Offset printing ink composition and printed material

Abstract

This product provides printed materials with pinholes on the substrate minimized to virtually zero, even when a uniform coating is formed across the entire surface of the substrate for all colors. [Solution] The offset printing ink composition of the present invention contains 10% to 30% by mass of pigment, 40% to 65% by mass of varnish, 0.01% to 5% by mass of starch particles, and polytetrafluoroethylene particles and / or polymethyl methacrylate particles. When polytetrafluoroethylene particles are included, the content of such particles is 0.5% to 5% by mass, and when polymethyl methacrylate particles are included, the content of such particles is 0.01% to 2% by mass.

Description

Technical Field

[0001] The present invention relates to an offset printing ink composition and a printed matter.

Background Art

[0002] In an oxidative polymerization drying type offset printing ink composition, the drying oil component (varnish) in the ink comes into contact with air, absorbs oxygen in the air, undergoes an oxidation reaction, polymerizes, and dries to form a cured film. As an oxidation polymerization accelerator, a liquid dryer in which naphthenates of manganese and cobalt are dissolved in an oil by a metal dryer is often used. Many sheet-fed lithographic ink compositions and letterpress ink compositions use this type.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the offset printing method, a high-viscosity colored paste is used as the composition for printing ink. Therefore, it is difficult to obtain a uniform coating surface on the substrate, and there is a problem that pinholes (white spots) occur on the substrate. Especially when the coloring material contains a black pigment, the black pigment contains a lot of carbon black etc. Therefore, the black pigment ink composition has a higher viscosity than the pigment ink compositions of other colors (cyan, magenta, yellow). Therefore, when trying to form an ink coating film of the black pigment ink composition over the entire surface of the substrate, it is even more difficult to obtain a uniform coating surface on the substrate, and it has been considered almost impossible to completely prevent pinholes (white spots).

[0005] This invention has been made in view of these circumstances, and its purpose is to provide a printed material in which pinholes on the substrate are suppressed to virtually zero, even when a uniform coating surface is formed over the entire surface of the substrate for all colors. [Means for solving the problem]

[0006] The inventors of the present invention have completely reviewed the formulation of the ink composition in order to solve the above problems. As a result, they have found that by using a material that is normally used as a backing inhibitor in a specific limited formulation, it is possible to suppress pinholes on the printed material substrate to virtually zero, even with ink compositions that have high viscosity, such as black inks, and have completed the present invention. Specifically, the present invention provides the following.

[0007] The invention relating to the first feature provides an offset printing ink composition containing 10% to 30% by mass of pigment, 40% to 65% by mass of varnish, 0.01% to 5% by mass of starch particles, and polytetrafluoroethylene particles and / or polymethyl methacrylate particles, wherein, when polytetrafluoroethylene particles are included, the content of the polytetrafluoroethylene particles is 0.5% to 5% by mass, and when polymethyl methacrylate particles are included, the content of the polymethyl methacrylate particles is 0.01% to 2% by mass.

[0008] According to the invention relating to the first feature, the material that would normally be used as a backing agent is formulated in a specific, limited composition. As a result, according to the invention relating to the first feature, the pinholes on the printed material substrate can be reduced to virtually zero, which is an exceptional effect.

[0009] The invention relating to the second feature provides a composition which is the invention relating to the first feature, wherein the pigment includes a black pigment and the composition is a black ink composition.

[0010] Ink compositions containing black pigment have a higher viscosity than ink compositions containing other colored pigments (cyan, magenta, and yellow). Therefore, when attempting to form an ink coating of a black pigment ink composition over the entire surface of a substrate, it is even more difficult to obtain a uniform coating surface on the substrate, and it was considered almost impossible to completely prevent pinholes (white spots).

[0011] According to the invention relating to the second feature, even if the ink composition is a black pigment ink composition, the number of pinholes on the printed material substrate can be reduced to virtually zero.

