JP7302708B1 - Ultraviolet laser printing paper, printed matter and its manufacturing method, processed product, and ink composition - Google Patents

Abstract

[Object] To provide an ultraviolet laser printing paper which can obtain printed spots with excellent printing clarity for each point when irradiated with an ultraviolet laser, a printed matter obtained by irradiating the ultraviolet laser printing paper with an ultraviolet laser to change the color of the irradiated area, and To provide a method for its production, as well as an ink composition for use in producing said UV laser printing paper. Further, to provide a processed product using the ultraviolet laser printing paper or printed matter. A print layer containing titanium oxide is provided on a paper substrate, the content of the titanium oxide in the print layer is 0.1 g/m2 or more, and the amount of titanium oxide in the print layer is 0.1 g/m2 or more. An ultraviolet laser printing paper having a crystallite size of 30 nm or more. [Selection figure] None

Description

TECHNICAL FIELD The present invention relates to an ultraviolet laser printing paper, a printed matter and its manufacturing method, a processed product, and an ink composition.

2. Description of the Related Art Conventionally, labeling or inkjet printing has been performed to display dates such as manufacturing dates and shipping dates, and variable information such as bar codes, on packages such as containers in which items are stored.
In addition, a method of printing by laser light irradiation has also been proposed. For example, Patent Document 1 discloses that by laser light irradiation, clear printing can be performed at high speed, and the printed part has excellent resistance to various lasers. Laminate for laser printing manufactured by coating white ink, black ink and overprint varnish (OP varnish) on the aluminum-deposited surface of aluminum-deposited paper for the purpose of providing a laminate for printing and its printed body. is disclosed.
Furthermore, in Patent Document 2, for the purpose of providing a technique that generates relatively little heat and is preferably applicable to laser marking of packaging materials, the average particle size contains first titanium oxide particles of 150 nm or less, and ultraviolet rays An ink composition is described that is used to form a laser marking layer that changes color upon irradiation with a laser.

JP-A-9-123607 JP 2020-75943 A

As means for printing on the surface of packages, labels, adhesive tapes, etc., there is a method in which ink is applied directly to the surface of packages using a thermal printer or an ink jet printer, which is currently in widespread use. However, consumables such as ink ribbons for thermal printers and ink for inkjet printers are expensive, and printing a large amount of variable information requires high running costs. In addition, failure to replace these consumables may result in printing failure. In addition, offset printing using UV curable ink is also used to directly print variation information on the packaging, but the printing is blurry and characters are missing due to stains on the surface of the packaging and uneven thickness of the packaging. may occur.
In the method described in Patent Document 1, although it is possible to increase the speed, the upper layer that easily absorbs the laser light is removed by irradiating the CO ₂ laser light to expose the lower layer, resulting in a difference in color between the upper layer and the lower layer. Since this is a technology that forms characters that can be seen from the outside, the upper layer is limited to materials that easily absorb laser light, while the lower layer is limited to materials that do not absorb laser light easily and have a color contrast with the upper layer. be done. That is, a carbon black-based material (black) that easily absorbs laser light is the upper layer, and a titanium oxide-based material (white) is the lower layer. Poor visibility. In addition, when removing the upper layer, there is a problem that the ink in the upper layer is dusted and causes contamination of the working environment.
Furthermore, when the coating layer prepared using the ink composition described in Patent Document 2 is printed with an ultraviolet laser, the print clarity of each printed spot may be poor.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ultraviolet laser printing paper which, when irradiated with an ultraviolet laser, provides printed spots with excellent printing clarity for each point. Further, the present invention provides a printed material obtained by irradiating the ultraviolet laser printing paper with an ultraviolet laser to change the color of the irradiated area, a method for producing the same, and an ink composition used for producing the ultraviolet laser printing paper. With the goal. A further object of the present invention is to provide a processed product using the ultraviolet laser printing paper or printed matter.

The present inventors found that in an ultraviolet laser printing paper having a printing layer containing titanium oxide on a paper substrate, the content of titanium oxide in the printing layer is set to a specific amount or more, and the crystallite size of titanium oxide is set to a specific amount. The present inventors have found that the above problem can be solved by setting it to a value or more, and have completed the present invention.
The present invention relates to the following <1> to <14>.
<1> A printed layer containing titanium oxide is provided on a paper substrate, the content of the titanium oxide in the printed layer is 0.1 g/m ² or more, and the amount of titanium oxide in the printed layer is An ultraviolet laser printing paper having a crystallite size of 30 nm or more.
<2> The ultraviolet laser printing paper according to <1>, wherein the titanium oxide has a crystallite size of 53 nm or less.
<3> The ultraviolet laser printing paper according to <1> or <2>, wherein the titanium oxide in the print layer is rutile-type titanium oxide, and the titanium oxide has a diffraction angle of 27.60° or less.
<4> The ultraviolet laser printing paper according to any one of <1> to <3>, wherein the length-weighted average fiber length of the pulp constituting the paper substrate is 2.0 mm or less.
<5> The ultraviolet laser printing paper according to any one of <1> to <4>, wherein the content of titanium oxide in the print layer is 10 g/m ² or less.
<6> Any one of <1> to <5>, wherein the number ratio of fine fibers having a fiber length of 0.2 mm or less in the pulp fibers constituting the paper base material is 4% or more and 40% or less Ultraviolet laser printing paper as described.
<7> The ultraviolet laser printing paper according to any one of <1> to <6>, wherein the pulp fibers constituting the paper substrate have a water retention rate of 100% or more.
<8> A printed material obtained from the ultraviolet laser printing paper according to any one of <1> to <7>, wherein the printed layer contains, at least in part, discolored titanium oxide. A printed material having a region, wherein the ratio of the Raman intensity derived from titanium oxide in the printed region to the Raman intensity derived from titanium oxide in the non-printed region is 0.70 or less.
<9> A processed product using the ultraviolet laser printing paper according to any one of <1> to <7> or the printed matter according to claim 8.
<10> A method for producing a printed matter, comprising a step of irradiating the ultraviolet laser printing paper according to any one of <1> to <7> with an ultraviolet laser to change the color of the irradiated area for printing.
<11> The printing step is a step of irradiating an ultraviolet laser so that the ratio of the Raman intensity derived from titanium oxide in the printed region to the Raman intensity derived from titanium oxide in the non-printed region is 0.70 or less. The method for producing a printed matter according to <10>.
<12> An ink composition containing titanium oxide having a crystallite size of 30 nm or more and used for forming a print layer that changes color upon irradiation with an ultraviolet laser.
<13> The ink composition according to <12>, wherein the titanium oxide has a crystallite size of 53 nm or less.
<14> The ink composition according to <12> or <13>, wherein the titanium oxide is rutile-type titanium oxide and has a diffraction angle of 27.60° or less.

ADVANTAGE OF THE INVENTION According to this invention, the ultraviolet-ray-laser printing paper which can obtain the printing spot which is excellent in the printing vividness for every point is provided when it is irradiated with an ultraviolet-ray laser. Further, according to the present invention, there are provided a printed matter obtained by irradiating the ultraviolet laser printing paper with an ultraviolet laser to change the color of the irradiated area, a method for producing the same, and an ink composition used for producing the ultraviolet laser printing paper. be done. Further, according to the present invention, there is provided a processed product using the ultraviolet laser printing paper or printed matter.

FIG. 1 is a photographic diagram showing an enlarged view of a printed matter. FIG. 2 is a conceptual perspective view of an example of a liquid container having a printed area.

[Ultraviolet laser printing paper]
The ultraviolet laser printing paper (hereinafter also simply referred to as "printing paper") of the present invention has a printing layer containing titanium oxide on a paper substrate, and the content of the titanium oxide in the printing layer is 0. .1 g/m ² or more, and the crystallite size of titanium oxide in the printed layer is 30 nm or more.
ADVANTAGE OF THE INVENTION According to this invention, the ultraviolet-ray-laser printing paper which can obtain the printing spot which is excellent in the printing vividness for every point is provided when it is irradiated with an ultraviolet laser.
Although the detailed reason why the above effect is obtained is unknown, part of it is considered as follows.
By having a print layer containing titanium oxide on a paper substrate, the titanium oxide in the print layer is discolored by laser irradiation with an ultraviolet laser, making it possible to print. The discoloration of the titanium oxide is caused by the ion valence of the titanium oxide contained in the printed layer changing from tetravalent to trivalent and oxygen defects occurring, resulting in a change from white to black, thereby becoming visible. It is thought that It is considered that the ionic valence of titanium oxide changes when it is irradiated with light energy corresponding to the bandgap of titanium oxide. Although the bandgap of titanium oxide varies depending on the crystal system, it is generally about 3.0 to 3.2 eV, and the corresponding light wavelength is 420 nm or less. Therefore, even if a laser beam with a wavelength exceeding 420 nm (eg, 532 nm, 1064 nm, 10600 nm) is used, it is difficult to perform printing caused by the ion valence change of titanium oxide as in the present invention. At this time, by setting the content of titanium oxide in the printing layer to 0.1 g/m ² or more, a printed matter having excellent visibility and excellent print sharpness for each print can be obtained.
In addition, when the crystallite size of titanium oxide is 30 nm or more, there are few crystal defects, the occurrence of recombination between excited electrons and holes is suppressed, and titanium oxide is easily reduced and easily discolored. It is considered that a printed spot with excellent print clarity was obtained.
In the present embodiment, the printable region means a region (portion) in which printing by ultraviolet laser irradiation is possible because the titanium oxide in the portion irradiated with the ultraviolet laser changes color from white to black. The printable area means a portion of the printable area where the titanium oxide is actually discolored by irradiation with the ultraviolet laser and becomes visible, that is, the area irradiated with the ultraviolet laser. Further, the non-printing area means an area (portion) in the printable area which is not irradiated with the ultraviolet laser.
The present invention will be described in more detail below.

Ultraviolet laser printing paper has printable areas containing titanium oxide.
The printing paper has a printing layer containing titanium oxide on a paper substrate. The printed layer may be formed on at least one side of the paper base material, and may be formed on both sides, but it is preferable that the printed paper has the printed layer only on one side. Moreover, although the printing paper may have the printing layer over the entire surface, it may have the printing layer only in a partial region (portion) where printing is desired.
In this embodiment, the surface of the paper substrate opposite to the surface on which the printed layer is provided may further have a layer, for example, an adhesive layer, a vapor deposition layer, a resin layer, or the like. may These layers may be one layer, or a plurality of layers may be provided.

