TWI670179B - Laminate film - Google Patents

Abstract

The present invention provides a polarizing plate which can be preferably used for a liquid crystal display by the following laminated film, especially a high-quality laminated film without color unevenness when mounted on a large-screen liquid crystal display. There are three or more layers laminated in the thickness direction, and the phase difference (Re) in the plane direction is 0 to 400 nm, the phase difference (Rth) in the thickness direction is 0 to 1500 nm, and the deviation of Re is 18% or less in the width direction. The laminated film has a film thickness of 40 μm or less and a film width of 400 mm or more.

Description

Laminated film

The present invention relates to a laminated film which can be preferably used as a protective film for polarizing plates. The present invention also relates to a polarizing plate using the laminated film as a polarizing plate protective film.

Thermoplastic resin films, especially biaxially stretched polyester films, are widely used in many applications such as magnetic recording materials and packaging materials due to their excellent mechanical properties, electrical properties, dimensional stability, transparency, and chemical resistance. As a substrate film. Especially in recent years, in the field of flat panel displays or touch panels, the demand for various optical films such as polarizing plate protective films or transparent conductive films has been increasing. Among them, in polarizing plate protective film applications, low moisture permeability and mechanical strength are required. For the purpose of application and low cost of physical properties with excellent thermal dimensional stability, the industry is actively studying to replace the polyester film with the conventional triacetyl cellulose (TAC) film.

[Prior technical literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 2014-12401

Patent Document 2: Japanese Patent Laid-Open No. 2009-42653

Patent Document 3: Japanese Patent Laid-Open No. 2013-210598

However, the biaxially stretched polyester film that has been studied has been The alignment of the composition results in a higher retardation (retardation) than that of the TAC film. Therefore, the interference color due to the retardation is generated when the liquid crystal display is assembled, and there is a problem that the quality of the image is lowered. In order to solve this problem, although a control method with a delay (sometimes expressed as Retardation) has been proposed, it can be said that it is still insufficient to take into account the degree or deviation of the delay. For example, although a laminated film having a retardation of 400 nm or less is proposed in the film, there is a problem that it cannot be used for a polarizing plate of a liquid crystal display because the retardation of the thickness is large (Patent Document 1). In addition, although a polyester film for polarizer protection has been proposed, the phase difference is large, and interference colors and rainbow unevenness are not sufficiently suppressed (Patent Document 2). Although a polyester film for polarizer protection having a UV (ultraviolet) blocking performance and a retardation of 400 nm or less has been proposed, the visibility is lowered due to the lower transmittance, and the use of bowing has increased. Because of the film forming conditions, there is a problem that the deviation of the phase difference in the width direction is large (Patent Document 3). That is, since the alignment state of the polymer differs in the width direction of the film when manufacturing a biaxially stretched film, there is a problem that even if a part of the film can achieve the target low delay, it cannot be used for A large-area film of a large-screen display uniformly obtains a film with a lower retardation, resulting in lower product yield and higher cost. In addition, since the retardation is proportional to the thickness of the film, it can also be suppressed by reducing the thickness of the film to a few μm. However, the extreme thinness will reduce the operability, and it is not used in the application of a polarizer protective film. practical. Furthermore, the polarizing plate protective film for the outermost layer is required to have high UV blocking property, and the cost increase, step contamination, and color and taste change caused by a large amount of ultraviolet absorbing materials are added to the problem.

The problem of the present invention is to solve the above problems. That is, the problem of the present invention The purpose is to provide a laminated film, which is a biaxially stretched polyester film that can be realized at a low cost and can be made into a thin film, and has a low retardation, so that color unevenness does not occur when it is mounted on a display device such as a large-screen liquid crystal display. Rainbow uneven. Interference color and excellent post-processability.

The above-mentioned problem can be achieved by a laminated film having three or more layers laminated in the thickness direction, and the in-plane phase difference (Re) is 0 to 400 nm, and the thickness direction phase difference (Rth) is 0 to 1500nm, the deviation of Re is 18% or less in the width direction, the Young's modulus in the length direction and the width direction is 2GPa or more, the elongation at break in the length direction and the width direction is 50% or more, and the film thickness of the laminated film is 40 μm or less The width of the film is more than 400mm.

When the laminated film of the present invention is used as a polarizing plate protective film and is mounted on a display device of a large-screen liquid crystal display, it exhibits the effects of less excellent unevenness, good appearance, and high-quality display. As a better aspect, it exhibits the effect of suppressing UV degradation of polarizers and liquid crystals by higher UV blocking. When mounted as a transparent conductive substrate film such as indium tin oxide (ITO, Indium Tin Oxides), there is no color unevenness. Rainbow uneven. Interference colors exert the same effect. With regard to this effect, when the observer observes through polarized sunglasses, the display does not become a black display called a black out phenomenon, but is displayed clearly and vividly.

Hereinafter, the laminated film of this invention is demonstrated in detail.

The laminated film of the present invention has three or more layers laminated in the thickness direction. Laminated film. Regarding the number of laminated layers, in terms of UV blocking property, retardation, and total film thickness, 51 to 1001 layers are preferable, 101 to 501 layers are more preferable, and 151 to 351 layers are more preferable. From the viewpoint of reducing the thickness and utilizing ultraviolet reflection based on interference reflection, it is particularly preferably 101 to 301 layers. When the number of laminated films is less than 3, when an amorphous resin is used as the thermoplastic resin B as described below, there may be poor film formation due to adhesion to manufacturing equipment such as rollers or jigs, or the surface of the laminated film This can cause problems such as poor planarity. In a case where the number of laminated layers is one, that is, a single film, the thickness must be reduced in order to control the delay, and the operability may be deteriorated. When the number of laminated layers 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 below. On the other hand, when the number of laminated layers exceeds 1001, the total thickness of the film may become too thick.

The laminated film of the present invention is preferably formed by alternately laminating a layer A containing a crystalline polyester as a main component and a layer B containing a thermoplastic resin B different from the crystalline polyester as a main component. In addition, the "main component" means that the ratio of the specific component to all the components is 50% by mass or more, and more preferably 80% by mass or more, and more preferably 90% by mass or more, particularly preferably 95% by mass or more. The so-called thermoplastic resin B which is different from the crystalline polyester A used in the A layer refers to those having different thermal characteristics from the crystalline polyester A used in the A layer, specifically, the differential scanning calorimetry ( DSC) shows different melting points or glass transition points. Here, the term “alternatively laminated” means that layers containing different thermoplastic resins are regularly arranged and laminated in the thickness direction. For example, when two types of thermoplastic resins A and B having different refractive indexes are included, if Representing each layer as the A layer and the B layer refers to those that are layered in a regular arrangement of A (BA) n (n is a natural number). By alternately laminating so different thermal characteristics The resin can highly control the alignment state of each layer when manufacturing a biaxially stretched film, and can further control retardation or UV blocking property.

In the laminated film of the present invention, it is preferable that the layer A containing crystalline polyester is the outermost layer. In this case, since the crystalline polyester becomes the outermost layer, a biaxially stretched film can be obtained in the same manner as a crystalline polyester film such as a polyethylene terephthalate film or a polyethylene naphthalate film. . When the thermoplastic resin A contains, for example, an amorphous resin, when a biaxially stretched film is obtained in the same manner as the general sequential biaxially stretched film described below, there is a film formation due to adhesion to manufacturing equipment such as a roll or a jig. This may be caused by problems such as defects or poor planarity of the laminated film surface. The crystalline polyester used in the present invention is preferably a polyester obtained by polymerizing a monomer derived from an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol as a main constituent. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, and 2,6 -Naphthalene dicarboxylic acid, 4,4'-diphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 4,4'-diphenylphosphonium dicarboxylic acid, and the like. Examples of the aliphatic dicarboxylic acid include adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexanedicarboxylic acid, and ester derivatives thereof. Among them, terephthalic acid and 2,6-naphthalenedicarboxylic acid which exhibit a relatively high refractive index are preferred. These acid components may be used alone, or two or more of them may be used in combination, and a part of an oxo acid such as hydroxybenzoic acid may be copolymerized.

Examples of the diol component include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, and 1, 5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol Ethylene glycol, polyalkylene glycol, 2,2-bis (4-hydroxyethoxyphenyl) propane, isosorbide (1,4: 3,6-dianhydroglucitol, 1,4: 3 , 6-dihydroanhydro-D-sorbitol), spirodiol, etc. Among them, ethylene glycol is preferably used. These diol components may be used alone or in combination of two or more. As the resin or thermoplastic resin B that can be added to the crystalline polyester used in the present invention, a chain polyolefin such as polyethylene, polypropylene, poly (4-methylpentene-1), or polyacetal can be used. ;drop Ring-opening metathesis polymerization of olefins Addition and polymerization of olefins Addition copolymers of olefins and other olefins are alicyclic polyolefins; biodegradable polymers such as polylactic acid and polybutyl succinate; polyamides such as nylon 6, nylon 11, nylon 12, and nylon 66; Aromatic polyamide, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, ethylene-vinyl acetate copolymer, polyacetal, polyglycolic acid, polybenzene Ethylene, styrene copolymerized polymethyl methacrylate, polycarbonate, polytrimethylene terephthalate, polyethylene terephthalate, polybutylene terephthalate, poly2,6-naphthalene Polyesters such as ethylene diformate; polyether fluorene, polyether ether ketone, modified polyphenylene ether, polyphenylene sulfide, polyether fluorene imine, polyfluorene, polyarylate, tetrafluoroethylene resin, Fluoroethylene resin, trifluorochloroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer, polyvinylidene fluoride, etc. Among them, the strength. Heat resistance. From the viewpoint of transparency and versatility, it is preferable to include polyester, and particularly, as a thermoplastic resin B different from crystalline polyester, in addition to strength. Heat resistance. Transparency. In addition to versatility, the adhesion with crystalline polyester is also considered. From the viewpoint of lamination properties, it is preferable to include polyester. These may be copolymers or mixtures.

