JP2016135838A - Liquid composition for forming low- refractive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid composition for forming a low-refractive film, which contains colloidal silica particles that hardly agglomerate, and which is for use in formation of a low-refractive film having a low refractive index and an excellent antifogging property.SOLUTION: The liquid composition for forming a low-refractive film is prepared by: mixing a hydrolysate of a silicon alkoxide with a silica sol, the hydrolysate being generated by adding a mixture of water and nitric acid to an alcoholic solution of tetramethoxysilane or tetraethoxysilane serving as a silicon alkoxide, the silica sol being obtained by dispersing beaded colloidal silica particles in a liquid medium; and further mixing with a glycol ether organic solvent. The glycol ether is a solvent having a flash point of 140°C or more and 160°C or less.SELECTED DRAWING: None

Description

  The present invention relates to a liquid composition for forming a low refractive index film used for display panels, solar cells, optical lenses, camera modules, sensor modules, mirrors, glasses and the like. More specifically, the present invention relates to a liquid composition for forming a low refractive index film which is less likely to aggregate the colloidal silica particles in the liquid composition, has a low refractive index, and is excellent in water wettability and antifogging property on the film surface. is there.

  A low refractive index film formed on the surface of a transparent substrate such as glass or plastic is a reflection of incident light on display panels such as cathode ray tubes, liquid crystals, organic EL, solar cells, optical lenses, glass for showcases, etc. It is used as an antireflection film for preventing the above. For example, an antireflection film for improving visibility is provided on the display surface side of the display panel, and in the field of solar cells, the reflection of incident sunlight is prevented to increase the light absorption rate. In addition, measures such as forming a low refractive index film as an antireflection film on the surface of a glass substrate are taken.

As a film for preventing such reflection, a single-layer film made of MgF ₂ , cryolite or the like formed by a vapor phase method such as a vacuum evaporation method or a sputtering method has been put into practical use. In addition, a multilayer film formed by alternately laminating a low refractive index film such as SiO ₂ and a high refractive index film such as TiO ₂ or ZrO ₂ on a base material has a high antireflection effect. It has been known. However, gas phase methods such as vacuum deposition and sputtering have problems in terms of manufacturing cost because the equipment is expensive. In addition, the method of forming a multilayer film by alternately laminating a low refractive index film and a high refractive index film is not practical because the manufacturing process is complicated and takes time and labor.

  Therefore, recently, a coating method such as a sol-gel method has attracted attention in terms of manufacturing cost and the like. However, in the sol-gel method, in general, a sol-gel solution is prepared and applied to a transparent substrate such as glass, and then a film is formed by drying, baking, or the like. As compared with a film formed by a vapor phase method such as a vacuum deposition method, a desired low refractive index cannot be obtained, and various problems such as poor adhesion to a substrate and generation of cracks remain.

  As a low refractive index film using such a sol-gel method, a silica sol (a) in which silica particles having a predetermined average particle diameter are dispersed, an alkoxysilane hydrolyzate, a metal alkoxide hydrolyzate, and a metal salt are included. Disclosed is a low-refractive-index antireflection film comprising at least one component (b) selected from the group, which is applied to a substrate with a coating solution containing the organic solvent in a desired ratio and then cured. (For example, refer to Patent Document 1). As the silica sol in the above coating, an organic solvent-based silica sol (organosilica sol) obtained by substituting water in the aqueous silica sol with an organic solvent by a distillation method or the like is shown. As the organic solvent, methanol (flash point: 12 ° C.) is preferable. ), Ethanol (flash point 13 ° C.), isopropanol (flash point 15 ° C.), butanol (flash point 37 ° C.), ethyl cellosolve (flash point 43 ° C.), butyl cellosolve (flash point 64 ° C.), ethyl carbitol Hydrophilic solvents of glycol ethers such as (flash point 94 ° C.), butyl carbitol (flash point 113 ° C.), diethyl cellosolve (flash point 35 ° C.), diethyl carbitol (flash point 82 ° C.) and the like are used. In Patent Document 1, by using the silica particles at a specific ratio, the film of Patent Document 1 has fine irregularities formed on the surface of the coating, and has a good antireflection effect for reducing the refractive index. It is described that it is obtained.

