KR20170088331A - Laminated film - Google Patents

Abstract

In-plane direction retardation (Re) of 0 to 400 nm, a thickness direction retardation (Rth) of 0 to 1500 nm, and a deviation of Re in the width direction of 18% or less, The laminated film is preferably used as a polarizing plate for a liquid crystal display by a laminated film having a film thickness of not more than 40 占 퐉 and a film width of not less than 400 mm and particularly a laminated film of high quality without color unevenness when mounted on a large- do.

Description

Laminated film {LAMINATED FILM}

The present invention relates to a laminated film which can be preferably used as a polarizing plate protective film. Further, the present invention relates to a polarizing plate comprising the laminated film as a polarizing plate protective film.

Thermoplastic resin films, in particular biaxially stretched polyester films, have excellent properties such as mechanical properties, electrical properties, dimensional stability, transparency, and chemical resistance, and are widely used as base films in many applications such as magnetic recording materials and packaging materials . Particularly in recent years, demand for various optical films such as a polarizing plate protective film and a transparent conductive film has been increasing in the fields of flat panel displays and touch panels. Among them, polarizing plate protective film applications are required to have low moisture permeability, excellent mechanical strength, For the purpose of application of properties and cost reduction, substitution of a conventional triacetyl cellulose (TAC) film with a polyester film has been actively studied.

Japanese Patent Application Laid-Open No. 2014-12401 Japanese Patent Application Laid-Open No. 2009-42653 Japanese Patent Application Laid-Open No. 2013-210598

However, in the biaxially stretched polyester film which has been investigated in the past, the retardation (retardation) is higher than that of the TAC film due to the orientation of the polymer at the time of stretching. Therefore, when assembled as a liquid crystal display, And there was a problem that the quality at the time of displaying an image was lowered. In order to solve this problem, a control method of retardation has been proposed, but it can not be said that it is still sufficient to satisfy both the degree of retardation and the deviation. For example, although a laminated film has been proposed to have a retardation of 400 nm or less, there is a problem that it can not be used for a polarizing plate of a liquid crystal display because of its large thickness retardation (Patent Document 1). Further, although a polarizer-protective polyester film has been proposed, the phase difference is large and the suppression of interference color and iridescence is not sufficient (Patent Document 2). A polyester film for polarizer protection having a retardation of 400 nm or less and a retardation of 400 nm has been proposed. However, since the film formation conditions in which the transmittance is low and the bowing is large are adopted, (Patent Document 3). That is, when the biaxially stretched film is produced, there is a difference in the orientation state of the polymer in the film width direction. Therefore, even if targeted retardation can be achieved in a part of the film, There is a problem in that a uniformly low retardation film can not be obtained in an area film, resulting in lower product yield and high cost. Since the retardation is proportional to the film thickness, it can be suppressed by thinning the film thickness to a few micrometers level, but the handling property is lowered due to the extremely thin film, and thus it is not practical for the use of the polarizing plate protective film. In addition, the polarizing plate protective film used for the outermost layer is required to have a high UV blocking property, and the increase in cost due to the addition of a large amount of the ultraviolet absorbing material, process contamination, and change in color tone have been problems.

An object of the present invention is to solve the above problems. In other words, it is a biaxially stretched polyester film which can be reduced in cost and thinned, has low phase difference, and is free from color unevenness, iridescence and interference color when mounted on a display device such as a liquid crystal display of a large screen, And to provide a laminated film.

The above problem is solved by a laminated film comprising three or more layers laminated in the thickness direction, wherein the in-plane direction retardation (Re) is 0 to 400 nm, the thickness direction retardation (Rth) is 0 to 1500 nm, % Or less, a Young's modulus in the longitudinal and transverse directions of 2 ㎬ or more, elongation at break in the longitudinal and width directions of 50% or more, a film thickness of the laminated film of 40 탆 or less, and a width of the film of 400 mm or more .

(Effects of the Invention)

When the laminated film of the present invention is used as a polarizing plate protective film and mounted on a display device of a liquid crystal display of a large screen, there is less color unevenness, and the display is good and has an effect of displaying high quality. As a more preferable form, it has an effect of suppressing UV deterioration of the polarizer and the liquid crystal due to high UV blocking. When mounted as a transparent conductive base film such as ITO, there is no color irregularity, rainbow unevenness, interference color, and the same effect is obtained. This effect is also displayed brightly and clearly without becoming a black display called a blackout phenomenon when an observer views the polarized sunglasses.

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

The laminated film of the present invention is a laminated film in which three or more layers are laminated in the thickness direction. From the viewpoints of UV barrier property, retardation and total film thickness, the number of laminated films is preferably from 51 to 1001, more preferably from 101 to 501, and even more preferably from 151 to 351. [ From the viewpoint of thinness and ultraviolet reflection due to interference reflection, it is particularly preferable that the layer is 101 to 301 layers. When the number of layers of the laminated film is less than three, when the amorphous resin is used as the thermoplastic resin B as described later, problems such as poor film formation due to adhesion to a production facility such as rolls and clips, and deterioration of the flatness of the surface of the laminated film . In the case where the number of laminated films is one layer, that is, a monolayer film, it is necessary to reduce the thickness in order to control the retardation and the handling property may be deteriorated. When the number of laminated films is less than 51, the UV blocking property may be insufficient. The relationship between the UV blocking property and the number of layers in the thickness direction will be described later. On the other hand, when the number of laminated films exceeds 1001, there is a possibility that the total thickness of the film becomes excessively thick.

It is preferable that the laminated film of the present invention is formed by alternately laminating the A layer containing the crystalline polyester as the main component and the B layer containing the thermoplastic resin B different from the crystalline polyester as the main component. The term " main component " means that the specific component accounts for at least 50 mass% of the total components, more preferably at least 80 mass%, further preferably at least 90 mass%, particularly preferably at least 95 mass% . The thermoplastic resin B different from the crystalline polyester A used in the A layer indicates different thermal properties from the crystalline polyester A used in the A layer and specifically refers to a polyester having a melting point Or a glass transition point temperature. Here, the alternate lamination means that layers made of other thermoplastic resins are laminated in a regular arrangement in the thickness direction. For example, the thermoplastic resins A and B having different refractive indexes In this case, each layer is referred to as an A layer and a B layer, and is stacked in a regular arrangement of A (BA) n (n is a natural number). By alternately laminating the resins having different thermal properties in this manner, it becomes possible to highly control the orientation state of each layer when manufacturing the biaxially oriented film, and further to control the retardation and the UV blocking property.

In the laminated film of the present invention, it is preferable that the layer A composed of the crystalline polyester is the outermost layer. In this case, since the crystalline polyester is the outermost layer, it is possible to obtain a biaxially oriented film like a crystalline polyester film such as a polyethylene terephthalate film or a polyethylene naphthalate film. When the thermoplastic resin A is made of, for example, an amorphous resin, if a biaxially stretched film is obtained in the same manner as the ordinary continuous biaxially stretched film to be described later, film formation defects due to adhesion to production facilities such as rolls and clips, There arises a problem that the flatness of the film surface is deteriorated. As the crystalline polyester to be used in the present invention, a polyester obtained by polymerization from an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a monomer mainly composed of a diol is preferable. Examples of the aromatic dicarboxylic acid include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,6- 4,4'-diphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, and 4,4'-diphenyl sulfone dicarboxylic acid. Examples of the aliphatic dicarboxylic acid include adipic acid, suberic acid, sebacic acid, dimeric acid, dodecanedioic acid, cyclohexanedicarboxylic acid and ester derivatives thereof. Among them, terephthalic acid and 2,6-naphthalene dicarboxylic acid which exhibit a high refractive index are preferable. These acid components may be used alone or in combination. Two or more kinds of acid components may be used, or oxyacids such as hydroxybenzoic acid may be partially copolymerized.

Examples of the diol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, Cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, Bis (4-hydroxyethoxyphenyl) propane, isosorbide (1,4: 3,6-dianhydroglycitol, 1,4: 3,6-dianhydro-D-sorbitol), spiroglycol, . Of these, ethylene glycol is preferably used. These diol components may be used alone or in combination of two or more.

Examples of the thermoplastic resin B that can be added to the crystalline polyester used in the present invention include polyolefins such as polyethylene, polypropylene, poly (4-methylpentene-1), chain polyolefins such as polyacetal, Cis-polymerization, addition polymerization, biodegradable polymers such as alicyclic polyolefins, polylactic acid and polybutyl succinate which are addition copolymers with other olefins, polyamides such as nylon 6, nylon 11, nylon 12 and nylon 66, But are not limited to, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, ethylene vinyl acetate copolymer, polyacetal, polyglycolic acid, polystyrene, styrene copolymer, polymethyl methacrylate, Polyesters such as polypropylene terephthalate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate Polyether ether ketone, modified polyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide, polyarylate, tetrafluoroethylene resin, tetrafluoroethylene resin, tetrafluoroethylene resin, tetrafluoroethylene resin, tetrafluoroethylene resin, A fluorinated ethylene-6-fluorinated propylene copolymer, and polyvinylidene fluoride. Among them, from the viewpoints of strength, heat resistance, transparency and general versatility, the thermoplastic resin B, which is different from the crystalline polyester in particular, is also referred to as an adhesion property and lamination property to a crystalline polyester in addition to strength, heat resistance, transparency, It is preferable that it is made of polyester. These may be copolymers or mixtures.

