JP2007283764A - Method for producing polymer film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily peel off a cast film from a support and to produce a film excellent in optical characteristics. <P>SOLUTION: A plurality of kinds of casting dope are prepared by adding additives into raw material dope containing a solvent and a cellulose acylate by a dope production apparatus 10. The plurality of kinds of casting dope are cast together from a casting die 89 onto a casting band 85 to form the cast film 70 comprising an underlying layer, a support surface layer and an air surface layer which are in contact with both sides of the underlying layer. After that, the cast film 70 is peeled from the casting band 85 to obtain a wet film 75. The wet film 75 is dried to prepare the film 76. Since the support surface layer is formed by using the cellulose acylate which has a low acetification degree and in which the contents of Ca and a fatty acid are adjusted, the cast film 70 is peeled easily from the casting band 85. Since the raw material dope and the additives are agitated/mixed uniformly by a static mixer to prepare the casting dope, the film 76 excellent in optical characteristics including a retardation value etc. can be obtained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a polymer film suitably used as an optical film which is a main member of a liquid crystal display device or the like.

  The polymer film has high transparency, excellent workability and handleability, and can be reduced in size and weight, for example, a polarizing plate protective film for protecting a polarizing plate of a liquid crystal display device, Widely used as a viewing angle widening film. Among them, a cellulose acylate film using cellulose acylate as a polymer has excellent optical properties such as a low raw material unit price, a wide viewing angle, and a high transmittance, so that high functionality and low cost can be realized. High attention as an optical film.

  When producing a polymer film, a solution casting method is mainly used. The solution casting method is a method of preparing a dope by mixing various raw materials of a film containing a polymer represented by cellulose acylate, an organic solvent, etc., and then casting the dope on a support that runs. A film is formed. And it is the method of manufacturing a polymer film by drying the film containing the solvent formed by peeling off this casting film from a support body, ie, a wet film.

  By the way, in the solution casting method, when the casting film is peeled off from the support, there is a problem that the casting film remains on the support or the time required for the peeling becomes long. In this case, the productivity is lowered as the workability is lowered and the manufacturing time is increased. Therefore, in order to improve the peelability, which is the ease of peeling when the cast film is peeled from the support, an additive having a peeling promoting effect such as a peeling accelerator or a peeling aid, that is, a peeling agent. Is generally included in the dope. As a method using such a release agent, for example, Patent Document 1 proposes a cellulose acylate film excellent in peelability containing a compound having a predetermined alkyl group or aralkyl group. .

In addition to a release agent, additives such as a UV absorber and a plasticizer are added to a polymer film typified by a cellulose acylate film, in order to improve the film properties. However, since each additive and polymer have different compatibility with the solvent, it is difficult to uniformly stir various raw materials to obtain a homogeneous dope. Here, it is not preferable to lengthen the stirring time for the purpose of improving the compatibility or increase the rotation speed of the stirrer, because this leads to an increase in manufacturing time or manufacturing cost. Therefore, as a method of obtaining a homogeneous dope after improving these problems, for example, in Patent Document 2, a stationary mixer equipped with a circular addition nozzle is installed at a substantially central portion of a pipe through which the dope flows. Thus, a method has been proposed in which various raw materials are mixed while adjusting the addition heating conditions and the dope pressure after adding the additive from the addition nozzle.
JP-A-2-110146 JP 2003-053752 A

  However, in the case of aiming to improve the peelability, in Patent Document 1, there is a possibility that a residue remains on the support, and an improvement for improving the peelability is required. In addition, it is desired to construct a technique for making a dope in which a release agent and other additives are uniformly dispersed. However, in Patent Document 2, it takes time for the additive to spread from the center of the pipe toward the inner peripheral wall. As a result, productivity is considered a problem. Here, if a mixer having a large number of elements is used, improvement in productivity can be expected, but this is not suitable because it may increase the equipment cost and increase the equipment size.

  The present invention aims to solve the above problems, and a first object is to provide a method capable of producing a polymer film with improved peelability. Furthermore, the second object is to provide a polymer film having excellent transparency and optical properties by uniformly mixing dope raw materials such as a polymer, an organic solvent, and an additive to prepare a homogeneous dope. In addition, as said additive, a release agent, a ultraviolet absorber, a plasticizer, etc. are contained.

  The method for producing a polymer film of the present invention includes a casting film in which a casting dope in which an additive is added to a raw material dope containing a polymer and an organic solvent is cast on a traveling support to form a casting film. A forming step, a peeling step of peeling the casting film from the support to form a wet film containing a solvent, and a drying step of drying the wet film, and the casting dope forms a base layer The dope for the base layer, the dope for the support surface layer for forming the support surface layer disposed so as to contact the surface of the base layer located on the support side, and the position facing the support surface layer with the base layer in between The air surface layer dope for forming an air surface layer disposed on the substrate, and the polymer contained in the support surface layer dope has a first degree of acetylation of 58.5% to 61.0%. Cellulose acylate, dope for base layer Polymer contained fine air surface layer dope is characterized by acetylation degree is the second cellulose acylate below 62.0% or more 61.0%.

  In the first cellulose acylate, the Ca content is preferably 0.1 ppm to 50 ppm, and the fatty acid content is preferably 0.1 ppm to 30 ppm. The fatty acid is preferably a long chain fatty acid in which 12 to 30 carbon atoms are arranged in a chain. The ratio of the thickness of the support surface layer to the thickness of the cast film is preferably 0.1% or more and 5% or less.

  It is preferable to stir and mix the raw material dope after adding the additive with an in-line mixer. The in-line mixer is attached to a pipe through which the raw material dope flows, and an addition nozzle having a slit-like addition port extending in the diameter direction of the in-line mixer is preferably provided on the upstream side of the in-line mixer.

  The addition port preferably has a length L parallel to the radial direction of the pipe of 20% to 80% of the inner diameter of the pipe. The slit gap C is preferably 0.1 mm or more and 1/10 mm or less of the inner diameter of the pipe. Moreover, it is preferable that the distance D from an addition port to an in-line mixer is 1 mm or more and 250 mm or less.

  It is preferable that the flow rate V1 of the additive flowing in the pipe and the flow rate V2 of the raw material dope satisfy 1 ≦ V1 / V2 ≦ 5. The casting is preferably co-casting in which the casting dope is cast simultaneously or sequentially on the support.

  ADVANTAGE OF THE INVENTION According to this invention, the peelability at the time of peeling a casting film from a support body can be improved, and the polymer film excellent in planarity can be manufactured. Moreover, the polymer film which is excellent in transparency and an optical characteristic can be provided by using a cellulose acylate as a polymer.

  The dope according to the present invention will be described. In the present invention, a polymer film having a multilayer structure comprising a base layer and a surface layer disposed so as to be in contact with both surfaces of the base layer is formed. Therefore, two types of surface layer dope and one type of base layer dope are prepared as casting dopes. The base layer in this invention is a layer which exists between the air surface layer which contacts air on a support body among surface layers, and a support body. On the other hand, among the surface layers, a layer existing between the base layer and the support is referred to as a support surface layer. In the following description, the dope for forming the base layer is referred to as the base layer dope, the support surface layer dope for forming the support surface layer, and the air surface layer dope for forming the air surface layer.

  As the polymer, cellulose acylate obtained by acetylating cellulose is preferably used. Among them, it is preferable to use triacetyl cellulose (TAC), and thereby a polymer film excellent in transparency can be produced.

  For the support surface layer dope, cellulose acylate having an acetylation degree of 58.5% or more and less than 61.0% is used. For the base layer and air surface layer dope, cellulose acylate having an acylation degree of 61.0% or more and 62.0% or less, which is a substitution degree of an acyl group with respect to a hydrogen atom in a hydroxyl group of cellulose, is used. . In the following description, cellulose acylate having an acetylation degree of 58.5% or more and less than 61.0% is referred to as a first cellulose acylate, and the acetylation degree is 61.0% or more and 62.0% or less. Some are referred to as second cellulose acylates.

  The first cellulose acylate preferably has a Ca content of 0.1 ppm to 50 ppm and a fatty acid content of 0.1 ppm to 30 ppm. More preferably, the proportion of Ca is 0.1 ppm to 20 ppm, the proportion of fatty acid is 0.1 ppm to 20 ppm, and particularly preferably, the proportion of Ca is 0.1 ppm to 10 ppm, and the proportion of fatty acid is 0.1 ppm to 10 ppm. It is as follows. In addition, the ratio in which Ca and a fatty acid are contained is based on 100 g of cellulose acylate, and the target cellulose acylate can be used as a sample, which can be measured by an analyzer such as gas chromatography. The fatty acid is preferably a long chain fatty acid in which 12 to 30 carbon atoms are arranged in a chain.

