TW202240881A - Micro-led display device - Google Patents

Abstract

Provided is a micro-LED display device that has excellent luminous efficiency and in which color mixture is suppressed. A micro-LED display device according to the present invention comprises, in this order from the back side: a micro-LED array substrate including a plurality of micro-LEDs; a sealing part that seals the plurality of micro-LEDs; a low-refractive-index layer; and a plurality of wavelength converting layers that are formed into partitions. Each of the wavelength converting layers is so formed as to pair up with a corresponding 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 part and the refractive index of the wavelength converting layers. The difference between the refractive index of the low-refractive-index layer and the refractive index of the sealing part is equal to or greater than 0.10. The difference between the refractive index of the low-refractive-index layer and the refractive index of the wavelength converting layers is equal to or greater than 0.10.

Description

Micro LED Display Device

The invention relates to a micro LED display device.

In recent years, in terms of new display devices, a micro LED display has been developed, which is constituted by arranging micro LEDs in pixels arranged in a matrix (for example, Patent Document 1, Patent Document 2). In the case of micro-LED displays, there is a literature that proposes a display that has: a micro-LED array substrate, which is composed of a plurality of micro-LEDs; and an array of wavelength conversion layers (fluorescent light-emitting layers), which are arranged on on the micro LED array substrate, and absorb the light from the micro LEDs, and convert the emission wavelengths of the light into red, green and blue light wavelengths respectively (for example, patent document 2). In the micro-LED display, each sub-pixel is composed of a micro-LED and a wavelength conversion layer. prior art literature patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2020-43073 Patent Document 2: Japanese Patent Application Publication No. 2016-523450

The problem to be solved by the invention In the above-mentioned micro-LED display, there is a problem that light from the micro-LED leaks to sub-pixels (adjacent sub-pixels, peripheral sub-pixels) other than those corresponding to the micro-LED to cause color mixing. Furthermore, there is also a problem that sufficient luminous efficiency cannot be obtained due to light returning to the back side due to scattering in the wavelength conversion layer.

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

means to solve problems The micro-LED display device of the present invention has: a micro-LED array substrate, which includes a plurality of micro-LEDs; and, sequentially from the side of the micro-LED array substrate: a sealing part, which seals a plurality of the micro-LEDs; low refractive index layer; and a plurality of wavelength conversion layers formed separately; each layer of the wavelength conversion layer is formed in a group corresponding to one of the micro LEDs in the thickness direction; the refractive index of the low refractive index layer is lower than the 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 refractive index of the low refractive index layer and the refractive index of the wavelength conversion layer The difference is 0.10 or more. In one embodiment, the low refractive index layer has a refractive index of 1.25 or less. In one embodiment, the above-mentioned low refractive index layer is a void layer made of a porous body, and the fine particles of the porous system are chemically bonded to each other. In one embodiment, the sealing portion is made of an adhesive. In one embodiment, the above wavelength conversion layers are arranged at intervals by partition walls. In one embodiment, the above-mentioned micro LEDs are blue LEDs or ultraviolet LEDs. In one embodiment, the micro LED display device further includes a color filter disposed on the surface of the wavelength conversion layer opposite to the low refractive index layer.

Invention effect According to the present invention, it is possible to provide a micro LED display device which is excellent in luminous efficiency and suppresses color mixing.

A. Micro LED display device FIG. 1 is a schematic cross-sectional view of a micro LED display device according to an embodiment of the present invention. The micro-LED display device 100 of the present embodiment is provided with: a micro-LED array substrate 10, which includes a plurality of micro-LEDs 11; Refractive index layer 30; and a plurality of wavelength conversion layers 40 formed at intervals. Representatively, the micro-LED array substrate 10 includes a driving substrate 12 and a plurality of micro-LEDs 11 , and the micro-LEDs 11 are arranged in an array (matrix) on the driving substrate 12 . Each wavelength conversion layer 40 is formed so as to correspond to one micro LED 11 in the thickness direction and form a group. Representatively, each sub-pixel includes a wavelength conversion layer 40 and a micro-LED 11 respectively. Red, green, and blue sub-pixels can be formed by transmitting the light from the micro LED 11 through the wavelength conversion layer 40 . In addition, when sub-pixels directly utilize light from micro LEDs (eg, when blue sub-pixels are formed by blue LEDs), the wavelength conversion layer is omitted there or can be replaced by other layers (eg, a light-diffusing layer). In one embodiment, the respective wavelength conversion layers are spaced apart by partition walls 50 (light-shielding layers).

In one embodiment, the above-mentioned low refractive index layer 30 is formed on the entire surface of the sealing portion 20 opposite to the micro LED array substrate 10 . Moreover, in one embodiment, the above-mentioned low-refractive-index layer 30 is provided on the sealing part 20 directly (that is, without interposing other layers).

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 part 20 is 0.10 or more. Also, 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, by disposing the low-refractive-index layer between the sealing portion and the wavelength conversion layer, a difference in refractive index is generated between the layers. As a result, at least a part of the light emitted from the micro LED, scattered in the wavelength conversion layer and returned to the rear side can be reflected at the interface between the wavelength conversion layer and the low refractive index layer and emitted toward the viewing side. As a result, luminous efficiency can be improved. Also, light is emitted obliquely from the micro LED, but cannot reach the corresponding wavelength conversion layer (the wavelength conversion layer in the same sub-pixel) and at least part of the light going to its periphery will be reflected at the interface between the low refractive index layer and the sealing part , and return to the back side. As a result, color mixing can be suppressed. The micro-LED display device of the embodiment of the present invention is not only high-definition, but also advantageous in terms of higher brightness and wide color gamut than conventional displays.

B. Low refractive index layer The refractive index of the low refractive index layer is preferably not more than 1.30, more preferably not more than 1.25, more preferably not more than 1.20, and especially preferably not more than 1.15. The lower the refractive index of the low-refractive index layer, the better, but the lower limit thereof is, for example, 1.07 or more (preferably 1.05 or more). In this specification, the refractive index refers to the refractive index measured at a wavelength of 550 nm.

As mentioned above, the difference between the refractive index of a low-refractive-index layer and the refractive index of a sealing part is 0.10 or more. The difference between the refractive index of the low-refractive index layer and the sealing portion is preferably 0.20 or more, more preferably 0.30 or more. If it is in the said range, the said effect will be remarkable. The upper limit of the difference between the refractive index of the low refractive index layer and the refractive index of the sealing part is, for example, 0.50 (preferably 0.70).

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 more. The difference between the refractive index of the low refractive index layer and the refractive index of the wavelength conversion layer is preferably at least 0.20, more preferably at least 0.30. If it is in the said range, the said effect will be remarkable. 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 above-mentioned low refractive index layer is preferably 0.01 µm to 1000 µm, more preferably 0.05 µm to 100 µm, more preferably 0.1 µm to 80 µm, and especially preferably 0.3 µm to 50 µm.

Any appropriate configuration can be adopted for the low-refractive index layer. In one embodiment, the low refractive index layer has voids. The low refractive index layer can preferably be formed by coating or printing. The material constituting the low-refractive index layer can be, for example, those described in International Publication No. 2004/113966, Japanese Patent Laid-Open No. 2013-254183, and Japanese Patent Laid-Open No. 2012-189802. Specifically, examples include: silicon dioxide-based compounds; hydrolyzable silanes, and their partial hydrolyzates and dehydration condensates; organic polymers; silicon compounds containing silanol groups; Activated silica obtained by contact; polymerizable monomers (such as (meth)acrylic monomers and styrene monomers); hardening resins (such as (meth)acrylic resins, fluorine-containing resins, and urethane ethyl ester resins); and combinations thereof. The low-refractive-index layer can be formed by applying or printing a solution or dispersion of the above material.

The porosity of the low-refractive index layer having voids is preferably at least 35% by volume, more preferably at least 38% by volume, and especially preferably at least 40% by volume. If it exists in the said range, the low-refractive-index layer with an especially low refractive index can be formed. The upper limit of the porosity of the low refractive index layer is, for example, 90% by volume or less, preferably 75% by volume or less. If it exists in the said range, the low-refractive-index layer excellent in strength can be formed. The porosity is calculated from the value of the refractive index measured with an ellipsometer, and the value of the porosity is calculated using Lorentz-Lorenz's formula.

