Method for manufacturing a printed matter, printing ink set, and printed matter

Abstract

The present invention addresses the problem of providing a printed matter manufacturing method and a printing ink set with which it is possible to obtain printed matter having excellent adhesion to a base material and hiding property.　The present invention provides a printed matter manufacturing method comprising in this order: (1) a step for printing at least one type of lithographic printing black or chromatic color ink and lithographic printing white ink (a) on a base material; and (2) a step for further printing printing white ink (b) different from the lithographic printing white ink (a).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a printed matter, a printing ink set, and a printed matter using the same.

Background Art

[0002] Lithographic printing is a printing method that is widely popular as a system for supplying printed matter at high speed, in large quantities, and at low cost. In recent years, in response to environmental issues, reduction of volatile components contained in ink has been demanded. For this reason, the use of active energy ray-curable ink that does not contain volatile components and instantaneously cures by irradiation with active energy rays has been promoted. In addition to the advantages in terms of the environment, the active energy ray-curable ink can shorten the drying process, and thus can improve the productivity of lithographic printing.

[0003] In recent years, especially for film printed matter, due to the diversification of packages, small lot production has been demanded, and the conversion from high-cost gravure printing to lithographic printing or flexographic printing has been promoted in small lots. Lithographic printing can use ink with a higher viscosity than flexographic printing and has a high adhesion to the film.

[0004] In packaging applications where film printed matter is preferably used, from the viewpoints of protecting the contents and imparting heat sealability, it is generally performed to laminate another plastic film, metal foil, hot melt film (sealant), etc. to the printed matter. Depending on the contents, further sterilization treatment with hot water may be performed. In these processes, since ink peeling is likely to occur, higher adhesion between the substrate and the ink is required.

[0005] In the case of printing on a transparent substrate such as film printing, in order to make characters, patterns, etc. appear clearer, it is common to enhance concealment by printing white ink. As a technique for enhancing the concealment of ink, a printing ink that is cured by an electron beam for letterpress printing or lithographic printing and has a coloring component content in the range of 20 to 70% by mass has been proposed (see, for example, Patent Document 1). Further, as a printing method capable of obtaining a printed matter excellent in whiteness and concealment, a method of flexographic printing using a specific anchor coating agent has been proposed (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, although the printing inks described in Patent Documents 1 and 2 are excellent in concealment, they still have the problem of being insufficient in terms of high adhesion to the substrate required in recent packaging applications and the like.

[0008] Therefore, an object of the present invention is to provide a method for manufacturing a printed matter and a printing ink set capable of obtaining a printed matter excellent in adhesion to a substrate and concealment.

Means for Solving the Problems

[0009] The present invention provides (1) a step of printing at least one type of lithographic printing ink or colored ink and a lithographic printing white ink (a) on a substrate, and (2) a step of further printing a printing white ink (b) different from the lithographic printing white ink (a). It is a method for manufacturing a printed matter having the following in this order.

[0010] The present invention also provides an ink set for printing, comprising at least one lithographic ink or colored ink, a white ink (a) for lithographic printing, and a white ink (b) for printing different from the white ink (a) for lithographic printing.

[0011] The present invention also provides a printed matter using the ink set for printing of the present invention, which is a printed matter having a cured film of the white ink (b) for printing on the cured film of the white ink (a) for lithographic printing.

Effects of the Invention

[0012] According to the method for manufacturing a printed matter and the ink set for printing of the present invention, a printed matter excellent in adhesion and concealability to a substrate can be obtained.

Modes for Carrying Out the Invention

[0013] First, as a first aspect of the present invention, a method for manufacturing a printed matter will be described. The method for manufacturing a printed matter of the present invention is (1) A step of printing at least one lithographic ink or colored ink and a white ink (a) for lithographic printing on a substrate (hereinafter, may be referred to as "step (1)"), and (2) A step of further printing a white ink (b) for printing different from the white ink (a) for lithographic printing (hereinafter, may be referred to as "step (2)"), having these in this order.

[0014] Generally, the color tone of a printed matter is expressed using ink and colored ink. Examples of colored ink include blue ink, red ink, yellow ink, etc. Two or more of these may be used.

[0015] As described above, in order to make characters, patterns, etc. appear clearer, it is common to print white ink. After printing a pattern with black ink and / or colored ink on a substrate, it is preferable to print white ink over the entire surface. At this time, the white ink forms a film on top of these inks in the areas where the black ink and colored ink are printed, and on the substrate in the areas where the black ink and colored ink are not printed. For this reason, the white ink is required to have adhesiveness to the substrate as well as hiding power. Therefore, in the present invention, two different types of white ink are used as the white ink. In step (1), a white ink (a) for lithographic printing, which has excellent adhesiveness to the substrate, is used, and in step (2), a printing white ink (b), which is different from the white ink (a) for lithographic printing, is used to improve the hiding power.

[0016] When the printing white ink (b) is printed on top of the white ink (a) for lithographic printing, since the printing white ink (b) does not affect the adhesiveness to the substrate, it is preferable to select an ink with excellent hiding power.

[0017] Here, the printing white ink (b) in the present invention may have a composition different from that of the white ink (a) for lithographic printing. For example, a white ink for lithographic printing with a composition different from that of the white ink (a) for lithographic printing, a white ink for flexographic printing, a white ink for gravure printing, a white ink for inkjet printing, etc. can be used. In the present invention, it is preferable to use the ink set of the present invention described later as the black or colored ink for lithographic printing, the white ink (a) for lithographic printing, and the printing white ink.

[0018] In step (1), at least one type of black or colored ink for lithographic printing and the white ink (a) for lithographic printing are printed on the substrate.

[0019] Examples of the substrate include art paper, coated paper, cast paper, synthetic paper, newsprint, plastic film, plastic film laminated paper, metal plate, metal vapor deposition paper, metal vapor deposition plastic film, etc. Two or more of these may be used.

[0020] Examples of the plastic film include films made of polyethylene terephthalate, polyethylene, polyester, polyamide, polyimide, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, and the like.

[0021] Examples of the plastic film laminated paper include those in which the aforementioned plastic film is laminated on paper.

[0022] Examples of the metal plate include plates made of zinc, copper, and the like.

[0023] Examples of the metal vapor deposition paper and the metal vapor deposition plastic film include those in which the aforementioned metal or its oxide is vapor deposited on paper or a plastic film.

