KR20230161930A - Micro LED display device - Google Patents

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 includes 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 in partitions from the back side. Provided in this order, each of the wavelength conversion layers is formed to be set to correspond to 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 wavelength conversion layer is 0.10 or more.

Description

Micro LED display device

The present invention relates to a micro LED display device.

In recent years, as a new display device, micro LED displays configured by arranging micro LEDs in pixels arranged in a matrix have been developed (for example, Patent Document 1 and Patent Document 2). The micro LED display includes a micro LED array substrate composed of a plurality of micro LEDs arranged on the micro LED array substrate, absorbs light from the micro LED, and changes the emission wavelength of the light into red, green, and blue light. A display including an array of wavelength conversion layers (fluorescent light-emitting layers) that each convert wavelengths into wavelengths has been proposed (for example, patent document 2). In such a micro LED display, each subpixel is configured with a set of micro LEDs and a wavelength conversion layer.

Japanese Patent Publication No. 2020-43073 Japanese Patent Publication No. 2016-523450

In the micro LED display as described above, there is a problem in that light from the micro LED leaks into subpixels (adjacent subpixels, peripheral subpixels) other than those corresponding to the micro LED, resulting in color mixing. Additionally, there is a problem that light returning to the back side occurs due to scattering in the wavelength conversion layer, making it impossible to obtain sufficient luminous efficiency.

The object of the present invention is to provide a micro LED display device that has excellent luminous efficiency and suppresses color mixing.

The micro LED display device of the present invention includes 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 to separate the micro LEDs. It is provided in this order from the array substrate side, and each of the wavelength conversion layers is formed to be set corresponding to one of the micro LEDs in the thickness direction, and the refractive index of the low refractive index layer is equal to the refractive index of the sealing portion and that of the wavelength conversion layer. It is lower than the refractive index, 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.

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

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

In one embodiment, the sealing portion is made of adhesive.

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

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

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

According to the present invention, a micro LED display device with excellent luminous efficiency and suppressed color mixing can be provided.

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 examples, and (b) is a schematic cross-sectional view showing the configuration provided in the comparative example.

A. Micro LED display device

1 is a schematic cross-sectional view of a micro LED display device according to one embodiment of the present invention. The micro LED display device 100 according to this embodiment includes a micro LED array substrate 10 including a plurality of micro LEDs 11, a sealing portion 20 that seals the plurality of micro LEDs 11, and a The refractive index layer 30 and a plurality of partitioned wavelength conversion layers 40 are provided in this order from the micro LED array substrate side. Typically, the micro LED array substrate 10 includes a driving substrate 12 and a plurality of micro LEDs 11 arranged in an array (matrix shape) on the driving substrate 12. Each wavelength conversion layer 40 is formed to correspond to one micro LED 11 in the thickness direction. Typically, one subpixel includes one wavelength conversion layer 40 and one micro LED 11. By transmitting light from the micro LED 11 through the wavelength conversion layer 40, red, green, and blue subpixels can be formed. In addition, in the case of a subpixel that uses light from a micro LED as is (for example, when a blue subpixel is formed by a blue LED), the wavelength conversion layer is omitted in the above location, or another layer (e.g. For example, it can be replaced with a light diffusion layer). In one embodiment, each wavelength conversion layer is spaced apart by a partition 50 (light-shielding layer).

In one embodiment, the low refractive index layer 30 is formed on the entire surface of the sealing portion 20 opposite to the micro LED array substrate 10. Additionally, in one embodiment, the low refractive index layer 30 is formed directly on the sealing portion 20 (i.e., without interposing another layer).

The refractive index of the low refractive index layer 30 is lower than the refractive index of the sealing part 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 more. 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 more.

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 part of the light generated from the micro LED, scattered in the wavelength conversion layer, and returning to the back side is reflected at the interface between the wavelength conversion layer and the low refractive index layer and can be emitted to the viewer side. As a result, luminous efficiency is improved. In addition, at least part of the light that is generated diagonally from the micro LED and does not reach the corresponding wavelength conversion layer (wavelength conversion layer in the same subpixel) and heads to the periphery is reflected at the interface between the low refractive index layer and the sealing portion, and is transmitted to the back side. It is returned. As a result, color mixing is suppressed. In addition to being high definition, the micro LED display device according to an embodiment of the present invention is advantageous over conventional displays in that it has high brightness and a wide color gamut.

B. Low refractive index layer

The refractive index of the low refractive index layer is preferably 1.30 or less, more preferably 1.25 or less, further preferably 1.20 or less, and particularly preferably 1.15 or less. The lower the refractive index of the low refractive index layer, the more preferable it is, but the lower limit is, for example, 1.07 or more (preferably 1.05 or more). In this specification, refractive index refers to the refractive index measured at a wavelength of 550 nm.

As mentioned above, 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 sealing portion is preferably 0.20 or more, and more preferably 0.30 or more. Within this range, the above effect becomes noticeable. The upper limit of the difference between the refractive index of the low refractive index layer and the refractive index of the sealing portion is, for example, 0.50 (preferably 0.70).

As mentioned 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 more. 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 more, and more preferably 0.30 or more. Within this range, the above effect becomes noticeable. 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).

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

The low refractive index layer may have any suitable configuration. In one embodiment, the low refractive index layer has voids. The low refractive index layer may preferably be formed by coating or printing. As the material constituting the low refractive index layer, for example, materials described in International Publication No. 2004/113966, Japanese Patent Application Publication No. 2013-254183, and Japanese Patent Application Publication No. 2012-189802 can be adopted. Specifically, for example, silica-based compounds; Hydrolyzable silanes, and their partial hydrolysates and dehydration condensates; organic polymer; Silicon compounds containing silanol groups; Activated silica obtained by contacting silicates with acids or ion exchange resins; polymerizable monomers (for example, (meth)acrylic monomers and styrene monomers); curable resins (for example, (meth)acrylic resins, fluorine-containing resins, and urethane resins); and combinations thereof can be given as examples. The low refractive index layer can be formed by applying or printing a solution or dispersion of these materials.

The porosity of the low refractive index layer having voids 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 value of the refractive index measured with an ellipsometer.

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

The size of voids (holes) can be quantified by the BET test method. Specifically, 0.1 g of sample (formed void layer) was charged into the capillary of a specific surface area measuring device (ASAP2020 manufactured by Micrometric Corporation), then dried under reduced pressure at room temperature for 24 hours to degas the gas in the void structure. do. Then, by adsorbing nitrogen gas to the sample, an adsorption isotherm is drawn and the pore distribution is obtained. By this, the gap size can be evaluated.

The haze of the low refractive index layer is, for example, less than 5%, and is preferably less than 3%. On the other hand, the haze is, for example, 0.1% or more, and is preferably 0.2% or more. The range of haze is, for example, 0.1% or more and less than 5%, and is preferably 0.2% or more and less than 3%. Haze can be measured, for example, by the following method. Additionally, haze is an indicator of the transparency of the low refractive index layer.

The void layer (low refractive index layer) is cut to a size of 50 mm x 50 mm, set in a haze meter (HM-150, manufactured by Murakami Shikisai Kijutsu Genkyusho Co., Ltd.), and the haze is measured. The haze value is calculated using the following formula.

