JP2019163353A - Ink, ink storage container, recording device, and recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the image density when, for example, an image formed by applying a pigment ink containing resin particles to a recording medium such as coated paper is heated. On the other hand, when the resin particles are not contained in the pigment ink, there is a problem that the fixability of the image to the recording medium and the storability of the pigment ink are reduced. That is, conventionally, it has been difficult to achieve both image density, fixability, and storage stability. SOLUTION: The copolymer contains water, a pigment, a copolymer, and a water-soluble polyester, and the copolymer has any one structural unit selected from a predetermined general formula and a structural unit having an anionic functional group. And an ink having: [Selection diagram] None

Description

  The present invention relates to an ink, an ink container, a recording apparatus, and a recording method.

  As inks used in the ink jet recording system, inks using dyes or pigments are known. In such an ink, an ink using a pigment is widely used from the viewpoint of weather resistance and water resistance. In recent years, the development of pigment inks for high-speed continuous entry machines has been promoted, and there is a demand for pigment inks that can provide high-quality images even when printing at high speed. In a high-speed continuous book machine, the target main media may be offset coated paper (also called coated paper), but this offset coated paper obtains high image quality when pigment ink is used. The mechanism is different from that of plain paper. Further, such pigment ink often contains resin particles for the purpose of improving the fixability of the image formed by applying the ink to the recording medium and the storage stability of the ink.

  Patent Document 1 discloses that a styrene acrylic resin particle is further contained in an ink containing water, a coloring material, and a predetermined copolymer.

  Patent Document 2 discloses that a black ink composition containing water, carbon black, and a water-soluble polyurethane resin further contains a fine particle emulsion.

  However, for example, when an image formed by applying a pigment ink containing resin particles to a recording medium such as coated paper is heated, there is a problem that the image density decreases. On the other hand, when the resin particles are not contained in the pigment ink, a decrease in image density due to heating is suppressed, but there is a problem in that the fixability of the image to the recording medium and the storage stability of the pigment ink are decreased. Therefore, it has been difficult to achieve both image density, fixability and storage stability.

The invention according to claim 1 contains water, a pigment, a copolymer, and a water-soluble polyester, and the copolymer is a structural unit represented by any one of the following general formulas (1) to (3): And an anionic functional group-containing structural unit.
(In the general formula (1), R ¹ represents a hydrogen atom or a methyl group, and A ₁ , A ₂ , and A ₃ are each independently —O—, —CO—O—, —O—CO—, Represents a divalent substituent selected from the group of —CO—NH—, —NH—CO—, —NH—CO—O—, —O—CO—NH—, wherein X ₁ and X ₂ are each independently A single bond, an alkylene group having 1 to 12 carbon atoms, an alkenylene group having 1 to 12 carbon atoms, a divalent group selected from the group consisting of general formula (4), general formula (5), and general formula (6). Represents a substituent, and Ar represents an aromatic group.)
(In the general formula (2), R ¹ , A ₁ , A ₂ , X ₁ , X ₂ and Ar each independently represent the same as in the general formula (1).)
(In the general formula (3), R ¹ , A ₁ , A ₂ , A ₃ , X ₁ , X ₂ and Ar each independently represent the same as in the general formula (1), and A ₄ represents —O Divalent substitution selected from the group of-, -CO-O-, -O-CO-, -CO-NH-, -NH-CO-, -NH-CO-O-, -O-CO-NH-. And Z represents a divalent hydrocarbon group.)
(In the general formula (4), l represents an integer of 1 or more and 10 or less.)
(In the general formula (5), m represents an integer of 1 or more and 10 or less.)
(In the general formula (6), n represents an integer of 1 or more and 10 or less.)

  The present invention has an excellent effect of achieving both image density, fixing property and storage stability.

FIG. 1 is an explanatory perspective view of the recording apparatus. FIG. 2 is an explanatory perspective view of the main tank.

  Hereinafter, an embodiment of the present invention will be described.

<< Ink >>
Hereinafter, a copolymer, an organic solvent, water, a pigment, a resin, an additive, and the like used for the ink will be described.

<Copolymer>
The copolymer contained in the ink has a structural unit represented by any one of the general formulas (1) to (3) and a structural unit having an anionic functional group, and if necessary, And other structural units.

-Structural unit represented by general formula (1)-
In general formula (1), R ¹ represents a hydrogen atom or a methyl group. A ₁ , A ₂ , and A ₃ are each independently —O—, —CO—O—, —O—CO—, —CO—NH—, —NH—CO—, —NH—CO—O—, Represents a divalent substituent selected from the group of —O—CO—NH—. X ₁ and X ₂ are each independently a single bond, an alkylene group having 1 to 12 carbon atoms, an alkenylene group having 1 to 12 carbon atoms, general formula (4), general formula (5), and general formula ( 6) represents a divalent substituent selected from the group of 6). Ar represents an aromatic group and is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a benzene ring, a condensed benzene ring, a non-benzene aromatic ring, and a composite aromatic ring. Specific examples include phenyl, tolyl, xylyl, naphthyl, methylnaphthyl, anthryl, phenanthrenyl, biphenyl, pyridinyl, triazinyl, phenanthryl, pyrenyl, and fluorenyl groups. .

In general formula (4), l represents an integer of 1 or more and 10 or less.

In general formula (5), m represents an integer of 1 or more and 10 or less.

In general formula (6), n represents an integer of 1 or more and 10 or less.

-Structural unit represented by general formula (2)-
In general formula (2), R ¹ , A ₁ , A ₂ , X ₁ , X ₂ and Ar each independently represent the same as in general formula (1).

-Structural unit represented by general formula (3)-
In the general formula ^{_{(3), R 1, A}} 1, A 2, A 3, X 1, X 2, and Ar are the same as the general formula (1) independently. A ₄ is selected from the group of —O—, —CO—O—, —O—CO—, —CO—NH—, —NH—CO—, —NH—CO—O—, —O—CO—NH—. Represents a divalent substituent. Z represents a divalent hydrocarbon group, and examples thereof include an aliphatic hydrocarbon group, a cycloaliphatic hydrocarbon group, an aromatic hydrocarbon group, and the like, an alkylene group having 2 to 15 carbon atoms, and a carbon number of 2 An alkenylene group having 15 to 15 carbon atoms, a cyclic saturated hydrocarbon group having 3 to 15 carbon atoms, a cyclic unsaturated hydrocarbon group having 3 to 15 carbon atoms, and an arylene group having 6 to 15 carbon atoms are preferable.

  Hereinafter, structural units represented by any one of the general formulas (1) to (3) will be exemplified.

  The aromatic group represented by Ar present at the ends of the general formula (1), the general formula (2), and the general formula (3) is excellent due to π-π stacking with a pigment that is a coloring material in the ink. Has a pigment adsorption power. When the above-mentioned copolymer is used in preparing a pigment dispersion in which a pigment is dispersed in water, since the adsorptive power with the pigment is high, the dispersion stability is increased and a dispersion having high storage stability is obtained. Further, even when a hydrophilic organic solvent is added to the ink, the dispersibility is maintained and an ink having high storage stability can be obtained.

  The content of the structural unit represented by any one of the general formulas (1) to (3) is not particularly limited and may be appropriately selected depending on the intended purpose. However, with respect to the total amount of the copolymer 30 mass% or more and 80 mass% or less is preferable, and 40 mass% or more and 70 mass% or less are more preferable. When the content is within a preferable range, it is advantageous in that the image density and storage stability are improved when used in an ink.

Moreover, it is preferable that the structural unit represented by any one of General formula (1) thru | or (3) is a structural unit represented by General formula (7) below.
In General Formula (7), R ² represents a hydrogen atom or a methyl group, and L represents an alkylene group having 2 to 16 carbon atoms. Hereinafter, although the specific example of the monomer which forms the structural unit of General formula (7) is given, it is not necessarily limited to these.

  In the general formula (7), polar groups such as —CO—O— group and —NH—CO— group contained in the structural unit are well-balanced in the structural unit, and the adsorbability with the pigment is sufficiently maintained. The dispersion state can be stably maintained even in the solvent used for the ink.

-Structural unit having an anionic functional group-
The structural unit having an anionic functional group is formed by copolymerizing a monomer having an anionic functional group. Examples of the monomer having an anionic functional group include an unsaturated carboxylic acid monomer, an unsaturated sulfonic acid monomer, and an unsaturated phosphoric acid monomer. These monomers having an anionic functional group may be used alone or in admixture of two or more.
Examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid.
Examples of the unsaturated sulfonic acid monomer include styrene sulfonic acid and 2-acrylamido-2-methylpropane sulfonic acid.
Examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acrylic acid. And leuoxyethyl phosphate.

