JP2021147600A - Ink, ink-stored container, printing device, and printing method - Google Patents

Abstract

To prevent occurrence of color unevenness (beading) due to ununiform distribution of a pigment in an ink during a time period when an applied ink is dried and then fixed, if the ink is applied onto a print medium to form a solid image.SOLUTION: An ink comprises: a pigment-containing matter containing a pigment; an organic solvent; water; and a compound represented by a predetermined general formula (1). A difference (Ra-R0) is 2.0 or less, provided that: Ra is a distance between a Hansen solubility parameter of the organic solvent and a Hansen solubility parameter of the pigment-containing matter determined by a Hansen solubility sphere method; and R0 is an interaction radius of the pigment-containing matter determined by the Hansen solubility sphere method.SELECTED DRAWING: None

Description

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

Inkjet recording devices have advantages such as low noise, low running cost, and easy color printing, and are widely used in general households as digital signal output devices. In recent years, inkjet technology has been used not only for home use but also for commercial use and industrial use.

In commercial and industrial applications, coated paper (coated paper) for printing with low ink absorption and plastic media with non-ink absorption may be used as recording media. Therefore, the inkjet recording method is also used for these media. Therefore, it is required to realize the image quality equivalent to that of the conventional offset printing.
In addition, since high productivity is required for commercial and industrial applications, instead of the conventional serial head method, which prints by operating the inkjet head multiple times, the inkjet head is fixed and printed at once. A certain line head method may be adopted.

Patent Document 1 discloses a water-based ink for inkjet recording containing a pigment (A), an organic solvent (B), a surfactant (C), and water. Specifically, the surfactant (C) ) Is one or more compounds (C-1) selected from polyoxyalkylene alkyl ether sulfate, polyoxyalkylene alkenyl ether sulfate and polyoxyalkylene aryl ether sulfate, and addition of alkylene oxides of acetylene glycol and acetylene glycol. It is disclosed that it contains one or more compounds (C-2) selected from the substances.

However, when ink is applied to a recording medium to form a solid image, the distribution of pigments in the ink becomes non-uniform until the applied ink dries and is fixed, resulting in uneven color (beading). ) Is a problem.

（上記一般式（１）中、Ｒ_１、Ｒ_２、Ｒ_３、及びＲ_４は、それぞれ独立して、水素原子又は炭素数１以上５以下のアルキル基を表し、ｎは、３以上１１以下の整数を表す。） The invention according to claim 1 contains a pigment-containing substance containing a pigment, an organic solvent, water, and a compound represented by the following general formula (1), and is based on the Hansen solubility parameter of the organic solvent and the Hansen dissolving sphere method. The difference (Ra-R ₀ ) between the distance Ra of the Hansen solubility parameter of the pigment-containing substance obtained and the interaction radius R ₀ of the pigment-containing substance obtained by the Hansen dissolving sphere method is 2.0 or less. It is an ink characterized by being present.

(In the above general formula (1), R ₁ , R ₂ , R ₃ and R ₄ independently represent a hydrogen atom or an alkyl group having 1 or more and 5 or less carbon atoms, and n is 3 or more and 11 or less. Represents an integer of.)

The ink of the present invention has an excellent effect of suppressing beading in an image formed by the ink.

FIG. 1 is a schematic view showing an example of a recording device.

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

<< Ink >>
The ink of the present embodiment contains a pigment-containing pigment-containing substance, an organic solvent, water, and a compound represented by the general formula (1), and has predetermined physical properties based on the Hansen solubility parameter (HSP). Further, if necessary, a resin, a surfactant, and other additives may be contained.
Here, the pigment-containing substance is a pigment alone or a complex of substances existing integrally with the pigment in the pigment and the ink. The substance that exists integrally preferably has, for example, a function of imparting dispersibility to the pigment. Further, "integrally present" is preferably, for example, a state in which the integrally present substance is physically or chemically bonded or adsorbed to the pigment. Since the pigment-containing substance does not contain a substance that does not exist integrally with the pigment, for example, resin particles added for the purpose of functioning as a binder or the like are not included.

<Physical characteristics of ink based on Hansen solubility parameter (HSP)>
First, the Hansen solubility parameter (HSP) will be described.
The Hansen Solubility Parameter (HSP) is a useful tool for predicting the compatibility of two substances and is a parameter discovered by Charles M. Hansen. The Hansen solubility parameter (HSP) is expressed by combining the following three experimentally and theoretically derived parameters (δD, δP, and δH). As the unit of Hansen solubility parameter (HSP), MPa ^0.5 or (J / cm ³ ) ^0.5 is used. In this embodiment, (J / cm ³ ) ^0.5 was used.
-ΔD: Energy derived from the London dispersion force.
-ΔP: Energy derived from dipole interaction.
-ΔH: Energy derived from hydrogen bonding force.
The Hansen solubility parameter (HSP) is a vector quantity expressed as (δD, δP, δH), and is represented by plotting on a three-dimensional space (Hansen space) having three parameters as coordinate axes. Since there is a known source such as a database for the Hansen solubility parameter (HSP) of a commonly used substance, for example, the Hansen solubility parameter (HSP) of a desired substance can be obtained by referring to the database. Can be done. For substances for which the Hansen solubility parameter (HSP) is not registered in the database, the chemical structure of the substance and the Hansen solubility parameter from the Hansen solubility parameter method described later can be used by using computer software such as Hansen Solubility Parameters in Practice (HSPiP). (HSP) can be calculated. The Hansen solubility parameter (HSP) of a mixture containing two or more substances is calculated as a vector sum of values obtained by multiplying the Hansen solubility parameter (HSP) of each substance by the volume ratio of each substance with respect to the entire mixture.

Next, a method for obtaining the Hansen solubility parameter (HSP) of a substance whose Hansen solubility parameter (HSP) is not known will be described.
First, a substance for which the Hansen solubility parameter (HSP) is to be obtained and several types of evaluation solvents whose Hansen solubility parameter (HSP) are known are prepared, and the compatibility test of the target substance with each evaluation solvent is performed. In the compatibility test, the Hansen solubility parameter (HSP) of the evaluation solvent showing compatibility and the Hansen solubility parameter (HSP) of the evaluation solvent not showing compatibility are plotted on the Hansen space, respectively. Based on the plotted Hansen solubility parameter (HSP) of each evaluation solvent, the Hansen solubility parameter (HSP) of the evaluation solvent group showing compatibility was included, and the Hansen solubility parameter of the evaluation solvent group showing no compatibility was included. A virtual sphere (Hansen sphere) that does not include the solubility parameter (HSP) is created in the Hansen space. The radius of the Hansen sphere is the radius of interaction R _{0 of} the substance, and the center is the Hansen solubility parameter (HSP) of the substance. The evaluation criteria (criteria for determining whether or not they are compatible) between the substance for which the Hansen solubility parameter (HSP) is to be obtained and the evaluation solvent for which the Hansen solubility parameter (HSP) is known are evaluated by the evaluator. Set by yourself. The evaluation criteria in this embodiment will be described later.

Next, the distance Ra of the Hansen solubility parameter (HSP) of the two substances will be described. In general, the closer the two substances are in the three-dimensional space (Hansen space), the more likely they are to dissolve (complicate with) each other.
Assuming that the Hansen solubility parameter (HSP) for each of the two substances (substance A and substance B) is as follows, the distance Ra can be calculated as follows.
^{· HSP A = (δD A,} δP A, δH A)
^{· HSP B = (δD B,} δP B, δH B)
· Ra = [4 × (δD A -δD B) 2 + (δP A -δP B) 2 + (δH A -δH B) 2] 1/2

The ink of the present embodiment contains the distance Ra of the Hansen solubility parameter (HSP) of the organic solvent and the Hansen solubility parameter (HSP) of the pigment-containing material obtained by the Hansen solubility parameter, and the pigment contained by the Hansen solubility parameter. The difference (Ra-R ₀ ) from the interaction radius R _{0 of the} object is 2.0 or less, and preferably 0 or less. When the difference (Ra-R ₀ ) is 2.0 or less, even if water evaporates in the ink droplets applied to the recording medium, the dispersibility of the pigment-containing material in the ink droplets is lowered. As a result, the occurrence of beading is suppressed in the image formed by the ink. Further, since the difference (Ra-R ₀ ) is 2.0 or less, even when the ink is used in an environment where water in the ink is likely to evaporate, such as in a decapped state for a long time, the ink is used. It is possible to suppress a decrease in the dispersibility of the pigment-containing material, and as a result, a decrease in the ejection recovery property of the ink is suppressed. Here, the decap state represents a state in which the protective cap that suppresses the drying of the ink in the nozzle of the inkjet head is not attached to the inkjet head. Further, the ejection recovery means that maintenance (for example, sucking ink from the nozzle, supplying ink to the nozzle, wiping the nozzle surface with a wiping member, etc.) is executed for the nozzle of the inkjet head. By doing so, it is preferable to indicate that the ink ejection stability is restored to a practical level, and it is more preferable to indicate that the ink ejection stability is restored to the same level as before the decapped state. The difference (Ra-R ₀ ) is preferably -10.0 or more.

