Laser-printed labels and packaging

Abstract

[Problem] To provide, with high productivity, a high-quality display body that has particularly high concealing properties among laser-printed display bodies, for which print peeling does not occur even when an external stimulation such as rubbing is applied, and for which characters are clearly visible due to the high density and definition of the printing. [Solution] This display body is characterized by: including at least one layer of a white print layer on which printing by laser irradiation is possible, the white print layer including a print section that is printed on by a laser and a non-print section; and satisfying the following (1) to (3). (1) An absolute value of a difference in color L* values between the print section and the non-print section is 1.0-10.0; (2) a total light transmittance of the non-print section is 8-50%; and (3) a thickness reduction rate of the print section in a cross-section direction is 1-80% by volume with respect to the non-print section.

Description

[Technical Field]

[0001] This invention relates to a display body that includes markings such as printing. In particular, this invention relates to a display body that is laser-printed on a white film. [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 (hereinafter sometimes referred to as "printing"). As a means of such display, 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 packaging. 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 number of contents increases, label management becomes complicated, increasing the risk of mislabeling. In addition, it is usually necessary to keep extra stock 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 various problems.

[0003] To resolve these issues, for example, Patent Document 2 discloses a thermal film having a thermal recording layer. The film in Patent Document 2 changes color when heated, so it has display properties on its own, eliminating the need for adhesive labels. Furthermore, by using a film like the one in Patent Document 2, printing can be completed in a single step by incorporating a thermal printer or other printing machine into the packaging process, thus contributing to labor savings and cost reduction. Due to these advantages, the method of directly printing on the film that forms the packaging 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 (outermost layer). Coating is a widely used method for providing these protective layers and other functional layers. However, coating requires at least the steps of application, drying, and winding, and the number of steps increases with each functional layer, thus reducing productivity. In addition, many of these functional layers contain particles, and in this case, there is a problem that transparency decreases as the layer thickness increases. Furthermore, both the ink-based printing technology used for tack labels and the heat-based printing technology used for thermal labels mentioned above failed to achieve the resolution required for human visual recognition (approximately 0.2 mm) when attempting to reduce the print size due to blurring. While there was a demand for smaller print sizes for packaging materials such as medicines, which require a large amount of information, the conventional technologies described above had limitations.

[0004] On the other hand, recently, in addition to the inks and heat mentioned above, laser-triggered marking technologies have also become widespread. For example, Patent Document 3 discloses a laser marking additive made of bismuth oxide. By kneading this additive into plastic, the area irradiated with a laser changes color, making it possible to print. Normally, plastic alone does not react to lasers, but this additive is excited by the laser energy, charring the plastic and changing color itself, making printing possible. Since the additive is located inside the film, this technology can solve the problem of peeling of the functional layer that was a problem with coatings. Furthermore, when using a laser, the printing is less likely to bleed, so it is possible to make the character size smaller than the resolution of the human eye. However, the metal particles disclosed in Patent Document 3 do not exhibit opacity when added to the film, so they have not been able to replace white marking materials such as tack labels. When the opacity of the substrate is poor, not only is the content more susceptible to degradation by light, but the printing also becomes difficult to see. Regarding the latter, a drawback has been pointed out: in the case of packaging made using a display printed on a transparent film, it becomes difficult to discern what is printed when the printing overlaps with the contents or the surrounding background. This is a drawback that has also been pointed out with the thermal film mentioned above. When a large amount of metal particles described in Patent Document 3 are added to improve opacity, the base film becomes colored black, but the laser printing also develops a color close to black, making it difficult to distinguish from the base material, and thus the visibility of the printing does not improve.

[0005] As a technology that can solve this problem, for example, Patent Document 4 discloses a laser marking ink composition containing titanium dioxide and a laminate using the same. Since this composition has titanium dioxide as its main component and is white, the laminate using it has good opacity and good visibility of the laser printing. However, when a composition like that in Patent Document 4 is laminated as a laser marking layer (hereinafter sometimes referred to as the "printing layer") on the outermost layer of a base film, the problem of the print peeling off due to external stimuli such as rubbing remains. Furthermore, if the laser marking layer is provided as an intermediate layer to avoid this peeling, the base film must be provided as the outermost layer, which increases the number of lamination steps and reduces productivity.

[0006] Patent documents 5 and 6 disclose laminates or polyester films that enable printing by directly incorporating a laser marking agent into the film. This technology is expected to solve the problems of opacity, print visibility, layer delamination, and productivity described above. However, the technologies in patent documents 5 and 6 were disclosed at least 10 years ago and do not currently satisfy the required printing performance (print density). Print density usually improves as the amount of laser marking agent added increases. The optimal amount of laser marking agent (hereinafter sometimes referred to as "laser pigment") varies depending on the type, but in the examples in patent documents 5 and 6, it is often around 1 to 5 wt%, with the highest being 18 wt%. When attempting to increase the amount of laser marking agent added beyond this to improve print density, problems such as film embrittlement, decreased heat resistance, and coloration other than white occur. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2002-362027 [Patent Document 2] Japanese Patent Publication No. 2017-209847 [Patent Document 3] International Publication No. 2014 / 188828 [Patent Document 4] Japanese Patent Publication No. 2020-2259 [Patent Document 5] Japanese Patent Publication No. 2005-144784 [Patent Document 6] Japanese Patent Publication No. 2008-80805 [Non-patent literature]

[0008] [Non-Patent Document 1] DY Tzou, Ultrafast Laser Heating on Metal Films: Effects of Microvoids, J. Thermophys. Heat. Trans., 2002, vol. 16, No. 1, p. 30-35. [Non-Patent Document 2] Michael Richter, Ingo Riedel, Christian Schubbert, Patrick Eraerds, Jurgen Parisi, Thomas Dalibor, Jorg Palm, Simulation study of the impact of interface roughness and void inclusions on Cu(In,Ga)(Se,S)2 solar cells, Physica Status Solidi (A) Applications and Materials, 2015, vol. 212, No. 2, p. 298-306. [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The present invention aims to solve the problems of the prior art described above. Specifically, the present invention aims to provide a high-quality display that, among laser-printed displays, has particularly high opacity, does not peel off even when subjected to external stimuli such as rubbing, and has high print density and resolution so that the characters can be clearly seen, all while maintaining high productivity. [Means for solving the problem]

