Micro LED display device

Abstract

A micro LED display device with excellent luminous efficiency and suppressed color mixing is provided. The micro LED display device of the present invention comprises a micro LED array substrate including a plurality of micro LEDs, a sealing portion for sealing the plurality of micro LEDs, a low refractive index layer, and a plurality of wavelength conversion layers formed by partitioning, in this order from the back side, and each of the wavelength conversion layers is formed to be set in correspondence with one of the micro LEDs in the thickness direction, and the refractive index of the low refractive index layer is lower than the refractive index of the sealing portion and the refractive index of the wavelength conversion layer, the difference between the refractive index of the low refractive index layer and the refractive index of the sealing portion is 0.10 or more, and the difference between the refractive index of the low refractive index layer and the refractive index of the wavelength conversion layer is 0.10 or more.

Description

Technology Field

[0001] The present invention relates to a micro LED display device. Background Technology

[0002] In recent years, as a new display device, a micro LED display configured by arranging micro LEDs within pixels arranged in a matrix has been developed (e.g., Patent Document 1, Patent Document 2). As a micro LED display, a display has been proposed comprising a micro LED array substrate configured by arranging a plurality of micro LEDs, and an array of wavelength conversion layers (fluorescent light-emitting layers) formed on the micro LED array substrate, which absorb light from the micro LEDs and convert the emission wavelength of the light into the wavelengths of red, green, and blue light, respectively (e.g., Patent Document 2). In such a micro LED display, a micro LED and a wavelength conversion layer are configured as a set for each subpixel. Prior art literature

[0003] Japanese Patent Publication No. 2020-43073 and Japanese Patent Publication No. 2016-523450 The problem to be solved

[0004] In the micro LED display described above, there is a problem in that light from the micro LED leaks into subpixels other than those corresponding to the micro LED (adjacent subpixels, surrounding subpixels), causing color mixing. Additionally, there is a problem in that sufficient luminous efficiency cannot be obtained because light returns to the back side due to scattering within the wavelength conversion layer.

[0005] The objective of the present invention is to provide a micro LED display device having excellent luminous efficiency and suppressed color mixing. means of solving the problem

[0006] The micro LED display device of the present invention comprises a micro LED array substrate including a plurality of micro LEDs, a sealing portion for sealing the plurality of micro LEDs, a low refractive index layer, and a plurality of wavelength conversion layers formed by partitioning, in this order from the micro LED array substrate side, and each of the wavelength conversion layers is formed to be set with one of the micro LEDs in the thickness direction, and the refractive index of the low refractive index layer is lower than the refractive index of the sealing portion and the refractive index of the wavelength conversion layer, the difference between the refractive index of the low refractive index layer and the refractive index of the sealing portion is 0.10 or more, and the difference between the refractive index of the low refractive index layer and the refractive index of the wavelength conversion layer is 0.10 or more.

[0007] In one embodiment, the refractive index of the low refractive index layer is 1.25 or less.

[0008] In one embodiment, the low refractive index layer is a porous layer composed of a porous body formed by chemically bonding fine particles to each other.

[0009] In one embodiment, the sealing part is composed of an adhesive.

[0010] In one embodiment, each of the wavelength conversion layers is spaced apart by a partition.

[0011] In one embodiment, the micro LED is a blue LED or an ultraviolet LED.

[0012] In one embodiment, the micro LED display device further has a color filter disposed on the side opposite to the low refractive index layer of the wavelength conversion layer. Effects of the invention

[0013] According to the present invention, a micro LED display device having excellent luminous efficiency and suppressed color mixing can be provided. Brief explanation of the drawing

[0014] FIG. 1 is a schematic cross-sectional view of a micro LED display device according to one embodiment of the present invention. Figure 2(a) is a schematic cross-sectional view showing the configuration provided in the example, and (b) is a schematic cross-sectional view showing the configuration provided in the comparative example. Specific details for implementing the invention

[0015] A. Micro LED display device

[0016] FIG. 1 is a schematic cross-sectional view of a micro LED display device according to one embodiment of the present invention. A micro LED display device (100) according to this embodiment comprises, in order from the micro LED array substrate side, a micro LED array substrate (10) including a plurality of micro LEDs (11), a sealing portion (20) for sealing the plurality of micro LEDs (11), a low refractive index layer (30), and a plurality of wavelength conversion layers (40) formed by partitioning. Typically, the micro LED array substrate (10) comprises a driving substrate (12) and a plurality of micro LEDs (11) arranged in an array (matrix) on the driving substrate (12). Each wavelength conversion layer (40) is formed to be set in correspondence with one micro LED (11) in the thickness direction. Typically, one wavelength conversion layer (40) and one micro LED (11) are each included in one subpixel. By transmitting light from the micro LED (11) to the wavelength conversion layer (40), red, green, and blue subpixels can be formed. Additionally, in the case of a subpixel that uses light from the micro LED as is (for example, when a blue subpixel is formed by a blue LED), the wavelength conversion layer may be omitted or replaced with another layer (for example, a light diffusion layer). In one embodiment, each wavelength conversion layer is spaced apart by a partition (50) (light-blocking layer).

[0017] In one embodiment, the low refractive index layer (30) is formed on the front surface of the side opposite to the micro LED array substrate (10) of the sealing part (20). In addition, in one embodiment, the low refractive index layer (30) is formed directly on the sealing part (20) (i.e., without interposing another layer).

[0018] The refractive index of the low refractive index layer (30) is lower than the refractive index of the sealing portion (20) and the refractive index of the wavelength conversion layer (40). The difference between the refractive index of the low refractive index layer (30) and the refractive index of the sealing portion (20) is 0.10 or greater. Additionally, the difference between the refractive index of the low refractive index layer (30) and the refractive index of the wavelength conversion layer (40) is 0.10 or greater.

[0019] In the present invention, a low-refractive-index layer is disposed between the sealing portion and the wavelength conversion layer, thereby creating a difference in refractive index between the layers. As a result, at least a portion of the light generated from the micro LED, which scatters within the wavelength conversion layer and attempts to return to the back side, is reflected at the interface between the wavelength conversion layer and the low-refractive-index layer and can be emitted toward the viewing side. Consequently, luminous efficiency is improved. Furthermore, at least a portion of the light generated diagonally from the micro LED, which does not reach the corresponding wavelength conversion layer (the wavelength conversion layer within the same subpixel) and heads toward the surrounding area, is reflected at the interface between the low-refractive-index layer and the sealing portion and returned to the back side. Consequently, color mixing is suppressed. The micro LED display device according to an embodiment of the present invention is advantageous in that, in addition to being highly fine, it has higher brightness and a wider color gamut than conventional displays.

[0020] B. Low refractive index layer

[0021] The refractive index of the low refractive index layer is preferably 1.30 or less, more preferably 1.25 or less, even more preferably 1.20 or less, and particularly preferably 1.15 or less. While it is preferable for the refractive index of the low refractive index layer to be lower, the lower limit thereof is, for example, 1.07 or more (preferably 1.05 or more). In this specification, the term "refractive index" refers to the refractive index measured at a wavelength of 550 nm.

[0022] As described above, the difference between the refractive index of the low-refractive-index layer and the refractive index of the seal is 0.10 or greater. The difference between the refractive index of the low-refractive-index layer and the refractive index of the seal is preferably 0.20 or greater, and more preferably 0.30 or greater. Within this range, the above effect becomes significant. The upper limit of the difference between the refractive index of the low-refractive-index layer and the refractive index of the seal is, for example, 0.50 (preferably 0.70).

[0023] As described above, the difference between the refractive index of the low-refractive-index layer and the refractive index of the wavelength conversion layer is 0.10 or greater. The difference between the refractive index of the low-refractive-index layer and the refractive index of the wavelength conversion layer is preferably 0.20 or greater, and more preferably 0.30 or greater. Within this range, the above effect becomes significant. The upper limit of the difference between the refractive index of the low-refractive-index layer and the refractive index of the wavelength conversion layer is, for example, 0.50 (preferably 0.70).

[0024] The thickness of the low refractive index layer is preferably 0.01㎛ to 1000㎛, more preferably 0.05㎛ to 100㎛, even more preferably 0.1㎛ to 80㎛, and particularly preferably 0.3㎛ to 50㎛.

[0025] Any suitable composition may be employed for the low refractive index layer. In one embodiment, the low refractive index layer has voids. The low refractive index layer may preferably be formed by coating or printing, etc. As a material constituting the low refractive index layer, for example, materials described in International Publication No. 2004 / 113966, Japanese Patent Publication No. 2013-254183, and Japanese Patent Publication No. 2012-189802 may be employed. Specifically, for example, silica-based compounds; hydrolyzable silanes, and their partial hydrolysates and dehydration condensates; organic polymers; silicon compounds containing silanol groups; active silica obtained by contacting silicates with acid or ion exchange resins; polymerizable monomers (e.g., (meth)acrylic monomers and styrene-based monomers); curable resins (e.g., (meth)acrylic resins, fluorine-containing resins, and urethane resins); Examples of combinations of these can be given. A low refractive index layer can be formed by applying or printing a solution or dispersion of such material.

