JP6476795B2 - Laminated film - Google Patents

Description

  The present invention relates to a laminated film.

  Conventionally, optical interference that selectively reflects light of a specific wavelength by utilizing the light interference phenomenon that occurs by alternately laminating two or more materials having different refractive indexes at the layer thickness of the wavelength of light. Multilayer films are known. Such a multilayer film is commercially available for various optical applications because it can be provided with various performances by setting the refractive index, the number of layers, and the thickness of each layer to a desired optical design. ing. For example, a cold mirror, a half mirror, a laser mirror, a dichroic filter, a heat ray reflective film, a near-infrared cut filter, a single color filter, a polarizing reflection film, and the like can be given.

  When such a multilayer film is obtained by the melt extrusion method, polyethylene terephthalate or polyethylene naphthalate is used as one resin for reasons such as transparency, heat resistance, weather resistance, chemical resistance, strength, and dimensional stability. A multilayer film using a low refractive index copolymer polyester as another resin is known (Patent Documents 1 and 2). In particular, when polyethylene naphthalate is used, the refractive index difference from the low-refractive-index copolymer polyester can be increased, which is useful for obtaining a light interference multilayer film having a high reflectance.

  However, when a multilayer film of polyethylene naphthalate and a low-refractive-index copolymer polyester is obtained by melt extrusion, peeling is likely to occur at the interface between these layers. For example, it is sandwiched between two glasses via an adhesive layer. In such a case, it may not be applicable as a final product, for example, peeling at the multilayer film interface.

JP 2010-17854 A Japanese Patent No. 3901911

  An object of the present invention is to provide a laminated film that suppresses peeling of a laminated film of a layer composed mainly of polyethylene naphthalate and a layer made of another resin and thereby does not impair reflectance and transparency.

  In order to solve the problem, in the present invention, two or more layers of a layer mainly composed of polyester resin A (A layer) and a layer mainly composed of polyester resin B different from polyester resin A (B layer) are laminated. It is a laminated film, and the polyester resin A is a resin composition containing a naphthalenedicarboxylic acid residue of 90 mol% or more as a dicarboxylic acid component and an ethylene glycol residue of 90 mol% or more as a diol component. And a resin C containing at least one residue among diols having 4 or more carbon atoms, aliphatic dicarboxylic acids, and aliphatic diols, and having an internal haze of 3.0% or less. The main point is that it is a laminated film.

  According to the present invention, it is possible to suppress peeling of a laminated film of a layer composed mainly of polyethylene naphthalate and a layer made of another resin, and thereby can be applied to various uses as a light interference multilayer film without impairing reflectance and transparency. A laminated film can be obtained.

  Embodiments of the present invention will be described below, but the present invention is not construed as being limited to the embodiments including the following examples, and can achieve the object of the invention and depart from the gist of the invention. Various changes within the range not to be made are naturally possible. Further, for the purpose of simplifying the explanation, some explanations will be made taking an example of a multilayer laminated film in which two kinds of polyester resins having different optical properties are alternately laminated, but three or more kinds of polyester resins were used. The case should be understood as well.

  The laminated film of the present invention needs to be made of a polyester resin. Polyester resins are generally cheaper than thermosetting resins and photocurable resins, and can be easily and continuously formed into sheets by known melt extrusion, so that a laminated film can be obtained at low cost. It becomes possible.

  In the laminated film of the present invention, two or more kinds of polyester resins having different optical properties need to be laminated. The different optical properties referred to here mean that the refractive index is different by 0.01 or more in any of two orthogonal directions arbitrarily selected in the plane and a direction selected from the direction perpendicular to the plane. The term “alternately laminated” as used herein means that layers made of different resins are laminated in a regular arrangement in the thickness direction, for example, two polyester resins A and polyester resins having different optical properties. In the case of B, if each layer is expressed as an A layer and a B layer, they are stacked in a regular arrangement such as A (BA) n (n is a natural number). Thus, by alternately laminating resins having different optical properties, it becomes possible to reflect light of a specific wavelength specified by the relationship between the refractive index difference of each layer and the layer thickness. In addition, the higher the number of layers to be stacked, the higher the reflectance can be obtained over a wide band. Preferably it is 50 layers or more, More preferably, it is 200 layers or more. The interference reflection described above can achieve a high reflectance with respect to light in a wider wavelength band as the number of layers increases, and a laminated film having high light-cutting performance can be obtained. In addition, although there is no upper limit to the number of layers, as the number of layers increases, the manufacturing cost increases due to the increase in the size of the manufacturing apparatus, and the handling properties deteriorate due to the increase in film thickness. Within 1000 layers is the practical range.

