JP2017009646A - Lamination film, and optical display device or touch panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film and an optical polyester film that have a main orientation axis inclined from a flow direction and prevent unevenness in phase difference in the width direction.SOLUTION: There is provided a lamination film that is suitably used as a polarizer protective film of a polarizing plate for a liquid crystal display, a phase difference film, and an ITO substrate of a capacitive touch panel with less mottled rainbow, and exhibits high quality without interference colors when implemented, particularly, when viewed obliquely with respect to a screen.SELECTED DRAWING: None

Description

  The present invention relates to a laminated film. In particular, the present invention relates to an optical film used on the outside of a polarizing plate used in a liquid crystal display.

In recent years, liquid crystal displays have been widely used as display devices for televisions, personal computers, digital cameras, and smartphones, and in particular, cases that are used outdoors, such as smartphones and car navigation systems, have been increasing. When used outdoors, sunglasses may be worn to protect the eyes, but the light emitted from the display image is linearly polarized because it passes through a polarizing plate, while sunglasses also emits incident light by polarization. Due to the attenuation, a phenomenon in which the display image becomes completely dark occurs when the polarization axis of the linearly polarized light of the display image and the linearly polarized light of the sunglasses are orthogonal (also referred to as a blackout phenomenon). In order to solve the above problem, a method of modulating linearly polarized light into circularly polarized light by providing a λ / 4 retardation film on the outer side (viewing side) of the display image is known. Since the phase difference film is manufactured by biaxial stretching in which longitudinal stretching and transverse stretching are combined, in principle, the orientation axis is substantially 0 ° or 90 ° with respect to the longitudinal direction of the film. In order to shift the phase by λ / 4 from the longitudinal direction, it is necessary to cut out from a long stretched film roll at an angle of 30 to 60 °, and thus there were many problems with productivity and loss. In addition, biaxially stretched films are known to be able to be used in roll-to-roll by using both ends in the width direction because the orientation axis is inclined by bowing as it goes to the end in the width direction. (Patent Document 1). However, since this method cannot be used except for the end of the film, there is a problem that the loss is very large and the retardation unevenness in the width direction is also large.

  Further, in recent years, demands for cost reduction and thinning of the polarizing plate have been increased, so that a polarizer protective film on the viewing side can also have a function of λ / 4 retardation without using a retardation film. It has been desired. On the other hand, a method for producing a long polarizer protective film in which an almost non-oriented film is slightly stretched in an oblique direction and the orientation axis is 30 to 60 ° with respect to the film longitudinal direction has been proposed (for example, Patent Documents). 2-4). By using a stretched film with an inclined orientation axis, roll-toe-roll bonding is possible instead of the conventional batch-type bonding, and productivity is dramatically improved. Is also significantly reduced. However, since a special oblique stretching apparatus is indispensable for performing oblique stretching, the amount of capital investment becomes enormous. In addition, the oblique stretching is limited in application to an amorphous resin such as TAC (triacetyl cellulose) or COP (cycloolefin polymer), so that the cost is high and film thinning is impossible. Although replacement of the conventional TAC film with a biaxially stretched polyester film has been actively studied for the purpose of reducing the cost and reducing the thickness of the polarizing plate, when oblique stretching is performed on a crystalline resin such as polyester, Stretching unevenness occurs, and only poor heat resistance can be obtained due to insufficient orientation. On the other hand, a polyester film is also known in which the retardation in the oblique direction is greatly increased to reduce interference unevenness (Patent Document 5). However, since the polyester film obtained by this production method is a uniaxially stretched film, the thermal dimensional stability is poor, and the problem of occurrence of unevenness in the width direction retardation due to bowing during heat treatment cannot be solved. At present, an obliquely oriented film that has improved all of these problems has not been achieved.

JP 2013-194107 A JP 2006-069192 A JP 2012-103651 A JP 2014-069436 A JP, 2015-004826, A

In view of the above problems, an object of the present invention is to provide a film that solves the following problems. (1) A laminated film having a biaxially oriented A layer and B layer, and each phase difference of the A layer and the B layer is subtracted from each other, thereby providing a low retardation film and uneven retardation in the width direction. In addition, since there is little unevenness of the orientation angle, there is little change in contrast and interference color even when it is mounted on a display device such as a large-screen liquid crystal display as a polarizer protective film, and a high-quality display can be obtained. According to a further preferred embodiment, (2) the orientation axis is inclined from the longitudinal direction, (3) the phase difference in the width direction is uniform, and (4) it can be produced by a conventional biaxial stretching apparatus. It can be created by roll-to-roll, and there is little production loss.

  The present invention has the following configuration. That is, it is a laminated film in which at least two layers are laminated, and has a biaxially oriented A layer and B layer, where the kth retardation from the surface layer is Re (k) and the total number of layers is n. The laminated film is characterized in that the total retardation Re of the laminated film satisfies the formulas (1) and (2).

  The present invention has a low retardation, and is prepared without loss of an obliquely oriented film with a conventional biaxial stretching apparatus. A retardation film, a polarizer protective film having a retardation function, a retardation for a touch panel It can be used for films and the like. In addition, because there is little unevenness in phase difference and orientation angle in the width direction, even when mounted on a display device such as a large-screen liquid crystal display as a polarizer protective film, there is little change in contrast and interference color, and high-quality display is achieved. There is an effect that can be obtained.

It is a related figure of the phase difference and orientation angle in the film width direction position by preferable embodiment of this invention. It is a related figure of the phase difference and orientation angle in the film width direction position by other embodiment of this invention. It is a related figure of the phase difference and orientation angle in the film width direction position by other embodiment of this invention. It is the schematic of the tenter rail width | variety at the time of straight extending | stretching. It is the schematic of the tenter rail width | variety at the time of onion extending | stretching. It is a related figure of the phase difference and orientation angle in the film width direction position by more preferable embodiment of this invention. It is a figure which shows a film state when laminating | stacking an A layer film and a B layer film. The arrow represents the flow direction in the film forming process. It is a related figure of the phase difference and orientation angle in the width direction position of the film obtained by the lamination of FIG. FIG. 8 is a diagram showing the relationship between the phase difference and the orientation angle at the position in the width direction of the remaining film after trimming and removing the center and both ends of the film obtained by the lamination of FIG. 7. It is a figure which shows a film state when laminating A layer films. It is a related figure of the phase difference and orientation angle in the width direction position of the film obtained by the lamination of FIG. It is a figure which shows a film state when the A layer film and the B layer film are trimmed and removed at the center and both ends, and the remaining film is laminated. It is a figure which shows a film state when A layer film removes by trimming a center part and both ends, and carries out + partial lamination from the remaining center part, and-part from a center part. It is a related figure of the phase difference and orientation angle in the width direction position of the film obtained by the lamination of FIG. It is a related figure of the phase difference and orientation angle in the width direction position of the film obtained by laminating | stacking the film from which thickness differs by the system shown in FIG. It is a related figure of the phase difference and orientation angle in the width direction position of the film obtained by laminating | stacking the film from which heat processing temperature differs by the system shown in FIG. It is sectional drawing of an example of a touchscreen laminated body. It is sectional drawing of an example of a touchscreen laminated body.