Examples of the thermoplastic resin B different from the crystalline polyester used in the present invention and the crystalline polyester include polyethylene terephthalate and its polymer, polyethylene naphthalate and its copolymer, polybutylene terephthalate And copolymers thereof, polybutylene naphthalate and copolymers thereof, polyhexamethylene terephthalate and copolymers thereof, polyhexamethylene naphthalate and copolymers thereof, and the like are preferably used.

The thermoplastic resin B of the present invention is preferably an amorphous polyester containing at least one copolymerizable component selected from isophthalic acid, cyclohexanedicarboxylic acid, spiroglycol, cyclohexanedimethanol, and isosorbide. The polyester containing these components is difficult to exhibit birefringence, and particularly when stretched, the polyester easily exhibits its effect. Therefore, when used as the laminated film of the present invention, not only the retardation from the front but also the retardation in the thickness direction It is possible to suppress color irregularity, rainbow stain, and interference color. Especially, spiroglycol and isosorbide can improve the heat resistance by increasing the copolymerization amount, and exhibit excellent processability in the production process of a transparent conductive film such as a polarizing plate and ITO. Incidentally, the color unevenness and rainbow unevenness are optical phenomena seen when a polyester film having birefringence is placed on a display panel which emits linearly polarized light, and the viewing angle dependency is examined when the back surface is displayed in white. The interference color is a color caused by a phase difference when a birefringent element is disposed between two polarizing plates whose absorption axes are orthogonal to each other and is irradiated with white light from below. In general, Michel-Levy's interference diagram shows a relationship between phase difference and color Known.

As a preferable combination of the crystalline polyester used in the laminated film of the present invention and the thermoplastic resin B different from the crystalline polyester, it is particularly preferable that the absolute value of the difference in the SP value of each thermoplastic resin is 1.0 or less. When the absolute value of the difference between the SP values is 1.0 or less, delamination between layers is less likely to occur. More preferably, the crystalline polyester and the thermoplastic resin B are preferably composed of a combination providing the same basic skeleton. The basic skeleton referred to herein is a repeating unit constituting the resin. For example, when polyethylene terephthalate is used as one thermoplastic resin, from the viewpoint of realizing a high-precision lamination structure, the basic skeleton is the same as that of polyethylene terephthalate It is preferable that the skeleton ethylene terephthalate is contained in the other thermoplastic resin. If the crystalline polyester and the thermoplastic resin B contain the same basic skeleton, a laminated structure having a high degree of lamination accuracy and in which delamination at the lamination interface is unlikely to occur can be obtained.

As a preferable combination of the crystalline polyester used in the laminated film of the present invention and the thermoplastic resin B different from the crystalline polyester, the difference between the glass transition temperatures of the crystalline polyester and the thermoplastic resin B is preferably 20 ° C or lower . When the glass transition temperature difference is larger than 20 占 폚, the thickness uniformity at the time of producing a laminated film becomes defective, which causes a deviation in retardation. In addition, when the laminated film is molded, a problem such as occurrence of over-stretching is likely to be seen.

The B layer of the laminated film of the present invention is preferably a thermoplastic resin B different from the crystalline polyester used for the A layer, which is made of an amorphous resin. Compared with the crystalline resin, since the amorphous resin is hardly aligned when the biaxially oriented film is produced, it is possible to suppress an increase in retardation of the B layer made of the thermoplastic resin B, and furthermore, It is easy to suppress the non-uniformity of the image. Particularly, when the biaxially oriented film is produced, a heat treatment step is provided, and this effect becomes remarkable. Specifically, it is possible to completely relax the orientation generated in the layer made of the amorphous resin in the stretching process in the longitudinal direction and the transverse direction of the film in the heat treatment step, and to obtain the retardation caused by the layer A Only the retardation as a laminated film is affected. The term amorphous resin as used herein refers to a resin which hardly shows a peak corresponding to the melting point in the differential scanning calorimetry.

As an example of a resin combination for satisfying the above conditions, in the laminated film of the present invention, the crystalline polyester comprises polyethylene terephthalate or polyethylene naphthalate, and the thermoplastic resin B is a polyester comprising spiroglycol desirable. The polyester comprising spiroglycol refers to a copolyester or homopolyester copolymerized with spiroglycol, or a polyester blended therewith. The polyester comprising spiroglycol is preferable because it has a small glass transition temperature difference from polyethylene terephthalate or polyethylene naphthalate and is therefore difficult to be stretched at the time of molding and also difficult to delaminate between layers. More preferably, the crystalline polyester is composed of polyethylene terephthalate or polyethylene naphthalate, and the thermoplastic resin B is a polyester comprising spiroglycol and cyclohexanedicarboxylic acid. If the polyester is composed of spiroglycol and cyclohexanedicarboxylic acid, crystallinity can be lowered, and retardation can be easily suppressed. In addition, since the difference in glass transition temperature from polyethylene terephthalate and polyethylene naphthalate is small and the adhesive property is excellent, it is difficult to form the film at the time of molding, and it is also difficult to delaminate between layers.

Further, the laminated film of the present invention is a polyester in which the crystalline polyester comprises polyethylene terephthalate or polyethylene naphthalate, and the thermoplastic resin B different from the crystalline polyester is cyclohexanedimethanol-containing polyester desirable. The polyester comprising cyclohexane dimethanol refers to a copolyester or homopolyester obtained by copolymerizing cyclohexane dimethanol or a polyester blended therewith. Polyesters containing cyclohexanedimethanol can deteriorate crystallinity and therefore can easily inhibit retardation. Further, since the difference in the glass transition temperature from polyethylene terephthalate or polyethylene naphthalate is small, And it is also difficult to delaminate between layers. More preferably, the thermoplastic resin B is an ethylene terephthalate polycondensate in which the copolymerization amount of cyclohexanedimethanol is 15 mol% or more and 60 mol% or less. By doing so, in addition to being capable of restraining retardation, it is possible to make the state almost amorphous, and in particular, the change of retardation due to heating or time lapse is small, and peeling between layers is difficult to occur. The ethylene terephthalate polycondensate having a copolymerization amount of cyclohexanedimethanol of 15 mol% or more and 60 mol% or less adheres very strongly to polyethylene terephthalate. Further, the cyclohexanedimethanol group has a cis-isomer or trans-isomer as a geometric isomer, and since it has a chair-like or boat-like structure as the isomer of the isomer, it is difficult to crystallize orientation with polyethylene terephthalate.

It is also preferable that the laminated film of the present invention is a polyester in which the crystalline polyester comprises polyethylene terephthalate or polyethylene naphthalate and the thermoplastic resin B different from the crystalline polyester is isophthalic acid-containing polyester . The polyester comprising isophthalic acid refers to a copolyester or homopolyester copolymerized with isophthalic acid or a polyester blended therewith. Since polyester containing isophthalic acid can lower crystallinity, retardation can be easily suppressed and the difference in glass transition temperature from polyethylene terephthalate or polyethylene naphthalate is small, so that it is difficult for the polyester to form at the time of molding , And delamination between layers is also difficult. More preferably, the thermoplastic resin B is an ethylene terephthalate polycondensate having a copolymerization amount of isophthalic acid of 10 mol% or more and 25 mol% or less.

It is also preferable that the laminated film of the present invention is a polyester in which the crystalline polyester comprises polyethylene terephthalate or polyethylene naphthalate and the thermoplastic resin B different from the crystalline polyester is isosorbide-containing polyester. The polyester comprising isosorbide refers to a copolyester or homopolyester obtained by copolymerizing isosorbide, or a polyester blended therewith. Since the polyester comprising isosorbide can lower the crystallinity and can easily suppress the retardation and the glass transition temperature difference between the polyethylene terephthalate and the polyethylene naphthalate is small and the compatibility is good, It is excellent in dehiscence and interlayer adhesion. The copolymerization amount of the preferred isosorbide is 3 mol% or more and 50 mol% or less of ethylene terephthalate. More preferably, the crystalline polyester is composed of polyethylene terephthalate or polyethylene naphthalate, and the thermoplastic resin B is a polyester comprising isosorbide and cyclohexanediol. The polyester containing isosorbide and cyclohexanedimethanol can further lower the polymerization and crystallinity, so that the retardation can be easily suppressed as the productivity is increased. The copolymerization amount of cyclohexane dimethanol is preferably 5 to 60 mol%.

The thermoplastic resin may contain various additives such as an antioxidant, a heat stabilizer, a weather stabilizer, an ultraviolet absorber, an organic lubricant, a pigment, a dye, an organic or inorganic fine particle, a filler, an antistatic agent, May be added.

The concentration of the ultraviolet absorber (UVA) to be added to the laminated film of the present invention is preferably 0.5 to 2 mass%, more preferably 0.7 to 1.8 mass%, further preferably 0.8 to 1.5 mass%, more preferably 1.0 to 1.5 mass %. If the concentration of UVA is less than 0.5% by mass, there is a possibility that the UV blocking property is lowered. On the other hand, when the concentration of UVA is more than 2% by mass, there is a possibility that process contamination, color tone change, and mechanical strength are lowered. As UVA, from the viewpoint of UV absorbing ability in a wavelength range of 300 to 400 nm, 2,2'-methylenebis [6- (2H-benzotriazol-2-yl) -4- (Tetramethylbutyl) phenol], 2,4,6-tris (2-hydroxy-4-hexyloxy-3-methylphenyl) -1,3,5-triazine, 2,2 '- (Phenylene) bis (4H-3,1-benzoxazine-4-one), 2- (4,6- - (2-ethylhexyloxy) -phenol, 2- (4,6-diphenyl-1,3,5-triazin- Phenoxy] phenol, or a mixture thereof can be preferably used.