[0026] The porosity of the low-refractive-index layer having pores is preferably 35 volume% or more, more preferably 38 volume% or more, and particularly preferably 40 volume% or more. Within this range, a low-refractive-index layer with a particularly low refractive index can be formed. The upper limit of the porosity of the low-refractive-index layer is, for example, 90 volume% or less, and preferably 75 volume% or less. Within this range, a low-refractive-index layer with excellent strength can be formed. The porosity is a value calculated by Lorentz-Lorenz's formula from the refractive index value measured by an ellipsometer.

[0027] The size of the void (hole) in the low refractive index layer refers to the diameter of the major axis among the diameter of the major axis and the diameter of the minor axis of the void (hole). The size of the void (hole) is, for example, 2 nm to 500 nm. The size of the void (hole) is, for example, 2 nm or larger, preferably 5 nm or larger, more preferably 10 nm or larger, and even more preferably 20 nm or larger. On the other hand, the size of the void (hole) is, for example, 500 nm or smaller, preferably 200 nm or smaller, and more preferably 100 nm or smaller. The range of the size of the void (hole) is, for example, 2 nm to 500 nm, preferably 5 nm to 500 nm, more preferably 10 nm to 200 nm, and even more preferably 20 nm to 100 nm. The size of the void (hole) can be adjusted to a desired size depending on the purpose and application, etc.

[0028] The size of the pores (holes) can be quantified by the BET test method. Specifically, 0.1 g of a sample (formed pore layer) is placed into the capillary of a specific surface area measuring device (Micromeritic: ASAP2020), and then vacuum drying is performed at room temperature for 24 hours to degas the gas within the pore structure. Then, by adsorbing nitrogen gas onto the sample, an adsorption isotherm is plotted and the pore distribution is determined. By doing so, the pore size can be evaluated.

[0029] The haze of the low refractive index layer is, for example, less than 5%, and preferably less than 3%. Meanwhile, the haze is, for example, 0.1% or more, and preferably 0.2% or more. The range of haze is, for example, 0.1% or more and less than 5%, and preferably 0.2% or more and less than 3%. The haze can be measured, for example, by the following method. In addition, haze is an indicator of the transparency of the low refractive index layer.

[0030] A void layer (low refractive index layer) is cut to a size of 50 mm × 50 mm and set in a haze meter (Murakami Shikisaigi Jutsu Genkyusho Co., Ltd.: HM-150) to measure the haze. The haze value is calculated using the following formula.

[0031] Haze (%) = [Diffuse Transmittance (%) / Total Light Transmittance (%)] × 100 (%)

[0032] As the low-refractive-index layer having internal voids, examples include a porous layer and / or a low-refractive-index layer having an air layer in at least a portion. The porous layer typically comprises an aerogel and / or particles (e.g., hollow microparticles and / or porous particles). The low-refractive-index layer is preferably a nanoporous layer (specifically, having a diameter of 10 or more of the micropores, with at least 90%). -1 nm~10 3 It can be a porous layer within the nm range.

[0033] As the above particles, any suitable particles may be employed. The particles are typically composed of silica-based compounds. Examples of particle shapes include spherical, plate-shaped, needle-shaped, string-shaped, and grape cluster-shaped particles. Examples of string-shaped particles include particles in which multiple particles having spherical, plate-shaped, or needle-shaped forms are connected in a bead-like manner, short-fiber particles (e.g., the short-fiber particles described in Japanese Patent Publication No. 2001-188104), and combinations thereof. String-shaped particles may be in a straight chain form or branched form. Examples of grape cluster-shaped particles include particles formed by the aggregation of multiple spherical, plate-shaped, and needle-shaped particles to form a grape cluster shape. The shape of the particles can be confirmed, for example, by observation using a transmission electron microscope.

[0034] The thickness of the low refractive index layer is preferably 0.2 μm to 5 μm, and more preferably 0.3 μm to 3 μm. When the thickness of the low refractive index layer is within this range, the damage prevention effect according to the present invention becomes significant. In addition, the desired thickness ratio can be easily realized.

[0035] The low refractive index layer can be formed by coating or printing, as described above. With this configuration, the low refractive index layer can be formed continuously by roll-to-roll. Any suitable printing method may be employed. Specifically, the printing method may be a plate-based printing method such as gravure printing, offset printing, or flexographic printing, or a plate-less printing method such as inkjet printing, laser printing, or electrostatic printing.

[0036] Hereinafter, an example of the specific composition of the low-refractive-index layer is described. The low-refractive-index layer of the present embodiment is composed of one or more types of constituent units that form a fine pore structure, and said constituent units are chemically bonded to each other through catalytic action. Examples of the shapes of the constituent units include particulate, fibrous, rod-shaped, and flat shapes. The constituent unit may have only one shape or may have two or more shapes combined. In one embodiment, the low-refractive-index layer is a pore layer composed of a porous body formed by the chemical bonding of fine particles. Hereinafter, the case in which the pore layer is composed mainly of a porous body formed by the chemical bonding of fine particles will be described.

[0037] Such a pore layer can be formed in a pore layer formation process, for example, by chemically bonding micropore particles together. Furthermore, in an embodiment of the present invention, the shape of the "particle" (for example, the micropore particles) is not particularly limited and may be spherical or have other shapes. In addition, in an embodiment of the present invention, the micropore particles may be, for example, sol-gel beads, nanoparticles (hollow nano-silica, nano-balloon particles), nanofibers, etc. The micropore particles typically include inorganic materials. Specific examples of inorganic materials include silicon (Si), magnesium (Mg), aluminum (Al), titanium (Ti), zinc (Zn), and zirconium (Zr). These may be used individually or in combination of two or more types. In one embodiment, the micropore particles are, for example, micropore particles of a silicon compound, and the porous body is, for example, a silicon porous body. The micropore particles of the silicon compound include, for example, a pulverized body of a gel-like silica compound. In addition, as another form of a low-refractive-index layer having a porous layer and / or an air layer in at least a portion, there is a porous layer composed of a fibrous material such as nanofiber, wherein the fibrous material is intertwined to form pores and forms a layer. The method of manufacturing such a porous layer is not particularly limited and is, for example, the same as in the case of a porous layer in which the micro-pore particles are chemically bonded to each other. In addition, other forms include a porous layer using hollow nanoparticles or nanoclay, or a porous layer formed using hollow nanoballoons or magnesium fluoride. The porous layer may be a porous layer composed of a single constituent material or a porous layer composed of multiple constituent materials. The porous layer may be composed of a single above-mentioned form or may be composed of multiple above-mentioned forms.

[0038] In the present embodiment, the porous structure of the porous body may be, for example, a continuous foam structure in which the pore structures are continuous. A continuous foam structure refers to, for example, a state in which the pore structures are connected three-dimensionally in the silicon porous body, and can also be described as a state in which the internal pores of the pore structures are continuous. By having a continuous foam structure, it is possible to increase the porosity. However, when using independent foam particles (particles each having a pore structure), such as hollow silica, a continuous foam structure cannot be formed. On the other hand, when using, for example, silica sol particles (pulverized material of a gel-like silicon compound forming a sol), since the particles have a three-dimensional tree-like structure, it is possible to easily form a continuous foam structure by allowing the tree-like particles to settle and deposit within the coating film (a coating film of a sol containing pulverized material of a gel-like silicon compound). More preferably, the low refractive index layer has a monolithic structure in which the continuous foam structure includes a distribution of multiple fine pores. A monolith structure refers to a hierarchical structure that includes, for example, a structure containing nano-sized fine pores and a continuous foam structure formed by the aggregation of such nano-pores. When forming a monolith structure, for example, membrane strength can be provided by fine pores while high porosity is provided by coarse continuous foam pores, thereby achieving both membrane strength and high porosity. Preferably, such a monolith structure can be formed by controlling the distribution of fine pores in the pore structure generated in the gel (gel-like silicon compound) prior to the stage of grinding into silica sol particles. Additionally, for example, when grinding the gel-like silicon compound, a monolith structure can be formed by controlling the particle size distribution of the silica sol particles after grinding to a desired size.

[0039] The low refractive index layer comprises, for example, ground particles of a gel-like compound as described above, and said ground particles are chemically bonded to each other. The form of chemical bonding (chemical bonding) between the ground particles in the low refractive index layer is not particularly limited, and examples include cross-linking, covalent bonding, and hydrogen bonding.

[0040] The gel form of a gel compound is not particularly limited. "Gel" generally refers to a solidified state in which solutes lose their independent mobility and aggregate for interaction. A gel compound may be, for example, a wet gel or a kicerogel. Furthermore, generally, a wet gel refers to a state in which a dispersion medium is included and the solutes take on the same structure within the dispersion medium, and a kicerogel refers to a state in which the solvent is removed and the solutes take on a network structure having pores.

