JP7575940B2 - Composite Resin Dispersion - Google Patents

Description

The present invention relates to a composite resin dispersion and a water-based ink.

Inkjet recording is a method of printing characters and images by ejecting ink droplets from extremely fine nozzles directly onto a recording medium. This method has become extremely popular due to its many advantages, including the ease of full-color printing, low cost, the ability to use plain paper as a recording medium, and no contact with the substrate.
In recent years, water-based pigment inks that use pigments as colorants and polymers to disperse the pigments have been attracting attention from the perspective of imparting weather resistance and water resistance to printed matter and reducing the burden on the working environment and the natural environment.

On the other hand, water-based pigment dispersions and water-based pigment inks have problems such as poor storage stability due to the presence of coarse particles derived from pigments and polymers.
Furthermore, in the commercial printing and industrial printing markets, low liquid-absorbent recording media such as resin films are widely used, but water-based pigment inks have poor adhesion to low liquid-absorbent recording media, particularly to polar resin films such as polyvinyl chloride (PVC), and the ink coating is prone to peeling off from the recording medium, impairing the aesthetic appeal of the recorded matter.
Therefore, various proposals have been made to improve these problems.
For example, Patent Literature 1 discloses an aqueous pigment dispersion having excellent storage stability and having a high print density while maintaining excellent adhesion to a non-water-absorbent print medium when used in an aqueous ink, the aqueous pigment dispersion being obtained by dispersing a pigment in an aqueous medium with a polymer dispersant, the polymer dispersant containing a (meth)acrylic resin and a polyester resin.

JP 2019-119890 A

Since the inkjet recording method is suitable for recording a wide variety of products in small quantities, the range of recording media for which it is applicable is expanding. As the range of applications expands, there is a demand for improved recording density and solvent resistance in commercial and industrial printing using low-absorbency resin films, etc.
Conventional water-based pigment dispersions and water-based inks using the same described in Patent Document 1 and the like have been desired to be further improved in terms of storage stability, adhesion to low-liquid-absorbent recording media, recording density, and solvent resistance.
An object of the present invention is to provide a composite resin dispersion and a water-based ink that can improve the storage stability of a water-based ink and give a recorded matter that is excellent in adhesion to a low water-absorbent recording medium, recording density, and solvent resistance.

The present inventors have found that, in a composite resin dispersion containing a polyester resin segment and a (meth)acrylic resin segment, the above-mentioned problem can be solved by including 3-methyl-1,5-pentanediol in an alcohol component constituting the polyester resin segment.
That is, the present invention provides the following [1] and [2].
[1] A composite resin dispersion comprising composite resin particles containing a polyester resin (A) segment and a (meth)acrylic resin (B) segment,
The alcohol component constituting the polyester resin (A) contains at least 3-methyl-1,5-pentanediol.
[2] A water-based ink containing composite resin particles and a pigment,
the composite resin comprises a polyester resin (A) segment and a (meth)acrylic resin (B) segment, the polyester resin (A) comprises a structural unit derived from an alcohol component and a structural unit derived from a carboxylic acid component, and the alcohol component comprises at least 3-methyl-1,5-pentanediol.

The present invention provides a composite resin dispersion and a water-based ink that can improve the storage stability of water-based inks and produce printed matter that has excellent adhesion to low-water-absorbency recording media, recording density, and solvent resistance.

[Composite resin dispersion]
The composite resin dispersion of the present invention is a composite resin dispersion containing composite resin particles containing a polyester resin (A) segment and a (meth)acrylic resin (B) segment,
The alcohol component constituting the polyester resin (A) contains at least 3-methyl-1,5-pentanediol.
Since the composite resin dispersion of the present invention can exert the above-mentioned effects even on low water-absorbent recording media, it can be used for inkjet recording, flexographic printing, gravure printing, etc., and is preferably used for inkjet recording.
In this specification, the term "recording" refers to a concept that includes printing and printing out characters and images, and the term "recorded matter" refers to a concept that includes printed matter and printed matter on which characters and images are recorded.
By "water-based" it is meant that water constitutes the largest proportion of the medium contained in the ink.
In addition, the term "low water absorption" is a concept that includes low liquid absorption and non-liquid absorption, and means that the amount of water absorption of the recording medium when the recording medium is in contact with pure water for 100 ms is 0 g/m2 or ^more and 10 g/m2 ^or less.

The composite resin dispersion of the present invention improves the storage stability of the water-based ink and makes it possible to obtain a recorded matter that is excellent in adhesion to a low water-absorbent recording medium, recording density, and solvent resistance. Although the reason for this is unclear, it is thought to be as follows.
In water-based pigment inks, when polyester resin is used as a pigment dispersion polymer, the main chain is cut due to hydrolysis of the polyester resin, and the molecular weight is significantly reduced over time. As a result, even if the polyester resin is adsorbed to the pigment, the adsorption state cannot be stably maintained for a long period of time, and the pigment and polymer gradually aggregate, resulting in the problem of generating coarse particles. As a means of preventing aggregation due to hydrolysis of the polyester resin, it is possible to combine it with other polymers, but for example, in the case of combining a polyester resin with a (meth)acrylic resin, there is a problem that the desired effect cannot be obtained because hydrolysis is unavoidable with a general polyester resin.

The present inventors have found that by using a composite resin containing a polyester resin (A) segment and a (meth)acrylic resin (B) segment as a composite resin dispersion and by including 3-methyl-1,5-pentanediol in the alcohol component constituting the polyester resin (A), the generation of coarse particles due to aggregation can be suppressed.
This is believed to be because the methyl group at the center of 3-methyl-1,5-pentanediol suppresses the affinity with the aqueous medium and also suppresses hydrolysis of the polyester resin (A), stabilizing the composite resin.
For this reason, when an aqueous ink containing the composite resin dispersion of the present invention is applied to a low water-absorbent recording medium, etc., in the resin coating film formed by drying the composite resin dispersion of the present invention, the polyester resin (A) segment portion strongly interacts with the low water-absorbent recording medium, which is thought to improve the adhesion of the aqueous ink.
In addition, the composite resin has excellent solvent resistance, and the (meth)acrylic resin (B) segment is considered to enhance the dispersion stability of the composite resin particles in the ink vehicle. As a result, it is considered that the water-based ink containing the composite resin dispersion of the present invention has excellent storage stability, and can provide recorded matter having excellent adhesion to low water-absorbent recording media, recording density, and solvent resistance.

<Composite Resin Particles>
The composite resin particles according to the present invention contain a polyester resin (A) segment and a (meth)acrylic resin (B) segment.
The composite resin is preferably a water-insoluble polymer.
Here, the term "water-insoluble" of a polymer means that when a polymer that has been dried at 105° C. for 2 hours and has reached a constant weight is dissolved in 100 g of water at 25° C., the amount of dissolution is 10 g or less, and the amount of dissolution of the polymer is preferably 5 g or less, more preferably 1 g or less. When the polymer is an anionic polymer, the amount of dissolution is the amount of dissolution when the anionic groups of the polymer are 100% neutralized with sodium hydroxide.

The mass ratio [(A)/(B)] of the polyester resin (A) segment to the (meth)acrylic resin (B) segment in the composite resin is preferably 20/80 or more, more preferably 30/70 or more, even more preferably 40/60 or more, even more preferably 50/50 or more, from the viewpoint of improving the storage stability of the water-based ink and obtaining a recorded matter having excellent adhesion to a low water-absorbency recording medium, recording density, and solvent resistance, and is preferably 98/2 or less, more preferably 95/5 or less, even more preferably 90/10 or less, and even more preferably 85/15 or less.

[Polyester Resin (A) Segment]
The polyester resin (A) segment contains a structural unit derived from an alcohol component and a structural unit derived from a carboxylic acid component, and can be obtained by polycondensation of the alcohol component and the carboxylic acid component.

(Alcohol content)
The alcohol component, which is a raw material monomer constituting the polyester resin (A), contains at least 3-methyl-1,5-pentanediol from the viewpoint of improving the storage stability of the water-based ink and obtaining a recorded matter having excellent adhesion to a low water-absorbency recording medium, recording density, and solvent resistance. 3-methyl-1,5-pentanediol is a diol that is an isomer of 1,6-hexanediol, and is considered to exhibit amorphousness due to the influence of the methyl group at its center, suppress the affinity with water-based media, and also suppress hydrolysis of the polyester resin (A), thereby stabilizing the composite resin.
From the same viewpoints as above, the content of 3-methyl-1,5-pentanediol in the alcohol component is preferably 30 mol% or more, more preferably 35 mol% or more, even more preferably 40 mol% or more, still more preferably 45 mol% or more, and preferably 85 mol% or less, more preferably 80 mol% or less, even more preferably 75 mol% or less, and still more preferably 70 mol% or less.

The alcohol component, which is a raw material monomer for the polyester resin (A), may contain other alcohol components in addition to 3-methyl-1,5-pentanediol.
As the other alcohol component, an aromatic diol is preferable, and an alkylene oxide adduct of bisphenol A is more preferable.
The alkylene oxide adduct of bisphenol A is a compound having a structure in which an oxyalkylene group is added to 2,2-bis(4-hydroxyphenyl)propane, and specifically, a compound represented by the following general formula (I) is preferred.

