Pigment dispersion liquid

Abstract

To provide a pigment dispersion that is excellent in dispersion stability and re-dispersibility, and is useful for gloss control.SOLUTION: A pigment dispersion contains a solvent (A), a pigment (B) with an oil absorption of 50 ml / 100 g or more and a dispersant (C). The dispersant (C) is a combination of a dispersant (c-1) and a dispersant (c-2) each having a specific weight average molecular weight.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a pigment dispersion liquid having excellent dispersion stability and redispersibility.

Background Art

[0002] Conventionally, for the protection of the frameworks of buildings, civil engineering structures, etc., for imparting design properties, and for improving aesthetics, painting finishes have been carried out, and various solvent-based coating materials have been widely used because they have excellent coating film physical properties.

[0003] In such coating materials, it is necessary to provide coating materials suitable for a wide variety of conditions. For example, even for coating materials of the same variety, it is necessary to prepare and correspond to those suitable for each gloss, such as glossy, 70% gloss, 50% gloss, 30% gloss, matte, etc.

[0004] In such a case, separately from the coating material, a pigment dispersion liquid for gloss adjustment can be prepared and, if necessary, mixed with the coating material for use. For example, in Patent Document 1, for example, a method of mixing a coating material and a matting agent to adjust the gloss is described.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In many cases, such pigment dispersion liquids have problems with dispersion stability and redispersibility. In particular, for pigment dispersion liquids for gloss adjustment, improvement of dispersion stability and redispersibility has been a problem.

Means for Solving the Problems

[0007] As a result of intensive studies, the present inventors have found that a pigment dispersion liquid excellent in dispersion stability and redispersibility and effective for gloss adjustment can be obtained by using a solvent and a pigment as essential components and further using a specific dispersant in combination, and have thus completed the present invention.

[0008] That is, the present invention has the following features. 1. A pigment dispersion liquid containing a solvent (A), a pigment (B) having an oil absorption of 50 ml / 100 g or more, and a dispersant (C), The solvent (A) has a proportion of aliphatic hydrocarbons of 30% by weight or more, wherein the dispersant (C) includes a dispersant (c-1) having a weight average molecular weight of 5000 or more and a dispersant (c-2) having a weight average molecular weight of less than 5000, and characterized by containing the same. 2. The pigment dispersion liquid according to 1, wherein the mixing ratio (weight ratio) of the solvent (A) to the pigment (B) is 0.5 part by weight or more and 50 parts by weight or less of the pigment (B) with respect to 100 parts by weight of the solvent (A). 3. The pigment dispersion liquid according to 1 or 2, wherein the mixing ratio (weight ratio) of the solvent (A) to the dispersant (C) is 0.1 part by weight or more and 20 parts by weight or less of the dispersant (C) with respect to 100 parts by weight of the solvent (A). 4. The pigment dispersion liquid according to any one of 1 to 3, wherein the mixing ratio (weight ratio) of the dispersant (c-1) to the dispersant (c-2) is (c-1):(c-2) = 1:9 to 9:1.

Effects of the Invention

[0009] The pigment dispersion liquid of the present invention is excellent in dispersion stability and redispersibility and is effective for gloss adjustment.

Modes for Carrying Out the Invention

[0010] Hereinafter, modes for carrying out the present invention will be described.

[0011] The pigment dispersion of the present invention contains a solvent (A), a pigment (B) having an oil absorption of 50 ml / 100 g or more, and a dispersant (C), and is characterized in that the dispersant (C) contains a dispersant (c-1) having a weight average molecular weight of 5000 or more and a dispersant (c-2) having a weight average molecular weight of less than 5000. By using such a dispersant (c-1) and dispersant (c-2) in combination, a dispersant excellent in dispersion stability and redispersibility can be obtained.

