WO2025173560A1 - Coating liquid composition and method for manufacturing light control member using same - Google Patents

Abstract

This coating liquid composition for forming an optical thin film 12 on a base material 11 includes: fine particles; a binder precursor for supplying a binder for fixing the fine particles; and a solvent. The coating liquid composition satisfies at least one condition selected from the group consisting of conditions (i) to (iii). Condition (i): The ratio of the binder to the fine particles is 0.5 or more on a mass basis. Condition (ii): A fine particle adhesion inhibitor for suppressing close contact between the fine particles in the optical film is also contained. Condition (iii): A dispersant corresponding to at least one selected from the group consisting of an anionic polymer dispersant and a polymer dispersant is also contained.

Description

Coating liquid composition and method for producing light control member using same

The present invention relates to a coating liquid composition and further to a method for producing a light control member using the same.

Light control components comprising a substrate and an optical thin film are widely used. One example of an optical thin film is a low-reflection film that reduces reflected light from the substrate. Examples of substrates include cover glass, lenses, prisms, and transmissive diffractive optical elements. Light control components include, for example, glass plates with low-reflection coatings, lenses with low-reflection coatings, prisms with low-reflection coatings, and transmissive diffractive optical elements with low-reflection coatings.

To form an optical thin film, a coating liquid composition containing fine particles, a binder precursor, and a solvent is sometimes used. One example of the fine particles is silica fine particles. As for fine particles, in addition to solid fine particles, hollow fine particles with internal voids are also known. The binder is generated from the binder precursor, for example, by the sol-gel method, after the coating liquid composition is applied, and fixes the fine particles by binding them to each other in the film and further binding the fine particles to the substrate.

Patent Document 1 discloses a coating liquid composition containing hollow microparticles and a binder precursor as a coating liquid composition for forming a low-reflection film. In the examples of Patent Document 1, the ratio of binder to hollow microparticles is 0.39 by mass. As in this example, the microparticles that impart desired properties are blended in greater amounts than the binder, which acts as a reinforcing material. Note that in the examples of Patent Document 1, the coating liquid composition is applied by flow coating.

Japanese Patent Application Laid-Open No. 2023-177176

In addition to flow coating, other known methods for applying coating liquid compositions include spin coating, roll coating, and spray coating. The present inventors have newly discovered that optical thin films applied by spray coating are prone to developing micro-defects. One of the objects of the present invention is to provide a coating liquid composition that can suppress the development of micro-defects in optical thin films, even when applied by spray coating.

The present invention provides
A coating liquid composition for forming an optical thin film on a substrate, comprising:
a binder precursor that provides a binder for fixing the fine particles; and a solvent;
the ratio of the binder to the fine particles is 0.5 or more by mass;
A coating liquid composition is provided.

Also, from another aspect, the present invention provides:
A coating liquid composition for forming an optical thin film on a substrate, comprising:
a binder precursor that provides a binder for fixing the fine particles; and a solvent;
The optical thin film further contains a particle adhesion inhibitor that suppresses contact between the particles.
A coating liquid composition is provided.

Furthermore, from another aspect, the present invention provides:
A coating liquid composition for forming an optical thin film on a substrate, comprising:
a binder precursor that provides a binder for fixing the fine particles; and a solvent;
Further comprising at least one dispersant selected from the group consisting of anionic polymer dispersants and polymer dispersants.
A coating liquid composition is provided.

That is, the present invention is
A coating liquid composition for forming an optical thin film on a substrate, comprising:
a binder precursor that provides a binder for fixing the fine particles; and a solvent;
In the coating liquid composition, at least one selected from the group consisting of condition (i), condition (ii), and condition (iii) is satisfied.
A coating liquid composition is provided.
Here, the condition (i) is a condition that the ratio of the binder to the fine particles is 0.5 or more by mass, the condition (ii) is a condition that the optical thin film further contains a fine particle contact inhibitor that suppresses contact between the fine particles in the optical thin film, and the condition (iii) is a condition that the optical thin film further contains at least one dispersant selected from the group consisting of anionic polymer-type dispersants and polymer-type dispersants.

Furthermore, from another aspect, the present invention provides:
A method for producing a light control member, comprising applying a coating liquid composition onto a substrate to form an optical thin film on the substrate,
the coating liquid composition includes fine particles, a binder precursor that provides a binder that fixes the fine particles, and a solvent;
In the coating liquid composition, at least one selected from the group consisting of condition (i), condition (ii), and condition (iii) is satisfied,
Applying the coating liquid composition onto the substrate by spray coating;
A method for manufacturing a light control member is provided.
Here, the conditions (i), (ii) and (iii) are as described above.

From another aspect, the present invention provides
A method for producing a light control member, comprising applying a coating liquid composition onto a substrate to form an optical thin film on the substrate,
the coating liquid composition includes fine particles, a binder precursor that provides a binder that fixes the fine particles, and a solvent;
In the method for producing the coating liquid composition, the conditions (a) and (b) are satisfied,
Applying the coating liquid composition onto the substrate by spray coating;
A method for manufacturing a light control member is provided.
Here, the condition (a) is a condition that the ratio of the binder to the fine particles in the optical thin film is less than 0.5 by mass, and the condition (b) is a condition that, in the spray coating, the distance between the spray nozzle that discharges the coating liquid composition and the substrate is 25 mm or more and 35 mm or less.

The present invention provides a coating liquid composition that is suitable for suppressing the occurrence of micro-defects in optical thin films, even when applied by spray coating. It also provides a method for manufacturing a light control member that can suppress the occurrence of micro-defects even when spray coating is used to form an optical thin film.

FIG. 2 is a cross-sectional view showing an example of a light control member. FIG. 10 is a cross-sectional view showing another example of a light control member. 1 shows the results of observing the optical thin film of Example 2 with a microscope. 10 shows the results of observation under a microscope of examples of optical thin films prepared in the same manner as in Examples 3 to 14. 14 shows the observation results of the optical thin film of Example 15. 1 shows the results of observing an example of an optical thin film before plasma treatment using a scanning electron microscope (SEM). 10 shows the results of SEM observation of an example of an optical thin film after plasma treatment.

