Film, and laminate

Abstract

To provide a film having flexibility extending with small force, and capable of easily expanding an area even in a film in which a material according to required properties is used, and a laminate therewith.SOLUTION: A film having a surface with an uneven shape extending in two directions and a back surface with an uneven shape extending in two directions according to the uneven shape on the surface satisfies, when a tensile modulus of elasticity is set to Ef, the tensile elastic modulus of the material constituting the film is set to Em, a height of the uneven shape of the film is set to H, and a thickness of the film is set to T, all of the following formulas 1 to 3 are satisfied: Formula 1 T<H; Formula 2<0.1×Em; Formula 3 7000 [N / m]<Em×T. Note that the tensile elastic modulus Ef of the film indicates the tensile elastic modulus in an arbitrary direction in the plane direction of the film.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a film and a laminate.

Background Art

[0002] Generally, plastic films have properties such as being lightweight, chemically stable, easy to process, flexible and strong, and capable of mass production, and are used in various applications. Examples of its uses include packaging materials for food products, pharmaceuticals, etc., drip packs, shopping bags, posters, tapes, optical films, protective films, decorative films, films attached to the body, window films attached to windows, greenhouses, building materials, and so on. Specific materials include, for example, thermoplastic resins such as polyethylene, polypropylene, polystyrene, acrylic polymethyl methacrylate, polycarbonate, polyamide, polyethylene terephthalate, polybutylene terephthalate, and thermosetting resins such as epoxy resins, polyurethanes, and polyimides.

[0003] An appropriate plastic material is selected according to the application, and furthermore, a plurality of them are stacked to form a laminate. In addition, there is also a way of using by mixing a plurality of plastic materials in one layer to compensate for the disadvantages of a single material. In many cases, an appropriate film material is selected according to heat resistance, mechanical strength, or transparency. However, it is difficult to say that the required physical properties such as heat resistance and mechanical strength and the flexibility to stretch with a light force are fully compatible only by devising these materials and layer configurations.

[0004] For example, in the case of patches, tapes, etc., which are formulations that are attached to the skin to deliver a medicinal ingredient into the body, it is required that the medicinal ingredient does not transfer or migrate to the support film. However, materials that meet these requirements have high strength but lack flexibility, so they do not follow the movement of the skin and have a problem that the usability during application is not good. Also, in another example, as a base film for various films, a polyethylene terephthalate (PET) film is often used from the viewpoints of heat resistance, durability, chemical resistance, mechanical properties, etc. However, the PET film has high strength and cannot be used for applications where it is expected to stretch with a small force.

[0005] Also, plastic films generally have the property that when pulled in one direction, they shrink in the direction perpendicular to it, that is, the so-called Poisson's ratio is positive. Therefore, when trying to stretch it in two directions to expand the area, there is a problem that a stronger force is required than when stretching it in one direction.

[0006] For example, when forming a film into a bag shape and filling the bag with contents, or when wanting to inflate the bag with a gas such as air, a considerably larger force is required compared to stretching it in one direction. Also, in another example, when trying to cover the surface of a curved object with a flat film, wrinkles will occur, but if it can stretch in two directions and expand three-dimensionally, it can firmly cover the curved surface without wrinkles.

[0007] In Patent Document 1, a technique for a film that can be stretched with a light force regardless of the plastic material and can be easily stretched simultaneously in two directions is disclosed. The film has a shape in which mountain folds and valley folds are repeated, a so-called bellows shape, and by making the bellows shape into a specific shape not in one dimension but in two dimensions, the bellows shape folded like origami spreads, so that the film can be stretched in any direction and can also be stretched in conjunction with the direction orthogonal to the stretching direction. Thus, it is claimed that even in a film using a material according to required characteristics such as heat resistance and mechanical strength, it has flexibility to stretch with a light force and can easily expand the area.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] According to the technique of Patent Document 1, when stretching, in order for the film to also expand in the direction orthogonal to the stretching direction, it is necessary to transmit a force in the orthogonal direction, and for that purpose, it is necessary to change the bellows shape in accordance with the stretching. However, if the material is too soft or the film thickness is too thin, instead of stretching due to the change in the bellows shape, the material itself stretches or a certain surface of the film is distorted, causing a shape change different from the design and resulting in stretching. If this happens, it cannot be expanded in the orthogonal direction and only stretches in the stretching direction, and as a result, there is a problem that it cannot stretch in conjunction in two directions.

