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

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

[0001] The present invention relates to a coating liquid composition, and further to a method for producing a light control member using the same.

[0002] Light control members 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 transmission-type diffractive optical elements. Examples of light control members include glass plates with low-reflection coatings, lenses with low-reflection coatings, prisms with low-reflection coatings, and transmission-type diffractive optical elements with low-reflection coatings.

[0003] To form an optical thin film, a coating liquid composition containing fine particles, a binder precursor, and a solvent is sometimes used. An example of the fine particles is silica fine particles. As fine particles, not only solid fine particles but also hollow fine particles having voids inside are known. The binder is generated from the binder precursor by, for example, a sol-gel method after applying the coating liquid composition, and fixes the fine particles by binding them to each other in the film and further binding the fine particles to the substrate.

[0004] Patent Document 1 discloses a coating liquid composition containing hollow fine particles 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 fine particles is 0.39 by mass. As in this example, the fine particles for imparting desired properties are blended in greater amounts than the binder, which is a reinforcing material. In the examples of Patent Document 1, the coating liquid composition is applied by flow coating.

[0005] Japanese Patent Application Laid-Open No. 2023-177176

[0006] In addition to flow coating, known methods for applying a coating liquid composition include spin coating, roll coating, spray coating, etc. The present inventors have newly discovered that optical thin films applied by spray coating are prone to microdefects. One object of the present invention is to provide a coating liquid composition that can suppress the occurrence of microdefects in optical thin films even when applied by spray coating.

[0007] The present invention provides a coating liquid composition for forming an optical thin film on a substrate, the coating liquid composition comprising: fine particles; a binder precursor that provides a binder that fixes the fine particles; and a solvent, wherein the ratio of the binder to the fine particles is 0.5 or more by mass.

[0008] In addition, from another aspect, the present invention provides a coating liquid composition for forming an optical thin film on a substrate, the coating liquid composition comprising: fine particles; a binder precursor that supplies a binder that fixes the fine particles; and a solvent; and further comprising a fine particle contact inhibitor that inhibits contact between the fine particles in the optical thin film.

[0009] Furthermore, from another aspect, the present invention provides a coating liquid composition for forming an optical thin film on a substrate, the coating liquid composition comprising: fine particles; a binder precursor that provides a binder for fixing the fine particles; and a solvent; and the coating liquid composition further comprises at least one dispersant selected from the group consisting of an anionic polymer-type dispersant and a polymer-type dispersant.

[0010] That is, the present invention provides a coating liquid composition for forming an optical thin film on a substrate, comprising: fine particles; a binder precursor that provides a binder that fixes the fine particles; and a solvent, wherein the coating liquid composition satisfies at least one condition selected from the group consisting of condition (i), condition (ii), and condition (iii). Here, condition (i) is a condition that the ratio of the binder to the fine particles is 0.5 or more by mass, condition (ii) is a condition that the coating liquid composition further contains a fine particle adhesion inhibitor that suppresses contact between the fine particles in the optical thin film, and condition (iii) is a condition that the coating liquid composition further contains at least one dispersant selected from the group consisting of an anionic polymer dispersant and a polymer dispersant.

[0011] Furthermore, from another aspect, the present invention provides a method for producing a light controlling member, comprising applying a coating liquid composition onto a substrate to form an optical thin film on the substrate, wherein the coating liquid composition comprises fine particles, a binder precursor that provides a binder for fixing the fine particles, and a solvent, and the coating liquid composition satisfies at least one selected from the group consisting of condition (i), condition (ii), and condition (iii), and the coating liquid composition is applied onto the substrate by spray coating, wherein condition (i), condition (ii), and condition (iii) are as described above.

[0012] From another aspect, the present invention provides a method for producing a light controlling member, comprising applying a coating liquid composition onto a substrate to form an optical thin film on the substrate, wherein the coating liquid composition comprises fine particles, a binder precursor that provides a binder that fixes the fine particles, and a solvent, and wherein the method for producing the coating liquid composition satisfies conditions (a) and (b), and the coating liquid composition is applied to the substrate by spray coating. Here, condition (a) is a condition that in the optical thin film, the ratio of the binder to the fine particles is less than 0.5 by mass, and condition (b) is a condition that in the spray coating, the distance between a spray nozzle that ejects the coating liquid composition and the substrate is 25 mm or more and 35 mm or less.