Here, (1) the Hansen solubility parameter (HSP) of the organic solvent required to calculate the difference (Ra-R ₀ ), and (2) the Hansen solubility parameter (HSP) of the pigment-containing substance obtained by the Hansen solubility parameter method. _{, And (3) how to obtain the interaction radius R0} of the pigment-containing material obtained by the Hansen solubility parameter method will be described in detail.

-(1) How to find Hansen solubility parameter (HSP) of organic solvent-
The Hansen solubility parameter (HSP) of an organic solvent is calculated as a vector sum of the values obtained by multiplying the Hansen solubility parameter (HSP) of each organic solvent contained in the ink by the volume ratio of each organic solvent to the entire organic solvent. ..
For example, the volume ratio x: y of the organic solvent x having the Hansen solubility parameter (HSP) of (δDx, δPx, δHx) and the organic solvent y having the Hansen solubility parameter (HSP) of (δDy, δPy, δHy). The Hansen solubility parameter (HSP) of the organic solvent z obtained by mixing with = a: b is expressed as follows.
ΔDz = (a × δDx + b × δDy) / a + b
・ ΔPz = (a × δPx + b × δPy) / a + b
・ ΔHz = (a × δHx + b × δHy) / a + b

The content of each organic solvent in the ink can be appropriately determined by a known method. For example, a method of measuring an ink diluted with tetrahydrofuran by GC-MS (Gas Chromatography-Mass Spectrometry) or the like can be used. Can be mentioned.

-(2) Hansen solubility parameter (HSP) of pigment-containing material and (3) How to obtain _{interaction radius R 0 of pigment-containing material-}
[1] Preparation of dispersion liquid containing pigment-containing material First, a dispersion liquid containing the pigment-containing material and dispersion medium is prepared. Specifically, a substance constituting the pigment-containing material is added to the dispersion medium so that the content of the pigment-containing material is 10% by mass or more and 35% by mass or less with respect to the total amount of the dispersion liquid. The dispersion medium may be a liquid that does not agglomerate the pigment, and is appropriately selected from water and an organic solvent. However, it preferably contains water and contains water as a main component (for example, 50% by mass or more based on the total amount of the dispersion medium). If) is more preferable.
When preparing a dispersion liquid containing a pigment-containing material from an ink containing a component other than the pigment-containing material such as resin particles, for example, the following method is used. First, the ink is diluted with tetrahydrofuran and centrifuged to separate it into two layers. The upper layer contains a large amount of components other than the pigment-containing material such as resin particles, and the lower layer contains a large amount of the pigment-containing material. The work of removing the upper layer to make only the lower layer, diluting with tetrahydrofuran again, centrifuging, and removing the upper layer is repeated. This work is carried out until it can be determined that the lower layer contains substantially only the pigment-containing substance. Then, water is added to the lower layer so that the content of the lower layer (pigment-containing material) is 10% by mass or more and 35% by mass or less with respect to the total amount of the dispersion liquid. Whether or not the lower layer can be judged to contain substantially only the pigment-containing substance is removed by evaporating the dispersion medium from the lower layer, and the solid component of the lower layer is observed with an electron microscope to obtain resin particles and the like. Judgment is made by confirming the ratio of particulate components other than the pigment-containing substance. Specifically, it represents a case where the area of the particulate component other than the pigment-containing substance such as resin particles is 3% or less with respect to the total area of the solid component in the range observed by the electron microscope. This is because if it is 3% or less, the same result as the case where it is not included at all (0%) can be obtained with respect to the result of the Hansen solubility parameter (HSP) obtained as follows. Here, as a method of centrifugation, for example, a method of centrifuging at a rotation speed of 15,000 rpm for 3 hours using Hitachi himac CP100WX can be mentioned.

[2] Evaluation of compatibility between the dispersion containing the pigment-containing material and the evaluation solvent Next, 18 types of the following evaluation solvents having a known Hansen solubility parameter (HSP) were prepared, and each of the dispersion liquids containing the pigment-containing material was prepared. A solvent for evaluation is added and dispersed well to prepare a mixed solution. The amount of the evaluation solvent added is such that the mass of the dispersion liquid is 20% of the mass of the mixed liquid. Then, the mixture is allowed to stand for 12 hours, and the dispersed state of the mixed solution after standing is visually observed to determine the presence or absence of aggregation.
~ Evaluation solvent (18 types) ~
Water, glycerin, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol di, 2,3-butanediol di, propylene glycol, 1-methoxy-2- Propanol, 3-methoxy-1-butanol, 3-methoxy-3-methyl-1-butanol, 2-pyrrolidone, 2-propanol, diethylene glycol, dipropylene glycol, 1,2-hexanediol, 3-ethyl-3-hydroxymethyl Oxetane, 3-methoxy-N, N-dimethylpropionamide

[3] Calculation of Hansen solubility parameter (HSP) and interaction radius _R0 of pigment-containing material Next, using the computer software Hansen Solubility Parameters in Practice (HSPiP), based on the results obtained in the above [2]. The Hansen solubility parameter (HSP) and the radius of interaction _R0 in the pigment-containing material are calculated. When the Fit obtained using HSPiP was less than 0.8, the types of evaluation solvents used in [2] were increased so that the Fit was 0.8 or more.

<Compound represented by the general formula (1)>
The ink contains a compound represented by the following general formula (1). The compound represented by the general formula (1) is a polyoxyalkylene alkyl ether. By including the compound represented by the general formula (1) in the ink, the ink dots formed by applying the ink to the recording medium or the like are likely to get wet and spread. As a result, the ink spreads uniformly and thinly on the surface of the recording medium or the like, so that the time until the ink applied to the recording medium dries is shortened, and the ink is applied until the applied ink dries and is fixed. Non-uniform distribution of the pigment inside is suppressed. As a result, the occurrence of color unevenness (beading) is suppressed in the solid image formed by the ink.

_{R 1} , R ₂ , R ₃ and R ₄ in the general formula (1) independently represent a hydrogen atom or an alkyl group having 1 or more and 5 or less carbon atoms.
The alkyl group having 1 to 5 carbon atoms may be a branched alkyl group or a non-branched alkyl group, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, or an n-butyl group. Examples thereof include a group, an s-butyl group, an isobutyl group, a t-butyl group, a pentyl group, an isopentyl group, and a neopentyl group.

N in the general formula (1) represents an integer of 3 or more and 11 or less, and is preferably an integer of 6 or more and 9 or less. When n is an integer of 3 or more and 11 or less, the ink dots formed by applying ink to the recording medium or the like are likely to get wet and spread, and the occurrence of beading is suppressed. Further, when n is an integer of 6 or more and 9 or less, the occurrence of beading is further suppressed.

The compound represented by the general formula (1) is not particularly limited and may be appropriately selected depending on the intended purpose, but the compound represented by the following general formula (2) is preferable.

_{R 5} , R ₆ , R ₇ , R ₈ and R ₉ in the general formula (2) independently represent a hydrogen atom or an alkyl group having 1 or more and 5 or less carbon atoms.
The alkyl group having 1 to 5 carbon atoms may be a branched alkyl group or a non-branched alkyl group, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, or an n-butyl group. Examples thereof include a group, an s-butyl group, an isobutyl group, a t-butyl group, a pentyl group, an isopentyl group, and a neopentyl group.

In the general formula (2), n represents an integer of 3 or more and 11 or less, and is preferably an integer of 6 or more and 9 or less. When n is an integer of 3 or more and 11 or less, the ink dots formed by applying ink to the recording medium or the like are likely to get wet and spread, and the occurrence of beading is suppressed. Further, when n is an integer of 6 or more and 9 or less, the occurrence of beading is further suppressed.

The compound represented by the general formula (1) is not particularly limited and may be appropriately selected depending on the intended purpose, but the compound represented by the following general formula (3) is more preferable. Examples of commercially available products contained in the compound represented by the general formula (3) include Triton HW-1000, TMN-3, TMN-6, TMN-100X, and TMN-10 (all manufactured by Dow Chemical Co., Ltd.). Can be mentioned.

