JP2019174636A - Oblique stretched film, polarizer, irregular shaped display and method for manufacturing oblique stretched film - Google Patents

Abstract

To reduce cracks occurring in a polarizer when punching a part of the polarizer prepared using an oblique stretched film into an irregular shape and after a durability test for the punched polarizer.SOLUTION: When setting orientation angles at optional adjacent two points in a plurality of points arranged at an interval of 100 mm from one end side toward the other end side in one direction of a width direction and a longitudinal direction in a film surface to θ1 (°) and θ2 (°) from the one end side and defining the gradients P of the orientation angles having a unit as °/mm at the two points by P=(θ2-θ1)/100, the oblique stretched film has a local 100 mm square region including the two points having an orientation angle gradient P of 0.001 or more and 0.06 or less in the film surface.SELECTED DRAWING: Figure 10

Description

  The present invention relates to an obliquely stretched film having a slow axis oriented in an oblique direction inclined with respect to the width direction in the film plane, a polarizing plate provided with the obliquely stretched film, and a deformed display device comprising the polarizing plate. And a method for producing the obliquely stretched film.

  Conventionally, a deformed display device called a free form display (FFD) is known. This odd-shaped display device is a display device that includes a free shape such as a curve in the outer shape of the display surface, with an emphasis on design and design. Such a deformed display device is expected to be applied to various fields, and as one of them, for example, application to an in-vehicle use (display panel for vehicle speed or the like) is currently being studied.

  On the other hand, a configuration in which a retardation film such as a QWP (Quarter Wave Plate) is used for enhancing the function of a display device has been known. For example, a configuration is known in which a QWP is disposed on the viewing side of a liquid crystal display device for the purpose of improving the visibility (preventing blackout) when an observer observes an image displayed on the liquid crystal display device through polarized sunglasses. ing. In addition, for the purpose of preventing reflection of external light in an organic EL (electroluminescence) display, a configuration in which a circularly polarizing plate including QWP is arranged on the viewing side of the display is also known. These retardation films are polarized so that the slow axis of the retardation film is inclined at a predetermined angle in the film plane with respect to the transmission axis of the polarizer constituting the polarizing plate (including the circularly polarizing plate). Bonded to the child. At this time, from the viewpoint of improving the production efficiency of the polarizing plate, a long retardation film (for example, an obliquely stretched film) is used instead of a batch type in which a retardation film having a predetermined shape is bonded to a polarizer having a predetermined shape one by one. A so-called roll-to-roll method is often employed in which a film is drawn from a roll, bonded to a long polarizer and wound.

  Here, the obliquely stretched film is a film in which the slow axis in the film plane is inclined with respect to both the width direction and the longitudinal direction. The angle formed by the slow axis with respect to the width direction in the film plane is called the orientation angle. Conventionally, it has been considered that it is desirable that the variation in the orientation angle is small in the obliquely stretched film. For example, in Patent Document 1, a first stretching process for stretching a long film in the width direction and a second stretching process for obliquely stretching a film after the first stretching process are performed under predetermined conditions. An obliquely stretched film with small corner variations is obtained. For example, in Patent Document 2, by appropriately setting the ratio between the tension of the inner clip and the tension of the outer clip before gripping both ends of the resin film with the inner clip and the outer clip and obliquely stretching the resin film, The amplitude of the orientation angle that periodically changes in the longitudinal direction of the film after oblique stretching is suppressed to less than 0.1 ° to improve the accuracy of the orientation angle in the longitudinal direction.

Japanese Patent No. 5257505 (see claim 1, paragraphs [0007], [0008], [0013], [0080] to [0089], FIG. 1) JP, 2006-179650, A (refer to claim 1, paragraphs [0006], [0007], [0010], FIGS. 1-4)

  By the way, when a polarizing plate having a retardation film such as QWP is applied to a deformed display device, the polarizing plate must also be formed in a deformed shape that matches the free shape of the display surface instead of the conventional rectangular shape. Such a deformed polarizing plate can be obtained, for example, by punching a part of a long polarizing plate into a deformed shape with a cutting member. In addition, as said irregular shape, various shapes, such as a shape with a rounded corner, a shape with a complicated curved surface, and a shape with a hole in the center, are conceivable.

  However, as in Patent Documents 1 and 2, when an irregularly shaped polarizing plate is produced using an obliquely stretched film having a small variation in the orientation angle, the irregularly shaped polarizing plate is not cracked (cracked, cracked, cracked, etc.). It was found that it was easy to occur. This is considered to be due to the following reason. When an obliquely stretched film with small variation in orientation angle is used, when punching a part of the polarizing plate into a specific curved shape, the angle between the direction of the cutting member blade and the orientation direction of the obliquely stretched film is small A location exists locally in the obliquely stretched film. In the above-mentioned portion of the obliquely stretched film, when the blade of the cutting member enters, the obliquely stretched film is easily torn along the orientation direction (not cut along the blade). It is considered that cracks are likely to occur in the polarizing plate following the tearing along the orientation direction of the obliquely stretched film at the time of punching the polarizing plate.

  Also, for example, if the residual stress (residual stress) due to stretching of the obliquely stretched film is too high, the dimensional variation before and after the endurance test due to stress relaxation of the obliquely stretched film when performing a durability test (for example, heat shock test) Therefore, there is a concern that cracks are likely to occur in the punched polarizing plate.

  Therefore, it is desired to form an obliquely stretched film so as to reduce the occurrence of cracks in the polarizing plate not only when stamping out the irregularly shaped polarizing plate but also after the durability test. However, such a diagonally stretched film has not been proposed yet.

  In view of the above circumstances, an object of the present invention is to provide a polarizing plate both when punching a part of a polarizing plate produced using an obliquely stretched film into an irregular shape and after a durability test on the punched polarizing plate. An object of the present invention is to provide an obliquely stretched film capable of reducing the occurrence of cracks, a polarizing plate provided with the obliquely stretched film, a deformed display device including the polarizing plate, and a method for producing the obliquely stretched film. .

  The above object of the present invention is achieved by the following configurations and methods.

1. An obliquely stretched film in which a slow axis is oriented in an oblique direction inclined with respect to both the width direction and the longitudinal direction perpendicular to each other in the film plane,
An angle at which the slow axis is inclined with respect to the width direction in the film plane is defined as an orientation angle (°), and from one end side in any one of the width direction and the longitudinal direction in the film plane. Among a plurality of points arranged at 100 mm intervals toward the other end side, the orientation angles of two arbitrary adjacent points are θ1 (°) and θ2 (°) from the one end side, and the gradient of the orientation angle at the two points When P is defined by the following formula (1), where the unit is ° / mm,
P = (θ2−θ1) / 100 (1)
An obliquely stretched film having a local region of 100 mm square including two points where the gradient P of the orientation angle is 0.001 or more and 0.06 or less in the film plane.

  2. 2. The obliquely stretched film according to 1 above, wherein a plurality of the local regions are provided in the width direction.

  3. The diagonally stretched film according to 1 or 2, wherein the local region is provided only in a part of the width direction.

  4). 4. The obliquely stretched film according to any one of 1 to 3, wherein a plurality of the local regions are provided in the longitudinal direction.

  5). 5. The obliquely stretched film according to any one of 1 to 4 above, wherein the local region has only a part in the longitudinal direction.

  6). 6. The obliquely stretched film according to any one of 1 to 5, wherein the orientation angle gradient P in the local region is 0.003 or more and 0.04 or less.

  7). In at least one of the width direction and the longitudinal direction in the film plane, an inflection point at which the gradient P of the orientation angle defined by the formula (1) changes from increasing to decreasing or from decreasing to increasing. The obliquely stretched film as described in any one of 1 to 6 above, which has

  8). The diagonally stretched film according to any one of 1 to 7 above, which contains any one of a polycarbonate resin, an acrylic resin, and a cycloolefin resin.

  9. A polarizing plate comprising the obliquely stretched film according to any one of 1 to 8 above and a polarizing film to which the obliquely stretched film is bonded, and having a curved portion on the outer shape.

  10. 10. A deformed display device comprising the polarizing plate according to 9 and a display cell to which the polarizing plate is bonded, and having an outer shape identical to that of the polarizing plate.

11. It is a manufacturing method of the diagonally stretched film which manufactures the diagonally stretched film in any one of said 1-8,
An oblique stretching step of obtaining the obliquely stretched film by stretching a long film in a direction inclined with respect to both the width direction and the longitudinal direction within the film plane in a stretching zone of an oblique stretching machine. When,
In the heat setting zone of the oblique stretching machine, including a heat setting step of conveying the obliquely stretched film while maintaining a constant width,
The method for producing an obliquely stretched film, wherein the temperature of the heat setting zone is lower than the temperature of the stretch zone.

  12 12. The method for producing an obliquely stretched film according to 11 above, wherein in the obliquely stretching step, a part of the obliquely stretched film in the width direction is cooled.

  13. 13. The method for producing an obliquely stretched film according to 11 or 12, wherein in the obliquely stretching step, the obliquely stretched film is intermittently cooled in the longitudinal direction.

  According to the configuration of the above-described obliquely stretched film, when a part of the polarizing plate produced using the obliquely stretched film is punched into an irregular shape, and after a durability test on the punched polarizing plate, the polarizing plate The generation of cracks can be reduced.

It is a top view of the deformed display apparatus which concerns on embodiment of this invention. It is sectional drawing which shows the structure of the outline of the liquid crystal display device which is an example of the said unusual shape display apparatus. It is a top view of the polarizing plate of the said unusual shape display apparatus. It is sectional drawing which decomposes | disassembles and shows the structure of the outline of the organic electroluminescence display which is another example of the said unusual shape display apparatus. It is explanatory drawing which shows the schematic structure of the manufacturing apparatus of the film base material used as the basis of the diagonally stretched film which comprises the said polarizing plate. It is a flowchart which shows the flow of the manufacturing process of the said film base material. It is a top view which shows typically the outline structure of the manufacturing apparatus of the said diagonally stretched film. It is a top view which shows typically an example of the rail pattern of the extending | stretching part with which the manufacturing apparatus of the said diagonally stretched film is equipped. It is explanatory drawing which expands and shows the local area | region in the said diagonally stretched film. It is a disassembled perspective view of the polarizing plate produced using the diagonally stretched film with a small orientation angle gradient in the width direction, and a polarizing film. It is a disassembled perspective view of the polarizing plate produced using the diagonally stretched film with a large orientation angle gradient in the width direction, and a polarizing film. It is explanatory drawing which shows an example of distribution of the orientation angle | corner of the said diagonally stretched film. It is a disassembled perspective view of the polarizing plate produced using the diagonally stretched film of FIG. 12, and a polarizing film. It is explanatory drawing which shows typically the other example of distribution of the orientation angle | corner of the said diagonally stretched film.

  An 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 numerical value range includes the values of the lower limit A and the upper limit B. The present invention is not limited to the following contents.

[Configuration of display device]
FIG. 1 is a plan view of the odd-shaped display device 1 of the present embodiment. The external shape of the irregular display device 1 in plan view is a shape obtained by combining the straight portion 1s and the curved portion 1c, and is different from a normal rectangular or square shape. The shape including the curved portion 1c in the outer shape in this way is referred to herein as an irregular shape. As shown in FIG. 1, the odd-shaped display device 1 can be applied to in-vehicle applications (display panel for displaying vehicle speed, engine speed, etc.), but can of course be applied to other applications.

