JP2015189193A - multilayer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer film the visible light reflecting properties of which can be enhanced.SOLUTION: The multilayer film includes first and second thermoplastic resin layers. An absolute value of a difference between the inherent refractive index of the first thermoplastic resin layer and that of the second thermoplastic resin layer is 0.03 or larger. Each of the first and second thermoplastic resin layers has 250 nm or smaller thickness. A unit is formed by piling up the first thermoplastic resin layer and the second thermoplastic resin layer alternately in the thickness direction so that the number of the piled resin layers becomes 40 in total. A laminate obtained by stacking 10 units in the direction of the piled resin layers is used as the multilayer film. The thickness of the selected first or second thermoplastic resin layer in one unit is made different from that of the unselected other first or second thermoplastic resin layer in the same unit.

Description

  The present invention relates to a multilayer film in which a plurality of thermoplastic resin layers are laminated.

  Reflective materials that reflect light in a specific wavelength range, particularly visible light range, are properly used for the purpose of imparting quality such as display image visibility, illuminance, gloss, color tone, and weather resistance. The reflective material is used particularly for image display devices, lighting fixtures, recording devices, mirrors, decorative materials, and the like. A film that has high light reflectivity, is thin, and has a flat surface is used as a composite material in a state where it is laminated or coated on other members, taking advantage of the features such as wide surface area, flexibility, and workability. It has been.

  As a film having light reflectivity, a composite film obtained by forming a thin film whose main component is a metal on the surface of a film-like substrate is known. The metal thin film is formed by a technique such as painting, vapor deposition, and bonding. By forming the metal thin film, it is possible to develop reflectivity that cannot be sufficiently obtained with a base material. In this way, composite films using metal thin films as reflective layers have reduced electromagnetic wave shielding properties, reduced recyclability, reduced film forming properties, reduced deformation processability, increased weight, increased environmental impact, and high cost. There are various problems in quality and industrialization from the viewpoint of commercialization.

  On the other hand, in a multilayer resin film in which a plurality of layers mainly made of resin are laminated in the thickness direction, light reflectivity is expressed by selecting and combining materials constituting the film according to the intrinsic refractive index. be able to. Further, by alternately laminating layers formed of resins having different intrinsic refractive indexes, light reflection at the layer interface occurs in a multiple manner, and high reflectivity is obtained. In addition, since the multilayer resin film is composed only of a resin material having a certain flexibility and flexibility, it can be formed into a film and can be combined with other members by extrusion, injection, pressing and stretching. Are better. For this reason, the multilayer resin film has high utility value in terms of quality and industrialization from the viewpoints of weight reduction, large area, reduction of environmental load, and cost reduction.

  An example in which the multilayer resin film is used as an optical member is described in Patent Document 1. However, the conventional multilayer resin film tends to have a low visible light reflectance. In addition, color unevenness of reflected light occurs and the color tone deteriorates, and the obtained optical function tends to be lowered. These are mainly attributed to the layer structure constituting the film. In addition, when the optical function is prioritized, other performances such as mechanical characteristics may be deteriorated. For example, since the formed resin is rigid, the deformation followability when the film is combined with other members is low. Or the adhesion between the layers may be lowered, and the workability may be impaired.

  On the other hand, in the multilayer resin film, the light reflectance such as visible light has a thickness of the layer corresponding to the wavelength of the reflected light, unless there is a certain difference in intrinsic refractive index among the plurality of resin materials constituting the layer. Without it, it does not fully develop. Resin materials are often similar in intrinsic refractive index, and there is a problem that it is not easy to increase the intrinsic refractive index difference between alternately laminated resin layers constituting a film. Therefore, it is important how densely the laminated structure in the multilayer resin film is constructed.

  Attempts have been made to design the laminated structure in the multilayer film according to the required function. Patent Documents 2 and 3 disclose a multilayer resin film having a laminated structure having a certain structure and a certain continuous structure, and a laminated structure having a certain regularity. However, in the multilayer film having the conventional laminated structure, the visible light reflectance is not sufficient. Further, the reflectance may vary depending on the wavelength of light, and color shading may occur.

JP 2008-200701 A Japanese Patent Laid-Open No. 2004-46214 JP 2005-509179 A

  Compared with a composite film or the like having a metal thin film, the multilayer resin film tends to have a lower light reflectance such as visible light. Moreover, the conventional multilayer resin film does not have a sufficient function as an alternative to the metallic reflector. Conventionally, sufficient examination has not been made yet about the laminated structure of the multilayer resin film.

  The objective of this invention is providing the multilayer film which can improve visible light reflectivity.

  According to a wide aspect of the present invention, the apparatus includes a plurality of first thermoplastic resin layers containing a thermoplastic resin and a plurality of second thermoplastic resin layers containing a thermoplastic resin, wherein the first heat The absolute value of the difference in intrinsic refractive index between the plastic resin layer and the second thermoplastic resin layer is 0.03 or more, and the thickness per layer of the plurality of first thermoplastic resin layers is 250 nm. The thickness per layer of all of the plurality of second thermoplastic resin layers is 250 nm or less, the plurality of first thermoplastic resin layers and the plurality of second thermoplastic resin layers, 10 or more units alternately laminated in the thickness direction in total in the thickness direction have a laminate laminated in the lamination direction of the first thermoplastic resin layer and the second thermoplastic resin layer, The first thermoplastic resin layer and the second heatable layer in the laminate. The total number of layers in the thickness direction with the conductive resin layer is 400 or more, and each of the first thermoplastic resin layers included in the unit is the other first thermoplastic resin in the same unit. All of the layers are different in thickness, or each of the second thermoplastic resin layers included in the unit is different in thickness from all of the other second thermoplastic resin layers in the same unit, A multilayer film is provided.

  In a specific aspect of the multilayer film according to the present invention, at least one of the thermoplastic resin contained in the first thermoplastic resin layer and the thermoplastic resin contained in the second thermoplastic resin layer is , A polyvinyl acetal resin.

  On the specific situation with the multilayer film which concerns on this invention, the reflectance of incident light is 60% or more in incident wavelength 350nm -800nm.

  The multilayer film according to the present invention is preferably a multilayer film used as an optical film.

  According to a wide aspect of the present invention, there is provided a multilayer film manufacturing method as described above, wherein a plurality of the first thermoplastic resin layers and a plurality of the second thermoplastic resin layers are 40 layers in the thickness direction in total. By using 10 or more units alternately laminated as described above, 10 or more units are laminated in the laminating direction of the first thermoplastic resin layer and the second thermoplastic resin layer to obtain a laminate. The manufacturing method of a multilayer film which provides a multilayer film provided with the process is provided.

  A multilayer film according to the present invention includes a plurality of first thermoplastic resin layers containing a thermoplastic resin and a plurality of second thermoplastic resin layers containing a thermoplastic resin, and the first thermoplastic resin The absolute value of the difference in intrinsic refractive index between the resin layer and the second thermoplastic resin layer is 0.03 or more, and the thickness per layer of the plurality of first thermoplastic resin layers is 250 nm or less. The thickness per layer of the plurality of second thermoplastic resin layers is 250 nm or less, and the plurality of first thermoplastic resin layers and the plurality of second thermoplastic resin layers are 10 or more units alternately laminated in the thickness direction in a total of 40 layers or more have a laminated body laminated in the laminating direction of the first thermoplastic resin layer and the second thermoplastic resin layer, The first thermoplastic resin layer and the second heat in the laminate The total number of layers in the thickness direction with the plastic resin layer is 400 layers or more, and each of the first thermoplastic resin layers included in the unit is the other first thermoplastic resin in the same unit. Since all the layers are different in thickness, or each of the second thermoplastic resin layers included in the unit is different in thickness from all the other second thermoplastic resin layers in the same unit. , Visible light reflectivity can be enhanced.