In formula (I), OR ¹ and R ² O each independently represent an oxyalkylene group having from 1 to 4 carbon atoms, and are preferably an oxyethylene group or an oxypropylene group.
x and y are the number of moles of alkylene oxide added, and each is independently a positive number of 0 or more. From the viewpoint of reactivity with the carboxylic acid component, the average value of the sum of x and y is preferably 2 or more, and is preferably 7 or less, more preferably 5 or less, and further preferably 3 or less.
Furthermore, x OR ¹ 's and y R ² O's may be the same or different, but are preferably the same from the same viewpoint as above.
The alkylene oxide adduct of bisphenol A is preferably a propylene oxide adduct of bisphenol A or an ethylene oxide adduct of bisphenol A, and more preferably a propylene oxide adduct of bisphenol A.
From the same viewpoints as above, the content of the alkylene oxide adduct of bisphenol A in the alcohol component is preferably 70 mol % or less, more preferably 65 mol % or less, even more preferably 60 mol % or less, still more preferably 55 mol % or less, and preferably 15 mol % or more, more preferably 20 mol % or more, even more preferably 25 mol % or more, and still more preferably 30 mol % or more.

Examples of other alcohol components include ethylene glycol, propylene glycol (1,2-propanediol), glycerin, pentaerythritol, trimethylolpropane, hydrogenated bisphenol A, sorbitol, and alkylene oxide adducts (having a carbon number of 2 to 4) thereof (average number of moles added: 1 to 16).
The alcohol components may be used alone or in combination of two or more.

(Carboxylic Acid Component)
The carboxylic acid component which is a raw material monomer of the polyester resin (A) includes carboxylic acid, its acid anhydride, and its alkyl (having 1 to 3 carbon atoms) ester.
Examples of the carboxylic acid component include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, and trivalent or higher polycarboxylic acids.
As the aromatic dicarboxylic acid, phthalic acid, isophthalic acid and terephthalic acid are preferred, and terephthalic acid is more preferred.
The aliphatic dicarboxylic acid may be unsaturated or saturated, and the unsaturated aliphatic dicarboxylic acid may be fumaric acid or maleic acid, more preferably fumaric acid. The saturated aliphatic dicarboxylic acid may be adipic acid or succinic acid, more preferably adipic acid.
As the alicyclic dicarboxylic acid, cyclohexanedicarboxylic acid, decalindicarboxylic acid, and tetrahydrophthalic acid are preferred.
As the trivalent or higher polyvalent carboxylic acid, trimellitic acid and pyromellitic acid are preferred, and trimellitic anhydride is also preferred.
The carboxylic acid components may be used alone or in combination of two or more kinds.
From the viewpoints of improving the storage stability of the aqueous ink and obtaining a recorded matter having excellent adhesion to a low water-absorbent recording medium, recording density, and solvent resistance, the carboxylic acid component preferably contains one or more selected from aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and trivalent or higher polycarboxylic acids, and it is more preferable to use these in combination.

(Production of Polyester Resin (A))
The polyester resin (A) can be obtained by polycondensing the alcohol component and the carboxylic acid component in an appropriate combination, for example, by polycondensing the alcohol component and the carboxylic acid component in an inert gas atmosphere at a temperature of 150° C. to 250° C. using an esterification catalyst as necessary.
Examples of the esterification catalyst include tin catalysts, titanium catalysts, and metal compounds such as antimony trioxide, zinc acetate, and germanium dioxide, and from the viewpoint of esterification reaction efficiency, tin catalysts are preferred. As the tin catalyst, dibutyltin oxide, tin(II)(2-ethylhexanoate), and salts thereof are preferred, and tin(II)(2-ethylhexanoate) is more preferred. If necessary, an esterification promoter such as gallic acid may be further used.
A radical polymerization inhibitor such as 4-tert-butylcatechol may also be used in combination.

The polyester resin (A) preferably has an acid group, from the viewpoints of improving the storage stability of the water-based ink and obtaining a recorded matter having excellent adhesion to a low water-absorbency recording medium, recording density, and solvent resistance.
The acid value of the polyester resin (A) is preferably 10 mgKOH/g or more, more preferably 12 mgKOH/g or more, even more preferably 15 mgKOH/g or more, and is preferably 90 mgKOH/g or less, more preferably 70 mgKOH/g or less, even more preferably 50 mgKOH/g or less.
From the same viewpoints as above, the softening point of the polyester resin (A) is preferably 85°C or higher, more preferably 90°C or higher, even more preferably 95°C or higher, and is preferably 180°C or lower, more preferably 160°C or lower, even more preferably 140°C or lower.

From the same viewpoints as above, the glass transition temperature of the polyester resin (A) is preferably 38° C. or higher, more preferably 40° C. or higher, even more preferably 42° C. or higher, and is preferably 80° C. or lower, more preferably 70° C. or lower, even more preferably 60° C. or lower.
From the same viewpoints as above, the number average molecular weight of the polyester resin (A) is preferably 2,000 or more, more preferably 3,000 or more, even more preferably 3,500 or more, and preferably 10,000 or less, more preferably 7,000 or less, even more preferably 5,000 or less.
The acid value, softening point, glass transition temperature, and number average molecular weight of the polyester resin can be measured by the method described in the Examples. These physical properties can be adjusted to the desired values by appropriately adjusting the type and blending ratio of the monomers used, the polycondensation temperature, and the reaction time.

[(Meth)acrylic resin (B) segment]
The (meth)acrylic resin (B) segment is a vinyl polymer containing a structural unit derived from (meth)acrylic acid, where (meth)acrylic acid means one or more selected from acrylic acid and methacrylic acid.
The (meth)acrylic resin (B) segment contains a structural unit derived from (meth)acrylic acid, and preferably further contains a structural unit derived from a hydrophobic monomer.
Here, the term "hydrophobic" in the hydrophobic monomer means that when the monomer is dissolved in 100 g of ion-exchanged water at 25° C. until saturation, the amount of the monomer dissolved is less than 10 g.
Specific examples of hydrophobic monomers include those described in paragraphs [0020] to [0022] of JP-A-2018-83938. Among these, one or more selected from alkyl (meth)acrylates having an alkyl group with 1 to 22 carbon atoms, styrene, α-methylstyrene, and benzyl (meth)acrylate are preferred, and one or more selected from alkyl (meth)acrylates having an alkyl group with 1 to 6 carbon atoms, styrene, and α-methylstyrene are more preferred.

The (meth)acrylic resin segment (B) may further contain a structural unit derived from a nonionic monomer.
Specific examples of the nonionic monomer include those described in paragraph [0018] of JP-A-2018-83938. Among these, one or more selected from methoxypolyethylene glycol (n = 1 to 30) (meth)acrylate and polypropylene glycol (n = 2 to 30) (meth)acrylate are preferred.
From the above viewpoints, it is more preferable that the (meth)acrylic resin (B) segment is a (meth)acrylic resin having a constituent unit derived from (meth)acrylic acid and a constituent unit derived from an alkyl (meth)acrylate having an alkyl group having 1 to 6 carbon atoms, or a constituent unit derived from one or more selected from styrene and α-methylstyrene.

(Content of each structural unit in (meth)acrylic resin (B) segment)
The content of each of the constituent units constituting the (meth)acrylic resin (B) segment is as follows, from the viewpoint of improving the storage stability of the aqueous ink and obtaining a recorded matter having excellent adhesion to a low water-absorbent recording medium, recording density, and solvent resistance.
The content of the constituent units derived from (meth)acrylic acid in all monomer constituent units constituting the (meth)acrylic resin (B) segment is preferably 10 mass% or more, more preferably 15 mass% or more, even more preferably 20 mass% or more, and is preferably 50 mass% or less, more preferably 45 mass% or less, even more preferably 40 mass% or less.
The content of the structural units derived from hydrophobic monomers in all monomer structural units constituting the (meth)acrylic resin (B) segment is preferably 90 mass% or less, more preferably 85 mass% or less, even more preferably 80 mass% or less, and is preferably 50 mass% or more, more preferably 55 mass% or more, even more preferably 60 mass% or more.
When a nonionic monomer constituent unit is contained, the content thereof is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 25% by mass or less, more preferably 20% by mass or less.

The content of the structural units derived from (meth)acrylic acid and hydrophobic monomer in the (meth)acrylic resin (B) segment can be determined by measurement, or can be substituted by the charging ratio of the raw material monomers containing (meth)acrylic acid and hydrophobic monomer during the production of the (meth)acrylic resin (B).

(Production of (meth)acrylic resin (B))
The (meth)acrylic resin (B) can be produced by copolymerizing a monomer mixture of (meth)acrylic acid and a hydrophobic monomer by a known polymerization method, preferably a solution polymerization method.
There is no limitation on the solvent used in the solution polymerization method, but polar solvents such as water, lower aliphatic alcohols, ketones such as methyl ethyl ketone, ethers, and esters are preferred.
In the polymerization, a polymerization initiator such as an azo compound or a persulfate, or a polymerization chain transfer agent such as a mercaptan, can be used. The polymerization temperature varies depending on the type of polymerization initiator, monomer, and solvent used, but is preferably 30° C. or higher, more preferably 50° C. or higher, and is preferably 95° C. or lower, more preferably 80° C. or lower.
Commercially available products may also be used as the (meth)acrylic resin (B), such as styrene-acrylic resins such as JONCRYL 67, 678, 683, and 690 manufactured by BASF Japan Ltd.

From the viewpoints of improving the storage stability of the aqueous ink and obtaining a recorded matter having excellent adhesion to a low water-absorbent recording medium, recording density, and solvent resistance, the number average molecular weight of the (meth)acrylic resin (B) is preferably 3,000 or more, more preferably 5,000 or more, and even more preferably 8,000 or more, and is preferably 100,000 or less, more preferably 80,000 or less, and even more preferably 50,000 or less.
From the same viewpoint as above, the acid value of the (meth)acrylic resin (B) is preferably 150 mgKOH/g or more, more preferably 170 mgKOH/g or more, even more preferably 180 mgKOH/g or more, and is preferably 300 mgKOH/g or less, more preferably 280 mgKOH/g or less, even more preferably 260 mgKOH/g or less.
The number average molecular weight and acid value of the (meth)acrylic resin (B) can be measured by the method described in the Examples.

