JPWO2018070146A1 - Optical film manufacturing method - Google Patents

Abstract

One aspect of the present invention is to prepare a dope containing a polyimide resin, a polyarylate resin or a cycloolefin resin, at least one alcohol solvent, and at least one good solvent for the resin in a solution casting film forming method. And casting the optical dope on a support, forming a web (casting film) on the support, peeling the web from the support, then winding the dried web and drying, In the method for producing an optical film, the present invention relates to a method for producing an optical film, which comprises a step of further adding a good solvent to the dope after adjusting the dope and a step of removing the good solvent thereafter.

Description

  The present invention relates to a method for producing an optical film containing a polyimide resin, a polyarylate resin or a cycloolefin resin.

  In the image display area of the liquid crystal display device, various optical films (for example, a transparent protective film for protecting a polarizing element of a polarizing plate) are disposed. In particular, a transparent resin film containing a polyimide resin, a polyarylate resin, a cycloolefin resin or the like is used for an optical film, mainly an optical compensation film for a liquid crystal display device. Such an optical film is often manufactured as a long resin film by, for example, a solution casting (film forming) method.

  However, resins such as polyimide resins, polyarylate resins and cycloolefin resins are synthetic polymers, and contain residual monomers, antioxidants, catalysts and the like as impurities during production. The presence of such residual monomers may cause process contamination during drying. In addition, residual impurities (antioxidants, catalysts, etc.) in the resin in the film cause a problem that the internal haze is increased.

  Removal of the unnecessary substance from the dope for optical film is conventionally performed also in the manufacture of a cellulose film, for example, in the dope containing a cellulose resin, the unnecessary substance is deposited and a chelating agent is added to the dope. A method of removing deposits has been reported (Patent Document 1).

  However, in the conventional method using a chelating agent, since the resin is precipitated by forming a complex with the resin impurities and the chelating agent, the dope may be discharged at the same time.

  The present invention has been made in view of such circumstances, and it is possible to efficiently remove impurities in the dope without using a chelating agent, and to use a high quality polyimide resin, polyarylate resin or cycloolefin resin having low internal haze. An object of the present invention is to provide a method of producing an optical film containing the same.

Patent No. 5729233 gazette

  As a result of intensive investigations, the present inventor has found that the above problems can be solved by the method for producing an optical film having the following constitution, and completed the present invention by repeating studies based on such findings.

  That is, in the method of producing an optical film according to one aspect of the present invention, in the solution casting film forming method, a polyimide resin, a polyarylate resin or a cycloolefin resin, at least one alcohol solvent, and at least one of the above resins The dope containing the type of good solvent was prepared, the optical dope was cast on the support, the web (casting film) was formed on the support, the web was peeled off from the support, and then peeled off. A method of producing an optical film by winding and drying a web, characterized in that the method comprises the steps of further adding a good solvent to the dope after adjusting the dope, and thereafter removing the good solvent. I assume.

FIG. 1 is a schematic view showing a basic configuration of an apparatus for producing an optical film by a solution casting method using an endless belt support.

  Hereinafter, although the embodiment concerning the present invention is described, the present invention is not limited to these.

  The method for producing an optical film according to the present embodiment is a solution-casting film-forming method comprising a polyimide resin, a polyarylate resin or a cycloolefin resin, at least one alcohol solvent, and a good solvent for at least one resin. Preparing the dope containing the optical fiber, casting the optical dope on the support, forming a web (cast film) on the support, peeling the web from the support, and then winding the peeled web The method for producing an optical film by drying is characterized by including the steps of further adding a good solvent to the dope after adjusting the dope, and then removing the good solvent.

  According to the above configuration, by removing impurities of the dope without using a chelating agent, an optical film containing a high quality polyimide resin, polyarylate resin or cycloolefin resin with low internal haze efficiently is produced. We can provide a way.

  In the present embodiment, the dope is a resin solution as a film raw material, and after casting on a support, a gelled material having a hardness as a film is referred to as a web (cast film). That is, the film in the process of drying to the finished optical film is referred to as a web. However, it should be noted that the boundary between the dome film, the web and the film formed by the dope is not strictly determined.

  Hereinafter, the solution casting film forming method will be described first.

Solution casting film forming method
FIG. 1 is an explanatory view showing a schematic configuration of an optical film manufacturing apparatus used in the present embodiment. In the method for producing an optical film according to the present embodiment, a dope containing a polymer (polyimide resin, polyarylate resin or cycloolefin resin) and a solvent is cast from a casting die on a traveling support, and then a film is produced. It uses a solution casting method that peels off. In addition, each code | symbol in FIG. 1 means the following. 1: Dissolution kettle, 2: Pump, 3: Casting die, 4: Decompression chamber, 5: Back and forth winding drum, 6: Endless belt for casting (support), 7: Peeling roll, 8: Web, 9: Tenter, 10: roll conveyance dryer, 11: warm air (dry air), 12: conveyance roll, 13: winder, F: film.

  The outline of the solution casting method will be described with reference to FIG. First, for example, a polyimide resin, a polyarylate resin or a cycloolefin resin is dissolved in a mixed solvent of a good solvent and a poor solvent in a dissolving pot 1, and additives such as a matting agent and an ultraviolet absorber are added thereto as necessary. The resin solution (dope) is prepared. In addition, the preparation method of each dope and a good solvent and a poor solvent are mentioned later.

  The dope is preferably filtered to remove insoluble matter, foreign matter and the like. The filter material to be used may be any filter material capable of removing insolubles and the like without causing clogging, for example, a filter medium having an absolute filtration accuracy of 0.008 mm or less, preferably 0.003 to 0.006 mm. It is preferred to use.

  Then, the dope prepared in the dissolution vessel 1 is fed to the casting die 3 through the pressure type metering gear pump 2 through the conduit to the casting die 3 and is cast on the support 6 consisting of the endlessly driven stainless steel endless belt. At the position, the dope is cast from the casting die 3 to form the web 8 as a cast film on the support 6.

  For casting the dope by the casting die 3, a doctor blade method in which the film thickness of the cast web is adjusted by a blade, a method by a reverse roll coater in which the film thickness of the cast web is adjusted by a reverse rotating roller, There is a method of using a pressure die, and the like. Among them, a method using a pressure die is preferable because the slit shape of the die part can be adjusted and the film thickness can be easily made uniform. The pressure dies include a coat hanger die and a T-die, and any of them can be preferably used.

