JP4879057B2 - Method for producing cellulose acylate film - Google Patents

Description

  The present invention relates to a method for producing a cellulose acylate film relating to optical applications such as a protective film, an optical compensation film, or a viewing angle widening film used for the purpose of protecting a polarizing plate of a liquid crystal display device.

  Cellulose acylate films (hereinafter referred to as “films”) have high transparency and are excellent in toughness and flame retardancy, and have long been used as bases for photographic photosensitive films. Recently, among cellulose acylates, a film using cellulose triacetate has attracted attention. Since the cellulose triacetate film is excellent in optical isotropy in addition to the above characteristics, it is used, for example, as a retardation film for the purpose of optical compensation of a liquid crystal display device.

  The retardation film is generally made by a solution casting method. The solution casting method is a method in which a polymer solution (dope) containing cellulose acylate, a solvent, and an additive is cast on a support that is running endlessly to form a cast film, and then the solution is cast from the support. In this method, the cast film is peeled off to form a wet film and then dried to form a film. Since the solution casting method can form a film without causing thermal damage, the completed film has high transparency and excellent optical properties.

By the way, various characteristics are calculated | required by the phase difference film according to the use, One of them has the height of the retardation value of the thickness direction. This is because the retardation value of the retardation film is low compared with the retardation plate constituting the liquid crystal display device, and there is a difference between the numerical values, but it is preferable to reduce this difference in order to realize optical compensation. Therefore, as a method of increasing the retardation value in the thickness direction, for example, Patent Document 1 proposes a method of including a retardation increasing agent. The retardation value is known to be affected by the molecular orientation of the film. Thus, for example, Patent Document 2 proposes a method for controlling the molecular orientation by suitably adjusting the relationship between the drying temperature in the drying step and the amount of residual solvent in the film to be sent here. In addition to this, Patent Document 3 proposes a method of promoting crystallization of a film by heating the film with a surface temperature within a predetermined range.
JP 2000-284124 A JP-A-7-108547 JP-A-7-112446

  However, when a retardation increasing agent is used as in Patent Document 1, the retardation increasing agent easily evaporates together with the solvent when the cast film or wet film is dried. For this reason, when a retardation increasing agent is used in a large amount, there is a concern about coloring of the film. Further, since Patent Documents 2 and 3 are methods for adjusting the molecular orientation with respect to the plane direction, the retardation value in the thickness direction cannot be adjusted. In order to control the molecular orientation in the thickness direction of the film, for example, it can be inferred that it is effective to apply a tension in the thickness direction, but it is difficult to actually perform the problem.

  Then, the objective of this invention aims at provision of the method which can manufacture the film which made the retardation value of the thickness direction high, without using a retardation raising agent excessively.

The method for producing a cellulose acylate film in the present invention includes a step of casting a dope containing cellulose acylate and a solvent on a support that runs endlessly to form a cast film, and a casting film from the support. The film is peeled off to form a wet film, and the wet film is moved while holding both side ends thereof, and is arranged in order from the upstream side in the moving direction of the pins that transport the wet film, and the temperature is adjusted and supplied. The internal temperature of the first drying area of the tenter composed of the first drying area, the second drying area, and the third drying area, the internal temperature of which is adjusted by the drying air, is set to 50 ° C. or more and 80 ° C. or less. a first drying step of drying by conveying the wet film while the width of the wet film that has been guided by the first drying area narrowed by the pin, the first The internal temperature of the drying area is increased in the range of 30 ° C. or higher 100 ° C. or less than the internal temperature of the first drying zone, the wet film while maintaining the width of the wet film by the pin in the second drying area the wet film and a second drying step of drying by conveying, the internal temperature of the third drying zone to below 140 ° C. 125 ° C. or higher, while expanding the width of the wet film by the pins in the third drying area And a third drying step for drying by transporting .