The structural unit having an anionic functional group may be neutralized with a base.
Examples of the base include sodium hydroxide, potassium hydroxide, lithium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide, tetrahexylammonium hydroxide. , Triethylmethylammonium hydroxide, tributylmethylammonium hydroxide, trioctylmethylammonium hydroxide, 2-hydroxyethyltrimethylammonium hydroxide, tris (2-hydroxyethyl) methylammonium hydroxide, propyltrimethylammonium hydroxide, hexyltrimethylammonium Hydroxide, octyltrimethylammonium hydride Xoxide, nonyltrimethylammonium hydroxide, decyltrimethylammonium hydroxide, dodecyltrimethylammonium hydroxide, tetradecyltrimethylammonium hydroxide, hexadecyltrimethylammonium hydroxide, octadecyltrimethylammonium hydroxide, didodecyldimethylammonium hydroxide, ditetradecyl Dimethylammonium hydroxide, dihexadecyldimethylammonium hydroxide, dioctadecyldimethylammonium hydroxide, ethylhexadecyldimethylammonium hydroxide, aqueous ammonia, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, Examples include ethanolamine, methylethanolamine, methyldiethanolamine, dimethylethanolamine, monopropanolamine, dipropanolamine, tripropanolamine, isopropanolamine, morpholine, N-methylmorphone, N-methyl-2-pyrrolidone, and 2-pyrrolidone. .
You may use the base as a neutralizing agent individually or in mixture of 2 or more types. The neutralization treatment may be performed when a monomer having an anionic functional group is copolymerized, or may be performed when the copolymer is dissolved.

  The content of the structural unit having an anionic functional group is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 30% by mass to 80% by mass with respect to the total amount of the copolymer. 40 mass% or more and 70 mass% or less is more preferable.

  The molar ratio between the structural unit represented by any one of the general formulas (1) to (3) and the structural unit having an anionic functional group is not particularly limited, and is appropriately determined depending on the purpose. It can be selected from the viewpoints of the balance between hydrophilicity and hydrophobicity of the copolymer, image density, and storage stability. For example, from the viewpoint of storage stability, “1.0: 1.2 to 1.0: 2.0” is preferable. Further, from the viewpoint of image density, “1.0: 1.5 to 1.0: 2.5” is preferable. Therefore, the molar ratio between the structural unit represented by any one of the general formulas (1) to (3) and the structural unit having an anionic functional group is “1.0: 1.5-1”. 0.0: 2.0 "is most preferred.

Moreover, as a structural unit which has an anionic functional group, it is preferable to have a structural unit represented by General formula (8).
In the general formula (8), R ³ represents a hydrogen atom or a methyl group, and X represents a hydrogen atom or a cation.

When X is a cation, the oxygen adjacent to the cation is present as O ⁻ . As cations, sodium ion, potassium ion, lithium ion, tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion, tetrapentylammonium ion, tetrahexylammonium ion, triethylmethylammonium ion, tributylmethyl Ammonium ion, trioctylmethylammonium ion, 2-hydroxyethyltrimethylammonium ion, tris (2-hydroxyethyl) methylammonium ion, propyltrimethylammonium ion, hexyltrimethylammonium ion, octyltrimethylammonium ion, nonyltrimethylammonium ion, decyltrimethyl Ammonium ion Dodecyltrimethylammonium ion, tetradecyltrimethylammonium ion, hexadecyltrimethylammonium ion, octadecyltrimethylammonium ion didodecyldimethylammonium ion, ditetradecyldimethylammonium ion, dihexadecyldimethylammonium ion, dioctadecyldimethylammonium ion, ethylhexadecyl Dimethylammonium ion, ammonium ion, dimethylammonium ion, trimethylammonium ion, monoethylammonium ion, diethylammonium ion, triethylammonium ion, monoethanolammonium ion, diethanolammonium ion, triethanolammonium ion, methylethanol ammonium ion Ion, methyldiethanolammonium ion, dimethylethanolammonium ion, monopropanolammonium ion, dipropanolammonium ion, tripropanolammonium ion, isopropanolammonium ion, morpholinium ion, N-methylmorpholinium ion, N-methyl-2- Examples include pyrrolidonium ions and 2-pyrrolidonium ions. X is preferably hydrogen in terms of reactivity with cations derived from cationic substances such as calcium ions contained in paper.

  In addition, the monomer that forms the general formula (8) is preferably a monomer having a carboxyl group, and more preferably acrylic acid or methacrylic acid, from the viewpoint of storage stability of the ink.

-Other structural units-
In addition to the structural unit represented by any one of the general formulas (1) to (3) and the structural unit having an anionic functional group, the copolymer further includes other structural units as necessary. Including.
Other structural units are structural units derived from, for example, a polymerizable hydrophobic monomer, a polymerizable hydrophilic monomer, a polymerizable surfactant, and the like.

-Synthesis Method of Copolymer Containing Structural Unit Represented by General Formula (1)-
The copolymer containing the structural unit represented by the general formula (1) is obtained by copolymerizing a monomer that is a base of the structural unit represented by the general formula (1), a monomer having an anionic functional group, and the like. can get.
As an example, the monomer that is the base of the structural unit represented by the general formula (1) can be synthesized and used as follows. That is, as shown in the following reaction formulas 1 and 2, first, the diisocyanate compound (A-1) and naphthol (A-2) are reacted in the presence of an acid acceptor such as an amine or pyridine, thereby producing a reaction intermediate. (A-3) is obtained. Subsequently, the monomer which becomes the origin of the structural unit represented by General formula (1) can be obtained by making hydroxyalkyl methacrylate (A-4) and (A-3) react.
(Reaction Formula 1)
(Reaction Formula 2)
As another method, (A-1) and (A-4) are reacted first, and then (A-2) is reacted with the element of the structural unit represented by the general formula (1). Can be obtained.
As another method, as shown in the following reaction formula 3, the diisocyanate compound (A-1), naphthol (A-2), and hydroxyalkyl methacrylate (A-4) are reacted, and represented by the general formula (1). It is also possible to obtain a monomer from which the structural unit is formed.
(Reaction Formula 3)

As a method for synthesizing the copolymer containing the structural unit represented by the general formula (1), a method using a radical polymerization initiator is preferable because the polymerization operation and the adjustment of the molecular weight are easy. A solution polymerization method is more preferable.
Preferred solvents for radical polymerization by the solution polymerization method include ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone, acetate solvents such as ethyl acetate and butyl acetate, and aromatic carbonization such as benzene, toluene and xylene. Examples thereof include hydrogen solvents, isopropanol, ethanol, cyclohexane, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, hexamethylphosphoamide, and the like, and ketone solvents, acetate solvents, and alcohol solvents are more preferable.
There is no restriction | limiting in particular as a radical polymerization initiator, According to the objective, it can select suitably. Examples thereof include peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxydicarbonates, peroxyesters, cyano azobisisobutyronitriles, azobis (2-methylbutyronitrile), Examples thereof include azobis (2,2′-isovaleronitrile), non-cyano dimethyl-2,2′-azobisisobutyrate, and the like. Among these, organic peroxides and azo compounds are preferable, and azo compounds are particularly preferable because the molecular weight is easily controlled and the decomposition temperature is low.
There is no restriction | limiting in particular in content of a radical polymerization initiator, Although it can select suitably according to the objective, 1-10 mass% is preferable with respect to the total amount of a polymerizable monomer.
An appropriate amount of a chain transfer agent may be added to adjust the molecular weight of the polymer.
Examples of chain transfer agents include mercaptoacetic acid, mercaptopropionic acid, 2-propanethiol, 2-mercaptoethanol, thiophenol, dodecyl mercaptan, 1-dodecanethiol, thioglycerol, and the like.
The polymerization temperature is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 50 ° C to 150 ° C, more preferably 60 ° C to 100 ° C. The polymerization time is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 3 to 48 hours.

-Synthesis Method of Copolymer Containing Structural Unit Represented by General Formula (2)-
The copolymer containing the structural unit represented by the general formula (2) is obtained by copolymerizing a monomer that is a base of the structural unit represented by the general formula (2), a monomer having an anionic functional group, and the like. can get.
As an example, the monomer that is the base of the structural unit represented by the general formula (2) can be synthesized and used as follows. That is, as shown in the following reaction formula 4, a diol compound (B-1) and a naphthalene derivative (B-2) having a carboxyl group are reacted in the presence of an acid catalyst to produce a reaction intermediate (B-3). )
(Reaction Formula 4)
As another method, as shown in the following reaction formula 5, an acid chloride (B-4) of a naphthalene derivative having a carboxyl group and a diol compound (B-1) are converted into an acid acceptor such as an amine or pyridine. The reaction intermediate (B-3) can also be obtained by reacting in the presence of.
(Reaction Formula 5)
Next, as shown in the following reaction formula 6, (meth) acrylic acid chloride (B-5) and (B-3) are reacted to form a monomer serving as a base of the structural unit represented by the general formula (2) You can also get
(Reaction Formula 6)

  As a method for synthesizing the copolymer including the structural unit represented by the general formula (2), a method similar to the method for synthesizing the copolymer including the structural unit represented by the general formula (1) is preferable.

