Dispersion liquid, dispersion liquid set, low refractive index layer, optical member, optical device, method for manufacturing low refractive index layer, method for manufacturing optical member, and method for manufacturing optical device

Abstract

To provide a dispersion liquid capable of ensuring the film thickness of a low refractive index layer and achieving in-plane film thickness uniformity.　A dispersion liquid in which particles are dispersed in a dispersion medium, wherein the particles are the condensation product of a raw material containing alkoxysilane, the concentration of the particles in the dispersion liquid is 3.5-15 wt %, the viscosity of the dispersion liquid is 4 mPa·s or more and less than 5000 mPa·s, and the particle diameter D50 of the particles is 20-400 nm.

Description

Dispersion, dispersion set, low refractive index layer, optical member, optical device, method for manufacturing low refractive index layer, method for manufacturing optical member, and method for manufacturing optical device

[0001] The present disclosure relates to a dispersion, a dispersion set, a low refractive index layer, an optical member, an optical device, a method for manufacturing a low refractive index layer, a method for manufacturing an optical member, and a method for manufacturing an optical device.

[0002] In optical devices, for example, an air layer with a low refractive index is used as a total reflection layer. Specifically, for example, optical film components (e.g., a light guide plate and a reflector) in a liquid crystal device are stacked with an air layer interposed therebetween. However, if each component is separated by an air layer, problems such as bending of the component may occur, especially when the component is large.

[0003] Therefore, it has been proposed to use a low refractive index layer instead of an air layer. For example, a method has been used in which a low refractive index layer is formed on a light guide plate to optically isolate the light to be guided into the light guide plate, thereby guiding the light without being affected by external factors such as dirt or scratches on the light guide plate. Patent Document 1 uses a method in which a low refractive index layer is laminated on a light guide plate via an adhesive layer that is bonded to the light guide plate for the purpose of protecting the light.

[0004] As a method for forming such a low refractive index layer, for example, Patent Document 2 discloses a method of applying a coating liquid by roll-to-roll coating.

[0005] Patent No. 6606518 Patent No. 6599699

[0006] When a low refractive index layer is laminated via an adhesive layer as in Patent Document 1, light guided through the light guide plate passes through the adhesive layer before being totally reflected by the low refractive index layer, which may cause a color shift or light scattering due to the adhesive layer, leading to a loss of light guide. Therefore, a method has been proposed in which a low refractive index layer is formed by applying a coating liquid directly onto a light guide plate without using an adhesive layer.

[0007] However, because light guide plates are manufactured using a batch process, direct liquid coating requires a coating method that differs from die coating used in conventional roll coating, such as a batch coater, spin coating, spray coating, or dipping. Among batch coating methods, spin coating is the method that most easily ensures in-plane smoothness. However, the liquid for forming the low refractive index layer described in Patent Document 2 is designed based on a roll-to-roll coating method, and is therefore insufficient in terms of ensuring the film thickness after drying in spin coating or taking into account the spreading of the liquid during spin coating. In particular, for AR / MR glass, which is a small device, ensuring the film thickness of the low refractive index layer and in-plane film thickness uniformity are important in order to maintain the parallelism between light guide plates. Therefore, even when designing the liquid for spin coating, it is necessary to appropriately manage and design factors such as viscosity and concentration.

[0008] Therefore, an object of the present disclosure is to provide a dispersion, a dispersion set, a low refractive index layer, an optical element, an optical device, a method for manufacturing a low refractive index layer, a method for manufacturing an optical element, and a method for manufacturing an optical device, which are capable of ensuring the film thickness of a low refractive index layer and realizing in-plane film thickness uniformity.

[0009] In order to achieve the above object, a first dispersion liquid of the present disclosure is a dispersion liquid in which particles are dispersed in a dispersion medium, the particles being a condensate of a raw material containing an alkoxysilane, the concentration of the particles in the dispersion liquid being 3.5 to 15 wt %, the viscosity of the dispersion liquid being 4 mPa·s or more and less than 5000 mPa·s, and the particle diameter D50 of the particles being 20 nm or more and 400 nm or less.

[0010] In order to achieve the above object, the second dispersion of the present disclosure is a dispersion in which a solid content including particles is dispersed in a dispersion medium, the particles being a condensate of a raw material including an alkoxysilane, the concentration of the solid content in the dispersion being 3.5 to 15 wt %, the viscosity of the dispersion being 4 Pa·s or more and less than 5000 mPa·s, and the particle diameter D50 of the particles being 20 nm or more and 400 nm or less. Note that, hereinafter, the term "dispersion of the present disclosure" includes both the first dispersion of the present disclosure and the second dispersion of the present disclosure, unless otherwise specified.

[0011] The dispersion set of the present disclosure is characterized by comprising the dispersion of the present disclosure and a catalyst-containing liquid containing a catalyst for chemically bonding the particles of the dispersion.

[0012] The low refractive index layer of the present disclosure is characterized in that it is obtained by applying the dispersion liquid or the dispersion liquid set of the present disclosure and drying it.

[0013] The optical member of the present disclosure is characterized by including the low refractive index layer of the present disclosure.

[0014] The optical device of the present disclosure is an optical device including an optical member.

[0015] The method for producing a low refractive index layer according to the present disclosure is characterized by including a step of applying the dispersion according to the present disclosure or the dispersion set according to the present disclosure onto a substrate, and a step of drying the applied dispersion.

[0016] The method for producing an optical member according to the present disclosure is a method for producing an optical member including a low refractive index layer, characterized in that the low refractive index layer is produced by the method for producing an optical member according to the present disclosure.

[0017] The method for manufacturing an optical device according to the present disclosure is a method for manufacturing an optical device including an optical member, characterized in that the optical member is manufactured by the manufacturing method according to the present disclosure.

[0018] According to the present disclosure, it is possible to provide a dispersion liquid, a dispersion liquid set, a low refractive index layer, an optical element, an optical device, a method for manufacturing a low refractive index layer, a method for manufacturing an optical element, and a method for manufacturing an optical device, which are capable of ensuring the film thickness of a low refractive index layer and realizing in-plane film thickness uniformity.

[0019] Next, the present disclosure will be described in more detail using examples, but the present disclosure is not limited to the following description.

[0020] In the present disclosure, a "solvent" (e.g., a solvent for producing a gel, a substitution solvent, a solvent for producing a low refractive index layer, etc., used in producing a dispersion) may not dissolve a gel or a pulverized product thereof, particles, etc., and may, for example, disperse or precipitate the gel or a pulverized product thereof, etc. in the solvent. For example, an organic solvent, etc. may be used as a dispersion medium in the dispersion of the present disclosure.