It is preferable to heat the wet film between the first drying step and the second drying step by setting the temperature rising time per second to 3 ° C. or more and 5 ° C. or less. It is preferable to send the wet film having a residual solvent amount of 20% by weight or more to the second drying region. It is preferable that the 130 lower than ° C. 115 ° C. or higher internal temperature of the second drying zone.

  The widening rate in the third drying step is preferably 0.1% or more and less than 5.0%.

The dope preferably contains a retardation increasing agent represented by the general formula of Chemical Formula 2 at a ratio of 0.1 wt% to 3.0 wt% with respect to the total amount of the dope.

  It is preferable that the surface temperature of the support is −10 ° C. or higher and 10 ° C. or lower, and the cast film is gelled by cooling to give self-supporting property and peel off.

  By this invention, the film which made the retardation value of the thickness direction high can be manufactured, without using a retardation increasing agent excessively.

  Hereinafter, the present invention will be specifically described with reference to embodiments according to the present invention. However, the forms listed here are merely examples according to the present invention, and do not limit the present invention.

  As shown in FIG. 1, the film manufacturing equipment 10 used in this embodiment includes a stock tank 11, a casting chamber 12, a tenter 13, a drying chamber 15, a cooling chamber 16, a winding chamber 17, and the like. Has been.

  The stock tank 11 includes a stirring blade 11 b that is rotated by a motor 11 a and a jacket 11 c provided on the outer peripheral surface of the stock tank 11, and stores a dope 21 that is a raw material of the film 20. The jacket 11c is supplied with a heat transfer medium whose temperature is adjusted inside the jacket 11c, and adjusts the internal temperature of the stock tank 11 within a predetermined range. The stirring blade 11b is rotated by the motor 11a and suppresses the generation of aggregates such as polymers in the dope 21. Thereby, the dope 21 stored in the stock tank 11 is adjusted so that its temperature becomes substantially constant, and uniform quality is maintained. A pump 25 and a filtration device 26 are provided downstream of the stock tank 11. The dope 21 will be described later in detail.

  The casting chamber 12 includes a casting die 30 for casting the dope 21, a casting drum 32 acting as a support, a decompression chamber 34 for decompressing the vicinity of the cast dope 21, and the casting chamber 12. A temperature control equipment 35 for adjusting the internal temperature of the steel, a stripping roller 36, a heat transfer medium circulating device 37 for supplying a heat transfer medium to the casting drum 32, a condenser (condenser) 39, and a recovery device 40. Is provided.

  The casting die 30 is formed with a discharge port for the dope 21, and the discharge port is installed in a state of opening toward the casting drum 32. The material of the casting die 30 is preferably a material having characteristics such as high corrosion resistance with respect to an electrolyte aqueous solution, a mixed solution of dichloromethane, methanol, and the like, and a low coefficient of thermal expansion. Further, the finishing accuracy of the wetted surface of the casting die 30 is preferably 1 μm or less in terms of surface roughness, and the straightness is preferably 1 μm / m or less in any direction. If such a casting die 30 is used, the casting film 33 without streaks and unevenness can be formed on the casting drum 32.

  The casting drum 32 is rotated endlessly about the axis of the cylinder by a driving device (not shown). The casting drum 32 has a cylindrical shape or a columnar shape, and the surface thereof is subjected to chrome plating in order to have sufficient corrosion resistance and strength. A flow path for the heat transfer medium is formed inside the casting drum 32. This heat transfer medium is supplied from a heat transfer medium circulation device 37 attached to the casting drum 32. By passing or circulating the heat transfer medium through the flow path, the surface temperature of the casting drum 32 is maintained at a desired temperature. In the present invention, instead of the casting drum 32, a casting band that runs around the rotating roller and runs endlessly may be used as the support.

  The decompression chamber 34 is installed on the casting roller 30 side of the casting die 30, and the back side of the dope 21 flow (casting bead) formed between the casting die 30 and the casting drum 32 is desired. Reduce the pressure to The back side of the casting bead referred to here is a surface that comes into contact with the surface of the casting drum 32 later. The stripping roller 36 supports the casting film 33 that is stripped from the casting drum 32. The condenser 39 condenses and liquefies the gas containing the solvent evaporated from the inside of the dope 21 and the casting film 33, and the recovery device 40 is for recovering the condensed and liquefied organic solvent. The recovered solvent is regenerated as a solvent for preparing a dope after being regenerated by a regenerating apparatus.