Hereinafter, the laminated film obtained by the production method of the present invention will be described. The laminated film of the present invention is a laminated film in which at least two layers are laminated, and has a biaxially oriented A layer and B layer. Here, the biaxial orientation refers to those obtained basically by biaxial stretching in the longitudinal direction and the width direction and strongly oriented in the longitudinal direction and the width direction. Further, when the retardation at the k-th from the surface layer is Re (k) and the total number of layers is n, the total retardation Re of the laminated film satisfies the expressions (1) and (2).

In general, the retardation is an in-plane retardation of a film or a layer, and is a value represented by (Nx−Ny) × d unless otherwise specified. Here, Nx represents a refractive index in a direction (in-plane direction) perpendicular to the thickness direction of the film or layer and giving the maximum refractive index. Ny represents the refractive index in the in-plane direction of the film or layer and perpendicular to the Nx direction. d represents the film thickness of the film or layer. Unless otherwise stated, the phase difference measurement wavelength is 590 nm. The phase difference can be measured using a commercially available phase difference measuring device (for example, “KOBRA-21ADH” manufactured by Oji Scientific Instruments, “WPA-micro” manufactured by Photonic Lattice) or the Senarmon method. The film is sandwiched between two polarizing plates provided so that the polarization directions are parallel, and the phase difference of the measurement sample and the refractive index on the film are determined from the change in transmitted light intensity when the polarizing plate is rotated. It is possible to measure the orientation angle, which is the direction in which becomes the largest. The phase difference Re (k) of each layer is a value obtained by peeling each layer and measuring each using a phase difference measuring device, and the total phase difference of the laminated film is a value obtained by measuring the laminated film itself.

  In the laminated film of the present invention, when the retardation in the k-th layer from the surface layer is Re (k) and the total number of layers is n, the total retardation Re of the laminated film is represented by the following formula (1).

Meet. Equation (1) shows that the retardation of the entire laminated film obtained by using a commercially available measuring device is obtained by measuring and calculating the retardation of each layer individually, and adding the respective retardations to 0. It means less than 85 times. More preferably, the retardation of the laminated film is preferably half or less of the total value of the retardation of each layer. Here, when measuring the phase difference of each layer, the film which peeled each layer and became a single film may be measured with a commercially available measuring device, or the surface layer as disclosed in JP-A-2014-149346, You may measure after grind | polishing with the abrasive cloth for plastics and making each layer into a single layer.

  In the laminated film of the present invention, Re needs to be 400 nm or less. In a film intended to be used via a polarizer, when the retardation value is increased, an interference color corresponding to the retardation is generated when mounted on a liquid crystal display, which causes a problem in that the quality is lowered. Here, if the phase difference is 400 nm or less, the generation of such interference colors can be suppressed. More preferably, it is 200 nm or less, More preferably, it is 100 nm or less. As the value of the phase difference decreases, interference colors are less likely to occur when mounted as a polarizer protective film on a liquid crystal display, which is preferable.

  In addition, the phase difference of the film greatly increases as the incident angle is changed. A phase difference at an incident angle of 50 ° is referred to as a thickness direction phase difference. When the thickness phase difference exceeds 300 nm, rainbow unevenness is observed, and therefore the thickness phase difference is preferably 300 nm or less. More preferably, it is 200 nm or less, More preferably, it is 150 nm or less.

  In the present invention, the total value ΣRe (k) of the retardation of each layer is lower than the total value of the laminated film. Conventionally, the retardation of the laminated film shows the same value as the total value of the respective retardations when the orientation axes of the respective layers are substantially coaxial. On the other hand, when the angle formed by the main alignment axis of the A layer and the main alignment axis of the B layer is 20 ° or more, the phase difference of each layer is not a simple addition, but shows a low value. The subtraction effect works and the retardation of the laminated film becomes lower. Therefore, in this invention, it is preferable that the angle which the main orientation axis | shaft of A layer and the main orientation axis | shaft of B layer which are contained in a laminated film make is 60-120 degrees. Within this range, the main alignment axis of the A layer and the main alignment axis of the B layer are orthogonal to each other, and therefore the phase difference between the A layer and the B layer is subtracted (in the present invention, the main layers of the A layer film and the B layer film are subtracted). The case where the inclination of the orientation axis is in the range of 60 to 120 ° is referred to as “orthogonal”). More preferably, the angle is 80 to 100 °, and in this way, the effect of subtracting the phase difference between the A layer and the B layer becomes very high.

  In the laminated film of the present invention, the inclination of the main orientation axis with respect to the film longitudinal direction is preferably 30 to 60 °. When the inclination of the main alignment axis with respect to the longitudinal direction of the film is 30 to 60 °, it becomes possible to supply a film having a circularly polarized light of λ / 4 by roll-to-roll, so that productivity is greatly improved. . More preferably, it is 40 to 50 °, and the effect of circularly polarized light becomes the highest.

  In the laminated film of the present invention, the retardation unevenness in the film width direction is preferably 50 nm / 200 mm or less. If the retardation unevenness in the film width direction is larger than 50 nm / 200 mm, it is not preferable because the interference color and brightness unevenness are conspicuous due to the difference in the location in the width direction when used for a large screen display. A more preferred value is 30 nm / 200 mm or less, and even more preferred is 10 nm / 200 mm or less. Moreover, the film longitudinal direction is a traveling direction of the film in the film forming process, and the width direction is a direction inclined by 90 ° from the longitudinal direction.

  In the laminated film of the present invention, the retardation unevenness in the film width direction of the A layer and the B layer is preferably 30/200 mm or more. When the retardation unevenness in the film width direction is smaller than 30/200 mm, it is difficult to set the inclination of the main alignment axis with respect to the film longitudinal direction to 30 to 60 ° in the biaxial stretching step.

  In the laminated film of the present invention, the absolute value of the difference in Young's modulus between the longitudinal direction and the width direction of the A layer and the B layer is preferably 1.5 GPa or less. If the absolute value of the difference between the Young's modulus in the longitudinal direction and the width direction is larger than 1.5 GPa, the anisotropy is too strong and the heat shrinkage rate is increased, which is not preferable.

  The laminated film of the present invention is composed of two or more layers having an inclination of the main orientation axis with respect to the film longitudinal direction of 30 to 60 °, and the angle formed by the main orientation axis of the A layer and the main orientation axis of the B layer is 60 to 120. Since it is difficult to achieve the temperature by simultaneously laminating the A layer and the B layer during melt film formation, it is preferable that the A layer and the B layer are laminated via an adhesive layer.

  A preferred method for producing the laminated film of the present invention will be described. The laminated film of the present invention bonds the wound film (A) and the wound film in a biaxial stretching process so that the traveling direction (also referred to as the film forming direction) is reversed. Step (B) is taken. In addition, as long as the effect of this invention is not inhibited between the process A and the process B, or after the process B, arbitrary processes may be included.