JP-A-8-122501 (Claim 1, paragraph [0008], paragraph [0020])

  However, the coating liquid (low refractive index film forming liquid composition) for forming the low refractive index antireflection film disclosed in Patent Document 1 is an alcohol or glycol ether used in the solvent and organic solvent-based silica sol. Since the flash point of all hydrophilic solvents is as low as 140 ° C, when used in a continuous application process for a long time in the atmosphere, and leaving the coating solution in the atmosphere, the solvent and organic solvent are likely to volatilize from the coating solution. The dispersion of silica particles in the coating solution becomes unstable. When the silica particles are aggregated, the aggregates adhere like projections on a uniform thin film and do not form a uniform film, which may not function as an optical film. Further, this kind of low refractive index film is required to have antifogging properties so as to maintain transparency in any environment, but is insufficient.

  An object of the present invention is to solve the above-mentioned problems, and to provide a low refractive index film that is less likely to aggregate the colloidal silica particles in the liquid composition, has a low refractive index, and is excellent in water wettability and antifogging property on the film surface. It is in providing the liquid composition for forming.

  The inventors of the present invention can stabilize the composition of the entire liquid composition by including a certain proportion of a high boiling point solvent having a flash point of 140 to 160 ° C. in the entire liquid composition for forming a low refractive index film. The present inventors have found that aggregation is suppressed and have reached the present invention.

  According to a first aspect of the present invention, there is provided a hydrolyzate of silicon alkoxide produced by adding a mixture of water and nitric acid to a tetramethoxysilane or tetraethoxysilane alcohol solution as a silicon alkoxide and stirring the mixture. Low refractive index, which is prepared by mixing silica sol in which colloidal silica particles are dispersed in a liquid medium and further mixing with an organic solvent of glycol ether, wherein the glycol ether has a flash point of 140 ° C. or higher and 160 ° C. or lower. It is a liquid composition for rate film formation.

  A second aspect of the present invention is the invention based on the first aspect, wherein the glycol ether, which is a solvent having a flash point of 140 ° C. or higher and 160 ° C. or lower, is polyethylene glycol monomethyl ether, triethylene glycol monobutyl ether, 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 according to 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 including the low refractive index film and the infrared shielding film according to the fourth aspect.

  According to the liquid composition of the first aspect of the present invention, since the 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 It becomes difficult to volatilize, the dispersion of the colloidal silica particles is stabilized, and the colloidal silica particles are less likely to aggregate. Moreover, it is excellent in compatibility with water in the liquid composition. On the other hand, glycol ethers having a flash point of 140 ° C. or higher and 160 ° C. or lower 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, a low refractive index film can be formed. In addition, the surface has a fine concavo-convex structure and is excellent in water wettability and antifogging on the film surface.

  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 higher and 160 ° C. or lower is polyethylene glycol monomethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol Since it is dimethyl ether or diethylene glycol monobenzyl ether, if such glycol ether is used as the solvent of the liquid composition, the colloidal silica in the liquid composition is less likely to aggregate, more reliably with a low refractive index, and water wettability on the film surface. And a low refractive index film excellent in antifogging property.

  According to the third method of the present invention, the low refractive index film-forming liquid composition according to the first or second aspect is used, and the low refractive index is excellent in water wettability and antifogging property on the film surface. A refractive index film can be formed.

  The fourth low refractive index film of the present invention has a low refractive index and is excellent in water wettability and antifogging property on the film surface.

  Since the composite film according to the fifth aspect of the present invention includes the low refractive index film and the infrared shielding film according to the fourth aspect, the composite film has an effect of shielding infrared rays and has a low refractive index and a composite. Excellent wettability and anti-fogging property on the film surface.

  Next, the form for implementing this invention is demonstrated.

