JP7228089B2 - Printed matter manufacturing method - Google Patents

Description

The present invention relates to a method for producing a printed matter by an inkjet recording method.

The inkjet recording method is a recording method in which ink (ink droplets) is directly ejected from extremely fine nozzles onto a recording medium to adhere the ink to obtain characters and images. According to this method, not only are the advantages of low noise and good operability of the device used, colorization is easy, and this method is widely used as an output machine in offices, homes, etc. there is

In the industrial world, methods of printing on recording media such as packaging materials and advertising media using inkjet printers are being studied. As an ink that can be used for printing on a recording medium, for example, an aqueous emulsion resin having a glass transition point of 16° C. or higher and an acid value of 10 mgKOH/g or higher and a pigment are combined so that the solid content is 15% by weight or higher. and an aminoalcohol as a dispersion stabilizer (see, for example, Patent Document 1 below).

JP 2011-12226 A

There are many types of recording media, and known examples include plastic films and corrugated cardboard (corrugated cardboard sheets) in which corrugated paperboard is sandwiched between two paperboards.

When using a recording medium (plastic film, etc.) that does not easily absorb the solvent (water, organic solvent, etc.) contained in the ink, make sure that the solvent dries quickly after the ink lands on the surface (recording surface) of the recording medium. In some cases, a method of warming the recording medium is used. However, when the recording medium is warmed, the ink-jet head located near the surface (recording surface) of the recording medium is also warmed, so the ink adhering to the ink ejection nozzles is more likely to dry. Due to nozzle clogging and abnormalities in the direction of ink ejection, symptoms generally referred to as nozzle clogging, twisting, and the like tend to occur.

In addition, when printing on a recording medium such as plastic film or cardboard by the inkjet recording method, the ink jet nozzle and the recording medium may be affected by warpage of the recording medium or surface unevenness caused by the corrugated paperboard that constitutes the corrugated board. may come into contact with each other and cause problems.

As a method of preventing the problem caused by the drying of the ink ejection nozzles and the contact between the ink ejection nozzles and the recording medium, it is conceivable to set a long distance between the inkjet head and the recording medium. However, when the distance is increased, the distance required for the ink ejected from the ink ejection port of the inkjet head to land on the surface of the recording medium is generally increased. For reasons such as the tendency to excessively occur, problems such as streaks may occur in the printed matter.

The problem to be solved by the present invention is the production of printed matter that can suppress the occurrence of streak-like printing defects even when the distance between the ink ejection port of the inkjet head and the recording medium is long in the inkjet recording method. to provide a method.

A method for producing a printed matter according to one aspect of the present invention includes a printing step of printing ink on a recording medium by an inkjet recording method to obtain a printed matter, and in the printing step, ink ejection openings of an inkjet head and the recording medium are The shortest distance to the medium is 2 mm or more, the viscosity of the ink at 32° C. is less than 15 mPa·s, and the contact angle between the ink and the recording medium is less than 20°.

According to the present invention, even when the distance between the ink ejection port of the inkjet head and the recording medium is long in the inkjet recording method, it is possible to suppress the occurrence of streak-like printing defects.

It is a schematic diagram of a microreactor.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail. In this specification, "(meth)acrylic acid" is a general term for acrylic acid and methacrylic acid corresponding thereto, and the same applies to other similar expressions such as "(meth)acrylate". .

The method for producing a printed matter according to the present embodiment includes a printing step for obtaining a printed matter by printing ink on a recording medium (printing medium) by an inkjet recording method. The shortest distance D to the recording medium is 2 mm or more, the viscosity of the ink at 32° C. is less than 15 mPa·s, and the contact angle between the ink and the recording medium is less than 20°.

According to such a method for producing a printed matter, even when the distance between the ink ejection port of the inkjet head and the recording medium is long (when the shortest distance is 2 mm or more) in the inkjet recording method (inkjet printing method), It is possible to suppress the occurrence of streak-like printing defects. When the contact angle between the ink and the recording medium is within the above range, the ink spreads well immediately after landing on the surface of the recording medium, and the droplets ejected from the inkjet head have a sufficient volume. Therefore, it is easy to reduce the displacement of the landing position on the recording medium caused by flight deflection. In addition, since the viscosity of the ink is within the above range, the wet spread of the ink during drying after landing is favorable. As a result, it is possible to suppress the occurrence of streak-like printing defects. However, the factor for obtaining the above effect is not limited to this factor.

Conventionally, non-absorbent or non-absorbent (slowly absorbent) recording media such as corrugated board, which has a colored layer on the surface of paperboard that does not readily absorb the solvent in the ink, and plastic films, have been used as recording media. When used, the landed ink is less likely to be absorbed by the recording medium and less likely to spread on the surface of the recording medium, resulting in streak-like printing defects. On the other hand, according to the present embodiment, it is possible to suppress the occurrence of streak-like printing defects even when using a non-absorbent or non-absorbent recording medium.

Further, in the present embodiment, the shortest distance D is 2 mm or more, so that the surface of the recording medium (recording surface, ink landing surface, printing surface) is heated during printing when producing printed matter. Even when the recording medium is heated after the printing process, it is possible to prevent problems caused by heating (for example, clogging of ink ejection nozzles). Furthermore, in the present embodiment, since the shortest distance D is 2 mm or more, it is possible to prevent the surface (recording surface) of the recording medium from coming into contact with the ink discharge ports even if the recording medium is large and easily warped. It is possible to effectively prevent ink ejection defects caused by damage to the ink ejection openings and deterioration of the water-repellent function that is often provided in the ink ejection openings.

The shortest distance D may be 3 mm or more, and may be 4 mm or more. The shortest distance D is preferably 10 mm or less, more preferably 5 mm or less, from the viewpoint of easily suppressing the occurrence of streak-like printing defects. The shortest distance D is from the surface (x) having the ink ejection openings of the inkjet head to the position (y) where the normal to the surface (x) (perpendicular to the surface (x)) intersects the recording medium. may be a distance (gap) of

The recording medium (for example, the recording surface of the recording medium) in the printing process may be warmed. Further, the method for manufacturing a printed matter according to the present embodiment may include a heating step of warming the recording medium (for example, the recording surface of the recording medium) after the printing step. The temperature of the recording medium in these cases is such that streaks and color mixture do not occur when ink lands on the surface of the recording medium even when the distance between the ink ejection port of the inkjet head and the recording medium is long. From the viewpoint of easy production of suppressed prints, the temperature is preferably 20 to 80°C, more preferably 25 to 80°C, even more preferably 40 to 80°C, particularly preferably 40 to 60°C, and extremely preferably 40 to 50°C. The temperature of the recording medium may have these temperatures without being intentionally warmed.

As a method for adjusting the temperature of the recording medium, for example, a method of directly irradiating infrared rays, microwaves, etc. from the printing surface side (upper surface side), lower surface side, or side surface side of the recording medium to heat it; A method of heating by applying wind heated by waves or the like can be mentioned. Further, as the adjustment method, for example, a stage, a carriage, a carriage roll, or the like on which the recording medium is placed is heated by a heating wire, infrared rays, microwaves, hot air, or the like, and the heat is applied to the recording medium. A method of transferring heat to Specifically, examples of the adjusting method include a method using a transport roll (heat roller) provided with heating means such as a heating wire, a transport table, a stage, or the like.

Heating methods using infrared rays include, for example, a halogen heater using a tungsten wire, a quartz tube heater using a nichrome wire, and a method using a radiant heat dryer equipped with a carbon heater. A method using a radiant heat dryer equipped with a high efficiency short-wave infrared heater, medium-wave infrared heater, medium-wave carbon heater, or the like is preferred.

The viscosity at 32° C. of the ink according to the present embodiment (the ink that can be used in the inkjet recording method in the method for manufacturing printed matter according to the present embodiment) is 15 mPa·15 mPa· less than s. The viscosity of the ink is preferably 12 mPa s or less, more preferably 10 mPa s or less, even more preferably 8 mPa s or less, and particularly 7 mPa s or less, from the viewpoint of easily suppressing the occurrence of streak-like printing defects. It is preferred, and 6 mPa·s or less is extremely preferred. The viscosity of the ink is preferably 1 mPa s or more, more preferably 2 mPa s or more, still more preferably 3 mPa s or more, and particularly 4 mPa s or more, from the viewpoint of easily suppressing the occurrence of streak-like printing defects. It is preferred, and 5 mPa·s or more is extremely preferred. From these points of view, the viscosity of the ink is preferably 1 mPa·s or more and less than 15 mPa·s, more preferably 2 to 12 mPa·s.

The viscosity of the ink can be measured using a cone-plate (cone-plate) rotational viscometer equivalent to an E-type viscometer under the following conditions.
Measuring device: TVE-25 type viscometer (manufactured by Toki Sangyo Co., Ltd., TVE-25 L)
Calibration standard solution: JS20
Measurement temperature: 32°C
Rotation speed: 10-100rpm
Injection volume: 1200 μL

The contact angle (the contact angle of the ink with respect to the recording medium) between the ink according to the present embodiment and the recording medium (for example, the surface (recording surface) of the recording medium) suppresses the occurrence of streak-like printing defects. It is less than 20° from the viewpoint of The recording medium has a portion that provides a contact angle of less than 20° between the ink and the recording medium. The contact angle between the ink and the recording medium is preferably 18.degree. ° or less is particularly preferred, 14.5° or less is very preferred, 14° or less is very preferred, and 13.5° or less is even more preferred. The contact angle between the ink and the recording medium is preferably 5° or more, more preferably 10° or more, still more preferably 11° or more, and 12° or more, from the viewpoint of easily suppressing the occurrence of streak-like printing defects. is particularly preferred, and 13° or more is extremely preferred. From these points of view, the contact angle between the ink and the recording medium is preferably 5° or more and less than 20°. The contact angle between the ink and the recording medium is the contact angle at 25°C. The contact angle between the ink and the recording medium is, for example, the contact angle at 1000 msec (msec) after dropping. The contact angle between the ink and the recording medium can be measured using, for example, a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., trade name “Drop Master DMo-501”). The contact angle between the ink and the recording medium is, for example, the dynamic contact angle. The contact angle between the ink and the recording medium is controlled, for example, by reducing the HLB value of the surfactant (e.g., 8 or less) and by reducing the number of ethylene oxide additions in the surfactant (e.g., 15 or less). , increasing the content of the surfactant (e.g., 0.5% by mass or more), increasing the number of carbon atoms in the main chain of the surfactant (e.g., 10 or more), etc. can be reduced. .

