Black pigment dispersion

Abstract

A black pigment dispersion prevents the dispersion from gelling, prevents changes in the viscosity of the dispersion during storage, and improves dispersibility when a pigment dispersion liquid containing a lactam black is prepared. A copolymer composed of a monomer A having a structure of Formula 1 as a dispersant, a monomer B having a nitrogen-containing aromatic heterocyclic group as a basic functional group, and a monomer C capable of polymerizing with the monomer A and the monomer B is used together with the lactam black. The content of the lactam black is 5 mass% or more and 25 mass% or less. The average particle diameter of the lactam black is preferably adjusted to 200 nm or less.

Description

TECHNICAL FIELD

[0001] The present application relates to a black pigment dispersion containing a lactam black, which has superior dispersibility. BACKGROUND

[0002] Backlights for liquid crystal displays are currently widely adopted in mobile terminals, televisions, and the like, because of features such as high resolution, low cost, thin form factor, and the like.

[0003] Recently, in order to cope with further high-precision and high-brightness of color liquid crystal displays, a color filter on array (COA) method in which a color filter is provided on a TFT element substrate side, and a black matrix on array (BOA) method in which only a black matrix is provided on a TFT element substrate side have been proposed in the field of active matrix type liquid crystal displays. According to these methods, compared to a case where a black matrix is formed on a color filter side, there is no need to leave a margin for alignment with a position on an active element side, and thus an aperture ratio can be improved, as a result of which high-brightness can be sought.

[0004] When such a structure is adopted, the black matrix requires a black coloring agent having a volume resistivity of a prescribed value or more and a relative dielectric constant of a prescribed value or less, in order not to cause a circuit short even if it is directly loaded on a TFT element. A black matrix using a plurality of organic coloring pigments and carbon black in pigments has been proposed as such a black matrix (Patent Document 1).

[0005] Further, a photosensitive composition for a black matrix using an organic black pigment as a pigment is known, and specifically, a photosensitive composition using an aniline black (Patent Document 2), a perylene black (Patent Document 3) is known.

[0006] A lactam black dispersion containing a lactam black (a black pigment having a lactam structure) having a particle diameter of 314 to 551 nm and a specific dispersant is disclosed in Patent Document 4 as a lactam black dispersion for electrophoretic display use (Table 1).

[0007] A black pigment dispersion composition for a liquid crystal display element, a solid-state imaging element, an infrared sensor, and the like, and a black photoresist composition containing the same, containing a lactam black, a violet pigment, a blue pigment, and / or a green pigment, and carbon black are disclosed in Patent Document 5.

[0008] Patent Literature 6 discloses a colored photosensitive resin composition for forming a separator of an organic electroluminescent element, which contains an organic black pigment, an acrylic dispersant, an epoxy (meth)acrylate resin, a photopolymerizable monomer, and a photopolymerization initiator, like Irgaphor (registered trademark) Black S0100CF as a lactam black.

[0009] Prior Art Documents:

[0010] Patent Literature:

[0011] Patent Literature 1: Japanese Patent Application Publication No. 2009-75446;

[0012] Patent Literature 2: Japanese Patent Application Publication No. H8-44049;

[0013] Patent Literature 3: Japanese Patent Application Publication No. 2006-235153;

[0014] Patent Literature 4: Japanese Patent Application Publication No. 2012-515240;

[0015] Patent Literature 5: Japanese Patent Application Publication No. 2019-81857;

[0016] Patent Literature 6: International Publication No. 2018 / 101314. SUMMARY

[0017] Problems to be Solved by the Invention:

[0018] Lactam black is a black pigment having advantages such as high infrared and ultraviolet transmittance, high insulation, and low permittivity, but poor dispersibility becomes a disadvantage when used as a pigment dispersion. That is, when a pigment dispersion liquid containing lactam black is prepared, problems such as gelation of the dispersion liquid and change in viscosity of the dispersion liquid during storage occur.

[0019] Means for Solving the Problems:

[0020] The present inventors have found that, when lactam black is used as a black pigment for a pigment dispersion, the dispersibility of the lactam black is improved by using a specific dispersant in a specific ratio, thereby completing the present invention, as a result of repeated and careful studies to solve the above problems.

