Classification method for label

Abstract

To improve classification efficiency of a label by easily identifying a label subjected to classification.SOLUTION: A print layer removable label 1 comprises a substrate 11 and a print layer 13, is configured to separate the print layer 13 from the substrate 11 when immersed in an alkaline solution, and further contains a light-emitting material which emits light by being irradiated with an energy beam. A classification method for the label includes: a step S1 of irradiating a label group including the print layer removable label 1 with the energy beam in an internal part 100 of a dark place; a step S2 of identifying the print layer removable label 1 by detecting the light, that the light-emitting material emits by being irradiated with the energy beam, by means of a sensor 120 including a photodetection section in the internal part 100 of the dark place; and a step S3 of classifying the identified print layer removable label 1 from the label group. A filter 130 which shields at least a part of a wavelength component included in the energy beam is provided in the photodetection section.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a method for sorting labels. [Background technology]

[0002] International Publication No. 2021 / 246230 (Patent Document 1) discloses a method for separating conventional labels with removable printed layers. Patent Document 1 discloses a process for carrying a group of labels into a first dark place, a process for irradiating the group of labels with energy rays from a light source disposed in the first dark place, a process for carrying the group of labels removed from the first dark place into a second dark place, and a process for separating and recovering the labels that appear to glow in the second dark place from normal labels that do not appear to glow in the second dark place. It is disclosed that the coat layer or ink layer (printed layer) of the removable printed layer label contains a material that emits light when irradiated with energy rays. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 246230 Summary of the Invention [Problem to be solved by the invention]

[0004] In the conventional sorting method, there is room for improvement in sorting efficiency, such as saving space for label sorting and improving label sorting speed. For example, in the conventional sorting method disclosed in Patent Document 1, after irradiating with energy rays, the label group is again carried inside a dark place to identify the luminous labels. Therefore, the inventors of the present disclosure have considered a method of identifying the luminous labels at the same time as irradiating with energy rays in order to improve the efficiency of label sorting.

[0005] However, the inventors of the present disclosure have discovered a problem in that even if one attempts to identify a label that emits light simultaneously with the irradiation of energy rays, the sensor detects the irradiated energy rays along with the light emitted by the label, making it difficult to identify the label.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a method for sorting labels with removable printed layers that makes it easy to identify the labels to be sorted and improves the sorting efficiency of the labels. [Means for solving the problem]

[0007] The label sorting method according to the present disclosure is a method for sorting labels with removable printed layers, the labels having a substrate and a printed layer, the printed layer being configured to be detachable from the substrate when immersed in an alkaline aqueous solution, and further including a luminescent material that emits light when irradiated with an energy ray. The label sorting method includes a step of irradiating a group of labels including the removable printed layer labels with an energy ray in a dark place, a step of detecting light emitted by the luminescent material when irradiated with the energy ray in the dark place with a sensor having a light receiving unit, thereby identifying the removable printed layer labels, and a step of selecting the identified removable printed layer labels from the group of labels. The light receiving unit is provided with a filter that blocks at least a portion of the wavelength components included in the energy ray.

[0008] In the present disclosure, the above-mentioned filter is provided in the light receiving section, so that the sensor can be prevented from detecting the wavelength component of the energy ray. Therefore, the method for separating labels with removable printed layers according to the present disclosure can easily identify the labels to be separated and can improve the efficiency of separating the labels. Effect of the Invention

[0009] According to the present disclosure, it is possible to easily identify labels to be separated and to improve the efficiency of separating labels. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view of a label identified and sorted in a label sorting method according to an embodiment of the present disclosure. FIG. [Diagram 2] FIG. 1 is a flow diagram illustrating a label sorting method according to an embodiment of the present disclosure. [Diagram 3] FIG. 2 is a schematic diagram showing a state in which an energy ray is irradiated to a label according to an embodiment of the present disclosure in a predetermined dark place. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a label sorting method according to an embodiment of the present disclosure will be described with reference to the drawings. In the following description of the embodiment, the same or corresponding parts in the drawings are denoted by the same reference characters, and the description thereof will not be repeated.

[0012] (label) First, a label to be identified and selected in the label sorting method according to the embodiment of the present disclosure will be described. Fig. 1 is a schematic cross-sectional view of a label to be identified and selected in the label sorting method according to the embodiment of the present disclosure. As shown in Fig. 1, the label 1 according to the embodiment of the present disclosure includes a substrate 11, a coating layer 12 located on the substrate 11, and a printing layer 13 located on the coating layer 12.

[0013] The label 1 is configured so that the printed layer 13 can be detached from the substrate 11 when immersed in an alkaline aqueous solution, and is a label in which the printed layer 13 can be removed. In this embodiment, the coating layer 12 contains an alkali-soluble resin, and therefore the label 1 is a label in which the printed layer 13 can be removed (details will be described later). The printed layer 13 may contain an alkali-soluble resin. In this case, the label 1 may have the printed layer 13 directly located on the substrate 11, and the label 1 may not have the coating layer 12.

[0014] The label 1 according to the present embodiment may be a heat-shrinkable label (shrink label) or a label without heat-shrinkability. The label 1 according to the embodiment of the present disclosure may be a stretch label with self-stretchability or a label without self-stretchability. The label 1 according to the embodiment of the present disclosure may be a wrap-around label (roll label), a wrap-around shrink label (ROSO label), an in-mold label, a heat-sensitive label, a tack label, or the like.

[0015] The label 1 further contains a luminescent material that emits light when irradiated with energy rays. In the label 1, at least one of the substrate, the coating layer, and the printing layer further contains a luminescent material. In the present embodiment, since the substrate 11 is preferably recyclable as described later, at least one of the coating layer 12 and the printing layer 13 preferably contains a luminescent material. First, this luminescent material will be described. In this specification, a layer containing a luminescent material among the substrate (layer) 11, the coating layer 12, and the printing layer 13 (each layer constituting the printing layer when the printing layer is composed of multiple layers) may be referred to as a "luminescent layer".

[0016] <Light-emitting materials> In the label 1 according to an embodiment of the present disclosure, the luminescent material is a fluorescent dye, such as an optical brightener, or a fluorescent pigment. In this embodiment, the luminescent material is preferably an optical brightener.

[0017] Fluorescent brighteners are a type of fluorescent dye. They absorb energy rays (specifically ultraviolet light) and emit a bluish-white light. Fluorescent dyes are used to dye resins. For this reason, fluorescent brighteners can make the luminescent layer emit light with a relatively small content compared to fluorescent pigments.

