KR102237333B1 - Liquid composition for forming low-refractive film - Google Patents

Abstract

This low-refractive-index film-forming liquid composition comprises a hydrolyzate of silicon alkoxide produced by adding and stirring a mixture of water and nitric acid to an alcohol solution of tetramethoxysilane or tetraethoxysilane as a silicon alkoxide, and a beaded colo. It is prepared by mixing silica sol in which silica particles are dispersed in a liquid medium, and further mixing an organic solvent of glycol ether. The glycol ether is a solvent having a flash point of 140°C or more and 160°C or less.

Description

Liquid composition for forming a low refractive index film {LIQUID COMPOSITION FOR FORMING LOW-REFRACTIVE FILM}

The present invention relates to a liquid composition for forming a low refractive index film. Specifically, the present invention relates to a liquid composition for forming a low refractive index film used for a display panel, a solar cell, an optical lens, a camera module, a sensor module, a mirror, and glasses. More specifically, it relates to a liquid composition for forming a low-refractive-index film in which colloidal silica particles in the liquid composition are not well agglomerated, have a low refractive index, and are excellent in water wettability and anti-fog properties on the surface of the film.

This application claims priority based on Japanese Patent Application No. 2015-008192 filed in Japan on January 20, 2015, and Japanese Patent Application No. 2015-025889 filed in Japan on February 13, 2015, I use the content here.

A low-refractive-index film formed on the surface of a transparent substrate such as glass or plastic is used as an antireflection film to prevent reflection of incident light in display panels such as CRT, liquid crystal, and organic EL, solar cells, optical lenses, and glass for showcase. Has become. For example, an antireflection film is formed on the display side of the display panel to improve visibility, or in the field of solar cells, in order to increase the absorption rate of light by preventing reflection of incident sunlight, a low refractive index on the surface of a glass substrate, etc. Countermeasures such as forming a film of as an antireflection film are taken.

_{As a film for preventing such reflection, conventionally, a single layer film made of MgF 2} , cryolite, etc. formed by a vapor phase method such as a vacuum evaporation method or sputtering method has been put into practical use. Further, _{it is known that a multilayer film formed by alternately laminating a low refractive index coating such as SiO 2} and a high refractive index coating such as TiO ₂ or ZrO ₂ on a substrate, etc., can obtain a high antireflection effect. However, in vapor phase methods such as vacuum evaporation and sputtering, there is a problem in terms of manufacturing cost and the like because the apparatus is expensive. In addition, in the method of forming a multilayer film by alternately stacking a low refractive index film and a high refractive index film, it is not very practical in that the manufacturing process is complicated and time and labor are required.

Therefore, in recent years, in terms of manufacturing cost, etc., coating methods such as a sol-gel method are attracting attention. In the sol-gel method, generally, a sol-gel solution is prepared, applied to a transparent substrate such as glass, and then dried or calcined to form a film. However, in the film formed by the sol-gel method, compared to the film formed by a vapor deposition method such as a vacuum evaporation method, a desired low refractive index is not obtained, or various problems such as poor adhesion to the substrate and occurrence of cracks remain.

As a low-refractive-index film using such a sol-gel method, at least one selected from the group consisting of a silica sol (a) in which silica particles having a predetermined average particle diameter are dispersed, a hydrolyzate of an alkoxysilane, a hydrolyzate of a metal alkoxide, and a metal salt Disclosed is a low-refractive-index antireflection film comprising a species component (b) and curing after applying a coating solution obtained by mixing a silica sol (a) and a component (b) with an organic solvent in a desired ratio to a substrate. (See, for example, Patent Document 1). As the silica sol in the coating liquid, an organic solvent-based silica sol (organo silica sol) obtained by substituting water in an aqueous silica sol with an organic solvent by a distillation method or the like is disclosed. As the organic solvent used for the organic solvent-based silica sol, preferably, alcohols such as methanol (flash point 12° C.), ethanol (flash point 13° C.), isopropanol (flash point 15° C.), butanol (flash point 37° C.), ethyl cello Solve (flash point 43°C), butyl cellosolve (flash point 64°C), ethylcarbitol (flash point 94°C), butylcarbitol (flash point 113°C), diethylcellosolve (flash point 35°C), diethylcarbitol Hydrophilic solvents such as glycol ethers such as (flash point 82°C) are used. In this Patent Document 1, by using the silica particles in a specific ratio, the film obtained by using the coating solution of Patent Document 1 has fine irregularities formed on the surface of the film, and has a good antireflection effect in reducing the refractive index. It is described that is obtained.