[0041] As a gel-like compound, for example, a gel product obtained by gelling a monomer compound can be cited. Specifically, as the gel-like silicon compound, for example, a gel product in which the silicon compounds of the monomers are bonded to each other, and as a specific example, a gel product in which the silicon compounds of the monomers are bonded to each other by covalent bonds, hydrogen bonds, or intermolecular forces. As for covalent bonds, for example, bonds formed by dehydration condensation can be cited.

[0042] The volume average particle diameter of the pulverized material in the low refractive index layer is, for example, 0.10 μm or more, preferably 0.20 μm or more, and more preferably 0.40 μm or more. Meanwhile, the volume average particle diameter is, for example, 2.00 μm or less, preferably 1.50 μm or less, and more preferably 1.00 μm or less. The range of the volume average particle diameter is, for example, 0.10 μm to 2.00 μm, preferably 0.20 μm to 1.50 μm, and more preferably 0.40 μm to 1.00 μm. The particle size distribution can be measured by, for example, a particle size distribution evaluation device such as dynamic light scattering or laser diffraction, and by electron microscopes such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). In addition, the volume average particle diameter is an indicator of the non-uniformity of the particle size of the pulverized material.

[0043] The type of gel compound is not particularly limited. As for the gel compound, a gel silicon compound can be cited as an example. Below, the case where the gel compound is a gel silicon compound is described as an example, but it is not limited to this.

[0044] The above-mentioned crosslinking is, for example, a siloxane bond. Examples of siloxane bonds include T2 bonds, T3 bonds, and T4 bonds, as shown below. When the void layer (low refractive index layer) has siloxane bonds, it may have one type of bond, two types of bonds, or all three types of bonds. Among the siloxane bonds, the higher the proportion of T2 and T3, the greater the flexibility and the more the inherent gel characteristics can be expected. On the other hand, the higher the proportion of T4, the easier it is for film strength to be developed. Therefore, it is desirable to change the ratios of T2, T3, and T4 depending on the purpose, application, desired characteristics, etc.

[0045]

[0046] In addition, in the low refractive index layer (pore layer), it is preferable that the silicon atoms included are siloxane-bonded, for example. As a specific example, among the total silicon atoms included in the pore layer, the proportion of unbonded silicon atoms (i.e., residual silanol) is, for example, less than 50%, preferably 30% or less, and more preferably 15% or less.

[0047] When the gel compound is a gel silicon compound, the silicon compound of the monomer is not particularly limited. As for the silicon compound of the monomer, for example, a compound represented by the following formula (1) can be given as an example. When the gel silicon compound is a gel product in which the silicon compounds of the monomer are hydrogen bonded or intermolecularly bonded to each other as described above, the monomers of formula (1) may be hydrogen bonded, for example, through each hydroxyl group.

[0048]

[0049] In formula (1), X is, for example, 2, 3, or 4, preferably 3 or 4. R 1 is, for example, a straight-chain or branched alkyl group. R 1 The number of carbon atoms is, for example, 1 to 6, preferably 1 to 4, and more preferably 1 to 2. Examples of straight-chain alkyl groups include, for example, methyl groups, ethyl groups, propyl groups, butyl groups, pentyl groups, hexyl groups, etc. Examples of branched alkyl groups include, for example, isopropyl groups, isobutyl groups, etc.

[0050] As a specific example of the silicon compound represented by formula (1), for instance, a compound represented by the following formula (1') where X is 3 can be cited. In the following formula (1'), R 1 is the same as in the case of formula (1), and is, for example, a methyl group. R 1 If this is a methyl group, the silicon compound is a tris(hydroxy)methylsilane. If X is 3, the silicon compound is a trifunctional silane having three functional groups, for example.

[0051]

[0052] Another specific example of the silicon compound represented by formula (1) is a compound in which X is 4. In this case, the silicon compound is, for example, a tetrafunctional silane having 4 functional groups.

[0053] The silicon compound of the monomer may be, for example, a hydrolyzed product of a silicon compound precursor. As for the silicon compound precursor, for example, it may be one that can produce a silicon compound by hydrolysis, and as a specific example, a compound represented by the following formula (2) may be given.

[0054]

[0055] In the above equation (2), X is, for example, 2, 3, or 4, and R 1 and R 2 Each is independent,

[0056] It is a straight-chain or branched alkyl group, and

[0057] R 1 and R 2 It doesn't matter if it is the same or different,

[0058] R 1 If X is 2, they may be the same or different, and

[0059] R 2 They may be the same or different from each other.

[0060] X and R 1 For example, X and R in Equation (1). 1 It is the same as. R 2 For example, R in Equation (1). 1 Examples of can be cited.

[0061] As a specific example of the silicon compound precursor represented by formula (2), for instance, a compound represented by the following formula (2') where X is 3 can be cited. In the following formula (2'), R 1 and R 2Each is the same as in the case of Equation (2). R 1 and R 2 In the case of this methyl group, the silicon compound precursor is trimethoxy(methyl)silane (hereinafter also referred to as “MTMS”).

[0062]

[0063] For the silicon compound of the monomer, a trifunctional silane is preferred, for example, due to its excellent low refractive index. Additionally, for the silicon compound of the monomer, a tetrafunctional silane is preferred, for example, due to its excellent strength (e.g., scratch resistance). The silicon compound of the monomer may be used as a single type or in combination of two or more types. For example, the silicon compound of the monomer may include only a trifunctional silane, only a tetrafunctional silane, both a trifunctional silane and a tetrafunctional silane, or additionally include other silicon compounds. When two or more types of silicon compounds are used as the silicon compound of the monomer, the ratio thereof is not particularly limited and can be appropriately set.

[0064] Below, an example of a method for forming such a low refractive index layer is described.

[0065] The above method typically includes a precursor formation process for forming a pore structure that is a precursor of a low-refractive-index layer (pore layer) on a resin film, and a crosslinking reaction process for causing a crosslinking reaction within the precursor after the precursor formation process. The above method further includes a liquid composition production process for producing a liquid composition containing micropore particles (hereinafter referred to as "liquid composition containing micropore particles" or simply "liquid composition"), and a drying process for drying the liquid composition. In the precursor formation process, the micropore particles within the dried body are chemically bonded to each other to form a precursor. The liquid composition is not particularly limited and, for example, is a suspension containing micropore particles. Furthermore, the following description mainly describes the case where the micropore particles are crushed material of a gel-like compound and the pore layer is a porous body (preferably a silicon porous body) containing crushed material of a gel-like compound. However, the low-refractive-index layer can be formed in the same way even if the micropore particles are not crushed material of a gel-like compound.

[0066] According to the method described above, for example, a low-refractive-index layer (void layer) having a very low refractive index is formed. The reason for this is speculated as, for example, below. However, the above speculation does not limit the method of forming the low-refractive-index layer.

[0067] Since the above-mentioned crushed material is obtained by crushing a gel silicon compound, the three-dimensional structure of the gel silicon compound prior to crushing is dispersed into a three-dimensional basic structure. Furthermore, in the above method, by applying the crushed material of the gel silicon compound onto a resin film, a precursor of a porous structure based on the three-dimensional basic structure is formed. That is, according to the above method, a new porous structure (three-dimensional basic structure) is formed by the application of the crushed material, which is different from the three-dimensional structure of the gel silicon compound. Because of this, the final pore layer can realize a low refractive index that functions to the extent of, for example, an air layer. In addition, in the above method, the three-dimensional basic structure is immobilized because the crushed materials are chemically bonded to each other. Because of this, the final pore layer can maintain sufficient strength and flexibility despite having a porous structure.

[0068] In addition, the above method performs the precursor formation process and the crosslinking reaction process as separate processes. Furthermore, the crosslinking reaction process is preferably performed in multiple stages. By performing the crosslinking reaction process in multiple stages, for example, the strength of the precursor can be further improved compared to performing the crosslinking reaction process in a single stage, thereby obtaining a low-refractive-index layer in which high porosity and strength are compatible. Although the mechanism is unknown, it is speculated as follows, for example. That is, as described above, if the membrane strength is improved by a catalyst or the like simultaneously with the formation of the pore layer, there is a problem in that the membrane strength improves but the porosity decreases due to the progress of the catalytic reaction. This is thought to be because, for example, as the number of crosslinks (chemical bonds) between micropore particles increases due to the progress of the crosslinking reaction between micropore particles by the catalyst, the bonds become stronger, but the entire pore layer condenses, causing the porosity to decrease. In contrast, it is believed that by performing the precursor formation process and the crosslinking reaction process as separate processes, and by performing the crosslinking reaction process in multiple stages, the number of crosslinks (chemical bonds) can be increased, for example, without significantly changing the overall shape of the precursor (for example, without causing significant overall condensation). However, these are merely examples of conjectured mechanisms and do not limit the method of forming the low-refractive-index layer.

