JP2019155684A - Laminate film - Google Patents

Abstract

To provide a laminate film having excellent moldability, conveyance performance, interlaminar strength and less color unevenness, which can be suitably used for a case of a personal computer or a television set or the like, a member of a household electric appliance or the like and a display device for a mirror or the like in decoration applications and can be suitably used for protecting a polarizer, for screen protection applications when used for a polarizer using the same, a transparent conductive film and a touch panel application using the same or an application for a screen constituting member using LED as a light source in optical applications.SOLUTION: There is provided a laminate film which is obtained by alternately laminating 25 or more layers of a layer consisting essentially of a thermoplastic resin A (A layer) and a layer consisting essentially of a thermoplastic resin B (B layer) in the thickness direction and satisfies the following (1) to (3): (1) the difference (|SP-SP|) between the dissolution parameter (SP) of the thermoplastic resin A and the dissolution parameter (SP) of the thermoplastic resin B is 0.01 MPaor more and 5.0 MPaor less, (2) both the number average molecular weight (MnA) of the thermoplastic resin A and the number average molecular weight (MnB) of the thermoplastic resin B are 3000 or more and 50000 or less and (3) both the degree of molecular weight dispersion (MzA/MnA), a ratio between the Z-average molecular weight (MzA) and the number average molecular weight (MnA) of the thermoplastic resin A and the degree of molecular weight dispersion (MzA/MnA), a ratio between the Z-average molecular weight (MzB) and the number average molecular weight (MnB) of the thermoplastic resin B are 1.5 or more and 23.0 or less.SELECTED DRAWING: None

Description

The present invention relates to a laminated film.

In recent years, with the growing awareness of the environment, there has been an increasing demand for solvent-less coating, plating replacement, etc. in the decoration of molding materials such as building materials, automobile parts, mobile phones, home appliances and personal computers, and the introduction of decoration methods using films Progressing.
In recent years, display devices (displays) have been diversified, and the demand for optical films constituting the display has also been diversified. When an optical film is used for, for example, a 3D display, a touch panel, a flexible display, or an organic EL display, it is required to be thin and durable while having moldability.
In response to such a flow, for example, by utilizing the light interference phenomenon that occurs by alternately laminating two or more kinds of resins having different refractive indexes at a layer thickness of the wavelength level of light, light of a specific wavelength is transmitted. An optical interference multilayer film that selectively cuts is known. Such a multilayer film achieves optical filters with various performances by setting the refractive index, number of layers, and thickness of each resin to the desired optical design, so that various decorative applications and optical applications can be achieved. It is used for. As a method for producing a laminated film, a co-extrusion method using a plurality of extruders and a laminating method in which films are laminated are known. Among them, the co-extrusion method is capable of laminating a large number of layers in one step, and is very advantageous in terms of productivity and cost. Therefore, it is widely used as a general laminated film manufacturing method. Yes. However, in the coextrusion method, when two or more kinds of laminated resins have different characteristics such as melting point, glass transition temperature, melt viscosity, affinity, etc., uneven thickness of the laminated film and uneven thickness of each laminated layer are likely to occur. There are problems of uniformity in film characteristics and surface quality deterioration such as uneven color tone and flow marks on the film surface.

  Under such circumstances, the feed block for laminating at least two kinds of resins in multiple layers has a configuration in which two or more slit plates are used, and in the slit plate, the slit width for forming the thick film layers positioned at both ends. However, it is manufactured using a feed block that is at least twice as wide as the slit width that forms the other thin film layer, realizing high stacking accuracy even when the number of layers increases, and reflecting light of a specific wavelength, or A transparent laminated film has been proposed (see Patent Document 1). Moreover, in addition to the said characteristic, it becomes possible to provide easy moldability (for example, refer patent document 2).

JP 2007-176154 A JP 2011-129110 A

However, in the method described in Patent Document 1 and Patent Document 2, the difference in compatibility of the resins used is large, and the interface layer is non-uniform, leading to uneven color. In addition, due to the non-uniform interface layer, stress is applied to each layer with different strain characteristics in the stretching process and post-processing process, so the formability, transportability, and interlayer strength are not sufficient, resulting in processing defects. was there.

  An object of the present invention is to provide a laminated film having excellent moldability, transportability, interlayer strength, and little color unevenness in view of the above-described problems of the prior art.

In order to solve the above problems, the present invention employs the following means. That is, the layer (A layer) mainly composed of the thermoplastic resin A and the layer (B layer) composed mainly of the thermoplastic resin B are alternately laminated in the thickness direction by 25 layers or more, the following (1) to A laminated film satisfying (3).
(1) The difference (| SP _A -SP _B |) between the solubility parameter (SP _A ) of the thermoplastic resin A and the solubility parameter (SP _B ) of the thermoplastic resin B is 0.01 MPa ^1/2 or more and 5.0 MPa ^{Must be 1/2} or less.
(2) The number average molecular weight (MnA) of the thermoplastic resin A and the number average molecular weight (MnB) of the thermoplastic resin B are both 3000 or more and 50000 or less.
(3) Molecular weight polydispersity (MzA / MnA), which is the ratio of z-average molecular weight (MzA) and number-average molecular weight (MnA) of the thermoplastic resin A, and z-average molecular weight (MzB) of the thermoplastic resin B The weight average molecular weight (MzB / MnB), which is the ratio of the number average molecular weight (MnB), is 1.5 to 23.0 in all cases.

The laminated film of the present invention has excellent moldability, transportability, interlaminar strength, and less color unevenness, so as a molded body using it, for example, in decoration applications, a housing such as a personal computer or a TV, It can be suitably used for members of home appliances, display devices for mirrors, and the like. In optical applications, polarizer protection applications, polarizing plates using the same, transparent conductive films, and screen protection applications such as when used for touch panels using the same, and screen components using LEDs as light sources Can be suitably used.

The laminated film of the present invention is formed by laminating 25 layers or more alternately in the thickness direction of layers mainly composed of thermoplastic resin A (A layer) and layers mainly composed of thermoplastic resin B (B layer). It is important to satisfy the following (1) to (3).
(1) The difference (| SP _A -SP _B |) between the solubility parameter (SP _A ) of the thermoplastic resin A and the solubility parameter (SP _B ) of the thermoplastic resin B is 0.01 MPa ^1/2 or more and 5.0 MPa ^{Must be 1/2} or less.
(2) The number average molecular weight (MnA) of the thermoplastic resin A and the number average molecular weight (MnB) of the thermoplastic resin B are both 3000 or more and 50000 or less.
(3) Molecular weight polydispersity (MzA / MnA), which is the ratio of z-average molecular weight (MzA) and number-average molecular weight (MnA) of the thermoplastic resin A, and z-average molecular weight (MzB) of the thermoplastic resin B The weight average molecular weight (MzB / MnB), which is the ratio of the number average molecular weight (MnB), is 1.5 to 23.0 in all cases.

  The laminated film of the present invention needs to have a configuration in which the A layer mainly composed of the thermoplastic resin A and the B layer mainly composed of the thermoplastic resin B are alternately laminated in the thickness direction. In the present invention, the main component means 50% by weight or more based on the total components.

  Further, the laminated film of the present invention needs to have a layer (A layer) mainly composed of the thermoplastic resin A and a layer (B layer) mainly composed of the thermoplastic resin B. From the viewpoint of adjusting stability and light transmittance, one of the thermoplastic resin A and the thermoplastic resin B is mainly composed of a crystalline thermoplastic resin, and either one is composed mainly of an amorphous thermoplastic resin. It is preferable that For example, it is preferable that the thermoplastic resin A is a crystalline thermoplastic resin and the thermoplastic resin B is an amorphous thermoplastic resin. By adopting such an embodiment, a film design having both the characteristics of a crystalline thermoplastic resin excellent in dimensional stability, heat resistance and mechanical properties and the characteristics of an amorphous thermoplastic resin excellent in moldability can be obtained. It becomes possible. Further, by adjusting the average refractive index difference between the layers caused by the difference in the resin characteristics of the A layer and the B layer, it becomes possible to adjust the light transmittance incidentally. Furthermore, since one layer is mainly composed of an amorphous thermoplastic resin, crystallization is less likely to occur even at high temperatures, so that problems such as whitening of the laminated film can be reduced. .

  The thermoplastic resin referred to in the present invention refers to a resin that has the characteristics of being softened by heating and having plasticity, and solidifying when cooled. Amorphous thermoplastic resin refers to a thermoplastic resin having a heat of crystal melting of less than 0.1 mJ / mg when the temperature is raised at a rate of temperature rise of 5 ° C./min in differential calorimetry (DSC), The crystalline thermoplastic resin refers to a thermoplastic resin having a heat of crystal melting of 0.1 mJ / mg or more when the temperature is raised at a rate of temperature rise of 5 ° C./min in differential calorimetry (DSC).