  The support 6 is held by a pair of front and rear drums 5 and 5 and a plurality of intermediate rolls (not shown). One or both of the drums 5 is provided with a drive (not shown) for applying tension to the support 6, whereby the support 6 is used in tension.

  The width of the support 6 is preferably about 1000 to 4000 mm, and the width of the film after winding is preferably about 1000 to 2500 mm. Thereby, a wide optical film for a liquid crystal display can be manufactured by a metal support system.

  The belt temperature at the time of film formation in the case of using an endless belt as the support 6 is a temperature of -50 ° C. to less than the boiling point of the solvent in a general temperature range, but less than the boiling point of the solvent having the lowest boiling point in the mixed solvent The temperature is preferably in the range of 5 ° C. to 70 ° C., and more preferably in the range of 5 to 40 ° C. At this time, the ambient humidity needs to be controlled to the dew point or more. The moving speed of the support 6 under production conditions is preferably 5 m minutes or more, preferably 10 to 180 m / min, and more preferably 80 m / min to 150 m / min.

  The dope cast on the support 6 in this manner also increases the strength (film strength) of the gel film by promoting the drying until the peeling.

  The web 8 formed by the dope cast on the support 6 is heated on the support 6 and the solvent is evaporated from the support 6 until the web can be peeled off by the peeling roll 7.

  In order to evaporate the solvent and dry the web, there are a method of blowing air from the web side, a method of transferring heat by liquid from the back surface of the support, a method of transferring heat from the front and back by radiant heat, etc. The method is preferable because the drying efficiency is good. Moreover, the method of combining them is also preferably used. It is preferable to dry the web on the support after casting on the support under an atmosphere of 30 to 100 ° C. In order to maintain the atmosphere at 30 to 100 ° C., it is preferable to apply warm air of this temperature to the upper surface of the web or to heat it by means such as infrared rays.

  It is preferable to peel the said web from a support body within 30 to 180 seconds from a viewpoint of surface quality, moisture permeability, and peelability.

  It is preferable that web temperature when peeling the web 8 from the support body 6 is -50-60 degreeC, Furthermore, it is 10-40 degreeC, More preferably, it is 11-30 degreeC.

  The residual solvent content of the web on the metal support at the time of peeling is preferably in the range of 15 to 100% by mass. Control of the amount of residual solvent is preferably performed at the drying temperature and the drying time in the solvent evaporation step.

  The residual solvent content of the web or film is defined by the following formula (Z).

Formula (Z)
Residual solvent amount (%) = (mass before heat treatment of web or film−mass after heat treatment of web or film) / (mass after heat treatment of web or film) × 100
In addition, the heat processing at the time of measuring the amount of residual solvents represents performing the heat processing for 1 hour at 115 degreeC.

  The peeling tension at the time of peeling the support 6 and the web 8 by the peeling roll 7 is larger than the peeling force obtained by measuring the peeling force as in JIS Z 0237. If the peeling force obtained by the measurement method is made equal, the peeling position may be brought to the downstream side or the like, so it is performed at a high level for stabilization. In addition, even if it forms into a film by the same peeling tension in a process, when the peeling force by a JIS measuring method falls, it is also confirmed that the variation in the cross nicol transmittance | permeability (CNT) of a film reduces large.

  The peeling tension value in the process is usually 20 to 400 N / m, but in the case of an optical film produced by thinning as compared to the prior art, the residual solvent amount of the web 8 is large at the time of peeling and it is easy to stretch in the transport direction For this reason, the film is easily shrunk in the lateral direction, and when drying and shrinking overlap, the end curls and folds, so that wrinkles easily occur. For this reason, it is preferable that peeling tension is the minimum tension -190N / m which can be peeled.

  Although FIG. 1 exemplifies a belt-like support as the support, the support of the present embodiment is not limited to the belt-like support, and for example, a drum-like support may be used. .

  After the web 8 is dried and solidified to a peelable film strength on the support 6, the web 8 is peeled off by the peeling roll 7, and then the web 8 is stretched in the tenter 9 in the stretching step.

  In addition, the production method of the present embodiment may include a stretching step of stretching the obtained web. By performing stretching treatment with a low stretching ratio under a specific residual solvent amount with a stretching device (tenter 9), the occurrence of minute crazes in the vicinity of the film surface can be suppressed and uniform distribution of the matting agent can be promoted. it can. Furthermore, by controlling the orientation of the molecules in the film, it is possible to obtain a retardation value Ro in a target in-plane direction and a retardation value Rt in a thickness direction.

  In the stretching step, a tenter method in which both side edges of the web 8 are fixed by a clip or the like and stretched is preferable in order to improve the planarity and dimensional stability of the film.

  In the present embodiment, in the step of stretching the film, the amount of residual solvent at the start of stretching is preferably 1% by mass or more and less than 25% by mass. More preferably, it is in the range of 5 to 20% by mass.

  The optical film of the present embodiment is preferably stretched in the longitudinal direction (MD direction, also referred to as casting direction) and / or the transverse direction (also referred to as TD direction), at least in the transverse direction by the stretching device. It is preferable to draw and manufacture.

  The stretching operation may be divided into multiple steps. Moreover, when performing biaxial stretching, simultaneous biaxial stretching may be performed and you may implement in steps. In this case, stepwise means that, for example, stretching in different stretching directions can be sequentially performed, or stretching in the same direction can be divided into multiple stages, and stretching in different directions can be added to any of the stages. Is also possible.

  The stretching temperature and the stretching ratio can be appropriately set in accordance with the resin to be used and the desired film characteristics.

  After the tenter 9 in the stretching step, the stretched film is heated and dried in the drying apparatus 10. In the drying apparatus 10, the web 8 is made to meander by a plurality of transport rolls 12 arranged in a staggered manner when viewed from the side, and the web 8 is dried in between.

  The means for drying the web 8 is not particularly limited, and is generally performed by hot air, infrared rays, heating rolls, microwaves, or the like. It is preferable to dry with hot air from the point of simplicity. For example, the drying air 11 is blown from the hot air inlet of the drying device 10, and the exhaust air is discharged from the outlet of the drying device 10, whereby the web 8 can be dried to form an optical film F. The temperature of the drying air 11 is preferably 40 to 350 ° C., and the drying time is preferably about 5 seconds to 30 minutes.

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

  Next, the dried film is taken up by a take-up device 13 to obtain an original film of the optical film F. By setting the amount of residual solvent in the film at the end of drying to 0.5% by mass or less, preferably 0.1% by mass or less, a film with good dimensional stability can be obtained.

