JP2022187667A - Inkjet recording ink - Google Patents

Abstract

To provide an inkjet recording ink capable of suppressing blurring of an image formed even when an image is formed on a low absorbent substrate and a non-absorbent substrate.SOLUTION: There is provided an inkjet recording ink which contains a pigment, a cellulose derivative, a first water-soluble organic solvent, a second water-soluble organic solvent and water. The first water-soluble organic solvent is a glycol ether. The second water-soluble organic solvent is a water-soluble organic solvent other than the glycol ether. The content ratio of the cellulose derivative is 0.01 mass% or more and 0.20 mass% or less based on the mass of the inkjet recording ink. The content ratio of the glycol ether is 6 mass% or more and 24 mass% or less based on the mass of the inkjet recording ink. The content ratio of the glycol ether is 20 mass% or more and 80 mass% or less based on the total mass of the first water-soluble organic solvent and the second water-soluble organic solvent.SELECTED DRAWING: None

Description

The present invention relates to ink for inkjet recording.

Low-absorbent substrates that absorb less water and non-absorbent substrates that do not absorb water are sometimes used in printing labels and packages. For example, Patent Literature 1 discloses an inkjet recording ink used in a step of discharging onto a non-absorbent substrate such as a polyvinyl chloride substrate.

JP 2020-94084 A

However, the inkjet recording ink described in Patent Document 1 is insufficient in suppressing the occurrence of bleeding in formed images when used for printing on low-absorbent substrates and non-absorbent substrates. It was found by the study of the present inventor.

The present invention has been made in view of the above problems, and an object of the present invention is to prevent bleeding from occurring in the formed image even when an image is formed on a low-absorbent base material and a non-absorbent base material. An object of the present invention is to provide an inkjet recording ink capable of suppressing the

The inkjet recording ink according to the present invention contains a pigment, a cellulose derivative, a first water-soluble organic solvent, a second water-soluble organic solvent, and water. The first water-soluble organic solvent is glycol ether. The second water-soluble organic solvent is a water-soluble organic solvent other than the glycol ether. The content of the cellulose derivative is 0.01% by mass or more and 0.20% by mass or less with respect to the mass of the inkjet recording ink. The content of the glycol ether is 6% by mass or more and 24% by mass or less with respect to the mass of the inkjet recording ink. The content of the glycol ether is 20% by mass or more and 80% by mass or less with respect to the total mass of the first water-soluble organic solvent and the second water-soluble organic solvent.

By using the inkjet recording ink according to the present invention, even when an image is formed on a low-absorbent base material and a non-absorbent base material, the formed image is less likely to bleed.

First, the terms used in this specification will be explained. Hereinafter, acryl and methacryl may be collectively referred to as "(meth)acryl". A mass average molecular weight means the mass average molecular weight of polystyrene conversion measured by a gel permeation chromatography. Dynamic surface tension means the surface tension at 50 milliseconds measured by the maximum bubble pressure method. For the measurement of dynamic surface tension by the maximum bubble pressure method, for example, a dynamic surface tensiometer (trade name: BP100, manufactured by Cruz Co., Ltd.) can be used. The viscosity of the ink is a value measured under an environment of 25° C. in accordance with the method described in “JIS (Japanese Industrial Standards) Z 8803:2011 Liquid Viscosity Measurement Method”. Each component described in the specification may be used alone or in combination of two or more. The terms used in this specification have been explained above.

<Ink for inkjet recording>
An ink jet recording ink (hereinafter sometimes simply referred to as “ink”) according to an embodiment of the present invention comprises a pigment, a cellulose derivative, a first water-soluble organic solvent, a second water-soluble organic solvent, including water. The first water-soluble organic solvent is a glycol ether. The second water-soluble organic solvent is a water-soluble organic solvent other than glycol ether. The content of the cellulose derivative is 0.01% by mass or more and 0.20% by mass or less with respect to the mass of the ink. The content of glycol ether is 6% by mass or more and 24% by mass or less with respect to the mass of the ink. The content of glycol ether is 20% by mass or more and 80% by mass or less with respect to the total mass of the first water-soluble organic solvent and the second water-soluble organic solvent.

The ink of this embodiment is a water-based ink containing water. Generally, water-based inks are difficult to be absorbed by low non-absorbent substrates with low water absorption and non-absorbent substrates that do not absorb water, and may bleed when printed on these substrates. However, since the ink of the present embodiment has the above-described predetermined configuration, it is preferable that ink bleeding occurs in the formed image even when printed on a low-absorbent substrate and a non-absorbent substrate. can be suppressed to Hereinafter, the "low-absorbent base material and non-absorbent base material" may be referred to as "predetermined base material".

