JP6989084B2 - Gravure printing method - Google Patents

Description

The present invention relates to a gravure printing method.

Gravure printing is a printing method in which ink is transferred to a printing substrate by using a gravure plate on which cells for receiving ink are formed. The print quality can be controlled by the cell depth and cell spacing (number of lines), and it is widely used because it enables high-definition printing.
Conventionally, oil-based ink has been used in gravure printing, but there are problems in terms of working environment, global environment, disaster prevention, and residual solvent when used in food-related fields. In addition, the amount of oil-based ink used increases, and there is a problem that it is difficult to meet the market needs of a wide variety of inks and small lots in recent years.
For the above reasons, a gravure printing method using a water-based ink has attracted attention. However, in water-based inks, due to poor drying and poor ink wetting on the plate surface due to surface tension, the same method as oil-based inks not only slows down the printing speed, but also causes problems of ink transfer and plate fog. There is a problem that high quality resin film printed matter cannot be obtained.

Therefore, various proposals have been made regarding gravure printing.
For example, Patent Document 1 prints on a resin film using an impression cylinder having a rubber hardness of 75 to 90 Hs, a ceramic-plated doctor blade having a cutting edge thickness of 50 to 70 μm, a plate having a chrome hardness of 950 to 1100 Hv, and a water-based gravure ink. The gravure printing method is disclosed.
In Patent Document 2, when the coating material is gravure-coated on the substrate to be coated using the impression cylinder and the gravure plate, the viscosity at 20 ° C. is 0 mPa using the impression cylinder having a rubber hardness of 40 to 60 degrees on the surface. A gravure coating method for applying a coating agent larger than s and 5 mPa · s or less to a resin film is disclosed.
Patent Document 3 describes an ethylenically unsaturated monomer (B) in an aqueous medium using a water-soluble resin (A) having a carboxyl group as a polymer emulsifier as a resin composition for water-based ink that can be developed for gravure printing. ) Is emulsion-polymerized to contain a core-shell type resin fine particle dispersion (C), a carbodiimide group-containing resin fine particle dispersion (D), and a water-insoluble epoxy group-containing compound (E). The composition is disclosed.

Japanese Patent Application Laid-Open No. 2003-21814 Japanese Unexamined Patent Publication No. 2011-206763 Japanese Unexamined Patent Publication No. 2016-060885

However, the techniques of Patent Documents 1 to 3 cannot satisfy the demands for improvement of ink transfer property and suppression of plate fog in gravure printing for printing on a resin film using water-based ink.
An object of the present invention is to provide a gravure printing method capable of improving the ink transfer property of a water-based ink to a resin film and suppressing plate fog.

The present inventors have focused on the relationship between the composition and physical properties of the water-based ink, the rubber hardness of the nip roll, and the operating conditions, and have found that the above problems can be solved by adjusting them.
That is, the present invention is a gravure printing method in which water-based ink is stored in an ink pan and printed on a resin film substrate using a nip roll.
The water-based ink contains pigments, polymers, organic solvents, surfactants, and water.
The SP value of the organic solvent is 8 or more and 11 or less.
The content of the organic solvent having a boiling point of 100 ° C. or higher and 260 ° C. or lower in the organic solvent is 0.3% by mass or more and 12% by mass or less.
The rubber hardness of the nip roll is 55 ° or more and 85 ° or less.
Provided is a gravure printing method in which the contact pressure of the nip roll in contact with the printing substrate is 0.04 MPa or more and 0.35 MPa or less.

According to the gravure printing method of the present invention, it is possible to provide a gravure printing method capable of improving the ink transfer property of a water-based ink to a resin film and suppressing plate fog.

It is sectional drawing which shows one Embodiment of the gravure printing machine used in this invention method.

[Gravure printing method]
The gravure printing method of the present invention is a gravure printing method in which water-based ink is stored in an ink pan and printed on a resin film substrate using a nip roll. And water, the SP value of the organic solvent is 8 or more and 11 or less, and the content of the organic solvent having a boiling point of 100 ° C. or more and 260 ° C. or less in the organic solvent is 0.3% by mass or more and 12% by mass or less. The rubber hardness of the nip roll is 55 ° or more and 85 ° or less, and the contact pressure of the nip roll in contact with the printing substrate is 0.04 MPa or more and 0.35 MPa or less.

<Gravure printing method>
In gravure printing, ink is supplied to the plate surface of the gravure roll while rotating the gravure roll (gravure plate) in which concave cells are formed on the surface, and the ink is scraped off with a doctor blade fixed in a predetermined position only in the cell. By crimping the continuously supplied printing base material to the gravure roll with a nip roll whose surface is made of rubber, leaving the ink, and transferring only the ink in the cell of the gravure roll to the printing base material, characters and characters can be printed. This is a method of printing an image.
FIG. 1 is a schematic cross-sectional view showing an embodiment of a gravure printing machine used in the method of the present invention. The gravure printing method by the gravure printing machine 1 will be described.
As shown in FIG. 1, the gravure printing machine 1 includes an ink pan 10, a finisher roll 11, a gravure roll 12, a doctor blade 13, and a nip roll 14. In the gravure printing machine 1, the finisher roll 11, the gravure roll 12, and the nip roll 14 are continuously rotated in the direction of the arrow in FIG.
The gravure printing machine 1 prints on the printing base material 20 which is continuously conveyed. The gravure printing machine 1 further includes a printing base material supply roll 15 for sending out a printing base material 20 to be printed, and a printing base material winding roll 16 for winding up the printed printing base material 20.

The ink pan 10 stores water-based ink used for printing on the printing substrate 20. The water-based ink contains a pigment, a polymer, an organic solvent, a surfactant, and water, and the SP value of the organic solvent is 8 or more and 11 or less, and the organic solvent having a boiling point of 100 ° C. or more and 260 ° C. or less is contained in the organic solvent. The amount is 0.3% by mass or more and 12% by mass or less.
The finisher roll 11 is provided so that the outer peripheral surface is immersed in the water-based ink in the ink pan 10. By rotating the finisher roll 11 in the direction of the arrow in FIG. 1, the water-based ink in the ink pan 10 adheres to the outer peripheral surface of the finisher roll 11.