The size of the void (pore) of 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 (pore). The size of the void (pore) is, for example, 2 nm to 500 nm. The size of the void (pore) is, for example, 2 nm or more, preferably 5 nm or more, more preferably 10 nm or more, more preferably 20 nm or more. On the other hand, the size of voids (pores) is, for example, 500 nm or less, preferably 200 nm or less, more preferably 100 nm or less. The size of the voids (pores) ranges, for example, from 2 nm to 500 nm, preferably from 5 nm to 500 nm, more preferably from 10 nm to 200 nm, more preferably from 20 nm to 100 nm. The size of the void (pore) can be adjusted to a desired size according to the purpose and application.

The size of voids (pores) can be quantified by the BET test method. Specifically, 0.1 g of the sample (formed void layer) was put into the capillary of a specific surface area measuring device (manufactured by Micromeritics: ASAP2020), and dried under reduced pressure at room temperature for 24 hours to remove the voids in the void structure. Gas outgassing. Then, the pore distribution was calculated by making the above-mentioned sample adsorb nitrogen gas and drawing an adsorption isotherm. From this the void size can be assessed.

The haze of the low refractive index layer is, for example, less than 5%, preferably less than 3%. On the other hand, the haze is, for example, 0.1% or more, preferably 0.2% or more. The range of the haze is, for example, not less than 0.1% and less than 5%, preferably not less than 0.2% and less than 3%. Haze can be measured by the following method, for example. In addition, the haze is an indicator of the transparency of the low-refractive index layer. The void layer (low refractive index layer) was cut out to a size of 50 mm×50 mm, and it was set on a haze meter (manufactured by Murakami Color Technology Laboratory Co., Ltd.: HM-150), and the haze was measured. The haze value can be calculated by the following formula. Haze (%)=[diffuse transmittance (%)/total light transmittance (%)]×100(%)

The aforementioned low-refractive-index layer having voids therein may be, for example, a porous layer and/or a low-refractive-index layer having at least a part of an air layer. The porous layer typically includes airgel and/or particles (for example, hollow fine particles and/or porous particles). The low refractive index layer is preferably a nanoporous layer (specifically, a porous layer in which more than 90% of the micropores have a diameter in the range of 10 ⁻¹ nm to 10 ³ nm).

Any appropriate particles can be used as the above-mentioned particles. Particles represent that the upper system is composed of silicon dioxide-based compounds. The shape of the particles can be, for example, spherical, plate-like, needle-like, string-like and grape-bunch-like. The string-like particles can be, for example, a plurality of spherical, plate-like or needle-like particles connected to form a bead-like particle, short fiber-like particles (such as the short-fibrous particles described in Japanese Patent Laid-Open No. 2001-188104) and combinations thereof. The string-like particles may be linear or branched. Grape-bunch-like particles can be, for example, grape-bunch-like aggregates of a plurality of spherical, plate-like, and needle-like particles. The particle shape can be confirmed by observation with a transmission electron microscope, for example.

The thickness of the low refractive index layer is preferably 0.2µm~5µm, more preferably 0.3µm~3µm. If the thickness of the low-refractive index layer is within the above-mentioned range, the damage prevention effect of the present invention will be remarkable. Furthermore, the desired thickness ratio described above can be easily realized.

Typically, the low refractive index layer can be formed by coating or printing as described above. According to the said structure, a low-refractive-index layer can be provided continuously by roll-to-roll. Printing can be done in any suitable manner. Specifically, the printing method can be gravure printing, offset printing, flexographic printing and other printing methods with a format, and can also be a non-format printing method such as inkjet printing, laser printing, and electrostatic printing.

Hereinafter, an example of a specific configuration of the low-refractive index layer will be described. The low-refractive-index layer in this embodiment is composed of one or more structural units capable of forming a fine void structure, and the structural units are chemically bonded to each other through the action of a catalyst. The shape of the constituent unit may, for example, be granular, fibrous, rod, or flat. A constituent unit may have only 1 type of shape, and may have 2 or more types of shapes in combination. In one embodiment, the above-mentioned low refractive index layer is a void layer made of a porous body, and the fine particles of the porous system are chemically bonded to each other. The following description will mainly focus on the case of a void layer composed of a porous body composed of fine particles chemically bonded to each other.

The void layer can be formed, for example, by chemically bonding micropore particles to each other in the void layer forming step. In addition, the shape of the "particle" (such as the microporous particle) in the embodiment of the present invention is not particularly limited, for example, it may be spherical or other shapes. In addition, in the embodiment of the present invention, the microporous particles may be, for example, sol-gel beaded particles, nanoparticles (hollow nano-silica, nanosphere particles), nanofibers, and the like. The microporous particles represent the inclusion of 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 alone or in combination of two or more. In one embodiment, the microporous particles are, for example, microporous particles of a silicon compound, and the porous body is, for example, a polysiloxane porous body. The microporous particles of the above-mentioned silicon compound include, for example, pulverized colloidal silicon dioxide compounds. Another form of the low-refractive index layer having at least a part of the porous layer and/or air layer includes, for example, a void layer: a layer formed of fibrous substances such as nanofibers entangled to form voids. The method for producing the void layer is not particularly limited, and it may be the same as the above-mentioned void layer of a porous body in which micropore particles are chemically bonded to each other, for example. More other forms can include void layers using hollow nanoparticles or nanoclay, void layers using hollow nanospheres or magnesium fluoride. The void layer may be a void layer composed of a single constituent substance, or may be a void layer composed of a plurality of constituent substances. The void layer may be composed of only one of the above-mentioned forms, 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, an open foam structure in which the pore structure is in a continuous state. The open foam structure means, for example, that the mesopore structure of the polysiloxane porous body is connected in a three-dimensional form, and it can also be said that the internal voids of the pore structure are in a continuous state. Since the porous body has an open foam structure, the porosity can be increased. However, when closed-pore particles (each having a pore structure) such as hollow silica are used, an open foam structure cannot be formed. On the other hand, for example, when using silica sol particles (a pulverized product of a colloidal silicon compound forming a sol), the particles have a three-dimensional tree structure, so the coating film (a sol containing a pulverized product of a colloidal silicon compound) In the coated film), the dendritic particles settle and accumulate to easily form an open foam structure. Preferably, the low-refractive index layer has an open foam structure comprising a monolith structure in which a plurality of fine pores are distributed. The monolithic structure refers to, for example, a hierarchical structure, which includes a structure with nanometer-sized microvoids and an open foam structure in which the nanovoids are assembled. When a monolithic structure is to be formed, for example, the strength of the film is imparted by the microscopic voids and the high porosity is imparted by the coarse open foamed voids, so that both the strength of the film and the high porosity can be achieved. The monolithic structure is preferably formed by controlling the pore distribution of the pore structure to be formed on the gel (colloidal silicon compound) before being pulverized into silica sol particles. Also, for example, when pulverizing a colloidal silicon compound, a monolithic structure can be formed by controlling the particle size distribution of the pulverized silica sol particles to a desired size.

The low-refractive-index layer contains, for example, pulverized colloidal compounds as described above, and the pulverized products are chemically bonded to each other. The form of chemical bonds (chemical bonds) between the pulverized materials in the low refractive index layer is not particularly limited, and examples thereof include crosslink bonds, covalent bonds, hydrogen bonds, and the like.

The gel form of the jelly compound is not particularly limited. Generally speaking, "gel" refers to a state in which solutes have a structure in which they lose their independent mobility due to interactions and are solidified. The jelly compound can be, for example, a wet gel or a dry gel. In addition, generally speaking, a wet gel refers to a solute that contains a dispersion medium and has the same structure in the dispersion medium, and a dry gel refers to a solute that has a network structure with voids after the solvent is removed.

The jelly compound may be, for example, a gelled product of monomeric compounds. Specifically, the above-mentioned colloidal silicon compound can be, for example, a gel formed by bonding silicon compounds of monomers to each other. Specific examples include covalent bonding, hydrogen bonding, or intermolecular bonding of silicon compounds of monomers. A gelatinized compound. The covalent bond may, for example, be bonded by dehydration condensation.

The volume average particle diameter of the pulverized matter in the low refractive index layer is, for example, 0.10 µm or more, preferably 0.20 µm or more, 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, 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, more preferably 0.40 µm to 1.00 µm. The particle size distribution can be measured, for example, using 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). In addition, the volume average particle diameter is an indicator of the particle size variation of the pulverized product.

