JP4463591B2 - Method for producing cobalt black pigment - Google Patents

Description

  The present invention relates to a cobalt-based black pigment, in particular, excellent in colorability and jetness, enabling stable coloring even under severe use conditions such as when mechanical shearing force is applied or heated at a high temperature. The present invention relates to a black pigment useful as a pigment for a black matrix such as a plasma display and a method for producing the same.

As black pigments, carbon black, copper / iron / manganese composite oxides, cobalt tetroxide starting from cobalt oxide, etc. are known, all of which are slightly reddish or have low blackness. (L ^* value is large) or has a defect such as small specific surface area and poor colorability.
Carbon black, magnetite black, copper / iron / manganese black, titanium black, etc. were used as the black pigment for coloring resins, glass, ceramics, etc. When used in resins, glass, ceramics, etc., when a mechanical shearing force or high heat is applied, they often exhibit redness or yellowness, and black pigments that can maintain pure black have not been known.

In addition to the conventionally known black pigments, cobalt-based oxides, particularly cobalt trioxide, can be considered as black substances that may satisfy the above-described requirements. Cobalt tetroxide was obtained by igniting cobalt-containing compounds such as cobalt monoxide, cobalt hydroxide, cobalt hydroxide carbonate, cobalt chloride, cobalt sulfate, cobalt nitrate, cobalt carbonate, and cobalt acetate in the atmosphere. When trying to obtain powder powder properties such as specific surface area, blackness, and degree of crystallization of powder, the raw material cobalt-containing compound has a large specific surface area, high melting point, no sublimation, and market availability When the pigment is made into a pigment, the specific surface area of the powder is large in the sense that the colorability is good, the blackness that does not show redness or yellowness (blackness) is excellent, and further, thermal and mechanical Many conditions must be solved, such as being stable even under severe use conditions.
In recent years, electronic materials, particularly black pigments used for black stripes in plasma display panels, have been increasingly demanded for black pigments that are not reddish or yellowish but have a slight green or blue color.

In response to this requirement, a black pigment of cobalt trioxide powder obtained by calcining cobalt hydroxide carbonate or cobalt hydroxide and a method for producing the same have been proposed (see Patent Document 1), but it is not sufficient.
JP 2003-138160 A

  Further, the addition and mixing of the blue pigment to add bluish color to the black pigment results in non-uniform dispersion and is easy to separate when the dispersion is mixed.

  An object of the present invention is to provide a black pigment which eliminates redness and yellowness of a conventional black pigment made of cobalt trioxide powder and exhibits a slight green or blue color and has no dispersion unevenness.

As a result of diligent research to solve the above-mentioned problems, the inventors of the present invention include a slight amount of aluminum in fine particles of cobalt trioxide obtained by firing fine particles of cobalt compounds such as cobalt carbonate and cobalt hydroxide. As a result, the above-mentioned problems have been solved, and it has been found that a black pigment having a slight green or blue color that cannot be obtained with a conventional black pigment can be obtained, and the present invention has been achieved.
That is , in the present invention, cobalt compound fine particles surface-treated with an aluminum compound are fired at a temperature of 200 to 500 ° C. in an oxygen-containing atmosphere, and the obtained aluminum-containing cobalt oxide fine particles are again 500 to 850 in an oxygen-containing atmosphere. A method for producing a composite metal oxide black pigment characterized by firing at a temperature of ° C., and cobalt obtained by firing untreated cobalt compound fine particles at a temperature of 200 to 500 ° C. in an oxygen-containing atmosphere After the oxide fine particles are surface-treated with an aluminum compound, the cobalt compound is produced by the method of producing a composite metal oxide black pigment characterized by firing again at a temperature of 500 to 850 ° C. in an oxygen-containing atmosphere. Is preferably cobalt carbonate or cobalt hydroxide, the aluminum compound It is desirable that the aluminum chelate.

  The composite metal oxide-based black pigment of the present invention has a slight green or bluish color and expresses an aesthetically pleasing blackness that could not be achieved with a conventional red or yellowish black pigment, In addition, excellent blackness is maintained even under severely or thermally severe use conditions. In addition, according to the production method of the present invention, uniform doping and compounding of aluminum into the cobalt tetroxide fine particles are achieved, and further, a uniform dispersion that does not separate with a mixed dispersion of different metal oxides is difficult. Is obtained.

  The aluminum content in the aluminum-containing cobalt trioxide fine particles of the present invention is 0.05 to 2% by weight, preferably 0.1 to 1.5% by weight. When the aluminum content is outside the above range, it is difficult to obtain the desired green or bluish blackness of the present invention.

The specific surface area of the composite metal oxide black pigment of the present invention, 1~140m ² / g approximately, preferably 2m ² / g or more, usually not more than 70m ² / g. If it is less than 1 m ² / g, the colorability becomes worse.

