Ink composition for ultraviolet laser marking, printed layer for ultraviolet laser marking, printing medium for ultraviolet laser marking, and printed matter and method for manufacturing the same

Abstract

To provide an ink composition for ultraviolet laser marking which enables formation of a printed layer for ultraviolet laser marking that enables production of a printed image excellent in printing density, when being irradiated with an ultraviolet laser, to provide a printed layer for ultraviolet laser marking which is obtained from the ink composition for ultraviolet laser marking, and a printing medium for ultraviolet laser marking having the printed layer, and a printed matter which is obtained from the printing medium for ultraviolet laser marking and a method for manufacturing the same.SOLUTION: An ink composition for ultraviolet laser marking contains at least a binder resin and a white pigment, wherein the white pigment contains titanium oxide, and the binder resin contains a silicone-based polymer compound.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ink composition for ultraviolet laser marking, a printing layer for ultraviolet laser marking, a printing medium for ultraviolet laser marking, and a printed matter and a method for producing the same. [Background technology]

[0002] BACKGROUND ART Conventionally, labeling or inkjet printing has been used to display dates such as manufacturing dates and shipping dates, and variable information such as barcodes on packaging such as containers that contain contents. A method of printing by irradiation with laser light has also been proposed. For example, Patent Document 1 discloses a laser printing laminate manufactured by applying white ink, black ink, and overprint varnish (OP varnish) to the aluminum vapor-deposited surface of aluminum vapor-deposited paper, with the aim of providing a laser printing laminate and a printed body that can produce clear printing at high speed by irradiation with laser light and have excellent resistance to various types of printing. Furthermore, Patent Document 2 describes an ink composition that contains first titanium oxide particles having an average particle size of 150 nm or less and is used to form a laser marking layer that changes color when irradiated with an ultraviolet laser, with the aim of providing a technology that generates relatively little heat and is preferably applicable to laser marking of packaging materials. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-123607 [Patent Document 2] Japanese Patent Publication No. 2020-75943 Summary of the Invention [Problem to be solved by the invention]

[0004] One widely used method for printing on the surfaces of packaging, labels, adhesive tape, etc. is to use thermal printers or inkjet printers to directly apply ink to the surface of the packaging. However, consumables such as ink ribbons for thermal printers and ink for inkjet printers are expensive, and printing a large amount of variable information results in high running costs. Furthermore, failure to replace these consumables can result in missing prints. Furthermore, variable information can also be printed directly onto packaging using offset printing with UV-curable ink, but this can result in faded prints or missing characters due to contamination on the packaging surface or uneven thickness of the packaging. Furthermore, while the method described in Patent Document 1 allows for high-speed processing, it involves removing an upper layer that readily absorbs laser light by irradiating it with a CO2 laser beam, exposing the lower layer, and forming visible characters or other elements based on the color difference between the upper and lower layers. Therefore, the upper layer is limited to materials that readily absorb laser light, while the lower layer is limited to materials that do not readily absorb laser light and that provide a contrasting color with the upper layer. In other words, the upper layer is made of a carbon black-based material (black), which readily absorbs laser light, and the lower layer is made of a titanium oxide-based material (white), resulting in characters or other elements formed by irradiating the laser beam as white characters on a black background, resulting in poor visibility. Furthermore, removing the upper layer poses the problem of the ink in the upper layer turning into dust, which can contaminate the work environment. Furthermore, when printing is performed with an ultraviolet laser on a coating layer prepared using the ink composition described in Patent Document 2, there is a problem that sufficient print density cannot be obtained.

[0005] An object of the present invention is to provide an ink composition for ultraviolet laser marking that can form a printing layer for ultraviolet laser marking that, when irradiated with an ultraviolet laser, produces a printed image with excellent print density. Another object of the present invention is to provide a printing layer for ultraviolet laser marking obtained from the ink composition for ultraviolet laser marking, and a printing medium for ultraviolet laser marking having the printing layer. A further object of the present invention is to provide a printed material obtained from the printing medium for ultraviolet laser marking, and a method for producing the same. [Means for solving the problem]

[0006] The present inventors have discovered that the above-mentioned problems can be solved by providing an ink composition for ultraviolet laser marking containing a white pigment and a binder resin, in which the white pigment contains titanium oxide and the binder resin contains a silicone polymer compound, and have thus completed the present invention. The present invention is as follows: <1> ~ <17> Regarding. <1> Contains at least a binder resin and a white pigment, The white pigment contains titanium oxide, The binder resin contains a silicone-based polymer compound. Ink composition for ultraviolet laser marking. <2> The content of the silicone polymer compound in the binder resin is 30% by mass or more. <1> 1. An ink composition for ultraviolet laser marking according to claim 1. <3> the degree of branching in the main chain skeleton of the silicone polymer compound is 0.2% or more and 3.0% or less; <1> or <2> 1. An ink composition for ultraviolet laser marking according to claim 1. <4> the mass ratio of the binder resin to the white pigment (binder resin:white pigment) is 5:95 or more and 95:5 or less; <1> ~ <3> 10. The ink composition for ultraviolet laser marking according to claim 9, wherein the ink composition is a fluororesin. <5> The content of titanium oxide in the white pigment is 3% by mass or more. <1> ~ <4> 10. The ink composition for ultraviolet laser marking according to claim 9, wherein the ink composition is a fluororesin. <6> The crystallite size of the titanium oxide is 30 nm or more and 55 nm or less. <1> ~ <5> 10. The ink composition for ultraviolet laser marking according to claim 9, wherein the ink composition is a fluororesin. <7> It is a water-based ink composition. <1> ~ <6> 10. The ink composition for ultraviolet laser marking according to claim 9, wherein the ink composition is a fluororesin. <8> A gravure printing ink composition or a flexographic printing ink composition, <1> ~ <7> 10. The ink composition for ultraviolet laser marking according to claim 9, wherein the ink composition is a fluororesin. <9> It is used to form a printing layer on a paper substrate or a film substrate that changes color when irradiated with an ultraviolet laser. <1> ~ <8> 10. The ink composition for ultraviolet laser marking according to claim 9, wherein the ink composition is a fluororesin. <10> <1> ~ <9> A printing layer for ultraviolet laser marking formed from the ink composition for ultraviolet laser marking described in any one of the above. <11> The content of titanium oxide in the printing layer is 0.1 g / m 2 That's all. <10> 2. The printing layer for ultraviolet laser marking according to claim 1. <12> The content of titanium oxide in the printed layer is 10 g / m 2 Below is the <10> or <11> 2. The printing layer for ultraviolet laser marking according to claim 1. <13> On the substrate <10> ~ <12> 10. A printing medium for ultraviolet laser marking, comprising a printing layer for ultraviolet laser marking according to any one of claims 1 to 9. <14> The substrate is a paper substrate or a film substrate. <13> 2. A printing medium for ultraviolet laser marking according to claim 1. <15> A packaging body, <13> or <14> 2. A printing medium for ultraviolet laser marking according to claim 1. <16> <13> ~ <15> A printed matter obtained from the ultraviolet laser markable printing medium according to any one of the above items, A printed matter, wherein the printed layer has, at least in part, a printed area containing titanium oxide that has been discolored by ultraviolet laser irradiation. <17> <13> ~ <15> 10. A method for producing a printed matter, comprising the step of irradiating an ultraviolet laser onto the ultraviolet laser marking printing medium described in any one of claims 1 to 9 with an ultraviolet laser to discolor the irradiated area, thereby printing. [Effects of the Invention]

[0007] According to the present invention, there is provided an ink composition for ultraviolet laser marking that can form a printing layer for ultraviolet laser marking that can produce a printed image with excellent print density when irradiated with an ultraviolet laser. The present invention also provides a printing layer for ultraviolet laser marking obtained from the ink composition for ultraviolet laser marking, and a printing medium for ultraviolet laser marking having the printing layer. Furthermore, the present invention also provides a printed matter obtained from the printing medium for ultraviolet laser marking, and a method for producing the same. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a conceptual perspective view of an example of a liquid container having a print area. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Ink composition for ultraviolet laser marking] The ink composition for ultraviolet laser marking of this embodiment (hereinafter also simply referred to as "ink composition") contains at least a binder resin and a white pigment, the white pigment contains titanium oxide, and the binder resin contains a silicone-based polymer compound. According to the ink composition of this embodiment, when a printing layer for ultraviolet laser marking (hereinafter also simply referred to as "printing layer") formed using the ink composition is irradiated with an ultraviolet laser to perform printing, a printed image with excellent print density is obtained. The detailed reasons why the above-mentioned effects are obtained are unknown, but some of the reasons are thought to be as follows. By including titanium oxide in the ink composition, the printing layer formed from the ink composition also contains titanium oxide. By including titanium oxide, the titanium oxide in the printing layer changes color upon irradiation with an ultraviolet laser, enabling printing. The discoloration of titanium oxide is thought to occur when the ionic valence of the titanium oxide contained in the printing layer changes from tetravalent to trivalent, resulting in oxygen defects, causing a change from white to black, making the color visible. The ionic valence of titanium oxide is thought to change when irradiated with light energy corresponding to the band gap of titanium oxide. The band gap of titanium oxide varies depending on the crystal system, but is generally approximately 3.0 to 3.2 eV, and the wavelength of light corresponding to this is 420 nm or less. Therefore, even when using laser light with a wavelength exceeding 420 nm (e.g., 532 nm, 1064 nm, 10600 nm), it is difficult to achieve printing due to the change in ionic valence of titanium oxide as in the present invention. The inventors discovered that when printing with the above-mentioned ultraviolet laser, titanium oxide scatters in the ultraviolet laser-irradiated areas of the printed layer, preventing sufficient print density. After extensive investigation into the cause, they concluded that the titanium oxide irradiated with the ultraviolet laser generates heat, causing the binder resin in the vicinity of the titanium oxide to deteriorate. Furthermore, they concluded that irradiation with the ultraviolet laser releases radicals from the titanium oxide, which in turn cuts and shortens the molecular chains of the binder resin, reducing the strength and damaging the printed layer, causing the discolored titanium oxide to scatter and preventing sufficient print density. Therefore, a silicone-based polymer with high molecular bonding energy and excellent heat resistance was used as the binder resin, resulting in an image with extremely excellent print density compared to when a printed layer formed using a conventional ink composition was irradiated with an ultraviolet laser. In this embodiment, the printable area refers to an area (portion) where printing by ultraviolet laser irradiation is possible because the titanium oxide in the irradiated area changes color from white to black, and the printable area refers to the part of the printable area where the titanium oxide has actually changed color by ultraviolet laser irradiation and become visible, i.e., the part irradiated with the ultraviolet laser. The non-printable area refers to the area (portion) of the printable area that is not irradiated with the ultraviolet laser. The present invention will be described in further detail below.

[0010] <Binder resin> The ink composition of this embodiment contains at least a binder resin, and the binder resin contains a silicone-based polymer compound. (Silicone polymer compound) In this embodiment, the silicone-based polymer compound is a linear or branched organopolysiloxane, and is preferably capable of preparing an emulsion or dispersion, more preferably an aqueous emulsion or dispersion.