FIG. 1 is a partially cutaway sectional view showing a multilayer film according to a first embodiment of the present invention. FIG. 2 is a scatter diagram showing the thickness distribution per layer in the units constituting the multilayer films obtained in Examples 1, 4, 5, 6, and 7 and Comparative Examples 2 and 6. FIG. 3 is a scatter diagram showing the thickness distribution per layer in the unit constituting the multilayer film obtained in Example 2. FIG. 4 is a scatter diagram showing the thickness distribution per layer in the unit constituting the multilayer film obtained in Example 3. FIG. 5 is a scatter diagram showing the thickness distribution per layer in the unit constituting the multilayer film obtained in Comparative Example 3. 6 is a scatter diagram showing a thickness distribution per layer in a unit constituting the multilayer film obtained in Comparative Example 4. FIG. FIG. 7 is a scatter diagram showing the thickness distribution per layer in the unit constituting the multilayer film obtained in Comparative Example 5.

  Hereinafter, the present invention will be described in detail.

[Multilayer film]
The multilayer film according to the present invention includes a plurality of first thermoplastic resin layers containing a thermoplastic resin and a plurality of second thermoplastic resin layers containing a thermoplastic resin. In the multilayer film according to the present invention, the absolute value of the difference in intrinsic refractive index between the first thermoplastic resin layer and the second thermoplastic resin layer is 0.03 or more. In the multilayer film according to the present invention, the thickness of each of the plurality of first thermoplastic resin layers is 250 nm or less. In the multilayer film according to the present invention, the thickness per layer of the plurality of second thermoplastic resin layers is 250 nm or less.

  Further, in the multilayer film according to the present invention, 10 units in which a plurality of the first thermoplastic resin layers and a plurality of the second thermoplastic resin layers are alternately laminated in the thickness direction in a total of 40 layers or more. Have more. And the multilayer film which concerns on this invention has a laminated body in which 10 or more units were laminated | stacked in the lamination direction of the said 1st thermoplastic resin layer and the said 2nd thermoplastic resin layer. As a result, in the multilayer film according to the present invention, the total number of layers in the thickness direction of the first thermoplastic resin layer and the second thermoplastic resin layer in the laminate is 400 or more. Therefore, the multilayer film according to the present invention has a multilayer structure in which a plurality of the above units are laminated, and the plurality of the first thermoplastic resin layers and the plurality of the second thermoplastic resin layers have a thickness. It has a multilayer structure that is alternately stacked in the direction.

  Further, in the multilayer film according to the present invention, each of the first thermoplastic resin layers included in the unit has a thickness different from all of the other first thermoplastic resin layers in the same unit, Or each of the said 2nd thermoplastic resin layer contained in the said unit differs in thickness from all the other said 2nd thermoplastic resin layers in the same said unit.

  Since the multilayer film which concerns on this invention is equipped with the structure mentioned above, the visible light reflectivity of a multilayer film can be improved. For this reason, since the multilayer film which concerns on this invention is excellent in the optical characteristic, it can be used suitably as an optical film.

  The intrinsic refractive indexes of the first thermoplastic resin layer and the second thermoplastic resin layer can be measured, for example, by the following method.

  The material for forming the first thermoplastic resin layer is supplied to a twin-screw extruder, melted and kneaded, introduced into a T die, widened, discharged from an opening, cooled and solidified, A thermoplastic resin sheet is obtained. A sheet piece having a width of 10 mm and a length of 30 mm is cut out at the center in the width direction of the thermoplastic resin sheet. Next, using an Abbe refractometer (ERMA "ER-7MW"), in accordance with JIS K7142, irradiating D-line (wavelength 589.3 nm) at 23 ° C, the refractive index nD of the sheet piece Is measured as the intrinsic refractive index. By the same method, the intrinsic refractive index of the second thermoplastic resin layer is measured.

  The absolute value of the difference between the intrinsic refractive index of the first thermoplastic resin layer and the intrinsic refractive index of the second thermoplastic resin layer may be 0.03 or more. The intrinsic refractive index of the first thermoplastic resin layer may be higher than the intrinsic refractive index of the second thermoplastic resin layer. The intrinsic refractive index of the second thermoplastic resin layer may be higher than the intrinsic refractive index of the first thermoplastic resin layer.

  The larger the absolute value of the difference in intrinsic refractive index, the higher the heat shielding property when the multilayer film has the same laminated structure. The absolute value of the difference between the intrinsic refractive index of the first thermoplastic resin layer and the intrinsic refractive index of the second thermoplastic resin layer is preferably 0.09 or more, more preferably 0.10 or more.

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

(First embodiment)
In FIG. 1, the multilayer film which concerns on the 1st Embodiment of this invention is typically shown with a partially notched cross-sectional view. In FIG. 1, the thickness and the number of layers of each layer are different from the actual thickness and the number of layers of each layer for convenience of illustration.

  The multilayer film 1 shown in FIG. 1 has a unit 11 in which a plurality of first thermoplastic resin layers 21 and a plurality of second thermoplastic resin layers 31 are alternately stacked in the thickness direction. In FIG. 1, the number of laminated layers in the total thickness direction of the first thermoplastic resin layer 21 and the second thermoplastic resin layer 31 per unit 11 is about 20 layers for convenience of illustration. Actually, the number of laminated layers in the thickness direction of the first thermoplastic resin layer and the second thermoplastic resin layer per unit 11 is 40 layers or more.

  The first thermoplastic resin layer 21 and the second thermoplastic resin layer 31 are laminated in the thickness direction of the multilayer film 1 and the unit 11. The composition of the plurality of first thermoplastic resin layers 21 may be the same or different. The compositions of the plurality of first thermoplastic resin layers 21 are preferably the same. The composition of the plurality of second thermoplastic resin layers 31 may be the same or different. The compositions of the plurality of second thermoplastic resin layers 31 are preferably the same.

  When the composition of the first thermoplastic resin layer is different or the composition of the second thermoplastic resin layer is different, regarding the relationship of the intrinsic refractive index, the first thermoplastic resin layer and the above The minimum value of the absolute value of the intrinsic refractive index difference with the second thermoplastic resin layer may be 0.1 or more.

  In the multilayer film 1, the plurality of first thermoplastic resin layers 21 and the plurality of second thermoplastic resin layers 31 are alternately stacked in the thickness direction. The multilayer film 1 has a portion in which the first thermoplastic resin layer 21 is sandwiched between two second thermoplastic resin layers 31. The multilayer film 1 has a portion in which a second thermoplastic resin layer 31 is sandwiched between two first thermoplastic resin layers 21. Thus, by having a multilayer structure in which the first thermoplastic resin layer 21 and the second thermoplastic resin layer 31 are alternately laminated in the thickness direction, the visible light reflectivity of the multilayer film is increased, And toughness and heat-shielding property become high.

  The multilayer film 1 includes a unit 11 (laminated resin unit) in which 40 layers of the first thermoplastic resin layer 21 and the second thermoplastic resin layer 31 are alternately laminated in the thickness direction in the thickness direction. It has the laminated body 3 laminated | stacked ten or more. In the first embodiment, the multilayer film 1 is a laminate 3. In FIG. 1, for convenience of illustration, about three units 11 are laminated, but in reality, ten or more units 11 are laminated. As a result, the first thermoplastic resin layer 21 and the second unit 11 are laminated. A total of 400 or more thermoplastic resin layers 31 are laminated in the thickness direction.

  It is not necessary that all of the first thermoplastic resin layer and the second thermoplastic resin layer laminated in total 400 layers or more are laminated alternately and continuously. If the multilayer structure in which the first thermoplastic resin layer and the second thermoplastic resin layer are alternately laminated is partially included, the visible light reflectivity of the multilayer film is increased, and the toughness and the heat shielding property are increased. Becomes higher. For example, by disposing another layer between the first thermoplastic resin layer and the second thermoplastic resin layer, the first thermoplastic resin layer and the second thermoplastic resin layer are interposed through the other layers. Even when these are laminated in the thickness direction, the effect of the present invention is obtained, and this case is also included in the present invention.

