Lithographic printing ink and method for producing printed matter

Abstract

To provide an ink for lithographic printing capable of obtaining a printed matter excellent in registration accuracy; and to provide a production method of a printed matter.SOLUTION: An ink for lithographic printing contains (a) a resin and (b) a compound having two or more reactive groups, in which an integral value of normal force (stress in a normal direction) measured by a rheometer is 200 N-s-s or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a lithographic printing ink and a method for producing a printed matter using the same. [Background technology]

[0002] Lithographic printing is a widely used printing method that provides high-speed, large-volume, and inexpensive printed materials. In recent years, in response to environmental issues, there has been a demand for reducing the volatile components contained in ink. For this reason, the use of actinic radiation-curable inks, which do not contain volatile components and cure instantly when exposed to actinic radiation, is being promoted. In addition to their environmental benefits, actinic radiation-curable inks can shorten the drying process, thereby improving the productivity of lithographic printing.

[0003] In recent years, there has been a demand for small-lot production, particularly for film-printed materials, due to the diversification of packaging, and there has been a shift from expensive gravure printing to lithographic printing for small lots.

[0004] With regard to film printing using lithographic printing, for example, there have been proposed lithographic printing inks characterized by containing (a) a pigment and (b) a resin having an ethylenically unsaturated group and a hydrophilic group, and methods for producing printed matter that include a step of applying the lithographic printing ink to a substrate such as a plastic film and irradiating it with active energy rays (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2017 / 47817 Summary of the Invention [Problem to be solved by the invention]

[0006] The films used for film printing are often around 10 to 50 μm thick, and because they are prone to breaking and stretching, there is a limit to the tension that can be applied for printing. In lithographic printing, the ink transferred to the blanket is transferred to the film by cleavage within the ink layer, but when the film tension is low, the ink cohesive force can cause the film to shift position, resulting in insufficient register accuracy, especially when the printing area is large.

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a lithographic printing ink and a method for producing a printed matter that can produce a printed matter with excellent register accuracy. [Means for solving the problem]

[0008] The present invention relates to a polymerizable composition comprising: (a) a resin; and (b) a compound having two or more reactive groups. and (c) compounds having one or less reactive groups. The integral value of normal force (stress in the normal direction) measured by a rheometer is 200 N·s·s or less. the difference between the solubility parameter of the (b) compound having two or more reactive groups and the solubility parameter of the (c) compound having one or less reactive groups is 3.5 or more and 8.2 or less, the (c) compound having one or less reactive groups has a molecular weight of 250 or more and 1,000 or less and a melting point of 25°C or more, the (b) compound having two or more reactive groups comprises a polyfunctional (meth)acrylate having a hydroxyl group and / or an ethylene oxide-modified group, and the (c) compound having one or less reactive groups comprises an alkyl (meth)acrylate having an aliphatic skeleton having 13 to 22 carbon atoms; It is an ink for lithographic printing. [Effects of the Invention]

[0009] The lithographic printing ink of the present invention makes it possible to obtain printed matter with excellent register accuracy. DETAILED DESCRIPTION OF THE INVENTION

[0010] First, the lithographic printing ink of the present invention will be described.

[0011] As mentioned above, in lithographic printing, ink transferred to the blanket is transferred to the film by cleavage within the ink layer. When lithographic printing is performed on film, there is a limit to the tension that can be applied to the film, and the cohesive force of the ink can easily cause the film to shift position. This problem becomes more pronounced as the printing area becomes larger. For example, when printing on transparent film, white ink or transparent ink such as varnish may be printed over the entire film or image to improve the appearance of the image. In such film printing with large printing areas, there is a strong demand for improved registration accuracy.

[0012] To improve registration accuracy even at low tensions, the inventors focused on ink releasability from the blanket and focused on the integral of normal force (stress in the normal direction) measured with a rheometer (hereinafter sometimes referred to as the "normal force integral") as an index of ink cohesion, which is related to the ease of cleavage within the ink layer. Specifically, the lithographic printing ink of the present invention (hereinafter sometimes referred to as the "ink") is characterized by a normal force integral of 200 N·s·s or less. The normal force integral represents the stress (ink cohesion) exerted when the ink is peeled from the blanket during printing. The smaller this value, the weaker the ink cohesion and the easier it is to peel from the blanket. If the normal force integral exceeds 200 N·s·s, the ink cohesion is high and the ink is difficult to peel from the blanket, which makes film misalignment more likely and reduces registration accuracy. The normal force integral is preferably 180 N·s·s or less, and more preferably 150 N·s·s or less. On the other hand, the integral value of the normal force is preferably 50 N·s·s or more from the viewpoint of suppressing background smearing.

[0013] Here, the integral value of normal force in the present invention is measured using a rheometer under the following conditions: 0.35 ml of ink is weighed out using an ink pipette, and a clearance of 0.1 mm is adjusted using parallel plates with a diameter of 25 mm. After removing the ink that has spilled from the plates, normal force is measured at a temperature of 25°C using the following program sequence. These conditions were selected to simulate the general state of ink during printing. (1) Leave it for 60 seconds. (2) The specimen is subjected to vibration motion for 60 seconds at a constant strain of 40% and a constant angular frequency of 100 rad / s. (3) Leave it for 60 seconds. (4) Narrow the clearance at a speed of 0.01 mm / s for 5 seconds. (5) The clearance is increased at a rate of 0.01 mm / s for 25 seconds, while the normal force is measured at 0.05 second intervals.