Regarding the crystalline polyester used in the present invention and the thermoplastic resin B different from the above crystalline polyester, for example, among the above polyesters, polyethylene terephthalate and its polymer, and polynaphthalene are preferably used. Ethylene formate and its copolymers, polybutylene terephthalate and its copolymers, polybutylene naphthalate and its copolymers, and then polyhexamethylene terephthalate and its copolymers, polymers Naphthalene Dicarboxylate and Its Copolymer Polymer, etc.

The thermoplastic resin B of the present invention is preferably an amorphous polymer containing one or more copolymerizable components selected from the group consisting of isophthalic acid, cyclohexanedicarboxylic acid, spirodiol, cyclohexanedimethanol, and isosorbide. ester. Polyesters containing these components do not easily exhibit birefringence, and especially exhibit their effects even when stretched. Therefore, when used as the laminated film of the present invention, not only the phase difference from the front can be reduced, but also Since the phase difference in the thickness direction can be reduced, color unevenness, rainbow unevenness, and interference color can be suppressed. In particular, with regard to spirodiol and isosorbide, heat resistance can be improved by increasing the amount of copolymerization thereof, and it has excellent processing adaptability in the manufacturing steps of a transparent conductive film such as a polarizing plate or ITO. In addition, the so-called color unevenness or rainbow unevenness refers to an optical phenomenon that can be seen when a polyester film having birefringence is placed on a display panel that emits linearly polarized light, and the viewing angle dependence is studied with a white display on the back. . The so-called interference color refers to the color caused by phase difference when a birefringent body is arranged between two polarizing plates whose absorption axes are orthogonal and visible from below with white light. Michel-Levy interference charts are generally known as Represents the relationship between phase difference and color.

As a preferable combination of the crystalline polyester used as the laminated film of the present invention and the thermoplastic resin B different from the above-mentioned crystalline polyester, the absolute value of the difference between the SP values of the thermoplastic resins is particularly preferably 1.0 or less. If the absolute value of the difference between the SP values is 1.0 or less, interlayer peeling is unlikely to occur. More preferably, the crystalline polyester and the thermoplastic resin B include a combination that provides the same basic skeleton. The basic skeleton referred to here refers to the repeating unit constituting the resin. For example, in the case where polyethylene terephthalate is used as a thermoplastic resin, it is preferable that the laminated structure is easy to realize. The same basic skeleton as polyethylene terephthalate is contained in another thermoplastic resin. If crystalline polyester and thermoplastic resin B contain the same basic skeleton The resin can have a laminated structure with high lamination accuracy, and it is difficult to cause interlayer peeling of the laminated interface.

In addition, as a preferable combination of the crystalline polyester used as the laminated film of the present invention and the thermoplastic resin B different from the crystalline polyester, the glass transition temperature difference between the crystalline polyester and the thermoplastic resin B is preferably 20 Below ℃. In the case where the glass transition temperature difference is greater than 20 ° C, the thickness uniformity when manufacturing the laminated film is poor, resulting in deviation in delay. In addition, problems such as occurrence of excessive elongation during the formation of the laminated film are likely to occur.

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, and includes an amorphous resin. Since amorphous resins are less prone to alignment when manufacturing biaxially stretched films than crystalline resins, it is possible to suppress the increase in retardation of layer B containing thermoplastic resin B, and it is easy to suppress the unevenness of retardation of laminated films. In particular, when a heat treatment step is provided when manufacturing a biaxially stretched film, this effect is remarkable. Specifically, the reason is that the orientation generated in the layer containing the amorphous resin in the extension step of the length and width directions of the film can be completely relaxed by the heat treatment step, so that the A The delay caused by the layer affects the delay as a laminated film. The term "amorphous resin" used herein refers to a resin that hardly shows a peak corresponding to the melting point in differential scanning calorimetry.

As an example of a combination of resins satisfying the above conditions, in the laminated film of the present invention, it is preferred that the crystalline polyester is made of polyethylene terephthalate or polyethylene naphthalate, and is thermoplastic. Resin B is a polyester containing spirodiol. The polyester containing spirodiol means a copolyester, a homopolyester, or a polyester obtained by copolymerizing spirodiol. Spirodiol-containing polyesters due to their glass transition temperature with polyethylene terephthalate or polyethylene naphthalate The difference is small, so it is not easy to excessively stretch during molding, and it is also difficult to peel off between layers, so it is preferable. More preferably, the crystalline polyester is a polyester containing polyethylene terephthalate or polyethylene naphthalate, and the thermoplastic resin B is a polyester containing spirodiol and cyclohexanedicarboxylic acid. If it is a polyester containing spirodiol and cyclohexanedicarboxylic acid, since crystallinity can be reduced, retardation can be suppressed easily. In addition, since the glass transition temperature difference with polyethylene terephthalate or polyethylene naphthalate is small and the adhesion is also excellent, it is not easy to excessively stretch during molding, and it is also difficult to cause interlayer peeling.

In addition, the laminated film of the present invention is also preferably made of a crystalline polyester based on polyethylene terephthalate or polyethylene naphthalate, and the thermoplastic resin B based on this crystalline polyester contains a ring Polyester made from hexanedimethanol. The polyester containing cyclohexanedimethanol refers to a copolyester, a homopolyester, or a polyester obtained by copolymerizing cyclohexanedimethanol. Polyesters containing cyclohexanedimethanol can reduce retardation easily because they can reduce the crystallinity, and because the glass transition temperature difference with polyethylene terephthalate or polyethylene naphthalate is lower. Because it is small, it is not easy to extend excessively during molding, and it is also difficult to cause interlayer peeling, so it is preferable. More preferred is a polyethylene terephthalate polycondensate having a copolymerization amount of thermoplastic resin B-based cyclohexanedimethanol of 15 mol% or more and 60 mol% or less. Thereby, since it can be made into a substantially amorphous state, retardation can be suppressed, and in particular, the variation in retardation due to heating or over time is small, and interlayer peeling is less likely to occur. A polyethylene terephthalate polycondensation system having a copolymerization amount of cyclohexanedimethanol of 15 mol% or more and 60 mol% or less is strongly bonded to polyethylene terephthalate. The cyclohexanedimethanol group has a cis-isomer or a trans-isomer as a geometric isomer, and a chair-type or boat-type as a configurational isomer. Ethylene formate is also difficult to align and crystallize when it is stretched together, so it is not easy to cause damage during manufacture.

Furthermore, the laminated film of the present invention is also preferably made of a crystalline polyester based on polyethylene terephthalate or polyethylene naphthalate, which is different from the thermoplastic resin B based on the crystalline polyester. Polyester made from phthalic acid. The polyester containing isophthalic acid refers to a copolyester, a homopolyester, or a polyester obtained by mixing isophthalic acid. Polyester containing isophthalic acid can easily suppress retardation because it can reduce crystallinity; and because the glass transition temperature difference with polyethylene terephthalate or polyethylene naphthalate is small Therefore, it is not easy to extend excessively during forming, and it is also difficult to peel off between layers, so it is preferable. More preferred is a polyethylene terephthalate polycondensate having a copolymerization amount of thermoplastic resin B-based isophthalic acid of 10 mol% or more and 25 mol% or less.

The laminated film of the present invention is also preferably made of crystalline polyester based on polyethylene terephthalate or polyethylene naphthalate, and thermoplastic resin B based on this crystalline polyester contains isosorbide Made of polyester. The polyester containing isosorbide means a copolyester, a homopolyester, or a polyester obtained by copolymerizing isosorbide. Isosorbide-containing polyesters can reduce the crystallinity, so they can easily suppress retardation. Also, because the glass transition temperature difference between polyethylene terephthalate and polyethylene naphthalate is small, Since the solubility is good, it is excellent in coextensibility and interlayer adhesion. The preferable copolymerization amount of the isosorbide of the thermoplastic resin B is an ethylene terephthalate polycondensate of 3 mol% or more and 50 mol% or less. More preferably, the crystalline polyester is a polyester containing polyethylene terephthalate or polyethylene naphthalate, and the thermoplastic resin B is a polyester containing isosorbide and cyclohexanedimethanol. If it is a polyester containing isosorbide and cyclohexanedimethanol, since polymerizability and crystallinity can be further reduced, productivity can be improved and delay can be easily suppressed. The copolymerization amount of cyclohexanedimethanol is preferably 5 to 60 mol%. In addition, various additives such as antioxidants, heat resistance stabilizers, weather resistance stabilizers, ultraviolet absorbers, organic slip agents, pigments, dyes, organic or inorganic materials may be added to the thermoplastic resin to such an extent that its characteristics are not deteriorated. Fine particles, fillers, antistatic agents, nucleating agents, etc. The concentration of the ultraviolet absorber (UVA) added to the laminated film of the present invention is preferably 0.5 to 2% by mass, more preferably 0.7 to 1.8% by mass, still more preferably 0.8 to 1.5% by mass, and even more preferably 1.0 to 1.5. quality%. When the concentration of UVA is less than 0.5% by mass, there is a possibility that the UV blocking property may be deteriorated. On the other hand, when the concentration of UVA exceeds 2% by mass, there is a possibility that step contamination, a change in color and taste, a decrease in mechanical strength, and the like may occur. In addition, as the UVA, from the viewpoint of UV absorption energy in a wavelength region of 300 to 400 nm, 2,2'-methylenebis [6- (2Hbenzotriazol-2-yl)- 4- (1,1,3,3-tetramethylbutyl) phenol], 2,4,6-tris (2-hydroxy-4-hexyloxy-3-methylphenyl) -1,3, 5-three , 2,2 '-(1,4-phenylene) bis (4H-3,1-benzo Benzoxazosin-4-one), 2- (4,6- (4-biphenyl) -1,3,5-tris 2-yl) -5- (2-ethylhexyloxy) -phenol, 2- (4,6-diphenyl-1,3,5-tri 2-yl) -5- [2- (2-ethylhexyloxy) ethoxy] phenol, or a mixture of these.

