JP2000169773A - Method for evaluating ink composition for ink jet recording and preparation thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish a universal standard for preparing an ink composition for ink jet recording having excellent performances. SOLUTION: The method for preparing an ink composition for ink jet recording comprises measuring the kinetic viscoelasticity of an ink composition comprising at least a water-soluble coloring material, a water-soluble organic solvent and water, calculating the logarithmic value of the shear rate (γ.) and the storage modulus of rigidity (G') of the ink composition, plotting these values on a two-dimensional coordinate thereby obtaining a gradient (α) and adjusting the composition so that the absolute value of the gradient (α) obtained becomes around zero.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an ink composition for ink jet recording having good performance, and a method for evaluating the ink composition.

2. Description of the Related Art Ink jet recording is a method of discharging a small droplet of an ink composition from a fine nozzle to record characters and figures on the surface of a recording medium. As an ink jet recording method, a method of converting an electric signal into a mechanical signal using an electrostrictive element, intermittently discharging an ink composition stored in a nozzle head portion, and recording characters or symbols on a recording medium surface or The ink composition stored in the nozzle head portion is heated rapidly at a location very close to the discharge portion to generate bubbles, and the bubbles are expanded intermittently to discharge characters and symbols on the recording medium surface by intermittent discharge. Methods have been developed and put into practical use.

[0003] The ink composition used for such ink jet recording has good ejection properties, no disturbance of printing due to satellites, good printing on various recording media, and color printing in multicolor printing. Are required to be mixed with each other.

Conventionally, whether or not a manufactured ink composition for ink jet recording has the above-described printing characteristics is evaluated by filling the manufactured ink composition into an ink jet recording apparatus and then printing on a recording medium. Was done by. The quality of the performance of the ink composition can be grasped only after the ink composition is manufactured and printed on a recording medium. That is,
The fact is that the production of the ink composition has been performed empirically. Here, if the ink composition can be manufactured based on universal evaluation criteria without depending on empirical rules, efficient manufacture of an ink composition having good performance becomes possible.

On the other hand, there is rheology as a science that deals with the deformation and flow of a substance in response to a mechanical force. In general, a substance has a viscoelastic property having both elasticity and viscosity, and the relation between the elastic behavior and the viscous behavior of the substance and time is grasped as “dynamic viscoelasticity”. Further, when considering dynamic viscoelasticity, a Maxwell model, which is a dynamic model of a viscoelastic liquid in which a spring exhibiting ideal elasticity and a dashpot exhibiting pure viscosity are connected in series, may be used. When an oscillating force σ ^* = σ ₀ exp (ιωt) is applied to this model, a complex quantity γ ^* = γ ₀ exp [ι (ωt−) with the same frequency and a phase delay of δ is applied to the model. δ)]. The relationship between σ ^* and γ ^* can be expressed as in the following formula (I), taking Maxul's viscoelastic equation into consideration.

[0006]

(Equation 1) (Where τ is the relaxation time given by η / G) Here, the ratio of σ ^* to γ ^* is defined as the complex rigidity G ^* = (G ′ + ι)
G '') can be expressed as in the following equation (II).

[0007]

(Equation 2) Here, the real part G ′ of G ^* is the storage rigidity, and the imaginary part G ″
Is called a loss rigidity, and a value obtained by dividing G ″ by ω is called a dynamic viscosity η ′. These are all functions of ω.

[0008] To the knowledge of the present inventors, it is assumed that the dynamic viscoelasticity of the ink composition is related to the performance of the ink composition, and that a clear and universal evaluation standard for obtaining a good ink composition has been established. There is no report.

[0009]

SUMMARY OF THE INVENTION The present inventor has paid attention to the dynamic viscoelasticity of an ink composition. The performance of the ink composition is related to the storage elastic modulus and the shear rate of the ink composition, and these are used as indices. And that a good ink composition was obtained.

Accordingly, an object of the present invention is to provide a method for evaluating an ink composition, which can evaluate the performance of the ink composition without performing an actual printing test.

Another object of the present invention is to provide a method for producing an ink composition for ink jet recording, which can provide an ink composition having good performance.

