JP7658565B2 - Black pigment dispersion - Google Patents

Description

The present invention relates to a black pigment dispersion containing perylene black and having excellent dispersibility.

A liquid crystal display device has a liquid crystal cell structure in which a liquid crystal material is filled between two glass substrates with opposing transparent electrodes. A column spacer is inserted between the two glass substrates to maintain a uniform gap between the substrates and provide a good image. Conventionally, bead spacers such as beaded glass have been used as such column spacers. However, it has been pointed out that the method using bead spacers has problems such as light leakage problems due to the beads simply being randomly dispersed in the gap, large variations in gap distance, and difficulty in controlling mechanical properties such as elasticity. In addition, more precise gap control is required due to market demands for higher image quality for liquid crystal display devices in recent years.

As a remedy for this, black column spacers using a black photosensitive resin composition instead of bead spacers have been proposed (Patent Documents 1 and 2). With black column spacers, it is possible to form column spacers at desired positions so that the variation in gap distance is small, and since it is relatively easy to control the properties of the photopolymerizable components, it is believed that more precise gap control is possible than with bead spacers. Furthermore, by including a black colorant in the column spacer, it is expected that visible light (wavelength 380 nm to 750 nm) will be blocked, improving contrast and color development effects. Patent Documents 1 and 2 cite perylene black as an example of such a black colorant. Patent Document 3 also discloses a pigment of a specific structure as an example of perylene black.

Patent Document 4 discloses a black pigment composition that can absorb light in the visible light range without using black carbon, can suppress absorption of infrared and ultraviolet rays, and has good solvent resistance, and contains perylene black of a specific structure, at least two types of colored organic pigments other than the perylene black, a dispersant, and a solvent.

Patent Document 5 discloses a color filter coloring composition that has excellent dispersibility, good fluidity, stability, and excellent developability, and contains a colorant, a resin-type dispersant, and a solvent, in which the colorant contains a pigment having an average primary particle size of 20 nm to 50 nm and an aspect ratio of the pigment particles of 1:1 to 1:3.5, and the resin-type dispersant is an A-B block copolymer or a B-A-B block copolymer consisting of an A block having solvent affinity and a B block having a functional group containing a nitrogen atom, and contains an acrylic block copolymer having an amine value of 10 mgKOH/g or more and 99 mgKOH/g or less in terms of effective solid content.

JP 2015-191234 A JP 2007-71994 A Patent No. 4980727 JP 2017-226821 A JP 2012-212054 A

Perylene black has excellent light-shielding properties, so a black matrix formed using a black coloring composition containing perylene black has excellent display contrast for color liquid crystal display devices, and because it has low dielectric constant characteristics, it is less likely to cause problems due to the electrical characteristics of the black matrix, such as disturbance of liquid crystal alignment and conduction between electrodes formed on a thin film transistor (TFT) substrate. In addition, because it has excellent transmittance in the near-infrared region, mask alignment work is possible, making it suitable as a driving substrate for TFT-type color liquid crystal display devices.

A drawback of perylene black is its poor dispersibility, and as disclosed in Patent Document 5, attempts have been made to improve its dispersibility in black coloring compositions (black pigment dispersions) by using dispersants. However, even if the dispersibility during preparation of the black pigment dispersion could be improved, there were cases where the dispersibility decreased during storage, leading to an increase in particle size and gelation. There were also cases where the viscosity of the dispersion increased, and there was a need to further improve the dispersibility of perylene black.

The present invention aims to provide a black pigment dispersion that contains perylene black as a black pigment and has excellent dispersibility not only during preparation but also during storage.

As a result of extensive research into solving the above problems, the inventors discovered that when perylene black is used as a black pigment in a pigment dispersion, the dispersibility of perylene black can be improved by using it in combination with a specific derivative and dispersant, and thus completed the present invention.