[0012] The invention relating to the third feature provides a composition relating to the first or second feature, wherein the starch particles are corn starch particles. The invention relating to the fourth feature provides a composition relating to any of the first to third features, wherein the average particle diameter of the polymethyl methacrylate particles is 10 μm or less. The invention relating to the fifth feature provides a composition relating to any of the first to fourth features, further containing 0.1% by mass or more and 5% by mass or less of wax. The invention relating to the sixth feature provides a composition relating to the fifth feature, wherein the wax is microcrystalline wax.

[0013] The invention relating to the third to sixth features provides the unique effect of being able to provide a black ink that further suppresses the generation of pinholes.

[0014] The invention relating to the seventh feature provides a printed article having a substrate and an ink coating film of a composition relating to any one of the first to sixth features of the invention disposed on the substrate. [Effects of the Invention]

[0015] According to the present invention, even when a uniform coating surface is formed across the entire surface of the substrate for any color, it is possible to provide printed materials in which pinholes on the substrate are suppressed to virtually zero. [Modes for carrying out the invention]

[0016] A preferred embodiment for carrying out the present invention will be described below with reference to the figures. However, this is merely one example, and the technical scope of the present invention is not limited thereto.

[0017] Firstly, although the following disclosures, figures, and / or claims are described either individually or in combination with one or more other aspects, the subject matter of the immediate disclosure is not intended to be limited in that way. That is, the immediate disclosures, figures, and claims are intended to encompass the various aspects described herein, either individually or in one or more combinations with each other. For example, even if the immediate disclosure describes and illustrates the first, second, and third embodiments in such a way that the first embodiment is described and illustrated particularly in relation to the second embodiment, or the second embodiment is described and illustrated only in relation to the third embodiment, the immediate disclosures and illustrations are not limited in that way and may include only the first embodiment, only the second embodiment, only the third embodiment, or one or more combinations of the first, second, and / or third embodiments, such as the first and second embodiments, the first and third embodiments, the second and third embodiments, or the first, second, and third embodiments.

[0018] In this text, the phrase "or" is used to mean a "non-exclusive" arrangement unless explicitly specified otherwise. For example, when we say "item x is A or B," it means either (1) item x is either A or B, or (2) item x is both A and B. In other words, the word "or" is not used to define an "exclusive" arrangement.

[0019] Furthermore, when the phrases "contain at least one" or "contain at least one of the following" are used in the text, they mean that the system or element contains one or more of the elements listed after the phrase. For example, if there are three types of elements, from element 1 to element 3, the phrases "contain at least one" or "contain at least one of the following" are interpreted as any of the following structural arrangements: a device containing element 1, a device containing element 2, a device containing element 3, a device containing element 1 and element 2, a device containing element 1 and element 3, a device containing element 2 and element 3, or a device containing element 1, element 2, and element 3.

[0020] The same interpretation is intended when the phrase "used in at least one of the following" is used in the text. Furthermore, "and / or" as used in the text is used as a linguistic conjunction to indicate that one or more of the listed elements or conditions are included or occur. For example, a device containing the first element, the second element, and / or the third element is interpreted as any of the following structural arrangements: a device containing the first element, a device containing the second element, a device containing the third element, a device containing the first and second elements, a device containing the first and third elements, a device containing the second and third elements, or a device containing the first, second, and third elements.

[0021] Furthermore, the use of the phrase "and / or" in this text signifies a "non-exclusive" arrangement, as stipulated in the Japanese Industrial Standard (JIS) "Format and Preparation Method of Standards Documents JIS Z 8301".

[0022] The following describes an example of a preferred embodiment for carrying out the present invention. However, this is merely an example, and the technical scope of the present invention is not limited thereto.

[0023] <Offset printing ink composition> The composition of the present invention is an offset printing ink composition. This composition contains a pigment, a varnish, starch particles, and polytetrafluoroethylene particles and / or polymethyl methacrylate particles.

