Patent Publication Number: US-2023140962-A1

Title: Multilayer structure

Description:
TECHNICAL FIELD 
     The present invention relates to a multilayer structure. 
     BACKGROUND ART 
     Multilayer structures in which two or more layers are laminated are known. As an example, a multilayer structure in which a silver reflecting layer is laminated on a thin glass layer (glass film) is given. Such a multilayer structure has surface hardness, dimensional stability, chemical resistance, lightness, and flexibility. Therefore, thin glass mirrors utilizing such a multilayer structure are capable of projecting a clear image because those thin glass mirrors are not only lightweight and free from problems such as scattering, but are also free from problems with conventional sheet glass mirrors, such as double reflection of images, due to a distance between the glass surface and the metal layer being extremely close. 
     RELATED ART DOCUMENTS 
     Patent Document 
     [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2013-231744 
     SUMMARY OF THE INVENTION 
     Problem to Be Solved By the Invention 
     However, such thin glass mirrors are difficult to handle, and have handling issues when installing large area mirrors on buildings and the like. 
     It is an object of the present invention to provide a large area multilayer structure that can be used as a thin glass mirror. 
     Means for Solving the Problem 
     In one aspect according to the present invention, a multilayered structure includes 
     a plurality of laminated portions arranged on a base material, wherein the laminated portions each include 
     resin layer, 
     a glass layer laminated over the resin layer via an adhesive layer, and 
     a metal layer formed on a surface of the glass layer, the surface being oriented toward the adhesive layer, wherein a thickness of the glass layer is 10 μm or more and 300 μm or less, and a thickness of the resin layer is 10 μm or more and 1000 μm or less. 
     Advantageous Effect of the Present Invention 
     According to the disclosed technology, a large area multilayer structure that can be used as a thin glass mirror may be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a plan view illustrating a multilayer structure according to a first embodiment. 
         FIG.  2    is a partially enlarged cross-sectional view illustrating the multilayer structure according to the first embodiment. 
         FIG.  3    illustrates a preferable relationship between the size of the base material, the number of laminated portions, and the size of a gap. 
         FIG.  4    is a cross-sectional view illustrating a multilayer structure according to a first modification of the first embodiment. 
         FIG.  5    is a cross-sectional view illustrating a multilayer structure according to a second modification of the first embodiment. 
         FIG.  6    is a plan view illustrating a multilayer structure according to a third modification of the first embodiment. 
     
    
    
     EMBODIMENTS FOR CARRYING OUT THE INVENTION 
     Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings. In each of the drawings, the same components are denoted by the same reference numerals, and duplicate descriptions may be omitted. 
     First Embodiment 
     Multilayer Structure 
       FIG.  1    is a plan view illustrating a multilayer structure according to a first embodiment.  FIG.  2    is a partially enlarged cross-sectional view illustrating the multilayer structure according to the first embodiment, which illustrates a sectional view taken along a line A-A in  FIG.  1   . 
     As illustrated in  FIGS.  1  and  2   , a multilayer structure  1  includes a plurality of laminated portions  10  arranged on a single base material  20 . 
     In the present embodiment, as an example, a planar shape of a multilayer structure  1  (a shape viewed from the direction normal to an upper surface  20   a  of the base material  20 ) is a rectangular shape, a short side direction of the rectangular shape is an X direction, a long side direction of the rectangular shape is a Y direction, and a thickness direction of the multilayer structure  1  is a Z direction. The X, Y, and Z directions are orthogonal to each other. When the planar shape of the multilayer structure  1  is rectangular, for example, the width (X direction) may be approximately 1 m to 10 m, and the height (Y direction) may be approximately 1.5 m to 3.5 m. 
     In the present embodiment, as an example, in the multilayer structure  1 , nine laminated portions  10  are arranged on the upper surface  20   a  of the base material  20 . However, in the multilayer structure  1 , the number of the laminated portions  10  arranged on the upper surface  20   a  of the base material  20  may be two more as desired. 
