JP2006281444A - Manufacturing method of resin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a resin film of high quality prevented from becoming "distorted" in its winding without causing a phenomenon different in left and right in the elongation in the MD direction of the film, that is, a cellulose ester resin or norbornene resin film useful as the protective film for the polarizing plate of a liquid crystal display device. <P>SOLUTION: In the method for manufacturing the resin film with a thickness of 30-125 μm by a solution flow casting film forming method, the residual amount of the solvent in a web 10 after peeling is set to 20-120 wt.%. The web width in the region where the residual amount of the solvent is 20-80 wt.% of the web 10 in a drying process is set to 1,400-2,500 mm, the free spun length S of a guide roll 7 is set to 100-950 mm, the thickness of the web 10 in the residual amount of the solvent is set to 45-180 μm, the feed tension of the web 10 is set to 80-190 N/m and the deflection of the guide roll 7 in that region is set to 5-70 μm. The precision of the core shift of a tenter dryer 4 is set to 0.02-2 mm/m. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a resin film used for, for example, a liquid crystal display device (LCD), and more particularly to a method for producing a resin film useful as a protective film for a polarizing plate of the liquid crystal display device.

  Conventionally, a liquid crystal display device (LCD) can be directly connected to an IC circuit with low voltage and low power consumption, and can be thinned, so that it is widely used as a display device for a word processor, a personal computer or the like. .

  By the way, this liquid crystal display device has a basic configuration in which polarizing plates are provided on both sides of a liquid crystal cell. Since the polarizing plate allows only light with a polarization plane in a certain direction to pass, it plays an important role in visualizing changes in the orientation of the liquid crystal due to the electric field in the liquid crystal display device. The performance of the liquid crystal display device depends on the performance of the polarizing plate. Is greatly affected.

  As a protective film for a polarizing plate, a cellulose ester resin film is often used because of its low birefringence.

  Taking a cellulose triacetate (TAC) film as an example of a protective film for LCD polarizing plates, the surface of the film is alkali-saponified, uniaxially stretched and iodine-stained on one or both sides of a polarizing film made of a polyvinyl alcohol film. In addition, it is used by being bonded through an adhesive such as polyvinyl alcohol.

  The cellulose triacetate film is produced, for example, by the following solution casting film forming method. This cellulose triacetate film is produced by first dissolving cellulose triacetate in a mixed solvent obtained by adding a good solvent for cellulose triacetate such as methylene chloride and a poor solvent for cellulose triacetate such as methanol, ethanol, butanol or cyclohexane. Then, a plasticizer, an ultraviolet absorber, and fine particles for improving the slipperiness of the film are added to prepare a cellulose triacetate solution (dope), and the dope is endlessly moved infinitely with a mirror-finished surface. A dope film (web) is obtained by uniformly casting from a casting die on a rotationally driven metal support (for example, a stainless steel endless belt or drum), which is dried on the support, and then peeled off. Peeled off with a roll And further dried with hot air or the like, after dried sufficiently, by winding in the winding machine, thereby obtaining a cellulose triacetate film.

  However, in such a method for producing a cellulose ester-based resin film or norbornene-based resin film by a conventional solution casting film-forming method, the elongation of the film in the MD direction of the film (film stretching longitudinal direction) As a result, there is a problem that the winding of the rolled up film becomes “bittery”.

  Here, the “winding of the film” means that the right and left side edges of the film are wound in a crease shape in the longitudinal direction (longitudinal direction) of the film. In addition, the sticking and deformation between the films due to the fold-like appearance defects become defects of the film itself, and the flatness of the film deteriorates, and accordingly, post-processing appropriateness such as coating may be impaired. There was a problem.

Conventionally, in such a method for producing a resin film, prior patent documents relating to a technique that defines the deviation of the MD length in the width direction of the film (the length in the stretched longitudinal direction of the film) include the following: There is.
JP, 2002-187148, A In this patent document 1, it is a cellulose-ester film manufactured by the solution casting film-forming method, Comprising: The difference of the length of the longest part in the width direction and the shortest part, The invention of a cellulose ester film that is 0.03% or less of the length of the shorter end of the film is disclosed, and according to Patent Document 1, when the cellulose triacetate film is wound around a winding core It is described that it is possible to prevent the occurrence of nicks and the occurrence of winding deviation due to poor winding appearance (occurrence of black band, occurrence of depression).

  However, although the invention described in Patent Document 1 specifies the deviation of the MD length in the width direction of the cellulose ester film, it does not describe means for correcting the deviation of the MD length. Therefore, in the invention described in Patent Document 1, it is insufficient to prevent the situation that the winding of the rolled-up film becomes “distorted”, and to prevent sticking between films and deformation of the film. Met.

  The purpose of the present invention is to solve the above-mentioned problems of the prior art, and for a resin film useful as a protective film for a polarizing plate of a liquid crystal display device, it is possible to prevent sticking between films and deformation of the film, An object of the present invention is to provide a method capable of producing a high-quality cellulose ester resin film or norbornene resin film having improved flatness and post-processing suitability.

  As a result of intensive research in order to solve the above-described problems of the prior art, the present inventor peeled off in a method for producing a resin film comprising a cellulose ester resin film or a norbornene resin film by a solution casting film forming method. The amount of residual solvent of the web afterwards, the amount of residual solvent of the web in the drying process depends on the free span length of the guide roll in a specific area, the film thickness of the web in the specific area, and the transport tension, as well as the swing of the guide roll, In addition, it has been found that by defining the accuracy of the misalignment of the tenter dryer, the difference in the MD length (length in the longitudinal direction of the film) of the right and left side edges of the wound film can be reduced. It came to complete.

