KR20080104260A - Process for production of granular cobalt oxide black pigment, and granular cobalt oxide black pigment - Google Patents

Abstract

Disclosed is a process for production of a granular cobalt oxide black pigment. The process involves the step of performing the mixing neutralization of an aqueous solution of a salt of cobalt (bivalent) with an alkaline solution at a pH ranging from 10 to 13. After the mixing neutralization is initiated or completed, an oxygen-containing gas is bubbled in the mixed solution continuously while keeping the temperature of the mixed solution at 10 to 40‹C to produce a cobalt hydroxide precursor. The precursor is filtered, washed, dried, triturated, and then burned in a closed air at 500 to 850‹C for 0.5 to 3 hours, thereby producing the granular cobalt oxide black pigment. ® KIPO & WIPO 2009

Description

PROCESS FOR PRODUCTION OF GRANULAR COBALT OXIDE BLACK PIGMENT, AND GRANULAR COBALT OXIDE BLACK PIGMENT}

The present invention relates to a method for producing a granular cobalt oxide black pigment, and to a granular cobalt oxide black pigment, wherein the proportion of cobalt (bivalent) in all cobalt to be contained is 35 to 70%. A method for producing a granular cobalt oxide black pigment having excellent blackness and high electrical resistance, particularly for use in black compositions such as a black matrix coloring composition, plasma display, plasma address liquid crystal, light shielding layer formation, and the like, and granular cobalt oxide black It relates to a pigment.

Black pigments used for coloring compositions for black matrices and the like are required to have excellent properties such as blackness, color, coloring power, hiding power, and the like, and are inexpensive. Carbon black and various metal oxide pigments are used depending on the application.

Carbon black is a material having excellent blackness and heat resistance, but its harmfulness has recently been revealed, which is problematic in terms of labor hygiene or environmental load. In view of this, attention has been paid to metal oxide pigments as substitute materials. Representative examples of the metal oxide pigments include metal oxide particles having a single composition such as manganese oxide and copper oxide, and composite oxide particles of the metal element, among which cobalt oxide pigments are excellent in blackness.

About the manufacturing method of the said cobalt oxide pigment, the neutralization of the cobalt salt aqueous solution represented by patent document 1 is followed by the wet reaction method which manufactures tricobalt tetraoxide with oxidizing gas, or cobalt hydroxide represented by patent document 2, and calcined tricobalt tetraoxide. Disclosed is a dry method for producing.

In addition, the present applicant first proposed a cobalt-containing granular black pigment, wherein the proportion of bivalent cobalt in all cobalt as an oxide containing at least cobalt is 40% to 70% (see Patent Document 3). ). This cobalt-containing granular black pigment is used to neutralize the cobalt (divalent) salt with an alkali hydroxide containing an alkali metal salt at a liquid temperature of 40 ° C. or lower to produce a slurry containing cobalt hydroxide (divalent). It is produced by continuously bubbling an inert gas into the resulting cobalt hydroxide (divalent), followed by filtration, washing, drying and pulverization, followed by firing at 400 ° C to 800 ° C.

[Patent Document 1] Japanese Unexamined Patent Publication No. 2002-68750

[Patent Document 2] Japanese Unexamined Patent Publication No. 2003-138160

[Patent Document 3] International Publication No. 2006/030896 Pamphlet

Black pigments suitable for coloring compositions for black matrices and the like require stable high electric resistance as well as blackness. In order to be more excellent in blackness and to have a high electric resistance, it is required to have excellent blackness of the particles constituting the powder and to have a small amount of coagulation while the particles are uniformly fined. Moreover, of course, in the manufacturing method, it must be a means which is excellent in productivity.

Patent Document 1 discloses a method for producing tricobalt tetraoxide, and the production can be performed only by wet reaction. However, in such a manufacturing method, the particle size obtained only by the wet reaction remains fine and no heat treatment (firing or the like) is performed. Due to this, the tricobalt tetraoxide obtained by the document production method is fine grain size, it is difficult to say that the blackness is a sufficient level. Moreover, it is also unsuitable for use of the coloring composition for black matrices etc. which receive heat processing by falling in stability of a form.

