH / g. The hydroxyl value in this disclosure was measured by the method described in the examples below.

[0060] The (meth)acrylic resin (α) may contain structural units derived from alkyl (meth)acrylates and other monomers copolymerizable with functional group-containing monomers. Examples include monomers having alkylene oxy groups and other vinyl monomers. Examples include methoxyethyl acrylate, methoxydiethylene glycol acrylate, vinyl acetate, vinyl crotate, styrene, acrylonitrile, and acrylamide. The structural units derived from the other monomers are preferably present in an amount of 0.1 to 10% by mass of 100% by mass of the (meth)acrylic resin (α).

[0061] (Meth)acrylic resin (α) is obtained by polymerizing an acrylic monomer mixture. A polymerization initiator may be used during polymerization as needed. The content of the polymerization initiator is, for example, 0.01 to 10% by mass per 100% by mass of the monomer mixture. The polymerization method is not limited. For example, polymerization can be carried out by solution polymerization, bulk polymerization, emulsion polymerization, or suspension polymerization, and solution polymerization is the most preferred due to the ease of polymerization control. Examples of solvents used in solution polymerization include acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl acetate, ethyl acetate, butyl acetate, toluene, xylene, anisole, cyclohexanone, and isopropyl alcohol. The polymerization temperature can be, for example, 60 to 120°C, and the polymerization time can be about 2 to 12 hours.

[0062] (Meth)acrylic resin(α) may be used alone or in combination of two or more types. The content of (meth)acrylic resin(α) is preferably 10 to 99% by mass, more preferably 40 to 97% by mass, and even more preferably 55 to 96% by mass, based on the total solid content (100% by mass) of the resin sheet. When two or more types of (meth)acrylic resin(α) are included, it is preferable that each (meth)acrylic resin(α) has a content of 5% by mass or more, and the total content is preferably 10 to 99% by mass. By setting the (meth)acrylic resin(α) content to 10 to 99% by mass, compatibility with polymerization initiators is improved, and storage stability is enhanced.

[0063] The glass transition temperature (Tg) of (meth)acrylic resin (α) is preferably -30°C to 80°C, more preferably -20°C to 50°C, even more preferably -10°C to 45°C, even more preferably 0°C to 40°C, and particularly preferably 5°C to 35°C. Setting the temperature to -30°C to 80°C reduces the residual stress of the (meth)acrylic resin (α) after the pressing process, resulting in favorable adhesion. The Tg can be calculated using the Fox formula from the Tg values ​​of the homopolymers of each (meth)acrylic acid monomer forming the structural unit of (meth)acrylic resin (α) as described in POLYMER HANDBOOK, 1999, FOURTH EDITION, and the blended mass ratio.

[0064] 2-3. Thermal polymerization initiator (B) The inclusion of a thermal polymerization initiator (B) improves adhesion and storage stability. The inclusion of a thermal polymerization initiator (B) allows for the initiation and promotion of the crosslinking reaction of (meth)acrylic resin (α) when resin (A) is, for example, (meth)acrylic resin (α). Examples of functional groups that can be used in thermal polymerization reactions in (meth)acrylic resin (α) include (meth)acryloyl groups, N-vinyl groups, vinyl ether groups, allyl groups, and unsaturated carboxylic acid groups, with (meth)acryloyl groups being preferred.

[0065] As the thermal polymerization initiator (B), thermal radical polymerization initiators and thermal cationic polymerization initiators are preferred. From the viewpoint of storage stability of the resin sheet, thermal radical polymerization initiators are preferred. Thermal radical polymerization initiators have the function of generating radicals by heat. Examples of thermal radical polymerization initiators include organic peroxide polymerization initiators and azo thermal polymerization initiators. Thermal cationic polymerization initiators have the function of generating ions when heated. Examples of thermal cationic polymerization initiators include sulfonium cations, quaternary ammonium cations, and iodonium cations as cationic components, and antimony hexafluoride anions, phosphorus hexafluoride anions, tetrakis(pentafluorophenyl) borate anions, and trifluoromethanesulfonic acid as anionic components.

[0066] Examples of organic peroxide polymerization initiators include dialkyl peroxides such as diacetyl peroxide, di-t-butyl peroxide, di-t-hexyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexine-3, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, 1,3-bis(t-butylperoxyisopropyl)hexane, and (2-ethylhexanoyl)(t-butyl) peroxide; Dipropionyl peroxide, t-butyl peroxyacetate, t-butyl peroxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, bis(3,5,5-trimethylhexanoyl)peroxide, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, α-cumyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-hexyl peroxyneodecanoate, t-butyl peroxyneoheptanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, t-amyl peroxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, Peroxyesters such as t-butyl peroxyisobutyrate, di-t-butyl peroxyhexahydroterephthalate, 1,1,3,3-tetramethylbutyl peroxy-3,5,5-trimethylhexanate, t-amyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxy-3,5,5-trimethylhexanoate, dibutyl peroxytrimethyl adipate, 2,5-dimethyl-2,5-di-2-ethylhexanoyl peroxyhexane, t-hexyl peroxy-2-ethylhexanoate, t-hexyl peroxyisopropyl monocarbonate, t-butyl peroxylaurate, t-butyl peroxyisopropyl monocarbonate, and t-butyl peroxy-2-ethylhexyl monocarbonate; Ketone peroxides such as methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, acetylacetone peroxide, cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, methylcyclohexanone peroxide, t-butyl benzoate, and pivaloyl t-butyl peroxide; Peroxyketals such as 2,2-bis(t-butylperoxy)butane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-hexylperoxy)cyclohexane, and 4,4-bis(t-butylperoxy)butyl pentanoate; Hydroperoxides such as t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylcyclohexane-2,5-dihydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, and p-menthane hydroperoxide; Diacyl peroxides such as dibenzoyl peroxide, didecanoyl peroxide, dilauroyl peroxide, diisobutyryl peroxide, bis-3,5,5-trimethylhexanol peroxide, m-toluylbenzoyl peroxide, succinate peroxide, and 2,4-dichlorobenzoyl peroxide; Examples of peroxydicarbonates include, but are not limited to, bis(t-butylcyclohexyl)peroxydicarbonate, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di(2-ethoxyethyl)peroxydicarbonate, t-butylperoxyisopropyl carbonate, di-2-ethylhexyl peroxycarbonate, di-sec-butylperoxycarbonate, di-3-methoxybutyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-amylperoxyisopropyl carbonate, t-butylperoxy-2-ethylhexyl carbonate, and 6-bis(t-butylperoxycarboxyloxy)hexane. From the viewpoint of storage stability, dialkyl peroxides and peroxyesters are preferred, and di-t-butyl peroxide and t-butyl peroxybenzoate are more preferred.

[0067] Examples of azo thermal polymerization initiators include 2,2'-azobisisobutyronitriles such as 2,2'-azobis(2-methylbutyronitrile); 2,2'-azobisvaleronitriles such as 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile); 1,1'-azobis-1-alkanenitriles such as 1,1'-azobis(cyclohexane-1-carbonitride); 2,2'-azobis(2-hydroxymethylpropionitrile), 2,2'-azobis(2-hydroxymethylpropionitrile), and other 2,2'-azobispropionitriles; 2,2'-azobispropionamides such as 2,2'-azobis(N-butyl-2-methylpropionamide) and 2,2'-azobis(N-cyclohexyl-2-methylpropionamide); Other examples include dimethyl-2,2'-azobis(2-methylpropionate), 2,2'-azobis[2-(2-imidazolin-2-yl)propane], and 1-[(1-cyano-1-methylethyl)azo]formamide. Azo compounds having carboxyl groups or hydroxyl groups include, but are not limited to, 4,4'-azobis(4-cyanopentanoic acid), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide), and 2,2'-azobis(N-(carboxyethyl)-2-methylpropionamidine)tetrahydrate. From the viewpoint of storage stability, 2,2'-azobispropionamides are preferred, and 2,2'-azobis(N-butyl-2-methylpropionamide) is more preferred.

[0068] The 10-hour half-life temperature of the thermal polymerization initiator (B) is preferably 60 to 200°C, more preferably 80 to 170°C, even more preferably 90 to 150°C, and particularly preferably 93 to 130°C. Setting the temperature above 60°C improves the storage stability of the resin sheet, while setting it below 200°C shortens the heating aging process.

[0069] The 10-hour half-life temperature is the temperature at which the thermal polymerization initiator (B) decreases to half of its initial value after 10 hours due to thermal decomposition. Specifically, a solution of thermal polymerization initiator (B) is prepared using a solvent inert to the radicals of thermal polymerization initiator (B), and sealed in a glass tube purged with nitrogen. This is then immersed in a constant temperature chamber set to a predetermined temperature for 10 hours to allow thermal decomposition, and the amount of remaining thermal polymerization initiator is measured. By performing this series of operations at several temperatures and plotting the results, the half-life can be determined from the resulting straight line.

[0070] The content of the thermal polymerization initiator (B) is preferably 0.01 to 20% by mass, more preferably 0.1 to 15% by mass, and even more preferably 1 to 10% by mass, based on the total solid content of the resin sheet. By setting the above content, adhesion and storage stability can be suitably adjusted.