(cellulose derivative)
By including a cellulose derivative in the ink of the present embodiment, it is possible to moderately increase the viscosity of the ink that has landed on the predetermined substrate. As a result, coalescence of the ink droplets that have landed on the predetermined substrate is suppressed, and a high-quality image with little bleeding can be obtained.

As already described, the content of the cellulose derivative is 0.01% by mass or more and 0.20% by mass or less with respect to the mass of the ink. If the content of the cellulose derivative is less than 0.01% by mass with respect to the mass of the ink, the ink that has landed on the predetermined base material will not thicken appropriately, and the ink droplets will coalesce, and the ink droplets will not adhere to the predetermined base material. Ink bleeding occurs in the formed image. If the content of the cellulose derivative is higher than 0.20% by mass with respect to the mass of the ink, the viscosity of the ink becomes too high, and the ejection stability of the ink from nozzles may deteriorate. When the content of the cellulose derivative is 0.01% by mass or more and 0.20% by mass or less with respect to the mass of the ink, the ink is stably ejected from the nozzle, and the ink droplets that land on the predetermined base material are reduced. Coalescence is suppressed, and a high-quality image with less bleeding can be easily obtained.

Examples of cellulose derivatives include sodium salt of carboxymethylcellulose (hereinafter sometimes referred to as "sodium carboxymethylcellulose"), calcium salt of carboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose, ethylcellulose, and methylethylcellulose. be done.

Sodium carboxymethylcellulose is preferable as the cellulose derivative from the viewpoint of ensuring the ejection stability of the ink. Carboxymethylcellulose has a structure in which a carboxymethyl group is ether-bonded to a hydroxyl group in the anhydroglucose unit of cellulose (in other words, a structure in which the hydrogen atoms of the hydroxyl groups in the anhydroglucose unit are substituted with carboxymethyl groups).

From the viewpoint of ensuring ink ejection stability, the degree of etherification of sodium carboxymethylcellulose is preferably 0.6 or more and 1.5 or less, more preferably 0.8 or more and less than 1.0, or 1.0 or more and 1.5. The following are more preferable. As used herein, the degree of etherification of sodium carboxymethylcellulose means the average number of moles of carboxymethyl groups per mole of anhydroglucose units.

A commercial item can be used as carboxymethylcellulose sodium. Examples of commercial products of carboxymethylcellulose sodium having a degree of etherification of 0.6 or more and 1.5 or less include CMC Daicel (registered trademark) 1120, CMC Daicel 1130, CMC Daicel 1140, and CMC Daicel 1150 manufactured by Daicel Miraise Co., Ltd. , CMC die cell 1220 , CMC die cell 1240 , CMC die cell 1250 , CMC die cell 1260 , CMC die cell 1330 , and CMC die cell 1350 .

The viscosity of the 1% by mass aqueous solution of sodium carboxymethylcellulose at 25° C. is preferably 10 mPa·s or more and 300 mPa·s or less. When the viscosity of the 1% by mass aqueous solution of sodium carboxymethylcellulose at 25° C. is within this range, the viscosity of the ink can be easily adjusted to a viscosity suitable for inkjet recording. For measuring the viscosity of a 1% by mass aqueous solution of sodium carboxymethylcellulose, for example, a vibration viscometer (manufactured by Sekonic Co., Ltd., trade name: VM-10A-L) can be used.

(First water-soluble organic solvent)
The first water-soluble organic solvent is a glycol ether. When the ink contains glycol ether, the ink easily wets the predetermined base material, and the occurrence of bleeding of the ink in the image formed on the predetermined base material is suppressed.

As the glycol ether, an alkyl ether having 1 to 6 carbon atoms of alkylene glycol having 2 to 6 carbon atoms is preferable, and an alkyl ether having 1 to 4 carbon atoms of alkylene glycol having 2 to 3 carbon atoms is preferable. is more preferred. As the glycol ether, at least one selected from the group consisting of propylene glycol monomethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, and triethylene glycol monobutyl ether (e.g., one ) is more preferred.

From the viewpoint of improving the wettability of the ink to the predetermined base material and suppressing the occurrence of bleeding in the image formed on the predetermined base material, the content of the glycol ether is 6% by mass or more with respect to the mass of the ink. It is 24% by mass or less.