[0024] [(A) Pigment] The pigment may be either an organic pigment or an inorganic pigment. Also, the pigment can be selected, for example, from pigments such as red or magenta, yellow, green, blue or cyan, and black described in the Colour Index (registered trademark) International according to the color of the image to be formed.

[0025] Examples of organic pigments include one or more selected from azo pigments, phthalocyanine pigments, anthraquinone pigments, quinacridone pigments, isoindolinone pigments, quinophthalone pigments, dye lake pigments, fluorescent pigments, etc. Examples of inorganic pigments include titanium oxide, graphite, zinc white, powdered lime carbonate, precipitated calcium carbonate, gypsum, clay (China Clay), silica powder, diatomaceous earth, talc, kaolin, alumina white, barium sulfate, aluminum stearate, magnesium carbonate, barite powder, abrasive powder, silicon, and glass beads, etc., and one or more selected therefrom.

[0026] Here, an ink composition containing a black pigment has a higher viscosity than an ink composition containing pigments of other colors (cyan, magenta, yellow). Therefore, when trying to form an ink coating film of the black pigment ink composition over the entire surface of the substrate, it is even more difficult to obtain a uniform coating film surface on the substrate, and it has been considered almost impossible to completely prevent pinholes.

[0027] In the present invention, even for a black offset printing ink composition, in terms of suppressing the generation of pinholes on the coating film surface, it is preferable that the pigment contains a black pigment.

[0028] Examples of black pigments include carbon black pigment containing carbon, lamp black pigment containing components obtained by burning oil, vegetable black pigment containing components obtained by carbonizing plant materials, bone black pigment containing components obtained by calcining animal bones, and graphite black pigment containing graphite.

[0029] Furthermore, the pigment may be a single type or a combination of two or more types, depending on the suitability of the printing equipment.

[0030] The pigment content is 10% by mass or more, and preferably 15% by mass or more, per 100% by mass of the ink composition. Too little pigment is undesirable because the ink coating applied to the substrate may not exhibit sufficient color.

[0031] The pigment content is 30% by mass or less, preferably 25% by mass or less, per 100% by mass of the ink composition. Too much pigment is undesirable because it can lead to excessive viscosity of the ink composition, potentially creating pinholes on the coating surface of the substrate.

[0032] In this specification, unless otherwise specified, all content figures refer to solid content.

[0033] (B) Varnish The varnish contains at least an ink binder. Preferably, the varnish contains vegetable oil. Including vegetable oil can reduce the amount of petroleum-based solvent used. This can also reduce the amount of fossil fuels used, which are a limited resource. Preferably, the varnish contains petroleum-based solvent. Including petroleum-based solvent can make the viscosity of the ink suitable for printing. Furthermore, drying the petroleum-based solvent can fix the ink to the printing area.

[0034] The varnish content is 40% by mass or more per 100% by mass of the ink composition, preferably 45% by mass or more, more preferably 50% by mass or more, and even more preferably 55% by mass or more. Too little varnish is undesirable because it can lead to the ink composition having too high a viscosity, potentially causing pinholes on the coating surface of the substrate.

[0035] The varnish content is 65% by mass or less per 100% by mass of the ink composition, and preferably 60% by mass or less. Too much varnish is undesirable because undried varnish may remain, potentially preventing the ink from adhering to the printing area.

[0036] [(C) Anti-backing agent] A backing-preventing agent (or back-transfer prevention agent) is an additive used during printing to prevent ink from transferring to the back of the substrate. Backing occurs when ink applied to the surface of a printed material adheres to the back of stacked sheets of paper before it has dried.

[0037] The present invention is characterized by reducing pinholes on the printed material substrate to virtually zero, even with ink compositions having high viscosity such as black inks, by using a specific, limited composition of a material that would normally be used as a backing agent. In the present invention, the backing agent comprises starch particles, polytetrafluoroethylene particles and / or polymethyl methacrylate particles, and optionally wax.

