WO2023013571A1

WO2023013571A1 - Printed matter manufacturing method, printing ink set, and printed matter

Info

Publication number: WO2023013571A1
Application number: PCT/JP2022/029444
Authority: WO
Inventors: 小清水昇; 辻祐一; 井上武治郎
Original assignee: 東レ株式会社
Priority date: 2021-08-06
Filing date: 2022-08-01
Publication date: 2023-02-09
Also published as: JPWO2023013571A1

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

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

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

Lithographic printing is a printing method that is widely used as a system that supplies printed matter at high speed, in large quantities, and at low cost. In recent years, there has been a demand for reducing volatile components contained in ink in order to deal with environmental problems. For this reason, the use of active energy ray-curable inks, which do not contain volatile components and are instantaneously cured by irradiation with active energy rays, has been promoted. Actinic energy ray-curable inks are environmentally friendly and can shorten the drying process, thereby improving the productivity of lithographic printing.

Also, in recent years, especially for film printed matter, there is a demand for small lot support due to the diversification of packages, and there is a shift from gravure printing, which is relatively expensive for small lots, to lithographic printing and flexographic printing. Compared to flexographic printing, lithographic printing can use ink with high viscosity and has high adhesion to the film.

In packaging applications where film prints are preferably used, it is possible to attach another plastic film, metal foil, heat-melting film (sealant), etc. to the printed matter from the viewpoint of protecting the contents and imparting heat-sealing properties. commonly done. Further, depending on the contents, sterilization treatment with hot water or the like is further performed. Since the ink tends to peel off in these steps, there is a demand for higher adhesion between the substrate and the ink.

In the case of printing on transparent substrates such as film printing, it is common to increase the concealability by printing with white ink in order to make characters and patterns appear more vivid. As a technique for enhancing the concealability of ink, a printing ink for letterpress printing or lithographic printing that is cured with an electron beam, characterized in that the content of a coloring component therein is in the range of 20 to 70% by mass. There has been proposed a printing ink that does so (see, for example, Patent Document 1). In addition, as a printing method capable of obtaining a printed matter excellent in whiteness and opacity, a method of flexographic printing using a specific anchor coating agent has been proposed (see, for example, Patent Document 2).

Japanese Patent Application Laid-Open No. 2004-123802 JP 2015-134914 A

However, although the printing inks described in Patent Documents 1 and 2 are excellent in concealability, they still have the problem of being insufficient in terms of the high adhesion to the base material that is required in packaging applications in recent years.

Therefore, an object of the present invention is to provide a method for producing a printed matter and a printing ink set that can obtain a printed matter that is excellent in adhesiveness to a substrate and hiding property.

The present invention
(1) a step of printing at least one lithographic ink or chromatic ink and a lithographic white ink (a) onto a substrate;
(2) a step of further printing a white ink for printing (b) different from the white ink for lithographic printing (a);
in this order.

Further, the present invention provides a printing ink containing at least one lithographic printing ink or chromatic ink, a lithographic printing white ink (a), and a printing white ink (b) different from the lithographic printing white ink (a). Ink set.

The present invention also provides a printed matter using the printing ink set of the present invention, wherein the printed matter has a cured film of the white ink for printing (b) on a cured film of the white ink for lithographic printing (a). be.

According to the method for producing a printed matter and the printing ink set of the present invention, it is possible to obtain a printed matter that is excellent in adhesion to the base material and hiding property.

First, as a first aspect of the present invention, a method for manufacturing a printed matter will be described. The printed matter manufacturing method of the present invention comprises:
(1) A step of printing at least one lithographic ink or chromatic ink and a lithographic white ink (a) on a substrate (hereinafter sometimes referred to as "step (1)"). ,and,
(2) a step of further printing a white ink for printing (b) different from the white ink for lithographic printing (a) (hereinafter sometimes referred to as "step (2)");
in this order.

In general, the shades of printed matter are expressed using black ink and chromatic ink. Examples of chromatic inks include indigo ink, red ink, and yellow ink. You may use 2 or more types of these.

As mentioned above, it is common to print with white ink in order to make characters and patterns appear more vivid. Printing with white ink is preferred. At this time, the white ink forms a film on the black ink and the chromatic ink in the areas printed thereon, and on the base material in the areas where the black ink and the chromatic ink are not printed. . For this reason, the white ink is required to have not only hiding properties but also adhesion to the substrate. Therefore, in the present invention, two different types of white inks are used. The white ink for printing (b) different from the ink (a) is used to improve the concealability.

When the white ink for printing (b) is printed on the white ink for lithographic printing (a), the white ink for printing (b) does not affect the adhesion to the substrate. Select is preferred.

Here, the white ink for printing (b) in the present invention may have a different composition from the white ink for lithographic printing (a). White ink for printing, white ink for flexographic printing, white ink for gravure printing, white ink for inkjet printing, and the like can be used. In the present invention, the ink set of the present invention, which will be described later, is preferably used as the planographic printing ink or chromatic ink, the planographic printing white ink (a), and the printing white ink.

In step (1), at least one type of lithographic printing ink or chromatic ink and lithographic printing white ink (a) are printed on the substrate.