[0012] The solvent (A) is not particularly limited, and an aromatic hydrocarbon solvent, an aliphatic hydrocarbon solvent, etc. can be used. Examples of the aromatic hydrocarbon solvent include toluene, xylene, benzene, ethylbenzene, ethyltoluene, cumene, cymene, trimethylbenzene, naphthalene, chlorobenzene, dichlorobenzene, benzyl phenyl ether, benzyl methyl ether, methyl phenyl ether, ethyl phenyl ether, propyl phenyl ether, butyl phenyl ether, 1,2-methylenedioxybenzene, 1,2-ethylenedioxybenzene, dibenzyl ether, diphenyl ether, etc., and one or more of these can be used. Examples of the aliphatic hydrocarbon solvent include n-butane, n-hexane, n-pentane, n-octane, isooctane, n-nonane, isononane, n-decane, isodecane, n-undecane, n-dodecane, cyclopentane, cyclohexane, cyclobutane, etc., and one or more of these can be used. Moreover, examples of those having an aliphatic hydrocarbon solvent as the main component include terpene oil, mineral spirit, white spirit, mineral terpene, isoparaffin, petroleum ether, solvent naphtha, petroleum naphtha, etc., and one or more of these can be used.

[0013] In particular, in the present invention, a solvent in which 30% by weight or more (preferably 40% by weight or more, more preferably 50% by weight or more) of the total solvent is an aliphatic hydrocarbon solvent is preferred. Furthermore, a mixture of an aliphatic hydrocarbon solvent and an aromatic hydrocarbon solvent is preferred, and the mixing ratio (weight ratio) is such that aliphatic hydrocarbon solvent: aromatic hydrocarbon solvent is from 90:10 to 30:70, more preferably from 85:15 to 40:60, and even more preferably from 80:20 to 50:50, and such a solvent can be preferably used. A solvent having such a mixing ratio can provide a pigment dispersion excellent in dispersion stability and redispersibility, without adversely affecting the color and physical properties of the coating film, and exhibits an excellent effect on the gloss adjustment function. Furthermore, those which do not contain toluene and xylene and correspond to the second petroleum oils having a flash point of 21°C or higher are preferable from the viewpoints of safety and hygiene.

[0014] In addition, as the solvent (A), alicyclic hydrocarbon solvents such as cyclohexane, cyclohexene, methylcyclohexane, and ethylcyclohexane, ester solvents such as ethyl acetate, butyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, alcohol solvents such as butanol, isopropyl alcohol, and cyclohexanol, and glycol solvents such as ethylene glycol monobutyl ether and propylene glycol monomethyl ether can also be included to the extent that the effects of the present invention are not impaired.

[0015] As the pigment (B), a pigment having an oil absorption of 50 ml / 100 g or more (more preferably 100 ml / 100 g or more, even more preferably 150 ml / 100 g or more) is used. By using such a pigment, a pigment dispersion effective for gloss adjustment can be obtained. In the present invention, even when such a pigment is used, a pigment dispersion excellent in dispersion stability and redispersibility and effective for gloss adjustment can be obtained by using the dispersant (c-1) and the dispersant (c-2) in combination. Examples of the pigment (B) include zeolite, sodium sulfate, alumina, allophane, white carbon, diatomaceous earth, wollastonite, siliceous shale, vermiculite, perlite, otani stone powder, activated clay, charcoal, activated carbon, wood powder, shirasu balloon, calcium carbonate, kaolin, clay, pottery clay, china clay, talc, barite powder, barium sulfate, barium carbonate, magnesium carbonate, silica powder, aluminum hydroxide, etc. One or more of these can be used. The oil absorption amount is a value measured according to JIS K 5101-13-1 (refined linseed oil method).

[0016] The average particle diameter of the pigment (B) is not particularly limited, but it is preferably 1 μm or more and 30 μm or less (more preferably 1.5 μm or more and 20 μm or less, still more preferably 2 μm or more and 15 μm or less). By using such a pigment (B), the present invention can obtain a pigment dispersion excellent in dispersion stability, redispersibility, and gloss adjustment.

[0017] The mixing ratio (weight ratio) of the solvent (A) and the pigment (B) is preferably 0.5 part by weight or more and 50 parts by weight or less of the pigment (B) with respect to 100 parts by weight of the solvent (A), more preferably 1 part by weight or more and 45 parts by weight or less, still more preferably 3 parts by weight or more and 40 parts by weight or less, and most preferably 5 parts by weight or more and 35 parts by weight or less. Within such a range, it is excellent in storage stability, redispersibility, and gloss adjustment, which is preferable.