The method for evaluating an ink composition for ink jet recording according to the present invention comprises the steps of:
An ink composition comprising at least water and water is prepared, the dynamic viscoelasticity of the ink composition is measured, and the logarithmic value of the shear rate (γ ·) and the storage rigidity (G ′) of the ink composition are calculated. Then, it is determined whether or not the absolute value of the inclination (α) obtained by taking the respective values on two axes is approximately zero.

Further, the method for producing an ink composition for ink jet recording according to the present invention is characterized in that the ink composition for ink jet recording comprising at least a coloring material, a water-soluble organic solvent and water is used when preparing the ink composition for ink jet recording. The dynamic viscoelasticity was measured, the logarithmic value of the shear rate (γ ·) of the ink composition and the storage rigidity (G ′) were calculated, and the absolute value of the gradient (α) obtained by taking each value as two axes was calculated. And adjusting the value so that the value is approximately zero.

[0014]

DETAILED DESCRIPTION OF THE INVENTION Measurement of Dynamic Viscoelasticity of Ink Composition In the method for evaluating and manufacturing an ink composition for ink jet recording according to the present invention , the dynamic viscoelasticity of the ink composition is measured. The principle of this measurement will be described with reference to FIG. The measuring device 1 includes a test liquid 2
And a precision measuring tube 5 having a radius a and a length L surrounded by a thermostat 4 and communicating with the test liquid reservoir 3. Vibration at a frequency f is given by a vibration device (not shown) via the control unit. The pressure P and the volume flow U applied to the test liquid 2 oscillating and flowing by this vibration are measured by the sensor means 7. The shear stress τ at the precision measurement tube wall is directly proportional to the pressure P, and the shear strain γ and the shear rate γ · are directly proportional to the volume flow rate U. Therefore, the shear stress τ, the shear strain γ, and the shear rate γ of the sample liquid can be calculated from the pressure number P and the volume flow rate U.

Shear stress: τ-P (a / 2L) Shear rate: γ · -U (4πa ³ ) Shear strain: γ = γ · / 2πf (where a is the radius of the measuring tube, L is the measuring tube Height, f indicates frequency) From these calculated values, the viscosity and elasticity (or storage and loss factor) of the ink composition is obtained.

In the method for evaluating and manufacturing the ink composition according to the present invention, when the dynamic viscoelasticity of the ink composition is measured, the frequency is the same from the start to the end of the measurement, and is not changed. preferable.

In the present invention, the device for measuring the dynamic viscoelasticity of the ink composition is not particularly limited as long as the above basic principle is followed. However, devices for measuring dynamic viscoelasticity are commercially available.
It is also possible to use these commercially available devices. For example, as a capillary type viscoelasticity measuring device, VILAS
TIC SCIENTIFIC's VILASTICV
-E SYSTEM and Paar Physica
The company's DCR can be used.

Method for Evaluating Ink Composition In the method for evaluating an ink composition according to the present invention, the dynamic viscoelasticity of the ink composition is measured as described above, and the logarithmic value of the shear rate (γ ·) is determined from the result. The absolute value of the inclination (α) obtained by taking the storage rigidity (G ′) as two axes is obtained. Then, it is determined whether or not the absolute value of the obtained inclination (α) is substantially in the vicinity of 0, preferably, is in a range of less than 1 × 10 ⁻⁵ . An ink composition having an absolute value of the gradient (α) of about 0 is excellent in performance, and particularly excellent in printing stability in an ink jet recording method. In other words, the ink droplets are ejected in a predetermined direction without clogging the nozzles and causing no flight bending. Conventionally, the performance of such an ink composition has been evaluated by preparing an ink composition and then actually printing the ink composition by an inkjet recording method. However, according to the present invention, the performance of the ink composition can be evaluated without actually performing printing. Therefore, according to the present invention, an efficient production of an ink composition for inkjet recording having excellent performance can be obtained extremely well.

