JP2023006418A - Carbon black fluid dispersion - Google Patents

Abstract

To provide a carbon black fluid dispersion which maintains dispersibility and furthermore has improved blackness.SOLUTION: A carbon black fluid dispersion is provided, including carbon black, a dispersant, and a solvent, wherein the carbon black includes a first carbon black having a surface pH of 7.0 or less and a second carbon black having a surface pH of more than 7.0, a difference between the second carbon black surface pH and the surface pH of the first carbon black is 2.0 or more, and a content of the second carbon black relative to a total amount of the first carbon black and the second carbon black (100 mass%) is less than 50 mass%.SELECTED DRAWING: None

Description

The present invention relates to carbon black dispersions.

Carbon black is fine particles composed almost exclusively of carbon, and is applied in various fields.

For example, in Patent Document 1, there is a sufficient internal antireflection effect even for optical elements with a high refractive index, and even when the paint is stored for a long time, the internal antireflection black color for optical elements can ensure the workability of the coating film. As a paint, an internal antireflection black paint for optical elements containing at least a metal oxide, carbon black, a binder resin, a dispersant and a solvent is disclosed.

Further, in Patent Document 2, as a light-shielding resin composition capable of forming a black matrix excellent in developability, resolution, adhesion, particularly linearity and adhesion, (A) a binder resin, (B) a monomer, ( C) a photopolymerization initiator, and (D) carbon black having an average particle size of 8 nm or more and 65 nm or less and a DBP oil absorption of 90 ml/100 g or less, and the content of potassium ions is based on the total solid content A light-shielding resin composition characterized by having a content of 20 ppm or less is disclosed.

Further, in Patent Document 3, a carbon black-containing resin composition having a high coating film OD value, excellent developing properties, and excellent coating film surface properties has an average primary particle diameter of 20 to 30 nm and a DBP absorption of 140 ml/100 g. A carbon black dispersion containing carbon black having a pH of 2.5 to 4 and an organic compound having an amine value of 1 to 100 mgKOH/g and a weight average molecular weight of 5000 to 12,000 is disclosed below.

Furthermore, in Patent Document 4, as a carbon black dispersion for a black matrix forming resist, which has a high light shielding rate and a low surface reflectance and can provide a thin film black matrix, the surface is coated with a resin and the volume Black matrix formation characterized by containing high resistance carbon black (a) having a specific resistance value of 100 Ω·cm or more, a dispersant (b) having an electron donating group, and a dispersion medium (c) A carbon black dispersion for resists is disclosed.

JP 2014-021231 A Japanese Patent Application Laid-Open No. 2007-316620 JP-A-2004-292672 Japanese Patent Application Laid-Open No. 2001-106938

As described above, carbon black is used as a black paint and a black matrix for color filters.

However, there is still room for improvement in the blackness of coating films obtained from carbon black dispersions, particularly in the blackness indexed by the L ^* value, which is the lightness index.

An object of the present invention is to improve the above circumstances, and an object thereof is to provide a carbon black dispersion having improved blackness while maintaining dispersibility.

The present invention for achieving the above object is as follows.

<Aspect 1>
including carbon black, a dispersant, and a solvent;
The carbon black comprises a first carbon black having a surface pH of 7.0 or less and a second carbon black having a surface pH of greater than 7.0,
The difference between the surface pH of the second carbon black and the surface pH of the first carbon black is 2.0 or more, and the total amount of the first carbon black and the second carbon black (100 mass %), the content of the second carbon black is less than 50% by mass,
Carbon black dispersion.
<Aspect 2>
The surface pH of the first carbon black is 4.0 or less, and the surface pH of the second carbon black is 8.0 or more.
A carbon black dispersion according to aspect 1.
<Aspect 3>
Aspect 1 wherein the content of the second carbon black is 0.1% by mass to 20% by mass with respect to the total amount (100% by mass) of the first carbon black and the second carbon black. Or the carbon black dispersion according to 2.
<Aspect 4>
4. The carbon black dispersion of any one of aspects 1-3, wherein the first carbon black comprises furnace black.
<Aspect 5>
The carbon black dispersion according to any one of aspects 1 to 4, wherein the second carbon black comprises acetylene black and/or ketjen black.
<Aspect 6>
The carbon black dispersion according to any one of aspects 1 to 5, wherein the dispersant is a polymeric dispersant having basic functional groups.
<Aspect 7>
The carbon black dispersion according to any one of aspects 1 to 6, wherein the carbon black content is 0.1 to 50% by mass.