[0013] According to the present invention, there is provided a coating liquid composition suitable for suppressing the occurrence of microdefects in an optical thin film even when the composition is applied by spray coating, and a method for producing a light control member that can suppress the occurrence of microdefects while applying spray coating to form an optical thin film.

[0014] 1 is a cross-sectional view showing an example of a light control member; FIG. 2 is a cross-sectional view showing another example of a light control member; FIG. 3 is a result of microscopic observation of the optical thin film of Example 2; FIG. 4 is a result of microscopic observation of examples of optical thin films prepared in the same manner as in Examples 3 to 14; FIG. 5 is a result of observation of the optical thin film of Example 15; FIG. 6 is a result of observation of an example of an optical thin film before plasma treatment with a scanning electron microscope (SEM); FIG. 7 is a result of observation of an example of an optical thin film after plasma treatment with a SEM.

[0015] Preferred embodiments of the present invention will be described below, 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 common than "optical film" as a technical term. The "fine" in "fine particle" is not used to limit the size of the "particle" to a particular range.

[0016] In this specification, "light control component" refers to a component that utilizes the properties of an optical thin film. "Particulate adhesion inhibitor" refers to a substance that inhibits the adhesion of particulates in an optical thin film. However, a "particulate adhesion inhibitor" does not necessarily have to completely eliminate contact between particulates; it is sufficient for it to mitigate the degree of adhesion. "Polymer dispersant" refers to a dispersant with an average molecular weight of 2000 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 1000, and at most less than 2000. All references to average molecular weight 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. "(Meth)acrylic" encompasses both acrylic and methacrylic.

[0017] In this specification, "microdefects" refers 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 an optical magnification of at least 20 times. Discolored areas may contain aggregates with a diameter of about 1 μm to several μm. As shown in Figure 3, such discolored areas are recognized as having a locally different color compared to the background color. The evaluation of whether there are many or few microdefects is carried out using a 50 mm 2This is done by counting the number of discolored areas with a maximum diameter exceeding 20 μm present within a rectangular area. It is presumed that this aggregation is embodied as a phenomenon in which a liquid composition containing particles adheres to the surface of an object and dries while the particles aggregate, resulting in a difference in color 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 to areas outside the spray target area (area B) is called misalignment. For example, even if coating is directed toward area A, if some of the composition adheres misaligned to area B, and then coating is directed exactly toward area B immediately before or after that, it is presumed that local variations in the drying of the composition will occur, and the misaligned areas will cause a difference in color of reflected light when observed from other areas, and will be visually recognized as discolored areas.

[0018] [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.

[0019] (Fine Particles) The fine particles may be inorganic fine particles 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.

[0020] The fine particles may be solid or hollow. The fine particles may include hollow fine particles. Hollow fine particles are advantageous for lowering the refractive index of optical thin films. The fine particles may include both solid and hollow fine particles. Hollow fine particles that are particularly desirable for lowering the refractive index are hollow silica fine particles and hollow magnesium fluoride fine particles. The fine particles may be hollow silica fine particles.

[0021] 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, further 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 value of the maximum particle size of each of 50 randomly selected microparticles. The average particle size described here is based on the so-called primary particle size.

[0022] (Binder and its precursor) The binder functions to bind fine particles to each other and to the underlying structure of the substrate, etc. The binder fixes fine 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.

[0023] The binder may contain an organic component together with a 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. The binder that is an inorganic-organic composite may be, for example, R 2 n Si(OR 1 ) 4-n where R 1 is an alkyl group having 1 to 4 carbon atoms, and R 2 is an organic group that provides an organic component to the binder, and n is 1 or 2, especially 1. 2 is not particularly limited, and may be an aliphatic group or an aromatic group, and may contain a heteroatom. 2 may be a hydrocarbon group having 1 to 10 carbon atoms, particularly an alkyl group having 1 to 10 carbon atoms, and more particularly an alkyl group having 1 to 4 carbon atoms. Silicon alkoxides (trialkoxysilanes) in which n is 1 provide binders called silsesquioxanes.

