Laser-printed labeling material and packaging using the same

Abstract

To provide: a display material that has high transparency and permits clear printing by laser; and a package.SOLUTION: A display material includes at least one layer that permits printing by laser irradiation. At least a part of the layer is subjected to printing by a color change due to the laser irradiation. When a printed part and a non-printed part are subjected to cross-section observation by a digital microscope, a significant difference is observed in at least one value of RGB values indicating elements of colors, and a thickness of the corresponding printed part is 5-200 μm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a display material having markings such as printing that can be made by laser irradiation, and packaging using the same. [Background technology]

[0002] Traditionally, packaging has been used for distributed goods such as food, pharmaceuticals, and industrial products. Many of these packages not only protect the contents but also serve to display information such as the product name, manufacturing date, and raw materials. As a means of such display, in addition to the conventional method of printing using ink, labels (tack labels) with an adhesive coating on the back of a substrate that can be printed on using ink or thermal transfer have been widely used, as described in Patent Document 1, for example. Tack labels are pre-printed on the front surface, which serves as the display surface, and are attached to a release liner (backing paper). When in use, they are peeled off the backing paper and attached to the display material. Since the backing paper becomes useless after the tack label is attached, waste increases with each label used. Furthermore, label users must have different labels with varying display content depending on the type of contents, and as the variety of contents increases, label management becomes complicated, increasing the risk of mislabeling. In addition, it is usually necessary to keep extra inventory to prepare for label shortages, and once the manufacturing and sales of the contents end, the labels are discarded as they have no further use. Thus, tack labels had drawbacks in various aspects.

[0003] To address the above problems, Patent Document 2 discloses a thermal film having a thermal recording layer. The film in Patent Document 2 changes color when heated, thus becoming a packaging body with its own display capabilities. Therefore, there is no need to use the above-mentioned tack labels. Furthermore, by incorporating a printing machine such as a thermal printer into the process of making packaging bodies using a film like the one in Patent Document 2, packaging and labeling can be completed in a single process, contributing to labor savings and cost reduction. Due to these advantages, the method of printing directly onto the packaging body itself has recently become popular. However, if a thermal layer is provided on the base film, there is a concern that the thermal layer may peel off due to friction with the outside, so a protective layer is usually provided on top of the thermal layer (on the surface side). Coating is widely used as a means of providing these functional layers. Coating involves at least the processes of application, drying, and winding, so the number of processes increases with each functional layer, reducing productivity. In addition, because these functional layers contain particles, there was also the problem that transparency decreased depending on the layer thickness.

[0004] On the other hand, in recent years, in addition to the inks and heat mentioned above, laser-triggered technologies have also become popular as a means of display (printing). For example, Patent Document 3 discloses a multilayer laminated film for laser printing in which the printing layer is made of an ink composition that can be printed by laser light. By using this film, the area irradiated with a laser changes color and can be printed. However, films like the one in Patent Document 3, like the film in Patent Document 2, require a printing layer to be provided on a film substrate, so problems such as layer peeling and reduced productivity have not been solved.

[0005] Furthermore, Patent Document 4 discloses a laser marking additive made of bismuth oxide. By incorporating this additive into plastic, the area irradiated with a laser changes color, allowing for printing. Normally, plastic alone does not react to lasers, but this additive is excited by the laser energy, causing the plastic to change color. Since the additive is located inside the film, it is useful in that it is less likely to cause the peeling of the functional layer that occurred with coatings. However, since the additive is made of metal particles, the problem of reducing the transparency of the film remains, similar to the coatings mentioned above. When printing by laser irradiation, the printing can only be recognized when the relevant area changes color. However, if the transparency of the plastic substrate itself is low, it becomes difficult to visually distinguish between the printed and unprinted areas when printed by laser irradiation, and the printing function cannot be satisfied. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2002-362027 [Patent Document 2] Japanese Patent Publication No. 2017-209847 [Patent Document 3] Japanese Patent Publication No. 2017-196896 [Patent Document 4] International Publication No. 2014 / 188828 [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention aims to resolve the problems of the prior art described above. Specifically, the objective of the present invention is to provide a display material and packaging that have high transparency and enable clear printing by laser. [Means for solving the problem]

[0008] The present invention has the following configuration. 1. A display material having at least one layer capable of being printed by laser irradiation, wherein at least a part of the layer is printed by color change due to laser irradiation, and when the printed part and the non-printed part are observed in cross-section with a digital microscope, a significant difference is observed in at least one value of the RGB values indicating color elements, and the thickness of the corresponding printed part is 5 μm or more and 200 μm or less. 2. The display material or package according to 1., wherein the thickness of the portion where color change occurs due to laser irradiation is 20 μm or more and 140 μm or less. 3. The display material according to either 1. or 2., wherein a pigment capable of causing a color change by laser irradiation is contained in the layer capable of being printed by laser irradiation at 100 ppm or more and 3000 ppm or less. 4. The display material according to any one of 1. to 3., wherein the pigment capable of being printed by laser irradiation contains a metal, and at least one of the metals is any one of bismuth, gadolinium, neodymium, titanium, antimony, tin, aluminum or an oxide thereof. 5. The display material according to any one of 1. to 4., wherein the haze is 1% or more and 40% or less. 6. A package containing the display material according to any one of 1. to 5.

Advantages of the Invention

[0009] The display material and package of the present invention have high transparency, and can provide a display material and a package capable of clear printing by laser.

Brief Description of the Drawings

[0010] [Figure 1] Image of the laser-printed display of Example 1 [Figure 2] Cross-sectional observation image of the display of Example 1

Modes for Carrying Out the Invention

[0011] The following describes the display materials of the present invention. The display material of the present invention must have at least one layer that is capable of being printed by laser irradiation (hereinafter sometimes referred to as the "laser printing layer").

[0012] 1. Raw materials that make up the laser printing layer 1.1. Pigments for laser printing The laser printing layer of the present invention requires the addition of a pigment (hereinafter sometimes simply referred to as "pigment") that has the function of changing the color of the plastic substrate when irradiated with a laser. Normally, plastic itself hardly reacts to laser light, so it is often not possible to print on it by laser irradiation. The pigment is excited by the energy of the laser light and carbonizes the surrounding resin (preferred conditions for laser irradiation will be described later). In addition to carbonizing the plastic, some types of pigments also change to black themselves. These color changes, either individually or in combination, make it possible to print on the laser printing layer. Considering printing accuracy, it is preferable to use a pigment that also changes color itself.

[0013] Examples of pigments include bismuth, gadolinium, neodymium, titanium, antimony, tin, and aluminum, either in elemental form or as an oxide. The particle size of the pigment is preferably between 0.1 μm and 10 μm. If the particle size is less than 0.1 μm, the color change during laser irradiation may be insufficient. If the particle size exceeds 10 μm, the haze of the display material tends to exceed 40%. A particle size of 0.5 μm to 9 μm is more preferable. Pigments that meet these conditions include "TOMATEC COLOR" (manufactured by Tokan Material Technology) and "Iriotec®" (manufactured by Merck Performance Materials), which are commercially available and can be suitably used.

[0014] The amount of pigment added to the laser printing layer is preferably between 100 ppm and 3000 ppm. If the amount of pigment added is less than 100 ppm, the laser printing density will be insufficient, making it difficult to see a significant difference in RGB values ​​between the printed and unprinted areas, which is undesirable. On the other hand, if the amount of pigment added exceeds 3000 ppm, the haze of the display material is likely to exceed 40%, which is also undesirable. The effect of pigment addition on haze occurs because the pigment itself is colored, and the pigment particles scatter light. One method for incorporating pigment into the plastic that constitutes the laser printing layer is to add it at any stage in the resin manufacturing process. Other methods include blending a slurry of particles dispersed in a solvent with a resin raw material using a vented kneading extruder, or blending dried particles with resin using a kneading extruder. Among these, the method of blending dried particles with plastic using a kneading extruder (masterbatch formation) is preferred.

[0015] 1.2. Types of Plastics The type of plastic constituting the laser printing layer included in this invention is not particularly limited and can be freely used without departing from the spirit of the invention. Examples of plastics include polyester, polyolefin, and polyamide. Examples of polyesters include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polytrimethylene terephthalate (PTT), polybutylene naphthalate (PBN), polylactic acid (PLA), polyethylene furanoate (PEF), and polybutylene succinate (PBS). In addition to the polyesters listed above, modified polyesters obtained by changing the monomers of the acid or diol portion may also be used. Examples of monomers for the acid portion include aromatic dicarboxylic acids such as isophthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and orthophthalic acid, as well as aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid, and alicyclic dicarboxylic acids. Furthermore, examples of monomers for the diol portion include neopentyl glycol, 1,4-cyclohexanedimethanol, diethylene glycol, 2,2-diethyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, 2,2-isopropyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, hexanediol, 1,4-butanediol, and other long-chain diols, as well as aliphatic diols such as hexanediol, and aromatic diols such as bisphenol A. In addition, the polyester may contain polyester elastomers containing ε-caprolactone or tetramethylene glycol as components. The polyester raw materials listed above may be used by mixing (dry blending) multiple homopolyesters in which carboxylic acid monomers and diol monomers are polymerized in a 1:1 ratio, or by copolymerizing two or more carboxylic acid monomers or two or more diol monomers. Alternatively, homopolyesters and copolymerized polyesters may be mixed and used.