In the general formula (3), n represents an integer of 3 or more and 11 or less, and is preferably an integer of 6 or more and 9 or less. When n is an integer of 3 or more and 11 or less, the ink dots formed by applying ink to the recording medium or the like are likely to get wet and spread, and the occurrence of beading is suppressed. Further, when n is an integer of 6 or more and 9 or less, the occurrence of beading is further suppressed.

The content of the compound represented by the general formula (1) is preferably 0.1% by mass or more and 2.0% by mass or less, and 0.5% by mass or more and 1.5% by mass or less, based on the mass of the ink. More preferably, it is less than%. When the content is 0.1% by mass or more and 2.0% by mass or less, the ink dots formed by applying the ink to the recording medium or the like are likely to get wet and spread, and the occurrence of beading is suppressed.

<Pigment-containing material>
The ink contains a pigment-containing material. As described above, the pigment-containing substance is a pigment alone or a complex of a substance existing integrally with the pigment in the pigment and the ink. The pigment and the substance existing integrally with the pigment include the distance Ra of the Hansen solubility parameter (HSP) of the organic solvent and the Hansen solubility parameter (HSP) of the pigment-containing material obtained by the Hansen solubility parameter method, and the Hansen solubility parameter. The difference (Ra-R _{0 ) from the interaction radius R 0} of the pigment-containing material obtained by the spherical method is not particularly limited as long as it is 2.0 or less, but for example, the materials described below can be used.

-Pigment-
As the pigment, an inorganic pigment or an organic pigment can be used. These may be used alone or in combination of two or more. Further, a mixed crystal may be used as the pigment.

As the pigment, for example, black pigment, yellow pigment, magenta pigment, cyan pigment, white pigment, green pigment, orange pigment, glossy color pigment such as gold or silver, metallic pigment and the like can be used.
As inorganic pigments, in addition to titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, and chrome yellow, carbon black produced by known methods such as contact method, furnace method, and thermal method. Can be used.
Examples of organic pigments include azo pigments and polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc.). , Dye chelate (for example, basic dye type chelate, acidic dye type chelate, etc.), nitro pigment, nitroso pigment, aniline black and the like can be used. Among these pigments, those having a good affinity with a solvent are preferably used. In addition, resin hollow particles and inorganic hollow particles can also be used.

As a specific example of the pigment, for black, carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black, channel black, or copper, iron (CI pigment black 11) , Metals such as titanium oxide, and organic pigments such as aniline black (CI pigment black 1).
Further, for color, 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 Calcium 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 Greens 1, 4, 7, 8, 10, 17, 18, 36, etc.

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

-Substances that exist integrally with pigments-
As described above, the substance that exists integrally with the pigment preferably has a function of imparting dispersibility to the pigment. Further, "integrally present" is preferably, for example, a state in which the integrally present substance is physically or chemically bonded or adsorbed to the pigment. Examples of the method of imparting dispersibility to the pigment by physically or chemically binding or adsorbing to the pigment include a method of coating the surface of the pigment with a resin and dispersing it, and a method of dispersing using a dispersant. , And so on.
Examples of the method of coating the surface of the pigment with a resin and dispersing the pigment include a method of encapsulating the pigment in the form of microcapsules with the resin so that the pigment can be dispersed in water. This can be rephrased as a resin coating pigment. In this case, all the pigments to be blended in the ink need not be coated with the resin, and uncoated pigments or partially coated pigments may be used.
Examples of the method of dispersing the pigment using a dispersant include a method of dispersing using a known low-molecular-weight dispersant and a high-molecular-weight dispersant represented by a surfactant. The dispersant can be appropriately selected depending on the pigment, and for example, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant and the like can be used.

-A method of coating the surface of the pigment with resin and dispersing it-
When the surface of the pigment is coated with a resin and dispersed, the resin is not particularly limited as long as the pigment can be dispersed, but for example, a styrene-acrylic resin is preferably used.

Examples of the styrene-acrylic resin include a styrene-acrylic acid copolymer, a styrene-methacrylic acid copolymer, a styrene-methacrylic acid-acrylic acid ester copolymer, and a styrene-α-methylstyrene-acrylic acid copolymer. , Styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer and the like. Among these, a styrene-acrylic acid copolymer is particularly preferable. As the form of the copolymer, any form of a random copolymer, a block copolymer, an alternating copolymer, and a graft copolymer can be used.

Further, the styrene-acrylic resin may contain a component derived from a monomer other than styrene-acrylic acid and methacrylic acid. Examples of such monomers include styrene derivatives such as α-methylstyrene and vinyltoluene, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and n-. Examples thereof include butyl (meth) acrylate, sec-butyl (meth) acrylate, and tert-butyl (meth) acrylate. One or more of these monomers can be added to the above-mentioned styrene and acrylic acid or methacrylic acid monomer components.

The weight average molecular weight of the styrene-acrylic resin is preferably in the range of 3,000 to 50,000, and more preferably in the range of 5,000 to 30,000. As the styrene-acrylic resin, a commercially available resin may be used. Specific examples of commercially available styrene-acrylic resins include John Krill 62J (manufactured by BASF Japan Ltd.).

The method for producing the styrene-acrylic resin coating pigment is not particularly limited, and for example, it can be produced as follows. That is, for example, it can be obtained by dispersing a pigment and a styrene-acrylic resin in a dispersion medium and kneading them.

-A method of dispersing pigments using a dispersant-
When the pigment is dispersed using a dispersant, the dispersant is not particularly limited as long as the pigment can be dispersed, but for example, a polymer-type dispersant is preferably used. The polymer-type dispersant is preferably a copolymer having a structural unit represented by the following general formula (4) and a structural unit represented by the following general formula (5).
The "structural unit" in the present embodiment indicates the minimum repeating unit of the polymer obtained by bonding the polymerizable monomers (monomers) to each other.

The copolymer preferably has a structural unit represented by the general formula (4). By having the structural unit represented by the general formula (4) in the copolymer, the ink dots formed by applying ink to the recording medium or the like are easily wetted and spread. As a result, the ink spreads uniformly and thinly on the surface of the recording medium or the like, so that the time until the ink applied to the recording medium dries is shortened, and the ink is applied until the applied ink dries and is fixed. Non-uniform distribution of the pigment inside is suppressed. As a result, the occurrence of color unevenness (beading) is suppressed in the solid image formed by the ink. Further, by having the structural unit represented by the general formula (4) in the copolymer, even when the copolymer is used in an environment where water in the ink is likely to evaporate, such as in a decapped state for a long time, the copolymer is used. It is possible to suppress a decrease in the dispersibility of the pigment-containing substance in the ink, and as a result, a decrease in the ejection recovery property of the ink is suppressed.

In the structural unit represented by the general formula (1), R ₁₀ is a hydrogen atom or a methyl group. Further, L ₁ is an alkylene group having 2 or more and 18 or less carbon atoms, preferably an alkylene group having 2 or more and 16 or less carbon atoms, and more preferably an alkylene group having 2 or more and 12 or less carbon atoms. .. When the number of carbon atoms is within the above range, the hydrophilic part and the hydrophobic part of the copolymer are arranged at an appropriate distance, and good dispersion stability is exhibited when the copolymer is used as a pigment dispersion resin. Can be done.

In the structural unit represented by the general formula (4), the naphthyl group having one end present at the end via the alkyl chain in the open end (open end, that is, the pendant structure portion) is a coloring material in the ink. It has excellent pigment adsorption power due to π-π stacking with a certain pigment.
As can be understood from the above description of "naphthyl group existing at the end via the alkyl chain in the pendant", the structural unit represented by the general formula (4) typically hangs down via the alkyl group. It may be the main chain of a copolymer having a pendant group such as a terminal naphthyl group. However, of course, it does not exclude the case where a part is included in the side chain.
For example, it is a well-known fact that it is difficult to completely eliminate the secondary radical polymerization reaction that produces a branched structure.
Further, when a copolymer is used when preparing a pigment dispersion in which a pigment is dispersed in water, a naphthyl group is present at the end of the side chain of the copolymer, so that it is easily adsorbed on the pigment surface and is easily adhered to the pigment. Since the adsorption power is high, a pigment dispersion having high dispersibility and being stable for a long period of time can be obtained.

The content of the structural unit represented by the general formula (4) in the copolymer is not particularly limited and may be appropriately selected depending on the intended purpose, but is 60% by mass or more with respect to the total amount of the copolymer. 90% by mass or less is preferable.