The pH of the ink according to the present embodiment tends to improve the storage stability and ejection stability of the ink, and wet spread, print density, and abrasion resistance when printing on an ink non-absorbent or non-absorbent recording medium. is preferably 7.0 or more, more preferably 7.5 or more, and still more preferably 8.0 or more, from the viewpoint of easily improving the The upper limit of the pH of the ink according to the present embodiment makes it easy to suppress the deterioration of the members (ink ejection port, ink flow path, etc.) that constitute the ink application or ejection device, and the influence when the ink adheres to the skin. is preferably 11.0 or less, more preferably 10.5 or less, and still more preferably 10.0 or less, from the viewpoint of easily reducing the

The ink according to this embodiment can be used as an inkjet ink. The ink according to this embodiment can contain, for example, an aqueous medium (A) and a coloring material (B). The ink according to this embodiment may be an aqueous ink containing an aqueous medium. By the way, due to the improvement of inkjet technology, the inkjet recording method is expected to be used in digital printing output machines in industrial applications, and non-absorbent or difficult-to-absorb substrates such as solvent inks and UV inks (for example, PVC ( Printers capable of printing on plastic substrates such as polyvinyl chloride) and PET (polyethylene terephthalate) are commercially available. In recent years, however, the demand for water-based inks containing water-based media has increased from the viewpoint of environmental considerations and the like. In recent years, the expansion of the application of the inkjet recording method is expected, such as non-absorbent base materials such as coated paper (coated paper), cardboard, non-absorbent base materials such as those used for outdoor advertisements, etc. There is a growing need for printing with water-based inks. Water-based inks tend to be repelled on these substrates, and conventionally, portions of the substrate to which the ink is originally applied tend to be exposed on the surface (streak-like printing defects tend to occur). On the other hand, according to the present embodiment, even when the ink contains the aqueous medium (A), it is possible to suppress the occurrence of streak-like printing defects.

The constituent components of the ink according to the present embodiment include a pigment dispersant (C), a binder resin (D), a compound (E) having a urea bond (hereinafter sometimes referred to as "compound (E)"), an organic solvent ( F), surfactant (G), other additives, and the like can be used. The ink according to the present embodiment preferably contains a binder resin (D) from the viewpoint of easily obtaining printed matter having excellent scratch resistance. The ink according to the present embodiment preferably contains the compound (E) from the viewpoint of improving the settability of the printed matter (the ability to prevent the ink from peeling off from the surface of the recording medium). From these points of view, the ink according to the present embodiment preferably contains the binder resin (D) and the compound (E). In the ink according to this embodiment, the coloring material (B), the binder resin (D), the compound (E), etc. are preferably dissolved or dispersed in the aqueous medium (A) as the solvent.

(Aqueous medium (A))
The ink according to this embodiment can contain the aqueous medium (A) as a solvent. As the aqueous medium (A), water alone or a mixed solvent of water and an organic solvent (F) can be used. As water, specifically, pure water or ultrapure water such as ion-exchanged water, ultrafiltrated water, reverse osmosis water, and distilled water can be used.

The content of the aqueous medium (A) is the total amount of the ink from the viewpoint of easily obtaining an ink that has excellent setting properties and high ejection stability required when ejecting by an inkjet recording method and can produce clear printed matter. On the other hand, 1 to 98% by mass is preferable, and 5 to 95% by mass is more preferable.

(Coloring material (B))
As the coloring material (B), known and commonly used pigments, dyes, and the like can be used. Among them, as the colorant (B), a pigment is preferable from the viewpoint of easy production of a printed matter excellent in weather resistance and the like. A coloring agent in which a pigment is coated with a resin can also be used as the coloring material (B).

The pigment is not particularly limited, and inorganic or organic pigments commonly used in water-based gravure inks and water-based inkjet recording inks can be used. Examples of inorganic pigments that can be used include iron oxide and carbon black produced by a contact method, furnace method, thermal method, or the like. Examples of organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, etc.), polycyclic pigments (phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinoflurone pigments, etc.), lake pigments (basic dye-type chelates, acid dye-type chelates, etc.), nitro pigments, nitroso pigments, aniline black and the like can be used. As the pigment, both non-acid-treated pigments and acid-treated pigments can be used.

Among the above pigments, examples of carbon black that can be used for black ink include No. 2300, No. 2200B, No. 900, No. 960, No. 980, No. 33, No. 40, No, 45, No. 45L, No. 52, HCF88, MA7, MA8, MA100, etc.; Columbia's Raven5750, Raven5250, Raven5000, Raven3500, Raven1255, Raven700, etc.; , Monarch900, Monarch1000, Monarch1100, Monarch1300, Monarch1400, etc.; Color Black FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Printex 35, U, V, 1400U, Special Black 6, 5, 4, 4A, NIPEX150, NIPEX160, NIPEX170, NIPEX180, etc. can be used.

Specific examples of pigments that can be used in yellow ink include C.I. I. Pigment Yellow 1, 2, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 120, 128, 129, 138, 150, 151, 154, 155, 174, 180, 185 and the like. Specific examples of pigments that can be used in magenta ink include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57:1, 112, 122, 123, 146, 176, 184, 185, 202, 209, 269, 282, etc.; C. I. Pigment Violet 19 and the like. Specific examples of pigments that can be used in cyan ink include C.I. I. Pigment Blue 1, 2, 3, 15, 15:3, 15:4, 16, 22, 60, 63, 66 and the like.

Specific examples of pigments that can be used in white ink include silicas, calcium silicate, alumina, alumina hydrate, titanium oxide, zinc oxide, talc, and clay. These may be surface-treated.

In order for the pigment to be stably present in the ink, it is preferable that a means for dispersing it well in the aqueous medium (A) is taken. Examples of the means include (i) a method of dispersing a pigment together with a pigment dispersant (C) in an aqueous medium (A) by a dispersing method described below; functional group and/or salt thereof) directly or indirectly via an alkyl group, an alkyl ether group, an aryl group, etc., dispersed and/or dissolved in an aqueous medium (A). There is a method to make

As the self-dispersing pigment, for example, a pigment is subjected to a physical or chemical treatment to bond (graft) a dispersibility-imparting group or an active species having a dispersibility-imparting group to the surface of the pigment. can do. For self-dispersing pigments, for example, vacuum plasma treatment, oxidation treatment with hypohalous acid and/or hypohalite; oxidation treatment with ozone; wet oxidation method in which the pigment surface is oxidized with an oxidizing agent in water; p-amino By bonding benzoic acid to the pigment surface, it can be produced by a method of bonding a carboxyl group via a phenyl group, or the like.

Since the water-based ink containing the self-dispersing pigment does not need to contain the pigment dispersant (C), there is almost no foaming caused by the pigment dispersant (C), and it is easy to prepare an ink with excellent ejection stability. . In addition, water-based inks containing self-dispersing pigments are easy to handle and can suppress a significant increase in viscosity caused by the pigment dispersant (C), making it possible to contain more pigments and improve print density. Can be used for the production of high print.

Commercially available products can be used as the self-dispersing pigment, and examples of such commercial products include Microjet CW-1 (trade name, manufactured by Orient Chemical Industry Co., Ltd.), CAB-O-JET200, and CAB. -O-JET300 (trade name, manufactured by Cabot Corporation) and the like.

The content of the coloring material (B) is easy to prevent the occurrence of streaks, maintain excellent dispersion stability of the coloring material (B), and easily improve the print density and abrasion resistance of the printed matter. From the point of view, it is preferably 0.5 to 20% by mass, more preferably more than 0.5% by mass and 20% by mass or less, even more preferably 1 to 20% by mass, and 1.5 to 15% by mass, based on the total amount of the ink. % is particularly preferred, 2-10% by weight is very preferred, 3-8% by weight is very preferred, and 4-6% by weight is even more preferred.

(Pigment dispersant (C))
The pigment dispersant (C) can be suitably used when a pigment is used as the colorant (B).

Examples of the pigment dispersant (C) include polyvinyl alcohols; polyvinylpyrrolidones; acrylic resins such as acrylic acid-acrylic acid ester copolymers; styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, styrene -Styrene-acrylic resins such as methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer; styrene-malein Aqueous resins such as acid copolymers, styrene-maleic anhydride copolymers, vinylnaphthalene-acrylic acid copolymers; and salts of the aforementioned aqueous resins. As the pigment dispersant (C), Ajinomoto Fine Techno Co., Ltd. Ajisper PB series, BYK-Chemie Japan Co., Ltd. Disperbyk series, BASF EFKA series, Nippon Lubrizol Co., Ltd. SOLSPERSE series, Evonik Co., Ltd. TEGO series, etc. can be used.

As the pigment dispersant (C), the following polymer (C1) is preferable from the viewpoint that coarse particles can be significantly reduced and, as a result, it is easy to impart good ejection stability required when ink is ejected by an inkjet recording method. .

As the polymer (C1), those having an anionic group can be used. Among them, the solubility in water is 0.1 g / 100 mL or less, and the number average molecular weight is 1000 to 6000, which is capable of forming fine particles in water when the neutralization rate of the anionic group with a basic compound is 100%. It is preferred to use polymers of

The water solubility of the polymer (C1) can be defined as follows. That is, first, 0.5 g of the polymer (C1) whose particle size was adjusted to a range of 250 μm to 90 μm using sieves with openings of 250 μm and 90 μm was sealed in a bag processed with a 400 mesh wire mesh, and immersed in 50 mL of water. The mixture is allowed to stand under gentle stirring for 24 hours at a temperature of 25°C. After immersion for 24 hours, the 400-mesh wire mesh enclosing the polymer (C1) is dried in a dryer set at 110° C. for 2 hours. The change in mass of the 400-mesh wire mesh enclosing the polymer (C1) before and after immersion in water is measured, and the solubility is calculated by the following formula.
Solubility [g / 100 mL] = (polymer-encapsulated 400-mesh wire mesh [g] before immersion - polymer-encapsulated 400-mesh wire mesh [g] after immersion) × 2

Whether or not fine particles are formed in water when the rate of neutralization of anionic groups by a basic compound is 100% can be determined as follows.
(1) The acid value of polymer (C1) is measured in advance by an acid value measurement method based on JIS test method K 0070-1992. Specifically, 0.5 g of polymer (C1) is dissolved in tetrahydrofuran, and the acid value is determined by titration with a 0.1 M potassium hydroxide alcohol solution using phenolphthalein as an indicator.
(2) After adding 1 g of polymer (C1) to 50 mL of water, 0.1 mol/L potassium hydroxide aqueous solution sufficient to neutralize the obtained acid value by 100% is added to achieve 100% neutralization.
(3) Irradiate the 100% neutralized liquid with ultrasonic waves in an ultrasonic cleaner (manufactured by SND Co., Ltd., ultrasonic cleaner US-102, 38 kHz self-oscillation) at a temperature of 25 ° C. for 2 hours. After that, it is left at room temperature for 24 hours.