[0021] In the present disclosure, the term "adhesive layer" refers to a layer formed of at least one of a pressure-sensitive adhesive and an adhesive. In the present disclosure, unless otherwise specified, the term "adhesive layer" may refer to a "pressure-sensitive adhesive layer" formed of a pressure-sensitive adhesive, an "adhesive layer" formed of an adhesive, or a layer containing both a pressure-sensitive adhesive and an adhesive. Furthermore, in the present disclosure, pressure-sensitive adhesives and adhesives may be collectively referred to as "adhesive adhesives." Generally, a material with relatively weak adhesive or bonding strength (e.g., a material that allows for re-detachment from an adherend) is referred to as a "pressure-sensitive adhesive," while a material with relatively strong adhesive or bonding strength (e.g., a material that is impossible or extremely difficult to re-detach from an adherend) is referred to as an "adhesive." In the present disclosure, there is no clear distinction between a pressure-sensitive adhesive and an adhesive. Furthermore, in the present disclosure, there is no clear distinction between "adhesive strength" and "adhesive strength."

[0022] In the present disclosure, unless otherwise specified, "mass %" and "wt %" may be read interchangeably, and "parts by mass" and "parts by weight" may be read interchangeably.

[0023] In addition, in the present disclosure, "on" or "on the surface" may refer to a state of being in direct contact with the surface or a state of being via another layer or the like.

[0024] [1. Dispersion] As described above, the first dispersion of the present disclosure is a dispersion in which particles are dispersed in a dispersion medium, wherein the particles are a condensate of a raw material containing an alkoxysilane, the concentration of the particles in the dispersion is 3.5 to 15 wt %, the viscosity of the dispersion is 4 mPa·smPa·s or more and less than 5000 mPa·s, and the particle diameter D50 of the particles is 20 nm or more and 400 nm or less.

[0025] As described above, the second dispersion of the present disclosure is a dispersion in which a solid content including particles is dispersed in a dispersion medium, the particles being a condensate of a raw material including an alkoxysilane, the concentration of the solid content in the dispersion being 3.5 to 15 wt %, the viscosity of the dispersion being 4 Pa ​​s or more and less than 5000 mPa s, and the particle diameter D50 of the particles being 20 nm or more and 400 nm or less.

[0026] [1-1. Particles of Condensate of Raw Materials Containing Alkoxysilane] In the dispersion liquid of the present disclosure, the particles are, as described above, a condensate of raw materials containing alkoxysilane. The alkoxysilane may be, for example, a saturated alkoxysilane or an unsaturated alkoxysilane having a UV-polymerizable unsaturated group. The saturated alkoxysilane may be, for example, a monomer, an oligomer, or a combination thereof. Specific examples of the saturated alkoxysilane monomer include methyltrimethoxysilane, methyltriethoxysilane, phenyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, diethoxydimethoxysilane, dimethyldimethoxysilane, and dimethyldiethoxysilane, and these may be used alone or in combination. The saturated alkoxysilane oligomer is preferably a condensation polymer of one or more of the above-mentioned monomers. The saturated alkoxysilane oligomer can be obtained, for example, by hydrolysis polymerization of a monomer. The alkoxysilane is preferably an alkoxysilane having a functional group with three or less functionalities (a saturated bond functional group). The unsaturated alkoxysilane may be, for example, a monomer, an oligomer, or a combination thereof. The unsaturated alkoxysilane monomer has, for example, an organic group having at least one double bond or triple bond and an alkoxy group.

[0027] In the dispersion liquid of the present disclosure, the particles may be, for example, particles of a silsesquioxane condensate, which is a condensate of a raw material containing a trifunctional organosilicon compound. In this case, the particles may be, for example, a condensate of a raw material consisting solely of a trifunctional organosilicon compound, or a condensate of a raw material containing a trifunctional organosilicon compound and another monomer. The content of the trifunctional organosilicon compound in the raw material (monomer) may be, for example, 0.1 mol% or more, 10 mol% or more, 30 mol% or more, 50 mol% or more, or 90 mol% or more. For example, it may be 100 mol% or less, 99 mol% or less, 90 mol% or less, 70 mol% or less, or 50 mol% or less, for example, 0.1 to 100 mol%, 1 to 99 mol%, 10 to 90 mol%, or 30 to 70 mol%.

[0028] The raw material (monomer) of the particles may contain, for example, an organosilicon compound represented by the following formula (1). In this case, the raw material may or may not further contain other components. The organosilicon compound of the following formula (1) has hydroxyl groups, and therefore, for example, hydrogen bonds or intermolecular force bonds can be formed via the respective hydroxyl groups.

[0029]

[0030] In the formula (1), for example, X is 2, 3, or 4, provided that at least a part of the raw material represented by the formula (1) is a trifunctional organosilicon compound in which X is 3, and R １ is a straight-chain or branched alkyl group. １ The number of carbon atoms is, for example, 1 to 6, 1 to 4, or 1 to 2. Examples of the linear alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group, and examples of the branched alkyl group include an isopropyl group and an isobutyl group. X is, for example, 3 or 4.

[0031] Among the organosilicon compounds represented by the formula (1), a trifunctional organosilicon compound in which X is 3 can be represented by the following formula (1'): １ is the same as in the formula (1), and is, for example, a methyl group. １ When X is a methyl group, the organosilicon compound is tris(hydroxy)methylsilane. When X is 3, the organosilicon compound is, for example, a trifunctional silane having three functional groups.

[0032]

[0033] Specific examples of the silicon compound represented by formula (1) include compounds in which X is 4. In this case, the silicon compound is, for example, a tetrafunctional silane having four functional groups.

[0034] The silicon compound may be, for example, a precursor that forms the silicon compound of formula (1) upon hydrolysis. The precursor may be, for example, any precursor that can generate the silicon compound upon hydrolysis, and a specific example thereof is a compound represented by the following formula (2):

[0035] In the formula (2), for example, X is 2, 3, or 4; １ and R ２ are each a linear or branched alkyl group, R １ and R ２ may be the same or different, R １ When X is 2, R may be the same or different, ２ may be the same or different from each other.

[0036] The X and R １ represents, for example, X and R in formula (1) described below. １ In addition, the R ２ is, for example, R in formula (1) described later. １ The following example can be used.

[0037] Specific examples 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 the formula (2). １ and R ２ When is a methyl group, the silicon compound is trimethoxy(methyl)silane (hereinafter also referred to as "MTMS"). The compound represented by the following formula (2') can be hydrolyzed to obtain the compound represented by the formula (1').