  In order to achieve the above-mentioned object, the invention according to claim 1 is characterized in that a cellulose ester-based resin film or a norbornene-based resin film raw material solution (dope) is rotated from a casting die by a solution casting film forming method. Casting step (hereinafter referred to as a support) to form a dope film (web), peeling step for peeling the web formed on the support from the support, and peeling from the support The final film thickness 30 to 30 comprising: a drying step of drying the web with a roll transport drying device; and a winding step of winding up the cellulose ester resin film or the norbornene resin film formed by drying the web in the drying step In the production method of the resin film having 125 μm, the residual solvent amount of the web after peeling is set to 20 to 120% by weight, and the drying process is performed. The web width in the region where the residual solvent amount of the web is 20 to 80% by weight is 1400 to 2500 mm, the free span length of the guide roll is 100 to 950 mm, and the film thickness of the web with the residual solvent amount is 45 to 180 μm. In addition, the conveyance tension is 80 to 190 N / m, and the deflection of the guide roll in that region is 5 to 70 μm.

  Invention of Claim 2 is a manufacturing method of the resin film of said Claim 1, Comprising: In the drying process which dries the web peeled from the support body, it equipped with the tenter drying apparatus following the roll conveyance initial drying apparatus. The center misalignment accuracy of the tenter dryer is 0.02 to 2 mm / m, the residual solvent amount of the web when passing through the tenter dryer is 5 to 55% by weight, and the film thickness of the web when passing through the tenter dryer is It is characterized by being 40-150 μm.

  In the method for producing a resin film according to claim 1 or 2, the product width of the resin film is preferably 1340 to 1980 mm.

  As described above, according to the first aspect of the present invention, in the method for producing a resin film by the solution casting film forming method, the residual solvent amount of the web after peeling is set to 20 to 120% by weight, and the web in the drying step is used. The web width in the region where the residual solvent amount is 20 to 80% by weight is 1400 to 2500 mm, the free span length of the guide roll is 100 to 950 mm, the film thickness of the web with the residual solvent amount is 45 to 180 μm, and the conveyance tension 80 to 190 N / m, and the guide roll deflection in that region is 5 to 70 μm. Therefore, for a resin film useful as a protective film for a polarizing plate of a liquid crystal display device, the MD direction of the resin film (film The film stretches in the longitudinal direction of the film), causing the film to roll up and become “bittery” without causing a phenomenon that differs between the left and right. High-quality cellulose ester resin film or norbornene resin film with improved flatness and post-processing suitability without causing film defects such as sticking or deformation between films. There is an effect that can be manufactured.

  Invention of Claim 2 is a manufacturing method of the resin film of said Claim 1, Comprising: In the drying process which dries the web peeled from the support body, it equipped with the tenter drying apparatus following the roll conveyance initial drying apparatus. The center misalignment accuracy of the tenter dryer is 0.02 to 2 mm / m, the residual solvent amount of the web when passing through the tenter dryer is 5 to 55% by weight, and the film thickness of the web when passing through the tenter dryer is According to the invention of the method for producing a resin film according to claim 2, the film is rolled up without causing a phenomenon that the elongation of the resin film in the MD direction differs from right to left. It is possible to further prevent the winding of the film from becoming “bittering”, thereby preventing film defects such as sticking or deformation between films, An effect that the surface properties, post-processing proper can be a cellulose ester based resin film or a norbornene resin film of a high quality with improved.

  The invention of the method for producing a resin film according to the first or second aspect of the present invention is particularly effective when the resin film product is wide, for example, when a wide wound film having 1340 to 1980 mm is stored, sticking, etc. It is possible to produce a cellulose ester resin film or a resin film made of a norbornene resin that is unlikely to fail during winding.

  Hereinafter, the present invention will be specifically described.

  The method for producing a resin film according to the present invention is obtained by casting a cellulose ester resin film or a norbornene resin film raw material solution (dope) from a casting die onto a rotationally driven metal support by a solution casting film forming method. , A casting process for forming a dope film (web), a peeling process for peeling the web formed on the support from the support, and a drying process for drying the web peeled from the support by a roll transport drying device And a winding step of winding the cellulose ester resin film or norbornene resin film formed by drying the web in the drying step.

  In the method of the present invention, examples of the cellulose ester resin used as a raw material for the film include cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, and cellulose acetate propionate. In the case of cellulose triacetate, cellulose triacetate having a polymerization degree of 250 to 400 and a bound acetic acid amount of 54 to 62.5% is particularly preferable, and a base strength having a bound acetic acid amount of 58 to 62.5% is strong and more preferable. As the cellulose triacetate, either cellulose triacetate synthesized from cotton linter or cellulose triacetate synthesized from wood pulp can be used alone or in combination.

  It is preferable to use a large amount of cellulose triacetate synthesized from a cotton linter that has good releasability from a belt or a drum because of high productivity efficiency. When the ratio of cellulose triacetate synthesized from cotton linter is 60% by weight or more and the effect of releasability becomes remarkable, 60% by weight or more is preferable, more preferably 85% by weight or more, and further, it can be used alone. Most preferred.

  On the other hand, in the method of the present invention, the norbornene-based resin, which is the main raw material of the norbornene-based resin film used as a film raw material, is a known resin, for example, JP-A-3-14882 and JP-A-3-122137. It is described in the gazette.

  Examples of the monomer constituting the norbornene resin film include norbornene, 5-methyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, and 5-methoxy. Carbonyl-2-norbornene, 5,5-dimethyl-2-norbornene, 5-cyano-2-norbornene, 5-methyl-5-methoxycarbonyl-2-norbornene, 5-phenyl-2-norbornene, 5-phenyl-5 -Methyl-2-norbornene and the like.

  The norbornene-based resin is, for example, (A) a resin obtained by hydrogenating a ring-opening polymer or ring-opening copolymer of a norbornene-based monomer, if necessary, such as maleic acid addition or cyclopentadiene addition, (B) Resin obtained by addition polymerization of norbornene monomer, (C) Resin obtained by addition polymerization of norbornene monomer and olefin monomer such as ethylene or α-olefin, (D) Norbornene monomer and cyclopentene, cyclooctene, 5 Examples include resins obtained by addition polymerization with cyclic olefin monomers such as 1,6-dihydrodicyclopentadiene, and modified products of these resins. These polymerizations can be carried out by conventional methods.