  Moreover, the thermoplastic resin A in the A layer of the laminated film of the present invention and the thermoplastic resin B in the B layer may be one type or plural types. Here, when there are a plurality of types of thermoplastic resins A in the A layer, the content of the thermoplastic resin A is calculated by adding up the resins corresponding to the thermoplastic resin A. The same applies to the thermoplastic resin B in the B layer.

  Examples of thermoplastic resins include polyolefin resins such as polyethylene, polypropylene, polystyrene and polymethylpentene, alicyclic polyolefin resins, polyamide resins such as nylon 6 and nylon 66, aramid resins, polyethylene terephthalate, polybutylene terephthalate and polypropylene terephthalate. Polyester resin such as polybutyl succinate, polyethylene-2,6-naphthalate, polycarbonate resin, polyarylate resin, polyacetal resin, polyphenylene sulfide resin, tetrafluoroethylene resin, trifluorinated ethylene resin, trifluorinated ethylene chloride resin Fluoropolymers such as tetrafluoroethylene-6fluoropropylene copolymer, vinylidene fluoride resin, acrylic resin, methacrylic resin, polyacetal resin, It can be used polyglycolic acid resin, polylactic acid resin, and the like. Among these, a polyester resin is particularly preferable from the viewpoint of strength, heat resistance, and transparency.

  In the laminated film of the present invention, the polyester resin refers to a polycondensate of a dicarboxylic acid component and a diol component. Each of the dicarboxylic acid component and the diol component may be a single component or a plurality of types of components. Here, the polyester resin in which both the dicarboxylic acid component and the diol component are single components is referred to as a homopolyester resin, and the polyester resin in which any one of the dicarboxylic acid component and the diol component is a plurality of components is referred to as a copolyester resin.

  Examples of the homopolyester resin in the present invention include the above-mentioned polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate, as well as poly-1,4-cyclohexanedimethylene terephthalate, polyethylene diphenylate, and the like. Can be mentioned.

  The copolyester resin in the present invention is preferably a copolyester resin comprising at least three or more components selected from the following dicarboxylic acid components and diol components. Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4 Examples include '-diphenylsulfone dicarboxylic acid, adipic acid, sebacic acid, dimer acid, cyclohexane dicarboxylic acid, and ester derivatives thereof. Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentadiol, diethylene glycol, polyalkylene glycol, 2,2-bis (4 ′ -Β-hydroxyethoxyphenyl) propane, isosorbate, 1,4-cyclohexanedimethanol, spiroglycol and the like.

  In the laminated film of the present invention, from the viewpoints of moldability, heat resistance, and transparency, production cost, and film formation stability, the crystalline thermoplastic resin A is a crystalline polyester, and is an amorphous thermoplastic resin. B is preferably an amorphous polyester. Furthermore, from the viewpoint of the absolute value of the difference in SP value between the resins described later, strength as a film, reflection performance improvement, suppression of changes in optical properties due to heating and aging, and reduction of peeling between layers, the crystalline polyester is More preferred is crystalline polyethylene terephthalate, and the amorphous polyester is spiroglycol copolymerized polyethylene terephthalate and / or cyclohexanedimethanol copolymerized polyethylene terephthalate.

  In consideration of forming a laminated film with a uniform thickness, crystalline thermoplastic resin A and amorphous thermoplastic resin B have a combination in which the difference in glass transition temperature between them is 20 ° C. or less. preferable. If the difference in glass transition temperature is greater than 20 ° C., the thickness uniformity when the laminated film is formed becomes poor, and the stability of the optical properties when the laminated film is formed may be impaired. When stretching the film, overstretching may occur.

  The laminated film of the present invention needs to have a structure in which 25 layers or more of the A layer and the B layer are alternately laminated in the thickness direction. More preferably, it is a structure in which 100 layers or more are alternately laminated in the thickness direction, and more preferably, a structure in which 250 layers or more are laminated. In the case of less than 25 layers, the number of interfaces where the A layer and the B layer are in contact is small, and when a laminated design is made to reflect a specific optical wavelength, sufficient reflectivity cannot be obtained or color unevenness occurs. The upper limit of the number of layers is 1000 layers or less in consideration of an increase in manufacturing costs due to an increase in the overall thickness of the laminated film due to an increase in the size of the device and an increase in the number of layers, and a decrease in lamination accuracy. It is preferable.

  When producing the laminated film of the present invention, the thermoplastic resin A and the thermoplastic resin B are each sent to a multi-layer laminating apparatus such as a feed block using two melt extruders, and are formed into a desired layer structure. Is discharged from the die. And the laminated body discharged from die | dye is extruded on rotary cooling bodies, such as a casting drum, and is cooled and solidified, and a casting film is obtained. The molten laminate formed in the multilayer laminating apparatus is discharged from the die, extruded onto a rotating cooling body such as a casting drum, and cooled until it is solidified. And interfacial layer is formed. In particular, the joining portion of the resin in the feed block is microscopically flowing from the capillary portion to the releasing portion, and the elongation flow is dominant in the mutual resin joining portion, and the crystallization temperature of the molten resin rises. Therefore, oriented crystallization advances, the interface layer becomes dominant in the crystal structure, and rigidity and interlayer strength are improved by the crystal-dominated structure of the interface layer formed when formed as a film. On the other hand, since the crystals in the formed interface layer exist at a high temperature, the macro Brownian motion of the molecules is large and does not grow sufficiently. For this reason, in the interface layer, the crystal structure is controlled and high amorphousness is maintained, so that it is possible to achieve both formability. The interface layer is formed by the difference in the solubility parameter between the thermoplastic resin A constituting the A layer and the thermoplastic resin B constituting the B layer, or the thermoplastic resin B constituting the A layer and the thermoplastic resin B constituting the A layer. It can be controlled by adjusting the number average molecular weight and molecular weight polydispersity.

As described above, in the production of a multilayer laminated film, the difference in affinity between the laminated polyester resins greatly contributes to the formation of the interface layer. In the laminated film of the present invention, the absolute value (| SP _A -SP _B |) of the difference between the solubility parameter (SP _A ) of the thermoplastic resin _A and the solubility parameter (SPB) of the thermoplastic resin B is 0.01 MPa ^1/2 above 5.0MPa is required to be ^1/2 or less, more preferably 0.10 MPa ^1/2 or more 4.5 MPa ^1/2 or less. The solubility parameter indicates that the closer the value is, the easier the resin becomes familiar. The absolute value of the difference between the solubility parameter (SP _A ) of the thermoplastic resin _A and the solubility parameter (SP _B ) of the thermoplastic resin B (| As the absolute value of the difference of SP _A -SP _B |) is smaller, the above-described interface layer is more easily formed. By making the absolute value of the difference between the solubility parameter (SP _A ) of the thermoplastic resin _A and the solubility parameter (SP _B ) of the thermoplastic resin B within the above range, the polymer affinity between the A layer and the B layer is not impaired. An interface having a sufficient thickness is formed, and water vapor barrier properties can be imparted while suppressing color unevenness. If the absolute value of the difference between the solubility parameters is less than 0.01 MPa ^1/2 , the interfacial layer becomes too thick and the characteristics of each bulk layer are lost. On the other hand, if the absolute value of the difference between the solubility parameters exceeds 5.0 MPa ^1/2 , an interface layer having a sufficient thickness is not formed, resulting in poor water vapor barrier properties and transportability, and uneven interface layer thickness. Color unevenness occurs, resulting in poor interlayer strength and transportability.

When the laminated film of the present invention is used for a decoration application, high reflection performance is required in the decoration application, and the thickness of the interface layer relative to the lamination thickness of the A layer and the B layer can be controlled so as not to be too thick. preferably, it is preferable that the absolute value of the difference between the solubility parameter of the thermoplastic resin a solubility parameter (SP _a) and the thermoplastic resin B (SP _B) is 1.0 MPa ^1/2 or more 5.0 MPa ^1/2 or less 1.1 MPa ^1/2 or more and 4.0 MPa ^1/2 or less is more preferable. On the other hand, when the laminated film of the present invention is used for optical applications, the thickness of the interface layer with respect to the laminated thickness of the A layer and the B layer promotes interface formation when the color unevenness is small and high water vapor barrier performance is required. The absolute value of the difference between the solubility parameter (SP _A ) of the thermoplastic resin _A and the solubility parameter (SP _B ) of the thermoplastic resin B is preferably 0.01 MPa ^1/2 or more and 1.5 MPa ^{1. / 2} or less, more preferably 0.01 MPa ^1/2 or more and 1.0 MPa ^1/2 or less.