The type of gel compound is not particularly limited. The colloidal compound may, for example, be a colloidal silicon compound. In the following, the case where the colloidal compound is a colloidal silicon compound is taken as an example for illustration, but it is not limited thereto.

The aforementioned crosslinks are, for example, siloxane bonds. Examples of the siloxane bond include T2 bond, T3 bond, and T4 bond shown below. When the void layer (low refractive index layer) has siloxane bonds, it may have any one of them, may have any two of them, or may have all three kinds of bonds. Among the siloxane bonds, the higher the ratio of T2 and T3, the more flexible and the more you can expect the original characteristics of the gel. On the other hand, the greater the ratio of T4, the easier it is to exhibit film strength. Therefore, it is appropriate to change the ratios of T2, T3, and T4 according to the purpose, application, desired characteristics, and the like.

[chemical formula 1]

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

When the colloidal compound is a colloidal silicon compound, the monomeric silicon compound is not particularly limited. The silicon compound of the monomer may be, for example, a compound represented by the following formula (1). When the colloidal silicon compound is a gel formed by hydrogen bonding or intermolecular bonding of silicon compounds such as the above-mentioned monomers, the monomers of formula (1) can be hydrogen bonded through their respective hydroxyl groups, for example.

[chemical formula 2]

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

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

[chemical formula 3]

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

The monomeric silicon compound can also be, for example, a hydrolyzate of a silicon compound precursor. As the silicon compound precursor, for example, any silicon compound can be generated by hydrolysis, and specific examples include compounds represented by the following formula (2).

[chemical formula 4]

In the aforementioned formula (2), X is, for example, 2, 3 or 4, R ¹ and R ² are each independently a straight-chain alkyl group or a branched-chain alkyl group, R ¹ and R ² can be the same or different, and X is 2 , R ¹ may be the same or different from each other, and R ² may be the same or different from each other.

X and R ¹ are, for example, the same as X and R ¹ in formula (1). R ² can be exemplified, for example, by citing R ¹ in formula (1).

Specific examples of the precursor of the silicon compound represented by the formula (2) include compounds represented by the following formula (2′) in which X is 3. In the following formula (2'), R ¹ and R ² are the same as those 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").

[chemical formula 5]

The silicon compound of the monomer is preferably a trifunctional silane, for example, from the viewpoint of excellent low refractive index properties. Moreover, the silicon compound of the monomer is preferably a tetrafunctional silane, for example, from the viewpoint of being excellent in strength (for example, scratch resistance). A single silicon compound may be used alone, or two or more types may be used in combination. For example, the monomeric silicon compound may only contain trifunctional silanes, may only contain tetrafunctional silanes, may contain both trifunctional silanes and tetrafunctional silanes, and may further contain other silicon compounds. When two or more silicon compounds are used as a single silicon compound, the ratio thereof is not particularly limited and can be appropriately set.

Hereinafter, an example of the formation method of the said low-refractive-index layer is demonstrated.

The method typically includes the following steps: a precursor forming step, which is to form a void structure of the precursor on the resin film, which is a low refractive index layer (void layer); and, a cross-linking reaction step, which is formed after the precursor forming step. The precursor internally initiates a crosslinking reaction. The method further comprises the following steps: a containing liquid preparation step, which is to prepare a containing liquid containing micropore particles (hereinafter sometimes referred to as "fine pore particle containing liquid" or simply "containing liquid"); and, a drying step, which is The containing liquid is dried; and in the precursor forming step, the microporous particles in the dried body are chemically bonded to form a precursor. The containing liquid is not particularly limited, and is, for example, a suspension containing micropore particles. In addition, the following description will mainly focus on the case where the micropore particles are pulverized colloidal compounds and the porous body (preferably polysiloxane porous body) contains pulverized colloidal compounds. However, the low-refractive index layer can be formed in the same manner even when the microporous particles are not pulverized colloidal compounds.

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 presumed, for example, as follows. However, the method of forming the low-refractive index layer is not limited by this speculation.

The above pulverized product is obtained by pulverizing the colloidal silicon compound, so the three-dimensional structure of the colloidal silicon compound before pulverization is in a state of being dispersed into a three-dimensional basic structure. Furthermore, in the above-mentioned method, a precursor of a porous structure mainly composed of a three-dimensional basic structure is formed by applying a crushed colloidal silicon compound on a resin film. That is, according to the above-mentioned method, a new porous structure (three-dimensional basic structure) formed by coating the pulverized material is formed, which is different from the three-dimensional structure of the colloidal silicon compound. Therefore, the resulting void layer can realize, for example, a low refractive index that can function to the same extent as an air layer. In addition, in the above method, the three-dimensional basic structure is immobilized in order to chemically bond the fragments. Therefore, even if the finally obtained void layer has a structure with voids, sufficient strength and flexibility can still be maintained.

In addition, the above-mentioned method is performed by performing the above-mentioned precursor forming step and the above-mentioned cross-linking reaction step as different steps. Also, it is preferable to carry out the cross-linking reaction step in multiple stages. By carrying out the cross-linking reaction step in multiple stages, for example, the strength of the precursor can be improved more than the cross-linking reaction step in one stage, and a low-refractive index layer with both high porosity and strength can be obtained. The mechanism is not yet clear, but it is speculated as follows, for example. That is, as mentioned above, if the film strength is increased by using a catalyst or the like while forming the void layer, although the film strength can be improved by carrying out the catalytic reaction, there is a problem that the porosity decreases. It is speculated that the reason for this is, for example, that by using a catalyst to carry out the crosslinking reaction between the micropore particles, the number of crosslinks (chemical bonds) between the micropore particles will increase, thereby making the bond stronger, but the void layer The whole will aggregate to reduce the porosity. In contrast, we think that by performing the step of forming the precursor and the step of the cross-linking reaction as different steps and performing the step of the cross-linking reaction in multiple stages, for example, the number of cross-links (chemical bonds) can be increased with little It will change the overall shape of the precursor (for example, it will hardly cause the overall condensation). However, these are examples of inferred mechanisms, and the method of forming the low-refractive index layer is not limited thereto.

In the step of forming a precursor, for example, particles having a certain shape are laminated to form a precursor of a void layer. Prior to this time point the intensity of the flood was very weak. Afterwards, a product that can chemically bond the microporous particles to each other (for example, a strong base catalyst produced by a photobase generator, etc.) is generated by, for example, photo- or thermally active catalyst reaction (the first stage of the cross-linking reaction step). We believe that further heating and aging (the second stage of the crosslinking reaction step) for efficient and short-term reaction can further promote the chemical bonding of microporous particles (crosslinking reaction) to improve the strength. For example, when the microporous particles are microporous particles of silicon compounds (such as pulverized colloidal silicon dioxide compounds), and there are residual silanol groups (Si-OH groups) in the precursor, the residual silanol groups will communicate with each other. chemical bond through reaction. However, this description is also an example, and the method of forming the low-refractive index layer is not limited thereto.

The above-mentioned method has a containing liquid preparation step of preparing a containing liquid containing micropore particles. When the microporous particles are pulverized colloidal compounds, the pulverized products can be obtained by pulverizing the colloidal compounds, for example. As mentioned above, by pulverizing the colloidal compound, the three-dimensional structure of the colloidal compound is destroyed and dispersed into a three-dimensional basic structure. One of the prepared pulverized products is as follows, for example.

The gelation of monomeric compounds can be performed, for example, by hydrogen bonding or intermolecular force bonding between monomeric compounds. The monomer compound may, for example, be a silicon compound represented by the above formula (1). The silicon compound of formula (1) has hydroxyl groups, so the monomers of formula (1) can undergo hydrogen bonding or intermolecular bonding through these hydroxyl groups.

Alternatively, the silicon compound may also be a hydrolyzate of the above-mentioned silicon compound precursor, for example, it may also be produced by hydrolyzing the silicon compound precursor represented by the above formula (2).

The method for hydrolyzing the precursor of the monomer compound is not particularly limited, for example, it can be carried out by 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 carried out, for example, by slowly dropping an oxalic acid aqueous solution at room temperature until the mixture (such as a suspension) of the silicon compound and dimethylsulfone solution is mixed, and then directly stirring for about 30 minutes. When the silicon compound precursor is hydrolyzed, for example, the alkoxy groups of the silicon compound precursor can be completely hydrolyzed, so that the subsequent gelation, aging, heating and immobilization after the formation of the void structure can be performed more efficiently.