[0014] In (5) above, the absolute value of the normal force (unit: N s) integrated over time (unit: s) for the section from when the normal force reaches 0 N s to the end of measurement (25 seconds later) is the integral value of the normal force (unit: N s s).

[0015] One way to keep the normal force integral of the ink at 200 N·s·s or less is to form a microphase-separated structure. It is believed that inks with a microphase-separated structure can reduce ink cohesion because the microseparated phases promote cleavage when the ink is peeled from the blanket. More specifically, one way to keep the normal force integral of the ink within the above range is to use a preferred composition, as described below.

[0016] Ink having a microphase-separated structure exhibits a glass transition point or melting point derived from each phase in differential scanning calorimetry. In the present invention, we focused on the glass transition point and melting point as indicators of the microphase-separated structure. The ink of the present invention preferably has two or more glass transition points and / or melting points in the range of -90°C to 100°C, which allows the normal force integral to be easily adjusted to the aforementioned preferred range and further improves registration accuracy. The ink may have two or more glass transition points, two or more melting points, or one or more glass transition points and one or more melting points within the above range.

[0017] The glass transition point and melting point of the ink in the present invention are measured using a differential scanning calorimeter (DSC) under the following conditions: 5 mg of ink is weighed into an aluminum pan, and using an empty aluminum pan as a reference and liquid nitrogen for cooling, the calorific value is measured according to the following program sequence: (1) After adjusting the temperature to 30°C, increase the temperature from 30°C to 100°C at a rate of 10°C / min. (2) Hold at 100°C for 5 minutes. (3) The temperature is decreased from 100°C to -90°C at a rate of 10°C / min. (4) Keep at -90°C for 5 minutes. (5) The temperature is increased from -90°C to 100°C at a rate of 10°C / min.

[0018] In the above (5), if a baseline shift is observed, the temperature at the intersection of the low-temperature baseline and the tangent line at the inflection point is taken as the glass transition point. If an endothermic peak is observed, the temperature at the peak top is taken as the melting point.

[0019] The microphase-separated structure can be formed, for example, by using a preferred composition as described below.

[0020] The ink of the present invention contains (a) a resin and (b) a compound having two or more reactive groups. The inclusion of (a) the resin can impart suitable fluidity to the ink, and the inclusion of (b) the compound having two or more reactive groups can impart the ink with the property of being cured by actinic energy rays.

[0021] Examples of the (a) resin include acrylic resin, styrene-acrylic resin, styrene-maleic acid resin, rosin-modified maleic acid resin, rosin-modified acrylic resin, epoxy resin, polyester resin, polyurethane resin, and phenolic resin. Two or more of these may be contained. Among these, acrylic resin, styrene-acrylic resin, and styrene-maleic acid resin are preferred in terms of ease of monomer availability, ease of synthesis, compatibility with other components in the ink, pigment dispersibility, and the like.

[0022] The weight-average molecular weight of the (a) resin is preferably 40,000 or less, which can suppress entanglement of molecular chains, further reduce ink cohesive force, and further improve register accuracy. On the other hand, the weight-average molecular weight of the (a) resin is preferably 5,000 or more, which can improve pigment dispersibility, further reduce ink cohesive force, and further improve register accuracy. The weight-average molecular weight of the (a) resin is more preferably 15,000 or more.

[0023] Here, the weight-average molecular weight of the (a) resin in the present invention is measured by gel permeation chromatography (GPC) using a column consisting of TSKgel SuperHM-H (manufactured by Tosoh Corporation), TSKgel SuperHM-H (manufactured by Tosoh Corporation), and TSKgel SuperH2000 (manufactured by Tosoh Corporation) connected in this order, with tetrahydrofuran as the mobile phase.

[0024] The acid value of the (a) resin is preferably 75 mgKOH / g or more, which improves pigment dispersibility and reduces ink cohesive force, thereby improving register accuracy. On the other hand, the acid value of the (a) resin is preferably 150 mgKOH / g or less, which reduces interactions between resins, reduces ink cohesive force, and improves register accuracy.

[0025] Here, the acid value of the (a) resin in the present invention is measured by the method described in Section 3.1 of the test method of JIS K 0070:1992, neutralization titration method.

[0026] The content of (a) resin in the ink is preferably 6% by weight or more, which keeps the viscosity at a moderate level, makes it easy to adjust the integral value of the ink's normal force to 50 N·s·s or more, and suppresses background scumming. On the other hand, the content of (a) resin is preferably 15% by weight or less, which suppresses entanglement of molecular chains, further reduces ink cohesion, and further improves register accuracy. The reactive group in the compound having two or more (b) reactive groups refers to a functional group that undergoes a polymerization reaction when exposed to active energy rays, and examples thereof include an epoxy group and an ethylenically unsaturated group. Examples of the ethylenically unsaturated group include an acrylic group, a methacrylic group, and a vinyl group. The compound having two or more (b) reactive groups of the present invention may be a monomer or an oligomer, and in the case of an oligomer, it is a polymer having a weight-average molecular weight of 5,000 or less.