According to the present invention, it is possible to provide a carbon black dispersion having improved blackness while maintaining dispersibility.

Embodiments of the present invention will be described in detail below. It should be noted that the present invention is not limited to the following embodiments, and can be carried out with various modifications within the scope of the gist of the invention.

《Carbon black dispersion》
The carbon black dispersion of the present invention is
including carbon black, a dispersant, and a solvent;
the carbon black comprises a first carbon black having a surface pH of 7.0 or less and a second carbon black having a surface pH of greater than 7.0;
The difference between the surface pH of the second carbon black and the surface pH of the first carbon black is 2.0 or more, and relative to the total amount (100% by mass) of the first carbon black and the second carbon black and the content of the second carbon black is less than 50% by mass,
It is a carbon black dispersion.

Conventional carbon black dispersions generally use carbon black with a low surface pH value. For example, in Patent Document 2, if the surface pH value of carbon black is high, the dispersant will not adhere easily, resulting in insufficient dispersibility. Therefore, carbon black with a surface pH value of 5.0 or less should be used. is preferred.

On the other hand, according to the intensive research of the present inventor, the dispersibility of the carbon black dispersion can be maintained by using two types of carbon black having different surface pHs and having a certain pH difference at specific contents. It was found that the degree of blackness can be improved while the blackness is improved. Although not limited to theory, this is because such a combination of carbon blacks improves blackness due to complementary absorption of light by multiple types of carbon blacks with different surface properties, and reduces the surface pH value. This is probably because the effect of improving dispersibility by carbon black can be obtained at the same time.

In the present invention, the degree of blackness is the degree of blackness indexed by the L ^* value, which is a lightness index, and here, the smaller the L ^* value, the higher the degree of blackness. In the present invention, the “blackness” and “L ^* value” of the carbon black dispersion are the average values of the blackness and L ^* value of the coating film obtained from the carbon black dispersion, especially the coating with a thickness of 1 μm. means the average of the blackness and L ^* value of the film.

Therefore, in the carbon black dispersion of the present invention, for example, the value of the formula "(L _x /L _ref ) × 100%" is 99% or less, 95% or less, 90% or less, 85% or less, 80% or less, It can be 75% or less, 70% or less, or 65% or less. This value may be 30% or more, 40% or more, or 50% or more.

“L _x ” and “L _ref ” in the above formula are respectively as follows:
L _x : L ^* value of the carbon black dispersion of the present invention,
L _ref : Containing carbon black with a surface pH value of 7.0 or less instead of carbon black with a surface pH value of more than 7.0, that is, containing only carbon black with a surface pH value of 7.0 or less as carbon black L* values for carbon black dispersions identical to the carbon black dispersions of the present invention, except for the L ^* values.

Therefore, a small value of the formula "(L _x /L _ref ) × 100%" means that the combination of specific carbon blacks improves the blackness of the carbon black dispersion of the present invention. are doing.

In addition, the L ^* value can be measured, for example, using a color meter SC-P manufactured by Suga Test Instruments Co., Ltd., and the specific measurement method can refer to the method shown in the examples described later. .

<Carbon black>
The carbon black dispersion of the present invention contains carbon black. Carbon black is defined as an aggregate of fine spherical particles obtained by incomplete combustion of various hydrocarbons or compounds containing carbon, and is a general term for almost pure carbon materials with a chemical composition of 98% or more carbon. is.

The carbon black of the present invention includes a first carbon black having a surface pH of 7.0 or less and a second carbon black having a surface pH of greater than 7.0.

The surface pH of carbon black can be adjusted, for example, by treating the surface of carbon black with an oxidizing agent or the like to impart surface acidic groups. Examples of surface acidic groups include, but are not limited to, carboxyl groups, hydroxyl groups, quinone groups, and lactone groups.

For the surface pH of carbon black, for example, 1.2 g of carbon black is added to distilled water (pH 7.0), placed in a glass bottle with a lid, model USK-4R (manufactured by AS ONE Corporation), high frequency After ultrasonic treatment for 1 minute with an ultrasonic cleaner with an output of 160 W, the pH of the muddy carbon black can then be determined by measuring it with a glass electrode pH meter.

