JPH11152425A - Coating solution for forming gray colored film and method for forming coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject coating solution capable of easily obtaining substrates with films of such as glass, excellent in guarding privacy and suppressing solar radiation and having no uneven and haze feelings by containing a Si-alkoxide, a coloring metal salts comprising Cu, Mn and Cr in a specific ratio and a solvent. SOLUTION: This coating solution is made to include (A) an Si-alkoxide (e.g. tetraethoxy silane, etc.), (B) at least 3 species of coloring metal salts of Cu, Mn and Cr and (C) a solvent. Mutual mole % of metals are adjusted to be 30-70 mole % of Cu, 20-50 mole % of Mn and 5-35 mole % of Cr. The concentration of Si in the objective coating solution is preferably 0.01-4.5 mol/kg. The substrate having transmitted color tone unbiased to any tone, plain gray color and <=30% transmittance is obtained by coating the said coating solution on a transparent and colorless substrate and baking at a temp. of >=450 deg.C after drying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating liquid for forming a gray colored film applied on a substrate and a method for forming the coating film. In particular, by applying the coating liquid for forming a gray colored film to a glass substrate to form a film, the glass liquid can be suitably adopted as a glass aiming at suppression of sunlight, protection of privacy, and the like for transportation equipment such as buildings, structures, and vehicles.

[0002]

2. Description of the Related Art Conventionally, a colored frit or a coloring agent is mixed in a glass raw material itself, or a colored frit or the like is mixed in a molten glass and melted and molded (plate making) to obtain a colored glass. (Referred to as body coloring) is known, and is itself manufactured by a large-scale glass manufacturing and plate-making apparatus. However, in recent years, a variety of demands such as color sense of users have been rapidly increasing, and it is difficult to change the color tone and density according to the demands in a flexible manner. Incurs considerable loss of raw materials.

[0003] As another means, there is a method in which a coating material in which an inorganic oxide pigment is dispersed is applied to glass and heat-treated.
It is not easy to uniformly disperse the inorganic oxide pigment, and the preparation of the coating solution becomes complicated, and the cost is not inexpensive,
In addition, there are disadvantages such as a haze feeling (white turbidity due to inorganic pigment powder) in the coating film.

It is also known to apply a mixed solution of a plurality of metal alkoxides such as Si-alkoxide to glass and heat-treat the glass. However, the colorable metal alkoxide of the present invention can be obtained or prepared easily and inexpensively. However, it is not suitable for obtaining a colored film having a desired color tone.

In general, a method is known in which a mixed solution of an alkoxide of a metal that is easily alkoxylated (for example, Si-alkoxide) and an inorganic salt of another metal is applied to a substrate and baked. Are scattered.

Japanese Patent Application Laid-Open No. Sho 62-158136 discloses a film for suppressing alkali diffusion of an alkali glass substrate in a glass with a conductive film or the like, which comprises silica sol starting from Si-alkoxyside, a phosphorus compound, Al and Cr. , Mo, Fe, or a solution in which at least one compound soluble in an organic solvent of Sn (chloride, acetate, etc.) is mixed, applied to a substrate, dried,
Baking to form a film is disclosed.

Japanese Patent Application Laid-Open No. 63-124331 discloses a method for forming an anti-glare and antistatic film on a cathode ray tube, and adding a halogen such as Fe, Co, Ni, and Cu to a silica sol solution based on Si-alkoxide or the like. Compound, nitrate, or sulfate, and spray it onto a CRT,
Firing is disclosed.

JP-A-4-97103 discloses a Ti-sol solution based on a Ti-alkoxide or the like, a liquid containing an inorganic salt of Ce (nitrate, chloride, sulfate) and a polyhydric alcohol. There is disclosed an ultraviolet cut filter formed by applying to a substrate and firing.

Japanese Patent Application Laid-Open No. 8-104546 discloses that Si is added to glass.
-Applying and drying a lower layer of a silica sol solution based on an alkoxide or the like, and then drying the Ti-alkoxide (sol), Ce-alkoxide (sol) or inorganic salt (chloride, nitrate, sulfate, etc.), Zn-alkoxide (sol) Alternatively, there is disclosed a glass with an ultraviolet absorbing film formed by applying one or more solutions of an inorganic salt, drying and firing, and further strengthening or bending at a higher temperature (650 ° C. or higher).

