JP2008221564A - Manufacturing method of cellulose acylate film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a cellulose acylate film which is almost impurity-free. <P>SOLUTION: First, an activated cellulose 15 is obtained by adding an acetic acid to cellulose 11 made of a natural material e.g. pulp etc. as a raw material. Then acetic anhydride as an acetylation reaction agent, acetic acid and sulfuric acid as a catalyst, are added, stirred and mixed, and a part of hydroxyl groups of the activated cellulose 15 is esterified to obtain a primary cellulose acylate 16. Next, the sulfuric acid added to the primary cellulose acylate 16 is neutralized to obtain a secondary cellulose acylate 19, and this secondary cellulose acylate 19 is filtered by a filter with a porous filter medium. Thus the impurity content of the secondary cellulose acylate 19 is caught, so that the cellulose acylate 23 with an extremely low level of the impurity content can be obtained. Further, a dope containing the cellulose acylate 23 is formed into a film by a film-forming process. Consequently, the film which has excellent planarity and is almost free from the impurity, is available despite the procedure to restrain the generation of a stain to the surface of a support. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a cellulose acylate film mainly used as an optical film.

  Cellulose acylate is widely used as a raw material for polymer films such as tobacco filters, acetate fibers, and photographic films because of its excellent chemical resistance, heat resistance, flame retardancy, and the like. Among these, when triacetyl cellulose is used, it is possible to form a film with excellent handleability and processability and to obtain a highly transparent film. This is used as various optical films such as a protective film for a polarizing plate of a liquid crystal display device and an optical compensation film, and the demand for the liquid crystal display device and the like has been remarkably increased.

  The cellulose acylate film is mainly produced by a solution casting method. The solution casting method is a method in which a cast film is formed by casting on a support running on a dope mixed with additives such as cellulose acylate, solvent and fine particles, and then the cast film is peeled off from the support. It is the method of taking and drying to make a film.

  By the way, the solution casting method has a problem in that dirt adheres to the surface of the support during film formation, and the dirt is transferred to the surface of the casting film, so that the flatness of the film is lowered. Contamination is considered to be the precipitation of impurities contained in the cast film. Examples of main impurities include alkaline earth metals derived from cellulose acylate, which is a raw material for the dope, and metal salts formed by reaction of fatty acids derived from cellulose acylate and additives. Therefore, in order to suppress the generation of dirt on the surface of the support, usually, an operation for removing impurities by passing the dope before being cast through a porous filter medium is performed. However, if the pore size of the filter medium is reduced in order to remove fine impurities, the trapping effect of the impurities is increased, but clogging is likely to occur, and the time required for filtration becomes longer and the filtration efficiency decreases. Yes.

Therefore, as a method for improving the filtration efficiency without reducing the pore size of the filter medium, for example, Patent Document 1 discloses a solution casting method that prevents clogging of the filter medium by filtering the dope with a porous filter aid. Proposed. According to this method, impurities in the dope can be adsorbed to the filter aid, and the impurities are deposited on the filter aid while the filtration is continued, and formed between the filter aid and the impurities. By using the gap, high filtration accuracy can be realized.
JP 2004-107629 A

  However, as in Patent Document 1, it is difficult to sufficiently remove impurities only by filtering the prepared dope with a predetermined filter medium, and it is difficult to prevent the generation of dirt on the surface of the support. Currently, for cellulose acylate films, there is a demand for films with low impurity content for the purpose of realizing high image quality by liquid crystal display devices, etc., but an effective method for this requirement has been established. Not.

  Therefore, the present invention prepares a dope with less impurities and uses this to prevent the adhesion of dirt on the surface of the support, resulting in the production of a cellulose acylate film that can produce a film with less impurities. It aims to provide a method.

  In the method for producing cellulose acylate of the present invention, a casting film was formed by casting a dope containing a solvent and cellulose acylate on a traveling support, and then the casting film was peeled off from the support. Thereafter, in the method for producing a cellulose acylate film by drying, a cellulose acylate is obtained by subjecting a cellulose acylate mixture produced by esterifying a cellulose and an acylating agent under an acidic catalyst to a porous material. It is characterized by removing impurities by passing through a filter medium.

  The filter medium is preferably a plurality of filter aids.

  The filter aid is preferably diatomaceous earth.

  The filter medium is preferably a filter in which a large number of pores having an average pore diameter of 0.1 μm or more and 50.0 μm or less are formed.

  In the cellulose acylate mixture sent to the filter medium, the proportion of cellulose acylate contained in the total weight of the cellulose acylate mixture is preferably 10% by weight or less.

  According to the present invention, in the production process, a dope is prepared using cellulose acylate that is efficiently and effectively removed even fine impurities by filtering with a predetermined filter medium, and a film is produced by this dope. Since it did in this way, the adhesion of the stain | pollution | contamination on the surface of a support body can be prevented, and a film with few impurities can be manufactured as a result.

  The method for producing cellulose acylate according to the present invention will be described with reference to embodiments.

〔material〕
The dope of the present invention contains a solvent and cellulose acylate. The cellulose acylate according to the present invention is produced by esterifying a cellulose and an acylating agent under an acidic catalyst. Specifically, for example, diacetyl cellulose, triacetyl cellulose (TAC), etc. Is mentioned.