[0010] The present invention consists of the following configuration. 1. A display body having at least one white printable layer that can be printed by laser irradiation, the white printable layer having a printed portion and a non-printable portion printed by the laser, and satisfying the following (1) to (3). (1) The absolute difference in color L* values ​​between the printed area and the non-printed area is between 1.0 and 10.0. (2) The total light transmittance of the non-printed area is 8% or more and 50% or less. (3) The thickness reduction rate of the printed area in the cross-sectional direction relative to the non-printed area 1% by volume or more and 80% by volume or less 2. The display body according to 1., characterized in that one or more elements or compounds selected from the group consisting of bismuth, gadolinium, neodymium, titanium, antimony, tin, aluminum, calcium, and barium are included in the white printing layer as a laser printing pigment. 3. The display body according to 2., characterized in that at least one of titanium dioxide or calcium carbonate is included in the white printing layer as a laser printing pigment. 4. A display element according to any one of 1 to 3, characterized in that the laser printing pigment contained in the white printing layer is 5% by mass or more and 50% by mass or less. 5. A display element according to any one of 1 to 4, characterized in that the void content of the non-printed portion is 10% by volume or more and 80% by volume or less. 6. A display body according to any one of 1 to 5, characterized in that the thickness of the non-printable portion in the white printable layer that can be printed by laser irradiation is 5 μm or more and 200 μm or less. 7. The display body according to any one of 1. to 6., wherein either the height or the width of the printing size in the printing section is 0.2 mm or more and 100 mm or less. 8. The display body according to any one of 1. to 7., wherein the resin constituting the white printing layer is mainly any one of polyester, polypropylene, and polyethylene. 9. A packaging body including a lid material or a label, characterized by using at least a part of the display body according to any one of 1. to 8.

Effects of the Invention

[0011] According to the present invention, it is possible to provide a display body that can reduce waste and display errors that have been problems with conventional tack labels, has high concealability, has no printing peeling due to external stimuli such as rubbing, and enables clear printing with high productivity.

Brief Description of the Drawings

[0012] [Figure 1] The printing section of the display body of Example 1. [Figure 2] A cross-sectional observation image of the non-printing section of the display body of Example 1. [Figure 3] A cross-sectional observation image of the printing section of the display body of Example 1.

Modes for Carrying Out the Invention

[0013] Hereinafter, the display body of the present invention will be described. 1. Characteristics of the display body The display body of the present invention has at least one white printable layer that can be printed by laser irradiation, and the white printable layer has a printed portion and an unprinted portion, and the following characteristics are essential or preferred requirements. In the following, "printed portion" and "unprinted portion" refer to the positional relationship in the in-plane direction of the display body, with the former being the portion that has turned black due to laser irradiation and the latter being the portion that has not been irradiated by the laser and remains white. Furthermore, "printed layer" and "other layers" refer to the arrangement of each layer in the cross-sectional (thickness) direction of the display body, and are unrelated to whether or not printing is present. Details of the "printed layer" and "other layers" will be described later. In addition, "display body" may also be referred to as "film" below.

[0014] 1-1. Color L* value (non-printed area - printed area) The display element of the present invention requires that the absolute difference in the color L* values ​​between the printed and unprinted areas (hereinafter sometimes simply referred to as "difference in L* values") be between 1.0 and 10.0. If this difference is less than 1.0, the color tones of the printed and unprinted areas become too similar, making it difficult to see the print even if the total light transmittance described later is between 8% and 50%. On the other hand, if the difference in L* values ​​exceeds 10.0, the print becomes easier to see, but this requires increasing the laser irradiation power, which is undesirable because it tends to cause the thickness reduction rate of the printed area described later to exceed 80% by volume. A difference in L* values ​​of 1.5 to 9.5 is more preferable, and a difference of 2.0 to 9.0 is even more preferable.

[0015] 1-2. Total light transmittance (non-printed area) The display element of the present invention requires a total light transmittance of 8% or more and 50% or less in the non-printed area. A lower total light transmittance of the non-printed area is preferable as it improves the opacity of the display element, but attempting to achieve less than 8% tends to result in a cavity content exceeding 80% by volume and a laser printing pigment content exceeding 50% by mass, which may reduce the mechanical strength of the display element. On the other hand, if the total light transmittance exceeds 50%, not only does the opacity of the display element decrease, but even if the color L* value is between 1 and 10, the film becomes nearly transparent, making it difficult to recognize the print, which is undesirable. A total light transmittance of 10% or more and 48% or less in the non-printed area is more preferable, and 12% or more and 46% or less is even more preferable.

[0016] 1-3. Thickness reduction rate (printed area) A key requirement of the present invention is that the thickness reduction rate of the printed portion in the cross-sectional direction is between 1% and 80% of the non-printed portion. The thickness reduction rate is determined by observing the cross-sections of the printed and non-printed portions of the display body with a digital microscope, and expressing the value as a percentage by dividing the thickness of the printed portion by the thickness of the non-printed portion. A detailed measurement method will be described later. When a laser is irradiated onto the display body, the laser marking agent contained in the display body is excited by the laser energy, and the plastic constituting the film is carbonized, thereby creating the print. At that time, the plastic undergoes carbonization, melting, and gasification, resulting in a decrease in volume (etching). Although there is still room for discussion regarding the parameters that affect the visibility of laser-formed prints, it is believed that this etching effect, in addition to the discoloration of the laser marking agent and plastic, also contributes to the visibility. In other words, laser irradiation creates physical irregularities (especially depressions) on the surface of the printed area (or the interface with other laminated layers if other layers are laminated on the surface), and the degree of light scattering (appearance) in this area changes compared to the non-printed area, thus improving the visibility of the print. As the thickness reduction rate increases, larger irregularities are formed, and therefore the visibility of the print improves. If the thickness reduction rate is less than 1 volume%, there are almost no irregularities due to etching, so the visibility of the print decreases. On the other hand, if the thickness reduction rate exceeds 80 volume%, the thickness of the printed area decreases drastically, making it more susceptible to perforation or breakage of the display due to tension. A thickness reduction rate of 5 volume% to 75 volume% is more preferable, and 10 volume% to 70 volume% is even more preferable.

[0017] 1-4.Cavity content The display body of the present invention preferably contains cavities, and the cavities are preferably 10% to 80% by volume relative to the entire cross-sectional area (all layers) of the display body. The cavity content is calculated by observing the cross-section of the display body with a digital microscope. A detailed calculation method will be described later. The effect of the cavity on the display performance of the present invention is explained below. Conventionally, laser printing was achieved using the aforementioned laser printing pigment, and the density of this pigment controlled the print density. However, the inventors discovered that when the pigment concentration is increased to more than 50% by mass in an attempt to improve print density, the amount of plastic constituting the printing layer in the display body relatively decreases, resulting in the display body becoming brittle (in this invention, the tensile breaking strength tends to fall below 40 MPa). In other words, they found that there is a trade-off relationship between print density and mechanical strength, and it is difficult to achieve both simultaneously. Therefore, the inventors have been studying the design of a printing layer that overcomes this trade-off relationship, particularly the effect of cavities that can efficiently utilize (absorb) the irradiated laser energy. This effect will be explained with reference to non-patent literature.