Specifically, the present invention provides
A black pigment dispersion containing at least a black pigment, a derivative, a dispersant and a solvent,
The black pigment is perylene black,
The derivative is a derivative represented by any one of Chemical Formula 1, Chemical Formula 2, and Chemical Formula 3,
The dispersant is
Monomer A having the structure of Chemical Formula 4;
A monomer B having a basic functional group;
A monomer C capable of polymerizing with said A and said B;
A copolymer consisting of
The monomer B is a monomer having a nitrogen-containing aromatic heterocyclic group as a basic functional group and/or a monomer having a structure of Chemical Formula 5,
The amine value of the dispersant is 120 mgKOH/g or more and 200 mgKOH/g or less.
This relates to a black pigment dispersion.

(In chemical formula 2, n = 1 to 2.)

(In chemical formula 4, R1 is hydrogen or a methyl group; R2 is an alkyl group having 1 to 8 carbon atoms; n=4 to 23.)

(In chemical formula 5, R3 is hydrogen or a methyl group; A is -COO- or -CONH-; B is an alkylene group having 1 to 6 carbon atoms; R4 and R5 are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, and R4 and R5 may combine with the adjacent nitrogen atom to form a 5- to 7-membered heterocycle.)

The black pigment dispersion of the present invention uses a derivative represented by any one of chemical formulas 1 to 3 in combination with a specific polymer dispersant, and as a result, is superior in dispersibility and stability of perylene black to conventional perylene black-containing black pigment dispersions.

The perylene black is preferably the perylene black shown in chemical formula 6 and/or chemical formula 7.

The average particle diameter (cumulant average particle diameter) of the perylene black is preferably 200 nm or less, and more preferably 170 nm or less. If the average particle diameter is 200 nm or less, the perylene black has excellent dispersibility. However, even if the average particle diameter is 170 nm or less, it is necessary that the particles do not aggregate over time (dispersion stability), and from the viewpoints of dispersion stability and light blocking properties, the average particle diameter is preferably 50 nm or more.

The content of the black pigment is preferably 5% by mass or more and 25% by mass or less, and more preferably 8% by mass or more and 15% by mass or less, of the total mass of the black pigment dispersion. If it is less than 5% by mass, the pigment concentration is low and coloring may be insufficient, and if it exceeds 25% by mass, the viscosity becomes high, which can easily cause problems such as poor handleability.

From the viewpoint of dispersion stability, the content of the derivative is preferably 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 40% by mass or less, relative to the pigment mass (the mass of the pigment contained in the black pigment dispersion).

From the viewpoint of optical properties such as dispersion stability, OD value, and color purity, the content of the dispersant is preferably 5% by mass or more and 80% by mass or less, and more preferably 20% by mass or more and 60% by mass or less, of the total mass of the pigment and derivative (total mass of the pigment and derivative contained in the black pigment dispersion). However, the optimal content of the derivative and dispersant can be appropriately adjusted depending on the type and combination of the pigment, derivative, and dispersant used.

The black pigment dispersion of the present invention may further contain an acrylic resin having an acidic group, a polyester resin, or a resin having a cardo structure. By containing such a resin, the effect of improving developability and adhesion can be obtained.

The black pigment dispersion of the present invention may further contain auxiliary components such as a viscosity modifier.

The black pigment dispersion of the present invention has excellent dispersibility of perylene black, does not gel during preparation, and is resistant to changes in average particle size and viscosity during storage.

The following describes an embodiment of the present invention.

(Black pigment)
As the perylene black, a known black organic pigment having a perylene structure can be used, for example, CI Pigment Black 31, CI Pigment Black 32, and perylene black represented by Chemical Formula 6 and/or Chemical Formula 7 can be used. Only one type of such perylene black may be used, or two or more types may be used. In addition, a commercially available perylene black can be used, for example, Lumogen (registered trademark) Black FK4280 (BASF), Paliogen (registered trademark) Black S0084 (BASF/CI Pigment Black 31), etc. can be used. Lumogen (registered trademark) Black FK4280 has a structure represented by Chemical Formula 6 or Chemical Formula 7.