  The tenter 13 is a drying device provided with a plurality of pins for holding both side ends of the wet film 38. The wet film 38 sent to the tenter 13 is dried to be the film 20 while being conveyed through the inside. The tenter 13 will be described in detail later with reference to another drawing.

  The ear clip device 43 is provided with a cutter inside, and cuts both end portions of the film 20 at predetermined positions. A crusher 44 for connecting the cut pieces of the film into chips is connected to the ear clip device 43.

  The drying chamber 15 is provided with a large number of rollers 47 and an adsorption / recovery device 48 for the solvent evaporated during drying, where the film 20 is sufficiently dried. The cooling chamber 16 provided along with the drying chamber 15 cools the film 20 to approximately room temperature. The forced charge removal device (charge removal bar) 49 appropriately adjusts the charged voltage of the film 20. In the present embodiment, a knurling roller 50 is provided downstream of the forced static elimination device 49 to impart knurling to the film 20. Inside the winding chamber 17, a winding roller 51 for winding the film 20 and a press roller 52 for pressing the film 20 are provided.

  Next, an example of a method for manufacturing the film 20 using the film manufacturing facility 10 will be described. In the stock tank 11, a heat transfer medium is caused to flow inside the jacket 11c, and the temperature of the dope 21 is adjusted to 25 to 35 ° C. Further, the quality of the dope 21 is kept uniform by constantly rotating the stirring blade 11b. An appropriate amount of the dope 21 is appropriately sent from the stock tank 11 to the filtration device 26 by the pump 25, and impurities in the dope 21 are removed.

  The casting drum 32 is continuously rotated at a predetermined rotational speed by a driving device. Further, the heat transfer medium is supplied from the heat transfer medium circulation device 37 to the flow path inside the casting drum 32, and the surface temperature thereof is kept substantially constant within a range of −10 ° C. to 10 ° C. The temperature of the dope 21 used for casting is preferably 30 to 35 ° C. The dope 21 is cast on the casting drum 32 from the discharge port of the casting die 30. The dope 21 that has reached the surface of the casting drum 32 is quickly cooled, and a gel-like casting film 33 is formed in a short time. As the time spent on the casting drum 32 becomes longer, the cooling proceeds and the gelation of the casting film 33 is further promoted. Thus, if the surface is cooled and the casting drum 32 is used as a support, the casting film 33 having self-supporting properties can be formed in a short time, so that the film forming speed can be improved. The casting film 33 having the self-supporting property is peeled off from the casting drum 32 while being supported by the peeling roller 36 to form a wet film 38.

  The internal temperature of the casting chamber 12 is adjusted by the temperature control equipment 35 so as to be substantially constant within a range of 10 to 30 ° C. In the present embodiment, the solvent gas evaporated from the dope 21 and the casting film 33 existing in the casting chamber 12 is condensed and liquefied by the condenser 39, and then collected by the collecting device 40 and further regenerated by the reproducing device. And reused as a solvent for dope preparation.

  In the tenter 13, pins are inserted into both end portions of the wet film 38 in the vicinity of the entrance, and both end portions of the wet film 38 are held. While the wet film 38 is conveyed through the inside of the tenter 13, drying proceeds and the film 20 is formed. In the vicinity of the exit of the tenter 14, the pins are pulled out from both end portions of the film 20 to release the holding.