The following describes preferred embodiments of the present invention, but the following description is not intended to limit the present invention to any particular embodiment. In this specification, "optical thin film" refers to a film for adjusting the reflection and/or transmission of light. The "thin" in this term is not intended to limit the thickness of the film, but is added in consideration of the fact that "optical thin film" is more commonly used as a technical term than "optical film." The "micro" in "microparticle" is not used to limit the size of the "particle" to a specific range.

As used herein, "light control component" refers to a component that utilizes the properties of an optical thin film. A "particulate adhesion inhibitor" refers to a substance that inhibits the adhesion of fine particles in an optical thin film. However, a "particulate adhesion inhibitor" does not necessarily have to completely eliminate contact between fine particles; it is sufficient for it to mitigate the degree of adhesion. A "polymeric dispersant" refers to a dispersant with an average molecular weight of 2,000 or more. The lower average molecular weight standard than the general definition of a polymer is due to common usage in the dispersant technical field. Surfactants commonly used as leveling agents, etc., typically have an average molecular weight of less than 1,000, and at most less than 2,000. All average molecular weights expressed in this specification are weight-average molecular weights. Furthermore, the element "silicon (Si)" is treated as a type of metallic element, in accordance with common usage in technical fields where the sol-gel process is applied. The term "(meth)acrylic" encompasses both acrylic and methacrylic.

As used herein, "microdefects" refer to discolored areas with a maximum diameter exceeding 20 μm when observed in a magnified image using a microscope equipped with an objective lens with at least 20x optical magnification. Discolored areas may contain aggregates with a diameter of 1 μm to several μm. As shown in Figure 3, such discolored areas are locally different in color from the background color. The presence or absence of microdefects is evaluated, for example, by counting the number of discolored areas with a maximum diameter exceeding 20 μm within a rectangular area of 50 ^mm² . Such aggregation is presumably embodied as a phenomenon in which a liquid composition containing particles adheres to the surface of an object and dries while agglomerating the particles, resulting in a color difference from other areas. In spray coating, even if the liquid composition is sprayed only toward the coating target area (area A), due to the nature of spray coating, it is inevitable that the composition will also adhere to areas outside the spray target area (area B). This adhesion of the composition outside the spray target area (area B) is referred to as non-directed adhesion. For example, even if coating is directed toward area A, some of the composition adheres out of the intended direction to area B, and if coating is then performed directly toward area B before or after this, it is thought that local variations will occur in the drying of the composition, and the areas that have adhered out of the intended direction will cause the reflected light to show a different color when observed from other areas, and will be visible as discolored areas.

[Coating liquid composition]
In this embodiment, the coating liquid composition contains at least fine particles, a binder precursor, and a solvent. The coating liquid composition satisfies at least one of the following: (i) the ratio of binder to fine particles is 0.5 or more by mass, (ii) a fine particle adhesion inhibitor is further contained, and (iii) an anionic polymer dispersant and/or a polymer dispersant is further contained. Each material constituting the coating liquid composition will be described below.

(fine particles)
The fine particles may be inorganic or organic fine particles. Examples of inorganic fine particles include oxide fine particles and halide fine particles, particularly oxide fine particles. Examples of oxide fine particles include silica fine particles, alumina fine particles, zirconia fine particles, and titania fine particles. The oxide fine particles may contain oxides of multiple elements, such as aluminosilicate fine particles. Examples of halide fine particles include chloride fine particles and fluoride fine particles. Examples of fluoride fine particles include magnesium fluoride fine particles and calcium fluoride fine particles. The organic fine particles may be resin fine particles. Examples of resins contained in the resin fine particles include (meth)acrylic resins, styrene resins, and urethane resins. However, when a treatment such as plasma irradiation (plasma treatment) described below is applied to the film, it is desirable that the fine particles be inorganic fine particles.

The microparticles may be solid or hollow. The microparticles may include hollow microparticles. Hollow microparticles are advantageous for lowering the refractive index of optical thin films. The microparticles may include both solid and hollow microparticles. Hollow microparticles that are particularly desirable for lowering the refractive index are hollow silica microparticles and hollow magnesium fluoride microparticles. The microparticles may be hollow silica microparticles.

The average particle size of the microparticles is, for example, in the range of 10 to 300 nm, 10 to 200 nm, 10 to 150 nm, or in some cases 10 to 100 nm. The average particle size may be in the range of 15 to 100 nm, or even 20 to 100 nm, or 30 to 100 nm. The average particle size may be in the range of 30 to 80 nm. The average particle size of the microparticles can be measured using a transmission electron microscope or a scanning electron microscope. This measurement is performed by calculating the average maximum particle size of 50 randomly selected microparticles. The average particle size mentioned here is based on the so-called primary particle size.

(Binder and its precursor)
The binder functions to bind the particles to each other and to the underlying structure, such as the substrate. The binder fixes the particles in the optical thin film and improves the abrasion resistance of the film. The binder is added as a precursor to the coating liquid composition. The binder includes, for example, an oxide component, more specifically, a metal oxide component. The binder precursor that supplies the metal oxide component may be a metal alkoxide. The metal alkoxide provides the metal oxide component using a technique called the sol-gel method. For example, silicon alkoxide provides the silica component through a hydrolysis reaction and a condensation polymerization reaction. The metal alkoxide is not limited to silicon alkoxide, but may also be aluminum alkoxide, zirconium alkoxide, titanium alkoxide, niobium alkoxide, tantalum alkoxide, etc.

The binder may contain an organic component in addition to the metal oxide component. The organic component may be a component derived from a metal alkoxide, more specifically, a component derived from an organic group bonded to a metal atom constituting the metal alkoxide. That is, the binder may be an inorganic-organic composite containing a metal oxide component and an organic component. An inorganic-organic composite binder may be provided, for example, from a silicon alkoxide represented by the formula R ² _n Si(OR ¹ ) _4-n . Here, R ¹ is an alkyl group having 1 to 4 carbon atoms, R ² is an organic group that provides the organic component to the binder, and n is 1 or 2, particularly 1. R ² is not particularly limited and may be an aliphatic group or an aromatic group, or may contain a heteroatom. R ² may be a hydrocarbon group having 1 to 10 carbon atoms, particularly an alkyl group having 1 to 10 carbon atoms, or even 1 to 4 carbon atoms. Silicon alkoxides (trialkoxysilanes) in which n is 1 provide binders called silsesquioxanes.