(Derivatives)
The derivatives used in the present invention are those represented by Chemical Formula 1, Chemical Formula 2, or Chemical Formula 3. Only one of these derivatives may be used, or two or more of these derivatives may be used. These derivatives can be synthesized and used according to standard methods. All of the derivatives represented by Chemical Formulas 1 to 3 have a sulfonic acid group, but a free acid is used instead of a metal salt.

(Dispersant)
As the monomer A, a monomer corresponding to the Light Acrylate series manufactured by Kyoeisha Chemical Co., Ltd. or the New Frontier (registered trademark) series manufactured by Daiichi Kogyo Seiyaku Co., Ltd. can be used.

Monomer B is a monomer having a nitrogen-containing aromatic heterocyclic group as a basic functional group and/or a monomer having the structure of chemical formula 5. As a monomer having a nitrogen-containing aromatic heterocyclic group as a basic functional group, 4-vinylpyridine, 2-vinylpyridine, etc. can be used. As a monomer having the structure of chemical formula 5, a monomer corresponding to the Light Ester series manufactured by Kyoeisha Chemical Co., Ltd., the Cosylmer (registered trademark) series manufactured by KJ Chemicals Co., Ltd., etc. can be used.

Monomer C is preferably a nonionic monomer from the viewpoint of not affecting the dispersibility of the pigment. As a nonionic monomer, a (meth)acrylic acid alkyl ester such as methyl methacrylate or butyl methacrylate is preferable.

The content of monomers A to C in the dispersant can be changed as appropriate so that the total content is 100 parts by mass, with monomer A being 10 to 60 parts by mass, monomer B being 10 to 50 parts by mass, and monomer C being 20 to 60 parts by mass.

The acid value and amine value of the dispersant, which is a copolymer of monomers A to C, are determined by the functional groups contained in the copolymer and their contents. The acid value (acid value converted into solid content) can be determined, for example, by a method conforming to DIN EN ISO 2114, and the amine value (amine value converted into solid content) can be determined, for example, by a method conforming to DIN 16945. The acid value of the dispersant is preferably 1 mgKOH/g or less. The amine value of the dispersant is preferably 120 mgKOH/g or more and 200 mgKOH/g or less, and more preferably 150 mgKOH/g or more and 180 mgKOH/g or less.

(solvent)
As the solvent, various organic solvents such as aromatic, ketone, ester, glycol ether, alcohol, aliphatic, etc. may be used. The organic solvent may be used alone or in combination of two or more kinds.

Examples of aromatic organic solvents include aromatic hydrocarbons such as toluene, xylene, and ethylbenzene.

Examples of ketone-based organic solvents include methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, acetylacetone, isophorone, acetophenone, and cyclohexanone.

Examples of ester-based organic solvents include ethyl acetate, n-butyl acetate, isobutyl acetate, isopropyl acetate, methyl propionate, 3-methoxybutyl acetate, ethyl glycol acetate, propylene glycol monomethyl ether acetate (PMA), propylene glycol monoethyl ether acetate, 3-methyl-3-methoxybutyl acetate, methyl monochloroacetate, ethyl monochloroacetate, butyl monochloroacetate, methyl acetoacetate, ethyl acetoacetate, butyl carbitol acetate, butyl lactate, ethyl 3-ethoxypropionate, ethylene glycol monobutyl ether acetate, ethylene glycol monomethyl ether acetate, propyl acetate, and 1,3-butylene glycol diacetate.

Examples of glycol ether-based organic solvents include water-soluble glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether, propylene glycol mono-n-butyl ether, and dipropylene glycol mono-n-butyl ether;
Examples of water-insoluble glycol ethers include ethylene glycol monohexyl ether, ethylene glycol 2-ethylhexyl ether, ethylene glycol phenyl ether, diethylene glycol n-hexyl ether, diethylene glycol 2-ethylhexyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, dipropylene glycol propyl ether, and propylene glycol methyl ether propionate.