[0018] Non-Patent Document 1 describes the effect of cavities within a 0.1 μm thick metal thin film on the laser reflectance (temperature change) when a laser is irradiated onto the metal thin film. Figure 3 of Non-Patent Document 1 shows that when a cavity exists directly below the laser irradiation position (to the left of the cavity in the Non-Patent Document), the laser reflectance decreases by about an order of magnitude compared to when no cavity exists. This decrease in external laser reflectance can be interpreted as the energy being absorbed into the metal. Although this document uses a metal substrate and the metal thickness and cavity size differ from those of the present invention, the inventors speculate that it suggests the possibility that the presence of cavities improves the efficiency of laser energy absorption.

[0019] Non-Patent Document 2 concerns thin-film solar cells, and although it is in a different technical field from Non-Patent Document 1, Non-Patent Document 2 investigates the power generation efficiency when the surface roughness and internal cavity size of thin-film solar cells are changed. Figure 8 shows the short-circuit current (Jsc), open-circuit voltage (Voc), and curve factor (FF) when the width of the cavity at the interface where the light-absorbing layer (CIGSSe) and the back electrode (Mo(Se,s)2) are joined is changed. Among these, it is shown that when the cavity width increases and the junction area becomes 30% or less, Jsc increases. This is stated to be due to the effect that incident light (infrared light) is reflected and re-incident to CIGSSe because the refractive index difference between CIGSSe and the cavity is greater than the refractive index difference between CIGSSe and Mo(Se,s)2, i.e., the absorption efficiency is improved. This document differs from the present invention in that the incident light is sunlight rather than a laser, but it can be interpreted that the absorption efficiency is improved because energy rays are reflected at the interface between the bulk and the cavity, and the inventors speculate that qualitatively, this suggests the same mechanism as in Non-Patent Document 1.

[0020] Based on the information inferred from the two non-patent documents mentioned above, the inventors diligently studied the design of an optimal cavity that can improve print density by increasing the energy absorption efficiency of the laser, and have completed the present invention. Specifically, the inventors have found that if the cavity is present in the print layer at a ratio of 10% to 80% by volume, and the cavity height described in "2-1-3. Cavity Height (Thickness Direction)" below is within a predetermined range, the number of laser reflections at the interface between the plastic in the print layer and the cavity, i.e., laser absorption into the print layer, occurs efficiently, and the print density is improved. If the cavity content is less than 10% by volume, the laser light reflection efficiency at the cavity interface becomes insufficient, resulting in a decrease in print density, which is undesirable. On the other hand, if the cavity content exceeds 80% by volume, the amount of plastic carbonized by the laser light decreases relatively, which may not only reduce the print density but also cause the tensile breaking strength of the display to fall below 40 MPa. The cavity content is more preferably 15% by volume or more and 75% by volume or less, and even more preferably 20% by volume or more and 70% by volume or less. The layer containing the cavity can be any of the layers that make up the display. For example, the cavity may be in the same layer as the "2-1. Printed Layer" described later, or the cavity may be in the central layer with the printed layers located on either side of it. In the latter case, it is thought that the laser reflected by the cavity in the central layer is re-incident to the outer printed layer and absorbed. To increase the laser absorption efficiency, it is preferable that the cavity is included in the printed layer.

[0021] 1-5. Height of the cavity (in the thickness direction) The cavities contained in the printed layer constituting the present invention preferably have a height (distance in the thickness direction of the display) of 1 μm or more and 8 μm or less. By setting the cavity height to 1 μm or more and 8 μm or less within the range of a cavity content of 10 volume% or more and 80 volume% or less, the number of cavities in the thickness direction of the printed layer becomes appropriate, increasing the number of laser reflections and improving energy absorption efficiency. If the cavity height is less than 1 μm, the interface between the cavity and the resin becomes unclear, making it difficult to set the cavity content to 10 volume% or more. On the other hand, if the cavity height exceeds 8 μm, not only is it easy for the cavity content to exceed 80 volume%, but the number of cavities contained in the thickness direction of the display is drastically reduced, which decreases the laser reflection and absorption efficiency and worsens the print density, so it is undesirable. The cavity height is more preferably 1.5 μm or more and 7.5 μm or less, and even more preferably 2 μm or more and 7 μm or less.

[0022] 1-6. Print size The size of the print on the display element of the present invention (the part whose color L* value differs from the white part of characters or designs) is preferably 0.2 mm or more and 100 mm or less in height or width. The resolution of the human eye is said to be about 0.2 mm, and if the character size is less than 0.2 mm, the difference in color L* values ​​tends to be less than 1, making it difficult to recognize the print. On the other hand, if the print size exceeds 100 mm, it is preferable as it makes it easier to recognize the print, but since the application of the present invention is intended for display on packaging, if the print size is too large, the amount of information that can be written on the packaging will be reduced, which is undesirable. The print size is more preferably 0.5 mm or more and 90 mm or less, and even more preferably 1 mm or more and 80 mm or less.

[0023] 1-7. Tensile breaking strength (non-printed area) The non-printable portion constituting the display body of the present invention preferably has a tensile breaking strength of 40 MPa to 400 MPa in at least one direction within the 360 ​​degrees of the plane. A tensile breaking strength below 40 MPa is undesirable because the display body will easily break under tension. The lower limit of the tensile breaking strength is more preferably 50 MPa, and even more preferably 60 MPa. On the other hand, a tensile breaking strength exceeding 400 MPa is desirable in terms of mechanical strength, but MPa is the upper limit in the art of the present invention. A tensile breaking strength of 390 MPa is sufficient for practical purposes.

[0024] 1-8. Thickness (non-printed area) The thickness of the non-printed portion constituting the display body of the present invention is preferably 5 μm or more and 200 μm or less. If this thickness is less than 5 μm, it becomes difficult to make the total light transmittance of the non-printed portion 50% or less, even if the concentration of the laser printing pigment or other white pigments described later is increased. On the other hand, while an increase in the thickness of the non-printed portion is desirable because it reduces the rate of reduction of total light, if it exceeds 200 μm, no further improvement in opacity can be expected, and it is undesirable because it only increases the chemical cost of the display body. The thickness of the non-printed portion is more preferably 10 μm or more and 190 μm or less, and even more preferably 15 μm or more and 185 μm or less.

