WO2007122954A1

WO2007122954A1 - Process for production of granular cobalt oxide black pigment, and granular cobalt oxide black pigment

Info

Publication number: WO2007122954A1
Application number: PCT/JP2007/055863
Authority: WO
Inventors: Tomoyuki Hoshino; Koichi Katsuyama; Shoichi Fujiyasu; Takashi Nakashima
Original assignee: Mitsui Mining & Smelting Co., Ltd.
Priority date: 2006-03-24
Filing date: 2007-03-22
Publication date: 2007-11-01
Also published as: KR101313045B1; JP2007284340A; JP4929002B2; KR20080104260A

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 40ºC to produce a cobalt hydroxide precursor. The precursor is filtered, washed, dried, triturated, and then burned in a closed air at 500 to 850ºC for 0.5 to 3 hours, thereby producing the granular cobalt oxide black pigment.

Description

Specification

Method for producing granular cobalt oxide black pigment, and granular cobalt oxide black pigment

Technical field

[0001] The present invention relates to a method for producing a granular cobalt oxide black pigment and a granular cobalt oxide black pigment. Specifically, the proportion of cobalt (divalent) in the total cobalt contained is 35 to 70%. A method for producing a granular cobalt oxide black pigment having excellent blackness and high electric resistance, particularly used for forming a black matrix coloring composition, a black electrode such as a plasma display and a plasma addressed liquid crystal, and a light shielding layer. And a particulate cobalt oxide black pigment. Background art

[0002] Black pigments used in black matrix coloring compositions and the like are required to be excellent in properties such as blackness, hue, coloring power, concealment, and the like, and inexpensive, such as carbon black and Various metal oxide pigments are used depending on applications.

[0003] Although carbon black is a material with excellent blackness and heat resistance, its toxicity has recently been addressed, and has been regarded as a problem in terms of occupational health and environmental burden. As a result, metal oxide pigments, which are alternative materials, are attracting attention. Representative examples of metal oxide pigments include metal oxide particles having a single composition such as manganese oxide and copper oxide, and composite oxide particles of these metal elements. Is excellent in blackness.

[0004] Regarding the above-described method for producing a cobalt oxide pigment, a wet reaction method, as represented by Patent Document 1, for producing tricobalt tetroxide using an oxidizing gas after neutralizing a cobalt salt aqueous solution. In addition, there is a disclosure such as a dry method for producing tricobalt tetroxide by firing cobalt hydroxide as represented by Patent Document 2.

[0005] Further, the applicant of the present invention is characterized in that it is an acid oxide containing at least cobalt, and the ratio power of divalent cobalt in all cobalt is 0% to 70%. A cobalt black-containing granular black pigment was proposed (see Patent Document 3). This cobalt-containing granular black The pigment is neutralized with cobalt (divalent) salt using an alkali metal salt containing alkali metal salt at a liquid temperature of 40 ° C or lower to produce a slurry containing cobalt hydroxide (divalent). In this process, inert gas is continuously published in the slurry, and the obtained cobalt hydroxide (divalent) is filtered, washed, dried and crushed, and then at 400 ° C to 800 ° C. Manufactured by firing.

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2002-68750

Patent Document 2: Japanese Patent Laid-Open No. 2003-138160

Patent Document 3: International Publication No. 2006Z030896 Pamphlet

[0007] A black pigment suitable for a black matrix coloring composition is required to have not only blackness but also stable high electrical resistance. In order to have higher blackness and higher electrical resistance, it is required that the particles constituting the powder have excellent blackness, that the particles are finely divided in a uniform manner, and that there is little aggregation. Needless to say, the manufacturing method must also be a highly productive means.

[0008] Patent Document 1 discloses a method for producing tetracobalt tetraacid tetracobalt, which can be produced only by a wet reaction. However, in a brilliant manufacturing method, the particle size obtained by only a wet reaction remains fine and no heat treatment (firing etc.) is performed. Due to these reasons, the tricobalt tetraacid obtained by the production method of the literature has a fine particle size, so the blackness is hardly a sufficient level. Further, it lacks stability in form and is unsuitable for use as a black matrix coloring composition that undergoes heat treatment.