[0069] In the precursor formation process, for example, particles having a specific shape are stacked to form a precursor of the pore layer. At this point, the strength of the precursor is very weak. Subsequently, a product capable of chemically bonding the micropore particles together (e.g., a strong base catalyst generated from a photobase generator) is generated by, for example, a photo- or thermally activated catalytic reaction (the first step of the cross-linking reaction process). It is believed that by performing additional heat aging (the second step of the cross-linking reaction process) to efficiently carry out the reaction in a short time, the chemical bonding (cross-linking reaction) between the micropore particles proceeds further, thereby improving the strength. For example, if the micropore particles are micropore particles of a silicon compound (e.g., a pulverized gel-like silica compound) and residual silanol groups (Si-OH groups) are present in the precursor, it is believed that the residual silanol groups will be chemically bonded together by the cross-linking reaction. However, this description is merely an example and does not limit the method of forming the low-refractive-index layer.

[0070] The above method comprises a process for producing a liquid containing microporous particles. When the microporous particles are a pulverized material of a gel-like compound, the pulverized material is obtained, for example, by grinding the gel-like compound. By grinding the gel-like compound, as described above, the three-dimensional structure of the gel-like compound is destroyed and dispersed into a three-dimensional basic structure. An example of the preparation of the pulverized material is as follows.

[0071] Gelation of monomer compounds can be performed, for example, by hydrogen bonding the monomer compounds to each other or by intermolecular force bonding. As a monomer compound, for example, a silicon compound represented by the above formula (1) can be cited. Since the silicon compound of formula (1) has hydroxyl groups, hydrogen bonding or intermolecular force bonding is possible between the monomers of formula (1), for example, through each hydroxyl group.

[0072] Alternatively, the silicon compound may be a hydrolyzed product of the silicon compound precursor, for example, produced by hydrolyzing the silicon compound precursor represented by the formula (2).

[0073] The method of hydrolyzing the monomer compound precursor is not particularly limited and can be carried out, for example, by a chemical reaction in the presence of a catalyst. Examples of catalysts include acids such as oxalic acid and acetic acid. The hydrolysis reaction can be carried out, for example, by slowly adding and mixing an aqueous solution of oxalic acid into a mixture (e.g., a suspension) of a silicon compound and dimethyl sulfoxide under room temperature conditions, and then stirring for about 30 minutes. When hydrolyzing the silicon compound precursor, for example, by completely hydrolyzing the alkoxy groups of the silicon compound precursor, subsequent gelation, aging, heating after the formation of a pore structure, and immobilization can be carried out more efficiently.

[0074] Gelation of monomer compounds can be carried out, for example, by a dehydration condensation reaction between monomers. The dehydration condensation reaction is preferably carried out, for example, in the presence of a catalyst, and examples of dehydration condensation catalysts include, for example, acid catalysts such as hydrochloric acid, oxalic acid, and sulfuric acid, and base catalysts such as ammonia, potassium hydroxide, sodium hydroxide, and ammonium hydroxide. As a dehydration condensation catalyst, a base catalyst is preferred. In the dehydration condensation reaction, the amount of catalyst added to the monomer compounds is not particularly limited. For example, the catalyst may be added in an amount of 0.1 to 10 moles, more preferably 0.05 to 7 moles, and even more preferably 0.1 to 5 moles per 1 mole of monomer compounds.

[0075] Gelation of the monomer compound is preferably carried out, for example, in a solvent. The ratio of the monomer compound to the solvent is not particularly limited. Examples of solvents include dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), dimethylformamide (DMF), γ-butyl lactone (GBL), acetonitrile (MeCN), and ethylene glycol ethyl ether (EGEE). The solvent may be used alone or in combination of two or more types. The solvent used for gelation is hereinafter referred to as the "gelation solvent."

[0076] The conditions for gelation are not particularly limited. The treatment temperature for the solvent containing the monomer compound is, for example, 20°C to 30°C, preferably 22°C to 28°C, and more preferably 24°C to 26°C. The treatment time is, for example, 1 minute to 60 minutes, preferably 5 minutes to 40 minutes, and more preferably 10 minutes to 30 minutes. When performing a dehydration condensation reaction, the treatment conditions are not particularly limited, and examples thereof may be used. By performing gelation, for example, siloxane bonds grow and silica primary particles are formed, and as the reaction proceeds further, the primary particles are connected to each other in a bead-like shape to produce a gel with a three-dimensional structure.

[0077] It is desirable to perform an aging treatment on the gel-like compound obtained by gelation after the gelation reaction. Through the aging treatment, for example, it is possible to further grow the primary particles of the gel having a three-dimensional structure obtained by gelation, thereby increasing the size of the particles themselves. Consequently, the contact state of the neck portions where the particles are in contact can be changed from point contact to surface contact (increasing the contact area). For example, the strength of the gel that has undergone the aging treatment increases, and consequently, the strength of the three-dimensional basic structure after grinding can be improved. By doing so, for example, during the drying process after applying the ground material, the shrinkage of the fine pore size of the pore structure in which the three-dimensional basic structure is deposited due to solvent volatilization during the drying process can be suppressed.

[0078] Aging treatment can be performed, for example, by incubating a gel-like compound at a predetermined temperature for a predetermined time. The aging temperature is, for example, 30°C or higher, preferably 35°C or higher, and more preferably 40°C or higher. Meanwhile, the aging temperature is, for example, 80°C or lower, preferably 75°C or lower, and more preferably 70°C or lower. The range of the aging temperature is, for example, 30°C to 80°C, preferably 35°C to 75°C, and more preferably 40°C to 70°C. The aging time is, for example, 5 hours or more, preferably 10 hours or more, and more preferably 15 hours or more. Meanwhile, the aging time is, for example, 50 hours or less, preferably 40 hours or less, and more preferably 30 hours or less. The range of the aging time is, for example, 5 hours to 50 hours, preferably 10 hours to 40 hours, and more preferably 15 hours to 30 hours. Furthermore, the aging conditions can be optimized, for example, to increase the primary silica particle size and the contact area of ​​the neck portion. Additionally, it is desirable to consider the boiling point of the solvent used; for instance, if the aging temperature is excessively high, the solvent may volatilize excessively, potentially leading to problems such as the closure of fine pores in the three-dimensional pore structure due to the concentration of the coating solution (gel solution). On the other hand, for instance, if the aging temperature is excessively low, not only is the effect of aging not fully obtained, but temperature non-uniformity increases over time during the mass production process, potentially resulting in a low-refractive-index layer with inferior properties.

[0079] For the aging treatment, a solvent such as that used for the gelation treatment may be used. Specifically, it is preferable to perform the aging treatment directly on the reactant after the gelation treatment (i.e., the solvent containing the gel-like compound). The molar content of the residual silanol groups contained in the gel (gel-like compound, e.g., gel-like silicon compound) after the aging treatment following gelation is, for example, 50% or less, preferably 40% or less, and more preferably 30% or less. Meanwhile, the molar content of the residual silanol groups is, for example, 1% or more, preferably 3% or more, and more preferably 5% or more. The range of the molar content of the residual silanol groups is, for example, 1% to 50%, preferably 3% to 40%, and more preferably 5% to 30%. For the purpose of increasing the hardness of the gel, it is preferable, for example, that the molar content of the residual silanol groups be lower. If the molar content of the silanol groups is excessively high, there is a possibility that the pore structure cannot be maintained, for example, until the precursor of the silicon porous body is cross-linked. On the other hand, if the number of moles of silanol groups is excessively low, for example, in the process of producing a liquid containing microporous particles (e.g., a suspension) and / or subsequent processes, it may become impossible to crosslink the pulverized gel-like compound, and thus it may not be possible to impart sufficient film strength. In addition, the number of moles of residual silanol groups is, for example, the ratio of residual silanol groups when the number of moles of alkoxy groups of the raw material (e.g., a monomer compound precursor) is 100. Furthermore, although the above is an example of a silanol group, for example, when the silicon compound of the monomer is modified with various reactive functional groups, the same matters and conditions may be applied to each functional group.

[0080] After gelling the monomer compound in a gelling solvent, the obtained gel compound is ground. For example, the grinding treatment may be performed directly on the gel compound in the gelling solvent, or the gelling solvent may be replaced with another solvent and the grinding treatment may be performed on the gel compound in the other solvent. In addition, for example, if the catalyst and solvent used in the gelling reaction remain after the aging process and cause gelation of the liquid over time (pot life) or a decrease in drying efficiency during the drying process, it is desirable to replace them with another solvent. The solvent other than the above is hereinafter referred to as the "grinding solvent."

[0081] The solvent for grinding is not particularly limited, and, for example, an organic solvent may be used. As for organic solvents, examples include solvents having a boiling point of, for example, 130°C or lower, preferably 100°C or lower, and more preferably 85°C or lower. Specific examples include isopropyl alcohol (IPA), ethanol, methanol, butanol, propylene glycol monomethyl ether (PGME), methyl cellosolve, acetone, dimethylformamide (DMF), isobutyl alcohol, etc. The solvent for grinding may be used alone or two or more types may be used in combination.

[0082] The combination of the gelling solvent and the crushing solvent is not particularly limited, and examples include combinations of DMSO and IPA, DMSO and ethanol, DMSO and methanol, DMSO and butanol, and DMSO and isobutyl alcohol. By substituting the gelling solvent with the crushing solvent in this way, a more uniform coating film can be formed, for example, in the coating film formation described later.

