JP5825832B2 - Bubble-containing multilayer film - Google Patents

Description

  The present invention relates to a bubble-containing multilayer film having a multilayer structure of two or more layers, and more particularly to a bubble-containing multilayer film having a bubble-containing layer containing bubbles.

  Conventionally, various films containing bubbles have been proposed and widely used in various applications. Generally, when fine bubbles are included in the film, the film becomes soft, the film can be reduced in weight, and the strength and rigidity of the film are not easily lowered, and creases tend not to occur.

  As an example of a film containing bubbles, the following Patent Document 1 has a layer having three or more fine bubbles and a layer separating the layers, and these layers are alternately laminated in the thickness direction. An aerated multi-layer film is disclosed. The layer having fine bubbles is formed using a thermoplastic resin and a thermoplastic resin that is incompatible with the thermoplastic resin.

  In recent years, from the viewpoint of energy saving, it has been studied to increase the heat insulation effect and increase the efficiency of air conditioning in buildings and vehicles. For this purpose, various wall materials and interior materials with high heat insulating properties have been developed. Moreover, in the member used for the opening part of a building and a vehicle, it is very important that not only the heat insulation is high but also that the daylighting property is good.

  A bubble-containing multilayer film that can be used as a lighting heat insulating material in a building is disclosed in Patent Document 2 below. This bubble-containing multilayer film has a layer containing bubbles. Specifically, Patent Document 2 describes a bubble-containing multilayer film in which two or more laminate units having at least one foamed layer are laminated.

Japanese Patent No. 3861657 JP 2008-74057 A

  Conventional bubble-containing multilayer films as described in Patent Documents 1 and 2 are low in transparency, are white, do not transmit light sufficiently, and have high light reflectance. Therefore, the conventional bubble-containing multilayer film may not be used as a print receiving substrate, a protective member for display, and a transparent heat insulating material for buildings or vehicles that require high transparency.

  Furthermore, in the bubble-containing multilayer film described in Patent Document 2, the thickness of each layer is 100 μm or more, and the thickness of the bubble-containing multilayer film is about 10 mm. For this reason, there exists a problem that a bubble containing multilayer film cannot be used easily, or cannot fully respond to the request | requirement of thickness reduction.

  An object of the present invention is to provide a bubble-containing multilayer film that can enhance transparency and heat insulation properties, and further has excellent cushioning properties.

  A limited object of the present invention is to provide a bubble-containing multilayer film having a thickness of less than 1 mm and excellent handleability.

  According to a wide aspect of the present invention, the cell has a multilayer structure of two or more layers, at least one layer is a bubble-containing layer containing a plurality of bubbles therein, and the average bubble diameter of the bubbles is less than 200 nm, A bubble-containing multilayer film having a visible light transmittance of 70% or more is provided.

  In a specific aspect of the bubble-containing multilayer film according to the present invention, the bubble-containing layer has a foaming ratio of less than 10 times.

  In another specific aspect of the bubble-containing multilayer film according to the present invention, the thickness of the bubble-containing layer is less than 3 μm.

  The thickness of the bubble-containing multilayer film according to the present invention is preferably less than 1 mm.

  In another specific aspect of the bubble-containing multilayer film according to the present invention, the bubble-containing layer contains a polycarbonate resin.

  In another specific aspect of the bubble-containing multilayer film according to the present invention, the bubble-containing layer has another layer different from the bubble-containing layer laminated on both surfaces of the bubble-containing layer, and the bubble-containing layer contains a thermoplastic resin. And the other layer contains a thermoplastic resin, and the melt mass flow rate of the thermoplastic resin contained in the bubble-containing layer is larger than the melt mass flow rate of the thermoplastic resin contained in the other layer. . In the bubble-containing multilayer film, the bubble-containing layer preferably contains a polycarbonate resin.

  In still another specific aspect of the bubble-containing multilayer film according to the present invention, the other layer includes an ethylene-vinyl acetate copolymer resin or a polystyrene resin.

  The bubble-containing multilayer film according to the present invention has a multilayer structure of two or more layers, at least one layer is a bubble-containing layer containing a plurality of bubbles therein, and the average bubble diameter of the bubbles is less than 200 nm. Since the visible light transmittance is 70% or more, transparency and heat insulation can be increased. Furthermore, since the bubble-containing multilayer film according to the present invention has the bubble-containing layer, it has excellent cushioning properties.

FIG. 1 is a cross-sectional view schematically showing a bubble-containing multilayer film according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing a bubble-containing multilayer film according to another embodiment of the present invention.

  Hereinafter, the present invention will be clarified by describing specific embodiments and examples of the present invention with reference to the drawings.

  The bubble-containing multilayer film according to the present invention has a multilayer structure of two or more layers, at least one layer is a bubble-containing layer containing a plurality of bubbles therein, and the average bubble diameter of the bubbles is less than 200 nm. The visible light transmittance is 70% or more. The bubble-containing layer contains fine bubbles.

  In FIG. 1, the bubble containing multilayer film which concerns on one Embodiment of this invention is typically shown with sectional drawing.

  The bubble-containing multilayer film 1 shown in FIG. 1 includes bubble-containing layers 11 to 16 containing a plurality of bubbles A therein, and layers 21 to 27 (hereinafter referred to as other layers) different from the bubble-containing layer. ). The bubble-containing layers 11 to 16 and the other layers 21 to 27 are alternately laminated in the thickness direction of the bubble-containing multilayer film 1. That is, the bubble-containing multilayer film 1 includes the other layer 21, the bubble-containing layer 11, the other layer 22, the bubble-containing layer 12, the other layer 23, the bubble-containing layer 13, the other layer 24, the bubble-containing layer 14, and the like. The layer 25, the bubble-containing layer 15, the other layer 26, the bubble-containing layer 16, and the other layer 27 are laminated in this order. The bubble-containing layers 11 to 16 are sandwiched between the layers 21 to 27, and the bubble-containing layers 11 to 16 are separated from each other by the layers 21 to 27, respectively.

