JP6992259B2 - Laminated film and its manufacturing method - Google Patents

Description

The present invention relates to a laminated film and a method for producing the same.

Thermoplastic resin films, especially biaxially stretched polyester films, have excellent mechanical properties, electrical properties, dimensional stability, transparency, chemical resistance, etc., and are therefore used in many magnetic recording materials and packaging materials. It is widely used as a base film in the above applications.

On the other hand, as the polyester film, a laminated film in which different resins are alternately laminated is used. Such a laminated film can be a film having a unique function that cannot be obtained with a single-layer film. For example, a tear-resistant film having increased tear strength (see Patent Document 1) and infrared rays can be used. Examples thereof include an infrared reflective film that reflects (see Patent Document 2) and a polarizing reflective film having polarization reflection characteristics (see Patent Document 3).
However, since laminated films such as these have a structure in which different resins are alternately laminated, the mechanical strength and dimensional stability tend to decrease due to the influence of the laminated thickness as compared with a single-layer film. There is. When the mechanical strength and dimensional stability of the laminated film are reduced, for example, the force applied to the film when punching, cutting, coating and laminating into a functional film in combination with various other films and members. Deformation and breakage occur, and problems such as deterioration of processing accuracy and yield during processing, deterioration of optical properties and quality of the obtained film occur, and dimensional changes when actually mounted on products etc. There was a problem that a problem occurred due to the above.

Japanese Patent No. 3960194 Japanese Patent No. 4310312 Japanese Unexamined Patent Publication No. 2014-124845

In response to the above problems, the present inventors have found that a film once biaxially stretched is stretched again to obtain a restretched film (International Application No. PCT / JP2016 / 055220). However, depending on the combination of resins used and the characteristics of the biaxially stretched film before stretching, a re-stretched film having poor stretchability when re-stretched and having physical properties satisfying the desired mechanical strength, dimensional stability, and optical characteristics can be obtained. I found that there are times when I can't. In particular, there is a problem that the optical characteristics typified by the polarization reflection characteristics disclosed in Patent Document 3 are not exhibited.

Therefore, an object of the present invention is to solve the above-mentioned problems and to provide high mechanical strength, dimensional stability, excellent optical characteristics by stretching again, and to process with high yield and high accuracy in various processing processes. It is an object of the present invention to provide a laminated film capable of forming a re-stretched film that does not cause any problems in actual use.

Another object of the present invention is to provide a polarizing reflector that exhibits excellent polarizing reflection characteristics while having high mechanical strength and dimensional stability by stretching the laminated film again.

The present invention is to solve the above-mentioned problems, and a total of 11 or more layers are alternately laminated with an A layer made of crystalline polyester and a B layer made of a thermoplastic resin B different from the crystalline polyester. The laminated film is characterized in that the difference (| ΔHc−ΔHm |) between the melting enthalpy (ΔHm) and the crystallization enthalpy (ΔHc) observed in the differential scanning calorimetry (DSC) is 20 J / g or less. It is a laminated film to be used.

According to the present invention, when the laminated film of the present invention is re-stretched to form a re-stretched film, it has high mechanical strength, dimensional stability, and excellent optical properties, and is punched and cut as various functional films. It is possible to obtain a laminated film which can be suitably used for processing and use such as coating and laminating, and which has the effect of becoming a re-stretched film that can be used without causing problems during mounting.

The re-stretched film obtained by re-stretching the laminated film of the present invention is a film having high mechanical strength, dimensional stability, and excellent optical properties, and therefore can be used as a process film or various optical films, especially a polarizing reflector. It will be a suitable film.

It is a schematic diagram showing the polarization perpendicular to the incident plane including the film longitudinal direction and the polarization parallel to the incident plane including the film longitudinal direction.

Next, the laminated film of the present invention and a method for producing the same will be described in detail.

The laminated film of the present invention has a layer (A layer) made of crystalline polyester (hereinafter, may be referred to as crystalline polyester A) and a thermoplastic resin (hereinafter, thermoplastic resin B) different from the above-mentioned crystalline polyester. It is a laminated film in which 11 or more layers in total are alternately laminated.

Here, the crystalline polyester A is specifically a resin obtained by performing differential scanning calorimetry (hereinafter, may be referred to as DSC) according to JIS K7122 (1999) and at a heating rate of 20 ° C./min. Is heated from 25 ° C. to 300 ° C. at a heating rate of 20 ° C./min (1stRUN), held in that state for 5 minutes, then rapidly cooled to a temperature of 25 ° C. or lower, and then again from 25 ° C. to 20 ° C. Polyester having a melting enthalpy (ΔHm) of 15 J / g or more obtained from the peak area of the melting peak in the differential scanning calorimetry chart of 2ndRUN obtained by raising the temperature to 300 ° C. at a heating rate of ° C./min. Refers to. More preferably, the melting enthalpy (ΔHm) is 20 J / g or more, and even more preferably 25 J / g or more.

Further, the thermoplastic resin B exhibits optical characteristics or thermal characteristics different from those of the crystalline polyester A used for the layer A. Specifically, in one of the two orthogonal directions arbitrarily selected in the plane of the laminated film and the direction perpendicular to the plane, the refractive point differs from that of the crystalline polyester A by 0.01 or more, or in the DSC. , Which shows a melting point different from that of crystalline polyester A and a glass transition point temperature.

Further, "alternately laminated" here means that the A layer and the B layer are laminated in a regular arrangement in the thickness direction. For example, they are stacked in a regular array represented by A (BA) n (n is a natural number). By alternately laminating resins having different optical properties in this way, it is possible to develop interference reflection that can reflect light of a wavelength designed from the relationship between the difference in refractive index of each layer and the layer thickness. It becomes.

Further, by alternately laminating resins having different thermal characteristics, it is possible to highly control the orientation state of each layer when the biaxially stretched film or the biaxially stretched film, which is a feature of the present invention, is re-stretched. This makes it possible to control optical characteristics, mechanical characteristics, dimensional stability, and the like.

The preferred laminated form of the laminated film is an A layer made of crystalline polyester A, a B layer made of a thermoplastic resin B different from the crystalline polyester A, and a thermoplastic resin different from the crystalline polyester A and the thermoplastic resin B. There is also a case where it has a C layer composed of C. In such a case, the layer C may be laminated on the outermost layer or the intermediate layer such as CA (BA) n, CA (BA) nC, and A (BA) nCA (BA) m.

Further, when the number of layers to be laminated is less than 11, for example, it is difficult to manufacture a biaxially stretched film due to the influence of laminating different thermoplastic resins on physical properties such as film forming property and mechanical property. May cause problems when combined with other components to make a product. Further, when the laminated film is stretched again, if the number of layers is less than 11, the re-stretched film tends to be brittle, and the handleability may be deteriorated.

On the other hand, in the case of a laminated film in which a total of 11 or more layers are alternately laminated like the laminated film of the present invention, each thermoplastic resin is uniformly arranged as compared with a laminated film having less than 11 layers. It is possible to stabilize the film-forming property and mechanical properties, especially the handling property of the re-stretched film by re-stretching, due to the interfacial tension at the laminated interface and the cushioning effect of the B layer made of the thermoplastic resin B. .. Further, as the number of layers increases, there is a tendency that the growth of orientation in each layer can be suppressed, and it becomes easier to control mechanical properties and heat shrinkage characteristics such as improvement of tear resistance by interfacial tension. In addition, it is possible to impart a unique optical characteristic of exhibiting an interference reflection function. The number of layers to be laminated is preferably 100 or more, and more preferably 200 or more. When 100 or more layers of film are laminated, it is possible to reflect light in a wide band with high reflectance, and when 200 or more layers are laminated, for example, the light of the entire visible light having a wavelength of 400 to 700 nm is emitted. It will be almost reflective. In addition, although there is no upper limit to the number of layers to be stacked, as the number of layers increases, it may cause an increase in manufacturing costs due to the increase in size and complexity of manufacturing equipment. Therefore, in reality, the practical range is within 10,000 layers. Will be.

The laminated film of the present invention has high mechanical strength, dimensional stability, and excellent optical characteristics by re-stretching the laminated film, and can be processed with high yield and high accuracy in various processing processes. It is characterized in that it is a re-stretched film that does not cause any problems during actual use.

Therefore, in the laminated film of the present invention, the difference (| ΔHc−ΔHm |) between the melting enthalpy (ΔHm) and the crystallization enthalpy (ΔHc) observed in the differential scanning calorimetry (DSC) is 20 J / g or less. is necessary. Here, the melting enthalpy is calculated from the peak area in the endothermic direction, and the crystallization enthalpy is calculated from the peak area in the exothermic direction. The enthalpy of fusion and the enthalpy of crystallization are used. The difference between the melting enthalpy (ΔHm) and the crystallization enthalpy (ΔHc) is a measure of the degree of crystallization of the laminated film. The larger the difference between the difference between the molten enthalpy (ΔHm) and the crystallization enthalpy (ΔHc), the more the crystallization of the laminated film is advanced. Especially in the laminated film with advanced crystallization, only the molten enthalpy is observed and crystallization. No enthalpy is observed. When the difference between the melting enthalpy (ΔHm) and the crystallization enthalpy (ΔHc) is larger than 20 J / g, the crystallization of the laminated film is in progress, and even if the laminated film is to be stretched again, its high stretching tension or Due to the low elongation at break, it becomes difficult to stretch, and it becomes difficult to obtain a re-stretched film having desired mechanical strength, dimensional stability, and optical properties. On the other hand, when the difference between the melting enthalpy (ΔHm) and the crystallization enthalpy (ΔHc) is 20 J / g or less, the crystallization of the laminated film has not completely progressed, so that the laminated film is easily stretched when it is stretched again. It is possible to obtain high mechanical strength, dimensional stability, and excellent optical properties by sufficiently re-stretching the stretched film.
Preferably, the difference between the melting enthalpy (ΔHm) and the crystallization enthalpy (ΔHc) is 3 J / g or more and 10 J / g or less. When the difference between the melting enthalpy (ΔHm) and the crystallization enthalpy (ΔHc) is less than 3 J / g, the crystallinity of the laminated film is low. May occur. If the difference between the melting enthalpy (ΔHm) and the crystallization enthalpy (ΔHc) is 3 J / g or more and 10 J / g or less, the stretching ratio can be increased even when the drawing is performed again, and as a result, the adjustment white of the stretching ratio is large. As a result, mechanical strength, dimensional stability, and optical characteristics can be optimized, and it becomes easy to obtain a re-stretched film with higher functionality and higher performance.

