JP2019034991A - Ink and printed matter - Google Patents

Abstract

To provide ink that has high discharge reliability in a point that discharge irregularity of the ink is not caused even when a printing operation is continued for several days, and can form printed matters excellent in visibility, wear resistance and adhesiveness.SOLUTION: The present invention relates to ink characterized by containing a binder such as an acrylic polymer or the like having a weight average molecular weight in the range of not smaller than 1000 and smaller that 4000, a colorant such as a dye or the like, and a ketone-based solvent as an organic solvent.SELECTED DRAWING: None

Description

  The present invention relates to an ink that can be used, for example, for continuous ink jet recording.

  The ink jet recording method is a recording method in which ink is ejected from nozzles and adhered to a recording medium. The recording method is suitable for printing on a recording medium having a curved surface or an irregularly shaped surface because the nozzle and the recording medium do not contact each other.

  Examples of the ink jet recording method include a continuous method (charge control method), an electrostatic attraction method, a piezo method that applies mechanical vibration or displacement to the ink using a piezoelectric element, and a pressure generated by heating and foaming the ink. There is known a thermal method that uses the above.

  In particular, continuous ink jet recording inks are widely used in printing scenes on plastic substrates such as polyolefins, metals, glass, etc., for example, inkjet printers containing ketone solvents and oil-based dyes. Ink-jet inks are further known, which further comprise styrene acrylic resin, chlorinated polyolefin resin, dimethyl silicone oil and epoxy resin (see, for example, Patent Document 1).

  However, when the ink for inkjet recording described in Patent Document 1 is intended to be ejected continuously over several days, the ink is ejected in a direction different from the direction in which it should be ejected, and components in the ink are deposited. In some cases, the fixing in the nozzle may cause ejection abnormalities such as the nozzle being blocked and ink not being ejected.

  By the way, the printing method using the ink jet recording ink in the continuous method may be applied in a scene where, for example, the expiration date is printed on a beverage container or a food container. The date such as the expiration date is usually printed in a size of about 5 dots in the horizontal direction and about 7 dots in the vertical direction due to dots that are a plurality of ink droplets. Therefore, when the dots are excessively wet spread on the surface of the recording medium, a difference in size from adjacent dots occurs, and as a result, it becomes difficult to clearly recognize the information such as the date visually. was there.

JP 2012-72236 A

  The problem to be solved by the present invention has high ejection reliability in that it does not cause abnormal ejection of ink even when continuously printing over several days, and has excellent visibility. It is to provide an ink capable of forming a printed matter.

  The present inventor has solved the above problems with an ink comprising a binder having a weight average molecular weight of 1000 or more and less than 4000, a colorant, and a ketone solvent as an organic solvent.

  Even when the ink of the present invention is continuously printed over several days, if the ink is continuously ejected over several days, the ink may be ejected in a direction different from the direction in which the ink should be ejected, It has high ejection reliability in that the components inside it deposit and adhere within the nozzle, so that the nozzle is blocked and no ejection abnormalities such as ink is not ejected. Further, the ink of the present invention has excellent storage stability and excellent adhesion to a recording medium. The ink of the present invention is excellent in abrasion resistance, for example, after landing on the surface of a low-absorbency recording medium such as a polyolefin recording medium, it is difficult to spread excessively, and a large difference in dot size is unlikely to occur. Color mixing is unlikely to occur, and a printed material that is easy to read can be obtained for characters.

  The ink of the present invention contains a binder having a weight average molecular weight of 1000 or more and less than 4000, a colorant, and a ketone solvent as an organic solvent. The ink of the present invention can be suitably used, for example, as an ink for ink jet recording, and can be suitably used for an ink for ink jet recording of a continuous method (charge control method).

[binder]
As the binder contained in the ink, those having a weight average molecular weight in the range of 1000 or more and less than 4000 are used. This ensures long-term ejection reliability, ink storage stability, adhesion to the recording medium, and durability of the printed matter without causing abnormal ejection such as non-ejection of ink due to nozzle clogging during continuous printing. Excellent wear and good visibility.