  The bubble-containing layers 11 to 16 are preferably foamed foam layers so as to contain a plurality of bubbles A. In the other layers 21 to 27, the number of bubbles per unit area of the other layers is preferably smaller than the number of bubbles per unit area of the bubble-containing layer, and more preferably substantially free of bubbles. . The other layers 21 to 27 are preferably resin layers formed of a resin. The materials of the bubble-containing layers 11 to 16 may be the same or different. The materials of the other layers 21 to 27 may be the same or different. Although the material of the bubble containing layers 11-16 and the material of the other layers 21-27 may be the same and may differ, the average bubble diameter of the bubble A can be easily controlled to less than 200 nm. The material of the bubble-containing layers 11-16 is preferably different from the material of the other layers 21-27. In addition, since the average bubble diameter of the bubbles A can be easily controlled to be less than 200 nm, when the bubble-containing layer and the other layer contain a resin, the resin contained in the bubble-containing layer is the resin contained in the other layer. Preferably they are different.

  In the bubble-containing multilayer film 1, the bubble-containing layers 11 to 16 and the other layers 21 to 27 are regularly stacked. The bubble-containing layer and other layers may be laminated randomly. The bubble-containing layer and the other layers are preferably laminated regularly, and more preferably alternately. The bubble-containing multilayer film according to the present invention preferably has another layer different from the bubble-containing layer laminated on both surfaces of the bubble-containing layer. The bubble-containing layer preferably contains a thermoplastic resin. The other layer preferably contains a thermoplastic resin.

  In FIG. 2, the bubble containing multilayer film which concerns on other embodiment of this invention is typically shown with sectional drawing.

  The bubble-containing multilayer film 51 shown in FIG. 2 has bubble-containing layers 61 to 73 containing a plurality of bubbles A inside. The bubble-containing layers 61 to 73 are laminated in the thickness direction of the bubble-containing multilayer film 51. The bubble-containing layers 61 to 73 are preferably foamed layers that are foamed so as to contain a plurality of bubbles A. The material of the bubble containing layers 61-73 may be the same and may differ.

  In the bubble-containing multilayer films 1 and 51, the average bubble diameter of the bubbles A contained in the bubble-containing layers 11 to 16 and 61 to 73 needs to be less than 200 nm. When the average bubble diameter of the bubbles A is large, light scattering increases. When the average bubble diameter is less than 200 nm, the visible light transmittance of the bubble-containing multilayer films 1 and 51 is 70% or more. From the viewpoint of further enhancing the transparency of the bubble-containing multilayer films 1 and 51, the average bubble diameter of the bubbles A is preferably 180 nm or less, more preferably 150 nm or less, and further preferably 100 nm or less. It is preferably 80 nm or less.

  The visible light transmittance of the bubble-containing multilayer film 1, 51 is preferably 75% or more, more preferably 79% or more, and further preferably 80% or more.

  Since the bubble-containing multilayer films 1 and 51 have the bubble-containing layers 11 to 16 and 61 to 73, they have excellent heat insulation properties and excellent cushioning properties. From the viewpoint of further improving the heat insulation and cushioning properties of the bubble-containing multilayer films 1, 51, the average bubble diameter of the bubbles A is preferably 30 nm or more, more preferably 50 nm or more, and 60 nm or more. More preferably.

  Regarding the “average bubble diameter”, when the bubble A is a closed cell and is a true sphere, the average bubble diameter is obtained from the diameter of the bubble. When the bubble A is a closed cell and has a shape other than a true sphere, the average bubble diameter is obtained from the longest length connecting the two points on the outer periphery of the bubble A, that is, the maximum diameter. Even when the bubble A is an open cell, the average bubble diameter is determined from the longest length connecting two points on the outer periphery of the bubble A, that is, the maximum diameter. The average bubble diameter indicates an average value of the bubble diameters of at least 10 bubbles, and is preferably an average value of the bubble diameters of 10 arbitrarily selected bubbles.

  In addition, the measurement of the “average bubble diameter” is performed by exposing a cross section of the bubble-containing layer by a frozen section method or a freeze fracture method, and using a transmission electron microscope (TEM) or a scanning electron microscope (SEM). This is done by observing the cross section of the bubble-containing layer. The average bubble diameter is prepared by, for example, preparing a sample so that the central portion in the thickness direction of the bubble-containing layer can be observed after exposing the cross section in the thickness direction of the bubble-containing layer by a frozen section method. The obtained sample is observed using a scanning electron microscope (SEM, model “S-3400N”) manufactured by Hitachi, Ltd., and is defined by an average value of the bubble diameters of 10 arbitrarily selected bubbles. It is preferable.

  As a result of intensive studies to make the average bubble diameter of the bubbles A less than 200 nm, the present inventor has found that it is optimal to make a multilayer film having a multilayer structure of two or more layers. Further, the present inventor, like the bubble-containing multilayer film 1, laminated the bubble-containing layers 11 to 16 and other layers 21 to 27 different from the bubble-containing layers 11 to 16 to average the bubbles A. It has also been discovered that the bubble diameter can easily be made below 200 nm.

  In order to make the average bubble diameter of the bubbles less than 200 nm, it is preferable that a layer different from the bubble-containing layer is laminated on at least one surface of the bubble-containing layer. It is preferable that different layers are laminated. In such a laminated structure, a layer different from the bubble-containing layer acts to hold the bubbles in the bubble-containing layer and suppress the disappearance of the bubbles. For example, bubbles existing inside the bubble-containing layer are held by other layers stacked on the bubble-containing layer. Further, the bubbles are effectively held by the presence of a layer different from the bubble-containing layer even by the pressure at the time of forming the bubble-containing multilayer film 1. If the retention capacity of the bubbles is small, the bubbles become too large, or the bubbles disappear from the bubble-containing layer. In order to prevent these, the viscosity of the material of the bubble-containing layer at the time of molding is preferably smaller than the viscosity of the material of the other layer at the time of molding. In particular, since the transparency and heat insulation of the bubble-containing multilayer film can be further increased, the viscosity of the bubble-containing layer at the time of molding is preferably smaller than the viscosity of the other layers at the time of molding. The viscosity relationship may be controlled by, for example, the viscosity of the resin itself used for the bubble-containing layer and other layers, or may be controlled by a change in viscosity due to temperature adjustment during molding. The molding time is defined as a state where the temperature of the resin itself is in an environment of 50 ° C. or higher and 300 ° C. or lower. Regarding the viscosity (fluidity) of the bubble-containing layer and other layers at the time of molding, the MFR (melt mass flow rate) of the bubble-containing layer at the time of molding is preferably larger than the MFR of the other layers at the time of molding. 5 (g / 10 min) or more is preferable, 1 (g / 10 min) or more is more preferable, 2 (g / 10 min) or more is more preferable, 3 (g / 10 min) or more is particularly preferable. . The upper limit of the MFR of the bubble-containing layer at the time of molding is not particularly limited, but is preferably 30 (g / 10 min) or less.