[0009] Further, Patent Document 2 discloses a cobalt tetroxide-cobalt powder. In this production method, 150 to 800 ° C is obtained by heating hydroxy cobalt carbonate or cobalt hydroxide in an oxidizing atmosphere. It is characterized by firing at a temperature of. In this manufacturing method, it is said that a cobalt tetroxide-cobalt powder can be obtained simply by calcining a conolate compound. However, it is difficult to say that blackness is sufficiently black due to the high ratio of the value cobalt.

[0010] From the above, the object of the present invention is to provide excellent blackness and high electrical resistance, which should be provided as a black pigment powder for forming a black electrode such as a plasma display or a plasma addressed liquid crystal or a light shielding layer. A granular cobalt oxide black face with a small particle size and sharp particle size distribution It is in providing the manufacturing method of a material.

Disclosure of the invention

[0011] As a result of earnest research, the inventors of the present invention have found that the wet neutralization calcining method has superior blackness and other characteristics as compared with the conventional tricobalt tetraoxide, and has a high divalent cobalt content. The present inventors have found that a cobalt black pigment can be produced and completed the present invention.

[0012] That is, the present invention neutralizes a cobalt (divalent) salt aqueous solution and an alkali solution at pH 10 to 13 and starts mixing neutralization or after mixing neutralization. Is maintained at 10 ° C. to 40 ° C. to continuously publish an oxygen-containing gas in the mixed solution to produce a cobalt hydroxide precursor, and the produced precursor is filtered, washed, dried, After pulverization, the precursor is calcined in a sealed atmosphere at 500 ° C to 850 ° C for 0.5 to 3 hours. Is called the first manufacturing method

) o

[0013] Further, the present invention provides a mixed neutralization of a cobalt (divalent) salt aqueous solution and an alkaline solution at a pH of 10 to 13, and the temperature of the mixed solution after the start of the mixed neutralization or after the completion of the mixed neutralization. Is maintained at 10 ° C. to 40 ° C. to continuously publish an oxygen-containing gas in the mixed solution to produce a cobalt hydroxide precursor, and the produced precursor is filtered, washed, dried, After pulverization, the precursor is calcined at 500 ° C to 850 ° C in an inert gas-enriched air atmosphere maintained at an oxygen concentration of 15% by volume or more and less than 22% by volume. This is a method for producing a cobalt oxide black pigment (hereinafter referred to as a second production method).

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described based on preferred forms thereof.

[0015] The granular cobalt oxide black pigment of the present invention is black particles whose main component is at least a cobalt oxide, and depending on required properties, Si, Al, Mn, Ni, Zn, Cu, Mg, At least one component such as Ti, Zr, W, Mo, and P may be selected and contained.

[0016] First, the first manufacturing method will be described.

In the method for producing the granular cobalt oxide black pigment of the present invention, a cobalt (divalent) salt aqueous solution and an alkali solution are mixed and neutralized at a pH of 10 to 13, and after mixing neutralization starts or after mixing neutralization ends, Oxygen contained in the mixture while maintaining the temperature of the mixture at 10 ° C to 40 ° C Gas is continuously published to produce a cobalt hydroxide precursor, and the produced precursor is filtered, washed, dried and crushed, and then in a sealed atmosphere at 500 ° C to 850 ° C. The precursor is calcined for 0.5 to 3 hours.

[0017] In the method for producing a granular cobalt oxide black pigment of the present invention, it is important to first perform neutralization of a cobalt (divalent) salt aqueous solution and an alkali solution at ρΗ10-13. The pH at the time of neutralization is important for making the form of cobalt in the obtained hydrated cobalt hydroxide precursor almost divalent.

