JP5120747B2 - Surface-modified carbon black, method for producing the same, and dispersion thereof - Google Patents

Description

  The present invention exhibits high dispersibility in nonpolar solvents such as silicone oil, low polarity solvents such as hydrocarbon solvents having isostructure and propylene glycol monomethyl ether acetate (PGMEA), and blended with resin TECHNICAL FIELD The present invention relates to a surface-modified carbon black used for a composition having excellent mechanical properties and an electronic device that can be driven at a low voltage, a method for producing the same, and a dispersion thereof.

  The surface of the carbon black particles is generally lipophilic and has extremely low dispersibility in a polar solvent such as water. Therefore, research and development of carbon black having excellent water dispersibility has been actively conducted in recent years mainly for uses such as ink for inkjet printers by chemically modifying the particle surface.

  In addition, there is a strong demand for improvement and improvement of dispersibility in nonpolar solvents and low polarity solvents. For example, compositions such as inks and paints, black matrices for color filters, display devices, black pigments for electronic paper, and copying machines Development of carbon black that is suitably used for toner and the like is desired.

  When used in black pigments for electronic paper or toners for copying machines, the migration of carbon black particles and the generation of static electricity are necessary for the applied voltage, so the surface of carbon black particles can be charged positively or negatively. Necessary. In particular, for electronic paper applications, it is necessary to charge the surface of carbon black particles positively or negatively and to have excellent dispersibility in a dispersion solvent.

  Therefore, Patent Document 1 discloses a polymer part containing a silicone component and carbon black as a carbon black graft polymer having excellent dispersibility in various media used for ink, toner for copying machines, paints, resin colorants, and the like. A carbon black graft polymer that includes a portion and has a breakdown voltage of 0.5 kV / mm or more when dispersed in silicone oil has been proposed. This is intended to impart sufficient dispersibility even in a low polarity solvent by including a polymer chain of a silicone component in the polymer portion of the carbon black graft polymer.

Patent Document 2 includes a segment (A) and a segment (B) having a chain structure different from that of the segment (A), and the segment (A) includes a group (1) having reactivity with a functional group on the surface of carbon black. A carbon black graft polymer obtained by reacting a polymer having a functional group on the surface of carbon black with segments (A) and (B) having a group (2) having reactivity with the matrix of the target medium Carbon black graft polymers have been proposed.
JP-A-8-337624 JP-A-9-272706

  However, since the graft polymer uses an epoxy group as a reactive group with the polymer, a metal-based or amine-based catalyst that opens the three-membered ring of the epoxy group is used to bond the polymer. There is a problem that these ionizable catalysts remain in the dispersion to prevent the dispersibility of the carbon black.

  In addition, carbon black imparted with chargeability to the particle surface, such as positively charged carbon black, is effective as a black pigment for electronic paper and a toner for copying machines.

  Therefore, the present inventors modified the carbon black particle surface to give excellent dispersibility in a nonpolar solvent or a low polarity solvent, and electrically charged the carbon black particle surface positively or negatively. It was confirmed that it can be suitably used as a black pigment for electronic paper, a toner for copying machines, and the like by, for example, positively charging the surface of carbon black particles.

That is, the present invention has been made based on this finding, and the surface-modified carbon black according to claim 1 is a triisocyanate having one isocyanate group or three isocyanate groups at the ends of a diisocyanate compound having isocyanate groups at both ends. one terminal isocyanate groups of the isocyanate compound is bonded with the hydroxyl group and / or carboxyl group of the carbon black particle surfaces, the other two terminal isocyanate groups of the other terminal isocyanate groups or triisocyanate compound di isocyanate compound, a cationic polymers with hydroxyl groups include polymers or anionic groups with hydroxyl groups having a sexual group (hereinafter, referred to as hydroxyl-modified charging polymer) characterized by being combined with the hydroxyl groups of the.

A method for producing a surface-modified carbon black according to claim 2 (hereinafter referred to as production method (1)) is a method for producing the surface-modified carbon black according to claim 1, wherein the non-reactive solvent is used as a non-reactive solvent. Carbon black and a diisocyanate compound having an isocyanate group at both ends or a triisocyanate compound having three isocyanate groups at both ends are added and mixed, and the hydroxyl group and / or carboxyl group on the surface of the carbon black particle and one of the diisocyanate compounds are mixed. The terminal isocyanate group or one terminal isocyanate group of the triisocyanate compound is bonded, and then the hydroxyl-modified chargeable polymer is added and mixed, and the other terminal isocyanate group of the diisocyanate compound or the other two terminal isocyanate groups of the triisocyanate compound are mixed. It is characterized in that an anate group is bonded to a hydroxyl group of a hydroxyl-modified chargeable polymer.

