Black gravure printing ink composition

Abstract

To provide a black gravure printing ink composition that achieves excellent dispersibility and favorable doctor cut-off.SOLUTION: A black gravure printing ink composition comprises carbon black, a binder resin, a dispersant, a dispersion aid, and an organic solvent, wherein the binder resin includes a cellulose-based resin, the dispersant includes a basic dispersant, the dispersion aid includes an acid group-containing pigment derivative, and a content of the dispersion aid is 1.0-10.0 mass% relative to the content of the carbon black.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a black ink composition for gravure printing. More specifically, the present invention relates to a black ink composition for gravure printing that has excellent dispersibility and good doctor cut. [Background technology]

[0002] Conventionally, a black ink composition for gravure printing containing carbon black has been developed (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-196787 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the ink composition described in Patent Document 1 has problems such as poor dispersibility due to the binder resin, and staining due to doctor cut problems in the resulting printed matter.

[0005] The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a black gravure printing ink composition which has excellent dispersibility and good doctor cut. [Means for solving the problem]

[0006] The present invention, which solves the above problems, mainly comprises the following configuration.

[0007] (1) A black gravure printing ink composition comprising carbon black, a binder resin, a dispersant, a dispersion aid, and an organic solvent, wherein the binder resin comprises a cellulose-based resin, the dispersant comprises a basic dispersant, and the dispersion aid comprises an acid group-containing pigment derivative, and the content of the dispersion aid is 1.0 to 10.0 mass % relative to the carbon black.

[0008] According to this configuration, the black gravure printing ink composition has excellent dispersibility of carbon black and excellent doctor wipeability.

[0009] (2) The black gravure printing ink composition according to (1), wherein the carbon black contains acidic carbon.

[0010] According to this configuration, the black gravure printing ink composition has better dispersibility.

[0011] (3) The black gravure printing ink composition according to (1) or (2), wherein the basic dispersant includes a pigment dispersant having a tertiary amino group or a nitrogen-containing heterocyclic structure.

[0012] According to this configuration, the black gravure printing ink composition has better dispersibility.

[0013] (4) The black gravure printing ink composition according to any one of (1) to (3), wherein the acid group-containing pigment derivative includes a pigment derivative having a phthalocyanine skeleton.

[0014] With this configuration, the black gravure printing ink composition can further improve the dispersibility of carbon black. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a black gravure printing ink composition that has excellent dispersibility and good doctor cut. DETAILED DESCRIPTION OF THE INVENTION

[0016] <Black gravure printing ink composition> A black gravure printing ink composition (hereinafter also referred to as "ink composition") according to one embodiment of the present invention contains carbon black, a binder resin, a dispersant, a dispersion aid, and an organic solvent. The binder resin contains a cellulose-based resin. The dispersant contains a basic dispersant. The dispersion aid contains an acid group-containing pigment derivative. The content of the dispersion aid is 1.0 to 10.0% by mass relative to the carbon black. Each of these components will be described below.

[0017] (carbon black) The carbon black is not particularly limited. For example, the carbon black may be a neutral carbon black, an acidic carbon black, or the like, which has been conventionally used in the technical field of ink compositions for gravure printing. The carbon black may be used in combination.

[0018] The carbon black of this embodiment preferably contains acidic carbon, which provides the ink composition with better dispersibility.

[0019] The pH of the acidic carbon black is preferably 2.0 or higher. The pH of the acidic carbon black is preferably 4.0 or lower. In this embodiment, the pH can be measured at 25°C using a glass electrode after preparing an aqueous suspension by adding 1.0 g of carbon black to 20 ml of decarbonated distilled water (pH 7.0) and mixing with a magnetic stirrer (German Industrial Standard DIN ISO 787 / 9).

[0020] The average primary particle diameter of the carbon black is preferably 15 nm or more, more preferably 20 nm or more. The average primary particle diameter is preferably 45 nm or less, more preferably 40 nm or less. By having the average primary particle diameter within the above range, the ink composition can achieve both excellent coloring properties and dispersibility, and can also improve doctoring. In this embodiment, the average primary particle diameter is the arithmetic mean diameter value determined by electron microscope observation.