[0018] When a fluorescent whitening agent is used as the luminescent material, it is preferable that the fluorescent whitening agent is highly safe for living organisms and has high light resistance. In the present embodiment, examples of the fluorescent whitening agent include naphthalene benzoxazolyl derivatives, thiophene benzoxazolyl derivatives, stilbene benzoxazolyl derivatives, coumarin derivatives, styrene biphenyl derivatives, pyrazolone derivatives, stilbene derivatives, styryl derivatives of benzene and biphenyl, bis(benzazol-2-yl) derivatives, carbostyryl, naphthalimide, derivatives of dibenzothiophene-5,5'-dioxide, pyrene derivatives, and pyridotriazole. One or more types of fluorescent whitening agents may be used alone, or two or more types may be used in combination.

[0019] The fluorescent whitening agent may be a commercially available product. Examples of the commercially available fluorescent whitening agent include TELALUX (registered trademark) OB (2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene) and KCB (1,4-bis(2-benzoxazolyl)naphthalene) from Clariant Japan.

[0020] When a fluorescent pigment is used as the luminescent material, examples of the fluorescent pigment include organic pigments and inorganic pigments. Examples of the organic pigments include fluorescein-based, coumarin-based, rhodamine-based, oxazole-based, pyrazoline-based, thiadiazole-based, spiropyran-based, pyrenesulfonic acid-based, benzimidazole-based, and diaminostilbene-based pigments. Examples of the inorganic pigments include zinc sulfide activated with copper, silver, manganese, or the like, zinc silicate activated with manganese, or the like, calcium sulfide activated with cadmium, bismuth, or the like, strontium sulfide activated with samarium, cerium, or the like, and calcium tungstate activated with lead, or the like.

[0021] More specifically, the red fluorescent pigment is, for example, Y 2 O 2 S:Eu,Y 2 O 3 :Eu, Y 2 SiO 5 :Eu, Y 3 AlO12 :Eu, Zn 3 (PO 4 ) 2 :Mn, YBO 3 :Eu, (Y, Gd)BO 3 :Eu, GdBO 3 :Eu, ScBO 3 :Eu or LuBO 3 :Eu, etc. can be used.

[0022] Examples of blue fluorescent pigments include BaMg 2 Al 16 O 27 :Eu, Y 2 SiO 5 :Ce, CaWO 4 : Pb, or BaMgAl 14 O 23 :Eu, etc. can be used.

[0023] Green fluorescent pigments include, for example, BaMg 2 Al 16 O 27 :(Eu,Mn),(Ba,Mg)Al 16 O 27 : (Eu, Mn), Zn 2 SiO 4 :Mn,BaAl 12 O 19 :Mn, SrAl 13 O 19 :Mn, CaAl 12 O 19 :Mn, YBO 3 :Tb, BaMgAl 14 O 23 :Mn, LuBO 3 :Tb, GdBO 3 :Tb, ScBO 3 :Tb or Sr 6 S 3 O 3 C 14 :Eu, etc. can be used.

[0024] The fluorescent pigment may be, for example, one of the above-mentioned pigments alone or a combination of two or more of the above-mentioned pigments. The average particle size of the fluorescent pigment is preferably 1 μm or more and 20 μm or less, and more preferably 5 μm or more and 15 μm or less.

[0025] The luminescent material has a different maximum absorption wavelength and a maximum fluorescence wavelength. The maximum absorption wavelength is the wavelength at which the absorbance is greatest in the absorption spectrum, which shows the relationship between the wavelength of light absorbed by the luminescent material and the absorbance at that wavelength. The maximum fluorescence wavelength is the wavelength at which the intensity is greatest in the emission spectrum, which shows the relationship between the wavelength of light emitted by the luminescent material by absorption and the intensity of the light at that wavelength. In the luminescent material, the maximum fluorescence wavelength is greater than the maximum absorption wavelength. For example, the luminescent material may have a maximum absorption wavelength of 300 nm or more and less than 400 nm. In addition, the luminescent material may have a maximum fluorescence wavelength of 400 nm or more and 450 nm or less. Furthermore, it is preferable that the difference between the maximum absorption wavelength and the maximum fluorescence wavelength of the luminescent material is 30 nm or more.

[0026] The content of the luminescent material in the luminescent layer is, for example, 0.3% by mass or more and 8.0% by mass or less. If the content of the luminescent material in the entire coating layer 12 and the printing layer 13 is 0.3% by mass or more, the label 1 according to the present disclosure can be sufficiently distinguished from a label to which no luminescent material is added by the emission of the luminescent material when the label 1 is irradiated with ultraviolet light. If it is 8.0% by mass or less, the deterioration of the printability of the composition for forming the luminescent layer can be suppressed. From the viewpoint of distinguishability, the content of the luminescent material is preferably 1.0% by mass or more. From the viewpoint of printability, the content of the luminescent material is preferably 5.0% by mass or less.

[0027] <Base material> Next, the substrate 11 will be described. The substrate 11 has a film-like outer shape. The substrate 11 may be a resin substrate or a paper substrate, but is preferably a recyclable substrate. When the substrate 11 is a resin substrate, examples of the resin contained in the substrate 11 include polyester-based resins (polyethylene terephthalate, polyethylene naphthalate, polylactic acid, etc.), polystyrene-based resins (polystyrene, styrene-butadiene copolymer, etc.), polyolefin-based resins (polyethylene-based resins, polypropylene-based resins, etc.), polyvinyl chloride-based resins, polyamide-based resins, aramid-based resins, polyimide-based resins, polyphenylene sulfide-based resins, and acrylic-based resins. The substrate 11 may contain one type of these resins, or may contain two or more types.

[0028] The resin contained in the base material 11 is preferably a polyester resin, and particularly preferably a polyethylene terephthalate resin (PET). PET is a polyester resin containing terephthalic acid as the main component of the dicarboxylic acid component and ethylene glycol as the main component of the diol component. PET may also contain, as other components, dicarboxylic acids such as isophthalic acid, phthalic acid, adipic acid, sebacic acid, or naphthalenedicarboxylic acid, and may also contain diol components such as diethylene glycol, neopentyl glycol, polyalkylene glycol, or 1,4-cyclohexanedimethanol. The resin contained in the base material 11 is also preferably a polyolefin resin, and more preferably a polyethylene resin or a polypropylene resin.