A method for producing a surface-modified carbon black according to claim 3 (hereinafter referred to as production method (2)) is a method for producing the surface-modified carbon black according to claim 1, wherein the non-reactive solvent is used as a non-reactive solvent. Carbon black, a diisocyanate compound having isocyanate groups at both ends or a triisocyanate compound having three isocyanate groups at both ends, and a hydroxyl-modified chargeable polymer are added and mixed to form hydroxyl groups and / or carboxyl groups on the surface of the carbon black particles. And one terminal isocyanate group of the diisocyanate compound or one terminal isocyanate group of the triisocyanate compound, and at the same time, the other two terminal isocyanate groups of the diisocyanate compound or the other two terminal isocyanate groups of the triisocyanate compound And a hydroxyl group of a hydroxyl-modified chargeable polymer.

Carbon black dispersion by claim 4, wherein the surface modified carbon black of claim 1, wherein is dispersed in non-polar solvents or low-polar solvent at a concentration of 1-20 wt%.

The process according to claim 5 by a surface modified carbon black according to claim 2 or 3, human Dorokishiru group of the carbon black particle surfaces, the amount of the carboxyl group or both functional groups, is 0.14μeq / m ² or more It is characterized by that .

  According to the present invention, excellent dispersibility in a nonpolar solvent or a low polarity solvent is exhibited, and since the surface of the carbon black particles is positively or negatively charged in the dispersion, it can function effectively electrically. For example, black pigments for electronic paper and toners for copying machines, compositions such as inks and paints, black matrices for color filters, surface-modified carbon blacks suitably used as display devices, methods for producing the same, and the like Dispersions can be provided and are very useful industrially.

  The type of carbon black used in the present invention is not particularly limited, and any of furnace black, thermal black, channel black, and the like can be used. Preferably, the primary particle diameter measured by observation with an electron microscope is 0.01 to Carbon black of 0.3 μm, more preferably 0.01 to 0.07 μm is used. Carbon black with a primary particle size of less than 0.01 μm has a large cohesive force acting between the particles and tends to aggregate. Conversely, when it exceeds 0.3 μm, the weight of the surface modified state increases, This is because carbon black tends to settle.

Surface modified carbon black of the present invention, one terminal isocyanate groups of the triisocyanate compound having one terminal isocyanate groups or terminal three isocyanate groups of a diisocyanate compound having an isocyanate group at both ends, the carbon black particle surface bonded to hydroxyl and / or carboxyl groups, in which the other two terminal isocyanate groups of the other terminal isocyanate groups or triisocyanate compound di isocyanate compound is bonded with the hydroxyl groups of the hydroxyl-modified charge polymer. In the following description, the triisocyanate compound having three isocyanate groups at the terminal is also referred to as a triisocyanate compound having an isocyanate group at the three terminals of the iso structure, or a triisocyanate compound having an iso structure having an isocyanate group at the three terminals.

  Various surface functional groups exist on the surface of the carbon black particles by the generation process or post-treatment such as oxidation, and these reactive functional groups include hydroxyl group, carboxyl group, quinone group, amino group, sulfone group, There are epoxy groups. And these reactive functional groups can be adjusted post-processed by the following method, for example.

(1) Hydroxyl group, carboxyl group, quinone group; method of exposing to an oxidizing gas atmosphere such as air, ozone, oxygen, NOx, SOx, method of low-temperature oxygen plasma treatment, hydrogen peroxide solution, peroxodiacid or salts thereof, A method of treating by gas phase oxidation or liquid phase oxidation, such as a method of stirring in an aqueous solution of an oxidizing agent such as hypohalite, dichromate, permanganate, nitric acid.
(2) Amino group: A method of oxidation, nitration with nitric acid / sulfuric acid mixture, and reduction with formaldehyde.
(3) Sulfone group: a method of sulfonation with concentrated sulfuric acid.
(4) Epoxy group: a method of reacting a hydroxyl group or a carboxyl group with a halide having an epoxy group.