[0027] Examples of the monomer having two or more reactive groups include monomers having two reactive groups such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, 1,3 butylene glycol di(meth)acrylate, 1,6 hexanediol di(meth)acrylate, 1,9 nonanediol di(meth)acrylate, and 1,10-decanediol di(meth)acrylate. 1,11-Undecanediol di(meth)acrylate, 1,12-Dodecanediol di(meth)acrylate, 1,13-Tridecanediol di(meth)acrylate, 1,14-Tetradecanediol di(meth)acrylate, 1,15-Pentadecanediol di(meth)acrylate, 1,16-Hexadecanediol di(meth)acrylate, 1,17-Heptadecanediol di(meth)acrylate, 1,18-Octadecanediol di(meth)acrylate, 4-Methyl-1,10-decanediol di(meth)acrylate, 4-Ethyl-1,Examples of the reactive groups include 10-decanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, linoleic acid, glycidyl (meth)acrylate, ethylene glycol diglycidyl ether, and their ethylene oxide adducts and propylene oxide adducts. Examples of the reactive groups include trimethylolpropane tri(meth)acrylate, glycerin tri(meth)acrylate, isocyanuric acid tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and their ethylene oxide adducts and propylene oxide adducts. Examples of monomers having four reactive groups include pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, diglycerin tetra(meth)acrylate, and their ethylene oxide adducts and propylene oxide adducts. Examples of monomers having five reactive groups include dipentaerythritol penta(meth)acrylate, and their ethylene oxide adducts and propylene oxide adducts. Examples of monomers having six reactive groups include dipentaerythritol hexa(meth)acrylate, and their ethylene oxide adducts and propylene oxide adducts. Two or more of these may be contained. Among these, (meth)acrylate is more preferred from the viewpoint of improving the dispersibility of the (a) resin, further reducing the ink coagulation force, and further improving registration accuracy. Here, "(meth)acrylate" is a general term for acrylate and methacrylate.

[0028] Examples of oligomers having two or more reactive groups include polymers of the monomers exemplified above as monomers having two or more reactive groups, and two or more of these may be contained.

[0029] Among these, polyfunctional (meth)acrylates having hydroxyl groups and / or ethylene oxide-modified groups are preferred. By combining them with alkyl (meth)acrylates having an aliphatic skeleton with 13 to 22 carbon atoms as compounds having one or less reactive groups (c) as described below, a stable microphase separation structure can be easily formed, and the normal force integral value can be easily adjusted to fall within the preferred range described above, thereby further improving registration accuracy.

[0030] The hydroxyl value of the (b) compound having two or more reactive groups is preferably 100 mgKOH / g or more, which improves the dispersibility of the (a) resin and pigment, further reduces the ink coagulation force, and further improves register accuracy. On the other hand, the hydroxyl value of the (b) compound having two or more reactive groups is preferably 160 mgKOH / g or less, which reduces the interaction between compounds having two or more reactive groups, further reduces the ink coagulation force, and further improves register accuracy. When two or more types of (b) compounds having two or more reactive groups are contained, it is preferable that the hydroxyl value of at least one of them is within the above range.

[0031] Here, the hydroxyl value of (b) the compound having two or more reactive groups in the present invention is measured by the method described in Section 7.1 of the test method of JIS K 0070:1992, neutralization titration method.

[0032] The content of (b) compounds having two or more reactive groups in the ink is preferably 35% by weight or more, which improves the dispersibility of (a) resins and pigments, further reduces ink cohesive force, and further improves register accuracy. On the other hand, the content of (b) compounds having two or more reactive groups is preferably 70% by weight or less, which maintains a moderately high viscosity and suppresses background scumming. The content of (b) compounds having two or more reactive groups is more preferably 49% by weight or less.

[0033] The ink of the present invention preferably further contains (c) a compound having one or less reactive groups. (c) The compound having one or less reactive groups acts as an aid to reduce ink cohesion. The reactive group in (c) the compound having one or less reactive groups has the same meaning as the reactive group in (b) the compound having two or more reactive groups, and the compound may or may not have one reactive group.

[0034] (c) Examples of compounds having one or less reactive groups include compounds having one reactive group, such as methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, butyl(meth)acrylate, pentyl(meth)acrylate, hexyl(meth)acrylate, heptyl(meth)acrylate, octyl(meth)acrylate, nonyl(meth)acrylate, decyl(meth)acrylate, and undecyl(meth)acrylate. Acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, heneicosyl (meth)acrylate, docosyl (meth)acrylate, isopropyl (meth)acrylate acrylate, isobutyl (meth)acrylate, isopentyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, isoundecyl (meth)acrylate, isododecyl (meth)acrylate, isotridecyl (meth)acrylate, isotetradecyl (meth)acrylate, isopentadecyl (meth)acrylate, isohexadecyl (meth)acrylate, isoheptadecyl (meth)acrylate, isooctadecyl (meth)acrylate, isononadecyl (meth)acrylate, isoeicosyl (meth)acrylate, isohenicosyl (meth)acrylate, isodocosyl (meth)acrylate, oleic acid, hexyl glycidyl ether, ethylene oxide adducts thereof, and propylene oxide adducts thereof. Among these, (meth)acrylates are more preferred from the viewpoint of improving the dispersibility of the (a) resin, further reducing the ink cohesive force, and further improving the register accuracy.Compounds having no reactive group include hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, eicosane, henicosane, docosane, acetone, tetrahydrofuran, water, methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, and undecane. Canol, dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, nonadecanol, eicosanol, henicosanol, docosanol, 2-propanol, 2-butanol, 2-pentanol, 2-hexanol, 2-heptanol, 2-octanol, 2-nonanol, 2-decanol, 2-undecanol, 2-dodecanol, 2-tridecanol, 2-tetradecane Canol, 2-pentadecanol, 2-hexadecanol, 2-heptadecanol, 2-octadecanol, 2-nonadecanol, 2-eicosanol, 2-heneicosanol, 2-docosanol, methanoic acid, ethanoic acid, propanoic acid, butanoic acid, pentanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonanoic acid Examples include decanoic acid, eicosanoic acid, heneicosanoic acid, docosanoic acid, phenol, 2-methylphenol, 3-methylphenol, 4-methylphenol, benzoic acid, 2-methylbenzoic acid, 3-methylbenzoic acid, 4-methylbenzoic acid, ethylene glycol, propylene glycol, glycerin, 4-methoxyphenol, polyethylene glycol, polypropylene glycol, ethylene oxide adducts thereof, and propylene oxide adducts thereof. Two or more of these may be contained.