  The laminated film of the present invention preferably has at least one reflection band having a relative reflectance of 30% or more. More preferably, it is 70% or more, More preferably, it is 80% or more. For example, by reflecting light having a wavelength of 900 to 1200 nm (about 18% of the intensity of total sunlight) slightly larger than the visible light region, it is possible to obtain a laminated film having high heat ray cutting performance. Or if it obtains the film which reflects 50% of light of visible light region (about 380-800 nm), it can apply to various uses, such as being applicable as a half mirror. Since such a film can be realized by increasing the difference in the in-plane refractive index of two or more kinds of resins having different optical characteristics, when a biaxially stretched film is formed, a layer made of a polyester resin that is crystalline; It is preferable to form a multilayer laminated film in which layers made of a low refractive index copolymerized polyester that is kept amorphous at the time of stretching or melted in a heat treatment step are alternately laminated. More preferably, it has at least one reflection band in which the relative reflectance is 30% or more in the wavelength range of 900 to 1200 nm. Sunlight has an intensity distribution mainly in the visible light region, and the intensity distribution tends to decrease as the wavelength increases. However, for use in applications where high transparency is required, high heat rays can be obtained by efficiently reflecting light having a wavelength of 900 to 1200 nm (approximately 18% of the intensity of total sunlight) slightly larger than the visible light region. Cut performance can be imparted. Preferably, the average reflectance at a wavelength of 900 to 1200 nm is 80% or more, and more preferably the average reflectance at a wavelength of 900 to 1200 nm is 90% or more. As the average reflectance at a wavelength of 900 to 1200 nm increases, high heat ray cutting performance can be imparted. Since such a film can be realized by increasing the difference in the in-plane refractive index of two or more kinds of resins having different optical characteristics, a biaxially stretched film is made of a resin made of a crystalline thermoplastic resin. And a multilayer laminated film in which amorphous layers are maintained at the time of stretching or layers made of a thermoplastic resin melted in a heat treatment step are alternately laminated.

  In the laminated film of the present invention, it is necessary that the crystalline polyester resin A contains 90 mol% or more of a naphthalenedicarboxylic acid residue as a dicarboxylic acid component and 90 mol% or more of an ethylene glycol residue as a diol component. By adopting such a configuration, the refractive index difference with the B layer using the amorphous polyester resin B can be made larger than when polyethylene terephthalate is used as the A layer, and the reflection performance is more excellent. An optical interference multilayer film can be obtained. The crystalline polyester resin A of the present invention can be obtained by polymerizing or copolymerizing 90 mol% or more of naphthalenedicarboxylic acid as a dicarboxylic acid component and 90 mol% or more of ethylene glycol as a diol component. Examples of the dicarboxylic acid component used include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid (1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid), 4,4 ′ -Diphenyldicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, adipic acid, sebacic acid, dimer acid, cyclohexanedicarboxylic acid and ester-forming derivatives thereof. Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentadiol, diethylene glycol, polyalkylene glycol, 2,2-bis (4 ′ -Β-hydroxyethoxyphenyl) propane, isosorbate, 1,4-cyclohexanedimethanol, spiroglycol, and ester-forming derivatives thereof. Among these, it is necessary to polymerize naphthalenedicarboxylic acid as the dicarboxylic acid component and ethylene glycol as the diol component, and to have a polyester resin A containing at least 90 mol% of naphthalenedicarboxylic acid and ethylene glycol residues. In addition, the layer which has the polyester resin A as a main component is made into A layer, and the main component here represents that the polyester resin A occupies 99 wt% or more among the components which comprise A layer.

  The amorphous polyester resin B used in the present invention is preferably a polyester obtained by polymerization from a monomer mainly composed of an aromatic dicarboxylic acid or aliphatic dicarboxylic acid and a diol or an ester-forming derivative thereof. It is also preferable to use a mixture of these. Here, examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenylether dicarboxylic acid, and 4,4′-diphenylsulfonedicarboxylic acid. be able to. Examples of the aliphatic dicarboxylic acid include adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexanedicarboxylic acid and ester derivatives thereof. Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentanediol. 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis (4- Hydroxyethoxyphenyl) propane, isosorbate, spiroglycol and the like. These diol components may be used alone or in combination of two or more. By setting it as such a structure, the refractive index difference of A layer and B layer can be enlarged, and the optical interference multilayer film which was more excellent in reflective performance can be obtained. In order to increase the refractive index difference from the A layer, the polyester resin B is preferably an amorphous resin. In addition, the layer which has the polyester resin B as a main component is made into B layer, and the main component here represents that the polyester resin B occupies 99 wt% or more among the components which comprise B layer.

  In the multilayer laminated film of the present invention, it is preferable that the difference in the in-plane average refractive index of layers composed of adjacent thermoplastic resins having different optical properties is 0.05 or more. More preferably, it is 0.10 or more, More preferably, it is 0.15 or more and 0.25 or less. When the difference in the in-plane average refractive index is smaller than 0.05, it becomes difficult to have a reflection band in which the relative reflectance is 30% or more. As an achievement method, the polyester resin A is crystalline, and the polyester resin B is an amorphous or a mixture of an amorphous thermoplastic resin and a crystalline thermoplastic resin. In this case, it is possible to easily provide a refractive index difference in the stretching and heat treatment steps in film production.