Of these reactive functional groups, acidic functional groups such as hydroxyl groups and carboxyl groups function effectively as functional groups that chemically bond with isocyanate groups. Therefore, the reactive functional group of carbon black is preferably a hydroxyl group or a carboxyl group, and the amount thereof is 0.14 μeq / m for the hydroxyl group, the carboxyl group, or the sum of both functional groups in order to bond uniformly with the isocyanate group. It is preferable that it is ² or more.

These functional groups are measured as follows.
(1) Carbon black nitrogen adsorption specific surface area (N ₂ SA; m ² / g);
Measured according to ASTM D3037-88 Method B.
(2) Amount of hydroxyl groups;
2,2′-Diphenyl-picrylhydrazyl (DPPH) is dissolved in carbon tetrachloride to prepare a solution with a concentration of 5 × 10 ⁻⁴ mol / l, and 0.1 to 0.6 g of carbon black is added to the solution. And stirring in a constant temperature bath at 60 ° C. for 6 hours. Thereafter, carbon black is filtered off from the reaction solution, and the hydroxyl group of the filtrate is measured with an ultraviolet absorptiometer. The value obtained by dividing the value measured in this way by the nitrogen adsorption specific surface area (N ₂ SA; m ² / g) of carbon black is the amount of hydroxyl groups formed per unit surface area of carbon black (μeq / m ² ). And
(3) carboxyl group amount;
After adding 2 to 5 g of carbon black in 50 ml of 0.976N sodium hydrogen carbonate and shaking for 6 hours, the carbon black was filtered off from the reaction solution, and 0.05N hydrochloric acid aqueous solution was added to the filtrate. Carry out neutralization titration test with 0.05N aqueous sodium hydroxide solution until 0 to measure carboxyl groups. A value obtained by dividing the measured value by the nitrogen adsorption specific surface area (N ₂ SA; m ² / g) of carbon black is defined as the amount of carboxyl groups (μeq / m ² ) formed per unit surface area of the carbon black.

  The diisocyanate compound having an isocyanate group at both ends is not particularly limited as long as it has an isocyanate group at both ends of the structure. Examples include methane diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), and hexane diisocyanate (HDI). it can. Among these diisocyanate compounds, MDI having high reactivity is suitable, but it is preferable to use properly depending on the reaction solvent.

  Further, the triisocyanate compound having an isocyanate group at the 3 terminal is not particularly limited as long as it has an isocyanate group at all 3 terminals, such as an isocyanurate structure, a biuret structure, and an adduct structure. Specific examples include D-127N, D-170N, D-170HM, D-172N, and D-177N manufactured by Mitsui Takeda Chemical Co., Ltd.

  Either a cationic polymer or an anionic polymer can be used as the hydroxyl-modified chargeable polymer that charges the surface of the carbon black particles depending on the purpose of positive or negative charge.

  As the cationic polymer, any polymer having a cationic group such as a primary amino group, a secondary amino group, a tertiary amino group, or a quaternary ammonium salt that functions as an electron-withdrawing group can be used. , Polyacrylamide, polyalkylacrylamide, polyethyleneimine, and the like. Specific examples include Kayo Master PD manufactured by Yokkaichi Gosei Co., Ltd., NO-290 manufactured by Fujikura Kasei Co., Ltd., and Eso Card Series manufactured by Lion.

  On the other hand, as an anionic polymer, any polymer having an anionic group such as a carboxyl group, a sulfo group, and a phosphoric acid group acting as an electron-donating group can be used. Polystyrene sulfonate, xanthan gum, There are carboxyvinyl polymer, polysaccharide, and the like, and specifically, the Afrock series manufactured by Mitsui Chemicals Aqua Polymer Co., Ltd. can be exemplified.

  The surface-modified carbon black of the present invention is a triisocyanate hexamethylene isocyanurate (Mitsui, Ltd.), which is an iso-structured triisocyanate compound having a hydroxyl group as a reactive functional group on the surface of carbon black particles and an isocyanate group at the three terminal as an isocyanate compound. D-177N) manufactured by Takeda Chemical Co., Ltd. A hydroxyl-modified chargeable polymer in which one terminal isocyanate group is bonded and two unbonded terminal isocyanate groups have hydroxyl groups in the side chain (manufactured by Yokkaichi Gosei Co., Ltd., Kathiomaster PD) The structural formula in the case of bonding to the hydroxyl group of is exemplified as Chemical Formula 1.

  As can be seen from Chemical Formula 1, the isocyanate compound functions as an intermediate substance for bonding the hydroxyl group, which is a reactive functional group on the surface of the carbon black particle, and the hydroxyl-modified chargeable polymer.