Examples of base materials include art paper, coated paper, cast paper, synthetic paper, newsprint, plastic film, plastic film laminated paper, metal plate, metallized paper, and metallized plastic film. You may use 2 or more types of these.

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

Examples of plastic film-laminated paper include those in which the aforementioned plastic film is laminated on paper.

Examples of metal plates include plates made of zinc, copper, and the like.

Examples of metal-deposited paper and metal-deposited plastic films include papers and plastic films on which the metals and their oxides are deposited.

Among these, plastic film, plastic film-laminated paper, metal plate, metal-deposited paper, and metal-deposited plastic film do not absorb ink. Therefore, it can be suitably used in the present invention in which the adhesion between the ink and the substrate is excellent.

The base material may be subjected to easy-adhesion treatment. The easy-adhesion treatment can further improve the transferability of the ink to the substrate and the adhesion between the substrate and the ink. Examples of the easy-adhesion treatment include primer coating, corona discharge treatment, plasma treatment, and other surface treatments.

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

Planographic printing is preferable as the printing method in step (1). As lithographic printing, either wet lithographic printing or waterless lithographic printing may be used.

Next, in step (2), white printing ink (b) is printed.

The white ink for printing (b) is preferably white ink for lithographic printing or white ink for flexographic printing, and more preferably white ink for flexographic printing. The white ink for flexographic printing can be used for flexographic printing even if it has a low viscosity, and can further improve the concealability.

As the printing method in step (2), flexographic printing is preferable because white ink for flexographic printing, which has excellent hiding properties, can be used.

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, the wet-on-wet printing method is preferably used from the viewpoint of productivity.

When a wet-on-wet printing method is adopted, from the viewpoint of suppressing the migration of the component of the white printing ink (b) to the white ink for lithographic printing (a) and further improving the adhesion to the substrate, lithographic printing As the white ink for industrial use (a) and the white ink for printing (b), it is preferable to use those whose surface tension, tack value, viscosity, etc. are within the preferred ranges described later.

In step (2), it is preferable to print so that the thickness of the cured film of the white ink for printing (b) is greater than the thickness of the cured film of the white ink for lithographic printing (a). In contrast to the white ink for lithographic printing (a), which improves the adhesion to the base material, the white ink for printing (b) is responsible for concealing properties, so the thickness of the cured film of the white ink for printing (b) is By increasing the size, the concealability can be further improved. The difference between the film thickness of the cured film of the white ink for lithographic printing (b) and the film thickness of the cured film of the white ink for printing (a) is preferably 0.1 mm or more, more preferably 0.5 mm or more, and more preferably 0.5 mm or more. Preferably, it is 1.0 mm or more.

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

The thickness of the cured film of the white printing ink (b) 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 concealability. In addition, the thickness of the cured film of the white printing ink (b) suppresses the migration of the components of the white printing ink (b) to the white ink for lithographic printing (a), thereby further improving the adhesion to the substrate. 4.0 mm or less is preferable, and 3.1 mm or less is more preferable from the viewpoint of increasing the thickness.

Here, the film thickness of the cured film of the white ink for lithographic printing (a) and the cured film of the white ink for printing (b) in the present invention is determined by observing the cross section of the printed matter with a scanning electron microscope. Measurement can be performed at 5 points each, and the average value can be used for calculation.

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

When the step (3) is provided, the white printing ink (b) is printed in the step (2) from the viewpoint of suppressing the migration of the components of the white printing ink (b) to the white ink for lithographic printing (a). The time from the step (3) to the electron beam irradiation is preferably 6.0 seconds or less, more preferably 3.0 seconds or less, and even more preferably 2.0 seconds or less.

In the method for producing a printed matter of the present invention, the difference in surface tension between the white ink for lithographic printing (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, migration of the components of the white printing ink (b) to the interface with the substrate via the white ink for lithographic printing (a) on the printed matter is suppressed. , the adhesion to the substrate can be further improved. The difference in surface tension is more preferably 8 mN/m or more, 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 printing ink (b) onto the white ink for lithographic printing (a) is enhanced, and the thickness of the white ink for printing (b) is increased. can be increased, and the concealability can be further improved. The difference in surface tension is more preferably 17 mN/m or less, more preferably 14 mN/m or less. Either the white ink for lithographic printing (a) or the white ink for printing (b) may have a higher surface tension.

The surface tension of the white ink for lithographic printing (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 can be easily peeled off from the blanket, and the surface of the ink transferred to the substrate becomes smooth, thereby further improving the concealability. The surface tension of the white ink (a) for lithographic printing is more preferably 50 mN/m or more, 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 white ink (a) for lithographic printing is more preferably 65 mN/m or less, still more preferably 60 mN/m or less.

The surface tension of the white ink for printing (b) can be appropriately selected within a range in which the difference from the white ink for lithographic printing (a) is within the above range.