In addition, Patent Document 2 discloses a cobalt trioxide powder, which is characterized in that hydroxycobalt carbonate or cobalt hydroxide is heated in an oxidizing atmosphere and calcined at a temperature of 150 to 800 ° C. In this production method, cobalt trioxide powder is obtained only by calcining a cobalt compound. Since cobalt trioxide obtained in this way is almost stoichiometric, the ratio of trivalent cobalt is high, which is attributed to this. It is difficult to say that it has sufficient blackness.

In view of the above, an object of the present invention is to combine black particles such as plasma display, plasma address liquid crystal, black pigment for forming a light shielding layer, excellent blackness and high electric resistance, and have a small particle size and a sharp particle size distribution. The present invention provides a method for producing a cobalt oxide black pigment.

The present inventors have found that in the wet neutralization-firing method, a granular cobalt oxide black pigment having a higher divalent cobalt content, which is superior in blackness and other properties, can be produced in the wet neutralization-calcination method. Completed.

That is, the present invention is mixed neutralization of the cobalt (divalent) salt aqueous solution and the alkaline solution to pH10 ~ 13, after the start of mixed neutralization or after the end of mixed neutralization, while maintaining the temperature of the mixed liquid at 10 ℃ ~ 40 ℃ in the mixed liquid Continuously bubbling an oxygen-containing gas to produce a cobalt hydroxide precursor, and filtering, washing, drying, and pulverizing the generated precursor, and calcining the precursor at 500 ° C. to 850 ° C. in a closed atmosphere for 0.5 to 3 hours. It is a manufacturing method of the granular cobalt oxide black pigment characterized by the following (it is called a 1st manufacturing method).

In addition, the present invention is mixed neutralization of the cobalt (divalent) salt aqueous solution and the alkaline solution to pH10 ~ 13, and after the start of mixed neutralization, or after the end of the mixed neutralization, while maintaining the temperature of the mixed solution at 10 ℃ ~ 40 ℃ oxygen in the mixed solution By continuously bubbling the containing gas to produce a cobalt hydroxide precursor, the generated precursor is filtered, washed, dried and pulverized, and the inert gas enrichment maintained at an oxygen concentration of 15% by volume or more and less than 22% by volume. It is a manufacturing method of the granular cobalt oxide black pigment which bakes the said precursor at 500 degreeC-850 degreeC in air atmosphere (henceforth a 2nd manufacturing method).

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated based on the preferable form.

The granular cobalt oxide black pigment of the present invention is a black particle whose main component is cobalt oxide at least, and according to necessary properties, components such as Si, Al, Mn, Ni, Zn, Cu, Mg, Ti, Zr, W, Mo, P, etc. You may select and contain at least 1 type or more.

First, the first manufacturing method will be described.

In the method for producing granular cobalt oxide black pigment of the present invention, the mixture is neutralized with an aqueous solution of cobalt (divalent) salt and an alkaline solution at pH 10-13, and after the start of mixed neutralization or after the end of mixed neutralization, the temperature of the mixed liquid is 10 ° C.-40. Continuously bubbling oxygen-containing gas in the mixed solution while maintaining the temperature at 0 ° C. to produce a cobalt hydroxide precursor, and filtering the resultant precursor, washing, drying and pulverizing the precursor to 500 ° C. to 850 ° C. in a closed atmosphere. It is characterized by firing for 0.5 to 3 hours.

In the production method of the granular cobalt oxide black pigment of the present invention, it is important to first carry out the mixing neutralization of the cobalt (divalent) salt aqueous solution and the alkaline solution at pH 10-13. The pH at the time of neutralization is important for making the form of cobalt in the obtained cobalt hydroxide precursor almost divalent.