In the laminated film of the present invention, it is preferable that the lamination ratio of the A layer and the B layer (the total thickness of the A layer / the total thickness of the B layer) is in the range of 0.2 to 1.5. The lamination ratio of the A layer and the B layer is more preferably from 0.5 to 1.4, more preferably from 0.7 to 1.3, and particularly preferably from 0.8 to 1.2. When the lamination ratio is less than 0.2, there is a possibility that the heat resistance is deteriorated when an amorphous resin is used for the B layer in particular. When the lamination ratio exceeds 1.5, there is a possibility that the retardation may excessively increase when an amorphous resin is used for the B layer. From the viewpoint of lowering the retardation in the thickness direction, which is related to rainbow stains and color unevenness, the smaller the lamination ratio is, the better.

The laminated film of the present invention has an in-plane retardation (Re) of 0 to 400 nm. Re is preferably 0 to 200 nm, more preferably 0 to 150 nm, even more preferably 0 to 100 nm, and even more preferably 0 to 50 nm. Generally, Re is calculated from the product of the film thickness and the maximum value of the difference in the refractive index in two orthogonal directions within the plane of the film. However, since the refractive index of the film can not be easily measured in the laminated film of the present invention, The retardation value is obtained by a value calculated by the following formula. Specifically, the value measured in the measuring method described later is used in the phase difference measuring apparatus KOBRA series manufactured by Oji Paper Co., Ltd. When Re exceeds 400 nm, an interference color may be generated when the polarizing plate protective film is mounted on a liquid crystal display.

The laminated film of the present invention has a thickness direction retardation (Rth) of 0 to 1500 nm. Rth is preferably from 0 to 1200 nm, more preferably from 0 to 1000 nm, even more preferably from 0 to 900 nm, and particularly preferably from 0 to 700 nm. When Rth exceeds 1500 nm, interference colors may be easily seen when the polarizing plate protective film is observed with an angle when mounted on a liquid crystal display.

Re and Rth as described above can be controlled by controlling the birefringence of each layer by the film forming conditions to be described later. More specifically, for example, thermoplastic resin B can be controlled to be zero in the process of producing the film by anisotropy (birefringence) of the refractive index in the layer B made of thermoplastic resin B. In this case, Re is the product of the anisotropy of the refractive index of the layer A made of crystalline polyester and the total thickness of the layer A, and Re can be suppressed as compared with a film made of only crystalline polyester having the same thickness.

In the laminated film of the present invention, the deviation of Re is 18% or less in the width direction. The deviation of Re is preferably 15% or less, more preferably 12% or less, more preferably 10% or less, and particularly preferably 8% or less. Most preferably not more than 6%. In this case, when the film width of the laminated film is 400 mm or more, Re is sampled at intervals of 50 mm in the entire width direction of the film, and Re at the center of each sample is measured. (Re difference (%) = (maximum value of Re - minimum value of Re) / (average value of Re) x 100). It is more preferable that the deviation of Re is not more than 18% at a film width of 600 mm or more, more preferably at a film width of 1000 mm or more. In the case of a roll-shaped laminated film, the winding direction of the roll is the film longitudinal direction, and the direction orthogonal to the film longitudinal direction corresponds to the width direction. On the other hand, in the case of the cut sheet shape, Re was measured at both ends (positions separated by 25 mm from both ends) in the direction orthogonal to the long side direction and the long side direction of the film, Quot; width direction " When the deviation of Re is more than 18% in the width direction, there is a possibility that color unevenness occurs when the polarizing plate protective film is mounted on a large-sized liquid crystal display, and the quality is degraded. The method of controlling the deviation in the width direction of Re as described above can be achieved by taking the resin and the film forming conditions to be described later.

The laminated film of the present invention has a Young's modulus in the longitudinal direction and the transverse direction of 2 mu m or more. The Young's modulus in the longitudinal direction and the width direction is preferably 2.2 GPa or more, more preferably 2.5 GPa or greater, more preferably 2.8 GPa or greater, and particularly preferably 3 GPa or greater. When the Young's modulus of either the longitudinal direction or the width direction is 2. Or less, there is a possibility that there is a problem in handling due to lack of elasticity in the film. As a method of controlling the Young's modulus in the longitudinal direction and the width direction as described above, it can be achieved by using the crystalline polyester described above and taking the film forming conditions to be described later.

The laminated film of the present invention has a elongation at break of 50% or more in the longitudinal direction and the width direction. The elongation at break in the longitudinal direction and the width direction is preferably 100% or more, more preferably 110% or more, further preferably 120% or more, and particularly preferably 130% or more. When the elongation at break of one of the lengthwise direction and the widthwise direction is 50% or less, the film may be retracted and the film may be broken when tension is applied during the processing. The method of controlling the elongation at break in the longitudinal direction and the width direction as described above can be achieved by using the crystalline polyester described above and selecting the film forming conditions to be described later.

The laminated film of the present invention has a film thickness of 40 mu m or less. The film thickness is preferably 5 to 35 mu m, more preferably 10 to 30 mu m, even more preferably 12 to 25 mu m, and particularly preferably 13 to 20 mu m in terms of handling. When the film thickness exceeds 40 탆, the retardation increases, or when used as a polarizing plate protective film, the polarizing plate becomes thick, so that the weight may be increased or increased when the polarizing plate is mounted on a liquid crystal display. Particularly, when the thickness becomes thick, the amount of pulling in the semi-running (longitudinal) direction due to the blowing-off ratio at the time of transverse stretching becomes large, so that the bowing phenomenon occurs strongly. That is, in the phase difference distribution in the width direction, the deviation between the center portion and the end portions gripped by the clips of the transverse stretching machine becomes large. The Boeing phenomenon refers to a phenomenon in which a straight line is transversely stretched in the film width direction with magic ink before the process of the transverse stretching process, and then deformed into an arcuate shape when it comes out from the transverse stretching process after the heat treatment.

The laminated film of the present invention has a width of 400 mm or more. The width of the film is preferably 600 mm or more, more preferably 1000 mm or more, more preferably 1,300 mm or more, and particularly preferably 1500 mm or more. When the width of the film is less than 400 mm, the liquid crystal display can not be mounted as a large-sized liquid crystal display.

In the laminated film of the present invention, the deviation of Re is preferably 20% or less in the longitudinal direction. The deviation in the longitudinal direction of Re is more preferably 15% or less, more preferably 12% or less, and particularly preferably 10% or less. The Re deviation at this time means that when the length direction of the laminated film is 400 mm or more, the center portion in the width direction of the film is sampled at intervals of 50 mm, and Re at the center of each sample is measured. (Re difference (%) = (maximum value of Re - minimum value of Re) / (average value of Re) x 100). When the laminated film is a cut sheet shape, the direction orthogonal to the width direction is the longitudinal direction. As a method for controlling the deviation in the longitudinal direction of Re as described above, this can be achieved by taking film forming conditions to be described later.

In the laminated film of the present invention, it is preferable that the deviation of the orientation angle is 20 DEG or less in the width direction. The deviation in the width direction of the orientation angle of the laminated film is more preferably 15 ° or less, more preferably 10 ° or less, and particularly preferably 7 ° or less. The orientation angle referred to herein refers to the direction in which the refractive index of the film is the largest, and is actually measured by an optical method as in the case of retardation. In general, the orientation angle means that both end portions in the above-mentioned width direction exhibit the highest value and the center portion shows the lowest value. Therefore, in the present invention, a portion and a central portion which are 25 mm apart from both ends in the width direction of the laminated film are sampled, and the orientation angle at the center of each sample is measured. From the value of the orientation angle of the medium- The value obtained by subtracting the value of the orientation angle of the central portion is defined as a deviation of the orientation angle of the laminated film (the widthwise deviation of the orientation angle (DEG) = the value of the orientation angle of the larger one in both ends - the value of the orientation angle of the central portion). When the deviation of the orientation angle in the width direction exceeds 20 degrees, it is possible to avoid the blackout phenomenon displayed on the display when the observer wears polarized sunglasses, so that the new value is connected. The blackout refers to a phenomenon in which linearly polarized light emitted from the display overlaps with the absorption axis of the polarizing sunglasses and the light does not enter the eye, resulting in darkness and no image is seen. However, if the angle between the direction of the linearly polarized light from the display and the orientation of the orientation angle is 10 degrees or more, the light is birefringent, so that light is also transmitted through the polarized sunglasses, and blackout can be avoided. In recent years, it has become important in the field of on-vehicle use, and in particular, there is a demand for an ITO base film used for a touch panel. That is, when the polarizing plate protective film is mounted in an IPS or VA mode liquid crystal display (linearly polarized light is orthogonal to the angle of view), when the orientation angle is 10 degrees or more, light leakage is caused, have. The method of controlling the deviation of the orientation angle in the width direction as described above can be achieved by increasing the longitudinal drawing magnification to 3.5 or more and taking the film forming conditions to be described later. When the amorphous resin is contained in the main layer side, it is preferable because the orientation angle becomes higher. Here, the amorphous resin is a resin which shows a melting point Tm which is an endothermic peak when the raw material is evaluated by a differential scanning calorimeter (DSC) is hardly revealed, and its melting enthalpy? Hm is 6 J / g or less even if it exists.

