JP2018180163A - Optical film, polarizing plate, display device, and method for manufacturing optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress dimensional changes in an obliquely stretched film in a high temperature environment.SOLUTION: An optical film has a slow axis that is tilted by 10 to 80° with respect to one side of the outer shape of the film within the film plane. When dimensional change rates in a fast axis direction and in a slow axis direction of the optical film after the optical film is left to stand for 120 hours at 90°C are denoted by ΔD(%) and ΔD(%), respectively, the optical film satisfies 0%≤ΔD<0.5% and ΔD<0% at the center portion and both ends in a direction along the one side; and the film has a residual solvent amount of 60 ppm or less.SELECTED DRAWING: Figure 8

Description

  The present invention relates to an optical film as an obliquely stretched film, a polarizing plate including the optical film, a display device including the polarizing plate, and a method of manufacturing the optical film.

  Conventionally, various methods have been proposed in which a resin film is stretched in an oblique direction with respect to the width direction to produce an obliquely stretched film. For example, in patent document 1, a resin film is drawn out from the direction different from the winding direction of the film after extending | stretching, the both ends of this resin film are hold | gripped and conveyed by a pair of holding tools. Then, the resin film is stretched in an oblique direction by changing the transport direction of the resin film halfway. This produces an obliquely stretched film having a slow axis at a desired angle of more than 0 ° and less than 90 ° with respect to the longitudinal direction or the lateral direction.

  The obliquely stretched film manufactured in this manner is applicable to, for example, a circularly polarizing plate for preventing external light reflection in an organic EL (electroluminescent) display device. The circularly polarizing plate described above is combined with the polarizer such that the slow axis of the obliquely stretched film intersects the film at a desired angle (for example, 45 °) with the absorption axis (or transmission axis) of the polarizer. For example, it can be obtained by laminating a diagonally stretched film by a roll-to-roll method. By manufacturing a circularly polarizing plate by roll-to-roll method, it is a circle compared to a batch method in which a circularly polarizing plate is manufactured one by one by laminating an obliquely stretched film of a predetermined size and a polarizer one by one. Productivity of the polarizing plate is dramatically improved.

Unexamined-Japanese-Patent No. 2010-173261 (refer Claim 1, FIG. 1 etc.)

  By the way, the solution casting film forming method and the melt-casting film forming method are known as a typical manufacturing method of manufacturing the resin film (long film) which becomes the origin of a diagonally stretched film. In the solution casting film forming method, a dope in which a resin and an additive are dissolved in a solvent is cast on a metal support and dried, and then the cast film (web) is peeled off from the metal support. It is a method of obtaining a resin film by stretching or holding the width and then drying the cast film. On the other hand, in the melt-casting film forming method, a resin composition containing a resin and an additive is heated and melted to a temperature showing fluidity, and thereafter, a flowable melt is cast to obtain a resin film. is there.

  The resin film formed by the solution casting film forming method is obliquely stretched, and the obtained obliquely stretched film is adhered to a polarizer to produce a polarizing plate. When an adhesive is used, it is heated in a high temperature environment by ultraviolet irradiation or at the time of heating to accelerate curing, when a water-based adhesive such as water paste is used at the time of heating to accelerate curing) Shrink in both the direction and the fast axis direction (direction perpendicular to the slow axis direction in the film plane). The inventors of the present invention speculate as to the reason.

  The resin film formed by the solution casting film forming method has a lower density of resin than the resin film formed by the melt casting film forming method. This is because, in the solution casting film forming method, the solvent contained in the cast film is evaporated by drying of the cast film after drawing, so that a gap (a space after the solvent evaporates and escapes) in the film ) Is caused. Thus, a film with a low density of resin is likely to be stretched in the stretching direction (diagonal direction (slow axis direction) with respect to the width direction) at the time of oblique stretching, and tension is exerted in the transport direction to be pulled. It becomes easy to extend also in the direction of the fast axis. Therefore, in the film, tensile stress remains in both the slow axis direction and the fast axis direction after oblique stretching. Under a high temperature environment, the film shrinks in both the slow axis direction and the fast axis direction because the tensile stress is relieved.

  As described above, when the obliquely stretched film shrinks in both the slow axis direction and the fast axis direction in a high temperature environment, the entire film shrinks due to dimensional change. As a result, curling occurs in the polarizing plate in which the polarizer and the obliquely stretched film are bonded, or the adhesion between the polarizer and the obliquely stretched film is reduced, and the obliquely stretched film is easily peeled off. As a result, in the organic EL display device to which the above-mentioned polarizing plate is applied, light leakage occurs due to external light reflection during black display.

  Even when a resin film formed by a melt-casting film forming method is obliquely stretched, and the obtained obliquely stretched film is bonded to a polarizer to produce a polarizing plate, depending on the stretching conditions at the time of oblique stretching, After oblique stretching, tensile stress remains in both the slow axis direction and the fast axis direction, and the diagonally stretched film shrinks in both the slow axis direction and the fast axis direction in a high temperature environment during bonding. It has been found from various studies that dimensional changes occur and the same problems as described above occur.

  On the other hand, in the liquid crystal display device, a circle on the viewing side with respect to the liquid crystal layer is provided so that the observer can wear the polarization sunglasses and can observe the displayed image even in the upright state or in the necked side. There is also a configuration in which a polarizing plate is disposed. In such a configuration, when the circularly polarizing plate is curled due to the dimensional change of the obliquely stretched film in a high temperature environment, the image visually recognized through the circularly polarizing plate is distorted, and the visibility of the display image Decreases.

  Therefore, in order to suppress light leakage due to external light reflection in the organic EL display device and a decrease in the visibility of the display image in the liquid crystal display device compatible with polarized sunglasses, under a high temperature environment when adhering the obliquely stretched film to the polarizer Therefore, it is necessary to suppress the dimensional change of the entire obliquely stretched film. However, such obliquely stretched films have not been proposed yet.

  The present invention has been made to solve the above problems, and an object thereof includes an optical film as an obliquely stretched film capable of suppressing dimensional change in a high temperature environment, and the optical film It is providing a polarizing plate and a display including the polarizing plate.

  The above object of the present invention is achieved by the following constitution.

1. An optical film in which the slow axis is inclined by 10 to 80 ° with respect to one side of the outer shape of the film in the film plane,
When the dimensional change rates in the fast axis direction and the slow axis direction before and after leaving the optical film at 90 ° C. for 120 hours are ΔD _F (%) and ΔD _L (%), respectively, along the one side At the center and at both ends of the
0% ≦ ΔD _F <0.5%
ΔD _L <0%
Satisfied
An optical film characterized in that a residual solvent amount is 60 ppm or less.

  2. 2. The optical film as described in 1 above, wherein the amount of residual solvent is 10 ppm or less.

3. In the optical film, a distance between two points aligned in the fast axis direction and before and after leaving the optical film for 120 hours at 90 ° C. is a1 (mm) and a2 (mm), respectively. age,
In the optical film, a distance between two points aligned in the slow axis direction and before and after leaving the optical film for 120 hours at 90 ° C. is b1 (mm) and b2 (mm), respectively. And when
ΔD _F = {(a2−a1) / a1} × 100
ΔD _L = {(b2−b1) / b1} × 100
The optical film as described in 1 or 2 above, which is characterized in that

4. In the central portion in the direction along one side, the dimensional change rate in the fast axis direction before and after leaving the optical film at 90 ° C. for 120 hours is ΔD _F−C (%),
At one end in the direction along one side, the dimensional change rate in the fast axis direction before and after leaving the optical film at 90 ° C. for 120 hours is ΔDF _-E1 (%),
When the dimensional change rate in the fast axis direction before and after leaving the optical film at 120 ° C. for 120 hours at the other end in the direction along the one side is ΔDF _-E2 (%),
(.DELTA.DF _-E1 + .DELTA.DF _-E2 ) / 2> .DELTA.DF _-C
The optical film as described in any one of 1 to 3 above, which is further satisfied.

5. The optical film is long and
5. The optical film according to any one of 1 to 4 above, wherein the direction along one side is a width direction perpendicular to the longitudinal direction in the film plane of the optical film.

6. The optical film according to any one of the above 1 to 5, and a polarizer,
The said optical film is located in one side with respect to the said polarizer so that the slow axis may cross | intersect the absorption axis of the said polarizer in a film surface, The polarizing plate characterized by the above-mentioned.

7. A polarizing plate described in the above 6 and a display cell;
The display device, 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 electroluminescent element.

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

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

12. It is a manufacturing method of the optical film in any one of said 1 to 5, Comprising:
The both ends in the width direction of the long film are held by a pair of holding tools, one holding tool is made to precede relative to the other holding tool, and the long film is bent in the film plane and conveyed By stretching the long film diagonally with respect to the lateral direction to obtain a diagonally stretched film constituting the optical film,
Before oblique drawing, at each end in the width direction of the long film, the force applied in the transport direction by each holding tool is respectively the same Tr (N),
During oblique stretching, at each end in the width direction of the long film, the force applied in the transport direction by the relatively delayed gripping tool and the relatively preceding gripping tool is expressed by To (N And Ti (N),
In the oblique stretching step,
(Ti-Tr) /Tr≧1.7
(Tr-To) /Tr≧1.5
And stretching the long film in the oblique direction so as to satisfy the above.

  13. In the oblique stretching step, the optical film according to the item 12 is characterized in that among the respective end portions in the lateral direction of the long film, the end portion gripped by the holding tool on the relatively delayed side is cooled. How to make a film.

  14. In the oblique stretching step, the long film is obliquely stretched such that the slow axis is oriented at an orientation angle larger than a desired orientation angle with respect to the lateral direction of the long film, and then the slow phase The method of producing an optical film as described in 12 or 13 above, wherein the long film is obliquely stretched such that the axis is oriented at the desired orientation angle.

The optical film is a so-called obliquely stretched film in which the slow axis is inclined by 10 to 80 ° with respect to one side of the outer shape of the film in the film plane. By satisfying the above conditional expressions with respect to dimensional change rates ΔD _F and ΔD _L in the fast axis direction and the slow axis direction at the central portion and both end portions in the direction along the one side of the optical film, the optical film Expands in the direction of the fast axis in a high temperature environment or does not change in size, and contracts 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) of the entire film can be suppressed even if the slow axis direction shrinks under a high temperature environment.

  Thus, even when the polarizer and the optical film are bonded at high temperature to produce a polarizing plate, the polarizing plate may be curled due to the dimensional change of the optical film, or the adhesion of the optical film to the polarizer may be reduced. It is possible to suppress As a result, in the organic EL display device to which the above-mentioned polarizing plate is applied, it is possible to suppress the occurrence of light leakage due to external light reflection at the time of black display. In addition, in a liquid crystal display device compatible with polarized sunglasses to which the above polarizing plate is applied, generation of distortion in an image visually recognized through the above polarizing plate can be suppressed, and a decrease in visibility of a display image can be suppressed. it can.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows typically the schematic structure of the manufacturing apparatus of the diagonal stretch film which concerns on embodiment of this invention. It is a top view which shows typically an example of the rail pattern of the extension part with which the above-mentioned manufacturing device is provided. It is a top view which shows the detail of a structure of the said extending | stretching part. It is a disassembled perspective view which shows the schematic structure of a polarizing plate. It is sectional drawing which decomposes | disassembles and shows the general | schematic structure of an organic electroluminescence display. It is sectional drawing which shows the outline | summary structure of a liquid crystal display device. It is explanatory drawing which shows typically the behavior in the center part and the width end part of the adhesive agent at the time of adhesive agent hardening, and an optical film. In the said extending | stretching part, it is explanatory drawing which shows typically the force of the conveyance direction applied to the both ends of the width direction of a long film. It is explanatory drawing which shows typically the other structure of the said extending | stretching part. It is explanatory drawing which shows typically the other structure of the said extending | stretching part.

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

  In the obliquely stretched film according to the present embodiment, by stretching a long resin film obliquely, a long diagonal having an in-plane slow axis at an arbitrary angle with respect to the width direction of the stretched film It is a sheet-like obliquely stretched film which is a stretched film or obtained by cutting a long diagonally stretched film along the lateral direction.

  Here, the term "long" refers to a length of at least about 5 times or more the width of the film, preferably 10 times or more, and specifically, the film is wound in a roll Refers to a length that can be stored or transported in the form of a film roll. In the method for producing a long film, the film can be produced to any desired length by continuously producing the film. In addition, the manufacturing method of a long diagonally stretched film forms a long film into a film and then winds it once on a winding core to make a wound body (long film raw fabric), and from this wound body A long film may be supplied to the oblique drawing process to produce an obliquely drawn film, or the oblique drawing may be continuously performed from the film forming process without winding up the long film after the film formation. It may be supplied to the process to produce an obliquely stretched film. Continuously performing the film forming step and the oblique drawing step feeds back the film thickness and optical value results of the film after drawing, changes the film forming conditions, and obtains the desired elongated oblique drawn film. Because it can be

  In the method for producing an obliquely stretched film according to the present embodiment, the slow axis is set at an angle of more than 0 ° and less than 90 ° (for example, an angle of 10 to 80 ° with respect to the width direction) with respect to the width direction of the film. The long diagonally stretched film which it has is manufactured. Here, the angle with respect to the width direction of the film is an angle in the film plane. Since the slow axis usually appears in the stretching direction or in the direction perpendicular to the stretching direction, in the manufacturing method according to this embodiment, the stretching is performed at an angle of more than 0 ° and less than 90 ° with respect to the width direction of the film. By carrying out, it is possible to produce a long obliquely stretched film having such a slow axis. The angle between the lateral direction of the long obliquely stretched film and the slow axis, that is, the orientation angle can be arbitrarily set to a desired angle in the range of more than 0 ° and less than 90 °. In addition, in this embodiment, when describing as a "long film", it shall refer to the elongate resin film before diagonal stretch.

<About long film>
First, a long film to be stretched in the present embodiment will be described.

  The long film of the present embodiment is not particularly limited, and any film may be used as long as it is a film made of a thermoplastic resin. However, for example, when using a stretched film for optical use, a desired wavelength The film which consists of resin which has a transparent property with respect to is preferable. As such resin, polycarbonate resin (PC), polyester resin, olefin polymer resin having alicyclic structure (cycloolefin resin, COP), polyether sulfone resin, polyethylene terephthalate resin, polyimide resin And polymethyl methacrylate resins, polysulfone resins, polyarylate resins, polyethylene resins, polyvinyl chloride resins, and the like.

  Polycarbonate-based resins are polyesters of carbonic acid and glycol or dihydric phenol, and are polymers having a carbonate bond of -O-CO-O-, and polymers of bisphenol and carbonate are most practically used. Commercially available from Teijin Limited (Panlight (registered trademark), Pure Ace (registered trademark), Kaneka Corporation (Elmeck (registered trademark)), Mitsubishi Engineering Plastics Corporation (Yupilon (registered trademark)), and the like. Of course, since a polymer obtained by copolymerizing a monomer having a fluorene group thereto (see, for example, JP-A-2005-189632) exhibits reverse wavelength dispersion of retardation, it is preferable to use such a polycarbonate depending on applications. it can.

  Examples of polyester resins include polyethylene terephthalate (PET), polyethylene naphthalate (PEN) and the like, and a polymer obtained by copolymerizing a monomer having a fluorene group with this shows reverse wavelength dispersion of retardation, so Such polyesters may also be preferred depending on the application.