  FIG. 2 is a cross-sectional view illustrating a schematic configuration of a liquid crystal display device 1 a which is an example of the odd-shaped display device 1. The liquid crystal display device 1 a includes a liquid crystal cell 2, two polarizing plates 3 and 4 sandwiching the liquid crystal cell 2, and a backlight 5 for illuminating the liquid crystal cell 2. The liquid crystal cell 2 is a display cell configured by sandwiching a liquid crystal layer between two transparent substrates, and is driven by, for example, a VA (Vertical Alignment) method, but an IPS (In-Plane-Switching) method, TN ( It may be driven by other methods such as Twisted Nematic).

  The polarizing plate 3 is located on the viewing side (the side opposite to the backlight 5) with respect to the liquid crystal cell 2, and includes a polarizer 11, a protective film 12, and a counter film 13. The protective film 12 is composed of a QWP (¼ wavelength plate) made of a diagonally stretched film described later, and is located on the opposite side (viewing side) to the liquid crystal cell 2 with respect to the polarizer 11. The polarizer 11 is composed of a polarizing film to which the obliquely stretched film is bonded, and transmits predetermined linearly polarized light. The protective film 12 and the polarizer 11 are bonded so that the angle formed between the slow axis of QWP and the transmission axis of the polarizer 11 is approximately 45 °. The counter film 13 is located on the liquid crystal cell 2 side with respect to the polarizer 11.

  Such a polarizing plate 3 is bonded to the liquid crystal cell 2 via the adhesive layer 6 on the counter film 13 side. The polarizing plate 3 may further have functional layers such as a hard coat layer, an antiglare layer, an antireflection layer, and an antistatic layer on the side opposite to the polarizer 11 with respect to the protective film 12.

  The polarizing plate 4 is located on the backlight 5 side with respect to the liquid crystal cell 2, and includes a polarizer 21, a protective film 22, and a counter film 23. The polarizer 21 transmits predetermined linearly polarized light and is disposed so that the transmission axis is orthogonal to the polarizer 11. The protective film 22 is located on the side opposite to the liquid crystal cell 2 (backlight 5 side) with respect to the polarizer 21. The counter film 23 is located on the liquid crystal cell 2 side with respect to the polarizer 21. The polarizing plate 4 is bonded to the liquid crystal cell 2 via the adhesive layer 7 on the counter film 23 side.

  As described above, the polarizing plate 3 is positioned on the viewing side with respect to the liquid crystal cell 2, and the protective film 12 (QWP) of the polarizing plate 3 is positioned on the opposite side of the liquid crystal cell 2 with respect to the polarizer 11. In the configuration of the display device 1a, the linearly polarized light emitted from the liquid crystal cell 2 and transmitted through the viewing-side polarizer 11 is converted into circularly polarized light or elliptically polarized light by the protective film 12. Therefore, when an observer wears polarized sunglasses and observes the display image of the liquid crystal display device 1a, no matter what angle the transmission axis of the polarizer 11 and the transmission axis of the polarized sunglasses form, A display component can be observed by guiding a light component parallel to the transmission axis of the polarized sunglasses to the viewer's eyes, and the visibility of the image observed through the polarized sunglasses can be improved.

  FIG. 3 is a plan view of the polarizing plate 3 described above. The polarizing plate 3 has a linear portion 3s and a curved portion 3c on the outer shape. The linear portion 3s of the polarizing plate 3 corresponds to the linear portion 1s of the liquid crystal display device 1a, and the curved portion 3c of the polarizing plate 3 corresponds to the curved portion 1c of the liquid crystal display device 1a. Therefore, the polarizing plate 3 includes at least a protective film 12 (an obliquely stretched film) and a polarizer 11 (a polarizing film) to which the obliquely stretched film is bonded, and has an outer shape having a curved portion 3c. You can also. Although not shown, the outer shape of the remaining polarizing plate 4 and the liquid crystal cell 2 is the same as that of the polarizing plate 3. According to the obliquely stretched film of the present embodiment, as will be described later, cracks occur in the polarizing plate 3 both when the deformed polarizing plate 3 is punched and after the endurance test on the punched polarizing plate 3. Therefore, it is possible to avoid a decrease in the yield of the odd-shaped polarizing plate 3. Further, the polarizing plate 3 can be easily applied to, for example, a vehicle-mounted application (for example, a display panel such as a vehicle speed) in which the environmental temperature changes drastically.

  In the liquid crystal display device 1 a, the polarizing plate 3 having the curved portion 3 c on the outer shape is bonded to the liquid crystal cell 2 having the same shape as the polarizing plate 3 through the adhesive layer 6. As a result, as shown in FIG. 1, the liquid crystal display device 1a has an outer shape having a curved portion 1c having the same shape as the curved portion 3c in plan view, as shown in FIG. From this, the liquid crystal display device 1 a includes at least the polarizing plate 3 and the liquid crystal cell 2 (display cell) to which the polarizing plate 3 is bonded, and the outer shape is the same shape as the polarizing plate 3. Can do. With such a configuration of the liquid crystal display device 1a, for example, the liquid crystal display device 1a can be sufficiently applied to applications where design is important.

  By the way, the odd-shaped display device 1 may be configured by a display device other than the liquid crystal display device 1a. FIG. 4 is an exploded cross-sectional view showing a schematic configuration of an organic EL display device 1b which is another example of the odd-shaped display device 1. The organic EL display device 1b is configured by forming a polarizing plate 50 via an adhesive layer 40 on an organic EL element 30 as a display cell. The organic EL element 30 includes a metal electrode 32, a light emitting layer 33, a transparent electrode (ITO, etc.) 34, and a sealing layer 35 in this order on a substrate 31 made of glass, polyimide, or the like. The metal electrode 32 may be configured by stacking a reflective electrode and a transparent electrode.

  The polarizing plate 50 is configured by laminating a λ / 4 retardation film 51, an adhesive layer 52, a polarizer 53, an adhesive layer 54, and a protective film 55 in this order from the organic EL element 30 side. The λ / 4 retardation film 51 is composed of an obliquely stretched film, which will be described later, and is attached to the polarizer 53 so that its slow axis intersects the transmission axis (or absorption axis) of the polarizer 53 at approximately 45 °. Are combined. Thereby, the polarizing plate 50 can function as a circularly polarizing plate which prevents reflection of external light.

  That is, when the organic EL element 30 is not emitting light, half of the external light incident from the outside of the organic EL element 30 due to indoor lighting or the like is absorbed by the polarizer 53 of the polarizing plate 50 and the other half is transmitted as linearly polarized light. Then, the light enters the λ / 4 retardation film 51. In the light incident on the λ / 4 retardation film 51, the transmission axis of the polarizer 53 and the slow axis of the λ / 4 retardation film 51 intersect at about 45 °. Is converted into circularly polarized light.

  When the circularly polarized light emitted from the λ / 4 retardation film 51 is specularly reflected by the metal electrode 32 of the organic EL element 30, the phase is inverted by 180 degrees and reflected as reverse circularly polarized light. The reflected light is incident on the λ / 4 retardation film 51 and converted into linearly polarized light perpendicular to the transmission axis of the polarizer 53 (parallel to the absorption axis). Will not be emitted. That is, the polarizing plate 50 can prevent external light reflection at the organic EL element 30.

  Similarly to the polarizing plate 3 shown in FIG. 3, the polarizing plate 50 also has a linear portion 50 s and a curved portion 50 c on the outer shape. The linear portion 50s of the polarizing plate 50 corresponds to the linear portion 1s of FIG. 1, and the curved portion 50c of the polarizing plate 50 corresponds to the curved portion 1c of FIG. Therefore, the polarizing plate 50 includes at least a λ / 4 retardation film 51 (an obliquely stretched film) and a polarizer 53 (a polarizing film) to which the obliquely stretched film is bonded, and has a curved portion 50c on the outer shape. I can say that there is. Although not shown, the outer shape of the organic EL element 30 as a display cell is the same as that of the polarizing plate 50. According to the obliquely stretched film of the present embodiment, as will be described later, cracks occur in the polarizing plate 50 both when the deformed polarizing plate 50 is punched and after the endurance test on the punched polarizing plate 50. Therefore, it is possible to avoid a decrease in yield of the odd-shaped polarizing plate 50. Further, the polarizing plate 50 can be easily applied to, for example, in-vehicle use in which the environmental temperature changes drastically.

  In the organic EL display device 1 b, a polarizing plate 50 having a curved portion 50 c on its outer shape is bonded to an organic EL display element 30 having the same shape as the polarizing plate 50 via an adhesive layer 40. As a result, the organic EL display device 1b has an outer shape having a curved portion 1c having the same shape as the curved portion 50cc in plan view, as shown in FIG. Accordingly, the organic EL display device 1b includes the polarizing plate 50 and the organic EL display element 30 (display cell) to which the polarizing plate 50 is bonded, and the outer shape is the same as the polarizing plate 50. be able to. With such a configuration of the organic EL display device 1b, for example, the organic EL display device 1b can be sufficiently applied to applications where design is important.

[Method for producing film substrate]
Next, the manufacturing method of the elongate film (film base material) used as the base of the diagonally stretched film which comprises the polarizing plate 3 * 50 mentioned above is demonstrated. The film substrate can be produced, for example, by a solution casting film forming method.

(Solution casting film forming method)
FIG. 5 is an explanatory diagram showing a schematic configuration of the film base manufacturing apparatus 60 of the present embodiment. Moreover, FIG. 6 is a flowchart which shows the flow of the manufacturing process of a film base material. As shown in FIG. 6, the manufacturing method of the film base material of this embodiment is a stirring preparation process (S1), a casting process (S2), a peeling process (S3), a stretching process (S4), and a drying process (S5). Cutting step (S6), embossing step (S7), and winding step (S8). Hereafter, each process is demonstrated, referring FIG. 5 and FIG.

(S1; stirring preparation step)
In the stirring preparation step, at least the resin and the solvent are stirred in the stirring tank 61a of the stirring device 61 to prepare a dope that is cast on the support 63 (endless belt).

(S2; casting process)
In the casting step, the dope prepared in the stirring preparation step is fed to the casting die 62 by a conduit through a pressurized metering gear pump or the like, and is transferred to the endless belt made of a rotationally driven stainless steel endless belt. The dope is cast from the casting die 62 at the casting position. The support 63 conveys the cast dope (casting dope) while supporting it. Thereby, the web 65 as a casting film is formed on the support 63.

  The support 63 is held by a pair of rolls 63a and 63b and a plurality of rolls (not shown) positioned therebetween. One or both of the rolls 63a and 63b are provided with a driving device (not shown) for applying tension to the support 63, whereby the support 63 is used in a tensioned state.

  In the casting step, the web 65 is heated on the support 63 and the solvent is evaporated until the web 65 can be peeled from the support 63 by the peeling roll 64. In order to evaporate the solvent, there are a method of blowing air from the web side, a method of transferring heat from the back surface of the support 63 with a liquid, a method of transferring heat from the front and back by radiant heat, and the like. That's fine.

(S3; peeling step)
In the casting step, after drying and solidifying or cooling and solidifying until the web 65 has a peelable film strength on the support 63, in the peeling step, the web 65 is peeled while having self-supporting properties. It peels with the roll 64. FIG. The peeled web 65 constitutes a film substrate.

  The residual solvent amount of the web 65 on the support 63 at the time of peeling is desirably in the range of 50 to 120% by mass depending on the strength of drying conditions, the length of the support 63, and the like. When peeling at a time when the amount of residual solvent is larger, if the web 65 is too soft, the flatness at the time of peeling is impaired, and wrinkles and vertical streaks are likely to occur due to the peeling tension. Therefore, the residual at the time of peeling due to the balance between economic speed and quality. The amount of solvent is determined. The residual solvent amount is defined by the following formula.