[0011] In this embodiment, the silicone polymer compound preferably has a branched structure in the main chain skeleton, and the degree of branching in the main chain skeleton is preferably 0.2% or more and 3.0% or less, more preferably 0.4% or more, even more preferably 0.5% or more, and more preferably 2.5% or less, even more preferably 2.0% or less, and still more preferably 1.5% or less. A branching degree of 0.2% or more in the main chain skeleton is preferred because it allows for a printing layer with excellent strength due to the network structure of the silicone polymer compound, while a branching degree of 3.0% or less in the main chain skeleton is preferred because it allows for an ink composition with an appropriate viscosity. The branching degree in the main chain of the silicone polymer compound is 29 It is calculated from Si-NMR measurement, specifically, by the method described in the Examples.

[0012] The weight-average molecular weight of the silicone polymer compound is preferably 1,000 or more and 1,000,000 or less, more preferably 2,000 or more, even more preferably 3,000 or more, and more preferably 500,000 or less, even more preferably 300,000 or less. A weight-average molecular weight of 1,000 or more of the silicone polymer compound is preferred because it results in a printed layer with excellent strength. Furthermore, a weight-average molecular weight of 1,000,000 or less of the silicone polymer compound is preferred because it provides an ink composition with an appropriate viscosity and is suitable for preparing emulsions and dispersions. The weight-average molecular weight can be determined as a polystyrene-equivalent weight-average molecular weight by gel permeation chromatography (GPC) analysis.

[0013] When the silicone polymer compound has a branch in the main chain skeleton, for example, the silicone polymer compound may be a compound represented by the formula (SiO 4 / 2 ) units (Q units) or (R 1 SiO 3 / 2 ) (T unit). 2 2SiO) (D unit). In the above formula, R 1 and R 2 are each independently a hydroxyl group or a monovalent organic group having 1 to 20 carbon atoms, which may have a substituent as necessary. R in the above formula 1 and R 2Specific examples of the alkyl group include alkyl groups having 1 to 20 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, cyclopentyl, cyclohexyl, and cycloheptyl; aryl groups having 6 to 20 carbon atoms, such as phenyl, tolyl, xylyl, and naphthyl; alkenyl groups having 2 to 20 carbon atoms, such as vinyl and allyl; and hydroxyl groups. These groups may have a substituent, if necessary. Examples of the substituent include halogen atoms, amino groups, acryloxyl groups, methacryloxyl groups, epoxy groups, mercapto groups, and polar group-containing substituents, such as carboxyl groups.

[0014] In the above formula, R 1 and R 2 are each independently preferably a hydroxyl group, a linear hydrocarbon group having 1 to 6 carbon atoms, or an aromatic hydrocarbon group having 5 to 7 carbon atoms, more preferably a methyl group, an ethyl group, or a phenyl group, and even more preferably a methyl group or a phenyl group.

[0015] In addition, a silicone polymer compound having a branch in its main chain skeleton may have a branched structure introduced by a hydrosilylation reaction with an organopolysiloxane having a vinyl group directly bonded to a terminal silicon atom.In this case, if the organopolysiloxane having a vinyl group is an organopolysiloxane having a vinyl group at one terminal, a branched structure will be introduced, and if the organopolysiloxane has vinyl groups at both terminals, a crosslinked structure may be formed in addition to the branched structure.When a branched structure is introduced by a hydrosilylation reaction, it is preferable to use a platinum catalyst as the catalyst.

[0016] Furthermore, the branched structure of the main chain skeleton may be introduced by, for example, hydrolyzing a silane compound such as a chlorosilane or an alkoxysilane, followed by a condensation reaction. Alternatively, crosslinks may be introduced by heating a peroxide above its decomposition temperature to generate free radicals.

[0017] As the silicone polymer compound, commercially available products may be used. As a silicone polymer compound having a branched main chain structure, for example, DOWSIL manufactured by Dow Toray Co., Ltd. TM IE-7170, SYL-OFF TM 7920NF, and KM-9772 manufactured by Shin-Etsu Chemical Co., Ltd. are examples. In addition, DOWSIL is a linear silicone polymer compound. TM 490EX, DOWSIL TM Examples include 8701EX.

[0018] From the viewpoint of obtaining a printed image with high print density, the content of the silicone polymer compound in the binder resin is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 65% ​​by mass or more, and the upper limit is not particularly limited, but is 100% by mass or less.

[0019] From the viewpoint of obtaining a printed image with high print density, the content of the silicone polymer compound in the solid content of the ink composition is preferably 3% by mass or more and 97% by mass or less, more preferably 5% by mass or more, even more preferably 8% by mass or more, still more preferably 12% by mass or more, even more preferably 18% by mass or more, even more preferably 25% by mass or more, and more preferably 90% by mass or less, even more preferably 75% by mass or less, still more preferably 60% by mass or less, even more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0020] (Other binder resins) In this embodiment, the binder resin may contain other binder resins in addition to the silicone polymer compound described above. The other binder resin may be appropriately selected from the viewpoints of affinity with the silicone polymer compound, high UV transmittance, adhesion to the substrate, resistance to UV laser, etc., and is not particularly limited. The other binder resin may be either a natural resin or a synthetic resin. Furthermore, the other binder resin is preferably a water-suspendable resin or a water-soluble resin. Other binder resins include, for example, urethane-based resins, polyester-based resins, styrene-butadiene-based resins, vinyl chloride-based resins, olefin-based resins, acrylic resins, maleic acid-based resins, and polyvinyl alcohol-based resins. Of these, urethane-based resins, olefin-based resins, and acrylic resins are preferred. When a paper substrate is used as the substrate, urethane resins and acrylic resins are preferred from the viewpoint of good adhesion to the substrate. Further, from the viewpoint of resistance to ultraviolet lasers, olefin resins are preferred.

[0021] When the binder resin contains other binder resins, the content of the other binder resins in the binder resin is preferably 3% by mass or more and 70% by mass or less, more preferably 10% by mass or more, even more preferably 20% by mass or more, and more preferably 50% by mass or less, even more preferably 40% by mass or less. From the viewpoint of print density, it is preferable that the ink composition does not contain other binder resins. On the other hand, from the viewpoint of obtaining the ink composition at low cost and improving adhesion to the substrate, other binder resins may be used in combination.

[0022] From the viewpoint of the strength of the printed layer and print density, the content of the binder resin in the solid content of the ink composition is preferably 3% by mass or more and 97% by mass or less, more preferably 5% by mass or more, even more preferably 8% by mass or more, still more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 25% by mass or more, and more preferably 90% by mass or less, even more preferably 75% by mass or less, still more preferably 60% by mass or less, even more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0023] <White pigment> The ink composition of this embodiment contains a white pigment, and the white pigment contains titanium oxide. (Titanium oxide) The titanium oxide contained in the printing layer is represented by the composition formula TiO2 and is also called titanium dioxide or titania. The titanium oxide may have any crystal structure, and is preferably at least one selected from rutile titanium oxide, anatase titanium oxide, and brookite titanium oxide. From the standpoints of availability and stability, it is more preferably at least one selected from rutile titanium oxide and anatase titanium oxide, and even more preferably rutile titanium oxide. The crystalline form of titanium oxide can be determined by known methods, specifically by analyzing Raman spectra, XRD patterns, etc. For example, when identifying from Raman spectra, the rutile form generally has a peak at 447±10 cm -1 , 609±10cm -1 A peak was confirmed at 395±10cm for the anatase type. -1 , 516±10cm -1 , 637±10cm -1 A peak is observed at . The titanium oxide may be used alone or in combination of two or more kinds.

[0024] The shape of the titanium oxide is not particularly limited, and may be any shape such as amorphous, spherical, rod-like, or needle-like. When the titanium oxide is amorphous or spherical, the average particle size of the titanium oxide is not particularly limited, but from the viewpoint of print clarity and smoothness of the printed layer, it is preferably 0.01 μm or more, more preferably 0.05 μm or more, even more preferably 0.1 μm or more, still more preferably 0.15 μm or more, particularly preferably 0.16 μm or more, and preferably 20.0 μm or less, more preferably 5.0 μm or less, even more preferably 1.5 μm or less, and even more preferably 0.50 μm or less.

[0025] Furthermore, when the titanium oxide is needle-shaped, the major axis of the titanium oxide is not particularly limited, but from the viewpoint of obtaining excellent print clarity per dot and a printing medium with excellent surface smoothness, it is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1.5 μm or more, and preferably 50.0 μm or less, more preferably 30.0 μm or less, and even more preferably 15.0 μm or less. Furthermore, the minor axis is preferably 0.01 μm or more, more preferably 0.03 μm or more, even more preferably 0.05 μm or more, and preferably 3.0 μm or less, more preferably 1.5 μm or less, and even more preferably 1.0 μm or less. Furthermore, when the titanium oxide is needle-shaped, the aspect ratio (major axis / minor axis) is preferably 5 or more, more preferably 10 or more, even more preferably 15 or more, and preferably 300 or less, more preferably 100 or less, and even more preferably 30 or less. The average particle size, major axis, and minor axis of titanium oxide are measured by the method described in the Examples. The particle size, major axis, and minor axis values ​​of the titanium oxide used as a raw material may be used, or catalog values ​​of the particle size, major axis, and minor axis of the titanium oxide used as a raw material may be used.

[0026] In this embodiment, the crystallite size of titanium oxide is preferably 30 nm or more. When the crystallite size of titanium oxide in the ink composition is 30 nm or more, the titanium oxide has fewer crystal defects, and the recombination of excited electrons and holes excited by ultraviolet laser irradiation is suppressed. As a result, the titanium oxide is easily reduced, and a printed image with excellent image density can be obtained. The crystallite size of titanium oxide is more preferably 35 nm or more, and more preferably 40 nm or more. Furthermore, the upper limit of the crystallite size of titanium oxide is not particularly limited, but from the viewpoint of dispersion stability in the ink composition and the printed layer, it is preferably 60 nm or less, more preferably 56 nm or less, and even more preferably 53 nm or less. If the upper limit of the crystallite size of titanium oxide is within the above range, the dispersion stability of titanium oxide in the coating liquid and the printed layer is good, and printing uniformity is improved, which is preferable. The crystallite size of titanium oxide is measured by the method described in the Examples. The crystallite size is determined by the Scherrer equation, and the Bragg angle is the measured value of the maximum intensity derived from the 101 plane in the case of anatase titanium oxide, or the 110 plane in the case of rutile titanium oxide.

[0027] (White pigments other than titanium dioxide) The ink composition of this embodiment may contain, in addition to the titanium oxide, a white pigment other than titanium oxide (hereinafter also referred to as "other white pigments") as the white pigment. By containing a white pigment other than titanium oxide (other white pigment), scattering of titanium oxide during irradiation with an ultraviolet laser is suppressed, and print density is improved, which is preferable. Examples of white pigments other than titanium oxide include calcium carbonate, talc, silica, kaolin, magnesium oxide, mica, aluminum hydroxide, and barium sulfate. Among these, at least one selected from the group consisting of calcium carbonate, talc, silica, kaolin, magnesium oxide, zinc oxide, and mica is preferred, at least one selected from the group consisting of calcium carbonate and talc is more preferred, and calcium carbonate is even more preferred. The white pigments other than titanium oxide may be used alone or in combination of two or more.