     In the multilayer structure  1 , each laminated portion  10  is fixed to the upper surface  20   a  of the base material  20  via an adhesive layer  15 . The laminated portions  10  each include a resin layer  11 , an adhesive, layer  12 , a metal layer  13 , and a glass layer  14 . The glass layer  14  is laminated over the resin layer  11  via the adhesive layer  12 . The metal layer  13  is formed on a surface of the glass layer  14  that is oriented toward the adhesive layer  12 . 
     Although the laminated portion  10  has flexibility, the, multilayer structure  1  as a whole need not necessarily have flexibility. The flexibility required for the multilayer structure  1  as a whole may be provided by adjusting the material and the thickness of the base material  20 , for example. 
     The planar shapes of the resin layer  11 , the adhesive layer  12 , the metal layer  13 , and the glass layer  14  are rectangular, that is, the planar shape of the laminated portion  10  is rectangular as an example in this embodiment. 
     The multilayer structure  1  can be used, for example, as a mirror, but it is preferable to make joints of the adjacent laminated portions  10  less visible. That is, it is preferable that the laminated portions  10  are arranged on the base material  20  without gaps. However, in practice, it is difficult to make the gap width between the adjacent laminated portions  10  zero, and as illustrated in  FIG.  2   , a gap S is formed at the joint of the laminated portions  10  adjacent to each other in the X direction. A similar gap is also formed at the joint of the laminated portions  10  adjacent to each other in the Y direction. 
     The gap S is preferably 10 μm or more and 500 μm or less. By making the gap S 500 μm or less, it is possible to make it difficult to visually identify the joint of the adjacent laminated portions  10 . The lower limit is set to 10 μm because a gap of approximately 10 μm is always formed practically even if the plurality of laminated portions  10  are fixed on the base material  20  with a target of the gap S being set to 0 μm. However, if the dimensional accuracy of the individually divided laminated portions  10  can be improved, there is a possibility that the gap S can be made smaller than 10 μm. 
     From the viewpoint of making the joint of the adjacent laminated portions  10  more difficult to be visually identified, the gap S is more preferably from 10 μm or more and 200 μm or less, more preferably from 10 μm or more and 100 μm or less, and particularly preferably from 10 μm or more and 50 μm or less. When the gap S is 50 μm or less, the joint of the adjacent laminated portions  10  is almost invisible. 
       FIG.  3    is a diagram illustrating a preferable relationship between the size of the base material, the number of laminated portions, and the size of the gap, and  FIG.  3    illustrates a single laminated portion  10 . When the planar shape, of the laminated portion  10  is a rectangular shape, the planar shape of the laminated portion  10  does not become a perfect rectangular shape due to manufacturing variation, etc., but becomes a shape as illustrated in  FIG.  3   , for example. In  FIG.  3   , the deviation of the laminated portion  10  from the rectangle is depicted in an emphasized manner. 
     In this case, L represents a length of a side in an X direction of the base material  20 , and x represents a length of a longer side of two sides of the laminated portion  10  that are substantially parallel to the X direction. Further, dy represents a length in the Y direction between two points at which lines drawn perpendicular to the X direction meet a shorter side of the two sides of the laminated portion  10  that are substantially parallel to the X direction. dy corresponds to a gap in the Y direction. 
     Under the above conditions, when n representing the closest value that satisfies L≤n×x (n is an integer of 2 or more) is obtained, 50 μm≤n×dy≤500 μm is preferably satisfied. In other words, when the number of the laminated portions  10  arranged in the X direction is n, it is preferable that 50 μm≤n×dy≤500 μm be satisfied. In this case, the size of the multilayer structure, the number of laminated portions, and the size of the gap have the most preferable relationship, and the gap becomes less conspicuous. 
