JP2018171901A - Film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film which is excellent in heat whitening resistance and does not inhibit transparency even through processing such as high temperature molding, and causes less interference color and interference fringe along with a multilayer structure.SOLUTION: There is provided a laminated film in which 5 or more layers of layers (layer A) formed of a thermoplastic resin A and layers (layers B) formed from a thermoplastic resin B are alternately layered, where in DSC curve obtained when a temperature is raised at 20°C/min to a temperature from 25°C to 300°C in differential scanning calorimeter (DSC), an endothermic peak at which a temperature of a peak top is highest in a range of 130-300°C is in a range of 160-246°C, and a crystal melting enthalpy (ΔHm) in a range of 130-300°C determined from the DSC curve is 5-19 J/g.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a film.

Thermoplastic resin films, especially biaxially stretched polyester films, have excellent properties such as mechanical properties, electrical properties, dimensional stability, transparency, and chemical resistance. Widely used as a substrate film in applications. Particularly in recent years, in the field of flat panel displays and touch panels, demand for various optical films such as a polarizing plate protective film (polarizer protective member), a circularly polarizing plate retardation film (circular polarizing plate member), and a transparent conductive film is increasing. Among them, in the polarizing plate protective film application, replacement of a conventional TAC (triacetyl cellulose) film with a biaxially oriented polyester film has been actively studied for the purpose of cost reduction. However, the biaxially oriented polyester film cannot sufficiently control the interference color generated when it is assembled as a liquid crystal display resulting from the orientation of the polyester during stretching, and the quality of the screen display is lowered. Therefore, the polyester used for the biaxially oriented polyester film is preferably a polyester with reduced crystallinity from the viewpoint of the quality when the screen is displayed, but the polyester with reduced crystallinity is heated in the heating step. There is a problem that whitening proceeds by crystallization. As one of the solutions, it is known that the biaxially oriented polyester film has a multi-layered structure, and this is known to suppress thermal crystallization (for example, Patent Document 1). In addition, it is known that multi-layer lamination of films exhibits various other effects. For example, polyethylene terephthalate, which is a crystalline thermoplastic resin, and sebacic acid copolymerized polyethylene terephthalate, which is a crystalline thermoplastic resin, are laminated. It has been proposed that the tear resistance is improved (for example, Patent Document 2). In addition, it has been proposed to improve folding resistance by stacking thermoplastic resins having different compatibility (for example, Patent Document 3). In addition, it has been proposed to cause interference reflection by regularly laminating resins having different refractive indexes in the thickness direction (for example, Patent Document 4). In addition, it has been proposed to improve pinhole resistance and gas barrier properties by multilayering polyethylene terephthalate and nylon (for example, Patent Document 5). Moreover, it is excellent in perforation cutting property and acoustic property by laminating a thermoplastic resin blended with each other's raw materials (for example, Patent Documents 6 and 7).

JP 2013-256110 A Japanese Patent Laid-Open No. 6-199095 Japanese Patent No. 4175077 JP 2007-55258 A Japanese Patent No. 4259049 JP 2007-55258 A JP 2009-96116 A

  However, the conventional multilayer laminated film has a problem that although whitening is suppressed to a certain extent by thermal crystallization, an interference color is generated by multilayering of resins having different refractive indexes, so that it cannot be used depending on applications.

  The subject of this invention is solving the above-mentioned subject. That is, an object of the present invention is to provide a film that does not produce interference color or interference fringes while suppressing whitening of the resin by multilayer lamination (hereinafter, the characteristic of suppressing whitening by heat may be referred to as heat-resistant whitening).

  The above-described problem is a laminated film in which layers (layer A) made of thermoplastic resin A and layers (layer B) made of thermoplastic resin B are alternately laminated in the thickness direction, and differential scanning calorimetry In the DSC curve obtained when the temperature is increased from 25 ° C. to 300 ° C. at 20 ° C./min in (DSC), the endothermic peak having the highest peak top temperature in the range of 130 to 300 ° C. is 160 to 300 ° C. It can be achieved by a film having a crystal melting enthalpy (ΔHm) of 5 to 19 J / g in the range of 246 ° C. and 130 to 300 ° C. determined from the DSC curve.

  Since the film of the present invention is excellent in heat-resistant whitening property by being multilayered, it hardly inhibits transparency even after processing such as high-temperature molding. Moreover, since there are few interference colors, interference fringes, etc. accompanying a multilayer structure, when it is used as an optical member, transparency is hardly hindered.

It is a figure which shows the spectral reflection curve of a multilayer laminated film. It is a figure which shows the spectrum which Fourier-transformed the spectral reflection curve of the multilayer laminated film.

  Hereinafter, the film of the present invention will be described in detail.

  The film of the present invention is a laminated film in which five or more layers (layer B) made of thermoplastic resin A and layers (layer B) made of thermoplastic resin B are alternately laminated in the thickness direction. The thermoplastic resins used as the thermoplastic resin A and the thermoplastic resin B are, for example, polyester, polyamide, polyacetal, polyphenylene sulfide, polyether ether ketone, liquid crystal polymer, polyethylene, polypropylene, polyvinyl alcohol, polyvinylidene chloride, syndiotactic It is represented by tic polystyrene. Among these, polyester is particularly preferable, and as the crystalline polyester, polyester obtained by polymerization from a monomer mainly composed of aromatic dicarboxylic acid or aliphatic dicarboxylic acid and diol is preferable. 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 4,4′-diphenyl. Examples thereof include dicarboxylic acid, 4,4′-diphenyl ether dicarboxylic acid, 4,4′-diphenylsulfone dicarboxylic acid, and the like. Examples of the aliphatic dicarboxylic acid include adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexanedicarboxylic acid and ester derivatives thereof. Of these, terephthalic acid and 2,6-naphthalenedicarboxylic acid exhibiting a high refractive index are preferable. These acid components may be used alone, but may be used in combination of two or more, and may further be partially copolymerized with oxyacids such as hydroxybenzoic acid.

  Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentanediol. 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis (4- Hydroxyethoxyphenyl) propane, isosorbide, spiroglycol and the like. Of these, ethylene glycol is preferably used. These diol components may be used alone or in combination of two or more.

  More specifically, polyethylene terephthalate, polyethylene-2,6-naphthalate, polymethylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexylene dimethylene terephthalate and the like are used. Of course, these resins such as polyesters may be homopolymers or copolymers. In the case of polyesters, examples of copolymerization components include diethylene glycol, neopentyl glycol, polyalkylene glycol, and bisphenol A ethylene oxide. Diol components such as adducts, dicarboxylic acid components such as dimer acid, adipic acid, sebacic acid, phthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid are used.

  In the film of the present invention, it is preferable that the thermoplastic resin A and / or the thermoplastic resin B contain spiroglycol and isosorbide components from the viewpoint of suppressing curling and wrinkling due to heat treatment of the polarizing plate. In particular, the isosorbide component is particularly preferable because it is inexpensive and easily obtains the above-described effects.