  As the binder, it is preferable to use a binder having a weight average molecular weight in the range of 1200 or more and less than 3500, and it is preferable to use a binder having a weight average molecular weight in the range of 1500 or more and less than 3200. In order to obtain an ink that can form a printed matter with excellent adhesion to the recording medium, wear resistance of the printed matter, and visibility, since the mass ratio of the binder contained in the ink can be set relatively high. preferable.

  As the binder, those having an acid value in the range of 200 to 300 are preferably used, and those having an acid value in the range of 220 to 270 are excellent in re-solubility of the ink, and polyolefin. It is more preferable for obtaining an ink having excellent adhesion to a recording medium such as a recording medium. Note that excellent ink re-dissolvability means that continuous ejection can be resumed without causing abnormal ejection even when continuous ejection of ink is interrupted and ejected again.

  As the binder, for example, it is possible to use a solvent that can be dissolved in a ketone solvent, particularly methyl ethyl ketone, which will be described later, and is difficult to precipitate in a normal temperature, a high temperature, and a low temperature environment for a long period of time. It is preferable for obtaining an ink having excellent properties.

  Specific examples of the binder include vinyl polymers such as acrylic resins and styrene maleic resins, epoxy resins, phenol resins, terpene phenol resins, polyester resins, rosin maleic resins, ketone resins, cellulose resins, and rosin esters. Nitrocellulose resin, urethane resin, butyral resin, etc. can be used alone or in combination of two or more. Among them, it is preferable to use a vinyl polymer as the binder, and in particular, use of a styrene-acrylic polymer provides an ink having excellent adhesion to a recording medium such as a polyolefin recording medium. More preferable.

  Specific examples of the styrene-acrylic polymer include styrene-α methylstyrene-acrylic acid copolymer, alkyl acrylate-alkyl methacrylate-styrene copolymer, styrene-acrylic copolymer, and modified acrylic copolymer. A polymer etc. can be used.

  The binder is preferably used in the range of 10% by mass to 30% by mass with respect to the total amount of the ink, and in particular in the range of 15% by mass to 25% by mass. Control system) can be used to produce printed matter with excellent adhesion to the recording medium such as polyolefin recording medium and excellent wear resistance. It is more preferable for obtaining ink.

[Colorant]
As the colorant contained in the ink of the present invention, dyes, organic pigments, inorganic pigments and the like can be used. Among them, it is preferable to use a dye as the colorant, and it is more preferable to use a dye that can be dissolved in a ketone solvent, particularly methyl ethyl ketone, which will be described later, in order to obtain a printed matter excellent in water resistance.

  Examples of the dye that can be dissolved in methyl ethyl ketone include chromium complex dyes, copper phthalocyanine dyes, nigrosine dyes, and salt-forming dyes.

  Specific examples of the dye include C.I. I. Solvent Black 22, 27, 29, 34, 43, 45, C.I. I. Acid Violet 66, C.I. I. Solvent Orange 62, C.I. I. Solvent Red 8, 89, 91, 92, 122, 124, 127, 132, C.I. I. Solvent Yellow 19, 21, 62, 79, 83, 83: 1, C.I. I. Solvent blue 38, 70 etc. can be used individually or in combination of 2 or more types.

  As the dye, it is preferable to use a chromium complex dye in order to obtain a printed matter excellent in water resistance and light resistance, and it is more preferable to use an azo-based chromium complex dye.

  The colorant is preferably used in a range of 3% by mass to 15% by mass, and preferably in a range of 5% by mass to 10% by mass with respect to the total amount of the ink. It is more preferable when obtaining the printed matter which has.

[Organic solvent]
As the organic solvent contained in the ink of the present invention, a ketone solvent is an essential component, and other organic solvents can be used in combination as required.

  As the ketone solvent, acetone, methyl ethyl ketone, methyl isobutyl ketone, and the like having high drying properties can be used, and among them, using methyl ethyl ketone has high drying properties, wear resistance, water resistance, and weather resistance. It is more preferable to obtain a printed material excellent in the above.

