JP2009280384A - Optical film, its winding method, polarizing plate using optical film, and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film used for a protective film or the like for a polarizing plate of a liquid crystal display (LCD) device, causing no air entrainment phenomenon by raking out entrainment air in a non-contact manner when winding the wide optical film, obtaining a wide film roll deformed little with the lapse of time, thereby meeting demands for the wide width and high quality of the protective film or the like for the polarizing plate, and to provide an optical film winding method, the polarizing plate using the optical film, and a display device. <P>SOLUTION: In winding the long-sized optical film with a width of 1,600-2,400 mm in roll shape, the film is wound while pressing it with air by spraying air from an air jet nozzle in a film winding upstream direction from a position on the outer surface of the film corresponding to an angle range of 0-45° in a film winding direction centering on a center axis of a film winding roll from a winding start position of the film winding roll. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to various functional films such as a protective film for polarizing plates used for liquid crystal display devices (LCDs), retardation films, viewing angle widening films, antireflection films used for plasma displays, and organic EL (electroluminescence) displays. It is related with the optical film which can be utilized also for various functional films etc. which are used by the above, the winding method, the polarizing plate using an optical film, and a display apparatus.

  Liquid crystal display devices have come to be used in televisions and large monitors due to improvements in image quality and high-definition technology. In particular, these liquid crystal display devices have been increased in size and reduced in cost through efficient production. Therefore, the demand for the liquid crystal display device is strengthened, and the widening of the optical film is required.

  In recent years, the demand for optical films has been increasing rapidly in response to the rapid growth of liquid crystal TVs, and there is a strong demand for improved productivity. In order to cope with an increase in the screen size of a liquid crystal TV, it is necessary to make a wide film that is wider than a conventional film.

  Conventionally, when such an optical film is produced, when using a solution casting film forming method, a solution in which a resin is dissolved in a solvent is cast on a metal support, and the solvent is removed in a drying step. Manufactured by winding a film. In addition, when using the melt casting film forming method, the resin is melted by heat, and the molten resin that has become hot is melt-extruded from a casting die onto a cooling roll to form a film, thereby reducing the temperature of the film. Manufactured by obtaining a transport process and winding the film.

  In any method, when winding the film after production into a roll, if air is caught between the films, the film roll may be unrolled, or the air may escape from the film roll over time, There was a problem that deformation occurred in the film roll.

  Conventionally, a method of removing air trapped in the film by so-called air knives installed on both sides of the film before winding is common, but in the conventional method using an air knife, the air is trapped in the film. There was a problem that there was a possibility.

  Therefore, in order to prevent the occurrence of such troubles during film winding, the following methods are proposed in Patent Documents 1 and 2 below.

  First, Patent Document 1 discloses that a film roll (winding portion) is air blown to a film roll in an angle range of 60 to 240 degrees in the winding direction from the winding start position, so-called black belts and wrinkles are wound. A method for preventing the occurrence of depression, winding and slipping is described. In this patent document 1, the width | variety of the film manufactured was 1000-1500m.

Patent Document 2 includes a touch roll that is pressed against a sheet material (film) wound on a winding shaft, and extrudes air with the pressing force of the touch roll to prevent the film roll from being turbulent. Is described.
JP 2005-96915 A JP 2000-86027 A

  However, in the method described in Patent Document 1, for example, when a long optical film having a wide width of 1600 to 2400 mm is wound in a roll shape, air is blown in the winding direction from the winding start position to 60 in the winding direction. When it is performed in an angle range of ˜240 degrees, there is a problem that the air is caught.

  Further, in the method using the touch roll described in Patent Document 2, it is necessary to replace the touch roll every time the film width is changed, and since it is a contact type, the optical film is charged and pressed, resulting in a failure. there were.

  The object of the present invention is to solve the above-mentioned problems of the prior art, and to scrape out the entrained air in a non-contact manner, and does not generate an air entrainment phenomenon when winding a wide optical film, and deforms over time. Optical film that can meet the demands of widening and high quality such as a protective film for polarizing plates, a winding method thereof, and a polarizing plate using the optical film And providing a display device.

  In order to achieve the above object, the invention of claim 1 is a method of winding an optical film in which a long optical film having a width of 1600 to 2400 mm is wound in a roll shape. Film winding from the film winding roll position relative to the film outer surface position corresponding to an angle range of 0 to 45 degrees in the film winding direction from the film winding roll winding start position to the center axis of the film winding roll It is characterized by blowing air while blowing the air toward the upstream direction from an air jet nozzle and pressing the film with air.

  The invention of claim 2 is the optical film winding method according to claim 1, wherein the film pressing force by the blown air is greatest at the center in the width direction of the film and gradually toward the both ends of the film. It is characterized by being made smaller.

  Invention of Claim 3 is the winding method of the optical film of Claim 1 or 2, Comprising: The ejection air from an air ejection nozzle winds up 0.7 to 1.0 time of a film width direction. It is characterized by being sprayed onto the film.

  Invention of Claim 4 is the winding method of the optical film as described in any one of Claims 1-3, Comprising: The pressing force of the film width direction center part by the jet air from a jet nozzle is, The pressure is 1.0 to 10.0 kPa, and the pressing force at both ends in the width direction of the film by the blown air is smaller than the pressing force at the center in the width direction of the film and is 0.5 to 9.5 kPa. Yes.

  Here, the central portion in the film width direction refers to a portion corresponding to 60 to 80% of the total film width, and both end portions in the film width direction are 10% of the film width inward from both ends of the film. The part corresponding to ~ 20% shall be said.

  Invention of Claim 5 is the winding method of the optical film as described in any one of Claims 1-4, Comprising: When winding a film, it is sprayed with respect to the film outer surface of a winding roll. Then, the air is sucked by an air intake device installed near the film on the upstream side in the winding direction from the winding start position at the lower end of the film winding roll.

  The invention of an optical film of claim 6 is characterized in that it is wound up by the method of winding up an optical film according to any one of claims 1 to 5.

  The invention of a polarizing plate according to a seventh aspect is characterized in that the optical film according to the sixth aspect is provided on at least one surface.

  An invention of a display device according to an eighth aspect is characterized by using the polarizing plate according to the seventh aspect.

  The method for winding an optical film according to the present invention is a method for winding an optical film in which a long optical film having a width of 1600 to 2400 mm is wound in a roll shape. Air from the winding start position to the film outer surface position corresponding to an angle range of 0 to 45 degrees in the film winding direction centering on the central axis of the film winding roll. The air is blown from the air jet nozzle, and the film is wound while being pressed with air. According to the invention of claim 1, the entrained air can be scraped out in a non-contact manner, and a wide optical film can be wound. Sometimes, it is possible to obtain a wide film roll with little deformation over time without causing an air entrainment phenomenon. An effect that it is possible to meet the requirements of the wide and high quality, such as Lum.

  The invention of claim 2 is the optical film winding method according to claim 1, wherein the film pressing force by the blown air is greatest at the center in the width direction of the film and gradually toward the both ends of the film. According to the invention of claim 2, since the air escape effect at the center in the width direction of the film is increased, the effect of reducing buckling after winding into a roll shape is achieved. .

  Invention of Claim 3 is the winding method of the optical film of Claim 1 or 2, Comprising: The ejection air from an air ejection nozzle winds up 0.7 to 1.0 time of a film width direction. According to the invention of claim 3, there is an effect that it is possible to suppress film roll deformation due to air loss over time without blowing air between the films.

  Invention of Claim 4 is the winding method of the optical film as described in any one of Claims 1-3, Comprising: The pressing force of the film width direction center part by the jet air from a jet nozzle is, It is 1.0-10.0 kPa, and the pressing force of the film width direction both ends by the same blowing air is smaller than the pressing force of the film width direction center part, and is 0.5-9.5 kPa.

  Here, the central portion in the film width direction refers to a portion corresponding to 60 to 80% of the total film width, and both end portions in the film width direction are 10% of the film width inward from both ends of the film. The part corresponding to ~ 20% shall be said.

  According to invention of Claim 4, since a pressing force can be provided without a deformation | transformation of a film without contact, there exists an effect that a film with high flatness can be provided.

  Invention of Claim 5 is the winding method of the optical film as described in any one of Claims 1-4, Comprising: When winding a film, it is sprayed with respect to the film outer surface of a winding roll. The air after the air is sucked in by an air intake device installed near the film on the upstream side in the winding direction from the winding start position at the lower end of the film winding roll. Since the amount of the entrained air that is blown away is reduced in the film roll, the film roll having an excellent appearance can be produced.

  The invention of the optical film of claim 6 is characterized in that it is wound by the method of winding an optical film according to any one of claims 1 to 5, and the optical film of claim 6 According to the invention, at the time of winding a wide optical film, it is possible to obtain a wide film roll with little deformation over time without causing an air entrainment phenomenon, and having optical characteristics excellent in transparency and flatness. There is an effect that it is a thing.

  Since the invention of the polarizing plate of claim 7 has the optical film of claim 6 on at least one surface, according to the invention of the polarizing plate of claim 7, this is incorporated into a display device. Even in this case, there is an effect that the visibility of the display device is excellent without causing color unevenness that looks whitish when viewed from the front and oblique directions.

  The invention of the display device of claim 8 uses the polarizing plate of claim 7, and according to the display device of claim 7, there is no color unevenness that appears whitish when viewed from the front and obliquely. There is an effect that the visibility of the display device is excellent.

  Next, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  1 and 2 are flow sheets showing an embodiment of an apparatus for carrying out an optical film winding method according to the present invention.

  The winding method of the optical film by this invention winds up the elongate optical film which has a width | variety of 1600-2400 mm in roll shape.

  First, referring to FIG. 1, a film (F) is fed from a roll (feeding means) (1) (1) of an original winding film such as a cellulose ester film produced by a solution casting film forming method or a melt casting film forming method. The case of winding in the unwinding and winding roll (winding means) (2) will be described.

  In the present invention, any film winding device may be used, but is not limited to the illustrated embodiment.

  In FIG. 1, a film (F) fed out from a feeding roll (feeding means) (1) includes a first conveying roll (11) to a third conveying roll (13), a dancer roll (14), and a fourth conveying roll. After (15), it is wound up by a winding roll (winding means) (2).

  Here, the winding roll (winding means) (2) includes a winding shaft (2a), a winding motor (not shown) that transmits rotation to the winding shaft (2a) and has a variable number of rotations. ing.

  The film winding speed by the winding roll (2) is set to be almost the same as the film feeding speed by the feeding roll (feeding means) (1) so that it becomes a trapezoidal speed curve consisting of acceleration, constant speed, and deceleration. Further, it is controlled by the control means.

  Referring to FIG. 2, the optical film winding method according to the present invention, when winding the film (F), starts from the winding start position of the film winding roll (2) and the central axis of the film winding roll (2). With respect to the film outer surface position corresponding to the angle range of 0 to 45 degrees, preferably 0 to 30 degrees in the film winding direction, air is blown from the position toward the upstream direction of film winding from the air blowing nozzle. The film (F) is wound while being pressed with air.