Residual solvent amount (mass%) = (mass before web heat treatment−mass after web heat treatment) /
(Mass after web heat treatment) × 100
Here, the heat treatment for measuring the residual solvent amount represents performing heat treatment at 115 ° C. for 1 hour.

(S4; stretching step)
In the stretching step, the web 65 (film base material) peeled from the support 63 is stretched in the transport direction and / or the width direction by the tenter 66. In the stretching step, a tenter method in which both side edges of the web 65 are fixed with a clip or the like and stretched is preferable in order to improve the flatness and dimensional stability of the film. In the tenter 66, drying may be performed in addition to stretching.

(S5; drying step)
The web 65 stretched by the tenter 66 is dried by a drying device 67. In the drying device 67, the web 65 is transported by a plurality of transport rolls arranged in a staggered manner as viewed from the side, and the web 65 is dried in the meantime. The drying method in the drying device 67 is not particularly limited, and the web 5 is generally dried using hot air, infrared rays, a heating roll, a microwave, or the like. From the viewpoint of simplicity, a method of drying the web 65 with hot air is preferable.

  The web 65 is transported toward the winding device 70 as an optical film after being dried by the drying device 67.

(S6: cutting step, S7: embossing step)
Between the drying device 67 and the winding device 70, a cutting portion 68 and an embossing portion 69 are arranged in this order. In the cutting part 68, the cutting process which cut | disconnects the both ends of the width direction with a slitter is performed, conveying the optical film formed into a film. In the optical film, the portion remaining after the cutting of both ends constitutes a product portion to be a film product. On the other hand, the portion cut from the optical film is collected by a shooter and reused as a part of the raw material for film formation.

  After the cutting step, embossing (knurling) is applied to both ends of the optical film in the width direction by the embossing part 69. Embossing is performed by pressing a heated embossing roller against both ends of the optical film. Fine irregularities are formed on the surface of the embossing roller, and the embossing roller is pressed against both ends of the optical film, thereby forming irregularities at the both ends. By such embossing, winding deviation and blocking (attachment between films) in the next winding process can be suppressed as much as possible.

(S8; winding process)
Finally, the optical film that has been embossed is wound up by the winding device 70 to obtain the original roll (film roll) of the optical film. That is, in a winding process, a film roll is manufactured by winding an optical film around a winding core. The winding method of the optical film may be a commonly used winder, and there are methods such as constant torque method, constant tension method, taper tension method, program tension control method with constant internal stress, etc. Should be used properly. The winding length of the optical film is preferably 1000 to 7200 m. In addition, the width at that time is desirably 500 to 3200 mm, and the film thickness is desirably 30 to 150 μm.

(Melt casting method)
The film substrate (optical film) of this embodiment can also be produced by a melt casting film forming method. In the melt casting film forming method, a resin composition containing an additive such as a resin and a plasticizer is heated and melted to a temperature showing fluidity, and then a melt having fluidity is cast to form a film. It is a method to do. 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 that can obtain a film having excellent mechanical strength and surface accuracy is preferable. Moreover, it is preferable that the plurality of raw materials used in the melt extrusion method are usually kneaded and pelletized in advance.

  Pelletization may be performed by a known method. For example, supplying dry resin, plasticizer, and other additives to the extruder with a feeder, kneading using a single or twin screw extruder, extruding into a strand from a die, water cooling or air cooling, cutting Can be pelletized.

  The additive may be mixed with the resin before being supplied to the extruder, or the additive and the resin may be supplied to the extruder with separate feeders. Moreover, in order to mix a small amount of additives, such as particle | grains and antioxidant, uniformly, it is preferable to mix with resin beforehand.

  The extruder is preferably processed at as low a temperature as possible so as to be able to be pelletized so that the shear force is suppressed and the resin does not deteriorate (decrease in molecular weight, 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. From the uniformity of kneading, the meshing type is preferable.

  A film is formed using the pellets obtained as described above. Of course, it is also possible to feed the raw material powder as it is to the extruder with a feeder and form a film as it is without pelletization.

  Using a single or twin screw extruder, the pellets are melted at a temperature of about 200 to 300 ° C., filtered through a leaf disk filter, etc. to remove foreign matter, and then the film is formed from the T die. And the film is nipped between a cooling roll and an elastic touch roll and solidified on the cooling roll.

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

  The extrusion flow rate is preferably performed stably by introducing a gear pump or the like. Further, a stainless fiber sintered filter is preferably used as a filter used for removing foreign substances. The stainless steel fiber sintered filter is a united stainless steel fiber body that is intricately intertwined and compressed, and the contact points are sintered and integrated. The density of the fiber is changed depending on the thickness of the fiber and the amount of compression, and the filtration accuracy is improved. Can be adjusted.

  Additives such as plasticizers and particles may be mixed with the resin in advance, 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 between the cooling roll and the elastic touch roll is preferably Tg (glass transition temperature) or more and Tg + 110 ° C. or less of the film. A known roll can be used as the roll having an elastic surface used for such a purpose.

  The elastic touch roll is also called a pinching rotator. As the elastic touch roll, a commercially available one can be used.

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

  In addition, the optical film formed 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 a coextrusion molding method, a co-casting molding method, a film lamination method, or a coating method. Of these, the coextrusion molding method and the co-casting molding method are preferable. When the coextrusion molding method (coextrusion T-die method) is adopted, there are a feed block method and a multi-manifold method in the co-extrusion T-die method. Particularly preferred.

[Film base]
In this embodiment, a polycarbonate resin, an acrylic resin, a cycloolefin resin (alicyclic olefin polymer), a polyester resin, or the like can be used as the resin constituting the film substrate.

(Polycarbonate resin)
Various polycarbonate resins can be used without any particular limitation, and aromatic polycarbonate resins are preferable from the viewpoint of chemical properties and physical properties, and polycarbonates having a fluorene skeleton and bisphenol A polycarbonate resins are particularly preferable. Among these, those using a bisphenol A derivative in which a benzene ring, a cyclohexane ring, an aliphatic hydrocarbon group and the like are introduced into bisphenol A are more preferable. Furthermore, a polycarbonate resin having a structure in which the anisotropy in the unit molecule is reduced, obtained by using a derivative in which the functional group is introduced asymmetrically with respect to the central carbon of bisphenol A, is particularly preferable.

  As such a polycarbonate resin, for example, two methyl groups in the center carbon of bisphenol A are replaced by benzene rings, and one hydrogen of each benzene ring of bisphenol A is centered by a methyl group or a phenyl group. A polycarbonate resin obtained by using an asymmetrically substituted carbon is particularly preferable. Specifically, 4,4′-dihydroxydiphenylalkane or a halogen-substituted product thereof can be obtained by a phosgene method or a transesterification method. For example, 4,4′-dihydroxydiphenylmethane, 4,4′-dihydroxydiphenyl Examples include ethane and 4,4'-dihydroxydiphenylbutane. In addition to this, specific examples of the polycarbonate resin include, for example, JP 2006-215465 A, JP 2006-91836 A, JP 2005-121183 A, and JP 2003-167121 A. And polycarbonate resins described in JP-A No. 2009-126128, JP-A 2012-67300, and International Publication No. 2000/026705.

(Acrylic resin)
Acrylic resins also include methacrylic resins. The Tg (glass transition temperature) of the (meth) acrylic resin is preferably 115 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 125 ° C. or higher, and particularly preferably 130 ° C. or higher. When the Tg is 115 ° C. or higher, the durability of the film is improved. Although the upper limit of Tg of the (meth) acrylic resin is not particularly limited, it is preferably 170 ° C. or lower from the viewpoint of moldability and the like.

  As the (meth) acrylic resin, any appropriate (meth) acrylic resin can be adopted as long as the effects of the present embodiment are not impaired. For example, poly (meth) acrylic acid ester such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester- (Meth) acrylic acid copolymer, (meth) methyl acrylate-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, Methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.). Preferably, C1-6 alkyl poly (meth) acrylates, such as poly (meth) acrylate methyl, are mentioned. More preferably, a methyl methacrylate-based resin containing methyl methacrylate as a main component (50 to 100% by mass, preferably 70 to 100% by mass) is used.

  Specific examples of the (meth) acrylic resin include, for example, Acrypet VH and Acrypet VRL20A, Dianal BR52, BR80, BR83, BR85, BR88 (manufactured by Mitsubishi Rayon Co., Ltd.), KT75 (manufactured by Denki Kagaku Kogyo Co., Ltd.) ), Delpet 60N, 80N (manufactured by Asahi Kasei Chemicals Co., Ltd.), (Meth) acrylic resin having a ring structure in the molecule described in JP-A-2004-70296, intramolecular crosslinking and intramolecular cyclization reaction Examples include the obtained high Tg (meth) acrylic resin system.

  As the (meth) acrylic resin, it is also preferable to use a (meth) acrylic resin having a lactone ring structure. Examples of the (meth) acrylic resin having a lactone ring structure include JP 2000-230016, JP 2001-151814, JP 2002-120326, JP 2002-254544, and JP 2005. No. 146084 and the like.

  In addition, as the (meth) acrylic resin, an acrylic resin having a structural unit of unsaturated carboxylic acid alkyl ester and a structural unit of glutaric anhydride can be used. Examples of the acrylic resin include Japanese Patent Application Laid-Open Nos. 2004-70290, 2004-70296, 2004-163924, 2004-292812, 2005-314534, and 2006. Examples described in JP-A-131898, JP-A-2006-206881, JP-A-2006-265532, JP-A-2006-283013, JP-A-2006-299005, JP-A-2006-335902, and the like. It is done.

  Moreover, as a (meth) acrylic-type resin, the thermoplastic resin which has a glutarimide unit, a (meth) acrylic acid ester unit, and an aromatic vinyl unit can be used. Examples of the thermoplastic resin include JP 2006-309033 A, JP 2006-317560 A, JP 2006-328329 A, JP 2006-328334 A, JP 2006-337491 A, and JP 2006. JP-A-337374, JP-A-2006-337493, JP-A-2006-337569, JP-A-2006-196522, JP-A-2017-164969, JP-A-2017-52920, JP-A-2017-137417. And the like described in Japanese Patent Publications.

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

  As the cyclic olefin, there are a polycyclic cyclic olefin and a monocyclic cyclic olefin. Such polycyclic olefins include norbornene, methylnorbornene, dimethylnorbornene, ethylnorbornene, ethylidenenorbornene, butylnorbornene, dicyclopentadiene, dihydrodicyclopentadiene, methyldicyclopentadiene, dimethyldicyclopentadiene, tetracyclododecene. , Methyltetracyclododecene, dimethylcyclotetradodecene, tricyclopentadiene, tetracyclopentadiene, and the like. Examples of monocyclic olefins include cyclobutene, cyclopentene, cyclooctene, cyclooctadiene, cyclooctatriene, and cyclododecatriene.

(Polyester resin)
Examples of the polyester resin include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). 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.

〔Additive〕
You may add an additive to a film base material as needed. Examples of the additive include a plasticizer, an ultraviolet absorber, a retardation adjusting agent, an antioxidant, a deterioration preventing agent, a peeling aid, a surfactant, a dye, and fine particles. In the present embodiment, additives other than fine particles may be added during the preparation of the dope, or may be added during the preparation of the fine particle dispersion.

[Manufacturing method and manufacturing apparatus of obliquely stretched film]
Next, a method and an apparatus for producing a long oblique stretched film using the above-described film substrate (long film, optical film) will be described.