[0029] The substrate 11 may be, for example, a film having heat shrinkability (shrink film). When the substrate 11 is a shrink film, it is possible to improve the processability (ability to conform to the container) and decorativeness of the label 1, and to further increase the display area of ​​the label 1. The substrate 11 may also be, for example, a stretch film having self-stretchability.

[0030] The substrate 11 may be a single-layer film made of one layer, or may be a multi-layer film made of two or more layers. The thickness of the substrate 11 may be, for example, 5 μm to 100 μm, but is not particularly limited.

[0031] <Coat layer> In this embodiment, the coating layer 12 is a layer containing an alkali-soluble resin, and the coating layer 12 is alkali-soluble. The coating layer 12 is provided on the substrate 11. Specifically, the coating layer 12 is located between the substrate 11 and the printing layer 13. The coating layer 12 may be provided only on a part of one surface of the substrate 11, but when the coating layer 12 contains a luminescent material, it is preferable that the coating layer 12 is provided on the entire one surface of the substrate 11 from the viewpoint of increasing the amount of light emitted by the luminescent material.

[0032] The coating layer 12 (resin) being alkali-soluble means that when a sample having a coating layer 12 (resin coating) measuring 4 cm x 4 cm formed on a substrate 11 of any size is immersed in a 1.5 mass% sodium hydroxide aqueous solution (i.e., 1.5% of the total mass of the sodium hydroxide aqueous solution is sodium hydroxide) at 85°C and stirred at 1500 rpm, 70% or more of the total area of ​​the coating layer 12 (resin coating) will be detached from the sample after an immersion time of 15 minutes.

[0033] The resin contained in the coating layer 12 may be, for example, a resin having the following (1) to (4): (1) containing a first resin which is an acrylic acid copolymer resin having a first glass transition temperature T1; (2) containing a second resin which is an acrylic acid copolymer resin having a second glass transition temperature T2 lower than the above T1; (3) the apparent acid value of the coating layer 12 is 40 mgKOH / g or more and 150 mgKOH / g or less; (4) The first resin and the second resin contained in the coating layer 12 account for 50 to 95% by mass in total of the coating layer 12 .

[0034] Resins having the above (1) to (4) have good alkali solubility. Therefore, when the label 1 has the alkali-soluble coating layer 12 between the substrate 11 and the printed layer 13, the printed layer 13 is also detached from the substrate 11 as the coating layer 12 is detached from the label 1 by alkali.

[0035] As shown in (1) and (2) above, the first resin and the second resin are each an acrylic acid copolymer resin. The acrylic acid copolymer resin is a resin that contains acrylic acid and / or methacrylic acid as a main repeating unit and also contains a copolymerizable monomer copolymerizable with the acrylic acid and / or methacrylic acid. The acrylic acid copolymer resin preferably has a total ratio of acrylic acid and / or methacrylic acid and the copolymerizable monomer in the resin of 60 mol % or more.

[0036] Examples of the copolymerizable monomer include (meth)acrylic acid alkyl esters (preferably lower alkyl esters of (meth)acrylic acid) such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and t-butyl (meth)acrylate; hydroxyl group-containing (meth)acrylates such as hydroxyethyl (meth)acrylate; glycidyl group-containing (meth)acrylates such as glycidyl (meth)acrylate; N,N'-dimethyl (meth)acrylic acid amines; Examples of the copolymerizable monomer include (meth)acrylamides such as N,N'-diethyl(meth)acrylamide, amino group-containing (meth)acrylates such as dimethylaminoethyl(meth)acrylate, styrenes such as styrene, vinyl toluene, α-methylstyrene, vinyl esters such as vinyl acetate and vinyl propionate, vinyl halides such as vinyl chloride, vinyl ethers such as methyl vinyl ether, carboxyl group-containing vinyls such as itaconic acid and maleic anhydride [excluding (meth)acrylic acid], cyano group-containing vinyls such as acrylonitrile and methacrylonitrile, olefins and dienes such as ethylene and propylene, etc. The copolymerizable monomers can be used alone or in combination of two or more.

[0037] Regarding the above (1) and (2), the glass transition temperatures of the first resin and the second resin can be controlled, for example, by adjusting the mass average molecular weight (Mm) of the acrylic acid copolymer resin. For example, the first resin and the second resin can be made to have a relationship of T1>T2 by making the Mm of the first resin larger than the Mm of the second resin. Preferably, the Mm of the first resin is 30,000 or more and 90,000 or less, and the Mm of the second resin is 10,000 or more and less than 30,000.

[0038] Regarding the above (1) and (2), T1, which is the glass transition temperature of the first resin, is preferably 90°C or higher, more preferably 95°C or higher, and particularly preferably 100°C or higher. The upper limit of T1 can be, for example, about 120°C, from the physical properties of the acrylic acid copolymer resin. T2, which is the glass transition temperature of the second resin, is preferably less than 80°C, more preferably 75°C or lower, and particularly preferably 65°C or lower. The lower limit of T2 can be, for example, about 30°C, from the viewpoint of ease of handling. For example, T1 and T2 preferably have a difference of 20°C or higher, more preferably a difference of 30°C or higher, and particularly preferably a difference of 40°C or higher. In this case, the deterioration of printability can be more effectively suppressed, and therefore the cosmetic properties of the printed layer 13 can be particularly improved.

[0039] With regard to the above (3), the apparent acid value of the coating layer 12 means the acid value of a mixed resin consisting of two or more kinds of resins contained in the coating layer 12. The apparent acid value of the coating layer 12 can be adjusted by controlling the acid values ​​of the first resin and the second resin. The acid values ​​of the first resin and the second resin can be adjusted, for example, by the blending ratio of (meth)acrylic acid and the copolymerizable monomer.

[0040] Regarding the above (3), the apparent acid value of the coating layer 12 is more preferably 50 mgKOH / g or more and 130 mgKOH / g or less, and particularly preferably 55 mgKOH / g or more and 125 mgKOH / g or less. In these cases, it is possible to particularly improve the alkali solubility and printability of the coating layer 12.

[0041] The acid value of the first resin and the acid value of the second resin are preferably 40 mgKOH / g or more and 150 mgKOH / g or less. In this case, the apparent acid value of the coating layer 12 can be easily set to 40 mgKOH / g or more and 150 mgKOH / g or less as in (3) above. The acid value of the first resin is preferably lower than the acid value of the second resin. The acid value of the first resin is preferably less than 60 mgKOH / g. The acid value of the second resin is preferably 80 mgKOH / g or more.

