KR20180113919A - Optical film, polarizing plate, display device, and method of manufacturing optical film - Google Patents

Abstract

An optical film is a film in which a slow axis is inclined by 10 to 80° with respect to one side of an appearance of the film in a film plane. When dimensional change ratios in a fast axis direction and a slow axis direction before and after leaving the optical film at 90°C for 120 hours are ΔDF (%) and ΔDL (%), respectively, the optical film satisfies 0%<=ΔD_F<0.5 and 0%<=ΔD_F<0% and the residual solvent amount is 60 ppm or less at the center end and both ends in a direction along the side.

Description

TECHNICAL FIELD [0001] The present invention relates to an optical film, a polarizing plate, a display, and a manufacturing method of the optical film.

The present invention relates to an optical film as an oblique stretched film, a polarizing plate provided with the optical film, a display provided with the polarizing plate, and a method for producing the optical film.

Conventionally, various methods for producing a warp stretched film by stretching a resin film in an oblique direction with respect to a width direction have been proposed. For example, in Patent Document 1, the resin film is unwound from a direction different from the winding direction of the stretched film, and both ends of the resin film are gripped and transported by the pair of wave earths. By changing the conveying direction of the resin film in the middle, the resin film is stretched in the oblique direction. Thereby, an oblique stretched film having a slow axis at a desired angle of more than 0 DEG and less than 90 DEG is produced in the longitudinal direction or the width direction.

The obliquely stretched film produced in this way can be applied to, for example, a circular polarizer for preventing reflection of external light in an organic EL (electroluminescence) display device. The circularly polarizing plate is a polarizer and an oblique stretched film, for example, so that the slow axis of the obliquely drawn film intersects the absorption axis (or transmission axis) of the polarizer at a desired angle (for example, 45 degrees) Roll-to-roll method. The productivity of the circularly polarizing plate is remarkably improved as compared with the batch formula in which the circularly polarizing plate is manufactured by joining the obliquely drawn film and the polarizer each having a predetermined size one by one by manufacturing the circularly polarizing plate in a roll to roll manner.

Japanese Patent Application Laid-Open No. 2010-173261 (refer to Claim 1, Fig. 1, etc.)

As a typical manufacturing method for producing a resin film (long film) serving as a base of an obliquely drawn film, a solution softening film forming method and a melt softening film forming method are known. In the solution casting film-forming method, a dope in which a resin and an additive are dissolved in a solvent is softened and dried on a metal support to stretch or maintain the width of the flexible film after peeling the flexible film (web) from the metal support, It is a method of obtaining a film. On the other hand, the melt soft film-forming method is a method in which a resin composition containing a resin and an additive is heated and melted to a temperature at which fluidity is exhibited, and then the melt having fluidity is softened to obtain a resin film.

When the polarizing plate is produced by obliquely stretching a resin film formed by the solution softening method and bonding the obtained obliquely drawn film to a polarizer, the polarizing plate can be obtained under a high temperature environment during bonding (for example, when an ultraviolet curable adhesive is used, When heated for accelerating curing, and when using an aqueous adhesive such as a water-soluble resin, the obliquely stretched film is stretched in the direction of the slow axis and the direction of the fast axis (perpendicular to the slow axis direction in the film plane) Direction). The reason for this is as follows.

The resin film formed by the solution soft film forming method has a lower resin density than the resin film formed by the melt soft film forming method. This is because, in the solution softening method, the solvent contained in the flexible film is evaporated by drying the flexible film after stretching, and a gap (space after the solvent evaporates and escapes) is generated in the film. The film having such a low resin density is liable to be easily stretched in the stretching direction (oblique direction (slow axis direction) with respect to the width direction) It is easy to extend in the direction as well. Therefore, after the oblique stretching, the film remains in tensile stress in both the slow axis direction and the fast axis direction. Under the high-temperature environment, since the tensile stress is relaxed, the film shrinks in both the slow axis direction and the fast axis direction.

Thus, under the high-temperature environment, when the warp stretched film shrinks in both the slow axis direction and the fast axis direction, the whole film undergoes dimensional change and shrinks. As a result, curling occurs in the polarizing plate bonded with the polarizer and the oblique stretched film, and the adhesiveness between the polarizer and the obliquely drawn film is reduced, and the obliquely drawn film is liable to be peeled off. As a result, in the organic EL display device to which the polarizing plate is applied, light leakage due to external light reflection occurs at the time of black display.

Further, even when the resin film formed by the melt soft-film formation method is obliquely stretched and the obtained obliquely stretched film is adhered to the polarizer to produce a polarizing plate, depending on the stretching conditions at the time of oblique stretching, The tensile stress remains in both directions in the fast axis direction, and under the high temperature environment at the time of bonding, the obliquely drawn film shrinks in both the direction of the slow axis and the direction of the fast axis, causing a dimensional change, , From various reviews.

On the other hand, in the liquid crystal display device, in order to allow the observer to attach the polarizing sunglasses and to observe the display image even when the head is tilted sideways even in the straight line state, a circular polarizing plate is arranged on the viewing side with respect to the liquid crystal layer There is also. In such a configuration, when curling occurs in the circularly polarizing plate due to the dimensional change of the obliquely drawn film under a high-temperature environment, distortion is generated in the image viewed through the circularly polarizing plate, and the visibility of the display image is lowered.

Therefore, in order to suppress light leakage due to reflection of external light in the organic EL display device and decrease in visibility of the display image in the liquid crystal display device for polarizing sunglasses, It is necessary to suppress the dimensional change of the stretched film as a whole. However, such a warp stretched film has not yet been proposed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and an object of the present invention is to provide an optical film as an obliquely stretched film capable of suppressing dimensional change under a high temperature environment, a polarizing plate comprising the optical film, And a display device.

The above object of the present invention can be achieved by the following arrangement.

1. An optical film in which a slow axis is inclined by 10 to 80 DEG with respect to one side of a film contour in a film plane,

When the optical film have been referred to as the fast axis direction and the rate of dimensional change of the slow axis direction in the before and after left to stand at 90 ℃ 120 hours, respectively ΔD _F (%) and ΔD _L (%), the central portion of the along the one side direction, And at both ends,

0%? D _F <0.5%

ΔD _L <0%

Lt; / RTI &gt;

Wherein the residual solvent amount is 60 ppm or less.

2. The optical film according to 1 above, wherein the residual solvent amount is 10 ppm or less.

3. The distances between the two points arranged in the fast axis direction of the optical film are a1 (mm) and a2 (mm), respectively, before and after the optical film is allowed to stand at 90 DEG C for 120 hours and,

When the distances between the two points arranged in the slow axis direction in the optical film are defined as b1 (mm) and b2 (mm) before and after the optical film is allowed to stand at 90 DEG C for 120 hours ,

? D _F = {(a2-a1) / a1} 100

DELTA D _L = {(b2-b1) / b1} x100

(1) or (2).

4. The dimensional change ratio in the fast axis direction before and after leaving the optical film at 90 占 폚 for 120 hours at the central portion in the direction along the above-mentioned side is referred to as? D _FC (%),

The dimensional change ratio in the fast axis direction before and after leaving the optical film at 90 占 폚 for 120 hours is referred to as? D _F-E1 (%) at one end in the direction along the above-

When the dimensional change ratio in the fast axis direction before and after leaving the optical film at 90 캜 for 120 hours is ΔD _F-E2 (%) at the other end in the direction along the above-mentioned side,

(? D _{F -E 1} +? D _{F -E} 2) / 2>? D _{F -C}

Wherein the optical film further satisfies the following conditional expression (1): &lt; EMI ID = 1.0 &gt;

5. The optical film has a long shape,

The optical film according to any one of 1 to 4 above, wherein the direction along the sides is a width direction perpendicular to the longitudinal direction within the film surface of the optical film.

6. An optical film comprising the optical film according to any one of 1 to 5 and a polarizer,

Wherein the optical film is located on one side with respect to the polarizer such that the slow axis in the film plane crosses the absorption axis of the polarizer.

7. A polarizing plate comprising the polarizing plate described in 6 above, and a display cell,

Wherein the polarizing plate is positioned on the viewing side with respect to the display cell.

8. The display device according to 7 above, wherein the optical film of the polarizing plate is positioned on the display cell side with respect to the polarizer.

9. The display device according to 8 above, wherein the display cell is an organic electroluminescence element.

10. The display device according to 7 above, wherein the optical film of the polarizing plate is located on the side opposite to the display cell with respect to the polarizer.

11. The display device according to 10 above, wherein the display cell is a liquid crystal cell.

12. A method for producing an optical film according to any one of 1 to 5,

The long film is held in a pair of gripping portions and one of the long strips is made to advance relative to the other of the waveguides so that the long film is bent and conveyed in the film surface, And an oblique stretching step of stretching the film in an oblique direction to obtain an obliquely stretched film constituting the optical film,

Before the oblique stretching, the force applied in the transport direction by each waveguide at each end in the width direction of the long film is referred to as the same Tr (N)

During the oblique stretching, the force applied in the transport direction by the waveguide on the relatively retarded side and the waveguide on the relatively preceding side at each end in the width direction of the long film is represented by To (N), Ti (N), &lt; / RTI &gt;

In the warp stretching step,

(Ti-Tr) /Tr?1.7

(Tr-To) /Tr? 1.5

Is stretched in the oblique direction so as to satisfy the following expression: &quot; (1) &quot;

13. The method for producing an optical film as described in 12 above, wherein the edge portion gripped by the waveguide on the relatively delayed side among the end portions in the width direction of the elongate film is cooled in the oblique stretching process.

14. In the oblique stretching step, the long film is obliquely stretched with respect to the width direction of the long film such that the slow axis is oriented at an orientation angle larger than a desired orientation angle, and thereafter, The method for producing an optical film according to the above 12 or 13, wherein the long film is subjected to oblique stretching so as to be oriented.

The optical film is a so-called warp stretched film in which the slow axis is inclined by 10 to 80 占 with respect to one side of the film contour in the film plane. The dimensional change rate? D _{F in the} fast axis direction and the slow axis direction in the center portion and both end portions in the direction along the above- And DELTA D _L , the optical film expands in the fast axis direction under high temperature environment, does not change in size, and shrinks in the slow axis direction. As described above, since the optical film does not shrink in the fast axis direction under a high temperature environment, the dimensional change (shrinkage) as a whole film can be suppressed even if shrinkage in the slow axis direction occurs under a high temperature environment.

This makes it possible to suppress curling of the polarizing plate due to dimensional change of the optical film and deterioration of the adhesiveness of the optical film to the polarizer even when polarizing plates are produced by bonding the polarizing film and the optical film at a high temperature . As a result, in the organic EL display device to which the polarizing plate is applied, occurrence of light leakage due to external light reflection during black display can be suppressed. In the polarizing sunglass-compatible liquid crystal display device to which the polarizing plate is applied, it is possible to suppress the occurrence of distortion in the image viewed through the polarizing plate, and to suppress deterioration of the visibility of the display image.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an explanatory view schematically showing a schematic configuration of an apparatus for producing an obliquely-drawn film according to an embodiment of the present invention. Fig.
2 is a plan view schematically showing an example of a rail pattern of a stretching portion provided in the manufacturing apparatus.
3 is a plan view showing the details of the configuration of the stretching portion.
4 is an exploded perspective view showing a schematic configuration of a polarizing plate.
Fig. 5 is a cross-sectional view showing an outline configuration of an organic EL display device.
6 is a cross-sectional view showing a schematic configuration of a liquid crystal display device.
7 is an explanatory view schematically showing the behavior of the adhesive and the optical film at the widthwise middle portion and the widthwise end portion of the adhesive when the adhesive is cured.
Fig. 8 is an explanatory view schematically showing the force in the transport direction applied to both end portions in the width direction of the elongate film in the stretching portion. Fig.
9 is an explanatory view schematically showing another configuration of the stretching portion.
Fig. 10 is an explanatory diagram schematically showing still another configuration of the stretching portion. Fig.

An embodiment of the present invention will be described with reference to the drawings as follows. In this specification, when numerical ranges are denoted by A to B, values of lower limit A and upper limit B are included in the numerical range. Further, the present invention is not limited to the following contents.

The obliquely drawn film according to the present embodiment may be a long oblong stretched film having an in-plane slow axis at an arbitrary angle with respect to the width direction of the stretched film by obliquely stretching the elongated resin film, And is a sheet-like warp stretched film obtained by cutting the stretched film along the width direction.

Herein, the term "long" refers to a length of at least about 5 times or more, preferably 10 times or more, with respect to the width of the film. Specifically, the film is wound in a roll form, Indicates length of conveyance. In the method of producing a long film, the film can be produced to a desired arbitrary length by continuously producing the film. In addition, a method of producing a long-shaped warp-stretched film is a method of winding a film having a long shape into a winding core (long film fabric) by winding it on a winding core once, To form an obliquely-stretched film. Alternatively, the oblong-oriented film may be continuously supplied from the film-forming step to the oblique-stretching step without winding the elongated film after film-forming. The film-forming step and the oblique stretching step are preferably carried out successively by feeding back the results of the film thickness and the optical value after stretching to change the film-forming conditions to obtain a warp-stretched film of a desired long shape.

In the method of producing an obliquely-drawn film according to this embodiment, a long oblique slope having a slow axis at an angle of more than 0 DEG and less than 90 DEG (for example, an angle of 10 to 80 DEG with respect to the width direction) To prepare a stretched film. Here, the angle of the film with respect to the width direction is an angle within the film plane. Since the slow axis is usually expressed in the stretching direction or the direction orthogonal to the stretching direction, in the manufacturing method according to the present embodiment, the stretching is performed at an angle of more than 0 DEG and less than 90 DEG with respect to the width direction of the film, A long oblong stretched film can be produced. The angle formed between the width direction and the slow axis of the oblong stretched film having a long shape, that is, the orientation angle can be arbitrarily set to a desired angle in a range of more than 0 DEG and less than 90 DEG. In the present embodiment, when "long film" is described, it refers to a resin film of a long shape before warping and stretching.

&Lt; About long film >

First, a long film to be drawn in this embodiment will be described.

The long film of the present embodiment is not particularly limited and may be any film composed of a thermoplastic resin. For example, when a stretched film is used for optical use, a resin having transparency to a desired wavelength Is preferred. Examples of such a resin include a polycarbonate resin (PC), a polyester resin, an olefin polymer resin having an alicyclic structure (cycloolefin resin, COP), a polyether sulfone resin, a polyethylene terephthalate resin, A polyimide resin, a polyamide resin, a polyarylate resin, a polyethylene resin, and a polyvinyl chloride resin.

The polycarbonate resin is a polymer of carbonic acid with glycol or dihydric phenol and having a carbonate bond of -O-CO-O-, and a polymer of bisphenol and carbonic ester is most practically used (Trade name, manufactured by Mitsubishi Engineering Plastics Co., Ltd.) (manufactured by Mitsubishi Chemical Industries, Ltd.), etc. . Of course, a polymer obtained by copolymerizing a monomer having a fluorene group (see, for example, Japanese Patent Application Laid-Open No. 2005-189632) exhibits an inverse wavelength dispersion of the retardation, and therefore such polycarbonate Can be used.

Examples of the polyester-based resin include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), and a polymer obtained by copolymerizing a monomer having a fluorene group with the monomer has an inverse wavelength dispersion of retardation. Polyesters can also be used favorably depending on the application.

As the polyethylene naphthalate resin, for example, polyethylene naphthalate prepared by polycondensation of a lower alkyl ester of naphthalene dicarboxylic acid with ethylene glycol can be suitably used. As commercially available products, Teonex (manufactured by Teijin Co., Ltd.) and the like can suitably be used.