[0010] The present invention has been made in view of such problems, and an object thereof is to provide a film that has flexibility to stretch with a light force and can easily expand the area even in a film using a material according to required characteristics, and a laminate using the same.

Means for Solving the Problem

[0011] In order to achieve the above object, a typical film of the present invention has a surface with a concavo-convex shape extending in two directions and a back surface with a concavo-convex shape extending in two directions corresponding to the concavo-convex shape of the surface. When the tensile elastic modulus of the film is Ef, the tensile elastic modulus of the material constituting the film is Em, the height of the concavo-convex shape of the film is H, and the thickness of the film is T, it is achieved by satisfying all of the following formulas 1 to 3. Formula 1: T < H Formula 2: Ef < 0.1 × Em Formula 3: 7000 [N / m] < Em × T Note that The tensile elastic modulus Em of the material constituting the film is 1100 MPa to 3300 MPa, the tensile elastic modulus Ef of the film represents the tensile elastic modulus in any direction in the film plane direction.

Advantages of the Invention

[0012] According to the present invention, it is possible to provide a film that has flexibility to stretch with a light force and can easily expand the area even in a film using a material according to required characteristics, and a laminate using the same. Problems, configurations, and effects other than those described above will be clarified by the description of the following embodiments.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Mode for Carrying Out the Invention

[0014] Hereinafter, embodiments of the film according to the present invention will be described with reference to the drawings. Note that each figure is a schematic diagram, and the size, shape, etc. of each part are exaggerated as appropriate for easy understanding. Also, for simplicity of explanation, the same reference numerals are assigned to corresponding parts in each figure. The front and back surfaces used in this specification are for convenience of description, and either of the pair of surfaces of the film may be regarded as the front or back surface.

[0015] The film 1 of the present invention is a film having concavo-convex shapes 4 on both the front surface 2 and the back surface 3, and the front surface 2 and the back surface 3 face each other in accordance with the concavo-convex shapes 4. That is, the film has a folded shape like origami. A perspective view showing an example of the film 1 is shown in FIG. 1, and a top view showing an example of the film 1 is shown in FIG. 2. Also, to clearly show the folded shape, a perspective view and a cross-sectional view showing a part of an example of the film 1 are shown in FIGS. 3 and 4.

[0016] At this time, when the tensile elastic modulus of the film 1 is Ef, the tensile elastic modulus of the material constituting the film 1 is Em, the height of the concavo-convex shape 4 of the film 1 is H, and the thickness of the film 1 is T, All of the following formulas 1 to 3 are satisfied. Formula 1: T < H Formula 2: Ef < 0.1 × Em Formula 3: 7000 [N / m] < Em × T Note that the tensile elastic modulus Ef of the film 1 indicates the tensile elastic modulus in any direction along the plane when the film 1 is placed on a plane (a plane parallel to the x direction and the y direction in FIG. 1). That is, formula 2 is satisfied in any direction on the plane.

[0017] Here, the tensile elastic modulus Ef of the film 1 is the tensile elastic modulus defined in JIS K 7161:2014, and the thickness giving the cross-sectional area of the film 1 is assumed to be the sum of the height H of the uneven shape and the film thickness T. That is, it is the apparent tensile elastic modulus. Also, the tensile elastic modulus Em of the material is the tensile elastic modulus of a flat film without an uneven shape, similarly defined in JIS K 7161:2014. At this time, the thickness giving the cross-sectional area of the film is T.

[0018] By satisfying Equation 1, that is, by the uneven shape height H exceeding the film thickness T, the film 1 does not have a straight extending portion along the direction in which the uneven shape is repeated. In other words, when the film 1 is cut by a plane along the x-direction and y-direction in FIG. 1 and at any position in the z-direction, the cut surface is discontinuous at any position in the z-direction and intermittent. Therefore, instead of the material stretching, it is possible to stretch by deforming the uneven shape 4 like origami, and flexibility to stretch with a light force can be produced.

[0019] Also, Equation 2 indicates that the tensile test force of the film 1 is sufficiently smaller than the tensile test force of a normal film without the uneven shape 4 made of the same material. By satisfying this Equation 2, first, the film 1 comes to stretch due to the deformation of the uneven shape 4 without depending on the deformation of the material itself. Depending on the uneven shape 4, the film shows anisotropy in tensile properties, but in this embodiment, Equation 2 is satisfied in any direction on the plane on which the film 1 is placed.