[0018] The dispersant (C) is characterized by containing a dispersant (c-1) having a weight average molecular weight of 5000 or more and a dispersant (c-2) having a weight average molecular weight of less than 5000.

[0019] Examples of the dispersant (C) include one or more selected from polyester polyol, polyether polyol, and acrylic polyol, or their amine salts, metal salts, a polycondensate of a polyvalent carboxylic acid and one or more selected from polyester polyol, polyether polyol, and acrylic polyol, or their amine salts, metal salts, The reaction product of a polymer containing an acid and one or more selected from polyhydric alcohols, polyester polyols, polyether polyols, and acrylic polyols, or its amine salt, metal salt, The polycondensate of an amine and a polyhydric alcohol, or its carboxylate, sulfonate, phosphate and the like can be mentioned.

[0020] Examples of the polyester polyol include those obtained by reacting a polyhydric carboxylic acid and a polyhydric alcohol, ring-opening polymers of cyclic esters (lactones), those obtained by reacting a polyhydric alcohol, a polyhydric carboxylic acid, and a cyclic ester, or their alkylene oxide adducts and the like. Examples of the polyhydric carboxylic acid include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, phthalic acid, terephthalic acid, isophthalic acid, hexahydrophthalic acid, tetrahydrophthalic acid, itaconic acid, lactic acid, citric acid, fumaric acid, maleic acid, cinnamic acid, hexanetricarboxylic acid, trimellitic acid, octanetetracarboxylic acid, pyromellitic acid, cyclobutanedicarboxylic acid, cyclopentanedicarboxylic acid, cyclohexanetricarboxylic acid, naphthalenedicarboxylic acid, naphthalenetricarboxylic acid, etc. One or more of these can be used. Examples of the polyhydric alcohol include ethanediol, propanediol, butanediol, pentanediol, neopentyl glycol, hexanediol, heptanediol, octanediol, decanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butene-1,4-diol, 2-butyne-1,4-diol, diethylene glycol, triethylene glycol, tetraethylene glycol, dibutylene glycol, tributylene glycol, tetrabutylene glycol, dihexylene glycol, trihexylene glycol, tetrahexylene glycol, glycerin, trimethylolpropane, trimethylolethane, butanetriol, pentaerythritol, dipentaerythritol, hydroquinone, resorcinol, catechol, naphthalenediol, biphenol, bisphenol A, bisphenol F, tetramethylbiphenol, etc., and also ethylene oxide adducts, hydrogenated products, etc. of these, and one or more of these can be used. In the ring-opening polymer of the cyclic ester, examples of the cyclic ester include propiolactone, β-methyl-δ-valerolactone, ε-caprolactone, etc.

[0021] Examples of the polyether polyol include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol monoalkyl ether, polypropylene glycol monoalkyl ether, those obtained by adding alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide using the above polyhydric alcohol as an initiator, and copolymers of alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide.

[0022] Examples of the acrylic polyol include polymers or copolymers of monomers containing a hydroxyl group-containing monomer, reactants of a carboxylic acid-containing monomer and a polyalkylene glycol, and the like. Examples of the monomer containing a hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, 2-hydroxy-2-methylpropyl (meth)acrylate, glycerol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol (meth)acrylate, caprolactone-modified (meth)acrylate, N-hydroxyethylacrylamide, and the like. One or more of these can be used. Examples of the carboxylic acid-containing monomer include (meth)acrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, and the like. One or more of these can be used. Examples of the polyalkylene glycol include polyethylene glycol, polypropylene glycol, polybutylene glycol, and the like. One or more of these can be used.

[0023] Examples of the polymer containing an acid include polymers of monomers containing a carboxylic acid-containing monomer such as (meth)acrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, and the like. In addition, as the polymer containing an acid, a polymer obtained by copolymerizing the above hydroxyl group-containing monomer and other known polymerizable monomers can also be used.

[0024] Examples of the amine include ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, neopentyldiamine, toluenediamine, diethyltoluenediamine, 4,4'-diaminodiphenylmethane, p-phenylenediamine, o-phenylenediamine, naphthalenediamine, triethanolamine, Mannich condensate, etc. One or more of these can be used.

