JPH0362550B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a fluororesin laminate having excellent bending resistance. To explain in more detail,
The present invention relates to a flexible laminate having excellent bending resistance, flexibility, weather resistance, oil resistance, stain resistance, and durability. The present invention relates to a laminate comprising a specially structured woven base fabric, a polyurethane layer, and a fluororesin layer, which has excellent resistance to bending and cracking especially in cold weather.

Technical Background Conventionally, flexible laminated sheets consisting of a fiber base fabric, especially a plain weave base fabric, coated with a polyurethane resin layer on one or both sides have been used as oil-resistant aprons, tarpaulins, etc. due to their versatility, oil resistance, economic efficiency, and other aspects. used in

Although this sheet essentially has the advantages of polyurethane resin, such as processability, economy, and oil resistance, on the other hand, during long-term use, sufficient consideration must be given to stabilizers, etc. However, the resin gradually decomposes, causing discoloration from the surface layer, and
It had serious drawbacks in terms of weather resistance, stain resistance, etc., such as a large amount of dust adhering to the surface, resulting in severe contamination.

As a countermeasure to the above-mentioned drawbacks of conventional laminated sheets, the present applicant discovered that forming a fluorine-based resin film layer on the polyurethane layer was highly effective, and filed the application in 1983-
Filed as No. 29384. However, even in such a laminate, if it is rubbed very strongly during use, cracks will occur in the thin resin film layer, and if this is further expanded, cracks will also occur in the underlying polyurethane layer. This phenomenon is particularly noticeable in cold weather, and it has been found that this phenomenon has the disadvantage of significantly shortening the service life of the laminate.

The present invention was made in view of the above circumstances and to eliminate the drawbacks of conventional laminated sheets. We investigated measures to prevent cracks in this surface layer by dispersing the stress caused by the load, and found that knitted fabrics that have a large degree of expansion and contraction under load are unsuitable for such applications due to the requirements of use, and knitted fabrics that have a low degree of expansion and contraction under load are unsuitable for such applications. Although plain woven fabrics are advantageous, it has been discovered that when such woven fabrics are made into a laminate as described above, stress applied to the fluororesin layer increases, making it easier for cracks to occur due to the base fabric, The present invention has been completed by eliminating such inconveniences.

OBJECT OF THE INVENTION An object of the present invention is to provide a fluororesin flexible laminate that is excellent in bending resistance, especially in cold weather, and also has excellent flexibility, weather resistance, oil resistance, and stain resistance. It's about doing.

Summary of the Invention The present invention provides a warp layer consisting of a large number of warp threads arranged parallel to each other, and a warp layer that is perpendicular to the warp threads.
A base fabric of a special structure woven fabric consisting of a weft layer consisting of a large number of weft yarns arranged parallel to each other, and a leno yarn that entangles and connects the warp yarns and weft yarns at their intersections, and formed on at least one surface thereof. and,
It comprises an intermediate layer made of polyurethane resin, and a surface layer formed on the intermediate layer and made of fluorine-based resin, and the thickness of the surface layer is within the range of 10 to 50 microns, and A large number of convex portions and concave portions are formed on the surface of the surface layer, and the height difference between the highest point of each convex portion and the lowest point of each concave portion adjacent thereto is 5 microns or more. To provide a resin laminate.

DETAILED DESCRIPTION OF THE INVENTION The laminate of the present invention comprises a specially structured woven fabric, an intermediate layer made of a polyurethane resin formed on at least one surface thereof, and a fluorine-based resin surface layer formed on the intermediate layer. It includes the following.

The special structure woven base fabric used in the laminate of the present invention includes natural fibers such as cotton and linen, inorganic fibers such as glass fiber, recycled fibers such as viscose rayon and Kyupra, semi-synthetic fibers, selected from, for example, di- and tri-acetate fibers, and synthetic fibers such as nylon 6, nylon 66, polyester (such as polyethylene terephthalate) fibers, aromatic polyamide fibers, acrylic fibers, polyvinyl chloride fibers, and polyolefin fibers. It consists of at least one species. The fibers in the base fabric may be in any form such as short fiber spun yarn, long fiber yarn, split yarn, or tape yarn. These are arranged in parallel to each other, and the warp and weft layers thus formed are laminated so as to intersect with each other, and are loosely connected by long leno threads at the intersections of the warp and weft threads.