Japanese Laid-Open Patent Publication No. Hei 8-122501 (Claim 1, paragraph [0008], paragraph [0020])

However, in the coating liquid (liquid composition for forming a low refractive index film) for forming the low refractive index antireflection film shown in Patent Document 1, the flash point of all hydrophilic solvents such as alcohols and glycol ethers used in the solvent and organic solvent-based silica sol It is as low as less than 140°C. Therefore, when the coating liquid is used in a continuous coating process in the air for a long time and the coating liquid is left in the air, the solvent and the organic solvent are liable to volatilize from the coating liquid, and the dispersion of silica particles in the coating liquid becomes unstable. When the silica particles are agglomerated, the agglomerates adhere like projections on a uniform thin film and do not form a uniform film, and thus there is a concern that they may not function as an optical film. In addition, in the low-refractive-index film formed on this kind of transparent substrate, anti-fogging properties are required so as to maintain transparency in all environments, but the low-refractive-index film obtained with the coating liquid disclosed in Patent Document 1 has anti-fogging properties. It was insufficient.

An object of the present invention is to solve the above problems, to provide a liquid composition for forming a low-refractive-index film that is not well agglomerated, has a low refractive index, and has excellent water wettability and anti-fogging properties on the surface of the liquid composition. It is in doing.

The present inventors believe that if a certain ratio of a high boiling point solvent, that is, a solvent having a flash point of 140 to 160°C, is contained with respect to the entire low refractive index film-forming liquid composition, the composition of the entire low-refractive-index film-forming liquid composition is stabilized. , The present invention was reached by finding that aggregation is inhibited.

The first aspect of the present invention is a hydrolyzate of silicon alkoxide produced by adding and stirring a mixture of water and nitric acid to an alcohol solution of tetramethoxysilane or tetraethoxysilane as a silicon alkoxide, and a beaded colloidal silica. It is a liquid composition for forming a low refractive index film, which is a solvent prepared by mixing a silica sol in which particles are dispersed in a liquid medium and further mixing an organic solvent of glycol ether, and the glycol ether has a flash point of 140°C or more and 160°C or less. .

A second aspect of the present invention is an invention based on the first aspect, wherein glycol ether, which is a solvent having a flash point of 140°C or more and 160°C or less, is polyethylene glycol monomethyl ether, triethylene glycol monobutyl ether, and tetraethylene glycol. Dimethyl ether, polyethylene glycol dimethyl ether, or diethylene glycol monobenzyl ether.

A third aspect of the present invention is a method of forming a low refractive index film using the liquid composition for forming a low refractive index film of the first or second aspect.

A fourth aspect of the present invention is a low refractive index film formed by the method of the third aspect.

A fifth aspect of the present invention is a composite film comprising the low-refractive-index film and the infrared shielding film of the fourth aspect.

According to the liquid composition of the first aspect of the present invention, since glycol ether, which is a solvent having a flash point of 140°C or higher and 160°C or lower, is used as the organic solvent in the liquid composition, the liquid component of the liquid composition is not easily volatilized, and colloidal silica particles Is stable, and colloidal silica particles are not easily agglomerated. On the other hand, glycol ethers having a flash point of 140°C or more and 160°C or less have a high viscosity of 3 to 30 cP, and colloidal silica particles do not collide with each other in the liquid composition. As a result, even in a continuous coating process for a long time, a film having a low refractive index can be formed. Further, the film obtained from the liquid composition has a fine uneven structure on its surface, and is excellent in water wettability and anti-fogging properties on the surface of the film.

According to the liquid composition of the second aspect of the present invention, glycol ether, which is a solvent having a flash point of 140°C or more and 160°C or less, is polyethylene glycol monomethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, or Since it is diethylene glycol monobenzyl ether, when such glycol ether is used as a solvent for the liquid composition, colloidal silica in the liquid composition is less agglomerated, more reliably low refractive index, and excellent water wettability and anti-fogging properties on the surface of the film. A low refractive index film can be formed.