     As can be seen from the relationship of 50 μm≤n×dy≤500 μm, it is necessary to reduce the gap dy in the Y direction as the number n of the laminated portion  10  in the X direction increases. That is, as the number n of the laminated portions  10  arranged in the X direction is larger, the laminated portions need to be arranged densely so that the gap dy in the Y direction becomes smaller. Iif the laminated portions arranged in this manner, the gap becomes less conspicuous. 
     Since handling becomes difficult the size of the laminated portion  10  as too large or too small, it is preferable that the laminated portion  10  be of an appropriate size that is easy to handle. As an example of the preferred size of the laminated portion  10 , the lengths in the X direction and the Y direction are each approximately 10 cm. 
     As described above, the multilayer structure  1  includes a plurality of laminated portions  10  arranged on the base material  20 . The laminated portion  10  has the resin layer  11  and the glass layer  14  laminated over the resin layer  11  through the adhesive layer  12 , and the metal layer  13  is formed on the surface of the glass layer  14  that is oriented toward the adhesive layer  12 . The thickness of the glass layer  14  is 10 μm or more and 300 μm or less. 
     In other words, the thickness of the glass layer  14  is small in each laminated portion  10  of the multilayer structure  1 , and the distance between the surface of the glass layer  14  and the metal layer  13  is very close. Therefore, in the multilayer structure  1 , it is possible to project a clear image by solving the problem of a conventional sheet glass in which an image is doubly reflected. The thinner the glass layer  14  is, the more difficult it is to visually identify the joints of the adjacent laminated portions  10 . 
     In addition, by the structure, in which the plurality of laminated portions  10  are fixed to the base material  20 , it is possible to provide a large area multilayer structure, which can project a clear image and can be used as a thin glass mirror. 
     Here, materials and the like of each part of the multilayer structure  1  will be described. 
     Resin Layer 
     The resin layer  11  is a base material on which the glass layer  14  and the like are laminated, and the resin layer  11  has flexibility. The resin layer  11  includes one or a plurality of layers. 
     Examples of the material of the resin layer  11  include polyester resins such as polyethylene terephthalate resins and polyethylene naphthalate resins, cycloolefin resins such as norbornene resins, polyether sulfone resins, polycarbonate resins, acrylic resins, polyolefin resins, polyimide resins, polyamide resins, polyimide amide resins, polyarylate resins, polysulfone resins, polyether imide resins, cellulose resins, and the like. Among these, polyethylene, terephthalate, triacetyl cellulose and acrylic are preferably used because of the toughness of the resin. From the viewpoint of industrialization, it is particularly preferable, to use a film-like polyethylene terephthalate. 
     The color of the resin layer  11  is not particularly specified, and may be transparent or opaque. The resin layer  11  may contain an additive such as inorganic particles. The thickness of the resin layer  11  (the total thickness when the resin layer  11  includes a plurality of layers) may be in the range of 10 μm or more and 1000 μm or less, preferably 25 μm or more and 500 μm or less, more preferably 25 μm or more and 300 μm or less, from the viewpoint of flexibility. 
     Glass Layer 
     The glass layer  14  is not particularly specified, and an appropriate glass layer can be adopted depending on the purpose. The glass layer  14  may be, for example, soda lime glass, boric acid glass, aluminosilicate glass, quartz glass or the like according to the classification by composition. According to the classification by the alkali component, alkali-free glass and low alkali glass are given. The content of the alkali metal component (For example, Na 2 O, K 2 O, Li 2 O) of the glass is preferably 15 wt % or less, more preferably 10 wt % or less. 
     The thickness of the glass layer  14  is preferably 10 μm or more in consideration of the surface hardness, airtightness, and corrosion resistance of the glass. The glass layer  14  is preferably flexible like a film and has a thickness of 300 μm or less to prevent double reflection of an image and to project a clear image. The thickness of the glass layer  14  is more preferably 30 μm or more and 200 μm or less, and particularly preferably 50 μm or more and 100 μm or less. 