  The production method (1) according to claim 2 of the present invention for producing this surface-modified carbon black comprises a non-reactive solvent, carbon black, a diisocyanate compound having isocyanate groups at both ends, or an iso-structure at the three ends. A triisocyanate compound having an isocyanate group is added and mixed to combine the reactive functional group on the surface of the carbon black particles with the terminal isocyanate group of the diisocyanate compound or one terminal isocyanate group of the triisocyanate compound, and then the hydroxyl-modified chargeable polymer. Is added and mixed to bond the unbonded terminal isocyanate group of the isocyanate compound and the hydroxyl group of the hydroxyl-modified chargeable polymer.

  Examples of the non-reactive solvent include esters and ketones. Carbon black and a diisocyanate compound having an isocyanate group at both ends or a triisocyanate compound having an isocyanate group at the three ends of the isostructure are added to the non-reactive solvent. Mix with stirring and defoaming with a stirrer and defoamer, and then thoroughly mix and knead using a ball mill or a three-roll mill, etc. One terminal isocyanate group of the isocyanate compound is reacted to form a urethane bond.

  This reaction is carried out by reacting a hydroxyl group as a reactive functional group on the surface of the carbon black particle with a hexane isocyanate compound having an isocyanurate structure as a triisocyanate compound having isocyanate groups at all three ends, and thereby reacting one end of the triisocyanate compound. The reaction formula in the case where an isocyanate group and a hydroxyl group are urethane-bonded is exemplified as Chemical Formula 2.

  Thus, after urethane bonding of the reactive functional group and the isocyanate group on the surface of the carbon black particles, a hydroxyl-modified chargeable polymer is added and stirred and defoamed with a stirring and defoaming machine, and a solvent is added and a three roll mill, Mixing and kneading with an ultrasonic homogenizer, high-pressure homogenizer, process homogenizer, ball mill, bead mill, etc., the unbonded isocyanate group of the isocyanate compound and the hydroxyl group of the hydroxyl-modified chargeable polymer are reacted to form a urethane bond.

  At this time, it is preferable to add a small amount of an addition reaction promoting catalyst or a dehydrating condensing agent since the urethane reaction easily proceeds. Dibutyltin dilaurate or the like can be used as the addition reaction promoting catalyst, and the dehydrating condensation agent is not particularly limited, and examples thereof include concentrated sulfuric acid and N, N-dicyclohexylcarbodiimide.

  The modification site of the hydroxyl-modified chargeable polymer can be used either at the side chain, at the end, or both, but preferably has a highly reactive one-end modification. The skeleton of the hydroxyl-modified chargeable polymer is preferably close to the structure of the target dispersion medium. For example, when dispersed in silicone oil, a polymer having a dimethylpolysiloxane skeleton is preferable, and an isoparaffin hydrocarbon solvent or propylene glycol monomethyl is preferable. When dispersed in a hydrocarbon solvent such as ether acetate (PGMEA), a polymer having an acrylic ester skeleton is preferred. However, it is not limited to these polymers, and any polymer can be used as long as it is soluble in the respective desired dispersion solvents and has a hydroxyl group that is a reactive functional group.

  The surface-modified carbon black of the present invention is dispersed with steric hindrance in a nonpolar solvent or a low polarity solvent by a polymer chain of a hydroxyl-modified chargeable polymer bonded to the carbon black particle surface by a urethane bond. The molecular weight of the polymer is preferably 500-30000. When the molecular weight is less than 500, the steric hindrance due to the polymer chain is small and the dispersibility is lowered. On the other hand, when the molecular weight exceeds 30000, the dispersion tends to settle in the dispersion due to the weight of the carbon black, and the viscosity further increases.

  In this way, the surface-modified carbon black of the present invention can be produced. This reaction is performed by reacting the hydroxyl group on the surface of the carbon black particles exemplified in Chemical Formula 2 with a hexane isocyanate compound to form a triisocyanate compound. A reaction formula when one terminal isocyanate group is urethane-bonded with a hydroxyl group and then reacted with Kathiomaster PD manufactured by Yokkaichi Gosei Co., Ltd. as a hydroxyl-modified chargeable polymer is exemplified as Chemical Formula 3.