  In this way, by blowing high-pressure air onto the peripheral surface of the film winding roll (2) and air-pressing the film (F), air that has been wound during film winding is removed in a so-called non-contact manner. It is.

  Here, the air ejection nozzle (3) has a film winding roll so that the width direction of the air nozzle opening (that is, the film width direction) and the central axis of the film winding roll (2) are parallel to each other. It is arrange | positioned near the lower peripheral surface of (2), and is 0-45 degree | times in a film winding direction centering | focusing on the central axis of a film winding roll (2) from the winding start position of a film winding roll (2) With respect to the position of the film outer surface corresponding to the angle range, it is arranged to blow air while pressing the film (F) with air by blowing air from the position toward the upstream direction of film winding from the air blowing nozzle. . Note that the number of installed air ejection nozzles (3) may not be one.

  Here, when winding the film (F), an angle range of 0 to 45 degrees in the film winding direction from the winding start position of the film winding roll (2) about the central axis of the film winding roll (2). Is directed to blow the air from the position toward the film winding upstream direction from the air jet nozzle to the position of the outer surface of the film, but the position is an angle of less than 0 degree or an angle of more than 45 degrees. If the position is on the outer surface of the film corresponding to, the blown air itself becomes entrained air and is wound on the film roll, which is not preferable.

  In the present invention, if the width of the optical film wound up in a roll shape is less than 1600 mm, the blown air wraps around from the side surface of the film roll, and the amount of entrained air increases. Moreover, when the width of the optical film wound up in a roll shape exceeds 2400 mm, the entrained air does not escape uniformly and the film roll is deformed, which is not preferable.

  A high pressure blower (not shown) is connected to the air ejection nozzle (3) as an air generation source, and a humidity / temperature adjusting device for the ejection air is provided on the way, for example, relative humidity of the ejection air: 20 to 24 %, And the temperature of the jet air: adjusted to 20 to 25 ° C.

  And in the winding method of the optical film by this invention, the film pressing force by blowing air is the largest in the width direction center part of a film (F), and it becomes small gradually as it goes to the both ends of a film (F). It is preferable to make it.

  Here, the slit-shaped air nozzle opening provided in the air ejection nozzle (3) becomes wider toward the both ends in the width direction, and the pressing force of the ejection air is reduced by the film (F). It has been adjusted so that the width center is the strongest. Thereby, air becomes easy to escape from the end face of the film winding roll (2).

  Furthermore, in the winding method of the optical film according to the present invention, it is preferable that the air ejected from the air ejection nozzle (3) is blown onto the winding film over 0.7 to 1.0 times in the width direction of the film.

  Here, if the air ejected from the air ejection nozzle (3) is less than 0.7 times the width direction of the film, the end of the film will float, and the air will be caught in the roll from there. It is not preferable. Further, if the air blown from the air blow nozzle (3) exceeds 1.0 times in the width direction of the film, the blown air is caught between the films and the roll appearance is impaired.

  Moreover, in the winding method of the optical film of this invention, the pressing force of the film width direction center part by the jet air from a jet nozzle (3) is 1.0-10.0 kPa, The film width by the jet air It is preferable that the pressing force at both ends in the hand direction is smaller than the pressing force at the center in the width direction of the film and is 0.5 to 9.5 kPa.

  Here, the central portion in the film width direction refers to a portion corresponding to 60 to 80% of the total film width, and both end portions in the film width direction are 10% of the film width inward from both ends of the film. The part corresponding to ~ 20% shall be said.

  And, if the pressing force at the central portion in the width direction of the film due to the air jetted from the jet nozzle (3) is less than 1.0 kPa, the amount of entrained air cannot be reduced because there is almost no pressing effect, and the roll appearance is in diameter. It is not preferable because it deteriorates. Further, if the pressing force at the center in the width direction of the film due to the air jetted from the jet nozzle (3) exceeds 10.0 kPa, a failure occurs in which the films stick to each other due to the jet air, which is not preferable.

  Further, the pressing force at both ends in the width direction of the film due to the blown air is smaller than the pressing force at the center portion in the width direction of the film and less than 0.5 kPa, or the pressing force at both ends in the width direction of the film due to the blown air is If it is smaller than the pressing force at the center in the width direction and exceeds 9.5 kPa, the air escape effect at the center in the width direction of the film is weakened, and buckling failure after winding in a roll shape increases, which is not preferable.

  When winding of the film (F) as described above is started by the method of the present invention, the length of the film (F) wound by the counter is measured, and when the counter value reaches a predetermined value, that is, When the film (F) is wound up to a predetermined length, the feeding roll (1) and the winding roll (2) are stopped, and the cutter (5) is operated to cut the film (F).

  Then, after setting the front-end | tip part of the subsequent part of the cut | disconnected film (F) to the winding shaft (2a) of a winding roll (2), said operation | movement is repeated.

  During the winding operation, when the lower limit detection sensor (17) detects the dancer roll (14) in order to keep the film feeding speed (= film winding speed) constant, the feeding speed of the feeding means is slightly lower. When the upper limit detection sensor (16) detects the dancer roller (14), the feeding speed is slightly increased so that the dancer roller (14) has a lower limit detection sensor (17) and an upper limit detection sensor (16). The film feeding speed (= film winding speed) is controlled to a constant speed.

  Here, the film winding speed by the winding roll (2) is substantially the same as the film feeding speed by the feeding roll (feeding means) (1), for example, 4 to 100 m / min.

  In addition, the dancer roll (14) is set to the stop state at the time of acceleration and deceleration of the film winding speed (film feeding speed) by the winding roll (2).

  Moreover, in the winding method of the optical film by this invention, when winding a film (F), the air after being sprayed with respect to the film outer surface of a winding roll (2) is film winding roll ( 2) It is preferable that the air is sucked by an air intake device (pressure reducing device) (4) installed near the upper part of the film (F) on the upstream side in the winding direction from the winding start position at the lower end.

  That is, since the air blown to the outer surface of the film of the take-up roll (2) diffuses somewhat, when the film (F) is taken up, the air is taken up by the film take-up roll (2). There is a risk that. Therefore, the air blower installed near the upper side of the film (F) on the upstream side in the winding direction from the winding start position at the lower end of the film winding roll (2) is blown from the air blowing nozzle (3) opening. (Decompression device) Intake by (4).

  The intake pressure by the intake device (decompression device) (4) at this time is preferably -50 to -600 Pa, for example.

  The method for winding an optical film according to the present invention is also applicable to the case of winding an optical film produced by any of the solution casting film forming method and the melt casting film forming method.

  Here, first, a method for producing an optical film by a solution casting film forming method will be described.

  Although not shown in the drawings, the method for producing an optical film by the solution casting method is to cast a resin solution (dope) containing a thermoplastic resin, an organic solvent, and an additive from a casting die onto a metal support. A casting process for forming a casting film (web) and peeling the web from the support, a drying process for drying the web while being transported by a transport roll, a stretching process for stretching the web with a tenter, and a stretching process. The latter drying process provided in the back side of this tenter, and the winding-up process which winds up the film which went out of the latter drying process are provided.

  In the method for producing an optical film by solution casting, a dope is first cast from a casting die on a metal support made of, for example, a stainless steel rotationally driven endless belt that is transported infinitely.

  The casting of the dope by the casting die includes a doctor blade method in which the film thickness of the cast dope film (web) is adjusted with a blade, or a reverse roll coater method in which the film is adjusted with a reverse rotating roll, etc. A method using a pressure die that can adjust the slit shape of the die portion and easily make the film thickness uniform is preferable. Examples of the pressure die include a coat hanger die and a T die, and any of them is preferably used. The casting die is usually provided with a decompression chamber.

  Here, the solid content concentration of the cellulose ester solution (dope) is preferably 15 to 30% by weight. If the solid content concentration of the cellulose ester solution (dope) is less than 15% by weight, sufficient drying on the metal support cannot be performed, and a part of the dope film (web) remains on the metal support during peeling, Since it leads to belt contamination, it is not preferable. On the other hand, when the solid content concentration exceeds 30%, the dope viscosity is increased, filter clogging is accelerated in the dope adjusting step, and pressure is increased during casting onto a metal support, which is not preferable.

  In the illustrated film forming apparatus having a rotationally driven endless belt as a metal support, the metal support is held by a pair of front and rear winding drums and a plurality of intermediate rolls. One or both of the winding drums at both ends of the metal support made of a rotationally driven endless belt are provided with a drive device that applies tension (not shown) to the belt metal support, whereby the metal support is tensioned. It is used in a state where it is hung and stretched.

  It is preferable that the width of the metal support is 1600 to 2400 mm, the casting width of the cellulose ester solution is 1500 to 2300 mm, and the width of the film after winding is 1600 to 2400 mm. Thereby, the wide optical film for liquid crystal display devices can be manufactured by a metal support body system.

  Moreover, it is preferable that the moving speed of a metal support body is 40-200 m / min.

  When an endless belt is used as the metal support, the belt temperature during film formation is from a general temperature range of 0 ° C. to a temperature lower than the boiling point of the solvent, and a mixed solvent having a temperature lower than the boiling point of the lowest boiling solvent. Furthermore, the range of 5 degreeC-solvent boiling point -5 degreeC is more preferable. At this time, it is necessary to control the ambient atmospheric humidity above the dew point.

  The dope cast on the surface of the metal support as described above also increases the strength (film strength) of the gel film by promoting drying until stripping.

  In the system using an endless belt as the metal support, the amount of residual solvent in the web is 150% by weight because the web is dried and solidified on the metal support until the web has a film strength that can be peeled off from the metal support by a peeling roll. It is preferable to dry to below, and 70 to 130 weight% is more preferable. Moreover, as for the web temperature when peeling a web from a metal support body, 0-30 degreeC is preferable. In addition, immediately after the web is peeled off from the metal support, the temperature once drops rapidly due to solvent evaporation from the metal support close-contact surface side, and volatile components such as water vapor and solvent vapor in the atmosphere tend to condense. The web temperature at that time is more preferably 5 to 30 ° C.

  Here, the residual solvent amount can be expressed by the following equation.

Residual solvent amount (% by weight) = {(M−N) / N} × 100
In the formula, M is the weight of the web at an arbitrary time point, and N is the weight when a weight M is dried at a temperature of 110 ° C. for 3 hours.

  The dope film (web) formed by the dope cast on the metal support is heated on the metal support, and the solvent is evaporated until the web can be peeled from the metal support by a peeling roll.

  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 metal support by a liquid, a method of transferring heat from the front and back by radiant heat, etc., which are used alone or in combination as appropriate. That's fine. It is preferable to dry with hot air from the viewpoint of simplicity. For example, it is dried by the drying air blown from the warm air inlet at the front portion of the bottom of the initial drying device and exhausted from the outlet at the rear portion of the ceiling of the initial drying device. It is dried by the wind being discharged.