From the viewpoint of improving the drying property of the ink that lands on the predetermined substrate, the content of the glycol ether is 20% by mass or more and 80% by mass with respect to the total mass of the first water-soluble organic solvent and the second water-soluble organic solvent. It is below. By improving the drying property of the ink, coalescence of the ink droplets that have landed on the substrate is suppressed, and a high-quality image with little bleeding can be obtained. From the same point of view, the content of glycol ether is preferably 40% by mass or more and 60% by mass or less with respect to the total mass of the first water-soluble organic solvent and the second water-soluble organic solvent.

(Second water-soluble organic solvent)
The second water-soluble organic solvent is a water-soluble organic solvent other than glycol ether. Examples of the second water-soluble organic solvent include 1,2-propanediol, 3-methyl-1,3-butanediol, 1,2-pentanediol, 2-methyl-1,3-propanediol, 1,3 -propanediol, dipropylene glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, ethylene glycol, 2-pyrrolidone, and glycerin.

As the second water-soluble organic solvent, alkanepolyol or polyalkylene glycol is preferable, alkanediol or dialkylene glycol is more preferable, and alkanediol having 3 to 6 carbon atoms or dialkylene glycol having 4 to 6 carbon atoms is more preferred. As the second water-soluble organic solvent, 1,2-propanediol, 3-methyl-1,3-butanediol, 1,2-pentanediol, 2-methyl-1,3-propanediol, 1,3-propane More preferably, at least one (eg, one) selected from the group consisting of diols, dipropylene glycol, 1,5-pentanediol, and 3-methyl-1,5-pentanediol.

(water)
The water contained in the ink of this embodiment is preferably ion-exchanged water (deionized water). From the viewpoint of improving the drying property of ink that has landed on a predetermined substrate, the water content is preferably 45% by mass or more, more preferably 50% by mass or more, relative to the mass of the ink. More preferably, it is at least 55% by mass. Although the upper limit of the water content is not particularly limited, the water content is, for example, 70% by mass or less with respect to the mass of the ink.

(pigment)
Pigments contained in the ink of the present embodiment are not particularly limited, but examples include black pigments, cyan pigments, magenta pigments, yellow pigments, white pigments, and other pigments (hereinafter referred to as other pigments). There is).

Examples of black pigments include carbon black produced by the furnace method or the channel method. Commercially available products of carbon black include, for example, Raven (registered trademark) 5000 Ultra II, Raven 3500, Raven 2000, Raven 1255, Raven 1250, Raven 1200, Raven 1190 Ultra, Raven manufactured by Aditya Birla Chemicals. 1170, Raven 1080 Ultra, and Raven 1060 Ultra. Examples of commercially available carbon black products include MONARCH (registered trademark) 1300, MONARCH 1000, MONARCH 800, MONARCH 700, MOGUL (registered trademark) L, REGAL (registered trademark) 400R, REGAL 660R, and REGAL 660R manufactured by Cabot Corporation. Also included is REGAL 330R. Examples of commercially available carbon black products include Mitsubishi (registered trademark) carbon black #2300, Mitsubishi carbon black #980, Mitsubishi carbon black #970, Mitsubishi carbon black #960, and Mitsubishi carbon black # manufactured by Mitsubishi Chemical Corporation. 950, Mitsubishi carbon black #900, Mitsubishi carbon black #850, Mitsubishi carbon black MCF88, Mitsubishi carbon black MA600, Mitsubishi carbon black #52, Mitsubishi carbon black #47, Mitsubishi carbon black #45, Mitsubishi carbon black #40, Mitsubishi carbon Also included are Black #33, Mitsubishi Carbon Black #25, Mitsubishi Carbon Black MA7, Mitsubishi Carbon Black MA8, and Mitsubishi Carbon Black MA100. Commercial products of carbon black include, for example, COLOUR BLACK FW 1, COLOUR BLACK FW 2, COLOUR BLACK FW 200, COLOUR BLACK FW 18, SPECIAL BLACK 6, COLOUR BLACK S 160, and SPECIAL manufactured by Orion Engineered Carbons. Also included are BLACK 5, PRINTEX® U, PRINTEX V, SPECIAL BLACK 4, SPECIAL BLACK 4A, PRINTEX 140 U, PRINTEX 140 V, and PRINTEX 35.

Examples of cyan pigments include C.I. I. Pigment Blue 1, C.I. I. Pigment Blue 2, C.I. I. Pigment Blue 3, C.I. I. Pigment Blue 15:3, C.I. I. Pigment Blue 15:4, C.I. I. Pigment Blue 16, C.I. I. Pigment Blue 22, C.I. I. Vat Blue 4, and C.I. I. Vat Blue 6 can be mentioned.