After standing for 24 hours, the liquid at a depth of 2 cm from the liquid surface was used as a sample liquid, and a dynamic light scattering particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., a dynamic light scattering particle size measuring device "Microtrac particle size distribution The presence of fine particles is confirmed by determining whether light scattering information due to fine particle formation can be obtained using a total UPA-ST150").

The particle diameter of the fine particles is preferably 5 to 1000 nm, more preferably 7 to 700 nm, even more preferably 10 to 500 nm, from the viewpoint of further improving the stability in water of the fine particles formed by the polymer (C1). In addition, the narrower the particle size distribution of the fine particles, the better the dispersion stability. However, even when the particle size distribution is wide, an ink having better dispersion stability than conventional inks can be obtained. In addition, the particle size and particle size distribution can be measured using a dynamic light scattering particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., a dynamic light scattering particle size measuring device "Microtrac Particle Size Distribution Meter") in the same manner as the method for measuring fine particles. UPA-ST150”).

The neutralization rate of polymer (C1) can be determined by the following formula.
Neutralization rate (%) = {(mass of basic compound [g] x 56 x 1000) / (acid value of polymer (C1) [mgKOH/g] x equivalent weight of basic compound x mass of polymer (C1) [ g])}×100

The acid value of polymer (C1) can be measured according to JIS test method K 0070-1992. Specifically, it can be determined by dissolving 0.5 g of a sample in tetrahydrofuran and titrating with a 0.1 M potassium hydroxide alcohol solution using phenolphthalein as an indicator.

The number-average molecular weight of the polymer (C1) is such that the aggregation of the coloring material (B) such as pigment in the aqueous medium (A) can be effectively suppressed, and the coloring material (B) has good dispersion stability. 1000 to 6000 is preferred, 1300 to 5000 is more preferred, and 1500 to 4500 is even more preferred, from the viewpoint of ease of obtaining. The number average molecular weight is a polystyrene-equivalent value measured by GPC (gel permeation chromatography), and specifically, a value measured under the following conditions.

[Method for measuring number average molecular weight (Mn)]
It was measured under the following conditions by a gel permeation chromatography (GPC) method.
Measuring device: high-speed GPC device ("HLC-8220GPC" manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation are connected in series and used.
"TSKgel G5000" (7.8mm I.D. x 30cm) x 1 "TSKgel G4000" (7.8mm I.D. x 30cm) x 1 "TSKgel G3000" (7.8mm I.D. x 30cm) x 1 Book "TSKgel G2000" (7.8 mm ID x 30 cm) x 1 Detector: RI (differential refractometer)
Column temperature: 40°C
Eluent: Tetrahydrofuran Flow rate: 1.0 mL/min Injection volume: 100 μL (tetrahydrofuran solution with a sample concentration of 0.4% by mass)
Standard sample: Create a calibration curve using the following standard polystyrene.
{standard polystyrene}
"TSKgel standard polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-550" manufactured by Tosoh Corporation

As the polymer (C1), a polymer that is insoluble or sparingly soluble in water in an unneutralized state and forms fine particles in a 100% neutralized state can be used. Polymers having hydrophobic groups in one molecule in addition to certain anionic groups can be used.

Examples of such polymers include block polymers having a polymer block having a hydrophobic group and a polymer block having an anionic group. In the polymer (C1), the number of anionic groups and the solubility in water are not necessarily specified by the acid value or the number of anionic groups at the time of polymer design. Even among polymers, those with a low molecular weight tend to have a high solubility in water, and those with a high molecular weight tend to have a low solubility in water. From this, the polymer (C1) is specified by its solubility in water.

The polymer (C1) may be a homopolymer, but is preferably a copolymer, and may be a random polymer, a block polymer, or an alternating polymer. is preferably Moreover, the polymer (C1) may be a branched polymer, but is preferably a linear polymer.

Polymer (C1) is preferably a vinyl polymer from the viewpoint of freedom of design, and methods for producing a vinyl polymer having a desired molecular weight and solubility properties include living radical polymerization, living cationic polymerization, and living anionic polymerization. It is preferably prepared by using "living polymerization".

Among them, the polymer (C1) is preferably a vinyl polymer produced using a (meth)acrylate monomer as one of raw materials, and examples of methods for producing such a vinyl polymer include living radical polymerization and living anionic polymerization. Living anionic polymerization is preferable, and furthermore, from the viewpoint that the molecular weight of the block polymer and each segment can be designed more precisely.

As the polymer (C1) produced by living anionic polymerization, specifically, a polymer represented by the following general formula (c1) can be used.

In general formula (c1), A ¹ represents an organolithium initiator residue, A ² represents a polymer block having a hydrophobic group, A ³ represents a polymer block having an anionic group, and n is , represents an integer of 1 to 5, and B represents an aromatic group or an alkyl group.

In general formula (c1), ^A1 represents an organolithium initiator residue. Specific examples of organic lithium initiators (polymerization initiators) include methyllithium, ethyllithium, propyllithium, butyllithium (n-butyllithium, sec-butyllithium, iso-butyllithium, tert-butyllithium, etc.), pentyl Alkyllithium such as lithium, hexyllithium, methoxymethyllithium, ethoxymethyllithium; benzyllithium, α-methylstyryllithium, 1,1-diphenyl-3-methylpentyllithium, 1,1-diphenylhexyllithium, phenylethyl Phenylalkylenelithium such as lithium; Alkenyllithium such as vinyllithium, allyllithium, propenyllithium and butenyllithium; Alkynyllithium such as ethynyllithium, butynyllithium, pentynyllithium and hexynyllithium; Phenyllithium and naphthyllithium aryllithium; heterocyclic lithium such as 2-thienyllithium, 4-pyridyllithium and 2-quinolyllithium; and alkyllithium magnesium complexes such as tri(n-butyl)magnesiumlithium and trimethylmagnesiumlithium.

In the organolithium initiator, the bond between the organic group and lithium is cleaved to generate an active terminal on the side of the organic group, from which polymerization is initiated. Therefore, organic groups derived from organolithium are bonded to the ends of the obtained polymer. In this specification, the organolithium-derived organic group attached to the polymer terminal is referred to as "organolithium initiator residue". For example, in the case of a polymer using methyllithium as an initiator, the organolithium initiator residue will be a methyl group, and in the case of a polymer using butyllithium as an initiator, the organolithium initiator residue will be a butyl group. .

In general formula (c1), ^A2 represents a polymer block having a hydrophobic group. A ² is preferably a group that is highly adsorbed to the pigment when in contact with the pigment, in addition to the purpose of balancing the appropriate solubility as described above. From the same viewpoint, A ² is an aromatic ring or A polymer block having a structural unit derived from a monomer having a heterocycle is preferred. A polymer block having a structural unit derived from a monomer having an aromatic ring or a heterocyclic ring is specifically a monomer having an aromatic ring such as a styrene-based monomer, or a monomer having a heterocyclic ring such as a vinylpyridine-based monomer. is a polymer block of a homopolymer or copolymer obtained by homopolymerizing or copolymerizing the

Examples of monomers having an aromatic ring include styrene, p-tert-butyldimethylsiloxystyrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, p-tert-butoxystyrene, m-tert-butoxystyrene, Styrenic monomers such as p-tert-(1-ethoxymethyl)styrene, m-chlorostyrene, p-chlorostyrene, p-fluorostyrene, α-methylstyrene, p-methyl-α-methylstyrene, vinyl naphthalene, vinylanthracene and the like. Monomers having a heterocyclic ring include vinylpyridine-based monomers such as 2-vinylpyridine and 4-vinylpyridine. Each of the monomers having an aromatic ring or heterocyclic ring can be used singly or in combination of two or more.

In general formula (c1), ^A3 represents a polymer block having an anionic group. ^A3 has the purpose of imparting appropriate solubility as described above, and also the purpose of imparting dispersion stability in water when it becomes a pigment dispersion.

Examples of the anionic group in the polymer block ^A3 include carboxyl group, sulfonic acid group and phosphoric acid group. Among them, a carboxyl group is preferable from the viewpoints of ease of preparation, variety of monomer types, availability, and the like. Also, two carboxyl groups may be intramolecular or intermolecular dehydration-condensed acid anhydride groups.

The method of introducing the anionic group of ^A3 is not particularly limited. For example, when the anionic group is a carboxyl group, a homopolymer or copolymer obtained by homopolymerizing (meth)acrylic acid or copolymerizing it with another monomer may be the polymer block (PB1) of, by deprotection, a homopolymer obtained by homopolymerizing (meth)acrylate having a regeneratable protecting group on the anionic group or copolymerizing it with another monomer Alternatively, it may be a polymer block (PB2) in which some or all of the protective groups regeneratable to the anionic groups of the copolymer are regenerated to anionic groups.

Specific examples of the (meth)acrylic acid and (meth)acrylate used in the polymer block ^A3 include (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, and (meth)acrylic acid. iso-propyl, allyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, (meth)acrylate n-amyl acrylate, iso-amyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-lauryl (meth)acrylate , n-tridecyl (meth)acrylate, n-stearyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, 4-tert-butyl (meth)acrylate Cyclohexyl, isobornyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentadienyl (meth)acrylate, adamantyl (meth)acrylate, glycidyl (meth)acrylate, tetrahydro (meth)acrylate Furfuryl, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, trifluoroethyl (meth)acrylate, ( meth)tetrafluoropropyl acrylate, pentafluoropropyl (meth)acrylate, octafluoropentyl (meth)acrylate, pentadecafluorooctyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, N,N- Dimethyl (meth)acrylamide, (meth)acryloylmorpholine, (meth)acrylonitrile, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, polyethylene glycol-polypropylene glycol (meth) acrylate, polyethylene glycol-polybutylene glycol (meth) Acrylate, polypropylene glycol-polybutylene glycol (meth)acrylate, methoxypolyethyleneglycol (meth)acrylate, ethoxypolyethyleneglycol (meth)acrylate, butoxypolyethyleneglycol (meth)acrylate, octoxypolyethyleneglycol (meth)acrylate Polyethylene glycol (meth)acrylate such as lauroxypolyethyleneglycol (meth)acrylate, stearoxypolyethyleneglycol (meth)acrylate, phenoxypolyethyleneglycol (meth)acrylate, methoxypolypropyleneglycol (meth)acrylate, octoxypolyethyleneglycol-polypropyleneglycol (meth)acrylate, etc. Alkylene oxide group-containing (meth)acrylates and the like are included. These monomers can be used individually by 1 type or in mixture of 2 or more types.