  In the system using an endless belt for the metal support, the peeling tension when peeling the web from the metal support with a peeling roll is peeled off with a tension larger than the peeling force obtained by peeling force measurement like JIS Z 0237. However, this is done at a higher level for stabilization because the peeling position may be taken downstream when the peeling tension is made equal to the peeling force obtained by the JIS measurement method during high-speed film formation. Even if the film is formed with the same peel tension in the process, it has been confirmed that the variation of the crossed Nicols transmittance (CNT) of the film is greatly reduced when the peel force by the JIS measurement method is lowered.

  As a peeling tension value in the process, when preparing a retardation film that requires a high retardation value, the web after peeling from the support is prevented from extending in the MD direction due to the conveyance tension (extends in the MD direction). Then, when it is stretched in the TD direction by a subsequent tenter, it is difficult to raise the desired retardation value), and in other applications, peeling is performed at a high tension of about 300 N / m from a low tension of about 50 N / m.

  Next, in the production of the film for a liquid crystal display device, the stretching step is preferably a tenter method in which both side edge portions of the web are fixed with clips or the like in order to improve the flatness and dimensional stability of the film.

  The residual solvent amount of the web immediately before entering the tenter of the stretching process is preferably 2 to 100% by weight.

  In this embodiment, the stretch ratio of the web in the tenter of the stretching process is 1.03 to 2 times, preferably 1.05 to 1.8 times, and more preferably 1.05 to 1.6 times. It is desirable. Moreover, the temperature of the warm air blown from the warm air blowing slit port in the tenter in the stretching process is 20 to 200 ° C, preferably 40 to 190 ° C, and more preferably 60 to 180 ° C.

  In the latter drying apparatus provided on the rear side of the tenter in the stretching process, the film (web) is meandered by a plurality of conveying rolls arranged in a staggered manner as viewed from the side, and the film is dried in the meantime. . The film transport tension in the drying process is affected by the physical properties of the dope, the amount of residual solvent in the peeling and film transport process, the drying temperature, and the like. It is 3 to 3N, and 0.4 to 2.7N is more preferable.

  The means for drying the film (web) is not particularly limited, and is generally performed with hot air, infrared rays, a heating roll, microwaves, or the like. It is preferable to dry with hot air from the viewpoint of simplicity. For example, it is dried by the drying air blown from the warm air inlet at the front portion of the bottom of the late dryer, and exhausted from the outlet at the rear portion of the ceiling of the late dryer. It is dried by the wind being discharged. The temperature of the drying air is preferably 40 to 160 ° C., more preferably 50 to 150 ° C. in order to improve the flatness and dimensional stability.

  These steps from casting to post-drying may be performed in an air atmosphere or in an inert gas atmosphere such as nitrogen gas. In this case, it goes without saying that the dry atmosphere is carried out in consideration of the explosion limit concentration of the solvent.

  For example, a cellulose ester film that has exited the late drying apparatus is generally subjected to a process of forming an emboss on the film by an embossing apparatus (not shown) at a stage prior to winding by a winding apparatus.

  Here, the height h (μm) of the emboss is set in the range of 0.05 to 0.3 times the film thickness T, and the width W is set in the range of 0.005 to 0.02 times the film width L. . Embossing may be formed on both sides of the film. In this case, the height h1 + h2 (μm) of the emboss is set in the range of 0.05 to 0.3 times the film thickness T, and the width W is set in the range of 0.005 to 0.02 times the film width L. . For example, when the film thickness is 40 μm, the embossing height h 1 + h 2 (μm) is set to 2 to 12 μm. The emboss width is set to 5 to 30 mm.

  The film after drying is taken up by a take-up device to obtain the original roll of the optical film. Film (2 having a good dimensional stability can be obtained by setting the residual solvent amount of 2 to 0.5% by weight or less, preferably 0.1% by weight or less.

  The winding method of the film may be a generally used winder, and there are methods for controlling the tension such as a constant torque method, a constant tension method, a taper tension method, a program tension control method with a constant internal stress, etc. Use it properly.

  The film may be joined to the winding core (winding core) by either a double-sided adhesive tape or a single-sided adhesive tape.

  In the optical film according to the present embodiment, the width of the film after winding is preferably 1600 to 2400 mm, for example.

  The optical film winding method according to the present invention winds an optical film such as a cellulose ester film manufactured by the solution casting method as described above by a winding roll (winding means) in the final stage of manufacturing. The case is also applicable.

  In this case, as shown in FIG. 2, the air ejection nozzle (3) includes a width direction of the air nozzle opening (that is, a film width direction), and a central axis of the film winding roll (2). Are arranged near the lower peripheral surface of the film winding roll (2) so as to be parallel to each other. And when winding up optical films (F), such as a cellulose-ester film manufactured by said solution casting film forming method, winding-up of a film winding roll (2) is started by the winding method of this invention. With respect to the position on the outer surface of the film corresponding to an angle range of 0 to 45 degrees in the film winding direction around the central axis of the film winding roll (2) from the position, air that is directed toward the upstream direction of the film winding from that position The film is blown from the air ejection nozzle (3) while pressing the film (F) with air.

  In this way, by blowing high-pressure air onto the peripheral surface of the film winding roll (2) and air-pressing the film (F), air that has been wound during film winding is removed in a so-called non-contact manner. It is. Note that the number of installed air ejection nozzles (3) may not be one.

  In addition, the following points are the same when an optical film such as a cellulose ester film manufactured by a solution casting film forming method is wound by a winding roll (winding means) (2) in the final stage of manufacturing. is there.

  That is, a high-pressure blower (not shown) is connected to the air ejection nozzle (3) shown in FIG. 2 as an air generation source, and a humidity / temperature adjusting device for the ejection air is provided on the way. The relative humidity is adjusted to 20 to 24%, and the temperature of the blown air is adjusted to 20 to 25 ° C.

  And in the winding method of the optical film by this invention, the film pressing force by blowing air is the largest in the width direction center part of a film (F), and it becomes small gradually as it goes to the both ends of a film (F). It is preferable to make it.

  Here, the slit-shaped air nozzle opening provided in the air ejection nozzle (3) becomes wider toward the both ends in the width direction, and the pressing force of the ejection air is reduced by the film (F). It has been adjusted so that the width center is the strongest. Thereby, air becomes easy to escape from the end face of the film winding roll (2).

  Furthermore, in the winding method of the optical film according to the present invention, it is preferable that the air ejected from the air ejection nozzle (3) is blown onto the winding film over 0.7 to 1.0 times in the width direction of the film.

  Moreover, in the winding method of the optical film of this invention, the pressing force of the film width direction center part by the jet air from a jet nozzle (3) is 1.0-10.0 kPa, The film width by the jet air It is preferable that the pressing force at both ends in the hand direction is smaller than the pressing force at the center in the width direction of the film and is 0.5 to 9.5 kPa.

  Moreover, in the winding method of the optical film by this invention, when winding a film (F), the air after being sprayed with respect to the film outer surface of a winding roll (2) is film winding roll ( 2) It is preferable that the air is sucked by an air intake device (pressure reducing device) (4) installed near the upper part of the film (F) on the upstream side in the winding direction from the winding start position at the lower end.

  In the method for producing an optical film by the solution casting method of the present embodiment, the dope for producing the optical film contains a thermoplastic resin such as a cellulose ester resin as a main material, and includes a plasticizer and a retardation. It contains at least one substance selected from a regulator, an ultraviolet absorber, fine particles, and a low molecular weight substance, and a solvent. Hereinafter, these will be described.

  In the method for producing an optical film by the solution casting film forming method of the present embodiment, various resins can be used as the film material, and among them, cellulose ester is preferable.

  A cellulose ester is a cellulose ester in which a hydroxyl group derived from cellulose is substituted with an acyl group or the like. Examples thereof include cellulose acylates such as cellulose acetate, cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate and cellulose acetate propionate butyrate, and cellulose acetate having an aliphatic polyester graft side chain. Among these, cellulose acetate, cellulose acetate propionate, and cellulose acetate having an aliphatic polyester graft side chain are preferable. Other substituents may be included as long as the effects of the present embodiment are not impaired.

  As an example of cellulose triacetate, the substitution degree of acetyl groups is preferably 2.0 or more and 3.0 or less. By setting the degree of substitution within this range, good moldability can be obtained, and desired in-plane retardation (Ro) and thickness direction retardation (Rt) can be obtained. If the substitution degree of the acetyl group is lower than this range, the heat resistance as a retardation film, particularly the dimensional stability under wet heat may be inferior, and if the substitution degree is too large, the necessary retardation characteristics will not be exhibited. There is a case.

  Although there is no limitation in particular as a cellulose of the raw material of the cellulose ester used for this Embodiment, Cotton linter, wood pulp, kenaf etc. can be mentioned. Moreover, the cellulose ester obtained from them can be mixed and used in arbitrary ratios, respectively.

  In the present embodiment, the number average molecular weight of the cellulose ester is preferably in the range of 60,000 to 300,000 because the mechanical strength of the resulting film is strong. Furthermore, 70,000-200,000 are preferable.

  In the present embodiment, various additives can be added to the cellulose ester.

  In the method for producing an optical film by the solution casting film forming method according to the present embodiment, an organic solvent having good solubility with respect to the cellulose derivative is referred to as a good solvent, and exhibits a main effect on dissolution, An organic solvent used in a large amount is called a main (organic) solvent or a main (organic) solvent.

  Examples of good solvents include ketones such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethers such as tetrahydrofuran (THF), 1,4-dioxane, 1,3-dioxolane, 1,2-dimethoxyethane, formic acid Esters such as methyl, ethyl formate, methyl acetate, ethyl acetate, amyl acetate, γ-butyrolactone, methyl cellosolve, dimethylimidazolinone, dimethylformamide, dimethylacetamide, acetonitrile, dimethyl sulfoxide, sulfolane, nitroethane, methylene chloride And 1,3-dioxolane, THF, methyl ethyl ketone, acetone, methyl acetate and methylene chloride are preferable.

  In addition to the organic solvent, the dope preferably contains 1 to 40% by weight of an alcohol having 1 to 4 carbon atoms. After the dope is cast on a metal support, the alcohol starts to evaporate and the ratio of the alcohol increases, thereby making the web gel, making the web strong and easy to peel off from the metal support. It is also used as a gelling solvent, and when these ratios are small, it also has a role of promoting the dissolution of the cellulose derivative of the non-chlorine organic solvent.

  Examples of the alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, and propylene glycol monomethyl ether. Of these, ethanol is preferred because it has excellent dope stability, has a relatively low boiling point, good drying properties, and no toxicity. These organic solvents alone are not soluble in cellulose derivatives and are called poor solvents.

  The most preferable solvent for dissolving a cellulose derivative, which is a preferable polymer compound satisfying such conditions, at a high concentration is a mixed solvent having a ratio of methylene chloride: ethanol of 95: 5 to 80:20. Alternatively, a mixed solvent having a methyl acetate: ethanol ratio of 60:40 to 95: 5 is also preferably used.