  The film of the present invention is a laminated film in which five or more layers (layer B) made of thermoplastic resin A and layers (layer B) made of thermoplastic resin B are alternately laminated in the thickness direction. By multilayering the films, thermal crystallization can be suppressed even when the degree of crystallinity of the film is low, so that the increase in whitening of the film is small even when heated at high temperatures. The effect of multilayer lamination varies depending on the combination of the resins to be combined and the number of laminated layers, in addition to the above-described uniformity in physical properties in the width direction and heat whitening resistance. The number of layers is 12 to 85 layers if you want to increase tear resistance, the number of layers is 20 to 99 if you want to increase fold resistance, and if you want to increase the uniformity of physical properties in the width direction. For example, the number of laminated layers is preferably 20 to 1000 layers, and the range of 100 to 1000 layers is preferable if it is desired to improve the heat-resistant whitening property. If the number of layers is out of this range, the desired effect may not be sufficiently obtained. Multi-layer lamination in the thickness direction is performed by a method of sending out from different flow paths using two or more extruders and feeding into a multi-layer laminating apparatus. As the multi-layer laminating apparatus, an apparatus having independent flow paths such as a multi-manifold die or a feed block and a combination thereof are preferable. In an apparatus for dividing and re-stacking layers such as a static mixer or a square mixer, as the number of elements increases, the accuracy of stacking thickness deteriorates, so the number of elements needs to be kept within one. Lamination using a feed block can be easily realized by applying the method described in the paragraphs [0053] to [0063] of JP-A-2007-307893. However, the gap and length of the slit plate are different because of design values that determine the layer thickness. The layer thickness may be constant, but if it exceeds 100 layers, the influence of coloring due to interference reflection increases, so the layer thickness from the front surface to the back surface changes gradually. Is preferred. Furthermore, it is preferable that the outermost layer has a thick film layer having a thickness of 1 μm or more from the viewpoint of suppressing a flow mark generated by an unstable phenomenon of the resin flow.

  The layer thickness of the film of the present invention is not particularly limited, but it is preferable that the thickness of each layer excluding the outermost layer is 60 nm or less. If the thickness per layer is 60 nm or less, the reflected color is not seen in the visible light region, which is preferable. It is further preferable that the thickness per layer is 30 nm or less because the effect is further enhanced. On the other hand, when the outermost layer thickness is thick, interference fringes may be seen. Therefore, when the outermost layer thickness is also set to 60 nm or less, or the outermost layer thickness exceeds 60 nm, in-plane refraction of the A layer and the B layer is performed. The difference in rate is reduced, specifically, the in-plane refractive index difference between the A layer and the B layer is set to 0.02 or less, more preferably 0.01 or less, and further preferably 0.005 or less. This makes it possible to reduce interference fringes.

  The film of the present invention has the highest peak in the range of 130 to 300 ° C. in the DSC curve obtained when the temperature is raised from 25 ° C. to 300 ° C. at a rate of 20 ° C./min by differential scanning calorimetry (DSC). An endothermic peak having a high top temperature is in the range of 160 to 246 ° C., and the crystal melting enthalpy (ΔHm) in the range of 130 to 300 ° C. determined from the DSC curve is 5 to 19 J / g. By taking such a configuration, the retardation of the film can be lowered. Preferably, the endothermic peak having the highest peak top temperature in the range of 130 to 300 ° C. is in the range of 210 to 246 ° C., and the crystal melting enthalpy (ΔHm) in the range of 130 to 300 ° C. determined from the DSC curve is 8-15 J / g. If the crystal melting enthalpy (ΔHm) is below this range, the flatness of the film may be impaired in the film-forming process due to insufficient heat resistance. Since the crystal melting enthalpy (ΔHm) of the film depends on the crystal melting enthalpy of the resin constituting each layer and the lamination ratio, a resin having low crystallinity is used as the resin constituting the A layer and / or the B layer, or It can be adjusted by lowering the ratio of the crystalline resin in the resin constituting the A layer and / or the B layer. If one of the A and B layers is made of a crystalline resin, and the other layer is made of an amorphous resin, interference color is likely to occur. It is preferable that the crystallinity of the resin is not so different, specifically, the difference in crystal melting enthalpy is 30 or less. More preferably, it is 10 or less. In addition, when a low crystalline resin is used, crystallization is insufficient in the film forming process, and thus the heat whitening resistance tends to be inferior. However, when the number of layers is 100 to 1000, this phenomenon is suppressed. The crystalline resin, the low crystalline resin, and the amorphous resin as used herein are those having a heat of crystal melting of 26 mJ / mg or more when the temperature is raised at a rate of temperature rise of 20 ° C./min in differential calorimetry (DSC). If it is less than 26 mJ / mg and 1 mJ / mg or more, it is a low crystalline resin, and if it is less than 1 mJ / mg, it is an amorphous resin. Further, when both the resin constituting the A layer and the resin constituting the B layer are low crystalline resins, the low crystallinity in the range of the heat of crystal melting of less than 26 mJ / mg and 5 mJ / mg or more from the viewpoint of film forming properties. It is preferable to use a functional resin.

  Further, when polyester resins are mixed, transesterification starts, and even between crystalline resins, the crystallinity is lowered and the crystal melting enthalpy (ΔHm) is lowered. The degree of reduction varies depending on the raw material type, compatibility, and raw material catalyst, but when melt-kneading multiple types of polyester resins during melt film formation, the decrease in crystal melting enthalpy (ΔHm) is significant when the kneading time is 10 minutes or longer. It becomes. Therefore, if a method of increasing the kneading time is used, the crystallinity can be lowered and the crystal melting enthalpy (ΔHm) can be reduced even when a plurality of crystalline resins are used. In particular, instead of melt-kneading once, a method of melt film-forming in a plurality of times using a chip obtained by increasing the melt-kneading speed with a twin screw extruder or the like is preferable.

The film of the present invention has a spectral reflectance curve obtained by measuring the reflectance at a wavelength of 300 to 2300 nm and plotting the vertical axis as the reflectance and the horizontal axis as the wavelength, satisfying the following (3) and (4). It is preferable.
(3) The maximum reflectance in the wavelength range of 300 to 2300 nm is 21% or less.
(4) The integrated value (I ₀ ) of the wavelength and reflectance in the wavelength range of 300 to 2300 nm is 30000 or less.
A spectral reflection curve is calculated | required using the measurement result of the reflectance in the wavelength range of 300 nm-2300 nm using a spectrophotometer (Hitachi Ltd. U-4100 Spectrophotometer). The reflectance of (3) represents the interference intensity between the layers of the multilayer laminated film. When this value is higher than 21%, interference fringes are easily seen. This tendency is particularly remarkable under a three-wavelength fluorescent lamp that is used as office lighting and has a high emission intensity at a specific wavelength. Moreover, it is preferable for the same reason that the reflectance is generally low in the wavelength range of 300 nm to 2300 nm, and the integral value (I ₀ ) of (4) represents this. In particular, it is preferable that the reflectance of (3) is 21% or less and the integral value (I ₀ ) of (4) is 30000 or less because the film transparency is excellent and interference colors and interference fringes are less likely to occur. (3) is more effective when it is preferably 18% or less and the integral value of (4) is 25000 or less. The lower limit of the integral value is not particularly limited. The integrated value is described in detail in the measurement method of the example. In the multilayer laminated film, the reflectivity increases depending on the in-plane refractive index difference between the A layer and the B layer and the number of layers. Therefore, in order to achieve (3) and (4), the number of layers must be reduced, A A method of reducing the in-plane refractive index difference between the layer and the B layer is exemplified. On the other hand, a certain number of layers (5 layers or more) are required to exhibit the effects of multilayer lamination such as heat-resistant whitening property. Therefore, in the film of the present invention, the in-plane refractive index difference between the A layer and the B layer is preferably low, and the refractive index difference between the A layer and the B layer is 0.02 or less, more preferably 0.01 or less. More preferably, a combination of resins of 0.005 or less is preferable. In addition, it is necessary to take into consideration that the refractive index changes in the course of biaxial stretching and heat treatment. For example, in the case of a crystalline resin and a low crystalline resin, the degree of refractive index generated by biaxial stretching is different, and the behavior of refractive index increase / decrease is different depending on the heat treatment. Therefore, the thermoplastic resin A and the thermoplastic resin B are It is preferable that both are crystalline resins or a combination of low crystalline resins because the refractive indexes of both are easily approximated. In particular, the combination of low crystalline resins reduces the phase difference and reduces the anisotropy in the triaxial direction due to stretching. Therefore, when used in a liquid crystal or organic EL screen display film, interference unevenness and rainbow Unevenness is reduced. The low crystalline resin has a drawback that the heat-resistant whitening property is inferior because crystallization is not sufficiently progressed, but the disadvantage is also suppressed in the formation of a multi-priesthood layer. In addition, since the heat-resistant whitening property is exhibited even in the lamination of the same resin, the method of laminating completely the same low crystalline resin is preferable from the viewpoint of suppressing interference unevenness, but it is more melted than the completely identical resin. A combination of resins having the same composition but having a viscosity of 0.05 to 0.2, more preferably a melt viscosity of 0.1 to 0.15 is more excellent in heat-resistant whitening. It is possible to finally obtain a biaxially stretched film that approximates the refractive index by combining a low refractive index crystalline resin and a high refractive index low crystalline resin. This is difficult.