[0035] Among these, alkyl(meth)acrylates having an aliphatic skeleton with 13 to 22 carbon atoms are preferred. Combining them with a polyfunctional (meth)acrylate having a hydroxyl group and / or an ethylene oxide-modified group as the compound having two or more reactive groups (b) facilitates stable formation of a microphase-separated structure, making it possible to easily adjust the normal force integral value within the preferred range and further improve registration accuracy. The carbon number of the aliphatic skeleton is more preferably 14 or more, and even more preferably 16 or more, because this facilitates moderately promoting the progression of phase separation and stably forming a microphase-separated structure. On the other hand, the carbon number of the aliphatic skeleton is more preferably 21 or less, and even more preferably 20 or less, because this facilitates moderately suppressing the progression of phase separation and stably maintaining a microphase-separated structure.

[0036] The difference between the solubility parameter (hereinafter sometimes referred to as "SP value") of (b) a compound having two or more reactive groups and the SP value of (c) a compound having one or less reactive groups is preferably 3.5 or more, which facilitates the stable formation of a microphase-separated structure, allowing the normal force integral value to be easily adjusted to the aforementioned preferred range and further improving registration accuracy. The difference in SP values ​​is more preferably 3.9 or more, and even more preferably 4.3 or more. On the other hand, the difference in SP values ​​is preferably 8.2 or less, which moderately suppresses the progression of phase separation and facilitates the stable maintenance of a microphase-separated structure, allowing the normal force integral value to be easily adjusted to the aforementioned preferred range and further improving registration accuracy. The difference in SP values ​​is more preferably 7.2 or less, and even more preferably 6.2 or less.

[0037] Here, the solubility parameter in the present invention is the solubility parameter (unit: J / cm) calculated by the Fedors method described in Polymer Handbook Third Edition (A Wiley-Interscience publication, 1989). 3 ) 1 / 2) is shown. When two or more compounds having two or more (b) reactive groups are contained, the SP value is calculated by weight averaging the SP value and content of each compound. For example, when two compounds having two or more (b) reactive groups are contained, namely, compound A (SP value: 11.5, content: 30 parts by weight) and compound B (SP value: 10, content: 20 parts by weight), the SP value of the (b) compound having two or more reactive groups is calculated as (11.5 x 30 + 10 x 20) ÷ (30 + 20) = 10.9.

[0038] When two or more (c) compounds having one or less reactive groups are contained, it is preferable that the difference in SP value between at least one of them and the SP value of the (b) compound having two or more reactive groups is within the above-mentioned range, and it is more preferable that all of the differences in SP value between each of them and the SP values ​​of the (b) compounds having two or more reactive groups are within the above-mentioned range.

[0039] The molecular weight of the (c) compound having one or less reactive groups is preferably 250 or more, which moderately promotes the progression of phase separation and facilitates the stable formation of a microphase-separated structure, thereby allowing the normal force integral to be easily adjusted to the aforementioned preferred range and further improving registration accuracy. The molecular weight is more preferably 275 or more, and even more preferably 300 or more. On the other hand, the molecular weight of the (c) compound having one or less reactive groups is preferably 1,000 or less, which moderately suppresses the progression of phase separation and facilitates the stable maintenance of a microphase-separated structure, thereby allowing the normal force integral to be easily adjusted to the aforementioned preferred range and further improving registration accuracy. The molecular weight is more preferably 700 or less, and even more preferably 500 or less.

[0040] (c) The melting point of the compound having one or less reactive groups is preferably 25°C or higher, which moderately suppresses the progression of phase separation during storage and printing and makes it easy to maintain a microphase-separated structure, making it possible to easily adjust the normal force integral value to the aforementioned preferred range and further improve register accuracy. A melting point of 27°C or higher is more preferable.

[0041] Here, the melting point of the compound (c) having one or less reactive groups is measured in the same manner as the melting point of the ink described above.

[0042] The content of the (c) compound having one or less reactive groups is preferably 1 part by mass or more per 100 parts by mass of the (b) compound having two or more reactive groups. This moderately promotes the progression of phase separation and facilitates the stable formation of a microphase-separated structure, making it possible to easily adjust the normal force integral value within the aforementioned preferred range and further improve registration accuracy. The content of the (c) compound having one or less reactive groups is more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more. On the other hand, the content of the (c) compound having one or less reactive groups is preferably 7 parts by mass or less. This moderately suppresses the progression of phase separation and facilitates the stable maintenance of a microphase-separated structure, making it possible to easily adjust the normal force integral value within the aforementioned preferred range and further improve registration accuracy. The content of the (c) compound having one or less reactive groups is more preferably 6 parts by mass or less, and even more preferably 5 parts by mass or less.