<Production of Composite Resin Dispersion>
The composite resin dispersion can be produced by any known method such as bulk polymerization-phase inversion emulsification method, seed polymerization method, or dispersion treatment method, and there is no particular limitation to the method.
The bulk polymerization-phase inversion emulsification method is a method in which, for example, a polyester resin is produced by bulk polymerization, a (meth)acrylic resin is added to the system to react and form a composite, followed by phase inversion emulsification, and further crosslinking treatment as necessary to produce a composite resin dispersion.
The seed polymerization method is a method in which, for example, raw material monomers of a (meth)acrylic resin are added to a polyester resin body, reacted, and, if necessary, crosslinked to produce a composite resin dispersion.
The dispersion treatment method is a method in which, for example, a polyester resin dispersion and a (meth)acrylic resin dispersion are dispersed under high pressure, and if necessary, a crosslinking treatment is further carried out to produce a composite resin dispersion.
Among these, the dispersion processing method is preferred from the viewpoint of operability.

The dispersion treatment method is preferably, for example, a method having the following steps 1 and 2. If necessary, it is preferable to further carry out the crosslinking step 3.
Step 1: Dispersing a mixture containing a (meth)acrylic resin (B) and water to obtain an aqueous dispersion of the (meth)acrylic resin (B); Step 2: Dispersing the aqueous dispersion obtained in Step 1 and an aqueous dispersion of a polyester resin (A) to obtain a dispersion of composite resin particles; Step 3: Crosslinking the dispersion obtained in Step 2 with a crosslinking agent (C) to obtain a dispersion of crosslinked composite resin particles. Note that as a method for producing the composite resin dispersion of the present invention, a method may be used in which, in the above Step 1, a mixture containing a polyester resin (A) and water is dispersed to obtain an aqueous dispersion of the polyester resin (A), and then, in Step 2, the obtained aqueous dispersion and an aqueous dispersion of the (meth)acrylic resin (B) are dispersed together.
The composite resin dispersion according to the present invention includes dispersions of composite resin particles before and after crosslinking.
The method for obtaining the aqueous dispersion of the (meth)acrylic resin (B) in step (1) will be described below.

(Step 1)
In step 1, a method is preferred in which the (meth)acrylic resin (B), water, a neutralizing agent, and optionally an organic solvent, a surfactant, and the like are mixed to obtain an aqueous dispersion of the (meth)acrylic resin (B).

In step 1, it is preferable to neutralize at least a part of the acid groups of the (meth)acrylic resin (B) with a neutralizing agent and adjust the pH to 7 or more and 11 or less.
As the neutralizing agent, from the viewpoint of improving storage stability, etc., an alkali metal compound or the like is preferable, an alkali metal hydroxide is more preferable, and sodium hydroxide is further preferable.
Furthermore, prior to step 1, the (meth)acrylic resin (B) may be neutralized in advance.
From the same viewpoint as above, the amount of the neutralizing agent used is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, and is preferably 150 mol% or less, more preferably 120 mol% or less, even more preferably 100 mol% or less.
The equivalent amount of the neutralizing agent used here can be calculated by the following formula, where the polymer before neutralization is designated as "polymer a'".
Equivalent amount of neutralizing agent used (mol %)=[{weight (g) of neutralizing agent added/equivalent amount of neutralizing agent}/[{acid value of polymer a' (mg KOH/g) x weight (g) of polymer a'}/(56 x 1,000)]] x 100
The dispersion treatment in step 1 can be carried out by a known method. As a dispersing machine, a commonly used mixing and stirring device such as an anchor blade or a disperser blade can be used.

(Step 2)
In step 2, the aqueous dispersion obtained in step 1 and an aqueous dispersion of the polyester resin (A) are subjected to a dispersion treatment to obtain a dispersion of composite resin particles.
As the aqueous dispersion of polyester resin (A), a dispersion in an aqueous medium of the resin obtained in the section (Production of polyester resin (A)) can be used.
The dispersion treatment can be carried out using a kneading machine such as a roll mill or a kneader, a high-pressure homogenizer such as a microfluidizer, a media-type dispersing machine such as a paint shaker or a bead mill, etc. Among these, it is preferable to use a high-pressure homogenizer from the viewpoint of reducing the particle size of the composite resin particles.
When the dispersion treatment is carried out using a high-pressure homogenizer, the average particle size of the composite resin particles in the aqueous dispersion of the composite resin particles can be adjusted by controlling the treatment pressure and the number of passes.
From the viewpoints of productivity and economy, the treatment pressure is preferably 60 MPa or more and 300 MPa or less, and the number of passes is preferably 3 or more and 30 or less.

At least a portion of the acid groups in the resulting composite resin is preferably neutralized with a neutralizing agent such as an alkali metal hydroxide.
The amount of neutralizing agent used in the composite resin is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, and is preferably 150 mol% or less, more preferably 120 mol% or less, even more preferably 100 mol% or less.
The equivalent amount of the neutralizing agent used for the composite resin obtained by the dispersion treatment method can be calculated according to the above formula:
Equivalent amount (mol %) of neutralizing agent used in composite resin=[{weight (g) of neutralizing agent added/equivalent amount of neutralizing agent}/[{acid value of polymer b' (mg KOH/g)×weight (g) of polymer b'}/(56×1,000)]]×100
Here, the "usage equivalent of neutralizing agent for the composite resin" refers to the total mass of the neutralizing agent used to neutralize the composite resin, the "acid value of polymer b'" refers to the weighted average of the acid value of the (meth)acrylic resin (B) and the acid value of the polyester resin (A), and the "mass of polymer b'" refers to the total mass of the (meth)acrylic resin (B) segment and the polyester resin (A) segment that constitute the composite resin.

(Step 3)
In step 3, the dispersion obtained in step 2 is crosslinked with a crosslinking agent (C) to obtain a dispersion of crosslinked composite resin particles. Although step 3 is an optional step, it is preferable to carry out step 3 from the viewpoint of improving the storage stability of the dispersion of composite resin particles of the present invention and the water-based ink of the present invention containing the dispersion of composite resin particles, and obtaining a recorded matter having excellent adhesion to a low water-absorbent recording medium, recording density, and solvent resistance.
By carrying out step 3, at least a part of the acid groups of the polyester resin (A) segment and the (meth)acrylic resin (B) segment constituting the composite resin reacts with the crosslinking agent (C) to crosslink, and a crosslinked structure is formed in the surface layer portion of the composite resin particle. That is, the composite resin particles in the dispersion are crosslinked by the crosslinking agent (C) to become crosslinked composite resin particles.

(Crosslinking Agent (C))
The crosslinking agent (C) is preferably a polyfunctional epoxy compound having two or more epoxy groups, preferably a glycidyl ether group, in the molecule, and more preferably a glycidyl ether compound of a polyhydric alcohol having a hydrocarbon group having 3 to 8 carbon atoms.
The number of epoxy groups in the polyfunctional epoxy compound is 2 or more, preferably 3 or more, per molecule from the viewpoint of enhancing the storage stability of the dispersion, and is preferably 6 or less, and more preferably 4 or less, per molecule from the viewpoint of market availability.
From the same viewpoints as above, the epoxy equivalent of the polyfunctional epoxy compound is preferably 100 or more, more preferably 110 or more, even more preferably 120 or more, and preferably 300 or less, more preferably 270 or less, even more preferably 250 or less.

Specific examples of polyfunctional epoxy compounds include polyglycidyl ethers such as polypropylene glycol diglycidyl ether, glycerin polyglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, 1,6-hexanediol diglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, and hydrogenated bisphenol A diglycidyl ether. Among these, one or more selected from trimethylolpropane polyglycidyl ether, 1,6-hexanediol diglycidyl ether, and pentaerythritol polyglycidyl ether are preferred.

From the viewpoints of reaction completion and economy, the temperature of the crosslinking reaction is preferably 50°C or higher, more preferably 60°C or higher, and preferably 95°C or lower, more preferably 85°C or lower. The reaction time is preferably 0.5 hours or higher, more preferably 1 hour or higher, and preferably 12 hours or lower, more preferably 10 hours or lower.

From the viewpoint of improving the storage stability of the dispersion of the composite resin particles of the present invention and the water-based ink of the present invention, and obtaining recorded matter having excellent adhesion to low water-absorbency recording media, recording density, and solvent resistance, the degree of crosslinking of the composite resin is preferably 10 mol % or more, more preferably 20 mol % or more, even more preferably 30 mol % or more, and is preferably 70 mol % or less, more preferably 60 mol % or less, even more preferably 50 mol % or less.
The crosslinking degree of the composite resin is an apparent crosslinking degree calculated from the acid values of the polyester resin (A) and the (meth)acrylic resin (B) and the equivalent weight of the epoxy group of the polyfunctional epoxy compound. In other words, the crosslinking degree is "the number of moles of the epoxy group of the polyfunctional epoxy compound added to the dispersion liquid/the number of moles of the carboxy group of the composite resin in the dispersion liquid".

The average particle size of the (crosslinked) composite resin particles in the composite resin dispersion of the present invention is, from the viewpoint of reducing coarse particles and improving adhesion and the like, preferably 80 nm or more, more preferably 85 nm or more, even more preferably 90 nm or more, and is preferably 300 nm or less, more preferably 200 nm or less, even more preferably 150 nm or less.
From the viewpoint of improving the storage stability and facilitating the preparation of an aqueous ink, the non-volatile component concentration (solid content concentration) of the composite resin dispersion of the present invention is preferably 10% by mass or more, more preferably 15% by mass or more, and is preferably 30% by mass or less, more preferably 25% by mass or less.
The average particle size and solid content are measured by the methods described in the Examples.