  As a film winding method, a generally used winder may be used, and there are methods for controlling tension such as a constant torque method, a constant tension method, a taper tension method, a program tension control method with constant internal stress, etc. It should be used properly. Bonding of the film to the winding core (winding core) may be either double-sided adhesive tape or single-sided adhesive tape. In the optical film F, the width of the film after winding is preferably 1000 to 2500 mm.

  The film thickness (final film thickness) after drying of the optical film of the present embodiment is preferably in the range of 5 to 40 μm as a finished film from the viewpoint of thinning of the liquid crystal display device. Here, the film thickness after drying means a film in which the amount of residual solvent in the film is 0.5% by mass or less.

  Next, features of the manufacturing method of the present embodiment will be described in more detail.

  The method for producing an optical film according to the present embodiment is a method for producing an optical film according to the above-described solution-casting film forming method, wherein a dope is a polyimide resin, a polyarylate resin or a cycloolefin resin, at least one alcohol solvent, and the resin. A major feature of the present invention is the adjustment of a dope containing at least one good solvent, and the steps of further adding a good solvent to the dope after adjusting the dope and then removing the good solvent. One of the

  In addition, liquid preparation of the dope of this embodiment can be performed using a well-known dope manufacturing apparatus. Specifically, for example, using a dope production apparatus having a feed port for charging the material in the upper part, a mixing pot provided with a rotating body for mixing the material, and an outlet port for taking out the sample mixed in the lower part. Adjust the dope.

  The dope preparation can be prepared by mixing the materials and then high temperature dissolution method or the like. The high temperature melting method heats the said mixed solution to the range of 30-200 degreeC under the pressurization of the range of 0.2-30 Mpa. The temperature range is preferably in the range of 40 to 150 ° C., and more preferably in the range of 40 to 100 ° C. As a heating method, for example, high pressure steam may be used, or an electric heat source may be used. When the dope is prepared by a high temperature melting method, the mixing pot is preferably a pressure resistant pressure tank.

  The alcohol solvent used for the dope of the present embodiment is not particularly limited, and examples thereof include methanol, ethanol, isopropanol, n-butanol, 2-butanol and the like. Among them, it is preferable to select from methanol, ethanol and butanol from the viewpoint of improving the releasability and enabling high-speed casting. In particular, it is preferable to use methanol or ethanol.

  Moreover, it is preferable that the density | concentration of the alcohol solvent at the time of adjusting dope is about 2-30 mass% with respect to the total solvent amount. When the ratio of the alcohol solvent in the solvent contained in the dope is in the above range, the web is appropriately gelled to facilitate peeling from the metal support, and dissolution of the resin and other compounds in the organic solvent It is thought to promote moderately. The ratio of the alcohol solvent in the total solvent is more preferably about 2 to 20% by mass.

  Next, the good solvent used when preparing the dope of the present embodiment is not particularly limited as long as it is a solvent which is easily solvated with a polymer (resin). Specifically, in this embodiment, a good solvent means a solvent which is transparent in a state in which the resin constituting the dope is dissolved in 10% by mass or more in the solvent. The term "transparent" means that the quartz cell is filled with a dope and the haze is measured by a haze meter, that is, the Δ haze (dope-filled haze-quartz cell haze) <3.0.

  More specific good solvents include, for example, dichloromethane and tetrachloromethane as a chlorine-based organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, methyl ethyl ketone, tetrahydrofuran, and a non-chlorine-based organic solvent. 3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3 3-pentafluoro-1-propanol, nitroethane, methanol, ethanol, n-propanol, iso-propanol, - butanol, sec- butanol, tert- butanol and the like. Among them, it is preferred if the resin is a polyarylate or cycloolefins in the case of dichloromethane, the resin is polyimide tetrachloromethane. The amount of the good solvent used for the dope is preferably 55% by mass or more, more preferably 70% by mass or more, and still more preferably 80% by mass or more based on the total amount of the solvent contained in the dope.

  In the production method of the present embodiment, a dope is prepared using a mixed solvent containing at least one kind of alcohol solvent and at least one good solvent as described above, and after preparing the dope, the good solvent is further added. As a good solvent to add, the same thing as the above-mentioned good solvent is mentioned. The good solvent used at the time of dope preparation and the good solvent to be added after preparation may be the same or different.

  Although a method of adding a good solvent to the dope after preparation is not particularly limited, a good solvent separately prepared after the preparation of the dope may be added as it is, or the good solvent in the dope volatilized by heating at the time of preparation of the dope may be used. It is also possible to cool back into droplets which are added by dripping. The timing for adding a good solvent is also not particularly limited, but there is a risk of volatilization even when the dope is at a high temperature, so the dope is supported after the temperature of the dope falls below the boiling point of the good solvent. It is preferable to add it before casting to the body.

  The addition amount of the good solvent after the preparation of the dope is preferably about 1 to 50% by mass with respect to the total amount of the dope. If the addition amount of the good solvent is within this range, the removal rate of the impurities increases, so it is possible to ensure the quality of the produced film, and to reduce the doping loss due to the solvent removal and to shorten the time, which is preferable. A more preferable addition amount is about 2 to 10% by mass with respect to the total amount of the dope.

  The manufacturing method of the present embodiment further includes the step of removing the good solvent after adding the good solvent. The means for removing the good solvent is not particularly limited, and can be removed by a conventionally known method. Specifically, for example, it may be taken out from the outlet of the above-described dope production apparatus, or the good solvent may be removed by branching the liquid delivery pipe and recycling / discarding only the solvent.

  The timing for removing the good solvent is not particularly limited, but it is preferable to remove it, for example, before the start of liquid feeding or during the change of the liquid feeding pot.

  The amount of the good solvent to be removed is preferably 80 to 100% by mass of the amount of the good solvent to be added. If the removal amount of the good solvent is within this range, the removal rate of the impurities increases, so that the film quality can be secured. The more preferable removal amount of the good solvent is about 90 to 100% by mass with respect to the amount of the good solvent to be added.

  According to the manufacturing method as described above, it is possible to efficiently remove the doped impurities and provide a method for manufacturing an optical film containing a high quality polyimide resin, polyarylate resin or cycloolefin resin having a low internal haze. it can.

[Dope]
(Doped for polyimide film)
The dope used for the polyimide resin containing optical film in this embodiment contains a polyamic acid or a polyimide as a main material.