[0025] 2. Display Unit Configuration The display element of the present invention must have at least one printable layer that turns black when irradiated with a laser, making it printable, and at least a portion of the printable layer must be printed by the laser. The following describes the essential or preferred configuration of the printable layer and the configuration of other layers.

[0026] 2-1. Printing layer 2-1-1. Types, amounts, and methods of adding laser printing pigments. To make the printing layer constituting the present invention laser printable, it is necessary to add a laser printing pigment that has a color-changing function upon laser irradiation. The plastic that constitutes the display body usually does not react much to laser light, so it cannot be printed by laser irradiation. The laser printing pigment is excited by the energy of the laser light, and printing becomes possible as the surrounding plastic is carbonized. In addition to the carbonization of the plastic, some types of laser printing pigments change to black themselves. Printing on the printing layer becomes possible through the combined or individual effects of this carbonization and the color-changing effect of the laser printing pigment. From the viewpoint of print density, it is preferable to select a laser printing pigment that has both the carbonization of plastic and the color-changing effect of itself. Furthermore, it is even more preferable to select a laser printing pigment that has opacity itself. Specific types of laser printing pigments include bismuth, gadolinium, neodymium, titanium, antimony, tin, aluminum, calcium, and barium, either as elements or oxides. Of these, the laser printing pigment is preferably titanium dioxide, calcium carbonate, bismuth trioxide, antimony trioxide, or barium sulfate, more preferably titanium dioxide or calcium carbonate, and even more preferably titanium dioxide. The particle size of the laser printing pigment is preferably 0.1 μm or more and 10 μm or less. If the particle size of the laser printing pigment is less than 0.1 μm, the color change during laser irradiation may not be sufficient. On the other hand, if the particle size of the laser printing pigment exceeds 10 μm, there is a concern that the cavity content in the printed layer will exceed 80%. The particle size of the laser printing pigment is more preferably 1 μm or more and 9 μm or less, and even more preferably 2 μm or more and 8 μm or less.

[0027] The amount of laser printing pigment added to the printing layer must be between 5% by mass and 50% by mass. If the amount of pigment added is less than 5% by mass, the printing density by the laser will not be sufficient, which is undesirable. On the other hand, if the amount of pigment added exceeds 50% by mass, the amount (volume) of plastic that is carbonized will relatively decrease, which will not only result in insufficient printing density but may also cause the tensile breaking strength of the display to fall below 40 MPa, which is also undesirable. The amount of laser printing pigment added is more preferably between 7% by mass and 48% by mass, and even more preferably between 9% by mass and 46% by mass. Laser printing pigments can be added at any stage in the manufacturing of the resin or film that will serve as the raw material for the display. For example, in the resin manufacturing stage, methods include blending a slurry of particles dispersed in a solvent with a plastic raw material using a vented kneading extruder, or blending dried particles with plastic resin using a kneading extruder (masterbatch formation). Among these methods, the method of using a masterbatch containing laser printing pigment as the raw material for the film is preferred.

[0028] 2-1-2. Types of Plastics The type of plastic constituting the printing layer 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.

[0029] The intrinsic viscosity (IV) of the polyester raw material is not particularly limited and any can be used, but it is preferably between 0.5 and 1.2 dL / g. If the IV is less than 0.5 dL / g, the molecular weight of the raw material is too low, which can easily lead to problems such as breakage during film formation and the tensile breaking strength of the display being less than 40 MPa. On the other hand, if the IV exceeds 1.2 dL / g, the resin pressure in the extrusion process during film formation becomes too high, which is undesirable as it can easily cause filter deformation. It is more preferable that the IV is between 0.55 dL / g and 1.15 dL / g, and even more preferable that it is between 0.6 dL / g and 1.1 dL / g.

[0030] 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.

[0031] 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 relative viscosity (RV) of the polyamide used as a raw material is preferably between 2.2 and 4. If the RV is less than 2.2, the crystallization rate becomes too fast, which can easily lead to breakage or other problems when stretching during the film-making process. On the other hand, if the RV exceeds 4, the load on the extruder becomes too high, which can easily cause filter deformation and other problems, which is undesirable. The RV is more preferably between 2.3 and 3.9, and even more preferably between 2.4 and 3.8. 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.

[0032] The type of plastic that makes up the laser printing layer is preferably polyester, polypropylene, or polyethylene, and more preferably polyester or polypropylene.

[0033] 2-1-3. Cavity-inducing agents As described in "1-4. Cavity Content" above, the printed layer of the present invention preferably contains cavities to improve the laser absorption efficiency. To contain cavities, methods such as mixing a cavity-generating agent into the plastic or increasing the stretching speed when stretching the film to cause micro-delamination within the plastic layer can be freely selected without departing from the spirit of the present invention. From the viewpoint of facilitating control of the cavity content and stabilizing film formation, mixing a cavity-generating agent is preferred. As the cavity-generating agent, organic or inorganic particles that are incompatible with the plastic that forms the base of the printed layer (hereinafter sometimes referred to as "base resin"), or foaming agents that generate gas can be freely selected. Among these, mixing organic or inorganic particles that are incompatible with the base resin is a preferred embodiment. In this case, by stretching the film while the incompatible particles are present in the base resin, the base resin is partially peeled off around the particles, and cavities are generated. Preferred requirements for the stretching method will be described later.

[0034] When using organic cavity-forming agents, a different type of resin with a different chemical structure (primary structure) is required for them to be incompatible with the base resin. For example, when polyester is used as the base resin, examples of cavity-forming agents include polyolefins, polyamides, polystyrenes, and acrylics. Examples of these cavity-forming agents include the resins described in "2-1-2. Types of Plastics" above or in "2-2. Layers other than the Laser Printing Layer" below. When using inorganic cavity-forming agents, any known cavity-forming agent can be selected, such as silica or calcium carbonate. Calcium carbonate also functions as a laser pigment, making it a preferred choice given the purpose of this invention to improve laser printing density.

[0035] The amount of cavity-forming agent added to the printing layer is preferably 5% by mass or more and 50% by mass or less. If the amount of cavity-forming agent is less than 5% by mass, the cavity content (described later) may be less than 10% by volume, which is undesirable. On the other hand, if the amount of cavity-forming agent exceeds 50% by mass, the cavity content tends to exceed 80% by volume, which is also undesirable. The amount of cavity-forming agent is more preferably 10% by mass or more and 45% by mass or less, and even more preferably 15% by mass or more and 40% by mass or less. The particle size of the cavity-inducing agent is preferably 1 μm or more and 10 μm or less. A particle size of less than 1 μm is undesirable because the cavity content may be less than 10 volume%. A particle size exceeding 10 μm is undesirable because the cavity content tends to exceed 80 volume%. A particle size of 1.5 μm or more and 9.5 μm or less is more preferable, and a particle size of 2 μm or more and 9 μm or less is even more preferable. As a method for incorporating the cavity-forming agent to be added to the printing layer, it can be added at any stage in the manufacturing of the plastic raw material, and the same method as described in "2-1-1. Types, amounts, and methods of addition of laser printing pigments" above can be used.