When the neutralization pH is lower than 10, trivalent cobalt hydroxides are easily generated during neutralization, which not only hinders the generation of the cobalt hydroxide precursors, but also causes fine grain size of the cobalt hydroxide precursors to deteriorate the filterability, or when the particles are fired as described below. There arises a problem such that sintering easily occurs. On the contrary, when pH is higher than 13, cobalt (divalent) salt may be easy to excessively oxidize and produce trivalent cobalt hydroxide. If such a cobalt hydroxide precursor is used to carry out the treatment after the next step, it is difficult to control a uniform shape or oxidation and a granular cobalt oxide black pigment having a high divalent cobalt content cannot be obtained. In consideration of more stable generation of the cobalt hydroxide precursor, the pH at the time of neutralization is preferably 11 to 12.

In addition, in the method for producing a granular cobalt oxide black pigment of the present invention, after the start of mixed neutralization of the cobalt (divalent) salt aqueous solution and the alkaline solution or after the end of the mixed neutralization, the mixed liquid is maintained at a temperature of 10 ° C to 40 ° C and contains oxygen. It is also important to continuously bubble the gas.

In particular, it is important to maintain the temperature of the reaction slurry at 10 ° C. to 40 ° C. after controlling the above-described pH to 10 to 13 to obtain a suitable cobalt hydroxide precursor. When this temperature exceeds 40 degreeC, in addition to continuously bubbling an oxygen containing gas, oxidation of cobalt hydroxide (bivalent) advances, and it is easy to precipitate cobalt oxyhydroxide (trivalent), but also in patent document 1 As disclosed, since tricobalt tetraoxide may be produced at this point, a stable cobalt hydroxide precursor for obtaining a uniform granular cobalt oxide black pigment having a high divalent cobalt content ratio as the object of the present invention is not obtained. On the contrary, if the temperature is less than 10 ° C, it will interfere with the formation of cobalt hydroxide, and there is no effect by lowering the liquid temperature, which is not practical.

After the start of the mixing neutralization or after the completion of the mixing neutralization, it is necessary to continuously bubble the oxygen-containing gas in the mixed liquid. When this operation is not performed, the cobalt hydroxide precursor which is a product obtained tends to aggregate, and it does not become a fine particle and a uniform particle size.

Although this reason is not fully understood, when the bivalent cobalt hydroxide precursor is produced from the cobalt (divalent) salt in the mixed liquid by continuously bubbling the oxygen-containing gas in a low temperature region, the precursor to which the bubbling oxygen-containing gas is to aggregate It is believed that a thin layer of oxide film is formed between the particles to penetrate the particles, thereby preventing the aggregation of the particles. This effect is not obtained by simple mechanical agitation.

In addition, the bubbling oxygen-containing gas may use air (oxygen concentration 22 vol%). In order to better control the oxidation adjustment, it is preferable to use inert gas-enriched air having an oxygen concentration of 5 vol% or more and less than 22 vol%. . At this time, the inert gas to be used is preferably nitrogen for practical use. By reducing the oxygen in the air in this range, it becomes easy to produce the target cobalt hydroxide precursor without precise control of the amount of bubbling gas or the bubbling time. When air is used for bubbling oxygen containing gas, it is preferable to bubble for about 1 hour-about 3 hours at 0.01 N liter / (L * min)-0.3N liter / (L * min) per unit volume of liquid mixture. When using inert gas enriched air, what is necessary is just to adjust a bubbling gas velocity and a bubbling time according to the total amount of oxygen in the bubbling gas.

As a cobalt (divalent) salt used as a starting material, it is preferable that it is a salt soluble in water, such as cobalt sulfate (divalent), cobalt chloride (divalent), and cobalt nitrate (divalent). As alkali used for neutralization, alkali hydroxides, such as sodium hydroxide and potassium hydroxide, are used industrially. In addition, the oxygen-containing gas used in the reaction is preferably air for practical use.