Examples of magenta pigments include C.I. I. Pigment Red 5, C.I. I. Pigment Red 7, C.I. I. Pigment Red 12, C.I. I. Pigment Red 48 (Ca), C.I. I. Pigment Red 48 (Mn), C.I. I. Pigment Red 57 (Ca), C.I. I. Pigment Red 57:1, C.I. I. Pigment Red 112, C.I. I. Pigment Red 122, C.I. I. Pigment Red 123, C.I. I. Pigment Red 146, C.I. I. Pigment Red 168, C.I. I. Pigment Red 184, C.I. I. Pigment Red 202, and C.I. I. Pigment Violet 19;

Examples of yellow pigments include C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 74, C.I. I. Pigment Yellow 83, C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 94, C.I. I. Pigment Yellow 95, C.I. I. Pigment Yellow 120, C.I. I. Pigment Yellow 128, C.I. I. Pigment Yellow 138, C.I. I. Pigment Yellow 150, C.I. I. Pigment Yellow 151, C.I. I. Pigment Yellow 154, C.I. I. Pigment Yellow 155, C.I. I. Pigment Yellow 180, and C.I. I. Pigment Yellow 185.

Examples of white pigments include C.I. I. Pigment White 4, C.I. I. Pigment White 5, C.I. I. Pigment White 6, C.I. I. Pigment White 6:1, C.I. I. Pigment White 7, C.I. I. Pigment White 18, C.I. I. Pigment White 19, C.I. I. Pigment White 20, C.I. I. Pigment White 21, C.I. I. Pigment White 23, C.I. I. Pigment White 24, C.I. I. Pigment White 25, C.I. I. Pigment White 26, C.I. I. Pigment White 27, and C.I. I. Pigment White 28 can be mentioned.

Other pigments include, for example, C.I. I. Pigment Green 7, C.I. I. Pigment Green 10, C.I. I. Pigment Green 36, C.I. I. Pigment Brown 3, C.I. I. Pigment Brown 5, C.I. I. Pigment Brown 25, C.I. I. Pigment Brown 26, C.I. I. Pigment Orange 2, C.I. I. Pigment Orange 5, C.I. I. Pigment Orange 7, C.I. I. Pigment Orange 13, C.I. I. Pigment Orange 14, C.I. I. Pigment Orange 15, C.I. I. Pigment Orange 16, C.I. I. Pigment Orange 24, C.I. I. Pigment Orange 34, C.I. I. Pigment Orange 36, C.I. I. Pigment Orange 38, C.I. I. Pigment Orange 40, C.I. I. Pigment Orange 43, C.I. I. Pigment Orange 62, C.I. I. Pigment Orange 63, C.I. I. Pigment Orange 64, and C.I. I. Pigment Orange 71;

From the viewpoint of ensuring ejection stability of the ink, the pigment content is preferably 0.1% by mass or more and 15% by mass or less with respect to the mass of the ink.

A pigment is usually used by dispersing it in a dispersion medium (for example, water). The method for dispersing the pigment is not particularly limited, but examples thereof include a method of dispersing the pigment in the dispersion medium using a dispersant, and a method of dispersing the pigment in the dispersion medium without a dispersant. The pigment may be, for example, a pigment dispersed in a dispersion medium by a dispersant (non-self-dispersing pigment). Dispersants include, for example, surfactants and polymer dispersants (hereinafter sometimes referred to as "pigment dispersion resins"). In addition, surfactant is mentioned later.

Pigment dispersion resins include, for example, acrylic resins, styrene-(meth)acrylic resins, styrene-maleic acid resins, and urethane resins. From the viewpoint of stably dispersing the pigment, the pigment dispersing resin is preferably a (meth)acrylic resin or a styrene-(meth)acrylic resin.

The weight average molecular weight of the pigment dispersion resin is preferably from 5,000 to 100,000, more preferably from 10,000 to 50,000, and even more preferably from 15,000 to 30,000. When the weight average molecular weight of the pigment dispersion resin is 5000 or more, the dispersion stability of the ink is improved. When the weight average molecular weight of the pigment dispersion resin is 100,000 or less, the ejection stability of the ink is improved.

The ratio of the mass of the pigment dispersion resin to the mass of the pigment is preferably 0.02 or more and 0.45 or less, more preferably 0.04 or more and 0.40 or less, and 0.05 or more and 0.35 or less. is more preferable. When the ratio of the mass of the pigment dispersion resin to the mass of the pigment is 0.45 or less, the viscosities of the pigment dispersion and the ink are easily adjusted to desired values. When the ratio of the mass of the pigment dispersing resin to the mass of the pigment is 0.02 or more, the dispersion stability of the ink is improved.