The film of the present invention is obtained by measuring the reflectance at a wavelength of 300 to 2300 nm after stretching to a surface magnification of 1.5 times under the conditions described later, and plotting the reflectance on the vertical axis and the wavelength on the horizontal axis. In the curve, the difference between (I ₀ ) and (I ₁ ) is preferably 2000 or less when the integral value (I ₁ ) of the wavelength and reflectance in the wavelength range of 300 to 2300 nm is used. The surface magnification shown here is a value obtained by dividing the film thickness before stretching by the film thickness after stretching (surface magnification = film thickness before stretching / film thickness after stretching). It is preferable that the difference between (I ₀ ) and (I ₁ ) is 2000 or less because the appearance does not change even if the film thickness changes in the molding process.

  The film of the present invention measures the reflectance at a wavelength of 313 to 800 nm, the spectrum obtained by Fourier analysis of the spectral reflection curve obtained by plotting the reflectance on the vertical axis and the wavelength on the horizontal axis, and the frequency on the vertical axis. When the intensity of the component and the frequency component are plotted on the horizontal axis, the sum of the intensities of the frequency components in the range of 0.05 to 0.3 is preferably 12 or less. In the multilayer laminated film, when there is a difference in refractive index between one layer and the other layer, interference fringes occur due to interference at the layer interface in the reflectance. As a result, in the spectral reflection curve, undulation in which the reflectivity oscillates up and down with changes in wavelength appears (FIG. 1), and the interference fringe becomes more noticeable as the amplitude of this undulation increases. In particular, in the case of a multilayer laminated film, undulations with a number of periods occur as the layer thickness increases and the refractive index difference increases, so that multiple interference fringes are observed. In the spectrum obtained by Fourier transforming this spectral reflection curve, a number of peaks are observed depending on the amplitude and number of waviness (FIG. 2). Interference fringes visually recognized by humans depend on the sum of the intensities of frequency components in this spectrum, particularly in the frequency range of 0.05 to 0.3. When this value is set to 12 or less, the interference fringes of the multilayer laminated film are reduced, and it is particularly preferable that the value is 8 or less.

  The spectral reflection curve of the multilayer laminated film can be obtained by using the above-mentioned spectrophotometer (U-4100 Spectrophotometer manufactured by Hitachi, Ltd.), and the Fourier transform can be performed by, for example, EXCEL data processing. Of course, since there are many known devices and software having the same function regarding the Fourier transform, it is not necessary to be limited to this method.

The film of the present invention preferably has a chroma C ^* of 4 or less. If it exceeds 4, discoloration may be observed in the transmission and reflection of the film. If it is 2 or less, it is more preferable because it becomes an achromatic color, and if it is 1.5 or less, it is more preferable because interference unevenness is also suppressed. The method for achieving the above is not particularly limited, but it is preferable to reduce the in-plane refractive index difference between the A layer and the B layer, and the refractive index difference between the A layer and the B layer is 0.02 or less, more preferably 0. .01 or less, and more preferably a combination of resins of 0.005 or less.

  The film of the present invention preferably has a front retardation Re of 400 nm or less. The phase difference here means a phase difference in the in-plane direction. Further, the front phase difference (hereinafter also referred to as “Re”) represents a phase difference when the incident angle is 0 °, and the incident angle of 0 ° is light incidence from a plane normal direction. The front phase difference is generally 0 to 200 nm from the viewpoint of suppressing interference colors observed by crossed Nicols and parallel Nicols observation, and rainbow unevenness observed with the naked eye on a liquid crystal display due to a birefringent material such as a polyester film. It is preferably 0 to 150 nm, more preferably 0 to 100 nm, and particularly preferably 0 to 50 nm. In general, the phase difference is calculated from the product of the maximum value of the refractive index difference between two orthogonal directions in the plane of the film and the film thickness. In the present invention, the front phase difference is Oji Scientific Instruments Co., Ltd. The values measured by the phase difference measuring device KOBRA series manufactured by the manufacturer shall be used. When the front phase difference exceeds 400 nm, an interference color may occur when mounted on a liquid crystal display as a polarizing plate protective film. If the front phase difference is 200 nm or less, the interference color disappears and is most preferable. As an achievement means, it is preferable to use a thermoplastic resin A or B or a resin having low crystallinity for both.

  As for the film of this invention, it is preferable that front phase difference Re (nm), thickness phase difference Rt (nm), and film thickness T (micrometer) satisfy | fill the following formula | equation.

Re / T ≦ 5 (1)
Rt / T ≦ 12 (2)
The thickness phase difference (hereinafter also referred to as Rt) represents the phase difference when the incident angle is 50 °, and if this value is 400 nm or less, the rainbow unevenness is small and the interference color is almost colorless. It is particularly preferable that Rt is 300 nm or less because the interference color is almost completely colorless. When Rt exceeds 400 nm, when the polarizing plate protective film is mounted on a liquid crystal display and observed at an angle, the interference color is likely to be seen, and the display quality may be degraded.

  Rt depends on the product of the refractive index in the in-plane direction, the anisotropy of the refractive index in the thickness direction, and the film thickness. Conventionally, as a method for reducing Rt, a method of thinning a film (less than 15 μm) has been adopted. However, when the film is thinned, there are problems that the difficulty of forming a polarizing plate increases, and that the secondary processing such as hard coating is poor in handling. As a result of diligent investigations by the present inventors, a film having a film thickness of more than 15 μm is selected by selecting a polymer material in which the molecular chains are hardly oriented as much as possible as the thermoplastic resin constituting the multilayer laminated film. Even so, it has been found that Rt can be reduced. Furthermore, by satisfying the relational expression (2) between Rt and film thickness, a film having both thickness retardation and handling property can be obtained. In order to achieve the formula (2), there is a method of increasing the ratio of the amorphous resin of the resin constituting the multilayer laminated film. For example, a method that uses a low crystalline resin or blended amorphous resin in one layer, uses an amorphous resin in the other layer, and increases the ratio of the layers using the amorphous resin ( The ratio of the layer of the low crystalline resin / the ratio of the layer of the amorphous resin is 0.4 or less, preferably 0.3 or less, and most preferably 0.2 or less). Rt / T is more preferably 11 or less.