[0018] When the neutralization pH is lower than 10, trivalent cobalt hydroxide is easily generated during neutralization. Not only does this interfere with the formation of a cobalt hydroxide precursor, but also a cobalt hydroxide precursor. The particle size becomes fine, resulting in problems such as poor filterability and the possibility of sintering between particles when firing, which will be described later. Conversely, if the pH is higher than 13, cobalt (divalent) salts are susceptible to excessive oxidation and may produce trivalent cobalt hydroxide. When such a hydroxy-cobalt precursor is used in the subsequent steps, it is difficult to control the uniform shape and oxidation, and a granular cobalt oxide black pigment having a high divalent cobalt content. Cannot be obtained. In view of more stable production of the hydroxy-cobalt precursor, the pH during neutralization is preferably 11-12.

[0019] In the method for producing a granular cobalt oxide black pigment of the present invention, the mixed solution is heated to a temperature of 10 after the start of neutralization of the cobalt (divalent) salt aqueous solution and the alkali solution or after the end of the neutralization. It is also important to continuously publish the oxygen-containing gas while maintaining the temperature between 40 ° C and 40 ° C.

[0020] In particular, maintaining the temperature of the reaction slurry at 10 ° C to 40 ° C while controlling the pH to 10 to 13 is important for obtaining a suitable cobalt hydroxide precursor. is there. When this temperature exceeds 40 ° C, the oxidation of cobalt hydroxide (divalent) proceeds with the continuous publishing of oxygen-containing gas, and oxyhydroxide-cobalt (trivalent) precipitates. However, as disclosed in Patent Document 1, tricobalt tetroxide may be formed at this point, so that the content ratio of the divalent cobalt as intended by the present invention is There is no stable hydric cobalt hydroxide precursor to obtain a high and well-balanced granular oxycobalt black pigment. Conversely, if the temperature is lower than 10 ° C, it will hinder the formation of hydroxide and cobalt. The effect of lowering the liquid temperature is not practical at all.

[0021] Further, it is necessary to continuously publish an oxygen-containing gas in the mixed solution after the start of the above-described mixed neutralization or after the completion of the mixed neutralization. If this operation is not performed, the resulting product, the cobalt hydroxide precursor, aggregates and does not immediately become fine and uniform in size.

[0022] Although the reason for this has not been fully investigated, by continuously bubbling an oxygen-containing gas in a low temperature range, a divalent hydroxide-cobalt precursor is obtained from a cobalt (divalent) salt in the mixed solution. When the body is formed, the publishing oxygen-containing gas enters between the precursor particles to be agglomerated, and a thin oxide film is formed between the particles, which seems to play a role in hindering the aggregation of the particles. This effect cannot be obtained by simple mechanical stirring! /.

[0023] Note that air (oxygen concentration: 22 vol%) may be used as the publishing oxygen-containing gas. However, in order to better control the adjustment of oxidation, the oxygen concentration is 5 vol% or more and less than 22 vol%. It is preferred to use active gas enriched air. In this case, the inert gas used is preferably nitrogen for practical use. By reducing oxygen in the air in this range, it becomes easy to produce the target cobalt hydroxide precursor without precise control of the publishing gas amount and bubbling time. When air is used as the publishing oxygen-containing gas, it is possible to publish from 0.01 N liter Z (L 'min) to 0.3 N liter Z (L * min) for 1 hour to 3 hours per unit volume of the mixture. preferable. When inert gas-enriched air is used, the publishing gas speed and publishing time may be adjusted according to the total amount of oxygen in the publishing gas.

[0024] The cobalt (divalent) salt used as a starting material is a salt that is soluble in water, such as cobalt sulfate (divalent), salt-cobalt (divalent), or nitrate (bivalent) nitrate. It is preferable. Further, as alkali used for neutralization, hydroxy-alkali hydroxide such as sodium hydroxide and potassium hydroxide is industrially used. The oxygen-containing gas used in the reaction is preferably air for practical use.