<Print layer>
The ultraviolet laser printing paper of this embodiment has a printing layer containing titanium oxide on a paper substrate. The printed layer may be provided by coating, or may be provided by lamination, and is not particularly limited. That is, the printed layer is preferably a coating layer containing titanium oxide or a laminate layer containing titanium oxide. In the present invention, the printed layer is more preferably provided by coating from the viewpoint of easy provision of the printed layer only at desired locations and from the viewpoint of ease of production. The above-mentioned "provided by coating" means that the printed layer is formed with a coating liquid (ink composition), and includes, for example, the case of forming by gravure printing, inkjet printing, and the like.
The printed layer contains titanium oxide, and the content of titanium oxide in the printed layer is 0.1 g/m ² or more.
The content of titanium oxide in the printed layer is 0.1 g/m ² or more, preferably 0.2 g/m ² or more, more preferably 0.3 g/m ² or more, from the viewpoint of obtaining sufficient print density. More preferably, it is 0.4 g/m ² or more, and from the viewpoint of obtaining printed spots with excellent print clarity for each point, the print density reaches a ceiling, and the cost increase due to containing more than the necessary amount of titanium oxide is suppressed. and from the viewpoint of suppressing the amount of smoke generated during ultraviolet laser irradiation (during printing), it is preferably 10 g/m ² or less, more preferably 7.5 g/m ² or less, even more preferably 5 g/m 2 or less, and more preferably 5 g/m ² or less. More preferably, it is 3.5 g/m ² or less.
If the content of titanium oxide in the printed layer is too high, there is a tendency to generate smoke, which is thought to be caused by scattering of titanium oxide during irradiation with an ultraviolet laser. In addition, as a result of the generation of smoke, a phenomenon occurs in which discolored titanium oxide is detached from the printed layer, which tends to deteriorate the print sharpness for each point.
It is sufficient that at least the printable region of the ultraviolet laser printing paper contains titanium oxide in the above content, and there may be a portion where the printing layer is not provided in the region where printing is not performed. , there may be regions provided with a printed layer having a titanium oxide content of less than 0.1 g/m ² . From the viewpoint of manufacturing simplicity, it is also preferable that a printing layer having a titanium oxide content of 0.1 g/m ² or more is provided over the entire area of the printing paper.

In this embodiment, the printing paper has an undercoat layer containing no titanium oxide or an undercoat layer containing less than 0.1 g/m ² of titanium oxide as a lower layer of the print layer containing titanium oxide. may In such a case, the content of titanium oxide is 0.1 g/m ² or more in all layers of the printing layer including the lower layer.
Moreover, when a resin layer, which will be described later, is provided on the printed layer, the resin layer does not correspond to the printed layer.

The mass (solid content, basis weight) per 1 m ² of the printed layer is preferably 1.0 g/m2 from the viewpoint of printing density, the viewpoint of printing clarity for each point, and the viewpoint of suppressing smoke generation during ultraviolet laser irradiation. m ² or more, more preferably 2.5 g/m ² or more, still more preferably 4.5 g/m ² or more, and preferably 50 g/m ² or less, more preferably 40 g/m ² or less, still more preferably 30 g/m ² or less.

The content of titanium oxide in the printing layer (solid content) is preferably 0.3% by mass or more, more preferably 1.0% by mass or more, and further preferably 0.3% by mass or more, more preferably 1.0% by mass or more, and It is preferably 2.0% by mass or more, and still more preferably 2.5% by mass or more. From the viewpoint of ease of formation and the viewpoint of suppressing smoke generation during ultraviolet laser irradiation, the content is preferably 95% by mass or less, more preferably 85% by mass or less, even more preferably 75% by mass or less, and even more preferably 60% by mass or less. be.

The thickness of the printed layer is preferably 0.3 μm or more, more preferably 0.5 μm or more, still more preferably 1.0 μm or more, from the viewpoint of the print clarity of each point and the ease of forming the printed layer. It is more preferably 2.0 μm or more, and from the viewpoint of the print density peaking out and the ease of forming a printed layer, it is preferably 40.0 μm or less, more preferably 30.0 μm or less, and still more preferably 25.0 μm. 20.0 μm or less, and more preferably 20.0 μm or less.
The thickness of the printing layer is measured from an electron microscope (SEM) observation image of a cross section of the printing paper.

The substrate of the printing paper is a paper substrate as described later, and the paper substrate itself may contain titanium oxide. When the paper substrate contains titanium oxide, the image tends to become clearer. In particular, when the thickness of the printed layer is thin, the paper substrate itself contains titanium oxide, so that a clear image tends to be obtained. In this case, the thickness of the printed layer is 2.0 μm or less. When the paper substrate contains titanium oxide, the effect tends to be remarkable.
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, still more preferably 15% by mass or more, and even more preferably It is 20% by mass or more.

The print layer preferably contains a thermoplastic resin in addition to titanium oxide. Furthermore, inorganic pigments other than titanium oxide may be contained. Each component will be described in detail below.
(titanium oxide)
Titanium oxide contained in the printed layer is represented by the composition formula TiO ₂ and is also called titanium dioxide or titania.
In this embodiment, the crystallite size of titanium oxide in the printed layer is 30 nm or more. When the crystallite size of titanium oxide in the printed layer is less than 30 nm, there are many crystal defects, and recombination of excited electrons and holes excited by ultraviolet laser irradiation is likely to occur, resulting in reduction of titanium oxide. It is difficult to print, and the sharpness of each print is poor. The crystallite size of titanium oxide is preferably 35 nm or more, more preferably 40 nm or more.
Although the upper limit of the crystallite size of titanium oxide is not particularly limited, it is preferably 60 nm or less, more preferably 56 nm or less, and still more preferably 53 nm or less from the viewpoint of dispersion stability in the coating liquid or in the printing layer. be. When 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 printing layer is good, and printing uniformity is improved, which is preferable.
The crystallite size of titanium oxide is measured by the method described in Examples.
The crystallite size is obtained by the Scherrer formula, and the Bragg angle is the measured value of the maximum intensity derived from the 101 plane in the case of anatase-type titanium oxide and the 110 plane in the case of rutile-type titanium oxide. use.

Titanium oxide may have any crystal structure, and is preferably at least one selected from rutile-type titanium oxide, anatase-type titanium oxide, and brookite-type titanium oxide. It is more preferably at least one selected from type titanium oxide and anatase type titanium oxide, and more preferably rutile type titanium oxide.
The crystal form of titanium oxide can be determined by a known method, specifically by Raman spectrum, XRD pattern analysis, and the like. For example, when identifying from the Raman spectrum, in general, the rutile type has peaks at 447±10 cm ⁻¹ and 609±10 cm ⁻¹ , and the anatase type has peaks at 395±10 cm ⁻¹ and 516±10 cm. A peak is confirmed at ⁻¹ , 637±10 cm ⁻¹ .
Titanium oxide may be used individually by 1 type, and may use 2 or more types together.

When the titanium oxide is rutile-type titanium oxide, the diffraction angle of the titanium oxide is preferably 27.60° or less from the viewpoint of print clarity for each point. The Bragg angle of rutile-type titanium oxide is originally around 27.40° (27.44°, for example, although it varies depending on the literature), but if the crystallinity is low, the diffraction angle tends to increase. When the diffraction angle of titanium oxide exceeds 27.60°, the crystallinity is low and discoloration is suppressed, so that the print sharpness of each point tends to be poor.
When titanium oxide is rutile-type titanium oxide, the diffraction angle of titanium oxide is preferably 27.60° or less, more preferably 27.55° or less, still more preferably 27.50° or less.
In the case of the rutile type, the diffraction angle of titanium oxide is the actual measurement value of the maximum intensity derived from the 110 plane, as described above.

The shape of titanium oxide is not particularly limited, and may be any shape such as irregular, spherical, rod-like, and needle-like.
When the titanium oxide is amorphous or spherical, the average particle size of the titanium oxide is not particularly limited, but is preferably 0.01 μm from the viewpoint of excellent print sharpness per point and from the viewpoint of obtaining printing paper with excellent surface smoothness. more preferably 0.05 μm or more, still more preferably 0.1 μm or more, still more preferably more than 0.15 μm, particularly preferably 0.16 μm or more, and preferably 20.0 μm or less, more preferably 5 0 μm or less, more preferably 1.5 μm or less, and even more preferably 0.50 μm or less.

When the titanium oxide is acicular, the major diameter of the titanium oxide is not particularly limited, but is preferably 0.1 μm or more from the viewpoint of excellent print clarity per point and from the viewpoint of obtaining printing paper with excellent surface smoothness. , more preferably 0.5 μm or more, still more preferably 1.5 μm or more, and preferably 50.0 μm or less, more preferably 30.0 μm or less, still more preferably 15.0 μm or less. In addition, the minor axis is preferably 0.01 μm or more, more preferably 0.03 μm or more, still more preferably 0.05 μm or more, and preferably 3.0 μm or less, more preferably 1.5 μm or less, and still more preferably is 1.0 μm or less. Further, when the titanium oxide is acicular, the aspect ratio (major axis/minor axis) is preferably 5 or more, more preferably 10 or more, still more preferably 15 or more, and preferably 300 or less, more preferably It is 100 or less, more preferably 30 or less.
The average particle size, major axis and minor axis of titanium oxide are measured by the method described in Examples. The values of the particle size, major axis and minor axis of the titanium oxide used as the raw material may be used, or the catalog values of the particle size, major axis and minor axis of the titanium oxide used as the raw material may be used. .

(Thermoplastic resin)
A thermoplastic resin used in the printing layer functions as a binder.
The thermoplastic resin for the printed layer is not particularly limited, but when the printed layer is provided by coating, it may be applied as a water-based coating liquid, or as an organic solvent-based coating liquid (oil-based coating liquid). may In addition, when providing a printing layer by coating, this printing layer is also called a coating layer. A composition used for forming a coating layer is also called a coating liquid or an ink composition.
When applied as an aqueous coating liquid, the thermoplastic resin is preferably a water-dilutable thermoplastic resin. Examples of water-dilutable resins include water-soluble, emulsion-type, and dispersion-type resins.
The water-dilutable thermoplastic resin may be either a natural resin or a synthetic resin. resins, styrene-butadiene-based resins, vinyl chloride-based resins, and polyolefin-based resins.
More specifically, acrylic resins include acrylic resins obtained by copolymerizing (meth)acrylic acid and its alkyl ester or styrene as monomer components, styrene-maleic acid resins, and styrene-acrylic acid-maleic acid. Examples include resins, olefin-(meth)acrylic acid copolymer resins (eg, ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers), and the like.
Among these, starch derivatives, casein, shellac, polyvinyl alcohol and its derivatives, acrylic resins, maleic acid resins, and styrene-butadiene resins are used from the viewpoint of the stability of the coating liquid and the solvent resistance of the printed layer. At least one selected is preferable, and at least one selected from starch derivatives, polyvinyl alcohol, polyvinyl alcohol derivatives, acrylic resins, maleic acid-based resins, and styrene-butadiene-based resins is more preferable, starch derivatives, polyvinyl alcohol, polyvinyl At least one selected from alcohol derivatives, acrylic resins, and styrene-butadiene-based resins is more preferred, and at least one selected from polyvinyl alcohols, polyvinyl alcohol derivatives, acrylic resins, and styrene-butadiene-based resins is even more preferred. .
These resins may be used individually by 1 type, and may use 2 or more types together.
When using an organic solvent-based coating liquid (oil-based coating liquid), cellulose resin (e.g., nitrocellulose, cellulose acetate, cellulose acetate propionate), polyurethane resin, acrylic resin, vinyl chloride copolymer It is preferable to use a known thermoplastic resin such as a base resin.

The content of the thermoplastic resin is not particularly limited, and may be appropriately selected according to the type of thermoplastic resin, the content of titanium oxide in the coating liquid, the content of inorganic pigments described later, etc. For example, the coating liquid of the solid content, preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and preferably 99% by mass or less, more preferably 98% by mass or less.

When the printed layer is provided by coating, the coating layer is preferably provided by applying and drying a coating liquid.
The coating liquid is preferably an aqueous coating liquid, and the aqueous medium used includes water or a mixture of water and a water-miscible solvent.
Water-miscible solvents include lower alcohols, polyhydric alcohols, and their alkyl ethers or esters. Specifically, 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, dipropylene glycol monomethyl ether and the like.
In the case of an organic solvent-based coating liquid, aromatic organic solvents such as toluene and xylene, ethyl acetate, n-propyl acetate, isobutyl acetate, ester-based organic solvents, and ketone-based organic solvents such as methyl ethyl ketone and methyl isobutyl ketone. , methanol, ethanol, isopropanol, n-butanol and other alcohol-based organic solvents, and methylcyclohexane and other hydrocarbon-based solvents.