[0042] With regard to the above (4), the first resin and the second resin in the coating layer 12 preferably account for 70% by mass or more and 95% by mass or less of the entire coating layer 12, and more preferably for 80% by mass or more and 95% by mass or less. In these cases, it is possible to particularly improve the alkali solubility and printability of the coating layer 12. Also, it is preferable that the content ratio of the first resin and the content ratio of the second resin are not significantly different. From the viewpoint of improving the synergistic effect of containing two types of resin, the first resin and the second resin, it is preferable that the ratio of the content of the first resin to the content of the second resin (the content of the resin with a relatively large content / the content of the resin with a relatively small content) is 3 or less.

[0043] The fact that the coating layer 12 contains an alkali-soluble resin can be confirmed, for example, by using various analytical techniques. For example, it can be confirmed that the acrylic acid copolymer resin is present in the coating layer 12 at a specific content by nuclear magnetic resonance (NMR), gas chromatography mass spectrometry (GCMS), pyrolysis gas chromatography (pyrolysis GCMS), etc. Also, the acid value of the coating layer 12 can be confirmed, for example, by titrating the coating layer 12. The titration of the coating layer 12 can be calculated based on the result of dissolving the coating layer 12 in a titration solvent such as a mixed solvent of xylene and dimethylformamide, and performing potentiometric titration using a potassium hydroxide solution of a predetermined concentration (for example, a 0.1 mol / L potassium hydroxide-ethanol solution). Also, it can be confirmed that the coating layer 12 contains the first resin and the second resin having the above Tg, for example, by subjecting a composition used to form the coating layer described below to a differential scanning calorimetry (DSC) method. The DSC method can be performed using a "DSC6200" manufactured by Seiko Instruments Inc. at a temperature rise rate of 10°C / min. The Mm of the first resin and the Mm of the second resin can be confirmed by, for example, gel permeation chromatography (GPC).

[0044] The first and second resins are preferably methacrylic acid-methyl methacrylic acid copolymers (hereinafter also referred to as "MM copolymers"). In this case, it is possible to significantly improve both the alkali solubility and printability of the coating layer 12. The MM copolymer may be synthesized or may be a commercially available product. Commercially available products suitable for the first resin include "Dianal LR-1941" or "Dianal BR-87" manufactured by Mitsubishi Rayon Co., Ltd. Commercially available products suitable for the second resin include "JONCRYL JDX-C3000" manufactured by BASF Japan Ltd., "ARUFON UC3000" manufactured by Toa Gosei Co., Ltd., or "BR-605" manufactured by Mitsubishi Rayon Co., Ltd. Among them, it is preferable to use a combination of "Dianal LR-1941" and "JONCRYL JDX-C3000" as the first and second resins.

[0045] The coating layer 12 may contain other components in addition to the first resin and the second resin. A preferred example of the other components is a cellulose derivative. When the coating layer 12 contains a cellulose derivative, it is possible to improve the blocking resistance and adhesion of the coating layer 12.

[0046] Examples of the cellulose derivative contained in the coating layer 12 include nitrocellulose, acetylcellulose, carboxymethylcellulose or a salt thereof, methylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, cellulose acetate butyrate, and cellulose acetate propionate. It is preferable to use nitrocellulose as the cellulose derivative contained in the coating layer 12. In the coating layer 12, the cellulose derivative may be used alone or in combination of two or more kinds.

[0047] The content of the cellulose derivative in the coating layer 12 is preferably 1% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 15% by mass or less, and particularly preferably 8% by mass or more and 12% by mass or less, based on the total mass of the coating layer 12. In these cases, the blocking resistance and printability of the coating layer 12 can be improved. The cellulose derivative preferably has a degree of polymerization of 35 to 380, more preferably 45 to 290, and particularly preferably 55 to 110. In these cases, the blocking resistance and printability of the coating layer 12 can be improved.

[0048] Furthermore, the coating layer 12 may contain, for example, a vinyl chloride-vinyl acetate copolymer (hereinafter, also referred to as a "VV copolymer") as a preferred other component. When the coating layer 12 contains a VV copolymer, it is possible to further improve the adhesion between the substrate 11 and the coating layer 12.

[0049] The content of the VV copolymer in the coating layer 12 is preferably 5 to 20 mass % of the total mass of the coating layer 12, more preferably 8 to 18 mass %, and particularly preferably 9 to 12 mass %. In these cases, the adhesion and printability of the coating layer 12 can be improved. The VV copolymer in the coating layer 12 preferably has an Mm of 10,000 to 40,000, and more preferably has an Mm of 15,000 to 35,000. In these cases, the adhesion of the coating layer 12 is significantly improved.

[0050] In the label 1, it is preferable that the coating layer 12 contains a luminescent material. When the coating layer 12 contains a luminescent material, the occurrence of blocking when the labels 1 are stacked can be suppressed compared to when the printing layer 13 contains a luminescent material.

[0051] When the coating layer 12 contains a luminescent material, the content of the luminescent material in the coating layer 12 is preferably, for example, 0.3% by mass or more and 8.0% by mass or less. From the viewpoint of distinguishability, the content of the luminescent material is more preferably 1.0% by mass or more. From the viewpoint of printability, the content of the luminescent material is more preferably 5.0% by mass or less. In the label 1, only the coating layer 12 may contain the luminescent material.

[0052] <Print layer> The printing layer 13 is located on the coating layer 12 on the opposite side of the substrate 11 from the coating layer 12. The printing layer 13 is formed, for example, by applying (printing) an ink resin composition onto the coating layer 12. In this embodiment, the ink resin composition is an organic solvent-based ink, which is a so-called oil-based ink. However, the printing layer 13 may also be formed by applying a so-called water-based ink onto the coating layer 12. The ink resin composition may contain, for example, a pigment, a resin, and an additive. In addition, the printing layer 13 is preferably a design printing layer. The design printing layer is a layer that contains a pigment and displays a visible pattern or characters, etc.

[0053] The printed layer 13 may be provided on the entire surface of the coating layer 12, or on a part of the coating layer 12. In the label 1, when the printed layer 13 contains a luminescent material, only the printed layer 13 may contain the luminescent material. The printed layer 13 may contain the above-mentioned alkali-soluble resin instead of the coating layer 12. This allows the printed layer 13 to be dissolved when the label 1 is immersed in an alkaline aqueous solution, thereby enabling it to be detached from the substrate 11. In this case, the label 1 does not need to contain the coating layer 12.

