JP2024014336A - Film, film body, and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film having excellent heat resistance, a film body, and a method for manufacturing the body, in which an uneven shape is not lost even if heat treatment is applied.

SOLUTION: In a film in which different thermoplastic resins are laminated at least in the order of a first layer and a second layer, first protruded parts and first recessed parts are alternately arrayed on the surface of the first layer, an interface between the first layer and the second layer has second protruded parts and second recessed parts at positions corresponding to the first protruded parts and the first recessed parts, the crystallization peak temperature of the thermoplastic resin of the first layer is lower than the melting peak temperature of the thermoplastic resin of the second layer, and the melting peak temperature of the thermoplastic resin of the second layer is lower than the melting peak temperature of the thermoplastic resin of the first layer.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a film, a film body, and a method for manufacturing the same.

In general, plastic films have properties such as being lightweight, chemically stable, easy to process, flexible and strong, and capable of mass production. For this reason, plastic films are used in various things. Applications of plastic films include, for example, packaging materials for foods and medicines, intravenous drip packs, shopping bags, posters, tapes, optical films used in LCD televisions, protective films, and windows attached to windows. A wide variety of products such as films, vinyl greenhouses, construction materials, etc. For such uses, appropriate plastic materials are selected depending on the use. Furthermore, multiple types of plastic films are stacked to form a laminate.

Furthermore, recently, a film has been proposed that looks like a normal film at first glance, but can exhibit characteristic functions such as stretching, by making the front and back surfaces of the film wave-shaped, that is, bellows-like. For example, Patent Document 1 shows that by using a material with drug barrier properties as the film material and making the film shape bellows, both drug barrier properties and stretchability can be achieved. For example, Patent Document 2 discloses that by making the film bellows-like, it is possible to give it the ability to stretch as a film while looking like a normal film, regardless of the film material. It has been shown that it is possible to impart a stretching function to printed layers, printed wiring, etc.

Japanese Patent Application Publication No. 2019-88765 Unexamined Japanese Patent Publication No. 2019-90006

Since the coating layer applied to the film surface can also have the ability to stretch, it is expected to be used, for example, in stretchable barrier films and base films for conductive wiring. Since heating is required during the process, the film is required to have a certain level of heat resistance. On the other hand, bellows-shaped films are sometimes processed directly during the extrusion process, and in that case, if heat treatment such as annealing or stretching treatment is applied after forming the bellows-shaped film, the bellows shape will disappear. Due to this problem, it was difficult to impart heat resistance.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a film, a film body, and a method for manufacturing the same, which have excellent heat resistance so that the uneven shape does not disappear even after heat treatment. .

In order to solve the above problems, one typical film of the present invention is a film in which different thermoplastic resins are laminated in the order of at least a first layer and a second layer, in which the surface of the first layer is Convex portions and first concave portions are arranged alternately, and the interface between the first layer and the second layer includes second convex portions and second concave portions at positions corresponding to the first convex portions and the first concave portions. The crystallization peak temperature of the thermoplastic resin of the first layer is lower than the melting peak temperature of the thermoplastic resin of the second layer, and the melting peak temperature of the thermoplastic resin of the second layer is This is achieved by lowering the melting peak temperature of the thermoplastic resin of the first layer.

One of the typical methods for manufacturing the film of the present invention is as follows:
While heating a flat laminate in which a flat first layer and a second layer each made of a thermoplastic resin are stacked, a first mold having an uneven shape and a second mold having a flat shape are heated. a first step of transferring and forming an uneven shape on the surface of the first layer by sandwiching the first layer;
a second step of forming a solidified film on the surface of the first layer by cooling and solidifying the first layer earlier than the second layer;
A third step of transferring and forming an uneven shape also on the interface between the first layer and the second layer by sandwiching the laminate between the first mold and the second mold during cooling. and,
a fourth step of annealing the first layer and the second layer at a temperature near the crystallization peak temperature of the first layer;
The crystallization peak temperature of the first layer material is lower than the melting peak temperature of the second layer material,
This is achieved by the melting peak temperature of the second layer material being lower than the melting peak temperature of the first layer material.

According to the present invention, it is possible to provide a film, a film body, and a method for manufacturing the same, which have excellent heat resistance so that the uneven shape does not disappear even when heat treated.
Problems, configurations, and effects other than those described above will be made clear by the description of the embodiments below.

