JPH08122501A - Low refractive index antireflection film - Google Patents

Abstract

PURPOSE: To provide a low refractive index-antireflection film for reducing the reflection on the surface of plastic or glass and a transparent substrate having this film. CONSTITUTION: A coating liquid consisting of (a) silica sol having 5-30nm particle size and (b) at least one component selected from the group consisting of hydrolyzate of alkoxysilane, hydrolyzate of metal alkoxide and metal salt, and contained in an organic solvent at the ratios of 10-50 pts.wt. (b) expressed in terms of metal oxide to 10-100 pts.wt. SiO2 of (a) is applied to a substrate. Then, it is cured to obtain the film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-refractive-index antireflection film for reducing reflection on the surfaces of plastics and glass, and further a transparent substrate having a low-refractive-index antireflection film useful for display surfaces, lenses and the like. The material is provided.

[0002]

2. Description of the Related Art Conventionally, it has been known that a reflectance of a substrate is lowered by applying a coating having a refractive index lower than that of the substrate, and a coating having a low refractive index is used as an antireflection film. . Generally, a low-refractive index film is obtained by forming a stable low-refractive index substance such as MgF ₂ on a substrate by a vapor phase method such as vacuum deposition.

On the other hand, it is known that a high antireflection effect can also be obtained by alternately laminating a low refractive index coating and a high refractive index coating on a base material to form a multilayer structure.
A low-refractive index material typified by ₂ and a high-refractive index material such as TiO ₂ and ZrO ₂ are alternately deposited to form a film by a vapor phase method or a sol-gel method. Formed by the method.

The formation of an antireflection film by a vapor phase method such as vacuum deposition generally requires a large-scale apparatus and is not suitable for forming a large area film. Further, a method of alternately laminating a low refractive index coating and a high refractive index coating by a vapor phase method to form a multilayer structure requires a long time for production and is not practical. As a method for forming a multilayer coating film, a coating method using a sol-gel method has been used in recent years.
It is not economical because coating and baking are repeated on a large area substrate, and it is difficult to form a uniform coating because the baking is repeated a large number of times, and the substrate is deformed or the coating cracks. There was a problem.

In order to solve these problems, there have been proposed some low refractive index film forming methods by a coating method which can easily obtain an antireflection film. Japanese Unexamined Patent Publication No. 5-105422 proposes a coating liquid containing MgF ₂ fine particles, but has problems such as poor mechanical strength of the obtained coating and poor adhesion to a substrate. In JP-A-6-157076, a mixture of hydrolysis-condensation products of alkoxysilanes having different molecular weights is used as a coating liquid to form fine irregularities on the surface of the coating film to form an antireflection film having a low refractive index. However, there have been problems such as the control of the surface roughness of the coating by controlling the relative humidity during the coating formation and the complicated production of the condensate having different molecular weights.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above problems and provides a low refractive index antireflection film having excellent mechanical strength and high adhesion to a substrate, and a low refractive index antireflection film. It is intended to provide an applied transparent substrate.

[0007]

The present invention provides 5-30 nm
A silica sol (a) having a particle size of, and at least one component (b) selected from the group consisting of a hydrolyzate of an alkoxysilane, a hydrolyzate of a metal alkoxide and a metal salt, and Obtained by applying a coating solution containing 10 to 50 parts by weight of (b) as a metal oxide to an organic solvent to 100 parts by weight of SiO ₂ and then curing it. It is a low refractive index antireflection film.

In the coating liquid for forming the above low refractive index antireflection film, the silica sol of the component (a) is 5 to 30 nm.
A sol in which silica particles having a particle diameter of (nanometer) are dispersed in water or an organic solvent. The silica sol used in the present invention is a method of de-alkalizing the alkali metal ion in the silicic acid alkali salt by ion exchange or a method of neutralizing the silicic acid alkali salt with a mineral acid to condense active silicic acid. A known aqueous silica sol obtained by the above, a known silica sol obtained by condensing an alkoxysilane in an organic solvent in the presence of a basic catalyst, and further, water in the above aqueous silica sol by a distillation method or the like. An organic solvent-based silica sol (organo silica sol) obtained by substituting with an organic solvent is used. Since the silica sol used in the present invention can be used as either an aqueous silica sol or an organic solvent-based silica sol, it is not necessary to completely replace water with an organic solvent in the production of the organic solvent-based silica sol. The silica sol used in the present invention contains a solid content of 5 to 50% by weight as SiO ₂ . In the present invention, silica particles are used to form fine irregularities on the surface of the substrate, but the silica particles in the silica sol may have any shape. For example, a spherical shape, a needle shape, a plate shape, a shape in which beads are connected, and the like can be given. The organic solvent used in the organic solvent-based silica sol, for example, alcohols such as methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, ketones such as methyl isobutyl ketone, methyl acetate, ethyl acetate, esters such as butyl acetate, Ethers such as diisopropyl ether, glycols such as ethylene glycol, propylene glycol, hexylene glycol, etc., glycol ethers such as ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, diethyl cellosolve, diethyl carbitol, hexane, heptane, etc. Of aliphatic hydrocarbons,
Aromatic hydrocarbons such as benzene, toluene, xylene,
N-methylpyrrolidone, dimethylformamide and the like can be mentioned, and these can be used alone or in combination, and hydrophilic solvents such as alcohols and glycol ethers are particularly preferable.

