JPH05254922A - Colored alumina-base ceramic and its production - Google Patents

Abstract

PURPOSE:To provide a black alumina-base ceramic low in chroma and appropriate for a large-sized ceramic surface plate to be calcined in the atmosphere and ornamental members. CONSTITUTION:Three kinds of colorants i.e., CuO, Fe2O3 and Co2O3, are admixed with an alumina-base ceramic material consisting essentially of Al2O3 and contg. a flux component of SiO2 and MgO, and the admixture is calcined in the atmosphere to obtain a black alumina-base ceramic low in chroma. The three kinds of oxides are jointly used as the colorant, and a black alumina-base ceramic low in chroma is obtained. A large-sized ceramic surface plate to be calcined in the atmosphere and a black alumina-base ceramic capable of being used as the ornamental members are provided by this method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a colored alumina-based ceramics and a method for producing the same, and more particularly to a colored alumina-based ceramics colored in black with low saturation suitable for a large ceramic surface plate or a decorative member and a method for producing the same. Regarding

[0002]

2. Description of the Related Art In order to use translucent alumina for an IC package or the like, the alumina has been conventionally colored.
Research and development for producing black alumina having a light-shielding property have been conducted. The conventional coloring means of this kind include (1) Al
The ₂ O ₃ ceramic material, a method of adding and mixing a coloring agent made of transition metal oxide of a wide mainly composed of TiO ₂ alone or TiO _2, in (2) Al ₂ O ₃ ceramic material, 2
A method of adding a spinel type pigment obtained by calcining a mixture of at least one kind of metal oxide, (3) adding fine metal powder of tungsten (W), molybdenum (Mo), etc. to an Al ₂ O ₃ -based ceramic raw material How to do so is known.

[0003]

However, the conventional coloring methods (1) to (3) have drawbacks and problems described in detail below. The method (1) above is a method mainly applied to a method for producing a colored alumina substrate in a non-oxidizing atmosphere, and is a method for coloring alumina by partially reducing TiO ₂ to TiO _{2 -X.} Therefore, there is a drawback in that good black color cannot be obtained by firing in air. Also,
The above method (2) requires a calcination step for obtaining a spinel type pigment and a step of re-grinding the same.

Moreover, in both the above-mentioned coloring methods (1) and (2), unless a coloring agent such as MnO ₂ or Cr ₂ O ₃ is added as a main component or as an indispensable auxiliary component, a sufficient blackening occurs. There was a constraint not to do it. By the way, this Mn
O ₂ and Cr ₂ O ₃ are usually often used as an auxiliary coloring agent, but the powder may adversely affect the human body and the environment.
It is desirable not to use O ₂ or Cr ₂ O ₃ .

Further, in the method (3), since the metal powder of W or Mo added by the method has a large specific gravity, it is difficult to uniformly mix it with the alumina raw material powder, and moreover, in the atmosphere. The firing has the drawback that the problem of oxidation cannot be avoided.

Therefore, the existing alumina coloring techniques such as the above (1) to (3) have many problems when applied to the production of large colored alumina products which need to be fired in the atmosphere. Therefore, an object of the present invention is to provide a colored (black) alumina-based ceramics and a method for producing the same, which solves the above-mentioned drawbacks and problems, and in particular, a large-sized ceramic surface plate that needs to be fired in the air. An object of the present invention is to provide a low-saturation black alumina-based ceramic suitable for a decorative member and a decorative member, and a method for producing the same.

[0007]

In order to achieve the above object, the present invention provides a coloring agent containing no MnO ₂ or Cr ₂ O ₃ , namely CuO, Fe ₂ O ₃ and Co ₂ O ₃ . Three
Disclosed is a colored alumina-based ceramic which is colored in black with low saturation and which can be sintered at a relatively low temperature in the atmosphere by using various kinds of colorants, and a method for producing the same. That is, the present invention is characterized in that (1) a colorant of CuO, Fe ₂ O ₃ and Co ₂ O ₃ is added and mixed to an alumina-based ceramic raw material containing Al ₂ O ₃ as a main component, followed by firing. Low-saturation colored alumina-based ceramics, (2) Alumina-based ceramic raw material containing Al ₂ O ₃ as the main component and SiO ₂ and MgO as the flux components, and CuO, Fe ₂ O ₃ and Co ₂ O ₃ A gist of the present invention is to provide a method for producing a colored alumina-based ceramics having low saturation, which comprises adding and mixing 3 kinds or more of coloring agents in an amount of 2% by weight or more and firing the mixture in the atmosphere.

The present invention will be described in detail below. As a result of intensive studies conducted by the present inventors to solve the problems in the conventional coloring method, the coloring without adding MnO ₂ or Cr ₂ O ₃ was observed. It was developed to obtain a large black alumina product with low saturation that can be sintered at a relatively low temperature in the air by mixing the agent. That is, the present inventors have found that CuO, Fe
_The present invention has been completed by finding out a coloring method of alumina in which three kinds of coloring agents of ₂ O ₃ and Co ₂ O ₃ are added to and mixed with an alumina raw material and fired in the air.