In the living anionic polymerization method, if the monomer used has a group with an active proton such as an anionic group, the active terminal of the living anionic polymer immediately reacts with the group with an active proton and deactivates. , the polymer is difficult to obtain. In living anionic polymerization, it is difficult to polymerize a monomer having a group with an active proton as it is. It is preferred to regenerate the bearing groups.

For this reason, it is preferable to use a (meth)acrylate-containing monomer having a protective group that can be regenerated to an anionic group by deprotection in the polymer block ^A3 . By using the monomer, the aforementioned inhibition of polymerization can be prevented during polymerization. An anionic group protected by a protecting group can be regenerated to an anionic group by deprotecting after obtaining a block polymer.

For example, when the anionic group is a carboxyl group, the carboxyl group can be regenerated by esterifying the carboxyl group and deprotecting it by hydrolysis or the like in a subsequent step. In this case, the protecting group convertible to a carboxyl group is preferably a group having an ester bond, such as a primary alkoxycarbonyl such as a methoxycarbonyl group, an ethoxycarbonyl group, an n-propoxycarbonyl group, and an n-butoxycarbonyl group. Group; secondary alkoxycarbonyl group such as isopropoxycarbonyl group and sec-butoxycarbonyl group; tertiary alkoxycarbonyl group such as t-butoxycarbonyl group; phenylalkoxycarbonyl group such as benzyloxycarbonyl group; ethoxyethylcarbonyl group and alkoxyalkylcarbonyl groups such as

When the anionic group is a carboxyl group, usable monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, sec - butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate (lauryl (meth) ) acrylate), tridecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate (stearyl (meth) acrylate), nonadecyl (meth) acrylate, icosanyl (meth) acrylate) ) acrylate and other alkyl (meth)acrylates; benzyl (meth)acrylate and other phenylalkylene (meth)acrylates; ethoxyethyl (meth)acrylate and other alkoxyalkyl (meth)acrylates. These (meth)acrylates can be used singly or in combination of two or more. Further, among these (meth)acrylates, one or more selected from the group consisting of t-butyl (meth)acrylate and benzyl (meth)acrylate is preferable from the viewpoint of facilitating the conversion reaction to a carboxyl group, and industrial t-butyl (meth)acrylate is more preferable from the viewpoint of easy availability.

In general formula (c1), B represents an aromatic group or an alkyl group. As the alkyl group, an alkyl group having 1 to 10 carbon atoms can be used. Further, n represents an integer of 1-5.

In the living anionic polymerization method, when an attempt is made to directly polymerize a (meth)acrylate monomer onto the active terminal of a strongly nucleophilic styrenic polymer, polymerization may fail due to nucleophilic attack on the carbonyl carbon. Therefore, when the (meth)acrylate monomer is polymerized in A ¹ -A ² , a reaction modifier can be used to adjust the nucleophilicity, and then the (meth)acrylate monomer can be polymerized. B in general formula (c1) is a group derived from a reaction modifier. Specific examples of reaction modifiers include diphenylethylene, α-methylstyrene, p-methyl-α-methylstyrene and the like.

The living anionic polymerization method can be carried out by a batch system as used in conventional free radical polymerization by adjusting the reaction conditions, or by a continuous polymerization method using a microreactor. Since the microreactor has good miscibility between the polymerization initiator and the monomer, the reactions start at the same time, the temperature is uniform, and the polymerization rate can be uniformed, so that the molecular weight distribution of the produced polymer can be narrowed. At the same time, since the growing ends are stable, it becomes easy to produce a block copolymer in which both block components are not mixed. In addition, since the controllability of the reaction temperature is good, it is easy to suppress side reactions.

A general method of living anionic polymerization using a microreactor is described with reference to FIG. 1, which is a schematic diagram of a microreactor.

First, a first monomer and a polymerization initiator for initiating polymerization are respectively introduced from tube reactors P1 and P2 into a T-shaped micromixer M1 equipped with a flow channel capable of mixing a plurality of liquids. In mixer M1, a first monomer is living anionically polymerized to form a first polymer (Step 1).

Next, the obtained first polymer is transferred to the T-shaped micromixer M2, and the growing terminal of the obtained polymer is trapped by the reaction modifier introduced from the tube reactor P3 in the same mixer M2. to adjust the reaction (step 2). At this time, it is possible to control the number of n in the general formula (c1) depending on the type and amount of the reaction modifier used.

Next, the reaction-controlled first polymer in the T-shaped micromixer M2 is transferred to the T-shaped micromixer M3, and the second monomer introduced from the tube reactor P4 is transferred to the T-shaped micromixer M3. and the first polymer subjected to the reaction control are continuously subjected to living anionic polymerization (step 3).

After that, a block copolymer is produced by quenching the reaction with a compound having an active proton (methanol, etc.).

When the polymer (C1) represented by the general formula (c1) is produced in the microreactor, a monomer having a hydrophobic group (for example, a monomer having an aromatic ring or a heterocyclic ring) is used as the first monomer. Then, by reacting using an organic lithium initiator as a polymerization initiator, A ² , a polymer block having a hydrophobic group (e.g., a polymer block having a structural unit derived from a monomer having an aromatic ring or a heterocyclic ring) (One end of the polymer block ^A2 is bound to an organic group which is the organolithium initiator residue of ^A1 ).

Next, after adjusting the reactivity of the growing terminal using a reaction modifier, a monomer containing a (meth)acrylate having a regeneratable protecting group for the anionic group is reacted as the second monomer to obtain a polymer. get a block

After that, the anionic group is regenerated by a deprotection reaction such as hydrolysis to obtain the A ³ (that is, the polymer block containing the anionic group).

A method for regenerating an anionic group by a deprotection reaction such as hydrolysis of an ester bond of a protective group capable of regenerating the anionic group will be described in detail below.

The hydrolysis reaction of an ester bond proceeds under both acidic and basic conditions, but the conditions differ slightly depending on the group having an ester bond. For example, when the group having an ester bond is a primary alkoxycarbonyl group such as a methoxycarbonyl group, or a secondary alkoxycarbonyl group such as an isopropoxycarbonyl group, hydrolysis is performed under basic conditions. A carboxyl group can be obtained. At this time, examples of the basic compound used under basic conditions include metal hydroxides such as sodium hydroxide and potassium hydroxide.

When the group having an ester bond is a tertiary alkoxycarbonyl group such as a t-butoxycarbonyl group, the carboxyl group can be obtained by hydrolysis under acidic conditions. At this time, examples of the acidic compound used under acidic conditions include mineral acids such as hydrochloric acid, sulfuric acid and phosphoric acid; breasted acids such as trifluoroacetic acid; and Lewis acids such as trimethylsilyl triflate. The reaction conditions for hydrolysis of a t-butoxycarbonyl group under acidic conditions are disclosed, for example, in “The Chemical Society of Japan, 5th Edition, Experimental Chemistry Course 16, Synthesis of Organic Compounds IV”.

As a method for converting a t-butoxycarbonyl group to a carboxyl group, for example, a method using a cation exchange resin in place of the above acid can be mentioned. Examples of cation exchange resins include resins having acid groups such as carboxyl groups (--COOH) and sulfo groups (--SO ₃ H) in side chains of polymer chains. Among these, a cation exchange resin having a sulfo group in the side chain of the resin and exhibiting strong acidity is preferable because the progress of the reaction can be accelerated. Commercially available cation exchange resins include strongly acidic cation exchange resin "Amberlite" manufactured by Organo Corporation. From the viewpoint of effective hydrolysis, the amount of the cation exchange resin used is preferably 5 to 200 parts by mass, more preferably 10 to 100 parts by mass, relative to 100 parts by mass of the polymer represented by the general formula (c1). preferable.

When the group having an ester bond is a phenylalkoxycarbonyl group such as a benzyloxycarbonyl group, it can be converted to a carboxyl group by hydrogenation reduction reaction. At this time, as the reaction conditions, the phenylalkoxycarbonyl group can be quantitatively regenerated to the carboxyl group by reacting with hydrogen gas as a reducing agent at room temperature in the presence of a palladium catalyst such as palladium acetate.

As described above, the reaction conditions for conversion to a carboxyl group differ depending on the ^type of group having an ester bond. A polymer obtained by copolymerization using will have a t-butoxycarbonyl group and an n-butoxycarbonyl group. Here, since the n-butoxycarbonyl group does not hydrolyze under acidic conditions where the t-butoxycarbonyl group hydrolyzes, it is possible to selectively hydrolyze only the t-butoxycarbonyl group to deprotect the carboxyl group. becomes. Therefore, it is possible to adjust the acid value of the hydrophilic block (A ³ ) by appropriately selecting a monomer containing a (meth)acrylate having a regeneratable protective group for the anionic group, which is a raw material monomer for A ³ .

From the viewpoint of improving the stability of the aqueous pigment dispersion in which the pigment is dispersed in water by the polymer (C1), in the polymer (C1) represented by the general formula (c1), the polymer block (A ² ) and the polymer block ( A ³ ) is not a random copolymer in which A 3 ) is randomly arranged and bonded, but a block copolymer in which the polymer blocks are regularly bonded together in a certain length. The aqueous pigment dispersion is a raw material used in the production of ink, and is a liquid in which a pigment is dispersed in water at a high concentration using the polymer (C1). The molar ratio A ² : A ³ of the polymer block (A ² ) and the polymer block (A ³ ) is, for example, from the viewpoint of easily maintaining good ejection stability required when ejecting ink in an inkjet recording method, and from the viewpoint of color development. 100:10 to 100:500 is preferable, and 100:10 to 100:450 is more preferable, from the viewpoint of easily obtaining an ink capable of producing a printed matter having even better properties.

In the polymer (C1) represented by the general formula (c1), the number of aromatic ring- or heterocyclic ring-containing monomers that give the polymer block (A ² ) is preferably 5 to 40, more preferably 6 to 30, and 7 to 25 is more preferred. The number of anionic groups constituting the polymer block (A ³ ) is preferably 3-20, more preferably 4-17, even more preferably 5-15.

The molar ratio ^{A 2 :} A ³ of the polymer block (A 2 ) and the polymer block (A ³ ) is the number of moles of the aromatic ring or heterocyclic ring constituting the polymer block (A ² ) and the polymer block (A ³ ). It is preferably 100:7.5 to 100:400 when represented by the molar ratio with the number of moles of the anionic group.