     The light transmittance of the glass layer  14  at a wavelength of 550 nm is preferably 85% or more. The refractive index of the glass layer  14  at a wavelength of 550 nm is preferably 1.4 to 1.65. The density of the glass layer  14  is preferably 2.3 g/cm 3  to 3.0 g/cm 3 , and more preferably 2.3 g/cm 3  to 2.7 g/cm 3 . 
     The method of forming the glass layer  14  is not particularly specified, and an appropriate method can be adopted depending on the purpose. Typically, the glass layer  14  can be prepared by melting a mixture containing a main raw material such as silica or alumina, an antifoaming agent such as mirabilite and antimony oxide, and a reducing agent such as carbon at a temperature of approximately 1400°C. to 1600°C., molding the mixture into a thin plate, and then cooling the thin plate. Examples of the method of forming the glass layer  14  include a slot-down draw method, a fusion method, and a float method. The glass layer formed in a plate-like shape by these methods may be chemically polished with a solvent such as hydrofluoric acid, as required, for thinning or enhancing smoothness. 
     Metal Layer 
     The metal layer  13  is formed on the surface of the glass layer  14  that is oriented toward the adhesive layer  12 . The metal layer  13  is a layer that reflects visible light incident through the glass layer  14 . As the material of the metal layer  13 , a material having a high visible light reflectance is preferable, for example, aluminum, silver, silver alloy, or the like. The thickness of the metal layer  13  is not particularly specified, but is, for example, approximately 10 nm to 500 nm. The metal layer  13  can be formed by, for example, a sputtering method, a vapor deposition method, a plating method, or the like. A functional layer such as an antifouling layer, an antireflection layer, and a conductive layer may be provided on a surface of the glass layer  14  (a surface of the glass layer  14  on which the metal layer  13  is not formed). 
     Adhesive Layer 
     Any suitable adhesive may be used as the adhesive layers  12  and  15 . From the viewpoint of appearance, the thickness of the adhesive layers  12  and  15  is preferably 0.5 μm or more and 25 μm or less, more preferably 0.5 μm or more and 20 μm or less, and more preferably 0.5 μm or more and 5 μm or less. 
     As the adhesive layers  12  and  15 , for example, an acrylic pressure-sensitive adhesive, a silicone pressure-sensitive adhesive, a rubber pressure-sensitive adhesive, an ultraviolet curable acrylic adhesive, an ultraviolet curable epoxy adhesive, a thermosetting epoxy adhesive, a thermosetting melamine adhesive, a thermosetting phenolic adhesive, an ethylene vinyl acetate (EVA) interlayer, a polyvinyl butyral (PVB) interlayer, or the like can be used. Among these, an epoxy adhesive for cohesion and durability may be preferably used. 
     In the present specification, a pressure-sensitive adhesive refers to a layer that has adhesiveness at room temperature and adheres to the adherent under light pressure. Accordingly, even when the adherend adhered to the pressure-sensitive adhesive is peeled off, the pressure-sensitive adhesive retains a practical tack strength. An adhesive, on the other hand, refers to a layer that can bind a substance by intervening between the substances. Therefore, when the adherend adhered to the adhesive is peeled off, the adhesive does not have a practical adhesive strength. 
     Base Material 
     The base material  20  is made of a material having higher rigidity than that of the laminated portion  10  in order to prevent the laminated portion  10  from bending. Examples of the material of the base material  20  include resin, glass, and metal. Among these, it is preferable to use glass because the dimensional change is small and the smoothness is excellent. Since the base material  20  is a lower layer of the metal layer  13  when viewed from the glass layer  14  side, the base material  20  does not have a function of a mirror. 
     When the base material  20  is thin, the entire multilayer structure  1  could become bent, and the image reflected on the multilayer structure  1 , which is a mirror, is distorted. Therefore, when the area of the upper surface  20   a  of the base material  20  is S (m 2 ) and the thickness of the base material  20  is T (mm), it is preferable to set the thickness T within a range satisfying 20S≥T≥S. Thus, the bending of the multilayer structure  1  can be prevented, and it is possible for the image reflected on the multilayer structure  1  to not be readily distorted. 