[0024] The binder may be supplied from only one precursor, or from two or more precursors. An example of a combination of two precursors is an alkyltrialkoxysilane and a tetraalkoxysilane. Again, the number of carbon atoms in the alkyl group is not particularly limited, and the alkyl group contained in the alkoxy group may have, for example, 1 to 4 carbon atoms, while the alkyl group bonded to the silicon atom may have, for example, 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.

[0025] The metal alkoxide such as silicon alkoxide may be contained in the coating liquid composition as a hydrolyzate. The hydrolyzate may be a partial hydrolyzate in which hydrolysis has progressed partially. The binder precursor may be a metal alkoxide or a hydrolyzate thereof, particularly an alkoxysilane or a hydrolyzate thereof.

[0026] (Ratio of Fine Particles to Binder) In the following description, the ratio of binder to fine particles is always based on mass. This ratio is calculated based on the components supplied to the film, not the precursor. Therefore, for example, R in the above general formula 1The difference in the binder to fine particle ratio does not affect the ratio. The binder to fine particle ratio is preferably 0.5 or more. This ratio may be 0.8 or more, 1.0 or more, 1.1 or more, 1.2 or more, 1.5 or more, 1.7 or more, or even 1.8 or more. When a coating liquid composition with a high ratio is applied by spray coating, the resulting optical thin film is less likely to suffer from micro-defects due to 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 or more and 100 or less, and 1.0 or more and 100 or less. However, when a fine particle adhesion inhibitor or dispersant is added, and when the discharge height of the spray nozzle 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 in some cases 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.

[0027] (Particle Adhesion Inhibitor) It is desirable to add a particle adhesion inhibitor to the coating liquid composition.

[0028] The particulate 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 particulate adhesion inhibitor is desirably higher than the curing temperature of the binder precursor. The curing temperature of the binder precursor is the highest temperature in the heating process applied to produce the binder from the binder precursor. Furthermore, the particulate adhesion inhibitor desirably has a boiling point higher than that of the solvent. When the coating liquid composition contains multiple types of compounds as solvents, the particulate 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 that of the first solvent, the boiling point of the particulate adhesion inhibitor may be higher than the boiling point of the second solvent.

[0029] 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, which is a film precursor, has a boiling point or thermal decomposition temperature of 300°C or higher and contains a particle adhesion inhibitor that inhibits the aggregation of particle particles. After the liquid composition is applied to the surface of the substrate, when components other than the 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 inhibiting the aggregation of particle particles. In such a case, it is believed that even when the liquid composition by non-directed adhesion and the liquid composition by directed adhesion are mixed, the variation in evaporation of components other than solid matter is suppressed to an extent that aggregation is not noticeable or aggregation is suppressed.

[0030] The particulate 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 particulate adhesion inhibitor may have a viscosity higher than the viscosity of all of the compounds contained as solvents. The relatively high viscosity of the particulate 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 particulate adhesion inhibitor may be higher than the viscosity of the second solvent. The viscosity can be measured at room temperature (25°C) using a vibration viscometer (e.g., manufactured by Sekonic Corporation, probe: PR-10L, controller: VM-10A). When the particulate adhesion inhibitor contains a solvent, the viscosity measurement is performed after removing the solvent.

[0031] The particulate adhesion inhibitor may be a polymer, especially a thermoplastic polymer. The particulate adhesion inhibitor may be a dispersant.

[0032] (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 the boiling point exemplified for the particulate adhesion inhibitor. The dispersant can have the viscosity exemplified for the particulate adhesion inhibitor.

[0033] The anionic polymer dispersant has an anionic group, such as a carboxylate group or a sulfonate group. The anionic polymer dispersant has a polymeric molecular structure, i.e., a molecular structure containing repeating units. The anionic polymer dispersant may be a homopolymer or a copolymer. It is desirable that the anionic polymer dispersant have an anionic group in the repeating unit.

[0034] 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 the salts include alkali metal salts such as sodium salts and potassium salts. Carboxylic acids derived from maleic anhydride may also exist as sodium salts.