(Process A)
Step A performs biaxial stretching and heat treatment on the unstretched film. The stretching in the longitudinal direction is usually performed by the difference in the peripheral speed of the roll. This stretching may be performed in one stage, or may be performed in multiple stages using a plurality of rolls. The draw ratio is within a range in which tearing does not occur due to thickness unevenness or a lateral magnification described later. Although the draw ratio varies depending on the resin used, it is preferably carried out in the range of 2.5 to 6.5 times from the viewpoint of productivity. Moreover, as extending | stretching temperature, the range of the glass transition temperature-glass transition temperature +60 degreeC of outermost layer resin which comprises a laminated | multilayer film is preferable. Next, the film is passed through a tenter and stretched in the width direction. The draw ratio at this time is within a range where thickness unevenness and tearing do not occur, and the refractive index difference (Δn: longitudinal direction refractive index−width direction refractive index) at the center in the film width direction is expressed by the following formula (3). Is preferably satisfied.
(3) -0.02>Δn> 0.03
When Δn is in this range, the orientation in the longitudinal direction and the width direction is isotropic, so that bowing is likely to occur remarkably by heating, and the range of the orientation angle of 30 to 60 ° in the width direction is widened. FIG. 1 shows the retardation and orientation angle distribution in the width direction of polyethylene terephthalate having a thickness of 15 μm and a width of 2700 mm formed under the condition of −0.02>Δn> 0.03 (for convenience, the central portion in the width direction). Is 0, the right hand direction is +, and the left hand direction is-). When Δn is lower than −0.02, it is not preferable because bowing is less likely to occur due to heating (FIG. 2). On the other hand, when Δn is larger than 0.02, bowing occurs remarkably, but the region where the orientation angle is larger than 60 ° in the width direction becomes wider (FIG. 3). A range of −0.015>Δn> 0.015 is more preferable, and bowing is more likely to occur.

  The transverse stretching is preferably performed by step-temperature stretching or onion stretching. In normal transverse stretching, the temperature of the stretching zone is set to be constant, but in stepwise temperature rising stretching, the tenter zone is divided into several sections, and the temperature is gradually raised and stretched. In addition, while normal straight stretching increases the stretch ratio in proportion to the ratio of the stretch section length L (FIG. 4), onion stretching is a method of increasing the stretch ratio at the beginning of the stretch section length. (FIG. 5) It is preferable to satisfy | fill the following formula | equation (4).

(4) Xl ≧ X0 + a × (X−X0) × Ll / L (a ≧ 1.1)
L: Stretching section length at the end of transverse stretching, Ll: Stretching section length X: Film width at the end of transverse stretching, X0: Film width at the start of transverse stretching X: Film width at the stretching section length Ll At this time, constant a Is preferably 1.1 or more, more preferably 1.2 or more. In onion stretching, it is preferable that the transverse stretching temperature (T0) at the start of stretching and the transverse stretching temperature (T) at the end of stretching satisfy the following formula (5).

(5) 60>T2-T1> 15
FIG. 6 shows the distribution of retardation and orientation angle in the width direction of the biaxially stretched film satisfying (3), (4), and (5). In FIG. 1, the distribution of the orientation angle was V-shaped, but satisfying (4) and (5) is more preferable because the region with the orientation angle of 30 to 60 ° spreads in the width direction. Further, such a transverse stretching method is preferable because the distribution shape of the orientation angle hardly changes even if a heat treatment is performed thereafter. Biaxial stretching is not limited to either simultaneous biaxial stretching or sequential biaxial stretching, but sequential biaxial stretching is preferred because the orientation angle distribution of FIG. 6 is easier to form. In the case of a crystalline resin, the film is preferably heat-treated at a temperature not lower than the transverse stretching temperature to a melting point of -20 ° C., since the film strength, surface uniformity, and thermal dimensional stability are maintained. After the heat treatment, it is gradually cooled and then cooled to room temperature and wound up.

(Process B)
In step B, the film obtained in step A is cut and laminated. As shown in FIG. 6, two film rolls having a width direction distribution in which the inclination of the main orientation axis with respect to the film longitudinal direction is 30 to 60 ° are prepared, and one of the films is rewound to reverse the traveling direction of the film. (For convenience, here, a non-rewinded film is referred to as an A-layer film, and a rolled-up film is referred to as a B-layer film). As shown in FIG. 7, the A layer film and the B layer film are laminated by roll-to-roll (FIG. 7). The laminate material used at this time is not particularly limited, but a member having excellent transparency is preferable. A method of pressure bonding with an optical transparent pressure-sensitive adhesive sheet (OCA) that is not affected by curing shrinkage is preferable to an adhesive (OCR) that is cured with heat, moisture, ultraviolet rays, etc. with a liquid resin.

  The laminated film thus obtained has a distribution in the width direction of the orientation angle and retardation as shown in FIG. The width direction center part (-300-300 mm) and edge part (-1200 mm or less, and 1200 mm or more) of this film were trimmed and removed, and the obtained two laminated films had a wide orientation angle of 30 to 60 °. And the phase difference is substantially uniform (FIG. 9). This is because, when the A layer film and the B layer film are overlapped, the main orientation axis is almost orthogonal except for the center and end in the width direction, so that the phase difference is almost simply subtracted. If the A-layer film and the B-layer film are the same film, the retardation unevenness in the width direction is also the same.

  In this manufacturing method, it is important that one of the films to be bonded is laminated with the traveling direction of the film reversed. As shown in FIG. 10, when laminating films having the same traveling direction without rewinding, the main alignment axes of the films are overlapped, so that the phase difference is added and the retardation in the width direction is deteriorated (FIG. 11). The film to be bonded is effective as long as it satisfies the expression (3), but in particular, if the film is made by a method that satisfies the expressions (4) and (5), the retardation of the film This is a preferable form because the subtraction effect is high.

  By passing through the said process (A) (B), the film which satisfy | filled all the structures of the following this invention is obtained.

  In the above description, a method of laminating using a full width film as it is is shown, but the present invention is not particularly limited. The roll film obtained in step A is first trimmed at the center and end, and the two roll films obtained are reversed in the traveling direction by rewinding one of the two roll films, and the same method is used for bonding. Since a sample can be obtained, the order of the steps may be arbitrarily changed (FIG. 12). In any case, in any method, it is essential to laminate the direction of travel reversed. FIG. 13 shows a schematic diagram when the films obtained by trimming the center part are laminated without rewinding. Although the orientation angles of the two films are orthogonal to each other, the phase difference is subtracted, but the phase difference is not subtracted evenly, so that the phase difference unevenness in the width direction is not eliminated as a result (FIG. 14).

  Since the above method is a method of eliminating the unevenness in the width direction phase difference by laminating the films, the main orientation axes of the A layer and the B layer are completely orthogonal and have the same phase difference over the entire width. If so, a laminated film having zero retardation over the entire width can be obtained. In reality, however, there are thickness unevenness, retardation unevenness and orientation angle unevenness in the flow direction and width direction of the film. Therefore, it is more preferable to take a process of reducing the thickness unevenness in order to reduce the width direction retardation unevenness and a method of making the orientation angle uniform in the width direction in order to enhance the effect of the present invention. Moreover, since the area | region to cut and discard is also reduced, it is preferable also in terms of cost.