The binder may be supplied from only one type of precursor, but can also be supplied from two or more types of precursors. One example of a combination of two types of precursors is an alkyltrialkoxysilane and a tetraalkoxysilane. Here, too, the number of carbon atoms in the alkyl group is not particularly limited; for example, the alkyl group contained in the alkoxy group has 1 to 4 carbon atoms, and for example, the alkyl group bonded to the silicon atom has 1 to 10 carbon atoms, particularly 1 to 4 carbon atoms. Tetraalkoxysilane corresponds to a compound in which n = 0 in the above general formula.

Metal alkoxides such as silicon alkoxides may be contained in the coating liquid composition as a hydrolysate. The hydrolysate may be a partial hydrolysate in which hydrolysis has progressed partially. The binder precursor may be a metal alkoxide or a hydrolysate thereof, in particular an alkoxysilane or a hydrolysate thereof.

(Fine particle to binder ratio)
In the following description, all binder to fine particle ratios are based on mass. This ratio is calculated based on the components supplied to the film, not the precursor. Therefore, for example, differences in ^R1 in the above general formula do not affect the ratio. The binder to fine particle ratio is preferably 0.5 or greater. This ratio may be 0.8 or greater, 1.0 or greater, 1.1 or greater, 1.2 or greater, 1.5 or greater, 1.7 or greater, or even 1.8 or greater. When a coating liquid composition with a high ratio is applied by spray coating, the resulting optical thin film is less likely to develop microdefects due to the aggregation of fine particles. The upper limit of this ratio is not particularly limited and may be 1,000 or less, particularly 100 or less. Examples of this ratio are 0.5 to 100, or 1.0 to 100 or less. However, when a fine particle adhesion inhibitor or dispersant is added, and when the spray nozzle discharge height is appropriately adjusted as described below, the binder to fine particle ratio may be 1 or less, less than 0.5, 0.3 or less, 0.2 or less, or even 0.1 or less. When a fine particle adhesion inhibitor or dispersant is added and when the discharge height of the spray nozzle is appropriately adjusted, this ratio may be 0.001 or more, 0.005 or more, 0.01 or more, or even 0.03 or more. When a fine particle adhesion inhibitor or dispersant is added and when the discharge height of the spray nozzle is appropriately adjusted, examples of this ratio are 0.001 or more and less than 0.5, 0.001 or more and 0.2 or less, or even 0.005 or more and 0.2 or less.

(Fine particle contact inhibitor)
It is desirable to add a fine particle adhesion inhibitor to the coating liquid composition.

The particle adhesion inhibitor may have a boiling point of, for example, 300°C or higher, or even 400°C or higher. The boiling point of the particle adhesion inhibitor is desirably higher than the curing temperature of the binder precursor. The curing temperature of the binder precursor is the maximum temperature in the heating process applied to produce the binder from the binder precursor. The particle adhesion inhibitor also desirably has a boiling point higher than that of the solvent. When the coating liquid composition contains multiple types of compounds as solvents, the particle adhesion inhibitor may have a boiling point higher than the boiling points of all of the compounds contained as solvents. When the coating liquid composition contains a first solvent and a second solvent, and the boiling point of the second solvent is higher than the boiling point of the first solvent, the boiling point of the particle adhesion inhibitor may be higher than the boiling point of the second solvent.

It is believed that controlling the evaporation of the liquid composition is important in suppressing micro-defects. In the above-described embodiment of the present invention, the liquid composition that is the precursor to the film has a boiling point or thermal decomposition temperature of 300°C or higher and contains a particle adhesion inhibitor that functions to suppress the aggregation of particle particles. After the liquid composition is applied to the surface of the substrate, when components other than solidifying components such as particles and binders are removed, it is desirable to remove the particle adhesion inhibitor relatively slowly in order to maintain the function of suppressing the aggregation of particle particles. In such cases, even when the liquid composition by non-directed deposition and the liquid composition by directed deposition are mixed, it is believed that the variation in evaporation of components other than solids is suppressed to an extent that aggregation is not noticeable or is suppressed.

The particle adhesion inhibitor may have a viscosity of, for example, 1000 mPa·s or more, 1200 mPa·s or more, 1400 mPa·s or more, 1600 mPa·s or more, or even 1800 mPa·s or more. When the coating liquid composition contains multiple compounds as solvents, the particle adhesion inhibitor may have a viscosity higher than the viscosity of all of the compounds contained as solvents. The relatively high viscosity of the particle adhesion inhibitor is particularly useful when applying the coating liquid composition to a curved surface. When the coating liquid composition contains a first solvent and a second solvent and the viscosity of the second solvent is higher than the viscosity of the first solvent, the viscosity of the particle adhesion inhibitor may be higher than the viscosity of the second solvent. Viscosity can be measured at room temperature (25°C) using a vibration viscometer (e.g., Sekonic Corporation, probe: PR-10L, controller: VM-10A). When the particle adhesion inhibitor contains a solvent, the viscosity is measured after removing the solvent.

The particulate adhesion inhibitor may be a polymer, particularly a thermoplastic polymer. The particulate adhesion inhibitor may also be a dispersant.

(Dispersant)
It is desirable to add at least one dispersant selected from the group consisting of anionic polymer dispersants and polymer dispersants to the coating liquid composition. The dispersant can function as a particulate adhesion inhibitor. The dispersant can have a boiling point as exemplified for the particulate adhesion inhibitor. The dispersant can have a viscosity as exemplified for the particulate adhesion inhibitor.

Anionic polymer dispersants have anionic groups, such as carboxylate and sulfonate groups. Furthermore, anionic polymer dispersants have a polymeric molecular structure, i.e., a molecular structure containing repeating units. Anionic polymer dispersants may be either homopolymers or copolymers. It is desirable for anionic polymer dispersants to have anionic groups in the repeating units.

Examples of anionic polymer dispersants include polyacrylates, polystyrene sulfonates, styrene-maleic anhydride copolymers, olefin-maleic anhydride copolymers, acrylamide-acrylate copolymers, alginates, and carboxymethylcellulose salts. Examples of salts include alkali metal salts such as sodium salts and potassium salts. Carboxylic acids derived from maleic anhydride can also exist as sodium salts, etc.