The laminated ratio of the A layer and the B layer of the laminated film of the present invention (total thickness of the A layer / total thickness of the B layer) is preferably in the range of 0.2 to 1.5. The laminated ratio of the A layer and the B layer is more preferably 0.5 to 1.4, more preferably 0.7 to 1.3, and particularly preferably 0.8 to 1.2. When the lamination ratio is less than 0.2, especially when an amorphous resin is used for the B layer, there is a possibility that the heat resistance may be deteriorated. When the lamination ratio exceeds 1.5, especially when an amorphous resin is used for the B layer, the phase difference may be excessively increased. From the viewpoint of reducing the phase difference in the thickness direction related to rainbow unevenness or color unevenness, the smaller the lamination ratio, the better.

The in-plane phase difference (Re) of the laminated film of the present invention is 0 to 400 nm. Re is preferably 0 to 200 nm, more preferably 0 to 150 nm, and still more preferably 0 to 100. nm, particularly preferably 0 to 50 nm. Generally speaking, Re is calculated based on the product of the maximum value of the refractive index difference in two orthogonal directions in the plane of the film and the thickness of the film. However, as the laminated film of the present invention cannot be easily measured as a film The refractive index is therefore a retardation value calculated by an indirect method. Specifically, a value measured in the following measuring method by a phase difference measuring device KOBRA series manufactured by Oji Measurement Co., Ltd. was used. When Re exceeds 400 nm, interference colors may be generated when mounted as a polarizing plate protective film on a liquid crystal display.

The thickness direction retardation (Rth) of the laminated film of the present invention is 0 to 1500 nm. Rth is preferably 0 to 1200 nm, more preferably 0 to 1000 nm, still more preferably 0 to 900 nm, and even more preferably 0 to 700 nm. When Rth exceeds 1500 nm, there is a case where interference colors are easy to be observed when viewed at an angle when mounted as a polarizing plate protective film on a liquid crystal display.

The method for controlling Re and Rth as described above can be achieved by controlling the birefringence of each layer using the following film formation conditions. Specifically, for example, by making the thermoplastic resin B non-orientated in the manufacturing process of the film, the anisotropy (birefringence) of the refractive index of the layer B containing the thermoplastic resin B can be made substantially zero. In this case, Re is the product of the anisotropy of the refractive index of the A layer containing the crystalline polyester and the total thickness of the A layer, and can suppress Re compared to a film made of only the crystalline polyester of the same thickness.

The deviation of Re of the laminated film of the present invention is 18% or less in the width direction. The deviation of Re is preferably 15% or less, more preferably 12% or less, still more preferably 10% or less, and even more preferably 8% or less. The best is below 6%. Regarding the deviation of Re at this time, when the film width of the laminated film is 400 mm or more, it means that after sampling at 50 mm intervals in the entire width direction of the film, the Re of the center of each sample is measured, and the maximum value of Re is set. The difference from the minimum value divided by the average value (Re Deviation (%) = (maximum value of Re-minimum value of Re) / (average value of Re) × 100). More preferably, the film width is 600 mm or more, and more preferably, the film width is 1000 mm or more. The deviation of Re is preferably 18% or less. In the case of a roll-shaped laminated film, the winding direction of the roll is taken as the length direction of the film, and the direction orthogonal thereto corresponds to the width direction. On the other hand, in the case of a cut sheet, the Re is measured at both ends of the film in a direction orthogonal to the long side direction (parts at a distance of 25 mm from the two ends), and The direction in which the difference in the center of the film is large is taken as the width direction of the so-called laminated film of the present invention. When the deviation of Re exceeds 18% in the width direction, there is a possibility that color unevenness and quality degradation may occur when the polarizing plate protective film is mounted on a particularly large-sized liquid crystal display. As a method of controlling the deviation in the width direction of Re as described above, it can be achieved by using a resin and the following film forming conditions.

The Young's modulus in the length direction and the width direction of the laminated film of the present invention is 2 GPa or more. The Young's modulus in the length direction and the width direction is preferably 2.2 GPa or more, more preferably 2.5 GPa or more, still more preferably 2.8 GPa or more, and even more preferably 3 GPa or more. When the Young's modulus in either the lengthwise direction or the widthwise direction is 2 GPa or less, there is a possibility that the film does not have toughness and may cause a problem in operability. As a method of controlling the Young's modulus in the length direction and the width direction as described above, it can be achieved by using the above-mentioned crystalline polyester and adopting the following film forming conditions.

The elongation at break in the longitudinal direction and the width direction of the laminated film of the present invention is 50% or more. The elongation at break in the longitudinal and width directions is preferably 100% or more, more preferably 110% or more, still more preferably 120% or more, and even more preferably 130% or more. When the elongation at break in either the longitudinal direction or the width direction is 50% or less, the film may become brittle and the film may be broken when a tension is applied in a processing step. As a method of controlling the elongation at break in the length and width directions as described above, This is achieved by using the crystalline polyester and using the following film-forming conditions.

The laminated film of the present invention has a film thickness of 40 μm or less. The thickness of the film is preferably 5 to 35 μm, more preferably 10 to 30 μm, even more preferably 12 to 25 μm, and particularly preferably 13 to 20 μm in terms of operation. When the film thickness exceeds 40 μm, the retardation becomes high, or when the film is used as a protective film for a polarizing plate, the thickness of the polarizing plate becomes thicker and the weight and size increase when mounted on a liquid crystal display. In particular, if the thickness becomes thicker, the amount of introduction in the reverse direction (longitudinal) direction due to Poisson's ratio when extending laterally becomes larger, so that a bending phenomenon occurs more strongly. That is, in the phase difference distribution in the width direction, the deviation between the central portion and the end portion held by the clamp of the lateral stretcher becomes large. The so-called bending phenomenon refers to the phenomenon that the straight line drawn along the width direction of the film by the marking ink before the step of the transverse stretcher is deformed into a bow shape when it is sent out from the transverse stretcher after being transversely stretched and then heat-treated.

The laminated film of the present invention has a film width of 400 mm or more. The width of the film is preferably 600 mm or more, more preferably 1000 mm or more, even more preferably 1300 mm or more, and even more preferably 1500 mm or more. When the width of the film is less than 400 mm, it may not be mounted as a large liquid crystal display.

The deviation of Re of the laminated film of the present invention is preferably 20% or less in the longitudinal direction. The deviation in the length direction of Re is more preferably 15% or less, further preferably 12% or less, and even more preferably 10% or less. Regarding the deviation of Re at this time, when the longitudinal direction of the laminated film is 400 mm or more, it means that the center of the width direction of the film is sampled at intervals of 50 mm, then the Re of the center of each sample is measured, and the maximum value of Re is determined. The difference from the minimum value divided by the average value is expressed in% (deviation of Re (%) = (maximum value of Re-minimum value of Re) / (average value of Re) x 100). In the case where the laminated film is in the form of a cut sheet, a direction orthogonal to the width direction is a length direction. As such The method of controlling the variation in the length direction of Re as described above can be achieved by using the following film forming conditions.

The deviation of the alignment angle of the laminated film of the present invention is preferably 20 ° or less in the width direction. The deviation in the width direction of the alignment angle of the laminated film is more preferably 15 ° or less, even more preferably 10 ° or less, and even more preferably 7 ° or less. The term "alignment angle" used herein refers to the direction in which the refractive index on the film is the largest, and is actually measured by an optical method in the same way as the retardation. In general, the so-called alignment angle is in the above-mentioned width direction, and the two ends show the highest value and the center show the lowest value. Therefore, in the present invention, a sample is taken at a location 25 mm apart from both ends in the width direction of the laminated film and at the center, and the alignment angle of the center of each sample is measured, and the larger of the two ends is aligned. The value obtained by subtracting the value of the alignment angle of the central portion from the value of the angle is used as the deviation of the alignment angle of the laminated film (the width direction deviation of the alignment angle (°) = the value of the larger alignment angle of the two end portions-the central portion Value of the alignment angle). In the case where the deviation of the alignment angle in the width direction exceeds 20 °, the black vision phenomenon that an observer can see on the display when wearing polarized sunglasses can generate new value. The so-called black vision refers to the phenomenon that the linearly polarized light emitted from the display overlaps with the absorption axis of polarized sunglasses, and the light does not reach the nitrile of the eye, so it becomes a dark field of view, and the image cannot be seen. However, if the angle between the direction of the linearly polarized light from the display and the orientation of the alignment angle is more than 10 degrees, the light will be birefringent, so even if it is polarized sunglasses, the light will pass through, preventing black vision. In recent years, it has attracted attention in automotive applications, and in particular, there has been a demand for a base film for ITO used in a touch panel. That is, when a liquid crystal display (linearly polarized light is orthogonal to the viewing angle) is installed as a polarizing plate protective film in an in-plane switching (IPS) or vertical alignment (VA) mode, if the alignment is When the angle is 10 ° or more, it is possible to suppress a decrease in brightness of an image due to light leakage. Control the width of the alignment angle as described above The method of deviation in the degree direction can be achieved by increasing the longitudinal stretching magnification to 3.5 or more, or using the following film forming conditions. In addition, if an amorphous resin is included on the main layer side, the alignment angle becomes high, which is preferable. Here, the term "amorphous resin" means that when a raw material is evaluated by a differential scanning calorimeter (DSC), the melting point Tm that becomes an endothermic peak hardly appears, and even if it exists, the melting enthalpy △ Hm shows 6J / g The following resins.