The cycloolefin-based resin is not particularly limited as long as it is a resin having a unit of a monomer containing a cyclic olefin (cycloolefin). The cycloolefin-based resin may be either a cycloolefin polymer (COP) or a cycloolefin copolymer (COC). The cycloolefin copolymer means an amorphous cyclic olefin resin that is a copolymer of a cyclic olefin and an olefin such as ethylene.

As the cyclic olefin, a polycyclic cyclic olefin and a monocyclic cyclic olefin exist. Examples of such polycyclic cyclic olefins include norbornene, methyl norbornene, dimethyl norbornene, ethyl norbornene, ethylidene norbornene, butyl norbornene, dicyclopentadiene, dihydrodicyclopentadiene, Methyldicyclopentadiene, dimethyldicyclopentadiene, tetracyclododecene, methyltetracyclododecene, dimethylcyclotetradodecene, tricyclopentadiene, tetracyclopentadiene, and the like. Examples of the monocyclic cyclic olefin include cyclobutene, cyclopentene, cyclooctene, cyclooctadiene, cyclooctatriene, cyclododecatriene, and the like.

Examples of the cycloolefin resin are commercially available products such as "ZEONOR" manufactured by Nippon Zeon Co., "ARTON" manufactured by JSR Corporation, "TOPAS" manufactured by Polyplastics Co., and "APEL" manufactured by Mitsui Chemicals, Inc. .

In addition, as the resin constituting the long film, a resin composition described in Japanese Patent Application Laid-Open No. 2006-45369 or an alkoxynic acid ester polymer described in Japanese Patent Application Laid-Open No. 2016-108544 can be used.

&Lt; Method for forming long film >

As a method for forming a long film, there are a solution casting film forming method and a melt casting film forming method described below. Hereinafter, each film-forming method will be described. Further, in the present embodiment, as described later, in order to obtain the property that the film after warp stretching does not shrink in the fast axis direction under a high temperature environment, a long film to be obliquely stretched is formed by the melt soft film forming method .

[Solution flexible film-forming method]

In the solution casting film forming method, there are a step of preparing a dope by dissolving a resin and an additive in a solvent, a step of dipping the dope on a belt-shaped or drum-shaped metal support, a step of drying a flexible dope as a flexible film (web) A step of peeling the web, a step of stretching or maintaining the width of the web, a step of drying the web, and a step of winding the finished film are performed.

The metal support of the flexible process preferably has a mirror-finished surface and is preferably a stainless steel belt or a drum finished with plating on the surface thereof by casting. The surface temperature of the metal support is set to a temperature of -50 ° C to a temperature at which the solvent does not foam by boiling. The higher the support temperature, the faster the drying speed of the web can be. However, if the support temperature is too high, the web may be foamed or the planarity may deteriorate.

The preferred support temperature is suitably determined at 0 to 100 캜, more preferably 5 to 30 캜. Alternatively, it is preferable that the web be gelled by cooling to peel off the drum in a state containing a large amount of residual solvent. A method of controlling the temperature of the metal support is not particularly limited, but there is a method of blowing hot air or cold air, or a method of bringing hot water to the side of the metal support. The use of hot water is preferable because heat is efficiently transferred and the time until the temperature of the metal support becomes constant becomes shorter.

In the case of using warm air, in consideration of the temperature drop of the web due to the latent heat of evaporation of the solvent, winds at a temperature higher than the target temperature may be used while preventing the foaming while using warm air above the boiling point of the solvent.

Particularly, it is preferable to change the temperature of the support body and the temperature of the drying wind during the period from the softening to the peeling, and to perform the drying efficiently.

In order for the resin film to be formed to exhibit good planarity, it is preferable that the amount of the residual solvent when peeling the web from the metal support is in a desired range. Here, the amount of the residual solvent is defined by the following formula.

Amount of residual solvent (mass% or%) = {(M-N) / N} 100

M is the mass (g) of the sample taken from the web or film at any point during or after the production, and N is the mass (g) after heating the M at 115 占 폚 for 1 hour.

In the film drying step, a roll drying method (a method in which webs are alternately passed through a plurality of rolls arranged in a vertical direction and then dried) or a method in which a web is conveyed by a tenter method is employed.

[Melting flexible film forming method]

The melt soft-film-forming method is a method in which a resin composition containing additives such as a resin and a plasticizer is heated and melted to a temperature at which fluidity is exhibited, and then a melt having fluidity is softened to form a film. The method of forming by melt casting can be classified into a melt extrusion (molding) method, a press molding method, an inflation method, an injection molding method, a blow molding method, and a stretch molding method. Among them, the melt extrusion method is preferable in which a film having excellent mechanical strength and surface precision is obtained. In addition, it is preferable that a plurality of raw materials used in the melt extrusion method are usually previously kneaded and pelletized.

The pelletization may be carried out by a known method. For example, drying resin, plasticizer, and other additives may be fed to an extruder as a feeder, kneaded using a uniaxial or biaxial extruder, extruded from a die into a strand shape, pelletized by water cooling or air cooling and cutting .

The additive may be mixed with the resin before being fed to the extruder, and the additive and the resin may be respectively fed to the extruder by separate feeders. In addition, small amounts of additives such as particles and antioxidants are preferably mixed with the resin in advance in order to uniformly mix them.

The extruder can be pelletized so as not to cause deterioration (decrease in molecular weight, coloration, gel formation, etc.) of the resin by suppressing the shearing force, and it is preferable to process the extruder at a low temperature as possible. For example, in the case of a twin-screw extruder, it is preferable to use a deep groove-type screw to rotate in the same direction. From the viewpoint of uniformity of kneading, an engaging type is preferable.

Film formation is carried out using the pellets obtained as described above. Of course, it is also possible to feed the powder of the raw material directly to the extruder as a feeder without forming pellets, and to form the film as it is.

The above pellets are extruded by using a uniaxial or biaxial type extruder and the extruded product is filtered at a temperature of about 200 to 300 DEG C by using a filter such as a leaf disc type filter to remove foreign matters, , Nip the film with the cooling roll and the elastic touch roll, and solidify on the cooling roll.

When introducing the pellets from the feed hopper into the extruder, it is preferable to prevent the oxidative decomposition or the like under vacuum or in an inert gas atmosphere under a reduced pressure.

The extrusion flow rate is preferably stably performed by introducing a gear pump. In addition, a stainless steel fiber sintered filter is preferably used as the filter used for removing the foreign matter. The stainless steel fiber sintering filter is obtained by forming a state in which the stainless steel fiber bodies are intricately intertwined with each other and then compressing them and sintering the contact portions to integrate them. The filtration accuracy can be adjusted by changing the density depending on the thickness of the fibers and the amount of compression .

Additives such as a plasticizer and particles may be mixed with a resin in advance, or may be kneaded and inserted in the middle of an extruder. In order to uniformly add it, it is preferable to use a mixing device such as a static mixer.

The film temperature at the touch roll side when nipping the film with the cooling roll and the elastic touch roll is preferably Tg (glass transition temperature) or higher and Tg + 110 占 폚 or lower. For the roll having the surface of the elastic body used for this purpose, a known roll may be used.

The elastic touch roll is also referred to as a nip pressurized rotating body. As the elastic touch roll, a commercially available one may be used.

When the film is peeled from the cooling roll, it is preferable to control the tension to prevent deformation of the film.

Further, the long film to be formed by each of the above-mentioned film forming methods may be a single layer or a laminated film of two or more layers. The laminated film can be obtained by a known method such as a coextrusion molding method, a shared softening molding method, a film lamination method, and a coating method. Of these, the co-extrusion molding method and the shared mold forming method are preferable.

<Specification of long film>

The thickness of the long film in the present embodiment is preferably 30 to 300 占 퐉, more preferably 40 to 150 占 퐉. In the present embodiment, the thickness unevenness sigma m in the flow direction (transport direction) of the long film supplied to the stretching zone to be described later is determined by keeping the pulling tension of the film at the entrance of the oblique stretching tenter to be described later constant, Is preferably less than 0.30 mu m, preferably less than 0.25 mu m, more preferably less than 0.20 mu m from the viewpoint of stabilizing optical characteristics such as retardation. If the thickness unevenness? M in the flow direction of the long film is 0.30 占 퐉 or more, fluctuations in optical characteristics such as retardation and orientation angle of the elongated stretched film may deteriorate.

Further, as the long film, a film having a thickness gradient in the width direction may be supplied. The gradient of the thickness of the long film can be obtained empirically by stretching a film having various thickness gradients experimentally so as to make the film thickness at the position where the stretching of the subsequent process is completed most uniform. The gradient of the thickness of the long film can be adjusted, for example, so that the thickness of the end of the thicker side is 0.5 to 3% greater than the thickness of the end of the thinner side.

The width of the long film is not particularly limited, but may be 500 to 4000 mm, preferably 1000 to 2000 mm.

The preferable modulus of elasticity at the stretching temperature at the time of oblique stretching of the long film is 0.01 MPa or more and 5000 MPa or less, more preferably 0.1 MPa or more and 500 MPa or less, When the modulus of elasticity is too low, the shrinkage ratio at the time of stretching or drawing is lowered, and wrinkles are less likely to disappear. When the modulus of elasticity is too high, the tensile force applied at the time of stretching becomes large, so that it is necessary to increase the strength of the portion that holds both side edges of the film, and the load on the tenter in the subsequent process increases.

As the long film, a film having no orientation or a film having orientation previously may be supplied. Further, if necessary, the distribution of the orientation of the long film in the width direction may be arch-shaped, or so-called bowing. The orientation of the long film can be adjusted so that the orientation of the film at the position where the drawing of the subsequent process is completed is desired.

&Lt; Method of manufacturing long obliquely drawn film &

Next, a description will be given of a method and apparatus for producing an obliquely-stretched film, in which the long film is stretched in an oblique direction with respect to the width direction to produce a long obliquely-stretched film.

(Overview of the device)

Fig. 1 is an explanatory view schematically showing a schematic configuration of an apparatus 1 for producing an obliquely-drawn film. The production apparatus 1 according to the present embodiment includes a film feed portion 2, a transport direction changing portion 3, a guide roll 4, and a stretching portion 5 A guide roll 6, a transport direction changing portion 7, a film cutting device 8, and a film winding portion 9, as shown in Fig. Details of the stretching portion 5 will be described later.

The film feeding portion 2 uncovers the long film and feeds it to the stretching portion 5. The film feeding portion 2 may be formed separately from the film forming apparatus of the long film or may be integrally formed. In the case of the former, the long film is wound around the winding core after film formation, and the long film is unwound from the film feeding portion 2 by loading the film with the winding body into the film feeding portion 2. On the other hand, in the latter case, after film formation of the long film, the film feeding portion 2 unwinds the long film to the stretching portion 5 without winding.

The transport direction changing section 3 changes the transport direction of the long film unwound from the film feed section 2 to the direction toward the entrance of the stretching section 5 as the warp stretch tenter. The carrying direction changing section 3 includes, for example, a turn bar for changing the carrying direction by folding while conveying the film, and a rotary table for rotating the turn bar in a plane parallel to the film.

By changing the conveying direction of the long film in the conveying direction changing section 3 as described above, it is possible to narrow the entire width of the manufacturing apparatus 1, and to finely control the conveying position and angle of the film Thus, it is possible to obtain a long stretched film having a small variation in film thickness and optical value. When the film feeding portion 2 and the conveying direction changing portion 3 are movable (slidable and pivotable), the right and left clips It is possible to effectively prevent defective bonding of the film to the film.

The film feed portion 2 may be slidable and pivotable so as to allow a long film to be ejected at a predetermined angle with respect to the entrance of the stretching portion 5. In this case, it is possible to adopt a configuration in which the installation of the transport direction changing section 3 is omitted.

At least one guide roll 4 is provided on the upstream side of the stretching portion 5 in order to stabilize the trajectory during traveling of the long film. The guide roll 4 may be constituted by a pair of upper and lower rolls sandwiching the film, or a plurality of pairs of rolls. The guide roll 4 closest to the entrance of the stretching portion 5 is a driven roll for guiding the running of the film and is rotatably supported by a bearing portion (not shown). As the material of the guide roll 4, known rollers can be used. In order to prevent the occurrence of scratches on the film, it is preferable to reduce the weight of the guide roll 4 by applying a ceramic coating to the surface of the guide roll 4 or chromium plating a light metal such as aluminum.

It is preferable that one of the rolls on the upstream side of the guide roll 4 closest to the entrance of the stretching section 5 is nipped by pressing the rubber roll. By using such a nip roll, it is possible to suppress fluctuation of the tensile tension in the film flow direction.

A pair of bearing portions at both ends (right and left) of the guide roll 4 closest to the entrance of the stretching portion 5 are provided with a film tension detecting device for detecting a tension generated in the film in the roll, A tension detecting device, and a second tension detecting device are provided, respectively. As the film tension detecting device, for example, a load cell can be used. As the load cell, a known type of tensile or compression type can be used. The load cell is a device that converts a load acting on a point of attachment to an electrical signal by a strain gauge attached to a base body and detects it.

The load cell is provided on the left and right bearing portions of the guide roll 4 closest to the entrance of the stretching section 5 so that the force exerted by the film during running on the roll, And independently detect the tension of left and right. Further, a strain gauge may be directly attached to the support constituting the bearing portion of the roll, and the load, that is, the film tension may be detected based on the distortion generated in the support. The relationship between the generated distortion and the film tension is measured in advance and is assumed to be known.

When the position and transport direction of the film supplied from the film feed portion 2 or the transport direction changing portion 3 to the stretching portion 5 are shifted from the position toward the entrance of the stretching portion 5 and the transport direction, A difference occurs in the tension in the vicinity of the both side edge portions of the film in the guide roll 4 closest to the entrance of the stretching section 5, depending on the displacement amount. Therefore, by detecting the tension difference by installing the film tension detecting device as described above, it is possible to determine the degree of the deviation. That is, when the conveying position and the conveying direction of the film are appropriate (the position and the direction toward the inlet of the stretching section 5), the load acting on the guide roll 4 is roughly equalized at both ends in the axial direction, Otherwise, difference in film tension occurs between right and left.

Therefore, in order to equalize the film tension difference between the left and right of the guide roll 4 closest to the entrance of the stretching section 5, for example, the position of the film and the conveying direction (The angle with respect to the entrance of the film 5) is appropriately adjusted, the holding of the film by the waveguide of the entrance portion of the stretching portion 5 is stabilized and the occurrence of troubles such as deviation from the waveguide can be reduced. In addition, it is possible to stabilize the physical properties of the film in the width direction after the warp stretching by the stretching portion (5).

At least one guide roll 6 is provided on the downstream side of the stretching section 5 in order to stabilize the trajectory of the obliquely stretched film (long obliquely stretched film) in running at the stretching section 5 .

The transport direction changing section 7 changes the film transport direction after stretching, which is transported from the stretching section 5, to the film winding section 9. The carrying direction changing section 7 can be constituted by, for example, a folding mechanism for folding the stretched film at least once along the direction parallel or perpendicular to the stretching direction in the plane of the long oblong stretched film.

Here, the film advancing direction at the entrance of the stretching section 5 and the film advancing direction at the exit of the elongating section 5 are set so as to correspond to the fine adjustment of the orientation angle (the direction of the in-plane slow axis in the film) It is necessary to adjust the angle.

In addition, it is preferable to continuously perform film formation and warp stretching in terms of productivity and yield. When the film forming process, the warp stretching process, and the winding process are continuously performed, the film advancing direction is changed by the carrying direction changing portion 3 and / or the carrying direction changing portion 7, As shown in Fig. 1, the moving direction (feeding direction) of the film unwound from the film feeding portion 2 and the direction in which the film is wound just before being wound in the film winding portion 9 (Winding direction), the width of the entire device in the film advancing direction can be made small.