The gravure roll 12 is installed at a position where it comes into contact with the finisher roll 11. A plurality of cells (recesses) are provided on the surface of the gravure roll 12, and the finisher roll 11 rotates while being in contact with the gravure roll 12 to cause water-based ink adhering to the outer surface of the finisher roll 11. Is transferred into each cell (recess) of the gravure roll 12 and is filled in each cell.
It is preferable that the water-based ink is filled only in each cell of the gravure roll 12, but among the inks sent from the outer surface of the finisher roll 11 to the gravure roll 12, the surplus ink that is not filled in each cell is also included. appear.

The doctor blade 13 is on the downstream side of the contact point between the finisher roll 11 and the gravure roll 12 in the rotation direction of the gravure roll 12 (the direction of the arrow in FIG. 1), and the contact between the gravure roll 12 and the nip roll 14 It is installed on the upstream side of the location.
By rubbing the outer surface of the gravure roll 12, the doctor blade 13 maintains the water-based ink filled in each cell of the gravure roll 12 as it is, and the gravure roll not filled in each cell. The excess ink on the surface of the convex portion of 12 is scraped off. At this time, the water-based ink filled in each cell (recess) of the gravure roll 12 is not scraped off by the doctor blade 13.

The nip roll 14 is in contact with the gravure roll 12 via the printing substrate 20 on the downstream side of the contact portion with the doctor blade 13 in the rotation direction of the gravure roll 12. The nip roll 14 sandwiches the printing base material 20 with the gravure roll 12, so that the printing base material 20 continuously sent out from the printing base material supply roll 15 has the water-based ink in each cell of the gravure roll 12. Is transferred and printing is performed.
The rubber hardness of the nip roll 14 is 55 ° or more and 85 ° or less, and the contact pressure at which the nip roll 14 comes into contact with the printing substrate is 0.04 MPa or more and 0.35 MPa or less.
The printing substrate 20 on which the water-based ink is transferred and printed is dried by a drying device (not shown). The dried printing base material 20 is wound up by the printing base material winding roll 16. In this way, a winding body of the printing base material 20 subjected to gravure printing is obtained.

The gravure printing machine 1 and the gravure printing method are not limited to the above-mentioned aspects, and various changes can be made.
For example, in the case of multicolor gravure printing, a mode and a method in which a plurality of printing units including an ink pan 10, a finisher roll 11, a gravure roll 12, a doctor blade 13, a nip roll 14, etc. for storing ink of each color are provided in series. Can be.

<Nip roll>
In the gravure printing method of the present invention, a nip roll 14 having a rubber hardness of 55 ° or more and 85 ° or less is used. Here, the rubber hardness is a value measured by a rubber hardness tester according to the methods specified in JIS K 6301-1975 and JIS K 7215-1986.
The rubber hardness is preferably 58 ° or higher, more preferably 60 ° or higher, more preferably 62 ° or higher, and preferably 83 ° from the viewpoint of improving the ink transfer property of the water-based ink and suppressing plate fog. Below, it is more preferably 82 ° or less, still more preferably 80 ° or less.
The materials used for the nip roll 14 are isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), ethylene-propylene rubber (EPDM / EPM), butyl rubber (IIR), and the like. Examples thereof include silicone rubber, chloropyrene rubber (CR), chlorosulfonated polyethylene rubber, acrylic rubber, hydrin rubber, urethane rubber, polysulfide rubber (thiocol), and fluororubber.
Among these, acrylonitrile-butadiene rubber (NBR), ethylene propylene rubber (EPDM / EPM), and butyl rubber (IIR) are preferably selected from the viewpoint of improving the ink transfer property of the water-based ink and suppressing plate fog. One or more.
The rubber wall thickness of the nip roll 14 is preferably 2 mm or more, more preferably 3 mm or more, further preferably 5 mm or more, and preferably 30 mm or less, more preferably 25 mm or less, still more preferably 20 mm or less.

The nip roll 14 is in contact with the gravure roll 12 via the printing base material 20, but the contact pressure at which the nip roll 14 comes into contact with the printing base material 20 improves ink transferability and suppresses plate fog. It is 0.04 MPa or more and 0.35 MPa or less. The contact pressure is preferably 0.05 MPa or more, more preferably 0.08 MPa or more, still more preferably 0.1 MPa or more, and preferably 0.32 MPa or less, more preferably 0.3 MPa or less, still more preferably. It is 0.28 MPa or less.

<Printing substrate>
As the printing base material used in the gravure printing method, a resin film such as a polyester film, a polyethylene film, a polypropylene film, a polystyrene film, a vinyl chloride film, and a nylon film is used. The printed substrate is more preferably a polyester film, a uniaxially stretched or a biaxially stretched polypropylene film, or the like, from the viewpoint of versatility and post-processing suitability such as punching after producing a printed matter.
Further, from the viewpoint of improving the gravure printability, a resin film obtained by surface-treating the polyester film, uniaxially stretched or biaxially stretched polypropylene film or the like by electric discharge machining such as corona discharge treatment or plasma discharge treatment is more preferable. ..
The thickness of the printing substrate is preferably 10 μm or more, more preferably 12 μm or more, and preferably 100 μm or less, more preferably 60 μm or less, still more preferably, from the viewpoint of improving ink transferability and suppressing plate fog. Is 40 μm or less.

<Water-based ink>
The water-based ink (hereinafter, also referred to as “ink”) used in the present invention includes pigments, polymers, organic solvents, surfactants, and water.
Here, the "water-based ink" means water or an ink that has become an aqueous solution or an aqueous dispersion using a mixture of water and an organic solvent as a diluting agent.
Hereinafter, each component contained in the water-based ink will be described.

<Pigment>
The pigment used in the water-based ink may be either an inorganic pigment or an organic pigment.
Examples of the inorganic pigment include carbon black and metal oxides, and carbon black is preferable for black ink. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black. Examples of the white ink include metal oxides such as titanium dioxide, zinc oxide, silica, alumina and magnesium oxide. These inorganic pigments may be surface-treated with a known hydrophobizing agent such as a titanium coupling agent, a silane coupling agent, or a higher fatty acid metal salt.
Examples of the organic pigment include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, quinophthalone pigments and the like.
The hue is not particularly limited, and any chromatic pigment such as yellow, magenta, cyan, red, blue, orange, and green can be used in the chromatic ink.

