JP2015224302A - Coating liquid for formation of low-refractive-index film, low-refractive-index film, production method of low-refractive-index film and application article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating liquid for formation of a low-refractive-index film which enables easy and inexpensive production of an anti-reflection film of a low refractive index without the need of addition of expensive materials.SOLUTION: A coating liquid 10 for formation of a low-refractive-index film is obtained by adding an alkoxysilane 1, a fluorine compound 2 and water 3 to a solvent 4 to prepare a solution subjecting the solution to a heating and stirring treatment H and adding an acid 5 to the resultant solution. The fluorine compound 2 is hydrofluoric acid or hexafluorosilicic acid (hydrosilicofluoric acid). The fluorine compound 2 is added in a ratio of 0.01-0.1 mol of fluorine to one mol of the alkoxysilane 1. The refractive index of the low-refractive-index film is 1.30-1.43.

Description

  The present invention relates to a coating solution for forming a low refractive index film, a low refractive index film, a method for producing a low refractive index film, and an applied product. The present invention relates to a coating solution for forming a low refractive index film, a low refractive index film, and the like that can be manufactured.

  By forming a film having a refractive index lower than that of the substrate on a transparent substrate such as glass or film, it is possible to reduce light reflection and increase the transmittance (light transmittance) of the substrate. For this reason, the low refractive index film-forming material is used in liquid crystal displays, touch sensors, solar cells and the like for antireflection applications.

  As a method for producing a low refractive index film, a multilayer film in which magnesium fluoride or silica is laminated by sputtering or vacuum deposition is known. However, the method of manufacturing by a physical method requires a large facility such as a vacuum chamber and takes time for stacking, and thus has a problem in cost.

  Therefore, a method of forming a low refractive index film by a chemical method has been performed. In particular, many methods for forming a low refractive index film by adding a fluorine compound having a low refractive index to silica have been studied. For example, Patent Document 1 listed below discloses a method of obtaining a low refractive index antireflection film having a refractive index of 1.33 to 1.38 by introducing a fluorine-containing organosilicon compound when preparing a silica coating solution.

  Patent Document 2 discloses a method of obtaining an antireflection film having a refractive index of 1.2 to 1.3 by using hollow silica fine particles and a fluorine-based resin, and Patent Document 3 further discloses a fluorine-containing silica sol solution and a substrate. A method of obtaining a low reflection substrate having a refractive index of 1.41 to 1.43 by bringing them into contact is disclosed.

Japanese Patent No. 5019014, “Antireflection Film, Method for Forming Antireflection Film, and Antireflection Glass” JP 2003-344603 A "Antireflection Film" Japanese Patent Application Laid-Open No. 2002-139603 “Method of Manufacturing Low Reflective Substrate, Low Reflective Substrate, Transparent Electrode Substrate, and Resistive Film Type Transparent Touch Panel”

  However, the methods disclosed in Patent Document 1 and Patent Document 2 are not preferable in terms of production cost because the fluorine organic compound and the hollow silica fine particles used are expensive. On the other hand, in the method disclosed in Patent Document 3, since hydrosilicic acid is added after silica sol preparation, silicon fluoride is volatilized from the liquid, and the stability of the liquid cannot be maintained.

  Accordingly, the problem to be solved by the present invention is based on the problems of the prior art, and it is possible to easily and inexpensively produce a low-refractive-index antireflection film without the need for expensive materials. It is to provide a coating liquid for forming a refractive index film. Furthermore, the subject of this invention is providing the coating liquid for low refractive index film | membrane formation etc. which can maintain stability of a liquid.

  As a result of studying the above problems, the inventors of the present application have found that by adding hydrofluoric acid or hexafluorosilicic acid (silicohydrofluoric acid) as a fluorine compound to the starting solution in the method for producing a low refractive index film by the sol-gel method, Has been found to be able to be solved, and based on this, the present invention has been completed. That is, the invention claimed in the present application, or at least the disclosed invention, as means for solving the above-described problems is as follows.

