Laminated film, packaging, and method for manufacturing packaging

Abstract

To provide a laminated film capable of improving contrast, a package and a method for producing a package.SOLUTION: There is provided a metal compound which is a transition metal oxide or transition metal sulfide, wherein a first particle 22A and a second particle 23A are the separate metal compounds which develop color by a laser, a metal compound contained in a color developing ink layer 22 is the first particle 22A, a metal compound contained in a white ink layer 23 is the second particle 23A, the color developing ink layer 22 has a color developing part and a non-color development part, the first particle 22A in the color developing part contains a colored first particle 22A, the first particle 22A in the non-color development part is uncolored, the second particle 23A in the white ink layer 23 is uncolored and the absorption end wavelength of the first particle 22A in the UV wavelength region is shorter than the absorption end wavelength of the second particle 23A.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a laminated film used for laser marking, a package formed from the laminated film, and a method for manufacturing the package.

Background Art

[0002] Packages for general consumer goods and medical pharmaceuticals have symbols such as one-dimensional symbols and two-dimensional symbols. The symbols encode the manufacturing date, expiration date, quantity, manufacturing number, and the like. Laser marking for forming the symbols prints elements in a predetermined range of the laminated film.

[0003] A first example of the laminated film includes a color-developing ink layer between a base material and an undercoat ink layer. The color-developing ink layer contains a metal oxide. The metal oxide is silicon oxide, iron oxide, magnesium oxide, cobalt oxide, lead oxide, tin oxide, indium oxide, manganese oxide, molybdenum oxide, or the like. The color-developing ink layer develops color by irradiation with a laser having a wavelength of 1064 nm. The undercoat ink layer has a white or yellow color and has a thickness of three times or more the thickness of the color-developing ink layer. The undercoat ink layer contains titanium oxide. The undercoat ink layer is overprinted on the color-developing ink layer and enhances the contrast as a base for the color-developing ink layer (see, for example, Patent Document 1).

[0004] The color-developing ink layer of the second example contains a bismuth compound such as bismuth hydroxide, bismuth oxide, or bismuth nitrate, or a molybdenum compound such as molybdenum dioxide, molybdenum trioxide, or molybdenum chloride. The color-developing ink layer develops color by irradiation with a 1064 nm laser. The undercoat ink layer contains a white pigment such as anatase-type titanium oxide, rutile-type titanium oxide, or calcium carbonate and clarifies the image of the color-developing ink layer (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2008-279701 [Patent Document 2] Japanese Patent Publication No. 2016-179559 [Overview of the project] [Problems that the invention aims to solve]

[0006] Suppressing the reading errors of the aforementioned symbols enables robust quality control of consumer goods and pharmaceuticals. While scanners and other reading devices provide sufficient reading accuracy to suppress reading errors, the print quality of the symbols still leaves room for improvement in suppressing reading errors.

[0007] For example, the particle density of the color-developing ink layer described above is, naturally, suitable for printing. The particle density suitable for printing is not in the high-density range where a good pot life cannot be obtained. The particle density suitable for printing is such that the underlying ink layer is visible through the color-developing ink layer. The organic components of the underlying ink layer that are visible through the color-developing ink layer are carbonized by the 1064nm laser that penetrates the color-developing ink layer. Discoloration of the underlying ink layer reduces the reflectivity of the underlying ink layer and also gives the laminated film transparency to the extent that the underlying layer is visible through the color-developing area and the underlying ink layer. Thus, there is still room for improvement in print quality such as contrast. [Means for solving the problem]

[0008] A laminated film for solving the above problems comprises a resin substrate layer that transmits a laser with a transmission wavelength in the ultraviolet wavelength range, a thermoplastic resin layer, a color-developing ink layer located between the resin substrate layer and the thermoplastic resin layer, and a white ink layer located between the color-developing ink layer and the thermoplastic resin layer. The metal compound is a transition metal oxide or a transition metal sulfide, the first particle and the second particle are separate metal compounds that develop color with the laser, the metal compound contained in the color-developing ink layer is the first particle, and the metal compound that exhibits white color in the white ink layer is the second particle. The color-developing ink layer comprises a colored portion and an uncolored portion, the first particle in the colored portion includes the colored first particle, the first particle in the uncolored portion is uncolored, the second particle in the white ink layer is uncolored, and the absorption edge wavelength of the first particle in the ultraviolet wavelength range is shorter than the absorption edge wavelength of the second particle.

[0009] A method for manufacturing a packaging body to solve the above problems includes irradiating a laminated film with a laser having a transmission wavelength that is in the ultraviolet wavelength range, and forming a packaging body by thermal fusion of the thermoplastic resin layers of the laminated film. The laminated film comprises a resin substrate layer that transmits the laser of the transmission wavelength, a thermoplastic resin layer, a color-developing ink layer located between the resin substrate layer and the thermoplastic resin layer, and a white ink layer located between the color-developing ink layer and the thermoplastic resin layer. The metal compound is a transition metal oxide or a transition metal sulfide, the first particle and the second particle are separate metal compounds that develop color with the laser, the metal compound contained in the color-developing ink layer is the first particle, and the metal compound that exhibits white color in the white ink layer is the second particle. The absorption edge wavelength of the first particle in the ultraviolet wavelength range is shorter than the absorption edge wavelength of the second particle. The laser irradiation is performed by irradiating the colored ink layer with a laser of the transmission wavelength through the resin substrate layer so that the second particles of the white ink layer remain uncolored, thereby separating the colored ink layer into an uncolored portion where the first particles are not colored and a colored portion containing the colored first particles.

[0010] According to the above configuration, the first particle develops color upon irradiation with a laser of a transmission wavelength in the ultraviolet wavelength range. Therefore, even if the laser irradiated onto the colored ink layer penetrates into the white ink layer, the organic components of the white ink layer are less likely to carbonize compared to irradiation with a 1064 nm laser. Furthermore, the second particle, which could develop color upon irradiation with a transmission wavelength laser, remains uncolored. Therefore, (A1) the uncolored second particle and (B1) the suppression of carbonization of the organic components work together to suppress the decrease in reflectivity of the white ink layer. As a result, the contrast derived from the difference in reflectivity between the colored and uncolored areas is increased.

[0011] Furthermore, the laminated film has a white ink layer positioned on the opposite side of the resin substrate layer that transmits the laser of the transmitted wavelength, and the color-developing ink layer contains first particles that develop color upon irradiation with the laser of the transmitted wavelength. In this way, the laminated film is configured to promote (A1) the non-development of the second particles and (B1) the suppression of carbonization of organic components. This also increases the likelihood of obtaining high contrast.

[0012] Furthermore, because the absorption edge wavelength of the first particle is shorter than that of the second particle, there is a wavelength within the ultraviolet wavelength range that is more likely to cause only the second particle to develop color. Therefore, if the color development of the first particle is weak, there is a risk that the color development of the second particle, and consequently the discoloration of the white ink layer, is progressing. In this way, by detecting the degree of color development of the first particle, it is possible to estimate whether or not there is a decrease in reflectivity in the white ink layer. In addition, by detecting the difference between the degree of color development of the first particle and the degree of color development of the second particle, it is possible to accurately determine whether the laser irradiated onto the laminated film is suitable. This, in turn, makes manufacturing control of the laminated film easier.

[0013] In the laminated film described above, the first particle may include at least one selected from the group consisting of bismuth trioxide and zinc oxide, and the second particle may include at least one selected from the group consisting of zinc sulfide and titanium oxide.

[0014] In the laminated film described above, the first particle may be bismuth trioxide, and the second particle may be zinc sulfide. In the laminated film described above, the organic component of the white ink layer does not need to be carbonized.

[0015] Each of the above configurations enhances the effectiveness of achieving the aforementioned contrast improvement effect. The laminated film for solving the above problems comprises a resin substrate layer that transmits a laser with a transmission wavelength in the ultraviolet wavelength range, a thermoplastic resin layer, a color-developing ink layer located between the resin substrate layer and the thermoplastic resin layer, and a white ink layer located between the color-developing ink layer and the thermoplastic resin layer. The metal compound is a transition metal oxide or a transition metal sulfide, the first particle and the second particle are separate metal compounds that develop color with the laser, the metal compound contained in the color-developing ink layer is the first particle, and the metal compound that exhibits white color in the white ink layer is the second particle. The absorption edge wavelength of the first particle in the ultraviolet wavelength range is shorter than the absorption edge wavelength of the second particle. The colored ink layer comprises a colored portion and a non-colored portion, the first particles of the colored portion include colored first particles, the first particles of the non-colored portion are non-colored, the organic components of the white ink layer are not carbonized, and the second particles in the portion of the white ink layer that is in contact with the non-colored portion are non-colored.

[0016] A method for manufacturing a packaging body to solve the above problems includes irradiating a laminated film with a laser having a transmission wavelength that is in the ultraviolet wavelength range, and forming a packaging body by thermal fusion of the thermoplastic resin layers of the laminated film. The laminated film comprises a resin substrate layer that transmits the laser of the transmission wavelength, a thermoplastic resin layer, a color-developing ink layer located between the resin substrate layer and the thermoplastic resin layer, and a white ink layer located between the color-developing ink layer and the thermoplastic resin layer. The metal compound is a transition metal oxide or a transition metal sulfide, the first particle and the second particle are separate metal compounds that develop color with the laser, the metal compound contained in the color-developing ink layer is the first particle, and the metal compound that exhibits white color in the white ink layer is the second particle. The absorption edge wavelength of the first particle in the ultraviolet wavelength range is shorter than the absorption edge wavelength of the second particle. The laser irradiation is performed by irradiating the colored ink layer with a laser of the transmission wavelength through the resin substrate layer, in such a way that the colored ink layer is divided into an uncolored portion where the first particles have not yet developed color and a colored portion containing the colored first particles, and without carbonizing the organic components of the white ink layer, the second particles in the portion of the white ink layer that is in contact with the uncolored portion remain uncolored.