Examples of the alcohol-based organic solvent include alkyl alcohols having 1 to 4 carbon atoms, such as ethanol, methanol, butanol, propanol, and isopropanol;
Examples of the glycol include ethylene glycol, propylene glycol, diethylene glycol, pentamethylene glycol, trimethylene glycol, 2-butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, tripropylene glycol, polyethylene glycols with a molecular weight of 2000 or less, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerin, mesoerythritol, and pentaerythritol.

Examples of aliphatic organic solvents include aliphatic hydrocarbons such as n-pentane, n-hexane, and n-heptane.

From the viewpoint of ease of handling, it is preferable to adjust the solvent content so that the solids concentration, including pigments, etc., is 6 to 40% by weight.

<Production Example of Black Pigment Composition>
A black pigment dispersion was produced using the following raw materials and production method.

(Black pigment)
As perylene black, Lumogen (registered trademark) Black FK4280 (BASF) and Paliogen (registered trademark) Black S0084 (BASF) were used.

(Derivatives)
As the derivatives, derivatives 1 to 8 and Solsperse (registered trademark) 5000 (having a sulfonic acid group (ammonium salt) manufactured by Lubrizol Japan Co., Ltd.) were used.

(Method for producing derivative 1)
20 parts by mass of CI Pigment Yellow 138 (BASF, Paliotol (registered trademark) Gelb K0961HD) and 300 parts by mass of 98% concentrated sulfuric acid were placed in a 500 mL separable flask and reacted at 120 ° C for 5 hours to obtain a sulfonated phthalimidoquinophthalone compound. The reaction mixture was poured into 3000 parts by mass of water while stirring to precipitate a sulfonated phthalimidoquinophthalone compound, and after stirring for 30 minutes, the mixture was filtered and washed with water three times. The obtained wet cake was washed with 300 parts by mass of 1% diluted sulfuric acid, filtered, and washed with water. The mixture was dried in a hot air dryer to obtain 54 parts by mass of derivative 1 represented by chemical formula 1.

The resulting derivative 1 was analyzed by mass spectrometry using a Hewlett-Packard liquid chromatography mass spectrometer "LC/MS" (Electro Spray Ionization), and m/z = 773 [M-H]- was detected.

(Method for producing derivative 2)
According to a conventional method, derivative 2 represented by chemical formula 8 was obtained.

(Method for producing derivative 3)
According to a conventional method, derivative 3 represented by chemical formula 9 was obtained.

(Method for producing derivative 4)
According to a conventional method, derivative 4 represented by chemical formula 10 was obtained.

(Method for producing derivative 5)
According to a conventional method, derivative 5 represented by chemical formula 11 was obtained.

(Method for producing derivative 6)
15 parts by mass of CI Pigment Orange 43, 1.6 parts by mass of paraformaldehyde, and 8.4 parts by mass of 4-aminophthalimide were added to 200 parts by mass of 98% concentrated sulfuric acid, and the mixture was allowed to react for 5 hours at 85° C. Next, this solution was added to 1 L of ice water, and filtered and washed with water to obtain 19.5 parts by mass of (4-aminophthalimidomethyl)-CI Pigment Orange 43 into which one 4-aminophthalimidomethyl group had been introduced.

Next, 10 parts by mass of (4-aminophthalimidomethyl)-C.I. Pigment Orange 43 was dispersed in 100 parts by mass of water, and 3.6 parts by mass of cyanuric chloride, an amount that reacts with one amino group, was added and reacted at 30°C for 1 hour. Next, 3.4 parts by mass of orthanilic acid (2-aminobenzenesulfonic acid) was added and reacted at 80°C for 2 hours, hydrolyzing the remaining Cl group and obtaining 15.2 parts by mass of derivative 6 represented by chemical formula 2.

The molecular ion peak of derivative 6 was measured in positive ion mode using an AXIMA CFR plus matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (Shimadzu Corporation) with α-cyano-4-hydroxycinnamic acid (CHCA) as the matrix. As a result, a peak was observed at m/z = 854. This ion peak corresponds to the compound with n = 1.