Polymer dispersants have an average molecular weight of 2000 or more, which is relatively larger than the low-molecular-weight dispersants that are general-purpose surfactants, and they act effectively on fine particles. The molecular weight of polymer dispersants may be 3000 or more, 4000 or more, 5000 or more, 6000 or more, 7000 or more, 8000 or more, 9000 or more, or even 10,000 or more. There is no particular upper limit to the molecular weight, but it is, for example, 200,000 or less, or even 100,000 or less. Polymer dispersants may be anionic, nonionic, or cationic, but anionic or nonionic dispersants are preferable.

Examples of anionic polymer dispersants are the same as those of anionic polymer dispersants. Examples of nonionic polymer dispersants include polyvinyl alcohol, polyethylene glycol, and polyacrylamide. Examples of cationic polymer dispersants include polyethyleneimine and polyvinylimidazoline.

(Amount of fine particle contact inhibitor, etc.)
The amount of the fine particle adhesion inhibitor or dispersant blended relative to the fine particles may be, on a mass basis, 0.4 or more, 0.5 or more, 1 or more, 2 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, or even 10 or more. The upper limit of this ratio is not particularly limited, and may be 1,000 or less, particularly 100 or less. Examples of this ratio are 0.4 to 100, 0.5 to 100, 1 to 100, 4 to 100, 6 to 100, 8 to 100, and even 10 to 100.

Like a binder, a particle adhesion inhibitor or dispersant can function to maintain the spacing between particles. When a particle adhesion inhibitor or dispersant is included, the ratio of the total amount of binder and particle adhesion inhibitor or dispersant to the particles is desirably 0.4 or greater. This ratio is also stated on a mass basis. This ratio may be 0.5 or greater, 0.8 or greater, 1.0 or greater, 1.1 or greater, 1.2 or greater, 1.5 or greater, 1.7 or greater, or even 1.8 or greater. There is no particular upper limit to this ratio, and it may be 1,000 or less, and in particular 100 or less. Examples of this ratio are 0.4 or greater and 100 or less, 0.5 or greater and 100 or less, and 1.0 or greater and 100 or less.

(solvent)
The solvent may be composed of a single type of solvent, but preferably contains two or more solvents with different boiling points. The solvent may include a first solvent and a second solvent, both of which are organic solvents, particularly polar organic solvents. The boiling point of the first solvent is suitably 70 to 150°C, 80 to 140°C, or even 90 to 130°C. The boiling point of the second solvent is suitably 150°C or higher (but not including 150°C), 165°C or higher, or particularly 170°C or higher. The boiling point of the second solvent may be 280°C or lower. An example of the boiling point of the second solvent is 150 to 280°C. When a particulate adhesion inhibitor or dispersant is included, the boiling point of the second solvent may be lower than the boiling point of the particulate adhesion inhibitor or dispersant.

The first and second solvents may be blended so that the ratio of the second solvent to the first solvent is less than 1, 0.8 or less, preferably 0.6 or less, and particularly 0.4 or less, by mass. The lower limit of this ratio may be 0.03 or more, 0.05 or more, or even 0.07 or more. This ratio is, for example, 0.03 or more and 0.8 or less, 0.05 or more and 0.5 or less, or even 0.07 or more and 0.4 or less. The total amount of solvent, expressed as a ratio to the solid content in the coating liquid composition, may be in the range of 10 to 50, or even 20 to 40, by mass. These ratios are particularly adjusted for coating liquid compositions to be applied to curved surfaces by spray coating.

It is advisable to select a combination of solvents with excellent compatibility as the first and second solvents. Such a combination can be easily achieved, for example, by using alkoxy group-containing alcohols as both the first and second solvents.

(Other ingredients)
The coating liquid composition may further contain a thickener, a thixotropy imparting agent, a surfactant, a crosslinking agent, a leveling agent, etc. The leveling agent is effective in improving the wetting of the fine particles. The coating liquid composition may further contain a surfactant. The surfactant is preferably one with a low molecular weight, specifically, an average molecular weight of less than 2000.

[Light control member and optical thin film]
FIG. 1 is a cross-sectional view showing an example of a light control member. The light control member 10 includes a base material 11 and an optical thin film 12 formed on the base material 11. The surface of the base material 11 on which the optical thin film 12 is formed is flat. The base material 11 is a substrate having two parallel surfaces as its main surfaces. The light control member 10 is, for example, a cover glass of an image display device. The optical thin film 12 is, for example, a low-reflection film.

Figure 2 is a cross-sectional view showing another example of a light control member. The light control member 20 includes a substrate 21 and an optical thin film 22 formed on the substrate 21. The surface of the substrate 21 on which the optical thin film 22 is formed is curved. The light control member 20 is, for example, a resin lens. The optical thin film 22 is, for example, a low-reflection film.

Optical thin films 12 and 22 may form a multilayer film together with other layers not shown. In this case, optical thin films 12 and 22 may form a multilayer optical interference film as layers having a predetermined thickness and refractive index. Optical thin films 12 and 22 may also be light-transmitting layers that transmit light while protecting underlying materials that have relatively low scratch resistance.

The light control member is not limited to the above, and can be any of a variety of optical members. Transparent materials such as glass and resin are desirable as materials for the substrate. Glass compositions and resin types known for use in light control members can also be used in this embodiment without particular restrictions.

The optical thin film on the light control member desirably includes an area where the number of microdefects per 50 ^mm2 is 5 or less, 3 or less, or even 1 or less, and particularly 0, in a planar view. It is more desirable that the optical thin film on the light control member has 5 or less, 3 or less, or even 1 or less, and particularly 0, microdefects per 50 ^mm2 in all areas in a planar view. The number of microdefects per 50 ^mm2 in the optical thin film can be obtained, for example, by using a metallurgical microscope, a confocal microscope (laser light source or white light source), or a stereomicroscope at 20 to 500 magnifications, and counting the number of discolored areas in the obtained image. The discolored areas that can be counted by the above counting method have a maximum diameter exceeding 20 μm. In detecting micro-defects, a confocal microscope equipped with an objective lens of at least 20x magnification may be used to detect and count the micro-defects, and in this case, the field of view projected on the observation monitor may be, for example, H×V=(500 μm to 1500 μm)×(500 μm to 1500 μm), where H is, for example, the horizontal direction (lateral direction) and V is, for example, the vertical direction (longitudinal direction).