These are different from the objectives of the present invention to obtain a gray colored privacy glass and a solar control glass, in particular, to obtain a glass which greatly reduces the visible light transmittance and has no unevenness or haze.

[0011] The present invention is a coating for forming a gray colored film which is excellent in privacy property and solar radiation suppression property, in particular, greatly reduces the visible light transmittance and can easily obtain a film-coated substrate such as glass without unevenness or haze. The present invention provides a liquid and a method for forming a gray colored coating film therewith.

[0012]

SUMMARY OF THE INVENTION The present invention comprises a Si-alkoxide and at least three coloring metal salts of Cu, Mn and Cr,
And a solvent, and wherein the mutual metal mole% of the colorable metal salt is adjusted to Cu 30 to 70, Mn 20 to 50, and Cr 5 to 35.

In the above, the Si concentration is 0.01 to 1.5 mol / kg.
And preferably 0.4 to 1.2 mol / kg. Furthermore, the ratio of the number of moles of Si to the total number of moles of coloring metal ΔM ΔM
/ Si is from 0.1 to 7, preferably from 0.5 to 4.

The present invention also relates to a method for forming a gray colored coating film in which the coating liquid for forming a colored film is applied to a transparent non-colored substrate, dried and baked at 450 ° C. or higher. Is preferred.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In a coating film forming substrate using the coating liquid of the present invention, the transmission color tone is not biased to any color tone.
There is no habit, so-called neutral or near neutral gray,
When this is applied to a colorless transparent substrate, the visible light transmittance can be adjusted in a wide range, but the transmittance is preferably in the order of 30% or less, more preferably 25% or less, and unevenness and haze A substrate without a film can be obtained, and it can be used as a good solar radiation suppressing, privacy protecting plate or glass.

The Si-alkoxide is indispensable for forming a vitreous coating film on the substrate, intimately adhering to the substrate and uniformly dispersing the coloring metal. As the Si-alkoxide, although not particularly specified, a material which is easily available and relatively inexpensive, for example, tetraethoxysilane, methyltriethoxysilane, methyltrimethoxysilane and the like can be employed. In addition, a part of Si is uncolored B, C
Substitution with a, Mg, P, Na or the like is also within the scope of the present invention.

As the coloring metal, a mixture of Cu, Mn, and Cr at a predetermined metal molar ratio is used to obtain a neutral to near neutral gray to dark gray coloring. AL, Fe, Co, Ni, T as other coloring metal or color adjusting metal
A small amount of i, Zr, etc. is acceptable, but in order to obtain a neutral or near-neutral gray tone for the purpose of the present invention, Cu,
The above metal is 10 mol% based on the total mol% (100) of Mn and Cr.
Should be around or below.

After coating and drying, the coating film baked at 450 ° C. or higher becomes a SiO ₂ —CuMnCrOx-based film, and its transmission color tone is as shown in FIG. Cu should be 30-70 mol%,
If it is less than 30 mol%, it is brown or an intermediate color between brown and gray. If it exceeds 70 mol%, it is almost colorless, brown, or an intermediate color between brown and gray. Mn is set to 20 to 50 mol%, and if it is less than 20 mol%, it is almost colorless, brown or an intermediate color between brown and gray, and if it exceeds 50 mol%, it becomes almost brown. Cr should be 5 to 35 mol%.
If it is less than mol%, it is almost colorless, brown or an intermediate color between brown and gray, and if it exceeds 35 mol%, it becomes brown or an intermediate color between brown and gray.

However, by mixing these Cu, Mn and Cr uniformly within the above range, a neutral or nearly neutral gray color can be obtained. As the salt of the coloring metal, it is easy to obtain and prepare, the Si- in the presence of water or alcohol solvent.
It is desirable to employ nitrates, acetates, chlorides and the like which can be uniformly dissolved in the alkoxide liquid and microscopically dispersed.

The molar concentration of Si in the coating liquid is 0.01 to 1.5 mol /
If the amount is less than 0.01 mol, the film tends to be cloudy and translucent, and good transparency cannot be obtained.
When the thickness exceeds, the film becomes too thick at the time of film formation, cracks are easily generated in the film, and a uniform film cannot be obtained. Preferably 0.4
~ 1.2 mol / kg.