The copolymer preferably has a structural unit represented by the general formula (5).

In the structural unit represented by the general formula (5), R ₁₁ is a hydrogen atom or a methyl group. Further, X is a hydrogen atom or a cation.
In the case of cations, the oxygen adjacent to the cation exists 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, Ethylhexadecyldimethylammonium ion, ammonium ion, dimethylammonium ion, trimethylammonium ion, monoethylammonium ion, diethylammonium ion, triethylammonium ion, monoethanolammonium ion, diethanolammonium ion, triethanolammonium ion, methylethanolammonium ion, Methyldiethanolammonium ion, dimethylethanolammonium ion, monopropanolammonium ion, dipropanolammonium ion, tripropanolammonium ion, isopropanolammonium ion, morpholinium ion, N-methylmorpholinium ion, N-methyl-2-pyrrolidoni Ammonium ion, 2-pyrrolidnium ion and the like can be mentioned.

The content of the structural unit represented by the general formula (5) in the copolymer is not particularly limited and may be appropriately selected depending on the intended purpose, but is 10% by mass or more and 40% by mass or more with respect to the copolymer. It is preferably mass% or less.

The copolymer can have a structural unit composed of other polymerizable monomers, if necessary, in addition to the structural units represented by the above general formulas (4) and (5). The other polymerizable monomer can be appropriately selected depending on the intended purpose, and examples thereof include a polymerizable hydrophobic monomer, a polymerizable hydrophilic monomer, and a polymerizable surfactant.

<Organic solvent>
Examples of the organic solvent that can be used for the ink include the distance Ra of the Hansen solubility parameter (HSP) of the organic solvent and the Hansen solubility parameter (HSP) of the pigment-containing material obtained by the Hansen solubility parameter method, and the Hansen solubility parameter method. The difference (Ra-R _{0 ) from the required interaction radius R 0} of the pigment-containing material is not particularly limited as long as it is 2.0 or less, but for example, the materials described below can be used.

The organic solvent 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 water-soluble organic solvent include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, and 1,4-butane. Diore, 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, Triethylene glycol, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4- Polyhydric alcohols such as trimethyl-1,3-pentanediol and petriol, 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 Polyhydric alcohol alkyl ethers such as monoethyl ether, polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2. Nitrogen-containing heterocyclic compounds such as −pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, γ-butyrolactone, formamide, N-methylformamide, N, N-dimethylformamide, 3-methoxy-N, Amidos such as N-dimethylpropionamide, 3-butoxy-N, N-dimethylpropionamide, amines such as monoethanolamine, diethanolamine and triethylamine, sulfur-containing compounds such as dimethylsulfoxide, sulfolane and thiodiethanol, propylene carbonate, Examples include ethylene carbonate. It is preferable to use an organic solvent having a boiling point of 250 ° C. or lower because it not only functions as a wetting agent but also has good drying properties.

Polyol compounds having 8 or more carbon atoms and glycol ether compounds are also preferably used. Specific examples of the polyol compound having 8 or more carbon atoms include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.
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. Ethers: Polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether can be mentioned.
The polyol compound having 8 or more carbon atoms and the glycol ether compound can improve the permeability of the ink when paper is used as the recording medium.

Among the above, the organic solvent contained in the ink is preferably at least one selected from 1,3-propanediol and glycerin. By containing at least one selected from 1,3-propanediol and glycerin in the ink, even when the ink is used in an environment where water in the ink is likely to evaporate, such as in a decapped state for a long time, the said matter. It is possible to suppress a decrease in the dispersibility of the pigment-containing substance in the ink, and as a result, a decrease in the ejection recovery property of the ink is suppressed.

The content of the organic solvent in the ink is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of the drying property and ejection reliability of the ink, 10% by mass or more of 60 with respect to the total amount of the ink. It is preferably 20% by mass or less, and more preferably 20% by mass or more and 60% by mass or less.

<Water>
The water content in the ink is not particularly limited and can be appropriately selected according to the purpose, but from the viewpoint of the drying property and ejection reliability of the ink, 10% by mass or more and 90% by mass with respect to the total amount of the ink. % Or less is preferable, and 20% by mass or more and 60% by mass or less is more preferable.

<Resin>
The type of resin is not particularly limited and may be appropriately selected depending on the intended purpose. For example, urethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, butadiene resin, styrene-butadiene. Examples thereof include based resins, vinyl chloride resins, acrylic styrene resins, and acrylic silicone resins.
Resin particles made of these resins may be used. It is possible to obtain ink by mixing resin particles with a material such as a coloring material or an organic solvent in the state of a resin emulsion in which water is dispersed as a dispersion medium. As the resin particles, those synthesized as appropriate may be used, or commercially available products may be used. Further, these may be used alone or in combination of two or more kinds of resin particles.

The volume average particle diameter of the resin particles is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of obtaining good fixability and high image hardness, 10 nm or more and 1,000 nm or less are preferable. More than 200 nm is more preferable, and 10 nm or more and 100 nm or less is particularly preferable.
The volume average particle size can be measured using, for example, a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack Bell Co., Ltd.).

The content of the resin is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of fixability and storage stability of the ink, 1% by mass or more and 30% by mass or less with respect to the total amount of the ink. Is preferable, and 5% by mass or more and 20% by mass or less is more preferable.

The particle size of the solid content in the ink is not particularly limited and can be appropriately selected depending on the intended purpose. From the viewpoint of improving image quality such as ejection stability and image density, the maximum frequency of the particle size of the solid content in the ink is preferably 20 nm or more and 1000 nm or less, and more preferably 20 nm or more and 150 nm or less in terms of the maximum number. The solid content includes resin particles, pigment particles, and the like. The particle size can be measured using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack Bell Co., Ltd.).

<Surfactant>
As the surfactant, any of a silicone-based surfactant, a fluorine-based surfactant, an amphoteric surfactant, a nonionic surfactant, and an anionic surfactant can be used.
The silicone-based surfactant is not particularly limited and may be appropriately selected depending on the intended purpose. Of these, those that do not decompose even at high pH are preferable. Examples of the silicone-based surfactant include side chain-modified polydimethylsiloxane, double-ended polydimethylsiloxane, single-ended modified polydimethylsiloxane, and side-chain double-ended modified polydimethylsiloxane. Those having a polyoxyethylene group and a polyoxyethylene polyoxypropylene group as the modifying group are particularly preferable because they exhibit good properties as an aqueous surfactant. Further, as the silicone-based surfactant, a polyether-modified silicone-based surfactant can also be used, and examples thereof include a compound in which a polyalkylene oxide structure is introduced into the Si side chain of dimethylsiloxane.
Examples of the fluorine-based surfactant include a perfluoroalkyl sulfonic acid compound, a perfluoroalkyl carboxylic acid compound, a perfluoroalkyl phosphate ester compound, a perfluoroalkyl ethylene oxide adduct, and a perfluoroalkyl ether group in the side chain. A polyoxyalkylene ether polymer compound is particularly preferable because it has a low foaming property. Examples of the perfluoroalkyl sulfonic acid compound include perfluoroalkyl sulfonic acid and perfluoroalkyl sulfonic acid salt. Examples of the perfluoroalkylcarboxylic acid compound include perfluoroalkylcarboxylic acid and perfluoroalkylcarboxylic acid salt. Examples of the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain include a sulfate ester salt of a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in the side chain and a poly having a perfluoroalkyl ether group in the side chain. Examples thereof include salts of oxyalkylene ether polymers. The counter ions of the salts in these fluorine-based surfactants are Li, Na, K, NH ₄ , NH ₃ CH ₂ CH ₂ OH, NH ₂ (CH ₂ CH ₂ OH) ₂ , NH (CH ₂ CH ₂ OH). _3rd grade can be mentioned.
Examples of amphoteric surfactants include laurylaminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.
Examples of the nonionic surfactant include polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ester, polyoxyethylene alkyl amine, polyoxyethylene alkyl amide, polyoxyethylene propylene block polymer, sorbitan fatty acid ester, and polyoxyethylene sorbitan. Examples thereof include a fatty acid ester and an ethylene oxide adduct of acetylene alcohol.
Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, lauryl salt, salt of polyoxyethylene alkyl ether sulfate, and the like.
These may be used alone or in combination of two or more.