  As shown in FIG. 1, the cellulose acylate production process 10 of the present embodiment includes a pretreatment process 13, an acetylation process 17, an aging process 20, a filtration process 22, and a posttreatment process 24.

  In the pretreatment step 13, an activated cellulose 15 is obtained by adding an acid to the cellulose 11. Cellulose 11 may be obtained from either cotton or wood, but is preferably obtained from wood for the purpose of preventing soiling on the support when the film is produced. Acetic acid is preferably used as the acid. In the pretreatment step 13, the sealed container containing the cellulose 11 and the acid is stirred for 0.1 to 3 hours while being kept at 20 to 60 ° C. to activate the cellulose 11.

  In the acetylation step 17, the activated cellulose 15 is reacted with an acylating agent under an acidic catalyst. The acylating agent is, for example, acetic anhydride or acetic acid, and the catalyst is preferably sulfuric acid. As a result, primary cellulose acylate 16 in which a part of hydroxyl groups of activated cellulose 15 is esterified is generated. The timing at which the ester reaction in the acetylation step 17 is completed can be known from the ratio of a part of the hydroxyl group being esterified, that is, the degree of acetylation. This acetylation degree can be calculated | required according to the measuring method of the acetylation degree of ASTM: D-817-91 (test methods, such as a cellulose acetate).

  In the aging step 20, a neutralizing agent such as Mg salt is added to the production system of the primary cellulose acylate 16. As a result, the sulfuric acid in the production system is neutralized, and secondary cellulose acylate 19 is produced. In the aging step 20, it is preferable that the temperature of the reaction system is 125 to 170 ° C. and the temperature is kept in the same temperature range for 3 minutes to 6 hours in order to effectively advance the neutralization reaction.

  Usually, as a method for producing cellulose acylate, cellulose acylate 23 is produced through post-treatment step 24 after each of the above steps. The post-processing step 24 includes a precipitation process 25, a cleaning process 28, and a drying process 29. In the precipitation treatment 25, the secondary cellulose acylate 19 is treated with a predetermined solution. As this solution, a dilute acetic acid aqueous solution is suitable. Thereby, the secondary cellulose acylate 19 is separated into the precipitate 26 and the separation liquid 27. Since the precipitate 26 is a component that becomes a precursor of the cellulose acylate 23, it is collected and used for the cleaning process 28. On the other hand, the separation liquid 27 is treated as a waste liquid because it is another insoluble liquid component. In the washing process 28, the precipitate 26 is washed with a washing liquid. The washing solution is not particularly limited, but a compound that is insoluble in the precipitate 26 and has few impurities is suitable, and distilled water is preferably used for reasons such as availability. . In the drying process 29, the washed precipitate 26 is dried to evaporate the solvent component to obtain the cellulose acylate 23.

  The present invention is characterized in that the filtration step 22 is performed before the post-treatment step 24. In the filtration step 22, the secondary cellulose acylate 19 is filtered by a filtration device equipped with a predetermined filter medium. As shown in FIG. 2, the filter medium 43 includes a filter 41 and a porous layer 42 located on the filter 41. The filter 41 is installed so that the surface having a large number of holes 41a is orthogonal to the flow of the secondary cellulose acylate to capture impurities in the secondary cellulose acylate 19, and here, mainly the diatomaceous earth 45 Acts as a support. The porous layer 42 is obtained by depositing a plurality of diatomaceous earths 45 on the filter 41. As the diatomaceous earth 45, those having an average particle diameter of 5 μm or more and 150 μm or less are preferably used, and the diatomaceous earth 45 is deposited so that voids are formed between the diatomaceous earths 45. Note that the arrows in FIG. 2 indicate the flow of the secondary cellulose acylate 19.

  When the secondary cellulose acylate 19 is passed through the filter medium 43, the impurities 47 present in the secondary cellulose acylate 19 are captured in the voids formed by the deposition of diatomaceous earth 45. Since the size of the voids depends on the particle diameter of the diatomaceous earth 45, even micron-order impurities are effectively captured. Further, as the filtration time becomes longer, the amount of impurities 47 deposited increases and the voids increase, so the filtration efficiency improves.

  As the filter 41, one having an average hole diameter of the holes 41a of 0.1 μm or more and 50.0 μm or less is preferably used. In the case of such very fine holes, clogging is likely to occur, but when used together with a filter aid such as diatomaceous earth 45 as in this embodiment, clogging is suppressed and high filtration is achieved. Accuracy can be maintained. Here, a filter having a pore diameter exceeding 50.0 μm is not suitable because it is difficult to capture fine impurities. On the other hand, if the pore diameter is smaller than 0.1 μm, clogging is likely to occur, and the time required for filtration becomes longer, which is not preferable. The material of the filter is preferably metal from the viewpoint of durability, but may be made of paper and is not particularly limited.

  In order to achieve and maintain a high filtration efficiency, the secondary cellulose acylate passed through the filter medium 43 contains a cellulose acylate precursor component with respect to the total weight of the secondary cellulose acylate. The ratio is preferably 10% by weight or less. This ratio can be adjusted by the amount of each solution used in the stage before the filtration step 22 is performed. Thereby, the raise of filtration pressure and the fall of filtration efficiency are suppressed. The proportion of the cellulose acylate precursor is influenced by the viscosity of the solution, and the lower the proportion, the more the above effect is improved. Here, the secondary cellulose acylate 19 in which the above ratio exceeds 10% by weight has a high viscosity, so that the filtration pressure is increased and the time required for filtration is increased and the filtration efficiency is lowered. The viscosity of the secondary cellulose acylate 19 can be determined with a commercially available viscometer.