  It is considered that the Ca salt is a factor that causes the peeling residue on the support. The Ca salt is an organic substance that is presumed to be produced by a reaction between Ca ions derived from Ca compounds used in producing cellulose acylate from cellulose and fatty acids contained in cellulose acylate, and film formation In the middle, it precipitates on the surface of the support. If such a Ca salt is deposited, the adhesive strength between the support and the cast film is uneven, and there is a high possibility that a peeling residue will occur at the portion where the Ca salt is deposited. Therefore, in the present invention, the film is produced using the dope made of cellulose acylate in which the content of Ca and fatty acid is reduced as described above, so the production amount of Ca salt can be reduced, As a result, the cast film can be peeled off from the support in a short time with a small peeling stress. Thereby, since reduction of energy cost and shortening of manufacturing time are implement | achieved, effects, such as being able to improve productivity and manufacturing a film, are acquired. Moreover, in this invention, since the 1st cellulose acylate with a small acetylation degree compared with the 2nd cellulose acylate was used for dope for support layers, the production | generation of Ca salt on a support body was suppressed more. Further, the peelability can be improved.

  The long-chain fatty acid according to the present invention means a fatty acid having 12 to 30 carbon atoms as described above, for example, carboxydodecane, carboxytridecane, carboxytetradecane, carboxypentadecane, carboxyhexadecane, carboxyheptadecane, Carboxyoctadecane, carboxynonadecane, carboxyicosane, carboxydicosane, carboxytricosane, cariboxytetracosane, carboxypentacosane, carboxyhexacosane, carboxyheptacosane, carboxyoctacosane, carboxynonacosane, carboxydecacosan, carboxydo Decene, carboxytridecene, carboxytetradecene, carboxypentadecene, carboxyhexadecene, carboxyheptadecene, carboxyoctadecene, Bokishinonadeken, carboxy equalizer Sen, carboxymethyl Zico Sen, carboxymethyl Trichoderma Sen, carboxytetramethylrhodamine co Sen, carboxymethyl pen octopus Sen, carboxymethyl hexamethylene co Sen, carboxymethyl hepta co Sen, carboxymethyl octa co Sen, carboxymethyl Roh Naco Sen, carboxymethyl Dekako Sen like.

  The ratio of Ca and fatty acid contained in cellulose acylate can be reduced by sufficiently washing the cellulose acylate. Such washing of cellulose acylate may be performed by dissolving cellulose acylate in an organic compound before preparing a dope to prepare a liquefied product, and then filtering the liquefied product at least once by a filtering means. In addition, when the dope before being cast on the support is filtered at least once by a filtering means, Ca and fatty acids can be efficiently and effectively removed.

  Only one type of acyl group may be used in the cellulose acylate of the present invention, or two or more types of acyl groups may be used. When two or more kinds of acyl groups are used, it is preferable that one of them is an acetyl group. The sum of the degree of substitution of hydroxyl groups at the 2nd, 3rd and 6th positions by acetyl groups is DSA, and the sum of the degree of substitution of the hydroxyl groups at the 2nd, 3rd and 6th positions by acyl groups other than acetyl groups When DSB is DSB, the value of DSA + DSB is preferably 2.22 to 2.90, and particularly preferably 2.40 to 2.88.

  The DSB is preferably 0.30 or more, particularly preferably 0.7 or more. Further, 20% or more of DSB is preferably a substituent at the 6-position hydroxyl group, more preferably 25% or more, further preferably 30% or more, and particularly preferably 33% or more. Further, the value of DSA + DSB at the 6-position of cellulose acylate is 0.75 or more, more preferably 0.80 or more, and particularly preferably cellulose acylate of 0.85 or more. These cellulose acylates Can be used to prepare a solution with higher solubility, that is, a dope. In particular, when a non-chlorine organic solvent is used, a dope having excellent solubility, low viscosity and excellent filterability can be prepared.

  Cellulose, which is a raw material for cellulose acylate, may be obtained from either linter cotton or pulp cotton, but the one obtained from linter cotton is easier to control the optical properties in producing an optical film, Moreover, it is preferable because a film with few impurities and excellent transparency can be obtained. However, the present invention can produce a film having excellent optical properties even when pulp cotton containing a relatively large amount of impurities is used as a raw material.

  The acyl group having 2 or more carbon atoms of the cellulose acylate in the present invention may be an aliphatic group or an aryl group, and is not particularly limited. Examples thereof include cellulose alkylcarbonyl ester, alkenylcarbonyl ester, aromatic carbonyl ester, aromatic alkylcarbonyl ester and the like, and each may further have a substituted group. Preferred examples of these include propionyl group, butanoyl group, pentanoyl group, hexanoyl group, octanoyl group, decanoyl group, dodecanoyl group, tridecanoyl group, tetradecanoyl group, hexadecanoyl group, octadecanoyl group, iso-butanoyl group. , T-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like. Among these, a propionyl group, a butanoyl group, a dodecanoyl group, an octadecanoyl group, a t-butanoyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, a cinnamoyl group, and the like are more preferable, and a propionyl group and a butanoyl group are particularly preferable. It is.

  In addition, when preparing the liquefied material containing a cellulose acylate, it is preferable to use the solvent used for dope preparation as the organic compound to be used. Thereby, it is easy to prepare a dope having desired properties. Next, the solvent for preparing the dope will be described.

  As the solvent that is a solvent for preparing the dope, it is preferable to use a compound that can dissolve cellulose acylate. For example, aromatic hydrocarbons (eg benzene, toluene etc.), halogenated hydrocarbons (eg dichloromethane, chloroform, chlorobenzene etc.), alcohols (eg methanol, ethanol, n-propanol, n-butanol, diethylene glycol etc.), Examples include ketones (eg, acetone, methyl ethyl ketone, etc.), esters (eg, methyl acetate, ethyl acetate, propyl acetate, etc.) and ethers (eg, tetrahydrofuran, methyl cellosolve, etc.). In the present invention, the dope means a polymer solution or dispersion obtained by dissolving or dispersing a polymer in a solvent.

  As the solvent, a hydrophobic one is preferable, and as this hydrophobic solvent, dichloromethane is most preferable. As said halogenated hydrocarbon, a C1-C7 thing is used preferably. In addition, from the viewpoints of solubility of cellulose acylate, peelability from a cast film support, and mechanical strength and optical properties of the film, one or more alcohols having 1 to 5 carbon atoms are added to dichloromethane. It is preferable to mix several types. The content of alcohol is preferably 2 to 25% by weight, more preferably 5 to 20% by weight, based on the entire solvent. Specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, etc., but methanol, ethanol, n-butanol, or a mixture thereof is preferable.

  Recently, a solvent composition not using dichloromethane has been proposed in order to minimize the influence on the environment. For this purpose, ethers having 4 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 3 to 12 carbon atoms are preferable, and these are used by being appropriately mixed. These ethers, ketones and esters may have a cyclic structure, and any one of the functional groups of the ether, ketone and ester (that is, —O—, —CO— and —COO—) may be A compound having two or more compounds can also be used as the organic solvent. The organic solvent may have other functional groups such as alcoholic hydroxyl groups. And in the case of the organic solvent which has 2 or more types of functional groups, the carbon atom number should just be in the prescription | regulation range of the compound which has any functional group, and it does not specifically limit.

  In addition, when using triacetylcellulose (TAC) as a polymer at the time of preparing dope, it is preferable that the TAC density | concentration in the raw material dope mentioned later is 5 to 40 weight%. More preferably, the TAC concentration is 15 to 30% by weight, and particularly preferably 17 to 25% by weight. A method for producing a dope for casting by a solution casting method for producing such a TAC film (for example, a raw material, a raw material dissolution method and addition method, a filtration method, defoaming, etc.) is disclosed in JP-A-2005-104148. [0517] paragraph to [0616] paragraph are described in detail, and these descriptions can also be applied to the present invention.

  Details of cellulose acylate are described in paragraphs [0140] to [0195] of JP-A-2005-104148, and these descriptions can also be applied to the present invention.

  Next, a method for preparing the dope by mixing the above various raw materials will be described. FIG. 1 is a schematic view of a dope manufacturing facility 10 used in the present embodiment. In addition, the form shown here is an example which concerns on this invention, and does not limit this invention.

  The dope manufacturing facility 10 manufactures a base layer dope manufacturing apparatus 10a for manufacturing a base layer dope and a support surface layer dope in order to prepare dopes having different compositions using different types of polymers, additives, and the like. It is comprised from the dope manufacturing apparatus 10b for support surface layers, and the dope manufacturing apparatus 10c for air surface layers which manufactures dope for air surface layers. Each device has the same form and the same procedure for producing the dope. Therefore, in the following description, the procedure and manufacturing conditions for manufacturing the support layer dope using the support surface layer dope manufacturing apparatus 10b will be described as a representative, and description of other apparatuses will be omitted.

