Thermoplastic resin films, labels, and in-mold labels

Abstract

To provide a thermoplastic resin film that has excellent external appearance and adhesive strength while reducing blisters and environmental load.SOLUTION: A thermoplastic resin film comprises: a heat-sealing resin receiving layer; and a heat-sealing layer containing heat-sealing resin on the heat-sealing resin receiving layer. The heat-sealing resin receiving layer contains thermoplastic resin, inorganic particles and surface treatment agent, and the content of the inorganic particles in the heat-sealing resin receiving layer is 40 to 80 mass%. The surface treatment agent is at least one kind selected from the group consisting of an acid having a hydrocarbon group of carbon number 8 to 20, ester of the acid, and a salt thereof. The level difference Rk on a core part of the surface of the heat-sealing layer is 1.2 to 9.0 μm, and a ratio Rzjis / Rk between a ten-point average roughness Rzjis on the surface of the heat-sealing layer and the level difference Rk is 3 to 10.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to thermoplastic resin films, labels, and in-mold labels. [Background technology]

[0002] One known method for molding resin containers is in-mold molding, in which air is blown into heated raw resin in a mold, causing it to expand and form the shape of the mold. An in-mold label is a label that is attached to the resin container within the mold during this in-mold molding process. In-mold labels typically have a heat-seal layer on their surface. When the expanding raw resin comes into contact with the heat-seal layer, the heat-seal layer melts due to the heat of the resin and adheres to the surface of the resin container. Text, images, or other designs are usually printed on the surface of the in-mold label opposite the heat-seal layer.

[0003] When the raw resin comes into contact with the in-mold label, air can remain between them, potentially leading to a decrease in the label's adhesive strength or a cosmetic defect known as blistering. Therefore, the adhesive surface of the in-mold label to the resin container, i.e., the heat-seal layer, is sometimes given an uneven surface. This uneven surface creates air channels between the resin container and the in-mold label, allowing the air to escape through these channels.

[0004] For example, Patent Document 1 discloses an in-mold label having a reverse gravure-type embossed pattern on the back side of the label that adheres to the container. The shape of the embossed dots and the number of embossed lines are adjusted to improve the adhesive strength of the label and suppress blistering. Patent Document 2 discloses a heat-sealable resin layer having a plurality of protruding microstructures arranged alternately and continuously. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 3-260689 [Patent Document 2] Japanese Patent Publication No. 2012-155153 [Overview of the project] [Problems that the invention aims to solve]

[0006] As described above, in-mold labels with embossed patterns sometimes had the embossed pattern transferred to the printed surface when stacked for storage after printing. This is because the heat-seal layer, which has an uneven surface due to the embossing process, is strongly pressed against the printed surface when stacked, causing unevenness to occur on the printed surface as well.

[0007] Furthermore, from an environmental protection perspective, there is a demand to reduce plastic waste, and a reduction in resin usage is required even in in-mold labels. By using inorganic fillers in labels and increasing their content, it is possible to relatively reduce the amount of resin used, but it is generally difficult to uniformly disperse a large amount of filler in the resin. Aggregates of inorganic fillers may form, potentially leading to a decrease in localized adhesive strength or poor appearance at the adhesive surface.

[0008] The present invention aims to provide a thermoplastic resin film that exhibits excellent appearance and adhesive strength while reducing blistering and environmental impact. [Means for solving the problem]

[0009] As a result of diligent research conducted by the inventors to solve the above problems, the present invention has been completed as described below.

[0010] [1] A thermoplastic resin film comprising a heat seal resin receiving layer and a heat seal layer containing a heat seal resin on the heat seal resin receiving layer, The heat seal resin receiving layer contains a thermoplastic resin, inorganic particles, and a surface treatment agent, and the content of the inorganic particles in the heat seal resin receiving layer is 40 to 80% by mass. The surface treatment agent is at least one selected from the group consisting of an acid having a hydrocarbon group with 8 to 20 carbon atoms, an ester of the acid, and a salt thereof. The level difference Rk of the core part on the surface of the heat-sealing layer is 1.2 to 9.0 μm. The ratio Rzjis / Rk of the ten-point average roughness Rzjis on the surface of the heat-sealing layer to the level difference Rk is 3 to 10. Thermoplastic resin film.

[0011] [2] The load length ratio Mr1 of the core part on the surface of the heat-sealing layer is 6.5 to 15%. The thermoplastic resin film according to [1] above.

[0012] [3] The smoothness of the surface of the heat-sealing layer is 1000 to 10000 seconds. The thermoplastic resin film according to [1] or [2] above.

[0013] [4] The heat-sealing resin receiving layer is a stretched porous layer. The melting point of the thermoplastic resin is higher than the melting point of the heat-sealing resin. The thermoplastic resin film according to any one of [1] to [3] above.

[0014] [5] A label including the thermoplastic resin film according to any one of [1] to [4] above.

[0015] [6] An in-mold label including the thermoplastic resin film according to any one of [1] to [4] above.

Effect of the Invention

[0016] According to the present invention, it is possible to provide a thermoplastic resin film excellent in appearance and adhesive strength while reducing blisters and environmental load.

Brief Description of the Drawings

[0017] [Figure 1]This figure shows an example of a smoothed roughness curve and load curve used to determine the level difference Rk and the ten-point average roughness Rzjis of the core. [Figure 2] This figure shows the load curve in Example 1. [Figure 3] This figure shows the load curve in Example 5. [Figure 4] This figure shows the load curve in Comparative Example 1. [Figure 5] This figure shows the load curve in Comparative Example 2. [Modes for carrying out the invention]

[0018] The thermoplastic resin film, label, and in-mold label of the present invention will be described in detail below. The following description is an example (representative example) of the present invention and is not limited thereto.

[0019] (Thermoplastic resin film) The thermoplastic resin film of the present invention comprises a heat-seal resin receiving layer and a heat-seal layer containing heat-seal resin on the same. The heat-seal resin receiving layer contains thermoplastic resin and inorganic particles. Since the inorganic particle content in the heat-seal resin receiving layer is relatively high at 40-80% by mass, it is possible to reduce the amount of resin used and reduce the environmental impact.

[0020] Normally, a high concentration of inorganic particles can lead to aggregation, resulting in poor appearance or a decrease in localized adhesive strength. However, in this invention, the heat-seal resin receiving layer contains a surface treatment agent for inorganic particles. The surface treatment agent is at least one selected from the group consisting of acids having hydrocarbon groups with 8 to 20 carbon atoms, esters of said acids, and salts thereof. These suppress the aggregation of inorganic particles and improve the uniformity of the dispersion of inorganic particles in the layer. Therefore, even if the heat-seal resin receiving layer contains a relatively large number of inorganic particles, a thermoplastic resin film with excellent appearance and adhesive strength can be obtained, making it possible to achieve both reduced environmental impact and excellent appearance and adhesive strength.

[0021] Furthermore, in this invention, the surface of the heat seal layer has a core level difference Rk of 1.2 to 9.0 μm, and the ratio of the ten-point average roughness Rzjis to the level difference Rk, Rzjis / Rk, is 3 to 10. The surface of the heat seal layer, where the level difference Rk and the ratio Rzjis / Rk are within the above specific ranges, has an appropriate uneven structure. When the heat seal layer comes into contact with the outer surface of the resin container, a space is formed between them due to the unevenness, allowing air to be efficiently discharged from between the heat seal layer and the resin container through this space. Therefore, it is possible to achieve both blister suppression and the excellent adhesive strength inherent in the heat seal layer.

[0022] Furthermore, when the level difference Rk and ratio Rzjis / Rk are within the specified range, when thermoplastic resin films are stacked, the uneven pattern of the surface of the heat-seal layer (hereinafter sometimes referred to as the heat-seal surface) is less likely to be transferred to the surface of the thermoplastic resin film opposite to the heat-seal layer (hereinafter sometimes referred to as the front surface). Therefore, even when a printed layer consisting of an ink composition is formed on the front surface by printing, the uneven pattern is less likely to appear on the printed layer. Thus, it is possible to achieve both the suppression of blistering due to the uneven structure and an excellent appearance.

[0023] <Surface properties of the heat seal layer> Various parameters related to the surface properties of the heat seal layer can be determined from the surface smoothing roughness curve and load curve. A specific method of determination will be explained with reference to Figure 1. Figure 1 shows an example of the surface smoothing roughness curve K1 of the heat seal layer and the load curve K2 obtained from the smoothing roughness curve K1. Note that the surface smoothing roughness curve and load curve of the heat seal layer in the present invention are not limited to the pattern exemplified in Figure 1.

[0024] <<Core level difference Rk>> In this invention, the "level difference Rk of the core" is the level difference (core roughness depth) of the core between the height of the protruding peak and the depth of the protruding valley of the roughness curve as defined in ISO 13565-2:1996 and JIS B0671-2:2002 "Geometric product specifications (GPS) - Features - Part 2: Local dimensions of measured centerlines, measured center planes and measured features of cylinders and cones".

[0025] To determine the level difference Rk of the core, first, the load curve K2 is obtained from the smoothing roughness curve K1, as illustrated in Figure 1. The vertical axis of the load curve K2 represents height. The horizontal axis of the load curve K2 represents the load length ratio Tp (%). The load length ratio Tp is the ratio of the solid portion to the void portion (the cumulative length of the solid portion relative to the reference length) (%) at the cutting position when the smoothing roughness curve K1 is cut horizontally at a certain height.

[0026] Next, the equivalent line K3 is determined on the load curve K2. The equivalent line K3 is the line with the gentlest slope among the secants that pass through two points on the load curve K2 where the difference ΔMr of the load length ratio Tp is 40%. At the positions where the load length ratio Tp is 0% and 100%, the core portion 51 is the area between the two height positions where the equivalent line K3 intersects the vertical axis, and the difference between these two height positions is the level difference Rk of the core portion 51. Generally, the larger the value of the level difference Rk, the larger the volume of the main recess on the surface (the recess of the core portion 51). Also, at the position where the load length ratio Tp is 0%, the part higher than the position where the equivalent line K3 intersects the vertical axis (the top of the core portion 51) is the protruding peak portion 52. The load length ratio Mr1 of the core portion 51 represents the ratio of the area occupied by the protruding peak portion 52 as seen from the measurement surface.

[0027] It is believed that increasing the level difference Rk of the core portion of the heat-seal surface increases the volume of the cavity that can form an air passage, thereby improving the air discharge performance between the thermoplastic resin film and the resin used to mold the container. From the viewpoint of this air discharge performance, in the present invention, the level difference Rk of the core portion of the heat-seal surface is 1.2 μm or more, preferably 1.5 μm or more, more preferably 2.5 μm or more, and even more preferably 3.0 μm or more.

[0028] On the other hand, if the level difference Rk becomes too large, the load length ratio Mr1 decreases, and the area of ​​the protruding peak portion 52 decreases relatively with respect to the measurement area. As a result, the contact area between the heat-sealed surface and the molding resin of the container decreases, which may lead to lower adhesive strength. Therefore, from the viewpoint of increasing the adhesive strength of the label (thermoplastic resin film) in a labeled container, in the present invention, the level difference Rk of the core portion of the heat-sealed surface is 9.0 μm or less, preferably 8.5 μm or less, and more preferably 8.0 μm or less.