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

  In order to produce the liquid composition for forming a low refractive index film of the present invention, first, an amount of 0.5 to 8.0 parts by mass with respect to 1 part by mass of tetramethoxysilane or tetraethoxysilane as silicon alkoxide. An organic solvent such as ethanol, isopropanol (IPA), propylene glycol monomethyl ether (PGME) is added, and the first liquid is preferably prepared by stirring at a temperature of 30 to 40 ° C. for 5 to 20 minutes. As the silicon alkoxide, tetraethoxysilane is preferred from the viewpoint of versatility and safety of raw materials.

  On the other hand, separately from the 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 30 The second liquid is prepared by stirring at a temperature of -40 ° C for 5-20 minutes.

  Next, the first liquid prepared as described above is preferably maintained at a temperature of 30 to 80 ° C. using a water bath or the like, and then the second liquid is added to the first liquid, preferably in a state where the temperature is maintained. Stir for 30-180 minutes. Thereby, the hydrolyzate of the said silicon alkoxide is produced | generated.

Next, in the silica sol in which the obtained hydrolyzate and beaded colloidal silica particles are dispersed, the proportion of SiO ₂ in the silica sol with respect to 1 part by mass of SiO ₂ in the hydrolyzate is 3 to 45 parts by mass. In addition, the glycol ether which is a hydrophilic solvent at a flash point of 140 ° C. or higher is added and mixed at a ratio of 5 to 50 parts by mass with respect to 1 part by mass of SiO ₂ in the hydrolyzate The liquid composition for forming a low refractive index film of the present invention is obtained by stirring and stirring.

  Specific examples of glycol ethers having a flash point of 140 ° C. or higher and 160 ° C. or lower include polyethylene glycol monomethyl ether (flash point 145 ° C.), triethylene glycol monobutyl ether (flash point 156 ° C.), tetraethylene glycol. Examples include hydrophilic solvents such as dimethyl ether (flash point 141 ° C.), polyethylene glycol dimethyl ether (flash point 147 ° C.) or diethylene glycol monobenzyl ether (flash point 158 ° C.). In the case of glycol ether having a flash point of less than 140 ° C., when the liquid composition is left in the atmosphere, the organic solvent is likely to volatilize from the liquid composition, and the dispersion of the beaded colloidal silica particles becomes unstable. Further, in the case of glycol ether exceeding 160 ° C., when forming a low refractive index film using this glycol ether, it is necessary to set the temperature for volatilizing this glycol ether to a high temperature exceeding 250 ° C. The base material of the film is limited to those having heat resistance.

  The silica sol contained in the liquid composition for forming a low refractive index film of the present invention 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 bead shape, spherical, needle-like or plate-like ones are widely known. In the present invention, a silica sol in which the bead-like colloidal silica particles are dispersed is used. . The reason why the bead-like colloidal silica particles are dispersed is that the presence of the bead-like colloidal silica particles makes it easy to form pores in the formed film, and a film having a very low refractive index can be formed. Because. Further, the size of the particles is small, and the haze of the film can be reduced.

  The beaded colloidal silica particles are obtained by joining a plurality of spherical colloidal silica particles having an average particle diameter of 5 to 50 nm with metal oxide-containing silica. Here, the average particle diameter of the plurality of spherical colloidal silica particles constituting the beaded colloidal silica particles is limited to the above range because the refractive index of the formed film is sufficiently lowered when the average particle diameter is less than the lower limit. On the other hand, if the upper limit is exceeded, the haze of the film increases due to the unevenness of the film surface. 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. The average particle diameter of the spherical colloidal silica particles was an average value obtained by measuring 200 particle shapes obtained by TEM observation.

  Moreover, as a metal oxide containing silica which joins a spherical colloidal silica particle, an amorphous silica, an amorphous alumina, etc. are illustrated, for example.