[0028] The shape of the white pigment other than titanium oxide (other white pigment) is not particularly limited, and may be any shape such as amorphous, spherical, plate-like, rod-like, or needle-like. When the other white pigment is amorphous, spherical, or plate-like, the average particle size of the other white pigment is not particularly limited, but from the viewpoint of obtaining a printed layer with excellent surface smoothness and suppressing the scattering of titanium oxide during ultraviolet laser irradiation, it is preferably 0.1 μm or more, more preferably 0.15 μm or more, even more preferably 0.20 μm or more, and preferably 10 μm or less, more preferably 5 μm or less, even more preferably 3 μm or less. Furthermore, when the inorganic pigment is needle-shaped, the major axis of the inorganic pigment is not particularly limited, but from the viewpoint of obtaining a printed layer with excellent surface smoothness and suppressing scattering of titanium oxide during ultraviolet laser irradiation, it is preferably 0.2 μm or more, more preferably 0.3 μm or more, even more preferably 0.5 μm or more, and preferably 100 μm or less, more preferably 10 μm or less, even more preferably 5 μm or less. Furthermore, the minor axis is preferably 0.01 μm or more, more preferably 0.05 μm or more, even more preferably 1.0 μm or more, and preferably 50 μm or less, more preferably 10 μm or less, even more preferably 1.0 μm or less. Furthermore, when the inorganic particles are needle-shaped, the aspect ratio (major axis / minor axis) is preferably 1.5 or more, more preferably 2.0 or more, even more preferably 3.0 or more, and preferably 100 or less, more preferably 50 or less, even more preferably 30 or less.

[0029] From the viewpoint of print density and suppressing scattering of titanium oxide during ultraviolet laser irradiation, the content of the white pigment in the solid content of the ink composition is preferably 2% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, still more preferably 30% by mass or more, and particularly preferably 50% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and still more preferably 80% by mass or less.

[0030] When the ink composition contains an inorganic pigment other than titanium oxide, the mass ratio of titanium oxide to the inorganic pigment other than titanium oxide (titanium oxide / inorganic pigment other than titanium oxide) is, from the viewpoint of print density and suppressing smoke generation during ultraviolet laser irradiation, preferably 0.01 or more, more preferably 0.03 or more, and even more preferably 0.05 or more. The upper limit is not particularly limited, but is preferably 100 or less, more preferably 30.0 or less, even more preferably 10.0 or less, and even more preferably 7.0 or less.

[0031] In this embodiment, the content of titanium oxide in the white pigment is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and even more preferably 20% by mass or more, from the viewpoint of print density and suppressing smoke generation during ultraviolet laser irradiation, and the upper limit is not particularly limited, but is 100% by mass or less.

[0032] The mass ratio of the binder resin to the white pigment (binder resin:white pigment) is preferably 5:95 or more and 95:5 or less, more preferably 10:90 or more, even more preferably 20:80 or more, and more preferably 90:10 or less, even more preferably 75:25 or less, still more preferably 50:50 or less, and even more preferably 40:60 or less. A mass ratio of 95:5 or less is preferred because the white pigment content is high and high image density can be obtained when marking with an ultraviolet laser, while a mass ratio of 5:95 or more is preferred because the printed layer has excellent strength and the amount of titanium oxide scattered during ultraviolet laser irradiation is reduced.

[0033] From the viewpoint of obtaining a printed image with high print density, the total content of the binder resin and the white pigment in the solid content of the ink composition is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and still more preferably 90% by mass or more. The upper limit is not particularly limited, but is 100% by mass or less.

[0034] In addition to the components described above (binder resin, white pigment), the ink composition of this embodiment may contain a catalyst (particularly a platinum catalyst) for introducing branches into the silicone polymer compound, a pigment dispersant, a film-forming agent, an anti-blocking agent, a wetting agent, a viscosity adjuster (such as a thickener), a pH adjuster, an anti-foaming agent, a general surfactant, and the like.

[0035] The ink composition of this embodiment is preferably a water-based ink composition. A water-based ink composition contains an aqueous medium as a solvent, and the aqueous medium used can be water or a mixed solvent of water and a water-miscible solvent. Examples of water-miscible solvents include lower alcohols, polyhydric alcohols, and alkyl ethers or alkyl esters thereof. Specific examples include lower alcohols such as methyl alcohol, ethyl alcohol, normal propyl alcohol, and isopropyl alcohol, polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, and glycerin, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoacetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monoacetate, diethylene glycol monomethyl ether, and dipropylene glycol monomethyl ether. When the ink composition is an organic solvent-based ink composition, examples of the solvent include known solvents such as aromatic organic solvents such as toluene and xylene, ester-based organic solvents such as ethyl acetate, n-propyl acetate, isobutyl acetate, ester-based organic solvents, ketone-based organic solvents such as methyl ethyl ketone and methyl isobutyl ketone, alcohol-based organic solvents such as methanol, ethanol, isopropanol, and n-butanol, and hydrocarbon-based solvents such as methylcyclohexane.

[0036] The solids concentration of the ink composition is not particularly limited, but from the viewpoints of obtaining the desired printing layer thickness, giving the ink composition a viscosity that makes it easy to apply, and ease of drying, it is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 70% by mass or less, and even more preferably 65% ​​by mass or less.

[0037] From the viewpoints of coatability, obtaining a desired coating layer thickness, and ease of drying, the viscosity of the ink composition, as measured with a Brookfield viscometer, is preferably 10 mPa·s (20°C) or more, more preferably 15 mPa·s (20°C) or more, even more preferably 20 mPa·s (20°C) or more, and is preferably 5000 mPa·s (20°C) or less, more preferably 3000 mPa·s (20°C) or less, even more preferably 1000 mPa·s (20°C) or less, and still more preferably 500 mPa·s (20°C) or less.

[0038] The ink composition is prepared by a conventionally known method. Specifically, it is obtained by mixing the various materials described above with an aqueous medium. Alternatively, titanium oxide, water, and optionally inorganic pigments other than titanium oxide, water-miscible solvents, pigment dispersants, pigment dispersing resins, etc. may be mixed and kneaded in advance, and then an emulsion or dispersion of a silicone polymer compound and the remaining specified materials may be added and mixed. Furthermore, when the coating liquid is an oil-based coating liquid, titanium oxide or a pigment other than titanium oxide may be added after mixing the organic solvent and the resin, and a pigment dispersant, pigment dispersing resin, etc. may be added in advance to the mixed liquid of the organic material and the resin, or may be added later. The coating liquid can be obtained by mixing and dispersing the above components using a high-speed mixer such as a homomixer or a lab mixer, or a disperser such as a Coles disperser, a three-roll mill or a bead mill.

[0039] The ink composition of this embodiment is used to form a printed layer on a substrate that is subject to ultraviolet laser marking (that changes color when irradiated with an ultraviolet laser). The method for applying the printed layer to the substrate is not particularly limited, and the printed layer may be applied to the substrate by flexographic printing, inkjet printing, gravure printing, screen printing, pad printing, spray coating, a Mayer bar, a gravure coater, an air knife coater, a blade coater, a rod coater, a die coater, a bar coater, or the like. Since the ink composition is preferably a water-based ink composition, it is preferable to apply it using various coaters, or to form a printed layer by gravure printing or flexographic printing. That is, in one preferred embodiment, the ink composition of this embodiment is an ink composition for gravure printing or an ink composition for flexographic printing.

[0040] The substrate on which the print layer of this embodiment is formed is preferably a paper substrate or a film substrate. That is, the ink composition of this embodiment is preferably used to form a printed layer on a paper substrate or a film substrate that changes color when irradiated with an ultraviolet laser. Paper substrates and film substrates are described below.

[0041] [Printing layer for ultraviolet laser marking and printing medium for ultraviolet laser marking] The print layer for ultraviolet laser marking of this embodiment (hereinafter also simply referred to as "print layer") is a print layer formed from the ink composition of this embodiment. The print medium for ultraviolet laser marking of this embodiment (hereinafter also simply referred to as "print medium") has the print layer of this embodiment on a substrate. The printed layer may be formed on at least one side of the substrate, and may be formed on both sides, but is preferably formed on only one side. The printed layer may be formed on the entire surface of the substrate, but may be formed only in a partial area (portion) where marking (printing) with an ultraviolet laser is desired. In this embodiment, the substrate may have an additional layer on the surface opposite to the surface on which the printed layer is provided, such as an adhesive layer, a vapor deposition layer, a resin layer, etc. One or more of these layers may be provided. Furthermore, another layer may be provided between the substrate and the printed layer.

[0042] <Print layer> The printing layer contains titanium oxide, and the content of titanium oxide in the printing layer is preferably 0.1 g / m 2 More than 10g / m 2 or less, more preferably 0.2 g / m 2 More preferably, 0.3 g / m 2 More preferably, 0.4 g / m 2 More preferably, it is 7.5 g / m or more. 2 or less, more preferably 5 g / m 2 or less, even more preferably 3.5 g / m 2 The following is the result. The content of titanium oxide in the printing layer is 0.1 g / m 2 When the content of titanium oxide in the printing layer is 10 g / m or more, sufficient printing density can be obtained, which is preferable. 2 If the amount is less than this, the printing density will reach a plateau, which will prevent costs from increasing due to the inclusion of more titanium oxide than necessary, and it is also preferable because it will prevent smoke generation that is thought to be caused by the scattering of titanium oxide during ultraviolet laser irradiation (printing). It is sufficient that at least the printable area of ​​the printing medium for ultraviolet laser marking contains titanium oxide in the above content, and there may be a portion in the area where printing is not performed where no printing layer is provided. 2 From the viewpoint of ease of production, it is preferable that the content of titanium oxide in the entire area of ​​the printing medium is 0.1 g / m. 2 It is also preferable that a printed layer having the above properties is provided.

[0043] In this embodiment, the print medium may have a titanium oxide-containing undercoat layer or a titanium oxide content of 0.1 g / m 2 as a layer below the print layer containing titanium oxide. 2 In such a case, the content of titanium oxide in the entire printing layer including the undercoat layer is 0.1 g / m or less. 2 That's all. Furthermore, when a resin layer, which will be described later, is provided on the print layer, the resin layer is not considered to be a print layer.

[0044] 1m of printing layer 2 The mass (solid content, basis weight) per unit area is preferably 0.2 g / m from the viewpoint of print density and suppression of smoke generation during ultraviolet laser irradiation. 2 More preferably, 0.5 g / m 2 More preferably, 1.0 g / m 2 More preferably, 2.0 g / m 2 More preferably, 3.0 g / m 2 and preferably 50 g / m 2 Less than 30 g / m, more preferably 2 or less, more preferably 15 g / m 2 or less, even more preferably 10 g / m 2 More preferably 7 g / m or less 2 The following is the result.