  In the laminated film of the present invention, the number average molecular weight (MnA) of the thermoplastic resin A and the number average molecular weight (MnB) of the thermoplastic resin B are both required to be 3000 or more and 50000 or less, both of which are 5000. More preferably, it is 10,000 or less. The number average molecular weight is an index that is easily affected by the presence of a low molecular weight among the indices representing the molecular weight. Low molecular weight molecules with a low degree of polymerization are more likely to diffuse in the resin than high molecular weight molecules. For this reason, if there are many low molecular weight molecules, the interface layer tends to be formed easily. On the other hand, if the molecular weight is too low, variations in the thickness of the interface layer are caused. By setting the number average molecular weight (MnA) of the thermoplastic resin A and the number average molecular weight (MnB) of the thermoplastic resin B to be 3000 or more and 50000 or less, the polymers of the A layer and the B layer are mixed. And an interface layer having an appropriate thickness and a uniform thickness is formed, and interlayer strength can be imparted. If either the number average molecular weight (MnA) of the thermoplastic resin A or the number average molecular weight (MnB) of the thermoplastic resin B is less than 3000, the molded film is not provided with sufficient rigidity and conveyed. Inferior to sex. In addition, if either the number average molecular weight (MnA) of the thermoplastic resin A or the number average molecular weight (MnB) of the thermoplastic resin B is greater than 50000, the thermal diffusion of the molecules becomes uneven and sufficient. An interface layer having a thickness is not formed, and the interface layer thickness becomes uneven, color unevenness occurs, or the interlayer strength is inferior. When the laminated film of the present invention is used for a decoration application, high reflection performance is required in the decoration application, and the thickness of the interface layer relative to the lamination thickness of the A layer and the B layer can be controlled so as not to be too thick. Preferably, the number average molecular weight (MnA) of the thermoplastic resin A and the number average molecular weight (MnB) of the thermoplastic resin B are both preferably 3000 or more and 20000 or less, and preferably 4000 or more and 10,000 or less. Is more preferable. On the other hand, when the laminated film of the present invention is used for optical applications, the thickness of the interface layer with respect to the laminated thickness of the A layer and the B layer promotes interface formation when the color unevenness is small and high water vapor barrier performance is required. The number average molecular weight (MnA) of the thermoplastic resin A and the number average molecular weight (MnB) of the thermoplastic resin B are both preferably 5,000 or more and 50,000 or less, More preferably, it is 10,000 or more and 40,000 or less.

  The laminated film of the present invention has a molecular weight polydispersity (MzA / MnA) which is a ratio of the z-average molecular weight (MzA) and the number-average molecular weight (MnA) of the thermoplastic resin A, and the z-average molecular weight (MzB) of the thermoplastic resin B. ) And the number average molecular weight (MnB), the molecular weight polydispersity (MzB / MnB) must be 1.5 or more and 23.0 or less, and 3.0 or more and 15.0 or less. More preferably, it is 4.0 or more and 12.0 or less. The z-average molecular weight is an index that is easily affected by the presence of a high molecular weight among the indices representing the molecular weight. The molecular weight polydispersity, which is the ratio of the z-average molecular weight (Mz) to the number-average molecular weight (Mn), is an index representing the variation in the molecular weight of the polymer. A large value indicates a large variation in the molecular weight. As described above, a low molecular weight molecule having a small degree of polymerization is more easily diffused in the resin than a high molecular weight molecule. Therefore, when the variation in the molecular weight of the polymer is large, the thickness of the interface layer tends to be uneven. By setting the molecular weight polydispersity to 1.0 or more and 23.0 or less, the thermal diffusion of the polymer of the A layer and the B layer becomes uniform, an interface having a uniform thickness is formed, color unevenness is suppressed, and interlayer strength is suppressed. Can be granted. When the molecular weight polydispersity is less than 1.5, the interfacial layer is too mixed and the molded film may be inferior in sufficient moldability. On the other hand, when the molecular weight polydispersity is greater than 23.0, the thermal diffusion of the molecules becomes non-uniform, and an interface layer having a uniform thickness is not formed, resulting in uneven color and poor interlayer strength.

  In the laminated film of the present invention, the average layer thickness of layers having a thickness of less than 1 μm per layer is preferably 20 nm or more and 400 nm or less. When the average layer thickness of layers having a thickness of less than 1 μm per layer is larger than 400 nm, the film characteristics are governed by the resin characteristics of the A layer and the B layer, and the moldability and transportability may be inferior. On the other hand, if the thickness is smaller than 20 nm, the entire film is dominated by the resin mixed layer, so that the film structure becomes unstable, and the rigidity and moldability inherent to the thermoplastic resin A and the thermoplastic resin B cannot be exhibited. Inferior formability. When the laminated film of the present invention is used for a decoration application, a high reflection performance is required in the decoration application. In order to obtain a high reflection performance, the average layer thickness of a layer having a thickness of less than 1 μm per layer is 50 nm. It is preferably larger than 300 nm. On the other hand, when the laminated film of the present invention is used for optical applications, the thickness per layer is used to suppress color unevenness by providing the interface layer with respect to the entire film and to provide water vapor barrier properties. It is preferable that the average layer thickness of a layer having a thickness of less than 1 μm is 30 nm or more and 50 nm or less. In the laminated film of the present invention, the number of layers having a thickness of less than 1 μm per layer is preferably 23 or more, and the number of layers having a thickness of less than 1 μm is 248 or more. Is more preferable.

  The laminated film of the present invention preferably has a film breaking elongation in the longitudinal direction of 150% or more and 300% or less. By setting the film breaking elongation in the longitudinal direction to 150% or more, it becomes possible to follow an uneven shape, and it can be suitably used for decoration applications and optical applications. On the other hand, if it is attempted to exceed 300%, the rigidity of the film may be impaired, and the appearance may be deteriorated due to film deformation due to the tension during conveyance when being bonded to the display member. More preferably, it is 200% or more and 250% or less. The method of satisfying that the film breaking elongation in the longitudinal direction of the laminated film of the present invention satisfies 150% to 300% is not particularly limited, but the affinity and diffusion of the thermoplastic resin A and the thermoplastic resin B so as to form an interface layer. A method of adjusting the speed, a method of adjusting the amount of the thermoplastic resin A with respect to the thermoplastic resin B, a method of adjusting the stretching ratio when stretching in the longitudinal direction, a method of adjusting the temperature in the longitudinal direction, and after lateral stretching The method of adjusting the temperature of heat processing is mentioned.

  The laminated film of the present invention preferably has a Young's modulus in the longitudinal direction of 2.7 GPa or more and 4.5 GPa or less. By setting the Young's modulus to 2.7 GPa or more, it is possible to suppress a minute film deformation due to a tension during conveyance at the time of bonding to a display member, and it is possible to suppress an appearance defect. On the other hand, if the Young's modulus is attempted to be larger than 4.5 GPa, there is a concern that the productivity is lowered due to film breakage, and therefore it is preferable to set the pressure to 4.5 GPa or less. More preferably, it is 3.0 GPa or more and 3.6 GPa or less. The method of satisfying the Young's modulus in the longitudinal direction of the laminated film of the present invention satisfying 2.7 GPa or more and 4.5 GPa or less is not particularly limited, but the affinity and diffusion of the thermoplastic resin A and the thermoplastic resin B so as to form an interface layer. A method of adjusting the speed, a method of adjusting the amount of the thermoplastic resin A with respect to the thermoplastic resin B, a method of adjusting the stretching ratio when stretching in the longitudinal direction, a method of adjusting the temperature in the longitudinal direction, and after lateral stretching The method of adjusting the temperature of heat processing is mentioned.