[0021] Specifically, the present invention relates to a black pigment dispersion,

[0022] which contains at least a black pigment, a dispersant, and a solvent;

[0023] the black pigment is a lactam black;

[0024] the dispersant is a copolymer composed of:

[0025] Monomer A having the structure of Formula 1;

[0026] Monomer B having a nitrogen-containing aromatic heterocyclic group as a basic functional group; and

[0027] Monomer C capable of polymerizing with the monomer A and the monomer B.

[0028]

Chemical Formula 1

[0029] CH2=C(R1)COO(CH2CH2O) n R2 ・・・ Chemical Formula 1.

[0030] (In the formula, R1 is hydrogen or methyl; R2 is an alkyl group having a carbon number of 1 to 8; and n = 4 to 23.)

[0031] The black pigment dispersion of the present application is superior in dispersibility of the lactam black, and does not gel during preparation, and the viscosity hardly changes during storage, when the average particle diameter (cumulative average particle diameter) of the lactam black is 200 nm or less, preferably 160 nm or less.

[0032] The content of the black pigment is preferably 5 mass% or more and 25 mass% or less. When it is less than 5 mass%, there is a possibility that the coloring is insufficient due to low pigment concentration, and when it exceeds 25 mass%, the viscosity becomes high, and there is a problem that the handleability is easily reduced.

[0033] The black pigment dispersion of the present application can also contain a derivative having an acidic group as a pigment derivative, for example, a derivative in which an acidic group is introduced into a quinophthalone skeleton. By containing such a pigment derivative, the effect that the particle diameter can be further reduced and the necessary amount of dispersant can be reduced is obtained.

[0034] The black pigment dispersion of the present application can also contain an acrylic resin, a polyester resin, or a resin having a cardo structure, which has an acidic group. By containing such a resin, the effect that the developability and the adhesiveness are improved is obtained.

[0035] The black pigment dispersion of the present application can also contain an auxiliary ingredient such as a viscosity adjusting agent.

[0036] Effects of the Invention

[0037] The black pigment dispersion of the present application is superior in dispersibility of the lactam black, and does not gel during preparation, and the viscosity hardly changes during storage. DETAILED DESCRIPTION

[0038] The embodiments of the present application will be described below.

[0039] (Black Pigment)

[0040] The examples of the lactam black include Black 582 manufactured by BASF Corporation, Irgaphor (registered trademark) Black S0100CF, and the like.

[0041] (Dispersant)

[0042] The monomer A can use the monomers belonging to the light acrylate series manufactured by Kyoeisha Chemical Co., Ltd., the New Frontier series manufactured by the First Industrial Co., Ltd.

[0043] Specific examples of the monomer B are 4-vinylpyridine, 2-vinylpyridine, and the like.

[0044] The monomer C is preferably a nonionic monomer from the viewpoint of not affecting the dispersibility of the pigment. The nonionic monomer is preferably an alkyl (meth)acrylate such as methyl methacrylate, butyl methacrylate, and the like.

[0045] The content rates of the monomers A to C in the dispersant are 20 to 60 parts by mass of the monomer A, 10 to 40 parts by mass of the monomer B, and 20 to 60 parts by mass of the monomer C, and can be appropriately changed so as to total 100 parts by mass.

[0046] The acid value and the amine value of the dispersant of the monomers A to C block copolymer are determined by the functional groups contained in the block copolymer and the content rates thereof. The acid value (acid value after conversion to solid content) can be obtained, for example, by the method according to DIN EN ISO 2114, and the amine value (amine value after conversion to solid content) can be obtained, for example, by the method according to DIN 16945. The acid value of the dispersant is preferably 1 mgKOH / g or less. The amine value of the dispersant is further preferably 50 mgKOH / g or more and 200 mgKOH / g or less.

[0047] (Solvent)

[0048] The solvent can use various organic solvents such as aromatic solvents, ketone solvents, ester solvents, glycol ether solvents, alcohol solvents, aliphatic solvents, and the like. The organic solvent can be only one kind, or two or more kinds in combination.