  The ketone solvent is preferably used in a range of 45 mass% to 65 mass% with respect to the total amount of the ink, and is preferably used in a range of 50 mass% to 62 mass% in a high temperature and low temperature environment. In this case, the deposition of the colorant and the binder can be suppressed, and a stable state dissolved for a long period of time can be maintained. As a result, it is preferable for preventing discharge abnormality and obtaining ink having excellent discharge reliability.

  As other organic solvents that can be used in combination with the ketone solvent, for example, highly safe lower alcohols, ester solvents and the like can be used alone or in combination of two or more.

  As the lower alcohol, an alcohol having 4 or less carbon atoms can be used. Specifically, methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, sec-butanol, tert-butanol Is mentioned.

  As the ester solvent, it is possible to use a solvent that can further increase the solubility of a colorant including a dye and has an effect of increasing the stability of the ink. For example, propylene glycol monoalkyl ether alkylate, Polypropylene glycol monoalkyl acetate, carboxylic acid ester, alkoxycarboxylic acid ester and the like are preferable.

  In the propylene glycol monoalkyl ether alkylate, the number of carbon atoms of the alkyl group constituting the monoalkyl ether and the number of carbon atoms of the alkyl group constituting the alkylate are preferably 1-10, and preferably 1-4. Is more preferable. The alkyl group may be linear or branched.

  Examples of the polypropylene glycol monoalkyl acetate include propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monobutyl ether acetate, propylene glycol monomethyl ether propionate, propylene glycol monomethyl ether butyrate and the like. It is even more preferable that propylene glycol monomethyl ether can be used to obtain good visibility by preventing the wet spreading of the printed dots, and also to prevent the precipitation of the dye in a low temperature environment. Acetate is particularly preferred.

  Examples of the carboxylic acid ester include ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, amyl acetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, butyl propionate, amyl propionate, hexyl propionate, and the like. It is more preferable to use methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, butyl propionate, amyl propionate, hexyl propionate, etc., and use ethyl propionate It is particularly preferable to do this.

  The other organic solvent is preferably used in the range of 10% by mass to 100% by mass, more preferably in the range of 20% by mass to 80% by mass with respect to the mass of the colorant, and 30% by mass. When used in the range of 70% by mass to 70% by mass, by preventing wetting and spreading of printed dots, good visibility can be obtained. Particularly preferred.

  In the ink of the present invention, the water content is preferably 2% by mass or less, more preferably 0 to 1.5% by mass, and substantially 0% by mass with respect to the total amount of the ink. It is particularly preferable for obtaining a printed matter having excellent water resistance.

[Optional ingredients]
In addition to the above-described components, the ink of the present invention can use, for example, a conductivity-imparting substance, a silicone compound, a fluorine compound, or the like as necessary. In particular, when the ink of the present invention is printed by the continuous method (charge control method), the use of the conductivity imparting substance charges the ink droplet before landing on the recording medium, and the ink droplet. By controlling the amount (size) and deflecting it with an electrostatic field, it is possible to land at a predetermined position on the recording medium, and there is no occurrence of abnormal discharge such as ink droplet bending. This is preferable for obtaining an ink capable of realizing excellent ejection properties.

  Examples of the conductivity-imparting substance include lithium nitrate, sodium nitrate, ammonium nitrate, tetramethylammonium nitrate, lithium perchlorate, sodium perchlorate, ammonium perchlorate, tetramethylammonium perchlorate, lithium tetraphenylborate, Sodium tetraphenylborate, ammonium tetraphenylborate, tetramethylammonium tetraphenylborate, benzyltributylammonium, benzyltributylammonium-4-hydroxynaphthalene-1-sulfonate and the like are preferable.

  The conductivity-imparting substance is preferably used in a range of 0.01 to 8 parts by mass with respect to a total of 100 parts by mass of ink excluding the conductivity-imparting substance, and a range of 0.2 to 5 parts by mass. It is more preferable to use in.