[0038] [Starch particles] The type of starch is not particularly limited and may be any of the following: corn starch, tapioca starch, wheat starch, modified starch, etc. Depending on the suitability of the printing equipment, there may be one type of starch or a combination of two or more types.

[0039] In particular, starch particles containing cornstarch are preferable because they are plant-derived, highly safe, have an appropriate particle size, and disperse uniformly in printed materials.

[0040] The average particle size of the starch particles is not particularly limited, but it is preferably 5 μm or larger, and more preferably 10 μm or larger. Having starch particles of a suitable size allows for adequate gaps between the paper surfaces and suppresses the generation of static electricity between the particles, thus preventing back-fading. Furthermore, finer particles help to suppress bleed-through.

[0041] Furthermore, the average particle size of the starch particles is preferably 50 μm or less, more preferably 40 μm or less, even more preferably 30 μm or less, and even more preferably 20 μm or less. Because the starch particles are smaller than a predetermined size, the particles can be uniformly dispersed in the ink composition, resulting in a uniformly dispersed state of particles on the coating surface of the substrate. In addition, improved dispersibility makes it easier to achieve a uniform coating surface.

[0042] In this specification, the average particle diameter is defined as the average particle diameter (Dv50) obtained by determining the area of ​​a particle by image analysis from an electron microscope image observed at a magnification of 500x using a scanning electron microscope (SEM), obtaining the equivalent diameter of a circle equal to that area, and then calculating the volume-based integrated value at 50% from this equivalent diameter.

[0043] The starch particle content is 0.1% by mass or more per 100% by mass of the ink composition, and preferably 0.5% by mass or more. Too little starch particles are undesirable because they may cause backing and promote the formation of pinholes.

[0044] Furthermore, the starch particle content is preferably 5% by mass or less, and more preferably 3% by mass or less, per 100% by mass of the ink composition.

[0045] [Polytetrafluoroethylene particles] Polytetrafluoroethylene (PTFE) particles have a relatively low coefficient of friction compared to other materials, which helps prevent the ink coating on the top surface of printed materials from adhering to the back surface of stacked materials. Furthermore, the dispersion of PTFE particles in the ink composition provides a smooth surface to the printed paper, reducing friction during stacking.

[0046] The average particle size of PTFE particles is not particularly limited, but it is preferably 0.1 μm or larger, and more preferably 1 μm or larger. Having PTFE particles of a suitable size suppresses the generation of static electricity between particles and the formation of secondary particles, thus maintaining a lower coefficient of friction compared to other materials. Furthermore, finer particles also help to suppress puncture.

[0047] Furthermore, the average particle size of the PTFE particles is preferably 10 μm or less, more preferably 7 μm or less, and even more preferably 5 μm or less. By keeping the PTFE particles smaller than a predetermined size, a lower coefficient of friction can be maintained compared to other materials.

[0048] The PTFE particle content is 0.1% by mass or more per 100% by mass of the ink composition, and preferably 0.5% by mass or more. Too little PTFE particles is undesirable because it may impair abrasion resistance.

[0049] Furthermore, the PTFE particle content should be 5% by mass or less per 100% by mass of the ink composition, and preferably 3% by mass or less. Too much PTFE particles can impair the fluidity of the ink and lead to the formation of pinholes, which is undesirable.

[0050] [Polymethyl methacrylate particles] Polymethyl methacrylate (PMMA) particles are a relatively hard resin material that strengthens the surface of printed materials and prevents ink peeling due to rubbing and abrasion. Furthermore, PMMA particles create tiny gaps between substrates, preventing ink bleed-through when stacked. PMMA particles also appropriately adjust the viscosity and fluidity of the ink, improving transferability during printing. In addition, because PMMA particles can be uniformly dispersed within the ink, unevenness in the coating on the substrate is reduced.

