A stretchable resin sheet having a light-diffusing portion, and a light-emitting sheet using the same.

Abstract

One aspect of the present invention relates to an elastic resin sheet formed using a resin composition which includes a thermosetting resin and a curing agent, wherein when the maximum height of a surface roughness on a first surface of the resin sheet is Rz1 (μm), the maximum height of a surface roughness on a second surface facing the first surface is Rz2 (μm), and a thickness is t (μm), Rz1, Rz2, and thickness t (μm) satisfy the following expression (1):(Rz1+Rz2) / t≤0.5. The elastic resin sheet comprises, on at least one among the first surface and the second surface, a light-diffusing portion having an uneven shape with an arithmetic mean roughness Ra of 0.3 μm to 5.0 μm, and has an initial tensile modulus of 0.5 MPa to 500 MPa.

Description

Technical Field

[0001] The present invention relates to a stretchable resin sheet having a light diffusing portion and a light emitting sheet using the same.

Background Art

[0002] In recent years, LEDs are becoming mainstream in the field of lighting. As a major difference from conventional incandescent bulbs and fluorescent lamps that have been used conventionally, LEDs are point light sources. Therefore, when using LEDs as lighting, a light diffusing sheet with strong diffusion and high light transmittance is required to eliminate the lamp image of the point light source.

[0003] For example, in Patent Document 1, while achieving both elimination of the actual image of the LED light source and high light transmittance, as a light diffusing film for LED lighting with rigidity, it has two or more transparent substrates, and in parts other than the outermost layer, a film containing two types of particle groups in which at least one of the refractive index n and the weight average particle diameter a is different together with a binder is disclosed.

[0004] However, the light diffusing film described in Patent Document 1 has no flexibility and cannot follow uneven surfaces or be applied to members having a curved surface, so its applications are limited.

[0005] On the other hand, a resin substrate having stretchability, a conductor substrate having an uneven shape (predetermined surface roughness) (Patent Document 2), and a sheet-shaped molded body made of an epoxy resin composition (Patent Document 3) have been reported.

[0006] However, the technology described in Patent Document 2 is a stretchable conductor substrate with improved surface stickiness, and diffusibility of transmitted light etc. are not considered. Also, the technology described in Patent Document 3 is a technology mainly used for flexible devices for interfaces, encapsulating materials for semiconductor encapsulation, etc., and also has low haze as a characteristic and cannot be used as a light diffusing film.

[0007] Recent needs include applications such as arranging LED chips or light-emitting compositions on stretchable circuit boards to create highly flexible light-emitting sheets. These applications require light-diffusing films that are flexible, heat-resistant, and resistant to breakage during stretching. However, no light-diffusing film that fully meets these needs has yet been reported.

[0008] This invention has been made in view of these circumstances, and aims to provide a light-diffusing film that is flexible, heat-resistant, and less prone to tearing during expansion and contraction. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2012-163716 [Patent Document 2] Japanese Patent Publication No. 2019-160965 [Patent Document 3] Japanese Patent Publication No. 2019-189798 [Overview of the project]

[0010] As a result of diligent research, the inventors discovered that the above problems could be solved by using a stretchable resin sheet with the following configuration, and based on this finding, they completed the present invention through further research.

[0011] In other words, a stretchable resin sheet relating to one aspect of the present invention is a resin sheet formed using a resin composition containing a thermosetting resin and a curing agent. When the maximum surface roughness height on the first surface of the resin sheet is Rz1 (μm), the maximum surface roughness height on the second surface facing the first surface is Rz2 (μm), and the thickness is t (μm), then Rz1, Rz2, and the thickness t (μm) satisfy the following relationship (1): (Rz1+Rz2) / t≦0.5 (1) At least one of the first surface and the second surface is provided with a light-diffusing portion having an uneven shape with an arithmetic mean roughness Ra of 0.3 μm or more and 5.0 μm or less. It is characterized by having an initial tensile modulus of 0.5 MPa or more and 500 MPa or less.

[0012] Furthermore, the present invention also includes a light-emitting sheet that comprises the above-mentioned resin sheet as a luminescent diffusion layer. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic cross-sectional view showing a comparison of the uneven surface patterns of a resin sheet according to an embodiment of the present invention and other resin sheets. [Figure 2] Figure 2 is a schematic cross-sectional view showing an example of the configuration of a light-emitting sheet using the resin sheet of this embodiment. [Modes for carrying out the invention]

[0014] According to the present invention, it is possible to provide a stretchable resin sheet that is flexible and heat-resistant, and less likely to break when stretched, and that can be used as a light-diffusing film, as well as a light-emitting sheet using the same. Embodiments of the present invention will be specifically described below with reference to the drawings, but the present invention is not limited to these. In each drawing, the reference numerals indicate: 1 stretchable resin sheet, 2 fiber sheet, 3 conductive layer, 4 LED element, and 10 light-emitting sheet.

[0015] <Stretchable resin sheet> The stretchable resin sheet of this embodiment is a sheet that can be stretched by 5% or more. Furthermore, there is no particular upper limit to the stretchability, but 100% is sufficient. Hereafter, the stretchable resin sheet of this embodiment may also be referred to as a resin sheet.

[0016] The resin sheet of this embodiment is a stretchable resin sheet formed using a resin composition containing a thermosetting resin and a curing agent, and has an initial tensile modulus of 0.5 MPa or more and 500 MPa or less.

[0017] With such a configuration, it is possible to obtain a resin sheet that has heat resistance and can withstand heating processes such as lamination, and also functions as a protective film. Furthermore, since it can follow uneven shapes and curved surfaces, etc., it can be suitably used as a light diffusion film, a protective film, etc. for lighting members of various shapes.

[0018] In this embodiment, the initial tensile elastic modulus means the elastic modulus calculated from the stresses at 1% and 5% elongation when the sheet is elongated by 5%.

[0019] When the initial tensile elastic modulus is less than 0.5 MPa, there is a problem such as poor restoring force and inability to return to the original shape, so it is not preferable. Also, when the initial tensile elastic modulus exceeds 500 MPa, there is a problem such that the stretchability deteriorates and it is likely to break, so it is not preferable. A more preferable initial tensile elastic modulus of the resin sheet is 1.0 MPa or more and 50 MPa or less.

[0020] Note that the initial tensile elastic modulus in this embodiment can be measured by the method as shown in the examples described later.

[0021] The resin sheet of this embodiment is a sheet formed using a resin composition containing a thermosetting resin and a curing agent as described above, but it may be a sheet (film) made of a cured product (so-called C stage) of the resin composition, or a resin sheet in a state where the resin composition is uncured (so-called A stage) or semi-cured (so-called B stage).