[0049] Examples of the aromatic solvent include aromatic hydrocarbons such as toluene, xylene, ethylbenzene, and the like.

[0050] Examples of the ketone solvent include methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, acetylacetone, isophorone, phenylethanone, cyclohexanone, and the like.

[0051] Examples of the ester-based organic solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, isopropyl acetate, methyl propionate, (3-methoxybutyl) acetate, ethylene glycol acetate, propylene glycol monomethyl ether acetate (PMA), propylene glycol monoethyl ether acetate, 3-methyl-3-methoxybutyl acetate, methyl chloroacetate, ethyl chloroacetate, butyl chloroacetate, methyl acetoacetate, ethyl acetoacetate, butyl carbitol acetate, butyl lactate, ethyl-3-ethoxypropyl acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monomethyl ether acetate, propyl acetate, 1,3-butanediol diacetate, and the like.

[0052] Examples of the glycol ether-based organic solvent 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-dibutyl ether, diethylene glycol mono-n-dibutyl ether, triethylene glycol mono-n-dibutyl ether, ethylene glycol mono-t-dibutyl ether, diethylene glycol mono-t-dibutyl ether, 1-methyl-l-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-dibutyl 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-dibutyl ether, dipropylene glycol mono-n-dibutyl ether, and the like; and water-insoluble glycol ethers such as ethylene glycol monohexyl ether, ethylene glycol-2-ethylhexanoate, ethylene glycol diphenyl ether, diethylene glycol-n-hexyl ether, diethylene glycol-2-ethylhexanoate, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, dipropylene glycol propyl ether, propylene glycol propionate methyl ether, and the like.

[0053] Examples of the alcohol-based organic solvent include alkyl alcohols having a carbon number of 1 to 4 such as ethanol, methanol, butanol, propanol, isopropanol, and the like; glycols such as ethylene glycol, propylene glycol, diethylene glycol, 1,5-pentanediol, propylene glycol, 2-buten-l,4-diol, 2-ethyl-l,3-hexanediol, 2-methyl-2,4-pentanediol, tripropylene glycol, polyethylene glycol having a molecular weight of 2000 or less, 1,3-propanediol, isopropyl glycol, isobutyl glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerol, meso-erythritol, pentaerythritol, and the like.

[0054] Examples of the aliphatic-based organic solvent include aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and the like.

[0055] The content of the solvent is preferably adjusted to a solid content concentration of 6 to 40% by weight in terms of ease of handling.

[0056] <Example of Production of Black Pigment Composition>

[0057] A black pigment dispersion was produced by the following raw materials and production method.

[0058] (Black pigment)

[0059] The lactam black used Irgaphor (registered trademark) Black S0100CF (BASF Corporation).

[0060] (Solvent)

[0061] The solvent used propylene glycol monomethyl ether acetate (PMA).

[0062] (Dispersant)

[0063] The dispersant used dispersants I to VI described later. The amine value, Mp (peak molecular weight), Mw / Mn (weight average molecular weight and number average molecular weight ratio), NV (solid content or non-volatile content), and monomer combination (the numbers indicate the mass ratio of the monomers) of each dispersant are shown in Table 1. In Table 1, the structure represented by the abbreviated symbols in the monomer combination column is shown in Table 2.

[0064] [Table 1]

[0065] .

[0066] [Table 2]

[0067] .

[0068] (Method for producing dispersant I)

[0069] Methyl methacrylate (MMA) 287.3 parts by mass, butyl methacrylate (BMA) 0.6 parts by mass, methoxy polyethylene glycol methacrylate (MPEG9MA) 142.4 parts by mass, N-(tert-butyl)-N-(1-diethylphosphine carboxyl-2,2-dimethylpropyl)-O-(2-carboxypropyl-2-yl) hydroxylamine (manufactured by Arkema, product name BlocBuilder MA) 15 parts by mass, propylene glycol monomethyl ether acetate (PMA) 436 parts by mass, propylene glycol monomethyl ether (PM) 218 parts by mass were extracted into a 2L capacity stainless steel separation flask. While stirring with nitrogen bubbling, the flask was heated to 125°C by an oil bath, and reacted for 4 hours.

