JPH0210103B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an ink for ceramics and glass, and more particularly to a black ink for ceramics and glass that uses a complex oxide black pigment as a coloring agent and has good discoloration resistance. .

(Prior art) Conventionally, one way to print on ceramics and glass products is to print on the surface of ceramics and glass products using ceramic and glass ink consisting of low melting point frits and pigments. A method of baking at a temperature of ~700°C is used. As pigments for such inks for ceramics and glass, pigments having high heat resistance are required, and therefore various inorganic pigments are usually used.

(Problems to be Solved by the Invention) Among the above inorganic pigments, complex oxide black pigments are widely used as pigments for inks for ceramics and glass because they have excellent various performances. Among them, complex oxide black pigments containing copper are particularly excellent in jet blackness, hiding power, coloring power, chemical resistance, and heat resistance.

However, if a ceramic or glass ink containing a copper-containing complex oxide black pigment is used to print on the surface of a ceramic or glass product and then baked, the atmosphere at the time of baking is a reducing atmosphere. This has the disadvantage that some of the copper in the pigment is reduced and the color develops red, impairing its jet black properties.
It becomes necessary to set complicated conditions during baking.

For this reason, there is a demand for the development of a complex oxide black pigment that does not cause discoloration during baking.

(Means for Solving the Problems) As a result of intensive research in response to the above-mentioned demands of the prior art, the present inventor has decided to apply a specific treatment to a complex oxide-based black pigment for ink for ceramics and glass. Therefore, the present invention was completed based on the finding that a composite oxide black pigment that does not change color even when baked in any atmosphere can be obtained.

That is, the present invention is an ink for ceramics and glass comprising a low melting point frit and a pigment, characterized in that the pigment is a composite oxide black pigment having a silica coating on the particle surface.

To explain the present invention in more detail, the complex oxide black pigment having a silica film used in the present invention and which mainly characterizes the present invention can be obtained by any conventionally known technique, but is particularly preferred. The method involves uniformly dispersing a complex oxide black pigment in water or a dilute aqueous silicate solution, and adding the aqueous silicate solution and an acid as a neutralizing agent to the dispersion while stirring the dispersion uniformly. This is a method of depositing and forming a silica film on the surface of a composite oxide black pigment by simultaneously and gradually adding the silica.

For example, the dispersion should be heated to 80°C or higher, preferably 85 to 95°C.
1 to 6% by weight silicate aqueous solution and 0.5% by weight.
Simultaneously and gradually add an aqueous solution of ~3% by weight acid while stirring, bringing the pH of the solution to ~9.0 during this time.
By adjusting the ratio to 9.5, a composite oxide black pigment having the best silica coating can be obtained.

To disperse the complex oxide black pigment in water or an aqueous silicate solution, any conventional pigment dispersion method can be used, for example, a dispersion machine such as a sand mill using glass beads as a medium can be used. .

The dispersion concentration of the composite oxide black pigment is not particularly limited, but in consideration of economic efficiency and product uniformity, it is preferably about 5 to 15% by weight.

In the above, the time required for adding the silicate aqueous solution and the acid aqueous solution varies depending on the scale of the product, but it is generally preferable to add the silicate aqueous solution and the acid aqueous solution for about 1 to 5 hours, since it is uneconomical if the time is too long.

The silicates used in the present invention may be any conventionally known water-soluble silicates, and may contain small amounts of zirconates, titanates, and other metal salts in addition to silicates. It may be hot.
Also in the present invention, the most preferred is an alkali metal silicate, particularly No. 3 sodium silicate.

The acid used as a neutralizing agent may be any inorganic or organic acid, but the most preferred is sulfuric acid with a concentration of about 0.5 to 3% by weight.

The main feature of the ink for ceramics and glass of the present invention is that it uses a complex oxide black pigment having a silica coating as described above, and other components such as low melting point frit and vehicle are all conventionally known. Things can be used as is.

For example, low melting point frits are mainly composed of lead oxide, and are also made of alumina, silica, calcium oxide, titanium oxide, sodium oxide, potassium oxide, zirconium oxide, zinc oxide, boron oxide, etc. Preferably, the melting point is adjusted to about 550°C to 620°C by adjusting the molar ratio of lead. All such low melting point frits are readily available on the market.

As the vehicle, squeegee oil, which is conventionally used in inks for ceramics and glass, is preferably used.

The ink for ceramics and glass of the present invention has the above-mentioned three components as essential components, but any conventionally known additives such as various inorganic pigments can be used in combination as necessary.

In the composite oxide black pigment having a silica coating obtained by the above preferred method or other methods, it is preferable that the silica coating accounts for about 2 to 10% by weight of the total amount, and less than about 2% by weight. If the amount exceeds about 10% by weight, the color fastness of the resulting composite oxide black pigment will be insufficient, and if the amount exceeds about 10% by weight, the coloring power, hiding power, and other pigments will deteriorate. It is not preferable because the properties of

As the complex oxide black pigment used in the above method, any conventionally known complex oxide black pigment can be used, such as those consisting of copper and chromium oxides, and those consisting of copper, iron, and chromium oxides. ,
Examples include those made of oxides of copper, chromium, and manganese.