When producing a cobalt hydroxide precursor, simply mixing an aqueous solution of cobalt (divalent) salt and an alkaline solution alone does not allow sufficient agitation when the amount of the mixed liquid at the beginning of mixing is small, making it difficult to obtain a uniform cobalt hydroxide precursor. There is a case. In such a case, you may prepare the alkali solution prepared in the range of pH10-13 of sufficient quantity for stirring, and add a cobalt (divalent) salt aqueous solution to this alkali solution, and produce a cobalt hydroxide precursor. Even in such a case, it is important to keep the pH of the cobalt hydroxide precursor slurry at 10 to 13 while further adding an alkaline solution.

The slurry containing the cobalt hydroxide precursor thus obtained is filtered and washed to evaporate the contained water.

Filtration and washing are performed to remove by-products, unreacted substances and excess alkali components. If by-products, unreacted materials, and excess alkali remain, there is a concern that the final cobalt oxide black pigment produced may have blackness, electrical resistance, and the like.

It is preferable that the moisture content of the dry body which evaporated water is 1 mass% or less. Control of the moisture content is carried out by appropriately adjusting the drying temperature and drying time. When the amount of water to be contained is 1% by mass or less, in more cases, the amount of water vapor generated in the firing step described later can be reduced, and a decrease in the firing efficiency can be prevented. Moreover, preferably, the moisture content is adjusted to 0.1 mass%-0.6 mass%.

Grinding operation is performed with respect to the dried body prepared with the moisture content below 1 mass%. If the pulverizing operation is not performed, the dried body is supplied to the calcination step described later in a coagulated state, which causes problems such as further coagulation by calcination. As a grinding | pulverization apparatus, a hammer mill, an impact mill, a disk mill, etc. of a high speed rotation type are preferable.

The dried product thus obtained is calcined at 500 ° C to 850 ° C for 0.5 to 3 hours in a sealed atmosphere. What is important here is that firing in the air may be performed, but air is not introduced from the outside in a sealed container. This reason is for suppressing peroxidation by introducing excess air. What is necessary is just to adjust the air capacity in a baking apparatus about 0.01-0.5m <3> / kg with respect to dry mass. This air capacity is determined by the inner volume of the firing apparatus.

On the other hand, the firing time and the firing temperature are important for promoting the dehydration of cobalt hydroxide while suppressing the sintering of the granular cobalt oxide black pigment to be produced to improve the crystallinity of the divalent oxide. If the firing temperature is less than 500 DEG C, the shape change is not sufficient, and sufficient blackness and high electric resistance are not obtained. On the contrary, when it exceeds 850 degreeC, sintering of particle | grains advances and there exists a possibility that it may become impossible to cancel aggregation and solidification also in a post process. More preferable temperature range of this baking temperature is 600 degreeC-800 degreeC.

If the firing time is less than 0.5 hour, even if the high temperature range is selected within the above temperature range, the shape change may not be sufficient or a deviation may occur and sufficient blackness and high electric resistance may not be obtained. In the case of more than 3 hours, even if the low temperature range is selected within the above temperature range, the sintering proceeds and the coagulation and solidification cannot be released during the post-process, and the cobalt is oxidized during the sintering process, thereby reducing the divalent cobalt content. There is.

The calcined product thus obtained has a slightly aggregated and solidified state, and thus the target granular black pigment can be obtained by subjecting the grinding method of the phase method.

In addition, the granular cobalt oxide black pigment thus obtained can further increase the electrical resistance by treating with a wheel-type mixing dough having a function of compression, shear, and spatula. Preferable treatment conditions are 10 to 90 minutes of treatment at a linear pressure of 30 kgf / cm to 160 kgf / cm. As a result, the electrical resistance of the granular cobalt oxide black pigment is improved by about one power. More preferable conditions are 30 kgf / cm-120 kgf / cm.

Next, a second manufacturing method will be described.

In the method for producing granular cobalt oxide black pigment of the present invention, the mixture is neutralized with an aqueous solution of cobalt (divalent) salt and an alkaline solution at pH 10-13, and after the start of mixed neutralization or after the end of mixed neutralization, the temperature of the mixed liquid is 10 ° C.-40. Continuously bubbling oxygen-containing gas in the mixed solution while maintaining the temperature at 0 ° C. to produce a cobalt hydroxide precursor, and maintaining the oxygen concentration at 15% by volume or more and 22% by volume after filtering, washing, drying and pulverizing the produced precursor. And firing the precursor at 500 ° C. to 850 ° C. in an inert gas-enriched air atmosphere.