[0029] <<Ten-point mean roughness Rzjis, ratio Rzjis / Rk>> In this invention, the "ten-point average roughness Rzjis" is the ten-point average roughness (ten-point height of roughness profile) as defined in Annex 1 of JIS B0601:1994 "Geometric product specifications (GPS) - Surface texture: Profile curve method - Terms, definitions and surface texture parameters". First, a reference length is extracted from the roughness curve in the direction of the average line. From the average line of this extracted portion, the absolute values ​​of the elevations (Yp) of the top five peaks from the highest peak and the absolute values ​​of the elevations (Yv) of the bottom five valleys from the lowest valley are calculated. By dividing the calculated sum by 5 and converting it to micrometers (μm), the ten-point average roughness Rzjis can be obtained. In Figure 1, the average of the peak heights from the highest peak to the fifth highest peak is represented as the 5-point average peak height avRpk, and the average of the valley depths from the deepest valley to the fifth deepest valley is represented as the 5-point average valley depth avRvk.

[0030] Generally, a larger ten-point average roughness Rzjis value indicates that the surface has deeper recesses (higher protrusions). Therefore, a larger ten-point average roughness Rzjis on the heat-seal surface results in deeper cavities that can form air passages, which is expected to improve air venting between the thermoplastic resin film and the molding resin of the container. From this viewpoint, the ten-point average roughness Rzjis of the heat-seal surface is preferably 9.0 μm or more, and more preferably 15 μm or more. On the other hand, if the ten-point average roughness Rzjis of the heat-seal surface is too large, the contact area between the heat-seal surface of the thermoplastic resin film and the molding resin decreases, which may result in lower adhesive strength. Therefore, from the viewpoint of increasing the adhesive strength of the label (thermoplastic resin film) on a labeled container, the ten-point average roughness Rzjis of the heat-seal surface is preferably 30 μm or less, and more preferably 25 μm or less.

[0031] Even if the cavity is deep, if the cavity width is narrow, sufficient air exhaust may not be obtained. The level difference Rk is an index of the cavity width. On the other hand, when thermoplastic resin films are stacked so that the heat-sealed surface and the front surface opposite the heat-sealed surface are in contact and a load is applied, if the contact area between the protrusions of the heat-sealed surface and the front surface is small, the pressure applied to that contact area will be high. Therefore, it is thought that the shape (uneven shape) of the protrusions of the heat-sealed surface is more likely to be transferred to the front surface. In order to suppress the transfer of the uneven shape of the heat-sealed surface to the front surface, an index is needed to evaluate the contact area between the protrusions of the heat-sealed surface and the front surface. One such index is the ratio Rzjis / Rk, and another is the load length ratio Mr1 of the core portion 51.

[0032] The ratio Rzjis / Rk is the ratio of the height of the protruding peak 52 to the height of the core 51. When the height of the core 51, i.e., the level difference Rk, is constant, a larger ratio Rzjis / Rk means that the bottom area of ​​the protruding peak 52 does not change, the height of the protruding peak 52 increases, and the protruding peak 52 has a steeper slope. Here, the area of ​​the protruding peak 52 corresponds to the load length ratio Mr1. ​​In other words, since it is better to narrow the bottom area of ​​the protruding peak 52 in order to widen the cavity, a larger ratio Rzjis / Rk tends to improve the air discharge between the heat seal surface and the raw resin. On the other hand, since it is better for the slope of the protruding peak 52 not to be steep in order to widen the contact area between the heat seal surface and the front surface, a smaller Rzjis / Rk tends to make it less likely for the uneven shape of the heat seal surface to be transferred to the front surface.

[0033] From the above points, in the present invention, the ratio Rzjis / Rk is 3 or more, preferably 4 or more, and more preferably 4.5 or more. Furthermore, the ratio Rzjis / Rk is 10 or less, preferably 9 or less, more preferably 8 or less, and even more preferably 7 or less. This suppresses the transfer of the uneven shape of the heat-sealed surface to the front surface when the thermoplastic resin films are stacked, and allows air to be efficiently discharged from between the thermoplastic resin film and the molding resin. This makes it possible to bond the thermoplastic resin film and the molding resin with high adhesive strength while suppressing the occurrence of blisters.

[0034] <<Core load length ratio Mr1>> In this invention, "core load length ratio Mr1" refers to the core load length ratio (material portion) as defined in ISO 13565-2:1996. As illustrated in Figure 1, the load length ratio Mr1 of the core portion 51 represents the load length ratio at the intersection of the separation line between the protruding peak 52 and the core portion 51 and the load curve K2. Furthermore, as described above, the load length ratio Mr1 can be considered as the ratio of the protruding peak 52 to the measurement area. Therefore, a smaller load length ratio Mr1 is desirable to increase the cavity volume, and a larger load length ratio Mr1 is desirable to increase the contact area between the heat seal surface and the front surface.

[0035] The load length ratio Mr1 of the core portion of the heat-seal surface is preferably 6.5% or more, more preferably 8.0% or more, and even more preferably 9.0% or more. Furthermore, the load length ratio Mr1 of the core portion of the heat-seal surface is preferably 15.0% or less, more preferably 12.0% or less, and even more preferably 11.0% or less. When the load length ratio Mr1 of the core portion 51 of the heat-seal surface is within the above range, the transfer of uneven shapes to the front surface is more easily suppressed when thermoplastic resin films are stacked, and air between the heat-seal surface of the thermoplastic resin film and the molding resin of the container is more efficiently discharged.

[0036] Instruments capable of measuring the level difference Rk specified in ISO 13565-2:1996 and the ten-point average roughness Rzjis specified in JIS B0601:1994 Annex 1 include non-contact surface shape measuring machines manufactured by Zygo Corporation, high-precision micro-shape measuring machines manufactured by Kosaka Laboratory Co., Ltd., laser microscopes manufactured by Keyence Corporation, or surface roughness measuring machines manufactured by Tokyo Seimitsu Co., Ltd. For details on the measurement method, please refer to the examples described below.

[0037] <<Arithmetic mean roughness Ra>> In this invention, "arithmetic mean roughness Ra" is the arithmetic mean roughness Ra defined in JIS B0601:2013 "Geometric product specifications (GPS) - Surface texture: contour curve method - Terms, definitions and surface texture parameters". The arithmetic mean roughness Ra of the heat-sealed surface is preferably 0.90 μm or more, more preferably 1.00 μm or more, and even more preferably 1.30 μm or more. The above arithmetic mean roughness Ra is preferably 2.60 μm or less, more preferably 2.30 μm or less, even more preferably 2.00 μm or less, and particularly preferably 1.80 μm or less.

[0038] <<Smoothness>> In this invention, "smoothness" refers to the Oken smoothness as defined in JIS P 8155:2010. The smoothness of the heat-seal surface is preferably 1000 seconds or more, more preferably 2000 seconds or more, and even more preferably 3000 seconds or more. Furthermore, the smoothness of the heat-seal surface is preferably 10000 seconds or less, more preferably 9000 seconds or less, and even more preferably 6000 seconds or less. When the smoothness of the heat-seal surface is within the above range, the transfer of uneven shapes to the front surface is further suppressed when thermoplastic resin films are stacked, and air between the heat-seal surface of the thermoplastic resin film and the molding resin of the container is more efficiently discharged during in-mold molding.

[0039] The thermoplastic resin film of the present invention may include layers other than the heat-seal resin receiving layer and the heat-seal layer, within the range in which the effects of the present invention are obtained. For example, the thermoplastic resin film of the present invention may include a base layer from the viewpoint of increasing rigidity, and the heat-seal resin receiving layer and the heat-seal layer may be provided on the base layer. The following explains each layer.

[0040] <Heat seal resin receiving layer> The heat seal resin receiving layer can serve as a support for the heat seal layer. As described above, the heat seal resin receiving layer contains a thermoplastic resin, inorganic particles, and a surface treatment agent.

[0041] From the viewpoint of adjusting the parameters of the surface properties of the heat-sealed surface described above to a desired range, it is preferable that the heat-seal resin receiving layer beneath the heat-seal layer be a stretched porous layer. A heat-seal resin receiving layer containing inorganic particles becomes a porous layer when stretched, as numerous fine pores originating from the inorganic particles are formed inside. These pores create depressions on the surface of the porous layer, and the heat-seal resin of the heat-seal layer melts and drips into these depressions, thus forming an uneven structure on the heat-sealed surface. The parameters of its surface properties can be adjusted by controlling the number of pores, pore diameter, and porosity, etc., by controlling the content, size, surface condition, or stretching conditions of the inorganic particles in the heat-seal resin receiving layer.

[0042] Furthermore, the porous heat-seal resin receiving layer has a higher porosity when it contains a large amount of inorganic particles. A higher porosity reduces the elastic modulus of the thermoplastic resin film, increasing its cushioning properties and thus improving its ability to conform to curved surfaces. Therefore, when a thermoplastic resin film is used as a label or in-mold label, it can be adhered to even complex shapes with many irregularities in the substrate or container, resulting in an excellent appearance.

[0043] <<Thermoplastic resin>> The thermoplastic resin for the heat seal resin receiving layer may be selected from the thermoplastic resins usable for the substrate layer described later. These may be used individually or in combination of two or more types.

[0044] From the viewpoint of reducing delamination between the heat seal layer and the heat seal resin receiving layer, it is preferable to use a thermoplastic resin with high adhesion to the heat seal resin in the heat seal layer as the thermoplastic resin in the heat seal resin receiving layer. If a base layer is provided, from the viewpoint of reducing delamination between the base layer and the heat seal resin receiving layer, it is preferable to use a thermoplastic resin with high adhesion to both the heat seal resin and the thermoplastic resin in the base layer.

[0045] The melting point of the thermoplastic resin in the heat seal resin receiving layer is preferably higher than the melting point of the heat seal resin in the heat seal layer, more preferably 10°C or more higher, even more preferably 20°C or more higher, and particularly preferably 30°C or more higher. Furthermore, it is preferable that the melting point of the thermoplastic resin in the heat seal resin receiving layer is higher than the melting point of the heat seal resin in the heat seal layer, and that the stretching temperature of the heat seal resin receiving layer is higher than the melting point of the heat seal resin in the heat seal layer and lower than the melting point of the thermoplastic resin in the heat seal resin receiving layer. This makes it possible to form an uneven structure on the heat seal surface, as the molten heat seal resin during film molding, etc., can easily melt and fall into the pores of the heat seal resin receiving layer when the heat seal resin receiving layer is a stretched porous layer.

[0046] From the viewpoint of improving air discharge between the heat-seal surface of the thermoplastic resin film and the molding resin of the container, the content of thermoplastic resin in the heat-seal resin receiving layer is preferably 15% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more. On the other hand, from the viewpoint of widening the contact area between the heat-seal surface and the molding resin, the content of thermoplastic resin is preferably 60% by mass or less, more preferably 55% by mass or less, even more preferably 50% by mass or less, even more preferably 45% by mass or less, and particularly preferably 40% by mass or less.