  In the method for producing the resin film of the present invention, the plasticizer that can be used is not particularly limited, but in the phosphate ester type, triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate , Trioctyl phosphate, tributyl phosphate, etc., phthalate ester type, diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, etc., glycolate ester type, triacetin, tributyrin, butyl Phthalyl butyl glycolate, ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycol Preferably alone or in combination rates.

  If necessary, two or more plasticizers may be used in combination. In this case, the proportion of the phosphate ester plasticizer used is 50% or less of the cellulose ester resin film or the norbornene resin film. It is preferable because it hardly causes hydrolysis and is excellent in durability.

  It is more preferable that the ratio of the phosphate ester plasticizer is small, and it is particularly preferable to use only a phthalate ester or glycolate ester plasticizer.

  In the present invention, in order to make the water absorption rate and moisture content within a specific range, the amount of the plasticizer is preferably 3% to 30% by weight, more preferably 3% by weight to the cellulose ester resin. Is 10 to 25% by weight, more preferably 15 to 25% by weight. If it exceeds 30% by weight, the mechanical strength and dimensional stability deteriorate.

  In the method for producing the resin film of the present invention, as an ultraviolet absorber that can be used, it has an excellent ability to absorb ultraviolet rays having a wavelength of 380 nm or less from the viewpoint of preventing deterioration of liquid crystals and polarizers, and from the viewpoint of good liquid crystal display properties Those having as little absorption of visible light as possible with a wavelength of 400 nm or more are preferably used. In particular, the transmittance at a wavelength of 380 nm needs to be 10% or less, preferably 5% or less, more preferably 2% or less.

  Examples of commonly used compounds include, but are not limited to, oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex compounds, and the like.

  In this invention, it is preferable to use 1 or more types of these ultraviolet absorbers, and you may contain 2 or more types of different ultraviolet absorbers.

  In the present invention, preferably used ultraviolet absorbers include benzotriazole ultraviolet absorbers and benzophenone ultraviolet absorbers. The embodiment in which the benzotriazole-based ultraviolet absorber is added to the cellulose ester-based resin film or the norbornene-based resin film is particularly preferable because unnecessary coloring is reduced.

  In addition, as the ultraviolet absorber, a triazine-based ultraviolet absorber or a polymer ultraviolet absorber described in JP-A-2001-154017 and JP-A-6-130226 previously proposed by the present applicant is also preferable. Used.

  In the present invention, the ultraviolet absorber is added by dissolving the ultraviolet absorber with another additive, a cellulose ester resin film or a norbornene resin in an organic solvent such as alcohol, methylene chloride, dioxolane, and the like. Added. For inorganic powders that do not dissolve in organic solvents, use a dissolver or sand mill in organic solvent and cellulose ester resin film or norbornene resin to disperse, and then cellulose ester resin film or norbornene resin solution Add to.

  The amount of the ultraviolet absorber used in the present invention is 0.1% to 2.5% by weight, preferably 0.5% to 2.0% by weight, more preferably% by weight based on the cellulose ester resin film or norbornene resin. Is 0.8 to 2.0% by weight. When the amount of the ultraviolet absorber used is more than 2.5% by weight, the transparency tends to deteriorate, which is not preferable.

  In the present invention, as the solvent for the cellulose ester resin, for example, lower alcohols such as methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol, lower aliphatic carbonization such as cyclohexanedioxane, and methylene chloride. Hydrogen chlorides and the like can be used.

  As the solvent ratio, for example, methylene chloride is preferably 70 to 95% by weight, and other solvents are preferably 30 to 5% by weight. The concentration of the cellulose ester resin is preferably 10 to 50% by weight. The heating temperature with the addition of the solvent is preferably a temperature not lower than the boiling point of the solvent used and in a range where the solvent does not boil, for example, preferably 60 ° C. or higher and 80 to 110 ° C. The pressure is determined so that the solvent does not boil at the set temperature.

  In the present invention, examples of the solvent for the norbornene resin include high-boiling solvents such as toluene, xylene, ethylbenzene, chlorobenzene, trimethylbenzene, diethylbenzene, and isopropylbenzene, and among these, toluene, xylene, and chlorobenzene are preferable. Alternatively, a mixed solvent of these high-boiling solvents and low-boiling solvents such as cyclohexane, benzene, tetrahydrofuran, hexane, and octane may be used.

  Further, as the solvent for the norbornene resin, methylene chloride may be used alone or mixed with the above solvent.

  For example, after dissolving the cellulose ester resin film or norbornene resin in a pressurized container, remove the solution from the container while cooling it, or remove it from the container with a pump and cool it with a heat exchanger, etc. Use for membranes.

  The type of the pressure vessel is not particularly limited as long as it can withstand a predetermined pressure and can be heated and stirred under pressure. In addition to the pressure vessel, other instruments such as a pressure gauge and a thermometer are appropriately disposed. The pressurization may be performed by a method of injecting an inert gas such as nitrogen gas or by increasing the vapor pressure of the solvent by heating. Heating is preferably performed from the outside. For example, a jacket type is preferable because temperature control is easy.

  The heating temperature with the addition of the solvent is preferably a temperature not lower than the boiling point of the solvent used and in a range where the solvent does not boil, for example, preferably 60 ° C. or higher and 80 to 110 ° C. The pressure is determined so that the solvent does not boil at the set temperature.

  After dissolution, take it out from the container while cooling, or extract it from the container with a pump and cool it with a heat exchanger, etc., and use it for film formation, but the cooling temperature at this time may be cooled to room temperature, Cooling to a temperature 5 to 10 ° C. lower than the boiling point and casting at that temperature is more preferable because the dope viscosity can be reduced.