(Outline of the device)
FIG. 7 is a plan view schematically showing a schematic configuration of the obliquely stretched film manufacturing apparatus 80. The production apparatus 80 includes, in order from the upstream side in the conveyance direction of the film base material, a film feeding unit 81, a conveyance direction changing unit 82, a guide roll 83, a stretching unit 84, a guide roll 85, and a conveyance direction changing unit 86. And a film take-up portion 87. Details of the extending portion 84 will be described later.

  The film feeding unit 81 feeds the film base material produced as described above to the stretching unit 84. The film supply unit 81 may be configured separately from the film substrate manufacturing apparatus 60 shown in FIG. 5 or may be configured integrally. In the former case, the film substrate is unwound from the film unwinding portion 81 by loading the film unwinding portion (film roll) into the film unwinding portion 81 once wound up on the core after film formation. It is. On the other hand, in the latter case, after the film base is formed, the film feed portion 81 is fed to the stretching portion 84 without winding the film base.

  The conveyance direction change part 82 changes the conveyance direction of the film base material drawn | fed out from the film delivery part 81 to the direction which goes to the entrance of the extending | stretching part 84 as an oblique stretch tenter. Such a conveyance direction changing unit 82 includes, for example, a turn bar that changes the conveyance direction by folding the film while conveying the film, and a turntable that rotates the turn bar in a plane parallel to the film.

  At least one guide roll 83 is provided on the upstream side of the extending portion 84 in order to stabilize the track during travel of the film base material. The guide roll 83 may be composed of a pair of upper and lower rolls sandwiching the film, or may be composed of a plurality of roll pairs. The guide roll 83 closest to the entrance of the extending portion 84 is a driven roll that guides the traveling of the film, and is rotatably supported via a bearing portion (not shown). As the material of the guide roll 83, a known material can be used. In order to prevent the film from being damaged, it is preferable to reduce the weight of the guide roll 83 by applying a ceramic coat on the surface of the guide roll 83 or applying chrome plating to a light metal such as aluminum.

  At least one guide roll 85 is provided on the downstream side of the stretching portion 84 in order to stabilize the trajectory during travel of the film obliquely stretched by the stretching portion 84. The transport direction changing unit 86 changes the transport direction of the stretched film transported from the stretching unit 84 to a direction toward the film take-up unit 87. Like the transport direction changing unit 82, the transport direction changing unit 86 rotates and rotates. Consists of tables.

  The film winding unit 87 winds the film conveyed from the stretching unit 84 via the conveyance direction changing unit 86, and includes, for example, a winder device, an accumulator device, a drive device, and the like. It is preferable that the film winding portion 87 has a structure that can be slid in the horizontal direction in order to adjust the film winding position.

  In addition, before winding up the long film after oblique stretching, for the purpose of preventing blocking between the films, the masking film may be overlapped on the obliquely stretched film and simultaneously wound, or the oblique stretching overlapped by winding. You may wind up, sticking a tape etc. to the edge of at least one (preferably both) of a film. The masking film is not particularly limited as long as it can protect a long oblique stretched film, and examples thereof include a polyethylene terephthalate film, a polyethylene film, and a polypropylene film.

(Details of stretched part)
Next, the detail of the extending | stretching part 84 mentioned above is demonstrated. FIG. 8 is a plan view schematically showing an example of the rail pattern of the extending portion 84. However, this is an example, and the configuration of the extending portion 84 is not limited to this.

  Production of the obliquely stretched film in the present embodiment is performed using a tenter (obliquely stretching machine) capable of oblique stretching as the stretching portion 84. This tenter is an apparatus that heats a film substrate to an arbitrary stretchable temperature and obliquely stretches the film substrate. This tenter includes a heating zone Z, a pair of rails Ri and Ro on the left and right, and a number of grippers Ci and Co that travel along the rails Ri and Ro to convey a film (in FIG. 8, a set of grippers). Only). Details of the heating zone Z will be described later. Each of the rails Ri and Ro is configured by connecting a plurality of rail portions with connecting portions (white circles in FIG. 8 are examples of connecting portions). The gripping tool Ci / Co is composed of a clip that grips both ends of the film in the width direction.

  In FIG. 8, the feeding direction D1 of the film base is different from the winding direction D2 of the elongated slanted stretched film after stretching, and forms a feeding angle θi with the winding direction D2. The feeding angle θi can be arbitrarily set to a desired angle in the range of more than 0 ° and less than 90 °.

  Thus, since the feeding direction D1 and the winding direction D2 are different, the rail pattern of the tenter has an asymmetric shape on the left and right. And a rail pattern can be adjusted now manually or automatically according to orientation angle (theta) given to the long diagonally stretched film which should be manufactured, a draw ratio, etc. FIG. In the oblique stretching machine used in the manufacturing method of the present embodiment, it is preferable that the positions of the rail portions and the rail connecting portions constituting the rails Ri and Ro can be freely set and the rail pattern can be arbitrarily changed.

  In the present embodiment, the tenter gripping tool Ci · Co travels at a constant speed with a constant distance from the front and rear gripping tools Ci · Co. The traveling speed of the gripping tool Ci / Co can be selected as appropriate, but is usually 1 to 150 m / min. The difference in travel speed between the pair of left and right grippers Ci / Co is usually 1% or less, preferably 0.5% or less, more preferably 0.1% or less of the travel speed. This is because if there is a difference in the traveling speed on the left and right of the film at the exit of the stretching process, wrinkles and shifts will occur at the exit of the stretching process, so the speed difference between the left and right grippers Ci / Co is substantially the same speed. Is required. In general tenter devices, etc., there are speed irregularities that occur on the order of seconds or less depending on the period of the sprocket teeth that drive the chain, the frequency of the drive motor, etc. This does not correspond to the speed difference described in the embodiment of the invention.

  In the oblique stretching machine used in the manufacturing method of the present embodiment, a rail that regulates the trajectory of the gripping tool is often required to have a high bending rate, particularly in a portion where the film is transported obliquely. In order to avoid interference between gripping tools due to sudden bending or local stress concentration, it is desirable that the trajectory of the gripping tool draws a curve at the bent portion.

  As described above, the oblique stretching tenter used for imparting the oblique orientation to the film substrate can freely set the orientation angle of the film by changing the rail pattern in various ways, and further the orientation axis of the film. It is preferred that the tenter be capable of orienting the (slow axis) in the left and right direction with high precision across the film width direction and controlling the film thickness and retardation with high precision.

  Next, the extending | stretching operation | movement in the extending | stretching part 84 is demonstrated. Both ends of the film base material are gripped by the left and right grippers Ci · Co, and are transported in the heating zone Z as the grippers Ci • Co travel. The left and right gripping tools Ci and Co are opposed to a direction substantially perpendicular to the film traveling direction (feeding direction D1) at the entrance portion (position A in the drawing) of the extending portion 84, and are asymmetrical rails. Each travels on Ri and Ro, and the film gripped at the exit portion (position B in the figure) at the end of stretching is released. The film released from the gripping tool Ci · Co is wound around the core by the film winding portion 87 described above. Each of the pair of rails Ri and Ro has an endless continuous track, and the grippers Ci and Co that have released the film at the exit portion of the tenter travel on the outer rail and sequentially return to the entrance portion. It is supposed to be.

  At this time, since the rails Ri and Ro are asymmetrical in the left and right directions, in the example of FIG. 8, the left and right gripping tools Ci and Co that are opposed to each other at the position A in the figure move as the rails Ri and Ro move. The gripping tool Ci traveling on the Ri side (in-course side) has a positional relationship preceding the gripping tool Co traveling on the rail Ro side (out-course side).

  That is, of the gripping tools Ci and Co that are opposed to the film feeding direction D1 at the position A in the figure, one gripping tool Ci is first in position B at the end of film stretching. When it reaches, the straight line connecting the gripping tools Ci and Co is inclined by an angle θL with respect to the direction substantially perpendicular to the film winding direction D2. With the above operation, the film substrate is obliquely stretched at an angle of θL with respect to the width direction. Here, “substantially vertical” indicates that the angle is in a range of 90 ± 1 °.

  Next, the details of the heating zone Z will be described. The heating zone Z of the extending part 84 is composed of a preheating zone Z1, a extending zone Z2, and a heat fixing zone Z3. In the stretching unit 84, the film gripped by the gripping tool Ci / Co passes through the preheating zone Z1, the stretching zone Z2, and the heat fixing zone Z3 in this order. In the present embodiment, the preheating zone Z1 and the stretching zone Z2 are separated by a partition, and the stretching zone Z2 and the heat fixing zone Z3 are separated by a partition.

  The preheating zone Z1 refers to a section in which the gripping tool Ci / Co that grips both ends of the film travels at the left and right (in the film width direction) while maintaining a constant interval at the entrance of the heating zone Z.

  The stretching zone Z2 refers to a section in which the gap between the gripping tools Ci and Co that grips both ends of the film opens and reaches a predetermined interval. As a result, the oblique stretching as described above is performed. That is, in the stretching zone Z2, an oblique stretching process for obtaining an obliquely stretched film by stretching a long film (film substrate) in an oblique direction inclined with respect to both the width direction and the longitudinal direction in the film plane. Is done. In addition, before and after oblique stretching, stretching in the longitudinal direction or the transverse direction may be performed as necessary.

  The heat setting zone Z3 refers to a section after the stretching zone Z2 in which the interval between the gripping tools Ci and Co is constant, and the gripping tools Ci and Co at both ends travel in parallel with each other. . That is, in the heat setting zone Z3, a heat setting process is performed in which the obliquely stretched film is conveyed while keeping the width constant.

  The stretched film passes through the heat setting zone Z3 and then passes through a section (cooling zone) in which the temperature in the zone is set to be equal to or lower than the glass transition temperature Tg (° C.) of the thermoplastic resin constituting the film. May be. At this time, considering the shrinkage of the film due to cooling, a rail pattern that narrows the gap between the gripping tools Ci and Co facing each other in advance may be used.

  The temperature of the preheating zone Z1 is Tg to Tg + 30 ° C., the temperature of the stretching zone Z2 is Tg to Tg + 30 ° C., and the temperature of the heat setting zone Z3 and the cooling zone is Tg-30 to Tg + 20 ° C. with respect to the glass transition temperature Tg of the thermoplastic resin. It is preferable to set.

  The lengths of the preheating zone Z1, the stretching zone Z2, and the heat setting zone Z3 can be appropriately selected. The length of the preheating zone Z1 is usually 100 to 150% of the length of the stretching zone Z2, and the length of the heat setting zone Z3. The length is usually 50-100%.

  When the width of the film before stretching is Wo (mm) and the width of the film after stretching is W (mm), the draw ratio R (W / Wo) in the stretching step is preferably 1.3 to 3. 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 preferably reduced. In the stretching zone Z2 of the oblique stretching tenter, if the stretching temperature is differentiated in the width direction, the width direction thickness unevenness can be further improved. In addition, said draw ratio R is equal to a magnification (W2 / W1) when the interval W1 between both ends of the clip held at the tenter inlet portion becomes the interval W2 at the tenter outlet portion.

[Quality of long diagonally stretched film]
The average thickness of the obliquely stretched film obtained by the production method of the present embodiment is 10 to 200 μm, preferably 10 to 80 μm, and more preferably 15 to 60 μm from the viewpoint of mechanical strength and the like. Moreover, since the uneven thickness in the width direction of the obliquely stretched film affects whether or not the film can be wound, it is preferably less than 3 μm, and more preferably 2 μm or less.