[0036] 2-1-6. Additives other than laser printing pigments The printing layer constituting the display body 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. Furthermore, if the printing layer is the outermost layer, it is preferable to add fine particles as a lubricant to improve slipperiness. Any fine particles can be selected. For example, inorganic fine particles include silica, alumina, kaolin, lead white, titanium white, zeolite, zinc oxide, and lithopon, while organic fine particles include acrylic particles, melamine particles, silicone particles, cross-linked polystyrene particles, carbon black, and iron oxide. The average particle size of the fine particles can be appropriately selected 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 mass, more preferably 0.015% by mass, and even more preferably 0.02% by mass. A content of less than 0.01% by mass may result in reduced slipperiness. The upper limit is preferably 1% by mass, more preferably 0.2% by mass, and even more preferably 0.1% by mass. Amounts exceeding 1% by mass are undesirable because they may reduce transparency. As for the method of incorporating particles into the laser printing layer, they can be added at any stage in the manufacturing of the plastic raw material, and the same method as described in "2-1-1. Type, amount, and method of addition of laser printing pigment" above can be used.

[0037] 2-2. Layers other than the printing layer The display body of the present invention may have layers other than the printing layer. Examples of layer configurations for the display body include a single layer consisting only of the printing layer, a two-layer configuration with a layer other than the printing layer laminated on one side, a three-layer configuration with two types of layers sandwiching the printing layer on both sides with the same layer other than the printing layer, and a three-layer configuration with three different layers sandwiching the printing layer. Generally, display materials are required to have various functions other than display function, such as mechanical strength, adhesion, and barrier properties. Furthermore, considering that the laser printing layer is etched and its thickness decreases, it is preferable to laminate other layers that have each of these functions. Any number of layers other than the laser printing layer can be laminated, but to make the thickness of the display body 200 μm or less, two-layer, two-layer, or three-layer configurations are preferred. Among these, a two-layer or three-layer configuration with another layer as the outermost layer is more preferable in order to protect the laser printing layer from external stimuli, etc. Since the present invention envisions a packaging body, and ordinary packaging bodies are constructed by adhesion, it is preferable that the other layers have adhesive properties (hereinafter, layers having adhesive properties may be simply referred to as "adhesive layers"). The adhesive layer is not particularly limited as long as it has adhesive properties, and conventionally known materials can be used arbitrarily without departing from the spirit of the present invention. Examples include a heat-sealing layer that exhibits adhesiveness upon heat, and an adhesive (tack) layer that has adhesiveness at room temperature.

[0038] Examples of plastics that make up the heat sealing layer 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.

[0039] 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.

[0040] 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.

[0041] 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. 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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. The display body 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.

[0046] 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.

[0047] 3. Manufacturing conditions for the display unit 3-1. Film Manufacturing Conditions 3-1-1. Raw material mixing and supply In manufacturing the display body of the present invention, it is necessary to add the laser printing pigment described in "2-1-1. Type, amount, and method of addition of laser printing pigment" above, and it is preferable to further add the cavity-forming agent described in "2-1-3. Cavity-forming agent". It is preferable to use raw materials that are incompatible with the base resin constituting the printing layer for the cavities. As described above, when two or more raw materials are mixed and fed into an extruder, variations (segregation) in the supply of raw materials are likely to occur. To prevent these variations, it is preferable to take measures such as installing a stirrer in the piping or hopper directly above the extruder, or inserting piping (inner pipes) into the hopper directly above the extruder filled with base resin to supply laser printing pigments and cavity-forming agents, or installing caps in each raw material hopper to reduce the particle pressure of the raw materials, when performing melt extrusion.

[0048] 3-1-2. Molten Extrusion The display body of the present invention can be obtained by melt-extruding the raw materials supplied in "3-1-1. Raw Material Mixing and Supply" from an extruder to form an unstretched film, and then proceeding through the predetermined steps shown below. If the film includes a printing layer and other layers, each layer can be laminated at any time. When laminating during melt-extrusion (co-extrusion), it is preferable to melt-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, where separately formed films are bonded together with an adhesive, or extrusion lamination, where molten plastic is poured onto the surface of a single or laminated film to laminate it. From the viewpoint of productivity, it is preferable to laminate each layer before stretching.

[0049] As a method for melt-extruding the raw material resin, a known method can be used, and a method using an extruder equipped with a barrel and a screw is preferred. In the case of raw materials (such as polyester) that decompose due to the influence of moisture during melting, it is preferable to dry them in advance using a dryer such as a hopper dryer or a paddle dryer, or a vacuum dryer until the moisture content becomes 100 ppm or less, more preferably 90 ppm or less, and even more preferably 80 ppm or less. After drying the raw material 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 adopted for extrusion.

[0050] Also, the shear rate when discharging the resin from the die mouth is preferably 100 sec -1 or more and 1500 sec -1 or less. By increasing the shear rate, the dispersion diameter of organic or inorganic particles as a void-forming agent becomes smaller. Therefore, by setting the shear rate to 100 sec -1 or more, it becomes easier to make the height of the voids 8 μm or less. On the other hand, if the shear rate exceeds 1500 sec -1 , not only is there a risk that the height of the voids will be less than 1 μm, but the viscosity of the resin during extrusion will extremely decrease, making it impossible to stably form a film due to breakage or the like, which is not preferable. The shear rate is more preferably 110 sec -1 or more and 1490 sec -1 or less, and even more preferably 120 sec -1 or more and 1480 sec -1 or less. The shear rate at the die outlet can be obtained from the following formula 1. γ = 6Q / (W × H 2 ) ·· Formula 1 γ: Shear rate (sec -1 ) Q: Discharge amount of the raw material from the extruder (cm 3 / sec) W: Width of the opening at the die outlet (die width) (cm) H: Length of the opening at the die outlet (lip gap) (cm)

[0051] Subsequently, an unstretched film can be obtained by rapidly cooling the film melted by extrusion. A suitable method for rapidly cooling the molten resin is to cast the molten resin from a die onto a rotating drum and rapidly cool and solidify it to obtain a substantially unoriented resin sheet. When casting the molten film onto the rotating drum, the take-up speed (draft ratio) is preferably 0.5 to 25. A higher draft ratio results in a smaller dispersion diameter for organic or inorganic particles acting as cavity-forming agents. A draft ratio of 0.5 or higher makes it easier to achieve a cavity height of 8 μm or less. On the other hand, a draft ratio exceeding 25 is undesirable because it tends to result in a cavity height of less than 1 μm. A draft ratio of 1 to 24.5 is more preferable, and 1.5 to 24 is even more preferable. V={Q / (W×H)} / V0...Equation 2 V: Draft ratio 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) V0: Cooling drum retrieval speed (cm / sec)

[0052] The film that will form the 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. However, considering that the preferred form of the voids used in the printing layer of the present invention is created by stretching, uniaxial stretching is preferred, and biaxial stretching is more preferred. In the following, the 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. Furthermore, a simultaneous biaxial stretching method, in which the longitudinal and transverse directions are stretched simultaneously, is also acceptable.