In the present invention, as the alumina-based ceramic raw material, it is preferable to use Al ₂ O ₃ as a main component, to which SiO ₂ and MgO powder are added as a flux component (sintering aid). That is, in the present invention,
Alumina-based ceramics containing SiO ₂ and MgO as flux components (sintering aids) are preferably colored. In the present invention, the purity of alumina used is not particularly limited.

Next, the method for producing the low-saturation colored alumina-based ceramics of the present invention will be specifically described. First, Al ₂ O ₃ powder is added to fluxes (sintering aids) of SiO ₂ and MgO powder and coloring agents CuO and Fe.
Powders of ₂ O ₃ and Co ₂ O ₃ are directly mixed and added together without forming spinel, and the mixture is molded.

Next, the molded body is fired in the atmosphere at about 1400 ° C. to obtain stable black alumina having no color difference between inside and outside of the sintered product and color unevenness. As the above-mentioned molding method, any molding method such as a casting molding method, a CIP molding method and a mechanical press molding method can be adopted, and the molding means is not particularly limited in the present invention.

Explaining the colorant used in the present invention, the use of CuO as one component of the colorant is one of the features of the present invention. The melting point of this CuO is about 1140 ° C., and it exists as a liquid phase at the sintering temperature of alumina. The presence of a small amount of CuO liquid phase greatly contributes to the densification of alumina, and has an action of promoting the densification. As shown in Table 1 below, in Comparative Example 2 in which only CuO was added,
It was confirmed that the density of the obtained alumina was the highest.

On the other hand, Fe ₂ O ₃ acts to inhibit densification (see Comparative Example 1 in Table 1 below), while
It was confirmed that Co ₂ O ₃ had little effect on this densification (see Comparative Example 3). As is clear from Table 1 below, even if these three types of colorants are added individually, they cannot be colored black, and the desired color can be obtained only by using these three types of colorants together. It can be colored (black).

From this, the present invention uses the above three kinds of oxides of CuO, Fe ₂ O ₃ and Co ₂ O ₃ as essential components as colorants, but the addition of these three types of colorants The ratio is not sensitive to color, but in order to obtain a deep black alumina, the oxide ratio of each coloring component is Fe ₂
O _3: CuO: Co ₂ O ₃ is approximately 8: 4: Preference is given to using those in proportions of 3.

Further, in the present invention, if the addition amount of the colorant is less than 2% by weight, the color becomes visibly thin and the desired saturation black is not exhibited, which is not preferable. On the other hand, if it exceeds 10% by weight, the strength decreases, which is also not preferable. From this, in the present invention, the addition amount of the colorant is preferably 2 to 10% by weight, and more preferably 4 to 10% by weight. In the range of 4 to 10% by weight, black alumina which does not change extremely is stably obtained, which is clear from the measurement result by the colorimeter.
The colored alumina thus obtained exhibits a black color with almost no saturation or tint.

As a coloring mechanism in the colored alumina-based ceramics of the present invention, according to the result of X-ray diffraction, the solid solution of the oxide in Al ₂ O ₃ is caused by the liquid phase formation of CuO which is one component of the coloring agent. It can be speculated that it is promoted and that it is due to the formation of a complex oxide. In the present invention, the low-saturation colored alumina-based ceramics are not particularly limited, but mainly mean those having a color tone in which the absolute values of the saturations a ^* and b ^* are smaller than 7 and 3, respectively (see For degrees a ^* and b ^* , see below).

[0017]

EXAMPLES Examples of the present invention will be given below together with comparative examples.
The present invention will be described in more detail. Needless to say, the following examples do not limit the present invention including other conditions such as the purity of alumina to be colored.

Examples 1 to 5 2372 g (79% by weight) of commercially available Al ₂ O ₃ powder, 297 g (10% by weight) of frog clay and Mg in a plastic bottle container (a container containing alumina balls) having an internal volume of 5 liters. Add 57 g (2% by weight) of (OH) ₂ powder, and
Fe ₂ O ₃ 145 g (4.8% by weight) as colorant, CuO 73
g (2.4% by weight) and Co ₂ O ₃ 55 g (1.8% by weight) were charged. To this, 750 g of water and 30 g of a deflocculant were added, and after mixing and pulverizing for 20 hours, 90 g of a binder was added and further mixed for 30 minutes. In addition, in Table 1, the content of the colorant is shown in% by weight.

The resulting slurry was vacuum degassed for 2 hours, cast into a 120 mm × 120 mm × 12 mm gypsum mold, the molded body was dried, and then the firing temperature shown in Table 1 (1300 to 15).
It was fired in the air at 00 ° C) to obtain a fired product. For this fired product, the density measurement by the underwater substitution method, the hardness measurement by the Vickers indentation method, the fracture toughness measurement and 4
Bending strength was measured by a point bending test. Furthermore, the surface roughness of the lap surface of the baked product was measured. The results of these measurements are shown in Table 1.