FIG. 1 is a top view (a) and a cross-sectional view (b) showing an example of the film of this embodiment. FIG. 2 is a diagram showing a cross section of a film when measuring interfacial peel strength. FIG. 3 is a sectional view showing an example of the film of this embodiment. FIG. 4 is a perspective view showing an example of the film of this embodiment. FIG. 5 is a perspective view showing an example of the film of this embodiment. FIG. 6 is a cross-sectional view schematically showing the shape of the surface of the film of this embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
Note that each figure is a schematic diagram, and the size, shape, etc. of each part are appropriately exaggerated for easy understanding. Further, to simplify the explanation, corresponding parts in each figure are given the same reference numerals.

As shown in FIG. 1, the film 10 of this embodiment is a film in which at least two layers are laminated, and in which the first layer 1 and the second layer 2 are laminated with different thermoplastic resins in this order. On the surface 3 of the first layer 1, first convex portions 4 and first concave portions 5 are arranged alternately to form an uneven shape. The interface 6 between the first layer 1 and the second layer 2 (that is, the surface of the second layer 2) has a second convex part 7 and a second concave part 7 corresponding to the positions corresponding to the first convex part 4 and the first concave part 5. It has two recesses 8. It is preferable that the back surface of the first layer 1 and the surface of the second layer 2 are in close contact with each other without any gaps. On the other hand, although the back surface of the second layer 2 is flat, it may have some shape.

Further, the crystallization peak temperature of the thermoplastic resin of the first layer 1 is lower than the melting peak temperature of the thermoplastic resin of the second layer 2, and the melting peak temperature of the thermoplastic resin of the second layer 2 is lower than the melting peak temperature of the thermoplastic resin of the second layer 2. It is lower than the melting peak temperature of the thermoplastic resin No. 1. Further, the interfacial peel strength between the first layer 1 and the second layer 2 is 0.02 N/width 15 mm or more and 0.4 N/width 15 mm or less.

Here, the crystallization peak temperature and the melting peak temperature are values measured by a method according to JIS K7121 (2012).

Further, the interfacial peel strength between the first layer 1 and the second layer 2 can be measured using a general tensile tester. FIG. 2 shows a cross section of the film 10 when measuring interfacial peel strength. After cutting out the first layer 1 and the second layer 2 to have a width of 15 mm and a length of 150 mm, the first layer 1 and the second layer 2 are separated by 50 mm at the interlayer interface. A tensile test is carried out by holding the peeled ends with the chucks 21 of a tensile testing machine and pulling them in the direction in which the first layer 1 and the second layer 2 are separated at a distance between the chucks of 50 mm and a tensile speed of 200 mm/min. The interfacial peel strength shall indicate the maximum value of the load obtained in this test. For example, when the maximum load is 0.3 N under the above test conditions, the interfacial peel strength is 0.3 N/width 15 mm.

Since the crystallization peak temperature of the thermoplastic resin of the first layer 1 is lower than the melting peak temperature of the thermoplastic resin of the second layer 2, when heat treatment is performed near the crystallization peak temperature of the first layer 1, the second layer 1 Since the layer 2 serves as a support, it is possible to prevent the uneven shape of the first layer 1 from changing. By doing this, the first layer 1 can be crystallized without changing the uneven shape of the first layer 1 while being supported by the second layer 2 whose uneven shape hardly changes, thereby improving heat resistance. can be improved. In addition, improvements in rigidity, gas barrier properties, and chemical resistance are also expected.

In addition, since the melting peak temperature of the thermoplastic resin of the second layer 2 is lower than the melting peak temperature of the thermoplastic resin of the first layer 1, the interface 6 between the first layer 1 and the second layer 2 is also firmly attached. It becomes possible to provide an uneven shape (second convex portion 7 and second concave portion 8). Details will be explained with reference to the manufacturing method below.

Furthermore, if the interfacial peel strength between the first layer 1 and the second layer 2 is 0.02 N/width 15 mm or more and 0.4 N/width 15 mm or less, it is possible to obtain a product with no problem in handling properties. Although the film 10 in which the first layer 1 and the second layer 2 are laminated can be used as it is, by peeling the second layer 2 from the first layer 1, the first layer 1 has an uneven shape formed on both sides. A film body (also referred to as a film) consisting of the following can be obtained. Therefore, when peeling the second layer from the film 10 to form a film body consisting only of the first layer, the interfacial peel strength becomes an important factor in handling properties.

If the interfacial peel strength is less than 0.02 N/width 15 mm, it is not preferable because the first layer 1 and the second layer 2 may be inadvertently peeled off during handling. On the other hand, if the interfacial peel strength exceeds 0.4 N/width 15 mm, it is not preferable because it becomes difficult to peel off the first layer 1 and the second layer 2 and use only the first layer 1. By peeling off the second layer 2, the first layer 1 becomes uneven on both sides, allowing it to exhibit characteristic functions such as ease of stretching.

