JPH06116510A - Production of iridescent luster pigment - Google Patents

Abstract

PURPOSE:To easily and efficiently produce an iridescent luster pigment exhibiting bright reflective interference color. CONSTITUTION:An iridescent luster pigment is produced by coating a transparent flaky substrate with titania, zirconia or their mixture and heat-treating the coated product. In the above process, the transparent flaky substrate has a light transmittance of <=50% for at least a part of light of a wavelength range of 400-800nm and is produced from a solution containing a hydrolyzable and polycondensable organometallic compound and a substance causing the light absorption.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a pearlescent pigment, and more particularly to a method for producing a pearlescent pigment having flake coated with metal oxide fine particles composed of titania, zirconia alone or a mixture thereof.

[0002]

2. Description of the Related Art At present, a pearlescent pigment having a semitransparent layer of fine titania particles formed on a mica flakes is widely used.

As a method of coating titania on the mica flakes, a method of hydrolyzing a sulfuric acid acid titanium oxysulfate solution at a boiling temperature (for example, Japanese Examined Patent Publication No. 43-25644),
Hydrolysis Method of Titanium Tetrachloride (For example, Japanese Patent Publication No. 49-38)
No. 24) is generally known. In these methods, after coating with titanium hydroxide, heat treatment is performed at 700 to 1000 ° C. to form a titania coating layer that is stable and has high brightness.

On the other hand, the present inventors have proposed to use flake-shaped glass instead of mica flakes to produce pearlescent pigments. The advantage of using glass flakes instead of mica flakes lies in the good surface smoothness of the glass flakes. That is, the glass flakes do not have large surface irregularities like mica, and when a titania layer is provided, multiple reflection in the titania layer is good, and the color tone is more beautiful.

Since neither mica nor flake-shaped glass has a low visible light transmittance, when these pigments coated with titania are placed on a bright background, a reflection interference color and a transmission interference color appear to be mixed. The reflection interference color and the transmission interference color are complementary to each other, and the mixed color thereof is white. Thus, this type of pigment placed on a bright background has the disadvantage that its characteristic reflection interference color is less likely to appear.

[0006]

As a method for solving this drawback, titanium dioxide coated on mica is reduced to form black as titanium oxide in a low oxidation state, and titanium dioxide is further coated thereon. Have been used to enhance reflection interference colors (for example, Fukuji Suzuki,
See New Ceramics, No. 1, 79-84 (1991).). However, this method has a problem in that the titanium dioxide coating, the reduction operation, and the titanium dioxide coating are complicated operations and are disadvantageous from the viewpoint of industrial use.

In view of the above-mentioned prior art, the present invention provides a method capable of easily and efficiently producing a pearlescent pigment having a vivid reflection interference color.

[0008]

That is, the present invention provides a method for producing a pearlescent pigment by coating a flake-shaped substrate with titania or zirconia alone or a mixture thereof, wherein the flake-shaped substrate is Prepared from a solution containing a hydrolyzable / polycondensable organometallic compound and a substance causing light absorption as a result, 400 n
A method for producing a pearlescent pigment, which comprises using a material having a light transmittance of 50% or less in at least a part of a wavelength range of m to 800 nm.

The flake-like substrate can be produced from a solution containing a hydrolyzable / polycondensable organometallic compound by the method already proposed by the inventors (Japanese Patent Laid-Open No. 3-285838).

That is, a solution containing an organometallic compound capable of being hydrolyzed and polycondensed is applied onto a substrate, dried to form a gel-like film, and then the gel is removed from the substrate to which the gel-like film is attached. The flaky film is peeled off and sintered to produce a flake-shaped substrate.

The hydrolyzable / polycondensable organometallic compound used as a raw material in the present invention may be basically any compound as long as it can be hydrolyzed and dehydrated and condensed.
Metal alkoxides having alkoxy groups are preferred.
More specifically, methoxides such as silicon, titanium, aluminum, zirconium, phosphorus and boron, ethoxides, propoxides, butoxides and the like are used alone or as a mixture. Therefore, the composition of the flake-like substrate obtained by the present invention is, for example, pure silica, silicate-based, titanate-based, aluminate-based, zirconate-based, phosphate-based, borate-based amorphous. Quality or crystalline.