  The film in the present embodiment includes a plasticizer that imparts processability, flexibility, and moisture resistance to the film, fine particles (matting agent) that impart slipperiness to the film, an ultraviolet absorber that imparts an ultraviolet absorbing function, You may contain the antioxidant etc. which prevent deterioration.

  The plasticizer used in the present embodiment is not particularly limited, but a cellulose derivative or a reactive metal compound capable of hydrolytic polycondensation so as not to generate haze, bleed out or volatilize from the film. It preferably has a functional group capable of interacting with the polycondensate of the above by a hydrogen bond or the like.

  Examples of such functional groups include hydroxyl groups, ether groups, carbonyl groups, ester groups, carboxylic acid residues, amino groups, imino groups, amide groups, imide groups, cyano groups, nitro groups, sulfonyl groups, sulfonic acid residues, Examples thereof include a phosphonyl group and a phosphonic acid residue, and a carbonyl group, an ester group and a phosphonyl group are preferred.

  Examples of such plasticizers include phosphate ester plasticizers, phthalate ester plasticizers, trimellitic acid ester plasticizers, pyromellitic acid plasticizers, polyhydric alcohol ester plasticizers, glycolate plasticizers. Agents, citric acid ester plasticizers, fatty acid ester plasticizers, carboxylic acid ester plasticizers, polyester plasticizers, etc. can be preferably used, but polyhydric alcohol ester plasticizers, glycolate plasticizers are particularly preferred. And non-phosphate ester plasticizers such as polycarboxylic acid ester plasticizers.

  The polyhydric alcohol ester is composed of an ester of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, and preferably has an aromatic ring or a cycloalkyl ring in the molecule.

  The polyhydric alcohol used in the present embodiment is represented by the following general formula (1).

R ^1- (OH) n (1)
In the formula, R ¹ represents an n-valent organic group, and n represents a positive integer of 2 or more.

Examples of preferred polyhydric alcohols include, but are not limited to, the following.

  Examples of preferred polyhydric alcohols include adonitol, arabitol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, 1, 2-butanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol, 1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol, gallium Examples include lactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol, trimethylolpropane, trimethylolethane, and xylitol. In particular, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, sorbitol, trimethylolpropane, and xylitol are preferable.

  There is no restriction | limiting in particular as monocarboxylic acid used for the polyhydric alcohol ester of this Embodiment, Well-known aliphatic monocarboxylic acid, alicyclic monocarboxylic acid, aromatic monocarboxylic acid, etc. can be used. Use of an alicyclic monocarboxylic acid or aromatic monocarboxylic acid is preferred in terms of improving moisture permeability and retention.

  Examples of preferred monocarboxylic acids include the following, but are not limited thereto.

  As the aliphatic monocarboxylic acid, a fatty acid having a straight chain or side chain having 1 to 32 carbon atoms can be preferably used. The number of carbon atoms is more preferably 1-20, and particularly preferably 1-10. When acetic acid is contained, the compatibility with the cellulose derivative is increased, and it is also preferable to use a mixture of acetic acid and another monocarboxylic acid.

  Examples of preferred aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, 2-ethyl-hexanecarboxylic acid, undecylic acid, lauric acid, Tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptacosanoic acid, montanic acid, mellicic acid, laccellic acid, etc., undecylen Examples thereof include unsaturated fatty acids such as acid, oleic acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid.

  Examples of preferred alicyclic monocarboxylic acids include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid, or derivatives thereof.

  Examples of preferred aromatic monocarboxylic acids include those in which an alkyl group is introduced into the benzene ring of benzoic acid such as benzoic acid and toluic acid, and two or more benzene rings such as biphenylcarboxylic acid, naphthalenecarboxylic acid, and tetralincarboxylic acid. Examples thereof include aromatic monocarboxylic acids and derivatives thereof, and benzoic acid is particularly preferable.

  The molecular weight of the polyhydric alcohol ester is not particularly limited, but is preferably 300 to 1,500, and more preferably 350 to 750. A higher molecular weight is preferred because it is less likely to volatilize, and a smaller one is preferred in terms of moisture permeability and compatibility with cellulose derivatives.

  The carboxylic acid used for the polyhydric alcohol ester may be one kind or a mixture of two or more kinds. Moreover, all the OH groups in the polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

  The glycolate plasticizer is not particularly limited, but a glycolate plasticizer having an aromatic ring or a cycloalkyl ring in the molecule can be preferably used. As preferred glycolate plasticizers, for example, butyl phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate and the like can be used.

  For phosphate ester plasticizers, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, etc. For phthalate ester plasticizers, diethyl phthalate, dimethoxy Ethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dicyclohexyl phthalate, etc. can be used, but in this embodiment, it is preferable that substantially no phosphate ester plasticizer is contained. .

  Here, “substantially does not contain” means that the content of the phosphoric ester plasticizer is less than 1% by weight, preferably less than 0.1% by weight, particularly preferably not added. . These plasticizers can be used alone or in combination of two or more.

  The amount of the plasticizer used is preferably 1 to 20% by weight. 6 to 16% by weight is further preferable, and 8 to 13% by weight is particularly preferable. If the amount of the plasticizer used is less than 1% by weight relative to the cellulose derivative, the effect of reducing the moisture permeability of the film is small, so this is not preferred. If it exceeds 20% by weight, the plasticizer bleeds out from the film, and the film Since the physical properties of the material deteriorate, it is not preferable.

  In order to impart slipperiness to the cellulose derivative in the present embodiment, it is preferable to add fine particles such as a matting agent. Examples of the fine particles include fine particles of an inorganic compound or fine particles of an organic compound.

  Examples of the fine particles of the inorganic compound include fine particles of silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, tin oxide and the like. Of these, fine particles of a compound containing a silicon atom are preferred, and fine silicon dioxide particles are particularly preferred. Examples of the silicon dioxide fine particles include Aerosil 200, 200V, 300, R972, R972V, R974, R202, R812, R805, OX50, and TT600 manufactured by Aerosil Co., Ltd.

  Examples of the organic compound fine particles include fine particles such as acrylic resin, silicone resin, fluorine compound resin, and urethane resin.

  The primary particle size of the fine particles is not particularly limited, but the average particle size in the film is preferably about 0.05 to 5.0 μm. More preferably, it is 0.1-1.0 micrometer.

  When the cellulose ester film is observed with an electron microscope or an optical microscope, the average particle diameter of the fine particles indicates an average value of the lengths in the major axis direction of the particles at the observation position of the film. As long as the particles are observed in the film, they may be primary particles or secondary particles in which the primary particles are aggregated, but most of the particles that are usually observed are secondary particles.

As an example of the measurement method, 10 vertical cross-sectional photographs are taken at random for one film, and the number of particles in 100 μm ² whose major axis length is in the range of 0.05 to 5 μm is determined for each cross-sectional photograph. Count. The average value of the major axis lengths of the particles counted at this time is obtained, and a value obtained by averaging the average values of 10 locations is defined as the average particle size.

  In the case of fine particles, the primary particle size, the particle size after being dispersed in a solvent, and the particle size after being added to the film often change, and what is important is that the fine particles are finally combined with the cellulose ester in the film. And controlling the particle size formed by aggregation.

  Here, when the average particle diameter of the fine particles exceeds 5 μm, haze deterioration or the like may be observed, or a failure may occur in the wound state as a foreign matter. Moreover, when the average particle diameter of fine particles is less than 0.05 μm, it becomes difficult to impart slipperiness to the film.

  The fine particles are used by adding 0.04 to 0.5% by weight to the cellulose ester. Preferably, 0.05 to 0.3% by weight, more preferably 0.05 to 0.25% by weight is added. When the amount of fine particles added is 0.04% by weight or less, the film surface roughness becomes too smooth and blocking occurs due to an increase in the friction coefficient. If the amount of fine particles added exceeds 0.5% by weight, the coefficient of friction on the film surface will be too low, causing winding misalignment during winding, and the transparency of the film will be low and haze will be high. The above range is essential because it has no value as a film.

  For the dispersion of the fine particles, it is preferable to treat a composition in which the fine particles and the solvent are mixed with a high-pressure dispersion apparatus. The high-pressure dispersion apparatus used in the present embodiment is an apparatus that creates special conditions such as high shear and high-pressure conditions by passing a composition in which fine particles and a solvent are mixed at high speed through a thin tube.

It is preferable that the maximum pressure condition inside the apparatus is 980 N / cm ² or more in a thin tube having a tube diameter of 1 to 2000 μm, for example, by processing with a high-pressure dispersion apparatus. More preferably, the maximum pressure condition inside the apparatus is 1960 N / cm ² or more. At that time, it is preferable that the maximum reaching speed reaches 100 m / sec or more, and the heat transfer speed reaches 4.1840 × 105 J / hr or more.

  Examples of the high-pressure dispersing device as described above include an ultra-high pressure homogenizer (trade name: Microfluidizer) manufactured by Microfluidics Corporation or a nanomizer manufactured by Nanomizer, and other manton gorin type high-pressure dispersing devices such as those manufactured by Izumi Food Machinery. A homogenizer etc. are mentioned.

  In the present embodiment, the fine particles are dispersed in a solvent containing 25 to 100% by weight of a lower alcohol and then mixed with a dope in which a cellulose ester (cellulose derivative) is dissolved in a solvent, and the mixed solution is mixed with a metal support. A cellulose ester film is obtained which is cast on and dried to form a film.

  Here, the content ratio of the lower alcohol is preferably 50 to 100% by weight, more preferably 75 to 100% by weight.

  Examples of lower alcohols preferably include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like.

  Although it does not specifically limit as solvents other than a lower alcohol, It is preferable to use the solvent used at the time of film formation of a cellulose ester.

  The fine particles are dispersed in the solvent at a concentration of 1 to 30% by weight. Dispersing at a concentration higher than this is not preferable because the viscosity increases rapidly. The concentration of the fine particles in the dispersion is preferably 5 to 25% by weight, more preferably 10 to 20% by weight.

  The ultraviolet absorbing function of the film is preferably imparted to various optical films such as a polarizing plate protective film, a retardation film, and an optical compensation film from the viewpoint of preventing deterioration of the liquid crystal. For such an ultraviolet absorbing function, a material that absorbs ultraviolet rays may be included in the cellulose derivative, and a layer having an ultraviolet absorbing function may be provided on a film made of the cellulose derivative.

  Examples of ultraviolet absorbers that can be used in the present embodiment include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like. A benzotriazole-based compound with little coloration is preferred. In addition, ultraviolet absorbers described in JP-A-10-182621 and JP-A-8-337574 and polymer ultraviolet absorbers described in JP-A-6-148430 are also preferably used.

  As the ultraviolet absorber, those having excellent absorption ability of ultraviolet rays having a wavelength of 370 nm or less from the viewpoint of preventing deterioration of a polarizer or liquid crystal and those having little absorption of visible light having a wavelength of 400 nm or more from the viewpoint of liquid crystal display properties. preferable.