  Although not particularly limited, it is preferable to use a polyamic acid or polyimide having a weight average molecular weight of 30,000 to 1,000,000. More specifically, for example, polyamic acid or polyimide as described in JP-A-2016-64642 can be used.

  As described above, a mixed solvent containing at least one alcohol solvent and at least one good solvent is used as the mixed solvent for dissolving the polyamic acid or the polyimide. Among them, it is preferable to use a solvent containing 50% by mass or more of tetrachloromethane as a good solvent.

  Specific examples of the preparation method of the dope in which the polyamic acid or the polyimide is dissolved in the mixed solvent containing 50 mass% or more of the above-mentioned tetrachloromethane include, for example, the following methods (i) to (iii). Not limited to these methods.

  (I) Preferably, an aromatic, aliphatic or alicyclic tetracarboxylic acid or a derivative thereof is added to a solution of diamine or a derivative thereof, or preferably a solution of an aromatic, aliphatic or an alicyclic tetracarboxylic acid component Then, a diamine or a derivative thereof is added and kept at a temperature of preferably 80 ° C. or less (more preferably 30 ° C. or less) for 0.5 to 3 hours to obtain a polyamic acid solution. As a solvent used here, the said polymerization solvent is used.

  The dope according to the present invention can be obtained by replacing the polymerization solvent in the obtained polyamic acid solution with a mixed solvent containing the above-mentioned tetrachloromethane and an alcohol solvent.

  (Ii) A dehydration reaction of the polyamic acid solution obtained in the above (i) can be performed to obtain a polyimide solution. In this case, it is preferable to add the above dehydrating agent and the above ring closing catalyst. Further, it is preferable to add a solvent such as toluene or xylene which is azeotroped with water to the polyamic acid solution, and carry out a dehydration reaction while removing generated water azeotropically out of the system. The reaction temperature is preferably in the temperature range of −20 to 50 ° C. when the ring closure catalyst is added, and is preferably in the temperature range of 80 to 300 ° C. when the ring closure catalyst is not added. .

  Thus, it is preferable to allow the ring closure reaction to proceed in the solution, since it is possible to remove byproducts and residual monomers of the dehydrating agent.

  The dope according to the present invention can be obtained by replacing the polymerization solvent in the polyimide solution obtained by any of the above methods with a mixed solvent containing the above tetrachloromethane and an alcohol solvent.

  (Iii) A dehydrating agent such as acetic anhydride is added to the polyamic acid solution obtained in the above (i) and imidization is performed by heating or addition of a ring closure catalyst, and then a solvent such as methanol having poor solubility in polyimide is added. Precipitate the polyimide. After separating as a solid by filtration, washing and drying, the dope according to the present invention can be obtained by dissolving in the above mixed solvent.

  The concentration of the polyamic acid or polyimide in the dope prepared as described above is preferably 1 to 50% by mass, and more preferably 10 to 40% by mass. If it is 50 mass% or less, the surface flatness of the polyimide film obtained will become favorable.

  The viscosity of the above-mentioned dope is preferably 1000 to 100000 cp, preferably 10000 to 50000 cp, as measured by a Brookfield viscometer, since stable liquid delivery is possible.

Various additives can be added to the dope containing the above-mentioned polyamic acid or polyimide, if necessary. Additives that can be used include inorganic fillers, surfactants, antioxidants, and other various functional materials (for example, conductive materials such as carbon nanotubes and nano metal materials, and ferroelectric materials such as barium titanate) And phosphors such as ZnS: Ag, ZnS: Cu, Y ₂ O ₂ S: Eu, UV absorbers, etc., flame retardants, and the like.

  In addition, when a web is formed using a polyamic acid, a polyimide film can be manufactured by giving an imidization process with respect to the obtained film.

By applying appropriate heat treatment to the film, imidization proceeds in the polymer chain molecules and between polymer chain molecules to improve the mechanical properties, but as the heat treatment is applied, the polyimide film changes color saturation with changes in absorption wavelength . In particular, in thin polyimide films of 4.0 to 15.0 μm, the higher the L * value, the thinner the color as a whole, and it is difficult to see lateral step unevenness due to thickness unevenness and the appearance becomes good, but the imidization Since the degree of progress is not sufficient, mechanical properties such as bending resistance and breaking strength of the polyimide film are deteriorated. On the other hand, if the L * value is too low, the color contrast due to thickness unevenness becomes clear, and not only the lateral unevenness gets worse, but the polyimide film is partially carbonized and becomes brittle and the mechanical properties of the film are remarkable fall back. From the above reasons, in the method for producing a polyimide film of the present invention, it is better to maintain an L * value of 30 to 55 for maintaining good mechanical properties, and more preferably, an L * value of 38 to 54 Is good.

The L * value of the film was measured using SM-7-CH manufactured by Suga Test Instruments. For each sample divided into five in the film width direction, a 30 mm × 30 mm range centered on the center position in the width direction was cut out and measured, and the five-point average value was taken. The L * value is 1 for films with a film thickness of 50 μm or more, and 50 μm or more for a film with a film thickness of 50 μm or less, because the sensitivity of the detector decreases as the film thickness decreases. It is a value measured by overlapping the minimum number of sheets.

As a heat treatment method for obtaining a film having an L * value of 30 to 55, for example, a method of adjusting the heat treatment amount using a known means such as hot air or an electric heater (for example, an infrared heater) Can be mentioned.

In the method for producing a polyimide film of the present embodiment, a solution of a polyamic acid which does not contain a ring-closing catalyst is cast to form a film, heat-dried on a support, and the film is peeled from the support It is possible to use a thermal imidization method in which imidization is performed by drying heat treatment below. In the case of this method, the reaction speed of imidation can be improved by containing the dehydrating agent in the polyamic acid solution, but it is preferable not to contain the dehydrating agent. By not containing the dehydrating agent, it is possible to suppress the decrease in the durability of the polyimide film due to the residual dehydrating agent. In the thermal imidization method, heat treatment can be performed, for example, by using an infrared heater.

In addition, a solution of a polyamic acid containing a ring-closing catalyst and a dehydrating agent is cast and formed into a film, and imidization is partially advanced on the support to form a film, and then the film is peeled from the support. It is also possible to use a chemical imidization method in which heat drying / imidization and heat treatment are performed. As the cyclization catalyst, the above-mentioned tertiary amines and the like can be used. In addition, in the case of this method, imidation can be advanced at a low temperature by containing a dehydrating agent in the polyamic acid solution, so that the decrease in the durability of the polyimide film can be suppressed.