Since the conditions at the time of baking in a 1st manufacturing method differ only about a 2nd manufacturing method, only that part is described below.

In the second production method, the slurry containing the cobalt hydroxide precursor obtained by the wet reaction is filtered and washed to evaporate the water contained therein, and when firing the dried body to which the grinding operation is applied, the oxygen concentration is 15 vol% or more, It is important to fire the precursor at 500 ° C. to 850 ° C. in an inert gas enriched air atmosphere maintained at less than 22 volume%.

In the second production method, by maintaining the oxygen concentration in the firing atmosphere at 15 vol% or more and less than 22 vol%, the degree of oxidation of the granular cobalt oxide black pigment produced without being bound by the firing time can be controlled. When the oxygen concentration in the firing atmosphere is more than 22% by volume, it is necessary to pay considerable attention to the adjustment of the firing time because it is in a state of air or oxygen. If it is less than 15% by volume, the firing time for producing the target granular cobalt oxide black pigment is inevitably long, and there is a possibility that the sintering may not proceed and the coagulation / solidification cannot be released in a later step.

In a 2nd manufacturing method, baking temperature is performed at 500 to 850 degreeC similarly to a 1st manufacturing method. The reason for setting the range is the same as in the first manufacturing method. Preferable temperature range is 600 degreeC-800 degreeC. The firing time tends to be lower in oxygen concentration in the firing atmosphere than in the first production method, so that the firing time may be somewhat longer. Although it is not necessary to determine strictly, it is preferable to bake about 1 to 4 hours in order to prevent aggregation and solidification by sintering.

Next, the granular cobalt oxide black pigment obtained by the manufacturing method of the said invention is demonstrated.

In the granular cobalt oxide black pigment of the present invention, the proportion of divalent cobalt in the total cobalt content is preferably 35% to 70%.

The ratio of bivalent cobalt to all cobalt content is the value multiplied by 100 divided by the value which divided | divided the bivalent cobalt content contained in the whole particle | grains by the total cobalt content contained in the whole particle | grain. Typical forms of cobalt oxide include tricobalt tetraoxide (Co ₃ O ₄ ) and cobalt oxide (CoO and Co ₂ O ₃ ). Co ₃ O ₄ accounts for 33% of bivalent cobalt in all cobalt. Also, CoO is divalent cobalt in all cobalt, and Co ₂ O ₃ is trivalent cobalt in all cobalt.

With respect to such cobalt oxide, the granular cobalt oxide black pigment of the present invention differs in the proportion of divalent cobalt in all cobalt, and its elemental constitution achieves both blackness and high electric resistance.

When the ratio of bivalent cobalt in all cobalt is less than 35%, blackness will become inadequate. When it is more than 70%, it becomes a cyan-colored pigment, not a black pigment, and the effect of this invention cannot be exhibited. The ratio of bivalent cobalt in all cobalt becomes like this. More preferably, it is 40 to 60%.

Moreover, it is preferable that the granular cobalt oxide black pigment of this invention is granular in shape. Particles in the shape of plates, etc., are inferior in terms of dispersibility and fluidity, and in the case of plate particles, the particle size in the thickness direction is about several tens of nm, causing deviation in the absorption wavelength of light, and thus the color as a black pigment. It is deteriorated and insufficient for black electrodes, such as a plasma display which considers blackness degree, a plasma address liquid crystal, and a light shielding layer formation use. The granularity here means a sphere, spindle shape, etc., and excludes plate-shaped particles.