  The method of using diatomaceous earth 45 as a filter aid is not limited to this embodiment. For example, a filter obtained by adding diatomaceous earth 45 to secondary cellulose acylate 19 in advance before passing through filter medium 43 is filtered. 41 is mentioned. In this case, as in FIG. 2, the porous layer 43 formed by randomly depositing diatomaceous earth 45 on the filter 41 is formed, and the impurities 47 can be effectively captured.

[Content of impurities]
The removal status of impurities in the secondary cellulose acylate can be judged by the content of impurities contained in the secondary cellulose acylate before and after filtration. The calculation method of the content rate includes the weight of impurities W0 (g), the weight W1 (g) of the filter medium before filtering the secondary cellulose acylate, and after filtering the secondary cellulose acylate, After measuring the weight W2 (g) of the filter medium washed with the filter medium washing liquid in which dichloromethane and methanol are mixed, the value is calculated by the following formula (1).
Impurity content (%) = {(W2−W1) / W0} × 100 (1)

Cellulose acylate has a ratio in which hydrogen of the hydroxyl group of cellulose is substituted with an acyl group, that is, the substitution degree of acyl group (hereinafter referred to as acyl substitution degree) satisfies all the conditions of the following formulas (I) to (III). What is satisfied is more preferable. In (I) to (III), A is the degree of substitution of the acetyl group, and B is the degree of substitution of the acyl group having 3 to 22 carbon atoms.
2.5 ≦ A + B ≦ 3.0 (I)
0 ≦ A ≦ 3.0 (II)
0 ≦ B ≦ 2.9 (III)

  Glucose units constituting cellulose and having β-1,4 bonds have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer in which some or all of these hydroxyl groups are esterified and hydrogen is substituted with an acyl group having 2 or more carbon atoms. In addition, since the substitution degree is 1 when the esterification of the hydroxyl group is 100%, in the case of cellulose acylate, the substitution is performed when the hydroxyl groups at the 2-position, 3-position and 6-position are each 100% esterified. The degree is 3.

  Here, the acyl substitution degree at the 2-position of the glucose unit is DS2, the acyl substitution degree at the 3-position is DS3, and the acyl substitution degree at the 6-position is DS6. The total degree of acyl substitution determined by DS2 + DS3 + DS6 is preferably 2.00 to 3.00, more preferably 2.22 to 2.90, and even more preferably 2.40 to 2.88. DS6 / (DS2 + DS3 + DS6) is preferably 0.32 or more, more preferably 0.322 or more, and further preferably 0.324 to 0.340.

  There may be only one kind of acyl group, or two or more kinds. When there are two or more acyl groups, it is preferable that one of them is an acetyl group. DSA + DSB, where DSA is the sum of the substitution degrees of the hydrogens of the hydroxyl groups at the 2nd, 3rd and 6th positions with the acetyl group, and DSB is the sum of the substitution degrees other than the acetyl groups at the 2nd, 3rd and 6th positions The value of is preferably 2.2 to 2.86, particularly preferably 2.40 to 2.80. DSB is preferably 1.50 or more, and particularly preferably 1.7 or more. Further, it is preferable that 28% or more of the DSB is a substituent at the 6-position hydroxyl group, more preferably 30% or more, still more preferably 31% or more, and particularly preferably 32% or more is a substituent at the 6-position hydroxyl group. Preferably there is. The 6-position DSA + DSB value of cellulose acylate is preferably 0.75 or more, more preferably 0.80 or more, and particularly preferably 0.85 or more. By using the cellulose acylate as described above, a dope having a preferable solubility and a dope having a low viscosity and a good filterability can be produced. In particular, when a non-chlorine organic solvent is used, the above cellulose acylate is preferable.

  The acyl group having 2 or more carbon atoms may be an aliphatic group or an aryl group, and is not particularly limited. For example, there are cellulose alkylcarbonyl ester, alkenylcarbonyl ester, aromatic carbonyl ester, aromatic alkylcarbonyl ester, etc., and these may each further have a substituted group. 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, cyclohexane Examples thereof include a carbonyl group, an oleoyl group, a benzoyl group, a naphthylcarbonyl group, and a cinnamoyl group. 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 preferable that 90% by weight or more of the cellulose acylate used as the dope material is particles having a particle diameter of 0.1 mm to 4 mm.

  The 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.

  Solvents for producing the dope include aromatic hydrocarbons (for example, benzene, toluene, etc.), halogenated hydrocarbons (for example, dichloromethane, chlorobenzene, etc.), alcohols (for example, methanol, ethanol, n-propanol, n-). Examples include butanol, diethylene glycol, etc., ketones (eg, acetone, methyl ethyl ketone, etc.), esters (eg, methyl acetate, ethyl acetate, propyl acetate, etc.) and ethers (eg, tetrahydrofuran, methyl cellosolve, etc.). Here, the dope is a polymer solution or dispersion obtained by dissolving a polymer in a solvent or dispersing in a dispersion medium.