  A clip tenter may be provided downstream of the tenter 13 to dry the film 20. The clip tenter is a drying device provided with a plurality of clips as gripping means for gripping both side ends of the film 20. Each clip is attached to a chain that travels endlessly, and moves in the clip tenter according to the movement of the chain. In the clip tenter, after the both ends of the film 20 are gripped by a large number of clips, drying is further promoted while the inside of the film 20 is conveyed. The distance between the clips facing each other when the film 20 is conveyed is widened to apply tension in the width direction of the film 20. By particularly stretching the film 20 in the width direction and adjusting the molecular orientation, the retardation value in the plane direction can be controlled. The amount of residual solvent in the film 20 immediately before being sent to the clip tenter is preferably 50 to 150% by weight. The residual solvent amount of the present invention indicates the amount of solvent remaining in the film on a dry basis. The amount of residual solvent is calculated by {(xy) / y} × 100, where a sample is taken from the target film, the weight of this sample is x, and the weight of the sample after drying is y. .

  The film 20 is sent to the ear-cutting device 43, and both end portions thereof are cut. The film 20 having both end portions cut off is taken up by the take-up roller 51 in the take-up chamber 17 via the drying chamber 15 and the cooling chamber 16. The completed film 20 has a width direction of preferably 600 mm or more, and more preferably 1400 mm or more and 2500 mm or less. The present invention is also effective when the width of the film 20 is greater than 2500 mm. Further, the present invention can be applied to a thin film 20 having a thickness of 20 μm to 100 μm. In addition, it is preferable that the thickness of the film 20 is 20 micrometers or more and 80 micrometers or less, Especially preferably, they are 30 micrometers or more and 70 micrometers or less.

  As shown in FIG. 2, the tenter 13 includes a pin plate 61 including a plurality of pins 60. The pin 60 is for holding the wet film 38. Each pin plate 61 is attached to a chain 62 that travels endlessly, and moves in the tenter 13 as the chain 62 travels. The chain 62 is installed at both ends of the conveyance path of the wet film 38 and is in a symmetrical position with the wet film 38 in between. In the vicinity of the entrance of the tenter 13, the pins 60 are inserted into both end portions of the wet film 38, and both end portions of the wet film 38 are held.

  As shown in FIG. 3, the chain 62 is wound around a pair of rails 63 installed at both ends of the drying path of the wet film 38. The interval between the rails 63 is arbitrarily adjusted in advance, and the expansion / contraction with respect to the wet film 38 is controlled by adjusting the interval. The chain 62 is rotationally driven by a chain sprocket (not shown) and travels on the rail 63 endlessly.

  The tenter 13 of the present embodiment is composed of a first drying area A1, a second drying area A2, and a third drying area A3 in which the rail interval is appropriately adjusted. In the first drying region A1, the rail interval is gradually reduced toward the exit of the tenter 13, and when the pin plate 61 moves, the width of the wet film 38 is gradually reduced. In the second dry region A2, the interval between the rails is kept substantially constant, and the width of the wet film 38 is maintained. In the third dry region A3, the distance between the rails is gradually increased toward the exit of the tenter 13, and the width of the wet film 38 is gradually increased as the pin plate 61 moves.

  Each of the drying regions A1 to A3 is provided with a drying device (not shown) for supplying drying air, and the temperature-controlled drying air is supplied to adjust the internal temperature. Here, the internal temperature of 2nd drying area | region A2 is made higher within the range of 30 degreeC or more and 100 degrees C or less than 1st drying area | region A1. In the first drying region A1 where the temperature is suppressed, the drying of the wet film 38 is advanced without randomly orienting the molecules. Next, in the second drying region A2 set to a high temperature with a predetermined temperature difference, the drying of the wet film 38 proceeds at a stroke, so that the solvent rapidly evaporates from the wet film 38 and the shrinkage force is exerted on the wet film 38. work. Thereby, since the molecular orientation in the surface direction and the thickness direction of the wet film 38 is controlled, the completed film 20 has a high retardation value in the thickness direction. In addition, if the temperature difference between the first drying area A1 and the second drying area A2 exceeds 100 ° C., the shrinkage force acting on the wet film is too large, and there is a concern about dimensional deformation and the like. Absent. On the other hand, if the temperature difference is less than 30 ° C., it is difficult to control the molecular orientation because the contraction force cannot be exerted sufficiently.