[0035] The polymer dispersant has an average molecular weight of 2000 or more, which is relatively larger than the low-molecular-weight dispersants that are general-purpose surfactants, and acts effectively on fine particles. The molecular weight of the polymer dispersant 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. The upper limit of the molecular weight is not particularly limited, but is, for example, 200,000 or less, or even 100,000 or less. The polymer dispersant may be anionic, nonionic, or cationic, but is preferably anionic or nonionic.

[0036] 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.

[0037] (Amount of fine particle adhesion inhibitor, etc.) The amount of fine particle adhesion inhibitor or dispersant added may be 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 by mass relative to the 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 0.4 or more and 100 or less, 0.5 or more and 100 or less, 1 or more and 100 or less, 4 or more and 100 or less, 6 or more and 100 or less, 8 or more and 100 or less, and further 10 or more and 100 or less.

[0038] The particle adhesion inhibitor or dispersant, like the binder, can maintain the spacing between particles. When the particle adhesion inhibitor or dispersant is included, the ratio of the total amount of the binder and the particle adhesion inhibitor or dispersant to the particle is desirably 0.4 or more. This ratio is also expressed on a mass basis. This ratio may be 0.5 or more, 0.8 or more, 1.0 or more, 1.1 or more, 1.2 or more, 1.5 or more, 1.7 or more, or even 1.8 or more. The upper limit of this ratio is not particularly limited and may be 1000 or less, particularly 100 or less. Examples of this ratio are 0.4 or more and 100 or less, 0.5 or more and 100 or less, and 1.0 or more and 100 or less.

[0039] (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 contain 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.

[0040] 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 preferably 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 may be, 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.

[0041] It is preferable to select a combination of solvents with excellent compatibility as the first and second solvents, which can be easily achieved, for example, by using alkoxy group-containing alcohols as both the first and second solvents.

[0042] (Other Components) 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.

[0043] [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 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.

[0044] 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.

[0045] The optical thin films 12 and 22 may form a multilayer film together with other layers (not shown). In this case, the optical thin films 12 and 22 may form a multilayer optical interference film as layers having a predetermined thickness and refractive index. The optical thin films 12 and 22 may be light-transmitting layers that transmit light while protecting underlying materials that have relatively low scratch resistance.

[0046] The light control member is not limited to the above and may be various optical members. Transparent materials such as glass and resin are desirable as materials for the substrate. Glass compositions and resin types known for light control members can be used in this embodiment without any particular restrictions.

[0047] The optical thin film on the light control member is 50 mm thick in plan view. 2 It is desirable that the optical thin film on the light control member includes an area where the number of micro defects per unit area is 5 or less, 3 or less, or even 1 or less, and particularly 0. 2 It is more desirable that the number of micro-defects per 50 mm in an optical thin film is 5 or less, 3 or less, or even 1 or less, and particularly 0. 2The number of micro-defects per unit area can be obtained by, for example, counting the number of discolored areas in the image obtained using a 20-500x magnification metallurgical microscope, a confocal microscope (laser light source or white light source), or a stereo microscope. Discolored areas that can be counted using the above counting method have a maximum diameter of more than 20 μm. Micro-defect detection and counting may be performed using a confocal microscope equipped with an objective lens with a nominal magnification of at least 20x. 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). Here, H is, for example, the horizontal direction (transverse direction), and V is, for example, the vertical direction (longitudinal direction).

[0048] The appropriate refractive index range of the optical thin film varies depending on the type of light control member, the type of substrate, the function required 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. Here, the refractive index can be measured by the method described in the Examples section. The appropriate thickness of the optical thin film also varies depending on the above-mentioned factors. 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. In this specification, unless otherwise specified, the refractive index refers to the refractive index at a wavelength of 550 nm.

[0049] 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 substrates and the optical thin films. Furthermore, the surfaces of the optical thin films 12 and 22 are both exposed. However, this is not limited to this and the surfaces of the optical thin films may be covered with another layer. The optical thin films are not limited to the single-layer film shown in the figures and may be one layer constituting a multilayer film. When the optical thin film is one layer constituting a multilayer film, the function of adjusting the reflection and / or transmission of light is exerted in cooperation with the other layers constituting the multilayer film.