  As the silicone compound, when improving the abrasion resistance of the printed matter, the transfer resistance for judging the degree of color transfer of the printed matter, the abrasion resistance with sharp projections or the like, that is, the scratch resistance, etc. Silicone oil, modified silicone oil, silicone resin, etc. can be used. Specifically, KF-56 (silicone oil) manufactured by Shin-Etsu Chemical Co., Ltd., TSF-410 manufactured by Momentive Performance Materials ( Higher fatty acid-modified silicone oil), TSF-4446, 4460 (polyether-modified silicone oil), TSF-4710 (amino-modified silicone oil), KR-216, KP-316, 360A (silicone resin) manufactured by Shin-Etsu Chemical Co., Ltd. ) Etc. can be used alone or in combination of two or more.

  Examples of the fluorine-based compound include fluorine-based surfactants. Specifically, Megafac F-470, F-173, F-177 and the like manufactured by DIC Corporation are used singly or in combination. can do. The fluorine compound can be used in combination with the silicone compound.

[Ink production method]
The ink of the present invention can be produced by mixing the binder, colorant, organic solvent and optional components as necessary, stirring with a high-speed stirrer typified by Dispamyl, and then filtering as necessary. it can.

[recoding media]
The ink of the present invention can be used for printing on various recording media.

  As the recording medium, for example, an absorptive medium capable of absorbing the solvent contained in the ink or a low absorptive medium that does not absorb or hardly absorb the solvent contained in the ink can be used. Even when the ink of the present invention is used for printing on a low-absorbency medium, a high-drying ketone-based solvent is used, so an excellent printed matter having a uniform dot diameter without wet spread. Can be obtained.

Examples of the low-absorbency medium include a recording medium containing a resin such as polyolefin, and a recording medium made of metal or glass.
[Printing method]
The ink of the present invention can be suitably used exclusively for printing by the ink jet printing method. In particular, the ink of the present invention preferably uses an ink containing a conductivity-imparting substance as an ink for inkjet printing in a continuous method (charge control method).

  Ink containing a conductivity-imparting substance forms an ink droplet of a certain size by vibrating the liquid column of the ink with an electrostrictive element, charges the ink droplet, By deflecting, it is preferable because it can land on a predetermined position of the recording medium and obtain a clear printed matter.

[Printed matter]
Examples of the printed matter using the ink of the present invention include paper packs, bottle labels, retort pouch packs, cans, packaging films, building materials, copper plates, tubes, chemical individual packaging boxes, cosmetic individual packaging boxes, and the like. These printed materials have adhesion, wear resistance, good visibility without printed dot wetting and spread, as well as heat resistance, solvent resistance, transfer resistance, boiling resistance, etc. It also has excellent characteristics that make it suitable for use.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
To 60.0 parts by mass of methyl ethyl ketone and 7.5 parts by mass of methanol, “Joncrill 682” (manufactured by BASF, styrene-acrylic polymer, weight average molecular weight 1700, acid value 238) 19.0 parts by mass, benzyltributylammonium-4 -3.0 parts by weight of hydroxynaphthalene-1-sulfonate (conductivity-imparting substance) and 3.0 parts by weight of “KR-216” (manufactured by Shin-Etsu Chemical Co., Ltd., silicone resin) are added to a dispersion stirrer ( The mixture was stirred and mixed for 60 minutes.

  Next, 7.5 parts by mass of “VALIFAST BLACK 3820” (manufactured by Orient Chemical Co., Ltd., Solvent Black 27) was added to the stirring mixture obtained above, and the mixture was stirred and mixed for 60 minutes with a dispersion stirrer (Dispamyl) Was filtered through a 0.45 μm membrane filter to obtain a black ink (1) for ink jet recording of a continuous method (charge control method).

(Example 2)
To 58 parts by mass of methyl ethyl ketone and 8.5 parts by mass of methanol, 18 parts by mass of “Johncrill 682” (manufactured by BASF, styrene-acrylic polymer, weight average molecular weight 1700, acid value 238), benzyltributylammonium-4-hydroxynaphthalene- Add 3.0 parts by mass of 1-sulfonate (conductivity-imparting substance) and 3.0 parts by mass of “KR-216” (manufactured by Shin-Etsu Chemical Co., Ltd., silicone resin), and use a dispersion stirrer (Dispamyl) And stirred for 60 minutes.