Haze (%) = [diffuse transmittance (%) / total light transmittance (%)] × 100 (%)

Examples of the low refractive index layer having voids therein include a porous layer and/or a low refractive index layer having at least a portion of an air layer. The porous layer typically includes airgel and/or particles (eg, hollow particulates and/or porous particles). The low refractive index layer may preferably be a nanoporous layer (specifically, a porous layer in which the diameter of 90% or more of the micropores is within the range of 10 ^-1 nm to 10 ³ nm).

As the particles, any suitable particle can be employed. The particles are typically made of a silica-based compound. Examples of particle shapes include spherical shape, plate shape, needle shape, string shape, and grape cluster shape. String-shaped particles include, for example, particles in which a plurality of particles having a spherical, plate-shaped, or needle-shaped shape are connected in a beads shape, and single fiber-shaped particles (for example, those described in Japanese Patent Application Laid-Open No. 2001-188104). single-fiber particles), and combinations thereof can be given as examples. The string-shaped particles may be linear or branched. Examples of grape cluster-shaped particles include those in which a plurality of spherical, plate-shaped, and needle-shaped particles are aggregated to form a grape cluster. The shape of the particle can be confirmed, for example, by observation with a transmission electron microscope.

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. If the thickness of the low refractive index layer is within this range, the damage prevention effect of the present invention becomes significant. Additionally, the desired thickness ratio can be easily achieved.

The low refractive index layer can typically be formed by coating or printing as described above. With this configuration, the low refractive index layer can be formed continuously from roll to roll. For printing, any suitable method may be employed. Specifically, the printing method may be a plate-type printing method such as gravure printing, offset printing, or flexo printing, or may be a plateless printing method such as inkjet printing, laser printing, or electrostatic printing.

Hereinafter, an example of a specific configuration of the low refractive index layer will be described. The low refractive index layer of the present embodiment is made of one or more types of structural units that form a fine void structure, and the structural units are chemically bonded to each other through catalytic action. The shape of the structural unit includes, for example, particle shape, fibrous shape, rod shape, and flat shape. The structural unit may have only one shape, or may have a combination of two or more shapes. In one embodiment, the low refractive index layer is a void layer made of a porous body formed by chemically bonding fine particles to each other. Below, the case where the porous layer is mainly composed of a porous body composed of fine particles chemically bonded to each other will be explained.

This void layer can be formed, for example, by chemically bonding fine pore particles to each other in the void layer forming process. In addition, in the embodiment of the present invention, the shape of the “particles” (for example, the above-mentioned microporous particles) is not particularly limited, and may be, for example, spherical or other shapes. In addition, in the embodiment of the present invention, the microporous particles may be, for example, sol-gel beads-shaped particles, nanoparticles (hollow nanosilica/nanoballoon particles), nanofibers, etc. Microporous particles typically contain inorganic substances. Specific examples of inorganic substances include silicon (Si), magnesium (Mg), aluminum (Al), titanium (Ti), zinc (Zn), and zirconium (Zr). These may be used individually, or two or more types may be used together. In one embodiment, the microporous particles are, for example, microporous particles of a silicon compound, and the porous body is, for example, a silicon porous body. The microporous particles of the silicon compound include, for example, pulverized gel-like silica compounds. In addition, another form of the low refractive index layer having at least a part of a porous layer and/or an air layer is, for example, a layer made of a fibrous material such as nanofibers, and the fibrous materials are intertwined to form voids to form a layer. There are layers. The method for producing such a void layer is not particularly limited, and is, for example, the same as the case of the void layer of a porous body in which the above-mentioned fine pore particles are chemically bonded to each other. Additionally, other examples include a void layer formed using hollow nanoparticles or nanoclay, and a void layer formed using hollow nanoballoons or magnesium fluoride. The void layer may be a void layer composed of a single constituent material, or may be a void layer composed of a plurality of constituent materials. The void layer may be composed of a single form, or may be composed of a plurality of the above-mentioned forms.

In this embodiment, the porous structure of the porous body may be, for example, a continuous foam structure in which the pore structure is continuous. A continuous bubble structure means, for example, in the silicon porous body, the pore structure is connected three-dimensionally, and can also be said to be a state in which the internal pores of the pore structure are continuous. By having a porous body having a continuous bubble structure, it is possible to increase the porosity. However, when independent foam particles (particles each having a pore structure) such as hollow silica are used, a continuous foam structure cannot be formed. On the other hand, for example, when using silica sol particles (pulverized material of a gel-like silicon compound that forms a sol), the particles have a three-dimensional tree-like structure, so the coating film (of the sol containing the pulverized material of the gel-like silicon compound) By settling and depositing the wood-shaped particles in the coating film, it is possible to easily form a continuous foam structure. The low refractive index layer more preferably has a monolithic structure in which the continuous bubble structure includes a plurality of fine pore distributions. A monolithic structure means, for example, a hierarchical structure including a structure in which fine nano-sized pores exist and a continuous bubble structure in which the nano-pores are gathered. When forming a monolithic structure, for example, membrane strength can be provided by fine pores while high porosity can be provided by coarse continuous bubble pores, so that both membrane strength and high porosity can be achieved. Such a monolithic structure can preferably be formed by controlling the distribution of fine pores in the resulting pore structure in the gel (gel-like silicon compound) at the stage before pulverizing it into silica sol particles. Also, for example, when pulverizing a gel-like silicon compound, a monolith structure can be formed by controlling the particle size distribution of the pulverized silica sol particles to a desired size.

For example, the low refractive index layer includes pulverized gel-like compounds as described above, and the pulverized materials are chemically bonded to each other. The type of chemical bond (chemical bond) between the pulverized materials in the low refractive index layer is not particularly limited, and examples include crosslinking, covalent bonding, and hydrogen bonding.

The gel form of the gel-like compound is not particularly limited. “Gel” generally refers to a state in which solutes have lost their independent mobility for interaction, have an aggregated structure, and have solidified. The gel-like compound may be, for example, a wet gel or a cicerogel. In addition, generally, a wet gel includes a dispersion medium and refers to a solute having the same structure in the dispersion medium, while a cicerogel refers to one in which the solvent is removed and the solute takes on a network structure with pores.

Examples of the gel-like compound include gelatinized products obtained by gelling a monomer compound. Specifically, the gel-like silicon compound includes, for example, a gelled product in which monomeric silicon compounds are bonded to each other, and as a specific example, a gelled product in which monomeric silicon compounds are covalently bonded, hydrogen bonded, or intermolecularly bonded to each other. . Examples of covalent bonds include bonds by dehydration condensation.

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. On the other hand, 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, for example, by a particle size distribution evaluation device such as a dynamic light scattering method or a laser diffraction method, and an electron microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Additionally, the volume average particle diameter is an indicator of the unevenness of the particle size of the pulverized material.

The type of gel compound is not particularly limited. Examples of the gel-like compound include a gel-like silicon compound. Hereinafter, the case where the gel-like compound is a gel-like silicon compound will be described as an example, but the case is not limited to this.

The crosslink is, for example, a siloxane bond. Examples of the siloxane bond include a T2 bond, a T3 bond, and a T4 bond as shown below. When the void layer (low refractive index layer) has a siloxane bond, it may have any one type of bond, any two types of bond, or all three types of bond. Among the siloxane bonds, the greater the ratio of T2 and T3, the greater the flexibility, and the original properties of the gel can be expected. On the other hand, the greater the ratio of T4, the easier it is for membrane strength to develop. Therefore, it is desirable to change the ratio of T2, T3 and T4 depending on the purpose, use, desired characteristics, etc.