The leno thread is made of polyester, nylon, aromatic polyamide and other known synthetic fibers, glass fiber,
It may be selected from steel fibers and other known inorganic fibers, with polyester filament yarns being particularly suitable.

Now, for example, as warp and warp yarns, we are using tensile strength single yarns.
When 1.3Kg of Vinylon 10S/1 spun yarn is used, the tensile strength per unit denier is as a leno yarn.
20g of aromatic polyamide filament yarn is used, and if yarns of the same material are used in consideration of ease of fabrication, for example, polyester filament yarn with a tensile strength of 8g per unit denier is used as the warp and warp yarns. Also, 10g of polyester filament yarn is used as the leno thread.

A particularly preferable structure of the special structure fabric for use in the present invention is disclosed in Japanese Patent Publication No. 57-1979 filed by the present applicant.
30381, a warp layer consisting of a large number of warps arranged in parallel to each other, a weft layer consisting of a large number of wefts arranged in parallel to each other so as to be perpendicular to the warps, and the warp and weft. and a tangle thread that entangles and connects them at their intersections. The leno yarn is longer than the warp and weft, and therefore loosely connects the warp and weft, and has at least one of its tensile strength, tensile elongation, and breaking work as compared to the warp and weft. The adhesion force to the resin material is preferably greater than that of the warp and weft and/or smaller than that of the warp and weft. As the leno yarn, yarns having the characteristics shown below are particularly preferred. That is, () A leno yarn whose strength is 10% or more per unit denier than the warp and weft yarns that make up the base fabric.

() Leno yarn whose breaking work is 10% or more greater than the warp and weft yarns that make up the base fabric.

() Leno yarn whose elongation at break is 5% or more greater than the warp and weft yarns that make up the base fabric.

() A leno yarn that has a lower adhesion force to the resin coating than the warp and weft yarns that make up the base fabric.

Among these leno yarns, the strength per unit denier is 10% or more higher than that of the warp and weft, preferably 20 to 30% or more, and the leno yarn has a strength per unit denier of at least 20 to 30%. %
This is what we are trying to prevent by using a large and strong leno thread, and the leno thread is longer than the warp and warp threads.
Therefore, since it has a greater degree of freedom in change and deformation than warp and warp yarns, it can flexibly deal with and absorb tearing forces that continuously act on the sheet. In other words, even if a tearing force acts on the sheet, causing the warp and warp threads to displace and eventually break, the leno threads follow the tearing force, displace and deform without being cut, and eventually absorb the tearing energy and stop tearing. can be done.

Next, as a leno yarn, the breaking work is preferably 10% or more, more preferably 20 to
30% higher threads can be used. The breaking work here is a value approximately expressed by the product of the strength at the time of cutting the yarn and the elongation at the time of cutting.

Work at break = Tensile strength at break x Tensile elongation at break For example, polyester filament yarn with a tensile strength at break of 8.0 g per unit denier and a tensile elongation at break of 13% per unit denier is used as the warp and warp threads, and as a leno yarn, the unit A polyamide fiber yarn with a denier of 7.0 g and a tensile elongation at break of 18% is used. At this time, the breaking work of the leno yarn is approximately 21% greater than that of the warp and warp yarns. Furthermore, in consideration of ease of processing, it is desirable to use threads made of the same material.

Furthermore, a leno yarn having a breaking elongation that is preferably 5% or more higher than that of the warp and warp yarns can also be used for the braided connection. When polyester filament yarn is used, the breaking elongation of the warp and warp yarns is preferably 15% or less, especially 8 to 12%, while the breaking elongation of the leno yarn is 15% or more, especially 20% or more, and there is no difference between the two. A difference of at least 5% or more gives good results. When the leno thread is a synthetic fiber, the degree of polymerization of the polymer material is adjusted at the time of manufacture to maintain a desired strength and a desired high elongation at break; A filament with a lower drawing ratio, for example, an undrawn yarn, or a leno yarn having a desired elongation at break can be obtained by crimping during secondary processing.