Here, the surface tension of the white ink for lithographic printing (a) and the white ink for printing (b) in the present invention can be calculated from the contact angle measured by the droplet method using an automatic contact angle meter. More specifically, first, the ink is applied smoothly onto a glass substrate (beveled, washed) having a thickness of 1 mm, a length of 50 mm, and a width of 50 mm. Let stand in the dark. Droplets of pure water and ethylene glycol having known surface tension values are deposited on the ink after standing by using a syringe. The contact angle is measured 30 seconds after the drop is applied, using an automatic contact angle meter (Drop Master DM-501, manufactured by Kyowa Interface Science Co., Ltd.) under the conditions of a temperature of 25° C. and a humidity of 50%.

Next, a method for calculating the surface tension from the contact angle will be described. In general, 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 as shown in the following formula (1).
γ = γ ^d + γ ^h (1)
When the solution B is dropped onto the substance A, the Young's formula shown in the following formula (2) is established between the substance A and the solution B. Here, in the following formula (2), γ _A is the surface tension of substance A, γ B is the surface tension of solution B, γ _AB is the surface tension between substance A and solution B, and γ _AB is the surface tension of substance A and solution B. is denoted as θ _AB .
γ _A = γ _AB + γ _B cos θ _AB (2)
Further, an extended Fowkes model shown in the following formula (3) has been proposed for the surface tension between substance A and solution B.

When using ink as the substance A and pure water and ethylene glycol as the 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 of ethylene glycol, the nonpolar dispersion force component, and the polar hydrogen bonding dispersion force component are E, E(d), and E(h), respectively, The polar hydrogen bonding dispersing force component of the surface tension γ _I of the ink is I(h), and the surface tension of pure water, the nonpolar dispersing force component, and the polar hydrogen bonding dispersing force component are W and W, respectively. W(d) and W(h), α is the contact angle between the ink and ethylene glycol, and β is the contact angle between the ink and pure water. Further, in the formulas (4) to (5), the values of the dispersion force components γ ^d and γ ^h are each 0 or more.

The surface tension of the ink is 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 using equations (1), (4), and (5). can do. The surface tension γ of pure water is 72.8 mN/m, the nonpolar dispersion force component ^γd is 21.8 mN/m, the polar hydrogen bonding dispersion force component ^γh is 51.0 mN/m, and ethylene glycol has a surface tension γ of 48.8 mN/m, a nonpolar dispersion force component ^γd of 32.8 mN/m, and a polar hydrogen bonding dispersion force component ^γh of 16.0 mN/m.

In the method for producing a printed matter of the present invention, the difference (A)−(B) between the tack value (A) of the white ink for lithographic printing (a) and the tack value (B) of the white ink for printing (b) is 2. 0 or more and 5.0 or less are preferable. The tack value is an index representing the tackiness of the ink, and the higher the tack value, the higher the tackiness of the ink. The tack value of the white ink for printing (b) is greater than the tack value (A) of the white ink for lithographic printing (a), and the difference (A) - (B) is 2.0 or more, It is possible to suppress the phenomenon called reverse trapping, in which the lower layer white ink printed on the upper layer is peeled off by the post-printing white ink, and the film thickness of the lower layer white ink and the post-printing white ink is reduced, and the hiding rate can be further improved. (A)-(B) is more preferably 2.5 or more, further preferably 3.0 or more. On the other hand, by setting (A)-(B) to 5.0 or less, (B) is kept moderately large, the cohesive force of the ink increases transferability, and the film thickness of the white printing ink (b) is increased. It is possible to increase the size and further improve the concealability. (A)-(B) is more preferably 4.5 or less, further preferably 4.0 or less.

The tack value (A) of the white ink for lithographic printing (a) is preferably 3.0 or more and 8.0 or less. By setting the tack value (A) to 3.0 or more, the cohesive force of the ink enhances the transferability, and the transferability of the white ink for printing (b) onto the white ink for lithographic printing (a) is enhanced. , the concealability 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, it is possible to enhance the transferability to the substrate and further improve the hiding property. (A) is more preferably 7.5 or less, even more preferably 7.0 or less.

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

Here, the tack value of the white ink for lithographic printing (a) and the white ink for printing (b) in the present invention was measured with an ink meter (76.2 mm diameter metal roll, It has a top roll made of EPDM rubber with a Shore A hardness of 70° and a diameter of 79.3 mm, and a vibration roll made of EPDM rubber with a Shore A hardness of 60° and a diameter of 50.8 mm. "TYPE V), the measurement can be performed under the conditions of 400 rpm of rotation and 38°C of temperature. Such rotational speed and temperature conditions simulate typical ink environments (temperature, shear rate) during printing. However, the value measured one minute after the start of measurement is taken as the tack value in the present invention.

In the method for producing a printed matter of the present invention, the difference (C) - (D) between the viscosity (C) of the white ink for lithographic printing (a) and the viscosity (D) of the white ink for printing (b) is 5 Pa s or more. 30 Pa·s or less is preferable. By setting the viscosity difference (C)-(D) to 5 Pa s or more, the component of the white printing ink (b) on the printed matter passes through the white ink for lithographic printing (a) to the substrate interface. It is possible to suppress the migration and further improve the adhesion to the base material. The difference in viscosity is more preferably 15 Pa·s or more, 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 for lithographic printing (a) is appropriately suppressed, and the white ink for lithographic printing (a) is applied onto the base material. By increasing the transferability of the lithographic printing white ink (a) and increasing the film thickness of the lithographic printing white ink (a), the components of the white printing ink (b) migrate to the substrate interface via the white ink for lithographic printing (a) can be suppressed, and the adhesion to the substrate can be further improved. The difference in viscosity is more preferably 25 Pa·s or less.