[0022] When the maximum height of the surface roughness on the first surface of the sheet is Rz1 (μm), the maximum height of the surface roughness on the second surface facing the first surface is Rz2 (μm), and the thickness is t (μm), the Rz1, the Rz2, and the thickness t (μm) of the resin sheet of this embodiment satisfy the following relationship of formula (): (Rz1 + Rz2) / t ≤ 0.5 (1)

[0023] This configuration makes it possible to create a resin sheet that is resistant to tearing even when stretched or compressed.

[0024] In this embodiment, the maximum height (Rz) of the surface roughness is a value measured using a laser microscope (Olympus Corporation, "OLS3000").

[0025] Furthermore, the thickness t of the resin sheet in formula (1) refers to the thickness including the uneven surface shape of the sheet, as shown in Figure 1.

[0026] The resin sheet of this embodiment has a light-diffusing portion with an uneven surface, and can be suitably used as a light-diffusing film. More specifically, the light-diffusing portion has an uneven surface on at least one of the first surface and the second surface, with an arithmetic mean roughness Ra of 0.3 μm or more and 5.0 μm or less. With this configuration, excellent light-diffusing properties can be achieved. A more preferred range for the arithmetic mean roughness Ra is 0.5 μm or more and 5.0 μm or less. The shape of the uneven surface is not particularly limited and may be angular or round. The combination of the shape of the recesses and the shape of the protrusions is also not particularly limited and may be a combination of two angular shapes, two round shapes, or a combination of a round shape and an angular shape.

[0027] In this embodiment, the surface roughness (arithmetic mean roughness Ra) is a value measured using a laser microscope (Olympus Corporation, "OLS3000").

[0028] In this embodiment of the resin sheet, the first surface and the second surface are opposite each other, and when one is the front surface, the other is the back surface. There is no particular limitation on which of the first and second surfaces is the front surface. However, in order to obtain excellent light diffusion properties, it is preferable that the surface with the light diffusion portion is the front surface (the outer side that is not in contact with a light source such as an LED).

[0029] In other words, it is preferable that the resin sheet of this embodiment has a light-diffusing portion as described above on at least its surface (outside). The surface roughness of the inner side, which is in contact with a light source such as an LED, is not particularly limited and may have the same surface roughness as the surface described above. However, from the viewpoint of adhesion, it is desirable that the arithmetic mean roughness Ra of the resin sheet on the side in contact with the light source be 0.0 μm or more and 0.5 μm or less. In this specification, an arithmetic mean roughness Ra of 0.04 μm or less is considered to be 0.0 μm.

[0030] Based on the above, the light-diffusing portion of the resin sheet in this embodiment has the shape shown in Pattern 1 of Figure 1. Note that the shape pattern in Figure 1 is merely an example, and the present invention is not limited to this.

[0031] The upper part of Figure 1 shows the case where the resin sheet has surface roughness on one of its first and second surfaces (i.e., one side), while the lower part shows the case where the resin sheet has surface roughness on both its first and second surfaces (i.e., both sides).

[0032] In Pattern 1, both the single-sided and double-sided versions satisfy the above equation (1) and have a textured surface that satisfies the specified arithmetic mean roughness Ra. However, in Pattern 2, the specified equation (1) is not satisfied, and the sheet is prone to tearing during expansion and contraction, making it undesirable. In Pattern 3, although the above equation (1) is satisfied, the textured surface does not satisfy the specified arithmetic mean roughness Ra, and the light transmittance is low, making it undesirable.

[0033] In this embodiment, the resin sheet is provided with a light-diffusing portion that satisfies both requirements, as shown in Pattern 1, thereby having a sufficient light diffusion rate while suppressing breakage when the sheet is stretched or contracted.

[0034] Furthermore, it is preferable that the resin sheet of this embodiment has an average length RSm of 1.0 μm or more and 100 μm or less of the roughness curve elements in the uneven shape of the light-diffusing portion.

[0035] This is thought to reduce the periodicity of the uneven shape in the light-diffusing portion, thereby achieving an even higher light diffusivity. A more preferable range for RSm is 1.0 μm or more and 10 μm or less.

[0036] In this embodiment, RSm is a value measured using a laser microscope (OLS3000 manufactured by Olympus Corporation).

[0037] The thickness of the resin sheet in this embodiment is not particularly limited, but from the viewpoint of elasticity and ease of handling during lamination, it is preferable that the thickness be approximately 10 μm to 200 μm for uncured and semi-cured resin sheets, and more preferably approximately 30 μm to 150 μm. Furthermore, if the resin sheet is a heated and dried cured film, it is preferable that the thickness be approximately 10 μm to 200 μm, and more preferably approximately 30 μm to 150 μm.

[0038] The resin composition used for the resin sheet in this embodiment is not particularly limited in composition, as long as it is a resin composition containing a thermosetting resin and a curing agent.

[0039] For example, the resin composition of this embodiment preferably contains a polyrotaxane resin or an epoxy resin as a thermosetting resin, and it is particularly desirable that it contains at least an epoxy resin. This makes it possible to obtain a resin sheet that has sufficient heat resistance and can withstand the heat during lamination and the like.

[0040] As a more specific embodiment, for example, there are resin compositions containing epoxy resin and a curing agent, and resin compositions containing polyrotaxane, thermosetting resin and a curing agent. Each component will be described in more detail below.

[0041] Next, in the case of a resin composition comprising a polyrotaxane, a thermosetting resin, and a curing agent, specific examples of the polyrotaxane include those described in, for example, Japanese Patent No. 4482633 or International Publication WO2015 / 052853. Commercially available products may also be used, specifically such as Cellum Superpolymer A1000, SH3400P, etc., manufactured by Advanced Soft Materials Co., Ltd.

[0042] Examples of thermosetting resins include epoxy resins, phenolic resins, polyimide resins, urea resins, melamine resins, unsaturated polyesters, and urethane resins, but epoxy resins are preferred.

[0043] Examples of the epoxy resins mentioned above include, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, aralkyl epoxy resin, phenol novolac type epoxy resin, alkylphenol novolac type epoxy resin, biphenol type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, epoxidized products of condensates of phenols and aromatic aldehydes having phenolic hydroxyl groups, triglycidyl isocyanurate, and alicyclic epoxy resins. Depending on the situation, one of these may be used alone, or two or more may be used in combination.

[0044] More preferably, the epoxy resin is one which contains two or more epoxy groups in a single molecule and has a molecular weight of 500 or more. Commercially available epoxy resins may be used as such, and examples include JER1003 (manufactured by Mitsubishi Chemical, molecular weight 1300, bifunctional), EXA-4816 (manufactured by DIC, molecular weight 824, bifunctional), YP50 (manufactured by Nippon Steel Sumitomo Metal Chemical, molecular weight 60000-80000, bifunctional), and PMS-14-67 (manufactured by Nagase ChemteX, molecular weight 300000, polyfunctional).