  The laminated film of the present invention includes a resin C containing at least one residue of a diol having 4 or more carbon atoms, a dicarboxylic acid, and an aliphatic diol as a constituent component in a layer (A layer) made of polyester resin A. It is necessary. Diols and aliphatic diols include ethylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentadiol, diethylene glycol, poly (trimethylene oxide) glycol, poly (Tetramethylene oxide) glycol, polyalkylene glycol, 2,2-bis (4′-β-hydroxyethoxyphenyl) propane, isosorbate, 1,4-cyclohexanedimethanol, spiroglycol, and ester-forming derivatives thereof. Can be mentioned. Examples of the dicarboxylic acid component include isophthalic acid, phthalic acid, naphthalenedicarboxylic acid (1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid), 4,4′-diphenyldicarboxylic acid, Examples include 4,4′-diphenylsulfone dicarboxylic acid, adipic acid, sebacic acid, dimer acid, cyclohexanedicarboxylic acid and ester-forming derivatives thereof. The resin C may be a combination of two or more. For example, a form containing at least terephthalic acid as the dicarboxylic acid and 1,4-butanediol and poly (tetramethylene oxide) glycol as the diol component is also preferable. As the resin C, a diol having 4 or more carbon atoms is particularly preferably used, and polybutylene terephthalate (also referred to as PBT) using 1,4-butanediol as the diol component and terephthalic acid as the dicarboxylic acid is preferable. It is also preferable to copolymerize an amorphous component such as poly (tetramethylene oxide) glycol as the diol component.

  In the laminated film of the present invention, it is preferable that the resin C has the above-described constituent components and the glass transition point (hereinafter also referred to as Tg) is 20 ° C. or less. By setting it as such a structure, since resin C softens at normal temperature, peeling at the interface of a layer becomes difficult to occur. In order to set the glass transition point of the resin C to 20 ° C. or less, it can be achieved by using a resin having a glass transition point of 20 ° C. or less or copolymerizing a resin C with a component having low crystallinity. This can be achieved by copolymerizing an aliphatic polyether and / or an aliphatic polyester. Aliphatic polyethers include poly (ethylene oxide) glycol, poly (propylene oxide) glycol, poly (trimethylene oxide) glycol, poly (tetramethylene oxide) glycol, poly (hexamethylene oxide) glycol, and a combination of ethylene oxide and propylene oxide. And a polymer, an ethylene oxide addition polymer of poly (propylene oxide) glycol, a copolymer glycol of ethylene oxide and tetrahydrofuran, and the like. Examples of the aliphatic polyester include poly (ε-caprolactone), polyenanthlactone, polycaprylolactone, polybutylene adipate, and polyethylene adipate. Among these, it is particularly preferable to use an ethylene oxide adduct of poly (tetramethylene oxide) glycol or poly (propylene oxide) glycol. Although there is no lower limit to the glass transition point, a practical range is −50 ° C. or more from the viewpoint of heat resistance.

  The laminated film of the present invention needs to have an internal haze of 3.0% or less. By doing in this way, it can be set as the laminated film which is transparent and reflects the light of a specific wavelength, and can apply widely also to the use as which transparency is requested | required, such as a half mirror and a heat ray reflective film. More preferably, the internal haze is 2.0% or less. In order to make an internal haze 3.0% or less, it is achieved by adjusting the kind and amount of the resin C contained in the A layer, and tends to be lower as the Tg of the resin C is higher. As the resin C, a resin containing at least one residue among diols having 4 or more carbon atoms, dicarboxylic acids, and aliphatic diols is used, and the resin C has an internal haze of 3.0% or less. Adjust the amount of. As a resin having an internal haze of 3.0% or less and a glass transition point of 20 ° C. or less, a resin obtained by copolymerizing the aliphatic polyether and / or aliphatic polyester with PBT is particularly preferably used. By adopting such a configuration, the laminated haze can be reduced in internal haze and excellent in interlayer adhesion in order to have better compatibility with the resin A than when other resins are used as the resin C. It can be.

  As an example of a combination of resins for satisfying the above conditions, in the laminated film of the present invention, the polyester resin A comprises polyethylene naphthalate, the polyester resin B is terephthalic acid as the dicarboxylic acid component, ethylene glycol as the diol component, and It includes a polyester obtained by polymerization from 1,4-cyclohexanedimethanol, and resin C contains polybutylene terephthalate. Usually, the laminate of the A layer made of the crystalline polyester resin A and the B layer made of the amorphous polyester resin B does not have sufficient adhesion between the A layer and the B layer. For example, the adhesion based on JIS K5400 Even when the test is performed, peeling is likely to occur. The peeling of the resin such as the A layer and the B layer is because the high refractive index, Young's modulus, Tg, surface energy, and SP value of the crystalline polyester resin A are different from the amorphous polyester resin B so far. However, the present inventors repeatedly investigated a single film of the polyester resin A, and paid attention to the fact that the tear strength of the polyester resin A is lower than that of other polyesters such as PET. It was discovered that the adhesion of the laminated film can be greatly improved by improving the tear strength of the film. Further, it was found that the tear strength is improved by adding a small amount of the resin C to the polyester resin A, and the interlayer adhesion of the laminated film is improved by adding the resin C. Conventional methods for improving the adhesion of the laminated film include a method in which the component of the B layer is added to the A layer, the component of the A layer is added to the B layer, or a crosslinking agent is added. However, according to these, there is a problem that the difference in refractive index between the A layer and the B layer is reduced and the reflectance is lowered, or the internal haze of the laminated film is increased to form a white surface. On the other hand, according to the technique of adding a small amount of the resin C to the crystalline polyester resin A, it is possible to suppress an increase in the internal noise without substantially changing the refractive index. The tear strength of a single film of crystalline polyester resin A is improved by adding a small amount (for example, 1% by weight) of resin C. This is because the polymer phase of resin C dispersed in layer A becomes resistance to tearing. It is considered that the tear strength is improved.

