Laser-markable container

Abstract

The present invention addresses the problem of providing a container capable of suppressing variation in visibility (that is, variation in a degree of blurring of a content) that may be caused by a difference in a position at which the container is viewed when the content of the container is viewed from the outside of the container (that is, the content is viewed through the container). The laser-markable container includes a laser-markable layer. When sampling is performed from any five portions of the container, a standard deviation of clarity is 0.1-2%, and the container can be discolored by a laser radiation having at least one wavelength in a wavelength range of 200-2000 nm. The average value of the clarity is preferably 20% or more.

Description

Laser markable containers

[0001] The present invention relates to a laser-markable container.

[0002] Many containers used to store goods in circulation, such as food, pharmaceuticals, and industrial products, not only protect the contents but also display information such as the product name, manufacturing date, ingredients, etc. A typical method of displaying information on containers is to use an ink ribbon, but problems have been pointed out, such as the fact that the printing and drawing quality (such as bleeding of characters) is easily affected by the surface condition of the object, there is a risk of the markings peeling due to external abrasion, and the need to temporarily stop production when replacing consumables such as the ink ribbon or printer head.

[0003] In recent years, laser marking has attracted attention as a means of solving these problems. This method forms a mark on a container by utilizing the phenomenon in which laser irradiation discolors the corresponding portion of the container. For example, Patent Document 1 discloses a manufacturing method in which a printed portion is formed by cutting, melting, and evaporating the surface of a PET bottle container body with a laser. This method solves the ink ribbon problem by maintaining the above-mentioned printing and drawing quality while eliminating the need to replace consumables. However, because this method physically deforms the bottle itself, there is a concern that holes may be made in the laser-printed portion if the container is dropped, etc.

[0004] Furthermore, Patent Document 2 discloses a packaging material that includes a background color layer containing titanium oxide and a binder resin, which changes color upon laser irradiation. In the examples of Patent Document 2, the background color layer is formed by coating on a substrate, with a thermoplastic resin layer provided on the outside of the background color layer. While this prevents the laser marking layer, i.e., the background color layer, from peeling due to external friction, providing layers with different functions requires repeated coating and drying, leaving room for improvement in productivity. Meanwhile, Patent Document 3 discloses a resin laminate that includes a laser marking layer, in which a laser marking agent is dispersed in the resin, as one layer of the laminate. This patent eliminates concerns about peeling of the laser-marked portion and does not require the provision of an outer protective layer, thereby contributing to improved productivity.

[0005] Japanese Patent Publication No. 2021-17248 Japanese Patent No. 7360783 Japanese Patent No. 6260265 Japanese Patent Publication No. 2021-71702

[0006] The inventors of the present invention investigated the application of laser marking technology to containers containing circulating goods and found that there were issues with the visibility of the circulating goods, i.e., the contents. Specifically, when a sufficient amount of laser marking pigment was dispersed in a resin to achieve high-quality printing and drawing, the particle size and dispersion of the laser marking pigment varied within the material constituting the container, resulting in variations in the visibility of the contents depending on the location of the container. Variations in content visibility can cause information such as the shape and fill volume of the contents to change depending on the viewing position of the container (contents), making it impossible to accurately read the content information, potentially resulting in problems with content management. The present invention aims to provide a container that can reduce variations in visibility (i.e., variations in the blurriness of the contents) that can occur depending on the viewing position of the container when viewing the contents from outside the container (i.e., viewing the contents through the container).

[0007] The present inventors have conducted extensive research to solve the above problems and have found that the visibility can be improved by suppressing the variation in particle size of the laser marking pigment contained in the laser marking layer of the container, and have completed the present invention.

[0008] 1. A laser-markable container comprising a laser-markable layer, wherein when sampling is performed from any five positions of the container, the standard deviation of clarity is 0.1% to 2%, and the container can be discolored by a laser of at least one wavelength in a wavelength range of 200 nm to 2000 nm. 2. The laser-markable container according to 1., wherein the laser-markable layer contains a laser-marking pigment, and the concentration of the laser-marking pigment in the laser-markable layer is 0.01% by weight to 3% by weight. 3. When a sample is taken from any one position including the laser-markable layer and a cross-section is observed, the average particle area of ​​the laser-marking pigment is 1 μm ２ 10 μm or more ２The laser-markable container according to 2., which is as follows: 4. The laser-markable container according to any one of 1. to 3., wherein the laser-markable layer comprises a polyester-based resin, a polyolefin-based resin, or a polyamide-based resin. 5. The laser-markable container according to any one of 1. to 4., wherein the laser-markable layer contains a laser-marking pigment, and the laser-marking pigment comprises at least one elemental metal selected from the group consisting of bismuth, gadolinium, aluminum, neodymium, tin, antimony, molybdenum, and titanium, and / or a compound of at least one metal selected from this group. 6. The laser-markable container according to any one of 1. to 5., which includes a laser-marked portion. 7. The laser-markable container according to 6., wherein the laser-marked portion is a portion marked with a laser of at least one wavelength in the wavelength range of 200 nm to 2000 nm. 8. 6. or 7., wherein the laser-marked portion is a portion marked with a UV laser or a YAG laser. 9. The laser-markable container according to claim 8, further comprising a non-laser-marked portion, and the color L of the laser-marked portion is ＊ value and the color L of the non-laser marked portion ＊The laser-markable container according to any one of 6. to 8., wherein the difference between the clarity value and the standard deviation is 3 or more and 20 or less in absolute value. 10. The laser-markable container according to any one of 1. to 9., wherein the standard deviation of the clarity is 1.9% or less or 1.8% or less. 11. The laser-markable container according to 10., wherein the standard deviation of the clarity is 0.2% or more or 0.3% or more. 12. The laser-markable container according to 10. or 11., wherein the standard deviation of the clarity is 0.4% or more. 13. The laser-markable container according to any one of 1. to 12., wherein, when sampled from any of the five locations, the average clarity value is 20% or more, or 25% or more. 14. The laser-markable container according to any one of 1. to 13., wherein, when sampled from any of the five locations, the average clarity value is 85% or less or 80% or less. 15. The laser-markable container according to 14., wherein, when sampled from any of the five locations, the average clarity value is 75% or less or 70% or less. 16. A laser-markable container according to any one of 1. to 15., wherein the standard deviation of the thickness of the laser-markable container is 300 μm or less or 290 μm or less when sampled from any five sites. 17. A laser-markable container according to 16., wherein the standard deviation of the thickness is 280 μm or less or 250 μm or less. 18. A laser-markable container according to 16. or 17., wherein the standard deviation of the thickness is 200 μm or less. 19. A laser-markable container according to any one of 1. to 18., wherein the standard deviation of the thickness of the laser-markable container is 5 μm or more or 10 μm or more when sampled from any five sites. 20. A laser-markable container according to any one of 1. to 19., wherein the average thickness of the laser-markable container is 2000 μm or less or 1500 μm or less when sampled from any five sites. 21. 20. The laser-markable container according to item 20, wherein the average thickness is 1000 μm or less or 800 μm or less.22. A laser-markable container according to any one of 1. to 21., wherein, when sampled from any five sites, the average thickness of the laser-markable container is 20 μm or more or 40 μm or more. 23. A laser-markable container according to any one of 1. to 22., wherein, when sampled from any five sites, the standard deviation of the thickness of the laser-markable layer is 300 μm or less or 290 μm or less. 24. A laser-markable container according to 23., wherein the standard deviation of the thickness of the laser-markable layer is 280 μm or less or 250 μm or less. 25. A laser-markable container according to 23. or 24., wherein the standard deviation of the thickness of the laser-markable layer is 200 μm or less. 26. A laser-markable container according to any one of 1. to 25., wherein, when sampled from any five sites, the standard deviation of the thickness of the laser-markable layer is 5 μm or more or 10 μm or more. 27. 26. The laser-markable container according to any one of 1. to 26., wherein, when sampled from any five positions, the average thickness of the laser-markable layer is 2000 μm or less or 1500 μm or less. 28. The laser-markable container according to 27., wherein, when sampled from any five positions, the average thickness of the laser-markable layer is 1000 μm or less or 800 μm or less. 29. The laser-markable container according to any one of 1. to 28., wherein, when sampled from any five positions, the average thickness of the laser-markable layer is 20 μm or more or 40 μm or more. 30. When sampled from any one position including the laser-markable layer and a cross section is observed, the average particle area of ​​the laser-marking pigment is 5.0 μm. ２ Less than or equal to 4.5 μm ２ 31. The laser-markable container according to any one of 1. to 29., wherein the average particle area is 4.0 μm or less. ２ Less than or equal to 3.5 μm ２ 32. The laser-markable container according to claim 30, wherein the particle area average value is 3.2 μm or less. ２33. The laser-markable container according to 30. or 31., wherein the average particle area of ​​the laser-markable pigment is 1.3 μm or less when a cross section of a sample taken from any one site including the laser-markable layer is observed. ２ or more or 1.5 μm ２ 34. The laser-markable container according to any one of 1. to 32., wherein the standard deviation of the laser-marking pigment when a sample is taken from any one site including the laser-markable layer and a cross section is observed is 5.0 μm ２ Less than or equal to 4.8 μm ２ 35. The laser-markable container according to any one of 1. to 33., wherein the standard deviation of the laser-markable pigment is 4.0 μm or less. ２ Less than or equal to 3.0 μm ２ 36. The laser-markable container according to claim 34, wherein the standard deviation of the laser-markable pigment is 2.5 μm or less. ２ Less than or equal to 2.0 μm ２ 34. The laser-markable container according to 34. or 35., wherein:

[0009] According to the present invention, a container can be provided that can reduce variations in visibility (i.e., variations in the degree of blurring of the contents) that can occur depending on the viewing position of the container when viewing the contents of the container from outside the container (i.e., viewing the contents through the container).

[0010] 1 is a photograph of a bottle after laser printing, produced in an example. 2 is an image of a cross section of a laser-printed layer of a sample cut out from the body of a bottle produced in an example, observed under a microscope.

[0011] A laser-markable container (hereinafter, sometimes simply referred to as "container") according to an embodiment of the present invention will be described. 1. Characteristics of the container 1.1. Standard deviation (variation) of clarity The standard deviation of clarity of the laser-markable container according to an embodiment of the present invention when sampled from any five locations is 0.1% to 2%. Clarity, as described in

[0040] to

[0044] of Patent Document 4 and in Figure 5 of Patent Document 4, is the light intensity L of straight (parallel) transmitted light (called straight light in Patent Document 4, and in Figure 5 of Patent Document 4, the straight light is denoted by the symbol LS). Ｃ and the light amount L of narrow-angle scattered light (denoted by the symbol LNS in FIG. 5 of Patent Document 4). Ｒ It is expressed by the following formula C using the formula: Clarity = (L Ｃ -L Ｒ ) / (L Ｃ +L Ｒ) × 100 (%) Formula C Here, straight transmitted light, i.e., parallel transmitted light, is transmitted light that travels straight relative to the optical axis of the parallel light incident on the sample. In other words, straight transmitted light is transmitted light that travels parallel to the optical axis of the parallel light incident on the sample. On the other hand, narrow-angle scattered light is scattered light whose angle with respect to the optical axis of the parallel light incident on the sample is within ±2.5°. Note that, during sampling, a sample including the inner and outer surfaces of the container is cut out from a portion including the laser-markable layer of the laser-markable container according to an embodiment of the present invention. When measuring clarity, the outer surface of the container is positioned closer to the light source than the inner surface of the container. Clarity can be measured using a HazeGuard i manufactured by BYK-Gardner. Clarity is an index of the visibility of the contents when placed in the container, and particularly indicates the degree of blurring of the contents. In other words, clarity is an index of how clearly the contents of the container appear when viewed from outside the container. The lower the clarity, the more blurred the contents appear when viewed from outside the container, i.e., when viewing the contents through the container. In other words, the lower the clarity, the worse the visibility of the contents. According to the laser-markable container of the present invention, the standard deviation of clarity is 2% or less, so when viewing the contents from outside the container (i.e., viewing the contents through the container), variations in visibility (i.e., variations in the degree of blurring of the contents) that may occur due to differences in the viewing position of the container can be reduced. Therefore, the laser-markable container of the present invention can improve the accuracy of content management (e.g., management of the shape of the contents). The upper limit of the standard deviation of clarity is preferably 1.9%, and more preferably 1.8%. On the other hand, the lower the standard deviation of clarity, the more reduced the variation in visibility, which is preferable, but the technical level of the present invention dictates a lower limit of 0.1%. In particular, in the case of containers manufactured with a design intent that the thickness varies from part to part, even if the particle size of the laser marking pigment described below is made uniform, the clarity will vary depending on the container thickness, making it even more difficult to achieve a standard deviation of zero.A standard deviation of clarity of 0.2% or more is sufficient for practical purposes.The standard deviation of clarity may be, for example, 0.3% or more, or 0.4% or more. The "five arbitrary locations" refer to five locations on the container where the contents can be seen. An example of a location on the container where the contents can be seen may be the body of the container. The "five arbitrary locations" are five locations arbitrarily selected from locations where the contents cannot be seen, such as the bottom of the container or a location covered with a lid or the like made of an opaque material different from the container. If the container has a printed portion, five locations without printing and where the contents can be seen are arbitrarily selected. Incidentally, if the container is too small to cut five samples from one container, five samples may be cut from two or more containers.

[0012] 1.2. Average Clarity Value The laser-markable container according to the embodiment of the present invention preferably has an average clarity value of 20% or more when sampled from any five locations mentioned above. If the average clarity value is below 20%, the visibility of the contents is poor. The average clarity value is more preferably 25% or more, and even more preferably 30% or more. On the other hand, the upper limit of the average clarity value is 100%. This is due to the amount of narrow-angle scattered light (L in formula C). Ｒ ) is zero, which is the most preferable form since there is absolutely no blurring of the contents. However, in the technical level of the present invention, the upper limit of the average clarity value is, for example, 85% because the laser marking pigment is included, and in practical terms, 80% is sufficient. The average clarity value may be 75% or less, or even 70% or less.

[0013] 1.3. Standard Deviation of Thickness In the laser-markable container according to the embodiment of the present invention, the standard deviation of the container thickness when sampled from any five locations is preferably 5 μm or more and 300 μm or less. As described above, if the thickness varies from location to location within the container, the clarity tends to vary. That is, if the standard deviation of the container thickness exceeds 300 μm, the standard deviation of the clarity may be excessively high. The upper limit of the standard deviation of the container thickness is more preferably 290 μm, and even more preferably 280 μm. The standard deviation of the container thickness may be 250 μm or less, or may be 200 μm or less. On the other hand, the lower the standard deviation of the container thickness, the lower the standard deviation of the clarity, which is preferable. However, according to the technical level of the present invention, the lower limit is, for example, 5 μm. In practice, a value of 10 μm is acceptable.