[0071] 2-4. Silane coupling agent (C) Silane coupling agents (C) are compounds in which hydrolyzable groups such as methoxy groups and ethoxy groups, and functional groups such as epoxy groups, are bonded to Si atoms via alkylene groups. Silane coupling agents (C) have the function of introducing Si-containing structural units into (meth)acrylic resin (α) by crosslinking with the functional groups of (meth)acrylic resin (α), thereby improving adhesion.

[0072] Silane coupling agent (C) is an alkoxysilane compound having a (meth)acryloxy group, such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropyltrippropoxysilane, 3-(meth)acryloxypropyltributoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, methacryloxyoctyltrimethoxysilane; Alkoxysilane compounds having a vinyl group, such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinylmethyldimethoxysilane, and vinylmethyldiethoxysilane; Alkoxysilane compounds having an amino group, such as 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltripropoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane; Alkoxysilane compounds having a mercapto group, such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltripropoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropylmethyldiethoxysilane; Alkoxysilane compounds having one epoxy group, such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltripropoxysilane, 3-glycidoxypropyltributoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; Tetraalkoxysilane compounds such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane; Examples include 3-chloropropyltrimethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-decyltrimethoxysilane, n-decyltriethoxysilane, styryltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate, 3-isocyanatetopropyltrimethoxysilane, 3-isocyanatetopropyltriethoxysilane, hexamethyldisilazane, and silicone resins having alkoxysilyl groups in the molecule. Alkoxysilane compounds are preferred from the viewpoint of adhesion, and 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, and methacryloxyoctyltrimethoxysilane are more preferred.

[0073] The content of the silane coupling agent (C) is preferably 0.01 to 15% by mass, more preferably 0.05 to 10% by mass, and even more preferably 0.1 to 5% by mass, based on the total solid content of the resin sheet. By setting it to 0.01 to 15% by mass, the adhesion can be suitably adjusted. Furthermore, the content of the alkoxysilane compound having one epoxy group is preferably 0.01 to 5% by mass, more preferably 0.05 to 3% by mass, and even more preferably 0.1 to 1% by mass, based on the total solid content of the resin sheet. By setting it to 0.01 to 5% by mass, the amount of chlorine eluted can be reduced.

[0074] 2-5. Other ingredients The resin sheet may contain crosslinkable components, organic fillers, inorganic fillers, and various additives, to the extent that it does not depart from the spirit of this disclosure. Specifically, examples include crosslinking agents, monomers, oligomers, curing accelerators, curing retarders, colorants, antioxidants, flame retardants, surface modifiers, softeners, antistatic agents, lubricants, antiblocking agents, and adhesion improvers.

[0075] <Cross-linking components (excluding components (A) to (C))> This resin sheet may contain crosslinking components such as crosslinking agents, monomers, oligomers, curing accelerators, and curing retarders. By including crosslinking components, the mechanical strength and elastic modulus of the insulating layer, which is the cured product of the resin sheet, can be adjusted. Furthermore, the curing speed during hot pressing and heat aging in the pressing process can be adjusted.

[0076] The crosslinking agent enhances the cohesive force of the resin composition and improves adhesion by crosslinking with the reactive functional groups of the resin (A). The crosslinking agent has one or more functional groups that can react with the functional groups of the resin (A). Examples of known crosslinking agents include epoxy compounds, aziridine compounds, imidazole compounds, isocyanate compounds, acid anhydride group-containing compounds, and amine compounds. From the viewpoint of adjusting the adhesion of the resin composition, epoxy compounds, aziridine compounds, imidazole compounds, and isocyanate compounds are preferred, and epoxy compounds and isocyanate compounds are more preferred.

[0077] The epoxy compound is a compound having two or more epoxy groups in one molecule, and is a compound other than (meth)acrylic resin (α) having a structural unit based on the epoxy group-containing monomer described above. Examples of epoxy compounds include glycidyl ether type epoxy compounds, glycidylamine type epoxy compounds, glycidyl ester type epoxy compounds, cyclic aliphatic (alicyclic) epoxy compounds, bisphenol type epoxy compounds, and hydrogenated bisphenol type epoxy compounds.

[0078] The epoxy compound content is preferably 0.01 to 10% by mass, more preferably 0.03 to 10% by mass, even more preferably 0.05 to 7% by mass, and particularly preferably 0.1 to 5% by mass, based on the total amount of solids (100% by mass) of the resin sheet. Adhesion can be suitably adjusted by setting the content to 0.01% by mass or more. Chlorine elution can be suitably adjusted by setting the content to 10% by mass or less.

[0079] Examples of aziridine compounds include trimethylolpropane tris[3-(aziridin-1-yl)propionate], tetramethylolmethane-tri-β-aziridinylpropionate, N,N'-diphenylmethane-4,4'-bis(1-aziridincarboxyamide), N,N'-hexamethylene-1,6-bis(1-aziridincarboxyamide), tris-2,4,6-(1-aziridinyl)-1,3,5-triazine, and 4,4'-bis(ethyleneiminocarbonylamino)diphenylmethane.

[0080] The isocyanate compound is an isocyanate having two or more isocyanate groups, and is a compound other than (meth)acrylic resin (α) having a structural unit based on the isocyanate group-containing monomer described above. The isocyanate compound is preferably an isocyanate monomer such as aromatic polyisocyanates, aliphatic polyisocyanates, aromatic aliphatic polyisocyanates, or alicyclic polyisocyanates, as well as their biuret, nurate, and adduct forms. From the viewpoint of forming a sufficient crosslinking structure, isocyanate compounds with three or more functions are preferred. More preferably, the isocyanate compounds are adducts and nurates, which are reaction products of an isocyanate monomer and a trifunctional low-molecular-weight active hydrogen-containing compound. The isocyanate compounds are preferably trimethylolpropane adducts of hexamethylene diisocyanate, nurates of hexamethylene diisocyanate, trimethylolpropane adducts of tolylene diisocyanate, nurates of tolylene diisocyanate, trimethylolpropane adducts of isophorone diisocyanate, and nurates of isophorone diisocyanate, and more preferably trimethylolpropane adducts of hexamethylene diisocyanate, trimethylolpropane adducts of tolylene diisocyanate, and trimethylolpropane adducts of isophorone diisocyanate.

[0081] The crosslinking agent content is preferably 0.01 to 20% by mass, more preferably 0.1 to 10% by mass, and even more preferably 0.5 to 5% by mass, based on the total amount of solids in the resin sheet. Adhesion can be suitably adjusted by setting the content to 0.01 to 20% by mass.

[0082] The monomers mentioned above are monomers added to the resin composition that forms the resin sheet, and do not include monomers used in the polymerization of resin (A). Examples of radically polymerizable functional groups include (meth)acryloyl groups, N-vinyl groups, vinyl ether groups, allyl groups, and unsaturated carboxylic acid groups. Among these, (meth)acryloyl groups are preferred. The monomers may be monofunctional monomers or polyfunctional monomers. In this specification, "monofunctional" refers to a compound having only one radically polymerizable functional group in one molecule, while "difunctional" and "trifunctional" refer to compounds having two and three radically polymerizable functional groups in one molecule, respectively. In this specification, compounds with two or more functionalities are collectively referred to as "polyfunctional."

[0083] Specifically, examples include, but are not limited to, monofunctional (meth)acrylate monomers having one (meth)acryloyl group in the molecule, monofunctional vinyl monomers having one N-vinyl group in the molecule, difunctional (meth)acrylate monomers having two (meth)acryloyl groups in the molecule, difunctional (meth)acrylate monomers having one (meth)acryloyl group and one allyl group in the molecule, trifunctional (meth)acrylate monomers having three (meth)acryloyl groups in the molecule, tetrafunctional (meth)acrylate monomers having four acryloyl groups in the molecule, pentafunctional (meth)acrylate monomers having five (meth)acryloyl groups in the molecule, and hexafunctional (meth)acrylate monomers having six (meth)acryloyl groups in the molecule. By including monomers, the film-forming properties of the resin composition of the resin sheet can be adjusted, the curing speed can be adjusted, and the ability to conform to the uneven shape of the adherend can be improved.

[0084] From the viewpoint of improving adhesion to the adherend and fluidity during the embedding process, the monomer content is preferably 0.01 to 30% by mass, more preferably 0.05 to 20% by mass, even more preferably 0.1 to 15% by mass, and particularly preferably 0.3 to 10% by mass, based on the total amount of solids in the resin sheet.

[0085] A curing accelerator may be included to adjust the crosslinking rate of the resin sheet. The curing accelerator is not particularly limited and can be selected as appropriate. Specific examples of curing accelerators include guanidine-based curing accelerators and metal-based curing accelerators.

[0086] <Inorganic filler> By mixing inorganic fillers into the binder component of a resin sheet, the properties of the binder component can be improved. For example, mechanical properties, thermal properties, processability, flame retardancy, transparency, refractive index, reflectivity, heat dissipation, etc., can be imparted. Inorganic fillers (inorganic pigments) that correspond to colorants described later will be classified as "colorants" in this specification.