When the laminated film of the present invention is measured by atomic force microscope-infrared spectroscopy (AFM-IR) in the thickness direction of the film, the peak intensity at 1720 cm ⁻¹ is α, 1410 cm ^−1. It is preferable that the minimum value of the ratio (α / β) when the peak intensity of β is β is 3.0 or more and 13.0 or less. Here, the measurement principle of AFM-IR will be described in comparison with FT-IR (Fourier transform-infrared spectrometer) which is a general IR measurement method. In general, FT-IR used in infrared analysis detects absorption of infrared light as a change in light intensity, and the spatial resolution is on the order of μm at the maximum. On the other hand, the AFM-IR detects the expansion of the sample due to infrared light absorption with an AFM cantilever. By the combination of IR and AFM, IR absorption can be analyzed with a spatial resolution of about 100 nm, which exceeds the conventional spectroscopic limit. In the detection procedure, first, a sample is irradiated with IR laser light having a certain wave number, the sample absorbs IR light, and undergoes thermal expansion due to absorption of infrared light by the sample functional group. Next, the cantilever is greatly displaced and excited by thermal expansion. At this time, if there is no infrared absorption of the functional group, the cantilever is hardly displaced. Finally, data similar to the infrared absorption spectrum can be obtained by sweeping the wavelength of the irradiation laser light and plotting the magnitude of the displacement of the cantilever at each wave number. As a feature, FT-IR and the like measure absorbance due to infrared molecular vibration, whereas AFM-IR observes displacement of a substance due to infrared molecular vibration. Accordingly, the AFM-IR can grasp how much the interaction is affected by observing the displacement of the substance due to thermal factors. For example, in polyethylene terephthalate or the like, 1720 cm ^−1, which is a carbonyl bond in the side chain of a phenyl group, interacts strongly due to the permanent dipole interaction between carbonyl groups with the surrounding polymer, whereas the response is insensitive to 1410 cm. The vibration of the phenyl group of ⁻¹ interacts weakly at the carbonyl group ratio due to the ππ interaction between the phenyl groups with the surrounding polymer, and the response is sensitive to the surrounding polymer packing state. Here, α / β is a parameter indicating the micromolecular interaction state of the polymer. The smaller the minimum value of α / β, the stronger the bonding state and the denser the packing area exists at any position in the film thickness direction. Suggest to do. By setting the difference between the minimum values of α / β to 13.0 or less, the interlayer strength can be improved by the portion where the packing state of molecules is dense. On the other hand, if the minimum value is to be made smaller than 3.0, the packing state becomes extremely dense and the moldability of the film may be impaired. The minimum value of α / β is more preferably 4.0 or more and 11.0 or less. When the laminated film of the present invention is used for a decoration application, high reflection performance and interlayer strength at the time of molding are required in the decoration application, and α / β may be 4.0 or more and 7.5 or less. Further preferred. On the other hand, when the laminated film of the present invention is used for optical applications, α / β is greater than 7.5 and less than 11.0 in order to promote interface formation and provide performance such as water vapor barrier properties and color unevenness suppression. It is more preferable that The means for setting the minimum value of α / β to 3.0 or more and 13.0 or less is not particularly limited. For example, the affinity and diffusion of the thermoplastic resin A and the thermoplastic resin B so as to form an interface layer in the feed block. Examples include a method for adjusting the speed, a method for adjusting the amount of the thermoplastic resin A relative to the thermoplastic resin B, a method for adjusting the tip shape of the comb teeth, and a method for adjusting the speed at which the resin merges.

  When the laminated film of the present invention is measured by atomic force microscope-thermal analysis (AFM-TA) in the film thickness direction, the lowest softening point drop temperature (° C.) observed is The temperature is preferably lower than both the softening point drop temperature (TspA (° C.)) of the thermoplastic resin A and the softening point drop temperature (TspB (° C.)) of the thermoplastic resin B. Here, the measurement principle of AFM-TA will be described. The AFM-TA is a device in which in a scanning probe microscope, the AFM needle (= probe) can be heated by an electric current, and the change in physical intensity with respect to the temperature of the sample can be measured. Therefore, local thermal analysis is possible. In the basic detection procedure, first, electricity is applied to the probe, and the resin at the probe tip is locally heated. Next, the displacement of the AFM needle at the time of temperature increase is confirmed with a laser, and the thermal vibration is monitored as a Defect value. Finally, when the sample reaches the phase inversion temperature and the sample surface melts, the needle sinks and the measurement ends. Characteristically, the tip diameter of the probe is 20 to 30 nm, and thermal diffusion occurs on the sample due to needle heating, so that the range in which heat is actually transmitted is said to be about 50 to 100 nm centering on the probe tip. Therefore, the glass transition point and the melting point of the sample electrode surface can be measured with a resolution of ˜100 nm on the measurement principle. On the other hand, the melting of a substance is determined by the ratio of melting enthalpy and melting entropy. In addition, it is known that the melting point decreases due to the entropy increase of the system in the mixing of substances. When the AFM-TA is measured in the film thickness direction, the lowest softening point drop temperature (° C.) observed is the softening point drop temperature (TspA (° C.)) of the thermoplastic resin A, and the softening point drop temperature of the thermoplastic resin B. When the temperature is lower than any of (TspB (° C.)), there is a region where the softening point is lowered by mixing the thermoplastic resin A and the thermoplastic resin B, and there is a thermally stabilized region. It shows that. When the AFM-TA is measured in the film thickness direction, the lowest softening point drop temperature (° C.) is lower than TspA (° C.) and TspA (° C.). For example, a method of adjusting the affinity and diffusion rate of the thermoplastic resin A and the thermoplastic resin B so as to form an interface layer in the feed block, a method of adjusting the amount of the thermoplastic resin A relative to the thermoplastic resin B, a comb There are a method of adjusting the tip shape of the tooth and a method of adjusting the speed at which the resin joins.

  The laminated film of the present invention has a softening point lowering temperature (° C.) that is the lowest observed when an atomic force microscope-thermal analysis (AFM-TA) is measured in the thickness direction of the film. However, it is preferably 2 ° C. or more and 20 ° C. or less lower than the lower temperature of TspA (° C.) and TspA (° C.). By setting the softening point lowering temperature within the above range, the interface portion is thermally stable, and it is possible to achieve both formability, transportability, and interlayer strength. If the softening point drop temperature is less than 2 ° C., the stability of the interface is not sufficient, the interlayer strength is insufficient, or the transportability is poor. If the softening point depression is higher than 20 ° C., the flexibility of the film is impaired and the moldability may be inferior. More preferably, it is 5 ° C. or more and 15 ° C. or less.

  The film thickness of the laminated film of the present invention is not particularly limited, and a thickness suitable for each application can be taken. For example, when the laminated film of the present invention is used for decorative purposes, the film thickness is preferably greater than 25 μm and not greater than 250 μm. More preferably, it is larger than 25 μm and not larger than 125 μm. When the film thickness is larger than 250 μm, the thickness of the crystalline layer that increases in proportion to the thickness increases, and the formability necessary for bonding to a complex shape such as a decoration application may be inferior. On the other hand, if the thickness is less than 25 μm, the number of stacked layers cannot be obtained, and it may be difficult to achieve reflective performance sufficient for practical use as a decoration application.

  On the other hand, when the laminated film of the present invention is used as an optical application, the film thickness is preferably 1 μm or more and 25 μm or less. More preferably, they are 1 micrometer or more and 15 micrometers or less. When the film thickness is larger than 25 μm, the thickness of the crystalline layer that increases in proportion to the thickness becomes large, and when used for an optical application, for example, in a display, it may be inferior in suppressing interference colors. The thinner the film thickness, the better. However, if it is smaller than 1 μm, the productivity is inferior.

  As long as the A layer and the B layer in the laminated film of the present invention do not impair the effects of the present invention, particles such as colloidal silica, titanium oxide, and crosslinked polystyrene are added in order to impart functions such as winding characteristics, rigidity, and optical characteristics. Can be included. The content of these resins and particles in the A layer and the B layer is not particularly limited as long as the effects of the present invention are not impaired, but is preferably 10% by mass or less when the entire layer is 100% by mass.

  In addition, the A layer and the B layer in the laminated film of the present invention are various additives such as an antioxidant, an antistatic agent, a crystal nucleating agent, an inorganic particle, an organic particle, and a viscosity reducing agent as long as the effects of the present invention are not impaired. An agent, a heat stabilizer, a lubricant, an infrared absorber, an ultraviolet absorber, a dopant for adjusting the refractive index, and the like may be contained.

  The laminated film of the present invention is preferably a uniaxial or biaxially oriented film from the viewpoint of increasing the rigidity of the film and maintaining the transportability. Here, the uniaxial or biaxially oriented film refers to a film in which molecular chains are oriented and crystallized in a uniaxial or biaxial direction at least in the A layer. Although it does not specifically limit as a method of making a film into a uniaxial or biaxially oriented film, unless the effect of this invention is impaired, The method of extending | stretching to a uniaxial or biaxial direction is mentioned.

  The laminated film of the present invention is more preferably a biaxially oriented film. When the laminated film is a uniaxially oriented film, it becomes a polarizing film that reflects only light rays that are incident in parallel to the molecular orientation direction. Reflection unevenness may occur. If it is a biaxially oriented film, since the A layer takes a crystal structure oriented in both the longitudinal direction and the width direction, uneven reflection due to the incident direction of light can be reduced.