[0017] According to the above configuration, the first particle develops color upon laser irradiation with a transmission wavelength in the ultraviolet wavelength range. Therefore, even if the laser irradiated onto the colored ink layer penetrates into the white ink layer, the organic components of the white ink layer are less likely to carbonize compared to irradiation with a 1064nm laser. As a result, the organic components of the white ink layer remain uncarbonized, and the second particle in the part of the white ink layer that is in contact with the uncolored area remains uncolored. Therefore, (A2) the suppression of color development of the second particle and (B2) the uncarbonization of the organic components work together to suppress the decrease in reflectivity of the white ink layer. As a result, the contrast derived from the difference in reflectivity between the colored and uncolored areas is increased.

[0018] Further, the laminated film has a white ink layer disposed on the side opposite to the resin base material layer that transmits the laser with a transmission wavelength, and the coloring ink layer includes first particles that are colored by irradiation with the laser having the transmission wavelength. Thus, the laminated film is configured to promote (A2) suppression of coloring of the second particles and (B2) non-carbonization of the organic components. Therefore, the probability of obtaining high contrast is also increased.

[0019] In addition, since the absorption edge wavelength of the first particles is shorter than the absorption edge wavelength of the second particles, there is a wavelength in the ultraviolet wavelength range at which only the second particles are likely to be colored. Therefore, if the coloring of the first particles is weak, the coloring of the second particles, and thus the discoloration of the white ink layer, may progress. Thus, by detecting the degree of coloring of the first particles, the presence or absence of a decrease in reflectance in the white ink layer can be estimated. Also, by detecting the difference between the degree of coloring of the first particles and the degree of coloring of the second particles, the suitability of the laser irradiated to the laminated film can be accurately determined. As a result, the traceability related to the production of the laminated film is enhanced.

[0020] The package for solving the above problems includes the laminated film described above.

Effects of the Invention

[0021] According to the above laminated film, package, and method for manufacturing the package, the contrast derived from the reflectance difference between the colored portion and the non-colored portion is increased.

Brief Description of the Drawings

[0022] [Figure 1] FIG. 1 is a plan view of the package. [Figure 2] FIG. 2 is a cross-sectional view of the laminated film. [Figure 3] FIG. 3 is a table showing the evaluation results of the test example. [Figure 4] FIG. 4 is a graph showing the ultraviolet transmission spectrum of the test example.

Embodiments for Carrying Out the Invention

[0023] The following describes one embodiment of a laminated film, a packaging body, and a method for manufacturing the packaging body. [Package 11] As shown in Figure 1, an example of packaging 11 is a four-sided sealed packaging for medical pharmaceuticals. The four sides of the storage section 13 of packaging 11 are sealed by heat-sealed sections 12. The storage section 13 contains pharmaceuticals such as tablets and powders. Packaging 11 is equipped with a symbol 14. An example of a symbol 14 is a data bar with multiple elements. An element consists of a bar and a space. The symbol 14 has standardized bar thickness, bar height, and element thickness. The symbol 14 encodes the product code, expiration date, quantity, manufacturing number, etc., related to the contents of packaging 11.

[0024] The packaging 11 is not limited to a four-sided sealed packaging, but may also be a side-sealed packaging, a two-sided sealed packaging, a three-sided sealed packaging, an envelope-type sealed packaging, a pillow-sealed packaging, a pleated sealed packaging, a flat-bottom sealed packaging, or a square-bottom sealed packaging. The packaging 11 may also be a one-piece type packaging, a two-piece type packaging, or a packaging equipped with a spout or a zipper for opening and closing. The packaging 11 may also be a self-standing packaging, a tube container, or a liquid-filled paper container including a paper base layer. The packaging 11 may contain various food and beverages such as food and beverages, fruit juice, juice, drinking water, alcohol, prepared foods, processed seafood products, frozen foods, meat products, stews, mochi, liquid soups, seasonings, etc., as well as liquid detergents, cosmetics, and chemical products.

[0025] Furthermore, symbol 14 is not limited to one-dimensional symbols such as data bars; it may also be a two-dimensional symbol such as a two-dimensional code, a string code, a numeric code, or a combination of these.

[0026] One example of a method for manufacturing the packaging 11 is a bag-making method using two laminated films 20 (see Figure 2). First, the two laminated films 20 are stacked so that the thermoplastic resin layers 25 are in contact with each other. Next, the thermoplastic resin layers 25 located on the four sides of the area that will become the containment section 13 are heat-sealed together, and the contents are placed in the containment section 13, thereby manufacturing a four-sided sealed packaging 11. The method for forming the heat-sealed section 12 can be, for example, a bar seal, a rotary roll seal, a belt seal, an impulse seal, a high-frequency seal, or an ultrasonic seal. During this process, a symbol 14 is formed by laser marking either before or after the contents are placed inside. This manufactures a packaging 11 with the symbol 14.

[0027] The manufacturing method for the packaging 11 may also be one of the two bag-making methods exemplified below. Another example of a method for manufacturing the packaging 11 uses a single laminated film 20 (see Figure 2). First, the laminated film 20 is folded in half so that the thermoplastic resin layers 25 of the single laminated film 20 are in contact with each other. Next, the thermoplastic resin layers 25 on three sides of the folded laminated film 20 are heat-sealed together to produce a three-sided sealed packaging 11 with a heat-sealed portion 12.

[0028] Another example of a method for manufacturing the packaging 11 uses a single laminated film 20 (see Figure 2). The laminated film 20 is bent into a cylindrical shape so that it is the inside of the cylindrical body of the single laminated film 20. Next, the thermoplastic resin layers 25 located at the connection points of the cylindrical surface are heat-sealed to form a back-sealed portion, and the thermoplastic resin layers 25 located at the upper and lower openings of the cylindrical surface are heat-sealed to form a pillow-seal type packaging 11 with a heat-sealed portion 12.

[0029] When the laminated film 20 is used as a material for the packaging 11, it is required to be strong, tough, and heat resistant. In this case, the laminated film 20 used as a material for the packaging 11 may further include an aluminum layer, or in addition to the aluminum layer, a barrier layer that prevents the permeation of, for example, oxygen gas or water vapor, cellophane, or a plastic film between the white ink layer 23 and the thermoplastic resin layer 25 (see Figure 2).

[0030] [Laminated film 20] As shown in Figure 2, the laminated film 20 comprises a resin substrate layer 21, a color-developing ink layer 22, a white ink layer 23, an adhesive resin layer 24, and a thermoplastic resin layer 25.

[0031] Laser marking involves irradiating a laser from the resin substrate layer 21 toward the color-developing ink layer 22. The wavelength of the laser irradiated onto the resin substrate layer 21 is in the ultraviolet wavelength range. The wavelength of the laser irradiated onto the resin substrate layer 21 is the transmission wavelength that penetrates the resin substrate layer 21. The ultraviolet wavelength range is near ultraviolet, and is between 200 nm and 400 nm. The ultraviolet wavelength range is classified into UV-A (315 nm to 380 nm), UV-B (280 nm to 315 nm), and UV-C (200 nm to 280 nm).

[0032] The resin substrate layer 21 is irradiated with a laser from outside the laminated film 20. The resin substrate layer 21 is located on the laser incidence side with respect to the color-developing ink layer 22. The color-developing ink layer 22 is located between the resin substrate layer 21 and the adhesive resin layer 24. The color-developing ink layer 22 is located on the laser incidence side with respect to the adhesive resin layer 24. The color-developing ink layer 22 contains first particles 22A. The adhesive resin layer 24 is located between the color-developing ink layer 22 and the thermoplastic resin layer 25. The adhesive resin layer 24 is located on the laser incidence side with respect to the thermoplastic resin layer 25.

[0033] The metal compound contained in the color-developing ink layer 22 is the first particle 22A. The metal compound that appears white in the white ink layer 23 is the second particle 23A. The first particle 22A and the second particle 23A are different metal compounds that develop color when irradiated with a laser of a transmitted wavelength. The metal compounds are transition metal oxides or transition metal sulfides. The color-developing ink layer 22 and the white ink layer 23 may be arranged throughout the entire laminated film 20, or they may be arranged only in the portion of the laminated film 20 where the symbol 14 is placed. The color-developing portion 221 printed on the color-developing ink layer 22 by laser marking constitutes the symbol 14.

[0034] The absorption edge wavelength of the first particle 22A in the ultraviolet wavelength range is shorter than the absorption edge wavelength of the second particle 23A. The absorption edge wavelength is the wavelength in the ultraviolet wavelength range in an ink layer with a unit thickness. The unit thickness is, for example, 1 μm. The absorption edge wavelength is the longest wavelength in the ultraviolet wavelength range that satisfies the requirement that the transmittance of the colored ink layer 22 containing the first particle 22A is less than 1%. The absorption edge wavelength is the longest wavelength in the ultraviolet wavelength range that satisfies the requirement that the transmittance of the white ink layer 23 containing the second particle 23A is less than 1%. The absorption edge wavelength of the first particle 22A may be directly derived from the ultraviolet transmission spectrum of the colored ink layer 22 containing the first particle 22A. The absorption edge wavelength of the second particle 23A may be directly derived from the ultraviolet transmission spectrum of the white ink layer 23 containing the second particle 23A.

[0035] The absorption edge wavelength of the first particle 22A may be indirectly derived from the ultraviolet transmission spectrum of a laminate comprising a colored ink layer 22 containing the first particle 22A and a white ink layer 23 containing the second particle 23A. For example, in comparing the ultraviolet transmission spectra of two laminates comprising a colored ink layer 22 containing mutually different first particles 22A and a white ink layer 23 containing a common second particle 23A, the white ink layer 23 functions as an internal standard. The common point of the two ultraviolet transmission spectra originates from the white ink layer 23, while the differences between the two ultraviolet transmission spectra originate from the respective colored ink layers 22. The longest wavelength at the common point of the two ultraviolet transmission spectra is considered to be the absorption edge wavelength of the second particle 23A. The longest wavelengths at the differences between the two ultraviolet transmission spectra are considered to be the absorption edge wavelengths of the separate first particles 22A.

[0036] Laser marking involves irradiating the color-developing ink layer 22 with a laser of a transmission wavelength to change the color of the first particles 22A contained in the irradiated area. Laser marking also involves either not irradiating the white ink layer 23 with a laser of a transmission wavelength, or irradiating the white ink layer 23 with a laser of a transmission wavelength to an extent that does not cause discoloration of the second particles 23A.