[0024] Among these, plastic films, plastic film laminated papers, metal plates, metal vapor deposition papers, and metal vapor deposition plastic films do not absorb ink, so the ink does not adhere due to ink absorption, and thus the adhesion with the ink tends to decrease. Therefore, they can be suitably used in the present invention having excellent adhesion between the ink and the base material.

[0025] The base material may be subjected to an easy adhesion treatment. By the easy adhesion treatment, the transferability of the ink to the base material and the adhesion between the base material and the ink can be further improved. Examples of the easy adhesion treatment include surface treatments such as primer coating, corona discharge treatment, and plasma treatment.

[0026] As the lithographic printing white ink (a), it is preferable to use the lithographic printing white ink (a) in the ink set of the present invention described later.

[0027] As the printing method in step (1), lithographic printing is preferable. As the lithographic printing, either water-based lithographic printing or waterless lithographic printing may be used.

[0028] Next, in step (2), white printing ink (b) for printing is printed.

[0029] As the white printing ink (b) for printing, an offset printing white ink or a flexographic printing white ink is preferable, and a flexographic printing white ink is more preferable. The flexographic printing white ink can be flexographically printed even with a low viscosity and can further improve the hiding power.

[0030] As the printing method in step (2), flexographic printing is preferable because a flexographic printing white ink with excellent hiding power can be used.

[0031] In addition, examples of the printing method in step (2) include a wet-on-wet printing method and a dry-on-wet printing method. Among these, from the viewpoint of productivity, the wet-on-wet printing method is preferably used.

[0032] When adopting the wet-on-wet printing method, from the viewpoint of suppressing the migration of the components of the white printing ink (b) for printing to the offset printing white ink (a) and further improving the adhesion to the substrate, as the offset printing white ink (a) and the white printing ink (b) for printing, those having surface tension, tack value, viscosity, etc. within the preferable ranges described later are preferably used.

[0033] In step (2), it is preferable to print such that the film thickness of the cured film of the white printing ink (b) for printing is larger than the film thickness of the cured film of the offset printing white ink (a). Since the white printing ink (b) is responsible for the hiding power with respect to the offset printing white ink (a) that improves the adhesion to the substrate, the hiding power can be further improved by increasing the film thickness of the cured film of the white printing ink (b). The difference between the film thickness of the cured film of the white printing ink (b) for printing and the film thickness of the cured film of the offset printing white ink (a) is preferably 0.1 mm or more, more preferably 0.5 mm or more, and even more preferably 1.0 mm or more.

[0034] The film thickness of the cured film of the white ink (a) for lithographic printing is preferably 0.5 mm or more and 2.0 mm or less, more preferably 0.8 mm or more and 2.0 mm or less, and even more preferably 1.1 mm or more and 2.0 mm or less, from the viewpoint of further improving the adhesion to the substrate.

[0035] The film thickness of the cured film of the white ink (b) for printing is preferably 2.0 mm or more, more preferably 2.5 mm or more, and even more preferably 3.0 mm or more, from the viewpoint of further improving the hiding property. Also, the film thickness of the cured film of the white ink (b) for printing is preferably 4.0 mm or less, more preferably 3.1 mm or less, from the viewpoint of suppressing the migration of the components of the white ink (b) for printing into the white ink (a) for lithographic printing and further improving the adhesion to the substrate.

[0036] Here, the film thickness of the cured film of the white ink (a) for lithographic printing and the cured film of the white ink (b) for printing in the present invention can be calculated by measuring the thickness in the direction perpendicular to the printed matter of each layer at five locations by scanning electron microscope observation of the cross-section of the printed matter and taking the average value.

[0037] In the present invention, when at least one of the lithographic printing ink or colored ink, the white ink (a) for lithographic printing, and the white ink for printing has the property of being cured by active energy rays, it is preferable to further include a step of irradiating the printed ink with active energy rays after step (2). By irradiating with active energy rays, the printed ink can be instantaneously cured, and productivity can be improved. Examples of the active energy rays include ultraviolet rays and electron beams. From the viewpoint of further improving the adhesion, electron beams are preferable. That is, in the present invention, it is preferable to further include (3) a step of irradiating with electron beams (hereinafter sometimes referred to as "step (3)") after step (2). In step (3), an electron beam apparatus having an energy ray of 10 kGy or more and 60 kGy or less is preferably used.

[0038] When providing step (3), from the perspective of suppressing the migration of the components of the white ink for printing (b) to the lithographic printing white ink (a), the time from printing the white ink for printing (b) in step (2) until irradiating with an electron beam in step (3) is preferably 6.0 seconds or less, more preferably 3.0 seconds or less, and even more preferably 2.0 seconds or less.

[0039] In the method for manufacturing a printed matter of the present invention, the difference in surface tension between the lithographic printing white ink (a) and the white ink for printing (b) is preferably 5 mN / m or more and 20 mN / m or less. By setting the difference in surface tension to 5 mN / m or more, the migration of the components of the white ink for printing (b) to the interface with the substrate via the lithographic printing white ink (a) on the printed matter can be suppressed, and the adhesion to the substrate can be further improved. The difference in surface tension is more preferably 8 mN / m or more, and even more preferably 11 mN / m or more. On the other hand, by setting the difference in surface tension to 20 mN / m or less, the transferability of the white ink for printing (b) onto the lithographic printing white ink (a) can be enhanced, the film thickness of the white ink for printing (b) can be increased, and the hiding power can be further improved. The difference in surface tension is more preferably 17 mN / m or less, and even more preferably 14 mN / m or less. Note that the surface tension of the lithographic printing white ink (a) and the white ink for printing (b) may be higher for either.

[0040] The surface tension of the lithographic printing white ink (a) is preferably 45 mN / m or more and 70 mN / m or less. By setting the surface tension to 45 mN / m or more, the ink is more likely to be peeled off from the blanket, and the surface of the ink transferred to the substrate becomes smooth, so that the hiding power can be further improved. The surface tension of the lithographic printing white ink (a) is more preferably 50 mN / m or more, and even more preferably 55 mN / m or more. On the other hand, by setting the surface tension to 70 mN / m or less, the transferability onto the substrate can be improved. The surface tension of the lithographic printing white ink (a) is more preferably 65 mN / m or less, and even more preferably 60 mN / m or less.