The form of the pigment is preferably one or more selected from self-dispersing pigments and pigment particles dispersed with a polymer, and more preferably pigment particles dispersed with a polymer (hereinafter, also referred to as “pigment particles A”). be.
A self-dispersing pigment can be dispersed in an aqueous medium without using a surfactant or a resin by bonding one or more of hydrophilic functional groups directly or via other atomic groups to the surface of the pigment. Means a pigment. In order to make the pigment a self-dispersing pigment, for example, the required amount of hydrophilic functional groups may be chemically bonded to the pigment surface by a conventional method.
The content of the pigment in the ink is preferably 2% by mass or more, more preferably 5% by mass or more, still more preferably 8% by mass or more, and preferably 30% by mass or less, from the viewpoint of print density. It is preferably 25% by mass or less, more preferably 20% by mass or less.

<Polymer>
The polymer used for the water-based ink may be a water-soluble polymer or a water-insoluble polymer, but a water-insoluble polymer is more preferable.
The water-soluble polymer is a polymer that has been dried at 105 ° C. for 2 hours and has reached a constant weight, and the dissolved amount is 10 g or more when dissolved in 100 g of water at 25 ° C., and the water-insoluble polymer is a water-insoluble polymer. , The polymer having a dissolved amount of less than 10 g.
Examples of the polymer used include polyester, polyurethane, and vinyl-based polymers. From the viewpoint of dispersion stability of the pigment, vinyl-based polymers obtained by addition polymerization of vinyl monomers such as vinyl compounds, vinylidene compounds, and vinylene compounds. Is preferable.
Examples of commercially available vinyl polymers include polyacrylic acid such as Aron AC-10SL (manufactured by Toagosei Co., Ltd.), John Krill 67, 611, 678, 680, and 690 (manufactured by BASF Japan Ltd.). Styrene-acrylic resin and the like can be mentioned.

The polymer is preferably used as pigment particles A (pigment particles A) dispersed in the polymer or polymer particles B containing no pigment, dispersed in an aqueous ink. Hereinafter, the polymer constituting the pigment particles A is also referred to as “polymer a”, and the polymer constituting the polymer particles B containing no pigment is also referred to as “polymer b”.
The content of the polymer in the water-based ink (total amount of the polymer a and the polymer b) is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 7% by mass from the viewpoint of pigment dispersibility and fixability. % Or more, preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less.

[Polymer a]
The polymer a is a polymer having a pigment-dispersing ability, and examples thereof include polyester, polyurethane, and vinyl-based polymers. Among these, a vinyl-based polymer obtained by addition polymerization of a vinyl monomer is preferable from the viewpoint of improving ink stability.
The vinyl-based polymer preferably contains (a1) a structural unit derived from an ionic monomer and (a2) a structural unit derived from a nonionic monomer.

(A1) As the ionic monomer, an anionic monomer is preferable, and examples thereof include a carboxylic acid monomer and a sulfonic acid monomer. Among these, a carboxylic acid monomer is more preferable, and one or more selected from acrylic acid and methacrylic acid is further preferable.
The (a2) nonionic monomer is a monomer having a high affinity with water or a water-soluble organic solvent, and polyalkylene glycol (meth) acrylate and alkoxypolyalkylene glycol (meth) acrylate are preferable, and methoxypolyethylene glycol (n = 1). ~ 30) (Meta) acrylate is more preferable. Examples of commercially available nonionic monomers include NK ester M series manufactured by Shin-Nakamura Chemical Industry Co., Ltd., Blemmer PE series, PME series, 50PEP series, 50PEEP series manufactured by NOF CORPORATION, and the like.

The polymer a may further contain a structural unit derived from (a3) a hydrophobic monomer. Examples of the hydrophobic monomer (a3) include alkyl (meth) acrylates, aromatic group-containing monomers, and macromonomers having a polymerizable functional group at one end.
The alkyl (meth) acrylate preferably has an alkyl group having 6 or more and 18 or less carbon atoms, and is, for example, methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or Tasha). Lee) Butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate and the like can be mentioned.
As the aromatic group-containing monomer, a vinyl-based monomer having an aromatic group having 6 or more and 22 or less carbon atoms is preferable, and a styrene-based monomer, an aromatic group-containing (meth) acrylate and the like are more preferable. As the styrene-based monomer, styrene, 2-methylstyrene, α-methylstyrene, vinyltoluene, divinylbenzene and the like are preferable, and as the aromatic group-containing (meth) acrylate, benzyl (meth) acrylate and the like are preferable.

(Content of each structural unit in polymer a)
The content of the structural units derived from the components (a1) to (a3) in the polymer a is as follows from the viewpoint of improving the dispersion stability of the ink.
The content of the component (a1) is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 15% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less. , More preferably 20% by mass or less.
The content of the component (a2) is preferably 20% by mass or more, more preferably 40% by mass or more, further preferably 60% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less. , More preferably 85% by mass or less.
The content of the component (a3) is preferably 15% by mass or less, more preferably 10% by mass or less, and further preferably 5% by mass or less.

(Manufacturing of polymer a)
The polymer a can be produced by copolymerizing a monomer mixture containing (a1) an ionic monomer, (a2) a nonionic monomer and the like by a known solution polymerization method or the like.
The weight average molecular weight of the polymer a is preferably 3,000 or more, more preferably 5,000 or more, still more preferably 10,000 or more, from the viewpoint of improving the dispersion stability of the ink and the fixability to the printing substrate. The amount is preferably 100,000 or less, more preferably 50,000 or less, and further preferably 30,000 or less.
The acid value of the polymer a is preferably 100 mgKOH / g or more, more preferably 150 mgKOH / g or more, still more preferably 200 mgKOH / g or more, and preferably 350 mgKOH / g or more from the viewpoint of the dispersibility of the pigment and the adsorptivity of the polymer. It is / g or less, more preferably 300 mgKOH / g or less, still more preferably 250 mgKOH / g or less.
The weight average molecular weight and the acid value can be measured by the method described in Examples.

(Manufacturing of Pigment Particles A Dispersed with Polymer)
The pigment particles A dispersed with the polymer are particles in which the polymer a is adsorbed on the surface of the pigment, and can be stably dispersed in the ink.
The pigment particles A can be efficiently produced by a method having the following step I as a dispersion. Further, it may be produced by a method having the following steps II and III.
Step I: A mixture containing a polymer a, an organic solvent, a pigment, and if necessary, a neutralizing agent, a surfactant, etc. is dispersed to obtain a dispersion of the pigment particles A. Step II: Obtained in Step I. Step III: The dispersion obtained in Step I or the aqueous dispersion obtained in Step II is mixed with the cross-linking agent to obtain an aqueous dispersion of the pigment particles A by removing the organic solvent from the obtained dispersion. Step of cross-linking to obtain an aqueous dispersion of polymer a particles (pigment particles A) containing a pigment The polymer a of the pigment particles A and the polymer b of the polymer particles B may be the same or different. That is, the polymers a and b may have different compositions, or may be the same polymer including the composition, and may differ only in the presence or absence of the pigment.