[0020] Furthermore, Equation 3 represents the relational expression necessary to transmit the force in the tensile direction to the orthogonal direction as well. In order to spread not only in the tensile direction but also in the orthogonal direction, it is necessary to transmit the force in the tensile direction to the orthogonal direction. At this time, due to the shape change of the uneven shape 4, it is necessary to develop changes in the tensile direction and the orthogonal direction. However, if Equation 3 is not satisfied, during tension, instead of the shape change of the uneven shape 4, the material itself will stretch or one slope of the uneven shape 4 will be distorted. Then, it will stretch by causing a shape change different from the design. In this case, it cannot be spread in the direction orthogonal to the tensile direction.

[0021] As described above, by satisfying Equations 1, 2, and 3, even in a film using a material according to the required characteristics, due to the shape change of the uneven shape 4, it has flexibility to stretch with a light force, and the force in the tensile direction can also be transmitted to the orthogonal direction, and the area can be easily expanded.

[0022] The uneven shape 4 has at least a continuous ridge portion 5 or valley portion 6, and the continuous ridge portion 5 or valley portion 6 extends while changing the direction of the ridge line.

[0023] A part of the uneven shape 4 is shown in FIG. 5. FIGS. 5(a) and 5(b) are cross-sectional views thereof, and FIG. 5(c) is a top view thereof. In FIG. 5(c), the dashed-dotted line indicates the ridge line of the ridge portion 5, and the dashed line indicates the ridge line of the valley portion 6. The same shall apply to the dashed-dotted line and the dashed line in FIGS. 6 and 7. As shown in FIG. 5(c), the ridge line of the continuous ridge portion 5 or valley portion 6 extending in the x direction changes its direction halfway and extends in the y direction. By having a shape that changes the direction in this way, it becomes possible to smoothly change the direction of the force with respect to the tensile direction to the orthogonal direction.

[0024] The modified part that changes the direction of the ridgeline of the mountain part 5 or the ridgeline of the valley part 6 may be rounded as shown in Fig. 6(a), or may have a mixture of non-rounded parts and rounded parts as shown in Fig. 6(b), or may be in a straight line shape as shown in Fig. 6(c). Also, the change in direction (the intersection angle between the x-direction and the y-direction) does not have to be 90°, and as shown in Figs. 7(a) and (b), it can be either an acute angle or an obtuse angle without any problem.

[0025] By arranging the structures as shown in Figs. 5 to 7, it is preferable that the uneven shape 4 is formed. Also, as shown in Fig. 8, taking the alternating arrangement of the uneven shapes as the basic form, for example, as shown in Fig. 9, there may be a difference in width in the arrangement of the uneven shapes, or as shown in Fig. 10, the direction and angle of the ridgeline may be changed and arranged, or as shown in Fig. 11, the alternating uneven shapes may be arranged while being inverted. In addition to the above, by arranging the structures as shown in Figs. 5 to 7, as long as the formed shape is valid, the above effects can be exhibited. It should be noted that Figs. 8, 9, 10, and 11 are merely diagrams for clearly showing the image of the structure schematically, and of course, they are not diagrams showing the size and detailed structure.

[0026] The film thickness T and the uneven shape height H do not have to be uniform within the film 1. For example, as shown in Fig. 12, different values such as T1, T2, and T3 may be adopted depending on the location of the uneven shape 4. Here, the film thickness Tn at each location is assumed to represent the distance between the opposing front surface 2 and back surface 3 as shown in Fig. 12. The film thickness T is represented by the average value obtained by multiplying the proportion occupied by each location and the thickness at that location. The same applies to the uneven shape height H, which may show different values depending on the location, and the uneven shape height H1 seen from the front surface 2 and the uneven shape height H2 seen from the back surface 3 may also be different. In that case, the uneven shape height H is represented by the average value.