     Manufacturing Method 
     The laminated portion  10  is obtained, for example, by laminating the glass layer  14 , on which the metal layer  13  is formed by sputtering or the like, on the resin layer  11  via the adhesive layer  12 , and dividing the glass layer into pieces in predetermined shapes by pressing or the like. Alternatively, the glass layer  14  on which the resin layer  11  and the metal layer  13  are formed may be continuously laminated by using a roll-to-roll process via the adhesive layer  12 , and then divided into pieces in an any desired size by pressing or the like. The individually divided laminated portions  10  are arranged on the base material  20  through the adhesive layer  15  by a laminator or the like. 
     Application 
     The multilayer structure  1  can be used as a thin glass mirror, and specifically used, for example, as a full-length mirror, a curved surface of a large security mirror, a mirror for solar thermal power generation, an optical camouflage mirror, a lighting mirror, etc. The same applies to the multilayer structures exemplified below. 
     Modifications of First Embodiment 
     Modifications of the first embodiment illustrate examples of a multilayer structure having a structure different from that of the first embodiment. In the modifications of the first embodiment, description of the same components as those of the above-described embodiment may be omitted. 
       FIG.  4    is a cross-sectional view illustrating a multilayer structure according to a first modification of the first embodiment. Note that a plan view of the multilayer structure according to the first modification of the first embodiment is the same as that of  FIG.  1   , and is therefore not illustrated. As illustrated in  FIG.  4   , a multilayer structure  1 A differs from the multilayer structure  1  (see  FIG.  2   , etc.) in that a light-scattering colored layer  22  is formed on the upper surface  20   a  of the base material  20 . 
     The colored layer  122  a layer, that coats the upper surface of the base material  20  with an opaque colored material, and the thickness of the layer is approximately 1 μm. The colored layer  22  may be a layer having a light scattering property with respect to light incident from the gap S, and may be, for example, a metallic silver or white layer. Here, the light scattering property is property that generates light traveling in a random direction by scattering at least a part of the light incident from the gap S. The colored layer  22  can be formed by forming a coating liquid, in which metal particles such as silver nanoparticles are dispersed, on the upper surface  20   a  of the base material  20  by a spray coating method, a spin coating method, or the like. Since the metal particles are dispersed in the colored layer  22 , the light scattering property can be enhanced. 
     Since the light-scattering colored layer  22  is formed on the upper surface  20   a  of the base material  20  in this manner, light incident from the gap S is scattered. Therefore, the joints can be made more difficult to be visually identified as compared with the case where the size of the gap S formed at the joints of the adjacent laminated portions  10  is the same, and the colored layer  22  not formed. Needless to say, it is more preferable to use a colored layer in combination with measures for reducing the gap S. 
       FIG.  5    is a sectional view illustrating a multilayer structure according to a second modification of the first embodiment. Note that a plan view of the multilayer structure according to the second modification of the first embodiment is the same as that of  FIG.  1   , and is therefore not illustrated. As illustrated in  FIG.  5   , a multilayer structure  1 B differs from the multilayer structure  1  (see  FIG.  2   ) in that a buffer layer  17  is laminated via the adhesive layer  16  on a side of the resin layer  11  opposite to the side of the resin layer  11  over which the glass layer  14  is laminated via the adhesive layer  12 . 
     The buffer layer  17  is a cushioning layer located between the base material  20  and the resin layer  11 . The thickness of the buffer layer  17  is preferably 100 μm or more and 2000 μm or less from the viewpoint of developing a good cushioning property. Examples of the material of the buffer layer  17  include a urethane resin and various foaming materials. Examples of the various foaming materials include a polyolefin resin, a polypropylene resin, a polystyrene resin, a polyethylene resin, and the like. A commercially available foamed sheet may be used as the buffer layer  17 . Examples of commercially available foamed sheets include SCF (registered trademark) manufactured by Nitto Denko Corporation. The adhesive layer  16  can be any adhesive or pressure-sensitive adhesive exemplified as the adhesive layers  12  and  15 . 