Furthermore, it is also possible to use leno threads that have a smaller adhesion force to the coating resin material than warp and warp threads. In this case, the leno thread may have its surface subjected to silicon processing or the like. In this case, the warp and warp threads are bonded to the coating resin material,
The degree of freedom for displacement and deformation decreases, but the degree of freedom for the leno thread is greater than that for the warp and warp threads, and when tearing force acts on the base fabric, the leno thread slips and is displaced and deformed. Therefore, tearing of the base fabric can be prevented.

In order to reduce the adhesive force, the surface of the leno yarn should be subjected to non-adhesive treatment such as silicone treatment or oil treatment, or it should be treated with yarns that are inherently small in adhesive properties, such as polyethylene yarns and polypropylene yarns. You can use

As described above, in the base fabric according to the present invention, it is preferable that the leno yarns for connecting the warp and warp yarns arranged in parallel in the warp and warp directions are substantially longer than the warp and warp yarns, and that the leno yarns are substantially longer than the warp and warp yarns. Even if the yarn is cut or displaced, at least a part of it is long enough not to be cut, is strong, has a large amount of work at break, and/or has a large elongation at break, or has adhesive strength. The tensile strength is maintained by the warp and warp yarns, and the leno threads are used to resist the impact force at the time of tearing or to absorb the tearing energy. absorb and further
By leaving the leno threads uncut, delamination between the resin coating and the sheet due to tearing can be prevented.

Regarding the special structure fabric according to the present invention, furthermore,
Related to the applicant's earlier application Fabrics described in JP-A-54-139688), JP-A-55-134242, JP-A-56-159165, JP-A-57-14031, JP-A-57-14032, etc. can be suitably used. These textiles typically have a structure as shown in FIG. In the figure, 1 is a warp, 2 is a weft, and 3 is a leno thread.

That is, the base fabric used in the present invention is useful for maintaining the mechanical strength of the obtained laminate at a high level.

In the laminate of the present invention, one or both sides of the special structure fabric base fabric is coated with an intermediate layer made of polyurethane resin.

The shape of the polyurethane resin used in the present invention can be freely selected, and plasticizers, stabilizers, colorants, lubricants, and various other tactile agents can be freely added within known ranges.

An example of polyurethane resin, particularly thermoplastic polyurethane elastomer resin, will be shown below.

As the polyurethane elastomer, one obtained by reacting an organic polyisocyanate with a polymer polyol and, if necessary, a chain extender is used.

Organic polyesocyanates include aliphatic, cycloaliphatic or aromatic polyisocyanates, such as hexamethylene diisocyanate, lysine diisocyanate, cyclohexylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate. , diphenylmethane diisocyanate (MDI), biphenylene diisocyanate, and naphthylene diisocyanate. MDI or an organic diisocyanate mainly composed of MDI is preferred.

Examples of the polymer polyol include polyether polyols, polyester polyols, polyether ester polyols, polymer polyols, and mixtures of two or more thereof.
Polyether polyols include those obtained by polymerizing or copolymerizing (block or random) alkylene oxides (ethylene oxide, propylene oxide, butylene oxide, etc.), heterocyclic ethers (tetrahydrofuran, etc.),
Examples include polyethylene glycol, polypropylene glycol, polyethylene-propylene (block or random) glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol, polyoctamethylene ether glycol, and mixtures of two or more thereof. As polyester polyol,
Dicarboxylic acids (adipic acid, succinic acid, sebacic acid, glutaric acid, maleic acid, fumaric acid, phthalic acid, etc.) and glycols (ethylene glycol, propylene glycol, 1,4-butanediol,
1,6-hexanediol, 1,8-octamethylene diol, neopentyl glycol, bishydroxymethylcyclohexane, bishydroxyethylbenzene, alkyl dialkanolamine, etc.), such as polyethylene adipate, poly Examples include butylene adipate, polyhexamethylene adipate, polyethylene/propylene adipate, polylactone diols such as polycaprolactone diols, and mixtures of two or more thereof. As the polyether ester polyol, ether group-containing diols (the above-mentioned polyether diols, diethylene glycol, triethylene glycol, dipropylene glycol, etc.) or mixtures of these and other glycols are combined with the above-mentioned dicarboxylic acids or dicarboxylic acid anhydrides (phthalic anhydride, etc.). acid, maleic anhydride, etc.) and alkylene oxide, such as poly(polytetramethylene ether) adipate.