The crystalline partial melting temperature (Tmeta) in the laminated film of the present invention is preferably 190 占 폚 or less. When Tmeta is 190 占 폚 or less, the uniformity of the retardation in the film width direction is improved and the retardation difference is preferable. If it is too low, heat shrinkage is large when polarizing the polarizing plate, which leads to quality problems. The method of adjusting Tmeta can be achieved by setting the maximum temperature of the heat treatment temperature in the production process of the film to 140 占 폚 or higher and 210 占 폚 or lower.

It is preferable that two or more tan? Peaks are observed in the dynamic viscoelasticity measurement (dynamic mechanical analysis measurement (DMA measurement)) in the longitudinal direction and / or the width direction of the laminated film of the present invention. Among the two or more peaks of the tan delta peak, the peak on the lowest temperature side is due to the Tg of the laminated film. The peaks other than Tg are due to the drawing history obtained at the time of film formation of the laminated film, and the presence of this peak is preferable from the viewpoint of the deviation of Re in the longitudinal direction and the width direction of the laminated film and mechanical properties. Further, when there is a second or more peak near the Tg, the smaller peak may be observed as a shoulder, but in this case, the number of the shoulders can be counted as the number of peaks.

In the laminated film of the present invention, it is preferable that the peak temperature of tan? Existing on the highest temperature side in the DMA measurement in the longitudinal direction and / or the width direction is 100 to 130 占 폚, or 130 to 160 占 폚. More preferably 100 to 120 deg. C, further preferably 105 to 120 deg. C, and particularly preferably 110 to 120 deg. C in view of the deviation of Re in the longitudinal direction and the width direction and mechanical properties. In the DMA measurement in the longitudinal direction and / or the width direction, when the peak temperature of tan? Existing on the highest temperature side is less than 100 占 폚 or when it exceeds 130 占 폚, the deviation of Re in the longitudinal direction and / There is a possibility to discard it. In the DMA measurement in the longitudinal direction and / or the width direction, two or more tan delta peaks are observed, and in order to control the peak temperature of tan delta at the highest temperature side in a preferable range, the crystalline polyester and the amorphous resin Layer structure, and taking the film forming conditions to be described later.

The laminated film of the present invention preferably has a storage elastic modulus E 'at 85 캜 of 2.5 ㎬ or more in dynamic viscoelasticity measurement. Since the drying temperature of the PVA (polyvinyl alcohol) serving as the polarizer in the production process of the polarizing plate is about 100 to 80 캜, the strength of elasticity in the vicinity of the temperature is required. If it is 2.5 GPa or more, it is preferable that the polarizing plate is less likely to curl or warp against shrinkage of the PVA. In addition, in order to impart the scratch resistance, it is important that the film hardly deforms, such as wrinkles, in the hard coat process. Preferably at least 2.8 kPa, and further preferably at least 3.1 kPa, and more preferably at least 3.5 kPa. As a method for achieving this, from the viewpoint of raising the E 'value at 85 캜, it is possible to incorporate spiroglycols and / or isosorbides into the components of the copolyester used in the thermoplastic resin B. From the viewpoints of stretching and adhesion, the copolymerization amount is preferably 5 mol% or more and 40 mol or less. As another method for achieving the other effect, a UV hardening type hard coat may be formed on one side or both sides. The thickness of the hard coat layer after curing is preferably 0.5 占 퐉 or more and 6 占 퐉 or less from the viewpoint of raising the value of E 'at 85 占 폚.

It is preferable that the laminated film of the present invention has a dynamic friction coefficient of 0.45 or less. When the coefficient of dynamic friction is more than 0.45, slipperiness is poor, wrinkles tend to enter, and winding properties are deteriorated. Therefore, the coefficient of dynamic friction is preferably 0.42 or less, more preferably 0.4 or less. Here, the coefficient of dynamic friction may be satisfied on at least one surface. For example, it is preferable that the coefficient of dynamic friction generated between the front surface and the back surface of the laminated film is 0.45 or less. In the ITO base material application, there is a post-process to form a maximum of four layers of a clear hard coat, a hard coat for oligomer blocking, a low refractive index layer (LR) and a high refractive index layer (HR) And 0.35 or less for the same purpose. The method of achieving this can achieve a kinetic friction coefficient of 0.4 or less by adding an inorganic particle inert to the primer layer, for example, colloidal silica having a particle size of 50 to 300 nm. It is also preferable to add inert particles to the outermost layer of the laminated film. The addition amount is preferably from 0.01% by weight to 1% by weight from the viewpoint of compatibility between transparency and lyophobicity. Further, a combination in which calcium carbonate or coagulated silica having an average particle diameter of 2.5 占 퐉 or less and 1 占 퐉 or more is added as large diameter particles and addition of silica alumina, alumina, or divinylbenzene having an average particle diameter of 0.5 占 퐉 or less as small particle diameter, .

Further, it is preferable that the laminated film of the present invention has a primer layer and / or a hard coat layer formed on at least one surface thereof. When the primer layer is formed on at least one surface, it is preferable from the viewpoint of adhesion with PVA. The primer layer is preferably applied as an aqueous coating agent during the film production process, and it is preferable that the primer layer has high general versatility selected from acrylic, polyester, urethane, acrylic modified polyester, acrylic modified urethane and the like. The crosslinking material is not particularly limited as long as it is a compound capable of causing a crosslinking reaction. However, the crosslinking material is not particularly limited as long as it is a compound causing a crosslinking reaction, but may be a urethane, Amide compounds, aziridine compounds, various silane coupling agents, and various titanate-based coupling agents. It is also preferable that the hard coat layer is formed on at least one surface from the viewpoint of measures against the scratch of the polarizing plate. The thickness of the hard coat layer is preferably 5 占 퐉 or less from the viewpoint of suppressing curling as much as possible, and is preferably 1 占 퐉 or more from the viewpoint of imparting hardness.

The laminated film of the present invention preferably has a transmittance of 30% or less at a wavelength of 380 nm from the viewpoint of UV barrier property. , More preferably not more than 25%, even more preferably not more than 20%, particularly preferably not more than 15%. When the transmittance at a wavelength of 380 nm is more than 30%, there is a possibility that the polarizer and the liquid crystal are deteriorated by ultraviolet rays when the polarizer protective film is mounted on a liquid crystal display. In order to control the transmittance at a wavelength of 380 nm in a preferable range, interference reflection of a UV absorber or a multilayer film is used. The interference reflection can be realized by setting the average layer thickness to 40 to 55 nm and increasing the difference in the in-plane refractive index of two or more kinds of resins having different optical characteristics. Therefore, in the case of biaxially oriented films, It is possible to achieve interference reflection by forming a laminated film in which amorphous at the time of stretching or a layer mainly composed of a thermoplastic resin melted in a heat treatment step are alternately laminated. Specifically, this can be achieved by laminating the above-mentioned polyester and the thermoplastic resin B with a predetermined lamination number. In addition, as described above, the inclusion of UVA within a preferable range is more preferable for the synergistic effect.

The laminated film of the present invention preferably has an average transmittance of 5% or less at a wavelength of 240 to 360 nm from the viewpoint of UV barrier property. More preferably 4% or less, further preferably 3% or less, particularly preferably 2% or less. When the average transmittance at a wavelength of 240 to 360 nm exceeds 5%, there is a possibility that the polarizer or the liquid crystal is deteriorated by ultraviolet rays when the polarizing plate protective film is mounted on a liquid crystal display. In order to control the average transmittance at a wavelength of 240 to 360 nm in a preferable range, it is possible to realize a biaxially oriented film by increasing the difference in in-plane refractive index of two or more kinds of resins having different optical characteristics. And a laminated film in which a layer mainly composed of a thermoplastic resin that maintains amorphousness at the time of stretching or is melted in a heat treatment process is alternately laminated. Specifically, this can be achieved by laminating the above-mentioned polyester and the thermoplastic resin B with a predetermined lamination number.

Next, a preferred method for producing the laminated film of the present invention will be described below. Of course, the present invention is not construed as being limited to the related examples. The laminated structure of the laminated film used in the present invention can be easily realized by a method similar to that described in paragraphs [0053] to [0063] of JP-A No. 2007-307893.

The thermoplastic resin is prepared in the form of pellets or the like. The pellets are dried in hot air or under vacuum, if necessary, and then fed to respective extruders. In the extruder, the extruded amount of the resin in the gear pump or the like is uniformized by heating the molten resin at a temperature higher than the melting point, and foreign matters or denatured resin are removed through a filter or the like. These resins are molded into a desired shape on a die and then discharged. Then, the laminated sheet discharged from the die is extruded onto a cooling body such as a casting drum, cooled and solidified to obtain a casting film. At this time, it is preferable to use an electrode such as a wire shape, a tape shape, an acicular shape, or a knife shape to adhere to a cooling body such as a casting drum by an electrostatic force to solidify rapidly. It is also preferable to eject air from a slit, spot, or surface device and adhere to a cooling body such as a casting drum to rapidly solidify or solidify it by adhering it to the cooling body with a nip roll.

Further, the crystalline polyester as the main component of the layer A and a plurality of resins of the thermoplastic resin B different from the crystalline polyester are sent out from the other flow path by using two or more extruders and fed into the multi-layer lamination apparatus. As the multi-layer lamination device, a multi-manifold die, a feed block, a static mixer or the like can be used, but in order to efficiently obtain the constitution 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 device does not become extremely large, there is less foreign matter due to thermal degradation, and even if the number of stacked layers is extremely large, high-precision stacking becomes possible. In addition, the stacking accuracy in the width direction also improves critically as compared with the conventional technique. Further, in this apparatus, since the thickness of each layer can be adjusted by the shape (length, width) of the slit, it is possible to achieve an arbitrary layer thickness.