  In the laminated film of the present invention, an easy-adhesion layer comprising an acrylic / urethane copolymer resin and two or more kinds of crosslinking agents may be provided on at least one surface of the laminated film. When a printed layer or a hard coat layer is applied to the laminated film, the adhesion at the interface may be lowered if an easy adhesion layer is not provided on the treated surface. Moreover, when applying a printing layer and a hard-coat layer on both surfaces of a laminated | multilayer film, it is preferable that the easily bonding layer is provided in both surfaces.

  As the acrylic / urethane copolymer resin constituting the easy-adhesion layer preferably used in the present invention, an acrylic monomer is, for example, an alkyl acrylate (the alkyl group is methyl, ethyl, n-propyl, n-butyl, isobutyl, t- Butyl, 2-ethylhexyl, cyclohexyl, etc.), 2-hydroxylethyl acrylate, 2-hydroxylethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate and other hydroxy group-containing monomers, acrylamide, methacrylamide, N-methyl methacrylamide N-methylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N, N-diethylaminoethyl acrylate, N, N-diethylaminoethyl methacrylate Amino group-containing monomers such as glycidyl acrylate, glycidyl methacrylate and other glycidyl group-containing monomers, acrylic acid, methacrylic acid and their salts (sodium salts, potassium salts, ammonium salts, etc.) carboxyl groups or monomers containing such salts, etc. Can be used. Moreover, as the urethane component in the present invention, a resin obtained by reacting a polyhydroxy compound and a polyisocyanate compound by a known urethane resin polymerization method such as emulsion polymerization or suspension polymerization can be used. Examples of the polyhydroxy compound constituting the urethane component include polyethylene glycol, polypropylene glycol, polyethylene / polypropylene glycol, polytetramethylene glycol, hexamethylene glycol, tetramethylene glycol, 1,5-pentanediol, diethylene glycol, triethylene glycol, poly Caprolactone, polyhexamethylene adipate, polyhexamethylene sebacate, polytetramethylene adipate, polytetramethylene sebacate, trimethylolpropane, trimethylolethane, pentaerythritol, polycarbonate diol, glycerin and the like can be used.

  As the crosslinking agent constituting the easy-adhesion layer in the present invention, it is preferable to copolymerize a crosslinkable functional group, for example, a melamine crosslinking agent, an isocyanate crosslinking agent, an aziridine crosslinking agent, an epoxy crosslinking agent, or a methylolation. Alternatively, alkylolized urea crosslinking agents, acrylamide crosslinking agents, polyamide crosslinking agents, oxazoline crosslinking agents, carbodiimide crosslinking agents, various silane coupling agents, various titanate coupling agents, and the like can be used. Further, from the viewpoint of heat-and-moisture resistance to the hard coat layer and the silicone-based adhesive layer, it is preferable to use two or more types of crosslinking agents. Specifically, at least one of the crosslinking agents is an oxazoline-based crosslinking agent or a carbodiimide. It is preferable to use a system crosslinking agent.

  Furthermore, since only the components of the easy-adhesion layer are easily charged, foreign matters may be mixed in various film processing steps, causing a problem of appearance defects. Therefore, it is preferable that the component of the easily adhesive layer contains a conductive polymer from the viewpoint of antistatic. As the conductive polymer, polypyrrole, polyaniline, polyacetylene, polythiophene vinylene, polyphenylene sulfide, poly-p-phenylene, polyheterocycle vinylene, particularly preferably (3,4-ethylenedioxythiophene) (PEDOT) is there.

  Next, the preferable manufacturing method of the polyester film of this invention is demonstrated below. Of course, the present invention is not construed as being limited to such examples. Moreover, the formation itself of the laminated structure of the multilayer laminated polyester film can be realized by referring to the description in [0053] to [0063] stages of JP-A-2007-307893.

  First, two types of thermoplastic resins A and B are prepared in the form of pellets. The pellets are dried in hot air or under vacuum as necessary, and then supplied to each of two extruders. In each extruder, the resin melted by heating to a temperature equal to or higher than the melting point is made uniform by the amount of resin extruded by a gear pump or the like, and foreign matters and denatured resin are removed through a filter or the like. The thermoplastic resin A and the thermoplastic resin B sent out from different flow paths using two extruders are each sent into a multilayer laminating apparatus. As the multilayer laminating apparatus, a multi-manifold die, a feed block, a static mixer, or the like can be used. In particular, in order to efficiently obtain the configuration of the present invention, at least two members having a large number of fine slits are separately provided. It is desirable to use a feed block including at least one. When such a feed block is used, the apparatus does not become extremely large, so that foreign matter due to thermal deterioration is small, and even when the number of layers is extremely large, it is possible to stack with high accuracy. Also, the stacking accuracy in the width direction is significantly improved as compared with the prior art. It is also possible to form an arbitrary layer thickness configuration. In this apparatus, since the thickness of each layer can be adjusted by the slit shape (length, width, gap), an arbitrary layer thickness can be achieved. For this reason, the layer structure which is the characteristic of this invention can be achieved easily. On the other hand, in a conventional apparatus, in order to achieve lamination of 100 layers or more, it is common to use a square mixer together. However, in such a method, the lamination flow is deformed and laminated in a similar system. In addition, it is difficult to achieve an arbitrary layer thickness.

  When two or more laminated structures are employed, a feed block including at least two members having a large number of fine slits is used. However, the layer thickness distribution changes immediately after merging at the location where the resin fed from this separate feed block merges, which is a factor in varying the mechanical and optical properties within the film plane. Furthermore, since the resin velocity near the pipe decreases due to the influence of the wall of the pipe in the path from the feed block to the base, the mechanical and optical characteristics in the film surface are more uniform due to the difference in flow velocity between the pipe wall and the center of the pipe. Was getting worse. Therefore, a laminated film that exhibits uniform mechanical properties and optical properties within the film plane without losing the lamination ratio by replacing a certain distance between the outermost layer portion of the film and the resin merging portion of separate feed blocks with the same polymer. Can be obtained. At this time, when the thick film layer on the outermost layer on both sides of the laminated film is the thermoplastic resin A, the layer made of the thermoplastic resin A corresponds to the outermost layer on both sides. Moreover, it is preferable that the resin used as the middle thick film layer is a highly crystalline resin in order to improve the trace resistance. In adjusting the thickness of the thick film layer, it is preferable to adjust each flow rate corresponding to the thickness of the corresponding layer by the gap between the slits. In this case, the gap accuracy of each slit gap is preferably ± 10 μm or less. By using such a special feed block, it is possible to obtain a multilayer laminated film which forms two or more laminated structures with high accuracy.

In the laminated film of the present invention, in order to provide a function of reflecting light in a specific wavelength band, it is preferable to design the layer thickness of each layer based on the following formula (1). The laminated film in the present invention can reflect / transmit light, but the reflectance is controlled by the difference in refractive index and the number of layers between the layer made of the thermoplastic resin A and the layer made of the thermoplastic resin B. be able to.
2 × (na · da + nb · db) = λ (1)
na: In-plane average refractive index of layer A nb: In-plane average refractive index of layer B da: Sum of half values of layer thickness of layer A and two adjacent interface layers (nm)
db: Sum of the thicknesses of the layer B and the half of the layer thicknesses of the two adjacent interface layers (nm)
λ: main reflection wavelength (primary reflection wavelength)
The molten laminate formed in the desired layer configuration in this way is then formed into a desired shape by a die and then discharged. And the sheet | seat laminated | stacked in the multilayer discharged | emitted from die | dye is extruded on rotary cooling bodies, such as a casting drum, and is cooled and solidified, and a casting film (non-stretched film) is obtained. At this time, it is preferable to use a wire-like, tape-like, wire-like, or knife-like electrode to be brought into close contact with a rotating 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 rotating cooling body such as a casting drum and rapidly cooled and solidified, or brought into close contact with a rotating cooling body with a nip roll and rapidly cooled and solidified. The layer thickness of the interface layer can also be controlled by controlling the time from when the molten laminate is discharged from the die to cooling and solidifying.

  The casting film (unstretched film) thus obtained is preferably biaxially stretched as necessary. Biaxial stretching refers to stretching in the longitudinal direction and the width direction. Stretching may be performed sequentially in biaxial directions or simultaneously in two directions. Further, the film may be re-stretched in the longitudinal direction and / or the width direction. In particular, in the present invention, it is preferable to use simultaneous biaxial stretching from the viewpoint of suppressing in-plane orientation differences and from the viewpoint of suppressing surface scratches.