(Content of each component in composite resin dispersion)
From the viewpoint of improving storage stability, the content of the composite resin particles in the composite resin dispersion of the present invention is preferably 15 mass % or more, more preferably 20 mass % or more, even more preferably 25 mass % or more, and is preferably 45 mass % or less, more preferably 40 mass % or less, even more preferably 35 mass % or less.
From the viewpoint of assuming that the composite resin dispersion of the present invention will be used as a component of a coating agent or clear ink, it is preferable that the composite resin dispersion does not contain a colorant component such as a pigment.

[Water-based ink]
The water-based ink of the present invention is a water-based ink containing composite resin particles and a pigment,
The composite resin contains a polyester resin (A) segment and a (meth)acrylic resin (B) segment, the polyester resin (A) contains a structural unit derived from an alcohol component and a structural unit derived from a carboxylic acid component, and the alcohol component contains at least 3-methyl-1,5-pentanediol.
The composite resin particles are as described above.
When the water-based ink is a clear ink, it does not contain a pigment.

<Pigments>
The pigments used in the present invention may be either inorganic or organic pigments, and lake pigments and fluorescent pigments may also be used. If necessary, these pigments may also be used in combination with extender pigments such as silica, calcium carbonate, and talc.
Specific examples of inorganic pigments include carbon black, metal oxides such as titanium oxide, iron oxide, red iron oxide, and chromium oxide, and pearlescent pigments. In particular, carbon black is preferred for black inks. Examples of carbon black include furnace black, lamp black, acetylene black, and channel black.
Specific examples of organic pigments include azo pigments such as azo lake pigments, insoluble monoazo pigments, insoluble disazo pigments, and chelate azo pigments; and polycyclic pigments such as phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, and threne pigments.

The hue is not particularly limited, and any of achromatic pigments such as white, black, and gray; and chromatic organic pigments such as yellow, magenta, cyan, blue, red, orange, and green can be used.
Specific examples of preferred organic pigments include one or more product numbers selected from C.I. Pigment Yellow, C.I. Pigment Red, C.I. Pigment Orange, C.I. Pigment Violet, C.I. Pigment Blue, and C.I. Pigment Green.
The above pigments may be used alone or in combination of two or more.

(Pigment-containing polymer particles)
The pigment used in the water-based ink of the present invention is preferably in the form of polymer particles containing the pigment (hereinafter also referred to as "pigment-containing polymer particles"), from the viewpoints of improving the storage stability of the water-based ink of the present invention and obtaining recorded matter that is excellent in adhesion to low water-absorbent recording media, recording density, and solvent resistance.
In this specification, "polymer particles containing a pigment" includes particles in a form in which a polymer encompasses the pigment, particles consisting of a polymer and a pigment, with part of the pigment exposed on the surface, particles in which a polymer is adsorbed to part of the pigment, and particles in a mixture of these forms, with the form of polymer particles encompassing the pigment being more preferred.
Moreover, the "pigment-containing polymer particles" are more preferably "pigment-containing crosslinked polymer particles" that are further crosslinked with a crosslinking agent.

The polymer constituting the pigment-containing polymer particles (hereinafter, also referred to as "polymer a") is not particularly limited as long as it has at least the ability to disperse the pigment.
From the viewpoint of dispersion stability of the pigment, the polymer a is preferably at least one selected from polyester resins and vinyl resins. The polymer a may be appropriately synthesized or may be a commercially available product.
The polymer a may be either a water-soluble polymer or a water-insoluble polymer, but is preferably a water-insoluble polymer. Even if the polymer used is a water-soluble polymer, the polymer can be made water-insoluble by subjecting the polymer to a crosslinking treatment.
The term "water-insoluble" for a polymer is defined above.

When the polymer a is a polyester resin, the polyester resin is preferably the polyester resin (A) described above. Specific examples and suitable examples of the polyester resin are the same as those of the polyester resin (A), so the description thereof will be omitted here.
In addition, when the polymer a is a vinyl resin, the vinyl resin is preferably the above-mentioned (meth)acrylic resin (B). Specific examples and suitable examples of the vinyl resin are the same as those of the (meth)acrylic resin (B), and therefore the description thereof will be omitted here.

[Preparation of pigment-containing polymer particles]
The pigment-containing polymer particles can be efficiently produced as a pigment aqueous dispersion by a method having the following steps I and II. If necessary, it is preferable to further carry out the following step III.
Step I: A step of dispersing a pigment mixture containing polymer a, an organic solvent, a pigment, and water to obtain a pigment dispersion. Step II: A step of removing the organic solvent from the pigment dispersion obtained in Step I to obtain an aqueous dispersion of pigment-containing polymer particles (hereinafter also referred to as "pigment aqueous dispersion (i)"). Step III: A step of adding a crosslinking agent to the pigment aqueous dispersion (i) obtained in Step II to crosslink the pigment-containing polymer particles to obtain an aqueous dispersion of pigment-containing crosslinked polymer particles (hereinafter also referred to as "pigment aqueous dispersion (I)").

The pigment dispersion in step I is preferably obtained by a method in which the polymer a is dissolved in an organic solvent, and then the pigment, water, and, if necessary, a neutralizing agent, a surfactant, and the like are added to and mixed with the obtained organic solvent solution to obtain an oil-in-water dispersion.
Although there is no limitation on the organic solvent used in step I, preferred are ketones, ethers, esters, aliphatic alcohols having from 1 to 3 carbon atoms, and from the viewpoint of improving the wettability to the pigment and the adsorption of polymer a to the pigment, more preferred are ketones having from 4 to 8 carbon atoms, and even more preferred is methyl ethyl ketone. When a vinyl resin is synthesized as polymer a by solution polymerization, the solvent used in the polymerization may be used as it is.

When the polymer a has acid groups, it is preferable to neutralize at least a part of the acid groups with a neutralizing agent and adjust the pH to 7 or more and 11 or less.
The neutralizing agent is as described above, with sodium hydroxide being preferred.
The polymer a may be neutralized in advance.
From the viewpoint of improving dispersion stability, the amount of the neutralizing agent used is preferably 20 mol % or more, more preferably 30 mol % or more, even more preferably 40 mol % or more, and is preferably 150 mol % or less, more preferably 120 mol % or less, even more preferably 100 mol % or less.
The equivalent amount of the neutralizing agent used here is as defined above.
The dispersion treatment in step I is the same as the dispersion treatment in step 2 in the above-mentioned "dispersion treatment method," so a description thereof will be omitted here.

The organic solvent in step II can be removed by a known method. It is preferable that the organic solvent in the resulting pigment water dispersion (i) has been substantially removed, but it may remain in an amount of, for example, 0.1% by mass or less, as long as it does not impair the object of the present invention.

In step III, which is optional, a crosslinking agent can be added to the pigment water dispersion (i) obtained in step II to crosslink a portion of the carboxy groups of the polymer a constituting the pigment-containing polymer particles, thereby forming a crosslinked structure on the surface layer portion of the pigment-containing polymer particles, thereby obtaining a pigment water dispersion (I) of pigment-containing crosslinked polymer particles.
As the crosslinking agent, the above-mentioned polyfunctional epoxy compound is preferable. Specific examples, preferred examples, and crosslinking treatment conditions of the polyfunctional epoxy compound are as described above, so description thereof will be omitted here.

From the viewpoint of improving the dispersion stability of the pigment water dispersion, the non-volatile component concentration (solid content concentration) of the resulting pigment water dispersion (I) is preferably 10% by mass or more, more preferably 15% by mass or more, and is preferably 45% by mass or less, more preferably 40% by mass or less.
The solids concentration is measured by the method described in the Examples.
From the viewpoint of dispersion stability, the content of the pigment in the pigment water dispersion (I) is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 12% by mass or more, and is preferably 45% by mass or less, more preferably 40% by mass or less.
From the viewpoint of dispersion stability, the average particle size of the pigment-containing (crosslinked) polymer particles is preferably 50 nm or more, more preferably 70 nm or more, even more preferably 80 nm or more, and is preferably 400 nm or less, more preferably 300 nm or less, even more preferably 200 nm or less.
The average particle size of the pigment-containing (crosslinked) polymer particles in the water-based ink of the present invention is substantially the same as the average particle size of the pigment-containing (crosslinked) polymer particles in the pigment water dispersion (i) or (I).
The average particle size is measured by the method described in the Examples.

In addition to the composite resin particles and pigment, the water-based ink of the present invention may contain a water-soluble organic solvent and, if necessary, various additives such as surfactants, moisturizers, wetting agents, penetrants, viscosity adjusters, defoamers, preservatives, antifungal agents, and rust inhibitors.

(Water-soluble organic solvent)
The water-soluble organic solvent used may be either liquid or solid at 25° C., but when the organic solvent is dissolved in 100 mL of water at 25° C., the amount of the dissolved organic solvent is 10 mL or more.
From the viewpoint of improving the wetting and spreading properties of the ink, the boiling point of the water-soluble organic solvent is preferably 100° C. or higher, more preferably 120° C. or higher, even more preferably 140° C. or higher, still more preferably 150° C. or higher, and preferably 250° C. or lower, more preferably 245° C. or lower, even more preferably 240° C. or lower, and still more preferably 235° C. or lower.
Examples of the water-soluble organic solvent include glycol ethers such as alkylene glycol ethers, polyhydric alcohols, amide compounds, etc. Among these, alkylene glycol ethers and polyhydric alcohols are preferred.

Examples of alkylene glycol ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monopropyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monoisobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monobutyl ether, and dipropylene glycol monomethyl ether.
Among these, one or more selected from diethylene glycol monoisobutyl ether, diethylene glycol monobutyl ether, ethylene glycol monomethyl ether, ethylene glycol isobutyl ether, diethylene glycol monomethyl ether, and dipropylene glycol monomethyl ether are preferred, and diethylene glycol monoisobutyl ether is more preferred.