  As the solvent for TAC, among these solvents, halogenated hydrocarbons having 1 to 7 carbon atoms are preferable, and dichloromethane is most preferable. And from the viewpoint of properties such as the solubility of TAC, the peelability of the cast film from the support, the mechanical strength of the film, and the optical properties of the film, one or several kinds of alcohols having 1 to 5 carbon atoms are selected. It is preferable to use it mixed with dichloromethane. At this time, the content of the alcohol is preferably 2% by weight to 25% by weight and more preferably 5% by weight to 20% by weight with respect to the whole solvent. Preferable specific examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, etc. Among them, methanol, ethanol, n-butanol, or a mixture thereof is preferably used.

  For the purpose of minimizing the influence on the environment, the dope may be manufactured without using dichloromethane. As the solvent in this case, an ether having 4 to 12 carbon atoms, a ketone having 3 to 12 carbon atoms, and an ester having 3 to 12 carbon atoms are preferable, and these may be appropriately mixed and used. These ethers, ketones and esters may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and —COO—) can also be used as the solvent. The solvent may have another functional group such as an alcoholic hydroxyl group in the chemical structure.

  For the dope, additives such as a plasticizer, a deterioration inhibitor, an ultraviolet absorber, an optical anisotropy control agent, a dye, a matting agent, and a release agent may be appropriately used. Details of additives and solvents that can be applied to the present invention are also described in detail in paragraphs [0196] to [0516] of JP-A-2005-104148, and these descriptions also apply to the present invention. Can do. Regarding the method for producing the dope, for example, the raw material, the raw material, the additive dissolution method and addition method, the filtration method, defoaming, and the like are similarly described in paragraphs [0517] to [0616] of JP-A-2005-104148. It is described in detail in the paragraphs, and these descriptions can also be applied to the present invention.

  Next, an example of a method for producing a polymer film using the cellulose acylate according to the present invention will be described. As shown in FIG. 3, the polymer film manufacturing facility 50 used in the present embodiment includes a casting chamber 51, a crossing portion 52, a tenter 53, a drying chamber 54, a cooling chamber 55, and a winding chamber 56. Is provided.

  When manufacturing a film, first, the dope prepared in the dope manufacturing facility 60 is sent to the first filtration device 61 and the second filtration device 62 by the pump P1. This dope is obtained by stirring and mixing the cellulose acylate according to the present invention, a solvent, and additives such as fine particles. In addition, a filter paper having a pore diameter smaller than that of the second filtration device 62 is provided inside the first filtration device 61. Thereby, impurities and insoluble matters mixed during the preparation of the dope are effectively removed regardless of the size.

  The dope after filtration is sent to the feed block 65 in the casting chamber 51. In the feed block 65, a dope flow path is formed in accordance with the layer structure of the casting film 51, and the arrangement of the dope is determined here. For example, if a feed block having a plurality of flow paths is used, a film having a multilayer structure can be produced. Thereafter, the dope is sent to the casting die 67.

  The casting die 67 is formed with a dope discharge port, and the dope is cast from the discharge port onto the surface of the casting drum 68. The casting drum 68 acts as a support and rotates endlessly by a driving device. In this embodiment, a cylindrical or columnar drum is used. For example, a casting band that travels endlessly may be used. Inside the casting drum 68, a flow path for the heat transfer medium is formed. A heat transfer medium whose temperature is adjusted is supplied from the heat transfer medium supply device 70 to the flow path, and the surface temperature of the casting drum 68 is kept substantially constant in a range of −40 ° C. or higher and 30 ° C. or lower by circulating or passing the flow medium. The The temperature of the dope used for casting is substantially constant in the range of −10 to 55 ° C. The temperature of the dope can be adjusted by adjusting the internal temperature of the feed block 65 and the casting die 67.

  The dope that has reached the surface of the casting drum 68 is cooled, and a gel-like casting film 71 is formed in a short time. As the time of staying on the casting drum 68 becomes longer, the gelation of the casting film 71 proceeds and the self-supporting property is imparted. The method using the casting drum 68 having the surface cooled as described above can increase the film forming speed by shortening the time for forming the casting film. The casting film 71 having the self-supporting property is peeled off from the casting drum 68 by being applied with a tension in the conveying direction while being supported by the peeling roller 80, thereby forming a wet film 81. At the time of casting, since the dope used in this embodiment uses cellulose acylate from which impurities are effectively removed, the generation of dirt on the surface of the casting drum 68 is suppressed even if the film is continuously formed. The For this reason, the strippability when stripping the casting film 71 from the casting drum 68 does not deteriorate.

  During the casting of the dope, the pressure on the back surface of the dope cast by the decompression chamber 73, that is, the upstream side of the casting drum 68 is made substantially constant in the range of (atmospheric pressure −2000 Pa) to (atmospheric pressure −10 Pa). . As a result, the dope is drawn toward the casting drum 68 to prevent air from being caught. Further, the internal temperature of the casting chamber 51 is constantly adjusted by the temperature control device 75 in the range of −10 to 57 ° C. In the casting chamber 51, the solvent gas evaporated from the dope and the casting film 71 is condensed and liquefied by the condenser (condenser) 82 and then collected by the collecting device 80. The recovered solvent gas is regenerated after removing impurities by a regenerating device (not shown) connected to the recovering device 83. When this solvent is reused as a solvent for preparing a dope, the raw material cost can be reduced.