[0045] Furthermore, while one type of epoxy resin may be used alone, two or more types may be used in combination.

[0046] In any resin composition, there are no particular restrictions on the curing agent, as long as it acts as a curing agent for thermosetting resins as described above. Examples of curing agents that can be preferably used as curing agents for epoxy resins include phenolic resins, amine compounds, acid anhydrides, imidazole compounds, sulfide resins, and dicyandiamides. Light- and ultraviolet curing agents and thermal cationic curing agents can also be used. Depending on the situation, one of these may be used alone or two or more may be used in combination. The resin composition may also contain a curing accelerator as needed. Examples of curing accelerators include imidazole compounds.

[0047] Furthermore, if the resin composition used in the resin layer in this embodiment is a resin composition containing polyrotaxane, a crosslinking agent may be added. Such a crosslinking agent is not particularly limited as long as it can form a structure that crosslinks with at least a portion of the cyclic molecule of the polyrotaxane (at least one reactive group possessed by the cyclic molecule of the polyrotaxane). Specifically, examples include isocyanates and cyanuryl chloride.

[0048] The proportion of each component in the resin composition is not particularly limited as long as the effects of the present invention can be achieved. For example, when the composition includes polyrotaxane, thermosetting resin, and curing agent, with a total of 100 parts by mass of the polyrotaxane, thermosetting resin, and curing agent, the proportions are approximately 10 to 80 parts by mass, more preferably 30 to 50 parts by mass of polyrotaxane; 10 to 89.9 parts by mass, more preferably 30 to 50 parts by mass of thermosetting resin; and 0.1 to 30 parts by mass, more preferably 0.1 to 20 parts by mass of curing agent.

[0049] If the resin composition contains an epoxy resin and a curing agent but does not contain polyrotaxane, then, with a total resin composition of 100 parts by mass, the epoxy resin is approximately 50 to 99 parts by mass, more preferably 60 to 80 parts by mass; and the curing agent is approximately 1 to 50 parts by mass, more preferably 1 to 40 parts by mass.

[0050] Furthermore, the resin composition according to this embodiment may optionally contain other additives, such as curing catalysts (curing accelerators), colorants, inorganic fine particles, ultraviolet absorbers, flame retardants, flame retardant aids, leveling agents, etc., to the extent that they do not impair the effects of the present invention.

[0051] When the curing accelerator is included, it is not particularly limited as long as it can accelerate the curing reaction of the resin composition of this embodiment. Specifically, examples include metal oxides, azo compounds, peroxides, imidazole compounds, phosphorus-based curing accelerators, amine-based curing accelerators, and the like. When the resin composition of this embodiment contains a curing accelerator, its content is preferably 0.01 to 5.0 parts by mass, and more preferably 0.01 to 3 parts by mass, per 100 parts by mass of the resin component (resin + curing agent).

[0052] In particular, when a coloring agent is included, it is preferable because it can be used to decorate the resin sheet, improving its design. Examples of coloring agents that can be used include dyes and pigments.

[0053] If the coloring agent is included, its content is preferably 0.1 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of the resin component (resin + hardener).

[0054] Furthermore, the light diffusion rate can be improved by incorporating inorganic fine particles. Examples of usable inorganic fine particles include silica, alumina, titanium dioxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, silica sand, clay, mica, wollastonite, diatomaceous earth, chromium oxide, cerium oxide, pengala, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride.

[0055] In this embodiment, the inorganic fine particles used preferably have an average particle diameter of 0.01 μm or more and 100 μm or less, from the viewpoint of further improving the light diffusivity.

[0056] When the inorganic fine particles are included, it is preferable that their content be between 0.1 parts by mass and 10 parts by mass per 100 parts by mass of the resin component (resin + curing agent). If the inorganic fine particle content is too high, the resin sheet will be prone to tearing, which is undesirable.

[0057] Furthermore, the resin composition of this embodiment has the advantage of suppressing the deterioration (yellowing) of the sheet due to ultraviolet light because it contains an ultraviolet absorber. Examples of usable ultraviolet absorbers include benzotriazole derivatives, benzophenone derivatives, benzoate derivatives, triazine derivatives, benzothiazole derivatives, and ultraviolet absorbers consisting of benzoylmethane.

[0058] If the aforementioned ultraviolet absorber is included, its content is preferably 0.1 parts by mass or more and 1.0 part by mass or less per 100 parts by mass of the resin component (resin + curing agent).

[0059] The method for preparing the resin composition of this embodiment is not particularly limited. For example, a resin varnish containing the resin composition of this embodiment can be obtained by first uniformly mixing a thermosetting resin such as epoxy resin, an organic component such as a curing agent and a crosslinking agent, and a solvent. The solvent used is not particularly limited. For example, toluene, xylene, methyl ethyl ketone, acetone, etc., can be used. These solvents may be used individually or in combination of two or more. In addition, organic solvents for adjusting viscosity and various additives may be added as needed.

[0060] The method for imparting the above-described shape (irregularities) to the resin sheet of this embodiment is not particularly limited, but examples include coating a resin varnish onto an irregular transfer substrate, reducing or removing the organic solvent by heating, curing by further heating, and then peeling off the substrate. Examples of such transfer substrates include release sheets.

[0061] Specifically, first, a resin varnish containing the resin composition is applied to a substrate such as a release sheet having a desired uneven shape. The application method is not particularly limited, but examples include bar coaters, comma coaters, die coaters, roll coaters, gravure coaters, etc.

[0062] After applying the resin varnish, heating can volatilize the organic solvent from the resin layer (Stage A) containing the uncured resin composition that includes the organic solvent, thereby reducing or removing the organic solvent. By heating the release sheet coated with the resin composition (resin varnish) under desired heating conditions, for example, 60-80°C for 1-120 minutes, an uncured or semi-cured resin layer (Stage B) with reduced or removed organic solvent can be obtained. In this embodiment, Stage B of the resin composition, i.e., the uncured state (uncured product) or semi-cured state (semi-cured product), refers to a state in which the resin composition can be further cured. For example, when a resin composition is heated, its viscosity gradually decreases at first, then curing begins, and the viscosity gradually increases. In such a case, a semi-cured state would be the state between when the viscosity begins to increase and when it is not yet completely cured.