[0050] [Method for manufacturing a 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 manufacturing 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.

[0051] Optical thin films formed by spray coating using a coating liquid composition containing fine particles, a binder precursor, and a solvent are more susceptible to micro-defects than optical thin films formed by other coating processes. One cause of this is presumably the adhesion of aggregates of fine particles. By using the above-described coating liquid composition, the occurrence of micro-defects is reduced and, in some cases, eliminated. Spray coating itself is a coating method that is highly suitable for mass production and can be applied to 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 improvement of the quality of optical thin films produced by spray coating.

[0052] The spray nozzle used in the coating process may be a one-fluid spray nozzle that discharges a fluid consisting of a coating liquid composition, or may be 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 may be 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.

[0053] The application form of the coating liquid composition in spray coating is not particularly limited. Spray coating is performed, for example, by positioning a substrate so that the surface to which the coating liquid composition is to be applied (coating surface) is horizontal, and by positioning a spray nozzle vertically above the coating surface of the substrate so that the overall fluid flow containing the coating liquid composition is directed vertically downward. The distance between the outlet of the spray nozzle and the coating surface of the substrate (spray nozzle discharge height) is preferably 25 mm or more and 35 mm or less, and more preferably 28 mm or more and 32 mm or less. 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 or more and 0.3 ml / min or less, and even more preferably 0.15 ml / min or more and 0.25 ml / min or less. When using such a spray nozzle discharge height, the coating liquid composition may or may not contain a particle adhesion inhibitor or dispersant. When a two-fluid spray nozzle is used, the flow rate of the liquid composition is determined by setting the flow rate of the supply air to 0, spraying and recovering only the liquid composition for 10 minutes, measuring the volume, and calculating the amount of liquid composition sprayed per unit time (1 minute).

[0054] 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 that discharges the coating liquid composition and the substrate is 25 mm or more and 35 mm or less.

[0055] In addition to the above-described conditions (a) and (b), the method for producing a light control member of this embodiment may also satisfy the following condition (c): Condition (c): The flow rate of the coating liquid composition ejected from the spray nozzle is 0.1 ml / min or more and 0.3 ml / min or less.

[0056] In the manufacturing method of the 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 a mixed fluid, more specifically a two-fluid spray nozzle that uses an annular liquid film atomization method.

[0057] The manufacturing method of the light control member of this embodiment can be applied to the manufacturing of only one light control member or the manufacturing of multiple light control members in succession. The manufacturing method of multiple light control members in succession includes a manufacturing method in which a coating liquid composition is spray-coated onto multiple substrates while the substrates are continuously conveyed at predetermined intervals along the conveyance direction. The multiple substrates may be arranged in a single row or multiple rows along the conveyance direction.

[0058] In the coating liquid composition applied to the substrate, a binder is generated from the binder precursor, and an optical thin film is formed. 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.

[0059] 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, the coating liquid composition comprising: fine particles, a binder precursor that provides a binder that fixes the fine particles, and a solvent, wherein the ratio of the binder to the fine particles is 0.5 or more by mass.

[0060] (Technology 2) The coating liquid composition according to Technology 1, wherein the ratio is 1.2 or more on a mass basis.

[0061] (Technology 3) A coating liquid composition for forming an optical thin film on a substrate, comprising: fine particles; a binder precursor that provides a binder for fixing the fine particles; and a solvent; and further comprising a fine particle adhesion inhibitor that inhibits the fine particles from adhering to each other in the optical thin film.

[0062] (Technology 4) The coating liquid composition according to Technology 3, wherein the fine particle adhesion inhibitor has a boiling point of 300°C or higher.

[0063] (Technology 5) The coating liquid composition according to Technology 3 or 4, wherein the fine particle adhesion inhibitor has a boiling point higher than that of the solvent.

[0064] (Technology 6) The coating liquid composition according to any one of Technologies 3 to 5, wherein the fine particle adhesion inhibitor has a higher viscosity than the solvent.

[0065] (Technology 7) The coating liquid composition according to any one of technologies 3 to 6, wherein the particulate adhesion inhibitor is a thermoplastic polymer.