  In the transfer section 52, while the wet film 81 is supported and transported by a plurality of pass rollers, drying is performed by blowing dry air at a desired temperature from the drying device 84. The temperature of the drying air is preferably substantially constant in the range of 20 ° C. or higher and 250 ° C. or lower.

  In the tenter 53, a plurality of pins are inserted into both end portions of the wet film 81, and both end portions of the wet film 81 are held. The pin is attached to a chain that travels endlessly, and moves in the tenter 53 in accordance with the movement of the chain. During this time, drying air is supplied from a drying device (not shown) to promote drying of the wet film 81, whereby the film 88 is obtained. In the vicinity of the exit of the tenter 53, the holding of the film 88 by the pins is released.

  A clip tenter including a plurality of clips may be installed downstream of the tenter 53. It is preferable that the clip tenter is partitioned inside and the temperature is adjusted for each section. This temperature is maintained substantially constant in the range of 120 ° C. or more and 180 ° C. or less by a temperature control device (not shown). Further, in the clip tenter, if tension is applied to the width direction of the film 88 by expanding and reducing the distance between the facing clips while the film 88 is conveyed, the molecular orientation in the width direction of the film 88 can be controlled. Therefore, a film 88 having a desired retardation value can be obtained.

  Both end portions of the film 88 are cut by the edge cutting device 89. The cut piece of the film 88 is sent to the crusher 90 and crushed into chips. In addition, although the said cutting process can also be abbreviate | omitted, when obtaining the film 88 with few defects, it is preferable to carry out in either the casting chamber 51 to the winding chamber 56. FIG.

  In the drying chamber 54, while the film 88 is conveyed while being wound around the plurality of rollers 93, the film surface temperature of the film 88 becomes substantially constant in the range of 60 ° C. to 145 ° C. by the temperature adjusting device 94. It is adjusted as follows. Thereby, the film 88 can be sufficiently dried without causing thermal damage. The film surface temperature of the film 88 can be facilitated by a thermometer provided on the conveyance path of the film 88 and in the vicinity of the surface. In the drying chamber 54, the solvent gas volatilized from the film 88 is recovered by the adsorption recovery device 95, the solvent component is removed, and the drying chamber 54 is supplied again as drying air. Thereby, solvent gas does not adhere to the surface of the film 88, and reduction of energy cost can be aimed at. In addition, when a preliminary drying chamber (not shown) is provided between the ear opener 89 and the drying chamber 54 to predry the film 88, the film surface temperature of the film 88 that may be generated in the drying chamber 54 is rapidly increased. The effect of preventing the shape change can be obtained.

  The degree of drying of the casting film 71 and the film 88 can be grasped using the residual solvent amount as a guide. The amount of residual solvent is {(xy) / y} × 100, where x is the weight of this sample and x is the weight of the sample after the sample is completely dried. The value is based on the dry weight calculated in step (1). When a plurality of solvents are used simultaneously, the residual solvent amount is calculated from the sum of those solvents.

  In the cooling chamber 55, the heated film 88 is cooled to approximately room temperature. Further, when a humidity control chamber (not shown) is provided between the drying chamber 54 and the cooling chamber 55 to cool the film 88 after the humidity has been adjusted, even if the surface of the film 88 is already wrinkled, the wrinkle is effective. It is preferable because an effect of extending the length can be obtained. The charged voltage of the film 88 is adjusted by the forced static eliminating device 99. The charged voltage of the film 88 is not particularly limited, but is preferably substantially constant in the range of −3 kV to +3 kV. Thereafter, both ends of the film 88 are embossed by a knurling roller 100 and knurled. In the take-up chamber 56, the film 88 is taken up by the take-up roller 107 while being pressed by the press roller 105.

  As described above, the film 88 having excellent flatness and few impurities can be manufactured at high speed and stably. According to the present invention, it is possible to continuously produce a film 88 that is at least 100 m in the transport direction and 1400 to 2500 mm in the width direction. However, the present invention is also effective for the film 88 whose width direction is larger than 2500 mm. Moreover, this invention exhibits an effect also in manufacture of a thin film whose thickness after completion is 20-100 micrometers. More preferably, the thickness of a film is 20-80 micrometers, Most preferably, it is 30-70 micrometers. However, the present invention is not particularly limited to the film thickness of the completed film 76.

  In this embodiment, although the form which manufactures the film of a single layer structure using one type of dope was shown, this invention exhibits an effect also when manufacturing the film of a multilayer structure. In the case of forming a film having a multilayer structure, it may be a sequential casting in the step of forming a casting film, or a method of casting a plurality of dopes at the same time, and is not particularly limited. Also, from the structure of casting die, decompression chamber, support, etc., co-casting, peeling method, stretching, drying conditions of each step, handling method, curling, winding method after flatness correction, solvent recovery method, film The recovery method is described in detail in paragraphs [0617] to [0889] of JP-A-2005-104148, and these descriptions can also be applied to the present invention.

  The performance of the completed film, the degree of curling, the thickness, and the measuring methods thereof are described in paragraphs [1073] to [1087] of JP-A-2005-104148, and these descriptions are also included in the present invention. Can be applied.

  When the completed film is used as an optical film, it is preferable to surface-treat at least one surface because the adhesiveness when bonded to other optical members can be improved. Examples of the surface treatment include vacuum glow discharge treatment, atmospheric pressure plasma discharge treatment, ultraviolet irradiation treatment, corona discharge treatment, flame treatment, acid treatment, alkali treatment, etc., and at least one of these treatments is performed. Is preferred.