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

When the gel-like compound is a gel-like silicon compound, the silicon compound of the monomer is not particularly limited. Examples of monomer silicon compounds include compounds represented by the following formula (1). As described above, when the gel-like silicon compound is a gelled product in which the silicon compounds of the monomers are hydrogen-bonded or intermolecularly bonded to each other, for example, the monomers of formula (1) can be hydrogen-bonded through each hydroxyl group.

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

Specific examples of the silicon compound represented by formula (1) include a compound represented by the following formula (1') where X is 3. In the following formula (1'), R ¹ is the same as in formula (1) and is, for example, a methyl group. When R ¹ is a methyl group, the silicon compound is tris(hydroxy)methyl silane. When X is 3, the silicon compound is, for example, a trifunctional silane having three functional groups.

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

For example, the silicon compound of the monomer may be a hydrolyzate of a silicon compound precursor. The silicon compound precursor may be any that can produce a silicon compound by hydrolysis, and specific examples include compounds represented by the following formula (2).

In the above formula (2), X is for example 2, 3 or 4, R ¹ and R ² are each independent,

It is a straight chain or branched alkyl group,

R ¹ and R ² may be the same or different,

R ¹ may be the same or different when X is 2,

R ² may be the same or different.

X and R ¹ are, for example, the same as X and R ¹ in formula (1). For R ² , for example, the example of R ¹ in Formula (1) can be used.

Specific examples of the silicon compound precursor represented by formula (2) include, for example, a compound represented by the following formula (2') where X is 3. In the following formula (2'), R ¹ and R ² are each the same as in formula (2). When R ¹ and R ² are methyl groups, the silicon compound precursor is trimethoxy(methyl)silane (hereinafter also referred to as “MTMS”).

For example, the monomer silicon compound is preferably a trifunctional silane because it has excellent low refractive index. Additionally, the monomer silicon compound is preferably a tetrafunctional silane because it has excellent strength (e.g., scratch resistance). Only one type of monomer silicon compound may be used, or two or more types may be used together. For example, the monomer silicon compound may contain only tri-functional silane, may contain only tetra-functional silane, may contain both tri-functional silane and tetra-functional silane, and may further contain other silicon compounds. . When two or more types of silicon compounds are used as the monomer silicon compound, the ratio is not particularly limited and can be set appropriately.

Hereinafter, an example of a method for forming such a low refractive index layer will be described.

The method typically includes a precursor formation process of forming a void structure that is a precursor of a low refractive index layer (void layer) on a resin film, and a crosslinking reaction process of causing a crosslinking reaction inside the precursor after the precursor formation process. do. The method includes a step of producing an containing liquid containing microporous particles (hereinafter sometimes referred to as “microporous particle containing liquid” or simply “containing liquid”), and drying the containing liquid. A drying process is further included, and in the precursor forming process, the fine pore particles in the dried body are chemically bonded to each other to form a precursor. The containing liquid is not particularly limited, and is, for example, a suspension containing microporous particles. In addition, the following mainly explains the case where the microporous particles are pulverized gel-like compounds and the void layer is a porous body (preferably a silicon porous body) containing pulverized gel-like compounds. However, the low refractive index layer can be formed similarly even when the microporous particles are other than pulverized products of the gel-like compound.

According to the method described above, for example, a low refractive index layer (void layer) having an extremely low refractive index is formed. The reason is assumed to be as follows, for example. However, the above guess does not limit the method of forming the low refractive index layer.

Since the pulverized product is obtained by pulverizing a gel-like silicon compound, the three-dimensional structure of the gel-like silicon compound before pulverization is dispersed into a three-dimensional basic structure. Additionally, in the above method, a precursor with a porous structure based on a three-dimensional basic structure is formed by applying a crushed product of a gel-like silicon compound onto a resin film. That is, according to the above method, a new porous structure (three-dimensional basic structure) is formed by applying the pulverized material, which is different from the three-dimensional structure of the gel-like silicon compound. For this reason, in the air gap layer finally obtained, for example, a low refractive index that functions to the same extent as the air layer can be realized. Additionally, in the above method, the three-dimensional basic structure is fixed because the chains are chemically bonded to each other. For this reason, the finally obtained void layer can maintain sufficient strength and flexibility despite its structure having voids.

Additionally, in the above method, the precursor formation process and the crosslinking reaction process are performed as separate processes. Additionally, the crosslinking reaction process is preferably carried out in multiple steps. By performing the crosslinking reaction process in multiple steps, for example, the strength of the precursor can be further improved compared to performing the crosslinking reaction process in one step, and a low refractive index layer with both high porosity and strength can be obtained. This mechanism is unknown, but is assumed to be as follows, for example. That is, as described above, if the membrane strength is improved by a catalyst or the like at the same time as the formation of the void layer, there is a problem that the porosity decreases although the membrane strength improves due to the progress of the catalytic reaction. This means, for example, that the number of cross-links (chemical bonds) between fine-porous particles increases due to the progress of the cross-linking reaction between fine-porous particles using a catalyst, and the bond becomes stronger, but the entire porous layer condenses and the porosity decreases. I think it's because it's deteriorating. In contrast, by performing the precursor formation process and the crosslinking reaction process as separate processes and performing the crosslinking reaction process in multiple stages, for example, the shape of the entire precursor is not changed much (e.g., the overall condensation process is reduced). It is thought that it can increase the number of cross-links (chemical bonds) without causing much. However, these are examples of possible mechanisms and do not limit the method of forming the low refractive index layer.

In the precursor formation process, for example, particles having a certain shape are stacked to form a precursor for the void layer. The strength of the precursor at this point is very weak. Thereafter, a product (e.g., a strong base catalyst generated from a photobase generator, etc.) that can chemically bond the fine pore particles to each other is generated by, for example, a light- or heat-activated catalytic reaction (cross-linking reaction process). 1st step). In order to efficiently proceed with the reaction in a short period of time, additional heat aging (the second step of the cross-linking reaction process) is performed, and the chemical bonding (cross-linking reaction) between fine pore particles is expected to proceed further, thereby improving strength. . For example, when the microporous particles are microporous particles of a silicon compound (e.g., pulverized gel-like silica compound) and residual silanol groups (Si-OH groups) are present in the precursor, the residual silanol groups are involved in a crosslinking reaction. It is thought that they will be chemically bonded together. However, this explanation is also an example and does not limit the method of forming the low refractive index layer.

The above method has a containing liquid production process for producing an containing liquid containing microporous particles. When the microporous particles are a pulverized product of a gel-like compound, the pulverized product is obtained, for example, by pulverizing the gel-like compound. By pulverizing the gel-like compound, the three-dimensional structure of the gel-like compound is broken and dispersed into a three-dimensional basic structure, as described above. An example of preparation of pulverized material is as follows.

Gelation of the monomer compound can be performed, for example, by hydrogen bonding the monomer compounds to each other or by bonding them through intermolecular force. Examples of the monomer compound include a silicon compound represented by the formula (1). Since the silicon compound of formula (1) has a hydroxyl group, for example, hydrogen bonding or intermolecular force bonding between monomers of formula (1) is possible through each hydroxyl group.

Alternatively, the silicon compound may be a hydrolyzate of the silicon compound precursor, and may be produced, for example, by hydrolyzing the silicon compound precursor represented by the formula (2).