（但し、一般式（Ｓ−１）式中、ｍ、ｎ、ａ、及びｂは、それぞれ独立に、整数を表わし、Ｒは、アルキレン基を表し、Ｒ’は、アルキル基を表す。）
上記のポリエーテル変性シリコーン系界面活性剤としては、市販品を用いることができ、例えば、ＫＦ−６１８、ＫＦ−６４２、ＫＦ−６４３（信越化学工業株式会社）、ＥＭＡＬＥＸ−ＳＳ−５６０２、ＳＳ−１９０６ＥＸ（日本エマルジョン株式会社）、ＦＺ−２１０５、ＦＺ−２１１８、ＦＺ−２１５４、ＦＺ−２１６１、ＦＺ−２１６２、ＦＺ−２１６３、ＦＺ−２１６４（東レ・ダウコーニング・シリコーン株式会社）、ＢＹＫ−３３、ＢＹＫ−３８７（ビックケミー株式会社）、ＴＳＦ４４４０、ＴＳＦ４４５２、ＴＳＦ４４５３（東芝シリコン株式会社）などが挙げられる。 The silicone-based surfactant is not particularly limited and may be appropriately selected depending on the intended purpose. For example, side-chain modified polydimethylsiloxane, double-ended modified polydimethylsiloxane, one-ended modified polydimethylsiloxane, side chain. Examples thereof include both-terminal modified polydimethylsiloxane, and a polyether-modified silicone-based surfactant having a polyoxyethylene group and a polyoxyethylene polyoxypropylene group as modifying groups is particularly preferable because it exhibits good properties as an aqueous surfactant. ..
As such a surfactant, an appropriately synthesized one may be used, or a commercially available product may be used. As commercially available products, for example, they can be obtained from Big Chemie Co., Ltd., Shin-Etsu Chemical Co., Ltd., Toray Dow Corning Silicone Co., Ltd., Nippon Emulsion Co., Ltd., Kyoeisha Chemical Co., Ltd., and the like.
The above-mentioned polyether-modified silicone-based surfactant is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the polyalkylene oxide structure represented by the general formula (S-1) is dimethylpoly. Examples thereof include those introduced into the Si part side chain of siloxane.

(However, in the general formula (S-1), m, n, a, and b each independently represent an integer, R represents an alkylene group, and R'represents an alkyl group.)
Commercially available products can be used as the above-mentioned polyether-modified silicone-based surfactant, for example, KF-618, KF-642, KF-643 (Shinetsu Chemical Industry Co., Ltd.), EMALEX-SS-5602, SS- 1906EX (Nippon Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (Toray Dow Corning Silicone Co., Ltd.), BYK-33, BYK-387 (Big Chemie Co., Ltd.), TSF4440, TSF4452, TSF4453 (Toshiba Silicon Co., Ltd.) and the like can be mentioned.

上記一般式（Ｆ−１）で表される化合物において、水溶性を付与するためにｍは０〜１０の整数が好ましく、ｎは０〜４０の整数が好ましい。

上記一般式（Ｆ−２）で表される化合物において、ＹはＨ、又はＣｍＦ_２ｍ＋１でｍは１〜６の整数、又はＣＨ_２ＣＨ（ＯＨ）ＣＨ_２−ＣｍＦ_２ｍ＋１でｍは４〜６の整数、又はＣｐＨ_２ｐ＋１でｐは１〜１９の整数である。ｎは１〜６の整数である。ａは４〜１４の整数である。
上記のフッ素系界面活性剤としては市販品を使用してもよい。この市販品としては、例えば、サーフロンＳ−１１１、Ｓ−１１２、Ｓ−１１３、Ｓ−１２１、Ｓ−１３１、Ｓ−１３２、Ｓ−１４１、Ｓ−１４５（いずれも、旭硝子株式会社製）；フルラードＦＣ−９３、ＦＣ−９５、ＦＣ−９８、ＦＣ−１２９、ＦＣ−１３５、ＦＣ−１７０Ｃ、ＦＣ−４３０、ＦＣ−４３１（いずれも、住友スリーエム株式会社製）；メガファックＦ−４７０、Ｆ−１４０５、Ｆ−４７４（いずれも、大日本インキ化学工業株式会社製）；ゾニール（Ｚｏｎｙｌ）ＴＢＳ、ＦＳＰ、ＦＳＡ、ＦＳＮ−１００、ＦＳＮ、ＦＳＯ−１００、ＦＳＯ、ＦＳ−３００、ＵＲ、キャプストーンＦＳ−３０、ＦＳ−３１、ＦＳ−３１００、ＦＳ−３４、ＦＳ−３５（いずれも、Ｃｈｅｍｏｕｒｓ社製）；ＦＴ−１１０、ＦＴ−２５０、ＦＴ−２５１、ＦＴ−４００Ｓ、ＦＴ−１５０、ＦＴ−４００ＳＷ（いずれも、株式会社ネオス社製）、ポリフォックスＰＦ−１３６Ａ，ＰＦ−１５６Ａ、ＰＦ−１５１Ｎ、ＰＦ−１５４、ＰＦ−１５９（オムノバ社製）、ユニダインＤＳＮ−４０３Ｎ（ダイキン工業株式会社製）などが挙げられ、これらの中でも、良好な印字品質、特に発色性、紙に対する浸透性、濡れ性、均染性が著しく向上する点から、Ｃｈｅｍｏｕｒｓ社製のＦＳ−３１００、ＦＳ−３４、ＦＳ−３００、株式会社ネオス製のＦＴ−１１０、ＦＴ−２５０、ＦＴ−２５１、ＦＴ−４００Ｓ、ＦＴ−１５０、ＦＴ−４００ＳＷ、オムノバ社製のポリフォックスＰＦ−１５１Ｎ及びダイキン工業株式会社製のユニダインＤＳＮ−４０３Ｎが特に好ましい。 As the fluorine-based surfactant, a compound having 2 to 16 carbon atoms substituted with fluorine is preferable, and a compound having 4 to 16 carbon atoms substituted with fluorine is more preferable.
Examples of the fluorosurfactant include a perfluoroalkyl phosphate ester compound, a perfluoroalkylethylene oxide adduct, and a polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain. Among these, a polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain is preferable because it has low foaming property, and is particularly a fluorine-based compound represented by the general formula (F-1) and the general formula (F-2). Surfactants are preferred.

In the compound represented by the general formula (F-1), m is preferably an integer of 0 to 10, and n is preferably an integer of 0 to 40 in order to impart water solubility.

In the compound represented by the above general formula (F-2), Y is H or CmF _{2m + 1} and m is an integer of 1 to 6, or CH ₂ CH (OH) CH _2- CmF _{2m + 1} and m is 4 to 6. It is an integer, or CpH _{2p + 1} and p is an integer of 1-19. n is an integer of 1-6. a is an integer of 4 to 14.
Commercially available products may be used as the above-mentioned fluorine-based surfactant. Examples of this commercially available product include Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, and S-145 (all manufactured by Asahi Glass Co., Ltd.); Full Lard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431 (all manufactured by Sumitomo 3M Co., Ltd.); Megafuck F-470, F -1405, F-474 (all manufactured by Dainippon Ink and Chemicals Co., Ltd.); Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR, Capstone FS-30, FS-31, FS-3100, FS-34, FS-35 (all manufactured by The Chemours Company); FT-110, FT-250, FT-251, FT-400S, FT-150, FT- 400SW (all manufactured by Neos Co., Ltd.), Polyfox PF-136A, PF-156A, PF-151N, PF-154, PF-159 (manufactured by Omniova), Unidyne DSN-403N (manufactured by Daikin Industries Co., Ltd.) Among these, the Chemours FS-3100, FS-34, and FS- 300, FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW manufactured by Neos Co., Ltd., Polyfox PF-151N manufactured by Omniova Co., Ltd. and Unidyne DSN-manufactured by Daikin Industries Co., Ltd. 403N is particularly preferable.

The content of the surfactant in the ink is not particularly limited and may be appropriately selected depending on the intended purpose. However, 0.001 mass is obtained from the viewpoint of excellent wettability and ejection stability and improvement in image quality. % Or more and 5% by mass or less are preferable, and 0.05% by mass or more and 5% by mass or less are more preferable.

<Other additives>
If necessary, an antifoaming agent, an antiseptic antifungal agent, a rust preventive agent, a pH adjuster and the like may be added to the ink.