  As shown in FIG. 1, a support surface layer dope manufacturing apparatus 10b includes a solvent tank 11 containing a solvent, a hopper 13 containing cellulose acylate as a polymer as a main raw material of the film, and a cellulose acylate. A mixing tank 15 that mixes a rate and a solvent to form a mixed solution 17; a heating device 22 that obtains a raw material dope 20 by heating and adjusting the temperature of the mixed solution 17 to dissolve the solid content in the solvent; And a device 23. The solvent stored in the solvent tank 11 acts as an organic solvent for dissolving the polymer. In addition, the first filtration device 25 and the second filtration device 26 for filtering the raw material dope 20, the stock tank 28 for storing the raw material dope 20 after filtration, and the concentration of the raw material dope 20 A flash device 31 for adjusting the pressure, a recovery device 32 for recovering the volatile solvent generated in the flash device 31, a regenerator 33 for regenerating the recovered solvent, and the like.

  A jacket 35 provided so as to wrap the outer surface of the mixing tank 15, a first stirrer 38 rotated by a motor 37, and a second stirrer 40 rotated by a motor 39 are attached. The first stirrer 38 is preferably provided with an anchor blade, and the second stirrer 40 is preferably a dissolver type eccentric stirrer. The internal temperature of the mixing tank 15 is controlled to be substantially constant by flowing a heat transfer medium whose temperature is adjusted inside the jacket 35. The internal temperature of the mixing tank 15 is preferably −10 to 55 ° C. In the mixing tank 15 in which the internal temperature is adjusted in this way, the first stirrer 38 and the second stirrer 40 are appropriately selected and rotated to stir and mix the dope raw material.

  The heating device 22 preferably uses a jacketed pipe capable of controlling the temperature in order to further increase the solubility of the solid content in the mixed solution 17. Further, in order to further improve the solubility, the mixed solution 17 is used as the heating device 22. It is preferable that a pressurizing means for pressurizing is provided. In the heating device 22, the heating temperature of the mixed liquid 17 is preferably set to 0 to 97 ° C. in order to improve the solubility without causing thermal damage to various raw materials contained in the mixed liquid 17. The heating by the heating device 22 in the present invention does not mean that the mixed liquid 17 is heated to a temperature of room temperature or higher, but means that the temperature of the mixed liquid 17 sent from the mixing tank 15 is increased. For example, when the temperature of the sent mixed liquid 17 is −7 ° C., the temperature may be set to 0 ° C.

  Even if it cools instead of the heating apparatus 22 and the liquid mixture 17 is cooled, the solubility of solid content with respect to a solvent can be improved. When such a cooling dissolution method is used, the mixed solution 17 is cooled to −100 to −10 ° C. If the heating dissolution method and the cooling dissolution method as described above are appropriately selected according to the properties of each raw material and the like, the solubility of the mixed solution 17 can be suitably controlled.

  The temperature control device 23 is a device that brings the mixed liquid 17 to substantially room temperature. The raw material dope 20 with high solubility of the cellulose acylate in the solvent is obtained by setting the mixed solution 17 with increased solubility to approximately room temperature by the temperature control device 23. Here, the liquid after exiting the temperature control device 23 is referred to as the raw material dope 20, but in many cases, the cellulose acylate is already dissolved in the solvent at the time of exiting the heating device 22. Therefore, in the present invention, a solution in which a polymer containing cellulose acylate is dissolved in a solvent, that is, a solution having high solubility is referred to as a raw material dope 20.

  The first filtration device 25 and the second filtration device 26 are provided with a filter having a desired average pore diameter, and foreign materials such as insoluble matters are removed by filtering the raw material dope 20. The average pore diameter of the filter is preferably 100 μm or less so that small foreign matters in the raw material dope 20 can be captured. Here, if the average pore size of the filter is too small, the time required for filtration becomes longer, and therefore the time required for the entire dope preparation becomes longer. On the other hand, if the average pore diameter of the filter is too large, it is difficult to remove minute foreign matters contained in the raw material dope. Therefore, the average pore diameter of the filter is not particularly limited, but is preferably selected as appropriate in consideration of the manufacturing time and the like. In addition, it is preferable that the filtration flow volume at the time of filtering the raw material dope 20 in the 1st filtration apparatus 25 and the 2nd filtration apparatus 26 shall be 50 L / hour or more. Thereby, work can be advanced without spending a long time for filtration.

  The stock tank 28 is provided with a jacket 43 that wraps the outer surface thereof and a stirrer 46 that is rotated by a motor 45. In the stock tank 28, as in the mixing tank 15, the heat transfer medium adjusted to a predetermined temperature is caused to flow inside the jacket 43, thereby adjusting the internal temperature. Further, while the raw material dope 20 is stored in the stock tank 28, the stirrer 46 is always rotated by the motor 45. Thereby, the uniform state of the raw material dope 20 is maintained without causing aggregation of foreign matters.

  In addition, a liquid supply line 51 is attached to the stock tank 28. The liquid feed line 51 is a flow path for the raw material dope 20, and one end thereof is connected to a casting die provided in the film manufacturing facility 50. Thereby, the dope manufacturing apparatus 10b for support surface layers is connected to the film manufacturing facility 50, and the raw material dope 20 is sent to the film manufacturing facility 50 as necessary. In the middle of the liquid feed line 51, a tank 52 in which the support surface layer additive solution 52a is placed and a static mixer 53, which is a static mixer, are attached.

  In addition, each apparatus and member are connected by stainless steel piping from advantages, such as being excellent in corrosion resistance and heat resistance. In addition, pumps P1 to P4 and valves V1 and V2 are attached to appropriate portions of each pipe. These pumps and valves can be changed in number of installations and locations as required, and are not limited to this embodiment.

  Next, a method for preparing the support surface layer dope using the support surface layer dope manufacturing facility 10b will be described. First, the valve V <b> 1 is opened and a predetermined amount of solvent is sent from the solvent tank 11 to the mixing tank 15. Further, a desired amount of cellulose acylate is fed from the hopper 13 into the mixing tank 15. As the polymer for the support surface layer, a second cellulose acylate having a degree of acetylation that satisfies a specified range is used.

  In the mixing tank 15 to which various raw materials are fed, the first stirrer 38 and the second stirrer 40 are appropriately rotated to mix various raw materials. Thereby, the liquid mixture 17 stirred uniformly is prepared. At this time, the internal temperature of the mixing tank 15 is adjusted to −10 to 55 ° C. by flowing a temperature-controlled heat transfer medium inside the jacket 35. In addition, although the order of the dope raw materials sent to the mixing tank 15 is the order of the solvent and the cellulose acylate, it is not limited to this order, and may be the order of the cellulose acylate and the solvent, for example.

  The liquid mixture 17 is fed into the heating device 22 while the flow rate is adjusted by the pump P1. In the heating device 22, the mixed liquid 17 is heated to a predetermined temperature, so that the solid content is dissolved in the solvent. In the present embodiment, a pipe having a jacket capable of controlling the temperature and a pressurizing function is used as the heating device 22 to pressurize the heating temperature in a range of 0 to 97 ° C.

  The liquid mixture 17 is sent to the temperature control device 23 and is brought to substantially room temperature. By the above, the raw material dope 20 with high solubility can be obtained. Thereafter, the raw material dope 20 is filtered by a first filtration device 25 including a filter having an average pore diameter of 100 μm or less, and foreign substances contained therein are removed. At this time, when the raw material dope 20 satisfies a desired concentration, it is fed into the stock tank 28 and stored therein until it is used for casting. In the stock tank 28, the stirrer 46 is constantly rotated to stir the raw material dope 28. In addition, the internal temperature of the jacket 43 is adjusted by flowing a heat transfer medium whose temperature is adjusted inside the jacket 43.

  In the method of preparing the raw material dope 20 having a desired concentration after preparing the mixed solution 17 as described above, the higher the concentration of the desired raw material dope 20, the longer the time required for the preparation, leading to an increase in manufacturing cost. Such problems arise. Therefore, in order to avoid such a problem, it is preferable to prepare a raw material dope 20 having a concentration lower than the target concentration and then concentrate the raw material dope 20 to a desired concentration. This embodiment also employs this method, and the details of the concentration method will be described below.

  First, a raw material dope 20 having a concentration lower than a desired concentration is prepared. The preparation method of the raw material dope 20 is as described above. Next, after the raw material dope 20 is filtered by the first filtering device 25, the raw material dope 20 is sent to the flash device 31 via the valve V <b> 2, where a part of the solvent contained in the raw material dope 20 is evaporated. Thereby, the raw material dope 20 can be concentrated and adjusted to a desired concentration. The solvent gas generated by evaporation is condensed and liquefied by a condenser (not shown), recovered by the recovery device 32, and further regenerated by the regeneration device 33. When this regenerated solvent is used when adjusting the liquid mixture 17, it is possible to obtain effects such as reduction in raw material costs.

  The concentrated raw material dope 20 is extracted from the flash device 31 by the pump P2, and then sent to the second filtration device 26 to remove foreign substances contained therein. And it is sent to the stock tank 28 and stored. In addition, it is preferable that the temperature of the raw material dope 20 at the time of filtering with the 2nd filtration apparatus 26 is 0-200 degreeC. Moreover, when extracting the raw material dope 20 from the flash device 31, it is preferable to perform a bubble removing process in order to remove bubbles generated in the raw material dope 20. As a method for removing bubbles, a known method can be applied, and examples thereof include an ultrasonic irradiation method.

