JP2010234737A - Method and apparatus for producing optical film and optical compensation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and apparatus for producing an optical film having reduced surface inferiority, large retardation and greatly inclined optical axis, and to provide an optical compensation film. <P>SOLUTION: The apparatus 10 for producing the film is provided with: a supplying process section 14 for supplying a molten resin containing a thermoplastic resin; a film forming process section 15 for forming the molten resin into a film shape by continuously pinching the molten resin in a pinching section A; and a film temperature adjusting process section 16 for cooling the formed resin film 12. In the film temperature adjusting process section 16, a cooling wind ejection section 40 blows cooling wind from a side opposite from a casting roll 26 to cool the resin film 12 during transportation of the resin film 12 on the casting roll 26 (equivalent to "a secondary pinching surface"). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method and apparatus for manufacturing an optical film, and an optical compensation film, and relates to a method and apparatus for manufacturing an optical film used for optical applications such as a liquid crystal display device, and an optical compensation film.

  In recent years, films (so-called optical films) having predetermined optical characteristics have been used for various purposes in optical applications such as liquid crystal display devices. Examples of the optical film include a protective film for a polarizing film in a liquid crystal display device, a retardation film that compensates for retardation of a liquid crystal cell, and the like.

  The optical film can be produced by various methods depending on the application.

  For example, Patent Documents 1 and 2 describe a method for producing an optical film in which the optical axis in the film thickness direction is inclined by sandwiching a film-like resin composition with two rolls having different peripheral speeds. Has been.

  Further, Patent Document 1 manufactures an optical film having birefringence and an inclined optical axis in the film thickness direction by sandwiching a molten resin composition with two rolls having different peripheral speeds. The so-called melt touch roll method is described.

JP-A-6-222213 JP 2003-25414 A JP 2007-38646 A

  In recent years, there has been a demand for further improvement in the quality of optical films, and there is a demand for the development of optical films that achieve both the size of retardation and the inclination of the optical axis. However, there is a trade-off between the pressing condition advantageous for the development of retardation and the pressing condition advantageous for the tilt of the optical axis. For example, in order to develop a large retardation, it is advantageous that the temperature of the resin composition in the pinched portion is higher. However, when the temperature of the resin composition increases, the optical axis tilt structure is relaxed and the optical axis is relaxed. It is difficult to maintain an inclined structure.

  On the other hand, when cooling (solidifying) the film formed in the pinching portion, surface defects may occur. For example, when the temperature of the film at the film peeling position (peeling position) is high, it is difficult to peel the film stably from the roll (casting roll), and striped unevenness along the width direction of the film (so-called peeling) Step unevenness) may occur. Moreover, when the temperature of a roll (casting roll) is low, a temperature difference will arise in the front and back of a film, and a wrinkle may generate | occur | produce in a film.

  The present invention has been made in view of the above-described circumstances, and a method and an apparatus for manufacturing an optical film with reduced surface defects, a large retardation, and a greatly inclined optical axis, and an optical compensation film The purpose is to provide.

  The method for producing an optical film according to the present invention includes a step of supplying a molten resin composition containing a thermoplastic resin by extruding it from a discharge port of a supply means, and a first nipping surface and a second nipping surface having different moving speeds. A step of forming a film by pressing the molten resin composition at a pressing portion formed by the pressing surface, and peeling the film from the first pressing surface and transporting the film by the second pressing surface. A step of cooling the film conveyed by the second clamping surface from a side opposite to the second clamping surface, and a step of peeling the cooled film from the second clamping surface at a peeling position It is characterized by including.

  According to the manufacturing method of the optical film, after the retardation and the optical axis inclined structure are expressed by the first clamping surface and the second clamping surface having different moving speeds, before the film is peeled off from the second clamping surface. By rapidly cooling the film, both the retardation and the optical axis tilt structure can be achieved.

  In addition, by cooling the film from the side opposite to the second pressing surface, the film is sufficiently cooled until reaching the peeling position while preventing wrinkles due to the temperature difference between the front and back of the film during film cooling. The occurrence of stripping unevenness can be prevented.

  In the method of manufacturing the optical film, in the step of cooling the film, cooling air may be blown onto the film from the side opposite to the second pressing surface.

  In this way, by blowing cooling air to the film from the side opposite to the second clamping surface, the film is quickly solidified while more reliably preventing wrinkles due to the temperature difference between the front and back surfaces of the film, and the optical axis The relaxation of the inclined structure can be further suppressed.

  Also, even if the optical axis tilt structure is somewhat relaxed, the molecular orientation is relaxed at the same speed on the front and back of the film by reducing the temperature difference between the front and back of the film. Accordingly, unevenness in alignment in the thickness direction can be suppressed.

  Furthermore, since a non-contact method called cooling air is used, it is possible to prevent generation of scratches on the film surface during film cooling.

  When the position of the pinching portion is X = 0 and the peeling position is X = L, the cooling air is preferably blown onto the film in a range of 0.2L ≦ X ≦ 1.0L.

  By blowing the cooling air in the above range, the film can be quickly cooled, and the relaxation of the optical axis inclination can be suppressed. Moreover, since a shrinkage | contraction suppression force can be made to work by solidifying a film, a deformation | transformation can be suppressed and generation | occurrence | production of a wrinkle can be suppressed.

The temperature T _{air of the} cooling _air is preferably (T ₁ −50) <T _air ≦ T _{1 when} the temperature T ₁ [° C.] of the second clamping surface is set.

By setting the temperature T _{air of the} cooling _air in the above range with respect to the temperature T ₁ [° C.] of the second pressure-clamping surface, the temperature difference between the front and back of the film can be reduced and wrinkle generation can be prevented.

  In the method of manufacturing the optical film, in the step of cooling the film, a cooling member may be brought into contact with the film from the side opposite to the second pressing surface.

  In this way, by bringing the cooling member into contact with the film from the side opposite to the second clamping surface, the film is quickly solidified while more reliably preventing wrinkles due to the temperature difference between the front and back surfaces of the film, and the light The relaxation of the shaft tilt structure can be further suppressed.

  Moreover, even if the optical axis tilt structure is somewhat relaxed, by reducing the temperature difference between the front and back of the film, the molecular orientation is relaxed at the same speed on the front and back of the film. Unevenness can be suppressed.

  In the method for producing an optical film, the second pinching surface has a high temperature region and a low temperature region having a temperature lower than the high temperature region, and the pinching portion is formed by the high temperature region of the second pressing surface. While heating, it is preferable to cool the film conveyed by the second pressing surface by the low temperature region of the second pressing surface.

  In this way, by heating the pinching portion with the high temperature region of the second pinching surface, the fluidity of the resin composition in the pinching portion can be increased and a larger retardation can be expressed. Further, by cooling the film in the low temperature region of the second pinching surface, the film can be stably peeled off from the second pressing surface while further suppressing the relaxation of the optical axis tilt structure.

  In addition, as a specific configuration of the second clamping surface having a high temperature region and a low temperature region, for example, a roll including a heater and a cooler inside, the roll being independent of the heater and the cooler A configuration in which the surface can rotate can be given.

In the method for producing an optical film, the temperature T ₁ [° C.] of the second clamping surface is (Tg−80) <T ₁ <Tg, where Tg [° C.] is the glass transition temperature of the resin composition. Preferably there is.

By setting the temperature T ₁ of the second clamping surface that conveys the film from the clamping unit to the peeling position within the above range, the film can be cooled quickly and sufficiently, and the relaxation of the optical axis tilt structure is suppressed, and the film Can be removed stably.

  In the manufacturing method of the optical film, it is preferable that a linear pressure applied to the resin composition in the pinching portion is 0.5 MPa or more and 100 MPa or less.

  In the method for producing an optical film, the temperature T [° C.] at the discharge outlet of the resin composition is (Tg + 120) <T <(Tg + 200), where Tg [° C.] is the glass transition temperature of the resin composition. Preferably there is.

  In the manufacturing method of the optical film, it is preferable that the first clamping surface and the second clamping surface are surfaces of a pair of rolls arranged to face each other.

  The optical compensation film according to the present invention is characterized by using an optical film manufactured by the above-described optical film manufacturing method.

  The optical film manufactured by the above optical film manufacturing method not only has a large retardation, the optical axis is largely inclined, but also surface defects such as peeling unevenness are reduced. It can be suitably used as a film.

  The apparatus for producing an optical film according to the present invention comprises a supply means for supplying a molten resin composition containing a thermoplastic resin, a first clamping surface and a second clamping surface, and the molten resin composition. A pressing means for forming a film by pressing at a pressing portion between the first pressing surface and the second pressing surface, and the film is peeled off from the first pressing surface and the second pressing surface The driving means for driving the first clamping surface and the second clamping surface and the downstream side of the clamping unit of the clamping means so as to be conveyed by the second clamping surface and conveyed by the second clamping surface An optical film comprising: cooling means for cooling the film from the side opposite to the second clamping surface; and peeling means for peeling the film cooled by the cooling means from the second clamping surface at a peeling position. Manufacturing apparatus, wherein the driving means , And drives the second nip-pressing surface and the first compression surface at a different speed.