The melting temperature (Tmeta) of the crystalline portion in the multilayer film of the present invention is preferably 190 ° C or lower. When Tmeta is 190 ° C. or lower, the uniformity of the retardation in the width direction of the film is improved and the retardation becomes low, which is preferable. If it is too low, the thermal shrinkage is large and the quality problem is caused when the polarizing plate is formed. Therefore, the temperature is preferably 150 ° C or higher. The method of adjusting Tmeta can be achieved by setting the highest temperature of the heat treatment temperature in the manufacturing steps of the film to 140 ° C or higher and 210 ° C or lower.

In the laminated film of the present invention, it is preferred that two or more tan δ peaks are observed in a dynamic viscoelasticity measurement (Dynamic Mechanical Analysis measurement (DMA measurement)) in the longitudinal direction and / or the width direction. Among the two or more peaks of the tan δ peak, the peak at the lowest temperature side is caused by the Tg of the laminated film. The peaks other than Tg are based on the extension history received during the film formation of the laminated film. From the viewpoint of the deviation or mechanical characteristics of Re in the longitudinal direction and the width direction of the laminated film, it is preferable that such a peak exists. When there are more than two peaks near Tg, smaller peaks are sometimes observed as shoulder peaks. In this case, the number of shoulder peaks can also be counted as the number of peaks.

The laminated film of the present invention preferably has a peak temperature of tan δ existing on the highest temperature side in the lengthwise and / or widthwise DMA measurement of 100 to 130 ° C, or 130 to 160 ° C. From the viewpoint of the deviation or mechanical characteristics of Re in the longitudinal direction and the width direction, it is more preferably 100 to 120 ° C, still more preferably 105 to 120 ° C, and even more preferably 110 ~ 120 ℃. When the peak temperature of tan δ existing on the highest temperature side in the DMA measurement in the length direction and / or width direction is less than 100 ° C, or when it exceeds 130 ° C, there are Re in the length direction and / or width direction. Possibility of worsening deviation. In order to observe two or more tan δ peaks in the DMA measurement in the length direction and / or width direction, and to control the peak temperature of tan δ existing in the highest temperature side to a preferable range, the crystallinity as described above can be used. A multilayer build-up structure of polyester and amorphous resin is achieved using the following film-forming conditions.

In the laminated film of the present invention, the storage elastic modulus E ′ at 85 ° C. in the dynamic viscoelasticity measurement is preferably 2.5 GPa or more. In the manufacturing step of the polarizing plate, since the drying temperature of the PVA (polyvinyl alcohol) that becomes the polarizer is about 100-80 ° C, the strength of toughness near this temperature is required. If it is 2.5 GPa or more, it is preferable that the shrinkage polarizing plate is less likely to be curled or warped than the shrinkable polarizing plate of PVA. In addition, in order to impart scratch resistance, it is important not to cause deformation such as wrinkles on the metal sheet during the hard coating step. It is preferably 2.8 GPa or more, more preferably 3.1 GPa or more, and still more preferably 3.5 GPa or more. As a method of achieving this, from the viewpoint of increasing E ′ at 85 ° C., the component of the copolymerized polyester used in the thermoplastic resin B includes spirodiol and / or isosorbide. From the viewpoint of extensibility and adhesion, the copolymerization amount thereof is preferably 5 mol% or more and 40 mol% or less. As another method for achieving this, a UV-curable hard coat layer may be formed on one or both sides. The thickness of the hard coat layer after curing is preferably 0.5 μm or more and 6 μm or less from the viewpoint of increasing the value of E ′ at 85 ° C.

The dynamic friction coefficient of the laminated film of the present invention is preferably 0.45 or less. If the dynamic friction coefficient exceeds 0.45, the sliding property is poor, wrinkles are likely to occur, and the winding characteristics are deteriorated. Therefore, there is a case where the polarization plate is affected. Therefore, the dynamic friction coefficient is preferably 0.42 or less, and more preferably 0.4 or less. The dynamic friction coefficient here is only required to be at least one The surface can be satisfied. For example, it is preferable that the kinetic friction coefficient generated between the front surface and the back surface of the laminated film is 0.45 or less. In the application of ITO substrate, it has a subsequent processing of up to 4 layers provided with a transparent hard coating layer, a hard coating layer for oligomer adhesion, a low refractive index layer (LR) and a high refractive index layer (HR). From the viewpoint that the laminated film itself requires high sliding properties, it is preferably 0.35 or less in the same application. The method for achieving this can be achieved by adding an inert inorganic particle to the undercoat layer, for example, a silicic acid gel having a particle diameter of 50 to 300 nm to achieve a dynamic friction coefficient of 0.4 or less. Furthermore, in order to achieve the above-mentioned dynamic friction coefficient, it is preferable to add inert particles to the outermost layer of the laminated film. From the viewpoint of considering both transparency and slipperiness, the added amount is preferably 0.01% by weight to 1% by weight. Further, in terms of slippery transparency, it is preferable to add calcium carbonate or agglomerated silica with an average particle diameter of 2.5 μm or less and 1 μm or more as large-sized particles, and further add silicic acid with an average particle diameter of 0.5 μm or less. A combination of aluminum, alumina, divinylbenzene, and the like as small-sized particles.

In addition, the laminated film of the present invention is preferably provided with an undercoat layer and / or a hard coat layer on at least one side. If an undercoat layer is provided on at least one side, it is preferable in terms of adhesion to PVA. The undercoat layer is preferably applied in the film manufacturing step by using an aqueous coating agent, and the main agent is preferably selected from the group consisting of acrylic acid, polyester, urethane, acrylic modified polyester, and acrylic modified urethane. Ester and the like have higher versatility. The cross-linking material is not particularly limited as long as it is a compound that causes a cross-linking reaction. Urea-based, melamine-based, urethane-based, acrylamine-based, and polyamine-based can be used by methylolation or hydroxyalkylation. System, epoxy compound, isocyanate compound, An oxazoline compound, a carbodiimide compound, an aziridine compound, various silane coupling agents, various titanate coupling agents, and the like. Furthermore, from the viewpoint of measures against damage to the polarizing plate, it is preferable to provide a hard coat layer on at least one side. The thickness of the hard-coat layer is preferably 5 μm or less from the viewpoint of suppressing curl as much as possible, and is preferably 1 μm or more from the viewpoint of imparting hardness.

In the laminated film of the present invention, from the viewpoint of UV blocking property, the transmittance at a wavelength of 380 nm is preferably 30% or less. It is more preferably 25% or less, still more preferably 20% or less, and even more preferably 15% or less. When the transmittance at a wavelength of 380nm exceeds 30%, there is a possibility that the polarizer or liquid crystal may be deteriorated due to 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 preferred range, interference absorption by a UV absorber or a multilayer film is used. Interference reflection can be achieved by setting the average layer thickness to 40 to 55 nm and increasing the difference in refractive index between two or more resins with different optical characteristics. Therefore, if a biaxially stretched film is made, Interference can be achieved by forming a laminated film composed of a layer comprising a crystalline polyester as a main component and a layer consisting of a thermoplastic resin which remains amorphous during elongation or a thermoplastic resin which melts during a heat treatment step as a main component. reflection. Specifically, this can be achieved by laminating the polyester and thermoplastic resin B as described above with a predetermined number of layers. Furthermore, when UVA is contained in a preferable range as described above, it is preferable because of the synergistic effect.

In the laminated film of the present invention, from the viewpoint of UV blocking property, the average transmittance at a wavelength of 240 to 360 nm is preferably 5% or less. It is more preferably 4% or less, still more preferably 3% or less, and even more 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 may be deteriorated due to ultraviolet rays when the polarizer protective film is mounted on the liquid crystal display. In order to control the average transmittance at a wavelength of 240 ~ 360nm in a better range, it can be achieved by increasing the difference in refractive index between two or more resins with different optical characteristics. Therefore, a biaxially stretched film is made. In this case, a layer made of a crystalline polyester as the main component and a thermoplastic resin that remains amorphous during elongation or melts during the heat treatment step can be used. A laminated film in which the layers as the main component are alternately laminated may be used. Specifically, this can be achieved by laminating the polyester and thermoplastic resin B as described above with a predetermined number of layers.

Next, a preferred method for manufacturing the laminated film of the present invention will be described below. Of course, this invention is not limited to this example and is explained. The laminated structure of the laminated film used in the present invention can be easily realized by the same method as described in paragraphs [0053] to [0063] of Japanese Patent Laid-Open No. 2007-307893.

A 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 supplied to each extruder. In the extruder, the resin melted by heating above the melting point is uniformized by a gear pump or the like, and foreign matter or modified resin is removed through a filter or the like. These resins are discharged after being formed into a target shape by a mold. Then, the laminated sheet discharged from the die is extruded onto a cooling body such as a casting drum, and is cooled and solidified to obtain a casting film. In this case, it is preferable to use a wire-shaped, tape-shaped, needle-shaped, or knife-shaped electrode to rapidly cool and solidify the laminated sheet in close contact with a cooling body such as a casting drum by electrostatic force. Furthermore, it is also preferable to blow air from a slit-like, dot-like, or planar device to tightly adhere the laminated sheet to a cooling body such as a casting drum for rapid cooling and curing, or to tightly adhere the laminated sheet to a nip roller. A method of quenching and solidifying a cooling body.

In addition, using two or more extruders, the crystalline polyester, which is the main component of layer A, and a variety of resins different from thermoplastic resin B, are sent from different flow paths, and sent to a multi-layer lamination device. As the multilayer build-up device, a multi-manifold mold, a feed module, or a static mixer can be used. In particular, in order to efficiently obtain the structure of the present invention, it is preferable to use a feed module having three or more fine slits. If such a feed module is used, the device will not be extremely large, so foreign matter generated by thermal degradation is relatively small. Even if the number of layers is extremely large, a high-precision layer can be achieved. In addition, the precision of the lamination in the width direction is also significantly improved compared with the conventional technology. Moreover, in this device, since the thickness of each layer can be adjusted by the shape (length, width) of the slit, an arbitrary layer thickness can be achieved.