In addition, as the polymer polyol, ethylenically unsaturated monomers (acrylonitrile, styrene, etc.) and those obtained by polymerizing them.

The average molecular weight of the polymer polyol (by hand titration of hydroxyl value) is usually 500-5000, preferably 700-5000.
4000, particularly preferably 2000 to 3500.

As the chain extender, low-molecular polyols with a molecular weight of less than 500, such as ethylene glycol, propylene glycol, 1,4-butanediol,
1,6-hexanediol, diethylene glycol, triethylene glycol, thiodiglycol (thiodiethanol, etc.): polyamines, e.g.
Aliphatic diamines such as ethylene diamine, propylene diamine, butylene diamine, and hexamethylene diamine; alicyclic polyamines such as piperazine, 1,4-diaminopiperazine, 1,3-cyclohexylene diamine, and dicyclohexylmethane diamine; diphenylmethane diamine; Aromatic polyamines such as diamine, phenylene diamine, aromatic-aliphatic polyamines such as xylylene diamine, hydrazine and monoalkylhydrazine: alkanolamines, such as ethanolamine, propanolamine: and mixtures of two or more thereof. It will be done. Preferred are low molecular weight diols (especially ethylene glycol).

However, any other thermoplastic polyurethane resin can be used without being limited to the above examples. This intermediate layer has a thickness sufficient to give the laminate the desired oil resistance, waterproofness, and mechanical strength, for example, a thickness of 0.05 mm or more, preferably 0.05 to 1.0 mm. be.

Next, the polyurethane resin formed on the surface or front and back surfaces of the base fabric is not only used as an adhesive, but also has a sufficient thickness, for example, 0.05 to 1.0 mm, in order to maintain oil resistance, abrasion resistance, and other necessary physical properties. It is necessary that the It may be thicker if it is financially acceptable. The polyurethane resin layer is formed by topping, calendering, coating, or other methods. When using the polyurethane resin, the shape of the resin can be freely selected, and it goes without saying that plasticizers, stabilizers, colorants, lubricants, and various other additives can be freely added to the resin within known ranges. The polyurethane resin may contain air bubbles.

Furthermore, depending on the use, the base fabric and the polyurethane resin intermediate layer may each be composed of a plurality of pieces.

A fluorine-based resin film surface layer is formed on at least one of the intermediate layers. Next, this fluorine-based resin film, which is the most important feature of the present invention, will be explained.

In general, fluorine-based resins are nonflammable and have excellent chemical resistance, so they are used for mechanical parts such as packing, tubes, and sheets, as well as electrical equipment parts and linings. However, this resin has a high degree of crystallinity and is not compatible with ordinary plastic adhesives, so it is extremely difficult to adhere it to the surface of a synthetic resin as it is.

In the present invention, a fluororesin film is subjected to a surface corona discharge treatment or the like to activate the surface as rough as possible, thereby producing a resin adhesive such as vinyl chloride, epoxy, acrylic, polyester, etc., or a mixture of these resins. It may also increase compatibility with adhesives. Usually, the above-mentioned treatment results in roughening of the surface portion of the fluororesin film having a thickness of 2 to 10 microns. For this purpose, discharge treatment is performed under the conditions of DC 100 to 200 V, 40 to 100 μF, and short circuit current of 1 to 2 A. Such discharge treatment allows the fluorine-based resin film to obtain the desired adhesion ability, but the surface treatment of the fluorine-based resin film used in the present invention is not limited to this, and other surface treatments can be used to achieve the same or higher effect. It is fine as long as it plays.

The fluorine-based resins constituting the fluorine-based resin film include various polyfluoroethylenes synthesized from monomers in which one or more hydrogen atoms of ethylene are replaced with fluorine atoms, such as polytetrafluoroethylene, There are various polyfluorochloroethylenes containing partial chlorine, such as polytrifluorochloroethylene, but also include polyvinyl fluoride, polyvinyritene fluoride, polydichlorodifluoroethylene, and others. All of these fluorine-based resins have high melting points, so normal calendar processing cannot be performed, so they are generally melted and then extruded, or powdered resin is heated under pressure and molded into a sheet. However, there are no particular limitations on the film forming method. The thickness of the fluororesin film layer is preferably 50μ or less, but
It can be made thinner than the above as long as it can achieve the objectives of improving flame resistance, stain resistance, and durability.