[0038] When the silicon compound is a precursor represented by the formula (2), the production method of the present invention may include, for example, a step of hydrolyzing the precursor.

[0039] Particles of a condensate of a raw material containing alkoxysilane can be produced, for example, as a sol particle liquid in which particles are dispersed in a dispersion medium. The method for producing the sol particle liquid is not particularly limited, and for example, it can be produced by pulverizing a gel of a condensate of a raw material containing alkoxysilane in a dispersion medium. The method for producing the gel of a condensate of a raw material containing alkoxysilane is also not particularly limited, and can be produced, for example, by a method similar to the method for producing a gel of a silicon compound described in WO 2019 / 065999 or WO 2019 / 065803. The method for pulverizing the gel of a condensate of a raw material containing alkoxysilane in a dispersion medium is also not particularly limited, and for example, the method described in Japanese Patent No. 7182358 may be used. The type of dispersion medium in the sol particle liquid is also not particularly limited, and may be, for example, the same as the dispersion medium of the sol particle liquid described in WO 2019 / 065999 or WO 2019 / 065803. The sol particle liquid can also be produced by the method described in "Reference Example 1" of the Examples of the present application, which will be described later.

[0040] [1-2. Dispersion and its Manufacturing Method] The method for manufacturing the dispersion of the present disclosure is not particularly limited, but it can be manufactured, for example, as follows.

[0041] First, a sol particle liquid is produced in which particles of a condensate of a raw material containing alkoxysilane are dispersed in a dispersion medium. The particles of the condensate of a raw material containing alkoxysilane may be, for example, silsesquioxane condensate particles, as described above. The sol particle liquid can be produced, for example, by the method described above. The concentration of the particles of the condensate of a raw material containing alkoxysilane in the sol particle liquid at this stage is not particularly limited, but may be, for example, 0.5 wt % or more, 1.0 wt % or more, 2.0 wt % or more, 2.5 wt % or more, or 3.0 wt % or more; for example, 3.5 wt % or less, 3.4 wt % or less, 3.3 wt % or less, 3.2 wt % or less, or 3.1 wt % or less; for example, 0.5 to 3.5 wt %, 1.0 to 3.4 wt %, 2.0 to 3.3 wt %, 2.5 to 3.2 wt %, or 3.0 to 3.1 wt %. Furthermore, the concentration of components other than the dispersion medium in the sol particle liquid at this stage (hereinafter may be referred to as "solid content" or "solid components") is not particularly limited, and may be, for example, 0.5 wt % or more, 1.0 wt % or more, 2.0 wt % or more, 2.5 wt % or more, or 3.0 wt % or more; for example, 3.5 wt % or less, 3.4 wt % or less, 3.3 wt % or less, 3.2 wt % or less, or 3.1 wt % or less; and may be, for example, 0.5 to 3.5 wt %, 1.0 to 3.4 wt %, 2.0 to 3.3 wt %, 2.5 to 3.2 wt %, or 3.0 to 3.1 wt %.

[0042] In the present disclosure, particle size can be measured using, for example, a laser diffraction particle size analyzer or a dynamic light scattering particle size analyzer (DLS). However, in the present disclosure, measurement using a dynamic light scattering particle size analyzer (DLS) is preferred because a more accurate value can be calculated based on the target particle size. By measuring the particle size distribution using these measurement methods, the particle size D50 can be calculated. D50 is also called the median diameter, and is the particle size at the center of the particle distribution, corresponding to a cumulative frequency of 50%.

[0043] Next, a "first pulverization step" is performed to pulverize the particles in the sol particle liquid. The pulverization method for the first pulverization step is not particularly limited, and for example, the method described in Japanese Patent No. 7182358 may be used. Among these, high-pressure media-less pulverization is preferable. The pressure in the first pulverization step is not particularly limited, and may be, for example, 30 MPa or more, 50 MPa or more, 70 MPa or more, 100 MPa or more, or 150 MPa or more, and may be, for example, 350 MPa or less, 300 MPa or less, 250 MPa or less, 200 MPa or less, or 180 MPa or less, and may be, for example, 30 to 350 MPa, 50 to 300 MPa, 70 to 250 MPa, 100 to 200 MPa, or 150 to 180 MPa. The particle size D50 of the particles of the condensate of the raw material containing the alkoxysilane after the first pulverization step is not particularly limited, and may be, for example, 25 nm or more, 30 nm or more, 35 nm or more, 40 nm or more, or 50 nm or more; for example, 350 nm or less, 300 nm or less, 250 nm or less, 200 nm or less, or 150 nm or less; for example, 25 to 350 nm, 30 to 300 nm, 35 to 250 nm, 40 to 200 nm, or 50 to 150 nm.

[0044] Next, a "concentration step" is carried out to concentrate the sol particle liquid after the first pulverization step. The concentration method in the concentration step is not particularly limited, and may be, for example, heating or pressurization, but pressurization is preferred. More specifically, for example, the sol may be concentrated to a predetermined concentration by pressurization using a filter, or the dispersion medium may be partially removed by heating or the like to concentrate to a predetermined concentration. The filter is also not particularly limited, and examples thereof include a rotary ceramic membrane filter and a crossflow filter. An example of the rotary ceramic membrane filter is a product manufactured by Mitsubishi Kakoki Kaisha under the trade name "Mitsubishi Dynafilter (DyF)". The concentration of the particles of the condensate of the raw material containing the alkoxysilane in the sol particle liquid after the concentration step is not particularly limited, and may be, for example, 3.6% by weight or more, 4.0% by weight or more, 4.5% by weight or more, 5.0% by weight or more, or 5.5% by weight or more; and may be, for example, 40% by weight or less, 30% by weight or less, 20% by weight or less, 18% by weight or less, or 15% by weight or less, and may be, for example, 3.6 to 40% by weight, 4.0 to 30% by weight, 4.5 to 20% by weight, 5.0 to 18% by weight, or 5.5 to 15% by weight. The concentration of solids (solid components) in the sol particle liquid after the concentration step is not particularly limited, and may be, for example, 3.6 wt % or more, 3.8 wt % or more, 4.0 wt % or more, 4.1 wt % or more, or 4.2 wt % or more; and may be, for example, 39 wt % or less, 38 wt % or less, 37 wt % or less, 36 wt % or less, or 35 wt % or less, and may be, for example, 3.6 to 39 wt %, 3.8 to 38 wt %, 4.0 to 37 wt %, 4.1 to 36 wt %, or 4.2 to 35 wt %.