  The raw material dope 20 stored in the stock tank 28 is appropriately fed into the liquid feeding line 51 by the pump P3. The support surface layer additive solution 52a is fed from the tank 52 to the raw material dope 20 flowing in the liquid feeding line 51 by the pump P4. Thereafter, the raw material dope 20 to which the support surface layer additive solution 52 a is added is stirred and mixed by the static mixer 53.

  The support surface layer additive solution 52 is a liquid in which a desired additive and a solvent are mixed in advance. Here, the solvent is not particularly limited, but if the same solvent as used for dope preparation is used, the compatibility with the raw material dope is good. Further, when the additive is liquid at room temperature, it can be used alone without being mixed with a solvent. Details of the additive will be described later.

  As shown in FIG. 2, the static mixer 53 is attached to a pipe 60 that constitutes the liquid feeding line 51, and the connection portion is firmly fixed by a fixing member 164. Elements 62 and 63 are alternately arranged in the longitudinal direction of the pipe. The elements 62 and 63 are formed by twisting a rectangular plate by 180 °, and the twisting directions of the element 62 and the element 63 are reversed. The elements 62 and 63 are shifted by 90 ° so that the side edges of the plates are orthogonal.

  On the upstream side of the static mixer 53, an addition pipe 65 through which the support surface layer additive solution 52a flows is disposed. The addition pipe 65 includes a circular pipe 66 penetrating the pipe 60 and an addition nozzle 68 attached to the tip of the pipe 66. Further, a slit-like addition port 69 is formed at the tip of the addition nozzle 68.

  As shown in FIG. 3, the addition nozzle 68 is formed so as to extend in the diameter direction of the pipe 60 over the tip. Then, the support surface layer additive solution 52a is added to the raw material dope 20 flowing in the pipe 60 from the slit-shaped addition port 69. Further, the longitudinal direction of the addition nozzle 68 and the addition port 69 and the side end portion 64 of the element 62 closest to the addition nozzle 68 are arranged so as to be orthogonal to each other. When the support surface layer additive solution 52a containing the additive is added from the addition port 69, the additive is surely divided from the top of the static mixer, and the additive is stably injected without rotating. Therefore, the raw material dope and the additive can be efficiently stirred and mixed. For this reason, the number of elements of the static mixer can be reduced, and the process can be reduced in size and cost. In FIG. 3, in order to avoid complication of the drawing, a joint portion between the pipe 60 and the static mixer 53 is not shown.

  In adding the additive to the raw material dope while efficiently and suitably dispersing the additive, the distance D from the addition port 69 to the side end portion 62a of the element 62 closest to the addition port 69 is 1 mm or more and 250 mm or less. It is preferable that the distance D is 2 mm or more and 250 mm or less. If the distance D is too close, the additive nozzle 68 may be clogged due to the resistance of the raw material dope, and conversely if too far, the additive cannot be added to the center of the static mixer 53.

  When the additive is uniformly added to the raw material dope flowing through the pipe 60 in the width direction, the length L of the slit of the addition port 69 is set to the inner diameter W (mm) of the pipe 60 as shown in FIG. On the other hand, it is preferably 20% or more and 80% or less. Here, when the length L of the slit is too short, the stirring efficiency is lowered. On the other hand, when L is too long, the additive may be put into the gap between the pipe 60 and the element 62, which is not preferable. Further, the gap C of the slit of the addition port 69 is preferably 0.1 mm or more and 1/10 or less of the inner diameter W of the pipe 60. Thereby, an additive can be more reliably and efficiently added to the raw material dope.

  To efficiently and uniformly disperse the additive with respect to the raw material dope, 1 ≦ V1 / V2 ≦ 5 when the flow rate of the support surface layer additive solution 52a is V1 and the flow rate of the raw material dope is V2. It is preferable. V1 is a flow rate of the support surface layer additive solution 52a when the liquid is fed into the pipe 60, and V2 is a flow rate of the raw material dope when the liquid is fed into the pipe 60. If the value of V1 / V2 is less than 1, there is a risk of running out of liquid in the liquid feeding direction. Conversely, as V1 / V2 exceeds 5 and becomes larger, the support surface layer additive solution 52a has energy, There is a risk of passing through the static mixer 53 vigorously, resulting in a decrease in dispersibility.

When the viscosity of the support surface layer additive solution 52a is N1 (Pa · s) and the viscosity of the raw material dope is N2 (Pa · s), N1 is 1 × 10 ⁻⁴ Pa · s to 1 × 10 ⁻¹ Pa. S, N2 is preferably 5 Pa · s to 5 × 10 ² Pa · s, and the viscosity ratio is preferably 1000 ≦ N2 / N1 ≦ 1000000. The above-mentioned viscosities are all measured values of shear viscosity at 20 ° C. and a shear rate of 1 (sec ⁻¹ ). A known viscometer may be used. The above-mentioned definition of the viscosity is not limited to the support surface layer additive solution 52a but also applies to other solutions. By adjusting the viscosity of the additive solution, the raw material dope viscosity after the additive is added can be controlled. Moreover, it is preferable that the shear rate V3 of the raw material dope flowing through the pipe 60 is 0.1 (sec ⁻¹ ) to 30 (sec ⁻¹ ). Shear rate V3 is might not proceed mixed is less than 0.1 sec ^-1, pressure loss is increased in the pipe 60 increases beyond 30 sec ^-1 Conversely, not tolerate a breakdown voltage of about 20 × 9.8 N There is a fear. For the same reason, regarding the raw material dope, it is preferable that the number of lay nozzles Re indicating the fluid flow state is Re ≦ 200.

  As described above, a homogeneous support surface layer dope in which the polymer, the solvent, and the additive are uniformly stirred and mixed is obtained. Further, as described above, similarly to the support surface layer dope, the base layer dope manufacturing facility 10a prepares the base layer dope, and the air surface layer dope manufacturing facility 10c prepares the air surface layer dope. The additive solution used when preparing the base layer dope and the air surface layer dope may be the same as or different from the support surface layer additive solution. In addition, in this embodiment, although the form which prepares each dope for base layers, a support body layer, and an air surface layer with a separate apparatus was shown, dope for base layers and air surface layers are polymer types to be used, etc. Can be prepared with a single device.

  In the above-described embodiment, an example in which a static mixer including an element formed by twisting a rectangular plate is used as the inline mixer has been described. However, the present invention is not limited to this, and other types of inline are used. A mixer may be used. As an in-line mixer, for example, it is conceivable to use a slewer mixer provided with elements formed by combining a plurality of strip-shaped plates in a lattice shape.

  Examples of the additive according to the present invention include a retardation control agent, an ultraviolet absorber, a peeling accelerator (for example, citrate ester) that facilitates peeling from a casting band as a support, and a film wound into a roll. A matting agent (for example, silicon dioxide, etc.) that suppresses adhesion between film surfaces when removed can be suitably used.

  A silicon dioxide derivative is preferably used as the fine particles. This silicon dioxide derivative is silicon dioxide, and includes a silicone resin having a three-dimensional network structure. In this way, when a silicon dioxide derivative is used as the fine particle and the surface thereof is alkylated, it has a hydrophobic treatment called an alkylation treatment, and therefore has good dispersibility in a solvent. . Therefore, since it is possible to produce a film while suppressing aggregation of fine particles, it is possible to produce a film with few planar defects and excellent transparency.

  In addition, the alkyl group introduced into the surface of the alkylated fine particles has 1 to 20 carbon atoms. More preferably, the alkyl group to be introduced has 1 to 12 carbon atoms, and particularly preferably 1 to 8 carbon atoms. In the fine particles into which such an alkyl group is introduced, aggregation of the fine particles can be further suppressed and dispersibility can be improved. The fine particles having an alkyl group having 1 to 20 carbon atoms on the surface as described above can be obtained, for example, by treating fine particles of silicon dioxide with octylsilane. An example of a silicon dioxide derivative having an octyl group on the surface is commercially available under the trade name Aerosil R805 (manufactured by Nippon Aerosil Co., Ltd.), which can also be preferably used in the present invention.

  The content of fine particles with respect to the solid content of the raw material dope is preferably 0.2% or less. The content of the fine particles may be adjusted by determining the amount of fine particles added to the solvent used for preparing the raw material dope. In this way, the raw material dope to which fine particles are added while controlling the content can suppress the generation of foreign matters due to the aggregation of fine particles, and thus exhibits excellent transparency. The fine particles preferably have an average particle size of 1.0 μm or less. More preferably, it is 0.3-1.0 micrometer, Most preferably, it is 0.4-0.8 micrometer.

  In addition to the above, additives that can be used in the present invention include, for example, retardation control agents, deterioration inhibitors, optical anisotropy control agents, dyes, and the like. JP-A 2005-104148 describes in detail in paragraphs [0196] to [0516], and these descriptions can also be applied to the present invention.