It is not necessary that the film advancing direction in the film forming process and the winding process necessarily coincides with each other but the direction of the film carrying section 2 and the film winding section 9 is not interfered, Or the carrying direction changing portion 7 to change the traveling direction of the film.

The above-described transport direction changing unit 3 · 7 can be realized by a known method such as using an air flow roll.

The film cutting device 8 cuts a film (long oblong stretched film) stretched in the stretching section 5 along the width direction at a portion of a predetermined film length (wound length), and cuts the cutter member 8a I have. The cutting member 8a is made of, for example, a scissors or a cutter (including a slitter and a band-shaped blade (Thompson blade)), but is not limited thereto, Or the like.

The film take-up portion 9 is for winding a film conveyed from the stretching portion 5 through the conveying direction changing portion 7 and is constituted by, for example, a winder device, an algebraic device, a drive device or the like. It is preferable that the film take-up portion 9 is a structure which can slide in the lateral direction in order to adjust the winding position of the film.

The film take-up portion 9 is capable of finely controlling the take-in position and angle of the film so that the film can be pulled at a predetermined angle with respect to the exit of the stretching portion 5. [ As a result, it is possible to obtain a long stretched film having a small deviation in film thickness and optical value. Further, wrinkle generation of the film can be effectively prevented, and at the same time, the winding-up property of the film is improved, so that the film can be wound up a long time. In this embodiment, it is preferable that the film pulling tension T (N / m) after stretching is adjusted within a range of 100 N / m <T <700 N / m, preferably 150 N / m <T <250 N / m.

When the pulling tension is 100 N / m or less, sagging or wrinkling of the film tends to occur, and the profile of the film in the width direction of the retardation and orientation angle is deteriorated. On the other hand, when the pulling tension is 700 N / m or more, the deviation of the film in the width direction of the orientation angle becomes large, and the width yield (acquisition efficiency in the width direction) may deteriorate.

In the present embodiment, it is preferable to control the fluctuation of the take-up tension T at an accuracy of less than ± 5%, preferably less than ± 3%. If the fluctuation of the take-up tension T is ± 5% or more, fluctuation of the optical characteristics in the width direction and the flow direction (transport direction) becomes large. As a method of controlling the fluctuation of the take-up tension T within the above range, the load applied to the first roll (guide roll 6) on the exit side of the stretching portion 5, that is, the tensile force of the film is measured, And the rotational speed of the take-up roll (the winding roll of the film take-up unit 9) is controlled by a general PID control method so as to be constant. As a method for measuring the load, there is a method of attaching a load cell to the bearing portion of the guide roll 6 and measuring the load applied to the guide roll 6, that is, the tensile force of the film. As the load cell, a known type of tensile type or compression type can be used.

After stretching the film, the gripping of the stretching portion 5 is released, the film is discharged from the outlet of the stretching portion 5, both ends (both sides) of the film gripped by the breaking portion are trimmed, And wound around a winding core (winding roll) to form a winding body of a long shape warp stretched film. The trimming may be performed as necessary.

Further, before winding the oblong stretched film with a long shape, the masking film may be wound and superposed on the oblong stretched film of the long shape at the same time for the purpose of preventing blocking between the films, And may be wound while adhering a tape or the like to at least one (preferably both) ends. The masking film is not particularly limited as long as it can protect the elongated warp stretched film, and examples thereof include a polyethylene terephthalate film, a polyethylene film and a polypropylene film.

Further, before winding the long warp stretched film, at both ends in the width direction of at least one surface (preferably both surfaces) of the film, a portion called bulging portion or embossing portion, which is larger in volume than the film surface ) May be formed so as to prevent the films from being blocked from each other when the film is wound. Further, the height and shape of the knurled portion may be different at both end portions in the width direction (may be asymmetrical).

(Details of extension section)

Next, the above-described elongating unit 5 will be described in detail. 2 is a plan view schematically showing an example of a rail pattern of a stretching portion 5. Fig. 3 is a plan view showing the details of the configuration of the stretching portion 5. In Fig. In addition, the present invention is not limited to these configurations as an example.

The manufacturing apparatus 1 is carried out by using a tenter (tapered stretching machine) that can be warp-stretched as the stretching portion 5. [ This tenter is a device for heating a long film to an arbitrary stretchable temperature and obliquely stretching it. This tenter has a heating zone Z, a pair of left and right rails Ri and Ro, and a plurality of waveguides 15 (in Fig. 2, for convenience, a pair of right and left waveguides Ci And only Co). Details of the heating zone Z will be described later.

Each of the rails Ri and Ro is constituted by connecting a plurality of rail portions at connection portions, and is a rail having an endless track (a white circle in Fig. 2 is an example of a connection portion). As shown in Fig. 3, the rail Ri at one end side (left side) in the width direction of the film has a traveling rail part 11 for advancing the waveguide 15 in the transporting direction of the long film, And a return rail portion 12 for moving the waveguide 15 in a direction opposite to the direction of the arrow. The rail Ro on the other end side (right side) in the width direction of the film is provided with a row rail portion 13 for advancing the waveguide 15 in the transporting direction of the long film, And a return rail part 14 for moving the return rail part 15 in the forward direction.

The waveguide 15 is constituted by a clip holding both ends in the width direction of the film and is provided corresponding to each of the rails Ri and Ro and is arranged at equal intervals As shown in FIG. One end side in the width direction of the film is gripped by a plurality of wave fringes 15 arranged along the transport direction (rail Ri), and the other end side is provided with a plurality of wave fringes 15 arranged along the transport direction (rail Ro) And in this state, the waveguide 15 travels along the rail Ri · Ro, whereby the film is transported.

The waveguide 15 traveling along the left rail Ri travels along the traveling rail part 11 in the state of gripping one end of the film and opens the holding of the film near the exit of the stretching part 5 , Travels along the return rail portion 12, returns to the vicinity of the entrance of the stretching portion 5, grasps one end portion of the film again, and repeats the same process as above (it runs around the rail Ri). On the other hand, the waveguide 15 running along the rail Ro on the right side travels along the running rail part 13 in the state of gripping one end of the film, and the gripping of the film is released in the vicinity of the exit of the stretching part 5 And then travels along the return rail portion 14 and returns to the vicinity of the entrance of the stretching portion 5 to grasp the other end portion of the film again and then repeats the same process as described above box).

In Fig. 2, the conveying direction D1 before stretching of the long film is different from the conveying direction D2 after stretching the long film, and forms the feeding angle? I in the conveying direction D2 after stretching. The feed angle &amp;thetas; i can be arbitrarily set to a desired angle in a range of more than 0 DEG and less than 90 DEG.

Since the transport direction D1 before stretching and the transport direction D2 after stretching are different from each other in this way, the rail pattern of the tenter is asymmetrical in shape. Then, the rail pattern can be manually or automatically adjusted in accordance with the orientation angle?, Stretching magnification, and the like applied to the oblong stretched film to be produced. In the warp stretching machine used in the present embodiment, it is preferable that the positions of the rail portions and the rail connecting portions configuring the rails Ri and Ro are freely set and the rail patterns can be arbitrarily changed.

In the present embodiment, the waveguide 15 is arranged so as to run at a constant speed while keeping a certain distance from the waveguide 15 (the waveguide 15 on the upstream side and the downstream side in the transport direction of the film) . The traveling speed of the wave earth 15 can be appropriately selected, but is usually 1 to 150 m / min. The difference in travel speed between a pair of left and right wave earths (for example, wave earth Ci · Co) is usually 1% or less, preferably 0.5% or less, more preferably 0.1% or less of the traveling speed. This is because, if there is a difference in the traveling speed between the right and left sides of the film at the exit of the stretching process, wrinkles and warps occur at the exit of the stretching process, and therefore the speed difference between the right and left breaking zones is required to be substantially the same. In a general tentering machine or the like, speed irregularities occur on the order of less than or equal to a second depending on the period of the teeth of the sprocket for driving the chain, the frequency of the drive motor, etc. and often cause several percent of irregularities. This does not apply to the speed difference described in Fig.

In a warp stretcher used in the production method of the present embodiment, a rail for regulating the trajectory of the crushing strip is often required to have a large bending rate, particularly at a position where the conveyance of the film becomes oblique. In order to avoid interference between waveguides due to abrupt bending or local concentration of stress, it is preferable that the trajectory of the waveguide is formed to have a smooth curve at the curved portion.

As described above, the oblique stretching tenters used for imparting the oblique directional orientation to the long film can freely set the orientation angle of the film by variously changing the rail pattern, and the orienting axis (slow axis) It is preferable that the film is a tenter capable of orienting the film in the widthwise direction of the film evenly and precisely and also capable of controlling film thickness and retardation with high precision.

Next, the drawing operation in the stretching section 5 will be described with reference to Fig. Both ends of the long film are gripped by the left and right wave regions Ci 占. O, and are conveyed in the heating zone Z with traveling of the waveguide Ci 占. O. The left and right wave regions Ci 占 상대 coexist in a direction substantially perpendicular to the advancing direction of the film (conveying direction D1 before stretching) at the entrance portion (position A in the drawing) of the stretching section 5, And travels along the asymmetrical rail Ri 占 Ro to open the film held in the vicinity of the exit portion (the position of B in the drawing) at the end of the stretching. The details of the timing of opening the grip will be described later. The film which is opened from the wave region Ci · Co is wound on the winding core in the film winding section 9 described above. As described above, each of the pair of rails Ri 占 Ri r has an endless continuous trajectory, and the waveguide Ci 占 한, which opens the grip of the film at the outlet of the stretching section 5, So as to return to the sequential inlet portion.

At this time, since the rail Ri 占 is asymmetric in the left and right directions in the example of Fig. 2, the left and right waveguides Ci 占 상대 opposed to the position A in the figure move along the rail Ri 占 Ro, And the running waveguide Ci becomes the preceding positional relationship with respect to the waveguide Co running on the rail Ro.

That is, when one waveguide Ci reaches the position B at the end of stretching of the film out of the waveguides Ci and Co opposed to each other in the direction substantially perpendicular to the carrying direction D1 before stretching the film at the position A , And a straight line connecting the waveguide Ci · Co is inclined by an angle θL with respect to a direction substantially perpendicular to the transport direction D2 after stretching the film. By doing so, the long film is obliquely elongated at an angle of? L with respect to the width direction. Here, the term &quot; substantially perpendicular &quot;

As described above, in the method of manufacturing an oblique-drawn film of the present embodiment, one end side in the width direction of the film is held by a plurality of waveguides 15 (including waveguide Ci) And the one waveguide 15 (for example, a plurality of waveguides 15 running along the rails Ri) on one side end and the other end side are grasped by the waveguide 15 (including the waveguide Co) And the film is transported by delaying the other waveguide 15 (for example, a plurality of waveguides 15 traveling along the rail Ro) relatively, thereby stretching the film in the oblique direction with respect to the width direction And may include an oblique stretching process. In the following description, the side on which the wave earth travels relatively earlier among the one end side and the other end side in the width direction of the film is referred to as a &quot; preceding side &quot;, and a side Quot; delay side &quot;. For example, in Fig. 2, in the width direction of the film, the side on which the wave earth Ci travels is the front side, and the side on which the wave earth Co travels is the retard side.

Next, the heating zone Z will be described in detail. The heating zone Z of the stretching section 5 is composed of a preheating zone Z1, a stretching zone Z2 and a heat fixing zone Z3. In the stretching section 5, the film held by the waveguide Ci 占 폚 passes through the preheating zone Z1, the stretching zone Z2, and the heat fixing zone Z3 in this order.

The preheating zone Z1 indicates a section in which the waveguide Ci 占 한 in which the both ends of the film are gripped at the entrance of the heating zone Z travels with left and right spacing in the width direction of the film.

The stretching zone Z2 indicates a section in which the above-described warp stretching process is performed. At this time, if necessary, the film may be stretched in the longitudinal direction or the transverse direction before and after the oblique stretching.

The heat-fixing zone Z3 is a period during which the heat fixing process for fixing the optical axis (slow axis) of the film is performed after the end of the warp stretching process.

The stretched film may pass through a section (cooling zone) where the temperature in the zone is set to be equal to or lower than the glass transition temperature Tg (占 폚) of the thermoplastic resin constituting the film after passing through the heat fixing zone Z3. At this time, in consideration of shrinkage of the film due to cooling, a rail pattern may be used in which the interval between the opposed wave cores Ci and Co is narrowed.

The temperature of the preheating zone Z1 is from Tg to Tg + 30 占 폚, the temperature of the stretching zone Z2 is from Tg to Tg + 30 占 폚, the temperature of the heat fixing zone Z3 is from Tg-30 to Tg 占 폚 .

In order to control the thickness unevenness of the film in the width direction, the temperature difference in the width direction in the stretching zone Z2 may be set. In order to set the temperature difference in the width direction in the stretching zone, there is a method of adjusting the opening degree of the nozzle for feeding warm air into the constant-temperature chamber so as to make a difference in the width direction, Method can be used. The length of the preheating zone Z1, the stretching zone Z2 and the length of the heat-fixing zone Z3 can be appropriately selected. In comparison with the length of the stretching zone Z2, the length of the preheating zone Z1 is usually 100 to 150% 100%.

When the width of the film before stretching is W0 (mm) and the width of the film after stretching is W (mm), the stretching magnification R (W / W0) in the stretching step is preferably 1.3 to 3.0 Preferably 1.5 to 2.8. When the stretching magnification is within this range, the thickness irregularity in the width direction of the film becomes small, which is preferable. In the stretching zone Z2 of the oblique stretching tenter, if the stretching temperature is differentiated in the width direction, the thickness non-uniformity in the width direction can be set to a better level. Further, the draw ratio R is equal to the magnification (W2 / W1) when the interval W1 between both ends of the clip gripped by the tenter inlet portion becomes equal to the interval W2 at the tenter outlet portion.

&Lt; Quality of long drawn film >

In the elongated warp-stretched film obtained by the production method according to the embodiment of the present invention, the orientation angle? Is inclined to a range of, for example, greater than 0 ° and less than 90 ° with respect to the winding direction, , It is preferable that the deviation of the in-plane retardation Ro in the width direction is 3 nm or less and the deviation of the orientation angle [theta] is less than 0.6 [deg.].

That is, in the oblong stretched film obtained by the production method according to the embodiment of the present invention, the deviation of the in-plane retardation Ro is 3 nm or less at 1300 mm in the width direction and 1 nm or less desirable. When the deviation of the in-plane retardation Ro is in the above-mentioned range, when a long oblong stretched film is joined to the polarizer to form a circularly polarizing plate and this is applied to an organic EL display device, Can be suppressed. In addition, when a long stretched film is used as, for example, a retardation film for a liquid crystal display device, the display quality can be made good.

Further, in the elongated warp stretched film obtained by the production method according to the embodiment of the present invention, the deviation of the orientation angle? Is preferably less than 0.6 degrees and less than 0.4 degrees at least at 1300 mm in the width direction . When a long oblong stretched film having a deviation of an orientation angle of 0.6 or more is joined to a polarizer to form a circularly polarizing plate and fixed to an image display device such as an organic EL display device, light leakage occurs, There may be a case where it is lowered.

The in-plane retardation Ro of the oblong drawn film of the long shape obtained by the manufacturing method according to the embodiment of the present invention is selected according to the design of the display device to be used. Ro is a value obtained by multiplying the difference between the refractive index nx in the in-plane slow axis direction and the refractive index ny in the plane perpendicular to the slow axis in the plane by an average thickness d of the film (Ro = (nx-ny) xd )to be.