[1] A coating solution for forming a low refractive index film, comprising an alkoxysilane and a fluorine compound, wherein the fluorine compound is either hydrofluoric acid or hexafluorosilicic acid.
[2] The coating solution for forming a low refractive index film according to [1], wherein the fluorine compound is added so as to form a film having a specific refractive index.
[3] The low content of [1] or [2], wherein the fluorine compound is added so that fluorine is 0.01 mol to 0.1 mol with respect to 1 mol of alkoxysilane. A coating solution for forming a refractive index film.

[4] A low refractive index film obtained using the coating liquid for forming a low refractive index film according to any one of [1] to [3].
[5] The low refractive index film according to [4], wherein the refractive index is in the range of 1.30 to 1.43.
[6] Low refractive index film production, wherein the low refractive index film forming coating liquid according to any one of [1] to [3] is applied to a base material, and a low refractive index film is obtained by heat treatment Method.

[7] The method for producing a low refractive index film according to [6], wherein the refractive index is adjusted by the addition amount of the fluorine compound.
[8] The method for producing a low refractive index film as described in [7], wherein at least one of tetraalkoxysilane or trialkoxysilane is used as the alkoxysilane.
[9] An applied product comprising the low refractive index film according to [4] or [5].

  Since the coating liquid for forming a low refractive index film, the low refractive index film, the low refractive index film manufacturing method and the applied product according to the present invention are configured as described above, according to this, an inexpensive material is not used and the An antireflective film having a refractive index can be easily and inexpensively manufactured. Moreover, the stability of the liquid can be maintained.

It is a flowchart which shows the structure of the coating liquid for low refractive index film | membrane formation of this invention with the manufacturing method. It is a flowchart which shows the low-refractive-index film manufacturing method of this invention. It is a correlation diagram of the reflectance and refractive index used for refractive index calculation in the Example.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a flowchart showing the structure of the coating solution for forming a low refractive index film according to the present invention by its manufacturing method. As shown in the figure, the coating liquid 10 for forming a low refractive index film comprises an alkoxysilane 1 and a fluorine compound 2, and the fluorine compound 2 is either hydrofluoric acid or hexafluorosilicic acid (silicohydrofluoric acid). That is the basic configuration.

  As shown in the figure, more specifically, a solution obtained by adding alkoxysilane 1, fluorine compound 2 and water 3 to solvent 4 is subjected to heating and stirring treatment H, and acid 5 is added to the resulting solution. Thus, the low refractive index coating liquid 10 of the present invention is obtained.

  With this configuration, the coating liquid 10 for forming a low refractive index film according to the present invention uses hydrofluoric acid or hexafluorosilicic acid (silicohydrofluoric acid) as the fluorine compound 2, and is therefore less expensive than conventional methods. . In addition, since the fluorine compound 2 is added during the preparation of the coating liquid, a stable low refractive index coating liquid 10 containing fluorine in the silica sol can be produced.

Examples of the alkoxysilane 1 include tetraalkoxysilane and trialkoxysilane, and tetramethoxysilane and tetraethoxysilane are particularly preferable. The addition amount of the alkoxysilane 1 or less 3 wt% in the liquid in terms of SiO _2. This is because if the amount added exceeds this value, the solution will gel during preparation and a film cannot be formed. As the acid 5, any one of nitric acid, hydrochloric acid, oxalic acid, and sulfuric acid can be suitably used. Examples of the solvent 4 include alcohols such as ethanol, isopropyl alcohol, and 1-propyl alcohol, and ketones such as methyl ethyl ketone and methyl isobutyl ketone. The solvent 4 can be used alone or in combination.

  In this coating liquid 10 for forming a low refractive index film, the fluorine compound 2 is added in such an amount that a film having a specific refractive index is formed. Specifically, it is assumed that the fluorine compound 2 is added in such an addition amount that fluorine is 0.01 mol or more and 0.1 mol or less with respect to 1 mol of the alkoxysilane 1.