The composite metal oxide black pigment composed of aluminum-containing cobalt trioxide fine particles of the present invention has an L ^* value of 0 to 20, an a ^* value of −3.0 to −1 in the L ^* a ^* b ^* color system. It is desirable to satisfy all the conditions of .6 and b ^* value -1.5 to 0.1.
The L ^* a ^* b ^* color system is a color system used to represent the color of an object. It was standardized by the International Commission on Illumination (CIE) in 1976 and adopted by JIS (Z8729) in Japan. ing. In the L ^* a ^* b ^* color system, lightness is represented by L ^* , and chromaticity indicating hue and saturation is represented by a ^* and b ^* .
If the value of L ^* a ^* b ^* is outside the above range, the greenness or bluish blackness intended by the present invention cannot be obtained.

  The composite metal oxide black pigment composed of fine particles of aluminum-containing cobalt trioxide of the present invention is obtained by surface-treating cobalt compound fine particles such as cobalt carbonate and cobalt hydroxide with an aluminum compound, and the surface-treated fine particles are in an oxygen-containing atmosphere. First, firing at a relatively low temperature and then firing at a relatively high temperature, or first firing untreated cobalt compound fine particles at a low temperature, and surface-treating the resulting cobalt oxide fine particles with an aluminum compound, followed by a high temperature It is obtained by the method of baking.

Examples of the aluminum compound for surface-treating the cobalt compound or cobalt oxide fine particles include organic or inorganic aluminum compounds that are usually used as a surface treatment agent. Examples of the organoaluminum compound include alkoxyaluminum (aluminum alcoholate), aluminum chelate, and cyclic aluminum oligomer. Examples of the inorganic aluminum compound include alumina sol.
Specifically, examples of the alkoxyaluminum (aluminum alcoholate) include aluminum isopropylate, aluminum trisec-butoxide, monosec-butoxyaluminum diisopropylate, and aluminum ethylate. Examples of the aluminum chelate include ethylacetoacetate aluminum diisopropylate. Cyclic aluminum oligomers such as aluminum tris (ethyl acetoacetate), alkyl acetoacetate aluminum diisopropylate, aluminum tris (acetylacetate), aluminum bisethylacetoacetate monoacetylacetonate, aluminum monoisopropoxy monooroxyethyl acetoacetate As for cyclic aluminum oxide isopropylate etc. It can Shimesuru.
Among the various organoaluminum compounds described above, aluminum chelates are most suitable because they have excellent adhesion to the surface of the fine particles, are less toxic, and are easy to handle.

  Examples of the surface treatment include a dry method in which an aluminum compound treatment solution is dropped or sprayed while stirring the cobalt compound or cobalt oxide fine particles, and optionally heat-dried, or a suspension of the cobalt compound or cobalt oxide fine particles. Examples thereof include a wet method in which an aluminum compound is added while stirring the suspension.

The firing temperature of the cobalt compound fine particles is first baked at 200 ° C. or more and less than 500 ° C., preferably 300 to 450 ° C. in an oxygen atmosphere, then cooled to less than 200 ° C., preferably less than 100 ° C., and again 500 to 500 ° C. in an oxygen atmosphere. It is necessary to bake at 850 ° C.
If the firing temperature is less than 200 ° C., firing is insufficient, and if it exceeds 850 ° C., the L ^* value increases and the blackness decreases. Further, sudden firing at a high temperature of 500 to 850 ° C. is not preferable because solidification due to sintering is likely to occur, and a fine powder is not obtained.
Further, when obtaining a black pigment that maintains blackness even under severe use conditions such as receiving a shearing force, it is preferable to perform the second baking at a high temperature of 650 to 850 ° C.
In addition, about baking time, appropriate time is defined according to a baking temperature, a baking processing amount, and a baking method.
In the cooling step, it is preferable that the preheated raw material is once transferred to another container and the thickened material is stirred. In addition, when firing using an electric furnace capable of several stages of temperature control, it is possible to set a temperature pattern and perform inline control of the cooling process using the same container.

  Next, the content of the present invention will be described in more detail with reference to examples. In addition, the crystal structure analysis of the black pigment shown in an Example and a comparative example, the measurement of the Al content in a pigment, and each physical-property value were measured with the test method shown below.

(1) Crystal structure analysis Using an X-ray diffractometer (manufactured by Rigaku Corporation, miniflex), a sample powder is set in a holder, CuKα (λ = 1.54056１．５) is used as a radiation source, and current and voltage are 15 mA each. , Measured at 30 kV.

(2) Content of Al in Pigment A sample obtained by subjecting 0.1 g of the sample to sulfuric acid decomposition under pressure was measured with a flame atomic absorption spectrometer (manufactured by Hitachi, Z5000).

(3) Specific surface area It measured using the BET method specific surface area measuring apparatus Micromeritex "ASAP 2010" (made by Shimadzu Corp.).

(4) L ^* value, a ^* value and b ^* value Using a spectrocolorimeter JS555 (manufactured by Color Techno System Co., Ltd.), each numerical value at a colorimetric change of 10 degrees was measured by a solid powder diffusion method with a D65 light source. .