In the coating solution for forming the low refractive index antireflection film, the component (b) is a precursor that forms a metal oxide and has a film forming function. The alkoxysilane hydrolyzate used as the component (b) is obtained by hydrolyzing the alkoxysilane in an organic solvent in the presence of an acidic catalyst or a basic catalyst. Examples of the acidic catalyst include mineral acids such as nitric acid and hydrochloric acid, and organic acids such as oxalic acid and acetic acid, and examples of the basic catalyst include ammonia. Examples of the alkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraalkoxysilanes such as tetrabutoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, and propyl. Trimethoxysilane, propyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, pentyltrimethoxysilane, pentyltriethoxysilane,
Hexyltrimethoxysilane, hexyltriethoxysilane, heptyltrimethoxysilane, heptyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, stearyltrimethoxysilane, stearyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 3-hydroxypropyltrimethoxysilane, 3
-Hydroxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxytriethoxysilane, 3-methacryloxytrimethoxysilane, 3-methacryloxytriethoxysilane,
Trialkoxysilanes such as phenyltrimethoxysilane, phenyltriethoxysilane, trifluoropropyltrimethoxysilane, trifluoropropyltriethoxysilane, and dialkoxysilanes such as dimethyldimethoxysilane and dimethyldiethoxysilane. These can be used alone or in combination of two or more. Among the above alkoxysilanes, tetraalkoxysilanes such as tetramethoxysilane and tetraethoxysilane, trialkoxysilanes such as methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane and ethyltriethoxysilane can be preferably used.

In the coating solution for forming the above low refractive index antireflection film, the hydrolyzate of the metal alkoxide used as the component (b) is a metal alkoxide in an organic solvent in the presence of an acidic catalyst or a basic catalyst. Obtained by hydrolysis. As this catalyst, the same catalyst as that used for the hydrolysis of the alkoxysilane can be used.
Examples of the metal alkoxide include titanium tetraethoxide, titanium tetrapropoxide, titanium tetraalkoxide compounds such as titanium tetrabutoxide, zirconium tetraethoxide, zirconium tetrapropoxide, zirconium tetraalkoxide compounds such as zirconium tetrabutoxide, aluminum tributoxide. , Aluminum triisopropoxide, aluminum trialkoxide compounds such as aluminum triethoxide, barium dialkoxide compounds such as barium diethoxide, tantalum pentapropoxide, tantalum pentaalkoxide compounds such as tantalum pentabutoxide, cerium tetramethoxy , Cerium tetraalkoxide compounds such as cerium tetrapropoxide, Examples include yttrium trialkoxide compounds such as yttrium tripropoxide, niobium pentamethoxide, niobium pentaethoxide, niobium pentaalkoxide compounds such as niobium pentabtoxide, cadmium dialkoxide compounds such as cadmium dimethoxide, and cadmium diealkoxide. The
These can be used alone or in combination of two or more. Among the above metal alkoxides, titanium tetraalkoxide compounds, zirconium tetraalkoxide compounds, aluminum trialkoxide compounds, and tantalum pentaalkoxide compounds can be preferably used.

In the coating liquid for forming the above low refractive index antireflection film, any metal salt can be used as the metal salt used as the component (b) as long as it has a film forming ability.
Examples thereof include aluminum, bismuth, yttrium, zirconium, cerium, indium, and other hydrochlorides, nitrates, sulfates, oxalates, acetates, and basic salts thereof. These are used alone or in combination of two or more. I can do things. Among the above metal salts, nitrates, hydrochlorides,
Oxalate is preferable, and when it is used for electronic materials, nitrate and oxalate are preferable from the viewpoint of impurities.