Moreover, when a desired functional layer is provided on both surfaces or one surface of the film obtained in the present invention as a base, it can be used as a functional film. Examples of the functional layer include an antistatic layer, a cured resin layer, an antireflection layer, an easy-adhesion layer, an antiglare layer, and an optical compensation layer. Among these, at least one layer is preferably provided. For example, when an antireflection layer is provided, a functional film antireflection film capable of obtaining an image antireflection effect of a liquid crystal display device or the like can be obtained. The functional layer preferably contains at least one of additives such as a surfactant, a slip agent, a matting agent, and an antistatic agent. In this case, the content is 0.1 to 1000 mg / m ² is preferable. In addition, the functional layer for forming various functions to the film, the forming method, and the like are described in detail in paragraphs [0890] to [1072] of JP-A-2005-104148, and these descriptions are also described in this book. It can be applied to the invention.

  The film obtained by the present invention has high transparency and retardation value and low humidity dependency. Therefore, although it can use suitably as a retardation film of a polarizing plate especially, it can utilize also as a protective film for protecting the surface of a polarizing plate. Regarding specific uses of the polymer film of the present invention, in Japanese Patent Application Laid-Open No. 2005-104148, for example, in paragraphs [1088] to [1265], TN type, STN type, VA type, OCB are used as liquid crystal display devices. A mold, a reflection type, and other examples are described in detail, and this description can also be applied to the present invention.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the examples and comparative examples shown here are merely examples of the present invention and do not limit the present invention.

  During the production of cellulose acylate, a dope was prepared using cellulose acylate 23 filtered through a predetermined filter medium. And the film 88 was manufactured from this dope with the film manufacturing equipment 50. FIG. Cellulose acylate uses cellulose 11 made of wood as a raw material. First, 100 parts by weight of cellulose 11 and 25 parts by weight of acetic acid are put into a sealed container and stirred for 1 hour while keeping at 50 ° C. Cellulose 15 was obtained. Next, 280 parts by weight of acetic anhydride as an acylating agent, 430 parts by weight of acetic acid as an acylating agent, and 3 parts by weight of sulfuric acid as a catalyst are stirred for 1 hour to produce primary cellulose acylate 16. It was. 24 parts by weight of magnesium acetate, which is an alkaline compound, was added to the primary cellulose acylate 16 to obtain a secondary cellulose acylate 19. The secondary cellulose acylate 19 was filtered with a filtration device. In the filtering device, a filter medium 43 having a porous filter 41 and a porous layer 42 composed of a plurality of diatomaceous earths 45 deposited on the filter 41 was used. At this time, the ratio of the cellulose acylate component to the total weight of the secondary cellulose acylate 19 was 15% by weight. A diluted acetic acid aqueous solution was added to the filtered secondary cellulose acylate 19 to produce a precipitate 26, and then the precipitate 26 was washed with water and dried to obtain cellulose acylate 23.

[Dope raw material]
The dope raw materials and blending amounts prepared in this example are as follows.
Cellulose acylate 100 parts by weight Dichloromethane 320 parts by weight Methanol 83 parts by weight 1-butanol 3 parts by weight Plasticizer A 7.6 parts by weight Plasticizer B 3.8 parts by weight UV agent a 0.7 parts by weight UV agent b 0.3 Parts by weight citrate ester mixture 0.006 parts by weight fine particles 0.05 parts by weight

  The details of the dope material are shown. The cellulose acylate has a substitution degree of 2.84, a viscosity average polymerization degree of 306, a water content of 0.2% by weight, a viscosity of 6% by weight in a dichloromethane solution of 315 mPa · s, an average particle diameter of 1.5 mm, and a standard deviation of 0. .5 mm powder. Plasticizer A is triphenyl phosphate, plasticizer B is diphenyl phosphate, UV agent a is 2 (2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole, UV Agent b is 2 (2'-hydroxy-3 ', 5'-di-tert-amylphenyl) -5-chlorobenzotriazole, citric acid ester compound is a mixture of citric acid, monoethyl ester, diethyl ester and triethyl ester The fine particles were silicon dioxide having an average particle diameter of 15 nm and a Mohs hardness of about 7. In preparing the dope, NN-di-m-toluyl-N-P-methoxyphenyl-1,3,5-triazine-2,4,6-triamine was used as a retardation control agent, This was added so as to be 4.0% by weight based on the total weight of the film.

  The dope is sent from the dope production facility 60 to the first filter device 61 provided with filter paper having a pore size of 40 μm and the second filter device 62 provided with filter paper having a pore size of 5 μm while adjusting the flow rate by the pump P1 and included in the dope. Impurities of various sizes were removed. The dope after filtration was sent to the casting die 68 through the feed block 65. The casting die 68 was provided with a slit-like discharge port having a width of 1.8 m so as to be parallel to the width of the casting drum 68. The casting die 68 was a type having a jacket (not shown) for adjusting its internal temperature, and was kept warm so that the temperature of the dope was 36 ° C. The feed block 65 and the pipe that is the dope flow path were of a type having a temperature adjustment function, and all the internal temperatures were kept at 36 ° C.