The silica sol used preferably has a SiO ₂ concentration of 5 to 40% by 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, the SiO ₂ in the silica sol tends to aggregate and the liquid may become unstable. . As a silica sol in which such beaded colloidal silica particles are dispersed, for example, a silica sol described in Japanese Patent No. 4328935 can be used.

In the low refractive index film-forming composition of the present invention, the hydrolyzate and the silica sol, the SiO ₂ minutes in the hydrolyzate when the 1 part by mass, SiO ₂ minutes of the silica sol is 3 to 45 It is prepared by mixing so as to be part by mass. If the ratio of silica sol is less than the lower limit, the refractive index of the film after formation does not sufficiently decrease, whereas if the upper limit is exceeded, the film thickness becomes uneven, resulting in increased film surface irregularities and increased haze. It is. Among these, it is preferable that the ratio of the silica sol is such that the SiO ₂ content of the silica sol is 10 to 30 parts by mass relative to 1 part by mass of SiO ₂ in the hydrolyzate.

  Next, a method for forming the low refractive index film of the present invention will be described. In the method for forming a low refractive index film of the present invention, first, a substrate such as glass or plastic is prepared, and the above-described liquid composition for forming a low refractive index film of the present invention is applied to the surface of the substrate, for example, by spin coating. Apply by the method, die coat method or spray method. After coating, it is preferably dried at a temperature of 50 to 100 ° C. for 5 to 60 minutes using a hot plate or an atmosphere firing furnace, and then preferably 100 to 300 ° C. using a hot plate or an atmosphere firing furnace. Bake at a temperature of 5 to 120 minutes to cure. The film thus formed exhibits a very low refractive index of about 1.15 to 1.4 due to the generation of appropriate pores inside the film. In addition, since the film surface is excellent in wettability and exhibits high water repellency, it is easy to form another film on the formed film surface, so that it is excellent in versatility. Therefore, for example, an antireflection film used for preventing reflection of incident light in a display panel such as a cathode ray tube, a liquid crystal, an organic EL, a solar cell, a glass for a showcase, or a refractive index difference used for a sensor, a camera module, or the like. Can be suitably used for forming an intermediate film or the like using Furthermore, since the surface has a fine concavo-convex structure and is excellent in antifogging properties, it can be suitably used as a film for coating on the surface of mirrors, glasses, infrared shielding films and the like.

   The film for coating on the surface of the infrared shielding film, that is, a composite film having a low refractive index film on the surface of the infrared shielding film will be described in detail.

  The infrared shielding film is prepared by mixing a surface-modified ITO powder (indium tin oxide powder) and a dispersion medium to prepare a dispersion, and mixing the dispersion with an organic solvent to form an infrared shielding film-forming paint. Then, it is applied to the surface of a transparent substrate such as a glass substrate or a plastic film and dried to form. The composite film is produced by forming the low refractive index film on the surface of the infrared shielding film by the method described above. Here, the base material to which the liquid composition for forming a low refractive index film of the present invention is applied is an infrared shielding film.

The surface-modified ITO powder is produced by the following method. First, a mixed aqueous solution in which an indium chloride (InCl ₃ ) aqueous solution and tin dichloride (SnCl ₂ .2H ₂ O) are mixed is prepared. Next, the mixed aqueous solution and the aqueous ammonia (NH ₃ ) solution are simultaneously dropped into water, adjusted to a predetermined pH, and then reacted at a predetermined liquid temperature for a predetermined time. Next, the precipitate formed by this reaction is repeatedly washed with ion-exchanged water. When the resistivity of the supernatant liquid 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 time, and then baked in the air at a predetermined temperature for a predetermined time. The aggregate formed by this firing is pulverized and loosened to obtain an ITO powder before surface modification. Subsequently, the ITO powder is impregnated in a surface treatment solution in which distilled water is slightly mixed with absolute ethanol. The ITO powder impregnated with the surface treatment liquid is heated at a predetermined temperature for a predetermined time in an inert gas atmosphere to obtain a surface-modified ITO powder.