The solid content concentration of the coating liquid is not particularly limited, but from the viewpoint of obtaining the desired thickness of the coating layer, the viewpoint of making the coating liquid a viscosity that facilitates coating, and the viewpoint of easiness of drying, it is preferably 10 mass. % or more, more preferably 20% by mass or more, still 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, still more preferably It is 65% by mass or less.

The viscosity of the coating liquid is preferably 10 mPa s (20° C.) or more as measured by a Brookfield viscometer from the viewpoints of coating suitability, obtaining a desired coating layer thickness, and drying easiness. More preferably 15 mPa s (20°C) or more, still more preferably 20 mPa s (20°C) or more, and preferably 5000 mPa s (20°C) or less, more preferably 4000 mPa s (20°C) or less , more preferably 3000 mPa·s (20°C) or less, still more preferably 2000 mPa·s (20°C) or less.

When the printed layer is provided by lamination, it is preferable to laminate a film containing titanium oxide on the substrate. In addition, when providing a printing layer by lamination, this printing layer is also called a lamination layer.
The thermoplastic resin that constitutes the laminate layer is not particularly limited as long as it can be processed into a film by encapsulating titanium oxide, and may be appropriately selected from known thermoplastic resins. Specifically, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polybutene, polybutadiene, ethylene-vinyl acetate copolymer, polyethylene, polypropylene, ethylene-propylene copolymer Polyolefin resins such as coalescence and polymethylpentene; polycarbonate; polyurethane; polyamide; polyacrylonitrile;
Among them, the resin constituting the laminate layer can be used for general purposes, has a high ultraviolet transmittance, and can discolor titanium oxide to the inside of the film. - preferably contains polyolefins such as propylene copolymers, polyesters such as polyethylene terephthalate, polybutylene terephthalate, polylactic acid, polybutylene succinate, polyethylene, polypropylene, ethylene-propylene copolymers, polyethylene terephthalate, polylactic acid, and polybutylene succinate, more preferably at least one selected from the group consisting of polyethylene, polypropylene, ethylene-propylene copolymer, polyethylene terephthalate, polylactic acid, and polybutylene succinate More preferably, at least one is selected. The resin constituting the laminate layer is more preferably polyolefin, and more preferably at least one selected from the group consisting of polyethylene and polypropylene. Polyethylene (PE) is roughly classified into linear low density polyethylene (LLDPE), low density polyethylene (LDPE), medium density polyethylene (MDPE), and high density polyethylene (HDPE). Among these, low-density polyethylene (LDPE) is preferred because of its excellent extrusion lamination properties.
As the resin constituting the laminate layer, it is preferable to use polyester, which is a biodegradable resin, in terms of reducing the environmental load. Examples thereof include polylactic acid and polybutylene succinate.
These resins may be used individually by 1 type, and may use 2 or more types together.

The content of the thermoplastic resin in the laminate layer is preferably 20% by mass or more, more preferably 30% by mass or more, still more preferably 50% by mass or more, and even more preferably, from the viewpoint of suppressing smoke generation during ultraviolet laser irradiation. is 70% by mass or more, particularly preferably 80% by mass or more, and is preferably 99% by mass or less, more preferably 98% by mass or less, and still more preferably 95% by mass or less.

(Inorganic pigment other than titanium oxide)
The printed layer may contain other components in addition to the titanium oxide and thermoplastic resin described above. Other components include inorganic pigments other than titanium oxide (hereinafter also simply referred to as "inorganic pigments"). By containing an inorganic pigment other than titanium oxide, scattering of titanium oxide is suppressed, smoking is suppressed during irradiation with an ultraviolet laser, and as a result, the sharpness of printing for each point is improved, which is preferable.
Examples of inorganic pigments include calcium carbonate, talc, silica, kaolin, magnesium oxide, mica, aluminum hydroxide, barium sulfate, among which calcium carbonate, talc, silica, kaolin, magnesium oxide, zinc oxide, and mica. It is preferably at least one selected from the group consisting of, more preferably at least one selected from the group consisting of calcium carbonate and talc.
An inorganic pigment may be used individually by 1 type, and may use 2 or more types together.

The shape of the inorganic pigment is not particularly limited, and may be any shape such as amorphous, spherical, plate-like, rod-like, and needle-like.
When the inorganic pigment has an irregular shape, a spherical shape, or a plate shape, the average particle size of the inorganic pigment is not particularly limited. It is 1 µm or more, more preferably 0.15 µm or more, still more preferably 0.20 µm or more, and preferably 10 µm or less, more preferably 5 µm or less, and still more preferably 3 µm or less.
When the inorganic pigment is acicular, the major diameter of the inorganic pigment is not particularly limited, but is preferably 0.5 μm or more, more preferably 0.5 μm or more, more preferably from the viewpoint of obtaining printing paper with excellent surface smoothness and suppressing smoke generation. is 1.0 μm or more, more preferably 2.0 μm or more, and is preferably 100 μm or less, more preferably 10 μm or less, still more preferably 5 μm or less. In addition, the minor axis is preferably 0.1 μm or more, more preferably 0.5 μm or more, still more preferably 1.0 μm or more, and preferably 50 μm or less, more preferably 10 μm or less, still more preferably 1.0 μm. It is below. Further, when the inorganic particles are acicular, the aspect ratio (major axis/minor axis) is preferably 1.5 or more, more preferably 2.0 or more, still more preferably 3.0 or more, and preferably It is 100 or less, more preferably 50 or less, still more preferably 30 or less.

When the printed layer contains an inorganic pigment other than titanium oxide, the content of the inorganic pigment in the printed layer is preferable from the viewpoint of improving the clarity of each print and from the viewpoint of suppressing smoke generation during ultraviolet laser irradiation. is 2% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, even more preferably 30% by mass or more, particularly preferably 50% by mass or more, and preferably 95% by mass or less, It is more preferably 90% by mass or less, still more preferably 85% by mass or less, and even more preferably 80% by mass or less.

When the printed layer 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) improves the clarity of each print. and from the viewpoint of suppressing smoke generation during ultraviolet laser irradiation, it is preferably 0.01 or more, more preferably 0.03 or more, still more preferably 0.10 or more, and preferably 4.0 or less. It is preferably 2.0 or less, more preferably 1.0 or less.

In addition to the components described above, the printing layer contains a film forming agent, a pigment dispersant, a pigment dispersing resin, an antiblocking agent, a wetting agent, a viscosity modifier, a pH adjuster, an antifoaming agent, general surfactants, and the like. may be

(Coating liquid)
When the print layer is provided by coating and the coating liquid (ink composition) is an aqueous coating liquid, it is preferable to mix the above various materials with an aqueous medium. Prior to mixing with the aqueous medium, titanium oxide, thermoplastic resin, water, and if necessary, inorganic pigments other than titanium oxide, water-miscible solvents, pigment dispersants, pigment-dispersing resins, etc. are mixed and kneaded. Then, water, optionally a water-miscible solvent, and the remainder of the prescribed materials may be added and mixed.
Further, 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. may be added to the mixed solution 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 stirrer such as a homomixer or a lab mixer, or a disperser such as a Colles disperser, a three-roll mill, or a bead mill.

The method of applying the coating liquid is not particularly limited, and flexographic printing, inkjet printing, gravure printing, screen printing, pad printing, spray coating, Meyer bar, gravure coater, air knife coater, blade coater, rod coater, die coater, bar The base material may be coated with a coater or the like.

[Laminate layer]
When the printed layer is a laminate layer, the film to be laminated is prepared by melt-kneading at least titanium oxide, a thermoplastic resin, and, if necessary, materials such as inorganic pigments, to prepare a raw material composition, which is formed into a film. After that, it is obtained by stretching as necessary.
In preparing the raw material composition, a masterbatch containing titanium oxide and inorganic pigments at a high concentration may be prepared and then mixed with the resin.
Moreover, the materials that have been uniformly mixed in advance may be charged into the molding machine, or the materials may be mixed in a hopper or a kneader integrated with the molding machine.
A method for forming a film may be appropriately selected from conventionally known methods, such as a melt extrusion method, a melt casting method, a calendering method, and the like.

The substrate and film may be attached via an adhesive layer, or preferably laminated.
The adhesive layer is not particularly limited, and may be appropriately selected from known adhesive layers and used. Specifically, the adhesive layer disclosed in JP-A-2012-57112 is exemplified.
Specific examples of the lamination process include laminating a paper substrate and a laminate layer by a heat lamination method, a dry lamination method, a wet lamination method, an extrusion lamination method, or the like.
Among these methods, the extrusion lamination method is preferable from the viewpoint of the manufacturing process because it does not require a step of adhering the laminate layer and the paper substrate.

<Paper substrate>
In this embodiment, a paper substrate is used as the substrate.
Examples of the raw pulp that constitutes the paper substrate include wood pulp, non-wood pulp, and deinked pulp. The wood pulp is not particularly limited. SP), dissolving pulp (DP), soda pulp (AP), chemical pulp such as oxygen bleached kraft pulp (OKP), semi-chemical pulp (SCP), semi-chemical pulp such as chemigroundwood pulp (CGP), groundwood pulp ( GP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP) and other mechanical pulps. Examples of non-wood pulp include, but are not limited to, cotton pulp such as cotton linter and cotton lint, and non-wood pulp such as hemp, straw, bamboo and bagasse. The deinked pulp is not particularly limited, but examples thereof include deinked pulp made from waste paper. The raw material pulp may be used singly or in combination of two or more. Organic synthetic fibers such as polyamide fibers and polyester fibers, regenerated fibers such as polynosic fibers, and inorganic fibers such as glass fibers, ceramic fibers, and carbon fibers may be mixed with the raw material pulp.
The raw material pulp is preferably wood pulp or deinked pulp from the viewpoint of availability. Among wood pulps, raw material pulp is preferably chemical pulp, more preferably kraft pulp, and still more preferably hardwood kraft pulp such as eucalyptus and acacia, and pine and cedar pulp, from the viewpoint of texture uniformity. One or more selected from softwood kraft pulp such as, more preferably one or more selected from hardwood bleached kraft pulp (LBKP) and softwood bleached kraft pulp (NBKP), particularly preferably LBKP .

The length-weighted average fiber length of the pulp constituting the paper substrate is preferably 0.6 mm or more, more preferably 0.65 mm or more, and still more preferably 0.65 mm or more, from the viewpoint of suppressing coating unevenness and improving print clarity. 0.7 mm or more, preferably 3.5 mm or less, more preferably 2.5 mm or less, even more preferably 2.0 mm or less, even more preferably 1.5 mm or less, and particularly preferably 1.0 mm or less is.
If the length-weighted average fiber length of the pulp that constitutes the paper base material is equal to or less than the above upper limit, the pulps will be tightly entangled with each other, reducing the voids in the paper base material and reducing the amount of coating when a coating layer is provided. It is preferable because it suppresses process unevenness, provides excellent print sharpness for each point, and gives printed matter excellent in print uniformity.
In addition, when the length-weighted average fiber length of the pulp constituting the paper substrate is equal to or greater than the above lower limit, the strength of the paper substrate is improved, and paper dust is reduced, so the dropout of printed parts is suppressed. It is preferable because it can be done.
The length-weighted average fiber length of the pulp constituting the paper substrate is measured by the method described in Examples.