[0054] The printed layer 13 may be a single layer, or may have multiple layers laminated together. In the configuration shown in Fig. 1, the printed layer 13 has a first printed layer 13a, a second printed layer 13b located on the opposite side of the first printed layer 13a to the substrate 11 and the coating layer 12, and a protective printed layer 13c located farthest from the substrate 11 in the stacking direction of the printed layer 13. The thickness of the printed layer 13 can be, for example, about 0.1 µm or more and 10 µm or less, but is not particularly limited.

[0055] The first printed layer 13a is, for example, a color ink printed layer. When the printed layer 13 is a design printed layer, the first printed layer 13a may be formed by applying ink of multiple colors in several separate layers. In other words, the first printed layer 13a may be formed by stacking multiple printed layers of different colors.

[0056] When the first printed layer 13a is a color ink printed layer, it is preferable that the first printed layer 13a does not contain a luminescent material. When the first printed layer 13a does not contain a luminescent material, the complexity of adjusting the content of the luminescent material depending on the color constituting the first printed layer 13a can be reduced.

[0057] The second printed layer 13b is, for example, a white ink printed layer. This improves the aesthetic appeal of the second printed layer 13b, which is a color ink printed layer, when the label 1 is viewed from the substrate 11 side. The second printed layer 13b, which is a white ink printed layer, may be a single layer, or may be formed from two printed layers by applying the white ink printed layer twice. Note that the printed layer 13 does not have to include the second printed layer 13b (white ink printed layer).

[0058] When the printed layer 13 contains a luminescent material, the second printed layer 13b (white ink printed layer) may be a luminescent layer containing a luminescent material. In the label 1, only the second printed layer 13b may contain a luminescent material. When the second printed layer 13b contains a luminescent material, the content of the luminescent material in the second printed layer 13b is preferably, for example, 0.3% by mass or more and 8.0% by mass or less. From the viewpoint of distinguishability, the content of the luminescent material is more preferably 1.0% by mass or more. From the viewpoint of printability, the content of the luminescent material is more preferably 5.0% by mass or less.

[0059] The protective printed layer 13c is a layer for protecting the printed layer 13 from external factors. The label 1 does not necessarily have to include the protective printed layer 13c. The label 1 may include another protective layer made of a resin film or the like instead of the protective printed layer 13c.

[0060] The protective print layer 13c may be transparent or opaque, but is preferably transparent, and more preferably colorless and transparent. The protective print layer 13c contains, for example, an acrylic resin as a main component. In this specification, the main component refers to the component (weight ratio) that is the largest among the resins contained in the layer, and is, for example, 60% by weight or more, preferably 80% by weight or more, and more preferably 90% by weight or more of the total resin.

[0061] Examples of the acrylic resin include resins containing the following monomer components: Examples of the monomer components include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, and dodecyl (meth)acrylate [preferably C1-12 (meth)acrylic acid alkyl esters]; etc.], carboxyl group-containing polymerizable unsaturated compounds or anhydrides thereof such as (meth)acrylic acid, crotonic acid, itaconic acid, fumaric acid, and maleic acid, and hydroxyl group-containing (meth)acrylic acid esters such as 2-hydroxymethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, diethylene glycol mono(meth)acrylate, and dipropylene glycol mono(meth)acrylate [preferably (meth)acrylic acid hydroxy C1-8 alkyl esters, etc.]. Here, "(meth)acrylic" means "acrylic" and / or "methacrylic".

[0062] In addition, as the monomer component, (meth)acrylic acid cycloalkyl esters such as cyclohexyl (meth)acrylate, (meth)acrylic acid amide derivatives such as N-methylol (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, and N,N-diethyl (meth)acrylamide, (meth)acrylic acid dialkylaminoalkyl esters such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dipropylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, and dipropylaminopropyl (meth)acrylate, styrene-based compounds such as styrene, vinyl toluene, and α-methylstyrene, vinyl esters such as vinyl acetate and vinyl propionate, vinyl halides such as vinyl chloride, vinyl ethers such as methyl vinyl ether, cyano group-containing vinyl compounds such as (meth)acrylonitrile, and polymerizable unsaturated compounds such as olefins and dienes such as ethylene and propylene can also be used.

[0063] The protective print layer 13c may contain a slipping component, if necessary, such as wax, silicone, inorganic fine particles, or organic fine particles.

[0064] The protective print layer 13c may contain additives as necessary, such as plasticizers, anti-settling agents, dispersants, stabilizers, defoamers, fillers, antioxidants, ultraviolet light absorbers, antistatic agents, fragrances, deodorants, slip agents, etc.

[0065] When the printed layer 13 contains a luminescent material, the protective printed layer 13c may be a luminescent layer containing a luminescent material. Even if the label 1 is exposed to strong light such as sunlight for a long time on the substrate 11 side, the luminescent material contained in the protective printed layer 13c is prevented from fading because the other printed layers act as a light shield. In the label 1, only the protective printed layer 13c may contain a luminescent material. When the protective printed layer 13c contains a luminescent material, the content of the luminescent material in the protective printed layer 13c is preferably, for example, 0.3% by mass or more and 8.0% by mass or less. From the viewpoint of identification, the above content of the luminescent material is more preferably 1.0% by mass or more. From the viewpoint of printability, the above content of the luminescent material is more preferably 5.0% by mass or less.

[0066] It is preferable that the thickest portion of the printed layer 13 is formed by applying ink overlays seven or less times, which can prevent blocking between the labels 1 after the printed layer 13 is formed.

[0067] (Label manufacturing method) The label 1 of the embodiment can be manufactured, for example, as follows: First, prepare the substrate 11. The substrate 11 can be prepared, for example, by forming a film by a method such as an extrusion method or a calendar method, and then, if necessary, subjecting the film to a stretching treatment.

[0068] Next, the coating layer 12 is formed on one surface of the substrate 11. The coating layer 12 can be formed, for example, by applying a composition (composition for forming a coating layer) containing the resin contained in the coating layer 12 onto one surface of the substrate 11 using a known printing method, and then solidifying (preferably drying and solidifying). As the printing method, gravure printing or flexographic printing is particularly preferable.