  Further, there may be a portion where the first thermoplastic resin layer is continuous, or a portion where the second thermoplastic resin layer is continuous. From the viewpoint of further enhancing the toughness and heat shielding properties of the multilayer film, all of the first thermoplastic resin layers and all of the second thermoplastic resin layers that are laminated in a total of 40 or more layers in one unit, It is preferable that the layers are alternately laminated continuously in the thickness direction. From the standpoint of further enhancing the toughness and heat shielding properties of the multilayer film, all of the first thermoplastic resin layer and all of the second thermoplastic resin layer in all the laminates in which 10 or more units are laminated. However, it is preferable that they are laminated alternately in the thickness direction.

  In the multilayer film 1 shown in FIG. 1, each of the first thermoplastic resin layers 21 included in the unit 11 is different in thickness from all the other first thermoplastic resin layers 21 in the same unit 11, and Each of the second thermoplastic resin layers 31 included in the unit 11 is different in thickness from all the other second thermoplastic resin layers 31 in the same unit 11. Each of the first thermoplastic resin layers 21 included in the unit 11 may have the same thickness as or different from all of the other second thermoplastic resin layers 31 in the same unit 11. Each of the second thermoplastic resin layers 31 included in the unit 11 may have the same thickness as or different from all of the first thermoplastic resin layers 21 in the same unit 11.

  The first thermoplastic resin layer 21 having a thickness different from that of all the other first thermoplastic resin layers 21 in the same unit 11 and the thickness and the thickness of all the other second thermoplastic resin layers 31 in the same unit 11. The total number of laminated layers with the second thermoplastic resin layers 31 having different values is preferably 40 layers or more, more preferably 80 layers or more.

  The thicknesses of the plurality of first thermoplastic resin layers 21 are different from each other and continuously change in the thickness direction. Similarly, the thicknesses of the plurality of second thermoplastic resin layers 31 are different from each other, and continuously change in the thickness direction. Thus, it is preferable that the 1st thermoplastic resin layer and 2nd thermoplastic resin layer from which thickness differs mutually are laminated | stacked. If the 1st thermoplastic resin layer from which thickness differs mutually and the 2nd thermoplastic resin layer from which thickness mutually differs are laminated | stacked, the visible light reflectivity of a multilayer film will become still higher. Since the visible light reflectivity of the multilayer film is further increased, a total of 40 or more first thermoplastic resin layers having different thicknesses and second thermoplastic resin layers having different thicknesses are laminated. It is more preferable that 70 or more layers are laminated.

  Further, since the visible light reflectivity of the multilayer film is further increased, the first thermoplastic resin layer having a thickness different from that of the one or two second thermoplastic resin layers in contact with the surface on one side or both sides; A multilayer in which one or two first thermoplastic resin layers in contact with the surface of one or both sides and a second thermoplastic resin layer having a different thickness are alternately laminated in total in the thickness direction of 40 layers or more It is preferable to have a structure portion, and it is more preferable to have a multilayer structure portion in which a total of 80 layers or more are alternately stacked in the thickness direction.

  In this case, if the second thermoplastic resin layer is in contact with only one surface of the first thermoplastic resin layer, “one or two second heats in contact with one or both surfaces. The “first thermoplastic resin layer having a thickness different from that of the thermoplastic resin layer” means “a first thermoplastic resin layer having a thickness different from that of the one second thermoplastic resin layer in contact with the surface on one side”. If the second thermoplastic resin layer is in contact with the surfaces on both sides of the first thermoplastic resin layer, then “one or two second thermoplastic resin layers in contact with one or both surfaces and the thickness. "The first thermoplastic resin layer having a different" means "a first thermoplastic resin layer having a thickness different from that of the two second thermoplastic resin layers in contact with the surfaces on both sides". The same applies to “one or two second thermoplastic resin layers in contact with one or both surfaces”.

  The shape of the plurality of units 11 stacked 10 or more may be the same or different. For example, in the multilayer film 1 shown in FIG. 1, the thicknesses of the plurality of first thermoplastic resin layers 21 and the plurality of second thermoplastic resin layers 31 constituting the unit 11 are the thicknesses of the multilayer film 1 and the unit 11. It changes continuously in the direction. In addition, there may be units in which the thicknesses of the plurality of first thermoplastic resin layers and the plurality of second thermoplastic resin layers are all the same.

  It is not necessary that all of the units stacked in total of 10 or more are stacked continuously. If there are 10 or more units 11 in which the first thermoplastic resin layers and the second thermoplastic resin layers are alternately laminated, the visible light reflectivity of the multilayer film becomes high, and the toughness and the heat shielding property become high. . For example, by preparing a plurality of units in which 40 layers of first thermoplastic resin layers and second thermoplastic resin layers are alternately and continuously stacked, and arranging other layers between the plurality of units, The effect of the present invention can be obtained even when the first thermoplastic resin layer and the second thermoplastic resin layer are laminated in the thickness direction through the other layers, and this case is also included in the present invention. Since the visible light reflectivity is effectively increased, it is preferable that 30 or more units 11 are stacked.

  Hereinafter, other details of the first thermoplastic resin layer and the second thermoplastic resin layer will be described.

(First thermoplastic resin layer and second thermoplastic resin layer)
The first thermoplastic resin layer contains a thermoplastic resin. The second thermoplastic resin layer contains a thermoplastic resin.

Thermoplastic resin:
The thermoplastic resin contained in the first thermoplastic resin layer and the thermoplastic resin contained in the second thermoplastic resin layer are the first thermoplastic resin layer and the second thermoplastic resin. The absolute value of the difference in intrinsic refractive index from the layer is appropriately selected so as to be 0.03 or more. In the first thermoplastic resin layer, only one type of the thermoplastic resin may be used, or two or more types may be used in combination. In the second thermoplastic resin layer, only one type of the thermoplastic resin may be used, or two or more types may be used in combination. The thermoplastic resin contained in the first thermoplastic resin layer and the thermoplastic resin contained in the second thermoplastic resin layer may be the same, but are preferably different.

  When the intrinsic refractive index of the first thermoplastic resin layer is 0.03 or more higher than the intrinsic refractive index of the second thermoplastic resin layer, the thermoplastic resin contained in the first thermoplastic resin layer is Polyvinyl acetal resin is preferable. In this case, the thermoplastic resin contained in the second thermoplastic resin layer is a thermoplastic resin having an intrinsic refractive index lower than that of the polyvinyl acetal resin contained in the first thermoplastic resin layer. A resin is preferred. Examples of the thermoplastic resin having an intrinsic refractive index lower than the intrinsic refractive index of the polyvinyl acetal resin included in the first thermoplastic resin layer include a fluororesin. Examples of the fluororesin include polytetrafluoroethylene.

  The thermoplastic resin contained in the first thermoplastic resin layer even when the intrinsic refractive index of the second thermoplastic resin layer is 0.03 or more higher than the intrinsic refractive index of the first thermoplastic resin layer. Is preferably a polyvinyl acetal resin. In this case, the thermoplastic resin contained in the second thermoplastic resin layer is a thermoplastic resin having an intrinsic refractive index higher than that of the polyvinyl acetal resin contained in the first thermoplastic resin layer. A resin is preferred. Examples of the thermoplastic resin having an intrinsic refractive index higher than the intrinsic refractive index of the polyvinyl acetal resin contained in the first thermoplastic resin layer include polyester resins, polycarbonate resins, polyamide resins, polyurethane resins, acrylic resins, and polystyrene resins. , Polypropylene resin, acetyl cellulose resin, polyvinyl chloride resin, and cyclic olefin resin. Polystyrene resin, polyester resin or polycarbonate resin is preferred because of its relatively high intrinsic refractive index.