According to the third method of the present invention, a low refractive index film having a low refractive index and excellent in water wettability and anti-fogging properties on the surface of the film can be formed using the liquid composition for forming a low refractive index film of the first or second aspect.

The fourth low-refractive-index film of the present invention has a low refractive index, and is excellent in water wettability and anti-fog properties on the surface of the film.

Since the composite film of the fifth aspect of the present invention includes the low-refractive-index film and the infrared shielding film of the fourth aspect, this composite film has an effect of shielding infrared rays, and has a low refractive index, and has a water wettability on the surface of the composite film. It has excellent anti-fogging properties.

Next, an embodiment for carrying out the present invention will be described.

The liquid composition for forming a low refractive index film of the present embodiment (hereinafter, a liquid composition may be omitted) is an organic solution of water, nitric acid and glycol ether in an alcohol solution of tetramethoxysilane or tetraethoxysilane as a silicon alkoxide. It is prepared by mixing a hydrolyzate of silicon alkoxide produced by adding and stirring a mixture of solvents and a silica sol in which beaded colloidal silica particles are dispersed in a liquid medium. And the glycol ether is a low refractive index film forming solution composition, characterized in that the solvent has a flash point of 140 ℃ 160 ℃ or less.

To prepare the low-refractive-index film-forming liquid composition of this embodiment, first, adding an alcohol solution in an amount of 0.5 to 8.0 parts by mass per 1 part by mass of tetramethoxysilane or tetraethoxysilane as a silicon alkoxide. desirable. As the alcohol solution, organic solvents such as ethanol, isopropanol (IPA), and propylene glycol monomethyl ether (PGME) can be used. The first liquid is prepared by stirring the mixed solution of the silicon alkoxide and the alcohol solution at a temperature of preferably 30 to 40°C for 5 to 20 minutes. As the silicon alkoxide, tetraethoxysilane is preferable from the viewpoint of versatility and safety of raw materials.

On the other hand, separately from this first liquid, 0.5 to 5.0 parts by mass of water and 0.005 to 0.5 parts by mass of nitric acid are added to 1 part by mass of the silicon alkoxide, and 5 to 20 parts by mass at a temperature of 30 to 40°C. A 2nd liquid is prepared by stirring for a minute.

Next, the prepared first liquid is maintained at a temperature of preferably 30 to 80°C using a water bath or the like, and then a second liquid is added to the first liquid, and the temperature is maintained. Is stirred for 30 to 180 minutes. Thereby, a hydrolyzate of the silicon alkoxide is produced.

Next, the hydrolyzate of silicon alkoxide, wherein the resulting salt columnar colloidal silica particles are dispersed silica sol, SiO ₂ of the silica sol on SiO 1 parts by weight of ₂ minutes (分) of the hydrolyzate of the silicon alkoxide The mixture is stirred and mixed at a ratio of 3 to 45 parts by mass of a minute. In addition, glycol ether, which is a hydrophilic solvent having a flash point of 140° C. or higher, is added and stirred to a mixed solution of a hydrolyzate of silicon alkoxide and a silica sol to obtain a liquid composition for forming a low refractive index film of the present embodiment. At this time, it is preferable to add 5 to 50 parts by mass of glycol ether with respect to ₂ minutes and 1 part by mass of SiO in the hydrolyzate of the silicon alkoxide.

Examples of glycol ethers that are solvents having a flash point of 140° C. or more and 160° C. or less include polyethylene glycol monomethyl ether (flash point 145° C.), triethylene glycol monobutyl ether (flash point 156° C.), and tetraethylene glycol dimethyl ether (flash point 141°C), polyethylene glycol dimethyl ether (flash point 147°C), or diethylene glycol monobenzyl ether (flash point 158°C). In a glycol ether having a flash point of less than 140°C, when the liquid composition is left in the air, the organic solvent is liable to volatilize from the liquid composition, and dispersion of the beaded colloidal silica particles becomes unstable. In addition, in the case of a glycol ether exceeding 160°C, when forming a low refractive index film using this glycol ether, the temperature for volatilizing the glycol ether needs to be set to a high temperature exceeding 250°C, so that the substrate of the low refractive index film is heat resistant. It is limited to what there is.