The organic solvent used in the hydrolysis of the above alkoxysilane and metal alkoxide and the dissolution of the metal salt is, for example, alcohols such as methanol, ethanol, propanol and butanol, ketones such as acetone and methyl ethyl ketone, and benzene. , Toluene, xylene and other aromatic hydrocarbons, ethylene glycol, propylene glycol, hexylene glycol and other glycols, ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, diethyl cellosolve,
Glycol ethers such as diethyl carbitol, N-
Methylpyrrolidone, dimethylformamide and the like can be mentioned, and they can be used alone or in combination of two or more kinds. Further, in order to improve the long-term storage stability of the coating solution, or for the purpose of preventing unevenness in drying when the coating solution is applied to the substrate, after the hydrolysis is completed, the low boiling point alcohol by-produced is distilled off, It is possible to increase the boiling point and viscosity of the solvent in the coating liquid.

The component (b) contains at least one component selected from the group consisting of a hydrolyzate of an alkoxysilane, a hydrolyzate of a metal alkoxide and a metal salt. When the decomposed product is used alone, when the alkoxysilane hydrolyzate and the metal salt are used together, when the metal alkoxide hydrolyzate and the metal salt are used together, the alkoxysilane hydrolyzate and the metal alkoxide hydrolyzate It is preferable to use three kinds of metal salt and metal salt at the same time. When two or more components are contained from the component (b), the composition ratio of the hydrolyzate of the alkoxysilane, the hydrolyzate of the metal alkoxide, and the metal salt is (part by weight) of the hydrolyzate of the alkoxysilane. : (Hydrolyzate of metal alkoxide): (metal salt) = 1: 0.
05-5: 0.05-5 are preferable. This composition ratio is
It can be applied to both cases of selecting two kinds of components from the component (b) and selecting three kinds of components. However, the hydrolyzate of the alkoxysilane is calculated as SiO ₂ , the hydrolyzate of the metal alkoxide is calculated as MO _{n / 2} (n is the valence of the metal atom M), and the metal salt is M′O _{n /.
2} (n is the valence of the metal atom M ′).

When the component (b) is a combination of an alkoxysilane or metal alkoxide and a metal salt, a method of hydrolyzing the alkoxysilane or metal alkoxide in the presence of the metal salt, or a method of hydrolyzing the above alkoxide There is a method of adding a metal salt. In the case of the method of hydrolyzing an alkoxysilane or a metal alkoxide in the presence of a metal salt, it is not necessary to add a catalyst at the time of hydrolysis if the metal salt used is an acid salt.

The above-mentioned hydrolysis of the alkoxide can be carried out by separately hydrolyzing the alkoxysilane and the metal alkoxide, or by simultaneously hydrolyzing the both, but by mixing the hydrolysis liquid of the alkoxysilane and the metal alkoxide, After that, a method of further promoting hydrolysis is preferable. At this time, the hydrolysis is carried out by adding 0.5 to 5 times mol, preferably 0.5 to 2.5 times mol of water, relative to the number of moles of the alkoxy group, and water is usually added at room temperature. However, if necessary, it can be carried out under heating at 50 to 150 ° C. 50 ~ 150 for the purpose of aging after the completion of hydrolysis
It can be heated at a temperature of ° C for 0.5 to 5 hours. When using an aqueous silica sol, even when the organic solvent-based silica sol contains water, or even when the catalyst used for hydrolysis is dissolved in water and used in the form of an aqueous solution, the total amount of water added to this hydrolysis reaction Is 5 times or less the molar number of the alkoxy group including the water in the silica sol and the water in the catalyst aqueous solution.

When a metal alkoxide is used as the component (b), the rate of hydrolysis is high, and therefore the β-diketones such as acetylacetone and ethyl acetoacetate, ethylene glycol, and the like are used for the purpose of controlling the rate of hydrolysis. Add stabilizers such as glycols such as xylene glycol,
The rate of hydrolysis can be controlled. When a metal salt is used as the component (b), it occurs because the metal salt is crystallized and deposited on the surface of the coated film during drying after coating the substrate with the coating liquid. A precipitation inhibitor may be added for the purpose of preventing nonuniformity of the coating components. Examples of this precipitation inhibitor include ethylene glycol, N-methylpyrrolidone, dimethylformamide, dimethylacetamide and their derivatives, and these can be used alone or as a mixture of two or more kinds. The amount of the metal salt is converted into M′O _{n / 2} [n is the valence of the metal atom M ′], and the precipitation inhibitor is added to 1 part by weight of M′O _{n / 2} by weight. Is at least 1 part by weight or more.