[0045] Next, a "second pulverization step" is performed to pulverize the particles in the sol particle liquid after the concentration step. The pulverization method for the second pulverization step is not particularly limited, and for example, the method described in Japanese Patent No. 7182358 may be used. Among these, high-pressure media-less pulverization is preferable. The pressure in the second pulverization step is not particularly limited, and may be, for example, 30 MPa or more, 50 MPa or more, 70 MPa or more, 100 MPa or more, or 150 MPa or more; for example, 350 MPa or less, 300 MPa or less, 250 MPa or less, 200 MPa or less, or 180 MPa or less; for example, 30 to 350 MPa, 50 to 300 MPa, 70 to 250 MPa, 100 to 200 MPa, or 150 to 180 MPa. The particle diameter D50 of the particles of the condensate of the raw material containing the alkoxysilane after the second pulverization step is 20 nm or more and 400 nm or less, which satisfies the conditions of the dispersion of the present disclosure, but may be, for example, 25 nm or more, 30 nm or more, 35 nm or more, 40 nm or more, or 50 nm or more, and may be, for example, 350 nm or less, 300 nm or less, 250 nm or less, 200 nm or less, 150 nm or less, 100 nm or less, or 80 nm or less, and may be, for example, 25 to 350 nm, 30 to 300 nm, 35 to 250 nm, 40 to 200 nm, 50 to 150 nm, or 20 to 100 nm.

[0046] From the viewpoint of minimizing the haze value of the low refractive index layer produced from the dispersion of the present disclosure, it is preferable that the particle diameter D50 of the condensate of the raw material containing the alkoxysilane is not too large. However, if the D50 is small, the viscosity of the dispersion of the present disclosure is likely to be low. In that case, for example, the viscosity of the dispersion of the present disclosure can be increased by increasing the concentration of the particles or the solid content in the dispersion of the present disclosure. Furthermore, from the viewpoint of transparency, it is preferable that the particle diameter D50 of the condensate of the raw material containing the alkoxysilane is not too large.

[0047] Furthermore, a "liquid concentration adjustment step" is performed in which a dispersion medium is added to the sol particle liquid after the second pulverization step to adjust the liquid concentration, thereby producing the dispersion of the present disclosure. At this time, the viscosity of the dispersion is adjusted to 4 mPa·s or more and less than 5000 mPa·s, which is the viscosity of the dispersion of the present disclosure. If the viscosity of the dispersion is too low, exceeding the range of the present disclosure, it becomes impossible to ensure the film thickness of the low refractive index layer. If the viscosity of the dispersion is too high, exceeding the range of the present disclosure, the film thickness of the low refractive index layer will vary greatly (in-plane film thickness uniformity will not be achieved), or cracks will occur in the low refractive index layer during drying, making it impossible to form the low refractive index layer at all. The viscosity of the dispersion of the present disclosure may be, for example, 5 mPa·s or more, 6 mPa·s or more, 7 mPa·s or more, 8 mPa·s or more, 9 mPa·s or more, 10 mPa·s or more, 11 mPa·s or more, 12 mPa·s or more, 13 mPa·s or more, 14 mPa·s or more, 15 mPa·s or more, 16 mPa·s or more, 17 mPa·s or more, 18 mPa·s or more, or 20 mPa·s or more, and may be, for example, 5000 mPa·s or less, 4000 mPa·s or less, 3500 mPa·s or less. The viscosity may be, for example, 16 to 5000 mPa s, 17 to 4000 mPa s, 18 to 3500 mPa s, or 20 to 3000 mPa s. In addition, the concentration of particles of the condensate of the raw material containing the alkoxysilane in the dispersion is set to, for example, 3.5 to 15 wt %, which is within the range of the first dispersion of the present disclosure. The concentration of the condensate particles of the raw material containing alkoxysilane in the dispersion of the present disclosure is preferably not too low from the viewpoint of ensuring the film thickness of the low refractive index layer.The concentration of the condensate particles of the raw material containing alkoxysilane in the dispersion of the present disclosure is preferably not too high from the viewpoint of suppressing or preventing the film thickness of the low refractive index layer from varying greatly (not being able to achieve in-plane film thickness uniformity) and the occurrence of cracks in the low refractive index layer during drying, which makes it impossible to form the low refractive index layer itself.The concentration of the alkoxysilane-containing raw material condensate particles in the dispersion of the present disclosure may be, for example, 3.6% by weight or more, 4.0% by weight or more, 4.5% by weight or more, 5.0% by weight or more, 5.5% by weight or more, or 6% by weight or more, and may be, for example, 40% by weight or less, 35% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, 15% by weight or less, 12% by weight or less, 10% by weight or less, 8% by weight or less, or 6% by weight or less, for example, 3.6 to 40% by weight, 4.0 to 35% by weight, 4.5 to 30% by weight, 5.0 to 25% by weight, 5.5 to 20% by weight, or 6.0 to 12.0% by weight. The concentration of solids (solid components) in the sol particle liquid after the concentration step is not particularly limited, but is, for example, 3.5 to 15% by weight, which is within the range of the second dispersion of the present disclosure. The solid content concentration in the dispersion of the present disclosure is preferably not too low from the viewpoint of ensuring the film thickness of the low refractive index layer, and is preferably not too high from the viewpoint of suppressing or preventing the film thickness of the low refractive index layer from varying greatly (making it impossible to achieve in-plane film thickness uniformity) and the occurrence of cracks in the low refractive index layer during drying, which makes it impossible to form the low refractive index layer itself. The concentration of solids in the dispersion of the present disclosure may be, for example, 3.6 wt% or more, 3.8 wt% or more, 4.0 wt% or more, 4.1 wt% or more, 4.2 wt% or more, or 6.0 wt% or more, for example, 39 wt% or less, 38 wt% or less, 37 wt% or less, 36 wt% or less, 35 wt% or less, 15 wt% or less, 12 wt% or less, 10 wt% or less, 8 wt% or less, or 6 wt% or less, for example, 3.6 to 39 wt%, 3.8 to 38 wt%, 4.0 to 37 wt%, 4.1 to 36 wt%, 4.2 to 35 wt%, or 6.0 to 12.0 wt%. In addition, at this time, together with the dispersion medium, a crosslinking auxiliary (also called a crosslinking agent), a catalyst, etc. may be added to promote crosslinking between particles of the condensate of the raw material containing the alkoxysilane for use in producing a low refractive index layer. The cross-linking may be, but is not particularly limited to, a covalent bond between particles of a condensate of raw materials containing the alkoxysilane, either directly or via the cross-linking auxiliary.The crosslinking auxiliary is not particularly limited, and may be, for example, a substance having multiple functional groups capable of forming covalent bonds with particles of the condensate of the raw material containing the alkoxysilane. Specific examples of the crosslinking auxiliary include bis(trimethoxysilyl)alkylene. Examples of the bis(trimethoxysilyl)alkylene include bis(trimethoxysilyl)hexane. Other examples of the crosslinking auxiliary are not particularly limited, and are described, for example, in Japanese Patent No. 7182358. The concentration of the crosslinking auxiliary in the dispersion of the present disclosure is not particularly limited, and is described, for example, in Japanese Patent No. 7182358. The catalyst is not particularly limited, and may be, for example, a photoactivated catalyst or a thermally activated catalyst, or an acid catalyst or a base catalyst. 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 the photoactive catalyst, a substance that generates a catalyst by light (photocatalyst generator) may be used, or in addition to or instead of the thermally active catalyst, a substance that generates a catalyst by heat (thermal catalyst generator) may be used. The photocatalyst generator is not particularly limited, but examples thereof include photobase generators (substances that generate a basic catalyst by light irradiation) and photoacid generators (substances that generate an acidic catalyst by light irradiation), and photobase generators are preferred.Examples of the photobase generator include 9-anthrylmethyl N,N-diethylcarbamate (trade name WPBG-018), (E)-1-[3-(2-hydroxyphenyl)-2-propenoyl]piperidine (trade name WPBG-027), 1-(anthraquinon-2-yl)ethyl imidazolecarboxylate (trade name WPBG-140), 2-nitrophenylmethyl 4-methacryloyloxypiperidine-1-carboxylate (trade name WPBG-165), and 1,2-diisopropyl-3-[bis(dimethylamino)methylene]guanidium. Examples of photoacid generators include 2-(3-benzoylphenyl)propionate (trade name WPBG-266), 1,2-dicyclohexyl-4,4,5,5-tetramethylbiguanidium n-butyltriphenylborate (trade name WPBG-300), and 2-(9-oxoxanthen-2-yl)propionic acid 1,5,7-triazabicyclo[4.4.0]dec-5-ene (Tokyo Chemical Industry Co., Ltd.), and a compound containing 4-piperidinemethanol (trade name HDPD-PB100, manufactured by Heraeus Chemical). All of the product names containing "WPBG" are trade names of Wako Pure Chemical Industries, Ltd. Examples of photoacid generators include aromatic sulfonium salts (trade name SP-170, manufactured by ADEKA), triarylsulfonium salts (trade name CPI101A, manufactured by San-Apro), and aromatic iodonium salts (trade name Irgacure 250, manufactured by Ciba Japan). The concentration of the catalyst or catalyst generator in the dispersion of the present disclosure is not particularly limited, but is as described in Japanese Patent No. 7,182,358, for example.