[About the obliquely stretched film of this embodiment]
The obliquely stretched film of the present embodiment is an obliquely stretched film in which a slow axis is oriented in an oblique direction inclined with respect to both the width direction and the longitudinal direction perpendicular to each other in the film plane, and the width in the film plane is The angle at which the slow axis inclines with respect to the hand direction is the orientation angle (°), and a plurality of lines are arranged at intervals of 100 mm from one end side to the other end side in either the width direction or the longitudinal direction within the film plane. Among these points, the orientation angles of any two adjacent points are θ1 (°) and θ2 (°) from the one end side, and the orientation angle gradient P at the two points is expressed in units of ° / mm. When defined by the following formula (1):
P = (θ2−θ1) / 100 (1)
In the film plane, it has a local area of 100 mm square including two points where the gradient P of the orientation angle is 0.001 or more and 0.06 or less. FIG. 9 is an enlarged view of the local region TR that satisfies the above formula (1) in the obliquely stretched film F of the present embodiment. The obliquely stretched film F has at least one local region TR in the film plane in at least one of the width direction and the longitudinal direction.

  FIG. 10 is an exploded perspective view of a polarizing plate 100 ′ manufactured using an obliquely stretched film F ′ having an orientation angle gradient P of 0.0008 in the width direction and a polarizing film PL. The arrows in the figure indicate the direction of the slow axis of the obliquely stretched film F ′, that is, the orientation direction. The obliquely stretched film F ′ is bonded to the polarizing film PL so that the slow axis is approximately 45 ° with respect to the optical axis (transmission axis) of the polarizing film PL, thereby polarizing plate (circularly polarizing plate) 100 ′. Is configured.

  When a part of such a polarizing plate 100 ′ is punched out using an irregularly shaped cutting member 200 (cutter), if the orientation angle gradient P in the obliquely stretched film F ′ is small, the blade of the irregularly shaped cutting member 200 is used. The crossing angle of the blades with respect to the orientation direction also changes depending on the orientation of the film, and in the obliquely stretched film 100 ′, a portion that is cut at a shallow angle (with a small crossing angle) with respect to the orientation direction and a large portion with respect to the orientation direction The part cut | disconnected by an intersection angle arises. In these places, the stress applied to the obliquely stretched film F ′ varies depending on the contact with the cutting member 200.

  For example, in a portion that is cut at a small crossing angle with respect to the orientation direction, the obliquely stretched film F ′ is easily torn along the stretch direction (for example, 45 ° direction with respect to the width direction). Resistance becomes difficult to work, and stress at the time of cutting is concentrated and easily applied. On the other hand, in a portion that is cut at a large crossing angle with respect to the orientation direction, the obliquely stretched film F ′ is not easily torn along the stretch direction, and resistance to the cutting member 200 becomes easy to work. Is less likely to occur. Therefore, in the polarizing plate after being punched, cracks due to stress concentration are likely to occur at a location where the polarizing plate is cut at a small crossing angle with respect to the orientation direction, and the punching property is deteriorated (the punching property is poor).

  On the other hand, FIG. 11 is an exploded perspective view of a polarizing plate 100 manufactured using an obliquely stretched film F having an orientation angle gradient P in the width direction of 0.004 and a polarizing film PL. In addition, the arrow in the figure shows the direction of the slow axis of the diagonally stretched film F, ie, the orientation direction. The obliquely stretched film F is bonded to the polarizing film PL so that the slow axis is approximately 45 ° with respect to the optical axis (transmission axis) of the polarizing film PL, thereby forming the polarizing plate (circular polarizing plate) 100. Has been.

  When a part of such a polarizing plate 100 is punched out using the odd-shaped cutting member 200, since the orientation angle gradient P in the obliquely stretched film F is large, the irregular shape is formed at a large angle with respect to the orientation direction as much as possible. The blades of the cutting member 200 intersect (select the relative position of the cutting member 200 with respect to the obliquely stretched film F so that the number of places where the cutting member 200 intersects at a small angle with respect to the orientation direction). The obliquely stretched film F can be cut. As described above, since the obliquely stretched film F is not easily torn along the stretching direction at the location where it is cut at a large crossing angle with respect to the orientation direction, and resistance to the cutting member 200 is likely to work, Concentration is less likely to occur. As a result, it is possible to improve the punchability by reducing the occurrence of cracks due to stress concentration in the polarizing plate after punching.

  In other words, the obliquely stretched film F of the present embodiment has a local region TR in which the orientation angle gradient P is 0.001 or more and 0.06 or less and the orientation angle varies greatly. A portion of the polarizing plate 100 is punched out so as to hit the local region TR, and tearing and stress concentration along the orientation direction of the obliquely stretched film F can be reduced. Thereby, it can reduce that a crack generate | occur | produces in the polarizing plate after punching.

  Further, in the obliquely stretched film F having the local region TR in which the orientation angle gradient P exceeds 0.06, the residual stress is increased due to the oblique stretching (high magnification stretching) at the time of production. For this reason, when a durability test (for example, a heat shock test) is performed on the polarizing plate after punching including the obliquely stretched film F, the residual stress is relaxed, so that the obliquely stretched film 100 before the durability test is performed. The dimensional variation increases, and the dimensional variation easily causes cracks in the polarizing plate after the durability test.

  However, in the obliquely stretched film F of the present embodiment, the gradient P of the orientation angle in the local region TR is 0.06 or less, and the residual stress due to the oblique stretching is suppressed, so the obliquely stretched film F before and after the durability test. Dimensional variation due to stress relaxation can be suppressed. Thereby, generation | occurrence | production of the crack after the endurance test of the polarizing plate after punching containing the diagonally stretched film F can be reduced.

  In particular, the obliquely stretched film F desirably has a plurality of local regions TR in the width direction. Even when the blade of the irregularly shaped cutting member 200 hits a plurality of positions in the width direction of the obliquely stretched film F, the angle formed by the direction of the blade of the cutting member 200 and the orientation direction of the obliquely stretched film F is increased, A part of the obliquely stretched film F and the polarizing plate 100 can be punched out. Thereby, it is possible to reduce tearing and stress concentration along the alignment direction at a plurality of locations in the width direction of the obliquely stretched film F, and to reduce the occurrence of cracks in the polarizing plate after punching.

  Here, FIG. 12 shows an example of the distribution of orientation angles in each local region TR when a plurality of local regions TR are arranged in the width direction of the obliquely stretched film F. As shown in the figure, the obliquely stretched film F is a local region TR that satisfies the orientation angle gradient P defined by the equation (1) only in a part of the width direction (in the figure, the central portion in the width direction). (In the region other than the central portion in the width direction, the distribution may be an orientation angle distribution that does not satisfy Expression (1)).

  FIG. 13 is an exploded perspective view of a polarizing plate 100 produced using the obliquely stretched film F having the orientation film distribution shown in FIG. 12 and the polarizing film PL. In addition, the arrow in the figure shows the direction of the slow axis of the diagonally stretched film F, ie, the orientation direction. The obliquely stretched film F is bonded to the polarizing film PL so that the slow axis is approximately 45 ° with respect to the optical axis (transmission axis) of the polarizing film PL, thereby forming the polarizing plate (circular polarizing plate) 100. Has been.

  Thus, even if it is the structure which has local region TR only in a part of the width direction of diagonally stretched film F, in each local region TR, the direction of the blade of cutting member 200 and the orientation direction of diagonally stretched film F It becomes possible to punch the obliquely stretched film F and a part of the polarizing plate 100 by applying the blade of the cutting member 200 to the obliquely stretched film F so as to increase the angle formed by. Thereby, it is possible to reduce tearing and stress concentration along the alignment direction at a plurality of locations in the width direction of the obliquely stretched film F, and to reduce the occurrence of cracks in the polarizing plate after punching. Further, in the width direction of the obliquely stretched film F, the region other than the local region TR has a small variation in the orientation angle (gradient P), so that the obliquely stretched film F and thus the polarizing plate 100 can exhibit good optical characteristics. it can.

  From the same viewpoint as described above, the obliquely stretched film F of the present embodiment may have a plurality of the local regions TR described above in the longitudinal direction. Even when the blade of the irregularly shaped cutting member 200 hits a plurality of positions in the longitudinal direction of the obliquely stretched film F, the angle formed by the direction of the blade of the cutting member 200 and the orientation direction of the obliquely stretched film F is increased, A part of the stretched film F and the polarizing plate 100 can be punched out. Thereby, it is possible to reduce tearing and stress concentration along the alignment direction at a plurality of locations in the longitudinal direction of the obliquely stretched film F, and reduce the occurrence of cracks in the polarizing plate after punching.

  Moreover, the structure which has the local area | region TR only in a part of longitudinal direction may be sufficient as the diagonally stretched film F of this embodiment. Even in this configuration, the blade of the cutting member 200 is applied to the obliquely stretched film F so that the angle formed by the direction of the blade of the cutting member 200 and the orientation direction of the obliquely stretched film F increases in each local region TR. Thus, a part of the obliquely stretched film F and the polarizing plate 100 can be punched out. Thereby, it is possible to reduce tearing and stress concentration along the alignment direction at a plurality of locations in the longitudinal direction of the obliquely stretched film F, and reduce the occurrence of cracks in the polarizing plate after punching. Further, in the longitudinal direction of the obliquely stretched film F, the region other than the local region TR has small variation in the orientation angle (gradient P), and therefore, the optical properties of the obliquely stretched film F and the polarizing plate 100 can be exhibited. .

  In the present embodiment, it is desirable that the orientation angle gradient P in the local region TR is 0.003 or more and 0.04 or less. When the orientation angle gradient P is 0.003 or more, the oblique stretched film F is cut so that the angle formed by the direction of the blade of the cutting member 200 and the orientation direction of the obliquely stretched film is increased in the local region TR. Easy to do. This reliably reduces the tearing and stress concentration along the orientation direction of the obliquely stretched film F when punching a part of the polarizing plate 100, and reliably reduces the occurrence of cracks when punching the polarizing plate. can do. In addition, since the orientation angle gradient P is 0.04 or less, the stress remaining on the film due to the oblique stretching is surely kept small, so that the dimensional variation of the obliquely stretched film F before and after the durability test is reliably restrained. It is possible to reliably reduce the occurrence of cracks in the polarizing plate after the durability test.

  FIG. 14 is an explanatory view schematically showing another example of the distribution of orientation angles of the obliquely stretched film F of the present embodiment. The obliquely stretched film F has an inflection point at which the gradient P of the orientation angle defined by the formula (1) changes from increasing to decreasing or decreasing to increasing in at least one of the width direction and the longitudinal direction in the film plane. It is desirable to have M. In this case, when the polarizing plate produced using the obliquely stretched film F is punched on both sides of the inflection point M in the film plane, the distribution of the orientation angles on both sides of the inflection point M (two orientation angles) By the gradient P), the effect of supporting the film against the cutting member can be increased (compared to the case where there is no inflection point M). This can further reduce the occurrence of cracks when the polarizing plate is punched.

  Further, the obliquely stretched film F of the present embodiment may be configured to include any of polycarbonate resin, acrylic resin, and cycloolefin resin. These resins are mechanically fragile, and when the obliquely stretched film F is applied to the polarizing plate 100, cracks are likely to occur at the time of punching. Therefore, the configuration of this embodiment described above is very effective.

  As shown in FIG. 7 and FIG. 8, the manufacturing method of the obliquely stretched film F of the present embodiment is the lateral and longitudinal directions in the film plane in the stretching zone Z2 of the oblique stretching machine (stretching portion 84). The width is kept constant in the oblique stretching step of obtaining the obliquely stretched film F and the heat setting zone Z3 of the obliquely stretching machine by stretching the long film in the direction inclined with respect to both directions (oblique direction). And a heat setting step of conveying the obliquely stretched film. In the present embodiment, the temperature of the heat setting zone Z3 is lower than the temperature of the stretching zone Z2.