[0016] Examples of polyolefins include polypropylene (PP) and polyethylene (PE). When using polypropylene, the stereoregularity is not particularly limited and may be isotactic, syndiotactic, or atactic, and each may be present in any proportion. When using polyethylene, its density (degree of branching) is not particularly limited and may be high density (HDPE), linear low density (LLDPE), or low density (LDPE). In addition to the homopolymers mentioned above, raw materials obtained by copolymerizing two or more different monomers may also be used. Examples of monomers used in copolymerization include ethylene and α-olefins, and examples of α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 4-methyl-1-pentene, and 4-methyl-1-hexene. The copolymerization can be random copolymerization or block copolymerization. Furthermore, in addition to the raw materials listed above, polyolefin elastomers and ionomers may also be used. The melt flow rate (MFR) of the polyolefin used as a raw material is not particularly limited and any can be used, but it is preferably between 1 and 10 g / 10 min. If the MFR is less than 1 g / 10 min, the melt viscosity of the raw material becomes too high, which leads to excessively high resin pressure during the extrusion process in film formation, making it prone to filter deformation and other problems, which is undesirable. On the other hand, if the MFR exceeds 10 g / 10 min, the molecular weight decreases drastically, which may lead to increased rupture during film formation or reduced blocking resistance. The MFR is more preferably 2 g / 10 min to 8 g / 10 min, and even more preferably 3 g / 10 min to 7 g / 10 min.

[0017] Examples of polyamides include one resin selected from polycapramid (nylon 6), polyhexamethylene adipamide (nylon 66), caprolactam / lauryl lactam copolymer (nylon 6 / 12), caprolactam / hexamethylenediammonium adipate copolymer (nylon 6 / 66), ethyleneammonium adipate / hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (nylon 6 / 66 / 610), polymer of metaxylylenediamine and adipic acid (MXD-6), and hexamethylene isophthalamide / terephthalamide copolymer (amorphous nylon), or mixed raw materials containing two or more of these. Furthermore, an adhesive modification layer can be provided on the surface of a film made from the plastics listed above. Examples of materials for the adhesive modification layer include acrylic, water-soluble or water-dispersible polyester, and hydrophobic polyester obtained by graft copolymerization of acrylic. The lower limit of the relative viscosity (RV) of the polyamide used as a raw material is preferably 2.2, and more preferably 2.3. If it is below this value, the crystallization rate may be too fast, making biaxial stretching difficult. On the other hand, the upper limit of the RV of the polyamide is preferably 4, and more preferably 3.9. If it exceeds this value, the load on the extruder may become too high, potentially reducing productivity. In this invention, relative viscosity refers to the value measured at 25°C using a solution obtained by dissolving 0.5g of polymer in 50ml of 97.5% sulfuric acid.

[0018] 1.3. Additives other than laser pigments The laser printing layer contained in the display material of the present invention may contain various additives as needed, such as waxes, antioxidants, antistatic agents, nucleating agents, viscosity reducers, heat stabilizers, coloring pigments, color inhibitors, and ultraviolet absorbers. It is also preferable to add fine particles as a lubricant to improve slipperiness. Any fine particles can be selected. For example, inorganic fine particles can be silica, alumina, titanium dioxide, calcium carbonate, kaolin, and barium sulfate, while organic fine particles can be acrylic particles, melamine particles, silicone particles, and cross-linked polystyrene particles. The average particle size of the fine particles can be appropriately selected as needed within the range of 0.05 to 3.0 μm when measured with a Coulter counter. The lower limit of the fine particle content is preferably 0.01% by weight, more preferably 0.015% by weight, and even more preferably 0.02% by weight. If it is less than 0.01% by weight, the slipperiness may decrease. The upper limit is preferably 1% by weight, more preferably 0.2% by weight, and even more preferably 0.1% by weight. Concentration exceeding 1% by weight is undesirable because it may reduce transparency. One method for incorporating particles into the laser printing layer is to add them at any stage in the manufacturing of the plastic raw material.

[0019] 1.4. Thickness of the laser-printed layer The thickness of the laser printing layer is preferably between 5 μm and 5000 μm. If the thickness of the laser printing layer is less than 5 μm, the print density decreases when irradiated with laser light, making the characters difficult to see, which is undesirable. On the other hand, if the thickness of the laser printing layer exceeds 5000 μm, it is more likely to exceed 40% haze, which is also undesirable. The thickness of the laser printing layer is more preferably between 10 μm and 2000 μm, and even more preferably between 20 μm and 1000 μm.

[0020] 2. Layers other than the laser printing layer As described above, the display material of the present invention must have at least one laser-printed layer as described in 1. "Laser-printed layer". The layer configuration of the display material may be a single layer of only the laser-printed layer, or layers other than the laser-printed layer may be laminated. Generally, considering that display materials are required to have various functions other than display function, such as mechanical strength, adhesiveness, and barrier properties, it is preferable to laminate layers having each of these functions. Among these, considering that the present invention is intended for packaging, it is even more preferable to provide an adhesive layer (hereinafter referred to as the "adhesive layer").

[0021] 2.1.Adhesive layer The adhesive layer included in the marking material of the present invention is not particularly limited as long as it has adhesive properties, and any conventionally known material can be used without departing from the spirit of the present invention. Examples include a heat-sealing layer that exhibits adhesive properties upon heating, and an adhesive (tack) layer that exhibits adhesive properties at room temperature. Examples of plastics that make up the heat sealing layer include polyester, polyolefin, and polyamide.

[0022] Examples of polyesters include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polytrimethylene terephthalate (PTT), polybutylene naphthalate (PBN), polylactic acid (PLA), polyethylene furanoate (PEF), and polybutylene succinate (PBS). In addition to the polyesters listed above, modified polyesters obtained by changing the monomers of the acid or diol portion may also be used. Examples of monomers for the acid portion include aromatic dicarboxylic acids such as isophthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and orthophthalic acid, as well as aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid, and alicyclic dicarboxylic acids. Furthermore, examples of monomers for the diol portion include neopentyl glycol, 1,4-cyclohexanedimethanol, diethylene glycol, 2,2-diethyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, 2,2-isopropyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, hexanediol, 1,4-butanediol, and other long-chain diols, as well as aliphatic diols such as hexanediol, and aromatic diols such as bisphenol A. In addition, the polyester may contain polyester elastomers containing ε-caprolactone or tetramethylene glycol as components. The polyester raw materials listed above may be used by mixing (dry blending) multiple homopolyesters in which carboxylic acid monomers and diol monomers are polymerized in a 1:1 ratio, or by copolymerizing two or more carboxylic acid monomers or two or more diol monomers. Alternatively, homopolyesters and copolymerized polyesters may be mixed and used.

[0023] Examples of polyolefins include polypropylene (PP) and polyethylene (PE). When using polypropylene, the stereoregularity is not particularly limited and may be isotactic, syndiotactic, or atactic, and each may be present in any proportion. When using polyethylene, its density (degree of branching) is not particularly limited and may be high density (HDPE), linear low density (LLDPE), or low density (LDPE). In addition to the homopolymers mentioned above, raw materials obtained by copolymerizing two or more different monomers may also be used. Examples of monomers used in copolymerization include ethylene and α-olefins, and examples of α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 4-methyl-1-pentene, and 4-methyl-1-hexene. The copolymerization can be random copolymerization or block copolymerization. Furthermore, in addition to the raw materials listed above, polyolefin elastomers and ionomers may also be used. The melt flow rate (MFR) of the polyolefin used as a raw material is not particularly limited and any can be used, but it is preferably between 1 and 10 g / 10 min. If the MFR is less than 1 g / 10 min, the melt viscosity of the raw material becomes too high, which leads to excessively high resin pressure during the extrusion process in film formation, making it prone to filter deformation and other problems, which is undesirable. On the other hand, if the MFR exceeds 10 g / 10 min, the molecular weight decreases drastically, which may lead to increased rupture during film formation or reduced blocking resistance. The MFR is more preferably 2 g / 10 min to 8 g / 10 min, and even more preferably 3 g / 10 min to 7 g / 10 min.