(Method for producing derivative 7)
18.4 parts by mass of cyanuric chloride and 17.3 parts by mass of orthanilic acid in an amount that reacts with one chlorine atom of cyanuric chloride were added to 100 parts by mass of water, and the mixture was reacted at 10° C. for 1 hour. 16.6 parts by mass of 3-amino-4-methoxybenzamide in an amount that reacts with two chlorine atoms of the reaction product was added to the reaction product, and the mixture was reacted at 85° C. for 1 hour. The reaction product was filtered, and the resulting residue was washed with water and then allowed to stand overnight in a thermostatic chamber at 100° C. to dry, obtaining 32.5 parts by mass of derivative 3 represented by chemical formula 3.

The molecular ion peak of derivative 7 was measured in positive ion mode using an AXIMA CFR plus matrix-assisted laser desorption ionization-time of flight mass spectrometer (Shimadzu Corporation) with α-cyano-4-hydroxycinnamic acid (CHCA) as the matrix. As a result, a peak was observed at m/z = 582.

(Method for producing derivative 8)
According to the method described in paragraph [0148] of JP2012-212054A, derivative 8, which is an aluminum salt of derivative 1, was obtained.

(solvent)
Propylene glycol monomethyl ether acetate (PMA) was used as the solvent.

(Dispersant)
Dispersants I to IV, which will be described later, were used as the dispersants. The amine value, Mp (peak top molecular weight), Mw/Mn (ratio of weight average molecular weight to number average molecular weight), NV (solid content or non-volatile content), and monomer composition (numbers indicate mass ratios of monomers) constituting each dispersant are as shown in Table 1. In Table 1, the structures indicated by the abbreviations in the monomer composition column are as shown in Table 2.

(Method for producing dispersant I)
287.3 parts by mass of methyl methacrylate (MMA), 0.6 parts by mass of butyl methacrylate (BMA), 142.4 parts by mass of methoxypolyethylene glycol methacrylate (MPEG9MA), 15 parts by mass of N-(tert-butyl)-N-(1-diethylphosphono-2,2-dimethylpropyl)-O-(2-carboxylprop-2-yl)hydroxylamine (Arkema, product name BlocBuilder MA), 436 parts by mass of propylene glycol monomethyl ether acetate (PMA), and 218 parts by mass of propylene glycol monomethyl ether (PM) were collected in a 2L stainless steel separable flask. The mixture was stirred with nitrogen bubbling, and the flask was heated to 125°C in an oil bath and reacted for 4 hours.

Next, 199.7 parts by mass of 4-vinylpyridine (4VPy), 196 parts by mass of PMA, and 98 parts by mass of PM were added to the flask, and the mixture was stirred while continuing to be bubbled with nitrogen and reacted at 125°C for 4 hours.

The solid content of the reaction mixture was 40.5% by weight. The resulting block copolymer was measured by GPC (gel permeation chromatography) and found to have a peak top molecular weight of 11,500 and an Mw/Mn ratio of 1.24. The amine value (solid content) was 168.6 mgKOH/g.

The block copolymer (dispersant I) thus obtained has a block having a constituent unit derived from MMA (monomer C), a constituent unit derived from BMA (monomer C), and a constituent unit derived from MPEG9MA (monomer A), and a block having a constituent unit derived from 4VPy (monomer B) as a basic group-containing unit. In other words, dispersant I is a linear block polymer having a block consisting of a basic group-containing unit at one end. Due to the monomer structure, dispersant I does not have an acidic group. The mass ratio of each constituent unit of dispersant I (MMA/BMA/MPEG9MA/4VPy) is 45.6/0.1/22.6/31.7.

(Preparation of Dispersant II)
Dispersant II was produced in the same manner as Dispersant I, except that DM was used instead of 4VPy. The mass ratio of each constituent unit of Dispersant II (MMA/BMA/MPEG9MA/DM) was 35.1/0.1/17.4/47.4.

(Preparation of Dispersant III)
Dispersant III was prepared in the same manner as Dispersant I, except that DMAPAA (registered trademark) was used instead of 4VPy. The mass ratio of each constituent unit of Dispersant III (MMA/BMA/MPEG9MA/DMAPAA) was 35.3/0.1/17.5/47.1.