  In the present invention, fine particles are added as a matting agent to the cellulose ester resin film or the norbornene resin film. Here, the kind of fine particles may be an inorganic compound or an organic compound, and examples of the inorganic compound include fine particles such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, and tin oxide. In this, it is preferable that it is a compound containing a silicon atom, and especially a silicon dioxide fine particle is preferable.

  Examples of such silicon dioxide fine particles include AEROSIL-200, 200V, 300, R972, R972V, R974, R202, R812, R805, OX50, and TT600 manufactured by Aerosil Co., Ltd. AEROSIL-200V and R972V are preferred in terms of controlling dispersibility and particle size.

  In the present invention, the fine particles are added in an amount of 0.05 to 0.5% by weight based on the film. Preferably, it is 0.10 to 0.35% by weight, more preferably 0.20 to 0.30% by weight.

  In the method of the present invention, for example, the fine particles are dispersed in a solvent containing 25 to 100% by weight of a water-soluble solvent, and then the fine particle dispersion is mixed with a water-insoluble organic solvent in an amount of 0.5 with respect to the water-soluble solvent. Add ~ 1.5 times and dilute. Next, this fine particle dispersion is mixed with a resin solution obtained by dissolving a resin such as cellulose ester resin in a solvent.

  As the water-soluble solvent, lower alcohols are mainly used. Preferred examples of lower alcohols include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol and the like.

  Further, the water-insoluble solvent is not particularly limited, but it is preferable to use a solvent used at the time of resin film formation, and those having a solubility in water of 30% by weight or less are used, such as methylene chloride, chloroform, methyl acetate, etc. Is mentioned.

  The fine particles are dispersed in a 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.

  Below, the manufacturing method of the resin film by this invention is demonstrated with reference to drawings.

  In the figure, first, a cellulose ester-based resin or a norbornene-based resin is dissolved in a mixed solvent of a good solvent and a poor solvent, and the above plasticizer or ultraviolet absorber is added thereto to prepare a resin solution (dope). . The dope is fed to the casting die (2) through, for example, a pressurized metering gear pump, and the dope is cast from the casting die (2) onto the endless belt support (1) at the casting position. The belt temperature during film formation can be cast at a temperature in the general temperature range of 0 ° C. to less than the boiling point of the solvent, and more preferably in the range of 5 ° C. to the boiling point of the solvent −5 ° C. At this time, it is necessary to control the ambient atmosphere temperature to be higher than the dew point.

  For casting the dope with the casting die (2), there is 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. However, a pressure die that can adjust the slit shape of the die portion and can 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.

  When casting the dope onto the support (1), the temperature is controlled below the boiling point of the solvent used for dissolving the raw resin, and below the boiling point of the solvent having the lowest boiling point in the mixed solvent. The temperature can be cast at a temperature in a general temperature range of 0 ° C. to less than the boiling point of the solvent, but is more preferably cast on a support (1) at 5 to 30 ° C.

  In the illustrated film forming apparatus having a rotationally driven endless belt as the support (1), the belt support (1) is disposed between the pair of drums (9) and the endless belt support (1). The upper transition part and the lower transition part are each composed of a plurality of rolls that support the rear side. In addition, one or both of the drums (9) at both ends of the rotary drive endless belt support (1) are provided with a drive device that applies tension to the belt support (1), whereby the belt support (1) is used under tension and tension.

  Then, the dope adjusted to have a dope viscosity of 1 to 200 poise is cast from the casting die (2) onto the support (1) so as to have a substantially uniform film thickness. When the residual solvent amount in the solid content weight is 200% or more, the casting membrane temperature is lower than the solvent boiling point, and in the range where the residual solvent amount is 100 to 200% solid weight, the solvent boiling point is + 10 ° C. or lower. In addition, the cast film (web) is dried with drying air so that the residual solvent amount is 100% or less to peeling until the solvent boiling point is + 20 ° C. or less.

  A dope is cast from a casting die (2) onto a stainless steel endless belt support (1) having a mirror-finished surface to obtain a dope film (web) (10), and the web (10) is an endless belt. When the substrate (1) has moved approximately 3/4 rounds by the rotation of the support (1), it is peeled off by the peeling roll (6).

  On the support (1), the web (10) is dried and solidified until the film strength becomes a peelable film from the support (1). Therefore, the residual solvent in the web (10) is dried to 150% by weight or less. Is preferable, and 80 to 120% by weight is more preferable.

  In the method for producing a resin film of the present invention, the residual solvent amount of the web (10) after peeling is 20 to 120% by weight, and the residual solvent amount of the web (10) is 20 to 80% by weight in the drying step. The web width in a certain area is 1400-2500 mm, the free span length (S) of the guide roll (conveying roll) (7) is 100-950 mm, the film thickness of the web (10) in the residual solvent amount is 45-180 μm, In addition, the conveying tension is 80 to 190 N / m, and the deflection of the guide roll (7) in that region is 5 to 70 μm.

  In the method for producing the resin film of the present invention, the residual solvent amount of the web (10) after peeling is 20 to 120% by weight. Here, the residual solvent amount of the web (10) after peeling is 20% by weight. If it is less than this, it is necessary to significantly reduce the production rate, which is not preferable. Further, if the residual solvent amount of the web (10) after peeling exceeds 120% by weight, the width shrinkage becomes large, the flatness is deteriorated, and the transfer of the roll deposit to the web (10) is likely to occur. It is not preferable.

  The temperature of the web (10) when peeling the web (10) from the support (1) is preferably 0 to 30 ° C. Further, immediately after the web (10) is peeled off from the support (1), the temperature is once lowered rapidly by the solvent catalyst from the contact surface side of the support (1), and volatile components such as water vapor and solvent vapor in the atmosphere are removed. Since it is easy to condense, the web temperature during peeling 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
Here, M is the weight of the web at any point in time, and N is the weight when a weight M is dried at 110 ° C. for 3 hours.