[0045] The thickness of the printing layer is preferably 0.30 μm or more, more preferably 0.5 μm or more, and even more preferably 0.8 μm or more, from the viewpoint of print density and ease of printing layer formation, and is preferably 40.0 μm or less, more preferably 20.0 μm or less, even more preferably 10.0 μm or less, and even more preferably 6.0 μm or less, from the viewpoint of the printing density reaching a plateau and ease of printing layer formation. The thickness of the print layer is measured from an observation image of a cross section of the print medium using a scanning electron microscope (SEM).

[0046] The substrate of the printing medium may be a paper substrate, as described below, or the paper substrate itself may contain titanium oxide. When the paper substrate contains titanium oxide, the image tends to have better print density. In particular, when the thickness of the printing layer is thin, the paper substrate itself contains titanium oxide, which tends to result in a clearer image. In this case, when the thickness of the printing layer is 2.0 μm or less, the effect of the paper substrate containing titanium oxide tends to be significant. When the paper substrate contains titanium oxide, the content of titanium oxide in the paper substrate is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and even more preferably 20% by mass or more.

[0047] <Print media> The print medium for ultraviolet laser marking of this embodiment has the print layer of this embodiment on a substrate. The substrate is not particularly limited and may be appropriately selected from paper, film, cloth, nonwoven fabric, metal, glass, etc. Among these, the substrate is preferably paper (paper substrate) or film (film substrate). (Paper base material) Examples of raw pulp constituting the paper base include wood pulp, non-wood pulp, and deinked pulp. Examples of wood pulp include, but are not limited to, chemical pulps such as bleached hardwood kraft pulp (LBKP), unbleached hardwood kraft pulp (LUKP), bleached softwood kraft pulp (NBKP), unbleached softwood kraft pulp (NUKP), sulfite pulp (SP), dissolving pulp (DP), soda pulp (AP), and oxygen-bleached kraft pulp (OKP); semi-chemical pulps such as semi-chemical pulp (SCP) and chemi-groundwood pulp (CGP); and mechanical pulps such as groundwood pulp (GP), thermomechanical pulp (TMP), and chemi-thermomechanical pulp (CTMP). Examples of non-wood pulp include, but are not limited to, cotton-based pulps such as cotton linters and cotton lint, and non-wood pulps such as hemp, straw, bamboo, and bagasse. The deinked pulp is not particularly limited, but examples include deinked pulp made from recycled paper. The raw material pulp may be one of the above types alone or a mixture of two or more types. The raw material pulp may also be mixed with organic synthetic fibers such as polyamide fiber and polyester fiber, recycled fibers such as polynosic fiber, and inorganic fibers such as glass fiber, ceramic fiber, and carbon fiber. From the viewpoint of availability, wood pulp and deinked pulp are preferred as the raw material pulp. Furthermore, among wood pulps, from the viewpoint of uniformity of texture, the raw material pulp is preferably chemical pulp, more preferably kraft pulp, even more preferably one or more selected from hardwood kraft pulp such as eucalyptus or acacia, and softwood kraft pulp such as pine or cedar, even more preferably one or more selected from hardwood bleached kraft pulp (LBKP) and softwood bleached kraft pulp (NBKP), and particularly preferably LBKP.

[0048] The Canadian standard freeness (CSF) of the wood pulp used in the paper base material is preferably 150 mL or more, more preferably 300 mL or more, even more preferably 400 mL or more, from the viewpoint of obtaining the desired fiber width and fiber length, fine fiber ratio, and water retention, and is preferably 800 mL or less, more preferably 750 mL or less, even more preferably 700 mL or less, and even more preferably 600 mL or less. Here, CSF refers to Canadian Standard Freeness according to JIS P 8121-2:2012.

[0049] The paper base material can be obtained by making paper from a pulp slurry to which internal additives have been added as needed. In addition to the above-mentioned pulp, known internal additives for papermaking, such as fillers, sizing agents, dry strength agents, wet strength agents (e.g., polyamidepolyamine epichlorohydrin), retention aids (e.g., aluminum sulfate), drainage aids, pH adjusters, softeners, antistatic agents, antifoaming agents, dyes and pigments, may be added to the paper base material as needed. Examples of fillers include kaolin, talc, titanium oxide, heavy calcium carbonate, light calcium carbonate, calcium sulfite, gypsum, calcined kaolin, white carbon, amorphous silica, delaminated kaolin, diatomaceous earth, magnesium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, and zinc hydroxide. Examples of sizing agents include rosin-based, alkyl ketene dimer-based, alkenyl succinic anhydride-based, styrene-acrylic, higher fatty acid-based, and petroleum resin-based sizing agents.

[0050] In the papermaking of the paper substrate, a known wet papermaking machine, such as a Fourdrinier papermaking machine, a gap former papermaking machine, a cylinder papermaking machine, or a short wire papermaking machine, can be appropriately selected and used. Next, the paper layer formed by the papermaking machine is transported on a felt and dried in a dryer. A multi-stage cylinder dryer may be used as a pre-dryer before drying in the dryer.

[0051] The paper substrate obtained as described above may be subjected to a surface treatment using a calendar to make the thickness and profile uniform and improve printability. A known calendaring machine can be appropriately selected and used for the calendaring treatment.

[0052] The paper substrate may be appropriately selected from conventionally known paper substrates such as liner base paper, kraft paper, fine paper, and coated paper. The paper substrate may be a single layer or a multi-layer, and may have a multi-layer structure with different pulp compositions.

[0053] The basis weight of the paper substrate is preferably 30 g / m from the viewpoint of improving the strength as a printing medium and printability. 2 More preferably, 35 g / m 2 and preferably 1000 g / m 2 Less than 700 g / m 2 or less, more preferably 500 g / m 2 The following is the result. The basis weight is measured by the method specified in JIS P 8124:2011.

[0054] The thickness of the paper substrate is not particularly limited, but from the viewpoint of improving the strength as a printing medium and printability, it is preferably 30 μm or more, more preferably 40 μm or more, even more preferably 50 μm or more, and preferably 1200 μm or less, more preferably 850 μm or less, even more preferably 600 μm or less. The thickness of the paper substrate can be measured by the method described in JIS P 8118:2014.

[0055] The density of the paper substrate is not particularly limited, but from the viewpoint of improving the strength as a printing medium and printability, it is preferably 0.3 g / cm 3 More preferably, 0.5 g / cm 3 More preferably, 0.7 g / cm 3 and preferably 1.2 g / cm 3 or less, more preferably 1.0 g / cm3 or less, more preferably 0.85 g / cm 3 The following is the result. The density of the paper substrate is calculated from the basis weight and thickness.

[0056] (Film substrate) The resin constituting the film substrate (hereinafter simply referred to as "resin") is not particularly limited, and may be any resin that can be processed into a film and may be appropriately selected from known thermoplastic resins. Specific examples include polyester-based resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polylactic acid, and polybutylene succinate; polyolefin-based resins such as polyvinyl chloride, polyvinylidene chloride, polybutene, polybutadiene, ethylene-vinyl acetate copolymer, polyethylene, polypropylene, ethylene-propylene copolymer, and polymethylpentene; polycarbonate; polyurethane; polyamide; polyacrylonitrile; poly(meth)acrylate; and the like. Among these, from the viewpoint of versatile use, the resin constituting the film substrate preferably contains polyolefins such as polyethylene, polypropylene, and ethylene-propylene copolymers, polyesters such as polyethylene terephthalate, polybutylene terephthalate, polylactic acid, and polybutylene succinate, and polyvinyl chloride, more preferably at least one selected from the group consisting of polyethylene, polypropylene, ethylene-propylene copolymers, polyethylene terephthalate, polylactic acid, and polybutylene succinate, and even more preferably at least one selected from the group consisting of polyethylene, polypropylene, ethylene-propylene copolymers, polyethylene terephthalate, polylactic acid, and polybutylene succinate. The resin constituting the film substrate is even more preferably polyolefin, even more preferably at least one selected from the group consisting of polyethylene and polypropylene, and particularly preferably contains at least polypropylene. It is preferable to use a biodegradable polyester resin as the resin constituting the film substrate in terms of reducing the environmental load, and examples thereof include polylactic acid and polybutylene succinate. These resins may be used alone or in combination of two or more.

[0057] The film substrate may be stretched or unstretched, and is not particularly limited. For example, when the film substrate is a polypropylene film, it may be a non-stretched polypropylene film (CPP) or a biaxially stretched polypropylene film (OPP).

[0058] In this embodiment, in addition to the resin described above, other components may be added to the film substrate within a range that does not impair the effects of the present invention. Examples of such components include pigments containing titanium oxide, antistatic agents, antiblocking agents, antioxidants, ultraviolet absorbers, HALS, plasticizers, lubricants, flame retardants, release agents, and colorants.

[0059] From the viewpoint of improving strength, the thickness of the film substrate is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more, and is preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 100 μm or less. The film thickness is measured by the method described in the Examples.

[0060] (cloth, non-woven fabric) When the substrate is a cloth or nonwoven fabric, examples of raw materials constituting the cloth or nonwoven fabric include natural fibers such as cotton, hemp, cellulose fibers, and wool; synthetic fibers such as polycarbonate, polyetherimide, polyester, polyurethane, and polyamide (nylon); and regenerated fibers such as rayon and acetate.

[0061] As the substrate, a commercially available substrate may be used as appropriate. For example, various types of commercially available paper may be used as the paper substrate, and a resin film of various resins may be used as the film substrate.

[0062] [Resin layer] The print medium of this embodiment may further have a resin layer on the print layer from the viewpoint of improving water resistance when a water-absorbent substrate such as paper is used as the substrate, or for the purpose of functioning as a protective layer. In other words, a print medium may be used in which a resin layer has been previously provided on the print layer.

[0063] The resin layer preferably has high ultraviolet transmittance, and the total light transmittance of the resin layer is preferably 40% or more, more preferably 60% or more, even more preferably 70% or more, still more preferably 80% or more, particularly preferably 90% or more, and is 100% or less. There is no particular upper limit. The total light transmittance is measured in accordance with JIS K 7361-1:1997.

[0064] The resin constituting the resin layer is not particularly limited as long as it has high UV transmittance, a total light transmittance of preferably 40% or more, and can be provided on a sheet substrate. However, from the viewpoint of transparency and ease of providing the resin layer, when the resin layer and a paper substrate having a printed layer are attached via an adhesive layer or laminated, or when the resin layer and a paper substrate having a printed layer are attached via an adhesive layer, the resin is preferably at least one selected from polyethylene, polypropylene, polyethylene terephthalate, polyvinyl alcohol, polyamide, and starch, more preferably at least one selected from polyethylene, polypropylene, polyethylene terephthalate, and polyvinyl alcohol, even more preferably polyethylene or polypropylene, and particularly preferably polyethylene. When the resin layer is provided by coating, examples of the resin include acrylic resin, styrene-maleic acid resin, water-soluble polyurethane resin, and water-soluble polyester resin. Examples of acrylic resins include resins obtained by copolymerizing (meth)acrylic acid with other monomers such as alkyl esters thereof, styrene, unsaturated carboxylic acids other than (meth)acrylic acid, ethylene, and propylene. Specific examples include ethylene-(meth)acrylic acid copolymers and styrene-acrylic acid-maleic acid resins, with ethylene-(meth)acrylic acid copolymers being preferred.