Although any of the above ring-closing methods may be employed in the method for producing a polyimide film, the chemical imidation method requires equipment for containing a ring-closing catalyst and a dehydrating agent in a solution of polyamic acid, but is self-supporting. It can be said that it is a more preferable method in that the film having it can be obtained in a short time.

(Dope for polyarylate film)

The dope used for the polyarylate resin-containing optical film in the present embodiment contains polyarylate as a main material. The polyarylate contains at least an aromatic dialcohol component unit and an aromatic dicarboxylic acid component unit. More specifically, for example, polyarylates as described in JP-A-2016-112773 can be used.

The glass transition temperature of the polyarylate used in this embodiment is preferably 260 ° C. or more and 350 ° C. or less, more preferably 265 ° C. or more and less than 300 ° C., and still more preferably 270 ° C. or more and less than 300 ° C. preferable. The glass transition temperature of polyarylate can be measured in accordance with JIS K 7121 (1987). Specifically, using a DSC 6220 manufactured by Seiko Instruments Inc. as a measurement apparatus, measurement can be performed under the conditions of a 10 mg sample of polyarylate and a temperature rising rate of 20 ° C./min.

The glass transition temperature of the polyarylate can be adjusted depending on the kind of aromatic dialcohol component constituting the polyarylate. In order to raise the glass transition temperature, for example, it is preferable to include “a unit derived from bisphenols containing a sulfur atom in the main chain” as an aromatic dialcohol component unit.

The intrinsic viscosity of the polyarylate used in this embodiment is preferably 0.3 to 1.0 dl / g, more preferably 0.4 to 0.9 dl / g, and 0.45 to 0.8 dl / g Is more preferably 0.5 to 0.7 dl / g. When the intrinsic viscosity of the polyarylate is 0.3 dl / g or more, the molecular weight of the resin composition tends to be a certain level or more, and a film having sufficient mechanical properties and heat resistance is easily obtained. When the intrinsic viscosity of the polyarylate is 1.0 dl / g or less, excessive increase in solution viscosity during film formation can be suppressed.

Intrinsic viscosity may be measured in accordance with ISO 1628-1. Specifically, a solution in which a polyarylate sample is dissolved in 1,1,2,2-tetrachloroethane to a concentration of 1 g / dl is prepared. The intrinsic viscosity of this solution at 25 ° C. is measured using a Ubbelohde viscosity tube.

The method for producing polyarylate may be a known method, and preferably an interface in which an aromatic dicarboxylic acid halide dissolved in an organic solvent incompatible with water and an aromatic dialcohol dissolved in an aqueous alkali solution are mixed. It may be a polymerization method (W. M. EARECKSON, J. Poly. Sci. XL 399, Japanese Patent Publication No. 40-1959).

The dope containing the above polyarylate may be, if necessary, a resin other than polyarylate, a heat stabilizer, an antioxidant, a light stabilizer, a colorant, an antistatic agent, a lubricant, a release agent, an ultraviolet ray absorbing agent An additive such as an agent may further be included.

As described above, the polyarylate as described above is dissolved in a mixed solvent containing at least one alcohol solvent and at least one good solvent to obtain a dope.

The concentration of polyarylate in the dope is preferably 10% by mass or more, preferably about 10 to 30% by mass.

(Dope for cyclo-olefin film)

The dope used for the cycloolefin resin-containing optical film in the present embodiment contains cycloolefin as a main component.

The cycloolefin resin used in this embodiment may be used alone or in combination of two or more cycloolefin resins. The preferred molecular weight of the cycloolefin resin used in this embodiment is 0.2 to ⁵ cm ³ / g, more preferably 0.3 to ³ cm ³ / g, and particularly preferably 0.4 to ³ cm ³ / g in intrinsic viscosity [η] inh. It is 1.5 cm ³ / g, and the number average molecular weight (Mn) in terms of polystyrene measured by gel permeation chromatography (GPC) is 800 to 100000, more preferably 10000 to 80000, and particularly preferably 12000 to 50000. The weight average molecular weight (Mw) is in the range of 20,000 to 300,000, more preferably 30,000 to 250,000, and particularly preferably 50,000 to 200,000.

When the intrinsic viscosity [水性] inh, the number average molecular weight and the weight average molecular weight are in the above ranges, the heat resistance, water resistance, chemical resistance, mechanical properties of the cycloolefin resin, and the molding process as the optical film of the present invention The quality is good.

The glass transition temperature (Tg) of the cycloolefin resin used in the present embodiment is preferably 130 ° C. or higher, preferably 130 to 350 ° C., more preferably 130 to 250 ° C., particularly preferably 130 to 220 ° C. When Tg is 130 ° C. or higher, deformation is less likely to occur by use under high temperature conditions or secondary processing such as coating and printing.

On the other hand, by setting Tg to 350 ° C. or less, it is possible to avoid the case where molding processing becomes difficult, and to suppress the possibility of the resin deteriorating due to the heat at the molding processing.

Moreover, a commercial item can be preferably used for a cycloolefin resin, As an example of a commercial item, Arton (Arton (registered trademark) G series, Arton F series, Arton R series, and Arton RX series from JSR Co., Ltd.) ZEONOR (Zeonor (registered trademark) ZF14, ZF16, 1420R, 1020R, 1060R, 1420R, etc. from Zeon Corporation (Japan), Zeonex (registered trademark) 250, 280, 480, 480R. E48R, F52R, 330R, RS420 and the like, which are commercially available under the trade names, and these can be appropriately selected and used according to the application.

In the above-mentioned dope containing a cycloolefin, if necessary, a resin other than a cycloolefin resin, a heat stabilizer, an antioxidant, a light stabilizer, a colorant, an antistatic agent, a lubricant, a release agent, an ultraviolet ray An additive such as an absorbent may further be included.

As described above, the cycloolefin as described above is dissolved in a mixed solvent containing at least one alcohol solvent and at least one good solvent to obtain a dope.

In order to dissolve the cycloolefin resin, a method under normal pressure, a method under the boiling point of the main solvent, a method under pressure above the boiling point of the main solvent, JP-A 9-95544, JP-A 9-95557 Or, various dissolution methods such as a method of cooling and dissolving as described in JP-A-9-95538, a method of performing at high pressure described in JP-A-11-21379, and the like can be used. It is preferred to carry out the process under pressure above the boiling point of the solvent.