  Since the phase difference is determined by the product of birefringence and thickness, it is also preferable to bond the A layer and the B layer having different thicknesses and birefringences. FIG. 15 shows the distribution in the width direction when PET films having a thickness of 20 μm and a thickness of 15 μm are bonded together by the same method. FIG. 16 shows the distribution in the width direction when films having a thickness of 15 μm having different heat treatment temperatures are bonded together. As shown in FIGS. 15 and 16, it is possible to adjust the phase difference by using films having different thicknesses or birefringence. On the other hand, since films having different thicknesses and heat treatment temperatures have slightly different orientation angle unevenness in the width direction and retardation distribution tendency, the larger the difference in retardation between the A layer and the B layer, the more final the film. The width direction retardation unevenness of the laminated film obtained tends to increase, and the usable film width is narrowed. Therefore, the difference in thickness of the films to be bonded is preferably within 10 μm, and the difference in heat treatment temperature is preferably within 30 ° C. The retardation of the laminated film finally obtained by bonding is 150 or less, more preferably 70. The following is preferable.

  The resin used in the present invention is not particularly limited as long as it has a state that can be melt plasticized, and may be any of a thermoplastic resin, a thermosetting resin, and a photocurable resin, and a single repeating unit. The resin may be a copolymer, or may be a copolymer or a blend of two or more resins. Here, as a case where a thermosetting resin or a photocurable resin can be used, there is a case where there is a state where it can be melt-plasticized before curing. More preferably, a thermoplastic resin is used because of good moldability. Moreover, the resin of A layer and B layer does not need to be the same, Different resin may be sufficient.

  Examples of thermoplastic resins include polyolefin resins such as polyethylene, polypropylene, polystyrene and polymethylpentene, alicyclic polyolefin resins, polyamide resins such as nylon 6 and nylon 66, aramid resins, polyethylene terephthalate, polybutylene terephthalate and polypropylene terephthalate. Polyester resin such as polybutyl succinate, polyethylene-2,6-naphthalate, polycarbonate resin, polyarylate resin, polyacetal resin, polyphenylene sulfide resin, tetrafluoroethylene resin, trifluorinated ethylene resin, trifluorinated ethylene chloride resin Fluorine resin such as tetrafluoroethylene-6-propylene copolymer resin, vinylidene fluoride resin, acrylic resin, methacrylic resin, polyacetal resin It can be used polyglycolic acid resin, polylactic acid resin and the like. It is preferable that the A layer and the B layer have a positive refractive index in the thickness direction. Here, having a positive refractive index means that there is a maximum value of the refractive index in the stretching direction of the film after biaxial stretching, and having a negative refractive index means that the refractive index is in the thickness direction of the film. The maximum value is present (also called negative intrinsic birefringence). Resins having a negative refractive index in the thickness direction are generally not preferred because of their poor biaxial stretchability. Examples of the resin having a negative refractive index include styrenic polymers. Moreover, it is preferable that it is resin provided with the drawability and followable | trackability which can endure shaping | molding. Among these, from the viewpoint of strength, heat resistance, and transparency, the A layer and the B layer are preferably polyester resins.

  In the present invention, the polyester refers to a homopolyester or a copolyester that is a polycondensate of a dicarboxylic acid component and a diol component. Here, typical examples of the homopolyester include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, and polyethylene diphenylate. In particular, polyethylene terephthalate is preferable because it is inexpensive and can be used in a wide variety of applications.

  Further, the copolyester is a resin in which two or more kinds of dicarboxylic acid components or diol components are used, or a resin in which a hydroxycarboxylic acid component is used in addition to the dicarboxylic acid component and diol component. Examples thereof include a polycondensate comprising at least three or more components selected from a component giving a dicarboxylic acid structural unit and a component giving a diol structural unit. Components having a dicarboxylic acid skeleton include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 4,4′-diphenyldicarboxylic acid. 4,4′-diphenylsulfone dicarboxylic acid, adipic acid, sebacic acid, dimer acid, cyclohexanedicarboxylic acid and ester-forming derivatives thereof. Examples of the component having a glycol skeleton include ethylene glycol, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentadiol, diethylene glycol, polyalkylene glycol, and 2,2-bis. (4′-β-hydroxyethoxyphenyl) propane, isosorbate, 1,4-cyclohexanedimethanol, spiroglycol and ester-forming derivatives thereof. In the present invention, the retardation when observed from the front can be arbitrarily changed, but the retardation in the thickness direction when the incident angle is inclined cannot be reduced. It is preferable because the directional phase difference can be reduced. In particular, it is more preferable that the heat treatment temperature is set higher than the melting point of the copolyester because orientation relaxation proceeds. Further, it is more preferable that the copolyester is an amorphous polyester. In the case of amorphous polyester, crystallization does not occur even after heating after orientation relaxation, and thus it is difficult to whiten by heating. The amorphous polyester needs to have a heat of crystal melting of less than 1 mJ / mg when the temperature is raised at a rate of temperature increase of 5 ° C./min in the differential calorimetry (DSC) from the polyesters described above. In particular, a copolyester obtained by polycondensation using three or more dicarboxylic acid components and diol components is preferable.

  The amorphous polyester is preferably a polyester containing isophthalic acid as a copolymerization component. Polyesters containing isophthalic acid can reduce crystallinity and can easily suppress retardation, and the refractive index in the thickness direction does not easily decrease even when biaxially stretched. Rainbow irregularities are less likely to occur when the corner is changed. A preferable copolymerization amount of isophthalic acid is 5 mol% or more and 35 mol% or less in the total carboxylic acid component. If it is less than 5 mol%, there is no effect, and if it exceeds 35 mol%, polymerization becomes difficult.

  In applications where heat resistance and low heat shrinkage are required, the glass transition temperature of the amorphous polyester is preferably high, preferably 85 ° C. or higher, more preferably 90 ° C. or higher, and particularly preferably 105 ° C. or higher. . Moreover, although the upper limit of glass transition temperature is not specifically limited, Usually, it is 130 degrees C or less. Commercially available raw materials can be preferably used as the amorphous polyester resin. For example, trade name: “ALTERSTER” (manufactured by Mitsubishi Gas Chemical Co., Ltd., using spiroglycol), trade name: “TRITAN” (EASTMAN) (Chemical Co., Ltd., 2,2,4,4-tetramethyl-1,3-cyclobutanediol is used), and product name: “ECOZEN” (SK Chemical Co., Ltd., uses isosorbide) Can do.

  In the laminated film of the present invention, the number of laminated layers is not particularly limited as long as the effects of the present invention are not impaired, but the number of laminated layers via the adhesive layer is preferably between 2 and 5. Among them, at least two layers included in the laminated film need to have orthogonal orientation axes.