The gelation of monomeric compounds can be performed, for example, by dehydration condensation reaction between monomers. The dehydration condensation reaction, for example, should be carried out in the presence of a catalyst, and the catalyst can include dehydration condensation catalysts such as acid catalysts and alkaline catalysts. The aforementioned acid catalysts include hydrochloric acid, oxalic acid, sulfuric acid, etc., and the aforementioned alkaline catalysts include ammonia , potassium hydroxide, sodium hydroxide, ammonium hydroxide, etc. The dehydration condensation catalyst is preferably an alkaline catalyst. In the dehydration condensation reaction, the addition amount of the catalyst to the monomer compound is not particularly limited. For example, the catalyst can be added in 0.1-10 mol, more preferably in 0.05-7 mol, more preferably in 0.1-5 mol relative to 1 mol of the monomer compound.

The gelling of monomeric compounds is preferably carried out in a solvent, for example. The ratio of the monomer compound to the solvent is not particularly limited. Solvents can be, for example, dimethylsulfide (DMSO), N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), dimethylformamide (DMF), γ-butylene Lactone (GBL), acetonitrile (MeCN), ethylene glycol ethyl ether (EGEE), etc. A solvent may be used individually or in combination of 2 or more types. Hereinafter, the solvent used for gelation is also referred to as "solvent for gelation".

The conditions of gelation are not particularly limited. The temperature for treating the solvent containing the monomer compound is, for example, 20°C-30°C, preferably 22°C-28°C, more preferably 24°C-26°C. The treatment time is, for example, 1 minute to 60 minutes, preferably 5 minutes to 40 minutes, more preferably 10 minutes to 30 minutes. When the dehydration condensation reaction is performed, the treatment conditions are not particularly limited, and such examples can be cited. Through the gelation, for example, siloxane bonds grow to form primary silica particles, and through the reaction, the primary particles are connected to each other to form a beaded form, forming a three-dimensional gel.

The jelly compound obtained by gelation is suitable for ripening after the gelation reaction. Through the aging treatment, for example, the primary particles of the gel with a three-dimensional structure obtained by gelation can be further grown to increase the size of the particles themselves. As a result, the contact state of the neck chain (neck) portion where the particles contact each other can be changed from point contact Become surface contact (increase contact area). The strength of the gel after aging treatment, such as the gel itself, will increase, and as a result, the strength of the three-dimensional basic structure after pulverization can be improved. Thereby, for example, in the drying step after coating the pulverized product, the shrinkage of the pore size of the void structure in which the three-dimensional basic structure is accumulated can be suppressed as the solvent evaporates during the drying process.

The aging treatment can be performed, for example, by incubating the jelly compound at a predetermined temperature for a predetermined time. The aging temperature is, for example, above 30°C, preferably above 35°C, more preferably above 40°C. On the other hand, the aging temperature is, for example, below 80°C, preferably below 75°C, more preferably below 70°C. The aging temperature ranges, for example, from 30°C to 80°C, preferably from 35°C to 75°C, more preferably from 40°C to 70°C. The aging time is, for example, 5 hours or more, preferably 10 hours or more, more preferably 15 hours or more. On the other hand, the aging time is, for example, less than 50 hours, preferably less than 40 hours, more preferably less than 30 hours. The aging time ranges, for example, from 5 hours to 50 hours, preferably from 10 hours to 40 hours, more preferably from 15 hours to 30 hours. In addition, the aging conditions can be optimized for increasing the size of the primary silica particles and increasing the contact area of the neck, for example. In addition, the boiling point of the solvent used should be considered. For example, if the curing temperature is too high, the solvent may volatilize excessively, and the three-dimensional void structure will cause pores to close due to the concentration of the coating liquid (gel liquid) concentration. On the other hand, for example, when the curing temperature is too low, not only the effect brought by the curing cannot be fully obtained, but also the temperature variation during the mass production process will increase, and a low-refractive index layer with poor characteristics may be produced.

For the aging treatment, for example, the same solvent as the gelling treatment can be used. Specifically, it is preferable to directly perform aging treatment on the reactant after the gel treatment (that is, the solvent containing the gel-like compound). The number of moles of residual silanol groups contained in the cured gel (colloidal compound, such as colloidal silicon compound) after gelatinization is, for example, 50% or less, preferably 40% or less, more preferably 30% or less . On the other hand, the molar number of residual silanol groups is, for example, 1% or more, preferably 3% or more, more preferably 5% or more. The molar number of the residual silanol groups ranges, for example, from 1% to 50%, preferably from 3% to 40%, more preferably from 5% to 30%. In order to improve gel hardness, for example, the lower the molar number of residual silanol groups, the better. If the molar number of silanol groups is too high, for example, the void structure may not be maintained until the precursor of the polysiloxane porous body is cross-linked. On the other hand, if the molar number of silanol groups is too low, for example, in the step of making a microporous particle-containing liquid (such as a suspension) and/or subsequent steps, the pulverized colloidal compound may not be able to cross-link and cannot Give sufficient film strength. In addition, the molar number of the remaining silanol groups is, for example, the ratio of the remaining silanol groups when the molar number of the alkoxy groups of the raw material (for example, monomer compound precursor) is 100. In addition, the above is an example of a silanol group, and for example, when a monomeric silicon compound is modified with various reactive functional groups, the same matters and conditions can also be applied to each functional group.

After the monomer compound is gelled in a solvent for gelling, the resulting gel-like compound is pulverized. For the pulverization, for example, the colloidal compound in the gelling solvent may be directly pulverized, or the colloidal compound in another solvent may be substituted for the gelling solvent and pulverized. Also, for example, when the catalyst and the solvent used in the gelation reaction are still left after the aging step, which causes the liquid to gel over time (use life), and the drying efficiency in the drying step is reduced, it should be replaced by other solvent. Hereinafter, the above-mentioned other solvents are also referred to as "solvent for pulverization".

The solvent for pulverization is not particularly limited, and for example, an organic solvent can be used. The organic solvent can be, for example, a solvent with a boiling point below 130°C, preferably below 100°C, more preferably below 85°C. Specific examples include isopropanol (IPA), ethanol, methanol, butanol, propylene glycol monomethyl ether (PGME), methylcellulus, acetone, dimethylformamide (DMF), and isobutanol. The pulverizing solvent may be used alone or in combination of two or more.

The combination of the gelling solvent and the pulverizing solvent is not particularly limited, and examples thereof include combinations of DMSO and IPA, DMSO and ethanol, DMSO and methanol, DMSO and butanol, and DMSO and isobutanol. As described above, by substituting the solvent for gelling with the solvent for crushing, for example, a more uniform coating film can be formed in the coating film formation described later.

The pulverization method of the colloidal compound is not particularly limited, for example, it can be carried out by the following devices: ultrasonic homogenizer, high-speed rotary homogenizer, and other pulverization devices utilizing cavitation phenomenon. Devices that perform media crushing such as bead mills, for example, destroy the pore structure of the gel by physical means during crushing. In contrast, the cavitation crushing devices such as homogenizers are media-free, so they use high-speed The shear force peels off the weakly bonded silica particle interface already embedded in the three-dimensional structure of the gel. In this way, the three-dimensional structure of the obtained gel can maintain a void structure with a certain range of particle size distribution, and the void structure can be formed again by stacking during coating and drying. The pulverization conditions are not particularly limited. For example, it is preferable to pulverize the gel without volatilizing the solvent by instantaneously imparting a high-speed flow. For example, it is preferable to pulverize into a pulverized product having a variable particle size (for example, volume average particle diameter or particle size distribution) as described above. Assuming that when the amount of work such as crushing time and intensity is insufficient, for example, coarse particles will remain, which will not only fail to form dense pores, but also increase appearance defects and may not be able to obtain high quality. On the other hand, when the amount of work is too much, for example, particles with a finer particle size distribution than expected will be formed, and the size of voids accumulated after coating and drying will become finer, and the desired porosity may not be obtained.