(Preparation of Dispersant IV)
Dispersant IV was prepared in the same manner as Dispersant I, except that DE was used instead of 4VPy. The mass ratio of each constituent unit of Dispersant IV (MMA/BMA/MPEG9MA/DE) was 53.1/0.1/26.2/20.6.

[Example 1]
In a polyethylene container, 9.6 parts by mass of perylene black (BASF, Lumogen (registered trademark) Black FK4280), 2.4 parts by mass of derivative 1 shown in chemical formula 1 as a derivative, 6.0 parts by mass of dispersant I as a dispersant in terms of solid content, and PMA as a solvent were collected. The amount of PMA was adjusted so that "perylene black + derivative + dispersant + solvent" was 100 parts by mass. 300 parts by mass of zirconia beads (φ0.5 mm) were placed in the container and dispersed for 60 minutes using a paint shaker manufactured by Asada Iron Works Co., Ltd., to obtain a black pigment dispersion of the example (perylene black concentration 9.6% by mass, derivative concentration 2.4% by mass, dispersant concentration 6.0% by mass).

[Example 2]
A black pigment dispersion of Example 2 was obtained in the same manner as in Example 1, except that Dispersant II was used as the dispersant in an amount of 6.0 parts by mass calculated as solid content.

[Example 3]
A black pigment dispersion of Example 3 was obtained in the same manner as in Example 1, except that Dispersant III was used in an amount of 6.0 parts by mass in terms of solid content as the dispersant.

[Comparative Example 1]
A black pigment dispersion of Comparative Example 1 was obtained in the same manner as in Example 1, except that the amount of perylene black was changed to 12.0 parts by mass and no derivative was used.

[Comparative Example 2]
A black pigment dispersion of Comparative Example 2 was obtained in the same manner as in Example 2, except that the amount of perylene black was 12.0 parts by mass and no derivative was used.

[Comparative Example 3]
A black pigment dispersion of Comparative Example 3 was obtained in the same manner as in Example 3, except that the amount of perylene black was changed to 12.0 parts by mass and no derivative was used.

[Comparative Example 4]
A black pigment dispersion of Comparative Example 4 was obtained in the same manner as in Example 1, except that 2.4 parts by mass of Solsperse (registered trademark) 5000 (Lubrizol Japan Co., Ltd./having a sulfonic acid group (ammonium salt)) was used as the derivative.

[Comparative Example 5]
A black pigment dispersion of Comparative Example 5 was obtained in the same manner as in Example 1, except that 2.4 parts by mass of Derivative 2 (a derivative having a secondary amino group) was used as the derivative.

[Comparative Example 6]
A black pigment dispersion of Comparative Example 6 was obtained in the same manner as in Example 1, except that 2.4 parts by mass of Derivative 3 (a derivative having a secondary amino group) was used as the derivative.

[Comparative Example 7]
A black pigment dispersion of Comparative Example 7 was obtained in the same manner as in Example 1, except that 2.4 parts by mass of Derivative 4 (a derivative having a carboxyl group) was used as the derivative.

[Comparative Example 8]
A black pigment dispersion of Comparative Example 8 was obtained in the same manner as in Example 1, except that 2.4 parts by mass of Derivative 5 (a derivative having a carboxyl group) was used as the derivative.

<Measurement of particle size of perylene black>
The black pigment dispersions of Examples 1 to 3 and Comparative Examples 1 to 8 were diluted with PMA to a concentration range of 0.001 to 10% by mass, and then the average particle size (cumulant average particle size; average particle size by cumulant analysis) was measured using an FPAR-1000 manufactured by Otsuka Electronics Co., Ltd. The average particle size was measured immediately after preparation and after storage for one week in a thermostatic chamber at 40°C.

<Viscosity Measurement of Black Pigment Dispersion>
The viscosity (25°C) of each of the black pigment dispersions of Examples 1 to 3 and Comparative Examples 1 to 8 was measured immediately after preparation and after storage for one week in a thermostatic chamber at 40°C using an E-type viscometer (TV-22) manufactured by Toki Sangyo Co., Ltd.