[0014] 1.4. Average Thickness For laser-markable containers according to embodiments of the present invention, the average thickness of the container, when sampled from any five locations, is preferably 20 μm or more and 2000 μm or less. As described above, clarity is likely to decrease as the container thickness increases. That is, if the average container thickness exceeds 2000 μm, the average clarity may be excessively low. On the other hand, if the average container thickness is less than 20 μm, not only may the desired stiffness and strength of the container be lacking, but also, even if the proportion of laser marking pigment added is increased, it may be impossible to achieve a suitable laser marking density (appearance). The average thickness is more preferably 30 μm or more and 1990 μm or less, and even more preferably 40 μm or more and 1980 μm or less. The average container thickness may be, for example, 1500 μm or less, 1000 μm or less, or 800 μm or less. When sampling to measure the standard deviation or average value of thickness, samples including the inner and outer surfaces are cut from a portion of the laser-markable container according to an embodiment of the present invention that includes the laser-markable layer. The description of "any five portions" from which samples for measuring the standard deviation or average value of thickness of the laser-markable container according to an embodiment of the present invention are cut out is omitted because it overlaps with the description of "any five portions" from which samples for measuring the standard deviation of clarity are cut out. Therefore, the description of "any five portions" from which samples for measuring the standard deviation of clarity can also be treated as the description of "any five portions" from which samples for measuring the standard deviation or average value of container thickness are cut out. Incidentally, the five samples for measuring the standard deviation or average value of container thickness may be five samples cut out from the container for measuring the standard deviation of clarity, or five separate samples, or five samples combining some of the samples cut out from the container for measuring the standard deviation of clarity with some separate samples. As mentioned above, if the container is too small to cut five samples from a single container, five samples may be cut out from two or more containers.

[0015] 2. Container Structure 2.1. Layer Structure The laser-markable container according to the embodiment of the present invention includes a laser-markable layer (hereinafter, sometimes referred to as a "laser layer" or "laser-marking layer"). The laser layer may be two or more layers, but in this case, it is preferable that the laser layers are adjacent to each other. For example, if a layer that is not laser-markable is present between the laser layers, such as a laser layer / other layer (not laser-markable) / laser layer, this is undesirable because it may cause problems such as double laser marking. Furthermore, the laser layer is preferably used as an intermediate layer other than the outermost surface of the container to avoid unintended changes (deterioration or chemical changes) due to external stimuli such as friction or the influence of the contents. The laser-markable container according to the embodiment of the present invention may include layers other than the laser layer. Considering that each layer typically has a different function, it is preferable for the container according to the embodiment of the present invention to have a layer other than the laser layer. Examples of layers other than the laser layer include a protective layer to prevent external abrasion, a gas barrier layer to prevent deterioration of the contents (e.g., oxidation), an adhesive layer connecting the gas barrier layer to adjacent layers, and an impact-resistant layer to prevent the container from breaking when dropped. The number of other layers is preferably 1 to 10. Although the number of layers may exceed 10, the average thickness of the container may easily exceed 2000 μm, potentially resulting in an excessively low average clarity. The number of other layers is more preferably 2 to 9, and even more preferably 3 to 8. Examples of preferred layer configurations include the following: protective layer / laser layer / protective layer; protective layer / adhesive layer / gas barrier layer / adhesive layer / laser layer / protective layer; impact-resistant layer / adhesive layer / gas barrier layer / adhesive layer / laser layer / protective layer; and impact-resistant layer. The preferred thickness of the other layers varies depending on the function exhibited by each layer, so a general description is not provided and is not particularly limited. For example, the thickness of the gas barrier layer is preferably 1 nm to 50 μm. This range ensures favorable gas barrier properties. The thickness of the protective layer is preferably 5 μm or more and 500 μm or less from the viewpoint of protecting the contents and the laser layer.

[0016] 2.2. Standard Deviation of Thickness of Laser Layer (i.e., Laser Marking Layer) It is preferable that the standard deviation of the laser layer thickness when sampled from any five locations is 5 μm or more and 300 μm or less. If the laser layer thickness varies from location to location, the clarity tends to vary. That is, if the standard deviation of the laser layer thickness exceeds 300 μm, the standard deviation of clarity may become excessively high. The upper limit of the standard deviation of the laser layer thickness is more preferably 290 μm, and even more preferably 280 μm. The standard deviation of the laser layer thickness may be, for example, 250 μm or less, or may be 200 μm or less. On the other hand, the lower the standard deviation of the laser layer thickness, the lower the standard deviation of clarity, which is preferable. However, according to the technical level of the present invention, the lower limit is, for example, 5 μm. In practice, a value of 10 μm is acceptable.

[0017] 2.3. Average Thickness of the Laser Layer (i.e., Laser Marking Layer) With regard to the laser layer, the average thickness of the laser layer when sampled from any five locations is preferably 20 μm or more and 2000 μm or less. As mentioned above, increasing the thickness of the container tends to decrease clarity. If the average thickness of the laser layer exceeds 2000 μm, the average clarity may be excessively low. On the other hand, if the average thickness of the laser layer is below 20 μm, it may be impossible to achieve a suitable laser marking density (appearance) even if the addition ratio of the laser marking pigment is increased. The average thickness of the laser layer is more preferably 30 μm or more and 1990 μm or less, and even more preferably 40 μm or more and 1980 μm or less. The average thickness of the laser layer may be, for example, 1500 μm or less, 1000 μm or less, or 800 μm or less. The description of "any five locations" from which samples for measuring the standard deviation or average value of the laser layer thickness are cut out will be omitted because it overlaps with the description of "any five locations" from which samples for measuring the standard deviation of clarity are cut out. Therefore, the description of "any five locations" from which samples for measuring the standard deviation of clarity can also be treated as the description of "any five locations" from which samples for measuring the standard deviation or average value of the laser layer thickness are cut out. Incidentally, the five samples for measuring the standard deviation or average value of the laser layer thickness may be five samples cut out from the container for measuring the standard deviation of clarity, or five other samples, or five samples combining some of the samples cut out from the container for measuring the standard deviation of clarity and some other samples.

[0018] 2.4 Particle Area of ​​Laser Marking Pigment The particle size of the laser marking pigment in the laser layer can be quantified as the particle area obtained from an observation image of the cross section of the container. The average particle area, i.e., the average particle area of ​​the laser marking pigment when sampled from any one site including the laser layer and observed in cross section, is 1 μm. ２ 10 μm or more ２In the following description, the particle diameter may be referred to as the particle area. ２ If the average particle area is less than 10 μm, it may be impossible to achieve a suitable laser marking density (appearance). ２ If the average particle area exceeds 1.3 μm, the average clarity of the container may become too low. ２ It may be 1.5 μm or more. ２ On the other hand, the average particle area may be 6 μm or more. ２ Preferably, 5.9 μm or less ２ More preferably, 5.8 μm or less ２ More preferably, 5.0 μm or less ２ More preferably, the average particle area is, for example, 4.5 μm ２ It may be 4.0 μm or less, ２ It may be 3.5 μm or less, ２ It may be 3.2 μm or less, ２ The standard deviation of the particle area of ​​the laser marking pigment may be 5 μm or less. ２ It is preferable that the standard deviation of the particle area is 5 μm or less. ２ If the standard deviation of the grain area exceeds 0.05 μm, the standard deviation of the clarity of the container may become excessively high. On the other hand, the lower the standard deviation of the grain area, the lower the standard deviation of the clarity of the container, which is preferable in terms of the appearance of the container. The lower limit of the standard deviation of the grain area is 0%, but from the technical level of the present invention, as an example, 0.3 μm ２ The lower limit of the standard deviation of the particle area is 0.4 μ ２ The standard deviation of the particle area of ​​the laser marking pigment is 4.9 μm. ２ More preferably, 4.8 μm or less ２ More preferably, the standard deviation of the particle area of ​​the laser marking pigment is, for example, 4.0 μm ２ It may be 3.0 μm or less, ２ It may be 2.0 μm or less, ２ It may be 1.5 μm or less, ２ It may be the following:

[0019] 2.5. Type and Amount of Laser Marking Pigment The laser marking pigment contained in the laser layer, i.e., the laser marking agent (hereinafter sometimes referred to as "laser pigment"), is a substance that has the ability to absorb laser light and is excited by absorbing laser light. When excited by laser light, the laser marking pigment generates heat, causing the surrounding resin (constituting the container) to change color, thereby establishing a marking. The laser marking pigment itself may also be capable of changing color upon excitation. Color-changing laser marking pigments are preferred because they can improve the density (appearance) of the marking. As the laser marking pigment, at least one metal selected from the group consisting of bismuth, gadolinium, aluminum, neodymium, tin, antimony, molybdenum, and titanium, and / or a compound of at least one metal selected from this group, are preferred. Among these metals, bismuth, aluminum, tin, antimony, and molybdenum are more preferred. The content of the laser marking pigment in the laser layer, i.e., the concentration of the laser marking pigment in the laser layer, is preferably 0.01% by weight or more and 3% by weight or less. If the content is below 0.01 wt%, the laser marking density will be excessively reduced, and the appearance of the marking may be extremely poor. On the other hand, if the content exceeds 3 wt%, the density of the laser marking will be improved, but the average clarity of the container may be excessively low, and the visibility of the contents may be excessively impaired. The content of the laser marking pigment in the laser layer is preferably 0.05 wt% or more, and more preferably 0.10 wt% or more. The content of the laser marking pigment in the laser layer may be, for example, 0.2 wt% or more, or 0.3 wt% or more. On the other hand, the content of the laser marking pigment in the laser layer may be, for example, 2 wt% or less, 1.5 wt% or less, or 1 wt% or less.