In the present invention, a film-like fluorine-based resin with a substantially smooth surface may be adhered to the upper surface of the polyurethane resin layer, but it is also possible to apply a fluorine-based resin solution such as an emulsion or solution. There is a way. With this method, the coating film is thin,
In addition, it is difficult to apply the coating to a uniform thickness, often resulting in uneven coating, and there are also areas where the coating is not applied, making it impossible to expect a complete effect, and dirt is likely to adhere. Furthermore, since the strength of the coating film is low, during use, the fluororesin film may be partially damaged due to scratching or the like, which poses a problem in terms of durability. The film strength of the fluororesin film according to the present invention is usually 100 kg/
It is preferable that it is at least cm ² .

A fluororesin surface layer is formed on at least one intermediate layer by conventionally known methods. The important features of the present invention include the use of a specially structured woven base fabric as described above, and the formation of a fluororesin film layer on the top surface of the polyurethane resin layer.

The fluororesin film layer also imparts weather resistance and stain resistance to the laminate. In particular, it prevents the plasticizer contained in the polyurethane resin layer from bleeding, and does not cause surface decomposition products of the layer or surface tackiness due to the bleeding. The fluorine-based resin film may also be produced by the T-die method, the inflation method, or any other method.
Further, it may be either stretched or unstretched. Usually, the thickness is about 10μ to 50μ.

As mentioned above, such a film can be attached using an adhesive, but it is also possible to attach it to the surface of a polyurethane resin layer whose surface has been melted by heating, for example, by applying a melt tack to the surface of the polyurethane resin layer heated to about 200°C. You can also attach it.

The laminate thus obtained exhibits less cracking in cold weather than laminates made from conventional textiles, such as plain weave fabrics. That is, while the conventional product can be used at approximately 5°C to -5°C, the product of the present invention can be used even at -20°C to 25°C. Furthermore, in some cases, it can be used at lower temperatures. This seems to be due to the fact that in the product of the present invention, the directionality of bending due to the base fabric structure is not particularly limited and can be bent in all directions, and is flexible. In addition, Scott type bending test (JIS-K-6328
-1981, 5.3.8 Massage Test) The results are also favorable, with the number of cracks occurring approximately 5 to 10 times. In particular, it is preferable for the fluorine-based resin film to be thin for practical purposes.
The fact that this effect is remarkable in the range of ~20μ is an epoch-making effect compared to conventional products.

As a result, it is thought that one of the reasons for the good results is that the laminate does not become harder than necessary even when the fluororesin film is applied.

In the laminate of the present invention, the fluororesin surface layer has a thickness within the range of 10 to 50 microns, and the surface is formed with many convex portions and concave portions, and the maximum of each convex portion is The height difference between the lowest point and the lowest point of each concave portion adjacent thereto is 5 microns or more, preferably 7 microns or more.

If the thickness of the surface layer is less than 10 microns, the drawbacks of the polyurethane resin intermediate layer cannot be sufficiently overcome, and if the thickness of the surface layer is greater than 50 microns, the flexibility and flexibility of the resulting laminate will be affected. becomes unsatisfactory. Furthermore, if the difference in height between the highest point of the convex portion and the lowest point of the concave portion is less than 5 microns, the effect of improving flexibility by forming the unevenness becomes unsatisfactory.

There are no particular limitations on the shape and dimensions of the concave portions and convex portions formed in the surface layer as long as the objective of the present invention can be achieved, but
It is desirable that 100 to 1,000,000 protrusions are formed.

To form a fluorine-based resin surface layer on the polyurethane resin intermediate layer, first prepare a fluorine-based resin film having a desired uniform thickness, place it on a smooth table or a roll having a smooth peripheral surface, This is pressed with a shaping plate or a shaping roll engraved with an uneven pattern of a predetermined shape and size, thereby forming a desired unevenness on one side of the fluororesin film. Of course, the uneven pattern mentioned above is
It may be formed on both sides of the film.

The fluororesin film prepared as described above and having irregularities on at least one side may be adhered onto the polyurethane resin intermediate layer using an adhesive, or the surface portion of the intermediate layer may be 140℃～200℃
This may be heated to melt it, and then a fluororesin film may be pressed and adhered thereon. Alternatively, a fluorine-based resin film may be adhered onto the intermediate layer by the method described above, and the fluorine-based resin surface layer of the resulting laminate may be shaped to have concavities and convexities similar to those described above.