In the ink composition to be evaluated in the present invention, the coloring material and / or other ink composition components are basically insoluble in water, that is, a part of the components constituting the ink composition is water. The ink composition is dispersed without being dissolved in the ink. According to a preferred embodiment of the present invention, the component unnecessary for water is generally a coloring material, and the method according to the present invention is used for evaluating the performance of an ink composition containing such a coloring component unnecessary for water. Is preferably used. Therefore, as the ink composition to which the evaluation method according to the present invention is applied, an ink composition containing a pigment as a coloring material, and further, the coloring material is a dye, and the dye does not substantially dissolve in water. And an ink composition dispersed to form an ink composition.

(A) Colorant According to a preferred embodiment of the present invention, the colorant contained in the ink composition of the present invention comprises a water-dispersible pigment and / or
Or a dye dispersible in water.

As pigments, inorganic pigments and organic pigments can be used. As the inorganic pigment, in addition to titanium oxide and iron oxide, carbon black produced by a known method such as a contact method, a furnace method, and a thermal method can be used.

Examples of the organic pigment include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, etc.) and polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridones) Pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinoflurone pigments, etc., dye chelates (eg, basic dye type chelates,
Acid dye type chelates), nitro pigments, nitroso pigments, aniline black and the like.

Examples of the dye include oil-soluble dyes, direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, disperse dyes, vat dyes, soluble vat dyes, and reactive disperse dyes.

In the present invention, the coloring material is dispersed in an aqueous medium with a dispersant. As a dispersant, a dispersant generally used to disperse a pigment, for example, a polymer powder,
Surfactants can be used. It will be apparent to those skilled in the art that the surfactant used to disperse the pigment will also function as the surfactant of the ink composition described below.

The polymer dispersant may be either a natural polymer or a synthetic polymer. Specific examples of natural polymers include proteins such as gelatin, casein and albumin, gum arabic and natural gums such as tragacanth gum,
Examples include glucosides such as saponin, alginic acid and propylene glycol esters of alginic acid, alginic acid derivatives such as triethanolamine alginate and ammonium alginate, and cellulose derivatives such as methylcellulose, carboxymethylcellulose, hydroxymethylcellulose and ethylhydroxycellulose.

Specific examples of the polymer dispersant include polyvinyl alcohols, polyvinylpyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymer,
Acrylic resins such as potassium acrylate-acrylonitrile copolymer, vinyl acetate-acrylate copolymer, acrylic acid-acrylate copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer Styrene-acrylic resin such as styrene-methacrylic acid-acrylate copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylate copolymer, styrene -Maleic acid copolymer, styrene-maleic anhydride copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer Polymer, vinyl acetate-maleate copolymer, vinegar And vinyl acetate copolymers such as vinyl acid-crotonic acid copolymer and vinyl acetate-acrylic acid copolymer, and salts thereof. Among them, a copolymer of a monomer having a hydrophobic group and a monomer having a hydrophilic group, and a polymer composed of a monomer having both a hydrophobic group and a hydrophilic group in a molecular structure are preferable.

The pigment is dispersed in water without a dispersant by a surface treatment such that at least one functional group of a carboxy group, a carboxyl group, a hydroxyl group, or a sulfone group or a salt thereof is bonded to the surface. Includes what has been done.

Specifically, it can be obtained by grafting a functional group or a molecule containing a functional group to the surface of carbon black by a physical treatment such as vacuum plasma or a chemical treatment with an oxidizing agent. In the present invention, the functional groups grafted to one carbon black particle may be single or plural.

The type and the degree of the functional group to be grafted may be appropriately determined in consideration of the dispersion stability in the ink composition, the color density, the drying property on the front surface of the ink jet head, and the like.

According to a preferred embodiment of the present invention, it is preferable to use a pigment having an average particle size of 50 to 200 nm as a pigment dispersion dispersed by any one of the above methods.

The amount of the coloring material added to the ink composition is 0.5
It is preferably about 25% by weight, more preferably about 2 to 15% by weight.

In the present invention, the ink composition for ink jet recording means a black ink when performing monochrome printing, and a color ink when performing color printing, specifically, a yellow ink and a magenta ink. , And cyan ink, and in some cases, black ink.