-Synthesis Method of Copolymer Containing Structural Unit Represented by General Formula (3)-
The copolymer containing the structural unit represented by the general formula (3) is obtained by copolymerizing a monomer that is a base of the structural unit represented by the general formula (3), a monomer having an anionic functional group, and the like. can get.
As an example, the monomer that is the base of the structural unit represented by the general formula (3) can be synthesized and used as follows. That is, as shown in the following reaction formulas 7 to 9, the diol compound (C-1) and the naphthalene acid compound (C-2) are first condensed to obtain a reaction intermediate (C-3). Next, the diisocyanate compound (C-4) and (C-3) are reacted in the presence of an acid acceptor such as amine or pyridine or in the presence of a metal catalyst such as tin or titanium, thereby producing a reaction intermediate (C -5) is obtained. Subsequently, the monomer represented by General formula (3) can be obtained by reacting hydroxyalkyl (meth) acrylate (C-6) and (C-5).
The compound represented by (C-2) is not particularly limited as long as it is a naphthalene acid compound that can be condensed with a hydroxy group, and the group represented by L is, for example, a carboxylic acid or a carboxylic acid ester such as a hydroxy group or an alkoxide group. Or a halogen-based leaving group such as chlorine, bromine and fluorine, or a leaving group such as tosyl group, mesyl group and ammonium ion, but is not limited thereto.
(Reaction Formula 7)
(Reaction Formula 8)
(Reaction Formula 9)
As another method, (C-4) and (C-6) are reacted first, and then (C-1) and (C-2) are reacted next. (C-1) And an intermediate obtained by reacting (C-2) with an intermediate obtained by reacting (C-4) and (C-6) separately, etc. Although the monomer represented by 3) can be obtained, there is no particular limitation on the order of reacting (C-1), (C-2), (C-4), and (C-6).
As another method, as shown in the following reaction formula 10, diol compound (C-1), naphthalene acid compound (C-2), diisocyanate compound (C-4), hydroxyalkyl (meth) acrylate (C- The monomer represented by the general formula (3) can also be obtained by reacting 6).
(Reaction Formula 10)

  As a method for synthesizing the copolymer containing the structural unit represented by the general formula (3), a method similar to the method for synthesizing the copolymer containing the structural unit represented by the general formula (1) is preferable.

-Physical properties of copolymer-
The weight average molecular weight of the copolymer is preferably 5000 to 50000 in terms of polystyrene. More preferably, it is 15000-40000. When the weight average molecular weight is within the preferred range, it is advantageous in that the image density and storage stability are good when used in ink.

-Amount of copolymer added-
The amount of the copolymer added relative to the total amount of the ink is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.05% by mass or more and 10.0% by mass or less in terms of solid content. 3 mass% or more and 5.0 mass% or less are more preferable. When the content is 0.05% by mass or more, the effect of dispersibility and storage stability is improved, and when the content is 10.0% by mass or less, the viscosity range is suitable for discharging ink from the head. Is possible.
The copolymer is not particularly limited, and can be used as a pigment dispersant or an additive to the pigment dispersion. When used as a pigment dispersant, further improvement in storage stability is observed in an ink having a high water-soluble organic solvent content. The content of the copolymer is not particularly limited when used as a pigment dispersant, and can be appropriately selected according to the purpose. For example, 1 part by mass or more and 100 parts by mass or less is preferable with respect to 100 parts by mass of the pigment, and 5 parts by mass or more and 80 parts by mass or less are more preferable. When the content is within the above range, it is advantageous in that image density and storage stability are improved. In addition, you may use another dispersing agent together in the range which does not impair the effect as a dispersing agent of a copolymer.

<Resin>
The ink of this embodiment contains a resin, and the resin is a water-soluble polyester. The “water-soluble” in the water-soluble polyester means that 10% by mass or more dissolves in water at room temperature (25 ° C.). By using the water-soluble polyester and the above-mentioned copolymer together, for example, even when an image formed by applying a pigment ink to a recording medium such as coated paper is heated, A reduction in image density can be suppressed. This will be described below.
In general, as recording media, plain paper having high water and ink absorbability and coated paper having low water and ink absorbency are known. And when trying to obtain an image with high image density on these recording media, if it is plain paper, in order to prevent the pigment from excessively penetrating into the plain paper and reducing the image density, the pigment Is designed so that the ink can be kept near the surface of the recording medium. On the other hand, in the case of coated paper, the pigment penetrates into the coated paper excessively, and it is less likely that the image density is reduced compared to plain paper. Ink is designed to improve the image density by making the dispersion state (surface shape of the image area) uniform.
However, even if the present inventors improve the image density by making the pigment dispersion state uniform in the image formed by applying the ink, the image portion is then used for the purpose of drying the image portion. A problem was found in which the dispersion state of the pigment in the image area changes and the image density decreases when the is heated. As a result of various studies, it has been found that the dispersion state of the image area is changed by the resin emulsion often contained in the ink during heating, and the image density is lowered.
On the other hand, when the resin particles are not contained in the ink, a decrease in the image density due to heating is suppressed, but there is a problem that the fixing property of the image to the recording medium and the storage stability of the ink are deteriorated. In addition, when a water-soluble resin is used in place of the resin particles in order to improve the fixability, the ink storage stability is lowered.
Therefore, when the above copolymer having a specific structure for improving the storage stability of the ink and the water-soluble polyester resin are used in combination, the change in the dispersion state of the pigment in the image portion is suppressed even when the image portion is heated, and the image It has been found that an ink having an excellent effect of achieving both density, fixing ability and storage stability can be obtained. In particular, when a water-soluble polyester resin having a low Tg is used, the fixability is improved even when the content of the water-soluble polyester resin is small, so that the storage stability can be further improved.
When water-soluble polyurethane resin or the like is used instead of the water-soluble polyester resin, those resins having a low Tg are generally used, so that the surface roughness Ra of the image portion is increased without going through a heating step. As a result, the image density is low from the beginning. Therefore, the kind of water-soluble resin needs to be a polyester resin.

What is marketed can be used suitably as water-soluble polyester, for example, plus coat (made by a mutual interaction chemical industry company) etc. are mentioned.
The Tg of the water-soluble polyester is preferably −20 ° C. or higher and 110 ° C. or lower, and more preferably −20 ° C. or higher and 20 ° C. or lower. In particular, when Tg is −20 ° C. or higher and 20 ° C. or lower, sufficient fixability and storage stability can be obtained even if the amount of water-soluble polyester added is small.
The content of the water-soluble polyester is preferably 0.1% by mass or more and 2.0% by mass or less, more preferably 0.5% by mass or more and 1.2% by mass or less, based on the total amount of the ink. More preferably, it is 0.5 mass% or more and 0.8 mass% or less. When the content of the water-soluble polyester is 2.0% by mass or less, the storage stability is improved, and when it is 0.1% by mass or more, the fixability is improved.
The mass ratio of the water-soluble polyester content in the ink to the content of the copolymer in the ink (water-soluble polyester / copolymer) is preferably 0.13 or more and 2.67 or less. More preferably, it is 0.67 or more and 1.60 or less. By being in this range, it is possible to achieve a good balance between image density, fixability and storage stability.

  Although this embodiment does not exclude that the resin emulsion is contained in the ink, it is preferable that the ink does not substantially contain the resin emulsion. By substantially not including a resin emulsion in the ink, it is possible to further suppress a decrease in image density. In addition, “substantially not containing” means that the content of the resin emulsion with respect to the total amount of ink is 0.1% by mass or less. Further, it is preferable that the ink does not contain any resin emulsion.

<Organic solvent>
The organic solvent used in the present invention is not particularly limited, and a water-soluble organic solvent can be used. Examples thereof include ethers such as polyhydric alcohols, polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines and sulfur-containing compounds.
Specific examples of the polyhydric alcohol include, for example, ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, and 1,4-butane. Diol, 2,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol 2,4-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, Glycerin, 1,2,6-hexanetriol, 2-ethyl-1,3- Hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl-1,3-pentanediol, petriol, and the like.
Examples of the polyhydric alcohol alkyl ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether and the like.
Examples of polyhydric alcohol aryl ethers include ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.
Examples of nitrogen-containing heterocyclic compounds include 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, and γ-butyrolactone. Can be mentioned.
Examples of amides include formamide, N-methylformamide, N, N-dimethylformamide, 3-methoxy-N, N-dimethylpropionamide, 3-butoxy-N, N-dimethylpropionamide and the like.
Examples of amines include monoethanolamine, diethanolamine, and triethylamine.
Examples of sulfur-containing compounds include dimethyl sulfoxide, sulfolane, thiodiethanol and the like.
Examples of other organic solvents include propylene carbonate and ethylene carbonate.
In addition to functioning as a wetting agent, it is preferable to use an organic solvent having a boiling point of 250 ° C. or lower because good drying properties can be obtained.