The unevenness formed on the shaped surface (peripheral surface) may correspond to the uneven pattern to be imparted to the fluorine-based resin surface layer, or when forming unevenness, the fluorine-based resin surface layer is It is preferable to heat the resin to a temperature within the range of 30° C. higher than the glass transition point (Tg) of the resin to 10° C. lower than its melting point (Tm). For this purpose, the fluororesin film (or surface layer) may be heated to a desired temperature in advance and subjected to the shaping process, and/or the shaping plate (roll) may be heated to a desired temperature. Good too.

The laminate of the present invention shown in FIGS. 2 and 3, like the laminate shown in FIG. 2, includes a specially structured textile base fabric 4 and polyurethane resin intermediate layers 5, 5'. A large number of fine irregularities are formed on the surface of the fluororesin surface layer 6 formed on the intermediate layer 5.

In the laminate of the present invention shown in FIGS. 2 and 3, the surface layer 6 is formed only on the intermediate layer 5, but other surface layers are formed on the intermediate layer 5'. Good too.

The bonding surface between the intermediate layer and the surface layer may be smooth as shown in FIG. 2, or may be uneven as shown in FIG. 3. In the latter case, the adhesive strength of both layers increases.

Moreover, a part of the polyurethane resin may penetrate into the base fabric. In this case, the adhesive strength between the base fabric and the intermediate layer increases. The laminate obtained in this way also has excellent flex cracking resistance at cold temperatures and stability in use, and has a bending performance of approximately -5°C of 10% higher than that of a laminate without surface irregularities. ~
The performance is also improved by about 20%.

Effects of the Invention In the laminate of the present invention, the fluororesin surface layer covers the specially structured woven base fabric and the polyurethane resin intermediate layer to improve the weather resistance of the laminate, and the fluororesin surface layer covers the laminate surface from the polyurethane resin intermediate layer. This not only improves the stain resistance of the laminate by preventing the plasticizer from bleeding into the fluorine resin surface layer, but also improves the bending resistance of the laminate due to the large number of minute irregularities formed on the surface of the fluororesin surface layer. It is possible to further improve this and prevent the occurrence of cracks in the surface layer. Therefore, the laminate of the present invention can be used for a long period of time without causing surface cracks or stains.

Since the present invention is based on the above-described structure, the present invention does not impair the advantages of conventional polyurethane sheets, and furthermore, a polyurethane resin is formed on a base fabric, and a fluorine-based resin film is further formed on the upper surface of the base fabric. In this case, a laminate with significantly superior flexibility, durability and strength will be constructed. The laminate of the present invention has particularly remarkable effects when used for tents, canopies, sheets, flexible containers, wide belts, food conveyance belts, aprons, cloaks, leather, oil fences, and other industrial materials. In particular, the effect can be particularly exhibited in canopies, seats, etc., which are subjected to severe bending action under strong winds, and belts, etc., which are subject to many bending actions.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing one embodiment of the base fabric useful in the present invention, and FIGS. 2 and 3 are cross-sectional explanatory diagrams of one embodiment of the laminate of the present invention, respectively. 1... warp, 2... weft, 3... twine, 4
... Base fabric, 5,5' ... Polyurethane intermediate layer, 6
...Fluorine resin surface layer.

Claims (1)

[Scope of Claims] 1. A warp layer consisting of a large number of warps arranged parallel to each other, a weft layer consisting of a large number of weft threads arranged parallel to each other so as to be perpendicular to the warps, and the warp and weft and leno threads entangled and bonded at their intersections, an intermediate layer formed on at least one surface of the base fabric and made of a polyurethane resin, and formed on the intermediate layer, and , and a surface layer made of a fluorine-based resin, the thickness of the surface layer is within the range of 10 to 50 microns, and a large number of convex portions and concave portions are formed on the surface of the surface layer. A flexible laminate, characterized in that the height difference between the highest point of each convex portion and the lowest point of each adjacent concave portion is 5 microns or more. 2. The laminate according to claim 1, wherein the surface layer has 100 to 1,000,000 convex portions per cm ² of horizontal surface area of the surface layer.