[0043] The ink of the present invention preferably further contains a pigment. Examples of pigments include organic pigments and inorganic pigments. Examples of organic pigments include phthalocyanine pigments, soluble azo pigments, insoluble azo pigments, lake pigments, quinacridone pigments, isoindoline pigments, threne pigments, and metal complex pigments. More specific examples include phthalocyanine blue, phthalocyanine green, azo red, monoazo red, monoazo yellow, disazo red, disazo yellow, quinacridone red, quinacridone magenta, and isoindoline yellow. Examples of inorganic pigments include titanium oxide, zinc oxide, alumina white, calcium carbonate, barium sulfate, oxide-coated glass, silicate minerals (mica), oxide-coated mica, oxide-coated metal particles, carbon black, and graphite. Two or more of these pigments may be contained.

[0044] The ink of the present invention can be used in various colors, such as chromatic inks such as indigo, red, and yellow, black ink, white ink, transparent ink, etc. Since a wide printing area is often required, transparent ink and white ink can be preferably used, and white ink can be particularly preferably used.

[0045] When the ink of the present invention is a transparent ink, the pigment is preferably an ionic compound such as calcium carbonate, barium sulfate, oxide-coated glass, or silicate mineral (mica) from the viewpoint of balancing transparency with misting resistance and background scumming prevention. When the ink of the present invention is a white ink, the pigment is preferably an ionic compound such as titanium oxide, zinc oxide, or alumina white. The interaction between the ionic compounds further reduces the ink cohesive force, making it easy to adjust the normal force integral value to the aforementioned preferred range, and further improving register accuracy.

[0046] The particle size of the white pigment for the white ink is preferably 200 nm or more and 300 nm or less.

[0047] The ink of the present invention preferably further contains a surfactant, which further improves the dispersibility of the pigment, further reduces the ink cohesive force, makes it easy to adjust the normal force integral value to fall within the aforementioned preferred range, and further improves register accuracy.

[0048] Examples of surfactants include "Anti-Terra" (registered trademark)-U, "Anti-Terra"-203 / 204, and "Disperbyk" (registered trademark)-101, 102, 103, 106, 107, 110, 111, 115, 118, 130, 140, 142, 145, 161, 162, 163, 164, 165, 166, 167, 168, 170, 171, 174, 180, 181, 182, 184, 185, 187, 190, 191, 192, 193, 199, 2000, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023, 2024, 2025, 2026, 2027, 2028, 2029, 2030, 2031, 2032, 2033, 2034, 2035, 2036, 2037, 2038, 2039, 2040, 2041, 2042, 2043, 2044, 2045, 2046, 2047, 2048, 2049, 2050, 2051, 2052, 2053, 2054, 2055, 205 001, 2008, 2009, 2010, 2012, 2013, 2015, 2022, 2025, 2026, 2050, 2055, 2060, 2061, 2070, 2096, 2150, 2151, 2152, 2155, 2163, 2164, 2200, 2205, 9067, 9076, "Bykumen" (registered trademark), "BYK" (registered trademark) - P104, P105, P104S, 240S, "Lactimon" (registered trademark), "EFKA" (registered trademark) 44, 46, 47 manufactured by Efka CHEMICALS, 48, 49, 54, 63, 64, 65, 66, 71, 701, 764, 766, "EFKAPOLYMER 100, 150, 400, 401, 402, 403, 450, 451, 452, 453, 745," manufactured by Kyoeisha Chemical Co., Ltd.; "FLOWLEN" (registered trademark) TG-710, "FLOWNON" (registered trademark) SH-290, SP-1000, "Polyflow No. 50E, No. 300," manufactured by Kusumoto Chemical Co., Ltd.; "DISPARLON" (registered trademark) 325, KS-860, 873SN, 874, 1401, #2150, #7004," manufactured by Kao Corporation; Examples include "Demol" (registered trademark) RN, N, MS, C, SN-B, EP, "Homogenol" (registered trademark) L-18, "Emulgen" (registered trademark) 920, 930, 931, 935, 950, 985, "Acetamine" (registered trademark) 24, 86, "Solsperse" (registered trademark) 5000, 13940, 17000, 24000GR, 32000, 33000, 39000, 41000, 53000 manufactured by Lubrizol, and "Ajisper" (registered trademark) PB821, 822, 824 manufactured by Ajinomoto Fine-Techno Co., Ltd. Two or more of these may be contained.

[0049] When the ink of the present invention is a white ink, (d) anionic surfactants are preferred among these, as they improve the dispersibility of white pigments such as titanium oxide, zinc oxide, and alumina white, thereby further reducing ink coagulation, easily adjusting the normal force integral value within the aforementioned preferred range, and further improving register accuracy. Examples of anionic surfactants include "Disperbyk" (registered trademark) 111 (manufactured by BYK Japan Co., Ltd.), sodium dodecylbenzenesulfonate, sodium laurate, sodium myristate, sodium palmitate, sodium stearate, sodium oleate, potassium laurate, potassium myristate, potassium palmitate, potassium stearate, potassium oleate, sodium N-stearoyl-L-glutamate, sodium N-stearoyl-N-methyl taurate, and sodium N-lauroyl-L-glutamate.

[0050] The content of the surfactant is preferably 1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the pigment.