[0066] (Technology 8) A coating liquid composition for forming an optical thin film on a substrate, comprising: fine particles; a binder precursor that provides a binder that fixes the fine particles; and a solvent; and further comprising at least one dispersant selected from the group consisting of an anionic polymer-type dispersant and a polymer-type dispersant.

[0067] (Technology 9) The coating liquid composition according to Technology 8, wherein the anionic polymer dispersant contains an anionic group in the repeating unit.

[0068] (Technology 10) The coating liquid composition according to any one of Technologies 3 to 9, 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.

[0069] (Technology 11) The coating liquid composition according to any one of technologies 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.

[0070] (Technology 12) The coating liquid composition according to any one of technologies 1 to 11, wherein the fine particles include hollow fine particles.

[0071] (Technology 13) The coating liquid composition according to any one of techniques 1 to 12, wherein the precursor comprises at least one selected from the group consisting of alkoxysilanes and hydrolysates of alkoxysilanes.

[0072] (Technology 14) The coating liquid composition according to any one of Technologies 1 to 13, which is a liquid composition for spray coating.

[0073] (Technology 15) The coating liquid composition according to any one of technologies 1 to 14, wherein the solvent includes 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.

[0074] (Technology 16) The coating liquid composition according to Technology 15, wherein the ratio of the second solvent to the first solvent is 0.8 or less by mass.

[0075] (Technology 17) A method for manufacturing a light control member, comprising applying a coating liquid composition onto a substrate to form an optical thin film on the substrate, wherein the coating liquid composition comprises fine particles, a binder precursor that provides a binder that fixes the fine particles, and a solvent, and wherein the coating liquid composition satisfies at least one selected from the group consisting of condition (i), condition (ii), and condition (iii), and wherein the coating liquid composition is applied to the substrate by spray coating. Here, condition (i) is a condition that the ratio of the binder to the fine particles is 0.5 or more by mass, condition (ii) is a condition that the optical thin film further contains a fine particle contact inhibitor that inhibits fine particles in the optical thin film from coming into direct and close contact with each other, and condition (iii) is a condition that the optical thin film further contains at least one dispersant selected from the group consisting of an anionic polymer dispersant and a polymer dispersant.

[0076] (Technology 18) The method for producing a light control member according to Technology 17, wherein at least the condition (ii) or the condition (iii) is satisfied in the coating liquid composition, and the method further comprises carrying out a treatment for removing at least a part of the fine particle close contact suppressor or the dispersant from the optical thin film.

[0077] (Technology 19) The method for manufacturing a light control member of technology 18, wherein the treatment includes plasma irradiation.

[0078] (Technology 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.

[0079] (Technology 21) The method for manufacturing a light control member according to Technology 20, wherein the optical thin film is a low-reflection film having a refractive index of 1.2 or less.

[0080] (Technology 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.

[0081] (Technology 23) A method for manufacturing a light control member, comprising applying a coating liquid composition onto a substrate to form an optical thin film on the substrate, wherein the coating liquid composition comprises fine particles, a binder precursor that provides a binder that fixes the fine particles, and a solvent, and wherein condition (a) and condition (b) are met in the method for manufacturing the coating liquid composition, and the coating liquid composition is applied to the substrate by spray coating. Here, condition (a) is a condition that in the optical thin film, the ratio of the binder to the fine particles is less than 0.5 by mass, and condition (b) is a condition that in the spray coating, the distance between a spray nozzle that ejects the coating liquid composition and the substrate is 25 mm or more and 35 mm or less.

[0082] (Technology 24) The method for producing a light control member according to Technology 23, wherein the method for producing the coating liquid composition further satisfies condition (c), wherein 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.

[0083] (Technology 25) The method for manufacturing a light control member according to Technology 23 or 24, wherein the spray nozzle is a two-fluid spray nozzle.

[0084] (Technology 26) The method for producing 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.

[0085] (Technology 27) The method for manufacturing a light control member according to Technology 26, wherein the two-fluid spray nozzle is a two-fluid spray nozzle of an annular liquid film atomization type.

[0086] (Technology 28) An optical thin film on a light control member, comprising: fine particles; and a binder for fixing the fine particles; wherein the ratio of the binder to the fine particles is less than 0.5 by mass; and when the optical thin film is observed at a magnification of 20 to 500 times, the optical thin film has an observation area of ​​50 mm 2 An optical thin film comprising an area having five or fewer micro-defects per area.