[0047] <<Inorganic particles>> Inorganic particles have a lower carbon dioxide emission coefficient during the manufacturing process than resins. Therefore, by including inorganic particles, it is possible to reduce the amount of resin used in the heat seal resin receiving layer, as well as reduce the carbon dioxide emissions during the manufacturing process, thereby reducing the environmental burden. Furthermore, if the heat seal resin receiving layer is a stretched porous layer, inorganic particles can act as nuclei to form voids that allow the heat seal resin to melt and drip through. By controlling the particle size, content, or surface state of the inorganic particles, the surface properties of the heat seal surface can be adjusted to a desired range.

[0048] From the viewpoint of reducing resin usage and lowering environmental impact, the inorganic particle content in the heat-seal resin receiving layer is 40% by mass or more, preferably 45% by mass or more, more preferably 50% by mass or more, and even more preferably 55% by mass or more. When the heat-seal resin receiving layer is a stretched porous layer, a higher inorganic particle content increases the porosity, further reducing the amount of resin used, and also makes it easier to control the level difference Rk and the ten-point average roughness Rzjis of the heat-seal surface to large values, which is preferable. From the viewpoint of film moldability, the inorganic particle content in the heat-seal resin receiving layer is 80% by mass or less, preferably 75% by mass or less, more preferably 70% by mass or less, and even more preferably 65% ​​by mass or less.

[0049] The inorganic particles are not particularly limited in type, as long as they can make the heat-seal resin receiving layer porous. Specific examples of inorganic particles include heavy calcium carbonate, light calcium carbonate, calcined clay, talc, diatomaceous earth, white clay, barium sulfate, magnesium oxide, zinc oxide, titanium oxide, barium titanate, silica, alumina, zeolite, mica, sericite, bentonite, sepiolite, vermiculite, dolomite, wollastonite, or glass fiber. Among these, heavy calcium carbonate, light calcium carbonate, calcined clay, or talc are preferred because they have good porosity and are inexpensive. You may use one of these individually, or you may use two or more in combination.

[0050] The average particle size (D50) in the particle size distribution of inorganic particles is preferably 0.5 μm or more, more preferably 1.0 μm or more, and even more preferably 4.5 μm or more. The average particle size of inorganic particles is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 6 μm or less. When the heat-seal resin receiving layer is a porous stretched layer, the surface properties parameters of the heat-sealed surface formed by the heat-seal resin melting into the pores can be controlled by the number of pores, the diameter of the pores, and the porosity. If the average particle diameter is 0.5 μm or more, it becomes easy to control the level difference Rk and the ten-point average roughness Rzjis of the heat-sealed surface to large values. Conversely, if the average particle diameter is 10 μm or less, it becomes easy to control the level difference Rk and the ten-point average roughness Rzjis of the heat-sealed surface to small values.

[0051] From the viewpoint of controlling the ten-point average roughness Rzjis or the ratio Rzjis / Rk to be small, the inorganic particles preferably have a ratio of D90 to D50 (D90 / D50) of 20 or less in their particle size distribution, more preferably 15 or less, even more preferably 10 or less, and particularly preferably 5 or less. From the viewpoint of controlling the ten-point average roughness Rzjis or the ratio Rzjis / Rk to be large, the above ratio (D90 / D50) may be 1.5 or more, or 2.0 or more.

[0052] The average particle size (D50) of the inorganic particles mentioned above refers to the particle size that accounts for 50% of the cumulative particle size distribution measured by a particle measuring device, such as the laser diffraction particle measuring device "Microtrac" (manufactured by Nikkiso Co., Ltd., product name). D90 refers to the particle size that accounts for 90% of the cumulative particle size distribution.

[0053] <<Surface treatment agent>> The surface treatment agent adheres to the surface of inorganic particles and can suppress their aggregation. This reduces molding defects or appearance defects in thermoplastic resin films due to aggregation, even if the inorganic particle content in the layer is high. Furthermore, it can adjust the nucleation state of voids during stretching by its affinity with the surrounding thermoplastic resin, thereby controlling the number of voids, void diameter, or porosity. In addition, when the heat-seal resin receiving layer is a stretched porous layer, the void diameter can be controlled to a small value by suppressing aggregation with the surface treatment agent, making it possible to control the level difference Rk and the ten-point average roughness Rzjis of the heat-seal surface to small values.

[0054] The heat seal resin receiving layer may contain a surface treatment agent by containing inorganic particles that have been pre-surface-treated and to which the surface treatment agent has been attached. Alternatively, the heat seal resin receiving layer may contain a surface treatment agent by mixing unsurface-treated inorganic particles with the surface treatment agent. In this case, the surface treatment agent adheres to the surface of the inorganic particles through mixing. From the viewpoint of obtaining a higher level of aggregation suppression effect by the surface treatment agent, it is preferable that the heat seal resin receiving layer contains a surface treatment agent that has been pre-attached to the surface of the inorganic particles by containing surface-treated inorganic particles, and it is more preferable that it contains both surface-treated inorganic particles and a surface treatment agent that is mixed separately.

[0055] The proportion of inorganic particles to which a surface treatment agent has been pre-treated by surface treatment, relative to the total inorganic particles used in the heat seal resin receiving layer, is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, particularly preferably 70% by mass or more, and most particularly preferably 80% by mass or more. If the above proportion is 40% by mass or more, aggregation of inorganic particles is suppressed, making it easier to reduce molding defects or appearance defects. In addition, it becomes easier to control the level difference Rk or the ten-point average roughness Rzjis to a small value by controlling the pore size to a small value.

[0056] From the viewpoint of reducing molding defects or appearance defects, the content of the separately mixed surface treatment agent in the heat seal resin receiving layer is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.2% by mass or more. From the viewpoint of suppressing a decrease in adhesion due to the surface treatment agent bleeding out onto the heat seal surface, and from the viewpoint of suppressing a decrease in the heat resistance of the resin, the content of the above surface treatment agent is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less.

[0057] From the viewpoint of suppressing aggregation, the surface treatment agent is preferably at least one selected from the group consisting of acids having hydrocarbon groups with 8 to 20 carbon atoms, esters of said acids, and salts thereof. Examples of such surface treatment agents include resin acids, fatty acids, organic acids, sulfate ester-type anionic surfactants, sulfonic acid-type anionic surfactants, petroleum resin acids, salts of these such as sodium, potassium, and ammonium, fatty acid esters of these, resin acid esters, waxes, paraffins, etc., as well as nonionic surfactants, diene polymers, titanate coupling agents, silane coupling agents, phosphoric acid coupling agents, etc. Examples of sulfate ester-type anionic surfactants include long-chain alcohol sulfates, polyoxyethylene alkyl ether sulfates, sulfated oils, and salts of these such as sodium and potassium. Examples of sulfonic acid-type anionic surfactants include alkylbenzene sulfonic acid, alkylnaphthalene sulfonic acid, paraffin sulfonic acid, α-olefin sulfonic acid, alkyl sulfosuccinic acid, and salts of these such as sodium and potassium. Examples of fatty acids include oleic acid, caproic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, linoleic acid, linolenic acid, and eleostearic acid. Examples of organic acids include maleic acid and sorbic acid. Examples of diene polymers include polybutadiene and isoprene. Examples of nonionic surfactants include polyethylene resin glycol ester type surfactants. These surface treatment agents can be used individually or in combination of two or more types.

[0058] <<Other additives>> The heat-seal resin receiving layer may optionally contain known additives as needed. Examples of usable additives include antioxidants, light stabilizers, UV absorbers, antiblocking agents such as higher fatty acid amides, dyes, pigments, plasticizers, nucleating agents, mold release agents, or flame retardants. These can be used insofar as they do not impair the printability or heat-sealability of the in-mold label made of thermoplastic resin film.

[0059] <<Porosity>> The porosity of the heat seal resin receiving layer is preferably 20% or more, more preferably 30% or more, and even more preferably 40% or more. The above porosity is preferably 70% or less, more preferably 65% ​​or less, and even more preferably 60% or less. If the above porosity is 20% or higher, it is easier to reduce the amount of resin used and lower the environmental impact. It also becomes easier to control the level difference Rk and the ten-point average roughness Rzjis of the heat-sealed surface to large values. The higher the porosity, the lower the elastic modulus of the thermoplastic resin film, improving cushioning and increasing conformability to curved surfaces, thus making it easier to label according to the shape of the adherend or container. If the above porosity is 70% or lower, it becomes easier to control the level difference Rk and the ten-point average roughness Rzjis of the heat-sealed surface to small values.

[0060] <<Thickness>> The thickness of the heat seal resin receiving layer is preferably 20 μm or more, more preferably 30 μm or more, even more preferably 40 μm or more, particularly preferably 50 μm or more, preferably 200 μm or less, and more preferably 100 μm or less, from the viewpoint of sufficiently forming voids for receiving the molten heat seal resin.

[0061] <Base material layer> The base layer improves the tensile modulus of the thermoplastic resin film and increases its mechanical strength. This makes handling easier, such as transporting the film during printing or labeling processes, and inserting it into molds during in-mold molding. The base layer can also impart properties such as water resistance, chemical resistance, and, if necessary, printability, opacity, lightness, or antistatic properties.

[0062] The base layer preferably contains a thermoplastic resin from the viewpoint of increasing the tensile modulus or mechanical strength. Examples of thermoplastic resins that can be used in the base layer include olefin resins; ester resins; amide resins such as nylon-6, nylon-6,6, nylon-6,10, and nylon-6,12; styrene resins such as polycarbonate, atactic polystyrene, and syndiotactic polystyrene; and polyphenylene sulfide. These may be used individually or in combination of two or more.

[0063] In particular, it is preferable to use an olefin resin or an ester resin, and more preferably to use an olefin resin. Examples of olefin resins include propylene resins, ethylene resins such as high-density polyethylene, medium-density polyethylene, and low-density polyethylene, poly-4-methyl-1-pentene, or ethylene-cyclic olefin copolymers. Also included are homopolymers of olefins such as ethylene, propylene, butylene, hexene, octene, butadiene, isoprene, chloroprene, and methyl-1-pentene, and copolymers composed of two or more of these olefins. Furthermore, functional group-containing olefin resins such as ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, metal salts (ionomers) of ethylene-(meth)acrylic acid copolymer, ethylene-alkyl acrylate copolymer, ethylene-alkyl methacrylate copolymer (preferably with 1 to 8 carbon atoms in the alkyl group), maleic acid-modified polyethylene, or maleic acid-modified polypropylene are also included. Examples of ester resins include polyethylene terephthalate and its copolymers, polyethylene naphthalate, polybutylene terephthalate, or aliphatic polyesters.

[0064] Among olefin resins, propylene resins are preferred from the viewpoint of film moldability, moisture resistance, mechanical strength, and cost. Examples of propylene resins include isotactic, syndiotactic, and homopolypropylenes having various stereoregularities, which are obtained by homopolymerizing propylene. Also, propylene copolymers having various stereoregularities can be obtained by copolymerizing propylene with α-olefins such as ethylene, 1-butene, 1-hexene, 1-heptene, 1-octene, and 4-methyl-1-pentene. The propylene copolymer may be a binary system or a multi-component system of three or more components, and may be a random copolymer or a block copolymer.