  The thickness of the laminated film of the present invention is not particularly limited, but is preferably in the range of 10 to 300 μm from the viewpoints of handleability and functionality. Further, as the film thickness increases, the thickness direction retardation increases, and rainbow unevenness is easily observed when the incident angle is changed. Therefore, a more preferable thickness is in the range of 10 to 100 μm. Moreover, in the use of a polarizer protective film, it is advantageous that the film thickness is thinner in order to reduce the retardation and to make the panel thin, and the preferred film thickness is 10 to 25 μm. Moreover, since the scattering prevention function is required as an ITO base material film for touch panels, the film thickness of 20-200 micrometers is preferable.

  Although the laminated film of the present invention can be freely set in thickness, it has a low phase difference, and the main orientation axis is inclined from the longitudinal direction, which may cause a blackout phenomenon when wearing sunglasses. And can be used for retardation films and polarizer protective films. As the polarizer, for example, a PVA sheet prepared by containing iodine in a commercially available PVA and orienting it can be used. The laminated film of the present invention is preferably bonded to a polarizer and used as a polarizing plate.

  Moreover, when using for a polarizer protective film, it is preferable that the transmittance | permeability of 250-380 nm is 30% or less. More preferably, it is 15% or less. The reason why ultraviolet light with a wavelength of 250 to 380 nm is required is to suppress the deterioration of the polarizer in the polarizing plate. The polarizer has a function of transmitting light having only a specific vibration direction, and a polyvinyl alcohol (PVA) film dyed with iodine or a dichroic dye is most frequently used. Since this polarizer is made of an organic material, there is a problem that it is easily deteriorated by ultraviolet rays. In particular, since deterioration occurs due to irradiation with ultraviolet rays having a wavelength of 250 to 380 nm, it is possible to prevent deterioration of the polarizer or liquid crystal by shielding the ultraviolet light in this region before reaching the polarizer. It becomes possible. In addition, when a fluorescent tube is used as the backlight of the image display device, the polarizing plate is directly irradiated with light from the fluorescent tube of the backlight. Become. As a mechanism for shielding light, it is preferable to reflect ultraviolet light by a multilayer structure. The setting of the reflection wavelength is determined by the layer thickness of each layer of the multilayer laminated film as described above. Absorption may be used in addition to reflection. When utilizing light absorption, you may add to the A layer containing the outermost layer of the laminated biaxially stretched film which is a preferable aspect of this invention, the B layer which is an inner layer, or both. Among these, it is most preferable to contain the ultraviolet absorber only in the B layer. When an ultraviolet absorber is added to the outermost layer, the phenomenon that the added ultraviolet absorber is deposited on the film surface and the phenomenon that it is volatilized easily occurs. It is not preferable because it has a negative effect. By adding only to the inner layer, the outermost layer plays a role as a lid for preventing the volatilization of the UV absorber, so that the precipitation phenomenon is less likely to occur.

  As the ultraviolet absorber contained in the film, an organic ultraviolet absorber is preferable. Inorganic ultraviolet absorbers are not preferable because they are incompatible with the base resin and lead to an increase in haze, leading to a reduction in visibility when liquid crystal is displayed.

  Examples of the organic ultraviolet absorber to be added include salicylic acid type, for example, phenyl salicylate, t-butylphenyl salicylate, p-octylphenyl salicylate, benzophenone type, for example, 2-hydroxy-4-benzyloxy Benzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-octoxybenzophenone, 2-hydroxy-dodecyloxybenzophenone, 2-2'-dihydroxy-4-methoxybenzophenone, 2,2 '-Dihydroxy-4,4'-dimethoxybenzophenone and the like, benzotriazole series, for example, 2- (2'-hydroxy-5'-t-octylphenyl) benzotriazole, 2- (2'-hydroxy-5'-t -Methylphenyl) benzotriazo 2- (2'-hydroxy-3 ', 5'-di-t-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5 Chlorobenzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) 5-chlorobenzotriazole, etc., natural product systems (for example, oryzanol, shea butter, baicalin etc.), biological systems ( Examples thereof include keratinocytes, melanin, urocanin, and the like. These organic ultraviolet absorbers can be used alone or in combination of two or more. These organic ultraviolet absorbers can be used in combination with hindered amine compounds as ultraviolet stabilizers.

  The content of the ultraviolet absorber is preferably 2.0 wt% or less, more preferably 1.00 wt% or less, even when added to both the A layer and the B layer. More preferably, it is 0.60 wt% or less.

  In addition, in polyester, various other additives other than ultraviolet absorbers, such as antioxidants, heat stabilizers, weather stabilizers, organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, charging agents. An inhibitor, a nucleating agent, or the like may be added to such an extent that the film properties that should be originally satisfied are not deteriorated.

  Moreover, it is preferable that the laminated | multilayer film of this invention are used also for the film for touch panels. The touch panel may be any of a resistance film type, an optical type, and a capacitance type. Capacitance type can be roughly divided into projection type and surface type. From the viewpoint of enabling multi-touch, the projection capacitance type is most preferable. The conductive layer is made of metal such as gold, silver, platinum, palladium, rhodium, indium, copper, aluminum, nickel, chromium, titanium, iron, cobalt, tin, and alloys thereof, tin oxide, indium oxide, titanium oxide, It can be formed by a composite film such as a metal oxide film such as antimony oxide, zinc oxide, cadmium oxide, indium tin oxide (ITO), or copper iodide. A thin film can be obtained from these transparent conductive films by vacuum deposition, sputtering, reactive RF ion plating, spray pyrolysis, chemical plating, electroplating, CVD, coating, or a combination thereof. In addition, as the conductive polymer, polypyrrole, polyaniline, polyacetylene, polythiophene, polyphenylene vinylene, polyphenylene sulfide, poly-p-phenylene, polyheterocycle vinylene, particularly preferably (3,4-ethylenedioxythiophene) ) (PEDOT). In addition, carbon nanotubes and nano silver are preferable because they exhibit high conductivity. These can be applied to a substrate by a coating method by dissolving in an organic solvent. As the coating method, various methods can be adopted in the same manner as the hard coat layer method. From the viewpoint of versatility, ITO is preferable.

  The out-cell type touch sensor is roughly classified into a glass sensor and a film sensor. Glass sensor types include GG, GG2, G2, and G1M. GG is cover glass / ITO / glass / ITO, GG2 is cover glass / glass / ITO / insulating layer / ITO, G2 (OGS) is cover glass / ITO / insulating layer / ITO, G1M is cover glass / ITO Is a basic configuration.

  From the viewpoint of scattering prevention, the laminated film of the present invention is preferably used between the touch panel and the liquid crystal panel. In this case, the glass sensor type is particularly preferably used.