A commercially available product can be used as the pigment dispersion resin. Commercial products of pigment dispersion resins include, for example, Joncryl (registered trademark) 586 and Joncryl 611 manufactured by BASF Japan Corporation; DISPERBYK (registered trademark)-190 and DISPERBYK-191 manufactured by BYK-Chemie Japan. and Solsperse 20000 and Solsperse 27000 manufactured by Lubrizol Japan.

(binder resin)
From the viewpoint of improving the scratch resistance of the resulting image, the ink of the present embodiment may contain a binder resin. The binder resin binds the pigment in the ink and the base material to each other after the ink has landed.

Examples of binder resins include, but are not limited to, urethane resins, (meth)acrylic resins, styrene-(meth)acrylic resins, (meth)acrylic-urethane resins, polyester resins, and modified polyolefin resins. Preferred binder resins are urethane resins, (meth)acrylic resins, and styrene-(meth)acrylic resins.

The binder resin is preferably used in the form of an aqueous resin emulsion. A commercially available product can be used as the resin emulsion.

The urethane resin is not particularly limited as long as it has a urethane bond in its molecule. Examples of commercially available urethane resin emulsions include Superflex (registered trademark) 170, Superflex 210, Superflex 820, and Superflex 870 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.; Takelac W-6010 and Takelac W-6020.

Commercial products of (meth)acrylic resin emulsions include, for example, Movinyl (registered trademark) 6718, Movinyl 6751D, Movinyl 6750, Movinyl 6760, Movinyl 6770, Movinyl 6800, Movinyl 6969D and Movinyl manufactured by Japan Coating Resin Co., Ltd. 6899D, and Movinyl 6820.

Examples of commercially available styrene-(meth)acrylic resin emulsions include Movinyl 6960, Movinyl 6963, and Movinyl RS-009C22 manufactured by Japan Coating Resin Co., Ltd.; and QE-1042 manufactured by Seiko PMC Co., Ltd. mentioned.

From the viewpoint of ensuring the ejection stability of the ink, the content of the binder resin is preferably 1% by mass or more and 10% by mass or less with respect to the mass of the ink.

(Surfactant)
The ink of this embodiment may contain a surfactant. Examples of surfactants include acetylenic surfactants, acrylic surfactants, silicone surfactants, and fluorosurfactants. A commercially available product can be used as the surfactant.

As used herein, an acetylenic surfactant means a surfactant having an acetylene bond (a triple bond between carbon atoms) in its molecule. Examples of commercially available acetylenic surfactants include Surfynol (registered trademark) 420, Surfynol 440, Olfine (registered trademark) E1010, Olfine EXP. 4200, and Olfine EXP. 4300 can be mentioned.

As used herein, an acrylic surfactant means a surfactant that is a polymer of (meth)acrylic acid or a derivative thereof. Examples of commercially available acrylic surfactants include BYK (registered trademark)-380 N and BYK-381 manufactured by BYK-Chemie Japan; and Polyflow KL-850 manufactured by Kyoeisha Chemical Co., Ltd. be done.

As used herein, a silicone-based surfactant means a surfactant having a siloxane bond in its molecule. Examples of commercially available silicone-based surfactants include Silface (registered trademark) SAG002 and Silface SAG503A manufactured by Nissin Chemical Industry Co., Ltd.

As used herein, a fluorosurfactant means a surfactant having a fluoro group in its molecule. Commercially available fluorine-based surfactants include, for example, Capstone FS-30, Capstone FS-31, Capstone FS-65, and Capstone FS-3100 manufactured by Chemours Corporation.

From the viewpoint of ensuring ink ejection stability, the surfactant is preferably an acetylenic surfactant or an acrylic surfactant.

The surfactant content is preferably 0.05% by mass or more and 2% by mass or less with respect to the mass of the ink. When the content of the surfactant is within this range, the dynamic surface tension of the ink can be easily adjusted to a range suitable for inkjet recording.

(other ingredients)
The ink of this embodiment may contain other components. Other ingredients include, for example, pH adjusters, chelating agents, preservatives, and antifungal agents. The content of other components is not particularly limited, but can be appropriately set as necessary.

(Ink viscosity and dynamic surface tension)
From the viewpoint of ensuring ejection stability of the ink, the viscosity of the ink of the present embodiment at 25° C. is preferably 4 mPa·s or more and 10 mPa·s or less, more preferably 5 mPa·s or more and 9 mPa·s or less. preferable.