[0051] The average particle size of PMMA particles is not particularly limited, but is preferably 0.1 μm or larger, more preferably 0.5 μm or larger, even more preferably 1 μm or larger, and even more preferably 2 μm or larger. The PMMA particles having a suitable size allows for adequate gaps to be created between the paper surfaces, thereby preventing backing. Furthermore, suppressing backing can reduce bleed-through.

[0052] Furthermore, the average particle size of the PMMA particles is preferably 10 μm or less, and more preferably 7 μm or less. Because the PMMA particles are smaller than a predetermined size, the particles can be uniformly dispersed in the ink composition, resulting in a uniformly dispersed state on the coating surface of the substrate. In addition, uniform dispersion improves the backing suppression effect and suppresses bleed-through.

[0053] If PMMA particles are included, the PMMA particle content is preferably 0.01% by mass or more per 100% by mass of the ink composition, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more.

[0054] Furthermore, the PMMA particle content is preferably 2% by mass or less per 100% by mass of the ink composition, more preferably 1% by mass or less, and more preferably 0.5% by mass or less. Too much PMMA particles are undesirable because they may impair the fluidity of the ink and lead to the formation of pinholes.

[0055] The ink composition may contain at least one of PTFE particles and PMMA particles, but it is preferable that the ink composition contains both PTFE particles and PMMA particles, as this provides superior performance in all aspects, including tack value (TV), flow value (DM), slope (SL), fluidity, transferability, drying properties, abrasion resistance, back-printing, and pinhole suppression.

[0056] [wax] Although not required, the ink composition may contain wax.

[0057] The wax forms a fine layer on the ink surface, reducing direct contact between stacked sheets of paper. This minimizes the risk of ink bleeding through to the other side before the printed surface dries. Additionally, the low friction of the wax reduces friction between stacked substrates, preventing ink from bleeding through.

[0058] Furthermore, the wax dispersed in the ink adjusts the fine irregularities of the ink film after drying, creating a surface that is less prone to bleed-through. The formation of a uniform ink layer reduces adhesion to the paper.

[0059] Furthermore, the wax adjusts the viscosity and fluidity of the ink, stabilizing its transferability during printing. By ensuring uniform ink drying, it reduces uneven drying and minimizes bleed-through.

[0060] The type of wax is not particularly limited; it may be synthetic wax, natural wax, petroleum-based wax, or specialty wax.

[0061] Examples of synthetic waxes include polyethylene (PE) wax, polypropylene (PP) wax, polytetrafluoroethylene (PTFE) wax, and ethylene bis-stearamide (EBS) wax.

[0062] Examples of natural waxes include carnauba wax and beeswax.

[0063] Examples of petroleum-based waxes include microcrystalline wax and paraffin wax.

[0064] Special waxes are waxes that have been modified or processed to enhance specific functions. Examples of special waxes include oxidized polyethylene wax, PTFE blend wax (wax blended with PTFE, PE, etc.), and polypropylene modified wax.

[0065] In particular, since preventing backing reduces the amount of blank space on the printed surface, the wax is preferably a petroleum-based wax, and more preferably a microcrystalline wax.

[0066] The average particle size of the wax particles is not particularly limited, but it is preferably 0.1 μm or larger, more preferably 0.5 μm or larger, even more preferably 1 μm or larger, and even more preferably 2 μm or larger. The wax particles having a suitable size allows for an appropriate gap to be created between the paper layers, thereby preventing back-printing. Furthermore, preventing back-printing reduces bleed-through on the printed surface.

[0067] Furthermore, the average particle size of the wax particles is preferably 10 μm or less, and more preferably 7 μm or less. Because the wax particles are smaller than a predetermined size, the particles can be uniformly dispersed in the ink composition, resulting in a uniformly dispersed state of particles on the coated film surface of the substrate. This also enhances the anti-sticking effect.

[0068] The wax particle content is preferably 0.1% by mass or more per 100% by mass of the ink composition, more preferably 1% by mass or more, and even more preferably 2% by mass or more. If the amount of wax particles is too low, the anti-sticking effect may be poor.