  As the polyethylene naphthalate resin, for example, polyethylene naphthalate produced by polycondensation of a lower alkyl ester of naphthalene dicarboxylic acid and ethylene glycol can be suitably used. As a commercial item, Theonex (made by Teijin Ltd.) etc. can be used suitably.

  It will not specifically limit, if it is resin which has a unit of the monomer which consists of cyclic olefin (cycloolefin) as cycloolefin type resin. The cycloolefin resin may be either a cycloolefin polymer (COP) or a cycloolefin copolymer (COC). The cycloolefin copolymer refers to a non-crystalline cyclic olefin resin which 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 are present. As such polycyclic cyclic olefins, norbornene, methyl norbornene, dimethyl norbornene, ethyl norbornene, ethylidene norbornene, butyl norbornene, dicyclopentadiene, dihydrodicyclopentadiene, methyl dicyclopentadiene, dimethyl dicyclopentadiene, tetracyclododecene And methyltetracyclododecene, dimethylcyclotetradodecene, tricyclopentadiene, tetracyclopentadiene and the like. Moreover, as a monocyclic cyclic olefin, cyclobutene, cyclopentene, cyclooctene, cyclooctadiene, cyclooctatriene, cyclododecatriene and the like can be mentioned.

  The cycloolefin resin is also available as a commercial product, and examples thereof include "ZEONOR" manufactured by Nippon Zeon Co., "ARTON" manufactured by JSR, "TOPAS" manufactured by Polyplastics, "APEL" manufactured by Mitsui Chemicals, etc. Be

  In addition, as resin which comprises a long film, the resin composition of Unexamined-Japanese-Patent No. 2006-45369 and the alkoxy cinnamate ester polymer of Unexamined-Japanese-Patent No. 2016-108544 can also be used. .

<Film forming method of long film>
As a film forming method of a long film, there are a solution casting film forming method and a melt casting film forming method shown below. Each film forming method will be described below. In the present embodiment, as described later, in order to obtain the property that the film after oblique stretching does not shrink in the direction of the fast axis under a high temperature environment, the long film to be the object of oblique stretching is melt casted into a film. The film is made by law.

Solution casting film forming method
In the solution casting film forming method, a step of preparing a dope by dissolving a resin and an additive in a solvent, a step of casting the dope on a belt-like or drum-like metal support, a cast film A step of drying as a (web), a step of peeling the web from the metal support, a step of stretching or holding the web, a further step of drying the web, and a step of winding the finished film are performed.

  The metal support in the casting step is preferably a mirror-finished surface, and a stainless steel belt or a drum having a surface plated with a casting is preferably used. The surface temperature of the metal support is set to −50 ° C. to a temperature at which the solvent does not boil to foam. A higher support temperature is preferable because the drying speed of the web can be increased, but if it is too high, the web may foam or the flatness may be deteriorated.

  As preferable support body temperature, it determines suitably at 0-100 degreeC, and 5-30 degreeC is still more preferable. Alternatively, it is also a preferable method to gelate the web by cooling and peel it from the drum in a state containing a large amount of residual solvent. The method of controlling the temperature of the metal support is not particularly limited, and there are a method of blowing warm air or cold air and a method of contacting warm water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently and the time until the temperature of the metal support becomes constant becomes short.

  When using warm air, in consideration of the temperature drop of the web due to the latent heat of evaporation of the solvent, it is possible to use a warm air higher than the boiling point of the solvent while using a wind higher than the target temperature while preventing foaming. is there.

  In particular, it is preferable to carry out drying efficiently by changing the temperature of the support and the temperature of the drying air between casting and peeling.

In order for the resin film to be formed to have a good flatness, it is preferable that the amount of residual solvent at the time of peeling the web from the metal support be within the desired range. Here, the amount of residual solvent is defined by the following equation.
Residual solvent amount (mass% or%) = {(M−N) / N} × 100
Here, M is the mass (g) of the sample collected at any time during or after the production of the web or film, and N is the mass (g) after heating M at 115 ° C. for 1 hour.

  In the film drying step, generally, a roll drying system (a system in which a web is alternately passed through a large number of rolls arranged above and below) and a tenter system are used for drying while conveying the web.

Melt casting film forming method
In the melt-casting film forming method, a resin composition containing a resin and an additive such as a plasticizer is heated and melted to a temperature showing fluidity, and thereafter, a melt having flowability is cast to form a film How to Methods formed by melt casting can be classified into melt extrusion (molding) methods, press molding methods, inflation methods, injection molding methods, blow molding methods, stretch molding methods, and the like. Among these, the melt-extrusion method which can obtain a film excellent in mechanical strength, surface accuracy and the like is preferable. Moreover, it is preferable to knead | mix and pelletize beforehand beforehand several raw materials used by the melt extrusion method.

  Pelletization may be performed by a known method. For example, dry resin, plasticizer and other additives are fed to an extruder by a feeder, mixed using a single or twin screw extruder, extruded from a die into strands, water cooled or air cooled, and cut. Can be pelletized.

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

  The extruder is preferably capable of being pelletized and processed at as low temperature as possible so as to suppress shearing force and prevent deterioration of the resin (molecular weight reduction, coloring, gel formation, etc.). For example, in the case of a twin-screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. The meshing type is preferred because of the uniformity of kneading.

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

  The pellet is extruded using a single- or twin-screw extruder at a melt temperature of about 200 to 300 ° C, filtered with a leaf disc type filter or the like to remove foreign matter, and then a film from a T-die Cast in the shape of a film, and the film is nipped by a cooling roll and an elastic touch roll, and solidified on the cooling roll.

  When the pellets are introduced from the feed hopper to the extruder, it is preferable to prevent oxidative decomposition and the like under vacuum, under reduced pressure or under an inert gas atmosphere.

  The extrusion flow rate is preferably stabilized by, for example, introducing a gear pump. Moreover, a stainless steel fiber sintered filter is preferably used as a filter used for removing foreign matter. A stainless steel fiber sintered filter is a combination of a stainless fiber body that is intricately intertwined and then compressed to sinter the contact point for integration. The density is changed by the thickness and compression amount of the fiber, and the filtration accuracy is It can be adjusted.

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

  The film temperature on the touch roll side when the film is nipped by the cooling roll and the elastic touch roll is preferably set to Tg (glass transition temperature) or more and Tg + 110 ° C. or less of the film. The roll which has an elastic body surface used for such a purpose can use a well-known roll.

  The elastic touch roll is also referred to as a pressure roller. As an elastic touch roll, what is marketed can also be used.

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

  The long film produced by each film forming method described above 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 coextrusion molding method, co-casting molding method, film lamination method, coating method and the like. Among these, coextrusion molding and co-casting are preferable.

<Specifications of long film>
The thickness of the long film in the present embodiment is preferably 30 to 300 μm, more preferably 40 to 150 μm. Further, in the present embodiment, the thickness unevenness σm in the flow direction (conveyance direction) of the long film supplied to the stretching zone described later maintains the take-up tension of the film at the entrance of the diagonal stretching tenter described later constant. From the viewpoint of stabilizing optical properties such as retardation and retardation, the thickness is preferably less than 0.30 μm, preferably less than 0.25 μm, and more preferably less than 0.20 μm. When the thickness unevenness σm in the flow direction of the long film is 0.30 μm or more, the variation of optical characteristics such as retardation and orientation angle of the long stretched film may be deteriorated.

  Moreover, the film which has a thickness gradient of the width direction may be supplied as a long film. The gradient of the thickness of the long film is empirically obtained by stretching the film having various thickness gradients experimentally so that the film thickness at the position where the stretching in the post process is completed can be most uniform. It can be asked. The gradient of the thickness of the long film can be adjusted, for example, such that the thickness of the thick end is about 0.5 to 3% greater than the thin end.

  Although the width of the long film is not particularly limited, it can be 500 to 4000 mm, preferably 1000 to 2000 mm.

  A preferable elastic modulus at a 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, represented by Young's modulus. If the modulus of elasticity is too low, the shrinkage during and after stretching will be low, making it difficult for the wrinkles to disappear. On the other hand, if the elastic modulus is too high, the tension applied at the time of stretching becomes large, and it becomes necessary to increase the strength of the portion holding the side edges of the film, and the load on the tenter in the subsequent step becomes large.

  As a long film, a non-oriented film may be used, or a film having an orientation may be supplied in advance. Further, if necessary, the distribution of the orientation of the long film in the lateral direction may be bowed, so-called bowing. The point is that the orientation state of the long film can be adjusted so that the orientation of the film at the position where the post-step stretching is completed can be made as desired.

<Method and Apparatus for Producing Long Oblique Stretched Film>
Next, the manufacturing method and manufacturing apparatus of the diagonal stretch film which extends | stretches the long film mentioned above in the diagonal direction with respect to the width direction, and manufactures a long diagonally stretched film are demonstrated.

(Overview of device)
FIG. 1: is explanatory drawing which shows typically the schematic structure of the manufacturing apparatus 1 of a diagonal stretch film. The manufacturing apparatus 1 of the present embodiment includes, in order from the upstream side of the transport direction of the long film, the film delivery portion 2, the transport direction change portion 3, the guide roll 4, the stretching portion 5, the guide roll 6, and the transport direction. A change unit 7, a film cutting device 8, and a film winding unit 9 are provided. In addition, the detail of the extending | stretching part 5 is mentioned later.

  The film delivery unit 2 delivers the above-described long film to the stretching unit 5. The film delivery unit 2 may be configured separately from the film forming apparatus for the long film, or may be configured integrally. In the case of the former, the long film is formed into a film, and once wound into a winding core, the long film is loaded from the film delivery unit 2 by being loaded into the film delivery unit 2. On the other hand, in the latter case, the film delivery unit 2 delivers the long film to the stretching unit 5 without taking up the long film after film formation.

  The conveyance direction changing unit 3 changes the conveyance direction of the long film fed from the film feeding unit 2 to the direction toward the entrance of the drawing unit 5 as the oblique drawing tenter. The transport direction changing unit 3 includes, for example, a turn bar that changes the transport direction by folding back the film, and a rotary table that rotates the turn bar in a plane parallel to the film.

  By changing the transport direction of the long film as described above by the transport direction changing unit 3, the width of the entire manufacturing apparatus 1 can be narrowed further, and the delivery position and angle of the film can be finely controlled. It becomes possible to obtain a long stretched film with a small variation in film thickness and optical value. If the film delivery unit 2 and the transport direction change unit 3 are movable (slidable and pivotable), the left and right clips (grippers) sandwiching both ends in the width direction of the long film in the stretching unit 5 Defective biting into the film can be effectively prevented.

  The above-mentioned film delivery unit 2 may be slidable and pivotable so that the long film can be delivered at a predetermined angle with respect to the inlet of the stretching unit 5. In this case, the installation of the conveyance direction changing unit 3 can be omitted.

  At least one guide roll 4 is provided on the upstream side of the stretching portion 5 in order to stabilize the track when the long film travels. The guide roll 4 may be configured by a pair of upper and lower rolls sandwiching a film, or may be configured by a plurality of roll pairs. The guide roll 4 closest to the inlet of the stretching unit 5 is a driven roll for guiding the traveling of the film, and is rotatably supported by bearings (not shown). A known material can be used as the material of the guide roll 4. In order to prevent the film from being damaged, it is preferable to reduce the weight of the guide roll 4 by applying a ceramic coating on the surface of the guide roll 4 or applying a chromium plating to a light metal such as aluminum.

  In addition, it is preferable that one of the rolls on the upstream side of the guide roll 4 closest to the inlet of the stretching portion 5 be in pressure contact with the rubber roll and nip it. By using such a nip roll, it becomes possible to suppress the fluctuation of the feeding force in the film flow direction.

  In a pair of bearings at both ends (right and left) of the guide roll 4 closest to the inlet of the stretching section 5, a first tension detection apparatus as a film tension detection apparatus for detecting tension generated in the film in the roll Second tension detection devices are provided respectively. For example, a load cell can be used as the film tension detection device. As a load cell, a known tensile or compressive type can be used. A load cell is a device that converts a load acting on a force application point into an electrical signal by a strain gauge attached to a strain generating body and detects the signal.

  The load cell is installed on the left and right bearings of the guide roll 4 closest to the entrance of the stretching section 5 so that the force exerted by the running film on the roll, that is, in the film traveling direction occurring near both side edges of the film. It detects tension independently. Alternatively, a strain gauge may be directly attached to a support constituting the bearing portion of the roll, and the load, that is, the film tension may be detected based on the strain generated in the support. The relationship between the generated strain and the film tension is to be measured in advance and known.

  When the position and the conveyance direction of the film supplied from the film delivery unit 2 or the conveyance direction changing unit 3 to the drawing unit 5 deviate from the position toward the entrance of the drawing unit 5 and the conveyance direction, A difference occurs in tension in the vicinity of both side edges of the film in the guide roll 4 closest to the inlet of the drawing section 5. Therefore, the degree of the deviation can be determined by providing the above-described film tension detection device and detecting the above-mentioned difference in tension. That is, if the transport position and transport direction of the film are appropriate (if it is the position and direction toward the inlet of the stretching section 5), the load acting on the guide roll 4 will be roughly even at both ends in the axial direction. If it is not right, there will be a difference in film tension on the left and right.

  Therefore, for example, the position and the conveyance direction (the angle with respect to the inlet of the drawing portion 5) of the film are changed by the above-described conveyance direction changing portion 3 so that the difference in film tension between the left and right of the guide roll 4 closest to the If properly adjusted, the gripping of the film by the gripping tool at the entrance of the stretching section 5 can be stabilized, and the occurrence of an obstacle such as removal of the gripping tool can be reduced. Furthermore, physical properties in the width direction of the film after oblique stretching by the stretching part 5 can be stabilized.

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

  The transport direction changing unit 7 is configured to change the transport direction of the stretched film transported from the stretching unit 5 in the direction toward the film winding unit 9. The transport direction changing unit 7 can be configured, for example, by a folding mechanism that folds back the film after stretching at least one time along a direction parallel or perpendicular to the stretching direction in the plane of the long oblique stretching film.

  Here, the film traveling direction at the entrance of the stretching portion 5 and the film traveling direction at the exit of the stretching portion 5 in order to correspond to fine adjustment of the orientation angle (direction of the in-plane slow axis of the film) and product variation. It is necessary to adjust the angle formed by

  In addition, continuous film formation and oblique stretching are preferable in terms of productivity and yield. When the film forming process, the oblique drawing process, and the winding process are continuously performed, the traveling direction of the film is changed by the conveyance direction changing unit 3 and / or the conveyance direction changing unit 7, and the film is formed in the film forming process and the winding process. The advancing direction of the film (the unwinding direction) taken out from the film unwinding portion 2 and the advancing direction of the film just before being taken up by the film winding portion 9 (that is, as shown in FIG. By matching the winding direction), the width of the entire apparatus with respect to the film traveling direction can be reduced.

  The traveling direction of the film does not have to be the same between the film forming step and the winding step, but the transport direction changing portion 3 and the film winding portion 9 do not interfere with each other. It is preferable to change the traveling direction of the film by the conveyance direction changing unit 7.

  As the above-mentioned conveyance direction change parts 3 and 7, it can implement | achieve by a well-known method, such as using an air flow roll.