Examples 1-2, Comparative Example 1
Alkyl acetoacetate aluminum diisopropylate (product of Ajinomoto Co., Inc., product name “Aluminum Chelate M”, molecular weight 490.9), an aluminum coupling agent, was used as a surface treatment solution in a propylene glycol monomethyl ether acetate / isopropanol / ethanol mixed solvent (weight ratio). 7/5/4) was used, and surface treatment was carried out on a hydroxy cobalt carbonate powder (manufactured by Nippon Chemical Industry Co., Ltd.) by a dry method. The pure processing amount of the coupling agent adhered to the surface of the fine particles was 3 and 5 parts by weight with respect to 100 parts by weight of the cobalt hydroxide carbonate powder. Each surface-treated sample powder and 10 g of untreated sample powder were put into an atmospheric furnace, fired at a temperature of 400 ° C. for 6 hours, cooled to room temperature, and further fired at a temperature of 600 ° C. for 3 hours. As a result of crystal structure analysis, the obtained powder formed a composite metal oxide of high purity cobalt tetroxide and aluminum-containing cobalt tetroxide substantially free of other cobalt compounds. The products obtained by calcining the cobalt hydroxide carbonate surface-treated with bismuth contained 0.26 and 0.47% by weight of aluminum, respectively. The specific surface area of the obtained powder and the L ^* value, a ^* value, and b ^* value of the L ^* a ^* b ^* color system were measured, and the test results are shown in Table 1.
The surface-treated samples of Examples 1 and 2 both had smaller a ^* and b ^* values than the untreated sample of Comparative Example 1, and exhibited a greenish and bluish black color.

Examples 3-5
Using the same hydroxy cobalt carbonate powder and coupling agent as in Examples 1 and 2, the pure treatment amount of the coupling agent adhered to the surface of the cobalt hydroxy carbonate fine particles was 8, 10 and 12 weights per 100 parts by weight of the hydroxy cobalt carbonate powder. The surface treatment was performed in the same manner as described above. Each 10 g of each surface-treated sample powder was put in an atmospheric furnace, fired at a temperature of 400 ° C. for 6 hours, cooled to room temperature, and further fired at a temperature of 550 ° C. for 3 hours. As a result of crystal structure analysis, the obtained powder formed a high-purity aluminum-containing cobalt trioxide complex metal oxide substantially free of other cobalt compounds. .94 and 1.06% by weight. The specific surface area of the obtained powder and the L ^* value, a ^* value, and b ^* value of the L ^* a ^* b ^* color system were measured, and the test results are shown in Table 1.
The surface-treated samples of Examples 3 to 5 both had smaller a ^* values and b ^* values than the untreated samples of Comparative Example 1, and exhibited a greenish and bluish black color.

Example 6 and Comparative Example 2
Using cobalt hydroxide powder (manufactured by Ise Chemical Industry Co., Ltd.), surface treatment was performed by the same coupling agent and treatment method as in Examples 1-5. The pure processing amount of the coupling agent adhered to the fine particle surface was 12 parts by weight with respect to 100 parts by weight of the cobalt hydroxide powder. 10 g of each of the surface-treated sample powder and the untreated sample powder were put in an atmospheric furnace, fired at a temperature of 400 ° C. for 6 hours, cooled to room temperature, and further fired at a temperature of 600 ° C. for 3 hours. As a result of crystal structure analysis, the obtained powder formed a composite metal oxide of high purity cobalt tetroxide and aluminum-containing cobalt tetroxide substantially free of other cobalt compounds. The product obtained by calcining the cobalt hydroxide powder surface-treated with aluminum contained 0.46% by weight of aluminum. The specific surface area of the obtained powder and the L ^* value, a ^* value, and b ^* value of the L ^* a ^* b ^* color system were measured, and the test results are shown in Table 1.
The surface-treated sample of Example 6 had both a ^* value and b ^* value smaller than the untreated sample of Comparative Example 2, and showed a greenish and bluish black color.

  The composite metal oxide black pigment according to the present invention is useful as a colorant for black matrix pigments such as cathode ray tubes, liquid crystal displays and plasma displays, paints, inks and ceramics.

Claims (4)

  The cobalt compound fine particles surface-treated with the aluminum compound are fired at a temperature of 200 to 500 ° C. in an oxygen-containing atmosphere, and the obtained aluminum-containing cobalt oxide fine particles are fired again at a temperature of 500 to 850 ° C. in an oxygen-containing atmosphere. A method for producing a composite metal oxide-based black pigment.   Untreated cobalt compound fine particles are fired at a temperature of 200 to 500 ° C. in an oxygen-containing atmosphere, and the obtained cobalt oxide fine particles are surface-treated with an aluminum compound, and then again at a temperature of 500 to 850 ° C. in an oxygen-containing atmosphere. A method for producing a composite metal oxide-based black pigment, characterized in that it is calcined at a temperature. The method for producing a composite metal oxide black pigment according to claim 1 or 2, wherein the cobalt compound is cobalt carbonate or cobalt hydroxide. The method for producing a composite metal oxide black pigment according to claim 1 or 2, wherein the aluminum compound is an aluminum chelate.