The solvent of the raw material solution containing the above-mentioned organometallic compound may be basically any solvent as long as it substantially dissolves the above-mentioned organometallic compound, but methanol, ethanol or propanol is used.
Most preferred are alcohols such as alcohol and butanol. The amount of this solvent used is 0.1 to 0.995, preferably 0.2 to 0.995, in volume ratio with respect to the total amount of the organometallic compound and the solvent.
9, more preferably 0.3 to 0.85.

Moisture is required for the hydrolysis of the above-mentioned raw material organometallic compound. It may be neutral, acidic or basic, but in order to accelerate hydrolysis, hydrochloric acid, nitric acid,
It is preferable to use water acidified with sulfuric acid or the like. The amount used is 1 mol to 100 mol of water with respect to 1 mol of the organometallic compound.
A molar range is preferred. The acid is used in a molar ratio of 0.01 to 2, preferably 0.0
It is 5 to 1.5.

The substrate used in the present invention is stainless steel, gold,
Use a material such as metal such as silver, glass, or plastic that has a smooth surface. On such a substrate,
Applying a liquid containing the above organometallic compound, 0.06-5
A thin liquid film of 0 μm is used. When this film dries, it shrinks, but the substrate does not shrink and cracks occur in the film. After peeling the gel film from the substrate, it is sintered to produce a glass flake.

The substance which causes light absorption as a result of use in the present invention is one which lowers the visible light transmittance of the flaky substance, such as an organic substance which remains carbonized, a metal ion such as iron or a colloid. Can be mentioned.

As the method for carbonizing and leaving the organic matter, the organic group in the raw material, which can be hydrolyzed and polycondensed, may be carbonized, or the organic material is positively added and added to the raw material solution. May be. As the former organometallic compound,
The use of an alkoxysilane such as dimethyldimethoxysilane, methyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane or a silane coupling agent is effective for carbonization. For example, the above-mentioned dimethyldimethoxysilane and methyltriethoxysilane are hydrolyzed.
Since it is a polycondensable organometallic compound and also a substance which causes light absorption as a result, it can be used in common. Any of the latter organic substances can be used, such as organic dyes and organic polymer compounds, as long as they have carbon atoms in the molecule and are soluble in the raw material solution.

As a result, the amount of the substance causing light absorption is usually 0.1 to 30% by weight based on the amount of the organometallic compound capable of being hydrolyzed and polycondensed. If the amount added is less than 0.1% by weight, a pearlescent pigment having a vivid reflection interference color cannot be obtained. Even if the amount added exceeds 30% by weight, the vividness of the reflection interference color of the pearlescent pigment is no longer improved, and the additive is wasted.

These raw material solutions are applied on a substrate, dried and peeled from the substrate, and then heat treated. If this heat treatment is performed in a reducing atmosphere, organic substances easily remain in the flakes as carbon. The heat treatment temperature is not particularly limited, but if the strength of the flake-like substrate is taken into consideration, it is 600-12.
It is preferable to perform heat treatment in the range of 00 ° C.

The flake-shaped glass substrate obtained is 400 n
It is necessary that at least a part of the light transmittance in the wavelength range of m to 800 nm is 50% or less in order to obtain a pearlescent pigment having a bright reflection interference color. Regarding the light transmittance, a flake-shaped substrate before coating with titania or zirconia alone or a mixture thereof was dispersed in a commercially available acrylic resin so that the concentration was 5% by weight, and a window having a thickness of 2 mm was used. It is defined as the value obtained by coating and drying on a glass plate to a thickness of about 100 μm and measuring the transmittance with a spectrophotometer. This transmittance is preferably 30% or less. The smaller this transmittance is, the higher the effect is, but the transmittance is 3%.
In the following, the effect will not be further enhanced. Therefore, a material having a transmittance higher than 3% is usually used. Regarding the size of the flake-shaped glass substrate used, the thickness is usually 0.05 μm to 5 μm. If it is thicker than 5 μm, the difference in the drying rate between the film portion on the free surface and the film portion near the substrate becomes too large, and the resulting flaky glass will be peeled between the films in the horizontal direction on the substrate. . When such peeling between films occurs, the film thickness distribution of the obtained glass flakes becomes wide, and the quality as a product deteriorates.
On the other hand, when the thickness is less than 0.05 μm, the adhesion between the substrate and the film becomes too large, and the film does not peel off from the substrate, and the flakes are not formed. The diameter of the glass flakes produced by the present invention is usually 10 μm to several mm, and the aspect ratio thereof is at least 5, preferably at least 1.
It is 0.