[0053] 3-1-3. 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 has been performed, 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 creates cavities in the printed layer. 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.

[0054] 3-1-4.Second (horizontal) 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 between 2.2 and 12.8 times, and more preferably between 2.4 and 12.6 times. Note that the stretching speed differs between longitudinal and lateral stretching (longitudinal stretching is faster), so the preferred range of stretching ratios differs. The area ratio obtained by multiplying the longitudinal and lateral stretching ratios is preferably between 2.2 and 64 times.

[0055] 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.

[0056] 3-1-5. Heat Treatment After passing through the intermediate zone, it is preferable to heat-treat the film in the heat treatment zone at 100 to 280°C. Heat treatment promotes crystallization of the film, which not only reduces the thermal shrinkage rate that occurred during the stretching process but also tends to increase the tensile breaking strength. Heat treatment temperatures below 100°C are undesirable because they tend to increase the thermal shrinkage rate of the film. On the other hand, heat treatment temperatures exceeding 280°C are undesirable because they tend to melt the film and tend to decrease the tensile breaking strength. Heat treatment temperatures of 110 to 270°C are more preferable, and 120 to 260°C are even more preferable. 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.

[0057] 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).

[0058] 3-1-6. 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 50°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.

[0059] 3-2. Lamination methods other than co-extrusion When manufacturing the display body of the present invention, if the printed layer is formed using the method described in "3-1. Film Manufacturing Conditions" above, and then laminated with the "2-2. Layers Other Than the Printed Layer" above, the lamination method is not particularly limited, and adjacent films can be bonded together using conventionally known dry lamination or extrusion lamination methods. In the case of dry lamination, commercially available dry lamination adhesives can be used. Representative examples include DIC Dry® LX-703VL and DIC KR-90, and Mitsui Chemicals Takenate® A-4 and Mitsui Chemicals Takelac® A-905. In the case of extrusion lamination, the plastic layers other than the printed layer are melted and bonded onto the printed layer, but an anchor coat can be provided in advance to improve the adhesion between layers.

[0060] 3-3. Laser printing conditions Examples of laser types (wavelengths) that can be used for printing in this invention include CO2 lasers (10600nm), YAG lasers (1064nm), YVO4 lasers (1064nm), fiber lasers (1064, 1090nm), green lasers (532nm), and UV lasers (355nm). Among these, the type of laser used for the marking material of this 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 this 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 laser printing equipment can be used, with representative examples including the Brother Industrial Printing LM-2550 (YAG laser), Omron MX-Z2000H-V1 (fiber laser), Trotec 8028 Trotec Speedy 100 flexx (fiber laser), Keyence MD-X1000 (YVO4 laser), and MD-U1000C (UV laser).

[0061] Laser printing conditions vary depending on the equipment manufacturer and model, as well as the type of film being printed on, so it is difficult to generalize. However, using the Keyence MD-U1000C (UV laser, wavelength 355nm) as an example, the conditions are as follows. The laser power is preferably 20% to 80% of the maximum device specification of 13W. An output of less than 20% is undesirable because it reduces print density and visibility. An output of more than 80% is undesirable because it can cause holes in the display surface. An output of 25% to 75% is more preferable, and 30% to 70% is even preferable. The pulse frequency is preferably 10kHz to 100kHz. A frequency below 10kHz is undesirable because the laser energy per pulse becomes high, making it easy for the thickness reduction rate of the printed area to exceed 80 vol%. Conversely, if the frequency exceeds 100kHz, it is easier to keep the thickness reduction rate of the printed area below 80 vol%, but it may be difficult to keep the difference in color L* values ​​of the printed area at 1 or more. A frequency of 15kHz to 95kHz is more preferable, and 20kHz to 90kHz is even preferable. The scan speed is preferably 10mm / sec to 3000mm / sec. If the scan speed falls below 10 mm / second, the printing speed decreases drastically, which is undesirable as it slows down the production speed of the display units. On the other hand, if the scan speed exceeds 3000 mm / second, the print density decreases, making it difficult to maintain a color L* value difference of 1 or more, which is also undesirable. A scan speed of 100 mm / second to 2900 mm / second is more preferable, and 200 mm / second to 2800 mm / second is even more preferable.

[0062] 4. Method for making bags for display items The display element of the present invention can be suitably used as a 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 center sealing are also included as packaging. It is sufficient that at least a part of the packaging is composed of the display element of the present invention. The display element of the present invention or packaging having the same can be suitably used on a variety of articles such as food, pharmaceuticals, and industrial products. [Examples]

[0063] 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. <Polyolefin raw materials> <Polyolefin A> As polyolefin A, FS2011DG3 manufactured by Sumitomo Chemical Co., Ltd. was used. <Polyolefin B> As polyolefin B, FS7053G3 manufactured by Sumitomo Chemical Co., Ltd. was used. <Polyolefin C> Polyolefin C was prepared by kneading 60% by mass of CaCO3 into polyolefin A. <Polyolefin D> Polyolefin D was prepared by kneading 60% by mass of TiO2 into polyolefin A.

[0064] <Polyester raw materials> [Polyester A] As polyester A, RE553 manufactured by Toyobo Co., Ltd. was used. [Polyester B] Polyester B was prepared by kneading 50% by mass of TiO2 into polyester A. [Polyester C] As polyester C, polyester A was mixed with the laser pigment "TOMATEC COLOR42-920A (main component Bi2O3)" (manufactured by Tokan Material Technology Co., Ltd.) in a mass ratio of 95:5 (dry blend), fed into a screw extruder, and 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 C (masterbatch). [Polyester D] As polyester D, we used RE555 manufactured by Toyobo Co., Ltd. (a masterbatch containing 7000 ppm of SiO2). Table 1 shows the composition of each polyolefin and polyester raw material.