[0048] The dispersion of the present disclosure can be produced in the manner described above. However, the method for producing the dispersion of the present disclosure is not limited thereto, and any production method may be used as long as the conditions for the dispersion of the present disclosure are met. For example, the method for producing the dispersion of the present disclosure may or may not include some or all of the steps described above, and may or may not include steps other than the steps described above. For example, the pulverization step is not limited to two steps, the first pulverization step and the second pulverization step, but may be one step or three or more steps, and the pulverization step may not be performed if not necessary. Furthermore, the concentration step and the liquid concentration adjustment step may or may not be performed.

[0049] [2. Low Refractive Index Layer and Manufacturing Method Thereof] As described above, the low refractive index layer of the present disclosure is characterized in that it is obtained by coating the dispersion of the present disclosure and drying it. The layer obtained by coating the dispersion of the present disclosure and drying it as necessary may be subjected to, for example, heating or light irradiation. By the heating or light irradiation, for example, particles of the condensate of the raw material containing the alkoxysilane can be crosslinked together directly or via the crosslinking auxiliary, thereby increasing strength.

[0050] The low refractive index layer of the present disclosure may be produced, for example, by applying the dispersion of the present disclosure to a substrate such as a film and drying it. The film may be, for example, a resin film. Generally, a relatively thin material is referred to as a "film" and a relatively thick material is referred to as a "sheet." However, in the present disclosure, no particular distinction is made between "film" and "sheet." The substrate is not particularly limited, and examples that can be used preferably include, but are not limited to, thermoplastic resin substrates, glass substrates, inorganic substrates such as silicon, plastics molded from thermosetting resins, semiconductor elements, and carbon fiber materials such as carbon nanotubes.

[0051] The method for producing the low refractive index layer of the present disclosure is not particularly limited, and the layer can be produced by, for example, a method similar to the method described in WO 2019 / 065999 or WO 2019 / 065803.

[0052] The low refractive index layer of the present disclosure may be, for example, a porous layer having voids. Alternatively, the low refractive index layer of the present disclosure may be, for example, a porous body in which microporous particles are chemically bonded to each other.

[0053] The low refractive index layer of the present disclosure may have a thickness of, for example, 500 nm or more, 700 nm or more, 800 nm or more, 1000 nm or more, nm or more, or 2000 nm or more; for example, 10,000 nm or less, 8,000 nm or less, 5,000 nm or less, 4,000 nm or less, or 3,000 nm or less; for example, 500 to 10,000 nm, 700 to 8,000 nm, 800 to 5,000 nm, 1000 to 4,000 nm, or 2,000 to 3,000 nm. The low refractive index layer of the present invention may have a porosity of, for example, 30 vol% or more, 35 vol% or more, 40 vol% or more, 45 vol% or more, or 50 vol% or more, and may have a porosity of, for example, 90 vol% or less, 80 vol% or less, 70 vol% or less, or 60 vol% or less, for example, 30 to 90 vol%, 35 to 80 vol%, 40 to 70 vol%, or 50 to 60 vol%. The low refractive index layer of the present invention may have a refractive index of, for example, 1.05 or more, 1.10 or more, or 1.13 or more, and may have a refractive index of, for example, 1.35 or less, 1.30 or less, or 1.25 or less, for example, 1.05 to 1.35, 1.10 to 1.30, or 1.13 to 1.25.

[0054] In the low refractive index layer of the present disclosure, the porosity can be measured by the following method.