The average thickness of the elongated warp stretched film obtained by the production method according to the embodiment of the present invention is preferably 10 to 200 占 퐉, more preferably 10 to 60 占 퐉, particularly preferably Is 10 to 35 mu m. Further, the thickness non-uniformity in the width direction of the warp stretched film is preferably 3 占 퐉 or less, and more preferably 2 占 퐉 or less, because it affects the availability of winding.

<Polarizer>

4 is an exploded perspective view showing a schematic structure of the polarizing plate 50 of the present embodiment. The polarizing plate 50 is constituted by laminating a polarizing plate protective film 51, a polarizer 52 and a retardation film 53 in this order. The polarizing plate protective film 51 is made of, for example, a cellulose ester film, but it may be composed of another transparent resin film (for example, a cycloolefin resin). The polarizing plate protective film 51 may also be composed of an optical compensation film for compensating optical characteristics such as enlargement of viewing angle.

As the polarizer 52, one obtained by stretching polyvinyl alcohol doped with iodine or dichromatic dye can be used. The film thickness of the polarizer is 5 to 40 占 퐉, preferably 5 to 30 占 퐉, and particularly preferably 5 to 20 占 퐉.

The retardation film 53 is composed of the optical film of this embodiment, that is, a warp stretched film. The slow axis of the retardation film 53 is inclined by 10 to 80 DEG with respect to one side (for example, side 53a) of the outer shape of the rectangular film in the film plane. The side 53a is a side corresponding to the width direction of the elongated oblong stretched film. The preferable range of the inclination angle of the slow axis with respect to the side 53a in the film plane is 30 to 60 degrees, more preferably 45 degrees. The angle made by the slow axis of the retardation film 53 and the absorption axis (or transmission axis) of the polarizer 52 is, for example, 10 to 80 degrees, preferably 15 to 75 degrees, 30 DEG to 60 DEG, and more preferably 45 DEG.

(For example, a hard coat layer, a low refractive index layer, an antireflection layer, and a liquid crystal (positive C plate) may be appropriately provided on the surface of the retardation film 53 opposite to the polarizer 52 in accordance with the application. An easy-adhesion layer may be provided on the surface of the retardation film 53 on the polarizer 52 side.

The polarizing plate 50 of the present embodiment has a structure in which a long polarizing plate protective film 51, a long polarizer 52 and a long retardation film 53 (long oblique stretched film) The polarizing plate may be a long polarizing plate or a sheet polarizing plate in which the long polarizing plate 50 is cut along the width direction perpendicular to the longitudinal direction.

The polarizing plate 50 can be manufactured by a general method. For example, the polarizer 52 and the retardation film 53 can be bonded with an ultraviolet curable adhesive (UV adhesive) to prepare the polarizing plate 50. The alkali saponified phase difference film 53 is formed by using a fully saponified polyvinyl alcohol aqueous solution (water-soluble) on one surface of a polarizer 52 produced by immersing and stretching a polyvinyl alcohol-based film in an iodine solution, . Further, the polarizing plate 52 and the polarizing plate protective film 51 may be adhered to each other using an ultraviolet curable adhesive or a water-based adhesive.

&Lt; Composition of ultraviolet curable adhesive >

As the ultraviolet curable adhesive composition for a polarizing plate, there are known a photo-radical polymerizable composition using photo-radical polymerization, a photo-cationic polymerizable composition using photo-cation polymerization, and a hybrid-type composition using both photo radical polymerization and photo cationic polymerization.

Examples of the photo-radical polymerization type composition include compositions containing a radical polymerizing compound containing a polar group such as a hydroxyl group or a carboxyl group and a radically polymerizable compound containing no polar group in a specific ratio described in JP-A-2008-009329 Is known. In particular, the radical polymerizing compound is preferably a compound having a radically polymerizable ethylenic unsaturated bond. Preferable examples of the compound having a radically polymerizable ethylenically unsaturated bond include a compound having a (meth) acryloyl group. Examples of the compound having a (meth) acryloyl group include N-substituted (meth) acrylamide-based compounds, (meth) acrylate-based compounds and the like. (Meth) acrylamide refers to acrylamide or methacrylamide.

As the photo cationic polymerization type composition, there may be mentioned (a) a cationic polymerizable compound, (?) A photo cationic polymerization initiator, (?) A A photosensitizer exhibiting maximum absorption in light, and an ultraviolet curable adhesive composition containing each component of (?) Naphthalene-based photo-sensitization assistant. However, other ultraviolet curable adhesives may be used.

(1) Pretreatment process

The pretreatment step is a step of performing the adhesion facilitating treatment on the adhesion surface of the retardation film and the polarizing plate protective film (here, they are collectively referred to as &quot; protective film &quot;) with the polarizer. Examples of the adhesion facilitating treatment include a corona treatment and a plasma treatment.

(Application step of ultraviolet curing type adhesive)

In the application step of the ultraviolet curable adhesive, the ultraviolet curable adhesive is applied to at least one of the polarizer and the protective film. When the ultraviolet curable adhesive is directly applied to the surface of the polarizer or the protective film, the application method is not particularly limited. For example, various wet coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. In addition, a method may be employed in which an ultraviolet curable adhesive is applied between the polarizer and the protective film (softened) and then pressed with a roller or the like to uniformly press the ultraviolet curable adhesive.

(2) Bonding process

After the ultraviolet curing type adhesive is applied by the above method, it is treated in the bonding step. In this bonding step, for example, when an ultraviolet curable adhesive is applied to the surface of the polarizer in the previous coating step, the protective film is superimposed thereon. Further, in the case of applying the ultraviolet curable adhesive on the surface of the protective film, the polarizer is superimposed thereon. Further, when an ultraviolet curable adhesive is poured between the polarizer and the protective film, the polarizer and the protective film overlap in this state. Normally, in this state, the protective film is pressed from the side of the protective film on both sides with a pressure roller or the like. As the material of the pressure roller, metal or rubber can be used. The pressure rollers disposed on both sides may be the same material or different materials.

(3) Curing process

In the curing step, ultraviolet rays are irradiated to an uncured ultraviolet curable adhesive to form a cationic polymerizable compound (for example, an epoxy compound or an oxetane compound) or a radical polymerizable compound (for example, an acrylate compound or an acrylamide compound Compound, etc.) is cured, and the polarizer and the protective film superimposed on each other through the ultraviolet curable adhesive are adhered to each other. In the configuration of the present embodiment in which the protective film is bonded to both surfaces of the polarizer, the protective film is superimposed on both surfaces of the polarizer via the ultraviolet curing type adhesive, and ultraviolet rays are irradiated to simultaneously cure the ultraviolet curing type adhesive It is advantageous.

The irradiation condition of the ultraviolet ray may be any suitable condition as long as the ultraviolet ray curable adhesive can be cured. The irradiation amount of the ultraviolet rays is preferably in the range of 50 to 1500 mJ / cm &lt; 2 &gt; and more preferably in the range of 100 to 500 mJ / cm &

When the production process of the polarizing plate is performed in a continuous line, the line speed varies depending on the curing time of the adhesive, but is preferably in the range of 1 to 500 m / min, more preferably in the range of 5 to 300 m / min, 10 to 100 m / min. When the line speed is 1 m / min or more, productivity can be ensured, or damage to the protective film can be suppressed, and a polarizer excellent in durability can be produced. When the line speed is 500 m / min or less, the curing of the ultraviolet curing type adhesive becomes sufficient, so that the ultraviolet curing type adhesive layer having the desired hardness and excellent adhesiveness can be formed.

<Organic EL Display Device>

Fig. 5 is a cross-sectional view showing a schematic configuration of the organic EL display device 100, which is an example of the display device of the present embodiment. The configuration of the organic EL display device 100 is not limited to this.

The organic EL display device 100 is configured by forming a polarizing plate 301 on an organic EL element 101 as a display cell through an adhesive layer 201. [ The organic EL element 101 includes a metal electrode 112, a light emitting layer 113, a transparent electrode (such as ITO) 114, and a sealing layer 115 on a substrate 111 made of glass or polyimide Consists of. The metal electrode 112 may be composed of a reflective electrode and a transparent electrode.

The polarizing plate 301 is formed by laminating a? / 4 retardation film 311, an adhesive layer 312, a polarizer 313, an adhesive layer 314 and a protective film 315 in this order from the organic EL element 101 side , The polarizer 313 is sandwiched between the? / 4 retardation film 311 and the protective film 315. The angle formed between the transmission axis (or absorption axis) of the polarizer 313 and the slow axis of the? / 4 retardation film 311 including the long obliquely extended film of the present embodiment is about 45 ° (or 135 °) The polarizer 301 (circular polarizer) is constituted. The protective film 315 of the polarizing plate 301, the polarizer 313 and the? / 4 retardation film 311 are the same as the polarizing plate protective film 51 of the polarizing plate 50 of FIG. 4, the polarizer 52, Respectively.

It is preferable that the protective film 315 is laminated with a cured layer. The cured layer not only prevents scratches on the surface of the organic EL display device but also has the effect of preventing warping by the polarizing plate 301. [ An antireflection layer may be provided on the cured layer. The thickness of the organic EL device 101 itself is about 1 占 퐉.

When a voltage is applied to the metal electrode 112 and the transparent electrode 114 in the above configuration, electrons are injected into the light emitting layer 113 from the metal electrode 112 and the transparent electrode 114, which are cathodes, , Holes are injected from the electrode serving as the anode, and both are recombined in the light emitting layer 113, so that visible light corresponding to the light emitting property of the light emitting layer 113 is emitted. The light generated in the light emitting layer 113 is directly or reflected by the metal electrode 112 and then is taken out to the outside through the transparent electrode 114 and the polarizing plate 301.

Generally, in an organic EL display device, a light emitting element (organic EL element) is formed by sequentially laminating a metal electrode, a light emitting layer, and a transparent electrode on a transparent substrate. Here, the light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer including a triphenylamine derivative and the like, and a light emitting layer containing a fluorescent organic solid such as anthracene, A multilayer body with an electron injecting layer including a hole injecting layer, a hole injecting layer, and a derivative, and a laminate of these hole injecting layers, a light emitting layer, and an electron injecting layer.

In the organic EL display device, when a voltage is applied to the transparent electrode and the metal electrode, holes and electrons are injected into the light emitting layer, and energy generated by the recombination of the holes and electrons excites the fluorescent substance, The light is emitted by the principle of emitting light. The mechanism of recombination in the middle is similar to that of a general diode, and as can be expected from this, the current and the light emission intensity exhibit strong nonlinearity accompanied by rectification with respect to the applied voltage.

In the organic EL display device, in order to extract light from the light emitting layer, at least one of the electrodes must be transparent, and a transparent electrode usually formed of a transparent conductor such as indium tin oxide (ITO) is used as the anode. On the other hand, it is important to use a substance having a low work function for the cathode in order to facilitate electron injection and increase the luminous efficiency, and metal electrodes such as Mg-Ag and Al-Li are generally used.

In the organic EL display device having such a structure, the light emitting layer is formed of a very thin film with a thickness of about 10 nm. As a result, the light emitting layer almost completely transmits the light, like the transparent electrode. As a result, the light incident on the surface of the transparent substrate at the time of non-light emission, the light transmitted through the transparent electrode and the light emitting layer, and reflected by the metal electrode again come out to the surface side of the transparent substrate. The display surface looks like a mirror surface.

The circularly polarizing plate of the present embodiment is suitable for organic EL display devices in which such external light reflection is particularly problematic.

That is, half of the external light incident from the outside of the organic EL element 101 is absorbed by the polarizer 313 of the polarizing plate 301 when the organic EL element 101 is not emitting light, and the other half Is transmitted as linearly polarized light, and is incident on the? / 4 retardation film 311. Since the transmission axis of the polarizer 313 and the slow axis of the? / 4 retardation film 311 intersect at 45 ° (or 135 °) with respect to the light incident on the? / 4 retardation film 311, And transmitted through the retardation film 311 to be converted into circularly polarized light.

The circularly polarized light emitted from the lambda / 4 retardation film 311 is inverted in phase by 180 degrees when it is mirror-reflected by the metal electrode 112 of the organic EL element 101, and is reflected as circularly polarized light in the reverse rotation direction. The reflected light is incident on the? / 4 retardation film 311 and is converted into linearly polarized light perpendicular to the transmission axis of the polarizer 313 (parallel to the absorption axis). Therefore, the reflected light is absorbed by the polarizer 313, It is not emitted. That is, the polarizing plate 301 can reduce the reflection of external light in the organic EL element 101.

<Liquid Crystal Display Device>

6 is a cross-sectional view showing a schematic structure of a liquid crystal display device 400, which is another example of the display device of the present embodiment. The liquid crystal display device 400 is constituted by disposing a polarizing plate 402 on one side of a liquid crystal cell 401.

 The liquid crystal cell 401 is a display cell in which a liquid crystal layer is sandwiched between a pair of substrates. A backlight for illuminating the liquid crystal cell 401 is provided on the other side of the liquid crystal cell 401 opposite to the polarizer 402 with a polarizing plate disposed in a crossed Nicol state with the polarizing plate 402, , Omitting their cities.

The liquid crystal display device 400 may have the front window 403 on the side opposite to the liquid crystal cell 401 with respect to the polarizing plate 402. [ The front window 403 serves as an external cover of the liquid crystal display 400, and is constituted by, for example, a cover glass. Between the front window 403 and the polarizing plate 402, a filler 404 containing, for example, an ultraviolet curable resin is filled. An air layer is formed between the front window 403 and the polarizing plate 402. When the front window 403 and the polarizing plate 402 are reflected at the interface between the air layer and the front window 403, The visibility of the displayed image may be lowered. However, since the air layer is not formed between the front window 403 and the polarizing plate 402 by the filler 404, deterioration of the visibility of the display image due to reflection of light at the interface can be avoided.

The polarizing plate 402 has a polarizer 411 which transmits a predetermined linearly polarized light. The? / 4 retardation film 413 and the cured layer 414 including the ultraviolet curable resin are laminated in this order on the one surface side (opposite to the liquid crystal cell 401) of the polarizer 411 through the adhesive layer 412 Respectively. A protective film 416 is bonded to the other surface side (liquid crystal cell 401 side) of the polarizer 411 through an adhesive layer 415. [

 The polarizer 411 is obtained, for example, by staining a polyvinyl alcohol film with a dichromatic dye and stretching it at a high magnification. After the polarizer 411 is subjected to an alkali treatment (also referred to as a saponification treatment), a? / 4 retardation film 413 is bonded to one side via an adhesive layer 412 and a protective film 416 is bonded to the other side of the adhesive layer 412 415, respectively. The protective film 416, the polarizer 411 and the? / 4 retardation film 413 of the polarizing plate 402 are the same as the polarizing plate protective film 51 of the polarizing plate 50 of FIG. 4, the polarizer 52, Respectively. The adhesive layer 412, 415 is, for example, a layer containing a polyvinyl alcohol adhesive (PVA adhesive, water-based adhesive), but may be a layer containing an ultraviolet curable adhesive (UV adhesive).

The? / 4 retardation film 413 is a layer which imparts an in-plane retardation of about 1/4 of the wavelength of transmitted light, and is constituted by the optical film (obliquely stretched film) of the present embodiment, 10 to 70 mu m. The angle formed by the slow axis of the? / 4 retardation film 413 and the absorption axis of the polarizer 411 (crossing angle) is, for example, 30 to 60 degrees, and more preferably 45 degrees. Thus, linearly polarized light from the polarizer 411 is converted into circularly polarized light or elliptically polarized light by the? / 4 retardation film 413.

The cured layer 414 (also referred to as a hard coat layer) is composed of an active energy ray curable resin (for example, an ultraviolet curable resin).