The metal molar ratio ΣM / Si of the number of moles of Si and the total number of moles of coloring metal ΣM is 0.1 to 7. ΣM / Si
If it is less than 0.1, sufficient solar shading and privacy cannot be obtained because the amount of the coloring metal is small relative to the silica matrix. On the other hand, if it exceeds 7, haze tends to occur in the film, and good transparency cannot be obtained. Preferably 0.5 to 4
And

The solvent in the coating liquid is alcohol,
Uses water (water also acts as a condensate of Si-alkoxide and acts as a silica sol-forming agent), and uses cellosolves such as ethyl cellosolve and methyl cellosolve that are compatible with the alcohol and water and adjust the viscosity of the coating solution. I do.

The coating liquid is applied to a transparent non-colored substrate, preferably glass such as soda-lime glass, aluminosilicate glass, borosilicate glass, etc. by roller coating, dipping, flow coating, spraying, spin coating. It is dried after being applied by an application means such as a method. In order to form a firmer film, it is necessary to fire at a temperature of 450 ° C or higher.

After coating and drying, a film can be formed at a firing temperature of 600 ° C. or more while also performing a bending treatment, a strengthening treatment, a laminated bending treatment and the like, and can be suitably used as, for example, a window glass for automobiles.

When a multilayer laminated film is formed on a substrate, at least one of these films can be formed by the above-mentioned gray colored coating film forming method.

[0026]

Example 1 [Example 1] 93.8 g of tetraethoxysilane was dissolved in 135 g of ethanol, and a small amount of water and nitric acid were added.
Further, ethanol was added so that the total amount became 300 g, and the mixture was stirred for 2 hours and hydrolyzed to obtain a silica sol solution.
The concentration of Si in this silica sol solution was 1.5 mol / kg.

In 150 g of this silica sol, 13.7 g of copper nitrate (trihydrate), 16.5 g of manganese nitrate (hexahydrate),
23.0 g of chromium nitrate (9 hydrate) was added and dissolved, and 96.9 g of ethanol was further added to make the total amount 300 g, followed by stirring for 1 hour to dissolve each colorable metal nitrate to obtain a coating liquid.

In this coating, the metal molar ratio of each coloring metal nitrate is Cu: Mn: Cr = 1: 1: 1 (33.3 mol% of Cu, 33.3 mol% of Mn at 100% of all coloring metal moles). mol
%, Cr 33.3 mol%), and the metal molar ratio of silicon to the total colorable metal (ΔM) is Si: ΔM = 4: 3. The Si concentration in this solution is 0.75 mol / kg. there were.

A soda-lime glass float plate having a size of 150 × 150 mm and a thickness of 3.5 mm was washed and dried, and a masking tape was stuck on the back surface to prepare a substrate for film formation.

This was immersed in the previously prepared coating solution, and was applied by pulling at a pulling speed of 6 mm / s. After peeling off the masking tape, it was heated at 350 ° C for 10 minutes, and then baked at 600 ° C for 10 minutes to obtain a film-formed glass sample.

The obtained glass was gray, and the visible light transmittance as determined from the spectral transmittance was 27.6%. The haze value was as low as 0.2%, and no unevenness or white turbidity was observed even when the external appearance was observed by irradiation with a halogen lamp.

Example 2 The silica sol solution of Example 1 133.
14.6 g of copper nitrate (trihydrate) and manganese nitrate (6
Hydrate) and 12.3 g of chromium nitrate (9-hydrate) were dissolved, and 100 g of ethanol and 22.3 of ethyl cellosolve were dissolved.
g to make the total amount 300 g.

In this coating liquid, the metal molar ratio of each coloring metal nitrate is Cu: Mn: Cr = 40: 40: 20,
In addition, the metal molar ratio of silicon and the total coloring metal is Si: Σ
M = 4: 3, and the Si concentration in the coating liquid at this time was 0.
It was 67 mol / kg.

The glass substrate coated, dried and baked in the same manner as in Example 1 has a slightly bluish gray color.
The visible light transmittance was 23%. The haze value is 0.1
%, And no external turbidity or unevenness was observed even when the external appearance was observed by irradiation with a halogen lamp.

Example 3 A 1.5 mol / kg silica sol solution was prepared using methyltriethoxysilane as a starting material in the same manner as in Example 1, and copper nitrate (trihydrate) was added to 133.3 g of this sol solution.
18.2 g, 11.0 g of manganese nitrate (hexahydrate), 15.3 g of chromium nitrate (9 hydrate) were dissolved, and a 1: 1 solution (weight ratio) of ethanol and methanol was added to make the total amount 400 g. The coating liquid was used.