[0065] The resin layer and the substrate having the printed layer may be laminated by any method, and are not particularly limited, but from the viewpoint of ease of production, it is preferable to attach the resin layer and the substrate having the printed layer via an adhesive layer, or to laminate them, or to apply a transparent coating in the form of a liquid coating. Alternatively, a printing layer may be formed on the resin layer in advance, and then attached to the paper substrate via an adhesive layer. When the resin layer is provided locally, it is preferable to attach it via an adhesive from the viewpoint of ease of production, whereas when the resin layer is provided over a wide area, it is preferable to use lamination processing. The adhesive layer is not particularly limited and may be appropriately selected from known adhesive layers. Specific examples include the pressure-sensitive adhesive layer disclosed in JP-A-2012-57112.

[0066] The thickness of the resin layer is not particularly limited, but from the viewpoint of obtaining clear prints and the handleability of printed matter and printing media, it is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, and preferably 100 μm or less, more preferably 75 μm or less, even more preferably 50 μm or less.

[0067] [Printed matter and method of manufacturing printed matter] The printed matter of this embodiment is a printed matter obtained from the ultraviolet laser marking printing medium of this embodiment, and the printing layer has, at least in part, a printed area containing titanium oxide discolored by ultraviolet laser irradiation. The printed area containing discolored titanium oxide is an area containing titanium oxide discolored by ultraviolet laser irradiation, and is an ultraviolet laser irradiated area, i.e., a printed area. The method for producing a printed matter of this embodiment also includes a step of irradiating the print medium for ultraviolet laser marking of this embodiment with an ultraviolet laser to discolor the irradiated area, thereby printing. The printing medium used in the method for producing a printed matter of this embodiment is exemplified by the printing medium described above, and the preferred ranges are also the same. In addition, in the method for producing a printed matter of this embodiment, it is sufficient that a printing layer is provided at least in the ultraviolet laser irradiated area, and a printing layer does not have to be provided in the non-irradiated area.

[0068] In the printed matter obtained in this embodiment, the non-printed areas are preferably white and the printed areas are preferably black. The non-printed area preferably has a Munsell color system brightness of 10, i.e., white, while the printed area preferably has a Munsell color system brightness of 0 to 8, more preferably 0 to 6, and even more preferably 0 to 4. In order to obtain a color in the Munsell color system described above, it is preferable to appropriately adjust the titanium oxide content of the printing layer in the printing medium, the crystallite size of the titanium oxide, the length-weighted average fiber length of the pulp that makes up the paper base material, other characteristics (type of titanium oxide, diffraction angle, proportion of fine fibers in the pulp that makes up the paper base material, water retention of the pulp that makes up the paper base material, amount of inorganic pigment, thickness of the printing layer, etc.), and irradiation conditions of the ultraviolet laser (for example, average output, repetition frequency, wavelength, etc.).

[0069] [Ultraviolet laser irradiation conditions] From the viewpoint of improving the visibility of the printed area, the wavelength of the ultraviolet laser is preferably 370 nm or less, more preferably 365 nm or less, even more preferably 360 nm or less, and is preferably 260 nm or more, more preferably 340 nm or more, even more preferably 350 nm or more.

[0070] From the viewpoint of improving the visibility of the printed area, the average output power of the ultraviolet laser is preferably 0.3 W or more, more preferably 0.8 W or more, even more preferably 1.2 W or more, and even more preferably 1.8 W or more, and from the viewpoint of economy, it is preferably 30 W or less, more preferably 25 W or less, even more preferably 20 W or less, even more preferably 15 W or less, even more preferably 10 W or less, and even more preferably 6 W or less.

[0071] From the viewpoint of improving the visibility of the printed area, the repetition frequency (frequency) of the ultraviolet laser is preferably 10 kHz or more, more preferably 20 kHz or more, even more preferably 30 kHz or more, and is preferably 100 kHz or less, more preferably 80 kHz or less, even more preferably 60 kHz or less.

[0072] From the viewpoint of obtaining a clear image and ease of printing, the spot diameter of the ultraviolet laser is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, and is preferably 300 μm or less, more preferably 240 μm or less, even more preferably 180 μm or less, even more preferably 120 μm or less.

[0073] From the viewpoints of high-speed printing and visibility of the printed area, the scanning speed of the ultraviolet laser is preferably 500 mm / sec or more, more preferably 1000 mm / sec or more, even more preferably 2000 mm / sec or more, and is preferably 7000 mm / sec or less, more preferably 6000 mm / sec or less, even more preferably 5000 mm / sec or less.

[0074] From the viewpoint of obtaining a clear image and the ease of obtaining the equipment, the filling interval (line pitch) of the ultraviolet laser is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, and is preferably 500 μm or less, more preferably 400 μm or less, even more preferably 350 μm or less.

[0075] [Method for producing printed matter] The method for producing a printed matter of the present invention can be carried out in various modes. Various examples of applications of the method for producing a printed matter of the present embodiment will be described below, but the method for producing a printed matter of the present embodiment is not limited to the following applications. The information to be printed is not particularly limited, but variable information is preferable. The method for producing a printed matter according to this embodiment is preferably carried out in-line. (1) Direct printing on packaging A first embodiment of the method for producing a printed matter of this embodiment is a method for printing information on a packaging body having a printing layer formed from the ink composition of this embodiment, and includes a step of printing directly on the packaging body using an ultraviolet laser while it is moving on a packaging line or while it is intermittently stopped. In the first method for producing a printed matter, a package is produced using a printing medium having a printing layer formed from the ink composition of this embodiment, and is then directly printed with an ultraviolet laser. Note that it is sufficient that the printing layer is formed on at least a part of the outermost layer of the printing area of ​​the package. Furthermore, examples of packaging include cardboard boxes and boxes, and it is preferable to print directly on the side or top surface of the packaging with an ultraviolet laser.

[0076] The packaging line may also have a coating mechanism, such as a contact printer, pad printer, spray coater, gravure printer, or flexographic printer. In this embodiment, the process includes a step of applying a printing layer to the packaging body using a coating mechanism while the packaging body is moving on the packaging line, and a further downstream step of printing directly onto the packaging body using an ultraviolet laser while the packaging body is moving on the packaging line or during intermittent stops.

[0077] (2) Printing on labels A second embodiment of the method for producing a printed matter of this embodiment is a method for printing information on a label having a printing layer formed from the ink composition of this embodiment. The printing layer is formed on the printing surface of the label. The printed label is preferably applied to the package using a label application device, of which various types have been proposed, and which has a printing layer on the surface that is irradiated with ultraviolet light. The first label application device applies adhesive to a roll of label base paper and then applies it to an article. More specifically, the roll labeler includes a cutting means for cutting the roll of label base paper into a predetermined length, a gluing and conveying means for receiving the label base paper cut by the cutting means with a label base paper holder coated with adhesive and applying the adhesive to the back surface of the label base paper, and an applying means for receiving the label base paper (label) with adhesive applied from the gluing and conveying means and applying it to an article such as a container. An example of a roll labeler is one in which a rotary conveying means having a label holding surface on its outer surface is provided between the cutting means and the gluing and conveying means, as disclosed in Japanese Patent Application Laid-Open No. 6-64637. Other examples include a roll labeler having a cutting means for cutting the rolled label base paper into a predetermined length one sheet at a time, a transfer roll for transferring the label base paper to an application roll, and a gluing roll for applying glue to the label base paper held by the application roll, and an embodiment in which the transfer roll is not required. The ultraviolet laser irradiation is preferably carried out before cutting the rolled label base paper to a predetermined length, or after cutting and before transferring to the next roll, etc. Depending on the type of roll labeler, the front or back surface of the rolled label base paper will become the front or back surface when attached to a package, so the ultraviolet laser irradiation is carried out accordingly.

[0078] The second label application device uses an adhesive label roll as the label, which has a print layer on the surface that is irradiated with the ultraviolet laser, which is the surface opposite to the surface on which the adhesive is applied. When an adhesive label roll with a release paper is used, for example, an example of an application device includes a release paper separating means for separating the adhesive label from the release paper, a delivery roll for receiving the adhesive label from which the release paper has been separated, and an application roll for sucking the adhesive label from the delivery roll and applying it to an article (package). Irradiation with an ultraviolet laser is preferably carried out before separating the release paper, or after separating the release paper and before the label is carried by the application roll. Another example is an apparatus that sets an adhesive label roll with a release liner, has a mechanism for separating the adhesive label from the release liner, and has a mechanism for applying a label immediately after separation, and prints with an ultraviolet laser before the release liner is separated from the set adhesive label roll. The above-mentioned adhesive label application method is also called flow application. Further examples include a label application device that has a mechanism for setting an adhesive label roll with a release liner, a mechanism for separating the release liner from the adhesive label, and a mechanism for applying the adhesive label to an article (package), wherein the application mechanism is a syringe type, an air jet type, or a robot arm type. Irradiation with an ultraviolet laser is preferably carried out between the time when the release liner is separated from the set adhesive label roll with the release liner.

[0079] Linerless adhesive labels may be used as the labels. Linerless adhesive labels are labels without release paper, and compared to adhesive label rolls with release paper, they have the advantage of being able to produce a larger number of labels per roll and being less expensive because there is no release paper. When using linerless adhesive labels, a printing layer is formed on the side that is irradiated with the ultraviolet laser, which is the side opposite to the side to which the adhesive is applied. An example of a label application device using linerless adhesive labels is one that has a mechanism for setting a linerless label roll, a cutting mechanism for cutting the linerless labels one by one, and an application mechanism for applying the cut linerless labels to an article (package), and the application mechanism is a cylinder type or a robot arm type. Printing by irradiation with an ultraviolet laser is preferably performed between the mechanism for setting the linerless label roll and the cutting mechanism, or while the cut linerless labels are being sent to the application mechanism.

[0080] The third labeling device applies a print medium on which a print layer made of the ink composition of this embodiment has been formed to an article (packaging), and then performs printing with an ultraviolet laser. For the method of attaching the label, reference is made to the first and second devices described above.

[0081] (3) Printing on adhesive tape In a third embodiment of the method for producing a printed matter according to the present invention, the print medium is an adhesive tape. In this case, a print layer is provided on the surface opposite to the surface on which the adhesive is applied. That is, the method for manufacturing a printed matter of the third embodiment includes a step of attaching an adhesive tape made from the printing medium to an item (packaging), and a step of printing with an ultraviolet laser before or after the attaching step. Alternatively, a printing device incorporating an ultraviolet laser printing device into a cardboard sealing machine may be used, specifically, a printing device having a mechanism for setting the adhesive tape winding, a conveyor for transporting the cardboard, a mechanism for folding the flaps of the cardboard, a mechanism for sealing the cardboard by applying adhesive tape, and a mechanism for printing on the adhesive tape with an ultraviolet laser while or after the adhesive tape is being applied.