[0055] (Method of measuring porosity) If the layer to be measured for porosity is a single layer containing only voids, the ratio (volume ratio) of the constituent material of the layer to air can be calculated by a standard method (for example, measuring the weight and volume to calculate the density), and the porosity (volume %) can be calculated from this. In addition, since there is a correlation between the refractive index and the porosity, the porosity can also be calculated from the refractive index value of the layer, for example. Specifically, the porosity is calculated from the refractive index value measured with an ellipsometer using the Lorentz-Lorenz's formula.

[0056] In the present disclosure, the refractive index of the low refractive index layer is a numerical value of the refractive index at a wavelength of 550 nm, measured and calculated by the following method.

[0057] (Method of measuring refractive index) After forming a low refractive index layer on a glass light guide plate, a prism coupler (manufactured by Metricon) is used to irradiate laser light (λ=407 nm) from the glass light guide plate side, and the refractive index at 407 nm is calculated from the measured value of the total reflection angle. Furthermore, from the wavelength dispersion of the low refractive index layer alone calculated separately using an ellipsometer (manufactured by J.A. Woollam), the measured value of the refractive index at 407 nm is converted to a refractive index at 550 nm, and the converted value is taken as the refractive index of the low refractive index layer.

[0058] The low refractive index layer of the present disclosure preferably has a thickness variation of, for example, 20% or less, 18% or less, 16% or less, 15% or less, or 10% or less. The lower limit is not particularly limited, but may be, for example, 0 or a value exceeding 0. The thickness variation is defined as the in-plane film thickness (thickness) variation of the low refractive index layer when the dispersion of the present disclosure is applied to a light guide plate made of glass or resin and having a surface roughness Rz of 50 nm or less, and the low refractive index layer has a refractive index of 1.25 or less, and is formed by spin coating. Note that, in the present disclosure, the in-plane film thickness (thickness) variation of the low refractive index layer is an index obtained by comparing the standard deviation of the film thickness measured at five points in the plane with the average film thickness.

[0059] [3. Optical Member and Optical Device] As described above, the optical member of the present disclosure is characterized by including the low refractive index layer of the present invention. The optical member of the present disclosure may or may not include components other than the low refractive index layer of the present invention.

[0060] The optical member of the present disclosure may be, for example, a laminate in which the low refractive index layer of the present invention is laminated on a substrate. The substrate is not particularly limited, but is, for example, as described above.

[0061] The optical member of the present disclosure may be, for example, a light guide plate with a low refractive index layer, in which the low refractive index layer of the present disclosure is laminated on a light guide plate. In this case, another layer such as an adhesive layer may be present between the light guide plate and the low refractive index layer of the present disclosure, but it is preferable that the low refractive index layer of the present disclosure is laminated directly on the light guide plate without any other layer interposed therebetween. In this case, for example, the dispersion of the present disclosure can be applied to the light guide plate and dried to produce the low refractive index layer of the present disclosure by the method described above.

[0062] The optical member of the present disclosure is not limited to a light guide plate, and may be, for example, a polarizing plate, a retardation film, a reflective polarizer, a brightness enhancement film, a diffusion film, a dye-containing layer, or a transparent or opaque layer or film having an optical function.

[0063] The optical device of the present disclosure is not particularly limited, and may be, for example, an image display device or a lighting device. Examples of image display devices include liquid crystal displays, organic electroluminescence (EL) displays, and micro-LED (light-emitting diode) displays. Examples of lighting devices include organic EL lighting.

[0064] Next, examples of the present disclosure will be described, but the present disclosure is not limited to the following examples.

[0065] In the following Reference Examples, Examples, and Comparative Examples, the number of parts (relative amount used) of each substance is in parts by mass (parts by weight) unless otherwise specified. In the following Reference Examples, Examples, and Comparative Examples, a pressure-sensitive adhesive (pressure-sensitive adhesive composition) described below was used as the pressure-sensitive adhesive. In the following Reference Examples, Examples, and Comparative Examples, the term "pressure-sensitive adhesive layer" corresponds to the term "pressure-sensitive adhesive layer." That is, in the following Reference Examples, Examples, and Comparative Examples, the terms "pressure-sensitive adhesive layer" and "pressure-sensitive adhesive layer" have the same meaning unless otherwise specified.

[0066] <Method for measuring concentration of coating liquid> The concentration of the total solid content (components other than the dispersion medium) in the coating liquid or the concentration (wt %) of particles of the condensate of raw materials containing alkoxysilane was calculated from the ratio of the weight (mass) of the total coating liquid weight (mass) to the weight (mass) of the total solid content in the coating liquid or the weight (mass) of particles of the condensate of raw materials containing alkoxysilane.

[0067] <Method for measuring viscosity of coating liquid> The viscosity of the coating liquid was measured at a measurement temperature of 25°C using an E-type viscometer with a 1° cone rotor.

[0068] <Method for Measuring Refractive Index> The refractive index was measured by the above-described method for measuring refractive index.

[0069] <Method of measuring particle size> The particle size D50 of the condensate of raw materials containing alkoxysilane was measured by the method described above. As described above, D50 is also called the median diameter, which is the particle diameter at the center of the particle distribution and corresponds to a cumulative frequency of 50%.

[0070] <Method of Measuring Film Thickness> The film thickness (thickness) and its variation of the low refractive index layer were measured as follows. The low refractive index layer formed on glass was measured for thickness at five points in the plane using a spectroscopic ellipsometer (manufactured by J.A. Woollam), and the average value and standard deviation were calculated. The ratio of this standard deviation to the average value was calculated, and this value was taken as the variation.

[0071] <Method for measuring haze value> A 100 mm x 100 mm laminate (void layer / glass substrate) was used as a measurement sample. The measurement sample was set in a spectroscopic haze meter (SH7000, manufactured by Nippon Denshoku Industries Co., Ltd.), and the haze value was measured. More specifically, the diffuse transmittance and total light transmittance were measured, and the haze value calculated from these values ​​using the following formula was used as the measured haze value: Haze value (%) = [Diffuse transmittance (%) / Total light transmittance (%)] x 100 (%)

[0072] Reference Example 1: Production of pulverized gel solution for forming low refractive index layer A pulverized gel solution (sol particle solution) for forming a low refractive index layer was produced as follows.

[0073] (1) Gelation of Silicon Compounds 9.5 kg of methyltrimethoxysilane (MTMS), a precursor of the silicon compound, was dissolved in 22 kg of dimethyl sulfoxide (DMSO) to prepare a mixed solution A. 5 kg of a 0.01 mol / L aqueous solution of oxalic acid was added to this mixed solution A, and the mixture was stirred at room temperature for 30 minutes to hydrolyze the MTMS, producing a mixed solution B containing tris(hydroxy)methylsilane.