<Physical characteristics of other inks>
The physical characteristics of the ink other than the above Hansen solubility parameter (HSP) are not particularly limited and can be appropriately selected depending on the intended purpose. For example, the viscosity, surface tension, pH and the like are preferably in the following ranges. ..
The viscosity of the ink at 25 ° C. is preferably 5 mPa · s or more and 30 mPa · s or less, preferably 5 mPa · s or more and 25 mPa · s or less, from the viewpoint of improving the print density and character quality and obtaining good ejection properties. More preferred. Here, for the viscosity, for example, a rotary viscometer (RE-80L manufactured by Toki Sangyo Co., Ltd.) can be used. As the measurement conditions, it is possible to measure at 25 ° C. with a standard cone rotor (1 ° 34'x R24), a sample liquid volume of 1.2 mL, a rotation speed of 50 rpm, and 3 minutes.
The surface tension of the ink is preferably 35 mN / m or less, more preferably 32 mN / m or less at 25 ° C. from the viewpoint that the ink is preferably leveled on the recording medium and the drying time of the ink is shortened.
The pH of the ink is preferably 7 to 12, more preferably 8 to 11, from the viewpoint of preventing corrosion of the metal member in contact with the liquid.

<< Recording medium >>
The recording medium can be used without particular limitation, and plain paper, glossy paper, special paper, cloth, etc. can be used, but it is particularly preferably used for a low-permeability base material (low-absorption base material). be able to.
The low-permeability base material means a base material having a surface having a low water permeability, absorbency, or adsorptivity, and includes a material having a large number of cavities inside but not opening to the outside. Examples of the low-permeability base material include coated paper used for commercial printing, recording media such as paperboard in which waste paper pulp is blended in the middle layer and the back layer and the surface is coated.
As the recording medium, cut paper capable of printing for each printing unit, continuous paper or roll paper capable of printing a plurality of printing units in the transport direction of the recording medium can be used.

<Low permeability base material>
As the low-permeability base material, for example, a recording medium such as coated paper having a support and a surface layer provided on at least one surface side of the support, and further having another layer as needed. Can be 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 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 may easily occur, and if it is too large, the ink dot diameter after image formation may be too small than the desired diameter. be.

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 may be insufficient, and if it is too large, the glossiness of the image portion after drying may be likely to be low. The amount of pure water transferred to the recording medium at the contact times of 100 ms and 400 ms can be measured on the surface of the recording medium on the side having the surface layer.

Here, the dynamic scanning absorptometer (DSA, Paper Technology Cooperative Magazine, Vol. 48, May 1994, pp. 88-92, Shigenori Kukan) has a liquid absorption amount in an extremely short time. It is a device that can accurately measure. The dynamic scanning liquid absorber reads the speed of liquid absorption directly from the movement of the meniscus in the capillary, makes the sample disk-shaped, and scans the liquid-absorbing head spirally on it, and scans the speed according to a preset pattern. The measurement is automated by a method of automatically changing and measuring the required number of points on one sample.

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

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 values of the transfer amounts at the contact times in the vicinity of each contact time.

-Support-
The support is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include paper mainly composed of wood fibers and sheet-like substances such as non-woven fabric mainly composed of wood fibers and synthetic fibers.
The thickness of the support is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 50 μm to 300 μm. The basis weight of the ^{support, 45g / m 2 ~290g / m} 2 is preferred.

-Surface layer-
The surface layer contains a pigment, a binder (binder), and, if necessary, a surfactant and other components.
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 amount of the organic pigment added 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 water-based resin, at least one of a water-soluble resin and a water-dispersible resin can be preferably used. The water-soluble resin is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include polyvinyl alcohol, cationically modified polyvinyl alcohol, acetal-modified polyvinyl alcohol, polyester, polyurethane, polyester and polyurethane.
The surfactant contained in the surface layer as needed is not particularly limited and may be appropriately selected depending on the intended purpose. Both can be used.
The method for forming the surface layer is not particularly limited and may be appropriately selected depending on the intended purpose, and can be carried out by impregnating or applying a liquid constituting the surface layer on the support. 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 device, recording method >>
A recording method and a recording device according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic view showing an example of a recording device.
The recording device 1 shown in FIG. 1 is a device that forms an image on the recording medium 10 by applying ink to the recording medium 10. The recording device 1 includes a paper feeding means 11, a means 12 for applying ink, a drying means 13, and a winding means 15.

<Papering means, paper feeding process>
The paper feeding means 11 is a means for feeding the recording medium 10 to a position where the ink applying means 12 applies the ink. The paper feeding process as one step of the recording method can be preferably carried out by the paper feeding means.
As the recording medium 10 to be fed, continuous paper is preferably used. The continuous paper is a recording medium that is continuous in the transport direction at the time of image formation and is longer than the length of the print unit (1 page) in the transport direction. The length of the continuous paper is preferably longer than the length of the transport path from the paper feeding means 11 to the winding means 15. As the continuous paper, for example, roll paper rolled into a roll shape can be used. In the example shown in FIG. 1, a roll-shaped recording medium 10 is set in the paper feeding means 11. Then, by winding the recording medium 10 fed from the paper feeding means 11 by using the winding means 15, the recording medium 10 is conveyed in the conveying direction (directions indicated by arrows 16 and 17 in FIG. 1). Will be done. The recording medium 10 is not limited to continuous paper, and cut paper may be used as the recording medium. The cut paper is an independent recording medium for each print unit (1 page) in the transport direction at the time of image formation.

<Means for applying ink, process for applying ink>
The means 12 for applying ink is a means for applying ink to the recording medium 10 fed in the direction of the arrow 16 from the paper feeding means 11 to form an image. As the means 12 for applying ink, a head unit composed of a single-pass type inkjet line head is preferable. In the case of the means for applying by the inkjet recording method, it is preferable to have four ejection heads corresponding to each of black (K), cyan (C), magenta (M) and yellow (Y) inks. Further, it may have a special color ink such as orange (O) and green (G), and a discharge head that discharges a post-treatment liquid that imparts gloss and performs other treatments. In addition to the inkjet recording method, ink is applied using, 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, or the like. Means to do. The step of applying ink as one step of the recording method can be preferably carried out by means for applying ink.
The size of the ink droplets to be ejected is preferably 2 pL or more and 40 pL or less, the ejection speed is preferably 5 m / s or more and 20 m / s or less, and the drive frequency is 1 kHz or more. Preferably, the resolution is 300 dpi or more.
Ink is supplied to each of the above-mentioned ejection heads from an ink container (an example of an ink container) that stores ink. The ink container may be used as long as it can store ink, and examples thereof include cartridges and bottles casing made of resin or the like. In the cartridge, the inner bag may be in a form in which ink is stored in an aluminum pouch made of resin such as polyethylene.

<Drying means, drying process>
The drying means 13 is a means for drying the ink applied to the recording medium 10 from the means 12 for applying the ink. The drying means 13 is preferably a heat drum that heats the recording medium 10 in contact with the non-inked surface. The temperature of the heat drum is preferably 100 ° C. or higher and 130 ° C. or lower, although it depends on the printing speed and the drying property of the ink. Examples of other drying means that can be combined with drying by a heat drum include means such as warm air heating, infrared irradiation, and ultraviolet irradiation, and means that combine these. The drying step as one step of the recording method can be preferably carried out by the drying means.

<Rewinding means, winding process>
The winding means 15 is arranged at a position facing the paper feeding means 11, and is a means for winding the recording medium 10 which has been fed from the paper feeding means 11 and has a print layer formed therein. By adjusting the rotation speeds of the paper feeding means 11 and the winding means 15, the tension acting on the recording medium 10 can be adjusted. Depending on the type of recording medium, the paper feeding means and the winding means may be omitted. The winding step as one step of the recording method can be preferably carried out by the winding means.

<Others>
This recording device can include not only a portion that ejects ink, but also a device called a pretreatment device, a posttreatment device, and the like.
As one aspect of the pretreatment device and the posttreatment device, it has a pretreatment liquid and a posttreatment liquid as in the case of inks such as black (K), cyan (C), magenta (M), and yellow (Y). There is an embodiment in which a liquid accommodating portion and a liquid discharge head are added, and a pretreatment liquid or a posttreatment liquid is discharged by an inkjet recording method.
As another aspect of the pretreatment device and the posttreatment device, there is a mode in which a pretreatment device and a posttreatment device by, for example, a blade coating method, a roll coating method, and a spray coating method are provided other than the inkjet recording method.