The method of hydrolyzing the monomer compound precursor is not particularly limited, and can be performed, for example, through a chemical reaction in the presence of a catalyst. Examples of the catalyst include acids such as oxalic acid and acetic acid. The hydrolysis reaction can be performed, for example, by slowly mixing an aqueous solution of oxalic acid dropwise into a mixture of a silicon compound and dimethyl sulfoxide (for example, a suspension) in a room temperature environment, and then stirring the mixture as is for about 30 minutes. When hydrolyzing the silicon compound precursor, for example, by completely hydrolyzing the alkoxy group of the silicon compound precursor, subsequent gelation, maturation, heating and fixation after forming the void structure can be further efficiently performed.

Gelation of the monomer compound can be performed, for example, by a dehydration condensation reaction between monomers. The dehydration condensation reaction is preferably performed in the presence of a catalyst, and examples of the catalyst include acid catalysts such as hydrochloric acid, oxalic acid, and sulfuric acid, and base catalysts such as ammonia, potassium hydroxide, sodium hydroxide, and ammonium hydroxide. , dehydration condensation catalysts are examples. As a dehydration condensation catalyst, a base catalyst is preferable. In the dehydration condensation reaction, the amount of catalyst added to the monomer compound is not particularly limited. For example, the catalyst may be added in an amount of preferably 0.1 mol to 10 mol, more preferably 0.05 mol to 7 mol, and even more preferably 0.1 mol to 5 mol, based on 1 mol of the monomer compound.

Gelation of the monomer compound is preferably performed in a solvent, for example. The ratio of monomer compound to solvent is not particularly limited. Solvents include, for example, dimethyl sulfoxide (DMSO), N-methyl pyrrolidone (NMP), N,N-dimethyl acetamide (DMAc), dimethyl formamide (DMF), γ-butyl lactone (GBL), Examples include acetonitrile (MeCN) and ethylene glycol ethyl ether (EGEE). Solvents may be used individually or two or more types may be used in combination. The solvent used for gelation is hereinafter also referred to as “solvent for gelation.”

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 processing conditions are not particularly limited, and these examples can be used. By performing gelation, for example, siloxane bonds grow, silica primary particles are formed, and as the reaction further progresses, the primary particles are connected to each other in the shape of beads, creating a gel with a three-dimensional structure.

The gel-like compound obtained by gelation is preferably subjected to aging treatment after the gelation reaction. By 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, and as a result, the size of the neck portion where the particles are in contact with each other is increased. The contact state can be changed from point contact to surface contact (increasing the contact area). For a gel that has been subjected to aging treatment, for example, the strength of the gel itself increases, and as a result, the strength of the three-dimensional basic structure after pulverization can be improved. As a result, for example, in the drying process after applying the pulverized material, it is possible to suppress shrinkage of the pore size of the pore structure in which the three-dimensional basic structure is deposited due to solvent volatilization during the drying process.

The aging treatment can be performed, for example, by incubating the gel-like compound at a predetermined temperature for a predetermined time. The ripening temperature is, for example, 30°C or higher, preferably 35°C or higher, and more preferably 40°C or higher. On the other hand, 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 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. On the other hand, 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 aging time is, for example, 5 hours to 50 hours, preferably 10 hours to 40 hours, and more preferably 15 hours to 30 hours. Additionally, aging conditions can be optimized to obtain, for example, an increase in the size of the silica primary particles and an increase in the contact area of the neck portion. Additionally, it is desirable to consider the boiling point of the solvent being used. For example, if the maturation temperature is too high, the solvent will volatilize excessively and the three-dimensional pore structure may be reduced by concentrating the concentration of the coating liquid (gel liquid). There is a possibility that problems such as holes being blocked may occur. On the other hand, for example, if the maturation temperature is too low, not only cannot the sufficient effect of maturation be obtained, but also temperature unevenness increases over time in the mass production process, resulting in a low refractive index layer whose characteristics are inferior. There is a possibility that this may occur.

The aging treatment can, for example, use a solvent such as a gelation treatment. Specifically, it is preferable to perform aging treatment on the reactant (i.e., solvent containing the gel-like compound) after the gel treatment as is. The number of moles of residual silanol groups contained in the gel (gel-like compound, for example, gel-like silicon compound) that has completed the aging treatment after gelation is, for example, 50% or less, preferably 40% or less, and more preferably 30%. It is as follows. On the other hand, the molar number of residual silanol groups is, for example, 1% or more, preferably 3% or more, and more preferably 5% or more. The range of the molar number of 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, for example, the lower the molar number of residual silanol groups, the more preferable. If the molar number of silanol groups is too high, for example, there is a possibility that the void structure cannot be maintained until the precursor of the silicon porous body is crosslinked. On the other hand, if the mole number of silanol groups is too low, for example, in the process of producing a liquid containing microporous particles (for example, a suspension) and/or in the subsequent processes, it becomes impossible to crosslink the ground product of the gel-like compound. , there is a possibility that sufficient membrane strength may not be provided. 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 in the raw material (for example, monomer compound precursor) is set to 100. In addition, although the above is an example of a silanol group, for example, when the monomer silicon compound is modified with various reactive functional groups, the same matters and conditions can be applied to each functional group.

After the monomer compound is gelled in a gelling solvent, the obtained gel-like compound is pulverized. For example, the gelatinous compound in the gelation solvent may be pulverized as is, or the gelatinization solvent may be replaced with another solvent, and then the gelatinous compound in the other solvent may be pulverized. Additionally, for example, if the catalyst used in the gelation reaction and the solvent used remain even after the aging process, causing gelation of the liquid over time (pot life) and a decrease in drying efficiency during the drying process, it is preferable to replace it with another solvent. . Solvents other than the above are hereinafter also referred to as “solvents for grinding.”

The solvent for grinding is not particularly limited, and for example, an organic solvent can be used. Examples of the organic solvent include solvents with 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), and isobutyl alcohol. The solvent for grinding may be used individually, or two or more types may be used in combination.

The combination of the solvent for gelation and the solvent for grinding 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. In this way, by substituting the solvent for gelation with the solvent for crushing, a more uniform coating film can be formed, for example, in the coating film formation described later.

The method of pulverizing the gel-like compound is not particularly limited and can be performed, for example, by an ultrasonic homogenizer, a high-speed rotation homogenizer, or other pulverizing devices that use the cavitation phenomenon. Devices that perform media pulverization, such as ball mills, physically destroy the pore structure of the gel during pulverization, whereas cavitation-type pulverizers, such as homogenizers, are medialess, for example. The bonding surface of the relatively weakly bonded silica particles already contained in the gel three-dimensional structure is peeled off with high-speed shear force. As a result, the resulting gel three-dimensional structure can, for example, maintain a void structure with a particle size distribution in a certain range, and the void structure can be reformed by deposition during application and drying. The conditions for pulverization are not particularly limited, and it is preferable that the gel can be pulverized without volatilizing the solvent, for example, by instantaneously applying a high-speed flow. For example, it is desirable to pulverize to obtain a pulverized product 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 and intensity, is insufficient, for example, not only will large particles remain and it will not be possible to form dense pores, but appearance defects will also increase and high quality may not be obtained. On the other hand, if the amount of work is excessive, for example, the particles may become finer than the desired particle size distribution, and the pore size deposited after application and drying may become fine, so that the desired porosity may not be obtained.