  Re represents the phase difference when the incident angle is 0 ° as described above, and is composed of the product of the maximum value of the refractive index difference in two orthogonal directions in the plane of the film and the film thickness. Adjustment is possible by balancing the stretching and film thickness. By satisfying the relational expression (1) between Re and film thickness, a film having both front phase difference and handling property can be obtained.

  The film of the present invention preferably has a haze change of 1.0% or less before and after being held for 12 hours in an atmosphere of a temperature of 100 ° C. and a relative humidity of 35 RH% or less. When the above properties are satisfied, the heat-resistant whitening property is excellent, and it can be used without problems even in use in a high temperature atmosphere or high temperature molding. The achievement method is not particularly limited, and examples thereof include a method of suppressing the crystallization rate by using a resin with low crystallinity or by setting the layer thickness to 150 nm or less per layer. . In differential scanning calorimetry (DSC), when the crystallization enthalpy (ΔHTc) when held at 100 ° C. for 1 hour is 0.5 J / g or less, the crystallization rate is sufficiently suppressed and heat resistance whitening resistance is particularly excellent. Therefore, it is preferable.

  The film of the present invention preferably has a bending strength of 2.5 g / 5 mm or less. When the bending strength of the film is lower than the above value, the vibration damping performance is excellent. Examples of the method for lowering the bending strength include a method of incorporating an elastomer or a resin having a melting point of 200 ° C. or lower into the resin constituting the A layer and the B layer, and in particular, in the range of 5 to 60% by weight. It is preferable. Examples of the elastomer or the resin having a melting point of 200 ° C. or less include a polyester elastomer in which a hard segment made of polyester and a soft segment made of aliphatic polycarbonate are bonded. Here, the term “bonded” means that the hard segment and the soft segment are not bonded by a chain extender such as an isocyanate compound, but the units constituting the hard segment and the soft segment are directly bonded by an ester bond or a carbonate bond. The state that is. For example, it is preferable to obtain the polyester constituting the hard segment, the polycarbonate constituting the soft segment, and if necessary, various copolymerization components while melting and repeating the transesterification reaction and depolymerization reaction for a certain period of time (hereinafter referred to as blocking reaction). Sometimes called). When the main hard segment is a polybutylene naphthalate / butylene isophthalate unit, the melting point of the resulting thermoplastic polyester elastomer is preferably 180 to 225 ° C. More preferably, it is 190-225 degreeC.

  The film of the present invention preferably has an elastic modulus of 2700 MPa or less. The elastic modulus of the film is an index of molecular orientation and crystallization, and the lower the film, the more flexible. An elastic modulus of 2700 MPa or less is preferable because it has high vibration damping properties and can be applied to vibration damping materials and polarizing plate protective films. On the other hand, since it will become unstable in terms of heat resistance and dimensional stability if it is too low, it is preferably 1800 MPa or more.

  The film of the present invention is used for damping vibrations at places where vibrations occur in vehicles, railways, aircraft, ships, home appliances / OA equipment, precision equipment, construction machinery, civil engineering buildings, housing equipment, medical equipment, shoes, sports equipment, and the like. It can be widely used as a material. It can also be used for vibration damping materials such as cassette tape labels, hard disks, handy cameras, and digital cameras.

  The laminated body which provided the indium tin oxide (ITO) film | membrane on the at least single side | surface of the film of this invention can be used suitably for the process film at the time of manufacturing an electroconductive film. The conductive film has a process of heat treatment at a high temperature for crystallization of the ITO film. However, if the film of the present invention is excellent in heat-resistant whitening property, problems such as reduced visibility due to whitening of the film appearance may occur. Can be suppressed. Moreover, when it uses for display members, such as a touch panel, it is calculated | required that a front phase difference is low, but the problem can also be solved if it is a film with a certain structure of this invention.

  The film thickness of the film of the present invention is not particularly limited. When the front retardation is desired to be 400 nm or less, or when it is used as a polarizer protective film which is becoming thinner or a laminate having an indium tin oxide (ITO) film on at least one surface, it is preferably 40 μm or less. Since the front phase difference is represented by the product of the thickness and the birefringence Δn, it may be difficult to reduce the phase difference when the film thickness is greater than 40 μm. On the other hand, the thickness of the film is preferably 25 μm or more and 75 μm from the viewpoint of handling in fields where the demand for film thinning is not so high, such as in-vehicle displays, and uses with many post-processing steps.

  Next, the preferable manufacturing method of the film of this invention is demonstrated below. Of course, the present invention should not be construed as being limited to such examples. Moreover, the laminated structure of the film used for this invention can be simply implement | achieved by the method similar to the content as described in the [0053]-[0063] stage of Unexamined-Japanese-Patent No. 2007-307893. In the present invention, the number of layers can be reduced so that a single slit plate can be used to form a multilayer, which is preferable from the viewpoint of stacking accuracy in the width direction as compared to using three slit plates. .

  A thermoplastic resin is prepared in the form of pellets. The pellets are dried in hot air or under vacuum as necessary, and then supplied to a separate extruder. In the extruder, the resin melted by heating to a temperature equal to or higher than the melting point is made uniform in the amount of resin extruded by a gear pump or the like, and foreign matter or denatured resin is removed through a filter or the like. These resins are formed into a desired shape by a die and then discharged. Then, the 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-like, tape-like, needle-like, or knife-like electrode to be brought into close contact with a cooling body such as a casting drum by an electrostatic force and rapidly solidify. Also preferred is a method in which air is blown out from a slit-like, spot-like, or planar device to be brought into close contact with a cooling body such as a casting drum and rapidly cooled and solidified, or brought into close contact with a cooling body with a nip roll and rapidly cooled and solidified.

  A plurality of resins of the thermoplastic resin A and a different thermoplastic resin B are sent out from different flow paths using two or more extruders, and are sent into the multilayer laminating apparatus. As the multilayer laminating apparatus, a multi-manifold die, a feed block, or the like can be used. In particular, in order to efficiently obtain the configuration of the present invention, it is preferable to use a feed block having three or more fine slits. When such a feed block is used, since the apparatus does not become extremely large, there is little foreign matter due to thermal degradation, and high-precision lamination is possible even when the number of laminations is extremely large. Also, the stacking accuracy in the width direction is significantly improved as compared with the prior art. Moreover, in this apparatus, since the thickness of each layer can be adjusted with the shape (length, width) of a slit, it becomes possible to achieve arbitrary layer thickness. Although the number of layers can be doubled by inserting a static mixer or the like in the flow path, the number of elements is limited to one because it may disturb the stacking accuracy.

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

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

  First, the case of sequential biaxial stretching will be described. Here, stretching in the longitudinal direction refers to stretching for imparting molecular orientation in the longitudinal direction to the film, and is usually performed by a difference in peripheral speed of the roll, and this stretching may be performed in one step. Alternatively, a plurality of roll pairs may be used in multiple stages. The draw ratio varies depending on the type of resin, but usually 2 to 15 times is preferable, and when polyethylene terephthalate is used for any of the resins constituting the laminated film, 2 to 7 times is preferably used. The ratio is preferably 3 to 5 times, more preferably 3 to 4 times, and particularly preferably 3 to 3.5 times from the viewpoint of suppressing variation in Re in the width direction. The stretching temperature is preferably the glass transition temperature of the resin constituting the film to the glass transition temperature + 100 ° C., more preferably 80 to 120 ° C., and still more preferably 90 to 110 ° C.