The thus obtained flaky base material having a low visible light transmittance is coated with titania or zirconia alone or a mixture thereof by a known method to give a pearlescent pigment having a vivid reflection interference color. Can be easily manufactured. By controlling the thickness of the titania or zirconia to be coated alone or a mixture thereof in the range of 50 to 200 nm, pearl luster such as silver, golden, red, magenta, blue and green can be obtained.

[0021]

EXAMPLES Examples will be shown below.

Example 1 Commercially available silicon tetraethoxide, ethanol, water,
The mixture was mixed at a volume ratio of 1: 2: 1, and a commercially available organic dye, methylene blue, was added to the mixed solution in an amount of 0.
It was added so as to be 1% by weight and stirred at room temperature for about 24 hours.

A stainless steel plate having a surface of 20 cm × 20 cm and a thickness of 1 mm is prepared as a base material, and the solution prepared above is formed into a film on the stainless steel plate base material by dip coating. It was left for 5 minutes in the atmosphere of 60% RH. Then, this was put in an oven at 120 ° C. and dried for 2 minutes, and the blue gel film peeled from the substrate was collected with a nylon brush. This blue color is derived from methylene blue mixed in the raw material.

The collected blue gel film was put into a crucible, and this was placed in a large crucible containing carbon pieces as a reducing agent. The lid was capped and heat-treated at 1000 ° C. for 2 hours to remove flaky brown silica glass. Obtained. The dimensions were such that the average thickness was about 0.5 μm and the average particle size was about 85 μm. This brown coloring is due to the fact that methylene blue in the gel film is decomposed, the carbon component is reduced, and carbon is dispersed in silica.

This flake-shaped brown silica glass was dispersed in a commercially available acrylic resin to a concentration of 5% by weight, and this was dispersed on a window glass plate having a thickness of 2 mm to about 100 μm.
When it was applied and dried at a thickness of m and the transmittance was measured with a spectrophotometer, the transmittance for 450 nm light was 8%, and it was a pale brown color when observed with the naked eye.

15 g of the above flake-shaped brown silica glass was dispersed in 100 ml of water and kept at 80.degree. here,
100 g of titanium oxysulfate aqueous solution corresponding to 12 g of titanium dioxide and 50 g of 50% sulfuric acid were slowly added.
This was heated and boiled for about one and a half hours. Titanium hydroxide is gradually generated on the surface of flaky brown silica glass by this heating boiling, but one drop of slurry is sometimes taken during the heating boiling and placed on a black background, and the interference color caused by the titania layer is generated. Was observed. When this color turned reddish orange, the boiling was stopped. The slurry was filtered, washed with water to remove sulfuric acid, and dried to obtain a titanium hydroxide-coated flaky brown silica glass.

The obtained titanium hydroxide-coated flakes were mixed with 1
It heat-processed at 000 degreeC for 1 hour. This heat treatment changed the titanium hydroxide in the coating layer to titania. The thickness of the coated titania was about 85 nm. The pearlescent pigment finally obtained was dispersed in an acrylic resin so that the concentration was about 5%, and the pearlescent pigment was applied and dried to a thickness of about 50 μm on a metal substrate on which a white paint was previously applied and dried. When viewed with the naked eye, the reflection color of the pearlescent pigment at this time was a vivid golden color, with the reflection interference color caused by the titania layer being emphasized.

Example-2 Iron-containing flakes were produced in the same manner as in Example-1 except that ferric chloride was added so as to have a concentration of 1% by weight instead of the organic dye. The flakes were dark brown, and the transmittance for light of 400 to 600 nm was measured by the method described in Example-1 to find that it was 10 to 25%. By the same method as described in Example-1, a titania coating having a thickness of about 130 nm was performed to obtain a pearlescent pigment having a blue reflection interference color.

Example 3 Commercially available silicon tetraethoxide, dimethyldiethoxysilane, ethanol and water in a volume ratio of 0.7: 0.3:
The mixture was mixed at a ratio of 2: 1 and stirred at room temperature for about 24 hours.

Using this solution, flaky brown silica glass was prepared in the same manner as in Example-1. This brown coloring is due to the carbon fine particles produced by the decomposition and reduction of dimethyldiethoxysilane. The transmittance of this flake for 550 nm light was about 10%.