Further, in the laminated film of the present invention, it is also preferable that the melting enthalpy (ΔHm) is 15 J / g or more. When the melt enthalpy (ΔHm) is less than 15 J / g, the re-stretched film is not sufficiently oriented and crystallized, and is made of crystalline polyester, especially in applications requiring optical performance such as a polarizing reflector. Since the reflection performance is exhibited depending on the magnitude of the difference in the refractive index of each layer of the B layer made of the thermoplastic resin B different from the A layer and the crystalline polyester, the orientation and crystallization of the crystalline polyester are not sufficient. In some cases, the desired optical performance may not be exhibited. When the melting enthalpy (ΔHm) is 15 J / g or more, the difference in refraction between the layer A made of crystalline polyester and the layer B made of thermoplastic resin B different from that of crystalline polyester can be easily introduced, which is desired. It becomes possible to obtain a re-stretched film having optical performance.

Further, in the laminated film of the present invention, it is also preferable that only one melting peak of 5 J / g or more is confirmed by differential scanning calorimetry (DSC). The fact that only one melting peak of 5 J / g or more is confirmed by differential scanning calorimetry (DSC) means that the melting peak is derived from crystalline polyester, so that the thermoplastic resin B is oriented and crystallized. It shows that it is not. Therefore, it becomes easy to increase the difference in the refractive index between the A layer made of crystalline polyester and the B layer made of thermoplastic resin B different from that of crystalline polyester, and a re-stretched film having high optical performance can be obtained. Is possible.

In the laminated film of the present invention, the MOR measured by the molecular orientation meter is preferably 1.5 or less. MOR represents the ratio of the maximum value and the minimum value of the permittivity in the in-plane direction of the film. In particular, in the case of a biaxially stretched film, the orientation and crystallization of the laminated film increase as the value of MOR increases. It is an indicator that you are there. When the MOR is 1.5 or less, the laminated film is not completely crystallized, so that it can be easily stretched when it is stretched again, and the stretched film is also sufficiently re-stretched. This makes it possible to obtain high mechanical strength, dimensional stability, and excellent optical characteristics.

In the laminated film of the present invention, it is preferable that the breaking elongation of a sample having a length of 150 mm and a width of 10 mm at 160 ° C. in the film longitudinal direction or a direction orthogonal to the film longitudinal direction is 200% or more. The film longitudinal direction referred to here is defined as follows. In the case of a film wound in a roll shape, the roll winding direction is the film longitudinal direction. When the flow direction at the time of film formation can be known from the film, the flow direction is defined as the film longitudinal direction. For samples that cannot be discriminated by the above two methods, the Young's modulus of the film is measured by changing the direction in the film surface every 10 °, and the direction in which the Young's modulus is maximized is defined as the film longitudinal direction. When the film is stretched again, it is generally stretched in the longitudinal direction of the film or in a direction orthogonal to the longitudinal direction. Here, 160 ° C. is shown as an example of the temperature at the time of re-stretching, but if the elongation at break at the time of re-stretching is 150% or more, the stretching can be easily performed at the time of re-stretching, and the stretching is possible. By sufficiently re-stretching the later film, it becomes possible to obtain high mechanical strength, dimensional stability, and excellent optical properties. The elongation at break at 160 ° C. is preferably 250% or more, and more preferably 300% or more. When re-stretching, the mechanical strength, dimensional stability, and optical characteristics can be optimized by increasing the stretch ratio or adjusting the draw ratio, resulting in a re-stretched film with higher functionality and performance. Becomes easier.

Further, the breaking elongation at 140 ° C. of the laminated film in the film longitudinal direction or the direction orthogonal to the longitudinal direction is preferably 150% or more, and more preferably the breaking elongation at 120 ° C. is 150% or more. If it is a laminated film that can be stretched even at a lower temperature, the choices of stretching method and stretching device are expanded, and the physical properties of the re-stretched film can be adjusted by adjusting not only the stretching ratio but also the stretching temperature. It is even easier to optimize the dimensional stability and optical characteristics. The breaking elongation of a sample having a length of 150 mm and a width of 10 mm does not match the breaking elongation in the actual film forming process due to the difference in sample width.

In the laminated film of the present invention, the transmittance at an incident angle of 0 ° is T1 for the polarizing component parallel to the incident surface including the longitudinal direction of the laminated film, and perpendicular to the incident surface including the longitudinal direction of the laminated film. When the transmittance at an incident angle of 0 ° is T2, the minimum values of the transmittances T1 and T2 at a wavelength of 400 to 1400 nm are preferably 60% or more. As described above, the laminated film of the present invention is characterized in that it exhibits reflection characteristics due to the difference in refractive index between the layer A made of crystalline polyester and the layer B made of thermoplastic resin B different from crystalline polyester. .. That is, the reflectance (100-transmittance,%) is an index indicating the strength of the orientation / crystallization of the A layer made of crystalline polyester, and the orientation / crystallization of the A layer increases as the reflectance increases. It shows that it is. Here, the transmittance at an incident angle of 0 ° is set to T1 for the polarizing component parallel to the incident surface including the longitudinal direction of the laminated film, and the incident is incident on the polarizing component perpendicular to the incident surface including the longitudinal direction of the laminated film. When the transmittance at an angle of 0 ° is T2, and the minimum values of the transmittances T1 and T2 at a wavelength of 400 to 1400 nm are both 60% or more, the orientation of the crystalline polyester completely crystallizes the laminated film. Is not advanced, so it can be easily stretched when re-stretched, and the stretched film is also sufficiently re-stretched to obtain high mechanical strength, dimensional stability, and excellent optical properties. Is possible. The minimum values of the transmittances T1 and T2 at a wavelength of 400 to 1400 nm are preferably 70% or more, and more preferably 80% or more. In this case, when stretching again, it becomes easy to increase the stretching ratio, and the mechanical strength, dimensional stability, and optical characteristics can be optimized by increasing the stretching ratio and increasing the adjustment white of the stretching ratio. It becomes easy to obtain a re-stretched film with higher functionality and higher performance.

Similarly, in the laminated film of the present invention, it is preferable that the maximum value of the degree of polarization P of the laminated film at a wavelength of 400 to 1400 nm obtained from the following formula (1) is 20% or less. The degree of polarization is an index similar to the minimum values of the transmittances T1 and T2 at a wavelength of 400 to 1400 nm, and is also an index showing the balance of orientation like MOR measured by a molecular orientation meter. The fact that the maximum value of the degree of polarization P of the laminated film at a wavelength of 400 to 1400 nm is 20% or less indicates that the orientation and crystallization of the crystalline polyester are suppressed to a sufficient extent for stretching again. Therefore, it is possible to easily stretch the laminated film when it is re-stretched, and the stretched film is also sufficiently re-stretched to obtain high mechanical strength, dimensional stability, and excellent optical properties. It will be possible to obtain. More preferably, the maximum value of the degree of polarization P of the laminated film at a wavelength of 400 to 1400 nm is 10% or less, and when it is stretched again, it becomes easy to increase the draw ratio, and the draw ratio can be increased or the draw ratio can be increased. By increasing the adjustment white, the mechanical strength, dimensional stability, and optical characteristics can be optimized, and it becomes easy to obtain a re-stretched film with higher functionality and higher performance.
P (λ) = (T2 (λ) -T1 (λ)) / (T2 (λ) + T1 (λ)) ... Equation (1)
λ: Measurement wavelength (nm, 400 to 1400 nm)
In the laminated film of the present invention, the layer A made of crystalline polyester A is preferably the outermost layer. In this case, since the crystalline polyester A is the outermost layer, it is possible to manufacture a biaxially stretched film in the same manner as a crystalline polyester film such as a polyethylene terephthalate film or a polyethylene naphthalate film. For example, when a thermoplastic resin B made of a non-crystalline resin instead of a crystalline polyester is used as the outermost layer, or when a biaxially stretched film is obtained in the same manner as a crystalline polyester film, it is used in manufacturing equipment such as rolls and clips. There may be problems such as poor film formation due to adhesion and deterioration of surface properties.

As the crystalline polyester A used in the present invention, a polyester obtained by polymerization of a monomer containing an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol as main constituents is preferably used.

Here, examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalene. Dicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, 6,6'-(ethylenedioxy) di-2-naphthoic acid, 6, Examples thereof include 6'-(trymethylenedioxy) di-2-naphthoic acid and 6,6'-(butyrenoxy) di-2-naphthoic acid. Examples of the aliphatic dicarboxylic acid include adipic acid, suberic acid, sebacic acid, dimer acid, dodecandioic acid, cyclohexanedicarboxylic acid and ester derivatives thereof. Only one of these acid components may be used, or two or more of these acid components may be used in combination.