[0025] When the hydroxy-cobalt precursor is produced, the amount of liquid mixture at the beginning of mixing is small by simply mixing an aqueous solution whose main component is a cobalt (divalent) salt and an alkali solution. In some cases, sufficient stirring cannot be achieved, and it is difficult to obtain a uniform cobalt hydroxide precursor. In such a case, an alkaline solution prepared in the pH range of 10 to 13 in an amount sufficient for stirring. A liquid may be prepared, and a cobalt (divalent) salt aqueous solution may be added to the alkaline solution to produce a hydroxy-cobalt precursor. Even in such a case, it is important to maintain the pH of the hydroxide-cobalt precursor slurry at 10-13 while adding more alkaline solution.

[0026] The slurry containing the cobalt hydroxide precursor thus obtained is filtered and washed to evaporate the contained water.

[0027] Filtration and washing are performed to remove by-products, unreacted substances, and excess alkali components. When by-products, unreacted substances, and excess alkali remain, the blackness and electrical resistance of the granular cobalt oxide black pigment to be finally produced may be affected.

[0028] The moisture content of the dried product obtained by evaporating moisture is preferably 1% by mass or less. The moisture content is controlled by appropriately adjusting the drying temperature and drying time. By making the amount of water contained 1% by mass or less, if it is more, the amount of water vapor generated in the firing step described later can be reduced, and a reduction in firing efficiency can be prevented. More preferably, the water content is adjusted to 0.1% by mass to 0.6% by mass.

[0029] A crushing operation is performed on a dried body having a water content of 1% by mass or less. If the crushing operation is not performed, the dried body is aggregated and supplied to a firing step to be described later, resulting in problems such as further aggregation being promoted by the firing. As the crushing device, a high-speed rotating hammer mill, impact mill, disk mill or the like is preferable.

[0030] The dried body thus obtained is calcined in a sealed atmosphere at 500 ° C to 850 ° C for 0.5 to 3 hours. Here, what is important is that firing may be performed in the atmosphere, but there is no need to introduce air in an enclosed container. The reason for this is to suppress peroxidation caused by introducing excessive air. The air volume in the firing device may be adjusted to about 0.01 to 0.5 m ³ / kg with respect to the dry mass. This air capacity is determined by the internal volume of the baking apparatus.

On the other hand, the firing time and the firing temperature are important for promoting the dehydration of cobalt hydroxide and improving the crystallinity of the divalent oxide while suppressing the sintering of the produced granular cobalt oxide black pigment. is there. When the firing temperature is less than 500 ° C, sufficient blackness and high electrical resistance that the shape change is not sufficient cannot be obtained. Conversely, if the temperature exceeds 850 ° C, the sintering of the particles proceeds and the post-process However, there is a risk that aggregation and solidification cannot be released. A more preferable temperature range of this firing temperature is 600. C-800. C.

[0032] When the firing time is less than 0.5 hours, even if a high temperature range is selected within the above temperature range, the shape change is sufficiently strong or uneven, resulting in sufficient blackness. High electrical resistance may not be obtained. If it exceeds 3 hours, sintering proceeds even if a low temperature range is selected within the above temperature range, and not only coagulation / solidification cannot be canceled in the subsequent process, but also the oxidation of cobalt occurs in the firing process. The divalent cobalt content may be low.

[0033] The fired product obtained in this way exhibits a slight aggregation and solidification state, and thus the intended granular black pigment can be obtained by carrying out a conventional crushing treatment.

[0034] In addition, the granular acid-cobalt black pigment obtained as described above can be further increased in electrical resistance by being processed by a wheel-type kneader having an action of compression 'shear'. It is. A preferable treatment condition is a treatment for 10 to 90 minutes at a linear pressure of 30 kgfZcm to 160 kgfZcm. This increases the electrical resistance of the granular cobalt oxide black pigment by about one power. Further preferable conditions are 30 kgfZcm to 120 kgfZcm.

Next, the second manufacturing method will be described.