[0020] 2.6. Types of Resins Constituting the Container The types of resins constituting the container according to the embodiment of the present invention (such as the resin type of the laser layer and the resin types of the protective layer, gas barrier layer, adhesive layer, and impact-resistant layer exemplified in "2.1. Layer Structure") can be freely used within the scope of the present invention. Examples of types of resins, specifically types of plastics, include polyesters, polyolefins, and polyamides. Hereinafter, polyester resins may be simply referred to as polyesters. Polyolefin resins may be simply referred to as polyolefins. Polyamide resins may be simply referred to as polyamides.

[0021] 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 in which the monomers at the acid or diol moiety are changed may also be used. Examples of monomers at the acid moiety include aromatic dicarboxylic acids such as isophthalic acid, 1,4-cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and orthophthalic acid; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decanedicarboxylic acid; maleic acid, itaconic acid, fumaric acid, and alicyclic dicarboxylic acids. Examples of monomers for the diol moiety include long-chain diols such as 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, and 1,4-butanediol; aliphatic diols such as hexanediol; and aromatic diols such as bisphenol A. Furthermore, polyester components may include polyester elastomers containing ε-caprolactone and tetramethylene glycol. The polyester raw materials listed above may be homopolyesters in which a carboxylic acid monomer and a diol monomer are polymerized in a one-to-one ratio, or may be mixed (dry blended) and used. Two or more carboxylic acid monomers or two or more diol monomers may be copolymerized and used. A mixture of a homopolyester and a copolymerized polyester may also be used.

[0022] The intrinsic viscosity (IV) of the polyester is preferably 0.6 dL / g or more and 1.3 dL / g or less. If the IV is less than 0.6 g / 10 min, the molecular weight will decrease, which may cause problems such as a decrease in the mechanical strength of the container. Furthermore, when the container is manufactured by blow molding, if the IV is less than 0.6 g / 10 min, the thickness deviation accuracy is likely to decrease due to drawdown, and the standard deviation of the clarity of the container may become excessively large. On the other hand, if the IV exceeds 1.3 dL / g, the melt viscosity of the raw material will become too high, which will result in excessively high resin pressure in the melt extrusion process, making the filter deformation and the like more likely to occur. The IV is more preferably 0.65 dL / g or more and 1.25 dL / g or less, and even more preferably 0.7 dL / g or more and 1.2 dL / g or less.

[0023] Examples of polyolefins include polypropylene (PP) and polyethylene (PE). When polypropylene is used, the stereoregularity is not particularly limited, and it may be isotactic, syndiotactic, or atactic, and each may be contained in any proportion. When polyethylene is used, the density (degree of branching) is not particularly limited, and it may be high density (HDPE), linear low density (LLDPE), or low density (LDPE). In addition to the above-mentioned homopolymers, 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. Examples of α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 4-methyl-1-pentene, 4-methyl-1-hexene, ethylene vinyl alcohol, maleic acid, itaconic acid, and fumaric acid. The copolymerization may be either random copolymerization or block copolymerization. Furthermore, in addition to the raw materials listed above, polyolefin elastomers and ionomers may also be used.

[0024] The melt flow rate (MFR) of the polyolefin raw material is preferably 0.5 g / 10 min or more and 20 g / 10 min or less. If the MFR is less than 0.5 g / 10 min, the melt viscosity of the raw material becomes too high, which results in excessive resin pressure during the melt extrusion process, making the filter more susceptible to deformation. On the other hand, if the MFR exceeds 20 g / 10 min, the molecular weight decreases, which may result in problems such as a decrease in the mechanical strength of the container. Furthermore, when the container is manufactured by blow molding, if the MFR exceeds 20 g / 10 min, the thickness deviation accuracy is likely to decrease due to drawdown, and the standard deviation of the clarity of the container may become excessively high. The MFR is more preferably 0.6 g / 10 min or more and 19 g / 10 min or less, and even more preferably 0.7 g / 10 min or more and 18 g / 10 min or less.

[0025] Examples of polyamides include one type of resin selected from polycapramide (nylon 6), polyhexamethylene adipamide (nylon 66), caprolactam / lauryllactam 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 hexamethyleneisophthalamide / terephthalamide copolymer (amorphous nylon), or a mixed raw material of two or more types thereof.

[0026] The lower limit of the relative viscosity (RV) of the polyamide used as a raw material is preferably 2.2, more preferably 2.3. If it is less than this, the crystallization rate may be too fast, resulting in a fragile container. Furthermore, if the container manufacturing method is blow molding, if it is less than 2.2, the wall thickness deviation accuracy may be reduced due to drawdown, and the standard deviation of the clarity of the container may become excessively high. On the other hand, the upper limit of the RV of the polyamide is preferably 6, more preferably 5.9. If it exceeds this limit, the load on the extruder may become too high, resulting in a decrease in productivity. Note that the relative viscosity in the present invention refers to the value measured at 25°C using a solution in which 0.5 g of polymer is dissolved in 50 ml of 97.5% sulfuric acid.

[0027] 2.7. Additives Other Than Laser Marking Pigments, Surface Treatments, etc. Various additives, such as waxes, antioxidants, antistatic agents, crystal nucleating agents, viscosity reducers, thermal stabilizers, coloring pigments, color inhibitors, and UV absorbers, can be added to the laser layer and other layers contained in the container according to the present invention as needed. Furthermore, fine particles can be added as lubricants to improve slipperiness, and any fine particles can be selected. For example, inorganic fine particles include silica, alumina, titanium dioxide, calcium carbonate, kaolin, and barium sulfate. Organic fine particles include acrylic particles, melamine particles, silicone particles, and cross-linked polystyrene particles. The average particle size of the fine particles, as measured with a Coulter counter, can be selected as needed within the range of 0.05 μm to 3.0 μm. When the weight of the container according to the present invention is taken as 100% by weight, the lower limit of the fine particle content in the container according to the present invention is preferably 0.01% by weight, more preferably 0.015% by weight, and even more preferably 0.02% by weight. If the content is less than 0.01% by weight, slipperiness may be reduced. The upper limit is preferably 1% by weight, more preferably 0.2% by weight, and even more preferably 0.1% by weight. If the content exceeds 1% by weight, transparency may decrease.

[0028] The method of blending particles into the laser layer can be to add them at any stage of the production of plastic raw materials. The container according to the embodiment of the present invention can also be provided with a layer that has been subjected to corona treatment, coating treatment, flame treatment, etc. to improve the printability and slipperiness of the surface, and can be provided as desired within the scope of the present invention.

[0029] For the purpose of improving the design, for example, letters or patterns may be provided on the surface of the container according to the embodiment of the present invention by printing. Known materials such as inks for gravure printing and flexographic printing can be used to form these letters and patterns. The number of printed layers may be one or multiple. To improve the design by printing in multiple colors, it is preferable to have a printed layer consisting of multiple layers.