  First, the case of sequential biaxial stretching will be described. Here, the stretching in the longitudinal direction refers to stretching for imparting molecular orientation to the film in the longitudinal direction. Usually, the stretching is performed by a difference in the peripheral speed of the roll. You may carry out in multiple steps using a roll pair of books. Although it changes with kinds of resin as a magnification of extending | stretching, 2 to 15 times is preferable normally, and when polyethylene terephthalate is used for either of the resin which comprises a laminated | multilayer film, 2 to 7 times are used especially preferably. Moreover, as extending | stretching temperature, the glass transition temperature-glass transition temperature +100 degreeC of resin which comprises a laminated | multilayer film are preferable.

  When providing an easily bonding layer in the laminated | multilayer film of this invention, the method of coating and laminating | coating a coating agent is preferable. As a method of coating the coating agent, a method of coating in a process separate from the production process of the laminated film in the present invention, a so-called off-line coating method, and an easy adhesion by performing coating during the production process of the laminated film in the present invention. There is a so-called in-line coating method in which the layers are laminated at once. It is preferable to adopt an in-line coating method from the viewpoint of cost and uniform coating thickness, and the solvent of the coating liquid used in that case is preferably an aqueous system from the viewpoint of environmental pollution and explosion-proof property, and water is used. It is the most preferred embodiment to use.

  When laminating the easy-adhesion layer by in-line coating, a coating material that constitutes the easy-adhesion layer is continuously applied to the uniaxially stretched laminated film. As a coating method of a coating (water-based coating) using water as a solvent, for example, a reverse coating method, a spray coating method, a bar coating method, a gravure coating method, a rod coating method, a die coating method, or the like can be used.

  Before applying the aqueous coating agent, it is preferable to subject the surface of the laminated film to a corona discharge treatment or the like. This is because the adhesiveness between the laminated film and the coating material is improved and the applicability is improved.

  The easy-adhesive layer has a crosslinking agent, antioxidant, heat-resistant stabilizer, anti-glare stabilizer, ultraviolet absorber, organic easy-to-lubricant, pigment, dye, organic or inorganic as long as the effect of the invention is not impaired. You may mix | blend particle | grains, a filler, surfactant, etc.

  Subsequent stretching in the width direction refers to stretching for imparting molecular orientation in the width direction of the film, usually using a tenter, transporting the film while holding both ends with clips, and applying heat to the film. After preheating, the film is stretched in the width direction. The aqueous coating applied just before the tenter is dried during this preheating. The stretching ratio varies depending on the type of resin, but usually 2 to 15 times is preferable, and 2 to 7 times is particularly preferable when polyethylene terephthalate is used for any of the resins constituting the laminated film in the present invention. . Moreover, as extending | stretching temperature, the glass transition temperature-glass transition temperature +120 degreeC of resin which comprises the laminated | multilayer film in this invention are preferable. The biaxially stretched laminated film is preferably subjected to a heat treatment not less than the stretching temperature and not more than the melting point in the tenter in order to impart flatness and dimensional stability. After being heat-treated in this way, it is gradually cooled gradually, cooled to room temperature, and wound up by a winder. Moreover, you may use a relaxation process etc. together in the case of annealing from heat processing as needed.

  Next, the case of simultaneous biaxial stretching will be described. In the case of simultaneous biaxial stretching, the coating material which comprises an easily bonding layer is apply | coated continuously to the obtained cast film. As a coating method of a coating (water-based coating) using water as a solvent, for example, a reverse coating method, a spray coating method, a bar coating method, a gravure coating method, a rod coating method, a die coating method, or the like can be used.

  Before applying the aqueous coating material, it is preferable to subject the surface of the laminated film in the present invention to corona discharge treatment. This is because the adhesiveness between the laminated film and the coating material is improved and the applicability is improved. Next, the cast film (non-stretched film) coated with the coating agent is guided to the simultaneous biaxial tenter, and conveyed while holding both ends of the film with clips, and stretched in the longitudinal and width directions simultaneously and / or stepwise. To do. As simultaneous biaxial stretching machines, there are pantograph method, screw method, drive motor method, linear motor method, but it is possible to change the stretching ratio arbitrarily and drive motor method that can perform relaxation treatment at any place or A linear motor system is preferred. The stretching magnification varies depending on the type of resin, but usually, the area magnification is preferably 6 to 50 times, and the area magnification is particularly preferably 8 to 30 times. In particular, in the case of simultaneous biaxial stretching, it is preferable to make the stretching ratios in the longitudinal direction and the width direction the same and to make the stretching speeds substantially equal in order to suppress the in-plane orientation difference. Moreover, as extending | stretching temperature, the glass transition temperature-glass transition temperature +120 degreeC of resin which comprises a laminated | multilayer film are preferable. The biaxially stretched film is preferably subsequently subjected to a heat treatment not less than the stretching temperature and not more than the melting point in the tenter in order to impart flatness and dimensional stability. In this heat treatment, in order to suppress the distribution of the main orientation axis in the width direction, it is preferable to perform a relaxation treatment instantaneously in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone. After being heat-treated in this way, it is gradually cooled gradually, cooled to room temperature, and wound up by a winder. Moreover, you may perform a relaxation | loosening process in a longitudinal direction and / or the width direction at the time of annealing from heat processing as needed. It is preferable to perform relaxation treatment in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone.

  The laminated film of the present invention has excellent moldability, transportability, interlaminar strength, and less color unevenness, so as a molded body using it, for example, in decoration applications, a housing such as a personal computer or a TV, It can be suitably used for members of home appliances, display devices for mirrors, and the like. In optical applications, polarizer protection applications, polarizing plates using the same, transparent conductive films, and screen protection applications such as when used for touch panels using the same, and screen components using LEDs as light sources Can be suitably used.

EXAMPLES Hereinafter, although this invention is demonstrated along an Example, this invention is not restrict | limited by these Examples.
(material)
(Resin 1)
To a mixture of 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, 0.09 parts by weight of magnesium acetate and 0.03 parts by weight of antimony trioxide are added with respect to the amount of dimethyl terephthalate, and the temperature is raised by a conventional method. Then, a transesterification reaction is performed. Subsequently, 0.020 part by weight of 85% aqueous solution of phosphoric acid is added to the transesterification reaction product with respect to the amount of dimethyl terephthalate, and then transferred to a polycondensation reaction tank. Further, the reaction system was gradually reduced in pressure while heating and heated, and a polycondensation reaction was performed at 290 ° C. under a reduced pressure of 1 mmHg to obtain polyethylene terephthalate (hereinafter sometimes referred to as PET).

(Resin 2-5)
Polyethylene terephthalate copolymerized with 21 mol% of spiroglycol (SPG) and 24 mol% of cyclohexanedicarboxylic acid (CHDC) with respect to all dicarboxylic acid components with respect to the total diol component has a weight average molecular weight described in Table 1. It was adjusted.

(Resin 6-9)
Copolymer polyethylene terephthalate obtained by mixing thermoplastic resin A and polyethylene terephthalate obtained by copolymerizing 32 mol% of cyclohexanedimethanol (CHDM) in a weight ratio of 49:51 with respect to the total diol component has a weight average molecular weight shown in Table 1. It adjusted so that it might become.

(Resin 10)
Polymethylene methacrylate (PMMA).

  Hereinafter, evaluation methods of physical property values used in the present invention will be described.

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

  A specific method for obtaining the laminated structure will be described. About 40,000 times as many TEM photographic images were captured with CanonScan D123U at an image size of 720 dpi. The image is saved in the JPEG format, and then image processing software Image-Pro Plus ver. 4 (sales company Planetron Co., Ltd.) was used to open this JPG file and perform image analysis. In the image analysis process, the relationship between the thickness in the thickness direction and the average brightness of the area sandwiched between the two lines in the width direction was read as numerical data in the vertical thick profile mode. In this image analysis, the thickness of the interface layer is determined as the thickness of the layer of the thermoplastic resin layer A or the thermoplastic resin B, in order to determine the film thickness in the brightness of the laminated part, and the influence of the interface layer And the thickness of each layer can be determined. Using the spreadsheet software (Excel2000), the position (nm) and brightness data were subjected to numerical processing of sampling step 6 (decimation 6) and 3-point moving average. Furthermore, the data obtained by periodically changing the brightness is differentiated, and the maximum value and the minimum value of the differential curve are read by the VBA program. Calculated. This operation was performed for each photograph, and the layer thicknesses of all layers were calculated. Among the obtained layer thicknesses, an average value of layers having a thickness of less than 1 μm was defined as an average layer thickness.