  The film cutting device 8 cuts the film (long diagonally stretched film) stretched at the stretching portion 5 along the width direction at a predetermined film length (rolled up length), and is cut. It has a member 8a. The cutting member 8a is formed of, for example, a scissors or a cutter (including a slitter and a strip-like blade (Thomson blade)), but is not limited thereto. Besides, a rotating circular saw, a laser irradiation device, etc. It is also possible to configure

  The film winding unit 9 winds up the film transported from the stretching unit 5 via the transport direction changing unit 7 and is configured of, for example, a winder device, an accumulator device, a drive device, and the like. The film winding unit 9 preferably has a structure that can slide in the lateral direction in order to adjust the film winding position.

  The film take-up unit 9 can finely control the take-up position and angle of the film so that the film can be taken off at a predetermined angle with respect to the outlet of the drawing unit 5. Thereby, it becomes possible to obtain a long stretched film with a small variation in film thickness and optical value. Moreover, while being able to prevent generation | occurrence | production of the wrinkles of a film effectively, since the winding property of a film improves, it becomes possible to roll up a film by a elongate. In the present embodiment, it is preferable to adjust the take-up tension T (N / m) of the film after stretching to 100 N / m <T <700 N / m, preferably 150 N / m <T <250 N / m.

  When the above-mentioned take-up tension is 100 N / m or less, slack and wrinkles of the film are easily generated, and the retardation and the profile in the film width direction of the orientation angle are also deteriorated. On the other hand, when the take-up tension is 700 N / m or more, the variation in the film width direction of the orientation angle may be deteriorated, and the width yield (take efficiency in the width direction) may be deteriorated.

  In the present embodiment, it is preferable to control the fluctuation of the take-up tension T with an accuracy of less than ± 5%, preferably less than ± 3%. When the variation in the take-up tension T is ± 5% or more, the variation in optical characteristics in the width direction and the flow direction (conveying 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 tension of the film is measured and the value becomes constant. Thus, there is a method of controlling the rotational speed of the take-up roll (winding roll of the film winding unit 9) by a general PID control method. As a method of measuring the said load, a load cell is attached to the bearing part of the guide roll 6, and the method of measuring the load added to the guide roll 6, ie, the tension of a film, is mentioned. As the load cell, known ones of a tension type and a compression type can be used.

  The film after drawing is released from the holding by the holding tool of the drawing unit 5, discharged from the outlet of the drawing unit 5, and after both ends (both sides) of the film held by the holding tool are trimmed (Wind-up roll) It winds up and it becomes a winding body of a long diagonally oriented film. Note that the above trimming may be performed as necessary.

  Moreover, before winding up a long diagonally stretched film, in order to prevent blocking of the films, the masking film may be overlapped on the long diagonally stretched film and wound simultaneously, or overlapping by winding up. It may be wound while sticking a tape or the like to the end of at least one (preferably both) of the long oblique stretched film. The masking film is not particularly limited as long as it can protect a long obliquely stretched film, and examples thereof include a polyethylene terephthalate film, a polyethylene film, and a polypropylene film.

  In addition, before winding the long diagonally stretched film, the film is bulkier than the film surface, which is called knurling or emboss, at both ends in the width direction of at least one surface (preferably both surfaces) of the film. By forming the formed portion (convex portion), blocking of the films may be prevented when the film is wound up. In addition, the height and shape of the knurling portion may be different at both ends in the lateral direction (it may be asymmetric).

(Details of the stretching section)
Next, the details of the above-described extending unit 5 will be described. FIG. 2 is a plan view schematically showing an example of the rail pattern of the extending portion 5. Moreover, FIG. 3 is a top view which shows the detail of a structure of the extending | stretching part 5. FIG. Note that these are merely examples, and the present invention is not limited to these configurations.

  The manufacturing apparatus 1 is performed using the tenter (diagonal stretcher) which can be diagonally stretched as the extending | stretching part 5. FIG. This tenter is an apparatus which heats a long film to any temperature which can be drawn, and carries out slanting extension. This tenter includes a heating zone Z, a pair of rails Ri and Ro on the left and right, and a plurality of grippers 15 (in FIG. 2, for convenience, a pair of grippers Ci and Co on the left and right of the plurality of grippers 15). (Only shown) and. The details of the heating zone Z will be described later.

  The rails Ri and Ro are each configured by connecting a plurality of rail portions by a connecting portion, and are rails of an endless track (white circles in FIG. 2 are an example of the connecting portion). As shown in FIG. 3, the rail Ri on one end side (left side) of the film in the lateral direction is the traveling rail portion 11 for advancing the holding tool 15 in the conveying direction of the long film, and the conveying direction of the long film. It connects with the return rail part 12 for advancing the holding | gripping tool 15 in a reverse direction. The rail Ro on the other end side (right side) of the film in the width direction holds the going rail portion 13 for advancing the holding tool 15 in the conveyance direction of the long film, and holds in the opposite direction to the conveyance direction of the long film It connects with the return rail part 14 for advancing a tool 15 and is comprised.

  The holding tool 15 is composed of clips for holding the both ends of the film in the lateral direction, and is provided corresponding to each rail Ri · Ro, and along the film conveyance direction (each Ri · Ro) A plurality is provided at equal intervals. One end side of the film in the lateral direction is gripped by a plurality of gripping tools 15 aligned along the transport direction (rail Ri), and the other end side is gripped by a plurality of gripping tools 15 aligned along the transport direction (rail Ro) In this state, the film is transported by the gripper 15 traveling along the rails Ri and Ro.

  The gripping tool 15 traveling along the left rail Ri travels along the traveling rail portion 11 in a state of gripping one end of the film and releases the gripping of the film near the exit of the stretching portion 5, and then the return rail It travels along the section 12, returns to the vicinity of the entrance of the stretching section 5, re-grasps one end of the film, and then repeats the same steps as described above (surrounding along the rail Ri). On the other hand, after the gripping tool 15 traveling along the right rail Ro travels along the going rail portion 13 while gripping one end of the film and releases the gripping of the film near the exit of the stretching portion 5, After traveling along the return rail portion 14 and returning to the vicinity of the entrance of the drawing portion 5 and gripping the other end of the film again, the same steps as described above are repeated (they are circulated along the rail Ro).

  In FIG. 2, the transport direction D1 before stretching of the long film is different from the transport direction D2 after stretching of the long film, and forms a delivery angle θi with the transport direction D2 after stretching. The delivery angle θi can be arbitrarily set to a desired angle in the range of more than 0 ° and less than 90 °.

  As described above, since the transport direction D1 before stretching and the transport direction D2 after stretching are different, the rail pattern of the tenter has an asymmetrical shape on the left and right. Then, the rail pattern can be adjusted manually or automatically according to the orientation angle θ, the draw ratio, and the like given to the long obliquely stretched film to be manufactured. In the oblique stretching machine used in the present embodiment, it is preferable that the positions of the rail portions and the rail connecting portion that configure the rails Ri and Ro can be freely set, and the rail pattern can be arbitrarily changed.

  In the present embodiment, the holding tool 15 travels at a constant speed while maintaining a constant distance from the front and rear holding tools 15 (the holding tools 15 on the upstream and downstream sides in the film transport direction). The traveling speed of the holding tool 15 can be selected as appropriate, but is usually 1 to 150 m / min. The difference in traveling speed between the pair of left and right gripping tools (for example, gripping tools Ci and Co) is usually 1% or less, preferably 0.5% or less, and more preferably 0.1% or less of the traveling speed. This is because if there is a difference in traveling speed between the left and right of the film at the exit of the drawing process, wrinkles and deviations occur at the exit of the drawing process, and therefore the speed difference between the left and right holding tools is required to be substantially the same speed It is for. In a typical tenter, etc., there is a speed unevenness that occurs on the order of seconds or less, depending on the period of the teeth of the sprocket driving the chain, the frequency of the drive motor, etc. It does not correspond to the speed difference described in the embodiments of the invention.

  In the oblique stretching machine used in the manufacturing method of the present embodiment, particularly in places where the film transport is oblique, a rail that regulates the trajectory of the holding tool often requires a large bending rate. In order to avoid interference between grasping tools due to rapid bending or local stress concentration, it is desirable to make the trajectory of the grasping tools have a smooth curve at the bending portion (curved portion).

  As described above, in the oblique stretching tenter used to impart the oblique direction orientation to the long film, the orientation angle of the film can be freely set by changing the rail pattern variously, and further, the orientation axis of the film It is preferable that the tenter be a tenter capable of orienting (slow axis) with high precision to the left and right equally in the film width direction and controlling the film thickness and retardation with high precision.

  Next, the stretching operation in the stretching unit 5 will be described based on FIG. The long film is held at its both ends by the left and right holding tools Ci and Co, and conveyed in the heating zone Z as the holding tools Ci and Co travel. The left and right holding tools Ci and Co are opposed to each other in a direction substantially perpendicular to the film traveling direction (the conveying direction D1 before stretching) at the entrance of the stretching portion 5 (position A in the figure). It travels along the asymmetrical rails Ri and Ro, respectively, and releases the film gripped near the exit portion (position B in the figure) at the end of stretching. The details of the timing of the grip release will be described later. The film released from the holding tool Ci · Co is wound around the core by the film winding unit 9 described above. As described above, the pair of rails Ri and Ro each have an endless continuous track, and the gripping tools Ci and Co, whose grips of the film are released at the exit of the stretching portion 5, travel on the outer rails Then, they are returned to the entrance sequentially.

  At this time, since the rails Ri and Ro are asymmetrical, in the example of FIG. 2, the left and right gripping tools Ci and Co that were opposite at the position A in the figure are rails as they travel on the rails Ri and Ro. The gripping tool Ci traveling on the Ri side has a positional relationship in which it precedes the gripping tool Co traveling on the rail Ro side.

  That is, of the holding tools Ci and Co facing each other in a direction substantially perpendicular to the transport direction D1 before the film is drawn at the position A in the figure, one holding tool Ci is at the position B at the end of film drawing. In the case where the straight line connecting the holding tools Ci and Co is inclined by an angle θL with respect to the direction substantially perpendicular to the transport direction D2 after the film is stretched. The long film is obliquely stretched at an angle of θL with respect to the lateral direction by the above-mentioned procedure. Here, substantially perpendicular means that it is in the range of 90 ± 1 °.

  From the above, in the manufacturing method of the obliquely stretched film of the present embodiment, one end side in the width direction of the film is held by a plurality of holding tools 15 (including the holding tools Ci) and the other end side is held in a plurality Holding by the tool 15 (including the holding tool Co) and relatively advancing one holding tool 15 (for example, a plurality of holding tools 15 traveling along the rail Ri) on one end side and the other end side, and holding the other It is said that it includes an oblique stretching step of stretching the film diagonally with respect to the width direction by conveying the film by relatively delaying the tool 15 (for example, a plurality of gripping tools 15 traveling along the rails Ro) be able to. In the following description, among the one end side and the other end side in the film width direction, the side on which the gripping tool travels relatively is referred to as the "preceding side", and the gripping tool is relatively delayed. The side on which the vehicle travels is also referred to as the "delay side". For example, in FIG. 2, in the film width direction, the side on which the gripping tool Ci travels is the leading side, and the side on which the gripping tool Co travels is the delay side.

  Next, the details of the above-described heating zone Z will be described. The heating zone Z of the drawing section 5 is composed of a preheating zone Z1, a drawing zone Z2, and a heat setting zone Z3. In the stretching unit 5, the film gripped by the gripping tools Ci and Co passes through the preheating zone Z1, the stretching zone Z2, and the heat setting zone Z3 in order.

  The preheating zone Z1 refers to a section where the gripping tools Ci · Co gripping the both ends of the film travel at the entrance of the heating zone Z while maintaining a constant distance between the left and right (in the film width direction).

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

  The heat setting zone Z3 is a section where the heat setting step of fixing the optical axis (slow axis) of the film is performed after the end of the oblique drawing step.

  In addition, after passing through the heat setting zone Z3, the stretched film passes a section (cooling zone) in which the temperature in the zone is set to the glass transition temperature Tg (° C.) or less of the thermoplastic resin constituting the film. May be At this time, in consideration of the shrinkage of the film due to cooling, a rail pattern may be set in advance to narrow the distance between the opposing gripping tools Ci and Co.

  The temperature of the preheating zone Z1 is set to Tg to Tg + 30 ° C, the temperature of the stretching zone Z2 is set to Tg to Tg + 30 ° C, and the temperature of the heat setting zone Z3 is set to Tg-30 to Tg ° C with respect to the glass transition temperature Tg of the thermoplastic resin. Is preferred.

  In addition, in order to control thickness unevenness of the film in the width direction, a temperature difference may be provided in the width direction in the stretching zone Z2. In order to make the temperature difference in the width direction in the drawing zone, there is a known method such as adjusting the opening degree of the nozzle for sending warm air into the temperature-controlled chamber so as to make the difference in the width direction. The following method can be used. The lengths of the preheating zone Z1, the drawing zone Z2 and the heat setting zone Z3 can be selected appropriately, and the length of the preheating zone Z1 is usually 100 to 150% of the length of the drawing zone Z2, and the length of the heat setting zone Z3 Is usually 50 to 100%.

  Further, assuming that the width of the film before drawing is Wo (mm) and the width of the film after drawing is W (mm), the draw ratio R (W / Wo) in the drawing step is preferably 1.3 to 3. It is 0, more preferably 1.5 to 2.8. When the draw ratio is in this range, the thickness unevenness in the width direction of the film is reduced, which is preferable. In the stretching zone Z2 of the oblique stretching tenter, when the stretching temperature is made different in the width direction, it is possible to make the thickness unevenness in the width direction even better. The above-mentioned draw ratio R is equal to the magnification (W2 / W1) when the distance W1 between both ends of the clip gripped at the tenter inlet becomes the distance W2 at the tenter outlet.

<Quality of Long Stretched Film>
In the long obliquely stretched film obtained by the manufacturing method according to the embodiment of the present invention, the orientation angle θ is inclined, for example, in the range of more than 0 ° and less than 90 ° with respect to the winding direction, Preferably, the variation in the in-plane retardation Ro in the lateral direction is 3 nm or less and the variation in the orientation angle θ is less than 0.6 ° in a width of at least 1300 mm.

  That is, in the long obliquely stretched film obtained by the manufacturing method according to the embodiment of the present invention, the variation in in-plane retardation Ro is 3 nm or less and 1 nm or less in at least 1300 mm in the width direction. Is preferred. By setting the variation of the in-plane retardation Ro in the above-mentioned range, a long obliquely stretched film is bonded to a polarizer to form a circularly polarizing plate, and when this is applied to an organic EL display device, Uneven color due to leakage of light reflected light can be suppressed. In addition, when a long stretched film is used as, for example, a retardation film for a liquid crystal display device, it is also possible to improve the display quality.

  Further, in the long obliquely stretched film obtained by the manufacturing method according to the embodiment of the present invention, the variation of the orientation angle θ is less than 0.6 ° at least at 1300 mm in the lateral direction, 0.4 Preferably it is less than °. When a long diagonally stretched film with a variation in orientation angle θ of 0.6 ° or more is bonded to a polarizer to form a circularly polarizing plate, and this is installed in an image display device such as an organic EL display device, light leakage occurs. , May reduce the contrast of light and dark.