[0025] In the production of the above dispersant, in addition to known catalysts and polymerization catalysts, components such as isocyanate-containing compounds, amine-containing compounds, phosphoric acid-containing compounds, and sulfonic acid-containing compounds can also be mixed and produced.

[0026] The dispersant (c-1) is a dispersant having a weight average molecular weight of 5000 or more, preferably 5000 or more and 50000 or less, more preferably 6000 or more and 40000 or less, and still more preferably 8000 or more and 30000 or less. By using a dispersant within such a range, a pigment dispersion excellent in dispersion stability, redispersibility, particularly redispersibility at low temperatures can be obtained. The weight average molecular weight is a value obtained by measurement using gel permeation chromatography.

[0027] Further, as the dispersant (c-1), it is preferably one having an acid value and a hydroxyl value. In particular, the acid value is preferably 0.1 mgKOH / g or more and 8 mgKOH / g or less (more preferably 0.2 mgKOH / g or more and 5 mgKOH / g or less), and the hydroxyl value is preferably 8 mgKOH / g or more and 100 mgKOH / g or less (more preferably 10 mgKOH / g or more and 50 mgKOH / g or less). Within such a range, it is excellent in redispersibility and redispersibility, which is preferable. Further, the dispersant (c-1) may have an amine value. When it has an amine value, the amine value is preferably 0.05 mgKOH / g or more and 10 mgKOH / g or less (more preferably 0.1 mgKOH / g or more and 5 mgKOH / g or less). Incidentally, the acid value is a value represented by the number of milligrams of potassium hydroxide equimolar to the acid groups contained in 1 g of the solid content, the hydroxyl value is a value represented by the number of milligrams of potassium hydroxide equimolar to the hydroxyl groups contained in 1 g of the solid content, and the amine value is a value represented by the number of milligrams of potassium hydroxide equivalent to the base equimolar to the amine groups contained in 1 g of the solid content.

[0028] In particular, in the present invention, as the dispersant (c-1), one or more selected from polyester polyol, polyether polyol, and acrylic polyol, a polycondensate of a polyvalent carboxylic acid and one or more selected from polyester polyol, polyether polyol, and acrylic polyol, and a reaction product of a polymer containing an acid and one or more selected from polyhydric alcohol, polyester polyol, polyether polyol, and acrylic polyol, one or more selected therefrom can be preferably used.

[0029] The dispersant (c-2) is a dispersant having a weight average molecular weight of less than 5000, preferably 500 or more and less than 5000, and more preferably 600 or more and 4000 or less. By using a dispersant within such a range, a pigment dispersion excellent in dispersion stability and redispersibility can be obtained.

[0030] Further, as the dispersant (c-2), it is preferably one having an acid value and an amine value. In particular, the acid value is 8 mgKOH / g or more and 50 mgKOH / g or less (more preferably 10 mgKOH / g or more and 40 mgKOH / g or less), and the amine value is 8 mgKOH / g or more and 50 mgKOH / g or less (more preferably 10 mgKOH / g or more and 40 mgKOH / g or less). If it is within such a range, it is excellent in redispersibility and redispersibility and is preferable. Further, as the dispersant (c-2), it may have a hydroxyl value. When it has a hydroxyl value, the hydroxyl value is preferably 0.05 mgKOH / g or more and 10 mgKOH / g or less (more preferably 0.1 mgKOH / g or more and 5 mgKOH / g or less).

[0031] In particular, in the present invention, as the dispersant (C-2), one or more amine salts selected from polyester polyols, polyether polyols, and acrylic polyols, amine salts of polycondensates of polyvalent carboxylic acids and one or more selected from polyester polyols, polyether polyols, and acrylic polyols, amine salts of reaction products of polymers containing acids and one or more selected from polyhydric alcohols, polyester polyols, polyether polyols, and acrylic polyols, polycondensates of amines and polyhydric alcohols or their carboxylates, sulfonates, and phosphates, one or more selected therefrom can be preferably used.