(B) Water, Water-Soluble Organic Solvent, and Other Components The solvent of the ink composition according to the present invention is water and an aqueous organic medium. Examples of the water-soluble organic solvent contained in the ink composition according to the present invention include alkyl alcohols having 1 to 4 carbon atoms such as ethanol, methanol, butanol, propanol and isopropanol; ethylene glycol monomethyl ether; ethylene glycol monoethyl ether; Ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-i
so-propyl ether, diethylene glycol mono-
iso-propyl ether, ethylene glycol mono-
n-butyl ether, diethylene glycol mono-n-
Butyl ether, triethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono- t-
Butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether,
Dipropylene glycol mono-n-propyl ether,
Dipropylene glycol mono-iso-propyl ether, propylene glycol mono-n-butyl ether,
Glycol ethers such as dipropylene glycol mono-n-butyl ether, formamide, acetamide, dimethyl sulfoxide, sorbit, sorbitan,
Acetin, diacetin, triacetin, sulfolane and the like can be mentioned.

The amount of the aqueous organic solvent added to the ink composition is preferably from 10 to 40% by weight, more preferably from 10 to 40% by weight.
About 20% by weight.

According to a preferred embodiment of the present invention, it is preferable to add a water-soluble glycol to the ink composition. Preferred examples of the water-soluble glycols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, molecular weight 2
000 or less polyethylene glycol, 1,3-propylene glycol, isopropylene glycol, isobutylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerin, There are mesoerythritol and pentaerythritol. Water-soluble glycols have an effect of suppressing drying of the ink composition on the front surface of the nozzle.

The amount of the glycol added to the ink composition is preferably 1 to 30% by weight, more preferably 5 to 2% by weight.
It is about 0% by weight.

According to a preferred embodiment of the present invention, many kinds of sugars can be used in the ink composition. Preferred examples of the saccharide used include monosaccharides and polysaccharides, and more specifically, glucose, mannose, fructose, ribose, xylose, arabinose, lactose, galactose, aldonic acid, glucitolose, maltose, cellobiose, sucrose, trehalose, maltose. In addition to triose and the like, there are alginic acid and salts thereof, cyclodextrins, celluloses and the like. The amount of the saccharide added to the ink composition is preferably about 0.1% to 30%.

According to a preferred embodiment of the present invention, the ink composition may contain a surfactant. The surfactant is preferably one having good compatibility with other components of the ink composition, and among the surfactants, those having high permeability and high stability are preferred.

Examples of the surfactant include anionic surfactants (eg, sodium dodecylbenzenesulfonate, sodium laurate, ammonium salts of polyoxyethylene alkyl ether sulfate, etc.), nonionic surfactants (eg, polyoxygenated surfactants). Ethylene alkyl ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyethylene alkylamide, etc.) and acetylene glycol.

These can be used alone or in combination of two or more. Acetylene glycol-based surfactants include, for example, Surfynol 465, TG, 104
(Air Products Co., Ltd.) and their modified organisms.

According to a preferred embodiment of the present invention, when the coloring material according to the present invention is a pigment, it is preferable that the ink composition further contains fine polymer particles. The addition of the polymer fine particles can improve the fixing property and the abrasion resistance of the print. The polymer fine particles are preferably used in the form of a polymer emulsion in which the continuous phase is water and the dispersed phase is a thermoplastic polymer.

The thermoplastic polymer includes ethylene-vinyl acetate copolymer, ethylene-acrylate copolymer,
Polyethylene, polypropylene, polystyrene, poly (meth) acrylate, (meth) acrylic acid-styrene copolymer, (meth) acrylic acid ester- (meth) acrylic acid copolymer, (meth) acrylic acid ester- (meth) ) Acrylic acid-styrene copolymer, styrene-
Maleic acid copolymer, styrene-itaconic acid ester copolymer, polyvinyl acetate, polyester, polyurethane, polyamide, acrylic resin, methacrylic resin,
Styrene-based resins, (meth) acrylate-styrene-based resins, and the like are included.

Further, the polymer emulsion used in the ink composition according to the present invention has a film-forming ability, and preferably has a minimum film-forming temperature of 30 ° C. or less.