[0041] The surface tension of the white ink for printing (b) can be appropriately selected preferably within the range where the difference from the lithographic printing white ink (a) is within the above-mentioned range.

[0042] Here, the surface tensions of the lithographic printing white ink (a) and the printing white ink (b) in the present invention can be calculated from the contact angles measured by the droplet method of an automatic contact angle meter. More specifically, first, after smoothly applying the ink on a glass substrate (beveled, cleaned product) with a thickness of 1 mm × length of 50 mm × width of 50 mm, it is left standing in the dark for 30 minutes to make the ink surface smoother. After standing, droplets of pure water and ethylene glycol with known surface tension values are dropped onto the ink using a syringe. After dropping, the contact angle at the time when 30 seconds have elapsed is measured using an automatic contact angle meter (Drop Master DM-501, manufactured by Kyowa Interface Science Co., Ltd.) under the conditions of an air temperature of 25°C and a humidity of 50%.

[0043] Next, a method for calculating the surface tension from the contact angle will be described. Generally, as shown in the following mathematical formula (1), the surface tension γ is decomposed into a non-polar dispersion force component γ d and a polar hydrogen-bonding dispersion force component γ h . γ = γ d + γ h (1) When a solution B is dropped onto a substance A, Young's equation shown in the following mathematical formula (2) holds for the substance A and the solution B. Here, in the following mathematical formula (2), the surface tension of the substance A is denoted as γ A , the surface tension of the solution B is denoted as γ B , the surface tension between the substance A and the solution B is denoted as γ A-B , and the contact angle between the substance A and the solution B is denoted as θ A-B . γ A = γ A-B + γ B cosθ A-B (2) Also, regarding the surface tension between the substance A and the solution B, the extended Fowkes model shown in the following mathematical formula (3) has been proposed.

[0044]

Equation

[0045] When ink is used as substance A and pure water and ethylene glycol are used as solution B, the following formulas (4) to (5) are derived from the above formulas (1) to (3). However, in formulas (4) to (5), the surface tension, non-polar dispersion force component, and polar hydrogen-bonding dispersion force component of ethylene glycol are represented as E, E(d), and E(h) respectively, and the surface tension γ of the ink I The polar hydrogen-bonding dispersion force component of is represented as I(h), the surface tension, non-polar dispersion force component, and polar hydrogen-bonding dispersion force component of pure water are represented as W, W(d), and W(h) respectively, the contact angle between the ink and ethylene glycol is represented as α, and the contact angle between the ink and pure water is represented as β. Also, in formulas (4) to (5), the dispersion force components γ d , γ h The values of are each 0 or more.

[0046]

Equation

[0047]

Equation

[0048] From formulas (1), (4), and (5), the surface tension of the ink can be calculated from the measured values of the contact angle θ I-EG between the ink and ethylene glycol and the contact angle θ I-W between the ink and pure water. The surface tension γ of pure water is 72.8 mN / m, the non-polar dispersion force component γ d is 21.8 mN / m, the polar hydrogen-bonding dispersion force component γ h is 51.0 mN / m, the surface tension γ of ethylene glycol is 48.8 mN / m, the non-polar dispersion force component γ d is 32.8 mN / m, and the polar hydrogen-bonding dispersion force component γ h is 16.0 mN / m.

[0049] In the method for manufacturing a printed matter of the present invention, the difference (A) - (B) between the tack value (A) of the white ink (a) for lithographic printing and the tack value (B) of the white ink (b) for printing is preferably 2.0 or more and 5.0 or less. The tack value is an index representing the adhesiveness of the ink, and the higher the tack value, the higher the adhesiveness of the ink. When the tack value of the white ink (b) for printing is larger than the tack value (A) of the white ink (a) for lithographic printing and the difference (A) - (B) is 2.0 or more, the phenomenon called reverse trapping, in which the underlying white ink printed on the substrate is peeled off by the overprint white ink and the film thicknesses of the underlying white ink and the overprint white ink become smaller, can be suppressed, and the hiding power can be further improved. (A) - (B) is more preferably 2.5 or more, and even more preferably 3.0 or more. On the other hand, by setting (A) - (B) to 5.0 or less, (B) is kept moderately large, the transferability is enhanced by the cohesive force of the ink, the film thickness of the white ink (b) for printing is increased, and the hiding property can be further improved. (A) - (B) is more preferably 4.5 or less, and even more preferably 4.0 or less.

[0050] The tack value (A) of the white ink (a) for lithographic printing is preferably 3.0 or more and 8.0 or less. By setting the tack value (A) to 3.0 or more, the transferability is enhanced by the cohesive force of the ink, and the transferability of the white ink (b) for printing onto the white ink (a) for lithographic printing is enhanced, so that the hiding power can be further improved. (A) is more preferably 4.5 or more, and even more preferably 6.0 or more. On the other hand, by setting the tack value (A) to 8.0 or less, the transferability to the substrate is enhanced, and the hiding power can be further improved. (A) is more preferably 7.5 or less, and even more preferably 7.0 or less.

[0051] The tack value (B) of the white ink (b) for printing is preferably 1.0 or more and 6.0 or less. By setting (B) to 1.0 or more, the transferability can be enhanced by the cohesive force of the ink, and the hiding property can be further improved. (B) is more preferably 1.5 or more, and even more preferably 2.0 or more. On the other hand, by setting the tack value (B) to 6.0 or less, the transferability onto the white ink (a) for lithographic printing can be enhanced, and the hiding property can be further improved. (B) is more preferably 4.0 or less, and even more preferably 3.0 or less.

[0052] Here, the tack values of the white ink (a) for lithographic printing and the white ink (b) for printing in the present invention can be measured using an Inkometer (a metal roll with a diameter of 76.2 mm, made of EPDM rubber with a Shore A hardness of 70°, a top roll with a diameter of 79.3 mm, and a vibration roll with a diameter of 50.8 mm and made of EPDM rubber with a Shore A hardness of 60°, manufactured by Tester Sangyo Co., Ltd., "INKO-GRAPH" TYPE V) for 1.31 ml of the ink weighed with an ink pipette under the conditions of a rotation speed of 400 rpm and a temperature of 38°C. Such conditions of the rotation speed and temperature simulate the typical environment (temperature, shear rate) of the ink during printing. However, the measured value 1 minute after the start of measurement is taken as the tack value in the present invention.