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

  Subsequently, stretching in the width direction refers to stretching for imparting orientation in the width direction to the film. Usually, the film is stretched in the width direction using a tenter while being conveyed while holding both ends of the film with clips. The stretching ratio varies depending on the type of resin, but is usually preferably 2 to 15 times. When polyethylene terephthalate is used for any of the resins constituting the film, 2 to 6 times is preferably used, and more preferably. Is preferably 3 to 6 times, more preferably 3 to 5.5 times, and particularly preferably 3.5 to 5 times from the viewpoint of suppressing the absolute values of Re and Rth and variation in Re, and the film is stretched at a higher ratio than the longitudinal stretching ratio. That is still preferred. The stretching temperature is preferably the glass transition temperature of the resin constituting the film to the glass transition temperature + 120 ° C., and preferably has a temperature gradient from the viewpoint of suppressing Re variation in the width direction, as it goes from upstream to downstream. The temperature is preferably increased. Specifically, when the transverse stretching section is divided into two, the difference between the upstream temperature and the downstream temperature is preferably 20 ° C. or more. More preferably, it is 30 degreeC or more, More preferably, it is 35 degreeC or more, Most preferably, it is 40 degreeC or more. The first stage stretching temperature is more preferably 80 to 120 ° C, still more preferably 90 to 110 ° C, and particularly preferably 95 to 105 ° C.

  The biaxially stretched film is preferably subjected to a heat treatment at a temperature not lower than the stretching temperature and not higher than the melting point in the tenter in order to impart flatness and dimensional stability. Specifically, 160 to 240 ° C is preferable, 160 to 235 ° C is more preferable, and 180 to 225 ° C is still more preferable. When the heat treatment temperature exceeds 240 ° C., a bowing phenomenon known as physical property unevenness in the film width direction is likely to occur in the tenter, and birefringence increases, leading to large front phase differences and width property variations. Therefore, 190-210 degreeC is especially preferable from a viewpoint of these suppression. By performing the heat treatment, the dimensional stability of the film is improved. Further, when the ratio of the amorphous resin in the film is increased in order to reduce the thickness retardation Rt, tearing or tearing occurs due to the heating air pressure of the tenter. Therefore, compared with the conventional film forming conditions, the wind speed of the heating air is preferably low and is preferably 2 m / second or less. After being heat-treated in this way, it is gradually cooled down uniformly, then cooled to room temperature and wound up. In addition, from the viewpoint of suppressing the occurrence of curling and wrinkling due to process heat treatment such as polarizing plate formation, it is preferable to use a relaxation treatment in combination during heat treatment and slow cooling. As a relaxation treatment method, the relaxation method in the width direction can be performed by narrowing the tenter width. In the longitudinal direction, a tenter equipped with a mechanism in which the clip is contracted in the longitudinal direction is used, or the peripheral speed difference between rolls is set. It is possible to implement by using. The order of the relaxation process is as follows: widthwise, longitudinally, widthwise, whether longitudinally relaxed after widthwise relaxation, or longitudinally relaxed after widthwise relaxation. Although it may be performed stepwise, it is preferable to perform relaxation in the longitudinal direction after relaxation in the width direction from the viewpoint of simplifying the process. The relaxation rate in the width direction during heat treatment is preferably 0.5 to 5%, more preferably 0.5 to 3%, still more preferably 0.8 to 2.5%, and dimensional stability and suppression of Re variation in the width direction. From the viewpoint of achieving both, 1 to 2% is particularly preferable. Further, the relaxation rate in the width direction during slow cooling is preferably 0.5 to 3%, more preferably 0.5 to 2%, still more preferably 0.5 to 1.5%, and dimensional stability and Re in the width direction. From the standpoint of coexistence of the dispersion variation, 0.5-1% is particularly preferable. The temperature at the time of slow cooling is preferably 90 to 180 ° C, more preferably 90 to 170 ° C, further preferably 100 to 160 ° C, and particularly preferably 100 to 150 ° C from the viewpoint of dimensional stability and film flatness. The temperature during relaxation in the longitudinal direction is preferably 90 to 180 ° C, more preferably 90 to 170 ° C, still more preferably 100 to 160 ° C, and particularly preferably 100 to 150 ° C in terms of dimensional stability and film flatness. The longitudinal relaxation rate is preferably 0.5 to 5%, more preferably 1 to 4%, still more preferably 1.5 to 3.5%, from the viewpoint of both dimensional stability and suppression of variation in Re in the width direction. 2 to 3.5% is particularly preferable. By performing the relaxation treatment in the longitudinal direction near the film temperature of 85 ° C., there is an effect that the heat yield at 85 ° C. is greatly reduced.

  The film of the present invention obtained as described above exhibits various effects by multilayer lamination, and is excellent in appearance and heat-resistant whitening property. In particular, since both layers have a low phase difference by using a low crystalline resin and the occurrence of uneven interference can be suppressed, it can be suitably used, for example, as a polarizing plate protective film. Furthermore, when it is used for an ITO film substrate, the occurrence of whitening can be suppressed in the processing step.

  Hereinafter, the present invention will be described in detail by way of examples. The characteristics were measured and evaluated by the following methods.

(1) Number of layers, maximum layer thickness The number of laminated layers was determined by observation with a transmission electron microscope (TEM) for a sample obtained by cutting a cross section using a microtome. That is, using a transmission electron microscope H-7100FA type (manufactured by Hitachi, Ltd.), the cross section of the film was observed under the condition of an acceleration voltage of 75 kV, a cross-sectional photograph was taken, and the number of layers was measured. In some cases, in order to obtain high contrast, a staining technique using RuO ₄ or OsO ₄ was used. Also, in accordance with the thickness of the thinnest layer (thin film layer) among all the layers that can be captured in one image, when the thin film layer thickness is less than 50 nm, the thin film layer thickness is 50 nm or more and 500 nm. When it was less than 40,000 times, and when it was 500 nm or more, observation was carried out at a magnification of 10,000 times. After confirming the total number of layers, the thickness of the thickest layer excluding the outermost layer thickness was defined as the maximum layer thickness.

(2) Film thickness n5 was measured with a constant pressure thickness measuring instrument PG-02J manufactured by Teclock, and the average value was taken.

(3) Front phase difference (Re) and thickness phase difference (Rt)
A phase difference measuring device (KOBRA-21ADH) manufactured by Oji Scientific Instruments was used. A sample was cut out from the central part in the film width direction at 3.5 cm × 3.5 cm, placed in the apparatus so that the film width direction was at an angle of 0 ° defined by this measuring apparatus, and Re at a wavelength of 590 nm was measured. . Rt was measured by the same method as Re except that the incident angle was 50 °.

(4) Endothermic peak of film, crystal melting enthalpy (ΔHm)
In the DSC curve obtained when the temperature is increased from 25 ° C. to 300 ° C. at a rate of 20 ° C./min using differential calorimetry (DSC), the endotherm having the highest peak top temperature in the range of 130 to 300 ° C. The peak temperature was read. The crystal melting enthalpy in the range of 130 to 300 ° C. was measured and calculated according to JIS-K-7122 (1987).
Equipment: “EXSTAR DSC6200” manufactured by Seiko Instruments Inc.
Data Analysis “MuseStandard Analysis Software, Version 6.1U”
Sample mass: 5 mg.