[0069] Next, the printing layer 13 is formed on the surface of the coating layer 12. The printing layer 13 can be formed, for example, by applying an ink resin composition for forming the printing layer 13 onto the surface of the coating layer 12 and then solidifying (preferably drying and solidifying). When the printing layer 13 has a plurality of layers as shown in FIG. 1, the printing layer 13 is formed by repeating application and solidification (preferably drying and solidifying) of a resin composition corresponding to each of the plurality of layers for each layer. As described above, the label manufacturing method according to the embodiment of the present disclosure includes, in this order, a step of preparing a substrate, a step of forming a coating layer on the substrate, and a step of forming a printing layer on the coating layer. The step of forming the coating layer and the step of forming the printing layer on the coating layer are both formed by the same printing method. The printing method is particularly preferably a gravure printing method.

[0070] (Label sorting method) A label sorting method according to an embodiment of the present disclosure will be described below. In the sorting method, an energy beam is irradiated onto a label group including a label 1, which is a removable printed layer label, and other labels, to separate the label 1. 2 is a flow diagram showing a label sorting method according to an embodiment of the present disclosure. As shown in FIG. 2, the label sorting method according to the embodiment of the present disclosure includes an irradiation step S1, a label identification step S2, and a sorting step S3.

[0071] Fig. 3 is a schematic diagram showing a state in which a label according to an embodiment of the present disclosure is irradiated with energy rays in a predetermined dark place. First, in the irradiation step S1, a label group including a label 1 having one or more removable printed layers and one or more other labels 9 is carried into a predetermined dark place 100 shown in Fig. 3. Specifically, the label 9 is a normal label whose printed layer is difficult to remove because the coating layer cannot be removed by alkali, and which does not contain a luminescent material.

[0072] Next, as shown in FIG. 3, the group of labels carried into the dark space 100 is irradiated with energy rays U. Specifically, the energy rays U include ultraviolet light irradiated by an ultraviolet light irradiator 110. The dominant wavelength of the energy rays U including ultraviolet light (the wavelength of the light having the strongest intensity (peak intensity) among the light included in the energy rays U) is not particularly limited, but is, for example, 365 nm or more and 400 nm or less. When the label 1 is irradiated with the energy rays U, the luminescent material included in the coating layer 12 of the label 1 emits visible light F. In the spectrum of the energy rays U, the intensity of the wavelength component that is the same as the maximum emission wavelength of the luminescent material is preferably 10% or less of the peak intensity of the energy rays U. In addition, the irradiator 110 is more preferably an LED ultraviolet light irradiator. This sufficiently reduces the intensity of the visible light included in the energy rays U irradiated by the irradiator 110, making it easy to identify the labels in the label identification step S2. It is preferable that the dominant wavelength of the energy rays U is shorter than the maximum absorption wavelength of the luminescent material. This can reduce the influence of the irradiated energy rays.

[0073] Then, in the label identification process S2, the label 1 from which the printed layer can be removed is identified by detecting the light emitted by the luminescent material contained in the label 1 when irradiated with energy rays U in the dark space 100 using a sensor 120 having a light receiving portion.

[0074] The light receiving section of the sensor 120 is preferably capable of detecting light of the maximum fluorescent wavelength of the luminescent material contained in the label 1. The sensor 120 is, for example, a camera.

[0075] The light receiving section of the sensor 120 is provided with a filter 130 that blocks at least a part of the wavelength components contained in the energy ray U. This can prevent the sensor 120 from detecting the wavelength components of the energy ray U in the dark space inside 100. This in turn makes it easier to detect the visible light F emitted by the luminescent material of the label 1. This makes it easier to identify the labels to be separated, improving the efficiency of separating the labels. In addition, it is preferable that the transmission band of the filter 130 includes the maximum fluorescent wavelength of the luminescent material contained in the label 1.

[0076] The filter 130 is preferably a bandpass filter. If the filter 130 is a bandpass filter, the influence of external light entering the sensor 120 from the entrance and exit of the dark space interior 100 can be reduced. In addition, the label group can be continuously introduced into the dark space interior 100 and discharged from the dark space interior 100, and the sorting efficiency of the label sorting can be further improved. The central wavelength of the transmission band of the bandpass filter is preferably larger than the maximum absorption wavelength of the luminescent material contained in the luminescent layer of the label 1. In addition, the central wavelength of the transmission band of the bandpass filter is preferably close to the maximum fluorescence wavelength of the luminescent material contained in the luminescent layer of the label 1. If the central wavelength is close to the maximum fluorescence wavelength, the luminescence of the luminescent material is detected while effectively suppressing erroneous detection of ambient light by the sensor. From this viewpoint, the central wavelength is, for example, 520 nm or less, preferably 490 nm or less, and more preferably 470 nm or less.

[0077] In addition, the central wavelength of the transmission band of the bandpass filter is preferably larger than the maximum fluorescence wavelength of the light-emitting material. This makes it possible to reduce the influence of the wavelength component of the energy ray in the sensor 120 when ultraviolet light containing an energy ray of the same wavelength as the maximum fluorescence wavelength is irradiated to the label 1. In addition, it is also preferable that the central wavelength is equal to or larger than the maximum fluorescence wavelength or longer than the maximum fluorescence wavelength. This makes it possible to suppress the sensor from erroneously detecting the energy ray (ultraviolet light) for making the light-emitting material emit light. From these viewpoints, the central wavelength is, for example, 380 nm or more, preferably 410 nm or more. The width of the transmission band of the bandpass filter is, for example, 10 to 100 nm, and preferably 30 to 90 nm. It is preferable that the lower limit of the transmission band of the bandpass filter is between the main wavelength of the irradiated energy ray U and the maximum fluorescence wavelength of the light-emitting material, between the maximum absorption wavelength and the maximum fluorescence wavelength of the light-emitting material, or between both of them.

[0078] By irradiating the label group with energy rays as described above, the label 1 according to this embodiment emits light due to the luminescent material contained in the luminescent layer and is detected by the sensor. On the other hand, the other labels 9 do not emit light because they do not contain the luminescent material, and are not detected by the sensor 120. In this way, the label 1 can be identified.

[0079] For the label group, irradiation and detection of luminescence may be performed for each label in the label group one by one in turn as shown in FIG. 3, or the entire label group may be irradiated with energy rays and the entire label group may be imaged with a camera as a sensor to detect and identify the luminescent labels.

[0080] Then, in the sorting step S3, the printed layer-removable labels identified in the label identifying step S2 are sorted out from the group of labels. In this manner, the printed layer-removable labels 1 are separated from the group of labels.

[0081] There is no particular limitation on the method for selecting the label 1 from the label group. The label 1 may be selected from the label group by blowing air onto the label, or the label 1 may be selected from the label group by being picked up by a mechanical arm. EXAMPLES

[0082] Hereinafter, an experimental example will be described in which it was confirmed that the labels separated by the separation method according to the present embodiment can be detected by using a filter in a dark place due to the emission of the luminescent material.