In the method for producing the granular cobalt oxide black pigment of the present invention, a cobalt (divalent) salt aqueous solution and an alkali solution are mixed and neutralized at a pH of 10 to 13, and after mixing neutralization starts or after mixing neutralization ends, While maintaining the temperature of the mixture at 10 ° C to 40 ° C, oxygen-containing gas is continuously published in the mixture to produce a cobalt hydroxide precursor, and the produced precursor is filtered and washed. After drying, crushing, firing the precursor at 500 ° C. to 850 ° C. in an inert gas-enriched air atmosphere maintained at an oxygen concentration of 15% by volume or more and less than 22% by volume. It is a feature.

[0036] Regarding the second manufacturing method, since only the conditions for firing in the first manufacturing method are different, only the differences will be described below.

[0037] For the second production method, the slurry containing the cobalt hydroxide precursor obtained by the wet reaction is filtered, washed, the contained water is evaporated, and further pulverized. When calcining the dried product to which oxygen is added, the precursor is calcined at 500 ° C to 850 ° C in an inert gas-enriched air atmosphere maintained at an oxygen concentration of 15% by volume or more and less than 22% by volume. Important to do It is.

[0038] In the second production method, by maintaining the oxygen concentration in the firing atmosphere at 15% by volume or more and less than 22% by volume, the granular oxidized cobalt black pigment to be produced is not limited by the firing time. The degree of acid can be adjusted. When the oxygen concentration in the firing atmosphere exceeds 22% by volume, it is in an air- or oxygen-rich state, so it is necessary to take great care in adjusting the firing time. volume. If the ratio is less than _0, the firing time for producing the target granular acid / cobalt black pigment has to be long, and the sintering proceeds and aggregation / solidification may not be released later.

[0039] In the second production method, as in the first production method, the firing temperature is 500 ° C to 850 ° C. The reason for setting the range is the same as in the first manufacturing method. A preferred temperature range is 600 ° C to 800 ° C. Compared to the first manufacturing method, the firing time tends to be lower in the oxygen concentration in the firing atmosphere, so a slightly longer firing time can be taken. Although it is not necessary to determine exactly, it is preferable to fire in about 1 to 4 hours in order to prevent aggregation and solidification by sintering.

[0040] Next, the granular acid-cobalt black pigment obtained by the production method of the present invention will be described.

[0041] The granular cobalt oxide black pigment of the present invention preferably has a proportion of divalent cobalt in the total cobalt content of 35% to 70%.

[0042] The ratio of divalent cobalt in the total cobalt content is the value obtained by dividing the divalent cobalt content contained in the entire particle by the total cobalt content contained in the entire particle, multiplied by 100. This value is Common forms of acid cobalt include tetraacid tetracobalt (Co O), acid

3 Cobalt (CoO and Co 2 O) is available. Co O is occupied by divalent cobalt in the total cobalt

2 3 3 4

The ratio is 33%. CoO is all divalent cobalt and Co O

All of the 2 3 cores are trivalent cobalt.

[0043] The granular cobalt oxide black pigment of the present invention differs from that of cobalt oxide in the proportion of divalent cobalt in the total cobalt, and the black effect that is the effect of the present invention depends on the element composition. Compatibility and high electrical resistance were achieved.

[0044] Blackness is insufficient when the proportion of divalent cobalt in the total cobalt is less than 35% It becomes. If it exceeds 70%, the pigment exhibits a blue-green color instead of a black pigment, and the effect of the present invention cannot be exhibited. The proportion of divalent cobalt in the total conoleto is more preferably 40 to 60%.

[0045] The granular cobalt oxide black pigment of the present invention preferably has a granular particle shape. Plate-like particles are not only inferior in dispersibility and fluidity, but in the case of plate-like particles, the particle size in the thickness direction is about several tens of nm, and the light absorption wavelength is biased. As a result, the hue as a black pigment is deteriorated, which is insufficient for forming a black electrode such as a plasma display or a plasma addressed liquid crystal in which blackness is regarded as important, and a light shielding layer. The term “granular” as used herein means a spherical shape or a spindle shape, and excludes plate-like particles.