[0037] [Resin base layer 21] The resin substrate layer 21 contains a resin that transmits lasers of the transmitted wavelength. The transmittance of the transmitted wavelength in the resin substrate layer 21 is higher than the transmittance of the transmitted wavelength in the first particle 22A. Laser transmittance includes both direct transmission and diffuse transmission. The high transmittance of the transmitted wavelength in the resin substrate layer 21 promotes discoloration of the first particle 22A by irradiation with a laser of the transmitted wavelength. The high transmittance of the transmitted wavelength in the resin substrate layer 21 suppresses discoloration of the resin substrate layer 21 by irradiation with a laser of the transmitted wavelength. The transmittance of the transmitted wavelength in the resin substrate layer 21 is, for example, 70% or more. From the viewpoint of making it easier for the laser of the transmitted wavelength to reach the color-developing ink layer 22, the transmittance of the transmitted wavelength in the resin substrate layer 21 is more preferably 80% or more, and even more preferably 90% or more.

[0038] The constituent material of the resin substrate layer 21 may be at least one selected from the group consisting of polyolefin resins, polyolefin copolymers, acid-modified polyolefins, chlorinated polyolefin resins, polyester resins, polystyrene resins, and polypropylene resins. The constituent material of the resin substrate layer 21 may be at least one selected from the group consisting of ethylene resins, acrylic resins, polyvinyl chloride resins, polyvinyl alcohol, ethylene-vinyl alcohol, and polyvinyl acetate resins. The constituent material of the resin substrate layer 21 may be at least one selected from the group consisting of polyacetal, acetyl-di or tricellulose cellulose derivatives, fluorine resins, polyamide resins, polyimide resins, and polyamide-imide resins. The constituent material of the resin substrate layer 21 may be at least one selected from the group consisting of polyarylphthalate resins, silicone resins, polysulfone resins, polyphenylene sulfide resins, and polyethersulfone resins. The constituent material of the resin substrate layer 21 may be at least one selected from the group consisting of urethane resin, polycarbonate resin, acetal resin, and cellulose resin. The constituent material of the resin substrate layer 21 may be a single material or a mixture of two or more materials.

[0039] The polyolefin resin may be polyethylene, polypropylene, methylpentene polymer, polybutene polymer, or cyclic polyolefin. The polyethylene may be low-density polyethylene, linear or linear low-density polyethylene, medium-density polyethylene, or high-density polyethylene. The polyolefin copolymer may be ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, or ionomer resin.

[0040] Acid-modified polyolefin resins may be resins obtained by modifying polyolefin resins such as polyethylene and polypropylene with unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, and itaconic acid. Chlorinated polyolefin resins may be resins having a structure in which hydrogen atoms in an α-olefin polymer are replaced with chlorine. Chlorinated polyolefin resins may also be copolymer resins of α-olefin and other monomers other than α-olefin.

[0041] The polystyrene resin may be an acrylonitrile-styrene copolymer or an acrylonitrile-butadiene-styrene copolymer. The polypropylene resin may be a blend of polypropylene and polybutene, a homopolypropylene resin, a propylene-ethylene random copolymer, a propylene-ethylene block copolymer, or a propylene-α-olefin copolymer.

[0042] The polyester resin may be polyethylene terephthalate (PET), polybutylene terephthalate (PBT), or polyethylene naphthalate. The polyamide resin may be, for example, nylon-6 or nylon-66. The cellulose resin may be a cellulose derivative of acetyldicellulose or acetyltricellulose.

[0043] The acrylic resin may be a resin mainly composed of acrylic acid ester or methacrylic acid ester, or a resin obtained by radical polymerization of acrylic monomers. The acrylic monomer may be methyl (meth)acrylate, ethyl (meth)acrylate, alkyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, or pentyl (meth)acrylate. The acrylic monomer may also be hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, or dodecyl (meth)acrylate. The acrylic monomer may also be tetradecyl (meth)acrylate, hexadecyl (meth)acrylate, or octadecyl (meth)acrylate. The acrylic monomer may have a benzene ring structure in the alkyl group of the above-mentioned examples, or it may have a hydroxyl group.

[0044] The ethylene-based resin may also be ethylene-vinyl acetate copolymer, ethylene-α-olefin copolymer, ethylene-methacrylic acid resin copolymer, ethylene-ethyl acrylate copolymer, or ethylene-acrylic acid copolymer.

[0045] Urethane resins are obtained from polyester polyols or polyether polyols and diisocyanate compounds. Urethane resins may also be obtained using chain extenders and reaction stoppers. Polyester polyols are condensates of dibasic acids such as adipic acid, phthalic anhydride, and isophthalic acid with glycols such as ethylene glycol, propylene glycol, and butanediol. Polyether polyols may be polyethylene glycol, polypropylene glycol, or polytetramethylene glycol. Diisocyanate compounds may be tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, or isophorone diisocyanate. Chain extenders may be ethylenediamine, hexamethylenediamine, or isophoronediamine. Reaction stoppers may be n-butylamine, monoethanolamine, methanol, or ethanol.

[0046] The resin substrate layer 21 is a stretched film or an unstretched film. The resin substrate layer 21 is a single substrate film or a laminate of multiple substrate films. From the viewpoint of reducing the scattering of the laser irradiated onto the laminated film 20, it is preferable that the resin substrate layer 21 be a single substrate film. Reducing laser scattering reduces the laser output required for laser marking and narrows the pulse width. Reducing laser scattering reduces the thermal load on the laminated film 20 caused by the laser. This suppresses blackening of the resin in the resin substrate layer 21 and thermoplastic resin layer 25, and the generation of volatile particles. It also suppresses the generation of pinholes in the resin substrate layer 21 and the colored ink layer 22. From the viewpoint of improving heat resistance and reducing material costs, it is preferable that the resin substrate layer 21 be a biaxially oriented PET film or a biaxially oriented polypropylene film (OPP film).

[0047] The thickness of the resin substrate layer 21 may be 3 μm or more and 40 μm or less. From the viewpoint of enhancing the protective function of the resin substrate layer 21 and enhancing the laser transmission function of the resin substrate layer 21, the thickness of the resin substrate layer 21 is preferably 4 μm or more and 30 μm or less. If the thickness of the resin substrate layer 21 is 3 μm or more, the color-developing ink layer 22 that is laser-marked is protected from the external environment. If the thickness of the resin substrate layer 21 is 40 μm or less, the laser irradiated onto the resin substrate layer 21 effectively reaches the color-developing ink layer 22. The thickness of the resin substrate layer 21 is appropriately selected considering the output and pulse width of the laser reaching the color-developing ink layer 22, the bending suitability and tensile strength of the laminated film 20, and the peel strength after heat fusion in the thermoplastic resin layer 25. From the viewpoint of making the difference between the discolored first particles 22A and the undiscolored first particles 22A within the color-developing ink layer 22 easily visible from the outside, the resin substrate layer 21 is preferably a transparent resin layer, and more preferably a colorless transparent resin layer.

[0048] [Color-developing ink layer 22] The colored ink layer 22 is composed of ink that has hardened due to the evaporation of a solvent. The colored ink layer 22 comprises a colored portion 221 and an uncolored portion 222. The colored portion 221 and the uncolored portion 222 are adjacent to each other. The colored portion 221 is the part of the colored ink layer 22 that has been irradiated with a laser of a transmission wavelength. The uncolored portion 222 is the part of the colored ink layer 22 that has not been irradiated with a laser. The colored portion 221 that constitutes the symbol 14 is read by a reading device.

[0049] The first particles 22A contained in the color-developing section 221 include colored first particles 22A. All of the first particles 22A contained in the color-developing section 221 may be colored first particles 22A. The first particles 22A contained in the color-developing section 221 may also include uncolored first particles 22A. All of the first particles 22A contained in the uncolored section 222 are uncolored first particles 22A.

[0050] The color-developing ink layer 22 is printed on one side of the resin substrate layer 21. The printing method for forming the color-developing ink layer 22 is appropriately selected from known printing methods, taking into consideration the printability of the resin substrate layer 21, design properties such as color tone, adhesion to other layers, and safety as a laminated film 20 or packaging formed from the laminated film 20. The printing method for forming the color-developing ink layer 22 may be gravure printing, offset printing, gravure offset printing, flexographic printing, or inkjet printing. From the viewpoint of high productivity of the color-developing ink layer 22 and high resolution of the color-developing ink layer 22, the printing method for forming the color-developing ink layer 22 is preferably gravure printing. The color-developing ink layer 22 may be printed on the entire surface of the resin substrate layer 21, or it may be printed only within the display area of ​​the symbol 14. The configuration in which the color-developing ink layer 22 is provided only within the display range of the symbol 14 reduces the amount of constituent material required for the color-developing ink layer 22 compared to a configuration in which the color-developing ink layer 22 is provided over the entire surface of the resin substrate layer 21.

[0051] The color-developing ink layer 22 contains first particles 22A that change color when irradiated with a laser of a transmitted wavelength, a first binder 22B, and a first curing agent 22C that crosslinks the first binder 22B. The first binder 22B and the first curing agent 22C are organic components that make up the color-developing ink layer 22. The organic components of the color-developing portion 221 and the organic components of the uncolored portion 222 are not carbonized and are colorless and transparent.

[0052] Furthermore, some of the organic components of the color-developing section 221 may exhibit black coloration through carbonization. The color-developing ink layer 22 may contain additives to improve printability and additives to improve the chemical stability of the color-developing ink layer 22. Examples of additives include leveling agents, defoaming agents, antistatic agents, infrared absorbers, and ultraviolet absorbers. The organic components of the color-developing section 221 may omit the first curing agent 22C.

[0053] The first particle 22A is dispersed almost uniformly within the color-developing ink layer 22. The constituent material of the first particle 22A may be colorless. Colorless includes not only colorless and transparent, but also achromatic white. White includes not only pure white, but also white-based colors. White-based colors include light beige, light eggshell, white, and ivory, which are more yellowish than pure white. White-based colors include oyster brown, which is more greenish than pure white, snow white, which is more bluish-purple than pure white, and moon white, which is more blue than pure white. White-based colors include grayish white, which has a lower brightness than pure white.