A titania layer having a thickness of about 120 nm was coated by the method described in Example 1 to obtain a pearlescent pigment having a red-purple reflection interference color.

Comparative Example-1 The blue gel flakes described in Example-1 were heat-treated as they were in the air at 1000 ° C. to obtain transparent flake silica glass. Unlike in the case of Example 1, the methylene blue in the gel film is not reduced and carbonized but is oxidized and decomposed, so that coloring does not occur.

When the transmittance for light in the range of 400 nm to 800 nm was measured by the method described in Example-1, it was 90 to 95% in this range.

Further, according to the method described in Example-1, about 85n
A m-thick titania coating was carried out, and the obtained pearlescent pigment was dispersed in an acrylic resin so as to be about 5% and applied onto a white substrate. The reflection color of the pearlescent pigment at this time is
It was a white color with a slight yellow color. This weak yellow coloring is due to the reflection interference color. When the titania-coated silica glass flakes on the white substrate are viewed from above the substrate, the light transmitted through the flakes is the light that once passed through the flakes and reflected on the white substrate. The intensity of this light is weaker than the intensity of the light reflected directly on the flake surface.
The same applies to the intensity of the reflected interference light and the intensity of the transmitted interference light, and a slightly strong reflected interference color is observed as a weak color in a portion that is not whitened by the complementary transmitted interference color.

Comparative Example-2 A pearlescent pigment was prepared by performing titania coating having a thickness of about 85 nm as in Example-1 except that commercially available muscovite was used as the flake-shaped substrate instead of the flake-shaped brown silica glass. Was produced. When this pigment was placed on a white substrate, the reflection interference color was weakened, and it became pale yellowish white. The muscovite used had a light transmittance of 85 to 95% in the range of 400 to 800 nm.

Example 4 Aqueous solution 30 in which pH was previously adjusted to 2.7 by adding urea.
Zirconium sulfate corresponding to 15 g of zirconium dioxide was dissolved in 0 ml. To this, 15 g of the flaky brown silica glass described in Example-1 was added, heated to 90 ° C., and kept at this temperature for about 2 hours while stirring well. Then, the slurry was filtered, washed with water and dried. 80 this
It was treated at 0 ° C. for 1 hour. The thickness of the zirconia layer is about 100
was nm.

Even when observed on a white substrate in the same manner as in Example 1, the reflection interference color did not fade and a bright golden color was observed.

Example 5 Commercially available methyltriethoxysilane, ethanol, and 0.1N hydrochloric acid were mixed at a volume ratio of 1: 1.8: 0.8, and stirred at 50 ° C. for about 24 hours. went. Flake-like gel was obtained by the same method as in Example-1 and heat-treated at 1000 ° C. for 1 hour in nitrogen gas to obtain flake-like brown silica glass. The thickness of this flake was about 0.7 μm. This brown coloring is due to the fact that the carbon generated by the decomposition of the methyl group, which is an organic residue in the gel film, is uniformly dispersed in the flakes. When the transmittance for 800 nm light was measured by the method described in Example-1, it was about 3
It was 0%.

In the same manner as described in Example-1, about 160 nm
A thick pearlescent pigment having a vibrant green reflection interference color that does not fade even on a white background was obtained by performing a thick titania coating.

[0040]

INDUSTRIAL APPLICABILITY According to the present invention, titania, zirconia alone or a mixture thereof has a visible light transmittance of 5 at least in the light in the range of 400 nm to 800 nm.
In the method of coating on 0% or less of a flake substance, a flake substance having a low visible light transmittance produced directly from a solution containing an organometallic compound was used as a substrate. This makes it possible to easily and efficiently obtain a pearlescent pigment having a vivid reflection interference color.

Claims (2)

[Claims] 1. A method for producing a pearlescent pigment by coating a flake-shaped substrate with titania or zirconia alone or a mixture thereof, and in the method for producing a pearlescent pigment, the flake-shaped substrate is a hydrolyzable / polycondensable organic material. A material having a light transmittance of 50% or less in at least a part of a wavelength range of 400 to 800 nm, which is manufactured from a solution containing a metal compound and a substance causing light absorption as a result. Manufacturing method of pearlescent pigment. 2. The substance which causes light absorption as a result is an organic substance having a carbon atom in the molecule, and the material is
The method for producing a pearlescent pigment according to claim 1, which is a glass containing carbon obtained by heat-treating a flaky gel produced from the solution.