Moreover, it is preferable that the granular cobalt oxide black pigment of this invention is 60 mass%-80 mass% with respect to the whole particle, and bivalent cobalt content with respect to the whole particle is 24 mass%-50 mass%. More preferably, while the total cobalt content with respect to the whole particle | grain is 65 mass%-75 mass%, the bivalent cobalt content with respect to the whole particle | grain is 26 mass%-45 mass%. By making total cobalt content with respect to the whole particle | grains 60 mass% or more, excess amount of components other than cobalt is prevented, and the effect of this invention improves. By setting it as 80 mass% or less, the charge balance of cobalt and oxygen becomes easy to be obtained, and it becomes a stable substance. Moreover, blackness is enough by making bivalent cobalt content with respect to the whole particle | grain at 24 mass% or more, and blackness is similarly sufficient by setting it as 50 mass% or less.

In addition, the granular cobalt oxide black pigment of the present invention preferably has a primary particle diameter of 0.02 µm to 0.6 µm. By setting the primary particle diameter to 0.02 µm or more, the redness of the color is prevented and the dispersibility is improved. Moreover, when it is 0.6 micrometer or less, color becomes enough and coloring power becomes sufficient also. When primary particle diameter is 0.05 micrometer-0.3 micrometer, it is easy to balance a hue and coloring power, and it is more preferable.

In addition, it is preferable that the granular cobalt oxide black pigment of the present invention has an L value of 38 or less and a b value of 0 or less at the time of color evaluation. More preferably, L value is 36 or less and b value is -0.5 or less. The evaluation method of coloring property is as follows. 0.5 g of black pigment and 1.5 g of titanium oxide (R800 manufactured by Ishihara Sangyo Co., Ltd.) are added with 1.3 피 of castor oil and kneaded with a Hoover automatic muller. 4.5 g of lacquer was added to 2.0 g of the kneaded sample, and further kneaded, and then coated on a mirror coated paper using a 4 mil applicator, followed by drying using a colorimeter (color analyzer TC-1800, manufactured by Tokyo Denshoku Co., Ltd.). L value) and color (a value, b value) are measured. When the L value is higher than 38, it is not sufficient coloration, and when the b value is higher than 0, the color becomes yellowish, which is not preferable.

In addition, the granular cobalt oxide black pigment of the present invention is characterized by high electrical resistance. Specifically, the electrical resistance value is preferably 1 × 10 ⁵ Ωcm or more. More preferably, it is 5 * 10 <^5> ohm-cm or more, More preferably, it is 1 * 10 <^6> ohm-cm. When the electrical resistance is lower than 1 × 10 ⁵ Ωcm, the function of black matrix on array type high light shielding film formation such as a plasma display and a plasma address liquid crystal cannot be sufficiently enhanced, which is undesirable.

<Example>

Hereinafter, the present invention will be described in detail by way of examples. However, the scope of the present invention is not limited to this embodiment.

Example 1

80 liters of an aqueous sodium hydroxide solution at pH 12 was charged into a 200 liter reaction vessel. Subsequently, 60 liters of an aqueous solution of cobalt sulfate (divalent) containing 1.2 mol / liter of cobalt (divalent) was continuously added to the reaction vessel at a rate of 1 liter / min. At the same time, the pH of the reaction slurry was adjusted to 12 using an aqueous sodium hydroxide solution. Meanwhile, the slurry temperature was maintained at 35 ° C. and air bubbling was performed at a rate of 5 N liters / min at all times. After mixing was complete, air bubbling was performed for 90 minutes at a rate of 15 N liters / minute while stirring was continued.

The cake obtained by filtering and washing the obtained cobalt hydroxide precursor slurry was dried at 80 degreeC. The dry matter thus obtained had a water content of 0.5% by mass. The moisture content was measured in accordance with the heating loss measurement method of JIS K 5101-1991. In addition, this dried body was ground with a hammer mill.

The pulverized dried product thus obtained was calcined at 700 ° C. for 2 hours in a sealed atmosphere to obtain particle powder.

The obtained particle powder was evaluated by the method shown below. The evaluation results are shown in Table 1.

[Assessment Methods]

(a) Total cobalt content for the whole particle

The sample was completely dissolved in acid, and the content of cobalt was determined by ICP.