  Specific examples of ultraviolet absorbers useful in the present embodiment include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert). -Butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butyl Phenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3 '-(3 ", 4", 5 ", 6" -tetrahydrophthalimidomethyl) -5'-methylphenyl) benzotriazole, 2,2 -Methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol, 2- (2'-hydro Cis-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol Octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy Examples include, but are not limited to, a mixture of -5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate.

  Further, as commercially available products of ultraviolet absorbers, TINUVIN 109, TINUVIN 171 and TINUVIN 326 (all manufactured by Ciba Specialty Chemicals) can be preferably used.

  Further, as specific examples of the benzophenone-based compound that is an ultraviolet absorber that can be used in this embodiment, 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy- Examples thereof include, but are not limited to, 5-sulfobenzophenone and bis (2-methoxy-4-hydroxy-5-benzoylphenylmethane).

  In this Embodiment, the compounding quantity of these ultraviolet absorbers has the preferable range of 0.01 to 10 weight% with respect to a cellulose ester (cellulose derivative), and also 0.1 to 5 weight% is preferable. If the amount of the ultraviolet absorber used is too small, the ultraviolet absorbing effect may be insufficient. If the amount of the ultraviolet absorber is too large, the transparency of the film may be deteriorated. The ultraviolet absorber is preferably one having high heat stability.

  Moreover, the ultraviolet absorber which can be used for the optical film of this Embodiment is the polymer ultraviolet absorber (or ultraviolet-absorbing polymer) of Unexamined-Japanese-Patent No. 6-148430 and 2002-47357. It can be preferably used. In particular, in general formula (1) described in JP-A-6-148430, general formula (2), or general formulas (3), (6), and (7) described in JP-A-2002-47357. The polymeric ultraviolet absorber represented is preferably used.

  In general, the antioxidant is also referred to as a deterioration inhibitor, but is preferably contained in a cellulose ester film as an optical film. That is, when a liquid crystal image display device or the like is placed in a high humidity and high temperature state, the cellulose ester film as an optical film may be deteriorated. The antioxidant has a role of delaying or preventing the film from being decomposed by, for example, halogen in the residual solvent in the film or phosphoric acid of the phosphoric acid plasticizer, so that it is preferably contained in the film. .

  As such an antioxidant, a hindered phenol compound is preferably used. For example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di- -T-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3 -(3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino)- 1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], octa Sil-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxy Benzyl) -isocyanurate and the like. In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] is preferred. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di-t A phosphorus-based processing stabilizer such as -butylphenyl) phosphite may be used in combination.

  The amount of these compounds added is preferably 1 ppm to 1.0% by weight, more preferably 10 to 1,000 ppm, by weight with respect to the cellulose derivative.

  In this Embodiment, the film thickness after drying of a cellulose-ester film has the preferable range of 20-150 micrometers as a finished film from a viewpoint of thickness reduction of a liquid crystal display device. Here, “after drying” refers to a film dried to a state where the amount of residual solvent in the film is 0.5% by weight or less.

  Here, when the film thickness of the cellulose ester film after winding is too thin, for example, the required strength as a protective film for a polarizing plate may not be obtained. If the film thickness is too thick, the advantage of thinning the film becomes less than the conventional cellulose ester film. To adjust the film thickness, control the dope concentration, pump feed volume, slit gap of the die of the casting die, extrusion pressure of the casting die, and the moving speed of the metal support to achieve the desired thickness. It is good to do. Further, as a means for making the film thickness uniform, it is preferable to use a film thickness detection means to feed back and adjust the programmed feedback information to each of the above devices.

  In the process from immediately after casting through the solution casting film forming method to drying, the atmosphere in the drying apparatus may be air, or may be performed in an inert gas atmosphere such as nitrogen gas or carbon dioxide gas. . Of course, the danger of the explosion limit of the evaporating solvent in the dry atmosphere must always be taken into account.

  In the present embodiment, the cellulose ester film has a moisture content of preferably 0.1 to 5%, more preferably 0.3 to 4%, and even more preferably 0.5 to 2%.

  In the present embodiment, the cellulose ester film desirably has a transmittance of 90% or more, more preferably 92% or more, and further preferably 93% or more.

  Further, the optical film wound up by the method of the present embodiment has a haze of 0.3 to 2.0 when three sheets are stacked, and according to the optical film of the present embodiment, the film Has a very low haze, and has optical properties excellent in transparency and flatness.

  Here, the haze of the optical film may be measured using, for example, a haze meter (1001DP type, manufactured by Nippon Denshoku Industries Co., Ltd.) according to a method defined in JIS K 6714.

  Moreover, the tensile elasticity modulus of MD direction (conveyance direction) of the cellulose ester film wound up by the method of the optical film according to the present embodiment is 1,500 to 3,500 MPa, and tensile elasticity in the TD direction (lateral direction). The rate is preferably 3,000 MPa to 4,500 MPa, and the ratio of the TD elastic modulus / MD elastic modulus of the film is preferably 1.40 to 1.90.

  Here, if the ratio of the elastic modulus in the TD direction / the elastic modulus in the MD direction of the optical film is less than 1.40, the sag of the central portion becomes large when winding a film having a width exceeding 1,650 mm, and the winding core Since sticking of a film increases, it is not preferable. Further, when the ratio of the elastic modulus in the TD direction / the elastic modulus in the MD direction exceeds 1.90, warpage occurs after heating on the deflecting plate, or the backlight is heated by the heat of the backlight when incorporated in the liquid crystal panel. Since the dimensional change behavior of the polarizing plate on the side and the surface side is greatly different, unevenness occurs at the corner, which is not preferable.

  As a specific method for measuring the tensile modulus of elasticity in the MD direction and TD direction of the film, for example, the method of JIS K 7217 can be mentioned.

  That is, using a tensile tester (TG-2KN, manufactured by Minebea Co., Ltd.), a sample was set at a chucking pressure: 0.25 MPa, a distance between marked lines: 100 ± 10 mm, and a pulling speed: 100 ± 10 mm / min. Pull on. As a result, from the obtained tensile stress-strain curve, the elastic modulus calculation start point is 10N, the end point is 30N, and the tangent line drawn between them is extrapolated to calculate the elastic modulus.

  Next, a method for producing an optical film by the melt casting method will be described.

  In general, in order to produce an optical film by the melt casting film forming method, the same resin as in the case of the above solution casting film forming method can be used.

  For example, cellulose ester films such as cellulose diacetate film, cellulose triacetate film, cellulose acetate butyrate film, cellulose acetate propionate film, polyester film, polycarbonate film, polyarylate film, polysulfone (including polyethersulfone) ) Film, polyester film such as polyethylene terephthalate, polyethylene naphthalate, polyethylene film, polypropylene film, cellophane, polyvinylidene chloride film, polyvinyl alcohol film, ethylene vinyl alcohol film, syndiotactic polystyrene film, polycarbonate film, cycloolefin film Polymer film (Arton ( SR Inc.), ZEONEX, ZEONOR (manufactured by ZEON CORPORATION), polymethylpentene film, polyetherketone film, polyetherketoneimide film, polyamide film, fluororesin film, nylon film, polymethylmethacrylate film, acrylic film Or a glass plate etc. Among them, a cellulose ester film, a cycloolefin polymer film, a polycarbonate film, and a polysulfone (including polyethersulfone) film are preferable.

  Here, in particular, the transparent resin film is a cellulose ester-based resin film or a resin film containing 80% or more of a cyclic olefin-based addition polymer in terms of production, cost, transparency, adhesiveness, and the like. Are preferably used.

  As the cellulose ester resin, at least one resin selected from the group consisting of cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate phthalate, and cellulose phthalate It is preferable that

  The degree of substitution of the acetyl group of the cellulose ester resin is preferably at least 1.5 or more because the resulting film has excellent dimensional stability. The method for measuring the substitution degree of the acyl group of the cellulose ester resin can be carried out in accordance with ASTM D-817-91. The molecular weight of the cellulose ester resin is preferably 50,000 to 300,000, particularly 60,000 to 200,000 as the number average molecular weight because the mechanical strength of the resulting film can be increased.

  In the cellulose ester resin, as in the case of the solution casting film forming method, a plasticizer, an ultraviolet absorber, an antioxidant, a matting agent, an antistatic agent, a flame retardant, a dye and an oil agent are used for various purposes. Etc. can be contained.

  In order to produce an optical film by a melt casting film forming method, for example, after mixing materials of a cellulose ester-based resin film, an extruder is used to melt and extrude from a casting die onto a cooling drum, The two cooling drums of the second cooling drum were sequentially circumscribed, cooled and solidified to form an unstretched film (web), and the unstretched film (web) peeled off by the peeling roll was then transferred to the film (web) by a stretching device. Hold both ends and stretch in the width direction.

  In this case, the uniformity of retardation of the film after stretching can be improved by adjusting the surface temperature of the two cooling drums and the rotational speed (circumferential speed) of the cooling drum.

  Here, a method in which a cellulose ester resin is melt-extruded from a casting die onto a cooling drum and cooled and solidified on the cooling drum is called a melt-casting film forming method.

  Examples of the melt casting film forming method include a method using a casting die, a melt extrusion method such as an inflation method, a calendar method, a hot press method, an injection molding method, etc., but the thickness unevenness is small and about 50 to 500 μm. In general, a method using a casting die that can be easily processed to a thickness of 5 mm and that can reduce unevenness in film thickness and retardation is generally employed.

  The material of the cellulose ester resin film is preferably dried in advance. It is desirable to dry the moisture to 1000 ppm or less, preferably 200 ppm or less, using a vacuum or reduced pressure dryer or a dehumidifying hot air dryer.

  Cellulose ester resins and stabilizers are preferably mixed with a mixer before melting, but plasticizers, UV absorbers, and matting agents are also mixed with a mixer before melting. You can also keep it. As the mixer, a general mixer such as a V-type mixer, a conical screw type mixer, a horizontal cylindrical type mixer, or the like can be used.

  For example, the cellulose ester resin dried under hot air, vacuum or reduced pressure is melted at an extrusion temperature of about 200 to 300 ° C. using the extruder 1, and filtered through a leaf disk type filter or the like to remove foreign matters.

  When introducing from the supply hopper to the extruder, it is preferable to prevent oxidative decomposition and the like under vacuum, reduced pressure, or inert gas atmosphere.

  When additives such as a plasticizer are not mixed in advance, they 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.

  In addition to the method of directly forming a film using an extruder after mixing the materials, it is also possible to form a film by once pelletizing and then melting the pellet with an extruder. In a system in which a plurality of materials having different melting points are mixed, a so-called braided semi-melt is once produced at a temperature at which only a material having a low melting point is melted, and the semi-melt is introduced into an extruder. It is also possible to film. When using resins and additives that are susceptible to thermal decomposition, in order to reduce the number of times the resin is melted, a method of directly forming a film without producing pellets, A method of forming a film from is preferred.