  On the other hand, as the film sensor type, there are GFF, GF2, G1F, GF1, PFF, and PF1, and any of them may be used. GFF is cover glass / ITO / film / ITO / film, GF2 is cover glass / ITO / film / ITO, or cover glass / ITO / insulating layer / ITO / film, and G1F is cover glass / ITO / ITO. / Film, GF1 is a cover glass / ITO / film, PFF is a cover plastic / ITO / film / ITO / film, P1M cover plastic / ITO, and the laminated film of the present invention is made of ITO. It is preferable to use it as a supporting substrate film. When the film has a single film structure, such as GF1 and GF2, the laminated film structure of the present invention can be used as it is. However, when the film has two sheets, such as GFF, the touch panel has a structure of A The case where the layer and the B layer are incorporated independently is also included in the present invention. An example of the configuration is shown in FIG. 17 (the transparent adhesive sheet is omitted). In this configuration, one of the film rolls of the A layer and the B layer is rolled back, and the main orientation axes of the A layer and the B layer If they are orthogonal, the effect of the present invention is obtained. Moreover, it can be used as a λ / 4 retardation film, not an ITO base film. FIG. 18 shows an example of the configuration (the transparent adhesive sheet is omitted). Even in this case, the main orientation axes of the A layer and the B layer need to be orthogonal to each other. Since the film at this time requires handling and anti-scattering functions, a film thickness of 20 to 200 μm is required. However, the laminated film of the present invention can have a low retardation regardless of the thickness. No coloring or rainbow unevenness occurs.

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

(1) Layer thickness, number of layers, and layered structure The layer structure of the film was determined by observing with a transmission electron microscope (TEM) a sample obtained by cutting a section using a microtome. That is, using a transmission electron microscope H-7100FA type (manufactured by Hitachi, Ltd.), a cross-sectional photograph of the film was taken under the condition of an acceleration voltage of 75 kV, and the layer configuration and each layer thickness were measured. In some cases, a staining technique using RuO ₄ or OsO ₄ was used to increase the contrast. Also, in accordance with the thickness of the thinnest layer (thin film layer) among all the layers that can be captured in one image, when the thin film layer thickness is less than 50 nm, the thin film layer thickness is 50 nm or more and 500 nm. When it was less than 40,000 times, and when it was 500 nm or more, observation was carried out at a magnification of 10,000 times.

(2) Total retardation of laminated film / retardation of each layer film The retardation was measured by using an Oji Scientific Instruments Co., Ltd. "KOBRA-21ADH" at 200 mm intervals from the center of the film to both ends. The phase difference at a wavelength of 590 nm at 0 ° was measured. The average phase difference is expressed as an average value of all measurement points. The total retardation of the laminated film is expressed as an average retardation obtained by measuring the laminated film as it is. The phase difference of each layer film is expressed by the average phase difference after peeling off each layer of the laminated film and removing the adhesive layer with methyl ethyl ketone and the like, measuring the phase difference in a single layer state.

(3) Phase difference unevenness The method for measuring the phase difference unevenness conforms to (2). The phase difference is measured at intervals of 200 mm from the center of the width of the film to both ends, and the difference between the largest value and the smallest value is defined as retardation unevenness.

(4) Orientation angle The method for measuring the orientation angle conforms to (2). A measurement sample is set in the apparatus so that the film width direction is an angle defined by the measurement apparatus of 0 °, and a wavelength of 590 nm at an incident angle of 0 ° is set at an interval of 200 mm from the center to the both ends of the width of the film. The orientation angle was measured. The largest value is the maximum orientation angle, and the smallest value is the minimum orientation angle. In addition, when measured with KOBRA, the orientation angle is output as a value of +90 to -90 °, but all are converted into positive numbers.

(5) Inclination of main alignment axis The method of measuring the inclination of the main alignment axis is in accordance with (4). The film longitudinal direction is set so that the angle defined by this measuring device is 0 °, the orientation angle of the films of the A layer and the B layer is measured, and the absolute value of the difference between the orientation angles of the A layer and the B layer Is the inclination of the main orientation axis. On the other hand, the orientation angle measured here is calculated without converting a negative number into a positive number.

(6) Calorie melting calorie / glass transition temperature The DSC curve of the measurement sample was measured according to JIS-K-7122 (1987) using differential calorimetry (DSC). In the test, the temperature was raised from 25 ° C. to 290 ° C. at 5 ° C./min, and the glass transition temperature and the heat of crystal melting at that time were measured. Two inflection points in the range of 40 to 140 ° C. were connected by a tangent line, and the intermediate point was defined as the glass transition temperature of the B layer.
Equipment: “Robot DSC-RDC220” manufactured by Seiko Electronics Industry Co., Ltd.
Data analysis "Disc Session SSC / 5200"
Sample mass: 5 mg.

(7) Heat resistance whitening The film was treated in an oven at 100 ° C. for 24 hours and then cooled to room temperature. A case where the change in haze value before and after the heat treatment was less than 3% was given as ◯, and a case where it was 3% or more was taken as x.

(8) Thermal contraction rate A film sample having a width direction of 150 mm and a longitudinal direction of 150 mm was collected from the central portion in the width direction of the film roll. A pair of marks was placed at the center of each sample so that the original length (L0) was 100 mm apart in each of the longitudinal direction and the width direction. The sample was heat-treated in an oven at 150 ° C. for 30 minutes and then cooled to room temperature, and the distance between the pair of marks was measured to obtain the length after treatment (L1). The thermal contraction rate in each position and direction was calculated according to 100 × (L0−L1) / L0. The average value of the obtained results was calculated for each of the longitudinal direction and the width direction to obtain the heat shrinkage rate of the film.

(9) Lightness unevenness in the width direction A polarizing film is orthogonally crossed on the LED trace board so as to be crossed Nicol. The laminated film is sandwiched between the polarizing films so that the longitudinal direction is 45 ° from the polarizing axis of the polarizing film. When the incident angle at this time was observed from directly above, it was determined by the following determination method.
A: There is almost no difference in brightness from the center to the end.
B: There is a slight difference in brightness from the center to the end.
C: A difference in brightness can be clearly confirmed from the center to the end.

(10) Visibility Samples were prepared by the same method as in (9), and coloring when the incident angle was observed from directly above and when tilted by 40 ° was determined by the following determination method.
A: Coloring is not seen at all even directly above and at 40 ° tilt observation.
B: Although there is no coloring when observed from right above, a slightly yellow coloring is observed when observed at a tilt of 40 °.
C: There is no coloration when observed from directly above, but yellow to pink color is observed when observed at 40 ° tilt. D: Clear color is observed even when observed directly above and at 40 ° tilt.

(11) A Young's modulus film is cut into a width of 10 mm × 200 mm, held with a chuck in the longitudinal direction, and stretched at a pulling speed of 100 mm / min with an Instron type tensile tester (Instron ultra-precision material tester MODEL 5848). did. The average Young's modulus obtained with n number of 5 was determined.

(12) Refractive index The refractive index of each layer film in the longitudinal direction (Nm), the width direction (Nt), and the thickness direction (Nz) was measured with an Atago Abbe refractometer NAR-1T. It is determined that Nm> Nz and Nt> Nt have a positive refractive index, and Nm <Nz and Nt <Nt have a positive refractive index.