In the coating solution for forming the low refractive index antireflection film of the present invention, the component (b) is converted to a metal oxide in an amount of 10 parts by weight per 100 parts by weight of SiO ₂ of the silica sol of the component (a). It may be used in an amount of 50 parts by weight, preferably 15 to 40 parts by weight. When the component (b) is converted into a metal oxide, the metal oxide is represented by a composition formula of a typical oxide of the metal. That is, the most stable oxide form of the metal is represented by the simplest integer ratio of the number of atoms of each of the metal atoms and oxygen atoms constituting the metal oxide, such as SiO ₂ and TiO ₂ .
₂ , ZrO ₂ , Al ₂ O ₃ , BaO, Ta ₂ O ₅ , Ce
O ₂ , Y ₂ O ₃ , Nb ₂ O ₅ , CdO, Bi ₂ O ₃ , I
Calculated as the form of n ₂ O ₃ . The coating liquid comprising the components (a) and (b) has a solid content of 0.1 to 15% by weight.
It is contained and has a viscosity of 1 to 150 [mPa · s], preferably 1 to 80 [mPa · s]. The above coating liquid may contain a thickener represented by a cellulosic compound, if desired.

The above-mentioned coating liquid can be applied to the substrate by a commonly used coating method such as dipping, spin coating, transfer printing, brush coating, roll coating, and spraying. The obtained coating film can be dried at a temperature of 50 to 80 ° C. and then cured at a temperature of 100 ° C. or higher, preferably 100 to 500 ° C. for 0.5 to 1 hour. This heat curing can be performed using an apparatus such as an oven furnace or a hot plate. The obtained film has a refractive index of 1.28 to
The surface hardness is 1.38 and the pencil hardness is 4H to 9H. Furthermore, when the component (b) in the coating liquid contains a metal alkoxide or a metal salt, 100 mJ / cm ² of ultraviolet ray (UV) having a wavelength of 180 to 400 nm is applied by a low pressure or high pressure mercury lamp after film formation and drying. By irradiating more than (millijoule / square centimeter), the curing reaction is accelerated in the coating film, and the coating film has high mechanical strength and high hardness even when cured at a relatively low temperature of 120 to 150 ° C. You can do it. In the present invention, a film having desired physical properties can be formed by coating and baking once.

In the present invention, a transparent substrate having the above-described low refractive index antireflection film can be obtained by using a transparent substrate as the substrate to be coated. Examples of the transparent base material include plastics and glass, which can be preferably used particularly for display surfaces such as LCD (liquid crystal display) and CRT (cathode ray tube display) and lenses.

[0020]

The silica sol used as the component (a) in the coating liquid for forming the low refractive index antireflection film of the present invention has fine particles on the surface of the coating film by using silica particles having a particle diameter in the range of 5 to 30 nm in a specific ratio. Since such unevenness is formed and the refractive index is lowered, a good antireflection effect can be obtained. This is the part (membrane surface) where minute irregularities are formed.
Is composed of the above silica particles (refractive index of about 1.45) and air (refractive index of 1.00), so that it is simulated from 1.28 to
Since it has a refractive index of about 1.38, it is lower than the refractive index of the base material (for example, the refractive index of glass is about 1.54, the refractive index of plastics is about 1.60), and the reflection It is thought that a preventive effect will appear.

However, a silica sol having a particle size of less than 5 nm is not preferable because it is difficult to stably produce it, and it is difficult to form irregularities on the coating surface, and when a silica sol having a particle size of more than 30 nm is used, The resulting coating is not preferable because it becomes cloudy due to light scattering and the transparency is reduced. In the above coating liquid, the hydrolyzate of the alkoxysilane, the hydrolyzate of the metal alkoxide, or the metal salt combined with the precipitation inhibitor as the component (b) each has a film forming ability. Further, the hydrolyzate and metal salt of metal alkoxide have functions such as improved chemical resistance, ultraviolet (UV) curability, and the ability to cure without applying high temperature. When the amount of the component (b) is less than 10 parts by weight in terms of the metal oxide with respect to 100 parts by weight of SiO ₂ of the silica sol of the component (a), the mechanical strength of the film obtained by heat curing and the compatibility with the base material Adhesiveness is reduced, which is not preferable, and when it exceeds 50 parts by weight, the proportion of silica particles decreases,
Formation of minute irregularities on the surface is insufficient, the refractive index is not sufficiently lowered, and the antireflection effect is insufficient.

When the solid content concentration of the coating solution used in the present invention is less than 0.1% by weight, the thickness of the coating film obtained by one coating is small, and the coating is repeated many times to obtain a predetermined thickness. Is required and not efficient. On the other hand, 15% by weight
If it is larger, the thickness of the coating obtained by one-time coating becomes thicker, it becomes difficult to obtain a uniform coating, and the storage stability of the coating liquid becomes poor, increasing the viscosity of the coating liquid, gelling, etc. It is not preferable because it causes.