  The extruder used for film formation may be a single screw extruder or a twin screw extruder. In the case of forming a film directly without forming pellets from the material, it is preferable to use a twin-screw extruder because an appropriate degree of kneading is necessary. However, even with a single-screw extruder, the screw shape is a Maddock type, Unimelt type. By changing to a kneading type screw such as a mold or a dull mage, moderate kneading can be obtained and film formation becomes possible. In both the single screw extruder and the twin screw extruder, it is desirable to provide a vent port and remove gas from the vent port using a vacuum pump or the like. Once a pellet or braided semi-melt is produced, it may be a single screw extruder or a twin screw extruder.

  In the cooling process in the extruder and after the extrusion, it is preferable to reduce the oxygen concentration by replacing with an inert gas such as nitrogen gas or reducing the pressure.

  Although the preferable conditions for the melting temperature of the resin in the extruder vary depending on the viscosity and discharge amount of the resin, the thickness of the sheet to be manufactured, etc., in general, the glass transition temperature relative to the glass transition temperature (Tg) of the molding material. The glass transition temperature (Tg) is preferably in the range of (Tg) to 100 ° C. or higher. More preferably, the melting temperature is glass transition temperature (Tg) + 10 ° C. or higher and glass transition temperature (Tg) + 90 ° C. or lower. The melt viscosity at the time of extrusion is 10 to 100,000 poise, preferably 100 to 10,000 poise. The residence time of the resin in the extruder is preferably short, and is within 5 minutes, more preferably within 3 minutes, and most preferably within 2 minutes. The residence time depends on the type of extruder and the extrusion conditions, but can be shortened by adjusting the material supply rate, L / D, screw rotation speed, screw groove depth, etc. It is.

  The shape, rotation speed, and the like of the screw of the extruder are appropriately selected depending on the viscosity and discharge amount of the resin. The shear rate in the extruder is preferably 1 / second to 10000 / second, more preferably 5 / second to 1000 / second, and most preferably 10 / second to 100 / second. In order to prevent biting of the gear pump and reduce the main filter load, it is preferable to provide a prefilter on the exit side of the extruder.

  For example, a 50/80/100 mesh screen or a metal fiber sintered filter is preferably provided as necessary. It is preferable to use a type that can be changed online.

  The extrusion flow rate is preferably performed stably by introducing a gear pump or the like. Moreover, it is preferable to provide a filter downstream of the prefilter. A stainless fiber sintered filter is preferably used. Stainless steel fiber sintered filter is made by compressing the stainless fiber body after creating a complex intertwined state, and sintering and integrating the contact points. The density is changed according to the thickness and compression amount of the fiber, and the filtration accuracy Can be adjusted. It is preferable to use a multilayer body in which the filtration accuracy is repeated coarsely and densely multiple times. Further, it is preferable to adopt a configuration in which the filtration accuracy is sequentially increased or a method in which coarse and dense filtration accuracy is repeated, so that the filtration life of the filter can be extended and the accuracy of capturing foreign matters and gels can be improved. The filtration accuracy is preferably 0.5 μm or more and 50 μm or less.

  The material of the cellulose ester-based resin film is melt-extruded from the casting T die using an extruder, and is circumscribed by the two cooling drums of the first cooling drum and the second cooling drum in order, and the surface is straightened and cooled and solidified. To obtain an unstretched film.

  When the cooling drum with which the material extruded from the casting die first comes into contact is the first cooling drum, the time until the material contacts the first cooling drum from the casting die is preferably shorter, preferably within 10 seconds. Is within 5 seconds, most preferably within 2 seconds. Further, the distance from the casting die to the first cooling drum is preferably 10 mm or more and 100 mm or less.

  At this time, the surface temperature of a 1st cooling drum and a 2nd cooling drum shall be the glass transition temperature (Tg) -100 degreeC or more of a film, and the glass transition temperature (Tg) -20 degrees C or less.

  By setting the surface temperatures of the first cooling drum and the second cooling drum within this range, it is possible to suppress the occurrence of slight retardation unevenness due to conveyance tension or the like.

  Further, when the peripheral speed of the first cooling drum is V1 and the peripheral speed of the second cooling drum is V2, the ratio of the peripheral speed of the second cooling drum and the peripheral speed of the first cooling drum: V2 / V1 0.950 or more and 0.999 or less.

  By setting the ratio of the peripheral speed of the second cooling drum to the peripheral speed of the first cooling drum: V2 / V1 within this range, the occurrence of slight retardation unevenness due to the transport tension or the like can be suppressed.

  In order to improve smoothness with respect to both surfaces of the film, it is preferable that a third cooling drum is disposed subsequent to the second cooling drum. For example, the surface temperature of the third cooling drum may be the second cooling drum. The surface temperature is preferably the same.

  If the peripheral speed of the third cooling drum is V3, the peripheral speed of the third cooling drum V3 and the second cooling are in the relationship between the peripheral speed V2 of the second cooling drum and the peripheral speed V1 of the first cooling drum. Ratio to the peripheral speed V2 of the drum: It is preferable that V3 / V2 = V2 / V1.

  In the melt casting film forming method, when flaws or foreign matters adhere to the casting die, streak-like defects may occur. Such a defect is called a die line, but in order to reduce surface defects such as the die line, the piping from the extruder to the casting die should have a structure that minimizes the resin retention. Is preferred. It is preferable to use a casting die that has as few scratches as possible inside the lip. Since the volatile component is deposited from the resin around the casting die and may cause a die line, it is preferable to suck the atmosphere containing the volatile component. Moreover, since it may precipitate also in apparatuses, such as an electrostatic application, it is preferable to apply alternating current or to prevent precipitation with another heating means.

  The casting die is not particularly limited as long as it is used for producing a sheet or a film, but a coat hanger die is preferable. The lip portion gap t is preferably 0.1 mm or more and 2 mm or less, and the land portion length L is preferably 5 mm or more and 50 mm or less. L / t is preferably 10 or more.

  Thickness adjustment mechanisms include a heater type that adjusts the temperature by dividing in the width direction, a manual bolt type that adjusts the lip opening mechanically, or a lip opening adjustment that uses expansion and contraction of the bolts with a heater. It is preferable to use a heat bolt system or the like.

  Casting die materials are hard chromium, chromium carbide, chromium nitride, titanium carbide, titanium carbonitride, titanium nitride, super steel, ceramic (tungsten carbide, aluminum oxide, chromium oxide), etc. Buffing, lapping using a # 1000 or higher grinding wheel, plane cutting using a # 1000 or higher diamond grinding wheel (the cutting direction is perpendicular to the resin flow direction), electrolytic polishing, electrolytic composite polishing, etc. Stuff.

  A preferred material for the die lip is the same as that of the casting die. The surface accuracy of the lip portion is preferably 0.5S or less, and more preferably 0.2S or less.

  Here, the cellulose ester resin is melt-extruded from the casting die onto the cooling drum. The temperature of the cooling drum is preferably adjusted by flowing a heat medium such as water or oil into the cooling drum.

  When the cellulose ester resin flows out from the casting die, it is preferable to attach a suction device in the vicinity of the casting die in order to prevent contamination of the casting die and the cooling drum with sublimates. The suction device needs to be treated such as heating with a heater so that the device itself does not become a place where the sublimate is attached. On the other hand, if the suction pressure is too large, film quality such as unevenness is affected. Conversely, if the suction pressure is too small, the sublimate cannot be sucked effectively.

  The film and the cooling drum are preferably in close contact with each other. As a method for bringing the film and the cooling drum into close contact, pressing using a touch roll, an electrostatic contact method, an air knife, a decompression chamber, or the like can be used.

  It is preferable that two or more cooling drums are provided in order to improve smoothness on both sides of the film, and that both sides are brought into contact with the cooling drum. Further, the cooling drum can be provided with cleaning equipment such as a cleaning roll.

  The temperature unevenness of the cooling drum is preferably 0.5 ° C. or less. The speed unevenness is preferably 0.5% or less. The surface of the cooling drum can use hard chrome plating, but is not limited thereto. The surface roughness is preferably 0.1 s or less. As the material of the touch roll, a metal or a material obtained by winding a resin, rubber or the like around a metal roll can be used.

  An unstretched cellulose ester-based resin film is obtained by cooling and solidifying a film-like cellulose ester-based resin in a molten state from a T die in close contact with the first cooling drum, the second cooling drum, and the third cooling drum. Get (web). The cooled and solidified film (web) peeled from the third cooling drum by the peeling roll is guided to a stretching machine through a dancer roll (film tension adjusting roll), where the film is stretched in the width direction.

  As a method of stretching the film in the width direction, a known tenter or the like can be preferably used. By this stretching, the molecules in the film are oriented. In particular, it is preferable to set the stretching direction to the width direction because lamination with the polarizing film can be performed in a roll form. By stretching in the width direction, the slow axis of the optical film made of the cellulose ester resin film becomes the width direction.

  The temperature of the hot air blown from the hot air blowing slit port in the tenter is 95 to 200 ° C, and preferably 100 to 150 ° C.

  On the other hand, the transmission axis of the polarizing film is also usually in the width direction. By incorporating a polarizing plate in which the transmission axis of the polarizing film and the slow axis of the optical film are parallel to each other into the liquid crystal display device, the display contrast of the liquid crystal display device can be increased and a good viewing angle can be obtained. Is obtained.

  The film thickness of the optical film varies depending on the purpose of use, but the film thickness range used as the finished film is 30 to 200 μm, and the range of 40 to 120 μm is preferable for the recent thin tendency, and the range of 40 to 100 μm is particularly preferable. preferable. The average film thickness of the film can be adjusted by controlling the extrusion flow rate, the gap of the casting port of the casting die, the speed of the cooling drum, and the like so as to obtain a desired thickness.

  After slitting the edge of the film to a product width with a slitter and cutting it off, the film is subjected to knurling (embossing) on both ends of the film by a knurling device consisting of an embossing ring and a back roll, and wound by a winder. This prevents sticking in the optical film (winding) and generation of scratches. The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. In addition, since the grip part of the clip of the both ends of a film is deform | transforming normally and cannot be used as a film product, it is cut out and reused as a raw material.

  Thus, the cellulose ester-based resin film formed by the method for producing an optical film by the melt casting film forming method has a thickness direction retardation (Rt) different from the resin film formed by the solution casting film forming method. There is a feature that it is small, and by stretching such a cellulose ester resin film, in-plane retardation (Ro) can be easily developed. In addition, since there is no need to increase the draw ratio, the risk of breakage is small and stable production can be achieved.

  The optical film winding method according to the present invention is a method in which an optical film such as a cellulose ester film manufactured by the melt casting film forming method as described above is wound by a winding roll (winding means) in the final stage of manufacturing. The case is also applicable.

  In this case, as shown in FIG. 2, the air ejection nozzle (3) includes a width direction of the air nozzle opening (that is, a film width direction), and a central axis of the film winding roll (2). Are arranged near the lower peripheral surface of the film winding roll (2) so as to be parallel to each other. And when winding up optical films (F), such as a cellulose-ester film manufactured by said melt-casting film forming method, winding-up of a film winding roll (2) is started by the winding method of this invention. With respect to the position on the outer surface of the film corresponding to an angle range of 0 to 45 degrees in the film winding direction around the central axis of the film winding roll (2) from the position, air that is directed toward the upstream direction of the film winding from that position The film is blown from the air ejection nozzle (3) while pressing the film (F) with air.