Table 3 shows the black pigment, derivative, functional group of the derivative, dispersant, amine value of the dispersant (mgKOH/g), solvent, average particle size (particle size A is the average particle size (nm) immediately after preparation, and particle size B is the average particle size (nm) after storage for one week in a thermostatic chamber at 40°C), particle size change rate (particle size B/particle size A), viscosity (viscosity A is the viscosity immediately after preparation (mPa·s/25°C), and viscosity B is the viscosity after storage for one week in a thermostatic chamber at 40°C (mPa·s/25°C)), viscosity change rate (viscosity B/viscosity A), and the results of practicality evaluation for the black pigment dispersions of Examples 1 to 3 and Comparative Examples 1 to 8.

In Examples 1 to 3 and Comparative Examples 4 to 8, the pigment concentration is 9.6% by mass, and in Comparative Examples 1 to 3, it is 12.0% by mass. In addition, in Examples 1 to 3 and Comparative Examples 4 to 8, the derivative concentration is 2.4% by mass. In all of the Examples and Comparative Examples in Table 3, the dispersant concentration is 6.0% by mass, and the solvent concentration is 82.0% by mass.

The practicality assessment is
Item 1) The average particle size immediately after preparation is 200 nm or less, and the rate of change in particle size is 0.85 to 1.15;
Item 2) The viscosity immediately after preparation is 10 (mPa·s/25°C) or less, and the rate of change in viscosity is 0.85 or more and 1.15 or less;
For the two items above, if both were met, it was judged as "○", otherwise it was judged as "×".

Comparative Examples 2, 3, 5, and 6 gelled during preparation, and the average particle size and viscosity were not measurable. Comparative Examples 1 and 4 were inappropriate for both items 1) and 2), and Comparative Examples 7 and 8 were inappropriate for only one of them, and the practicality of all of them was judged to be "X."

On the other hand, Examples 1 to 3 met both criteria 1) and 2) and were judged to be of practical use "○".

Comparing Examples 1 to 3 with Comparative Examples 1 to 3, it was confirmed that even if the types of pigment and dispersant were the same, the use of Derivative 1 as the derivative improved the dispersibility of perylene black and reduced the rate of change in particle size and viscosity. In addition, comparing Example 1 with Comparative Examples 4 to 8, it was confirmed that even if the types and concentrations of the pigment and dispersant were the same, when a derivative without a sulfonic acid group was used, the pigment dispersion gelled or the rate of change in particle size or viscosity increased,

[Example 4]
A black pigment dispersion of Example 4 was obtained in the same manner as in Example 1, except that 2.4 parts by mass of Derivative 6 was used as the derivative.

[Example 5]
A black pigment dispersion of Example 5 was obtained in the same manner as in Example 1, except that 2.4 parts by mass of Derivative 7 was used as the derivative.

[Example 6]
A black pigment dispersion of Example 6 was obtained in the same manner as in Example 1, except that 9.6 parts by mass of perylene black (BASF, Paliogen (registered trademark) Black S0084) was used as the black pigment.

[Comparative Example 9]
A black pigment dispersion of Comparative Example 9 was obtained in the same manner as in Example 1, except that 2.4 parts by mass of Derivative 8 (a derivative having a sulfonic acid group (aluminum salt)) was used as the derivative.

[Comparative Example 10]
A black pigment dispersion of Comparative Example 10 was obtained in the same manner as in Example 2, except that 2.4 parts by mass of Derivative 8 (a derivative having a sulfonic acid group (aluminum salt)) was used as the derivative.

[Comparative Example 11]
A black pigment dispersion of Comparative Example 11 was obtained in the same manner as in Example 3, except that 2.4 parts by mass of Derivative 8 (a derivative having a sulfonic acid group (aluminum salt)) was used as the derivative.

[Comparative Example 12]
A black pigment dispersion of Comparative Example 12 was obtained in the same manner as in Example 1, except that Dispersant IV was used in an amount of 6.0 parts by mass in terms of solid content as the dispersant.