  Next, 9 parts by mass of “VALIFAST RED 3320” (manufactured by Orient Chemical Industry Co., Ltd., Solvent Red 132) was added to the stirring mixture obtained above, and the mixture was stirred and mixed with a dispersion stirrer (Dispamyl) for 60 minutes. By filtering with a 0.45 μm membrane filter, a red ink (2) for ink jet recording of a continuous system (charge control system) was obtained.

(Example 3)
To 59 parts by mass of methyl ethyl ketone and 9.5 parts by mass of methanol, 18 parts by mass of “Johncrill 682” (manufactured by BASF, styrene-acrylic polymer, weight average molecular weight 1700, acid value 238), benzyltributylammonium-4-hydroxynaphthalene- Add 4.0 parts by mass of 1-sulfonate (conductivity-imparting substance) and 3.5 parts by mass of “KR-216” (manufactured by Shin-Etsu Chemical Co., Ltd., silicone resin), and use a dispersion stirrer (Dispam) And stirred for 60 minutes.

  Next, 6 parts by mass of “VALIFAST BLUE 2680” (manufactured by Orient Chemical Co., Ltd., Solvent Blue 70) is added to the stirring mixture obtained above, and the mixture is stirred and mixed for 60 minutes with a dispersion stirrer (Dispamyl). By filtering with a 0.45 μm membrane filter, a blue ink (3) for ink jet recording of a continuous system (charge control system) was obtained.

Example 4
To 54 parts by mass of methyl ethyl ketone and 9 parts by mass of methanol, 21 parts by mass of “Johncrill 682” (manufactured by BASF, styrene-acrylic polymer, weight average molecular weight 1700, acid value 238), benzyltributylammonium-4-hydroxynaphthalene-1- Add 4 parts by weight of sulfonate (conductivity-imparting substance) and 3 parts by weight of “KR-216” (manufactured by Shin-Etsu Chemical Co., Ltd., silicone resin), and stir for 60 minutes using a dispersion stirrer (Dispamyl). Mixed.

  Next, 3.5 parts by weight of “Orasol BLUE 855” (manufactured by BASF, Solvent Blue 70) and 5.5 parts by weight of “Orasol YEllow 081” (manufactured by BASF, Solvent Blue 70) are added to the stirring mixture obtained above. The mixture obtained by stirring and mixing for 60 minutes with a dispersion stirrer (Dispamyl) was filtered with a 0.45 μm membrane filter to obtain a green ink (4) for ink jet recording of a continuous method (charge control method).

(Comparative Example 1)
To 69 parts by mass of methyl ethyl ketone and 7.5 parts by mass of methanol, 10 parts by mass of “Johncrill 683” (manufactured by BASF, styrene-acrylic polymer, weight average molecular weight 8000, acid value 160), benzyltributylammonium-4-hydroxynaphthalene— Add 1 part of 1-sulfonate (conductivity-imparting substance) and 3 parts by weight of “KR-216” (manufactured by Shin-Etsu Chemical Co., Ltd., silicone resin) and use a dispersion stirrer (Dispamyl) for 60 minutes. , Stirred and mixed.

  Next, 7.5 parts by mass of “VALIFAST BLACK 3820” (manufactured by Orient Chemical Industry Co., Ltd., Solvent Black 27) was added to the stirring mixture obtained above, and the mixture was stirred and mixed with a dispersion stirrer (Dispamyl) for 60 minutes. Was filtered through a 0.45 μm membrane filter to obtain a black ink (H1) for ink jet recording of a continuous method (charge control method).

(Comparative Example 2)
To 74 parts by mass of methyl ethyl ketone and 7.5 parts by mass of methanol, 5 parts by mass of “Johncrill 690” (manufactured by BASF, styrene-acrylic polymer, weight average molecular weight 16500, acid value 240), benzyltributylammonium-4-hydroxynaphthalene— Add 1 part of 1-sulfonate (conductivity-imparting substance) and 3 parts by weight of “KR-216” (manufactured by Shin-Etsu Chemical Co., Ltd., silicone resin) and use a dispersion stirrer (Dispamyl) for 60 minutes. , Stirred and mixed.