The molten multilayer laminate formed in this manner in a desired layer configuration is guided to a mold, and a cast film is obtained as described above.

The cast film obtained in this way is preferably biaxially stretched. Here, the so-called biaxial extension extends in the longitudinal direction and the width direction. The extension can extend in two directions one after the other, or in both directions at the same time. After biaxial stretching, it may be further extended in the longitudinal direction and / or the width direction. In particular, the heat treatment is preferably performed after the biaxial stretching, and then the stretching in the longitudinal direction. That is, in the laminated film of the present invention, from the viewpoint of uniformizing the phase difference in the width direction of the film infinitely, it is preferable to adopt a production method that mainly includes crystalline polyester A and amorphous polyester. B, an unstretched film having a layer number of 3 or more, and a layer ratio (A / B) of the layer A including the crystalline polyester A and the layer B including the amorphous polyester B of 2 to 0.2 at an elongation temperature of 70 The biaxial extension of the length direction and the width direction is performed in the range of ~ 145 ° C, followed by heat fixing at a temperature of 120 ~ 235 ° C, and then at least 1.02 ~ 1.95 in the extension temperature range of 80 ~ 150 ° C in the length direction. It is then extended again, and then heat-fixed again at a temperature of 90 to 235 ° C and coiled.

First, a case of sequential biaxial extension will be described. Here, the so-called extension in the longitudinal direction refers to the extension of the molecular orientation for imparting the longitudinal direction to the film, which is usually implemented by the difference in the peripheral speed of the roller. The extension in the traveling direction can be carried out in one step, and also This is done in multiple stages using multiple roller pairs. The stretching ratio varies depending on the type of resin, but it is usually preferably 2 to 15 times. In the case of using any one of polyethylene terephthalate, it is preferable to use 2 to 7 times, more preferably 3 to 5 times, and even more preferably 3 to 4 times, the length and width are suppressed. From the viewpoint of the deviation of the direction Re or the deviation of the alignment angle, it is particularly preferably 3 to 3.5 times. In addition, as the elongation temperature, the glass transition temperature of the resin constituting the laminated film ~ the glass transition temperature + 100 ° C is preferable, and specifically, it is more preferably 70 to 120 ° C, and still more preferably 80 to 110 ° C. From the viewpoint of the deviation of Re in the direction and width direction or the deviation of the alignment angle, it is particularly preferably 95 to 110 ° C. In the case of using a naphthalenedicarboxylic acid-containing polyester such as polyethylene naphthalate, the glass transition temperature is high, so it is preferably 105 ° C or higher and 155 ° C or lower.

After the uniaxially stretched film obtained by this treatment is subjected to a surface treatment such as corona treatment, flame treatment, or plasma treatment, if necessary, it can also be provided with in-line coating for easy slip, easy adhesion, and antistatic. Sex and other functions.

Next, the so-called widthwise extension refers to the extension of the film in the direction of the width direction. Generally, the tenter method is used to carry the film while holding both ends of the film with a clamp to carry it and extend in the width direction. The stretching ratio varies depending on the type of the resin, and is usually preferably 2 to 15 times. When any of the resins constituting the laminated film uses polyethylene terephthalate, it is preferably 2 to 5 Times, more preferably 3 to 5 times, and further preferably 3 to 4.5 times. From the viewpoint of suppressing Re or Rth, the deviation of Re in the width direction or the deviation of the alignment angle, it is particularly preferably 3.5 to 4 times, and more It is preferable to extend at a higher ratio than the longitudinal extension ratio. In addition, as the elongation temperature, the glass transition temperature of the resin constituting the laminated film ~ glass transition temperature + 120 ° C is preferable. From the viewpoint of suppressing the deviation of Re in the width direction or the deviation of the alignment angle, it is preferable to make the temperature have Gradient, more preferably, the temperature becomes higher as it goes from upstream to downstream. Specifically, in the case where the horizontally extending interval is divided into two equal parts, the upstream temperature is preferred. The difference from the downstream temperature is 20 ° C or more. More preferably, it is 30 degreeC or more, More preferably, it is 35 degreeC or more, Most preferably, it is 40 degreeC or more. The extension temperature of the first stage is more preferably 80 to 120 ° C, further preferably 90 to 110 ° C, and even more preferably 95 to 105 ° C. In the case of using a naphthalenedicarboxylic acid-containing polyester such as polyethylene naphthalate, the glass transition temperature is high, so it is preferably 105 ° C or higher and 155 ° C or lower.

Furthermore, in the laminated film of the present invention, from the viewpoint of suppressing the deviation of Re in the width direction or the deviation of the alignment angle, it is preferable to set a difference in the lateral extension speed. Specifically, the lateral extension interval is divided into two. In the case of equal parts, it is preferable that the stretch amount of the film at the middle point of the transverse extension interval (the width of the film at the measurement site-the width of the film before stretching) is 60% or more of the stretch at the end of the transverse extension interval, and more preferably 70% The above is more preferably 75% or more, particularly preferably 80% or more.

In order to impart planarity and dimensional stability, the biaxially stretched film is preferably heat-treated in a tenter above the stretching temperature and below the melting point. Specifically, since the upper limit of the general drying temperature in the manufacturing process of the polarizing plate is about 120 ° C., it is preferable to perform heat fixing in a range of 120 to 235 ° C. If the temperature is lower than 140 ° C, thermal dimensional stability cannot be obtained, and thus curling or warping of the polarizing plate may be caused. If it is 235 ° C or higher, bending and the like may increase, and the uniformity of the retardation in the width direction of the film may be deteriorated. From a viewpoint of suppressing Re or Rth, the deviation of Re in the width direction, or the deviation of the alignment angle, it is particularly preferably 190 to 225 ° C. From the viewpoint of reducing the deviation of Re in the width direction, it is preferable to perform an additional heat treatment of 1 to 10% in the first half of the heat treatment. From the viewpoint of not increasing the heat shrinkage rate in the width direction, it is preferably 2 to 8%. After the heat treatment is performed in this manner, the mixture is slowly cooled uniformly, and then cooled to room temperature to be taken up. In addition, if necessary, a relaxation treatment may be used in combination with heat treatment or slow cooling. The relaxation rate during heat treatment is preferably 0.5 to 5%, more preferably 0.5 to 3%, and still more preferably 0.8 to From the viewpoint of suppressing the deviation of Re in the width direction or the deviation of the alignment angle, 2.5% is particularly preferably 1 to 2%. The relaxation rate during slow cooling is preferably 0.5 to 3%, more preferably 0.5 to 2%, and still more preferably 0.5 to 1.5%. From the viewpoint of suppressing the deviation of Re in the width direction or the deviation of the alignment angle, , Especially preferably 0.5 ~ 1%. The temperature during the slow cooling is preferably 80 to 150 ° C, more preferably 90 to 130 ° C, and even more preferably 100 to 130 ° C. In terms of the planarity of the laminated film, 100 to 120 ° C is particularly preferred.

Next, a case of simultaneous biaxial extension will be described. In the case of simultaneous biaxial stretching, the obtained cast film may be subjected to surface treatments such as corona treatment, flame treatment, and plasma treatment, if necessary, and then be provided with in-line coating for easy slip and easy adhesion. And antistatic properties.

Next, the cast film is guided to a simultaneous biaxial tenter, and the two ends of the film are transported while holding both ends of the film with a clamp, so that the film is extended simultaneously and / or stepwise in the length direction and the width direction. As the simultaneous biaxial stretching machine, there are a zooming method, a spiral method, a driving motor method, and a linear motor method. Preferably, the driving motor method or linear motor method can be used to arbitrarily change the stretching magnification and can be relaxed at any place. The stretch magnification varies depending on the type of resin, but it is usually preferably 6 to 50 times in terms of area magnification. When any of the resins constituting the laminated film uses polyethylene terephthalate, as the area magnification, It is preferable to use 8 to 30 times, more preferably 9 to 25 times, and still more preferably 9 to 20 times. From the viewpoint of suppressing the deviation of Re or Rth, the length and width directions of Re, or the deviation of the alignment angle, , Especially preferably 10 to 15 times. Especially in the case of simultaneous biaxial extension, in order to suppress the in-plane alignment difference, it is preferable to make the extension ratios in the length direction and the width direction the same and the extension speeds to be approximately the same. In addition, as the elongation temperature, the glass transition temperature of the resin constituting the laminated film is preferably glass transition temperature + 120 ° C, specifically, 80 to 160 ° C, and more preferably 90 to 160 ° C. 150 ° C is particularly preferably 100 to 140 ° C from the viewpoint of suppressing deviations in Re in the longitudinal direction and width direction or deviations in the alignment angle.

In order to impart planarity and dimensional stability, such a biaxially stretched film is preferably heat-treated above the extension temperature and below the melting point in a heat-fixing chamber in the tenter, and the conditions are the same as those for successive biaxial stretching .

The laminated film of the present invention is preferably subjected to successive biaxial stretching as described above, and the film after further heat treatment is further re-stretched at least in the longitudinal direction at a stretching temperature of 80 to 150 ° C in the range of 1.02 to 1.95 times. Then, it is heat-fixed again in the range of 90-235 ° C, and then coiled.

The phase difference of the laminated film of the present invention obtained in the above manner is low, and the occurrence of color unevenness can be suppressed by controlling the deviation to be small, and it can be preferably used as a protective film for polarizing plates. In addition, the above-mentioned polarizing plate protective film can be bonded to a PVA sheet made of commercially available PVA by containing iodine and aligning it, and is also preferably used as a polarizing plate.