[0027] However, the film thickness Tn at each location shall be within the range of 0.5T ≦ Tn ≦ 2T regardless of the location. Preferably, 0.6T ≦ Tn ≦ 1.5T. Also, the film thickness T is desirably 1 μm or more and 100 μm or less, and more preferably 5 μm or more and 50 μm or less. The uneven shape height Hn is within the range of 0.6H ≦ Hn ≦ 1.5H regardless of the location or the front and back surfaces, and preferably 0.8H ≦ Hn ≦ 1.2H. Also, the uneven shape height H is desirably 5 μm or more and 500 μm or less, and more preferably 10 μm or more and 200 μm or less. As described above, the uneven shape height H needs to exceed the film thickness T, and furthermore, it is desirable that the uneven shape height H exceeds twice the film thickness T. By being within such a range, it is possible to have the characteristic of stretching more flexibly. Furthermore, the pitch of the uneven shape (the interval between adjacent uneven shapes) is desirably 30 μm or more and 1000 μm or less, more preferably 50 μm or more and 500 μm or less, and even more preferably 50 μm or more and 200 μm or less. The inclination angle of the uneven shape, with the case of no uneven shape being 0° and the case perpendicular to the film normal direction being 90°, is desirably 40° or more and 90° or less at the maximum value, and more preferably 45° or more and 85° or less. This is because by doing so, it is possible to have the characteristic of stretching more flexibly.

[0028] Also, although the cross-sectional shape of the film has been illustrated as being triangular above, it is not limited to a triangular shape. Other examples are shown in Fig. 13. For example, as shown in Fig. 13(a), the top of the cross-section of the uneven shape may be rounded, or as shown in Fig. 13(b), it may be a shape in which arc-shaped convex shapes are repeated side by side, or as shown in Fig. 13(c), the uneven shape may be trapezoidal, or as shown in Fig. 13(d) and (e), the convex shapes may be arranged at intervals, or as shown in Fig. 13(f), only a part of the cross-section of the uneven shape may be rounded. Also, these shapes may be combined, and several shapes may be combined in one film 1.

[0029] The tensile elastic modulus Ef of the film 1 is preferably 1 MPa < Ef < 100 MPa. If it is less than 1 MPa, it will be difficult to handle because it will stretch with a light force. On the other hand, if it exceeds 100 MPa, a large force is required to stretch it, and it is difficult to say that it can stretch to a practical useable extent.

[0030] Also, the tensile elastic modulus Em of the material constituting the film 1 is preferably 800 MPa < Em < 3000 MPa. If it is within this range, with an appropriate thickness, Equation 3 can be satisfied, and other physical properties can also be made appropriate as a film.

[0031] The ratio (surface area ratio) S of the surface area of the film 1 including the uneven shape 4 to the area of the film 1 when viewed from above (in the z direction) is preferably 1.2 or more and 2 or less. The larger the surface area ratio S, the greater the possibility of increasing the amount of elongation due to the shape change of the uneven shape 4, which is preferable. Therefore, when the surface area ratio S is less than 1.2, a sufficient amount of elongation cannot be ensured. On the other hand, when the surface area ratio S is greater than 2, it becomes difficult to form the uneven shape 4.

[0032] Also, the film 1 may be configured by arranging a plurality of regions having the above-described characteristics (referred to as section 1A). That is, as shown in FIG. 14, in the film plane of the film 1, there may be a plurality of sections 1A, and each section 1A may have the characteristics of the film 1. At this time, there may be no uneven shape 4 between adjacent sections 1A. By doing so, the film 1 as a whole can be handled without stretching even when pulled, but by cutting out section 1A or a part of section 1A before use, it is possible to obtain a film that stretches with a light force in any direction.

[0033] The sections 1A may be arranged continuously, or may be arranged at intervals as shown in FIG. 15. Also, the structure of each section 1A does not have to be the same, and for example, it may include a plurality of different structures as shown in FIGS. 8, 9, 10, and 11.

[0034] Since the film 1 of this embodiment has the effect of stretching even when a force is applied in the film normal direction, it also has the effect of high impact resistance. Moreover, not only that, but even when the film 1 cannot stretch due to the surrounding environment when a force is applied in the film normal direction, the impact absorbency due to the collapse of the uneven shape 4 is also high.

[0035] In addition, by using a transparent material, it is possible to provide a certain degree of transparency despite having the uneven shape 4. This is because the front surface 2 and the back surface 3 basically face each other with the uneven shape 4 in between. However, since the uneven shape 4 exists, it is difficult to make it completely transparent, but conversely, it is also possible to give it a design property by making it translucent or opaque.