[0083] The method of grinding the gel-like compound is not particularly limited and can be performed, for example, by an ultrasonic homogenizer, a high-speed rotary homogenizer, or other grinding device utilizing the cavitation phenomenon. While media grinding devices such as ball mills physically destroy the pore structure of the gel during grinding, cavitation-type grinding devices such as homogenizers, for example, are media-free, and thus exfoliate the relatively weakly bonded silica particle interfaces already contained within the gel's three-dimensional structure using high-speed shear force. As a result, the gel's three-dimensional structure obtained can maintain a pore structure having a particle size distribution within a certain range, for example, and can re-form the pore structure through deposition during coating and drying. The grinding conditions are not particularly limited, but it is preferable to be able to grind the gel without evaporating the solvent by, for example, applying a high-speed flow instantaneously. For example, it is preferable to grind to produce a material with non-uniform particle size (e.g., volume average particle diameter or particle size distribution) as described above. If the amount of work, such as grinding time or intensity, is insufficient, for example, large particles may remain, making it impossible to form dense fine pores and increasing appearance defects, potentially resulting in an inability to obtain high quality. On the other hand, if the amount of work is excessive, for example, the particles may become finer than the desired particle size distribution, causing the pore size deposited after application and drying to become fine, potentially making it impossible to achieve the desired porosity.

[0084] In this manner, a liquid (e.g., a suspension) containing micropore particles (pulverized material of a gel-like compound) can be prepared. Additionally, a liquid containing micropore particles and a catalyst can be prepared by adding a catalyst that chemically bonds the micropore particles to each other after preparing the liquid containing the micropore particles, or during the preparation process. The catalyst may be, for example, a catalyst that promotes cross-linking between micropore particles. As a chemical reaction for chemically bonding the micropore particles to each other, it is preferable to use a dehydration condensation reaction of residual silanol groups contained in silica sol molecules. By promoting the reaction between the hydroxyl groups of the silanol groups using a catalyst, continuous film formation that hardens the pore structure in a short time is possible. Examples of catalysts include photo-activated catalysts and thermal-activated catalysts. In the case of a photo-activated catalyst, for example, micropore particles can be chemically bonded (e.g., cross-linked) without heating during the precursor formation process. According to this, for example, in the precursor formation process, since shrinkage of the entire precursor is difficult to occur, a higher porosity can be maintained. In addition to the catalyst, or in place of it, a catalyst-generating substance (catalyst-generating agent) may be used. For example, in addition to the photoactive catalyst, or in place of it, a substance that generates a catalyst by light (photocatalyst-generating agent) may be used, and in addition to the thermally active catalyst, or in place of it, a substance that generates a catalyst by heat (thermal catalyst-generating agent) may be used. Examples of photocatalyst-generating agents include photobase-generating agents (substances that generate basic catalysts by light irradiation) and photoacid-generating agents (substances that generate acidic catalysts by light irradiation), and photobase-generating agents are preferred.As photobase generators, for example, 9-anthrylmethyl N, N-diethylcarbamate (trade name WPBG-018), (E)-1-[3-(2-hydroxyphenyl)-2-propenoyl]piperidine (trade name WPBG-027), 1-(anthraquinone-2-yl)ethylimidazolecarboxylate (trade name WPBG-140), 2-nitrophenyl methyl 4-methacryloyloxypiperidine-1-carboxylate (trade name WPBG-165), and 1,2-diisopropyl-3-〔bis(dimethylamino)methylene〕guanidinium Examples include 2-(3-benzoylphenyl)propionate (trade name WPBG-266), 1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidinium n-butyltriphenylborat (trade name WPBG-300), 2-(9-oxoxanthene-2-yl)propionic acid 1,5,7-triazabicyclo[4.4.0]deca-5-en (Tokyo Kasei High School Co., Ltd.), and a compound containing 4-piperidine methanol (trade name HDPD-PB100: manufactured by Heraeus Co., Ltd.). In addition, all trade names containing "WPBG" are trade names of Wako Junyaku Co., Ltd. Examples of photocatalytic agents include aromatic sulfonium salts (product name SP-170: ADEKA), triaryl sulfonium salts (product name CPI101A: San Apro), and aromatic iodinium salts (product name Irgacure250: Chiba Japan). In addition, the catalyst that chemically bonds the micropore particles together is not limited to photoactive catalysts and photocatalytic agents, but may also be a thermally active catalyst or a thermal catalyst such as urea. Examples of catalysts that chemically bond the micropore particles together include base catalysts such as potassium hydroxide, sodium hydroxide, and ammonium hydroxide, and acid catalysts such as hydrochloric acid, acetic acid, and oxalic acid.Among these, a base catalyst is preferred. The catalyst or catalyst generator that chemically bonds the microporous particles together may be used, for example, by adding it immediately before application to a sol particle solution (e.g., a suspension) containing ground material (microporous particles), or as a mixture in which the catalyst or catalyst generator is mixed with a solvent. The mixture may be, for example, a coating solution dissolved by directly adding it to the sol particle solution, a solution in which the catalyst or catalyst generator is dissolved in a solvent, or a dispersion solution in which the catalyst or catalyst generator is dispersed in a solvent. The solvent is not particularly limited and may be, for example, water, a buffer solution, etc.

[0085] In addition, for example, a crosslinking aid may be added to the gel-containing liquid to indirectly bond the pulverized parts of the gel. When this crosslinking aid is inserted between the particles (the pulverized parts), the particles and the crosslinking aid interact or bond with each other, making it possible to bond even particles that are somewhat far apart, thereby enabling efficient strength enhancement. As the crosslinking aid, a multi-crosslinked silane monomer is preferred. Specifically, the multi-crosslinked silane monomer may, for example, have two or more and three or fewer alkoxysilyl groups, and the chain length between the alkoxysilyl groups may have a carbon number of 1 or more and 10 or fewer, and may also include elements other than carbon. Examples of the above-mentioned crosslinking aids include bis(trimethoxysilyl)ethane, bis(triethoxysilyl)ethane, bis(trimethoxysilyl)methane, bis(triethoxysilyl)methane, bis(triethoxysilyl)propane, bis(trimethoxysilyl)propane, bis(triethoxysilyl)butane, bis(trimethoxysilyl)butane, bis(triethoxysilyl)pentane, bis(trimethoxysilyl)hexane, bis(trimethoxysilyl)hexane, bis(trimethoxysilyl)-N-butyl-N-propyl-ethane-1,2-diamine, tris-(3-trimethoxysilylpropyl)isocyanurate, tris-(3-triethoxysilylpropyl)isocyanurate, etc. The amount of this crosslinking aid added is not particularly limited, but, for example, is 0.01 to 20% by weight, 0.05 to 15% by weight, or 0.1 to 10% by weight with respect to the weight of the ground silicon compound.

[0086] Next, a liquid containing microporous particles (e.g., a suspension) is applied onto the sealing portion (application process). For example, various application methods described below may be used for application, but are not limited to these. By directly applying a liquid containing microporous particles (e.g., crushed gel-like silica compounds) onto the sealing portion, a coating film containing microporous particles and a catalyst can be formed. The coating film may be referred to as a coating layer, for example. By forming the coating film, a new three-dimensional structure is constructed, for example, by allowing the crushed material with a destroyed three-dimensional structure to settle and deposit. Additionally, for example, the liquid containing microporous particles may not contain a catalyst that chemically bonds the microporous particles together. For example, as described below, a precursor formation process may be performed after or while spraying a catalyst that chemically bonds the microporous particles together onto the coating film. However, the liquid containing micropore particles may include a catalyst that chemically bonds the micropore particles to each other, and may form a precursor of a porous body by chemically bonding the micropore particles to each other through the action of the catalyst included in the coating film.

[0087] The above solvent (hereinafter also referred to as "coating solvent") is not particularly limited, and, for example, an organic solvent may be used. As for organic solvents, for example, a solvent with a boiling point of 150°C or lower may be used. Specific examples include IPA, ethanol, methanol, n-butanol, 2-butanol, isobutyl alcohol, pentanol, etc., and also, a solvent such as a grinding solvent may be used. When the method for forming a low refractive index layer includes a process of grinding a gel-like compound, in the process of forming the coating film, for example, a grinding solvent containing the ground gel-like compound may be used as is.

[0088] In the coating process, for example, it is preferable to apply a sol-shaped crushed material dispersed in a solvent (hereinafter also referred to as "sol particle liquid") onto the sealing part. For example, after applying and drying the sol particle liquid onto the sealing part, it is possible to continuously form a pore layer having a film strength of a certain level or higher by performing the chemical crosslinking. Furthermore, in the embodiments of the present invention, "sol" refers to a state in which silica sol particles of a nano-three-dimensional structure, which retain a part of the pore structure by crushing the three-dimensional structure of a gel, are dispersed in a solvent and exhibit fluidity.