  In this way, by blowing high-pressure air onto the peripheral surface of the film winding roll (2) and air-pressing the film (F), air that has been wound during film winding is removed in a so-called non-contact manner. It is. Note that the number of installed air ejection nozzles (3) may not be one.

  In addition, the following points are the same even when an optical film such as a cellulose ester film produced by a melt casting film forming method is wound by a winding roll (winding means) (2) in the final stage of production. is there.

  That is, a high-pressure blower (not shown) is connected to the air ejection nozzle (3) shown in FIG. 2 as an air generation source, and a humidity / temperature adjusting device for the ejection air is provided on the way. The relative humidity is adjusted to 20 to 24%, and the temperature of the blown air is adjusted to 20 to 25 ° C.

  And in the winding method of the optical film by this invention, the film pressing force by blowing air is the largest in the width direction center part of a film (F), and it becomes small gradually as it goes to the both ends of a film (F). It is preferable to make it.

  Here, the slit-shaped air nozzle opening provided in the air ejection nozzle (3) becomes wider toward the both ends in the width direction, and the pressing force of the ejection air is reduced by the film (F). It has been adjusted so that the width center is the strongest. Thereby, air becomes easy to escape from the end face of the film winding roll (2).

  Furthermore, in the winding method of the optical film according to the present invention, it is preferable that the air ejected from the air ejection nozzle (3) is blown onto the winding film over 0.7 to 1.0 times in the width direction of the film.

  Moreover, in the winding method of the optical film of this invention, the pressing force of the film width direction center part by the jet air from a jet nozzle (3) is 1.0-10.0 kPa, The film width by the jet air It is preferable that the pressing force at both ends in the hand direction is smaller than the pressing force at the center in the width direction of the film and is 0.5 to 9.5 kPa.

  Moreover, in the winding method of the optical film by this invention, when winding a film (F), the air after being sprayed with respect to the film outer surface of a winding roll (2) is film winding roll ( 2) It is preferable that the air is sucked by an air intake device (pressure reducing device) (4) installed near the upper part of the film (F) on the upstream side in the winding direction from the winding start position at the lower end.

  The optical film wound up by the method of the present embodiment is preferably used for a liquid crystal display member, specifically, a protective film for a polarizing plate. In particular, in a protective film for a polarizing plate that has strict requirements on both moisture permeability and dimensional stability, the optical film wound up by the method of the present embodiment is preferably used.

  By using the protective film for polarizing plates made of the optical film of the present embodiment, it is possible to provide a polarizing plate excellent in durability, dimensional stability, and optical isotropy as well as in a thin film.

  By the way, the polarizing film is a film that has been conventionally stretched by treating a film that can be stretched and oriented, such as a polyvinyl alcohol film, with a dichroic dye such as iodine. Since the polarizing film itself does not have sufficient strength and durability, a polarizing plate is generally obtained by adhering a cellulose ester film having no anisotropy as a protective film to both surfaces thereof.

  The polarizing film may be prepared by laminating the optical film wound by the method of the present embodiment as a retardation film, and the optical film wound by the method of the present embodiment The film may be directly bonded to a polarizing film so as to serve as a phase difference film and a protective film. The method of bonding is not particularly limited, but can be performed with an adhesive composed of an aqueous solution of a water-soluble polymer. As this water-soluble polymer adhesive, a completely saponified polyvinyl alcohol aqueous solution is preferably used. Furthermore, a long polarizing plate is obtained by laminating a long polarizing film stretched in the longitudinal direction and treated with a dichroic dye and a long retardation film wound up by the method of the present embodiment. be able to. A polarizing plate is a sticking type in which a peelable sheet is laminated on one or both sides thereof via a pressure-sensitive adhesive layer (for example, an acrylic pressure-sensitive adhesive layer). It can be easily attached to a cell or the like.

  The polarizing plate thus obtained can be used for various display devices. In particular, a liquid crystal display device using a VA mode liquid crystal molecule in which liquid crystal molecules are substantially vertically aligned when no voltage is applied, or a TN mode liquid crystal cell in which liquid crystal molecules are substantially horizontal and twisted when no voltage is applied. It is preferable to use for.

  By the way, a polarizing plate can be produced by a general method. For example, there is a method in which an optical film or a cellulose ester film is subjected to alkali saponification treatment, and a polyvinyl alcohol film is immersed and stretched in an iodine solution and bonded to both surfaces of a polarizing film using a completely saponified polyvinyl alcohol aqueous solution. is there. The alkali saponification treatment refers to a treatment of immersing the cellulose ester film in a high-temperature strong alkaline solution in order to improve the wetness of the water-based adhesive and improve the adhesiveness.

  The optical film wound up by the method of the present embodiment includes a hard coat layer, an antiglare layer, an antireflection layer, an antifouling layer, an antistatic layer, a conductive layer, an optical anisotropic layer, a liquid crystal layer, an alignment layer, Various functional layers such as an adhesive layer, an adhesive layer, and an undercoat layer can be provided. These functional layers can be provided by a method such as coating or vapor deposition, sputtering, plasma CVD, or atmospheric pressure plasma treatment.

  Thus, the obtained polarizing plate is provided in the one or both surfaces of a liquid crystal cell, and a liquid crystal display device is obtained using this.

  In the present embodiment, the liquid crystal display device includes a liquid crystal cell in which rod-like liquid crystal molecules are sandwiched between a pair of glass substrates, a polarizing film disposed so as to sandwich the liquid crystal cell, and transparent protective layers disposed on both sides thereof. It has two polarizing plates.

  To provide a polarizing plate excellent in durability, dimensional stability, and optical isotropy as well as thinning by using a protective film for a polarizing plate comprising an optical film wound up by the method of the present embodiment. Can do. Furthermore, a liquid crystal display device using this polarizing plate or retardation film can maintain stable display performance over a long period of time.

  Hereinafter, the present embodiment will be described more specifically by way of examples, but the present invention is not limited to these examples.

Example 1
(Preparation of dope)
Cellulose triacetate 100 parts by weight Triphenyl phosphate 5.5 parts by weight Ethylphthalyl ethyl glycolate 5.5 parts by weight Methylene chloride 400 parts by weight Ethanol 45 parts by weight The above cellulose ester blend was placed in an airtight container and mixed. After the temperature was raised to 80 ° C., the mixture was stirred for 3 hours and completely dissolved. Thereafter, stirring was stopped, the liquid temperature was lowered to 43 ° C., and filtration was performed using a filter paper having a filtration accuracy of 0.005 mm. By allowing this to stand overnight, the bubbles in the dope were degassed.

(Production of cellulose triacetate film)
A support comprising a stainless steel endless belt having a width of 2000 mm, mirror-treated from a casting die of a solution casting film forming apparatus (not shown), adjusted to a dope temperature of 35 ° C. and a support temperature of 25 ° C. using the dope. Cast on top.

  The web was peeled off from the support by a peeling roll with a peeling residual solvent amount of 110% by weight, introduced into the next drying apparatus with a transport tension of 100 N, and dried.

  Next, the web after the drying step was stretched in the width direction of the web while holding both ends of the web with clips using a tenter. At this time, the web stretch ratio by the tenter was set to 30%, and a drying air of 140 ° C. was introduced into the tenter to set the stretch temperature to 140 ° C.

  The stretched cellulose triacetate film is introduced into a late drying apparatus and dried with a drying air at 120 ° C., and finally a cellulose triacetate film having a film thickness of 60 μm and a film width of 2000 mm is produced. 3000 m of the film was wound up into a roll.

  This rolled cellulose triacetate film was stored for 7 days under the conditions of a temperature of 24 ° C. and a humidity of 55 RH%.

  Next, as shown in FIG. 1 and FIG. 2, the original film (F) made of the roll-shaped cellulose triacetate film after storage is fed out from the feeding roll (feeding means) (1), and the winding method of the present invention is used. Then, it was wound up in a winding roll (winding means) (2).

  Referring to FIG. 2, in the film winding method according to the present invention, when the film (F) is wound, air is blown from the air ejection nozzle (3) to the film outer surface of the winding roll (2). The film roll (2) is blown in the film winding direction from the winding start position at the lower end of the film winding roll (2) in the film winding direction at an angle range of 0 to 45 degrees, and the film (F) is pressed with air. In Example 1, the air ejection nozzle (3) is moved in the width direction of the air nozzle opening (that is, the film width direction) and the central axis of the film winding roll (2). Is placed near the lower peripheral surface of the film take-up roll (2) so that the winding start position at which the film (F) is taken up by the film take-up roll (2) is 0 degree. Winding At an angle of 20 degrees in the direction, and blowing air on the film (F) by the air ejection nozzle (3).

  The air ejection nozzle (3) is connected to a high pressure air blower (FLB No. 13) manufactured by Yotsuba Machinery Co., Ltd. as an air generation source, and is provided with a humidity / temperature adjusting device for the ejection air. The relative humidity was 22%, and the temperature of the blown air was high pressure air adjusted to 23 ° C.

  And it set so that the film pressing force by blowing air might be the largest in the width direction center part of a film (F), and it may become small gradually as it goes to the both ends of a film (F). Thereby, air became easy to escape from the end surface of a film winding roll (2).

  And in this Example 1, the ejection air from an air ejection nozzle (3) was sprayed on the winding film over 0.8 times of the film width direction.

  Moreover, the pressing force of the film width direction center part by the blowing air from a jet nozzle (3) is 7.2 kPa, and the pressing force of the film width direction both ends by the blowing air is a film width direction center part. The pressing force was 5.9 kPa.

  Here, the central portion in the width direction of the film is a portion corresponding to 70% of the total width of the film, and both end portions in the width direction of the film correspond to 15% of the total width of the film inward from both ends of the film. It was a part.

  During the winding operation, when the lower limit detection sensor (17) detects the dancer roll (14) in order to keep the film feeding speed (= film winding speed) constant, the feeding speed of the feeding means is slightly lower. When the upper limit detection sensor (16) detects the dancer roller (14), the feeding speed is slightly increased so that the dancer roller (14) moves between the lower limit detection sensor (17) and the upper limit detection sensor (16). The film feeding speed (= film winding speed) was controlled to a constant speed.

  Here, the film winding speed by the winding roll (2) was almost the same as the film feeding speed by the feeding roll (feeding means) (1), and was 30 m / min.

  Moreover, in this Example 1, when winding a film (F), the air after being sprayed with respect to the film outer surface of a winding roll (2) is taken up by the film winding roll (2) lower end. Intake air was taken in by an air intake device (decompression device) (4) installed near the upper part of the film (F) on the upstream side in the winding direction from the start position, and the intake pressure at this time was set to −100 Pa.

  Table 1 below shows the air spray angle (degrees), the air spray width / film width (times), and the film pressing force (kPa) by air.