As the organic solvent, a polyol compound having 8 or more carbon atoms and a glycol ether compound are also preferably used. Specific examples of the polyol compound having 8 or more carbon atoms include 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, and the like.
Specific examples of glycol ether compounds include polyhydric alcohol alkyls such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether. Examples of ethers include polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.

  A polyol compound having 8 or more carbon atoms and a glycol ether compound can improve ink permeability when paper is used as a recording medium.

  The content of the organic solvent in the ink is not particularly limited and can be appropriately selected according to the purpose, but is preferably 10% by mass or more and 60% by mass or less from the viewpoint of the drying property and ejection reliability of the ink, 20 mass% or more and 60 mass% or less are more preferable.

<Water>
The water content in the ink is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 10% by mass or more and 90% by mass or less, and 20% by mass from the viewpoint of ink drying property and ejection reliability. % To 60% by mass is more preferable.

<Pigment>
An inorganic pigment or an organic pigment can be used as the pigment. These may be used alone or in combination of two or more. A mixed crystal may be used as the pigment.
As the pigment, for example, a black pigment, a yellow pigment, a magenta pigment, a cyan pigment, a white pigment, a green pigment, an orange pigment, a glossy pigment such as gold or silver, a metallic pigment, or the like can be used.
Carbon black produced by known methods such as contact method, furnace method, thermal method in addition to titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow as inorganic pigments Can be used.
Organic pigments include azo pigments, polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments). Dye chelates (for example, basic dye type chelates, acidic dye type chelates), nitro pigments, nitroso pigments, aniline black, and the like can be used. Of these pigments, those having good affinity with the solvent are preferably used. In addition, resin hollow particles and inorganic hollow particles can also be used.
Specific examples of pigments include black for carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black, channel black, or copper, iron (CI pigment black 11). And metal pigments such as titanium oxide, and organic pigments such as aniline black (CI Pigment Black 1).
Further, for color use, C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104 , 108, 109, 110, 117, 120, 138, 150, 153, 155, 180, 185, 213, C.I. I. Pigment orange 5, 13, 16, 17, 36, 43, 51, C.I. I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48: 2, 48: 2 (Permanent Red 2B (Ca)), 48: 3, 48: 4, 49: 1, 52: 2, 53: 1, 57: 1 (Brilliant Carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81, 83, 88, 101 (Bengara), 104, 105, 106, 108 ( Cadmium red), 112, 114, 122 (quinacridone magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 184, 185, 190, 193, 202, 207, 208, 209, 213, 219, 224, 254, 264, C.I. I. Pigment violet 1 (rhodamine lake), 3, 5: 1, 16, 19, 23, 38, C.I. I. Pigment Blue 1, 2, 15 (phthalocyanine blue), 15: 1, 15: 2, 15: 3, 15: 4 (phthalocyanine blue), 16, 17: 1, 56, 60, 63, C.I. I. Pigment Green 1, 4, 7, 8, 10, 17, 18, 36, etc.

  The content of the pigment in the ink is preferably 0.1% by mass or more and 15% by mass or less, more preferably 1% by mass or more and 10% by mass or less from the viewpoints of improvement in image density, good fixability and ejection stability. It is.

As a method of obtaining an ink by dispersing a pigment, a method of introducing a hydrophilic functional group into the pigment to form a self-dispersing pigment, a method of coating and dispersing the surface of the pigment with a resin, and a dispersing agent are used. Method, etc.
As a method of introducing a hydrophilic functional group into a pigment to obtain a self-dispersing pigment, for example, a method of making it dispersible in water by adding a functional group such as a sulfone group or a carboxyl group to the pigment (for example, carbon) Is mentioned.
As a method for coating the surface of the pigment with a resin and dispersing it, a method in which the pigment is included in microcapsules and dispersible in water can be mentioned. This can be paraphrased as a resin-coated pigment. In this case, it is not necessary that all pigments blended in the ink are coated with a resin, and within a range where the effects of the present invention are not impaired, uncoated pigments and partially coated pigments are dispersed in the ink. It may be.
Examples of the method of dispersing using a dispersant include a method of dispersing using a known low-molecular type dispersant or high-molecular type dispersant represented by a surfactant.
As the dispersant, for example, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, or the like can be used depending on the pigment.
As the dispersant, RT-100 (nonionic surfactant) manufactured by Takemoto Yushi Co., Ltd. and Naphthalenesulfonic acid Na formalin condensate can also be suitably used as the dispersant.
A dispersing agent may be used individually by 1 type, or may use 2 or more types together.

<Pigment dispersion>
An ink can be obtained by mixing a material such as water or an organic solvent with a pigment. Further, it is also possible to produce an ink by mixing a pigment, other water, a dispersant, and the like into a pigment dispersion and mixing a material such as water or an organic solvent.
The pigment dispersion is obtained by mixing and dispersing water, a pigment, a pigment dispersant, and other components as necessary, and adjusting the particle size. For dispersion, a disperser is preferably used.
The particle size of the pigment in the pigment dispersion is not particularly limited, but the maximum frequency is 20 nm or more in terms of maximum number because the pigment dispersion stability is good and the image quality such as ejection stability and image density is also high. 500 nm or less is preferable and 20 nm or more and 150 nm or less are more preferable. The particle size of the pigment can be measured using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack Bell Co., Ltd.).
The content of the pigment in the pigment dispersion is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of obtaining good ejection stability and increasing the image density, 0.1% by mass The content is preferably 50% by mass or less and more preferably 0.1% by mass or more and 30% by mass or less.
The pigment dispersion is preferably degassed by filtering coarse particles with a filter, a centrifugal separator or the like, if necessary.

<Additives>
If necessary, a surfactant, an antifoaming agent, an antiseptic / antifungal agent, a rust inhibitor, a pH adjuster, and the like may be added to the ink.

<Ink physical properties>
In this embodiment, a coating layer is formed on a support, the surface roughness Ra is 30 nm or more and 35 nm or less, and the transfer of pure water to the recording medium at a contact time of 100 ms measured with a dynamic scanning absorptiometer. Adhesion amount to a recording medium having an amount of 2 ml / m ² or more and 35 ml / m ² or less and a transfer amount of pure water to the recording medium of 3 ml / m ² or more and 40 ml / m ² or less at a contact time of 400 ms. When a solid image is formed by applying ink so as to be 500 mg / A4 or more and 700 mg / A4 or less and heating at 100 ° C. for 2 minutes, the surface roughness Ra of the solid image becomes 15 nm or more and 25 nm or less. Ink is preferred. By using the above copolymer together with a water-soluble polyester resin, even when the image area is heated, the change in the dispersion state of the pigment in the image area is suppressed, and as a result, the surface roughness Ra of the solid image increases. Is suppressed. And by suppressing that surface roughness Ra becomes large, it will be suppressed that image density becomes low.

  Here, in this embodiment, the measured values of the surface roughness Ra of the solid image and the surface roughness Ra of the recording medium are defined as values measured using an AFM (atomic force microscope). The size of the visual field when quantifying the surface roughness Ra is 1 μm square. In the measurement of the surface roughness Ra, methods / apparatuses such as an optical microscope, a confocal microscope, and an AFM are often used. When the surface roughness Ra is measured with a field of view of 1 μm square using the AFM, The highest correlation with the image density is obtained. The AFM measurement at this time is preferably performed in the tapping mode. When the measurement is performed in the contact mode, there is a problem that the image surface is destroyed. Further, since the measurement is performed in the air, the measurement in the non-contact mode may be performed. However, since the resolution of the atomic image level is not required, the measurement in the non-contact mode is not particularly required.