  The in-plane retardation Ro of the long obliquely stretched film obtained by the manufacturing method according to the embodiment of the present invention is selected to be an optimum value depending on the design of the display device used. The value 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 by the average thickness d of the film (Ro = (nx -Ny) x d).

  The average thickness of the long obliquely stretched film obtained by the manufacturing method according to the embodiment of the present invention is preferably 10 to 200 μm, more preferably 10 to 60 μm, particularly preferably 10 from the viewpoint of mechanical strength and the like. ~ 35 μm. In addition, the thickness unevenness in the width direction of the obliquely stretched film affects the possibility of winding, so it is preferably 3 μm or less, and more preferably 2 μm or less.

<Polarizer>
FIG. 4 is an exploded perspective view showing a schematic configuration of the polarizing plate 50 of the present embodiment. The polarizing plate 50 is configured 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 may be made of another transparent resin film (for example, a cycloolefin resin). In addition, the polarizing plate protective film 51 may be made of an optical compensation film that compensates for optical characteristics such as widening of the viewing angle.

  As the polarizer 52, a stretched polyvinyl alcohol doped with iodine or a dichroic dye can be used. The film thickness of the polarizer is 5 to 40 μm, preferably 5 to 30 μm, and particularly preferably 5 to 20 μm.

  The retardation film 53 is composed of the optical film of the present embodiment, that is, an obliquely stretched film. The slow axis of the retardation film 53 is inclined by 10 to 80 ° with respect to one side (for example, the side 53a) of the outer shape of the rectangular film in the film plane. The side 53 a is a side corresponding to the lateral direction of the long oblique stretched film. The desirable range of the inclination angle of the slow axis with respect to the side 53a in the film plane is 30 to 60 °, more preferably 45 °. The angle between 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 °, preferably 15 to 75 °, and more preferably 30 to It is 60 °, more preferably 45 °.

  Other layers (for example, a hard coat layer, a low refractive index layer, an antireflective layer, and a liquid crystal (positive C-type plate) are appropriately provided on the surface of the retardation film 53 opposite to the polarizer 52 according to the application. In addition, an easily bonding layer may be provided on the surface of the retardation film 53 on the side of the polarizer 52.

  In the polarizing plate 50 of the present embodiment, a long polarizing plate protective film 51, a long polarizer 52, and a long retardation film 53 (long oblique stretched film) are laminated in this order. It may be a long polarizing plate, or may be a sheet-like polarizing plate obtained by cutting the long polarizing plate 50 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 curing adhesive (UV adhesive) to produce the polarizing plate 50. In addition, the alkali saponified retardation film 53 is attached to one surface of a polarizer 52 prepared by immersing and drawing a polyvinyl alcohol-based film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution (water glue) It may be combined. Moreover, also about adhesion | attachment of the polarizer 52 and the polarizing plate protective film 51, an ultraviolet curable adhesive or water paste can be used.

(Composition of UV curable adhesive)
As a UV curable adhesive composition for polarizing plate, a photo radical polymerization type composition using photo radical polymerization, a photo cation polymerization type composition utilizing photo cationic polymerization, and a combination of photo radical polymerization and photo cationic polymerization Hybrid compositions are known.

  The photo radical polymerizable composition contains a radical polymerizable compound containing a polar group such as a hydroxy group or a carboxy group described in JP-A-2008-009329 and a radical polymerizable compound not containing a polar group in a specific ratio. Composition etc. are known. In particular, the radically polymerizable compound is preferably a compound having a radically polymerizable ethylenic unsaturated bond. Preferred examples of the compound having a radically polymerizable ethylenic unsaturated bond include a compound having a (meth) acryloyl group. Examples of the compound having a (meth) acryloyl group include N-substituted (meth) acrylamide compounds, (meth) acrylate compounds and the like. (Meth) acrylamide means acrylamide or methacrylamide.

  In addition, as the cationic photopolymerizable composition, (α) cationic polymerizable compound, (β) cationic photopolymerization initiator as disclosed in JP 2011-028234 A, (γ) wavelength longer than 380 nm The ultraviolet curable adhesive composition which contains each component of the photosensitizer which shows maximum absorption to the light of (1), and ((delta)) naphthalene type photosensitizer adjuvant is mentioned. However, other UV curable adhesives may be used.

(1) Pretreatment Step The pretreatment step is a step of subjecting the surface of the retardation film and the polarizing plate protective film (here collectively referred to as "protective film") to the surface to be adhered to the polarizer to an easy adhesion treatment. . Examples of the easy adhesion treatment include corona treatment and plasma treatment.

(UV-curable adhesive application process)
In the application step of the UV curable adhesive, the UV curable adhesive is applied to at least one of the adhesive surfaces of the polarizer and the protective film. When the ultraviolet curable adhesive is applied directly 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 doctor blade, wire bar, die coater, comma coater, and gravure coater can be used. Moreover, after apply | coating (casting) an ultraviolet curable adhesive between a polarizer and a protective film, the method of pressurizing with a roller etc. and spreading an ultraviolet curable adhesive uniformly can also be utilized.

(2) Bonding process After apply | coating an ultraviolet curable adhesive by said method, it is processed by the bonding process. In this bonding step, for example, when an ultraviolet curable adhesive is applied to the surface of the polarizer in the previous application step, a protective film is superposed thereon. Moreover, in the case of the system which apply | coats an ultraviolet curing adhesive on the surface of a protective film, a polarizer is superimposed there. When an ultraviolet curing adhesive is cast between the polarizer and the protective film, the polarizer and the protective film are superposed in this state. Then, normally, in this state, pressure is applied from both sides of the protective film side with a pressure roller or the like. The material of the pressure roller can be metal, rubber or the like. The pressure rollers disposed on both sides may be the same material or different materials.

(3) Curing Step In the curing step, the uncured ultraviolet curable adhesive is irradiated with ultraviolet light to carry out cationically polymerizable compounds (eg, epoxy compounds and oxetane compounds) and radically polymerizable compounds (eg, acrylate compounds, acrylamides) The UV curable adhesive layer containing a compound such as a compound) is cured, and the polarizer and the protective film are bonded to each other through the UV curable adhesive. In the configuration of the present embodiment in which the protective film is pasted on both sides of the polarizer, the ultraviolet rays are irradiated in a state where the protective film is superposed on both sides of the polarizer via the ultraviolet curing adhesive respectively. It is advantageous to cure the curable adhesive simultaneously.

As the irradiation conditions of ultraviolet light, any appropriate conditions can be adopted as long as the conditions can harden the ultraviolet curing adhesive. Preferably the dose of ultraviolet rays in the range of 50~1500mJ / cm ² in accumulated light quantity, and even more preferably in the range of 100 to 500 mJ / cm ^2.

  When the production process of the polarizing plate is carried out in a continuous line, the line speed depends on the curing time of the adhesive, preferably in the range of 1 to 500 m / min, more preferably 5 to 300 m / min, still more preferably 10 to 10 m / min. It is in the range of 100 m / min. If the line speed is 1 m / min or more, productivity can be ensured, or damage to the protective film can be suppressed, and a polarizing plate excellent in durability can be produced. In addition, if the line speed is 500 m / min or less, the curing of the ultraviolet curing adhesive is sufficient, and the ultraviolet curing adhesive layer having the target hardness and excellent in adhesiveness can be formed.

<Organic EL Display Device>
FIG. 5 is an exploded cross-sectional view of the 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 via an adhesive layer 201 on an organic EL element 101 as a display cell. The organic EL element 101 is configured by sequentially including a metal electrode 112, a light emitting layer 113, a transparent electrode (ITO or the like) 114, and a sealing layer 115 on a substrate 111 using glass, polyimide or the like. The metal electrode 112 may be configured of a reflective electrode and a transparent electrode.

  The polarizing plate 301 is formed by laminating the λ / 4 retardation film 311, the adhesive layer 312, the polarizer 313, the adhesive layer 314, and the protective film 315 in this order from the organic EL element 101 side, and the polarizer 313 has λ / 4 position. It is held by the phase difference film 311 and the protective film 315. The angle between the transmission axis (or absorption axis) of the polarizer 313 and the slow axis of the λ / 4 retardation film 311 made of a long obliquely stretched film of this embodiment is about 45 ° (or 135 °). The polarizing plate 301 (circularly polarizing plate) is configured by pasting the two together so that The protective film 315, the polarizer 313, and the λ / 4 retardation film 311 of the polarizing plate 301 correspond to the polarizing plate protective film 51, the polarizer 52, and the retardation film 53 of the polarizing plate 50 of FIG. 4, respectively. .

  It is preferable that a cured layer is laminated on the above-mentioned protective film 315. The cured layer not only prevents the surface flaw of the organic EL display device, but also has an effect of preventing the warping by the polarizing plate 301. Furthermore, an antireflective layer may be provided on the cured layer. The thickness of the organic EL element 101 itself is about 1 μm.

  In the above configuration, when a voltage is applied to the metal electrode 112 and the transparent electrode 114, electrons are injected from the metal electrode 112 and the transparent electrode 114 to the light emitting layer 113 as the cathode, and the electrode becomes the anode. Holes are injected from the light emitting layer 113 and both are recombined in the light emitting layer 113 to emit light of visible light corresponding to the light emitting characteristics of the light emitting layer 113. The light generated in the light emitting layer 113 is taken out to the outside through the transparent electrode 114 and the polarizing plate 301 directly or after being reflected by the metal electrode 112.

  Generally, in an organic EL display device, an element (organic EL element) which is a light emitting body 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 made of triphenylamine derivative etc., and a light emitting layer made of a fluorescent organic solid such as anthracene, etc. There is known a configuration having various combinations such as a laminate of a light emitting layer and an electron injection layer made of a perylene derivative or the like, a hole injection layer of these, a light emitting layer, and a laminate of an electron injection layer.

  In the organic EL display, by applying a voltage 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 these holes and electrons excites the phosphor. It emits light on the principle that the excited fluorescent substance emits light when it returns to the ground state. The mechanism of recombination on the way is similar to that of a general diode, and as can be expected from this, the current and the light emission intensity show strong non-linearity with rectification against the applied voltage.

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

  In the organic EL display of such a configuration, the light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the light emitting layer also transmits light almost completely like the transparent electrode. As a result, light is incident from the surface of the transparent substrate when light is not emitted, and light transmitted through the transparent electrode and the light emitting layer and reflected by the metal electrode is emitted again to the surface side of the transparent substrate. The display surface of the EL display looks like a mirror surface.

  The circularly polarizing plate of the present embodiment is suitable for an organic EL display device in which such external light reflection particularly poses a problem.

  That is, when the organic EL element 101 is not emitting light, half of the external light incident from the outside of the organic EL element 101 by room lighting or the like is absorbed by the polarizer 313 of the polarizing plate 301 and the other half is transmitted as linearly polarized light. , Λ / 4 retardation film 311. The light incident on the λ / 4 retardation film 311 is λ / 4 because the transmission axis of the polarizer 313 and the slow axis of the λ / 4 retardation film 311 intersect at 45 ° (or 135 °). By transmitting through the retardation film 311, it is converted into circularly polarized light.

  When the circularly polarized light emitted from the λ / 4 retardation film 311 is mirror-reflected by the metal electrode 112 of the organic EL element 101, the phase is inverted by 180 degrees, and is reflected as the circularly polarized light in the opposite direction. This reflected light is converted into linearly polarized light perpendicular to the transmission axis of the polarizer 313 (parallel to the absorption axis) by being incident on the λ / 4 retardation film 311, and thus all is absorbed by the polarizer 313 and is externally It will not be emitted. That is, external light reflection in the organic EL element 101 can be reduced by the polarizing plate 301.

<Liquid crystal display device>
FIG. 6 is a cross-sectional view showing a schematic configuration 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 configured by disposing a polarizing plate 402 on one surface side of the 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. Note that on the opposite side of the liquid crystal cell 401 to the polarizing plate 402, another polarizing plate disposed in a crossed nicol state with the polarizing plate 402 and a backlight for illuminating the liquid crystal cell 401 are provided. In 6, those illustration is omitted.

  The liquid crystal display device 400 may have a front window 403 on the opposite side of the polarizing plate 402 to the liquid crystal cell 401. The front window 403 is to be an exterior cover of the liquid crystal display device 400, and is made of, for example, a cover glass. A filler 404 made of, for example, an ultraviolet-curable resin is filled between the front window 403 and the polarizing plate 402. When the filler 404 is not present, an air layer is formed between the front window 403 and the polarizing plate 402, and light is reflected at the interface between the front window 403 and the polarizing plate 402 and the air layer, thereby Visibility may be reduced. However, since the air layer is not formed between the front window 403 and the polarizing plate 402 by the filling material 404 described above, it is possible to avoid a decrease in the visibility of the display image due to the reflection of light at the interface.

  The polarizing plate 402 has a polarizer 411 that transmits predetermined linear polarized light. On one side of the polarizer 411 (opposite to the liquid crystal cell 401), a λ / 4 retardation film 413 and a cured layer 414 made of an ultraviolet curable resin are disposed in this order via an adhesive layer 412. It is stacked. In addition, a protective film 416 is attached to the other surface side (liquid crystal cell 401 side) of the polarizer 411 via an adhesive layer 415.

  The polarizer 411 is obtained, for example, by dyeing a polyvinyl alcohol film with a dichroic dye and stretching the film at high magnification. The polarizer 411 is subjected to alkali treatment (also referred to as saponification treatment), and then the λ / 4 retardation film 413 is bonded to one surface via the adhesive layer 412, and the protective film 416 is adhesive to the other surface. It is pasted through 415. The protective film 416, the polarizer 411, and the λ / 4 retardation film 413 of the polarizing plate 402 correspond to the polarizing plate protective film 51, the polarizer 52, and the retardation film 53 of the polarizing plate 50 of FIG. 4, respectively. . The adhesive layers 412 and 415 are layers made of, for example, polyvinyl alcohol adhesive (PVA adhesive, water paste), but may be layers made of an ultraviolet curing adhesive (UV adhesive).

  The λ / 4 retardation film 413 is a layer that imparts an in-plane retardation of about 1⁄4 of the wavelength to the transmitted light, and is made of the optical film (obliquely stretched film) of the present embodiment. For example, 10 to 70 μm. The angle (crossing angle) between the slow axis of the λ / 4 retardation film 413 and the absorption axis of the polarizer 411 is, for example, 30 to 60 °, and more preferably 45 °. Thereby, the linearly polarized light from the polarizer 411 is converted by the λ / 4 retardation film 413 into circularly polarized light or elliptically polarized light.

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

  The protective film 416 is made of, for example, a resin film made of a cellulose-based resin (cellulose-based polymer), an acrylic resin, a cyclic polyolefin (COP), and a polycarbonate (PC). The protective film 416 is provided merely as a film that protects the back surface side of the polarizer 411, but may be provided as an optical film that doubles as a retardation film having a desired optical compensation function.

  In the case of a liquid crystal display device, another polarizing plate disposed on the opposite side of the liquid crystal cell 401 (liquid crystal cell) to the polarizing plate 402 is configured by sandwiching the surface of the polarizer with two optical films. However, as the above-mentioned polarizer and optical film, the same as the polarizer 411 and the protective film 416 of the polarizing plate 402 can be used.