[0024] Examples of polyamides include one resin selected from polycapramid (nylon 6), polyhexamethylene adipamide (nylon 66), caprolactam / lauryl lactam copolymer (nylon 6 / 12), caprolactam / hexamethylenediammonium adipate copolymer (nylon 6 / 66), ethyleneammonium adipate / hexamethylenediammonium adipate / hexamethylenediammonium sebacate copolymer (nylon 6 / 66 / 610), polymer of metaxylylenediamine and adipic acid (MXD-6), and hexamethylene isophthalamide / terephthalamide copolymer (amorphous nylon), or mixed raw materials containing two or more of these. Furthermore, an adhesive modification layer can be provided on the surface of a film made from the plastics listed above. Examples of materials for the adhesive modification layer include acrylic, water-soluble or water-dispersible polyester, and hydrophobic polyester obtained by graft copolymerization of acrylic. The lower limit of the relative viscosity (RV) of the polyamide used as a raw material is preferably 2.2, and more preferably 2.3. If it is below this value, the crystallization rate may be too fast, making biaxial stretching difficult. On the other hand, the upper limit of the RV of the polyamide is preferably 4, and more preferably 3.9. If it exceeds this value, the load on the extruder may become too high, potentially reducing productivity. In this invention, relative viscosity refers to the value measured at 25°C using a solution obtained by dissolving 0.5g of polymer in 50ml of 97.5% sulfuric acid. Examples of plastics that make up the adhesive layer include polyester, polyolefin, polystyrene, and acrylic, with those having a glass transition temperature (Tg) below room temperature (around 25°C) being particularly preferred.

[0025] As an example of a polyester, it is preferable to use a saturated carboxylic acid component or a saturated diol component as a monomer that can lower the Tg. Examples of saturated carboxylic acids include adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid. Among these, adipic acid and azelaic acid are preferred. Examples of saturated diol components include long-chain diols such as ethylene glycol, diethylene glycol, 1,3-propanediol, 2,2-diethyl-1,3-propanediol, and 1,4-butanediol, and aliphatic diols such as hexanediol. Among these, diethylene glycol, 1,3-propanediol, and 1,4-butanediol are preferred. Furthermore, a polyester elastomer containing ε-caprolactone or tetramethylene glycol may be used as a component constituting the polyester resin. Polyester elastomers can be suitably used because they have the effect of lowering the Tg.

[0026] Examples of polyolefin-based materials include polyolefin elastomers. Examples of polyolefin elastomers include ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-propylene-1-butene copolymer, ethylene-propylene-1-hexene copolymer, ethylene-1-butene-1-hexene copolymer, propylene-1-butene copolymer, propylene-1-hexene copolymer, propylene-1-octene copolymer, propylene-4-methyl-1-pentene copolymer, propylene-1-butene-1-hexene copolymer, and propylene-1-butene-4-methyl-1-pentene copolymer. In addition, small amounts of styrene elastomers such as SBS and SEBS may be added to these.

[0027] Examples of polystyrene include polystyrene-based elastomers. Examples of polystyrene-based elastomers include polymers obtained by block copolymerization of aromatic alkenyl compounds and conjugated dienes, and aromatic alkenyl compounds include, for example, styrene, tert-butylstyrene, α-methylstyrene, p-methylstyrene, p-ethylstyrene, divinylbenzene, 1,1-diphenylethylene, vinylnaphthalene, vinylanthracene, N,N-dimethyl-p-aminoethylstyrene, N,N-diethyl-p-aminoethylstyrene, and Examples of conjugated diene monomers include vinylpyridine, and diolefins such as 1,3-butadiene, 1,2-butadiene, isoprene, 2,3-dimethylbutadiene, 1,3-pentadiene, 2-methyl-1,3-butadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 1,3-cyclohexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, myrcene, and chloroprene.

[0028] The acrylic may be a copolymer of acrylic monomers, or a copolymer of an acrylic monomer and other copolymerizable monomers. Examples of acrylic monomers include alkyl esters of (meth)acrylates such as (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, decyl (meth)acrylate, octadecyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate; cyclic esters of (meth)acrylates such as cyclohexyl (meth)acrylate, benzyl (meth)acrylate, and phenyl (meth)acrylate; and vinyl (meth)acrylates such as allyl (meth)acrylate, 1-methylallyl (meth)acrylate, and 2-methylallyl (meth)acrylate. Examples of copolymers derived from monomers include unsaturated group-containing (meth)acrylic acid esters, heterocyclic-containing (meth)acrylic acid esters such as glycidyl (meth)acrylate and methyl (3,4-epoxycyclohexyl)methyl (meth)acrylate, amino group-containing (meth)acrylic acid esters such as N-methylaminoethyl (meth)acrylate, N-tributylaminoethyl (meth)acrylate, and N,N-dimethylaminoethyl (meth)acrylate, alkoxysilyl group-containing (meth)acrylic acid esters such as 3-methacryloxypropyltrimethoxysilane, (meth)acrylic acid derivatives such as methoxyethyl (meth)acrylate and ethylene oxide adducts of (meth)acrylic acid, perfluoroalkyl (meth)acrylic acid esters such as perfluoroethyl (meth)acrylate and perfluorobutyl (meth)acrylate, and polyfunctional (meth)acrylic acid esters such as trimethylolpropane tri(meth)acrylate. Furthermore, examples of copolymerizable monomers other than acrylics include maleic acid, maleic anhydride, itaconic acid, and itaconic anhydride, which have at least one carboxyl group in their radically polymerizable unsaturated group.Furthermore, examples of monomers having at least one hydroxyl group in addition to a radically polymerizable unsaturated group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and diethylene glycol mono(meth)acrylate. In addition, examples of vinyl monomers copolymerizable with acrylic monomers include aromatic vinyl monomers such as styrene and α-styrene; trialkyloxysilyl group-containing vinyl monomers such as vinyltrimethoxysilane; nitrile group-containing vinyl monomers such as acrylonitrile and methacrylonitrile; acrylamide and methacrylamide group-containing vinyl monomers; and vinyl esters such as vinyl acetate and vinyl versatate.

[0029] The above-mentioned types of plastics can be used as raw materials to produce films by unstretched, uniaxially stretched, or biaxially stretched methods, or as coating agents dispersed in a solvent, etc. When producing films, unstretched or uniaxially stretched film is preferable for exhibiting adhesive properties, and unstretched film is even more preferable.

[0030] 2.2. Gas Barrier Layer In addition to the layer configuration described above, a gas barrier layer may also be provided. The presence of a gas barrier layer improves the gas barrier properties of the display material and extends the shelf life of the contents. The gas barrier layer is preferably composed of an inorganic thin film mainly composed of metal or metal oxide, and may be located in either the outermost layer or the intermediate layer. Furthermore, the gas barrier layer is preferably transparent. In addition to the gas barrier made of the inorganic thin film described above, the present invention may also include an anchor coat layer provided below the inorganic thin film layer (between the plastic film and the inorganic thin film) and an overcoat layer provided on top of the inorganic thin film layer. By providing these layers, improvements in adhesion to the gas barrier layer and improved gas barrier properties can be expected.

[0031] 2.2.1. Raw material types and composition of the gas barrier layer The raw materials for the gas barrier layer are not particularly limited, and conventionally known materials can be used. They can be appropriately selected according to the purpose in order to satisfy the desired gas barrier properties. Examples of raw materials for the gas barrier layer include metals such as silicon, aluminum, tin, zinc, iron, and manganese, and inorganic compounds containing one or more of these metals. Examples of applicable inorganic compounds include oxides, nitrides, carbides, and fluorides. These inorganic materials or inorganic compounds may be used individually or in combination. In particular, using silicon dioxide (SiOx) and aluminum oxide (AlOx) individually (as a single element) or in combination (as a binary element) is preferable because it can improve the transparency of the display material or packaging with the gas barrier layer. When the inorganic compound consists of a binary of silicon dioxide and aluminum oxide, the aluminum oxide content is preferably 20% by mass or more and 80% by mass or less, and more preferably 25% by mass or more and 70% by mass or less. If the aluminum oxide content is 20% by mass or less, the density of the gas barrier layer will decrease, which may reduce the gas barrier properties, so this is undesirable. Furthermore, if the aluminum oxide content exceeds 80% by mass, the flexibility of the gas barrier layer decreases, making it more prone to cracking, which may result in a decrease in gas barrier properties and is therefore undesirable. For metal oxides used in the gas barrier layer, an oxygen / metal elemental ratio of 1.3 or higher and less than 1.8 is preferable because it minimizes variations in gas barrier properties and consistently provides excellent gas barrier performance. The oxygen / metal elemental ratio can be determined by measuring the amounts of each element, oxygen and metal, using X-ray photoelectron spectroscopy (XPS) and calculating the oxygen / metal elemental ratio.

[0032] 2.2.2. Method for Deposition of Gas Barrier Layer The method for forming the gas barrier layer is not particularly limited, and known manufacturing methods can be used as long as they do not impair the objectives of the present invention. Among known manufacturing methods, vapor deposition is preferred. Examples of vapor deposition methods include PVD methods (physical vapor deposition) such as vacuum deposition, sputtering, and ion plating, or CVD methods (chemical vapor deposition). Among these, vacuum deposition and physical vapor deposition are preferred, and vacuum deposition is particularly preferred from the viewpoint of production speed and stability. As a heating method in vacuum deposition, resistance heating, high-frequency induction heating, electron beam heating, etc., can be used. In addition, reactive vapor deposition using means such as introducing oxygen, nitrogen, water vapor, etc. as a reactive gas, or adding ozone, or ion assist may be used. Furthermore, the film formation conditions can be changed as long as they do not impair the objectives of the present invention, such as applying a bias to the substrate or raising or cooling the substrate temperature.