[0065] [Table 1]

[0066] [Film 1] For layer A, polyolefin A, polyolefin C, and polyolefin D were mixed in a mass ratio of 47:50:3, and for layer B, polyolefin A, polyolefin B, and polyolefin C were mixed in a mass ratio of 20:60:20. The mixed raw materials for layers A and B were each fed into separate screw extruders, melted, and extruded from T-dies at a shear rate of 1420 sec⁻¹. The molten resins were joined by a feed block midway through the flow path and extruded from the T-dies. The unstretched laminated film was obtained by taking it up with a draft ratio of 0.8 while 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 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 guided to a longitudinal stretching machine with multiple rolls arranged in a series, preheated on a preheating roll until the film temperature reached 125°C, and then stretched four times its original size. After longitudinal stretching, the film was guided to a transverse stretching machine (tenter) and preheated for 8 seconds until the surface temperature reached 155°C, and then stretched 9.8 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 155°C for 9 seconds. At the same time as the heat treatment, the clip spacing in the width direction of the film was narrowed, thereby performing a 6% 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 80 μm was continuously produced over a predetermined length. The properties of the obtained film were evaluated by the method described above. The manufacturing conditions and evaluation results are shown in Table 2.

[0067] [Film 2-11] Films 2 through 11 were produced in the same manner as film 1, with various conditions being changed in a continuous process. Note that film 7 is a uniaxially oriented film produced only by transverse stretching (stretching ratio of 1), without longitudinal stretching. Table 2 shows the manufacturing conditions and evaluation results for each film. [Example 1] Film 1 was cut to A4 size (290mm in the long direction x 210mm in the wide direction), and a display object was created by printing "12345ABCDE" in the center of the film using a 355nm wavelength UV laser (Keyence MD-U1000C laser marker) with a pulse frequency of 20kHz, a scan speed of 1000mm / min, and an output of 50%. The size of each character was approximately 1mm in height x 1mm in width. The conditions for creating the display object are shown in Table 3.

[0068] [Example 2] Film 1 was cut to A4 size (290mm in the long direction x 210mm in the wide direction), and a display object was created by printing "12345ABCDE" in the center of the film using a fiber laser with a wavelength of 1064nm (Trotec Laser Marker 8028 Trotec Speedy 100 flexx) at a pulse frequency of 20kHz, a scan speed of 1000mm / min, and an output of 80%. The size of each character was approximately 10mm in height x 5mm in width. The conditions for creating the display object are shown in Table 3.

[0069] [Examples 3-9, Comparative Examples 1-7] Examples 3-8 and Comparative Examples 1-7 were fabricated in the same manner as in Example 1 or 2, by varying the type of film used, the laser source, and the irradiation conditions. For UV lasers, a Keyence MD-U1000C laser marker was used in all cases, and for fiber lasers, a Trotec 8028 Trotec Speedy 100 flexx laser marker was used in all cases. The fabrication conditions for the display bodies are shown in Table 3.

[0070] [Reference example] As a reference example, a commercially available label printed with an ink ribbon was used. Specifically, the expiration date printed on the back of the outer packaging (the largest size containing the nine individually wrapped pies) of Lotte's CHOCO PIE Party Pack (containing 9 pies) was used as the reference label.

[0071] [Table 2A]

[0072] [Table 2B]

[0073] <Film Evaluation Methods> The film evaluation method is as follows: For non-printed samples, a portion at least 1 mm away from the printed area was cut out and used as the sample. If the length and width directions cannot be immediately determined due to the small area of ​​the film, the length and width directions can be provisionally determined and measured accordingly. There is no particular problem if the provisionally determined length and width directions are 90 degrees different from the true directions.

[0074] [Film thickness (printed area, non-printed area)] 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 out of the printed letters "12345ABCDE" such that the base of the "A" and the unprinted (transparent) portion combined to be 1 cm wide, and the perpendicular direction between them was 3 cm. Two-part epoxy adhesive (Cemedine EP001N) was bonded to both surfaces of this sample using Toyobo Co., Ltd.'s Ester Film (registered trademark) E5100-100 μm to create an embedded sample for cross-sectional observation. After microtomizing the cross-section of this embedded sample, the cross-section was observed using a HIROX RH-2000 digital microscope, and the thickness of the printed and unprinted portions was measured. For the reference example, an arbitrary portion of the letters indicating the expiration date was measured. For measurement, the software included with the HIROX RH-2000 digital microscope was used to determine the thickness of the observed cross-sectional image as shown in Figure 2. This process was repeated three times, and the average values ​​were used as the thickness of the printed and unprinted areas. Using the measured thicknesses of the printed and unprinted areas, the thickness reduction rate was calculated from Equation 3 below. Thickness reduction rate = (T1 - T2) / T2 × 100 Equation 3 T1: Thickness of the printed area T2: Thickness of the non-printed area

[0075] [Print size] As shown in Figure 1, the height and width of the characters "345ABC" in the printed text "12345ABCDE" were measured visually in 0.5mm increments using a stainless steel straight ruler (KOKUYO TZ-RS15), and the average value was used as the print size. For the reference example display, a random portion of the characters indicating the expiration date was measured. If the print size was less than 0.5mm, the print size was measured separately using a HIROX RH-2000 digital microscope. The software included with the HIROX RH-2000 digital microscope was used to measure the print size.

[0076] [Color L* value (printed area, non-printed area)] A spectrophotometer (ZE-6000, manufactured by Nippon Denshoku Co., Ltd.) was used to measure the L* values ​​of both the printed and unprinted areas of a single film sample using the reflection method. The measurement method for the printed area was specifically as follows: As shown in Figure 1, a 3cm square sample was cut out so that all the letters "B" in the printed "12345ABCDE" were included, and measured (it is acceptable for letters other than "B" to be included). A 6φ sample stage (with an opening approximately 1cm in diameter where the measurement light hits) and a 6φ eyepiece were used as the measurement light source for the colorimeter, and the letters "B" were placed within the opening of the sample stage. If the printing does not fit within the opening of the sample stage (overflows), the sample stage may be changed as needed (e.g., 10φ, 30φ, etc.). Even if the printing overflows, it is sufficient if a part of the printing enters the opening of the sample stage and is hit by the measurement light. For the reference example display, any part of the letters indicating the expiration date was measured. Furthermore, for the non-printed areas, a 3cm square sample was cut from the unprinted portion, and the color L* value was measured using a 6φ eyepiece and sample stage of the colorimeter. Note that the eyepiece and sample stage of the colorimeter may be changed to 10φ, 30φ, etc., as needed, and in that case, the sample size can be any size as long as it covers the opening of the sample stage (preventing leakage of measurement light).