  In the laminated film of the present invention, it is necessary that the polyester resin A constituting the laminated film is a crystalline polyester resin and the polyester resin B is an amorphous polyester resin. The crystallinity here means that the heat of fusion is 5 J / g or more in differential scanning calorimetry (DSC). On the other hand, “amorphous” means that the heat of fusion is similarly less than 5 J / g. The crystalline polyester resin can have an in-plane refractive index higher than that in an amorphous state before stretching by orientation crystallization in the stretching / heat treatment step. On the other hand, in the case of an amorphous polyester resin, by performing the heat treatment at a temperature far exceeding the glass transition temperature in the heat treatment step, it is possible to completely relieve some of the orientation that occurs in the drawing step, and the low refractive index in the amorphous state. The rate can be maintained. Thus, since the refractive index difference can be easily provided between the crystalline polyester resin and the amorphous polyester resin in the stretching and heat treatment steps in the production of the film, the relative reflectance is 30% or more as described above. It is possible to have at least one reflection band. More preferably, the heat of fusion in the differential scanning calorimetry (DSC) of the crystalline polyester is preferably 20 J / g or more. In this case, since orientational crystallization can be more strongly performed in the stretching / heat treatment step, a refractive index difference from the amorphous resin polyester resin can be easily provided.

  Next, a preferred method for producing the laminated film of the present invention will be described below with reference to an example using two types of polyester resins, crystalline polyester resin A and amorphous polyester resin B. Of course, the present invention is not construed as being limited to such examples. In addition, the formation of the laminated structure of the laminated film can be realized by referring to the descriptions in [0053] to [0063] stages of JP-A No. 2007-307893.

  Prepare polyester resin in the form of pellets. The pellets are dried in hot air or under vacuum as necessary, and then supplied to a separate extruder. In the extruder, the resin melted by heating to a temperature equal to or higher than the melting point is made uniform in the amount of resin extruded by a gear pump or the like, and foreign matter or denatured resin is removed through a filter or the like. These resins are formed into a desired shape by a die and then discharged. And the sheet | seat laminated | stacked in the multilayer discharged | emitted from die | dye is extruded on cooling bodies, such as a casting drum, and is cooled and solidified, and a casting film is obtained. At this time, it is preferable to use a wire-like, tape-like, needle-like, or knife-like electrode to be brought into close contact with a cooling body such as a casting drum by an electrostatic force and rapidly solidify. Also preferred is a method in which air is blown out from a slit-like, spot-like, or planar device to be brought into close contact with a cooling body such as a casting drum and rapidly cooled and solidified, or brought into close contact with a cooling body with a nip roll and rapidly cooled and solidified.

  Moreover, when producing the laminated film which consists of a some polyester resin, several resin is sent out from a different flow path using two or more extruders, and is sent into a lamination apparatus. As the laminating apparatus, a multi-manifold die, a feed block, a static mixer, or the like can be used. Particularly, in order to efficiently obtain the configuration of the present invention, at least two members having a large number of fine slits are separately provided. It is preferred to use a feed block that contains. When such a feed block is used, since the apparatus does not become extremely large, there is little foreign matter due to thermal degradation, and high-precision lamination is possible even when the number of laminations is extremely large. Also, the stacking accuracy in the width direction is significantly improved as compared with the prior art. It is also possible to form an arbitrary layer thickness configuration. In this apparatus, since the thickness of each layer can be adjusted by the shape (length, width) of the slit, any layer thickness can be achieved.

  The molten multilayer laminate formed in the desired layer structure in this way is led to a die, and a casting film is obtained in the same manner as described above.

  The casting film thus obtained is preferably biaxially stretched. Here, biaxial stretching refers to stretching in the longitudinal direction and the width direction. Stretching may be performed sequentially in two directions or simultaneously in two directions. Further, re-stretching may be performed in the longitudinal direction and / or the width direction.

  First, the case of sequential biaxial stretching will be described. Here, stretching in the longitudinal direction refers to stretching for imparting molecular orientation in the longitudinal direction to the film, and is usually performed by a difference in peripheral speed of the roll, and this stretching may be performed in one step. Alternatively, a plurality of roll pairs may be used in multiple stages. The stretching ratio varies depending on the type of resin, but usually 2 to 15 times is preferable, and when polyethylene naphthalate is used for any of the resins constituting the laminated film, 2 to 7 times is particularly preferably used. . Moreover, as extending | stretching temperature, the range of the glass transition temperature-glass transition temperature +100 degreeC of resin which comprises a multilayer laminated film is preferable.

  The uniaxially stretched film thus obtained is subjected to surface treatment such as corona treatment, flame treatment, and plasma treatment as necessary, and then functions such as slipperiness, easy adhesion, and antistatic properties are provided. It may be applied by in-line coating.

  The stretching in the width direction refers to stretching for giving the film an orientation in the width direction. Usually, the tenter is used to convey the film while holding the both ends with clips and stretch in the width direction. The stretching ratio varies depending on the type of resin, but usually 2 to 15 times is preferable, and when polyethylene naphthalate is used for any of the resins constituting the laminated film, 2 to 7 times is particularly preferably used. . Moreover, as extending | stretching temperature, the range of the glass transition temperature of the resin which comprises a multilayer laminated film-glass transition temperature +120 degreeC is preferable.