When the polymer a is an anionic polymer, a neutralizing agent may be used to neutralize the anionic groups in the polymer. When a neutralizing agent is used, it is preferable to neutralize the pH so that the pH is 7 or more and 11 or less. Examples of the neutralizing agent include bases such as lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, and various amines. Further, the polymer may be neutralized in advance.
The degree of neutralization of the anionic group of the polymer a is preferably 10 mol% or more and 100 mol% or less, more preferably 20 mol% or more and 90 mol% or less, with respect to the anionic group, from the viewpoint of improving the dispersion stability of the ink. It is preferable, and more preferably 30 mol% or more and 80 mol% or less.

When the polymer a is an anionic polymer having an anionic group, the cross-linking agent is preferably a compound having a functional group that reacts with the anionic group, more preferably a compound having two or more functional groups in the molecule, and a molecule. A compound having 2 or more and 6 or less in the compound is more preferable.
Preferable examples of the cross-linking agent include a compound having two or more epoxy groups in the molecule, a compound having two or more oxazoline groups in the molecule, and a compound having two or more isocyanate groups in the molecule. Among these, a compound having two or more epoxy groups in the molecule is preferable, and trimethylolpropane polyglycidyl ether is more preferable.
The cross-linking rate of the acid component in the polymer a is preferably 5 mol% or more, more preferably 10 mol% or more, still more preferably 20 mol% or more, and preferably 80 mol% or more from the viewpoint of storage stability of the ink. It is mol% or less, more preferably 70 mol% or less, still more preferably 60 mol% or less.

The content of the pigment particles A in the ink is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, and preferably 40% by mass or more from the viewpoint of print density and fixability. It is mass% or less, more preferably 35% by mass or less, still more preferably 30% by mass or less.
The content of the polymer a in the ink is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, still more preferably 0.3% by mass or more, and preferably 0.3% by mass or more, from the viewpoint of fixability. Is 10% by mass or less, more preferably 5% by mass or less, still more preferably 2% by mass or less.
The mass ratio of the polymer a to the pigment in the ink [polymer a / pigment] is preferably 0.2 / 99.8 to 70/30, more preferably 0.5 / 99. It is 5 to 60/40, more preferably 1/99 to 50/50.

(Polymer particles B containing no pigment)
The water-based ink preferably contains polymer particles B (polymer particles B) containing no pigment from the viewpoint of forming a film on the printing substrate to improve the fixability. The polymer particles B are water-insoluble polymer particles that do not contain a pigment and are composed of the polymer alone.
Examples of the polymer b constituting the polymer particles B include acrylic resins, styrene resins, urethane resins, polyester resins, styrene-acrylic resins, butadiene resins, vinyl chloride resins and the like, and have ink transfer properties. Acrylic resin and vinyl chloride-acrylic resin are preferable, and a combination thereof is also preferable, from the viewpoint of improving plate fogging and suppressing plate fog.
The polymer particles B are preferably used as an aqueous dispersion in which they are dispersed in water. As the polymer particles B, those synthesized as appropriate may be used, or commercially available products may be used.

[Polymer b]
As the acrylic resin, a water-insoluble vinyl polymer obtained by copolymerizing a monomer mixture B containing (b1) an ionic monomer and (b2) a hydrophobic monomer is preferable.
The component (b1) is the same as the component (a1), but among them, an anionic monomer is preferable, a carboxylic acid monomer is more preferable, and acrylic acid and methacrylic acid are selected from the viewpoint of improving dispersion stability. More than one kind is more preferable.
Examples of the component (b2) include an alkyl (meth) acrylate similar to the component (a3), an aromatic group-containing monomer, a macromonomer and the like. Among these, alkyl (meth) acrylates are preferable, those having an alkyl group having 1 or more and 22 or less carbon atoms, preferably 1 or more and 10 or less carbon atoms are more preferable, and the above-mentioned exemplified compounds are more preferable, and methyl (meth) acrylates and the like. Combination with 2-ethylhexyl (meth) acrylate is even more preferable.

(Content of each structural unit in polymer b)
The content of the structural units derived from the components (b1) and (b2) in the polymer b is as follows from the viewpoint of improving the fixability to the printed substrate.
The content of the component (b1) is preferably 1% by mass or more, more preferably 3% by mass or more, further preferably 5% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less. , More preferably 15% by mass or less.
The content of the component (b2) is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 70% by mass or more, and preferably 99% by mass or less, more preferably 97% by mass or less. , More preferably 95% by mass or less.

The polymer b can be produced by copolymerizing a monomer mixture containing (b1) an ionic monomer, (a2) a nonionic monomer and the like by a known solution polymerization method or the like.
Examples of commercially available dispersions of polymer particles B include Neocryl A1127 (made by DSM NeoResins, anionic self-crosslinked water-based acrylic resin), John Krill 390 (manufactured by BASF Japan, Inc.) and other acrylic resins, WBR-2018. Urethane-based resins (manufactured by Taisei Fine Chemical Co., Ltd.), styrene-butadiene resins such as SR-100 (manufactured by Nippon A & L Co., Ltd.), John Krill 7100, 734, 538 (manufactured by BASF Japan Co., Ltd.), etc. Examples thereof include styrene-acrylic resin, vinyl chloride-acrylic resin such as Viniblanc 700 and 701 (manufactured by Nissin Chemical Industry Co., Ltd.).

The weight average molecular weight of the polymer b is preferably 100,000 or more, more preferably 200,000 or more, still more preferably 300,000 or more, and preferably 2.5 million or less, more preferably 1 million or less, from the viewpoint of fixability. , More preferably 600,000 or less.
The acid value of the polymer b is preferably 1 mgKOH / g or more, more preferably 3 mgKOH / g or more, still more preferably 5 mgKOH / g or more, and preferably 70 mgKOH / g or less, more preferably 70 mgKOH / g or more, from the viewpoint of ink stability. Is 65 mgKOH / g or less, more preferably 60 mgKOH / g or less.
The weight average molecular weight and acid value of the polymer b are measured by the method described in Examples.