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

<Example 1>
First, tetraexylsilane (TEOS) was prepared as a silicon alkoxide and charged into a separable flask. An amount of ethanol of 1.0 part by mass was added to 1 part by mass of this silicon alkoxide, and the first liquid was prepared by stirring at a temperature of 30 ° C. for 15 minutes.

  Separately from this first liquid, ion exchange water in an amount of 0.8 parts by mass and nitric acid in an amount of 0.01 parts by mass with respect to 1 part by mass of silicon alkoxide are charged into a beaker and mixed. The second liquid was prepared by stirring at a temperature of 30 ° C. for 15 minutes. Next, after maintaining the prepared first liquid at a temperature of 55 ° C. in a water bath, the second liquid was added to the first liquid and stirred for 60 minutes while maintaining the temperature. Thereby, the hydrolyzate of the silicon alkoxide was obtained.

Then, the hydrolyzate obtained above and a silica sol in which beaded colloidal silica particles are dispersed are stirred at a ratio of 20 parts by mass of SiO ₂ in the silica sol to 1 part by mass of SiO ₂ in the hydrolyzate. Furthermore, polyethylene glycol monomethyl ether (flash point 145 ° C.) as a glycol ether solvent having a flash point of 140 ° C. or higher is 22 parts by mass with respect to 1 part by mass of SiO ₂ in the hydrolyzate. The mixture was stirred and mixed at a ratio to obtain a liquid composition.

<Example 2>
A liquid composition was prepared in the same manner as in Example 1 except that the glycol ether solvent having a flash point of 140 ° C. or higher was changed to triethylene glycol monobutyl ether (flash point 156 ° C.).

<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 a glycol ether solvent having 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 a glycol ether solvent having 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 a glycol ether solvent having 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 having a flash point of less than 140 ° C.

<First comparative test and its evaluation>
Cohesiveness of 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 of the film Sex was evaluated. These results are shown in Table 1 below. The evaluation test was conducted by the following method.

(1) Aggregation property of colloidal silica in liquid composition Evaluation of the aggregation state of 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 this container was left 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. Further, in the second evaluation method, the liquid composition is allowed to stand for 5 days in an air atmosphere at room temperature of 25 ° C., and whether or not the dispersion of the colloidal silica particles in the liquid composition is stable over time. The presence or absence of particle aggregates was confirmed visually. The thing in which the white floating thing was confirmed was set as "bad", and the thing without a floating thing was set as "good".

(2) Refractive index of 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 this coating film was formed was dried at a temperature of 50 ° C. for 10 minutes using an atmosphere firing furnace, and then baked and cured at a temperature of 250 ° C. using an atmosphere firing furnace to obtain a thickness. A film of about 80 nm was formed on the surface of the glass substrate. The refractive index of this film was measured using a spectroscopic ellipsometry apparatus (manufactured by JAWoollam Japan, model number: M-2000). The value of 633 nm in the analyzed optical constant was taken as the refractive index.

(3) Water wettability on film surface (contact angle)
The film wettability on the film surface was evaluated for a film produced in the same manner as the film formed for evaluating the refractive index. Using a drop master DM-700 manufactured by Kyowa Interface Science, ion exchange water is prepared in the syringe, and a 2 μL droplet is ejected from the tip of the syringe needle. Next, the substrate to be evaluated is brought close to the droplet, and the droplet is attached to the substrate. The contact angle of the adhered water was measured. The value obtained by analyzing the contact angle 5 seconds after the water touched the film surface in a static state by the θ / 2 method was defined as the water contact angle, and the water wettability of the film surface was evaluated.

(4) Antifogging property of film The antifogging property of the film surface was evaluated with respect to the film | membrane produced similarly to the film | membrane formed in order to evaluate a refractive index. Place the glass substrate horizontally so that the membrane on the glass substrate faces the opening of the beaker heated to 40 ° C. with ion-exchanged water, and expose the membrane on the glass substrate to hot water in the beaker. did. After 30 seconds, the transparency of the glass substrate through the film was visually confirmed in that state. If the bottom of the beaker is clearly visible through the glass substrate without clouding on the film surface, it is set as `` Good ''. If the film surface on the glass substrate is cloudy, the bottom of the beaker is cloudy enough to make it slightly visible. “Bad”.