[0023]

【Example】

Preparation of component (a) Silica sol (a1): A silica sol having a particle diameter of 15 nm and containing 30% by weight of silica particles as SiO ₂ and having IPA (isopropanol) as a dispersion medium. Silica sol (a2): particle size 8 nm, 3 as SiO ₂
A silica sol containing 0% by weight of silica particles and using methanol as a dispersion medium.

Silica sol (a3): S with a particle size of 12 nm
A silica sol containing 30% by weight of silica particles as iO ₂ and using methanol as a dispersion medium. Silica sol (a4): A silica sol having a particle diameter of 25 nm and containing 30% by weight of silica particles as SiO ₂ and using methanol as a dispersion medium. Silica sol (a5): Tetraethoxysilane is hydrolyzed with aqueous ammonia in ethanol to give a particle size of 15n.
A silica sol prepared by producing a silica sol of m, performing solvent substitution with methanol, and using methanol containing 10% by weight of silica particles as SiO ₂ as a dispersion medium.

Silica sol (a6): S with a particle size of 40 nm
A silica sol containing 30% by weight of silica particles as iO ₂ and using methanol as a dispersion medium. Silica sol (a7): A silica sol having a particle diameter of 80 nm and containing 30% by weight of silica particles as SiO ₂ and using methanol as a dispersion medium. Preparation of component (b) (film forming component) Film forming component (b1): Tetraethoxysilane 2 as alkoxysilane in a reaction flask equipped with a reflux tube.
0.8 g and 70.1 g of ethanol as a solvent were added, and the mixture was stirred and mixed using a magnetic stirrer.
What dissolved oxalic acid 0.1g in water 9g as a catalyst was added and mixed there. After mixing, the liquid temperature exothermed about 10 ° C. Continue stirring for 30 minutes, then at 60 ° C for 60 minutes.
After heating for 1 minute and then cooling to room temperature, a film-forming component (b1) having a solid content concentration of 6% by weight as SiO _2.
It was created.

Film-forming component (b2): equipped with a reflux tube
As an alkoxysilane,
14.6 g of xysilane and butyl cellosolve as a solvent
Add 38.8 g and stir with a magnetic stirrer.
Stir and mix. Zirconyl nitrate 2 as a metal salt there
2.3 g of the hydrate was added to 3.8 g of water and 0.4% of 60% strength nitric acid.
g as a precipitation inhibitor.
Mixed with 7.6 g of glycol glycol
It was added to the mixture and mixed. After mixing, the liquid temperature is 20 ℃ to 28 ℃
Fever. Continue to stir for 30 minutes as it is and alkoxy sila
And a metal salt. Another reflux tube
Tet as a metal alkoxide in the equipped reaction flask
2.5g lapropoxy titanium and butyl cello as solvent
Add 30.0 g of rubbing and stir for 30 minutes, then continue stirring
While mixing the above alkoxysilane hydrolyzate and metal salt,
Compound is added and mixed, and the solid content concentration is converted to metal oxide [Si
O ₂+ ZrO₂+ TiO₂] 6% by weight
The component (b2) was prepared.

Film-forming component (b3): 15.13 g of methyltriethoxysilane as an alkoxysilane and 45.6 g of butyl cellosolve as a solvent were placed in a reaction flask equipped with a reflux tube, and the mixture was stirred and mixed using a magnetic stirrer. . 3.8 g of aluminum nitrate nonahydrate as a metal salt was dissolved and mixed in 1.6 g of water and 2.5 g of ethylene glycol as a precipitation inhibitor, and the mixture was added thereto. After mixing, the liquid temperature exothermed from 20 ° C to 28 ° C. The mixture was stirred for 30 minutes as it was to obtain a mixture of a hydrolyzate of alkoxysilane and a metal salt. In a reaction flask equipped with another reflux tube, 1.4 g of tetrapropoxy titanium as a metal alkoxide and butyl cellosolve 3 as a solvent.
After adding 0.0 g and stirring for 30 minutes, the mixture of the alkoxysilane hydrolyzate and the metal salt was added and mixed while continuously stirring, and the solid content concentration was converted to metal oxide [SiO ₂ +
A film forming component (b3) containing 6% by weight of Al ₂ O ₃ + TiO ₂ ] was prepared.

Film-forming component (b4): In a reaction flask equipped with a reflux tube, 44.3 g of aluminum nitrate nonahydrate as a metal salt was dissolved in 30.7 g of ethylene glycol as a precipitation inhibitor using a magnetic stirrer. Then, 25.0 g of butyl cellosolve was further added to prepare a film-forming component (b4) having a solid content of metal oxide [Al ₂ O ₃ ] of 6% by weight.