The concentration of the cycloolefin resin in the dope is preferably in the range of 10 to 40% by mass.

The optical film produced by the production method of the present embodiment is useful as a functional film used for various displays such as liquid crystal displays, plasma displays, organic EL displays, particularly liquid crystal displays, and a polarizing plate protective film, retardation film, It can also be used as an antireflective film, a brightness enhancement film, or an optical compensation film such as a wide viewing angle.

  Although the present specification discloses various aspects of the technology as described above, the main technologies are summarized below.

  The method for producing an optical film according to one aspect of the present invention is a solution casting film forming method comprising: a polyimide resin, a polyarylate resin or a cycloolefin resin; at least one alcohol solvent; and at least one of the resins. A dope containing a good solvent is prepared, the optical dope is cast on a support, a web (casting film) is formed on the support, the web is peeled off from the support, and the peeled web is then peeled off. A method for producing an optical film by winding and drying, which comprises the steps of further adding a good solvent to the dope after adjusting the dope, and thereafter removing the good solvent. .

  With such a configuration, it is possible to produce an optical film containing high quality polyimide resin, polyarylate resin or cycloolefin resin with low internal haze by removing impurities of the dope without using a chelating agent. it can.

  Furthermore, in the method for producing an optical film, the good solvent is preferably dichloromethane or tetrachloromethane. Thereby, the above-mentioned effect can be obtained more reliably.

  In the method for producing an optical film, the amount of the good solvent to be added is preferably 1 to 50% by mass with respect to the total amount of the dope. Thereby, the above-mentioned effect can be obtained more reliably.

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

Example 1
The polyarylate film was manufactured by the method shown below.

(Composition of polyarylate 1)
After adding 2514 parts by weight of water to a reaction vessel equipped with a stirrer, 22.7 parts by weight of sodium hydroxide, 9,9-bis (3,5-dimethyl-4-hydroxyphenyl as an aromatic dialcohol component ) 35.6 parts by weight of fluorene (BCF), 18.5 parts by weight of 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane (TMBPA), p-tert-butylphenol (PTBP) as a molecular weight regulator 0.049 parts by weight was dissolved and 0.34 parts by weight of a polymerization catalyst (tributylbenzylammonium chloride) was added and stirred.

  On the other hand, 26.8 parts by weight of an equal mixture of terephthalic acid chloride and isophthalic acid chloride as an aromatic dicarboxylic acid component was weighed and dissolved in 945 parts by weight of methylene chloride. The methylene chloride solution was added to the aqueous alkaline solution prepared above under stirring to initiate polymerization. The polymerization reaction temperature was adjusted to be 15 ° C. or more and 20 ° C. or less. The polymerization was carried out for 2 hours, after which acetic acid was added to the system to terminate the polymerization reaction, and the organic phase and the aqueous phase were separated.

  The obtained organic phase was washed with twice as much ion-exchanged water as the organic phase for each washing, and the operation of separating the organic phase and the aqueous phase was repeated. The washing was finished when the conductivity of the washing water was less than 50 μS / cm. The organic phase after washing was placed in a warm water tank equipped with a homomixer at 50 ° C., and methylene chloride was evaporated to obtain a powdery polymer. Further dehydration and drying were performed to obtain polyarylate 1.

(Preparation of dope)
(Composition of main dope)
Dichloromethane 360 parts by mass Ethanol 40 parts by mass Polyarylate 1 100 parts by mass Particles: Nippon Aerosil Co., Ltd. R812 (primary particle diameter 7 nm) 0.1 parts by mass

  A main dope of the above composition was prepared. First, dichloromethane (MC) and ethanol (ETOH) were added as a mixed solvent to a pressure dissolution tank. In addition, content of the alcohol in a mixed solvent was 10 mass%. The polyarylate 1 prepared above was charged into a pressure dissolution tank containing the mixed solvent while stirring. The mixture is heated and completely dissolved while stirring, and this is dissolved in Azumi Filter Paper No. After filtration using 244, the remaining components were added and stirred to dissolve to prepare the main dope.

  Then, the dichloromethane which was volatilized during heating and stirring was coagulated into a liquid using a cooling facility, and added dropwise to the dope so that the addition amount with respect to the total amount of the dope was 50% by mass.

(Casting process)
Then, using an endless belt casting apparatus, the dope was uniformly cast on a stainless steel belt support at a temperature of 30 ° C. and a width of 1500 mm. The temperature of the stainless steel belt was controlled at 30 ° C.

(Peeling process)
The solvent was evaporated on a stainless steel belt support until the amount of residual solvent in the casted film was 75%, and then peeled off from the stainless steel belt support with a peeling tension of 180 N / m.

(Drying process)
The web with a residual solvent ratio of 25% by mass peeled is dried at a drying temperature at which the amount of residual solvent is less than 0.1% by mass with a conveying tension of 100 N / m and a drying time of 15 minutes by a conveying roll. Film was obtained. The obtained film was wound up.

(Heating process)
The film thus wound up was subjected to heat treatment at 300 ° C. for 5 minutes with an infrared heater to obtain a polyimide film 1.

Example 2
The same procedure as in Example 1 was carried out except that, in the preparation of the dope, dichloromethane volatilized during heating and stirring was condensed to a liquid using a cooling facility and added to the dope so that the added amount was 30% by mass with respect to the total amount of the dope. The polyarylate film 2 was obtained.

[Example 3]
The same procedure as in Example 1 was carried out except that, in the preparation of the dope, dichloromethane volatilized during heating and stirring was condensed to a liquid using a cooling facility and added to the dope so that the added amount was 10% by mass with respect to the total amount of the dope. The polyarylate film 3 was obtained.

Example 4
The same procedure as in Example 1 was carried out except that, in the preparation of the dope, dichloromethane volatilized during heating and stirring was coagulated into a liquid using a cooling facility and added to the dope so that the added amount was 1% by mass with respect to the total amount of the dope. The polyarylate film 4 was obtained.

[Example 5]
A polyarylate film 5 was obtained in the same manner as in Example 3, except that the content of alcohol in the mixed solvent was changed to 2% by mass in the preparation of the dope.

[Example 6]
A polyarylate film 6 was obtained in the same manner as in Example 3, except that the content of alcohol in the mixed solvent was changed to 30% by mass in the preparation of the dope.

[Example 7]
A polyarylate film 7 was obtained in the same manner as in Example 3 except that methanol was used as the alcohol in the mixed solvent in the preparation of the dope.