Examples of polyhydric alcohols include propylene glycol, ethylene glycol, butanediol, diethylene glycol, dipropylene glycol, glycerin, etc. Among these, propylene glycol is preferred.
It is more preferable that the water-based ink of the present invention uses diethylene glycol monoisobutyl ether and propylene glycol in combination.

<Surfactant>
The water-based ink of the present invention preferably contains a surfactant from the viewpoints of maintaining the surface tension of the ink at an appropriate level and improving the wettability of the ink to a recording medium.
The surfactant is not particularly limited, but a nonionic surfactant is preferred, and one or more surfactants selected from acetylene glycol surfactants and silicone surfactants are more preferred.
Examples of acetylene glycol surfactants include acetylene diols such as 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyne-3-ol, 2,4-dimethyl-5-hexyne-3-ol, 2,5-dimethyl-3-hexyne-2,5-diol, and 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, and ethylene oxide adducts thereof.
Commercially available examples of acetylene glycol surfactants include the "Surfynol" series and "Olfine" series manufactured by Nissin Chemical Industry Co., Ltd., and the "Acetylenol" series manufactured by Kawaken Fine Chemicals Co., Ltd.

(Silicone surfactant)
Examples of silicone surfactants include dimethylpolysiloxane, polyether-modified silicone, amino-modified silicone, and carboxy-modified silicone, with polyether-modified silicone being preferred from the same viewpoint as above.
Specific examples of polyether-modified silicones include PEG-3 dimethicone, PEG-9 dimethicone, PEG-9PEG-9 dimethicone, PEG-9 methyl ether dimethicone, PEG-10 dimethicone, PEG-11 methyl ether dimethicone, PEG/PPG-20/22 butyl ether dimethicone, PEG-32 methyl ether dimethicone, PEG-9 polydimethylsiloxyethyl dimethicone, and the like.
Examples of commercially available polyether-modified silicones include the silicone KF series manufactured by Shin-Etsu Chemical Co., Ltd.
The above surfactants may be used alone or in combination of two or more.

(Content of each component in the water-based ink of the present invention)
The contents of the various components in the water-based ink of the present invention are as follows, from the viewpoints of improving storage stability and obtaining recorded matter that is excellent in adhesion to low water-absorbent recording media, recording density, and solvent resistance.
(Content of Composite Resin Particles)
The content of the composite resin particles in the water-based ink is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, and is preferably 12% by mass or less, more preferably 10% by mass or less, even more preferably 8% by mass or less.
(Pigment content)
The content of the pigment in the water-based ink of the present invention is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 2.5% by mass or more, and is preferably 10% by mass or less, more preferably 8% by mass or less.
The content of the pigment-containing polymer particles in the water-based ink of the present invention is preferably 3% by mass or more, more preferably 4% by mass or more, and is preferably 20% by mass or less, more preferably 15% by mass or less.

The total content of the water-soluble organic solvents in the water-based ink is preferably 10% by mass or more, more preferably 15% by mass or more, and is preferably 45% by mass or less, more preferably 35% by mass or less.
The content of the surfactant in the water-based ink is preferably 0.2% by mass or more, more preferably 0.5% by mass or more, and is preferably 4% by mass or less, more preferably 3% by mass or less.
The water content in the water-based ink is preferably 45% by mass or more, more preferably 50% by mass or more, and is preferably 80% by mass or less, more preferably 75% by mass or less.

(Physical properties of the water-based ink of the present invention)
The viscosity of the water-based ink of the present invention at 32°C is preferably 2 mPa·s or more, more preferably 2.5 mPa·s or more, and is preferably 12 mPa·s or less, more preferably 9 mPa·s or less, from the viewpoint of adhesion to low water-absorbent recording media, etc.
The pH of the water-based ink of the present invention is preferably 7.0 or more, more preferably 7.2 or more, and is preferably 11 or less, more preferably 10 or less, from the viewpoints of storage stability, reduction in corrosiveness, etc.

The water-based ink of the present invention can be loaded into a known inkjet printing device and ejected as ink droplets onto a recording medium having low water absorption or the like to record an image or the like.
There are three types of ink droplet ejection methods: piezo, thermal, and electrostatic, with the piezo method being the most preferable. In the piezo method, a large number of nozzles are each connected to a pressure chamber, and ink droplets are ejected from the nozzles by vibrating the walls of the pressure chambers with a piezo element.

Examples of low water-absorbent recording media include low water-absorbent coated paper, art paper, and resin films.
Examples of coated paper include general-purpose glossy paper and multi-color form glossy paper.
The resin film may be a transparent synthetic resin film, such as a polyester film, a polyvinyl chloride film, a polypropylene film, a polyethylene film, a nylon film, etc. These films may be biaxially stretched films, uniaxially stretched films, or non-stretched films.

In the following manufacturing examples, examples, and comparative examples, "parts" and "%" are "parts by mass" and "% by mass" unless otherwise specified. The methods for measuring each physical property are as follows.

(1) Acid Value of Resin The acid value of resin was measured according to the neutralization titration method described in JIS K0070-1992, except that the measurement solvent was changed from a mixed solvent of ethanol and ether to a mixed solvent of acetone and toluene [acetone:toluene=1:1 (volume ratio)].

(2) Softening point of resin Using a flow tester (Shimadzu Corporation, product name: CFT-500D), 1 g of a sample was heated at a temperature increase rate of 6° C./min, while applying a load of 1.96 MPa with a plunger, and extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. The plunger descent amount of the flow tester was plotted against the temperature, and the temperature at which half of the sample flowed out was taken as the softening point.

(3) Glass transition temperature (Tg) of resin
Using a differential scanning calorimeter (Perkin Elmer, product name: Pyris 6 DSC), the sample was heated to 200°C, cooled from that temperature at a rate of 10°C/min to 0°C, and then heated at a rate of 10°C/min. The glass transition temperature (Tg) was determined as the temperature at the intersection of an extension of the baseline below the maximum endothermic peak temperature and a tangent line showing the maximum slope from the rising part of the peak to the top of the peak.

(4) Number average molecular weight (Mn) of resin
The number average molecular weight was determined by the following gel permeation chromatography (GPC) method.
(4-1) Preparation of sample solution A sample was dissolved in tetrahydrofuran at 40° C. to a concentration of 0.5 g/100 mL. Next, this solution was filtered using a PTFE-type membrane filter "DISMIC-25JP" (manufactured by Toyo Roshi Kaisha, Ltd.) with a pore size of 0.20 μm to remove insoluble components, thereby obtaining a sample solution.
(4-2) Molecular weight measurement Using the following measurement device and analytical column, tetrahydrofuran was passed as an eluent at a flow rate of 1 mL per minute, and the column was stabilized in a thermostatic bath at 40°C. 100 μL of the sample solution was injected therein and measurement was performed. The molecular weight of the sample was calculated based on a calibration curve prepared in advance.
Measuring device: HLC-8220GPC (manufactured by Tosoh Corporation)
Analytical column: TSKgel GMHXL + TSKgel G3000HXL (Tosoh Corporation)
For the calibration curve, several types of monodisperse polystyrene (A-500 (5.0× ¹⁰² ), A-1000 (1.01× ¹⁰³ ), A-2500 (2.63× ¹⁰³ ), A-5000 (5.97× ¹⁰³ ), F-1 (1.02× ¹⁰⁴ ), F-2 (1.81× ¹⁰⁴ ), F-4 (3.97× ¹⁰⁴ ), F-10 (9.64× ¹⁰⁴ ), F-20 (1.90× ¹⁰⁵ ), F-40 (4.27× ¹⁰⁵ ), F-80 (7.06× ¹⁰⁵ ), F-128 (1.09× ¹⁰⁶ ) manufactured by Tosoh Corporation) were used as standard samples. The molecular weight is shown in parentheses.

(5) Measurement of average particle size of pigment aqueous dispersion: Particle size was measured by dynamic light scattering using a laser particle analysis system (manufactured by Otsuka Electronics Co., Ltd., product name: ELS-8000), and calculated by cumulant method analysis.
The measurement conditions were a temperature of 25°C, an angle between the incident light and the detector of 90°, and 100 cumulative measurements, and the refractive index of water (1.333) was input as the refractive index of the dispersion solvent. The measurement sample was prepared by weighing out an aqueous pigment dispersion into a screw tube (No. 5, manufactured by Maruemu Co., Ltd.), adding water so that the solids concentration was 2 x ^10-4 mass%, and stirring with a magnetic stirrer at 25°C for 1 hour.

(6) Measurement of solid content concentration 10.0 g of sodium sulfate, which had been brought to a constant weight in a desiccator, was weighed out into a 30 mL polypropylene container (φ: 40 mm, height: 30 mm), and about 1.0 g of the sample was added thereto and mixed, then weighed, and maintained at 105° C. for 2 hours to remove volatile matter, and further left in the desiccator for 15 minutes, and the mass was measured. The mass of the sample after removing the volatile matter was taken as the solid content, and was divided by the mass of the sample added to obtain the solid content concentration.

(7) Measurement of pH The pH of the ink at 20° C. was measured using a tabletop pH meter (manufactured by Horiba, Ltd., product name: F-71) equipped with a pH electrode (manufactured by Horiba, Ltd., product name: 6337-10D).