[0030] 3. Method for Manufacturing Containers Containers according to embodiments of the present invention can be molded by heating and melting the resins exemplified above in "2.6. Types of Resins Constituting the Container" as raw resins using an extruder or the like. Examples of molding methods include injection molding, in which molten resin is injected into a mold, and blow molding, in which a parison is formed in a mold and then a gas such as air is blown into the mold to form the parison. Alternatively, the molten resin may be cast into a drum roll to form a sheet, and the sheet may be thermoformed to produce a container. The method for manufacturing the container can be selected arbitrarily within the scope of the present invention.

[0031] The following describes in detail blow molding, in which compressed air is blown into molten resin. A container according to an embodiment of the present invention contains a laser marking pigment. When adding a laser marking pigment to the laser layer of a container, methods include preparing a masterbatch of a resin containing the laser marking pigment and mixing it with other resins forming the container, and adding the laser marking pigment directly when extruding the resin constituting the laser layer (side feed). Any of these methods can be used to add the laser marking pigment. To reduce the standard deviation of clarity, it is preferable to have the laser marking pigment uniformly dispersed in the laser layer. Here, we describe a preferred method, which involves preparing a masterbatch and mixing it with other resins.

[0032] In the mixing process, the masterbatch and other resins are mixed. Mixing can be performed, for example, using a mixer installed upstream of a hopper. After mixing, the mixed pellets are transferred from the mixer to the hopper. A feeder may be installed between the mixer and the hopper. Alternatively, mixing may be performed within the hopper. In the mixing process, it is preferable that the difference in absolute values ​​of the angles of repose of the resins being mixed be 10 degrees or less. When three or more types of resins are used, the largest and smallest angles of repose are used to calculate the absolute value of the angle of repose. In other words, the "difference in absolute values ​​of the angles of repose of the resins being mixed" refers to the absolute value of the difference between the angle of repose of the resin with the largest angle of repose and the angle of repose of the resin with the smallest angle of repose when three or more types of resins are used. If the absolute value of the difference in the angles of repose exceeds 10 degrees, the resin is more likely to segregate as it flows through the hopper, resulting in variations in the resin composition during the melt extrusion process. In an embodiment of the present invention, the concentration of the laser marking pigment contained in the laser layer is likely to vary, which may result in an excessively high standard deviation of clarity. The absolute value of the difference in the angle of repose is most preferably 0. The absolute value of the difference in the angle of repose is more preferably 9 degrees or less, and even more preferably 8 degrees or less.

[0033] The resin types used are as exemplified in "2.6. Types of Resins Constituting Containers" above. However, scraps generated during the container manufacturing process are also preferred. Scraps here refer to burrs and defective moldings generated during container formation. These scraps are preferably crushed and cut into fluff or flakes using a grinder, which are then melt-extruded in an extruder to form resin (repelletized). Resinizing scraps and reusing them as container raw materials reduces losses during container manufacturing. This not only improves the container's energy consumption but also reduces greenhouse gas emissions during container manufacturing. Because scraps are typically crushed and resinized into the entire container, the scrap resin contains laser marking pigments. Therefore, scrap resin is preferably mixed into the laser layer or a layer adjacent to the laser layer. However, this does not apply if the laser layer can be separated during the scrap resinization process.

[0034] Next, the mixed resin is supplied from the hopper to the extruder. The hopper can be provided above the supply port of the extruder. The hopper is preferably funnel-shaped. The hopper may be provided with a device for promoting the discharge of the mixed pellets, such as a vibrator, an air knocker, or a screw. The inclination angle of the hopper (the angle formed by the inner surfaces of a pair of opposing hoppers) may be, for example, 40 degrees or more, 45 degrees or more, or 50 degrees or more. On the other hand, the inclination angle of the hopper may be, for example, 80 degrees or less, 75 degrees or less, or 70 degrees or less.

[0035] In the container manufacturing process, particularly the melt extrusion process, the particle size (particle area obtained from a cross-sectional observation image, i.e., the particle area of ​​the laser marking pigment when a sample is taken from any location including the laser layer and the cross-section is observed) of the laser marking pigment particles varies due to aggregation and disintegration. In an embodiment of the present invention, the standard deviation of the particle area of ​​the laser marking pigment is set to 5.0 μm. ２To achieve the following, it is preferable to maintain a constant level of agglomeration or crushing during the extrusion process. Crushing, in particular, is thought to occur due to shear stress from the screw and cylinder inner wall during the extrusion process. If the melt viscosity of the resin filling the extruder cylinder is low, this shear stress is also low, and the particle crushing effect is thought to be reduced. After extensive investigations, the inventors discovered that fluctuations in ambient temperature during the resin supply process to the extruder cause fluctuations in the viscosity of the molten extruded resin. Inside the extruder cylinder, the resin, initially supplied in a solid state, gradually melts due to heat from the cylinder inner wall and shear heat generated between the cylinder or screw and the resin. In other words, fluctuations in the resin temperature in the resin supply section (hereinafter sometimes referred to as the "extruder supply section") cause fluctuations in the timing (position within the cylinder) of subsequent resin melting. The inventors believed that this fluctuation in the resin's thermal history resulted in fluctuations in melt viscosity. As described below, fluctuations in the melt viscosity of the resin affect the particle size of the laser marking pigment, potentially resulting in an excessively high standard deviation in the clarity of the container. The inventors discovered that suppressing temperature changes in the resin supply section can maintain a constant viscosity of the molten resin, suppressing fluctuations in the particle size of the laser marking pigment, and ultimately reducing the standard deviation of the clarity of the container. To suppress temperature changes in the resin supply section, preferred embodiments include attaching a heat-insulating material to the relevant section (i.e., the resin supply section) or flowing a fluid, with the latter being preferred. Examples of fluids include water, oil, and air, but water is preferred from the perspective of cooling efficiency and ease of handling. Furthermore, it is preferable to maintain a constant temperature of the water used as the temperature-regulating medium by passing it through an external chiller or other device installed in advance.

[0036] In the next melt extrusion process (hereinafter sometimes referred to as the "extrusion process"), the mixed pellets are melted and extruded in an extruder to form a parison. The extruder includes a screw and a cylinder surrounding the screw. That is, the extruder includes a cylinder and a screw inside the cylinder. The extruder can melt the mixed pellets using a rotating screw and extrude them at a constant rate. Examples of extruders include single-screw extruders, twin-screw extruders, triple-screw extruders, and four-screw extruders. A die is attached to the extruder after it leaves the extruder. The die can be attached to the cylinder via a head (i.e., extruder head). The die may also include a head. If necessary, a gear pump to increase the constant rate of the molten resin or a filter to collect foreign matter may be installed between the extruder and the die. Specifically, in the extrusion process, the mixed pellets are melted in an extruder, and the melted mixed pellets are stacked with melts from other extruders as needed, and then the melt, i.e., the parison, is extruded through a die. These melts can be stacked in the head or the die. The number of other extruders may be one or more.

[0037] When using resin recycled from scraps generated during container manufacturing, the melt viscosity of the resin comprising the layer containing the scrap resin is lower. The scraps undergo a first thermal cycle during container manufacturing, and then a second thermal cycle during re-resinization. In other words, the scraps undergo more thermal history than the container, resulting in a correspondingly lower melt viscosity. Therefore, the greater the amount of scrap resin used (addition ratio), the smaller the shear stress experienced during extrusion, resulting in a larger particle size of the laser marking pigment. Furthermore, because scrap resin is produced using an extruder (typically separate from the extruder used for container manufacturing), there can be some variation in the melt viscosity of the resulting resin. Therefore, when producing scrap resin, it is preferable to maintain a constant temperature in the extruder supply section, just as in the container manufacturing process described above.