The average fiber width of the pulp fibers constituting the paper substrate is preferably 14.0 μm or more, more preferably 15.0 μm or more, still more preferably 15.5 μm or more, still more preferably 16.0 μm or more, and It is preferably 35.0 μm or less, preferably 33.0 μm or less, more preferably 31.0 μm or less, still more preferably 28.0 μm or less, still more preferably 24.0 μm or less, and even more preferably 21.0 μm or less. be.
When the average fiber width of the pulp fibers constituting the paper substrate is 35.0 μm or less, the pulps are tightly entangled with each other, thereby smoothing the surface of the paper substrate and preventing uneven coating when a printed layer is provided. is suppressed and the surface of the printed layer is smoothed, so that a printed matter having excellent print sharpness and excellent print uniformity can be obtained. In addition, when the average fiber width is 14.0 μm or more, the strength as a paper base material is improved, and furthermore, paper dust is reduced, so dropout of printed portions can be suppressed, which is preferable.
The average fiber width of the pulp fibers constituting the paper substrate can be measured by the method described in Examples.

In the pulp constituting the paper substrate, the number ratio of fine fibers having a fiber length of 0.2 mm or less is preferably 4% or more, more preferably 5% or more, still more preferably 6% or more, and even more preferably 10%. As mentioned above, it is particularly preferably 15% or more, and preferably 40% or less, more preferably 30% or less, further preferably 20% or less.
When the number ratio of fine fibers is 40% or less, the strength as a paper base material can be ensured, and paper dust due to detachment of fine fibers is suppressed, resulting in excellent printing uniformity, which is preferable. In addition, when the ratio of the number of fine fibers is 4% or more, the fine fibers are arranged so as to fill the gaps between the fibers, the gaps in the paper substrate are reduced, and when a coating layer is provided, uneven coating is caused. It is preferable because it is suppressed, and as a result, the print uniformity is improved.
The ratio of the number of fine fibers having a fiber length of 0.2 mm or less in the pulp constituting the paper base material is obtained by defiberizing the paper base material by the method described in the Examples, and calculating the fiber length of the obtained pulp slurry. It is calculated by measuring with a measuring device (for example, Model FS-5, manufactured by Valmet, with a UHD base unit). Fibers having a fiber length of 0.2 mm or less and a fiber width of 75 μm or less are defined as fine fibers, and the ratio of the number of fine fibers to the measured number of pulp is calculated.

The water retention of the pulp fibers constituting the paper substrate is preferably 100% or more, more preferably 105% or more, still more preferably 110% or more, and even more preferably, from the viewpoint of suppressing smoke generation due to ultraviolet laser printing. It is 115% or more, and although the upper limit is not particularly limited, it is preferably 200% or less, more preferably 170% or less, and still more preferably 150% or less from the viewpoint of ease of production.
It is considered that the titanium oxide that absorbs the light of the ultraviolet laser generates heat, and smoke is generated due to scattering of the titanium oxide. By setting the water retention degree of the pulp constituting the paper substrate located directly under the printed layer to 100% or more, the amount of moisture in the paper substrate increases, and the heat generated by titanium oxide is released as heat of vaporization. It is thought that scattering of titanium is suppressed and smoke generation is suppressed.
The water retention of pulp fibers tends to be high when the hemicellulose content in the pulp fibers is high. Therefore, when a dissolving pulp having a high α-cellulose content and a reduced hemicellulose content is used as raw material pulp, the water retention tends to decrease.
In addition, when the beating degree of pulp fibers is high, the water retention tends to be improved. Therefore, from the viewpoint of water retention, it is preferable to use pulp fibers having a low Canadian Standard freeness (CSF) and a high beating degree.
The water retention of the pulp fibers constituting the paper substrate is measured by the method described in Examples.

The Canadian standard freeness (CSF) of the wood pulp used for the paper substrate is preferably 150 mL or more, from the viewpoint of obtaining the desired fiber width and fiber length, the number ratio of fine fibers and the water retention. It is preferably 300 mL or more, more preferably 400 mL or more, 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 is the Canadian standard freeness according to JIS P 8121-2:2012.

A paper base material is obtained by paper-making a pulp slurry to which an internal additive is added as necessary.
In addition to the pulp described above, the paper base material includes fillers, sizing agents, dry strength agents, wet strength agents (e.g., polyamide polyamine epichlorohydrin), retention aids (e.g., aluminum sulfate), Known internal additives for papermaking such as drainage improvers, pH adjusters, softeners, antistatic agents, antifoaming agents, dyes and pigments can be added as necessary.
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, hydroxide Aluminum, calcium hydroxide, magnesium hydroxide, zinc hydroxide and the like can be exemplified.
Examples of sizing agents include rosin-based, alkylketene dimer-based, alkenyl succinic anhydride-based, styrene-acrylic, higher fatty acid-based, and petroleum resin-based sizing agents.

In the papermaking of the paper substrate, a known wet paper machine such as a fourdrinier paper machine, a gap former paper machine, a cylinder paper machine, a short mesh paper machine, etc., is appropriately selected and used. be able to. Next, the paper layer formed by the paper machine is transported by felt and dried by a dryer. A multi-stage cylinder dryer may be used as a pre-dryer before drying.

Further, the paper base material obtained as described above may be subjected to a surface treatment with a calender to make the thickness and profile uniform, thereby improving the printability. For calendering, a known calendering machine can be appropriately selected and used.

The paper substrate may be appropriately selected and used from conventionally known paper substrates such as liner base paper, kraft paper, woodfree paper, and coated paper.
Moreover, the paper substrate may be of a single layer or multiple layers, or may have a multilayer structure with different pulp compositions.

The basis weight of the paper substrate is preferably 30 g/m ² or more, more preferably 35 g/m ² or more, and preferably 1000 g/m ² or less, from the viewpoint of strength as printing paper and improvement of printability. , more preferably 700 g/m ² or less, and still more preferably 500 g/m ² or less.
The basis weight is measured by the method specified in JIS P 8124:2011.

The thickness of the paper substrate is not particularly limited, but is preferably 30 μm or more, more preferably 40 μm or more, still more preferably 50 μm or more, and preferably 1200 μm from the viewpoint of strength as printing paper and improvement of printability. Below, more preferably 850 μm or less, still more preferably 600 μm or less.
The thickness of the paper substrate can be measured by the method described in JIS P 8118:2014.

Although the density of the paper base material is not particularly limited, it is preferably 0.3 g/cm ³ or more, more preferably 0.5 g/cm ³ or more, and still more preferably 0 from the viewpoint of strength as printing paper and improvement of printability. .7 g/cm ³ or more, preferably 1.2 g/cm ³ or less, more preferably 1.0 g/cm ³ or less, and even more preferably 0.8 g/cm ³ or less.
The density of the paper substrate is calculated from the basis weight and thickness.

[Resin layer]
The printing paper of this embodiment may further have a resin layer on the printing layer from the viewpoint of improving the water resistance of the printing paper and for the purpose of functioning as a protective layer. A printing paper having a resin layer provided in advance on the printing layer may also be used.

The total light transmittance of the resin layer is preferably 40% or higher, more preferably 60% or higher, still more preferably 70% or higher, still more preferably 80% or higher, and particularly preferably 90% or higher. % or less. The upper limit is not particularly limited.
Total light transmittance is measured according to JIS K 7361-1:1997.

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

The paper substrate having the resin layer and the printed layer may be laminated by any method, and is not particularly limited. It is preferably applied through layers or laminated, or the clear coat is applied in the form of a liquid coat. Alternatively, a printed layer may be formed on the resin layer in advance and attached via the paper substrate and the adhesive layer.
When the resin layer is provided locally, it is preferable to stick it through an adhesive from the viewpoint of ease of manufacture. Moreover, when providing a resin layer in a wide range, it is preferable to laminate.
The adhesive layer is not particularly limited, and may be appropriately selected from known adhesive layers and used. Specifically, the adhesive layer disclosed in JP-A-2012-57112 is exemplified.

Although the thickness of the resin layer is not particularly limited, it is preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 15 μm or more from the viewpoint of obtaining clear printing and the handling of printed matter and printing paper, and , preferably 100 μm or less, more preferably 75 μm or less, still more preferably 50 μm or less.

[Printed Matter and Method for Producing Printed Matter]
The printed matter of the present embodiment is a printed matter obtained from the ultraviolet laser printing medium described above, and has a printed area having discolored titanium oxide in at least a portion thereof. The ratio of the Raman intensity derived from titanium oxide in the printed region to the Raman intensity derived from titanium oxide in the non-printed region is preferably 0.70 or less. Further, the printed region having discolored titanium oxide is a region containing titanium oxide discolored by irradiation with an ultraviolet laser, and is an ultraviolet laser irradiated region, that is, a printed region.
Further, the method for producing a printed matter according to the present embodiment includes the step of irradiating the above-described printing medium with an ultraviolet laser to change the color of the irradiated area for printing.
Examples of the printing medium used in the method for producing a printed matter of the present embodiment include the printing medium described above, and the preferred range is also the same. In addition, in the method for producing a printed matter of the present embodiment, it is sufficient that at least the ultraviolet laser irradiation region is provided with the print layer, and the non-irradiation region need not be provided with the print layer.

It is preferable to irradiate the ultraviolet laser so that the ratio of the Raman intensity derived from titanium oxide in the printed region to the Raman intensity derived from titanium oxide in the non-printed region is 0.70 or less.
In the printed matter, the printed region means a region (portion) containing discolored titanium oxide in the printable region, and is a region (portion) printed with an ultraviolet laser. The non-printing area means a non-printing area (portion) in the printable area. In addition, the printable region is a region containing titanium oxide, which is a combination of a region that can be printed with an ultraviolet laser and a region (portion) printed with an ultraviolet laser, if any, in the ultraviolet laser printing paper or printed matter. Overall, the non-printable area means an area other than the printable area on the ultraviolet laser printing paper or printed material.
The ratio of the Raman intensity derived from titanium oxide in the printed region to the Raman intensity derived from titanium oxide in the non-printed region (Raman intensity in the printed region/Raman intensity in the non-printed region) is 0.70 or less. Printing is preferred. By setting the ratio of Raman intensities within the above range, a printed matter with excellent visibility can be obtained.
When rutile-type titanium oxide is used as titanium oxide, the Raman intensity ratio (Raman intensity in printed area/Raman intensity in non-printed area) is 447±10 cm ⁻ as Raman intensity derived from titanium oxide. Contrast the maximum Raman intensity in the wavenumber range of ¹ . When anatase-type titanium oxide is used as titanium oxide, the maximum Raman intensity in the wavenumber range of 516±10 cm ⁻¹ is compared as the Raman intensity derived from titanium oxide.
When rutile-type titanium oxide and anatase-type titanium oxide coexist, Raman intensity derived from rutile-type titanium oxide is used for comparison.

The printed matter obtained in this embodiment preferably has a white non-printed area and a black printed area.
The non-printing area preferably has a brightness of No. 10 in the Munsell color system, that is, white. On the other hand, the printed area is preferably No. 0 to No. 8, more preferably No. 0 to No. 6, and even more preferably No. 0 to No. 4 in the Munsell color system.
In order to obtain the color in the above Munsell color system, the content of titanium oxide in the printing layer in the printing paper, the crystallite size of titanium oxide, the length weighted average fiber length of the pulp constituting the paper substrate, and other characteristics (type of titanium oxide, diffraction angle, number ratio of fine fibers in the pulp that makes up the paper base material, degree of water retention of the pulp that makes up the paper base material, amount of inorganic pigment blended, thickness of the printed layer, etc.), ultraviolet rays It is preferable to appropriately adjust laser irradiation conditions (eg, average output, repetition frequency, wavelength, etc.).