The acid value of the polymer (C1) represented by the general formula (c1) is, for example, from the viewpoint of easy maintenance of good ejection stability required when ejecting ink in an inkjet recording method, and from the point of view of abrasion resistance and the like. 40 to 400 mgKOH/g is preferable, 40 to 300 mgKOH/g is more preferable, and 40 to 190 mgKOH/g is even more preferable, from the viewpoint of easily obtaining an ink capable of producing even more excellent prints. The acid value of the polymer (C1) was determined by the same acid value measurement method as the fine particle measurement method of the polymer (C1).

In the ink according to this embodiment, the anionic group of the polymer (C1) is preferably neutralized.

As the basic compound that neutralizes the anionic groups of the polymer (C1), any known and commonly used basic compound can be used, for example, inorganic basic substances such as alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. Alternatively, organic basic compounds such as ammonia, triethylamine and alkanolamine can be used.

The neutralized amount of polymer (C1) present in the aqueous pigment dispersion need not be 100% neutralized relative to the acid value of the polymer. Specifically, the neutralization rate of the polymer (C1) is preferably 20 to 200%, more preferably 80 to 150%.

(Binder resin (D))
Examples of the binder resin (D) include polyvinyl alcohol, gelatin, polyethylene oxide, polyvinylpyrrolidone, acrylic resin, urethane resin, dextran, dextrin, carrageenan (κ, ι, λ, etc.), agar, pullulan, water-soluble polyvinyl Butyral, hydroxyethyl cellulose, carboxymethyl cellulose and the like can be used singly or in combination. Among them, as the binder resin (D), an acrylic resin is preferably used, and an acrylic resin having an amide group is more preferably used.

In the ink containing the binder resin (D), even if the ink in the ink ejection port solidifies due to solvent evaporation due to drying, the solidified matter can be easily transferred into the ink by recirculating the ink through the ejection port. Excellent dispersibility (redispersibility). As a result, when ejecting from the inkjet head, even if the ejection is restarted after being interrupted for a certain period of time, it is less likely that the ejected droplets will be bent or the ejection port will be clogged. can be effectively prevented.

As the acrylic resin having an amide group, a polymer of an acrylic monomer having an amide group and other monomers used as necessary can be used.

Examples of acrylic monomers having an amide group include (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, and N-methylol(meth)acrylamide. , N-isopropyl (meth)acrylamide, N-butyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-dipropyl (meth)acrylamide, N,N -Dimethylaminopropyl (meth)acrylamide, diacetone (meth)acrylamide, hydroxyethyl (meth)acrylamide, acrylamide, N,N-dimethyl (meth)acrylamide and the like can be used.

Other monomers that can be used in the production of the acrylic resin include, for example, (meth)acrylic acid and alkali metal salts thereof; methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2 - Ethylhexyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate and other (meth) acrylate monomers; (meth) acrylonitrile, 2-dimethylaminoethyl (meth) acrylate, glycidyl ( Acrylic monomers such as meth)acrylates; aromatic vinyl compounds (styrene, α-methylstyrene, p-tert-butylstyrene, vinylnaphthalene, vinylanthracene, etc.), vinylsulfonic acid compounds (vinylsulfonic acid, styrenesulfonic acid etc.), vinylpyridine compounds (2-vinylpyridine, 4-vinylpyridine, naphthylvinylpyridine, etc.), vinyltriethoxysilane, vinyltrimethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3 -methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, and the like can be used.

As the other monomer, a monomer having an aromatic group, such as styrene and benzyl (meth)acrylate, is preferable from the viewpoint of further improving the affinity with the pigment.

The amide group-containing acrylic resin imparts the effect of improving the redispersibility to the ink and has excellent dispersion stability in the aqueous medium (A). In the acrylic resin having an amide group, the amount of the acrylic monomer having an amide group used is from the viewpoint of further improving the redispersibility of the ink and the dispersion stability of the ink component in the aqueous medium (A). Therefore, it is preferably 0.5 to 5% by mass, more preferably 0.5 to 4% by mass, and still more preferably 1.5 to 3% by mass, based on the total amount of the monomers used in the production of the acrylic resin. .

The acrylic resin may contain a component that is insoluble in tetrahydrofuran (THF), which is a developing solvent for molecular weight measurement by gel permeation chromatography, and whose molecular weight is difficult to measure. From the viewpoint of further improving the adhesion of ink to plastics and metals that do not easily absorb solvents such as water, or highly hydrophobic coated paper and art paper, the content of THF-insoluble components at 25 ° C. is 20 mass. %, more preferably less than 5% by mass, and still more preferably no THF-insoluble components.

The number average molecular weight of the acrylic resin (eg, acrylic resin soluble in THF) is preferably 10,000 to 100,000, more preferably 20,000 to 100,000. The acrylic resin preferably has a weight average molecular weight of 30,000 to 1,000,000, more preferably 50,000 to 1,000,000.

Polyolefin, for example, can also be used as the binder resin (D).

As the polyolefin, a homopolymer or copolymer of a monomer containing an olefinic monomer as a main component can be used. Examples of olefinic monomers that can be used include α-olefins such as ethylene, propylene, butene, hexene, methylbutene, methylpentene and methylhexene; and cyclic olefins such as norbornene.

Oxidized polyolefins can also be used as polyolefins. As the oxidized polyolefin, for example, a polyolefin in which oxygen atoms are introduced into the molecule by thermal decomposition, chemical decomposition using an acid or alkaline component, or the like can be used. The oxygen atom constitutes, for example, a polar carboxyl group.

The melting point of the polyolefin is preferably from 90 to 200°C, more preferably from 120°C to less than 160°C. In these cases, even when the printed matter is superimposed immediately after printing, it is possible to impart good settability such that the ink on the surface of the recording medium does not peel off and excellent abrasion resistance. The melting point of polyolefin refers to the value measured by a melting point measuring apparatus conforming to JIS K 0064.

As described above, the polyolefin is preferably dissolved or dispersed in a solvent such as the aqueous medium (A), and more preferably in an emulsion state dispersed in the solvent such as the aqueous medium (A).

In that case, the average particle diameter of the polyolefin particles formed by the polyolefin is, for example, 10 from the viewpoint of easily achieving both good ink ejection stability and good settability after printing when printing by an inkjet recording method. ~200 nm is preferable, and 30 to 150 nm is more preferable. The average particle size of the polyolefin (A) is a value measured by a dynamic light scattering method using a Microtrac UPA particle size distribution meter manufactured by Nikkiso Co., Ltd.

From the viewpoint of easily preventing the occurrence of the streaks, and from the viewpoint of improving the print density and scratch resistance of the printed matter and imparting good gloss, the binder resin (D) is used in an amount of 2 to 7 with respect to the total amount of the ink. % by mass is preferred, and 2 to 5% by mass is more preferred. In addition, the ink containing the binder resin (D) in these ranges further improves the abrasion resistance of the printed matter by cross-linking the binder resin (D) through the heating process after printing to form a strong film. can be made In addition, even when water is dropped on the printed material or rubbed with a cloth containing water, the ink on the surface of the recording medium is not peeled off, so that good water resistance can be imparted.

In the ink according to this embodiment, the binder resin (D) and the compound (E) can be used in combination. By using the binder resin (D) and the compound (E) in combination, it is possible to impart good settability to the printed matter and excellent abrasion resistance.

(Compound (E) having a urea bond)
As the compound (E) having a urea bond, one or more selected from the group consisting of urea and urea derivatives can be used. Since urea and urea derivatives have a high moisturizing function and function as a wetting agent, they prevent drying and solidification of the ink at the ink ejection port of the inkjet head, and easily ensure excellent ejection stability. As a result, even if the shortest distance between the ink ejection port of the inkjet head and the recording medium is 2 mm or more, the occurrence of streaks in printed matter can be easily reduced. In addition, since urea and urea derivatives are likely to release water when heated, from the viewpoint of obtaining printed matter with even better setting properties, when using urea or urea derivatives, non-absorbent or difficult-to-absorb absorbents are preferred. Heat drying is preferably performed after printing the ink on the recording medium.

Urea derivatives include ethylene urea, propylene urea, diethyl urea, thiourea, N,N-dimethyl urea, hydroxyethyl urea, hydroxybutyl urea, ethylenethiourea, diethylthiourea and the like, and these may be used alone or in combination of two. Any combination of the above can be used. Among them, the compound (E) is preferably one or more selected from the group consisting of urea, ethylene urea and 2-hydroxyethyl urea, from the viewpoint of obtaining printed matter with even better setting properties.

The content of the compound (E) is 1 to 20% by mass with respect to the total amount of the ink from the viewpoint of the ejection stability required when the ink is ejected by an inkjet recording method and the printed matter with excellent settability. is preferred, 2 to 15 mass % is more preferred, and 3 to 10 mass % is even more preferred.

When the ink contains the binder resin (D) and the compound (E), the mass ratio of the binder resin (D) to the compound (E) [binder resin (D)/compound (E)] has the effect of improving the settability of the printed matter. 1/6 to 6/1 is preferable, 1/6 to 3/1 is more preferable, and 1/5 to 1/1 is still more preferable from the viewpoint of easy obtaining.

(Organic solvent (F))
Examples of the organic solvent (F) include ketones such as acetone, methyl ethyl ketone, methyl butyl ketone and methyl isobutyl ketone; Alcohols; ethers such as tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane; dimethylformamide, N-methylpyrrolidone, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, polyethylene glycol, polypropylene Glycols such as glycols; Diols such as butanediol, pentanediol, hexanediol, and diols of the same family; Glycol esters such as propylene glycol laurate; Diethylene glycol monoethyl, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, propylene glycol ether , dipropylene glycol ether, and cellosolve including triethylene glycol ether; butyl alcohol such as methanol, ethanol, isopropyl alcohol, 1-propanol, 2-propanol, 1-butanol and 2-butanol, pentyl alcohol , alcohols such as alcohols homologous thereto; sulfolane; lactones such as γ-butyrolactone; lactams such as N-(2-hydroxyethyl)pyrrolidone; can be used.

As the organic solvent (F), in addition to those mentioned above, the organic solvent (F) has a boiling point of 100 to 200, in addition to those mentioned above, from the viewpoint of easily obtaining a quick-drying effect in which the ejected liquid droplets are quickly dried on the recording medium after they land on the surface of the recording medium. °C and a vapor pressure of 0.5 hPa or more at 20°C (f1) is preferred.

Water-soluble organic solvents (f1) include 3-methoxy-1-butanol, 3-methyl-3-methoxy-1-butanol, 3-methoxy-3-methyl-1-butyl acetate, ethylene glycol monomethyl ether, and ethylene glycol. Monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol-t-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monomethyl ether acetate , diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, 4-methoxy-4-methyl-2-pentanone, ethyl lactate and the like, and these may be used alone or in combination of two or more. can be done.