Production Example I-1 (Production of Acrylic Resin A1)
60 parts of acrylic acid, 130 parts of styrene, and 10 parts of α-methylstyrene were mixed to prepare a monomer mixture. 20 parts of methyl ethyl ketone (MEK), 0.3 parts of 2-mercaptoethanol (polymerization chain transfer agent), and 10% of the monomer mixture were mixed in a reaction vessel, and nitrogen gas replacement was performed thoroughly. Meanwhile, a mixture of the remainder of the monomer mixture (90% of the monomer mixture), 0.27 parts of the polymerization chain transfer agent, 60 parts of MEK, and 2.5 parts of an azo-based radical polymerization initiator (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name: V-65, 2,2'-azobis(2,4-dimethylvaleronitrile)) was placed in a dropping funnel, and the monomer mixture in the reaction vessel was heated to 65°C while being stirred under a nitrogen atmosphere, and the mixture in the dropping funnel was dropped over 3 hours. After 2 hours had elapsed at 65° C. from the end of the dropwise addition, a solution in which 0.3 parts of the polymerization initiator was dissolved in 5 parts of MEK was added, and the mixture was further aged at 65° C. for 2 hours and at 70° C. for 2 hours to obtain a solution of acrylic resin A1. The results are shown in Table 1.

Production Example I-2 (Production of Acrylic Resin A2)
Acrylic resin A2 was obtained in the same manner as in Production Example I-1, except that the conditions in Production Example I-1 were changed to those shown in Table 1. The results are shown in Table 1.

Production Examples II-1 to II-6 (Production of Composite Resins H1 to H6)
Trimellitic anhydride, fumaric acid, and raw material monomers for polyester resin other than acrylic resin, an esterification catalyst, and an esterification promoter shown in Table 2 were placed in a 10 L four-neck flask equipped with a thermometer, a stainless steel stirring rod, a downflow condenser, and a nitrogen inlet tube, and the temperature was raised to 235° C. in a mantle heater in a nitrogen atmosphere, and polycondensation was carried out at 235° C. for 10 hours.
Next, after lowering the temperature to 200° C., trimellitic anhydride, fumaric acid, and acrylic resin A1 or A2 obtained by drying the polymer solution obtained in Production Example I-1 or I-2 under reduced pressure were added, and the reaction was carried out at 200° C. and 8.0 kPa until the softening point shown in Table 2 was reached, thereby obtaining composite resins H1 to H6. The results are shown in Table 2.

Production Examples III-1 to III-2 (Production of Polyester Resins P1 and P2)
In a 10 L four-neck flask equipped with a nitrogen inlet tube, a stirrer, and a thermocouple, raw material monomers other than trimellitic anhydride and fumaric acid, an esterification catalyst, and an esterification co-catalyst shown in Table 3 were placed, and the temperature was raised to 235° C. under a nitrogen atmosphere, followed by polycondensation at 235° C. for 10 hours.
Then, after lowering the temperature to 200° C., trimellitic anhydride and fumaric acid shown in Table 3 were added and reacted at 200° C. for 1 hour. Then, the reaction was continued at 200° C. and 8 kPa until the softening point shown in Table 3 was reached, to obtain polyester resins P1 and P2. The results are shown in Table 3.

Comparative Production Example III-1 (Production of Polyester Resin P3)
The raw material monomers, esterification catalyst, and polymerization inhibitor shown in Table 3 were placed in a 10 L four-neck flask equipped with a nitrogen inlet tube, a stirrer, and a thermocouple, and the temperature was raised to 210° C. over 10 hours under a nitrogen atmosphere. Polycondensation was then carried out at 210° C. for 1 hour, and the reaction was continued at 40 kPa until the softening point shown in Table 3 was reached, to obtain polyester resin P3. The results are shown in Table 3.

Examples I-1 to I-6 (Preparation of Crosslinked Composite Resin Dispersions 1 to 6)
In a 1 L four-neck flask equipped with a nitrogen inlet tube, a reflux condenser, a stirrer (manufactured by Shinto Scientific Co., Ltd., product name: Three-One Motor BL300) and a thermocouple, the composite resins of the types and amounts shown in Table 4 were placed and mixed with 200 g of MEK at 30°C to dissolve each of the composite resins H1 to H6 obtained in Production Examples II-1 to II-6.
Next, a 48% aqueous sodium hydroxide solution shown in Table 4 was added in an amount such that the degree of neutralization of the composite resin was 60 mol%, and the mixture was stirred for 30 minutes, after which the entire amount of ion-exchanged water shown in Table 4 was added dropwise at a rate of 20 mL/min at 30° C. with stirring. Next, the temperature was raised to 60° C., and the pressure was gradually reduced from 80 kPa to 30 kPa while distilling off MEK and further distilling off a portion of the water. After cooling to 25° C., the mixture was filtered through a 150 mesh wire net, and ion-exchanged water was added to adjust the solids concentration of the dispersion to 30%.
The obtained dispersion was placed in a screw-top glass bottle, and the amount of crosslinking agent (trimethylolpropane polyglycidyl ether, Nagase ChemteX Corporation, product name: Denacol EX-321L) shown in Table 4 was added, the bottle was sealed, and the bottle was heated at 70° C. for 5 hours while stirring with a stirrer. After that, the temperature was lowered to room temperature, and ion-exchanged water was added to adjust the solid content concentration of the dispersion to 25%.
The obtained dispersion was filtered with a 25 mL syringe (manufactured by Terumo Corporation) equipped with a filter having a pore size of 5 μm (acetyl cellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) to obtain crosslinked composite resin dispersions 1 to 6. The results are shown in Table 4.

Examples I-7 to I-9, Comparative Example I-1 (Preparation of Crosslinked Composite Resin Dispersions 7 to 9, and 21)
Into a 1 L four-neck flask equipped with a nitrogen inlet tube, a reflux condenser, a stirrer (manufactured by Shinto Scientific Co., Ltd., product name: Three-One Motor BL300) and a thermocouple, the polyester resins P1, P2 and P3 obtained in Production Examples III-1 to III-2 and Comparative Production Example III-1 were placed in the amounts shown in Table 5, and mixed with 200 g of MEK at 30° C. to dissolve the polyester resins.
Next, a 48% aqueous sodium hydroxide solution shown in Table 5 was added in an amount such that the degree of neutralization of the polyester resin was 60 mol%, and the mixture was stirred for 30 minutes, after which the entire amount of ion-exchanged water shown in Table 5 was added dropwise at a rate of 20 mL/min at 30° C. with stirring. Next, the temperature was raised to 60° C., and the pressure was gradually reduced from 80 kPa to 30 kPa while distilling off MEK, and further distilling off a portion of the water. After cooling to 25° C., the mixture was filtered through a 150 mesh wire net and adjusted to a solid content of 30% with ion-exchanged water to obtain a polyester resin dispersion.
The obtained polyester resin dispersion was put into a 1L four-neck flask equipped with a reflux condenser, a stirrer (product name: Three-One Motor BL300) and two dropping funnels in the amount shown in Table 5, and nitrogen gas replacement was performed thoroughly. A mixture of the raw material monomers of the acrylic resin shown in Table 5 was added to one dropping funnel, and a 1% potassium persulfate aqueous solution was added to the other funnel. The dispersion in the flask was heated to 70°C while stirring under a nitrogen atmosphere, and the raw materials in each dropping funnel were dropped over 1 hour. After 2 hours at 70°C from the end of the dropping, 1% potassium persulfate was further added, and the mixture was further aged at 70°C for 2 hours and 75°C for 1 hour. After cooling to room temperature, the solid content concentration was adjusted to 25% with ion-exchanged water to obtain a composite resin dispersion.
The obtained composite resin dispersion in the amount shown in Table 5 was placed in a screw-capped glass bottle, and a 48% aqueous sodium hydroxide solution and a crosslinking agent (product name: Denacol EX-321L) were added, and then crosslinked composite resin dispersions 7 to 9 and 21 (solid content concentration: 25%) were obtained in the same manner as in Examples I-1 to I-6. The results are shown in Table 5.

Example I-10 (Preparation of Composite Resin Dispersion 10)
The solution of the acrylic resin A1 obtained in Production Example I-1 was dried under reduced pressure to obtain a polymer (35 parts) which was mixed with 40 parts of MEK, and 7.3 parts of a 48% aqueous sodium hydroxide solution was added to neutralize the resin A1 so that the equivalent of the neutralizer used was 60 mol %. Next, 180 parts of ion-exchanged water was added, and the mixture was stirred for 15 minutes at 20°C with a Disper (manufactured by Asada Iron Works Co., Ltd., product name: Ultra Disper) rotating the Disper blade at 1,400 rpm.
315 parts of polyester resin P1 obtained in Production Example III-1 and 5.6 parts of 48% sodium hydroxide were added, and the rotation conditions of the disperser blade were changed to 7,000 rpm, and stirring was performed for 60 minutes to obtain a preliminary dispersion liquid. The preliminary dispersion liquid obtained was subjected to 10-pass dispersion treatment at a pressure of 200 MPa using a Microfluidizer (trade name, manufactured by Microfluidics Corporation) to obtain a dispersion liquid.
200 parts of ion-exchanged water was added to the obtained dispersion, and after stirring, MEK was removed at 60° C. under reduced pressure, and some water was further removed, and the mixture was filtered with a 25 mL needleless syringe (manufactured by Terumo Corporation) equipped with a filter (acetyl cellulose membrane, outer diameter: 2.5 cm) having a pore size of 5 μm to remove coarse particles, thereby obtaining a resin dispersion with a solid content concentration of 30%. The obtained dispersion was transferred to a screw-capped glass bottle, sealed, and heated at 70° C. for 5 hours while stirring with a stirrer. Thereafter, the temperature was lowered to room temperature, and ion-exchanged water was added to adjust the solid content concentration of the dispersion to 25%.
The obtained dispersion was filtered with a 25 mL syringe (Terumo Corporation) equipped with a filter (acetyl cellulose membrane, outer diameter: 2.5 cm, Fujifilm Wako Pure Chemical Industries, Ltd.) having a pore size of 5 μm to obtain a composite resin dispersion 10 (solid content concentration: 25%). The results are shown in Table 6.