[0089] The concentration of the ground material in the coating solvent is not particularly limited, and is, for example, 0.3% (v / v) to 50% (v / v), preferably 0.5% (v / v) to 30% (v / v), and more preferably 1.0% (v / v) to 10% (v / v). If the concentration of the ground material is excessively high, for example, the fluidity of the sol particle liquid is significantly reduced, and there is a possibility of causing agglomeration and non-uniformity of coating during coating. If the concentration of the ground material is excessively low, for example, not only does it take a considerable amount of time to dry the solvent of the sol particle liquid, but the residual solvent immediately after drying also increases, so there is a possibility that the porosity will decrease.

[0090] The physical properties of the sol are not particularly limited. The shear viscosity of the sol is, for example, 100 cPa·s or less at a shear rate of 10001 / s, preferably 10 cPa·s or less, and more preferably 1 cPa·s or less. If the shear viscosity is excessively high, for example, non-uniformity of coating may occur, and problems such as a decrease in the transfer rate of gravure coating may appear. Conversely, if the shear viscosity is excessively low, for example, the wet coating thickness during coating cannot be increased, and there is a possibility that the desired thickness cannot be obtained after drying.

[0091] The amount of ground material applied is not particularly limited and can be appropriately set, for example, depending on the thickness of the desired silicon porous body (as a result, a low-refractive-index layer). As a specific example, when forming a silicon porous body with a thickness of 0.1 μm to 1000 μm, the amount of ground material applied is 1 m² of the applied surface area. 2 The amount of sugar is, for example, 0.01 μg to 60,000 μg, preferably 0.1 μg to 5,000 μg, and more preferably 1 μg to 50 μg. Since the preferred coating amount of the sol particle solution is related to, for example, the concentration of the solution or the coating method, it is difficult to define it unconditionally; however, considering productivity, it is desirable to apply it as thin a layer as possible. If the coating amount is excessively large, for example, there is a high possibility that it will be dried in a drying oven before the solvent volatilizes. As a result, the nano-grinded sol particles settle and deposit in the solvent, and as the solvent dries before forming a pore structure, the formation of pores is inhibited, which may lead to a significant decrease in porosity. On the other hand, if the coating amount is excessively thin, there is a possibility that the risk of coating cratering will increase.

[0092] In addition, the method for forming a low refractive index layer comprises, for example as described above, a precursor forming process for forming a pore structure that is a precursor of the pore layer (low refractive index layer). The precursor forming process is not particularly limited, but for example, the precursor (pore structure) may be formed by a drying process in which a coating film produced by applying a liquid containing micropore particles is dried. By the drying treatment in the drying process, for example, not only is the solvent (solvent contained in the sol particle liquid) in the coating film removed, but the sol particles are also precipitated and deposited during the drying treatment to form a pore structure. The temperature of the drying treatment is, for example, 50°C to 250°C, preferably 60°C to 150°C, and more preferably 70°C to 130°C. The time of the drying treatment is, for example, 0.1 min to 30 min, preferably 0.2 min to 10 min, and more preferably 0.3 min to 3 min.

[0093] The drying process may be, for example, natural drying, heat drying, or vacuum drying. Among these, heat drying is preferred when the process is intended for continuous industrial production. The method of heat drying is not particularly limited, and general heating means may be used. Examples of heating means include hot air blowers, heating rollers, and far-infrared heaters. Furthermore, regarding the solvent used, a solvent with low surface tension is preferred to suppress the occurrence of shrinkage stress due to solvent volatilization during drying and the resulting cracking of the pore layer (silicon porous body). Examples of solvents include lower alcohols such as isopropyl alcohol (IPA), hexane, and perfluorohexane. Additionally, a small amount of perfluoro-based surfactant or silicone-based surfactant may be added to the above IPA, etc., to lower the surface tension.

[0094] In addition, as described above, the method for forming a low refractive index layer includes a crosslinking reaction process that induces a crosslinking reaction within the precursor after the precursor formation process, and in the crosslinking reaction process, a basic substance is generated by light irradiation or heating, and the crosslinking reaction process is multi-stage. In the first stage of the crosslinking reaction process, for example, micropore particles are chemically bonded together by the action of a catalyst (basic substance). By this, for example, the three-dimensional structure of the pulverized material in the coating film (precursor) is immobilized. In the case of immobilization by conventional sintering, for example, high-temperature treatment of 200°C or higher is performed to induce the dehydration condensation of silanol groups and the formation of siloxane bonds. In the present formation method, by reacting various additives that catalyze the above dehydration condensation reaction, the pore structure can be continuously formed and immobilized at a relatively low drying temperature of around 100°C and a short treatment time of less than a few minutes.

[0095] The method of chemical bonding is not particularly limited and can be appropriately determined, for example, depending on the type of gel silicon compound. As a specific example, chemical bonding can be performed, for example, by chemical cross-linking between the pulverized particles. Additionally, for example, when inorganic particles such as titanium oxide are added to the pulverized particles, chemical cross-linking between the inorganic particles and the pulverized particles can also be conceived. Furthermore, when supporting a biocatalyst such as an enzyme, chemical cross-linking between the pulverized particles and a site different from the catalytic active site can also be conceived. Accordingly, the method for forming a low refractive index layer can be applied not only to a pore layer (silicon porous body) formed from sol particles, for example, but also to organic-inorganic hybrid pore layers, host-guest pore layers, etc.

[0096] The chemical reaction in the presence of the catalyst is not particularly limited to any stage in the method for forming a low-refractive-index layer, and is performed, for example, at least one stage in the multi-stage crosslinking reaction process. For example, in the method for forming a low-refractive-index layer, as described above, the drying process may also serve as a precursor formation process. Furthermore, for example, after the drying process, a multi-stage crosslinking reaction process may be performed, and in at least one stage, the micropore particles may be chemically bonded together by the action of the catalyst. For example, as described above, if the catalyst is a photoactive catalyst, the micropore particles may be chemically bonded together by light irradiation during the crosslinking reaction process to form a porous precursor. Furthermore, if the catalyst is a thermally active catalyst, the micropore particles may be chemically bonded together by heating during the crosslinking reaction process to form a porous precursor.

[0097] The above chemical reaction may be carried out, for example, by light irradiation or heating on a coating film containing a catalyst previously added to a sol particle solution (e.g., a suspension), or by light irradiation or heating after spraying the catalyst onto the coating film, or by light irradiation or heating while spraying the catalyst. The integrated light amount during light irradiation is not particularly limited, and, for example, 200 mJ / cm² when converted to a wavelength of 360 nm. 2 ~800 mJ / cm² 2 is, preferably 250 mJ / cm² 2 ~600 mJ / cm² 2 is, and more preferably 300 mJ / cm² 2 ~400 mJ / cm² 2 It is. From the perspective of preventing the effect from becoming insufficient due to insufficient irradiation dose, which prevents decomposition by light absorption of the catalyst from proceeding, 200 mJ / cm² 2The above accumulated light quantity is desirable. The conditions for the heat treatment are not particularly limited. The heating temperature is, for example, 50°C to 250°C, preferably 60°C to 150°C, and more preferably 70°C to 130°C. The heating time is, for example, 0.1 min to 30 min, preferably 0.2 min to 10 min, and more preferably 0.3 min to 3 min. Alternatively, the process of drying the coated sol particle liquid (e.g., suspension) as described above may also include a process of performing a chemical reaction in the presence of a catalyst. That is, in the process of drying the coated sol particle liquid (e.g., suspension), the crushed particles (fine pore particles) may be chemically bonded together by a chemical reaction in the presence of a catalyst. In this case, the crushed particles (fine pore particles) may be further strongly bonded together by additionally heating the coating film after the drying process. In addition, it is presumed that chemical reactions in the presence of a catalyst may also occur during the process of preparing a micropore particle-containing solution (e.g., a suspension) and the process of applying the micropore particle-containing solution. However, this presumption does not limit the method of forming the low refractive index layer. Furthermore, regarding the solvent used, for example, a solvent with low surface tension is preferred to suppress the occurrence of shrinkage stress due to solvent volatilization during drying and the resulting cracking of the pore layer. Examples include lower alcohols such as isopropyl alcohol (IPA), hexane, and perfluorohexane.

[0098] In the method for forming a low-refractive-index layer, the strength of the porosity layer (low-refractive-index layer) can be further improved compared to, for example, when the crosslinking reaction process is in a single stage, by making the crosslinking reaction process multi-stage. Hereinafter, the process from the second stage of the crosslinking reaction process onwards may be referred to as the "aging process." In the aging process, the crosslinking reaction within the precursor may be further promoted, for example, by heating the precursor. Although the phenomena and mechanisms occurring during the crosslinking reaction process are unknown, they are, for example, as described above. For example, in the aging process, the heating temperature is set to a low temperature to induce a crosslinking reaction while suppressing the shrinkage of the precursor, thereby improving strength and achieving a balance between high porosity and strength. The temperature in the aging process is, for example, 40°C to 70°C, preferably 45°C to 65°C, and more preferably 50°C to 60°C. The time for performing the aging process is, for example, 10 to 30 hours, preferably 13 to 25 hours, and more preferably 15 to 20 hours.