  In addition, on the adhesive layer 412 side of the λ / 4 retardation film 413, an easy adhesion layer may be provided to improve the adhesiveness of the λ / 4 retardation film 413. The easy adhesion layer is formed by performing an easy adhesion treatment on the side of the adhesion layer 412 of the λ / 4 retardation film 413. Examples of the easy adhesion treatment include corona (discharge) treatment, plasma treatment, flame treatment, itro treatment, glow treatment, ozone treatment, primer coating treatment and the like, and at least one of them may be carried out. Among these easy adhesion treatments, corona treatment and plasma treatment are preferable as the easy adhesion treatment from the viewpoint of productivity.

  Thus, the polarizing plate 402 is located on the viewing side with respect to the liquid crystal cell 401, and the λ / 4 retardation film 413 of the polarizing plate 402 is located on the opposite side of the liquid crystal cell 401 with respect to the polarizer 411. In the configuration of the liquid crystal display device 400, linearly polarized light emitted from the liquid crystal cell 401 and transmitted through the polarizer 411 on the viewing side is converted into circularly polarized light or elliptically polarized light by the λ / 4 retardation film 413. Therefore, when the observer wears polarized sunglasses and observes the display image of the liquid crystal display device 400, the transmission axis of the polarizer 411 and the transmission axis of the polarized sunglasses form any angle, The component of light parallel to the transmission axis of polarized sunglasses can be directed to the observer's eye to view the displayed image.

<On the dimensional change of diagonally stretched film>
Next, the dimensional change rate of the obliquely stretched film (optical film) used as the retardation film (for example, λ / 4 retardation film) of the polarizing plate described above will be described.

The optical film of the present embodiment, that is, an optical film having a slow axis inclined by 10 to 80 ° with respect to one side of the outer shape of the film in the film plane, before and after leaving for 120 hours at 90 ° C. Let the dimensional change rates in the phase axis direction be ΔD _F (%) and ΔD _L (%), respectively. That is, in the optical film, the distance between two points aligned in the fast axis direction and before and after leaving the optical film for 120 hours at 90 ° C. is a1 (mm) and a2 (mm), respectively. In the optical film, the distance between two points aligned in the slow axis direction and before and after leaving the optical film for 120 hours at 90 ° C. is b1 (mm) and b2 (mm), respectively. And when
ΔD _F = {(a2−a1) / a1} × 100
ΔD _L = {(b2−b1) / b1} × 100
It is. And in this embodiment, in the center part and the both ends of the direction along the above-mentioned one side of a film outline,
0% ≦ ΔD _F <0.5% (1)
ΔD _L <0% (2)
I am satisfied.

By satisfying the above conditional expressions (1) and (2) for the dimensional change rates ΔD _F and ΔD _{L in the} direction of the fast axis and the slow axis of the optical film, the optical film has the fast axis in a high temperature environment. It expands in the direction or does not change in size, and contracts in the slow axis direction.

The reason why the optical film shrinks in the slow axis direction under a high temperature environment is as follows. The slow axis direction is the same as the stretching direction, and after stretching, tensile stress remains in the slow axis direction in the optical film. In a high temperature environment, the optical film contracts in the slow axis direction because the tensile stress is relieved. In addition, whether the optical film expands in the fast axis direction or does not change in size in a high temperature environment is that contraction stress remains in the fast axis direction after stretching, or shrinkage stress and tensile stress are in the fast axis direction. this is because not remain, but will be described later in detail means for realizing such a dimensional change [Delta] D _F.

  By satisfying the conditional expressions (1) and (2), the optical film of this embodiment does not shrink in the direction of the fast axis under a high temperature environment, so even if the shrinkage in the slow axis direction occurs under a high temperature environment, The dimensional change (shrinkage) of the entire film can be suppressed as compared to a film which shrinks in both the fast axis direction and the slow axis direction in a high temperature environment. Thus, the optical film and the polarizer of the present embodiment are bonded with an adhesive so that the slow axis of the optical film and the absorption axis (or transmission axis) of the polarizer are at a desired angle (for example, 45 °). Even in the case of producing a polarizing plate by adhesion, the polarizing plate may be curled due to a dimensional change of the optical film, or the adhesion of the optical film to the polarizer may be reduced to peel the optical film from the polarizer And so on, it is possible to suppress the deterioration of the quality of the polarizing plate.

  That is, if the above adhesive is, for example, an ultraviolet curing adhesive, it becomes a high temperature environment by ultraviolet irradiation or heating for accelerating the curing. On the other hand, when the above-mentioned adhesive is a water-based adhesive such as water paste, it becomes a high temperature environment by heating or drying for accelerating the curing of the adhesive. Even in such an environment where the temperature is high at the time of bonding, the optical film of this embodiment does not shrink in the direction of the fast axis as described above, and can suppress dimensional change (shrinkage) of the entire film. The curl of the polarizing plate and the decrease in the adhesion of the optical film can be suppressed.

  Thus, by suppressing the curling of the polarizing plate, light leakage due to reflection of external light during black display can be suppressed in the organic EL display device to which the polarizing plate is applied. In addition, in a liquid crystal display device compatible with polarized sunglasses, in which the polarizing plate is disposed on the viewing side of the liquid crystal cell, distortion in the image visually recognized through the polarizing plate can be suppressed, and the visibility of the display image Can reduce the

  Also, recently, in order to improve visibility from any angle, a high retardation film having a retardation of 10000 nm or more, which is made of polyethylene terephthalate or polyethylene naphthalate, has also been proposed. Even in the case of forming a polarizing plate using such a film, when the polarizing plate is curled due to the dimensional change of the film, the visibility of the display image is reduced. However, even with such a film, by satisfying the conditional expressions (1) and (2), the dimensional change of the entire film under a high temperature environment can be suppressed, and the curling of the polarizing plate can be suppressed. Also in the liquid crystal display device to which the high retardation film is applied, the decrease in visibility can be suppressed.

When the dimensional change rate ΔD _F in the fast axis direction becomes 0.5% or more, the dimensional change (expansion) in the fast axis direction with respect to the dimensional change (contraction) in the slow axis direction under high temperature environment Is too large, and distortion of the optical film 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 ΔD _{F in} the fast axis direction is defined to be 0.5%.

  In addition, since the optical film of the present embodiment is a film in which the amount of residual solvent is 60 ppm or less, it is possible to design a film which simultaneously satisfies the conditional expressions (1) and (2) described above. More specifically, it is as follows.

  In the film formation of the film by the solution casting film forming method, since the solvent is used for film formation, the residual solvent amount of the film formed into the film far exceeds 60 ppm. As described above, the film formed by the solution casting film forming method has a low density of resin and easily extends in both the slow axis direction and the fast axis direction at the time of oblique drawing. Tensile stress remains in both the axial direction and the fast axis direction. And under high temperature environment, as a result of the above-mentioned tensile stress being relieved, the above-mentioned film contracts in both the slow axis direction and the fast axis direction. For this reason, even if the optical film satisfies the conditional expression (2), the optical film does not satisfy the conditional expression (1).

  On the other hand, a film having a residual solvent amount of 60 ppm or less can be formed, for example, by a melt casting film forming method. The film formed by the melt-casting film forming method has a higher density of resin than the film formed by the melt-casting film forming method (the components other than the solvent are the same). It becomes difficult to extend in the direction of the phase axis, and it is forcibly extended in the direction of the slow axis by the force in the extending direction. For this reason, in the film after oblique stretching, while tensile stress remains in the slow axis direction, tensile stress does not easily remain in the fast axis direction. Therefore, even if the film shrinks in the slow axis direction in a high temperature environment, it does not easily shrink in the fast axis direction, and it becomes possible to design a film which simultaneously satisfies the conditional expressions (1) and (2).

  From the viewpoint of reliably increasing the density of the resin contained in the film and ensuring film design simultaneously satisfying the conditional expressions (1) and (2), the preferable range of the residual solvent amount of the optical film of this embodiment Is less than 10 ppm.

  In addition, for example, a transversely stretched film is a film stretched in the lateral direction, but at the time of stretching, a tension for transport of the film is applied in the transport direction (longitudinal direction). The tensile stress remains in both the axial direction (the lateral direction which is the stretching direction) and the fast axis direction (the transport direction). Therefore, as a result of the tensile stress being relieved in the high temperature environment of the film, the film shrinks in both the slow axis direction and the fast axis direction, and the conditional expression (1) is not satisfied.

  The longitudinally stretched film is a film stretched in the transport direction (longitudinal direction), and at the time of stretching, it is considered to extend in the longitudinal direction (long axis direction) and shrink in the lateral direction (fast axis direction) However, it does not necessarily contract in the lateral direction positively, and the contraction force in the fast axis direction is considered to be small. For this reason, the residual stress in the fast axis direction is small, and even if the residual stress in the fast axis direction is relieved in the high temperature environment of the film, the film does not expand in the fast axis direction. Rather, in the high temperature environment, the shrinkage in the slow axis direction is large, so that the entire film tends to shrink, and therefore, it is considered that the film shrinks in the fast axis direction, though to some extent. Therefore, the longitudinally stretched film also fails to satisfy the conditional expression (1).

  From the above, the optical film of the present embodiment which simultaneously satisfies the conditional expressions (1) and (2) can be obtained by stretching methods other than transverse stretching and longitudinal stretching, that is, stretching in the oblique direction with respect to the width direction of the long film. It is realized by the obliquely stretched film formed into a film.

In addition, as for the optical film of this embodiment, it is desirable to further satisfy the following conditional expressions (1a). That is,
0% <ΔD _F <0.5% (1a)
It is.

  The optical film satisfying the conditional expression (1a) expands in the direction of the fast axis under a high temperature environment, so even when the slow axis shrinks under the high temperature environment, the dimensional change (shrinkage) of the entire film is This can be reliably suppressed as compared with a film which shrinks in both the fast axis direction and the slow axis direction in a high temperature environment. Therefore, curling is reliably suppressed when an optical film and a polarizer are bonded to form a polarizing plate, and light leakage due to external light reflection when the polarizing plate is applied to an organic EL display device, the polarizing plate Can be reliably suppressed when applied to a liquid crystal display device compatible with polarized sunglasses.

By the way, in an optical film (obliquely stretched film) whose slow axis is inclined by 10 to 80 ° with respect to one side (for example, a side corresponding to the width direction of the long film) of the film outer shape (for example, rectangular) in the film plane. In the central portion in the direction along one side, the dimensional change rate in the fast axis direction before and after leaving the optical film for 120 hours at 90 ° C. is ΔD _F−C (%), and is along the side The dimensional change rate in the fast axis direction before and after leaving the optical film at 120 ° C. for 120 hours at one end of the direction (for example, the end on the leading side at the time of oblique drawing) is ΔDF _-E1 (%) At the other end in the direction along one side (for example, the end on the delay side at the time of oblique drawing), the dimensional change in the fast axis direction before and after leaving the optical film for 120 hours at _F-E2 and (%) When I,
(.DELTA.DF _-E1 + .DELTA.DF _-E2 ) / 2> .DELTA.DF _-C (3)
It is desirable to further satisfy The reason is as follows.

  When the optical film of the present embodiment is adhered to a polarizer via an adhesive to form a polarizing plate, the adhesive is usually a UV curable adhesive or a water paste. Shrink at the same time (under high temperature environment). At this time, in the case of adhesion using an ultraviolet curing adhesive, when irradiating an ultraviolet ray which is an active energy ray, the width center of the adhesive (corresponding to the center of the optical film) and the width end ( In many cases, there is a difference in the amount of received ultraviolet light, and the amount of received ultraviolet light is greater at the center portion of the width hand than at the width end of the optical film. For this reason, it is estimated that the curing shrinkage of the adhesive at the time of ultraviolet irradiation is larger at the center portion of the width hand than at the end portion of the width hand.

  The difference in the amount of light received between the center of the width and the end of the width is that when using a UV light source that emits ultraviolet light with a width smaller than the required width, In this case, the ultraviolet rays are irradiated from one side and the other side of the side of the width direction with respect to the normal of the coated surface of the adhesive, while the method of the coated surface of the adhesive is performed at the width end. This is because the ultraviolet rays are irradiated only from one side in the lateral direction with respect to the line. In addition, in order to reduce the variation in the width direction of the amount of ultraviolet light reception, for example, a method of irradiating ultraviolet light with a width wider than the required width may be considered, but this method requires a large-sized UV lamp, It is not desirable because it is very expensive.

  In addition, even in the case of heating for accelerating the curing of the adhesive (ultraviolet curing adhesive, water paste), heat is more likely to be accumulated at the center of the side compared with the end of the side, and the temperature at the end of the side It is known to go down. For this reason, even when heating is performed to accelerate the curing of the adhesive, it is estimated that the curing shrinkage of the adhesive is larger at the center portion than at the width end.

  As a result of examining the method corresponding to the deformation of the polarizing plate due to the curing shrinkage of the adhesive while securing the sufficient adhesive force by the adhesive between the optical film and the polarizer, the phase advancing in the width direction of the optical film It was found that the curl of the polarizing plate can be further suppressed in the entire width direction by making the amount of expansion in the axial direction different. FIG. 7 schematically shows the behavior of the adhesive and the optical film at the center portion and the end portion of the width of the adhesive when the adhesive is cured in the present embodiment. Since contraction and expansion are behaviors in opposite directions, for example, when the contraction of the adhesive is large at the same position in the lateral direction and the expansion of the optical film is also large, the polarizing plate has a concave on the adhesive side. Curling (so that the optical film side is convex).

  By satisfying the conditional expression (3) described above, the expansion in the fast axis direction of the optical film becomes small at the width center portion where the shrinkage of the adhesive is large, and at the width end portion where the shrinkage of the adhesive is small, Expansion in the fast axis direction of the optical film is increased. Thus, in the central portion of the widthwise side, it is possible to suppress the curling of the polarizing plate due to the large shrinkage of the adhesive by the small expansion of the optical film in the direction of the fast axis. Similarly, even at the widthwise end, it is possible to suppress the tendency of the polarizing plate to curl due to the large expansion in the fast axis direction of the optical film by small contraction of the adhesive. As a result, the curling of the polarizing plate can be further suppressed in the entire area in the lateral direction. In addition, by further suppressing the curling of the polarizing plate, the adhesiveness between the optical film and the polarizer by the adhesive can be sufficiently secured, and the peeling of the optical film can be reliably suppressed.

The optical film of the present embodiment is long, and it is preferable that the direction along the one side of the outer shape of the film is a width direction perpendicular to the longitudinal direction in the film plane of the optical film. In this case, a long optical film satisfying the conditional expressions (1) and (2) with respect to dimensional change rates ΔD _F and ΔD _L can be realized at the central portion and both end portions in the lateral direction. Moreover, a polarizing plate can be manufactured by a roll-to-roll method using such a long optical film.

  The polarizing plate of the present embodiment (for example, the polarizing plate 301 of FIG. 5, the polarizing plate 402 of FIG. 6) includes the optical film of the above-described embodiment (for example, λ / 4 retardation films 311 and 413) and a polarizer (for example, And polarizers 313 and 411). The optical film is positioned on one side with respect to the polarizer so that the slow axis intersects with the absorption axis (or transmission axis) of the polarizer in the film plane. The optical film of the present embodiment does not shrink in the direction of the fast axis under a high temperature environment, and dimensional change of the entire film can be suppressed. Therefore, when the optical film and the polarizer are bonded to produce a polarizing plate However, it is possible to suppress the curling of the polarizing plate and the peeling of the optical film caused by the dimensional change of the optical film in a high temperature environment at the time of bonding.