[Irradiation conditions of ultraviolet laser]
The wavelength of the ultraviolet laser is preferably 370 nm or less, more preferably 365 nm or less, still more preferably 360 nm or less, and preferably 260 nm or more, more preferably 340 nm or more, from the viewpoint of improving the visibility of the printed area. More preferably, it is 350 nm or more.

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

The repetition frequency (frequency) of the ultraviolet laser is preferably 10 kHz or higher, more preferably 20 kHz or higher, still more preferably 30 kHz or higher, and preferably 100 kHz or lower, more preferably 100 kHz or higher, from the viewpoint of improving the visibility of the printed area. is 80 kHz or less, more preferably 60 kHz or less.

The spot diameter of the ultraviolet laser is preferably 10 μm or more, more preferably 20 μm or more, still more preferably 30 μm or more, and preferably 300 μm or less, more preferably 300 μm or less, from the viewpoint of obtaining a clear image and from the viewpoint of printability. It is 240 μm or less, more preferably 180 μm or less, further preferably 120 μm or less.

The scan speed of the ultraviolet laser is preferably 500 mm/sec or more, more preferably 1000 mm/sec or more, still more preferably 2000 mm/sec or more, and preferably 7000 mm/sec, from the viewpoint of high-speed printing and visibility of the printed area. sec or less, more preferably 6000 mm/sec or less, and even more preferably 5000 mm/sec or less.

The filling interval (line pitch) of the ultraviolet laser is preferably 10 μm or more, more preferably 20 μm or more, and still more preferably 30 μm or more, from the viewpoint of obtaining a clear image and from the viewpoint of easy availability of the device. is 300 μm or less, more preferably 250 μm or less, still more preferably 200 μm or less.

[Aspect of method for manufacturing printed matter]
The method for producing printed matter of the present invention can be carried out in various ways.
Various aspects to which the method for producing printed matter according to the present embodiment can be applied are illustrated below, but the method for producing printed matter according to the present embodiment is not limited to the following aspects. Although the information to be printed is not particularly limited, it is preferably variable information.
It is preferable that the printed matter manufacturing method of the present embodiment be performed in-line.
(1) Direct printing on the package The first embodiment of the method for producing printed matter of the present embodiment is a method for printing information on the package having the printing paper of the present embodiment, moving on the packing line It has a process of printing directly on the package during or intermittently stopped with an ultraviolet laser.
In the first method for producing a printed matter, a package is produced from the ultraviolet laser printing paper of the present embodiment, and printed directly with an ultraviolet laser. At least the outermost layer of the printed area of the package should be made of the printing paper.
Examples of the package include corrugated cardboard and boxes, and it is preferable to print directly on the side or top surface of the package with an ultraviolet laser.

Moreover, you may have a coating (coating) mechanism in a packing line. Examples of the coating mechanism include a contact printer, a pad printer, and a spray coater.
In this aspect, the step of applying a printed layer by a coating mechanism while the package is moving on the packing line, and further downstream, while the packing line is moving or intermittently stopping, the package is irradiated with an ultraviolet laser. It has a direct printing process.

(2) Printing on a Label A second embodiment of the printed matter manufacturing method of the present embodiment is a method of printing information on a label having the printing paper of the present embodiment. The printing paper forming the printing surface of the label is the printing paper of the present embodiment.
The printed label is preferably applied to the package using a label applicator. Various labeling devices have been proposed as labeling devices. At this time, a printed layer is provided on the surface irradiated with ultraviolet rays.
The first labeling apparatus applies an adhesive to a roll of label base paper, which is then attached to an article. More specifically, a cutting means for cutting a roll of label base paper sheet by sheet into a predetermined length, and the label base paper cut by the cutting means is held by a label base paper holder coated with an adhesive. Gluing conveying means for receiving and applying adhesive to the back surface of the label base paper, and pasting means for receiving the label base paper (label) to which adhesive is applied from the pasting conveying means and applying it to an article such as a container. As for the roll labeler, there is exemplified a roll labeler in which a rotary conveying means having a label holding surface on the outer surface is provided between the cutting means and the pasting conveying means.
In addition, a cutting means for cutting the roll-shaped label base paper sheet by sheet to a predetermined length, a delivery roll for transferring to the pasting roll, and a gluing roll for applying glue to the label base paper held by the pasting roll. Examples include a roll labeler having a roll labeler and an embodiment in which the delivery roll is not required.
It is preferable to irradiate the ultraviolet laser before cutting the rolled label base paper into a predetermined length, or after cutting and before transferring to the next roll or the like. Depending on the mode of the roll labeler, the surface or the back surface of the label base paper wound in a roll will be the surface or the back surface when attached to the package, so irradiation with an ultraviolet laser is performed in accordance with this.

A second labeling machine uses adhesive label rolls as labels. In this case, the print layer is provided at least on the surface to be irradiated with the ultraviolet laser, which is the surface opposite to the surface to which the adhesive is applied.
When using an adhesive label roll with a release paper, for example, a release paper separating means for separating the adhesive label and the release paper, a delivery roll for receiving the adhesive label from which the release paper has been separated, and the adhesive label from the delivery roll A sticking device having a sticking roll that sticks to an article (package) by suction is exemplified. Irradiation with an ultraviolet laser is preferably carried out before the release paper is separated, or after the release paper is separated and before it is borne on the sticking roll.
In addition, it has a mechanism for setting an adhesive label roll with release paper, separating the adhesive label and the release paper, having a mechanism for attaching the label immediately after separation, and separating the release paper from the set adhesive label roll. An apparatus for printing with an ultraviolet laser is exemplified. The sticking method of the adhesive label described above is also called flow sticking.
Furthermore, it has a mechanism for setting an adhesive label roll with a release paper, separating the release paper from the adhesive label, and a mechanism for attaching the adhesive label to the article (package), and the attachment mechanism is a syringe system. , air jet, or robot arm type labeling devices are exemplified. Irradiation with an ultraviolet laser is preferably performed until the release paper is separated from the set adhesive label roll with the release paper.

A linerless adhesive label may be used as the label. A linerless adhesive label is a label without release paper, and compared to the case of using an adhesive label roll with release paper, there are more labels per roll, and there is no release paper, so it is cheaper. have. When using a linerless pressure-sensitive adhesive label, a printed layer is formed on the surface to be irradiated with an ultraviolet laser, which is the opposite surface to the surface to which the pressure-sensitive adhesive is applied.
A label applying device using a linerless adhesive label includes a mechanism for setting a linerless label roll, a cutting mechanism for cutting the linerless label one by one, and the cut linerless label on an article (package). An apparatus having a sticking mechanism for sticking, wherein the sticking mechanism is a cylinder system or a robot arm system is exemplified. It is preferable that the printing by the irradiation of the ultraviolet laser is performed between the mechanism for setting the linerless label roll and the cutting mechanism, or while the cut linerless label is sent to the applying mechanism.

The third labeling device prints with an ultraviolet laser after the printing paper of the present embodiment is pasted on an article (package).
As for the label application method, reference is made to the first and second devices described above.

(3) Printing on Adhesive Tape A third embodiment of the printed matter manufacturing method of the present embodiment is a mode in which the printing paper is an adhesive tape. In this case, it has a printed layer on the side opposite to the side to which the pressure-sensitive adhesive is applied.
That is, the method for producing a printed matter according to the third embodiment has a step of attaching an adhesive tape made from the printing paper to an article (package), and before the attaching step or after the attaching step , printing with an ultraviolet laser.
Also, a printing device in which a printing device using an ultraviolet laser is incorporated in a corrugated cardboard sealing machine may be used. Specifically, it has a mechanism for setting the adhesive tape winding, a conveyor for transporting the cardboard, a mechanism for folding the flap of the cardboard, and a mechanism for sealing the cardboard by applying the adhesive tape. It has a mechanism for printing on the adhesive tape with an ultraviolet laser during or after the application.

The method for producing a printed matter according to the present embodiment is not limited to the above aspect, and can be applied to various uses requiring printing.

In this embodiment, the printed matter obtained by the method for producing a printed matter is suitably used for packages, labels, adhesive tapes, and the like.
Examples of packages include outer bags, outer boxes, milk cartons, aseptic paper packs, paper cups and other liquid containers for beverages (preferably liquid paper containers for beverages), and skin packs. Labels and adhesive sheets are exemplified, and adhesive tapes are exemplified by adhesive tapes and craft tapes.

[Processed goods]
The ultraviolet laser printing paper and printed matter of this embodiment are applied to various processed products. That is, the processed product of the present embodiment uses the ultraviolet laser printing paper of the present embodiment or the printed matter of the present embodiment.
Packages, labels, adhesive tapes, and the like are suitable as processed products of the present embodiment.
Examples of packages include cardboard liner base paper (especially outermost liner base paper), outer bags, outer boxes, milk cartons, aseptic paper packs, liquid containers for beverages such as paper cups (preferably liquid paper containers for beverages), Food trays and skin packs are exemplified, labels are exemplified by label base paper, adhesive labels and adhesive sheets, and adhesive tapes are exemplified by adhesive tapes and kraft tapes.
As shown in FIG. 2, a liquid container 10 as an example of a package has, for example, a printed area 20 on its surface. The print area 20 is irradiated with an ultraviolet laser and characters such as a date are printed.

[Ink composition]
The ink composition of the present embodiment contains titanium oxide having a crystallite size of 30 nm or more, and is used to form a printing layer that changes color when irradiated with an ultraviolet laser. By irradiating an ultraviolet laser onto an ultraviolet laser print medium having a print layer formed from the ink composition of the present embodiment, an image with excellent print sharpness can be obtained for each point.
Examples of the titanium oxide contained in the ink composition and its content include the titanium oxide contained in the printing layer of the above-mentioned ultraviolet laser printing paper and the content of titanium oxide in the coating liquid, and the preferred range is also the same. .
In addition, other components contained in the ink composition include components that may be contained in the coating liquid described above, such as thermoplastic resins, inorganic pigments, film forming agents, pigment dispersants, pigment dispersing resins, blocking Each component such as an inhibitor, a wetting agent, a viscosity modifier, a pH adjuster, an antifoaming agent, and a general surfactant may be contained. is.

The features of the present invention will be described more specifically below with reference to examples and comparative examples. The materials, amounts used, proportions, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed to be limited by the specific examples shown below. "Parts" and "%" mean "mass parts" and "mass%" unless otherwise specified.

[Titanium oxide]
The titanium oxides used in Examples and Comparative Examples are shown in Table 1 below.