[0053] In the method for manufacturing a printed matter of the present invention, the difference (C) - (D) between the viscosity (C) of the white ink (a) for lithographic printing and the viscosity (D) of the white ink (b) for printing is preferably 5 Pa·s or more and 30 Pa·s or less. By setting the viscosity difference (C) - (D) to 5 Pa·s or more, the migration of the components of the white ink (b) for printing to the substrate interface via the white ink (a) for lithographic printing on the printed matter can be suppressed, and the adhesion to the substrate can be further improved. The viscosity difference is more preferably 15 Pa·s or more, and even more preferably 20 Pa·s or more. On the other hand, by setting the viscosity difference (C) - (D) to 30 Pa·s or less, the viscosity of the white ink (a) for lithographic printing can be appropriately suppressed, the transferability of the white ink (a) for lithographic printing onto the substrate can be enhanced, and by increasing the film thickness of the white ink (a) for lithographic printing, the migration of the components of the white ink (b) for printing to the substrate interface via the white ink (a) for lithographic printing can be suppressed, and the adhesion to the substrate can be further improved. The viscosity difference is more preferably 25 Pa·s or less.

[0054] The viscosity (C) of the white ink (a) for lithographic printing is preferably 15 Pa·s or more and 40 Pa·s or less. By setting (C) to 15 Pa·s or more, the transferability can be enhanced by the cohesive force of the ink, and the hiding power can be further improved. Also, the migration of the components of the white ink (b) for printing to the substrate interface via the white ink (a) for lithographic printing can be suppressed, and the adhesion to the substrate can be further improved. (C) is more preferably 20 Pa·s or more. On the other hand, by setting the viscosity (C) to 40 Pa·s or less, the transferability to the substrate can be enhanced, and the hiding power can be further improved. Also, the migration of the components of the white ink (b) for printing to the substrate interface via the white ink (a) for lithographic printing can be suppressed, and the adhesion to the substrate can be further improved. (C) is more preferably 30 Pa·s or less, and even more preferably 25 Pa·s or less.

[0055] The viscosity (D) of the white ink (b) for printing is preferably 0.1 Pa·s or more and 20 Pa·s or less. By setting (D) to 0.1 Pa·s or more, the transferability can be enhanced by the cohesive force of the ink, and the hiding property can be further improved. On the other hand, by setting the viscosity (D) to 20 Pa·s or less, the transferability onto the lithographic printing white ink (a) can be enhanced, and the hiding property can be further improved. Also, the migration of the components of the white ink (b) for printing to the substrate interface via the lithographic printing white ink (a) can be suppressed, and the adhesion to the substrate can be further improved. (D) is more preferably 10 Pa·s or less, and even more preferably 5 Pa·s or less.

[0056] Here, the viscosities of the lithographic printing white ink (a) and the white ink (b) for printing in the present invention can be measured by a cone plate type rotational viscometer equipped with a cone plate (cone angle 1°, φ = 40 mm) under the conditions of a temperature of 35°C and a rotation speed of 70 rpm for 0.35 ml of the ink weighed with an ink pipette. Such conditions of rotation speed and temperature simulate the typical environment (temperature, shear rate) of the ink during printing.

[0057] As a combination of the lithographic printing white ink (a) and the white ink (b) for printing that satisfy the above-described characteristics, it is preferable to use the lithographic printing white ink (a) and the white ink (b) for printing in the ink set of the present invention described later.

[0058] Next, as a second aspect of the present invention, the printing ink set of the present invention will be described. The printing ink set of the present invention includes at least one type of lithographic printing ink or colored ink, the lithographic printing white ink (a), and a white ink (b) for printing different from the lithographic printing white ink (a). Similar to the first aspect, the white ink (b) for printing in the present invention may have a composition different from that of the lithographic printing white ink (a).

[0059] The lithographic ink or colored ink, the white ink (a) for lithographic printing, and the white ink (b) for printing preferably each contain a resin, a polyfunctional (meth)acrylate, a pigment, and a surfactant. Here, “(meth)acrylate” is a general term for acrylate and methacrylate. Examples of the ink containing these, such as the lithographic ink or colored ink, include the inks described in

[0037] to

[0090] of International Publication No. 2018 / 062108. Among these, examples of the white ink (a) for lithographic printing include the inks described in

[0037] ,

[0039] ,

[0041] ,

[0043] to

[0049] ,

[0052] ,

[0053] ,

[0055] ,

[0056] ,

[0062] to

[0066] , [0069 to 0090] of International Publication No. 2018 / 062108. Examples of the white ink (b) for printing include the inks described in

[0037] ,

[0039] ,

[0041] ,

[0043] to

[0049] ,

[0053] ,

[0055] ,

[0056] ,

[0062] to

[0066] , [0069 to 0090] of International Publication No. 2018 / 062108. Further, among these, examples of the combination of the lithographic ink or colored ink include ink sets described in

[0095] to

[0157] of International Publication No. 2018 / 062108. Also, as the white ink (b) for printing, a white ink for flexographic printing is preferred.

[0060] In the ink set of the present invention, the difference in surface tension between the white ink for lithography (a) and the white ink for printing (b), the tack value (A) of the white ink for lithography (a) and the tack value (B) of the white ink for printing (b), and the difference (A)-(B) therebetween, and the viscosity (C) of the white ink for lithography (a) and the viscosity (D) of the white ink for printing (b), and the difference (C)-(D) therebetween are preferably within the ranges described in the first aspect. In order to make these properties within the aforementioned preferable ranges, the white ink for lithography (a) preferably contains a resin having a hydrophilic group, a polyfunctional (meth)acrylate having a hydrophilic group, a polyfunctional (meth)acrylate having no hydrophilic group, a pigment, and a surfactant. Further, the white ink for printing (b) preferably contains a resin having a hydrophilic group, a polyfunctional (meth)acrylate having a hydrophilic group, a (meth)acrylate having an aliphatic skeleton having 6 to 18 carbon atoms, a pigment, and a surfactant.

[0061] Here, examples of the hydrophilic group include a hydroxyl group, an amino group, a mercapto group, a carboxyl group, a sulfo group, a phosphoric acid group, etc. Two or more of these may be used.