  Further, when the bubble-containing layer and other layers contain a resin, the transparency and heat insulation of the bubble-containing multilayer film can be further increased, so that the MFR of the resin contained in the bubble-containing layer is different from that of the other layers. It is preferably larger than the MFR of the resin contained, preferably 0.5 (g / 10 min) or more, more preferably 1 (g / 10 min) or more, and more preferably 2 (g / 10 min) or more. More preferably, it is particularly preferably 3 (g / 10 min) or more. The MFR of the resin contained in the bubble-containing layer is not particularly limited, but is preferably 30 (g / 10 min) or less.

  Moreover, since the bubble which exists in the inside of a bubble containing layer can be maintained efficiently, it is preferable that the gas barrier property of another layer is higher than the gas barrier property of a bubble containing layer. In order to make the gas barrier property of the other layer higher than the gas barrier property of the bubble-containing layer, it is preferable to use a resin having a low gas permeability as the material of the other layer. The MFR measurement method conforms to ISO1133.

  The present inventor has also found that the average bubble diameter can be reduced as the bubble-containing layer is thinner. Therefore, the larger the number of layers of the bubble-containing multilayer film, particularly, the larger the number of bubble-containing layers, the smaller the average bubble diameter.

  Further, if the bubble-containing multilayer film has the same number of layers, the bubble diameter decreases as the thickness of the bubble-containing multilayer film decreases. For example, when producing a bubble-containing multilayer film having the same thickness, the larger the number of bubble-containing layers, and the thinner each bubble-containing layer, the smaller the average bubble diameter of the bubbles in the bubble-containing layer. Therefore, by controlling the number of layers in the bubble-containing multilayer film and the thickness of the bubble-containing multilayer film, a bubble-containing multilayer film having a bubble-containing layer containing bubbles having an average bubble diameter of less than 200 nm can be easily obtained. .

  The bubble-containing layer contains a plurality of bubbles inside, and the bubbles form a “layer of air that does not move”. Such a layer imparts a high heat insulating effect and cushioning properties to the bubble-containing multilayer film.

  The bubble-containing multilayer film preferably has two or more bubble-containing layers. In the bubble-containing multilayer film having two or more bubble-containing layers, compared to the bubble-containing multilayer film having only one bubble-containing layer, particularly compared to the bubble-containing multilayer film having only one thick bubble-containing layer. In addition, since the effect of reducing thermal radiation is further enhanced, the heat insulation effect is further enhanced.

  The material constituting the bubble-containing layer and the other layers is preferably a resin. Examples of the resin include thermoplastic resins, thermosetting resins, and photocurable resins. Since the average bubble diameter in the bubble-containing layer can be more easily controlled, it is more preferable that the bubble-containing layer and the other layers are each formed of a thermoplastic resin. As the thermoplastic resin, a crystalline resin may be used, or an amorphous resin may be used.

  The resin constituting the bubble-containing layer and the other layers is not particularly limited. For example, polyolefin resin, PET (polyethylene terephthalate) resin, PBT (polybutylene terephthalate) resin, polycarbonate resin, EVA (ethylene-vinyl acetate) Copolymer) resin, polystyrene resin, vinyl chloride resin, ABS (acrylonitrile-butadiene-styrene copolymer) resin, AS (acrylonitrile-styrene copolymer) resin, polyvinyl acetal resin, thermoplastic elastomer, and A thermoplastic resin such as (meth) acrylic resin may be used. Among these, a crystalline resin such as a polyolefin-based resin is preferable. The bubble-containing layer preferably contains a polycarbonate resin. Furthermore, the other layer preferably contains an ethylene-vinyl acetate copolymer resin or a polystyrene resin. As for the said resin, only 1 type may be used and 2 or more types may be used together.

  The polyolefin resin is not particularly limited. For example, a homopolymer such as ethylene, propylene or α-olefin, a copolymer of ethylene and propylene, a copolymer of ethylene and α-olefin, propylene and α- Examples include copolymers with olefins and copolymers of two or more α-olefins. As for the said polyolefin resin, only 1 type may be used and 2 or more types may be used together.

  The α-olefin is not particularly limited, and examples thereof include 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene and 1-octene.

  The thermoplastic resin may be alloyed or blended with a polymer compound. A layered silicate may be added to the thermoplastic resin. Furthermore, for example, a small amount of a polymer compound grafted with a carboxylic acid such as maleic acid may be added to a thermoplastic resin to increase the affinity between the thermoplastic resin and the layered silicate.

  Examples of the vinyl chloride resin include vinyl chloride homopolymers, copolymers of vinyl chloride and polymerizable monomers other than vinyl chloride polymerizable with the vinyl chloride, and polymer resins other than vinyl chloride polymers. Examples thereof include a graft copolymer obtained by grafting a vinyl chloride polymer.

  The polymerizable monomer is not particularly limited as long as it has a reactive double bond. Examples of the polymerizable monomer include α-olefins such as ethylene, propylene and butylene, vinyl esters such as vinyl acetate and vinyl propionate, vinyl ethers such as butyl vinyl ether and cetyl vinyl ether, and methyl (meth) acrylate. (Meth) acrylates such as ethyl (meth) acrylate and phenyl (meth) acrylate, aromatic vinyls such as styrene and α-methylstyrene, vinyl halides such as vinylidene chloride and vinyl fluoride, and And N-substituted maleimides such as N-phenylmaleimide and N-cyclohexylmaleimide. As for the said polymerizable monomer, only 1 type may be used and 2 or more types may be used together.

  The polymer resin is not particularly limited. For example, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-carbon monoxide copolymer, ethylene-ethyl (meth) acrylate copolymer, ethylene-methyl (meth) acrylate. Examples include copolymers, ethylene-propylene copolymers, acrylonitrile-butadiene copolymers, polyurethane resins, chlorinated polyethylene resins, and chlorinated polypropylene resins. As for the said polymeric resin, only 1 type may be used and 2 or more types may be used together.

  Examples of the ABS resin include acrylonitrile-butadiene-styrene terpolymer.