  In the oblique stretching process, when the long film is stretched in an oblique direction, for example, because the movement trajectory of the gripping part (clip) that grips both ends of the long film differs between the one end side and the other end side in the width direction. In the obtained obliquely stretched film F, there is a difference in residual stress between the one end side and the other end side in the width direction. Yes. Generally, in order to relieve the residual stress of the obliquely stretched film, the temperature of the heat setting zone is set to be equal to the temperature of the stretch zone. However, as in this embodiment, since the temperature of the heat setting zone Z3 is lower than the temperature of the drawing zone Z2, the residual stress generated by the oblique drawing in the drawing zone Z2 is completely relaxed in the heat setting zone Z3. Therefore, the orientation angle is likely to change in the width direction due to the difference in residual stress between the one end side and the other end side in the width direction. As a result, it becomes possible to manufacture the obliquely stretched film F in which the local region TR having the above-described orientation angle gradient P exists.

  Here, in the oblique stretching step, a part of the obliquely stretched film F in the width direction may be cooled. By locally cooling a part of the obliquely stretched film F in the width direction, in the subsequent heat setting step, the relaxation of the residual stress can be intentionally and nonuniformly advanced in the width direction. This makes it possible to manufacture an obliquely stretched film having an inflection point M at which the orientation angle gradient P decreases or increases or decreases. In addition, as a cooling means, the air injection apparatus which injects air with respect to a diagonally stretched film can be used, for example. In addition, said air should just be temperature lower than temperature T2 of extending | stretching zone Z2, for example, the wind of about room temperature (for example, 25 degreeC) may be sufficient.

  In the oblique stretching step, the obliquely stretched film F may be intermittently cooled in the longitudinal direction. By such intermittent cooling in the longitudinal direction, the residual stress can be intentionally and nonuniformly advanced in the longitudinal direction in the subsequent heat setting step. As a result, an obliquely stretched film F having a plurality of local regions TR in the longitudinal direction can be produced, and an obliquely stretched film F having an inflection point M at which the orientation angle gradient P decreases or increases or decreases is increased. It becomes possible to do. In addition, intermittent cooling in the longitudinal direction can be performed using an air injection device similar to the above. For example, the obliquely stretched film F can be intermittently cooled in the longitudinal direction by intermittently ejecting air with an air jet device while transporting the obliquely stretched film F in the longitudinal direction.

  In addition, the cooling in the width direction or the longitudinal direction of the obliquely stretched film F may be performed in the heat setting step, or may be performed in both the oblique stretching step and the heat setting step.

〔Example〕
Hereinafter, specific examples of the obliquely stretched film in the present embodiment will be described with reference to comparative examples. The present invention is not limited to the following examples.

(Preparation of long film 1)
A polycarbonate-based resin film (PC film) as the long film 1 was produced by the following production method (melt casting film formation method).

Polymerization was carried out using a batch polymerization apparatus comprising two vertical reactors equipped with a stirring blade 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 / ISB / DEG / DPC / magnesium acetate = 0.348 / 0.490 / 0.162 / 1.005 / 1.00 × 10 ⁻⁵ . After sufficiently replacing the inside of the reactor with nitrogen (oxygen concentration 0.0005 to 0.001 vol%), heating was performed with a heating medium, and stirring was started when the internal temperature reached 100 ° C. After 40 minutes from the start of temperature increase, the internal temperature was reached to 220 ° C., and control was performed so as to maintain this temperature. The phenol vapor produced as a by-product with the polymerization reaction was led to a reflux condenser at 100 ° C., a monomer component contained in a slight amount in the phenol vapor was returned to the reactor, and the non-condensed phenol vapor was led to a 45 ° C. condenser and recovered.

  Nitrogen was introduced into the first reactor and the pressure was once restored to atmospheric pressure, and then the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Subsequently, the temperature increase 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 obtained. When a predetermined power is reached, nitrogen is introduced into the reactor and the pressure is restored. The reaction solution is extracted in the form of a strand, pelletized with a rotary cutter, and BHEPF / ISB / DEG = 34.8 / 49.0 / A polycarbonate resin A having a copolymer composition of 16.2 [mol%] was obtained. This polycarbonate resin A had a reduced viscosity of 0.430 dL / g and a glass transition temperature of 138 ° C.

  The obtained polycarbonate resin A was vacuum-dried at 80 ° C. for 5 hours, and then a single-screw extruder (manufactured by Isuzu Chemical Industries, screw diameter 25 mm, cylinder set temperature: 220 ° C.), T die (width 900 mm, set temperature) : 220 ° C.), a film-forming apparatus equipped with a chill roll (set temperature: 120 to 130 ° C.) and a winder, and a polycarbonate resin film having a thickness of 130 μm was prepared as the long film 1.

(Preparation of long film 2)
An alicyclic olefin polymer resin film (COP film) as the long film 2 was produced by the following production method.

<< Manufacture of cycloolefin resin pellets >>
In a nitrogen atmosphere, 500 parts by mass of dehydrated cyclohexane, 1.2 parts by mass of 1-hexene, 0.15 parts by mass of dibutyl ether and 0.30 parts by mass of triisobutylaluminum were mixed in a reactor at room temperature, and then mixed at 45 ° C. 13 parts by mass of tricyclo [4.3.12,5] deca-3,7-diene (dicyclopentadiene, hereinafter abbreviated as DCP), 8-methyl-8-methoxycarbonyltetracyclo [4 4.0.12, 5.17,10] Dodec-3-ene (hereinafter abbreviated as MMT) 87 parts by mass of norbornene monomer mixture and tungsten hexachloride (0.7% toluene solution) 40 parts by mass Were continuously added over 2 hours for polymerization. To the polymerization solution, 1.06 parts by mass of butyl glycidyl ether and 0.52 parts by mass of isopropyl alcohol were added to deactivate the polymerization catalyst and stop 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 further 5 parts by mass of a nickel-alumina catalyst (manufactured by JGC Catalysts & Chemicals) as a hydrogenation catalyst. In addition, the pressure was increased to 5 MPa with hydrogen and the mixture was heated to 200 ° C. with stirring and then reacted for 4 hours to obtain a reaction solution containing 20% of a DCP / MMT ring-opening polymer hydrogenated polymer.

  After removing the hydrogenation catalyst by filtration, a soft polymer (manufactured by Kuraray Co., Ltd .; Septon 2002) and an antioxidant (manufactured by Ciba Specialty Chemicals Co., Ltd .; Irganox 1010) were added to the resulting solutions, respectively. And dissolved (both 0.1 parts by mass per 100 parts by mass of the polymer). Next, cyclohexane and other volatile components, which are solvents, are removed from the solution using a cylindrical concentration dryer (manufactured by Hitachi, Ltd.), and the hydrogenated polymer is extruded in a strand form from an extruder in a molten state. After cooling, it was pelletized and collected. When the copolymerization ratio of each norbornene monomer in the polymer was calculated from the composition of residual norbornenes in the solution after polymerization (by gas chromatography method), DCP / MMT / = 13/87 almost equal to the charged composition. It was. The hydrogenated product of this ring-opening polymer had a weight average molecular weight (Mw) of 89000, a molecular weight distribution (Mw / Mn) of 2.5, a hydrogenation rate of 99.9%, and a Tg of 161 ° C.

  The resulting cycloolefin-based resin pellet of the ring-opened polymer hydrogenated product was dried at 70 ° C. for 2 hours using a hot air dryer in which air was circulated to remove moisture.

<< Manufacture of fine particles 1 >>
The polymer particle aggregate produced in the following production example was produced as fine particles 1.

<Manufacture of seed particles>
A polymerization vessel equipped with a stirrer and a thermometer was charged with 1000 g of deionized water, charged with 200 g of methyl methacrylate and 6 g of t-dodecyl mercaptan, and heated to 70 ° C. while purging with nitrogen under stirring. The internal temperature was kept at 70 ° C., 20 g of deionized water in which 1 g of potassium persulfate was dissolved was added as a polymerization initiator, and then polymerization was performed for 10 hours. The average particle size of the polymer particles in the obtained emulsion was 0.44 μm.

<Manufacture of polymer particles>
A polymerization vessel equipped with a stirrer and a thermometer was charged with 800 g of deionized water in which 3 g of polyoxyethylene tridecyl ether ammonium sulfate was dissolved, and 144 g of methyl acrylate, 22 g of styrene and 34 g of ethylene glycol dimethacrylate as a monomer mixture. Then, a mixed solution with 1 g of azobisisobutyronitrile was added as a polymerization initiator. Then, the mixed solution was T.P. The mixture was stirred with a K homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to obtain a dispersion.

  Further, 60 g of the above emulsion containing seed particles was added to the dispersion, and the mixture was stirred at 30 ° C. for 1 hour to allow the seed particles to absorb the monomer mixture. Next, the absorbed monomer mixture was polymerized by heating at 50 ° C. for 5 hours under a nitrogen stream, and then cooled to room temperature (about 25 ° C.) to obtain a slurry containing polymer particles. The average particle diameter of the obtained polymer particles (organic fine particles) was 0.3 μm.

<Manufacture of polymer particle aggregate>
After cooling, 50 g of Snowtex O-40 (manufactured by Nissan Chemical Industries, Ltd .: 40% solid content as colloidal silica (inorganic powder), particle size: 0.02-0.03 μm) was added to the resulting slurry. The mixture was stirred for 10 minutes with a K homomixer (manufactured by Tokushu Kika Kogyo Co.). This slurry was spray-dried under the following conditions with a spray dryer (model: atomizer take-up system, model number: TRS-3WK) manufactured by Sakamoto Giken Co., Ltd. as a spray dryer to obtain polymer particle aggregates. The average particle diameter of the polymer particle aggregate was 30 μm.
Supply speed: 25 ml / min
Atomizer speed: 11000 rpm
Air volume: 2m ³ / min
Slurry inlet temperature of spray dryer: 130 ° C
Polymer particle assembly outlet temperature: 70 ° C.

<< Preparation of fine particle dispersion 1 >>
1.0 part by mass of fine particles 1 and 100 parts by mass of methylene chloride were stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin to obtain a fine particle dispersion 1.

<< Preparation of dope >>
Next, a main dope 1 having the following composition was prepared. First, methylene chloride, ethanol and toluene were added to the pressure dissolution tank. Next, the cycloolefin-based resin pellets prepared above and the additive (LA-F70) were added to the pressurized dissolution tank while stirring. Next, the fine particle dispersion 1 prepared above was added, and this was heated to 60 ° C. and completely dissolved while stirring. The heating temperature was raised from room temperature at 5 ° C./min, dissolved in 30 minutes, and then lowered at 3 ° C./min.

The viscosity of the obtained solution was 7000 cp, and the water content was 0.50%. This was filtered using SHP150 manufactured by Loki Techno Co., Ltd. at a filtration flow rate of 300 L / m ² · h and a filtration pressure of 1.0 × 10 ⁶ Pa to obtain a main dope 1.

<Composition of main dope 1>
Cycloolefin-based resin pellets 100 parts by mass Methylene chloride 270 parts by mass Ethanol 20 parts by mass Additive (ADK STAB LA-F70 (made by ADEKA Corporation)) 3 parts by mass Fine particle dispersion 1 30 parts by mass

《Filming》
Then, using an endless belt casting apparatus, the main dope 1 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 conveyance speed of the stainless steel belt was 20 m / min.