In particular, the carboxylic acid component constituting the crystalline polyester A used in the laminated film of the present invention develops a high refractive acid after maximum stretching, and from the viewpoint of enhancing mechanical strength and dimensional stability represented by Young's modulus. , Terephthalic acid and 2,6-naphthalenedicarboxylic acid are preferably used. Since terephthalic acid and 2,6-naphthalenedicarboxylic acid contain an aromatic ring with high symmetry, it is easy to achieve both high refractive index and excellent mechanical properties by orientation and crystallization. .. In particular, when the carboxylic acid component constituting the crystalline polyester A contains 2,6-naphthalenedicarboxylic acid, the volume ratio of the aromatic ring increases, so that the cost is low and it is extremely possible to form a melt film. It is possible to achieve high refractive index and excellent mechanical properties.

Further, the carboxylic acid component constituting the crystalline polyester A used in the laminated film of the present invention preferably contains isophthalic acid in addition to the above-mentioned terephthalic acid and 2,6-naphthalenedicarboxylic acid. By containing isophthalic acid, the orientation and crystallinity of the laminated film can be appropriately suppressed as compared with the case where only terephthalic acid or 2,6-naphthalenedicarboxylic acid is used, and the orientation after re-stretching can be easily improved. It will be possible.

In the laminated film of the present invention, the crystalline polyester preferably contains 50 mol% or more of naphthalene dicarboxylic acid among the carboxylic acid components constituting the crystalline polyester. By containing 50 mol% or more of naphthalene dicarboxylic acid, the laminated film can be easily oriented and crystallized by further stretching, and it becomes easy to increase the Young's modulus. Preferably, it contains 50 mol% or more and 90 mol% or less of naphthalene dicarboxylic acid. By setting the content of naphthalene carboxylic acid contained in the carboxylic acid component to 90 mol% or less, the orientation and crystallinity of the crystalline polyester can be appropriately suppressed, so that the stretching ratio can be increased when re-stretching or at a lower temperature. Since it becomes easy to stretch, it can be preferable as a laminated film to be stretched again.

Examples of the diol component constituting the crystalline polyester include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, and 1,4-butanediol. 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 can be mentioned. Above all, from the viewpoint of easy polymerization, ethylene glycol is a preferable embodiment as a main component.

Here, the main component means that it is 50 mol% or more of the diol component. Only one of these diol components may be used, or two or more of these diol components may be used in combination. It is also possible to partially copolymerize an oxyacid such as hydroxybenzoic acid.

In the laminated film of the present invention, it is also preferable that the diol component is composed of at least two kinds and the content of the main diol component is 50 mol% or more and 90 mol% or less. In this case, since the orientation and crystallinity of the crystalline polyester can be appropriately suppressed, it becomes easy to increase the draw ratio when re-stretching and to stretch at a lower temperature, which is preferable as a laminated film to be re-stretched. Can be.

In the laminated film of the present invention, when the sum of all the dicarboxylic acid components constituting the crystalline polyester and all the diol components is 200 mol%, the sum of the main dicarboxylic acid component and the dicarboxylic acid other than the diol component and the diol component is It is also preferable that it is less than 20 mol%. Since the sum of the dicarboxylic acid other than the main dicarboxylic acid component and the diol component and the diol component is less than 20 mol%, the stretching ratio is increased when the film is re-stretched while having appropriate crystallinity, and the film is stretched at a lower temperature. Therefore, the laminated film to be re-stretched can be preferable, and the actually obtained laminated film can have high polarization reflection performance.

More preferably, the layer A made of the crystalline polyester A of the present invention is made of a mixture of two or more kinds of crystalline polyester and the thermoplastic resin B. Even in the case of a mixture of two or more types of crystalline polyester or thermoplastic resin B, the orientation and crystallinity of the crystalline polyester can be appropriately suppressed, so that the stretching ratio is increased when stretching again and the film is stretched at a lower temperature. Therefore, it can be preferable as a laminated film to be stretched again. Further, when the orientation and crystallinity are controlled by the composition of the crystalline polyester, the crystallinity of the resin itself is lowered, so that there may be a problem in drying or extrusion of the resin when forming a film. When two types of crystalline polyester or thermoplastic resin B are mixed, each resin has excellent drying and extrudability, so that it becomes easy to stably form a film. As a more preferable effect of mixing two or more kinds of polyesters, each crystalline polyester is dispersed with a minute region called a domain without being completely mixed, so that crystallization within each domain progresses, and crystallization progresses. Although it has low orientation and crystallinity required for re-stretching, it has the effect of suppressing film-forming troubles such as roll adhesion during stretching.

The thermoplastic resin B used in the present invention includes chain polyolefins such as polyethylene, polypropylene, and poly (4-methylpentene-1); ring-opening metathesis polymerization of norbornenes, addition polymerization, and addition-copolymerization with other olefins. Polymer alicyclic polyolefin; polyamides such as nylon 6, nylon 11, nylon 12, nylon 66, aramid, polymethylmethacrylate, polyvinyl chloride, vinylidene chloride, polyvinyl alcohol, polyvinylbutyral, ethylene vinyl acetate copolymer, polyacetal , Polyglucol acid, polystyrene, styrene copolymer polymethylmethacrylate, polycarbonate; polypropylene such as polypropylene terephthalate, polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polylactic acid, polybutylsuccinate; polyether Sulfon, polyether ether ketone, modified polyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide, polyarylate, tetrafluoroethylene resin, trifluoroethylene resin, trifluorochloride ethylene resin, tetrafluorinated ethylene-6 foot Polypropylene copolymer, polyvinylidene fluoride and the like can be used.

Among these, polyester is preferably used from the viewpoints of strength, heat resistance, transparency and versatility, as well as adhesion and stackability with the crystalline polyester A used for the A layer. These are used whether they are copolymers or mixtures.

In the laminated film of the present invention, when the thermoplastic resin B is polyester, the polyester obtained by polymerization from a monomer mainly composed of an aromatic dicarboxylic acid component and / or an aliphatic dicarboxylic acid component and a diol component. Is preferably used. Here, as the aromatic dicarboxylic acid component, the aliphatic dicarboxylic acid component and the diol component, the components mentioned in the crystalline polyester A are preferably used.

In the laminated film of the present invention, the thermoplastic resin B is preferably an aromatic polyester containing an aromatic dicarboxylic acid component and a diol component as main constituents. Further, in order to obtain a laminated film having an interference reflection function, it is also preferable that the thermoplastic resin B is an amorphous resin. Since the amorphous resin is less likely to be oriented when the biaxially stretched film is produced as compared with the crystalline resin, it is possible to suppress the increase in the refractive index due to the oriented crystallization of the B layer made of the thermoplastic resin B, and the crystals are crystallized. It is possible to easily generate a difference in refractive index from the layer A made of the sex polyester A.

The amorphous resin referred to here is a resin heated at a temperature rise rate of 20 ° C./min from 25 ° C. to 300 ° C. at a temperature rise rate of 20 ° C./min (1stRUN) according to JIS K7122 (1999). After holding for 5 minutes in that state, the mixture was rapidly cooled to a temperature of 25 ° C. or lower, and then heated again from room temperature to a temperature of 300 ° C. at a heating rate of 20 ° C./min to obtain the 2nd RUN. In the differential scanning calorimetry chart, the resin having a crystal melting heat amount ΔHm obtained from the peak area of the melting peak is 5 J / g or less, and more preferably a resin showing no peak corresponding to crystal melting.

Further, in order to obtain a laminated film having an interference reflection function when the laminated film is re-stretched to obtain a re-stretched film, the thermoplastic resin B has a melting point of 20 ° C. or more lower than the melting point of the crystalline polyester A. Crystalline resins are also preferably used. In this case, by further heat-treating at a temperature between the melting point of the thermoplastic resin B and the melting point of the crystalline polyester A after re-stretching, the heat treatment can be completely relaxed in the heat treatment step, and the polyester A is made of crystalline polyester. The difference in refractive point from the layer A can be maximized. Preferably, the difference in melting point between the crystalline polyester A and the thermoplastic resin B is 40 ° C. or higher. In this case, since the temperature selection range in the heat treatment step is widened, it becomes easier to promote the relaxation of the orientation of the thermoplastic resin B and control the orientation of the crystalline polyester.

As a preferable combination of the crystalline polyester A and the thermoplastic resin B, the absolute value of the difference between the SP values of the two is preferably 1.0 or less. When the absolute value of the difference between the SP values is 1.0 or less, delamination between the A layer and the B layer is less likely to occur. More preferably, the crystalline polyester A and the thermoplastic resin B are made of a combination having the same basic skeleton.

The basic skeleton here is a repeating unit that constitutes a resin. For example, as crystalline polyester A, a polyethylene naphthalate having a carboxylic acid component consisting of only 2,6-naphthalenedicarboxylic acid or a polyethylene naphthalate copolymer containing 2,6-naphthalenedicarboxylic acid as a main component containing 50% or more of the carboxylic acid component. When a coalescence is used, it is preferable to use an amorphous polyethylene naphthalate copolymer or a crystalline polyethylene naphthalate copolymer having a lower melting point than the crystalline polyester A as the thermoplastic resin B.

Further, in order to obtain a laminated film having an interference reflection function when the laminated film is re-stretched to obtain a re-stretched film, the glass transition temperature of the thermoplastic resin B is 10 ° C. or higher than the glass transition temperature of the crystalline polyester A. It is preferably low. In this case, even in each stretching step, when the optimum stretching temperature is taken for stretching the crystalline polyester, the orientation of the thermoplastic resin B does not proceed, so that the refractive index difference from the layer A made of the crystalline polyester is different. Can be taken large. More preferably, the glass transition temperature of the thermoplastic resin B is 20 ° C. or more lower than the glass transition temperature of the crystalline polyester A.