  As is clear from Table 1, regarding the cohesiveness of the colloidal silica particles, the mass reduction rate in Comparative Example 1 was as high as 11.5%. On the other hand, in Examples 1-5, the mass reduction rate was very small, 2.7-4.2%, and it turned out that the liquid composition of Examples 1-5 has few cohesiveness of colloidal silica particles. Further, regarding the visual observation of the liquid composition, in Comparative Example 1, a white floating substance was confirmed, which was defective. On the other hand, in Examples 1-5, the suspended | floating matter was not observed at all but was favorable. Further, the refractive index of the film is 1.28 in Comparative Example 1 and 1.22 to 1.27 in Examples 1 to 5, which is slightly lower than Comparative Example 1, and both films are Good at low refractive index. It is considered that the refractive index of the film depends on the solid matter of the liquid composition.

  Further, the water wettability (contact angle) of the film was as high as 7.1 degrees in Comparative Example 1. On the other hand, in Examples 1-5, it was as low as 3.2-4.6 degree | times, and it turned out that the water wettability of the film | membrane of Examples 1-5 is high. Furthermore, regarding the antifogging property of the film, in Comparative Example 1, fogging occurred on the film surface on the glass substrate, and the antifogging effect was poor. On the other hand, in Examples 1-5, the film | membrane surface on a glass substrate did not generate | occur | produce fogging at all, but it was clear and favorable.

<Example 6>
An ITO dispersion liquid (1.0 g) in which the surface-modified ITO powder was dispersed and 3.0 g of ethanol were mixed to prepare a coating material for forming an infrared shielding film. This paint was spin-coated on a glass substrate at a rotation speed of 1000 rpm. After spin coating, the film was dried in an atmosphere firing furnace at a temperature of 50 ° C. for 10 minutes 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. As a result, a composite film having 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 produced by the following method. 50 mL of an indium chloride (InCl ₃ ) aqueous solution (containing 18 g of In metal) and 3.6 g of tin dichloride (SnCl ₂ .2H ₂ O) are mixed, and this mixed aqueous solution and an aqueous ammonia (NH ₃ ) solution are added to 500 ml of water. The solution was added dropwise at the same time, adjusted to pH 7, and reacted at a liquid temperature of 30 ° C. for 30 minutes. The generated precipitate was repeatedly washed with ion-exchange water. When the resistivity of the supernatant liquid reached 50000 Ω · cm or more, the precipitate (In / Sn coprecipitated hydroxide) was separated by filtration to obtain coprecipitated indium tin hydroxide. The solid-liquid separated indium tin hydroxide was dried at 110 ° C. overnight and then calcined at 550 ° C. for 3 hours in the atmosphere. The aggregate formed by this firing was pulverized and loosened to obtain about 25 g of ITO powder before surface modification. 25 g of this ITO powder was impregnated in a surface treatment solution (mixing ratio of 5 parts by weight of distilled water with respect to 95 parts by weight of ethanol) mixed with absolute ethanol and distilled water, and then placed in a glass petri dish and a nitrogen gas atmosphere Below, it heated at 330 degreeC for 2 hours, and obtained ITO powder which carried out surface modification processing.

Moreover, the ITO dispersion liquid in which the ITO powder subjected to the surface modification treatment used in Example 6 was dispersed was prepared by the following method. 20 g of the above-mentioned surface-modified ITO powder and 29.42 g of the dispersion medium are placed in a Laboran standard bottle No. 10 together with 100 g of 0.5 mmφ ZrO ₂ beads, and dispersed with a paint shaker for 10 hours. Obtained. ZrO ₂ beads were used to uniformly disperse ITO powder in a dispersion medium. This dispersion medium comprises 0.020 g of distilled water, 23.8 g of triethylene glycol-di-2-ethylhexanoate, 2.1 g of anhydrous ethanol, 1.0 g of phosphoric acid polyester, 2.0 g of 2-ethylhexanoic acid, and It is a mixed solution of 0.5 g of 2,4-pentanedione.