[Example 8]
A polyarylate film 8 was obtained in the same manner as in Example 3, except that the alcohol in the mixed solvent was changed to butanol in the preparation of the dope.

[Example 9]
A polyarylate film 9 was obtained in the same manner as in Example 3 except that in the preparation of the dope, after the preparation of the dope, dichloromethane separately prepared was added so that the addition amount with respect to the total amount of the dope was 10% by mass.

[Example 10]
In the preparation of the dope, a polyarylate film 10 was obtained in the same manner as in Example 3 except that, after the preparation of the dope, separately prepared chloroform was added such that the addition amount was 10% by mass with respect to the total amount of the dope.

[Example 11]
A polyarylate film 11 was obtained in the same manner as in Example 3 except that in the preparation of the dope, separately prepared tetrahydrofuran (THF) was added after the preparation of the dope so that the addition amount was 10% by mass with respect to the total amount of the dope.

[Example 12]
In the preparation of the dope, Example 3 was used except that the good solvent of the main dope was methyl ethyl ketone (MEK), MEK volatilized during heating and stirring was cooled, and added to the dope so that the addition amount was 10% by mass relative to the total amount of the dope. Polyarylate film 12 was obtained in the same manner as in.

[Example 13]
The cycloolefin film was manufactured by the method shown below.

(Cyclo-olefin)
The cycloolefin resin (COP) was subjected to dope adjustment using commercially available ARTON G7810 (manufactured by JSR Corporation, weight average molecular weight (Mw) = 140,000). The cycloolefin resin is a resin having a glass transition temperature of 178 ° C. and an alkoxycarbonyl group as a polar group.

(Preparation of dope)
(Composition of main dope)
Dichloromethane 198 parts by mass Ethanol 22 parts by mass The above cycloolefin resin 100.0 parts by mass Particles: Nippon Aerosil Co., Ltd. R812 (primary particle diameter 7 nm) 0.1 parts by mass

  A main dope of the above composition was prepared. First, dichloromethane (MC) and ethanol (ETOH) were added as a mixed solvent to a pressure dissolution tank. In addition, content of the alcohol in a mixed solvent was 10 mass%. The above prepared polyimide A was charged into a pressure dissolution tank containing the mixed solvent while stirring. The mixture is heated and completely dissolved while stirring, and this is dissolved in Azumi Filter Paper No. After filtration using 244, the remaining components were added and stirred to dissolve to prepare the main dope.

  And the dichloromethane which volatilized at the time of heating stirring was cooled, and it added dropwise to the dope so that the addition amount with respect to the dope whole quantity might be 10 mass%.

(Casting process)
Then, using an endless belt casting apparatus, the dope was uniformly cast on a stainless steel belt support at a temperature of 30 ° C. and a width of 1500 mm. The temperature of the stainless steel belt was controlled at 30 ° C.

(Peeling process)
The solvent was evaporated on a stainless steel belt support until the amount of residual solvent in the cast film was 30%, and then peeled off from the stainless steel belt support with a peeling tension of 180 N / m.

(Drying process)
The web with a residual solvent ratio of 10% by mass peeled is dried by a conveying roll at a conveying temperature of 100 N / m and a drying time of 15 minutes at a drying temperature at which the residual solvent amount is less than 0.1 mass%. Film was obtained. The obtained film was wound up.

(Heating process)
The film thus wound up was subjected to a heat treatment at 100 ° C. for 5 minutes by an infrared heater to obtain a cycloolefin film 1.

Example 14
The cycloolefin was prepared in the same manner as in Example 13 except that the cycloolefin resin (COP) was used as a commercially available RX 4500: ARTON-RX 4500 (manufactured by JSR Corporation, weight average molecular weight (Mw) = 63000). The film 14 was obtained.

[Example 15]
The polyimide film was manufactured by the method shown below.

(Synthesis of Polyimide A)
100 g (0.31 mol) of 2,2'-bis (trifluoromethyl) benzidine, 500 g of hexafluoroisopropyl alcohol, (2.5% Pt-2.5% Pd / in a 1 l autoclave equipped with a stirrer. C) 17 g of supported catalyst was added.

  After the inside of the reactor was replaced with hydrogen while stirring was stopped, the bath temperature was gradually raised, and the reduction reaction was performed at a hydrogen pressure of 1.0 MPa while adjusting the internal temperature to around 100 ° C. Since the absorption of hydrogen was almost completed in 2 hours, the reactor was ice-cooled and hydrogen in the reactor was gradually purged. The reaction solution was filtered to remove the catalyst (2.5% Pt-2.5% Pd / C), and the product was isolated by distillation to obtain about 22 g of diamine (yield 21. 6%).

  In a 300 ml three-necked flask equipped with a stirrer, 1.18 g (3.54 mmol) of the diamine synthesized above, 1.57 g (3.54 mmol) of 4,4 '-(hexafluoroisopropylidene) diphthalic anhydride, N- 13.4 ml of methyl 2-pyrrolidone was added, and it stirred at 80 degreeC under nitrogen stream for 3 hours. The resulting reaction solution was allowed to cool to room temperature and then poured into methanol / water (1/1% by volume) to precipitate a polymer. After collected by filtration, it was dried under reduced pressure at 35 ° C. to obtain 2.61 g of polyamic acid A as white powder represented by the following formula (yield: 95%).

  54 g of the polyamic acid A repeatedly synthesized as described above was weighed and dissolved in dimethylacetamide. Next, after developing on a clean glass plate, heat treatment was performed at 200 ° C. for 1 hour and 310 ° C. for 1 hour in a nitrogen stream, and 47 g of polyimide A represented by the following formula was obtained as a transparent polyimide (collected 92%).

(Preparation of dope)
(Composition of main dope)
Tetrachloromethane 396 parts by mass Ethanol 4 parts by mass Polyimide A (weight-average molecular weight: 203000, imidation ratio: 100%)
100.0 parts by mass Particles: Nippon Aerosil Co., Ltd. R812 (primary particle diameter 7 nm) 0.1 parts by mass

  A main dope of the above composition was prepared. First, tetrachloromethane and ethanol (ETOH) were added as a mixed solvent to a pressure dissolution tank. In addition, content of the alcohol in a mixed solvent was 10 mass%. The above prepared polyimide A was charged into a pressure dissolution tank containing the mixed solvent while stirring. The mixture is heated and completely dissolved while stirring, and this is dissolved in Azumi Filter Paper No. After filtration using 244, the remaining components were added and stirred to dissolve to prepare the main dope.