Example 1
Polyethylene terephthalate (PET) having a melting point of 258 ° C. and a crystal melting heat of 40 mJ / mg was used, put into a single screw extruder, melted at 280 ° C., kneaded, and extruded from a die. The molten sheet extruded from the die was adhered and solidified by electrostatic application to a rotating drum cooled to 25 ° C. to obtain a smooth cast film. The obtained cast film was heated in a roll group set to a preheating roll of 65 ° C. and a drawing roll of 85 ° C., and then rapidly heated from both sides of the film by a radiation heater between the drawing section lengths of 100 mm. The film was stretched 3 times and then cooled once. This uniaxially stretched film was guided to a tenter, preheated with hot air at 100 ° C., and then stretched 3.4 times in the film width direction at a temperature of 110 ° C. The stretching section here was divided into three sections, and the stretching ratio and stretching temperature were as shown in Pattern 1 in Table 1. The stretched film is directly heat-treated in a tenter with hot air of 215 ° C., then subjected to a relaxation treatment of 3% in the width direction at the same temperature, and then gradually cooled to room temperature, wound up, and 2800 mm in width. A layer film having a thickness of 25 μm was obtained. Moreover, let the film obtained by rewinding a part of A layer film be a B layer film.

  As shown in FIG. 5, the A layer film and the B layer film were laminated with a transparent adhesive sheet (LUCIACS manufactured by Nitto Denko Corporation). The obtained laminated film had a width of 2800 mm, a central portion of 600 mm and both end portions were trimmed and removed by 200 mm to obtain two laminated films having a width of 900 mm.

  The phase difference of the full width other than the trimmed part was measured using KOBRA. The results are shown in Table 2. The orientation angle was 28 to 56 ° over the entire width, and by laminating the A layer film and the B layer film that had been rolled back, the retardation and retardation unevenness of the entire width were small. As for visibility, although coloring was not seen when observed from the front, coloring was conspicuous when the incident angle was tilted.

(Example 2)
The transverse stretching conditions were the same as in Example 1 except that the conditions were as shown in Pattern 2 of Table 1. The results are shown in Table 2. The orientation angle was 30 to 52 ° over the entire width, and by laminating this film, the retardation and retardation unevenness of the entire width were small. Compared with Example 1, the retardation unevenness was slightly improved.

(Example 3)
The transverse stretching conditions were the same as in Example 1 except that the conditions were as shown in Pattern 3 of Table 1. The results are shown in Table 2. The orientation angle was 44 to 51 ° over the entire width, and by laminating this film, the retardation and retardation unevenness of the entire width were also reduced. Compared with Example 2, the phase difference and the phase difference unevenness were improved.

(Comparative Example 1)
The transverse stretching conditions were the same as in Example 1 except that the conditions were as shown in Pattern 4 of Table 1. The results are shown in Table 2. Since most orientation angles in the film width direction are less than 30 °, even when this film is laminated, the retardation is hardly subtracted, so that the retardation of the entire width and retardation unevenness are significantly worse than those of Example 1. In addition, the color unevenness was severely unusable.

Example 4
The transverse stretching conditions were the same as in Example 1 except that the conditions were as shown in Pattern 5 of Table 1. The results are shown in Table 2. By laminating this film, the full width retardation and retardation unevenness were reduced, but worse than Example 1. This is because there is a portion where the orientation angle is 23 to 49 and the orientation angle is less than 30 °, and therefore, the effect of subtracting the phase difference in that portion is considered to be low.
Even when this film was bonded, the effect of subtracting the retardation was low. In addition, the phase difference unevenness of the full width was slightly improved as compared with Comparative Example 2, but it was still poor, and the color unevenness was extremely unusable.

(Comparative Example 2)
Example 1 was the same as Example 1 except that the longitudinal draw ratio was 3.1 times and the transverse draw ratio was 3.7 times. Since the orientation angle is 0 to 7 ° over the entire width, the phase difference is added when this film is bonded, the phase difference of the entire width is greatly deteriorated as compared with Example 1, and the color unevenness cannot be used due to severe color unevenness. It was a thing.

(Example 5)
The same as Example 1 except that the thickness was 8 μm. The results are shown in Table 2. The orientation angle was 30 to 45 ° over the entire width, and by laminating this film, the retardation and retardation unevenness of the entire width were small. In addition, by reducing the film thickness, the thickness direction retardation also decreased, and the visibility was greatly improved.

(Example 6)
The same as Example 2 except that the thickness was 8 μm. The results are shown in Table 2. The orientation angle was 32 to 48 ° over the entire width, and by laminating this film, the retardation and retardation unevenness of the entire width were small. In addition, by reducing the film thickness, the thickness direction retardation also decreased, and the visibility was greatly improved.

(Example 7)
The same as Example 3 except that the thickness was 8 μm. The results are shown in Table 2. The orientation angle was 36 to 49 ° over the entire width, and by laminating this film, the retardation and retardation unevenness of the entire width were small. In addition, by reducing the film thickness, the thickness direction retardation also decreased, and the visibility was greatly improved.

(Comparative Example 3)
As shown in FIG. 8, without using a B layer film, it was the same as Example 7 except that a laminated film was obtained by laminating two A layer films. Although the orientation angle is 36 to 49 ° over the entire width, the phase difference is added because the orientation angles of the films to be bonded are aligned, and the retardation of the entire width is greatly deteriorated as compared with Example 7.

(Example 8)
The biaxially stretched film formed under the same conditions as in Example 7 was trimmed and removed from the width of 2800 mm by 600 mm at the center and 200 mm at both ends, thereby obtaining two biaxially stretched films. One of these is an A layer film, and the film obtained by winding the remaining one is a B layer film. As shown in FIG. 10, the A layer film and the B layer film were laminated with a transparent adhesive sheet (LUCIACS manufactured by Nitto Denko Corporation) to obtain a laminated film. The results are shown in Table 2. The orientation angle was 36 to 49 ° over the entire width, and by laminating this film, the retardation and retardation unevenness of the entire width were small.

(Comparative Example 4)
As shown in FIG. 11, without using the B layer film, it was the same as Example 8 except that a laminated film was obtained by laminating two A layer films. Although the orientation angle is 36 to 49 ° over the entire width, the orientation angles of the films to be bonded are aligned, so the phase difference is added, and the retardation of the entire width is greatly deteriorated compared to Example 8.

Example 9
PET in which 28 mol% of PET and cyclohexanedicarboxylic acid were copolymerized was used (hereinafter also referred to as PETG). Each resin was put into two single screw extruders, melted at 280 ° C., and kneaded. Next, each was merged into 3 layers with pinol, so that PET became the surface layer and PETG became the core layer. The lamination ratio (PET // PETG) at this time was adjusted to be 1 at the discharge amount. Otherwise, it was the same as Example 7. The results are shown in Table 3. The orientation angle was 46 to 54 ° over the entire width, and by laminating this film, the retardation and retardation unevenness of the entire width were small. Due to the use of amorphous polyester, the thickness direction retardation is lowered and the visibility is further improved.