The protective film 416 is composed of a resin film including, for example, a cellulose resin (a cellulose polymer), an acrylic resin, a cyclic polyolefin (COP), and a polycarbonate (PC). Although the protective film 416 is provided as a film for simply protecting the back surface of the polarizer 411, it may be provided as an optical film serving also as a retardation film having a desired optical compensation function.

In the case of a liquid crystal display device, a separate polarizing plate disposed on the side opposite to the polarizing plate 402 with respect to the liquid crystal cell 401 (liquid crystal cell) is constituted by sandwiching the surface of the polarizing plate with two optical films. As the polarizer and the optical film, those similar to the polarizer 411 and the protective film 416 of the polarizing plate 402 can be used.

The easy-adhesion layer for improving the adhesiveness of the? / 4 retardation film 413 may be provided on the adhesive layer 412 side of the? / 4 retardation film 413. The adhesion facilitating layer is formed by performing the adhesion facilitating treatment on the adhesive layer 412 side of the? / 4 retardation film 413. Examples of the adhesion facilitating treatment include a corona discharge treatment, a plasma treatment, a frame treatment, an itro treatment, a glow treatment, an ozone treatment, a primer coating treatment, and the like. Among these adhesion facilitating treatments, from the viewpoint of productivity, the corona treatment and the plasma treatment are preferable as the adhesion facilitating treatment.

As described above, the polarizing plate 402 is positioned on the viewing side with respect to the liquid crystal cell 401, and the? / 4 retardation film 413 of the polarizing plate 402 is disposed on the opposite side of the polarizing plate 411 from the liquid crystal cell 401 The linearly polarized light emitted from the liquid crystal cell 401 and transmitted through the polarizer 411 on the viewer side is converted into circularly polarized light or elliptically polarized light by the? / 4 retardation film 413 . Thus, in the case where the observer attaches the polarizing sunglasses and observes the display image of the liquid crystal display device 400, regardless of the angle between the transmission axis of the polarizer 411 and the transmission axis of the polarizing sunglass, The display image can be observed by guiding the component of the light parallel to the axis to the observer's eye.

&Lt; About the rate of dimensional change of the obliquely drawn film &

Next, the dimensional change rate of the obliquely drawn film (optical film) used as the retardation film (for example, a? / 4 retardation film) of the above-mentioned polarizing plate will be described.

The optical film of this embodiment, that is, the optical film in which the slow axis is inclined by 10 to 80 degrees with respect to one side of the film contour in the film plane, is moved in the fast axis direction and the slow axis direction Are referred to as? D _F (%) and? D _{L (} %), respectively. That is, the distance between two points arranged in the fast axis direction in the optical film, and the distances before and after the optical film is allowed to stand at 90 占 폚 for 120 hours are a1 (mm) and a2 (mm) In the optical film, when distances between two points arranged in the slow axis direction are assumed to be b1 (mm) and b2 (mm) before and after the optical film is allowed to stand at 90 DEG C for 120 hours,

? D _F = {(a2-a1) / a1} 100

DELTA D _L = {(b2-b1) / b1} x100

to be. In the present embodiment, in the central portion and the both end portions in the direction along the one side of the outline of the film,

0%? D _F <0.5% ... (One)

ΔD _L <0% ... (2)

Respectively.

By satisfying the conditional expressions (1) and (2) with respect to the dimensional change rates? D _F and? D _L in the fast axis direction and the slow axis direction of the optical film, the optical film can expand in the fast axis direction under a high temperature environment, And shrinks in the direction of the slow axis.

Further, the reason why the optical film shrinks in the slow axis direction under a high temperature environment is as follows. The direction of the slow axis is the same as the stretching direction, and after stretching, the tensile stress remains in the direction of the slow axis in the optical film. In the high temperature environment, since the tensile stress is relaxed, the optical film shrinks in the slow axis direction. The reason why the optical film expands or does not change in the fast axis direction under a high temperature environment is that shrinkage stress remains in the fast axis direction after stretching or shrinkage stress and tensile stress do not remain in the fast axis direction Details of means for realizing such dimensional change rate? D _F will be described later.

By satisfying the conditional expressions (1) and (2), the optical film of the present embodiment does not shrink in the fast axis direction under a high temperature environment. Therefore, even if there is contraction in the slow axis direction under a high temperature environment, Can be suppressed in comparison with a film which shrinks in both the fast axis direction and the slow axis direction under a high temperature environment. Thus, when the polarizing plate is manufactured by adhering the optical film and the polarizer of this embodiment with an adhesive so that the slow axis of the optical film and the absorption axis (or transmission axis) of the polarizer become a desired angle (for example, 45 degrees) It is possible to suppress the deterioration of the quality of the polarizing plate, such as the curling of the polarizing plate due to the dimensional change of the optical film, the deterioration of the adhesion of the optical film to the polarizing element, and the peeling of the optical film from the polarizing element .

That is, if the adhesive is, for example, an ultraviolet curable adhesive, it becomes a high-temperature environment by heating for irradiation of ultraviolet rays or acceleration of curing. On the other hand, in the case where the adhesive is an aqueous adhesive such as a wool or the like, it becomes a high-temperature environment by heating or drying for promoting curing of the adhesive. Even in an environment where the temperature becomes high at such bonding, the optical film of the present embodiment can suppress the dimensional change (shrinkage) of the film as a whole without shrinking in the fast axis direction as described above. Can be suppressed.

As described above, curling of the polarizing plate is suppressed, so that in the organic EL display device to which the polarizing plate is applied, light leakage due to reflection of external light in black display can be suppressed. Further, in the liquid crystal display device corresponding to the polarizing sunglasses in which the polarizing plate is disposed on the viewer side of the liquid crystal cell, it is possible to suppress the occurrence of distortion in the image viewed through the polarizing plate, thereby suppressing deterioration of the visibility of the display image .

Recently, a high retardation film having a retardation of 10000 nm or more including polyethylene terephthalate and polyethylene naphthalate has also been proposed in order to improve the visibility even at an angle. Even when a polarizing plate is constituted by using such a film, when curling is generated in the polarizing plate due to the dimensional change of the film, the visibility of the display image is lowered. However, even in such a film, satisfying the above-described conditional expressions (1) and (2) can suppress the dimensional change of the entire film under a high-temperature environment and curl the polarizing plate, Also in the liquid crystal display device, deterioration of visibility can be suppressed.

Further, when the rate of dimensional change ΔD _F in the fast axis direction is 0.5% or more, the dimensional change (expansion) in the fast axis direction becomes too large as compared with the dimensional change (contraction) in the slow axis direction under a high temperature environment, Distortion may occur, which may cause curling of the polarizing plate or peeling of the optical film as described above. For this reason, in the conditional expression (1), the upper limit of the dimensional change rate? D _{F in} the fast axis direction is specified as 0.5%.

Further, since the optical film of the present embodiment is a film in which the residual solvent amount is 60 ppm or less, it is possible to design a film satisfying the above-mentioned conditional expressions (1) and (2) at the same time. More specifically, it is as follows.

In the film formation of the solution by the solution softening method, the residual solvent amount of the formed film is much more than 60 ppm in that a solvent is used for the film formation. As described above, since the film formed by the solution softening method has a low density of the resin and is liable to elongate both in the direction of the slow axis and the direction of the fast axis during the warp stretching, Tensile stress remains in both directions. And under a high temperature environment, as a result of the relaxation of the tensile stress, the film shrinks in both the slow axis direction and the fast axis direction. Therefore, even if the optical film satisfies the conditional formula (2), the conditional formula (1) is not satisfied.

On the other hand, a film having a residual solvent amount of 60 ppm or less can be formed by, for example, a melt soft-film forming method. Since the film formed by the melt soft-film-forming method has a higher resin density than the film (the components other than the solvent are the same) formed by the melt soft-film-forming method, the film is elongated in the fast- So that it is unreasonably extended by the force in the stretching direction in the slow axis direction. As a result, tensile stress remains in the slow axis direction in the film after warp stretching, and tensile stress hardly remains in the fast axis direction. Therefore, even if the film shrinks in the slow axis direction under a high temperature environment, it is difficult to shrink in the fast axis direction, and it is possible to design a film satisfying the conditional expressions (1) and (2) at the same time.

From the viewpoint of surely increasing the density of the resin contained in the film and making sure that the film design satisfying the conditional expressions (1) and (2) is satisfied at the same time, the preferable range of the residual solvent amount of the optical film of the present embodiment, 10 ppm or less.

Further, for example, the transversely stretched film is a film stretched in the width direction, but at the time of stretching, the tension for transporting the film is applied in the transporting direction (longitudinal direction), and therefore, Tensile stress is left in both directions of the fast axis direction (conveying direction) and the fast axis direction (conveying direction). Therefore, as a result of the relaxation of the tensile stress under the high-temperature environment of the film, the film shrinks in both the direction of the slow axis and the direction of the fast axis, and the condition (1) is not satisfied.

The longitudinally stretched film is a film stretched in the carrying direction (longitudinal direction). It can be considered that the stretched film extends in the longitudinal direction (slow axis direction) and contracts in the width direction (fast axis direction) Direction, and the contraction force in the fast axis direction is considered to be small. As a result, the residual stress in the fast axis direction is small, and even if the residual stress in the fast axis direction is relaxed under the high temperature environment of the film, the film never expands in the fast axis direction. On the contrary, under a high-temperature environment, the shrinkage in the direction of the slow axis is large, so that the entire film is liable to shrink. As a result, it is thought that the film shrinks slightly in the fast axis direction. Therefore, the longitudinally stretched film also does not satisfy condition (1).

As described above, the optical film of the present embodiment satisfying the conditional expressions (1) and (2) at the same time can be obtained by a stretching method other than the transverse stretching and the longitudinal stretching, that is, the oblique stretching Film.

It is preferable that the optical film of the present embodiment further satisfies the following conditional expression (1a). In other words,

0% <? D _F <0.5% ... (1a)

to be.

Since the optical film satisfying the conditional expression (1a) expands in the fast axis direction under a high temperature environment, even if there is shrinkage in the slow axis direction under a high temperature environment, the optical film changes the dimensional change (shrinkage) It can be surely suppressed as compared with a film which shrinks in both directions in the slow axis direction. Therefore, it is possible to reliably suppress the curl when the polarizing plate is formed by bonding the optical film and the polarizer, and to prevent leakage of light due to external light reflection when the polarizing plate is applied to the organic EL display device, It is possible to reliably suppress deterioration of visibility when applied to a display device.

On the other hand, when the optical axis of the optical axis of the optical axis of the optical axis of the optical axis of the optical axis of the optical axis of the optical axis of the optical axis is changed, , ΔD _FC (%) represents the rate of dimensional change in the fast axis direction before and after the optical film is allowed to stand at 90 ° C. for 120 hours at the central portion in the direction along the above-mentioned side, The dimensional change ratio in the fast axis direction before and after leaving the optical film at 90 占 폚 for 120 hours at the one end (for example, the end which becomes the leading side in oblique stretching) is defined as? D _{F -E1} (% a dimensional change in the (end to which the retarded side at the time for example oblique stretching), the other end portion of the along the one side direction, the optical film to stand at 90 ℃ 120 sigan fast axis in the front-rear direction, ΔD _{F - E2} (%),

(? D_{F -E1}+ ΔD_{F -E2}) / 2>? D_{F - C} ... (3)

Is satisfied. The reason is as follows.

When the polarizing plate is formed by adhering the optical film of the present embodiment to a polarizer through an adhesive, the adhesive shrinks at the time of curing (in a high temperature environment), even if it is an ultraviolet curable adhesive or a water-soluble adhesive. At this time, in the case of bonding using the ultraviolet curing type adhesive, when the ultraviolet ray as the active energy ray is irradiated, the amount of ultraviolet light received is measured at the widthwise center portion (corresponding to the widthwise center portion of the optical film) and the widthwise end The amount of light received by the ultraviolet ray is larger at the widthwise center portion than at the width end portion. Thus, it is presumed that the curing shrinkage of the adhesive at the time of ultraviolet ray irradiation is larger at the widthwise center portion than at the width end portion.

The difference in the amount of ultraviolet light received at the widthwise middle portion and the widthwise end portion means that when a UV light source for irradiating ultraviolet light with a narrower width than the necessary width is used, the widthwise center portion is different from the normal direction of the adhesive surface The ultraviolet rays are irradiated only on one side in the width direction with respect to the normal line of the application surface of the adhesive on the width end portion. In order to reduce fluctuations in the width direction of the ultraviolet light receiving amount, for example, a method of irradiating ultraviolet light with a width larger than a necessary width can be considered. However, this method requires a large UV lamp, Which is not preferable.

It is also known that, even when heating for accelerating the curing of the adhesive (ultraviolet curable adhesive, watercolor), the heat is easier to stay at the width center portion than at the width end portion, and the temperature is lowered at the width end portion. Therefore, even when heating is performed for accelerating the curing of the adhesive, it is presumed that the curing shrinkage of the adhesive is larger at the center of the width than at the width end.

A method of dealing with the deformation of the polarizing plate due to the curing shrinkage of the adhesive while ensuring a sufficient adhesive force between the optical film and the polarizer by the adhesive has been studied and as a result it has been found that the difference in the amount of expansion in the fast axis direction It has been found that the curl of the polarizing plate can be further suppressed in the entire width direction. 7 schematically shows the behavior of the adhesive and the optical film at the widthwise middle portion and the widthwise end portion in the curing of the adhesive in the present embodiment. Since the shrinkage and expansion are opposite to each other, for example, when the shrinkage of the adhesive is large and the expansion of the optical film is large at the same position in the width direction, the polarizing plate is formed so that the adhesive side is concave Curl.

By satisfying the condition (3), expansion of the optical film in the fast axis direction becomes small at the large width central portion of the shrinkage of the adhesive, and at the small width end portion of the adhesive shrinkage, It grows. Thereby, at the center of the width, it is possible to suppress what the polarizing plate tends to curl due to large shrinkage of the adhesive by small expansion in the fast axis direction of the optical film. Likewise, at the width end portion, it is possible to suppress what the polarizing plate tends to curl due to a large expansion in the fast axis direction of the optical film by small shrinkage of the adhesive. As a result, curl of the polarizing plate can be further suppressed in the entire width direction. Further, since the curl of the polarizing plate is further suppressed, the adhesiveness between the optical film and the polarizer by the adhesive can be sufficiently ensured and the peeling of the optical film can be reliably suppressed.

The optical film of the present embodiment is elongated and the direction along the sides of the outline of the film is preferably a width direction perpendicular to the longitudinal direction in the film plane of the optical film. In this case, in the central portion and each end in the width direction, he is possible to realize the long shape of the optical film satisfying the above condition equation (1) (2) with respect to the dimensional change rate ΔD and ΔD _{F L.} In addition, a polarizing plate can be produced by a roll-to-roll method using such an elongated optical film.

The polarizing plate (for example, the polarizing plate 301 of Fig. 5 and the polarizing plate 402 of Fig. 6) of the present embodiment can be used in combination with the optical film (for example,? / 4 retardation films 311 and 413) And a polarizer (for example, a polarizer 313 · 411). The optical film is located on one side with respect to the polarizer such that the slow axis in the film plane crosses the absorption axis (or transmission axis) of the polarizer. Since the optical film of the present embodiment can suppress the dimensional change of the entire film without shrinking in the fast axis direction under a high temperature environment, even when a polarizing plate is produced by bonding the optical film and the polarizer, It is possible to suppress the curling of the polarizing plate or the peeling of the optical film due to the dimensional change of the optical film under the environment.