The content of the polymer particles B in the ink is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, and preferably 30% by mass from the viewpoint of ink fixability. % Or less, more preferably 20% by mass or less, still more preferably 15% by mass or less.
The mass ratio [polymer / pigment] of the polymer (total amount of polymer a and polymer b) to the pigment in the ink is preferably 20/100 to 300/100, more preferably 30/100 to, from the viewpoint of ink stability. It is 200/100, more preferably 40/100 to 100/100.

<Organic solvent>
As the organic solvent used for the water-based ink, a water-soluble organic solvent is preferable. The water-soluble organic solvent is an organic solvent that is liquid or solid at room temperature and has a dissolution amount of 10 ml or more when the solvent is dissolved in 100 ml of water at 25 ° C.
The organic solvent has a boiling point of preferably 100 ° C. or higher, more preferably 110 ° C. or higher, still more preferably 115 ° C. or higher, still more preferably 118 ° C. or higher, from the viewpoint of improving ink transferability and suppressing plate fog. And, preferably 260 ° C. or lower, more preferably 250 ° C. or lower, still more preferably 240 ° C. or lower, still more preferably 235 ° C. or lower.
Here, the boiling point means a standard boiling point (boiling point under 1 atm), and when two or more kinds are used, it is a weighted average value weighted by the content (mass%) of each water-soluble organic solvent.
The content of the organic solvent used in the water-based ink is 0.3% by mass or more with a boiling point of 100 ° C. or higher and 260 ° C. or lower from the viewpoint of improving ink transferability and suppressing plate fog. It is preferably 1% by mass or more, more preferably 2% by mass or more, further preferably 3% by mass or more, and from the viewpoint of reducing the environmental load, it is 12% by mass or less, preferably 11% by mass or less. It is preferably 10% by mass or less, more preferably 9% by mass or less.

The water-based ink may contain an organic solvent having a boiling point of less than 100 ° C., but the content thereof is in the water-based ink from the viewpoint of improving the ink transfer property and suppressing the plate fog while suppressing the drying property. It is preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 1% by mass or less.
Examples of the organic solvent below 100 ° C. include monohydric alcohols such as ethanol, isopropyl alcohol and n-propyl alcohol.

The SP value (solubility parameter) of the organic solvent is 8 (MPa) ^1/2 or more and 11 (MPa) ^1/2 or less from the viewpoint of improving ink transferability and suppressing plate fog.
Hansen's SP value is used as the dissolution parameter. As the SP value of Hansen, the type of interaction energy acting between the molecules of the substance is divided into three, and the one calculated based on the chemical structure can be used. Specifically, the following equation can be used.
δ ＝ (δ _d ² ＋ δ _p ² ＋ δ _h ² ) ^1/2
Here, δ _d is called the London dispersion force term, δ _p is called the molecular polarization term, and δ _h is called the hydrogen bond term. _{Δ d} , δ _p , and δ _h of each water-soluble organic solvent are described in detail in "HANSEN SOLBILITY PARAMETERS" A User's Handbook Second Edition.
If the SP value cannot be obtained by the above method, it is described in "Solubility Parameter Values" VII / 675-714, etc. of Polymer Handbook Fourth Edition (Wiley, 1999). You may use what has been done.
The SP value of the organic solvent is preferably 8.2 (MPa) ^1/2 or more, more preferably 8.3 (MPa) ^1/2 or more, and further, from the viewpoint of improving ink transferability and suppressing plate fog. It is preferably 8.5 (MPa) ^1/2 or more, preferably 10.8 (MPa) ^1/2 or less, more preferably 10.6 (MPa) ^1/2 or less, still more preferably 10.4. (MPa) ^1/2 or less.

Preferred water-soluble organic solvents include polyhydric alcohols such as propylene glycol and glycerin, polyhydric alcohol ethers, nitrogen-containing heterocyclic compounds, amides, amines and the like, and among these, glycol ethers are preferable.
The glycol ether is an alkylene glycol monoalkyl ether or alkylene glycol having an alkyl group having 1 or more carbon atoms, preferably 2 or more carbon atoms, and preferably 6 or less, more preferably 4 or less, still more preferably 3 or less. Dialkyl ethers can be mentioned.
Among these, ethylene glycol monomethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, triethylene glycol monomethyl ether, propylene glycol monomethyl ether, etc. Is preferable, ethylene glycol monomethyl ether (boiling point 125 ° C.), ethylene glycol monoisopropyl ether (boiling point 142 ° C.), ethylene glycol monobutyl ether (boiling point 171 ° C.), diethylene glycol monoisobutyl ether (boiling point 220 ° C.), propylene glycol monomethyl ether (boiling point). 121 ° C.) and one or more selected from triethylene glycol monomethyl ether (boiling point 249 ° C.) are more preferable.

<Surfactant>
The surfactant used for the water-based ink is not particularly limited, but a silicone-based surfactant and an acetylene glycol-based surfactant are preferable from the viewpoint of improving ink transferability and suppressing plate fog.
As the silicone-based surfactant, a polyether-modified silicone-based surfactant is preferable. The polyether-modified silicone-based surfactant has a structure in which the hydrocarbon group at the side chain and / or the terminal of the silicone oil is replaced with a polyether group. As the polyether group, a polyethylene oxy group, a polypropylene oxy group, a polyalkylene oxy group in which an ethylene oxy group (EO) and a propylene oxy group (PO) are added in a block shape or at random are preferable, and a polyalkylene oxy group is added to the silicone main chain. A compound grafted with an ether group, a compound in which a silicone and a polyether group are bonded in a block shape, and the like can be used.
Specific examples of the polyether-modified silicone-based surfactant include KF series manufactured by Shin-Etsu Chemical Co., Ltd., Silface SAG manufactured by Nisshin Chemical Industry Co., Ltd., BYK series manufactured by Big Chemie Japan Co., Ltd., and the like.

As the acetylene glycol-based surfactant, acetylene glycol having 8 or more and 22 or less carbon atoms and an ethylene adduct of the acetylene glycol are preferable, and acetylene glycol having 8 or more and 22 or less carbon atoms is more preferable.
Examples of these commercially available products include Surfinol 104 (2,4,7,9-tetramethyl-5-decyne-4,7-diol) manufactured by Air Products and Chemicals Co., Ltd., and 104E (ethylene glycol 50 of Surfinol 104). % Diluted product), 104PG-50 (50% diluted propylene glycol of Surfinol 104), Surfinol 420 (Eo average 1.3 mol adduct of Surfinol 104), Acetylenol E13T manufactured by Kawaken Fine Chemicals Co., Ltd. ( EO average number of moles added: 1.3) and the like.