-2-基)丙酸1,5,7-三氮雜雙環[4.4.0]癸-5-烯(東京化成工業股份公司)、含4-哌啶甲醇之化合物(商品名HDPD-PB100：Heraeus公司製)等。此外，上述包含「WPBG」之商品名皆為和光純藥工業股份公司之商品名。光酸產生劑可舉例如芳香族鋶鹽(商品名SP-170：ADEKA公司)、三芳基鋶鹽(商品名CPI101A：San-Apro Ltd.)、芳香族錪鹽(商品名Irgacure250：Ciba Japan公司)等。又，使微細孔粒子彼此化學鍵結之觸媒不限於光活性觸媒及光觸媒產生劑，例如亦可為熱活性觸媒或脲等這類熱觸媒產生劑。使微細孔粒子彼此化學鍵結之觸媒可舉例如鹼性觸媒及酸觸媒等，前述鹼性觸媒有氫氧化鉀、氫氧化鈉、氫氧化銨等，前述酸觸媒有鹽酸、乙酸、草酸等。該等中以鹼性觸媒為宜。使微細孔粒子彼此化學鍵結之觸媒或觸媒產生劑，例如可在將要進行塗敷前才添加至含粉碎物(微細孔粒子)之溶膠粒子液(例如懸浮液)中作使用，或可作成已將觸媒或觸媒產生劑混合至溶劑中之混合液來使用。混合液例如可為：直接添加於溶膠粒子液中而溶解之塗敷液、使觸媒或觸媒產生劑溶解於溶劑中之溶液、或是使觸媒或觸媒產生劑分散於溶劑中之分散液。溶劑無特別限制，可舉例如水、緩衝液等。A liquid (such as a suspension) containing microporous particles (crushed colloidal compounds) can be produced in the above-mentioned manner. Furthermore, after preparing the liquid containing microporous particles or during the production process, by adding a catalyst capable of chemically bonding the microporous particles to each other, a liquid containing microporous particles and a catalyst can be produced. The catalyst may be, for example, a catalyst that promotes cross-linking between microporous particles. The chemical reaction to chemically bond the microporous particles to each other should utilize the dehydration condensation reaction of the residual silanol groups contained in the silica sol molecules. By promoting the reaction between the hydroxyl groups of the silanol groups through the catalyst, continuous film formation that hardens the void structure in a short period of time can be achieved. The catalyst can be, for example, a photoactive catalyst and a thermally active catalyst. With the photoactive catalyst, for example, the microporous particles can be chemically bonded (eg, cross-linked) to each other without heating in the step of forming the precursor. Thereby, for example, in the step of forming the precursor, it is not easy to cause shrinkage of the entire precursor, so a higher porosity can be maintained. Also, a substance capable of generating a catalyst (catalyst generating agent) may be used in addition to the catalyst, or may be substituted for it. For example, in addition to photoactive catalysts, substances that generate catalysts by light (photocatalyst generators) can also be used, or simply replaced; in addition to thermally active catalysts, substances that generate catalysts by heat (thermal catalysts) can also be used. mediators), or simply replace them. The photocatalyst generator can be, for example, a photobase generator (a substance that generates an alkaline catalyst by light irradiation), a photoacid generator (a substance that generates an acidic catalyst by light irradiation), etc., and is preferably a photobase generator. Photobase generators can include, for example: 9-anthrylmethyl N, N-diethylcarbamate (9-anthrylmethyl N, N-diethylcarbamate, trade name WPBG-018), (E)-1-[3 -(2-Hydroxyphenyl)-2-acryloyl]piperidine ((E)-1-[3-(2-hydroxyphenyl)-2-propenoyl]piperidine, trade name WPBG-027), 1-(anthracene Quinone-2-yl)ethyl imidazolecarboxylate (1-(anthraquinon-2-yl)ethyl imidazolecarboxylate, trade name WPBG-140), 2-nitrophenylmethyl 4-methylpropionyloxypiperidine -1-carboxylate (trade name WPBG-165), 1,2-diisopropyl-3-[bis(dimethylamino)methylene]guanidinium 2-(3-benzoylphenyl ) propionate (trade name WPBG-266), 1,2-dicyclohexyl-4,4,5,5-tetramethylbis-butanyl triphenyl borate (trade name WPBG-300), and 2-(9-oxo 𠮿

-2-yl)propionic acid 1,5,7-triazabicyclo[4.4.0]dec-5-ene (Tokyo Chemical Industry Co., Ltd.), a compound containing 4-piperidinemethanol (trade name HDPD-PB100: Heraeus company), etc. In addition, the above-mentioned trade names including "WPBG" are all trade names of Wako Pure Chemical Industries, Ltd. The photoacid generators include, for example, aromatic permeic acid salts (trade name SP-170: ADEKA Corporation), triaryl permeic acid salts (trade name CPI101A: San-Apro Ltd.), aromatic iodonium salts (trade name Irgacure 250: Ciba Japan Inc. )Wait. Also, the catalyst for chemically bonding micropore particles is not limited to photoactive catalysts and photocatalyst generating agents, and may be thermally active catalysts or thermal catalyst generating agents such as urea, for example. Catalysts that chemically bond micropore particles to each other include alkaline catalysts and acid catalysts. The aforementioned alkaline catalysts include potassium hydroxide, sodium hydroxide, and ammonium hydroxide. The aforementioned acid catalysts include hydrochloric acid and acetic acid. , oxalic acid, etc. Among them, an alkaline catalyst is suitable. The catalyst or catalyst generating agent that chemically bonds the microporous particles to each other can be added to the sol particle liquid (such as a suspension) containing the pulverized material (microporous particles) just before coating, or can be used It is used as a mixed solution in which a catalyst or a catalyst generating agent has been mixed in a solvent. The mixed liquid can be, for example, a coating liquid that is directly added to the sol particle liquid and dissolved, a solution in which a catalyst or a catalyst generator is dissolved in a solvent, or a solution in which a catalyst or a catalyst generator is dispersed in a solvent. Dispersions. The solvent is not particularly limited, and examples include water, buffer, and the like.

In addition, for example, a crosslinking auxiliary agent for indirectly bonding the above-mentioned pulverized products of the gel may be further added to the gel-containing liquid. The cross-linking auxiliary agent will enter between the particles (the above-mentioned pulverized products), so that the particles and the cross-linking auxiliary agent can interact or bond each other, so that the particles that are slightly separated by distance can also be bonded to each other, and can effectively improve strength. The aforementioned crosslinking auxiliary agent is preferably a multi-crosslinking silane monomer. Specifically, the multi-crosslinked silane monomer may have, for example, 2 or more and 3 or less alkoxysilyl groups, and the chain length between the alkoxysilyl groups may be 1 or more and 10 or less, and may also contain elements other than carbon. The above-mentioned crosslinking auxiliary agent can be listed for example: bis(trimethoxysilyl)ethane, bis(triethoxysilyl)ethane, bis(trimethoxysilyl)methane, bis(triethoxysilyl)methane, bis(trimethoxysilyl)methane, bis(trimethoxysilyl)methane, bis(trimethoxysilyl)methane, (triethoxysilyl)propane, bis(trimethoxysilyl)propane, bis(triethoxysilyl)butane, bis(trimethoxysilyl)butane, bis(triethoxysilyl)pentane, Bis(trimethoxysilyl)pentane, bis(trimethoxysilyl)hexane, bis(trimethoxysilyl)hexane, bis(trimethoxysilyl)-N-butyl-N-propyl-ethyl Alkane-1,2-diamine, ginseng-(3-trimethoxysilylpropyl) isocyanate, ginseng-(3-triethoxysilylpropyl) isocyanate, etc. The addition amount of the crosslinking auxiliary agent is not particularly limited, for example, it is 0.01-20% by weight, 0.05-15% by weight or 0.1-10% by weight relative to the weight of the pulverized silicon compound.

Next, a liquid containing microporous particles (for example, a suspension) is applied on the sealing portion (coating step). For the coating, for example, various coating methods described below can be used, but are not limited thereto. A coating film containing microporous particles and a catalyst can be formed by directly coating a liquid containing microporous particles (for example, pulverized colloidal silica compound) on the sealing portion. The coating film can also be called a coating layer, for example. By forming a coating film, for example, crushed objects whose three-dimensional structure has been destroyed will settle and accumulate to construct a new three-dimensional structure. In addition, the containing liquid containing microporous particles may not contain, for example, a catalyst for chemically bonding the microporous particles. For example, as will be described later, the precursor forming step may be performed after spraying a catalyst for chemically bonding microporous particles to the coating film, or performing the precursor forming process while blowing. However, the containing solution containing micropore particles may also contain a catalyst for chemically bonding the micropore particles to each other, and the precursor of the porous body is formed by chemically bonding the micropore particles to each other through the action of the catalyst contained in the coating film. things.