  The biaxially stretched film is preferably subjected to a heat treatment at a temperature not lower than the stretching temperature and not higher than the melting point in the tenter in order to impart flatness and dimensional stability. By performing the heat treatment, the dimensional stability of the film is improved. After being heat-treated in this way, it is gradually cooled down uniformly, then cooled to room temperature and wound up. Moreover, you may use a relaxation process etc. together in the case of annealing from heat processing as needed.

  In the laminated film of the present invention, it is preferable that the heat treatment temperature after stretching is not higher than the melting point of the polyester resin A and not lower than the melting point of the polyester resin B. In this case, since the polyester resin A maintains a high orientation state, the orientation of the polyester resin B is relaxed, so that the refractive index difference between these resins can be easily provided.

  Next, the case of simultaneous biaxial stretching will be described. In the case of simultaneous biaxial stretching, the resulting cast film is subjected to surface treatment such as corona treatment, flame treatment, and plasma treatment as necessary, and then, such as slipperiness, easy adhesion, antistatic properties, etc. The function may be imparted by in-line coating.

  Next, the cast film is guided to a simultaneous biaxial tenter, and conveyed while holding both ends of the film with clips, and stretched in the longitudinal direction and the width direction simultaneously and / or stepwise. As simultaneous biaxial stretching machines, there are pantograph method, screw method, drive motor method, linear motor method, but it is possible to change the stretching ratio arbitrarily and drive motor method that can perform relaxation treatment at any place or A linear motor system is preferred. Although the stretching magnification varies depending on the type of resin, it is usually preferably 6 to 50 times as the area magnification. When polyethylene terephthalate is used as one of the resins constituting the multilayer laminated film, the area magnification is 8 to 30. Double is particularly preferably used. In particular, in the case of simultaneous biaxial stretching, it is preferable to make the stretching ratios in the longitudinal direction and the width direction the same and to make the stretching speeds substantially equal in order to suppress the in-plane orientation difference. Moreover, as extending | stretching temperature, the range of the glass transition temperature of the resin which comprises a multilayer laminated film-glass transition temperature +120 degreeC is preferable.

  The film thus biaxially stretched is preferably subsequently subjected to a heat treatment not less than the stretching temperature and not more than the melting point in the tenter in order to impart flatness and dimensional stability. In order to suppress the distribution of the main alignment axis in the width direction during this heat treatment, it is preferable to perform a relaxation treatment in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone. After being heat-treated in this way, it is gradually cooled down uniformly, then cooled to room temperature and wound up.

  Hereinafter, it demonstrates using the Example of the laminated | multilayer film of this invention.

[Methods for measuring physical properties and methods for evaluating effects]
The characteristic value evaluation method and the effect evaluation method are as follows.

(1) Layer thickness, number of layers, layered structure The layer structure of the film was determined by observation with a transmission electron microscope (TEM) for a sample obtained by cutting a cross section using a microtome. That is, using a transmission electron microscope H-7100FA type (manufactured by Hitachi, Ltd.), the cross section of the film was magnified 10000 to 40000 times under the condition of an acceleration voltage of 75 kV, a cross-sectional photograph was taken, the layer configuration and the thickness of each layer Was measured. In some cases, in order to obtain high contrast, a staining technique using a known RuO ₄ or OsO ₄ was used.

(2) Reflectance / Transmittance A sample cut out at 5 cm × 5 cm was subjected to reflectivity / transmittance measurement with a basic configuration using an integrating sphere attached to a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd. In the reflectance measurement, the measurement was performed using the sub-white plate of aluminum oxide attached to the apparatus as a reference. In the reflectance measurement, the sample was placed behind the integrating sphere with the longitudinal direction of the sample in the vertical direction. In the transmittance measurement, the sample was placed in front of the integrating sphere with the longitudinal direction of the sample in the vertical direction. Measurement conditions: The slit was set to 2 nm (visible) / automatic control (infrared), the gain was set to 2, the scanning speed was measured at 600 nm / min, and the reflectance at an azimuth angle of 0 degree was obtained.

(3) Refractive index It measured according to JIS K7142 (1996) A method.

(4) Heat of fusion, melting point, glass transition point A sample mass of 5 g was collected from polyester resins A and B, and a differential scanning calorimeter (DSC) was used with a robot DSC-RDC220 manufactured by Seiko Denshi Kogyo Co., Ltd. JIS-K- 7122 (1987). In the measurement, the temperature was raised from 25 ° C. to 290 ° C. at 5 ° C./min, and the integral value from the baseline in the range of melting point ± 20 ° C. at this time was defined as the heat of fusion. In addition, the melting point here is the point where the difference from the baseline of DSC is maximized. Here, a resin having a heat of fusion of 20 J / g or more is a crystalline resin, and a resin having a heat of fusion of 5 J / g or less is an amorphous resin.

(5) Structural analysis of the material constituting the multilayer laminated film The method for analyzing the structure of the material constituting the multilayer laminated film is not particularly limited, and examples thereof include the following methods. For example, first, a weight peak is confirmed by gas chromatograph mass spectrometry (GC-MS). Next, by Fourier transform infrared spectroscopy (FT-IR), the presence or absence of a peak derived from the bond between each atom of the estimated structure is confirmed. Furthermore, the position of the chemical shift derived from the position of the hydrogen atom on the structural formula and the proton absorption line area derived from the number of hydrogen atoms are confirmed by proton nuclear magnetic resonance spectroscopy (1H-NMR). It is preferable to comprehensively judge these results together.