[0074] To 55 kg of DMSO, 3.8 kg of 28 wt % aqueous ammonia and 2 kg of pure water were added, and then the above mixed solution B was further added and stirred at room temperature for 15 minutes to gel the tris(hydroxy)methylsilane, thereby obtaining mixed solution C containing a gel-like silicon compound.

[0075] (2) Aging Treatment The mixed solution C containing the gel-like silicon compound prepared as described above was poured into a stainless steel container measuring 30 cm x 30 cm x 5 cm, and incubated at 40°C for 20 hours to carry out an aging treatment.

[0076] (3) Pulverization Next, isobutyl alcohol, the substitution solvent, was poured onto the gel synthesized in the stainless steel container, and the cutting blade of the cutting tool was slowly inserted into the gel from above, and the gel was cut into a rectangular parallelepiped measuring 1.5 cm x 2 cm x 5 cm. The cut gel was transferred to another container, and while maintaining the shape of the gel, isobutyl alcohol was added in an amount four times the volume of the gel. After leaving it for 6 hours, solvent replacement was performed four times. The gel (gel-like silicon compound) was pulverized using a continuous emulsification and dispersion machine (manufactured by Pacific Machinery Co., Ltd., Milder MDN304 type) to obtain a coarse pulverization liquid. Further, a pulverization process was carried out under a pressure of 100 MPa using a high-pressure medialess pulverization machine (manufactured by Sugino Machine Co., Ltd., Starburst HJP-25005 type). In this way, an isobutyl alcohol dispersion (liquid containing pulverized gel) in which nanometer-sized particles (pulverized gel) were dispersed was obtained.

[0077] [Example 1] IBA (isobutyl alcohol) was added to the gel pulverized solution obtained in Reference Example 1 to adjust the concentration of condensate particles of raw materials containing alkoxysilane to 3.5 wt%. Next, this gel pulverized solution was subjected to nano-pulverization using Starburst (a trade name of Sugino Machine Co., Ltd.) under a high pressure of 150 MPa, adjusting the pulverization time so that the particle diameter D50 of the particles after pulverization was 190 nm, thereby obtaining a nano-pulverized solution containing 3.5 wt% of condensate particles of raw materials containing alkoxysilane (first pulverization step). Next, the solution was concentrated using Mitsubishi Dynafilter (DyF) (a trade name of Mitsubishi Kakoki Co., Ltd.) until the concentration of condensate particles of raw materials containing alkoxysilane was 6 wt% (concentration step). Next, nano-pulverization was performed again using the Starburst under a high pressure of 150 MPa, adjusting the pulverization time so that the particle diameter D50 of the particles after pulverization was 130 nm (second pulverization step). Thereafter, 0.24 g of bis(trimethoxysilyl)hexane as a crosslinking aid and 0.24 g of photobase catalyst WPBG-266 (Wako) were added to 100 g of the liquid, and IBA (isobutyl alcohol) was further added to adjust the solids concentration of the entire liquid to 4.2 wt % (the concentration of particles of the condensate of raw materials containing alkoxysilane was 3.86 wt %), thereby producing a dispersion liquid of the present disclosure. The dispersion liquid was formed into a film by spin coating, dried, and then subjected to a fluence of 350 mJ / cm ２ The particles of the condensate of the raw material containing alkoxysilane were crosslinked with each other by UV irradiation (at 360 nm), thereby producing the low refractive index layer of the present disclosure.

[0078] [Example 2] A dispersion liquid and a low refractive index layer of the present disclosure were produced in the same manner as in Example 1, except that the second grinding step was not performed and concentration adjustment and additive mixing were performed after the concentration step.

[0079] Example 3 A dispersion liquid and a low refractive index layer according to the present disclosure were produced by the same procedure as in Example 1, except that in the first grinding step, the grinding time was adjusted so that the particle diameter D50 of the particles after grinding was 80 nm, and in the second grinding step, the grinding time was adjusted so that the particle diameter D50 of the particles after grinding was 50 nm, and then the amount of IBA added was changed to adjust the solid content concentration of the entire liquid to 9.5 wt % (the concentration of particles of the condensate of raw materials containing alkoxysilane was 9.03 wt %).

[0080] Example 4 A dispersion liquid and a low refractive index layer according to the present disclosure were produced by the same procedure as in Example 1, except that in the first grinding step, the grinding time was adjusted so that the particle diameter D50 of the particles after grinding was 80 nm, and in the second grinding step, the grinding time was adjusted so that the particle diameter D50 of the particles after grinding was 65 nm, and then the amount of IBA added was changed to adjust the solid content concentration of the entire liquid to 8.0 wt % (the concentration of particles of the condensate of the raw materials containing alkoxysilane was 7.73 wt %).

[0081] [Comparative Example 1] The dispersion liquid and the low refractive index layer of this comparative example were produced by the same procedure as described in Example 1, except that the second grinding step was carried out without carrying out the concentration step and the film was formed as is.

[0082] [Comparative Example 2] The same operations as in Example 1 were performed up to the first grinding step, and then the concentration of particles of the condensate of the raw material containing alkoxysilane was concentrated to 15.1 wt% in the concentration step. As a result, the viscosity of the liquid began to increase immediately after the concentration step, and the viscosity of the liquid was too high to form a low refractive index layer. In addition, particle aggregation progressed during the liquid concentration adjustment and additive mixing steps, and it was not possible to control it within the range of the present disclosure.

[0083] The optical properties and film (low refractive index layer) appearance of the low refractive index layers produced in each of the Examples and Comparative Examples were evaluated using the methods described above. The evaluation results are summarized in Table 1 below. In Table 1 below, "coating liquid" refers to the dispersion of the present disclosure produced in each of the Examples or the dispersion of the Comparative Examples. "Coating liquid concentration" refers to the concentration of the total solid content in the dispersion of the present disclosure produced in each of the Examples or the dispersion of the Comparative Examples. "Particle concentration" refers to the concentration of siloxane condensate particles in the dispersion of the present disclosure produced in each of the Examples or the dispersion of the Comparative Examples. "Coating liquid viscosity" refers to the viscosity of the total solid content in the dispersion of the present disclosure produced in each of the Examples or the dispersion of the Comparative Examples. "Particle size D50 of coating liquid" refers to the particle size D50 of the siloxane condensate particles in the dispersion of the present disclosure produced in each of the Examples or the dispersion of the Comparative Examples. "Film refractive index" represents the refractive index of the low refractive index layer produced in each of the above examples and comparative examples. "Film thickness" represents the thickness of the low refractive index layer produced in each of the above examples and comparative examples. "Film thickness variation" represents the variation in thickness of the low refractive index layer produced in each of the above examples and comparative examples. "Haze" represents the haze value of the low refractive index layer produced in each of the above examples and comparative examples.