Since glycol ether, which is a solvent having a flash point of 140°C or more and 160°C or less, is a hydrophilic solvent, it has excellent compatibility with water in a liquid composition. In addition, glycol ether, which is a solvent having a flash point of 140°C or more and 160°C or less, has a high viscosity of 3 to 30 cP, and colloidal silica particles do not collide with each other in the liquid composition.

The silica sol contained in the liquid composition for forming a low refractive index film of the present embodiment is a sol in which beaded colloidal silica particles are dispersed in a liquid medium. In general, as the silica particles contained in the silica sol, in addition to the beads, spherical, needle, or plate are widely known, but in the present embodiment, a silica sol in which beads of colloidal silica particles are dispersed is used. The reason why the beaded colloidal silica particles are dispersed is because, by the presence of the beaded colloidal silica particles, voids are likely to occur in the formed film, and a film having a very low refractive index can be formed. Further, the beaded colloidal silica particles have a small particle size and can reduce the haze of the film.

In the beaded colloidal silica particle, a plurality of spherical colloidal silica particles having an average particle diameter of 5 to 50 nm are bonded to each other by metal oxide-containing silica. Here, limiting the average particle diameter of the plurality of spherical colloidal silica particles constituting the beaded colloidal silica particles to the above range means that when the average particle diameter is less than the lower limit, the refractive index of the film after formation is not sufficiently lowered, while on the other hand, the upper limit is exceeded. This is because the haze of the film increases due to the irregularities on the surface of the lower film. Among these, the average particle diameter of the plurality of spherical colloidal silica particles constituting the beaded colloidal silica particles is preferably in the range of 5 to 30 nm. In addition, the average particle diameter of the spherical colloidal silica particles used was an average value obtained by measuring 200 points of the particle shape obtained by TEM observation.

Moreover, as the metal oxide-containing silica which bonds spherical colloidal silica particles, amorphous silica, amorphous alumina, etc. are illustrated, for example.

_{It is preferable that the SiO 2} concentration of the silica sol used is 5 to 40 mass%. _{If the SiO 2} concentration of the silica sol to be used is too low, the refractive index of the film after formation may not be sufficiently lowered. On the other hand, if it is too high, SiO ₂ in the silica sol tends to aggregate and the solution may become unstable. As the silica sol in which such beaded colloidal silica particles are dispersed, for example, a silica sol described in Japanese Patent No. 4 2 28935 can be used.

In the liquid composition for forming a low refractive index film of the present embodiment, the hydrolyzate and the silica sol are mixed so that ₂ minutes of SiO in the silica sol is _{3 to 45 parts by mass when 2 minutes of SiO in the hydrolyzate is 1 part by mass.} It is prepared by doing. This is because when the ratio of silica sol is less than the lower limit, the refractive index of the film after formation is not sufficiently lowered, whereas when the ratio of the silica sol exceeds the upper limit, the film thickness becomes non-uniform, resulting in increased unevenness on the surface of the film, resulting in an increase in haze. Among these, the ratio of the silica sol is preferably a ratio of 10 to 30 parts by mass _{of SiO 2} minutes of the silica sol with respect to 1 part by mass _{of SiO 2 in the hydrolyzate.}

Subsequently, a method of forming the low refractive index film of the present embodiment will be described. In the method for forming a low refractive index film of the present embodiment, first, a substrate such as glass or plastic is prepared, and the liquid composition for forming a low refractive index film of the present embodiment described above is applied to the surface of the substrate, for example, a spin coating method, It is applied by a die coating method or a spray method. After coating, using a hot plate or an atmosphere sintering furnace, preferably, drying for 5 to 60 minutes at a temperature of 50 to 100°C, and then using a hot plate or an atmosphere sintering furnace, or the like, preferably 100 to 300°C. It is cured by firing at a temperature of 5 to 120 minutes. The film thus formed exhibits a very low refractive index of about 1.15 to 1.4 by generating appropriate voids in the film. Further, since the film surface has excellent wettability and high water repellency, it is easy to form another film on the formed film surface, so it is also excellent in versatility and the like. Therefore, for example, an antireflection film used to prevent reflection of incident light in a display panel such as a CRT, a liquid crystal, or an organic EL, a solar cell, or a glass for a showcase, or an interlayer film using a difference in refractive index used for a sensor or a camera module. It can be suitably used for formation of the like. In addition, since it has excellent antifogging properties due to a fine uneven structure on the surface, it can be preferably used for a film for coating the surface of a mirror, eyeglasses, infrared shielding film, or the like.