<Method for Synthesizing Titanium Oxide C, F to H>
Titanium oxide (amorphous) was synthesized by hydrolytic condensation polymerization of titanium tetraisopropoxide (TTIP) and crystallized by firing.
Specifically, it was synthesized by the following steps (1) to (6).
(1) Using TTIP (manufactured by Tokyo Chemical Industry Co., Ltd., product code: T0133), isopropanol (manufactured by Tokyo Chemical Industry Co., Ltd., purity 99.5% or more, product code: I0163) and ion-exchanged water, the following solution A to C were produced.
Solution A: 35.6 parts by mass of TTIP, 200 parts by mass of isopropanol Solution B: 200 parts by mass of isopropanol, 6.3 parts by mass of ion-exchanged water Solution C: 200 parts by mass of isopropanol, 24.4 parts by mass of ion-exchanged water (2) Teflon While stirring solution A with a (registered trademark) stirring blade, solution B was slowly added dropwise, and then stirring was continued for 10 minutes.
(3) Solution C was slowly added dropwise to the mixed liquid of solution A and solution B obtained in (2) above, and after continuing stirring for 1 minute, the mixture was allowed to stand at room temperature for 24 hours.
(4) Solid-liquid separation of the precipitate was performed with a membrane filter (manufactured by Advantech, material: cellulose acetate).
(5) After washing with isopropanol, it was dried at 100° C. for 5 hours to obtain titanium oxide (amorphous).
(6) Firing in a muffle furnace to crystallize titanium oxide.
The firing temperature was set at the temperature shown in the table, and the heating rate was 10° C./min.

[Example 1]
<Manufacturing paper substrate>
A pulp slurry of hardwood bleached kraft pulp (LBKP, α-cellulose: 86%) is beaten using a double disc refiner so that the defiberization freeness (CSF: Canadian standard freeness) is 450 mL, A pulp slurry was obtained. To 100 parts of the obtained pulp slurry, 0.30 parts (solid content conversion) of an amphoteric polyacrylamide-based paper strength agent (manufactured by Seiko PMC Co., Ltd., DS4430) as an internal paper strength agent, and an internal sizing agent A rosin sizing agent (Size Pine N-811, manufactured by Arakawa Chemical Industries, Ltd.) was added as 0.5 part (solid content conversion) and aluminum sulfate 1.0 part (solid content conversion) was added to prepare a paper material. This stock was used to make paper with a basis weight of 40 g/m ² using a Fourdrinier Yankee paper machine. The resulting paper substrate had a basis weight of 40 g/m ² , a thickness of 51 μm, and a density of 0.78 g/cm ³ .

<Preparation of coating solution>
As shown in Table 2 as a solid content, 68 parts of titanium oxide A and 32 parts of ion-exchanged water were mixed to prepare a solid content concentration of 68%. Thereafter, a pigment dispersion was prepared using a colless disperser, and ethylene-acrylic emulsion (Chemipearl S-300, manufactured by Mitsui Chemicals, Inc., solid content concentration 35%) was 3691.4 parts as an emulsion (1291 as solid content .9 parts) was added to prepare a coating solution having a solid concentration of 35.9%. After that, it was diluted with ion-exchanged water to adjust the solid content concentration to 35.0%.

<Manufacture of UV laser printing paper>
Using a Meyer bar, the coating solution prepared as described above was applied onto a paper substrate so that the coating amount of titanium oxide was as shown in Table 2, and heated at 140°C for 1 minute. to form a printed layer and obtain an ultraviolet laser printing paper.

[Examples 2 to 8, Comparative Examples 1 and 2]
An ultraviolet laser printing paper was obtained in the same manner as in Example 1, except that the titanium oxide used in preparation of the coating liquid was changed to the titanium oxide shown in Table 2.

[Example 9]
In the preparation of the coating liquid, the amount of ethylene-acrylic emulsion added was changed to 19234.3 parts (6732.0 parts as solid content), and the content of titanium oxide in the printed layer was the content shown in Table 2. An ultraviolet laser printing paper was obtained in the same manner as in Example 4, except that the coating was applied on the paper substrate so as to have (basis weight).

[Example 10]
In the preparation of the coating liquid, the amount of ethylene-acrylic emulsion added was changed to 582.9 parts (204.0 parts as solid content), and the content of titanium oxide in the printed layer was the content shown in Table 2. An ultraviolet laser printing paper was obtained in the same manner as in Example 4, except that the coating was applied on the paper substrate so as to have (basis weight).

[Example 11]
In the preparation of the coating liquid, the amount of ethylene-acrylic emulsion added was changed to 237.5 parts (83.1 parts as solid content), and the content of titanium oxide in the printed layer was the content shown in Table 2. An ultraviolet laser printing paper was obtained in the same manner as in Example 4, except that the coating was applied on the paper substrate so as to have (basis weight).

[Example 12]
In the preparation of the coating liquid, the amount of ethylene-acrylic emulsion added was changed to 1748.6 parts (612.0 parts as solid content), and the content of titanium oxide in the printed layer was the content shown in Table 2. An ultraviolet laser printing paper was obtained in the same manner as in Example 4, except that the coating was applied on the paper substrate so as to have (basis weight).

[Example 13]
In the preparation of the coating liquid, the amount of ethylene-acrylic emulsion added was changed to 1020.0 parts (357.0 parts as solid content), and the content of titanium oxide in the printed layer was the content shown in Table 2. An ultraviolet laser printing paper was obtained in the same manner as in Example 4, except that the coating was applied on the paper substrate so as to have (basis weight).

[Example 14]
In the preparation of the coating liquid, the amount of ethylene-acrylic emulsion added was changed to 9520.0 parts (3332.0 parts as solid content), and the content of titanium oxide in the printed layer was the content shown in Table 2. An ultraviolet laser printing paper was obtained in the same manner as in Example 4, except that the coating was applied to the paper substrate so as to have (basis weight).

[Example 15]
In the production of the paper substrate, 30 parts of bleached hardwood kraft pulp (LBKP, α-cellulose: 86%) and 70 parts of bleached softwood kraft pulp (NBKP, α-cellulose: 85%) are mixed so that the defibering freeness becomes 550 mL. An ultraviolet laser printing paper was obtained in the same manner as in Example 4, except that the paper was beaten before use.

[Example 16]
Ultraviolet laser printing was performed in the same manner as in Example 4, except that 100 parts of softwood bleached kraft pulp (NBKP, α-cellulose: 86%) was beaten so that the deaggregation freeness was 580 mL in the production of the paper base material. got the paper.

[Example 17]
In the production of the paper base material, 70 parts of the same hardwood bleached kraft pulp (LBKP) as in Example 4 and 30 parts of powdered pulp prepared from the LBKP as follows were used, and the defibration freeness was adjusted to 400 mL. An ultraviolet laser printing paper was obtained in the same manner as in Example 4, except that the materials were mixed and beaten.
<Powder pulp>
The powder pulp was prepared by mechanically pulverizing a dry sheet of bleached hardwood kraft pulp (LBKP) with a cutter mill (HA8 2542 30E, manufactured by Horai Co., Ltd., screen 0.24 mm).

[Example 18]
In the production of the paper base material, hardwood dissolving pulp (LBDP, α-cellulose: 94%) was made with a pulp machine and dried to obtain dry pulp. An ultraviolet laser printing paper was obtained in the same manner as in Example 4, except that the dry pulp was re-macerated and beaten so as to have a maceration freeness of 550 mL.

[Example 19]
In the preparation of the coating liquid, 20 parts of titanium oxide D shown in Table 2 as solid content, calcium carbonate (manufactured by Fimatech Co., Ltd., product number: FMT-97W, heavy calcium carbonate, average particle size 0.95 μm (catalog value) , amorphous) were mixed, 0.08 part of sodium polyacrylate was added as a dispersant, and ion-exchanged water was added to adjust the solid content concentration to 67.5%. After that, a pigment dispersion is prepared using a colless disperser, and 10 parts of styrene-butadiene latex (manufactured by Nippon A&L Co., Ltd., product number: PB5453) is added as a solid content, and the solid content concentration is 62.3%. A liquid was prepared. The coating liquid prepared as described above was applied to the paper substrate used in Example 4 with an air knife coater so that the content of titanium oxide in the printed layer was the content (weight) shown in Table 2. An ultraviolet laser printing paper was obtained in the same manner as in Example 4, except that the coating was applied to .

[Example 20]
An ultraviolet laser printing paper was obtained in the same manner as in Example 19, except that kaolin (KAOFINE90 manufactured by Tiele, tabular particles, average particle size 0.21 μm (catalog value)) was used instead of calcium carbonate.

[Example 21]
<Manufacturing method of masterbatch>
A masterbatch was produced according to the following procedure according to Japanese Patent Application Laid-Open No. 2015-96568.
After mixing 60 parts of PE resin (polyethylene resin, LC522, manufactured by Japan Polyethylene Co., Ltd.) and 40 parts of titanium oxide D in a tumbler mixer (TM-65S, manufactured by Eishin Co., Ltd.) at 45 rpm for 1 hour, A screw extruder (manufactured by The Japan Steel Works, Ltd., TEX30XCT, L/D = 42) is melted and kneaded under the conditions of a screw rotation speed of 250 rpm and a cylinder temperature of 200°C, extruded into strands, and cooled in a water tank. A masterbatch was obtained by pelletizing into a columnar shape having an average shaft diameter of 2.0 mm and an average shaft length of 3.0 mm using a pelletizer.

(Addition of laminate layer (film))
The masterbatch and the PE resin were mixed with a single screw extruder (manufactured by Toyo Seiki Seisakusho Co., Ltd.) so that the content of titanium oxide in the printed layer when forming a 20 μm printed layer was the value shown in Table 2. , 50C150), melt-laminated by extrusion lamination so that the thickness of the laminate layer, which is the printed layer, on the surface of the paper base used in Example 1 is 20 μm, and then quickly adjusted to 20 ° C. and cooled. It was quenched while sandwiched between rolls to obtain an ultraviolet laser printing paper having a laminate layer as a printing layer. The melting temperature was 320°C.

[Example 22]
<Preparation of coating solution>
In the preparation of the coating liquid, 16.1 parts of titanium oxide D shown in Table 2 as a solid content was added to a gravure ink medium (Lami CP medium manufactured by DIC Corporation, resin component: nitrocellulose, solid content concentration: 24.1% ) was mixed with 100 parts by mass, and using a Colles disperser, an ink for gravure printing having a titanium oxide concentration of 40% by mass in the solid content was prepared.

<Manufacture of UV laser printing paper>
Using a gravure printing machine (10-color machine, plate depth: 50 μm, drying temperature after printing 80° C., printing speed 80 m ² /min), the paper base material of Example 1 was prepared so that the titanium oxide content in the table was obtained. printed to The titanium oxide content in the table was determined using printing plates for three colors.

[Comparative Example 3]
<Preparation of coating solution>
As shown in Table 2 as a solid content, 68 parts of titanium oxide D and 32 parts of ion-exchanged water were mixed to prepare a solid content concentration of 68%. Thereafter, a pigment dispersion is prepared using a colless disperser, and 42980 parts of ethylene-acrylic emulsion (Chemipearl S-300, solid content concentration 35%, manufactured by Mitsui Chemicals, Inc.) as emulsion (15043 parts as solid content). A coating solution having a solid content concentration of 35.9% was prepared by adding these. After that, it was diluted with ion-exchanged water to adjust the solid content concentration to 35.1%.
Ultraviolet laser printing paper was obtained in the same manner as in Example 4, except that the content of titanium oxide in the printed layer was coated on the paper substrate so that the content (basis weight) shown in Table 2 was obtained. .

[Measurement/Evaluation]
The following measurements and evaluations were performed on the paper substrates and ultraviolet laser printing papers obtained in Examples and Comparative Examples, and various raw materials.