(6) Adhesion A test was performed based on JIS K5400. Evaluation was performed based on the following criteria. ○ The above was considered as a good result.
A: There is no peeling in the eyes of all lattices.

    ○: Lattice peeling is less than 5%.

    X: The occurrence of peeling of the lattice is 5% or more.

(7) Internal haze Three points (three pieces) of a square-shaped laminated film sample having a side of 5 cm are prepared. The sample is then allowed to stand for 40 hours in a normal state (23 ° C., relative humidity 50%). Each sample was measured using a turbidimeter “NDH5000” manufactured by Nippon Denshoku Industries Co., Ltd., and the total light transmittance was measured according to JIS “Testing method of total light transmittance of plastic transparent material” (K7361-1, 1997). The haze was measured by a method according to JIS “How to Obtain Haze of Transparent Materials” (K7136 2000 version). The internal haze was measured according to JIS-K-7105. In order to remove light scattering due to the unevenness of the film surface, the internal haze was measured with the sample immersed in a quartz cell filled with liquid paraffin. The values of three points (three pieces) were averaged to obtain the internal haze value of the laminated film.

(8) Tear propagation resistance Using a light load tear tester (manufactured by Toyo Seiki Seisakusho: Model D), measured and calculated according to JIS-K7128. The number of samples was measured at 3, and the value obtained by dividing the average value of the obtained tear strength by the average value of the sample thickness was taken as the tear propagation resistance (unit: N / mm).

Example 1
GN001 which is PET obtained by copolymerizing polyethylene naphthalate (indicated as PEN (1) in the table) with an intrinsic viscosity of 0.60 and a melting point of 266 ° C. as the polyester resin A and 30 mol% of cyclohexanedimethanol as the polyester resin B Using a mixture of [Eastman Chemical] and PET [Toray] in a weight ratio of 82:18 (shown as copolymerized PET in the table), Resin C is a polybutylene terephthalate Toraycon 1200S [Toray]. The resin C used was 1% by weight added to the polyester resin A.

  The prepared polyester resin A (including resin C) and polyester resin B were melted at 290 ° C. with a vented twin-screw extruder and then fed into a 201-layer feed block via a gear pump and a filter. Merged. In addition, both surface layer parts of the laminated film were made to be the polyester resin A, and the layer thickness of the B layer made of the polyester resin B adjacent to the A layer made of the polyester resin A was made substantially the same. After merging with a 201-layer feed block, it was led to a T-die and formed into a sheet shape, and then rapidly cooled and solidified on a casting drum maintained at a surface temperature of 25 ° C. by electrostatic application to obtain a cast film. The discharge amount was adjusted so that the weight ratio of the polyester resin A and the polyester resin B was about 1: 1 so that the thickness ratio of the adjacent layers was about 1.

  The obtained cast film was heated with a roll group set at 130 ° C., and then stretched 4.5 times in the longitudinal direction while rapidly heating from both sides of the film with a radiation heater between 100 mm in the stretch zone length. Cooled down. The film temperature during stretching was 135 ° C. Subsequently, both sides of this uniaxially stretched film were subjected to corona discharge treatment in air, the wetting tension of the base film was set to 55 mN / m, and the treated surface (polyester resin having a glass transition temperature of 18 ° C.) / (Glass transition) Polyester resin having a temperature of 82 ° C.) / Laminate-forming film coating liquid composed of silica particles having an average particle diameter of 100 nm was applied to form a transparent, easy-sliding, and easy-adhesion layer.

This uniaxially stretched film was guided to a tenter, preheated with hot air at 115 ° C., and stretched 4.2 times at a temperature of 135 ° C. at a uniform stretching speed in the transverse direction. The stretched film was directly heat-treated in a tenter with hot air of 235 ° C., subsequently subjected to a relaxation treatment of 3% in the width direction at the same temperature, and then gradually cooled to room temperature and wound up. The thickness of the obtained laminated film was 40 μm.
The obtained laminated film had a flat reflectance distribution with substantially no reflection at a wavelength of 400 to 800 nm in the visible light region while reflecting light of 900 to 1200 nm. Although the internal haze value was slightly high, it was transparent and the adhesion was only slight peeling. The results are shown in Table 1.

(Example 2)
A laminated film was obtained in the same manner as in Example 1 except that Hytrel 5557 [manufactured by Toray DuPont] (Tg: −20 ° C.), which is a copolymer of PBT and polyether, was used as the resin C.

  The obtained laminated film had a flat reflectance distribution with substantially no reflection at a wavelength of 400 to 800 nm in the visible light region while reflecting light of 900 to 1200 nm. Excellent transparency and good adhesion with no peeling at all. The results are shown in Table 1.

(Example 3)
A laminated film was obtained in the same manner as in Example 2 except that a 51-layer feed block was used.

  The obtained laminated film had a flat reflectance distribution with almost no reflection at a wavelength of 400 to 800 nm in the visible light region, although the reflectance of light at 900 to 1200 nm was low. Excellent transparency and good adhesion with no peeling at all. The results are shown in Table 1.

Example 4
A laminated film was obtained in the same manner as in Example 2 except that a two-layer feed block was used.