[0069] Furthermore, the wax particle content is preferably 10% by mass or less per 100% by mass of the ink composition, more preferably 7% by mass or less, and even more preferably 5% by mass or less. Too much wax particles are undesirable because they may impair fluidity.

[0070] [(D) Other additives] Offset printing ink compositions may contain other additives. Examples of other additives include binders, metal soaps, and organic solvents.

[0071] [binder] Examples of binders include those comprising one or more of the following: a resin, an unsaturated compound that can harden by reacting with oxygen in the air, and an electromagnetically curable resin that can harden by electromagnetic rays used as a light source for printing.

[0072] The resin is not particularly limited and may include one or more thermoplastic resins, such as phenolic resins exemplified by rosin-modified phenolic resins, alkyd resins exemplified by rosin-modified alkyd resins, vinyl resins exemplified by vinyl chloride resins, acrylic resins, polyamide resins, polyester resins, epoxy resins, urethane resins, and fluororesins. Generally, thermoplastic resins have better toughness than thermosetting resins. Therefore, by including a thermoplastic resin in the binder, an ink with good spreadability can be achieved. The resin may also include one or more thermosetting resins, such as vinyl chloride-vinyl acetate copolymer resins. Thermosetting resins harden with heat. By including a thermosetting resin in the binder, an ink that hardens with heat can be provided.

[0073] The unsaturated compound is not particularly limited and may include one or more of the following: (polymerized) drying oils exemplified by linseed oil, isomerized linseed oil, tuni oil, dehydrated castor oil, fish oil, and oyster oil; drying oils such as urethaneized oil, maleated oil, and / or cyclopentadienylated oil produced using these drying oils; phenolic resins exemplified by rosin-modified phenolic resins; alkyd resins exemplified by drying oil-modified alkyd resins, urethaneized alkyd resins, acrylic-modified alkyd resins, and phenol-modified alkyd resins; drying oil fatty acid-modified epoxy ester resins; and unsaturated hydrocarbon resins derived from petroleum resins having unsaturated double bonds that exhibit an iodine value, and compounds having conjugated double bonds exemplified by butadiene, etc.

[0074] In this embodiment, electromagnetic waves refer to electromagnetic waves having a predetermined wavelength, and examples include radio waves, light, X-rays, and gamma rays, in order of decreasing wavelength. Radio waves refer to electromagnetic waves with a wavelength of 100 μm or more and a frequency of 3 THz or less, and are subdivided into low frequency, very long wave, long wave, medium wave, short wave, very short wave, and microwave depending on the wavelength range. Light refers to electromagnetic waves with a wavelength of about 1 mm to 2 nm, and is subdivided into infrared, visible light, and ultraviolet depending on the wavelength range. X-rays refer to electromagnetic waves with a wavelength of 10 nm or less that are generated from electron excitation (and electron-derived mechanisms such as bremsstrahlung), and gamma rays refer to electromagnetic waves with a wavelength of 10 pm or less that are generated from intranuclear excitation.

[0075] By including an electromagnetically curable resin in the binder, it is possible to provide recycled ink that hardens using electromagnetic rays emitted from the light source of offset printing. This makes it possible to provide, for example, a recycled black ink for UV offset printing that can be used in UV offset printing, where drying time can be shortened by irradiation with ultraviolet light.

[0076] The electromagnetically curable resin is not particularly limited as long as it is a reactive compound capable of absorbing electromagnetic rays and undergoing a crosslinking reaction, and examples include (meth)acrylic resins, epoxy resins, and oxetane resins.

[0077] In particular, since electromagnetically curable resins are frequently used as light sources for offset printing, they are preferably photocurable resins, and more preferably ultraviolet curable resins.