[0032] The mixing ratio (weight ratio) of the solvent (A) and the dispersant (C) is not particularly limited, but it is preferably 0.1 part by weight or more and 20 parts by weight or less, more preferably 0.5 part by weight or more and 18 parts by weight or less, still more preferably 1 part by weight or more and 16 parts by weight or less, and most preferably 3 parts by weight or more and 15 parts by weight or less, based on 100 parts by weight of the solvent (A). If it is within such a range, it is excellent in dispersion stability and redispersibility, especially redispersibility at low temperatures, which is preferable. Also, the mixing ratio (weight ratio) of the dispersant (C-1) and the dispersant (C-2) is preferably such that the ratio of dispersant (C-1):dispersant (C-2) is from 1:9 to 9:1 (more preferably from 2:8 to 8:2). If it is within such a range, it is excellent in storage stability and redispersibility, especially redispersibility at low temperatures, which is preferable.

[0033] The pigment dispersion of the present invention can be prepared by mixing the solvent (A), the pigment (B), and the dispersant (C), and other additives if necessary, and dispersing them with a dispersing device. As the dispersing device, known devices such as an attritor, a ball mill, a sand mill, a homomixer, and a paint shaker can be used.

[0034] The viscosity of the pigment dispersion is not particularly limited, but it is preferably 0.5 Pa·s or more and 10 Pa·s or less. The viscosity is a value measured with a B-type rotational viscometer (rotation speed: 20 rpm) at a temperature of 23°C and a relative humidity of 50%RH. Also, the thixotropy index (TI value) of the pigment dispersion is not particularly limited, but is preferably 3 or more and 10 or less. The TI value is a value obtained by the following formula using a B-type rotational viscometer at a temperature of 23°C and a relative humidity of 50%RH. (Formula) TI value = η1 / η2 (However, η1: Viscosity at 2 rpm (Pa·s: Pointer value at the second rotation), η2: Viscosity at 20 rpm (Pa·s: Pointer value at the fourth rotation))

[0035] Examples of the additive include synthetic resins, preservatives, fungicides, algicides, defoamers, leveling agents, anti-settling agents, anti-dripping agents, catalysts, curing accelerators, dehydrating agents, ultraviolet absorbers, light stabilizers, and the like.

Examples

[0036] Examples are shown below to clarify the features of the present invention. In the production of the pigment dispersion, the following components were used.

[0037] · Solvent A: Aromatic hydrocarbon solvent / aliphatic hydrocarbon (mineral spirit) mixed solution (ratio of aliphatic hydrocarbon: 88% by weight, aliphatic hydrocarbon solvent: aromatic hydrocarbon solvent is 88:12) · Solvent B: Aromatic hydrocarbon solvent / mineral spirit mixed solution (ratio of aliphatic hydrocarbon: 70% by weight, aliphatic hydrocarbon solvent: aromatic hydrocarbon solvent is 70:30) · Pigment A: White carbon (oil absorption 210 ml / 100 g, average particle diameter 10 μm) · Pigment B: Wollastonite (oil absorption 56 ml / 100 g, average particle diameter 5 μm) · Pigment C: Calcium carbonate (oil absorption 25 ml / 100 g, average particle diameter 10 μm) · Dispersant A: Acrylic polyol, acid value 3 mgKOH / g, hydroxyl value 35 mgKOH / g, weight average molecular weight 11000 · Dispersant B: Acrylic polyol, acid value 2 mgKOH / g, hydroxyl value 30 mgKOH / g, weight average molecular weight 13000 · Dispersant C: Polyester polyol, acid value 6 mg KOH / g, hydroxyl value 25 mg KOH / g, weight average molecular weight 7000 · Dispersant D: Amine salt of acrylic polyol, acid value 20 mg KOH / g, hydroxyl value 5 mg KOH / g, amine value 30 mg KOH / g, weight average molecular weight 4500 · Dispersant E: Amine salt of polyester polyol, acid value 15 mg KOH / g, amine value 20 mg KOH / g, weight average molecular weight 3000 · Dispersant F: Amine salt of polyester polyol, acid value 20 mg KOH / g, amine value 25 mg KOH / g, weight average molecular weight 2000 · Solvent-based coating material A: One-component weakly solvent-based acrylic resin coating material (white) (proportion of aliphatic hydrocarbons in the solvent: 70% by weight)

[0038] (Examples 1 - 12, Comparative Examples 1 - 3) Using the above components, they were mixed at the blending ratios shown in Table 1 and dispersed with a dissolver for 1 hour under standard conditions (temperature 25°C, relative humidity 50%) to obtain a pigment dispersion. The following tests were conducted on the pigment dispersion.