[0033] The following describes a method for forming a gas barrier layer using vacuum deposition. When forming the gas barrier layer, the marking material or packaging of the present invention is conveyed to the gas barrier layer manufacturing apparatus via metal rolls. An example of the configuration of the gas barrier layer manufacturing apparatus is a winding roll, a coating drum, a winding roll, an electron beam gun, a crucible, and a vacuum pump. The marking material or packaging is set on the winding roll, passes through the coating drum, and is wound up by the winding roll. The pass line of the marking material or packaging (inside the gas barrier layer manufacturing apparatus) is depressurized by a vacuum pump, and the inorganic material set in the crucible is evaporated by a beam emitted from the electron gun and deposited onto the marking material or packaging as it passes through the coating drum. During the deposition of the inorganic material, heat is applied to the marking material or packaging, and tension is also applied between the winding roll and the winding roll. If the temperature applied to the marking material or packaging is too high, not only will the thermal shrinkage of the marking material or packaging increase, but softening will also progress, making it easier for stretching deformation due to tension to occur. Furthermore, after exiting the vapor deposition process, the temperature of the labeling material or packaging decreases significantly (cooling), leading to a large amount of shrinkage after expansion (different from thermal shrinkage). This can cause cracks in the gas barrier layer, making it difficult to achieve the desired gas barrier properties, which is undesirable. On the other hand, a lower temperature applied to the labeling material or packaging is preferable because it suppresses deformation of the labeling material or packaging. However, a lower evaporation rate of the inorganic material reduces the thickness of the gas barrier layer, raising concerns that the desired gas barrier properties may not be met. The temperature applied to the labeling material or packaging is preferably 100°C to 180°C, more preferably 110°C to 170°C, and even more preferably 120°C to 160°C.

[0034] The gas barrier laminate thus constructed has a water vapor transmission rate of 0.05 [g / (m³)] in an environment with a temperature of 40°C and a relative humidity of 90% RH. 2 ·d)] or more than 4[g / (m 2 It is preferable that the water vapor transmission rate is 4 [g / (m³) or less. 2·d)] exceeds this value, it is not preferable because when used as a package containing the contents, the shelf life of the contents will be shortened. On the other hand, when the water vapor permeability is less than 0.05 [g / (m 2 ·d)], the gas barrier property is enhanced and the shelf life of the contents is prolonged, which is preferable. However, at the current technical level, 0.05 [g / (m 2 ·d)] is the lower limit. Even if the lower limit of the water vapor permeability is 0.05 [g / (m 2 ·d)], it can be said that it is sufficient for practical use. The upper limit of the water vapor permeability is preferably 3.8 [g / (m 2 ·d)], and more preferably 3.6 [g / (m 2 ·d)]. In addition, the gas barrier laminate preferably has an oxygen permeability of 0.05 [cc / (m 2 ·d·atm)] or more and 4 [cc / (m 2 ·d·atm)] or less under the environment of a temperature of 23°C and a relative humidity of 65%RH. When the oxygen permeability exceeds 4 [cc / (m 2 [[ID=ID=18]]·d·atm)], it is not preferable because the shelf life of the contents will be shortened. On the other hand, when the oxygen permeability is less than 0.05 [cc / (m 2 ·d·atm)], the gas barrier property is enhanced and the shelf life of the contents is prolonged, which is preferable. However, at the current technical level, the oxygen permeability of 0.05 [cc / (m 2 ·d·atm)] is the lower limit. Even if the lower limit of the oxygen permeability is 0.05 [cc / (m 2 ·d·atm)], it can be said that it is sufficient for practical use. The upper limit of the oxygen permeability is preferably 3.8 [cc / (m 2 ·d·atm)], and more preferably 3.6 [cc / (m 2 ·d·atm)].

[0035] 2.3. Overcoat layer The gas barrier laminate using the display material of the present invention (in this section, these are collectively referred to as "display material") can be provided with an overcoat layer on the gas barrier layer formed as described in the above "2.2. Gas barrier layer" for the purpose of improving scratch resistance and further improving the gas barrier property.

[0036] 2.3.1. Types of Overcoat Layers The type of overcoat layer is not particularly limited, but conventionally known materials such as compositions consisting of urethane resin and silane coupling agents, compounds consisting of organosilicon and its hydrolysates, and water-soluble polymers having hydroxyl or carboxyl groups can be used, and can be appropriately selected according to the purpose in order to satisfy the desired gas barrier properties, etc. Furthermore, the overcoat layer may contain one or more additives for the purpose of providing antistatic properties, UV absorption, coloring, thermal stability, slipperiness, etc., to the extent that it does not impair the objectives of the present invention, and the types and amounts of additives can be appropriately selected according to the desired objectives.

[0037] 2.3.2. Method for forming the overcoat layer When forming the overcoat layer, the substrate marking material or packaging is transported to the coating equipment via metal rolls. Examples of equipment configurations include an unwinding roll, a coating process, a drying process, and a winding process. During overcoating, the laminate set on the unwinding roll is guided via metal rolls through the coating and drying processes, and finally to the winding roll. The coating method is not particularly limited, and conventionally known methods such as gravure coating, reverse coating, dipping, raw coating, air knife coating, comma coating, screen printing, spray coating, gravure offset, die coating, and bar coating can be used and selected as appropriate according to the desired purpose. Among these, gravure coating, reverse coating, and bar coating are preferred from the viewpoint of productivity. For drying, one or more heating methods such as hot air drying, hot roll drying, high-frequency irradiation, infrared irradiation, and UV irradiation can be used. In the drying process, the base material or packaging is heated, and tension is also applied between metal rolls. If the temperature at which the base material or packaging is heated in the drying process is too high, not only will the thermal shrinkage of the base material or packaging increase, but softening will also progress, making it easier for stretch deformation due to tension to occur, and cracks will easily form in the gas barrier layer of the base material or packaging. Furthermore, after exiting the drying process, the temperature of the laminate drops (cooling) significantly, and the amount of shrinkage after expansion (different from thermal shrinkage) increases accordingly, causing cracks in the gas barrier layer and overcoat layer, making it difficult to achieve the desired gas barrier properties, which is undesirable. On the other hand, the lower the temperature at which the base material or packaging is heated, the more the deformation of the base material or packaging is suppressed, which is preferable, but the solvent of the coating liquid will not dry easily, raising concerns that the desired gas barrier properties may not be achieved. The temperature at which the base material or packaging is heated is preferably 60°C to 200°C, more preferably 80°C to 180°C, and even more preferably 100°C to 160°C.

[0038] 2.4 Other Layers The display material of the present invention may also be provided with a layer that has been treated with corona treatment, coating treatment, or flame treatment to improve the printability and slipperiness of the surface, and can be provided as desired without sacrificing the requirements of the present invention. Furthermore, the display material of the present invention may have characters or patterns added to it for the purpose of improving its design, in addition to printing by laser irradiation. Known materials such as gravure printing inks or flexographic printing inks can be used to constitute these characters or patterns. The number of printing layers may be one or multiple. To improve the design by using multiple colors, it is preferable to have multiple printing layers. The printing layers may be located at the outermost layer or in the middle layers.

[0039] 3. Characteristics of the displayed material 3.1.Printed area 3.1.1. RGB values The laser-printed layer constituting the display material of the present invention must show a significant difference between the printed and unprinted portions when observed in cross-section with a digital microscope, in at least one of the RGB values ​​representing the color elements. RGB values ​​are values ​​that specify a color, where R represents red, G represents green, and B represents blue. Each RGB value can range from 0 to 255, and the combination of these values ​​determines the color. Here, "showing a significant difference" means that when the RGB values ​​of the printed and unprinted portions are obtained at any 10 points each (n=10) from the same image and the 95% confidence interval (1.96 times the standard error) is calculated, the upper limit of one does not overlap with the lower limit of the other, i.e., the difference between the two is greater than zero. The method of cross-sectional observation and the method of calculating the 95% confidence interval will be described later in the examples. By showing a significant difference in any one of the RGB values ​​of the printed and unprinted portions, the printing can be clearly recognized by visual inspection. Preferably, there are two values ​​showing a significant difference, and more preferably three (all RGB values). The difference between the upper and lower limits of the 95% confidence interval for RGB values ​​is preferably 5 or more, more preferably 10 or more, and particularly preferably 15 or more.