[0063] Furthermore, the resin layer can be cured by heating. A fiber layer coated or impregnated with the resin composition (resin varnish) is heated under desired heating conditions, for example, 80 to 200°C for 1 to 120 minutes, to obtain a cured resin layer (C stage). In this embodiment, the C stage of the resin composition, i.e., the cured state (cured product), refers to a state in which the curing reaction has progressed and the resin has crosslinked, so that it does not melt even when heated.

[0064] Afterward, the resin sheet of this embodiment can be obtained by peeling off the release sheet.

[0065] In addition to the above, uneven surfaces can also be imparted to the uncured or semi-cured resin composition by heat compression molding using an uneven surface transfer substrate to transfer a desired uneven surface pattern and then peeling off the substrate; by heat compression molding using a nanoimprint mold; or by imparting an uneven surface to the resin composition surface using a laser processing machine.

[0066] If the resin sheet of this embodiment is in an uncured or semi-cured state, a protective film and / or support may be laminated as necessary. As the support, for example, a polyethylene film such as polyethylene terephthalate (PET) can be used. A similar film can also be used as the protective film.

[0067] <Luminous Sheet> Next, the basic configuration of the light-emitting sheet of this embodiment will be described.

[0068] As shown in Figure 2, the light-emitting sheet 10 of this embodiment comprises a light-diffusing layer 1, a fiber sheet 2, a conductor layer 3, and an LED element 4, wherein the light-diffusing layer 1 is formed of the resin sheet of this embodiment described above. Specifically, the light-emitting sheet 10 comprises a fiber sheet 2, a conductor layer 3 laminated on the fiber sheet 2, an LED (LED element) 4 electrically connected to the conductor layer 3, and a light-diffusing layer 1 made of the resin sheet described above that covers the LED 4.

[0069] This configuration makes it possible to provide a light-emitting sheet that is flexible, resistant to breakage, and has excellent light-diffusing properties.

[0070] (Fiber sheet) The fiber sheet 2 according to this embodiment preferably comprises a fiber layer and a resin layer, is capable of elongation of 1% or more, and has an initial tensile modulus of 1 MPa or more and 10 GPa or less.

[0071] In the light-emitting sheet of this embodiment, the initial tensile modulus is the same as that described for the stretchable resin sheet above.

[0072] If the initial tensile modulus is less than 1 MPa, it is undesirable because it results in poor restorative force and failure to return to its original shape. Also, if the initial tensile modulus exceeds 10 GPa, it is undesirable because it results in poor elasticity, and for example, if the luminescent sheet of this embodiment is used in clothing, it may not be comfortable to wear. A more preferable initial tensile modulus for the fiber sheet is 5 MPa or more and 1 GPa or less, and even more preferably 5 MPa or more and 500 MPa or less.

[0073] The initial tensile modulus in this embodiment can be measured using the same method as described above for the stretchable resin sheet.

[0074] (Resin layer in fiber sheet) The resin layer in the fiber sheet is not particularly limited as long as it is a resin layer such that the initial tensile modulus of the fiber sheet falls within the range described above. For example, a thermosetting resin commonly used as a stretchable insulating layer for electronic substrates can be used to form the resin layer in this embodiment. The resin layer in this embodiment preferably contains a thermosetting resin, which is thought to result in a resin layer that exhibits high heat resistance and suppresses melting and thermal decomposition even in high-temperature atmospheres. The heat resistance of the resin layer offers advantages such as enabling the soldering of various LED elements. It also suppresses deformation and deterioration of the fiber sheet due to the heat generated by the LEDs.

[0075] In the fiber sheet 2 of this embodiment, the resin layer may be formed on the entire surface of one or both sides of the fiber layer, or it may be formed on at least a portion of the surface of at least one side of the fiber layer.

[0076] Furthermore, the resin layer may be impregnated into the fiber layer. Alternatively, not the entire resin layer, but a portion of it, may be impregnated into at least a portion of one side of the fiber layer.

[0077] In particular, if at least a portion of the resin layer is impregnated into the fiber layer, the resin layer and the fiber layer become more integrated, making them less prone to breakage and other damage.

[0078] Furthermore, in the fiber sheet of this embodiment, the thickness of the resin layer is not particularly limited and can be set appropriately depending on the application, but for example, a thickness of 50 μm to 5000 μm is preferable in terms of handling, optical properties, and ease of installation.

[0079] Preferably, the thermosetting resin of this embodiment includes at least an epoxy resin. This is thought to ensure more reliable heat resistance.

[0080] Furthermore, it is preferable that the thermosetting resin and the resin layer have a glass transition temperature of 60°C or lower. This allows for greater flexibility in the fiber sheet. While there is no particular lower limit for the glass transition temperature, it is preferable that it be -40°C or higher to avoid stickiness at room temperature.

[0081] Furthermore, it is preferable that the thermosetting resin is elongated by 1% or more. This allows the fiber sheet to be elongated by 1% or more. Also, it is preferable that the thermosetting resin has an initial tensile modulus of 1 MPa or more and 10 GPa or less. This ensures that the initial tensile modulus of the fiber sheet is 1 MPa or more and 10 GPa or less.

[0082] The resin composition used in the resin layer of this embodiment is not particularly limited as long as it possesses the properties described above.

[0083] For example, the resin composition of this embodiment preferably contains a polyrotaxane resin or an epoxy resin as a thermosetting resin, and it is particularly desirable that it contains an epoxy resin. Furthermore, it is preferable that it contains a curing agent. This makes it possible to obtain a fiber sheet that has sufficient heat resistance and can withstand the heat when mounting components in a reflow process. In addition, by curing the uncured resin composition after bonding it to the fiber layer, it becomes easy to integrate the resin layer with the fiber layer. Preferably, the resin composition used for the resin layer of the fiber sheet of this embodiment can be the same resin composition used for the stretchable resin sheet described above.

[0084] Furthermore, the resin composition according to this embodiment may optionally contain other additives, such as curing catalysts (curing accelerators), flame retardants, flame retardant aids, leveling agents, colorants, etc., to the extent that they do not impair the effects of the present invention.

[0085] The method for preparing the resin composition of this embodiment is not particularly limited. For example, the resin composition of this embodiment can be obtained by first uniformly mixing epoxy resin, curing agent, crosslinking agent, thermosetting resin, and solvent. The solvent used is not particularly limited. For example, toluene, xylene, methyl ethyl ketone, acetone, etc., can be used. These solvents may be used individually or in combination of two or more. In addition, organic solvents for adjusting viscosity and various additives may be added as needed.

[0086] In the fiber sheet of this embodiment, the resin layer is formed, for example, by immersing a fiber layer (described later) in the resin composition described above, applying the resin composition to the fiber layer, or laminating a film-like resin composition to the fiber layer. The method of applying the resin composition is not particularly limited, but examples include bar coaters, comma coaters, die coaters, roll coaters, gravure coaters, etc.