In the present invention, the first carbon black has a surface pH of 7.0 or less, more specifically 7.0 or less, 6.5 or less, 6.0 or less, 5.5 or less, 0 or less, 4.5 or less, 4.0 or less, 3.5 or less, 3.0 or less, or 2.5 or less, and 1.0 or more, 1.5 or more, or 2.0 or more It's okay.

In addition, the second carbon black has a surface pH of more than 7.0, more specifically more than 7.0, 7.5 or more, 8.0 or more, 8.5 or more, 9.0 or more , or 9.5 or more, and may be 14.0 or less, 12.0 or less, or 10.0 or less.

In the present invention, the difference between the surface pH of the second carbon black (“pH ₂ ”) and the surface pH of the first carbon black (“pH ₁ ”) (“ΔpH”, ΔpH=pH ₂ −pH ₁ ) is greater than or equal to 2.0. More specifically, this difference ("ΔpH") is 2.0 or greater, 2.5 or greater, 3.0 or greater, 3.5 or greater, 4.0 or greater, 4.5 or greater, 5.0 or greater, 5.5 or more, 6.0 or more, 6.5 or more, 7.0 or more, or 7.5 or more, and 13.0 or less, 10.0 or less, 9.0 or less, or 8.0 may be:

In addition, the surface pH of carbon black partially depends on the production method in addition to the oxidation treatment described above.

Specific examples of the first and second carbon blacks are not particularly limited as long as they satisfy the ranges of pH value and pH value difference described above. For example, furnace black can be used as the first carbon black, and acetylene black and/or ketjen black can be used as the second carbon black. Using acetylene black as the second carbon black is preferable from the viewpoint of improving the optical density value (also referred to as “OD value”).

Here, the "OD value" is an indicator of the shielding property of the coating film obtained from the carbon black dispersion, and the larger the value, the higher the shielding property of the coating film. Further, for the method of measuring the "OD value", the method shown in Examples described later can be referred to.

In the present invention, the content of the second carbon black is less than 50% by mass with respect to the total amount (100% by mass) of the first carbon black and the second carbon black. More specifically, the content of the second carbon black is less than 50% by mass, 45% by mass or less, 40% by mass with respect to the total amount (100% by mass) of the first and second carbon blacks 35 mass % or less, 30 mass % or less, 25 mass % or less, or 20 mass % or less, and 0.1 mass % or more, 0.5 mass % or more, 1.0 mass % or more, 1 .5% by mass or more, 2.0% by mass or more, 2.5% by mass or more, 3.0% by mass or more, 3.5% by mass or more, 4.0% by mass or more, 4.5% by mass or more, or 5 0% by mass or more. If the content of the second carbon black is less than 50% by mass with respect to the total amount (100% by mass) of the first and second carbon blacks, it is preferable from the viewpoint of improving the dispersibility. Moreover, it is preferable from the viewpoint of improving the degree of blackness if the content of the second carbon black is 0.1% by mass or more with respect to the total amount (100% by mass) of the first and second carbon blacks.

In the carbon black dispersion of the present invention, the content of carbon black is, for example, 0.1% by mass or more, 0.5% by mass or more, 1.0% by mass or more, 2.0% by mass or more, 3.0% by mass % or more, 4.0 mass % or more, 5.0 mass % or more, 6.0 mass % or more, 7.0 mass % or more, 8.0 mass % or more, 9.0 mass % or more, or 10 mass % or more and may be 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, or 15% by mass or less.

<Dispersant>
The carbon black dispersion of the present invention contains a dispersant. The dispersant is useful for finely dispersing carbon black and stabilizing the dispersed state.

In the present invention, the dispersant includes surfactants such as nonionic, cationic, and anionic surfactants, polymeric dispersants, and the like. A polymeric dispersant having a basic functional group such as an amino group, a pyridine, a pyrimidine, a nitrogen-containing heterocycle such as pyrazine (in the present invention, a polymeric dispersant having such a basic functional group is referred to as a "basic polymer (referred to as "dispersants") are advantageously used.

Examples of the basic polymer dispersant include, but are not limited to, urethane-based dispersants, polyethyleneimine-based dispersants, polyallylamine-based dispersants, acrylic-based dispersants, and the like. Among these dispersants, urethane-based dispersants are preferred.