Among them, the water-soluble organic solvent (f1) is easy to maintain good dispersion stability of the ink and, for example, it is easy to suppress deterioration of the ink ejection nozzle provided in the inkjet device due to the influence of the solvent contained in the ink. From the point of view, it is preferable to use a water-soluble organic solvent whose HSP (Hansen Solubility Parameter) hydrogen bond term _δH is in the range of 6-20.

Specific examples of the water-soluble organic solvent having an HSP hydrogen bond term within the above range include 3-methoxy-1-butanol, 3-methyl-3-methoxy-1-butanol, ethylene glycol monomethyl ether, and ethylene glycol monoethyl ether. , ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol-t-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and propylene glycol monopropyl ether 1 selected from the group consisting of More than one species is preferred, and one or more selected from the group consisting of 3-methoxy-1-butanol and 3-methyl-3-methoxy-1-butanol is more preferred.

As the organic solvent that can be used in combination with the aqueous medium (A), from the viewpoint of easily achieving both the effect of drying the ink quickly on the recording medium and the effect of preventing drying and solidification of the ink at the ink ejection port, a water-soluble In addition to the organic solvent (f1) or together with the water-soluble organic solvent (f1), propylene glycol (f2) and one or more organic solvents selected from the group consisting of glycerin, glycerin derivatives, diglycerin and diglycerin derivatives (f3) is preferably used in combination.

As the organic solvent (f3), for example, glycerin, diglycerin, polyglycerin, diglycerin fatty acid ester, polyoxypropylene (n) polyglyceryl ether represented by the following general formula (f1), represented by the following general formula (f2) Polyoxyethylene (n) polyglyceryl ether and the like can be used singly or in combination of two or more. Among them, the organic solvent (f3) is excellent in settability of the printed matter, and from the viewpoint that it is easy to obtain the effect of preventing drying and solidification of the ink at the ink ejection port, glycerin and polyoxypropylene (n = 8 to 15) (n ) one or more selected from the group consisting of polyglyceryl ethers.

m1, m2, n1, n2, p1, p2, q1 and q2 in general formula (f1) and general formula (f2) each independently represents an integer of 1 to 10.

The content of the organic solvent (F) is preferably 1 to 30% by mass with respect to the total amount of the ink, from the viewpoint of excellent settability of the printed matter and easy to obtain the effect of preventing drying and solidification of the ink at the ink ejection port. 5 to 25% by mass is more preferable.

The mass ratio of the water-soluble organic solvent (f1) to the propylene glycol (f2) [water-soluble organic solvent (f1)/propylene glycol (f2)] is excellent in settability of printed matter and prevents drying and solidification of ink at the ink ejection port. From the viewpoint of easily obtaining the effect of preventing, 1/25 to 2/1 is preferable, 1/25 to 1/1 is more preferable, and 1/20 to 1/1 is even more preferable.

The mass ratio of the propylene glycol (f2) to the organic solvent (f3) [propylene glycol (f2)/organic solvent (f3)] is excellent in settability of the printed matter and has the effect of preventing drying and solidification of the ink at the ink ejection port. From the viewpoint of easy availability, 1/4 to 8/1 is preferred, 1/3 to 6/1 is more preferred, and 1/2 to 5/1 is even more preferred.

(Surfactant (G))
By using the surfactant (G), after the ink ejected from the ejection port of the inkjet head lands on the recording medium, it is easy to wet and spread on the surface of the recording medium. Furthermore, by using the surfactant (G), the surface tension of the ink can be lowered, and the leveling property of the ink can be improved.

As the surfactant (G), various anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, and the like can be used. From the viewpoint of easily suppressing, one or more selected from the group consisting of anionic surfactants and nonionic surfactants is preferred.

Examples of anionic surfactants include alkylbenzenesulfonates, alkylphenylsulfonates, alkylnaphthalenesulfonates, higher fatty acid salts, sulfuric acid ester salts of higher fatty acid esters, sulfonates of higher fatty acid esters, and sulfuric acid of higher alcohol ethers. ester salts and sulfonates, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, etc.; Specific examples include dodecylbenzenesulfonate, isopropylnaphthalenesulfonate, monobutylphenylphenol monosulfonate, monobutylbiphenylsulfonate, and dibutylphenylphenoldisulfonate.

Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, poly Oxyethylene glycerin fatty acid ester, polyglycerin fatty acid ester, sucrose fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene fatty acid amide, fatty acid alkylolamide, alkylalkanolamide, acetylene glycol, oxyethylene adduct of acetylene glycol, polyethylene glycol and polypropylene glycol block copolymers, among which polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester. , polyoxyethylene sorbitan fatty acid ester, fatty acid alkylolamide, acetylene glycol, oxyethylene adduct of acetylene glycol, and polyethylene glycol polypropylene glycol block copolymer.

The ink according to the present embodiment preferably contains an acetylenic surfactant from the viewpoint of easily suppressing the occurrence of streak-like printing defects. Acetylene-based surfactants are surfactants having an acetylene structure in the molecule. The acetylene-based surfactant preferably contains one or more selected from the group consisting of acetylene glycol and oxyethylene adducts of acetylene glycol, from the viewpoint of easily suppressing the occurrence of streak-like printing defects.

Other surfactants include silicone-based surfactants such as polysiloxane oxyethylene adducts; fluorine-based surfactants such as perfluoroalkylcarboxylates, perfluoroalkylsulfonates, and oxyethylene perfluoroalkyl ethers; Biosurfactants such as spiculisporic acid, rhamnolipids, lysolecithin and the like can also be used.

The content of the acetylenic surfactant is preferably 80 to 100% by mass, based on the total amount of the surfactant (G), from the viewpoint of easily suppressing the occurrence of streak-like printing defects, and 85 to 99.5% by mass. 9% by mass is more preferred, 90 to 99.5% by mass is even more preferred, and 95 to 99.3% by mass is particularly preferred.

The number of carbon atoms in the main chain of the acetylenic surfactant is preferably 20 or less, more preferably 18 or less, still more preferably 15 or less, and particularly preferably 13 or less, from the viewpoint of easily suppressing the occurrence of streak-like printing defects. . The number of carbon atoms in the main chain of the acetylenic surfactant is preferably 5 or more, more preferably 8 or more, still more preferably 10 or more, and particularly preferably 11 or more, from the viewpoint of easily suppressing the occurrence of streak-like printing defects. , 12 or higher are highly preferred. The number of carbon atoms in the main chain is the number of carbon atoms in the longest molecular chain (eg, carbon chain) containing acetylene bonds.

The HLB value of the surfactant (G) is from the viewpoint that it is easy to suppress the occurrence of streak-like printing defects, and the state in which the surfactant (G) is dissolved in the ink containing water as the main solvent is stabilized. From the viewpoint of easy maintenance, 1 to 12 are preferred, 1 to 10 are more preferred, 2 to 9 are even more preferred, 3 to 8 are particularly preferred, and 4 to 8 are extremely preferred. The HLB value of the acetylenic surfactant is from the viewpoint of easily suppressing the occurrence of streak-like printing defects, and stably maintains the state in which the surfactant (G) is dissolved in the ink whose main solvent is water. These ranges are preferable from the viewpoint of ease of operation. The HLB value of the surfactant (G) can be determined, for example, by Griffin's method.

The content of the surfactant (G) is preferably 0.001 to 5% by mass, more preferably 0.001 to 3% by mass, even more preferably 0.001 to 2% by mass, relative to the total amount of the ink. 0.001 to 1.5% by weight is particularly preferred, 0.01 to 1.5% by weight is particularly preferred, 0.1 to 1.5% by weight is very preferred, 0.5 to 1.5% by weight is More preferably, 0.8 to 1.5% by mass is more preferable, and 1 to 1.5% by mass is particularly preferable. The ink containing the surfactant (G) at these contents has good wettability of the ejected droplets on the surface of the recording medium, and tends to have sufficient wetting and spreading on the recording medium. It is easy to obtain the effect of preventing the occurrence of streaks. Furthermore, the ink containing the surfactant (G) within each of the above ranges tends to obtain the effect of improving the leveling properties of the coating film. From the same point of view, it is preferable that the content of the acetylenic surfactant is within the ranges described above.

(Other additives)
The ink according to the present embodiment includes a wetting agent (drying inhibitor), a penetrant, a preservative (for example, ACTICIDE B-20 manufactured by So Japan Co., Ltd.), a viscosity adjuster, a pH adjuster, a chelating agent, and a plasticizer. Other additives such as agents, antioxidants, UV absorbers, etc. can be included.

A wetting agent can be used for the purpose of preventing drying of the ink in the ejection nozzles of the inkjet head. The content of the humectant is preferably 3 to 50% by mass with respect to the total amount of ink.

The wetting agent is preferably one that is miscible with water and has an effect of preventing clogging of the ejection port of the inkjet head. Examples thereof include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol having a molecular weight of 2000 or less, and dipropylene glycol. , tripropylene glycol, isopropylene glycol, isobutylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, mesoerythritol, pentaerythritol and the like.

Penetrants include lower alcohols such as ethanol and isopropyl alcohol; ethylene oxide adducts of alkyl alcohols such as ethylene glycol hexyl ether and diethylene glycol butyl ether; and propylene oxide adducts of alkyl alcohols such as propylene glycol propyl ether. The content of the penetrant is preferably 3% by mass or less, more preferably 1% by mass or less, and still more preferably substantially no penetrant, relative to the total amount of the ink.

(Ink manufacturing method)
The ink according to the present embodiment can be produced by mixing the aqueous medium (A) and the colorant (B). For example, in addition to the aqueous medium (A) and the colorant (B), a pigment It can be produced by mixing a dispersant (C), a binder resin (D), a compound (E), an organic solvent (F), a surfactant (G) and the like.

For the mixing, a dispersing machine such as a bead mill, an ultrasonic homogenizer, a high-pressure homogenizer, a paint shaker, a ball mill, a roll mill, a sand mill, a sand grinder, a Dyno mill, a Dispermat, an SC mill, and a nanomizer can be used.

As an example of the method for producing the ink according to the present embodiment, there is a method for producing by mixing each component together and then stirring the mixture.

Another example of the method for producing the ink according to the present embodiment includes a method for production through the following steps <1> to <4>.
<1> A pigment dispersant (C) such as a polymer (C1), a coloring material (B) such as a pigment, and, if necessary, a solvent or the like are mixed to contain the coloring material (B) at a high concentration. Step of producing colorant dispersion a <2> Step of producing composition b by mixing compound (E) and, if necessary, a solvent <3> Binder resin (D) and aqueous medium (A <4> A step of mixing the colorant dispersion a, the composition b, and the composition c

From the viewpoint of removing impurities mixed in the ink, the ink obtained by the above method is preferably subjected to a centrifugal separation treatment or a filtration treatment as necessary.