In this coating solution, the metal molar ratio of each coloring metal nitrate is Cu: Mn: Cr = 50: 25: 25, and the metal molar ratio of silicon to all coloring metals is Si: ΔM = 4:
3, and the Si concentration in the coating solution was 0.50 mol / kg.

As in the first embodiment, the lifting speed is 9 mm / s
After applying, drying and firing the coating liquid on the glass substrate,
The color was gray, and the transmittance was 30.3%. Further, the haze value was as low as 0.1%, and no unevenness was observed.

Example 4 100 g of the silica sol solution of Example 1
In the same manner as in Example 1, 33.3 g of a 1.5 mol / kg silica sol solution using methyltrimethoxysilane as a starting material was added, and 12.1 g of copper nitrate (trihydrate) and manganese nitrate (hexahydrate) were further added. ) And 20.2 g of chromium nitrate (9 hydrate)
g was dissolved, and ethanol was further added to make a total amount of 200 g, which was used as a coating liquid. In this coating liquid, the metal molar ratio of each coloring metal nitrate is Cu: Mn: Cr = 33.3: 50: 16.7, and the metal molar ratio of silicon to all coloring metals is Si:
ΣM = 4: 3, and the Si concentration in the coating liquid was 1.0 mol / k
g.

In the same manner as in Example 1, the coating liquid formed on a glass substrate at a film forming rate of 2 mm / s and baked was a slightly bluish gray color, with a transmittance of 37.9% and a haze value of Is
At 0.1%, no unevenness was observed.

Example 5 The silica sol solution of Example 1 133.
18.2 g of copper nitrate (trihydrate) and manganese nitrate (6
Hydrate) and 10.2 g of chromium nitrate (9-hydrate), and then add isopropyl alcohol to make a total of 450 g.
I made it.

In this coating liquid, the metal molar ratio of each coloring metal nitrate is Cu: Mn: Cr = 50: 33.3: 16.7, and the metal molar ratio of silicon to all coloring metals is Si: ΣM =
4: 3, and the Si concentration in the coating liquid was 0.44 mol / kg.

As in the case of Example 1, the one coated, dried and baked on a glass substrate at a film formation rate of 1 cm / s is a slightly bluish gray color, has a low transmittance of 24.5%, and has a haze value of
At 0.1%, no unevenness was observed.

Example 6 The silica sol of Example 1 133.
18.2 g of copper nitrate (trihydrate) and manganese nitrate (6
Hydrate) and 10.2 g of chromium nitrate (9-hydrate) were dissolved.

In this solution, the metal molar ratio of each coloring metal nitrate is Cu: Mn: Cr = 50: 33.3: 16.7.
The metal molar ratio of silicon to the total coloring metal is Si: ΣM =
4: 3, and the Si concentration in the coating solution was 1.2 mol / kg.

As in Example 1, a film formed and fired on a glass substrate at a film formation rate of 1 mm / s is a slightly bluish gray color, has a low transmittance of 24.5% and a haze value of 0.1. %
And no unevenness was observed.

Example 7 The silica sol solution of Example 1 133.
12.1 g of copper nitrate (trihydrate) and manganese nitrate (6
Hydrate) and 15.3 g of chromium nitrate (9-hydrate) were dissolved, and a 3: 1 solution (weight ratio) of ethanol and 1-methoxy-2-propanol was added to make a total amount of 300 g.

In this coating liquid, the metal molar ratio of each coloring metal nitrate is Cu: Mn: Cr = 33.3: 41.8: 25, and the metal molar ratio of silicon to all coloring metals is Si: ΣM
= 4: 3, and the Si concentration in the coating liquid was 0.67 mol / kg.

The glass substrate coated, dried and baked in the same manner as in Example 1 was gray, had a low transmittance of 28.6%, a haze of 0.2%, and no unevenness was observed.

Example 8 The silica sol of Example 1 133.
In 3 g, 17.2 g of copper acetate (monohydrate), 10.8 g of manganese acetate (tetrahydrate) and 7.4 g of chromium acetate (hexahydrate) are dissolved,
Further, a 3: 1 solution of ethanol and ethyl cellosolve was added to make the total amount 300 g.