  In order to increase the retardation value in the thickness direction, it is effective to adjust the drying temperature in each drying region. Specifically, the drying temperature of the first drying region A1 is set to 50 ° C. or more and 80 ° C. or less, the drying temperature of the second drying region A2 is set to 115 ° C. or more and less than 130 ° C., and the drying temperature of the third drying step A3 is 125 ° C. It is effective to set the temperature below 140 ° C. The set temperature of each region is not particularly limited as long as the temperature difference between the first and second drying regions is within a predetermined range, and may be appropriately selected. The drying temperature of each drying area can be easily controlled by controlling the temperature setting of the drying apparatus to be used. For example, when a heater is used as a method of supplying drying air adjusted to a predetermined temperature or a drying device, the heating temperature may be set within a predetermined range. In addition, it is preferable to install a thermometer in each drying area, always measure the temperature, and adjust the drying temperature based on this measured value.

  Further, in order to control the molecular orientation in the thickness direction of the wet film 38, the residual solvent amount of the wet film 38 is 20% by weight to 50% by weight, and the film surface temperature of the wet film 38 is 60 ° C. or higher and 80 ° C. In the following cases, it is effective to heat the wet film 38 by setting the temperature rising time per second to 3 ° C. or more and 5 ° C. or less. If it is performed between the first dry region A1 and the second dry region A2, a very excellent molecular orientation control effect is exhibited. Here, when the residual solvent amount of the wet film 38 exceeds 50% by weight, the shrinkage force becomes large, and there is a concern about the dimensional deformation of the film as described above. On the other hand, in a state where the drying proceeds so that the residual solvent amount is less than 20% by weight, it is difficult to control the molecular orientation because the shrinkage force does not work. The film surface temperature of the wet film 38 can be easily measured by installing a thermometer near the conveyance path of the wet film 38. In addition, although said temperature rising time points out the film surface temperature of the wet film 38, the film surface temperature of the wet film 38 is substantially equivalent to the preset temperature of a dry area | region. For this reason, the above conditions can be realized by controlling the temperature in the drying region.

  The residual solvent amount in the present invention indicates the amount of solvent remaining in the film on a dry basis. The measurement method is that a sample is taken from the target film, the weight of this sample is x, and the weight after drying the sample is y, which is calculated as {(xy) / y} × 100. To do.

  In order to maintain the state of the wet film 38 controlled by the first and second dry regions A1 and A2, in the third dry region A3, the widening rate of the wet film 38 is 0.1% or more and less than 5.0%. It is preferable that This widening ratio is represented by {(W4−W3) / W3} × 100 by the width W1 of the wet film 38 at the entrance of the third dry region A3 and the width W4 sent out from the third dry region A3. In addition, the ratio which narrows the width | variety of the wet film 38 in 1st dry area | region A1 is not specifically limited.

  In the present invention, a film having an increased retardation value in the thickness direction can be obtained without excessive use of a retardation increasing agent. For this reason, the elastic modulus of the film 20 does not decrease. Moreover, when forming a gel-like casting film like this embodiment, since gelation can be advanced efficiently, the film-forming speed can be expected to be increased.

Since the film 20 obtained by the present invention has a high retardation value Rth in the thickness direction, it can be suitably used as a retardation film. The film 20 has a retardation value Re in the plane direction of 5 nm to 50 nm and a retardation value Rth in the thickness direction of 70 nm to 300 nm. Re and Rth are given by the following formula, where d is the thickness of the film 20, nx is the refractive index in the transport direction, ny is the refractive index in the width direction, and nz is the refractive index in the thickness direction. It is represented by Note that the degree of molecular orientation in the film 20 is obtained by taking a part of the film 20 as a sample and applying it to an analyzer such as Raman spectroscopic analysis or infrared spectroscopic analysis to determine the degree of binding between the molecules. Can be measured as
Formula (1): Re = (nx−ny) × d
Formula (2): Rth = [{(nx + ny) / 2} −nz] × d

  The dope according to the present invention will be described below.