(2) Number average molecular weight (Mn), molecular weight polydispersity (Mz / Mn)
Gel permeation chromatograph GCP-244 (manufactured by WATERS) equipped with two Shodex HFIP 806M (manufactured by Showa Denko KK) as a column and a differential refractive index RI (2414 type, sensitivity 256, manufactured by WATERS) as a detector ) And GPC measurement was performed at 40 ° C. and a flow rate of 0.5 mL / min using PET-DMT (standard product). Using the obtained elution volume (V) and molecular weight (M), the coefficient (A ₁ ) of the third-order approximate expression of the following formula (2) was calculated to draw a calibration curve.

Log (M) = A ₀ + A ₁ V + A ₂ V ² + A ₃ V ³ (2)
Next, using a thermoplastic resin A and a thermoplastic resin B alone, a single film was formed under the same film forming conditions as the multilayer laminated polyester film. In this case, the unstretched film was formed by the same method up to casting. When each of the thermoplastic resin A and the thermoplastic resin B contains an insoluble material such as inorganic particles, after removal, hexafluoropropanol (0.005N-sodium trifluoroacetate) is used as the solvent. A solution dissolved to 0.05 wt% was prepared, and GPC measurement was performed using the solution. The measurement conditions were an injection amount of 0.200 ml and a flow rate of 0.5 ml / min. The obtained elution curve molecular weight curve and molecular weight calibration curve are overlapped to obtain the molecular weight corresponding to each outflow time, and the number average molecular weight and the molecular weight polydispersity are obtained from the following formula (3) and formulas (4) and (5). It was.
z average molecular weight (Mw) = Σ (Ni · Mi ³ ) / Σ (Ni · Mi ² ) (3)
Number average molecular weight (Mn) = ΣNiMi / ΣNi (4)
Molecular weight polydispersity = Mz / Mn (5)
(Here, Ni is the molar fraction, and Mi is the molecular weight of each elution position of the GPC curve obtained via the molecular weight calibration curve.)
(3) Solubility parameters 15 kinds of solvents with different solubility, water, acetone, 2-butanone, cyclopentanone, isopropyl alcohol, ethanol, 1-octanol, toluene, hexane, acetic acid, butyl acetate, aniline, methanamide , 2-aminoethanol, and 2-butoxyethanol were added in small portions each until they were completely dissolved. Based on the saturated solution concentration at this time, there are 6 levels of solubility in each solvent (6: insoluble, 5: mass percent concentration less than 5%, 4: mass percent concentration between 5% and less than 10%, 3: mass percent concentration of 10%. Or more, less than 30%, 2: mass percent concentration of 30% or more and less than 50%, 1: mass percent concentration of 50% or more. Based on the solubility information in each solvent thus obtained, Hansen Solubility Parameter in Practice (HSPIP) ver. The dissolution parameters were calculated according to 3.1.17.

(4) Film thickness About the obtained laminated film, the film thickness of arbitrary 10 points | pieces was measured using the digital micrometer micromate M-30 by Sony Precision Technology, and the average value was laminated film. The total thickness was used.

(5) Breaking elongation in the longitudinal direction, Young's modulus A sample is cut out at a size of 100 mm × 100 mm at an arbitrary point of the film, and a microwave molecular orientation meter MOA-2001A (frequency 4 GHz) manufactured by KS Systems (currently Oji Scientific Instruments). Was used to determine the main orientation axis in the plane of the polyester film, and the direction perpendicular to the main orientation axis was taken as the longitudinal direction. Subsequently, using a tensile tester (TENSILON / UTM-4-100 manufactured by TOYO BALDWIN CO. LTD), the breaking elongation in the longitudinal direction was measured with a tensile speed of 300 mm / min, a width of 10 mm, and a test length of 100 mm. The Young's modulus was measured according to ASTM D-882-67 from the rising slope of the start point in the stress-strain curve recorded in the tensile test, and the unit was expressed in GPa.

(6) AFM-IR
Using AFM-IR (nanoIR2: manufactured by Anasys Instruments), a tapping probe (PR-EX-TnIR-A-10) is installed on the light source used, ELSPLA, Model # NT-277 / 3-XIR3-1K replicate 1 kHz. And measured. First, the background measurement was performed at a total of 254 times and a resolution of 2 cm ⁻¹ . Next, a sample to be measured was cut by a microtome at an angle of 1 ° formed by a plane and a blade edge, and the sample was fixed to a dedicated iron plate having a diameter of about 15 mm with a double-sided tape, and the sample was neutralized for 1 minute. The double-sided tape used was a Nichiban Rimuka double-sided tape. The sample was fixed to the apparatus, and the position of IR light with respect to the AFM needle was adjusted. The validity of the position adjustment was measured with reference to the laser intensity, and the laser intensity was 1 to 4 V (yellow to green sensitivity). After adjusting the phase of the AFM needle, the AFM needle was grounded to the sample, and an AFM image was collected. Scanning conditions were setpoint: Setpoint: 0.4 V, Strength: 10%, Igain: 5, and Pgain: 10. The irradiation position (Optimize) of the IR pulse light to the sample was adjusted. ^{1100 cm} -1 in the irradiation position ^{adjustment, 1260cm -1, 1410cm -1,} using pulsed light of 1720 cm ^-1. The AFM tip was moved to the measurement position, IR pulse output: 6.84%, integration number: 254, resolution: 2 cm ⁻¹ were set, and continuous measurement was performed at a 0.115 μm pitch in the thickness direction. From the obtained profiles, the maximum peak values of 1720 ± 10 cm ⁻¹ and 1410 ± 10 cm ⁻¹ are defined as α value and β value at the measurement position, α is divided by β, and the value is divided in the film depth direction. The minimum value at was defined as α / β.

(7) AFM-TA
Measurement was carried out with a thermal probe (for contact mode: PR-EX-AN2-300-5) installed in an AFM-TA (VESTA: manufactured by Anasys Instruments) device. The apparatus was previously calibrated with reference samples specified by the manufacturer at PCL: 55 ° C, PE: 116 ° C, and PET: 235 ° C. A sample to be measured was prepared by cutting with a microtome at an angle of 1 ° formed by a flat surface and a blade edge on a special iron plate having a diameter of about 15 mm. The sample was fixed with double-sided tape, and the sample was discharged for 1 minute. The double-sided tape used was a Nichiban Rimuka double-sided tape. Next, the sample was fixed to the apparatus, and the light source for detecting the phase of AFM and the position of the tip of the AFM needle were adjusted. The validity of the position adjustment was measured with reference to the laser intensity, and the laser intensity was 1 to 4 V (yellow to green sensitivity). Thereafter, the AFM needle was grounded to the sample, and continuous measurement was performed at a pitch of 0.115 μm in the thickness direction. The measurement conditions were as follows: measurement region: 50 ° C. to 400 ° C. (10 V), temperature increase rate: 10 ° C./s, measurement end, setting: Defect Δ−0.3 V. Among the peak top values of the obtained profile, the minimum value in the film thickness direction was defined as the softening point drop temperature in the film thickness direction. The softening points TspA and TspB of the thermoplastic resin A and the thermoplastic resin B were average values when the central portion of the laminated portion was measured for each laminated portion.

(8) Formability It tested using the vacuum forming apparatus SANWA KOGYO PLAVAC TYPE FB-7. Two types of cylindrical cups having a diameter of 50 mm and a depth of 15 mm and 5 mm were pressed against a sample heated to 200 ° C., and the air in the cup was taken out for a moment to make a vacuum, and evaluation was performed according to the following criteria.

  A: The sample deforms following the shape of any cup.

          Δ: Although the sample deforms following any of the cups, the corner portion is not sufficiently formed in a cup having a depth of 15 mm.

          X: The sample does not follow any cup and hardly deforms.

(9) Transportability (bonding test)
The following urethane-based thermosetting adhesive was applied to a 100 mm width polyester film with a tension of 200 N on the surface of the polyester film in a wet thickness of 5 g / m ² , dried at a drying temperature of 90 ° C. for 1 minute, and a PET film (manufactured by Toray Industries, Inc. Using a product name: Lumirror, type U35, product number 188), a nip roll was used at a nip pressure of 0.4 MPa and a temperature of 50 ° C. to obtain a laminated film. The obtained laminated film was evaluated according to the following criteria.
A: No streak or wrinkle was generated on the film.

      Δ: A stripe or wrinkle was generated in the film, but the stripe or wrinkle was less than 3 mm in thickness and less than 10 mm in length.

      X: One or more streaks or wrinkles having a thickness of 3 mm or more or a length of 10 mm or more can be confirmed on the film.