[0039] (Dispersion stability test) The pigment dispersion was placed in a 1000 ml container, sealed, and after storing for 1 day under standard conditions, the internal state of the container was visually confirmed. The evaluation is as follows. The results are shown in Table 2. ◎: No abnormality ○: Almost no abnormality △: Some abnormality (some precipitates) ×: Abnormality (sediment formation, separation)

[0040] (Redispersibility test 1) The pigment dispersion was placed in a 1000 ml container, sealed, and after storing for 30 days under standard conditions, it was vibrated at 10 Hz for 30 seconds using a paint shaker, and the internal state of the container was visually confirmed. The evaluation is as follows. The results are shown in Table 2. ◎: No abnormality ○: Almost no abnormality △: Some abnormality (some precipitates) ×: Presence of abnormality (sediment generation, separation generation)

[0041] (Redispersibility test 2) The pigment dispersion was put into a 1000 ml container, sealed, stored at a temperature of 5°C for 30 days, then vibrated at 10 Hz for 30 seconds using a paint shaker, and the state inside the container was visually confirmed. The evaluation is as follows. The results are shown in Table 2. ◎: No abnormality ○: Almost no abnormality △: Partially abnormal (with some sediment) ×: Presence of abnormality (sediment generation, separation generation)

[0042] (Matting property test 1) 10 parts by weight of the pigment dispersion after the redispersibility test 1 was mixed with 90 parts by weight of the solvent-based coating material A described above to prepare a coating material. This coating material was spray-coated on a slate plate pre-coated with a sealer at an application rate of 0.3 kg / m2 and then dried for 14 days under standard conditions to obtain a test specimen. Also, for only the solvent-based coating material A without using the pigment dispersion, a comparative test specimen was prepared by spray-coating on a slate plate pre-coated with a sealer at an application rate of 0.3 kg / m2 and then drying for 14 days under standard conditions. For the obtained test specimen and comparative test specimen, the 20-degree gloss was measured at 10 points each, and the difference in the average values was compared and evaluated. The evaluation is as follows. The results are shown in Table 2. ◎: The difference is 10 or more ○: The difference is 5 or more and less than 10 △: The difference is 3 or more and less than 50 ×: The difference is less than 3

[0043] (Matting property test 2) The test was conducted in the same manner as in the matting property test 1, except that the pigment dispersion after the redispersibility test 2 was used as the pigment dispersion. The results are shown in Table 2.

[0044]

Table 1

Claims

1. A pigment dispersion liquid containing a solvent (A), a pigment (B) having an oil absorption of 50 ml / 100 g or more, and a dispersant (C), wherein the proportion of aliphatic hydrocarbons in the solvent (A) is 30% by weight or more, and the dispersant (C) includes a dispersant (c-1) having a weight average molecular weight of 5000 or more and a dispersant (c-2) having a weight average molecular weight of less than 5000. The pigment dispersion liquid is characterized by including the above.

2. The pigment dispersion liquid according to Claim 1, wherein the mixing ratio (weight ratio) of the solvent (A) and the pigment (B) is 0.5 parts by weight or more and 50 parts by weight or less of the pigment (B) with respect to 100 parts by weight of the solvent (A).

3. The pigment dispersion liquid according to Claim 1 or Claim 2, wherein the mixing ratio (weight ratio) of the solvent (A) and the dispersant (C) is 0.1 parts by weight or more and 20 parts by weight or less of the dispersant (C) with respect to 100 parts by weight of the solvent (A).

4. The pigment dispersion liquid according to any one of Claims 1 to 3, wherein the mixing ratio (weight ratio) of the dispersant (c-1) and the dispersant (c-2) is such that (c-1):(c-2) is 1:9 to 9:1.

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