[0084]

[0085] As shown in Table 1, the dispersions (coating solutions) of the present disclosure produced in Examples 1 to 4 all ensured a sufficiently large film thickness and produced low-refractive-index layers with little film thickness variation (achieved in-plane film thickness uniformity). In contrast, the dispersion (coating solution) of Comparative Example 1 had too low a concentration, resulting in a small film thickness of the low-refractive-index layer. Furthermore, the dispersion (coating solution) of Comparative Example 2 had too high a concentration, resulting in a low-refractive-index layer not being formed.

[0086] Although the present disclosure has been described above with reference to embodiments and examples, the present disclosure is not limited to the above-described embodiments and examples. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0087] The present disclosure can be described, for example, as in the following supplementary notes: However, the supplementary notes below are examples, and the present disclosure is not limited to these forms.

[0088] (Appendix 1) A dispersion liquid having particles dispersed in a dispersion medium, wherein the particles are a condensate of raw materials including an alkoxysilane, the concentration of the particles in the dispersion liquid is 3.5 to 15 wt %, the viscosity of the dispersion liquid is 4 mPa·s or more and less than 5000 mPa·s, and the particle diameter D50 of the particles is 20 nm or more and 400 nm or less. (Appendix 2) The dispersion liquid according to Appendices 1, wherein the concentration of the particles in the dispersion liquid is 6.0 to 12.0 wt %, the viscosity of the dispersion liquid is 4 to 50 mPa·s, and the particle diameter D50 of the particles is 20 to 100 nm. (Appendix 3) A dispersion in which a solid content including particles is dispersed in a dispersion medium, wherein the particles are a condensation product of raw materials including an alkoxysilane, the concentration of the solid content in the dispersion is 3.5 to 15 wt %, the viscosity of the dispersion is 4 Pa·s or more and less than 5000 mPa·s, and the particle diameter D50 is 20 nm or more and 400 nm or less. (Appendix 4) The dispersion according to Appendices 3, wherein the concentration of the solid content in the dispersion is 6.0 to 12.0 wt %, the viscosity of the dispersion is 4 to 50 mPa·s, and the particle diameter D50 is 20 to 100 nm. (Appendix 5) The dispersion according to any one of Appendices 1 to 4, wherein the particles are pulverized products of the condensation product. (Appendix 6) The dispersion according to any one of Appendices 1 to 5, wherein the particles are a condensation product of raw materials including an alkoxysilane having three or less functional groups. (Appendix 7) A dispersion set comprising the dispersion according to any one of Appendices 1 to 6 and a catalyst-containing liquid containing a catalyst for chemically bonding the particles of the dispersion. (Appendix 8) A dispersion set according to Appendices 7, further comprising a crosslinking auxiliary-containing liquid containing a crosslinking auxiliary for indirectly bonding the particles together. (Appendix 9) A low refractive index layer obtained by coating and drying the dispersion according to any one of Appendices 1 to 6 or the dispersion set according to Appendices 7 or 8. (Appendix 10) An optical member comprising the low refractive index layer according to Appendices 9. (Appendix 11) An optical device comprising the optical member according to Appendices 10.(Appendix 12) A method for producing a low refractive index layer, comprising the steps of applying the dispersion according to any one of Appendices 1 to 6 or the dispersion set according to Appendices 7 or 8 onto a substrate, and drying the applied dispersion. (Appendix 13) A method for producing an optical member including a low refractive index layer, wherein the low refractive index layer is produced by the production method according to Appendices 12. (Appendix 14) A method for producing an optical device including an optical member, wherein the optical member is produced by the production method according to Appendices 13.

[0089] As described above, the present disclosure can provide a dispersion, a dispersion set, a low refractive index layer, an optical member, an optical device, a method for manufacturing a low refractive index layer, a method for manufacturing an optical member, and a method for manufacturing an optical device, which can ensure the film thickness of a low refractive index layer and achieve in-plane film thickness uniformity. The applications of the present disclosure are not particularly limited. For example, the optical device of the present disclosure is not particularly limited, and examples thereof include image display devices and lighting devices. Examples of the image display devices include liquid crystal displays, organic electroluminescence displays, and micro LED displays. Examples of the lighting devices include organic electroluminescence lighting.

[0090] This application claims priority based on Japanese Patent Application No. 2024-026037, filed on February 22, 2024, the disclosure of which is incorporated herein in its entirety by reference.

Claims

1. A dispersion liquid in which particles are dispersed in a dispersion medium, the particles are a condensation product of a raw material containing an alkoxysilane, the concentration of the particles in the dispersion is 3.5 to 15% by weight; The viscosity of the dispersion is 4 mPa s or more and less than 5000 mPa s, The dispersion liquid is characterized in that the particle diameter D50 of the particles is 20 nm or more and 400 nm or less.

2. the concentration of the particles in the dispersion is 6.0 to 12.0 wt %; The viscosity of the dispersion is 4 to 50 mPa s, The particle diameter D50 of the particles is 20 to 100 nm; The dispersion of claim 1.

3. 2. The dispersion according to claim 1, wherein the particles are pulverized products of the condensation product.

4. 2. The dispersion according to claim 1, wherein the particles are a condensation product of a raw material containing an alkoxysilane having three or less functional groups.

5. The dispersion liquid according to claim 1, wherein the dispersion medium is an organic solvent.

6. A dispersion set comprising: the dispersion according to claim 1; and a catalyst-containing liquid containing a catalyst for chemically bonding the particles of the dispersion.

7. 7. The dispersion set according to claim 6, further comprising a cross-linking aid-containing liquid containing a cross-linking aid for indirectly bonding the particles together.

8. A low refractive index layer obtained by coating the dispersion according to claim 1 or the dispersion set according to claim 6 and drying the coating.

9. An optical member comprising the low refractive index layer according to claim 8.

10. An optical device comprising the optical member according to claim 9.

11. 10. A method for producing a low refractive index layer, comprising the steps of: applying the dispersion according to claim 1 or the dispersion set according to claim 6 onto a substrate; and drying the applied dispersion.

12. A method for producing an optical member including a low refractive index layer, the method comprising producing the low refractive index layer by the method according to claim 11.

13. 13. A method for manufacturing an optical device including an optical member, the method comprising the steps of: manufacturing the optical member by the manufacturing method according to claim 12.