  In order to improve heat resistance, the thermoplastic resin may be copolymerized with aromatic vinyls such as α-methylstyrene and N-phenylmaleimide.

  It does not specifically limit as said polyvinyl acetal type resin, For example, polyvinyl butyral etc. are mentioned.

  The thermoplastic elastomer is not particularly limited, and examples thereof include styrene / butadiene elastomers, ethylene / propylene elastomers, and acrylic elastomers.

In order to obtain desired physical properties, for example, an additive such as an antioxidant, a light-resistant agent, a UV absorber, heat ray shielding particles such as ITO particles or LaB ₆ particles, a lubricant, a flame retardant, or an antistatic agent. However, it may be appropriately added to the thermoplastic resin. As for the said additive, only 1 type may be used and 2 or more types may be used together. A small amount of a compound that can serve as a crystal nucleating agent may be added to the thermoplastic resin to refine the crystal and improve the uniformity of physical properties.

  The molecular weight and molecular weight distribution of the thermoplastic resin are not particularly limited. The weight average molecular weight of the thermoplastic resin is preferably 5000 or more, more preferably 20,000 or more, preferably 5 million or less, more preferably 300,000 or less. The molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) of the thermoplastic resin is preferably 2 or more, more preferably 3 or more, preferably 80 or less, more preferably 40 or less.

  The weight average molecular weight (Mw) and the number average molecular weight (Mn) are values obtained using polystyrene as a standard substance using gel permeation chromatography (GPC). The weight average molecular weight (Mw) and number average molecular weight (Mn) were measured by a measuring device manufactured by Waters (column: Shodex GPC LF-804 (length 300 mm) x 2 manufactured by Showa Denko KK), measuring temperature: 40 ° C., flow rate: It means a value measured using 1 mL / min, solvent: tetrahydrofuran, standard substance: polystyrene).

  The bubbles in the bubble-containing layer may be independent bubbles that are independent of each other, may be continuous bubbles that are in communication with each other, or may be a mixture of closed cells and continuous bubbles. The closed cell has a smaller sound absorption effect than the open cell, and the smaller the ratio of the number of closed cells to the number of open cells, the higher the sound absorbing effect of the bubble-containing multilayer film.

  The bubble-containing layer is preferably a foamed foam layer. The expansion ratio in the bubble-containing layer is appropriately determined depending on the use of the bubble-containing multilayer film. The foaming ratio of the bubble-containing layer is preferably less than 10 times. When the expansion ratio is less than 10 times, the transparency of the bubble-containing multilayer film can be further increased, and the visible light transmittance is easily set to 70% or more. Furthermore, when the expansion ratio is less than 10, the mechanical strength of the bubble-containing multilayer film can be further increased. From the viewpoint of improving the balance between transparency and heat insulation, the foaming ratio of the bubble-containing layer is preferably 5 times or less, more preferably 3 times or less, and even more preferably 2.5 times or less. From the viewpoint of further improving the cushioning property and heat insulation of the bubble-containing layer, the foaming ratio of the bubble-containing layer is preferably 1.1 times or more, more preferably 1.3 times or more, and even more preferably 1.5 times. That's it.

  The “foaming ratio” is obtained by the formula: S0 / (S0−S1), where S0 is the cross-sectional area of the bubble-containing layer and S1 is the total area of the bubbles occupying the cross-sectional area S0.

  In the same manner as the measurement of the “average bubble diameter”, the “foaming ratio” is measured by exposing the cross section of the bubble-containing layer by a frozen section method, a freeze fracture method, or the like, and transmitting electron microscope (TEM) or scanning type. This is done by observing the cross section of the bubble-containing layer using an electron microscope (SEM). From the observation result of TEM or SEM, the expansion ratio can be obtained by hand calculation or image processing calculation.

For example, by exposing the cross section of the central portion in the thickness direction of the bubble-containing layer by a frozen section method, a sample is prepared so that the central portion in the thickness direction of the bubble-containing layer can be observed, manufactured by Hitachi, Ltd. Using a scanning electron microscope (SEM, model “S-3400N”), the cross section of the central portion in the thickness direction of the bubble-containing layer is observed. Using a scanning electron microscope, the cross section was observed at a magnification of 10,000 times. The observed cross sectional area was S0 (5 μm long × 5 μm wide, 25 μm ² ), and the total S1 of the cross sectional areas of all the bubbles observed was It is preferable to calculate and obtain the foaming ratio by the formula: S0 / (S0-S1).

  The thickness of the bubble-containing layer is appropriately determined depending on the use of the bubble-containing multilayer film. Each thickness of the bubble-containing layer is preferably less than 3 μm. When the thickness of one layer of the bubble-containing layer is less than 3 μm, the transparency of the bubble-containing multilayer film can be further improved, and the visible light transmittance can be 70% or more. From the viewpoint of further improving the heat insulation and cushioning properties of the bubble-containing multilayer film, the thickness of the bubble-containing layer is preferably 30 nm or more, more preferably 50 nm or more, and further preferably 60 nm or more. preferable.

  The bubble-containing multilayer film 1 has six bubble-containing layers, and the bubble-containing multilayer film 51 has 13 bubble-containing layers. The number of the bubble-containing layers in the bubble-containing multilayer film is not particularly limited as long as it is 1 or more, and is appropriately determined depending on the thickness or use of the bubble-containing multilayer film. The number of the bubble-containing layers in the bubble-containing multilayer film is preferably 20 or more, more preferably 40 or more, and still more preferably 80 or more. For example, when the bubble-containing multilayer film is used for a building or vehicle transparent heat insulating material, the number of the bubble-containing layers is preferably 20 or more. When the number of the bubble-containing layers is 20 or more, the heat insulating property of the bubble-containing multilayer film can be further enhanced. From the viewpoint of further increasing the heat insulation, the number of the bubble-containing layers is more preferably 40 or more. The upper limit of the number of the bubble-containing layers is not particularly limited. The number of the bubble-containing layers may be 20,000 or less, or 20,000 or more. From the viewpoint of further enhancing the transparency, the number of the bubble-containing layers is preferably 10,000 or less, more preferably 5000 or less, further preferably 1000 or less, and preferably 800 or less. Particularly preferred.