As the surfactant, other surfactants other than the above may be contained. As the other surfactant, a nonionic surfactant is preferable, and an alcohol-based surfactant is more preferable.
Examples of commercially available alcohol-based surfactants include the "Emargen" series manufactured by Kao Corporation.
The content of the surfactant in the ink is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, as the total amount of the surfactant from the viewpoint of improving the wettability to the printing substrate. It is more preferably 0.4% by mass or more, and preferably 10% by mass or less, more preferably 7% by mass or less, still more preferably 5% by mass or less.

(Thickener, etc.)
The water-based ink can contain various additives such as a thickener, a pH adjuster, a defoaming agent, a preservative, and a rust preventive as optional components.
Examples of the thickener include a cellulose-based thickener, a polyacrylic acid-based thickener, a polyether polyol-based thickener, a polyether urethane-based thickener, and the like.
Examples of commercially available products of polyacrylic acid-based thickeners include the Primal ASE series manufactured by Roam & Haas, and examples of commercially available products of polyether polyol-based thickeners include the RHEOLATE series manufactured by RHEOX. Examples of commercially available modified thickeners include Adecanol UH series manufactured by ADEKA Corporation and DK Thinner SCT series manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.
The blending amount of the thickener is appropriately adjusted according to the desired viscosity, but is usually 0.1% by mass or more and 5% by mass or less in the water-based ink.

(water)
The content of water in the water-based ink is preferably 45% by mass or more, more preferably 50% by mass or more, still more preferably 55% by mass or more, and from the viewpoint of improving ink transferability and suppressing plate fog. Therefore, it is preferably 75% by mass or less, more preferably 70% by mass or less, and further preferably 65% by mass or less.

<Physical characteristics of water-based ink>
The average particle size of the pigment particles, particularly the pigment particles A in which the pigment is dispersed with a polymer, is preferably 120 nm or more, more preferably 130 nm or more, and further, from the viewpoint of improving ink transferability and suppressing plate fog. It is preferably 140 nm or more, more preferably 150 nm or more, and preferably 350 nm or less, more preferably 340 nm or less, still more preferably 320 nm or less, still more preferably 300 nm or less.
The average particle size of the polymer particles B containing no pigment in the ink is preferably 20 nm or more, more preferably 40 nm or more, still more preferably 60 nm or more, from the viewpoint of improving ink transferability and suppressing plate fog. Then, it is preferably 300 nm or less, more preferably 200 nm or less, and further preferably 150 nm or less.
The average particle size of the pigment particles A and the polymer particles B is measured by the method described in Examples.

The static surface tension of the water-based ink at 20 ° C. is preferably 20 mN / m or more, more preferably 22 mN / m or more, still more preferably 23 mN / m or more, from the viewpoint of improving ink transferability and suppressing plate fog. Yes, and it is preferably 40 mN / m or less, more preferably 38 mN / m or less, more preferably 34 mN / m or less, still more preferably 30 mN / m or less.
The viscosity of the ink at 20 ° C. by the Zahn cup method is preferably 10 seconds or longer, more preferably 12 seconds or longer, still more preferably 14 seconds or longer, and more preferably 14 seconds or longer, from the viewpoint of improving ink transferability and suppressing plate fog. It is preferably 25 seconds or less, more preferably 23 seconds or less, still more preferably 21 seconds or less.
The pH of the ink at 20 ° C. is preferably 5.5 or more, more preferably 6.0 or more, still more preferably 6.5 or more, and member resistance and skin irritation, from the viewpoint of improving dispersion stability. From the viewpoint of the above, it is preferably 11.0 or less, more preferably 10.0 or less, and further preferably 9.5 or less.

In the following production examples, preparation examples, examples and comparative examples, "parts" and "%" are "parts by mass" and "% by mass" unless otherwise specified. The measurement method for each physical property is as follows.

(1) Measurement of weight average molecular weight of polymer The molecular weight of the polymer is determined by using a solution prepared by dissolving phosphoric acid and lithium bromide in N, N-dimethylformamide at concentrations of 60 mmol / L and 50 mmol / L, respectively. It was measured by a gel permeation chromatography method [GPA apparatus manufactured by Toso Co., Ltd. (HLA-8120GPA), column manufactured by Toso Co., Ltd. (TSK-GEL, α-M × 2), flow velocity: 1 mL / min]. As a standard substance, monodisperse polystyrene having a known molecular weight was used.

(2) Measurement of acid value of polymer In an automatic potential difference titrator (Kyoto Denshi Kogyo Co., Ltd., electric burette, model number: APB-610), the resin is dissolved in a titration solvent in which toluene and acetone (2 + 1) are mixed, and potential difference titration is performed. Titration was performed with a 0.1N potassium hydroxide / ethanol solution by the method, and the inflection point on the titration curve was taken as the end point. The acid value was calculated from the titration to the end point of the potassium hydroxide solution.

(3) Measurement of solid content concentration In a 30 ml polypropylene container (φ = 40 mm, height = 30 mm), 10.0 g of sodium sulfate homogenized in a desiccator was weighed, and about 1.0 g of a sample was added thereto. After mixing, the mixture was accurately weighed, maintained at 105 ° C. for 2 hours to remove volatiles, and then left in a desiccator for 15 minutes to measure the mass. The mass of the sample after removing the volatile matter was taken as the solid content and divided by the mass of the added sample to obtain the solid content concentration.

(4) Measurement of average particle size of pigment particles A and polymer particles B containing no pigment Measure the average particle size of cumulant using a laser particle analysis system (manufactured by Otsuka Electronics Co., Ltd., model number: ELS-8000, cumulant analysis). The average particle size of the cumulant was defined as the average particle size of the pigment particles A or the average particle size of the polymer particles B containing no pigment. For the measurement sample, a dispersion diluted with water was used so that the concentration of the particles to be measured was 5 × 10 ^-3%. The measurement conditions were a temperature of 25 ° C., an angle of 90 ° between the incident light and the detector, and 100 times of integration, and the refractive index of water (1.333) was input as the refractive index of the dispersion solvent.