  Next, the production method (2) according to the third aspect of the present invention for producing the surface-modified carbon black of the present invention comprises a non-reactive solvent, carbon black, and a diisocyanate compound or isopropanol having isocyanate groups at both ends. A triisocyanate compound having an isocyanate group at the three ends of the structure and a hydroxyl-modified chargeable polymer are added and mixed, and the reactive functional group on the surface of the carbon black particle and one end of the diisocyanate compound or one end of the triisocyanate compound are mixed. It is combined with an isocyanate group, and at the same time, an unbonded terminal isocyanate group of the isocyanate compound and a hydroxyl group of the hydroxyl-modified chargeable polymer are bonded together.

  That is, in the production method (2), the surface-modified carbon black exemplified in the chemical formula 1 is produced by simultaneously performing the chemical reactions 2 and 3 exemplified in the production method (1).

  The carbon black dispersion of the present invention is obtained by dispersing the above surface-modified carbon black in a nonpolar solvent or a low polarity solvent at a concentration of 1 to 20% by weight, and the same nonpolar solvent as the solvent in which the carbon black is dispersed In addition, the carbon black can be modified by the above-described production method (1) or (2) in a low-polarity solvent, and a dispersion in which the modified carbon black is dispersed at a desired concentration can also be obtained.

  Alternatively, the surface-modified carbon black can be obtained by dispersing it in a nonpolar solvent or a low polarity solvent using a dispersing device such as an ultrasonic homogenizer, a high pressure homogenizer, or a process homogenizer. In this case, since the surface-modified carbon black dispersed in the solvent has a polymer bonded to the surface of the carbon black particles, once dried, the polymer chains can be entangled near the carbon black particle surface and re-dispersed in the solvent. Since it may be difficult, it may be desirable to obtain a dispersion dispersed in a target solvent. However, even after drying, it can be redispersed by mechanically dispersing with a homogenizer such as a high-pressure homogenizer or an ultrasonic homogenizer.

  Examples of the present invention will be specifically described below in comparison with comparative examples. However, the present invention is not limited to these examples.

Example 1
Reactive functionality prepared by oxidizing, drying, crushing, and classifying in a 2N sodium persulfate aqueous solution using TB # 7550F (nitrogen adsorption specific surface area of 135 m ² / g) manufactured by Tokai Carbon Co., Ltd. as carbon black Carbon black having a hydroxyl group of 0.74 μeq / m ² and a carboxyl group of 4.8 μeq / m ² was used as a sample.

  This carbon black was moistened by adding 35.9 g of Expar Mobil Chemical Co., Ltd. Isopar G, followed by 4.725 g of Mitsui Takeda Chemical Co., Ltd. D-177N, and Yokkaichi Gosei Co., Ltd. Cachio Master PD. 17.5 g was added and mixed, and after kneading for 2 minutes with stirring and defoaming for 2 minutes using Shintaro Awatori Nertaro Co., Ltd., kneaded for 30 minutes with three rolls, and dibutyltin dilaurate 0 .Isopar G solution in which 47225 g was dissolved to a concentration of 10 wt% was added, and the mixture was further kneaded with a three roll for 30 minutes. At this time, since Isopar G was diffused little by little, Isopar G was appropriately added.

  Isopar G is added to the above kneaded product to make a total amount of 250 g, treated with an ultrasonic homogenizer for 10 minutes and mechanically dispersed, and then made with Tokai Nanomizer TL-1500 at 50 to 150 MPa. Further mechanical dispersion was performed.

  This dispersion was put into a separable flask (capacity: 1 liter) and heat-treated at 70 ° C. for 6 hours with stirring. Then, Isopar G was added again to make the total amount 250 g, and the surface modification was self-dispersed in 10 wt% Isopar G. A carbon black dispersion 1 was obtained.

Example 2
In Example 1, instead of oxidation in an aqueous sodium persulfate aqueous solution, gas phase oxidation with ozone and carbon black having a hydroxyl group of 1.03 μeq / m ² and a carboxyl group of 3.22 μeq / m ² were used as samples. Surface-modified carbon black dispersion 2 was obtained by the same method as in Example 1.

Example 3
Surface modified carbon black dispersion by the same method as in Example 1 except that channel black (Special Black 4 manufactured by Degussa; hydroxyl group 0.16 μeq / m ² , carboxyl group 4.2 μeq / m ² ) was used as carbon black. 3 was obtained.