(Examples 6 to 9) The content (% by weight) of the coloring agent shown in Examples 6 to 9 in Table 1 was blended, and the composition was baked at the baking temperature (1450 ° C) shown in Table 1. Except for this, a fired product was obtained in the same manner as in Examples 1 to 5 above. The same measurement as in Examples 1 to 5 was performed on the obtained fired product, and the results are shown in Table 1.

(Example 10) A slurry having the same composition as in Examples 1 to 5 was vacuum degassed, and after CIP molding, 1400
150mm × 150mm × by firing in the air at ℃
A 30 mm large black alumina plate was manufactured. This black alumina plate had a little difference in color tone between the as-baked surface and the ground surface and had a deep black color with no color unevenness on the polished surface.

(Comparative Examples 1 to 3) For comparison, the colorant components of the present invention were individually blended (blended at 9% by weight) and shown in Table 1.
A fired body product was produced under the same conditions as in Examples 1 to 5 except that firing was performed at the firing temperature (1450 ° C) shown in. The density of the obtained fired product was measured by the underwater substitution method, and the results are shown in Table 1.

[0023]

[Table 1]

(Explanation of "Color Tone" in Table 1) In Table 1, as the color tone, the expression of colors is digitized and displayed clearly. For color measurement, JIS Z 8722 definition 45-0
The measurement was performed using a color-difference meter (CR-321 type, manufactured by Minolta Camera Co., Ltd.) manufactured in accordance with the law. L ^* is lightness, a ^* and b
^* Represents saturation and has the following meanings. L ^* , a ^* , and b ^* are standardized by the International Commission on Illumination (see CIE 1976L ^* a ^* b ^* ). a ^* = + 60, b ^* = 0 → pure red a ^* = − 60, b ^* = 0 → pure green b ^* = + 60, a ^* = 0 → pure yellow b ^* = − 60, a ^* = 0 → pure blue L ^* max = 100, a ^* = 0, b ^* = 0 → pure white L ^* min = 0, a ^* = 0, b ^* = 0 → pure black

In Table 1, in Examples 1 to 5, 9% by weight was added as a colorant, and the oxide ratio of each colorant component Fe ₂ O ₃ : CuO: Co ₂ O ₃ was 8: It is set to 4: 3, and is an example in which the firing temperature is changed to 1300 to 1500 ° C. It can be seen that among these Examples 1 to 5, when the firing temperature is a relatively low sintering temperature of 1400 ° C. (Example 3), dense colored alumina can be obtained. Further, when firing at a temperature higher than necessary (Example 5), hardness and strength decrease due to grain growth.

Further, Examples 6 to 9 are examples in which the oxide ratio of each colorant component is the same, but the addition amount of this colorant is changed. In Examples 6 to 9, the amount of colorant added was
Below 4% by weight (Examples 8 and 9) the color is considerably lighter, whereas above this (Examples 6 and 7) the color does not change noticeably. As described above, as is clear from Table 1, the best example as an example in the present invention is the case of the firing temperature of 1400 ° C. of Example 3 among Examples 1 to 5, and of Examples 6 to 9. Among them, the colorant of Example 7 was 5.
It can be understood that black alumina having good density, Vickers hardness, strength, surface roughness and color tone can be obtained in all cases where the amount is 6% by weight.

Comparative Examples 1 to 3 are examples in which the colorant components of the present invention were individually blended, but the addition of CuO most promotes densification and may play a role of liquid phase sintering. It can be understood from Comparative Example 2 in Table 1. Further, it was confirmed that Comparative Example 1 containing Fe ₂ O ₃ acts to inhibit densification, while Comparative Example 3 containing Co ₂ O ₃ does not significantly affect the densification. Was given. And, as is clear from Table 1, even if these three kinds of colorants were added individually, they could not be colored black, and from the examples 1 to 9 of Table 1, these three kinds of coloring It can be understood that the desired color (black) can be colored only when the agent is used in combination.

[0028]

As described in detail above, the present invention uses black oxide ceramics of low saturation by using three kinds of oxides of CuO, Fe ₂ O ₃ and Co ₂ O ₃ as colorants. The effect that is obtained occurs. Further, in the present invention, a coloring agent such as MnO ₂ or Cr ₂ O ₃ is not used, which is preferable from the viewpoint of environmental hygiene, and it is a large ceramic surface plate or a decoration which needs to be fired especially in the atmosphere. It is possible to provide a black alumina-based ceramic with low saturation that can be used for members and the like.

Claims (2)

[Claims] 1. Saturation characterized by being formed by adding and mixing a coloring agent of CuO, Fe ₂ O ₃ and Co ₂ O ₃ to an alumina-based ceramic raw material containing Al ₂ O ₃ as a main component and firing the mixture. Low-colored alumina ceramics. 2. SiO ₂ and Mg containing Al ₂ O ₃ as a main component
2% by weight or more of three kinds of colorants of CuO, Fe ₂ O ₃ and Co ₂ O ₃ are added to and mixed with an alumina ceramic raw material containing O as a flux component, and the mixture is fired in the atmosphere. For producing colored alumina-based ceramics having a low content.