[0099] The low refractive index layer formed as described above has excellent strength, so it can be formed into a porous body in the form of a roll, for example, and has advantages such as good manufacturing efficiency and ease of handling.

[0100] The low-refractive-index layer (pore layer) formed in this way may be laminated with another film (layer), for example, to form a laminated structure including a porous structure. In this case, each component of the laminated structure may be laminated by, for example, interposing an adhesive or a bonding agent.

[0101] Details regarding the specific composition and method of forming a low-refractive-index layer are described, for example, in International Publication No. 2019 / 151073. The description in the said publication is incorporated herein by reference.

[0102] C. Micro LED array substrate

[0103] As a micro LED array substrate, any micro LED array substrate of a suitable configuration may be used. Typically, as shown in FIG. 1, the micro LED array substrate (10) comprises a driving substrate (12) and a plurality of micro LEDs (11) arranged in a matrix on the driving substrate (12).

[0104] Micro LED refers to an LED with a chip size of, for example, 1㎛ to 100㎛.

[0105] In one embodiment, a single type of micro LED may be used as a plurality of micro LEDs. In one embodiment, the micro LED is a blue LED or an ultraviolet LED.

[0106] The driving board can be configured to switch-drive each micro LED individually. Since the driving board is well known to those skilled in the art, a description is omitted here.

[0107] D. Sealing part

[0108] The seal may be formed from any suitable transparent material. Examples of materials constituting the seal include epoxy resin, silicone resin, acrylic resin, etc. Additionally, the seal may be formed from molten glass. Examples of glass constituting the seal include acrylic glass, crown glass, flint glass, borosilicate glass, etc.

[0109] The sealing portion may be composed of an adhesive or a pressure-sensitive adhesive. In one embodiment, the sealing portion is composed of a pressure-sensitive adhesive.

[0110] As an adhesive, any suitable adhesive may be used. Examples include water-based adhesives such as isocyanate-based, polyvinyl alcohol-based, gelatin-based, vinyl latex-based, water-based polyurethane, and water-based polyester, as well as curing adhesives such as UV-curing adhesives and electron beam-curing adhesives.

[0111] Any suitable adhesive may be used as the adhesive. Examples include rubber-based, acrylic-based, silicone-based, urethane-based, vinyl alkyl ether-based, polyvinyl alcohol-based, polyvinyl pyrrolidone-based, polyacrylamide-based, and cellulose-based adhesives. Among these, acrylic adhesives are preferably used because they have excellent optical transparency and also excellent adhesive properties, weather resistance, and heat resistance.

[0112] The sealing part may have a light transmittance (23°C) of at least 80% for a wavelength of 590 nm, for example, preferably at least 85%, and more preferably at least 90%. In addition, the average light transmittance of the sealing part for a wavelength of 450 nm to 500 nm is preferably at least 70%, more preferably at least 75%, and even more preferably at least 80%. In addition, the average light transmittance of the sealing part for a wavelength of 500 nm to 780 nm is preferably at least 80%, more preferably at least 85%, and even more preferably at least 90%.

[0113] The refractive index of the seal is preferably 1.40 or higher, more preferably 1.40 to 2.00, and even more preferably 1.45 to 1.80.

[0114] The thickness of the sealing portion is preferably 200 μm or less, more preferably 150 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less. If the thickness of the sealing portion is reduced, the effect of suppressing color mixing becomes significant. The lower limit of the thickness of the sealing portion is, for example, 10 μm. In addition, the thickness of the sealing portion may be the distance from the surface of the low refractive index layer of the micro LED to the surface of the sealing portion on the micro LED side.

[0115] E. Wavelength conversion layer

[0116] The wavelength conversion layer is a layer that absorbs excitation light from a micro LED and emits a predetermined color. When a blue LED is used as the micro LED, a red subpixel is formed by a wavelength conversion layer that absorbs excitation light from the micro LED and emits red light, and a green subpixel is formed by a wavelength conversion layer that absorbs said excitation light and emits green light. Additionally, when an ultraviolet LED is used, a red subpixel is formed by a wavelength conversion layer that is excited by ultraviolet light and emits red light, a green subpixel is formed by a wavelength conversion layer that is excited by ultraviolet light and emits green light, and a blue subpixel is formed by a wavelength conversion layer that is excited by ultraviolet light and emits blue light.

[0117] In one embodiment, the wavelength conversion layer comprises phosphor particles. The wavelength conversion layer typically comprises a matrix and phosphor particles dispersed within the matrix. Any suitable material may be used as the material constituting the matrix (hereinafter also referred to as the matrix material). Examples of such materials include resins, organic oxides, and inorganic oxides. The matrix material is preferably a resin. The resin may be a thermoplastic resin, a thermosetting resin, or an active energy beam curable resin (e.g., electron beam curable resin, UV curable resin, visible light curable resin). Preferably, it is a thermosetting resin or a UV curable resin, and more preferably, a thermosetting resin. The resin may be used alone or in combination (e.g., as a blend or copolymer).

[0118] In one embodiment, quantum dots may be used as phosphor particles. Quantum dots can control the wavelength conversion characteristics of the wavelength conversion layer. Specifically, by appropriately combining quantum dots having different emission center wavelengths, a wavelength conversion layer can be formed to realize light having a desired emission center wavelength. The emission center wavelength of the quantum dots can be adjusted by the material and / or composition, particle size, shape, etc. of the quantum dots. As quantum dots, for example, a quantum dot having an emission center wavelength in a wavelength range of 600 nm to 680 nm (hereinafter, quantum dot A), a quantum dot having an emission center wavelength in a wavelength range of 500 nm to 600 nm (hereinafter, quantum dot B), and a quantum dot having an emission center wavelength in a wavelength range of 400 nm to 500 nm (hereinafter, quantum dot C) are known. Quantum dot A is excited by excitation light (light from a micro LED) and emits red light, quantum dot B emits green light, and quantum dot C emits blue light. By appropriately combining these, if light of a predetermined wavelength is incident on and passed through a wavelength conversion layer, light having a center wavelength of emission in a desired wavelength band can be realized.

[0119] Quantum dots can be composed of any suitable material. Quantum dots can preferably be composed of inorganic materials, more preferably inorganic conductive materials or inorganic semiconductor materials. Examples of semiconductor materials include semiconductors of Group II-VI, Group III-V, Group IV-VI, and Group IV. Specific examples include Si, Ge, Sn, Se, Te, B, C (including diamond), P, BN, BP, BAs, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, InSb, ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdSeZn, CdTe, HgS, HgSe, HgTe, BeS, BeSe, BeTe, MgS, MgSe, GeS, GeSe, GeTe, SnS, SnSe, SnTe, PbO, PbS, PbSe, PbTe, CuF, CuCl, CuBr, CuI, Si3N4, Ge3N4, Al2O3, (Al, Ga, In)2(S, Se, Te)3, and Al2CO. These may be used individually or in combination of two or more types. The quantum dot may contain a p-type dopant or an n-type dopant.

[0120] The size of the quantum dot can be any suitable size depending on the desired emission wavelength. The size of the quantum dot is preferably 1 nm to 10 nm, and more preferably 2 nm to 8 nm. If the size of the quantum dot is within this range, green and red light each exhibit sharp emission, and high color rendering can be realized. For example, green light can be emitted with a quantum dot size of approximately 7 nm, and red light can be emitted with a quantum dot size of approximately 3 nm. The size of the quantum dot is the average particle size when the quantum dot is, for example, spherical, and the dimension along the minimum axis of the shape when the quantum dot has other shapes. Furthermore, any suitable shape can be adopted for the quantum dot depending on the purpose. Specific examples include spherical, flake-like, plate-like, elliptical, and irregular shapes.

[0121] Quantum dots can be incorporated in a ratio of preferably 1 to 50 parts by weight, more preferably 2 to 30 parts by weight, with respect to 100 parts by weight of the matrix material. If the amount of quantum dots incorporated is within this range, a display with excellent color balance of all RGB can be provided.

[0122] Details of quantum dots are described, for example, in Japanese Patent Publication No. 2012-169271, Japanese Patent Publication No. 2015-102857, Japanese Patent Publication No. 2015-65158, Japanese Patent Publication No. 2013-544018, Japanese Patent Publication No. 2013-544018, and Japanese Patent Publication No. 2010-533976, and the descriptions in these publications are incorporated herein by reference. Commercially available quantum dots may be used.

[0123] In another embodiment, the phosphor particles are particles that exhibit luminescence due to their composition. Examples of such phosphor particles include materials based on sulfides, aluminates, oxides, silicates, nitrides, YAG, and terbium aluminum garnet (TAG).