[0046] The granular cobalt oxide black pigment of the present invention has a total cobalt content of 60% by mass to 80% by mass with respect to the entire particle, and a divalent cobalt content with respect to the entire particle of 24% by mass to 50%. It is preferable that it is mass%. More preferably, the total cobalt content with respect to the whole particle is 65% by mass to 75% by mass, and the divalent cobalt content with respect to the whole particle is 26% by mass to 45% by mass. By making the total cobalt content with respect to the whole particle 60 mass% or more, it is prevented that the amount of components other than cobalt is excessive, and the effect of the present invention is enhanced. By setting it to 80% by mass or less, it becomes easy to obtain a balance between cobalt and oxygen charge, and it becomes a stable substance. Further, when the divalent cobalt content with respect to the entire particle is 24% by mass or more, the blackness is sufficient, and when it is 50% by mass or less, the blackness is similarly sufficient.

[0047] 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 m or more, the tint is prevented from being reddish, and the dispersibility is improved. In addition, when the thickness is 0.6 m or less, the color becomes sufficient and the coloring power is also sufficient. It is more preferable that the primary particle diameter is 0.05 / ζ πι to 0.3 μΐη because the hue and coloring power are easily balanced.

[0048] Further, the granular cobalt oxide black pigment of the present invention preferably has an L value of 38 or less and a b value of 0 or less at the time of evaluation of colorability. More preferably, the L value is 36 or less, and the b value is 0.5 or less. The evaluation method of colorability is as follows. Add 0.5g of black pigment and titanium oxide (R800 manufactured by Ishihara Sangyo Co., Ltd.) l. Add 3cc of castor oil to 5g and knead with Hoover-type Mahler. this Sample kneaded 2. Add 5 g of Og cocoon lacquer, knead further, apply this onto mirror coated paper using a 4 mil applicator, dry, and color difference meter (manufactured by Tokyo Denshoku Co., Ltd.) Measure blackness (L value) and hue (a value, b value) with Color Analyzer TC-1800. When the L value is higher than 38, it cannot be said that sufficient coloring properties are obtained, and when the b value is higher than 0, the hue is yellowish, which is preferable.

[0049] 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 Q cm or more, and still more preferably IX 10 ⁶ Ωcm. When the electrical resistance is lower than 1 X 10 ⁵ Q cm, it is difficult to sufficiently enhance the function as a material for forming a black matrix array type high light-shielding film such as a plasma display or plasma addressed liquid crystal. Absent.

Example

Hereinafter, the present invention will be specifically described with reference to examples and the like. However, the scope of the present invention is not limited to the powerful embodiments.

Example 1

80 liters of PH12 sodium hydroxide aqueous solution was put into a 200 liter reaction vessel. 1. Next, 60 liters of cobalt sulfate (divalent) aqueous solution containing 2 mol Z liters of cobalt (divalent) was continuously charged into the reaction vessel at a rate of 1 liter Z minutes. At the same time, an aqueous sodium hydroxide solution was used to appropriately adjust the pH of the reaction slurry to 12. During that time, the slurry temperature was maintained at 35 ° C, and air publishing was always performed at a speed of 5 N liters Z minutes. After mixing was completed, air publishing was performed for 90 minutes at a rate of 15 N liters Z while continuing stirring.

[0051] The obtained cobalt hydroxide precursor slurry was filtered and washed, and the obtained cake was dried at 80 ° C. The dried product thus obtained had a water content of 0.5% by mass. The water content was measured according to the JIS K 5101-1991 heating loss measurement method. Further, this dried product was crushed with a hammer mill.

[0052] The crushed dry product thus obtained was calcined at 700 ° C for 2 hours in a sealed atmosphere to obtain a particle powder. [0053] The obtained particle powder was evaluated by the following method. Table 1 shows the evaluation results.