[adhesive]
5 parts by weight of urethane prepolymer solution “Takenate” (registered trademark) A-971 manufactured by Mitsui Chemicals Polyurethanes Co., Ltd. 0.5 weight of urethane prepolymer solution “Takelac” (registered trademark) A-3 manufactured by Mitsui Chemicals Polyurethanes Co., Ltd. Part of which was dissolved in 5 parts by weight of ethyl acetate.

(10) Interlaminar strength (peeling test)
The test was conducted according to JIS K5600 (2002). The film was regarded as a hard substrate, and 25 lattice patterns were cut at intervals of 2 mm. Further, a tape cut to a length of about 75 mm was adhered to the lattice portion, and the tape was peeled off at an angle close to 60 ° in a time of 0.5 to 1.0 seconds. Here, Sekisui's cello tape (registered trademark) no. 252 (width 18 mm) was used. At this time,
◎: No delamination between layers occurs. ○: The number of lattices completely separated by one lattice is 1. Δ: The number of lattices completely separated by one lattice is 2-5. ×: One lattice (11) Color unevenness A sample is cut out with a size of 100 mm × 100 mm at an arbitrary point of the film, and a spectrophotometer Konica Minolta Co., Ltd. CM-3600d is used. The sample is set so that the angle between the normal of the film plane and the incident light is 60 °, and the chromaticity a ^* , chromaticity b ^* , and lightness L ^* at any location on the sample are measured with a diameter of 25 mm. Measured with transmitted light under a target mask condition of 4 mm. Thereafter, the sample was moved so as to be 30 mm or more away from the center of the measurement location, and the same measurement was repeated four times (measurement was performed at five arbitrary points). Next, the color difference ΔE was obtained using the formula ΔE = ((ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* ) ² ) ^1/2 . For uneven color tone, the difference between the maximum value and the minimum value of five color differences ΔE obtained by measuring at a distance of 30 mm in a 100 mm × 100 mm sample was evaluated according to the following criteria: ○: very good, Δ: good , X: Impossible.
A: 4.0 or less Δ: Greater than 4.0 and 5.0 or less x: Greater than 5.0

Example 1
The resin 1 and the resin 2 are set to a discharge ratio (resin 1 discharge / resin 2 discharge) of 1.10, and each is melted at 280 ° C. with a separate twin-screw extruder with a vent. Then, the 803 layers of feed blocks were joined so that 803 layers were alternately stacked in the thickness direction. In addition, both surface layer parts become the thermoplastic resin A so that the thickness after stretching becomes 3 μm, and the layer thicknesses of the A layer made of the adjacent thermoplastic resin A and the B layer made of the thermoplastic resin B are the same on both sides of the film. The first layer and the second layer were removed from the surface layer so that they were almost the same. Thereafter, the molten resin flow was filled in the manifold portion inside the T die and further widened, and then extruded into a sheet form from the die slit. Next, it was brought into close contact with a casting drum maintained at a surface temperature of 25 ° C. by electrostatic application, and rapidly cooled and solidified to obtain a cast film.

  The obtained cast film was heated with a roll group set at 75 ° C., then stretched 3.3 times in the longitudinal direction while rapidly heating from both sides of the stretch section with a radiation heater between 100 mm in length, and then cooled once. Thus, a uniaxially stretched film was obtained.

  The obtained uniaxially stretched film was guided to a tenter, and after preheating with 100 ° C hot air, it was stretched 3.6 times in the transverse direction at a temperature of 110 ° C. The stretched film is directly heat-treated in a tenter with hot air of 230 ° C., then subjected to a relaxation treatment of 7% in the width direction at the same temperature, and then cooled to room temperature and wound with a winder. An axially stretched film was obtained. The film thickness of the obtained biaxially stretched laminated film was 102 μm. The thickness of each layer after stretching was less than 1 μm except for both surface layers. Table 1 shows the characteristics and evaluation results of this multilayer laminated film.

(Example 2)
A multilayer laminated film was obtained in the same manner as in Example 1 except that the number of slits in the feed block, the slit width, and the film thickness in Example 1 were adjusted as shown in Table 1. The evaluation results are shown in Table 1.

(Examples 3 to 8)
A multilayer laminated film was obtained in the same manner as in Example 1 except that the number of slits in the feed block and the slit width in Example 1 were adjusted and the resin used and the film thickness were as shown in Table 1. The evaluation results are shown in Table 1.

(Comparative Examples 1-4)
A multilayer laminated film was obtained in the same manner as in Example 1 except that the number of slits in the feed block and the slit width in Example 1 were adjusted and the resin used and the film thickness were as shown in Table 1. The evaluation results are shown in Table 1.

  The films obtained in the examples were satisfactory in terms of color unevenness, moldability, transportability, and interlayer strength, and were sufficient for use as molded articles. In particular, the films obtained in Examples 1 and 2 were accompanied by excellent reflection performance, and were excellent as decorative films. Further, the film obtained in Example 3 had no interference color when combined with a display member, and was excellent as an optical film.

The present invention provides a laminated film having excellent moldability, transportability, interlayer strength, and less color unevenness. As a molded body using the same, for example, in decoration applications, it can be suitably used for housings such as personal computers and televisions, members such as home appliances, display devices for mirrors, and the like. In optical applications, polarizer protection applications, polarizing plates using the same, transparent conductive films, and screen protection applications such as when used for touch panels using the same, and screen components using LEDs as light sources Can be suitably used.

Claims (14)

The following (1) to (3) are formed by alternately laminating 25 layers or more alternately in the thickness direction of a layer (A layer) mainly composed of the thermoplastic resin A and a layer (B layer) mainly composed of the thermoplastic resin B. A laminated film satisfying
(1) The difference (| SP _A -SP _B |) between the solubility parameter (SP _A ) of the thermoplastic resin A and the solubility parameter (SP _B ) of the thermoplastic resin B is 0.01 MPa ^1/2 or more and 5.0 MPa ^{Must be 1/2} or less.
(2) The number average molecular weight (MnA) of the thermoplastic resin A and the number average molecular weight (MnB) of the thermoplastic resin B are both 3000 or more and 50000 or less.
(3) Molecular weight polydispersity (MzA / MnA), which is the ratio of z-average molecular weight (MzA) and number-average molecular weight (MnA) of the thermoplastic resin A, and z-average molecular weight (MzB) of the thermoplastic resin B The molecular weight polydispersity (MzB / MnB), which is the ratio of the number average molecular weight (MnB), is 1.5 to 23.0 in all cases. The laminated film according to claim 1, wherein an average layer thickness of layers having a thickness of less than 1 µm per layer is 20 nm or more and 400 nm or less. The laminated film according to claim 1 or 2, wherein the thermoplastic resin A is a crystalline thermoplastic resin, and the thermoplastic resin B is an amorphous thermoplastic resin. The crystalline thermoplastic resin is polyethylene terephthalate, and the non-crystalline thermoplastic resin is spiroglycol copolymerized polyethylene terephthalate and / or cyclohexanedimethanol copolymerized polyethylene terephthalate. Laminated film. When atomic force microscope-infrared spectroscopy (AFM-IR) was measured in the thickness direction of the film, the peak intensity at 1720 cm ⁻¹ was α, and the peak intensity at 1410 cm ⁻¹ was β. The laminated film according to claim 4, wherein the minimum value of the ratio (α / β) is 3.0 or more and 13.0 or less. The laminated film according to any one of claims 1 to 5, wherein the film breaking elongation in the longitudinal direction is from 150% to 300%. The laminated film according to any one of claims 1 to 6, wherein Young's modulus in the longitudinal direction is 2.7 GPa or more and 4.5 GPa or less. When the atomic force microscope-thermal analysis (AFM-TA) is measured in the thickness direction of the film, the lowest softening point drop temperature (° C.) observed is the softening of the thermoplastic resin A. the temperature Tsp _a (℃), when the softening temperature of the thermoplastic resin B was _{Tsp B (℃), Tsp a} (℃), at a temperature lower than either of Tsp _a (℃), claim 1 8. The laminated film according to any one of 7 above. When the atomic force microscope-thermal analysis (AFM-TA) is measured in the thickness direction of the film, the lowest softening point drop temperature (° C.) observed is Tsp _A (° C.), Tsp The laminated film according to claim 8, which is 2 ° C. or more and 20 ° C. or less lower than the lower temperature of _A (° C.). The laminated film according to claim 1, wherein the film thickness is 1 μm or more and 25 μm or less. The laminated film according to claim 10, which is used for a display member. The laminated film according to claim 1, wherein the film thickness is greater than 25 μm and 250 μm or less. The laminated film according to claim 12, which is used for decoration purposes. A molded body on which the laminated film according to claim 1 is placed.