[0051] Next, a method for producing the ink of the present invention will be described. The ink of the present invention can be obtained, for example, by mixing and dispersing (a) a resin, (b) a compound having two or more reactive groups, and optionally (c) a compound having one or less reactive groups, a pigment, a surfactant, and other components. Prior to mixing and dispersing, the components may be dissolved at 5 to 100°C, or degassed under vacuum or reduced pressure during and / or after mixing and dispersing. Examples of mixing equipment include agitators and kneaders such as a kneader, a three-roll mill, a ball mill, a planetary ball mill, a bead mill, a roll mill, an attritor, a sand mill, a gate mixer, a paint shaker, a homogenizer, and a planetary / revolutionary agitator.

[0052] Next, a method for producing a printed matter of the present invention will be described. The method for producing a printed matter of the present invention includes the step of transferring the ink of the present invention onto a substrate and the step of irradiating with active energy rays. Since the ink of the present invention is cured by irradiation with active energy rays, a printed matter having a cured ink film can be obtained by the step of irradiating with active energy rays.

[0053] First, the process of transferring the ink of the present invention onto a substrate will be described.

[0054] Examples of substrates include art paper, coated paper, cast paper, synthetic paper, newsprint, plastic film, plastic film-laminated paper, metal film, metal-vapor-deposited paper, and metal-vapor-deposited plastic film. Two or more of these may be used. Examples of plastic films include films made of polyethylene terephthalate, polyethylene, polyester, polyamide, polyimide, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, and the like. Examples of plastic film-laminated paper include those in which the aforementioned plastic films are laminated on paper. Examples of metal films include films made of zinc, copper, and the like. Examples of metal-vapor-deposited paper and metal-vapor-deposited plastic films include those in which the aforementioned metals or their oxides are vapor-deposited on paper or plastic film. Among these, plastic film, plastic film-laminated paper, metal film, metal-vapor-deposited paper, and metal-vapor-deposited plastic film do not absorb ink and therefore do not adhere to the ink due to ink absorption. Therefore, they are suitable for use in the present invention, in which the ink can be cured and adhered by irradiation with active energy rays.

[0055] The substrate may be subjected to an adhesion-facilitating treatment to improve the transferability of the ink to the substrate. Examples of adhesion-facilitating treatments include surface treatments such as primer application, corona discharge treatment, and plasma treatment.

[0056] When used for flexible packaging, the thickness of the substrate is preferably 10 μm or more and 30 μm or less.

[0057] The substrate may be either a sheet or a roll film. When a thin film is used for flexible packaging, it is preferable to use a roll film and transfer the film by roll-to-roll transfer.

[0058] The method for transferring the ink of the present invention to a substrate is preferably lithographic printing, and examples of lithographic printing include water-based printing and waterless printing.

[0059] The thickness of the ink transfer film on the substrate is preferably set to 0.1 to 50 μm after curing, which allows for both good print quality and reduced ink usage.

[0060] When transferring white ink onto a substrate, it is preferable to transfer the white ink two or more times, which improves the hiding power, reduces the amount of ink transferred per transfer, and further improves register accuracy.

[0061] Examples of methods for transferring ink multiple times include, in the case of transfer by printing, a wet-on-wet printing method, a dry-on-wet printing method, etc. Among these, the wet-on-wet printing method is preferred from the viewpoint of productivity.

[0062] Next, the step of irradiating with active energy rays will be described. By irradiating the ink transferred onto the substrate with active energy rays, the ink can be cured instantaneously. Examples of active energy rays include ultraviolet rays and electron beams, with electron beams being preferred from the viewpoint of improving curing properties and suppressing odor generation. Examples of ultraviolet ray irradiating devices include high-pressure mercury lamps, xenon lamps, metal halide lamps, and light-emitting diodes (LEDs). From the viewpoint of power saving, it is preferable to use ultraviolet rays (LED-UV) using light-emitting diodes that emit emission lines with wavelengths of 350 to 420 nm as a light source. As electron beams, energy rays of 100 to 500 eV are preferred. [Example]

[0063] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0064] <Ink raw materials> (a) Resin Resin: 0.55 equivalents of glycidyl methacrylate was added to the carboxyl groups of a copolymer consisting of 25% by mass of methyl methacrylate, 25% by mass of styrene, and 50% by mass of methacrylic acid to obtain Resin 1, which has ethylenically unsaturated groups and hydrophilic groups. The resulting resin had a weight-average molecular weight of 34,000, an acid value of 105 mgKOH / g, and an iodine value of 2.0 mol / kg. (b) Compounds with two or more reactive groups Monomer 1: a mixture of 65% by weight of pentaerythritol triacrylate and 35% by weight of pentaerythritol tetraacrylate (manufactured by MIWON, "Miramer" (registered trademark) M340), hydroxyl value 115 mg KOH / g, SP value as a mixture 22.7 (J / cm 3 ) 1 / 2 Monomer 2: Trimethylolpropane EO-modified triacrylate (MIWON, "Miramer" (registered trademark) M3190), hydroxyl value 10 mg KOH / g, solubility parameter 19.6 (J / cm 3 ) 1 / 2 Monomer 3: Dipentaerythritol hexaacrylate (MIWON, "Miramer" (registered trademark) M600), hydroxyl value 5 mg KOH / g, solubility parameter 21.3 (J / cm 3 ) 1 / 2 pigment Pigment 1: "Tipake" (registered trademark) CR58-2 (manufactured by Ishihara Sangyo Kaisha, Ltd.) Pigment 2: Carmine 6B 1483LT (manufactured by Dainichi Seika Color & Chemicals Co., Ltd.) (c) Compounds with one or less reactive groups Auxiliary agent 1: Octadecyl acrylate (Tokyo Chemical Industry Co., Ltd.), molecular weight 325, melting point 28°C, solubility parameter 17.8 (J / cm 3 ) 1 / 2 Auxiliary agent 2: Dodecyl acrylate (Tokyo Chemical Industry Co., Ltd.), molecular weight 240, melting point 4°C, solubility parameter 17.8 (J / cm 3 ) 1 / 2 (d) Anionic surfactants Surfactant 1: "Disperbyk" (registered trademark) 111 (manufactured by BYK Japan Co., Ltd.) others Surfactant 2: "Solsperse" (registered trademark) 54000 (manufactured by Lubrizol), a polymer surfactant.