Production Example 1 (Production of Pigment Aqueous Dispersion A)
(1) Weigh 236 parts of ion-exchanged water in a 2 L flask, and add 60 parts of acrylic polymer (trade name: John Krill 690, weight average molecular weight 16500, acid value 240 mgKOH / g, Tg 105 ° C.) and 5N hydroxide. 36.5 parts of sodium solution (sodium neutralization degree 60 mol%) was added. The mixture was stirred at 200 rpm for 2 hours using an anchor blade to obtain 332.5 parts (solid content concentration 19.9%) of an aqueous acrylic polymer solution.
331.7 parts of the above aqueous solution and 448.3 parts of ion-exchanged water are added to a vessel having a disper wing and a volume of 2 L, and while cooling in a water bath at 0 ° C., the disper (manufactured by Asada Iron Works Co., Ltd., Ultra Disper: trade name) ) Was stirred at 1400 rpm for 15 minutes.
(2) Next, 220 parts of carbon black (manufactured by Mitsubishi Chemical Corporation, trade name: # 40, primary particle diameter 24 nm) was added, and the mixture was stirred at 6400 rpm for 1 hour. The dispersion is put into a wet disperser (Hiroshima Metal & Machinery Co., Ltd., product name: Ultra Apex Mill UAM05) filled with 80% of zirconia beads (manufactured by Nikkato Co., Ltd., product name: XTZ ball, 0.3 mmφ). Then, while cooling with cooling water at 5 ° C., the product was dispersed in 5 passes at a peripheral speed of 8 m / s and a flow rate of 200 g / min, and then filtered using a 200 mesh wire mesh.
(3) Denacol EX-321L (manufactured by Nagase ChemteX Corporation, trimethylolpropane polyglycidyl ether, epoxy equivalent 129) 7.3 parts (polymer) in 500 parts (110 parts of pigment, 33 parts of polymer) of the filtrate obtained above. Add 1 part of Proxel LV (S) (manufactured by Lonza Japan Co., Ltd., antifungal agent, effective content 20%) to the carboxylic acid that is the cross-linking reaction point contained in the acrylic acid inside, and further solidify. 17.9 parts of ion-exchanged water was added so that the component concentration became 28.6%, and the mixture was stirred at 70 ° C. for 3 hours and then filtered through a 200-mesh wire net to contain 28.6% of polymer particles containing a pigment. 526.2 parts of the dispersion A (pigment aqueous dispersion A; average particle size 190 nm) was obtained.

Production Example 2 (Production of water-insoluble polymer particle dispersion liquid containing no pigment)
0.5 part of methacrylic acid, 14.5 parts of methyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.), 5.0 parts of 2-ethylhexyl acrylate (manufactured by Wako Pure Chemical Industries, Ltd.) in a reaction vessel equipped with a dropping funnel. , Latemul E-118B (11.1 parts of polyoxyethylene alkyl ether sodium sulfate, manufactured by Kao Co., Ltd., surfactant), 0.2 parts of potassium persulfate (manufactured by Wako Pure Chemical Industries, Ltd.) as a polymerization initiator, After adding 282.8 parts of ion-exchanged water and mixing at 150 pm, nitrogen gas substitution was performed to obtain an initial charged monomer solution.
9.5 parts of methacrylic acid, 275.5 parts of methyl methacrylate, 95.0 parts of 2-ethylhexyl acrylate, 35.1 parts of Latemul E-118B, 0.6 parts of potassium persulfate, 183.0 parts of ion-exchanged water at 150 prism. The mixed dropping monomer solution was placed in the dropping funnel and replaced with nitrogen gas.
Under a nitrogen atmosphere, the initial charged monomer solution in the reaction vessel was heated from room temperature to 80 ° C. over 30 minutes while stirring at 150 prism, and the monomer in the dropping funnel was gradually added over 3 hours while maintaining the temperature at 80 ° C. It was dropped into the reaction vessel. After completion of the dropping, the mixture was stirred for 1 hour while maintaining the temperature in the reaction vessel, and 204.7 parts of ion-exchanged water was added. Then, it was filtered through a stainless wire mesh (200 mesh) to obtain a dispersion liquid of water-insoluble polymer particles (solid content concentration 40%, average particle size 100 nm, acid value 16 mgKOH / g, Tg 48 ° C.).

<Preparation of ink for gravure printing>
Preparation Example 1 (Preparation of Ink 1)
In order to obtain the ink composition shown in Table 1, 54.5 parts of the pigment aqueous dispersion A obtained in Production Example 1 (corresponding to the pigment concentration of 11.5% in the ink) and the neutralizing agent 0 were placed in the production container. .77 parts (5N sodium hydroxide solution manufactured by Wako Pure Chemical Industries, Ltd.) and 19.5 parts of a dispersion liquid of water-insoluble polymer particles containing no pigment obtained in Production Example 2 (polymer concentration in ink 8.0) %, Solid content concentration 41%) was added, and the mixture was stirred at 150 rpm.
Furthermore, 7 parts of diethylene glycol monoisobutyl ether, 1.0 part of silicone-based surfactant (manufactured by Shin-Etsu Chemical Co., Ltd., trade names: KF-6011, PEG-11 methyl ether dimethicone) and 1.0 part of acetylene glycol-based surfactant. (Manufactured by Shin-Etsu Chemical Co., Ltd., trade name: Surfactant 104PG50, 2,4,7,9-tetramethyl-5-decine-4,7-diol, effective content 50%, propylene glycol solution), thickener Add 0.8 parts (manufactured by ADEKA Co., Ltd., trade name: Adecanol UH-420, 30% effective aqueous solution) and 15.4 parts of ion-exchanged water, stir for 30 minutes at room temperature, and then use a stainless wire net (200). It was filtered with a mesh) to obtain ink 1.

The symbols in Table 1 indicate the following.
-IBDG: Diethylene glycol monoisobutyl ether (manufactured by Wako Pure Chemical Industries, Ltd., boiling point 220 ° C., SP value 8.7)
-MFG: Propylene glycol monomethyl ether (manufactured by Wako Pure Chemical Industries, Ltd., boiling point 121 ° C, SP value 10.4)
-BG: Ethylene glycol monobutyl ether (manufactured by Wako Pure Chemical Industries, Ltd., boiling point 171 ° C., SP value 9.8)
-IPA: Isopropyl alcohol (manufactured by Wako Pure Chemical Industries, Ltd., boiling point 88 ° C, SP value 11.5)
-DEE: Diethyl ether (manufactured by Wako Pure Chemical Industries, Ltd., boiling point 35 ° C., SP value 7.6)
-BTG: Triethylene glycol monobutyl ether (manufactured by Wako Pure Chemical Industries, Ltd., boiling point 271 ° C., SP value 9.6)

Preparation Examples 2 to 10 (preparation of inks 2 to 10)
Inks 2 to 10 were obtained in the same manner as in Preparation Example 1 except that the compounding formulation of Preparation Example 1 was changed to the conditions shown in Table 1.