[0036] Furthermore, regarding the flexural rigidity, it can be improved in both directions. The flexural rigidity is determined by the integral of the product of the second moment of area and the Young's modulus. The film 1 of this embodiment can increase this second moment of area compared to a normal film with the same resin amount, so the flexural rigidity can be increased.

[0037] Furthermore, the uneven shape 4 also has the effect of improving the surface area of the film. The surface area of the film affects the speed and amount of release and adsorption of the materials kneaded into the film. In addition, by improving the surface area, the efficiency of the exchange of particles, ions, temperature, electricity, etc. through the film can also be improved.

[0038] (Film material) As the material of the film 1, a thermoplastic resin is preferable. For example, polyethylene, polypropylene, polystyrene, polymethyl methacrylate, ethylene-vinyl acetate copolymer, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinylidene chloride, polyacrylonitrile, polylactic acid, cyclic polyolefin, polycarbonate, polyamide, polyethylene terephthalate, polybutylene terephthalate, polyacetal, and derivatives thereof can be mentioned, but it is not particularly limited. Also, there is no problem even if it is a cured resin or a metal. These materials may be used alone, or a plurality of these materials may be combined and used. Further, a multilayer structure (also referred to as a laminate) in which a plurality of layers are stacked may be formed.

[0039] (Manufacturing method of the film) Regarding the manufacturing method, for example, a method by hot pressing or a method by extrusion molding can be used.

[0040] In the method by hot pressing, the formed film can be produced by passing it between a pair of heating rolls having an uneven shape on the surface or through a pair of heated flat plate presses. At this time, it is important that the upper and lower concave and convex shapes are precisely aligned so that the front and back of the film after pressing have a structure in which valleys and ridges are repeated continuously. Also, in the method by extrusion molding, in the cooling step for forming the molten resin extruded from the T-die into a film, by using a pair of cooling rolls and nip rolls having a pair of unevenness corresponding to the uneven structure and cooling while applying nip pressure, an uneven structure can be provided. Also in this method, it goes without saying that precise alignment of the uneven shapes of the cooling roll and the nip roll is related to the film performance.

[0041] In another method by extrusion molding, a plurality of extruders are used, and different types of resins are co-extruded by a feed block method or a multi-manifold method to obtain a film with a multi-layer structure of two or more layers. At this time, in the cooling process for forming the film, by using a cooling roll with unevenness corresponding to the uneven shape on the surface and a nip roll without unevenness, and cooling while applying nip pressure, an uneven structure can be formed on the film surface in contact with the cooling roll. Further, at this time, when the height of the uneven shape is large with respect to the film thickness of the first resin layer in contact with the cooling roll, an uneven structure is similarly added to the interface between the first resin layer and the second resin layer adjacent thereto. Therefore, if the second resin layer is peeled off from the multi-layer film after cooling, a first resin layer having uneven shapes on both sides, that is, Film 1 can be obtained. In addition, any method for adding an uneven structure such as injection molding can be selected, and the method is not particularly limited.

[0042] (Laminate) Film 1 may be a single layer, or a laminate can be formed by laminating a plurality of Film 1s by increasing the layer structure. For example, the first layer can be a gas barrier layer or a non-drug adsorption layer, and the second layer can be an inexpensive resin layer (bulk-increasing layer), a high-rigidity layer, or a layer that compensates for the physical properties of the first layer. Of course, the film lamination can be three or more layers. Also, as shown in FIG. 16, a laminate can be formed by laminating a functional layer 7 such as a vapor deposition layer, a hard coat layer, an anti-reflection layer, or a printing layer on Film 1 by dry coating or wet coating in a subsequent process. At this time, an effect can be obtained in which the layer coated on the surface can also be stretched according to Film 1. This is because it stretches due to the shape change of the uneven shape 4. That is, for example, by applying it to a vapor deposition barrier film, it is possible to have stretchability in two directions while suppressing the destruction of the vapor deposition layer. Examples of the vapor deposition film include metal oxides such as alumina and silica, and metals such as aluminum, gold, silver, and copper. Of course, regarding the expressed functions, not only the barrier property, but also the same applies to light shielding property, design property, conductivity, etc., and furthermore, it is not limited to these functions.