[0054] The constituent material of the first particle 22A is selected from the group consisting of dibismuth trioxide and zinc oxide. The constituent material of the first particle 22A may be a single material or a mixture of two or more materials. The first particle 22A changes color when irradiated with a laser having a transmission wavelength.

[0055] The content of the first particles 22A is 5% by mass or more and 90% by mass or less, with a more preferable value of 10% by mass or more and 65% by mass or less, relative to the weight of the color-developing ink layer 22, that is, relative to the total amount of solid components in the ink for forming the color-developing ink layer 22. If the content of the first particles 22A is 5% by mass or more, it is possible to use the first particles 22A as achromatic while suppressing the lifting of the resin substrate layer 21, and to apply it to GS1 barcode printing and the like. If the content of the first particles 22A is 90% by mass or less, the pot life of the ink can be ensured, and high adhesion between the resin substrate layer 21 and the color-developing ink layer 22 can be ensured by adding the first curing agent 22C.

[0056] The first binder 22B is a resin having functional groups that are crosslinked by the first curing agent 22C. The transmittance of the first binder 22B at the transmission wavelength is higher than the transmittance of the first particle 22A at the transmission wavelength. Preferably, the transmittance of the first binder 22B at the transmission wavelength is such that the first binder 22B does not change color when the first particle 22A changes color due to laser irradiation. The transmittance of the first binder 22B at the transmission wavelength may be 70% or higher. From the viewpoint of making it easier for the laser at the transmission wavelength to reach the first particle 22A, it is more preferable that the transmittance of the first binder 22B at the transmission wavelength be 80% or higher, and even more preferable that be 90% or higher.

[0057] The first binder 22B may be at least one selected from the group consisting of vinyl chloride-vinyl acetate copolymer resin, vinyl acetate resin, ethylene-vinyl acetate copolymer resin, acrylic resin, acrylic-modified urethane resin, urethane resin, ethylene-acrylic copolymer resin, polyamide resin, hydroxyethylcellulose, hydroxypropylcellulose, nitrocellulose resin, polyester resin, polyvinyl chloride resin, polyvinyl acetal resin, and styrene-acrylic resin. The binder resin may be a single resin or a mixture of two or more resins.

[0058] From the viewpoint of high adhesion between the resin substrate layer 21 and the color-developing ink layer 22, it is preferable that the first binder 22B is an acrylic-modified urethane resin and a urethane resin. The acrylic-modified urethane resin and the urethane resin are obtained by the reaction of a polyester polyol or polyether polyol with a diisocyanate compound. The urethane resin is obtained using a chain extender or reaction stopper. It is preferable that the urethane resin is obtained by a chain extension reaction between a urethane prepolymer and an organic diamine. The urethane prepolymer is obtained by the reaction of a polyol with a diisocyanate compound and has an isocyanate group at the end. The diisocyanate compound may be at least one selected from the group consisting of aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates.

[0059] Aromatic diisocyanates may also be naphthylene diisocyanate, diphenylmethane diisocyanate, or phenylene diisocyanate. Aliphatic diisocyanates may also be butane diisocyanate, hexamethylene diisocyanate, isopropyl diisocyanate, methylene diisocyanate, or trimethylhexamethylene diisocyanate. Alicyclic diisocyanates may also be cyclohexane diisocyanate, isophorone diisocyanate, m-xylylene diisocyanate, or dicyclohexylmethane diisocyanate.

[0060] The first curing agent 22C is dispersed almost uniformly within the color-developing ink layer 22. The first curing agent 22C reacts with the first binder 22B, crosslinking the first binder 22B. Through the crosslinking of the first binder 22B, the first curing agent 22C improves the adhesion between the resin substrate layer 21 and the color-developing ink layer 22.

[0061] The first curing agent 22C may be a diisocyanate-based curing agent. The diisocyanate-based curing agent may be at least one selected from the group consisting of aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates. The aromatic diisocyanate may be naphthylene diisocyanate, diphenylmethane diisocyanate, or phenylene diisocyanate. The aliphatic diisocyanate may be butane diisocyanate, hexamethylene diisocyanate (HMDI), isopropyl diisocyanate, methylene diisocyanate, or trimethylhexamethylene diisocyanate. The alicyclic diisocyanate may be cyclohexane diisocyanate, isophorone diisocyanate (IPDI), m-xylylene diisocyanate (XDI), or dicyclohexylmethane diisocyanate.

[0062] The content of the first curing agent 22C is preferably 4% by mass or less relative to the weight of the color-developing ink layer 22, that is, relative to the total solid components in the ink for forming the color-developing ink layer 22. If the content of the first curing agent 22C is 4% by mass or less, the first binder 22B can be crosslinked so that sufficient adhesion between the resin substrate layer 21 and the color-developing ink layer 22 is obtained after laser marking. Furthermore, if the content of the first curing agent 22C is 4% by mass or less, it is possible to suppress blocking during the formation of the color-developing ink layer 22 and to improve solvent resistance during the lamination of the thermoplastic resin layer 25. In other words, it becomes possible to employ a gravure printing method with high productivity in the formation of the color-developing ink layer 22.

[0063] The thickness of the color-developing ink layer 22 is, for example, 0.5 μm to 2 μm, preferably 0.8 μm to 1.8 μm. If the thickness of the color-developing ink layer 22 is 1 μm or more, it is easy to form the color-developing ink layer 22 using a gravure printing method that has high productivity while obtaining sufficient ink content to recognize the color difference between the discolored first particles 22A and the undiscolored first particles 22A. If the thickness of the color-developing ink layer 22 is 2 μm or less, it is possible to obtain suitable bending properties in the laminated film 20 even when the color-developing ink layer 22 has been cured by the first curing agent 22C, so in this respect as well, it is possible to adopt the gravure printing method. Furthermore, it is possible to obtain suitable bending properties in the packaging 11 formed from the laminated film 20. The color-developing ink layer 22 may be a single-layer structure formed by one printing, or a multi-layer structure formed by two or more overlapping printings.

[0064] The solvent in the color-developing ink for forming the color-developing ink layer 22 is at least one selected from the group consisting of ketone-based solvents such as methyl ethyl ketone and methyl butyl ketone, alcohol-based solvents such as isopropyl alcohol and butanol, ester-based solvents such as ethyl acetate and butyl acetate, and hydrocarbon-based solvents such as toluene and xylene.

[0065] [White ink layer 23] The white ink layer 23 is composed of ink that has hardened due to the evaporation of the solvent. The second particles 23A contained in the white ink layer 23 are uncolored metal compounds that can develop color when irradiated with a laser of a transmitted wavelength. The second particles 23A in the portion 231 of the white ink layer 23 that is in contact with the colored portion 221 are uncolored. The second particles 23A in the portion 232 of the white ink layer 23 that is in contact with the uncolored portion 222 are also uncolored. However, if the organic components of the white ink layer 23 are not carbonized, i.e., if the organic components of the white ink layer 23 are not carbonized, the second particles 23A in the portion of the white ink layer 23 that is in contact with the colored portion 221 may contain colored second particles 23A.

[0066] The white ink layer 23 is printed on one side of the color-developing ink layer 22. The printing method for forming the white ink layer 23 is appropriately selected from known printing methods, taking into consideration the printability of the white ink layer 23, its design properties such as color tone, its adhesion to other layers, and the safety of the laminated film 20 and the packaging formed from the laminated film 20. The printing method for forming the white ink layer 23 may be gravure printing, offset printing, gravure offset printing, flexographic printing, or inkjet printing. From the viewpoint of high productivity of the white ink layer 23 and the high resolution of the white ink layer 23, the printing method for forming the white ink layer 23 is preferably gravure printing. The white ink layer 23 may be printed on the entire surface of the resin substrate layer 21 including the display area of ​​the symbol 14, or it may be printed only within the display area of ​​the symbol 14. The configuration in which the white ink layer 23 is provided only within the display range of the symbol 14 reduces the amount of constituent material required for the white ink layer 23 compared to the configuration in which the white ink layer 23 is provided over the entire surface of the resin substrate layer 21.

[0067] The white ink layer 23 contains second particles 23A that change color when irradiated with a laser of a transmission wavelength, a second binder 23B, and a second curing agent 23C that crosslinks the second binder 23B. The second binder 23B and the second curing agent 23C are organic components that make up the white ink layer 23. The organic components of the white ink layer 23 are not carbonized and are colorless and transparent.

[0068] Furthermore, if all of the second particles 23A contained in the white ink layer 23 are uncolored, the organic components in the portion of the white ink layer 23 that are in contact with the colored portion 221 may turn black due to carbonization. In this case, the organic components in the portion of the white ink layer 23 that are in contact with the uncolored portion 222 are not carbonized and remain colorless and transparent.

[0069] The white ink layer 23 may contain additives to improve printability and additives to improve the chemical stability of the white ink layer 23. Examples of additives include leveling agents, defoaming agents, antistatic agents, infrared absorbers, and ultraviolet absorbers. The organic components of the white ink layer 23 may omit the second curing agent 23C.

[0070] The second particle 23A is dispersed almost uniformly within the white ink layer 23. The constituent material of the second particle 23A is white. White includes pure white as well as white-based colors. White-based colors include light beige, light eggshell, white, and ivory, which are more yellowish than pure white. White-based colors include oyster brown, which is more greenish than pure white; snow white, which is more bluish-purple than pure white; and moon white, which is more blue than pure white. White-based colors include grayish white, which has a lower brightness than pure white. The constituent material of the second particle 23A is at least one selected from the group consisting of zinc sulfide and titanium(IV) oxide. The constituent material of the second particle 23A may be a single material or a mixture of two or more materials. The second particle 23A changes color when irradiated with a laser having a transmission wavelength.

[0071] The content of the second particles 23A is 5% by mass or more and 90% by mass or less, with a more preferable value of 10% by mass or more and 65% by mass or less, relative to the weight of the white ink layer 23, that is, relative to the total amount of solid components in the ink for forming the white ink layer 23. If the content of the second particles 23A is 5% by mass or more, it is possible to increase the reflectivity of light toward the uncolored area 222 while suppressing the lifting of the white ink layer 23. If the content of the second particles 23A is 90% by mass or less, the pot life of the ink can be ensured, and high adhesion between the colored ink layer 22 and the white ink layer 23 can be ensured by adding the first curing agent 22C.