  Further, in the present embodiment, as a method of adding various additives to the raw material dope, a mode in which a solution in which various materials are mixed in advance with a solvent has been shown, but when these materials are solid, a hopper or the like May be used to feed into each liquid feed line. Furthermore, when it is desired to add a plurality of types of the above materials to the raw material dope, after preparing a solution in which a desired material is dissolved in a solvent in advance, the solution may be sent to each liquid feeding line using a tank. When each material is a liquid at normal temperature, it may be sent as it is to each liquid feeding line without using a solvent. Moreover, you may add an additive at the time of preparing raw material dope.

  Next, a method for producing a film using the casting dope will be described. FIG. 5 is a schematic diagram of a film manufacturing facility 50 used in the present embodiment.

  The film production facility 50 includes a casting chamber 72 for casting a casting dope on the support to form the casting film 70, and a solvent formed by peeling the casting film 70 from the support. A transfer part 77 that transports the film, that is, the wet film 75, a tenter 78 that is dried while holding and transporting both end portions of the wet film 75, and a drying chamber 80 that further accelerates the drying of the film 76. And a cooling chamber 81 for cooling the film 76 and a winding chamber 82 for winding the film 76 in a roll shape.

  Inside the casting chamber 72, a casting band 85 that is wound around the rotating rollers 86a and 86b and acts as a support is disposed. Further, a casting block in which a feed block 88 to which a dope for casting is supplied from the dope production facility 10 and a slit to be a casting port for the casting dope are formed at a predetermined position immediately above the casting band 85 is formed. And a die 89. In addition, a blower 90 that sends dry air to dry the casting film 70 formed on the casting band 85, and a heat transfer medium circulation device 91 that sends the heat transfer medium into the rotation rollers 86a and 86b, and A condenser (condenser) 92, a recovery device 93, and a peeling roller 95 are provided. A temperature control facility 97 that adjusts the internal temperature is attached to the outside of the casting chamber 72.

  The casting die 89 is provided with a decompression chamber 98 used for stably casting the casting dope. In addition, a wind shielding plate 99 is attached to the casting die 89 side of the blower 90 for the purpose of preventing the flat surface of the casting film 70 from being undulated by the dry air sent from the blower 90.

  The casting band 85 travels endlessly by rotating the rotating roller 86b by a driving device (not shown). The moving speed (casting speed) of the casting band 85 is preferably 10 to 200 m / min. A heat transfer medium flow path (not shown) is formed in advance in the rotary rollers 86a and 86b, and after the heat transfer medium adjusted to a predetermined temperature is sent into the flow path, the heat transfer medium By circulating with the circulation device 91, the surface temperature of each of the rotating rollers 86a and 86b is adjusted to a desired value. The surface temperature of the casting band 85 is preferably substantially constant within the range of -20 to 40 ° C.

  The width of the casting band 85 is not particularly limited, but it is preferably 1.1 to 2.0 times the width of the dope to be cast. Moreover, the length is 20-200 m, and it is preferable that thickness is 0.5-2.5 mm. In addition, it is preferable to use a casting band 85 that has been polished so that the overall thickness unevenness is 0.5% or less and the surface roughness is 0.05 μm or less. Thereby, since the casting film 70 can be formed without scratching the surface, the casting film 70 having excellent flatness can be obtained. The casting band 85 is preferably made of stainless steel in consideration of durability, heat resistance, ease of peeling of the casting film 70, etc. Among them, the casting band 85 is made of SUS316 having sufficient corrosion resistance and strength. Preferably there is. In addition, you may use metal drums, such as stainless steel, as a support body replaced with a casting band.

  The internal temperature of the casting chamber 72 is constantly adjusted by the temperature control equipment 97 so as to be in a temperature range suitable for drying the casting film 70. When the casting film 70 is dried, a large amount of the solvent evaporated from the casting film 70 floats inside the casting chamber 72, but the evaporated solvent is condensed and liquefied by the condenser (condenser) 72. After being collected, it is collected by the collection device 93. The recovered volatile solvent is made into a regenerated solvent after impurities are removed by a regenerator (not shown), and then reused as a solvent for preparing the dope, thereby reducing the raw material cost, that is, the manufacturing cost. I can plan.

The casting die 89 is preferably a coat hanger type. The width of the casting die 89 is not particularly limited, but is in the range of 1.05 to 1.5 times the casting width of the casting dope. On the other hand, it is preferable to use a thing about 1.01-1.3 times. Further, in order to smoothly cast the dope for casting, it is preferable to use a polished surface so that the surface roughness is 0.05 μm or less. In consideration of durability and corrosion resistance, it is preferable to use a material that does not cause pitting (perforation) at the gas-liquid interface even if it is immersed in a mixture of dichloromethane or methanol and water for 3 months. It is preferably made of stainless steel. A more preferable casting die 89 is made of SUS316 having sufficient corrosion resistance and strength as in this embodiment. However, it is not particularly limited because it can be preferably used as long as it has a corrosion resistance substantially equivalent to that of SUS316 by a forced corrosion test with an aqueous electrolyte solution. In addition, it is preferable to use a casting die 89 made of a material having a thermal expansion coefficient of 2 × 10 ⁻⁵ (° C. ⁻¹ ) or less because the need to consider thermal damage is reduced.

  The casting die 89 is preferably produced by grinding a die that has passed one month or more after casting. Thus, since the casting dope can flow smoothly and uniformly inside the casting die 89, it is possible to form the casting film 70 having excellent flatness without generating streaks or the like. However, in order to obtain the above-mentioned effect, the finishing accuracy of the wetted surface of the casting die 89 is 1 μm or less in terms of surface roughness, and the straightness is 1 μm / m or less in any direction. Is preferred. Moreover, it is preferable to use what can adjust the clearance of a slit in the range of 0.5-3.5 mm by automatic adjustment. Further, it is preferable to use a material having R of 50 μm or less over the entire width of the slit at the corner of the liquid contact portion at the lip end of the casting die 89. In addition, it is preferable to use what was adjusted so that the shear rate inside the casting die 89 might be set to 1-5000 (1 / second).

  As the casting die 89, it is preferable to use a die attached with a temperature controller (not shown), and the inner temperature of the casting dope is preferably maintained within a predetermined range while the dope for casting is cast. Then, a thickness adjusting bolt (heat bolt) and an automatic thickness adjusting mechanism using this heat bolt are attached at predetermined intervals in the width direction of the casting die 89, and the heat bolt is controlled by a preset program. Therefore, it is preferable to adjust the liquid feeding amount of a pump (not shown) used when the dope for casting is sent out from the dope manufacturing facility 10. Further, a thickness gauge (for example, an infrared thickness gauge) may be provided inside the film manufacturing facility 11 and feedback control may be performed by an adjustment program based on the profile. Note that the thickness difference between any two points excluding the casting edge is adjusted within 1 μm, the difference between the minimum and maximum thickness in the width direction is 3 μm or less, and the thickness accuracy is ± 1.5 μm. It is preferable to use what is adjusted below.

A cured film is preferably formed on the lip end of the casting die 89 for the purpose of improving wear resistance and the like. The method for forming the cured film is not particularly limited, and examples thereof include ceramic coating, hard chrome plating, and a nitriding treatment method. However, when ceramic is used as the cured film, it can be ground and has low porosity, excellent brittleness and corrosion resistance, and excellent adhesion to the casting die 89. Is preferably inferior in adhesion. Concretely, there are tungsten carbide (WC) and _{Al 2 O 3, TiN, Cr} 2 O 3 and the like. Among them, it is preferable to use WC. The WC coating can be performed by a thermal spraying method.

  A solvent supply device (not shown) is attached to both ends of the slit to solubilize the dope (for example, a mixed solvent of 86.5 parts by weight of dichloromethane, 13 parts by weight of methanol, and 0.5 parts by weight of n-butanol). Is preferably supplied to both ends of the casting bead and the gas-liquid interface between the slit and the outside air. Thus, the casting dope is not locally dried and solidified while casting the casting dope from the slit. The supply amount of the solubilizing solvent is not particularly limited, but if it is supplied in the range of 0.1 to 1.0 mL / min for each side of the slit end, the amount of foreign matter to the inside of the casting film 70 is reduced. Since mixing can be prevented, it is preferable. When supplying the solubilizing solvent, it is preferable to use a pump having a pulsation rate of 5% or less.

  Further, while the casting dope is cast, the flow of the casting dope between the slit and the casting band 85, that is, the back surface of the casting bead is preferably decompressed by the decompression chamber 98. . By adjusting the degree of decompression at the back of the casting bead in this way, the surface of the casting bead does not wavy due to the surrounding wind, so it becomes possible to form a stable casting bead and wrinkle. The cast film 70 having excellent flatness can be formed without causing any damage. In addition, although the pressure reduction degree of the back surface of a casting bead is not specifically limited, In order to obtain the casting film 70 excellent in flatness, it is set to (atmospheric pressure −2000 Pa) or more (atmospheric pressure −10 Pa) or less. It is preferable.