The above-mentioned solvent (hereinafter also referred to as "coating solvent") is not particularly limited, and for example, an organic solvent can be used. The organic solvent may, for example, have a boiling point of 150°C or lower. Specific examples include IPA, ethanol, methanol, n-butanol, 2-butanol, isobutanol, pentanol, and the like, and the same ones as the pulverization solvent can be used. When the method of forming the low-refractive index layer includes the step of pulverizing the colloidal compound, in the step of forming the coating film, for example, a pulverization solvent containing the pulverized product of the colloidal compound can be used as it is.

For example, in the coating step, it is preferable to apply a sol-like pulverized product dispersed in a solvent (hereinafter also referred to as "sol particle liquid") to the sealing part. The sol particle liquid, for example, is applied on the sealing part and dried, and then the above-mentioned chemical crosslinking is performed to continuously form a film of a void layer having a film strength higher than a certain level. In addition, the "sol" in the embodiment of the present invention refers to a state in which fluidity is exhibited by dispersing silica sol particles with a nanometer three-dimensional structure maintaining a partial void structure in a solvent by pulverizing the three-dimensional structure of the gel.

The concentration of pulverized matter in the coating solvent is not particularly limited, for example, it is 0.3% (v/v) ~ 50% (v/v), preferably 0.5% (v/v) ~ 30% (v/v), More preferably 1.0% (v/v) ~ 10% (v/v). If the concentration of pulverized matter is too high, for example, the fluidity of the sol particle liquid will decrease significantly, and agglomerates and coating marks may occur during coating. If the concentration of the pulverized product is too low, not only will it take a considerable amount of time to dry the solvent of the sol particle liquid, but also the residual solvent immediately after drying will increase, and the porosity may decrease.

The physical properties of the sol are not particularly limited. The shear viscosity of the sol is, for example, less than 100 cPa·s at a shear rate of 1000 l/sec, preferably less than 10 cPa·s, more preferably less than 1 cPa·s. If the shear viscosity is too high, for example, coating marks may occur and the transfer rate of gravure coating may decrease. On the contrary, when the shear viscosity is too low, for example, it may not be possible to thicken the wet coating thickness during coating, and it may not be possible to obtain the desired thickness after drying.

The coating amount of the pulverized product is not particularly limited, and can be appropriately set in accordance with, for example, the desired thickness of the polysiloxane porous body (resulting in a low refractive index layer). To give a specific example, when forming a polysiloxane porous body with a thickness of 0.1µm~1000µm, the coating amount of the pulverized material is 0.01µg~ ^60000µg per 1m2 of the coated surface, preferably 0.1µg~5000µg , preferably 1µg~50µg. The ideal application amount of the sol particle liquid is related to the concentration of the liquid or the application method, etc., so it is difficult to make a univocal definition, but considering the productivity, it is better to apply it as a thin layer as possible. If the amount of coating is too large, for example, the possibility of drying in a drying oven before the solvent volatilizes becomes high. In this way, the solvent may be dried before the nano-pulverized sol particles settle and accumulate in the solvent to form a void structure, which hinders the formation of voids and greatly reduces the void ratio. On the other hand, if the coating amount is too thin, the risk of cissing may increase.

In addition, the method for forming the low refractive index layer includes, for example, the step of forming a precursor as described above, and this step is to form a void structure that is a precursor of the void layer (low refractive index layer). The step of forming the precursor is not particularly limited, and for example, the precursor (void structure) may be formed by a drying step of drying a coating film formed by applying a microporous particle-containing liquid. The drying process in the drying step not only removes the solvent in the above-mentioned coating film (solvent contained in the sol particle liquid), but also allows the sol particles to settle and accumulate to form a void structure during the drying process. The temperature of the drying treatment is, for example, 50°C~250°C, preferably 60°C~150°C, more preferably 70°C~130°C. The drying treatment time may be, for example, 0.1 minutes to 30 minutes, preferably 0.2 minutes to 10 minutes, more preferably 0.3 minutes to 3 minutes.

The drying treatment may be, for example, natural drying, heat drying, or reduced pressure drying. Among them, it is preferable to use heat drying on the premise of industrial continuous production. The method of heating and drying is not particularly limited, for example, a general heating mechanism can be used. The heating mechanism may, for example, be an air heater, a heating roller, or a far-infrared heater. In addition, regarding the solvent used, in order to suppress the shrinkage stress that occurs with the volatilization of the solvent during drying and the crack phenomenon caused by the void layer (polysiloxane porous body), a solvent with a low surface tension is preferable. Examples of the solvent include lower alcohols represented by isopropanol (IPA), hexane, perfluorohexane, and the like. In addition, a small amount of perfluorinated surfactant or polysiloxane-based surfactant may be added to the above-mentioned IPA to lower the surface tension.

Moreover, the method of forming the low refractive index layer includes a crosslinking reaction step as described above, which is to initiate a crosslinking reaction inside the precursor after the precursor forming step; in the crosslinking reaction step, light irradiation or heating To produce alkaline substances, and the cross-linking reaction steps are multi-stage. In the first stage of the cross-linking reaction step, for example, microporous particles are chemically bonded to each other through the action of a catalyst (basic substance). Thereby, for example, the three-dimensional structure of the pulverized material in the coating film (precursor) is immobilized. When using conventional sintering for immobilization, for example, high temperature treatment above 200°C is performed to stimulate dehydration condensation of silanol groups and form siloxane bonds. In this formation method, by reacting various additives that can catalyze the above-mentioned dehydration condensation reaction, for example, the void structure can be continuously formed and immobilized at a low drying temperature around 100°C and a short processing time of less than a few minutes. .

The method of chemical bonding is not particularly limited, for example, it can be appropriately determined according to the type of colloidal silicon compound. To give a specific example, chemical bonding can be carried out by chemical cross-linking between pulverized materials, for example, when adding inorganic particles such as titanium oxide to the pulverized product, the inorganic particles and pulverized product can also be conceived. Perform chemical cross-linking. In addition, there are also cases where biocatalysts such as enzymes are carried, or where other parts different from the active sites of the catalyst are chemically cross-linked with the pulverized product. Therefore, the formation method of the low-refractive index layer is not limited to, for example, a void layer (polysiloxane porous body) formed by sol particles, but can also be extended to an organic-inorganic hybrid void layer, a host-guest void layer, and the like.

The chemical reaction in the presence of the above-mentioned catalyst is not particularly limited at which stage in the formation method of the low refractive index layer, for example, it can be carried out at least one stage among the above-mentioned multi-stage crosslinking reaction steps. For example, in the method of forming the low refractive index layer, as described above, the drying step can also be used as the precursor forming step. Also, for example, after the drying step, a multi-stage crosslinking reaction step may be performed, and in at least one stage, the microporous particles may be chemically bonded to each other through the action of a catalyst. For example, when the catalyst is a photoactive catalyst as mentioned above, in the cross-linking reaction step, the microporous particles can be chemically bonded to each other by light irradiation to form a precursor of a porous body. In addition, when the catalyst is a thermally active catalyst, in the cross-linking reaction step, the microporous particles can be chemically bonded to each other by heating to form the precursor of the porous body.

The above-mentioned chemical reaction, for example, can be carried out by irradiating light or heating a coating film containing a catalyst previously added to a sol particle liquid (such as a suspension), or by blowing and attaching a catalyst to the coating film and then applying light. It may be performed by irradiation or heating, or may be performed by performing light irradiation or heating while blowing the catalyst. There is no particular limitation on the accumulated light quantity of light irradiation. It is converted to a wavelength of 360nm, for example, 200mJ/cm ² ~800mJ/cm ² , preferably 250mJ/cm ² ~600mJ/cm ² , more preferably 300mJ/cm ² ~400mJ/cm ² . From the viewpoint of preventing the decomposition by the photoabsorption of the catalyst from progressing due to insufficient irradiation dose and insufficient effect, the accumulated light dose of 200 mJ/cm ² or more is preferable. The conditions of the heat treatment are not particularly limited. The heating temperature is, for example, 50°C-250°C, preferably 60°C-150°C, more preferably 70°C-130°C. The heating time is, for example, 0.1 minute to 30 minutes, preferably 0.2 minute to 10 minutes, more preferably 0.3 minute to 3 minutes. Alternatively, as mentioned above, the step of drying the coated sol particle liquid (such as a suspension) can also be used as a step of carrying out a chemical reaction in the presence of a catalyst. That is, in the step of drying the applied sol particle liquid (for example, a suspension), the pulverized matter (microporous particles) may be chemically bonded to each other by utilizing a chemical reaction in the presence of a catalyst. At this time, by further heating the coating film after the drying step, the pulverized materials (microporous particles) can be more firmly bonded to each other. In addition, we speculate that the chemical reaction in the presence of a catalyst may also occur in the step of preparing a microporous particle-containing liquid (such as a suspension) and the step of applying the microporous particle-containing liquid. However, the method of forming the low-refractive index layer is not limited by this speculation. Also, regarding the solvent used, for example, in order to suppress the shrinkage stress that occurs with the volatilization of the solvent during drying and the cracking phenomenon caused by the void layer, a solvent with a low surface tension is preferable. Examples thereof include lower alcohols typified by isopropanol (IPA), hexane, perfluorohexane, and the like.