[0065] As the thermoplastic resin in the base layer, it is preferable to use a thermoplastic resin with high adhesion to the thermoplastic resin in the heat seal resin receiving layer, from the viewpoint of preventing delamination between the base layer and the heat seal resin receiving layer during adhesion or use.

[0066] From the viewpoint of reducing environmental impact, the base layer preferably contains inorganic particles, and more preferably is a stretched porous layer containing inorganic particles. The inorganic particles that can be used in the base layer are the same as those listed in the section on the heat seal resin receiving layer, and the preferred types of inorganic particles are also the same as those listed in the section on the heat seal resin receiving layer. Furthermore, the base layer may optionally contain known additives similar to those found in the heat-seal resin receiving layer, as needed.

[0067] From the viewpoint of improving the moldability or mechanical strength of the film, the thermoplastic resin content in the base layer is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. On the other hand, from the viewpoint of imparting opacity or lightness to the thermoplastic resin film, the thermoplastic resin content in the base layer is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less.

[0068] The base layer may have a single-layer structure or a multilayer structure. A multilayer structure is preferred from the viewpoint of each layer exhibiting different functions. Examples of layers that exhibit such functions include a low-density layer for whiteness, opacity, or weight reduction, a skin layer to suppress the generation of foreign matter when extruding from a die and to increase adhesion to the heat-seal resin receiving layer, and an ink receiving layer that has excellent ink adhesion and is provided on the front surface of the thermoplastic resin film.

[0069] <<Thickness>> From the viewpoint of mechanical strength, the thickness of the base layer is preferably 30 μm or more, more preferably 40 μm or more, and even more preferably 50 μm or more. From the viewpoint of conformability to curved surfaces, the thickness of the base layer is preferably 300 μm or less, more preferably 200 μm or less, and even more preferably 100 μm or less.

[0070] <Heat seal layer> The heat seal layer contains a heat seal resin and acts as an adhesive to bond the thermoplastic resin film to other resins.

[0071] <<Heat sealable resin>> Examples of heat-sealable resins include thermoplastic resins such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid alkyl ester copolymer (alkyl group has 1 to 8 carbon atoms), and metal salts of ethylene-(meth)acrylic acid copolymer (e.g., salts with metals selected from Zn, Al, Li, K, and Na). Examples of heat-sealing resins include thermoplastic resins such as random copolymers or block copolymers of α-olefins obtained by copolymerizing at least two comonomers selected from α-olefins having 2 to 20 carbon atoms in their molecules. Examples of α-olefins with 2 to 20 carbon atoms include ethylene, propylene, 1-butene, 2-methyl-1-propene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-pentene, 3,3-dimethyl-1-butene, 1-heptene, methyl-1-hexene, dimethyl-1-pentene, ethyl-1-pentene, trimethyl-1-butene, methylethyl-1-butene, 1-octene, 1-heptene Examples include ethylene, methyl-1-pentene, ethyl-1-hexene, dimethyl-1-hexene, propyl-1-heptene, methylethyl-1-heptene, trimethyl-1-pentene, propyl-1-pentene, diethyl-1-butene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, and octadecene. Among these, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and 1-octene are preferred from the viewpoint of ease of copolymerization or cost. Among these, low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, or ethylene copolymer copolymerized using a metallocene catalyst are preferred. These thermoplastic resins may be used individually or in combination of two or more types.

[0072] For example, when the heat seal resin is a random copolymer of ethylene and α-olefin, it is preferable to use an ethylene-α-olefin copolymer copolymerized using a metallocene catalyst as the heat seal resin, from the viewpoint of speeding up the shot cycle during in-mold molding. As a catalyst for synthesizing the ethylene-α-olefin copolymer, a metallocene catalyst, particularly a metallocene-almoxane catalyst, or a catalyst consisting of a metallocene compound and a compound that reacts with the metallocene compound to form a stable anion, such as those disclosed in International Publication No. WO92 / 01723, is preferred.

[0073] From the viewpoint of improving adhesion, the heat seal resin content in the heat seal layer is preferably 50% by mass or more, more preferably 65% ​​by mass or more, even more preferably 80% by mass or more, and may also be 100% by mass.

[0074] From the viewpoint of adjusting the heat-sealed surface to a desired surface condition, it is preferable that the heat-seal layer (i) contains particles, or (ii) contains at least two types of thermoplastic resins that are incompatible with each other. The heat-seal layer may be a combination of (i) and (ii). In the heat seal layer containing the particles described in (i) above, the surface properties of the heat seal surface can be controlled to desired parameters by adjusting the particle size or amount of particles added in the heat seal layer. In the heat seal layer described in (ii) above, irregularities are formed on the surface of the heat seal layer by at least two types of thermoplastic resins that are incompatible with each other. Therefore, by adjusting the types and amounts of thermoplastic resins combined, it is possible to control the surface properties of the heat seal surface to desired parameters. From the viewpoint of controlling the surface properties of the heat seal surface, it is also possible to combine the heat seal layer described in (i) or (ii) above with a heat seal resin receiving layer which is a stretched porous layer.

[0075] (i) Heat seal layer containing particles When particles are present, the heat-seal resin is preferably low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, or an ethylene-based copolymer copolymerized using a metallocene catalyst, and one of these can be used alone or in combination of two.

[0076] The types of particles that can be used in the heat seal layer are not particularly limited, as long as they can create an uneven surface on the heat seal layer; for example, inorganic particles or organic particles can be used.

[0077] Specific examples of inorganic particles include those similar to those described in the section on the heat-seal resin receiving layer. From the viewpoint of good shape-forming properties and low cost, heavy calcium carbonate, light calcium carbonate, alumina, silica, zeolite, or titanium oxide are preferred as inorganic particles.

[0078] The organic particles are preferably immiscible with the heat-seal resin, have a melting point or glass transition temperature higher than the heat-seal resin, and are finely dispersed under the melt-kneading conditions of the heat-seal resin. Specific examples of resins constituting the organic particles include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyamide, polycarbonate, nylon-6, nylon-6,6, cyclic polyolefin, polystyrene, polymethacrylate, polyethylene sulfide, polyphenylene sulfide, polyimide, polyether ketone, polyether ether ketone, polymethyl methacrylate, poly-4-methyl-1-pentene, homopolymers of cyclic olefins, or copolymers of cyclic olefins and ethylene. Furthermore, these resins can be used after being crosslinked. Alternatively, fine powders of thermosetting resins such as melamine resin may be used.

[0079] The inorganic and organic particles described above may be used individually or in combination of two or more types. When combining two or more types, a combination of inorganic and organic particles is acceptable, but it is preferable to use either inorganic or organic particles, and from the viewpoint of environmental protection, it is preferable to use inorganic particles.

[0080] The heat seal layer may contain a surface treatment agent for particles to suppress particle detachment and reduce appearance defects caused by particle aggregation. The same surface treatment agents as those listed in the section on the heat seal resin receiving layer can be used in the heat seal layer.

[0081] From the viewpoint of controlling the level difference Rk and the ten-point average roughness Rzjis of the heat-sealed surface to large values, the average particle diameter of the particles is preferably 0.5 μm or more, more preferably 2 μm or more, and even more preferably 5 μm or more. From the viewpoint of controlling the level difference Rk and the ten-point average roughness Rzjis of the heat-sealed surface to small values, the average particle diameter of the particles is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less.

[0082] From the viewpoint of suppressing particle shedding from the heat seal layer and adjusting the level difference Rk and ratio Rzjis / Rk to a predetermined range, the ratio of the average particle diameter of the particles to the thickness of the heat seal layer is preferably 50% or more, preferably 100% or more, preferably 1000% or less, and more preferably 500% or less.

[0083] The definition of the average particle diameter of inorganic particles is as explained in the section on the heat-seal resin receiving layer. The average particle diameter of organic particles is the average dispersed particle diameter of organic particles dispersed in the thermoplastic resin by melt kneading and dispersion, and refers to the average of the maximum diameters of at least 10 particles measured by electron microscopy observation of the cross-section of the thermoplastic resin film.

[0084] From the viewpoint of controlling the level difference Rk and the ten-point average roughness Rzjis of the heat-sealed surface to large values, the particle content in the heat-sealed layer is preferably 3% by mass or more, and more preferably 5% by mass or more. From the viewpoint of increasing the adhesive strength of the heat-sealed surface, the particle content is preferably 30% by mass or less, and more preferably 15% by mass or less.

[0085] (ii) A heat seal layer containing at least two thermoplastic resins that are incompatible with each other. When two or more thermoplastic resins that are mutually immiscible are mixed, heated and melted, and then cooled and solidified, a surface with irregularities is spontaneously formed during the cooling and solidification process due to the difference in the thermal shrinkage rates of each thermoplastic resin. Preferably, all of the two or more thermoplastic resins are heat-sealable resins. It is possible to impart irregularities to the heat-sealed surface, and the level difference Rk or ratio Rzjis / Rk can be adjusted to a desired range depending on the type or content of the thermoplastic resins.

[0086] Here, "incompatible with each other" means that in a differential scanning calorimetry (DSC) of a mixture of two or more thermoplastic resins, the melting peaks of each thermoplastic resin are observed independently. A combination of at least two thermoplastic resins that are incompatible with each other may be a combination of two thermoplastic resins that are incompatible with each other, or a combination of three or more thermoplastic resins that are incompatible with each other. In the case of a combination of three or more thermoplastic resins that are incompatible with each other, each thermoplastic resin only needs to be incompatible with at least one of the other thermoplastic resins, and does not need to be incompatible with all of the thermoplastic resins.

[0087] Furthermore, the thermoplastic resin in the heat seal layer may consist only of thermoplastic resins that are incompatible with each other, or it may contain, in addition to thermoplastic resins that are incompatible with each other, a thermoplastic resin that is compatible with any of the thermoplastic resins (hereinafter referred to as a compatible resin). From the viewpoint of forming uneven surfaces, it is preferable that the content of the compatible resin is smaller than that of the thermoplastic resins that are incompatible with each other.

[0088] For example, combinations of thermoplastic resins that are mutually immiscible include ethylene-based resins such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, and linear low-density polyethylene, and propylene homopolymers, (propylene-ethylene) random copolymers, etc. Also, combinations of ethylene-based copolymers such as ethylene-vinyl acetate copolymers, ethylene-(meth)acrylic acid copolymers, ethylene-(meth)acrylate alkyl ester copolymers, and ethylene-α-olefin copolymers, and propylene homopolymers, etc.

[0089] Preferably, among the thermoplastic resins contained in the heat seal layer, the thermoplastic resins that are incompatible with each other are component (A) with the largest mass percentage relative to the total mass of the thermoplastic resins contained in the heat seal layer, and component (B) with the next largest mass percentage. This makes it possible to easily adjust the level difference Rk or ratio Rzjis / Rk of the heat seal surface to a predetermined range.

[0090] The ratio of the content of component (A) to component (B) (content of component (A) / content of component (B)) is preferably 80 / 20 to 55 / 45, more preferably 30 / 70 to 55 / 45, and even more preferably 40 / 60 to 55 / 45, from the viewpoint of adjusting the level difference Rk or ratio Rzjis / Rk to a predetermined range.