In the ink for ceramics and glass of the present invention,
The composite oxide black pigment having a silica coating is preferably used in an amount of about 4 to 8% by weight in the ink, and the low melting point frit is used in an amount of about 60 to 70% by weight in the ink. It is preferred that the vehicle be used in the ink at approximately
It is preferably used in a proportion of 25 to 30% by weight.

The ink for ceramics and glass of the present invention can be produced by a conventionally known method, for example, by sufficiently mixing, grinding, and kneading the composition using a three-roll machine or the like.

(Function/Effect) The ink for ceramics and glass of the present invention as described above is useful as an ink for imparting patterns such as various letters and figures to the surfaces of various ceramics, glassware, enamel products, etc. The ink for ceramics and glass of the invention is printed with any desired pattern using silk screen printing or other various curved surface printing techniques, and this is baked at a temperature of about 500 to 700°C to create a black color with various fastness properties. Excellent patterns can be added.

The biggest feature of the ink for ceramics and glass of the present invention is that in conventional inks for ceramics and glass that use a complex oxide black pigment as a coloring component, if the atmosphere at the time of baking is reducing, the pigment In contrast, the ink for ceramics and glass of the present invention had to be created in an oxidizing atmosphere because some of the copper in the ink was reduced and developed a red color, and the jet blackness of the complex oxide black pigment was lost.However, the ink for ceramics and glass of the present invention - Even when baking is performed in either a reducing atmosphere, the complex oxide black pigment in the ink does not change color and can provide a pattern with excellent coloring properties.

Therefore, by using the ink for ceramics and glass of the present invention, excellent colored ceramics, colored glassware, colored enamel products, etc. can be provided at low cost with simple equipment.

Next, the present invention will be explained in more detail with reference to Examples. Note that % in the text is based on weight.

Example 1 200g of a composite oxide black pigment (black pigment consisting of Cu-Cr oxides) was sufficiently dispersed in water 2, heated to 85°C, and then mixed with No. 3 into the slurry while maintaining this temperature. Sodium silicate (Na2O/SiO2=
Add 34 g of 1/3, 30% aqueous solution to 400 ml of water to dilute it, and add diluted sulfuric acid simultaneously and gradually over a period of 3 hours with stirring. During this time, the pH of the slurry is adjusted to 9.2 to 9.5.

After dropping, stop stirring and keep stirring for about 1 hour.
Aging time and then neutralizing with dilute sulfuric acid to make the slurry pH
Adjust to 7 to complete the silica coating.

Then, it is filtered, washed with water and dried by a conventional method.
210g of complex oxide black pigment with silica coating
I got it. The silica film in this pigment accounted for 5% by weight of the pigment.

Example 2 A composite oxide black pigment (a black pigment consisting of Cu-Cr-Mn oxide system) was used, and the other conditions were the same as in Example 1, except that a composite oxide-based black pigment with a silica coating (5% by weight) was used. A black pigment was obtained.

Example 3 A composite oxide black pigment (a black pigment consisting of Cu-Fe-Cr oxide system) was used, and the other conditions were the same as in Example 1, except that a composite oxide-based black pigment with a silica coating (5% by weight) was used. A black pigment was obtained.

Example 4 0.5 g of the composite oxide black pigment having a silica coating obtained in Examples 1 to 3, and 5 g of low melting point frit
and 2 g of squeegee oil were mixed and dispersed using three ceramic rolls to obtain inks A (Example 1), B (Example 2) and C (Example 3) for ceramics and glass of the present invention. On the other hand, comparative ceramic and glass inks A' (pigment corresponding to Example 1) and B' were prepared in the same manner using composite oxide black pigments without silica coating corresponding to Examples 1 to 3, respectively. (Example 2
(pigment corresponding to Example 3) and C' (pigment corresponding to Example 3) were obtained.

Inks A to C for ceramics and glass of the present invention described above
and ceramic/glass ink A′ for comparison
C' was screen printed on a glass container and then baked at 620℃ for 20 minutes in a reducing atmosphere.
Inks using inks A to C for ceramics and glass of the present invention each exhibited jet-black coloring, but all inks using comparative inks A' to C' for ceramics and glass had a reddish tone. It was inferior to the jet black color.

Claims (1)

[Claims] 1. Ceramics and pigments made of low melting point frits and pigments.
An ink for ceramics and glass, characterized in that the pigment is a composite oxide black pigment having a silica coating on the particle surface. 2. The ink for ceramics and glass according to claim 1, in which the amount of the silica film is 2 to 10% by weight based on the entire pigment. 3. The ink for ceramics and glass according to claim 1, wherein the low melting point frit is a lead oxide based low melting point frit. 4. The ink for ceramics and glass according to claim 1, wherein the complex oxide black pigment contains copper.