Example I-11 (Preparation of Crosslinked Composite Resin Dispersion 11)
In Example I-10, the dispersion was placed in a screw-top glass bottle, 1.1 parts of a crosslinking agent (product name: Denacol EX-321L) was added, and the bottle was sealed. The procedure was then repeated in the same manner as in Production Example 1-10 to obtain a crosslinked composite resin dispersion 11 (solid content concentration: 25%). The results are shown in Table 6.

Example I-12 (Preparation of Crosslinked Composite Resin Dispersion 12)
The solution of acrylic resin A2 obtained in Production Example I-2 was dried under reduced pressure to obtain a polymer (35 parts) that was mixed with 40 parts of MEK, and 6.1 parts of a 48% aqueous sodium hydroxide solution was added to neutralize resin A2 so that the equivalent of the neutralizing agent used was 60 mol %. Next, 180 parts of ion-exchanged water was added, and the mixture was stirred for 15 minutes at 20°C with a Disper (manufactured by Asada Iron Works Co., Ltd., product name: Ultra Disper) while rotating the Disper blade at 1,400 rpm.
140 parts of polyester resin P1 obtained in Production Example III-1 and 2.5 parts of 48% sodium hydroxide were added, and the procedure thereafter was the same as in Example I-10 to obtain a resin dispersion with a solid content concentration of 30%. The obtained dispersion was placed in a screw-capped glass bottle, 1.5 parts of a crosslinking agent (product name: Denacol EX-321L) was added, the bottle was sealed, and the bottle was heated at 70°C for 5 hours while stirring with a stirrer. Thereafter, the temperature was lowered to room temperature, and ion-exchanged water was added to adjust the solid content concentration of the dispersion to 25%.
The obtained dispersion was filtered with a 25 mL syringe (manufactured by Terumo Corporation) equipped with a filter (acetyl cellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) having a pore size of 5 μm to obtain a crosslinked composite resin dispersion 12 (solid content concentration: 25%). The results are shown in Table 6.

Comparative Example I-2 (Preparation of Crosslinked Composite Resin Dispersion 22)
A resin dispersion having a solid content concentration of 30% was obtained in the same manner as in Example I-11, except that 315 parts of the polyester resin P1 obtained in Production Example III-1 was changed to 82 parts of the polyester resin P3 obtained in Production Example III-3. Then, a crosslinked composite resin dispersion 22 (solid content concentration: 25%) was obtained in the same manner as in Example I-11, except that the crosslinking agent (product name: Denacol EX-321L) was changed to 2.3 parts. The results are shown in Table 6.

Examples II-1 to II-12 and Comparative Examples II-1 to II-3 (Preparation of Clear Ink)
Composite resin dispersions 1 to 12 obtained in Examples I-1 to I-12, polyester resin dispersion P2 obtained in Production Example III-2, or composite resin dispersions 21 and 22 obtained in Comparative Examples I-1 to I-2 (solid content concentration: 25%) 22 parts (5.5% in clear ink), propylene glycol 10 parts, diethylene glycol monoisobutyl ether (iBDG) 15 parts, acetylene glycol surfactant (manufactured by Nissin Chemical Industry Co., Ltd., product name: Olfine E1010) 1 part, polyether-modified silicone surfactant (PEG-11 methyl ether dimethicone, manufactured by Shin-Etsu Chemical Co., Ltd., product name: KF-6011) 1 part, and ion-exchanged water were mixed (total 100 parts) and stirred at room temperature for 15 minutes using a magnetic stirrer to obtain clear inks 1 to 12 and 21 to 23.
The storage stability and resin film adhesion after long-term storage were evaluated using each of the obtained clear inks by the following methods. The results are shown in Table 7.
The amount of each component in Table 7 is the effective amount (solid content).

(i) Evaluation of storage stability of clear ink Clear ink was stored in a sealed container in a constant temperature room at 60°C, and after 35 days, it was removed and the average particle size after storage was measured. The rate of change in the average particle size after storage at 60°C for 35 days was calculated using the following formula (rounded down to the nearest whole number), and the storage stability was evaluated according to the following evaluation criteria.
Rate of change in average particle size (%) = [(average particle size after storage/average particle size before storage) - 1] x 100
(Evaluation Criteria)
A: The absolute value of the rate of change in average particle size is less than 5%.
B: The absolute value of the rate of change in average particle size is 5% or more and less than 15%.
C: The absolute value of the rate of change in average particle size is 15% or more and less than 30%. D: The absolute value of the rate of change in average particle size is 30% or more and less than 50%.
If the evaluation result is B or above, there is no problem in practical use.

(ii) Evaluation of Adhesion to Resin Film (PVC) After Long-Term Storage The clear ink obtained in (i) above after storage at 60°C for 35 days was used to coat a polyvinyl chloride (PVC) film (manufactured by 3M Japan Ltd., product name: 3M ^TM Scotchcal ^TM Graphic Film IJ40-10R (white gloss)) at a speed of 6 m/min using a bar coater No. 6 and a tabletop coater (manufactured by Mitsui Electric Seiki Co., Ltd., product name: TC-1), and then dried for 5 minutes in a dryer at 80°C to form a coating film.
Next, 11 cuts (1 mm apart) were made on the surface of the coating film using a cutter knife, reaching the PVC film base, to create a grid of 100 squares. Cellophane tape (registered trademark) (manufactured by Nichiban Co., Ltd., product name: CT15) was then attached to the grid, and the tape was peeled off at an angle of 90° at a speed of 10 cm/sec, and the number of squares that did not peel off was visually confirmed.
Table 7 shows the number of squares that did not peel off per 100 squares.
The greater the number of squares that are not peeled off, the better the adhesion to the resin film (PVC).

From Table 7, it can be seen that the clear inks containing the composite resin particles of the present invention obtained in Examples II-1 to II-12 have superior storage stability in a hydrophobic system and superior adhesion to a resin film (PVC) even after long-term storage, compared to the clear inks obtained in Comparative Examples II-1 to II-3.
In Comparative Example II-1, the resin used does not contain a (meth)acrylic resin segment and is not a composite resin, so that the storage stability is poor.
In Comparative Examples II-2 and II-3, the composite resin used contains a polyester resin segment and an acrylic resin segment, but the alcohol component constituting the polyester resin does not contain 3-methyl-1,5-pentanediol, and therefore the storage stability and ink adhesion after long-term storage are poor.

Production Example IV-1 (Production of Pigment Water Dispersion C1 of Pigment-Containing Acrylic Resin Particles)
The solution of acrylic resin A1 obtained in Production Example I-1 was dried under reduced pressure, and 37 parts of the obtained polymer were dissolved in 148 parts of MEK. To the solution, 7.7 parts of a 48% aqueous sodium hydroxide solution as a neutralizing agent and 372 parts of ion-exchanged water were added, and further, 100 parts of a cyan pigment (C.I. Pigment Blue 15:3, manufactured by DIC Corporation, product name: TGR-SD) was added to obtain a pigment mixed liquid (degree of neutralization: 60 mol%).
The obtained pigment mixture was mixed for 1 hour under conditions of 7,000 rpm and 20°C using a Disper (manufactured by Asada Iron Works Co., Ltd., product name: Ultra Disper), and then further subjected to a dispersion treatment for 15 passes at a pressure of 180 MPa using a high-pressure homogenizer (manufactured by Microfluidics, product name: Microfluidizer M-140K).
The obtained aqueous dispersion of pigment-containing polymer particles was cooled to 60° C. under reduced pressure to remove MEK, and then some of the water was removed. The mixture was centrifuged, and the liquid layer was filtered through a Minisart syringe filter (pore size: 5 μm) to remove coarse particles. The solid content was adjusted to 22% with ion-exchanged water.
100 parts of the obtained pigment water dispersion was placed in a screw-top glass bottle, 1.5 parts of a crosslinking agent (Denacol EX-321L) was added, the bottle was sealed, and the bottle was heated at 70° C. for 5 hours while stirring with a stirrer. Thereafter, the temperature was lowered to room temperature, and the solid content was adjusted with ion-exchanged water. The obtained pigment water dispersion was filtered with a 25 mL syringe (manufactured by Terumo Corporation) equipped with a filter with a pore size of 5 μm (acetyl cellulose membrane, outer diameter: 2.5 cm), to obtain a pigment water dispersion C1 (solid content concentration: 20%, pigment: 13.7%, polymer: 6.3%, average particle size: 104 nm) of pigment-containing acrylic resin particles.

Production Example IV-2 (Production of Pigment Water Dispersion C2 of Pigment-Containing Polyester Resin Particles)
(1) Production of polyester resin B1 4828 parts of propylene oxide (2.2) adduct of 2,2-bis(4-hydroxyphenyl)propane, 1374 parts of terephthalic acid, 35 parts of tin (II) 2-ethylhexanoate as an esterification catalyst, and 3.5 parts of gallic acid as an esterification promoter were placed in a 10 L four-neck flask equipped with a nitrogen inlet tube, a stirrer, and a thermocouple, and the mixture was heated to 235° C. under a nitrogen atmosphere, and then polycondensed at 235° C. for 5 hours. Next, after lowering the temperature to 180° C., 480 parts of fumaric acid, 318 parts of trimellitic anhydride, and 3.5 parts of 4-tert-butylcatechol as a polymerization inhibitor were added, and the temperature was raised stepwise to 210° C. over 3 hours to react. Next, the reaction was carried out at 210° C. under a reduced pressure of 66.7 kPa for 3 hours to obtain a polyester resin B1 (acid value: 30 mg KOH/g, glass transition temperature: 72.2° C., softening point: 123.5° C.).
(2) Production of Pigment Water Dispersion C2 42.7 parts of the polyester resin B1 obtained in (1) above was dissolved in 142.7 parts of MEK, and 1.6 parts of a 48% aqueous sodium hydroxide solution (neutralization degree: 85 mol%) as a neutralizing agent and 240 parts of ion-exchanged water were further added, followed by stirring and mixing for 15 minutes at 2,000 rpm using a disper blade at 10 to 15° C. Next, 100 parts of a cyan pigment (product name: TGR-SD) was added, and the mixture was stirred and mixed for 3 hours at 7,000 rpm using a disper blade at 10 to 15° C.
The obtained dispersion was filtered through a 150 mesh filter, diluted with 110 parts of ion-exchanged water, and then subjected to 15-pass dispersion treatment at a pressure of 150 MPa using a high-pressure homogenizer (manufactured by Microfluidics, product name: Microfluidizer, model: M-110K).
The obtained dispersion was cooled to 60° C. under reduced pressure to remove MEK, and then a portion of the water was removed. The mixture was then centrifuged, and the liquid layer was filtered through a filter having a pore size of 10 μm (manufactured by Pall Corporation) to remove coarse particles. Ion exchanged water was then mixed and the mixture was filtered through the same filter having a pore size of 10 μm to obtain a pigment water dispersion C2 of pigment-containing polyester resin particles (solid content concentration: 20%, pigment: 14%, polymer: 6%, average particle size: 120.5 nm).