The viscosity (C) of the white ink for lithographic printing (a) is preferably 15 Pa·s or more and 40 Pa·s or less. By setting (C) to 15 Pa·s or more, the cohesive force of the ink enhances the transferability, and the concealability can be further improved. In addition, the migration of the components of the white ink for printing (b) to the substrate interface via the white ink for lithographic printing (a) 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 base material can be enhanced, and the hiding power can be further improved. In addition, the migration of the components of the white ink for printing (b) to the substrate interface via the white ink for lithographic printing (a) 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.

The viscosity (D) of the white ink for printing (b) 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 cohesive force of the ink enhances the transferability, and the concealability can be further improved. On the other hand, by setting the viscosity (D) to 20 Pa s or less, the transferability onto the white ink for lithographic printing (a) can be enhanced, and the hiding property can be further improved. It is possible to suppress the migration of the component b) to the substrate interface via the white ink for lithographic printing (a), thereby further improving the adhesion to the substrate. (D) is more preferably 10 Pa·s or less, and even more preferably 5 Pa·s or less.

Here, the viscosities of the white ink for lithographic printing (a) and the white ink for printing (b) according to the present invention were determined by measuring 0.35 ml of ink weighed with an ink pipette under the conditions of a temperature of 35° C. and a rotation speed of 70 rpm. It can be measured with a cone-plate rotary viscometer equipped with a plate (cone angle 1°, φ = 40 mm). Such rotational speed and temperature conditions simulate typical ink environments (temperature, shear rate) during printing.

As a combination of the white ink for lithographic printing (a) and the white ink for printing (b) that satisfy the above characteristics, the white ink for lithographic printing (a) and the white ink for printing (b) in the ink set of the present invention described later. is preferably used.

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 contains at least one lithographic printing ink or chromatic ink, a lithographic printing white ink (a) and a printing white ink (b) different from the lithographic printing white ink (a). include. As in the first embodiment, the white ink for printing (b) in the present invention may have a composition different from that of the white ink for lithographic printing (a).

The planographic printing ink or chromatic ink, the planographic printing white ink (a), and the printing white ink (b) preferably each contain a resin, a polyfunctional (meth)acrylate, a pigment, and a surfactant. Here, "(meth)acrylate" is a generic term for acrylate and methacrylate. Planographic printing ink or chromatic ink Examples of inks containing these include inks described in [0037] to [0090] of WO 2018/062108. Among these, as the white ink for lithographic printing (a), for example, [0037], [0039], [0041], [0043] to [0049], [0052], [0052] of WO 2018/062108 0053], [0055], [0056], [0062] to [0066], and [0069 to 0090]. As the white ink (b) for printing, ], [0062] to [0066], and [0069 to 0090]. Among these, combinations of lithographic printing inks or chromatic inks include, for example, ink sets described in [0095] to [0157] of International Publication No. 2018/062108. Moreover, as white ink for printing (b), white ink for flexographic printing is preferable.

In the ink set of the present invention, the difference in surface tension between the white ink for lithographic printing (a) and the white ink for printing (b), the tack value (A) of the white ink for lithographic printing (a) and the white ink for printing (b) ) tack value (B) and its difference (A) - (B), the viscosity (C) of the white ink for lithographic printing (a) and the viscosity (D) of the white ink for printing (b) and the difference (C) -(D) is preferably within the range described in the first aspect. In order to bring these properties into the preferred ranges described above, the lithographic printing white ink (a) contains a hydrophilic group-containing resin, a hydrophilic group-containing polyfunctional (meth)acrylate, and a hydrophilic group-free polyfunctional It preferably contains (meth)acrylates, pigments and surfactants. The white ink for printing (b) includes 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 an interface. It preferably contains an active agent.

Here, the hydrophilic group includes, for example, a hydroxyl group, an amino group, a mercapto group, a carboxyl group, a sulfo group, a phosphate group, and the like. You may use 2 or more types of these.

The (meth)acrylate having an aliphatic skeleton having 6 to 18 carbon atoms preferably does not have a hydrophilic group, 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 (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 ) 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 Acrylates, 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, polyester di(meth)acrylate having an aliphatic skeleton having 6 to 18 carbon atoms as a repeating unit, and the like.

Resins with hydrophilic groups and polyfunctional (meth)acrylates with hydrophilic groups affect the surface tension of the ink, and the more hydrophilic groups there are, the higher the surface tension tends to be. In addition, the interaction between hydrophilic groups affects the tack and viscosity of the ink, and the more hydrophilic groups there are, the higher the tack value and viscosity tend to be. As the hydrophilic group, a carboxyl group is preferable because it has excellent pigment dispersibility and can easily adjust the above-described properties within a desired range.