  The peeling tension when peeling the support (1) and the web (10) is usually 20 to 25 kg / m. However, in the case of the resin film thinned by the production method of the present invention, the peeling is performed. Since wrinkles easily enter the web (10), it is preferable to peel at a minimum tension of 17 kg / m, more preferably at a minimum tension of 14 kg / m.

  Next, in the drying step of the web (10) peeled from the support (1), generally, a method of drying while transporting the film by the roll suspension method or the pin tenter method as described above is adopted. For the liquid crystal display member, it is preferable to dry while maintaining the width by a tenter method in order to improve the dimensional stability. In particular, in the drying step of the web (10) after peeling from the support (1), the web (or film) (10) tends to shrink in the width direction due to evaporation of the solvent. Shrinkage increases with drying at higher temperatures. In order to improve the flatness of the finished film, it is preferable to dry while suppressing the shrinkage as much as possible. From this point, for example, the entire drying process or a part of the drying process as disclosed in Japanese Patent Application Laid-Open No. 62-46625 is performed while holding the width at both ends of the web (10) with a clip in the width direction. The method / tenter method is preferable, and it is particularly preferable to maintain the width where the amount of residual solvent is large because the effect of improving the dimensional stability is more exhibited.

  In the method of the present invention, the peeled web (10) is first introduced into a roll transport initial drying device (3). In the roll conveying initial drying device (3), the web (10) is meandered by 5 to 200 guide rolls (7), and the web (10) is in front of the bottom of the drying device (3). And is dried by warm air (12) discharged from the rear part of the ceiling of the drying device (3). In addition, the length of a roll conveyance initial stage drying process is 5-200 m, for example.

  In the method of the present invention, in the roll conveying initial drying device (3), the web width in the region where the residual solvent amount of the web (10) is 20 to 80% by weight is set to 1400 to 2500 mm. Here, if the web width is less than 1400 mm, productivity is poor, and if the web width exceeds 2500 mm, not only the apparatus cost becomes enormous, but also conveyance becomes difficult.

  Similarly, in the method of the present invention, in the roll conveying initial drying apparatus (3), the free span length (S) of the guide roll (7) in the region where the residual solvent amount of the web (10) is 20 to 80% by weight. ) Is 100 to 950 mm. Here, if the free span length (S) of the guide roll (7) is less than 100 mm, the web (10) contracts on the roll, and the web (10) is laterally scratched. Further, if the free span length (S) of the guide roll (7) exceeds 950 mm, creases and wrinkles due to shrinkage of the web (10) are likely to occur, which is not preferable.

  Further, in the method of the present invention, in the roll conveying initial drying device (3), the film thickness of the web (10) in the region where the residual solvent amount of the web (10) is 20 to 80% by weight is 45 to 180 μm, And conveyance tension shall be 80-190 N / m.

  Here, if the film thickness of the web (10) is less than 45 μm, the film strength is inferior and it is easy to break, which is not preferable. On the other hand, when the thickness of the web (10) exceeds 180 μm, a stretching ratio of 100% or more is required, which is not preferable in terms of apparatus cost and optical characteristics.

  Furthermore, if the conveyance tension in the same region is less than 80 N / m, the web (10) flutters, the guide roll (7) cannot follow, and scratches tend to occur, which is not preferable. When the conveyance tension exceeds 190 N / m, the web (10) is liable to break, which is not preferable.

  In the above drying step, the deflection of the guide roll (7) in the region where the residual solvent amount of the web (10) is 20 to 80% by weight and in that region is 5 to 70 μm. If the deflection of the guide roll (7) is less than 5 μm, there is almost no merit of web conveyance and the equipment cost is remarkably increased. On the other hand, if the guide roll (7) has a deflection of more than 70 μm, the web (10) is liable to be crushed and wrinkled, which is not preferable.

  In the method of the present invention, the web (10) is then introduced into the tenter dryer (4). Therefore, the side edges of the web (10) are gripped with a clip and stretched, and the web (10) is dried. In the tenter dryer (4), the web (10) is blown from the front portion of the bottom of the tenter dryer (4) and discharged from the rear portion of the ceiling of the tenter dryer (4) (13 ).

  In the roll transport initial drying device (3) and the tenter drying device (4), the hot air (12) (13) is used for drying, respectively, but the means for drying the film is not particularly limited, as described above. It is performed with hot air, or with infrared rays, a heating roll, microwaves, or the like. It is preferable to carry out with hot air in terms of simplicity. The drying temperature is preferably in the range of 40 ° C. to 150 ° C. and divided into 3 to 5 stages, and it is preferable to increase the temperature step by step, more preferably in the range of 80 ° C. to 140 ° C. in order to improve dimensional stability. .

  In the drying process of drying the web (10) by the tenter drying device (4), the tenter drying device (4) has a core misalignment accuracy of 0.02 to 2 mm / m, and the web when passing through the tenter drying device (4). The residual solvent amount of (10) is 5 to 55% by weight, and the film thickness of the web (10) when passing through the tenter dryer (4) is 40 to 150 μm. Here, if the accuracy of the misalignment of the tenter drying device (4) is less than 0.02 mm / m, there is almost no merit in improving the specifications and the equipment cost is remarkably increased. Further, if the accuracy of the misalignment of the tenter drying device (4) exceeds 2 mm / m, it is not preferable because unevenness in the width direction of the optical properties of the web (10) after stretching occurs. At this time, if the residual solvent amount of the web (10) when passing through the tenter dryer is less than 5% by weight, the draw ratio cannot be increased, and the optical properties cannot be adjusted. Further, if the amount of residual solvent of the web (10) when passing through the tenter dryer exceeds 55% by weight, there is almost no movement of the optical properties due to the draw ratio, so that the optical properties cannot be adjusted. Furthermore, if the film thickness of the web (10) when passing through the tenter dryer is less than 40 μm, it is not preferable because breakage due to stretching tends to occur. If the film thickness of the web (10) when passing through the tenter dryer exceeds 150 μm, a stretching ratio of 80% or more is required to obtain the desired thickness, which not only increases the cost of the apparatus but also adjusts the optical properties. Is also not preferable because it becomes difficult.