[0040] 3.1.2. Thickness The laser-printed layer constituting the display material of the present invention needs to have a laser-printed portion with a thickness of 5 μm to 200 μm when observed in cross-section with a digital microscope. As the thickness of the laser-printed portion increases while there is a significant difference in the RGB values ​​mentioned above, the visually perceived print density is amplified. If the thickness is less than 5 μm, it becomes difficult to visually recognize the print, even if there is a significant difference in the RGB values ​​mentioned above. On the other hand, if the thickness is 200 μm or more, the print density is amplified, which is preferable, but the haze in the non-printed portion tends to exceed 40%, making it difficult to visually distinguish the print, which is undesirable. The thickness of the laser-printed portion is preferably 10 μm to 180 μm, more preferably 15 μm to 160 μm, and particularly preferably 20 μm to 140 μm.

[0041] 3.2. Non-printing area (all layers) 3.2.1. Haze The non-printed portion, including the entire layer of the display material of the present invention, preferably has a haze of 1% to 40%. A haze exceeding 40% is undesirable because it reduces the transparency of the display material and impairs the visibility of the contents. Unlike conventionally disclosed discoloration techniques using simple laser marking, the display material of the present invention requires a high degree of clarity because the printing created by laser irradiation must be legible. A haze of 35% or less is more preferable, and 30% or less is even more preferable. On the other hand, a lower haze value is preferable because it improves transparency, but in the state of the art of the present invention, 1% is the lower limit, and even if the lower limit is 2%, it is practically sufficient.

[0042] 3.2.2. L* value The non-printable portion, including the entire layer of the display material of the present invention, preferably has an L* value of 70 to 95, which indicates color. The L* value represents brightness, and the higher the value, the higher the brightness. An L* value of less than 70 is undesirable because it causes the display material to exhibit a dull color and is unattractive. As with the haze described above, the display material of the present invention requires a high degree of clarity because the printing created by laser irradiation must be readable. An L* value of 70.5 or higher is more preferable, and 71 or higher is even more preferable. On the other hand, in the art of the present invention, the upper limit of the L* value is 95, and even if the upper limit is 94.5, it is practically sufficient.

[0043] 3.2.3. Thickness The total thickness of the display material of the present invention is preferably 8 μm or more and 5000 μm or less. If the total thickness is less than 8 μm, the handling becomes poor and it becomes difficult to handle during secondary processing such as printing, so this is undesirable. On the other hand, the total thickness may exceed 5000 μm, but this is undesirable because the haze of the display material tends to exceed 40%, as well as the weight used increases and chemical costs rise. The total thickness is more preferably 13 μm or more and 4500 μm or less, and even more preferably 18 μm or more and 4000 μm or less.

[0044] 4. Manufacturing conditions for the laser printing layer 4.1. Raw material mixing and supply In manufacturing the display material of the present invention, as described in "1. Laser Printing Layer" above, the laser printing layer must contain a pigment that can be printed by laser irradiation. Since it is preferable to use the pigment in masterbatch form, two or more raw materials are usually mixed. Conventionally, when two or more raw materials are mixed and fed into an extruder, variations (segregation) occur in the supply of the raw materials, which leads to large variations in RGB values, making it difficult to distinguish between laser-printed and non-printed areas. In other words, the confidence interval (described later) of the RGB values ​​increases due to variations in the supply of raw materials, making it easier for the confidence intervals of the RGB values ​​in the printed and non-printed areas to overlap. To prevent this and narrow the confidence interval of the RGB values ​​to facilitate color distinction, it is preferable to install an agitator in the piping directly above the extruder or in the hopper to uniformly mix the raw materials before melt extrusion.

[0045] 4.2. Molten Extrusion The display material or packaging of the present invention can be obtained by supplying the raw materials described in 1. "1. Laser Printing Layer" to an extruder in the manner described in 4.1. "Raw Material Mixing and Supply," melting and extruding the raw materials from the extruder to form an unstretched film, and then stretching it by the predetermined method shown below. If the film includes a laser printing layer and other layers, the timing of laminating each layer may be before or after stretching. When laminating before stretching, it is preferable to melt and extrude the resins that will be the raw materials for each layer using separate extruders and join them using a feed block or the like in the middle of the resin flow path. When laminating after stretching, it is preferable to use lamination, in which separately formed films are bonded together with an adhesive, or extrusion lamination, in which molten plastic is poured onto the surface of a single or laminated film to laminate it. From the viewpoint of productivity, the method of laminating each layer before stretching is preferred.

[0046] Known methods can be used for melt extrusion of the raw material resin, and a method using an extruder equipped with a barrel and a screw is preferred. In the case of raw materials that decompose due to the influence of moisture during melting (such as polyester), it is preferable to dry them beforehand using a dryer such as a hopper dryer or paddle dryer, or a vacuum dryer, until the moisture content is 100 ppm or less, more preferably 90 ppm or less, and even more preferably 80 ppm or less. After drying the raw materials in this way, an unstretched film can be obtained by rapidly cooling the resin melted by the extruder. Any existing method such as the T-die method or the tubular method can be used for extrusion.

[0047] Furthermore, a higher shear rate when extruding resin from the die opening is preferable because it reduces thickness unevenness in the width direction of the film (especially in the deepest recess). This is because a higher shear rate stabilizes the pressure during resin extrusion at the T-die exit. A preferred shear rate is 100 sec. -1 The above, and more preferably 150 seconds -1 The above is particularly preferably 170 seconds -1 That concludes the explanation. A higher draft ratio is preferable as it results in better thickness uniformity in the longitudinal direction, but if the draft ratio is too high, resin residue and other debris will adhere to the resin discharge part of the die, reducing productivity, so it is not desirable for it to be too high. The shear rate at the die exit can be calculated from the following equation 1.

[0048] γ = 6Q / (W × H) 2 ) ···Formula 1 γ: Shear rate (sec -1 ) Q: Discharge volume of raw material from the extruder (cm³) 3 / sec) W: Width of the die exit opening (cm) H: Length of the die exit opening (lip gap) (cm)

[0049] Subsequently, an unstretched film can be obtained by rapidly cooling the film melted by extrusion. As a method for rapidly cooling the molten resin, a method of casting the molten resin from a die onto a rotating drum and rapidly cooling and solidifying it to obtain a substantially unoriented resin sheet can be suitably employed. The film to be used as the laser printing layer may be manufactured using any of the following methods: unstretched, uniaxially stretched (stretched in at least one direction, either longitudinal or transverse), or biaxially stretched. From the viewpoint of mechanical strength and productivity, uniaxial stretching is preferred, and biaxial stretching is more preferred. The following explanation will focus on the sequential biaxial stretching method using longitudinal stretching followed by transverse stretching, but transverse stretching followed by longitudinal stretching is also acceptable, as only the main orientation direction changes. Simultaneous biaxial stretching, where the film is stretched in both the longitudinal and transverse directions at the same time, is also acceptable.

[0050] 4.3. First (Vertical) Extension For stretching in the first direction (longitudinal or longitudinal direction), the film is preferably introduced into a longitudinal stretcher with multiple rolls arranged in a continuous pattern. For longitudinal stretching, it is preferable to preheat the film with a preheating roll. The preheating temperature should be set between the glass transition temperature Tg and the melting point Tm + 50°C, using the Tg of the plastic constituting the film as a reference. If the preheating temperature is lower than Tg, it becomes difficult to stretch the film in the longitudinal direction and breakage is more likely to occur, which is undesirable. Also, if the heating temperature is higher than Tm + 50°C, the film tends to stick to the rolls and become prone to wrapping around them, which is also undesirable. Longitudinal stretching is performed when the film reaches Tg~Tm+50℃. The longitudinal stretching ratio should be between 1x and 5x. Since 1x means no longitudinal stretching, the longitudinal stretching ratio should be 1x to obtain a transversely oriented film, and 1.1x or higher to obtain a biaxially oriented film. A longitudinal stretching ratio of 1.1x or higher is preferable because it gives molecular orientation in the longitudinal direction of the film, increasing its mechanical strength. There is no upper limit to the longitudinal stretching ratio, but if the longitudinal stretching ratio is too high, breakage is likely to occur during the subsequent transverse stretching, so it is preferable to keep it at 10x or lower. A longitudinal stretching ratio of 1.2x to 9.8x is more preferable, and 1.4x to 9.6x is even more preferable.

[0051] 4.4.Second (lateral) stretching After the first (longitudinal) stretching, it is preferable to perform transverse stretching at a stretching ratio of approximately 2 to 13 times at Tg to Tm + 50°C while holding both ends of the film in the width direction (direction perpendicular to the longitudinal direction) with clips inside the tenter. It is preferable to preheat before performing transverse stretching, and preheating should be carried out until the surface temperature of the labeling material or packaging reaches Tg to Tm + 50°C. The lateral stretching ratio is more preferably 2.2 times or more and 12.8 times or less, and more preferably 2.4 times or more and 12.6 times or less. Note that the stretching speed differs between longitudinal stretching and lateral stretching (longitudinal stretching is faster), so the range of preferred stretching ratios differs.