  Then, tetrachloromethane volatilized during heating and stirring was coagulated into a liquid using a cooling facility, and added dropwise to the dope so that the addition amount was 10% by mass with respect to the total amount of the dope.

(Casting process)
Then, using an endless belt casting apparatus, the dope was uniformly cast on a stainless steel belt support at a temperature of 30 ° C. and a width of 1500 mm. The temperature of the stainless steel belt was controlled at 30 ° C.

(Peeling process)
The solvent was evaporated on a stainless steel belt support until the amount of residual solvent in the casted film was 75%, and then peeled off from the stainless steel belt support with a peeling tension of 180 N / m.

(Drying process)
The web with a residual solvent ratio of 30% by mass peeled is dried by a conveying roll at a conveying tension of 100 N / m and a drying time of 15 minutes at a drying temperature at which the residual solvent amount is less than 0.1 mass%. Film was obtained. The obtained film was wound up.

(Heating process)
The film thus wound up was subjected to heat treatment at 300 ° C. for 5 minutes with an infrared heater to obtain a polyimide film 1.

Comparative Example 1
Polyarylate film in the same manner as in Example 3 except that in the preparation of the dope, pure ethanol different from ethanol prepared as a component of the main dope was added to the dope so that the addition amount was 10% by mass based on the total amount of the dope. I got thirteen.

Comparative Example 2
A polyarylate film 14 was obtained in the same manner as in Example 3 except that the main dope was changed to the following dope in the preparation of the dope.

(Composition of main dope)
Dichloromethane 400 parts by mass Polyarylate 1 100 parts by mass Particles: Nippon Aerosil Co., Ltd. R812 (primary particle diameter 7 nm) 0.1 parts by mass

[Reference example]
(Composition of main dope)
Dichloromethane 440 parts by mass Ethanol 40 parts by mass Cellulose triacetate (acetization degree 61.0%, Mn = 148000, Mw = 310000, Mw / Mn = 2.1)
100 parts by mass Particles: Nippon Aerosil Co., Ltd. R812 (primary particle diameter 7 nm) 0.1 parts by mass

  When a cellulose triacylate film was produced in the same manner as in Example 3 except that the main dope was used, no film could be formed.

  It is considered that the affinity between the cellulose dope and the dichloromethane is high, and the dope is partially diluted by the post-added solvent to cause concentration unevenness.

<Evaluation>
The following evaluation test was done about each film (Examples 1-15 and Comparative Examples 1-2) obtained as mentioned above.

[Scatterability evaluation]
The obtained optical film is disposed between two polarizing plates in orthogonal (cross Nicol) state, light is applied from one polarizing plate side, and visually observed from the other polarizing plate side, The number (number / m ² ) of the bright spot foreign matter was measured. At that time, a central portion, an end portion, and the like in the width direction were observed at a plurality of locations within the length of 100 m of the optical film.

  Then, in the case where the number of the bright spot foreign matter is 1/2 or less of the film manufactured by the ordinary process, "◎", equivalent to 1/2 to "を", and the deteriorated one was evaluated as "x".

[Internal Haze]
For each film, the internal haze of the film was measured according to the following method. First, glass / glycerin / film / glycerin / glass was stacked in this order using a cleanly cleaned slide glass. Glycerin was added dropwise (0.05 ml), taking care not to let air bubbles enter. After that, using an internal haze measuring device (Haze meter (turbidimeter) (model: NDH 2000, manufactured by Nippon Denshoku Co., Ltd.)), the light source is a 5V 9W halogen bulb, Attached) and measurement were performed according to JIS K-7136 to measure the internal haze (%).

  Slide glass used: MICRO SLIDE GLASS S9213 MATSUNAMI, cover glass: Matsunami cover glass 24 × 50 mm (KN3321827), glycerin: Kanto Chemical Co., Ltd. deer special grade (purity> 99.0%), refractive index 1.47 .

Evaluation criteria were as follows:
X: 0.2 or more real harm △: more than 0.15 to less than 0.2 real no ○: 0.1 to 0.15 good ◎: less than 0.1 good Table 1 shows the results.

[Discussion]
As can be seen from Table 1, in Examples 1 to 13 obtained by the production method of the present invention, it was shown that impurities in the dope can be efficiently removed, and a high quality optical film with low internal haze can be produced.

  On the other hand, in Comparative Example 1 in which no good solvent was added after the preparation of the dope, bright spot foreign matter was observed, and the internal haze was also high. This is considered to be because the impurities in the dope could not be removed.

  In addition, in Comparative Example 2 in which alcohol was not added as a main dope solvent, bright spot foreign matter was observed, and the internal haze was slightly high. It is considered that this is because the affinity between the dope and dichloromethane is sufficient to dilute the dope, and the effect of removing the impurities in the dope is not obtained.

  On the other hand, it was also found from the results of Examples 1 and 2 that as the amount of the good solvent added after the preparation of the dope is larger, the impurities can be further removed and the scattering property and the internal haze are more excellent.

  This application is based on Japanese Patent Application No. 2016-200596 filed on Oct. 12, 2016, the contents of which are included in the present application.

  Although the present invention has been described appropriately and sufficiently through the embodiments with reference to specific examples etc. in order to express the present invention, those skilled in the art can easily change and / or improve the aforementioned embodiments. It should be recognized that it is possible to Therefore, unless a change or improvement performed by a person skilled in the art is at a level that deviates from the scope of the claims of the claims, the change or the improvement is the scope of the claims of the claim It is interpreted as being included in

  The present invention has broad industrial applicability in the technical field relating to optical films and methods of making the same.

Claims (3)

In a solution casting film forming method, a dope containing a polyimide resin, a polyarylate resin or a cycloolefin resin, at least one alcohol solvent, and at least one good solvent for the resin is prepared, and an optical on a support is prepared. In a method of manufacturing an optical film, the dope is cast, a web (cast film) is formed on a support, the web is peeled from the support, and then the peeled web is taken up and dried. ,
A method for producing an optical film, comprising the steps of: adding a good solvent to the dope after adjusting the dope; and removing the good solvent thereafter.   The method for producing an optical film according to claim 1, wherein the good solvent is dichloromethane or tetrachloromethane.   The manufacturing method of the optical film of Claim 1 or 2 whose amount of good solvents to add is 1-50 mass% with respect to the dope whole quantity.

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