  The crossing section 77 is provided with a plurality of rollers and a drying device 100 for accelerating drying by blowing dry air adjusted to a desired temperature onto the wet film 75. In addition, the tenter 78 is provided with a chain that travels according to the arrangement of the rails and has a number of clips attached thereto, and a drying device (both not shown). Then, downstream of the tenter 78, an ear clip device 102 for cutting both side ends of the film 76 is provided.

  The drying chamber 80 is provided with a plurality of rollers 105 and an adsorption recovery device 106. The drying chamber 80 is provided with a temperature adjusting device (not shown) that adjusts the temperature inside the drying chamber 80, and is adjusted to a predetermined range. In this embodiment, a forced static elimination device (static elimination bar) 107 and a knurling roller 108 are provided downstream of the cooling chamber 81. The film 76 in the middle of conveyance is adjusted so that the charged voltage is within a predetermined range (for example, −3 to +3 kV) by the forced static elimination device 107, and further, the knurling is applied by the knurling application roller 108, so that the wrinkles are stretched. It will be in the state which is excellent in flatness. The winding chamber 82 is provided with a winding roller 110 and a press roller 111.

  Next, a procedure for manufacturing the film 76 by the film manufacturing facility 50 will be described.

  The dope for the base layer, the dope for the support surface layer, and the dope for the air surface layer, which are the casting dopes prepared in the dope manufacturing facility 10, are sent to the pipes 51, 55, and 56, respectively. Sent. Inside the feed block 88, the flow path of each dope is formed so as to have a desired arrangement. Here, each dope has a desired arrangement.

  Next, as shown in FIG. 6, the base layer dope 120, the air surface dope 121, and the support surface dope 122 are simultaneously cast from the casting die 89 on the casting band 85. Thereby, the casting film 70 having a three-layer structure in which the air surface layer 121a and the support surface layer 122a are arranged as the surface layers on both surfaces of the base layer 120a is formed.

  Here, the thickness of the support surface layer 122 a is preferably 0.1% or more and 5% or less with respect to the thickness of the casting film 70. When a support surface layer with such a thickness is formed, even if cellulose acylate with a low degree of acetylation is used for the purpose of improving peelability, it is a very thin film, so it has optical properties such as transparency and retardation value. An excellent film can be obtained. Moreover, since the surface layer can be formed into a thin film, the film can be formed in a short time, so that a film having excellent flatness can be obtained without causing undulation or the like by the wind. In addition, in FIG. 6, although the form which fully took the thickness of each film | membrane in a casting film is shown for convenience of explanation, actually, a different form is shown such that the support surface layer is a thin form with respect to the base layer. .

  In the casting chamber 72, the drying air adjusted to a desired temperature is sent to the casting film 70 from the blower device 90 provided with the air blowing ports in the transport direction of the casting film. Drying of is promoted. In this way, from the blower provided with the blower opening, the drying air is sent out substantially in parallel in the transport direction of the casting film 70, and therefore, the thickness of the casting film 70 such as uneven thickness and wrinkles is caused by the drying air. Occurrence is suppressed. In the casting chamber 72, the solvent evaporated from the casting film 70 is condensed and liquefied by the condenser 92 and then collected by the collecting device 93. The recovered solvent is regenerated by a regenerator (not shown) and reused for dope preparation.

  The casting film 70 whose drying has been promoted until it has the self-supporting property is peeled off from the casting band 85 while being supported by the peeling roller 95 to form a wet film 75. Here, in the present invention, since the support surface layer 122a is formed using cellulose acylate having a low Ca and fatty acid content and a low degree of acetylation, the casting film 70 can be easily formed from the casting band 85. Can be peeled off. The residual solvent amount of the wet film 75 immediately after formation is preferably 10 to 200% by weight. Then, the wet film 75 is fed into the crossover part 77. In the transfer section 77, drying of the wet film 75 is promoted by the drying air sent out from the drying apparatus 100 while being supported and conveyed by a large number of rollers. In addition, it is preferable that the temperature of the drying air sent out from the drying apparatus 100 is made substantially constant at 20-250 degreeC. The temperature of the drying air may be arbitrarily determined within the above range in consideration of the raw material species such as the polymer and additive used for the casting dope, the production rate, and the like.

  In addition, the residual solvent amount in this invention is the quantity of the solvent contained in a cast film, a wet film, a film, etc. The amount of the residual solvent is based on the dry amount. When the weight of the sample at the time of sampling is x and the weight after the sample is completely dried is y, {(xy) / y} × 100 This is a calculated value.

  In the crossover portion 77, the rotational speed of the rollers disposed on the downstream side, that is, in the vicinity of the exit of the crossover portion 77, among the plurality of rollers is made higher than the rotational speed of the rollers disposed on the upstream side, that is, on the entrance side of the crossover portion 77. It is preferable. Thereby, an appropriate tension is applied to the wet film 75 to be conveyed, and the occurrence of wrinkles and wrinkles is suppressed. Further, since tension is applied to the wet film 75 having a high residual solvent amount, the molecular orientation can be easily adjusted. Therefore, it is easy to control the retardation value as a film.

  Subsequently, the wet film 75 is fed into the tenter 78. In the tenter 78, since the both ends of the wet film 75 are gripped by clips (not shown) and then the drying air is supplied from the drying device (not shown) while being transported, the wet film 75 is further dried. Is promoted to form a film 76. In the tenter 78, it is preferable to adjust the retardation value of the film 76 to be formed to a desired value by stretching the wet film 75 to be conveyed in the width direction. Further, the inside of the tenter 78 is preferably divided into a plurality of compartments, and the temperature of each compartment is preferably adjusted to a different temperature by the above-described drying apparatus. Thus, since the wet film 75 can be dried stepwise at different temperatures while the wet film 75 is conveyed, it is possible to obtain a film 76 having excellent flatness by suppressing a change in shape due to rapid evaporation of the solvent. it can. In this embodiment, as the tenter 78, a clip type tenter having a plurality of clips as gripping means for the wet film 75 is shown. However, instead of the clip, a pin is used, and the pins are inserted into both end portions of the wet film 75. After fixing with, it can be stretched in the width direction during conveyance. Such a pin type tenter is effective when conveying a wet film 75 having a relatively large amount of solvent and an unstable shape.

  The process of stretching or relaxing the wet film 75 in the width direction can also be performed at the transition portion 77. At this time, in the crossover part 77 and the tenter 78, it is preferable to stretch at least one direction in the casting direction and the width direction of the wet film 75 at a ratio of 0.5 to 300% with respect to the width before stretching. It should be noted that the drying temperature is preferably kept substantially constant while tension is applied to the wet film 75 at the crossover portion 77 or the tenter 78. Thereby, it can prevent that a difference arises in the extent of extending | stretching by the difference in drying temperature.

  The film 76 is fed into the ear-cutting device 102, and both end portions thereof are cut and removed. At this time, both end portions of the cut film 76 are fed into the crusher 103 and crushed as chips. Thus, when the edge-cutting device 102 is provided downstream of the tenter 78 and both end portions of the film 76 are cut and removed, both end portions damaged by the tenter 78 can be removed, and thus the film 76 having excellent flatness is obtained. Can be obtained. In addition, although this process which cut | disconnects the both ends of the film 76 can also be abbreviate | omitted, it is preferable to carry out in any one from the casting chamber 72 to the winding chamber 82. FIG.

  Thereafter, the film 76 is fed into the drying chamber 80. In the drying chamber 80, drying is sufficiently accelerated while the film 76 is supported and conveyed by a number of rollers 105. The internal temperature of the drying chamber 80 is not particularly limited. However, when the film temperature of the film 76 is adjusted to 60 to 145 ° C., it is effective while suppressing thermal damage of the polymer constituting the film 76. It is preferable because the solvent can be evaporated. In the present embodiment, the gas containing the volatile solvent evaporated from the film 76 floating inside the drying chamber 80 is recovered by the adsorption recovery device 106, the solvent component is removed, and then the drying chamber 80 is returned to the drying chamber 80 again. Send in dry air. As a result, the energy cost can be reduced, and the manufacturing cost can be reduced.

  In addition, when a preliminary drying chamber (not shown) is provided between the ear opener 102 and the drying chamber 80 and the film 76 is preliminarily dried, the shape change due to a sudden rise in the film surface temperature of the film 76 in the drying chamber 805. It is preferable because an effect such as being able to be suppressed can be obtained.

  The fully dried film 76 is fed into the cooling chamber 81. In the cooling chamber 81, since the film 76 is gradually cooled until it reaches substantially room temperature, it can be cooled while suppressing the occurrence of wrinkles and wrinkles on the surface thereof. If a humidity control chamber (not shown) is provided between the drying chamber 80 and the cooling chamber 81 to condition the film 76 and then send it to the cooling chamber 81, the surface of the film 76 is excellent. It is preferable because a wrinkle stretching effect can be obtained.