  Therefore, in the organic EL display device 100 in which the display cell is the organic EL element 101 and the λ / 4 retardation film 311 of the polarizing plate 301 is positioned on the organic EL element 101 side with respect to the polarizer 313, By suppressing the curling, it is possible to suppress the light leakage due to the reflection of external light at the time of black display.

  In the liquid crystal display device 400 compatible with polarized sunglasses, the display cell is the liquid crystal cell 401, and the λ / 4 retardation film 413 of the polarizing plate 402 is located on the opposite side of the polarizer 411 to the liquid crystal cell 401. By suppressing the curling of the plate 402, it is possible to suppress the occurrence of distortion in the image visually recognized through the polarizing plate 402, and it is possible to suppress the decrease in the visibility of the display image.

<Means for realizing dimensional change in the fast axis direction>
Next, the optical film of the present embodiment described above, the means for implementing a dimensional change [Delta] D _F of the fast axis direction defined by the conditional expression (1) will be specifically described.

(Setting of the force (tension) in the transport direction applied to both ends in the width direction at the time of oblique stretching)
FIG. 8 schematically shows the force in the transport direction applied to both end portions in the width direction of the long film in the stretching section 5 of the obliquely stretched film manufacturing apparatus 1 shown in FIG. 1. In the stretching portion 5, the both ends in the width direction of the long film are gripped by the pair of gripping tools Ci and Co, and one gripping tool Ci is made to precede relative to the other gripping tool Co, and the long film The film is bent in the film plane and conveyed, whereby a long film is stretched in an oblique direction with respect to the width direction, and an oblique stretching step of obtaining an obliquely stretched film constituting the above optical film is performed.

Here, before the oblique drawing (for example, in the preheating zone Z1), at each end in the width direction of the long film, the force applied in the conveyance direction by the movement of the holding tools Ci and Co in the conveyance direction is , And respectively the same Tr (N). Also, during oblique stretching (for example, at the stretching zone Z2), at each end in the width direction of the long film, the gripping tool Co on the relatively delayed side and the gripping tool Ci on the relatively preceding side Forces applied in the transport direction by movement in the gripping and transport directions are To (N) and Ti (N), respectively. At this time, in the above-described oblique stretching step,
(Ti-Tr) /Tr≧1.7 (A)
(Tr-To) /Tr≧1.5 (B)
To stretch the long film diagonally with respect to the lateral direction. The above conditional expressions (A) and (B) can be modified as the following conditional expressions (A ′) and (B ′), respectively. That is,
Ti 2.7 2.7 Tr (A ')
To ≦ −0.5 Tr (B ′)
It is.

  The gripping tools Ci and Co are attached to a chain moving along the rails Ri and Ro at the extension portion 5, and the chains are each zone (preheating zone Z1, stretching zone Z2, heat setting zone Z3) It moves by the rotation of the drive roller inside. The force Tr · Ti · To can be replaced by the driving force of the motor for rotating the driving roller in each zone, and in the present embodiment, the conditional expression (A And (B) are obtained (oblique stretched film).

  By satisfying the conditional expressions (A) and (B) (or by satisfying the conditional expressions (A ′) and (B ′)), the end on the leading side of the width direction of the long film is inclined While the force in the transport direction applied during oblique stretching with respect to that before stretching is increased, the force in the transport direction applied during oblique stretching with respect to that before oblique stretching is reduced at the end on the delay side. The amount of change (increase) in the force in the transport direction at the end of the head and the amount of change (decrease) in the force in the transport direction at the end on the delay side are also large.

  By performing oblique stretching under such conditions, at each position in the width direction of the long film (at least at the center and at both ends in the lateral direction), the film is in the direction of the oblique stretch (slow axis direction) While extending, in the transport direction, it is possible to create a state in which the film shrinks against tension during transport, or in balance with said tension so that the film neither stretches nor shrinks. At this time, although the transport direction and the fast axis direction do not necessarily coincide with each other, even if they are misaligned, the amount of displacement is small. Therefore, the film shrinks in the transport direction by contracting in the transport direction. Stress can be left on the film. Also, with a film that does not extend or shrink in the transport direction, it is possible to obtain a film that hardly stretches or shrinks in the fast axis direction.

Therefore, in a high temperature environment, residual stress (shrinkage stress) is relieved in the direction of the fast axis, and the film can be expanded or neither expanded nor contracted, as defined by the conditional expression (1) described above. The dimensional change rate ΔD _F in the fast axis direction can be realized.

(Cooling of the delay end at the time of oblique drawing)
FIG. 9 schematically shows another configuration of the extending portion 5. The extension unit 5 may have a cooling mechanism 21. The cooling mechanism 21 cools the end portion gripped by the gripping tool Co on the relatively delayed side of the respective end portions in the width direction of the long film in the oblique stretching step in the stretching portion 5. Such a cooling mechanism 21 can be configured, for example, by a blower mechanism (cooler, fan, etc.) that blows cold air onto the long film.

In the oblique drawing process, by cooling the film end on the delay side by the cooling mechanism 21, a contraction stress can be applied to the film end. Thereby, it is possible to further increase the contraction stress remaining in the direction of the fast axis by oblique stretching satisfying the conditional expressions (A) and (B) described above. Therefore, in a high temperature environment, the film can be further expanded by the relaxation of the residual stress (shrinkage stress) in the direction of the phase advancing axis of the obliquely stretched film, and the dimensional change in the direction of the phase advancing axis defined by the conditional expression (1) It becomes possible to realize rate ΔD _F reliably.

(Multi-step diagonal stretching)
FIG. 10 schematically shows still another configuration of the extending portion 5. In the oblique drawing step by the drawing part 5, the long axis is such that the slow axis is oriented at an orientation angle (for example, 60 °) larger than a desired orientation angle (for example, 45 °) with respect to the lateral direction of the long film. The film may be diagonally stretched, and then the long film may be diagonally stretched so that the slow axis is oriented at a desired orientation angle (for example, 45 °). Such multistage oblique stretching can be realized by appropriately changing the rail pattern of the stretching portion 5.

In the oblique drawing step, the tensile stress in the slow axis direction increases as the drawing angle (pivotal angle at the time of bending) increases, that is, as the orientation angle of the slow axis due to oblique drawing increases. Shrinkage stress is increased. In this way, once generating a large contraction stress in the fast axis direction, even if the drawing angle is subsequently reduced, the large contraction stress still remains (although the above-mentioned contraction stress is somewhat reduced). it can. Therefore, in a high temperature environment, the film can be further expanded by the relaxation of the residual stress (shrinkage stress) in the direction of the phase advancing axis of the obliquely stretched film, and the dimensional change in the direction of the phase advancing axis defined by the conditional expression (1) It becomes possible to realize rate ΔD _F reliably. At this time, although the cooling of the above-mentioned delay side end is not essential, the effect can be further enhanced by performing the cooling of the delay side end together with the multi-step oblique drawing.

<Example>
Specific examples of the present invention will be described below, but the present invention is not limited to these examples.

[Production of long film]
(Preparation of long film A1)
A polycarbonate resin film (PC film) as the long film A1 was produced by the following production method (melt-casting film-forming method).

The polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and a reflux condenser controlled at 100 ° C. 9,9- [4- (2-hydroxyethoxy) phenyl] fluorene (BHEPF), isosorbide (ISB), diethylene glycol (DEG), diphenyl carbonate (DPC), and magnesium acetate tetrahydrate in a molar ratio of BHEPF / It was charged so that ISB / DEG / DPC / magnesium acetate = 0.348 / 0.490 / 0.162 / 1.005 / 1.00 x 10 ^-5 . After the inside of the reactor was sufficiently purged with nitrogen (oxygen concentration: 0.0005 to 0.001 vol%), heating was performed with a heat medium, and stirring was started when the internal temperature reached 100 ° C. The internal temperature was allowed to reach 220 ° C. 40 minutes after the start of heating and controlled to maintain this temperature, and at the same time depressurization was started, and it reached 13.3 kPa in 90 minutes after reaching 220 ° C. The phenol vapor by-produced together with the polymerization reaction was led to a 100 ° C. reflux condenser, the monomer components contained in a small amount in the phenol vapor were returned to the reactor, and the non-condensing phenol vapor was led to a 45 ° C. condenser and recovered.

  Nitrogen was introduced into the first reactor and the pressure was once reduced to atmospheric pressure, and then the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Subsequently, the temperature rise and pressure reduction in the second reactor were started, and the internal temperature was 240 ° C. and the pressure was 0.2 kPa in 50 minutes. Thereafter, polymerization was allowed to proceed until a predetermined stirring power was reached. When a predetermined power is reached, nitrogen is introduced into the reactor and pressure is restored, and the reaction solution is withdrawn in the form of a strand, pelletized with a rotary cutter, and BHEPF / ISB / DEG = 34.8 / 49.0 / Polycarbonate resin A having a copolymer composition of 16.2 [mol%] was obtained. The reduced viscosity of the polycarbonate resin A was 0.430 dL / g, and the glass transition temperature was 128 ° C.

  The obtained polycarbonate resin A is vacuum dried at 80 ° C. for 5 hours, and then a single-screw extruder (made by Isuzu Kako Co., screw diameter 25 mm, cylinder set temperature: 220 ° C.), T-die (width 900 mm, set temperature) : A polycarbonate-based resin film having a thickness of 195 μm and a residual solvent content of 10 ppm is produced as a long film A1 using a film forming apparatus equipped with a temperature of 220 ° C., a chill roll (setting temperature: 120 to 130 ° C.) and a winding machine. did.

(Preparation 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).

<Dope composition>
Polycarbonate resin A (the same as the resin used in the preparation of the long film A1)
100 parts by mass Methylene chloride 430 parts by mass Methanol 90 parts by mass The above composition was charged into a closed vessel, kept warm at 80 ° C. under pressure, and completely dissolved while stirring to obtain a dope composition.

  The dope composition was then filtered, cooled and kept at 33 ° C., cast uniformly on a stainless steel band and dried at 33 ° C. for 5 minutes. Thereafter, the drying time is adjusted at 65 ° C., and after peeling off from the stainless steel band, the drying is finished while being transported by a large number of rolls, and a polycarbonate resin film having a film thickness of 75 μm and a residual solvent amount of 110 ppm is a long film Obtained as A2.

(Preparation 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 casting film forming method).

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

  Subsequently, 270 parts by mass of cyclohexane is 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 JGC Catalysts Chemical Co., Ltd.) is further added as a hydrogenation catalyst. In addition, hydrogen was pressurized to 5 MPa with hydrogen and heated to a temperature of 200 ° C. with stirring, and then reacted for 4 hours to obtain a reaction solution containing 20% of DCP / MTF / MTD ring-opened polymer hydrogenated polymer.

  After removing the hydrogenation catalyst by filtration, a soft polymer (manufactured by Kuraray Co., Ltd .; Septon 2002) and an antioxidant (Cibas Specialty Chemicals Co., Ltd .; Irganox 1010) are respectively added to the obtained solution And dissolved (both in 0.1 part by mass per 100 parts by mass of the polymer). Next, the solvent cyclohexane and other volatile components are removed from the solution using a cylindrical concentrator dryer (manufactured by Hitachi, Ltd.), and the hydrogenated polymer is extruded in the form of strands from the extruder in the form of strands. After cooling, it was pelletized and recovered. When the copolymerization ratio of each norbornene-based monomer in the polymer is calculated from the residual norbornene composition (by gas chromatography) in the solution after polymerization, it is almost charged at DCP / MTF / MTD = 10/70/20. It was equal to the composition. The hydrogenated ring-opened polymer has 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 ° C. there were.

  The resulting pellet of the ring-opened polymer hydride was dried at 70 ° C. for 2 hours using a hot air drier through which air was allowed to flow to remove water. Next, the pellet is melted using a short shaft extruder having a coat hanger type T die (manufactured by Mitsubishi Heavy Industries, Ltd .: screw diameter 90 mm, T die lip member is tungsten carbide, peel strength 44N with molten resin) Extrusion molding was carried out, and an alicyclic olefin polymer based resin film (COP film) having a thickness of 75 μm and a residual solvent content of 10 ppm was obtained as a long film B1.

(Preparation of long film B2)
A dope composition was prepared using the hydrogenated polymer obtained in the preparation of the long film B1 instead of the polycarbonate resin A, and the dope composition was prepared using the prepared dope composition. An alicyclic olefin polymer resin film (COP film) having a residual solvent content of 110 ppm was produced as a long film B2 in the same manner as in the production of the scale film A2.

(Production of long film C)
A polyethylene naphthalate resin film (PEN film) as a long film C was produced by the following production method (melt-casting film-forming method).

Synthesis of polyethylene naphthalate
100 parts by mass of 2,6-naphthalenedicarboxylic acid dimethyl ester and 60 parts by mass of ethylene glycol were transesterified according to a conventional method using 0.03 parts by mass of cobalt acetate tetrahydrate as a transesterification catalyst. Thereafter, 0.023 parts by mass of trimethyl phosphate was added to substantially complete the transesterification reaction. Subsequently, 0.024 parts by mass of antimony trioxide is added, and a polycondensation reaction is carried out as usual under high temperature and high vacuum to obtain an intrinsic viscosity (phenol / tetrachloroethane mixed solvent (mass ratio 1: 1) 35). Measured at ° C.) 0.62 dL / g of polyethylene naphthalate was obtained.

<Production of film>
The pellets of the obtained polyethylene naphthalate were dried at 180 ° C. for 3 hours and then fed to the extruder hopper. A polyethylene naphthalate resin film having a residual solvent content of 8 ppm is elongated by melting at a melting temperature of 300 ° C. and extruding the molten polymer on a rotary cooling drum with a surface temperature of 40 ° C. through a 9.0 mm slit die. Obtained as film C.

(Production of long film D)
A cellulose ester-based resin film (CE film) as a long film D was produced by the following production method (solution casting 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 above components were stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gaulin.

<Fine particle addition liquid>
Based on the following composition, the above-mentioned fine particle dispersion was slowly added to a dissolution tank containing methylene chloride while being sufficiently stirred. Furthermore, dispersion was performed with an attritor so that the particle size of the secondary particles had a predetermined size. The resultant was filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.
Methylene chloride 99 parts by mass Fine particle dispersion 5 parts by mass

<Main dope solution>
The main dope solution of the following composition was prepared. First, methylene chloride and ethanol were added to a pressure dissolution tank. The cellulose acetate was charged into a pressurized dissolution tank containing a solvent while being stirred. This was heated and completely dissolved while stirring. This is referred to as Azumi filter paper No. The mixture was filtered using H.244 to prepare a main dope. In addition, the sugar ester compound used the compound synthesize | combined by the following synthesis example.

<< Composition of main dope solution >>
Cellulose acetate propionate (acetyl substitution degree 1.39, propionyl substitution degree 0.50, total substitution degree 1.89) 100 parts by mass sugar ester compound 5.0 parts by mass fine particle additive liquid 1 part by mass methylene chloride 340 parts Part Ethanol 64 parts by mass

(Synthesis of sugar ester compound)
The sugar ester compound was synthesized by the following steps.