[0062] In addition, as the (meth)acrylate having an aliphatic skeleton with 6 to 18 carbon atoms, those having no hydrophilic group are preferable. For example, hexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, 1,6 - hexanediol di(meth)acrylate, 1,9 - nonanediol di(meth)acrylate, 1,7 - heptanediol di(meth)acrylate, 1,8 - octanediol di(meth)acrylate, 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 - 1,10 - decanediol di(meth)acrylate, and polyester di(meth)acrylate having an aliphatic skeleton with 6 to 18 carbon atoms as a repeating unit can be mentioned.

[0063] The resin having a hydrophilic group and the polyfunctional (meth)acrylate having a hydrophilic group affect the surface tension of the ink. The more hydrophilic groups there are, the greater the tendency to increase the surface tension. In addition, the interaction between hydrophilic groups affects the tack and viscosity of the ink. The more hydrophilic groups there are, the greater the tendency to increase the tack value and viscosity. As the hydrophilic group, a carboxyl group is preferable because it has excellent pigment dispersibility and it is easy to adjust the above - mentioned properties within a desired range.

[0064] On the other hand, the polyfunctional (meth)acrylate having no hydrophilic group appropriately maintains the content of the resin having a hydrophilic group and the polyfunctional (meth)acrylate having a hydrophilic group in the ink, making it easy to adjust the surface tension, tack value, and viscosity within a desired range.

[0065] Examples of the pigment include titanium dioxide, calcium carbonate, barium sulfate, alumina white, etc. Two or more of these may be used. Among these, titanium dioxide is preferable because of its excellent hiding power. Although titanium dioxide shows basicity, from the viewpoint of well dispersing titanium dioxide in the ink, it is preferable to contain a polymer surfactant as a surfactant in order to adjust the surface tension to the aforementioned preferable range.

[0066] A preferable embodiment of the lithographic printing white ink (a) will be described.

[0067] In order to adjust the surface tension, tack value (A) and viscosity (C) to the aforementioned preferable ranges, the acid value of the resin having a hydrophilic group is preferably 75 mgKOH / g or more and 150 mgKOH / g or less, the weight average molecular weight of the resin having a hydrophilic group is preferably 15,000 or more and 50,000 or less, and the content of the resin having a hydrophilic group in the lithographic printing white ink (a) is preferably 5% by mass or more and 10% by mass or less. In particular, in order to adjust the tack value (A) and viscosity (C) to the aforementioned preferable ranges, the content of the resin having a hydrophilic group is more preferably 6.5% by mass or more and 9.5% by mass or less.

[0068] In order to adjust the surface tension, tack value (A) and viscosity (C) to the aforementioned preferable ranges, the hydroxyl value of the polyfunctional (meth)acrylate having a hydrophilic group is preferably 80 mgKOH / g or more and 130 mgKOH / g or less, and the content of the polyfunctional (meth)acrylate having a hydrophilic group in the lithographic printing white ink (a) is preferably 20% by mass or more and 45% by mass or less. In particular, in order to adjust the surface tension to the aforementioned preferable range, the content of the polyfunctional (meth)acrylate having a hydrophilic group in the lithographic printing white ink (a) is more preferably 27% by mass or more and 40% by mass or less.

[0069] In order to adjust the surface tension, tack value (A), and viscosity (C) to the aforementioned preferred ranges, the content of the polyfunctional (meth)acrylate having no hydrophilic group in the white ink (a) for lithographic printing is preferably 5% by mass or more and 25% by mass or less. In particular, in order to adjust the surface tension to the aforementioned preferred range, the content of the polyfunctional (meth)acrylate having no hydrophilic group in the white ink (a) for lithographic printing is more preferably 10% by mass or more and 20% by mass or less.

[0070] From the viewpoint of easily adjusting the surface tension to the aforementioned preferred range, the content of the polymer surfactant in the white ink (a) for lithographic printing is preferably 0.6% by mass or more and 1.5% by mass or less.

[0071] Next, the preferred embodiments of the printing ink (b) will be described.

[0072] In order to adjust the tack value (B) and viscosity (D) to the aforementioned preferred ranges, the acid value of the resin having a hydrophilic group is preferably 50 mgKOH / g or more and 120 mgKOH / g or less, the weight average molecular weight of the resin having a hydrophilic group is preferably 5,000 or more and 40,000 or less, and the content of the resin having a hydrophilic group in the white ink (b) for printing is preferably 2% by mass or more and 5% by mass or less. In particular, in order to adjust the tack value (B) to the aforementioned preferred range, the content of the resin having a hydrophilic group in the printing ink (b) is more preferably 2.5% by mass or more and 4.5% by mass or less.

[0073] In order to adjust the surface tension, tack value (B), and viscosity (D) to the aforementioned preferred ranges, the hydroxyl value of the polyfunctional (meth)acrylate having a hydrophilic group is preferably 5 mgKOH / g or more and 130 mgKOH / g or less, and the content of the polyfunctional (meth)acrylate having a hydrophilic group in the white ink (b) for printing is preferably 20% by mass or more and 45% by mass or less.

[0074] In order to adjust the tack value (B) and the viscosity (D) to the above-mentioned preferable ranges, it is preferable to contain a (meth)acrylate having an aliphatic skeleton with 6 to 18 carbon atoms, and the content of the (meth)acrylate having an aliphatic skeleton with 6 to 18 carbon atoms in the white ink (b) for printing is preferably 3% by mass or more and 20% by mass or less.

[0075] The content of the polymer surfactant in the white ink (b) for printing is preferably 1.7% by mass or more and 3.0% by mass or less.

[0076] From the viewpoint of the productivity of printed matter, in the ink set for printing of the present invention, it is preferable that at least one of the lithographic printing ink or colored ink, the white ink (a) for lithographic printing, and the white ink (b) for printing is an electron beam curable type that is cured by electron beam irradiation. More preferably, all of these inks are electron beam curable types. An ink set containing the above-mentioned polyfunctional (meth)acrylate can be cured by electron beam irradiation.

[0077] The printed matter of the present invention is a printed matter using the above-mentioned ink set for printing, and has a cured film of the white ink (b) for printing on the cured film of the white ink (a) for lithographic printing.

[0078] Similar to the above-mentioned first aspect, also in the printed matter of the present invention, it is preferable that the film thickness of the cured film of the white ink (b) for printing is larger than the film thickness of the cured film of the white ink (a) for lithographic printing. As the difference between the film thickness of the cured film of the white ink (b) for lithographic printing and the film thickness of the cured film of the white ink (a) for printing in the printed matter of the present invention, 0.1 mm or more is preferable, more preferably 0.5 mm or more, and still more preferably 1.0 mm or more.