In the above manner, a liquid (for example, a suspension) containing fine porous particles (pulverized gel-like compound) can be produced. Additionally, a liquid containing microporous particles and a catalyst can be produced by adding a catalyst that chemically bonds the microporous particles to each other after producing the liquid containing the microporous particles or during the production process. The catalyst may be, for example, a catalyst that promotes crosslinking between microporous particles. As a chemical reaction for chemically bonding microporous particles to each other, it is preferable to use a dehydration condensation reaction of the residual silanol group contained in the silica sol molecule. By promoting the reaction between the hydroxyl groups of silanol groups with a catalyst, continuous film formation is possible to harden the void structure in a short time. Examples of catalysts include light-activated catalysts and heat-activated catalysts. According to the photoactive catalyst, for example, in the precursor formation process, microporous particles can be chemically bonded (for example, cross-linked) to each other without heating. According to this, for example, in the precursor formation process, shrinkage of the entire precursor is unlikely to occur, and thus a higher porosity can be maintained. Additionally, in addition to or instead of the catalyst, a substance that generates a catalyst (catalyst generator) may be used. For example, in addition to or instead of a photo-activated catalyst, a substance that generates a catalyst by light (photocatalyst generator) may be used, or in addition to or instead of a thermally-activated catalyst, a material that generates a catalyst by heat may be used. You may use a substance (thermal catalyst generator) that Examples of the photocatalyst generator include a photobase generator (a substance that generates a basic catalyst by light irradiation), a photoacid generator (a substance that generates an acidic catalyst by light irradiation), etc. Photobase generators are preferred. As a photobase generator, for example, 9-anthrylmethyl N, N-diethylcarbamate (brand name WPBG-018), (E)-1-[3-(2) -hydroxyphenyl)-2-propenoyl] piperidine ((E)-1-[3-(2-hydroxyphenyl)-2-propenoyl] piperidine, brand name WPBG-027), 1- (anthraquinone-2 -yl)ethylimidazolecarboxylate (1-(anthraquinon-2-yl)ethylimidazolecarboxylate, brand name WPBG-140), 2-nitrophenyl methyl4-methacryloyloxy piperidine-1-carboxylate ( Product name WPBG-165), 1, 2-diisopropyl-3-[bis(dimethylamino)methylene] guanidinium 2-(3-benzoylphenyl) propionate (Product name WPBG-266), 1,2-DC Chlohexyl-4, 4, 5, 5-tetramethyl biguanidinium n-butyltriphenylborat (trade name WPBG-300), and 2-(9-oxo-xanthen-2-yl)propionic acid 1, 5, 7 -Triaza bicyclo[4.4.0]deca-5-ene (Tokyo Kasei Kogyo Co., Ltd.), a compound containing 4-piperidine methanol (product name HDPD-PB100: manufactured by Heraeus), etc. can be given as examples. . In addition, all product names including “WPBG” above are product names of Wako Pure Chemical Industries, Ltd. Examples of photoacid generators include aromatic sulfonium salt (brand name SP-170: ADEKA), triaryl sulfonium salt (brand name CPI101A: San-Apro), and aromatic iodonium salt (brand name Irgacure250: Chiba Japan). An example can be given. In addition, the catalyst that chemically bonds microporous particles to each other is not limited to a photoactive catalyst and a photocatalyst generator, and may be, for example, a thermally active catalyst or a thermal catalyst generator such as urea. Catalysts that chemically bond microporous particles to each other include, for example, 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, base catalysts are preferred. Catalysts or catalyst generators that chemically bond microporous particles to each other are, for example, used by adding to a sol particle solution (e.g., suspension) containing pulverized material (microporous particles) immediately before application, or as a catalyst. Alternatively, it can be used as a mixed solution in which a catalyst generator is mixed with a solvent. The mixed solution may be, for example, a coating solution obtained by directly adding and dissolving the sol particle solution, a solution in which a catalyst or catalyst generator is dissolved in a solvent, or a dispersion in which the catalyst or catalyst generator is dispersed in a solvent. The solvent is not particularly limited, and examples include water and buffer solutions.

Additionally, for example, a crosslinking aid for indirectly bonding the pulverized products of the gel to each other may be added to the gel-containing liquid. This cross-linking aid enters between the particles (the pulverized material), and the particles and the cross-linking aid each interact or combine, making it possible to bond even particles that are somewhat distant in distance, thereby efficiently increasing the strength. As the crosslinking aid, a polyvalent silane monomer is preferable. Specifically, the polyvalent silane monomer may have, for example, 2 to 3 alkoxysilyl groups, the chain length between alkoxysilyl groups may be 1 to 10 carbon atoms, and may also contain elements other than carbon. Examples of the crosslinking aid include bis(trimethoxysilyl)ethane, bis(triethoxysilyl)ethane, bis(trimethoxysilyl)methane, bis(triethoxysilyl)methane, and bis(triethoxy). Silyl)propane, bis(trimethoxysilyl)propane, bis(triethoxysilyl)butane, bis(trimethoxysilyl)butane, bis(triethoxysilyl)pentane, bis(trimethoxysilyl)pentane, bis. (triethoxysilyl)hexane, bis(trimethoxysilyl)hexane, bis(trimethoxysilyl)-N-butyl-N-propyl-ethane-1, 2-diamine, tris-(3-trimethoxysilyl) Examples include propyl)isocyanurate and tris-(3-triethoxysilylpropyl)isocyanurate. The amount of this crosslinking aid added is not particularly limited, but is, for example, 0.01 to 20% by weight, 0.05 to 15% by weight, or 0.1 to 10% by weight based on the weight of the ground product of the silicon compound.

Next, a containing liquid (for example, suspension) containing microporous particles is applied onto the sealed portion (application step). Application can be performed using, for example, various application methods described later, and is not limited to these. By directly applying a containing liquid containing microporous particles (for example, pulverized gel-like silica compound) onto the seal, a coating film containing microporous particles and a catalyst can be formed. For example, the coating film may be referred to as an application layer. By forming a coating film, for example, a new three-dimensional structure is constructed by settling and depositing pulverized material whose three-dimensional structure has been destroyed. Additionally, for example, the containing liquid containing microporous particles does not need to contain a catalyst that chemically bonds the microporous particles to each other. For example, as described later, the precursor formation step may be performed after or while spraying a catalyst that chemically bonds fine pore particles to the coating film. However, the containing liquid containing microporous particles contains a catalyst that chemically bonds the microporous particles to each other, and by the action of the catalyst contained in the coating film, the microporous particles are chemically bonded to each other to form a precursor of the porous body. It's also good.

The solvent (hereinafter also referred to as “coating solvent”) is not particularly limited, and for example, an organic solvent can be used. Examples of the organic solvent include solvents with a boiling point of 150°C or lower. Specific examples include IPA, ethanol, methanol, n-butanol, 2-butanol, isobutyl alcohol, pentanol, etc. Additionally, a solvent such as a grinding solvent can be used. When the method of forming the low refractive index layer includes a step of pulverizing the gel-like compound, in the coating film forming step, for example, a pulverizing solvent containing the pulverized product of the gel-like compound may be used as is.

In the application step, for example, it is preferable to apply a pulverized sol dispersed in a solvent (hereinafter also referred to as “sol particle liquid”) onto the sealed portion. The sol particle liquid can be continuously formed into a film having a film strength of a certain level or higher by, for example, applying and drying the sol particle liquid onto the seal and then performing the chemical crosslinking. In addition, “sol” in the embodiment of the present invention refers to a state in which silica sol particles with a nano three-dimensional structure maintaining a part of the void structure are dispersed in a solvent and exhibit fluidity by pulverizing the three-dimensional structure of the gel.