By making the first layer 1 uneven on both sides, especially when the height difference H between the first convex part 4 and the first concave part 5 is larger than the film thickness T1 of the first layer 1, as shown in FIG. , it becomes possible to impart good elongation properties. This is because the elongation occurs not due to the elongation derived from the material, but due to changes in the shape of the uneven shape. The biggest feature here is that it stretches by changing the shape of the uneven shape, making it possible to stretch even materials that normally do not stretch. For example, polymethyl methacrylate resin (PMMA). Although this resin is extremely fragile and will break immediately if stretched by 1 to 2%, it is possible to stretch it by more than 10% by making the film into an uneven shape. Another example is that even if conductive ink is printed on a stretchable base material such as polyurethane, the conductive ink will break when it stretches and the conductivity will deteriorate. In some cases, it becomes possible to prevent deterioration of conductivity. Of course, the examples are not limited to this.

In order to obtain such characteristics of ease of stretching, the height difference H between the first convex portion 4 and the first concave portion 5 is preferably 20 μm or more and 150 μm or less, and the film thickness T1 of the first layer 1 is It is preferable that the thickness is 3 μm or more and 50 μm or less. If the height difference H is less than 20 μm, the elongation effect will be reduced, and if it exceeds 150 μm, it will be difficult to produce the film 10. If the thickness T1 of the first layer 1 is less than 3 μm, the strength of the film will be too low, and if it exceeds 50 μm, the elongation effect will be reduced. Here, the elongation effect does not mean elongation by applying a strong force, but refers to a reduction in elasticity in which the material elongates with a small force.

Further, by making the film of such a size, the uneven shape is not directly visible to the naked eye, so it is possible to obtain a more elongated effect even though it looks similar to a normal film at first glance.

Strictly speaking, the load is applied locally to the parts where the shape of the uneven shape changes, mainly the corners of the uneven shape, but by rounding the corners, the load can be dispersed, so the load is higher than usual. It becomes possible to extend it. Further, by forming the film into an uneven shape, the surface area of the film can be greatly increased, and the elongation rate can also be controlled.

Note that the film thickness T1 of the first layer 1 indicates the thickness in the direction perpendicular to the surface 3 or the interface 6, and may be non-uniform depending on the location. However, the ratio of the thinnest part to the thickest part is preferably 3 times or less. This is because if the thickness ratio exceeds 3 times, the thin portion may show elongation due to the material rather than elongation due to shape change.

The uneven shape of the first layer 1 may be a shape in which unevenness is repeated in one direction as shown in FIG. 1, or a shape in which unevenness is repeated in two directions as shown in FIGS. 4 and 5. If the shape has concavities and convexities repeated in one direction, it has the effect of being very well extended in a direction perpendicular to the extending direction, that is, in the direction in which the concavities and convexities are lined up. Further, if the shape has repeated irregularities in two directions, it is difficult to exhibit flexibility as much as in one direction depending on the shape, but it is possible to have the effect of stretching in either direction. Furthermore, since the elongation occurs due to shape change, the apparent Poisson's ratio, that is, the behavior of elongation and contraction in the direction perpendicular to the direction of tension, can also be controlled.

Furthermore, by forming the first layer 1 in an uneven shape, it is possible to improve not only elongation but also impact absorption and increase the surface area. By improving shock absorption, it can be used as a buffer material, and by increasing its surface area, it can be used to control the volatilization rate and permeation rate of medicinal ingredients.

In other words, with the film of the present invention, it is possible to obtain a film with an uneven shape, and even when subjected to heat treatment such as annealing, the uneven shape does not disappear, and the heat resistance is improved while maintaining the characteristics of the uneven shape. can be done.

Note that the second layer 2 can not only maintain the shape during annealing treatment, but also serve to reinforce the first layer 1 during handling and serve as a protective layer for the first layer 1.

The back side of the second layer 2, which is the opposite side to the interface 6, is preferably substantially flat. This is because the shape retention effect of the first layer 1 during heat treatment becomes higher when the first layer 1 is substantially flat. Here, "substantially flat" means that the height difference H between the first protrusion 4 and the first recess 5 is sufficiently smaller, specifically, 1/10 or less of the height difference H. shall be indicated.

The first convex portions 4 and the first concave portions 5 on the surface 3 of the first layer 1 and the first convex portions of the second convex portions 7 and the second concave portions 8 on the interface 6 between the first layer 1 and the second layer 2 The cross-sectional shape in the direction in which the first recesses 4 and the first recesses 5 are arranged alternately may be a trapezoidal shape as shown in FIG. 1, or a triangular shape as shown in FIGS. It does not matter whether the shape is a semicircle, a shape with rounded corners, a shape with flat parts spaced apart, or a wave shape, and the shape is not limited to these.