[0021] In this embodiment, "doctor cut" is a measure of the degree to which ink is scraped off from the margins, and can be evaluated by the evaluation method introduced in the Journal of the Japanese Society of Printing Science, Vol. 30, No. 3 (1993). Specifically, it can be evaluated based on the state of the printed surface when the ink composition is printed using a gravure printing machine.

[0022] The DBP oil absorption of the carbon black is preferably 35 ml / 100 g or more, more preferably 40 ml / 100 g or more. The DBP oil absorption of the carbon black is preferably 80 ml / 100 g or less, more preferably 75 ml / 100 g or less. In this embodiment, the DBP oil absorption can be determined from the specifications of the pigment manufacturer.

[0023] The specific surface area of ​​carbon black is 35m 2 / g or more is preferable, and 40m 2 It is more preferable that the specific surface area of ​​carbon black is 80 m / g or more. 2 / g or less, and 2 / g or less is more preferable. In this embodiment, the specific surface area can be determined based on the specifications of the pigment manufacturer.

[0024] Preferred commercially available carbon blacks for this embodiment include, for example, Raven 1080 (average primary particle size 28 nm, pH 2.4) and Raven 1100 (average primary particle size 32 nm, pH 2.9) manufactured by Columbia Chemicals, MA-8 (average primary particle size 24 nm, pH 3.0) and MA-100 (average primary particle size 22 nm, pH 3.5) manufactured by Mitsubishi Chemical, and Special Black 250 (average primary particle size 56 nm, pH 3.0), Special Black 350 (average primary particle size 31 nm, pH 3.0), Special Black 550 (average primary particle size 25 nm, pH 4.0), and NEROX 305 (average primary particle size approximately 28 nm, pH approximately 2.8) manufactured by Orion Engineered Carbons. Note that the pH and average primary particle size of these carbon blacks are catalog values.

[0025] The carbon black content in the ink composition is preferably 5% by mass or more, and more preferably 10% by mass or more. The carbon black content in the ink composition is preferably 30% by mass or less, and more preferably 25% by mass or less. By keeping the carbon black content within the above range, the ink composition can achieve both excellent colorability and dispersibility, and can also improve doctor line sharpness.

[0026] The ink composition of this embodiment may contain various inorganic pigments and organic pigments other than carbon black, as long as the effects of the ink composition are not impaired.

[0027] Inorganic pigments include colored pigments such as titanium oxide, red iron oxide, antimony red, cadmium yellow, cobalt blue, Prussian blue, ultramarine, iron black, chromium oxide green, and graphite (including achromatic colored pigments such as white and black), and extender pigments such as calcium carbonate, kaolin, clay, barium sulfate, aluminum hydroxide, and talc.

[0028] Examples of organic pigments include dye lake pigments, azo-based, benzimidazolone-based, phthalocyanine-based, quinacridone-based, anthraquinone-based, dioxazine-based, indigo-based, thioindigo-based, perylene-based, perinone-based, diketopyrrolopyrrole-based, isoindolinone-based, nitro-based, nitroso-based, anthraquinone-based, flavanthrone-based, quinophthalone-based, pyranthrone-based, and indanthrone-based pigments.

[0029] (binder resin) The binder resin includes a cellulose-based resin. The cellulose-based resin is not particularly limited. Examples of the cellulose-based resin include lower acyl-substituted cellulose such as nitrocellulose (nitrocellulose, nitro group-substituted cellulose), cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate (CAB), and lower alkyl-substituted cellulose such as methyl cellulose and ethyl cellulose.

[0030] Nitrogen cellulose is obtained by reacting native cellulose with nitric acid to replace three hydroxyl groups in the six-membered ring of the anhydroglucopyranose group in the native cellulose with nitric acid groups, resulting in a nitric acid ester. The nitrocellulose used in this embodiment preferably has a nitrogen content of 10 to 13% and an average degree of polymerization of 35 to 90. Specific examples of nitrocellulose include SS1 / 2, SS1 / 4 (0.155 Pa·s), SS1 / 8 (0.150 Pa·s), TR1 / 16 (0.065 Pa·s), and NCRS-2 (all manufactured by KOREA CNC). The above viscosity is measured at 30 rpm at 25°C in a 20% solids solution containing a 90:10 mixture of ethyl acetate and isopropyl alcohol.