  According to the film manufacturing method of the present invention, after the retardation and the optical axis inclined structure are expressed by the first and second clamping surfaces having different moving speeds, before the film is peeled off from the second clamping surface. In addition, by rapidly cooling the film, both retardation and an optical axis tilt structure can be achieved.

  In addition, by cooling the film from the side opposite to the second pressing surface, the film is sufficiently cooled until reaching the peeling position while preventing wrinkles due to the temperature difference between the front and back of the film during film cooling. The occurrence of stripping unevenness can be prevented.

It is a model diagram which shows the structural example of the film manufacturing apparatus used for the manufacturing method of the film of this invention. It is a figure which shows the structural example of a cooling wind injection part. (A) is a side view which shows a cooling wind injection part, (b) is sectional drawing which shows a cooling wind injection part. It is a side view which shows the other example of the film temperature control part shown in FIG. It is a side view which shows the other example of a casting roll. It is a table | surface figure which shows the test condition result of an Example.

  Hereinafter, preferred embodiments of a film production method according to the present invention will be described with reference to the accompanying drawings.

≪Film production method≫
FIG. 1 is a schematic configuration diagram illustrating an example of an optical film manufacturing apparatus. As shown in FIG. 1, the film manufacturing apparatus 10 mainly includes a supply process unit 14 that supplies a molten resin containing a thermoplastic resin, and continuously presses the molten resin in the pressing unit A to form a film. A film forming process unit 15 for molding, a film temperature adjusting process unit 16 for cooling the molded resin film 12, and the molded resin film 12 are peeled off from the clamping surface at the peeling position B, and then the film is stretched in the longitudinal direction. It comprises a longitudinal stretching process section 17, a lateral stretching process section 18 that laterally stretches, and a winding process section 20 that winds the stretched resin film 12.

  The molten resin (hereinafter also referred to as “melt”) supplied by the supply process unit 14 is continuously formed between the first and second clamping surfaces constituting the clamping device by the film forming process unit 15. The resin film 12 is formed by clamping. In FIG. 1, description will be given by using an example in which a touch roll 25 and a casting roll 26 are used as the first and second pressing surfaces constituting the narrow pressure device. In the present embodiment, the moving speed of the first pinching surface is made faster than the moving speed of the second confining surface. As a clamping device having different speeds on the first clamping surface and the second clamping surface, in addition to a combination of two rolls (touch roll 25 and casting roll 26) having different peripheral speeds as shown in FIG. Examples include a combination of a roll and a touch belt having different speeds described in Japanese Patent Laid-Open No. 2000-219752, and a combination of a roll and a multi-stage roll. Among these, two rolls having different peripheral speeds are preferable from the viewpoint of formability control and machine maintenance. The roll pressure can be measured by passing a pressure measurement film (manufactured by FUJIFILM Corporation, prescale for medium pressure, etc.) through two rolls.

  While the resin film 12 is in contact with the casting roll 26 in the film temperature adjusting process section 16, the front and back of the resin film 12 are uniformly cooled by the casting roll 26 and the cooling means. After being peeled off from the casting roll 26, the film is sent in order to the longitudinal stretching process section 17 and the lateral stretching process section 18 and stretched, and is wound up in a roll shape by the winding process section 20. Thereby, the stretched resin film 12 is manufactured. Hereinafter, details of each process part will be described.

<Supply process section>
In the method of the present invention, first, a composition containing a thermoplastic resin (sometimes referred to as “thermoplastic resin composition”) is melt-extruded. Prior to melt extrusion, the thermoplastic resin composition is preferably pelletized. Commercially available thermoplastic resins (for example, TOPAS # 6013, Toughlon MD1500, Delpet 980N, DayLark D332, etc.) may be pelletized, but if not pelletized, the following method may be used. it can.

(Pelletized)
The thermoplastic resin composition is dried, melted at 150 ° C. to 300 ° C. using a twin-screw kneading extruder, and then extruded into noodles, and solidified in air or water and cut. Further, after melting by an extruder, it can be pelletized by an underwater cutting method in which it is cut while being directly extruded from a die into water. Extruders used for pelletization include single screw extruders, non-meshing different direction rotating twin screw extruders, meshing different direction rotating twin screw extruders, and meshing same direction rotating twin screw extruders. Etc. can be used. The number of revolutions of the extruder is preferably 10 rpm to 1000 rpm, more preferably 20 rpm to 700 rpm. The extrusion residence time is 10 seconds to 10 minutes, more preferably 20 seconds to 5 minutes. No particular limitation is imposed on the size of the pellets is generally about 10mm ³ ~1000mm ^3, more preferably about 30 mm ³ 500 mm ^3.

  It is preferred to reduce the moisture in the pellets prior to melt extrusion. A preferable drying temperature is 40 to 200 ° C, more preferably 60 to 150 ° C. Thereby, the moisture content is preferably 1.0% by mass or less, and more preferably 0.1% by mass or less. Drying may be performed in air, nitrogen, or vacuum.

(Kneading and melting)
Next, the dried pellets are supplied into the cylinder through the supply port of the extruder 22, and are kneaded and melted. The inside of the cylinder is composed of, for example, a supply unit, a compression unit, and a measurement unit in order from the supply port side. The screw compression ratio of the extruder is preferably 1.5 to 4.5, the ratio of the cylinder length to the cylinder inner diameter (L / D) is preferably 20 to 70, and the cylinder inner diameter is preferably 30 mm to 150 mm. The extrusion temperature is determined according to the melting temperature of the thermoplastic resin, but generally about 190 to 300 ° C is preferable. Furthermore, in order to prevent the molten resin from being oxidized by residual oxygen, it is also preferable to carry out the inside of the extruder in an inert (nitrogen or the like) air flow or while evacuating using an extruder with a vent.

(filtration)
It is preferable to provide a filtration apparatus incorporating a breaker plate type filtration or a leaf type disk filter for filtering foreign matter in the thermoplastic resin composition. Filtration may be performed in one stage or may be performed in multistage filtration. The filtration accuracy is preferably 15 μm to 3 μm, more preferably 10 μm to 3 μm. It is desirable to use stainless steel as the filter medium. As the configuration of the filter medium, a knitted wire, a sintered metal fiber or metal powder (sintered filter medium) can be used, and among them, a sintered filter medium is preferable.

(Gear pump)
In order to reduce the fluctuation of the discharge amount and improve the thickness accuracy, it is preferable to provide a gear pump between the extruder and the die. Thereby, the resin pressure fluctuation width in the die can be within ± 1%. In order to improve the quantitative supply performance by the gear pump, a method of controlling the pressure before the gear pump to be constant by changing the number of rotations of the screw can also be used.

(Die)
The molten resin is melted by the extruder configured as described above, and the molten resin is continuously fed to the die via a filter and a gear pump as necessary. The die may be any of a T die, a fish tail die, and a hanger coat die. It is also preferable to insert a static mixer immediately before the die to increase the uniformity of the resin temperature. The clearance of the T-die outlet portion is generally 1.0 to 30 times the film thickness, preferably 5.0 to 20 times.

  In addition to the single layer deposition apparatus, it is possible to manufacture using a multilayer deposition apparatus.

  Thus, the residence time from when the resin enters the extruder through the supply port until it exits from the die is preferably 3 to 40 minutes, more preferably 4 to 30 minutes. It should be noted that the fluctuation of the discharge pressure discharged from the die 24 is preferably within a range of 10%.

  The temperature T [° C.] of the resin composition at the discharge port of the die 24 preferably satisfies Tg + 120 ≦ T ≦ Tg + 200. The temperature T of the resin composition immediately after being extruded from the discharge port 16A of the die 16 can be measured by a contact thermometer or a non-contact thermometer. Tg [° C.] means the glass transition temperature of the resin composition, and can be measured by the following procedure using, for example, a scanning differential calorimeter (DSC).

  First, a resin composition is put in a measurement pan of a scanning differential calorimeter (DSC), and this is heated from 30 ° C. to 300 ° C. at 10 ° C./min in a nitrogen stream (1st-run) and then to 30 ° C. It cools at -10 degreeC / min, and heats up again from 30 degreeC to 300 degreeC at 10 degreeC / min (2nd-run). The temperature at which the baseline starts to deviate from the low temperature side at 2nd-run can be calculated as the glass transition temperature Tg of the resin composition.

  In addition, in FIG. 1, embodiment which used the extruder and die | dye which melt | dissolve a thermoplastic resin plastic material and discharge it in a film form as a melt supply means was demonstrated. The present invention is not limited to this. For example, a resin is supplied in a film form, melted by a heating means, a molten resin is formed, and a melt is formed between the touch roll 25 and the casting roll 26 which are film forming steps. It can also be supplied.