[0087] After applying or impregnating with a resin varnish, heating can be used to volatilize the organic solvent from the resin layer (Stage A) containing the uncured resin composition with an organic solvent, thereby reducing or removing the organic solvent. By heating the fiber layer to which the resin composition (resin varnish) has been applied or impregnated under desired heating conditions, an uncured or semi-cured resin layer (Stage B) with reduced or removed organic solvent can be obtained. Further heating can also be used to cure the resin layer.

[0088] When laminating the film-like resin composition to a fiber layer, for example, the resin composition is first coated onto a desired plastic film, metal foil, etc., to obtain a resin layer containing the resin composition before curing (Stage A) which includes an organic solvent, or a resin layer in an uncured or semi-cured state (Stage B) which is heated under desired heating conditions, for example, 80-120°C for 1-120 minutes. This is then laminated to the fiber layer and fixed to the fiber layer by external energy such as pressure or heat. The resin layer may be in an uncured or semi-cured state (Stage B), or it may be further cured by heating to obtain a cured resin layer (Stage C).

[0089] (Fiber layer in a fiber sheet) The fiber layer in the fiber sheet is not particularly limited, but for example, a fiber layer composed of woven fabric, knitted fabric, braided fabric, nonwoven fabric, or a combination thereof can be used. The fiber layer may be a unidirectionally arranged woven fabric. This has the advantage of being able to obtain a fiber sheet that is stretchable only in a desired direction.

[0090] Furthermore, in the fiber layer, it is preferable that the woven fabric, knitted fabric, braided fabric, or nonwoven fabric described above is composed of plant fibers, animal fibers, synthetic fibers, semi-synthetic fibers, regenerated fibers, inorganic fibers, or a combination thereof.

[0091] Since the fiber sheet of this embodiment is preferably elastic, it is also desirable that the fiber layer has a certain degree of elasticity and stretchability. Specifically, the fiber layer should have an initial tensile modulus of elasticity of 1 MPa to 1 GPa. For example, the modulus of elasticity of the fiber layer is preferably around 0.01 MPa to 1 GPa, the stretchability is preferably around 1% to 1000%, and more preferably 5% to 1000%. In other words, the fiber layer of this embodiment does not include a base material such as glass cloth that has almost no stretchability.

[0092] More specifically, the fibers used in the fiber layer of this embodiment include fibers commonly used as fabrics. Specifically, plant fibers include cotton, seed hair fibers such as kapok, bark fibers such as flax, taima, choma, jute, mitsumata, and kozo, and leaf vein fibers such as Manila hemp and sisal hemp. Animal fibers include wool, angora, cashmere, mohair, camel, alpaca, and silk. Animal fibers may also include leather, and include mammals such as cows, pigs, horses, sheep, and goats, reptiles such as crocodiles and snakes, birds such as ostriches, and fish such as sharks. Synthetic fibers include nylon fibers, aramid fibers, vinylon fibers, polyvinylidene chloride synthetic fibers, polyvinyl chloride synthetic fibers, polyester synthetic fibers, polyacrylonitrile synthetic fibers, polyethylene synthetic fibers, polypropylene synthetic fibers, polyurethane synthetic fibers, and polylactic acid fibers. Synthetic fibers may also include artificial leather and synthetic leather. Examples of semi-synthetic fibers include acetate fibers. Examples of regenerated fibers include viscose fibers and copper ammonia fibers. Examples of inorganic fibers include glass fibers, carbon fibers, and metal fibers.

[0093] For example, when the light-emitting sheet of this embodiment is used for wearable applications, the fibers of the fiber layer can be made from fabric used for clothing. Alternatively, it could be fabric used for tents or truck beds, for example. This makes it possible to integrate the fabric and various LED elements into fabrics used in a variety of situations.

[0094] Furthermore, in the fiber sheet of this embodiment, the thickness of the fiber layer is not particularly limited and can be set as appropriate depending on the application, but for example, a thickness of 50 μm to 5000 μm is preferable from the viewpoint of elasticity and handling.

[0095] (Conductor layer) Furthermore, the light-emitting sheet of this embodiment includes a conductive layer 3. In Figure 2, the conductive layer 3 is provided on one side of the fiber sheet 2, but is not limited to this; the conductive layer can also be provided on both sides of the light-emitting sheet or inside it. Examples of the conductive layer include wiring formed from metal foil or a conductive composition, an extremely thinly coated conductive layer, conductive threads, and metal molded products.

[0096] In the light-emitting sheet of this embodiment, the conductive layer 3 serves as a control circuit that sends signals for controlling the LED element 4 (described later) from an LED control means (not shown), a voltage application circuit from a power supply means (not shown), and a transmission circuit for control information sent from a smartphone or personal computer (PC) via wireless communication means (not shown).

[0097] • Metal foil There are no particular limitations on the metal foil, but examples include copper foil (plated), aluminum foil, stainless steel foil, etc. Furthermore, these metal foils may be surface-treated with a silane coupling agent or the like.

[0098] When forming a conductive layer using metal foil, one or more of the above-mentioned fiber sheets are stacked, and then metal foil such as copper foil is placed on both the top and bottom surfaces, or on part or all of one side, and this is heated and pressurized to create a laminated body with metal foil on both sides or on one side. Alternatively, one or more of the above-mentioned fiber sheets are stacked, and then metal foil such as copper foil coated with a resin layer is placed on both the top and bottom surfaces, or on part or all of one side, and this is heated and pressurized to create a laminated body with metal foil on both sides or on one side. Alternatively, one or more fiber layers without a resin layer are stacked, and then metal foil such as copper foil coated with a resin layer is placed on both the top and bottom surfaces, or on part or all of one side, and this is heated and pressurized to create a laminated body with metal foil on both sides or on one side. After that, a conductive layer (wiring) can be provided as a circuit on the surface of the laminate containing the fiber sheets as described above by etching the metal foil or the like to form a circuit (wiring). When forming circuits using metal foil by etching, it is preferable to mask the fiber layer to prevent it from being immersed in the etching solution. For example, it can be manufactured using the following procedure. An opening of the desired shape is made in a solvent-resistant plastic film, such as polyimide, as a cover film, and a resin layer with metal foil on one side is attached to cover it. When this is laminated and integrated together with the fiber layer by heating and pressing, only the opening is impregnated by the fiber layer. To prevent the fiber layer from coming into contact with the etching solution, this laminate is attached to a plastic plate with tape or the like, and the etching process is performed. Finally, the cover film is cut along the boundary of the opening, so that a resin layer is provided in the shape of the opening, and a metal foil circuit is formed on its surface.