The liquid composition of the present embodiment can also be applied (coated) to the surface of the infrared shielding film.

The composite film provided with the low refractive index film of this embodiment on the surface of the infrared shielding film will be described in detail.

In the infrared shielding film, a dispersion is prepared by mixing the surface-modified ITO powder (indium tin oxide powder) and a dispersion medium, and the dispersion is mixed with an organic solvent to form a paint for forming an infrared shielding film. It is formed by applying it to the surface of a transparent substrate and drying it. And the said composite film is produced by forming the low-refractive-index film of this embodiment on the surface of this infrared ray shielding film by the above-mentioned method. Here, the base material to which the liquid composition for forming a low refractive index film of the present embodiment is applied is an infrared shielding film.

The surface-modified ITO powder is produced by the following method. First, a mixed aqueous solution obtained by mixing an aqueous solution of indium chloride (InCl ₃ ) and tin dichloride (SnCl ₂ ·2H _{2 O) is prepared.} Subsequently, this mixed aqueous solution and an aqueous ammonia (NH ₃ ) aqueous solution are simultaneously added dropwise to water, adjusted to a predetermined pH, and then reacted at a predetermined liquid temperature for a predetermined time. Next, the precipitation produced by this reaction is repeatedly washed with ion-exchanged water to perform decantation washing. When the resistivity of the supernatant becomes 50000 Ω·cm or more, the precipitate (In/Sn coprecipitated hydroxide) is separated by filtration to obtain coprecipitated indium tin hydroxide. Subsequently, the solid-liquid-separated indium tin hydroxide is dried at a predetermined temperature for a predetermined period of time, and then fired in the air at a predetermined temperature for a predetermined period of time. The aggregate formed by this firing is pulverized and released to obtain ITO powder before surface modification. Subsequently, this ITO powder is impregnated into a surface treatment liquid obtained by slightly mixing distilled water with absolute ethanol. The ITO powder impregnated with the surface treatment liquid is heated in an inert gas atmosphere at a predetermined temperature for a predetermined time to obtain a surface-modified ITO powder.

Example

Next, examples of the present invention will be described in detail together with comparative examples.

<Example 1>

First, tetraethoxysilane (TEOS) was prepared as a silicon alkoxide, and it was put into a separable flask. A first liquid was prepared by adding ethanol in an amount equal to 1.0 parts by mass with respect to 1 part by mass of this silicon alkoxide, and stirring at 30°C for 15 minutes.

In addition to this first liquid, ion-exchanged water in an amount equal to 0.8 parts by mass and nitric acid in an amount equal to 0.01 parts by mass per 1 part by mass of the silicon alkoxide was added to the beaker, followed by mixing. A 2nd liquid was prepared by stirring for a minute. Next, the prepared first liquid was maintained at a temperature of 55°C in a water bath, and then a second liquid was added to the first liquid, followed by stirring for 60 minutes while maintaining the temperature. Thereby, a hydrolyzate of the silicon alkoxide was obtained.

Then, the obtained hydrolyzate and the silica sol having beaded colloidal silica particles dispersed therein were stirred and mixed at a ratio of 20 parts by mass _{of SiO 2} minutes in the silica sol relative to _{2 minutes 1 part by mass of SiO in the hydrolyzate.} In addition, polyethylene glycol monomethyl ether (flash point 145° C.) as a glycol ether solvent exhibiting a flash point of 140° C. or higher was added to the mixed solution of the hydrolyzate and silica sol, based on ₂ minutes and 1 part by mass of SiO in the hydrolyzate. The mixture was stirred and mixed at a ratio of 22 parts by mass of ether to obtain a liquid composition.

<Example 2>

A liquid composition was prepared in the same manner as in Example 1, except that it was changed to triethylene glycol monobutyl ether (flash point 156°C) as a glycol ether solvent exhibiting a flash point of 140°C or higher.