Thus, the molten multi-layer laminate formed with the desired layer structure is guided to the die to obtain the casting film as described above.

The cast film thus obtained is preferably biaxially stretched. Here, biaxial stretching means stretching in the longitudinal direction and the width direction. The stretching may be effected in two directions by an alternating movement, or may be stretching in two directions at the same time. After biaxial stretching, re-stretching may also be performed in the longitudinal direction and / or the width direction. In particular, after the biaxial stretching, it is most preferable to conduct the heat treatment after re-stretching in the longitudinal direction. That is, the laminated film of the present invention is mainly composed of the crystalline polyester A and the amorphous polyester B, and has three or more layers, and the layer A composed of the crystalline polyester A and the layer B composed of the amorphous polyester B (A / B) of 2 to 0.2 is stretched in a longitudinal direction and a width direction in a range of a stretching temperature of 70 to 145 deg. C, and thereafter, a biaxial stretching in a range of 120 to 235 deg. And then reheating and stretching at a stretch ratio of 1.02 to 1.95 at a stretching temperature of 80 to 150 캜 in the longitudinal direction at least in the longitudinal direction and thereafter reheating at 90 to 235 캜 for winding, From the viewpoint of endlessly equalizing the phase difference in the film width direction.

The case of sequential biaxial stretching will be described first. Here, the stretching in the longitudinal direction refers to stretching in order to impart molecular orientation in the longitudinal direction to the film, and is usually carried out by the peripheral speed difference of the roll. The stretching in the running direction may be performed in one step, A plurality of roll pairs may be used. The stretching magnification varies depending on the type of resin, but is usually 2 to 15 times, and when polyethylene terephthalate is used for any of the resins constituting the laminated film, 2 to 7 times is preferably used, and more preferably 3 To 5 times, more preferably 3 to 4 times, and particularly preferably 3 to 3.5 times from the viewpoints of the deviation of Re in the longitudinal direction and the width direction and the deviation of the orientation angle. The stretching temperature is preferably the glass transition temperature to the glass transition temperature + 100 占 폚 of the resin constituting the laminated film, more preferably 70 to 120 占 폚, further preferably 80 to 110 占 폚, And 95 to 110 占 폚 are particularly preferable from the viewpoints of the deviation of the Re in the width direction and the deviation of the orientation angle. When a polyester containing naphthalene dicarboxylic acid such as polyethylene naphthalate is used, the glass transition temperature is preferably 105 占 폚 or more and 155 占 폚 or less because of its high glass transition temperature.

When the uniaxially stretched film thus obtained is subjected to surface treatment such as corona treatment, frame treatment, plasma treatment or the like, if necessary, and then the functions such as lyophobicity, adhesiveness, and antistatic property are imparted by inline coating good.

Subsequently, stretching in the transverse direction refers to stretching in order to impart orientation to the film in the transverse direction. Normally, both ends of the film are transported while holding the film by a tenter method, and stretched in the transverse direction. The stretching magnification varies depending on the type of the resin, but is preferably 2 to 15 times, and when polyethylene terephthalate is used in any of the resins constituting the laminated film, 2 to 5 times, preferably 3 to 3 times, To 5 times, more preferably from 3 to 4.5 times, from the viewpoints of Re or Rth, deviation of Re in the width direction, and suppression of deviation of the orientation angle. Particularly preferably, the stretching is performed at a magnification higher than the longitudinal stretching ratio It is also desirable. The stretching temperature is preferably from the glass transition temperature to the glass transition temperature + 120 占 폚 of the resin constituting the laminated film, and it is preferable that the temperature is inclined at a temperature from the viewpoints of the deviation of Re in the width direction and the deviation of the orientation angle , It is preferable that the temperature increases as it goes from upstream to downstream. Specifically, when the transverse stretching section is divided into two, it is preferable that the difference between the upstream temperature and the downstream temperature be 20 DEG C or more. More preferably 30 DEG C or higher, even more preferably 35 DEG C or higher, particularly preferably 40 DEG C or higher. The stretching temperature in the first stage is more preferably 80 to 120 占 폚, more preferably 90 to 110 占 폚, and particularly preferably 95 to 105 占 폚. When a polyester containing naphthalene dicarboxylic acid such as polyethylene naphthalate is used, the glass transition temperature is preferably 105 占 폚 or more and 155 占 폚 or less because of its high glass transition temperature.

In addition, in the laminated film of the present invention, it is preferable to give a difference in transverse stretching speed from the viewpoint of the deviation of Re in the width direction and the deviation of the orientation angle. Specifically, when the transverse stretching section is divided into two, It is preferable that the stretching amount of the film at the intermediate point (film width at the measuring point-film width before stretching) is 60% or more of the stretching amount at the end of the transverse stretching section, more preferably 70% 75% or more, and particularly preferably 80% or more.

The biaxially stretched film is preferably subjected to a heat treatment at a stretching temperature or higher and a melting point or lower in the tenter in order to impart flatness and dimensional stability. Specifically, since the upper limit of the general drying temperature in the polarizing plate manufacturing process is about 120 deg. C, it is preferable to perform heat fixing in the range of 120 to 235 deg. If it is less than 140 캜, thermal dimensional stability can not be obtained, which may cause curling or warping of the polarizing plate. When the temperature is higher than 235 DEG C, bowing or the like becomes large and the uniformity of retardation in the film width direction may be deteriorated. Particularly preferably from 190 to 225 DEG C from the standpoints of Re or Rth, a variation of Re in the width direction, or a deviation of the orientation angle. From the viewpoint of reducing the deviation of the Re in the width direction, it is preferable to carry out heat treatment draw stretching of 1 to 10% in the entire heat treatment (front half). But is preferably 2 to 8% from the viewpoint of not increasing the heat shrinkage ratio in the width direction. After the heat treatment in this manner, it is uniformly annealed, cooled to room temperature, and wound. If necessary, a relaxation treatment or the like may be used in combination with the heat treatment or the cold treatment. The relaxation rate at the time of the heat treatment is preferably 0.5 to 5%, more preferably 0.5 to 3%, still more preferably 0.8 to 2.5%, and from the viewpoints of the deviation of Re in the width direction and the deviation of the orientation angle, % Is particularly preferable. Further, the relaxation rate in the fast freezing state is preferably from 0.5 to 3%, more preferably from 0.5 to 2%, still more preferably from 0.5 to 1.5%, and from the viewpoint of the deviation of Re in the width direction and the deviation of the orientation angle, 0.5 To 1% is particularly preferable. The temperature of the cold state is preferably 80 to 150 占 폚, more preferably 90 to 130 占 폚, further preferably 100 to 130 占 폚, and particularly preferably 100 to 120 占 폚 in view of the planarity of the laminated film.

The case of simultaneous biaxial stretching will be described below. In the case of simultaneous biaxial stretching, the obtained casting film is subjected to surface treatment such as corona treatment, frame treatment and plasma treatment, if necessary, and then the functions such as lubricity, adhesiveness and antistatic property are given by inline coating It is also good.

Then, the casting film is guided to the simultaneous biaxial tenter, and both ends of the film are held while being held by a clip, and are simultaneously and elongated in the longitudinal direction and in the width direction. The simultaneous biaxial stretching machine includes a pantograph system, a screw system, a drive motor system, and a linear motor system. However, a drive motor system or a linear motor system capable of arbitrarily changing the stretching magnification and capable of relaxation at an arbitrary place is preferable Do. The stretching magnification varies depending on the type of resin, but is usually preferably 6 to 50 times as an area magnification, and when polyethylene terephthalate is used for any of the resins constituting the laminated film, the area ratio is preferably 8 to 30 times , More preferably from 9 to 25 times, more preferably from 9 to 20 times, and particularly preferably from 10 to 15 times from the viewpoints of Re and Rth, the Re deviation in the longitudinal direction and the width direction, and the deviation of the orientation angle . In particular, in the case of simultaneous biaxial stretching, it is preferable that the stretching magnifications in the longitudinal direction and the transverse direction are made the same and the stretching speed is substantially the same in order to suppress the in-plane orientation difference. The stretching temperature is preferably the glass transition temperature to the glass transition temperature + 120 占 폚 of the resin constituting the laminated film, more preferably 80 to 160 占 폚, further preferably 90 to 150 占 폚, And particularly preferably from 100 to 140 占 폚 in terms of the deviation of Re in the width direction and the deviation of the orientation angle.

In order to impart planarity and dimensional stability to the film thus biaxially stretched in this manner, it is preferable to carry out heat treatment at a stretching temperature or higher and lower than the melting point in the open and closed room in the tenter, and the conditions are the same as those for biaxial stretching.

In the laminated film of the present invention, after the biaxial stretching as described above, the heat-treated film is re-stretched at least in the longitudinal direction at a stretching temperature in the range of 80 to 150 占 폚 in the range of 1.02 to 1.95 times, Lt; RTI ID = 0.0 > C, < / RTI >

The laminated film of the present invention obtained as described above has a low retardation and a small deviation to suppress the occurrence of color unevenness and can be suitably used as a polarizing plate protective film. The polarizing plate protective film may be suitably used as a polarizing plate after being bonded to a PVA sheet produced by orienting the polarizing plate containing iodine in a commercially available PVA.