  The obtained laminated film did not reflect light of 900 to 1200 nm, and had a flat reflectance distribution with almost no reflection even at a wavelength of 400 to 800 nm in the visible light region. Excellent transparency and good adhesion with no peeling at all. The results are shown in Table 1.

( Reference Example 5 )
A laminated film was obtained in the same manner as in Example 2 except that the amount of resin C added was changed to 2% by weight.

  The obtained laminated film had a flat reflectance distribution with substantially no reflection at a wavelength of 400 to 800 nm in the visible light region while reflecting light of 900 to 1200 nm. Although the internal haze value was slightly high, it had transparency and good adhesion with no peeling at all. The results are shown in Table 1.

( Reference Example 6 )
A laminated film was obtained in the same manner as in Example 2 except that the amount of resin C added was changed to 3% by weight.

  The obtained laminated film had a flat reflectance distribution with substantially no reflection at a wavelength of 400 to 800 nm in the visible light region while reflecting light of 900 to 1200 nm. Although the internal haze value was slightly high, it had transparency and good adhesion with no peeling at all. The results are shown in Table 1.

(Example 7)
A laminated film was obtained in the same manner as in Example 2 except that Hytrel 4047N (manufactured by Toray DuPont) (Tg: −42 ° C.), which is a copolymer of PBT and polyether, was used as the resin C.

  The obtained laminated film had a flat reflectance distribution with substantially no reflection at a wavelength of 400 to 800 nm in the visible light region while reflecting light of 900 to 1200 nm. Although the internal haze value was slightly high, it had transparency and good adhesion with no peeling at all. The results are shown in Table 1.

(Example 8)
A laminated film was obtained in the same manner as in Example 2 except that Hytrel 6347 (manufactured by Toray DuPont) (Tg: 3 ° C.), which is a copolymer of PBT and polyether, was used as the resin C.

  The obtained laminated film had a flat reflectance distribution with substantially no reflection at a wavelength of 400 to 800 nm in the visible light region while reflecting light of 900 to 1200 nm. Excellent transparency and good adhesion with no peeling at all. The results are shown in Table 1.

Example 9
A laminated film was obtained in the same manner as in Example 2 except that Hytrel 7247 (manufactured by Toray DuPont) (Tg: 12 ° C.), which is a copolymer of PBT and polyether, was used as the resin C.

  The obtained laminated film had a flat reflectance distribution with substantially no reflection at a wavelength of 400 to 800 nm in the visible light region while reflecting light of 900 to 1200 nm. Excellent transparency and good adhesion with no peeling at all. The results are shown in Table 1.

(Example 10)
A laminated film was obtained in the same manner as in Example 2 except that Hytrel 4047N (manufactured by Toray DuPont) (Tg: −42 ° C.), which is a copolymer of PBT and polyether, was used as the resin C.

  The obtained laminated film had a flat reflectance distribution with substantially no reflection at a wavelength of 400 to 800 nm in the visible light region while reflecting light of 900 to 1200 nm. It was excellent in transparency and adhesion was only slight peeling. The results are shown in Table 1.

(Example 11)
A laminated film was obtained in the same manner as in Example 2 except that copolymerized PEN (indicated in the table as PEN (2)) in which 10 mol% of terephthalic acid was copolymerized with naphthalenedicarboxylic acid was used as polyester resin A.

  The obtained laminated film had a flat reflectance distribution with substantially no reflection at a wavelength of 400 to 800 nm in the visible light region while reflecting light of 900 to 1200 nm. Excellent transparency and good adhesion with no peeling at all. The results are shown in Table 1.

(Example 12)
As polyester resin A, a copolymerized PEN (denoted as PEN (3) in the table) obtained by copolymerizing 10 mol% of terephthalic acid with respect to naphthalenedicarboxylic acid and 10 mol% of 1,4-butanediol with respect to ethylene glycol was used. A laminated film was obtained in the same manner as Example 2 except for the above.

  The obtained laminated film had a flat reflectance distribution with substantially no reflection at a wavelength of 400 to 800 nm in the visible light region while reflecting light of 900 to 1200 nm. Although the internal haze value was slightly high, it had transparency and good adhesion with no peeling at all. The results are shown in Table 1.

(Example 13)
A laminated film was obtained in the same manner as in Example 2 except that copolymerized PEN (indicated in the table as PEN (4)) in which 10 mol% of isophthalic acid was copolymerized with naphthalenedicarboxylic acid was used as polyester resin A.

  The obtained laminated film had a flat reflectance distribution with substantially no reflection at a wavelength of 400 to 800 nm in the visible light region while reflecting light of 900 to 1200 nm. Excellent transparency and good adhesion with no peeling at all. The results are shown in Table 1.

(Comparative Example 1)
A laminated film was obtained in the same manner as in Example 1 except that the resin C was not used.

  The obtained laminated film had a flat reflectance distribution with substantially no reflection at a wavelength of 400 to 800 nm in the visible light region while reflecting light of 900 to 1200 nm. Excellent transparency, but poor adhesion and peeling occurred. The results are shown in Table 1.

(Comparative Example 2)
A laminated film was obtained in the same manner as in Comparative Example 1 except that a 51-layer feed block was used.

  The obtained laminated film had a flat reflectance distribution with almost no reflection at a wavelength of 400 to 800 nm in the visible light region, although the reflectance of light at 900 to 1200 nm was low. Excellent transparency, but poor adhesion and peeling occurred. The results are shown in Table 1.