Further, in the present embodiment, the recording layer is formed on the support, the surface roughness Ra is 30 nm or more and 35 nm or less, and the pure water is recorded on the recording medium at a contact time of 100 ms measured by a dynamic scanning absorption meter. For a recording medium having a transition amount of 2 ml / m ^{2 to} 35 ml / m ² and a transition amount of pure water to the recording medium at a contact time of 400 ms of 3 ml / m ^{2 to} 40 ml / m ² , A solid image was formed by applying ink so that the adhesion amount was 500 mg / A4 or more and 700 mg / A4 or less and then heating at 100 ° C. for 2 minutes, and the solid image was obtained by measuring with a goniophotometer. An ink in which the peak half-width (full width at half maximum) σ is 2.0 or more and 2.4 or less is created by fitting a peak near 45 degrees regular reflection with the normal distribution function of the following formula (1). Good to be Arbitrariness. By using the above copolymer and a water-soluble polyester resin together, even if the image portion is heated, the change in the dispersion state of the pigment in the image portion is suppressed, and as a result, the full width at half maximum σ of the solid image may be increased. It is suppressed. A solid image with a small half-value width σ indicates that the dispersion state of the pigment does not change from a uniform state to a non-uniform state even when the image portion is heated, in other words, irregular reflection occurs as the surface roughness increases. Indicates not. Such an image is suppressed from lowering the image density.

The coating layer is formed on the support, the surface roughness Ra is 30 nm or more and 35 nm or less, and the transfer amount of pure water to the recording medium at a contact time of 100 ms measured with a dynamic scanning absorption meter is 2 ml. / M ^{2 to} 35 ml / m ² and the transfer amount of pure water to the recording medium at a contact time of 400 ms is 3 mg / m ² or more and 40 ml / m ² or less. When a solid image is formed by applying ink so as to be A4 or more and 700 mg / A4 or less and heating at 100 ° C. for 2 minutes, the surface roughness Ra of the solid image is 15 nm or more and 25 nm or less, and the solid image The peak half-value width σ created by fitting a peak near 45 ° specular reflection obtained by measuring with a goniophotometer with the normal distribution function of the following formula (1) is 2.0 or less. For 2.4 or less should be ink of the present embodiment.

<< Recording medium >>
The recording medium can be used without particular limitation, and plain paper, glossy paper, special paper, cloth, etc. can be used, but a low-permeability substrate (also referred to as a low-absorption recording medium or a low-absorption substrate). ) Particularly preferably.
The low-permeability base material means a base material having a surface with low water permeability, absorbability, or adsorptivity, and includes a material that does not open to the outside even if there are many cavities inside. Examples of the low-permeability substrate include coated paper used for commercial printing, and a recording medium such as paperboard in which used paper pulp is blended in the middle layer and the back layer and the surface is coated.

<Low permeability substrate>
As the low-permeability substrate, for example, a recording medium such as a coated paper having a support and a surface layer provided on at least one side of the support, and further having other layers as necessary Is mentioned.

A recording medium having a support and a surface layer, the transfer amount of pure water of the recording medium at a contact time of 100ms measured by a dynamic scanning liquid absorption meter, 2 mL / ^{m 2} or more 35 mL / ^{m 2} or less is preferable, 2 mL / M ² or more and 10 mL / m ² or less is more preferable.

  If the transfer amount of ink and pure water at a contact time of 100 ms is too small, beading is likely to occur. If it is too large, the ink dot diameter after image formation may be too smaller than the desired diameter. is there.

Transfer amount of pure water of the recording medium in a dynamic scanning liquid absorption contact time measured by meter 400ms is preferably 3 mL / ^{m 2} or more 40 mL / ^{m 2} or less, and more is 3 mL / ^{m 2} or more 10 mL / ^{m 2} or less preferable.

  If the amount of transfer at a contact time of 400 ms is small, the drying property is insufficient, and if it is too large, the gloss of the image area after drying tends to be low. The amount of pure water transferred to the recording medium at the contact time of 100 ms and 400 ms can be measured on the surface of the recording medium having the surface layer.

  Here, a dynamic scanning absorptiometer (DSA, Kojipa Gikyogaku, Vol. 48, May 1994, pp. 88-92, Kuju Shigenori) has a very short time. It is a device that can measure accurately. The dynamic scanning absorptiometer reads the liquid absorption speed directly from the movement of the meniscus in the capillary, makes the sample a disk, and then scans the liquid absorption head in a spiral, and changes the scanning speed according to a preset pattern. The measurement is automated by a method of automatically changing and measuring the number of points required for one sample.

  A liquid supply head for a paper sample is connected to a capillary via a Teflon (registered trademark) tube, and the position of the meniscus in the capillary is automatically read by an optical sensor. Specifically, the transfer amount of pure water or ink can be measured using a dynamic scanning absorption meter (K350 series D type, manufactured by Kyowa Seiko Co., Ltd.).

  The transfer amount at the contact time of 100 ms and the contact time of 400 ms can be obtained by interpolation from the measured value of the transfer amount at the contact time adjacent to each contact time.

-Support-
There is no restriction | limiting in particular as a support body, According to the objective, it can select suitably, For example, the sheet-like substance like the nonwoven fabric mainly composed of paper mainly made of wood fiber, wood fiber, and synthetic fiber etc. are mentioned.
There is no restriction | limiting in particular in the thickness of a support body, Although it can select suitably according to the objective, 50 micrometers-300 micrometers are preferable. The basis weight of the ^{support, 45g / m 2 ~290g / m} 2 is preferred.

-Surface layer-
The surface layer contains a pigment and a binder (binder), and further contains a surfactant and other components as necessary.
As the pigment, an inorganic pigment or a combination of an inorganic pigment and an organic pigment can be used. Examples of inorganic pigments include kaolin, talc, heavy calcium carbonate, light calcium carbonate, calcium sulfite, amorphous silica, titanium white, magnesium carbonate, titanium dioxide, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, and water. Examples include zinc oxide and chlorite. The amount of the inorganic pigment added is preferably 50 parts by mass or more with respect to 100 parts by mass of the binder.
Examples of the organic pigment include water-soluble dispersions such as styrene-acrylic copolymer particles, styrene-butadiene copolymer particles, polystyrene particles, and polyethylene particles. The addition amount of the organic pigment is preferably 2 parts by mass to 20 parts by mass with respect to 100 parts by mass of the total pigment in the surface layer.
As the binder, it is preferable to use an aqueous resin. As the aqueous resin, at least one of a water-soluble resin and a water-dispersible resin can be suitably used. There is no restriction | limiting in particular as water-soluble resin, According to the objective, it can select suitably, For example, polyvinyl alcohol, cation modified polyvinyl alcohol, acetal modified polyvinyl alcohol, polyester, polyurethane, polyester, polyurethane, etc. are mentioned.
The surfactant contained as necessary in the surface layer is not particularly limited and may be appropriately selected depending on the intended purpose. However, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants can be selected. Either can be used.
There is no restriction | limiting in particular as a formation method of a surface layer, According to the objective, it can select suitably, It can carry out by the method of impregnating or apply | coating the liquid which comprises a surface layer on a support body. Adhesion amount of the liquid constituting the surface layer is not particularly limited and may be appropriately selected depending on the purpose, the solid content ^is preferably ^{0.5g / m 2 ~20g / m 2} , 1g / m 2 ~ 15 g / m ² is more preferable.

<Recording apparatus and recording method>
The ink of the present invention can be suitably used for various recording apparatuses using an ink jet recording method, such as a printer, a facsimile apparatus, a copying apparatus, a printer / fax / copier complex machine, and a three-dimensional modeling apparatus.
In the present invention, the recording apparatus and the recording method are an apparatus capable of ejecting ink, various treatment liquids, and the like to a recording medium, and a method of performing recording using the apparatus. The recording medium means a medium on which ink or various processing liquids can be temporarily attached.
The recording apparatus can include not only a head portion that ejects ink but also means for feeding, transporting, and discharging a recording medium, and other devices called pre-processing devices and post-processing devices. .
The recording apparatus and the recording method may include a heating unit used in the heating step and a drying unit used in the drying step. The heating means and the drying means include, for example, a means for heating and drying the printing surface and the back surface of the recording medium. Although it does not specifically limit as a heating means and a drying means, For example, a warm air heater and an infrared heater can be used. Heating and drying can be performed before printing, during printing, after printing, and the like. In the recording apparatus and the recording method of the present embodiment, after the ejection step of ejecting ink from the ejection means for ejecting ink, a heating step is performed using a heating unit for heating and drying the ink on the ejected recording medium. It is preferable. When heating, it is preferable to heat the recording medium at a temperature of 100 ° C. or higher.
Further, the recording apparatus and the recording method are not limited to those in which significant images such as characters and figures are visualized by ink. For example, what forms patterns, such as a geometric pattern, etc. includes what forms a three-dimensional image.
Further, the recording apparatus includes both a serial type apparatus that moves the ejection head and a line type apparatus that does not move the ejection head, unless otherwise specified.
Furthermore, this recording apparatus can use not only a desktop type but also a wide recording apparatus that can print on an A0 size recording medium, for example, a continuous paper wound up in a roll shape as a recording medium. Also included are continuous paper printers.
An example of the recording apparatus will be described with reference to FIGS. FIG. 1 is a perspective view of the apparatus. FIG. 2 is an explanatory perspective view of the main tank. An image forming apparatus 400 as an example of a recording apparatus is a serial type image forming apparatus. A mechanism unit 420 is provided in the exterior 401 of the image forming apparatus 400. Each ink storage portion 411 of the main tank 410 (410k, 410c, 410m, 410y) for each color of black (K), cyan (C), magenta (M), yellow (Y) is packaged, for example, an aluminum laminate film It is formed by a member. The ink storage unit 411 is stored in, for example, a plastic container case 414. As a result, the main tank 410 is used as an ink cartridge for each color.
On the other hand, a cartridge holder 404 is provided on the inner side of the opening when the cover 401c of the apparatus main body is opened. A main tank 410 is detachably attached to the cartridge holder 404. Thus, the ink discharge ports 413 of the main tank 410 and the discharge heads 434 for the respective colors communicate with each other via the supply tubes 436 for the respective colors, and ink can be discharged from the discharge heads 434 to the recording medium.