(5) Maximum reflectance, integral value I ₀
The relative reflectance at an incident angle φ = 10 degrees was measured for a 5 cm square sample of the film using a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd. The inner wall of the attached integrating sphere is barium sulfate, and the standard plate is aluminum oxide. The measurement wavelength was 300 nm to 2300 nm, the slit was 5 nm (visible) / 10 nm (infrared), the gain was set to 2, and the scanning speed was measured at 600 nm / min in increments of 1 nm. At the time of sample measurement, a black vinyl tape (registered trademark) manufactured by Nitto Denko was attached to the back surface of the sample in order to eliminate interference due to reflection from the back surface of the sample. The switching wavelength of the visible light and infrared light detectors is 850 nm. The maximum value in the obtained spectral curve was taken as the maximum reflectance in the wavelength range of 300 nm to 2300 nm. The integrated value in the range of 300 to 2300 nm of the spectral reflection curve obtained by plotting the vertical axis as the reflectance and the horizontal axis as the wavelength was defined as I ₀ .

(6) Integral value I ₁ after stretching at a surface magnification of 1.5 times
The film is made into a size of 10 cm in length, 11 cm in width and 20 to 40 mm in depth with a molding machine “Multi-Back” R095 manufactured by Tokyo Food Machinery Co., Ltd. (surface thickness before molding) / Drawing was performed so that the film thickness after molding = 1.5). The temperature condition at this time was 120 ° C. and heating for 20 seconds. The film after molding was subjected to integral values I ₁ and I ₀ and I _{1 in} the same manner as in (5).

(7) Saturation C *
Cut out 5cm x 5cm from the center of the film in the width direction, and then remove the reflected light from the back side of the film. ) Using a CM-3600d manufactured under the conditions of a target mask (CM-A106) with a measurement diameter of φ8 mm, L *, a *, and b * values were measured by the SCI method including specularly reflected light, respectively. C * was determined as the square root of the sum of the squares of the SCI a * and b * values. The n number was 3 and the average value was obtained. The white calibration plate and zero calibration box were calibrated using the following. Furthermore, D65 was selected as the light source used for calculating the colorimetric values.
White calibration plate: CM-A103
Zero calibration box: CM-A104.

(8) Heat-resistant whitening resistance If the haze change value before and after holding the film in an oven at 100 ° C. and a relative humidity of 35 RH% or less for 12 hours is 1.0 or less, the haze change value is larger than 1.0. When it was 5 or less, it was evaluated as ◯, when it was larger than 1.5 and 3.0 or less, Δ, when it was larger than 3.1, it was marked as x. The haze was measured using a haze meter (HGM-2DP manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS-K7136. In addition, the measurement was performed twice and the average value was calculated | required.

(9) Bending resistance It measured according to JIS-P-8115. Using a MIT testing machine (manufactured by Toyo Seiki Seisakusho Co., Ltd.), the number of times of MIT folding is measured. Test piece: 110 mm (length) x 5 mm (width)
Load: 24.5MPa
(10) Pinhole Resistance Tester The number of pinholes after carrying out repeated bending tests at 0 ° C. and 500 times was measured using a gel bot tester BE-1005 with a thermostatic bath manufactured by Sangyo Co., Ltd. The measurement sample is 180 mm × 260 mm.

(11) Oxygen permeability Using an oxygen permeability meter “OXTRAN” -100 manufactured by Modern Control, the value measured under conditions of humidity 80% and temperature 20 ° C. in units of ml / m ² · day · MPa Show.

(12) Water vapor transmission rate Using a water vapor transmission rate meter “PERMATRAN” W3 / 31 manufactured by Modern Control Co., Ltd., a value measured in a humidity of 90% and a temperature of 40 ° C. is shown in units of g / m ² · day. .

(13) Elastic modulus Measured using an Instron type tensile tester according to the method defined in ASTM-D882. The measurement is performed under the following conditions.
Measuring device: Orientec Co., Ltd. film strong elongation automatic measuring device “Tensilon AMF / RTA-100”
Sample size: width 10 mm x test length 100 mm,
Tensile speed: 200 mm / min Measurement environment: temperature 23 ° C., humidity 65% RH.

(14) Appearance A sample was cut out in A4 size from the center in the film width direction. Next, a fluorescent lamp having an emission spectrum of F10 determined by CIE and a black cardboard on which a sample was placed were prepared. The prepared fluorescent lamp and the sample on the black cardboard were placed so that the relationship between the viewing direction and the reflection direction was regular reflection, and the occurrence of interference colors and interference fringes was observed. Evaluation was based on the following criteria.
A: Interference color and interference fringe cannot be confirmed.
○: The interference color cannot be confirmed, but the interference fringes can be slightly confirmed.
Δ: Green and red interference fringes are blurred and can be confirmed slightly. X: Interference colors look clear.

(15) Mold Discoloration Deep drawing was performed by the molding method shown in (6) so that the surface magnification was 1.5 times, and the appearance of the molded film was evaluated according to the criteria shown in (14).

(16) Intensity sum of frequency components 512 points of spectral reflection data having a wavelength of 313 to 800 nm obtained by the measurement method of (5) were subjected to Fourier analysis using EXCEL (2013 version). Since the output data is represented by a complex number, the intensity of each frequency component can be obtained by converting the absolute value into an absolute value using the function IMABS and dividing the absolute value by the value of data number / 2 (here, 256). Further, a value obtained by dividing the number of measurement points (1, 2, 3,...) By the number of data × the sampling interval (512 in this case) is a frequency component. A curve obtained by arranging frequency components on the horizontal axis and frequency component intensities on the vertical axis is defined as an integrated sum of intensity of frequency components in the range of 0.05 to 0.3.

(Comparative Example 1)
As thermoplastic resin A, polyethylene terephthalate (glass transition temperature 78 ° C. melting point 250 ° C.) obtained by copolymerizing 1.5 mol% of sodium sulfoisophthalic acid with respect to the whole dicarboxylic acid component having an intrinsic viscosity of 0.72 is used for agglomerated silica (average aggregated particles) What added 0.02 weight% (diameter 2.0 micrometers) was used (it describes with PET / SSIA in a table | surface). As the thermoplastic resin B, Toray nylon 6 (Ny6) “Amilan (registered trademark) 1010T” having a melting point of 226 ° C. was used. These thermoplastic resins A and B were each dried and then supplied to an extruder. Each of the thermoplastic resins A and B was melted at 270 ° C. with an extruder, passed through a gear pump and a filter, laminated in 9 layers with a feed block, and then joined. The joined thermoplastic resins A and B have a structure in which 5 elements are passed through a static mixer and 129 layers are alternately laminated in the thickness direction. At this time, the maximum value of the widening ratio X of the widened portion in the thickness direction in the dew was 1.1, and the dew shape was square. The stacking thickness ratio (total thickness of layer A / total thickness of layer B) was adjusted by the discharge amount so that A / B = 3. The laminate consisting of the total of 129 layers thus obtained was supplied to a T-die and formed into a sheet, and then rapidly cooled and solidified on a casting drum maintained at a surface temperature of 20 ° C. while applying an electrostatic force. The obtained cast film was heated with a roll group set at 90 ° C., stretched 3.0 times in the longitudinal direction, led to a tenter, preheated with hot air at 100 ° C., and stretched 3.3 times in the lateral direction. The stretched film was directly heat-treated in a tenter with hot air at 190 ° C., gradually cooled to room temperature, and wound up. The thickness of the obtained film was 15 μm. The obtained results are shown in Table 1. Although it has excellent pinhole resistance and gas barrier properties, it has poor appearance due to interference colors.