From the viewpoint of ensuring the continuous ejection stability of the ink, the dynamic surface tension of the ink of the present embodiment is preferably 30 mN/m or more and 40 mN/m or less. When the dynamic surface tension of the ink is 30 mN/m or more, the continuous ejection stability during high-speed printing is improved.

(Method for producing pigment dispersion)
A method for producing a pigment dispersion is not particularly limited, but an example thereof includes a method of mixing a pigment, water, and, if necessary, a dispersant, and then dispersing the mixture using a dispersing machine.

Examples of dispersers include, but are not limited to, ball mills and bead mills. Among these, it is preferable to use a bead mill. Examples of the bead mill include Attritor (registered trademark) (manufactured by Nippon Coke Kogyo Co., Ltd.), Sand Grinder (manufactured by Imex Co., Ltd.), Dyno (registered trademark) Mill (manufactured by WAB), and Ultra Apex Mill (Hiroshima Metal Co., Ltd.). & Machinery).

When coarse particles are contained in the obtained pigment dispersion, the coarse particles are preferably removed by filtration or centrifugation. By removing the coarse particles, clogging of the nozzles of the recording head can be prevented.

(Ink manufacturing method)
The ink manufacturing method of the present embodiment includes, for example, a step of mixing a pigment-containing pigment dispersion, a cellulose derivative, a first water-soluble organic solvent, a second water-soluble organic solvent, and water. If necessary, at least one selected from the group consisting of binder resins, surfactants and other components may be further mixed. The ink manufacturing method of the present embodiment may further include a step of removing insoluble matter by filtration.

(Inkjet recording method)
Next, an example of the inkjet recording method will be described. The inkjet recording method includes, for example, a process of forming an image by ejecting ink from a recording head of an inkjet recording apparatus and causing the ink to land on a substrate. The ink used in the inkjet recording method is the ink of this embodiment. The inkjet recording method can be performed using a known inkjet recording apparatus.

The inkjet recording method may further include a step of heating the substrate.

In one example of the heating step, the substrate is heated when the ink droplets land on the substrate. From the viewpoint of improving the drying property of the ink landed on the base material, the surface temperature of the heated base material is preferably 30° C. or higher and 70° C. or lower. By improving the drying property of the ink, coalescence of the ink droplets that have landed on the substrate is suppressed, and a high-quality image with little bleeding can be obtained.

In another example of the heating step, the substrate may be heated after recording an image by ejecting ink from a recording head and landing the ink on the substrate. From the viewpoint of improving the scratch resistance of the obtained image, the surface temperature of the heated substrate is preferably 40° C. or higher and 100° C. or lower. When the surface temperature of the substrate is within this range, the film-forming properties of the binder resin can be improved. By improving the film-forming properties of the binder resin, it becomes easier to obtain an image with excellent scratch resistance.

The method for heating the substrate is not particularly limited, but examples thereof include a method of heating with hot air and a method of heating with infrared rays. These may be implemented individually by 1 type, and may be implemented in combination of 2 or more type.

As already described, the ink of the present embodiment can suppress ink bleeding in an image formed on a predetermined base material, and therefore can be suitably used for printing on a predetermined base material.

The base material used in the inkjet recording method is not particularly limited, and examples thereof include plain paper, high-quality paper, and predetermined base materials.

Low-absorbent substrates among the predetermined substrates include, for example, art paper, coated paper, and cast-coated paper.

Non-absorbent substrates of the given substrates include, for example, foil papers, synthetic papers, and plastic substrates. Plastic substrates include, for example, polyester (PET) substrates, polypropylene substrates, polystyrene substrates, and polyvinyl chloride substrates.

One side or both sides of the predetermined base material may be subjected to surface treatment. Surface treatments include, for example, corona discharge treatment, plasma treatment, and primer treatment.

EXAMPLES Hereinafter, examples are given to describe the present invention in more detail, but the present invention is not limited to these.

<Production of pigment dispersion>
First, a pigment dispersion was prepared for use in making the ink. C.I. I. Pigment Blue 15:3 (manufactured by BASF Japan Co., Ltd., product name: Heliogen (registered trademark) Blue D 7088) 15 parts by mass, pigment dispersion resin (manufactured by BYK-Chemie Japan Co., Ltd., product name: DISPERBYK-190, non-volatile content: 40 10 parts by mass, dispersion medium: water) and 75 parts by mass of water were mixed and pre-dispersed using a disper to obtain a pre-dispersion. Next, using a bead mill filled with zirconia beads with a diameter of 0.3 mm (“Dyno (registered trademark) mill” manufactured by WAB), the preliminary dispersion is further dispersed to obtain a pigment dispersion (specifically, a cyan pigment dispersion). body).