A urethane-based dispersant can generally be prepared by reacting a polyisocyanate compound and a polyol to generate a main chain having a urethane bond. Polyurethanes with various structures can be obtained by selecting polyisocyanate compounds, polyols, and reaction conditions. Also, a urethane-based dispersant into which a desired functional group has been introduced can be obtained by reacting it with a compound having a specific functional group. Dispersants having such urethane bonds in the main chain are, for example, JP-A-4-210220, JP-A-2000-506436, JP-A-2007-502903, JP-A-2008-542523, and JP-A-2008-542523. 2010-235945, JP 2010-509165, etc. can also be obtained by the method described.

Moreover, a commercial item can be used as a urethane-type dispersant. Specifically, for example, Lubrizol Solsperse series (76500), BYK Disperbyk series (161, 162, 163, 164, 165, 166, 167, 170, 174, 182, 183, 184, 185, 2150 , 2155, 2163, 2164), BASF Efka series (4015, 4046, 4047, 4050, 4055, 4061, 4080), etc., but not limited thereto.

Moreover, these dispersants may be used individually by 1 type, and may be used in mixture of 2 or more types.

In the carbon black dispersion of the present invention, the content of the dispersant is not particularly limited, and may be adjusted as appropriate according to the type and amount of carbon black to be used, for example. As an example, the content of the dispersant in the carbon black dispersion of the present invention may be 0.001% by mass or more, 0.1% by mass or more, or 0.5% by mass or more, and 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, 10% by mass or less, 5.0% by mass or less; It may be 0% by mass or less.

<solvent>
The carbon black dispersion of the present invention contains a solvent. The solvent is useful for dissolving or dispersing carbon black, dispersant, other optional ingredients, etc., or for adjusting viscosity.

In the present invention, the solvent is not particularly limited and can be appropriately selected according to the purpose or application of the dispersion. Therefore, examples of solvents include, but are not limited to, the following.

Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol-t-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, methoxymethyl Glycol monoalkyl ethers such as pentanol, propylene glycol monoethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monomethyl ether, 3-methyl-3-methoxybutanol, tripropylene glycol methyl ether;

glycol dialkyl ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether;

Ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, methoxybutyl acetate, 3-methoxybutyl acetate, methoxypentyl acetate, dipropylene glycol Glycol alkyl ether acetates such as monomethyl ether acetate, 3-methyl-3-methoxybutyl acetate;

Ethers such as diethyl ether, dipropyl ether, diisopropyl ether, butyl ether, diamyl ether, ethyl isobutyl ether, dihexyl ether;

Acetone, methyl ethyl ketone, methyl amyl ketone, methyl isopropyl ketone, methyl isoamyl ketone, diisobutyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl amyl ketone, methyl butyl ketone, methylhexyl ketone, methyl nonyl ketone, N-methyl-2-pyrrolidone ketones;

Monohydric or polyhydric alcohols such as ethanol, propanol, butanol, hexanol, cyclohexanol, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, glycerin;

Aliphatic hydrocarbons such as n-pentane, n-octane, diisobutylene, n-hexane, hexene, isoprene, dipentene, dodecane;

Alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, methylcyclohexene, bicyclohexyl;

aromatic hydrocarbons such as benzene, toluene, xylene, cumene;

Amyl formate, ethyl formate, ethyl acetate, butyl acetate, propyl acetate, amyl acetate, ethylene glycol acetate, ethyl propionate, propyl propionate, butyl butyrate, isobutyl butyrate, methyl isobutyrate, ethyl caprylate, butyl stearate rate, ethyl benzoate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, 3-methoxy Chain or cyclic esters such as propyl propionate, butyl 3-methoxypropionate, γ-butyrolactone;

Alkoxycarboxylic acids such as 3-methoxypropionic acid and 3-ethoxypropionic acid;

Halogenated hydrocarbons such as butyl chloride, amyl chloride;

ether ketones such as methoxymethylpentanone;

Nitriles such as acetonitrile, benzonitrile;

One of these solvents may be used alone, or two or more thereof may be used in combination.

In the carbon black dispersion of the present invention, the content of the solvent is not particularly limited, for example, it may be 99% by mass or less, or 90% by mass or less, and 20% by mass or more, 30% by mass or more, 40% by mass Above, it may be 50% by mass or more, 60% by mass or more, 70% by mass or more, or 80% by mass or more.