<Example 3>

A liquid composition was prepared in the same manner as in Example 1, except that tetraethylene glycol dimethyl ether (flash point 141°C) was used as the glycol ether solvent exhibiting a flash point of 140°C or higher.

<Example 4>

A liquid composition was prepared in the same manner as in Example 1, except that polyethylene glycol dimethyl ether (flash point 147°C) was used as the glycol ether solvent exhibiting a flash point of 140°C or higher.

<Example 5>

A liquid composition was prepared in the same manner as in Example 1, except that diethylene glycol monobenzyl ether (flash point 158°C) was used as the glycol ether solvent exhibiting a flash point of 140°C or higher.

<Comparative Example 1>

A liquid composition was prepared in the same manner as in Example 1, except that ethylene glycol monobutyl ether (butyl cellosolve) (flash point 64°C) was used as a glycol ether solvent exhibiting a flash point of less than 140°C.

<The first comparative test and its evaluation>

The cohesiveness of the colloidal silica particles in the liquid compositions prepared in Examples 1 to 5 and Comparative Example 1, the refractive index of the film formed from this liquid composition, the water wettability (contact angle) of the film, and the antifogging property of the film were evaluated. These results are shown in Table 1 below. The evaluation test was performed by the following method.

(1) Cohesiveness of colloidal silica in liquid composition

The evaluation of the aggregated state of the colloidal silica particles was performed by the following first and second methods.

In the first evaluation method, 1 g of the liquid composition was weighed in an open glass container, and the container was left standing in an atmosphere furnace maintained at 45°C for 6 hours. The mass of the liquid composition at the time of weighing was set to 100%, the mass of the liquid composition after standing was measured, and the reduced mass was evaluated as a percentage (mass reduction ratio). Further, in the second evaluation method, the liquid composition was allowed to stand for 5 days in an air atmosphere at room temperature of 25° C., and whether the dispersion of colloidal silica particles in the liquid composition was stable over time, and the presence or absence of aggregates of colloidal silica particles. Was confirmed visually. A white floating object was identified as "poor", and a white floating object was determined as "good".

(2) the refractive index of the film

The prepared liquid composition was applied to the surface of a glass substrate by a spin coating method to form a coating film. The glass substrate on which the coating film was formed was dried for 10 minutes at a temperature of 50° C. using an atmosphere sintering furnace, and then calcined and cured at a temperature of 250° C. using an atmosphere sintering furnace, thereby forming a film having a thickness of about 80 nm on the surface of the glass substrate. I did. For this film, the refractive index was measured using a spectroscopic ellipsometry device (manufactured by J. A. Woollam Japan, model number: M-2000). The value of 633 nm in the analyzed optical constant was made into the refractive index.

(3) water wettability of the membrane surface (contact angle)

For the film produced in the same manner as the film formed to evaluate the refractive index, the water wettability of the film surface was evaluated. Using the Kyowa Interface Science Drop Master DM-700, ion-exchanged water is prepared in a syringe, and a droplet of 2 μL is protruded from the tip of the needle of the syringe. Subsequently, the substrate to be evaluated is brought close to the droplet, and the droplet is attached to the substrate. The contact angle of the attached water was measured. The contact angle after 5 seconds when water touched the film surface in a stationary state was analyzed by the θ/2 method as the contact angle of water, and the water wettability of the film surface was evaluated.

(4) anti-fogging properties of the membrane

In the same manner as the film formed to evaluate the refractive index, the film surface was evaluated for antifogging properties. A glass substrate was placed horizontally on the opening of the beaker heated to 40° C. with ion-exchanged water so that the film on the glass substrate faced, and the film on the glass substrate was exposed to water vapor of hot water in the beaker. After 30 seconds had elapsed, the transparency of the glass substrate through the film was visually confirmed in that state. If haze does not occur on the film surface and the lower part of the beaker is clearly visible through the glass substrate, it is set as ``good'', and if haze has occurred on the film surface on the glass substrate, the case where the lower part of the beaker becomes faintly visible is ``defective''. I did it.