<Ink production>
Next, inks (A-1) to (A-16) according to Examples and inks (B-1) to (B-5) according to Comparative Examples were produced. The compositions of these inks are shown in Tables 1 to 5 below.

(Production of ink (A-1))
Using a stirrer, each component was mixed so as to have the composition shown in the column of ink (A-1) in Table 1 to obtain a mixture. The mixture was filtered using a membrane filter with an opening of 5 μm to obtain ink (A-1).

(Production of inks (A-2) to (A-16) and (B-1) to (B-5))
Ink except that each component was mixed so as to have the composition shown in each of the ink columns (A-2) to (A-16) and (B-1) to (B-5) in Tables 1 to 5. Each of inks (A-2) to (A-16) and (B-1) to (B-5) was produced by the same method as (A-1).

<Evaluation of Suppression of Bleeding>
An inkjet recording apparatus equipped with a recording head (manufactured by Kyocera Corporation, product name: KJ4B-QA, resolution: 600 dpi×600 dpi) was used as an evaluation machine. The cyan ink tank of the evaluation machine was filled with the ink obtained in <Ink production>. The ink drop volume was set to 5 pL.

Using an evaluator, a 1-dot line was printed on the following reference substrate. By observing using an optical microscope, the line width of a 1-dot line printed on the reference base material was measured and used as the reference base material line width. Next, using an evaluation machine, a 1-dot line was printed on the given base material 1 below. By observing using an optical microscope, the line width of a 1-dot line printed on the predetermined base material 1 was measured and used as the predetermined base material line width. Then, the ratio of the predetermined substrate line width to the reference substrate line width (line width ratio) was calculated. The line width ratios of the predetermined base materials 2 and 3 were also calculated by the same method as for the predetermined base material 1, except that the predetermined base material 1 was changed to the following predetermined base materials 2 and 3.

Reference base material: matte paper (manufactured by Seiko Epson Corporation, product name: super fine paper)
Predetermined base material 1 (low absorbency base material): Cast coated paper (manufactured by Oji Paper Co., Ltd., trade name: Mirror Coat (registered trademark) Gold, paper thickness: 88 μm)
Predetermined base material 2 (non-absorbent base material): Synthetic paper (manufactured by Yupo Corporation, trade name: New Yupo FGS, paper thickness: 80 μm)
Predetermined base material 3 (non-absorbent base material): PET film (manufactured by Toray Industries, Inc., trade name: polyester film Lumirror (registered trademark) #150-T60)

Based on the obtained line width ratio, it was evaluated whether or not ink bleeding was suppressed in an image formed on a predetermined base material according to the following criteria. A smaller value of the line width ratio indicates that the occurrence of ink bleeding is suppressed in an image formed on a predetermined base material. Inks rated A or B were determined to be acceptable, and inks rated C were determined to be unacceptable. Evaluation results are shown in Tables 1 to 5.

(Evaluation Criteria for Suppression of Ink Bleeding)
A: The line width ratio is less than 1.0.
B: The line width ratio is 1.0 or more and less than 1.1.
C: The line width ratio is 1.2 or more.

The meanings of terms described in Tables 1 to 5 are as follows.
Part: part by mass.
Pigment Dispersion: Pigment dispersion obtained in <Preparation of Pigment Dispersion> above.
CMC Daicel 1330: Sodium carboxymethylcellulose (manufactured by Daicel Miraise Co., Ltd., trade name: CMC Daicel 1330, degree of etherification: 1.3).
CMC Daicel 1220: Sodium carboxymethylcellulose (manufactured by Daicel Miraise, trade name: CMC Daicel 1220, degree of etherification: 0.9).
Metolose MCE-100: Methyl cellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Metolose (registered trademark) MCE-100).
Metolose NE-100: Hydroxypropyl methylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Metolose NE-100).
Binder resin: urethane resin emulsion (Daiichi Kogyo Seiyaku Co., Ltd., product name: Superflex 870, non-volatile content: 30% by mass, dispersion medium: water).
Surfactant: Acetylene-based surfactant (manufactured by Nissin Chemical Industry Co., Ltd., trade name: Surfynol (registered trademark) 440, active ingredient concentration: 100% by mass).
Water: deionized water.
(1)/[(1)+(2)]: Glycol ether content relative to the total mass of the first water-soluble organic solvent (glycol ether) and the second water-soluble organic solvent (unit: % by mass).
-: Does not use the corresponding component.
Remainder: Remaining amount, that is, the amount such that the total mass of the components contained in the ink is 100.00 parts by mass. For example, the amount of water contained in ink (A-1) is 39.54 parts by mass (=100.00-(20.00+0.06+12.00+18.00+10.00+0.40)).
Unable to eject: Ink could not be stably ejected, so suppression of bleeding could not be evaluated.