In a production method suitable for obtaining the laminated film of the present invention described later or a re-stretched film further stretched again, the oriented crystallization of the thermoplastic resin B is likely to proceed and the desired interference reflection function may not be obtained. By lowering the glass transition temperature of the thermoplastic resin B to 20 ° C. or more lower than the glass transition temperature of the crystalline polyester A, orientation crystallization can be suppressed.

In addition, various additives such as antioxidants, heat-resistant stabilizers, weather-resistant stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, and antistatic resins are contained in the thermoplastic resin. Inhibitors, nucleating agents and the like can be added to the extent that their properties are not deteriorated.

Next, a preferable method for producing the laminated film of the present invention will be described below.

Further, the laminated structure of the laminated film used in the present invention can be easily realized by the same method as the contents described in columns [0053] to [0063] of JP-A-2007-307893.

First, crystalline polyester A and thermoplastic resin B are prepared in the form of pellets or the like. The pellets are, if necessary, dried in hot air or under vacuum before being fed to a separate extruder. In the extruder, the resin that has been heated and melted is equalized in the amount of resin extruded by a gear pump or the like, and foreign substances and modified resin are removed via a filter or the like. These resins are fed into the multilayer stacking device.

As the multi-layer stacking device, a multi-manifold die, a feed block, a static mixer, or the like can be used, but in order to efficiently obtain the configuration of the present invention, it is preferable to use a feed block having 11 or more fine slits. .. By using such a feed block, since the apparatus does not become extremely large, there are few foreign substances due to thermal deterioration, and even when the number of layers is extremely large, high-precision lamination is possible. In addition, the stacking accuracy in the width direction is significantly improved as compared with the conventional technique. Further, in this device, since the thickness of each layer can be adjusted by the shape (length, width) of the slit, it is possible to achieve an arbitrary layer thickness.

Then, the laminated sheet discharged from the die is extruded onto a cooling body such as a casting drum and cooled and solidified to obtain a casting film. At this time, it is preferable to use a wire-shaped, tape-shaped, needle-shaped or knife-shaped electrode to bring the discharged sheet into close contact with the cooling body by electrostatic force to quench and solidify it. Further, as a method of bringing the discharged sheet into close contact with the cooling body, a method of blowing air from a slit-shaped, spot-shaped and planar device, and a method of using a nip roll are also preferable embodiments.

The casting film thus obtained is preferably biaxially stretched. Here, biaxial stretching means stretching the film in the longitudinal direction and the width direction. By biaxial stretching, it becomes possible to impart appropriate orientation and crystallinity to the crystalline polyester, and it becomes possible to obtain a laminated film suitable for re-stretching.

The obtained cast film is first stretched in the longitudinal direction. The stretching in the longitudinal direction is usually performed by the difference in peripheral speed of the roll. This stretching may be carried out in one step, or may be carried out in multiple steps using a plurality of roll pairs. The stretching ratio varies depending on the type of resin, but is preferably 2 to 5 times. The purpose of this first stretching in the longitudinal direction is to provide the minimum necessary orientation in order to improve the uniform stretchability during the subsequent stretching in the film width direction. Therefore, when the stretch ratio is set to a magnification larger than 5 times, it may not be possible to obtain a film having a sufficient stretch ratio when stretching in the film width direction and stretching the laminated film again, which will be described later. Further, when the draw ratio is less than 2 times, the minimum orientation required for the next step cannot be imparted at the time of stretching, and thickness unevenness may occur in the longitudinal direction of the film to deteriorate the quality. The stretching temperature is preferably a temperature from the glass transition temperature to the glass transition temperature + 30 ° C. of the crystalline polyester A constituting the laminated film.

The uniaxially stretched film thus obtained is subjected to surface treatment such as corona treatment, frame treatment and plasma treatment as necessary, and then has functions such as slipperiness, adhesiveness and antistatic property in-line. It can be imparted by coating.

Subsequently, the uniaxially stretched film is stretched in the width direction. Stretching in the width direction is usually carried out by using a tenter while gripping both ends of the film with clips and transporting the film in the width direction. The stretching ratio varies depending on the type of resin, but is usually preferably 2 to 5 times. The purpose of the stretching in the width direction is to provide the minimum necessary orientation for imparting the high stretchability required when the laminated film is stretched again. Therefore, when the draw ratio is set to a ratio larger than 5 times, it may not be possible to obtain a re-stretched film having a sufficient draw ratio when the laminated film is re-stretched. Further, when the draw ratio is less than 2 times, the thickness may be uneven in the film width direction during stretching and the quality may be deteriorated. The stretching temperature is preferably between the glass transition temperature of the crystalline polyester A constituting the laminated film and the glass transition temperature + 30 ° C., or between the glass transition temperature and the crystallization temperature of the crystalline polyester. The crystallization temperature of the crystalline polyester referred to here is the crystallization temperature observed in the differential scanning calorimetry (DSC) of the uniaxially stretched film. When the film is stretched at a temperature higher than 30 ° C. from the glass transition temperature, the minimum orientation required for the laminated film cannot be imparted for re-stretching, or the thickness unevenness worsens and the laminated film is re-stretched. The quality of the stretched film may deteriorate. Further, when the polyester is stretched at a temperature higher than the crystallization temperature of the crystallized polyester, the orientation and crystallization of the crystalline polyester may proceed during stretching, and it may not be possible to impart the high stretchability required for re-stretching. There is. When the laminated film obtained by stretching between the glass transition temperature of the crystalline polyester A constituting the laminated film and the glass transition temperature + 30 ° C. or the glass transition temperature and the crystallization temperature of the crystalline polyester is stretched again. It is possible to easily stretch the glass, and by sufficiently re-stretching the stretched film, it is possible to obtain high mechanical strength, dimensional stability, and excellent optical properties.

Usually, the biaxially stretched film thus obtained may be heat-treated in a tenter at a temperature equal to or higher than the stretching temperature and lower than the melting point in order to impart flatness and dimensional stability. In the laminated film of No. 1, it is preferable not to apply heat higher than the stretching temperature after stretching. This is because crystallization may be promoted by applying heat equal to or higher than the stretching temperature after stretching.

The laminated film of the present invention is a film suitable for re-stretching. By re-stretching by the following method, it is possible to impart high mechanical strength, dimensional stability, and optical characteristics.

An example of the method of stretching again is shown below.

One example is the case where the obtained biaxially stretched film is stretched again in the longitudinal direction. This longitudinal stretching is usually performed by the difference in peripheral speed of the rolls. This stretching may be carried out in one step, or may be carried out in multiple steps using a plurality of roll pairs. The stretching ratio varies depending on the type of resin, but is preferably 1.3 to 4 times. Since the laminated film of the present invention has excellent stretchability even when it is stretched again, it can be easily stretched 1.3 to 4 times. Further, by stretching 1.3 to 4 times, it is possible to obtain a film exhibiting mechanical characteristics, dimensional stability and optical characteristics as described later. When the draw ratio is less than 1.3 times, changes in mechanical properties, dimensional stability, and optical properties due to repeated stretching may be slight, and a re-stretched film having desired physical properties may not be obtained. On the other hand, when the draw ratio is larger than 4 times, the orientation of the re-stretched film becomes strong, so that although improvement in mechanical properties, dimensional stability, and optical characteristics can be achieved, the re-stretched film becomes brittle, depending on the intended use. May result in unsuitable film.

Further, as another example, there is a case where the obtained biaxially stretched film is stretched again in the width direction. This stretching in the width direction is usually carried out by using a tenter while grasping both ends of the film with clips and transporting the film in the width direction. The preferred stretching ratio and the like are the same as in the case of stretching in the longitudinal direction. In this way, as an effect of stretching in the width direction again, the orientation and crystal state of the laminated film are fixed by cooling the laminated film once as compared with the case where the stretching ratio in the initial width direction is increased, and then again. By re-stretching, there is an effect that the re-stretched film can give a stronger orientation.

It is also preferable that the re-stretched film thus obtained is heat-treated at a temperature equal to or higher than the stretching temperature and lower than the melting point in order to impart flatness and dimensional stability. By performing the heat treatment, the effect of promoting the alignment crystallization and improving the mechanical properties can be obtained, and the dimensional stability is also improved along with the promotion of the alignment crystallization. After being heat-treated in this manner, it is uniformly slowly cooled, cooled to room temperature, and wound up. Further, if necessary, after heat treatment, relaxation treatment or the like can be performed at the time of slow cooling.

The physical characteristics of the obtained stretched film are shown below.

By re-stretching the laminated film of the present invention, Young's modulus in the re-stretched direction can be improved. By setting the Young's modulus to 6 GPa, deformation can be suppressed even when a force is applied to the laminated film during processing processes such as punching, cutting, coating and laminating, or when used as a functional film, and the film is deformed. It becomes easy to suppress processing defects and performance changes during use. In the film re-stretched using the laminated film of the present invention, the ratio of Young's modulus in the last stretched direction of the laminated film and the direction orthogonal to the last stretched direction can be 2 or more, and thus isotropic. It becomes easy to achieve a high Young's modulus as compared with the case of stretching to a high magnification.