Film-forming component (b5): In a reaction flask equipped with a reflux tube, 9.4 g of aluminum nitrate nonahydrate as a metal salt, 1.1 g of water, and 21.8 g of ethylene glycol as a precipitation inhibitor were magnetically added. Dissolve using a stirrer, and add 1 butyl cellosolve as a solvent.
4.5 g was added and mixed. Into a reaction flask equipped with another reflux tube, 16.8 g of tetrapropoxy titanium as a metal alkoxide and 36.4 g of hexylene glycol as a stabilizer were put and stirred for 30 minutes, and then the above-mentioned aluminum nitrate solution was added while stirring. And mixed for 30 minutes. Then, a film-forming component (b5) having a solid content concentration of metal oxide [Al ₂ O ₃ + TiO ₂ ] of 6% by weight was prepared.

Film-forming component (b6): 21.3 g of tetrapropoxytitanium as a metal alkoxide and 30.0 g of hexylene glycol as a stabilizer were placed in a reaction flask equipped with a reflux tube, and a magnetic stirrer was used for 30 minutes. After stirring, a mixed solution of 0.8 g of nitric acid having a concentration of 60% by weight as a catalyst, 1.4 g of water, and 46.5 g of putylcellosolve as a solvent was added with stirring and mixed, and then the stirring was continued for 30 minutes. And a film-forming component (b) having a solid content concentration of 6% by weight of metal oxide [TiO ₂ ].
6) was created.

Film-forming component (b7): In a reaction flask equipped with a reflux tube, 17.2 g of tetraethoxysilane as an alkoxysilane and butyl cellosolve 3 as a solvent.
After adding 5.3 g and stirring with a magnetic stirrer, aluminum nitrate nonahydrate 7.7 as a metal salt was added.
What was dissolved in 4.5 g of water and 35.3 g of ethylene glycol as a precipitation inhibitor was added and mixed. After mixing, the liquid temperature exothermed from 20 ° C to 25 ° C. 30 as it is
Stir for minutes and convert the solid content to metal oxide [Si
O ₂ + Al ₂ O ₃ ], 6% by weight of film-forming component (b7)
It was created.

Solvent (s1): ethanol. Solvent (s2): butyl cellosolve. Example 1 10 g of the above film-forming component (b1) and a particle diameter of 15 nm
IP containing 30% by weight of silica particles as SiO ₂
Silica sol with A (isopropanol) as a dispersion medium (a
1) 13.3 g and ethanol (s1) 3 as a solvent
4.2 g and butyl cellosolve (s2) 57.5 g were mixed using a magnetic stirrer to obtain a coating liquid.
The solid content weight ratio (coating-forming component b1 / silica particles a1) of this coating solution is 6/40. The composition of this coating solution is shown in Table 1. The coating liquid thus obtained was deposited on a 1.1 mm thick soda lime glass substrate having a transmittance of 91% at a wavelength of 550 nm using a spin coater,
After drying on a hot plate at 80 ° C for 5 minutes, 30
Heat in a 0 ° C clean oven for 60 minutes to obtain a film thickness of about 10
It was a cured film of 00Å (angstrom). And a spectrophotometer with a wavelength of 550 nm (manufactured by Shimadzu Corporation, W-
The transmittance was measured with a 160 type). The results are shown in Table 2. A cured coating having a film thickness of about 1000 Å (angstrom) was formed on a silicon substrate by the same method, and the refractive index was measured. The refractive index was measured by an ellipsometer (manufactured by Mizojiri Optical Co., Ltd.). Further, the film-forming property was evaluated by visually observing the above-mentioned film formed on the substrate, and if it was colorless and transparent, it was evaluated as (◯), and the others were evaluated as (white turbidity). The results are shown in Table 2.

Examples 2 to 6 Film-forming component (b1) and silica sol (a1 to a4)
And the solvent were mixed at the ratios shown in Table 1 to obtain a coating liquid.
By the same method as in Example 1, a cured coating having a film thickness of about 1000Å was formed on the glass plate using the obtained coating solution, and the transmittance at a wavelength of 550 nm and the film thickness of about 100 on a silicon substrate.
A 0 Å cured film was prepared and the refractive index was measured. Further, the film forming property was evaluated. The measurement results are shown in Table 2.

Example 7 10 g of the film-forming component (b1) and Si having a particle diameter of 15 nm
Silica sol (a1) 1 containing 30% by weight of silica particles as O ₂ and IPA (isopropanol) as a dispersion medium
3.3 g and 70 g of ethanol (s1) as a solvent were mixed using a magnetic stirrer to obtain a coating liquid.
The solid content weight ratio (coating-forming component b1 / silica particles a1) of this coating solution is 6/40. The composition of this coating solution is shown in Table 1.