In the present invention, cellulose acylate is suitable as a polymer as a raw material for the film. As the cellulose acylate, cellulose triacetate (TAC) is particularly preferable because a film with higher transparency can be obtained. Further, among cellulose acylates, those in which the substitution degree of the acyl group to the hydroxyl group of cellulose satisfies all of the following formulas (I) to (III) are more preferable. In the following formulas (I) to (III), A and B represent the substitution degree of the acyl group with respect to the hydrogen atom in the hydroxyl group of cellulose, A represents the substitution degree of the acetyl group, and B represents 3 to 3 carbon atoms. 22 is the substitution degree of the acyl group. Here, it is preferable that 90% by mass or more of TAC is particles of 0.1 to 4 mm. However, the polymer that can be used in the present invention is not limited to cellulose acylate.
(I) 2.5 ≦ A + B ≦ 3.0
(II) 0 ≦ A ≦ 3.0
(III) 0 ≦ B ≦ 2.9

  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with an acyl group having 2 or more carbon atoms. The degree of acyl substitution means the ratio at which the hydroxyl group of cellulose is esterified at each of the 2-position, 3-position and 6-position (the substitution degree is 1 in the case of 100% esterification).

  The total degree of acylation substitution, that is, the value of DS2 + DS3 + DS6 is preferably 2.00 to 3.00, more preferably 2.22 to 2.90, and particularly preferably 2.40 to 2.88. Further, the value of DS6 / (DS2 + DS3 + DS6) is preferably 0.28 or more, more preferably 0.30 or more, and particularly preferably 0.31 to 0.34. Here, DS2 is the ratio of the hydrogen of the hydroxyl group at the 2-position in the glucose unit (hereinafter referred to as the acyl substitution degree at the 2-position), and DS3 is the hydroxyl group at the 3-position in the glucose unit. This is the rate at which hydrogen is substituted by an acyl group (hereinafter referred to as the 3-position acyl substitution degree), and DS6 is the rate at which the hydrogen at the 6-position hydroxyl group is substituted by an acyl group in a glucose unit (hereinafter, (Referred to as the degree of acyl substitution at the 6-position).

  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, 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 By using, a solution (dope) having better solubility can be produced. In particular, when a non-chlorine organic solvent is used, a dope having excellent solubility, low viscosity and excellent filterability can be produced.

  Cellulose, which is a raw material for cellulose acylate, may be obtained from either linter cotton or pulp cotton, but is preferably obtained from linter cotton.

  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.

  Solvents for preparing the dope include aromatic hydrocarbons (eg, benzene, toluene, etc.), halogenated hydrocarbons (eg, dichloromethane, chlorobenzene, etc.), alcohols (eg, methanol, ethanol, n-propanol, n-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.). In the present invention, the dope means a polymer solution or dispersion obtained by dissolving or dispersing a polymer in a solvent.

  Among the above halogenated hydrocarbons, halogenated hydrocarbons having 1 to 7 carbon atoms are preferable, and dichloromethane is most preferable. From the viewpoint of physical properties such as solubility of TAC, peelability of cast film from the support, mechanical strength of the film, and optical properties, one or several kinds of alcohols having 1 to 5 carbon atoms in addition to dichloromethane It is preferable to mix. As for content of alcohol, 2-25 mass% is preferable with respect to the whole solvent, More preferably, it is 5-20 mass%. Examples of the alcohol include methanol, ethanol, n-propanol, isopropanol, n-butanol, etc., but methanol, ethanol, n-butanol, or a mixture thereof is preferably used.

  Recently, a solvent composition not using dichloromethane has been studied for the purpose of minimizing the influence on the environment. In this case, an ether having 4 to 12 carbon atoms, a ketone having 3 to 12 carbon atoms, an ester having 3 to 12 carbon atoms, and an alcohol having 1 to 12 carbon atoms are preferable. Sometimes used. For example, a mixed solvent of methyl acetate, acetone, ethanol, and n-butanol can be mentioned. These ethers, ketones, esters, and alcohols may have a cyclic structure. A compound having two or more functional groups of ether, ketone, ester, and alcohol (that is, —O—, —CO—, —COO—, and —OH) can also be used as the solvent.