Therefore, when the display cell is the organic EL element 101 and the? / 4 retardation film 311 of the polarizing plate 301 is disposed on the organic EL display device 100 , It is possible to suppress light leakage due to external light reflection in black display by suppressing curling of the polarizing plate 301. [

The display cell is a liquid crystal cell 401 and the? / 4 retardation film 413 of the polarizing plate 402 is disposed on the side opposite to the liquid crystal cell 401 with respect to the polarizer 411, (400) suppresses curling of the polarizing plate (402), thereby preventing occurrence of distortion in an image viewed through the polarizing plate (402), and suppressing deterioration of the visibility of the display image.

&Lt; Means for Realizing the Rate of Dimensional Change in the Accelerating Axial Direction >

Next, the means for realizing the dimensional change rate? D _F in the fast axis direction defined by the conditional expression (1) in the above-described optical film of the present embodiment will be specifically described.

(Setting of the force (tension) in the carrying direction applied to both end portions in the width direction at the time of oblique drawing)

Fig. 8 schematically shows forces in the carrying direction applied to both end portions in the width direction of the elongated film in the elongating portion 5 of the obliquely-drawn film producing apparatus 1 shown in Fig. In the stretching portion 5, both end portions in the width direction of the long film are held by the pair of wave portions Ci · Co, one wave portion Ci is relatively advanced with respect to the other wave portion Co, The oblique stretching step of stretching the long film in the oblique direction with respect to the width direction and obtaining the warped stretched film constituting the optical film is performed.

Here, the force applied in the carrying direction by the grasping of each waveguide Ci · Co and the movement in the carrying direction at each end in the width direction of the long film before the oblique drawing (for example, in the preheating zone Z1) (N), respectively. Further, during the warp stretching (for example, in the stretching zone Z2), at the end portions in the width direction of the long film, the gripping and transporting directions of the waveguide Co on the relatively delayed side and the waveguide Ci on the relatively- (N) and Ti (N), respectively. At this time, in the oblique stretching step,

(Ti-Tr) /Tr?1.7 ... (A)

(Tr-To) /Tr? 1.5 ... (B)

The long film is stretched in the oblique direction with respect to the width direction. The above conditional expressions (A) and (B) can be modified as the following conditional expressions (A ') and (B'), respectively. In other words,

Ti? 2.7Tr ... (A ')

To? -0.5Tr ... (B ')

to be.

The waveguide Ci 占 Co co is attached to a chain moving along the rail Ri 占 Ro in the stretching section 5, and the chain is divided into zones (preheating zone Z1, stretching zone Z2, heat fixing zone Z3 ) By the rotation of the drive roller. The force Tr · Ti · To can be replaced by the driving force of the motor for rotating the driving roller in each zone. In the present embodiment, by controlling the driving force, it is possible to satisfy the conditional expressions (A) and Thereby obtaining an optical film (oblique stretched film).

(The conditional expressions (A ') and (B') are satisfied) by satisfying the conditional expressions (A) and (B) The force in the conveying direction which is applied during the warp stretching before the oblique stretching decreases at the end on the delay side and the amount of change (increase amount) of the force in the conveying direction at the end on the preceding side, The amount of change (reduction amount) of the force in the carrying direction at the end portion on the side of the end portion is also large.

By performing oblique stretching under these conditions, the film is stretched in the oblique stretching direction (slow axis direction) at each position in the width direction of the long film (at least at the center portion and the both end portions in the width direction) A state in which the film is shrunk against the tensile during transportation or a state in which the film is not elongated or contracted due to the balance with the tensile can be made. At this time, although the conveying direction and the fast axis direction do not always coincide with each other, the film is shrunk in the conveying direction because the amount of displacement is small even if the two are shifted, so that stress that contracts in the fast axis direction can be left on the film . Further, in the film which neither extends nor shrinks in the carrying direction, a film which does not largely elongate or shrink in the fast axis direction can be obtained.

Therefore, under a high temperature environment, the residual stress (shrinkage stress) in the fast axis direction can be relaxed, and the film can be prevented from expanding, expanding, and shrinking, and the dimensional change rate? D in the fast axis direction _F can be realized.

(Cooling of the delay side end portion in oblique stretching)

Fig. 9 schematically shows another configuration of the stretching section 5. Fig. The stretching section 5 may have a cooling mechanism 21. The cooling mechanism 21 cools the end gripped by the waveguide Co on the relatively delayed side of each end in the width direction of the long film in the warp stretching process in the stretching section 5. [ This cooling mechanism 21 can be constituted by, for example, a blower mechanism (a cooler, a fan, or the like) blowing a cold wind to a long film.

In the oblique stretching process, by shrinking the retarded film end portion by the cooling mechanism 21, contraction stress can be imparted to the film end portion. Thereby, the shrinkage stress remaining in the fast axis direction can be further increased by oblique stretching satisfying the above-described conditional expressions (A) and (B). Therefore, under a high temperature environment, the film can be further expanded by relaxation of the residual stress (shrinkage stress) in the fast axis direction of the warp stretched film, and the dimensional change rate? D _F in the fast axis direction defined by the conditional expression (1) It becomes possible to reliably realize it.

(Multi-step gradient elongation)

Fig. 10 schematically shows another configuration of the stretching section 5. As shown in Fig. In the oblique stretching process by the stretching section 5, a long film is stretched in the transverse direction of the long film such that the slow axis is oriented at an orientation angle (for example, 60 degrees) larger than a desired orientation angle (for example, 45 degrees) The long film may be obliquely stretched so that the slow axis is oriented at a desired orientation angle (for example, 45 DEG). Such multilevel oblique stretching can be realized by appropriately changing the rail pattern of the stretching portion 5.

In the oblique stretching process, as the elongation angle (turning angle at the time of bending) becomes larger, that is, as the orientation angle of the slow axis by the oblique stretching becomes larger, the tensile stress in the slow axis direction becomes larger and the shrinkage stress Is increased. As described above, by generating a large shrinkage stress in the fast axis direction once, the large shrinkage stress can still remain (although the shrinkage stress is somewhat reduced) even after the drawing angle is reduced. Therefore, under a high temperature environment, the film can be further expanded by relaxation of the residual stress (shrinkage stress) in the fast axis direction of the warp stretched film, and the dimensional change rate? D _F in the fast axis direction defined by the conditional expression (1) It becomes possible to reliably realize it. At this time, cooling of the delay side end portion is not essential, but the effect of cooling the delay side end portion together with multistage warp stretching can be further enhanced.

<Examples>

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

[Production of long film]

(Production of long film A1)

A polycarbonate resin film (PC film) as the long film A1 was produced by the following production method (melt flexible film-forming method).

Polymerization was carried out using a batch polymerization apparatus comprising two vertical type reactors having a stirring blade and a reflux condenser controlled at 100 ° C. (BHEPF), isosorbide (ISB), diethylene glycol (DEG), diphenyl carbonate (DPC), and magnesium acetate tetrahydrate BHEPF / ISB / DEG / DPC / magnesium acetate = 0.348 / 0.490 / 0.162 / 1.005 / 1.00 10 ^-5 in molar ratio. After sufficiently replacing the inside of the reactor with nitrogen (oxygen concentration 0.0005 to 0.001 vol%), heating was carried out with a heating medium, and stirring was started when the internal temperature reached 100 占 폚. After 40 minutes from the start of the temperature rise, the internal temperature was controlled to reach 220 ° C and maintained at this temperature, and the decompression was started. After reaching 220 ° C, the temperature was changed from 90 minutes to 13.3 kPa. The phenol vapor produced as a byproduct together with the polymerization reaction was led to a reflux condenser at 100 ° C to return the monomer component slightly contained in the phenol vapor to the reactor and to recover the non-condensed phenol vapor by the condenser at 45 ° C.

Nitrogen was introduced into the first reactor to once pressurize to atmospheric pressure, and then the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Then, the temperature rise and the decompression in the second reactor were started, and the temperature was increased from 240 ° C to 0.2 kPa in 50 minutes. Thereafter, the polymerization was allowed to proceed until a predetermined stirring power was reached. Nitrogen was introduced into the reactor at a point of time when the predetermined power was reached, and the reaction solution was extracted in the form of strands and pelletized with a rotary cutter to obtain a solution of BHEPF / ISB / DEG = 34.8 / 49.0 / 16.2 To obtain a polycarbonate resin A having a copolymerization composition. The polycarbonate resin A had a reduced viscosity of 0.430 dL / g and a glass transition temperature of 128 캜.

The resulting polycarbonate resin A was vacuum-dried at 80 DEG C for 5 hours, and then extruded through a single screw extruder (manufactured by Isuzaku Corporation, screw diameter 25 mm, cylinder set temperature 220 DEG C), T die (width 900 mm, : 220 占 폚), a cooling roll (set temperature: 120 to 130 占 폚), and a winding machine was used to produce a polycarbonate resin film having a thickness of 195 占 퐉 and a residual solvent amount of 10 ppm as a long film A1 Respectively.

(Production of long film A2)

A polycarbonate resin film (PC film) as the long film A2 was produced by the following production method (solution casting film-forming method).

<Doping composition>

Polycarbonate resin A (the same resin as used in the production of the long film A1) 100 parts by mass

Methylene chloride 430 parts by mass

Methanol  90 parts by mass

The above composition was put in a hermetically sealed container, kept at 80 캜 under pressure, and completely dissolved with stirring to obtain a dope composition.

The dope composition was then filtered, cooled, maintained at 33 占 폚, uniformly plied onto a stainless steel band, and dried at 33 占 폚 for 5 minutes. Thereafter, the drying time was adjusted at 65 캜, peeled off from the stainless steel band, and the drying was terminated while transferring the film to a plurality of rolls to obtain a polycarbonate resin film having a film thickness of 75 탆 and a residual solvent amount of 110 ppm, A2.

(Production of long film B1)

An alicyclic olefin polymer-based resin film (COP film) as the long film B1 was produced by the following production method (melt flexible film-forming method).

1.2 parts by mass of 1-hexene, 0.15 parts by mass of dibutyl ether and 0.30 parts by mass of triisobutylaluminum were put into a reactor at room temperature and mixed in 500 parts by mass of dehydrated cyclohexane in a nitrogen atmosphere. 20 parts by weight of cyclo [4.3.0.12,5] dec-3,7-diene (dicyclopentadiene, hereinafter abbreviated as DCP), 1,4-methano-1,4,4a, 9a-tetrahydrofluorene 140 parts by mass of a norbornene monomer mixture (hereinafter abbreviated as MTF) and 40 parts by mass of 8-methyl-tetracyclo [4.4.0.12,5.17,10] -dodeca-3-ene And 40 parts by mass of tungsten hexachloride (0.7% toluene solution) were continuously added over 2 hours to polymerize. 1.06 parts by mass of butyl glycidyl ether and 0.52 parts by mass of isopropyl alcohol were added to the polymerization solution to inactivate the polymerization catalyst to terminate the polymerization reaction.

Subsequently, 270 parts by mass of cyclohexane was added to 100 parts by mass of the reaction solution containing the obtained ring-opening polymer, and 5 parts by mass of a nickel-alumina catalyst (manufactured by Nikkiso Co., Ltd.) was further added as a hydrogenation catalyst. The reaction solution was heated to 200 DEG C while being stirred with stirring at 5 MPa and reacted for 4 hours to obtain a reaction solution containing 20% of DCP / MTF / MTD ring opening polymerized hydrogenated polymer.

After the hydrogenation catalyst was removed by filtration, a soft polymer (Septon 2002, manufactured by Kuraray Co., Ltd.) and an antioxidant (Irganox 1010, manufactured by Ciba Specialty Chemicals) were added and dissolved in the obtained solution, respectively (All 0.1 parts by mass per 100 parts by mass of the polymer). Subsequently, cyclohexane and other volatile components as a solvent were removed from the solution by using a cylindrical condenser dryer (manufactured by Hitachi Seisakusho Co., Ltd.), and the hydrogenated polymer was extruded from the extruder in a molten state into a strand shape, Pelletized and recovered. The copolymerization ratio of the respective norbornene monomers in the polymer was calculated by the composition of residual norbornenes in the solution after the polymerization (by gas chromatography), and it was found that DCP / MTF / MTD = 10/70/20 Respectively. The ring opening polymer hydrogenation product had a weight average molecular weight (Mw) of 31,000, a molecular weight distribution (Mw / Mn) of 2.5, a hydrogenation rate of 99.9% and a glass transition temperature Tg of 134 캜.

The resulting ring-opening polymeric hydrogenated product pellets were dried at 70 ° C for 2 hours using a hot-air drier through which air was circulated to remove moisture. Then, the pellets were melt-kneaded using a single-screw extruder (T-die lip material: Tungsten carbide, peel strength with molten resin: 90 mm, screw diameter 90 mm, manufactured by Mitsubishi Kagaku Kogyo Co., Ltd.) And an alicyclic olefin polymerization system resin film (COP film) having a thickness of 75 mu m and a residual solvent amount of 10 ppm was obtained as a long film B1.

(Production of long film B2)

Except that the dope composition was prepared by using the hydrogenated polymer obtained by the production of the long film B1 instead of the polycarbonate resin A and the prepared dope composition was used in the same manner as the production of the long film A2 by the solution casting film forming method , And an alicyclic olefinic polymer resin film (COP film) having a residual solvent amount of 110 ppm was produced as a long film B2.

(Production of long film C)

A polyethylene naphthalate-based resin film (PEN film) as the long film C was produced by the following production method (melt softening film-forming method).

&Lt; Synthesis of polyethylene naphthalate >

100 parts by mass of 2,6-naphthalenedicarboxylic acid dimethyl ester and 60 parts by mass of ethylene glycol were subjected to ester exchange reaction using 0.03 part by mass of cobalt acetate 4 hydrate as an ester exchange catalyst according to a conventional method. Thereafter, 0.023 parts by mass of trimethyl phosphate was added, and the transesterification reaction was substantially terminated. Then, 0.024 part by mass of antimony trioxide was added and the polycondensation reaction was carried out under a high temperature and high vacuum in a usual manner to obtain a copolymer having an intrinsic viscosity of 0.62 dL / g at a phenol / tetrachloroethane mixed solvent (mass ratio 1: 1) g of polyethylene naphthalate was obtained.

<Production of Film>

The resulting polyethylene naphthalate pellets were dried at 180 DEG C for 3 hours and fed to an extruder hopper. The molten polymer was melted at a melting temperature of 300 占 폚 and passed through a slit-shaped die of 9.0 mm and extruded on a rotary cooling drum having a surface temperature of 40 占 폚 to obtain a polyethylene naphthalate-based resin film having a residual solvent amount of 8 ppm as a long film C.

(Production of Long Film D)

A cellulose ester based resin film (CE film) as the long film D was produced by the following production method (solution flexible film-forming method).

<Fine Particle Dispersion>

Fine particles (Aerosil R972V manufactured by Nippon Aerosil Co., Ltd.) 11 parts by mass

ethanol 89 parts by mass

 The mixture was stirred with a dissolver for 50 minutes, and then dispersed with Manton-Gaulin.

&Lt; Particulate additive liquid &

On the basis of the following composition, the fine particle dispersion was added slowly while stirring well in a dissolution tank containing methylene chloride. And dispersed by an attritor so that the particle diameter of the secondary particles became a predetermined value. The solution was filtered with Fine Mat NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle addition liquid.

Methylene chloride 99 parts by mass

Fine particle dispersion   5 parts by mass

&Lt;

To prepare a main dope liquid having the following composition. First, methylene chloride and ethanol were added to the pressurization-dissolving tank. Cellulose acetate was added to the pressurized dissolution tank containing the solvent while stirring. This was heated and completely dissolved while stirring. This was measured with an Azumi Co., Ltd., manufactured by Azumi Co., Ltd. 244 was used for filtration to prepare a main dope solution. As the sugar ester compound, the compound synthesized by the following synthesis example was used.