In the formation method of the low-refractive index layer, the strength of the void layer (low-refractive index layer) can be increased more than when the cross-linking reaction step is one step, for example, by having multiple steps of the cross-linking reaction step. Hereinafter, the steps after the second stage of the crosslinking reaction step may be referred to as "aging step". In the curing step, for example, the precursor can be heated to further promote the cross-linking reaction inside the precursor. The phenomenon and mechanism occurring in the cross-linking reaction step are not clear, but are, for example, as described above. For example, in the curing step, the heating temperature is set to a low temperature, and the cross-linking reaction is induced while suppressing the shrinkage of the precursor, thereby improving the strength, and achieving both high porosity and strength. The temperature of the aging step is, for example, 40°C-70°C, preferably 45°C-65°C, more preferably 50°C-60°C. The time for performing the aging step is, for example, 10 hr to 30 hr, preferably 13 hr to 25 hr, more preferably 15 hr to 20 hr.

The low-refractive index layer formed in the above manner has excellent strength, so it can be made into a roll-shaped porous body, for example, and has the advantages of high production efficiency and easy handling.

For example, the low-refractive-index layer (void layer) formed in the above manner can be further laminated with other thin films (layers) to form a laminated structure including a porous structure. In this case, the constituent elements of the laminated structure can be laminated with, for example, an adhesive or an adhesive.

Details of the specific composition and formation method of the low-refractive index layer are described in, for example, International Publication No. 2019/151073. In this specification, the description of this publication is cited as a reference.

C. Micro LED array substrate As the micro LED array substrate, any suitable micro LED array substrate can be used. Representatively as shown in FIG. 1 , the micro LED array substrate 10 has a driving substrate 12 and a plurality of micro LEDs 11 , and the plurality of micro LEDs 11 are arranged in a matrix on the driving substrate 12 .

Micro-LEDs refer to LEDs whose chip size is, for example, 1 µm square to 100 µm square.

In one embodiment, a single type of micro LED can be used for the plurality of micro LEDs. In one embodiment, the above-mentioned micro LEDs are blue LEDs or ultraviolet LEDs.

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

D. Sealing Department The sealing portion can be formed of any suitable transparent material. The material constituting the sealing portion can be, for example, epoxy resin, polysiloxane resin, acrylic resin and the like. Moreover, the sealing part can also be formed by molten glass. The glass constituting the sealing portion may, for example, be acrylic glass, crown glass, flint glass, or borosilicate glass.

The sealing part can also be made of an adhesive or an adhesive. In one embodiment, the sealing portion is made of an adhesive.

As the adhesive, any appropriate adhesive can be used. Examples include water-based adhesives such as isocyanate-based, polyvinyl alcohol-based, gelatin-based, vinyl-based latex-based, water-based polyurethane, and water-based polyester, UV-curable adhesives, electron beam-curable adhesives, etc. Hardening adhesives, etc.

Adhesive Any suitable adhesive can be used. Examples include rubber-based, acrylic-based, silicone-based, urethane-based, vinyl alkyl ether-based, polyvinyl alcohol-based, polyvinylpyrrolidone-based, polyacrylamide-based, cellulose-based, etc. The adhesive. Among them, an acrylic adhesive is preferably used from the viewpoint of excellent optical transparency, adhesive properties, weather resistance, heat resistance, and the like.

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

The refractive index of the sealing part is preferably above 1.40, more preferably 1.40~2.00, more preferably 1.45~1.80.

The thickness of the sealing part is preferably not more than 200 µm, more preferably not more than 150 µm, more preferably not more than 100 µm, and especially preferably not more than 50 µm. If the thickness of the sealing part is reduced, the effect of suppressing color mixing is remarkable. 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 micro-LED on the low-refractive-index layer side to the surface of the sealing portion on the micro-LED side.

E. Wavelength conversion layer The wavelength conversion layer is a layer that absorbs the excitation light from the micro LED and emits light of a predetermined color. When a blue LED is used as a micro LED, the excitation light from the micro LED is absorbed, and a red sub-pixel is formed by a wavelength conversion layer that emits red light, and a green sub-pixel is formed by absorbing the excitation light and a green light is emitted by a wavelength conversion layer that emits green light sub-pixel. In addition, when ultraviolet LEDs are used, red sub-pixels are formed through the wavelength conversion layer emitting red light after being excited by ultraviolet rays, and green sub-pixels are formed through the wavelength conversion layer emitting green light after being excited by ultraviolet rays. A blue sub-pixel is formed by a wavelength conversion layer that 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. Any appropriate material can be used for the material constituting the matrix (hereinafter also referred to as a matrix material). The material may, for example, be resin, organic oxide, or inorganic oxide. The matrix material is preferably resin. The resin may be a thermoplastic resin, a thermosetting resin, or an active energy ray curable resin (such as an electron beam curable resin, an ultraviolet curable resin, or a visible light curable resin). It is preferably a thermosetting resin or an ultraviolet curable resin, more preferably a thermosetting resin. The resins may be used alone or in combination (for example, blending, copolymerization).

In one embodiment, quantum dots can be used for the phosphor particles. Quantum dots can control the wavelength conversion properties of the wavelength conversion layer. Specifically, by appropriately combining and using quantum dots having different emission center wavelengths, it is possible to form a wavelength conversion layer capable of realizing light having a desired emission center wavelength. The central wavelength of light emission of quantum dots can be adjusted according to the material and/or composition, particle size and shape of quantum dots. Quantum dots are known, for example: quantum dots having a central wavelength of light emission in the wavelength range of 600nm to 680nm (hereinafter referred to as quantum dots A), quantum dots having a central wavelength of light emission in the wavelength range of 500nm to 600nm ( Hereinafter referred to as quantum dots B), quantum dots having a central wavelength of light emission in the wavelength band of 400nm to 500nm (hereinafter referred to as quantum dots C). The quantum dot A is excited by the excitation light (light from the micro-LED) to emit red light, the quantum dot B emits green light, and the quantum dot C emits blue light. By appropriately combining these, light having a predetermined wavelength is incident on and passes through the wavelength conversion layer, and light having an emission center wavelength in a desired wavelength band can be realized.

Quantum dots can be made of any suitable material. Quantum dots can preferably be made of inorganic materials, more preferably can be made of inorganic conductor materials or inorganic semiconductor materials. The semiconductor material can be, for example, II-VI, III-V, IV-VI, and IV semiconductors. 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. These may be used individually or in combination of 2 or more types. Quantum dots can also contain p-type dopants or n-type dopants.

The size of the quantum dots can be any appropriate size according to the desired emission wavelength. The size of the quantum dots is preferably 1 nm to 10 nm, more preferably 2 nm to 8 nm. If the size of the quantum dots is within the above-mentioned range, each of the green and red colors can exhibit distinct luminescence, and high color rendering can be realized. For example, green light can emit light at a quantum dot size of about 7nm, while red light can emit light at about 3nm. The size of the quantum dot is the average particle diameter when the quantum dot is, for example, a true spherical shape, and the size along the smallest axis of the shape when it is other than that. In addition, the shape of the quantum dots can be any appropriate shape depending on the purpose. Specific examples include true spherical shape, scaly shape, plate shape, ellipsoidal shape, and amorphous shape.

With respect to 100 parts by weight of the matrix material, quantum dots are preferably blended in a ratio of 1 to 50 parts by weight, preferably 2 to 30 parts by weight. If the blending amount of quantum dots is within the above-mentioned range, a display with excellent color balance of all RGB can be provided.