  On the stainless steel belt support, the solvent was evaporated until the amount of residual solvent in the cast film was 30%. Subsequently, it peeled from the stainless steel belt support body with the peeling tension of 128 N / m. While the peeled film was transported by many rollers, it was stretched 1.2 times in the transport direction at 120 ° C. The residual solvent at the start of stretching was 10% by mass. Next, the film-like material was stretched 1.1 times in the width direction using a tenter under conditions of 150 ° C. Then, the edge part pinched with the tenter clip was slit with a laser cutter, and then wound up to obtain a long film 2 having a film thickness of 60 μm.

(Preparation of long film 3)
An MS resin film made of a methyl (meth) acrylate-styrene copolymer as the long film 3 was produced by the following production method.

  A film forming apparatus for coextrusion molding of three types and three layers (type of forming a film composed of three layers with three types of resins) was prepared.

  Next, pellets of acrylic resin (“Optimas 6000” manufactured by Mitsubishi Gas Chemical Co., Ltd., glass transition temperature 127 ° C.) were put into a first single-screw extruder equipped with a double flight type screw and melted. This acrylic resin corresponds to the resin A.

  Subsequently, pellets of styrene-maleic anhydride copolymer resin (Denka “Regisphi R100”, glass transition temperature 129 ° C.) were put into a second single-screw extruder equipped with a double-flight screw, Melted. This styrene-maleic anhydride copolymer resin corresponds to the resin B.

  The molten resin A at 260 ° C. was supplied to the first manifold of a multi-manifold die (die slip surface roughness Ra = 0.1 μm) through a pleated polymer filter having an opening of 5 μm. In addition, the melted resin B at 260 ° C. was supplied to the second manifold through a leaf disk-shaped polymer filter having an opening of 5 μm. Further, the melted resin A at 260 ° C. was supplied to the third manifold through a pleated polymer filter having an opening of 5 μm. The resin A supplied to the third manifold is also referred to as resin C.

  Resin A, Resin B, and Resin C are simultaneously extruded from the multi-manifold die at 260 ° C., and the resin layer a containing the resin A and the resin containing the resin B provided on one surface of the resin layer a The layer b and the resin layer b were provided on the surface of the resin layer b opposite to the resin layer a, and formed into a film having a three-layer structure including the resin layer a containing the resin A (= resin C). The molten resin coextruded into a film in this way is cast on a cooling roll adjusted to a surface temperature of 120 ° C., and then passed between two cooling rolls adjusted to a surface temperature of 115 ° C. A three-layer film before stretching having a resin layer b and a resin layer a in this order was obtained as a laminate before stretching (coextrusion step). The resulting unstretched film had a width of 1500 mm and a thickness of 120 μm. Moreover, the thickness of each layer of the film before stretching was resin layer a / resin layer b / resin layer a = 15 μm / 90 μm / 15 μm in the vicinity of the width center.

<Example 1>
(Preparation of diagonally stretched film 1)
The roll body (film roll) of the long film 1 produced above was set in an obliquely stretched film manufacturing apparatus 80 (see FIGS. 7 and 8), and the long film 1 was fed out. And this elongate film 1 is passed through the preheating zone Z1 of a extending part, the elongate film 1 is heated to preheating temperature, Then, it passes along the extending | stretching zone Z2, and is diagonally stretched by 3 times of draw ratio, and then, Then, an obliquely stretched film 1 having a film thickness of 50 μm, a width of 1500 mm, and an orientation angle θ = 45 ° (value at the width center) was produced by passing through the heat setting zone Z3. The produced diagonally stretched film 1 was wound up into a film roll. Note that the temperature T1 (preheating temperature) of the preheating zone Z1 in the stretching portion is (Tg + 15) ° C., the temperature T2 (stretching temperature) of the stretching zone Z2 is (Tg + 11) ° C., and the temperature T3 of the heat setting zone Z3 is , (Tg + 9) ° C.

<Example 2>
(Preparation of diagonally stretched film 2)
A diagonally stretched film 2 was produced in the same manner as in Example 1 except that the temperature T3 of the heat setting zone Z3 was changed to (Tg + 6) ° C.

<Example 3>
(Preparation of obliquely stretched film 3)
In the stretching zone Z2, the position at a distance of 200 mm from the end of the front side in the width direction of the obliquely stretched film (the side on which the gripping tool Ci travels first) is set to (Tg + 6) ° C. by air injection from the air injection device. Cooled down. Other than that was carried out similarly to Example 1, and produced the diagonally stretched film 3. FIG. The local temperature (cooling temperature) of the film in the width direction of the stretching zone Z2 was measured with a temperature sensor (Rayomatic 14-814-10HT manufactured by Eurotron). In Example 3, since the temperature T2 of the stretching zone Z2 itself is the same (Tg + 11) ° C. as in Example 1, the temperature difference in the width direction in the stretching zone Z2 is (Tg + 11) − (Tg + 6) = 5 ° C.

<Example 4>
(Preparation of obliquely stretched film 4)
In the stretching zone Z2, the position at a distance of 200 mm from the end of the front side in the width direction of the obliquely stretched film (the side on which the gripping tool Ci travels first) is set to (Tg + 4) ° C. by air injection from the air injection device. Cooled down. Other than that was carried out similarly to Example 1, and produced the diagonally stretched film 3. FIG. In Example 4, the temperature difference in the width direction in the $ stretch zone Z2 was (Tg + 11) − (Tg + 4) = 7 ° C.

<Example 5>
(Preparation of obliquely stretched film 5)
An obliquely stretched film 5 was produced in the same manner as in Example 2, except that the long film 1 was replaced with the long film 3 (MS resin film) and obliquely stretched.

<Example 6>
(Preparation of obliquely stretched film 6)
An obliquely stretched film 6 was produced in the same manner as in Example 2, except that the long film 1 was replaced with the long film 2 (COP film) and obliquely stretched.

<Comparative Example 1>
(Preparation of obliquely stretched film 7)
In the production of the obliquely stretched film 1 described above, the obliquely stretched film 7 is produced in the same manner as in Example 1 except that the temperature T3 of the heat setting zone Z3 is the same (Tg + 11) ° C. as the temperature T2 of the stretched zone Z2. did.

<Comparative example 2>
(Preparation of diagonally stretched film 8)
The stretching ratio in the stretching zone Z2 is set to 3 times, and in the stretching zone Z2, the position at a distance of 200 mm from the end on the leading side in the width direction of the obliquely stretched film (the side on which the gripping tool Ci runs first) is It was cooled to (Tg + 2) ° C. by air injection from an injection device. Other than that was carried out similarly to Example 1, and produced the diagonally stretched film 8. FIG. In Comparative Example 2, the temperature difference in the width direction in the stretching zone Z2 was (Tg + 11) − (Tg + 2) = 9 ° C.

<Measurement of orientation angle gradient P and presence of inflection points>
Using a phase difference measuring device (manufactured by Oji Scientific Co., Ltd., KOBRA-WX200), in the width direction of each of the obliquely stretched films 1 to 8 produced above, the orientation angle θ (°) at each point arranged at intervals of 100 mm It was measured. For all combinations of two adjacent points, the orientation angle at one point is θ1 (°), the orientation angle at the other point is θ2 (°), and the orientation angle is calculated based on the following formula (1). The slope P was determined.
P = (θ2−θ1) / 100 (1)

  Next, in the film plane of each of the obliquely stretched films 1 to 8, the gradient P of the obtained orientation angle changes from increasing to decreasing or decreasing to increasing as it goes from one end side to the other end side in the width direction. The presence or absence of music points was examined. As a result, in the stretched zone Z2, the inflection points are present in the obliquely stretched films 3, 4, and 8 of Examples 3 and 4 and Comparative Example 2 in which a part of the width direction is locally cooled by an air jet device. Was confirmed. At this time, it was found that the position of the inflection point in the width direction corresponds to the position of the air injection device in the width direction. Further, in the obliquely stretched films 3, 4, and 8, the orientation angle gradient P is 0.001 or more and 0.00 in part of the width direction in the film plane (on both sides of the width direction with respect to the inflection point). It was confirmed that there was a 100 mm square area (local area) of 06 or less, that is, a plurality of the local areas existed in the width direction.

<Evaluation of crack>
(Production of polarizer)
A long polyvinyl alcohol film having a polymerization degree of 2400, a saponification degree of 99.9 mol%, a thickness of 60 μm, and a width of 3300 mm (trade name “Kuraray Vinylon PE3000” manufactured by Kuraray Co., Ltd.) is used as a raw film, and is as follows. To make a polarizing film. Stretching was performed with a difference in peripheral speed between the driving nip rolls before and after the treatment tank.

  First, the film was sufficiently swollen by immersing in a swelling tank containing pure water at 37 ° C. for 80 seconds while keeping the tension in the machine direction (flow direction) so that the original film did not sag. The roll speed ratio between the inlet and outlet of the swelling tank accompanying the swelling was 1.2. After draining with a nip roll provided at the outlet of the swelling tank, it was immersed in a water immersion tank containing 30 ° C. pure water for 160 seconds. The draw ratio in the machine direction of the film in the water immersion tank was 1.04.

  Next, the film was immersed in a dyeing tank containing an aqueous solution of iodine / potassium iodide / water at a weight ratio of 0.04 / 1.5 / 100, and uniaxially stretched at a stretch ratio of about 1.6 times. . Thereafter, the first boric acid was immersed in a first boric acid bath containing an aqueous solution of 12 / 3.6 / 100 by weight of potassium iodide / boric acid / water at a temperature of 56.5 ° C. for 130 seconds. While being processed, uniaxial stretching was performed until the cumulative stretch ratio from the original fabric reached 5.3 times. Further, a second boric acid treatment is performed by immersing in a second boric acid bath containing an aqueous solution of potassium iodide / boric acid / water at a weight ratio of 12 / 1.5 / 100 at a temperature of 30 ° C. for 60 seconds. It was. Subsequently, after immersing in a washing tank containing 10 ° C. pure water for about 16 seconds and then washing, it is sequentially passed through a drying oven at about 60 ° C. and a drying oven at about 85 ° C., and the total residence time in these drying ovens is totaled. Drying was performed for 160 seconds. Thus, a 12 μm-thick polarizer (polarizing film) on which iodine was adsorbed and oriented was obtained.

(Preparation of polarizing plate)
Corona treatment was performed on one side of each of the obliquely stretched films prepared in Examples and Comparative Examples. As another optical film, Konica Minoltak KC2UA (produced by Konica Minolta Opto Co., Ltd.) subjected to alkali saponification treatment was prepared.

  The obliquely stretched film, KC2UA, and the polarizer were bonded so that the corona-treated surface of the obliquely stretched film and the alkali-saponified surface of KC2UA were in contact with the polarizer. At this time, a 3% by mass aqueous solution of polyvinyl alcohol (Kuraray PVA-117H) was used as an adhesive. In addition, when pasting, the obliquely stretched film of the example or the comparative example is such that the absorption axis of the polarizer and the slow axis are parallel, and the other optical film on the opposite side is the absorption of the polarizer. Bonding was performed so that the axis and the slow axis were orthogonal. The laminated film was dried with warm air at 60 ° C. for 5 minutes to obtain a polarizing plate.

(Preparation of polarizing plate with adhesive)
A commercially available thermosetting acrylic pressure-sensitive adhesive sheet formed on the release film with a thickness of 25 μm was used. The storage elastic modulus of this pressure-sensitive adhesive at 80 ° C. was 0.42 Mpa. This pressure-sensitive adhesive sheet was attached to the optical film side of the polarizing plate to obtain a polarizing plate with a pressure-sensitive adhesive.