Using the coating liquid thus obtained,
A film is formed on both sides of a 1.1 mm thick soda lime glass substrate by dip coating, dried in a 80 ° C. clean oven for 10 minutes, and then heated in a 300 ° C. clean oven for 30 minutes to obtain a film thickness. A hardened film of about 1000Å was used. Similarly, a film thickness of about 1000Å on a silicon substrate
A cured coating of was prepared. Then, in the same manner as in Example 1, the transmittance of the cured coating on the glass substrate was measured with light having a wavelength of 550 nm, and the refractive index of the cured coating on the silicon substrate was measured. Further, the film forming property was evaluated. The measurement results are shown in Table 2.

Example 8 10 g of the film-forming component (b2) and Si having a particle diameter of 15 nm
Silica sol (a1) 1 containing 30% by weight of silica particles as O ₂ and IPA (isopropanol) as a dispersion medium
3.3 g and 34.2 g of ethanol (s1) as a solvent
And 57.5 g of butyl cellosolve (s2) were mixed using a magnetic stirrer to obtain a coating liquid. The weight ratio of the solid content of this coating solution (film-forming component b2 / silica particles a)
1) is 6/40. The composition of this coating solution is shown in Table 1. The coating liquid thus obtained has a thickness of 1.
A film was formed on a 1 mm soda lime glass substrate using a spin coater and dried on a hot plate at 80 ° C. for 5 minutes, and then a high pressure mercury lamp (1000 W, illuminance 200 m
J / cm ² , wavelength 360nm) for 5 minutes UV (ultraviolet)
Irradiation was performed and heating was further performed in a cleansing oven at 300 ° C. for 30 minutes to obtain a cured film having a film thickness of about 1000Å. A cured film having a film thickness of about 1000Å was formed on a silicon substrate by the same method. Then, by the same method as in Example 1, the transmittance of the cured coating on the glass substrate was measured with light having a wavelength of 550 nm, and further, the refractive index of the cured coating on the silicon substrate was measured. Further, the film forming property was evaluated. The measurement results are shown in Table 2.

Example 9 10 g of the film-forming component (b3) and Si having a particle diameter of 15 nm
Silica sol (a1) 1 containing 30% by weight of silica particles as O ₂ and IPA (isopropanol) as a dispersion medium
3.3 g and 34.2 g of ethanol (s1) as a solvent
And 57.5 g of butyl cellosolve (s2) were mixed using a magnetic stirrer to obtain a coating liquid. Solid content weight ratio of this coating solution (coating forming component b3 / silica particles a
1) is 6/40. The composition of this coating solution is shown in Table 1. The coating liquid thus obtained was treated at a wavelength of 550
A film was formed on a polyethylene terephthalate film having a transmittance of 86% of 86% by using a spin coater and dried on a hot plate at 80 ° C. for 5 minutes, and then a high pressure mercury lamp (1000 W, illuminance 200 mJ / cm ² , wavelength 360 n).
m) for 5 minutes, and UV (ultraviolet) irradiation was performed for 60 minutes in a clean oven at 120 ° C. to obtain a cured film having a film thickness of about 1000 Å. Similarly, a film thickness of about 100 on a silicon substrate
A 0Å cured coating was created. Then, in the same manner as in Example 1, the cured film on the glass substrate was coated with a wavelength of 550 nm.
The light transmittance of the cured film was measured with the light of Example 1, and the refractive index of the cured film on the silicon substrate was measured. Further, the film forming property was evaluated. The measurement results are shown in Table 2.

Example 10 10 g of the film-forming component (b1), 40 g of methanol-dispersed silica sol (a5), and ethanol (s1) as a solvent.
7.5 g and butyl cellosolve (s2) 57.5 g were mixed using a magnetic stirrer to obtain a coating liquid.
The solid content weight ratio (coating-forming component b1 / silica particles a5) of this coating solution is 6/40. The composition of this coating solution is shown in Table 1. By the same method as in Example 1, a cured film having a film thickness of about 1000 Å was prepared on the glass plate using the obtained coating solution, and a transmittance of wavelength 550 nm and a cured film having a film thickness of about 1000 Å were formed on the silicon substrate. It was created and the refractive index was measured. Further, the film forming property was evaluated. The measurement results are shown in Table 2.