[0043] In addition, as shown in FIG. 17, a laminate in which another layer (or film) 8 is laminated on the film 1 can also be used. At this time, the film 1 and the other layer 8 may be in contact with each other only in a part as shown in FIG. 17(a), or may be in contact with each other in all the uneven shapes 4 as shown in FIG. 17(c). Further, it may be in the middle as shown in FIG. 17(b). At this time, the other layer 8 is preferably made of a soft material so as not to impair the flexibility of the film 1.

[0044] (Use applications of the film) For example, the film 1 or the laminate using the same can be considered for use as a barrier film, a packaging material, an adhesive support film such as a poultice, a support film for a tape to be attached to the skin or an object, a decorative film, an optical film, a protective film, a wearable base material, various film base materials, a design film, etc., but the applications are not limited to these.

[0045] In the case of the adhesive support film which is an application example, resistance, non-adsorbability or barrier property against the chemicals and additives contained in the adhesive are required, and further, it is desirable to have stretchability. By adding an uneven shape to a material having high chemical resistance, non-adsorbability and barrier property and making the film 1 stretchable with a light force, all these requirements can be satisfied. Examples of the material having high chemical resistance, non-adsorbability and barrier property include cyclic polyolefin, ethylene-vinyl alcohol copolymer, polyethylene terephthalate and the like. In addition, since the stress applied to the film 1 is also small at the same elongation, it is possible to make it difficult to feel a sense of discomfort such as being pulled during stretching.

[0046] As described above, although the embodiments of the present invention have been illustrated, it goes without saying that the present invention is not limited to the above embodiments. In addition, it is optional to use the above embodiments in combination.

Example

[0047] Hereinafter, the examples created by the present inventors will be described in detail, but the present invention is not limited only to the following examples.

[0048] Comparative Examples 1, 2, and 3 were flat films without the concavo-convex shape 4, and polyethylene terephthalate (PET) resin "Verpet EFG70" manufactured by Bell Polyester Products Co., Ltd., ethylene-vinyl alcohol copolymer (EVOH) resin "Soarnol D4403" manufactured by Mitsubishi Chemical Corporation, and polymethyl methacrylate (PMMA) resin "Acrypet VH000" manufactured by Mitsubishi Chemical Corporation were used as the materials constituting the films, respectively. The film thickness T was all 10 μm. Hereinafter, when referring to PET resin, EVOH resin, and PMMA resin, all refer to equivalent resins.

[0049] Comparative Examples 4 and 5 had a shape in which the concavo-convex shape 4 extended only in one direction as shown in FIG. 3, and the cross section thereof was a shape in which triangular shapes with rounded tops as shown in FIG. 13(a) were arranged, and the valley apex angle was 90°. The concavo-convex shape height H was both 60 μm, and PET resin was used as the material. The film thicknesses T were 15 μm and 3 μm, respectively.

[0050] Comparative Examples 6, 7, 8, 9, and 10 had a shape in which the concavo-convex shape 4 extended in two directions as shown in FIG. 1 or FIG. 8, and the direction of the ridge line changed in a zigzag manner. The cross section thereof was a shape in which triangular shapes with rounded tops as shown in FIG. 13(a) were arranged, and the valley apex angle was 100° for Comparative Example 6, 90° for Comparative Example 7, and 60° for Comparative Examples 8, 9, and 10. The concavo-convex shape height H was 42 μm when the valley apex angle was 100°, 50 μm when the valley apex angle was 90°, and 80 μm when the valley apex angle was 60°. PET resin was used for the film materials of Comparative Examples 6 and 8, and EVOH resin was used for Comparative Examples 7, 9, and 10. The film thicknesses T were 15 μm, 22 μm, 3 μm, 5 μm, and 3 μm for Comparative Examples 6, 7, 8, 9, and 10, respectively.

[0051] Table 1 shows a summary of the concavo-convex shape 4, film material, concavo-convex shape height H, and film thickness T of the comparative examples.

[0052]

Table 1

[0053] Example 1 had an uneven shape 4 extending in two directions as shown in Fig. 18. Its ridge line was straight and did not change direction, and its cross-section was trapezoidal as shown in Fig. 13(c). The height H of the uneven shape was 80 μm, the material was PET resin, and the film thickness T was 15 μm.