[Method for measuring particle size of titanium oxide]
The particle size of the titanium oxide contained in the printed layer is determined by a SEM image (2 Next electron image).
Specifically, when the paper base material does not contain titanium oxide, the ash content was obtained under the same conditions as the measurement of [crystallite size] described later.
Further, when the paper substrate contains titanium oxide, the printed layer is ground using an industrial razor (manufactured by Feather Safety Razor Co., Ltd., product number: 099769), and the collected printed layer is used as a sample and similarly ashed. got ash.
The ash sample to be subjected to the scanning electron microscope was dispersed in ethanol for 5 minutes with an ultrasonic cleaner (manufactured by AS ONE Co., Ltd., LSC-63, etc.) to obtain a 0.1% by mass slurry, and then placed in an aluminum dish. It was made by casting 0.1 mL on top and drying at 100°C. Adjacent particles were selected by visual inspection, and the geometric mean of the major axis and minor axis of one particle was taken as the particle diameter. At this time, even if the primary particles and the secondary particles in the aggregated state are mixed, if they can be clearly distinguished, each is counted as one particle, and the average diameter of 100 randomly selected particles is the particle diameter. and The magnification during observation of the SEM image was appropriately selected depending on the particle size of the titanium oxide, and was set to about 20000 times. When particles other than titanium oxide were contained, particles containing titanium element were measured using an energy dispersive X-ray analyzer (EMAX, manufactured by HORIBA, Ltd.) attached to the SEM.
In addition, in the case of acicular particles, the major diameter was measured for 100 particles, and the average was taken as the particle diameter.

[Crystallite size calculation method]
<Measurement sample preparation method>
The ultraviolet laser printing papers obtained in Examples and Comparative Examples were burned at 450° C. using a muffle furnace (manufactured by Yamato Scientific Co., Ltd., model number FO300) and incinerated. When the paper substrate contained titanium oxide, the following pretreatment was performed to separate the printed layer from the paper substrate.
(Ultraviolet laser printing paper provided with a coating layer)
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 similarly ashed as a sample.
(Ultraviolet laser printing paper with laminated layer)
The ultraviolet laser printing papers obtained in Examples and Comparative Examples were impregnated with an aqueous solution of cellulase (manufactured by Genencor, model number: VISCAMYL FLOW, concentration 20% (diluted twice)) and allowed to stand at 40°C for 40 hours. The printed layer was separated by dissolving the paper substrate. After thoroughly washing with ion-exchanged water, it was similarly incinerated.

<Measurement by X-ray diffraction method>
The test samples obtained by ashing were filled in sample holders and measured using a high speed detector. At the time of filling, the sample measurement surface was adjusted to the same height as the edge of the sample holder by using a suitable height adjusting jig according to the amount of sample.
(Measurement condition)
X-ray diffractometer: RINT-Ultima III manufactured by Rigaku Corporation
Voltage: 40kV
Current: 40mA
Optical system: parallel beam (CBO)
Detector: High-speed detector D/teX Ultra 2 manufactured by Rigaku Corporation
Goniometer: Ultima III horizontal goniometer Tube: Cu
Wavelength: 1.541 Å (Kα1)
Scan mode: CONTINUOUS
Scan speed: 1.0000deg/min
Step width: 0.0500deg
Scan axis: 2Theta/Theta
Scan range: 5.0000 to 60.0000deg
Entrance slit: 1.0mm
Longitudinal limit slit: 10mm
Light receiving slit 1: open Light receiving slit 2: open Sample holder: ASC-6 sample holder (Part number 2455E442)
Material: Aluminum Dimensions: φ23mm x 2.0mm
Holder height adjustment jig: transparent disk-shaped plate (self-made)
Material: Polymethyl acrylate Dimensions: φ23mm x 0.8mm

<Processing of data obtained by X-ray diffraction>
The obtained diffraction profile was subjected to background processing and profile fitting processing using integrated powder X-ray analysis software (manufactured by Rigaku Corporation, PDXL2).
All settings for data processing were performed using the default settings of the software unless otherwise specified.
From the information on the peak position and peak intensity of the diffraction profile, the crystal phase was identified based on the database (ICDD).

<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 formula to calculate the crystallite size.
The X-ray diffraction peaks of titanium oxide used for the calculation are as follows.
Anatase: 101 faces Rutile: 110 faces The Scherrer formula is as follows.

D: crystallite size (nm)
K: Scherrer constant λ: X-ray wavelength (nm)
B: FWHM (rad)
θ: Bragg angle (rad)
The value of K is 0.89, B is the value of FWHM obtained by measurement, the value of λ is 0.154, and the value of θ is the 101 plane for anatase and the 110 plane for rutile. value.

[CSF]
The Canadian standard freeness (CSF) of raw material pulp was measured according to JIS P 8121-2:2012.

[Basis weight of paper substrate]
The basis weight of the paper substrate was measured according to JIS P 8124:2011. The printed layer was removed using a grinding device (manufactured by Sagawa Seisakusho Co., Ltd., whetstone dimensions φ50.8×12.7 mm) and used for the measurement.

[Thickness of paper substrate]
The thickness of the paper substrate was measured according to JIS P 8118:2014. The printed layer was removed using a grinding device (manufactured by Sagawa Seisakusho Co., Ltd., whetstone dimensions φ50.8×12.7 mm) and used for the measurement.

[Length Weighted Average Fiber Length, Fiber Width, and Fine Fiber Content of Pulp Fiber Constituting the Paper Base Material]
The length-weighted average fiber length, fiber width and fine fiber content of the pulp constituting the paper substrate were measured by the following methods.
The printing media of Examples and Comparative Examples were cut into 40-cm squares, and ion-exchanged water of about 50 times the mass was added to them and soaked for 24 hours.
After soaking for 24 hours, the pulp was defiberized by using a standard defiberizer (manufactured by Kumagai Riki Kogyo Co., Ltd.) until there were no undisintegrated fibers. In the case of having a resin layer, the slurry (dispersion of pulp fibers) after defibering excluding the resin layer is separated, and a fiber length measuring machine (model FS-5 with UHD base unit, manufactured by Valmet) is used. "Length-weighted average fiber length (ISO)", "fine fiber content", and "fiber width" were measured.
The "length-weighted average fiber length (ISO)" is the length-weighted average fiber length calculated by selecting fibers of 0.2 mm or more and 7.6 mm or less. The "amount of fine fibers" is the ratio of the number of fine fibers having a fiber width of 75 µm or less and a length of 0.08 mm or more and 0.20 mm or less in the disaggregated pulp fibers. "Fiber width" is the length-weighted average fiber width calculated by selecting fibers having a width of 10 μm or more and 75 μm or less.

[Water retention]
(Ultraviolet laser printing paper provided with a coating layer)
The ultraviolet laser printed papers of Examples and Comparative Examples were ground using an industrial razor (manufactured by Feather Safety Razor Co., Ltd., product number: 099769) to remove the printed layer. In addition, the grinding was performed while confirming with a microscope so as not to grind the paper base material.
After that, ion-exchanged water was added to the printing paper from which the printing layer was removed by about 50 times the mass of the printing paper, and the paper was allowed to stand for 24 hours. After being allowed to stand for 24 hours, the pulp was disaggregated into fibrous form using a standard type disaggregator (manufactured by Kumagai Riki Kogyo Co., Ltd.) until there were no undisaggregated fibers. Ion-exchanged water was added to the slurry (pulp fiber dispersion) after defibering to adjust the concentration to 0.5%.
About the obtained pulp fiber, JAPAN TAPPI No. 26 (2000) (pulp - water retention test method), the water retention was measured.
(Ultraviolet laser printing paper with laminated layer)
Ion-exchanged water was added to the ultraviolet laser printing paper of Examples and Comparative Examples in an amount of about 50 times the mass of the printing paper, and the paper was allowed to stand still for 24 hours. After being allowed to stand for 24 hours, the pulp was disaggregated into fibrous form using a standard type disaggregator (manufactured by Kumagai Riki Kogyo Co., Ltd.) until there were no undisaggregated fibers. The resin layer was removed from the slurry after disaggregation, and ion-exchanged water was added to adjust the concentration to 0.5%.
About the obtained pulp fiber, JAPAN TAPPI No. 26 (2000) (pulp - water retention test method), the water retention was measured.

[Content of titanium oxide]
1. When a non-printable area is included in the printable medium (preparation of test piece)
A printable region and a non-printable region (region where no coating layer is provided) of the printing medium were cut out to an appropriate size to obtain a sample (test piece), and the cut out area was recorded.
(Dissolution of test piece)
A mixed solvent of nitric acid: hydrofluoric acid = 50:5 (% by volume) and a test piece were put into a Teflon (registered trademark) container of an autoclave device (CEM Japan, MARS5), and autoclaved at 210 ° C. for 120 minutes. , dissolved the specimen. The area of the test piece may be changed as appropriate, and when the test piece remains undissolved, the ratio of nitric acid and hydrofluoric acid, the treatment temperature, the treatment time, etc. may be changed as appropriate.
After dissolving the test piece, the volume was accurately adjusted using ultrapure water.
(Measurement of amount of titanium oxide in solution)
(1) ICP apparatus and measurement conditions are as follows.
ICP device: ICP-OEC device (manufactured by Rigaku Corporation, CIROS1-20)
Measurement condition:
・Carrier gas: argon gas ・Argon gas flow rate 0.9 L/min
・Plasma gas flow rate 14L/min
・Plasma output 1400W
・Pump speed: 2
・Measurement wavelength Ti: 334.941 nm
(2) Preparation of calibration curve A general-purpose mixed standard solution (SPEX, XSTC-622B) is accurately measured so as to have the following concentrations, and is subjected to measurement under the above measurement conditions, corresponding to the emission wavelength of titanium atoms. The intensity at 334.941 nm was measured.
・ Concentration for calibration curve creation: 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 Dissolved Solution The solution in which the test piece was dissolved was diluted with ultrapure water so as to fall within the above calibration curve, and was subjected to ICP measurement.
(4) Titanium oxide content calculation method The titanium oxide content was calculated by the following formula. Incidentally, the molecular weight of titanium oxide÷the atomic weight of titanium≈1.669.
Titanium oxide content (g/m ² ) = ICP measurement concentration (ppm) x dilution factor x constant volume (L) x 1.669 x 1000/area (m ² )
The content of titanium oxide in the coating layer was obtained by subtracting the content of titanium oxide in the non-printable region from the content of titanium oxide in the printable region.

2. When the non-printable area is not included in the printing medium (preparation of test piece)
Two sheets of printing medium were cut into appropriate sizes, and the cut area was recorded.
One of the cut test pieces was used as a reference sample by scraping off only the printed layer (coating layer) using a grinder (manufactured by Sagawa Seisakusho Co., Ltd., grindstone dimensions φ50.8×12.7 mm). When a resin layer was further provided on the printed layer, the resin layer was also removed in the same manner.
The cross section was appropriately observed using an electron microscope so as not to excessively scrape off.
(subsequent processing)
1. The difference in titanium oxide content between the two sheets was taken as the titanium oxide content of the coating layer.

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

[Thickness of printed layer]
The thickness of the printed layer was measured from image data obtained from a scanning electron microscope.
(1) Preparation of Measurement Sample A sample was embedded in a photocurable resin (D-800, manufactured by Toagosei Co., Ltd.), and a cross-section of the printing medium was taken with an ultramicrotome. A diamond knife was used for cutting, and cutting was performed at room temperature.
The cut section was subjected to gold vapor deposition to a thickness of about 20 nm and tested for measurement with a scanning electron microscope.
(2) Measuring device and conditions Measuring device: S-3600 (manufactured by Hitachi High-Tech Co., Ltd.)
Measurement conditions: magnification of 2000 times The type of scanning microscope is not limited to the above, but a device that displays a scale bar was used.
When the printed layer was thin, an appropriate magnification was selected to acquire the image data.
(3) Measurement method Using an energy dispersive X-ray spectrometer attached to the scanning electron microscope, after confirming that the printed layer to be observed contained titanium element, image data was acquired at a magnification of 2000. After printing the obtained image data on printing paper, measure the thickness of the target printing layer (the length of the boundary from the boundary with other layers) with a ruler, and compare it with the scale bar to compare it with the actual printing layer ( The thickness of the coating layer or laminate layer) was measured. Obtain image data at 5 randomly selected locations from one measurement sample, measure the thickness of the thickest printed layer and the thinnest printed layer from the image data at one location, a total of 10 locations. The average was taken as the thickness of the printed layer. Note that the observation magnification may be changed depending on the thickness of the printed layer to be observed.
In addition, when it has a resin layer further on a printing layer, the thickness of a resin layer can be measured by the same method.