[0072] The second binder 23B is a resin having functional groups that are crosslinked by the second curing agent 23C. The transmittance of the second binder 23B at the transmitted wavelength is higher than the transmittance of the second particle 23A at the transmitted wavelength. The transmittance of the second binder 23B at the transmitted wavelength is such that the second binder 23B does not change color when irradiated with a laser that passes through the color-developing ink layer 22. The transmittance of the second binder 23B at the transmitted wavelength may be 70% or higher. From the viewpoint of preventing the laser at the transmitted wavelength from carbonizing the second binder 23B, the transmittance of the first binder 22B at the transmitted wavelength is more preferably 80% or higher, and even more preferably 90% or higher.

[0073] The second binder 23B may be at least one selected from the group consisting of vinyl chloride-vinyl acetate copolymer resin, vinyl acetate resin, ethylene-vinyl acetate copolymer resin, acrylic resin, acrylic-modified urethane resin, urethane resin, ethylene-acrylic copolymer resin, polyamide resin, hydroxyethylcellulose, hydroxypropylcellulose, nitrocellulose resin, polyester resin, polyvinyl chloride resin, polyvinyl acetal resin, and styrene-acrylic resin. The binder resin may be a single resin or a mixture of two or more resins.

[0074] From the viewpoint of high adhesion between the colored ink layer 22 and the white ink layer 23, it is preferable that the second binder 23B is an acrylic-modified urethane resin and a urethane resin. The acrylic-modified urethane resin and the urethane resin are obtained by the reaction of a polyester polyol or polyether polyol with a diisocyanate compound. The urethane resin is obtained using a chain extender or reaction stopper. It is preferable that the urethane resin is obtained by a chain extension reaction between a urethane prepolymer and an organic diamine. The urethane prepolymer is obtained by the reaction of a polyol with a diisocyanate compound and has an isocyanate group at the end. The diisocyanate compound may be at least one selected from the group consisting of aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates.

[0075] Aromatic diisocyanates may also be naphthylene diisocyanate, diphenylmethane diisocyanate, or phenylene diisocyanate. Aliphatic diisocyanates may also be butane diisocyanate, hexamethylene diisocyanate, isopropyl diisocyanate, methylene diisocyanate, or trimethylhexamethylene diisocyanate. Alicyclic diisocyanates may also be cyclohexane diisocyanate, isophorone diisocyanate, m-xylylene diisocyanate, or dicyclohexylmethane diisocyanate.

[0076] The second curing agent 23C is dispersed almost uniformly within the white ink layer 23. The second curing agent 23C reacts with the second binder 23B, crosslinking the second binder 23B. Through the crosslinking of the second binder 23B, the second curing agent 23C improves the adhesion between the colored ink layer 22 and the white ink layer 23.

[0077] The second curing agent 23C may be a diisocyanate-based curing agent. The diisocyanate-based curing agent may be at least one selected from the group consisting of aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates. Aromatic diisocyanates may be naphthylene diisocyanate, diphenylmethane diisocyanate, or phenylene diisocyanate. Aliphatic diisocyanates may be butane diisocyanate, hexamethylene diisocyanate (HMDI), isopropyl diisocyanate, methylene diisocyanate, or trimethylhexamethylene diisocyanate. Alicyclic diisocyanates may be cyclohexane diisocyanate, isophorone diisocyanate (IPDI), m-xylylene diisocyanate (XDI), or dicyclohexylmethane diisocyanate.

[0078] The content of the second curing agent 23C is preferably 4% by mass or less relative to the weight of the white ink layer 23, that is, relative to the total solid components in the ink for forming the white ink layer 23. If the content of the second curing agent 23C is 4% by mass or less, the second binder 23B can be crosslinked so that sufficient adhesion between the colored ink layer 22 and the white ink layer 23 is obtained after laser marking. Furthermore, if the content of the second curing agent 23C is 4% by mass or less, it is possible to suppress blocking when forming the white ink layer 23 and to improve solvent resistance when laminating the thermoplastic resin layer 25. In other words, it becomes possible to employ a gravure printing method with high productivity when forming the white ink layer 23.

[0079] The thickness of the white ink layer 23 is, for example, 0.5 μm to 2 μm, preferably 0.8 μm to 1.8 μm. If the thickness of the white ink layer 23 is 1 μm or more, it is easy to form the white ink layer 23 using a gravure printing method that has high productivity while obtaining a sufficient content to increase the reflectivity of light directed toward the uncolored portion 222. If the thickness of the white ink layer 23 is 2 μm or less, it is possible to obtain suitable bending properties in the laminated film 20 even when the white ink layer 23 has been cured by the second curing agent 23C, so the gravure printing method can also be used in this respect. Furthermore, it is possible to obtain suitable bending properties in the packaging 11 formed from the laminated film 20.

[0080] The solvent in the white ink for forming the white ink layer 23 is at least one selected from the group consisting of ketone solvents such as methyl ethyl ketone and methyl butyl ketone, alcohol solvents such as isopropyl alcohol and butanol, ester solvents such as ethyl acetate and butyl acetate, and hydrocarbon solvents such as toluene and xylene.

[0081] [Adhesive resin layer 24] The adhesive resin layer 24 is, for example, a dry lamination adhesive such as a two-component curing urethane resin, and it bonds the white ink layer 23 and the thermoplastic resin layer 25. Here, the adhesive resin layer 24 is formed between the white ink layer 23 and the thermoplastic resin layer 25 by a dry lamination method, and it bonds the white ink layer 23 and the thermoplastic resin layer 25.

[0082] The adhesive resin layer 24 may be a thermoplastic resin formed between the white ink layer 23 and the thermoplastic resin layer 25 by an extrusion lamination method, and may be a layer that adheres the white ink layer 23 and the thermoplastic resin layer 25. The thermoplastic resin may be a polyolefin resin such as molten low-density polyethylene resin, a polyolefin copolymer, an acid-modified polyolefin, a thermoplastic polyester resin, a polypropylene resin, or a polyvinyl chloride resin. The adhesive resin layer 24 may also be a polyvinyl acetate resin, a thermoplastic polyamide resin, a urethane resin, a nylon resin, an ethylene resin, a polyether resin, an ethylene-vinyl acetate copolymer saponified product, or a polyester-isocyanate resin. The adhesive resin layer 24 may also be an ethylene-acrylic acid copolymer such as molten ethylene-acrylic acid copolymer resin, an ethylene-ethyl acrylate copolymer, an ethylene-methacrylic acid copolymer, an ethylene-methyl methacrylate copolymer, an ethylene-propylene copolymer, an ethylene-vinyl acetate copolymer saponified product, or polyacrylonitrile. The adhesive resin layer 24 is one of the thermoplastic resins described above, or a combination of two or more of them.

[0083] [Thermoplastic resin layer 25] The thermoplastic resin layer 25 is a heat-sealable resin layer. The heat-sealable resin layer is a layer that can be heat-sealed to other thermoplastic resin layers 25. The constituent material of the thermoplastic resin layer 25 is a thermoplastic resin. The thermoplastic resin is at least one selected from the group consisting of, for example, polyolefin resins, polyolefin copolymers, acid-modified polyolefins, thermoplastic polyester resins, polypropylene resins, polyvinyl chloride resins, polyvinyl acetate resins, thermoplastic polyamide resins, urethane resins, nylon resins, ethylene resins, polyether resins, ethylene-vinyl acetate copolymer saponified products, polyester-isocyanate resins, ethylene-acrylic acid copolymers, ethylene-ethyl acrylate copolymers, ethylene-methacrylic acid copolymers, ethylene-methyl methacrylate copolymers, ethylene-propylene copolymers, ethylene-vinyl acetate copolymer saponified products, and polyacrylonitrile.

[0084] The thermoplastic resin layer 25 is either a stretched film or an unstretched film. The thermoplastic resin layer 25 may be a single film or a laminate consisting of multiple films. The thickness of the thermoplastic resin layer 25 is appropriately selected depending on the object to which the thermoplastic resin layer 25 is heat-sealed and the peel strength of the thermoplastic resin layer 25 after heat sealing. For example, the thickness of the thermoplastic resin layer 25 is 5 μm or more and 200 μm or less.

[0085] Furthermore, the constituent material of the thermoplastic resin layer 25 can be made of a material that is easy to peel from the plastic container. The fact that the thermoplastic resin layer 25 is made of an easy-peel material makes it possible to impart easy-openability to the laminated film 20. For example, polyolefin resins are commonly used for the easy-peel thermoplastic resin layer 25. Polyolefin resins include, for example, ethylene-based resins such as low-density polyethylene, medium-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-α-olefin copolymer, and ethylene-methacrylic acid resin copolymer. Polyolefin resins also include polypropylene-based resins such as polyethylene and polybutene blend resin, homopolypropylene, propylene-ethylene random copolymer, propylene-ethylene block copolymer, and propylene-α-olefin copolymer.

[0086] [Aluminum layer] The laminated film 20 may include an aluminum layer. The laminated film 20 including the aluminum layer has, in order from the side irradiated by the laser, a resin substrate layer 21, a color-developing ink layer 22, a white ink layer 23, an adhesive resin layer 24, an aluminum layer, a second adhesive resin layer, and a thermoplastic resin layer 25. The aluminum layer is located on the laser incident side relative to the second adhesive resin layer and the thermoplastic resin layer 25. The second adhesive resin layer is located on the laser incident side relative to the aluminum layer.

[0087] The aluminum layer suppresses the transmission of lasers with a transmission wavelength, thereby preventing lasers with that wavelength from reaching the inner layers beyond the aluminum layer. Furthermore, in the packaging 11 formed from the laminated film 20, the aluminum layer also functions as a barrier layer to protect the contents.