[0091] Furthermore, from the viewpoint of adjusting the level difference Rk or ratio Rzjis / Rk to a predetermined range, the melting point of component (B) is preferably higher than that of component (A), more preferably the difference between the melting points of component (B) and component (A) is 20 to 110°C, and even more preferably 40 to 90°C. Specifically, the melting point of component (A) is preferably 60°C or higher, more preferably 70°C or higher, preferably 140°C or lower, and more preferably 120°C or lower. Also, the melting point of component (B) is preferably 100°C or higher, more preferably 120°C or higher, preferably 200°C or lower, and more preferably 180°C or lower.

[0092] The combination of component (A) and component (B) can be appropriately selected from the above-mentioned "combinations of thermoplastic resins that are incompatible with each other." Among these, for example, when component (A) is linear low-density polyethylene and component (B) is a propylene homopolymer, the increase in the ten-point average roughness Rzjis is more significant than the increase in the level difference Rk, and the ratio Rzjis / Rk tends to increase. Also, when component (A) is linear low-density polyethylene and component (B) is a (propylene-ethylene) random copolymer, the increase in the level difference Rk is more significant than the increase in the ten-point average roughness Rzjis, and the ratio Rzjis / Rk tends to decrease. It is preferable to select components (A) and (B) taking these tendencies into consideration.

[0093] <<Additives>> From a handling perspective, such as transportability in the printing process, the heat seal layer may contain an antistatic agent to the extent that it does not affect the heat seal performance. Examples of usable antistatic agents include compounds having a primary to tertiary amine or quaternary ammonium salt structure, and complete or partial fatty acid esters such as ethylene glycol, propylene glycol, glycerin, polyethylene glycol, and polyethylene oxide.

[0094] From the viewpoint of incorporating it into the resin composition of the heat-seal layer and gradually migrating to the surface to exert an antistatic effect, a low-molecular-weight antistatic agent can be used. Furthermore, from the viewpoint of exerting a sustained antistatic effect at low concentrations, a high-molecular-weight antistatic agent can be used. It is also possible to use both low-molecular-weight and high-molecular-weight antistatic agents in combination.

[0095] From the viewpoint of exhibiting the predetermined performance of the antistatic agent, the content of the antistatic agent in the heat seal layer is preferably 0.01% by mass or more, and more preferably 0.05% by mass or more. From the viewpoint of ensuring adhesive strength when the in-mold label is attached to the container, the content of the antistatic agent is preferably 3% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less.

[0096] Methods for adding the antistatic agent include directly incorporating it into the resin composition for the heat seal layer, and incorporating a masterbatch obtained by blending a high concentration of the antistatic agent into a thermoplastic resin compatible with the thermoplastic resin used in the heat seal layer, into the resin composition for the heat seal layer.

[0097] From the viewpoint of suppressing blocking, the heat seal layer may contain an antiblocking agent. Examples of usable antiblocking agents include polymer microparticles prepared using emulsion polymerization, dispersion polymerization, suspension polymerization, or seed polymerization; inorganic microparticles such as silica, alumina, or synthetic zeolite; and fatty acid amides such as N,N′-ethylenebisstearamide, N,N′-ethylenebisoleamide, erucamide, oleamide, stearamide, or behenamide. Among these, polymer microparticles or fatty acid amides are preferred because they are less likely to damage the front surface of the thermoplastic resin film superimposed on the heat seal layer when thermoplastic resin films are superimposed. Furthermore, these antiblocking agents may be used individually or in combination of two or more types.

[0098] From the viewpoint of exhibiting the predetermined performance of the antiblocking agent, the content of the antiblocking agent in the heat seal layer is preferably 0.05% by mass or more, and more preferably 0.5% by mass or more. On the other hand, from the viewpoint of increasing the adhesive strength with the adherend or container, the content of the antiblocking agent is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less.

[0099] Methods for adding the antiblocking agent include directly incorporating it into the resin composition for forming the heat seal layer, and incorporating a masterbatch obtained by blending a high concentration of the antiblocking agent into a thermoplastic resin compatible with the thermoplastic resin used for the heat seal layer, into the resin composition for forming the heat seal layer.

[0100] The heat seal layer may optionally contain known additives listed in the section on the heat seal resin receiving layer, as needed. From the viewpoint of ensuring the additives exhibit their intended performance, the content of these additives in the heat seal layer is preferably 0.05% by mass or more, and more preferably 0.5% by mass or more. From the viewpoint of increasing the adhesive strength with the adherend or container, the content of the above additives is preferably 7.5% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[0101] <<Thickness>> From the viewpoint of increasing adhesive strength, the thickness of the heat seal layer is preferably 0.5 μm or more, more preferably 2 μm or more, even more preferably 3 μm or more, and for example, 10 μm or less. In particular, when the heat seal resin receiving layer is a stretched porous layer, from the viewpoint of forming a desired uneven structure on the heat seal surface due to the melting and dripping of the heat seal resin, the above thickness is preferably 7 μm or less, and more preferably 5 μm or less.

[0102] (Method for manufacturing thermoplastic resin films) The thermoplastic resin film of the present invention can be manufactured, for example, by forming and laminating films from a resin composition containing the components of each layer. The film is stretched as needed. The method for forming, laminating, or stretching the film is not particularly limited and can be any known technique used individually or in combination.

[0103] Film forming methods include, for example, casting, calendering, rolling, and inflation molding, in which a molten resin composition is extruded into a sheet shape using single-layer or multi-layer T-dies, I-dies, etc., connected to a screw-type extruder.

[0104] Film lamination methods include dry lamination, wet lamination, and fusion lamination using various adhesives, as well as multi-layer die lamination (co-extrusion) using a feed block or multi-manifold, extrusion lamination using multiple dies, and coating methods using various coaters. It is also possible to use a combination of multi-layer die lamination and extrusion lamination.

[0105] Stretching methods include longitudinal stretching between rolls using the difference in peripheral speed of the roll group, transverse stretching using a tenter oven, and sequential biaxial stretching combining these methods. Other methods include rolling using roll pressure, simultaneous biaxial stretching using a combination of a tenter oven and a pantograph, and simultaneous biaxial stretching using a combination of a tenter oven and a linear motor. Another method is simultaneous biaxial stretching (inflation molding), in which molten resin is extruded into a tube shape using a circular die connected to a screw-type extruder, and then air is blown into it.

[0106] Each layer may be stretched individually before lamination, or they may be stretched together after lamination. Furthermore, stretched layers may be stretched again after lamination. From the viewpoint of pore formation, it is preferable that the heat seal resin receiving layer and the heat seal layer are stretched in at least one axial direction after lamination. The number of stretching axes for the base layer / heat seal resin receiving layer / heat seal layer may be 2 axes / 1 axis / 1 axis, 1 axis / 2 axes / 2 axes, 2 axes / 2 axes / 1 axis, or 2 axes / 2 axes / 2 axes.

[0107] In particular, a preferred method is to form a laminated film by laminating the resin compositions of each layer in the order of base layer / heat seal resin receiving layer / heat seal layer in a multilayer die and extruding it, and then stretching it in a uniaxial or biaxial direction; to simultaneously or sequentially laminate a heat seal resin receiving layer and a heat seal layer onto a single-layer or multilayer unstretched film that will serve as the base layer, and then further stretch it in a uniaxial or biaxial direction; or to simultaneously or sequentially laminate a heat seal resin receiving layer and a heat seal layer onto a single-layer or multilayer uniaxially stretched film that will serve as the base layer, and then further stretch it in a uniaxial or biaxial direction.

[0108] From the viewpoint of forming voids in the heat seal resin receiving layer, the stretching temperature of the thermoplastic resin film is preferably above the glass transition temperature of the thermoplastic resin used in the heat seal resin receiving layer if the thermoplastic resin used in the heat seal resin receiving layer is an amorphous resin. If the thermoplastic resin used in the heat seal resin receiving layer is a crystalline resin, it is preferably above the glass transition temperature of the amorphous portion of the thermoplastic resin and below the melting point of the crystalline portion. On the other hand, from the viewpoint of melting the heat seal resin in the heat seal layer into the voids, it is preferable that the stretching temperature is higher than the melting point of the crystalline portion of the thermoplastic resin used in the heat seal layer. For example, if the thermoplastic resin used in the heat seal resin receiving layer is a propylene homopolymer (glass transition temperature approximately -20°C, melting point 155~167°C) and the heat seal resin used in the heat seal layer is high-density polyethylene (melting point 121~136°C), then 123~165°C is preferable.

[0109] The stretching speed is not particularly limited, but it is preferably in the range of 20 to 350 m / min for stable stretching and molding of the thermoplastic resin film.

[0110] The stretching ratio is determined appropriately, taking into consideration the stretching characteristics of the thermoplastic resin used in the thermoplastic resin film. For example, when the thermoplastic resin used in the thermoplastic resin film is a homopolymer or copolymer thereof of propylene, the stretching ratio when stretching the thermoplastic resin film in one direction is preferably about 1.5 times or more, more preferably 2 times or more, preferably 12 times or less, and more preferably 10 times or less. When biaxially stretched, the stretching ratio is preferably 1.5 times or more in terms of area stretching ratio, more preferably 4 times or more, preferably 60 times or less, and more preferably 50 times or less.

[0111] In the present invention, it is preferable to select materials such that the melting point of the thermoplastic resin contained in the heat seal resin receiving layer is higher than the melting point of the heat seal resin contained in the heat seal layer, and to perform stretching at a temperature higher than the melting point of the heat seal resin contained in the heat seal layer but lower than the melting point of the thermoplastic resin contained in the heat seal resin receiving layer. This allows for the formation of voids in the heat seal resin receiving layer, into which the heat seal resin of the heat seal layer can melt and drip. By forming numerous recesses on the heat seal surface, the level difference Rk and ratio Rzjis / Rk of the heat seal surface can be easily adjusted to a desired range. From the viewpoint of imparting an uneven surface structure to the heat seal layer, when the heat seal layer contains inorganic particles, it is preferable to stretch the heat seal layer after it has been laminated onto the heat seal resin receiving layer. Stretching makes it easier for the shape of the inorganic particles to be reflected in the surface shape of the heat seal layer, thus making it easier to impart an uneven surface. Furthermore, when the heat seal layer is stretched, it is easier to adjust the level difference Rk and ratio Rzjis / Rk to a specific range even with a smaller amount of inorganic particles compared to the case without stretching, and there is an effect of not reducing the adhesive strength with the adherend or container.

[0112] When the thermoplastic resin contained in the heat seal layer is a combination of two or more incompatible resins, a surface with irregularities can be spontaneously formed even without stretching; however, it is preferable to stretch the heat seal layer after lamination molding. By combining stretching, the irregularities tend to be emphasized on the surface of the heat seal layer. In this case, since component (B) forms islands in a sea-island structure, it is preferable that the stretching temperature is higher than the melting point of component (A) and lower than the melting point of component (B).