  The thickness of the layer different from the bubble-containing layer, that is, the thickness of the other layer is appropriately determined depending on the use of the bubble-containing multilayer film. The thickness of the other layer is preferably less than 3 μm. When the thickness of the other layer is less than 3 μm, the transparency of the bubble-containing multilayer film can be further improved, and the visible light transmittance can be 70% or more. The thickness of the other layer is more preferably 2 μm or less, further preferably 1 μm or less, and most preferably 0.5 μm or less. From the viewpoint of further improving the heat insulation and cushioning properties of the bubble-containing multilayer film, the thickness of the other layer is preferably 50 nm or more.

  The number of the other layers is preferably 20 or more, more preferably 40 or more, and still more preferably 80 or more. The upper limit of the number of other layers is not particularly limited. The number of other layers may be 20,000 or less, or 20,000 or more. From the viewpoint of further enhancing the transparency, the number of other layers is preferably 10,000 or less, more preferably 5000 or less, further preferably 1000 or less, and preferably 800 or less. Particularly preferred.

  From the viewpoint of meeting the demand for thinning and further improving the handleability, the thickness of the bubble-containing multilayer film is preferably less than 1 mm. From the viewpoint of further improving the heat insulation and cushioning properties, the thickness of the bubble-containing multilayer film is preferably 10 μm or more.

  Although the thickness of the bubble-containing layer is not particularly limited, it is preferably 2 μm or less, more preferably 1 μm or less, and further preferably 0.5 μm or less because the transparency of the bubble-containing multilayer film is further enhanced. Is particularly preferred. From the viewpoint of further enhancing the heat insulation and cushioning properties of the bubble-containing multilayer film, the thickness of the bubble-containing layer is preferably 50 nm or more, and is larger than the average bubble diameter of the bubbles present inside the bubble-containing layer. It is more preferable.

(Method for producing bubble-containing multilayer film)
The method for producing the bubble-containing multilayer film according to the present invention is not particularly limited. Examples of the method for producing the bubble-containing multilayer film include a wet lamination method, a dry lamination method, an extrusion coating method, a multilayer extrusion method, a hot melt lamination method, and a heat lamination method.

  It is preferable that the bubble-containing multilayer film is obtained by a multilayer extrusion method because the production of the bubble-containing multilayer film is easy and the bubble diameter in the bubble-containing layer can be easily controlled. Examples of the multilayer extrusion method include a multi-manifold method and a feed block method.

  The bubble-containing layer is preferably formed of a resin composition containing a resin and a foaming agent, and is preferably formed of a resin composition containing a thermoplastic resin and a foaming agent. By foaming the foaming agent in the unfoamed resin composition (unfoamed layer), fine bubbles are formed, and a bubble-containing layer (foamed layer) is obtained. When producing a bubble-containing multilayer film by the multilayer extrusion method, the time when the unfoamed layer is foamed to form a foamed layer may be before being extruded from the multilayer extrusion apparatus, or after being extruded from the multilayer extrusion apparatus. There may be.

  As a method of foaming the unfoamed layer, for example, a pyrolytic foaming agent is kneaded into the above-described thermoplastic resin and heated to a temperature higher than the decomposition temperature of the pyrolytic foaming agent to foam. After injecting a gas or a volatile liquid having a boiling point below the melting point of a thermoplastic resin such as butane, pentane or dichlorodifluoromethane (Freon R-12) into the thermoplastic resin melt Examples thereof include a gas foaming method in which a foam is released into a low-pressure region, and a supercritical method in which a predetermined chemical substance is impregnated in a supercritical state in the composite of the thermoplastic resin and the layered silicate, and the like.

  In the chemical foaming agent method, a foamed layer having uniform and fine closed cells can be obtained. On the other hand, since the decomposition product of the foaming agent tends to remain as a residue in the foamed layer, discoloration of the foamed layer, generation of odors, food hygiene problems, and the like may occur.

  In the gas foaming method, when the foaming agent is a low-boiling organic solvent such as butane or pentane, an explosive gas is generated during the production of the foamed layer, and there is a risk of explosion. In the gas foaming method, when the foaming agent is dichlorodifluoromethane (Freon R-12), there is little risk of explosion, and the foamed layer can be rapidly cooled and solidified by the latent heat of vaporization accompanying vaporization during foaming. Furthermore, since the gas permeability to the cell membrane is small, it is easy to obtain a foam having a high expansion ratio. However, in view of environmental problems such as ozone layer destruction, it is preferable to use a gas other than the fluorocarbon gas.

  As the chemical substance used in the supercritical method, when the thermoplastic resin is a crystalline resin, the thermoplastic resin is amorphous within the range of (melting point−20 ° C.) to (melting point + 20 ° C.). In the case of a resin, any organic or inorganic gas in a gaseous state can be used within the range of (glass transition temperature −20 ° C.) to (glass transition temperature + 20 ° C.). Examples of such gases include carbon dioxide (carbon dioxide), nitrogen, oxygen, argon and water, and Freon, low molecular weight hydrocarbons, chlorinated aliphatic hydrocarbons, fluorinated aliphatic hydrocarbons, alcohols, Examples thereof include organic gases such as benzene, toluene, xylene and mesitylene. In particular, a gas that is a gas at normal temperature (23 ° C.) and normal pressure (atmospheric pressure) is preferably used.

  Examples of the low molecular weight hydrocarbon include pentane, butane and hexane. Examples of the chlorinated aliphatic hydrocarbon include methyl chloride and methylene chloride.

  Since recovery of gas is unnecessary and can be handled safely, carbon dioxide is preferably used as the chemical substance. Carbon dioxide can be supercritical by relatively low temperature and low pressure, and acts effectively on dispersion when in a supercritical fluid.

  The “supercritical state” refers to a state where the temperature and pressure are higher than the critical point of the chemical substance to be impregnated. The “supercritical state” does not distinguish between a gas and a liquid, and has an intermediate property between a gas and a liquid, a high thermal conductivity, a high diffusion rate, and a low viscosity.

  The chemical substance may be liquid at normal temperature. Examples of chemical substances that are liquid at room temperature include saturated hydrocarbons such as pentane, neopentane, hexane and heptane, chlorine compounds such as methylene chloride, trichloroethylene and dichloroethane, and CFC-11, CFC-12, CFC-113 and Fluorine compounds such as CFC-141b can be mentioned.

  The method for impregnating the thermoplastic resin with the above-mentioned chemical substance is not particularly limited, and examples thereof include a method in which a gas as a chemical substance is sealed in a sealed autoclave and pressure is applied. This method makes it easy to control the pressure and temperature.