(recording medium)
The ink according to the present embodiment may be a recording medium having excellent ink absorption such as copy paper (PPC paper) generally used in copiers, a recording medium having an ink absorption layer, or a recording medium having an ink absorption layer. It is possible to print on a non-absorbent recording medium that has no water absorption property at all, or a non-absorbent recording medium with low ink absorption. In particular, the ink according to the present embodiment suppresses the occurrence of streak-like printing defects even when printed on a recording medium that is non-absorbent or difficult to absorb ink, and has excellent settability and durability. It is possible to obtain a printed matter excellent in abrasion resistance and water resistance.

Specific examples of the recording medium that can be used include plain paper, cloth, corrugated board, wood, inkjet paper, art paper, coated paper, lightly coated paper, and plastic film. As the corrugated board, corrugated board having a layer with a water absorption of 10 g/m ² or less may be used. As the coated paper, lightweight coated paper may be used.

From the viewpoint of obtaining a printed matter with even more excellent scratch resistance and water resistance, the non-absorbent recording medium should have a water absorption amount of 10 g at a contact time of 100 msec between the recording medium and water. /m ² or less is preferably used in combination with the ink according to the present embodiment.

The amount of water absorption was measured using an automatic scanning liquid absorption meter (KM500win, manufactured by Kumagai Riki Kogyo Co., Ltd.) under the conditions of 23° C. and 50% relative humidity, and the amount of transfer at a contact time of 100 msec with pure water. It can be measured and taken as the water absorption for 100 msec. Measurement conditions are shown below.

[Spiral Method]
Contact Time: 0.010 to 1.0 (sec)
Pitch: 7 (mm)
Lencth per sampling: 86.29 (degree)
Start Radius: 20 (mm)
End Radius: 60 (mm)
Min Contact Time: 10 (msec)
Max Contact Time: 1000 (msec)
Sampling pattern: 50
Number of sampling points: 19
[Square Head]
Slit span: 1 (mm)
Width: 5 (mm)

Examples of recording media that absorb ink include plain paper, cloth, cardboard, and wood. Further, examples of the recording medium having the absorption layer include ink-jet paper and the like, and specific examples thereof include Pictorico Pro Photo Paper manufactured by Pictorico Co., Ltd. and the like.

Non-absorbent recording media with low ink absorbency include corrugated board, art paper such as printing paper, coated paper (e.g. lightweight coated paper), Lightly coated paper or the like can be used. These non-absorbent recording media are made by applying a coating material to the surface of fine paper, neutral paper, etc., which is mainly composed of cellulose and is generally not surface-treated, to provide a coating layer. Lightly coated paper such as "OK Everlight Coat" manufactured by the company and "Aurora S" manufactured by Nippon Paper Industries Co., Ltd.; "OK Coat L" manufactured by Oji Paper Co., Ltd. and "Aurora L" manufactured by Nippon Paper Industries Co., Ltd. Light weight coated paper (A3) of Oji Paper Co., Ltd. “OK Topcoat + (basis weight 104.7 g / m ² , water absorption at contact time 100 msec (the following water absorption is the same) 4.9 g / m ² ) "Aurora Coat" manufactured by ^{Nippon Paper} Industries Co., Ltd ^.; , water absorption 4.4 g/m ² ) coated paper (A2, B2); art paper (A1) such as "OK Kinto +" manufactured by Oji Paper Co., Ltd. and "Tokubishi Art" manufactured by Mitsubishi Paper Mills It is possible to use a plastic film such as

Examples of the plastic film include polyester films made of polyethylene terephthalate, polyethylene naphthalate, etc.; polyolefin films made of polyethylene, polypropylene, etc.; polyamide films made of nylon, etc.; polystyrene films; polyvinyl alcohol films; polyvinyl chloride films; polyacrylonitrile film; polylactic acid film; As the plastic film, a polyester film, a polyolefin film, or a polyamide film is preferably used, and a polyethylene terephthalate film, a polypropylene film, or a nylon film is more preferably used.

As the plastic film, a film coated with polyvinylidene chloride or the like for imparting barrier properties; a metal layer such as aluminum; good.

The plastic film may be an unstretched film, or may be uniaxially or biaxially stretched. The surface of the film may be untreated, but preferably subjected to various treatments for improving adhesiveness, such as corona discharge treatment, ozone treatment, low-temperature plasma treatment, flame treatment and glow discharge treatment.

The film thickness of the plastic film is appropriately changed depending on the application. It is preferably 100 μm, more preferably 10 to 30 μm. Specific examples thereof include Pyrene and Espet (both registered trademarks) manufactured by Toyobo Co., Ltd.

Among the recording media, the ink according to the present embodiment is corrugated cardboard composed of paperboard that easily absorbs the solvent contained in the ink; It can be suitably used for printing on corrugated cardboard, plastic film, fabric, and the like.

As the corrugated board, for example, a corrugated corrugated core with a liner attached to one or both sides thereof can be used, and single-faced corrugated board, double-faced corrugated board, double-faced corrugated board, double-faced corrugated board, etc. can be used. be able to.

Specifically, the ink according to the present embodiment is corrugated cardboard made of paperboard that easily absorbs the solvent contained in the ink; It can be suitably used for printing on corrugated cardboard or the like. The ink according to the present embodiment can be used when a non-absorbent or non-absorbent recording medium such as corrugated cardboard is provided with a colored layer that does not easily absorb the solvent in the ink, a waterproof layer, etc. on the surface of the paperboard. Even if there is, the landed ink tends to wet and spread on the surface of the recording medium, and as a result, the occurrence of streaks in printed matter can be effectively suppressed.

Further, when inkjet printing is performed on cardboard with the ink according to the present embodiment, from the surface (x) having the ink ejection port to the position (y) where the perpendicular line of the surface (x) intersects the recording medium Even if the distance is 2 mm or more, the droplets spread sufficiently after landing on the recording medium, so that streaks on printed matter can be effectively prevented.

Among the corrugated cardboards, the corrugated board provided with a colored layer, a waterproof layer, etc. on the surface is coated with a coloring agent or a waterproofing agent on the surface of the corrugated board made of the above-mentioned paperboard, for example, by a curtain coating method, a roll coating method, or the like. It is possible to use the one on which a coating film is formed.

Examples of the colored layer include those having a whiteness of 70% or more.

Regarding layers such as colored layers and waterproof layers possessed by cardboard, the amount of water absorbed by the recording medium when the recording surface of the recording medium such as cardboard is in contact with water for 100 msec is 10 g/m from the viewpoint of easily obtaining the waterproof effect of the printed matter. m ² or less is preferred.

According to the method for manufacturing a printed matter according to the present embodiment, it is possible to obtain a printed matter that effectively suppresses the occurrence of printing defects such as missing nozzles, twisting, streaks, and the like. Therefore, the printed matter obtained by such a method can be used for, for example, packaging materials such as cardboard; plastic films and packaging materials using the same; and textile products such as T-shirts.

EXAMPLES The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples.

<Preparation of polymer (P-1)>
A hexane solution of normal butyl lithium (BuLi) and a styrene solution in which styrene is dissolved in tetrahydrofuran in advance are introduced from the tube reactors P1 and P2 shown in FIG. got a union.
Next, the polymer obtained in the above step is transferred to the T-shaped micromixer M2 through the tube reactor R1 shown in FIG. -methylstyrene (α-MeSt)).
Next, a tert-butyl methacrylate solution prepared by dissolving tert-butyl methacrylate in tetrahydrofuran in advance was introduced from the tube reactor P4 shown in FIG. The coalescence and continuous living anionic polymerization reactions were carried out. Thereafter, a block copolymer (PA-1) composition was produced by quenching the living anionic polymerization reaction by supplying methanol. A block copolymer (PA-1) composition was recovered from tube reactor R3.

When producing the block copolymer (PA-1) composition, the reaction temperature was set to 24° C. by immersing the entire microreactor shown in FIG. 1 in a constant temperature bath. The molar ratio of the monomers constituting the block copolymer (PA-1) composition obtained by the above method is (BuLi/styrene/α-methylstyrene/tert-butyl methacrylate) = 1.0/12.0/ 2.0/8.1. The obtained block copolymer (PA-1) composition was hydrolyzed by treatment with a cation exchange resin, then distilled off under reduced pressure, and the resulting solid was pulverized to obtain a powdery polymer ( P-1) was obtained.

The physical properties of the obtained polymer (P-1) were measured as follows.

(Measurement of number average molecular weight (Mn))
It was measured under the following conditions by a gel permeation chromatography (GPC) method.
Measuring device: high-speed GPC device ("HLC-8220GPC" manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were connected in series and used.
"TSKgel G5000" (7.8mm I.D. x 30cm) x 1 "TSKgel G4000" (7.8mm I.D. x 30cm) x 1 "TSKgel G3000" (7.8mm I.D. x 30cm) x 1 Book "TSKgel G2000" (7.8 mm ID x 30 cm) x 1 Detector: RI (differential refractometer)
Column temperature: 40°C
Eluent: Tetrahydrofuran Flow rate: 1.0 mL/min Injection volume: 100 μL (tetrahydrofuran solution with a sample concentration of 0.4% by mass)
Standard sample: A calibration curve was created using the following standard polystyrene.

{standard polystyrene}
"TSKgel standard polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel standard polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel standard polystyrene F-550" manufactured by Tosoh Corporation

(Measurement of acid value)
The acid value was measured according to JIS test method K 0070-1992. A 0.5 g sample was dissolved in tetrahydrofuran, and the acid value was determined by titration with a 0.1 M potassium hydroxide alcohol solution using phenolphthalein as an indicator.

(Measurement of solubility in water)
0.5 g of a polymer whose particle size is adjusted to a range of 250 μm to 90 μm using sieves with mesh openings of 250 μm and 90 μm is sealed in a bag processed with a 400 mesh wire mesh, immersed in 50 mL of water, and heated at 25 ° C. for 24 hours. The mixture was left to stir gently for a period of time. After soaking for 24 hours, the polymer-encapsulated 400 mesh wire mesh was dried in a dryer set at 110° C. for 2 hours. The change in mass of the 400-mesh wire mesh enclosing the polymer before and after immersion in water was measured, and the solubility was calculated by the following equation.
Solubility [g / 100 mL] = (polymer-encapsulated 400-mesh wire mesh [g] before immersion - polymer-encapsulated 400-mesh wire mesh [g] after immersion) × 2

(Method for judging fine particle formation in water and method for measuring volume average particle diameter [nm])
(1) The acid value of the polymer was determined according to the acid value measurement method described above.
(2) After adding 1 g of polymer to 50 mL of water, add 0.1 mol/L potassium hydroxide aqueous solution to neutralize the acid value of the polymer obtained in the above (1) by 100%, and 100% neutralization. bottom.
(3) Irradiate the 100% neutralized liquid with ultrasonic waves at a temperature of 25 ° C. for 2 hours in an ultrasonic cleaner (Ultrasonic cleaner US-102 manufactured by SND Co., Ltd., 38 kHz self-excited transmission). After being dispersed, it was allowed to stand at room temperature for 24 hours.