  It is preferable that at least one of the thermoplastic resin contained in the first thermoplastic resin layer and the thermoplastic resin contained in the second thermoplastic resin layer is a polyvinyl acetal resin. A thermoplastic resin layer containing a polyvinyl acetal resin is excellent in adhesiveness to other layers, and is also excellent in film formability by coextrusion. In particular, a thermoplastic resin layer containing a polyvinyl acetal resin has higher adhesive strength than a metal layer and the like, and exhibits low birefringence and good optical characteristics.

  The polyvinyl acetal resin is obtained, for example, by acetalizing polyvinyl alcohol (PVA) with an aldehyde. As for the said polyvinyl acetal resin, only 1 type may be used and 2 or more types may be used together.

  The PVA can be obtained, for example, by saponifying polyvinyl acetate. The saponification degree of the PVA is generally in the range of 70 to 99.9 mol%. The degree of saponification of the PVA is preferably 80 mol% or more, preferably 99.8 mol% or less.

  The average degree of polymerization of the polyvinyl acetal resin is not particularly limited. In consideration of moldability, film formability and expression of various physical properties, the average degree of polymerization of the PVA is preferably 200 or more, more preferably 500 or more, further preferably 1700 or more, preferably 5000 or less, more preferably 3000 or less. More preferably, it is 2500 or less, and particularly preferably 2300 or less. When the average degree of polymerization is not less than the above lower limit and not more than the above upper limit, the strength of the multilayer film is further increased, and the moldability of the multilayer film, film formability, processability with glass, and the like are further enhanced.

  The average degree of polymerization of the PVA is determined by a method based on JIS K6726 “Testing method for polyvinyl alcohol”.

  The aldehyde is not particularly limited. In general, an aldehyde having 1 to 10 carbon atoms is preferably used as the aldehyde. Examples of the aldehyde having 1 to 10 carbon atoms include formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-valeraldehyde, n-hexylaldehyde, 2-ethylbutyraldehyde, benzaldehyde, and n-octyl. Examples include aldehyde, n-nonyl aldehyde, and n-decyl aldehyde. Of these, n-butyraldehyde, n-valeraldehyde or n-hexylaldehyde is preferable, and n-butyraldehyde is more preferable. As for the said aldehyde, only 1 type may be used and 2 or more types may be used together.

  The polyvinyl acetal resin may be a copolyvinyl acetal resin in which two or more aldehydes are used in combination at the time of acetalization.

  The hydroxyl group content (hydroxyl group amount) of the polyvinyl acetal resin is preferably 15 mol% or more, more preferably 18 mol% or more, preferably 40 mol% or less, more preferably 35 mol% or less. The adhesiveness of a multilayer film becomes it still higher that the content rate of the said hydroxyl group is more than the said minimum. When the content of the hydroxyl group is not more than the above upper limit, the flexibility of the multilayer film is increased and the handleability of the multilayer film is enhanced. Moreover, the intrinsic refractive index of the said thermoplastic resin layer can be made high by making high the content rate of the hydroxyl group of the said polyvinyl acetal resin.

  The content of hydroxyl groups in the polyvinyl acetal resin is a value obtained by dividing the amount of ethylene groups to which hydroxyl groups are bonded by the total amount of ethylene groups in the main chain, as a percentage (mol%). . The amount of ethylene group to which the hydroxyl group is bonded can be determined, for example, by measuring the amount of ethylene group to which the hydroxyl group of the polyvinyl acetal resin is bonded in accordance with JIS K6728 “Testing method for polyvinyl butyral”. .

  The degree of acetylation (acetyl group amount) of the polyvinyl acetal resin is preferably 0.1 mol% or more, more preferably 0.3 mol% or more, still more preferably 0.5 mol% or more, preferably 30 mol% or less. More preferably, it is 25 mol% or less, More preferably, it is 20 mol% or less, Most preferably, it is 10 mol% or less. When the acetylation degree is not less than the above lower limit, the compatibility between the polyvinyl acetal resin and the plasticizer is further enhanced. When the acetylation degree is not more than the above upper limit, the moisture resistance of the multilayer film is further increased. Moreover, the intrinsic refractive index of the said thermoplastic resin layer can be made low by making the acetylation degree of the said polyvinyl acetal resin high.

  The degree of acetylation is obtained by subtracting the amount of ethylene groups to which acetal groups are bonded and the amount of ethylene groups to which hydroxyl groups are bonded from the total amount of ethylene groups of the main chain, This is a value expressed as a percentage (mol%) of the mole fraction obtained by dividing by. The amount of ethylene group to which the acetal group is bonded can be measured, for example, according to JIS K6728 “Testing method for polyvinyl butyral”.

  The degree of acetalization of the polyvinyl acetal resin is preferably 40 mol% or more, more preferably 50 mol% or more, still more preferably 60 mol% or more, preferably 85 mol% or less, more preferably 75 mol% or less. When the degree of acetalization is not less than the above lower limit, the compatibility between the polyvinyl acetal resin and the plasticizer is further enhanced. When the degree of acetalization is less than or equal to the above upper limit, the reaction time required for producing a polyvinyl acetal resin is shortened. Moreover, the intrinsic refractive index of the said thermoplastic resin layer can be made high by making the acetalization degree of the said polyvinyl acetal resin high.

  The degree of acetalization is a value obtained by dividing the amount of ethylene groups to which acetal groups are bonded by the total amount of ethylene groups in the main chain, and expressed as a percentage (mol%).

  The degree of acetalization was determined by measuring the degree of acetylation (acetyl group content) and the hydroxyl group content (vinyl alcohol content) according to JIS K6728 “Testing methods for polyvinyl butyral”. It can be calculated by calculating the fraction and then subtracting the degree of acetylation and the hydroxyl content from 100 mol%.

  When the polyvinyl acetal resin is a polyvinyl butyral resin, the degree of acetalization (degree of butyralization) and the degree of acetylation were measured by a method according to JIS K6728 “Testing methods for polyvinyl butyral” or ASTM D1396-92. It can be calculated from the result. Measurement by a method according to ASTM D1396-92 is preferred.

  The polyvinyl acetal resin is preferably a polyvinyl butyral resin, and more preferably a polyvinyl butyral resin obtained by converting PVA into butyral with n-butyraldehyde.

Plasticizer:
When the first thermoplastic resin layer contains the polyvinyl acetal resin, the first thermoplastic resin layer preferably contains a plasticizer. When the second thermoplastic resin layer contains the polyvinyl acetal resin, the second thermoplastic resin layer preferably contains a plasticizer.

  In the said thermoplastic resin layer, the moldability of a multilayer film, a softness | flexibility, and toughness become high by adding a plasticizer to polyvinyl acetal resin. Furthermore, when the first thermoplastic resin layer contains a polyvinyl acetal resin and the intrinsic refractive index of the second thermoplastic resin layer is higher than the intrinsic refractive index of the first thermoplastic resin layer, the polyvinyl acetal resin By adding a plasticizer, the intrinsic refractive index of the first thermoplastic resin layer is lowered, and the absolute value of the difference in intrinsic refractive index between the first thermoplastic resin layer and the second thermoplastic resin layer is obtained. It is possible to obtain a multilayer film that can be further increased and has higher visible light and reflectivity. Furthermore, the visible light reflectivity of the multilayer film can be further enhanced.

  A conventionally known plasticizer can be used as the plasticizer. As for the said plasticizer, only 1 type may be used and 2 or more types may be used together.

  Examples of the plasticizer include organic ester plasticizers such as monobasic organic acid esters and polybasic organic acid esters, and phosphate plasticizers such as organic phosphate plasticizers and organic phosphorous acid plasticizers. It is done. Of these, organic ester plasticizers are preferred. The plasticizer is preferably a liquid plasticizer.