  The film 76 that has been brought to substantially room temperature is fed into the forced static elimination device 107 and adjusted so that its charged voltage is within a predetermined range (for example, −3 to +3 kV). In addition, in FIG. 5, although the installation location of the forced static elimination apparatus 107 is shown as the downstream of the cooling chamber 81, it is not limited to this position. Further, the film 76 is embossed on both side ends by the knurling roller 108. When knurling is applied in this way, the effect of improving the flatness of the film 76 is obtained.

  Finally, in the winding chamber 82, the film 76 is wound around the winding roller 110 while the tension at the time of winding is adjusted by the press roller 111, and a roll-shaped film product is manufactured. It is more preferable that the tension during winding is gradually changed from the start to the end of winding. Moreover, it is preferable that the film 76 to wind up shall be at least 100 m or more in a conveyance direction, and it is preferable that the width direction is 1400-2500 mm. However, the present invention can obtain an effect even when it is larger than 2500 mm.

  In addition, it is preferable that the thickness of the completed film 76 is 20-100 micrometers. More preferably, the thickness is 20 to 80 μm, and particularly preferably 30 to 70 μm. However, the present invention is not particularly limited to the film thickness of the completed film 76.

  The film obtained by the present invention has excellent transparency. Moreover, since the addition method to the raw material dope and the mixing method have been devised, even when a retardation agent is used as an additive, a homogeneous dope can be obtained by efficiently dispersing without waste. Therefore, the retardation value of the film also shows an excellent value. That is, the front retardation value at the wavelength λ nm of the film is Re (nm), the retardation value in the film thickness direction at the wavelength λ nm is Rth (nm), and Re and Rth when λ = 400 are Re ′, Rth ′, λ When Re and Rth at Re = 700 are equal to Re ′ and Rth ″, | Re′−Re ″ | <10, and | Rth′−Rth ″ | <35. A film exhibiting such a value is preferable as an optical film used in devices such as liquid crystal display devices because of its excellent optical properties. Re is the refractive index in the slow axis direction (transport direction) in the plane of the film nx, the refractive index in the fast axis direction (width direction) in the plane of the film is ny, and the film thickness of the film is d ( nm) is a numerical value represented by Re (λ) = (nx−ny) × d, and Rth is Rth (λ) = {(when the refractive index in the thickness direction of the film is nz. nx + ny) / 2−nz} × d.

  The method for casting the dope for casting is not particularly limited, and a known method capable of casting a plurality of dopes may be used. As in the present embodiment, two or more types of dopes may be cast simultaneously, or a plurality of dopes may be cast sequentially. Furthermore, a method of casting simultaneously or sequentially may be combined. When casting a plurality of dopes sequentially, a plurality of casting dies 150 to 153 corresponding to the number of dopes are installed above the casting band 85 as shown in FIG. A dope for the support surface layer, a dope for the base layer, and a dope for the air surface layer are appropriately sent from the dope manufacturing facility to each casting die 150 to 153, and sequentially cast from the dope for the support surface layer on the casting band 85. The As a result, the base layer and the air surface layer are sequentially stacked on the support surface layer to form a casting film 160 having a three-layer structure. Further, the casting die may be one with a feed block attached or a multi-manifold type. When a film having a multilayer structure is formed by co-casting, the thickness of the layer on the air surface side and the thickness of the layer on the support side are 0.5% to 30% with respect to the thickness of the entire film, respectively. It is preferable. In FIG. 7, the same members as those of the film manufacturing facility 50 are denoted by the same reference numerals and description thereof is omitted.

  From casting die, decompression chamber, support structure, co-casting, peeling method, stretching, drying conditions for each step, handling method, curling, winding method after flatness correction, solvent recovery method, film recovery method Up to this point, the details are described in paragraphs [0617] to [0889] of JP-A-2005-104148, and these descriptions can also be applied to the present invention.

[Performance / Measurement method]
(Curl degree / thickness)
The performance of the wound cellulose acylate film and the measuring method thereof are described in paragraphs [1073] to [1087] of JP-A-2005-104148, and these descriptions are also applied to the present invention. Can do.

[surface treatment]
In this cellulose acylate film, it is preferable that at least one surface is surface-treated. The surface treatment is preferably at least one of vacuum glow discharge treatment, atmospheric pressure plasma discharge treatment, ultraviolet irradiation treatment, corona discharge treatment, flame treatment, acid treatment or alkali treatment.

[Functional layer]
(Antistatic, hardened layer, antireflection, easy adhesion, antiglare)
At least one surface of the cellulose acylate film may be undercoated.

Furthermore, it is preferable to use a cellulose acylate film as a base film and a functional material provided with other functional layers. As the functional layer, it is preferable to provide at least one of an antistatic layer, a cured resin layer, an antireflection layer, an easy adhesion layer, an antiglare layer, and an optical compensation layer. Then, the functional layer, at least one surfactant preferably contains 0.1 to 1000 mg / ^{m 2,} it is preferable that at least one 0.1 to 1000 mg / ^{m 2} containing a slip agent. Moreover, it is preferable that a functional layer contains 0.1-1000 mg / m < ² > of at least 1 type of mat agent, and it is preferable that 1-1000 mg / m < ² > of at least 1 type of antistatic agent is contained. In addition to the above, the method for imparting a surface-treated functional layer to the cellulose acylate film for realizing various functions and properties is not limited to the above, from paragraph [0890] of JP-A-2005-104148, [1072]. Detailed conditions and methods are described in the paragraph, and these descriptions can also be applied to the present invention.

  The use of the film obtained by the present invention will be described. The film obtained by the present invention has a high retardation value and is excellent in transparency. Therefore, it is particularly useful as a polarizing plate protective film. In addition, the liquid crystal display device produced by sticking two polarizing plates which bonded this film to the polarizer on the liquid crystal layer shows the features such as excellent liquid crystal display capability. However, the arrangement of the liquid crystal layer and the polarizing plate is not limited, and various known arrangements can be employed. Japanese Patent Application Laid-Open No. 2005-104148 (for example, paragraphs [1088] to [1265]) describes TN type, STN type, VA type, OCB type, reflective type, and other examples in detail as liquid crystal display devices. This method can also be applied to the present invention. In addition, in the same application, a description of a cellulose acylate film provided with an optically anisotropic layer, a cellulose acylate film provided with antireflection and antiglare functions, and biaxiality imparting appropriate optical performance. The use as an optical compensation film as a cellulose acylate film is also described. This can also be used as a polarizing plate protective film. These descriptions can also be applied to the present invention.

  Examples according to the present invention will be described below. However, the embodiment shown here does not limit the present invention.

  The raw materials shown below were mixed to prepare a support surface layer dope, an air surface layer dope, and a base layer dope. In each example, a second solvent tank containing the following second solvent was prepared in addition to the solvent tank 11 containing the first solvent in the corresponding dope manufacturing facility.

The following materials were mixed, and a dope A was prepared as a support surface layer dope by the dope manufacturing facility 10 shown in FIG.
[Dope A]
Cellulose triacetate (substitution degree 2.86, viscosity average polymerization degree 305, viscosity of dichloromethane solution 6% by weight viscosity 400 mPa · s) 100 parts by weight dichloromethane (first solvent) 390 parts by weight methanol (second solvent) 60 parts by weight -Retardation reducing agent shown in Chemical formula 12-Part by weight-Wavelength dispersion adjusting agent shown in Chemical formula-1.8 parts by weight-Fine particles (silicon dioxide (average particle size 15 nm), Mohs hardness about 7) 0.05 part by weight of cellulose triacetate The acetylation degree was 60.5% to 61.0%, the Ca content was 5 ppm, and the long-chain fatty acid content was 5 ppm. Of the above, the retardation reducing agent, the wavelength dispersion adjusting agent and the fine particles were used as the support surface layer additive solution 52a.

  First, an appropriate amount of dichloromethane was sent from the solvent tank 11 to the mixing tank 15, and an appropriate amount of methanol was sent from the second solvent tank to the mixing tank 15. Further, cellulose triacetate was fed from the hopper 13. Thereafter, in the mixing tank 15, various materials were stirred and mixed to obtain a mixed solution 17. Next, the mixed liquid 17 was fed into the heating device 22 and the cellulose acylate was dissolved in a solvent, and then the raw material dope before concentration was obtained with the temperature adjusting device 23 at approximately room temperature. And this raw material dope was sent to the flash apparatus 31, and the raw material dope 20 of the desired density | concentration was obtained by evaporating a solvent here.

  The concentrated raw material dope 20 was extracted from the flash device 31 by the pump P2, and then subjected to foam removal by an ultrasonic irradiation method. And after filtering with the 2nd filtration apparatus 26 and removing an impurity, it sent to the stock tank 28 and stored here.

  Next, a part of the raw material dope 20 was fed into the first liquid feeding line L1. Subsequently, the support surface layer additive solution 52a is sent from the first tank 52 toward the raw material dope 20 by the pump P4, and the raw material flowing in the dope pipe 60 from the slit-shaped addition port 69 as shown in FIG. The support surface layer additive solution 52 a was added to the dope 20. Then, this was stirred and mixed by the first static mixer 53 to prepare a homogeneous base layer dope.