  The dope was discharged on the continuously rotating casting drum 68 while adjusting the discharge amount so that the thickness of the dried film 88 was 80 μm. The casting drum 68 is a drum made of SUS316 whose rotation speed can be controlled by a driving device (not shown), and uses a type in which a flow path of a refrigerant supplied from the cooling medium supply device 78 is formed. did. And the refrigerant | coolant was supplied to said flow path and the surface temperature of the casting drum 68 was set to -5 degreeC by circulating this. The inside of the casting chamber 51 was always set to 35 ° C. by the temperature control device 75. As described above, the casting film 71 was formed by cooling and gelling the dope on the surface of the casting drum 68.

The casting film 71 that was allowed to cool and gelled to give self-supporting property was peeled off from the casting drum 68 while being supported by the peeling roller 80. The cast film 71 was sent to the crossing section 52 and dried by supplying a drying air of 40 ° C. from the drying device 84 while being supported and transported by a plurality of pass rollers. The cast film 71 that has been dried is sent to the tenter 53, and both end portions of the cast film 71 are fixed with a plurality of pins, and then, while being transported while gradually stretching in the width direction, a drying device (not shown) ) Was supplied with dry air. As a result, the casting film 71 was stretched in the width direction to control the molecular orientation, and drying was sufficiently promoted until the residual solvent amount reached 1% by weight, whereby a film 88 was obtained. Within 30 seconds from the exit of the tenter 53, an ear-cutting device 89 equipped with an NT-type cutter was provided, and the film 88 was cut at a position of 50 mm inward from both side ends. Both side ends of the cut film 88 were sent to a crusher 90 by a cutter blower (not shown) and crushed into chips of about 80 mm ^{2 on} average.

  A pre-drying chamber (not shown) was provided between the ear opener 89 and the drying chamber 54 and the film 88 was preheated by supplying a drying air at 100 ° C. and then carried into the drying chamber 54. In the drying chamber 54, drying was promoted while being transported while being wound around a plurality of rollers 93 in the drying chamber 54 whose internal temperature was adjusted by the temperature adjusting device 94 so that the film surface temperature of the film 88 was 140 ° C. . The drying time of the film 88 by the drying chamber 54 was 10 minutes. The film surface temperature of the film 88 was measured using a thermometer (not shown) provided immediately above the conveyance path of the film 88 and in the vicinity of the surface. Further, in the drying chamber 54, after recovering the solvent gas volatilized from the film 88 using an adsorption recovery device 95 having an adsorbent composed of activated carbon and a desorbent composed of dry nitrogen, the moisture content is 0.3 weight. The water content of the solvent gas was removed until the concentration became less than or equal to%.

  A humidity control chamber (not shown) is provided between the drying chamber 54 and the cooling chamber 55, and after supplying air with a temperature of 50 ° C. and a dew point of 20 ° C. to the film 88, the humidity is directly 90 ° C. and humidity 70% air was blown to adjust the humidity, and the curl generated on the film 88 was corrected. Next, the film 88 was sent to the cooling chamber 55 and gradually cooled to 30 ° C. or lower, and then the charged voltage of the film 88 was set to −3 kV or higher and +3 kV or lower using the forced static eliminator 99. Then, knurling was applied to both end portions of the film 88 using the knurling roller 100 to correct the unevenness generated on the surface. In addition, the width of the knurling applied to the film 88 is 10 mm, and the pressing force by the knurling roller is adjusted so that the uneven height is 12 μm higher than the average thickness of the film 88 to emboss the film 88. Went.

  The film 88 was sent to the take-up chamber 56 and taken up by a take-up roller 107 having a diameter of 169 mm while applying a pressing force of 50 N / m to the film 88 by the press roller 105. At the time of winding, the tension at the beginning of winding of the film 88 was 300 N / m, and the tension at the end of winding was 200 N / m. From the above, the film thickness of the completed film 88 was 80 μm. In addition, the average drying rate of the cast film 71 and the film 88 was set to 20% by weight / min throughout the entire process.

  The effect of this invention was grasped | ascertained by measuring and evaluating the reflectance of the casting drum 68 when 100 hours passed from the start of film forming, and the number of the foreign materials contained in the completed film. Details of each evaluation method are as follows.

[Reflectance of support]
The reflectivity of the casting drum 68 after 100 hours from the start of film formation was determined by the following method, and the degree of generation of dirt on the surface of the casting drum 68 was evaluated. As shown in FIG. 4, a light source 110 for irradiating the surface of the casting drum 68 after the casting film 71 is peeled off with halogen light, and an image sensor 111 (Takenaka Electronics Co., Ltd.) for measuring the reflected light. The intensity at the reflection angle θ2 when the incident angle θ1 was 20 ° was measured. Here, X ₀ is the reflection light intensity before starting the film, X ₁₀₀ and the respectively measured 100 hours after the start of film is the intensity of reflected light after the lapse of the respective measurements of the following formula By substituting into (2), the reflectivity of the casting drum 68 after 100 hours from the start of film formation was determined. The closer the reflection degree is to 100, the less dirt is formed on the surface of the casting drum 68 due to the precipitation of impurities. On the other hand, the lower the reflection degree is from 60% to 0, the more the casting drum is. It means that impurities are deposited on the surface of 68 and a large amount of dirt is generated.
Reflectivity of support (%) = (X ₁₀₀ / X ₀ ) × 100 (2)

[Number of foreign substances contained in film]
The number of foreign matters contained in the completed film 88 was measured, and the proportion of impurities contained was evaluated. The number of foreign matters was measured with a microscope in a state where the completed film 88 was sandwiched between two polarizing plates and the polarizers of the polarizing plates were superposed at right angles, and the number of foreign matters having a pore diameter of 20 μm or more was measured. . Here, the area for observing the number of foreign substances was set to 1500 mm wide × 1 m long.