[0099] In addition to the methods described above, other methods for circuit formation include, for example, circuit formation by the semi-additive process (SAP) or the modified semi-additive process (MSAP). Furthermore, by laminating these using uncured or semi-cured resin layers, or fiber sheets containing them, a laminate containing a conductive layer can be produced.

[0100] In this embodiment, if copper foil is used as a conductive layer in the light-emitting sheet, it will have heat resistance and good solder wetting properties, making it possible to mount components (such as LED elements) using a reflow process, thus providing a fabric device with high operational reliability. Furthermore, LED elements can be mounted on both sides by various means, or mounted LED elements can be further enclosed within the sheet.

[0101] ·Conductive composition Furthermore, the conductive layer in this embodiment may be formed from a conductive composition. Preferably, the conductive composition in this embodiment is a stretchable conductive composition. This allows for the creation of a fabric device, etc., that does not hinder the stretchability or elasticity of the fiber sheet and has excellent operational reliability. An example of a stretchable conductive composition is shown below.

[0102] The conductive composition specifically comprises a resin that serves as an elastic binder, a curing agent that reacts with the resin, and a conductive filler, wherein the resin has functional groups with a functional group equivalent of 400 g / eq or more and 10,000 g / eq or less, and the cured product of the resin and the conductive composition has a glass transition temperature (Tg) or softening point of 40°C or less, or an elastic modulus of less than 1.0 GPa at 30°C, and the conductive filler (F) has an intrinsic volume resistivity of 1 × 10⁻¹⁶ at room temperature. -4Examples include resin compositions made of conductive materials with a conductivity of Ω·cm or less. Examples of the functional groups include epoxy groups, vinyl groups, (meth)acryloyl groups, hydroxyl groups, carboxyl groups, amino groups, alkoxy groups, and carbonyl groups.

[0103] The following describes each of its components.

[0104] Specific examples of the resin include epoxy-modified (meth)acrylic acid esters, hydroxyl-group-modified (meth)acrylic acid esters, carboxyl-group-modified (meth)acrylic acid esters, and the like.

[0105] Furthermore, in this embodiment, the resin preferably has a weight-average molecular weight of 50,000 or more. This is thought to reduce the likelihood of bleeding when printing conductive patterns using the conductive composition of this embodiment. On the other hand, there are no particular limitations on the upper limit of the weight-average molecular weight, but if the molecular weight exceeds 3 million, the viscosity will increase and handling may deteriorate. Therefore, the weight-average molecular weight range of the resin is preferably 50,000 to 3 million, more preferably 100,000 to 1 million.

[0106] As long as the curing agent has the reactivity with the resin as described above, various curing agents can be used without particular limitations. Specific examples of curing agents include imidazole compounds, amine compounds, phenol compounds, acid anhydride compounds, isocyanate compounds, mercapto compounds, onium salts, radical generators such as peroxides, and photoacid generators.

[0107] The conductive filler has an intrinsic volume resistivity of 1 × 10⁻¹⁶ at room temperature. -4 It consists of a conductive material with a resistivity of Ω·cm or less. Its intrinsic volume resistivity at room temperature is 1 × 10⁻⁶. -4 When using materials with a resistivity exceeding Ω·cm, the volume resistivity of a conductive composition is approximately 1 × 10⁻⁶, although this depends on the amount of material used. -3 Ω·cm~1×10 -2The resistance becomes Ω·cm. Therefore, when this is implemented in a circuit, the resistance value becomes high, resulting in significant power loss.

[0108] The conductive material (with an intrinsic volume resistivity of 1 × 10 at room temperature) -4 Examples of conductive materials with a conductivity of Ω·cm or less include elements such as silver, copper, and gold, as well as compounds such as oxides, nitrides, carbides, and alloys containing these elements. In addition to the conductive filler (F), conductive or semiconductive conductive additives may be added to the conductive composition to further improve conductivity. Such conductive or semiconductive additives can include conductive polymers, ionic liquids, carbon black, acetylene black, carbon nanotubes, and inorganic compounds used as antistatic agents, and one type may be used, or two or more types may be used simultaneously.

[0109] The conductive filler is preferably flattened, and its aspect ratio between thickness and longitudinal direction in plane is preferably 10 or more. When the aspect ratio is 10 or more, the surface area relative to the mass ratio of the conductive filler increases, which not only improves the efficiency of conductivity but also improves adhesion with the resin component and enhances elasticity. From the viewpoint of ensuring better conductivity and printability, the aspect ratio is preferably between 10 and 1000, and more preferably between 20 and 500. An example of a conductive filler having such an aspect ratio is one with a tap density of 6.0 g / cm³ measured by the tap method. 3 The following conductive fillers are examples. Furthermore, the tap density is 2.0 g / cm³. 3 The following conditions are preferable because they result in a larger aspect ratio.

[0110] Regarding the proportion of conductive filler in the conductive composition, it is preferable that the proportion of conductive filler is 40 to 95% by mass relative to the total amount of the conductive composition, in terms of conductivity, cost, and printability, and more preferably 60 to 85% by mass.

[0111] There are no particular restrictions on the particle size of the conductive filler used in this embodiment, but from the viewpoint of printability during screen printing and achieving appropriate viscosity during mixing of the formulation, the average particle size (particle size at 50% volume accumulation; D50) measured by laser light scattering is preferably 0.5 μm or more and 30 μm or less, and more preferably 1.5 μm or more and 20 μm or less.

[0112] In addition to the components mentioned above, additives may be added to the conductive composition depending on the purpose. Examples of additives include elastomers, surfactants, dispersants, colorants, fragrances, plasticizers, pH adjusters, viscosity adjusters, UV absorbers, antioxidants, and lubricants.

[0113] • Conductor layer using a conductive composition By applying or printing the conductive composition of this embodiment onto the resin layer of the fiber sheet as described above, a coating film of the conductive composition can be formed, thereby forming a conductor layer such as a desired wiring (conductive pattern).

[0114] The process of applying the conductive composition of this embodiment onto a substrate is not particularly limited, but for example, coating methods such as applicators, wire bars, comma rolls, and gravure rolls, or printing methods such as screen printing, flat offset printing, flexographic printing, inkjet printing, stamping, dispensing, and squeegees can be used.

[0115] Furthermore, the conductive layer may be formed inside the fiber sheet.