On the other hand, a polyfunctional (meth)acrylate having no hydrophilic group maintains an appropriate content of the resin having a hydrophilic group and the polyfunctional (meth)acrylate having a hydrophilic group in the ink, thereby reducing surface tension and tackiness. Makes it easier to adjust the value and viscosity to the desired range.

Pigments include titanium dioxide, calcium carbonate, barium sulfate, and alumina white. You may use 2 or more types of these. Among these, titanium dioxide is preferable because it is more excellent in hiding properties. Titanium dioxide exhibits basicity, but from the viewpoint of dispersing titanium dioxide well in the ink, it is possible to include a polymeric surfactant as a surfactant in order to adjust the surface tension within the preferred range described above. preferable.

A preferred embodiment of the white ink (a) for lithographic printing will be described.

In order to adjust the surface tension, tack value (A) and viscosity (C) to the preferred ranges described above, the acid value of the resin having a hydrophilic group is preferably 75 mgKOH/g or more and 150 mgKOH/g or less, and the hydrophilic group is 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 white ink for lithographic printing (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) within the preferred ranges described above, the content of the hydrophilic group-containing resin is more preferably 6.5% by mass or more and 9.5% by mass or less.

In order to adjust the surface tension, tack value (A) and viscosity (C) to the preferred ranges described above, 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. , The content of the polyfunctional (meth)acrylate having a hydrophilic group in the white ink (a) for lithographic printing is preferably 20% by mass or more and 45% by mass or less. In particular, in order to adjust the surface tension to the preferred range described above, the content of the polyfunctional (meth)acrylate having a hydrophilic group in the white ink for lithographic printing (a) is 27% by mass or more and 40% by mass or less. more preferred.

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

The content of the polymeric surfactant in the white ink for lithographic printing (a) is preferably 0.6% by mass or more and 1.5% by mass or less from the viewpoint of easily adjusting the surface tension to the preferred range described above. .

Next, preferred aspects of the printing ink (b) will be described.

In order to adjust the tack value (B) and viscosity (D) within the preferred ranges described above, 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 is preferably 5,000 or more and 40,000 or less, and the content of the hydrophilic group-containing resin in the white printing ink (b) is preferably 2 mass % or more and 5 mass % or less. In particular, in order to adjust the tack value (B) to the preferred range described above, the content of the resin having a hydrophilic group in the printing ink (b) should be 2.5% by mass or more and 4.5% by mass or less. more preferred.

In order to adjust the surface tension, tack value (B) and viscosity (D) to the preferred ranges described above, 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. , The content of the polyfunctional (meth)acrylate having a hydrophilic group in the white printing ink (b) is preferably 20% by mass or more and 45% by mass or less.

In order to adjust the tack value (B) and the viscosity (D) to the preferred ranges described above, it preferably contains a (meth)acrylate having an aliphatic skeleton having 6 to 18 carbon atoms, and the white ink for printing (b) The content of (meth)acrylate having an aliphatic skeleton having 6 to 18 carbon atoms in the mixture is preferably 3 to 20 mass %.

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

In the printing ink set of the present invention, at least one of the lithographic printing ink or chromatic ink, the lithographic printing white ink (a), and the white printing ink (b) is an electronic It is preferably an electron beam curing type that is cured by radiation. Further, it is more preferable that all of these inks are electron beam curable. An ink set containing the aforementioned polyfunctional (meth)acrylate can be cured by electron beam irradiation.

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

As in the first aspect described above, in the printed matter of the present invention, the thickness of the cured film of the white ink for printing (b) is larger than the thickness of the cured film of the white ink for lithographic printing (a). preferable. In the printed matter of the present invention, the difference between the thickness of the cured film of the white ink for lithographic printing (b) and the thickness of the cured film of the white ink for printing (a) is preferably 0.1 mm or more, more preferably. It is 0.5 mm or more, more preferably 1.0 mm or more.

The film thickness of the cured film of the white ink for lithographic printing (a) 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, from the viewpoint of further improving the adhesion to the substrate. 0 mm or less, and more preferably 1.1 mm or more and 2.0 mm or less.

The film thickness of the cured film of the white printing ink (b) in the printed material of the present invention is preferably 2.0 mm or more, more preferably 2.5 mm or more, and further preferably 3.0 mm or more, from the viewpoint of further improving the hiding property. preferable. In addition, the thickness of the cured film of the white printing ink (b) suppresses the migration of the components of the white printing ink (b) to the white ink for lithographic printing (a), thereby further improving the adhesion to the substrate. 4.0 mm or less is preferable, and 3.1 mm or less is more preferable from the viewpoint of increasing the thickness.

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these.