  Moreover, the water 3 is added so that it may become 4-10 mol with respect to 1 mol alkoxysilane 1. FIG. When the amount is 4 mol or less, the hydrolysis reaction does not proceed well, so that it is difficult to obtain a low refractive index film. On the other hand, when the amount is 10 mol or more, the water content increases and a uniform film is difficult to obtain.

Moreover, the acid 5 is added so that it may be 0.03 mol or more with respect to 1 mol of alkoxysilane 1. The acid 5 serves to disperse the SiO ₂ fine particles generated by the sol-gel reaction, but at 0.03 mol or less, there is a possibility that the particles are aggregated without being dispersed.

Further, the heating temperature in the heating and stirring treatment H is desirably 55 ° C. or higher and 75 ° C. or lower. At 55 ° C. or lower, the introduction of fluorine into SiO ₂ does not proceed, so that a low refractive index film cannot be obtained satisfactorily. On the other hand, at 75 ° C. or higher, the reaction proceeds rapidly and it is difficult to form a homogeneous film. . The stirring time is not particularly limited, but is preferably 3 hours or more.

  FIG. 2 is a flowchart showing the method for producing a low refractive index film of the present invention. As shown in the figure, this manufacturing method applies the above-described coating solution 10 for forming a low refractive index film to the substrate 20 (application process P1), and heats the coated substrate 30 (heating process P2), thereby coating the liquid. 10 is thermally cured to obtain a low refractive index film 50. As described above, the low refractive index film 50 can be easily manufactured only by adjusting the amount of the fluorine compound 2 added during the preparation of the coating liquid 10.

  In particular, as alkoxysilane 1, tetramethoxysilane or tetraethoxysilane, acid 5 is any of nitric acid, hydrochloric acid, oxalic acid or sulfuric acid, and as a solvent, alcohols or ketones are recommended. Various conditions for obtaining better results are as described above.

  The low refractive index film 50 itself obtained by using the coating liquid 10 for forming a low refractive index film in this manner is also within the scope of the present invention. In particular, according to the present invention, a low refractive index film 50 having a refractive index in the range of 1.30 to 1.43 can be obtained. This can be applied to a liquid crystal display, a touch sensor, a solar cell and the like as an antireflection film.

Examples of the present invention will be described below, but the present invention is not limited thereto.
[Example 1]
A solution prepared by adding 4.30 g of water, 0.47 g of 10% hydrofluoric acid and 6.93 g of tetraethyl orthosilicate to 88.12 g of methyl ethyl ketone was heated to 65 ° C. with stirring and maintained for 5 hours. After cooling, 0.18 g of 60% nitric acid was added and stirred for 30 minutes to obtain an antireflection coating solution.

[Example 2]
A solution prepared by adding 4.42 g of water, 0.33 g of 10% hydrofluoric acid and 6.93 g of tetraethyl orthosilicate to 88.13 g of methyl ethyl ketone was heated to 65 ° C. with stirring and maintained for 5 hours. After cooling, 0.18 g of 60% nitric acid was added and stirred for 30 minutes to obtain an antireflection coating solution.

Example 3
A solution obtained by adding 4.54 g of water, 0.20 g of 10% hydrofluoric acid and 6.93 g of tetraethyl orthosilicate to 88.15 g of methyl ethyl ketone was heated to 65 ° C. with stirring and maintained for 5 hours. After cooling, 0.18 g of 60% nitric acid was added and stirred for 30 minutes to obtain an antireflection coating solution.

Example 4
A solution obtained by adding 13.83 g of water, 0.51 g of 33% hexafluorosilicic acid and 20.80 g of tetraethyl orthosilicate to 264.33 g of isopropyl alcohol was heated to 65 ° C. with stirring and maintained for 5 hours. After cooling, 0.53 g of 60% nitric acid was added and stirred for 30 minutes to obtain an antireflection coating solution.