<Other ingredients>
In addition to the above, the carbon black dispersion of the present invention may optionally contain other components, for example, other carbon materials such as carbon nanotubes, or dispersion aids described later, etc., but limited to these not.

(dispersion aid)
Examples of dispersing aids include pigment derivatives. Pigment derivatives include azo, phthalocyanine, quinacridone, benzimidazolone, quinophthalone, isoindolinone, dioxazine, anthraquinone, indanthrene, perylene, perinone, diketopyrrolopyrrole, Examples include derivatives such as dioxazine pigments. Substituents of pigment derivatives include sulfonic acid groups, sulfonamide groups and their quaternary salts, phthalimidomethyl groups, dialkylaminoalkyl groups, hydroxyl groups, carboxyl groups, amide groups, and the like, which may be directly attached to the pigment skeleton or may be attached to the skeleton of the pigment. Those bonded via a ring group or the like can be mentioned, preferably a sulfonamide group, a quaternary salt thereof, and a sulfonic acid group, more preferably a sulfonic acid group. A single pigment skeleton may be substituted with a plurality of these substituents, or a mixture of compounds having different numbers of substitutions may be used. Specific examples of pigment derivatives include sulfonic acid derivatives of azo pigments, sulfonic acid derivatives of phthalocyanine pigments, sulfonic acid derivatives of quinophthalone pigments, sulfonic acid derivatives of anthraquinone pigments, sulfonic acid derivatives of quinacridone pigments, and sulfonic acid derivatives of diketopyrrolopyrrole pigments. Examples thereof include derivatives, sulfonic acid derivatives of dioxazine pigments, and the like.

Moreover, a commercial item can be used as a dispersing aid. Specifically, for example, Solsperse series (5000s) manufactured by Lubrizol Co., Ltd., etc. may be mentioned, but not limited thereto.

<<Method for producing carbon black dispersion>>
Predetermined amounts of carbon black, dispersant, solvent, and other optional components are weighed, and the carbon black is dispersed in a dispersion treatment step to produce a liquid black carbon black dispersion.

Here, in the dispersion treatment step, a paint conditioner (paint shaker), sand grinder, ball mill, roll mill, stone mill, jet mill, homogenizer, etc. can be used.

Further, glass beads or zirconia beads having a diameter of 0.1 to 8 mm, for example, can be used for dispersion. After dispersion, these beads can be separated from the dispersion using a filter or the like.

The temperature during the dispersing treatment may be usually set in the range of 0.degree. C. to 100.degree. C., preferably in the range of room temperature to 80.degree. In addition, the appropriate dispersion time varies depending on the composition of the carbon black dispersion and the size of the apparatus for dispersing, so it can be adjusted as appropriate. For example, the dispersion time may be 30 minutes or more, 1 hour or more, or 2 hours or more from the viewpoint of improving the dispersibility, and from the viewpoint of maintaining the stability of the dispersion, it may be 24 hours. within 12 hours, or within 5 hours.

《Application》
As described above, the carbon black dispersion of the present invention can improve the degree of blackness while maintaining dispersibility as compared with conventional dispersions. Therefore, the carbon black dispersion of the present invention can be applied to various fields such as, for example, not only coloring materials for inks and paints, but also light-shielding materials around cameras, sensors, and the like.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these.

<<Comparative example 1>>
<Preparation of carbon black dispersion>
Each composition (mass%) of the "carbon black dispersion" of Comparative Example 1 shown in Table 1 was dispersed together with zirconia beads having a diameter of 0.3 mm for 1 hour with a paint shaker, and the beads and the dispersion were filtered. was separated to obtain a carbon black dispersion of Comparative Example 1. In each table below, the numerical value for each composition of the "carbon black dispersion" represents the compounding amount (% by mass) unless otherwise specified.

<Viscosity measurement>
The viscosity (liquid temperature: 25° C.) of the obtained carbon black dispersion of Comparative Example 1 was measured at 100 rpm using a cone-plate rotary viscometer (manufactured by Toki Sangyo Co., Ltd., 1°34′ R24 cone). The measurement results are shown in Tables 1 and 2.

<Preparation of Coating Film Consisting of Carbon Black Dispersion>
Using the obtained carbon black dispersion liquid of Comparative Example 1, a square plate glass wafer of 10 mm×10 mm was coated by a spin coating method to form a thin film having a thickness of 1 μm. Thereafter, the thin film was sufficiently dried under conditions of 25° C. and humidity of 30 to 85% to prepare a coating film for L ^* value measurement and OD value measurement.