[0079] The film thickness of the cured film of the white ink (a) for lithographic printing in the printed matter of the present invention is preferably 0.5 mm or more and 2.0 mm or less, more preferably 0.8 mm or more and 2.0 mm or less, and still more preferably 1.1 mm or more and 2.0 mm or less from the viewpoint of further improving the adhesion to the substrate.

[0080] From the perspective of further improving concealment, the film thickness of the cured film of the white printing ink (b) in the printed matter of the present invention is preferably 2.0 mm or more, more preferably 2.5 mm or more, and even more preferably 3.0 mm or more. Also, from the perspective of suppressing the migration of the components of the white printing ink (b) for printing to the white printing ink (a) for lithography and further improving the adhesion to the substrate, the film thickness of the cured film of the white printing ink (b) for printing is preferably 4.0 mm or less, and more preferably 3.1 mm or less.

Examples

[0081] Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited only to these.

[0082] <Ink raw materials> Resin: A copolymer composed of 25% by mass of methyl methacrylate, 25% by mass of styrene, and 50% by mass of methacrylic acid was subjected to an addition reaction with 0.55 equivalents of glycidyl methacrylate with respect to its carboxyl group to obtain Resin 1 having an ethylenically unsaturated group and a hydrophilic group. The obtained Resin 1 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. (Meth)acrylate 1: A mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (manufactured by MIWON Co., Ltd., “Miramer” (registered trademark) M340), hydroxyl value 115 mgKOH / g (Meth)acrylate 2: Tricyclodecane dimethanol diacrylate (manufactured by Daicel Ornex Co., Ltd., EBECRYL 130), hydroxyl value 0 mgKOH / g (Meth)acrylate 3: 1,10 - Decanediol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., NK Ester A-DOD-N), hydroxyl value 0 mgKOH / g (Meth)acrylate 4: Trimethylolpropane EO-modified triacrylate (manufactured by MIWON Co., Ltd., “Miramer” (registered trademark) M3130), hydroxyl value 10 mgKOH / g (Meth)acrylate 5: Stearyl acrylate (manufactured by MIWON Co., Ltd., “Miramer” (registered trademark) M180), hydroxyl value 0 mgKOH / g Pigment 1: Carbon Black MA8 (manufactured by Mitsubishi Chemical Corporation) Pigment 2: Seikashianin Blue 4920 (manufactured by Dainichi Seika Chemicals Co., Ltd.) Pigment 3: Carmine 6B 1483LT (manufactured by Dainichi Seika Chemicals Co., Ltd.) Pigment 4: Fast Yellow 2300 (manufactured by Dainichi Seika Chemicals Co., Ltd.) Pigment 5: "Taypek" (registered trademark) CR58-2 (manufactured by Ishihara Sangyo Kaisha, Ltd.) Surfactant 1: "Disperbyk" (registered trademark) 2013 (manufactured by ALTANA) Surfactant 2: "Solsperse" (registered trademark) 54000 (manufactured by Lubrizol), a polymeric surfactant Surfactant 3: "Solsperse" (registered trademark) 3000 (manufactured by Lubrizol), a polymeric surfactant.

[0083] <Analysis Method of Ink Raw Materials> (1) Weight-average molecular weight A dilution solution was prepared by diluting the resin with tetrahydrofuran to a concentration of 0.25% by mass. Using a mix rotor (MIX-ROTAR VMR-5, manufactured by AS ONE Corporation), the dilution solution was stirred at a rotation speed of 100 rpm for 5 minutes to dissolve the resin, and then filtered using a 0.2 μm filter (Z227536-100EA, manufactured by SIGMA). Using the obtained filtrate, the weight-average molecular weight of the resin was measured by gel permeation chromatography (GPC) with tetrahydrofuran as the mobile phase.

[0084] For GPC, HLC-8220 (manufactured by Tosoh Corporation) was used, and columns were connected in the order of TSKgel SuperHM-H (manufactured by Tosoh Corporation), TSKgel SuperHM-H (manufactured by Tosoh Corporation), and TSKgel SuperH2000 (manufactured by Tosoh Corporation), and the measurement was performed by RI detection. The calibration curve was created using a polystyrene standard substance. 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.

[0085] (2) Acid value The acid value of the resin was measured by the method described in the neutralization titration method in Section 3.1 of the test method of JIS K 0070:1992.

[0086] (3) Iodine value The iodine value of the resin was measured by the method described in Section 6.0 of the test method of JIS K 0070:1992.

[0087] (4) Hydroxyl value The hydroxyl value of (meth)acrylate was measured by the method described in the neutralization titration method in Section 7.1 of the test method of JIS K 0070:1992.

[0088] <Evaluation method> (1) Surface tension After applying the ink used in each example and comparative example onto a glass substrate (chamfered, cleaned, manufactured by Ishida Rika Co., Ltd.) with a thickness of 1 mm × length of 50 mm × width of 50 mm, in order to make the ink surface smoother, it was left standing in the dark for 30 minutes. Droplets of pure water and ethylene glycol with known surface tension values were dropped onto the ink after standing using a syringe, and the contact angle 30 seconds after dropping was measured under the conditions of an air temperature of 25°C and a humidity of 50% using an automatic contact angle meter (Drop Master DM-501, manufactured by Kyowa Interface Science Co., Ltd.).

[0089] Next, from the contact angle, the surface tension γ of the ink was calculated using Formulas (1), (4), and (5). I was calculated. γ = γ d + γ h (1)

[0090]

Number

[0091] Note that the surface tension γ of pure water is 72.8 mN / m, the non-polar dispersive force component γ d is 21.8 mN / m, the polar hydrogen-bonding dispersive force component γ h is 51.0 mN / m, the surface tension γ of ethylene glycol is 48.8 mN / m, and the non-polar dispersive force component γd is 32.8 mN / m, and the polar hydrogen-bonding dispersive force component γ h is 16.0 mN / m.