[0078] When the binder contains an electromagnetic polymerization initiator, it is preferable that the binder also contains an electromagnetic sensitizer, which assists electromagnetic polymerization by transferring energy obtained from absorbing electromagnetic rays to the electromagnetic polymerization initiator. By including an electromagnetic sensitizer in the binder, electromagnetic polymerization can be suitably carried out even when using a light source with a narrow emission wavelength range, such as an LED. This makes it possible to provide a black recycled ink for UV offset printing that hardens more reliably, for example, by electromagnetic rays emitted from an offset printing light source.

[0079] [Metal soaps] The ink composition preferably contains a metal soap, including a manganese-based metal soap and / or a cobalt-based metal soap. This allows for appropriate control of the drying time, resulting in a recycled ink with a good balance of low odor and excellent drying properties.

[0080] The ink composition more preferably contains a metal soap that includes both a manganese-based metal soap and a cobalt-based metal soap. This allows the manganese and cobalt, which act as catalysts in the multi-stage drying process, to act on different reaction processes, enabling balanced drying of the surface and interior of the ink film (coating) after printing.

[0081] The manganese-based metal soap is not particularly limited and may be a metal soap containing one or more manganese salts of fatty acids, such as stearic acid, lauric acid, ricinoleic acid, naphthenic acid, and octic acid.

[0082] The cobalt-based metal soap is not particularly limited and may be a metal soap containing one or more cobalt salts of fatty acids, such as stearic acid, lauric acid, ricinoleic acid, naphthenic acid, and octic acid.

[0083] In particular, the metal soap is preferably a metal soap containing both a manganese naphthenate or octylate and a cobalt naphthenate or octyl acid. This allows for desirable performance in terms of curing catalytic activity, weather resistance, coating coloration, cost-effectiveness, solubility, and stability.

[0084] [Organic solvents] The type of organic solvent is not particularly limited and includes hydrocarbon solvents, silicone solvents, and alcohol solvents. Examples of hydrocarbon solvents include industrial naphtha, kerosene, naphthenic hydrocarbon solvents, paraffinic hydrocarbon solvents such as isoparaffin, and aromatic hydrocarbon solvents. Examples of alcohol solvents include methanol, ethanol, n-propanol, 2-propanol, n-butanol, and 2-methylpropanol.

[0085] [Other materials] The first mixing step may include a procedure for adding and mixing other materials to the various materials described above. The other materials are not particularly limited and may be one or more of the materials contained in conventional inks, such as colorants; metal soaps; additives that impart abrasion resistance, anti-blocking properties, slipperiness, and / or scratch resistance (e.g., waxes using polyethylene-based organic compounds, etc.); additives that impart storage stability to the ink; ultraviolet absorbers; infrared absorbers; odor molecule adsorbents exemplified by silver ion-containing zeolites; antioxidants exemplified by hydroquinone (HQ), tert-butyl hydroquinone (TBHQ), ascorbic acid (vitamin C), cyclohexanone oxime, and methylhydroquinoline, etc.; anti-bleed agents exemplified by waxes, starches, etc.; aldehyde scavengers exemplified by composites of amine-based organic compounds and silicate-based inorganic compounds, etc.; and antibacterial agents, etc.

[0086] [Method for manufacturing offset printing ink composition] Printing ink compositions can be prepared by conventionally known methods. For example, an ink composition can be prepared by mixing each component, then kneading it in a shot mill, bead mill, roll mill, etc. to disperse pigments and colorants such as gray recycled ink, adding additives as needed, stirring and mixing, and adjusting the viscosity as needed.

[0087] <Printed material> The printed material of the present invention comprises a substrate and an ink coating of an offset printing ink composition disposed on the substrate.

[0088] The printed material is obtained by printing with the above-described printing ink composition using a lithographic offset printing press. There are no particular restrictions on the substrate, and conventionally known materials can be used, such as coated paper, matte coated paper, and fine paper. [Examples]

[0089] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. There isn't one.

[0090] [Table 1]

[0091] <Preparation of Ink Composition> The ink compositions for the examples and comparative examples were prepared according to the formulations listed in Table 1. The amounts in Table 1 are in parts by mass. In preparing the ink compositions, the remaining materials were mixed with the varnish in predetermined parts by mass and kneaded in a three-roll mill to obtain the ink composition.