  The monobasic organic acid ester is not particularly limited. For example, a glycol ester obtained by reaction of glycol with a monobasic organic acid, and triethylene glycol or tripropylene glycol with a monobasic organic acid. Examples include esters. Examples of the glycol include triethylene glycol, tetraethylene glycol, and tripropylene glycol. Examples of the monobasic organic acid include butyric acid, isobutyric acid, caproic acid, 2-ethylbutyric acid, heptylic acid, n-octylic acid, 2-ethylhexylic acid, n-nonylic acid, and decylic acid.

  The polybasic organic acid ester is not particularly limited, and examples thereof include an ester compound of a polybasic organic acid and an alcohol having a linear or branched structure having 4 to 8 carbon atoms. Examples of the polybasic organic acid include adipic acid, sebacic acid, and azelaic acid.

  The organic ester plasticizer is not particularly limited, and triethylene glycol di-2-ethylbutyrate, triethylene glycol di-2-ethylhexanoate, triethylene glycol dicaprylate, triethylene glycol di-n- Octanoate, triethylene glycol di-n-heptanoate, tetraethylene glycol di-n-heptanoate, dibutyl sebacate, dioctyl azelate, dibutyl carbitol adipate, ethylene glycol di-2-ethyl butyrate, 1,3-propylene glycol di 2-ethyl butyrate, 1,4-butylene glycol di-2-ethyl butyrate, diethylene glycol di-2-ethyl butyrate, diethylene glycol di-2-ethyl hexanoate, dipropylene glycol Di-2-ethylbutyrate, triethylene glycol di-2-ethylpentanoate, tetraethylene glycol di-2-ethylbutyrate, diethylene glycol dicaprylate, dihexyl adipate, dioctyl adipate, hexylcyclohexyl adipate, adipine Examples include a mixture of heptyl acid and nonyl adipate, diisononyl adipate, diisodecyl adipate, heptylnonyl adipate, dibutyl sebacate, oil-modified sebacic acid alkyd, and a mixture of phosphate ester and adipic acid ester. Organic ester plasticizers other than these may be used. Other adipic acid esters other than the above-mentioned adipic acid esters may be used.

  The organophosphate plasticizer is not particularly limited, and examples thereof include tributoxyethyl phosphate, isodecylphenyl phosphate, triisopropyl phosphate, and the like.

  The plasticizer preferably includes a diester plasticizer represented by the following formula (1). By using this diester plasticizer, the sound insulation of the laminated glass is further enhanced.

  In said formula (1), R1 and R2 respectively represent a C5-C10 organic group, R3 represents an ethylene group, an isopropylene group, or n-propylene group, p represents the integer of 3-10. . R1 and R2 in the above formula (1) are each preferably an organic group having 6 to 10 carbon atoms.

  The plasticizer preferably contains at least one of triethylene glycol di-2-ethylhexanoate (3GO) and triethylene glycol di-2-ethylbutyrate (3GH). More preferably, it contains 2-ethylhexanoate.

  In the thermoplastic resin layer containing the polyvinyl acetal resin and the plasticizer, the content of the plasticizer contained in the thermoplastic resin layer is 100 parts by mass of the polyvinyl acetal resin contained in the thermoplastic resin layer. Preferably it is 20 mass parts or more, More preferably, it is 30 mass parts or more, Preferably it is 100 mass parts or less, More preferably, it is 80 mass parts or less, More preferably, it is 60 mass parts or less. When the content of the plasticizer is not less than the above lower limit, the plasticizing effect of the polyvinyl acetal resin is further increased, and the moldability of the multilayer film is further enhanced. When the content of the plasticizer is not more than the above upper limit, the plasticizer bleed-out hardly occurs, and the adhesiveness of the multilayer film is further enhanced.

Other ingredients:
The first thermoplastic resin layer and the second thermoplastic resin layer are each provided with an antioxidant (anti-aging agent), a heat stabilizer, a light stabilizer, an ultraviolet absorber, and an adhesive force adjuster, as necessary. Further, it may contain various additives such as a moisture proofing agent, a lubricant, a colorant, a heat ray reflective agent, a heat ray absorbent, an antistatic agent and a flame retardant. As for the said additive, only 1 type may be used and 2 or more types may be used together.

(Other details of multilayer film)
The method for producing the multilayer film uses 10 or more units in which a plurality of the first thermoplastic resin layers and a plurality of the second thermoplastic resin layers are alternately laminated in the thickness direction for a total of 40 layers or more. And it is preferable to provide the process of obtaining a laminated body by laminating | stacking 10 or more of the said units in the lamination direction of a said 1st thermoplastic resin layer and a said 2nd thermoplastic resin layer.

  The manufacturing method of the said multilayer film is not specifically limited, A conventionally well-known method can be used. For example, a material for forming a thermoplastic resin layer is supplied to an extruder, melted and kneaded, extruded from a mold attached to the tip of the extruder into a film, and then subjected to an electrostatic printing cast method, a touch roll It is possible to use a melt extrusion method in which a film is cooled and solidified on a cooling roll and formed into a long film by an air knife casting method. In addition, after casting a solution in which the material for forming the thermoplastic resin layer is dissolved in an organic solvent onto a drum or an endless belt, the organic solvent is evaporated to obtain a long film. A forming method such as a solution casting method for forming a film can be used. The melt extrusion method is preferred because it is easy to manufacture and has low manufacturing costs.

  The method for producing the multilayer film is a method for producing a multilayer film in which a plurality of the first thermoplastic resins and a plurality of the second thermoplastic resin layers are laminated in the thickness direction, and the thermoplastic resin is melted. A first step of melt-kneading by an extrusion method, extending the lamination, forming into a film shape, and obtaining a molten resin laminate (hereinafter sometimes abbreviated as a resin laminate), and the molten resin laminate Is discharged from the die opening and cooled by a cooling roll to obtain a multilayer film, and a second step of obtaining a multilayer film.

  The first step is a step of obtaining a molten resin laminate by melt-kneading a thermoplastic resin by a melt-extrusion method and then laminating and then expanding, or forming and forming a film by laminating after expansion. It is.

  With respect to the melt extrusion method, since the die lip opening needs to be elongated in order to form a film, the T-die forming method is preferable. In the T-die molding method, the T die is provided with a resin inflow portion and a manifold. The manifold is longer in the width direction than the resin inflow portion, and has a structure connected to the resin inflow portion. The resin supplied from the resin inflow portion flows so as to expand in the width direction within the manifold, and is then transported to the lip land at the die opening.

  Examples of the melt extrusion method include a melt extrusion method in which a material for forming a thermoplastic resin layer is formed into a film and laminated to form a resin laminate. Examples of the melt extrusion method include a co-extrusion method. The co-extrusion method is a method in which a plurality of materials are extruded from individual molding machines in a molten state, introduced into a mold, and laminated in a molten state inside and outside the mold. The co-extrusion method is roughly classified into several types such as a feed block method, a multi-manifold method, a multi-slot die method, and a static mixer method, depending on the timing at which the extruded materials are laminated and the forming accuracy. From the viewpoint of laminating many thermoplastic resin layers with high accuracy, the above feed block method is preferable.

  In the above feed block method, two or more kinds of materials are laminated in the resin inflow part, supplied to the flat die manifold, and expanded in the width direction while maintaining the laminated state in the manifold, and laminated from the die lip opening. This is a method of discharging. In the above feed block method, there is no need to provide a manifold for each thermoplastic resin layer to be laminated, so the flat die structure can be simplified compared to other methods, and therefore the operability and maintainability are improved. Excellent.

  The feed block mainly includes a plurality of upstream channels, a merging portion, and a downstream channel. A plurality of materials flowing from the upstream flow path are divided by introducing the material (resin) into the plurality of flow paths at the junction in the feed block, and the divided materials are alternately stacked. Next, the flow paths are alternately arranged and merged in a laminated state in the thickness direction, and the merged laminated body is flowed from the downstream flow path to the downstream flow path adapter, flat die or the like to form a laminated structure. .