The amount of the polymer particles added to the ink composition may be appropriately determined. For example, it is preferably about 1 to 10% by weight, more preferably about 1 to 5% by weight. The ink composition according to the present invention may further include a preservative, a pH adjuster, a fungicide, and the like as components other than those described above.

Method for Producing Ink Composition As described above, according to the method for evaluating an ink composition according to the present invention, it is possible to determine whether or not the ink composition has excellent performance. Viewing this evaluation method from another viewpoint, a method for producing an ink composition having excellent performance is provided. Therefore, as a second aspect of the present invention, there is provided a method for producing an ink composition for inkjet recording having excellent performance, especially excellent printing characteristics. In the method for producing an ink composition for inkjet recording according to the second aspect of the present invention, when preparing the ink composition, the logarithmic value of the shear rate (γ ·) and the storage rigidity (G ′) are taken as two axes. The gradient (α) is adjusted so that the absolute value of the obtained gradient (α) is almost zero, preferably less than 1 × 10 ⁻⁵ . In the present invention, “preparing” means any act of producing an ink composition for inkjet recording, such as selection of components constituting the ink composition, amounts of the selected components, and mixing conditions of the components.

The components and amounts of the ink composition obtained by the method for producing the ink composition according to the present invention are determined by taking the logarithmic value of the shear rate (γ ·) and the storage rigidity (G ′) as two axes. The absolute value of (α) is almost zero,
Preferably, the components and the amounts of the components of the ink composition described in the method for evaluating the ink composition according to the present invention described above may be the same as long as the value is less than 1 × 10 ⁻⁵ .

[0047]

EXAMPLES An ink composition having the following composition was prepared, and its dynamic viscoelasticity was measured. Measurements were made using VILASTIC SC
VIENTICV-E SYS of IENTIFIC
Performed by TEM. The frequency in the measurement is 2H
z. Example 1 Sugar 7 parts by weight Glycerin 10 parts by weight 2-Pyrrolidone 2 parts by weight Triethanolamine 0.9 parts by weight KOH 0.1 parts by weight Pigment (carbon black 5 parts by weight (solid content) MA7 manufactured by Mitsubishi Chemical Corporation) Dispersion Agent Solsperse 27000 1 part by weight (manufactured by Zeneca Corporation) 1 polymer emulsion 3 parts by weight (solid content) Joncryl 390 (manufactured by Johnson Polymer)

The dynamic viscoelasticity of the prepared ink composition was measured, and the logarithmic value of the shear rate (γ ·) and the storage rigidity (G ′) were calculated. ) = | Δ (G ′ / log (γ ·)) | Its value was 4.494 × 10 ⁻⁶ .

Using this ink composition, ruled lines (thickness: 110 μm) were printed by an inkjet printer MJ500C (manufactured by Seiko Epson Corporation). As a result, even when 2,000 sheets were printed, no bending of the scribe line occurred, and the printing characteristics were favorable.

Example 2 10 parts by weight of glycerin 0.9 parts by weight of triethanolamine 0.1 part by weight of KOH Pigment (carbon black 5 parts by weight (solid content) MA7 manufactured by Mitsubishi Chemical Corporation) Dispersant Solsperse 27000 1 part by weight ( Zeneca Corporation) Polymer emulsion 10 parts by weight (solid content) John Krill 352 (manufactured by Johnson Polymer)

The dynamic viscoelasticity of the prepared ink composition was measured, and the logarithmic value of the shear rate (γ ·) and the storage rigidity (G ′) were measured.
Is calculated, and the respective values are taken as two axes and the inclination (α2)
= | Δ (G ′ / log (γ ·)) | Its value was 1.316 × 10 ⁻⁵ .

Using this ink composition, ruled lines were printed by the ink jet recording method in the same manner as in Example 1. As a result, the bending of the ruled line was observed when 500 sheets were printed.