  The method of using the ink is not limited to the ink jet recording method, and can be widely used. Besides the ink jet recording method, for example, a blade coating method, a gravure coating method, a bar coating method, a roll coating method, a dip coating method, a curtain coating method, a slide coating method, a die coating method, a spray coating method and the like can be mentioned.

<< Usage >>
The use of the ink of the present invention is not particularly limited and can be appropriately selected depending on the purpose. For example, it can be applied to printed materials, paints, coating materials, foundations and the like. Furthermore, it can be used not only to form two-dimensional characters and images using ink, but also as a three-dimensional modeling material for forming a three-dimensional three-dimensional image (three-dimensional modeled object).
A known three-dimensional modeling apparatus for modeling a three-dimensional model can be used, and is not particularly limited. For example, a three-dimensional modeling apparatus including an ink storage unit, a supply unit, a discharge unit, a drying unit, or the like is used. be able to. The three-dimensional structure includes a three-dimensional structure obtained by repeatedly applying ink. Further, a molded product obtained by processing a structure provided with ink on a substrate such as a recording medium is also included. The molded product is obtained by subjecting a recorded matter or a structure formed in a sheet shape or a film shape to a molding process such as heat stretching or punching, for example, an automobile, OA equipment, It is suitably used for applications in which the surface is molded after decorating, such as meters for electronic devices and cameras, and panels for operation units.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

<Measurement of weight average molecular weight of copolymer>
The measurement was performed by GPC (Gel Permeation Chromatography) under the following conditions.
・ Device: GPC-8020 (manufactured by Tosoh Corporation)
Column: TSK G2000HXL and G4000HXL (manufactured by Tosoh Corporation)
・ Temperature: 40 ℃
・ Solvent: THF (tetrahydrofuran)
-Flow rate: 1.0 mL / min 1 mL of a copolymer having a concentration of 0.5% by mass was injected, and a molecular weight calibration curve prepared from a monodisperse polystyrene standard sample from the molecular weight distribution of the copolymer measured under the above conditions was used. The number average molecular weight Mn and the weight average molecular weight Mw of the copolymer were calculated.

<Example 1>
(Synthesis of copolymer)
62.0 g (525 mmol) of 1,6-hexanediol (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 700 mL of methylene chloride, and 20.7 g (262 mmol) of pyridine was added. To this solution, a solution prepared by dissolving 50.0 g (262 mmol) of 2-naphthalenecarbonyl chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) in 100 mL of methylene chloride was dropped with stirring over 2 hours, and then stirred at room temperature for 6 hours. . After the obtained reaction solution was washed with water, the organic phase was isolated and dried over magnesium sulfate, and the solvent was distilled off. The residue was purified by silica gel column chromatography using a mixed solvent of methylene chloride / methanol (volume ratio 98/2) as an eluent to obtain 52.5 g of 2-naphthoic acid-2-hydroxyhexyl ester.
Next, 42.1 g (155 mmol) of 2-naphthoic acid-2-hydroxyethyl ester was dissolved in 80 mL of dry methyl ethyl ketone and heated to 60 ° C. To this solution, a solution of 24.0 g (155 mmol) of 2-methacryloyloxyethyl isocyanate (produced by Showa Denko KK, Karenz MOI) dissolved in 20 mL of dry methyl ethyl ketone was added dropwise with stirring over 1 hour, and then 70 ° C. For 12 hours. After cooling to room temperature, the solvent was distilled off. The residue was purified by silica gel column chromatography using a mixed solvent of methylene chloride / methanol (volume ratio 99/1) as an eluent, and 57.0 g of the following monomer (1 )

  Next, 1.20 g (16.7 mmol) of acrylic acid (manufactured by Aldrich) and 4.45 g (10.4 mmol) of the monomer (1) were dissolved in 40 mL of dry methyl ethyl ketone to prepare a monomer solution (above The molar ratio of monomer (1) to acrylic acid is “1: 1.6”). After heating 10% of the monomer solution to 75 ° C. under an argon stream, 0.273 g (1.67 mmol) of 2,2′-azoiso (butyronitrile) (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in the remaining monomer solution. Was added dropwise over 1.5 hours and stirred at 75 ° C. for 6 hours. After cooling to room temperature, the resulting reaction solution was dropped into hexane. The precipitated copolymer was separated by filtration and dried under reduced pressure to obtain 8.13 g of copolymer (1) (weight average molecular weight (Mw): 19400, number average molecular weight (Mn): 8200).

  Next, 2.00 g of the obtained copolymer (1) was dissolved in a tetraethylammonium hydroxide aqueous solution so that the concentration of the copolymer was 2.38% by mass and the pH was 8.0. An aqueous solution of copolymer (1) was prepared.

(Adjustment of pigment dispersion)
Next, 16.0 g of carbon black (NIPEX150, manufactured by Degussa) was added to 84.0 g of the aqueous solution of the copolymer (1) and stirred for 12 hours. The obtained mixture was circulated and dispersed for 1 hour at a peripheral speed of 10 m / s using a disk-type bead mill (Shinmaru Enterprises Co., Ltd., KDL type, media: using zirconia balls with a diameter of 0.1 mm), and then the pore size was 1 The mixture was filtered through a 2 μm membrane filter, and a prepared amount of ion-exchanged water was added to obtain 95.0 g of a pigment dispersion (1) (pigment solid content in the pigment dispersion: 16% by mass).

(Ink adjustment)
The following formulation mixture was stirred for 1 hour and then filtered through a membrane filter having a pore size of 1.2 μm to obtain ink (1).
Pigment dispersion (1): 37.5% by mass (solid pigment content in ink: 6.0% by mass, copolymer content in ink: 0.75% by mass)
Water-soluble polyester (Tg: -20 ° C, plus coat Z-3310, manufactured by Kyoyo Chemical Industry Co., Ltd.) ... 0.5% by mass (solid content)
・ 2-ethyl-1,3-hexanediol: 2.0% by mass
・ Propylene glycol: 41.0% by mass
・ Surfactant (DSN-403N, manufactured by Daikin Industries, Ltd.) ... 1.0% by mass
・ High purity water: remaining amount

<Example 2>
Ink (2) was prepared in the same manner as in Example 1 except that the water-soluble polyester was changed from “Plus Coat Z-3310” to “Plus Coat Z-880” in the adjustment of the ink of Example 1.
Water-soluble polyester (Tg: 20 ° C., plus coat Z-880, manufactured by Kyoyo Chemical Industry Co., Ltd.)

<Example 3>
Except for changing the content of the water-soluble polyester “Plus Coat Z-3310” from “0.5% by mass” to “1.2% by mass” in the adjustment of the ink of Example 1, the same procedure as in Example 1 was performed. Ink (3) was prepared.

<Example 4>
Except that the content of the water-soluble polyester “Plus Coat Z-880” was changed from “0.5% by mass” to “1.2% by mass” in the adjustment of the ink of Example 2, the same as in Example 1. Ink (4) was prepared.

<Example 5>
Except for changing the content of the water-soluble polyester “Plus Coat Z-3310” from “0.5% by mass” to “0.1% by mass” in the adjustment of the ink of Example 1, the same procedure as in Example 1 was performed. Ink (5) was prepared.

<Example 6>
Except that the content of the water-soluble polyester “Plus Coat Z-3310” was changed from “0.5% by mass” to “2.0% by mass” in the adjustment of the ink of Example 1, the same as in Example 1 Ink (6) was prepared.