(Example 10)
Example 9 was the same as Example 9 except that PET and PET obtained by copolymerizing 25 mol% of isophthalic acid having a melting point of 194 ° C. (hereinafter also referred to as PET / I-1) were used. The results are shown in Table 3. The orientation angle was 39 to 47 ° over the entire width, and by laminating this film, the retardation and retardation unevenness of the entire width were small. Moreover, since PET / I was used, the thickness direction phase difference also became low and visibility was further improved. On the other hand, heat resistance whitening property deteriorated because PET / I whitened by heating.

(Example 11)
Using PET and PET (hereinafter also referred to as PET / I-2) copolymerized with 12 mol% of isophthalic acid having a melting point of 224 ° C., the lamination ratio (PET // PET / I-2) was set to 0.5. Except for this, it was the same as Example 9. The results are shown in Table 3. The orientation angle was 36 to 51 ° over the entire width, and by laminating this film, the retardation and retardation unevenness of the entire width were small. Further, since the heat treatment temperature was lower than the melting point of PET / I-2, the heat resistance whitening property was improved as compared with Example 10.

(Example 12)
The same as Example 11 except that the thickness was 25 μm. As the thickness is increased, the phase difference and the visibility are deteriorated, but are significantly improved as compared with Example 3 having the same thickness.

(Example 13)
Example 7 was the same as Example 7 except that PET (hereinafter also referred to as PET / I-3) was copolymerized with 8 mol% of isophthalic acid having a melting point of 236 ° C. The results are shown in Table 3. The orientation angle was 40 to 52 ° over the entire width, and by laminating this film, the retardation and retardation unevenness of the entire width were small. Moreover, since the thickness retardation is low, there was no problem in visibility. On the other hand, the heat shrinkage rate slightly deteriorated because the film supportability was lowered.

(Example 14)
Polyethylene naphthalate having a melting point of 264 (hereinafter also referred to as PEN), PET (hereinafter referred to as PET / IS) copolymerized with 20 mol% of cyclohexanedimethanol and 14 mol% of isosorbate, and a lamination ratio (PEN // PET / IS−) The mixture was melted and kneaded at 280 ° C. with 1) being 0.5. After heating the obtained cast film with a roll group set to a preheating roll of 75 to 95 ° C. and a drawing roll of 135 ° C., the film is longitudinally heated while rapidly heating from both sides of the film with a radiation heater between 100 mm of the drawing section length. The film was stretched 3.3 times and then cooled once. This uniaxially stretched film was led to a tenter, preheated with hot air at 115 ° C., and stretched 3.35 times in the film width direction at a temperature of 110 ° C. The stretching section here was divided into three sections, and the stretching ratio and stretching temperature were as shown in pattern 3 in Table 1. The stretched film was directly heat-treated with hot air at 230 ° C. in a tenter. Otherwise, it was the same as Example 7. The results are shown in Table 3. The orientation angle was 33 to 49 ° over the entire width, and by laminating this film, the retardation and retardation unevenness of the entire width were small. Moreover, the thing with a low heat shrinkage rate was obtained by using resin with a high glass transition temperature.

(Example 15)
Except for using PEN and PET copolymerized with 15 mol% of cyclohexanedimethanol and 12% of 2,2,4,4-tetramethyl-1,3-cyclobutanediol (hereinafter also referred to as PET / TMCD). Same as Example 14. The results are shown in Table 3. The orientation angle was 30 to 46 ° over the entire width, and by laminating this film, the retardation and retardation unevenness of the entire width were small. Moreover, the thing with a low heat shrinkage rate was obtained by using resin with a high glass transition temperature.

(Example 16)
Example 14 was the same as Example 14 except that PET copolymerized with 45 mol% of PEN and spiroglycol (hereinafter also referred to as PET / SPG) was used. The results are shown in Table 3. The orientation angle was 40 to 48 ° over the entire width, and by laminating this film, the retardation and retardation unevenness of the entire width were small. Moreover, the thing with a low heat shrinkage rate was obtained by using resin with a high glass transition temperature.

(Example 17)
Example 8 was the same as Example 11 except that the 8 μm film obtained in Example 11 was used for the A layer film, and the film which had been rewound with a thickness of 12 μm was used for the B layer. The orientation angle was 36 to 51 ° over the entire width, and by laminating this film, a laminated film having a retardation of 50 was obtained while suppressing retardation unevenness.

(Example 18)
Example 11 is the same as Example 11 except that the film obtained in Example 11 was used for the A layer film, the transverse stretch ratio was 3.45 times, the heat treatment temperature was 235 ° C., and the film that had been rewound was used for the B layer film. Same as above. The orientation angle was 36 to 51 ° over the entire width, and by laminating this film, a laminated film having a retardation of 30 was obtained while suppressing retardation unevenness.

  In the examples and comparative examples, the raw materials used are all polyester resins, which are resins having a positive refractive index.

  The laminated film obtained by the production method of the present invention is used as a substrate for a protective film for a polarizer, a polarizing plate or a retardation plate, an ITO substrate for a touch panel, a glass scattering prevention film, an AR substrate, or an LCD organic display. It can be suitably used as a filter to be used. In particular, it is suitable as a protective film for polarizers, polarizing plates, and retardation plates, which are constituent members of large liquid crystal display devices.

1 Cover glass 2 Retardation film (A layer)
3 ITO film 4 ITO base film 5 Retardation film (B layer)
6 LCD module

Claims (12)

A laminated film in which at least two layers are laminated, having a biaxially oriented A layer and a B layer, laminated when the phase difference at the k-th from the surface layer is Re (k) and the total number of layers is n A laminated film, wherein the total retardation Re of the film satisfies formulas (1) and (2).

The laminated film is composed of two or more layers having an inclination of the main orientation axis with respect to the film longitudinal direction of 30 to 60 °, and the angle formed by the main orientation axis of the A layer and the main orientation axis of the B layer contained in the laminated film is It is 60-120 degrees, The laminated film of Claim 1 characterized by the above-mentioned. 3. The laminated film according to claim 1, wherein the retardation unevenness in the film width direction is 50 nm / 200 mm or less. The laminated film according to any one of claims 1 to 3, wherein the retardation unevenness in the film width direction of the A layer and the B layer is 30/200 mm or more. The laminated film according to any one of claims 1 to 4, wherein an absolute value of a difference in Young's modulus between the longitudinal direction and the width direction of the A layer and the B layer is 1.5 GPa or less. The laminated film according to any one of claims 1 to 5, wherein the A layer and the B layer are laminated via an adhesive layer. The laminated film according to claim 1, wherein the A layer and the B layer have a positive refractive index in the thickness direction. The laminated film according to any one of claims 1 to 7, wherein the A layer and the B layer are polyester resins. The laminated film according to claim 1, which is used for a polarizer protective film. The laminated film according to any one of claims 1 to 9, wherein the laminated film is used for a base film for a touch panel. 11. The optical display device according to claim 1, wherein a laminated film is used. A laminated film is used, The touch panel in any one of Claim 1 to 10 characterized by the above-mentioned.

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