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

  Next, the stretched resin film (web) (10) is introduced into the drying device (5) after roll conveyance. In the drying apparatus (5) after roll conveyance, the web (10) is meandered by 50 to 1000 guide rolls (7), and the web (10) is, for example, the bottom of the drying apparatus (5) after roll conveyance. The air is blown into the winder (8) as a resin film (11) by being blown from the front part and dried by the warm air (14) discharged from the rear part of the ceiling of the drying device (5) after roll conveyance. It is done.

  The winder (8) related to the production of the resin film of the present invention may be a commonly used one such as a constant tension method, a constant torque method, a taper tension method, a program tension control method with a constant internal stress, etc. It can be wound up by a winding method.

  In the present invention, the cellulose ester resin film or the norbornene resin film is generally used in a thickness of 30 to 125 μm. However, it is desired to reduce the thickness and weight of the polarizing plate used in the LCD. Therefore, the thickness is preferably 30 to 100 μm, and more preferably 30 to 80 μm. If it is thinner than this, the stiffness of the film (11) will be reduced, so troubles due to wrinkles etc. are likely to occur in the polarizing plate preparation process. The contribution to is small.

  Next, the product of the resin film (11) produced by the method of the present invention has a film width of 1340 to 1980 mm. Here, if the film width is less than 1340 mm, the quotation of the film thickness deviation becomes large, which is not preferable. On the other hand, if the film width exceeds 1980 mm, the cost of the apparatus increases, which is not preferable.

  The production method of the polarizing plate using the cellulose ester resin film or the norbornene resin film produced by the above method of the present invention is not particularly limited, and can be produced by a general method. For example, as an example of a cellulose ester film, there is a method in which the film is bonded to both surfaces of a polarizing film produced by alkali treatment and immersed in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution.

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

Example 1
A cellulose triacetate dope was prepared as follows.

Dope prescription 1
Cellulose triacetate 100 parts by weight Methylene chloride 350 parts by weight Ethanol 12 parts by weight Triphenyl phosphate 12 parts by weight Tinuvin 326 (manufactured by Ciba Specialty Chemicals) 0.5 part by weight Silicon dioxide fine particles 0.1 part by weight (trade name: AEROSIL-200V, (Made by Nippon Aerosil)
The materials of the above dope formulation 1 are sequentially put into a sealed container, the temperature in the container is raised from 20 ° C. to 80 ° C., and the mixture is stirred for 3 hours while maintaining the temperature at 80 ° C. Dissolved.

(Production of film sample)
After filtering the dope prepared as described above, using the solution casting film forming apparatus shown in FIG. 1, the dope is passed through a casting die (2) kept at 30 ° C. to support a stainless steel endless belt. Cast on body (1). The dope viscosity at the time of casting was 50 poise. Then, after the web (10) was dried on the support (1), the web (10) was peeled from the support (1) by the peeling roll (6). The residual solvent amount of the web (10) after peeling was 80% by weight.

  Next, the peeled web (10) is dried with hot air (12) at 50 ° C. in a roll conveying initial drying device (3) having 50 guide rolls (7), and then a tenter drying device (4 ), Grip the edges of both sides of the web (10) with a clip, apply the drying air (13) at 105 ° C while keeping the width, and then roll the web (10) It introduced into the post-drying apparatus (5), and it dried with the drying wind (14) of 100 degreeC or more. The obtained cellulose triacetate film (11) was finally cooled to 20 ° C. and wound on a winder (8).

  Here, the web width in the region where the residual solvent amount of the web (10) in the roll conveying initial drying device (3) is 20 to 80% by weight is 1600 mm, and the free span length (S) max of the guide roll (7) is The thickness of the web (10) with the residual solvent amount of 500 mm was 48 to 72 μm, the transport tension was 100 N / m, and the deflection max of the guide roll (7) in that region was 40 μm. Further, in the drying step of drying the web (10) with the tenter drying device (4), the core misalignment accuracy of the tenter drying device (4) is 0.1 mm / m, The amount of residual solvent was 5 to 15% by weight, and the film thickness of the web (10) when passing through the tenter dryer was 42 to 46 μm. Finally, a cellulose triacetate film (11) having a film width of 1420 mm and a film thickness of 40 μm was produced.

  Note that the free span length (S) of the guide roll (7) and the runout of the guide roll (7) in the roll conveying initial drying device (3) are each measured for one roll (7). However, in this embodiment, since the roll transport initial drying device (3) is provided with 50 guide rolls (7), the maximum free span length (S) and The runout was expressed as the free span length (S) max and the runout max of the guide roll (7), respectively.

Example 2
(Production of film sample)
A cellulose triacetate film (11) is produced using the solution of the dope formulation 1 in the same manner as in Example 1, but the residual solvent amount of the web (10) after peeling from the support (1) is 100. % By weight. In the roll conveying initial drying apparatus (3), the web width in the region where the residual solvent amount of the web (10) is 20 to 80% by weight is 1600 mm, and the free span length (S) max of the guide roll (7) is 500 mm. The film thickness of the web (10) with the residual solvent amount was 96 to 114 μm, the transport tension was 100 N / m, and the runout max of the guide roll (7) in that region was 40 μm. Further, in the drying step of drying the web (10) with the tenter drying device (4), the core misalignment accuracy of the tenter drying device (4) is 0.1 mm / m, The residual solvent amount was 10 to 30% by weight, and the film thickness of the web (10) when passing through the tenter dryer was 88 to 104 μm. Finally, a cellulose triacetate film (11) having a film width of 1420 mm and a film thickness of 80 μm was produced.