[0031] The content of soluble nitrocellulose in the ink composition is preferably 8.0% by mass or more, more preferably 10.0% by mass or more. The content of soluble nitrocellulose in the ink composition is preferably 15.0% by mass or less, more preferably 13.0% by mass or less. When the content of soluble nitrocellulose is within the above range, the ink composition has excellent adhesion to films.

[0032] (dispersant) The dispersant includes a basic dispersant. The basic dispersant is not particularly limited. Examples of the basic dispersant include poly(lower alkyleneimine) derivatives, polyallylamine or polyvinylamine derivatives, urethane-based dispersants which are reaction products of diisocyanates and / or triisocyanates with polyesters having a hydroxyl group at one end and / or polyesters having hydroxyl groups at both ends, and basic group-containing carbodiimide-based dispersants. Among these, the basic dispersant preferably includes a pigment dispersant having a tertiary amino group or a nitrogen-containing heterocyclic structure. This provides the ink composition with better dispersibility.

[0033] Commercially available basic dispersants include Solsperse 20000, 24000, 26000, and 28000 (all manufactured by Lubrizol Nippon Corporation), Ajisper PB711, PB811, and PB821 (all manufactured by Ajinomoto Co., Inc.), and Disperbyk 160, 161, 162, and 163 (all manufactured by BYK-Chemie). From the viewpoint of obtaining excellent fluidity, the ink composition of this embodiment preferably contains a dispersant having a tertiary amino group or a nitrogen-containing heterocyclic structure.

[0034] The content of the dispersant in the ink composition is preferably 1.0% by mass or more, more preferably 1.5% by mass or more. The content of the dispersant in the ink composition is preferably 5.0% by mass or less, more preferably 3.5% by mass or less. By having the content of the dispersant within the above range, the ink composition has excellent fluidity and stability.

[0035] (Dispersion aid) The dispersing aid includes an acid group-containing pigment derivative. The acid group-containing pigment derivative is not particularly limited. Examples of the acid group-containing pigment derivative include a phthalocyanine pigment derivative that is a sulfonated product of copper phthalocyanine, an anthraquinone pigment derivative having an acid group, and a naphthalene pigment derivative having an acid group. Among these, the acid group-containing pigment derivative preferably includes a sulfonated product of copper phthalocyanine, in order to further improve the dispersibility of carbon black.

[0036] Specific examples of sulfonated copper phthalocyanine include Solsperse 5000 and Solsperse 12000 manufactured by Lubrizol Japan, and BYK-SYNERGIST 2100 manufactured by BYK-Chemie.

[0037] The content of the dispersing aid may be 1.0% by mass or more, and preferably 2.5% by mass or more, relative to the carbon black. The content of the dispersing aid may be 10.0% by mass or less, and preferably 8.5% by mass or less, relative to the carbon black. If the content of the dispersing aid is less than 1.0% by mass, the ink composition will not have sufficient fluidity or stability. On the other hand, if the content of the dispersing aid is more than 10.0% by mass, the ink composition will have poor adhesion to the film.

[0038] (organic solvent) The ink composition of this embodiment contains an organic solvent as a dispersion medium.

[0039] In consideration of the environment, the organic solvent of this embodiment is preferably an organic solvent that does not contain an aromatic hydrocarbon-based organic solvent. Organic solvents that do not contain an aromatic hydrocarbon-based organic solvent are mainly alcohol-based organic solvents such as methanol, ethanol, n-propanol, isopropanol, and butanol; ketone-based organic solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ester-based organic solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; aliphatic hydrocarbon-based organic solvents such as n-hexane, n-heptane, and n-octane; and alicyclic hydrocarbon-based organic solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, cycloheptane, and cyclooctane. In consideration of the environmental aspect, it is preferable to avoid ketone-based organic solvents as much as possible among the above organic solvents.

[0040] The content of the organic solvent is not particularly limited. For example, the content of the organic solvent in the ink composition is preferably 10% by mass or more, and more preferably 29% by mass or more. Furthermore, the content of the organic solvent in the ink composition is preferably 90% by mass or less, and more preferably 80% by mass or less. When the content of the organic solvent is within the above range, the ink composition has excellent printability. The organic solvent may be used in combination.