Further, by re-stretching the laminated film of the present invention, the absolute value of the linear expansion coefficient at a temperature of 40 ° C. to 50 ° C. in the re-stretched direction can be set to 10 ppm / ° C. or less. The linear expansion coefficient is an index showing the variability of the film size when the temperature is changed, and by reducing the absolute value of the thermal expansion coefficient, processing processes such as punching, cutting, coating, and laminating Deformation of the film can be suppressed even when the temperature of the laminated film changes at times or when used as a functional film, and it becomes easy to suppress processing defects and performance changes during use due to film deformation. ..

By re-stretching the laminated film of the present invention, it becomes easy to obtain a polarized reflector.

In the laminated film of the present invention, the magnification at which the film breaks when the laminated film is stretched in the longitudinal direction is X times, and the magnification at which the film breaks when the laminated film is stretched in the direction orthogonal to the longitudinal direction is X'fold. When the above was the case, the laminated film was obtained by stretching the laminated film (X-0.2) times in the longitudinal direction, or the laminated film was stretched (X'-0.2) times in the direction orthogonal to the longitudinal direction. For the polarizing component parallel to the incident surface including the stretching direction of the film, the reflectance at an incident angle of 10 ° is R3, and for the polarizing component perpendicular to the incident surface including stretching, the reflectance at an incident angle of 10 ° is R4. , It is preferable that the reflectance at a wavelength of 550 nm satisfies the following equations (2) and (3). By satisfying the following equations (2) and (3), it is possible to impart a polarization reflection characteristic of reflecting one of the polarizations and transmitting the other polarization. In order to obtain a film satisfying the following formula (2), the difference in refractive index between the A layer and the B layer in the final stretched direction of the laminated film is 0.08 or more, more preferably 0.1 or more, and further. Preferably, it can be adjusted by selecting a combination of resins having a value of 0.15 or more and film forming conditions. In order to obtain a film satisfying the following formula (3), the difference in refractive index between the A layer and the B layer in the direction orthogonal to the last stretched direction of the laminated film is 0.02 or less, more preferably 0. It can be adjusted by a combination of resins having a value of 01 or less, more preferably 0.005 or less. An example of the optimum combination is as described above.

R3 (550) ≧ 70% ・ ・ ・ Equation (2)
R4 (550) ≤ 40% ... Equation (3).

(Characteristic measurement method and effect evaluation method)
The method for measuring the characteristics and the method for evaluating the effect in the present invention are as follows.

(1) Number of layers:
The layer structure of the laminated film was determined by observing a sample whose cross section was cut out using a microtome using a transmission electron microscope (TEM). That is, using a transmission electron microscope H-7100FA type (manufactured by Hitachi, Ltd.), a cross-sectional photograph of the film was taken under the condition of an acceleration voltage of 75 kV, and the number of layers was confirmed.

(2) Film crystallization enthalpy (ΔHc), melting enthalpy (ΔHm), number of melting peaks of 5 J / g or more:
Sampling was performed from the laminated film to be measured, and the DSC curve of the measurement sample was measured according to JIS-K-7122 (1987) using differential calorimetry (DSC). In the test, the temperature was raised from 25 ° C. to 290 ° C. at 20 ° C./min, and the number of crystallization enthalpy and melting enthalpy at that time and the number of melting peaks of 5 J / g or more were measured. The devices used are as follows.
-Device: "Robot DSC-RDC220" manufactured by Seiko Electronics Inc.
-Data analysis "Disk Session SSC / 5200"
-Sample mass: 5 mg
(3) MOR
The sample size was 10 cm × 10 cm, and the sample was cut out at the center in the film width direction. The MOR was determined using the molecular orientation meter MOA-2001 manufactured by KS Systems Co., Ltd. (currently Oji Measuring Instruments Co., Ltd.).

(4) Measurement of reflectance and transmittance for incident light having a polarizing component:
In the laminated film, the film was cut out at a size of 5 cm × 5 cm from the center of the alignment axis on the line segment having the maximum length in the orientation axis direction (one of the definitions of the longitudinal direction) determined by Young's modulus measurement. The basic configuration was based on the integrating sphere attached to the spectrophotometer manufactured by Hitachi, Ltd. (U-4100 Spectrophotometer), and the measurement was performed using the aluminum oxide secondary white plate attached to the device as a reference. The sample was placed behind the integrating sphere with the orientation axis of the laminated film perpendicular to it. In addition, an attached splitter manufactured by Grantera Co., Ltd. was installed to inject linearly polarized light in which the polarizing component was polarized at 0 and 90 °, and the reflectance and transmittance at a wavelength of 400 to 1400 nm were measured. For the polarizing component parallel to the incident surface including the longitudinal direction of the film, the transmittance at an incident angle of 0 ° is T1, and for the polarizing component perpendicular to the incident surface including the longitudinal direction of the laminated film, the transmittance is transmitted at an incident angle of 0 °. The ratio was T2, and the minimum values of the transmittances T1 and T2 at a wavelength of 400 to 1400 nm were obtained.
Similarly, in the re-stretched laminated film, it was cut out at a size of 5 cm × 5 cm from the center of the direction orthogonal to the re-stretched direction. The cut-out sample was placed behind the integrating sphere with the re-stretched direction of the laminated film in the vertical direction.
The film longitudinal direction referred to here is defined as follows. In the case of a film wound in a roll shape, the roll winding direction is the film longitudinal direction. When the flow direction at the time of film formation can be known from the film, the flow direction is defined as the film longitudinal direction. For samples that cannot be discriminated by the above two methods, the Young's modulus of the film is measured by changing the direction in the film surface every 10 °, and the direction in which the Young's modulus is maximized is defined as the film longitudinal direction.

The measurement conditions are as follows. The slit was set to 2 nm (visible) / automatic control (infrared), the gain was set to 2, and the scanning speed was measured at 600 nm / min to obtain the reflectance at an azimuth angle of 0 to 180 degrees. When measuring the reflection of the sample, it was painted black with Magic Ink (registered trademark) in order to eliminate interference due to reflection from the back surface.

Further, the transmittance of the similarly cut out sample was measured in the same manner without blackening, and the degree of polarization P was obtained from the obtained transmittance data in the wavelength range of 400 to 1400 nm by the following equation (1). ..
P (λ) = (T2 (λ) -T1 (λ)) / (T2 (λ) + T1 (λ)) ... Equation (1)
(5) Young's modulus of re-stretched film:
The re-stretched laminated film was cut into a strip shape having a length of 150 mm and a width of 10 mm to prepare a sample. A tensile test was conducted using a tensile tester (Tencilon UCT-100 manufactured by Orientec) with an initial tensile chuck distance of 50 mm and a tensile speed of 300 mm / min. The measurement was carried out in an atmosphere of room temperature of 23 ° C. and relative humidity of 65%, and Young's modulus was obtained from the obtained load-strain curve. The measurement was performed 5 times for each sample, and the average value was used for evaluation.
(6) Breaking elongation of laminated film:
The laminated film was cut into strips having a length of 150 mm and a width of 10 mm in the orientation axis direction and the direction orthogonal to the orientation axis direction determined by Young's modulus measurement, and used as a sample. A tensile test was conducted using a constant temperature bath whose temperature was adjusted at 160 ° C. and a tensile tester (Tencilon UCT-100 manufactured by Orientec) with an initial tensile chuck distance of 50 mm and a tensile speed of 300 mm / min. The point at which the maximum load was obtained from the obtained load-strain curve was defined as the elongation at break. The measurement was performed 5 times for each sample, and the average value was used for evaluation.

(7) Breaking ratio when re-stretched in the longitudinal direction of the laminated film The laminated film was slit to a width of 400 mm and then heated to 125 ° C. with six rolls having a diameter of 200 mm. Then, after heating with a radiation heater, nip from above and below with two rolls (stretching rolls) having a diameter of 120 mm heated to 160 ° C., and cooled to 25 ° C. installed so that the length of the stretched section is 124 mm. The film was passed through a roll (cooling roll) having a diameter of 120 mm and then wound up. After that, the magnification between the stretching roll and the cooling roll is increased by 1.1 to 0.1 times until the film breaks, and the magnification X at which the film breaks when the film is stretched in the longitudinal direction at the breaking magnification. did.

(8) Breaking ratio when re-stretched in the direction orthogonal to the longitudinal direction of the laminated film After slitting the laminated film to a width of 400 mm, both ends of the film are gripped with a clip of a tenter, and the film is directed from the inlet to the outlet. It was widened and stretched so that the rail width was 1.1 times, and wound at the tenter outlet. After that, the rail width is widened by 0.1 times, and the film is broken when the film is stretched in the direction orthogonal to the longitudinal direction with a magnification of being torn in the longitudinal direction or the direction orthogonal to the longitudinal direction. '.

(9) Linear expansion coefficient:
The re-stretched laminated film was cut into strips having a length of 25 mm and a width of 4 mm in the direction of the orientation axis, and used as samples. Using a TMA tester (TMA / SS6000 manufactured by Seiko Instruments), the initial tension chuck distance is 15 mm, and the temperature inside the tester is 5 ° C / from 25 ° C to 150 ° C while the tensile tension is kept constant at 29.4 mN. The temperature was raised in minutes, and TMA measurement was performed for the orientation axis direction of the laminated film. From the obtained TMA-temperature curve, the linear expansion coefficient at a temperature of 40 ° C to 50 ° C was obtained. The linear expansion coefficient was obtained from the difference between the values of ± 5 ° C. of the temperature to be measured for both TMA and temperature.

(10) Workability:
A roll-shaped film was introduced into a punching machine, the length was set to 500 mm, and punching was performed using a rectangular die having a width of 95% of the film width. The punching interval in the longitudinal direction was 40 mm. The following A, B and C evaluations were performed. A and B were accepted.
A: The film could be continuously conveyed and processed without breaking.
B: Although the film was partially broken, continuous transport in the longitudinal direction was possible and continuous processing was possible.
C: The film was completely broken, and continuous machining in the longitudinal direction became impossible.