[0070] Next, 4-vinylpyridine (4VPy) 199.7 parts by mass, PMA 196 parts by mass, PM 98 parts by mass were added to the flask, and stirring was continued while bubbling with nitrogen, and reacted at 125°C for 4 hours.

[0071] The solid amount of the reaction mixture was 40.5 wt%. The obtained block copolymer was subjected to GPC (gel permeation chromatography) measurement, and the top peak molecular weight was 11500, and Mw / Mn was 1.24. The amine value (solid amount) was 168.6 mgKOH / g.

[0072] The block copolymer thus obtained (dispersant I) had a block having a constituting unit from MMA (monomer C), a constituting unit from BMA (monomer C), a constituting unit from MPEG9MA (monomer A), and a block having a constituting unit from 4VPy (monomer B) as a basic group-containing unit. That is, dispersant I was a linear block polymer having a block composed of a basic group-containing unit at one end portion thereof. Dispersant I did not have an acidic group in terms of monomer constitution. The mass ratio of each constituting unit of dispersant I (MMA / BMA / MPEG9MA / 4VPy) was 45.6 / 0.1 / 22.6 / 31.7.

[0073] (Production of dispersant II)

[0074] Dispersant II was produced in the same manner as dispersant I except that DM was used instead of 4VPy. The mass ratio of each constituting unit of dispersant II (MMA / BMA / MPEG9MA / DM) was 35.1 / 0.1 / 17.4 / 47.4.

[0075] (Production of dispersant III)

[0076] Dispersant III was produced in the same manner as dispersant I except that DE was used instead of 4VPy. The mass ratio of each constituting unit of dispersant III (MMA / BMA / MPEG9MA / DE) was 29.4 / 0.1 / 14.6 / 55.9.

[0077] (Production of dispersant IV)

[0078] Dispersant IV was produced in the same manner as dispersant I except that DMAPAA was used instead of 4VPy. The mass ratio of each constituting unit of dispersant IV (MMA / BMA / MPEG9MA / DMAPAA) was 35.3 / 0.1 / 17.5 / 47.1.

[0079] (Production of dispersant V)

[0080] Dispersant V was produced in the same manner as dispersant I except that DMAPMA was used instead of 4VPy. The mass ratio of each constituting unit of dispersant V (MMA / BMA / MPEG9MA / DMAPMA) was 32.5 / 0.1 / 16.1 / 51.3.

[0081] (Production of dispersant VI)

[0082] The dispersant VI was produced in the same manner as the dispersant I except that PMPMA was used instead of 4VPy. The mass ratio of each constituent unit of the dispersant VI (MMA / BMA / MPEG9MA / PMPMA) was 38.2 / 0.1 / 18.9 / 42.8.

[0083] [Example]

[0084] A polyethylene container was charged with 12 parts by mass of a lactam black, 7.2 parts by mass of the dispersant I as a dispersant, and PMA as a solvent. The amount of PMA was adjusted so that the total of the lactam black, the dispersant, and the solvent was 100 parts by mass. A zirconia ball (φ 0.3 mm) was added to the container, and a paint shaker manufactured by Hatta Tekko Co., Ltd. was used to perform dispersion treatment for 90 minutes, thereby obtaining a black pigment dispersion of the example (lactam black concentration: 12 mass%, dispersant concentration: 7.2 mass%).

[0085] [Comparative Example 1]

[0086] A black pigment dispersion of Comparative Example 1 was obtained in the same manner as the example except that 7.2 parts by mass of the dispersant II as a dispersant was used. In addition, the black pigment dispersions of Comparative Examples 1 to 5 each had a lactam black concentration of 12 mass% and a dispersant concentration of 7.2 mass%.

[0087] [Comparative Example 2]

[0088] A black pigment dispersion of Comparative Example 2 was obtained in the same manner as the example except that 7.2 parts by mass of the dispersant III as a dispersant was used.

[0089] [Comparative Example 3]

[0090] A black pigment dispersion of Comparative Example 3 was obtained in the same manner as the example except that 7.2 parts by mass of the dispersant IV as a dispersant was used.