[0083] (Experimental Example 1) <Creating labels> As the label according to Experimental Example 1, a label having the configuration shown in FIG. 1 was produced as follows.

[0084] First, a polyethylene terephthalate film (PET film) having a thickness of 20 μm was prepared as the substrate 11. Next, a composition for forming the coating layer 12 was applied onto one entire surface of the PET film using the first printing unit of a gravure printing machine having multiple printing units, and then dried (drying and solidifying) to form the coating layer 12.

[0085] The composition for forming the coating layer 12 was prepared by adding 0.5 parts by mass of a fluorescent brightener having a maximum absorption wavelength of 379 nm and a maximum fluorescence wavelength of 444 nm to 100 parts by mass of the composition shown in Table 1 below.

[0086] [Table 1]

[0087] Next, using the next printing unit of the gravure printing machine, a color ink resin composition containing an oil-based indigo ink (manufactured by Sakata Inx Corporation, product name "Shrink Pack Etna") as an organic solvent-based color ink was applied onto the coating layer 12, and then dried (drying and solidifying) to form a first printing layer 13a.

[0088] Next, using the next printing unit of the gravure printing machine, a white ink resin composition containing an oil-based white ink (manufactured by Dainichi Seikagaku Kogyo Co., Ltd., "NT Hilamic (NF) 701 White") was applied onto the first printed layer 13a, and then dried (dryed and solidified) to form the second printed layer 13b.

[0089] Then, a colorless transparent ink containing an acrylic resin as a main component was applied onto the second printed layer 13b using the next printing unit of the gravure printing machine, and then the ink was dried (drying and solidifying) to form the protective printed layer 13c. This completed the label according to Experimental Example 1.

[0090] <Light irradiation treatment> Before measuring the brightness of the label, the label was subjected to a light irradiation treatment by irradiating the label from the substrate side with a sunshine lamp for 29 hours.

[0091] <Measurement of brightness> Under the same conditions as the irradiation step S1 and the label identification step S2 in the above-mentioned embodiment, the label according to the experimental example 1 that had been subjected to the light irradiation treatment was irradiated with ultraviolet light by an ultraviolet light irradiator ("LDL-339X12UV3-365W" manufactured by CCS Corporation) while measuring the brightness of the label according to the experimental example 1 by a sensor (camera). For the measurement of brightness, "FH-SCX" manufactured by OMRON Corporation was used. The main wavelength of the ultraviolet light by the ultraviolet light irradiator was 365 nm, and the central wavelength of the transmission band of the bandpass filter provided on the light receiving part of the camera was 460 nm (peak wavelength 470 nm, transmission band 425 nm to 495 nm). In addition, in the dark place, the label was placed so that the ultraviolet light irradiator and the sensor were located on the substrate side of the label.

[0092] (Experimental Example 2) A label according to Experimental Example 2 was produced in the same manner as in Experimental Example 1, except that the fluorescent whitening agent was not included in the composition for forming the coating layer 12, but was added in 5 parts by mass to the white ink resin composition for forming the second printed layer 13b. The light irradiation treatment and the measurement of brightness were carried out in the same manner as in Experimental Example 1.

[0093] (Experimental Example 3) A label according to Experimental Example 3 was produced in the same manner as in Experimental Example 1, except that the fluorescent whitening agent was added in 5 parts by mass to the resin composition for forming the protective print layer 13c, rather than to the composition for forming the coating layer 12. The light irradiation treatment and the measurement of brightness were carried out in the same manner as in Experimental Example 1.

[0094] (Experimental Example 4) A label according to Experimental Example 4 was produced in the same manner as in Experimental Example 1, except that the protective printed layer 13c was formed directly on the first printed layer 13a, so that the printed layer 13 did not have the second printed layer 13b. The light irradiation treatment and the measurement of the brightness were carried out in the same manner as in Experimental Example 1.

[0095] (Experimental Examples 5 to 8) Labels according to Experimental Examples 5-8 were produced in the same manner as Experimental Examples 1-4, except that a color ink resin composition containing an oil-based black ink (manufactured by Dainichi Seika Chemicals Co., Ltd., product name "NT Hilamic (NF)") was used in forming the first printed layer 13a. Light irradiation treatment and brightness measurement were performed in the same manner as Experimental Example 1.

[0096] (Experimental Examples 9-12) Labels according to Experimental Examples 9 to 12 were produced in the same manner as in Experimental Examples 1 to 4, except that a color ink resin composition containing an oil-based yellow ink (manufactured by Sakata Inx Corporation, product name "Shrink Pack Etna") was used in forming the first printed layer 13a. Light irradiation treatment and brightness measurement were performed in the same manner as in Experimental Example 1.

[0097] (Experimental Example 13) A label according to Example 13 was produced in the same manner as in Example 1, except that the first printed layer 13a was formed as a black-based design printed layer by overlaying a plurality of single-color ink resin compositions. The light irradiation treatment and the measurement of the brightness were carried out in the same manner as in Example 1.

[0098] (Experimental Example 14) A label according to Experimental Example 14 was produced in the same manner as in Experimental Example 1, except that the first printed layer 13a was formed as a yellow-based design printed layer by overlaying a plurality of single-color ink resin compositions. The light irradiation treatment and the measurement of the brightness were carried out in the same manner as in Experimental Example 1.

[0099] (Experimental Examples 15 and 16) In Experimental Examples 15 and 16, similar brightness measurements were carried out on the same labels as in Experimental Examples 5 and 7, respectively, except that the labels were not subjected to light irradiation treatment.

[0100] (Experimental Examples 17 and 18) In experimental examples 17 and 18, similar brightness measurements were performed on a label similar to that of experimental example 5, except that the central wavelengths of the transmission bands of the bandpass filters were set to 517.5 nm (peak wavelength 505 nm, transmission band 485 nm to 550 nm) and 527.5 nm (peak wavelength 525 nm, transmission band 500 nm to 555 nm), respectively.

[0101] (Experimental Example 19) In experimental example 19, similar brightness measurements were performed on a label similar to that of experimental example 5, except that the label was placed in a dark place so that the ultraviolet light irradiator and sensor were located on the protective printing layer side of the label.