The concentration of the pulverized material in the application 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 pulverized material is too high, for example, the fluidity of the sol particle liquid is significantly reduced, and there is a possibility of generating aggregates and uneven application during application. If the concentration of the pulverized material is too low, for example, not only does it take a considerable amount of time to dry the solvent in the sol particle liquid, but the residual solvent immediately after drying also increases, so the porosity may decrease.

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 too high, for example, uneven application may occur and problems such as a decrease in the transfer rate of gravure application may occur. Conversely, if the shear viscosity is too low, for example, the wet application thickness cannot be increased during application, and there is a possibility that the desired thickness cannot be obtained after drying.

The application amount of the pulverized material is not particularly limited and can be appropriately set depending on, for example, the desired thickness of the silicon porous body (resulting in 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 application amount of the pulverized material is, for example, 0.01 μg to 60000 μg, preferably 0.1 μg to 5000 μg, per 1 m ² of the area of the coated surface, and more preferably 0.1 μg to 5000 μg. is 1 μg to 50 μg. It is difficult to define the preferred application amount of the sol particle liquid, for example, because it is related to the concentration of the liquid and the application method, but considering productivity, it is preferable to apply it in as thin a layer as possible. If the application amount is too large, for example, the possibility of drying in a drying furnace before the solvent volatilizes increases. As a result, nano-pulverized sol particles precipitate and deposit in the solvent, and the solvent dries before forming a void structure, which may inhibit the formation of voids and significantly reduce the porosity. On the other hand, if the application amount is too thin, the risk of application cratering may increase.

Additionally, the method of forming a low refractive index layer has a precursor forming process for forming a void structure that is a precursor of a void layer (low refractive index layer), for example, as described above. The precursor formation process is not particularly limited, but for example, the precursor (pore structure) may be formed through a drying process of drying a coating film produced by applying a liquid containing microporous particles. By drying treatment in the drying process, for example, not only the solvent in the coating film (solvent contained in the sol particle liquid) is removed, but also the sol particles are precipitated and deposited during the drying treatment to form a void structure. can do. 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 drying treatment time is, for example, 0.1 to 30 minutes, preferably 0.2 to 10 minutes, and more preferably 0.3 to 3 minutes.

The drying treatment may be, for example, natural drying, heat drying, or reduced pressure drying. Among these, when industrial continuous production is assumed, it is preferable to use heat drying. The method of heat drying is not particularly limited, and for example, a general heating means can be used. Examples of the heating means include a heat gun, a heating roll, and a far-infrared heater. Additionally, regarding the solvent used, a solvent with low surface tension is preferred for the purpose of suppressing the generation of shrinkage stress due to solvent volatilization during drying and the resulting cracking phenomenon in the porous 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 IPA or the like to reduce the surface tension.

In addition, as described above, the method of forming a low refractive index layer includes a crosslinking reaction process of causing a crosslinking reaction inside the precursor after the precursor formation process, and in the crosslinking reaction process, a basic material is formed by light irradiation or heating. Additionally, the crosslinking reaction process is multi-step. In the first step of the crosslinking reaction process, for example, microporous particles are chemically bonded to each other through 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 fixed. When performing immobilization by conventional sintering, for example, high temperature treatment of 200°C or higher causes dehydration condensation of silanol groups and formation of siloxane bonds. In this formation method, various additives that catalyze the above dehydration condensation reaction are reacted to continuously form a void structure, for example, at a relatively low drying temperature of around 100°C and with a short processing time of less than a few minutes. It can be fixed.

The method of chemically 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 materials. In addition, for example, when inorganic particles such as titanium oxide are added to the pulverized materials, the inorganic particles It is also conceivable to chemically cross-link the pulverized material. Additionally, in cases where biocatalysts such as enzymes are supported, the pulverized material may be chemically cross-linked with a site different from the catalytic active site. Therefore, the method for forming the low refractive index layer can be considered to be applied not only to a porous layer (silicon porous body) formed by sol particles, but also to an organic-inorganic hybrid porous layer, a host-guest void layer, etc.

The chemical reaction in the presence of the catalyst is not particularly limited at which step in the method of forming the low refractive index layer, and is, for example, at least one step in the multi-step crosslinking reaction step. For example, in the method of forming a low refractive index layer, the drying process may also serve as the precursor forming process, as described above. Additionally, for example, after the drying process, a multi-step crosslinking reaction process may be performed, and in at least one step, the microporous particles may be chemically bonded to each other through the action of a catalyst. For example, when the catalyst is a light-activated catalyst as described above, in the crosslinking reaction step, the fine pore particles may be chemically bonded to each other by light irradiation to form a precursor of the porous body. Additionally, when the catalyst is a thermally active catalyst, in the crosslinking reaction step, the microporous particles may be chemically bonded to each other by heating to form a precursor of the porous body.

The above chemical reaction can be performed, for example, by light irradiation or heating on a coating film containing a catalyst previously added to a sol particle solution (e.g., suspension), or by spraying a catalyst onto the coating film and then light irradiation or heating. Alternatively, it can be performed by irradiating light or heating while spraying the catalyst. The accumulated amount of light during light irradiation is not particularly limited, and is, for example, 200 mJ/cm ² to 800 mJ/cm ² in terms of wavelength 360 nm, preferably 250 mJ/cm ² to 600 mJ/cm ² , and more preferably 250 mJ/cm 2 to 600 mJ/cm 2 . It is 300mJ/cm ² to 400mJ/cm ² . From the viewpoint of preventing decomposition due to light absorption of the catalyst from proceeding due to insufficient irradiation amount and the effect becoming insufficient, an integrated light amount of 200 mJ/cm ² or more is preferable. Conditions for 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 to 30 minutes, preferably 0.2 to 10 minutes, and more preferably 0.3 to 3 minutes. Alternatively, the process of drying the applied sol particle liquid (for example, suspension) as described above may also serve as a process of carrying out a chemical reaction in the presence of a catalyst. That is, in the process of drying the applied sol particle liquid (for example, suspension), the pulverized products (microporous particles) may be chemically bonded to each other through a chemical reaction in the presence of a catalyst. In this case, the pulverized materials (microporous particles) may be further firmly bonded to each other by additionally heating the coating film after the drying process. In addition, it is assumed that chemical reactions in the presence of a catalyst may also occur in the process of producing a liquid containing microporous particles (for example, a suspension) and in the process of applying the liquid containing microporous particles. However, this guess does not limit the method of forming the low refractive index layer. Additionally, regarding the solvent used, for example, a solvent with low surface tension is preferable for the purpose of suppressing the occurrence of shrinkage stress due to solvent volatilization during drying and cracking of the void layer due to this. For example, lower alcohols such as isopropyl alcohol (IPA), hexane, perfluorohexane, etc. can be mentioned.

In the method of forming the low refractive index layer, the crosslinking reaction process is multi-step, for example, so that the strength of the void layer (low refractive index layer) can be further improved compared to the case where the crosslinking reaction process is one step. Hereinafter, the process after the second stage of the crosslinking reaction process may be referred to as the “aging process.” In the aging process, the crosslinking reaction inside the precursor may be further promoted, for example, by heating the precursor. The phenomena and mechanisms that occur in the crosslinking reaction process are unknown, but are, for example, as described above. For example, in the aging process, the heating temperature is set to a low temperature and the strength is improved by causing a crosslinking reaction while suppressing shrinkage of the precursor, thereby achieving both 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 hr to 30 hr, preferably 13 hr to 25 hr, and more preferably 15 hr to 20 hr.