[0092] (2) Tack value The ink used in each example and comparative example was weighed at 1.31 ml using an ink pipette, and measured using an inkometer (“INKO-GRAPH” TYPE V, manufactured by Tester Sangyo Co., Ltd.) having a metal roll with a diameter of 76.2 mm, an EPDM rubber with a Shore A hardness of 70°, a top roll with a diameter of 79.3 mm, and a vibration roll with a diameter of 50.8 mm and an EPDM rubber with a Shore A hardness of 60° under the conditions of a rotation speed of 400 rpm and a temperature of 38°C. However, the measured value 1 minute after the start of measurement was used as the tack value in the present invention.

[0093] (3) Viscosity The ink used in each example and comparative example was weighed at 0.35 ml using an ink pipette, and the viscosity was measured using a cone-plate type rotational viscometer rheometer (MCR301, manufactured by Anton Paar) equipped with a cone plate (cone angle 1°, φ = 40 mm) under the conditions of a temperature of 35°C and a rotation speed of 70 rpm.

[0094] (4) Film thickness The cross-section of the printed matter obtained in each example and comparative example was magnified and observed using a scanning electron microscope (S-5500, manufactured by Hitachi High-Technologies Corporation), and the thickness in the direction perpendicular to the printed matter of each layer was randomly measured at 5 locations, and the average value thereof was used as the film thickness.

[0095] (5) Concealability For the portion of the printed matter obtained in each example and comparative example where only white ink was printed, the concealment rate was measured from the substrate surface in the concealment rate measurement mode using a densitometer (xEact Basic, manufactured by X-rite). If the concealment rate was less than 60%, the concealability was insufficient; if it was 60% or more and less than 65%, the concealability was slightly good; if it was 65% or more and less than 70%, the concealability was good; and if it was 70% or more, it was determined that the concealability was extremely good.

[0096] (6) Adhesion Among the printed matters obtained in each of the examples and comparative examples, on the cured film of the ink at the location where only white ink was printed, a mixture of "Takelac" (registered trademark) A-626 (manufactured by Mitsui Chemicals, Inc.) and "Takenate" (registered trademark) A-50 (manufactured by Mitsui Chemicals, Inc.) with a mass ratio of 8 / 1 was applied by the bar coating method as an adhesive. At this time, the coating amount after drying at 80°C for 1 minute was adjusted to be 4.0 g / m 2 After laminating the printed matter coated with the adhesive and an unstretched polypropylene film "Trefan" (registered trademark) ZK207 (manufactured by Toray Industries, Inc., thickness 70 μm) as a sealant using a hand roller, it was aged at 40°C for 72 hours to obtain a film laminate of sealant / adhesive / cured film of ink / polyester film.

[0097] From the film laminate, a slice with a width of 15 mm and a length of 50 mm was cut out, and using a tensilon universal material testing machine (manufactured by A&D Company, model number "RTG-1210"), the peel strength between the polyester film and the sealant was measured by the 90-degree T-peel method (JIS K 6854-3:1999), and the value at the first maximum point was taken as the laminate peel strength. The peel strength was measured under the conditions of an air temperature of 25°C, a humidity of 50%, and a test speed of 300 mm / min.

[0098] When the peel strength was less than 1.0 N / 15 mm, the adhesion was insufficient; when it was 1.0 N / 15 mm or more and less than 2.0 N / 15 mm, the adhesion was somewhat good; when it was 2.0 N / 15 mm or more and less than 3.0 N / 15 mm, the adhesion was good; and when it was 3.0 N / 15 mm or more, it was judged that the adhesion was extremely good.

[0099] <Preparation of Lithographic Printing Ink or Colored Ink> In the "Type of Ink" in Table 1, "Litho" means lithographic printing ink, and "Flexo" means flexographic printing ink.

[0100] Weighed the resin and (meth)acrylate shown in each color of the ink or colored pigments in Table 1, and while stirring at a rotation speed of 500 rpm using a dispersing blade, heated at 95 °C for 390 minutes to obtain a varnish.

[0101] To the obtained varnish, added the ink or colored pigment of each color and surfactant in Table 1, and passed it through 5 times with a gap of 1 using a three-roll mill “EXAKT” (registered trademark) M-80S (manufactured by EXAKT) to obtain an offset printing ink.

[0102] [Example 1] <Preparation of white ink> In Table 1, “first-layer white” means the white ink printed in the first layer of the white ink, and “second-layer white” means the white ink printed in the second layer.

[0103] Weighed the resin and (meth)acrylate shown in the first-layer white in Table 1, and while stirring at a rotation speed of 500 rpm using a dispersing blade, heated at 95 °C for 390 minutes to obtain a varnish. To the obtained varnish, added the pigment and surfactant described in Table 1, and passed it through 5 times with a gap of 1 using a three-roll mill “EXAKT” (registered trademark) M-80S (manufactured by EXAKT) to obtain an offset printing white ink.

[0104] Weighed the resin and (meth)acrylate shown in the second-layer white in Table 1, and while stirring at a rotation speed of 500 rpm using a dispersing blade, heated at 95 °C for 390 minutes to obtain a varnish. To the obtained varnish, added the pigment and surfactant described in Table 1, and dispersed it using an Eiger mill (using zirconia beads with a diameter of 0.5 mm as the medium) to obtain a flexographic printing white ink.

[0105] <Manufacture of printed matter> Using an offset and flexo hybrid printing press (CI-8, manufactured by Comexi), waterless offset printing plates (TAN-E, manufactured by Toray Industries, Inc.) were installed on the 1st to 5th cylinders, and a flexo printing plate (“Cyrel” (registered trademark) EASY FAST EFX, manufactured by DuPont) was installed on the 8th cylinder. Offset printing inks, blue, red, yellow, white for the first layer, and white for the second layer were installed on the 1st to 5th and 8th cylinders in sequence. On a polyester film PTM12 (manufactured by Unitika, thickness 12 μm) as the substrate, under the conditions of ink feed rate: 50%, chill roller setting temperature for the impression cylinder: 30 °C, and chill roller setting temperature for the oscillating roller and ink pot: 28 °C, using T414 (manufactured by King Yang, thickness 1.95 mm) for the blanket, printing was performed at a speed of 100 m / min by the wet-on-wet printing method. After printing all the inks, an electron beam with an energy of 110 kV and a dose of 40 kGy was irradiated using the electron beam irradiation device attached to the printing press to cure the inks and obtain a printed matter. At this time, an image was configured so that there would be a portion in the printed matter where only the white ink for offset printing (a) was printed as the first layer and the white ink for printing (b) was printed as the second layer on the substrate.