[0116] (LED element) The LED element 4 used in this embodiment is not particularly limited as long as it emits light, and an appropriate LED element can be selected as appropriate depending on the application of the light-emitting sheet. Specifically, the LED element in this embodiment may be an LED element that emits at least one selected from visible light, ultraviolet light, and infrared light. For example, visible light can be used when the light-emitting sheet is used as a display device, ultraviolet light when it is used as a sterilization device or deodorization device, and infrared light when it is used as a security system, distance measuring device, signal transmission device, etc. Depending on the application, the type of light emitted by the LED element, as well as the size, number, color, arrangement, permutation, etc. of the LED element can be appropriately selected. In addition, different types of LED elements can be combined, for example, by using visible light to indicate the ON / OFF status of a non-visible light LED.

[0117] As shown in Figure 1, in this embodiment, the LED element 4 is placed on the conductive layer 3 and can emit light when current flows through the conductive layer 3 from, for example, a power supply means described later.

[0118] (Light Diffusion Layer) The light diffusion layer 1 in the light-emitting sheet 10 of this embodiment is formed from the resin sheet of this embodiment described above. Because the resin sheet of this embodiment is flexible, it can conform to the uneven surface and cover the LED elements even with the configuration shown in Figure 2, exhibiting excellent light diffusion properties. Furthermore, it has excellent heat resistance, providing strong resistance to the heat of the LED elements.

[0119] (Other electronic components) The light-emitting sheet of this embodiment may further include other electronic components in addition to the LED elements. The electronic components that can be mounted are not particularly limited and include general passive elements, active elements, integrated circuits, displays, motors, speakers, piezoelectric elements, switches, fuses, antennas, heat sinks, acceleration sensors, temperature sensors, humidity sensors, light sensors, ultrasonic sensors, pH sensors, gas sensors, motion sensors, angle sensors, magnetic sensors, gyro sensors, pressure sensors, compass sensors, radiation sensors, sound sensors, GPS receivers, and the like.

[0120] (Method for manufacturing a light-emitting sheet) The light-emitting sheet of this embodiment is obtained by, for example, immersing the fiber layer in a thermosetting resin composition that constitutes the resin layer as described above, applying the resin composition to the fiber layer, or laminating a film-like resin composition to the fiber layer, on a fiber sheet on which the above-described conductive layer, LED elements, and optionally LED control means are provided, and further laminating the above-described resin sheet on top of that.

[0121] The mounting method for installing the LED elements on the conductive layer is not particularly limited. Examples include using a soldering iron, printing various types of solder paste, mounting the LED elements using various component mounting equipment, and then mounting them using various reflow equipment. In particular, considering the heat resistance of the fiber layer, it is preferable to use a means to heat only the metal parts using induction heating, microwaves, etc.

[0122] Furthermore, there are no particular limitations on the method of providing the light-diffusing layer on the LED element. For example, the above-mentioned resin sheet can be formed by laminating it on the fiber sheet 2, the conductor layer 3, and the LED element 4 such that the light-diffusing portion of the resin sheet overlaps the LED element.

[0123] (Application) The light-emitting sheet of this embodiment can be used in a variety of applications that require high levels of ease of installation, shape conformability, and heat resistance. Specifically, it can be used in, for example, display devices, sterilization devices, clothing, and fashion accessories.

[0124] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited thereto. [Examples]

[0125] First, the materials used in this embodiment are as follows:

[0126] (Epoxy resin) Epoxy resin 1 Acrylonitrile was used as polymerization unit (a), isobornyl acrylate as polymerization unit (b), and polymerization unit (c) represented by the following formula (1) were polymerized in a ratio (polymerization %) of (a):(b):(c) of 10:20:70. Furthermore, glycidyl methacrylate was added as polymerization unit (d) so that the epoxy equivalent relative to the total amount of acrylic resin was the value shown in Table 1. Subsequently, the mixture was polymerized to obtain acrylic resin 1 (manufactured by Nagase ChemteX Corporation, "PMS-14-67EK40") containing methyl ethyl ketone as a solvent. The solids content ratio was 40% by weight.

[0127] [ka] (In the formula, R1 is hydrogen or a methyl group, R2 is hydrogen or an alkyl group, and X is an integer.) • Bisphenol-type epoxy resin (Mitsubishi Chemical Corporation's "jER1006FS")

[0128] (Polyrotaxane resin) • Polyrotaxane (SH3400P, manufactured by Advanced Soft Materials)

[0129] (Hardening agent) • Acid anhydride-based curing agent ("Ricacid TBN-100" manufactured by Shin Nippon Rika Co., Ltd.) • Carboxylic acid-based curing agent ("TN-1" manufactured by NOF Corporation) • Phenolic hardening agent (BIOC-E, manufactured by Asahi Organic Chemicals Co., Ltd.) • Acid anhydride-based curing agent (H-TM-An, manufactured by Mitsubishi Gas Chemical Company, Inc.)

[0130] (Curing accelerator) • Imidazole (2PZ-CN, manufactured by Shikoku Chemicals Co., Ltd.)

[0131] (Surfactants) • Surfactant (BYK-3440, manufactured by BIC Chemie Japan Co., Ltd.)

[0132] (Inorganic fine particles) • Surface-treated hydrophobic silica ("RX200" manufactured by Nippon Aerosil Co., Ltd.)

[0133] (UV absorber) • UV absorber (ULS-1933D, manufactured by Lion Specialty Chemicals Co., Ltd.)

[0134] (solvent) Methyl ethyl ketone

[0135] <Preparation of stretchable resin sheets 1-19> Resin varnishes 1 to 9 were prepared by adding the formulations (parts by mass) shown in Table 1 to a solvent (methyl ethyl ketone) so that the solid content of the composition was approximately 43% by mass. After standing degassing, the resin varnishes 1 to 9 were applied to the release sheets 1 to 8, which had been treated for mold release, using a bar coater. Next, the sheets were heated in an oven at 80°C for 60 minutes to obtain semi-cured resin sheets, and then heated at 180°C for 120 minutes to obtain resin films (light-diffusing films) 1 to 19 of Examples 1 to 13 and Comparative Examples 1 to 6.

[0136] The resin varnish and release sheet used for each light-diffusing film are shown in Tables 2 and 3.

[0137] The release sheets used were "Coating Mat Release Sheets" manufactured by Otsuki Kogyo Co., Ltd., each having a specific shape (surface roughness). By using these release sheets 1 to 8, an uneven surface shape was formed on the first surface of each film, having Ra1 (arithmetic mean roughness of the first surface), Rz1 (maximum surface roughness height on the first surface), Rz2 (maximum surface roughness height on the first surface), and RSm (average length of roughness curve elements) as shown in Tables 2 and 3.

[0138] In Example 4 and Comparative Example 4, a release sheet treated with a release agent was further bonded to the second surface of a semi-cured resin sheet and pressure-molded to form an uneven shape having the Ra2 (arithmetic mean roughness of the second surface) shown in Tables 2 and 3.