[0102] (Reference example) A label was created as a reference example to evaluate the detectability of the label according to each experimental example based on the brightness in each experimental example. The label according to the reference example was created in the same manner as the label according to experimental example 5, except that the first printed layer 13a was formed directly on the substrate 11 without forming a coating layer as a light-emitting layer, and a protective printed layer was not formed. In other words, the label according to the reference example is a label in which the printed layer is not removable and does not have a light-emitting layer.

[0103] The label of the Reference Example was not subjected to light irradiation treatment, and the brightness was measured in the same manner as the label of the Experimental Example 5.

[0104] The results of measuring the brightness of each of the experimental examples and the reference example are shown in Table 2. The brightness values ​​are normalized to be within the range of 0 to 255.

[0105] [Table 2]

[0106] As described above, the labels according to each of Experimental Examples 1 to 19 are print-removable labels, and further contain a luminescent material. The lightness of the labels according to each of Experimental Examples 1 to 19 is measured in a dark place by a sensor having a light-receiving part provided with a filter, which measures the light emitted by the luminescent material when irradiated with energy rays. As shown in Table 2, the lightness of the labels according to each of Experimental Examples 1 to 19 is higher than that of the label according to the Reference Example (a label that does not have a coating layer, so the printing layer cannot be removed, and does not contain a luminescent material).

[0107] Therefore, it is understood that the labels of each of the experimental examples 1 to 19 can be easily identified by irradiating them with energy rays in a dark place and detecting the light emitted by the luminescent material with a sensor having a light receiving unit, and the light receiving unit is provided with a filter that blocks some of the wavelength components contained in the energy rays, and that the identified printed layer removable labels can be efficiently separated from the group of labels.

[0108] In addition, in Experimental Examples 1 to 12, the luminescent material is contained in any one of the coating layer, the second printed layer, and the protective printed layer. It is understood that the luminescent material is contained in any one of these layers, and the printing layer removable label can be easily identified by the identification method according to the present embodiment.

[0109] In the labels according to Experimental Examples 5 to 8, the first printed layer is a black ink printed layer. The labels according to Experimental Examples 5 to 8 have lower brightness than the labels according to Experimental Examples 1 to 4, in which the first printed layer is an indigo ink printed layer. The lower brightness is believed to be due to the relatively high light absorptivity of the black ink printed layer for all wavelengths of light (such as ultraviolet light contained in energy rays and light emitted from luminescent materials). However, it is understood that even if the first printed layer is a black ink printed layer, it is possible to identify a label with a removable printed layer by the identification method according to this embodiment.

[0110] In the labels according to Experimental Examples 9 to 12, the first printed layer is a yellow ink printed layer. The labels according to Experimental Examples 9 to 12 have lower brightness than the labels according to Experimental Examples 1 to 4, in which the first printed layer is an indigo ink printed layer. It is considered that the lower brightness is caused by the yellow ink printed layer having a relatively high light absorption rate in the vicinity of the wavelength of light emitted from the light-emitting material. However, it is understood that even if the second printed layer is a yellow ink printed layer, it is possible to identify a label with a removable printed layer by the identification method according to this embodiment.

[0111] Furthermore, the label according to Experimental Example 1 differs from the label according to Experimental Example 4, which does not have a second printed layer (white ink printed layer), in that it has a second printed layer (white ink printed layer). The label according to Experimental Example 1 has a higher brightness than the label according to Experimental Example 4. This is believed to be because the white ink layer transmits ultraviolet light without reflecting it, and reflects light emitted from the light-emitting material.

[0112] In addition, the label according to Experimental Example 5, in which the coating layer contains a luminous material, has a luminance value reduced by 159 by light irradiation treatment, compared to the label according to Experimental Example 15. On the other hand, the label according to Experimental Example 7, in which the protective printing layer contains a luminous material, has a luminance value reduced by 114 by light irradiation treatment, compared to the label according to Experimental Example 16. In this way, by including a luminous material in the protective printing layer located farthest from the substrate in the stacking direction of the printing layers, even if the label is exposed to relatively strong light from the substrate side, the first printing layer and the second printing layer absorb or reflect this light, reducing fading of the luminous material. In addition, it is possible to prevent the label with a removable printing layer from becoming difficult to identify.

[0113] Moreover, in Experimental Example 1, in which the brightness was measured using a camera equipped with a filter having a central wavelength of 460 nm in the transmission band, the brightness was greater than in Experimental Examples 17 and 18, in which the brightness of similar labels was measured using cameras equipped with bandpass filters having central wavelengths of 517.5 nm and 527.5 nm, respectively. In this way, by making the central wavelength of the transmission band of the bandpass filter closer to the maximum fluorescence wavelength of the light-emitting material, the printed layer-removable label can be more easily identified.

[0114] In addition, referring to Experimental Examples 5 and 19, even for the same label, the brightness value measured by the camera was significantly different depending on whether the side of the label irradiated with the energy beam was the substrate side or the protective print layer side. However, it is understood that the above-mentioned identification method can identify the print layer removable label regardless of which side of the label is irradiated.

[0115] In the above-described embodiments and examples, configurations that can be combined with each other may be combined as appropriate.

[0116] The embodiments and examples disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0117] 1, 9 label, 11 substrate, 12 coating layer, 13 printing layer, 13a first printing layer, 13b second printing layer, 13c protective printing layer, 100 dark interior, 110 irradiator, 120 sensor, 130 filter.

Claims

1. A method for separating labels with removable printed layers, the labels comprising a substrate and a printed layer, the printed layer being configured to be detachable from the substrate when immersed in an alkaline aqueous solution, and further comprising a light-emitting material that emits light when irradiated with energy rays, comprising: Irradiating a group of labels including the printed layer removable labels with energy rays in a dark place; a step of detecting light emitted from the light-emitting material by irradiation with the energy beam in the dark place using a sensor having a light-receiving unit, thereby identifying the printed layer-removable label; and selecting the identified removable printed label from the group of labels; A label sorting method, wherein the light receiving section is provided with a filter that blocks at least a portion of the wavelength components contained in the energy beam.

2. The label sorting method according to claim 1 , wherein the filter is a band-pass filter.

3. The printed layer removable label further includes a coating layer that is located between the substrate and the printed layer and contains an alkali-soluble resin, The label sorting method according to claim 1 or 2, wherein the coating layer contains the luminescent material.

4. The printing layer has a plurality of layers laminated together, The plurality of layers includes a transparent protective printing layer located farthest from the substrate in the stacking direction, The label sorting method according to claim 1 or 2, wherein the protective print layer contains the luminescent material.

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