<Deposition process section>
Next, in the film forming step, the film 12 is formed by continuously pressing the molten resin formed by the supply unit between the first and second pressing surfaces constituting the pressing device. In FIG. 1, description will be given by using an example in which a touch roll 25 and a casting roll 26 are used as the first and second pressing surfaces constituting the pressing device.

  A molten resin containing a thermoplastic resin is extruded from the die 24 in the form of a film, and is passed through a pressing part A between two rolls consisting of a touch roll (first roll) 25 and a casting roll (second roll) 26, Cool and solidify to obtain a film. The surface of the touch roll 25 or the casting roll 26 has an arithmetic average height Ra of usually 100 nm or less, preferably 50 nm or less, more preferably 25 nm or less.

  The touch roll 25 and the casting roll 26 are rotated at different peripheral speeds by driving means (not shown). Thereby, when a molten resin passes two rolls, a shear stress is provided and the optical film in which the optical axis inclined was manufactured. The peripheral speed ratio is preferably 0.60 to 0.99, and more preferably 0.75 to 0.98. Here, the peripheral speed ratio of the two rolls means the peripheral speed of the slow roll / the peripheral speed of the fast roll.

  The larger the peripheral speed ratio between the two rolls, the larger the absolute value of the difference between Re (40 °) and Re (−40 °) of the obtained film. On the other hand, if the difference in peripheral speed is too large, the resulting film It becomes easy to be damaged on the surface. When the peripheral speed ratio of the two rolls is within the above range, the film surface is hardly scratched and a film having good smoothness can be produced stably.

  In order to obtain a desired film, whichever speed of the two rolls may be high, when the touch roll 25 is slow, a bank is formed on the touch roll 25 side. Since the touch roll 25 has a short contact time with the melt, the bank formed on the touch roll side cannot be sufficiently cooled, and a peeling dan is generated, which easily causes a surface failure. Therefore, it is preferable that the slow roll = casting roll (second roll) 26 and the fast roll = touch roll (first roll) 25.

  Furthermore, it is preferable to use a roll having a large diameter. Specifically, it is preferable to use two rolls having a diameter of 350 to 600 mm, more preferably 350 to 500 mm. When a roll with a large diameter is used, the contact area between the film-like melt and the roll becomes wide, and the time for shearing becomes longer. Therefore, a film with a large difference between Re (40 °) and Re (−40 °) is used. And it can manufacture, suppressing the dispersion | variation. The diameters of the two rolls may be the same or different.

  The two rolls may be driven or driven independently, but are preferably driven independently in order to suppress variations. As described above, the two rolls are driven at different peripheral speeds. However, in order to further increase the difference between Re [40 °] and Re [−40 °], the surface temperature of the two rolls is adjusted. You may make a difference. A preferable temperature difference is 5 ° C to 80 ° C, more preferably 20 ° C to 80 ° C, and further preferably 20 ° C to 60 ° C. At that time, the temperature of the two rolls is Tg−70 ° C. to Tg + 20 ° C., more preferably Tg−50 ° C. to Tg + 10 ° C., more preferably Tg−40 ° C. to Tg + 5 ° C., using the glass transition temperature Tg of the resin. Set to. Such temperature control can be achieved by passing a temperature-controlled liquid or gas through the touch roll.

  The linear pressure (nip pressure) in the clamping part between the touch roll 25 and the casting roll 26 is not particularly limited, and can be set to, for example, a linear pressure of 0.5 MPa to 100 MPa. Among these, from the viewpoint of developing a larger retardation, the pressure is preferably 10 MPa or more and 80 MPa or less, more preferably 20 MPa or more and 60 MPa or less, and further preferably 30 MPa or more and 50 MPa or less. By setting the nip pressure at the clamping part to 10 MPa or more, the molten resin is suddenly pushed out when passing through the clamping part, causing elongation deformation, and the flow direction (in-plane direction) and thickness of the resin composition. A large retardation develops in the direction. Thereby, for example, an optical film having a retardation Re in the in-plane direction at a wavelength of 550 nm of 40 nm or more can be formed.

  The nip pressure of the clamping device is that the pressure measurement film “Prescale” manufactured by Fuji Film Co., Ltd. is pressed at the nip point to develop color, and then the degree of color development is determined by the prescale dedicated densitometer FPD-305 and the prescale dedicated pressure. It can be obtained by converting into a pressure value using a converter FPD-306.

  As the touch roll 28 and the casting roll 18, for example, a rubber roll whose surface is coated with a metal (for example, a rubber roll described in JP-A-2003-25414) or a metal rigid roll can be used. In particular, the rigid roll is not easily deformed even when a high nip pressure is applied, and thus can be suitably used when a film having a high retardation is formed.

  Examples of the rigid roll that can be used for the touch roll 28 and the casting roll 18 include metal rolls having a Shore hardness of 45 HS or more (more preferably 50 HS or more). Here, the shore hardness can be obtained from an average value of values measured at 5 points in the roll width direction and at 5 points in the circumferential direction using the method of JIS Z 2246.

  In order to achieve the Shore hardness, the material of the two rolls is preferably a metal, more preferably stainless steel, and a roll whose surface is plated is also preferred. On the other hand, a rubber roll or a metal roll lined with rubber is preferably used because it has large surface irregularities and is easily scratched on the surface of the film.

  As for the touch roll, for example, JP-A-11-314263, JP-A-2002-36332, JP-A-11-235747, WO97 / 28950, JP-A-2004-216717, JP2003. -145609 can be used.

  In addition, it is preferable to keep the melt warm until just before contacting at least one of the two rolls melt-extruded from the die, and reduce the temperature distribution in the width direction. It is preferable to set the temperature within a temperature range. In order to reduce the temperature distribution, a member having a heat insulating function or a heat reflecting function is arranged in at least a part of the passage between the melt die and the two rolls to shield the melt from the outside air. Is preferred. Thus, by arranging the heat insulating member in the passage and shielding it from the outside air, it is possible to suppress the influence of the external environment, for example, wind, and to suppress the temperature distribution in the width direction of the film. The temperature distribution in the width direction of the film-like melt is more preferably within ± 3 ° C., and even more preferably within ± 1 ° C.

  Further, when the shielding member is used, since the film-like melt can be passed between rolls in a high temperature state, that is, in a state where the melt viscosity is low, there is an effect that the film can be easily produced.

  The temperature distribution of the film-like melt can be measured with a contact thermometer or a non-contact thermometer.

  A shielding board is provided inside the both ends of two rolls, for example, via the width direction side surface of die | dye, and a clearance gap. The shielding plate may be directly fixed to the side surface of the die, or may be supported and fixed by a support member. For example, the width of the shielding plate is preferably equal to or greater than the width of the side surface of the die so that the rising airflow due to heat dissipation of the die can be efficiently blocked.

  The gap between the shielding plate and the widthwise end of the film-like melt is preferably narrowly formed to efficiently shield the rising airflow flowing along the surface of the roll, and the widthwise end of the film-like melt More preferably, it is about 50 mm from the part. Note that the gap between the side surface of the die and the shielding plate is not necessarily provided, but is preferably formed to an extent capable of discharging the airflow in the space surrounded by the shielding plate, for example, 10 mm or less.

  In addition, as the material having a heat insulating function and / or a heat reflecting function, a material excellent in wind shielding properties and heat retaining properties is preferable. For example, a metal plate such as stainless steel can be preferably used.

  As a method of eliminating the variation, there is a method of increasing the adhesion when the film-like melt comes into contact with the casting roll. Specifically, the adhesion can be improved by combining electrostatic application method, air knife method, air chamber method, vacuum nozzle method and the like. Such an adhesion improving method may be performed on the entire surface of the film-like melt or may be partially performed.

<Film temperature control process part>
The resin film 12 formed in the film forming process section 15 is sandwiched between a touch roll 25 and a casting roll 26 having different peripheral speeds, thereby developing retardation and forming an optical axis tilt structure. ing. However, when the temperature of the molded film is equal to or higher than Tg, the optical axis tilt structure is relaxed.

  Therefore, in this embodiment, as shown in FIG. 1, while the resin film 12 is conveyed on the casting roll (corresponding to the “second pressing surface”) 26 in the film temperature adjusting process section 16, the casting roll 26. From the opposite side (the non-contact surface side of the casting roll 26), cooling air is blown by the cooling air jet unit 40 to cool the resin film 12. Thereby, cooling of the resin film 12 can be performed rapidly and an optical axis inclination structure can be maintained. Moreover, even if the optical axis tilt structure is somewhat relaxed, by reducing the temperature difference between the front and back of the film, the molecular orientation is relaxed at the same speed on the front and back of the film. Unevenness can be suppressed. Furthermore, since a non-contact method called cooling air is used, it is possible to prevent generation of scratches on the film surface during film cooling.

  In addition to cooling by the casting roll 26, the resin film 12 is cooled from the side opposite to the casting roll 26, thereby preventing the wrinkles due to the temperature difference between the front and back surfaces of the resin film 12 and reaching the peeling position B. By sufficiently cooling the film, the occurrence of peeling step unevenness can be prevented.