[0082] The method for producing a printed matter according to the present embodiment is not limited to the above-described embodiment, but can be applied to various uses where printing is required.

[0083] In this embodiment, the printed matter obtained by the method for producing a printed matter is suitable for use in packaging, labels, adhesive tapes, and the like. Examples of packaging bodies include outer bags, outer boxes, liquid containers for beverages such as milk cartons, aseptic paper cartons, and paper cups (preferably paper containers for liquid beverages), and skin packs; examples of labels include label base paper, adhesive labels, and adhesive sheets; and examples of adhesive tapes include adhesive tape and craft tape.

[0084] [Processed products] The print medium and printed matter of the present embodiment are applied to various processed products. That is, the processed products of the present embodiment are made using the print medium of the present embodiment or the printed matter of the present embodiment. Suitable processed products of this embodiment include packaging, labels, adhesive tapes, and the like. Examples of packaging materials include cardboard liner base paper (particularly the outermost liner base paper), outer bags, outer boxes, milk cartons, aseptic paper cartons, liquid containers for beverages such as paper cups (preferably paper containers for liquid beverages), food trays, and skin packs; examples of labels include label base paper, adhesive labels, and adhesive sheets; and examples of adhesive tapes include adhesive tape and kraft tape. 1, a liquid container 10 as an example of a package has, for example, a printed layer formed on the surface using the ink composition of this embodiment as a printed area 20. The printed area 20 is irradiated with an ultraviolet laser and has characters such as a date printed thereon. [Example]

[0085] The features of the present invention will be explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below. Note that "parts" and "%" mean "parts by mass" and "% by mass" unless otherwise specified.

[0086] [Example 1] <Preparation of Ink Composition for UV Laser Marking> 1.75 parts of Dispersant A (Toagosei Co., Ltd., Aron T-50, solids concentration 40%) was added to 28.25 parts of tap water and mixed using a homodisper. 70 parts of Titanium Oxide A (Ishihara Sangyo Kaisha, Ltd., R-780, rutile-type titanium oxide, average particle size: 0.24 μm, crystallite size: 45 nm) was then added to prepare a titanium oxide dispersion with a solids concentration of 70%. A pigment dispersion was then prepared using a Coles disperser. The obtained pigment dispersion was mixed with silicone resin emulsion A (Dow Toray Co., Ltd., DOWSIL TM 63.03 parts of IE-7170 Emulsion (48% solids concentration) (30 parts per 70 parts of titanium dioxide in terms of solids) and 5 parts (1 part in terms of solids) of an antifoaming agent (TEGO-FOAMEX 805N, Evonik Japan Co., Ltd., 20% solids concentration) were added and mixed using a homodisper. Tap water was then added to bring the solids concentration to 50%, and 2.86 parts (1 part in terms of solids) of a thickener (Rheocoat 35, Arkema Japan Co., Ltd., 35% solids concentration) was added so that the viscosity of the ink composition after mixing was 100 mPa s, to prepare UV laser marking ink composition 1.

[0087] <Manufacturing printing media for ultraviolet laser marking> Using a Mayer bar, the obtained ultraviolet laser marking ink composition 1 was applied to a substrate in a coating amount (solid content) of 5.0 g / m 2 To achieve this, paper substrate A (Oji Materia Co., Ltd., OK Blizzard (single-sided gloss bleached kraft paper), basis weight: 70 g / m 2 The coating was applied to the glossy surface of a 88 μm thick sheet of paper and dried at 140° C. for 1 minute to obtain a print medium 1 for ultraviolet laser marking (print paper for ultraviolet laser marking) having a print layer for ultraviolet laser marking.

[0088] [Example 2] An ultraviolet laser marking ink composition 2 was prepared in the same manner as in Example 1, except that, as the resin emulsion to be added to the pigment dispersion, 42.02 parts of silicone resin emulsion A (20 parts per 70 parts of titanium oxide in terms of solid content) and 24.81 parts of polyurethane resin emulsion A (ADEKA Corporation, HUX-564, solid content concentration 40%) (10 parts per 70 parts of titanium oxide in terms of solid content) were added instead of 63.03 parts of silicone resin emulsion A. Thereafter, in the same manner as in Example 1, a print medium 2 for ultraviolet laser marking was obtained.

[0089] [Example 3] Ink composition 3 for ultraviolet laser marking was prepared in the same manner as in Example 1, except that, instead of 63.03 parts of silicone resin emulsion A, 21.01 parts of silicone resin emulsion A (10 parts per 70 parts of titanium oxide in solids content) and 49.62 parts of polyurethane resin emulsion A (20 parts per 70 parts of titanium oxide in solids content) were added as the resin emulsion to be added to the pigment dispersion. Thereafter, in the same manner as in Example 1, a print medium 3 for ultraviolet laser marking was obtained.

[0090] [Example 4] As the resin emulsion to be added to the pigment dispersion, 63.03 parts of silicone resin emulsion A was replaced with silicone resin emulsion B (Dow Toray Co., Ltd., DOWSIL TM An ultraviolet laser marking ink composition 4 was prepared in the same manner as in Example 1, except that 81.74 parts of 490EX Emulsion, 37%) was used (30 parts per 70 parts of titanium oxide in terms of solid content). Thereafter, in the same manner as in Example 1, a printing medium 4 for ultraviolet laser marking was obtained.

[0091] [Example 5] As the resin emulsion to be added to the pigment dispersion, 63.03 parts of silicone resin emulsion A was replaced with silicone resin emulsion C (Dow Toray Co., Ltd., SYL-OFF TM7920NF Emulsion Coating, 40%) was used at 75.00 parts (30 parts per 70 parts of titanium dioxide in terms of solid content), and a catalyst (Dow Toray Co., Ltd., SYL-OFF TM An ultraviolet laser marking ink composition 5 was prepared in the same manner as in Example 1, except that 15.00 parts of 7924 Catalyst Emulsion (solid content concentration 40%) (6 parts in terms of solid content per 30 parts of resin emulsion) was added. Thereafter, in the same manner as in Example 1, a printing medium 5 for ultraviolet laser marking was obtained.

[0092] [Example 6] Ink composition 6 for ultraviolet laser marking was prepared in the same manner as in Example 1, except that 21.01 parts of silicone resin emulsion A (10 parts per 90 parts of titanium oxide in terms of solid content) was used instead of 63.03 parts of silicone resin emulsion A as the resin emulsion to be added to the pigment dispersion. Thereafter, in the same manner as in Example 1, a printing medium 6 for ultraviolet laser marking was obtained.

[0093] [Example 7] 0.25 parts of Dispersant A was added to 89.75 parts of tap water and mixed using a Homodisper. 10 parts of Titanium Oxide A was then added to prepare a titanium oxide dispersion with a solids concentration of 10%. A pigment dispersion was then prepared using a Coles disperser. Ink composition 7 for ultraviolet laser marking was prepared in the same manner as in Example 1, except that the resin emulsion added to the obtained pigment dispersion was changed from 63.03 parts of silicone resin emulsion A to 189.08 parts of silicone resin emulsion A (90 parts per 10 parts of titanium oxide in terms of solid content). Thereafter, in the same manner as in Example 1, a printing medium 7 for ultraviolet laser marking was obtained.

[0094] [Example 8] Instead of 70 parts of titanium oxide A, 60 parts of titanium oxide A and 10 parts of heavy calcium carbonate (Fimatec Co., Ltd., FMT-90, average particle size 0.97 μm) were added to prepare a titanium oxide dispersion with a solids concentration of 70%. Thereafter, a pigment dispersion was prepared using a Coles disperser. The obtained pigment dispersion was mixed with silicone resin emulsion A (Dow Toray Co., Ltd., DOWSIL TM An ultraviolet laser marking ink composition 8 was prepared in the same manner as in Example 1, except that 63.03 parts of IE-7170 Emulsion (solid content concentration: 48%) (30 parts per 60 parts of titanium oxide in terms of solid content) was added. Thereafter, in the same manner as in Example 1, a printing medium 8 for ultraviolet laser marking was obtained.

[0095] [Example 9] Instead of 70 parts of titanium oxide A, 5 parts of titanium oxide A and 65 parts of heavy calcium carbonate (Fimatec Co., Ltd., FMT-90, average particle size 0.97 μm) were added to prepare a titanium oxide dispersion with a solids concentration of 70%. Thereafter, a pigment dispersion was prepared using a Coles disperser. The obtained pigment dispersion was mixed with silicone resin emulsion A (Dow Toray Co., Ltd., DOWSIL TM An ultraviolet laser marking ink composition 9 was prepared in the same manner as in Example 1, except that 63.03 parts of IE-7170 Emulsion (solid content concentration: 48%) (30 parts per 5 parts of titanium oxide in terms of solid content) was added. Thereafter, in the same manner as in Example 1, a printing medium 9 for ultraviolet laser marking was obtained.

[0096] [Example 10] An ultraviolet laser marking ink composition 10 was prepared in the same manner as in Example 1, except that titanium oxide A was replaced with titanium oxide B (Ishihara Sangyo Kaisha, Ltd., TTO-51(A), rutile-type titanium oxide, particle diameter: 0.01 to 0.03 μm, crystallite size: 10 nm). Thereafter, in the same manner as in Example 1, a print medium 10 for ultraviolet laser marking was obtained.

[0097] [Example 11] In the same manner as in Example 1, an ink composition 1 for ultraviolet laser marking was prepared. A printing medium 11 for ultraviolet laser marking was obtained in the same manner as in Example 1, except that a polyethylene terephthalate film (PET film, Higashiyama Film Co., Ltd., HK-33WF, thickness 100 μm) was used instead of the paper substrate A.

[0098] [Example 12] In the same manner as in Example 1, an ink composition 1 for ultraviolet laser marking was prepared. In a center drum flexographic printing machine, the ink composition 1 for ultraviolet laser marking was printed on the glossy side of the paper substrate A using a 150 line / inch anilox roll to obtain a print medium 12 for ultraviolet laser marking. The coating amount was 2.0 g / m 2 It was.

[0099] [Example 13] In the same manner as in Example 1, an ink composition 1 for ultraviolet laser marking was prepared. In a gravure printing machine, the ink composition 1 for ultraviolet laser marking was printed on the glossy surface of the paper substrate A using a gravure roll with a plate depth of 200 μm, to obtain a print medium 13 for ultraviolet laser marking. The coating amount was 4.0 g / m 2 It was.

[0100] [Comparative Example 1] An ultraviolet laser marking ink composition 11 was prepared in the same manner as in Example 1, except that 74.44 parts of polyurethane resin emulsion A (30 parts per 70 parts of titanium oxide in terms of solids content) was used instead of 63.03 parts of silicone resin emulsion A as the resin emulsion to be added to the pigment dispersion. Thereafter, in the same manner as in Example 1, a print medium 14 for ultraviolet laser marking was obtained.