<Ink raw materials>
Resin: A copolymer consisting of 25% by mass of methyl methacrylate, 25% by mass of styrene, and 50% by mass of methacrylic acid is added with 0.55 equivalent of glycidyl methacrylate with respect to the carboxyl group to obtain an ethylenic A resin 1 having unsaturated groups and hydrophilic groups was obtained. 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: mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (manufactured by MIWON, "Miramer" (registered trademark) M340), hydroxyl value 115 mgKOH/g
(Meth) acrylate 2: tricyclodecanedimethanol diacrylate (EBECRYL 130, manufactured by Daicel-Ornex Co., Ltd.), hydroxyl value 0 mgKOH/g
(Meth) acrylate 3: 1,10-decanediol diacrylate (NK Ester A-DOD-N, manufactured by Shin-Nakamura Chemical Co., Ltd.), hydroxyl value 0 mgKOH/g
(Meth) acrylate 4: trimethylolpropane EO-modified triacrylate (manufactured by MIWON, "Miramer" (registered trademark) M3130), hydroxyl value 10 mgKOH/g
(Meth) acrylate 5: stearyl acrylate (manufactured by MIWON, "Miramer" (registered trademark) M180), hydroxyl value 0 mgKOH/g
Pigment 1: carbon black MA8 (manufactured by Mitsubishi Chemical Corporation)
Pigment 2: Seika Cyanine Blue 4920 (manufactured by Dainichi Seika Co., Ltd.)
Pigment 3: Carmine 6B 1483LT (manufactured by Dainichi Seika Co., Ltd.)
Pigment 4: Fast Yellow 2300 (manufactured by Dainichi Seika Co., Ltd.)
Pigment 5: “Tipake” (registered trademark) CR58-2 (manufactured by Ishihara Sangyo Co., Ltd.)
Surfactant 1: "Disperbyk" (registered trademark) 2013 (manufactured by ALTANA)
Surfactant 2: "Solsperse" (registered trademark) 54000 (manufactured by Lubrizol), polymeric surfactant Surfactant 3: "Solsperse" (registered trademark) 3000 (manufactured by Lubrizol), polymeric surfactant .

<Method for analyzing ink raw materials>
(1) Weight-average molecular weight A resin was diluted with tetrahydrofuran to a concentration of 0.25% by mass to prepare a diluted solution, and a mix rotor (MIX-ROTAR VMR-5, manufactured by AS ONE Corporation) was used to The diluted solution was stirred at 100 rpm for 5 minutes to dissolve the resin, and 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) using tetrahydrofuran as a mobile phase.

GPC is HLC-8220 (manufactured by Tosoh Corporation), columns are TSKgel SuperHM-H (manufactured by Tosoh Corporation), TSKgel SuperHM-H (manufactured by Tosoh Corporation), and TSKgel SuperH2000 (manufactured by Tosoh Corporation) in that order. and measured by RI detection. A calibration curve was constructed using polystyrene standards. The measurement conditions were an injection amount of 10 μL, an analysis time of 30 minutes, a flow rate of 0.4 mL/min, and a column temperature of 40°C.

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

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

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

<Evaluation method>
(1) Surface tension After applying the ink used in each example and comparative example to a glass substrate (chamfered, washed product, manufactured by Ishida Rika Co., Ltd.) with a thickness of 1 mm × length 50 mm × width 50 mm, the ink It was left in the dark for 30 minutes to make the surface smoother. Drops of pure water and ethylene glycol with known surface tension values are placed on the ink after it has been allowed to stand still using a syringe. Using a goniometer (Drop Master DM-501, manufactured by Kyowa Interface Science Co., Ltd.), the measurement was performed under the conditions of a temperature of 25° C. and a humidity of 50%.

Next, from the contact angle, the surface tension _γI of the ink was calculated from Equations (1), (4) and (5).
γ = γ ^d + γ ^h (1)

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, and 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 nonpolar dispersion force component ^γd is 32.8 mN/m, and the polar hydrogen bonding dispersion force component ^γh is 16.0 mN/m.

(2) Tack value 1.31 ml of the ink used in each example and comparative example was weighed using an ink pipette, and measured by an incometer (metal roll with a diameter of 76.2 mm, made of EPDM rubber, Shore A hardness of 70°, diameter A top roll of 79.3 mm and a vibration roll made of EPDM rubber with a Shore A hardness of 60° and a diameter of 50.8 mm were used. , and a temperature of 38°C. However, the value measured 1 minute after the start of measurement was taken as the tack value in the present invention.

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

(4) Film thickness The cross section of the printed material obtained in each example and comparative example was enlarged and observed using a scanning electron microscope (S-5500, Hitachi High-Technologies Corporation), and the thickness of each layer in the vertical direction of the printed material was measured. Measurements were taken at five points at random, and the average value was taken as the film thickness.

(5) Concealability Among the printed materials obtained in each example and comparative example, the portions where only white ink was printed were measured using a densitometer (xEact Basic, manufactured by X-rite) in the concealment rate measurement mode. The hiding rate was measured from the substrate surface. When the concealment rate is less than 60%, the concealability is insufficient, when it is 60% or more and less than 65%, the concealability is slightly good, and when it is 65% or more and less than 70%, the concealability is good, When it was 70% or more, it was judged that the hiding property was extremely good.