     Thus, providing the buffer layer  17  as a lower layer of the resin layer  11 , the cushioning property of the multilayer structure  1 B can be enhanced, and the impact applied to the multilayer structure  1 B from the outside can be softened. Instead of the buffer layer  17  or in addition to the buffer layer  17 , a layer having another function such as a heat insulating layer may be laminated. 
     In the multilayer structure  1 A illustrated in  FIG.  4   , the adhesive layer  16  and the buffer layer illustrated in  FIG.  5    may also be laminated between the resin layer  11  and the adhesive layer  15 . 
       FIG.  6    is a plan view illustrating a multilayer structure according to a third modification of the first embodiment. A cross-sectional structure of the multilayer structure according to the third modification of the first embodiment may be, for example, the same as any one of those of  FIGS.  2 ,  4 , and  5   . 
     As illustrated in  FIG.  6   , in a multilayer structure  1 C, two types of laminated portions  10 A and  10 B are mixed and arranged in a rectangular shape as a whole. In the example of  FIG.  6   , the laminated portion  10 B has the same length in the X-direction as the laminated portion  10 A, but the laminated portion  10 B has a length in the Y-direction that is half the length of the laminated portion  10 A. 
     As described above, it is not necessary to have one type of laminated portion constituting the multilayer structure, and two types of laminated portions may be used. Alternatively, the multilayer structure may have three or more types of laminated portions. 
     The planar shape of the laminated portions are not limited to a rectangular shape, but may be a triangular shape, a hexagonal shape, or the like, or may be a mixture of these shapes. The shape of the multilayer structure as a whole does not have to be rectangular, and laminated portions having different planar shapes can be mixed together to form any desired shape, for example. 
     The multilayer structure need not be in a planar shape parallel to the XY plane, but may be curved, for example, in a semicylindrical shape or a dome-like shape. Here, the dome-like shape means a shape in which the position of the surface of the multilayer structure (the surface of the glass layer) in the Z direction gradually increases from the periphery toward the center. 
     In the case of  FIG.  1    of the first embodiment, there are two places where three joints of the laminated portions adjacent to each other in the Y direction are linearly aligned in the X direction. By contrast, in the case of  FIG.  6    there is no place where two or more joints of laminated portions adjacent to each other in the Y direction are aligned in the X direction. In other words, in the case of  FIG.  6   , the joints of the laminated portions adjacent to each other in the Y direction are arranged in a staggered manner, the joints are not aligned with each other, and the joints are discontinuous with each other. 
     As described above, since there are places where the joints of the adjacent laminated portions are discontinuous with each other, it is possible to make the joints more difficult to visually identify even when the sizes of the gaps S are the same. Although  FIG.  6    illustrates an example in which the joints of the laminate portions adjacent to each other in the Y direction are discontinuous, the same advantageous effect is achieved when the joints of the laminate portions adjacent to each other in the X direction are discontinuous. That is, it is preferable that the joints are discontinuous with each other in at least one of the X direction or the Y direction. 
     Although the preferred and the like have been described in detail above, various modifications and substitutions can be made to the embodiments and the like without departing from the scope of the claims. 
     This international application claims priority under Japanese Patent Application No. 2020-059418, filed with the Japanese Patent Office on Mar. 30, 2020, and the entire contents of Japanese Patent Application No. 2020-059418 are incorporated herein by reference. 
     DESCRIPTION OF REFERENCE CODES 
     
         
           1 ,  1 A,  1 B,  1 C multilayer structure 
           10 ,  10 A,  10 B laminated portion 
           11  resin layer 
           12 ,  15 ,  16  adhesive layer 
           13  metal layer 
           14  glass layer 
           17  buffer layer 
           20  base material 
           20   a  upper surface 
           22  colored layer