[0038] When continuously manufacturing containers, the blending ratio of scrap resin rarely remains constant. Typically, the amount of scrap produced varies depending on the container yield, so a preferred embodiment involves adjusting the material balance by changing the blending ratio of scrap resin accordingly. In this case, since the melt viscosity of the extruded resin may vary depending on the blending ratio of scrap resin, it is preferable to use resins with different melt viscosities as raw materials other than the scrap resin to maintain a constant melt viscosity of the container. The blending ratio of scrap resin to the entire container is preferably 5% by weight or more and 60% by weight or less. If the blending ratio of scrap resin is less than 5%, the benefits of using scrap resin listed above are reduced. On the other hand, while a higher blending ratio of scrap resin increases the benefits described above, a blending ratio of scrap resin exceeding 60% by weight is likely to raise concerns such as an excessively high standard deviation of the clarity of the container and an excessively low average clarity value.

[0039] In the blow molding process, a parison is blown. For example, compressed gas (e.g., compressed air) is blown into the parison, forcing it against the inner surface of a mold. This produces a hollow molded product, specifically a container. The blow molding may be, for example, direct blow molding (i.e., extrusion blow molding) or injection blow molding. The parison may consist of only the laser-markable layer, i.e., a single layer, or may contain multiple layers. When the parison contains multiple layers, the parison may further contain a layer containing an ethylene-vinyl alcohol copolymer (i.e., EVOH). The inclusion of a layer containing an ethylene-vinyl alcohol copolymer in the parison can improve the gas barrier properties of the container. The parison may also contain a layer containing a polyolefin (e.g., a polyolefin having a functional group) between the layer containing the ethylene-vinyl alcohol copolymer and the laser-markable layer. A container can be produced using this procedure. The container may also be processed as needed.

[0040] 4. Laser Marking 4.1. Laser Marking Conditions The container according to the embodiment of the present invention can be discolored by a laser having at least one wavelength in the wavelength range of 200 nm to 2000 nm. Therefore, the container according to the embodiment of the present invention can be marked by a laser having at least one wavelength in the wavelength range of 200 nm to 2000 nm. Examples of types (wavelengths) of lasers that can be used for laser marking (for example, laser printing) on ​​the container according to the embodiment of the present invention include CO ２ Laser (10600 nm), YAG laser (1064 nm), YVO ４ Laser (1064 nm), fiber laser (1064, 1090 nm), green laser (532 nm), UV laser (355 nm). ２ Lasers are often used to burn through plastics, and are often used for purposes other than printing, which is the object of the present invention, and are therefore not preferred as laser sources. ４ Lasers, fiber lasers, green lasers, and UV lasers are preferred as laser sources, YAG lasers, fiber lasers, and UV lasers are more preferred, and YAG lasers and UV lasers are even more preferred. UV lasers are particularly preferred because they cause less thermal damage. Commercially available devices can be used for laser marking, and representative examples include the LM-2550 (YAG laser) manufactured by Brother Industrial Printing Co., Ltd., the MX-Z2000H-V1 (fiber laser) manufactured by Omron, the 8028 Trotec Speedy 100 flexx (fiber laser) manufactured by Trotec, and the MD-X1000 (YVO) manufactured by Keyence. ４ Examples include the MD-U1000C (UV laser), and the MD-U1000C (UV laser). Laser marking conditions cannot be generalized as the specifications and configurable conditions vary depending on the device manufacturer and model, and also depend on the container being marked, but the following is an example using the MD-U1000C (UV laser, wavelength 355 nm) manufactured by Keyence.

[0041] The laser power is preferably 20% to 90% of the maximum 13 W specified by the device specifications. If the output is less than 20%, the print density will decrease, reducing the visibility of the print. If the output is 90% or more, there is a risk of holes being formed in the container. The output is more preferably 25% to 85%, and even more preferably 30% to 80%. The pulse frequency is preferably 10 kHz to 100 kHz. If the frequency is below 10 kHz, the laser energy per irradiation will be high, making it more likely to form holes in the container. Conversely, if the frequency is above 100 kHz, the print density may decrease. The frequency is more preferably 15 kHz to 95 kHz, and even more preferably 20 kHz to 90 kHz. The scan speed is preferably 10 mm / s to 3000 mm / s. If the scan speed is below 10 mm / s, the print speed will be extremely low, resulting in a decrease in the production rate of printed containers. On the other hand, if the scan speed exceeds 3000 mm / sec, the print density may decrease. The scan speed is more preferably 100 mm / sec or more and 2900 mm / sec or less, and even more preferably 200 mm / sec or more and 2800 mm / sec or less. The area to be laser marked on the container according to the embodiment of the present invention is arbitrary, and may be a part or the entire area.

[0042] 4.2. Color L of laser marked area ＊ Value and color L of the part not laser marked ＊ When the container according to the embodiment of the present invention is marked with a laser having at least one wavelength in the wavelength range of 200 nm to 2000 nm, the color L of the laser-marked portion is ＊ value (hereinafter referred to as "L ＊ １ The color L of the part that is not laser marked is also called the "value". ＊ value (hereinafter referred to as "L ＊ ２ It is preferable that the absolute value of the difference between the ＊ This is sometimes called the "value." ΔL ＊If the value is 3 or more, the color tone of the laser-marked portion is not close to the color tone of the non-laser-marked portion, and the mark made by the laser tends to be easy to see. ＊ If the value is 20 or less, there is no need to excessively increase the power of laser irradiation when marking with a laser, so that damage that may be caused to the container by laser irradiation can be reduced, and therefore, perforation and deformation can be reduced or avoided. ＊ The value is more preferably 3.5 or more and 19.5 or less, and even more preferably 4.0 or more and 19 or less.

[0043] 5. Others The container according to the embodiment of the present invention may include a laser-marked portion and a non-laser-marked portion.

[0044] An example of a container according to an embodiment of the present invention may be a bottle.

[0045] Next, the present invention will be specifically explained using examples and comparative examples, but the present invention is not limited to the aspects of these examples and can be appropriately modified within the scope of the present invention.

[0046] Example 1 Using an extrusion blow molding machine (manufactured by Tahara Corporation), a bottle with a volume of 550 mL was molded at a maximum cylinder temperature of 280°C, a die temperature of 280°C, a screw rotation speed of 45 rpm, a molding cycle of 20 seconds, and a mold temperature of 30°C. In the process of supplying the raw material from the hopper to the extruder, a cooling water jacket was provided in the extruder supply section, and cooling water adjusted to 30±1°C using an external chiller was circulated through the cooling water jacket. The layer structure of this bottle and the materials of each layer are as follows: (Layer Structure) Outer layer: Polyester mixed material 1 (IV = 0.70 dL / g), 100 μm Laser layer: Laser pigment mixed material 1 (IV = 0.72 dL / g), 300 μm Inner layer: Polyester mixed material 1 (IV = 0.70 dL / g), 100 μm Polyester mixed material 1 was obtained by mixing polyester copolymerized with neopentyl glycol, polyethylene terephthalate, and polyethylene terephthalate with 7000 ppm of silica added as a lubricant in a ratio of 70:22:8 wt%. The maximum difference in angle of repose between the three raw materials used for the outer layer (the difference between the raw material with the largest angle of repose and the raw material with the smallest angle of repose) was 3°. Laser pigment mixed material 1 was obtained by preparing masterbatch 1 by kneading 20 wt% antimony trioxide into polyethylene terephthalate, and then mixing masterbatch 1 with polyester copolymerized with neopentyl glycol in a ratio of 3:97 wt%. The laser layer was extruded as a single layer using an extrusion blow molding machine, and the intrinsic viscosity (IV) was measured and found to be 0.72 dL / g. The difference in angle of repose between the two raw materials used for the laser layer was 3 degrees.