[Example]

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

(1) Number of layers

The number of laminated layers is determined by observing a sample obtained by cutting out a cross section with a microtome under a transmission electron microscope (TEM). That is, using a transmission electron microscope H-7100FA (manufactured by Hitachi, Ltd.), the cross section of the film was observed under the condition of an acceleration voltage of 75 kV, a photograph of the cross section was taken, and the number of layers was measured. In addition, in order to improve contrast, a dyeing technique using RuO ₄ or OsO _{4 is} used. In addition, according to the thickness of the thinnest layer (thin film layer) among all the layers captured in an image, if the thickness of the thin film layer is less than 50 nm, the observation is performed at a magnification of 100,000 times, and the thickness of the thin film layer is In the case of 50 nm or more and less than 500 nm, the observation is performed at a magnification of 40,000 times, and in the case of 500 nm or more, the observation is performed at a magnification of 10,000 times.

(2) In-plane phase difference (Re), thickness direction phase difference (Rth), alignment angle

A phase difference measuring device (KOBRA-21ADH) manufactured by Oji Measurement Co., Ltd. was used. The sample was cut out from the central part of the film width direction by 3.5cm × 3.5cm, and set on the device such that the film width direction became an angle of 0 ° defined by the measurement device, and measured Re, Rth and its alignment angle at a wavelength of 590nm . In addition, Rth is calculated by inclination of the late phase axis and by a second approximation of each phase difference value at an incident angle of 0 to 50 ° (every 10 °). Re is a value of 0 ° incident angle.

(3) Deviation in width direction of Re

In a laminated film with a film width of 400 mm or more, after sampling at intervals of 50 mm in the entire width direction of the film by the method described in (2) above, the Re of the center of each sample is measured, and the maximum value of Re and The difference between the minimum value is divided by the average value, and the value in% is taken as the deviation in the width direction of Re of the laminated film. In the case of a roll-shaped laminated film, the winding direction of the roll is taken as the length direction of the film, and the direction orthogonal to it is equivalent to the width direction. On the other hand, in the case of cutting into a sheet shape, Re is measured at both ends of the film in the long-side direction and in a direction orthogonal to the long-side direction (parts spaced apart from the two ends by 25 mm), and the The direction in which the center difference is large is the width direction of the so-called laminated film of the present invention.

(4) Deviation in length direction of Re

In a laminated film with a length of 400 mm, the center of the width direction of the film was sampled at 50 mm intervals by the method described in (2) above, and the Re of the center of each sample was measured, and the maximum and minimum Re The difference between the values is divided by the average value, and the value represented by% is taken as the deviation in the length direction of Re of the laminated film. The longitudinal direction of the laminated film refers to a direction orthogonal to the width direction described in the item (3).

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

In a laminated film having a film width of 400 mm or more, a total of 3 locations in the width direction were sampled in the width direction by the method described in (2) above, and each sample was measured. The central alignment angle is determined by taking the larger value in the case of the difference between the value at both ends and the central portion as the deviation in the width direction of the alignment angle of the laminated film. The width direction of the laminated film refers to the definition described in the above item (3).

(6) Young's modulus, elongation at break

The sample was cut from the central portion in the width direction of the film at 15 cm in the length direction and 1.5 cm in the width direction as a sample for measuring the Young's modulus in the length direction. Similarly, a sample for measuring the Young's modulus in the width direction was cut out at 15 cm in the width direction and 1.5 cm in the length direction. The Young's modulus and elongation at break were measured at a temperature of 23 ° C. and a humidity of 65% RH using Robot Tensilon RTA (manufactured by Orientec) for measurement according to JIS-K7127-1999. The stretching speed was set to 300 mm / min.

(7) Film thickness

The measurement was performed with a Litematic VL-50A (10.5 mm Φ superhard spherical probe, measuring load 0.06 N) manufactured by a contact film thickness meter Mitsutoyo. The measurement was performed 10 times while changing the location, and the average value was used as the thickness of the laminated film.

(8) Dynamic viscoelasticity (DMA) measurement (E 'and tanδ)

The sample was cut out from the central portion in the width direction of the film at 7 cm × 1 cm, and was set on the sample support so as to be a sample measuring 2 cm in length × 1 cm in width of the film. Using the DMS6100 manufactured by Seiko Instruments Co., Ltd., the storage elastic modulus E 'was measured in a tensile mode at a temperature range of room temperature 20 ° C to 240 ° C, a displacement of 10 μm, a vibration frequency of 1 Hz, and a heating rate of 2 ° C / min. And loss coefficient tanδ. tan δ is obtained from the ratio of the loss elastic modulus E "to the storage elastic modulus E '. The length direction of the film is set to the measurement length.

(9) Visibility test

On one side of a polarizing plate with a polarization degree of 99.9%, which is made by absorbing and aligning iodine in PVA, a sample cut from the central portion in the width direction of the film with a size of 420 mm in the width direction and 310 mm in the length direction Make a test piece. The prepared test piece was overlapped with a polarizing plate without a film attached by the configuration of a cross polarizer, and placed on a white LED light source (A3-101 manufactured by Tritek) to confirm the visibility in the above case.

SS: There is less light leakage and almost no interference color is seen.

S: Interference color is hardly seen.

A: Although the interference color is slightly seen, there is no problem in practical use.

B: Since interference colors are clearly seen, it is not suitable for display applications.

(10) UV blocking

The sample was cut out from the central portion in the width direction of the film at 5 cm × 5 cm, and the transmittance at a wavelength of 240 to 800 nm was measured using a spectrophotometer (U-4100 Spectrophotomater) manufactured by Hitachi High-Technologies. The inner wall of the integrating sphere is barium sulfate, and the standard plate is an attached alumina. Measurement conditions: The slit is set to 2nm (visible) / automatic control (infrared), the gain value is set to 2, the measurement is performed at a scanning speed of 600nm / min, and the transmittance at a wavelength of 380nm and a wavelength of 240 at an incident angle of 0 degrees ~ 360nm average transmittance. The UV blocking property was evaluated based on the following criteria.

S: The average transmittance of the wavelength 240 ~ 360nm is less than 2%

A: The average transmittance of the wavelength 240 ~ 360nm is 3% or more and 5% or less

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

(11) Composition analysis of copolymerized polyethylene terephthalate (Co-PET)

The composition of the copolymerized PET of the present invention is to adjust the amount of monomers of the copolymerization component during polymer polymerization by adjusting the blending amount of the diol component and the dicarboxylic acid component, but it can be measured by ¹ H-NMR and thermal decomposition GC / MS The monomer identification and composition ratio were calculated. About 30 mg of copolymerized PET flakes were collected and dissolved in a mixed solution of deuterated chloroform (CDCl ₃ ) and deuterated hexafluoroisopropanol (HFIP-d2), and then subjected to 1H-NMR measurement at a temperature of 40 ° C. The ratio of the mixed solution was set to CDCl ₃ : HFIP-d2 = 2: 1. At the time of identification, based on the existing data of the individual spectra of various monomers of spirodiol, cyclohexanedicarboxylic acid, cyclohexanedimethanol, and isosorbide, the composition was calculated based on the peak area ratio of the spectrum. ratio.

(12) Dynamic friction coefficient (μd)

According to ASTM-D-1894, based on the stress (resistance value) detected by the resistance strain gage after the slip tester started to slide under the conditions of a sliding speed of 150 mm / min and a load of 200 g, the following formula (1 ). Moreover, the dynamic friction coefficient is the resistance value of the stable region after sliding out.

Coefficient of Friction = Resistance (G) / Load (G) ... Formula (1)

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

A differential scanning calorimeter (DSC) was used to raise the temperature from 25 ° C to 290 ° C at 20 ° C / min. The melting point Tm and the crystal melting enthalpy ΔH were calculated for the resin composition used in accordance with JIS K7121 and 7122. Judgment of crystalline polyester resin. Tm hardly appeared and ΔH was less than 6j / g. Further, in the laminated film, an endothermic wave peak near the heat treatment temperature occurring at a melting point Tm or less was determined as the crystalline part melting temperature Tmeta.

Device: Seiko Instruments Co., Ltd. Manufacturing: SII Robot DSC (model DSC6220)

Data analysis "standard analysis"

Sample weight: 5mg.

(14) Full light transmittance. Haze

The measurement was performed using a haze meter NDH5000 (manufactured by Nippon Denshoku Industries) in accordance with JIS K 7361-1, JIS K 7136, and ASTM-D1003.

(15) Follow-up processability when hard coating is given

A 1.5 μm-thick hard coat layer was formed on the laminated film as a protective film. The coating method is to prepare the coating agent shown below, and apply it evenly to the film with a # 10 hard coater. It was dried in a hot air convection dryer at 90 ° C for 1 minute to remove the solvent, and then subjected to ultraviolet irradiation at 80 W / cm and a conveying speed of 5 m / minute.

UA-122P (Shin Nakamura Chemical Industry) 40 parts of urethane acrylate

Takenate B830 (Mitsui Chemicals Polyurethanes) blocked isocyanate 2.5 parts

1.5 parts of Irgacure184 (Ciba Specialty Chemicals) light starter

MEK 110 servings

The uncoated part at the end is cut out into a slit and wound into a roll shape. At this time, the state of the film was observed, and subsequent processability was evaluated.

S: No wrinkles and good flatness.

A: Some wrinkles can be seen, but there is no problem

B: Tin wrinkles and curls are clearly visible.