[0054] [Evaluation method]

(a) Total cobalt content relative to the whole particle

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

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

Sample and ammonium iron sulfate (divalent) are dissolved completely in acid at the same time, and the concentration of divalent iron ions in the solution is adjusted to the standard solution of potassium dichromate using sodium diphenylamine sulfonate as an indicator. Determined by titration used.

Next, the trivalent iron ion concentration was determined by calculating the difference between the divalent iron ion concentration added by force and the divalent iron ion concentration obtained by titration.

Since trivalent iron ions are generated by the following chemical reaction, this concentration was included in the sample to obtain the trivalent cobalt ion concentration.

Co ³⁺ + Fe ²⁺ → Co ²⁺ + Fe ³⁺

(c) Particle shape, primary particle size

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

(d) Electric resistance

The samples were placed 10g in the holder, after forming the pressure 600KgfZcm ² in tablet mosquitoes卩Ete 25Paiiotapaiiota phi, was measured in a pressurized state of attaching the electrode 150kgfZcm ^2. The electrical resistance value was calculated from the thickness, cross-sectional area and resistance value of the sample used for the measurement.

(e) Blackness, hue

Measurement of blackness of powder The measurement was carried out in accordance with ίO IS K5101-1991. Sample 2. Castor oil in Og 1. Add 4cc and knead with Hoover-type Mahler. This kneaded sample 2. Add 7.5 g of lacquer to Og, knead it further, apply this onto mirror-coated paper using a 4 mil applicator, and after drying, a color difference meter (manufactured by Tokyo Denshoku Co., Ltd. The blackness (L value) and hue (a value, b value) were measured with an analyzer TC-1800.

(f) Colorability (Evaluation of dispersibility and hue during coating)

Sample 0.5g and titanium oxide (Ishihara Sangyo R800) l. Add 5cc castor oil 1. This kneaded sample is kneaded with a one-bar type Mahler. 2. Add 4.5g of lacquer to Og, knead it further, apply it on a mirror-coated paper using a 4mil applicator, dry, and color difference The blackness (L value) and hue (a value, b value) were measured with a meter (Color Analyzer TC-1800, manufactured by Tokyo Denshoku Co., Ltd.).

(g) Specific surface area

It was measured with Shimadzu 1 Micromeritics 2200 type BET meter.

() Oil absorption

This was performed in accordance with JIS K 5101—1991.

[Example 2]

A granular powder was obtained in the same manner as in Example 1 except that the oxygen concentration was 10% by volume and neutralized 10 liters Z minutes during neutralization, and after mixing was blown into the reaction slurry at 30 liters Z minutes. . The obtained particle powder was evaluated in the same manner as in Example 1.

[Example 3]

A particle powder was obtained in the same manner as in Example 1 except that firing was performed in an atmosphere maintained at an oxygen concentration of 18% by volume. The obtained particle powder was evaluated in the same manner as in Example 1.

[Comparative Example 1]

A particle powder was obtained in the same manner as in Example 1 except that the reaction slurry temperature was 50 ° C. The obtained particle powder was evaluated in the same manner as in Example 1.

[Comparative Example 2]

A particle powder was obtained in the same manner as in Example 1 except that the pH of the reaction slurry was 9. The obtained particle powder was evaluated in the same manner as in Example 1.

[Comparative Example 3]

A particle powder was obtained in the same manner as in Example 1 except that outside air was introduced into the baking apparatus and the gas concentration was about the same as that of the outside air. The obtained particle powder was evaluated in the same manner as in Example 1.

[Comparative Example 4]

Particle powder was obtained in the same manner as in Example 1 except that nitrogen was introduced into the firing apparatus and the firing atmosphere was maintained at 10% by volume of oxygen. The obtained particle powder was obtained in the same manner as in Example 1.