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

<Synthesis example of copolymer a>
62.0 g (525 mmol) of ethylene glycol (manufactured by Tokyo Kasei Co., Ltd.) was dissolved in 700 mL of methylene chloride, and 20.7 g (262 mmol) of pyridine was added. A solution prepared by dissolving 50.0 parts by mass (262 mmol) of 2-naphthalenecarbonyl chloride (manufactured by Tokyo Kasei Co., Ltd.) in 100 mL of methylene chloride was added dropwise to this solution with stirring over 2 hours, and then at room temperature 6 Stirred for hours. After washing the obtained reaction solution with water, the organic phase was isolated, 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 parts by mass of 2-naphthoic acid-2-hydroxyethyl ester. rice field.
Next, 42.1 parts by mass (155 mmol) of 2-naphthoic acid-2-hydroxyethyl ester was dissolved in 80 mL of dry methyl ethyl ketone and heated to 60 ° C. A solution prepared by dissolving 24.0 parts by mass (155 mmol) of 2-methacryloyloxyethyl isocyanate (Carens MOI, manufactured by Showa Denko KK) in 20 mL of dry methyl ethyl ketone was added dropwise to this solution with stirring over 1 hour. , 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 to obtain 57.0 parts by mass of the monomer represented by the following structural formula (1). rice field.

Next, 1.30 parts by mass (22.0 mmol) of acrylic acid (manufactured by Aldrich) and 6.29 parts by mass (14.7 mmol) of the monomer represented by the above structural formula (1) are dissolved in 40 mL of dry methyl ethyl ketone. To prepare a monomer solution. After heating 10% by mass of the monomer solution to 75 ° C. under an argon stream, 0.273 parts by mass (1.67 mmol) of 2,2'-azoiso (butyronitrile) (manufactured by Tokyo Kasei Co., Ltd.) was added to the remaining monomer solution. The solution was added dropwise over 1.5 hours, and the mixture was stirred at 60 ° C. for 11 hours. After cooling to room temperature, the obtained reaction solution was dropped into hexane. The precipitated copolymer was filtered off and dried under reduced pressure to obtain 8.13 parts by mass of the copolymer.
The obtained copolymer is dissolved in a dimethylethanolamine aqueous solution so as to neutralize 100%, and the concentration of the copolymer is adjusted with ion-exchanged water so that the concentration of the copolymer becomes 10% by mass to obtain the copolymer a. Obtained.
The obtained copolymer a had a weight average molecular weight of 20,000 when measured using GPC, and 160 mgKOH / g when the acid value was measured by acid value titration.

<Preparation example of pigment dispersion 1>
・ Cyanine Blue A220JC (CI Pigment Blue 15: 3, manufactured by Dainichi Seika Co., Ltd.): 15.0 parts by mass ・ Polymer a (polymer concentration 10% by mass): 37.5 parts by mass ・ Ion Exchanged water: 47.5 parts by mass Add the copolymer a to the ion-exchanged water to dissolve it, mix cyanine blue A220JC, stir and sufficiently moisten it, and then use Dynomill KDL A type (manufactured by WAB) as a kneading device. Was filled with zirconia beads having a diameter of 0.2 mm and kneaded at 2,000 rpm for 20 minutes. The mill base was taken out and filtered through a filter having an average pore size of 1 μm to obtain a pigment dispersion 1 containing a pigment-containing substance (pigment-containing substance concentration: 18.75% by mass).

<Preparation example of pigment dispersion 2>
-Inkjet Magenta E5B 02 (CI Pigment Violet 19, manufactured by Clariant Japan Co., Ltd.): 15.0 parts by mass-Copolymer a (copolymer concentration 10% by mass): 37.5 parts by mass-Ion exchange Water: 47.5 parts by mass Copolymer a was added to ion-exchanged water to dissolve it, and Inkjet Magenta E5B 02 was mixed, stirred and sufficiently moistened. Was filled with zirconia beads having a diameter of 0.2 mm and kneaded at 2,000 rpm for 60 minutes. The mill base was taken out and filtered through a filter having an average pore size of 1 μm to obtain a pigment dispersion 2 containing a pigment-containing substance (pigment-containing substance concentration: 18.75% by mass).

<Synthesis example of copolymer b>
Methyl ethyl ketone in the reaction vessel of an automatic polymerization reaction device (manufactured by Todoroki Sangyo Co., Ltd .: polymerization tester DSL-2AS type) equipped with a reaction vessel equipped with a stirrer, a dropping device, a temperature sensor, and a reflux device having a nitrogen introduction device at the top. Was charged, and the inside of the reaction vessel was replaced with nitrogen while stirring. After heating the inside of the reaction vessel to 80 ° C. while maintaining a nitrogen atmosphere, 75.0 g of -2-hydroxyethyl methacrylate, 77.0 g of methacrylic acid, 80.0 g of styrene, and 150 of butyl methacrylate were added by a dropping device. A mixed solution of 0.0 g, 98.0 g of butyl acrylate, 20.0 g of methyl methacrylate, and 40.0 g of "Perbutyl (registered trademark) O" (manufactured by Nippon Oil & Fats Co., Ltd.) was added dropwise over 4 hours. After completion of the dropwise addition, the reaction was continued at the same temperature for 15 hours to obtain methyl ethyl ketone B of an anionic group-containing styrene-acrylic copolymer A having an acid value of 100, a weight average molecular weight of 21,000, and a Tg (calculated value) of 31 ° C. Obtained liquid. After completion of the reaction, a part of methyl ethyl ketone was distilled off under reduced pressure to obtain a copolymer b solution having a non-volatile content adjusted to 50%.

<Preparation example of pigment dispersion 3>
In a mixing tank equipped with a cooling jacket, 1,000 g of copper phthalocyanine (SEIKALIGHT BLUE A612 manufactured by Dainichiseika Kogyo Co., Ltd.), 800 g of copolymer b solution, 143 g of 10% sodium hydroxide aqueous solution, and 100 g of methyl ethyl ketone. , And 1,957 g of water were charged and mixed by stirring. The mixed solution is passed through a dispersion device (manufactured by Mitsui Mining Co., Ltd .: SC Mill SC100) filled with zirconia beads having a diameter of 0.3 mm, and the dispersion method (a method of returning the dispersion liquid discharged from the dispersion device to the mixing tank) is used for 6 hours. Distributed. The rotation speed of the disperser was set to 2,700 rpm, and cold water was passed through the cooling jacket so that the dispersion temperature was maintained at 40 ° C. or lower. After completion of the dispersion, the dispersion stock solution was withdrawn from the mixing tank, and then the mixing tank and the flow path of the dispersion device were washed with 10,000 g of water to obtain a diluted dispersion stock solution together with the dispersion stock solution. A diluted dispersion was placed in a glass distillation apparatus, and the entire amount of methyl ethyl ketone and a part of water were distilled off. After cooling to room temperature, 10% hydrochloric acid was added dropwise with stirring to adjust the pH to 4.5, and then the solid content was filtered with a Nutche type filtration device (manufactured by Nippon Kagaku Kikai Seisakusho Co., Ltd., pressure filter) and washed with water. The cake was placed in a container, 200 g of a 20% potassium hydroxide aqueous solution was added, the cake was dispersed with Dispa (TK Homo Disper manufactured by Tokushu Kika Kogyo Co., Ltd.), and water was further added to adjust the non-volatile content. As a result, the pigment dispersion 3 (pigment-containing material concentration: 20) containing composite particles (pigment-containing material) in which copper phthalocyanine is coated with a carboxyl group-containing styrene-acrylic copolymer neutralized in potassium hydroxide. .0% by mass) was obtained.

<Ink preparation example>
-Preparation of ink 1-
1,3-Propanediol 35.0% by mass, polyoxyalkylene alkyl ether (trade name: TRITON HW-1000, compound in which n is 6 in the general formula (3), manufactured by Dow Chemical Co., Ltd.) 1.0% by mass , And ion-exchanged water were stirred for 1 hour and mixed uniformly, 2.0% by mass of rosin-modified maleic acid resin (manufactured by Harima Kasei Co., Ltd .: Harimac R-100) was added, and the mixture was further stirred for 1 hour and mixed uniformly. Pigment dispersion 1 was added in an amount of 30.0% by mass, and the mixture was further stirred for 1 hour and mixed uniformly. This mixture was pressure-filtered with a polyvinylidene fluoride membrane filter having an average pore size of 0.8 μm to remove coarse particles and dust to obtain Ink 1.

-Preparation of inks 2-28-
Inks 2 to 28 were obtained in the same manner as in the preparation of ink 1 except that the compositions in Tables 1 to 3 below were changed in the preparation of ink 1. The unit of each numerical value of the composition in Tables 1 to 3 is "mass%".