  In a four-headed kolbene equipped with a stirrer, reflux condenser, thermometer and nitrogen gas inlet, 34.2 g (0.1 mol) of sucrose, 180.8 g (0.6 mol) of benzoic anhydride, pyridine 379. 7 g (4.8 mol) was charged, and while stirring, the temperature was raised while bubbling nitrogen gas from a nitrogen gas introduction pipe, and an esterification reaction was performed at 70 ° C. for 5 hours.

Next, the pressure in the Kolben is reduced to 4 × 10 ² Pa or less, and after excess pyridine is distilled off at 60 ° C., the pressure in the Kolben is reduced to 1.3 × 10 Pa or less, and the temperature is raised to 120 ° C. Most of the acid and benzoic acid formed were distilled off.

Finally, 100 g of water is added to the separated toluene layer, and after washing with water at normal temperature for 30 minutes, the toluene layer is separated and the toluene is distilled off at 60 ° C. under reduced pressure (4 × 10 ² Pa or less). A mixture of A-1, A-2, A-3, A-4 and A-5 (sugar ester compound) was obtained.

  The obtained mixture was analyzed by HPLC and LC-MASS to find that A-1 is 1.3% by mass, A-2 is 13.4% by mass, A-3 is 13.1% by mass, and A-4 is 31. .7 mass%, A-5 was 40.5 mass%. The average degree of substitution was 5.5.

<Measurement conditions for HPLC-MS>
1) LC part apparatus: JASCO Corporation column oven (JASCO CO-965), detector (JASCO UV-970-240 nm), pump (JASCO PU-980), degasser (JASCO DG-980-50)
Column: Inertsil ODS-3 particle diameter 5 μm 4.6 × 250 mm (manufactured by GL Science Inc.)
Column temperature: 40 ° C
Flow rate: 1 ml / min
Mobile phase: THF (1% acetic acid): H ₂ O (50: 50)
Injection volume: 3 μl
2) MS unit Device: LCQ DECA (manufactured by Thermo Quest Co., Ltd.)
Ionization method: Electrospray ionization (ESI) method Spray Voltage: 5kV
Capillary temperature: 180 ° C
Vaporizer temperature: 450 ° C

  Then, the main dope was uniformly cast on a stainless steel belt support using an endless belt casting apparatus. The solvent is evaporated on the stainless steel belt support until the residual solvent content in the cast (cast) long film reaches 75%, and the solvent is peeled off from the stainless steel belt support and transported by a large number of rolls. Drying was completed, and a cellulose ester resin film having a thickness of 75 μm and a residual solvent content of 600 ppm was obtained as a long film D.

[Preparation of obliquely stretched film]
(Preparation of obliquely stretched film 101)
The wound body of the long film A1 (PC film, residual solvent content: 10 ppm) obtained above is set in the film delivery unit 2 of the obliquely stretched film manufacturing apparatus 1 shown in FIG. 1, and the film delivery unit The long film A1 was drawn out from 2 and supplied to the drawing section 5, and was obliquely drawn in the drawing section 5, to obtain a diagonally drawn film 101 having a thickness of 45 μm. Then, the obliquely stretched film 101 was conveyed to the film winding unit 9 and wound in a roll. In addition, about the temperature conditions at the time of extending | stretching in the extending | stretching part 5, it selected suitably in the range of (Tg-10) degreeC-(Tg + 30) degreeC of a film.

  Also, before oblique drawing, at each end in the width direction of the long film, the force applied in the transport direction by each holding tool Co · Ci is respectively the same Tr (N), and during the oblique drawing, the long film At each end in the width direction, the force applied in the transport direction by the relatively delayed holding tool Co and the relatively preceding holding tool Ci is denoted by To (N), Ti (N) and In the oblique drawing process at the drawing section 5, the long film was drawn in an oblique direction such that (Ti-Tr) /Tr=1.3 and (Tr-To) /Tr=1.0. . As the force Tr · Ti · To, the driving force of the motor for rotating the drive roller when driving the chain for conveying the gripping tools Co · Ci by the drive roller in the extension portion 5 (Readable by controller) was applied.

  The stretching angle of the film at the stretching section 5 was set to 45 °. In addition, said extending | stretching angle points out the angle (orientation angle) of the in-plane slow axis of a film, and the film width direction to make at the time of completion | finish of a diagonal extending process. 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 stretched portion 5.

(Preparation of obliquely stretched film 102)
In the stretching portion 5, the long film A1 is inclined (45 ° with respect to the lateral direction) so that (Ti−Tr) /Tr=2.0 and (Tr−To) /Tr=1.5. Stretched to Other than that was carried out similarly to preparation of the diagonal stretch film 101, and the diagonal stretch film 102 was produced.

(Preparation of obliquely stretched film 103)
In the stretching portion 5, the long film A1 is inclined (45 ° with respect to the lateral direction) so that (Ti−Tr) /Tr=3.0 and (Tr−To) /Tr=2.0. Stretched to An obliquely stretched film 103 was produced in the same manner as the obliquely stretched film 101 except for the above.

(Preparation of obliquely stretched film 104)
In the stretching portion 5, the long film A1 is obliquely oriented (45 ° with respect to the lateral direction) so that (Ti−Tr) /Tr=3.0 and (Tr−To) /Tr=3.0. Stretched to At the same time, among the ends in the width direction of the long film A1, the end held by the relatively delayed holding tool Co was cooled by the blowing of the cooling air. At this time, in the width direction of the long film A1, the end held by the holding tool Co on the delay side was cooled so as to be 10 ° C. lower than the end held by the holding tool Ci on the preceding side. Other than that was carried out similarly to preparation of the diagonal stretch film 101, and the diagonal stretch film 104 was produced.

(Preparation of obliquely stretched film 105)
In the stretching portion 5, the long film A1 is inclined (45 ° with respect to the lateral direction) so that (Ti−Tr) /Tr=3.5 and (Tr−To) /Tr=3.5. Stretched to At the same time, the long film A1 is obliquely stretched so that the slow axis is oriented at 60 ° larger than the desired orientation angle (here, 45 °) with respect to the width direction of the long film A1; Thereafter, the long film A1 was obliquely stretched such that the slow axis was oriented at 45 °. Other than that was carried out similarly to preparation of the diagonal stretch film 101, and the diagonal stretch film 105 was produced.

(Preparation of obliquely stretched film 106)
In the stretching portion 5, the long film A1 is inclined (45 ° with respect to the lateral direction) so that (Ti−Tr) /Tr=4.0 and (Tr−To) /Tr=4.0. Stretched to At the same time, among the ends in the width direction of the long film A1, the end held by the relatively delayed holding tool Co was cooled by the blowing of the cooling air. At this time, in the width direction of the long film A1, the end held by the holding tool Co on the delay side was cooled so as to be 10 ° C. lower than the end held by the holding tool Ci on the preceding side. Furthermore, at the same time, the long film A1 is obliquely stretched so that the slow axis is oriented at 60 ° larger than the desired orientation angle (here, 45 °) with respect to the width direction of the long film A1. Then, long film A1 was obliquely stretched such that the slow axis was oriented at 45 °. Other than that was carried out similarly to preparation of the diagonal stretch film 101, and the diagonal stretch film 106 was produced.

(Preparation of obliquely stretched film 107)
A diagonally stretched film 107 was produced in the same manner as the diagonal stretched film 104 except that the long film A2 (PC film, residual solvent content: 110 ppm) was used instead of the long film A1 to carry out the diagonal stretching. .

(Preparation of obliquely stretched film 108)
An obliquely stretched film 108 was produced in the same manner as in the production of the obliquely stretched film 103 except that the rail pattern at the stretching portion 5 was changed and the diagonal stretching was performed so that the orientation angle was 75 °.

(Preparation of obliquely stretched film 109)
An obliquely stretched film 109 was produced in the same manner as the obliquely stretched film 103 except that the rail pattern in the stretched portion 5 was changed and the diagonal stretching was performed so that the orientation angle was 15 °.

(Preparation of obliquely stretched film 110)
An obliquely stretched film 110 was produced in the same manner as production of the obliquely stretched film 103 except that oblique stretching was carried out using a long film D (CE film, residual solvent content: 600 ppm) instead of the long film A1.

(Preparation of obliquely stretched film 111)
An obliquely stretched film 111 was produced in the same manner as the obliquely stretched film 110 except that the rail pattern in the stretched portion 5 was changed and the diagonal stretching was performed so that the orientation angle was 75 °.

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

(Preparation of obliquely stretched film 113)
An obliquely stretched film 113 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 B1 (COP film, residual solvent content: 10 ppm) instead of the long film A1.

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

(Preparation of obliquely stretched film 115)
In the stretching portion 5, the long film A1 is inclined (45 ° with respect to the lateral direction) so that (Ti−Tr) /Tr=2.0 and (Tr−To) /Tr=2.0. Stretched to Other than that was carried out similarly to preparation of the diagonal stretch film 101, and the diagonal stretch film 115 was produced.

(Preparation of obliquely stretched film 116)
In the stretching portion 5, the long film A1 is inclined (45 ° with respect to the lateral direction) so that (Ti−Tr) /Tr=4.0 and (Tr−To) /Tr=5.5. Stretched to Other than that was carried out similarly to preparation of the diagonal stretch film 101, and the diagonal stretch film 116 was produced.

(Preparation of obliquely stretched film 117)
In the stretching portion 5, the long film A1 is obliquely oriented (45 ° with respect to the lateral direction) so that (Ti−Tr) /Tr=1.7 and (Tr−To) /Tr=1.5. Stretched to An obliquely stretched film 117 was produced in the same manner as the obliquely stretched film 101 except for the above.

[Measurement of dimensional change rate ΔD _F , ΔD _L ]
The central part C in the width direction of the obliquely stretched films 101 to 117 manufactured above, one end E1 (the end gripped by the preceding gripping tool), the other end E2 (gripped by the delay gripping tool) Mark the two points aligned in the fast axis direction, measure the distance a1 (mm) between the two points with a ruler, etc., and mark the two points aligned in the slow axis direction. The distance b1 (mm) between the two points was measured by scale measurement or the like. 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 in the film plane, so the slow axis direction on the obliquely stretched films 101 to 117. It is easy to identify the fast axis direction.

Next, the obliquely stretched films 101 to 117 are allowed to stand at 90 ° C. for 120 hours, and then, in each of the central portion C in the lateral direction of each film, one end E1 and the other end E2, in the fast phase direction The distance a2 (mm) between two points aligned was measured by a scale, and the distance b2 (mm) between two points aligned in the slow axis direction was measured by a scale. Then, the dimensional change rate ΔD _F (%) in the fast axis direction and the dimensional change rate ΔD _L (%) in the slow axis direction are calculated for each of the central portion C and the end portions E1 and E2 of the film did.
ΔD _F = {(a2−a1) / a1} × 100
ΔD _L = {(b2−b1) / b1} × 100

Table 1 shows various parameters relating to the obliquely stretched films 101 to 117, including the dimensional change rate ΔD _F · ΔD _L. In Table 1, the dimensional change rate ΔD _F in the fast axis direction at the central portion C in the lateral direction of the film and the end portions E1 and E2 is represented by ΔD _{F -C} , ΔD _{F -E1} and ΔD _F -E2. The dimensional change rate ΔD _L in the slow axis direction at the central portion C and the end portions E1 and E2 is represented by ΔD _{L -C} , ΔD _{L -E1} and ΔD _L -E2.

[Production of polarizing plate]
(Preparation of Polarizing Plate 201)
<Production of Polarizers>
A continuous polyvinyl alcohol film with a thickness of 60 μm is continuously transported through a guide roll and immersed in a dyeing bath (30 ° C) containing iodine and potassium iodide to perform a dyeing process and a 2.5-fold stretching process. Then, in an acid bath (60 ° C.) to which boric acid and potassium iodide have been added, the film is subjected to a stretching treatment and a crosslinking treatment to a total of 5 times, and the obtained 12 μm-thick iodine-PVA polarizer is obtained. The film was dried in a drier at 50 ° C. for 30 minutes to obtain a polarizer having a moisture content of 4.9%.

Preparation of UV-curable adhesive
The following components were mixed to prepare a liquid UV-curable adhesive (UV adhesive).
3,4-Epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate 40 parts by mass Bisphenol A epoxy resin 60 parts by mass Diphenyl [4- (phenylthio) phenyl] sulfonium hexafluoroantimonate (cationic polymerization initiator) 4.0 Parts by mass

<Pasting>
After applying a corona treatment to the bonding surface of the obliquely stretched film 101, the above-prepared ultraviolet curable adhesive was applied with a thickness of 3 μm by a coating apparatus equipped with a chamber doctor. After applying corona treatment to the bonding surface of the protective film 1 (Konica Minolta Tac KC 4 UY, 40 μm thick, Konica Minolta Co., Ltd. product), the above-mentioned UV curable adhesive is similarly 3 μm thick. It was coated.

Thereafter, the obliquely stretched film 101 was immediately bonded to one side of the polarizer prepared above, and the protective film 1 was bonded to the other side by a bonding roll via the coated surface of the ultraviolet curable adhesive. At this time, both were pasted together so that the width direction of the obliquely stretched film 101 and the absorption axis (or transmission axis) of the polarizer coincide with each other (the slow axis of the obliquely stretched film 101 and the absorption axis of the polarizer The angle is 45 degrees). Thereafter, the metal halide lamp is turned on at a line speed of 20 m / min, ultraviolet rays are irradiated from the side of the obliquely stretched film 101 so that the integrated light quantity at a wavelength of 280 to 320 nm becomes 320 mJ / cm ^2. After curing, a polarizing plate 201 was produced. In addition, since preparation of the polarizing plate 201 is performed by a roll-to-roll method, finally, the sheet-like polarizing plate 201 is obtained by cutting the long polarizing plate 201 along the lateral direction. The

(Preparation of Polarizing Plates 202 to 217)
Polarizing plates 202 to 217 were produced in the same manner as in the production of the polarizing plate 201 except that the obliquely stretched film 101 was changed to the obliquely stretched 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 stretched film 103 and the polarizer, and the polarizer and the protective film 1 were adhered with a water paste (polyvinyl alcohol adhesive, respectively). The polarizing plate 218 was dried at 80 ° C. for 2 minutes for the purpose of accelerating the curing of the adhesive.

(Production of Polarizing Plate 219)
A polarizing plate 219 was produced in the same manner as the production of the polarizing plate 203, except that the protective film 2 was used instead of the protective film 1. In addition, the protective film 2 is produced as follows.

<Production of Protective Film 2>
<< Preparation of fine particle dispersion >>
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 by stirring with a dissolver for 50 minutes, and then dispersed with Manton Gorin to prepare a fine particle dispersion.

  Next, 5 parts by mass of the fine particle dispersion was slowly added to fully stirred dichloromethane (100 parts by mass) in the dissolution tank. Furthermore, dispersion was performed with an attritor so that the particle size of the secondary particles would be a predetermined size. The resultant was filtered with FINEMET NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.

<< Preparation of dope >>
The main dope of the following composition was prepared. First, dichloromethane and ethanol were added to the pressure dissolution tank. Then, the cycloolefin resin A (antioxidant added), the ultraviolet light absorber and the fine particle addition solution were introduced into the pressure dissolution tank while stirring. The mixture was heated and completely dissolved while stirring, and Azumi filter paper No. Filtered using 244 to prepare the main dope.
Cycloolefin resin A 100 parts by mass Antioxidant (IRGNOX 1010 (manufactured by BASF Japan Ltd.) 0.5 parts by mass Dichloromethane 200 parts by mass Ethanol 10 parts by mass Ultraviolet absorber (Tinuvin 928 (manufactured by BASF Japan manufactured by Japan) 3 Mass part Fine particle addition liquid 3 mass parts

  In addition, cycloolefin resin A is a thing of the following structure.