In addition, since each component is added so as to obtain 100.00 parts by mass of the ink, the amount of each component shown in the "Composition" column of Tables 1 to 5 (unit: parts by mass) is the mass of the ink. corresponds to the content of each component (unit: mass%). For example, the amount (unit: parts by mass) shown in the "cellulose derivative" column of Tables 1 to 5 corresponds to the content of the cellulose derivative with respect to the mass of the ink (unit: mass %). The amount (unit: parts by mass) shown in the column "(1) Glycol ether" in Tables 1 to 5 corresponds to the glycol ether content (unit: % by mass) relative to the mass of the ink.

As shown in Table 5, ink (B-1) did not contain a cellulose derivative. The glycol ether content of the ink (B-3) is more than 24% by mass relative to the mass of the ink, and the glycol ether content relative to the total mass of the first water-soluble organic solvent and the second water-soluble organic solvent is It was more than 80% by mass. The glycol ether content of the ink (B-4) is less than 6% by mass relative to the mass of the ink, and the glycol ether content relative to the total mass of the first water-soluble organic solvent and the second water-soluble organic solvent is It was less than 20% by mass. Ink (B-5) did not contain a glycol ether as the first water-soluble organic solvent. Therefore, the inks (B-1) and (B-3) to (B-5) were evaluated as C for suppression of ink bleeding, and ink bleeding could not be suppressed in the image formed on the predetermined base material.

As shown in Table 5, the content of the cellulose derivative in ink (B-2) was more than 0.20% by mass relative to the mass of the ink. Therefore, the ink (B-2) could not be stably ejected from the nozzles of the recording head of the inkjet recording apparatus.

On the other hand, as shown in Tables 1 to 4, inks (A-1) to (A-16) contain at least a cellulose derivative, a first water-soluble organic solvent, glycol ether, and a second water-soluble organic solvent. contained. The content of the cellulose derivative was 0.01% by mass or more and 0.20% by mass or less with respect to the mass of the ink. The content of glycol ether was 6% by mass or more and 24% by mass or less with respect to the mass of the ink. The content of glycol ether was 20% by mass or more and 80% by mass or less with respect to the total mass of the first water-soluble organic solvent and the second water-soluble organic solvent. Therefore, the inks (A-1) to (A-16) are evaluated as A or B in terms of suppression of bleeding, which means that bleeding of the ink is suppressed in an image formed using the ink on a predetermined base material. rice field.

From the above, it was found that the inks of the present invention including the inks (A-1) to (A-16) caused bleeding in the formed image even when an image was formed on a predetermined base material. It was shown that it can be suppressed.

The ink according to the present invention can be used, for example, to form an image on a recording medium using an inkjet recording apparatus.

Claims (4)

An inkjet recording ink comprising a pigment, a cellulose derivative, a first water-soluble organic solvent, a second water-soluble organic solvent, and water,
the first water-soluble organic solvent is a glycol ether,
The second water-soluble organic solvent is a water-soluble organic solvent other than the glycol ether,
The content of the cellulose derivative is 0.01% by mass or more and 0.20% by mass or less with respect to the mass of the inkjet recording ink,
The content of the glycol ether is 6% by mass or more and 24% by mass or less with respect to the mass of the inkjet recording ink,
An ink for inkjet recording, wherein the content of the glycol ether is 20% by mass or more and 80% by mass or less with respect to the total mass of the first water-soluble organic solvent and the second water-soluble organic solvent. The inkjet recording ink according to claim 1, wherein the cellulose derivative is a sodium salt of carboxymethylcellulose. The glycol ether is at least one selected from the group consisting of propylene glycol monomethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, and triethylene glycol monobutyl ether. 3. The ink for inkjet recording according to 1 or 2. The second water-soluble organic solvent is 1,2-propanediol, 3-methyl-1,3-butanediol, 1,2-pentanediol, 2-methyl-1,3-propanediol, 1,3-propane 4. The diol, dipropylene glycol, 1,5-pentanediol, and at least one selected from the group consisting of 3-methyl-1,5-pentanediol, according to any one of claims 1 to 3. Ink for inkjet recording.