[0047] Example 2 A bottle with a volume of 550 mL was molded in the same manner as in Example 1. The bottle produced in Example 1, or scraps generated during production, were crushed and melt-extruded in a twin-screw extruder to produce pellets (hereinafter referred to as "Repellets 1"), which were used as the raw material for the laser layer. In the process of producing Repellets 1, when the crushed scraps serving as the raw material were supplied from a hopper to the extruder, a cooling water jacket was provided in the extruder supply section, and cooling water adjusted to 30±1°C using an external chiller was circulated through the cooling water jacket. The IV of the obtained Repellets 1 was 0.68 dL / g. (Layer structure) Outer layer: Polyester mixed material 1 (IV = 0.70 dL / g), 100 μm Laser layer: Laser pigment mixed material 2 (IV = 0.70 dL / g), 300 μm Inner layer: Polyester mixed material 1 (IV = 0.70 dL / g), 100 μm Laser pigment mixed material 2 was obtained by mixing Masterbatch 1, polyester copolymerized with neopentyl glycol, and Repellet 1 in a ratio of 3:67:30 wt%. The laser layer was extruded as a single layer using an extrusion blow molding machine, and the intrinsic viscosity (IV) was measured and confirmed to be 0.70 dL / g. The maximum difference in the angle of repose between the three raw materials used for the laser layer (the difference between the raw material with the largest angle of repose and the raw material with the smallest angle of repose) was 5 degrees.

[0048] Example 3 Using an extrusion blow molding machine (manufactured by Tahara Corporation), a 550 mL bottle was molded at a maximum cylinder temperature of 200°C, a die temperature of 200°C, a screw rotation speed of 45 rpm, a molding cycle of 20 seconds, and a mold temperature of 30°C. During the process of supplying raw materials from the hopper to the extruder, a cooling water jacket was installed in the extruder supply section, and cooling water maintained at 25±1°C using an external chiller was circulated through the cooling water jacket. The layer structure and materials of each layer of this bottle were as follows: (Layer Structure) Outer layer: Polypropylene raw material 1 (MFR = 2.0 g / 10 min), 30 μm Laser layer: Laser pigment mixed raw material 3 (MFR = 1.8 g / 10 min), 600 μm Inner layer: Polypropylene raw material 1 (MFR = 2.0 g / 10 min), 30 μm Noblen FS2012 manufactured by Sumitomo Chemical was used as polypropylene raw material 1. Laser pigment mixed raw material 3 was obtained by preparing masterbatch 2 by kneading 5% by weight of bismuth trioxide into Sumitomo Chemical's Noblen S131 (MFR = 1.7 g / 10 min), and then mixing masterbatch 2 with Sumitomo Chemical's Noblen S131 in a ratio of 3:97% by weight. The laser layer was extruded as a single layer using an extrusion blow molding machine, and the melt viscosity (MFR) was measured, confirming it to be 1.8 g / 10 min. The difference in angle of repose between the two raw materials used for the laser layer was 4 degrees.

[0049] Example 4 A bottle with a volume of 550 mL was molded in the same manner as in Example 3. The bottle produced in Example 3, or scraps generated during production, were crushed and melt-extruded in a twin-screw extruder to produce pellets (hereinafter referred to as "Repellets 2"), which were used as the raw material for the laser layer. In the process of producing Repellets 2, when the crushed scraps serving as the raw material were supplied from a hopper to the extruder, a cooling water jacket was provided in the extruder supply section, and cooling water adjusted to 25±1°C using an external chiller was circulated through the cooling water jacket. The MFR of the obtained Repellets 2 was 2.1 g / 10 min. (Layer structure) Outer layer: Polypropylene raw material 1 (MFR = 2.0 g / 10 min), 30 μm Laser layer: Laser pigment mixed raw material 4 (MFR = 2.1 g / 10 min), 600 μm Inner layer: Polypropylene raw material 1 (MFR = 2.0 g / 10 min), 30 μm Laser pigment mixed raw material 4 was obtained by mixing Masterbatch 2, Sumitomo Chemical's Noblen S131, and Repellet 2 in a ratio of 3:52:40 wt%. The laser layer alone was extruded as a single layer using an extrusion blow molding machine, and the melt viscosity (MFR) was measured and confirmed to be 2.1 g / 10 min. The maximum difference in the angle of repose between the three raw materials used for the laser layer (the difference between the raw material with the largest angle of repose and the raw material with the smallest angle of repose) was 6 degrees.

[0050] Example 5 A bottle with a volume of 450 mL was molded in the same manner as in Example 3. The layer structure of this bottle and the materials of each layer are as follows: (Layer structure) Outermost layer: Polyethylene raw material 1 (MFR = 1.4 g / 10 min), 60 μm Adhesive layer: Maleic acid-ethylene copolymer (MFR = 1.4 g / 10 min), 5 μm Gas barrier layer: EVOH (MFR = 1.6 g / 10 min), 10 μm Adhesive layer: Maleic acid-ethylene copolymer (MFR = 1.4 g / 10 min), 5 μm Laser layer: Laser pigment mixed raw material 5 (MFR = 1.4 g / 10 min), 200 μm Innermost layer: Polyethylene raw material 1 (MFR = 1.4 g / 10 min), 60 μm Sumikathene C215 manufactured by Sumitomo Chemical was used as polyethylene raw material 1. The maleic acid-ethylene copolymer used was Admer LB548 manufactured by Mitsui Chemicals, and the EVOH used was Eval F101B manufactured by Kuraray. Laser pigment mixed raw material 5 was obtained by preparing masterbatch 3 by kneading 20% ​​by weight of ammonium octamolybdate into Novatec LB420M (MFR = 0.7 g / 10 min) manufactured by Japan Polypropylene, and then mixing masterbatch 3 with Sumikathene C215 manufactured by Sumitomo Chemical in a ratio of 3:97% by weight. The laser layer alone was extruded as a single layer using an extrusion blow molding machine, and the melt viscosity (MFR) was measured and confirmed to be 1.4 g / 10 min. The difference in angle of repose between the two raw materials used for the laser layer was 3 degrees.

[0051] Example 6 A bottle with a volume of 450 mL was molded in the same manner as in Example 3. The bottle produced in Example 5, or scraps generated during production, was crushed and melt-extruded in a twin-screw extruder to produce pellets (hereinafter referred to as "Repellets 3"), which were used as the raw material for the laser layer. During the process of producing Repellets 3, when the crushed scraps serving as the raw material were fed from a hopper to the extruder, a cooling water jacket was installed in the extruder feed section, and cooling water adjusted to 25±1°C using an external chiller was circulated through the cooling water jacket. The MFR of the resulting Repellets 3 was 1.6 g / 10 min. The maximum difference in the angle of repose between the three raw materials used in the laser layer (the difference between the raw material with the largest angle of repose and the raw material with the smallest angle of repose) was 5 degrees. (Layer structure) Outermost layer: Polyethylene raw material 1 (MFR = 1.4 g / 10 min), 60 μm Adhesive layer: Maleic acid-ethylene copolymer (MFR = 1.4 g / 10 min), 5 μm Gas barrier layer: EVOH (MFR = 1.6 g / 10 min), 10 μm Adhesive layer: Maleic acid-ethylene copolymer (MFR = 1.4 g / 10 min), 5 μm Laser layer: Laser pigment mixed raw material 6 (MFR = 1.6 g / 10 min), 200 μm Innermost layer: Polyethylene raw material 1 (MFR = 1.4 g / 10 min), 60 μm Laser pigment mixed raw material 6 was obtained by mixing Masterbatch 3, Sumikathene C215 manufactured by Sumitomo Chemical, and Repellet 3 in a ratio of 3:77:20 wt%. In advance, the laser layer alone was extruded as a single layer using an extrusion blow molding device, and the melt viscosity (MFR) was measured and found to be 1.6 g / 10 min.

[0052] Comparative Example 1 A bottle was produced in the same manner as in Example 2, except that the circulation of cooling water to the extruder supply section during bottle molding in Example 2 was stopped. In other words, a bottle was produced in the same manner as in Example 2, except that cooling water was not circulated during extrusion blow molding.

[0053] Comparative Example 2 A bottle was produced in the same manner as in Example 4, except that the circulation of cooling water to the extruder supply section during bottle molding in Example 4 was stopped. In other words, a bottle was produced in the same manner as in Example 4, except that cooling water was not circulated during extrusion blow molding.