Since the low refractive index layer formed as described above has excellent strength, it can be used as a roll-shaped porous body, for example, and has advantages such as good manufacturing efficiency and ease of handling.

The low refractive index layer (porous layer) formed in this way may be further laminated with another film (layer), for example, to form a laminated structure containing a porous structure. In this case, each component in the laminated structure may be laminated through, for example, an adhesive or adhesive.

Details of the specific structure and formation method of the low refractive index layer are described, for example, in International Publication No. 2019/151073. The description in the above publication is incorporated herein by reference.

C. Micro LED array board

As the micro LED array substrate, a micro LED array substrate of any suitable configuration can be used. Typically, as shown in FIG. 1, the micro LED array substrate 10 includes a driving substrate 12 and a plurality of micro LEDs 11 arranged in a matrix on the driving substrate 12.

Micro LED refers to an LED whose chip size is, for example, 1㎛ to 100㎛ on one side.

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

The driving substrate can be configured to individually switch and drive the micro LEDs. Since the driving substrate is well known to those skilled in the art, description is omitted here.

D. Sealing part

The seal may be formed of any suitable transparent material. Examples of materials constituting the sealing portion include epoxy resin, silicone resin, and acrylic resin. Additionally, the sealing portion may be formed of molten glass. Examples of glass constituting the sealing portion include acrylic glass, crown glass, flint glass, and borosilicate glass.

The sealing portion may be comprised of an adhesive or adhesive. In one embodiment, the seal is made of adhesive.

As the adhesive, any suitable adhesive can be used. For example, water-based adhesives such as isocyanate-based, polyvinyl alcohol-based, gelatin-based, vinyl-based latex-based, water-based polyurethane, water-based polyester, and curable adhesives such as ultraviolet curing adhesives and electron beam curing adhesives.

As the adhesive, any suitable adhesive can be used. For example, adhesives 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 them, an acrylic adhesive is preferably used because it has excellent optical transparency, and is also excellent in adhesive properties, weather resistance, heat resistance, etc.

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

The refractive index of the sealed portion is preferably 1.40 or more, more preferably 1.40 to 2.00, and still more preferably 1.45 to 1.80.

The thickness of the sealed portion is preferably 200 μm or less, more preferably 150 μm or less, further preferably 100 μm or less, and particularly preferably 50 μm or less. If the thickness of the sealing portion is thinned, the effect of suppressing color mixing becomes more noticeable. The lower limit of the thickness of the sealed portion is, for example, 10 μm. Additionally, the thickness of the sealing portion may be the distance from the surface on the low refractive index layer side of the micro LED to the surface on the micro LED side of the sealing portion.

E. Wavelength conversion layer

The wavelength conversion layer is a layer that absorbs excitation light from the micro LED and emits light of a predetermined color. As a micro LED, when a blue LED is used, a red subpixel is formed by a wavelength conversion layer that absorbs the excitation light from the micro LED and emits red color, and a wavelength conversion layer that absorbs the excitation light and emits green color. A green subpixel may be formed. In addition, when an ultraviolet LED is used, a red subpixel is formed by a wavelength conversion layer that is excited by ultraviolet rays and emits red, and a green subpixel is formed by a wavelength conversion layer that is excited by ultraviolet rays and emits green, A blue subpixel is formed by a wavelength conversion layer that is excited by ultraviolet rays and emits blue light.

In one embodiment, the wavelength conversion layer includes phosphor particles. The wavelength conversion layer typically includes a matrix and phosphor particles dispersed in the matrix. As the material constituting the matrix (hereinafter also referred to as matrix material), any suitable material can be used. Examples of such materials include resin, organic oxide, and inorganic oxide. The matrix material is preferably a resin. The resin may be a thermoplastic resin, a thermosetting resin, or an active energy ray-curable resin (for example, an electron beam-curable resin, an ultraviolet ray-curable resin, or a visible ray-curable resin). Preferably, it is a thermosetting resin or an ultraviolet curable resin, and more preferably, it is a thermosetting resin. Resins may be used individually or in combination (e.g., blend, copolymerization).

In one embodiment, quantum dots can be used as phosphor particles. Quantum dots can control the wavelength conversion characteristics of the wavelength conversion layer. Specifically, by using quantum dots with different emission center wavelengths in an appropriate combination, a wavelength conversion layer that realizes light with a desired emission center wavelength can be formed. The emission center wavelength of the quantum dot can be adjusted by the material and/or composition, particle size, shape, etc. of the quantum dot. Quantum dots include, for example, quantum dots (hereinafter referred to as quantum dot A) having an emission center wavelength in the wavelength range of 600 nm to 680 nm, and quantum dots (hereinafter referred to as quantum dots) having an emission center wavelength in the wavelength range of 500 nm to 600 nm. , quantum dot B), and a quantum dot (hereinafter referred to as quantum dot C) having an emission center wavelength in the wavelength range of 400 nm to 500 nm 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, when light of a predetermined wavelength is incident on and passes through the wavelength conversion layer, light with an emission center wavelength in a desired wavelength band can be realized.

Quantum dots can be composed of any suitable material. Quantum dots may preferably be composed of inorganic materials, more preferably inorganic conductor 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, Si ₃ N ₄ , Ge ₃ N ₄ , Al ₂ O ₃ , (Al, Ga, In) ₂ (S, Se, Te) ₃ , Al ₂ CO Examples include: These may be used individually, or two or more types may be used in combination. The quantum dot may contain a p-type dopant or an n-type dopant.

The size of the quantum dot may be any appropriate 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, each of green and red emits sharp light, and high color rendering can be achieved. For example, green light can emit light when the quantum dot size is about 7 nm, and red light can emit light when the quantum dot size is about 3 nm. The size of the quantum dot is the average particle diameter when the quantum dot is, for example, spherical, and when it has a shape other than that, it is the dimension along the minimum axis of the shape. Additionally, as the shape of the quantum dot, any appropriate shape may be adopted depending on the purpose. Specific examples include spherical shape, scaly shape, plate shape, ellipsoidal shape, and irregular shape.

Quantum dots can be blended in a ratio of preferably 1 part by weight to 50 parts by weight, more preferably 2 parts by weight to 30 parts by weight, based on 100 parts by weight of the matrix material. If the amount of quantum dots is within this range, a display with excellent color balance in both RGB and RGB can be provided.

Details of quantum dots are, for example, Japanese Patent Application Laid-Open No. 2012-169271, Japanese Patent Application Laid-Open No. 2015-102857, Japanese Patent Application Laid-Open No. 2015-65158, Japanese Patent Application Publication No. 2013-544018, and Japanese Patent Publication No. 2013- It is described in Publication No. 544018 and Japanese Patent Publication No. 2010-533976, and the descriptions of these publications are incorporated herein by reference. Quantum dots may be commercially available.

In another embodiment, the phosphor particles are particles that exhibit luminescence due to their composition. Examples of such phosphor particles include materials based on sulfide, aluminate, oxide, silicate, nitride, YAG, and terbium aluminum garnet (TAG).