[0087] Examples of inorganic fillers include inorganic compounds such as alumina, zirconium oxide, tin oxide, magnesium hydroxide, calcium carbonate, antimony trioxide, talc, mica, montmorillonite, bentonite, boron nitride, aluminum nitride, magnesium carbonate base, and titanium nitride. Among these, silica, alumina, zirconium oxide, calcium carbonate, and titanium nitride are preferred from the viewpoint of improving the brightness of the optical semiconductor device, with alumina and zirconium oxide being more preferred. From the viewpoint of coating film resistance, two or more types of inorganic fillers may be combined.

[0088] When imparting high refractive index to the insulating layer, which is a cured resin sheet, it is preferable that the total light transmittance of the resin sheet in the visible light band (380-780 nm) be 70% or more, and the refractive index be 1.47-1.56. A total light transmittance of 80% or more is more preferable, 85% or more is even more preferable, 90% or more is even more preferable, and 92% or more is particularly preferable. The lower limit of the refractive index is preferably 1.47, more preferably 1.49, and even more preferably 1.50. The upper limit of the refractive index is more preferably 1.54, and even more preferably 1.53. From the viewpoint of adjusting the refractive index, inorganic fillers such as alumina and zirconium oxide can be added. Total light transmittance is the ratio of the total amount of transmitted light that passes through the cured layer to the total amount of incident light that enters the cured layer obtained by heat-treating the resin sheet at 150°C for 120 minutes.

[0089] To impart wavelength conversion properties to the insulating layer, which is the cured product of a resin sheet, fluorescent dyes and luminescent dyes can be added to the resin composition forming the resin sheet. Furthermore, to impart heat dissipation properties to the insulating layer, which is the cured product of a resin sheet, a thermally conductive filler can be added to the resin composition forming the resin sheet. Examples of thermally conductive fillers include silica, alumina, aluminum nitride, and boron nitride.

[0090] From the viewpoint of dispersibility, inorganic fillers are preferably surface-modified with a surface modifier. Examples of surface modifiers include organic acids, silane coupling agents, surfactants, titanium coupling agents, and metal impurities, with the inclusion of organic acids being preferable. From the viewpoint of dispersibility, the inorganic filler should have a specific surface area of ​​5 to 400 m² as determined by the BET method. 2 It is preferable that the value be / g, and 10-150m 2 It is more preferable that the amount be / g, and 20-90m 2 It is even more preferable that it be / g.

[0091] When imparting high refractive index to the insulating layer, which is a cured resin sheet, the average primary particle diameter of the inorganic filler is 5 to 50 nm. Preferably, the average primary particle diameter is 5 to 30 nm, more preferably 7 to 25 nm, and particularly preferably 10 to 20 nm. By using this range, the fluidity of the resin composition layer is improved, and the embedding ability is enhanced. In addition, it is easier to maintain the viscosity of the resin composition at a level suitable for coating. Furthermore, the dispersibility in the resin is improved, and the refractive index adjustment function is more easily exhibited. The average primary particle diameter of the inorganic particles can be observed from an image magnified to about 50,000 to 1,000,000 times using a transmission electron microscope (TEM), and can be determined from the average value of about 20 primary particles. If the particle shape of the inorganic filler has an average aspect ratio (long axis length / short axis length) of 1.5 or more, the particle diameter is determined by averaging the long axis lengths.

[0092] The inorganic filler content (total content if two or more types are included) is preferably 0.01 to 40% by mass, more preferably 0.1 to 30% by mass, and even more preferably 0.5 to 20% by mass, based on the total amount of solids in the resin sheet, from the viewpoint of embedding properties. Including 0.01 to 40% by mass of inorganic filler makes it easier to increase the fluidity of the resin sheet during the pressing process, thereby improving embedding properties.

[0093] Dispersers used for mechanical crushing as a dispersion process include ball mills, roll mills, sand mills, bead mills, and nanomizers. Among these, bead mills are preferred. Examples of commercially available bead mills include Supermill, Sandgrinder, Agitatormill, Glenmill, Dynomill, Pearlmill, and Cobolmill (all are trade names).

[0094] It is preferable to use a dispersant for the dispersion treatment. From the viewpoint of storage stability of the dispersion, resin (A) may be used as the dispersant. From the viewpoint of compatibility, resin (A) is preferably a resin that is highly compatible with the binder component, more preferably the same type of resin, and even more preferably (meth)acrylic resin (α). In addition, dispersants other than resin (A) can also be suitably used. A suitable example of a dispersant other than resin (A) is a dispersant with a molecular weight of 1,000 or more and less than 10,000. The acid value of the dispersant is preferably 5 to 450 mg KOH / g, more preferably 46 to 300 mg KOH / g, and even more preferably 50 to 200 mg KOH / g. Furthermore, it is preferable that the dispersant contains one or more amines in its molecule. The amine value of the dispersant is preferably 0.2 to 350 mg KOH / g, and more preferably 0.5 to 300 mg KOH / g. Having an appropriate acid value and / or amine value provides an excellent electrostatic repulsion effect and results in a dispersion with excellent storage stability. By using a dispersant, the adsorption rate to inorganic fillers is improved, resulting in a dispersion with excellent stability.

[0095] The dispersant may be a pigment derivative type dispersant, or a surfactant selected from cationic, anionic, or nonionic surfactants. From the viewpoint of storage stability of the dispersion, a pigment derivative type dispersant is preferred. Pigment derivative-type dispersants are compounds having acidic groups, basic groups, neutral groups, etc., in their organic pigment residues. Examples include compounds having acidic substituents such as sulfo groups, carboxyl groups, or phosphate groups, as well as their amine salts, compounds having basic substituents such as sulfonamide groups, amide groups, or tertiary amino groups at the terminal, and compounds having neutral substituents such as phenyl groups or phthalimidoalkyl groups. Examples of organic pigments include phthalocyanine pigments, diketopyrrolopyrrole pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, perinone pigments, perylene pigments, thiaidine indigo pigments, triazine pigments, benzimidazolone pigments, indole pigments such as benzoisoindole, isoindoline pigments, isoindolinone pigments, quinophthalone pigments, naphthol pigments, surene pigments, metal complex pigments, and azo pigments such as azo, disazo, and polyazo. By using these pigment dispersants, it is possible to prevent the aggregation of inorganic fillers contained in the resin sheet over time and provide a highly reliable insulating layer.

[0096] The dispersant content is preferably 0.01 to 15% by mass, and more preferably 0.1 to 10% by mass, based on the total amount of solids in the resin sheet. Including 0.01% by mass or more of pigment dispersant improves the brightness of the optical semiconductor device, and having 15% by mass or less results in a suitable viscosity range for the dispersion, leading to good coating suitability.

[0097] <Coloring agent> The colorants that may be added to this resin sheet are not particularly limited and can be appropriately selected depending on the application. When providing light-shielding, shielding, or light-diffusion prevention properties, it is preferable to set the optical density of the resin sheet to 4 or higher. The lower limit of the optical density is more preferably 5. The upper limit of the optical density is not particularly limited, but 6 is preferred. By setting the optical density of the resin sheet to 4 or higher, an insulating layer with excellent light-shielding properties can be obtained. By using such an insulating layer, color mixing of adjacent micro-LEDs can be prevented. Furthermore, when providing light reflectivity, it is preferable to set the reflectance of the resin sheet in the visible light band to 70% or higher. The reflectance can be adjusted by the type and amount of colorant added. The reflectance is more preferably 80% or higher, and even more preferably 90% or higher. By setting the reflectance of the resin sheet to 70% or higher, an insulating layer with excellent reflectivity can be obtained.

[0098] When the optical density of the resin sheet is to be 4 or higher, it is preferable to add a black pigment. Suitable examples include carbon black, perylene black, aniline black, and titanium black. Suitable examples of carbon black include channel black, furnace black, thermal black, lamp black, acetylene black, and Ketjen black. Specific examples of carbon black include Birla Carbon's "Raven 3500, 1180, 1080 Ultra, 1060 Ultra, 1040", Tokai Carbon's "TOKABLACK #8300, #7360SB", Orion Engineered Carbons' "Special Black 350, 250, 100, 550, 5, 4, 4A, 6", "Nipex 160IQ, 170IQ", "Printex U, V, 140U, 140V, 95, 90, 85, 80, 75, 55, 45, P, 60, L6, L, 300, 30, 3, 35, 25, A, G", "ColorBlack FW200, FW2, S170", and Cabot's "REGAL 400R, 330R, 250R", "MOGUL Examples include "E, L", "MONARCH1300, 280", and Mitsubishi Chemical's "MA7, 8, 11, 14, 77, 100, 100R, 100S, 220, 230", "#2650, #2600, #2350, #2300, #1000, #980, #970, #960, #950, #900, #850, #750B, #650B, #52, #47, #45, #45L, #44, #40, #33, #32, #30, #25, #20, #10, #5, #95", etc. Perylene black may contain, for example, at least one component selected from the group consisting of color index (CI) pigment black 31 and color index (CI) pigment black 32.

[0099] Carbon black (hereinafter also referred to as CB) may contain sulfur as an impurity. It is preferable to select CB with a low sulfur content. From the viewpoint of dispersibility, the specific surface area of ​​CB by the BET method should be 10 to 400 m². 2 / g is preferred, 50-250m 2 / g is more preferable. Specific surface area can be measured according to JIS Z 8830 using the BET method.