  Then, using an endless belt casting apparatus, the main dope was uniformly cast on a stainless steel belt support at a temperature of 31 ° C. and a width of 1800 mm. The temperature of the stainless steel belt was controlled at 28 ° C. The conveying speed of the stainless steel belt was 20 m / min.

  The solvent was evaporated on a stainless steel belt support until the amount of residual solvent in the cast film was 30%. Then, the cast film was peeled off from the stainless steel belt support at a peeling tension of 128 N / m. The peeled cast film was stretched 2.2 times in the width direction at 160 ° C. The residual solvent at the start of stretching was 5% by mass. Then, the drying is carried out by conveying the drying zone with a large number of rollers, and the end sandwiched by the tenter clips is slit with a laser cutter, and then wound up to obtain a protective film 2 with a film thickness of 40 μm.

[Evaluation]
(Curl amount)
The produced polarizing plates 201 to 219 were cut into a size of 30 cm × 30 cm to obtain polarizing plate samples. And the obtained polarizing plate sample was arrange | positioned so that the surface of the convex side of this sample faced the stage surface. And the height from the stage surface of four corner parts ad of a polarizing plate sample was measured, respectively, and curling amount C was calculated | required by the following relational expression.
C = [(Ha + Hb + Hc + Hd) / 4] / L
However,
Ha: Height of the corner a from the stage surface (mm)
Hb: height of the corner b from the stage surface (mm)
Hc: height of the corner c from the stage surface (mm)
Hd: height of the corner portion d from the stage surface (mm)
L: Length of polarizing plate sample (= 300 mm)
It is. Then, the curling amount of the polarizing plate was evaluated based on the following evaluation criteria.
"Evaluation criteria"
◎: The curling amount C is 0% or more and less than 3%.
○: Curl amount C is 3% or more and less than 6%.
Fair: Curl amount C is 6% or more and less than 10%.
X: Curl amount C is 10% or more.

(Adhesiveness)
At the ends of the produced polarizing plates 201 to 219, the cutting edge of the cutter was inserted between the polarizer and the optical film (obliquely stretched film). And in the said insertion part, the polarizer and the optical film were hold | gripped, it pulled in the opposite direction, respectively, and adhesiveness was evaluated based on the following evaluation criteria.
"Evaluation criteria"
Good: The polarizer or the optical film is broken and can not be peeled off, and the adhesion is good.
Fair: Partial peeling between the polarizer and the optical film, but in a range without any problem.
X: It peels completely between a polarizer and an optical film, and adhesiveness is bad.

(Light leakage)
The polarizing plates 201 to 219 obtained above are cut into a predetermined size, and attached to the visible side of an organic EL panel (trade name 15EL9500 manufactured by LG Display Co., Ltd.) through an acrylic adhesive to form an organic EL display device 301. -319 were produced. At this time, in the polarizing plates 201 to 219, the obliquely stretched film was placed on the organic EL panel side with respect to the polarizer. In addition, the said organic electroluminescent panel used for evaluation peeled and used the anti-reflective film bonded together on the surface previously.

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 criteria"
○ ... I can not see the light leak at all.
・ ・ ・ ... light leakage is slightly visible, but there is no problem in practical use.
× · · · · · · leak light is visible, there is a problem in practical use.

(Visibility)
In the 21.5-inch liquid crystal display device (IPS 226 V-PN, LG Electronics Japan Co., Ltd.), the observer side (viewing side, back light and the like) of the two pairs of polarizing plates disposed across the liquid crystal layer. The opposite side of the polarizing plate is peeled off, and the polarizing plates 201 to 219 prepared above are made to be an oblique adhesive film with respect to the polarizer on the visible side (the opposite side to the liquid crystal cell) with an optical adhesive It bonded to the glass of a liquid crystal cell, and produced liquid crystal displays 401-419. At this time, the viewing side polarizing plate was disposed such that the transmission axis of the viewing side polarizing plate was orthogonal to the transmission axis of the polarizing plate on the backlight side.

Images were displayed on the obtained liquid crystal display devices 401 to 419, observed through polarized sunglasses, and the visibility was evaluated based on the following evaluation criteria.
"Evaluation criteria"
◎: There is no distortion in the displayed image, and the visibility is very good.
Good: There is almost no distortion in the displayed image, and the visibility is good.
Fair: There is a slight distortion in the displayed image, but there is no problem in practical use.
X: The displayed image is distorted and the visibility is poor.

  The results of various evaluations of the polarizing plates 201 to 219 are shown in Table 2.

From Table 1 and Table 2, the dimensional change rate ΔD _F in the fast axis direction and the dimensional change rate ΔD _{L in the} slow axis direction are respectively at the central portion C in the film width direction and the end portions E1 and E2.
0% ≦ ΔD _F <0.5%
ΔD _L <0%
In the case of a polarizing plate using an obliquely stretched film having a residual solvent amount of 60 ppm (an intermediate value of 110 ppm and 10 ppm) or less, good results are obtained for both the curl amount and the adhesiveness (see Table 1). See the obliquely stretched film and polarizing plate of the examples in the following). This is because the above-mentioned obliquely stretched film does not shrink in the direction of the fast axis even when it shrinks in the slow axis direction under a high temperature environment, so the shrinkage of the whole film can be suppressed, and a diagonally stretched film requiring high temperature Even in the case of adhesion between a film and a polarizer (in the case of ultraviolet irradiation when using an ultraviolet-curing adhesive, even when heating for acceleration of curing when using a water paste when using a water paste), the shrinkage of the entire film can be suppressed. It is thought that As a result, in the organic EL display device using the polarizing plate of the example, the reflection (light leakage) of the external light is in a range that causes no problem in actual use, and it is compatible with polarized sunglasses using the polarizing plate of the example. In the liquid crystal display device, the decrease in the visibility due to the distortion of the display image is a range that causes no problem in practical use.

In oblique stretching film 107,110～112 was stretched long film which is a film with a solution casting film forming method, all of the dimensional change rate [Delta] D _F of the fast axis direction is negative, the process proceeds in a high temperature environment It has the characteristic of contracting in the phase axis direction. This is considered to be due to the following reasons. In the solution casting film forming method, since a solvent is used to form a film, the density of resin of the formed film is low, and the direction of the slow axis and the direction of the phase advancing axis close to the conveying direction at the time of oblique drawing It extends in both directions. For this reason, after oblique stretching, tensile stress remains at least in the direction of the fast axis, and as a result of the above-mentioned tensile stress being relieved in a high temperature environment, it contracts in the fast axis direction.

Therefore, from this, in order to make the dimensional change rate ΔD _F in the fast axis direction be 0 or more, a long film is formed using a film forming method other than the solution casting film forming method, and this long It is desirable to obliquely stretch the film, and in particular, from the results of the obliquely stretched film 102 and the like, it can be said that it is desirable to diagonally stretch a long film produced using a melt-casting film forming method. In other words, since the residual solvent amount is 60 ppm or less (desirably 10 ppm or less), the long film produced by the melt-casting film forming method has a residual solvent amount of 60 ppm or less (desirably 10 ppm or less) said of the long film can be oblique stretching, desirable in manufacturing the diagonally stretched film dimensional change [Delta] D _F of the fast axis direction is zero or more.

Moreover, in the diagonal stretch film 101 stretched on the conditions of (Ti-Tr) /Tr=1.3 and (Tr-To) /Tr=1.0 at the time of diagonal stretch, it forms into a film by the melt-casting film forming method. been despite the stretched long film A1 diagonal, dimensional change rate [Delta] D _F of the fast axis direction is a negative, and has a characteristic which contracts the fast axis direction in a high temperature environment . This is considered to be due to the following reasons. That is, at the time of oblique drawing, the amount of change (increase) in the force in the transport direction at the leading end of the film and the change (decrease) in the force in the transport direction at the end of the delay are small. While the film extends in the direction of stretching (the slow axis direction), in the transport direction, the film shrinks against tension during transport, or the film does not stretch or shrink in proportion to the tension. It can not be made, and tensile stress remains in the direction of the fast axis near the direction of conveyance. Then, the tensile stress is relieved in a high temperature environment, so that it contracts in the fast axis direction.

Therefore, according to the results of the obliquely stretched films 102 to 117 and the polarizing plates 202 to 217, in the obliquely stretching step at the stretching portion 5,
(Ti-Tr) /Tr≧1.7
(Tr-To) /Tr≧1.5
It can be said that it is desirable to obliquely stretch a long film (formed by a melt-casting film forming method) in which the amount of residual solvent is 60 ppm or less so as to satisfy the above.

  Moreover, in the polarizing plates 204-206 using the diagonal stretch film 104-106, compared with the other polarizing plates (for example, the polarizing plate 203), evaluation of curl amount and adhesiveness is high. This is because in the preparation of the obliquely stretched films 104 to 106, the end of the width is cooled in the oblique stretching step, so that a larger shrinkage stress can be left in the direction of the fast axis at the end of the width. When the above-mentioned shrinkage stress is relieved in a high temperature environment at the time of bonding with a polarizer, the obliquely stretched film is expanded in the direction of the fast axis, thereby causing the dimension of the entire film even if it is contracted in the slow axis direction. It is considered that the change (contraction) can be further suppressed. In particular, in the preparation of the obliquely stretched film 106, in the oblique stretching step, in addition to end cooling, two-step stretching is performed at the same time. It is possible to make it possible to further suppress the dimensional change (shrinkage) of the whole film under a high temperature environment when adhering to a polarizer. For this reason, it is considered that the highest evaluation was obtained in the curl amount and the adhesion.

Moreover, in the polarizing plate (for example, polarizing plate 202) using the diagonal stretch film which satisfies the conditions of ((DELTA) _DF-E1 + (DELTA) _DF-E2 ) / 2> (DELTA) _DF-C , the diagonal stretch film which does not satisfy the said conditions is used. The curl amount and the adhesion evaluation are at least one rank higher than those of the polarizing plate (for example, the polarizing plates 215 and 217). This is because the dimensional change rate (expansion amount in the direction of the fast axis) at the center and the end in the width direction of the obliquely stretched film in consideration of uneven curing shrinkage at each position in the width direction of the adhesive. In the center of the width direction, the curling of the polarizing plate due to a large curing shrinkage of the adhesive is suppressed by a small expansion in the direction of the fast axis of the obliquely stretched film. It is considered that the curling of the polarizing plate due to the large expansion in the fast axis direction is suppressed by the small curing shrinkage of the adhesive, whereby the curling is surely suppressed in the entire lateral direction of the polarizing plate.

  The optical film of the present invention can be used, for example, as a circularly polarizing plate for preventing external light reflection of an organic EL display device or a polarizing plate of a liquid crystal display device compatible with polarized sunglasses.

50 Polarizing Plate 52 Polarizer 53 Retardation Film (Optical Film)
100 Organic EL Display Device 101 Organic EL Element (Display Cell)
301 Polarizer 311 λ / 4 retardation film (optical film)
313 Polarizer 400 Liquid Crystal Display Device 401 Liquid Crystal Cell (Display Cell)
402 Polarizing plate 411 Polarizer 413 λ / 4 retardation film (optical film)
Co grasper Ci grasper

Claims (14)

An optical film in which the slow axis is inclined by 10 to 80 ° with respect to one side of the outer shape of the film in the film plane,
When the dimensional change rates in the fast axis direction and the slow axis direction before and after leaving the optical film at 90 ° C. for 120 hours are ΔD _F (%) and ΔD _L (%), respectively, along the one side At the center and at both ends of the
0% ≦ ΔD _F <0.5%
ΔD _L <0%
Satisfied
An optical film characterized in that a residual solvent amount is 60 ppm or less.   The optical film according to claim 1, wherein a residual solvent amount is 10 ppm or less. In the optical film, a distance between two points aligned in the fast axis direction and before and after leaving the optical film for 120 hours at 90 ° C. is a1 (mm) and a2 (mm), respectively. age,
In the optical film, a distance between two points aligned in the slow axis direction and before and after leaving the optical film for 120 hours at 90 ° C. is b1 (mm) and b2 (mm), respectively. And when
ΔD _F = {(a2−a1) / a1} × 100
ΔD _L = {(b2−b1) / b1} × 100
The optical film according to claim 1 or 2, characterized in that: In the central portion in the direction along one side, the dimensional change rate in the fast axis direction before and after leaving the optical film at 90 ° C. for 120 hours is ΔD _F−C (%),
At one end in the direction along one side, the dimensional change rate in the fast axis direction before and after leaving the optical film at 90 ° C. for 120 hours is ΔDF _-E1 (%),
When the dimensional change rate in the fast axis direction before and after leaving the optical film at 120 ° C. for 120 hours at the other end in the direction along the one side is ΔDF _-E2 (%),
(.DELTA.DF _-E1 + .DELTA.DF _-E2 ) / 2> .DELTA.DF _-C
The optical film according to any one of claims 1 to 3, further satisfying The optical film is long and
The optical film according to any one of claims 1 to 4, wherein the direction along one side is a width direction perpendicular to the longitudinal direction in the film plane of the optical film. A film comprising the optical film according to any one of claims 1 to 5 and a polarizer,
The said optical film is located in one side with respect to the said polarizer so that the slow axis may cross | intersect the absorption axis of the said polarizer in a film surface, The polarizing plate characterized by the above-mentioned. And a display cell.
The display device, wherein the polarizing plate is positioned on the viewing side with respect to the display cell.   The display device according to claim 7, wherein the optical film of the polarizing plate is positioned on the display cell side with respect to the polarizer.   The display device according to claim 8, wherein the display cell is an organic electroluminescent element.   The display device according to claim 7, wherein the optical film of the polarizing plate is located on the opposite side to the display cell with respect to the polarizer.   The display device according to 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, wherein
The both ends in the width direction of the long film are held by a pair of holding tools, one holding tool is made to precede relative to the other holding tool, and the long film is bent in the film plane and conveyed By stretching the long film diagonally with respect to the lateral direction to obtain a diagonally stretched film constituting the optical film,
Before oblique drawing, at each end in the width direction of the long film, the force applied in the transport direction by each holding tool is respectively the same Tr (N),
During oblique stretching, at each end in the width direction of the long film, the force applied in the transport direction by the relatively delayed gripping tool and the relatively preceding gripping tool is expressed by To (N And Ti (N),
In the oblique stretching step,
(Ti-Tr) /Tr≧1.7
(Tr-To) /Tr≧1.5
And stretching the long film in the oblique direction so as to satisfy the above.   13. The oblique stretching process according to claim 12, wherein among the respective end portions in the width direction of the long film, the end portion held by the relatively delayed holding tool is cooled. Optical film production method.   In the oblique stretching step, the long film is obliquely stretched such that the slow axis is oriented at an orientation angle larger than a desired orientation angle with respect to the lateral direction of the long film, and then the slow phase The method for producing an optical film according to claim 12 or 13, wherein the long film is obliquely stretched such that the axis is oriented at the desired orientation angle.

Images