[0087] (Technology 29) An optical thin film on a light control member, comprising: fine particles; and a binder that fixes the fine particles; wherein the ratio of the binder to the fine particles is 0.5 or more by mass.

[0088] (Technology 30) An optical thin film on a light control member, comprising: fine particles; and a binder for fixing the fine particles; and further comprising a fine particle adhesion inhibitor for suppressing the fine particles from adhering to each other in the optical thin film.

[0089] (Technology 31) An optical thin film on a light control member, comprising: fine particles; and a binder that fixes the fine particles; and further comprising at least one dispersant selected from the group consisting of an anionic polymer dispersant and a polymer dispersant.

[0090] [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 point solvent, and a high-boiling point solvent to obtain a coating liquid composition. The coating liquid composition was prepared by mixing raw materials in the mass ratio shown in Table 1, and the film to be formed was mixed in the mass ratio shown in Table 2. In Table 2, the binder precursors TEOS and MTES were used as binders, i.e., SiO2 and CH3SiO, respectively. 1.5 is converted and displayed.

[0091] Next, the coating liquid composition was applied to the surface of the glass plate by spray coating. A two-fluid spray nozzle with a circular liquid film atomization system (manufactured by Shimada Appli LLC) was used as the spray nozzle for spray coating. Subsequently, the glass plate to which the coating liquid composition had been applied was naturally dried for 10 minutes, and then heated in an oven set at 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.

[0092] ・Fine particles: hollow silica fine particles, Balloonsil (registered trademark) Nano (manufactured by Toyoda Chemical Industries, average particle size 40 nm) ・Binder precursor 1: tetraalkoxysilane (TEOS), orthosilicate ethyl (manufactured by Tama Chemical Industries, 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 Fuji Film Wako) B: polyethylene glycol 600 (manufactured by Fuji Film Wako) C: polyethylene glycol 1000 (manufactured by Fuji Film 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 (Kyoeisha Chemical) H: Acrylic polymer Polyflow No. 99C (Kyoeisha Chemical) I: Acrylic copolymer Flowlen DOPA-35 (Kyoeisha Chemical) J: Mixture of nonionic surfactant and polycarboxylic acid Flowlen DOPA-100 (Kyoeisha Chemical) K: Polycarboxylic acid Flowlen G-700 (Kyoeisha Chemical) L: Modified carboxylic acid-containing copolymer Flowlen G-1500 (Kyoeisha Chemical) Low boiling point solvent: 1M2P (1-methoxy-2-propanol), boiling point 120°C (Tokyo Chemical Industry Co., Ltd.) High boiling point solvent: 3M3M1B (3-methoxy-3-methyl-1-butanol), boiling point 174°C (Tokyo Chemical Industry Co., Ltd.) Leveling agent: Polyether-modified silicone, KP-341 (Shin-Etsu Silicone Co., Ltd.)

[0093] For Examples 1 to 15, the application conditions for spray coating were all set to A out of the following application conditions A to D. <Application condition A> Spray nozzle discharge height: 60 mm, flow rate of coating liquid composition: 0.2 ml / min. <Application condition B> Spray nozzle discharge height: 30 mm, flow rate of coating liquid composition: 0.2 ml / min. <Application condition C> Spray nozzle discharge height: 10 mm, flow rate of coating liquid composition: 0.2 ml / min. <Application condition D> Spray nozzle discharge height: 30 mm, flow rate of coating liquid composition: 0.4 ml / min.

[0094] At least the average molecular weight of the above D, F, K, and L is equivalent to 2000 or more. KP-341 (polyether-modified silicone) is a surfactant suitable as a leveling agent, and its average molecular weight is equivalent to less than 2000.

[0095]

[0096]

[0097] (Measurement of refractive index) The refractive index was measured for the 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 the treatment.

[0098] 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.