Details of quantum dots have been described in, for example, Japanese Patent Laid-Open No. 2012-169271, Japanese Patent Laid-Open No. 2015-102857, Japanese Patent Laid-Open No. 2015-65158, Japanese Patent Publication No. 2013-544018, Japanese Patent Laid-Open No. In Japanese Patent Application Publication No. 2013-544018 and Japanese Patent Application Publication No. 2010-533976, the description of these publications is used as a reference in this specification. Commercially available quantum dots can also be used.

In another embodiment, the phosphor particles are photoluminescent particles due to their composition. The phosphor particles can be, for example, sulfide, aluminate, oxide, silicate, nitride, YAG, and TAG-based materials.

In addition, as phosphor particles, red phosphors and green phosphors described below can also be used. The red phosphor can be, for example, a composite fluoride phosphor activated with Mn ⁴⁺ . The so-called composite fluoride phosphor refers to the following coordination compound: it contains at least one coordination center (such as M described later), and is surrounded by fluoride ions that function as ligands, and as required by counter ions ( For example, A) to obtain charge compensation described later. 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 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. It is preferably a composite fluoride phosphor having a coordination number of 6 in the coordination center. The details of the red phosphor are described in, for example, Japanese Patent Application Laid-Open No. 2015-84327. In this specification, the entire description of this publication is incorporated by reference.

The green phosphor is, for example, a compound containing a solid solution of silicon aluminum oxynitride having a β-type Si ₃ N ₄ crystal structure as a main component. It is preferable to perform treatment so that the amount of oxygen contained in the silicon aluminum oxynitride crystal is not more than a specific amount (for example, 0.8% by mass). By performing such processing, a green phosphor having a narrow peak width and emitting bright light can be obtained. The details of the green phosphor are described in, for example, Japanese Patent Laid-Open No. 2013-28814. In this specification, the entire description of this publication is incorporated by reference.

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

As described above, in one embodiment, the respective wavelength conversion layers are spaced apart by partition walls (light-shielding layers). The width of the partition wall (that is, the distance between adjacent wavelength conversion layers) is preferably 0.1 µm to 100 µm, more preferably 1 µm to 50 µm. In the present invention, even if the width of the partition wall is narrow, color mixing can be sufficiently suppressed. By narrowing the width of the partition wall, a micro LED display device with excellent luminous efficiency can be obtained.

As mentioned above, when constituting a sub-pixel that directly utilizes light from a micro LED (for example, when a blue sub-pixel is formed by a blue LED), the wavelength conversion layer can be replaced by a light diffusion layer. The light-scattering layer preferably contains light-scattering particles. The material constituting the light-scattering particles includes, for example, alumina, zirconia, titania, barium sulfate, and the like.

In one embodiment, the above-mentioned micro LED display device further has a color filter disposed on the surface of the wavelength conversion layer (and/or light diffusion layer) opposite to the low refractive index layer. The color filter can be made into any appropriate configuration according to the color of the sub-pixels. In one embodiment, a color filter that cuts off colors other than the desired color is arranged in each sub-pixel. For example, a color filter such as a blue-cut color filter can be used in the red sub-pixel and the green sub-pixel.

Example Hereinafter, the present invention will be described in detail by means of examples, but the present invention is not limited by these examples.

[Example 1] Regarding the structure shown in FIG. 2(a), the brightness of red light emission and the brightness of green light emission were obtained by optical simulation. The structure shown in FIG. The green phosphor is provided with a blue LED directly below the green phosphor via a low-refractive index layer (refractive index: 1.20) and a sealing portion (refractive index: 1.50). All of the wavelength conversion layers were obtained by adding 10% by weight of wavelength conversion particles (refractive index: 1.80) to the matrix portion (refractive index: 1.47). The refractive indices of the wavelength conversion layers are all 1.50. The optical characteristics in this example, and the examples and comparative examples described later were calculated using the optical simulation software (Lighttools) of Synopsys. The optical modules used in the simulation are as follows. The thickness of each RGB wavelength conversion layer was set to 100 µm, and the width was set to 100 µm. The width of the partition wall arranged between each RGB was set to 50 nm. LEDs are arranged at positions facing each wavelength conversion layer. In this simulation, in order to investigate the influence of color mixing, only LEDs corresponding to the Green wavelength conversion layer were 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. Also, this size is assumed to be 78 inches with 4K resolution (3840x2160). The partition wall is arranged at 50.0µm between the wavelength conversion layers, and the transmittance is set to 0%. Also, a photoreceiver is arranged on each pixel.

[Comparative example 1] Regarding the structure shown in FIG. 2(b), the brightness of red light emission and the brightness of green light emission were obtained by optical simulation. The structure shown in FIG. A green phosphor is provided, and a blue LED is disposed directly under the green phosphor via a sealing portion (no low-refractive index layer is disposed).

＜Evaluation＞ The ratio of the brightness of Example 1 to the brightness (100%) of Comparative Example 1 is listed in Table 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 above-mentioned luminance at each thickness setting was obtained. In the above configuration, the green phosphor and the blue LED form a green-emitting sub-pixel, so there is a relationship that the brightness of green light emission > the brightness of red light emission, and the greater the difference in brightness between green light emission and red light emission, the greater the effect of suppressing color mixing big. It is evident from Table 1 that in the present invention, by disposing the low-refractive index layer, unnecessary red light emission can be suppressed, and color mixing can be appropriately suppressed. Moreover, the said effect becomes remarkable by setting appropriately the thickness of the sealing part between LED and a wavelength conversion layer.

[Table 1]

[Example 2] Regarding the structure shown in FIG. 2(a), the brightness of red light emission and the brightness of green light emission were obtained by optical simulation. The structure shown in FIG. The green phosphor is interposed between the low refractive index layer and the sealing part (thickness between the LED and the wavelength conversion layer: 75µm), and a blue LED is arranged directly below the green phosphor (thickness of the wavelength conversion layer is 100µm, And the width is 100µm, the thickness of the partition wall is 50µm, and the thickness of the low refractive index layer is 1.0µm).

[Comparative example 2] Regarding the structure shown in FIG. 2(b), the brightness of red light emission and the brightness of green light emission were obtained by optical simulation. The structure shown in FIG. A green phosphor, and a blue LED is placed directly under the green phosphor through a sealing part (thickness 75 µm) (without a low-refractive index layer).

＜Evaluation＞ The ratio of the brightness of Example 2 to the brightness (100%) of Comparative Example 2 is listed in Table 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 above-mentioned brightness in each setting of the refractive index was obtained. It is evident from Table 2 that, in the present invention, by arranging the low-refractive index layer, unnecessary red light emission can be suppressed, and color mixing can be appropriately suppressed.

[Table 2]

10: Micro LED array substrate 11: Micro LED 12:Drive substrate 20: sealing part 30: low refractive index layer 40: wavelength conversion layer 50: next door (shading layer) 100: Micro LED display device

FIG. 1 is a schematic cross-sectional view of a micro LED display device according to an embodiment of the present invention. In FIG. 2, (a) is a schematic sectional view showing the structure provided in the Example; (b) is a schematic sectional view showing the structure provided in the Comparative Example.

10: Micro LED array substrate

11: Micro LED

12:Drive substrate

20: sealing part

30: low refractive index layer

40: wavelength conversion layer

50: next door (shading layer)

100: Micro LED display device

Claims (7)

A micro LED display device, comprising: a micro LED array substrate comprising a plurality of micro LEDs; and From the side of the micro-LED array substrate in order: a sealing part, which seals a plurality of the micro-LEDs; a low refractive index layer; and Multiple wavelength conversion layers formed by partitioning; The wavelength conversion layer of each layer is formed in a manner corresponding to one micro LED 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 part 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. The micro LED display device according to claim 1, wherein the refractive index of the aforementioned low refractive index layer is 1.25 or less. The micro-LED display device according to claim 1 or 2, wherein the aforementioned low-refractive index layer is a void layer made of a porous body, and the fine particles of the porous system are chemically bonded to each other. The micro-LED display device according to any one of claims 1 to 3, wherein the sealing part is made of an adhesive. The micro-LED display device according to any one of claims 1 to 4, wherein the aforementioned wavelength conversion layers are arranged at intervals by partition walls. The micro LED display device according to any one of claims 1 to 5, wherein the micro LEDs are blue LEDs or ultraviolet LEDs. The micro-LED display device according to any one of Claims 1 to 6, further comprising a color filter disposed on the surface of the wavelength conversion layer opposite to the low refractive index layer.

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