  The thermoplastic resin may be put into a melt extruder, a vent type screw may be used as a screw, and the gas may be injected into the vent portion from the middle of the cylinder. In this case, by performing pressure sealing on the molten resin, the thermoplastic substance can be effectively impregnated with the chemical substance, and a foamed layer can be continuously produced.

The pressure of the gas when impregnating the thermoplastic with the chemical substance is preferably 9.8 × 10 ⁵ Pa or more, more preferably, when the gas that is a gas at normal temperature and pressure is used as the chemical substance. It is 9.8 × 10 ⁶ Pa or more.

  When a gaseous gas at normal temperature and pressure is used as the chemical substance, the conditions under which the gas becomes a supercritical fluid vary depending on the type of chemical substance. As described above, carbon dioxide exhibits a supercritical state property under relatively mild conditions, and becomes a supercritical fluid at 60 ° C. and 60 atm, for example.

  The temperature at which the above-mentioned chemical substance is impregnated into the thermoplastic resin is not particularly limited, and is appropriately adjusted to a temperature at which the resin does not deteriorate. The higher the temperature, the higher the amount of the chemical substance dissolved in the thermoplastic resin, and the higher the expansion ratio. Therefore, a higher impregnation temperature is preferable. From the viewpoint of obtaining a good foamed state, the temperature at which the above-mentioned chemical substance is impregnated into the thermoplastic resin is within the range of (melting point−20 ° C.) to (melting point + 20 ° C.) when the thermoplastic resin is a crystalline resin. More preferably, when the thermoplastic resin is an amorphous resin, it is more preferably within the range of (glass transition temperature −20 ° C.) to (glass transition temperature + 20 ° C.). When the temperature for impregnating the above chemical substance is (melting point + 20 ° C.) or lower or (glass transition temperature + 20 ° C.) or lower, the molecular motion of the thermoplastic resin is not activated too much, and the chemical substance dissolved in the composite is a composite. It becomes difficult to come off. When the temperature at which the chemical substance is impregnated is equal to or higher than the melting point or the glass transition temperature, the thermoplastic resin can sufficiently undergo molecular motion, and the chemical substance can be sufficiently dissolved in the composite.

  The bubble-containing layer may be formed by impregnating a thermoplastic resin with the chemical substance and then expanding the chemical substance in the thermoplastic resin. The method of expanding the volume of the chemical substance is appropriately selected according to the type of the chemical substance. The volume expansion of the chemical substance is performed, for example, by impregnating a thermoplastic resin with a gas that is the chemical substance at a relatively high pressure and then reducing the pressure or heating.

  The temperature for volume expansion of the chemical substance is not particularly limited. The temperature at which the chemical substance is volume-expanded is preferably within the range of (melting point−50 ° C.) to (melting point + 10 ° C.) when the thermoplastic resin is a crystalline resin. When it is a crystalline resin, it is preferably within the range of (glass transition temperature-50 ° C.) to (glass transition temperature + 50 ° C.). When the temperature for volume expansion is (melting point + 10 ° C.) or lower or (glass transition temperature + 50 ° C.) or lower, the dissolved gas is difficult to escape, so that the foam structure can be easily maintained. When the temperature for volume expansion is (melting point−50 ° C.) or higher or (glass transition temperature−50 ° C.) or higher, the molecular motion of the thermoplastic resin is hardly restrained, and the expansion ratio can be increased.

  When the bubble-containing multilayer film is produced by the multilayer extrusion method described above and the bubble-containing layer is formed by the supercritical method, a predetermined part is supplied to the portion that supplies the resin composition to be the bubble-containing layer in the multilayer extrusion device described above. The supercritical apparatus may be attached so that a chemical substance in a supercritical state can be supplied to the resin composition that becomes the bubble-containing layer.

(Use of bubble-containing multilayer film)
The use of the bubble-containing multilayer film according to the present invention is not particularly limited. Examples of the use of the bubble-containing multilayer film include, for example, a print receiving substrate, a display protective member, a transparent heat insulating material for buildings or vehicles, a multilayer sound absorbing material, a multilayer sound insulating material, a heat insulating material, a decorative multilayer body, and an interior sound insulating material. , Interior sound-absorbing materials, high-gloss decorative interior materials and water-tight seal materials. Since the bubble-containing multilayer film according to the present invention can be thinned, it can be suitably used as a print receiving substrate, a protective member for display, and a transparent heat insulating material for buildings or vehicles.

  The bubble-containing multilayer film can be used for vehicle-related applications. Specifically, for example, a bubble-containing multilayer film can be used as glazing for automobile window glass such as front, roof, rear, side and rear side.

  Grazing requires transparency and heat insulation. Since the heat insulation and heat resistance are high, the bubble-containing multilayer film can be suitably used as a transparent heat insulating material including glazing for vehicles. Grazing may further require functions such as viewing angle selection, dimming, ultraviolet cut, and expansion / contraction suppression by low linear expansion. These functions can also be imparted to the bubble-containing multilayer film according to the present invention.

  When the bubble-containing multilayer film is used for glazing for vehicles, the bubble-containing multilayer film is required to have transparency and heat insulation. Accordingly, the bubble-containing layer and the other layer are preferably formed of a transparent resin, respectively, and are polycarbonate resin, (meth) acrylic resin, ethylene-vinyl acetate copolymer resin, polystyrene resin, or polyvinyl chloride. More preferably, it is formed of a resin. In this case, the structure of the bubble-containing multilayer film includes, for example, a bubble-containing layer formed of polycarbonate resin, polycarbonate resin, (meth) acrylic resin, ethylene-vinyl acetate copolymer resin, polystyrene resin, or vinyl chloride. A structure in which a bubble-containing layer formed of a resin is laminated, a bubble-containing layer formed of polycarbonate, a polycarbonate resin, a (meth) acrylic resin, an ethylene-vinyl acetate copolymer resin, a polystyrene resin, or a vinyl chloride type A structure in which other layers formed of resin are laminated, a bubble-containing layer formed of (meth) acrylic resin, polycarbonate resin, (meth) acrylic resin, ethylene-vinyl acetate copolymer resin, polystyrene resin or With a bubble-containing layer formed of vinyl chloride resin Structure, a bubble-containing layer formed of (meth) acrylic resin, and other layers formed of polycarbonate resin, (meth) acrylic resin, ethylene-vinyl acetate copolymer resin, polystyrene resin or vinyl chloride resin And a bubble-containing layer formed of a vinyl chloride resin, and a bubble formed of a polycarbonate resin, a (meth) acrylic resin, an ethylene-vinyl acetate copolymer resin, a polystyrene resin, or a vinyl chloride resin. A structure in which a content layer is laminated, and a bubble content layer formed of a vinyl chloride resin and a polycarbonate resin, a (meth) acrylic resin, an ethylene-vinyl acetate copolymer resin, a polystyrene resin, or a vinyl chloride resin. The structure etc. which were laminated | stacked with the other layer made | formed are mentioned. Among them, a structure in which a bubble-containing layer formed of a polycarbonate resin and a bubble-containing layer formed of a polycarbonate resin, an ethylene-vinyl acetate copolymer resin or a polystyrene resin are laminated, or formed of a polycarbonate resin. A structure in which a bubble-containing layer and another layer formed of a polycarbonate resin, an ethylene-vinyl acetate copolymer resin, or a polystyrene resin are laminated is preferable. The bubble-containing layer formed of a polycarbonate resin, and ethylene-vinyl acetate A structure in which another layer formed of a copolymer resin or a polystyrene resin is laminated is more preferable.