Also, a coating film having a thickness of 1 μm was formed. In addition, adjustment of the film thickness was performed by arbitrary rotation speeds.

In the following L ^* value measurement and OD value measurement, one coated film of Comparative Example 1 prepared was measured at 5 points each in the coated film, and the average value was calculated. 1 measurement result.

<Measurement of L ^* value and evaluation of blackness>
(Measurement of L ^* value)
It was measured using SC-P (manufactured by Suga Test Instruments Co., Ltd.) as a measuring device.
The L ^* value of Comparative Example 1 was used as a reference. Therefore, the results of Comparative Example 1 are shown in both Tables 1 and 2 for convenience of comparison.

(Evaluation of blackness)
The blackness of each example and comparative example was evaluated using the formula “(Lx/L _ref )×100%”. In the formula, the L ^* value of Comparative Example 1 was calculated as "L _ref ", and the L ^* value of each Example and Comparative Examples other than Comparative Example 1 was calculated as "L _x ".

"S" when the obtained value is 70% or less; "A" when it is more than 70% and 90% or less; "B" when it is more than 90% and less than 100%; 100% or more The blackness of each example and comparative example was evaluated with the case of "C". The respective results are shown in Tables 1 and 2.

<Measurement of OD value and evaluation of shielding>
(Measurement of OD value)
The OD value was measured using X-Rite 361T (V) (manufactured by X-Rite). The OD value of Comparative Example 1 was used as a reference. Therefore, the results of Comparative Example 1 are shown in both Tables 1 and 2 for convenience of comparison.

(Shielding evaluation)
Using the formula “(OD _x /OD _ref )×100%”, the shielding properties of each example and comparative example were evaluated. In the formula, the OD value of Comparative Example 1 was calculated as "OD _ref ", and the OD values of each Example and Comparative Examples other than Comparative Example 1 were calculated as "OD _x ".

If the obtained value is 105% or more, "A"; if it is less than 105% and 100% or less, it is "B"; if it is less than 100%, it is "C". Shielding properties were evaluated. The respective results are shown in Tables 1 and 2.

<<Examples 1 to 5 and Comparative Examples 2 to 7>>
Using each composition of the "carbon black dispersion" of Examples 1 to 5 and Comparative Examples 2 to 7 shown in Tables 1 and 2, in the same manner as in Comparative Example 1 above, each carbon black dispersion prepared and evaluated. The respective results are shown in Tables 1 and 2.

As is clear from Tables 1 and 2, each of the carbon black dispersions of Examples 1 to 5 has good dispersibility, and the blackness of the coating film is as high as that of the coating film of Comparative Example 1. I have found that it has improved.

In addition, the carbon black dispersions of Comparative Examples 2 to 7 were poorly coated compared to Examples 1 to 5, so the L ^* value and OD value could not be measured. It is presumed that this is because the carbon black dispersions of Comparative Examples 2 to 7 did not have sufficient dispersibility.

Claims (7)

including carbon black, a dispersant, and a solvent;
The carbon black comprises a first carbon black having a surface pH of 7.0 or less and a second carbon black having a surface pH of greater than 7.0,
The difference between the surface pH of the second carbon black and the surface pH of the first carbon black is 2.0 or more, and the total amount of the first carbon black and the second carbon black (100 mass %), the content of the second carbon black is less than 50% by mass,
Carbon black dispersion. The surface pH of the first carbon black is 4.0 or less, and the surface pH of the second carbon black is 8.0 or more.
The carbon black dispersion of Claim 1. The content of the second carbon black is 0.1% by mass to 20% by mass with respect to the total amount (100% by mass) of the first carbon black and the second carbon black. 3. The carbon black dispersion according to 1 or 2. The carbon black dispersion of any one of claims 1-3, wherein the first carbon black comprises furnace black. The carbon black dispersion according to any one of claims 1 to 4, wherein the second carbon black comprises acetylene black and/or ketjen black. The carbon black dispersion according to any one of claims 1 to 5, wherein the dispersant is a polymeric dispersant having basic functional groups. The carbon black dispersion according to any one of claims 1 to 6, wherein the carbon black content is 0.1 to 50% by mass.