  The thickness per layer of the plurality of first thermoplastic resin layers contained in the multilayer film is 250 nm or less, preferably 200 nm or less. The thickness per layer of all of the plurality of first thermoplastic resin layers contained in the multilayer film is preferably 50 nm or more, more preferably 80 nm or more. Furthermore, the thickness per layer of the plurality of second thermoplastic resin layers contained in the multilayer film is 250 nm or less, preferably 200 nm or less. The thickness of all the second thermoplastic resin layers contained in the multilayer film is preferably 50 nm or more, more preferably 80 nm or more. When the thickness per layer of the first thermoplastic resin layer and the second thermoplastic resin layer is not more than the upper limit, visible light and infrared rays are converted into wavelengths by the multilayer structure existing in the multilayer film. Accordingly, it becomes possible to reflect selectively, and a multilayer film that is more excellent in visible light reflectivity and heat shielding property can be obtained.

  In the multilayer film, the thickness per layer of all of the plurality of first thermoplastic resin layers is 250 nm or less, and the thickness per layer of all of the plurality of second thermoplastic resin layers is 250 nm or less. More preferably, there are 40 or more total first and second thermoplastic resin layers having different thicknesses and second thermoplastic resin layers having different thicknesses. In this preferable multilayer film, since the thicknesses of the first thermoplastic resin layer and the second thermoplastic resin layer constituting the multilayer film are different from each other, reflection characteristics with respect to a wide range of light wavelengths are exhibited, and particularly visible light is generated. It becomes possible to reflect strongly, and the multilayer film which was further excellent by visible light reflectivity is obtained.

  In order to make the thicknesses of the first thermoplastic resin layer and the second thermoplastic resin layer different from each other, there may be 40 or more resin flow paths in the merging portion in the feed block, and the widths of the resin flow paths may be different from each other. preferable. The ratio of the channel widths corresponds to the layer thickness ratio in the resulting multilayer film. Therefore, the channel width is appropriately set according to the desired layer thickness and optical characteristics.

  It is preferable that ten or more of the above units are laminated with the molten resin laminate as a unit. The method for laminating 10 or more units is not particularly limited, and for example, a method using a multi-layer block can be mentioned. As the multi-layer block, the resin laminate obtained by joining in the feed block is in a direction perpendicular to the surface of the resin laminate and parallel to the flow direction of the resin laminate during production, By stacking the divided resin laminate again in the thickness direction and repeating this, a flow path block capable of obtaining a resin laminate having more layers can be used.

  When using the above coextrusion method, the composition of the material forming the thermoplastic resin layer, the type of thermoplastic resin contained in the material, the thickness and film width of the target layer, the molding environment and operability, etc. The equipment specifications, methods and conditions can be selected as appropriate.

  When the said thermoplastic resin is an amorphous thermoplastic resin, let the glass transition temperature of an amorphous thermoplastic resin be Tg. In the step (1), the temperature at which the material for forming the thermoplastic resin layer is melt-kneaded is preferably (Tg + 50) or higher, preferably (Tg + 200) ° C. or lower. By melt-kneading at the above temperature, the resin fluidity at the time of extrusion molding becomes good, and a multilayer film excellent in dimensional accuracy such as thickness and length can be obtained.

  The Tg is a glass transition temperature at the time of final temperature rise measured using a differential scanning calorimeter (“DSC2920 Modulated DSC” manufactured by TA Instruments) under the following temperature program conditions.

Temperature program conditions:
The temperature is raised from room temperature (23 ° C.) to 50 ° C. at a rate of 10 ° C./min and held at 50 ° C. for 5 minutes. The temperature is raised from 50 ° C. to 200 ° C. at 10 ° C./min and held at 200 ° C. for 5 minutes. The temperature is lowered from 200 ° C. to −50 ° C. at 10 ° C./min, and held at −50 ° C. for 5 minutes. The temperature is raised from −50 ° C. to 200 ° C. at 10 ° C./min and held at 200 ° C. for 5 minutes.

  The molten resin laminate is formed by the first step described above.

  The first step is a step of discharging the molten resin laminate from a die opening and cooling with a cooling roll to obtain a multilayer film. Although it does not specifically limit as a method of cooling the said molten resin laminated body with the said cooling roll, The electrostatic printing cast method, the touch roll method, and the air knife cast method are mentioned. In the second step, the resin laminate is cooled and solidified on a cooling roll and formed into a long multilayer film.

  In the second step, the molten resin laminate is rapidly cooled to form a multilayer film and to obtain a multilayer film having substantially no molecular orientation. When the said thermoplastic resin is an amorphous thermoplastic resin, let the glass transition temperature of an amorphous thermoplastic resin be Tg. The surface temperature of the cooling roll is preferably (Tg−150) ° C. or higher, preferably (Tg) ° C. or lower.

  The laminated body and the multilayer film are formed by the second step described above.

  The total number of layers in the thickness direction of the first thermoplastic resin layer and the second thermoplastic resin layer of the multilayer film is 400 layers or more. When the number of laminated layers is 400 or more, the number of layer interfaces that contribute to the reflection of visible light is increased, and thus the visible light reflectivity of the laminated glass is further increased, and the visible light reflectivity is further improved. A multilayer film is obtained. From the viewpoint of expressing these performances more satisfactorily, the total number of laminated layers in the thickness direction of the first thermoplastic resin layer and the second thermoplastic resin layer is preferably 500 layers or more, more preferably 550 layers or more, more preferably 650 layers or more.

  The thickness of the multilayer film is not particularly limited. The thickness of the multilayer film is practically preferably 0.02 mm or more, more preferably 0.04 mm or more, preferably 3 mm or less, more preferably 0.8 mm or less. When the thickness of the multilayer film is not less than the above lower limit and not more than the above upper limit, the visible light reflectivity of the multilayer film is further increased, the mechanical strength is increased, and the durability due to long-term use is enhanced.

  The reflectance of the incident light of the multilayer film is preferably 60% or more, more preferably 70% or more at an incident wavelength of 350 to 800 nm. When the reflectance of the incident light of the multilayer film is not less than the above lower limit, the visible light reflectivity of the multilayer film is further improved, and a multilayer film that is more excellent in visible light reflectivity is obtained.

  The method for measuring the reflectance of the incident light is not particularly limited, but is preferably measured according to the following procedure. After polishing the surface of the resulting multilayer film with # 400 sandpaper, a black paint is applied to obtain a measurement piece. Using “U-4100” manufactured by Hitachi High-Technology Corporation, light having a wavelength of 350 to 2500 nm is incident at an incident angle of 5 ° from the non-polished surface of the measurement piece, and the reflectance is measured at a wavelength of 1 nm. The average value of the measurement data at a wavelength of 350 to 800 nm calculated from the obtained reflectance data is taken as the reflectance.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited only to the following examples.

(Example 1)
100 parts by mass of polyvinyl butyral resin (average polymerization degree 1700, hydroxyl group content 30.3 mol%, acetylation degree 0.7 mol%, butyralization degree 69 mol%) and triethylene glycol di-diene which is a plasticizer 40 parts by mass of 2-ethylhesanoate and an amount in which the amount of magnesium is 50 ppm in a multilayer film from which a mixture having a 1: 1 mass ratio of magnesium acetate / 2-ethylbutyrate as an adhesive force regulator is obtained. It supplied to the twin-screw type extruder I, and melt-kneaded, and the material (intrinsic refractive index = 1.4809) for forming a 1st thermoplastic resin layer was obtained.