(b) Divalent cobalt content with respect to the whole particle

The sample and iron ammonium sulfate (divalent) were completely dissolved in acid simultaneously, and the divalent iron ion concentration in the solution was determined by titration using potassium dichromate standard solution using sodium diphenylamine sulfonate as an indicator.

Next, the difference between the divalent iron ion concentration added in advance and the divalent iron ion concentration determined by titration was calculated by calculation to determine the trivalent iron ion concentration.

Since trivalent iron ion is produced by the following chemical reaction, this concentration was made into the trivalent cobalt ion concentration contained in the sample.

Co ^{3 +} + Fe ^{2 +} → Co ^{2 +} + Fe ^{3 +}

(c) particle shape, primary particle diameter

The particle shape was observed with the scanning microscope (40,000 times magnification). At the same time, a Ferret's diameter of 200 particles was arbitrarily measured, and the number average thereof was set as the primary particle diameter.

(d) electrical resistance

10 g of the sample was placed in a holder, and a pressure of 600 kgf / cm 2 was applied to form a tablet with a diameter of 25 mm, and the electrode was weighed to measure a pressure of 150 kgf / cm 2. The electrical resistance value was computed from the thickness, cross-sectional area, and resistance value of the sample used for the measurement.

(e) Black, color

The blackness of the powder was measured in accordance with JIS K5101-1991. Add 1.4 ㏄ of castor oil to 2.0 g of the sample and knead it with Hoover Muller. 7.5 g of lacquer was added to 2.0 g of the kneaded sample, further kneaded, and then coated on a mirror coated paper using a 4 mil applicator, followed by drying using a color meter (Tokyo Denshoku Co., Color Analyzer TC-1800 type). (L value) and color (a value, b value) were measured.

(f) Coloring (evaluation of dispersibility and color during painting)

After adding 1.3 g of castor oil to 0.5 g of sample and 1.5 g of titanium oxide (R800 manufactured by Ishihara Sangyo) and kneading with a Hoover Muller, 4.5 g of lacquer was added to the kneaded sample and further kneaded. After application using a 4mil applicator on the coated paper and drying, blackness (L value) and color (a value, b value) were measured with a colorimeter (color analyzer TC-1800 manufactured by Tokyo Denshoku Co., Ltd.).

(g) specific surface area

It measured with the 2200 type BET meter made from Shimadzu-Micromeritics.

(h) oil absorption

It carried out based on JIS K 5101-1991.

Example 2

Particle powder was obtained in the same manner as in Example 1 except that the oxygen-containing gas was brought into the reaction slurry at 10 liters / min at the time of neutralization and 30 liters / min after the mixing was completed at an oxygen concentration of 10 vol%. The obtained particle powder was evaluated by the same method as Example 1.

Example 3

Particle powder was obtained in the same manner as in Example 1 except that the product was calcined in an atmosphere maintained at an oxygen concentration of 18 vol%. The obtained particle powder was evaluated by the same method as Example 1.

Comparative Example 1

Particle powder was obtained in the same manner as in Example 1 except that the reaction slurry temperature was set at 50 ° C. The obtained particle powder was evaluated by the same method as Example 1.

Comparative Example 2

Particle powder was obtained in the same manner as in Example 1 except that the pH of the reaction slurry was changed to 9. The obtained particle powder was evaluated by the same method as Example 1.

Comparative Example 3

Particle powder was obtained in the same manner as in Example 1 except that the outside air was introduced into the calcination apparatus and the gas concentration was the same as that of the outside air. The obtained particle powder was evaluated by the same method as Example 1.

[Comparative Example 4]

Nitrogen was introduced into the calcination apparatus, and the particle powder was obtained in the same manner as in Example 1 except that the calcination atmosphere was maintained at 10% by volume of oxygen. The obtained particle powder was evaluated by the same method as Example 1.

As is apparent from Table 1, the particle powder of the Example exhibits excellent blackness, high electrical resistance, small particle diameter and sharp particle size distribution, and thus, black electrodes such as black matrix coloring compositions, plasma displays, and plasma address liquid crystals, and light shielding. It is excellent as a material for layer formation.