&Quot; Composition of the main doping solution &quot;

Cellulose acetate propionate (acetyl group substitution degree: 1.39, propionyl group substitution degree: 0.50, total substitution degree: 1.89) 100 parts by mass

Ester ester compound 5.0 parts by mass

The particulate additive liquid   1 part by mass

Methylene chloride 340 parts by mass

ethanol      64 parts by mass

(Synthesis of sugar ester compound)

A sugar ester compound was synthesized by the following process.

34.2 g (0.1 mol) of sucrose, 180.8 g (0.6 mol) of anhydrous benzoic acid, and 379.7 g (4.8 mol) of pyridine were fed to four-necked colbins equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen gas- The temperature was elevated while nitrogen gas was bubbled through the nitrogen gas introduction tube, and the esterification reaction was carried out at 70 DEG C for 5 hours.

Subsequently, the inside of the colb inside was reduced to 4 x 10 ² Pa or less, excess pyridine was distilled off at 60 ° C, the pressure in the chamber was reduced to 1.3 x 10 Pa or less, and the temperature was raised to 120 캜 to obtain an anhydrous benzoic acid Most of the benzoic acid was distilled off.

Finally, 100 g of water was added to the separated toluene layer, and the mixture was washed with water at room temperature for 30 minutes. Then, the toluene layer was collected and toluene was distilled off at 60 캜 under reduced pressure (4 × 10 ² Pa or less) 1, A-2, A-3, A-4 and A-5 (sugar ester compound).

The obtained mixture was analyzed by HPLC and LC-MASS to find that the content of A-1 was 1.3 mass%, that of A-2 was 13.4 mass%, that of A-3 was 13.1 mass%, that of A-4 was 31.7 mass%, that of A- %. The average degree of substitution was 5.5.

&Lt; Measurement conditions of HPLC-MS >

1) LC section

(JASCO CO-965), detector (JASCO UV-970-240 nm), pump (JASCO PU-980), deaerator (JASCO DG-980-50) manufactured by Nihon Bunko Co.,

Column: Inertsil ODS-3 Particle diameter 5 mu m 4.6 x 250 mm (manufactured by GL Sciences Inc.)

Column temperature: 40 DEG C

Flow rate: 1 ml / min

Mobile phase: THF (1% acetic acid): H ₂ O (50:50)

Injection volume: 3μl

2) MS Department

Apparatus: LCQ DECA (Thermo Quest Co., Ltd.)

Ionization method: Electrospray ionization (ESI) method

Spray Voltage: 5 kV

Capillary temperature: 180 ° C

Vaporizer temperature: 450 ° C

Subsequently, the main dope liquid was uniformly plied on the stainless steel belt support using an endless belt fusing device. On the stainless steel belt support, the solvent was evaporated until the amount of the residual solvent in the long film (cast) was 75%, peeled off from the stainless steel belt support, Mu m and a residual solvent amount of 600 ppm was obtained as a long film D. [

[Production of warp stretched film]

(Production of warp stretched film 101)

The rolled body of the long film A1 (PC film, residual solvent amount: 10 ppm) obtained above was set in the film feed portion 2 of the oblique drawn film production apparatus 1 shown in Fig. 1, and the film feed portion 2, the long film A1 was loosened, fed to the stretching section 5, and subjected to oblique stretching in the stretching section 5 to obtain a long oblong stretched film 101 having a thickness of 45 mu m. Then, the warp stretched film 101 was conveyed to the film winding section 9 and wound in a roll shape. The temperature condition at the time of stretching in the stretching portion 5 was appropriately selected in the range of (Tg-10) DEG C to (Tg + 30) DEG C of the film.

Further, before the oblique stretching, the forces applied in the transport direction by the wave coils Co and Ci at the respective end portions in the width direction of the long film are respectively the same Tr (N) (N) and Ti (N), respectively, of the force applied in the carrying direction by the waveguide Co on the relatively delayed side and the waveguide Ci on the relatively preceding side, In the oblique stretching step in the stretching section 5, the long film was stretched in the oblique direction so that (Ti-Tr) /Tr=1.3, (Tr-To) /Tr=1.0. In addition, as the force Tr · Ti · To, the driving force of the motor for rotating the driving roller (the control of the motor Device readable).

In addition, the stretching angle of the film in the stretching portion 5 was set at 45 degrees. The elongation angle refers to an angle (orientation angle) formed by the in-plane slow axis of the film at the end of the warp stretching process and the width direction of the film. The stretching angle was adjusted by changing the length of the rail, the degree of bending, and the like in the bent portion (stretching zone Z2) of the stretching portion 5.

(Production of warp stretched film 102)

The elongated film A1 was stretched in the oblique direction (45 ° direction with respect to the width direction) so as to be (Ti-Tr) /Tr=2.0 and (Tr-To) /Tr=1.5 in the stretching section 5. Otherwise, the oblique stretched film 102 was produced in the same manner as the oblique stretched film 101 was produced.

(Production of warp stretched film 103)

The elongated film A1 was stretched in the oblique direction (45 ° direction with respect to the width direction) so as to satisfy (Ti-Tr) /Tr=3.0 and (Tr-To) /Tr=2.0 in the stretching portion 5. Otherwise, the obliquely drawn film 103 was produced in the same manner as in the production of the obliquely drawn film 101.

(Production of warp stretched film 104)

The elongated film A1 was stretched in the oblique direction (45 ° direction with respect to the width direction) so as to satisfy (Ti-Tr) /Tr=3.0 and (Tr-To) /Tr=3.0 in the stretching portion 5. Further, of the respective end portions in the width direction of the long film A1, the end portions held by the wave earth Co on the relatively delayed side were cooled by injection of cooling wind. At this time, in the width direction of the long film A1, the end gripped by the wave earth Co on the delay side was cooled by 10 DEG C lower than the end gripped by the wave front Ci on the preceding side. Otherwise, in the same manner as in the production of the warped stretched film 101, the warped stretched film 104 was produced.

(Production of warp stretched film 105)

In the stretching portion 5, the long film A1 was stretched in the oblique direction (45 ° direction with respect to the width direction) so that (Ti-Tr) /Tr=3.5 and (Tr-To) /Tr=3.5. Further, with respect to the width direction of the long film A1, the long film A1 is obliquely stretched so that the slow axis is oriented at 60 degrees, which is larger than the desired orientation angle (here, 45 degrees), and then the slow axis is oriented at 45 degrees , And the long film A1 was obliquely stretched. Otherwise, the obliquely drawn film 105 was produced in the same manner as in the production of the obliquely drawn film 101.

(Production of warp stretched film 106)

The elongated film A1 was stretched in the oblique direction (45 ° direction with respect to the width direction) so as to satisfy (Ti-Tr) /Tr=4.0 and (Tr-To) /Tr=4.0 in the stretching portion 5. Further, of the respective end portions in the width direction of the long film A1, the end portions held by the wave earth Co on the relatively delayed side were cooled by injection of cooling wind. At this time, in the width direction of the long film A1, the end gripped by the wave earth Co on the delay side was cooled by 10 DEG C lower than the end gripped by the wave front Ci on the preceding side. Further, with respect to the width direction of the long film A1, the long film A1 is obliquely stretched so that the slow axis is oriented at 60 DEG which is larger than the desired orientation angle (herein, 45 DEG), and thereafter, , A long film A1 was obliquely drawn. Otherwise, the oblique stretched film 106 was produced in the same manner as the oblique stretched film 101.

(Production of warp stretched film 107)

An oblique stretched film 107 was produced in the same manner as in the production of the obliquely stretched film 104 except that oblique stretching was performed using the long film A2 (PC film, residual solvent amount: 110 ppm) instead of the long film A1.

(Production of warp stretched film 108)

The oblique stretched film 108 was produced in the same manner as in the production of the obliquely stretched film 103 except that the rail pattern in the stretching section 5 was changed and oblique stretching was performed so that the orientation angle was 75 °.

(Production of warp stretched film 109)

An oblique stretched film 109 was produced in the same manner as in the production of the obliquely drawn film 103 except that the rail pattern in the stretching section 5 was changed and oblique stretching was performed so that the orientation angle was 15 °.

(Production of warp stretched film 110)

An oblique stretched film 110 was produced in the same manner as in the production of the warped stretched film 103 except that oblique stretching was performed using a long film D (CE film, residual solvent amount 600 ppm) instead of the long film A1.

(Production of warp stretched film 111)

An oblique stretched film 111 was produced in the same manner as in the production of the warped stretched film 110 except that the rail pattern in the stretching section 5 was changed and oblique stretching was performed so that the orientation angle was 75 °.

(Production of warp stretched film 112)

An oblique stretched film 112 was produced in the same manner as in the production of the obliquely stretched film 103 except that oblique stretching was performed using a long film B2 (COP film, residual solvent amount 110 ppm) instead of the long film A1.

(Production of warp stretched film 113)

An oblique stretched film 113 was produced in the same manner as in the production of the obliquely drawn film 103 except that oblique stretching was performed using the long film B1 (COP film, residual solvent amount 10 ppm) instead of the long film A1.

(Production of warp stretched film 114)

An oblique stretched film 114 was prepared in the same manner as in the production of the warp stretched film 103 except that oblique stretching was performed using a long film C (PEN film, residual solvent amount 8 ppm) instead of the long film A1.

(Production of warp stretched film 115)

The elongated film A1 was stretched in the oblique direction (45 ° direction with respect to the width direction) so that the stretching portion 5 had (Ti-Tr) /Tr=2.0 and (Tr-To) /Tr=2.0. Otherwise, in the same manner as in the production of the warp stretched film 101, the warp stretched film 115 was produced.

(Production of warp stretched film 116)

The elongated film A1 was stretched in the oblique direction (45 ° direction with respect to the width direction) so as to be (Ti-Tr) /Tr=4.0 and (Tr-To) /Tr=5.5 in the stretching portion 5. Otherwise, the obliquely drawn film 116 was produced in the same manner as in the production of the obliquely drawn film 101.

(Production of warp stretched film 117)

The elongated film A1 was stretched in the oblique direction (45 ° direction with respect to the width direction) so as to be (Ti-Tr) /Tr=1.7 and (Tr-To) /Tr=1.5 in the stretching section 5. Otherwise, the obliquely drawn film 117 was produced in the same manner as in the production of the obliquely drawn film 101.

[Measurement of rate of dimensional change? D _F ,? D _L ]

(Width direction center portion C), one end portion E1 (end portion gripped by the preceding side waveguide) and the other end portion E2 (end portion gripped by the delay side waveguide) of the obliquely drawn films 101 to 117 produced above , The distance a1 (mm) between two points is measured with a ruler or the like, and two points arranged in the direction of the ground axle are displayed, and the distance between two points b1 (mm) was measured with a ruler or the like. Since the slow axis direction is the stretching direction (orientation angle direction) and the fast axis direction is the direction perpendicular to the slow axis direction within the film plane, the slow axis direction and the fast axis direction on the obliquely stretched films 101 to 117 It is easy to specify.

Next, the warp stretched films 101 to 117 were allowed to stand at 90 占 폚 for 120 hours. Then, in each of the widthwise central portion C, one end portion E1 and the other end portion E2 of each film, And the distance b2 (mm) between the two points arranged in the direction of the slow axis was measured with a ruler or the like. Then, the central portion of the film C, the ends E1 · E2 each, and calculates the fast axis dimensional change ΔD _F (%) _L ΔD and dimensional change of the slow axis direction (%) in a direction by the following equation.

? D _F = {(a2-a1) / a1} 100

DELTA D _L = {(b2-b1) / b1} x100

Dimensional change rate ΔD _F · ΔD _L These and shows a variety of parameters related to the inclined oriented films (101 to 117) are shown in Table 1. In Table 1, the dimensional change rate? D _F in the width direction center portion C and the end portions E1 and E2 of the film in the fast axis direction is represented by? D _{F -C ,?} D _{F -E1} and? D _{F -E2} , The rate of dimensional change DELTA D _L in the slow axis direction at the end portions E1 and E2 is represented by DELTA D _{L -C} , DELTA D _{L -E1} and DELTA D _{L -E2} .

[Production of polarizer]

(Preparation of Polarizer 201)

<Production of Polarizer>

A long polyvinyl alcohol film having a thickness of 60 mu m was dipped in a dyeing bath (30 DEG C) containing iodine and potassium iodide while being continuously conveyed through a guide roll, subjected to dyeing treatment and 2.5 times of stretching treatment and then treated with boric acid and potassium iodide , And the obtained iodine-PVA polarizer having a thickness of 12 占 퐉 was dried in a dryer at 50 占 폚 for 30 minutes to obtain a film having a water content of 4.9% Polarizers were obtained.

&Lt; Preparation of ultraviolet curable adhesive >

The following components were mixed to prepare a liquid ultraviolet curable adhesive (UV adhesive).

3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate

40 parts by mass

Bisphenol A type epoxy resin 60 parts by mass

Diphenyl [4- (phenylthio) phenyl] sulfonium hexafluoroantimonate (cationic polymerization initiator) 4.0 parts by mass

<Junction>

After the corrugated surface of the warp stretched film 101 was subjected to corona treatment, the prepared ultraviolet curing type adhesive was applied to a thickness of 3 탆 by a coating machine equipped with a chamber doctor. The bonding surface of the protective film 1 (Konica Minolta Tact KC4UY, thickness 40 μm, manufactured by Konica Minolta Co., Ltd.) was subjected to corona treatment, and then the above-described ultraviolet curable adhesive was similarly applied to a thickness of 3 μm.

Immediately thereafter, the obliquely stretched film 101 was bonded to one surface of the polarizer prepared above, and the protective film 1 was bonded to the other surface of the polarizer through the coating rolls of the ultraviolet curable adhesive, respectively. At this time, both were bonded so that the width direction of the obliquely drawn film 101 and the absorption axis (or transmission axis) of the polarizer coincided (the angle formed by the slow axis of the obliquely drawn film 101 and the absorption axis of the polarizer is 45 ). Thereafter, a metal halide lamp was turned on at a line speed of 20 m / min to irradiate ultraviolet rays from the obliquely drawn film 101 side so as to have an accumulated light quantity of 320 mJ / cm 2 at a wavelength of 280 to 320 nm, To prepare a polarizing plate 201. Since the production of the polarizing plate 201 is performed in a roll-to-roll manner, finally, the long polarizing plate 201 is cut along the width direction to obtain a sheet-like polarizing plate 201.

(Production of polarizing plates 202 to 217)

Polarizing plates 202 to 217 were produced in the same manner as in the production of polarizing plate 201 except that the obliquely drawn film 101 was changed to obliquely drawn films 102 to 117. [

(Production of polarizing plate 218)

A polarizing plate 218 was produced in the same manner as in the production of the polarizing plate 203 except that the obliquely drawn film 103, the polarizer, the polarizer and the protective film 1 were bonded using a water-shed (polyvinyl alcohol adhesive) . Further, for the purpose of promoting curing of the adhesive, the polarizing plate 218 was dried at 80 DEG C for 2 minutes.

(Production of polarizing plate 219)

A polarizing plate 219 was produced in the same manner as in the production of the polarizing plate 203 except that the protective film 2 was used in place of the protective film 1. The protective film 2 is manufactured as follows.

&Lt; Fabrication of Protective Film (2)

&Quot; Preparation of fine particle dispersion &quot;

11.3 parts by mass of fine particles (Aerosil R812, manufactured by Nippon Aerosil Co., Ltd.) and 84 parts by mass of ethanol were mixed and stirred with a dissolver for 50 minutes and then dispersed with mannitol-gaulin to prepare a fine particle dispersion.