The following materials were used for each component in Tables 1 to 3.
-TMN-3 (Compound in which n is 3 in the general formula (3), manufactured by Dow Chemical Co., Ltd.)
TMN-6 (Compound in which n is 8 in the general formula (3), manufactured by Dow Chemical Co., Ltd.)
TMN-100X (Compound in which n is 9 in the general formula (3), manufactured by Dow Chemical Co., Ltd.)
TMN-10 (Compound in which n is 11 in the general formula (3), manufactured by Dow Chemical Co., Ltd.)
-Polyoxyethylene laureth ether sodium sulfate (average number of moles of ethylene oxide: 18 moles)
・ Surfinol 420 (manufactured by Air Products & Chemicals)

<Measurement of Hansen solubility parameter (HSP) and interaction radius _{R0 of pigment-containing material>
Hereinafter, the Hansen solubility parameter (HSP) and the interaction radius R0} of the pigment-containing material were determined according to the procedures [1] to [3].

[1] Preparation of dispersion liquid containing pigment-containing material First, an aqueous dispersion liquid containing a pigment-containing material was prepared. Specifically, in the pigment dispersions 1 to 3, the content of the pigment-containing material was adjusted to be 30% by mass with respect to the total amount of the pigment dispersions 1 to 3.

[2] Evaluation of compatibility between the dispersion containing the pigment-containing material and the evaluation solvent Next, 18 types of the following evaluation solvents having a known Hansen solubility parameter (HSP) were prepared, and the aqueous dispersion containing the pigment-containing material was prepared. Each evaluation solvent was added and dispersed well to prepare a mixed solution. The amount of the evaluation solvent added was such that the mass of the aqueous dispersion was 20% of the mass of the mixed solution. Then, the mixture was allowed to stand for 12 hours, and the dispersed state of the mixed solution after standing was visually observed to determine the presence or absence of aggregation.
~ Evaluation solvent (18 types) ~
Water, glycerin, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol di, 2,3-butanediol di, propylene glycol, 1-methoxy-2- Propanol, 3-methoxy-1-butanol, 3-methoxy-3-methyl-1-butanol, 2-pyrrolidone, 2-propanol, diethylene glycol, dipropylene glycol, 1,2-hexanediol, 3-ethyl-3-hydroxymethyl Oxetane, 3-methoxy-N, N-dimethylpropionamide

[3] Calculation of Hansen solubility parameter (HSP) and interaction radius _R0 of pigment-containing material Next, using the computer software Hansen Solubility Parameters in Practice (HSPiP), based on the results obtained in the above [2]. The Hansen solubility parameter (HSP) and the radius of interaction _R0 in the pigment-containing material were calculated. The results are shown below. The numerical values in parentheses below represent the vector amounts (δD, δP, δH) of the Hansen solubility parameter (HSP).
− Pigment dispersion 1-
Hansen solubility parameter (HSP): (16.0, 12.8, 32.1)
・ Interaction radius R ₀ : 10.1
-Pigment dispersion 2-
Hansen solubility parameter (HSP): (16.6, 12.5, 31.9)
・ Interaction radius R ₀ : 11.0
− Pigment dispersion 3-
Hansen solubility parameter (HSP): (12.0, 24.5, 27.2)
・ Interaction radius R ₀ : 17.1

<Calculation of difference (Ra-R _0)>
First, the Hansen solubility parameter (HSP) of the organic solvent in each ink was determined. The Hansen solubility parameter (HSP) of the organic solvent was calculated as a vector sum of the values obtained by multiplying the Hansen solubility parameter (HSP) of each organic solvent contained in the ink by the volume ratio of each organic solvent to the entire organic solvent.
Next, the distance Ra was calculated based on the Hansen solubility parameter (HSP) of the organic solvent and the Hansen solubility parameter (HSP) of the pigment-containing substance. Further, the difference (Ra-R ₀ ) was calculated based on the distance Ra and the interaction radius R _0. The results are shown in Table 4.

Using the obtained ink, "beading property" and "ejection recovery property" were evaluated as follows. The results are shown in Table 4.

[Beading]
Using the recording device shown in FIG. 1, ink is ejected onto a recording medium (Oji Paper Co., Ltd .: OK top coat + [basis weight: 127.8 gsm]), and warm air at 100 ° C. and heating at 100 ° C. are performed in the drying process. The rollers were brought into contact with each other for 10 seconds to dry, and a print sample was obtained. As the ink applying means of the recording device, a head mounted on an inkjet recording device (IPSiO GXe-5500: manufactured by Ricoh Co., Ltd.) was used, and the print chart was a solid image of 3 cm square formed by a dot pattern. Next, the solid portion of the solid image of 3 cm square formed by the dot pattern of the print sample was visually observed, and the "beading property" was evaluated based on the following evaluation criteria. It is preferable that the evaluation is B or higher.
(Evaluation criteria)
A: Beading cannot be observed from a distance of 20 cm B: Slight beading can be observed from a distance of 20 cm C: Beading can be clearly observed from a distance of 20 cm.

[Discharge recovery]
After leaving the head of the inkjet recording device (IPSiO GXe-5500: manufactured by Ricoh Co., Ltd.) in a decapped state for 10 hours, the head cleaning was performed once, and the recording medium (manufactured by Oji Paper Co., Ltd .: OK top coat + [basis weight: 127. 8gsm]) was printed with a nozzle check chart. By observing the dots forming the obtained nozzle check chart, the presence or absence of ejection abnormality in the nozzle was confirmed. When there was a discharge abnormality, the head cleaning was performed twice more, and the nozzle check chart was printed again on the recording medium (Oji Paper Co., Ltd .: OK top coat + [basis weight: 127.8 gsm]). After that, by observing the dots forming the obtained nozzle check chart, the presence or absence of ejection abnormality in the nozzle was confirmed, and "discharge recovery" was evaluated based on the following evaluation criteria. It is preferable that the evaluation is B or higher.
(Evaluation criteria)
A: No nozzle discharge abnormality after 1 cleaning B: No nozzle discharge abnormality after 3 cleaning C: Nozzle with discharge abnormality occurs even after 3 cleaning

1 Recording device 10 Recording medium 11 Paper feeding means 12 Means for applying ink 13 Drying means 15 Winding means 16 Transporting direction of recording medium 17 Transporting direction of recording medium

JP-A-2018-104490

Claims (11)

It contains a pigment-containing substance containing a pigment, an organic solvent, water, and a compound represented by the following general formula (1).
Difference between the distance Ra of the Hansen solubility parameter of the organic solvent and the Hansen solubility parameter of the pigment-containing substance obtained by the Hansen solubility parameter method and the interaction radius R _{0 of the pigment-containing substance obtained by the Hansen solubility ball method.} (Ra-R ₀ ) is an ink characterized in that it is 2.0 or less.

(In the above general formula (1), R ₁ , R ₂ , R ₃ and R ₄ independently represent a hydrogen atom or an alkyl group having 1 or more and 5 or less carbon atoms, and n is 3 or more and 11 or less. Represents an integer of.) The ink according to claim 1, wherein the difference (Ra-R _{0) is 0 or less.} The ink according to claim 1 or 2, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (2).

(In the above general formula (2), R ₅ , R ₆ , R ₇ , R ₈ and R ₉ each independently represent a hydrogen atom or an alkyl group having 1 or more and 5 or less carbon atoms, and n is 3 It represents an integer of 11 or more.) The ink according to claim 1 or 2, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (3).

(In the above general formula (3), n represents an integer of 3 or more and 11 or less.) The ink according to any one of claims 1 to 4, wherein n represents an integer of 6 or more and 9 or less. The pigment-containing material comprises claims 1 to 5 containing the pigment and a copolymer having a structural unit represented by the following general formula (4) and a structural unit represented by the following general formula (5). The ink according to any one of the above.

(In the structural unit represented by the general formula (4), R ₁₀ is a hydrogen atom or a methyl group, and L ₁ is an alkylene group having 2 or more and 18 or less carbon atoms.)

(In the structural unit represented by the general formula (5), R ₁₁ is a hydrogen atom or a methyl group, and X is a hydrogen atom or a cation.) The ink according to any one of claims 1 to 6, wherein the pigment-containing material contains a styrene-acrylic resin-coated pigment in which at least a part of the surface of the pigment is coated with a styrene-acrylic resin. The ink according to any one of claims 1 to 7, wherein the organic solvent is at least one selected from 1,3-propanediol and glycerin. An ink container containing the ink according to any one of claims 1 to 8. A recording device comprising the ink containing container according to claim 9 and an ink applying means for applying the contained ink. A recording method comprising an ink applying step of applying the ink according to any one of claims 1 to 8.

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