On the other hand, the particle powders of Comparative Examples 1 and 2 have various characteristics such as a decrease in blackness or color due to a decrease in the divalent cobalt content in all cobalt or the whole particle because the reaction conditions deviate from the manufacturing conditions of the production method of the present invention. There is a problem.

Moreover, the particle | grains of the comparative example 3 introduce | transduce and process external air at the time of baking, and the ratio which the bivalent cobalt in all the cobalt occupies is falling, and the color became inferior because of this.

In addition, the particle powder of Comparative Example 4 was treated in a low oxygen concentration atmosphere during firing, but the primary particle diameter was small and the specific surface area was also large due to the residual cobalt oxide particles due to insufficient cobalt oxide due to insufficient firing. Thereby, various characteristics, such as blackness, a hue, or coloring power, fell remarkably.

As described above in detail, the granular cobalt oxide black pigment prepared by the manufacturing method of the present invention has a high proportion of bivalent cobalt in all cobalt, which has excellent blackness and high electric resistance, and particle size distribution with small particle diameter. Since it is sharp, it is suitable for applications, such as black electrodes, such as a plasma display and a plasma address liquid crystal, and black pigment powder for shading a light shielding layer.

Claims (9)

Mixing neutralization of the cobalt (divalent) salt aqueous solution and alkaline solution to pH10-13, and after the start of mixed neutralization or after the end of mixed neutralization, the oxygen-containing gas in the mixed solution continuously while maintaining the temperature of the mixed solution at 10 ℃ ~ 40 ℃ After forming a cobalt hydroxide precursor by bubbling, the resulting precursor is filtered, washed, dried, and pulverized, and then the precursor is baked at 500 ° C. to 850 ° C. in a sealed atmosphere for 0.5 to 3 hours. Iii) a method for producing a cobalt oxide black pigment. The method of claim 1, A method for producing a granular cobalt oxide black pigment, wherein an inert gas enriched air having an oxygen concentration of 5% by volume or more and less than 22% by volume is used as the oxygen-containing gas. The method according to claim 1 or 2, The alkaline solution is a method for producing a granular cobalt oxide black pigment, characterized in that the aqueous sodium hydroxide solution or potassium hydroxide solution. Mixing neutralization of the cobalt (divalent) salt aqueous solution and alkaline solution to pH10-13, and after the start of mixed neutralization or after the end of mixed neutralization, the oxygen-containing gas in the mixed solution continuously while maintaining the temperature of the mixed solution at 10 ℃ ~ 40 ℃ Cobalt hydroxide precursors were bubbled to form the resulting precursor, which was filtered, washed, dried and pulverized, followed by 500 ° C. to 850 ° C. in an inert gas-enriched air atmosphere maintained at an oxygen concentration of at least 15 vol% and less than 22 vol%. A method for producing a granular cobalt oxide black pigment, wherein the precursor is fired. The method of claim 4, wherein A method for producing granular cobalt oxide black pigment, wherein an inert gas-enriched air having an oxygen concentration of not less than 5 vol% and less than 22 vol% is used as the oxygen-containing gas. The method according to claim 4 or 5, The alkaline solution is a method for producing a granular cobalt oxide black pigment, characterized in that the aqueous sodium hydroxide solution or potassium hydroxide solution. As an oxide containing at least cobalt obtained by the manufacturing method of the granular cobalt oxide black pigment as described in any one of Claims 1-6, Granular cobalt oxide black pigment, characterized in that the proportion of divalent cobalt in all cobalt is 35% to 70%. The method of claim 7, wherein A granular cobalt oxide black pigment, wherein the total cobalt content of the whole particle is 60% by mass to 80% by mass while the divalent cobalt content of the whole particle is 24% by mass to 50% by mass. The method according to claim 7 or 8, Granular cobalt oxide black pigment, characterized in that the primary particle diameter is 0.02㎛ ~ 0.6㎛.