[0052] After transverse stretching, it is preferable to pass the film through an intermediate zone where no active heating is performed. The temperature in the final heat treatment zone is higher than in the transverse stretching zone of the tenter, so if an intermediate zone is not provided, the heat from the final heat treatment zone (hot air itself and radiant heat) will flow into the transverse stretching process. In this case, the temperature in the transverse stretching zone will not be stable, resulting in variations in physical properties. Therefore, it is preferable to pass the transversely stretched film through an intermediate zone for a predetermined time before performing the final heat treatment. In this intermediate zone, it is important to block the accompanying flow associated with the movement of the film and the hot air from the transverse stretching zone and the final heat treatment zone so that when a strip of paper is hung down without the film passing through, the strip hangs almost completely vertically. A passage time of about 1 to 5 seconds in the intermediate zone is sufficient. If it is shorter than 1 second, the length of the intermediate zone will be insufficient, and the heat blocking effect will be inadequate. On the other hand, a longer intermediate zone is preferable, but if it is too long, the equipment will become large, so about 5 seconds is sufficient.

[0053] 4.5. Heat Treatment After passing through the intermediate zone, it is preferable to perform heat treatment in the heat treatment zone at Tg to Tm + 150°C. Heat treatment promotes crystallization of the film, which not only reduces the thermal shrinkage rate that occurred in the stretching process but also tends to increase the tensile breaking strength. If the heat treatment temperature is below Tg, the thermal shrinkage rate of the film tends to increase, which is undesirable. On the other hand, if the heat treatment temperature exceeds Tm + 150°C, the haze tends to exceed 40%, which is also undesirable. The heat treatment temperature is more preferably Tg + 10°C to Tm + 140°C, and even more preferably Tg + 20°C to Tm + 130°C. The passage time through the heat treatment zone is preferably between 2 seconds and 20 seconds. If the passage time is less than 2 seconds, the film will pass through the heat treatment zone before its surface temperature reaches the set temperature, rendering the heat treatment ineffective. The longer the passage time, the more effective the heat treatment becomes, so 5 seconds or more is even more preferable. However, increasing the passage time would require larger equipment, so in practical terms, 20 seconds or less is sufficient.

[0054] During heat treatment, the thermal shrinkage rate in the width direction can be reduced by shortening the distance between tenter clips by an arbitrary factor (relaxation in the width direction). Therefore, in the final heat treatment, it is preferable to perform relaxation in the width direction within the range of 0% to 10% (a relaxation rate of 0% means no relaxation is performed). Although the shrinkage rate in the width direction decreases as the relaxation rate in the width direction increases, the upper limit of the relaxation rate (the shrinkage rate in the width direction of the film immediately after transverse stretching) is determined by the raw materials used, the stretching conditions in the width direction, and the heat treatment temperature, so relaxation cannot be performed beyond this limit. In the laser printing layer that constitutes the display material of the present invention, the upper limit of the relaxation rate in the width direction is 10%. Furthermore, during heat treatment, it is also possible to shorten the distance between clips in the longitudinal direction by an arbitrary factor (relaxation in the longitudinal direction).

[0055] 4.6. Cooling After passing through the heat treatment zone, it is preferable to cool the film in the cooling zone using cooling air at a temperature of 10°C to 30°C for a period of 2 to 20 seconds. Then, by cutting and removing the ends of the film while winding it up, you can obtain a film roll.

[0056] 5. Lamination and bag-making method for display materials 5.1. Lamination method of the laser-printed layer and other layers When manufacturing the display material of the present invention, the method of laminating the laser-printed layer and the "layers other than the laser-printed layer" described in 2. above is not particularly limited, and adjacent films can be bonded to each other by conventionally known dry lamination or extrusion lamination. In the case of dry lamination, commercially available dry lamination adhesives can be used. Typical examples include DIC Dry® LX-703VL and DIC KR-90 manufactured by DIC Corporation, Takenate® A-4 and Takelac® A-905 manufactured by Mitsui Chemicals Corporation. In the case of extrusion lamination, the plastics that make up the layers other than the laser-printed layer are melted and bonded between the layers, or between the layers and other layers, but it is also preferable to laminate an anchor coat layer to improve the adhesion of the surface of the layers, etc.

[0057] 5.2. Method for making bags for the indicated material The marking material of the present invention (in this section, "the marking material of the present invention" includes laminates having the gas barrier layer described in "2.2. Gas Barrier Layer" and laminates having the overcoat layer described in "2.3. Overcoat Layer") can be suitably used as printed packaging. Examples of packaging include bags made by heat sealing, such as vertical pillow bags, horizontal pillow bags, and gusset bags, and heat-sealed bags. Adhesives such as hot melt may be used for bonding these. Furthermore, lids for plastic containers and bottle labels formed into a cylindrical shape by solvent-based center sealing are also included as packaging. It is sufficient that at least a part of the packaging is made of the marking material of the present invention.

[0058] 6. Types of lasers Examples of laser types (wavelengths) include CO2 lasers (10600nm), YAG lasers (1064nm), YVO4 lasers (1064nm), fiber lasers (1090nm), green lasers (532nm), and UV lasers (355nm). Among these, the type of laser used for the display material of the present invention is not particularly limited, but CO2 lasers are often used to burn through plastics and are often used for purposes other than printing, which is the essence of the present invention, so they are not preferred as a laser source. YAG lasers, YVO4 lasers, fiber lasers, green lasers, and UV lasers are preferred as laser sources, and YAG lasers, fiber lasers, and UV lasers are more preferred. Commercially available equipment can be used for laser printing, and typical examples include the Brother Industrial Printing LM-2550 (YAG laser), Omron MX-Z2000H-V1 (fiber laser), and Keyence MD-U1000 (UV laser). The labeling material or packaging of the present invention can be suitably used as labeling material or packaging for various articles such as food, pharmaceuticals, and industrial products. [Examples]

[0059] Next, the present invention will be specifically described using examples and comparative examples. However, the present invention is not limited in any way to the embodiments of these examples, and can be modified as appropriate without departing from the spirit of the invention. <Preparation of polyester raw materials> [Example of combination] In a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, 100 mol% dimethyl terephthalate (DMT) as the dicarboxylic acid component and 100 mol% ethylene glycol (EG) as the polyhydric alcohol component were charged so that the molar ratio of ethylene glycol was 2.2 times that of dimethyl terephthalate. Using 0.05 mol% zinc acetate (relative to the acid component) as a transesterification catalyst, the transesterification reaction was carried out while distilling off the resulting methanol. Subsequently, 0.225 mol% antimony trioxide (relative to the acid component) was added as a polycondensation catalyst, and the polycondensation reaction was carried out at 280°C under reduced pressure of 26.7 Pa to obtain polyester A with an intrinsic viscosity of 0.75 dl / g. This polyester A is ethylene terephthalate. The composition of polyester A is shown in Table 1.

[0060] [Mixing example 1] Polyester A obtained in the above synthesis example and the laser pigment "TOMATEC COLOR42-920A (main component Bi2O3)" (manufactured by Tokan Material Technology Co., Ltd.) were mixed (dry blended) in a weight ratio of 95:5 and fed into a screw extruder. The mixture was heated at 275°C to melt and mix. This molten resin was continuously extruded in a cylindrical shape from a strand die and cut with a strand cutter to obtain chip-shaped polyester B (masterbatch). The intrinsic viscosity IV of polyester B was 0.72 dL / g. The composition of polyester B is shown in Table 1.

[0061] [Mixing example 2] Polyester A and the laser pigment "IRIOTEC® 8825 (main components Sn, Sb)" (manufactured by Merck Performance Materials) were mixed (dry blended) in a weight ratio of 95:5 to obtain polyester C (masterbatch) in the same manner as in mixing example 1. The intrinsic viscosity IV of polyester C was 0.72 dL / g. The composition of polyester C is shown in Table 1.

[0062] [Mixing example 3] Polyester A was mixed (dry blended) with the lubricant "Silysia® 266 (SiO2)" (manufactured by Fuji Silysia Co., Ltd.) to a concentration of 7000 ppm, and polyester D (masterbatch) was obtained in the same manner as in Mixing Example 1. The intrinsic viscosity IV of polyester D was 0.72 dL / g. The composition of polyester D is shown in Table 1.

[0063] <Preparation of polyolefin raw materials> [Polyolefin A] As polyolefin A, Sumitomo Noblen® FS2011DG3 (polypropylene (PP) manufactured by Sumitomo Chemical) was used.

[0064] [Mixing example 4] The above polyolefin A and the laser pigment "TOMATEC COLOR42-920A (main component Bi2O3)" (manufactured by Tokan Material Technology Co., Ltd.) were mixed (dry blended) in a weight ratio of 95:5 and fed into a screw extruder for melting and mixing. This molten resin was continuously extruded in a cylindrical shape from a strand die and cut with a strand cutter to obtain chip-shaped polyolefin B.

[0065] [Mixing example 5] Polyolefin A and the laser pigment "IRIOTEC® 8825" (manufactured by Merck Performance Materials) were mixed (dry blended) in a weight ratio of 95:5 to obtain polyolefin C in the same manner as in Mixing Example 1.