[0113] (Physical properties of thermoplastic resin films) <thickness> The thickness of the thermoplastic resin film of the present invention is preferably 30 μm or more, more preferably 40 μm or more, and even more preferably 50 μm or more, from the viewpoint of providing sufficient rigidity to the label or in-mold label and suppressing problems in the printing process or mold insertion process. Furthermore, from the viewpoint of drop resistance in large bottle containers, the thickness of the thermoplastic resin film is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less. The thickness of the above thermoplastic resin film shall be measured in accordance with JIS K7130:1999 "Plastics - Films and Sheets - Method for Measuring Thickness".

[0114] <Tensile modulus> The tensile modulus of the thermoplastic resin film of the present invention in the transverse direction (TD) is preferably 200 MPa or higher, more preferably 350 MPa or higher, and even more preferably 400 MPa or higher. The above tensile modulus is preferably 3600 MPa or lower, more preferably 3300 MPa or lower, and even more preferably 3100 MPa. If the tensile modulus is 200 MPa or higher, the rigidity of the film tends to increase, making it possible to provide in-mold labels that are less prone to bending during molding. If the tensile modulus is 3600 MPa or lower, the ability to conform to curved surfaces tends to increase, making it possible to provide labels with a good appearance even when attached to substrates or containers with complex shapes that have convex or concave parts. The tensile modulus of elasticity described above was measured in accordance with JIS K7161-1:2014 "Plastics - Method for determining tensile properties". Five test specimens, each 10 mm wide and 80 mm long, were prepared from the film to be measured, in both the longitudinal (MD) and transverse (TD) directions. The tensile stress and tensile strain of each test specimen were measured at a test speed of 100 mm / min according to the method described in JIS K7161-1, and the tensile modulus of elasticity E was calculated using the following formula. E=(σ2-σ1) / (ε2-ε1) However, E: tensile modulus (MPa), σ1: tensile stress measured at strain ε1 = 0.0005, σ2: tensile stress measured at strain ε2 = 0.0025.

[0115] <Density> The density of the thermoplastic resin film is preferably 0.6 g / cm 3 or more from the viewpoint of giving sufficient rigidity to the in-mold label and reducing troubles in the printing process or the mold insertion process, more preferably 0.65 g / cm 3 or more, and still more preferably 0.7 g / cm 3 or more. Also, from the viewpoint of reducing the weight of the label, the density of the thermoplastic resin film is preferably 0.95 g / cm 3 or less, more preferably 0.9 g / cm 3 or less, and still more preferably 0.85 g / cm 3 or less. When the thermoplastic resin film is used as an in-mold label, a pattern called orange peel may appear on the appearance of the label after molding. If the orange peel is not required as a design, a higher value (0.8 g / cm 3 or more) within the above range may be selected. If the orange peel is required as a design, a lower value (less than 0.8 g / cm 3 ) within the above range may be selected.

[0116] The density of the above thermoplastic resin film is obtained by dividing the basis weight measured based on JIS P8124:2011 "Paper and Paperboard - Method for Measuring Basis Weight" by the thickness of the above thermoplastic resin film.

[0117] <Surface Resistivity> The surface resistivity of the front surface on the side opposite to the heat-sealing surface of the thermoplastic resin film is preferably 1×10 8 Ω or more, more preferably 5×10 8 Ω or more, and still more preferably 1×10 9 Ω or more. Also, the surface resistivity of the front surface is preferably 1×10 12 Ω or less, preferably 5×10 11 Ω or less, and preferably 1×10 11It is even more preferable that the impedance is Ω or less. This suppresses the overlapping transport of two or more films (double feeding) in printing processes, label processing processes, etc., and also reduces the likelihood of in-mold labels falling when placed in a mold using a charged inserter. The above surface resistivity is measured using a double-ring electrode method in accordance with JIS K-6911:1995 "General Test Methods for Thermosetting Plastics" under conditions of a temperature of 23°C and a relative humidity of 50%.

[0118] (Labels and in-mold labels) The labels and in-mold labels of the present invention comprise the thermoplastic resin film of the present invention described above. The labels of the present invention adhere to the adherend by heating, forming a heat-seal layer. The in-mold labels of the present invention adhere to the outer surface of a container molded from a molding resin by the heat of the molding resin molten during in-mold molding.

[0119] <Print> The labels and in-mold labels of the present invention can have information such as barcodes, manufacturer names, distributor names, characters, product names, or instructions for use printed on their front surface. The printing method is not particularly limited, and for example, gravure printing, offset printing, flexographic printing, sticker printing, or screen printing can be used. It is preferable that the front surface of the thermoplastic resin film used as the label or in-mold label is surface-treated to have printability. Examples of surface treatment methods include surface oxidation treatment such as corona discharge and application of a substance with excellent ink fixation properties.

[0120] Conventional labels or in-mold labels made of thermoplastic resin film tend to show a prominent embossed pattern when printed on the front surface, as the uneven surface of the embossed heat-sealed surface is strongly transferred to the front surface when stacked. In contrast, with labels or in-mold labels using the thermoplastic resin film of the present invention, the embossed pattern is either not visible at all on the printed surface or is barely noticeable. The appearance of the printed area also changes minimally after storage, maintaining an excellent appearance.

[0121] <Punching process> By die-cutting the thermoplastic resin film of the present invention, labels or in-mold labels of the required shape and dimensions can be obtained. When printing information on the labels or in-mold labels, the die-cutting process may be performed before or after the printing process, but it is usually performed after the printing process. The die-cut labels or in-mold labels may be large in size to be attached to the entire surface of a resin container, or small in size to be attached to a part of it. For example, an in-mold label may be used as a blank label that surrounds the side of an injection-molded cup-shaped resin container, or as a label that is attached to the front and back surfaces of a hollow-molded bottle-shaped resin container.

[0122] (Labeled plastic container) By using the in-mold label of the present invention and performing in-mold molding, it is possible to manufacture a labeled resin container in which the in-mold label of the present invention is attached to the surface of the resin container.

[0123] <Plastic container> Examples of materials for resin containers include ester resins such as polyethylene terephthalate (PET) or its copolymers; olefin resins such as polypropylene (PP) or polyethylene (PE); and polycarbonate resins. Among these, ester resins or olefin resins are preferred because they are easy to blow mold. It is also preferable to use a thermoplastic resin composition mainly composed of these thermoplastic resins.

[0124] The shape of the body of the resin container is not particularly limited; the cross-sectional shape may be a perfect circle, an ellipse, or a rectangle. If the cross-section is rectangular, it is preferable that the corners have curvature. From the viewpoint of strength, it is preferable that the cross-section of the body be a perfect circle or an ellipse close to a perfect circle, and most preferably a perfect circle.

[0125] <In-mold molding> Examples of in-mold molding methods include hollow molding, injection molding, and differential pressure molding.

[0126] For example, in hollow molding, an in-mold label is placed in the cavity of at least one mold so that the heat-sealed surface of the in-mold label faces the cavity side of the mold (so that the front surface is in contact with the mold), and then fixed to the inner wall of the mold by suction or static electricity. Next, a molding resin such as a parison or preform made from the raw resin of the container is heated and guided between the molds and clamped. Then, by hollow molding using a conventional method, a labeled resin container is formed in which the label is integrally attached to the outer surface of the resin container.

[0127] In injection molding, the in-mold label is placed in the cavity of the female mold with the heat-sealed surface facing the mold cavity (so that the front surface is in contact with the mold), then fixed to the inner wall of the mold by suction or static electricity, and the mold is clamped. Next, the molten resin for molding the container is injected into the mold to form the container, thereby forming a labeled resin container in which the label is integrally attached to the outer surface of the resin container.

[0128] In differential pressure molding, an in-mold label is placed in the cavity of the lower female mold of a differential pressure molding die with the heat-sealed surface of the label facing the cavity side of the mold (so that the front surface is in contact with the mold), and then fixed to the inner wall of the mold by suction or static electricity. Next, molten sheet-like molding resin is guided to the upper part of the lower female mold, and differential pressure molding is performed by a conventional method to form a labeled resin container in which the label is integrally attached to the outer surface of the resin container. Differential pressure molding can be performed using either vacuum forming or pressure forming, but generally, it is preferable to use both in combination and to perform differential pressure molding using plug assist. The in-mold labels of the present invention are particularly useful for hollow molding or injection molding, where the container resin temperature is low during molding.

[0129] <Adhesive strength> The adhesive strength between the resin container and the label is preferably 2N / 15mm or higher, more preferably 4N / 15mm or higher, and more preferably 6N / 15mm or higher, under conditions where blistering does not occur. This reduces the likelihood of the label peeling off during use. The above adhesive strength shall be measured in accordance with JIS K 6854-3:1999 "Adhesives - Test methods for peel adhesion strength - Part 3: T-type peel". [Examples]

[0130] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. Unless otherwise specified, "parts," "%," etc., in the examples refer to mass-based measurements.

[0131] (Measurement method) The physical properties of the thermoplastic resin film were measured as follows:

[0132] <thickness> The total thickness (μm) of the thermoplastic resin film was measured using a constant-pressure thickness gauge (TECLOCK Co., Ltd., "PG-01J") in accordance with JIS K7130:1999. The thickness of each layer (μm) was determined by observing the cross-section of the thermoplastic resin film using a scanning electron microscope, and then multiplying the ratio of the thicknesses of each layer by the total thickness.

[0133] <density> Density of thermoplastic resin film (g / cm³) 3 The basis weight of the thermoplastic resin film was calculated by dividing it by the thickness obtained above. The basis weight of the thermoplastic resin film was measured by weighing a 100mm x 100mm die-cut sample using an electronic balance, in accordance with JIS P8124:2011 "Paper and cardboard - Method for measuring basis weight".

[0134] <Smoothness> The smoothness (seconds) of thermoplastic resin films was measured using a digital Oguri-type air permeability and smoothness tester (EYO-55-1M, manufactured by Asahi Seiko Co., Ltd.) in accordance with JIS P 8155:2010 "Paper and cardboard - Smoothness test method - Oguri method".

[0135] <Tensile modulus> The tensile modulus in the longitudinal (MD) and transverse (TD) directions of the thermoplastic resin film was determined based on JIS K7161-1:2014.

[0136] <Ten-point mean roughness Rzjis> The ten-point average roughness Rzjis of the heat-sealed surface of a thermoplastic resin film was measured using a surface roughness measuring instrument ("SURFCOM 1500DX" manufactured by Tokyo Seimitsu Co., Ltd.) conforming to Annex 1 of JIS B0601:1994, under the condition of measuring a measurement length of 30 mm on the heat-sealed surface. For the measurement, a sample of thermoplastic resin film cut to 50 mm x 50 mm was used.

[0137] <Arithmetic mean roughness Ra, core level difference Rk, protruding peak height Rpk, and protruding valley depth Rvk, core load length ratio Mr1, ratio Rzjis / Rk> The surface shape of the heat-sealed surface of a thermoplastic resin film was measured using a non-contact 3D surface roughness analyzer (Zygo Corporation, "NewView5010") compliant with ISO 13565-1:1996. Specifically, the 3D surface shape in the planar direction was measured under conditions of a measurement area of ​​2 mm × 2 mm, an objective lens of 20x magnification, and cutting wavelengths of 14 μm or less. The measurement results were analyzed using analysis software (Zygo Corporation, "MetroPro") compliant with ISO 13565-2:1996 to determine the 3D surface shape in the planar direction (arithmetic mean roughness Ra, core level difference Rk, protruding peak height Rpk, and protruding valley depth Rvk, core load length ratio Mr1, and ratio Rzjis / Rk).