(11) Implementation test:
A laminated film as a sample was cut out from the position of the central portion in the film width direction in a size of 1450 mm in the longitudinal direction × 820 mm in the width direction. Next, a 50% diffuser plate, a microlens sheet, a polarizing reflector, and a polarizing plate were installed in this order on a 32-inch LCD TV LHD32K15JP backlight manufactured by Hisense Japan Co., Ltd., and subjected to a 60 ° C heat resistance test and a 60 ° C 90% RH. The flatness of the polarizing reflector after performing the moisture resistance test for 12 hours was visually evaluated.

The evaluation of flatness was judged by the following A, B and C. A was accepted.
A: No appearance problem in heat resistance test and moisture resistance heat test B: Appearance problem in any of the tests.

(12) Naphthalene dicarboxylic acid content:
The A layer of the laminated film made of crystalline polyester was dissolved in deuterated hexafluoroisopropanol (HFIP) or a mixed solvent of HFIP and deuterated chloroform, and the composition was analyzed using ¹ H-NMR and ¹³ C-NMR. ..

Hereinafter, Examples 1 to 4, 9, and 10 will be referred to as reference examples.
(Example 1)
As crystalline polyester A, the melting point is 266 ° C. and the glass transition temperature is 122 ° C., 2,6-
Polyethylene naphthalate (PEN) was used. Further, as the thermoplastic resin B, it is an amorphous resin having no melting point, the glass transition temperature is 103 ° C., and 50 mol% of 2,6-naphthalenedicarboxylic acid and 50 mol% of terephthalic acid are used as dicarboxylic acid components as diol components. Copolymerized PEN (copolymerized PE) copolymerized with 100 mol% of ethylene glycol
N1) was used.

The prepared crystalline polyester A and thermoplastic resin B were put into two single-screw extruders, respectively, melted at a temperature of 290 ° C., and kneaded. Next, the crystalline polyester A and the thermoplastic resin B are mixed by a laminating device having 11 slits while being weighed by a gear pump after passing through five FSS type leaf disc filters, respectively, in the thickness direction. A laminated body in which 11 layers were alternately laminated was obtained. The method for forming a laminated body was carried out according to the method described in Japanese Patent Laid-Open No. 2007-307893 [0053] to [0056].

Here, the length and spacing of the slits are all constant. The obtained laminate had 6 layers of crystalline polyester A and 5 layers of thermoplastic resin B, and had a laminated structure in which the layers were alternately laminated in the thickness direction. Further, the value obtained by dividing the length in the film width direction of the base lip, which is the widening ratio inside the base, by the length in the film width direction at the inlet portion of the base is set to 2.5.

The obtained cast film was heated in a roll group set at a temperature of 120 ° C., then stretched 3.3 times with a roll set at a temperature of 135 ° C. in the longitudinal direction of the film, and then cooled once. The uniaxially stretched film thus obtained is guided to a tenter, preheated with hot air at a temperature of 115 ° C., and then stretched 3.5 times in the film width direction at a temperature of 135 ° C. to obtain a biaxially stretched film as a film roll. rice field.

The physical characteristics of the obtained laminated film are shown in Table 1. The difference between the melting enthalpy and the crystallization enthalpy was small, and both the MOR and the transmittance were low.

When the obtained laminated film was further heated in a roll group set to a temperature of 160 ° C. and then stretched until the film broke, the stretching ratio (breaking elongation X at 160 ° C.) was 1.6 times. .. Therefore, the film was stretched 1.4 times in the longitudinal direction to obtain a re-stretched film.

Table 1 shows the physical characteristics of the obtained re-stretched film. It shows a high Young's modulus and a low linear expansion coefficient (40 to 50 ° C.) in the longitudinal direction of the film, which corresponds to the re-stretching direction. It could be used well even in actual use. On the other hand, although it exhibited interference reflection characteristics due to the difference in refractive index between the crystalline polyester A and the thermoplastic resin B, it did not have sufficient performance for use as a polarizing reflector.

(Example 2)
A laminated film was obtained in the same manner as in Example 1 except that the laminating device used was an device having 101 slits.

The physical characteristics of the obtained laminated film are shown in Table 1. The difference between the melting enthalpy and the crystallization enthalpy was small, and both the MOR and the transmittance were low.

When the obtained laminated film was further heated in a roll group set to a temperature of 160 ° C. and then stretched until the film broke, the stretching ratio (breaking elongation X at 160 ° C.) was 1.9 times. .. Therefore, the film was stretched 1.7 times in the longitudinal direction to obtain a re-stretched film.

Table 1 shows the physical characteristics of the obtained re-stretched film. It shows a high Young's modulus and a low linear expansion coefficient (40 to 50 ° C.) in the longitudinal direction of the film, which corresponds to the re-stretching direction. It could be used well even in actual use. In addition, it shows the interference reflection characteristics derived from the difference in the refractive index between the crystalline polyester A and the thermoplastic resin B, and showed higher polarization reflection characteristics as compared with Example 1.

(Example 3)
A laminated film was obtained in the same manner as in Example 1 except that the laminating device used was a device having 201 slits.

The physical characteristics of the obtained laminated film are shown in Table 1. The difference between the melting enthalpy and the crystallization enthalpy was small, and both the MOR and the transmittance were low.

When the obtained laminated film was further heated in a roll group set to a temperature of 160 ° C. and then stretched until the film broke, the stretching ratio (breaking elongation X at 160 ° C.) was 2.1 times. .. Therefore, the film was stretched 1.9 times in the longitudinal direction to obtain a re-stretched film.
Table 1 shows the physical characteristics of the obtained re-stretched film. It shows a high Young's modulus and a low linear expansion coefficient (40 to 50 ° C.) in the longitudinal direction of the film, which corresponds to the re-stretching direction. It could be used well even in actual use. Further, it exhibits interference reflection characteristics due to the difference in refractive index between the crystalline polyester A and the thermoplastic resin B, exhibits higher polarization reflection characteristics as compared with Example 2, and can be used as a polarization reflection member. It was at a possible level.

(Example 4)
A laminated film was obtained in the same manner as in Example 1 except that the laminating device used was an device having 401 slits.

The physical characteristics of the obtained laminated film are shown in Table 1. The difference between the melting enthalpy and the crystallization enthalpy was small, and both the MOR and the transmittance were low.

When the obtained laminated film was further heated in a roll group set to a temperature of 160 ° C. and then stretched until the film broke, the stretching ratio (breaking elongation X at 160 ° C.) was 2.4 times. .. Therefore, the film was stretched 2.2 times in the longitudinal direction to obtain a re-stretched film.
Table 1 shows the physical characteristics of the obtained re-stretched film. It shows a high Young's modulus and a low linear expansion coefficient (40 to 50 ° C.) in the longitudinal direction of the film, which corresponds to the re-stretching direction. It could be used well even in actual use. Further, it exhibits interference reflection characteristics due to the difference in refractive index between the crystalline polyester A and the thermoplastic resin B, exhibits high polarization reflection characteristics as compared with Example 3, and is extremely high as a polarization reflection member. It was performance.

(Example 5)
Copolymerization of crystalline polyester at a glass transition temperature of 119 ° C. using 100 mol% of 2,6-naphthalenedicarboxylic acid as a dicarboxylic acid component and 90 mol% of ethylene glycol and 10 mol% of neopentyl glycol as a diol component. A laminated film was obtained in the same manner as in Example 4 except that PEN (copolymerized PEN2) was used.

The physical characteristics of the obtained laminated film are shown in Table 1. The difference between the melting enthalpy and the crystallization enthalpy was even smaller than that of Example 4, and both the MOR and the transmittance were low.

When the obtained laminated film was further heated in a roll group set to a temperature of 160 ° C. and then stretched until the film broke, the stretching ratio (breaking elongation X at 160 ° C.) was 2.8 times. .. Therefore, the film was stretched 2.6 times in the longitudinal direction to obtain a re-stretched film.
Table 1 shows the physical characteristics of the obtained re-stretched film. It shows a high Young's modulus and a low linear expansion coefficient (40 to 50 ° C.) in the longitudinal direction of the film, which corresponds to the re-stretching direction. It could be used well even in actual use. Further, it exhibits interference reflection characteristics due to the difference in refractive index between the crystalline polyester A and the thermoplastic resin B, and exhibits even higher polarization reflection characteristics as compared with Example 4, and is extremely used as a polarization reflection member. It was a high performance.

(Example 6)
As a crystalline polyester, a copolymerized PEN copolymerized with a glass transition temperature of 117 ° C., 90 mol% of 2,6-naphthalenedicarboxylic acid and 10 mol% of terephthalic acid as a dicarboxylic acid component, and 100 mol% of ethylene glycol as a diol component. A laminated film was obtained in the same manner as in Example 4 except that (copolymerized PEN3) was used.

The physical characteristics of the obtained laminated film are shown in Table 1. The difference between the melting enthalpy and the crystallization enthalpy was even smaller than that of Example 4, and both the MOR and the transmittance were low.