Table 4 shows the results of the black pigment, derivative, functional groups of the derivative, dispersant, amine value of the dispersant (mgKOH/g), solvent, average particle size (particle size A is the average particle size (nm) immediately after preparation, and particle size B is the average particle size (nm) after storage for one week in a thermostatic chamber at 40°C), particle size change rate (particle size B/particle size A), viscosity (viscosity A is the viscosity immediately after preparation (mPa·s/25°C), and viscosity B is the viscosity after storage for one week in a thermostatic chamber at 40°C (mPa·s/25°C)), viscosity change rate (viscosity B/viscosity A), and practicality evaluation for the black pigment dispersions of Examples 4 to 6 and Comparative Examples 9 to 12.

Comparative Examples 10 and 11 gelled after storage at 40°C for one week, and the average particle size and viscosity were not measurable after storage. Comparative Examples 9 and 12 had suitable average particle size and viscosity measurements at the time of preparation, but the particle size change rate and viscosity change rate exceeded the standard values, and the practicality was judged to be "X" due to lack of stability.

On the other hand, Examples 4 to 6 met both criteria 1) and 2) and were judged to be of practical use "○".

From Tables 3 and 4, it was confirmed that the black pigment dispersion using perylene black as the black pigment has an average particle size and viscosity within the preferred range not only during preparation but also after storage testing, and has excellent pigment dispersibility and stability, by combining any of the derivatives shown in Chemical Formula 1, Chemical Formula 2, or Chemical Formula 3 having a sulfonic acid group as a functional group with a specific dispersant.

The above-mentioned Patent Document 5 discloses the use of Derivative 8 as a derivative in a pigment dispersion. However, as shown in Tables 3 and 4, for a black pigment dispersion using perylene black as the black pigment, Derivative 8 does not sufficiently improve dispersibility, and it has been confirmed that dispersibility and stability can be improved only by combining a derivative having a sulfonic acid group (free acid) such as Derivative 1 with a specific dispersant.

The black pigment dispersion of the present invention is useful in technical fields such as displays, solid-state imaging devices, and infrared sensors.

Claims (4)

A black pigment dispersion containing at least a black pigment, a derivative, a dispersant and a solvent,
The black pigment is perylene black,
The derivative is a derivative represented by any one of Chemical Formula 1, Chemical Formula 2, and Chemical Formula 3,
The dispersant is
Monomer A having the structure of Chemical Formula 4;
A monomer B having a basic functional group;
A monomer C capable of polymerizing with said A and said B;
A copolymer consisting of
The monomer B is a monomer having a nitrogen-containing aromatic heterocyclic group as a basic functional group and/or a monomer having a structure represented by Chemical Formula 5,
The amine value of the dispersant is 120 mgKOH/g or more and 200 mgKOH/g or less.
Black pigment dispersion.
(In chemical formula 2, n=1 to 2.)
(In Chemical Formula 4, R1 is hydrogen or a methyl group; R2 is an alkyl group having 1 to 8 carbon atoms; and n=4 to 23.)
(In Chemical Formula 5, R3 is hydrogen or a methyl group; A is -COO- or -CONH-; B is an alkylene group having 1 to 6 carbon atoms; R4 and R5 are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, and R4 and R5 may combine with the adjacent nitrogen atom to form a 5- to 7-membered heterocycle.) The black pigment dispersion according to claim 1 , wherein the perylene black is the perylene black represented by Chemical Formula 6 and/or Chemical Formula 7.
The black pigment dispersion according to claim 1 or 2, wherein the average particle size of the perylene black is 200 nm or less. The content of the black pigment is 5% by mass or more and 25% by mass or less of the total mass of the black pigment dispersion,
The content of the derivative is 5% by mass or more and 50% by mass or less based on the pigment mass,
The content of the dispersant is 5% by mass or more and 80% by mass or less based on the total mass of the pigment and the derivative.
The black pigment dispersion according to claim 1 .