[0099] (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 film was formed on the concave surface of the lens. The number of defects was measured by counting the number of defects in an image obtained with a confocal microscope (laser microscope OPTELICS HYBRID L7 manufactured by Lasertec Corporation; xenon white light source; objective lens magnification = ×20; field of view range H × V = 750 μm × 750 μm (observation magnification on monitor = 370 times)). The observation area with the stereo microscope was 50 mm 2 The measurement result for Example 2 is shown in FIG. 3, one of the measurement results for Examples 3 to 14 is shown in FIG. 4, and the measurement result for Example 15 is shown in FIG.

[0100] In Examples 3 to 14, the occurrence of defects could be 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 was substantially the same. On the other hand, in Example 15, in which the binder / fine particle ratio was appropriately adjusted, the occurrence of defects could be eliminated.

[0101] The changes before and after plasma treatment of the films of Examples 3 to 14 were observed using an SEM. An example is 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.

[0102] [Examples 16 to 18] (Formation of film) As shown in Table 3, the application conditions of spray coating were changed to any one of B to D in Examples 16 to 18, and low-reflection films were formed from the coating liquid compositions in the same manner as in Example 2.

[0103]

[0104] For Examples 16 to 18, the refractive index and defects were measured in the same manner as in Examples 1 to 15. Furthermore, color unevenness was observed as follows.

[0105] (Confirmation of the Presence or Absence of Color Unevenness) When measuring defects, color unevenness of the optical thin film was confirmed by visual inspection of the obtained image, and the case where color unevenness was not observed was marked with ◯, and the case where color unevenness was observed was marked with ×.

[0106]

[0107] In Examples 17 and 18, in which the discharge height of the spray nozzle was appropriately adjusted, the occurrence of defects was suppressed. In Example 18, in which the flow rate of the coating liquid composition was also appropriately adjusted, color unevenness did not occur. In Example 17, in which 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, in which the discharge height of the spray nozzle 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

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

2. The coating liquid composition according to claim 1, wherein the ratio is 1.2 or more on a mass basis.

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

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

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.

6. The coating liquid composition according to claim 3, wherein the fine particle adhesion suppressant has a higher viscosity than the solvent.

7. The coating liquid composition according to claim 3, wherein the particulate adhesion inhibitor is a thermoplastic polymer.

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

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

10. The coating liquid composition according to claim 3 or 8, wherein the ratio of the total amount of the binder and the agent for suppressing adhesion of fine particles or the dispersant to the fine particles is 0.4 or more by mass.

11. The coating liquid composition according to claim 3 or 8, wherein the ratio of the fine particle adhesion inhibitor or the dispersant to the fine particles is 0.4 or more by mass.

12. The coating liquid composition according to any one of claims 1, 3 and 8, wherein the fine particles include hollow fine particles.

13. 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.

14. The coating liquid composition according to any one of claims 1, 3 and 8, which is a liquid composition for spray coating.

15. The coating liquid composition according to any one of claims 1, 3 and 8, wherein the solvent comprises 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.

16. 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.

17. A method for manufacturing a light control member, comprising applying a coating liquid composition onto a substrate to form an optical thin film on the substrate, wherein the coating liquid composition contains microparticles, a binder precursor that provides a binder for fixing the microparticles, and a solvent, and wherein the coating liquid composition satisfies at least one condition selected from the group consisting of condition (i), condition (ii), and condition (iii), and wherein the coating liquid composition is applied to the substrate by spray coating. Here, condition (i) is a condition that the ratio of the binder to the microparticles is 0.5 or more by mass, condition (ii) is a condition that the optical thin film further contains a microparticle adhesion inhibitor that suppresses contact between the microparticles, and condition (iii) is a condition that the optical thin film further contains at least one dispersant selected from the group consisting of anionic polymer dispersants and polymer dispersants.

18. A method for producing a light control member as described in claim 17, wherein at least the condition (ii) or the condition (iii) is satisfied in the coating liquid composition, and the method further comprises carrying out a process for removing at least a portion of the fine particle adhesion suppressant or the dispersant from the optical thin film.

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

20. The method for manufacturing a light control member according to claim 17, wherein the optical thin film is a low-reflection film having a refractive index of 1.4 or less.

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.

22. The method for producing a light control member according to claim 17, wherein the substrate has a curved surface, and the coating liquid composition is applied to the curved surface.

Images