[0100] The CB content is preferably 5 to 45% by mass, more preferably 10 to 35% by mass, and even more preferably 15 to 30% by mass, based on the total solid content of the resin sheet. A CB content of 5 to 45% by mass results in an excellent level of optical density. The inorganic filler and colorant content is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 35% by mass or less, based on the total solid content of the resin sheet.

[0101] When imparting reflectivity to the insulating layer, which is a cured resin sheet, the reflectivity of the resin sheet in the visible light band is preferably 70% or higher. When the reflectivity of the resin sheet is 70% or higher, it is preferable to add a white pigment. Examples of white pigments include titanium dioxide, zinc oxide, barium sulfate, kaolinite, sericite, magnesium oxide, and antimony oxide. The reflectivity is more preferably 80% or higher, and even more preferably 90% or higher. The visible light band refers to the range of 380 to 780 nm, and reflectivity refers to the reflectivity in the visible light band.

[0102] As the titanium dioxide, known titanium dioxide such as rutile-type titanium dioxide and anatase-type titanium dioxide can be used. From the viewpoint of resin degradation due to light, rutile-type titanium dioxide is preferred. Specific examples of rutile-type titanium dioxide include "Typeque R-820, R-830, R-930, R-550, R-630, R-680, R-670, R-680, R-670, R-780, R-850, CR-50, CR-57, CR-80, CR-90, 90-2, CR-93, CR-95, CR-97, CR-63, CR-58, UT771" from Ishihara Sangyo Co., Ltd., "Typeque R-101, R-103, R-104, R-105, R-108, R-900, R-902+, R-960, R-706" from DuPont, and "TITONE" from Sakai Chemical Industry Co., Ltd. Examples include "R-25, R-21, R-32, R-7E, R-5N, R-62N, R-42, R-45M, GTR-100, D-918," etc.

[0103] The content of the white pigment is preferably 3 to 45% by mass, more preferably 10 to 35% by mass, and even more preferably 20 to 30% by mass, based on the total solid content of the resin sheet. A white pigment content of 3 to 45% by mass results in an excellent level of optical density.

[0104] The average primary particle size (hereinafter referred to as particle size) of the black pigment is preferably 10 to 100 nm. A particle size of 10 nm or more makes it easier to maintain the viscosity of the resin composition in coating form at a level suitable for coating. A particle size of 100 nm or less improves blackness and results in high optical density. If the particle shape of the black pigment has an average aspect ratio (long axis length / short axis length) of 1.5 or more, the particle size is determined by averaging the long axis lengths. The particle size of the black pigment can be determined from the average value of about 20 primary particles observed in an image magnified to approximately 50,000 to 1,000,000 times using a transmission electron microscope (TEM).

[0105] The average primary particle diameter (hereinafter referred to as particle diameter) of the white pigment is preferably 1 to 1200 nm. A particle diameter of 1 nm or more makes it easier to maintain the viscosity of the resin composition at a level suitable for coating. Furthermore, a particle diameter of 1200 nm or less improves the coating film resistance. A particle diameter of 5 to 1000 nm is more preferable for the white pigment, 10 to 700 nm is even more preferable, and 50 to 300 nm is particularly preferable. The particle diameter of the white pigment can be determined from the average value of about 20 primary particles observed from an image magnified to approximately 50,000 to 1,000,000 times using a transmission electron microscope (TEM). If the particle shape of the white pigment has an average aspect ratio (long axis length / short axis length) of 1.5 or more, the particle diameter is determined by averaging the long axis lengths.

[0106] The colorant is preferably dispersed in resin (A), and more preferably in (meth)acrylic resin (α). The dispersants listed under inorganic fillers can also be suitably used. By forming a dispersion, repulsive forces are imparted between the particles, preventing aggregation of the colorant and improving homogeneous dispersibility within the resin sheet. Furthermore, the film-forming properties of the resin sheet can be improved. The disperser used for mechanical crushing should refer to the description of inorganic fillers. Suitable dispersions, types of dispersants, and their contents should refer to the description of inorganic fillers.

[0107] When incorporating a colorant into a resin composition for forming a resin sheet, the colorant itself may be added, but adding a colorant dispersion is preferable from the viewpoint of uniform dispersion. A dispersant and a solvent are used to prepare the colorant dispersion. The type of dispersant is not limited, but resin (A) is preferred. From the viewpoint of dispersibility, the volatile content of the dispersion is preferably 0.1 to 15% by mass.

[0108] From the viewpoint of improving coating film resistance, it is preferable to use colorants together or a mixture of colorants and inorganic fillers. Preferred examples include combinations of one or more selected from silica, zirconium oxide, alumina, zinc oxide, calcium carbonate, and titanium nitride with titanium oxide.

[0109] 3. Method for manufacturing resin sheets The method for manufacturing this resin sheet is not particularly limited, but a preferred example is a method in which a resin composition in the form of a coating is applied by adding an arbitrary solvent to the components constituting the resin sheet to obtain a coating film. The purpose of adding the solvent is to adjust the viscosity level to be suitable for coating and to adjust the film thickness. The solvent can be appropriately selected considering the compatibility and dispersibility of the components of the resin sheet, for example, ester-based, ether-ester-based, ether-based, alcohol-based, aromatic-based solvents. Examples include acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, cyclohexanone, toluene, xylene, isopropyl alcohol, and N-methyl-2-pyrrolidone. For stirring, known stirring devices such as dispersers, mixers, shakers, and homogenizers can be used. When adding carbon black, it is preferable to prepare a dispersion using a dispersant beforehand and then mix it with the other components. To obtain the resin composition, a manufacturing process of two or more steps may be followed, firstly by preparing a mixture of (meth)acrylic resin (α), a flow regulator, and carbon black in an optional solvent, and secondly by adding (meth)acrylic resin (α), a thermal polymerization initiator (B), a silane coupling agent (C), and other components as needed.

[0110] For coating, known coating machines and techniques such as comma coaters, die coaters, roll coaters, lip coaters, reverse coaters, gravure coaters, bar coaters, curtain coaters, dip coating, spin coating, silkscreen, and casting are used. After coating, the solvent is removed by a drying process (for example, by heating and drying using an infrared heater). After forming the resin sheet separately, it may be transferred to another support such as a protective film or release liner using a laminator.

[0111] The linear expansion coefficient of this resin sheet at -50°C to 50°C can be adjusted by the composition, amount, and degree of crosslinking of the compounding components. In resin (A), increasing the content of resins with a small Mw lowers the linear expansion coefficient at -50°C to 50°C, while increasing the content of resins with a large Mw raises the linear expansion coefficient at -50°C to 50°C. Furthermore, the linear expansion coefficient at -50°C to 50°C can be adjusted by the degree of crosslinking. Adding a thermal polymerization initiator (B) and / or a crosslinking agent is effective in introducing a crosslinking structure. Increasing the content of thermal polymerization initiator (B) lowers the linear expansion coefficient at -50°C to 50°C, while decreasing the content of thermal polymerization initiator (B) raises the linear expansion coefficient at -50°C to 50°C. The same applies to crosslinking agents. In addition, the linear expansion coefficient at -50°C to 50°C can be adjusted by the content of the flow regulator. Increasing the content of the flow modifier lowers the coefficient of linear expansion in the -50°C to 50°C range. Furthermore, increasing the content of the flow modifier to 0.3 to 30% by mass can improve embedding properties.

[0112] The storage modulus (G'60) of this resin sheet at 60°C can be adjusted by the type and amount of resin (A), the type and amount of crosslinking agent, etc. Increasing the content of resins with low Mw or resins with low Tg in resin (A) will lower G'60. Conversely, increasing the content of resins with high Mw or resins with high Tg in resin (A) will increase G'60. Increasing the content of thermal polymerization initiator (B) will also increase G'60, and to lower G'60, the opposite adjustment will be made. In addition, using a flow regulator with a high softening point temperature or increasing the content of the flow regulator will also increase G'60, and to lower G'60, the opposite adjustment will be made.

[0113] The loss tangent (tanδ60) at 60°C of this resin sheet can be adjusted by the type and amount of resin (A) used, the content of the thermal polymerization initiator (B), and the content of carbon black, which will be described later. Increasing the content of the thermal polymerization initiator (B) can increase tanδ60, and conversely, if you want to lower tanδ60, adjust it in the opposite direction. Similarly, increasing the content of carbon black can lower tanδ60, and conversely, if you want to raise tanδ60, adjust it in the opposite direction. Furthermore, using a flow regulator with a high softening point temperature or increasing the content of the flow regulator can increase tanδ60, and conversely, if you want to lower tanδ60, adjust it in the opposite direction.

[0114] In this resin sheet, reducing sulfur-containing compounds such as mercapto groups and heterocycles containing sulfur atoms is effective in meeting the aforementioned sulfur content requirements. Furthermore, sulfur atoms may be present as impurities. For example, sulfur may be present as an impurity in carbon black. In such cases, the sulfur content can be reduced by selecting carbon black that is sulfur-free or has a low sulfur content.