[0124] In addition, the following red phosphors and green phosphors may be used as phosphor particles. As for the red phosphor, for example, Mn 4+ An example of a complex fluoride phosphor activated by this can be given. A complex fluoride phosphor refers to a coordination compound containing at least one coordination center (e.g., M described below), surrounded by fluoride ions acting as ligands, and having its charge compensated by a counter ion (e.g., A described below) as needed. A specific example thereof is A2[MF5]:Mn 4+ , A3[MF6]:Mn 4+ , Zn2[MF7]:Mn 4+ , A[In2F7]:Mn 4+ , A2[M'F6]:Mn 4+ , E[M'F6]:Mn 4+ , A3[ZrF7]:Mn 4+ , Ba 0.65 Zr 0.35 F 2.70 :Mn 4+ Examples can be given. Here, A is Li, Na, K, Rb, Cs, NH4, or a combination thereof. M is Al, Ga, In, or a combination thereof. M' is Ge, Si, Sn, Ti, Zr, or a combination thereof. E is Mg, Ca, Sr, Ba, Zn, or a combination thereof. A composite fluoride phosphor having a coordination number of 6 at the coordination center is preferred. Details of such a red phosphor are described, for example, in Japanese Patent Publication No. 2015-84327. The entire description of the said publication is incorporated herein by reference.

[0125] As for the green phosphor, for example, a compound comprising a solid solution of sialon having a β-type Si3N4 crystal structure as a main component can be given. Preferably, a treatment such as reducing the amount of oxygen contained in such sialon crystals to a specific amount (e.g., 0.8 mass%) or less is performed. By performing such a treatment, a green phosphor emitting sharp light with a narrow peak width can be obtained. Details of such a green phosphor are described, for example, in Japanese Patent Publication No. 2013-28814. The entire description of the said publication is incorporated herein by reference.

[0126] The thickness of the wavelength conversion layer is preferably 5㎛ to 100㎛, and more preferably 30㎛ to 50㎛. If the thickness of the wavelength conversion layer is within this range, the conversion efficiency and durability can be excellent.

[0127] As described above, in one embodiment, each wavelength conversion layer is spaced apart by a partition (light-blocking layer). The width of the partition (i.e., the spacing between adjacent wavelength conversion layers) is preferably 0.1 μm to 100 μm, and more preferably 1 μm to 50 μm. In the present invention, sufficient suppression of color mixing is possible even if the width of the partition is narrow. By narrowing the width of the partition, a micro LED display device with excellent luminous efficiency can be obtained.

[0128] As described above, when configuring a subpixel that utilizes light directly from a micro LED (for example, when forming a blue subpixel using a blue LED), the wavelength conversion layer at the above location may be replaced with a light diffusion layer. It is preferable for the light scattering layer to contain light-scattering particles. Examples of materials constituting the light-scattering particles include alumina, zirconium oxide, titanium oxide, and barium sulfate.

[0129] In one embodiment, the micro LED display device further comprises a color filter disposed on a side opposite to the low-refractive-index layer of the wavelength conversion layer (and / or light diffusion layer). The color filter may be configured in any suitable way depending on the color of the subpixel. In one embodiment, a color filter is disposed in each subpixel to cut off color development other than the desired color. For example, a color filter is used in the red subpixel and the green subpixel to cut off blue color development.

[0130] (Example)

[0131] The present invention will be specifically described below by way of examples, but the present invention is not limited by these examples.

[0132] [Example 1]

[0133] For the configuration shown in FIG. 2(a), that is, a configuration in which a red phosphor and a green phosphor are arranged as a wavelength conversion layer, and a blue LED is placed directly below the green phosphor by interposing a low refractive index layer (refractive index: 1.20) and a sealing portion (refractive index: 1.50), the luminance of the red emission and the luminance of the green emission were determined by optical simulation. The wavelength conversion layer consists of a matrix portion (refractive index 1.47) with 10 wt% of wavelength conversion particles (refractive index 1.80) added. The refractive index of the wavelength conversion layer is 1.50.

[0134] The optical characteristics in this embodiment, and in the embodiments and comparative examples described below, were calculated using Synopsys' optical simulation software (Lighttools). The optical model used for the simulation is as follows.

[0135] The thickness and width of each RGB wavelength conversion layer were set to 100 μm and 100 μm, respectively. The width of the barrier placed between each RGB layer was set to 50 nm. LEDs were placed at positions opposite each wavelength conversion layer. In this simulation, for the purpose of investigating the effect of color mixing, only the LED corresponding to the Green wavelength conversion layer was placed, and a sealing layer (adhesive layer) was placed between the LED and the wavelength conversion layer. The thickness of the sealing layer between the LED and the wavelength conversion layer is as shown in Table 1. The thickness of the low refractive index layer was set to 1.0 μm. Additionally, the dimensions shown here assume a 78-inch screen with 4K resolution (3840x2160). The barrier was placed between the wavelength conversion layers with a width of 50.0 μm, and the transmittance was set to 0%. Additionally, a light receiver was placed on each pixel.

[0136] [Comparative Example 1]

[0137] For the configuration shown in Fig. 2(b), that is, a red phosphor and a green phosphor arranged as a wavelength conversion layer, with a sealing portion interposed (without a low refractive index layer), and a blue LED placed directly below the green phosphor, the luminance of the red emission and the luminance of the green emission were obtained by optical simulation.

[0138] <Evaluation>

[0139] Table 1 shows the ratio of the luminance in Example 1 to the luminance (100%) in Comparative Example 1. In addition, the thickness of the sealing portion between the LED and the wavelength conversion layer was set to 25 μm, 75 μm, and 125 μm, and the ratio of the luminance for each thickness setting was calculated.

[0140] In the above configuration, a green phosphor and a blue LED constitute a green-emitting subpixel, and thus, the relationship is such that the luminance of green emission > the luminance of red emission, and furthermore, the greater the difference in luminance between green emission and red emission, the greater the color mixing suppression effect.

[0141] As is clear from Table 1, in the present invention, by arranging a low refractive index layer, unnecessary red light emission is suppressed, and color mixing is also preferably suppressed. Furthermore, this effect is made significant by appropriately setting the thickness of the sealing portion between the LED and the wavelength conversion layer.

[0142]

[0143] [Example 2]

[0144] For the configuration shown in Fig. 2(a), that is, a red phosphor and a green phosphor arranged as a wavelength conversion layer, a low refractive index layer and a sealing portion (thickness between the LED and the wavelength conversion layer: 75 μm) interposed, and a blue LED placed directly below the green phosphor (the thickness of the wavelength conversion layer is 100 μm, the width is 100 μm, the thickness of the barrier is 50 μm, and the thickness of the low refractive index layer is 1.0 μm), the brightness of the red emission and the brightness of the green emission were obtained by optical simulation.

[0145] [Comparative Example 2]

[0146] For the configuration shown in Fig. 2(b), that is, a red phosphor and a green phosphor arranged as a wavelength conversion layer, with a sealing portion (thickness 75 μm) interposed (without a low refractive index layer), and a blue LED placed directly below the green phosphor, the luminance of the red emission and the luminance of the green emission were obtained by optical simulation.

[0147] <Evaluation>

[0148] Table 2 shows the ratio of the luminance in Example 2 to the luminance (100%) in Comparative Example 2. In addition, the refractive index of the low refractive index layer was set to 1.10, 1.20, 1.25, and 1.30, and the ratio of the luminance at each refractive index setting was calculated.

[0149] As is clear from Table 2, in the present invention, by arranging a low refractive index layer, unnecessary red light emission is suppressed, and also, color mixing is preferably suppressed.

[0150] Explanation of the symbols

[0151] 10 micro LED array substrate 11 micro LED 12 driving boards 20 sealing parts 30 low refractive index layer 40 wavelength conversion layers 100 micro LED display device

Claims

Claim 1 A micro LED display device comprising a micro LED array substrate including a plurality of micro LEDs, a sealing portion for sealing the plurality of micro LEDs, a low refractive index layer, and a plurality of wavelength conversion layers formed by partitioning, in this order from the micro LED array substrate side, wherein each of the wavelength conversion layers is formed to be set in correspondence with one of the micro LEDs in the thickness direction, wherein the refractive index of the low refractive index layer is lower than the refractive index of the sealing portion and the refractive index of the wavelength conversion layer, the difference between the refractive index of the low refractive index layer and the refractive index of the sealing portion is 0.10 or more, the difference between the refractive index of the low refractive index layer and the refractive index of the wavelength conversion layer is 0.10 or more, the thickness of the low refractive index layer is 0.3 μm to 3 μm, and the low refractive index layer is a porous layer composed of a porous body formed by chemically bonding of fine particles. Claim 2 A micro LED display device according to claim 1, wherein the refractive index of the low refractive index layer is 1.25 or less. Claim 3 delete Claim 4 A micro LED display device according to claim 1, wherein the sealing portion is composed of an adhesive. Claim 5 A micro LED display device according to claim 1, wherein each of the wavelength conversion layers is spaced apart by a partition. Claim 6 A micro LED display device according to claim 1, wherein the micro LED is a blue LED or a UV LED. Claim 7 A micro LED display device according to claim 1, further comprising a color filter disposed on a side opposite to the low refractive index layer of the wavelength conversion layer.

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