Example 3
A cellulose triacetate dope was prepared as follows.

Dope prescription 2
Cellulose triacetate 100 parts by weight Methyl acetate 450 parts by weight Acetone 50 parts by weight Ethylphthalyl ethyl glycolate 1 part by weight Tinuvin 326 (manufactured by Ciba Specialty Chemicals) 0.5 part by weight Silicon dioxide fine particles 0.1 part by weight (trade name: AEROSIL -200V, manufactured by Nippon Aerosil Co., Ltd.)
These were put into an airtight container and completely dissolved while maintaining agitation at 80 ° C. under pressure.

(Production of film sample)
After filtering the solution of the dope formulation 2, a cellulose triacetate film (11) is produced in the same manner as in Example 1, but the residual solvent amount of the web (10) after peeling from the support (1) Was 80% by weight. Further, the web width in the region where the residual solvent amount of the web (10) is 20 to 80% by weight in the roll conveying initial drying device (3) is 1600 mm, and the free span length (S) max of the guide roll (7) is 700 mm. The film thickness of the web (10) with the residual solvent amount was 48 to 72 μm, the conveyance tension was 120 N / m, and the deflection max of the guide roll (7) in that region was 40 μm. Further, in the drying step of drying the web (10) with the tenter drying device (4), the core misalignment accuracy of the tenter drying device (4) is 0.1 mm / m, The amount of residual solvent was 5 to 15% by weight, and the film thickness of the web (10) when passing through the tenter dryer was 42 to 46 μm. Finally, a cellulose triacetate film (11) having a film width of 1440 mm and a film thickness of 40 μm was produced.

Example 4
(Production of film sample)
A cellulose triacetate film (11) is produced using the solution of the dope formulation 2 in the same manner as in Example 1, except that the residual solvent amount of the web (10) after peeling from the support (1) is 100. % By weight. Further, the web width in the region where the residual solvent amount of the web (10) is 20 to 80% by weight in the roll conveying initial drying device (3) is 1600 mm, and the free span length (S) max of the guide roll (7) is 700 mm. The film thickness of the web (10) with the residual solvent amount was 96 to 114 μm, the transport tension was 120 N / m, and the runout max of the guide roll (7) in that region was 40 μm. Further, in the drying process of drying the web (10) with the tenter drying device (4), the core misalignment accuracy of the tenter drying device (4) is 0.1 mm / m, The residual solvent amount was 10 to 30% by weight, and the film thickness of the web (10) when passing through the tenter dryer was 88 to 104 μm. Finally, a cellulose triacetate film (11) having a film width of 1440 mm and a film thickness of 80 μm was produced.

Comparative Example 1
For comparison, a cellulose triacetate film (11) is produced in the same manner as in Example 1, but the amount of residual solvent of the web (10) after peeling from the support (1) is within the scope of the present invention. It was 30% by weight which is outside. Moreover, the web width | variety in the area | region where the residual solvent amount of the web (10) in a roll conveyance initial drying apparatus (3) is 20-30 weight% is 1600 mm, The free span length (S) max of a guide roll (7), 1000 mm which is outside the scope of the present invention, the film thickness of the web (10) at the residual solvent amount is 48 to 52 μm, the transport tension is 100 N / m, and the run-out max of the guide roll (7) in that region is 80 μm, which is outside the scope of the present invention. Further, in the drying process of drying the web (10) by the tenter dryer (4), the accuracy of the misalignment of the tenter dryer (4) is 3 mm / m, which is outside the scope of the present invention, and passes through the tenter dryer. The residual solvent amount of the web (10) was 3 to 6% by weight, and the film thickness of the web (10) when passing through the tenter dryer was 41 to 42 μm. Finally, a cellulose triacetate film (11) having a film width of 1330 mm and a film thickness of 40 μm outside the scope of the present invention was produced.

Example 5
A norbornene resin film (11) was prepared in substantially the same manner as in Examples 1 to 4 except that a norbornene resin was used in place of cellulose triacetate.

[Preparation of fine particle dispersion]
Ethanol 27 parts by weight Silicon dioxide fine particles 3 parts by weight (trade name: AEROSIL-R972V, primary particle size: 16 nm)
The above materials were mixed in a predetermined container, stirred for 30 minutes at 500 rpm, dispersed with a Manton Gorin type high-pressure disperser at a pressure of 250 kgf / cm ² , and then the dispersion was mixed with methylene chloride 27. The fine particle dispersion was prepared by diluting with parts by weight.

[Preparation of norbornene resin solution]
Norbornene resin (Arton G JSR) 80 parts by weight Ethyl phthalyl ethyl glycolate (plasticizer) 2 parts by weight Triphenyl phosphate (plasticizer) 8 parts by weight Methylene chloride (boiling point: 39.8 ° C.) 250 parts by weight Ethanol 10 Part by weight The above materials were put into a dissolution vessel, heated to 70 ° C., and while stirring, the norbornene resin was completely dissolved to obtain a norbornene resin solution. The time required for dissolution was 4 hours.

[Preparation of additive solution]
75 parts by weight of the norbornene resin solution
2- (2′-hydroxy-3 ′, 5′-di-t-butylphenyl) benzotriazole Tinuvin 326 (manufactured by Ciba Specialty Chemicals) 5 parts by weight The above fine particle dispersion 60 parts by weight Methylene chloride 290 parts by weight Then, a part of the norbornene-based resin solution after filtration was added while stirring the methylene chloride, and then added in the order of the ultraviolet absorbent and the fine particle dispersion. After the addition, the mixture was heated to 40 ° C. and dissolved for 30 minutes to prepare the additive solution.