[0115] The gel fraction of the cured resin sheet can be adjusted by the composition and content of the resin (A) and the content of the thermal polymerization initiator (B). Increasing the amount of crosslinkable functional groups in resin (A) can increase the gel fraction, while decreasing it can be achieved by adjusting the composition and content in the opposite direction. Similarly, increasing the content of the thermal polymerization initiator (B) can increase the gel fraction, while decreasing it can be achieved by adjusting the content in the opposite direction.

[0116] 4. Laminated sheet This resin sheet may be a laminated sheet 33 in which the resin sheet 30 is sandwiched between a release liner 31 and a protective film 32, as shown in Figure 5, until immediately before use.

[0117] The release liner 31 and protective film 32 are not particularly limited as long as they possess both release properties and protective properties. Examples include polyester films such as polybutylene terephthalate and polyethylene naphthalate, polyolefin films such as polypropylene and polyethylene, polyvinyl chloride films, polyurethane films, nylon films, polyolefin films, triacetylcellulose films, and cycloolefin films. The protective film may also have other functional layers, such as antistatic properties.

[0118] The release liner 31 and the protective film 32 may be made of the same film, but from the viewpoint of handling, it is preferable to have a difference in release strength.

[0119] The resin sheet 30 may consist of multiple layers having different functions. When laminating, it is preferable to laminate a water vapor barrier layer, a layer with excellent alcohol resistance, a layer with excellent abrasion resistance, a gas barrier layer, a hard coat layer, and the like.

[0120] It is preferable to wind the laminated sheet onto a core in a roll shape after manufacturing the laminated sheet, or while manufacturing the laminated sheet, to form a laminated sheet roll.

[0121] 5. Manufacturing method of the mounted substrate Below, an example of the process of forming an insulating layer 3 on a micro-LED 2 mounted on a substrate 1 will be explained with reference to Figure 6. Note that this process may be applied to other optical semiconductor devices instead of micro-LEDs. Furthermore, the manufacturing method of the mounting substrate described herein is not limited to this method.

[0122] Process (a): Laminated sheet or resin sheet placement process The release liner 31 (see Figure 5) is peeled off the laminated sheet 33, and the laminated sheet 33 with the resin sheet 30 exposed is placed on the substrate 1 on which multiple microLEDs 2 are mounted, as shown in Figure 6(a). The size of the microLEDs is, for example, 100 μm or less in thickness and 40,000 μm in area when viewed from above. 2 The following conditions apply: Thickness of 50 μm or less, and a planar area of ​​10,000 μm².2 The following may also be applied: thickness of 20 μm or less, and area in plan view of 2,500 μm. 2 The following may also be applied.

[0123] The spacing between microLEDs mounted on the substrate is, for example, 10 to 5,000 μm. When red, green, and blue microLEDs are mounted on the substrate as a set of one pixel, the spacing between pixels is, for example, 10 to 2,000 μm, preferably 20 to 1,800 μm, and more preferably 500 to 1,500 μm. The spacing between microLEDs within one pixel is, for example, 10 to 200 μm, preferably 10 to 100 μm, and more preferably 20 to 60 μm.

[0124] Process (b): Pressing process After step (a), a pressing step is performed. The resin sheet 30 is made to flow by pressing, and the resin sheet 30 fills the gaps between the multiple micro LEDs 2 formed on the substrate 1 (see Figure 6(b)). The pressing method is not particularly limited, but hot pressing and vacuum pressing are preferred. From the viewpoint of embedding the resin sheet, the pressing temperature is preferably 20 to 200°C, more preferably 30 to 150°C, even more preferably 40 to 130°C, and particularly preferably 60 to 110°C. From the viewpoint of embedding the resin sheet, the pressing time is preferably 5 seconds to 20 minutes, more preferably 10 seconds to 10 minutes, even more preferably 30 seconds to 5 minutes, and particularly preferably 1 to 3 minutes. From the viewpoint of embedding the resin sheet, the pressing pressure is preferably 0.01 to 10 MPa, more preferably 0.05 to 5 MPa, even more preferably 0.07 to 3 MPa, and particularly preferably 0.09 to 1 MPa. The pressing step and curing treatment may be performed simultaneously, or the curing treatment may be performed after the pressing step.

[0125] After the resin sheet 30 softens and flows and fills the gaps between the micro-LEDs 2, a curing treatment is performed by heat aging to improve adhesion to the micro-LEDs and the adherend, thereby obtaining a cured insulating layer 3. The heating temperature is preferably 40 to 250°C, more preferably 80 to 220°C, and even more preferably 100 to 190°C. The heating time is preferably 30 to 300 minutes, more preferably 60 to 240 minutes, and even more preferably 90 to 180 minutes. Performing such an aging process can remove residual stress in the insulating layer. It can also promote smoothing of the adhesion surface. Note that heat aging may be performed after step (c) described later. The protective film 32 of the laminated sheet 33 may be peeled off before or after heat aging.

[0126] Process (c): Etching process After step (b), an etching step (step (c)) may be performed as needed to remove or thin the insulating layer 3 formed from the resin sheet on the micro-LED. If step (c) is performed, it is preferable to do so after peeling off the protective film. By removing the excess insulating layer 3, the brightness of the micro-LED can be improved, and the visibility when emitting light can be enhanced. The thickness of the insulating layer may be about the same as the thickness of the micro-LED as shown in Figure 6(c), or it may be less than or equal to the thickness of the micro-LED as shown in Figure 2. Note that it is not necessary to completely remove the insulating layer from the micro-LED; it is sufficient if it is substantially removed, and it is acceptable if a thin film remains. The etching method is not particularly limited, but examples include wet etching methods such as chemical polishing using chemical agents; physical polishing using abrasives; laser etching; plasma etching using argon plasma or oxygen plasma; and dry etching methods such as ion beam etching. From the viewpoint of reducing surface irregularities, a combination of wet etching and dry etching methods is preferred. Plasma etching is preferred as the dry etching method. Examples of plasma etching conditions include using an anisotropic plasma apparatus with a mixed gas of CF4 / O2 / N2, at an output of 1500-3000W, for 180-600 seconds. In this case, the gas supply rate of CF4 is, for example, 50-100 sccm, the gas supply rate of O2 is, for example, 500-1000 sccm, and the gas supply rate of N2 is, for example, 50-100 sccm.

[0127] As shown in Figure 4, when forming a partition with the insulating layer 3, a protective layer (not shown) can be formed in advance on top of the micro-LED 2, and after forming the insulating layer and etching the insulating layer up to the top of the protective layer of the micro-LED 2 in process (c), the protective layer of the micro-LED can be removed.

[0128] An insulating layer is obtained from this resin sheet through processes (a) to (c), etc. This resin sheet allows for the simultaneous formation of an insulating layer on an array of numerous regularly spaced optical semiconductor elements on a substrate. [Examples]

[0129] The present disclosure will be described in detail below with reference to examples and comparative examples, but this disclosure is not particularly limited to the examples. In the following description, "parts" and "%" refer to "parts by mass" and "% by mass," respectively, unless otherwise specified.

[0130] (a) Raw materials for resin sheets, etc. <Resin (A)> [(Meth)acrylic resin (A-1) solution manufacturing] In a reaction vessel (hereinafter simply referred to as "reaction vessel") equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen inlet tube, 80 parts ethyl acetate, 3 parts n-butyl acrylate, 50 parts n-butyl methacrylate, 40 parts 2-ethylhexyl methacrylate, 5 parts 2-hydroxyethyl methacrylate, and 0.1 parts 2,2'-azobisisobutyronitrile as an initiator were charged, and the atmosphere in the reaction vessel was replaced with nitrogen gas. Then, under a nitrogen atmosphere, the mixture was heated to 75°C with stirring to start the reaction. The reaction solution was then reacted at 75°C for 4 hours. After the reaction was complete, it was cooled and diluted with ethyl acetate to obtain a (meth)acrylic resin (A-1) intermediate solution. Two parts of Karenz MOI (2-methacryloyloxyethyl isocyanate, manufactured by Resonaq) were added to the obtained intermediate solution as a modifier, and the mixture was stirred at 60°C for 24 hours. Dilution with ethyl acetate as needed was then performed to produce a (meth)acrylic resin (α) solution containing a methacryloyl group. The results were Mw: 35,000, Tg: 6.9°C, and solids content: 25%.

[0131] [Production of (meth)acrylic resin (A-2) solution] A solution of (meth)acrylic resin (A-2) containing a methacryloyl group was prepared by the same method as the production of (meth)acrylic resin (A-1), except that the monomer amounts were changed as follows: 3 parts n-butyl acrylate to 2 parts methyl acrylate, 50 parts n-butyl methacrylate to 32 parts methyl methacrylate, 40 parts 2-ethylhexyl methacrylate to 60 parts 2-ethylhexyl methacrylate, 5 parts 2-hydroxyethyl methacrylate to 3 parts methacrylic acid, and 2 parts 2-methacryloyloxyethyl isocyanate to 3 parts glycidyl methacrylate. The results were Mw: 140,000, solids content: 25%, acid value: 10 mg KOH / g, and Tg: 24.1℃.

[0132] [Preparation of (meth)acrylic resin (A-3) solution] A solution of (meth)acrylic resin (A-3) containing an acryloyl group was prepared by diluting cyclomer P(ACA)Z254F (manufactured by Daicel Ornex) with ethyl acetate. The results were Mw: 21,000, solids content: 25%, acid value: 70 mgKOH / g, and Tg: 88°C.