As is clear from Table 1, regarding the cohesiveness of colloidal silica particles, in Comparative Example 1, the mass reduction rate was as high as 11.5%. On the other hand, in Examples 1 to 5, the mass reduction ratio was very small, from 2.7 to 4.2%, and it was found that the liquid compositions of Examples 1 to 5 had little cohesiveness of colloidal silica particles. Moreover, with respect to the visual observation of the liquid composition, in Comparative Example 1, a white floating substance was confirmed, and it was defective. On the other hand, in Examples 1-5, no floating matter was observed, and it was favorable. In addition, the refractive index of the film was 1.28 in Comparative Example 1, whereas it was 1.22 to 1.27 in Examples 1 to 5, which was slightly lower than that of Comparative Example 1, and both films were good at low refractive index. It is thought that this is because the refractive index of the film depends on the solid material of the liquid composition.

Moreover, about the water wettability (contact angle) of a film, it was 7.1 degrees high in Comparative Example 1. On the other hand, in Examples 1-5, it was low 3.2-4.6 degrees, and it turned out that the water wettability of the membrane|membrane of Examples 1-5 was high. Further, regarding the antifogging properties of the film, in Comparative Example 1, haze occurred on the surface of the film on the glass substrate, and the antifogging effect was poor. On the other hand, in Examples 1 to 5, no haze occurred on the surface of the film on the glass substrate, and it was clear and satisfactory.

<Example 6>

A coating for forming an infrared shielding film was prepared by mixing 1.0 g of an ITO dispersion in which the surface-modified ITO powder was dispersed and 3.0 g of ethanol. This paint was spin-coated on a glass substrate at a rotational speed of 1000 rpm. After spin coating, it was dried for 10 minutes at a temperature of 50°C in an atmosphere sintering furnace to form an infrared shielding film on the glass substrate. On the surface of this infrared shielding film, the low-refractive-index film-forming liquid composition obtained in Example 2 was applied in the same manner as in Example 2 to form a low-refractive-index film. Thus, a composite film provided with a low refractive index film on the surface of the infrared shielding film was obtained.

The surface-modified ITO powder used in Example 6 was prepared by the following method. 50 mL of indium chloride (InCl ₃ ) aqueous solution (containing 18 g of In metal _{) and 3.6 g of tin dichloride (SnCl 2} ·2H ₂ O) were mixed, and the mixed aqueous solution and ammonia (NH ₃ ) aqueous solution were added to 500 ml of water. At the same time, it was added dropwise, adjusted to pH 7, and reacted for 30 minutes at a liquid temperature of 30°C. The resulting precipitate was repeatedly washed with ion-exchanged water to perform decantation washing. When the resistivity of the supernatant reached 50000 Ω·cm or more, the precipitate (In/Sn coprecipitated hydroxide) was separated by filtration to obtain a coprecipitated indium tin hydroxide. The solid-liquid-separated indium tin hydroxide was dried overnight at 110°C, and then calcined at 550°C in air for 3 hours. The aggregate formed by this firing was pulverized and released to obtain about 25 g of ITO powder before surface modification. 25 g of this ITO powder was impregnated in a surface treatment liquid (mixing ratio of 5 parts by weight of distilled water per 95 parts by weight of ethanol) and impregnated in a mixture of absolute ethanol and distilled water, and then put into a glass dish and placed in a nitrogen gas atmosphere at 330°C. Heated for 2 hours to obtain ITO powder subjected to surface modification treatment.

In addition, the ITO dispersion in which the surface-modified ITO powder used in Example 6 was dispersed was prepared by the following method. 20 g of the surface-modified ITO powder and 29.42 g of a dispersion medium _{were put together with 100 g of 0.5 mmφ ZrO 2} beads into a Laboran standard bottle No. 10, and dispersed for 10 hours with a paint shaker to obtain the ITO dispersion. ZrO ₂ beads were used to uniformly disperse the ITO powder in the dispersion medium. This dispersion medium is distilled water 0.020 g, triethylene glycol-di-2-ethylhexanoate 23.8 g, absolute ethanol 2.1 g, phosphoric acid polyester 1.0 g, 2-ethylhexanoic acid 2.0 g, and 2,4-pentanedione 0.5 It is a mixture of g.