<Example 7>
The same solution as in Example 6 was prepared by mixing and dissolving 15 g of absolute ethanol, 0.99 g of epoxy acrylate resin beam set 577 (Arakawa Chemical) and 0.01 g of photopolymerization initiator Irgacure 907 (BASF). 4.0 g of the ITO dispersion prepared by the method was added to prepare an infrared shielding film-forming coating material. This paint was spin-coated on a glass substrate at a rotation speed of 1000 rpm. After spin coating, the film was dried in an atmosphere firing furnace at a temperature of 50 ° C. for 10 minutes. After drying, the resin was cured by using a UV irradiation device (manufactured by USHIO) and irradiated with 3-pass ultraviolet rays at a metal halide lamp output of 80 W and a feed rate of 5.0 m / s 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. As a result, a composite film having a low refractive index film on the surface of the infrared shielding film was obtained.

<Example 8>
1.63 g of a mixed solution was prepared by mixing 0.33 g of the ITO dispersion prepared by the same method as in Example 6 and 1.30 g of absolute ethanol. The mixture was mixed with 1.00 g of the hydrolyzate of silicate alkoxide prepared in Example 1 to prepare an infrared shielding film-forming coating material. This paint was spin-coated on a glass substrate at a rotation speed of 1000 rpm. After spin coating, the film was dried at a temperature of 50 ° C. for 10 minutes in an atmosphere firing 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. As a result, a composite film having a low refractive index film on the surface of the infrared shielding film was obtained.

<Second 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 (contact angle) of the film and the antifogging property of the film, the refractive index of the infrared shielding properties evaluated by the following method, The water wettability (contact angle) of the film and the antifogging property of the film were evaluated by the methods described above.

(5) Infrared shielding properties Infrared shielding properties were measured by irradiating the composite film with infrared rays having a wavelength of 1500 nm using an ultraviolet-visible spectrophotometer (Hitachi High Technologies: U-4100).

  As is apparent from Table 2, the composite films obtained in Examples 6 to 8 have a low refractive index of 1.22 to 1.24, and a water wettability (contact angle) of the film of 3.2 to 2. It was found to be as low as 3.4 degrees and the water wettability of the film was high. In the composite films obtained in Examples 6 to 8, the film surface on the glass substrate did not generate any fogging and was clear and good. Furthermore, when the infrared rays having a wavelength of 1500 nm were irradiated onto the composite films obtained in Examples 6 to 8, the transmittance was 12 to 35%, and it was found that the infrared rays were sufficiently shielded.

  The liquid composition of the present invention is used to form a low refractive index film used for coating the surface of display panels, solar cells, optical lenses, camera modules, sensor modules, mirrors, glasses, infrared shielding films, and the like. it can.

Claims (5)

  Silicon alkoxide hydrolyzate produced by adding a mixture of water and nitric acid to a tetramethoxysilane or tetraethoxysilane alcohol solution as silicon alkoxide and stirring, and beaded colloidal silica particles are contained in the liquid medium. A liquid composition for forming a low refractive index film, which is prepared by mixing a dispersed silica sol and further mixing an organic solvent of glycol ether, wherein the glycol ether is a solvent having a flash point of 140 ° C. or higher and 160 ° C. or lower.   2. The glycol ether which is a solvent having a flash point of 140 ° C. or higher and 160 ° C. or lower is polyethylene glycol monomethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol dimethyl ether or diethylene glycol monobenzyl ether. A liquid composition for forming a low refractive index film.   A method for forming a low refractive index film using the liquid composition for forming a low refractive index film according to claim 1.   A low refractive index film formed by the method according to claim 3.   A composite film comprising the low refractive index film according to claim 4 and an infrared shielding film.