The appropriate refractive index range for an optical thin film varies depending on the type of light control member, the type of substrate, the desired function of the optical thin film, and other factors. For example, for a single-layer low-reflection film formed directly on a substrate, the refractive index may be 1.4 or less, 1.38 or less, 1.35 or less, 1.3 or less, 1.25 or less, or even 1.2 or less in some cases. The lower limit of the refractive index is not particularly limited, but is, for example, 1.07 or more. The refractive index can be measured using the method described in the Examples section. The appropriate thickness of the optical thin film also varies depending on the factors mentioned above. For example, for a single-layer low-reflection film formed directly on a substrate, the refractive index may be 50 nm to 350 nm, or even 80 nm to 200 nm. Unless otherwise specified, the refractive index in this specification refers to the refractive index at a wavelength of 550 nm.

In the light control members 10 and 20, the substrates 11 and 21 and the optical thin films 12 and 22 are in direct contact with each other, but this is not limited to this and another film may be interposed between the substrate and the optical thin film. Furthermore, the surfaces of the optical thin films 12 and 22 are both exposed. However, this is not limited to this and the surface of the optical thin film may be covered with another layer. The optical thin film is not limited to the single layer shown in the figure, but may be one layer constituting a multilayer film. When it is one layer constituting a multilayer film, the function of the optical thin film to adjust the reflection and/or transmission of light is exerted in cooperation with the other layers constituting the multilayer film.

[Method of manufacturing light control member]
The coating liquid composition of this embodiment can be subjected to various coating processes, but is suitable for application by spray coating. In view of this, the method for producing a light control member of this embodiment includes applying the above-mentioned coating liquid composition onto a substrate by spray coating. Spray coating is a well-known coating process in which the coating liquid composition is sprayed from a spray nozzle.

Optical thin films formed by spray coating using a coating liquid composition containing microparticles, a binder precursor, and a solvent are more likely to develop microdefects than optical thin films formed by other coating processes. One cause of this is thought to be the adhesion of microparticle aggregates. By using the above-mentioned coating liquid composition, the occurrence of microdefects is reduced and, in some cases, eliminated. Spray coating itself is a coating method that is highly suitable for mass production and can be used on curved surfaces, and is also a coating process that can continuously form films on multiple substrates. The manufacturing method of this embodiment is highly useful in that it enables the quality of optical thin films to be improved by spray coating.

The spray nozzle used in the coating process may be a one-fluid spray nozzle that discharges a fluid consisting of the coating liquid composition, or a two-fluid spray nozzle that discharges a mixed fluid of a carrier gas such as air and the coating liquid composition. When a two-fluid spray nozzle is used, the two-fluid spray nozzle may be a normal two-fluid spray nozzle that generates a linear flow of the mixed fluid, or a two-fluid spray nozzle that generates a swirling flow of the mixed fluid. An example of a two-fluid spray nozzle that generates a swirling flow of the mixed fluid is a two-fluid spray nozzle that uses an annular liquid film atomization method.

The application form of the coating liquid composition in spray coating is not particularly limited. Spray coating is performed, for example, by positioning the substrate so that the surface to which the coating liquid composition is to be applied (the application surface) is horizontal, and by positioning the spray nozzle vertically above the application surface of the substrate so that the overall fluid flow containing the coating liquid composition is directed vertically downward. The distance between the spray nozzle outlet and the application surface of the substrate (spray nozzle discharge height) is preferably 25 mm to 35 mm, and more preferably 28 mm to 32 mm. When using such a spray nozzle discharge height, the flow rate of the coating liquid composition discharged from the spray nozzle is preferably 0.1 ml/min to 0.3 ml/min, and even more preferably 0.15 ml/min to 0.25 ml/min. When using such a spray nozzle discharge height, the coating liquid composition may or may not contain a particulate adhesion inhibitor or dispersant. When using a two-fluid spray nozzle, the flow rate of the liquid composition is determined by setting the supply air flow rate to 0, spraying and recovering only the liquid composition for 10 minutes, measuring the volume, and calculating the amount sprayed per unit time (1 minute).

That is, the method for manufacturing a light control member of this embodiment may satisfy the following conditions (a) and (b).
Condition (a): In the optical thin film, the ratio of binder to fine particles is less than 0.5 by mass.
Condition (b): In the spray coating, the distance between the spray nozzle for discharging the coating liquid composition and the substrate is 25 mm or more and 35 mm or less.

In the method for manufacturing a light control member of this embodiment, in addition to the above conditions (a) and (b), the following condition (c) may also be satisfied.
Condition (c): The flow rate of the coating liquid composition discharged from the spray nozzle is 0.1 ml/min or more and 0.3 ml/min or less.

In the manufacturing method for a light control member of this embodiment, the spray nozzle may be a two-fluid spray nozzle, specifically a two-fluid spray nozzle that generates a swirling flow of mixed fluid, and more specifically a two-fluid spray nozzle that uses an annular liquid film atomization method.

The manufacturing method for a light control member of this embodiment can be applied to both the manufacturing of a single light control member and the continuous manufacturing of multiple light control members. When manufacturing multiple light control members continuously, one example is a manufacturing method in which multiple substrates are continuously transported at predetermined intervals along the transport direction, and a coating liquid composition is ejected onto the substrates by spray coating. The multiple substrates may be arranged in a single row or multiple rows along the transport direction.

In the coating liquid composition applied to the substrate, a binder is generated from the binder precursor, forming an optical thin film. The particulate adhesion inhibitor or dispersant contained in the formed optical thin film may then be at least partially removed. Specifically, the particulate adhesion inhibitor or dispersant can be removed by various treatments of the optical thin film. Examples of such treatments include plasma treatment, corona treatment, UV cleaning, high-temperature treatment, organic cleaning, acid cleaning, and alkali cleaning. Plasma treatment can be performed by irradiating the optical thin film with an oxidizing active species, such as oxygen plasma.

As described above, the present embodiment provides the following techniques.
(Technology 1)
A coating liquid composition for forming an optical thin film on a substrate, comprising:
a binder precursor that provides a binder for fixing the fine particles; and a solvent;
the ratio of the binder to the fine particles is 0.5 or more by mass;
Coating liquid composition.