[0065] <Analysis method for ink raw materials> (1) Weight average molecular weight The resin was diluted with tetrahydrofuran to a concentration of 0.25% by mass. The diluted solution was stirred at 100 rpm for 5 minutes using a mix rotor (MIX-ROTAR VMR-5, AS ONE Corporation) to dissolve the resin. The solution was then filtered through a 0.2 μm filter (Z227536-100EA, SIGMA). The resulting filtrate was subjected to gel permeation chromatography (GPC) using tetrahydrofuran as the mobile phase to measure the weight-average molecular weight of the resin. The GPC was performed using an HLC-8220 (Tosoh Corporation) and columns consisting of TSKgel SuperHM-H (Tosoh Corporation), TSKgel SuperHM-H (Tosoh Corporation), and TSKgel SuperH2000 (Tosoh Corporation) in this order. The measurement was performed using radioisotope detection. A calibration curve was prepared using polystyrene standards. The measurement conditions were an injection volume of 10 μL, an analysis time of 30 minutes, a flow rate of 0.4 mL / min, and a column temperature of 40°C.

[0066] (2) Acid value The acid value of the resin was measured by the neutralization titration method described in Section 3.1 of the test method of JIS K 0070:1992.

[0067] (3) Iodine value The iodine value of the resin was measured according to the method described in Section 6.0 of the test method of JIS K 0070:1992.

[0068] (4) Hydroxyl value The hydroxyl value of (b) a compound having two or more reactive groups was measured by the method described in Section 7.1 of the test method of JIS K 0070:1992, which is based on the neutralization titration method.

[0069] (5) Solubility parameter The SP values ​​(unit: J / cm) of the components (b) and (c) used in each example and comparative example were measured by the Fedors method described in the Polymer Handbook Third Edition (A Wiley-Interscience publication, 1989). 3 ) 1 / 2 ) was calculated. However, (b) the SP value of a compound having two or more reactive groups was calculated by weight averaging the SP value and content of each compound.

[0070] (6) Melting point The melting points of the components (c) used in the examples and comparative examples were measured by the method described in <Evaluation Methods> (2) below.

[0071] <Evaluation method> (1) Integral value of normal force (stress in the normal direction) A parallel plate (MEASURING PLATE PP25, diameter 25 mm) was attached to an Anton Paar MCR301 rheometer. 0.35 ml of the ink prepared in each example and comparative example was weighed out using an ink pipette and placed on the parallel plate, with the clearance adjusted to 0.1 mm. Any ink spilling over the plate was removed, and normal force was measured at 25°C using the following program sequence: (1) Leave it for 60 seconds. (2) The specimen is subjected to vibration motion for 60 seconds at a constant strain of 40% and a constant angular frequency of 100 rad / s. (3) Leave it for 60 seconds. (4) Narrow the clearance at a speed of 0.01 mm / s for 5 seconds. (5) The clearance is increased at a rate of 0.01 mm / s for 25 seconds, while the normal force is measured at 0.05 second intervals.

[0072] In (5) above, the absolute value of the normal force (unit: N·s) integrated over time (unit: s) for the period from when the normal force reached 0 N·s to the end of measurement (25 seconds later) was taken as the integral value of the normal force (stress in the normal direction) (unit: N·s·s).

[0073] (2) Glass transition point and melting point Using a differential scanning calorimeter (DSC6200) manufactured by Seiko Instruments Inc., 5 mg of the ink obtained in each of the Examples and Comparative Examples was weighed into an aluminum pan at a nitrogen flow rate of 40 mL / min and using liquid nitrogen for cooling. Using an empty aluminum pan as a reference, the calorific value was measured according to the following program sequence: (1) After adjusting the temperature to 30°C, increase the temperature from 30°C to 100°C at a rate of 10°C / min. (2) Hold at 100°C for 5 minutes. (3) The temperature is decreased from 100°C to -90°C at a rate of 10°C / min. (4) Keep at -90°C for 5 minutes. (5) The temperature is increased from -90°C to 100°C at a rate of 10°C / min.

[0074] In the above (5), if a baseline shift was observed, the temperature at the intersection of the low-temperature baseline and the tangent line at the inflection point was taken as the glass transition point. If an endothermic peak was observed, the temperature at the peak top was taken as the melting point.

[0075] (3) Register accuracy and background scumming <Preparation of crimson ink for lithographic printing> 15% by mass of the aforementioned resin, 45.0% by mass of Monomer 1, 20.0% by mass of Monomer 2, and 2.0% by mass of Monomer 3 were weighed out and heated at 95°C for 390 minutes while stirring at 500 rpm using a disperser blade to obtain a varnish. 18.0% by mass of Pigment 2 was added to the obtained varnish, and the mixture was passed five times using a three-roll mill "EXAKT" (registered trademark) M-80S (manufactured by EXAKT) at a gap of 1 to obtain a crimson ink for lithographic printing.