  When the bubble-containing multilayer film is used for an interior sound insulating material, the bubble-containing layer preferably has open cells, and further preferably has a smaller average bubble diameter. When the bubble-containing multilayer film is used as the inner layer sound insulating material, the bubble-containing layer and the other layers are preferably formed of a material having a glass transition temperature at room temperature. In this case, the structure of the bubble-containing multilayer film is preferably the structure described in the case of use for the above-described vehicle glazing. Among them, a structure in which a bubble-containing layer formed of a polycarbonate resin and a bubble-containing layer formed of a polycarbonate resin, an ethylene-vinyl acetate copolymer resin or a polystyrene resin are laminated, or formed of a polycarbonate resin. A structure in which a bubble-containing layer and another layer formed of a polycarbonate resin, an ethylene-vinyl acetate copolymer resin, or a polystyrene resin are laminated is preferable. The bubble-containing layer formed of a polycarbonate resin, and ethylene-vinyl acetate A structure in which another layer formed of a copolymer resin or a polystyrene resin is laminated is more preferable.

  In the case where a viewing angle selection function is imparted to the vehicle glazing, the bubble-containing layer is preferably stretched and flat-foamed at the time of production, for example, and preferably contains flat bubbles. The bubble-containing layer and the other layers are each preferably formed of a transparent resin, and preferably formed of a polycarbonate resin, a (meth) acrylic resin, and a polyvinyl chloride resin. In addition, the said flat foaming means the foaming whose cross-sectional shape of the bubble in the said bubble containing layer is other than circles, such as an ellipse. In this case, the structure of the bubble-containing multilayer film is preferably the structure described in the case of using for the above-described vehicle glazing, for example. Among them, a structure in which a bubble-containing layer formed of a polycarbonate resin and a bubble-containing layer formed of a polycarbonate resin, an ethylene-vinyl acetate copolymer resin or a polystyrene resin are laminated, or formed of a polycarbonate resin. A structure in which the bubble-containing layer and another layer formed of polycarbonate resin, ethylene-vinyl acetate copolymer resin, or polystyrene resin are laminated is preferable.

  When the light control function is imparted to the vehicle glazing, the other layer preferably contains an additive having a conductive function. Further, the bubble-containing layer and the other layer each preferably contain a transparent resin, and contain a polycarbonate resin, a (meth) acrylic resin, an ethylene-vinyl acetate copolymer resin, a polystyrene resin or a polyvinyl chloride resin. It is more preferable. Each of the bubble-containing layer and the other layer is preferably formed of a transparent resin, and is made of a polycarbonate resin, a (meth) acrylic resin, an ethylene-vinyl acetate copolymer resin, a polystyrene resin, and a polyvinyl chloride resin. More preferably, it is formed. In this case, as the configuration of the bubble-containing multilayer film, a bubble-containing layer formed of a polycarbonate resin and another layer formed of a polycarbonate resin, a (meth) acrylic resin or a vinyl chloride resin are laminated. Configuration: A cell-containing layer formed of (meth) acrylic resin and a layered structure of polycarbonate resin, (meth) acrylic resin or other layers formed of vinyl chloride resin, formed of vinyl chloride resin A configuration in which the bubble-containing layer and another layer formed of a polycarbonate resin, a (meth) acrylic resin, or a vinyl chloride resin are laminated, or the like can be given. Especially, the structure by which the bubble containing layer formed with polycarbonate resin and the other layer formed with polycarbonate was laminated | stacked is preferable. Moreover, the bubble-containing multilayer film etc. which were demonstrated in the case where it uses for the glazing for vehicles mentioned above may have the electroconductive butyral layer to which tungsten oxide was added, for example.

  In the case where a light control function is imparted to the vehicle glazing, the structure of the bubble-containing multilayer film is preferably the structure described in the case of using the above-described vehicle glazing, for example. A structure in which a bubble-containing layer containing a polycarbonate resin and a bubble-containing layer containing a polycarbonate resin are laminated, a structure in which a bubble-containing layer containing a polycarbonate resin and another layer containing a polycarbonate resin are laminated, and a polycarbonate resin A structure in which a bubble-containing layer and another layer containing an ethylene-vinyl acetate copolymer resin or a polystyrene resin are laminated is preferable. Among them, a structure in which a bubble-containing layer formed of a polycarbonate resin and a bubble-containing layer formed of a polycarbonate resin are laminated, a bubble-containing layer formed of a polycarbonate resin, and another formed of a polycarbonate resin. A structure in which layers are laminated, a bubble-containing layer formed of polycarbonate resin, and a structure in which other layers formed of ethylene-vinyl acetate copolymer resin or polystyrene resin are laminated are preferable.

  Hereinafter, the present invention will be specifically described by giving examples and comparative examples. The present invention is not limited to the following examples.

  In Examples 1 to 7 and Comparative Examples 2 to 5, a multi-layer extrusion apparatus is used, and a multi-layer extrusion molding is used to form a bubble-containing layer (foamed layer) containing a plurality of bubbles using a resin described below and a resin described below The other layer (resin layer) containing no bubbles was used to form a bubble-containing multilayer film. The bubble-containing layer and the resin layer were alternately laminated in the thickness direction of the bubble-containing multilayer film. The foamed layer in the bubble-containing multilayer film was produced by a carbon dioxide gas impregnation method.