[0054] Comparative Example 3 A bottle was produced in the same manner as in Example 4, except that the circulation of cooling water to the extruder supply section was stopped when producing Repellet 2 and when producing a bottle. That is, a bottle was produced in the same manner as in Example 4, except that cooling water was not circulated when producing Repellet 2 and when extrusion blow molding was performed.

[0055] Next, we will explain how to measure thickness, clarity, etc.

[0056] <Bottle Thickness> A total of five samples were cut out from the body of one bottle. Specifically, five randomly selected locations on the body of each bottle were cut out to produce a total of five samples. The thickness of the five samples was measured using a dial gauge in accordance with JIS K7130:1999 Method A. The average thickness and standard deviation were determined from the five samples. The standard deviation was calculated using the following formula 1: Standard deviation = [{(X1 - X0) 2 + (X2-X0) 2 +...+(X n -X0) 2} / n] 1 / 2 Formula 1 where X n , X0, n are as follows: X n : Measurement value of nth sample X0: Average value of measurement value n: Number of samples (5 points)

[0057] <Thickness of laser layer> A total of five samples were cut out from the body of one bottle. Specifically, five locations on the body of each bottle were randomly selected, and a total of five samples were cut out. The five samples were solidified with modified urethane resin, and their cross sections were cut out with a microtome. The thickness of the laser layer was measured by observing it under a microscope. The average value and standard deviation of the thickness of the laser layer were determined from the five samples. The standard deviation was calculated using the above formula 1.

[0058] <Particle Area of ​​Laser Pigment> One sample was cut from the body of one bottle. Specifically, one sample was cut from any location on the body of each bottle. The sample was solidified with modified urethane resin, and its cross section was cut with a microtome. The particle area of ​​the laser pigment contained in the laser layer was observed and measured under a microscope. The observed image was binarized using image processing software ImageJ to determine the particle area. Approximately circular bright spots (i.e., approximately circular spots with a chromaticity different from that of the resin constituting the bottle; see Figure 2) contained in the observed image were defined as particles, and the area of ​​each particle (specifically, the area output by ImageJ's ROI Manager) was defined as the particle area of ​​each particle. The average particle area and standard deviation were calculated from the determined particle area (i.e., the area per particle). The standard deviation was calculated using the above formula 1.

[0059] <Clarity> A total of five samples were cut from the body of one bottle. Specifically, five randomly selected regions of the body of each bottle were cut into a total of five samples. Each sample included the inner and outer surfaces of the bottle. The clarity of the five samples was measured using a Hazeguard i manufactured by BYK-Gardner. The clarity was measured with the outer surface of the sample (i.e., the outer surface of the bottle) positioned closer to the light source than the inner surface of the sample (i.e., the inner surface of the bottle). The average value and standard deviation of clarity were calculated from the five samples. The standard deviation was calculated using the above formula 1. The average value of clarity is measured in %, and the standard deviation of clarity is also measured in %. Furthermore, the obtained standard deviation of clarity was used to determine whether the clarity variation was acceptable or unacceptable according to the following criteria: Good: The standard deviation of clarity is 2 or less. Bad: The standard deviation of clarity is greater than 2.

[0060] <ΔL ＊ As shown in Figure 1, a laser was irradiated onto the bottle body to print "ABC123" on the bottle body. In other words, laser printing was performed. The printer used was an ultraviolet (UV) laser marker (MD-U1000, manufactured by Keyence Corporation) with a wavelength of 355 nm, and the laser was irradiated under the conditions of laser power 80%, scan speed 1000 mm / sec, pulse frequency 40 kHz, and spot variable -20. Color L ＊ The color difference values ​​were evaluated using a spectrophotometer (ZE-6000, manufactured by Nippon Denshoku Co., Ltd.). ＊ The value was measured by a reflection method. The measurement method for the printed part is specifically as follows.

[0061] A 3 cm square sample was cut out so that all of the letters "B" from the printed "ABC123" were included in the measurement (letters other than "B" may also be included). A 6 mm diameter sample stage (the opening onto which the measurement light hits is approximately 1 cm in diameter) and a 6 mm diameter sight glass were used as the measurement light source for the color difference meter, and the letter "B" was placed in the opening of the sample stage. If the print does not fit completely into the opening of the sample stage (it overflows), the sample stage may be changed as needed (for example, 10 mm diameter, 30 mm diameter, etc.). Even if the print overflows, it is sufficient as long as part of the print is within the opening of the sample stage and is hit by the measurement light. Meanwhile, for the non-printed portion, a 3 cm square sample was cut out from a portion of the bottle body that had no printing or other processing such as printing, and a 6 mm diameter sight glass and sample stage for the color difference meter were used to measure the color L. ＊ The sample size of the sample holder and the sight glass of the color difference meter may be changed to 10φ, 30φ, etc. as needed, and in that case, the sample size may be any size as long as it covers the opening of the sample holder (i.e., prevents leakage of measurement light).

[0062] The resulting printed color L ＊ value (i.e., L ＊ １ value) and the color L of the non-printed area ＊ value (i.e., L ＊ ２ Using the values ​​of these colors, the following formula 2 is used to calculate the color L ＊ ΔL, which is the absolute value of the difference between the values ＊ The value was obtained. ＊ Value = |L ＊ １ Value - L ＊ ２ Value | Equation 2 ΔL ＊ Based on the value, the pass / fail of the laser printing density was judged according to the following criteria: ＊ Value is 3 or more: × ΔL ＊ Value less than 3

[0063] <Results> The results of evaluation by each of the above evaluation methods are shown in Table 1. All of the bottles of Examples 1 to 6 had a small standard deviation in clarity (i.e., small clarity variation). The laser markings were also clear. On the other hand, in both Comparative Examples 1 and 2, there was no circulation of cooling water to the extrusion supply section during bottle production, so the standard deviation was large (i.e., clarity variation was large). Therefore, the bottles produced in Comparative Examples 1 and 2 had large variations in the degree of blurring of the contents. Furthermore, there was no circulation of cooling water during bottle production as well as during the production of Repellet 2, so the clarity variation was larger than that of Comparative Example 2 in Comparative Example 3. Therefore, the bottle produced in Comparative Example 3 also had large variations in the degree of blurring of the contents.

[0064]

[0065] The present invention can provide a laser-markable container and is therefore industrially applicable.

Claims

1. A laser-markable container comprising a laser-markable layer, wherein the standard deviation of clarity is 0.1% or more and 2% or less when sampling from any five locations on the container, and the container can be discolored by a laser of at least one wavelength in the wavelength range of 200 nm to 2000 nm.

2. The laser-markable container according to claim 1, wherein the laser-markable layer contains a laser-marking pigment, and the concentration of the laser-marking pigment in the laser-markable layer is 0.01% by weight or more and 3% by weight or less.

3. When a sample is taken from any one site including the laser-markable layer and a cross section is observed, the average particle area of ​​the laser-marking pigment is 1 μm ２ 10 μm or more ２ 3. The laser-markable container of claim 2, wherein:

4. The laser-markable container of claim 1, wherein the laser-markable layer comprises a polyester-based resin, a polyolefin-based resin, or a polyamide-based resin.

5. The laser-markable container according to claim 1, wherein the laser-markable layer contains a laser-markable pigment, and the laser-markable pigment contains at least one elemental metal selected from the group consisting of bismuth, gadolinium, aluminum, neodymium, tin, antimony, molybdenum, and titanium, and / or a compound of at least one metal selected from this group.

6. The laser-markable container of claim 1, including a laser-marked portion.

7. The laser-markable container according to claim 6, wherein the laser-marked portion is a portion marked with a laser having at least one wavelength in the wavelength range of 200 nm to 2000 nm.

8. The laser-markable container according to claim 6, wherein the laser-marked portion is a portion marked with a UV laser or a YAG laser.

9. The laser-marked portion further includes a portion that is not laser-marked, and the color L of the laser-marked portion ＊ value and the color L of the non-laser marked portion ＊ The laser-markable container according to claim 6 , wherein the absolute value of the difference between the values ​​is 3 or more and 20 or less.

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