[Preparation of dope for norbornene resin film]
Dope prescription 3
The dope for norbornene-based resin film was prepared by adding the additive solution from the flow pipe in-line to the main part (remainder) of the norbornene-based resin solution and mixing with a static mixer.

[Preparation of norbornene-based resin film sample]
After filtering the dope for norbornene-based resin film of the above dope formulation 3, using a solution casting film forming apparatus shown in FIG. 1, from a casting die (2) at a dope temperature of 35 ° C., from a stainless steel endless belt This was uniformly cast on a 30 ° C. support (1). After holding for 60 seconds on the support (1) and drying to a peelable range, the web (10) was peeled from the support (1) by a peeling roll (6). The residual solvent amount of the web (10) after peeling was 80% by weight.

  Next, the peeled web (10) is dried with hot air (12) at 50 ° C. in a roll conveying initial drying device (3) having 50 guide rolls (7), and then a tenter drying device (4 ), Grip the edges of both sides of the web (10) with a clip, apply the drying air (13) at 105 ° C while keeping the width, and then roll the web (10) It introduced into the post-drying apparatus (5), and it dried with the drying wind (14) of 100 degreeC or more. And the obtained norbornene-type resin film (11) was finally cooled at 20 degreeC and wound up by the winder (8).

  Here, the web width in the region where the residual solvent amount of the web (10) in the roll conveying initial drying device (3) is 20 to 80% by weight is 1600 mm, and the free span length (S) max of the guide roll (7) is The thickness of the web (10) with the residual solvent amount of 500 mm was 48 to 72 μm, the transport tension was 100 N / m, and the deflection max of the guide roll (7) in that region was 40 μm. Further, in the drying step of drying the web (10) with the tenter drying device (4), the core misalignment accuracy of the tenter drying device (4) is 0.1 mm / m, The amount of residual solvent was 5 to 15% by weight, and the film thickness of the web (10) when passing through the tenter dryer was 42 to 46 μm. Finally, a norbornene resin film (11) having a film width of 1420 mm and a film thickness of 40 μm was produced.

(Evaluation of resin film)
Next, after the resin films of Examples 1 to 5 and Comparative Example 1 of the present invention were stored for about 2 weeks in an atmosphere of normal temperature / normal humidity, the failure in winding was evaluated, and the film ( 11) Measurement was made as to whether or not sticking with a diameter of 5 mm or more occurred in the winding, and whether or not a minute deformation of the film occurred in the winding, and the obtained results are shown in Table 1 below. Indicated.

  As is apparent from the results of Table 1 above, according to the resin films of Examples 1 to 5 according to the present invention, in any case, there is no sticking failure with a diameter of 5 mm or more in the film winding, and the film No minute deformation during winding occurred.

  Thus, according to the method for producing a resin film of the present invention, the residual solvent amount of the web (10) after peeling, the residual solvent amount of the web (10) in the roll transport initial drying device (3) in the drying step is as follows. Free span length (S) of the guide roll (7) in a specific area, the film thickness of the web (10) and the transport tension in the specific area, as well as the swing of the guide roll (7), and a tenter dryer By defining the accuracy of the misalignment in (4), the difference in the MD length (length in the stretched longitudinal direction of the film) of the right and left side edges of the winding film (11) can be reduced. According to the method, with respect to the cellulose triacetate film and norbornene-based resin film useful for the protective film for polarizing plate used in the liquid crystal display device (LCD), the elongation of the film in the MD direction of the film (the stretching longitudinal direction of the film) Right and left It is possible to prevent the winding of the rolled-up film from becoming “distorted” without causing a phenomenon. As a result, it was possible to produce a high-quality cellulose triacetate and norbornene resin film (11) with improved flatness and post-processing suitability without causing film defects such as sticking or deformation between films.

  On the other hand, according to the resin film of Comparative Example 1, 4 or more sticking failures with a diameter of 10 mm or more occurred, and further, the number of minute deformations occurred 10 or more, which is used as a protective film for polarizing plate. It was not suitable for.

It is a schematic sectional drawing of the solution casting film forming apparatus which enforces the method of this invention.

Explanation of symbols

1: Endless belt support 2: Casting die 3: Roll transport initial drying device 4: Tenter drying device 5: Post-roll transport drying device 6: Peeling roll 7: Guide roll (transport roll)
8: Winder 10: Web 11: Resin film S: Free span length

Claims (3)

  A cellulose ester resin film or norbornene resin film raw material solution (hereinafter referred to as “dope”) is cast from a casting die onto a rotationally driven metal support (hereinafter referred to as a support) by a solution casting film forming method. A casting process for forming a dope film (hereinafter referred to as “web”), a peeling process for peeling the web formed on the support from the support, and a web transporting and drying apparatus for peeling the web peeled from the support. A method for producing a resin film having a final film thickness of 30 to 125 μm, comprising: a drying step of drying by a step of winding and a winding step of winding up a cellulose ester resin film or a norbornene resin film formed by drying a web in the drying step The residual solvent amount of the web after peeling is set to 20 to 120% by weight, and the residual solution of the web is dried in the drying process. The web width in the region where the amount is 20 to 80% by weight is 1400 to 2500 mm, the free span length of the guide roll is 100 to 950 mm, the film thickness of the web with the residual solvent amount is 45 to 180 μm, and the conveyance tension is 80 A method for producing a resin film, characterized in that the deflection of the guide roll in that region is set to 5 to 70 μm.   In the drying step of drying the web peeled from the support, the tenter drying device is provided following the roll conveying initial drying device, and the tenter drying device has a core misalignment accuracy of 0.02 to 2 mm / m. The method for producing a resin film according to claim 1, wherein the residual solvent amount of the web when passing through the drying device is 5 to 55 wt%, and the film thickness of the web when passing through the tenter drying device is 40 to 150 µm.   The method for producing a resin film according to claim 1 or 2, wherein the product width of the resin film is 1340 to 1980 mm.

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