[0138] (material) Table 1 lists the materials used in the manufacture of thermoplastic resin films. [Table 1]

[0139] (Example 1) Table 1 lists the thermoplastic resin PP2 (propylene homopolymer (manufactured by Nippon Polypropylene Co., Ltd., product name: Novatec PP MA3, MFR (JIS-K7210): 11 g / 10 min, density: 0.906 g / m³): 11 g / 10 min, density: 0.906 g / m³ 3 25% by mass of thermoplastic resin PP3 (propylene homopolymer (manufactured by Nippon Polypropylene Co., Ltd., product name: Novatec PP FY6, MFR (JIS-K7210): 2.5 g / 10 min, density: 0.906 g / m³)), melting point (JIS-K7121): 167°C, thermoplastic resin PP3 (propylene homopolymer (manufactured by Nippon Polypropylene Co., Ltd., product name: Novatec PP FY6, MFR (JIS-K7210): 2.5 g / 10 min, density: 0.906 g / m³) 3 , melting point (JIS-K7121): 167℃) 13.5% by mass, inorganic particles CA1 (heavy calcium carbonate (surface treated with stearate ester, manufactured by Bihoku Powdering Industry Co., Ltd., product name: Lighton 32X, average particle size (D50): 0.7μm, D90: 2μm, density: 2.71g / m³ 3)) 60% by mass, surface treatment agent SA (oleic acid (manufactured by Kao Corporation, product name: Lunac OV)) 0.5% by mass, inorganic particles TIO (rutile-type titanium dioxide (manufactured by Ishihara Sangyo Co., Ltd., product name: Typeque CR-60, average particle size: 0.2 μm, density: 4.23 g / m³) 3 A resin composition for the heat seal resin receiving layer was prepared by mixing )) in a proportion of 1% by mass.

[0140] Also, the heat-sealing resin PE2 (metallocene polyethylene) listed in Table 1 (manufactured by Nippon Polyethylene Co., Ltd., product name: Harmolex NF444N, MFR (JIS-K7210): 2g / 10 min, density: 0.912g / cm³) 3 100% by mass of a material with a melting point (JIS-K7121): 121°C and a crystallization point (JIS-K7121): 95°C was prepared as a resin composition for the heat seal layer.

[0141] The resin compositions for the heat seal resin receiving layer and the heat seal layer were melt-kneaded in two extruders set to 230°C, and then co-extruded into a sheet using a T-die set to 230°C to obtain an unstretched sheet having a two-layer structure of a heat seal resin receiving layer and a heat seal layer. This unstretched sheet was reheated in a tenter oven to a surface temperature of 160°C, then stretched nine times in the transverse direction (TD) using a tenter, and further annealed in a heat setting zone adjusted to 170°C. After cooling to approximately 60°C with a cooling roll, the edges were slit to obtain a two-layer uniaxially oriented resin film. This was guided to a corona discharge treatment chamber with a guide roll, and 50 W·min / m was applied to the surface on the heat seal resin receiving layer side. 2 Corona discharge treatment was performed with the specified processing volume. This was then wound up using a winding machine to obtain the thermoplastic resin film of Example 1.

[0142] Figure 2 shows the load curve of the thermoplastic resin film of Example 1. The thermoplastic resin film of Example 1 has a total thickness of 78 μm (thickness of the heat seal resin receiving layer: 74 μm / thickness of the heat seal layer: 4 μm) and a density of 0.90 g / cm³. 3The smoothness was 5664 seconds, the tensile modulus (MD) was 124 MPa, the tensile modulus (TD) was 2740 MPa, and the surface roughness parameters were Ra: 1.33 μm, Rzjis: 17.63 μm, Rk: 3.79 μm, Rpk: 1.24 μm, Rvk: 2.64 μm, Mr1: 8.34%, and Rzjis / Rk: 4.65.

[0143] (Example 2) Heat seal resin PE1 (metallocene polyethylene (manufactured by Nippon Polyethylene Co., Ltd., product name: Harmolex NJ744N, MFR (JIS-K7210): 12g / 10 min, density: 0.911g / cm³) 3 A resin composition for the heat seal layer was prepared by mixing 50% by mass of a material with a melting point (JIS-K7121): 120°C and a crystallization point (JIS-K7121): 95°C with 50% by mass of heat seal resin PE2. A thermoplastic resin film was obtained in the same manner as in Example 1, except that a heat seal layer was formed using this resin composition. The components, stretching conditions, and measurement results of each physical property of the thermoplastic resin film of Example 2 are shown in Tables 2 to 4.

[0144] (Example 3) Thermoplastic resin PP2: 25% by mass, Thermoplastic resin PP3: 13.5% by mass, Inorganic particles CA1: 40% by mass, Inorganic particles CA2 (heavy calcium carbonate (no surface treatment, manufactured by Bihoku Funka Kogyo Co., Ltd., product name: Softon #1800, average particle size (D50): 1.25 μm, D90: 7.5 μm), Density: 2.71 g / m³ 3 A resin composition for the heat seal resin receiving layer was prepared by mixing 20% ​​by mass of ) with 0.5% by mass of the surface treatment agent SA and 1% by mass of inorganic particles TIO. Furthermore, 100% by mass of the heat-seal resin PE1 was prepared as a resin composition for the heat-seal layer. A thermoplastic resin film was obtained in the same manner as in Example 1, except that a heat-seal resin receiving layer and a heat-seal layer were formed using the above-mentioned resin compositions. The components, stretching conditions, and measurement results of each physical property of the thermoplastic resin film of Example 3 are shown in Tables 2 to 4.

[0145] (Example 4) In a resin composition for a heat-seal resin receiving layer, inorganic particles CA3 (heavy calcium carbonate (untreated surface, manufactured by Bihoku Funka Kogyo Co., Ltd., product name: BF200, average particle size (D50): 5 μm, D90: 30 μm), density: 2.71 g / m³) are used instead of inorganic particles CA2. 3 A thermoplastic resin film was obtained in the same manner as in Example 3, except that 20% by mass of ) was used. The components, stretching conditions, and measurement results of each physical property of the thermoplastic resin film of Example 4 are shown in Tables 2 to 4.

[0146] (Examples 5-7, 11 and 12, Comparative Examples 3 and 4) Except for changing the proportions of each component in the heat-seal resin receiving layer as shown in Table 2, thermoplastic resin films for Examples 5-7, 11 and 12, and Comparative Examples 3 and 4 were obtained in the same manner as in Example 3. The parameters of each thermoplastic resin film, including its components, stretching conditions, physical properties, tensile modulus, and surface properties, are shown in Tables 2-4. The load curve for the thermoplastic resin film of Example 5 is shown in Figure 3.

[0147] (Example 8) A resin composition for the heat seal layer was prepared by mixing 70% by mass of heat seal resin PE1 and 30% by mass of inorganic particles CA1. A heat seal layer was formed using this resin composition, and the thermoplastic resin film of Example 8 was obtained in the same manner as in Example 3, except that the proportions of each component of the heat seal resin receiving layer were changed as shown in Table 2. The components, stretching conditions, and measurement results of each physical property of the thermoplastic resin film are shown in Tables 2 to 4.

[0148] (Example 9) A thermoplastic resin film was prepared in the same manner as in Example 3, except that an unstretched sheet was reheated with a hot roll to a sheet surface temperature of 130°C, stretched twice in the longitudinal direction (MD), cooled with a cooling roll to a sheet surface temperature of approximately 60°C to obtain a double-stretched sheet, then reheated to 150°C and stretched twice in the transverse direction to obtain a biaxially oriented resin film. The components, stretching conditions, and measurement results of each physical property of the thermoplastic resin film are shown in Tables 2 to 4.

[0149] (Example 10) Thermoplastic resin PP1 (propylene homopolymer (manufactured by Nippon Polypropylene Co., Ltd., product name: Novatec PP MA4, MFR (JIS-K7210): 5g / 10 min, density: 0.906g / m³): 5g / 10 min, density: 0.906g / m³ 3 A resin composition for the base layer was prepared by mixing 84% by mass of a material with a melting point (JIS-K7121): 167°C and 16% by mass of inorganic particles CA1.

[0150] The resin composition for the base layer described above was melt-kneaded in an extruder set to 250°C, then supplied to a T-die set to 250°C and extruded into a sheet. This sheet was then cooled to approximately 60°C using a cooling roll to obtain an unstretched sheet. Next, this unstretched sheet was reheated with a hot roll to a sheet surface temperature of 140°C, then stretched four times in the longitudinal direction (MD) using the difference in peripheral speed of the roll group, and finally cooled to approximately 60°C using a cooling roll to obtain a four-fold stretched sheet.

[0151] Next, the resin compositions for the heat seal resin receiving layer and the heat seal layer prepared in Example 1 were melt-kneaded in two other extruders set to 230°C. This was extruded into a sheet using a T-die set to 230°C and laminated onto the 4x stretched sheet to obtain a 3-layer sheet with the base layer / heat seal resin receiving layer / heat seal layer laminated in that order. The 3-layer sheet was reheated in a tenter oven to a surface temperature of 160°C, then stretched 9x in the transverse direction (TD) using a tenter, and further annealed in a heat setting zone adjusted to 170°C. It was cooled to approximately 60°C using a cooling roll, and the edges were slit to obtain a 3-layer biaxially oriented resin film. This was guided to a corona discharge treatment chamber using a guide roll, and 50 W·min / m was applied to the surface on the base layer side. 2 Corona discharge treatment was performed at the specified processing rate. The material was then wound up using a winding machine to obtain a thermoplastic resin film.

[0152] The resulting thermoplastic resin film had a total thickness of 80 μm (substrate layer thickness: 50 μm, heat seal resin receiving layer thickness: 26 μm / heat seal layer thickness: 4 μm) and a density of 0.75 g / cm³. 3The smoothness was 6542 seconds, the tensile modulus (MD) was 967 MPa, the tensile modulus (TD) was 2478 MPa, and the surface roughness parameters were Ra: 1.43 μm, Rzjis: 18.74 μm, Rk: 4.12 μm, Rpk: 1.33 μm, Rvk: 2.51 μm, Mr1: 9.54%, and Rzjis / Rk: 4.55.

[0153] (Comparative Example 1) A resin composition for a heat seal resin receiving layer was prepared by mixing thermoplastic resin PP2 at a ratio of 30% by mass, thermoplastic resin PP3 at a ratio of 13.5% by mass, inorganic particles CA1 at a ratio of 55% by mass, surface treatment agent SA at a ratio of 0.5% by mass, and inorganic particles TIO at a ratio of 1% by mass. Furthermore, 100% by mass of thermoplastic resin PE1 was prepared as a resin composition for the heat seal layer.