[0101] Comparative Example 2 An ink composition 12 for ultraviolet laser marking was prepared in the same manner as in Example 1, except that the resin emulsion added to the pigment dispersion was changed from 63.03 parts of silicone resin emulsion A to 132.16 parts by mass of polyacrylic resin emulsion A (SAKATA INX CORPORATION, N61-PR1, solids concentration 23%) (30 parts per 70 parts of titanium oxide in terms of solids). Thereafter, in the same manner as in Example 1, a print medium 15 for ultraviolet laser marking was obtained.

[0102] Comparative Example 3 Instead of 70 parts of titanium oxide A, 70 parts of heavy calcium carbonate (Fimatec Corporation, FMT-90, average particle size 0.97 μm) was used, and as the resin emulsion to be added to the pigment dispersion, 63.03 parts of silicone resin emulsion A was replaced with silicone resin emulsion C (Dow Toray Co., Ltd., SYL-OFF TM An ultraviolet laser marking ink composition 13 was prepared in the same manner as in Example 1, except that 75.00 parts of 7920NF Emulsion Coating, 40%) was used (30 parts per 70 parts of calcium carbonate in terms of solid content). Thereafter, in the same manner as in Example 1, a printing medium 16 for ultraviolet laser marking was obtained.

[0103] [Measurement and Evaluation] The ultraviolet laser marking print media and various raw materials obtained in the examples and comparative examples were subjected to the following measurements and evaluations.

[0104] [Method for measuring particle size of titanium oxide] The particle size of titanium oxide contained in the printed layer was calculated from SEM images (secondary electron images) obtained with a scanning electron microscope (SEM, Hitachi High-Tech Corporation, SU7000, etc.) of the ash obtained by burning the printing medium or printed matter in a muffle furnace. Specifically, when the substrate did not contain titanium oxide, the ash content was obtained under the same conditions as in the measurement of the crystallite size described below. When the substrate (e.g., paper substrate) contains titanium oxide, the printed layer was ground using an industrial razor (manufactured by Feather Safety Razor Co., Ltd., product number: 099769), and the collected printed layer was used as a sample and similarly ashed to obtain an ash content. The ash content sample to be tested with a scanning electron microscope was dispersed in ethanol for 5 minutes using an ultrasonic cleaner (manufactured by AS ONE Corporation, such as LSC-63) to obtain a 0.1 mass% slurry, and then 0.1 mL was cast onto an aluminum dish and dried at 100 °C to prepare. Particles that could be clearly distinguished from adjacent particles were visually selected, and the geometric mean of the long diameter and short diameter of one particle was taken as the particle diameter. At this time, even if primary particles and secondary particles in an aggregated state were mixed, when they could be clearly distinguished, each was counted as one particle, and the average diameter of 100 randomly selected particles was taken as the particle diameter. The magnification during SEM image observation was appropriately selected according to the particle diameter of titanium oxide and was set to about 20,000 times. Also, when particles other than titanium oxide were included, particles containing titanium element were measured using an energy dispersive X-ray analyzer (manufactured by Horiba, Ltd., such as EMAX) attached to the SEM. In the case of needle-like particles, the long diameters of 100 particles were measured, and the average was taken as the particle diameter.

[0105] 〔Method for calculating crystallite size〕 <Method for preparing measurement sample> The printed media obtained in the examples and comparative examples were fired and ashed at 450 °C using a muffler furnace (manufactured by Yamato Scientific Co., Ltd., model number FO300). When the substrate contained titanium oxide, the following pretreatment was performed to separate the printed layer and the substrate. The printed layer was ground using an industrial razor (manufactured by Feather Safety Razor Co., Ltd., product number: 099769), and the collected printed layer was used as a sample and similarly ashed.

[0106] <Measurement by X-ray diffraction method> The test sample obtained by ashing was filled into a sample holder and measured using a high-speed detector. During filling, an appropriate height adjustment jig was used according to the sample amount to adjust so that the sample measurement surface was at the same height as the edge of the sample holder. (Measurement conditions) X-ray Diffractometer: Rigaku Corporation, RINT-Ultima III Voltage: 40 kV Current: 40 mA Optical System: Parallel Beam (CBO) Detector: Rigaku Corporation, High-Speed Detector D / teX Ultra 2 Goniometer: Ultima III Horizontal Goniometer X-ray Tube: Cu Wavelength: 1.541 Å (Kα1) Scan Mode: CONTINUOUS Scan Speed: 1.0000 deg / min Step Width: 0.0500 deg Scan Axis: 2Theta / Theta Scan Range: 5.0000 - 60.0000 deg Incident Slit: 1.0 mm Longitudinal Restriction Slit: 10 mm Receiving Slit 1: Open Receiving Slit 2: Open Sample Holder: ASC-6 Sample Holder (Part Number 2455E442) Material: Aluminum Dimensions: φ23 mm × 2.0 mm Holder Height Adjustment Fixture: Transparent Disk-Shaped Plate (Self-Made) Material: Poly(methyl acrylate) Dimensions: φ23 mm × 0.8 mm

[0107] <Processing of Data Obtained by X-ray Diffraction> For the obtained diffraction profile, background processing and profile fitting processing were performed using integrated powder X-ray analysis software (Rigaku Corporation, PDXL2). Regarding the settings for data processing, all those not specifically described were performed with the default settings of the software. Based on the information of the peak position and peak intensity of the diffraction profile, the crystal phase was identified using a database (ICDD).

[0108] <Calculation of crystallite size based on data obtained by X-ray diffraction> The half-value width (FWHM) and Bragg angle (θ) of the strongest diffraction line obtained from the diffraction profile after data processing were substituted into the Scherrer equation to calculate the crystallite size. The X-ray diffraction peaks of titanium oxide used in the calculation are as follows. Anatase: 101 plane Rutile: 110 plane The Scherrer equation is as follows.

[0109]

Equation

[0110] D: Crystallite size (nm) K: Scherrer constant λ: Wavelength of X-ray (nm) B: FWHM (rad) θ: Bragg angle (rad) The value of K was 0.89, B was the value of FWHM obtained by measurement, the value of λ was 0.154, and the value of θ was the measured value of the maximum intensity derived from the 101 plane in the case of anatase and the 110 plane in the case of rutile.

[0111] 〔Basis weight of the substrate〕 The basis weight of the paper substrate was measured in accordance with JIS P 8124:2011. When measuring the basis weight of the paper substrate from a printed medium or printed matter, the printing layer was removed using a grinding device (manufactured by Sagawa Seisakusho Co., Ltd., grinding wheel dimensions φ50.8×12.7 mm) and used for the measurement. The basis weight of the film substrate was calculated by measuring the mass of the film cut out into 200 mm×200 mm and dividing by the area.

[0112] 〔Thickness of the substrate〕 The thickness of the paper substrate was measured in accordance with JIS P 8118:2014. When measuring the thickness of the paper substrate from a printed medium or printed matter, the printing layer was removed using a grinding device (manufactured by Sagawa Seisakusho Co., Ltd., grinding wheel dimensions φ50.8×12.7 mm) and used for the measurement. The thickness of the film substrate was measured in accordance with JIS K 7130:1999.

[0113] [Branching Degree of Silicone Polymer Compound] (1) Preparation and measurement of samples from resin emulsion (Method of preparing measurement samples) 3g of the emulsion solution was placed in an aluminum cup, dried at 140℃ for 3 hours, and then dried under the following conditions. 29 Si-NMR analysis was performed. <When the sample is solid (Silicone A and Silicone C)> When the sample was solid, 25 mg was placed in a measuring tube and measured under the following conditions. Equipment: JEOL JNM-ECZ600R Probe: 3.2mm AUTOMAS probe Sample amount: Approximately 25 mg (the sample was finely chopped and packed into a sample tube) Measurement temperature: room temperature Measurement mode: DD-MAS method Sample rotation speed: 6kHz Measurement nuclei: 29 Si (119.2MHz), observation range: 29.9kHz, data points: 8192 Accumulation count: 8000 times Delay time: 60s

[0114] <When the sample is liquid (Silicone B)> 300 mg was dissolved in CDCl3 and measured under the following conditions. Equipment: JEOL JNM-ECZ600R Probe: 5mm ROYAL probe Sample amount: approx. 300 mg Solvent: deuterated chloroform (50 mM chromium(III) acetylacetate added) Measurement temperature: room temperature Measurement mode: Single decoupling method Measurement nuclei: 29 Si (119.2MHz), observation range: 44.6kHz, data points: 65536 Total number of times: 15,659 Delay time: 2 seconds

[0115] (Calculation of branching degree) The obtained NMR spectrum was integrated within the following range, and the branching degree was calculated from the obtained value. M unit: 12~-12 ppm D unit: -15 to -40 ppm T unit: -55 to -75 ppm Q unit: -85 to -120 ppm The degree of branching means the number of siloxane bonds contributed by T units and Q units relative to the total number of siloxane bonds. Here, a siloxane bond (Si-O-Si) is formed by two Si atoms and one O atom. Therefore, one Si atom contributes to x / 2 siloxane bonds (x=1 (M unit), x=2 (D unit), x=3 (T unit), x=4 (Q unit)). That is, an M unit contributes 1 / 2 siloxane bonds, a D unit contributes 2 / 2 siloxane bonds, a T unit contributes 3 / 2 siloxane bonds, and a Q unit contributes 4 / 2 siloxane bonds. Here, the total number of siloxane bonds in the silicone polymer is expressed by the following formula (A). Total number of siloxane bonds = 1 / 2 × (number of M units) + 2 / 2 × (number of D units) + 3 / 2 × (number of T units) + 4 / 2 × (number of Q units) Formula (A) The number of siloxane bonds contributed by T units and Q units in a silicone polymer is expressed by the following formula (B). Number of siloxane bonds contributed by T and Q units = 3 / 2 × (number of T units) + 4 / 2 × (number of Q units) Equation (B) From the above formulas (A) and (B), the degree of branching is expressed by formula (C). Branching degree (%) = Number of siloxane bonds contributed by T units and Q units / Total number of siloxane bonds × 100 ={(3 / 2 × (integral value in T units) + 4 / 2 × (integral value in Q units)) / (1 / 2 × (integral value in M ​​units) + 2 / 2 × (integral value in D units) + 3 / 2 × (integral value in T units) + 4 / 2 (integral value in Q units))} × 100

[0116] (2) Preparation and measurement of samples from ultraviolet laser marking ink compositions (Method of preparing measurement samples) The paint was diluted to a solids concentration of about 30%, and the resin emulsion and pigment were separated using a centrifuge (15,000 rpm, 30 minutes).The supernatant containing the resin emulsion was then placed in an aluminum cup and dried at 140°C for 3 hours. Then similarly 29 Si-NMR measurements and analysis were carried out.