  FIG. 2A is a side view showing a peripheral portion of the cooling air jet portion 40, and FIG. 2B is a cross-sectional view of the peripheral portion of the cooling jet portion 40 along the film width direction.

  As shown to Fig.2 (a), it is preferable that the cooling wind injection part 40 is the structure by which multiple injection nozzles 42 were arrange | positioned along the film conveyance direction from a viewpoint of cooling a film reliably. The spray nozzle 42 is preferably a diffusion type nozzle.

  The cooling air injection by the cooling air injection unit 40 is performed by setting the position of the pinching part A between the touch roll 25 and the casting roll 26 to X = 0 and setting the peeling position B where the resin film 12 is peeled off from the casting roll 26. When X = L, it is preferable to carry out in the range of 0.2L ≦ X ≦ 1.0L.

  By blowing the cooling air in the above range, the film can be quickly cooled, and the relaxation of the optical axis inclination can be suppressed. Moreover, since a shrinkage | contraction suppression force can be made to work by solidifying a film, a deformation | transformation can be suppressed and generation | occurrence | production of a wrinkle can be suppressed.

  Further, as shown in FIG. 2B, it is preferable that a plurality of the injection nozzles 42 be arranged in the width direction of the resin film 12 from the viewpoint of uniformizing the temperature in the width direction of the resin film 12.

  The cooling air can be blown without any particular limitation as long as the surface of the resin film 12 is not uneven, but the air pressure is preferably 0.001 to 2 MPa, more preferably 0.1 to 1 MPa. is there. Moreover, 0.1-500 mm is preferable and, as for the distance of the resin sheet film (casting roll 26) and the injection nozzle 42, 1.0-200 mm is more preferable.

The temperature T ₁ [° C.] of the casting roll 26 is preferably (Tg−80) <T ₁ <(Tg + 10), more preferably (Tg), where the glass transition temperature of the thermoplastic resin is Tg. −10) <T ₁ <(Tg + 10). The temperature T ₁ of the casting roll 26 for transporting the film from the holding part A to the peeling position B is in the above range, the cooling of the film went quickly and sufficiently, while suppressing the relaxation of the optical axis inclination structure, The film can be peeled off stably.

The temperature T _air [° C.] of the cooling _air is preferably (T ₁ -50) <T _air <T ₁ , more preferably (T ₁ -20) <T _air <(T ₁ -5). is there. By setting the temperature T _{air of the} cooling _air in the above range with respect to the temperature T ₁ [° C.] of the casting roll 26, the temperature difference between the front and back of the resin film 12 can be reduced, so the orientation in the thickness direction Sexual relaxation can be suppressed to the same extent. As a method for controlling the temperature T _air of the cooling air, it can be adjusted by adjusting the cooling air to a desired temperature by the temperature adjusting means 44 and blowing it from the injection nozzle 42 as shown in FIG. .

  In this way, the temperature difference between the front and back surfaces of the resin film 12 at the peeling position B where the resin film 12 whose temperature has been adjusted by the film temperature adjusting process unit 16 is peeled off from the casting roll 26 is 0 to 0.5 ° C. Is preferred. The temperature distribution in the width direction of the casting roll 26 is also preferably 0 to 0.5. By setting it as the said temperature range, when peeling the resin film 12 from the casting roll 26, since it can peel stably, generation | occurrence | production of peeling step unevenness can be suppressed.

  The conveying speed of the resin film 12 can be appropriately changed according to the temperature of the casting roll 26 and the temperature of the cooling air, but is preferably 0.1 m / min or more and 50 m / min or less, more preferably 5 m / min or more and 30 m / min. It is below min.

  The resin film 12 peeled from the casting roll 26 is preferably trimmed at both ends. The portion cut off by trimming may be crushed and used again as a raw material. Further, it is also preferable to perform a thickness increasing process (knurling process) on one or both ends. The height of the unevenness due to the thickness increasing process is preferably 1 μm to 50 μm, more preferably 3 μm to 20 μm. Thickening processing may be convex on both sides or convex on one side. The width of the thickness increasing process is preferably 1 mm to 50 mm, more preferably 3 mm to 30 mm. Extrusion can be performed at room temperature to 300 ° C. It is also preferable to attach a lami film on one side or both sides before winding. The thickness of the laminated film is preferably 5 μm to 100 μm, more preferably 10 μm to 50 μm. The material is not particularly limited, such as polyethylene, polyester, and polypropylene.

  The resin film produced in the film forming process unit 15 can be wound into a roll and transported to the next process before performing longitudinal stretching and lateral stretching. The winding tension is preferably 2 kg / m width to 50 kg / m width, more preferably 5 kg / m width to 30 kg / m width.

[Stretching process]
Furthermore, after the film is formed by the above method, stretching and / or relaxation treatment may be performed. For example, each process can be implemented by the following combinations (a) to (g).
(A) transverse stretching (b) transverse stretching → relaxation treatment (c) longitudinal stretching (d) longitudinal stretching → relaxation treatment (e) longitudinal (transverse) stretching → lateral (longitudinal) stretching (f) longitudinal (transverse) stretching → lateral (Longitudinal) stretching → relaxation treatment (g) Transverse stretching → relaxation treatment → longitudinal stretching → relaxation treatment Among these, the steps (a) to (d) are particularly preferable. In addition, FIG. 1 is a manufacturing apparatus used for the manufacturing method which has the process of performing horizontal stretching after performing vertical stretching.

<Longitudinal stretch process section>
Longitudinal stretching can be achieved by making the peripheral speed on the outlet side faster than the peripheral speed on the inlet side while heating between two pairs of rolls. Under the present circumstances, the expression property of the retardation of the thickness direction can be changed by changing the space | interval (L) between and the film width (W) before extending | stretching. When L / W (referred to as aspect ratio) is 2 to 50 or less (long span stretching), it is easy to produce a film having a small Rth, and when L / W is 0.01 to 0.3 (short span), a film having a large Rth is used. Can be made. In this embodiment, any of long span stretching, short span stretching, and a region between them (intermediate stretching = L / W exceeds 0.3 and 2 or less) may be used. Span stretching and short span stretching are preferred. Further, when aiming at high Rth, it is more preferable to use short span stretching, and when aiming at low Rth, it is distinguished from long span stretching.

  The stretching temperature is preferably Tg-10 ° C to Tg + 60 ° C, more preferably Tg-5 ° C to Tg + 45 ° C, and further preferably Tg-10 ° C to Tg + 20 ° C or less. Moreover, a preferable lateral stretch ratio is 1.2 to 3.0 times, more preferably 1.2 to 2.5 times, and still more preferably 1.2 to 2.0 times.

<Horizontal stretch process section>
The transverse stretching can be performed using a tenter. That is, the film is stretched by holding both ends in the width direction with clips and widening the film in the lateral direction. At this time, the stretching temperature can be controlled by sending wind at a desired temperature into the tenter. The stretching temperature is preferably Tg-10 ° C to Tg + 60 ° C, more preferably Tg-5 ° C to Tg + 45 ° C, and further preferably Tg-10 ° C to Tg + 20 ° C or less. Moreover, a preferable lateral stretch ratio is 1.2 to 3.0 times, more preferably 1.2 to 2.5 times, and still more preferably 1.2 to 2.0 times.

  By performing preheating before stretching and heat setting after stretching, the Re and Rth distribution after stretching can be reduced, and the variation in orientation angle associated with bowing can be reduced. Either preheating or heat setting may be performed, but both are more preferable. These preheating and heat setting are preferably performed by holding with a clip, that is, preferably performed continuously with stretching.

  Preheating can be performed at a temperature about 1 ° C. to 50 ° C. higher than the stretching temperature, preferably 2 ° C. to 40 ° C. or less, more preferably 3 ° C. or more and 30 ° C. or less. The preheating time is preferably 1 second or longer and 10 minutes or shorter, more preferably 5 seconds or longer and 4 minutes or shorter, and even more preferably 10 seconds or longer and 2 minutes or shorter. During preheating, it is preferable to keep the width of the tenter substantially constant. Here, “substantially” refers to ± 10% of the width of the unstretched film.

  The heat setting can be performed at a temperature 1 ° C. or more and 50 ° C. or less lower than the stretching temperature, more preferably 2 ° C. or more and 40 ° C. or less, and further preferably 3 ° C. or more and 30 ° C. or less. More preferably, it is less than the stretching temperature and less than Tg. The preheating time is preferably 1 second or longer and 10 minutes or shorter, more preferably 5 seconds or longer and 4 minutes or shorter, and even more preferably 10 seconds or longer and 2 minutes or shorter. During the heat setting, it is preferable to keep the width of the tenter substantially constant. Here, “substantially” refers to 0% (the same width as the tenter width after stretching) to −10% (shrinking by 10% from the tenter width after stretching = reduced width) of the tenter width after stretching. If the width is wider than the stretched width, residual strain tends to occur in the film, which is not preferable.