Example

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 laminated layers

The number of stacked layers of the laminated film was determined by observing a transmission electron microscope (TEM) of a sample cut from a cross section using a microtome. That is, a sectional photograph was taken by observing the cross section of the film under the condition of a transmission electron microscope model H-7100FA (manufactured by Hitachi Seisakusho Co., Ltd.) under the condition of an acceleration voltage of 75 kV, and the number of layers was measured. In some cases, in order to obtain a high contrast, a dyeing technique using RuO ₄ , OsO ₄ or the like was used. When the thickness of the thin film layer is less than 50 nm and the thickness of the thin film layer is less than 50 nm and less than 500 nm, the thickness of the thinnest layer (thin film layer) In the case of 500 nm or more, observation was carried out at an enlargement magnification of 10,000 times.

(2) In-plane direction retardation Re, thickness direction retardation (Rth), orientation angle

A phase difference measuring apparatus (KOBRA-21ADH) manufactured by Oji Kikuki Kikai Co., Ltd. was used. The sample was cut into 3.5 cm x 3.5 cm at the center in the film width direction and installed in the apparatus so that the film width direction was 0 deg. Defined by the present measuring apparatus. The Re, Rth and its orientation at a wavelength of 590 nm The angle was measured. Further, Rth was calculated by second approximation of each retardation value at an incidence angle of 0 to 50 degrees (every 10 degrees) while inclining the slow axis. Re is a value at an incident angle of 0 DEG.

(3) Deviation of Re in the width direction

In the laminated film having a film width of 400 mm or more, samples were sampled at intervals of 50 mm in the entire width direction of the film by the method described in the above (2), and Re at the center of each sample was measured. Of the laminated film was divided by the average value and the value indicated as% was defined as the deviation in the width direction of Re of the laminated film. In the roll-shaped laminated film, the winding direction of the roll is the film length direction, and the direction orthogonal to the film length direction corresponds to the width direction. On the other hand, in the case of the cut sheet shape, Re was measured at both ends (positions separated by 25 mm from both ends) in the direction orthogonal to the long side direction and the long side direction of the film, Quot; width direction "

(4) Deviation of Re in the longitudinal direction

In the laminated film having the longitudinal direction of 400 mm, the middle portion in the width direction of the film was sampled at intervals of 50 mm by the method described in the above (2), and Re at the center of each sample was measured. Of the difference between the average value and the value indicated in% is the deviation in the longitudinal direction of Re of the laminated film. The longitudinal direction of the laminated film is a direction orthogonal to the width direction described in (3).

(5) Deviation of the orientation angle in the width direction

In the laminated film having a film width of 400 mm or more, sampling was carried out at three points in the center portion in the width direction and in the portions spaced 25 mm from the both end portions by the method described in the above (2), and the central orientation angle of each sample was And the larger value obtained by subtracting the difference in the central portion from the values at the both ends was regarded as the deviation in the width direction of the orientation angle of the laminated film. The width direction of the laminated film refers to the definition described in the above (3).

(6) Young's modulus, breaking elongation

The sample was cut to 15 cm in the longitudinal direction and 1.5 cm in the width direction from the central portion in the width direction of the film to obtain a sample for measuring the Young's modulus in the longitudinal direction. Likewise, the sample was cut into 15 cm in the width direction and 1.5 cm in the longitudinal direction to obtain a sample for measuring the Young's modulus in the width direction. The Young's modulus and the elongation at break were measured at a temperature of 23 캜 and a humidity of 65% RH using a Robot Tensilon RTA (Orientech) in accordance with JIS-K7127-1999. The tensile speed was 300 mm / min.

(7) Film thickness

The contact type film thickness measuring instrument was measured by Light Math VL-50A manufactured by Mitsutoyo Co., Ltd. (10.5 mm? Diameter spherical surface measuring instrument, measurement load: 0.06 N). The measurement was carried out ten times by changing the location, and the average value was taken as the thickness of the laminated film.

(8) Dynamic viscoelasticity (DMA) measurement (E 'and tan?)

The sample was cut out to a size of 7 cm x 1 cm at the center in the film width direction, and placed in a sample holder so as to be a sample having a measurement length of 2 cm x film width of 1 cm. (DMS 6100 manufactured by Seiko Instruments Inc.) under the conditions of room temperature 20 ° C. to 240 ° C. in the tensile mode, displacement 10 μm, vibration frequency 1 Hz, and temperature raising rate 2 ° C./min, the storage elastic modulus E ' tan? was measured. tan? is determined by the ratio of the loss elastic modulus E "and the storage elastic modulus E '.

(9) Visibility test

The sample was cut into a size of 420 mm in the width direction and 310 mm in the longitudinal direction from the widthwise central portion of the film on one surface of the polarizing plate having the polarization degree of 99.9% produced by adsorption / orientation of iodine in the PVA, thereby obtaining a test piece . The prepared test piece and the polarizing plate to which the film was not attached were polymerized by the arrangement of crossed Nicol to confirm the visibility in the case of placing it on a white LED light source (Tridec A3-101).

SS: Less light leakage and little interference color.

S: Interference color is almost invisible.

A: The interference color is slightly visible, but there is no problem in practical use.

B: The interference color is clearly visible, which is not suitable for display applications.

(10) UV blocking property

The sample was cut into 5 cm x 5 cm from the center in the film width direction, and the transmittance at a wavelength of 240 to 800 nm was measured using a spectrophotometer (U-4100 spectrophotometer, manufactured by Hitachi High Technologies). The inner wall of the integrating sphere is barium sulfate, and the standard plate is the attached aluminum oxide. Measuring conditions: The slit was set to 2 nm (visible) / automatic control (infrared), the gain was set to 2, the scanning speed was measured at 600 nm / min, the transmittance at a wavelength of 380 nm at an incident angle of 0 deg. An average transmittance of 240 to 360 nm was obtained. The UV barrier properties were evaluated according to the following criteria.

S: an average transmittance at a wavelength of 240 to 360 nm of not more than 2%

A: an average transmittance at a wavelength of 240 to 360 nm of not less than 3% and not more than 5

B: The average transmittance at a wavelength of 240 to 360 nm is 6% or more.

(11) Composition Analysis of Coated Polyethylene Terephthalate (Co-PET)

The composition of the copolymerized PET of the present invention is such that the monomer content of the copolymerization component is adjusted by the amount of the diol component and the dicarboxylic acid component to be blended in polymer polymerization. However, by the ¹ H-NMR and pyrolysis GC / MS measurement, Can be calculated. Approximately 30 mg of the copolymerized PET chip was sampled and dissolved in a mixture of deuterated chloroform (CDCl ₃ ) and deuterated hexafluoroisopropanol (HFIP-d 2), and then subjected to ¹ H-NMR measurement at a temperature of 40 ° C. The ratio of the mixed solution was CDCl ₃ : HFIP-d 2 = 2: 1. At the time of identification, the copolymerization ratio was calculated from the existing data of the individual spectra of various monomers of spiroglycol, cyclohexanedicarboxylic acid, cyclohexanedimethanol and isosorbide, and the composition was calculated from the peak area ratio of the spectrum.

(12) Coefficient of dynamic friction (μd)

(Resistance value) detected by the electrical resistance strain meter after the slip tester started to slip under the conditions of a slip speed of 150 mm / min and a load of 200 g in accordance with ASTM-D-1894 by the following formula (1). The coefficient of dynamic friction is a resistance value in the stable region after slipping out.

Friction coefficient = resistance value (G) / load (G) ... Equation (1)

(13) Crystallinity, amorphousness, and crystalline partial melting temperature (Tmeta) of the resin composition [

The temperature was raised from 25 占 폚 to 290 占 폚 at 20 占 폚 / min using a differential scanning calorimeter (DSC), and the melting point Tm and crystal melting enthalpy? H were determined for the resin composition to be used according to JIS K7121, 7122, The determination of the qualitative polyester resin was carried out. Tm was almost not revealed, and ΔH was set to amorphous less than 6 j / g. Further, an endothermic peak in the vicinity of the heat treatment temperature, which is lower than the melting point Tm in the laminated film, was determined as the crystalline partial melting temperature Tmeta.

Device: Seiko Instruments Inc.: SII Robot DSC (Model DSC6220)

       Data Analysis "standard Analysis"

Sample mass: 5 mg.

(14) Total light transmittance · haze

Measurement was carried out in accordance with JIS K 7361-1, JIS K 7136, and ASTM-D1003 using a haze meter NDH5000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.).

(15) Post-processability at the time of hard coat application

A hard coat layer having a thickness of 1.5 탆 was formed as a protective film on the laminated film. The coating agent shown below was adjusted and applied to a film uniformly with a # 10 bar coater and dried in a hot air convection type drier at 90 캜 for one minute to remove the solvent. Then, the solvent was removed at 80 W / cm and a conveying speed of 5 m / min Under ultraviolet irradiation. UA-122P (Shin Nakamura Kagaku Kogyo) Urethane acrylate 40 parts

Takenate B830 (Mitsui Kagaku Polyurethane) blocked isocyanate 2.5 parts

Irgacure 184 (Ciba Specialty Chemicals) Photoinitiator 1.5 part

MEK 110 parts

The end portions were slit and wound in a roll shape. At that time, the state of the film was observed and the post-processability was evaluated.

S: No wrinkles, good planarity.

A: Some wrinkles appear, but no problem levels

B: The wrinkles and curls are noticeable.