  At the same time, polystyrene resin (“Toyostyrene, HRM26” manufactured by Toyo Styrene Co., Ltd., intrinsic refractive index = 1.5910) was added to the twin-screw extruder I (cylinder diameter D = 30 mm, L / D = 45) and melt-kneaded to obtain a material for forming the second thermoplastic resin layer.

  The material for forming the first thermoplastic resin layer and the material for forming the second thermoplastic resin layer are each described as a 40-layer feed block (hereinafter referred to as “FB”) through a feed pipe. The resin laminate was obtained by joining them in the FB.

  The merged first thermoplastic resin layer has 20 layers, the merged second thermoplastic resin layer has 20 layers, and the first thermoplastic resin layer 20 and the second thermoplastic resin layer A total of 40 layers of 20 thermoplastic resin layers were alternately laminated in the thickness direction to prepare a resin laminate.

  Furthermore, a total of 5 sets of multi-layer blocks that can be divided into two layers can be attached to the downstream portion of the FB, and the total number of layers can be increased by stacking 32 resin laminates (number of layers 40) in the thickness direction. Was introduced into a T-die as a 1280 layer, widened, and discharged from a die lip opening to obtain a molten resin laminate. The T die was provided with a straight manifold, the die lip opening was rectangular, the longitudinal width was 1500 mm, and the width in the direction perpendicular to the longitudinal direction was 2.5 mm.

  The molten resin laminate is melt-extruded at a take-up speed of 10 m / min onto a cooling roll that is chrome-plated and temperature-adjusted to 20 ° C. from the die lip opening of the T die, and is cooled and solidified to be continuously in a sheet form. A film was formed. In the slit process, the film end was removed by slitting with a shear blade installed symmetrically from the film center. The film was wound in a roll shape around a vinyl chloride resin core with a winding tension of 70 N / m width. In this way, a multilayer film having an average thickness in the width direction of 90 μm was produced.

  The obtained multilayer film has a flow path shape and a resin in the FB so that the thicknesses of the first thermoplastic resin layer and the second thermoplastic resin layer in the unit are the thicknesses shown in FIG. Thirty-two units obtained by adjusting the extrusion amount are stacked in the thickness direction.

(Example 2)
Adjust the flow path shape and resin extrusion amount in the FB so that the thickness of each layer of the first thermoplastic resin layer and the second thermoplastic resin layer in the unit is the thickness shown in FIG. A multilayer film having an average thickness in the width direction of 90 μm was obtained in the same manner as in Example 1 except that the unit was obtained.

  The obtained multilayer film has a flow path shape and a resin in the FB so that the thicknesses of the first thermoplastic resin layer and the second thermoplastic resin layer in the unit are as shown in FIG. Thirty-two units obtained by adjusting the extrusion amount are stacked in the thickness direction.

(Example 3)
The number of merged first thermoplastic resin layers is 40, the number of merged second thermoplastic resin layers is 40, and the first thermoplastic resin layer 40 and the second A unit was formed by alternately stacking 80 thermoplastic resin layers in the thickness direction, and a total of 5 sets of multilayer blocks were attached, and 32 resin laminates (80 layers) in the thickness direction were attached. A multilayer film having an average thickness in the width direction of 182 μm was obtained in the same manner as in Example 1 except that the total number of laminated layers was changed to 2560 by laminating.

  The obtained multilayer film has a flow path shape and a resin in the FB so that the thicknesses of the first thermoplastic resin layer and the second thermoplastic resin layer in the unit are as shown in FIG. Thirty-two units obtained by adjusting the extrusion amount are stacked in the thickness direction.

Example 4
A total of 4 sets of multi-layer blocks are attached, and the width of the resin laminate (40 layers) is laminated in the thickness direction by laminating 16 pieces in the thickness direction, so that the total number of layers is changed to 640 layers. A multilayer film having an average thickness in the direction of 45 μm was obtained.

  The obtained multilayer film has a flow path shape and a resin in the FB so that the thicknesses of the first thermoplastic resin layer and the second thermoplastic resin layer in the unit are the thicknesses shown in FIG. Sixteen units obtained by adjusting the extrusion amount are stacked in the thickness direction.

(Example 5)
Example 1 except that the polystyrene resin used for the material for forming the second thermoplastic resin layer was changed to a polycarbonate resin (“Panlite 1225L” manufactured by Teijin Chemicals Ltd., intrinsic refractive index = 1.951). Similarly, a multilayer film was obtained.

  The obtained multilayer film has a flow path shape and a resin in the FB so that the thicknesses of the first thermoplastic resin layer and the second thermoplastic resin layer in the unit are the thicknesses shown in FIG. Thirty-two units obtained by adjusting the extrusion amount are stacked in the thickness direction.

(Example 6)
Example 1 except that the polystyrene resin used as the material for forming the second thermoplastic resin layer was changed to a polyester resin (EASTMAN Chemical Co., Ltd. “EASTER, GN001, intrinsic refractive index = 1.5726”). In the same manner, a multilayer film was obtained.

  The obtained multilayer film has a flow path shape and a resin in the FB so that the thicknesses of the first thermoplastic resin layer and the second thermoplastic resin layer in the unit are the thicknesses shown in FIG. Thirty-two units obtained by adjusting the extrusion amount are stacked in the thickness direction.

(Example 7)
The polyvinyl butyral resin used as a material for forming the first thermoplastic resin layer was changed to a polymethyl methacrylate resin (manufactured by Kuraray Co., Ltd., trade name “Parapet HR-L, intrinsic refractive index = 1.4902”). A multilayer film was obtained in the same manner as in Example 1 except that the intrinsic refractive index of the material for forming the first thermoplastic resin layer was changed to 1.4902.

  The obtained multilayer film has a flow path shape and a resin in the FB so that the thicknesses of the first thermoplastic resin layer and the second thermoplastic resin layer in the unit are the thicknesses shown in FIG. Thirty-two units obtained by adjusting the extrusion amount are stacked in the thickness direction.

(Comparative Example 1)
A multilayer having an average thickness of 95 μm in the width direction in the same manner as in Example 1 except that the extruder II, FB and the multilayer block were not used and only the extruder I was used to obtain a single-layer multilayer film. A film was prepared.

(Comparative Example 2)
A total of 3 sets of multilayer blocks were attached, and the width of the resin laminate (40 layers) was laminated in the thickness direction by laminating 8 pieces in the thickness direction to change the total number of layers to 320 layers. A multilayer film having an average thickness in the direction of 90 μm was obtained.

  The obtained multilayer film has a flow path shape and a resin in the FB so that the thicknesses of the first thermoplastic resin layer and the second thermoplastic resin layer in the unit are the thicknesses shown in FIG. Eight units obtained by adjusting the extrusion amount are stacked in the thickness direction.

(Comparative Example 3)
A unit is obtained by adjusting the flow path shape and the resin extrusion amount in the FB so that the thicknesses of the first thermoplastic resin layer and the second thermoplastic resin layer are the thicknesses shown in FIG. A multilayer film having an average thickness in the width direction of 45 μm was obtained in the same manner as in Example 1 except that.

  The obtained multilayer film has the flow path shape and resin in the FB so that the thicknesses of the first thermoplastic resin layer and the second thermoplastic resin layer in the unit are as shown in FIG. Thirty-two units obtained by adjusting the extrusion amount are stacked in the thickness direction.

(Comparative Example 4)
The merged first thermoplastic resin layer has 10 layers, the merged second thermoplastic resin layer has 10 layers, and the first thermoplastic resin layer 10 and the second thermoplastic resin layer A unit was formed by laminating a total of 20 layers of 10 thermoplastic resin layers alternately in the thickness direction, and a total of 5 sets of multi-layer blocks were attached, and 32 resin laminates (20 layers) in the thickness direction. A multilayer film having an average thickness in the width direction of 48 μm was obtained in the same manner as in Example 1 except that the total number of layers was changed to 640 by laminating.