(Example 1)

As the crystalline polyester, polyethylene terephthalate (PET) having a melting point of 258 ° C was used. As the thermoplastic resin B, an ethylene terephthalate (PE / SPG.T) obtained by copolymerizing 15 mol% of spirodiol and 25 mol% of cyclohexanedicarboxylic acid as an amorphous resin having no melting point was used. / CHDC). In order to convert the above PE / SPG. 98% by mass of T / CHDC, 2,4,6-tris (2-hydroxy-4-hexyloxy-3-methylphenyl) -1,3,5-tris as UVA 2% by mass is used to feed raw materials from the measuring hopper to the twin-screw extruder in a manner of mixing at this ratio, melt-kneaded at 280 ° C, and discharged from the mold in a strand shape, cooled and solidified in a 25 ° C water tank, and cut into A small plate shape was obtained to obtain a thermoplastic resin composition (B-1).

Separate the prepared PET and thermoplastic resin composition (B-1) The method of moisture content was sufficiently dried under vacuum and high temperature, and then charged into two uniaxial extruders and melt-kneaded at 280 ° C. Then, after passing through 50 FSS-type leaf disc filters, the lamination ratio of each layer including PET and each layer including the thermoplastic resin composition (B-1) (total thickness of the layer including PET / including the thermoplastic resin) The total thickness of the layers of the composition (B-1) is 1.0, and the measurement is performed by a gear pump. One side is combined in a layering device with 251 slits to alternately layer the layered layer with 251 layers in the thickness direction. The bulk form was extruded from a T-die and cast on a casting drum whose surface temperature was controlled to 25 ° C to obtain a cast film. The method of forming a laminated body is performed in accordance with the description in paragraphs [0053] to [0056] of Japanese Patent Laid-Open No. 2007-307893. Here, the slit length and interval are constant. The obtained laminated body had a layer including PET of 126 layers, a layer including thermoplastic resin composition (B-1) of 125 layers, and a laminated structure having alternate layers in the thickness direction. In addition, the value obtained by dividing the length in the film width direction of the nozzle opening, which is the widening ratio inside the nozzle, by the length in the film width direction of the nozzle inlet is 2.5.

After the obtained cast film was heated by a roller group set to 95 ° C, it was heated rapidly from both sides of the film by a radiant heater while the length of the extended section was 400 mm, and the temperature of the film at the time of extension was set to 103. ℃ and extended 3.3 times along the length of the film, and then cooled temporarily. Then, both sides of the uniaxially stretched film were subjected to a corona discharge treatment in the air, and the wetting tension of the base film was set to 55 mN / m. Polyester resin) / (polyester resin with a glass transition temperature of 82 ° C) / silicon dioxide particles with an average particle diameter of 100 nm are formed into a film coating liquid to form a transparent coating. Easy to slip. Easy-to-adhesive primer.

The uniaxially stretched film was guided to a tenter, preheated by hot air at 95 ° C, and then stretched along the width of the film at a temperature of 105 ° C in the first stage and 140 ° C in the second stage. The direction extends 4.5 times. Here, in the case where the horizontally extending section is divided into two equal parts, the amount of film extension at the middle point of the horizontally extending section (the film width at the measurement site-the film width before stretching) is the amount of extension at the end of the horizontally extending section 80% of the way is extended in 2 stages. The transversely stretched film is directly heat treated in a tenter in a stepwise manner with hot air at 180 ° C to a heat treatment temperature of 225 ° C, and then subjected to a 1% relaxation treatment in the width direction at the temperature condition, and then quenched to 100 ° C and then A 1% relaxation treatment was performed in the width direction, followed by winding up to obtain a laminated film. The evaluation results of the obtained laminated film are shown in Table 1.

(Example 2)

In Example 1, the laminated film was obtained in the same manner as in Example 1 except that the stretching ratio when stretching in the film width direction was 3.6 times and the heat treatment temperature was 200 ° C. The evaluation results of the obtained laminated film are shown in Table 1.

(Example 3)

A laminated film was obtained in the same manner as in Example 1 except that the heat treatment temperature was set to 235 ° C in Example 2. The evaluation results of the obtained laminated film are shown in Table 1.

(Example 4)

In Example 1, the same procedure as in Example 1 was carried out except that a lamination device with 51 slits was used, and PET was set to 26 layers and the thermoplastic resin composition (B-1) was set to 25 layers. Laminated film. The evaluation results of the obtained laminated film are shown in Table 1.

(Example 5)

In Example 1, a laminate device having three slits was used, and two layers of PET and one layer of thermoplastic resin composition (B-1) were used. Laminated film. The evaluation results of the obtained laminated film are shown in Table 1.

(Example 6)

In Example 1, a lamination device having 801 slits was used, PET was set to 401 layers, the thermoplastic resin composition (B-1) was set to 400 layers, and the stretching ratio when extending in the film width direction was set. A laminated film was obtained in the same manner as in Example 1 except that the heat treatment temperature was set at 200 ° C and 3.6 times. The evaluation results of the obtained laminated film are shown in Table 2.

(Example 7)

As the thermoplastic resin B, polyethylene terephthalate (PETG) obtained by copolymerizing 1,4-cyclohexanedimethanol at 30 mol% as an amorphous resin having no melting point was used. As the UVA, 2,2'-methylenebis [6- (2Hbenzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) Phenol] 4 mass% is mixed in this ratio to feed raw materials from the measuring hopper to the twin-screw extruder, melt-knead at 280 ° C, and discharge from the mold in a strand shape, and cool and solidify in a 25 ° C water tank. It cut into small pieces 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 instead of the thermoplastic resin composition (B-1). The evaluation results of the obtained laminated film are shown in Table 2.

(Example 8)

As the thermoplastic resin B, polyethylene terephthalate (PET / I) obtained by copolymerizing 20 mol% of isophthalic acid as an amorphous resin having no melting point was used. PET / I 196% by mass as UVA 2,2'-methylenebis [6- (2Hbenzotriazol-2-yl) -4- (1,1,3,3-tetramethyl Butyl) phenol] 4 mass% is mixed in this ratio to feed the raw material from the measuring hopper to the biaxial extruder, melt-kneaded at 280 ° C, and discharged from the mold in a strand shape in a water tank at 25 ° C. It was cooled and solidified, and cut into small pieces to obtain a thermoplastic resin composition (B-3).

A laminated film was obtained in the same manner as in Example 1 except that PET / I, which is the thermoplastic resin composition (B-3), was used instead of the thermoplastic resin composition (B-1). The evaluation results of the obtained laminated film are shown in Table 2.

(Example 9)

In Example 1, the slit length was changed linearly, and the slit design was performed so that the average layer thickness of the adjacent A layer and the B layer became 40 to 55 nm, and a laminated body with each layer thickness gradually changed was made. Then, the longitudinal stretching temperature was changed to 105 ° C so that the thickness of the laminated film became 13 μm, the heat treatment temperature was set to 215 ° C, and the conditions of the heat treatment and additional extension were changed to about 3% in the first half of the heat treatment. In the same manner as in Example 1, a laminated film was obtained. It is a transparent film with a total light transmittance of 91% and a haze of 0.7%. The evaluation results of the obtained laminated film are shown in Table 2.

(Example 10)

A laminated film was obtained in the same manner as in Example 9 except that the heat treatment temperature of Example 9 was changed to 190 ° C. The evaluation results of the obtained laminated film are shown 于 表 2。 In Table 2.

(Example 11)

Except for the thickness, the laminated film obtained under the same conditions as in Example 10 was further oriented in the longitudinal direction, re-stretched 1.2 times at 150 ° C, and then subjected to relaxation treatment at 190 ° C. The evaluation results of the obtained laminated film are shown in Table 3.

(Example 12)

As the thermoplastic resin B, an ethylene terephthalate (PE / SPG.T) copolymerized with 21 mol% of spirodiol and 5 mol% of cyclohexanedicarboxylic acid as an amorphous resin having no melting point was used. / CHDC). Except for this, a laminated film was obtained in the same manner as in Example 1. The evaluation results of the obtained laminated film are shown in Table 3. Furthermore, in the dynamic viscoelasticity measurement, the number of tan δ peaks is apparently one because the tan δ peaks on the low temperature side move to the high temperature side.

(Example 13)

As the thermoplastic resin B, an ethylene terephthalate (PET / ISB.CHDM) copolymerized with 5 mol% of isosorbide and 24 mol% of cyclohexanedimethanol as an amorphous resin having no melting point was used. . Except for this, a laminated film was obtained in the same manner as in Example 1. The evaluation results of the obtained laminated film are shown in Table 3.

(Example 14)

As the thermoplastic resin B, a terephthalic acid copolymerized with 5 mol% of isosorbide and 24 mol% of cyclohexanedimethanol as an amorphous resin having no melting point was used. Ethylene terephthalate (PET / ISB.CHDM) is an ethylene terephthalate copolymerized with 20 mol% of spirodiol and 30 mol% of cyclohexanedicarboxylic acid as an amorphous resin without a melting point. (PE / SPG.T / CHDC) Compounded by 1: 1. Except for this, a laminated film was obtained in the same manner as in Example 1. The evaluation results of the obtained laminated film are shown in Table 3.

(Example 15)

As the thermoplastic resin A, an ethylene terephthalate (PET / ISB.CHDM) copolymerized with 15 mol% of isosorbide and 24 mol% of cyclohexanedimethanol as an amorphous resin having no melting point was used. An alloy resin compounded with polyethylene terephthalate at a ratio of 1: 3. On the other hand, as the thermoplastic resin B, an ethylene terephthalate (PET that is copolymerized with 15 mol% of isosorbide and 20 mol% of cyclohexanedimethanol, which is also an amorphous resin having no melting point, is used. /ISB.CHDM) is an alloy resin compounded with PET / I with 20 mol% isophthalic acid content at a ratio of 1: 1. In addition, the lamination device was changed to alternately laminate the thermoplastic resin A 401 layer and the thermoplastic resin B 400 layer, and the laminated layer ratio of the A layer / B layer was changed to 0.33, and a laminated film was obtained in the same manner as in Example 1. . The evaluation results of the obtained laminated film are shown in Table 3. The obtained film had excellent visibility and was the most excellent. In addition, since the change in the alignment angle is large and the light leakage under the cross polarizer is large, it has the characteristics that it is difficult to cause black vision, so it is suitable for a thin film for ITO substrate.