[0154] The resin compositions for the heat-seal resin receiving layer and the heat-seal layer were melt-kneaded in two extruders set to 230°C, and then co-extruded into a sheet using a T-die set to 230°C to obtain a sheet with a two-layer structure of a heat-seal resin receiving layer and a heat-seal layer. This sheet was guided between a metal cooling roll with a #150 gravure embossed pattern and a matte rubber roll, with the heat-seal layer side in contact with the metal cooling roll, and the two were pressed together while transferring the embossed pattern to the heat-seal layer side. This was then cooled with the cooling roll to obtain an unstretched sheet with a two-layer structure of a heat-seal resin receiving layer and a heat-seal layer. This unstretched sheet was reheated in a tenter oven to a sheet surface temperature of 160°C, then stretched nine times in the transverse direction (TD) using a tenter, and further annealed in a heat-setting zone adjusted to 170°C. It was cooled to approximately 60°C with a cooling roll, and the edges were slit to obtain a two-layer uniaxially oriented resin film. This is guided by a guide roll to a corona discharge treatment unit, and 50 W·min / m is applied to the surface on the heat seal resin receiving layer side. 2 Corona discharge treatment was performed with the specified processing volume. This was then wound up using a winding machine to obtain the thermoplastic resin film of Comparative Example 1. Tables 2 to 4 show the composition, stretching conditions, and measurement results of each physical property of the thermoplastic resin film of Comparative Example 1. Figure 4 shows the load curve of the thermoplastic resin film of Comparative Example 1.

[0155] (Comparative Example 2) Heat seal resin PE3 (metallocene polyethylene, manufactured by The Dow Company, product name: Engage 8401, MFR (ASTM D1238): 30g / 10 min, density: 0.885g / cm³) 3 A resin composition for the heat seal layer was prepared by mixing 50% by mass of a material with a melting point (JIS-K7121): 81°C and 50% by mass of thermoplastic resin PP2. A thermoplastic resin film was obtained in the same manner as in Example 1, except that a heat seal layer was formed using this composition. The components, stretching conditions, and measurement results of each physical property of the thermoplastic resin film of Comparative Example 2 are shown in Tables 2 to 4. The load curve of the thermoplastic resin film of Comparative Example 2 is shown in Figure 5.

[0156] Table 2 lists the components of each thermoplastic resin film. Table 3 lists the physical properties of each thermoplastic resin film, including stretching conditions, thickness, density, and smoothness. Table 4 lists the physical properties of each thermoplastic resin film, including tensile modulus and surface properties parameters. In each table, HS stands for heat seal. [Table 2]

[0157] [Table 3]

[0158] [Table 4]

[0159] (Evaluation method) Labels and in-mold labels were manufactured from each thermoplastic resin film, and their suitability was evaluated as follows.

[0160] <Label printability> Labels were manufactured by slitting a thermoplastic resin film into small pieces. One side of the labels was flexographically printed under conditions of 23°C and 50% relative humidity. A flexographic printing press (Tyōkai Machinery Co., Ltd., "TCL") and UV-curing flexographic ink (T&K TOKA Co., Ltd., "UV Flexo CF") were used to print text information such as the product name, manufacturer, distributor name, usage instructions, and precautions, as well as a barcode and design, in four colors at a speed of 60 m / min. The printed material was then passed under a UV irradiator (iGraphic Co., Ltd., metal halide lamp, 100 W / cm, 1 lamp) at a speed of 60 m / min to dry the ink on the printed surface and obtain a flexographic print.

[0161] The printed surface of the printed material was observed, and its printability was evaluated according to the following criteria. ◎: Good (No external defects observed under magnification) ○: Good (Slight fluctuations are visible in the outlines of the letters when viewed with a magnifying glass) △: Acceptable (Defects in the outline of the letters are visible under magnification) ×: Defective (white spots visible upon visual inspection)

[0162] <Assessment of suitability of in-mold labels> In-mold labels were manufactured from each thermoplastic resin film, and labeled containers were manufactured by in-mold molding using these in-mold labels. The adhesive strength of the labels on the labeled containers and the appearance of the labels were evaluated as follows.

[0163] <<Manufacturing of labeled containers>> In-mold labels were manufactured by die-cutting a thermoplastic resin film into a rectangle measuring 120 mm wide and 150 mm long. This in-mold label was placed on one side of a blow molding die capable of forming a 3L bottle, with the heat-sealing surface facing the cavity, and fixed to the die using suction. A protrusion projecting outward was provided on the inner wall of the die, and the in-mold label was positioned so that the heat-sealing surface was located on this protrusion. Next, high-density polyethylene (manufactured by Nippon Polyethylene Co., Ltd., product name: Novatec HD HB420R, MFR (JIS K7210:1999): 0.2g / 10min, melting peak temperature (JIS K7121:2012): 133℃, crystallization peak temperature (JIS K7121:2012): 115℃, density (JIS K7112:1999): 0.956g / cm³) was used. 3 The material was melted at 160°C and extruded in a parison shape between the molds, with the parison where the label would be attached set to 160°C. After clamping the molds, 4.2 kg / cm³ was applied. 2 Compressed air was supplied into the parison, and the parison was expanded for 16 seconds to make it adhere tightly to the mold, forming a container shape and fusing the label with it. After the molded product cooled in the mold, the mold was opened to obtain a container with a label. The cooling temperature of the mold was 20°C, and the shot cycle time was 38 seconds / cycle.

[0164] <<Adhesion strength>> The above-mentioned labeled resin containers were stored for one week at 23°C and 50% relative humidity. Then, in accordance with JIS K 6854-3:1999, the label portion of the labeled containers was cut into 15mm wide strips to prepare samples. Using a tensile testing machine (Shimadzu Corporation, "Autograph AGS-D"), the samples were peeled in a T-shape at a tensile speed of 300mm / min to measure the adhesive strength (N / 15mm) between the label and the container.

[0165] <<Overall appearance of the label>> The entire label of the labeled container was observed and evaluated as follows. ◎: Excellent (No cosmetic defects or peeling observed) ○: Good (Some minor cosmetic imperfections, but no peeling is observed) △: Acceptable (Orange peel may occur, but no peeling is observed, and there are no practical problems.) ×: Defective (blistering, misalignment causing cosmetic defects, or peeling)

[0166] <<Appearance of the raised part of the label>> The raised portion of the label on the labeled container was observed and evaluated as follows. ◎: Excellent (conforms well to uneven surfaces) ○: Good (Some wrinkles appear, but it conforms well and no peeling is observed) △: Acceptable (Although its ability to conform to recessed areas is slightly inferior, the unevenness of the container is still visible, and there are no practical problems.) ×: Defective (Does not conform to uneven surfaces; the unevenness of the container is not visible)

[0167] <Porosity of the heat-seal resin receiving layer> A sample was cut from a thermoplastic resin film, embedded in epoxy resin, and solidified. The sample was then cut perpendicular to the surface direction (thickness direction) using a microtome. The epoxy resin containing the embedded sample was attached to an observation plate so that the cut surface would be the observation surface, and gold or gold-palladium was deposited onto the observation surface. Next, the voids in the cut surface were observed at an arbitrary magnification (e.g., 500x to 3000x) using a scanning electron microscope. The observed area was captured as image data and processed to determine the percentage (%) of voids relative to the total area of ​​the heat-seal resin receiving layer. Samples were cut at arbitrary locations from 10 to 30 points, and the percentage of voids was measured. The average value was calculated as the porosity (%) of the heat-seal resin receiving layer.

[0168] <Volume ratio of resin in thermoplastic film> The volume ratio (%) of the resin composition constituting the thermoplastic film was determined. The porosity (%) of the entire thermoplastic resin film was calculated using the same method as for the porosity of the heat-seal resin receiving layer described above. The volume ratio of the resin in the thermoplastic resin film was calculated using the following formula. Volume ratio of resin in thermoplastic film (%) = Volume ratio of resin composition (%) × (1 - Total porosity of thermoplastic film (%))

[0169] Table 5 shows the evaluation results. [Table 5]

[0170] As shown in Table 5, Examples 1 to 12, in which the level difference Rk and ratio Rzjis / Rk are within a specific range, exhibit fewer blisters and achieve sufficient adhesive strength of 5N / 15mm or higher. Furthermore, due to the high inorganic particle content of the heat-seal resin receiving layer, they contribute significantly to environmental protection. The heat-seal resin receiving layer, with its high porosity due to stretching, also exhibits improved conformability to the raised areas of the label, resulting in an excellent appearance.

[0171] On the other hand, in Comparative Examples 1 to 4, the level difference Rk or ratio Rzjis / Rk is not within a specific range, resulting in poor appearance of the printed surface or reduced adhesive strength leading to delamination. Comparative Example 3, which has a low inorganic particle content, has a low contribution to the environment, and because the porosity of the heat seal resin receiving layer is also low, it does not adequately conform to protrusions.

Claims

1. A thermoplastic resin film comprising a heat seal resin receiving layer and a heat seal layer containing a heat seal resin on the heat seal resin receiving layer, The heat seal resin receiving layer contains a thermoplastic resin, inorganic particles, and a surface treatment agent, and the content of the inorganic particles in the heat seal resin receiving layer is 40 to 80% by mass. The heat seal resin receiving layer contains, as the inorganic particles and the surface treatment agent, inorganic particles surface-treated with the surface treatment agent and the surface treatment agent separately mixed with the surface-treated inorganic particles. The proportion of the surface-treated inorganic particles to the total amount of inorganic particles in the heat-seal resin receiving layer is 40% by mass or more. The content of the separately mixed surface treatment agent in the heat seal resin receiving layer is 0.05% by mass or more and 5% by mass or less. The surface treatment agent is at least one selected from the group consisting of acids having hydrocarbon groups with 8 to 20 carbon atoms, esters of said acids, and salts thereof. The level difference Rk of the core portion on the surface of the heat seal layer is 1.2 to 9.0 μm. The ratio Rzjis / Rk of the ten-point average surface roughness Rzjis of the heat seal layer to the level difference Rk is 3 to 10. Thermoplastic resin film.

2. The load length ratio Mr1 of the core portion on the surface of the heat seal layer is 6.5 to 15%. The thermoplastic resin film according to claim 1.

3. The surface smoothness of the heat seal layer is 1,000 to 10,000 seconds. The thermoplastic resin film according to claim 1 or 2.

4. The heat seal resin receiving layer is a stretched porous layer, The melting point of the thermoplastic resin is higher than the melting point of the heat-sealing resin. A thermoplastic resin film according to any one of claims 1 to 3.

5. The thermoplastic resin film according to any one of claims 1 to 4, wherein the ratio (D90 / D50) of the average particle diameter D90, which accounts for 90% of the cumulative particle size distribution of inorganic particles, to the average particle diameter D50, which accounts for 50% of the cumulative particle size distribution, is 5 or less.

6. The thermoplastic resin film according to any one of claims 1 to 5, wherein the porosity of the heat-seal resin receiving layer is 20% or more and 70% or less.

7. A thermoplastic resin film according to any one of claims 1 to 6, wherein the tensile modulus in the transverse direction (TD) is 200 MPa or more and 3600 MPa or less.

8. A label comprising a thermoplastic resin film according to any one of claims 1 to 7.

9. An in-mold label comprising a thermoplastic resin film according to any one of claims 1 to 7.

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