[Comparative Example 1]
A coating liquid was prepared in the same manner as in Example 1 except that the heating temperature was 50 ° C. in Example 1.
[Comparative Example 2]
In Example 1, a coating solution was prepared in the same manner as in Example 1 except that 10% hydrofluoric acid was not added.

[Combination ratio]
Table 1 shows the preparation conditions of the coating liquids in Examples 1 to 4 and Comparative Examples 1 and 2.

[Film formation]
The coating liquid obtained in each example and comparative example was applied to a glass substrate with a bar coater and heat-treated at 150 ° C. for 30 minutes to form a film. As the glass substrate, a slide glass manufactured by Matsunami Glass Industry Co., Ltd. having a size of 76 mm × 26 mm × thickness 1.2 mm was used.

[Measurement of reflectance and refractive index]
The reflectance was measured for the resultant film formed in each example and comparative example. The reflectance was measured using a Minolta spectrocolorimeter CM-2002, and the reflectance was measured in the wavelength range of 400 to 700 nm to obtain the average reflectance. The refractive index was calculated using an approximate expression obtained in advance from a correlation diagram of the reflectance and the refractive index (shown in FIG. 3). In addition, a small high-speed spectroscopic ellipsometer UNECS-2000 manufactured by ULVAC, Inc. was used for the measurement of the refractive index used in the approximate expression. The measurement results are shown in Table 2.

  As shown in the table, all of the films of Examples 1 to 4 were able to obtain a lower refractive index than Comparative Example 2 in which no fluorine compound was added. In Examples 1 to 3, the fluorine compound content was changed from 0.03 to 0.07 in terms of fluorine / alkoxysilane molar ratio, but the molar ratio was high, that is, the fluorine content was high. It was confirmed that a film having a lower refractive index can be obtained with a larger number. That is, it was shown that the refractive index can be controlled by the addition amount of the fluorine compound.

  In Comparative Example 1 prepared at a heating temperature of 50 ° C., no film was formed when the coating liquid was applied to the glass substrate. That is, under the conditions of Comparative Example 1, it was confirmed that the sol-gel reaction did not proceed.

  According to the coating liquid for forming a low refractive index film, the low refractive index film and the like of the present invention, an antireflective film having a low refractive index can be easily and inexpensively manufactured without using an expensive material. Therefore, the invention is highly industrially applicable in this field and all related fields.

DESCRIPTION OF SYMBOLS 1 ... Alkoxysilane 2 ... Fluorine compound 3 ... Water 4 ... Solvent 5 ... Acid 10 ... Coating liquid 20 for low refractive index film formation ... Base material 30 ... Applied base material 50 ... Low refractive index film H ... Thermal stirring process P1 ... Application process P2 ... Heating process

Claims (9)

A coating solution for forming a low refractive index film, comprising an alkoxysilane and a fluorine compound, wherein the fluorine compound is either hydrofluoric acid or hexafluorosilicic acid. 2. The coating liquid for forming a low refractive index film according to claim 1, wherein the fluorine compound is added so as to form a film having a specific refractive index. The low-refractive-index film-forming material according to claim 1 or 2, wherein the fluorine compound is added so that fluorine is 0.01 mol or more and 0.1 mol or less with respect to 1 mol of alkoxysilane. Coating liquid. A low refractive index film obtained by using the coating liquid for forming a low refractive index film according to claim 1. The low refractive index film according to claim 4, wherein the refractive index is in a range of 1.30 or more and 1.43 or less. A method for producing a low refractive index film, comprising: applying a coating liquid for forming a low refractive index film according to any one of claims 1 to 3 to a substrate; and heat-treating the coating liquid. The method for producing a low refractive index film according to claim 6, wherein the refractive index is adjusted by the addition amount of the fluorine compound. The method for producing a low refractive index film according to claim 7, wherein at least one of tetraalkoxysilane or trialkoxysilane is used as the alkoxysilane. 6. An applied product comprising the low refractive index film according to claim 4 or 5.

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