Example 1
As the thermoplastic resin A, Toray nylon 6 (Ny6) “Amilan (registered trademark) 1010T” having a melting point of 226 ° C. was used. As thermoplastic resin B, ethylene terephthalate (PET / SSIA / CHDC) was used. Each was dried under sufficiently high temperature and high vacuum so as not to contain moisture, and then charged into two single-screw extruders and melt-kneaded at 270 ° C. Next, after passing through five FSS type leaf disk filters, the lamination ratio of each layer made of composition A and each layer made of composition B (total thickness of layer A / total thickness of layer B) was 0.33. Casting with a gear pump so that it can be merged in a laminating apparatus with 101 slits, extruded from a T-die as a laminated body with 101 layers laminated alternately in the thickness direction, and the surface temperature controlled to 25 ° C. A casting film was obtained by casting on a drum. The method for forming a laminate was carried out according to the description in paragraphs [0053] to [0056] of JP-A-2007-307893. Here, the slit length and interval are all constant.

  The obtained casting film was obtained under the same film forming conditions as in Comparative Example 1. The obtained results are shown in Table 1. Although it has the same physical properties as Comparative Example 1, it has excellent heat-resistant whitening property and the refractive index difference between the A layer and the B layer is low, so the appearance is improved.

(Comparative Example 2)
As the thermoplastic resin A, polyethylene terephthalate (PET) having an intrinsic viscosity of 0.65 was used. Further, polycarbonate (PC) was used as the thermoplastic resin B. These thermoplastic resins A and B were each dried and then supplied to an extruder. The thermoplastic resins A and B were each melted at 280 ° C. with an extruder, passed through a gear pump and a filter, and then joined with a feed block. The joined thermoplastic resins A and B were supplied to a static mixer and had a structure in which 13 layers of thermoplastic resin A and 12 layers of thermoplastic resin B were alternately stacked in the thickness direction. Here, the discharge amount was adjusted so that the lamination thickness ratio was A / B = 2/1. The maximum thickness ratio of the thermoplastic resins A and B was adjusted to 2 or less. The laminated pair consisting of a total of 25 layers thus obtained was supplied to a T-die and molded into a sheet, and then rapidly cooled and solidified on a casting drum maintained at a surface temperature of 25 ° C. while being electrostatically applied, and unstretched. A film was obtained. This unstretched film is guided to a plurality of rolls heated to 90 ° C. and preheated, and then longitudinally stretched at a stretching ratio of 3.0 times, and led to a tenter that grips both ends with clips at 3.2 ° C. at 3.2 ° C. After double-stretching, heat treatment was performed at 210 ° C. at a wind speed of 5 m / sec, and after slow cooling to room temperature, it was wound up. The thickness of the obtained film was 100 μm. The obtained results are shown in Table 1. The heat-resistant whitening property is poor due to the precipitation of oligomers.

(Example 2)
As the thermoplastic resin A, polyethylene terephthalate (PET / I5) having an intrinsic viscosity of 0.72 in which 5 mol% of isophthalic acid was copolymerized with respect to the entire dicarboxylic acid component was used. Further, polycarbonate (PC) was used as the thermoplastic resin B. In addition, the unstretched film was stretched longitudinally at a magnification of 3.0 times with a tenter simultaneous biaxial stretching machine, and subsequently stretched 3.2 times at 100 ° C., followed by heat treatment at 210 ° C. and gradually brought to room temperature. After cooling, it was wound up. Other conditions were obtained under the same film forming conditions as in Comparative Example 2. The obtained results are shown in Table 1. While having the same physical properties as Comparative Example 2, the heat-resistant whitening property was excellent, and the difference in refractive index between the A layer and the B layer was low, so the appearance was improved. Moreover, the heat-resistant whitening property was also improved.

(Comparative Example 3)
As the thermoplastic resin A, PET having an intrinsic viscosity of 0.65 was used. As the thermoplastic resin B, polybutylene terephthalate (hereinafter referred to as PBT) having an intrinsic viscosity of 1.26 (glass transition temperature 55 ° C., melting point 215 ° C.) was used. These thermoplastic resins A and B were each dried and then supplied to an extruder. Thermoplastic resins A and B were each melted at 270 ° C. with an extruder, passed through a gear pump and a filter, and then joined with a feed block. The joined thermoplastic resins A and B were supplied to a static mixer, and had a structure in which the thermoplastic resin A and the thermoplastic resin B were alternately laminated in the thickness direction consisting of 9 layers and 8 layers of the thermoplastic resin B. At this time, the shape of the dew was square. As a specific laminating method, it was designed so as to be 129 layers using a square mixer after laminating 9 layers with a fee block. Further, the thermoplastic resin A was both surface layers, and the total lamination thickness ratio was adjusted by the discharge amount so that A / B = 1. The laminated body composed of 129 layers thus obtained was supplied to a T-die and formed into a sheet shape, and then rapidly cooled and solidified on a casting drum maintained at a surface temperature of 20 ° C. while applying electrostatic force. The obtained cast film was heated with a roll group set at 90 ° C., stretched 3.0 times in the longitudinal direction, led to a tenter, preheated with hot air at 100 ° C., and stretched 3.3 times in the lateral direction. The stretched film was directly heat-treated in a tenter with hot air at 190 ° C., gradually cooled to room temperature, and wound up. The thickness of the obtained laminated film was 6 μm. The evaluation results of the obtained laminated film are shown in Table 1. The obtained laminated film was excellent in gas barrier properties, pinhole resistance, and surface impact resistance, but slight interference fringes were observed. Moreover, heat resistance whitening property is bad by precipitation of an oligomer.

(Comparative Example 4)
A thermoplastic resin obtained by mixing PET with an intrinsic viscosity of 0.65 and PBT having an intrinsic viscosity of 1.26 at a weight ratio of 60/40 and melt-mixing for 10 minutes or more to form a chip. Although it carried out on the film forming conditions similar to the comparative example 3, the lamination apparatus was not used and the single film | membrane film was obtained (the total melting time of a PET and PBT mixture is 20 minutes or more). The obtained results are shown in Table 1. The ratio of the raw materials to Comparative Example 3 was the same, but the mechanical properties and heat-resistant whitening properties were deteriorated.

(Example 3)
As the thermoplastic resin A, a material obtained by mixing PET having an intrinsic viscosity of 0.65 and PBT having an intrinsic viscosity of 1.26 at a weight ratio of 70/30, melt-mixing for 10 minutes or more, and forming a chip. As thermoplastic resin B, PET and PBT were mixed at a weight ratio of 50/50, and melted and mixed for 10 minutes or more to form chips. The films were joined by a laminating apparatus having 201 slits, and a film was obtained under the same film forming conditions as in Comparative Example 3 (the total melting time of the PET and PBT mixture was 20 minutes or more). The obtained results are shown in Table 1. Although the ratio of the raw materials was the same as that in Comparative Example 4, the heat-resistant whitening property was excellent, and the difference in refractive index between the A layer and the B layer was low, so the appearance was good.