  Next, 7.5 parts by mass of “VALIFAST BLACK 3820” (manufactured by Orient Chemical Industry Co., Ltd., Solvent Black 27) was added to the stirring mixture obtained above, and the mixture was stirred and mixed with a dispersion stirrer (Dispamyl) for 60 minutes. Was filtered through a 0.45 μm membrane filter to obtain a black ink (H2) for inkjet recording of a continuous system (charge control system).

(Comparative Example 3)
To 31 parts by mass of methyl ethyl ketone and 32.5 parts by mass of methanol, 10 parts by mass of “Johncri 678” (manufactured by BASF, styrene-acrylic polymer, weight average molecular weight 8500, acid value 215), benzyltributylammonium-4-hydroxynaphthalene- Add 1 part of 1-sulfonate (conductivity-imparting substance) and 3 parts by weight of “KR-216” (manufactured by Shin-Etsu Chemical Co., Ltd., silicone resin) and use a dispersion stirrer (Dispamyl) for 60 minutes. , Stirred and mixed.

  Next, 7.5 parts by mass of “VALIFAST BLACK 3820” (manufactured by Orient Chemical Industry Co., Ltd., Solvent Black 27) was added to the stirring mixture obtained above, and the mixture was stirred and mixed with a dispersion stirrer (Dispamyl) for 60 minutes. Was filtered through a 0.45 μm membrane filter to obtain a black ink (H3) for inkjet recording of a continuous system (charge control system).

[Evaluation method of ink storage stability]
(1) Method for evaluating storage stability at high temperature of 60 ° C. First, the viscosity of the ink immediately after production was measured at 20 ° C. using an E-type viscometer (TV-20 type, cone type rotor manufactured by Toki Sangyo Co., Ltd.). It was measured under the environment (initial viscosity X1).

  Next, the ink was allowed to stand in an environment of 60 ° C. for 1440 hours.

  The ink after the standing was taken out from the environment at 60 ° C., and the ink was left in a room temperature environment until the ink reached a room temperature.

  The viscosity of the ink at room temperature was measured in an environment of 20 ° C. (viscosity X2) using an E-type viscometer (TV-20 type manufactured by Toki Sangyo Co., Ltd., using a cone-type rotor).

The viscosity change rate was calculated using the initial viscosity X1 and the viscosity X2 measured by the above method and the following formula.
Viscosity change rate (%) = [{(viscosity X2) − (initial viscosity X1)} / initial viscosity (X1)] × 100

○ Viscosity change rate is less than ± 5% △ Viscosity change rate is ± 5% or more and less than ± 10% × Viscosity change rate is ± 10% or more

(2) Evaluation Method of Storage Stability at Low Temperature—5 ° C. First, the viscosity of the ink immediately after production was measured at 20 ° C. using an E-type viscometer (TV-20 type manufactured by Toki Sangyo Co., Ltd., using a cone type rotor). (Initial viscosity X1).

  Next, the ink was allowed to stand for 1440 hours in an environment of −5 ° C.

  The ink after the standing was taken out from the −5 ° C. environment and allowed to stand in a room temperature environment until the ink reached a room temperature.

  The viscosity of the ink at room temperature was measured in an environment of 20 ° C. (viscosity X2) using an E-type viscometer (TV-20 type manufactured by Toki Sangyo Co., Ltd., using a cone-type rotor).

The viscosity change rate was calculated using the initial viscosity X1 and the viscosity X2 measured by the above method and the following formula.
Viscosity change rate (%) = [{(viscosity X2) − (initial viscosity X1)} / initial viscosity (X1)] × 10

○ Viscosity change rate is less than ± 5% △ Viscosity change rate is ± 5% or more and less than ± 10% × Viscosity change rate is ± 10% or more

(3) Evaluation method of filterability test The ink immediately after production was allowed to stand in an environment of 60 ° C for 1440 hours. Moreover, the ink immediately after manufacture was left still for 1440 hours in -5 degreeC environment.