  In Example 1, the reflectivity of the casting drum 68 after the elapse of 100 hours from the start of film formation is 80%, and the generation of dirt is sufficiently suppressed despite the continuous production of the film for a long time. I was able to. Further, only two foreign matters were confirmed, and it was confirmed that the film had very few impurities.

  Example 2 is the same as Example 1 except that secondary cellulose acylate 19 having a cellulose acylate component content of 10% by weight is filtered using a porous filter medium having a pore size of 3 μm. Cellulose acylate 23 was produced by this method. And when the film 88 was manufactured using this cellulose acylate 23, the reflectivity of the casting drum 68 after 100 hours passed became 83%, and although it was manufactured continuously for a long time, the film 88 was soiled. The generation could be suppressed sufficiently. Further, only 0.5 foreign matter was confirmed on the film 88, and a film with very few impurities was obtained.

  In Example 3, the dope containing cellulose acylate 23 prepared in the same manner as in Example 1 is filtered only by the second filtration device 62 provided with filter paper having a pore diameter of 5 μm without using the first filtration device 61. A film 88 was manufactured in the same manner as in Example 1 except for the above. Then, the reflectivity of the casting drum 68 after 100 hours passed was 83%, and it was possible to sufficiently suppress the generation of stains despite the continuous production of the film for a long time. In addition, although three foreign substances were confirmed on the film 88, it was at a level with no problem as a product.

  In Example 4, when the cellulose acylate 23 was produced, the film 88 was the same as in Example 1 except that only a porous filter medium having a pore size of 50 μm was used without using diatomaceous earth as a filter aid. Manufactured. Then, the reflectivity of the casting drum 68 after the lapse of 100 hours was 83%, and it was possible to sufficiently suppress the generation of dirt even though the film was continuously manufactured for a long time. Moreover, although 3.5 foreign materials were confirmed on the film, it was at a level with no problem as a product.

  In Example 5, cellulose acylate was used in the same manner as in Example 1 except that filtration was performed using a porous filter medium having a pore size of 60 μm without using diatomaceous earth as a filter aid when producing cellulose acylate. 23 was produced. Then, when a film was produced using this cellulose acylate 23, the reflectivity of the casting drum 68 after 100 hours was 83%, and the generation of stains despite the production of the film continuously for a long time. Was sufficiently suppressed. Moreover, although 4.5 foreign materials were confirmed on the film, it was at a level with no problem as a product.

[Comparative Example 1]
A film was produced in the same manner as in Example 1 using cellulose acylate 23 produced without filtering secondary cellulose acylate 19 having a solid content of 15% of the total amount. Then, the reflectivity of the casting drum 68 after 100 hours was 50%, and the generation of dirt could not be suppressed. Moreover, five foreign substances were confirmed on the film, and the product level could not be satisfied.

  From the above results, when the film is produced by the solution casting method using the dope made from the cellulose acylate according to the present invention, the production of the stain on the surface of the support despite the long production time. It was confirmed that it was suppressed. Therefore, when the cellulose acylate is produced in the middle of the production of the cellulose acylate and the secondary cellulose acylate having a low viscosity, ie, a low viscosity, is filtered through the porous filter medium, the filtration pressure increases, Since the impurities contained in the secondary cellulose acylate can be efficiently and effectively captured and removed without causing a decrease in filtration efficiency, it was confirmed that a cellulose acylate suitable as a raw material for an optical film can be obtained. .

It is explanatory drawing of the manufacturing method of the cellulose acylate concerning this invention. It is the schematic of an example of the filtration process which concerns on this invention. It is the schematic of the film manufacturing equipment used by this embodiment. It is explanatory drawing which concerns on the measurement of the reflectivity of a casting drum.

Explanation of symbols

10 Cellulose acylate production process 22 Filtration process 23 Cellulose acylate 43 Filter medium 45 Diatomaceous earth 47 Impurity

Claims (5)

Cellulose is formed on a running support by casting a dope containing a solvent and cellulose acylate to form a cast film, and then the cast film is peeled off from the support and then dried to form a film. In the method for producing an acylate film,
The cellulose acylate is obtained by removing impurities by passing a cellulose acylate mixture produced by esterifying a cellulose and an acylating agent under an acidic catalyst through a porous filter medium. A method for producing a cellulose acylate film.   The method for producing a cellulose acylate film according to claim 1, wherein the filter medium is a plurality of filter aids.   The method for producing a cellulose acylate film according to claim 2, wherein the filter aid is diatomaceous earth.   The method for producing a cellulose acylate film according to claim 1, wherein the filter medium is a filter in which a large number of pores having an average pore diameter of 0.1 µm to 50.0 µm are formed.   The cellulose acylate mixture sent to the filter medium has a ratio of the cellulose acylate contained in the total weight of the cellulose acylate mixture of 10% by weight or less. The manufacturing method of the cellulose acylate film as described in one.

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