Next, 5 parts by mass of the fine particle dispersion was slowly added to dichloromethane (100 parts by mass) sufficiently stirred in the dissolution tank. In addition, the particles were dispersed in the attritor so that the particle size of the secondary particles became a predetermined size. The solution was filtered with Fine Mat NF (manufactured by Nippon Seisen Co., Ltd.) to prepare a fine particle addition liquid.

"Preparation of DOP"

The main dope of the following composition was prepared. First, dichloromethane and ethanol were added to the pressure melting tank. Then, the cycloolefin resin A (the antioxidant was added), the ultraviolet absorber, and the fine particle addition liquid were added to the pressure melting tank with stirring. The solution was heated and completely dissolved while stirring, to obtain an aziric acid solution (product of Azumi Co., Ltd., product of Azumi Co., Ltd.). 244, and the main dope was prepared.

Cycloolefin resin A 100 parts by mass

Antioxidant (IRGNOX1010 (BASF Japan) 0.5 parts by mass

Dichloromethane 200 parts by mass

ethanol  10 parts by mass

UV absorber (TINUVIN 928 (BASF Japan)   3 parts by mass

The particulate additive liquid     3 parts by mass

The cycloolefin resin A has the following structure.

Subsequently, the main dope was uniformly plied on the stainless steel belt support at a temperature of 31 DEG C and 1800 mm width using an endless belt fusing device. The temperature of the stainless steel belt was controlled at 28 占 폚. The conveyance speed of the stainless steel belt was 20 m / min.

On the stainless steel belt support, the solvent was evaporated until the amount of residual solvent in the cast (cast) film was 30%. Then, the flexible film was peeled off on the stainless steel belt support at a peel tension of 128 N / m. The peeled coherent film was stretched 2.2 times in the width direction under the condition of 160 캜. The residual solvent at the start of the stretching was 5% by mass. Subsequently, the drying zone was conveyed with a plurality of rollers, and the end portion of the tenter clip was slit with a laser cutter, and then wound to obtain a protective film 2 having a thickness of 40 m.

[evaluation]

(Curl amount)

The prepared polarizing plates 201 to 219 were cut to a size of 30 cm x 30 cm to obtain a polarizing plate sample. Then, the obtained polarizing plate sample was arranged such that the convex side of the sample faced the stage surface. Then, the height of the four corner portions a to d of the sample of the polarizing plate from the stage surface was measured, and the curl amount C was obtained by the following relational expression.

C = [(Ha + Hb + Hc + Hd) / 4] / L

only,

Ha: Height (mm) of the corner portion a from the stage surface

Hb: height (mm) of the corner portion b from the stage surface

Hc: height (mm) of the corner portion c from the stage surface

Hd: height of the corner d from the stage surface (mm)

L: length of the polarizing plate sample (= 300 mm)

to be. Then, the curl amount of the polarizing plate was evaluated based on the following evaluation criteria.

"Evaluation standard"

?: Curl amount C is 0% or more and less than 3%

?: Curl amount C is not less than 3% and less than 6%

DELTA: Curl amount C is not less than 6% and less than 10%

X: Curly amount C of not less than 10%

(Adhesive property)

At the end of the prepared polarizing plates 201 to 219, the cutter edge was inserted between the polarizer and the optical film (oblique stretched film). Then, the polarizer and the optical film were held in the inserting portion, and each of them was pulled in the opposite direction, and the adhesiveness was evaluated based on the following evaluation criteria.

"Evaluation standard"

?: The polarizer or the optical film was broken and could not be peeled off, and the adhesion was good.

?: A part of the film was peeled off between the polarizer and the optical film, but this is in a range without any problem.

X: The entirety was peeled off between the polarizer and the optical film, and the adhesion was poor.

(Light leakage)

The polarizing plates 201 to 219 obtained above were cut to a predetermined size and bonded to the viewer side of an organic EL panel (15EL9500, trade name, manufactured by LG Display Co., Ltd.) through an acrylic pressure-sensitive adhesive to prepare organic EL displays 301 to 319 . At this time, in the polarizing plates 201 to 219, the obliquely stretched film was arranged so as to be on the side of the organic EL panel with respect to the polarizer. The organic EL panel used in the evaluation was used after peeling the antireflection film bonded to the surface in advance.

Then, the organic EL panel was displayed in black, light leakage due to external light reflection at that time was visually confirmed, and light leakage was evaluated based on the following evaluation criteria.

"Evaluation standard"

○: No light leakage at all

?: Light leakage is slightly seen, but no problem in actual use

X: Light leakage is seen and there is a problem in actual use

(Visibility)

(Polarizing plate on the viewer side and the backlight side) of the two polarizing plates sandwiching the liquid crystal layer in a 21.5-inch liquid crystal display device (IPS226V-PN, LG Electronics Japan Ltd.) , The polarizing plates 201 to 219 prepared above were made to be on the observer side (opposite to the liquid crystal cell) of the obliquely stretched film relative to the polarizer, and were bonded to the glass of the liquid crystal cell with the optical adhesive, 419). At this time, the viewing-side polarizing plate was arranged such that the transmission axis of the viewer-side polarizing plate and the transmission axis of the polarizing plate on the backlight-side were perpendicular to each other.

An image was displayed on the obtained liquid crystal display devices 401 to 419, observed through polarized sunglasses, and visibility was evaluated based on the following evaluation criteria.

"Evaluation standard"

&Amp; cir &amp;: The display image has no distortion, and the visibility is very good.

&Amp; cir &amp;: The display image has almost no distortion and visibility is good.

?: The display image is slightly distorted, and there is no problem in actual use.

X: The display image is distorted and the visibility is poor.

Table 2 shows the results of various evaluations of the polarizers 201 to 219.

From Table 1 and Table 2, in each of the central portion of the film in the width direction C, the end E1 · E2, dimensional change of the fast axis direction ΔD _F and dimensional change of the slow axis direction _L ΔD,

0%? D _F <0.5%

ΔD _L <0%

(Average value of 110 ppm and 10 ppm) or less and a residual solvent amount of 60 ppm (an intermediate value between 110 ppm and 10 ppm), both of the curl amount and the adhesiveness were obtained (see the warp stretched film and polarizer plate ). This is because, even if the obliquely-drawn film shrinks in the direction of the slow axis under the high-temperature environment, the shrinkage of the film as a whole can be suppressed because the film does not shrink in the fast axis direction, and when the polarizer is adhered to the obliquely- (In the case of using an ultraviolet curing type adhesive for ultraviolet ray irradiation and for water for promoting curing when water is used), shrinkage of the entire film can be suppressed. As a result, in the organic EL display device using the polarizing plate of the embodiment, reflection (light leakage) of external light is in a range where there is no problem in actual use, and in the liquid crystal display device for polarized sunglasses using the polarizing plate of the embodiment, And the lowering of the visibility due to the above-mentioned problems is within a range where there is no problem in actual use.

Further, in the warp stretched films 107 and 110 to 112 formed by stretching a long film formed by the solution soft film-forming method, the rate of dimensional change ΔD _F in the fast axis direction is negative, and shrinkage in the fast axis direction . This is considered to be due to the following reasons. In the solution soft film forming method, since the solvent is used for film formation of the film, the film density of the film formed is low, so that it is extended in both directions of the slow axis direction in the slow axis direction and the fast axis direction in which the direction is close to the conveyance direction easy. As a result, after the oblique stretching, the tensile stress remains at least in the fast axis direction, and the tensile stress is relaxed under a high temperature environment, so that it contracts in the fast axis direction.

Therefore, in order to make the rate of dimensional change? D _F in the fast axis direction greater than 0, it is preferable to form a long film by a film forming method other than the solution casting method and to obliquely draw the long film, , The warp stretched film 102 and the like, it is preferable to obliquely stretch the long film formed by the melt soft film forming method. In other words, since the long film formed by the melt soft-film forming method has a residual solvent amount of 60 ppm or less (preferably 10 ppm or less), a long film having a residual solvent amount of 60 ppm or less (preferably 10 ppm or less) , It is preferable to prepare an obliquely-drawn film in which the rate of dimensional change? D _F in the fast axis direction is 0 or more.

In the oblique stretching film 101 stretched under the conditions of (Ti-Tr) /Tr=1.3 and (Tr-To) /Tr=1.0 at the time of oblique stretching, the long film A1 formed by the melt softening film- Despite the oblique stretching, the rate of dimensional change? D _F in the fast axis direction is negative, and shrinks in the fast axis direction under a high temperature environment. This is considered to be due to the following reasons. That is, at the time of oblique stretching, since the amount of force change (amount of increase) in the carrying direction at the end on the leading side of the film and the amount of force change (amount of decrease) in the carrying direction at the end on the retarding side are all small, Axis direction). On the other hand, in the carrying direction, the film is in a state of shrinking against the tensile force during conveyance or in balance with the tensile force, The tensile stress remains in the fast axis direction close to the direction. Then, under the high temperature environment, the tensile stress is relaxed and contracts in the fast axis direction.

Therefore, from the results of the obliquely drawn films 102 to 117 and the polarizing plates 202 to 217, in the warp stretching process in the stretching section 5,

(Ti-Tr) /Tr?1.7

(Tr-To) /Tr? 1.5

It is preferable to obliquely stretch a long film (the film formed by the melt soft-film formation method) in which the residual solvent amount is 60 ppm or less.

Further, in the polarizers 204 to 206 using the oblique stretched films 104 to 106, the evaluation of the curl amount and the adhesiveness is high as compared with other polarizers (for example, the polarizer 203). This is because, in the production of the obliquely-elongated films 104 to 106, since the width end portion is cooled in the oblique stretching step, a large shrinking stress can be left at the width end portion in the fast axis direction, (Shrinkage) of the entire film can be suppressed even if the warp stretched film is expanded in the fast axis direction by shrinking in the slow axis direction due to relaxation of the shrinkage stress in the high temperature environment of the film. In particular, in the production of the obliquely-drawn film 106, since the two-step stretching is performed in addition to the end cooling in the oblique stretching step, a larger shrinking stress can be left in the width direction end portion in the width direction, (Shrinkage) of the entire film under a high-temperature environment at the time of adhesion with the film. Thus, it is considered that the highest evaluation was obtained in the amount of curl and adhesion.

Further, in a polarizing plate (for example, the polarizing plate 202) using an oblique stretched film satisfying the conditions of (ΔD _{F -E1} + ΔD _{F -E2} ) / 2> ΔD _{F -C} , The evaluation of the curl amount and the adhesion property is at least one grade higher than that of the polarizing plate using the film (for example, the polarizing plate 215 占 217). This is because difference in dimensional change (expansion amount) in the direction of the fast axis direction from the widthwise center portion and the end portion of the warp stretched film is made different from each other in consideration of non-uniform curing shrinkage at each position in the width direction of the adhesive, The curl of the polarizing plate due to large expansion in the fast axis direction of the warp stretched film is suppressed by small expansion of the obliquely stretched film due to large curing shrinkage of the polarizing plate at the wide end portion, And the curl is surely suppressed in the entire width direction of the polarizing plate.

The optical film of the present invention can be used, for example, for a circular polarizer for preventing reflection of external light of an organic EL display device or a polarizer of a liquid crystal display device for polarized sunglasses.

50: polarizer
52: Polarizer
53: retardation film (optical film)
100: organic EL display device
101: Organic EL device (display cell)
301: polarizer
311:? / 4 retardation film (optical film)
313: Polarizer
400: liquid crystal display
401: liquid crystal cell (display cell)
402: polarizer
411: Polarizer
413:? / 4 retardation film (optical film)
Co: Far East
Ci: Pe district

Claims (14)

An optical film in which a slow axis is inclined by 10 to 80 DEG with respect to one side of a film contour in a film plane,
When the optical film have been referred to as the fast axis direction and the rate of dimensional change of the slow axis direction in the before and after left to stand at 90 ℃ 120 hours, respectively ΔD _F (%) and ΔD _L (%), the central portion of the along the one side direction, And at both ends,
0%? D _F <0.5%
ΔD _L <0%
Lt; / RTI &gt;
Wherein the residual solvent amount is 60 ppm or less. The method according to claim 1,
Wherein the residual solvent amount is 10 ppm or less. 3. The method according to claim 1 or 2,
In the optical film, the distances between two points arranged in the fast axis direction are a1 (mm) and a2 (mm), respectively, before and after the optical film is allowed to stand at 90 DEG C for 120 hours,
When the distances between the two points arranged in the slow axis direction in the optical film are defined as b1 (mm) and b2 (mm) before and after the optical film is allowed to stand at 90 DEG C for 120 hours ,
? D _F = {(a2-a1) / a1} 100
DELTA D _L = {(b2-b1) / b1} x100
Wherein the optical film is an optical film. 4. The method according to any one of claims 1 to 3,
The dimensional change ratio in the fast axis direction before and after leaving the optical film at 90 DEG C for 120 hours is denoted by? D _FC (%) at the central portion in the direction along the above-
The dimensional change ratio in the fast axis direction before and after leaving the optical film at 90 占 폚 for 120 hours is referred to as? D _F-E1 (%) at one end in the direction along the above-
When the dimensional change ratio in the fast axis direction before and after leaving the optical film at 90 캜 for 120 hours is ΔD _F-E2 (%) at the other end in the direction along the above-mentioned side,
(? D _{F -E 1} +? D _{F -E} 2) / 2>? D _{F -C}
Is satisfied. &Lt; / RTI &gt; 5. The method according to any one of claims 1 to 4,
The optical film has a long shape,
Wherein the direction along the sides is a width direction perpendicular to the longitudinal direction within the film surface of the optical film. A polarizing plate comprising the optical film according to any one of claims 1 to 5 and a polarizer,
Wherein the optical film is located on one side with respect to the polarizer such that the slow axis in the film plane crosses the absorption axis of the polarizer. A polarizing plate according to claim 6, and a display cell,
Wherein the polarizing plate is positioned on the viewing side with respect to the display cell. 8. The method of claim 7,
Wherein the optical film of the polarizing plate is positioned on the display cell side with respect to the polarizer. 9. The method of claim 8,
Wherein the display cell is an organic electroluminescence element. 8. The method of claim 7,
And the optical film of the polarizing plate is located on the side opposite to the display cell with respect to the polarizer. 11. The method of claim 10,
Wherein the display cell is a liquid crystal cell. A method of producing an optical film according to any one of claims 1 to 5,
The long film is held in a pair of gripping portions and one of the long strips is made to advance relative to the other of the waveguides so that the long film is bent and conveyed in the film surface, And an oblique stretching step of stretching the film in an oblique direction to obtain an obliquely stretched film constituting the optical film,
Before the oblique stretching, the force applied in the transport direction by each waveguide at each end in the width direction of the long film is referred to as the same Tr (N)
During the oblique stretching, the force applied in the transport direction by the waveguide on the relatively retarded side and the waveguide on the relatively preceding side at each end in the width direction of the long film is represented by To (N), Ti (N), &lt; / RTI &gt;
In the warp stretching step,
(Ti-Tr) /Tr?1.7
(Tr-To) /Tr? 1.5
Wherein the stretching step stretches the long film in the oblique direction. 13. The method of claim 12,
Wherein in the oblique stretching step, an end portion held by the waveguide on the side relatively delayed from each end portion in the width direction of the elongate film is cooled. The method according to claim 12 or 13,
In the oblique stretching step, the long film is obliquely stretched so that the slow axis is oriented at an orientation angle larger than the desired orientation angle with respect to the width direction of the long film, and then the slow axis is oriented at the desired orientation angle , And the long film is subjected to oblique stretching.

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