  The dope may contain a retardation increasing agent. As the retardation increasing agent, those represented by the general formula of Chemical Formula 3 are preferably used. This retardation increasing agent is preferably included at a ratio of 0.1 wt% or more and 3.0 wt% or less with respect to the total amount of the dope. Thus, even if the addition amount of the retardation value is suppressed, in the present invention, the retardation value can be increased by suitably controlling the molecular orientation in the thickness direction. If the ratio of adding the retardation increasing agent exceeds 3.0% by weight, it is difficult to stably cast the dope because the viscosity of the dope decreases and the liquid runs out during the casting.

  In addition, various additives such as plasticizers, deterioration inhibitors, ultraviolet absorbers (UV agents), optical anisotropy control agents, dyes, matting agents, release agents, release accelerators are added to the dope. May be. Each additive may be used alone or in combination of two or more, and may be appropriately selected according to the desired application.

  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. The same applies to additives such as solvents, plasticizers, deterioration inhibitors, UV absorbers (UV agents), optical anisotropy control agents, retardation control agents, dyes, matting agents, release agents, release accelerators, and the like. It is described in detail in paragraphs [0196] to [0516] of Kai 2005-104148, and these descriptions can also be applied to the present invention.

  In the solution casting method of the present invention, when casting a dope, two or more types of dopes are simultaneously co-cast and laminated, or a plurality of dopes are sequentially co-cast. Sequential lamination co-casting can be performed. In addition, you may combine both casting. When performing simultaneous lamination and co-casting, a casting die to which a feed block is attached may be used, or a multi-manifold casting die may be used. However, it is preferable that at least one of the thickness of the layer on the air surface side and the thickness of the layer on the support side is 0.5 to 30% of the thickness of the entire film of the film composed of multiple layers by co-casting. . In addition, when performing simultaneous lamination and co-casting, it is preferable that the high-viscosity dope is enveloped by the low-viscosity dope when the dope is cast from the die slit to the support, and is formed from the die slit to the support. Of the casting beads, the dope in contact with the outside world preferably has a higher alcohol composition ratio than the inner dope.

  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 Until now, 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.

  Examples of the present invention will be described below to explain the effects of the present invention. In addition, the Example and comparative example shown here are examples which concern on this invention, and do not limit this invention.

[Film production]
In the film production facility 10, the surface is subjected to chrome plating and mirror finishing, and the casting film 33 is formed by casting the dope 21 with a dry thickness of 80 μm on the surface of the cylindrical casting drum 32 having a diameter of 1000 mm. did. While the casting film 33 having self-supporting property was supported by the peeling roller 36, the wet film 38 was peeled off.

  In the tenter 13, the pins 60 were inserted and held at both end portions of the wet film 38 near the entrance, and the wet film 38 having a residual solvent amount of 46% by weight was sent to the first drying region and dried. Subsequently, the wet film 38 having a residual solvent amount of 25% by weight was sent to the second drying region and dried to obtain a film 20. In Example 1, the drying temperature T1 of the first drying region A1 was 75 ° C., and the drying temperature T2 of the second drying region A2 was 120 ° C. Therefore, Δ (T2−T1), which is a difference in drying temperature between the first drying region and the second drying region, is 45 ° C. Further, the wet film 38 was dried while being stretched by 1% in the width direction in an atmosphere in which the drying temperature T3 of the third drying region A3 was 130 ° C.

  After cutting both side ends of the film 20 with the edge-cutting device 43 installed downstream of the tenter 13, the film 20 was sufficiently accelerated to be dried while being wound around the plurality of rollers 47 in the drying chamber 15. After the film 20 was cooled to approximately room temperature in the cooling chamber 16, the charged voltage was adjusted by the forced static eliminator 49. Then, the film 20 imparted with knurling by the knurling roller 50 was sent to the winding chamber 17 and wound around the winding roller 51 while applying a pressing force by the press roller 52 to obtain a roll-shaped film 20.