However, if the shape is a trapezoid with a flat part as shown in Figures 6(a) and (b), or if the shape is spaced apart with flat parts as shown in Figures 6(c) and (d), it will not be suitable for printing. It is good because it improves the compatibility with other films. For example, with such a shape, it is possible to print only on the top surface using gravure printing. By doing so, the design ink does not expand or contract even when it expands or contracts, and damage such as cracks or breaks can be prevented. Moreover, since adhesive can be firmly applied to the upper surface portion, adhesion with other films can be improved. Since the area of the upper surface portion allows the contact area to be increased, it is also possible to control the adhesion strength.

On the other hand, a wavy shape as shown in Figure 6(f) or a shape with rounded corners as shown in Figures 6(b) and (g) will prevent it from getting caught when it rubs, and will also prevent it from getting caught in certain parts when expanding or contracting. Load can be reduced. For example, when conductive ink is printed on the first layer 1, local stress concentration can be prevented, so changes in conductivity during expansion and contraction can be reduced. In another example, when a metal or oxide is deposited, the change in barrier properties can be similarly reduced even when stretched. Of course, this effect is an effect achieved by the uneven shape, so it can be obtained with other shapes as well, but it is easier to obtain this effect with a wavy shape with rounded corners.

Examples of materials for the first layer 1 include polyethylene, polypropylene, polystyrene, polymethyl methacrylate, ethylene vinyl acetate copolymer, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinylidene chloride, polyacrylonitrile, polylactic acid, cyclic Examples include polyolefin, polycarbonate, polyamide, polyethylene terephthalate, polybutylene terephthalate, polyolefin elastomer, polystyrene elastomer, polyurethane elastomer, polyester elastomer, and derivatives thereof. However, these materials are not particularly limited, and these materials may be used alone, or a plurality of these materials may be used in combination.

Examples of materials for the second layer 2 include polyethylene, polypropylene, polystyrene, polymethyl methacrylate, ethylene-vinyl acetate copolymer, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinylidene chloride, polyacrylonitrile, polylactic acid, cyclic Examples include polyolefin, polycarbonate, polyamide, polyethylene terephthalate, polybutylene terephthalate, polyolefin elastomer, polystyrene elastomer, polyurethane elastomer, polyester elastomer, and derivatives thereof. However, these materials are not particularly limited, and these materials may be used alone, or a plurality of these materials may be used in combination. Even if the first layer 1 and the second layer 2 are made of the same material, by making the ingredients different, the crystallization peak temperature of the material of the first layer 1 is made lower than the crystallization peak temperature of the material of the second layer. Furthermore, the melting peak temperature of the second layer material can be lower than the melting peak temperature of the first layer material.

Among these, the material for the first layer 1 is preferably polyethylene terephthalate (PET) resin, and the material for the second layer 2 is preferably polypropylene (PP) resin. Currently, PET film is used as a variety of film base materials, and by using PET resin as the material for the first layer 1, it can be replaced with a film with uneven shapes without changing properties such as solvent resistance. becomes. However, PET resin cannot have sufficient heat resistance unless it is heat treated. Therefore, it is preferable to use a PP resin having a melting peak temperature higher than the crystallization peak temperature of the PET resin as the second layer 2. With this combination, the melting peak temperature of PP resin is lower than that of PET resin, the interfacial peel strength is 0.02N/width 15mm or more and 0.4N/width 15mm or less, and the cost can be reduced. Therefore, it is preferable.

The film 10 of this embodiment can be produced, for example, by heat pressing or extrusion molding.

(1st step)
In the heat press method, a flat film (a flat intermediate laminate) in which a flat first layer 1 and a flat second layer 2 are stacked is passed between heated rolls with an uneven shape or through a heated flat press machine ( The first convex portions 4 and the first concave portions 5 are transferred and formed on the surface 3 of the first layer 1 by sandwiching between a first mold having an uneven shape and a second mold having a flat shape. It is possible to do so. At this time, by adjusting the press temperature, press pressure, and press time, the second convex portions 7 and the second concave portions 8 can also be provided at the interface 6 between the first layer 1 and the second layer 2.

(Modified example of the first step)
In addition, in the extrusion molding method, a film with a multilayer structure of two or more layers can be obtained by using multiple extruders and coextruding multiple types of different resins using the feedblock method or multi-manifold method. can.

In the cooling process for film formation, the surface of the first layer 1 is cooled by applying nip pressure to the surface on which the first layer 1 is arranged using a cooling roll with unevenness on the surface. 3 can be provided with a first protrusion 4 and a first recess 5. At this time, by adjusting the resin temperature, the cooling roll temperature, and the size of the height difference H with respect to the thickness T1 of the first layer 1, the second convex portion 7 is also formed at the interface 6 between the first layer 1 and the second layer 2. , a second recess 8 can be provided.