C98SS0 / .00Zdf / X3d £ 1 1 ^ 6 dynamic 0 OAV

[0062] As is apparent from Table 1, the particle powders of the examples have excellent blackness, high electrical resistance, small particle size, sharp particle size distribution, black matrix coloring composition, and plasma display. It is excellent as a material for forming black electrodes such as plasma addressed liquid crystal and light shielding layers.

[0063] In contrast, the particle powders of Comparative Examples 1 and 2 contain divalent cobalt in the total cobalt or the entire particle because the reaction conditions deviate from the manufacturing conditions of the production method of the present invention. This is a problem in terms of various properties, such as a decrease in the amount, inferior blackness and hue.

[0064] Further, the particle powder of Comparative Example 3 was treated by introducing outside air during firing, so that the proportion of divalent cornole in the total cobalt decreased, and this was caused by The hue was inferior.

[0065] In addition, the particle powder of Comparative Example 4 was treated in a low oxygen concentration atmosphere at the time of firing, but due to the remaining of the acid oxycobalt particles that were insufficiently fired and sufficiently converted to acid-hycobalt, the primary particle diameter force and ratio were reduced. The surface area was also large. As a result, various characteristics such as blackness, hue, and coloring power were remarkably inferior.

Industrial applicability

[0066] As described above in detail, the granular cobalt oxide black pigment produced by the production method of the present invention has excellent blackness and high electrical resistance in which the proportion of divalent cobalt in the total cobalt is high. And has a small particle size and a sharp particle size distribution, it is suitable for applications such as black electrodes for plasma displays and plasma addressed liquid crystals, and black pigment powder for forming a light shielding layer.

Claims

The scope of the claims

[1] Cobalt (divalent) salt aqueous solution and alkali solution are mixed and neutralized at pH 10 to 13, and the temperature of the mixed solution is 10 ° C to 40 ° after the start of mixing neutralization or after the completion of mixing neutralization. While maintaining C, oxygen-containing gas is continuously published in the mixed solution to produce a cobalt hydroxide precursor, and the produced precursor is filtered, washed, dried, crushed and then sealed. A method for producing a granular acid cobalt black pigment, characterized in that the precursor is calcined in the atmosphere at 500 ° C. to 850 ° C. for 0.5 to 3 hours.

[2] The granular cobalt oxide black pigment according to claim 1, characterized in that 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. Manufacturing method.

[3] The method for producing a granular cobalt oxide black pigment according to claim 1 or 2, wherein the alkaline solution is an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution.

[4] Conoretate (divalent) salt solution and alkali solution are mixed and neutralized at a pH of 10 to 13, and the temperature of the mixture is changed from 10 ° C to 40 While maintaining at ° C, an oxygen-containing gas is continuously published in the mixed solution to produce a cobalt hydroxide precursor. The produced precursor is filtered, washed, dried and crushed, and then oxygenated. Production of granular cobalt oxide black pigment characterized by calcining the precursor at 500 ° C. to 850 ° C. in an inert gas-enriched air atmosphere maintained at a concentration of 15% by volume or more and less than 22% by volume Method

[5] The granular cobalt oxide black pigment according to claim 4, wherein the oxygen-containing gas is an air enriched with an inert gas having an oxygen concentration of 5% by volume or more and less than 22% by volume. Production method.

[6] The method for producing a granular cobalt oxide black pigment according to claim 4 or 5, wherein the alkaline solution is an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution.

[7] An acid oxide containing at least conolate obtained by the method for producing a granular cobalt oxide black pigment according to any one of claims 1 to 6 and claim 6, A granular acid-cobalt black pigment characterized in that the proportion of divalent cobalt in cobalt is 35% to 70%.

[8] The total cobalt content with respect to the whole particle is 60% by mass to 80% by mass, and the divalent coroline content with respect to the whole particle is 24% by mass to 50% by mass. The granular acid-cobalt black pigment according to claim 7,

[9] The granular cobalt oxide black pigment according to claim 7 or 8, wherein the primary particle diameter is 0.02 μm to 0.6 μm.