(Comparative Example 3)
A laminated film was obtained in the same manner as in Comparative Example 1 except that a two-layer feed block was used.

  The obtained laminated film did not reflect light of 900 to 1200 nm, and had a flat reflectance distribution with almost no reflection even at a wavelength of 400 to 800 nm in the visible light region. Excellent transparency, but poor adhesion and peeling occurred. The results are shown in Table 1.

(Comparative Example 4)
A laminated film was obtained in the same manner as in Example 2 except that as the polyester resin A, copolymerized PEN (indicated in the table as PEN (6)) in which 20 mol% of terephthalic acid was copolymerized with naphthalenedicarboxylic acid was used.

  The obtained laminated film had a low reflectance of 900 to 1200 nm, and had a flat reflectance distribution with almost no reflection at a wavelength of 400 to 800 nm in the visible light region. Although the internal haze value was slightly high, it had transparency and good adhesion with no peeling at all. The results are shown in Table 1.

(Comparative Example 5)
As the polyester resin A, a copolymerized PEN (indicated as PEN (7) in the table) obtained by copolymerizing 20 mol% of terephthalic acid with respect to naphthalenedicarboxylic acid and 20 mol% of 1,4-butanediol with respect to ethylene glycol was used. A laminated film was obtained in the same manner as Example 2 except for the above.

  The obtained laminated film had a low reflectance of 900 to 1200 nm, and had a flat reflectance distribution with almost no reflection at a wavelength of 400 to 800 nm in the visible light region. Although the internal haze value was slightly high, it had transparency and good adhesion with no peeling at all. The results are shown in Table 1.

(Comparative Example 6)
A laminated film was obtained in the same manner as in Example 2, except that copolymer PEN (indicated in the table as PEN (8)) obtained by copolymerizing 20 mol% of isophthalic acid with naphthalenedicarboxylic acid was used as polyester resin A.

  The obtained laminated film had a low reflectance of 900 to 1200 nm, and had a flat reflectance distribution with almost no reflection at a wavelength of 400 to 800 nm in the visible light region. Excellent transparency and good adhesion with no peeling at all. The results are shown in Table 1.

(Comparative Example 7)
A laminated film was obtained in the same manner as in Example 2 except that polystyrene 679 [manufactured by PS Japan] (shown as composition 6 in the table) having a Tg of 87 ° C. was used as the resin C.

  The obtained laminated film had high transparency while reflecting light of 900 to 1200 nm, and had a flat reflectance distribution with almost no reflection at a wavelength of 400 to 800 nm in the visible light region. . Although the internal haze value was high and the transparency was poor, the adhesion was good with no peeling at all. The results are shown in Table 1.

(Comparative Example 8)
A laminated film was obtained in the same manner as in Example 2 except that ULTEM1000 [manufactured by SABIC Innovative Plastics] (shown as composition 7 in the table), which is a polyetherimide having a Tg of 217 ° C., was used as the resin C.

  The obtained laminated film had high transparency while reflecting light of 900 to 1200 nm, and had a flat reflectance distribution with almost no reflection at a wavelength of 400 to 800 nm in the visible light region. . Excellent transparency, but poor adhesion and peeling occurred. The results are shown in Table 1.

(Comparative Example 9)
A laminated film was obtained in the same manner as in Example 2 except that Iupilon S-2000 [manufactured by Mitsubishi Engineering Plastics] (shown as composition 8 in the table), which is polycarbonate having a Tg of 130 ° C., was used as the resin C.

  The obtained laminated film had high transparency while reflecting light of 900 to 1200 nm, and had a flat reflectance distribution with almost no reflection at a wavelength of 400 to 800 nm in the visible light region. . Internal haze value was high, transparency was poor, adhesion was poor, and peeling occurred. The results are shown in Table 1. The results are shown in Table 1.

The present invention is used in various applications such as building materials, automobiles, and liquid crystal displays, and can be used as an optical film that reflects light of a specific wavelength.

Claims (6)

A laminated film in which two or more layers mainly composed of a crystalline polyester resin A (A layer) and an amorphous polyester resin B (B layer) are laminated. A is a resin composition containing a naphthalenedicarboxylic acid residue of 90 mol% or more as a dicarboxylic acid component and an ethylene glycol residue of 90 mol% or more as a diol component, and the polyester resin B is an aromatic dicarboxylic acid and a diol or an ester thereof. And a resin C containing at least one residue of a diol having 4 or more carbon atoms, a dicarboxylic acid, and an aliphatic diol as a constituent component in the layer A, A laminated film having an internal haze of 3.0% or less.   The laminated film according to claim 1, wherein the resin C has a glass transition point of 20 ° C. or lower.   The laminated film according to claim 1, wherein the laminated film has a structure in which the A layer and the B layer are alternately laminated by 50 or more layers.   The said resin C is a copolymer with PBT and / or PBT, The laminated | multilayer film in any one of Claims 1-3 characterized by the above-mentioned.   The laminated film according to any one of claims 1 to 4, which has at least one reflection band having a relative reflectance of 30% or more. The laminated film according to any one of claims 1 to 5, which has at least one reflection band having a relative reflectance of 30% or more in a wavelength range of 900 to 1200 nm.