<Example 7>

15 g of anhydrous ethanol, epoxy acrylate resin beam set 577 (manufactured by Arakawa Chemical) 0.99 g, and 0.01 g of photopolymerization initiator Irgacure 907 (manufactured by BASF) were mixed and dissolved in a mixed solution, prepared in the same manner as in Example 6. One ITO dispersion was added to 4.0 g to prepare a paint for forming an infrared shielding film. This paint was spin-coated on a glass substrate at a rotational speed of 1000 rpm. After spin coating, it was dried for 10 minutes at a temperature of 50°C in an atmosphere sintering furnace. After drying, the resin was cured by irradiating 3-pass ultraviolet rays at a metal halide lamp output of 80 W and a feed rate of 5.0 m/s using a UV irradiation apparatus (manufactured by USHIO) to form an infrared shielding film. On the surface of this infrared shielding film, the low-refractive-index film-forming liquid composition obtained in Example 2 was applied in the same manner as in Example 2 to form a low-refractive-index film. Thus, a composite film provided with a low refractive index film on the surface of the infrared shielding film was obtained.

<Example 8>

0.33 g of an ITO dispersion prepared in the same manner as in Example 6 and 1.30 g of absolute ethanol were mixed to prepare 1.63 g of a mixed solution. To this mixed solution, 1.00 g of a hydrolyzate of alkoxide silicate prepared in Example 1 was mixed to prepare a paint for forming an infrared shielding film. This paint was spin-coated on a glass substrate at a rotational speed of 1000 rpm. After spin coating, it was dried for 10 minutes at a temperature of 50°C in an atmosphere sintering furnace to form an infrared shielding film. On the surface of this infrared shielding film, the low-refractive-index film-forming liquid composition obtained in Example 2 was applied in the same manner as in Example 2 to form a low-refractive-index film. Thus, a composite film provided with a low refractive index film on the surface of the infrared shielding film was obtained.

<The 2nd comparative test and its evaluation>

For the composite films obtained in Examples 6 to 8, in addition to the evaluation of the refractive index, the water wettability of the film (contact angle), and the antifogging property of the film, infrared shielding properties were evaluated by the following method. The refractive index, the water wettability (contact angle) of the film, and the antifogging property of the film were evaluated by the method described above.

(5) Infrared shielding properties

Infrared shielding properties were irradiated with infrared rays having a wavelength of 1500 nm to the composite film using an ultraviolet visible spectrophotometer (Hitachi High Technologies: U-4100), and the transmittance was measured.

As is clear from Table 2, the composite membranes obtained in Examples 6 to 8 had a low refractive index of 1.22 to 1.24 of the membrane, and a low water wettability (contact angle) of 3.2 to 3.4 degrees, and it was found that the water wettability of the membrane was high. Further, in the composite films obtained in Examples 6 to 8, no haze occurred on the surface of the film on the glass substrate, and it was clear and satisfactory. Further, the transmittance when irradiating infrared rays having a wavelength of 1500 nm to the composite films obtained in Examples 6 to 8 was 12 to 35%, indicating that the infrared rays were sufficiently shielded.

Industrial applicability

The liquid composition of the present invention can be used to form a low refractive index film used to coat the surface of a display panel, a solar cell, an optical lens, a camera module, a sensor module, a mirror, glasses, an infrared shielding film, and the like.

Claims (5)

Silica in which a hydrolyzate of silicon alkoxide produced by adding and stirring a mixture of water and nitric acid to an alcohol solution of tetramethoxysilane or tetraethoxysilane as a silicon alkoxide, and beaded colloidal silica particles are dispersed in a liquid medium A sol is mixed and prepared by further mixing an organic solvent of glycol ether, and the glycol ether is a solvent having a flash point of 140°C or more and 160°C or less,
The low refractive index of glycol ether, which is a solvent having a flash point of 140°C or more and 160°C or less, is polyethylene glycol monomethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether or diethylene glycol monobenzyl ether Film-forming liquid composition. A method of forming a low-refractive-index film using the liquid composition for forming a low-refractive-index film according to claim 1. A method of forming a low-refractive-index film by the method according to claim 2, and forming a composite film by forming the low-refractive-index film on the surface of the infrared shielding film. delete delete