<Example 7>
Ink (7) was produced in the same manner as in Example 1, except that the water-soluble polyester was changed from “Plus Coat Z-3310” to “Plus Coat Z-446” below in the adjustment of the ink of Example 1.
Water-soluble polyester (Tg: 47 ° C., plus coat Z-446, manufactured by Kyoyo Chemical Industry Co., Ltd.)

<Example 8>
(Synthesis of copolymer)
In the synthesis of the copolymer of Example 1, the same procedure as in Example 1 was performed except that the molar ratio “1: 1.6” of the monomer (1) to acrylic acid was changed to “1: 0.5”. Copolymer (2) (weight average molecular weight (Mw): 19100, number average molecular weight (Mn): 7100) was obtained. Next, an aqueous solution of the copolymer (2) was prepared in the same manner as in Example 1 except that the “copolymer (2)” was used instead of the “copolymer (1)”.

(Adjustment of pigment dispersion)
Next, in the preparation of the pigment dispersion of Example 1, a pigment was prepared in the same manner as in Example 1 except that “an aqueous solution of copolymer (2)” was used instead of “an aqueous solution of copolymer (1)”. Dispersion (2) (pigment solid content in pigment dispersion: 16% by mass) was obtained.

(Ink adjustment)
Ink (8) was obtained in the same manner as in Example 1, except that, in the preparation of the ink of Example 1, “Pigment Dispersion (2)” was used instead of “Pigment Dispersion (1)”.

<Example 9>
Ink (9) was prepared in the same manner as in Example 1, except that the water-soluble polyester was changed from “Plus Coat Z-3310” to “Plus Coat Z-880” in the adjustment of the ink of Example 8.

<Example 10>
Except for changing the content of the water-soluble polyester “Plus Coat Z-3310” from “0.5% by mass” to “1.2% by mass” in preparing the ink of Example 8, the same procedure as in Example 8 was performed. Ink (10) was prepared.

<Example 11>
Except that the content of the water-soluble polyester “Plus Coat Z-880” was changed from “0.5% by mass” to “1.2% by mass” in the adjustment of the ink of Example 9, the same as in Example 9 Ink (11) was prepared.

<Comparative Example 1>
(Ink adjustment)
The following formulation mixture was stirred for 1 hour and then filtered through a membrane filter having a pore size of 1.2 μm to obtain ink (12).
Pigment dispersion (1): 37.5% by mass (solid pigment content in ink: 6.0% by mass, copolymer content in ink: 0.75% by mass)
Acrylic resin particles (Boncoat 40-418EF, manufactured by DIC Corporation) 3.5% by mass (solid content)
・ 2-ethyl-1,3-hexanediol: 2.0% by mass
・ Propylene glycol: 41.0% by mass
・ Surfactant (DSN-403N, manufactured by Daikin Industries, Ltd.) ... 1.0% by mass
・ High purity water: remaining amount

<Comparative example 2>
Ink (13) was prepared in the same manner as in Comparative Example 1 except that the resin particles were changed from “acrylic resin particles” to the following “urethane resin particles” in the adjustment of the ink of Comparative Example 1.
-Urethane resin particles (Permarin UA-368T, manufactured by Kyoyo Chemical Industry Co., Ltd.)

<Comparative Example 3>
(Synthesis of copolymer)
In a reaction vessel equipped with a gas introduction tube, a thermometer, and a reflux condenser, 182 g of N, N-dimethylformamide (DMF, manufactured by Kanto Chemical Co., Inc.) was placed in an argon atmosphere and heated to 75 ° C. Thereto, 223 g of an aqueous solution obtained by dissolving 30 g of acrylic acid (manufactured by Aldrich) in 193 g of water, 24 g of benzyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) and N- [3- (dimethylamino) propyl] acrylamide (Tokyo Chemical Industry Co., Ltd.) 218 g of DMF solution obtained by dissolving 6 g in 182 g of DMF and 2,2′-azobisisobutyronitrile (manufactured by Tokyo Chemical Industry / hereinafter abbreviated as AIBN) 187.4 g of DMF solution dissolved in DMF was added in 12 portions each 30 minutes. Stirring was further continued at 75 ° C. for 4 hours after all the components had been added, and then the polymerization was stopped by cooling to obtain a copolymer (3).

  Next, 2.00 g of the obtained copolymer (3) was dissolved in a tetraethylammonium hydroxide aqueous solution so that the concentration of the copolymer was 2.38% by mass and the pH was 8.0. An aqueous solution of copolymer (3) was prepared.

(Adjustment of pigment dispersion)
Next, in the preparation of the pigment dispersion of Example 1, the pigment was prepared in the same manner as in Example 1 except that “the aqueous solution of copolymer (3)” was used instead of “the aqueous solution of copolymer (1)”. Dispersion (3) (pigment solid content in the pigment dispersion: 16% by mass) was obtained.

(Ink adjustment)
The following formulation mixture was stirred for 1 hour and then filtered through a membrane filter having a pore size of 1.2 μm to obtain ink (14).
Pigment dispersion (3) 37.5% by mass (solid pigment content in ink: 6.0% by mass, copolymer content in ink: 0.75% by mass)
Acrylic resin particles (Boncoat 40-418EF, manufactured by DIC Corporation) 3.5% by mass (solid content)
・ 2-ethyl-1,3-hexanediol: 2.0% by mass
・ Propylene glycol: 41.0% by mass
・ Surfactant (DSN-403N, manufactured by Daikin Industries, Ltd.) ... 1.0% by mass
・ High purity water: remaining amount

<Comparative example 4>
In the preparation of the ink of Comparative Example 3, the acrylic resin particle “Boncoat 40-418EF” is changed to the water-soluble polyester “Plus Coat Z-3310”, and the content of the water-soluble polyester “Plus Coat Z-3310” is 0.5 mass%. An ink (15) was produced in the same manner as in Comparative Example 3 except that the above was changed.

  Table 1 below shows the formulations of the inks (1) to (15) of Examples 1 to 11 and Comparative Examples 1 to 4. In addition, the unit of content in each prescription in Table 1 is “mass%”.

  Next, the inks produced in Examples 1 to 11 and Comparative Examples 1 to 4 and the characteristics of images formed using these inks were evaluated according to the following methods and evaluation criteria. The results are shown in Table 2.

[Image density]
A chart with general symbols of 64 point characters JIS X 0208 (1997), 2223 prepared by filling an ink jet printer (manufactured by Ricoh Co., Ltd., IPSiO GX5000) with ink prepared by Microsoft Word 2000 (manufactured by Microsoft), It printed on the offset coat paper (Lumi Art Gloss) in 23 degreeC and 50% RH environment. After printing, the printed material is immediately put into a thermostat set at 100 ° C. for 2 minutes and heated, and then the general symbol part of JIS X 0208 (1997), 2223 on the printed surface is set to X-Rite 938 (X-Rite Corporation). Color), and evaluated according to the following evaluation criteria. When the evaluation was B or more, it was judged that it was a practical case.
In addition, the printing mode in the inkjet printer is a mode in which the “glossy paper-standard clean” mode is changed to “no color correction” from the user setting of plain paper with a driver attached to the printer. The amount of adhesion during printing was adjusted to 500 to 700 mg / A4.
-Evaluation criteria-
A: 2.20 or more B: 2.05 or more and less than 2.20 C: 1.85 or more and less than 2.05 D: Less than 1.85

[Surface roughness Ra]
A printed material was prepared in the same manner as the printed material used in the above image density measurement. Next, the image portion of the produced printed matter was measured by AFM, and the surface roughness Ra when observed in a 1 μm square field of view was calculated. AFM measurement conditions were as follows.
When the surface roughness of the offset coated paper (Lumi Art Gloss) was measured under the same measurement conditions, the surface roughness Ra was 30 nm or more and 35 nm or less. In addition, the transfer amount of pure water to offset coated paper (Lumi Art Gloss) at a contact time of 100 ms measured with a dynamic scanning absorption meter is 2 ml / m ² or more and 35 ml / m ² or less, and pure water at a contact time of 400 ms. The amount of transfer to offset coated paper (Lumi Art Gloss) was 3 ml / m ² or more and 40 ml / m ² or less.
-Measurement conditions-
・ Device: Bruker Dimension Icon
Measurement mode: Tapping mode Cantilever: Olympus AC240TS (resonance frequency 70 kHz, spring constant 2 N / m)
・ Scan Rate: 1Hz
Samples / Line: 256
・ Lines: 256
Amplitude Setpoint: 250 mV
-Tilt correction: primary

[Variable photometer measurement]
A printed material was prepared in the same manner as the printed material used in the above image density measurement. Next, the image part of the produced printed matter was measured by a three-dimensional variable angle spectral colorimetry system GCMS-11 (manufactured by Murakami Color Research Laboratory). The measurement conditions were as follows.
-Measurement conditions-
・ Light source: D50 / 2deg
-Incident angle: 45 deg
-Light receiving angle: -75-5deg
・ Evaluation wavelength: 550 nm
・ Evaluation properties: reflectance

When the measurement is performed under the above conditions, a peak derived from specular reflection appears in the portion of −45 deg due to the gloss of the image portion. Therefore, fitting the peak shape with a normal distribution function (Equation 1) Asked.