A dynamic light scattering particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., dynamic light scattering particle size measuring device " Microtrac particle size distribution meter UPA-ST150") was used to confirm the presence or absence of fine particle formation from the light scattering information of the particles, and if fine particles were present, their volume average particle diameter was measured.

(Measurement of static surface tension)
The static surface tension was measured with a Wilhelmy surface tensiometer using the same sample liquid as the sample liquid obtained in the method for judging fine particle formation in water.

Table 1 shows the raw materials, reaction conditions, and various physical properties of the polymer (P-1) obtained above. In Table 1, BuLi represents normal butyl lithium, St represents styrene, α-MeSt represents α-methylstyrene, and tBMA represents tert-butyl methacrylate.

<Preparation of aqueous pigment dispersion>
(Production example 1)
Fastgen Blue Pigment (colorant (B), phthalocyanine pigment, manufactured by DIC Corporation: CI Pigment 15:3) 150 parts by weight, polymer (P-1) (pigment dispersant (C)) 45 parts by weight , 150 parts by mass of triethylene glycol (organic solvent (F)) and 20 parts by mass of a 34% by mass potassium hydroxide aqueous solution were charged into a 1.0 L intensive mixer (Japan Eirich Co., Ltd.), and the rotor peripheral speed was 2.94 m. /sec and a pan peripheral speed of 1 m/sec for 25 minutes.
Next, while continuing to stir, 450 parts by mass of ion-exchanged water (first ion-exchanged water) is gradually added to the kneaded material in the intensive mixer container, and then ion-exchanged water (second ion-exchanged water) is added. ) was further added and mixed to obtain an aqueous pigment dispersion having a pigment concentration of 15% by mass.

(Production Examples 2-4)
Aqueous pigment dispersions (K-1), (M-1) and (Y-1) were prepared in the same manner as in Production Example 1 except that the raw materials and blending ratios were changed to the raw materials and blending ratios shown in Table 2. ).

PB15:3 in Table 2 represents the phthalocyanine pigment Fastgen Blue Pigment, PB7 represents Pigment Black 7, PR122 represents Pigment Red 122, PY74 represents Pigment Yellow 74, and TEG represents triethylene glycol.

<Synthesis of binder resin>
In a four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen introduction tube, 16 g of "New Coal 707SF" (manufactured by Nippon Emulsifier Co., Ltd., an anionic emulsifier), "Noigen TDS-200D" (Daiichi Kogyo Seiyaku Co., Ltd., nonionic emulsifier) 6.5 g and deionized water 220 g were charged, the temperature was raised to 80 ° C. under a nitrogen stream, and an aqueous solution in which 0.8 g of ammonium persulfate was dissolved in 16 g of deionized water was added. bottom. Further, a mixture of 60 g of 2-ethylhexyl acrylate, 100 g of styrene, 27 g of methyl methacrylate, 0.4 g of 3-methacryloxypropyltrimethoxysilane, 3 g of acrylamide, and 6 g of methacrylic acid was added dropwise over 3 hours. After the dropwise addition, the mixture was allowed to react for 2 hours, then cooled to 25°C, neutralized with 1.5 g of 28% by mass ammonia water, and deionized water was added to obtain a glass transition temperature (Tg) of 35°C and an average particle size. An aqueous acrylic resin dispersion (X-1) of 50 nm was obtained. The solid content concentration of the acrylic resin dispersion (X-1) was 39% by mass.

<Preparation of aqueous ink>
(Preparation Example 1)
37.5 g of the above aqueous pigment dispersion (K-1) (mass of dispersion containing water etc.), 3 MB (manufactured by Daicel Corporation, 3-methoxy-1-butanol) 6 g, propylene glycol 4 g, glycerin 9 g, Triethylene glycol 0.8 g, SC-P1000 (manufactured by Sakamoto Pharmaceutical Co., Ltd., polyoxypropylene (14) polyglycerol ether) 2 g, ethylene urea 5.6 g, triethanolamine (pH adjuster) 0.2 g, DYNOL604 ( Acetylene-based surfactant manufactured by Evonik Japan) 1.2 g, TEGO Wet KL-245 (manufactured by Tomoe Kogyo Co., Ltd., polyether-modified siloxane copolymer) 0.012 g, ACTICIDE B-20 (manufactured by So Japan Co., Ltd., Preservative) 0.1 g, 11.3 g of the acrylic resin aqueous dispersion (X-1) described above (mass of aqueous dispersion containing water, etc.), and 22.288 g of ion-exchanged water are added and stirred, and aqueous An ink (J1) was obtained.

(Preparation Examples 2-10)
Aqueous inks (J2) to (J10) were obtained in the same manner as in Preparation Example 1 except that the raw materials and blending ratios were changed to those shown in Table 3.

Abbreviations in Table 3 are as follows.
3MB: 3-methoxy-1-butanol PG: propylene glycol GLY: glycerin TEG: triethylene glycol SC-P1000: polyoxypropylene (14) polyglycerol ether TEA: triethanolamine DYNOL604: acetylenic surfactant (Evonik Japan company, main chain carbon number: 12, HLB value: 8)
DYNOL607: Acetylene-based surfactant (manufactured by Evonik Japan, main chain carbon number: 12, HLB value: 8)
Surfynol465: acetylenic surfactant (manufactured by Evonik Japan, main chain carbon number: 10, HLB value: 13)
KL-245: silicone surfactant (manufactured by Evonik Japan, TEGO Wet KL-245)
B-20: ACTICIDE B-20 (preservative manufactured by So Japan Co., Ltd. Active ingredient 20% by mass)

<Measurement of Viscosity of Aqueous Ink>
Using a cone-plate type (cone-plate type) rotary viscometer corresponding to an E-type viscometer, the viscosity of the water-based ink was measured under the following conditions. Table 4 shows the results.
Measuring device: TVE-25 type viscometer (manufactured by Toki Sangyo Co., Ltd., TVE-25 L)
Calibration standard solution: JS20
Measurement temperature: 32°C
Rotation speed: 10-100rpm
Injection volume: 1200 μL

<Measurement of contact angle of water-based ink>
Using a contact angle meter (trade name “Drop Master DMo-501” manufactured by Kyowa Interface Science Co., Ltd.), the dynamic contact angle was measured by the droplet method (change over time). Specifically, an ink film was formed on the substrate by dropping water-based ink onto the substrate and then drying the ink. Next, the water-based ink was placed in a contact angle meter, and the value of the dynamic contact angle at 1000 msec was determined when the timing of dropping the water-based ink onto the ink film at 25° C. was 0 msec. Table 4 shows the results.

<Evaluation of streaks in printed matter>
Inkjet heads KJ4B-YH manufactured by Kyocera Corporation are each filled with the aforementioned water-based ink, and the supply pressure is adjusted by setting the water head difference of the ink sub-tank from the head nozzle plate surface to +35 cm and the negative pressure to -5.0 kPa. bottom. In addition, the shortest distance between the ink ejection port of the inkjet head and the recording medium (from the surface (x) having the ink ejection port of the inkjet head, the perpendicular line assumed to the surface (x) intersects the recording medium The distance (gap) to the position (y) was set to 2 mm, 3 mm or 4 mm. As a recording medium, corrugated cardboard having a thickness of about 2 mm and having a white colored layer was used.
The corrugated cardboard is placed on a table (stage) for fixing the corrugated cardboard, and the temperature of the surface (recording surface) on which the ink lands is raised to 25°C by heating from the underside of the stage using a heat roller. It was adjusted. The temperature of the surface of the recording medium was measured using a surface thermometer.
The drive conditions of the head were the standard voltage and standard temperature of the ink jet head, the droplet size was set to 18 pL, and 100% solid printing was performed (head temperature: 32° C.) to obtain a print. The distance between the inkjet heads was set to 6 cm, and printed matter was produced using a 600 dpi head.

The printed matter was read with a scanner, and the percentage of the area where ink was not applied (ratio of streaks) was calculated using image analysis software "ImageJ". The streak ratio indicates the ratio of the area of the area where the water-based ink was not applied to the area of the area where the above-described 100% solid printing was performed. Table 4 shows the results of evaluation based on the following criteria.
A: streak rate of less than 3% in printed matter B: streak rate of printed matter of 3% or more and less than 5% C: streak rate of printed matter of 5% or more and less than 10% D: streak rate of printed matter of 10% or more

M1, M2, M3... T-shaped micromixer, P1, P2, P3, P4... Tube reactor, R1, R2, R3... Tube reactor.

Claims (7)

Equipped with a printing process for obtaining a printed matter by printing ink on a recording medium by an inkjet recording method,
In the printing step, the shortest distance between the ink ejection port of the inkjet head and the recording medium is 2 mm or more,
the ink is an aqueous ink,
the ink contains a compound having a urea bond,
The content of the compound having a urea bond is 1 to 20% by mass with respect to the total amount of the ink,
The viscosity of the ink at 32° C. is less than 15 mPa·s,
A method for producing a printed matter, wherein the dynamic contact angle at 1000 msec after dropping the ink onto the recording medium is less than 20°. 2. The method for producing printed matter according to claim 1, wherein the ink further contains an acetylenic surfactant. 3. The method for producing a printed matter according to claim 2, wherein the acetylenic surfactant contains one or more selected from the group consisting of acetylene glycol and oxyethylene adducts of acetylene glycol. 4. The method for producing a printed matter according to claim 2, wherein the acetylenic surfactant has an HLB value of 4 to 8. The method for producing a printed matter according to any one of claims 2 to 4, wherein the content of the acetylenic surfactant is 0.001 to 5% by mass with respect to the total amount of the ink. the ink further contains a coloring material,
The method for producing a printed matter according to any one of claims 1 to 5, wherein the content of the coloring material is more than 0.5% by mass and 20% by mass or less with respect to the total amount of the ink. 7. The recording medium according to any one of claims 1 to 6, wherein the recording medium is plain paper, fabric, corrugated board, wood, inkjet paper, art paper, coated paper, lightly coated paper, or plastic film. A method for producing printed matter.

Images