[0088] The aluminum layer is, for example, a flexible aluminum foil that can be laminated, and is an aluminum foil equivalent to JIS 1N30, JIS 8021, or JIS 8079. Furthermore, the aluminum layer is not limited to aluminum foil bonded by lamination, but may also be an aluminum layer deposited or sputtered onto the adhesive resin layer 24. The thickness of the aluminum layer is, for example, 5 μm to 20 μm, and is appropriately selected according to the barrier properties, bendability, cost suitability, etc. required for the laminated film 20. The aluminum foil has a matte surface and a glossy surface on the opposite side of the matte surface, but either surface may face the adhesive resin layer 24. In addition, the aluminum layer may be aluminum foil with matte surfaces on both sides, or aluminum foil with glossy surfaces on both sides.

[0089] The second adhesive resin layer functions as a layer that adheres the aluminum layer and the thermoplastic resin layer 25. The second adhesive resin layer is, for example, the resin exemplified as the resin constituting the adhesive resin layer 24. The resin constituting the second adhesive resin layer may be the same resin as the resin constituting the adhesive resin layer 24, or it may be a different resin. The second adhesive resin layer is formed between the aluminum layer and the thermoplastic resin layer 25 by methods such as dry lamination lamination or extrusion lamination lamination, thereby adhering the aluminum layer and the thermoplastic resin layer 25.

[0090] [Additives] The adhesive resin layer 24 and the thermoplastic resin layer 25 may also contain additives. Additives contained in the adhesive resin layer 24 and the thermoplastic resin layer 25 include, for example, compounding agents, lubricants, crosslinking agents, antioxidants, UV absorbers, light stabilizers, fillers, reinforcing agents, flame retardants, fire retardants, foaming agents, antifungal agents, pigments, and dyes. Additives contained in the laminated film 20 include, for example, surfactants, dispersants, wetting agents, adhesion aids, leveling agents, defoaming agents, antistatic agents, trapping agents, antiblocking agents, curing agents, and silane coupling agents.

[0091] [Surface treatment] Each layer constituting the laminated film 20 may also include a surface treatment layer to improve adhesion and other properties. The surface treatment layer is, for example, a surface layer that has undergone oxidation treatment using corona discharge treatment, ozone treatment, low-temperature plasma treatment, glow discharge treatment, or chemicals. Alternatively, the surface treatment layer may be a coating layer formed from a surface pretreatment agent such as a primer coat agent, undercoat agent, anchor coat agent, adhesive, or vapor deposition anchor coat agent.

[0092] In addition to being used as packaging material, the laminated film 20 can also be used as a security medium for personal authentication, such as driver's licenses, ID cards, and passports. Because the laminated film 20 forms information on the color-developing ink layer 22, it is possible to suppress forgery, tampering, and alteration.

[0093] [Method for manufacturing laminated film 20] One example of a method for manufacturing the laminated film 20 is to first print a color-developing ink layer 22 and a white ink layer 23 onto a resin substrate layer 21 using gravure printing. Next, using a dry lamination method, an adhesive resin layer 24 is applied between the laminate, which has the color-developing ink layer 22 and the white ink layer 23 printed on the resin substrate layer 21, and the thermoplastic resin layer 25. The laminate of the resin substrate layer 21, the color-developing ink layer 22, and the white ink layer 23 is bonded to the thermoplastic resin layer 25 via the applied adhesive resin layer 24. Finally, laser marking is applied to the color-developing ink layer 22.

[0094] In one example of a manufacturing method for a laminated film 20 with an aluminum layer, a gravure printing method is used to print a color-developing ink layer 22 and a white ink layer 23 onto a resin substrate layer 21. Next, using a dry lamination method, an adhesive resin layer 24 is applied between the laminate of the resin substrate layer 21, the color-developing ink layer 22 and the white ink layer 23 and the aluminum layer, and the applied adhesive resin layer 24 is used to bond the laminate of the resin substrate layer 21, the color-developing ink layer 22 and the white ink layer 23 to the aluminum layer. Then, using a dry lamination method, a second adhesive resin layer is applied between the laminate of the resin substrate layer 21, the color-developing ink layer 22 and the white ink layer 23, the adhesive resin layer 24 and the aluminum layer and the thermoplastic resin layer 25. Next, the laminate of the resin substrate layer 21, the color-developing ink layer 22, the white ink layer 23, the adhesive resin layer 24, and the aluminum layer is bonded to the thermoplastic resin layer 25 via the applied second adhesive resin layer. Then, laser marking is applied to the color-developing ink layer 22.

[0095] [Laser marking] The laser marking of the laminated film 20 is described below. The laminated film 20 is printed with symbols 14 using a transmission wavelength laser. The transmission wavelength laser is irradiated, for example, from the resin substrate layer 21 toward the color-developing ink layer 22 by a laser oscillator. The laser output has a wavelength in the ultraviolet wavelength range that discolors the first particle 22A but does not discolor the second particle 23A. The transmission wavelength is preferably 315 nm to 380 nm, and more preferably 355 nm, which is UV-A.

[0096] Because the transmitted wavelength is included in the ultraviolet wavelength range, laser absorption and vaporization are suppressed in the resin substrate layer 21, binders 22B, 23B, curing agents 22C, 23C, adhesive resin layer 24, and thermoplastic resin layer 25 compared to the infrared wavelength range and visible wavelength range. In other words, carbonization of the organic components of the colored ink layer 22 and the white ink layer 23 is suppressed. The suppression of carbonization of organic components, combined with the improved adhesion between the resin substrate layer 21 and the colored ink layer 22 by the first curing agent 22C, and the improved adhesion between the colored ink layer 22 and the white ink layer 23 by the second curing agent 23C, suppresses lifting of the resin substrate layer 21. In addition, it suppresses the generation of pinholes and fumes in the resin substrate layer 21 and binders 22B, 23B, and discoloration of the white ink layer 23 near the boundary between the colored part 221 and the white ink layer 23.

[0097] The laser with the transmission wavelength is irradiated by a laser oscillator. The type of laser is, for example, a YVO4 laser. The YVO4 laser has low transmittance to the first particle 22A, enabling highly visible laser marking. Other types of lasers include, for example, YAG lasers, excimer lasers, and fiber lasers. Furthermore, the type of laser may be a gas laser, a solid-state laser, or even a liquid laser.

[0098] The quality of laser marking also depends on the laser power, scanning speed, and Q-switch frequency. The laser power is adjusted as needed to ensure clear information. The scanning speed is used to adjust the density of the dots, the spacing between dots, and the laser irradiation time. The Q-switch frequency is the frequency at which pulses are generated and is used to adjust the laser output and pulse width.

[0099] The metal compounds constituting the first particle 22A and the second particle 23A change to various colors depending on the arrangement of oxygen atoms relative to each metal atom and the bonding state between the metal atoms and oxygen. The absorption edge wavelength of the ink layer containing the metal compound indicates the wavelength range that the metal compound can absorb. The metal compound can change color when exposed to light that it can absorb.

[0100] For example, ink layers containing yellowish α-bismuth trioxide or pale yellowish β-bismuth trioxide exhibit broad absorption in the ultraviolet wavelength range and have an absorption edge wavelength around 340 nm. Bismuth trioxide takes on a deep black color with structural changes upon irradiation with light in the ultraviolet wavelength range.

[0101] For example, an ink layer containing zinc oxide, which is nearly colorless and transparent white, exhibits a steep absorption rise in the ultraviolet wavelength range and has an absorption edge wavelength around 380 nm. Zinc oxide turns brownish due to structural changes caused by irradiation with light in the ultraviolet wavelength range.

[0102] For example, an ink layer containing whitish zinc sulfide of the zincblende type does not exhibit significant absorption in the range of 300 nm to 390 nm. Zinc sulfide of the zincblende type undergoes a structural change and turns dark gray when irradiated with light in the ultraviolet wavelength range.

[0103] For example, an ink layer containing white anatase-type titanium dioxide exhibits a steep absorption rise in the ultraviolet wavelength range and has an absorption edge wavelength around 380 nm. Anatase-type titanium dioxide undergoes a structural change and takes on a light gray color upon irradiation with light in the ultraviolet wavelength range.

[0104] A laser with a transmission wavelength penetrates the resin substrate layer 21 and reaches the color-developing ink layer 22. The laser that reaches the color-developing ink layer 22 discolors the first particles 22A. The first particles 22A that have been discolored by the laser form a colored portion 221. The first particles 22A in the colored portion 221 may contain uncolored first particles 22A. The first particles 22A in the parts not irradiated by the laser are uncolored. The uncolored first particles 22A form an uncolored portion 222. All of the first particles 22A in the uncolored portion 222 are uncolored. The laser may penetrate the color-developing ink layer 22 and reach the white ink layer 23. The intensity of the laser that reaches the white ink layer 23 is such that it does not discolor the second particles 23A.

[0105] The fact that the second particle 23A of the white ink layer 23 is uncolored suppresses the color development of the white ink layer 23 itself, acting as a base for the colored area 221 and the uncolored area 222. Furthermore, the fact that the transmitted wavelength is in the ultraviolet wavelength range does not carbonize the organic components as much as 1064nm, suppressing the color development of the white ink layer 23, acting as a base for the colored area 221 and the uncolored area 222.

[0106] (A1) In a white ink layer 23 in which the second particle 23A is uncolored and (B1) the organic component is less likely to carbonize, the reduction in reflectivity of the white ink layer 23 itself is suppressed. Furthermore, such a white ink layer 23 is less likely to separate from the colored ink layer 22 and is less likely to form voids or other structures at the interface with the colored ink layer 22.

[0107] (A2) The second particles 23A do not easily develop color, and (B2) the organic components are not carbonized. Such a white ink layer 23 also suppresses a decrease in the reflectivity of the white ink layer 23 itself. Furthermore, such a white ink layer 23 does not easily separate from the colored ink layer 22, and voids are less likely to form at the interface between the colored ink layer 22 and the white ink layer 23.

[0108] Furthermore, the crosslinking of the first binder 22B by the first curing agent 22C and the transmission of the laser of the transmission wavelength by the first binder 22B, etc., combine to enhance adhesion between the resin substrate layer 21 and the first binder 22B. The crosslinking of the second binder 23B by the second curing agent 23C and the transmission of the laser of the transmission wavelength by the second binder 23B, etc., combine to enhance adhesion between the colored ink layer 22 and the second binder 23B. Adhesion is also enhanced between the adhesive resin layer 24 and the second binder 23B. In addition, discoloration of the first binder 22B around the first particles 22A and discoloration of the second binder 23B in contact with the colored portion 221 are suppressed.