Example 4
Same as Example 1 except that 20 wt% of aliphatic ester alcohol wiseinol EHP01 manufactured by Yokkaichi Synthesis Co., Ltd. was added to the carbon black during the 70 ° C. holding step to terminate the unreacted isocyanate group. Surface-modified carbon black dispersion 4 was obtained by the method.

Example 5
Surface-modified carbon black dispersion 5 was obtained by the same method as in Example 1 except that PGMEA was used instead of Isopar G as a solvent to be dispersed.

Example 6
Other than using 17.5 g of Akofloc A120UH (molecular weight 2100) made by Mitsui Chemicals Aqua Polymer Co., Ltd., which is an anionic chargeable polymer, instead of Kayo Master PD of Yokkaichi Gosei Co., Ltd. of Example 1 as the chargeable polymer A surface-modified carbon black dispersion 6 was obtained by the same method as in Example 1.

Comparative Example 1
Example 1 except that 17.5 g of an acrylic polymer UT-1001 manufactured by Soken Chemical Co., Ltd., which has no charging property, was used as the chargeable polymer instead of Yokkaichi Kagaku Master PD manufactured by Yokkaichi Gosei Co., Ltd. Surface-modified carbon black dispersion 7 was obtained by the same method.

  These dispersions were allowed to stand at a temperature of 70 ° C. for 4 weeks, and a carbon black aggregate in the dispersion was obtained using a Microtrac particle size analyzer (Honeywell 9340-UPA150) every week. The average particle diameter of the dispersion was measured, and the viscosity of the dispersion was measured with a vibratory viscometer (manufactured by Yamaichi Electronics Co., Ltd., VM-100A-L). The results are shown in Table 1.

  Next, for each dispersion immediately after production, the amount of carbon black charge in the dispersion was measured using a zeta potential meter (ZEECOM manufactured by Microtech Nichion Co., Ltd.). The results are shown in Table 2.

  From Tables 1 and 2, all of the dispersions 1 to 6 are excellent in dispersibility, and can be positively or negatively charged by binding a cationic or anionic chargeable polymer. Therefore, depending on the purpose of use, the surface of the carbon black particles in the dispersion can be positively or negatively charged to effectively function electrically.

Claims (5)

One terminal isocyanate group of the diisocyanate compound having isocyanate groups at both ends or one terminal isocyanate group of the triisocyanate compound having three isocyanate groups at the ends are bonded to hydroxyl groups and / or carboxyl groups on the surface of the carbon black particles. other two terminal isocyanate groups of the other terminal isocyanate groups or triisocyanate compound di isocyanate compound, a polymer having hydroxyl groups has a polymer or anionic groups with a hydroxyl group having a cationic group (hereinafter, A surface-modified carbon black characterized by bonding with hydroxyl groups of a hydroxyl-modified chargeable polymer) . A method for producing the surface-modified carbon black according to claim 1, wherein the non-reactive solvent is carbon black, and a diisocyanate compound having isocyanate groups at both ends or a triisocyanate compound having three isocyanate groups at both ends. And mixing the hydroxyl group and / or carboxyl group on the surface of the carbon black particles with one terminal isocyanate group of the diisocyanate compound or one terminal isocyanate group of the triisocyanate compound. In addition, mixing is performed, and the other terminal isocyanate group of the diisocyanate compound or the other two terminal isocyanate groups of the triisocyanate compound and the hydroxyl group of the hydroxyl-modified chargeable polymer are combined. A method for producing surface-modified carbon black. A method for producing the surface-modified carbon black according to claim 1, wherein the non-reactive solvent is carbon black, and a diisocyanate compound having isocyanate groups at both ends or a triisocyanate compound having three isocyanate groups at both ends. And the hydroxyl-modified chargeable polymer is added and mixed to bond the hydroxyl group and / or carboxyl group on the surface of the carbon black particles with one terminal isocyanate group of the diisocyanate compound or one terminal isocyanate group of the triisocyanate compound; Simultaneously, the other terminal isocyanate group of the diisocyanate compound or the other two terminal isocyanate groups of the triisocyanate compound and the hydroxyl group of the hydroxyl-modified chargeable polymer are bonded. A method for producing surface-modified carbon black. Carbon black dispersion, wherein the surface modified carbon black of claim 1, wherein is dispersed in non-polar solvents or low-polar solvent at a concentration of 1-20 wt%. Claim 2 or 3 surface modified carbon black manufacturing method according to wherein the amount of human Dorokishiru group, a carboxyl group or both functional groups, of the carbon black particle surface is 0.14μeq / m ² or more.