<Relaxation treatment>
Furthermore, dimensional stability can be improved by performing relaxation treatment after these stretching. The thermal relaxation is preferably performed after film formation, after longitudinal stretching, after lateral stretching, or both. The relaxation treatment may be performed online continuously after stretching, or may be performed offline after winding after stretching.

  Thermal relaxation is (Tg-30) ° C to (Tg + 30) ° C, more preferably (Tg-30) ° C to (Tg + 20) ° C, and more preferably (Tg-15) ° C to (Tg + 10) ° C for 1 second to 10 minutes. More preferably 5 seconds to 4 minutes, still more preferably 10 seconds to 2 minutes, 0.1 kg / m to 20 kg / m, more preferably 1 kg / m to 16 kg / m, still more preferably 2 kg / m to 12 kg / m. It is preferable to carry out while conveying with tension.

  As mentioned above, although the manufacturing method of the optical film which concerns on one Embodiment of this invention was demonstrated, this invention is not limited to this, In the range which does not deviate from the summary of this invention, you may perform various improvement and deformation | transformation. Of course.

  For example, in the above-described embodiment, the example in which the resin film 12 is cooled from the side opposite to the casting roll 26 by the cooling air jet unit 40 has been described, but after passing through the pinching unit A as the film temperature adjusting step unit 16. A cooling member may be brought into contact with the resin film 12. In this case, the resin film 12 may be immersed in the liquid using a liquid as the cooling member, or the cooling roll or the cooling band may be brought into contact with the resin film 12 using a cooling roll or a cooling band as the cooling member. Good.

  FIG. 3 is a side view showing a configuration in which the resin film 12 is cooled by a cooling roll. As shown in FIG. 3, by bringing the cooling roll 46 into contact with the resin film 12 from the side opposite to the casting roll 26, the film is rapidly solidified while preventing wrinkles due to the temperature difference between the front and back sides of the film. Thus, relaxation of the optical axis tilt structure can be suppressed. Moreover, even if the optical axis tilt structure is somewhat relaxed, by reducing the temperature difference between the front and back of the film, the molecular orientation is relaxed at the same speed on the front and back of the film. Unevenness can be suppressed.

  Further, the casting roll 26 has a configuration in which the temperature of the molten resin around the pinching part A and the temperature of the resin film 12 at the pinching part A to the peeling position B (particularly around the peeling position B) can be controlled independently. It may be used.

  FIG. 4 is a diagram showing a casting roll 26 having a configuration capable of independently controlling the temperature of the molten resin around the pinching portion A and the temperature of the resin film 12 at the pinching portion A to the peeling position B. As shown in FIG. 4, a roll temperature adjusting unit 48 including a high temperature part 48 </ b> A and a bass part 48 </ b> B is provided inside the casting roll 26. The roll temperature adjusting unit 48 is independent of the rotational motion of the casting roll 26 and has a configuration that does not move even when the casting roll 26 rotates. As a roll temperature control part of such a structure, what was described in Unexamined-Japanese-Patent No. 2006-256159 can be used, for example.

  The surface of the casting roll 26 is divided into a high temperature region around the pinching portion A and a low temperature region around the peeling position B by the roll temperature adjusting unit 48 having the above configuration. Therefore, by heating the pinching part A by the high temperature region of the casting roll 26, the fluidity of the molten resin in the pinching part A can be increased and a larger retardation can be expressed. Moreover, by cooling the resin film 12 in the pinching part A to the peeling position B by the low temperature region of the casting roll 26, the film is stably peeled off from the second pinching surface while suppressing the relaxation of the optical axis inclined structure. be able to.

  In addition, regarding the film temperature adjustment process part 16, although the cooling wind injection part 40, the cooling member (cooling roll 46), and the roll temperature adjustment 48 were demonstrated, you may combine these structures suitably from a viewpoint of improving cooling efficiency. .

≪Film≫
The film produced by the film production method of the present invention contains a thermoplastic resin, and in a plane including the film longitudinal direction and the film normal, retardation Re [0 °] at a wavelength of 550 nm measured from the normal. And retardation Re [+ 40 °] measured from a direction inclined + 40 ° and retardation Re [−40 °] measured from a direction inclined −40 ° with respect to the normal line are expressed by the following relational expression (I ) And (II) are both satisfied.

60 nm ≦ Re [0 °] ≦ 300 nm (I)
40 nm ≦ | Re [+ 40 °] −Re [−40 °] | ≦ 300 nm (II)
In this specification, the “direction inclined by θ ° from the normal” is defined as a direction inclined in the film surface direction by θ ° from the normal direction, with the film longitudinal direction being the inclination direction. That is, the normal direction of the film surface is a direction with an inclination angle of 0 °, and an arbitrary direction within the film surface is a direction with an inclination angle of 90 °.

  | Re [+ 40 °] -Re [−40 °] | of the film is 60 to 250 nm, preferably 60 to 200 nm, and more preferably 80 to 180 nm. Moreover, in-plane retardation Re (0 degree) is 60-250 nm, More preferably, Re (0 degree) is 60-200 nm, More preferably, it is 80-180 nm. Furthermore, the retardation Rth in the thickness direction is preferably 40 to 500 nm, more preferably 40 to 350 nm, and still more preferably 40 to 300 nm.

  When the optical film in the above range is used for optical compensation of a liquid crystal display device such as a TN mode, an ECB mode, and an OCB mode, it contributes to the improvement of viewing angle characteristics and can achieve a wide viewing angle.

  The thickness of the optical compensation film of the present invention is not particularly limited, but when used for a liquid crystal display or the like, it is preferably 100 μm or less, more preferably 80 μm or less, and 60 μm or less from the viewpoint of thinning. More preferably, it is more preferably 40 μm or less. In the manufacturing method of the present invention, such a thin film can be produced, which is one of the differences from the prior art.

  Variations in Re (0 °), Re (40 °), and Re (−40 °) appear as display unevenness when used in a liquid crystal display, and the variation is preferably as small as possible. It is preferably ± 3 nm, and more preferably within ± 1 nm. Similarly, the variation in the angle of the slow axis also causes display unevenness. Therefore, the variation is preferably as small as possible, specifically within ± 1 °, preferably within ± 0.5 °. Is more preferable, and ± 0.25 ° is particularly preferable. The direction of the slow axis of the film depends on the production method of the film described later. For example, when a resin exhibiting positive intrinsic birefringence is passed through two rolls, the slow axis is the same as the longitudinal direction of the film.

  The optical characteristic value can be measured by the following method.

  Re (0 °), Re (40 °), and Re (−40 °) of the film are in-plane including the longitudinal direction of the film and the film normal using KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments) , The longitudinal direction is the tilt direction, and the phase difference at an inclination angle of 40 degrees and the phase difference at an inclination angle of -40 degrees are measured. The measurement wavelength is 550 nm. A film made of a general thermoplastic resin by a melt film formation method has a relationship of | Re (40 °) −Re (−40 °) | ≈0 nm. That is, when | Re (40 °) −Re (−40 °) | is measured with the longitudinal direction as the tilt direction, a phase difference of 0 nm or more can be expressed.

  In addition, variations in Re (0 °), Re (40 °), and Re (−40 °) can be measured by the following method. Sampling is performed at 10 points in the width direction of the film and 10 points in the transport direction at equal intervals, and Re (0 °), Re (40 °), and Re (−40 °) are measured by the above method. The difference between the minimum values can be a variation.

  Further, the variation of the slow axis can be determined by the difference between the maximum value and the minimum value when the measurement is performed at 10 points in the width direction of the film and at 10 points in the transport direction at equal intervals.

  Rth is calculated by substituting the refractive index nx, ny, and nz of each direction of the refractive index ellipsoid into numerical formula (A), assuming that the refractive index ellipsoid is uniformly inclined by β °. Can do.

Rth = ((nx + ny) / 2−nz) × d Formula (A)
In the film of the present invention, ny is the refractive index in the film width direction. nx is the refractive index in the direction in which the projection component on the x-axis of the film is larger than the projection component on the z-axis, and nz is the refractive index in the direction in which the projection component on the z-axis is larger than the projection component on the x-axis.
The method for obtaining nx, ny, and nz is described in the technical data of Oji Scientific Instruments Co., Ltd. (http://www.oji-keisoku.co.jp/products/kobra/kobra.html). For example, it is possible to calculate from the values of Re (0 °), Re (40 °), Re (−40 °), the average refractive index n _ave , and the film thickness value d using the following formula (B). I can do it.

  In the formula, Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction. In addition, β in the mathematical formula (B) represents an inclination angle when it is assumed that the refractive index ellipsoid is uniformly inclined, and is used when the structure of the inclined retardation film is simply grasped.

  In the above measurement, as the assumed value of the average refractive index, values in the polymer handbook (John Wiley & Sons, INC) and catalogs of various optical compensation films can be used. Moreover, about the thing whose average refractive index value is not known, it can measure with an Abbe refractometer. The average refractive index values of the main optical compensation films are exemplified below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49) Polystyrene (1.59).