[0139] [Table 1]

[0140] [Table 2]

[0141] [Table 3]

[0142] Note that the values ​​for t (resin film thickness), Ra1 (arithmetic mean roughness of the first surface), Ra2 (arithmetic mean roughness of the second surface), Rz1 (maximum surface roughness height on the first surface), Rz2 (maximum surface roughness height on the first surface), and RSm (average length of roughness curve elements) in Tables 2 and 3 were measured using a laser microscope (Olympus Corporation, "OLS3000").

[0143] [Evaluation Test] <Method for evaluating light transmittance> Cured light-diffusing films from each example and comparative example were mounted on a haze meter (NDH7000SP II, manufactured by Nippon Denshoku Co., Ltd.), and the total light transmittance was measured under conditions compliant with ASTM D1003. For evaluation of light transmittance, a total light transmittance of 90% or more was marked with ◎, 80% or more and less than 90% with ○, and less than 80% with ×.

[0144] <Method for evaluating light diffusion> Cured light-diffusing films from each example and comparative example were mounted on a haze meter (NDH7000SP II, manufactured by Nippon Denshoku Co., Ltd.), and the haze value was measured under conditions compliant with ASTM D1003. For evaluation of light diffusion, a haze value of 80 or higher was marked with ◎, 50 or higher and less than 80 with ○, and less than 50 with ×.

[0145] <Methods for evaluating flexibility and stretchability> The light-diffusing films for each example and comparative example were cut into 150mm x 5.5mm strips and mounted on a universal testing machine (AGS-X, Shimadzu Corporation). Tests were conducted at a tensile speed of 500mm / min, and the initial tensile modulus was calculated by determining the slope of r-σ from all stress (σ) data corresponding to the strain (r) at 1% and 5% elongation of the light-diffusing film using the least squares method. Strain (r) = x / x0 (where x is the distance moved by the gripper and x0 is the initial distance between the grippers) Stress (σ) = F / (d·l) (where F is the test force, d is the film thickness, and l is the width of the test specimen) For evaluating flexibility, the initial tensile modulus was rated as follows: less than 50 MPa was marked with ◎, 50 MPa to less than 500 MPa was marked with ○, and 500 MPa or more was marked with ×.

[0146] Furthermore, the elongation rate at the time of breakage of each cured resin film was measured. For the evaluation of elongation, a break elongation rate of 100% or more was marked with ◎, 50% or more but less than 100% was marked with ○, and less than 50% was marked with ×.

[0147] <Method for evaluating heat resistance> Light-diffusing films from each example and comparative example were cut to 10 mm x 30 mm and mounted on a dynamic viscoelasticity measuring device (DMS6100, manufactured by Seiko Instruments Inc.). Tests were conducted with a strain amplitude of 10 μm, a frequency of 10 Hz (sine wave), and a heating rate of 5 °C / min, and the storage modulus at 250 °C was measured. For evaluation of heat resistance, a storage modulus of 0.1 MPa or higher was considered a pass, and a value less than 0.1 MPa was considered a fail.

[0148] The results above are summarized in Tables 4 and 5.

[0149] [Table 4]

[0150] [Table 5]

[0151] (Consideration) As is clear from the results in Table 4, the stretchable resin sheet of the present invention was confirmed to have light-diffusing properties, flexibility, and heat resistance, and to be resistant to breakage during stretching.

[0152] On the other hand, as shown in Table 5, the films of Comparative Examples 1 and 2, which did not have the required roughness on both the first and second surfaces, could not obtain sufficient light diffusion.

[0153] Furthermore, in the resin sheets of Comparative Examples 3 and 4, the arithmetic mean surface roughness Ra and the maximum surface roughness height Rz were outside the specified range, resulting in poor light transmittance. In particular, the resin sheet of Comparative Example 4 did not meet the specified Rz for the first and second surfaces, resulting in poor tensile strength and immediate fracture.

[0154] Comparative Example 5 failed to achieve heat resistance because it used a resin sheet made with a resin composition that did not contain a curing agent.

[0155] Furthermore, the resin sheet of Comparative Example 6 had an initial tensile modulus exceeding 500 MPa, resulting in poor elongation and immediate fracture.

[0156] This application is based on Japanese Patent Application No. 2021-69766, filed on April 16, 2021, the contents of which are included in this application.

[0157] In order to express the present invention, the invention has been adequately and sufficiently described above through embodiments with reference to specific examples and drawings, etc. However, those skilled in the art should recognize that it is easy to modify and / or improve the embodiments described above. Therefore, unless the modifications or improvements implemented by those skilled in the art fall outside the scope of the claims described in the claims, such modifications or improvements shall be interpreted as being included within the scope of the claims. [Industrial applicability]

[0158] The present invention has broad industrial applicability in the technical fields of electronic materials, electronic devices, optical devices, and the like.

Claims

1. A resin sheet formed using a resin composition containing a thermosetting resin and a curing agent. When the maximum surface roughness height on the first surface of the resin sheet is Rz1 (μm), the maximum surface roughness height on the second surface facing the first surface is Rz2 (μm), and the thickness is t (μm), then Rz1, Rz2, and the thickness t (μm) satisfy the following relationship (1): (Rz1+Rz2) / t≦0.5 (1) At least one of the first surface and the second surface is provided with a light-diffusing portion having an uneven shape with an arithmetic mean roughness Ra of 0.3 μm or more and 5.0 μm or less. An expandable resin sheet having an initial tensile modulus of 0.5 MPa or more and 500 MPa or less.

2. The stretchable resin sheet according to claim 1, wherein the average length RSm of the roughness curve elements in the aforementioned uneven shape is 1.0 μm or more and 100 μm or less.

3. The stretchable resin sheet according to claim 1, wherein the thermosetting resin includes an epoxy resin.

4. The stretchable resin sheet according to claim 3, wherein the epoxy resin contains two or more epoxy groups in one molecule and has a molecular weight of 500 or more.

5. The stretchable resin sheet according to claim 3, further containing a curing accelerator.

6. The stretchable resin sheet according to claim 3, further containing inorganic fine particles.

7. The stretchable resin sheet according to claim 3, further containing an ultraviolet absorber.

8. Fiber sheet and A conductive layer laminated on the aforementioned fiber sheet, An LED electrically connected to the aforementioned conductor layer, The LED is covered by a light-diffusing layer made of the stretchable resin sheet described in claim 1, Luminous sheet.

9. The light-emitting sheet according to claim 8, wherein the fiber sheet comprises a fiber layer and a resin layer, is elongated by 1% or more, and has an initial tensile modulus of elasticity of 1 MPa or more and 10 GPa or less.

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