[0092] Subsequently, printing was performed across the entire surface of a 110mm wide A2 coated paper using a printability tester (RI Tester, manufactured by Akira Seisakusho Co., Ltd.). The printing was carried out over a roll of paper 210mm in length.

[0093] <Rating> [Tack value (TV)] The tack value was measured using a rotary tack meter in accordance with JIS K 5701-1 (Test Method for Lithographic Inks). The results are shown in Table 1.

[0094] [Flow Value (DM)] Tack flow values ​​were measured using a spread meter in accordance with K 5701-1 (Test Method for Lithographic Inks). The results are shown in Table 1.

[0095] [Slope (SL)] The slope was measured using a spread meter in accordance with K 5701-1 (Lithographic Ink Testing Method). The results are shown in Table 1.

[0096] [Liquidity] Liquidity was evaluated by comparing flow values. A value of 35.5 ± 0.5 was marked as "○", a value greater than 36.0 was marked as "△", and a value less than 35.0 was marked as "×". The results are shown in Table 1.

[0097] [Drying] Drying properties were evaluated by conducting tests in accordance with JIS K 5701-1 (Test Method for Lithographic Inks). A "○" indicated that the performance was equivalent to the standard ink, a "△" indicated that it was approximately equivalent to the standard ink, and a "×" indicated that it was inferior to the standard ink. The results are shown in Table 1.

[0098] [Abrasion resistance] Abrasion resistance was evaluated by conducting tests in accordance with JIS K 5701-1 (Test Method for Lithographic Inks). A score of "○" indicated no color transfer to the paper being rubbed and no scratches on the printed surface; "△" indicated slight color transfer and minor scratches on the printed surface; and "×" indicated significant color transfer and scratches on the printed surface. The results are shown in Table 1.

[0099] [Transfer to the other side] Back-printing was evaluated by comparing the degree of back-printing after color development. "○" indicated no back-printing, "△" indicated almost no back-printing, and "×" indicated back-printing. The results are shown in Table 1.

[0100] [Pinhole] Pinholes were evaluated by printing on an actual machine and visually inspecting the printed material. A "○" indicated good results, a "△" indicated average results, and a "×" indicated poor results. The results are shown in Table 1.

[0101] <Result> Using the ink composition of the example, it was possible to provide printed materials with virtually zero pinholes on the substrate, even when a uniform coating surface was formed across the entire substrate for all colors, including black. In this case, other properties such as tack value (TV), flow value (DM), slope (SL), fluidity, drying properties, abrasion resistance, and transfer-to-back were also excellent.

[0102] In particular, the ink composition of Example 2 was superior in terms of suppressing the amount of pinholes, and also excelled in all other properties such as tack value (TV), flow value (DM), slope (SL), fluidity, drying properties, abrasion resistance, and bleed-through.

[0103] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above. Furthermore, the effects described in the embodiments above are merely a list of the most preferred effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments above. In addition, the embodiments described above have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described above.

Claims

1. Pigment in an amount of 10% by mass or more and 30% by mass or less, Varnish 40% by mass or more and 65% by mass or less, Starch particles 0.01% by mass or more and 5% by mass or less, An offset printing ink composition containing 0.01% to 2% by mass of polymethyl methacrylate particles having an average particle diameter of 10 μm or less.

2. The aforementioned pigment includes a black pigment, The composition according to claim 1, wherein the composition is a black ink composition.

3. The composition according to claim 1, wherein the starch particles are corn starch particles.

4. The composition according to claim 1, further containing 0.1% by mass or more and 5% by mass or less of wax.

5. The composition according to claim 4, wherein the wax is a microcrystalline wax.

6. Substrate and A printed article having an ink coating film of the composition according to any one of claims 1 to 5 disposed on the substrate.

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