Examples 11 to 14 Film-forming components (b4 to b7) and silica sol (a1)
And the solvent were mixed at the ratios shown in Table 1 to obtain a coating liquid.
Using the obtained coating liquid, a cured film having a film thickness of about 1000Å was formed on the glass plate and the silicon substrate by the same curing method as in Example 8. Then, in the same manner as in Example 1, the transmittance of the cured coating on the glass substrate was measured with light having a wavelength of 550 nm, and the refractive index of the cured coating on the silicon substrate was measured. Further, the film forming property was evaluated. The measurement results are shown in Table 2.

Comparative Example 1 10 g of the film-forming component (b1) and Si having a particle size of 40 nm
Using a magnetic stirrer, 13.3 g of silica sol (a6) containing 30% by weight of silica particles as O ₂ and methanol as a dispersion medium, 34.2 g of ethanol (s1) and 57.5 g of butyl cellosolve (s2) as a solvent were used. And mixed to obtain a coating solution. The solid content weight ratio (coating-forming component b1 / silica particles a6) of this coating solution is 6/40. The composition of this coating solution is shown in Table 1.

In the same manner as in Example 1, a cured coating having a film thickness of about 1000 Å was formed on a glass plate using the obtained coating solution, and a transmittance of wavelength 550 nm and a film thickness of about 10 on a silicon substrate.
A cured film of 00Å was formed and the refractive index was measured. Further, the film forming property was evaluated. The measurement results are shown in Table 2. Comparative Examples 2 to 3 Film forming component (b1) and silica sol (a7, a1)
And the solvent were mixed at the ratios shown in Table 1 to obtain a coating liquid.
In the same manner as in Example 1, a cured coating having a film thickness of about 1000Å was formed on a glass plate using the obtained coating liquid, and a wavelength of 550 nm
And a refractive index was measured by forming a cured film having a film thickness of about 1000Å on a silicon substrate. Further, the film forming property was evaluated. The measurement results are shown in Table 2.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

As can be seen from Examples 1 to 14 in the table, in the present invention, silica sol (a) having a particle size of 5 to 30 nm is used.
And at least one component (b) selected from the group consisting of a hydrolyzate of an alkoxysilane, a hydrolyzate of a metal alkoxide, and a metal salt, and SiO _{2 of} (a)
With respect to 100 parts by weight, (b) is converted to a metal oxide in an amount of 10 to 50 parts by weight, and a coating solution containing an organic solvent is applied to a substrate and then cured to obtain a low refractive index. A cured coating having an antireflection function is obtained.

The measurement of the transmittance in Example 9 was carried out because a polyethylene terephthalate film having a transmittance of 86% was used in place of the soda lime glass having a transmittance of 91%.
The transmittance of the obtained cured film was 91.5%, but the film of the present invention lowered the refractive index of the base material (polyethylene terephthalate film), so that the transmittance of the base material was also relatively improved. A good antireflection effect was obtained. Further, the transmittance of Example 7 is as high as 98.1%, but since it is formed on both sides of the substrate by dip coating, the transmittance is further improved and a very good antireflection effect is obtained. .

However, in Comparative Example 1 or 2, when the particle diameter of the silica sol used exceeds 30 nm, diffuse reflection of light occurs on the surface of the cured coating, and the cured coating becomes cloudy. Further, in Comparative Example 3, when the amount of silica particles present in the obtained cured coating is small, the refractive index also becomes high and a good antireflection effect cannot be obtained.

[0048]

According to the present invention, the mechanical strength can be improved by a simple method such as a spin coating method or a dip coating method without using a large-scale apparatus used in a vapor deposition method or the like, and by applying and baking once. A low-refractive-index antireflection film that is excellent and has high adhesion to a substrate can be obtained. Further, in the present invention, since the cured film obtained has a low refractive index of 1.28 to 1.38, a film having an antireflection function can be provided on the surface of plastics or glass products. In particular, it is suitable for providing a film having an antireflection function on the surface of a transparent substrate such as a display and a lens.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takakazu Nakata 1 722, Tsuboi-cho, Funabashi-shi, Chiba Nissan Chemical Industry Co., Ltd. Central Research Laboratory

Claims (3)

[Claims] 1. A silica sol (a) having a particle size of 5 to 30 nm, and at least one component (b) selected from the group consisting of a hydrolyzate of an alkoxysilane, a hydrolyzate of a metal alkoxide, and a metal salt. And a coating solution containing (a) in an organic solvent at a ratio of 10 to 50 parts by weight in terms of metal oxide based on 100 parts by weight of SiO ₂ was applied to the substrate. A low-refractive-index antireflection film obtained by subsequent curing. 2. The low refractive index antireflection film according to claim 1, which has a refractive index of 1.28 to 1.38. 3. A transparent substrate having the low refractive index antireflection film according to claim 1 or 2.