[0133] <Thermal polymerization initiator (B)> B-1: Luperox DI (di-t-butyl peroxide, manufactured by Arkema Yoshitomi Co., Ltd.) B-2: VAM-110 (2,2'-Azobis(N-butyl-2-methylpropionamide), manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) <Silane coupling agent (C)> C-1: KBM-402 (3-Glycidoxypropylmethyldimethoxysilane, manufactured by Shin-Etsu Silicone Co., Ltd.) C-2: KBM-502 (3-methacryloxypropylmethyldimethoxysilane, manufactured by Shin-Etsu Silicone Co., Ltd.) C-3: KBM-5803 (8-methacryloxyoctyltrimethoxysilane, manufactured by Shin-Etsu Silicone Co., Ltd.) <Dispersion (D)> [Colorant dispersion] [Example of carbon black dispersion (D-1) manufacturing process] 800 parts of (meth)acrylic resin (A-1) solution, 800 parts of carbon black (P-1) MA100R (manufactured by Mitsubishi Chemical Corporation, particle size 24 nm, pH 3.5, for black), 400 parts of methyl ethyl ketone as a solvent, and 2 parts of Solsperse 5000 (manufactured by Lubrizol Corporation) as a pigment derivative type dispersant were mixed and pre-dispersed in a disperser. Then, the main dispersion was carried out for 2 hours in a 0.6 L volume Dynomill filled with 1800 g of zirconia beads with a diameter of 1.0 mm to obtain CB dispersion (D-1) (solid content: 50%).

[0134] [Example of carbon black dispersion (D-2) manufacturing process] CB dispersion (D-2) (solids content: 50%) was produced by the same method as the production of CB dispersion (D-1), except that 800 parts of (meth)acrylic resin (A-1) solution were replaced with 800 parts of (meth)acrylic resin (A-2) solution.

[0135] [Example of carbon black dispersion (D-3) manufacturing process] CB dispersion (D-3) (solid content: 50%) was produced in the same manner as the production of CB dispersion (D-2), except that carbon black (P-1) MA100R was changed to carbon black (P-2) #52 (manufactured by Mitsubishi Chemical Corporation, particle diameter 27 nm, pH 8, for black).

[0136] [Production Example of Titanium Oxide Dispersion (D-4)] Titanium oxide dispersion (D-4) (solid content: 50%) was produced in the same manner as the production of CB dispersion (D-1), except that carbon black (P-1) MA100R was changed to titanium oxide (P-3) type peek CR-97 (manufactured by Ishihara Sangyo Co., Ltd., particle diameter 250 nm, for white), and the pigment derivative type dispersant Solsperse 5000 was changed to the dispersant DISPEARBYK 142 (manufactured by BYK).

[0137] [Inorganic Filler Dispersion] [Production Example of Zirconium Oxide Dispersion (D-5)] Zirconium oxide dispersion (D-5) (solid content: 50%) was produced in the same manner as the production of titanium oxide dispersion (D-4), except that titanium oxide (P-3) type peek CR-97 was changed to zirconium oxide (Q-1) PCS-60 (manufactured by Shin Nippon Chemical Co., Ltd., BET method 60 m 2 / g, for high refractive index transparency).

[0138] [Crosslinkable Component] E-1: jER828 (epoxy compound, manufactured by Mitsubishi Chemical Corporation), Mw: 370 E-2: ST-6100 (epoxy compound, manufactured by Nippon Steel Chemical & Material Co., Ltd.), Mw: 2,000 [Flow Regulator] Table 1 shows the product names, presence or absence of hydrogenation treatment, softening point temperature, acid value and hydroxyl value of flow regulators T1 to T5.

Table 1

[0139] [Solid content] The solid content of each component was determined by the following method. First, the mass (W0) of the aluminum cup was weighed using a precision balance. Next, approximately 1g of each sample was placed in the aluminum cup, and the mass of the sample in the aluminum cup (W1) was weighed using a precision balance. The sample in the aluminum cup was heated in a 150°C oven for 120 minutes, then removed from the oven and allowed to return to room temperature. The residual mass (W2) of the heated sample in the aluminum cup was weighed using a precision balance. Then, the solid content was calculated using the formula (W2-W0) / (W1-W0)×100(%).

[0140] [Acid value] The acid value represents the acid value per gram of solid content for both resin (A) and the flow regulator, and was determined by potentiometric titration in accordance with JIS K 0070-1992. [Hydroxyl value] The hydroxyl value represents the hydroxyl value per gram of solid content for both resin (A) and the flow regulator, and was determined by potentiometric titration in accordance with JIS K 0070-1992.

[0141] [Softening point] The softening point of rosin-based flow regulators was measured using the ring-and-ball method in accordance with JIS K 5902 (2006). The softening point of petroleum resin-based materials was also measured using the ring-and-ball method in accordance with JIS K 2207 (2006).

[0142] [Glass transition temperature (Tg)] A coating solution of resin (A) was applied to the release layer of a 75 μm thick protective film (Mitsui Chemicals Tohcello, SP-PET-O3) so that the thickness after drying would be 20 μm. After drying in a 100°C hot air oven for 3 minutes, the release layer side of a 50 μm thick release liner (Mitsui Chemicals Tohcello, SP-PET-O1) was bonded to the resin (A) side. The protective film and release liner were then peeled off, and the Tg of the obtained resin (A) was measured using a differential scanning calorimetry analyzer (TA Instruments, "Discovery DSC 2500"). Approximately 2 mg of the sample was placed in an aluminum pan, weighed, and set in the differential scanning calorimetry analyzer. An empty aluminum pan of the same type was used as a reference, and the analyzer was held at 100°C for 5 minutes, after which it was rapidly cooled to -50°C using liquid nitrogen. Subsequently, the temperature was increased at a rate of 5°C / min, and the glass transition temperature (Tg) of resin (A) was determined from the resulting DSC chart. If multiple glass transition temperatures (Tg) were found, the one with the highest temperature was used as the glass transition temperature (Tg). [Reflectance] The reflectance in the visible light band was measured using a V-570 ultraviolet-visible spectrophotometer manufactured by JASCO Corporation under a 25°C atmosphere. [Transmittance] Total light transmittance was measured using a haze meter (NDH-2000, manufactured by Tokyo Denshoku Co., Ltd.) in accordance with JIS K 7361-1. [Refractive index] Using an ATAGO Abbe refractometer "DR-M2," the refractive index of the cured layer obtained by heating a resin sheet at 150°C for 120 minutes was determined in a 25°C atmosphere in the sodium D line (wavelength 594 nm). [Linear expansion coefficient of cured resin sheets at -50°C to 50°C] Using a thermal analyzer (TA Instruments, TMA Q400), a 4mm x 30mm resin sheet was heat-treated at 150°C for 120 minutes to obtain a cured product. After cooling the obtained cured product to -50°C, the temperature was increased from -50°C to 150°C at a heating rate of 5°C / min. In tensile mode, the dimensional change of the sample was measured under conditions of nitrogen gas flow rate: 50.0 mL / min and applied load: 0.0196 N. From the obtained data, the slope of the dimensional change from -50°C to 50°C was calculated, and the coefficient of linear expansion (ppm / °C) of the cured resin sheet from -50°C to 50°C was determined.

[0143] [Storage modulus of resin sheet at 60°C (G'60) and loss tangent at 60°C (tanδ60)] Samples were prepared so that the resin sheet thickness was 1 mm or more. Specifically, the resin sheet was laminated a specified number of times and laminated as needed to achieve a thickness of 1 mm or more. Alternatively, samples could be obtained by coating the resin sheet to a thickness of 1 mm. The storage modulus G' of the obtained resin sheet was measured using a rheometer (TA Instruments, DHR-2) with a φ8 mm measuring probe under the conditions of a strain of 0.1%, a frequency of 1 Hz, and a heating rate of 3°C / min from -50 to 150°C. From these measurement results, the storage modulus at 60°C (G'60) was read, and the loss tangent (tanδ60) at 60°C was calculated by dividing the simultaneously measured loss modulus G'' at 60°C by G'60.

[0144] [Chlorine elution amount from resin sheets] A 10g resin sheet was finely shredded and placed in a sample bottle. 90g of purified water was added while irradiating with ultrasound. The sample was then allowed to stand for 24 hours at 90°C. After standing, the lower aqueous layer was filtered using a membrane filter to obtain a sample for chlorine elution measurement. The chlorine elution amount of this sample was measured using an ion chromatograph (Dionex DX-500). If the value was below the detection limit (50ppm), it was indicated as ND (Not Detected).

[0145] [Sulfur content of resin sheets] Approximately 0.25 g of resin sheet was accurately weighed into a Teflon® container in a microwave sample decomposition apparatus (Analytic Jena, TOPwave), 7 mL of nitric acid was added, and the mixture was allowed to stand for 1 hour. Then, the container was placed in the apparatus with a dedicated lid and outer container, and heat-treated at 200°C for 10 minutes. After heat treatment, the mixture was cooled to room temperature, and the treated solution was transferred to a 50 mL volumetric flask. The treated Teflon container was then washed with ultrapure water and transferred to the same volumetric flask. If insoluble matter was observed, the solution was filtered through No. 6 filter paper, and the volume was adjusted to 50 mL with ultrapure water to obtain the measurement sample. The obtained treated solution was then measured using an ICP analyzer (SPECTRO, AECOS), and the sulfur content in the resin sheet was quantified using a calibration curve prepared with standard solutions of the target element. If the value was below the detection limit (50 ppm), it was indicated as ND (Not Detected).