Example 1
Using the ink of Preparation Example 1, printing was performed on the corona discharge-treated surface of a biaxially stretched polypropylene film (manufactured by Futamura Chemical Co., Ltd., trade name: FOR-AQ # 20, laminate grade, thickness 20 μm). Printing is performed by gravure roll A (manufactured by Nabe Process Co., Ltd., laser plate making method, roll diameter 200 mm, roll length 1100 mm, gravure 250 lines, cell depth 8 μm, paper polishing treatment # 1000) and doctor blade (manufactured by Echo Blade Co., Ltd., Printing with a gravure printing machine (Okazaki Machinery Co., Ltd., gravure 3-color test machine) equipped with a ceramic composite doctor, plating: nickel / ceramic composite type, Vickers hardness 850 Hv, plating thickness 10 μm, cutting edge thickness 90 μm, parallel blade) Speed: 75 m / min, drying temperature 70 ° C, finisher roll material NBR, finisher roll pressure 0.3 MPa, finisher rotation speed 15% with respect to 100% gravure roll, contact pressure between doctor blade and gravure roll Printing was performed under the conditions of 0.15 MPa, the nip roller material NBR, and the contact pressure of the nip roll in contact with the printing substrate of 0.15 MPa (see FIG. 1).

Example 2-5, Reference Example 6-7, Example 8-14, Comparative Examples 1-9
The procedure was the same as that of Example 1 except that the conditions of Example 1 were changed to the conditions shown in Tables 2 and 3.

The details of the printed base materials in Tables 2 and 3 are as follows.
-OPP: Futamura Chemical Co., Ltd., OPP film, FOR-AQ # 20, laminate grade, corona treatment, thickness 20 μm
-PET: Futamura Chemical Co., Ltd., PET film, FE2001 # 12, corona treatment, thickness 12 μm
-CPP: Futamura Chemical Co., Ltd., CPP film, FHK2 # 20, laminate grade, corona treatment, thickness 20 μm
・ NY: Toyobo Co., Ltd., nylon film, Harden film, N1100 # 25, general type, corona treatment, thickness 25 μm
・ PS: Asahi Kasei Chemicals Co., Ltd., OPS film, GM # 14, general type, thickness 14 μm
-PE: Futamura Chemical Co., Ltd., LLDPE film, LL-UL # 40, corona treatment, thickness 40 μm

<Ink evaluation>
For the obtained ink, the ink transfer rate and the plate fog density were evaluated by the following evaluation methods. The results are shown in Tables 2 and 3.

<Evaluation method of ink transfer rate>
A 100 mm × 100 mm solid printed matter printed with 100% halftone dots was cut, the initial mass was measured, and the ink was removed with Bencotton using acetone. Then, the printed matter was dried with warm air at 40 ° C. for 12 hours, and the mass was measured. The difference between the initial mass and the mass after ink removal and drying was taken as the ink transfer amount. The ink transfer rate (%) was calculated from the cell (concave) volume of the gravure roll plate surface and the amount of ink transfer from the following formula, and evaluated according to the following criteria.
Ink transfer rate (%) = (ink transfer amount / gravure cell volume) x 100
(Evaluation criteria)
⊚: Ink transfer rate 61-70%
◯: Ink transfer rate 56 to 60%
Δ: Ink transfer rate 51-55%
X: Ink transfer rate 40 to 50%
△ The above is a level where there is no practical problem.

<Evaluation method of plate fog concentration>
Using a spectrophotometer (manufactured by Gretag Macbeth, trade name: SpectroEye), cut out 10 unprinted non-image areas, stack 10 of them, and measure in the density measurement mode (DIN, Abs). The results were evaluated according to the following criteria.
(Evaluation criteria)
⊚: Plate cover concentration 0.30 to 0.35
◯: Plate cover concentration 0.36 to 0.40
Δ: Plate cover concentration 0.41 to 0.45
X: Plate cover concentration 0.46 to 0.55
△ The above is a level where there is no practical problem.

From Tables 2 and 3, according to the printing methods of Examples 1 to 5, 8 to 14, the ink transfer rate is high and stable in continuous printing as compared with the printing methods of Reference Examples 6 to 7 and Comparative Examples 1 to 9. It can be seen that high-quality printed matter can be obtained by suppressing plate fog at the same time as being able to perform high-quality printing.

1: Gravure printing machine 10: Ink pan 11: Finisher roll 12: Gravure roll 13: Doctor blade 14: Nip roll 15: Printing base material supply roll 16: Printing base material winding roll 20: Printing base material

Claims (5)

A gravure printing method in which water-based ink is stored in an ink pan and printed on a resin film substrate using a nip roll.
The water-based ink contains pigments, polymers, organic solvents, surfactants, and water.
The SP value of the organic solvent is 8 or more and less than 9.8, and the SP value is 8 or more and less than 9.8.
Organic solvent is an organic solvent having a boiling point of 100 ° C. exceeding 260 ℃ less, the content of that is, in the aqueous ink is 10 mass% or less than 0.3 wt%,
The surfactant contains an acetylene glycol-based surfactant, and the surfactant contains an acetylene glycol-based surfactant.
The rubber hardness of the nip roll is 62 ° or more and 82 ° or less.
A gravure printing method in which the contact pressure at which the nip roll comes into contact with the printing substrate is 0.04 MPa or more and 0.35 MPa or less. The gravure printing method according to claim 1, wherein the organic solvent is at least one selected from diethylene glycol monoisobutyl ether and triethylene glycol monomethyl ether. The gravure printing method according to claim 1 or 2 , wherein the material used for the nip roll is one or more selected from acrylonitrile-butadiene rubber, ethylene propylene rubber, and butyl rubber. The gravure printing method according to any one of claims 1 to 3, wherein the printing substrate is a resin film and the thickness thereof is 10 μm or more and 100 μm or less. The gravure printing method according to any one of claims 1 to 4 , wherein the content of the surfactant is 0.1% by mass or more and 10% by mass or less.

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