(Technology 2)
The coating liquid composition of Technology 1, wherein the ratio is 1.2 or more by mass.

(Technology 3)
A coating liquid composition for forming an optical thin film on a substrate, comprising:
a binder precursor that provides a binder for fixing the fine particles; and a solvent;
The optical thin film further contains a particle adhesion inhibitor that inhibits the particles from adhering to each other.
Coating liquid composition.

(Technology 4)
The coating liquid composition of Technology 3, wherein the fine particle adhesion inhibitor has a boiling point of 300°C or higher.

(Technology 5)
5. The coating liquid composition according to claim 3, wherein the fine particle adhesion inhibitor has a boiling point higher than that of the solvent.

(Technology 6)
6. The coating liquid composition according to any one of techniques 3 to 5, wherein the fine particle adhesion inhibitor has a higher viscosity than the solvent.

(Technology 7)
7. The coating liquid composition of any one of techniques 3 to 6, wherein the particulate adhesion inhibitor is a thermoplastic polymer.

(Technology 8)
A coating liquid composition for forming an optical thin film on a substrate, comprising:
a binder precursor that provides a binder for fixing the fine particles; and a solvent;
Further comprising at least one dispersant selected from the group consisting of anionic polymer dispersants and polymer dispersants.
Coating liquid composition.

(Technology 9)
9. The coating liquid composition according to claim 8, wherein the anionic polymer dispersant contains an anionic group in a repeating unit.

(Technology 10)
10. The coating liquid composition according to any one of techniques 3 to 9, wherein the ratio of the total amount of the binder and the fine particle adhesion inhibitor or the dispersant to the fine particles is 0.4 or more by mass.

(Technology 11)
11. The coating liquid composition according to any one of techniques 3 to 10, wherein the ratio of the fine particle adhesion inhibitor or the dispersant to the fine particles is 0.4 or more by mass.

(Technology 12)
12. The coating liquid composition according to any one of techniques 1 to 11, wherein the fine particles include hollow fine particles.

(Technology 13)
13. The coating liquid composition according to any one of claims 1 to 12, wherein the precursor comprises at least one selected from the group consisting of alkoxysilanes and hydrolysates of alkoxysilanes.

(Technology 14)
14. The coating liquid composition according to any one of techniques 1 to 13, which is a liquid composition for spray coating.

(Technology 15)
the solvent includes a first solvent and a second solvent,
15. The coating liquid composition according to any one of claims 1 to 14, wherein the boiling point of the second solvent is higher than the boiling point of the first solvent.

(Technology 16)
16. The coating liquid composition of claim 15, wherein the ratio of the second solvent to the first solvent is 0.8 or less by mass.

(Technology 17)
A method for producing a light control member, comprising applying a coating liquid composition onto a substrate to form an optical thin film on the substrate,
the coating liquid composition includes fine particles, a binder precursor that provides a binder that fixes the fine particles, and a solvent;
In the coating liquid composition, at least one selected from the group consisting of condition (i), condition (ii), and condition (iii) is satisfied,
Applying the coating liquid composition onto the substrate by spray coating;
A method for manufacturing a light control member.
Here, the condition (i) is a condition that the ratio of the binder to the fine particles is 0.5 or more by mass, the condition (ii) is a condition that the optical thin film further contains a fine particle adhesion inhibitor that inhibits the fine particles in the optical thin film from coming into direct close contact with each other, and the condition (iii) is a condition that the optical thin film further contains at least one dispersant selected from the group consisting of anionic polymer-type dispersants and polymer-type dispersants.

(Technology 18)
In the coating liquid composition, at least the condition (ii) or the condition (iii) is satisfied,
18. The method for manufacturing a light control member according to Art. 17, further comprising: performing a process for removing at least a part of the particle close contact suppressant or the dispersant from the optical thin film.

(Technology 19)
19. The method for manufacturing a light control member according to claim 18, wherein the treatment includes plasma irradiation.

(Technology 20)
20. The method for manufacturing a light control member according to any one of techniques 17 to 19, wherein the optical thin film is a low-reflection film having a refractive index of 1.4 or less.

(Technology 21)
21. The method for manufacturing a light control member according to claim 20, wherein the optical thin film is a low-reflection film having a refractive index of 1.2 or less.

(Technology 22)
22. The method for producing a light control member according to any one of techniques 17 to 21, wherein the substrate has a curved surface, and the coating liquid composition is applied to the curved surface.

(Technology 23)
A method for producing a light control member, comprising applying a coating liquid composition onto a substrate to form an optical thin film on the substrate,
the coating liquid composition includes fine particles, a binder precursor that provides a binder that fixes the fine particles, and a solvent;
In the method for producing the coating liquid composition, the conditions (a) and (b) are satisfied,
Applying the coating liquid composition onto the substrate by spray coating;
A method for manufacturing a light control member.
Here, the condition (a) is a condition that the ratio of the binder to the fine particles in the optical thin film is less than 0.5 by mass, and the condition (b) is a condition that, in the spray coating, the distance between the spray nozzle that discharges the coating liquid composition and the substrate is 25 mm or more and 35 mm or less.

(Technology 24)
24. The method for producing a light control member according to Art. 23, wherein the method for producing the coating liquid composition further satisfies condition (c).
Here, the condition (c) is a condition that the flow rate of the coating liquid composition discharged from the spray nozzle is 0.1 ml/min or more and 0.3 ml/min or less.

(Technology 25)
25. The method for manufacturing a light control member according to claim 23 or 24, wherein the spray nozzle is a two-fluid spray nozzle.

(Technology 26)
The method for manufacturing a light control member according to Technology 25, wherein the two-fluid spray nozzle is a two-fluid spray nozzle that generates a swirling flow of a mixed fluid of the coating liquid composition and a carrier gas.

(Technology 27)
The two-fluid spray nozzle is a two-fluid spray nozzle of an annular liquid film atomization type, and the manufacturing method of the light control member of technology 26.

(Technology 28)
An optical thin film on a light control member,
The composition includes fine particles and a binder that fixes the fine particles,
the ratio of the binder to the particulates is less than 0.5 by weight;
When the optical thin film is observed at a magnification of 20 to 500 times, the optical thin film includes a region in which there are 5 or less microdefects per 50 ^mm2 of observation area.
Optical thin film.