When the obtained laminated film was further heated in a roll group set to a temperature of 160 ° C. and then stretched until the film broke, the stretching ratio (breaking elongation X at 160 ° C.) was 3.0 times. .. Therefore, the film was stretched 2.8 times in the longitudinal direction to obtain a re-stretched film.
Table 1 shows the physical characteristics of the obtained re-stretched film. It shows a high Young's modulus and a low linear expansion coefficient (40 to 50 ° C.) in the longitudinal direction of the film, which corresponds to the re-stretching direction. It could be used well even in actual use. Further, it exhibits interference reflection characteristics due to the difference in refractive index between the crystalline polyester A and the thermoplastic resin B, and exhibits even higher polarization reflection characteristics as compared with Example 4, and is extremely used as a polarization reflection member. It was a high performance.

(Example 7)
As a crystalline polyester, a copolymerized PEN copolymerized with a glass transition temperature of 117 ° C., using 70 mol% of 2,6-naphthalenedicarboxylic acid and 30 mol% of terephthalic acid as a dicarboxylic acid component, and 100 mol% of ethylene glycol as a diol component. A laminated film was obtained in the same manner as in Example 4 except that (copolymerized PEN4) was used.

The physical characteristics of the obtained laminated film are shown in Table 1. The difference between the melting enthalpy and the crystallization enthalpy was even smaller than that of Example 4, and both the MOR and the transmittance were low.

When the obtained laminated film was further heated in a roll group set to a temperature of 160 ° C. and then stretched until the film broke, the stretching ratio (breaking elongation X at 160 ° C.) was 4.0 times. .. Therefore, the film was stretched 3.8 times in the longitudinal direction to obtain a re-stretched film.
Table 1 shows the physical characteristics of the obtained re-stretched film. It shows a high Young's modulus and a low linear expansion coefficient (40 to 50 ° C.) in the longitudinal direction of the film, which corresponds to the re-stretching direction. It could be used well even in actual use. Further, although the interference reflection characteristics were exhibited due to the difference in the refractive index between the crystalline polyester A and the thermoplastic resin B, the polarization reflection characteristics were slightly lower than those of Example 4, reflecting the characteristics of the crystalline polyester. Indicated.

(Example 8)
The cast film obtained in the same manner as in Example 5 was used as a biaxially stretched film by the following manufacturing method.
The cast film was heated by a roll group set to a temperature of 120 ° C., then stretched 2.8 times by a roll set to a temperature of 135 ° C. in the longitudinal direction of the film, and then cooled once. The uniaxially stretched film thus obtained is guided to a tenter, preheated with hot air at a temperature of 115 ° C., and then stretched 3.5 times in the film width direction at a temperature of 135 ° C. to obtain a biaxially stretched film as a film roll. rice field.

The physical characteristics of the obtained laminated film are shown in Table 1. The difference between the melting enthalpy and the crystallization enthalpy was even smaller than that of Example 5, and both the MOR and the transmittance were low.

When the obtained laminated film was further heated in a roll group set to a temperature of 160 ° C. and then stretched until the film broke, the stretching ratio (breaking elongation X at 160 ° C.) was 4.2 times. .. Therefore, the film was stretched 4.0 times in the longitudinal direction to obtain a re-stretched film.
Table 1 shows the physical characteristics of the obtained re-stretched film. It shows a high Young's modulus and a low linear expansion coefficient (40 to 50 ° C.) in the longitudinal direction of the film, which corresponds to the re-stretching direction. It could be used well even in actual use. Further, it exhibits interference reflection characteristics derived from the difference in refractive index between the crystalline polyester A and the thermoplastic resin B, exhibits the same level of polarization reflection characteristics as in Example 5, and has extremely high performance as a polarization reflection member. there were. On the other hand, some performance unevenness was observed in the longitudinal direction of the film.

(Example 9)
The cast film obtained in the same manner as in Example 5 was used as a biaxially stretched film by the following manufacturing method.
The cast film was heated by a roll group set to a temperature of 10 ° C., then stretched 4.2 times by a roll set to a temperature of 135 ° C. in the longitudinal direction of the film, and then cooled once. The uniaxially stretched film thus obtained is guided to a tenter, preheated with hot air at a temperature of 115 ° C., and then stretched 3.5 times in the film width direction at a temperature of 135 ° C. to obtain a biaxially stretched film as a film roll. rice field.

The physical characteristics of the obtained laminated film are shown in Table 1. The difference between the molten enthalpy and the crystallization enthalpy, the MOR, and the transmittance are also larger than those in Example 5.
When the obtained laminated film was further heated in a roll group set to a temperature of 160 ° C. and then stretched until the film broke, the stretching ratio (breaking elongation X at 160 ° C.) was 2.0 times. .. Therefore, the film was stretched 1.8 times in the longitudinal direction to obtain a re-stretched film.
Table 1 shows the physical characteristics of the obtained re-stretched film. It shows a high Young's modulus and a low linear expansion coefficient (40 to 50 ° C.) in the longitudinal direction of the film, which corresponds to the re-stretching direction. It could be used well even in actual use. Further, although the interference reflection characteristics are exhibited due to the difference in the refractive index between the crystalline polyester A and the thermoplastic resin B, the polarization reflection characteristics are slightly lower than those in Example 5.

(Example 10)
Using the laminated film obtained in Example 5, it was re-stretched as follows to obtain a re-stretched film.

The obtained laminated film was further guided to a tenter, preheated with hot air at a temperature of 115 ° C., and then stretched at a temperature of 160 ° C. until the film broke. It was stretched 0 times. Therefore, the film was stretched 1.8 times in the width direction of the film to obtain a re-stretched film.
Table 1 shows the physical characteristics of the obtained re-stretched film, which showed a high Young's modulus and a low linear expansion coefficient (40 to 50 ° C.) in the film width direction corresponding to the re-stretching direction. The value was slightly lower than that, and even during processing into a product and during actual use, a slight curl was observed in the moist heat test. Further, although the interference reflection characteristics were exhibited due to the difference in the refractive index between the crystalline polyester A and the thermoplastic resin B, the polarization reflection characteristics were lower than those in Example 5.

(Example 11)
A laminated film was obtained in the same manner as in Example 4 except that 10% by weight of the copolymerized PEN1 and 90% by weight of the copolymerized PEN2 were mixed and used as the crystalline polyester.

The physical characteristics of the obtained laminated film are shown in Table 1. The difference between the melting enthalpy and the crystallization enthalpy was small as in Example 5, and both the MOR and the transmittance were low.

When the obtained laminated film was further heated in a roll group set to a temperature of 160 ° C. and then stretched until the film broke, the stretching ratio (breaking elongation X at 160 ° C.) was 3.4 times. .. Therefore, the film was stretched 3.2 times in the longitudinal direction to obtain a re-stretched film.
Table 1 shows the physical characteristics of the obtained re-stretched film. It shows a high Young's modulus and a low linear expansion coefficient (40 to 50 ° C.) in the longitudinal direction of the film, which corresponds to the re-stretching direction. It could be used well even in actual use. Further, it exhibits interference reflection characteristics derived from the difference in refractive index between the crystalline polyester A and the thermoplastic resin B, and has a higher polarization due to the effect of using two kinds of resins in a mixed manner as compared with Example 5. It showed reflection characteristics and had very high performance as a polarizing reflection member.

(Example 12)
As the crystalline polyester, the glass transition temperature is 112 ° C., 2,6-naphthalenedicarboxylic acid 95 mol% and isophthalic acid 5 mol% are used as the dicarboxylic acid component, and ethylene glycol 90 mol% and neopentyl glycol 10 mol% are used as the diol component. The copolymerized PEN (copolymerized PEN5) is an amorphous resin having no melting point as the thermoplastic resin B, has a glass transition temperature of 98 ° C., and contains 2,6-naphthalenedicarboxylic acid as a dicarboxylic acid component of 50 mol%. , Copolymerized PEN (copolymerized PEN6) copolymerized with 50 mol% of terephthalic acid, 90 mol% of ethylene glycol and 10 mol% of neopentyl glycol as a diol component, and laminated in the same manner as in Example 4. I got a film.

The physical characteristics of the obtained laminated film are shown in Table 2. The difference between the melting enthalpy and the crystallization enthalpy was even smaller than that of Example 5, and both the MOR and the transmittance were low.

When the obtained laminated film was further heated in a roll group set to a temperature of 160 ° C. and then stretched until the film broke, the stretching ratio (breaking elongation X at 160 ° C.) was 3.2 times. .. Therefore, the film was stretched 3.0 times in the longitudinal direction to obtain a re-stretched film.
Table 2 shows the physical characteristics of the obtained re-stretched film. It shows a high Young's modulus and a low linear expansion coefficient (40 to 50 ° C.) in the longitudinal direction of the film, which corresponds to the re-stretching direction. It could be used well even in actual use. Further, it exhibits interference reflection characteristics due to the difference in refractive index between the crystalline polyester A and the thermoplastic resin B, and exhibits even higher polarization reflection characteristics as compared with Example 4, and is extremely used as a polarization reflection member. It was a high performance.

(Example 13)
As the thermoplastic resin B, it is an amorphous resin having no melting point, has a glass transition temperature of 92 ° C., uses 35 mol% of 2,6-naphthalenedicarboxylic acid and 65 mol% of terephthalic acid as the dicarboxylic acid component, and ethylene glycol as the diol component. A laminated film was obtained in the same manner as in Example 12 except that a copolymerized PEN (copolymerized PEN6) copolymerized with 90 mol% and 10 mol% of neopentyl glycol was used.

The physical characteristics of the obtained laminated film are shown in Table 2. The difference between the melting enthalpy and the crystallization enthalpy was even smaller than that of Example 5, and both the MOR and the transmittance were low.