≪Film material≫
The thermoplastic resin used in the present invention is not particularly limited as long as it has the above-mentioned optical characteristics. However, when it is produced using a melt extrusion method, it is preferable to use a material having good melt extrusion moldability. In cycloolefins, cellulose acylates, polycarbonates, polyesters, transparent polyethylene, polyolefins such as transparent polypropylene, polyarylates, polysulfones, polyethersulfones, maleimide copolymers, transparent nylons, It is preferable to select transparent fluororesins, transparent phenoxys, polyetherimides, polystyrenes, acrylic copolymers, and styrene copolymers. One kind of the resin may be contained, or two or more kinds of the resins different from each other may be contained. Among these, cellulose acylates, cycloolefin resins obtained by addition polymerization, polycarbonates, styrene copolymers, and acrylic copolymers are preferable.

  In particular, cellulose acylates exhibiting positive intrinsic birefringence, and cycloolefin resins and polycarbonates obtained by addition polymerization, when shear deformation is added by two rolls, the slow axis faces the MD direction. A film of | Re (40 °) −Re (−40 °) |> 0 can be produced with the longitudinal direction as the tilt direction.

  In addition, acrylic and styrene copolymers exhibiting negative intrinsic birefringence, when processed as described above, have a slow axis in the TD direction and a longitudinal direction in the tilt direction, and | Re (40 °) − A film of Re (−40 °) |> 0 can be produced.

  When this film is applied to a liquid crystal display device as a viewing angle compensation film, the positive or negative intrinsic birefringence resin is appropriately selected in consideration of the characteristics of the liquid crystal display device and the convenience of polarizing plate processing. Can be used.

  Examples of cycloolefin copolymers that can be used in the present invention include resins obtained by polymerization of norbornene compounds. It may be a resin obtained by any polymerization method of ring-opening polymerization and addition polymerization.

  Examples of addition polymerization and the resin obtained thereby include, for example, Japanese Patent No. 3517471, Japanese Patent No. 3559360, Japanese Patent No. 3867178, Japanese Patent No. 3871721, Japanese Patent No. 3907908, Japanese Patent No. 3945598, and Japanese Translation of PCT International Publication No. 2005-527696. JP-A-2006-28993, JP-A-2006-11361, International Publication WO 2006/004376, International Publication WO 2006/0307077, and the like. Among these, those described in Japanese Patent No. 3517471 are particularly preferable.

  Examples of the ring-opening polymerization and the resin obtained thereby include WO 98/144499 pamphlet, Japanese Patent 30605532, Japanese Patent 3220478, Japanese Patent 373046, Japanese Patent 3404027, Japanese Patent 3428176, Patent Examples are described in Japanese Patent No. 3687231, Japanese Patent No. 3873934, and Japanese Patent No. 3912159. Of these, those described in International Publication WO 98- / 14499 pamphlet and Japanese Patent No. 30605532 are particularly preferable.

  Among these cycloolefins, those of addition polymerization are preferable from the viewpoints of birefringence development and melt viscosity. For example, “TOPAS # 6013” (manufactured by Polyplastics) can be used.

  Examples of cellulose acylates that can be used in the present invention include any cellulose acylate in which three hydroxyl groups in a cellulose unit are at least partially substituted with acyl groups. The acyl group (preferably an acyl group having 3 to 22 carbon atoms) may be either an aliphatic acyl group or an aromatic acyl group. Among them, cellulose acylate having an aliphatic acyl group is preferable, those having an aliphatic acyl group having 3 to 7 carbon atoms are more preferable, those having an aliphatic acyl group having 3 to 6 carbon atoms are more preferable, and carbon number More preferably has 3 to 5 aliphatic acyl groups. A plurality of these acyl groups may be present in one molecule. Examples of preferred acyl groups include acetyl, propionyl, butyryl, pentanoyl, hexanoyl and the like. Among these, cellulose acylate having one or more selected from acetyl group, propionyl group and butyryl group is more preferable, and more preferable one has both acetyl group and propionyl group. Cellulose acylate (CAP). CAP is preferable in terms of easy resin synthesis and high stability of extrusion molding.

When producing an optical film by a melt extrusion method such as the method of the present invention, the cellulose acylate used preferably satisfies the following formulas (S-1) and (S-2). Cellulose acylate satisfying the following formula has a low melting temperature and improved meltability, and is therefore excellent in melt extrusion film formability Formula (S-1) 2.0 ≦ X + Y ≦ 3.0
Formula (S-2) 0.25 <= Y <= 3.0
In the formula, X represents the degree of substitution of the acetyl group with respect to the hydroxyl group of cellulose, and Y represents the sum of the degree of substitution of the acyl group with respect to the hydroxyl group of cellulose. The “degree of substitution” in the present specification means the total of the ratio of substitution of hydrogen atoms of hydroxyl groups at the 2-position, 3-position and 6-position of cellulose. When the hydrogen atoms of all hydroxyl groups at the 2nd, 3rd and 6th positions are substituted with acyl groups, the degree of substitution is 3.

Furthermore, it is more preferable to use a cellulose acylate that satisfies the following formula:
2.3 ≦ X + Y ≦ 2.95
1.0 ≦ Y ≦ 2.95
It is more preferable to use a cellulose acylate that satisfies the following formula.

2.7 ≦ X + Y ≦ 2.95
2.0 ≦ Y ≦ 2.9
There is no restriction | limiting in particular about the mass average polymerization degree and number average molecular weight of cellulose acylates. In general, the mass average degree of polymerization is about 350 to 800, and the number average molecular weight is about 70000 to 230,000. The cellulose acylates can be synthesized using acid anhydrides or acid chlorides as acylating agents. In the industrially most general synthesis method, cellulose obtained from cotton linter, wood pulp, etc. is converted into organic acids (acetic acid, propionic acid, butyric acid) corresponding to acetyl groups and other acyl groups, or their acid anhydrides (anhydrous anhydride). A cellulose ester is synthesized by esterification with a mixed organic acid component containing acetic acid, propionic anhydride, and butyric anhydride). As a method for synthesizing cellulose acylate satisfying the above formulas (S-1) and (S-2), the Technical Report of the Japan Society of Invention (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention) 7 Pp. 12 to 12, JP-A-2006-45500, JP-A-2006-241433, JP-A-2007-138141, JP-A-2001-188128, JP-A-2006-142800, JP-A-2007. Reference can be made to the method described in Japanese Patent No. 98917.

  Examples of the polycarbonates usable in the present invention include polycarbonate resins having a bisphenol A skeleton, which are obtained by reacting a dihydroxy component and a carbonate precursor by an interfacial polymerization method or a melt polymerization method. Those described in 2006-277914, JP-A-2006-106386, and JP-A-2006-284703 can be preferably used. For example, “Taflon MD1500” (manufactured by Idemitsu Kosan Co., Ltd.) can be used as a commercial product.

  Examples of the styrenic copolymer that can be used in the present invention include styrene-acrylonitrile resins, styrene-acrylic resins, and multi-component (binary, ternary, etc.) copolymer polymers thereof. Among these, styrene maleic anhydride resin is preferable from the viewpoint of film strength.

  In the styrene maleic anhydride resin, the mass composition ratio of styrene and maleic anhydride is preferably styrene: maleic anhydride = 95: 5 to 50:50, and styrene: maleic anhydride = 90: 10 to 70. : 30 is more preferable. In order to adjust the intrinsic birefringence, hydrogenation of a styrene resin can be preferably used.

  Examples of the styrene maleic anhydride resin include “Daylark D332” manufactured by Nova Chemical Co., Ltd.

  The acrylic copolymer of the present invention is a resin obtained by polymerizing styrene and acrylic acid, methacrylic acid and derivatives thereof and derivatives thereof, and is not particularly limited as long as the effects of the present invention are not impaired. Among these resins, those containing 30 mol% or more of MMA units (monomer) among all monomers constituting the resin are preferable. In addition to MMA, at least one of a lactone ring unit, a maleic anhydride unit, and a glutaric anhydride unit More preferably, for example, the following units can be used.

(1) Acrylic resin containing a lactone ring unit JP 2007-297615 A, JP 2007-63541 A, JP 2007-70607 A, JP 2007-100044 A, JP 2007-254726 A, JP 2007-254727 A, JP 2007-2007 A1. 261265, JP2007-293272, JP2007-297619, JP2007-316366, JP2008-9378, JP2008-76764, and the like can be used. Among these, the resin described in JP-A-2008-9378 is more preferable.

(2) Acrylic resin containing maleic anhydride units JP2007-113109, JP2003-292714, JP6-279546, JP2007-51233 (acid-modified vinyl described herein), JP2001-270905, JP-A-2002-167694, JP-A-2000-302988, JP-A-2007-111110, JP-A-2007-11565 can be used. Among these, the one described in JP-A-2007-113109 is more preferable. A commercially available maleic acid-modified MAS resin (for example, Delpet 980N manufactured by Asahi Kasei Chemicals Corporation) can also be preferably used.