(Example 16)

Except for the thickness, the laminated film obtained under the same conditions as in Example 14 was further oriented in the longitudinal direction, and re-extended at 150 ° C for 1.2 times, and then at 190 ° C. Next, a relaxation process is performed. Table 4 shows the evaluation results of the obtained laminated film.

(Example 17)

In the PET of Example 9, 20% by mass of a copolymerized PET having an isophthalic acid content of 20 mol% was added, the lamination ratio was set to 0.6, and the longitudinal extension ratio was set to 3.4 times. 9 In the same manner, a laminated film having a thickness of 13 μm was obtained. Table 4 shows the evaluation results of the obtained laminated film. A hard coat layer was obtained on one side of the obtained laminated film, and its 85 ° C storage elastic modulus E 'was 2.8 GPa.

(Example 18)

Except changing the casting speed and changing the longitudinal stretching temperature to 105 ° C and the heat treatment temperature to 140 ° C, a laminated film was obtained under the same conditions as in Example 1. The laminated film was further oriented in the longitudinal direction, and was performed at 160 ° C 1.3 times the extension, and then stepwise heat treatment at 130 ~ 190 ° C, and length and width relaxation treatment at 100 ° C. 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 became 13 μm. Samples with uniform alignment angle and phase difference in the film width direction were successfully taken. In addition, regarding the alignment direction of the molecules, the display length direction was confirmed based on the result of the phase difference measurement device.

(Example 19)

As the crystalline polyester, polyethylene naphthalate (PEN) having a melting point of 265 ° C was used. As the thermoplastic resin B, a pair obtained by copolymerizing 15 mol% of isosorbide and 20 mol% of cyclohexanedimethanol as an amorphous resin having no melting point was used. Ethylene phthalate (PET / ISB.CHDM).

The prepared PEN and thermoplastic resin B were sufficiently dried under vacuum and high temperature so as not to contain moisture, and then put into two uniaxial extruders and melt-kneaded at 300 ° C. Then, in the same manner as in Example 1, they were combined in a lamination device having 131 slits, and extruded from a T-shaped die in the form of a laminated body having 131 layers alternately laminated in the thickness direction, and the surface was extruded. Casting was performed on a casting drum controlled at a temperature of 25 ° C to obtain a cast film. The method of forming a laminated body is performed in accordance with the description in paragraphs [0053] to [0056] of Japanese Patent Laid-Open No. 2007-307893. Here, the gap is made constant, the slit length is gradually changed, and the slit design is performed so that the average layer thickness becomes 40 to 55 nm. The obtained laminated body had a laminated structure including 66 layers including PEN, 65 layers including thermoplastic resin B, and alternately laminating in the thickness direction. In addition, the value obtained by dividing the widening ratio inside the nozzle, that is, the length in the film width direction of the nozzle opening by the length in the film width direction of the inlet portion of the nozzle, was 2.5.

After the obtained cast film was heated by a roller group whose temperature was set to 140 ° C, it was heated rapidly from both sides of the film by a radiant heater while extending the length of 400 mm between the extension sections, and the film temperature at the time of extension was set to 143. ℃ and extended 3.3 times along the length of the film, and then cooled temporarily. Then, both sides of the uniaxially stretched film were subjected to a corona discharge treatment in the air, and the treated surfaces of both sides of the film were coated with (polyester resin having a glass transition temperature of 18 ° C) / (glass transition temperature of 82 ° C). Polyester resin) / Silicon dioxide particles with an average particle diameter of 100nm. Easy to slip. Easy-to-adhesive primer.

The uniaxially stretched film was guided to a tenter, and preheated by hot air at 150 ° C, and then along the width of the film at a temperature of 145 ° C in the first stage and 155 ° C in the second stage. The direction extends 4.5 times. Here, in the case where the horizontally extending section is divided into two equal parts, the amount of film extension at the middle point of the horizontally extending section (film width at the measurement site-film width before stretching) is to be the amount of extension at the end of the horizontally extending section. 80% of the ways are extended in 2 stages. The transversely stretched film is directly heat-treated in a tenter by hot air at 205 ° C, and then is subjected to a 1% relaxation treatment in the width direction under the temperature condition, and then quenched to 100 ° C and then subjected to a 1% relaxation treatment in the width direction. Then, it is 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 was used as in Example 14, and film forming conditions other than the number of layers were set to Example 14, thereby obtaining a laminated film. Table 4 shows the evaluation results of the obtained laminated film.

(Example 21)

PET / polyetherimide (PEI) 5% by mass / calcium carbonate with an average particle diameter of 1.1 μm 0.025% by mass / crosslinked polystyrene with an average particle size of 0.3 μm 0.1% by mass was supplied to a biaxial extruder as a raw material The mixture was melt-kneaded at 280 ° C, discharged from the mold in a strand shape, cooled and solidified in a water tank at 25 ° C, and cut into small pieces 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 has a total light transmittance of 90% and a haze of 1.5%. The visibility is very good, and it can be applied in terms of subsequent processability. In addition, since the change in the alignment angle is large, the light leakage under the cross polarizer is large, so it is difficult to provide Due to the characteristics of black vision, it is suitable for thin films for ITO substrates.

(Comparative example 1)

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

(Comparative example 2)

In Example 1, the extension amount of the film at the middle point of the extension section (the width of the film at the measurement site-the width of the film before the extension) was changed to 50% of the extension amount at the end of the horizontal extension section, and there was no step A laminated film was obtained in the same manner as in Example 1 except that the temperature was raised, and the heat treatment temperature was set to 245 ° C. after completion of the lateral stretching. Table 5 shows the evaluation results of the obtained laminated film.

(Comparative example 3)

In Example 1, in the longitudinal stretching step, the output of rapid heating by a radiant heater was reduced from both sides of the film, the film temperature during stretching was set to 85 ° C, and the relaxation rate when the film was slowly cooled was set to Except for 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)

In Example 1, the lamination film was obtained in the same manner as in Example 1 except that the casting speed was adjusted and the film thickness was set to 45 μm. The evaluation results of the obtained laminated film are shown in Table 6. The phase difference in the thickness direction is large, and the interference color can be seen more strongly when viewed from the oblique direction in the visibility test.

(Comparative example 5)

A laminated film was obtained in the same manner as in Example 1, except that it was extended 5.3 times in the film width direction. The evaluation results of the obtained laminated film are shown in Table 6.

(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-2) instead of the thermoplastic resin composition (B-1). . The evaluation results of the obtained laminated film are shown in Table 6.

(Industrial availability)

The laminated film of the present invention can suppress the occurrence of color unevenness by lowering the phase difference and controlling the deviation to a small extent, so it can be preferably used as a polarizing plate protective film of a polarizing plate built into a display device such as a liquid crystal display. Or it can be used as the base film of transparent conductive film such as ITO for automotive display.

Claims (11)

A laminated film in which three or more layers are laminated in a thickness direction, and a layer A having a crystalline polyester as a main component and a layer B having a thermoplastic resin B different from the crystalline polyester as a main component are alternated It is formed by layering, and the phase difference (Re) in the plane direction is 0 ~ 400nm, the phase difference (Rth) in the thickness direction is 0 ~ 1500nm, the deviation of Re is 18% or less in the width direction, and the Yang type in the length direction and the width direction The modulus is 2 GPa or more, and the elongation at break in the length and width directions is 50% or more. The thermoplastic resin B contains one or more selected from isophthalic acid, cyclohexanedicarboxylic acid, spirodiol, and cyclohexanedi. Amorphous polyester with copolymerized components in methanol and isosorbide; the thickness of the laminated film is 40 μm or less, and the width of the film is 400 mm or more. For example, the laminated film of claim 1, wherein the deviation of Re is 20% or less in the length direction. For example, the laminated film of claim 1 or 2, wherein the deviation of the alignment angle is 20 ° or less in the width direction. The laminated film of claim 1 or 2, wherein the melting temperature Tmeta of the crystalline portion is 190 ° C or lower. For example, the laminated film of claim 1 or 2, wherein two or more tan δ peaks are observed in the dynamic viscoelasticity measurement in the length direction and / or the width direction. For example, the laminated film of claim 1 or 2, wherein the storage elastic modulus E ′ at 85 ° C. in the dynamic viscoelasticity measurement is 2.5 GPa or more. For example, the laminated film of claim 1 or 2, wherein the number of laminated films is 51 to 1001 layers. For example, the laminated film of claim 1 or 2, wherein the dynamic friction coefficient is 0.45 or less, and an undercoat layer and / or a hard coat layer are provided on at least one side. The laminated film of claim 1 or 2 is used as a protective film for polarizing plates. The laminated film as claimed in item 1 or 2 is used as an ITO substrate film. A method for manufacturing a laminated film, which is the method for manufacturing a laminated film according to claim 1, characterized in that the laminated film mainly includes crystalline polyester A and amorphous polyester B, and the number of layers is 3 or more. An unstretched film having a laminate ratio (A / B) of layer A containing crystalline polyester A and layer B containing amorphous polyester B of 2 to 0.2 is stretched in the lengthwise direction in the range of 70 to 145 ° C. The biaxial extension in the width direction is followed by thermal fixation at a temperature of 120 to 235 ° C, and then at least 1.02 to 1.95 times of the extension temperature in the range of 80 to 150 ° C in the length direction, and then at 90 After reheating in the range of ~ 235 ° C, coiling is performed.