(Technology 29)
An optical thin film on a light control member,
The composition includes fine particles and a binder that fixes the fine particles,
the ratio of the binder to the fine particles is 0.5 or more by mass;
Optical thin film.

(Technology 30)
An optical thin film on a light control member,
The composition includes fine particles and a binder that fixes the fine particles,
The optical thin film further contains a particle adhesion inhibitor that inhibits the particles from adhering to each other.
Optical thin film.

(Technology 31)
An optical thin film on a light control member,
The composition includes fine particles and a binder that fixes the fine particles,
Further comprising at least one dispersant selected from the group consisting of anionic polymer dispersants and polymer dispersants.
Optical thin film.

[Examples 1 to 15]
(Film formation)
A binder mixture was prepared by mixing tetraalkoxysilane (TEOS), methyltriethoxysilane (MTES), and 0.3% formic acid in a mass ratio of 8.7:3.7:7.6. This mixture was mixed with fine particles, a dispersant, a leveling agent, a low-boiling solvent, and a high-boiling solvent to obtain a coating liquid composition. The coating liquid composition was prepared by mixing the raw materials in the mass ratio shown in Table 1 and the resulting film in the mass ratio shown in Table 2. In Table 2, the binder precursors TEOS and MTES are expressed as binders, i.e., converted to _SiO2 and _{CH3SiO1.5 ,} respectively.

The coating liquid composition was then applied to the surface of the glass plate by spray coating. A two-fluid spray nozzle with a circular liquid film atomization method (manufactured by Shimada Appli LLC) was used as the spray nozzle for spray coating. The glass plate with the coating liquid composition applied was then allowed to air dry for 10 minutes, and then heated in an oven set to 200°C for 10 minutes to obtain a low-reflection film as an optical thin film. The film thickness of the formed low-reflection film was in the range of 50 nm to 350 nm. The raw materials used are as follows:

Fine particles: hollow silica fine particles, Balloonsil (registered trademark) Nano (manufactured by Toyoda Chemical Industries, Ltd., average particle size 40 nm)
Binder precursor 1: tetraalkoxysilane (TEOS), ethyl orthosilicate (manufactured by Tama Chemicals Co., Ltd.)
Binder precursor 2: methyltriethoxysilane (MTES), KBE-13 (manufactured by Shin-Etsu Silicones Co., Ltd.)
Fine particle contact inhibitor (dispersant) A-L below:
A: Polyethylene glycol 400 (manufactured by Fujifilm Wako)
B: Polyethylene glycol 600 (manufactured by Fujifilm Wako)
C: Polyethylene glycol 1000 (manufactured by Fujifilm Wako)
D: Styrene-maleic anhydride copolymer BYK-2013 (manufactured by BYK)
E: Solution of block copolymer having basic pigment affinity group BYK-2150 (manufactured by BYK)
F: Hyperbranched polyester BYK-2152 (manufactured by BYK)
G: Acrylic polymer Polyflow No. 36 (manufactured by Kyoeisha Chemical Co., Ltd.)
H: Acrylic polymer Polyflow No. 99C (manufactured by Kyoeisha Chemical Co., Ltd.)
I: Acrylic copolymer FLOWLEN DOPA-35 (manufactured by Kyoeisha Chemical Co., Ltd.)
J: Mixture of nonionic surfactant and polycarboxylic acid, FLOWLEN DOPA-100 (Kyoeisha Chemical Co., Ltd.)
K: Polycarboxylic acid Florene G-700 (Kyoeisha Chemical Co., Ltd.)
L: Modified carboxylic acid-containing copolymer, FLOWLEN G-1500 (manufactured by Kyoeisha Chemical Co., Ltd.)
Low boiling point solvent: 1M2P (1-methoxy-2-propanol), boiling point 120°C (manufactured by Tokyo Chemical Industry Co., Ltd.)
High boiling point solvent: 3M3M1B (3-methoxy-3-methyl-1-butanol), boiling point 174°C (manufactured by Tokyo Chemical Industry Co., Ltd.)
Leveling agent: Polyether-modified silicone, KP-341 (manufactured by Shin-Etsu Silicones Co., Ltd.)

In all of Examples 1 to 15, the spray coating conditions were A among the following conditions A to D.
<Coating Condition A>
Discharge height of spray nozzle: 60 mm, flow rate of coating liquid composition: 0.2 ml/min.
<Coating Condition B>
Discharge height of spray nozzle: 30 mm, flow rate of coating liquid composition: 0.2 ml/min.
<Coating Condition C>
Discharge height of spray nozzle: 10 mm, flow rate of coating liquid composition: 0.2 ml/min.
<Coating Condition D>
Discharge height of spray nozzle: 30 mm, flow rate of coating liquid composition: 0.4 ml/min.

Note that at least the average molecular weight of the above D, F, K, and L is equivalent to 2000 or more. Also, KP-341 (polyether-modified silicone) is a surfactant suitable as a leveling agent, and its average molecular weight is equivalent to less than 2000.

(Measurement of refractive index)
The refractive index was measured for films formed in the same manner as above for Examples 1 to 15, except that the substrate was a silicon wafer. To measure the refractive index, an Olympus USPM was used to measure the spectral reflectance of the film in the visible light range, and the refractive index was obtained by fitting the film structure by simulation using optical film design software (TFCalc, manufactured by Hulinks Co., Ltd.) from this spectral reflectance data. For the films obtained in Examples 3 to 14, plasma treatment was applied under the following conditions, and the refractive index was measured before and after treatment.

Plasma Treatment The substrate on which the film was formed was set in the chamber of a vacuum plasma device (PIB-20 manufactured by Vacuum Device Co., Ltd.), and after evacuation, the film surface was plasma-treated by discharging for 90 seconds at an argon:oxygen flow ratio of 1:1, atmospheric pressure of 50 Pa, and discharge current of 30 mA.

(Measurement of defects)
For Examples 1 to 15, films using a cycloolefin resin lens as a substrate were prepared in the same manner as described above, and the number of defects was measured. The films were formed on the concave surface of the lens. The number of defects was measured by counting the number of defects in an image obtained using a confocal microscope (Lasertec Corporation, OPTELICS HYBRID L7 laser microscope; xenon white light source; objective lens magnification = ×20; field of view range H × V = 750 μm × 750 μm (monitor observation magnification = 370x)). The observation area under the stereo microscope was 50 ^mm2 . The measurement results for Example 2 are shown in Figure 3, one of the measurement results for Examples 3 to 14 is shown in Figure 4, and the measurement results for Example 15 is shown in Figure 5.