(Example 1)

As the crystalline polyester, polyethylene terephthalate (PET) having a melting point of 258 占 폚 was used. Ethylene terephthalate (PE / SPG 占 / / CHDC) copolymerized with 15 mol% of spiroglycol and 25 mol% of cyclohexanedicarboxylic acid as amorphous resins having no melting point was used as thermoplastic resin B. 98% by mass of the PE / SPG 占 / / CHDC, 2% by mass of 2,4,6-tris (2-hydroxy-4-hexyloxy-3-methylphenyl) -1,3,5- The mixture was melt-kneaded at 280 DEG C and discharged from the die in a strand shape, cooled and solidified in a water bath at 25 DEG C and cut into chips to obtain a thermoplastic resin composition (B -1).

The prepared PET and the thermoplastic resin composition (B-1) were sufficiently dried under vacuum at a high temperature so as not to contain moisture, and then put into two single screw extruders and melt-kneaded at 280 캜. Subsequently, 50 sheets of FSS-type leaf disk filters were laminated, and then the lamination ratio of each layer made of PET and the thermoplastic resin composition (B-1) (total thickness of PET layer / thermoplastic resin composition B-1) was 1.0 while being weighed by a gear pump while being stacked in a lamination apparatus of 251 slits, and extruded from a T-die as a laminated body in which 251 layers were stacked alternately in the thickness direction, To obtain a casting film by casting on a cast drum whose surface temperature was controlled. A method of forming a laminate was carried out according to the description of steps [0053] to [0056] of JP-A-2007-307893. Here, the slit length and the interval were all made constant. The resulting laminate had a laminate structure in which 126 layers of PET and 125 layers of thermoplastic resin composition (B-1) were stacked alternately in the thickness direction. The value obtained by dividing the length in the film width direction of the perimeter lip, which is the wider width in the interior of the housing, by the length in the film width direction at the inlet opening of the housing was 2.5.

The obtained casting film was heated in a roll set at 95 占 폚 and then rapidly heated from both sides of the film at a stretching section length of 400 mm by a radiant heater while the film temperature at the stretching was 103 占 폚 3.3 times, and then cooled once. Subsequently, both surfaces of the uniaxially stretched film were subjected to corona discharge treatment in the air to give a base film having a wet tension of 55 mN / m and a polyester resin having a glass transition temperature of 18 캜 ) / (A polyester resin having a glass transition temperature of 82 占 폚) / silica particles having an average particle diameter of 100 nm was applied to form a primer layer to be transparent, transparent, and adhered.

The uniaxially stretched film was led to a tenter, and after being preheated by 95 ° C hot air, it was stretched 4.5 times in the film width direction at a temperature of 105 ° C in the first stage and 140 ° C in the second stage. Here, when the transverse stretching section is divided into two, the stretching amount (film width at the measuring point-film width before stretching) of the film at the midpoint of the transverse stretching section is 80% of the stretching amount at the end of the transverse stretching section So as to be stretched in two steps. The transversely stretched film was subjected to heat treatment in a tenter in a tenter in a stepwise manner at 180 ° C with hot air at a heat treatment temperature of 225 ° C, followed by 1% relaxation treatment in the transverse direction at the same temperature condition, quenched to 100 ° C, To give a relaxation treatment of 1%, and then wound up to obtain a laminated film. Table 1 shows the evaluation results of the obtained laminated film.

(Example 2)

A laminated film was obtained in the same manner as in Example 1 except that the stretching magnification in stretching in the film width direction was 3.6 times and the heat treatment temperature was 200 占 폚 in Example 1. Table 1 shows the evaluation results of the obtained laminated film.

(Example 3)

A laminated film was obtained in the same manner as in Example 1 except that the heat treatment temperature in Example 2 was 235 캜. Table 1 shows the evaluation results of the obtained laminated film.

(Example 4)

A laminated film was obtained in the same manner as in Example 1, except that the lamination apparatus of 51 slits was used and the PET 26 layer and the thermoplastic resin composition (B-1) 25 layers were used. Table 1 shows the evaluation results of the obtained laminated film.

(Example 5)

A laminated film was obtained in the same manner as in Example 1 except that the lamination apparatus of three slits was used and the PET two layers and the thermoplastic resin composition (B-1) were one layer. Table 1 shows the evaluation results of the obtained laminated film.

(Example 6)

In the same manner as in Example 1 except that 801 slit apparatuses were used and 400 sheets of PET 401 layer and thermoplastic resin composition (B-1) were used. The stretching magnification in stretching in the film width direction was 3.6 times, A laminated film was obtained in the same manner as in Example 1 except that the temperature was changed to 200 占 폚. Table 2 shows the evaluation results of the obtained laminated film.

(Example 7)

As the thermoplastic resin B, polyethylene terephthalate (PETG) obtained by copolymerizing 30 mol% of 1,4-cyclohexanedimethanol as an amorphous resin having no melting point was used. 4 mass% of 2,2'-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol] The mixture was melt-kneaded at 280 占 폚, discharged from the die in a strand shape, cooled and solidified in a water bath at 25 占 폚 and cut into chips to obtain a thermoplastic resin composition (B-2 ).

A laminated film was obtained in the same manner as in Example 1 except that the thermoplastic resin composition (B-2) was used in place of the thermoplastic resin composition (B-1). Table 2 shows the evaluation results of the obtained laminated film.

(Example 8)

As the thermoplastic resin B, polyethylene terephthalate (PET / I) copolymerized with 20 mol% of isophthalic acid which is an amorphous resin having no melting point was used. 4 mass% of 2,2'-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol] as UVA, Were extruded from a die and cooled and solidified in a water bath at 25 DEG C and cut into chips to obtain a thermoplastic resin composition B -3).

A laminated film was obtained in the same manner as in Example 1 except that the thermoplastic resin composition (B-3) used in Example 1 was replaced with PET / I in place of the thermoplastic resin composition (B-1). Table 2 shows the evaluation results of the obtained laminated film.

(Example 9)

In Example 1, the slit length was linearly changed, and slit design was performed so that the average layer thickness of the adjacent A layer and B layer was 40 to 55 nm, and the layer thickness was gradually changed. Subsequently, in the same manner as in Examples 1 and 2 except that the longitudinal drawing temperature was changed to 105 캜 so that the thickness of the laminated film was 13 탆, the heat treatment temperature was set to 215 캜, Similarly, a laminated film was obtained. A transparent film having a total light transmittance of 91% and a haze of 0.7%. Table 2 shows the evaluation results of the obtained laminated film.

(Example 10)

A laminated film was obtained in the same manner as in Example 9 except that the heat treatment temperature in Example 9 was changed to 190 캜. Table 2 shows the evaluation results of the obtained laminated film.

(Example 11)

Except for the thickness, the laminated film obtained under the same conditions as in Example 10 was further guided to longitudinal stretching and re-stretched at a temperature of 150 캜 at a stretch ratio of 1.2, followed by relaxation treatment at 190 캜. Table 3 shows the evaluation results of the obtained laminated film.

(Example 12)

Ethylene terephthalate (PE / SPG 占 / / CHDC) obtained by copolymerizing 21 mol% of spiroglycol and 5 mol% of cyclohexanedicarboxylic acid as amorphous resins having no melting point was used as thermoplastic resin B. A laminated film was obtained in the same manner as in Example 1 except for the above. Table 3 shows the evaluation results of the obtained laminated film. Further, in the dynamic viscoelasticity measurement, since the tan? Peak on the low-temperature side had moved to the high-temperature side, the number of tan? Peaks seemed to be one.

(Example 13)

As the thermoplastic resin B, ethylene terephthalate (PET / ISB · CHDM) copolymerized with 5 mol% of isophorone, which is a noncrystalline resin having no melting point, and 24 mol% of cyclohexanedimethanol was used. A laminated film was obtained in the same manner as in Example 1 except for the above. Table 3 shows the evaluation results of the obtained laminated film.

(Example 14)

(PET / ISB.CHDM) copolymerized with 5 mol% of isophorone and 24 mol% of cyclohexanedimethanol, which are amorphous resins having no melting point as thermoplastic resin B, and spiroglycols (PE / SPG 占 / / CHDC) copolymerized with 20 mol% of cyclohexanedicarboxylic acid and 30 mol% of cyclohexanedicarboxylic acid was used. A laminated film was obtained in the same manner as in Example 1 except for the above. Table 3 shows the evaluation results of the obtained laminated film.

(Example 15)

(PET / ISB.CHDM) copolymerized with 15 mol% of isosorbide and 24 mol% of cyclohexanedimethanol as amorphous resins having no melting point as a thermoplastic resin A and polyethylene terephthalate in a ratio of 1: 3 Compounded resin was used. On the other hand, an ethylene terephthalate (PET / ISB.CHDM) copolymerized with 15 mol% of isophorone and 20 mol% of cyclohexanedimethanol, which is an amorphous resin having no melting point as a thermoplastic resin B, and 20 mol% of PET / I was compounded at a ratio of 1: 1. The lamination device was changed to change the lamination ratio of the A layer / B layer to 0.33, and the lamination ratio of the thermoplastic resin A to the thermoplastic resin A and the thermoplastic resin B to 400 were alternately laminated. A film was obtained. Table 3 shows the evaluation results of the obtained laminated film. The visibility of the obtained film was very good and was the most excellent. Further, since the alignment angle was large and the light leakage under the orthogonal Nicole was large, it was suitable for an ITO-based film because of its characteristics that it is difficult to black out.

(Example 16)

The laminated film obtained under the same conditions as in Example 14 except for the thickness was further guided to the longitudinal stretching and re-stretched at a temperature of 150 캜 at a stretch ratio of 1.2, followed by relaxation treatment at 190 캜. Table 4 shows the evaluation results of the obtained laminated film.