In this coating liquid, the metal molar ratio of each colorable metal salt is Cu: Mn: Cr = 57.1: 28.6: 14.3.
The metal molar ratio of silicon to the total coloring metal is Si: ΣM =
4: 3, and the Si concentration in the coating liquid was 0.67 mol / kg.

The film formed and fired on the glass substrate in the same manner as in Example 1 had a gray color, a low transmittance of 26.6%, a haze value of 0.2%, and no unevenness was observed.

[Example 9] The silica sol solution of Example 1 13
To 3.3 g, 12.8 g of copper chloride (dihydrate) and manganese chloride (4
Hydrate) 11.4g, Chromium chloride (hexahydrate) 5.1g dissolved,
Ethanol and ethyl cellosolve 3: 1 (weight ratio)
The solution was added to a total volume of 300 g.

In this coating liquid, the metal molar ratio of each coloring metal nitrate is Cu: Mn: Cr = 50: 37.5: 12.5, and the metal molar ratio of silicon to all coloring metals is Si: ΔM
= 4: 3, and the Si concentration in the coating liquid was 0.67 mol / kg.

The film formed and baked on the glass substrate in the same manner as in Example 1 has a bluish gray color and a transmittance of 2
As low as 3.8%, the haze value was 0.2%, and no unevenness was observed.

Example 10 The silica sol 13 of Example 1
To 3.3 g, 26.2 g of copper nitrate (trihydrate), 19.5 g of manganese nitrate (hexahydrate), and 6.8 g of chromium nitrate (9 hydrate)
After dissolution, ethanol was further added to bring the total amount to 300 g.

In this coating liquid, the metal molar ratio of each coloring metal nitrate is Cu: Mn: Cr = 44.4: 44.4: 11.1, and the metal molar ratio of silicon to all coloring metals is Si: ΣM
= 4: 3, and the Si concentration in the coating liquid was 0.67 mol / kg.

A film formed and fired on a glass substrate in the same manner as in Example 1 was gray and had a low transmittance of 28.4%.
The haze value was 0.2%, and no unevenness was observed.

[Examples 11 to 19] As in Example 1, except that the metal molar ratio of the coloring metal nitrate was Cu: Mn: Cr = 62.
5: 25: 12.5 (Example 11), 45.5: 45.5: 9.1 (Example 12), 66.7: 22.2: 11.1 (Example 13), 60:30:
10 (Example 14), 46.7: 26.7: 26.7 (Example 15),
36.7: 31.7: 31.7 (Example 16), 40:30:30 (Example 17), 53.3: 23.3: 23.3 (Example 18), 33.3: 40:
In the same manner as in Example 1, a coating liquid in which the metal molar ratio of silicon to the total colorable metal was Si: ΔM = 4: 3 was formed on a glass substrate and baked as in Example 1. Table 1 shows the results. All are gray or slightly bluish gray, and the haze value is 0.3% or less.
No unevenness was observed.

[Comparative Example 1] The silica sol solution of Example 1 133.
Dissolve 3 g of 9.1 g of copper nitrate (trihydrate), 11.0 g of manganese nitrate (hexahydrate), and 30.6 g of chromium nitrate (9 hydrate), and add ethanol to make the total amount 300 g. did.

In this coating liquid, the metal molar ratio of each coloring metal nitrate is Cu: Mn: Cr = 25: 25: 50, and the metal molar ratio of silicon to all coloring metals is Si: ΣM = 4:
3, and the Si concentration in the coating liquid was 0.67 mol / kg.

The glass substrate coated, dried and fired in the same manner as in Example 1 had a transmittance of 30.1%, but had an intermediate color between gray and bronze, and did not show a gray color. .

[Comparative Examples 2 to 11] As in Example 1, except that the metal molar ratio of each coloring metal nitrate was Cu: Mn: Cr = 2.
5:50:25 (Comparative Example 2), 50: 0: 50 (Comparative Example 3), 7
5:15:10 (Comparative Example 4), 60:10:30 (Comparative Example 5), 5
0:10:40 (Comparative Example 6), 66.7: 16.7: 16.7 (Comparative Example 7), 33.3: 26.7: 40 (Comparative Example 8), 33.3: 53.3: 13.3
(Comparative Example 9), 40: 60: 0 (Comparative Example 10), 60: 40: 0
(Comparative Example 11) A coating liquid obtained by applying, drying, and firing a coating liquid in which the metal molar ratio of silicon and the total colorable metal was Si: ΔM = 4: 3 in the same manner as in Example 1. Table 2 shows the results. Each of them showed an intermediate color between bronze and gray, and did not become gray.