[0076] <Lithographic printing> A waterless lithographic printing plate (TAN-E, manufactured by Toray Industries, Inc.) measuring 1,070 mm in width (width direction) and 674 mm in length (printing direction) and having a 0.1 mm line-thick cross (register mark) for checking register accuracy positioned at the center in the printing direction and 50 mm from both ends of the plate in the width direction was placed on the first cylinder of a flexographic hybrid printing press (CI-8, manufactured by COMEXI). A waterless lithographic printing plate (TAN-E, manufactured by Toray Industries, Inc.) measuring 1,070 mm horizontally (widthwise) and 674 mm vertically (printing direction), with a 100% solid image area measuring 900 mm horizontally (widthwise) and 500 mm vertically (printing direction) at the center of the plate, and with 0.1 mm line-thick cross (register mark) marks for checking register accuracy positioned at the center in the printing direction and 50 mm from each end of the plate in the widthwise direction, was placed on the sixth and seventh cylinders of the flexographic hybrid printing press. The crimson ink for lithographic printing obtained by the above method was placed on the first cylinder, and the white ink for lithographic printing obtained in each of the Examples and Comparative Examples was placed on the sixth and seventh cylinders.

[0077] The base material was polyester film PTM12 (Unitika Ltd., 12 μm thick), and the ink feed rate for cylinder 1 was 5%, for cylinders 6 and 7, 40%, the chiller temperature for the impression cylinder was set at 25°C, and the chillers for the oscillating roller and ink fountain were set at 28°C. Using a T414 blanket (Kinyosha, 1.95 mm thick), the wet-on-wet printing method was used with lithographic red ink and lithographic white ink at a speed of 100 m / min. After printing all the inks, the printer was irradiated with 110 kV, 40 kGy of electron beams using the electron beam irradiation device attached to the printing press to cure the inks and obtain a print.

[0078] During printing, the cross (register mark) marks for checking register accuracy for each color were aligned in the same position, and printing was continued without any adjustments. After 30 seconds, the distance between the red cross (register mark) mark and the white cross (register mark) mark that was furthest from the red cross (register mark) mark was measured for the printed product, and the register accuracy was evaluated according to the following criteria. Distance between register marks exceeding 0.3mm: Insufficient Distance between registration marks: over 0.2 mm and 0.3 mm or less: Fairly good Distance between register marks more than 0.1mm and less than 0.2mm: Good Distance between registration marks 0.1 mm or less: Very good After 120 seconds, the non-printing areas of the print were visually inspected to evaluate the presence or absence of scumming due to the white ink.

[0079] [Example 1] <Preparation of white ink> Components (a) and (b) listed in Table 1 were weighed out and heated at 95°C for 390 minutes while stirring at 500 rpm using a disperser blade to obtain a varnish. The pigment, components (c) and (d) listed in Table 1 were added to the obtained varnish, and the mixture was passed through a three-roll mill "EXAKT" (registered trademark) M-80S (manufactured by EXAKT) five times at a gap of 1 to obtain a white ink for lithographic printing. The obtained white ink for lithographic printing was evaluated using the methods described above, and the results are shown in Table 1.

[0080] [Examples 2 to 10, Comparative Example 1] <Preparation of white ink> White inks for lithographic printing were obtained in the same manner as in Example 1, except that the composition of the white ink was changed as shown in Table 1. The resulting lithographic printing inks were evaluated using the methods described above, and the results are shown in Table 1.

[0081] [Table 1]

Claims

1. a lithographic printing ink comprising (a) a resin, (b) a compound having two or more reactive groups, and (c) a compound having one or less reactive groups, wherein the integrated value of normal force (stress in the normal direction) measured with a rheometer is 200 N s s or less, the difference between the solubility parameter of the (b) compound having two or more reactive groups and the solubility parameter of the (c) compound having one or less reactive groups is 3.5 or more and 8.2 or less, the molecular weight of the (c) compound having one or less reactive groups is 250 or more and 1,000 or less and the melting point is 25°C or higher, the (b) compound having two or more reactive groups comprises a polyfunctional (meth)acrylate having a hydroxyl group and / or an ethylene oxide-modified group, and the (c) compound having one or less reactive group comprises an alkyl (meth)acrylate having an aliphatic skeleton having from 13 to 22 carbon atoms.

2. 2. The lithographic printing ink according to claim 1, which has a total of two or more glass transition points and / or melting points in the range of -90°C or higher and 100°C or lower.

3. A lithographic printing ink as described in claim 1 or 2, wherein the content of the compound (c) having one or less reactive groups is 1 part by mass or more and 7 parts by mass or less per 100 parts by mass of the compound (b) having two or more reactive groups.

4. A lithographic printing ink described in any one of claims 1 to 3, which is a white ink.

5. A lithographic printing ink as described in claim 4, further comprising (d) an anionic surfactant.

6. A method for producing a printed matter, comprising the steps of transferring the lithographic printing ink described in any one of claims 1 to 5 onto a substrate and irradiating it with active energy rays.

7. A method for producing a printed matter as described in Claim 6, wherein the active energy rays are electron beams.

8. A method for producing a printed matter as described in claim 6 or 7, comprising a step of applying the lithographic printing ink as described in claim 4 or 5 two or more times.

9. A method for producing a printed matter described in any one of claims 6 to 8, which is printed using a wet-on-wet printing method.

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