When the obtained laminated film was further heated in a roll group set to a temperature of 160 ° C. and then stretched until the film broke, the stretching ratio (breaking elongation X at 160 ° C.) was 3.4 times. .. Therefore, the film was stretched 3.2 times in the longitudinal direction to obtain a re-stretched film.
Table 2 shows the physical characteristics of the obtained re-stretched film. It shows a high Young's modulus and a low linear expansion coefficient (40 to 50 ° C.) in the longitudinal direction of the film, which corresponds to the re-stretching direction. It could be used well even in actual use. Further, it exhibits interference reflection characteristics due to the difference in refractive index between the crystalline polyester A and the thermoplastic resin B, and exhibits even higher polarization reflection characteristics as compared with Example 4, and is extremely used as a polarization reflection member. It was a high performance.

(Example 14)
As the crystalline polyester, the glass transition temperature is 110 ° C., 90 mol% of 2,6-naphthalenedicarboxylic acid and 10 mol% of isophthalic acid are used as the dicarboxylic acid component, and 90 mol% of ethylene glycol and 10 mol% of neopentyl glycol are used as the diol component. A laminated film was obtained in the same manner as in Example 13 except that the copolymerized PEN (copolymerized PEN8) was used.

The physical characteristics of the obtained laminated film are shown in Table 2. The difference between the melting enthalpy and the crystallization enthalpy was even smaller than that of Example 5, and both the MOR and the transmittance were low.

When the obtained laminated film was further heated in a roll group set to a temperature of 160 ° C. and then stretched until the film broke, the stretching ratio (breaking elongation X at 160 ° C.) was 3.0 times. .. Therefore, the film was stretched 2.8 times in the longitudinal direction to obtain a re-stretched film.
Table 2 shows the physical properties of the obtained re-stretched film. It shows a high Young's modulus and a low linear expansion coefficient (40 to 50 ° C.) in the longitudinal direction of the film corresponding to the re-stretching direction, but is slightly younger than that of Example 4. The coefficient was low and the handleability during processing was slightly inferior. Further, although the interference reflection characteristics are exhibited due to the difference in the refractive index between the crystalline polyester A and the thermoplastic resin B, the polarization reflection characteristics are slightly lower than those in Example 4.

(Comparative Example 1)
A film (corresponding to the laminated film of Example 1) was obtained in the same manner as in Example 1 except that a single-layer film of PEN was used as the cast film. The physical characteristics of the obtained film are shown in Table 2, and the difference between the melting enthalpy and the crystallization enthalpy was large, and the MOR was higher than that of Example 1.

When the obtained film was further heated in a roll group set to a temperature of 160 ° C. and then stretched until the film broke, the stretching ratio (breaking elongation X at 160 ° C.) was 1.5 times. Therefore, the film was stretched 1.3 times in the longitudinal direction to obtain a re-stretched film.

The physical characteristics of the obtained re-stretched film are shown in Table 2, which shows a high Young's modulus and a low linear expansion coefficient (40 to 50 ° C.) in the longitudinal direction of the film corresponding to the re-stretching direction, because they do not have a laminated structure. In addition, the film did not show any peculiar reflection performance, and the film was brittle as compared with the film of Example 1, so that the handleability was deteriorated. This film was inferior in continuous productivity due to film breakage during processing into a product.

(Comparative Example 2)
A film (corresponding to the laminated film of Example 1) was obtained in the same manner as in Example 1 except that the laminating device used was an device having three slits. The physical characteristics of the obtained film are shown in Table 2, and the difference between the melting enthalpy and the crystallization enthalpy was large, and the MOR was higher than that of Example 1.

When the obtained film was further heated in a roll group set to a temperature of 160 ° C. and then stretched until the film broke, the stretching ratio (breaking elongation X at 160 ° C.) was 1.6 times. Therefore, the film was stretched 1.4 times in the longitudinal direction to obtain a re-stretched film.

The physical characteristics of the obtained re-stretched film are shown in Table 2, which shows a high Young's modulus and a low linear expansion coefficient (40 to 50 ° C.) in the longitudinal direction of the film corresponding to the re-stretching direction, because they do not have a laminated structure. In addition, the film did not show any peculiar reflection performance, and the film was brittle as compared with the film of Example 1, so that the handleability was deteriorated. This film was inferior in continuous productivity due to film breakage during processing into a product.

(Comparative Example 3)
The cast film obtained in the same manner as in Example 5 was heated by a roll group set to a temperature of 120 ° C., and then stretched 4.5 times by a roll set to a temperature of 135 ° C. in the longitudinal direction of the film. After that, it was once cooled.

The uniaxially stretched film thus obtained is guided to a tenter, preheated with hot air at a temperature of 135 ° C., and then stretched 4.5 times in the film width direction at a temperature of 150 ° C. to obtain a biaxially stretched film as a film roll. rice field.

The physical characteristics of the obtained laminated film are shown in Table 2, and the difference between the molten enthalpy and the crystallization enthalpy, the MOR, and the transmittance are also larger than those in Example 5.
When the obtained laminated film was further heated in a roll group set to a temperature of 160 ° C. and then stretched until the film broke, the stretching ratio (breaking elongation X at 160 ° C.) was 1.5 times. .. Therefore, the film was stretched 1.3 times in the longitudinal direction to obtain a re-stretched film.
Table 2 shows the physical properties of the obtained re-stretched film. The Young's modulus and linear expansion coefficient (40 to 50 ° C.) in the longitudinal direction of the film corresponding to the re-stretching direction are both lower than those in Example 5. Film breakage occurred during processing into products, resulting in poor continuous productivity.

(Comparative Example 4)
The cast film obtained in the same manner as in Example 5 was heated by a roll group set to a temperature of 120 ° C., and then stretched 4.5 times by a roll set to a temperature of 135 ° C. in the longitudinal direction of the film. After that, it was once cooled.

The uniaxially stretched film thus obtained is guided to a tenter, preheated with hot air at a temperature of 135 ° C., stretched 4.5 times in the film width direction at a temperature of 150 ° C., and continuously heated to 220 ° C. The heat treatment was carried out by transporting the film in the oven. By trimming both ends of the obtained biaxially stretched film, the desired laminated film was obtained as a film roll.

The physical characteristics of the obtained laminated film are shown in Table 2, and the difference between the molten enthalpy and the crystallization enthalpy, the MOR, and the transmittance are also larger than those in Example 5.
The obtained laminated film was further heated in a roll group set at a temperature of 160 ° C., and then stretched until the film broke. there were.

1. 1. Film longitudinal direction 2. 2. Polarization perpendicular to the plane of incidence including the longitudinal direction of the film. Polarization parallel to the plane of incidence, including the longitudinal direction of the film

Claims (7)

A laminated film in which a layer A made of crystalline polyester and a layer B made of a thermoplastic resin B different from the crystalline polyester are alternately laminated in a total of 11 or more layers, which is observed in differential scanning calorimetry (DSC). The difference (| ΔHc−ΔHm |) between the melting enthalpy (ΔHm) and the crystallization enthalpy (ΔHc) is 3 J / g or more and 10 J / g or less, and 160 in the longitudinal direction or the direction orthogonal to the longitudinal direction of the laminated film. A sample having a length of 150 mm and a width of 10 mm at ° C. has a breaking elongation of 300% or more, contains 50 mol% or more and 90 mol% or less of naphthalenedicarboxylic acid among the carboxylic acid components constituting the crystalline polyester, and is thermoplastic. A laminated film characterized in that the resin B is an amorphous polyethylene naphthalate copolymer resin . The laminated film according to claim 1 , wherein the MOR at the center in the film width direction measured by the molecular orientation meter is 1.5 or less. For the polarizing component parallel to the incident surface including the longitudinal direction of the laminated film, the transmittance at an incident angle of 0 ° is T1, and for the polarizing component perpendicular to the incident surface including the longitudinal direction of the laminated film, the incident angle is 0 °. The laminated film according to claim 1 or 2 , wherein when the transmittance is T2, the minimum values of the transmittances T1 and T2 at a wavelength of 400 to 1400 nm are both 60% or more. The laminated film according to any one of claims 1 to 3 , wherein the maximum value of the degree of polarization P of the laminated film at a wavelength of 400 to 1400 nm obtained from the following formula (1) is 20% or less.
P (λ) = (T2 (λ) -T1 (λ)) / (T2 (λ) + T1 (λ)) ... Equation (1)
λ: Measurement wavelength (nm, 400 to 1400 nm) The laminated film according to any one of claims 1 to 4 , wherein only one melting peak having a differential scanning calorimetry (DSC) of 5 J / g or more is confirmed. When the magnification at which the film breaks when the laminated film is stretched in the longitudinal direction is X times, and the magnification at which the film breaks when the laminated film is stretched in the direction orthogonal to the longitudinal direction is X'fold, the laminated film is said. Includes a re-stretched film obtained by stretching (X-0.2) times in the longitudinal direction, or a re-stretched film obtained by stretching the laminated film (X'-0.2) times in a direction orthogonal to the longitudinal direction. When the reflectance at an incident angle of 10 ° is R3 for the polarization component parallel to the incident surface and R4 is taken for the polarization component perpendicular to the incident surface including the stretching direction at an incident angle of 10 °. The laminated film according to any one of claims 1 to 5 , wherein the reflectance at 550 nm satisfies the following formulas (2) and (3).
R3 (550) ≧ 70% ・ ・ ・ Equation (2)
R4 (550) ≤ 40% ... Equation (3). A method for producing a polarized reflector, wherein the laminated film according to any one of claims 1 to 6 is stretched 1.3 to 4 times to produce a polarized reflector satisfying the following formulas (2) and (3).
R3 (550) ≧ 70% ・ ・ ・ Equation (2)
R4 (550) ≤ 40% ... Equation (3).

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