[0109] The symbols 14 formed by laser marking may be applied not only before the contents are filled into the packaging 11, but also after the contents have been filled into the packaging 11. In this regard, irradiation with a transmitting wavelength laser suppresses the carbonization of organic components in the colored ink layer 22 and the white ink layer 23, thereby suppressing the occurrence of pinholes and fumes. Therefore, even when laser marking is performed after the contents have been filled into the packaging 11, it is possible to suppress volatile particles from contaminating the contents, altering the contents, or contaminating the packaging 11 itself. Furthermore, it is possible to suppress the accumulation of volatile particles in the laser processing equipment, preventing the accumulated material from falling onto the packaging 11, and preventing the fallen material from becoming foreign matter inside the packaging 11.

[0110] Next, we will explain each test example. [Test Example 1] A color-developing ink layer 22 was printed onto a resin substrate layer 21 using gravure printing. Next, a white ink layer 23 was printed onto the color-developing ink layer 22 using gravure printing, thereby obtaining a laminate in which the color-developing ink layer 22 and the white ink layer 23 were laminated on the resin substrate layer 21. Then, an aluminum layer was bonded to the laminate via an adhesive resin layer 24 using extrusion lamination. Finally, a thermoplastic resin layer 25 was bonded to the aluminum layer via a second adhesive resin layer using extrusion lamination. This obtained the laminated film 20 of Test Example 1, which comprises an aluminum layer and a second adhesive resin layer. The composition of the resin substrate layer 21, color-developing ink layer 22, white ink layer 23, adhesive resin layer 24, aluminum layer, and thermoplastic resin layer 25 is as follows.

[0111] • Resin substrate layer 21: PET film • Thickness of resin substrate layer 21: 12 μm • Particle 1 22A: Bismuth trioxide • First binder 22B: Vinyl chloride vinyl acetate copolymer • Blending ratio of the first particle 22A: 70% by mass • Blending ratio of the first binder 22B: 30% by mass • Second particle 23A: Zinc sulfide • Thickness of the color-developing ink layer 22: 1 μm • Second binder 23B: Vinyl chloride vinyl acetate copolymer • Blending ratio of the second particle 23A: 70% by mass • Mixing ratio of the second binder 23B: 30% by mass • Thickness of white ink layer 23: 1 μm • Adhesive resin layer 24: Non-solvent adhesive • Thickness of adhesive resin layer 24: 1 μm • Thickness of the aluminum layer: 7 μm • Thickness of adhesive resin layer 24: 1 μm • Thermoplastic resin layer 25: Low-density polyethylene film • Thickness of thermoplastic resin layer 25: 10 μm

[0112] In Test Example 1, a laser with a transmission wavelength of 355 nm was irradiated onto the laminated film 20 to form a colored area 221 on the colored ink layer 22. The GS1 DataBar limited composite symbol CC-A was printed as symbol 14. The laser marking conditions were as follows: • Laser oscillator: MD-U1020C (manufactured by Keyence Corporation) Output: 2.5W • Laser power: 60% • Number of prints: 1 • Working distance: 300mm

[0113] [Test Example 2] The thickness of the white ink layer 23 was changed to 2 μm by repeating the printing of the white ink layer 23 twice, while keeping all other conditions the same as in Test Example 1, to obtain the laminated film 20 of Test Example 2. Then, using the same conditions as in Test Example 1, the symbol 14 was formed on the laminated film 20 of Test Example 2.

[0114] [Test Example 3] The first particle 22A was replaced with zinc oxide, and the rest of the laminated film 20 of Test Example 3 was obtained, with the same conditions as in Test Example 1. Then, the symbol 14 was formed on the laminated film 20 of Test Example 3 using the same laser marking conditions as in Test Example 1.

[0115] [Test Example 4] The first particle 22A was replaced with zinc oxide, and the rest of the laminated film 20 of Test Example 4 was obtained, with the same conditions as in Test Example 2. Then, the symbol 14 was formed on the laminated film 20 of Test Example 4 using the same laser marking conditions as in Test Example 1.

[0116] [Test Example 5] The first particle 22A was replaced with titanium(IV) oxide, and the printing of the white ink layer 23 was omitted, while all other conditions were the same as in Test Example 1 to obtain the laminated film 20 of Test Example 5. Then, using the same laser marking conditions as in Test Example 1, the symbol 14 was formed on the laminated film 20 of Test Example 5.

[0117] [Test Example 6] The thickness of the color-developing ink layer 22 was changed to 2 μm by repeating the printing of the color-developing ink layer 22 twice, while keeping all other conditions the same as in Test Example 5, to obtain the laminated film 20 of Test Example 6. Then, using the same laser marking conditions as in Test Example 1, the symbol 14 was formed on the laminated film 20 of Test Example 6.

[0118] [Test Example 7] The thickness of the color-developing ink layer 22 was changed to 3 μm by repeating the printing of the color-developing ink layer 22 three times, while keeping all other conditions the same as in Test Example 5, to obtain the laminated film 20 of Test Example 7. Then, using the same laser marking conditions as in Test Example 1, the symbol 14 was formed on the laminated film 20 of Test Example 7.

[0119] [evaluation] For the laminates of Test Examples 1 to 4, in which a color-developing ink layer 22 and a white ink layer 23 were laminated on a resin substrate layer 21, the Lab values ​​observed from a measurement point opposite the resin substrate layer 21 were measured. For the laminates of Test Examples 5 to 7, in which the color-developing ink layer 22 was laminated on the resin substrate layer 21, the Lab values ​​observed from a measurement point opposite the resin substrate layer 21 were measured. For the laminated films 20 of Test Examples 1, 2, 5, and 6, the Lab values ​​observed from a measurement point opposite the resin substrate layer 21 were measured. Lab values ​​were obtained using a spectrophotometer (X-Rite eXact / X-Rite). Figure 3 shows the measurement results of Lab values ​​for each test example.

[0120] As shown in Figure 3, in the laminate, the L value of Test Example 2 is higher than the L value of Test Example 1. The L value of Test Example 4 is higher than the L value of Test Example 3. The L value of Test Example 6 is higher than the L value of Test Example 5. The L value of Test Example 7 is higher than the L value of Test Example 6. The difference in L values ​​between Test Example 5 and Test Example 6 is approximately twice the difference in L values ​​between Test Example 6 and Test Example 7. As a result, the following (i) and (ii) were observed. (i) The overlapping of the white ink layers 23 increases the brightness of the laminated film 20. (ii) A thickness of 0.5 μm to 1.5 μm effectively enhances brightness.

[0121] Furthermore, the L values ​​in test examples 6 and 7 are slightly higher than those in test examples 1 to 4. Therefore, it was found that when there is a requirement to increase the brightness of the laminated film 20, it is preferable to include titanium dioxide in the second particle 23A of the laminated film 20.

[0122] In the laminated film 20, the L value of Test Example 1 is approximately the same as the L value of Test Example 2. The L value of Test Example 1 is approximately the same as the L values ​​of Test Examples 5 and 6. On the other hand, the b value in the laminated film 20 of Test Examples 1 and 2 is shifted in the positive direction from the b value in the laminates of Test Examples 1 and 2. The b value in the laminated film 20 of Test Examples 5 and 6 is also shifted in the positive direction from the b value in the laminates of Test Examples 5 and 6. The relative improvement in the L value in Test Example 1 is not due to an improvement in brightness due to the reflection of the white ink layer 23, but rather to an improvement in brightness due to the reflection of the aluminum layer. As a result, the following (iii) and (iv) were observed. (iii) The presence of the aluminum layer enhances the brightness of the laminated film 20. (iv) The presence of the aluminum layer shifts the b value of the complementary color dimension in the positive direction.

[0123] For each test example, the ultraviolet transmission spectrum in the ultraviolet wavelength range was measured for the laminated film 20. Figure 4 shows the ultraviolet transmission spectra for each test example. As shown in Figure 4, the absorption edge wavelengths of the laminated films 20 in Test Examples 1 and 2 are between 340 nm and 360 nm. The ultraviolet transmittance of the laminated films 20 in Test Examples 1 and 2 increases gradually from the absorption edge wavelength. The ultraviolet absorption spectra of Test Example 1 and Test Example 2 are almost identical. The absorption edge wavelength of zinc sulfide corresponding to the difference between the ultraviolet absorption spectra of Test Examples 1 and 2 is 400 nm or higher.

[0124] The absorption edge wavelengths of the laminated films 20 in Test Examples 3 and 4 are between 360 nm and 380 nm. The ultraviolet transmittance of the laminated films 20 in Test Examples 3 and 4 increases sharply from the absorption edge wavelength. The ultraviolet absorption spectra of Test Example 3 and Test Example 4 are almost identical. The absorption edge wavelength of zinc sulfide corresponding to the difference between the ultraviolet absorption spectra of Test Examples 3 and 4 is 400 nm or higher.

[0125] The absorption edge wavelength of the laminated film 20 in Test Examples 5 to 7 is 380 nm or higher. The ultraviolet transmittance of the laminated film 20 in Test Examples 5 to 7 rises sharply from the absorption edge wavelength. As a result, the following (v) and (vi) were observed. (v) Absorption edge wavelength of dibismuth trioxide < Absorption edge wavelength of zinc oxide < Absorption edge wavelength of zinc sulfide (vi) Absorption edge wavelength of zinc oxide < Absorption edge wavelength of titanium oxide

[0126] In the laser marking of Test Examples 1 to 7, it was confirmed that no fumes were generated. For symbols 14 in Test Examples 1 to 4, cross-sectional observation with a stereomicroscope was performed, and it was confirmed that no discoloration occurred in the white ink layer 23, including the color development of the second particle 23A and the carbonization of organic components. Furthermore, it was confirmed that no lifting occurred on the surface of symbols 14 in Test Examples 1 to 7.

[0127] For symbols 14 in Test Examples 1 to 6, the maximum reflectance, minimum reflectance, and contrast (the difference between the maximum and minimum reflectance) observed from the measurement point opposite the resin substrate layer 21 were measured. The maximum reflectance, minimum reflectance, and contrast were obtained from the scanned reflectance waveform using a reading device (XaminerELITE / Munazo Co., Ltd.). Figure 3 shows the measurement results for the maximum reflectance, minimum reflectance, and contrast in each test example.