(6) Adhesion Among the printed matter obtained in each example and comparative example, on the cured film of ink where only white ink was printed, "Takelac" (registered trademark) A-626 (Mitsui A mixture of Kagaku Co., Ltd.) and “Takenate” (registered trademark) A-50 (Mitsui Chemicals Co., Ltd.) in a mass ratio of 8/1 was applied by a bar coating method. At this time, the coating amount was adjusted to 4.0 g/m ² after drying at 80°C for 1 minute. After laminating the printed material coated with the adhesive and a non-stretched polypropylene film "Torayfan" (registered trademark) ZK207 (manufactured by Toray Industries, Inc., thickness 70 μm) as a sealant using a hand roller, the temperature was adjusted to 72°C at 40°C. After aging for a period of time, a film laminate of sealant/adhesive/cured ink film/polyester film was obtained.

A section of 15 mm in width and 50 mm in length is cut out from the film laminate, and a Tensilon universal material testing machine (manufactured by A&D, model number "RTG-1210") is used to apply the 90 degree T-type peeling method (JIS K 6854-3: 1999), the peel strength between the polyester film and the sealant was measured, and the value at the first maximum point was taken as the laminate peel strength. The peel strength was measured under conditions of temperature of 25° C., humidity of 50%, and test speed of 300 mm/min.

If the peel strength is less than 1.0 N/15 mm, the adhesion is insufficient, if it is 1.0 N/15 mm or more and less than 2.0 N/15 mm, the adhesion is slightly good, It was judged that the adhesion was good when it was less than 0 N/15 mm, and the adhesion was extremely good when it was 3.0 N/15 mm or more.

<Preparation of ink for lithographic printing or chromatic ink>
In the "type of ink" in Table 1, "lithographic" means lithographic printing ink, and "flexographic" means flexographic printing ink.

The resins and (meth)acrylates shown in each black or chromatic color in Table 1 were weighed and heated at a temperature of 95°C for 390 minutes while stirring at a rotation speed of 500 rpm using a disper blade to obtain a varnish.

To the obtained varnish, ink or chromatic color pigments and surfactants shown in Table 1 are added, and a three-roll mill "EXAKT" (registered trademark) M-80S (manufactured by EXAKT) is used to grind the varnish with a gap of 1 to 5. It was passed through to obtain an ink for lithographic printing.

[Example 1]
<Preparation of white ink>
In Table 1, "1st layer white ink" means the white ink printed on the first layer of the white inks, and "2nd layer white ink" means the white ink printed on the second layer.

The resin and (meth)acrylate shown in the first layer mesh in Table 1 were weighed and heated at a temperature of 95°C for 390 minutes while stirring at a rotation speed of 500 rpm using a disper blade to obtain a varnish. To the obtained varnish, the pigment and surfactant shown in Table 1 are added, and the three-roll mill "EXAKT" (registered trademark) M-80S (manufactured by EXAKT) is passed five times at a gap of 1, followed by lithography. A white printing ink was obtained.

The resin and (meth)acrylate shown in Table 1 for the second layer were weighed and heated at a temperature of 95°C for 390 minutes while stirring at a rotation speed of 500 rpm using a disper blade to obtain a varnish. The pigments and surfactants shown in Table 1 were added to the obtained varnish and dispersed using an Eiger mill (using zirconia beads with a diameter of 0.5 mm as media) to obtain a white ink for flexographic printing.

<Manufacture of printed matter>
Using a lithographic and flexo hybrid printing machine (CI-8, COMEXI), a waterless lithographic printing plate (TAN-E, manufactured by Toray Industries, Inc.) is used for the 1st to 5th cylinders, and a flexographic printing plate ("Cyrel" (registered trademark) EASY FAST EFX, manufactured by DuPont) is installed, and each ink for lithographic printing, indigo, red, yellow, 1st layer and 2nd layer, is installed in order on the 1st to 5th and 8th cylinders. was installed. On a polyester film PTM12 (manufactured by Unitika Ltd., thickness 12 μm) as a base material, ink feed rate: 50%, impression cylinder chiller set temperature: 30°C, swing roller and ink fountain chiller set temperature: 28°C. Then, using T414 (manufactured by Kinyo Co., Ltd., thickness 1.95 mm) as a blanket, printing was performed at a speed of 100 m / min by a wet-on-wet printing method. The ink was cured by irradiation with an electron beam of 40 kGy to obtain a printed matter. At this time, the image is constructed so that there are places in the printed material where only the white ink for lithographic printing (a) as the first layer and the white ink for printing (b) as the second layer are printed on the base material. bottom.

Table 1 shows the results of evaluating each ink and the resulting printed matter by the method described above. The hiding power and adhesion were very good.

[Examples 2 to 4]
<Preparation of white ink>
A white ink for lithographic printing and a white ink for flexographic printing 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 shown in Table 1.

<Manufacture of printed matter>
A printed matter was obtained in the same manner as in Example 1, except that the first layer mesh white ink shown in Table 1 was used.

Table 1 shows the results of evaluating each ink and the resulting printed matter by the method described above.

[Example 5]
<Preparation of white ink>
A white ink for lithographic printing and a white ink for flexographic printing were obtained in the same manner as in Example 1, except that the composition of the second-layer mesh white ink was changed as shown in Table 2.