[Preservation]
Each ink was filled in an ink container and stored at 70 ° C. for 1 week. The change rate of the viscosity after storage with respect to the viscosity before storage was obtained from the following formula and evaluated according to the following criteria. Note that B and above are practical.
For measurement of the viscosity, a viscometer (RE80L, manufactured by Toki Sangyo Co., Ltd.) was used, and the viscosity at 25 ° C. was measured at 50 revolutions.
-Evaluation criteria-
A: Change rate of viscosity is within ± 5% B: Change rate of viscosity exceeds ± 5% and within ± 8% C: Change rate of viscosity exceeds ± 8% and within ± 10% D: Change in viscosity The rate exceeds ± 10%

[Fixability]
A printed material was prepared in the same manner as the printed material used in the above image density measurement. Next, an offset coated paper (Lumi Art Gloss) on which printing was not performed was brought into contact with the image portion of the produced printed matter and rubbed 20 times. Next, the degree of transfer stain on the offset coated paper that was not printed was visually observed and evaluated according to the following criteria. Note that B and above are practical.
-Evaluation criteria-
A: Transfer dirt is not visually observed B: Transfer dirt is slightly observed visually C: Transfer dirt is clearly observed visually

400 Image forming apparatus 401 Exterior of image forming apparatus 401c Cover of apparatus main body 404 Cartridge holder 410 Main tank 410k, 410c, 410m, 410y For each color of black (K), cyan (C), magenta (M), yellow (Y) Main tank 411 Ink storage section 413 Ink discharge port 414 Storage container case 420 Mechanism section 434 Discharge head 436 Supply tube

JP 2017-88706 A JP 2006-342323 A

Claims (17)

Contains water, pigments, copolymers, water-soluble polyesters,
The copolymer is an ink having a structural unit represented by any one of the following general formulas (1) to (3) and a structural unit having an anionic functional group.
(In the general formula (1), R ¹ represents a hydrogen atom or a methyl group, and A ₁ , A ₂ , and A ₃ are each independently —O—, —CO—O—, —O—CO—, Represents a divalent substituent selected from the group of —CO—NH—, —NH—CO—, —NH—CO—O—, —O—CO—NH—, wherein X ₁ and X ₂ are each independently A single bond, an alkylene group having 1 to 12 carbon atoms, an alkenylene group having 1 to 12 carbon atoms, a divalent group selected from the group consisting of general formula (4), general formula (5), and general formula (6). Represents a substituent, and Ar represents an aromatic group.)
(In the general formula (2), R ¹ , A ₁ , A ₂ , X ₁ , X ₂ and Ar each independently represent the same as in the general formula (1).)
(In the general formula (3), R ¹ , A ₁ , A ₂ , A ₃ , X ₁ , X ₂ and Ar each independently represent the same as in the general formula (1), and A ₄ represents —O Divalent substitution selected from the group of-, -CO-O-, -O-CO-, -CO-NH-, -NH-CO-, -NH-CO-O-, -O-CO-NH-. And Z represents a divalent hydrocarbon group.)
(In the general formula (4), l represents an integer of 1 or more and 10 or less.)
(In the general formula (5), m represents an integer of 1 or more and 10 or less.)
(In the general formula (6), n represents an integer of 1 or more and 10 or less.)   The ink according to claim 1, wherein Ar in the general formulas (1), (2), and (3) has a naphthyl group. The ink according to claim 1 or 2, wherein the structural unit represented by any one of the general formulas (1) to (3) has a structural unit represented by the following general formula (7).
(In the general formula (7), R ² represents a hydrogen atom or a methyl group, and L represents an alkylene group having 2 to 16 carbon atoms.) The ink according to claim 1, wherein the structural unit having an anionic functional group has a structural unit represented by the following general formula (8).
(In the general formula (8), R ³ represents a hydrogen atom or a methyl group, and X represents a hydrogen atom or a cation.)   The ink according to any one of claims 1 to 4, wherein the content of the water-soluble polyester is 0.5% by mass or more and 1.2% by mass or less based on the total amount of the ink.   The ink according to claim 1, wherein Tg of the water-soluble polyester is −20 ° C. or higher and 20 ° C. or lower.   The ink according to any one of claims 1 to 6, wherein the pigment is carbon black.   The ink according to any one of claims 1 to 7, which is substantially free of resin particles.   The mass ratio (water-soluble polyester / copolymer) of the content of the water-soluble polyester to the content of the copolymer is 0.13 or more and 2.67 or less, according to any one of claims 1 to 8. The ink described. A coating layer is formed on the support, the surface roughness Ra is 30 nm or more and 35 nm or less, and the transfer amount of pure water to the recording medium at a contact time of 100 ms measured with a dynamic scanning absorption meter is 2 ml / m. ² or 35 ml / ^{m 2} or less, and the amount of transferred onto the recording medium of pure water at a contact time of 400ms to the 3 ml / ^{m 2} or more 40 ml / ^{m 2} or less is a recording medium, the amount of adhesion 500 mg / A4 or 2. The surface roughness Ra of the solid image is 15 nm or more and 25 nm or less when a solid image is formed by applying the ink to 700 mg / A4 or less and heating at 100 ° C. for 2 minutes. The ink as described in any one of thru | or 9. A coating layer is formed on the support, the surface roughness Ra is 30 nm or more and 35 nm or less, and the transfer amount of pure water to the recording medium at a contact time of 100 ms measured with a dynamic scanning absorption meter is 2 ml / m. ² or 35 ml / ^{m 2} or less, and the amount of transferred onto the recording medium of pure water at a contact time of 400ms to the 3 ml / ^{m 2} or more 40 ml / ^{m 2} or less is a recording medium, the amount of adhesion 500 mg / A4 or A solid image is formed by applying the ink to 700 mg / A4 or less and then heating at 100 ° C. for 2 minutes,
The peak half-value width σ created by fitting a peak near 45 ° specular reflection obtained by measuring the solid image with a goniophotometer with the normal distribution function of the following formula (1) is 2 The ink according to any one of Claims 1 to 10, which is from 0.0 to 2.4.
A coating layer is formed on the support, the surface roughness Ra is 30 nm or more and 35 nm or less, and the transfer amount of pure water to the recording medium at a contact time of 100 ms measured with a dynamic scanning absorption meter is 2 ml / m. ² or 35 ml / ^{m 2} or less, and the amount of transferred onto the recording medium of pure water at a contact time of 400ms to the 3 ml / ^{m 2} or more 40 ml / ^{m 2} or less is a recording medium, the amount of adhesion 500 mg / A4 or When a solid image is formed by applying the ink so as to be 700 mg / A4 or less and then heating at 100 ° C. for 2 minutes, the surface roughness Ra of the solid image is 15 nm or more and 25 nm or less,
The peak half-value width σ created by fitting a peak near 45 ° specular reflection obtained by measuring the solid image with a goniophotometer with the normal distribution function of the following formula (1) is 2 Ink that is not less than 0.0 and not more than 2.4.
  An ink storage container that stores the ink according to claim 1.   A recording apparatus comprising: the ink container according to claim 13; a discharge unit that discharges the stored ink; and a heating unit that heats the discharged ink at 100 ° C. or higher. An ink container according to claim 13, and a discharge means for discharging the stored ink to a recording medium,
The recording medium has a coating layer formed on a support, has a surface roughness Ra of 30 nm or more and 35 nm or less, and transfers pure water to the recording medium at a contact time of 100 ms as measured by a dynamic scanning absorption meter. A recording apparatus having an amount of 2 ml / m ² or more and 35 ml / m ² or less and a transfer amount of pure water to the recording medium at a contact time of 400 ms of 3 ml / m ² or more and 40 ml / m ² or less. An ink storage container according to claim 13, discharge means for discharging the stored ink to a recording medium, and heating means for heating the discharged ink at 100 ° C or higher,
The recording medium has a coating layer formed on a support, has a surface roughness Ra of 30 nm or more and 35 nm or less, and transfers pure water to the recording medium at a contact time of 100 ms as measured by a dynamic scanning absorption meter. A recording apparatus having an amount of 2 ml / m ² or more and 35 ml / m ² or less and a transfer amount of pure water to the recording medium at a contact time of 400 ms of 3 ml / m ² or more and 40 ml / m ² or less.   A recording method comprising a discharge step of discharging the ink according to claim 1.