[0054] Examples 2 to 11 had an uneven shape 4 extending in two directions as shown in Fig. 1 or Fig. 8. The direction of its ridge line changed in a zigzag pattern, and its cross-section was a shape formed by arranging triangular shapes with rounded tops as shown in Fig. 13(a). The valley apex angles were 120° for Examples 2 and 3, 100° for Example 4, 90° for Examples 5, 6, and 7, and 60° for Examples 8, 9, 10, and 11. The height H of the uneven shape was 28 μm when the valley apex angle was 110°, 42 μm when the valley apex angle was 100°, 50 μm when the valley apex angle was 90°, and 80 μm when the valley apex angle was 60°. As the film materials, PET resin was used for Examples 2, 3, 4, 5, 6, 8, and 9, EVOH resin was used for Examples 7 and 10, and PMMA resin was used for Example 11. The film thickness T was 8 μm for Examples 2, 4, 6, 8, 10, and 11, 5 μm for Examples 3 and 9, and 15 μm for Examples 5 and 7.

[0055] Table 2 shows a summary of the uneven shape 4, film material, height H of the uneven shape, and film thickness T of the examples.

[0056]

Table 2

[0057] Tensile tests were carried out as an evaluation to calculate the tensile elastic moduli Em and Ef.

[0058] The tensile test evaluation was carried out in accordance with JIS K 7161:2014 using a tensilon universal material testing machine (RTC-1250A) manufactured by A&D Company, Limited. The sample width was 15 mm, the distance between chucks was 50 mm, and the tensile speed was 100 mm / min. At this time, in order to consider the anisotropy of the sample, the evaluation was carried out for five directions with the angle changed by 22.5° from the MD (machine direction) to the TD (transverse direction). The average value of the elastic modulus in five directions of the comparative example 1, 2, and 3 samples without the concave-convex shape 4 was taken as the tensile elastic modulus Em of the material, and the maximum value of the elastic modulus in five directions of the other examples and comparative examples was taken as the tensile elastic modulus Ef-max. The thickness required to calculate the tensile elastic modulus Ef-max is the sum of the concave-convex shape height H and the film thickness T, that is, the apparent thickness (H + T).

[0059] As an evaluation to confirm the effect of the present invention of "having flexibility to stretch with a light force and being able to easily expand the area", a push-in test evaluation and a tensile test evaluation were carried out.

[0060] The push-in test evaluation was carried out using a texture analyzer (EZ-SX) manufactured by Shimadzu Corporation. The sample was fixed to a metal plate with a hole of 50 mm in diameter, and the center of the hole was pushed in with a plunger of 30 mm in diameter, and the push-in distance and push-in force at that time were evaluated. The push-in distance was measured with the position where the plunger touches the sample as zero until it reaches the 40 mm position or until the sample breaks. The push-in speed was 10 mm / min. As the push-in determination, when the push-in distance was 5 mm, if the push-in force exceeded 10 N, it was marked as ×, if it was 10 N or less, it was marked as 〇, and if it was 5 N or less, it was marked as ◎. Also, at this time, the sample was observed, and if necking occurred where only a part was clearly stretched, it was marked as × as the necking evaluation result, and if it could not be confirmed otherwise, it was marked as 〇.

[0061] The tensile test evaluation was carried out using a Tensilon universal material testing machine (RTC-1250A) manufactured by A&D Company, Limited. The sample width was 15 mm, the distance between chucks was 50 mm, the tensile speed was 100 mm / min, and the sample was stopped when it was stretched by 10% (i.e., 5 mm). By evaluating the sample width at that time, it was evaluated whether it widened in the width direction. At this time, the evaluation was carried out for three directions with the angle changed by 45° from the MD direction to the TD direction. As the evaluation of the spread in the width direction, if the width shrank in even one direction, it was marked as ×, if there was no significant change in any direction, it was marked as 〇, and if it widened in any direction, it was marked as ◎.

[0062] As a comprehensive judgment, among the three judgments of push-in judgment, neck-in evaluation, and spread evaluation in the width direction, if even one of them was ×, it was marked as ×, if all were ○ or above, it was marked as 〇. In particular, if both the push-in judgment with ◎ judgment and the spread evaluation in the width direction were ◎, and the neck-in evaluation was also 〇, it was marked as ◎.

[0063] Table 3 and Table 4 respectively show the summary of the evaluation results of the comparative examples and the examples.