(Second process)
In particular, when the melting peak temperature of the second layer 2 is lower than that of the first layer 1, in the extrusion molding method, the first layer 1 cools and hardens in the cooling process. A solidified film membrane can be formed on the surface.

(Third step)
In this state, by applying nip pressure, the second convex portion 7 and the second concave portion 8 are firmly formed also on the interface 6 between the first layer 1 and the second layer 2 (that is, the surface of the second layer 2). Ru. By doing so, the uneven shape can be accurately provided on both sides of the first layer 1. If the magnitude of the melting point peak temperature is reversed, the first convex portion 4 and the first concave portion 5 can be provided on the surface 3, but the second convex portion 7 and the second concave portion 8 can be provided on the interface 6. It becomes difficult to do so.

(4th step)
Thereafter, the film 10 in which the first layer 1 and the second layer 2 are laminated is subjected to an annealing treatment as a heat treatment near the crystallization peak temperature of the first layer 1. Moreover, by peeling the second layer 2 from the film 10, a film body consisting of the first layer 1 with uneven shapes provided on both sides can be obtained.

Furthermore, the film 10 according to the present embodiment is a laminate in which a functional layer such as a printing layer or an adhesive layer is laminated on the front surface 3 or the back surface of the first layer 1 after the second layer 2 is peeled off in a subsequent step. You can also do that. When the second layer 2 is peeled off from the film 10 in which the functional layer, the first layer 1, and the second layer 2 are laminated, the film body consists of the first layer 1 and the functional layer having an uneven shape.

Although the embodiments of the present invention have been illustrated above, it goes without saying that the present invention is not limited to the above embodiments. Furthermore, it is optional to use the above embodiments in combination.

Examples created by the present inventors will be described in detail in comparison with comparative examples, but the present invention is not limited to the following examples.

(Example 1)
The material for the first layer 1 is polyethylene terephthalate (PET) resin "Bellpet EFG70" manufactured by Bell Polyester Products Co., Ltd., and the material for the second layer 2 is homopolypropylene (PP) resin "PC412" manufactured by Sunallomer Co., Ltd. A film with a two-layer structure in which two layers are laminated by co-extrusion molding, the first layer 1 side is nipped with a roll with unevenness, and a first convex part 4 and a first concave part 5 are provided on the surface 3. Got 10. The thickness T1 of the first layer 1 was 15 μm, and the thickness T2 of the second layer 2 was 45 μm on average. The shapes of the first convex portion 4 and the first concave portion 5 were such that the cross-sectional shape was a trapezoidal shape A (see FIG. 6(a)) as shown in FIG. 1, and the ridge line extended linearly in one direction. The height difference H between the first convex portion 4 and the first concave portion 5 was 60 μm, and the pitch was 175 μm.

(Comparative Examples 1, 2, 3)
In Comparative Examples 1, 2, and 3, the material of the second layer 2 was High Density Polyethylene (HDPE) resin "HIZEX 2100J" manufactured by Prime Polymer Co., Ltd., and Low Density Polyethylene (LDPE) resin manufactured by Japan Polyethylene Co., Ltd., respectively. "Novatec LD LC600A" and a polyethylene terephthalate (PET) resin "Bellpet EFG70" manufactured by Bell Polyester Products Co., Ltd. were used, and the rest was the same as in Example 1.

(Example 2)
In Example 2, the cross-sectional shape of the first convex portion 4 and the first concave portion 5 is a trapezoidal shape B (see FIG. 6(a)) with a height difference of 100 μm and a pitch of 425 μm, and the other parts are the same as in Example 1. I did the same.

(Comparative Examples 4, 5, 6)
In Comparative Examples 4, 5, and 6, the material of the second layer 2 was high-density polyethylene (HDPE) resin "HIZEX 2100J" manufactured by Prime Polymer Co., Ltd., and low-density polyethylene (LDPE) resin manufactured by Japan Polyethylene Co., Ltd., respectively. "Novatec LD LC600A" and a polyethylene terephthalate (PET) resin "Bellpet EFG70" manufactured by Bell Polyester Products Co., Ltd. were used, and the rest was the same as in Example 2.

(Comparative example 7)
In Comparative Example 7, the material of the first layer 1 was polylactic acid (PLA) resin "Ingeo 3052D" manufactured by NatureWorks LLC, and the rest was the same as in Example 1.

(Example 3)
In Example 3, the material of the second layer 2 was a low-density polyethylene (LDPE) resin "Novatec LD LC600A" manufactured by Japan Polyethylene Co., Ltd., and the rest was the same as in Comparative Example 7.