[0041] (optional ingredient) The ink composition of this embodiment may contain various additives, such as other binder resins, plasticizers, tackifiers, crosslinking agents, lubricants, anti-blocking agents, antistatic agents, and surfactants, as appropriate.

[0042] The other binder resin is not particularly limited, and examples thereof include vinyl chloride-vinyl acetate copolymer resin, rosin resin, acrylic resin, and urethane resin.

[0043] The vinyl chloride-vinyl acetate copolymer resin may be a copolymer of vinyl chloride monomer and vinyl acetate monomer conventionally used in ink compositions. Among these, vinyl chloride-vinyl acetate copolymer resins containing hydroxyl groups are preferred because they are advantageous for achieving a balanced improvement in the performance required for the present invention in an environmentally friendly organic solvent system for inks. Such vinyl chloride-vinyl acetate copolymer resins containing hydroxyl groups can be obtained, for example, by partially saponifying the acetate ester moieties. In the case of vinyl chloride-vinyl acetate copolymer resins containing hydroxyl groups obtained by partially saponifying the acetate ester moieties, the film properties and dissolution behavior of the resin are determined by the ratio of the structural units based on the reactive sites of vinyl chloride (Formula 1 below), the structural units based on the reactive sites of vinyl acetate (Formula 2 below), and the structural units based on the saponification of the reactive sites of vinyl acetate (Formula 3 below) in the molecule. That is, the structural units based on the vinyl chloride reactive sites impart toughness and hardness to the resin film, the structural units based on the vinyl acetate reactive sites impart adhesiveness and flexibility, and the structural units based on the saponification of the vinyl acetate reactive sites impart good solubility to the environmentally friendly ink in organic solvent systems. Formula 1 -CH2-CHCl- Formula 2 -CH2-CH(OCOCH3)- Formula 3 -CH2-CH(OH)-

[0044] The number average molecular weight of the vinyl chloride-vinyl acetate copolymer resin of this embodiment is preferably 10,000 or more, more preferably 15,000 or more, and is preferably 35,000 or less, more preferably 30,000 or less.

[0045] A plasticizer is preferably blended in the ink composition to reduce residual solvent. The plasticizer is not particularly limited. Examples of the plasticizer include dioctyl sebacate, epoxidized soybean oil, fatty acid triglyceride, ethyl toluenesulfonamide, acetyl tributyl citrate, 2-ethylhexyl stearate, and 2-ethylhexyl palmitate.

[0046] When a plasticizer is contained, the content of the plasticizer is not particularly limited. For example, the content of the plasticizer in the ink composition is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. Furthermore, the content of the plasticizer in the ink composition is preferably 5.0% by mass or less, and more preferably 3.0% by mass or less. By keeping the content of the plasticizer within the above range, the resulting ink composition is likely to have a reduced residual solvent.

[0047] The method for producing the ink composition of this embodiment is not particularly limited. For example, the ink composition can be produced by stirring and mixing carbon black, a binder resin, a dispersant, a dispersing aid, an organic solvent, and various optional components, then producing a masterbatch using various types of dispersing and kneading equipment, and then adding the remaining materials. The viscosity of the ink composition is preferably adjusted appropriately to a range of 3 to 20 mPa·s.

[0048] The ink composition is preferably diluted with an organic solvent as necessary so that the number of seconds appropriate for the printing conditions at the ambient temperature during printing, specifically until the flow time in seconds using a Zahn cup No. 3 is about 14 to 18 seconds, preferably about 15 to 17 seconds. Alternatively, instead of the above-mentioned production method, the ink composition for printing may be prepared by mixing materials without using a masterbatch or the like.

[0049] As described above, according to this embodiment, a black ink composition for gravure printing having excellent dispersibility and good doctor cut can be obtained.

[0050] <Printed materials and printing methods> A printing method according to one embodiment of the present invention is a method in which the ink composition described above is printed on a printing substrate by gravure printing using a gravure plate. That is, the ink composition can be printed using a general gravure printing method. The conditions for the gravure printing method are the same as those of conventionally known methods and conditions. The printing substrate may be uncoated paper, coated paper, or laminated paper.