  The ink after standing was allowed to stand in a room temperature environment until the ink reached room temperature.

  Next, the ink was filtered through a membrane filter having a pore size of 0.6 μm.

  The case where precipitates (residues) could be visually confirmed on the membrane filter was evaluated as “x”, and the case where precipitates could not be confirmed was evaluated as “◯”.

[Discharge reliability evaluation method]
The ink obtained in Examples and Comparative Examples was continuously ejected for 1500 hours using a charge control inkjet printer (continuous inkjet printer manufactured by Hitachi Industrial Equipment Systems Co., Ltd.). The ejected ink was collected by a gutter and set to be ejected again through an ink path in the printer.

  An ink ejection direction abnormality that occurred after 1500 hours was not collected by gutter, and the area around the gutter was colored with ink was evaluated as “x”. Even after 1500 hours, ink ejection direction abnormality No ink was generated and all of the ejected ink was collected with gutter was evaluated as “◯”.

[Adhesion evaluation method]
100 dots (10 cm × 10 cm) were printed on the surface of the polyethylene film using the ink obtained in the examples and comparative examples, using a charge control inkjet printer.

  The printed material was allowed to stand for 30 minutes in an environment of 25 ° C., and then a cellophane adhesive tape (manufactured by Nichiban) was attached to the surface of the printed material. Next, the cellophane adhesive tape was peeled in the direction of 180 degrees with respect to the surface of the printed material, and the state of the printed surface was visually confirmed.

  Evaluated as “◯” when the number of dots on the printed surface was 0, and evaluated as “△” when 1 or more and less than 25 dots were peeled off, and removed 25 or more dots. Evaluated as “x”.

[Abrasion resistance evaluation method]
100 dots (10 cm × 10 cm) were printed on the surface of the polyethylene film using the ink obtained in the examples and comparative examples, using a charge control inkjet printer.

  The print was allowed to stand in an environment of 25 ° C. for 30 minutes, and then the surface of the print was rubbed with a cotton swab 20 times to visually confirm the state.

  Evaluated as “◯” when the number of dots on the printed surface was 0, and evaluated as “△” when 1 or more and less than 25 dots were peeled off, and removed 25 or more dots. Evaluated as “x”.

[Visibility evaluation method]
Using the ink obtained in the examples and comparative examples, 100 dots (10 cm in length × 10 cm in length) on the surface of the polyethylene film using a charge control ink jet printer (continuous ink jet printer manufactured by Hitachi Industrial Equipment Systems Co., Ltd.) In the range of 10 cm in width, 10 dots in length × 10 dots in width were printed and dried in an environment of 25 ° C. for 30 minutes to obtain a printed matter.

  Check the printed matter visually, evaluate the printed matter that was able to confirm 100 independent dots without overlapping the dots as “○”, and spread the dots on the surface of the polyethylene film to spread more than two dots. Were partially overlapped and formed one large dot, which was evaluated as “x”.

Claims (9)

An ink comprising a binder having a weight average molecular weight of 1000 or more and less than 4000, a colorant, and a ketone solvent as an organic solvent. The ink according to claim 1, wherein the binder is a styrene-acrylic polymer. The ink according to claim 1 or 2, wherein the binder has an acid value in the range of 200 to 300. The ink according to any one of claims 1 to 3, wherein the ketone solvent is in a range of 45 mass% to 65 mass% with respect to the total amount of the ink. The ink according to claim 1, wherein the colorant is a dye that dissolves in methyl ethyl ketone. The ink according to any one of claims 1 to 5, further comprising a conductivity imparting substance. The ink according to any one of claims 1 to 4, which is used for printing on a polyolefin recording medium. The ink according to claim 1, which is printed on a recording medium by an ink jet printing method. A printed matter in which the ink according to any one of claims 1 to 8 is printed on a low-absorbency medium by an inkjet printing method.