(Example 4)
In Example 4, the cross-sectional shapes of the first convex portion 4 and the first concave portion 5 are wave-shaped with a height difference H of 40 μm and a pitch of 100 μm (see FIG. 6(f)), and the other parts are the same as in Example 1. I did the same.

(Example 5)
In Example 5, the cross-sectional shape of the first convex portion 4 and the first concave portion 5 is triangular with a height difference H of 50 μm and a pitch of 100 μm (see FIG. 6(g)), and the rest is the same as in Example 1. I made it.

(Evaluation of crystallization peak temperature and melting peak temperature)
The crystallization peak temperature of the first layer 1 and the melting peak temperature of the first layer 1 and the second layer 2 were determined using a differential scanning calorimeter DSC7020 manufactured by Hitachi High-Tech Science Co., Ltd. by a method according to JISK7121 (2012). It was measured. Specifically, the temperature was raised from room temperature at a rate of 10° C./min, the melting peak temperature was calculated, and the temperature was measured to a temperature 30° C. higher than the melting peak temperature. Thereafter, the temperature was maintained for 10 minutes, and the temperature was lowered to room temperature at a rate of 10° C./min, and the crystallization peak temperature was calculated.

(Evaluation of film production)
In order to confirm whether each Example and Comparative Example were manufactured, a cross section in the direction in which the first convex portion 4 and the first concave portion 5 are lined up was cut with a razor, and a digital microscope (VHX-1000 manufactured by Keyence Corporation) was used. The cross-sectional shape was observed using the following.

(Shape evaluation after annealing treatment)
In order to confirm whether the shape did not change even after the annealing treatment, using an oven "Fine Oven DF411S" manufactured by Yamato Scientific Co., Ltd., Examples 1, 2, 4, 5, Comparative Examples 1, 2, 3, 4, 5 and 6 were heat-treated at 138°C for 10 minutes, and Example 3 and Comparative Example 7 were heat-treated at 102°C for 10 minutes. After heating and cooling at room temperature, the first protrusion 4 and the first A cross section in the direction in which the recesses 5 were lined up was cut with a razor, and the shape of the cross section was observed using a digital microscope (VHX-1000, manufactured by Keyence Corporation).

(Interfacial peel strength evaluation)
Finally, in order to obtain the first layer 1 whose heat resistance was improved by the annealing treatment, an interfacial peeling test was conducted between the first layer 1 and the second layer 2 after the annealing treatment. Using Autograph AGS-500NX manufactured by Shimadzu Corporation, the first layer 1 and the second layer 2 were cut out to a width of 15 mm and a length of 150 mm, and then peeled off by 50 mm at the interlayer interface between the first layer 1 and the second layer 2. Then, a tensile test was carried out by holding each peeled end with the chuck 21 of a tensile tester and pulling it in the direction in which the first layer 1 and the second layer 2 were separated at a distance between the chucks of 50 mm and a tensile speed of 200 mm/min. . The maximum value of the load obtained in this test was defined as the interfacial peel strength. Here, it is necessary to peel off 50 mm in order to hold it in the chuck, but those that could not be peeled off were designated as "ND".

(Film version judgment)
Based on the evaluation of film production described above, the first convex portion 4, the first concave portion 5, the second convex portion 7, and the second concave portion 8 are formed on the surface 3 and the interface 6 as intended. Items were marked as "○", and those that did not meet the target were marked as "x".

(Heat treatment judgment)
As a heat treatment evaluation, by evaluating the shape after the annealing treatment, those in which the surface 3 and interface 6 did not change before and after annealing were rated "O", and those in which they had changed were rated "x". Here, whether the change has occurred is whether the height difference H between the first convex part 4 and the first concave part 5 or the height difference between the second convex part 7 and the second concave part 8 has changed by 10% or more. I judged it based on whether it was true or not.

(Handling performance judgment)
As a determination of handling properties, the ease of handling the film 10 and the first layer 1 was sensory evaluated by touch. In both cases, the ease of interfacial peeling between the first layer 1 and the second layer 2 is also considered as an evaluation point in the evaluation of the first layer 1. Items that were easy to handle were rated ``〇'', and items that were difficult to handle were rated ``x''.

(comprehensive evaluation)
In the above film formation evaluation, heat treatment evaluation, and handling property evaluation, all evaluations of "〇" were given an overall evaluation of "〇." If even one item was rated “×”, the overall evaluation was given as “×”.

Table 1 shows a list of conditions and evaluation results for each example and comparative example.