Example 1
Polycarbonate resin (manufactured by Mitsubishi Gas Chemical Company, Iupilon E2000, MFR = 5.3 (g / 10 min)) was supplied to the main extruder, and CO ₂ was injected under pressure. Moreover, ethylene-vinyl acetate copolymer resin (Mitsui DuPont Polychemical Co., Ltd., EV460, MFR = 2.5 (g / 10 min)) was supplied to the sub-extruder. A multilayer feed block was attached to the ends of the main extruder and the sub-extruder, and a laminate was obtained such that each raw material was alternately laminated so that a total of 20 layers containing the bubble-containing layer and the other layers were laminated. Furthermore, several sets of multi-layer blocks that can be divided and laminated are attached to the downstream portion, and the number of layers is increased by laminating eight 20-layer laminates to obtain a bubble-containing multilayer film having 160 layers and a thickness of 80 μm. .

(Examples 2 to 5)
The thicknesses of the bubble-containing layer and other layers are as shown in Table 1 below, and the number of layers of the 20-layer laminate is changed to be as shown in Table 1 below. In addition, a bubble-containing multilayer film was obtained in the same manner as in Example 1 except that the expansion ratio of the bubble-containing layer was as shown in Table 1 below.

(Example 6)
The number of layers and the thickness of 80 μm were the same as in Example 1 except that the material of the bubble-containing layer was changed to polystyrene resin (Toyostyrene Co., Ltd., Toyostyrene HRM-26, MFR = 1.5 (g / 10 min)). A bubble-containing multilayer film was obtained.

(Example 7)
The number of layers was 640 and the thickness was 128 μm in the same manner as in Example 2 except that the material of the bubble-containing layer was changed to polystyrene resin (Toyostyrene Co., Ltd., Toyostyrene HRM-26, MFR = 1.5 (g / 10 min)). A bubble-containing multilayer film was obtained.

(Comparative Example 1)
A glass plate having a thickness of 2 mm was prepared.

(Comparative Examples 2 to 5)
The thicknesses of the bubble-containing layer and other layers are as shown in Table 1 below, and the number of layers of the 20-layer laminate is changed to be as shown in Table 1 below. In addition, a bubble-containing multilayer film was obtained in the same manner as in Example 1 except that the expansion ratio of the bubble-containing layer was as shown in Table 1 below.

(Evaluation)
(1) Average thickness of each layer The obtained bubble-containing multilayer film was cut. Using a scanning electron microscope (SEM) (manufactured by Hitachi, Ltd.), the cross section of the bubble-containing multilayer film was observed at a magnification of 10,000 times, 10 cross-sectional photographs were randomly selected, and the bubble-containing layer and other layers were The thickness was determined, and the average thickness of the bubble-containing layer and other layers was calculated.

(2) Average bubble diameter After exposing the cross section of the center part in the thickness direction of a bubble containing layer by the frozen section method, the sample was prepared so that the center part in the thickness direction of a bubble containing layer could be observed. Using a scanning electron microscope (SEM, model “S-3400N”) manufactured by Hitachi, Ltd., the obtained sample was observed, and 10 bubbles contained in the bubble-containing layer were randomly selected. The bubble diameter of the bubbles was determined, and the average bubble diameter was calculated.

(3) Thermal conductivity The obtained bubble-containing multilayer film was cut out to a diameter of 10 mm. The thermal conductivity of the bubble-containing multilayer film was measured using a thermal laser flash type thermal conductivity measuring device (manufactured by ULVAC-RIKO).

(4) Expansion ratio After exposing the cross section of the central portion in the thickness direction of the bubble-containing layer by the frozen section method, a sample was prepared so that the central portion in the thickness direction of the bubble-containing layer could be measured. The cross section of the center part in the thickness direction of the bubble-containing layer was observed using a scanning electron microscope (SEM, model “S-3400N”) manufactured by the company. Using a scanning electron microscope, the cross section was observed at a magnification of 10,000 times. The observed cross sectional area was S0 (5 μm long × 5 μm wide, 25 μm ² ), and the total S1 of the cross sectional areas of all the bubbles observed was The foaming ratio was calculated by the formula: S0 / (S0-S1).

(5) Visible light transmittance By using a method based on JIS R3106, the visible light transmittance of the obtained bubble-containing multilayer film was measured using a visible light transmittance meter ("U-4100" manufactured by Hitachi Keiki Co., Ltd.). It was measured.

  The results are shown in Table 1 below.

DESCRIPTION OF SYMBOLS 1 ... Bubble containing multilayer film 11-16 ... Bubble containing layer 21-27 ... Layer different from a bubble containing layer (other layers)
51 ... Bubble-containing multilayer film 61-73 ... Bubble-containing layer A ... Bubble

Claims (8)

It has a multilayer structure of 20 layers or more,
At least 20 layers are bubble-containing layers containing a plurality of bubbles therein, and the average bubble diameter of the bubbles is less than 200 nm,
The bubble-containing layer contains a resin;
A bubble-containing multilayer film having a visible light transmittance of 70% or more.   The bubble-containing multilayer film according to claim 1, wherein the bubble-containing layer has an expansion ratio of less than 10 times.   The bubble-containing multilayer film according to claim 1 or 2, wherein the bubble-containing layer has a thickness of less than 3 µm.   The bubble-containing multilayer film according to any one of claims 1 to 3, wherein the thickness is less than 1 mm. The bubble-containing multilayer film according to any one of claims 1 to 4 , wherein the bubble-containing layer contains a polycarbonate resin. Having another layer different from the bubble-containing layer laminated on both sides of the bubble-containing layer,
The bubble-containing layer contains a thermoplastic resin,
The other layer contains a thermoplastic resin,
The bubble according to any one of claims 1 to 4 , wherein a melt mass flow rate of the thermoplastic resin contained in the bubble-containing layer is larger than a melt mass flow rate of the thermoplastic resin contained in the other layer. Containing multilayer film. The bubble-containing multilayer film according to claim 6 , wherein the bubble-containing layer contains a polycarbonate resin. The bubble-containing multilayer film according to claim 6 or 7 , wherein the other layer contains an ethylene-vinyl acetate copolymer resin or a polystyrene resin.

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