<Manufacture of printed matter>
A printed matter was obtained in the same manner as in Example 1 except that the two-layer mesh white ink shown in Table 2 was used.

Table 2 shows the results of evaluating each ink and the resulting printed matter by the method described above.

[Example 6]
<Preparation of white ink>
A white ink for lithographic printing and a white ink for flexographic printing were obtained in the same manner as in Example 1, except that the composition of the first layer white ink was changed as shown in Table 2.

<Manufacture of printed matter>
A printed matter was obtained in the same manner as in Example 1, except that the first-layer mesh white ink shown in Table 2 was used.

[Comparative Example 1]
<Manufacture of printed matter>
Waterless lithographic printing plates (TAN-E, manufactured by Toray Industries, Inc.) are set on cylinders 1 to 6, and ink for lithographic printing, indigo, red, yellow, 1st layer mesh white, A printed matter was obtained in the same manner as in Example 1, except that each ink for the two-layer mesh was applied.

Table 2 shows the results of evaluating each ink and the resulting printed matter by the method described above. In Comparative Example 1, in which white inks for lithographic printing having the same composition were used for the first and second layers, the hiding property was insufficient.

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

Table 2 shows the results of evaluating each ink and the resulting printed matter by the method described above. In Comparative Example 2, in which only the white ink for flexographic printing was used as the first layer mesh, the adhesion was insufficient.

Claims

(1) a step of printing at least one lithographic ink or chromatic ink and a lithographic white ink (a) onto a substrate;
(2) a step of further printing a white ink for printing (b) different from the white ink for lithographic printing (a);
in this order.
2. The method for producing a printed matter according to claim 1, wherein the white ink for printing (b) is a white ink for flexographic printing.
3. The method for producing a printed matter according to claim 1, wherein the difference in surface tension between the white ink for lithographic printing (a) and the white ink for printing (b) is 5 mN/m or more and 20 mN/m or less.
The difference (A)−(B) between the tack value (A) of the white ink for lithographic printing (a) and the tack value (B) of the white ink for printing (b) is 2.0 or more and 5.0 or less. The method for producing a printed matter according to any one of claims 1 to 3.
The difference (C)-(D) between the viscosity (C) of the white ink for lithographic printing (a) and the viscosity (D) of the white ink for printing (b) is 5 Pa s or more and 30 Pa s or less. Item 5. A method for producing a printed matter according to any one of items 1 to 4.
6. The printing method according to any one of claims 1 to 5, wherein printing is performed so that the thickness of the cured film of the white printing ink (b) is larger than the thickness of the cured film of the white ink for lithographic printing (a). A method for producing printed matter.
The thickness of the cured film of the white ink for lithographic printing (a) is 0.5 μm or more and 2.0 μm or less, and the thickness of the cured film of the white ink for printing (b) is 2.0 μm or more and 4.0 μm or less. 7. The method for producing a printed matter according to claim 6, wherein the printed matter is printed as follows.
8. The method for producing a printed matter according to any one of claims 1 to 7, wherein the substrate comprises a plastic film, plastic film-laminated paper, metal plate, metal-deposited paper, or metal-deposited plastic film.
9. The method for producing a printed matter according to any one of claims 1 to 8, wherein printing is performed by a wet-on-wet printing method in the step (2).
10. The method for producing a printed matter according to claim 1, further comprising the step of (3) irradiating with an electron beam after the step of (2).
A printing ink set comprising at least one lithographic ink or chromatic ink, a lithographic white ink (a) and a white lithographic ink (b) different from the lithographic white ink (a).
12. The printing ink set according to claim 11, wherein the white printing ink (b) is a white flexographic ink.
13. The printing ink set according to claim 11 or 12, wherein the difference in surface tension between the white ink for lithographic printing (a) and the white ink for printing (b) is 5 mN/m or more and 20 mN/m or less.
The difference (A)−(B) between the tack value (A) of the white ink for lithographic printing (a) and the tack value (B) of the white ink for printing (b) is 2.0 or more and 5.0 or less. The printing ink set according to any one of claims 11 to 13.
The difference (C)-(D) between the viscosity (C) of the white ink for lithographic printing (a) and the viscosity (D) of the white ink for printing (b) is 5 Pa s or more and 30 Pa s or less. Item 15. The printing ink set according to any one of items 11 to 14.
Printing according to any one of claims 11 to 15, wherein at least one of said lithographic black or chromatic ink, lithographic white ink (a) and said white printing ink (b) is electron beam curable. ink set for
A printed material using the printing ink set according to any one of claims 11 to 16, wherein a cured film of the white printing ink (b) is formed on a cured film of the white ink for lithographic printing (a). Printed matter with.
18. The printed matter according to claim 17, wherein the thickness of the cured film of the white ink for printing (b) is greater than the thickness of the cured film of the white ink for lithographic printing (a).
The thickness of the cured film of the white ink for lithographic printing (a) is 0.5 μm or more and 2.0 μm or less, and the thickness of the cured film of the white ink for printing (b) is 2.0 μm or more and 4.0 μm or less. 19. The printed product of claim 18.