(Evaluation results)
In Example 1, the crystallization peak temperature of the first layer 1 is lower than the melting peak temperature of the second layer 2, the melting peak temperature of the second layer 2 is lower than the melting peak temperature of the first layer 1, and the first Although the interfacial peel strength between layer 1 and second layer 2 satisfies the requirements of 0.02 N/width 15 mm or more and 0.4 N/width 15 mm or less, first layer 1 has an uneven shape, and changes in shape due to annealing were also confirmed. The overall rating was ``〇'' because the car's handling was also good.

On the other hand, in Comparative Example 1, the resin of the second layer 2 was changed, and the crystallization peak temperature of the first layer 1 was higher than the melting peak temperature of the second layer 2. At this time, the shapes of the surface 3 and interface 6 changed before and after annealing, and the heat treatment evaluation became "x", so the overall evaluation also became "x". The same applies to Comparative Example 2.

In Comparative Example 3, by using the same resin, the melting peak temperature of the second layer 2 and the melting peak temperature of the first layer 1 were equal, and the first layer 1 and the second layer 2 could not be separated. . At this time, although there was no change in the shape of the surface 3 and interface 6 before and after annealing, the shape of the second convex part 7 and second concave part 8 of the interface 6 was not sufficiently formed from the time of film formation, and the film formation judgment was made. It was "x". Furthermore, since the same resin was laminated, the first layer 1 and the second layer 2 could not be separated, and the handling property evaluation was also "x", and the overall evaluation was also "x".

Although Example 2 and Comparative Examples 4, 5, and 6 differed from Example 1 and Comparative Examples 1, 2, and 3 in the cross-sectional shapes of the surface 3 and interface 6, there was no difference in the judgment.

In Comparative Example 7, by changing the material of the first layer 1 from Example 1, the melting peak temperature of the first layer 1 is lower, and the melting peak temperature of the second layer 2 is lower than the melting peak temperature of the first layer 1. The price has also increased. At this time, the first convex part 4 and the first concave part 5 on the surface 3 were firmly formed, but the shape of the second convex part 7 and the second concave part 8 on the interface 6 was not sufficiently imparted, and the film formation judgment was " "x", and the overall judgment was "x".

In Example 3, the melting peak temperature of the second layer 2 was lower than that of the first layer 1 because the melting peak temperature of the second layer 2 was lower than that of Comparative Example 7. At this time, the shapes of the surface 3 and the interface 6 were firmly imparted, and the film formation evaluation was "O", and the other evaluations were also good, so the overall evaluation was also "O".

Examples 4 and 5 are examples in which the cross-sectional shapes of the surface 3 and the interface 6 are different from those of Examples 1 and 2, but there was no difference in the judgment.

As described above, the crystallization peak temperature of the first layer 1 is lower than the melting peak temperature of the second layer 2, the melting peak temperature of the second layer 2 is lower than the melting peak temperature of the first layer 1, and the crystallization peak temperature of the first layer 1 is lower than the melting peak temperature of the second layer 2. Those that satisfied the interfacial peel strength between layer 1 and second layer 2 of 0.02 N/width 15 mm or more and 0.4 N/width 15 mm or less were rated “〇” in all evaluations, and the overall evaluation was also “〇”. .

(Additional processing)
Three additional processes were performed on Examples 1, 2, 4, and 5: gravure printing, dry lamination to bond with another polyethylene terephthalate (PET) film, and friction test with another polyethylene (PE) film. did. As a result, when gravure printing and dry lamination were carried out in Examples 1 and 2, the ink did not bleed and it was firmly bonded to the PET film, giving good results. However, in Examples 4 and 5, Although it was within a usable range, the ink smeared slightly and the lamination strength was insufficient. On the other hand, regarding the friction test, it was confirmed that Example 4 was the best and was less prone to scratches.

This specification includes disclosures of the following inventions.
(Invention A)
In a film in which different thermoplastic resins are laminated in the order of at least a first layer and a second layer,
The surface of the first layer has first convex portions and first concave portions arranged alternately,
The interface between the first layer and the second layer has a second convex part and a second concave part at positions corresponding to the first convex part and the first concave part,
The crystallization peak temperature of the thermoplastic resin of the first layer is lower than the melting peak temperature of the thermoplastic resin of the second layer,
The melting peak temperature of the thermoplastic resin of the second layer is lower than the melting peak temperature of the thermoplastic resin of the first layer.
A film characterized by

(Invention B)
The interfacial peel strength of the first layer and the second layer is 0.02 N/width 15 mm or more and 0.4 N/width 15 mm or less,
The film of invention A characterized by the following.