[0146] [Gel fraction] The laminated sheets of each example and comparative example were allowed to stand at 180°C for 120 minutes to prepare cured products. The obtained cured products were allowed to return to room temperature, cut to a width of 30 mm and a length of 100 mm, and test pieces made of cured resin sheets were obtained. After removing the release liner and protective film from the test pieces, the mass (W0) of a 300-mesh stainless steel wire mesh was measured. Next, the wire mesh was folded while attaching the test piece to it, and the mass (W1) was measured. The wire mesh, with the test piece wrapped inside, was immersed in an extract (methyl ethyl ketone) and allowed to stand at 40°C for 24 hours. After immersion, the wire mesh was removed from the extract, washed with a small amount of methyl ethyl ketone, dried at 100°C for 30 minutes, and then the mass (W2) was measured. The gel fraction was calculated using the following formula based on these masses. Gel fraction (%) = {(W2-W0) / (W1-W0)} × 100 W0: Mass of the wire mesh W1: Mass of wire mesh + test specimen W2: Mass of wire mesh + test specimen after drying

[0147] [Change in b* value after lightfastness test] A 1.1 mm thick glass plate (blue glass, manufactured by Kawamura Kyuzo Shoten Co., Ltd.) was prepared. The laminated sheet from Example 1, described later, was cut to 2 cm x 5 cm, and the release liner was peeled off to expose the resin sheet. The laminated sheet was then placed on the glass plate. Subsequently, a 50 μm thick TPX (Opulan X-44B, manufactured by Mitsui Chemicals Tohcello Co., Ltd.) and a 2.0 mm thick PVC film (Celeb T, manufactured by Okamoto Co., Ltd.) were laminated in order as cushioning material on top of the protective film, and cardboard was further laminated to prevent sticking. The laminate consisting of the glass plate / resin sheet / protective film / cushioning material (TPX / PVC film) / cardboard was pressed from above against the substrate surface at 1 MPa and 100°C for 3 minutes, pressing the glass plate and resin sheet together and forming an insulating layer on the glass plate. After pressing, the cardboard and cushioning material were peeled off. A test specimen consisting of a glass plate, an insulating layer, and a protective film was left to stand at 150°C for 120 minutes, and then the protective film was peeled off to create a test specimen for lightfastness testing by ensuring close contact between the glass plate and the insulating layer. Subsequently, the initial b* value was obtained by measuring using a color difference meter CR-300 (manufactured by Konica Minolta Corporation) according to the method described in JIS-Z8722. An insulating layer on a glass plate was placed in a Suga Test Instruments XL75 xenon weather meter and exposed for 250 hours under conditions of a black panel temperature of 40°C and an irradiation dose of 100,000 Lux. After cooling at 23°C-50%RH for 24 hours, it was measured in the same way as the initial b*, and the obtained value was defined as the post-exposure b*. The change in b* was calculated using the formula "|initial b* - post-exposure b*| = change in b*".

[0148] [Optical density] The release liner and protective film were removed from the resin sheet, and the optical density (visual) of the exposed resin sheet was measured using an optical densitometer (361T desktop transmission densitometer, manufactured by X-RITE).

[0149] (c) Manufacturing of resin compositions, resin sheets, laminated sheets and laminates [Example 1] Sixty parts of CB dispersion (D-1) (24 parts of carbon black (P-1), 6 parts of resin (A-1), 30 parts of solvent), 244 parts of (meth)acrylic resin (A-1) solution (61 parts of (meth)acrylic resin (A-1), 183 parts of solvent), 3 parts of Luperox DI (manufactured by Arkema Yoshitomi Co., Ltd.) as a thermal polymerization initiator (B-1), 1 part of KBM-402 (manufactured by Shin-Etsu Silicone Co., Ltd.) as a silane coupling agent (C-1), 5 parts of KE-100 (manufactured by Arakawa Chemical Co., Ltd.) as a flow regulator (T-1), and 63 parts of toluene as a solvent were sequentially added with a disperser while stirring until homogeneous. Next, the mixture was filtered through a 10 μm pore size membrane filter to remove coarse foreign matter that could cause uneven coating, and a resin composition with a solid content of 27% was obtained. The solid content equivalent amounts of each component are listed in Table 2. In addition, the "Content Rate" in the "Resin (A)" column of Table 2, etc., shall not include the content rate of resin (A) in the colored dispersion.

[0150] The resin composition of Example 1 was applied to the release layer of a 50 μm thick protective film (SP-PET-O3-BU (manufactured by Mitsui Chemicals Tohcello Co., Ltd.)) so that the thickness after drying was 20 μm, and the resin sheet of Example 1 was dried in a 100°C hot air oven for 3 minutes. Next, the release layer side of a 25 μm thick release liner (SP-PET-O1-BU, manufactured by Mitsui Chemicals Tohcello Co., Ltd.) was bonded to the exposed resin sheet surface. After that, it was aged for 7 days in a 0°C environment to obtain the laminated sheet of Example 1, in the order of release liner / resin sheet / protective film.

[0151] [Examples 2-34], [Comparative Examples 1-9] Resin compositions, resin sheets, and laminated sheets were prepared in the same manner as in Example 1, except that the raw materials and their contents were changed as shown in Tables 2 to 4. Other components were also added at the same time. Note that the amounts of resin (A), thermal polymerization initiator (B), silane coupling agent (C), CB dispersion, flow regulator, and other components in Tables 2 to 4 are all based on solid content, and blank spaces indicate that the component was not included.

[0152] [Table 2]

[0153] [Table 3]

[0154] [Table 4]

[0155] (d) Evaluation The following evaluations were performed on the resin sheets of each example and comparative example. The results are shown in Tables 5 to 7.

[0156] [Embedding] A test substrate (a 25mm x 25mm glass plate with a recessed area of ​​200μm width, a raised area of ​​5μm height, and a raised area of ​​200μm width formed on one side) was prepared to mimic the uneven surface of a micro-LED substrate. A schematic cross-sectional view of the test substrate is shown in Figure 7. The laminated sheet from Example 1 was cut to a size of 30mm x 30mm, the release liner was peeled off to expose the resin sheet, and the resin sheet was placed on the surface of the test substrate where the uneven areas were formed. Then, as cushioning material, a 50μm thick TPX (Opulan X-44B, manufactured by Mitsui Chemicals Tohcello Co., Ltd.) and a 2.0mm thick PVC film (Celeb T, manufactured by Okamoto Co., Ltd.) were laminated in order on top of the protective film, and cardboard was further laminated to prevent sticking. A laminate consisting of a resin sheet, protective film, cushioning material (TPX / PVC film), and cardboard was placed on a glass substrate with protrusions. The laminate was then pressed from above against the substrate surface at 0.3 MPa and 100°C for 5 minutes, filling the recesses of the test substrate with the resin sheet to form an insulating layer. After pressing, the cushioning material and cardboard were removed. The insulating layer was cured by leaving the obtained insulating layer-coated test substrate in a 150°C oven for 2 hours. The insulating layer that had protruded from the sides of the cured insulating layer-coated test substrate was roughly removed using a cutter, and then the remaining insulating layer on the sides of the insulating layer-coated test substrate was removed by sanding, exposing the sides of the test substrate so that the uneven surfaces could be observed. The embedding ability was evaluated by observing 15 recesses in the central region of the test substrate with a microscope. In the recesses of the test substrate, if the maximum gap between the insulating layer and the test substrate was 1 μm or less, it was judged that the groove was embedded, and it was evaluated according to the following criteria. AA: There are 15 embedded grooves. A: There are 12 to 14 embedded grooves. B: There are 10 to 11 embedded grooves. C: There are 8-9 embedded grooves. D: There are 7 or fewer embedded grooves.

[0157] [Migration potential] A laminated sheet, with the release liner removed to expose the resin sheet, was placed on a test substrate on which comb-shaped electrodes (material: silver-plated copper foil, pattern pitch: 50 μm, L / S = 25 μm / 25 μm) were formed on a polyimide film substrate. Then, a 50 μm thick TPX (Opulan X-44B, manufactured by Mitsui Chemicals Tohcello Co., Ltd.) and a 2.0 mm thick PVC film (Celeb T, manufactured by Okamoto Co., Ltd.) were sequentially laminated as cushioning material on top of a protective film, and cardboard was further laminated to prevent sticking. The laminate consisting of the test substrate / resin sheet / protective film / cushioning material (TPX / PVC film) / cardboard was pressed from above against the substrate surface at 1 MPa and 100°C for 3 minutes, pressing the test substrate and resin sheet together and forming an insulating layer on the test substrate. After pressing, the cardboard and cushioning material were removed. A test specimen consisting of a test substrate, an insulating layer, and a protective film was left to stand for 120 minutes under conditions of 150°C, and then the protective film was peeled off to create a test specimen for migration evaluation by ensuring close contact between the test substrate and the insulating layer. This test specimen was subjected to a voltage of 50V for 1,000 hours at two non-conducting points on the comb-type electrode under conditions of 85°C and 85% humidity. Subsequently, the insulation resistance value was measured at room temperature (23°C). Note that "leak touch" below refers to dielectric breakdown due to a short circuit, where the resistance momentarily drops and current flows. The absence of leak touch means that the insulation performance does not decrease. Migration performance was judged according to the following criteria. A: Resistance value is 1 × 10 8 Omega or higher, and no leaks. B: Excluding criterion A, the resistance value is 1 × 10 6 Ω or higher, and with one or fewer leak touches. C: Resistance value is 1 × 10 6 Omega or higher, and two leak touches. D: Resistance value is 1 × 10 6 Less than Ω, or 3 or more leak touches.