[0117] (3) Preparation and measurement of samples from printed media for ultraviolet laser marking (Method of preparing measurement samples) The printed layer was ground using an industrial razor (Feather Safety Razor Co., Ltd., product number: 099769), and the collected printed layer was used as a sample. 29 Si-NMR measurements and analysis were carried out.

[0118] [Titanium oxide content] 1. When non-printable areas are included in the print media (Preparation of test specimens) The printable area and non-printable area (area where no coating layer is provided) of the print medium were each cut out to an appropriate size to prepare samples (test pieces), and the areas of the cut-out pieces were recorded. (Dissolution of test specimen) A mixed solvent of nitric acid and hydrofluoric acid (50:5 by volume) and the test piece were placed in a Teflon (registered trademark) container of an autoclave (MARS5, manufactured by CEM Japan), and the test piece was dissolved by autoclaving at 210°C for 120 minutes. The area of ​​the test piece may be changed as appropriate, and if the test piece remains undissolved, the ratio of nitric acid to hydrofluoric acid, the treatment temperature, the treatment time, etc. may be changed as appropriate. After dissolving the test piece, the solution was accurately adjusted to a fixed volume using ultrapure water. (Measurement of titanium oxide content in solution) (1) The ICP device and measurement conditions are as follows: ICP device: ICP-OEC device (Rigaku Corporation, CIROS1-20) Measurement conditions: Carrier gas: Argon gas Argon gas flow rate: 0.9L / min Plasma gas flow rate: 14 L / min Plasma output 1400W Pump RPM: 2 ·Measurement wavelength Ti:334.941nm (2) Preparation of a calibration curve A general-purpose mixed standard solution (manufactured by SPEX Corporation, XSTC-622B) was accurately measured to have the following concentration, and subjected to measurement under the above measurement conditions, and the intensity at 334.941 nm, which corresponds to the emission wavelength of titanium atoms, was measured. Concentrations for creating calibration curves: 0 ppm, 0.01 ppm, 0.05 ppm, 0.1 ppm, 0.5 ppm, 1.0 ppm, 3.0 ppm, 5.0 ppm (3) Measurement of titanium oxide content in the solution The solution containing the dissolved test pieces was diluted with ultrapure water so that the solution was within the range of the calibration curve, and then subjected to ICP measurement. (4) Titanium oxide content calculation method The titanium oxide content was calculated using the following formula: (molecular weight of titanium oxide / atomic weight of titanium) ≈ 1.669. Titanium oxide content (g / m 2 ) = ICP measured concentration (ppm) × dilution ratio × fixed volume (L) × 1.669 × 1000 ÷ area (m 2 ) The titanium oxide content in the coating layer was determined by subtracting the titanium oxide content in the non-printable area from the titanium oxide content in the printable area.

[0119] 2. When the print media does not include non-printable areas (Preparation of test specimens) Two sheets of printed media were cut to an appropriate size and the area of ​​the cut-outs was recorded. One of the cut test pieces was used to remove only the printed layer (coating layer) using a grinding machine (manufactured by Sagawa Corporation, grinding wheel dimensions: φ50.8 × 12.7 mm) to prepare a reference sample. If a resin layer was present on top of the printed layer, the resin layer was also removed in the same manner. The cross section was observed using an electron microscope as needed to avoid excessive scraping. (Subsequent processing) The same treatment as in 1 was carried out, and the difference in the titanium oxide content between the two sheets was taken as the titanium oxide content of the coating layer.

[0120] [Inorganic pigment content] The content of inorganic pigments was measured in the same manner as for titanium oxide content, except that the ICP measurement wavelength was changed to a wavelength specific to the metal atom contained in each inorganic pigment. Calcium element was measured at a wavelength of 422.673 nm, and magnesium element was measured at a wavelength of 285.213 nm.

[0121] [Viscosity of Ink Composition] The viscosity of the ink composition is a value measured at 20°C using a Brookfield viscometer in accordance with JIS Z 8803:2011. A Brookfield viscometer (BM II, manufactured by Toki Sangyo Co., Ltd.) can be used as the measuring device.

[0122] [Printing layer thickness] The thickness of the printed layer was measured from image data obtained by a scanning electron microscope. (1) Preparation of measurement samples The sample was embedded in a photocurable resin (D-800, manufactured by Toagosei Co., Ltd.), and the cross section of the print medium was extracted using an ultramicrotome. A diamond knife was used for cutting at room temperature. The cut cross section was coated with gold vapor deposition to a thickness of approximately 20 nm and subjected to measurement using a scanning electron microscope. (2) Measurement equipment and conditions Measuring device: S-3600 (Hitachi High-Tech Corporation) Measurement conditions: 2000x magnification The type of scanning electron microscope is not limited to the above, but an apparatus that displays a scale bar was used. When the printed layer was thin, an appropriate magnification was selected to acquire image data. (3)Measurement method After confirming that the printed layer being observed contained titanium element using an energy dispersive X-ray spectrometer attached to a scanning electron microscope, image data was obtained at a magnification of 2000x. The obtained image data was printed on a print medium, and the thickness of the target printed layer (the length from boundary to boundary with other layers) was measured with a ruler and compared with a scale bar to measure the actual thickness of the printed layer (coating layer or laminate layer). Image data was obtained from five randomly selected locations on one measurement sample, and the thickness of the thickest and thinnest printed layers was measured from the image data of one location, and the average of the 10 locations was taken as the thickness of the printed layer. The observation magnification may be changed depending on the thickness of the printed layer being observed. When a resin layer is further provided on the print layer, the thickness of the resin layer can be measured in the same manner.

[0123] [Print density] <Laser marking method> For the print media for ultraviolet laser marking obtained in the examples and comparative examples, a 10 mm square was printed on the sample surface using an ultraviolet laser irradiation machine (manufacturer: Keyence Corporation, model number: MD-U1020C). (Printing conditions) (1) Base conditions Wavelength: 355nm Output: 80% (2.5W at 100% output) Frequency: 40kHz Focal length: 300 mm (focusing is performed using the height correction provided with the device) Spot diameter: 40 μm (when focused) Fill interval: 300 μm Scan speed: 3000mm / sec Spot variable: 100 (2) Low power conditions Wavelength: 355nm Output: 40% (2.5W at 100% output) Frequency: 40kHz Focal length: 300 mm (focusing is performed using the height correction provided with the device) Spot diameter: 40 μm (when focused) Fill interval: 300 μm Scan speed: 3000mm / sec Spot variable: 100 (3) High-speed conditions Wavelength: 355nm Output: 80% (2.5W at 100% output) Frequency: 40kHz Focal length: 300 mm (focusing is performed using the height correction provided with the device) Spot diameter: 40 μm (when focused) Fill interval: 300 μm Scan speed: 6000mm / sec Spot variable: 100

[0124] <Print density evaluation> The blackness of the square immediately after printing with the ultraviolet laser was measured using a print densitometer (RD-19I SPI / U (equipped with a spectral filter based on ISO 5-3:2009) manufactured by Gretag Macbeth). The measurement was carried out in visual mode, and the reference surface was an area where a printing layer was provided but no printing was performed (non-printed area). The evaluation was carried out according to the following criteria. AA: Measurement value is 0.50 or more A: Measurement value is less than 0.50 and 0.40 or more B: Measurement value is less than 0.40 and 0.30 or more C: Measurement value is less than 0.30 and 0.20 or more D: Measurement value is less than 0.20

[0125] [Table 1]

[0126] According to the results in Table 1, by printing with an ultraviolet laser on a printing medium on which a printing layer was formed using the ink composition of the example, a printed material having a printed image with high image density (print density) was obtained, and a high print density was obtained even with a low-power ultraviolet laser. When using the printing medium of Example 10, which contains titanium oxide with a small crystallite size of 10 nm, a slight decrease in print density was observed. Furthermore, in Comparative Examples 1 and 2, which do not contain a silicone polymer compound and use polyurethane resin or polyacrylic resin as the binder resin, sufficient print density was not obtained. Furthermore, in Comparative Example 3, which does not contain titanium oxide, printing with an ultraviolet laser was not possible. [Industrial Applicability]

[0127] The printed layer formed by the ink composition of the present invention, and the printing medium having the printed layer, can provide printed matter with excellent visibility due to the discoloration of titanium oxide by irradiation with an ultraviolet laser, and further, have excellent print density even at low output. The printing medium of the present invention is suitable for use in processed products such as packaging, labels, and adhesive tapes on which variable information such as dates and barcodes is printed. Furthermore, the method for producing printed matter of the present invention is suitable for use in printing variable information on packaging, labels, adhesive tapes, etc.

Claims

1. Contains at least a binder resin and a white pigment, The white pigment contains titanium oxide, The binder resin contains a silicone-based polymer compound. Ink composition for ultraviolet laser marking.

2. 2. The ink composition for ultraviolet laser marking according to claim 1, wherein the content of the silicone polymer compound in the binder resin is 30% by mass or more.

3. 2. The ink composition for ultraviolet laser marking according to claim 1, wherein the degree of branching in the main chain of the silicone polymer compound is from 0.2% to 3.0%.

4. 2. The ink composition for ultraviolet laser marking according to claim 1, wherein a mass ratio of the binder resin to the white pigment (binder resin:white pigment) is 5:95 or more and 95:5 or less.

5. 2. The ink composition for ultraviolet laser marking according to claim 1, wherein the content of titanium oxide in the white pigment is 3% by mass or more.

6. 2. The ink composition for ultraviolet laser marking according to claim 1, wherein the titanium oxide has a crystallite size of 30 nm or more and 55 nm or less.

7. The ink composition for ultraviolet laser marking according to claim 1, which is a water-based ink composition.

8. 2. The ink composition for ultraviolet laser marking according to claim 1, which is an ink composition for gravure printing or an ink composition for flexographic printing.

9. 2. The ink composition for ultraviolet laser marking according to claim 1, which is used to form a printed layer on a paper substrate or a film substrate that changes color when irradiated with an ultraviolet laser.

10. A printable layer for ultraviolet laser marking formed from the ink composition for ultraviolet laser marking according to any one of claims 1 to 9.

11. The content of titanium oxide in the printing layer is 0.1 g / m ２ The printing layer for ultraviolet laser marking according to claim 10 .

12. The content of titanium oxide in the printing layer is 10 g / m ２ The printing layer for ultraviolet laser marking according to claim 10, wherein:

13. A print medium for ultraviolet laser marking, comprising a substrate and a print layer for ultraviolet laser marking according to claim 10 on the substrate.

14. 14. The ultraviolet laser markable print medium of claim 13, wherein the substrate is a paper substrate or a film substrate.

15. 14. The ultraviolet laser markable print medium of claim 13, which is a package.

16. A printed matter obtained from the ultraviolet laser markable printing medium according to claim 13, A printed matter, wherein the printed layer has, at least in part, a printed area containing titanium oxide that has been discolored by ultraviolet laser irradiation.

17. 14. A method for printing an ultraviolet laser markable printing medium according to claim 13 by irradiating the ultraviolet laser with an ultraviolet laser to discolor the irradiated area. Methods for producing printed materials.

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