In Examples 3 to 14, the occurrence of defects was suppressed. The decrease in refractive index due to plasma treatment in Examples 3 to 14 sometimes reached 0.1 or more. For example, a film with a refractive index of 1.27 became a film with a refractive index of 1.16 after plasma treatment. Even after plasma treatment, the number of defects in Examples 3 to 14 remained substantially the same. On the other hand, in Example 15, where the binder/fine particle ratio was appropriately adjusted, the occurrence of defects was eliminated.

The changes in the films of Examples 3 to 14 before and after plasma treatment were observed using an SEM. Examples are shown in Figure 6 (before treatment) and Figure 7 (after treatment). It can be seen that an increase in voids in the film resulted in a decrease in the refractive index.

[Examples 16 to 18]
(Film formation)
The spray coating conditions were as shown in Table 3. In Examples 16 to 18, low-reflection films were formed from the coating liquid compositions in the same manner as in Example 2, except that the spray coating conditions were set to any one of B to D.

For Examples 16 to 18, refractive index and defect measurements were carried out in the same manner as for Examples 1 to 15. Furthermore, color unevenness was observed using the following methods.

(Check for color unevenness)
When measuring defects, the obtained image was visually inspected to check for color unevenness in the optical thin film, and the case where no color unevenness was observed was marked with ◯, and the case where color unevenness was observed was marked with ×.

In Examples 17 and 18, where the spray nozzle discharge height was appropriately adjusted, the occurrence of defects was suppressed. In Example 18, where the flow rate of the coating liquid composition was also appropriately adjusted, no color unevenness occurred. In Example 17, where the flow rate of the coating liquid composition was not appropriately adjusted, the optical thin film was formed thicker in the central part of the concave surface of the substrate (concave lens) than in other parts, resulting in color unevenness. On the other hand, in Examples 2 and 16, where the spray nozzle discharge height was not appropriately adjusted, the occurrence of defects could not be suppressed. Note that color unevenness did not occur in Examples 1 to 15.

Claims (22)

A coating liquid composition for forming an optical thin film on a substrate, comprising:
a binder precursor that provides a binder for fixing the fine particles; and a solvent;
the ratio of the binder to the fine particles is 0.5 or more by mass;
Coating liquid composition. The coating liquid composition according to claim 1, wherein the ratio is 1.2 or greater by mass. A coating liquid composition for forming an optical thin film on a substrate, comprising:
a binder precursor that provides a binder for fixing the fine particles; and a solvent;
The optical thin film further contains a particle adhesion inhibitor that inhibits the particles from adhering to each other.
Coating liquid composition. The coating liquid composition according to claim 3, wherein the fine particle adhesion inhibitor has a boiling point of 300°C or higher. The coating liquid composition according to claim 3, wherein the fine particle adhesion inhibitor has a boiling point higher than that of the solvent. The coating liquid composition according to claim 3, wherein the particle adhesion inhibitor has a higher viscosity than the solvent. The coating liquid composition according to claim 3, wherein the particulate adhesion inhibitor is a thermoplastic polymer. A coating liquid composition for forming an optical thin film on a substrate, comprising:
a binder precursor that provides a binder for fixing the fine particles; and a solvent;
Further comprising at least one dispersant selected from the group consisting of anionic polymer dispersants and polymer dispersants.
Coating liquid composition. The coating liquid composition according to claim 8, wherein the anionic polymer dispersant contains an anionic group in the repeating unit. The coating liquid composition according to claim 3 or 8, wherein the ratio of the total amount of the binder and the particle adhesion inhibitor or the dispersant to the amount of the particles is 0.4 or more by mass. The coating liquid composition according to claim 3 or 8, wherein the ratio of the microparticle adhesion inhibitor or the dispersant to the microparticles is 0.4 or more by mass. The coating liquid composition according to any one of claims 1, 3, and 8, wherein the microparticles include hollow microparticles. The coating liquid composition according to any one of claims 1, 3, and 8, wherein the precursor comprises at least one selected from the group consisting of alkoxysilanes and hydrolysates of alkoxysilanes. The coating liquid composition according to any one of claims 1, 3, and 8, which is a liquid composition for spray coating. the solvent includes a first solvent and a second solvent,
The coating liquid composition according to claim 1 , wherein the boiling point of the second solvent is higher than the boiling point of the first solvent. The coating liquid composition according to claim 15, wherein the ratio of the second solvent to the first solvent is 0.8 or less by mass. A method for producing a light control member, comprising applying a coating liquid composition onto a substrate to form an optical thin film on the substrate,
the coating liquid composition includes fine particles, a binder precursor that provides a binder that fixes the fine particles, and a solvent;
In the coating liquid composition, at least one selected from the group consisting of condition (i), condition (ii), and condition (iii) is satisfied,
Applying the coating liquid composition onto the substrate by spray coating;
A method for manufacturing a light control member.
Here, the condition (i) is a condition that the ratio of the binder to the fine particles is 0.5 or more by mass, the condition (ii) is a condition that the optical thin film further contains a fine particle contact inhibitor that suppresses contact between the fine particles in the optical thin film, and the condition (iii) is a condition that the optical thin film further contains at least one dispersant selected from the group consisting of anionic polymer-type dispersants and polymer-type dispersants. In the coating liquid composition, at least the condition (ii) or the condition (iii) is satisfied,
The method for manufacturing a light control member according to claim 17 , further comprising carrying out a process for removing at least a part of the particle contact suppressant or the dispersant from the optical thin film. The method for manufacturing a light control member according to claim 18, wherein the treatment includes plasma exposure. The method for manufacturing a light control member described in claim 17, wherein the optical thin film is a low-reflection film having a refractive index of 1.4 or less. The method for manufacturing a light control member described in claim 20, wherein the optical thin film is a low-reflection film having a refractive index of 1.2 or less. The method for manufacturing a light control member described in claim 17, wherein the substrate has a curved surface and the coating liquid composition is applied to the curved surface.