(Invention C)
The thermoplastic resin of the first layer is a polyethylene terephthalate resin, and the thermoplastic resin of the second layer is a polypropylene resin.
The film according to invention A or B, characterized in that:

(Invention D)
In a cross section of the film in a direction in which the first convex portions and the first concave portions are arranged alternately,
The shape of the surface of the first layer and the shape of the interface between the first layer and the second layer are trapezoidal.
The film according to any one of inventions A to C, characterized by:

(Invention E)
In a cross section of the film in a direction in which the first convex portions and the first concave portions are arranged alternately,
The shape of the surface of the first layer and the shape of the interface between the first layer and the second layer are wavy.
The film according to any one of inventions A to C, characterized by:

(Invention F)
consisting of the first layer formed by peeling the second layer from the film of any of inventions A to E;
A film body characterized by:
By peeling off the second layer from the film, a film body made of the first layer can be formed. In such a case, the film body can be viewed as a product invention specified in a so-called product-by-process format. Here, in a film body consisting of a first layer having an uneven shape on both sides, it is difficult to determine whether the uneven shape of the first layer is formed by peeling off the second layer. Something happens. In other words, in the form body of Invention F, there are circumstances in which it is impossible or impractical to directly specify the object by its structure or characteristics ("impossible/impractical circumstances"). It is.

(Invention G)
While heating a flat laminate in which a flat first layer and a second layer each made of a thermoplastic resin are stacked, a first mold having an uneven shape and a second mold having a flat shape are heated. a first step of transferring and forming an uneven shape on the surface of the first layer by sandwiching the first layer;
a second step of forming a solidified film on the surface of the first layer by cooling and solidifying the first layer earlier than the second layer;
A third step of transferring and forming an uneven shape also on the interface between the first layer and the second layer by sandwiching the laminate between the first mold and the second mold during cooling. and,
a fourth step of annealing the first layer and the second layer at a temperature near the crystallization peak temperature of the first layer;
The crystallization peak temperature of the first layer material is lower than the melting peak temperature of the second layer material,
The melting peak temperature of the second layer material is lower than the melting peak temperature of the first layer material.
A method for producing a film characterized by:

(Invention H)
a step of peeling the second layer from the first layer;
A method for producing a film according to Invention G, characterized in that:

1 First layer 2 Second layer 3 Surface 4 First convex portion 5 First concave portion 6 Interface 7 Second convex portion 8 Second concave portion 10 Film 21 Chuck H Height difference T1 between first convex portion 4 and first concave portion 5 Film thickness of first layer 1

Claims (8)

In a film in which different thermoplastic resins are laminated in the order of at least a first layer and a second layer,
The surface of the first layer has first convex portions and first concave portions arranged alternately,
The interface between the first layer and the second layer has a second convex part and a second concave part at positions corresponding to the first convex part and the first concave part,
The crystallization peak temperature of the thermoplastic resin of the first layer is lower than the melting peak temperature of the thermoplastic resin of the second layer,
The melting peak temperature of the thermoplastic resin of the second layer is lower than the melting peak temperature of the thermoplastic resin of the first layer.
A film characterized by The interfacial peel strength of the first layer and the second layer is 0.02 N/width 15 mm or more and 0.4 N/width 15 mm or less,
The film according to claim 1, characterized in that: The thermoplastic resin of the first layer is a polyethylene terephthalate resin, and the thermoplastic resin of the second layer is a polypropylene resin.
The film according to claim 1, characterized in that: In a cross section of the film in a direction in which the first convex portions and the first concave portions are arranged alternately,
The shape of the surface of the first layer and the shape of the interface between the first layer and the second layer are trapezoidal.
The film according to claim 1, characterized in that: In a cross section of the film in a direction in which the first convex portions and the first concave portions are arranged alternately,
The shape of the surface of the first layer and the shape of the interface between the first layer and the second layer are wavy.
The film according to claim 1, characterized in that: The first layer is formed by peeling the second layer from the film according to any one of claims 1 to 5.
A film body characterized by: While heating a flat laminate in which a flat first layer and a second layer each made of a thermoplastic resin are stacked, a first mold having an uneven shape and a second mold having a flat shape are heated. a first step of transferring and forming an uneven shape on the surface of the first layer by sandwiching the first layer;
a second step of forming a solidified film on the surface of the first layer by cooling and solidifying the first layer earlier than the second layer;
A third step of transferring and forming an uneven shape also on the interface between the first layer and the second layer by sandwiching the laminate between the first mold and the second mold during cooling. and,
a fourth step of annealing the first layer and the second layer at a temperature near the crystallization peak temperature of the first layer;
The crystallization peak temperature of the first layer material is lower than the melting peak temperature of the second layer material,
The melting peak temperature of the second layer material is lower than the melting peak temperature of the first layer material.
A method for producing a film characterized by: a step of peeling the second layer from the first layer;
8. The method for producing a film according to claim 7.

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