[0077] [Total light transmittance (non-printed area)] In accordance with JIS-K-7136, the total light transmittance of the non-printed area was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., 300A). The measurement was performed twice, and the average value was calculated.

[0078] [Void content (non-printed area)] The void content of the display was calculated from the cross-section of the non-printed area observed in the [film thickness (printed area, non-printed area)] described above. To calculate the void content, the automatic counting function of the software included with the HIROX RH-2000 digital microscope was used to count the voids present in the film from the cross-sectional image observed as shown in Figure 2. This process was repeated three times, and the average value was taken as the void content.

[0079] [Height of the cavity (thickness direction, non-printed area)] In the cross-section of the non-printed portion observed in the above [film thickness (printed area, non-printed area)], the height of the voids in the thickness direction of the display object was calculated. From the cross-sectional image observed as shown in Figure 2, 10 arbitrary voids were selected and their heights were measured. Software included with the HIROX RH-2000 digital microscope was used to calculate the void heights. This process was repeated three times, and the average value was taken as the void content.

[0080] [Evaluation of the printed area (visual inspection)] The legibility of the characters "12345ABCDE" printed on the display unit was judged according to the following criteria. Judgment: ○ Characters can be recognized visually. Judgment: Unable to recognize characters visually. Furthermore, the presence or absence of holes in the printed area was determined based on the thickness reduction rate according to the following criteria. Judgment: ○ Thickness reduction rate is 80% or less. Judgment: × Thickness reduction rate exceeds 80%

[0081] [Abrasion resistance of the printed area] The abrasion resistance of the printed area was evaluated using a simple abrasion resistance tester (Imoto Seisakusho Co., Ltd., IMC-1557 model). A 150mm x 150mm piece of film including the printed area was cut to serve as the measurement sample. The sample was placed in the abrasion resistance tester so that the printed area was in contact with the steel wool, and the printed area was rubbed with the steel wool at a back-and-forth distance of 10cm, 10 strokes, and a speed of 15 seconds per 10 strokes. The steel wool was #0000 grit, and no weight was used (200g). The printed area after being rubbed with steel wool was visually evaluated according to the following criteria. Verification: ○ The characters can be recognized visually (the characters do not disappear due to friction). Judgment: × The characters cannot be recognized visually (the characters disappear due to friction).

[0082] [Tensile breaking strength] In accordance with JIS K7113, a strip-shaped film sample was prepared with a measurement direction of 140 mm and a direction perpendicular to the measurement direction (film width direction) of 20 mm. Using a universal tensile testing machine "Autograph AG-Xplus" (manufactured by Shimadzu Corporation), both ends of the test piece were gripped with chucks, 20 mm on each side (chuck distance 100 mm), and a tensile test was performed under conditions of ambient temperature 23°C and tensile speed 200 mm / min. The strength (stress) at the time of tensile fracture was defined as the tensile fracture strength (MPa). The measurement directions were the longitudinal direction and the width direction.

[0083] [Table 3A]

[0084] [Table 3B]

[0085] [Film manufacturing conditions and evaluation results] The display devices from Examples 1 to 9 all exhibited the excellent physical properties listed in Table 3, and favorable evaluation results were obtained. On the other hand, Comparative Examples 1 to 7 all yielded unfavorable results for the following reasons. Comparative Example 1 had a cavity height exceeding 8 μm and a cavity content exceeding 80 vol%, resulting in perforation upon laser irradiation and making it unsuitable as a display object. The reason the cavity characteristics did not satisfy the predetermined range was that the shear rate and draft ratio of the film 8 used did not meet the predetermined range. In Comparative Example 2, even with increased laser power, the thickness reduction rate was 0%, and the difference in color L* value was less than 1.0, making it impossible to recognize the print. This was because the film 9 used did not contain voids, and the laser pigment content exceeded 50% by mass. In Comparative Example 3, although the cavity height was 3.2 μm and the thickness reduction rate was 4%, the amount of cavity-forming agent was less than 5 wt%, resulting in a difference in color L* value of less than 1.0 and a total light transmittance of less than 50% in the laser-irradiated area, making it impossible to recognize the printed text.

[0086] Comparative Example 4 had a color L* value of 6.5, indicating a significant color change. However, because the cavity content was 0%, etching did not occur, and the total light transmittance was also high at 89%, resulting in difficulty in recognizing the printed text. In Comparative Example 5, when the laser irradiation power was increased using the same film as in Example 2, the etching became extreme, resulting in holes being created. In Comparative Example 6, when the laser irradiation power was reduced using the same film as in Example 1, the difference in color L* value became 0.5, making it impossible to recognize the printed text. Comparative Example 7 used the same film as Example 1, but when the print size was reduced to 0.1 mm, the characters became unrecognizable to the naked eye. At this time, the difference in color L* value was 0.8. [Industrial applicability]

[0087] The display element of the present invention has high opacity, is resistant to peeling due to external stimuli such as abrasion, and can provide a clear printable display element with high productivity, making it suitable for use in packaging including labels and lids.

Claims

1. A display body having at least one white printable layer that can be printed by laser irradiation, the white printable layer having a printed portion and a non-printable portion, satisfying the following conditions (1) to (5), and characterized in that the void content of the non-printable portion is 10 volume% or more and 80 volume% or less. (1) The absolute difference between the color L* values ​​of the printed area and the non-printed area is 1.0 or greater and 10.0 or less. (2) The total light transmittance of the non-printed area is 8% or more and 50% or less. (3) The thickness reduction rate of the printed area in the cross-sectional direction is 1 volume% or more and 80 volume% or less compared to the non-printed area. (4) The white printing layer contains one or more elements or compounds selected from the group consisting of bismuth, gadolinium, neodymium, titanium, antimony, tin, aluminum, calcium, and barium as laser printing pigments. (5) The amount of laser printing pigment contained in the white printing layer is 5% by mass or more and 50% by mass or less.

2. The display body according to claim 1, characterized in that at least one of titanium dioxide or calcium carbonate is included in the white printing layer as a laser printing pigment.

3. The display body according to either claim 1 or 2, characterized in that the thickness of the non-printable portion in the white printable layer, which can be printed by laser irradiation, is 5 μm or more and 200 μm or less.

4. The display body according to any one of claims 1 to 3, characterized in that the height or width of the printed size in the printed area is 0.2 mm or more and 100 mm or less.

5. A display body according to any one of claims 1 to 4, characterized in that it contains one or more of polyester, polypropylene, and polyethylene as the resin constituting the white printing layer.

6. A packaging body including a lid and a label, characterized in that at least a portion of it uses the display element described in any one of claims 1 to 5.

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