[0051] The printing plate may be a conventional plate cylinder (an intaglio plate made by a normal gravure platemaking method, for example, engraving gravure), or may be one in which shallower cells are formed than in a conventional plate cylinder (shallower plate). The printing method of this embodiment allows a laminate (printed matter) to be obtained by printing the ink composition at the time of printing using the conventional printing plate or the shallower printing plate.

[0052] The obtained printed matter has excellent doctor wipeability because the above-mentioned ink composition is used. [Example]

[0053] The present invention will be described in more detail below with reference to examples. The present invention is not limited to these examples. Unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass."

[0054] The raw materials used and the methods for preparing the raw materials are shown below.

[0055] (Preparation of cellulose-based resin solution) To 33 parts of industrial nitrocellulose SS1 / 4 (nitrocellulose, 70% solid content, IPA wet, manufactured by KOREA CNC), 24 parts of isopropanol and 43 parts of ethyl acetate were added and thoroughly mixed to prepare a nitrocellulose resin. (carbon black) Acidic carbon black 1 (average primary particle diameter 40 nm, DBP oil absorption 47 ml / 100 g, specific surface area 60 m 2 / g, pH 2.8) Acidic carbon black 2 (average primary particle diameter 28 nm, DBP adsorption capacity 50 ml / 100 g, specific surface area 70 m 2 / g, pH 2.4) (dispersant) Solsperse 20000 (manufactured by Lubrizol Japan, basic dispersant) Ajisper PB821 (Ajinomoto Fine-Techno Co., Ltd., basic dispersant) (Dispersion aid) Solsperse 5000 (manufactured by Lubrizol Japan, phthalocyanine sulfonic acid amine salt) Solsperse 12000 (manufactured by Lubrizol Japan, phthalocyanine sulfonic acid amine salt) BYK-SYNERGIST 2100 (Byk Japan, phthalocyanine sulfonic acid amine salt) (organic solvent) Ethyl acetate Isopropanol

[0056] (Examples 1 to 7, Comparative Examples 1 and 2) Preparation of ink composition for gravure printing The raw materials were kneaded according to the mass proportions (mass %) shown in Table 1 below to obtain black gravure printing ink compositions.

[0057] [Table 1]

[0058] The dispersibility and doctor wipeability of the ink compositions of Examples 1 to 7 and Comparative Examples 1 and 2 were evaluated by the following evaluation methods. The results are shown in Table 1.

[0059] <Dispersibility> The ink composition was placed in a glass bottle and stored at an ambient temperature of 60°C for 14 days, after which the presence or absence of sedimentation of carbon black was evaluated according to the following evaluation criteria. (Evaluation criteria) ◯: No sedimentation was observed, and the storage stability of the ink composition was good. ×: Sedimentation was observed, and the storage stability of the ink composition was poor.

[0060] <Dragon cutting ability> The ink composition was printed using a gravure printing machine at a printing speed of 150 m / min, and the state of the printed surface was evaluated according to the following evaluation criteria. (Evaluation criteria) ◯: No plate fogging, solid streaks, or line stains occurred. ×: Plate fogging, solid streaks, and line stains (linear stains) occurred frequently.

[0061] As shown in Table 1, all of the ink compositions of Examples 1 to 7 of the present invention had excellent dispersibility of carbon black and good doctor wipeability.

Claims

1. The ink contains carbon black, a binder resin, a dispersant, a dispersion aid, and an organic solvent, the binder resin includes a cellulose-based resin, The dispersant comprises a basic dispersant, the dispersing aid contains an acid group-containing pigment derivative, The black gravure printing ink composition, wherein the content of the dispersing aid is 1.0 to 10.0 mass % relative to the carbon black.

2. 2. The black gravure printing ink composition according to claim 1, wherein the carbon black comprises acidic carbon.

3. 3. The black gravure printing ink composition according to claim 1, wherein the basic dispersant comprises a pigment dispersant having a tertiary amino group or a nitrogen-containing heterocyclic structure.

4. 3. The black gravure printing ink composition according to claim 1, wherein the acid group-containing pigment derivative comprises a pigment derivative having a phthalocyanine skeleton.

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