[Comparative Example 12] The silica sol solution 13 of Example 1
To 3.3 g, 12.1 g of copper nitrate (trihydrate) and chromium nitrate (9
(Hydrate) was dissolved in 40.8 g, and ethanol was further added to make the total amount 300 g.

In this coating liquid, the metal molar ratio of each coloring metal nitrate is Cu: Cr = 33.3: 66.7, and the metal molar ratio of silicon and all coloring metals is Si: ΔM = 4: 3. The Si concentration in the coating solution was 0.67 mol / kg.

The film formed and fired on the glass substrate in the same manner as in Example 1 had a transmittance of 51.6%, was a bronze color, and did not show a gray color.

[Comparative Examples 13 to 30] As in Example 1,
However, the metal molar ratio of the coloring metal nitrate is Cu: Mn: Cr = 3
3.3: 16.7: 50 (Comparative Example 13), 33.3: 58.3: 8.3 (Comparative Example 14), 33.3: 66.7: 0 (Comparative Example 15), 40:20:
40 (Comparative Example 16), 20:40:40 (Comparative Example 17), 0:10
0: 0 (Comparative Example 18), 0: 0: 100 (Comparative Example 19), 5
0: 50: 0 (Comparative Example 20), 0:50:50 (Comparative Example 2)
1), 80: 20: 0 (Comparative Example 22), 0:70:30 (Comparative Example 23), 0:55:45 (Comparative Example 24), 0:20:80 (Comparative Example 25), 33.3: 13.3 : 53.3 (Comparative Example 26), 33.3: 6
6.7: 0 (Comparative Example 27), 46.7: 53.3: 0 (Comparative Example 2)
8), 53.3: 46.7: 0 (Comparative Example 29), 66.7: 33.3: 0
(Comparative Example 30) The result of applying, drying, and firing a coating liquid on a glass substrate in the same manner as in Example 1 with a coating liquid in which the metal molar ratio of silicon and the total colorable metal was Si: ΔM = 4: 3 was used. It is shown in Table 2. Each of them showed a bronze color and did not become a gray color.

[Comparative Example 31] The silica sol solution 13 of Example 1
36.4 g of copper nitrate (trihydrate) was dissolved in 3.3 g, and ethanol was further added to bring the total amount to 300 g. This coating liquid was applied to a glass substrate in the same manner as in Example 1, dried and fired,
It was colorless and transparent.

The color tone, transmittance, and haze value of the samples obtained in each of the examples and comparative examples are shown in Table 1, respectively.
Table 2 shows the relationship between the composition and the transmission color tone of these examples and comparative examples, as shown in FIG. 1. In the range of this example, a good gray color tone, a low haze value, and no unevenness were observed. A glass is obtained.

[0069]

[Table 1]

[0070]

[Table 2]

[0071]

The coating liquid of the present invention is inexpensive and easily available and can be prepared. Further, in a transparent substrate on which a coating film is formed using the coating liquid, the transmission color tone is not biased to any color tone and has no habit. A substrate having a gray color and having a transmittance of the order of 30% or less, preferably 25% or less can be obtained. Applicable to colorless transparent glass substrates.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the composition and the transmission color tone of an example according to the present invention and a comparative example.

Claims (4)

[Claims] 1. The method according to claim 1, wherein the metal alkoxide contains at least three kinds of coloring metal salts of Cu, Mn and Cr, and a solvent, and the mutual metal mole% of the coloring metal salt is Cu 30 to 70, Mn
A coating liquid for forming a gray colored film, prepared in the range of 20 to 50 and Cr of 5 to 35. 2. The coating solution for forming a gray colored film according to claim 1, wherein the Si concentration is 0.01 to 1.5 mol / kg. 3. The coating solution for forming a gray colored film according to claim 1, wherein the metal molar ratio ΔM / Si of the number of moles of Si and the total number of moles of coloring metal ΔM is 0.1 to 7. . 4. A method for forming a gray colored coating film, comprising applying the coating liquid for forming a colored film according to claim 1 to a transparent uncolored substrate, drying and firing at 450 ° C. or higher.