[0064]

Table 3

[0065]

Table 4

[0066] From Table 3 and Table 4, it can be seen that the concavo-convex shape 4, the film material, the concavo-convex height H, and the film thickness T are important parameters, but it cannot be judged whether the effects can be obtained only by these. On the other hand, those that satisfy Formulas 1, 2, and 3 all obtain certain effects.

[0067] In Comparative Examples 1, 2, and 3 that do not satisfy Equation 1 (T < H), no elongation occurred and all the determinations were "×". Also, in Comparative Examples 4, 5, 6, and 7 that do not satisfy Equation 2 (Ef-max < 0.1 × Em), all the neck-in determinations were "×". In Comparative Examples 4 and 6, it was extremely difficult to cause elongation during pushing-in in the first place, and the pushing-in force exceeded 10 N. In Comparative Examples 5 and 7, the pushing-in force was 10 N or less, but this indicates that the film was quite thin and the film itself was plastically deformed and elongated. Furthermore, in Comparative Examples 5, 8, 9, and 10 that do not satisfy Equation 3 (7000 [N / m] < Em × T), the determination of spreading in the width direction was "×", that is, the result was that there was no spreading. Also, in Comparative Example 10, Ef-max was less than 1 MPa, and it was extremely difficult to handle as a sample in the first place.

[0068] On the other hand, Examples 1 to 11 all satisfied Equations 1, 2, and 3, and the evaluation results were good. However, in Example 1 in which the ridge line extending in two directions did not change its direction, the "spreading in the width direction" was not sufficient and the determination of "spreading in the width direction" did not reach ◎, so the overall determination was also ○. Also, in Examples 2 and 5 in which Ef-max exceeded 100 MPa, although the pushing-in force was 10 N or less, it exceeded 5 N and could not be said to be sufficiently soft, and the "pushing-in" determination did not reach ◎, so the overall determination was also ○. Also, in Examples 2 and 3 in which the surface area ratio S was less than 1.2, although the pushing-in force was 10 N or less, it exceeded 5 N and could not be said to be sufficiently soft, and the "pushing-in" determination did not reach ◎, so the overall determination was also ○. Since a softer result is obtained as the surface area ratio S is larger, an attempt was made to produce a sample of the uneven shape 4 with a value exceeding 2, but it was difficult to produce the film and as a result, it could not be obtained.

Explanation of Symbols

[0069] 1 Film 2 Surface 3 Back surface 4 Uneven shape 5 Crest 6 Trough 7 Functional layer 8 Another layer Section 1A Height of the H concavo-convex shape 4 Thickness of the T film 1

Claims

1. A film having a surface with a concavo-convex shape extending in two directions and a back surface with a concavo-convex shape extending in two directions corresponding to the concavo-convex shape of the surface, wherein when the tensile elastic modulus of the film is Ef, the tensile elastic modulus of the material constituting the film is Em, the height of the concavo-convex shape of the film is H, and the thickness of the film is T, the film is characterized by satisfying all of the following formulas 1 to 3. Formula 1: T < H Formula 2: Ef < 0.1 × Em Formula 3: 7000 [N / m] < Em × T The tensile elastic modulus Em of the material constituting the film is 1100 MPa to 3300 MPa, and the tensile elastic modulus Ef of the film indicates the tensile elastic modulus in any direction in the film plane direction.

2. The film according to claim 1, wherein 1 MPa < Ef < 100 MPa.

3. The concavo-convex shape has at least a continuous ridge or valley, and the continuous ridge or valley extends while changing the direction of the ridgeline, The film according to claim 1 or 2, characterized by the above.

4. The ratio S of the surface area of the film including the concavo-convex shape to the area of the film when viewed from above is 1.2 or more and 2 or less, The film according to any one of claims 1 to 3, characterized by the above.

5. The concavo-convex shape is formed within a section, a plurality of the sections are arranged, and there is no concavo-convex shape between adjacent sections, The film according to any one of claims 1 to 4, characterized by the above.

6. A laminate characterized by laminating a functional layer on at least one surface of the film according to any one of claims 1 to 5.

7. A laminate characterized by laminating a plurality of the films according to any one of claims 1 to 5.

8. A laminate characterized by laminating another film on the film according to any one of claims 1 to 5.

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