(Comparative Example 5)
As a thermoplastic resin, polyethylene terephthalate (PET / I10) having an intrinsic viscosity of 0.72 in which 10 mol% of isophthalic acid is copolymerized with respect to the entire dicarboxylic acid component, and 12 mol% of isophthalic acid with respect to the entire dicarboxylic acid component are copolymerized. The resultant polyethylene terephthalate (PET / I12) having an intrinsic viscosity of 0.72 was mixed at a weight ratio of 50/50, and melted and mixed for 10 minutes or more to form a chip. Although it carried out on the film forming conditions similar to the comparative example 3, the laminating apparatus was not used and the single film was obtained. The obtained results are shown in Table 1. Since the crystallinity is low, the heat whitening resistance is poor.

Example 4
A film was obtained under the same film forming conditions as Example 3 except that PET / I10 was used as the thermoplastic resin A and PET / I12 was used as the thermoplastic resin B. The obtained results are shown in Table 1 (in the layer thickness evaluation, no difference in staining was observed between the A layer and the B layer, and the maximum layer thickness was unknown). Although the ratio of the raw materials was the same as that of Comparative Example 5, the heat resistance whitening property was excellent, and the difference in refractive index between the A layer and the B layer was low, so the appearance was good.

(Comparative Example 6)
A film was obtained under the same film-forming conditions as in Comparative Example 3 except that PET was used as the thermoplastic resin, and a laminating apparatus was not used and a single film was used. The obtained results are shown in Table 1. It deteriorated in mechanical properties and heat-resistant whitening property.

(Comparative Example 7)
As a thermoplastic resin, polyethylene terephthalate (PET / I12-1) having an intrinsic viscosity of 0.75 obtained by copolymerizing 12 mol% of isophthalic acid with respect to the entire dicarboxylic acid component, and 12 mol% of isophthalic acid with respect to the entire dicarboxylic acid component. A copolymerized polyethylene terephthalate (PET / I12-2) having an intrinsic viscosity of 0.62 was mixed at a weight ratio of 50/50, and melted and mixed for 10 minutes or more to form a chip (PET / I12-3). ). Although it carried out on the film forming conditions similar to the comparative example 3, the laminating apparatus was not used and the single film was obtained. The obtained results are shown in Table 1. Since the crystallinity is low, the heat whitening resistance is poor.

(Example 5)
A film was obtained under the same film forming conditions as Example 3 except that PET / I12-1 was used as the thermoplastic resin A and PET / I12-2 was used as the thermoplastic resin B. The obtained results are shown in Table 1 (in the layer thickness evaluation, no difference in staining was observed between the A layer and the B layer, and the maximum layer thickness was unknown). Although the same raw material as Comparative Example 7 was used, the heat-resistant whitening property was good.

(Example 6)
As the thermoplastic resin B, polyethylene terephthalate (PET / ISB · CHDM), which is an amorphous resin having no melting point, copolymerized with 15 mol% of isosorbide and 20 mol% of cyclohexanedimethanol with respect to the entire diol component, and isophthalic acid A raw material obtained by mixing polyethylene terephthalate (PET / I25) having an intrinsic viscosity of 0.65 copolymerized with 25 mol% at a weight ratio of 50/50 was used. Further, as the thermoplastic resin A, a raw material obtained by mixing polyethylene terephthalate (PET) having an intrinsic viscosity of 0.65 and PET / ISB · CHDM at a weight ratio of 75/25 is used, and the lamination ratio A / B becomes 0.3. A film having a thickness of 25 μm was obtained under the same film forming conditions as in Example 3 except that the discharge amount was adjusted so as to be. The obtained results are shown in Table 1.

(Example 7)
Example 6 was the same as Example 6 except that the lamination ratio was 0.17. The wind speed of the hot air in the tenter at this time was 0.5 m / sec. The obtained results are shown in Table 1.

(Example 8)
Example 6 was the same as Example 6 except that the lamination ratio was 1. The obtained results are shown in Table 1.

Example 9
As the thermoplastic resin B, polyethylene terephthalate (PET / SPG), which is an amorphous resin having no melting point, is obtained by copolymerizing 30 mol% of spiroglycol with respect to the entire diol component and 15 mol% of cyclohexanedicarboxylic acid with respect to the entire dicarboxylic acid component. -CHDC) was used. Further, as the thermoplastic resin A, a raw material obtained by mixing polyethylene terephthalate (PET) having an intrinsic viscosity of 0.65 and PET / SPG · CHDC at a weight ratio of 75/25, the lamination ratio A / B is set to 0.3. A film having a thickness of 25 μm was obtained under the same film forming conditions as in Example 3 except that the discharge amount was adjusted so as to be. The obtained results are shown in Table 1.

(Comparative Example 8)
Film formation similar to Example 3 except that polyethylene terephthalate (PET / I25) having an intrinsic viscosity of 0.72 in which 25 mol% of isophthalic acid was copolymerized with respect to the entire diol component was used for thermoplastic resins A and B Went. As a result, the film shape could not be maintained due to insufficient heat resistance of the resin.

  The film of the present invention is excellent in heat-resistant whitening resistance, and has few interference colors and interference fringes, so that it can be used as a polarizing plate protective film for polarizing plates incorporated in display devices such as liquid crystal displays and an ITO base film used for touch panels. It can be used suitably.

Claims (13)

It is a laminated film in which a layer made of thermoplastic resin A (layer A) and a layer made of thermoplastic resin B (layer B) are alternately laminated in the thickness direction by 5 layers or more, and in differential scanning calorimetry (DSC) In the DSC curve obtained when the temperature is raised from 25 ° C. to 300 ° C. at 20 ° C./min, the endothermic peak having the highest peak top temperature in the range of 130 to 300 ° C. is in the range of 160 to 246 ° C. A film having a crystal melting enthalpy (ΔHm) in the range of 130 to 300 ° C. determined from the DSC curve of 5 to 19 J / g. The reflectance obtained by measuring the reflectance at a wavelength of 313 to 800 nm, the vertical axis representing the reflectance, and the horizontal axis representing the wavelength is obtained by Fourier analysis of the spectral reflection curve. The vertical axis represents the intensity of the frequency component and the horizontal axis 2. The film according to claim 1, wherein when the frequency components are plotted in FIG. 1, the intensity sum of the frequency components in the range of 0.05 to 0.3 is 12 or less. The film according to claim 1 or 2, wherein the chroma C ^* is 4 or less. The film according to any one of claims 1 to 3, wherein the thermoplastic resin A and the thermoplastic resin B are polyester. The film according to claim 1, wherein the thermoplastic resin A and / or the thermoplastic resin B contains an isosorbide component. The film according to any one of claims 1 to 5, wherein the front phase difference Re is 400 nm or less. The film according to claim 1, wherein the front phase difference Re (nm), the thickness phase difference Rt (nm), and the film thickness T (μm) satisfy the following formulas.
Re / T ≦ 5 (1)
Rt / T ≦ 12 (2) The film according to any one of claims 1 to 7, wherein each layer excluding the outermost layer has a thickness of 60 nm or less. The film according to any one of claims 1 to 8, wherein a change in haze before and after being held for 12 hours in an atmosphere having a temperature of 100 ° C and a relative humidity of 35 RH% or less is 1.0% or less. The film according to any one of claims 1 to 8, which has an elastic modulus of 2700 MPa or less. The film according to claim 1, which is used for a vibration damping material. The film according to claim 1, which is used for protecting a polarizing plate. The laminated body which provided the indium tin oxide (ITO) film | membrane on the at least single side | surface of the film in any one of Claims 1-12.

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