Additionally, as the phosphor particles, the following red phosphor and green phosphor may be used. Examples of red phosphors include complex fluoride phosphors activated with Mn ⁴⁺ . A complex fluoride phosphor contains at least one coordination center (e.g., M, described later), is surrounded by fluoride ions that act as a ligand, and is surrounded by a counter ion (e.g., A, described later) as needed. It refers to a coordination compound that compensates for charge. Specific examples thereof include A ₂ [MF ₅ ]:Mn ⁴⁺ , A ₃ [MF ₆ ]:Mn ⁴⁺ , Zn ₂ [MF ₇ ]:Mn ⁴⁺ , A[In ₂ F ₇ ]:Mn ⁴⁺ , A Examples include ₂ [M'F ₆ ]:Mn ⁴⁺ , E[M'F ₆ ]:Mn ⁴⁺ , A ₃ [ZrF ₇ ]:Mn ⁴⁺ , Ba _0.65 Zr _0.35 F _2.70 :Mn ⁴⁺ . Here, A is Li, Na, K, Rb, Cs, NH ₄ 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 with a coordination number of 6 at the coordination center is preferred. Details of this red phosphor are described in, for example, Japanese Patent Application Laid-Open No. 2015-84327. The entire disclosure of the above-mentioned publication is incorporated herein by reference.

Examples of the green phosphor include compounds containing a solid solution of sialon with a β-type Si ₃ N ₄ crystal structure as a main component. Preferably, a treatment is performed to reduce the amount of oxygen contained in these sialon crystals to a specific amount (for example, 0.8% by mass) or less. By performing this treatment, a green phosphor that emits sharp light with a narrow peak width can be obtained. Details of this green phosphor are described in, for example, Japanese Patent Application Laid-Open No. 2013-28814. The entire disclosure of the above-mentioned publication is incorporated herein by reference.

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

As described above, in one embodiment, each wavelength conversion layer is spaced apart by a partition (light-shielding layer). The width of the partition (that is, 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, even if the width of the partition is narrow, sufficient color mixing can be suppressed. By narrowing the width of the partition wall, a micro LED display device with excellent luminous efficiency can be obtained.

As described above, when constructing a subpixel using light from a micro LED as is (for example, when forming a blue subpixel with a blue LED), the wavelength conversion layer is replaced with a light diffusion layer in the above location. It can be. It is preferable that the light scattering layer contains light scattering particles. Examples of materials constituting the light scattering particles include alumina, zirconium oxide, titanium oxide, and barium sulfate.

In one embodiment, the micro LED display device further has a color filter disposed on a side of the wavelength conversion layer (and/or light diffusion layer) opposite to the low refractive index layer. The color filter can have any suitable configuration depending on the color development of the subpixel. In one embodiment, a color filter is disposed in each subpixel to cut out colors other than the desired color. For example, in the red subpixel and the green subpixel, a color filter that cuts out the color of blue is used.

(Example)

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples.

[Example 1]

The configuration shown in Figure 2(a), that is, the red phosphor and green phosphor as the wavelength conversion layer are arranged, and a low refractive index layer (refractive index: 1.20) and a sealing portion (refractive index: 1.50) are interposed, directly below the green phosphor. For a configuration in which blue LEDs were arranged, the luminance of red light emission and the luminance of green light emission were determined by optical simulation. All wavelength conversion layers are made by adding 10% by weight of wavelength conversion particles (refractive index 1.80) to the matrix portion (refractive index 1.47). The refractive index of the wavelength conversion layer is all 1.50.

The optical properties in this example and the examples and comparative examples described later were calculated using Synopsys optical simulation software (Lighttools). The optical model used in the simulation is as follows.

The thickness of each RGB wavelength conversion layer was 100 μm and the width was 100 μm. The width of the partition wall placed between each RGB was set to 50 nm. LEDs were placed in positions opposite to 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 part (adhesive layer) was placed between the LED and the wavelength conversion layer. The thickness of the sealing portion 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, this dimension assumes 78 inches with 4K resolution (3840x2160). The partition wall was placed at 50.0 μm between the wavelength conversion layers, and the transmittance was set to 0%. Additionally, a light receiver was placed on each pixel.

[Comparative Example 1]

The configuration shown in Figure 2(b), that is, a configuration in which red phosphor and green phosphor as wavelength conversion layers are arranged, a blue LED is arranged directly below the green phosphor through a sealing portion (without arranging a low refractive index layer). Regarding this, the luminance of red light emission and the luminance of green light emission were obtained by optical simulation.

<Evaluation>

Table 1 shows the ratio of the luminance in Example 1 to the luminance (100%) in Comparative Example 1. Additionally, 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 brightness at each thickness setting was determined.

In the above configuration, the green phosphor and the blue LED constitute a green-colored subpixel, and therefore, there is a relationship of luminance of green light > luminance of red light, and the larger the difference in luminance between green and red light, the more suppressed color mixing becomes. It becomes a big effect.

As is clear from Table 1, in the present invention, by disposing the low refractive index layer, unnecessary red light emission is suppressed and color mixing is preferably suppressed. Additionally, this effect becomes noticeable by appropriately setting the thickness of the sealing portion between the LED and the wavelength conversion layer.

[Example 2]

The configuration shown in Figure 2 (a), that is, the red phosphor and green phosphor as the wavelength conversion layer are arranged, and the green phosphor is interposed between the low refractive index layer and the sealing portion (thickness between the LED and the wavelength conversion layer: 75 μm). Optical simulation for a configuration in which a blue LED is placed directly below the phosphor (the thickness of the wavelength conversion layer is 100 ㎛, the width is 100 ㎛, the partition wall is 50 ㎛, and the thickness of the low refractive index layer is 1.0 ㎛) The luminance of red light emission and the luminance of green light emission were obtained.

[Comparative Example 2]

The configuration shown in Figure 2(b), that is, the red phosphor and green phosphor as the wavelength conversion layer are arranged, and a sealing portion (thickness of 75 μm) is interposed (without the low refractive index layer), directly below the green phosphor. For a configuration in which blue LEDs were arranged, the luminance of red light emission and the luminance of green light emission were determined by optical simulation.

<Evaluation>

Table 2 shows the ratio of the luminance in Example 2 to the luminance (100%) in Comparative Example 2. Additionally, 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 brightness at each refractive index setting was obtained.

As is clear from Table 2, in the present invention, by disposing the low refractive index layer, unnecessary red light emission is suppressed and color mixing is preferably suppressed.

10 micro LED array board
11 micro LEDs
12 driving board
20 seal
30 Low refractive index layer
40 wavelength conversion layer
100 micro LED display device

Claims (7)

A micro LED array substrate including a plurality of micro LEDs,
a sealing portion that seals the plurality of micro LEDs;
a low refractive index layer,
A plurality of partitioned wavelength conversion layers are provided in this order from the micro LED array substrate side,
Each of the wavelength conversion layers is formed to be set to correspond to one of the micro LEDs in the thickness direction,
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 wavelength conversion layer is 0.10 or more,
Micro LED display device. According to claim 1,
A micro LED display device wherein the low refractive index layer has a refractive index of 1.25 or less. The method of claim 1 or 2,
The low refractive index layer is a micro LED display device that is a porous layer made of a porous body composed of fine particles chemically bonded to each other. The method according to any one of claims 1 to 3,
A micro LED display device wherein the sealing portion is made of adhesive. The method according to any one of claims 1 to 4,
A micro LED display device in which each of the wavelength conversion layers is spaced apart by a partition. The method according to any one of claims 1 to 5,
A micro LED display device wherein the micro LED is a blue LED or an ultraviolet LED. The method according to any one of claims 1 to 6,
A micro LED display device further comprising a color filter disposed on a side of the wavelength conversion layer opposite to the low refractive index layer.