(Punchability evaluation)
A part of the pressure-sensitive adhesive polarizing plate produced above was punched into the shape of the in-vehicle display panel shown in FIG. In FIG. 3, the downwardly concave curve located at the top of the figure of the polarizing plate is a shape along the outer periphery of a perfect circle having a radius of 60 mm that is assumed to be in contact with two adjacent circles inside the figure. Next, the release film was peeled off from the deformed polarizing plate, and the pressure-sensitive adhesive side was bonded to a glass substrate for a liquid crystal cell manufactured by Corning. Ten such samples were prepared for each polarizing plate. In this state, first, it was visually confirmed whether or not a break (crack) occurred in the polarizer, and the number of samples with cracks was counted. And based on the following evaluation criteria, the shape punching property was evaluated from the number of polarizing plates with cracks.
"Evaluation criteria"
A: The number of cracks was 0.
A: The number of cracks was one.
○: The number of cracks was two.
Δ: The number of cracks was 3-5.
X: The number of cracks was 6 or more.

(Durability evaluation after punching)
Next, each sample produced above was subjected to a heat shock test (durability test). Specifically, each sample was subjected to 1000 cycles of a heat cycle test in which the step of maintaining at −40 ° C. for 30 minutes and the step of maintaining at a temperature of 85 ° C. for 30 minutes were one cycle. After the test, it was visually confirmed whether or not the polarizer was broken, and the number of samples with cracks was counted. And based on the following evaluation criteria, durability was evaluated from the number of polarizing plates with cracks.
"Evaluation criteria"
A: (number of cracks after endurance test−number of cracks before endurance test) was 0.
O: (Number of cracks after endurance test-Number of cracks before endurance test) was 1-2.
Δ: (number of cracks after endurance test−number of cracks before endurance test) was 3-5.
X: (Number of cracks after endurance test-Number of cracks before endurance test) was 6 or more.

  Table 1 shows the stretching conditions and the results of evaluation for each of the obliquely stretched films 1 to 8 produced above. In addition, in Table 1, only the largest gradient is shown among the gradient P of the some orientation angle measured about each diagonally stretched film 1-8 for convenience.

  From Table 1, in Comparative Example 1 (obliquely stretched film 7), the punchability is poor (many cracks are generated in the punched polarizing plate). This is presumed to be due to the following reason. Since the maximum inclination angle P of the orientation angle is very small as 0.0005 and the variation in the orientation angle is small in the width direction, when the obliquely stretched film is cut with the irregularly shaped cutting member, the shallow angle with respect to the orientation direction In this case, a portion cut at a small crossing angle and a portion cut at a large crossing angle with respect to the alignment direction are generated. Since the obliquely stretched film is easily torn along the stretching direction at a location where it is cut at a small crossing angle with respect to the orientation direction, resistance to the cutting member is difficult to work, and stress at the time of cutting is concentrated. For this reason, it becomes easy to generate | occur | produce the crack by stress concentration, and punching property falls.

  Moreover, in the comparative example 2 (diagonally stretched film 8), the durability after punching is poor. In Comparative Example 2, the maximum gradient P of the orientation angle is as large as 0.1, and the variation in the orientation angle in the width direction is large, so that the punchability is good. However, when the oblique stretching is performed so that the orientation angle gradient P becomes 0.1, the residual stress during the oblique stretching increases, and the temperature T2 in the stretching zone Z2 and the temperature T3 in the heat setting zone Z3. Since the difference is as large as 9 ° C., the residual stress during oblique stretching in the stretching zone Z2 cannot be alleviated in the heat fixing zone Z3. Therefore, it is considered that after the endurance test, the dimensional variation due to the residual stress was greatly generated, and as a result, cracks due to the dimensional variation of the obliquely stretched film occurred.

  In contrast, in Examples 1 to 6 (obliquely stretched films 1 to 6), the maximum gradient P of the orientation angle is 0.001 or more and 0.06 or less. Since the variation in the orientation angle in the obliquely stretched film is large (because the orientation angle gradient P is large), the irregularly shaped cutting member is formed so that the number of places where the cutting member intersects at a small angle with respect to the orientation direction is as small as possible. It becomes possible to arrange and cut the obliquely stretched film. As a result, the obliquely stretched film is less likely to be torn along the stretching direction, and resistance to the cutting member is facilitated in the obliquely stretched film and stress concentration at the time of cutting is less likely to occur. It is thought that the generation of cracks due to concentration can be reduced.

  In particular, in Examples 2, 3, and 6 (obliquely stretched films 2, 3, and 6), both punchability and durability are good. The maximum inclination P of the orientation angle is 0.003 or more, and the variation in the orientation angle is larger than that of the first embodiment, so that the punching that makes the angle between the blade of the cutting member and the orientation direction larger is reliably realized. can do. Thereby, it is considered that tearing and stress concentration along the orientation direction of the obliquely stretched film during punching can be reliably reduced, and as a result, the occurrence of cracks can be reliably reduced. In addition, since the maximum gradient P of the orientation angle is 0.04 or less, the residual stress of the film due to the oblique stretching can be reliably suppressed, and the dimensional variation of the obliquely stretched film due to the durability test can be reliably suppressed. It is considered that the occurrence of cracks after the durability test can be reliably reduced.

  Further, from the comparison between Examples 2 and 3, the punchability is improved when the inflection point about the orientation angle gradient P is present in the width direction of the obliquely stretched film. By punching the polarizing plate so that the inflection point is sandwiched from both sides within the film surface, the effect of supporting the film against the cutting member by the distribution of the orientation angles on both sides of the inflection point (gradient of two orientation angles) It is considered that the cracks are less likely to occur at the time of punching.

  Further, from Examples 1 to 6, even when any of polycarbonate resin (PC), acrylic resin (for example, MS resin), and cycloolefin resin (COP) is used as the resin constituting the obliquely stretched film, the orientation angle is used. It can be said that a polarizing plate having good punchability and durability can be realized by the existence of a region where the gradient P of the film is 0.001 or more and 0.06 or less.

  In general, in the obliquely stretched film, the temperature T3 in the heat setting zone Z3 is set to be equal to the temperature T2 in the stretch zone Z2 in order to relax the residual stress due to the oblique stretching. However, as in Examples 1 to 6, when the temperature T3 of the heat setting zone Z3 is lower than the temperature T2 of the drawing zone Z2, the residual stress generated by the oblique drawing in the drawing zone Z2 is caused by the above-described residual stress. Therefore, the orientation angle tends to change in the width direction due to the difference in the residual stress in the width direction caused by the oblique stretching. As a result, it becomes possible to manufacture an obliquely stretched film having a region where the orientation angle gradient P is 0.001 or more and 0.06 or less.

  Further, as in Examples 3 and 4, in the stretching zone Z2, by cooling a part of the obliquely stretched film in the width direction, the relaxation of the residual stress becomes nonuniform in the width direction. This makes it possible to produce an obliquely stretched film having the above-mentioned inflection point, and contribute to the improvement of punchability when producing an irregularly shaped polarizing plate.

<Example 7>
(Preparation of obliquely stretched film 9)
In the stretching zone Z2, an obliquely stretched film 9 was produced in the same manner as in Example 4 except that the air injection device was intermittently driven to intermittently cool the film in the longitudinal direction. In addition, intermittent cooling in the longitudinal direction was performed by setting the drive time of the air injection device to 5 seconds and the stop time to 5 seconds. Moreover, the conveyance speed of the diagonally stretched film 9 at this time was 8 mm / sec.

  A polarizing plate was produced by the same method as above using the obliquely stretched film 9 of Example 7, and the punchability and durability were evaluated based on the same evaluation criteria as described above.

  Table 2 shows the stretching conditions and the evaluation results for each of the obliquely stretched films 9 produced above.

  In Example 7, the punchability is further improved as compared to Example 4 (the occurrence of cracks during punching is reduced). Due to intermittent cooling in the longitudinal direction, the residual stress is not uniformly relaxed in the longitudinal direction, so that an obliquely stretched film having an inflection point in the longitudinal direction can be produced. Thereby, it becomes possible to arrange the irregularly shaped cutting member so as to further reduce the stress concentration and cut the obliquely stretched film, and as a result, it is considered that the occurrence of cracks is further reduced.

  The obliquely stretched film of the present invention can be used for an irregularly shaped polarizing plate and an irregularly shaped display device.

1 Atypical display device 1a Liquid crystal display device (Atypical display device)
1b Organic EL display device (Atypical display device)
2 Liquid crystal cell (display cell)
3 Polarizing plate 11 Polarizer (polarizing film)
12 Protective film (obliquely stretched film)
30 Organic EL elements (display cells)
50 Polarizing plate 51 λ / 4 retardation film (obliquely stretched film)
53 Polarizer (polarizing film)
F Obliquely stretched film M Inflection point PL Polarized film TR Local area

Claims (13)

An obliquely stretched film in which a slow axis is oriented in an oblique direction inclined with respect to both the width direction and the longitudinal direction perpendicular to each other in the film plane,
An angle at which the slow axis is inclined with respect to the width direction in the film plane is defined as an orientation angle (°), and from one end side in any one of the width direction and the longitudinal direction in the film plane. Among a plurality of points arranged at 100 mm intervals toward the other end side, the orientation angles of two arbitrary adjacent points are θ1 (°) and θ2 (°) from the one end side, and the gradient of the orientation angle at the two points When P is defined by the following formula (1), where the unit is ° / mm,
P = (θ2−θ1) / 100 (1)
An obliquely stretched film having a local region of 100 mm square including two points where the gradient P of the orientation angle is 0.001 or more and 0.06 or less in the film plane.   The diagonally stretched film according to claim 1, wherein a plurality of the local regions are provided in the width direction.   The diagonally stretched film according to claim 1, wherein the local region is provided only in a part of the width direction.   The diagonally stretched film according to claim 1, wherein a plurality of the local regions are provided in the longitudinal direction.   The obliquely stretched film according to any one of claims 1 to 4, wherein the local region has only a part in the longitudinal direction.   6. The obliquely stretched film according to claim 1, wherein the orientation angle gradient P in the local region is 0.003 or more and 0.04 or less.   In at least one of the width direction and the longitudinal direction in the film plane, an inflection point at which the gradient P of the orientation angle defined by the formula (1) changes from increasing to decreasing or decreasing to increasing. The obliquely stretched film according to claim 1, wherein the obliquely stretched film is provided.   The obliquely stretched film according to any one of claims 1 to 7, comprising any one of a polycarbonate resin, an acrylic resin, and a cycloolefin resin.   A polarizing plate comprising the obliquely stretched film according to any one of claims 1 to 8 and a polarizing film to which the obliquely stretched film is bonded, and having a curved portion in its outer shape.   An odd-shaped display device comprising the polarizing plate according to claim 9 and a display cell to which the polarizing plate is bonded, and having an outer shape identical to that of the polarizing plate. It is a manufacturing method of the diagonally stretched film which manufactures the diagonally stretched film in any one of Claim 1 to 8, Comprising:
An oblique stretching step of obtaining the obliquely stretched film by stretching a long film in a direction inclined with respect to both the width direction and the longitudinal direction within the film plane in a stretching zone of an oblique stretching machine. When,
In the heat setting zone of the oblique stretching machine, including a heat setting step of conveying the obliquely stretched film while maintaining a constant width,
The method for producing an obliquely stretched film, wherein the temperature of the heat setting zone is lower than the temperature of the stretch zone.   The method for producing an obliquely stretched film according to claim 11, wherein in the obliquely stretching step, a part of the obliquely stretched film in the width direction is cooled.   The method for producing an obliquely stretched film according to claim 11 or 12, wherein in the obliquely stretching step, the obliquely stretched film is intermittently cooled in the longitudinal direction.

Images