[0106] The results of evaluating each ink and the obtained printed matter by the above-described method are shown in Table 1. The hiding power and adhesion were extremely good.

[0107] [Examples 2 to 4] [Preparation of White Ink] Offset printing white ink and flexo printing white ink were obtained in the same manner as in Example 1, except that the composition of the white ink for the first layer was changed as described in Table 1.

[0108] [Manufacture of Printed Matter] A printed matter was obtained in the same manner as in Example 1, except that the white ink for the first layer described in Table 1 was used.

[0109] The results of evaluating each ink and the obtained printed matter by the above-described method are shown in Table 1.

[0110] [Example 5] [Preparation of White Ink] Offset printing white ink and flexographic printing white ink were obtained in the same manner as in Example 1, except that the composition of the second-layer white ink was changed as described in Table 2.

[0111] <Manufacture of Printed Matter> A printed matter was obtained in the same manner as in Example 1, except that the second-layer white ink described in Table 2 was used.

[0112] Table 2 shows the results of evaluating each ink and the obtained printed matter by the above-described method.

[0113] [Example 6] <Preparation of White Ink> Offset printing white ink and flexographic printing white ink were obtained in the same manner as in Example 1, except that the composition of the first-layer white ink was changed as described in Table 2.

[0114] <Manufacture of Printed Matter> A printed matter was obtained in the same manner as in Example 1, except that the first-layer white ink described in Table 2 was used.

[0115] Table 2 shows the results of evaluating each ink and the obtained printed matter by the above-described method.

[0116] [Comparative Example 1] <Manufacture of Printed Matter> A printed matter was obtained in the same manner as in Example 1, except that a waterless offset printing plate (TAN-E, manufactured by Toray Industries, Inc.) was installed on the first to sixth cylinders, and offset printing ink, blue, red, yellow, first-layer white, and second-layer white inks were installed on the first to sixth cylinders in order.

[0117] Table 2 shows the results of evaluating each ink and the obtained printed matter by the above-described method. In Comparative Example 1, in which the same composition of offset printing white ink was used for the first-layer white and the second-layer white, the hiding power was insufficient.

[0118] [Comparative Example 2] A waterless lithographic printing plate (TAN-E, manufactured by Toray Industries, Inc.) was installed on the 1st to 4th cylinders, and a flexographic printing plate ("Cyrel" (registered trademark) EASY FAST EFX, manufactured by DuPont) was installed on the 8th cylinder. Lithographic printing ink, blue, red, yellow, and white ink for the first layer were installed on the 1st to 4th and 8th cylinders in that order. A printed matter was obtained in the same manner as in Example 1, except that the image was configured so that a portion where only white ink for flexographic printing was printed on the substrate was obtained in the printed matter.

[0119] The results of evaluating each ink and the obtained printed matter by the above-described method are shown in Table 2. In Comparative Example 2, where only white ink for flexographic printing was used as the white ink for the first layer, the adhesion was insufficient.

[0120]

Table 1

[0121]

Table 2

Claims

1. (1) A step of printing at least one type of lithographic printing ink or colored ink and a white lithographic printing ink (a) on a substrate, and (2) A step of further printing a white printing ink (b) different from the white lithographic printing ink (a), having these steps in this order, wherein the difference (C) - (D) between the viscosity (C) of the white lithographic printing ink (a) and the viscosity (D) of the white printing ink (b) is 5 Pa·s or more and 30 Pa·s or less, A method for manufacturing a printed matter.

2. The method for manufacturing a printed matter according to claim 1, wherein the white printing ink (b) is a white flexographic printing ink.

3. The method for manufacturing a printed matter according to claim 1 or 2, wherein the difference in surface tension between the white lithographic printing ink (a) and the white printing ink (b) is 5 mN / m or more and 20 mN / m or less.

4. The method for manufacturing a printed matter according to claim 1 or 2, wherein the difference (A) - (B) between the tack value (A) of the white lithographic printing ink (a) and the tack value (B) of the white printing ink (b) is 2.0 or more and 5.0 or less.

5. The method for manufacturing a printed matter according to claim 1 or 2, wherein printing is performed such that the film thickness of the cured film of the white printing ink (b) is greater than the film thickness of the cured film of the white lithographic printing ink (a).

6. The method for manufacturing a printed matter according to claim 5, wherein printing is performed such that the film thickness of the cured film of the white lithographic printing ink (a) is 0.5 μm or more and 2.0 μm or less, and the film thickness of the cured film of the white printing ink (b) is 2.0 μm or more and 4.0 μm or less.

7. The method for manufacturing a printed matter according to claim 1 or 2, wherein printing is performed by a wet-on-wet printing method in the step (2).

8. The method for manufacturing a printed matter according to claim 1 or 2, further including a step (3) of irradiating with an electron beam after the step (2).

9. An ink set for printing, comprising at least one lithographic printing ink or colored ink, a white ink (a) for lithographic printing, and a white ink (b) for printing different from the white ink (a) for lithographic printing, wherein the difference (C) - (D) between the viscosity (C) of the white ink (a) for lithographic printing and the viscosity (D) of the white ink (b) for printing is 5 Pa·s or more and 30 Pa·s or less.

10. The ink set for printing according to claim 9, wherein the white ink (b) for printing is a white ink for flexographic printing.

11. The ink set for printing according to claim 9 or 10, wherein the difference in surface tension between the white ink (a) for lithographic printing and the white ink (b) for printing is 5 mN / m or more and 20 mN / m or less.

12. The ink set for printing according to claim 9 or 10, wherein the difference (A) - (B) between the tack value (A) of the white ink (a) for lithographic printing and the tack value (B) of the white ink (b) for printing is 2.0 or more and 5.0 or less.

13. A printed matter using the ink set for printing according to claim 9 or 10, wherein the printed matter has a cured film of the white ink (b) for printing on the cured film of the white ink (a) for lithographic printing.

14. The printed matter according to claim 13, wherein the film thickness of the cured film of the white ink (b) for printing is larger than the film thickness of the cured film of the white ink (a) for lithographic printing.

15. The printed matter according to claim 14, wherein the film thickness of the cured film of the white ink (a) for lithographic printing is 0.5 μm or more and 2.0 μm or less, and the film thickness of the cured film of the white ink (b) for printing is 2.0 μm or more and 4.0 μm or less.

Images