Examples III-1 to III-12 and Comparative Examples III-1 to III-3 (Preparation of Water-Based Inks)
A 100 mL screw tube was charged with 10 parts of propylene glycol, 15 parts of diethylene glycol monoisobutyl ether (iBDG), 1 part of an acetylene glycol surfactant (manufactured by Nissin Chemical Industry Co., Ltd., product name: Olfine E1010), 1 part of a polyether-modified silicone surfactant (PEG-11 methyl ether dimethicone, manufactured by Shin-Etsu Chemical Co., Ltd., product name: KF-6011), and 21.7 parts of ion-exchanged water, and the mixture was stirred at room temperature for 15 minutes using a magnetic stirrer to obtain a mixed solution.
Next, 29.3 parts of the pigment aqueous dispersion C1 of the pigment-containing acrylic resin particles obtained in Production Example IV-1 (corresponding to 4% pigment in the aqueous ink) was added to the mixed solution while stirring with a magnetic stirrer, and 22 parts of the composite resin dispersion shown in Table 8 was added dropwise with a dropper while stirring and mixing (total 100 parts). Next, the mixture was filtered through a filter with a pore size of 5.0 μm (manufactured by Sartorius Stedim Biotech, product name: Minisart) to obtain aqueous inks 1 to 12 and 21 to 23 (composite resin particles: 5.5%, pigment: 4.0%, pigment-containing polymer particles: 5.9%).

Example III-13 (Preparation of Water-Based Ink)
A water-based ink 13 (composite resin particles: 5.5%, pigment: 4.0%, pigment-containing polymer particles: 5.7%) was obtained in the same manner as in Example III-12, except that 22.5 parts of ion-exchanged water and 28.5 parts of pigment water dispersion C2 of pigment-containing polyester resin particles were used instead of the pigment water dispersion C1 of pigment-containing acrylic resin particles in Example III-12.
Using each of the obtained water-based inks, storage stability, resin film adhesion after long-term storage, print density, and solvent resistance (alcohol) were evaluated by the following methods. The results are shown in Table 8.
The amount of each component in Table 8 is the effective amount (solid content).

(1) Evaluation of storage stability 1 (average particle size change rate) The water-based ink was stored in a sealed container in a thermostatic chamber at 60°C, and after 28 days, it was removed and the average particle size after storage was measured. The average particle size change rate after storage at 60°C for 28 days was calculated using the following formula (rounded down to the nearest whole number), and the storage stability was evaluated according to the following evaluation criteria.
Rate of change in average particle size (%) = [(average particle size after storage/average particle size before storage) - 1] x 100
(Evaluation Criteria)
A: The absolute value of the rate of change in average particle size is less than 5%.
B: The absolute value of the rate of change in average particle size is 5% or more and less than 15%.
C: The absolute value of the rate of change in average particle size is 15% or more and less than 30%. D: The absolute value of the rate of change in average particle size is 30% or more and less than 50%.
E: The absolute value of the rate of change in average particle size is 50% or more, or the water-based ink has lost fluidity and is not in a state where the average particle size can be measured.
If the evaluation result is B or above, there is no problem in practical use.

(2) Evaluation of storage stability 2 (pH ratio) The water-based ink was stored in a sealed container in a constant temperature room at 60° C., and after 28 days, it was taken out and the pH of the water-based ink was measured. The ratio of the pH of the water-based ink after storage to the pH of the water-based ink before storage (pH after storage/pH before storage) was calculated.
The closer the pH ratio is to 1, the better the storage stability is, and if it is 0.8 or higher, there is no problem in practical use.

(3) Evaluation of resin film (PVC) adhesion after long-term storage The aqueous ink obtained above after 28 days of storage at 60°C was filled into an inkjet printer (manufactured by Ricoh Co., Ltd., product name: IPSiO GX 2500, piezoelectric type), and an A4 solid image was printed on a polyvinyl chloride (PVC) film (product name: 3M ^TM Scotchcal ^TM Graphic Film IJ40-10R (white gloss)). Then, it was dried for 5 minutes in a dryer at 80°C, and left to stand for 1 day in an environmental chamber at room temperature of 25°C and relative humidity of 50%, to obtain a print for evaluation.
A cutter knife was used to make 11 vertical and horizontal cuts (1 mm apart) on the printed surface of the evaluation print that reached the PVC film base, creating a grid of 100 squares. Cellotape (registered trademark) (product name: CT15) was then attached to the grid, and the tape was peeled off at an angle of 90° at a speed of 10 cm/sec, and the number of squares that did not peel off was visually confirmed.
Table 8 shows the number of squares that did not peel off per 100 squares.
The greater the number of squares that are not peeled off, the better the adhesion to the resin film (PVC). If the number is 70 or more, there is no problem in practical use.

(4) Evaluation of print density after long-term storage A print for evaluation was obtained in the same manner as in the evaluation of adhesion in (3) above. The print obtained was measured at five points, the center and four corners, using a Macbeth densitometer (manufactured by GretagMacbeth, product number: Spectroeye), and the average value was calculated.
The larger the value, the better the print density of the ink after long-term storage, and a value of 1.6 or more poses no problem in practical use.

(5) Evaluation of Solvent (Alcohol) Resistance After Long-Term Storage Printed materials for evaluation were obtained in the same manner as in the evaluation of adhesion in (3) above.
Ethanol was diluted with ion-exchanged water to prepare aqueous ethanol solutions with different mass concentrations of ethanol for evaluation (aqueous solutions were prepared in 10% increments in the range of 0 to 100%). Next, a cotton swab impregnated with the aqueous ethanol solution (each mass concentration) was used to gently rub the printed surface back and forth 10 times at a speed of one back and forth per second with a width of 2 to 3 cm. The state of the rubbed printed surface was visually observed, and the highest mass concentration of ethanol at which the printed surface did not show any changes such as scratches, peeling, or cloudiness is shown in Table 8 as an index of solvent (alcohol) resistance.
The higher the mass concentration of ethanol, the better the alcohol resistance. If it is 50% or more, there is no problem in practical use, but it is preferably 60% or more.

From Table 8, it can be seen that the water-based inks containing the composite resin particles of the present invention obtained in Examples III-1 to III-13 have excellent storage stability in a hydrophobic system compared to the water-based inks obtained in Comparative Examples III-1 to III-3, and can give printed matter having excellent adhesion to the resin film (PVC), print density, and solvent resistance (ethanol) even after long-term storage.
In Comparative Example III-1, the resin used does not contain a (meth)acrylic resin segment and is not a composite resin, so that the storage stability, adhesion of the ink to the resin film (PVC) after long-term storage, print density of the printed matter, and solvent resistance (alcohol) are poor.
In Comparative Examples III-2 and III-3, the composite resin used contains a polyester resin segment and an acrylic resin segment, but the alcohol component constituting the polyester resin does not contain 3-methyl-1,5-pentanediol. Therefore, the storage stability, adhesion of the ink to the resin film (PVC) after long-term storage, print density of the printed matter, and solvent resistance (ethanol) are poor.

Claims (8)

A composite resin dispersion comprising composite resin particles containing a polyester resin (A) segment and a (meth)acrylic resin (B) segment,
The alcohol component constituting the polyester resin (A) contains at least 3-methyl-1,5-pentanediol, and the content of 3-methyl-1,5-pentanediol in the alcohol component is 30 mol % or more and 85 mol % or less . The composite resin dispersion according to claim 1, wherein the content of the (meth)acrylic acid-derived constituent units constituting the (meth)acrylic resin (B) segment is 10% by mass or more and 50% by mass or less of all monomer constituent units constituting the (meth)acrylic resin (B) segment. The composite resin dispersion according to claim 1 or 2, wherein the acid value of the (meth)acrylic resin (B) is 150 mg KOH/g or more and 300 mg KOH/g or less. The composite resin dispersion according to any one of claims 1 to 3, wherein the mass ratio [(A)/(B)] of the polyester resin (A) segment to the (meth)acrylic resin (B) segment is 20/80 or more and 98/2 or less. The composite resin dispersion according to any one of claims 1 to 4, wherein the composite resin particles are crosslinked composite resin particles crosslinked with a crosslinking agent (C). The composite resin dispersion according to any one of claims 1 to 5, which is for inkjet recording. A water-based ink containing composite resin particles and a pigment,
the composite resin comprises a polyester resin (A) segment and a (meth)acrylic resin (B) segment, the polyester resin (A) comprises a structural unit derived from an alcohol component and a structural unit derived from a carboxylic acid component, and the alcohol component comprises at least 3-methyl-1,5-pentanediol. The water-based ink of claim 7, wherein the pigment is in the form of pigment-containing polymer particles.