(3) Acrylic resin containing glutaric anhydride unit JP-A-2006-241263, JP-A-2004-70290, JP-A-2004-702296, JP-A-2004-126546, JP-A-2004-163924, JP-A-2004-291302 2004-292812, JP 2005-314534, JP 2005-326613, JP 2005-331728, JP 2006-131898, JP 2006-134882, JP 2006-206881, JP 2006-241197, JP 2006-2006. 283013, JP 2007-118266, JP 2007-176982, JP 2007-178504, JP 2007-197703, JP 2008-74918, WO 2005/105918, and the like can be used. Of these, the one described in JP-A-2008-74918 is more preferable.

  The glass transition temperature (Tg) of these resins is preferably 106 ° C. or higher and 170 ° C. or lower, more preferably 110 ° C. or higher and 160 ° C. or lower, and further preferably 115 ° C. or higher and 150 ° C. or lower. As a commercial product, “Delpet 980N” (manufactured by Asahi Kasei Chemicals Corporation) can be used.

  The optical compensation film of the present invention may contain a material other than the thermoplastic resin, but contains one or more of the thermoplastic resins as a main component (most content in all materials in the composition). In the embodiment containing two or more kinds of the resin, it means that the total content ratio thereof is higher than the content ratios of the other materials. Examples of materials other than the thermoplastic resin include various additives, and examples thereof include a stabilizer, an ultraviolet absorber, a light stabilizer, a plasticizer, fine particles, and an optical adjusting agent.

(I) Stabilizer The optical film of the present invention may contain at least one stabilizer. The stabilizer is preferably added before or when the thermoplastic resin is heated and melted. The stabilizer has effects such as preventing oxidation of the film constituting material, capturing an acid generated by decomposition, and suppressing or inhibiting a decomposition reaction caused by radical species caused by light or heat. Stabilizers are useful for suppressing the occurrence of alterations such as coloring and molecular weight reduction and the generation of volatile components due to various decomposition reactions including unresolved decomposition reactions. Even at a melting temperature for forming a resin film, the stabilizer itself is required to function without being decomposed. Typical examples of stabilizers include phenol-based stabilizers, phosphorous acid-based stabilizers (phosphite-based), thioether-based stabilizers, amine-based stabilizers, epoxy-based stabilizers, and lactone-based stabilizers. Stabilizers, amine stabilizers, metal deactivators (tin stabilizers) and the like are included. These are described in JP-A-3-199201, JP-A-5-1907073, JP-A-5-194789, JP-A-5-271471, JP-A-6-107854, and the like. Then, it is preferable to use at least one or more of a phenol-based or phosphorous acid-based stabilizer. Among phenolic stabilizers, it is particularly preferable to add a phenolic stabilizer having a molecular weight of 500 or more. Preferable phenolic stabilizers include hindered phenolic stabilizers.

  These materials are readily available as commercial products and are sold by the following manufacturers. From Ciba Specialty Chemicals, Irganox 1076, Irganox 1010, Irganox 3113, Irganox 245, Irganox 1135, Irganox 1330, Irganox 259, Irganox 565, Irganx 565, Irganx 565, Ir35x10 Moreover, it can obtain from Asahi Denka Kogyo Co., Ltd. as ADK STAB AO-50, ADK STAB AO-60, ADK STAB AO-20, ADK STAB AO-70, and ADK STAB AO-80. Furthermore, from Sumitomo Chemical Co., Ltd., it can obtain as Sumilizer BP-76, Sumilizer BP-101, Sumilizer GA-80. In addition, it is also possible to obtain as Sinox 326M and Sinox 336B from Sipro Kasei Corporation.

  Moreover, as said phosphorous acid type stabilizer, the compound as described in [0023]-[0039] of Unexamined-Japanese-Patent No. 2004-182979 can be used more preferably. Specific examples of the phosphite ester stabilizer include JP-A-51-70316, JP-A-10-306175, JP-A-57-78431, JP-A-54-157159, Examples thereof include compounds described in Japanese Utility Model Laid-Open No. 55-13765. Furthermore, as other stabilizers, the materials described in detail on pages 17 to 22 of the Japan Institute of Invention Disclosure Bulletin (Public Technical No. 2001-1745, issued March 15, 2001, Japan Society of Invention) are preferably used. be able to.

  The phosphite stabilizer is useful to have a high molecular weight in order to maintain stability at high temperature, has a molecular weight of 500 or more, more preferably a molecular weight of 550 or more, and particularly a molecular weight of 600 or more. Is preferred. Furthermore, at least one substituent is preferably an aromatic ester group. The phosphite ester stabilizer is preferably a triester, and is desirably free of impurities such as phosphoric acid, monoester and diester. When these impurities are present, the content is preferably 5% by mass or less, more preferably 3% by mass or less, and particularly 2% by mass or less. These include compounds described in [0023] to [0039] of JP-A No. 2004-182979, JP-A-51-70316, JP-A-10-306175, JP-A-57. The compounds described in JP-A-78431, JP-A-54-157159, and JP-A-55-13765 can also be mentioned. Preferred specific examples of the phosphite stabilizer include the following compounds, but the phosphite stabilizer that can be used in the present invention is not limited thereto.

  These are commercially available from Asahi Denka Kogyo Co., Ltd. as ADK STAB 1178, 2112, PEP-8, PEP-24G, PEP-36G, and HP-10, and Sandostab P-EPQ from Clariant. Is possible. Furthermore, a stabilizer having phenol and phosphite in the same molecule is also preferably used. These compounds are further described in detail in JP-A-10-273494. Examples of the compounds are included in the examples of the stabilizer, but are not limited thereto. As a typical commercial product, Sumitizer GP is available from Sumitomo Chemical Co., Ltd. These are commercially available from Sumitomo Chemical Co., Ltd. as Sumilizer TPL, TPM, TPS, TDP. Also available from Asahi Denka Kogyo Co., Ltd. as ADK STAB AO-412S.

  The stabilizers can be used alone or in combination of two or more, and the blending amount thereof is appropriately selected within a range not impairing the object of the present invention. Preferably, the addition amount of the stabilizer is preferably 0.001 to 5% by mass, more preferably 0.005 to 3% by mass, and still more preferably 0.01 to 0% with respect to the mass of the thermoplastic resin. 0.8% by mass.

(Ii) Ultraviolet absorber The optical film of the present invention may contain one or more ultraviolet absorbers. From the viewpoint of preventing deterioration, the ultraviolet absorbent is preferably excellent in the ability to absorb ultraviolet light having a wavelength of 380 nm or less and has little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of transparency. Examples include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. Particularly preferred ultraviolet absorbers are benzotriazole compounds and benzophenone compounds. Among these, a benzotriazole-based compound is preferable because unnecessary coloring with respect to the cellulose mixed ester is small. These are disclosed in JP-A-60-235852, JP-A-3-199201, 5-1907073, 5-194789, 5-271471, 6-107854, 6-118233, 6 -148430, 7-11056, 7-11055, 7-11056, 8-29619, 8-239509, and JP-A-2000-204173.

  The addition amount of the ultraviolet absorber is preferably 0.01 to 2% by mass of the thermoplastic resin, and more preferably 0.01 to 1.5% by mass.

(Iii) Light Stabilizer The optical film of the present invention may contain one or more light stabilizers. Light stabilizers include hindered amine light stabilizer (HALS) compounds, more specifically, US Pat. No. 4,619,956, columns 5-11 and US Pat. No. 4,839. No. 405, columns 3-5, 2, 2, 6, 6-tetraalkylpiperidine compounds, or their acid addition salts or complexes of them with metal compounds. These are commercially available from Asahi Denka as ADK STAB LA-57, LA-52, LA-67, LA-62, LA-77, and TINUVIN 765, 144 from Ciba Specialty Chemicals. .

  These hindered amine light stabilizers can be used alone or in combination of two or more. These hindered amine light stabilizers may of course be used in combination with additives such as plasticizers, stabilizers, UV absorbers, etc., or may be introduced into a part of the molecular structure of these additives. Good. The blending amount is determined within a range not impairing the effects of the present invention, and is generally about 0.01 to 20 parts by mass, preferably 0.02 to 15 parts per 100 parts by mass of the thermoplastic resin. About mass parts, and particularly preferably about 0.05 to 10 mass parts. The light stabilizing agent may be added at any stage of preparing the melt of the thermoplastic resin composition, for example, at the end of the melt preparation process.

(Iv) Plasticizer The optical film of the present invention may contain a plasticizer. The addition of a plasticizer is preferable from the viewpoint of film modification such as improvement of mechanical properties, imparting flexibility, imparting water absorption resistance, and reducing moisture permeability. In addition, when the optical film of the present invention is produced by a melt film formation method, the purpose is to lower the melting temperature of the film constituting material by adding a plasticizer rather than the glass transition temperature of the thermoplastic resin to be used. It will be added for the purpose of lowering the viscosity at the same heating temperature than the added thermoplastic resin. For the optical film of the present invention, for example, a plasticizer selected from a phosphoric acid ester derivative and a carboxylic acid ester derivative is preferably used. Further, a polymer obtained by polymerizing an ethylenically unsaturated monomer having a weight average molecular weight of 500 to 10,000 described in JP-A-2003-12859, an acrylic polymer, an acrylic polymer having an aromatic ring in the side chain, or cyclohexyl An acrylic polymer having a group in the side chain is also preferably used.