  The obtained multilayer film has a flow path shape and a resin in the FB so that the thicknesses of the first thermoplastic resin layer and the second thermoplastic resin layer in the unit are as shown in FIG. Thirty-two units obtained by adjusting the extrusion amount are stacked in the thickness direction.

(Comparative Example 5)
A total of 5 sets of multi-layer blocks were attached, and the width of the resin laminate (40 layers) was laminated in the thickness direction, so that the total number of laminated layers was changed to 1280 layers. A multilayer film having an average thickness in the direction of 90 μm was obtained.

  The obtained multilayer film has a flow path shape and a resin in the FB so that the thicknesses of the first thermoplastic resin layer and the second thermoplastic resin layer in the unit are the thicknesses shown in FIG. Thirty-two units obtained by adjusting the extrusion amount are stacked in the thickness direction.

(Comparative Example 6)
Example except that the polystyrene resin used for the material for forming the second thermoplastic resin layer was changed to a polymethyl methacrylate resin (“Parapet HR-L, intrinsic refractive index = 1.4902” manufactured by Kuraray Co., Ltd.) In the same manner as in Example 1, a multilayer film was obtained.

  The obtained multilayer film has a flow path shape and a resin in the FB so that the thicknesses of the first thermoplastic resin layer and the second thermoplastic resin layer in the unit are the thicknesses shown in FIG. Thirty-two units obtained by adjusting the extrusion amount are stacked in the thickness direction.

(Evaluation)
The intrinsic refractive index of the first thermoplastic resin layer, the intrinsic refractive index of the second thermoplastic resin layer, the thickness of the first thermoplastic resin layer in the unit, the thickness of the second thermoplastic resin layer in the unit, and The evaluation method of the reflectance is as follows.

(1) Intrinsic Refractive Index A material for forming the first thermoplastic resin layer is supplied to a twin screw extruder, melted and kneaded, introduced into a T die, widened, and discharged from an opening. It was melt-extruded at a take-up speed of 10 m / min on a cooling roll that had been chrome-plated and temperature-adjusted to 20 ° C., and was cooled and solidified to obtain a sheet-like thermoplastic resin sheet. A sheet piece having a width of 10 mm and a length of 30 mm was cut out from the central portion in the width direction of the obtained thermoplastic resin sheet. Using an Abbe refractometer (ERMA "ER-7MW"), the refractive index nD of the sheet piece is measured by irradiating the D-line (wavelength 589.3 nm) at 23 ° C in accordance with JIS K7142. The intrinsic refractive index of the first thermoplastic resin layer was used. Further, the intrinsic refractive index of the second thermoplastic resin layer was measured by the same method.

(2) The number of layers per unit of multilayer film and the thickness per layer per unit The central portion in the width direction of the multilayer film is cut parallel to the longitudinal direction by a microtome, and the cross section of the multilayer film is exposed. I let you. The cross section was observed using a scanning electron microscope (SEM) (“S-4800” manufactured by Hitachi, Ltd.) or a digital microscope (“VHX-200” manufactured by Keyence Co., Ltd.), and an image was taken. An enlarged image of the center of the direction was obtained.

  From the obtained image, the number of all the layers present in the cross section (the number of stacked layers) was evaluated.

  In addition, an arbitrary unit is selected from the obtained images, the thicknesses of all the layers in the unit are measured using the measurement function attached to the SEM or the digital microscope, and the obtained measurement values are scattered. Plotted on the figure according to the stacking order in the above units to obtain the unit thickness distribution (FIGS. 2 to 7), and the maximum and minimum layer thicknesses in the unit are shown in Table 1 below. In addition, in cross-sectional observation and image capturing, the SEM was used in Examples 1 to 7 and Comparative Examples 3 to 6, and the microscope was used in Comparative Examples 1 and 2.

(3) Visible light reflectance After the surface of the obtained multilayer film was polished with # 400 sandpaper, a black paint was applied to obtain a measurement piece. Using “U-4100” manufactured by Hitachi High-Technology Corporation, light having a wavelength of 350 to 2500 nm was incident at an incident angle of 5 ° from the non-polished surface of the measurement piece, and the reflectance was measured at a wavelength of 1 nm. The average value of the measurement data at wavelengths of 350 to 800 nm calculated from the obtained reflectance data was taken as the visible light reflectance.

  Details and results are shown in Table 1 below. In Table 1 below, “PVB” indicates a polyvinyl butyral resin, “PS” indicates a polystyrene resin, “PC” indicates a polycarbonate resin, “PES” indicates a polyester resin, and “PMMA” indicates polymethyl. Methacrylate resin is shown.

DESCRIPTION OF SYMBOLS 1 ... Multilayer film 3 ... Laminate 11 ... Unit 21 ... 1st thermoplastic resin layer 31 ... 2nd thermoplastic resin layer

Claims (5)

A plurality of first thermoplastic resin layers containing a thermoplastic resin, and a plurality of second thermoplastic resin layers containing a thermoplastic resin,
The absolute value of the difference in intrinsic refractive index between the first thermoplastic resin layer and the second thermoplastic resin layer is 0.03 or more;
The thickness per one of the plurality of first thermoplastic resin layers is 250 nm or less,
The thickness per one of the plurality of second thermoplastic resin layers is 250 nm or less,
Ten or more units in which a plurality of the first thermoplastic resin layers and a plurality of the second thermoplastic resin layers are alternately laminated in a thickness direction in a total of 40 layers or more are the first thermoplastic resin layers. And in the total thickness direction of the first thermoplastic resin layer and the second thermoplastic resin layer in the laminate, the laminate laminated in the lamination direction of the second thermoplastic resin layer. The number of layers is 400 or more,
Each of the first thermoplastic resin layers included in the unit has a thickness different from all of the other first thermoplastic resin layers in the same unit, or the second thermoplastic resin layer included in the unit. Each of the thermoplastic resin layers is a multilayer film having a thickness different from all of the other second thermoplastic resin layers in the same unit.   2. The at least one of the thermoplastic resin contained in the first thermoplastic resin layer and the thermoplastic resin contained in the second thermoplastic resin layer is a polyvinyl acetal resin. Multilayer film.   The multilayer film according to claim 1 or 2, wherein the reflectance of incident light is 60% or more at an incident wavelength of 350 nm to 800 nm.   The multilayer film according to any one of claims 1 to 3, which is a multilayer film used as an optical film. A method for producing a multilayer film according to any one of claims 1 to 4,
Using ten or more units in which a plurality of the first thermoplastic resin layers and a plurality of the second thermoplastic resin layers are alternately laminated in the thickness direction in a total of 40 layers or more,
A step of obtaining a laminate by laminating 10 or more units in the laminating direction of the first thermoplastic resin layer and the second thermoplastic resin layer,
A plurality of first thermoplastic resin layers containing a thermoplastic resin, and a plurality of second thermoplastic resin layers containing a thermoplastic resin, the first thermoplastic resin layer and the second heat The absolute value of the difference in intrinsic refractive index from the plastic resin layer is 0.03 or more, the thickness of all of the plurality of first thermoplastic resin layers is 250 nm or less, and the plurality of second The thickness per layer of all the thermoplastic resin layers is 250 nm or less, and the plurality of the first thermoplastic resin layers and the plurality of the second thermoplastic resin layers are 40 layers or more in the thickness direction in total. The alternately laminated units have a laminated body in which 10 or more are laminated in the laminating direction of the first thermoplastic resin layer and the second thermoplastic resin layer, and the first heat in the laminated body. Total thickness of the plastic resin layer and the second thermoplastic resin layer The number of laminated layers is 400 or more, and each of the first thermoplastic resin layers included in the unit has a thickness different from all of the other first thermoplastic resin layers in the same unit, Alternatively, each of the second thermoplastic resin layers included in the unit obtains a multilayer film having a thickness different from all of the other second thermoplastic resin layers in the same unit. .

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