[0091] [Comparative Example 4]

[0092] A black pigment dispersion of Comparative Example 4 was obtained in the same manner as the example except that 7.2 parts by mass of the dispersant V as a dispersant was used.

[0093] [Comparative Example 5]

[0094] A black pigment dispersion of Comparative Example 5 was obtained in the same manner as the example except that 7.2 parts by mass of the dispersant VI as a dispersant was used.

[0095] <Particle diameter measurement of the lactam black>

[0096] After diluting the black pigment dispersions of Examples and Comparative Examples 1 to 5 with PMA to a concentration range of 0.001 to 10 mass%, the average particle diameter (cumulative amount average particle diameter; average particle diameter according to the cumulative amount analysis method) was measured using FPAR-1000 manufactured by Otsuka Electronics Co., Ltd. The average particle diameter measurement was performed at the time of just preparation, and after storage in a constant temperature chamber at 40°C for 1 week.

[0097] <Viscosity measurement of the black pigment dispersion>

[0098] The viscosity (25°C) of the black pigment dispersions of Examples and Comparative Examples 1 to 5 was measured at the time of just preparation, and after storage in a constant temperature chamber at 40°C for 1 week, using an E-type viscometer (TV-22) manufactured by Toyo Seiki Co., Ltd.

[0099] The average particle diameter and viscosity measurement results of the lactam black for the black pigment dispersions of Examples and Comparative Examples 1 to 5 are shown in Table 3.

[0100] [Table 3]

[0101] .

[0102] The black pigment dispersions other than the Examples gelled at the time of preparation, and the average particle diameter of the lactam black and the viscosity of the dispersion could not be measured.

[0103] The average particle diameter of the lactam black for the black pigment dispersions of the Examples was 148 nm and 146 nm at the time of preparation and after storage at 40°C, and hardly changed. Also, the initial viscosity was 5.06 mPa s, and the viscosity after storage at 40°C was 5.22 mPa s, and the viscosity hardly changed (viscosity change rate was 5.22 / 5.06 = 1.03).

[0104] As shown in Table 3, it was confirmed that the dispersion using the lactam black as the black pigment gelled at the time of preparation depending on the type of the dispersant used, but in the case of combining with the dispersant which is a copolymer of Monomers A to C, the average particle diameter and the viscosity of the lactam black hardly changed even in storage.

[0105] If the content (concentration) of the lactam black in the black pigment dispersion is 5 mass% or more and 25 mass% or less, the average particle diameter and the viscosity of the lactam black also hardly change in storage, as with the black pigment dispersion of the Examples.

[0106] The average particle diameter of the lactam black is preferably 200 nm or less, and further preferably 160 nm or less, from the viewpoint of optical concentration and surface smoothness.

[0107] The rate of change in viscosity of the black pigment dispersion (viscosity after storage in a constant-temperature chamber at 40°C for 1 week / viscosity immediately after preparation (25°C)) is preferably 0.8 to 1.2 times, further preferably 0.9 to 1.1 times.

[0108] Industrial applicability:

[0109] The black pigment dispersion of the present application is useful in technical fields such as displays, solid-state imaging elements, infrared sensors, and the like.

Claims

1. A black pigment dispersion, characterized in that, It is a black pigment dispersion containing at least black pigment, dispersant and solvent; The black pigment is lactam black; The dispersant is a copolymer composed of the following: Monomer A; Monomer B, possessing a nitrogen-containing aromatic heterocyclic group as its basic functional group; and Monomer C that can polymerize with both A and B; In the black pigment dispersion The monomer A is methoxy polyethylene glycol methacrylate MPEG9MA. The monomer B is 4-vinylpyridine 4Vpy. The monomer C is methyl methacrylate (MMA) and butyl methacrylate (BMA); The content of monomers A to C in the mass fraction of the dispersant 100 is as follows: The monomer A is 20 to 60 parts by mass; The monomer B is 10 to 40 parts by mass; The monomer C is 20 to 60 parts by mass.

2. The black pigment dispersion according to claim 1, characterized in that, The average particle size of lactam black is less than 200 nm.

3. The black pigment dispersion according to claim 1, characterized in that, The content of the black pigment is more than 5% by mass and less than 25% by mass.