Example 3 Glycerin 10 parts by weight Triethanolamine 0.9 parts by weight KOH 0.1 parts by weight Pigment (carbon black 8 parts by weight (solid content) MA7 manufactured by Mitsubishi Chemical Corporation) Dispersant Solsperse 27000 1 part by weight ( 1 Polymer emulsion 5 parts by weight (solid content) Joncryl 780 (manufactured by Johnson Polymer)

The dynamic viscoelasticity of the prepared ink composition was measured, and the logarithmic value of the shear rate (γ ·) and the storage rigidity (G ′) were measured.
Is calculated, and the respective values are biaxially inclined (α3)
= | Δ (G ′ / log (γ ·)) | Its value was 4.577 × 10 ^-5 .

Using this ink composition, ruled lines were printed by the ink jet recording method in the same manner as in Example 1. As a result, the bending of the ruled line was observed when 100 sheets were printed.

[Brief description of the drawings]

FIG. 1 is a schematic view of a capillary type viscoelasticity measuring device for measuring dynamic viscoelasticity of an ink composition.

FIG. 2 shows a relationship between a logarithmic value of a measured value of a shear rate (γ ·) of an ink composition and a logarithmic value of a measured value of a storage rigidity (G ′).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Measuring device 2 Test liquid 3 Test liquid reservoir 4 Constant temperature device 5 Precision measurement tube 6 Thin film 7 Sensor means

 ────────────────────────────────────────────────── ─── Continued on front page F term (reference) 2C056 FC01 4J039 AD01 AD03 AD08 AD09 AD10 AD13 AE04 AE06 AE08 BA04 BA13 BA35 BA37 BC17 BC39 BC60 BE01 BE03 BE04 BE05 BE07 BE08 BE09 BE12 BE22 CA06 EA36 EA43 EA48 GA24

Claims (14)

[Claims] 1. A method for evaluating an ink composition for ink jet recording, comprising: preparing an ink composition for ink jet recording comprising at least a coloring material, a water-soluble organic solvent, and water; The viscoelasticity was measured, the logarithmic value of the shear rate (γ ·) of the ink composition and the storage rigidity (G ′) were calculated, and the absolute value of the gradient (α) obtained by taking each value as two axes was calculated. An evaluation method comprising determining whether or not the value is approximately zero. 2. The evaluation method according to claim 1, wherein it is determined whether or not the absolute value of the gradient (α) is less than 1 × 10 ⁻⁵ . 3. The evaluation method according to claim 1, wherein the coloring material comprises a water-dispersible pigment and / or a water-dispersible dye. 4. The evaluation method according to claim 1, further comprising polymer fine particles. 5. The evaluation method according to claim 4, wherein the polymer fine particles are added to the ink composition in the form of a polymer emulsion having water as a continuous phase. 6. An ink jet recording method in which droplets of an ink composition are ejected, and the droplets are attached to a recording medium to perform printing, wherein the ink composition is any one of claims 1 to 5. An ink-jet recording method using an ink composition determined to have an absolute value of the gradient (α) of about 0 in the evaluation method described above. 7. A recorded matter recorded by the ink jet recording method according to claim 6. 8. A method for producing an ink composition for ink jet recording, comprising: preparing an ink composition for ink jet recording comprising at least a coloring material, a water-soluble organic solvent, and water; The viscoelasticity was measured, the logarithmic value of the shear rate (γ ·) of the ink composition and the storage rigidity (G ′) were calculated, and the absolute value of the gradient (α) obtained by taking each value as two axes was calculated. A manufacturing method comprising preparing the solution so as to show a value near 0. 9. The method according to claim 8, wherein the absolute value of the gradient (α) is less than 1 × 10 ⁻⁵ . 10. The method according to claim 8, wherein the coloring material is a water-dispersible pigment and / or a water-dispersible dye. 11. The production method according to claim 8, further comprising polymer fine particles. 12. The method according to claim 11, wherein the polymer fine particles are added to the ink composition in the form of a polymer emulsion having water as a continuous phase. 13. An ink jet recording method for ejecting droplets of an ink composition and attaching the droplets to a recording medium to perform printing, wherein the ink composition is any one of claims 8 to 12. An inkjet recording method using the ink composition produced by the production method described above. 14. A recorded matter recorded by the ink jet recording method according to claim 13.