[0128] As shown in Figure 3, the maximum reflectances of Test Examples 1 to 6 are approximately the same, ranging from 80% to 83%. A laminated film 20 having a white ink layer 23 as a base for the colored ink layer 22 can obtain a maximum reflectance similar to that of a laminated film 20 consisting only of a colored ink layer 22 with titanium dioxide as the first particle 22A. On the other hand, the minimum reflectances of Test Examples 1 and 2 are 10% to 11%, which is significantly lower than the minimum reflectances of Test Examples 5 and 6, and the contrast reaches 70%. The minimum reflectances of Test Examples 3 and 4 are also 13% to 14%, which is lower than the minimum reflectances of Test Examples 5 and 6, and the contrast exceeds 65%.

[0129] According to the above embodiment, the following effects can be obtained. (1) The first particle 22A develops color when irradiated with a transmission wavelength in the ultraviolet wavelength range. Therefore, even if the laser irradiated onto the colored ink layer 22 penetrates into the white ink layer 23, the organic components of the white ink layer 23 are less likely to carbonize compared to irradiation with a 1064 nm laser. Furthermore, the second particle 23A remains uncolored. Therefore, (A1) the uncolored second particle 23A and (B1) the suppression of carbonization of the organic components work together to suppress the decrease in reflectivity of the white ink layer 23. As a result, the contrast derived from the difference in reflectivity between the colored part 221 and the uncolored part 222 is increased.

[0130] (2) The laminated film 20 has a white ink layer 23 on the opposite side of the resin substrate layer 21 that transmits the laser of the transmitted wavelength, and the first particles 22A that develop color when irradiated with the laser of the transmitted wavelength are provided in the colored ink layer 22. In this way, the laminated film 20 is configured to promote (A1) non-color development of the second particles 23A and (B1) suppression of carbonization of organic components. As a result, the likelihood of obtaining high contrast, which is an effect similar to (1), is also increased.

[0131] (3) The first particle 22A develops color when irradiated with a laser of a transmission wavelength in the ultraviolet wavelength range. Therefore, even if the laser irradiated onto the colored ink layer 22 penetrates into the white ink layer 23, the organic components of the white ink layer 23 are less likely to carbonize compared to irradiation with a 1064 nm laser. As a result, the organic components of the white ink layer 23 remain uncarbonized. Furthermore, the second particle 23A in the portion of the white ink layer 23 that is in contact with the uncolored portion 222 remains uncolored. Therefore, (A2) the suppression of color development of the second particle 23A and (B2) the uncarbonization of the organic components work together to suppress the decrease in reflectivity of the white ink layer 23. As a result, the contrast derived from the difference in reflectivity between the colored portion 221 and the uncolored portion 222 is increased.

[0132] (4) The laminated film 20 has a white ink layer 23 on the opposite side of the resin substrate layer 21 that transmits the laser of the transmitted wavelength, and the first particles 22A that develop color when irradiated with the laser of the transmitted wavelength are provided in the color-developing ink layer 22. In this way, the laminated film 20 is configured to promote (A2) suppression of the development of the second particles 23A and (B2) non-carbonization of organic components. As a result, the likelihood of obtaining high contrast, which is an effect similar to (3), is also increased.

[0133] (5) Because the absorption edge wavelength of the first particle 22A is shorter than that of the second particle 23A, there is a wavelength in the ultraviolet wavelength range that is more likely to cause only the second particle 23A to develop color. For this reason, if the color development of the first particle 22A is weak, there is a risk that the color development of the second particle 23A, and consequently the discoloration of the white ink layer 23, is progressing. In this way, by detecting the degree of color development of the first particle 22A, it is possible to estimate whether or not there is a decrease in reflectivity in the white ink layer 23. Furthermore, by detecting the difference between the degree of color development of the first particle 22A and the degree of color development of the second particle 23A, it is possible to accurately determine whether the laser irradiated onto the laminated film 20 is suitable. This also makes it easier to manage the manufacturing of the laminated film 20.

[0134] (6) The first particle 22A may contain at least one selected from the group consisting of bismuth trioxide and zinc oxide. The second particle 23A may contain at least one selected from the group consisting of zinc sulfide and titanium dioxide. Alternatively, the first particle 22A may be bismuth trioxide and the second particle 23A may be zinc sulfide. These configurations increase the effectiveness of obtaining the effects described in (1) to (5) above.

[0135] The above embodiment can be implemented with the following modifications. The laminated film 20 may have bismuth trioxide in the first particle 22A and zinc oxide in the second particle 23A. The laminated film 20 may have bismuth trioxide in the first particle 22A and titanium oxide in the second particle 23A.

[0136] The laminated film 20 may have zinc oxide in the first particle 22A and titanium oxide in the second particle 23A. [Explanation of symbols]

[0137] 11...Packaging 12…Heat-fused joint 13...Detention Unit 14…Symbol 20…Laminated film 21...Resin base material layer 22...Color-developing ink layer 22A…first particle 22B…Binder 1 22C...Coloring ink hardener 23... White ink layer 23A…Second particle 23B…Second Binder 23C... White ink hardener 24…Adhesive resin layer 25...Thermoplastic resin layer

Claims

1. A resin substrate layer that transmits a laser with a transmission wavelength in the ultraviolet wavelength range, A thermoplastic resin layer, A color-developing ink layer located between the resin substrate layer and the thermoplastic resin layer, A white ink layer located between the color-developing ink layer and the thermoplastic resin layer, A laminated film comprising, Metal compounds are transition metal oxides or transition metal sulfides. The first particle and the second particle are separate metal compounds that emit color when the laser is used. The metal compound contained in the color-developing ink layer is the first particle, The metal compound that exhibits a white color in the white ink layer is the second particle, The aforementioned color-developing ink layer comprises a color-developing portion and an uncolor-developing portion. The first particles of the color-developing portion include the color-developed first particles, The first particle in the uncolored portion is uncolored, The second particles in the white ink layer are uncolored. The absorption edge wavelength of the first particle in the ultraviolet wavelength range is shorter than the absorption edge wavelength of the second particle. A laminated film characterized by the following features.

2. The first particle comprises at least one selected from the group consisting of dibismuth trioxide and zinc oxide, The second particle comprises at least one selected from the group consisting of zinc sulfide and titanium oxide. The laminated film according to claim 1.

3. The aforementioned first particle is bismuth trioxide, The second particle is zinc sulfide. The laminated film according to claim 1.

4. The organic components of the aforementioned white ink layer are not carbonized. The laminated film according to claim 1.

5. A resin substrate layer that transmits a laser with a transmission wavelength in the ultraviolet wavelength range, A thermoplastic resin layer, A color-developing ink layer located between the resin substrate layer and the thermoplastic resin layer, A white ink layer located between the color-developing ink layer and the thermoplastic resin layer, A laminated film comprising, Metal compounds are transition metal oxides or transition metal sulfides. The first particle and the second particle are separate metal compounds that emit color when the laser is used. The metal compound contained in the color-developing ink layer is the first particle, The metal compound that exhibits a white color in the white ink layer is the second particle, The aforementioned color-developing ink layer comprises a color-developing portion and an uncolor-developing portion. The first particles of the color-developing portion include the color-developed first particles, The first particle in the uncolored portion is uncolored, The organic components of the aforementioned white ink layer are not carbonized. The second particles in the white ink layer that are in contact with the uncolored portion are uncolored. The absorption edge wavelength of the first particle in the ultraviolet wavelength range is shorter than the absorption edge wavelength of the second particle. A laminated film characterized by the following features.

6. A packaging body comprising the laminated film according to any one of claims 1 to 5.

7. Irradiating a laminated film with a laser of a transmission wavelength, which is in the ultraviolet wavelength range, The packaging is formed by heat-sealing the thermoplastic resin layers of the laminated film, A method for manufacturing a package containing, The laminated film is A resin substrate layer that transmits the laser of the aforementioned transmission wavelength, A thermoplastic resin layer, A color-developing ink layer located between the resin substrate layer and the thermoplastic resin layer, It comprises a white ink layer located between the color-developing ink layer and the thermoplastic resin layer, Metal compounds are transition metal oxides or transition metal sulfides. The first particle and the second particle are separate metal compounds that emit color when the laser is used. The metal compound contained in the color-developing ink layer is the first particle, The metal compound that exhibits a white color in the white ink layer is the second particle, The absorption edge wavelength of the first particle in the ultraviolet wavelength range is shorter than the absorption edge wavelength of the second particle. Irradiating with the aforementioned laser means The colored ink layer is irradiated with the laser of the transmission wavelength through the resin substrate layer so that the second particles of the white ink layer remain uncolored, thereby dividing the colored ink layer into an uncolored portion where the first particles remain uncolored and a colored portion containing the colored first particles. A method for manufacturing a package, characterized by the following:

8. Irradiating a laminated film with a laser of a transmission wavelength, which is in the ultraviolet wavelength range, The packaging is formed by heat-sealing the thermoplastic resin layers of the laminated film, A method for manufacturing a package containing, The laminated film is A resin substrate layer that transmits the laser of the aforementioned transmission wavelength, A thermoplastic resin layer, A color-developing ink layer located between the resin substrate layer and the thermoplastic resin layer, It comprises a white ink layer located between the color-developing ink layer and the thermoplastic resin layer, Metal compounds are transition metal oxides or transition metal sulfides. The first particle and the second particle are separate metal compounds that emit color when the laser is used. The metal compound contained in the color-developing ink layer is the first particle, The metal compound that exhibits a white color in the white ink layer is the second particle, The absorption edge wavelength of the first particle in the ultraviolet wavelength range is shorter than the absorption edge wavelength of the second particle. Irradiating with the aforementioned laser means The colored ink layer is divided into an uncolored portion where the first particles are not colored and a colored portion containing the colored first particles, and the organic components of the white ink layer are not carbonized, and the portion of the second particles in contact with the uncolored portion within the white ink layer remains uncolored, by irradiating the colored ink layer with the laser of the transmission wavelength through the resin substrate layer. A method for manufacturing a package, characterized by the following:

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