[0066] [Table 1]

[0067] <Examples of film production> [Film 1] Polyester A and polyester B were mixed in a mass ratio of 97:3 as the raw material for the laser printing layer (A), and polyester A and polyester D were mixed in a mass ratio of 95:5 as the raw material for the other layer (layer B). The mixed raw materials for layers A and B are fed into separate screw extruders, and both layers A and B are melted at 285°C and extruded through a T-die at a shear rate of 280 sec. -1 The material was extruded using this method. A stirrer was installed directly above the extruder, and the mixed raw materials were fed into the extruder while being stirred by this stirrer. Each molten resin was joined by a feed block midway through the flow path and discharged from a T-die, and an unstretched film was obtained by cooling it on a chill roll set to a surface temperature of 30°C. The flow path of the molten resin was set so that the central layer of the laminated film was layer A and both outermost layers were layer B (a 2-type, 3-layer structure of B / A / B), and the discharge amount was adjusted so that the thickness ratio of layer A to layer B was 90 / 10 (B / A / B = 5 / 90 / 5). The unstretched laminated film, obtained by cooling and solidifying, was guided to a longitudinal stretching machine with multiple rolls arranged in a series. After preheating on a preheating roll until the film temperature reached 90°C, it was stretched to 3.4 times its original size.

[0068] After longitudinal stretching, the film was guided to a transverse stretching machine (tenter) and preheated for 5 seconds until the surface temperature reached 115°C. Then, it was stretched 3.8 times in the width direction (transverse direction). The transversely stretched film was then guided directly to the intermediate zone and passed through in 1.0 second. In the intermediate zone of the tenter, the hot air from the heat treatment zone and the hot air from the transverse stretching zone were blocked so that when a strip of paper was hung down without the film passing through, the strip of paper would hang almost completely vertically. Subsequently, the film that had passed through the intermediate zone was guided to the heat treatment zone and heat-treated at 220°C for 7 seconds. At the same time as the heat treatment, the clip spacing in the width direction of the film was narrowed, thereby performing a 3% relaxation treatment in the width direction. After passing through the final heat treatment zone, the film was cooled with 30°C cooling air for 5 seconds. By cutting off both edges and winding the film into a roll with a width of 400 mm, a biaxially oriented film with a thickness of 70 μm was continuously produced over a predetermined length. The manufacturing conditions are shown in Table 2.

[0069] [Film 2, 3] Films 2 and 3 were produced in the same manner as film 1, by continuously changing the raw material mixing conditions, discharge conditions, longitudinal stretching temperature, longitudinal stretching ratio, transverse stretching temperature, transverse stretching ratio, and heat treatment temperature. The manufacturing conditions for each film are shown in Table 2.

[0070] [Film 4] Film 4 is produced by feeding a raw material, which is a mixture of polyester A and polyester D in a mass ratio of 95:5, into a screw extruder, melting it at 285°C, and then shearing it through a T-die at a speed of 280 sec. -1 The film was extruded. Similar to film 1, film 4 also had a stirrer mounted directly above the extruder, and the mixed raw materials were fed into the extruder while being stirred by this stirrer. The molten resin extruded in this way was cooled on a chill roll set to a surface temperature of 30°C to obtain an unstretched film. The obtained unstretched film was subjected to longitudinal stretching, transverse stretching, and heat treatment under the same conditions as for film 1, and wound into a roll with a width of 400 mm to continuously produce a biaxially oriented film with a thickness of 12 μm over a predetermined length.

[0071] A gas barrier laminate was continuously fabricated by laminating a gas barrier layer onto one side of this film roll to obtain a roll. Specifically, using aluminum as the deposition source, aluminum oxide (AlOx) was deposited onto one side of the film by vacuum deposition while introducing oxygen gas in a vacuum deposition machine. The thickness of the gas barrier layer was 10 nm. Subsequently, an overcoat layer was continuously fabricated on the gas barrier layer side of the obtained gas barrier laminate roll to obtain another roll. Specifically, a solution of tetraethoxysilane hydrolysis solution and polyvinyl alcohol mixed in a 50:50 ratio was continuously applied, and then the roll was guided into a drying oven set to a temperature of 120°C and an air velocity of 15 m / s to continuously deposit the overcoat layer. The thickness of the overcoat layer was 300 nm. The manufacturing conditions for the obtained laminate are shown in Table 2.

[0072] [Film 5] Polyolefin A and polyolefin B were mixed in a mass ratio of 97:3 as the raw material for the laser printing layer (layer A), while polyolefin A alone (100%) was used as the raw material for the other layers (layer B). The mixed raw materials for layers A and B were fed into separate screw extruders, and both layers A and B were melted at 250°C and extruded from the T-die at a shear rate of 280 sec⁻¹. Similar to film 1, a stirrer was installed directly above the extruder for film 5, and the mixed raw materials were fed into the extruder while being stirred by this stirrer. The molten resins of each layer were joined by a feed block midway through the flow path and discharged from the T-die, and cooled on a chill roll set to a surface temperature of 30°C to obtain an unstretched laminated film. The flow path of the molten resin was set so that the central layer of the laminated film was layer A and both outermost layers were layer B (a 2-type, 3-layer structure of B / A / B), and the discharge amount was adjusted so that the thickness ratio of layer A to layer B was 90 / 10 (B / A / B = 5 / 90 / 5). The unstretched laminated film obtained by cooling and solidifying was used to continuously produce films with various longitudinal stretching temperature, longitudinal stretching ratio, transverse stretching temperature, transverse stretching ratio, and heat treatment temperature, similar to film 1. The manufacturing conditions are shown in Table 2.

[0073] [Film 6, 7] Films 6 and 7 were produced in the same manner as film 5, with various changes in raw material mixing conditions, discharge conditions, longitudinal stretching temperature, transverse stretching temperature, and transverse stretching ratio. The manufacturing conditions are shown in Table 2. Note that film 7 does not contain laser printing pigment.

[0074] [Film 8] Polyester A and polyester B were mixed in a mass ratio of 97:3 as the raw material for the laser printing layer (A), and polyester A and polyester D were mixed in a mass ratio of 95:5 as the raw material for the other layer (layer B). The mixed raw materials for layers A and B were separately fed into screw extruders without a stirrers. Both layers A and B were melted at 285°C and extruded from a T-die at a shear rate of 80 sec⁻¹. The molten resins were joined together by a feed block midway through the flow path and extruded from the T-die. An unstretched film was obtained by cooling on a chill roll set to a surface temperature of 30°C. The flow path of the molten resin was set so that the central layer of the laminated film was layer A and the outermost layers on both sides were layer B (a 2-type, 3-layer structure of B / A / B). The extrusion rate was adjusted so that the thickness ratio of layers A to B was 90 / 10 (B / A / B = 5 / 90 / 5). The unstretched laminated film obtained by cooling and solidifying was used to continuously produce films with various longitudinal stretching temperature, longitudinal stretching ratio, transverse stretching temperature, transverse stretching ratio, and heat treatment temperature, similar to film 1. The manufacturing conditions are shown in Table 2. [Film 9] Film 9 used was L4102-30μm Rixfilm (registered trademark) manufactured by Toyobo Co., Ltd.

[0075] [Table 2]

[0076] <Examples of materials used for displays> [Example 1] The display material was prepared by laminating film 1 and film 9 using a dry lamination adhesive (Takelac® A-950, manufactured by Mitsui Chemicals, Inc.). A display object was fabricated by irradiating the obtained display material with a laser to print the characters "ABC123". A 355nm ultraviolet (UV) laser marker (MD-U1000, manufactured by Keyence Corporation) was used as the printing machine, and the laser was irradiated under the following conditions: laser power 40%, scan speed 1000 mm / sec, pulse frequency 40 kHz, and spot variable -20. The physical properties of the obtained display object are shown in Table 3.

[0077] [Examples 2-5, Comparative Examples 1-3] In the same manner as in Example 1, various films were laminated to create a display material, and a display body was fabricated by laser printing. The physical properties of the obtained display body are shown in Table 3. Note that the laser-printed layer in Comparative Example 2 was made by laminating two layers of film 2 (thickness 240 μm).

[0078] <Evaluation method for display materials> The evaluation method for the display material is as follows: For the measurement samples, the printed and unprinted portions of the display material were cut out and used.

[0079] [Thickness] A 5cm x 5cm section of the unprinted area was cut out and used as a sample. The thickness of this sample was measured at 10 different points using a micrometer, and the average thickness (μm) was calculated.