(Example 17)

A laminated film having a thickness of 13 탆 was obtained in the same manner as in Example 9 except that 20% by mass of 20% by mole of copolymerized PET of isophthalic acid component was added to PET of Example 9, and the lamination ratio was 0.6 and the longitudinal stretching magnification 3.4 times. Table 4 shows the evaluation results of the obtained laminated film. The hard coat layer was provided on one side of the obtained laminated film, and the storage elastic modulus E 'at 85 캜 was 2.8..

(Example 18)

The laminated film obtained under the same conditions as in Example 1 was further subjected to longitudinal stretching except that the casting speed, the longitudinal stretching temperature, and the heat treatment temperature were changed to 105 캜 and 140 캜, respectively, and re-stretching was carried out at 160 캜 at 1.3 캜, , And subjected to relaxation treatment at 100 캜 in the length and width directions. Table 4 shows the evaluation results of the obtained laminated film. The casting speed was adjusted so that the thickness of the obtained laminated film was 13 mu m. It was possible to obtain a sample in which the orientation angle and the retardation are uniform in the film width direction. It was also confirmed that the orientation direction of the molecules indicates the longitudinal direction from the result of the phase difference measuring apparatus.

(Example 19)

Polyethylene naphthalate (PEN) having a melting point of 265 DEG C was used as the crystalline polyester. As the thermoplastic resin B, ethylene terephthalate (PET / ISB.CHDM) copolymerized with 15 mol% of isosorbide and 20 mol% of cyclohexanedimethanol as amorphous resins having no melting point was used.

The prepared PEN and the thermoplastic resin B were sufficiently dried at a high vacuum temperature so as not to contain moisture, respectively, and then put into two single-screw extruders and melt-kneaded at 300 ° C. Subsequently, in the same manner as in Example 1, 131 pieces of slits were combined in a laminating apparatus, and the laminate was laminated by 131 layers alternately in the thickness direction, extruded from a T die, cast on a cast drum controlled at 25 캜, A film was obtained. A method of forming a laminate was carried out according to the description of steps [0053] to [0056] of JP-A-2007-307893. Here, the slit is designed so that the gap is constant and the slit length is gradually changed so that the average layer thickness becomes 40 to 55 nm. The obtained laminate had a laminate structure in which 66 layers of PEN and 65 layers of thermoplastic resin B were laminated alternately in the thickness direction. The value obtained by dividing the length of the perimeter of the perimeter rib in the width direction of the film by the length in the film width direction at the inlet portion of the film was 2.5.

The obtained casting film was heated in a roll set at 140 占 폚 and then rapidly heated from both sides of the film at a stretching section length of 400 mm by a radiating heater while the film temperature at the stretching was 143 占 폚 and 3.3 And then cooled once. Subsequently, the uniaxially stretched film was subjected to air-corona discharge treatment on both sides, and a polyester (resin having a glass transition temperature of 18 DEG C) / (polyester having a glass transition temperature of 82 DEG C Resin) / silica particles having an average particle diameter of 100 nm was applied to form a primer layer to be bonded, transparent, and bonded.

The uniaxially stretched film was led to a tenter and preheated by hot air at 150 DEG C and then stretched 4.5 times in the film width direction at 145 DEG C in the first stage and 155 DEG C in the second stage. Here, when the transverse stretching section is divided into two, the stretching amount of the film at the midpoint of the transverse stretching section (film width at the measuring point-film width before stretching) is 80% of the stretching amount at the end of the transverse stretching section And stretched in two steps. The transversely stretched film was subjected to a heat treatment in a tenter by hot air at 205 占 폚, followed by 1% relaxation treatment in the width direction at the same temperature condition, and 1% relaxation treatment in the width direction after quenching to 100 占 폚 And then wound up to obtain a laminated film. Table 4 shows the evaluation results of the obtained laminated film.

(Example 20)

In Example 5, the same thermoplastic resin B as in Example 14 was used, and the film forming conditions other than the number of lamination were set to Example 14 to obtain a laminated film. Table 4 shows the evaluation results of the obtained laminated film.

(Example 21)

5% by mass of PET / polyetherimide (PEI) / 0.025% by mass of calcium carbonate having an average particle diameter of 1.1 占 퐉 / 0.1% by mass of crosslinked polystyrene having an average particle diameter of 0.3 占 퐉 was supplied to a twin-screw extruder and melt-kneaded at 280 占 폚, The mixture was discharged from the die in a strand shape, cooled and solidified in a water bath at 25 DEG C, and cut into chips to obtain a thermoplastic resin composition (A-1).

A laminated film was obtained in the same manner as in Example 1 except that the thermoplastic resin composition (A-1) was used instead of PET in Example 17. Table 5 shows the evaluation results of the obtained laminated film. The obtained film had a total light transmittance of 90% and a haze of 1.5%, and was very good in visibility and applicable to post-processing. In addition, since the alignment angle was large and the light leakage under the orthogonal Nicole was large, it was suitable for an ITO substrate film because the characteristics were hard to black out.

(Comparative Example 1)

A laminated film was obtained in the same manner as in Example 1 except that PET was used as the PET film in Example 1. Table 5 shows the evaluation results of the obtained laminated film.

(Comparative Example 2)

The stretching amount (film width at the measuring point-film width before stretching) of the film at the middle point of the stretching section in Example 1 was changed to be 50% of the stretching amount at the end of the transverse stretching section, A laminated film was obtained in the same manner as in Example 1 except that the heat treatment temperature was changed to 245 占 폚 after the end of the transverse stretching. Table 5 shows the evaluation results of the obtained laminated film.

(Comparative Example 3)

Except that in Example 1, the output of the rapid heating by both sides of the film was reduced from both sides of the film in the longitudinal stretching step, the film temperature at the time of stretching was set to 85 캜, and the relaxation rate of the film was set at 5% A laminated film was obtained in the same manner as in Example 1. Table 5 shows the evaluation results of the obtained laminated film.

(Comparative Example 4)

A laminated film was obtained in the same manner as in Example 1 except that the casting speed was adjusted and the film thickness was changed to 45 탆. Table 6 shows the evaluation results of the obtained laminated film. The phase difference in the thickness direction was large, and in the visibility test, the interference color was observed strongly when observed from the oblique direction.

(Comparative Example 5)

A laminated film was obtained in the same manner as in Example 1 except that the film was stretched 5.3 times in the film width direction. Table 6 shows the evaluation results of the obtained laminated film.

(Comparative Example 6)

A laminated film was obtained in the same manner as in Example 1 except that the thermoplastic resin composition (B-2) was replaced with the thermoplastic resin composition (B-1) and the laminate was elongated 5.3 times in the film width direction. Table 6 shows the evaluation results of the obtained laminated film.

(Industrial availability)

Since the laminated film of the present invention can suppress the occurrence of color unevenness by controlling the phase difference to be low and the deviation to be small, it is possible to provide a polarizing plate protective film of a polarizing plate built in a display device such as a liquid crystal display, Can be suitably used as a base film of a film.

Claims (13)

In-plane retardation (Re) of 0 to 400 nm, a retardation in thickness direction (Rth) of 0 to 1500 nm, a deviation of Re of not more than 18% in the transverse direction, And a Young's modulus in the transverse direction of 2 ㎬ or more, a elongation at break in the longitudinal direction and a transverse direction of 50% or more, a film thickness of the laminated film of 40 탆 or less, and a width of the film of 400 mm or more. The method according to claim 1,
And the deviation of Re is not more than 20% in the longitudinal direction. 3. The method according to claim 1 or 2,
And the deviation of the orientation angle is 20 DEG or less in the width direction. 4. The method according to any one of claims 1 to 3,
A laminated film comprising an A layer containing a crystalline polyester as a main component and a B layer containing a thermoplastic resin B different from the crystalline polyester as a main component alternately. 5. The method according to any one of claims 1 to 4,
Wherein the thermoplastic resin B is an amorphous polyester containing at least one copolymerizable component selected from isophthalic acid, cyclohexanedicarboxylic acid, spiroglycol, cyclohexanedimethanol, and isosorbide. 6. The method according to any one of claims 1 to 5,
And the crystalline partial melting temperature Tmeta is 190 占 폚 or lower. 7. The method according to any one of claims 1 to 6,
Wherein at least two tan? Peaks are observed in the dynamic viscoelasticity measurement in the longitudinal direction and / or the width direction. 8. The method according to any one of claims 1 to 7,
Wherein the storage elastic modulus E 'at 85 캜 in the dynamic viscoelasticity measurement is 2.5 ㎬ or more. 9. The method according to any one of claims 1 to 8,
Wherein the number of layers is 51 to 1001 layers. 10. The method according to any one of claims 1 to 9,
A coefficient of dynamic friction is 0.45 or less, and a primer layer and / or a hard coat layer is formed on at least one surface. 11. The method according to any one of claims 1 to 10,
A laminated film used as a polarizer protective film. 11. The method according to any one of claims 1 to 10,
A laminated film used as an ITO base film. The method for producing a laminated film according to claim 1, wherein the laminated film is composed mainly of a crystalline polyester A and an amorphous polyester B, and the number of layers is three or more, An unstretched film having a lamination ratio (A / B) of 2 to 0.2 in the layer B of the qualitative polyester B was subjected to biaxial stretching in the longitudinal direction and the width direction at a stretching temperature of 70 to 145 캜, Heat-setting is carried out in the range of 120 to 235 ° C, and thereafter re-stretching is carried out in the range of 1.02 to 1.95 times in the range of the drawing temperature of 80 to 150 ° C at least in the longitudinal direction, And then winding up the laminated film.