[0158] [Adhesion] One sheet of each example and comparative example was cut to 25mm x 100mm and prepared. The release liner was removed to expose the resin sheet. The exposed resin sheet surface was then placed on a glass plate (25mm x 100mm x 1.1mm, blue glass, manufactured by Kawamura Kyuzo Shoten Co., Ltd.). On the protective film, a 50μm thick TPX (Opulan X-44B, manufactured by Mitsui Chemicals Tohcello Co., Ltd.) and a 2.0mm thick PVC film (Celeb T, manufactured by Okamoto Co., Ltd.) were laminated in order as cushioning material, and then cardboard was laminated to prevent sticking. Next, the laminate consisting of the glass plate / resin sheet / protective film / cushioning material (TPX / PVC film) / cardboard was pressed from above against the substrate surface at 1MPa and 100℃ for 3 minutes to press the glass plate and resin sheet together. This formed an insulating layer on the glass plate. After pressing, the cardboard and cushioning material were peeled off. A test specimen consisting of a glass plate, an insulating layer, and a protective film was left to stand for 120 minutes under conditions of 150°C. After the protective film was removed, the glass plate and the insulating layer were brought into close contact, resulting in a test specimen having a cured insulating layer. Following the JIS K 5600-5-6 (cross-cut method), a 1mm square right-angle grid pattern (25 squares) was created on the insulating layer of the test specimen using a cross-cut guide and a utility knife. Adhesive tape (CT1835, manufactured by Nichiban Co., Ltd.) was then applied to the grid-cut areas and firmly adhered to the insulating layer. Within 5 minutes of adhesion, the tape was pulled off at an angle close to 60° for 0.5 to 1.0 seconds. The detached insulating layer was observed, and its adhesion was evaluated according to the following criteria. If the insulating layer detached from the glass plate during the removal of the protective film, it was given a rating of D. A: There are 0 squares that have been peeled off. B: One or two squares have peeled off. C: 3 to 5 squares have peeled off. D: 6 to 25 squares have peeled off.

[0159] [Storage stability] The laminated sheets of each example and comparative example were left to stand for 24 hours under conditions of 35°C, and then the embedding process was carried out in the same manner as in the embedding test. The curing process was not performed, and the sheets were evaluated using the same criteria as for embedding. Furthermore, the laminated sheets of each example and comparative example were subjected to the same tests and evaluations as under the 35°C conditions, but with the temperature changed from 35°C to 50°C. The evaluation criteria were as follows. A: More than 14 grooves embedded after standing at 50°C, and more than 14 grooves embedded after standing at 35°C. B: The number of grooves embedded after standing at 50°C is 13 or less, and the number of grooves embedded after standing at 35°C is 14 or more. C: After standing at 50°C, the number of embedded grooves is 13 or less, and after standing at 35°C, the number of embedded grooves is 8 or more and 13 or less. D: No more than 13 grooves embedded after standing at 50°C, and no more than 7 grooves embedded after standing at 35°C.

[0160] [Yellowing prevention] Sample pieces for each example and comparative example were prepared in the same manner as the "adhesion" evaluation described above. Then, the exposed surface of the resin sheet was measured before and after the test using a colorimeter CR-300 (manufactured by Konica Minolta Corporation) according to the method described in JIS-Z8722, and the b* value expressed in the L*a*b* color system was determined. The value before the test was taken as the initial value, and the value obtained after the lightfastness test was taken as the b* after exposure. The change in b* (Δb* value) was calculated using the formula "|initial b* - b* after exposure| = change in b*". Note that a smaller Δb* value indicates less yellowing. If the total light transmittance of the sample piece was 70% or higher, the b* value for transmission was measured, and the obtained value was used as the initial b* value. If the total light transmittance of the sample piece was less than 70%, the b* value for reflection was measured, and the obtained value was used as the initial b* value. The following criteria were used for evaluation. Grades A through C were considered good. A: The Δb* value is less than 0.9. B: The Δb* value is 0.9 or greater and less than 1.2. C: Δb* value is 1.2 or greater, and less than 1.4. D: Δb* value is 1.4 or higher.

[0161] The evaluation was rated A, B, and C in descending order of performance, with D indicating failure to meet the target performance. Furthermore, products with particularly excellent embedding capabilities received an AA rating.

[0162] [Table 5]

[0163] [Table 6]

[0164] [Table 7]

[0165] Examples 1-3 confirmed that the optical density of the resin sheet was 4 or higher, and that a black layer was obtained in the insulating layer. Example 15 confirmed that the reflectance of the resin light in the visible light band was 70% or higher, and that a white layer was obtained in the insulating layer. Example 16 showed that the cured product obtained by heat-treating the resin sheet at 150°C for 120 minutes had a total light transmittance in the visible light band of 80% or higher and a refractive index of 1.47 or higher. Furthermore, it was confirmed that the insulating layer formed using Example 16 was a high refractive index layer.

[0166] When the content of the flow modifier in the resin sheet exceeds 30% by mass relative to 100% by mass of the resin sheet, it was confirmed that there are problems with embedding, migration, storage stability, and yellowing suppression, as shown in Comparative Example 2. Furthermore, when the storage modulus (G'60) is less than 100 kPa, problems with embedding, as shown in Comparative Example 1, and problems with adhesion, as shown in Comparative Example 4, were confirmed. Moreover, when the storage modulus (G'60) exceeds 100 MPa, problems with embedding were confirmed, as shown in Comparative Examples 3 and 5. The resin composition of Comparative Example 3 failed to meet the target performance for embedding and migration, and also had problems with the overall performance balance, including storage stability, and could not satisfy the required performance at a high level. Furthermore, when the coefficient of linear expansion of the resin composition at -50°C to 50°C exceeds 250 ppm / °C, problems with migration were confirmed, as shown in Comparative Examples 3 and 6. In contrast, the resin sheets of Examples 1 to 29 exhibited excellent embedding properties, as well as superior migration properties, adhesion, and storage stability. [Explanation of Symbols]

[0167] 1: Circuit board 2: Micro LED 3: Insulating layer 4: Test board 30: Resin sheet 31: Release Liner 32: Protective film 33: Laminated sheet 100: Micro LED board

Claims

1. A resin sheet for forming an insulating layer on a substrate on which multiple optical semiconductor elements are mounted, When 10 g of the aforementioned resin sheet is immersed in 90 g of purified water at 90°C for 24 hours, the amount of chlorine leached out is 500 ppm or less. The coefficient of linear expansion of the cured product obtained by heat-treating the resin sheet at 150°C for 120 minutes is 20 to 250 ppm / °C at -50 to 50°C. The storage modulus (G'60) at 60°C obtained by dynamic viscoelasticity measurement of the resin sheet is 100 kPa to 100 MPa. The aforementioned resin sheet contains a resin (A) with a weight-average molecular weight of 10,000 or more, and a flow regulator which is a hydrogenated hydrocarbon resin. The content of the flow regulator is 0.3 to 30% by mass relative to 100% by mass of the solid content of the resin sheet. A resin sheet that satisfies at least one of the following conditions (I) and (II). (I) The acid value of the flow regulator is 0.5 to 400 mg KOH / g. (II) The acid value of resin (A) is 1 to 50 mg KOH / g.

2. The resin sheet according to claim 1, wherein the softening temperature of the flow regulator is 70 to 140°C.

3. The resin sheet according to claim 1, wherein the optical density is 4 or higher.

4. The resin sheet according to claim 1, wherein the reflectivity is 70% or more.

5. The resin sheet according to claim 1, wherein the cured product obtained by heat-treating the resin sheet at 150°C for 120 minutes has a total light transmittance in the visible light band of 80% or more and a refractive index of 1.47 to 1.

56.

6. The resin sheet according to claim 1, wherein resin (A) comprises (meth)acrylic resin.

7. The resin sheet according to claim 1, wherein the resin sheet contains a thermal polymerization initiator (B) and may also contain a silane coupling agent (C).

8. The resin sheet according to claim 1, wherein the sulfur content is 1000 ppm or less.

9. The device comprises a substrate on which multiple optical semiconductor elements are mounted, and an insulating layer formed on the substrate. An optoelectronic device wherein the insulating layer is a cured resin sheet according to any one of claims 1 to 8.

10. An electronic device having the optoelectronic device described in claim 9.

Images