[Measurement of Raman spectrum]
Raman spectra were measured by the following method. In this example, the measurement of the Raman spectrum was performed on a printed matter obtained with the sharpness of one point of printing, which will be described later.
<Measurement conditions>
The measurement conditions for Raman spectra are as follows, but if the printed matter is damaged by the laser used for measurement, if the fluorescence is strong, if the peak intensity is weak, etc., adjust the laser output, irradiation time, etc. as appropriate. The following measurement conditions can be changed. However, values measured under the same conditions are used for the Raman intensities of the printed area and the non-printed area.
・Apparatus: inVia Raman microscope QUONTOR manufactured by Renishaw
・Excitation laser: 532 nm
・Laser power: 50mW (at 100% output)
・Laser output: 10%
・Measurement mode: confocal mode ・Irradiation time: 2.5 sec
・Number of accumulated times: 50 times ・Laser spot diameter: 2.5 μm
・Objective lens: 20x

<Measurement method>
Measurement was performed by the following method.
(1) A standard sample (single crystal silicon, manufactured by Renishaw) was used to calibrate the Raman shift position (520.5 cm ⁻¹ of single crystal silicon).
(2) A sheet-like sample was placed on a sample table. Pressers were installed as necessary to keep the sheet flat.
(3) Observation was performed with the apparatus focused as shown in FIG. 1 (the simulated laser was set to have the smallest focus). When measuring the printed area, the blackest part that can be visually confirmed was measured so that it was positioned at the center of the guide displayed at the time of measurement. When measuring the non-printing area, the measurement was performed with a distance of 300 μm or more from the printing area.
(4) The obtained Raman spectrum was subjected to baseline correction (intelligent correction) using processing software (manufactured by Renishaw, Wire 5.2) attached to the apparatus. The baseline was corrected with polynomial 11 of the processing software.
(5) The maximum value (maximum intensity) in the wavenumber range of 447±10 cm ⁻¹ for rutile-type titanium oxide and 516±10 cm ⁻¹ for anatase-type titanium oxide was read, and the Raman intensity ratio was calculated by the following formula.
Raman intensity ratio = Maximum intensity of printed area/Maximum intensity of non-printed area (6) 10 points were measured for each of the printed area (printed area) and the non-printed area (non-printed area), and the average value was taken as the measurement result. .
From the viewpoint of suppressing variations in the measured values, it is preferable to measure the Raman intensity count in the printed area within a range of 10,000 or less. Therefore, the measurement conditions were appropriately changed so that the Raman intensity count in the printed area was within the range of 10,000 or less. In addition, measurements were performed 10 times under the following measurement conditions, values exceeding the average value ± 2 SD (standard deviation) were excluded, and averaged again to obtain the average value of Raman intensities.
The Raman intensity ratio was evaluated using A to C below.
A: Raman intensity ratio is 0.3 or less B: Raman intensity ratio is over 0.3 and 0.7 or less C: Raman intensity ratio is over 0.7

[Clearness of one print]
<Laser marking method>
Using an ultraviolet laser irradiation machine (manufacturer: KEYENCE CORPORATION, model number: MD-U1020C), a 10 mm square was printed on the sample surface of the substrates obtained in Examples and Comparative Examples.
(Printing conditions)
Wavelength: 355nm
Output: 80% (2.5W at 100% output)
Frequency: 40kHz
Focal length: 300 mm (Focus is performed using the height correction attached to the device)
Spot diameter: 40 μm (at the time of focusing)
Fill interval: 0.3mm
Scan speed: 5000mm/sec
Spot variable: 100
In addition, only Example 22 was carried out at an output of 40%.

<Clearness evaluation>
Using a digital microscope (manufacturer name: KEYENCE CORPORATION, model number: VHX-8000), a depth-stacked image of the vicinity of the printing area to be evaluated was acquired (FIGS. 1(a) and 1(b)). A depth stacking image is an image obtained by moving the focal length to obtain a plurality of images, extracting the in-focus portion from each image, and constructing one image. Focus stacking images were acquired using the live focus stacking function installed in the digital microscope.
Note that FIG. 1A is a focus stacking image of Comparative Example 2, and FIG. 1B is a focus stacking image of Example 4. FIG.
After that, using the brightness extraction mode of the automatic area measurement function, the area of the area darker than the threshold was measured in the printing unit. The brightness extraction mode is a mode in which the luminance level of an image is hierarchized from -255 to 255 and an area above or below an arbitrary threshold is extracted. Regarding the printed part, it was decided that the larger the area where the luminance level was lower than the threshold value, the more "dark printed" it was.
(Settings when shooting images)
Shutter speed: Auto mode (set value 70)
Gain: 0dB
Magnification: 1000 times Lighting: Ring lighting (brightness extraction mode setting)
Magnification when acquiring a depth composite image: 1000x Lighting: coaxial epi-illumination 100%
Shutter speed: Auto mode 70
Gain: 0dB
Threshold: -10
Extraction area: Inside a circle with a radius of 50 μm from the center of the printed area (evaluation criteria for the darkness of the printed area)
A: The area of a region with a luminance level lower than -10 is 70% or more of the extracted region B: The area of a region with a luminance level lower than -10 is 65% or more and less than 70% of the extracted region C: The luminance level is lower than -10 The area of the region is 60% or more and less than 65% of the extraction region D: The area of the region with a luminance level lower than -10 is 40% or more and less than 60% of the extraction region E: The area of the region with a luminance level lower than -10 is the extraction region less than 40% of

[Print uniformity]
Using an ultraviolet laser irradiation machine (manufacturer: Keyence Corporation, model number: MD-U1020C), a 10 mm square was printed on the sample surface of the ultraviolet laser printing paper obtained in Examples and Comparative Examples.
(Printing conditions)
Wavelength: 355nm
Output: 80% (2.5W at 100% output)
Frequency: 40kHz
Focal length: 300 mm (Focusing is performed using the height correction attached to the device)
Spot diameter: 40 μm (when focused)
Fill interval (line pitch): 0.05mm
Scan speed 3000mm/sec
Spot variable: -100

(Evaluation of print uniformity)
100 squares were printed, and the print uniformity was evaluated according to the following criteria based on the number of squares in which a density difference (printing non-uniformity) was visually identifiable in one square.
A: less than 3 squares with a gradation difference per 100 squares B: 3 or more and less than 5 squares with a gradation difference per 100 squares C: per 100 squares , The number of squares with gradation difference is 5 or more and less than 10 D: The number of squares with gradation difference is 10 or more per 100 squares

[Smoke]
When evaluating print uniformity, the amount of smoke generated when a 10 mm×10 mm square was printed on the sample surface by ultraviolet laser irradiation was evaluated according to the following criteria.
(criterion)
A: Smoke generation cannot be visually confirmed, or smoke generation can be confirmed faintly, but very little B: Smoke generation can be visually confirmed, but the amount of smoke generation is small C: Smoke generation can be visually confirmed, but it affects printing Not as much D: Smoke generation can be easily confirmed visually, and the amount of smoke generation is large enough to scatter the light of the ultraviolet laser and affect printing.

According to the results in Table 2, by printing with an ultraviolet laser using the printing paper of the example, a printed matter having a printed image with excellent print clarity for each point was obtained.
The printing paper of Example 6 using titanium oxide having a crystallite size of 55.3 nm, which has a relatively large crystallite size, exhibited a decrease in printing uniformity, presumably due to a decrease in the dispersion stability of titanium oxide. Admitted.
When the printing papers of Comparative Examples 1 and 2 containing titanium oxide having a crystallite size of less than 30 nm were used, printed images with poor print sharpness were obtained even when printed with an ultraviolet laser. . Further, even with the printing paper of Comparative Example 3 in which the content of titanium oxide in the printing layer was less than 0.1 g/m ² , sufficient print sharpness was not obtained for each point.

In the printing paper of the present invention, the titanium oxide is discolored by irradiation with an ultraviolet laser, so that printed matter with excellent visibility can be provided, and the printing clarity of each point is excellent. The ultraviolet laser printing paper of the present invention is suitably applied to processed products such as packages, labels, and adhesive tapes on which variable information such as dates and bar codes are printed. Furthermore, the method for producing printed matter of the present invention is suitably applied to printing variable information on packages, labels, adhesive tapes, and the like.

Claims (15)

Having a printed layer containing titanium oxide on a paper substrate,
The content of the titanium oxide in the printed layer is 0.1 g/m ² or more,
The crystallite size of titanium oxide in the printed layer is 30 nm or more,
Ultraviolet laser printing paper. 2. The ultraviolet laser printing paper according to claim 1, wherein said titanium oxide has a crystallite size of 53 nm or less. 2. The ultraviolet laser printing paper according to claim 1, wherein the titanium oxide in the printing layer is rutile type titanium oxide, and the diffraction angle of said titanium oxide is 27.60[deg.] or less. 2. The ultraviolet laser printing paper according to claim 1, wherein the length-weighted average fiber length of the pulp constituting the paper substrate is 2.0 mm or less. 2. The ultraviolet laser printing paper according to claim 1, wherein the content of titanium oxide in said printing layer is 10 g/m ^<2> or less. 2. The ultraviolet laser printing paper according to claim 1, wherein the number ratio of fine fibers having a fiber length of 0.2 mm or less is 4% or more and 40% or less in the pulp fibers constituting the paper substrate. 2. The ultraviolet laser printing paper according to claim 1, wherein the pulp fibers constituting the paper substrate have a water retention of 100% or more. A printed matter obtained from the ultraviolet laser printing paper according to any one of claims 1 to 7,
The printed layer has, at least in part, a printed region containing discolored titanium oxide,
A printed matter, wherein the ratio of the Raman intensity derived from titanium oxide in the printed region to the Raman intensity derived from titanium oxide in the non-printed region is 0.70 or less. A processed product using the ultraviolet laser printing paper according to any one of claims 1 to 7. A processed product using the printed matter according to claim 8 . A step of printing by irradiating the ultraviolet laser printing paper according to any one of claims 1 to 7 with an ultraviolet laser to change the color of the irradiated area,
A method for producing printed matter. The step of printing is a step of irradiating an ultraviolet laser so that the ratio of the Raman intensity derived from titanium oxide in the printed region to the Raman intensity derived from titanium oxide in the non-printed region is 0.70 or less. The method for producing a printed matter according to claim 11. An ink composition containing titanium oxide having a crystallite size of 30 nm or more and used for forming a printed layer that changes color when irradiated with an ultraviolet laser. 14. The ink composition according to claim 13, wherein the titanium oxide has a crystallite size of 53 nm or less. 15. The ink composition according to claim 13 or 14, wherein the titanium oxide is rutile-type titanium oxide and has a diffraction angle of 27.60° or less.

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