[0080] [Type and amount of laser printing pigment contained in the laser printing layer] Quantitative determination of Nd, Bi, Sb, Sn, and P 0.1 g of the sample was accurately weighed into a Teflon® container of a microwave sample decomposition apparatus (Anton Paar, Multiwavepro), 6 mL of concentrated nitric acid was added, and the sample was placed in the apparatus with a dedicated lid and outer container. The apparatus was then heated at a final temperature of 200°C for 60 minutes. After cooling to room temperature, the treated solution was placed in a 50 mL digital tube, and the treated Teflon® container was washed with ultrapure water and placed in the same tube to a final volume of 50 mL, preparing the measurement sample. Subsequently, the treated solution was measured using a high-frequency inductively coupled plasma atomic emission spectrometer (Hitachi High-Tech Science, SPECTROBLUE), and the amount of metallic elements in the sample was quantified using a calibration curve created with standard solutions of the target elements. The element content in the sample was denoted as A (ppm), the element concentration in the pretreatment solution as B (mg / L), and the element concentration in the blank solution (measurement blank) as C (mg / L). The amount of metallic elements in 0.1 g of the sample was calculated using the following formula 2.

[0081] A=(BC)×50 / 0.1 Formula 2

[0082] [Determination of other metallic elements] 0.1 g of the sample was weighed into a platinum crucible and pre-carbonized on a hot plate to 400°C. Then, ashing was performed at 550°C for 8 hours using a Yamato Scientific FO610 electric furnace. After ashing, 3 mL of 6.0 N hydrochloric acid was added, and acid decomposition was performed on a hot plate at 100°C, heating until the hydrochloric acid completely evaporated. After acid decomposition, the solution was diluted to a final volume using 20 mL of 1.2 N hydrochloric acid. The treated solution was then measured using a high-frequency inductively coupled plasma atomic emission spectrometer (Hitachi High-Tech Science, SPECTROBLUE), and the amount of metallic elements in the sample was quantified using a calibration curve created with standard solutions of the target elements. The elemental content in the sample was denoted as A (ppm), the elemental concentration in the pre-treatment solution as B (mg / L), and the elemental concentration in the blank solution (measurement blank) as C (mg / L). The amount of metallic elements in 0.1 g of the sample was calculated using the following formula 3.

[0083] A=(BC)×20 / 0.1 Equation 3

[0084] [Hayes] A 5cm x 5cm section of the unprinted portion was cut out and used as a sample. Measurements were taken in accordance with JIS-K-7136 using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., 300A). Two measurements were taken, and the average value was calculated.

[0085] [Color L* value] A 5cm x 5cm non-printed portion was cut out and used as a sample. Using a spectrophotometer (Nippon Denshoku Co., Ltd., ZE-6000), the color tone (L* value, b* value) was measured on one sample of the display material or packaging using the reflectance method.

[0086] [Water vapor transmission rate] Water vapor transmission was measured according to JIS K7126 Method B. A water vapor transmission analyzer (PERMATRAN-W3 / 33MG, manufactured by MOCON) was used to measure the transmission rate in an atmosphere of 40°C and 90% RH, with the conditioned gas permeating from the heat-seal layer side. Prior to measurement, the sample was conditioned by being left in a 65% RH environment for 4 hours.

[0087] [Oxygen permeability] Oxygen permeability was measured according to the JIS K7126-2 method. Using an oxygen permeability analyzer (OX-TRAN 2 / 20, manufactured by MOCON), oxygen permeability was measured in the direction of oxygen permeation from the heat seal layer side under an atmosphere of 23°C and 65% RH. Prior to measurement, the sample was left in a 65% RH environment for 4 hours to conditioned it.

[0088] [Print evaluation] Visual evaluation The characters printed with a laser were judged according to the following criteria. Judgment: ○ Characters can be recognized visually. Judgment: Unable to recognize characters visually.

[0089] • Quantitative evaluation of RGB values ​​by cross-sectional observation with a digital microscope. The printed portion was cut out, and a microtome was used to create a cross-section of the printed area. Specifically, as shown in Figure 1, a sample was cut from the printed letters "ABC123" such that the base of the "A" and the unprinted (transparent) portion combined had a width of 1 cm, and the perpendicular direction between them was 3 cm. Toyobo Co., Ltd.'s Ester Film (registered trademark) E5100-100 μm was bonded to both surfaces of this sample using a two-component epoxy adhesive (Cemedine Co., Ltd. EP001N) to create an embedded sample for cross-sectional observation. After scraping the cross-section of this embedded sample with a microtome, the cross-section (the 3 cm sample side) was observed using a HIROX RH-2000 digital microscope, and the RGB values ​​of the printed and unprinted portions were obtained. The included software was used to obtain the RGB values. The observation conditions were as follows:

[0090] Lens MXB-5000REZ Light source High brightness LED (color temperature 5700K) Magnification 600x (MID Range) H field of view 513.01μm Resolution 0.27μm Brightness level 100 (Automatic) No gamma correction Color correction 2 Edge Correction 14 White balance: Red 175, Blue 128, Green 142

[0091] When setting observation conditions, ensure that the boundary between printed and unprinted areas is discernible (avoiding extreme brightness or white balance in the observation field, resulting in overexposure or complete darkness). This is achieved by setting at least one RGB value in either the printed or unprinted area to less than 200 and greater than 50. If either RGB value falls outside this range, the observation conditions are inappropriate, and adjustments to brightness levels, white balance, etc., are necessary. Figure 2 shows a cross-sectional image of Example 1. The sample position was adjusted so that the printed and unprinted areas could be observed simultaneously on one screen. RGB values ​​were obtained from 10 arbitrary points in both the printed and unprinted areas, excluding the 100 μm boundary between them (the center of Figure 2). The mean and standard error of the obtained RGB values ​​were calculated using equations 4 and 5 below.

[0092] Average = (X1 + X2 + ... + X n ) / n expression 4 Standard error=s / (n 1 / 2 ) Equation 5 Standard deviation=[{(X1-X0) 2 +(X2-X0) 2 +···+(X n -X0) 2} / n] 1 / 2 X n :nth data X0: Average value n: Number of data points (10) s: standard deviation

[0093] From the obtained mean and standard error, the upper and lower limits of the 95% confidence interval for each data point were calculated using equations 6 and 7 below.

[0094] 95% confidence interval upper limit = mean + standard error × 1.96 Equation 6 Lower limit of 95% confidence interval = Mean - Standard error × 1.96 Equation 7 For each of the RGB values ​​in the printed and unprinted areas, a statistically significant difference was determined if the upper limit of one 95% confidence interval did not overlap with the lower limit of the other.

[0095] Example) R value in Example 1 → Significant difference found Printed portion 95% confidence interval = 112.6~133.0 Non-printed portion 95% confidence interval = 164.0~179.2 R-value for Example 3 → No significant difference Printed portion 95% confidence interval = 138.9~170.1 95% confidence interval for the unprinted portion = 145.2 to 160.8

[0096] [Thickness of the laser printing layer] The thickness of the printed portion in the laser-printed layer was measured from the cross-sectional observation images obtained in the "Quantitative RGB Evaluation by Cross-Sectional Observation" described above. The measurement was performed using the software included with the HIROX RH-2000 digital microscope.

[0097] [Table 3]

[0098] [Evaluation results of display materials] The materials used in Examples 1 through 5 all exhibited the excellent physical properties listed in Table 3, and favorable evaluation results were obtained. On the other hand, Comparative Example 1 did not contain laser pigment, so it did not print when irradiated with a laser, and cross-sectional observation did not show a significant difference in RGB values. Furthermore, although Comparative Example 2 contained laser pigment, the laser-printed layer was thick at 240 μm, and the haze in the non-printed area exceeded 40%, making it difficult to recognize the print. Cross-sectional observation also showed no significant difference in RGB values. Although Comparative Example 3 contains laser pigment, when the film that forms the laser printing layer is manufactured, there was a large variation in the raw material composition. As a result, the confidence intervals for the RGB values ​​in the printed and unprinted areas overlapped, making it difficult to distinguish between printed and unprinted areas. [Industrial applicability]

[0099] The display material of the present invention has high transparency and allows for clear laser printing, making it suitable for use as a display material and packaging.

Claims

1. A display material having at least one laser-printable layer and an adhesive layer, wherein at least a portion of the laser-printable layer is printed by a color change caused by laser irradiation, and when the printed portion and the unprinted portion are observed in cross-section with a digital microscope, a significant difference is observed in at least one of the RGB values ​​indicating the color element, the thickness of the corresponding printed portion is 5 μm or more and 200 μm or less, and the laser-printable layer is a stretched film layer made of polyester, polyolefin, or polyamide.

2. The display material or packaging according to claim 1, characterized in that the thickness of the portion that undergoes a color change due to laser irradiation is 20 μm or more and 140 μm or less.

3. The marking material according to either claim 1 or 2, characterized in that a layer capable of being printed by laser irradiation contains a pigment capable of causing a color change by laser irradiation in an amount of 100 ppm to 3000 ppm.

4. The marking material according to any one of claims 1 to 3, characterized in that the pigment, which enables printing by laser irradiation, contains a metal, and the metal includes at least one of the elements or oxides of bismuth, gadolinium, neodymium, titanium, antimony, tin, or aluminum.

5. A labeling material according to any one of claims 1 to 4, characterized in that the haze is 1% or more and 40% or less.

6. A package containing the labeling material described in any one of claims 1 to 5.

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