(V) Fine particles The optical film of the present invention may contain fine particles. Examples of the fine particles include fine particles of inorganic compounds and fine particles of organic compounds, and any of them may be used. The average primary particle size of the fine particles contained in the thermoplastic resin in the present invention is preferably 5 nm to 3 μm, more preferably 5 nm to 2.5 μm, more preferably 10 nm to 2.0 μm from the viewpoint of keeping haze low. More preferably. Here, the average primary particle size of the fine particles is determined by observing the thermoplastic resin with a transmission electron microscope (magnification of 500,000 to 1,000,000 times) and determining the average value of the primary particle sizes of 100 particles. The addition amount of the fine particles is preferably 0.005 to 1.0% by mass with respect to the thermoplastic resin, more preferably 0.01 to 0.8% by mass, and further preferably 0.02 to 0%. 4% by mass.

(Vi) Optical adjusting agent The optical film of the present invention may contain an optical adjusting agent. Examples of the optical adjusting agent include a retardation adjusting agent, for example, those described in JP-A Nos. 2001-166144, 2003-344655, 2003-248117, and 2003-66230. Can be used. By adding an optical adjusting agent, in-plane retardation (Re) and thickness direction retardation (Rth) can be controlled. A preferable addition amount is 0 to 10% by mass, more preferably 0 to 8% by mass, and further preferably 0 to 6% by mass.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[Example]
Films were produced using TOPAS # 6013 (cycloolefin copolymer, Tg = 140 ° C.) as a resin and 0.5 wt% of Irganox 1010 (radical top agent) as an additive.

  The film was formed in the order of film formation by an extruder for kneading and melting the raw materials, a die and a roll, and cooling by cooling air. Film formation was performed with a touch roll speed of 5.3 m / min, a casting roll speed of 5 m / min, and a diameter of each roll of 400 mm. Further, the temperature of the touch roll was fixed at 120 ° C., and the temperatures of the casting roll and the cooling air were changed according to the examples. The film was manufactured so that the thickness of the formed film was 100 μm.

  FIG. 5 summarizes the relationship between the film forming conditions and the optical properties of the obtained film in a list with respect to Examples (1-13) and Comparative Examples (1-4) of the present invention. Note that “cooling roll” in FIG. 5 indicates a condition for cooling the film from the side opposite to the casting roll 26 using the cooling roll 46 (temperature 60 ° C., diameter 20 mm) shown in FIG.

  In addition, the wrinkles and stripping unevenness in FIG. 5 were evaluated according to the following criteria. In addition, if it is evaluation more than (circle), it is the range acceptable as a product.

[Evaluation method of wrinkles]
The film was cut into 2 cm strips in the flow direction, and the amount of fluctuation of the strip length was used as an indicator of wrinkles.
◎ ・ ・ ・ Variation ± 0.1% or less ○ ・ ・ ・ Variation ± 0.1 to 1.0%
Δ: Variation ± 1.0-3.0%
× ・ ・ ・ Variation amount ± 3.0% or more [Evaluation method of stripping unevenness]
The evaluation was performed based on whether or not visual discrimination was possible and whether or not discrimination was possible under the unevenness enhancement condition by the point light source projection method.
◎ ・ ・ ・ I cannot see the unevenness.
○: Not visible by visual inspection, but visible by projection method.
Δ: Visible by visual inspection.
X: Visible visually.

  As shown in FIG. 5, the films of Examples 1 to 6 and 8 to 13 rapidly cool the film by blowing cooling air from the side opposite to the casting roll, and maintain the optical axis tilt structure. Thus, | Re (40 °) −Re (−40 °) | and Re (0 °) could both be achieved. In addition, by blowing cooling air to the film from the opposite side of the casting roll, the film can be cooled quickly, and the generation of wrinkles due to the temperature difference between the front and back of the film and the occurrence of peeling unevenness can be prevented. I understood.

  In addition, the film of Example 7 also brought the cooling roll into contact with the film from the side opposite to the casting roll, thereby rapidly cooling the film and maintaining the optical axis tilting structure. | Re (40 °)- Re (−40 °) | and Re (0 °) were compatible. In addition, by bringing the cooling roll into contact with the film from the opposite side of the casting roll, the film can be cooled quickly, and the generation of wrinkles due to the temperature difference between the front and back of the film and the occurrence of peeling unevenness can be prevented. I understood.

  On the other hand, about Comparative Examples 1-4 which did not cool the film from the opposite side to a casting roll, the problem generate | occur | produced in the point of the optical characteristic of a film, or a surface defect.

  Specifically, in Comparative Examples 1 and 3, although the retardation was large, peeling of the film from the casting roll was unstable, and peeling step unevenness occurred.

  Further, in Comparative Example 2 in which the casting roll temperature was low and the cooling air was not blown, wrinkles were generated on the film and the film was lifted from the casting roll, and the optical characteristics could not be measured.

  Furthermore, in Comparative Example 4 where the nip pressure (touch pressure) was low, a sufficiently large retardation could not be expressed.

  DESCRIPTION OF SYMBOLS 10 ... Film manufacturing apparatus, 12 ... Resin film, 14 ... Supply process part, 15 ... Film-forming process part, 16 ... Film temperature control process part, 17 ... Longitudinal stretch process part, 18 ... Lateral stretch process part, 20 ... Winding Process part, 22 ... Extruder, 24 ... Die, 25 ... Touch roll, 26 ... Casting roll, 40 ... Cooling air jet part, 42 ... Injection nozzle, 44 ... Temperature control means, 46 ... Cooling roll, 48 ... Roll temperature control Part, 48A ... high temperature part, 48B ... low temperature part

Claims (11)

A step of supplying a molten resin composition containing a thermoplastic resin by extruding from a discharge port of a supply means;
A step of forming a film by pressing the molten resin composition in a pressing portion formed by a first pressing surface and a second pressing surface having different moving speeds;
Peeling the film from the first clamping surface and transporting the film by the second clamping surface;
Cooling the film conveyed by the second clamping surface from the side opposite to the second clamping surface;
And a step of peeling the cooled film from the second clamping surface at the peeling position.   2. The method for producing an optical film according to claim 1, wherein in the step of cooling the film, cooling air is blown onto the film from a side opposite to the second clamping surface. When the position of the clamping part is X = 0 and the peeling position is X = L,
The method for producing an optical film according to claim 2, wherein the cooling air is blown onto the film in a range of 0.2 L ≦ X ≦ 1.0 L. Temperature _{T air} of the cooling air, when the temperature _{T 1} [° C.] of the second nip-pressing _surface, according to claim 2 or 3, characterized in that it is _{(T 1 -50) <T air} ≦ T 1 Manufacturing method of the optical film.   5. The method of manufacturing an optical film according to claim 1, wherein in the step of cooling the film, a cooling member is brought into contact with the film from a side opposite to the second pressing surface. . The temperature T ₁ [° C.] of the second clamping surface is (Tg−80) <T ₁ <Tg, where Tg [° C.] is the glass transition temperature of the resin composition. The manufacturing method of the optical film as described in any one of 1 thru | or 5.   The method for producing an optical film according to claim 1, wherein a linear pressure applied to the resin composition in the pinching portion is 0.5 MPa or more and 100 MPa or less.   The temperature T [° C.] at the discharge port of the resin composition is (Tg + 120) <T <(Tg + 200), where Tg [° C.] is the glass transition temperature of the resin composition. The manufacturing method of the optical film of 1 thru | or 7.   The method for producing an optical film according to any one of claims 1 to 8, wherein the first clamping surface and the second clamping surface are surfaces of a pair of rolls arranged to face each other.   An optical compensation film using the optical film produced by the production method according to claim 1. A supply means for supplying a molten resin composition containing a thermoplastic resin;
Clamping pressure having a first clamping surface and a second clamping surface, and molding the film by clamping the molten resin composition at a clamping portion between the first clamping surface and the second clamping surface Means,
Driving means for driving the first clamping surface and the second clamping surface so that the film is peeled off from the first clamping surface and conveyed by the second clamping surface;
A cooling means that is disposed downstream of the pressure-clamping portion of the pressure-clamping means and cools the film conveyed by the second pressure-clamping surface from the side opposite to the second pressure-clamping surface;
An apparatus for producing an optical film, comprising: a peeling means for peeling off the film cooled by the cooling means from the second clamping surface at a peeling position;
The said drive means drives the said 1st clamping surface and the said 2nd clamping surface with a different moving speed, The manufacturing apparatus of the optical film characterized by the above-mentioned.

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