  Dope B was prepared as a base layer dope and an air surface layer dope by mixing the following raw materials. In this example, since both dopes have the same composition and composition, a common dope manufacturing facility was used.

[Dope B]
Cellulose triacetate (substitution degree 2.94, viscosity average polymerization degree 305, viscosity of 6 wt% dichloromethane solution 397 mPa · s) 100 parts by weight dichloromethane (first solvent) 390 parts by weight methanol (second solvent) 60 parts by weight The acetylation degree of said cellulose triacetate is 61.5%-62.0%.

  Then, as shown in FIG. 6, the base layer dope 120, the air surface layer dope 121, and the support surface layer dope 122 prepared as described above are formed into a film by the film manufacturing facility 50 shown in FIG. did. First, the above-mentioned three kinds of dopes are cast together from a casting die 89 on a traveling casting band 85, and a three-layer structure having an air surface layer 121a and a support surface layer 122a on each surface of the base layer 120a. A film 70 was formed. At this time, the casting amount of the dope was adjusted so that the film thickness of the completed film was 80 μm to control the thickness, and the film thickness of the support surface layer was 5 μm. Next, the casting film 70 was peeled off from the casting band 85 to form a wet film 75, and then dried with a transfer part 77 and a tenter 78 to obtain a film 76. Thereafter, the film 76 was continuously fed into the drying chamber 80, and drying was sufficiently promoted while being conveyed while being wound around a large number of rollers 105. Finally, a take-up film 76 was produced by the take-up roller 110 in the take-up chamber 82. The amount of residual solvent in the completed film 76 was 0.4% by weight, the film width was 1900 mm, and the film thickness was 80 μm. The thickness of the support surface layer of this film 76 was 1.0 μm.

  In Example 1, the addition nozzle 68 having a length L of the addition port 69 of 90% with respect to the inner diameter of the pipe 60 and a slit gap C of 3 mm was used. The distance D from the addition port 69 to the element of the in-line mixer closest to the addition port 69 was 15 mm. Furthermore, V1 / V2, which is a ratio between the flow velocity V1 of the support surface layer additive solution 52a flowing in the pipe 60 and the flow velocity V2 of the raw material dope 20, was set to 5. These manufacturing conditions were the same when preparing the base layer dope and the air surface layer dope.

  In order to evaluate the effects of the present invention, peelability and optical properties were evaluated by the following methods.

・ Peelability
In the middle of film formation, the state when the casting film 70 is peeled off from the casting band 85 is observed with the naked eye, and there is no peeling residue on the casting band 85 and it can be easily peeled off. There is no problem in manufacturing, but a little peeling residue or something that took time to peel off is marked as ○, a large amount of peeling residue is confirmed on the surface of the casting band 85, and it takes time to peel off, The level that caused a problem in production was marked with x.

[2. optical properties〕
Using the completed film as a sample, the front retardation value Re (nm) was measured in two ways: Re (400) at a wavelength λ = 400 nm and Re (700) at λ = 700 nm. Then, the value of Re (400) −Re (700) is calculated, and when this value is less than 10 and it is considered as an excellent optical characteristic as a product, the value is ○, and this value is 10 or more and the optical characteristic is obtained as a product. An inferior case was evaluated as x, and an optical birefringence meter (KOBRA-21ADH manufactured by Oji Scientific Instruments Co., Ltd.) was used to measure the optical characteristics of the film.

  As a result of each evaluation, in Example 1, the peelability was good (◎). In addition, Re (400) −Re (700) = 5, and the optical characteristic showed an excellent value (◯).

  In Example 2, an 80 μm film 76 was manufactured by the same material and manufacturing method as in Example 1. However, the thickness of the completed support surface layer was set to 5.0 μm. Further, when the peelability and the optical properties were evaluated in the same manner as in Example 1, the peelability was confirmed to be a slight level (O), although the peelability was slightly observed, whereas the optical properties were satisfactory. Re (400) −Re (700) = 15, which was bad (×) as the product level.

[Comparative Example 1]
In Comparative Example 1, an 80 μm film 76 was manufactured using the same materials and manufacturing method as in Example 1. However, the dope A was used as the base layer dope, and the dope B was used as the air surface layer dope and the support surface layer dope. In addition, the thickness of the support body layer in the completed film 76 was 1.0 micrometer. Further, when the peelability and optical properties were evaluated in the same manner as in Example 1, the optical properties were Re (400) −Re (700) = 5 and good (◯), but it was confirmed that the peelability was not peeled off. It was x by doing.

[Comparative Example 2]
In Comparative Example 2, an 80 μm film 76 was manufactured using the same materials and manufacturing method as in Example 1. However, the dope A was used as the air dope, and the dope B was used as the base layer dope and the support surface layer dope. In addition, the thickness of the support body layer in the completed film 76 was 1.0 micrometer. Further, when the peelability and optical properties were evaluated in the same manner as in Example 1, the optical properties were Re (400) −Re (700) = 5 and good (◯), but it was confirmed that the peelability was not peeled off. It was x by doing.

  From the above results, the cellulose acylate in which the Ca content and fatty acid content that can be unstripped components as in the present invention are reduced and the acetylation degree is smaller than the cellulose acylate used for the air surface layer and the base layer is obtained. When the film is produced using this dope after being contained in the dope for the support surface layer, the cast film can be easily peeled off from the support, and the film is produced while improving the peelability. Confirmed that it can. Moreover, since the film obtained by this invention is formed from homogeneous dope by stirring and mixing a polymer, a solvent, and an additive uniformly, it confirmed that it showed the outstanding optical characteristic.

It is the schematic of an example of dope manufacturing equipment used by this embodiment. It is explanatory drawing of an example at the time of adding an additive to raw material dope using a static mixer. It is the schematic of an example of piping and the additive nozzle vicinity which concern on this invention. It is sectional drawing of piping and the additive nozzle vicinity seen from the radial direction of piping. It is the schematic of an example of the film manufacturing equipment used by this embodiment. It is the schematic of an example near a casting die. It is the schematic of an example which casts several dope sequentially.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Dope manufacturing equipment 10b Dope manufacturing apparatus 50 for support surface layers Film manufacturing equipment 53 Static mixer 70 Casting film 85 Casting band 120a Base layer 121a Air surface layer 122a Support surface layer

Claims (11)

A casting film forming step of casting a casting dope in which an additive is added to a raw material dope containing a polymer and an organic solvent on a traveling support to form a casting film;
A stripping step of stripping the cast film from the support to form a wet film containing a solvent;
A drying step of drying the wet film,
The casting dope includes a base layer dope for forming a base layer, and a support surface layer dope for forming a support surface layer disposed so as to be in contact with the surface of the base layer located on the support side. The air surface layer dope for forming an air surface layer disposed at a position facing the support surface layer with the base layer in between,
The polymer contained in the support surface layer dope is a first cellulose acylate having an acetylation degree of 58.5% or more and 61.0% or less,
The method for producing a polymer film, wherein the polymer contained in the base layer dope and the air surface layer dope is a second cellulose acylate having an acetylation degree of 61.0% to 62.0%. .   2. The polymer film according to claim 1, wherein the first cellulose acylate has a Ca content of 0.1 ppm to 50 ppm and a fatty acid content of 0.1 ppm to 30 ppm. Manufacturing method.   The method for producing a polymer film according to claim 1 or 2, wherein the fatty acid is a long chain fatty acid in which 12 to 30 carbon atoms are arranged in a chain.   The method for producing a polymer film according to any one of claims 1 to 3, wherein a ratio of the thickness of the support surface layer to the thickness of the cast film is 0.1% or more and 5% or less.   The method for producing a polymer film according to any one of claims 1 to 4, wherein the raw material dope after adding the additive is stirred and mixed with an in-line mixer. The in-line mixer is attached to a pipe through which the raw material dope flows,
6. The method for producing a polymer film according to claim 5, wherein an addition nozzle having a slit-like addition port extending in a diameter direction of the in-line mixer is provided on the upstream side of the in-line mixer.   The method for producing a polymer film according to claim 6, wherein the addition port has a length L that is parallel to the radial direction of the pipe and is 20% to 80% of the inner diameter of the pipe.   The method for producing a polymer film according to claim 6 or 7, wherein a gap C of the slit is 0.1 mm or more and 1/10 mm or less of the inner diameter of the pipe.   The method for producing a polymer film according to any one of claims 6 to 8, wherein a distance D from the addition port to the in-line mixer is 1 mm or more and 250 mm or less.   The method for producing a polymer film according to any one of claims 6 to 9, wherein a flow rate V1 of the additive flowing in the pipe and a flow rate V2 of the raw material dope satisfy 1 ≦ V1 / V2 ≦ 5.   The method for producing a polymer film according to any one of claims 1 to 10, wherein the casting is a co-casting in which the casting dope is cast simultaneously or sequentially on the support.

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