Examples 2-5
The cellulose triacetate film is wound up in the same manner as in Example 1 above, but in Examples 2 to 5, as shown in Table 1 below, air is blown out against the film outer surface of the winding roll (2). The angle at which air was blown from the nozzle (3) was different from that in Example 1. That is, in Example 2, the angle at which air is blown from the air ejection nozzle (3) to the film outer surface of the winding roll (2) is set from the winding start position at the lower end of the film winding roll (2). Centering on the central axis of the roll (2), it was 0 degree in the film winding direction, 30 degrees in Example 3, 35 degrees in Example 4, and 45 degrees in Example 5.

  The other points were the same as in Example 1 above, and the cellulose triacetate films of Examples 2 to 5 were wound up.

Examples 6-9
The cellulose triacetate film is wound up in the same manner as in Example 1 above, but in Examples 6 to 9, as shown in Table 1 below, air is blown onto the film outer surface of the winding roll (2). The width for blowing air from the nozzle (3) was different from that in Example 1. That is, in Example 6, the jet air from the air jet nozzle (3) is 0.6 times the film width direction with respect to the film outer surface of the winding roll (2). In Example 7, the film width is The film was sprayed on the wound film over 0.7 times the direction, 1.0 times in the film width direction in Example 8, and 1.1 times in the film width direction in Example 9.

  The other points were the same as in Example 1 above, and the cellulose triacetate films of Examples 6 to 9 were wound up.

Examples 10-14
The cellulose triacetate film is wound up in the same manner as in Example 1 above, but in Examples 10 to 14, as shown in Table 1 below, the film width direction center by the jet air from the jet nozzle (3) The pressing force of the film and the pressing force of the both ends in the width direction of the film due to the blown air were different from those in Example 1. That is, in Example 10, the pressing force at the central part in the film width direction due to the air jetted from the jet nozzle (3) is 0.8 kPa, and the pressing force at both ends in the film width direction due to the jet air is It is smaller than the pressing force at the center in the width direction and is 0.6 kPa, and in Example 11, the pressing force at the center in the width direction of the film due to the air blown from the ejection nozzle (3) is 1.1 kPa. The pressing force at both ends in the film width direction by air is set to 0.9 kPa smaller than the pressing force at the center in the film width direction, and in Example 12, the center in the film width direction by the air blown from the jet nozzle (3) The pressing force at the film width is 5.3 kPa, and the pressing force at both ends in the width direction of the film due to the jet air is smaller than the pressing force at the center in the width direction of the film and is 4.8 kPa. In Example 13, the pressing force at the central portion in the film width direction due to the air jetted from the jet nozzle (3) was set to 9.8 kPa, and the pressing force at both ends in the width direction of the film due to the jet air was set as the film width. It is smaller than the pressing force in the center in the hand direction and is 8.2 kPa. In Example 14, the pressing force in the center in the width direction of the film due to the air jetted from the jet nozzle (3) is 10.5 kPa. The pressing force at both ends in the width direction of the film was smaller than the pressing force at the center in the width direction of the film and 9.5 kPa.

  The other points were the same as in Example 1 above, and the cellulose triacetate films of Examples 11 to 14 were wound up.

Comparative Example 1
For comparison, it is carried out in the same manner as in the case of Example 1 except that the film (F) is different from the case of Example 1 in that the film (F) is a film winding roll (2 ) Is set to 0 degree, and air is blown to the film (F) by the air ejection nozzle (3) at an angle of 50 degrees toward the film winding direction.

  The other points were the same as in Example 1 above, and the cellulose triacetate film of Comparative Example 1 was wound up.

(Appearance evaluation of winding film)
Next, about the cellulose triacetate film wound up in said Examples 1-14 and the comparative example 1, the external appearance evaluation of the wound film was performed as follows.

  The external appearance of the cellulose triacetate film roll wound up in Examples 1 to 14 and Comparative Example 1 was evaluated according to the following ranks for three points of winding misalignment, roll deformation, and so-called black belts sticking to each other. The results obtained are shown in Table 1.

  Here, the roll deformation means a phenomenon in which the air entrained in the film roll escapes with time and the roll is depressed or buckled.

Rank of film deformation (depression) ◎: No roll deformation ○: Almost no roll deformation △: There is a slight buckling point ×: There is a roll deformation, and the whole is uneven. This means that the film is displaced in the width direction because the winding tension is weak or the air is entrained frequently.

Rank of roll misalignment ◎: No deviation in the width direction of the film ○: Little deviation in the width direction of the film △: There is a slight deviation in the width direction of the film ×: There is a considerable deviation in the width direction of the film The failure of sticking between films means that the film called so-called black belt caused by sticking between films adheres because of a strong pressing force.

Rank of sticking failure (black belt) ◎: No black belt-like sticking failure ○: Little black belt-like sticking failure △: Some black belt-like sticking failure ×: Black belt-like sticking failure There is considerable (preparation of polarizing plate)
Next, using the cellulose triacetate film wound up in the above Examples 1 to 14 and Comparative Example 1 as a protective film for polarizing plate, various polarizing plates were prepared by the following method and evaluated.

(Preparation of polarizing film)
A long polyvinyl alcohol film having a thickness of 120 μm was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). This was immersed in an aqueous solution composed of 0.075 g of iodine, 5 g of potassium iodide, and 100 g of water for 60 seconds, and then immersed in an aqueous solution at 68 ° C. composed of 6 g of potassium iodide, 7.5 g of boric acid, and 100 g of water. . This was washed with water and dried to obtain a long polarizing film.

  Subsequently, this polarizing film and the cellulose triacetate film wound up in Examples 1 to 14 and Comparative Example 1 were bonded together according to the following steps 1 to 5 to produce a polarizing plate.

  Step 1: The cellulose triacetate films wound up in Examples 1 to 14 and Comparative Example 1 were immersed in a 2 mol / L sodium hydroxide solution at a temperature of 50 ° C. for 90 seconds, then washed with water and dried.

  On the other hand, a commercially available long cellulose ester film was immersed in a 2 mol / L sodium hydroxide solution at a temperature of 50 ° C. for 90 seconds, then washed with water and dried.

  Step 2: The long polarizing film was immersed in a polyvinyl alcohol adhesive tank having a solid content of 2% by weight for 1 to 2 seconds.

  Step 3: Excess adhesive adhered to the polarizing film in Step 2 was lightly removed, and the long cellulose triacetate films of Examples 1 to 14 and Comparative Example 1 that were alkali-treated in Step 1 and a commercially available long length Laminated and placed between cellulose ester films.

Process 4: These films were laminated together at a speed of about 2 m / min at a pressure of ^{20 to} 30 N / cm ² with two rotating rollers. At this time, care was taken to prevent bubbles from entering.

  Step 5: The film sample produced in Step 4 was dried for 2 minutes in a dryer at 80 ° C. to produce a polarizing plate.

(Production of liquid crystal display panel)
Carefully peel off the polarizing plate on the outermost surface of a commercially available liquid crystal display panel (NEC color liquid crystal display, MultiSync, LCD1525J, model name LA-1529HM), and paste the various polarizing plates prepared above in accordance with the polarization direction. A liquid crystal display panel was produced.

  Color unevenness was visually observed on a polarizing plate using the cellulose triacetate film wound up in Examples 1 to 14 and Comparative Example 1 as a protective film.

(Visual evaluation of polarizing plate)
About each liquid crystal display panel produced as mentioned above, the color unevenness which looks whitish when it sees from the front and diagonally by several evaluators was observed, and it was set as evaluation of a polarizing plate. The obtained results are shown in Table 1 below.

A: None of the evaluators can see color unevenness at all. ○: The evaluator hardly sees color unevenness. Δ: The evaluator may slightly see color unevenness.
Level that can be used as a product ×: A level that many evaluators can confirm color unevenness and cannot be used as a product

  As is clear from the results of Table 1 above, according to the cellulose triacetate film wound up in Examples 1 to 14 of the present invention, the wound film roll has an excellent appearance and produces a wide cellulose triacetate film. We were able to. As a result, it was possible to meet the demand for widening and high quality of protective films for polarizing plates. Moreover, even after the cellulose triacetate film wound up in Examples 1 to 14 of the present invention was processed into a polarizing plate, whitish color unevenness was not confirmed.

  On the other hand, in the cellulose triacetate film of Comparative Example 1, the appearance of the wound film roll was inferior, and it was not possible to meet the demand for high quality optical films such as a protective film for polarizing plates. Moreover, after processing into the polarizing plate, the cellulose triacetate film wound up by the comparative example 1 was found to be whitish color unevenness and could not be used as a protective film product for polarizing plate.

It is a flow sheet which shows embodiment of the apparatus which enforces the winding method of the optical film of this invention. It is a principal part expanded side view of FIG. 1, and shows the film winding roll and the air ejection nozzle installed in the vicinity.

Explanation of symbols

1: Film feeding roll (feeding means)
2: Film winding roll (winding means)
2a: Winding shaft 3: Air ejection nozzle 4: Intake device (pressure reduction device)
5: Cutter 11: 1st conveyance roll 12: 2nd conveyance roll 13: 3rd conveyance roll 14: Dancer roll 15: 4th conveyance roll 16: Upper limit detection sensor 17: Lower limit detection sensor F: Film

Claims (8)

  An optical film winding method for winding a long optical film having a width of 1600 to 2400 mm into a roll shape. When the film is wound, the film winding roll is moved from the winding start position of the film winding roll. The air is blown from the air jet nozzle toward the upstream direction of film winding from the position on the outer surface of the film corresponding to the angle range of 0 to 45 degrees in the film winding direction with the central axis as the center. A method for winding an optical film, wherein the film is wound while being pressed.   2. The winding of an optical film according to claim 1, wherein the film pressing force by the blown air is greatest at the center in the width direction of the film and gradually decreases toward both ends of the film. Method.   The method of winding an optical film according to claim 1 or 2, wherein the air blown from the air jet nozzle is blown onto the winding film over 0.7 to 1.0 times in the width direction of the film. The pressing force at the center in the width direction of the film due to the air ejected from the ejection nozzle is 1.0 to 10.0 kPa, and the pressing force at both ends in the width direction of the film due to the ejection air is at the center in the width direction of the film. The method for winding an optical film according to any one of claims 1 to 3, wherein the method is smaller than the pressing force and 0.5 to 9.5 kPa.
Here, the central portion in the film width direction refers to a portion corresponding to 60 to 80% of the total film width, and both end portions in the film width direction are 10% of the film width inward from both ends of the film. The part corresponding to ~ 20% shall be said.   The air after being blown against the film outer surface of the take-up roll when winding the film is taken up by an air intake device installed near the film on the upstream side in the take-up direction from the winding start position at the lower end of the film take-up roll. The method for winding an optical film according to claim 1, wherein the air is sucked.   An optical film wound up by the method of winding up an optical film according to any one of claims 1 to 5.   A polarizing plate comprising the optical film according to claim 6 on at least one surface.   A display device comprising the polarizing plate according to claim 7.

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