[Dope]
The dope raw materials used in Example 1 are as follows.
Cellulose triacetate 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 part by weight UV agent b 0.3 part by weight Part by weight 0.05 part by weight Retardation increasing agent 2 parts by weight

  The cellulose triacetate 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 0.8. 5 mm powder, plasticizer A is triphenyl phosphate, plasticizer B is diphenyl phosphate, and 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, and the citrate ester compound is It is a mixture of acid, monoethyl ester, diethyl ester and triethyl ester, and the fine particles have a mean particle size of 15 nm and a Mohs hardness of about 7 It is silicon. And it added as a retardation raising agent so that it might become 1.7 weight% with respect to the total weight when the compound shown to Chemical formula 3 was used as a film.

  When the retardation value Rthm in the thickness direction of the completed film 20 and the retardation value Re in the plane direction are obtained, the case where the film satisfies the product level is ○, while the case where the values of Rth and Re do not satisfy the product level × As described above, the effect of the present invention was evaluated. As a result, in Example 1, Rth = 90 nm and Re = 7 nm, and a film suitable as a retardation film was obtained (◯). Of the above retardation values, Rth and Re were determined by KOBRA 21ADH (manufactured by Oji Scientific Instruments).

  In Example 2, in the tenter 13, the residual solvent amounts of the wet film 38 sent to the first drying region and the second drying region are 48% by weight and 30% by weight, respectively, and the drying temperature T1 of the first drying region A1 is 70%. A film was produced in the same manner as in Example 1 except that the drying temperature T2 of the second drying region A2 was 122 ° C. Δ (T2−T1) is 52 ° C. As a result, Rth and Re both showed high values, and a film satisfying the product level was obtained (◯).

  In Example 3, in the tenter 13, the residual solvent amounts of the wet film 38 sent to the first drying region and the second drying region are 48% by weight and 25% by weight, respectively, and the drying temperature T1 of the first drying region A1 is 75. A film was produced in the same manner as in Example 1 except that the drying temperature T2 in the second drying region A2 was 105 ° C. Δ (T2−T1) is 30 ° C. As a result, Rth and Re both showed high values, and a film satisfying the product level was obtained (◯).

  In Example 4, in the tenter 13, the residual solvent amounts of the wet film 38 sent to the first drying region and the second drying region are 46% by weight and 25% by weight, respectively, and the drying temperature T1 of the first drying region A1 is 75. A film was produced in the same manner as in Example 1 except that the drying temperature T2 of the second drying region A2 was 135 ° C. Δ (T2−T1) is 60 ° C. As a result, Rth and Re both showed high values, and a film satisfying the product level was obtained (◯).

[Comparative Example 1]
In Comparative Example 1, in the tenter 13, the residual solvent amounts of the wet film 38 sent to the first drying region and the second drying region are 46% by weight and 25% by weight, respectively, and the drying temperature T1 of the first drying region A1 is 75. A film was produced in the same manner as in Example 1 except that the drying temperature T2 of the second drying region A2 was 100 ° C. Δ (T2−T1) is 25 ° C. As a result, Re was only slightly reduced, but Rth was significantly reduced, and the finished film could not satisfy the product level (×).

[Comparative Example 2]
In Comparative Example 2, in the tenter 13, the residual solvent amounts of the wet film 38 sent to the first drying region and the second drying region are 46% by weight and 25% by weight, respectively, and the drying temperature T1 of the first drying region A1 is 75. A film was produced in the same manner as in Example 1 except that the drying temperature T2 in the second drying region A2 was 90 ° C. Δ (T2−T1) is 15 ° C. As a result, Re was only slightly reduced, but Rth was significantly reduced, and the finished film could not satisfy the product level (×).

It is explanatory drawing which shows the outline | summary of a film manufacturing equipment. It is the enlarged view which notched a part of wet film holding | maintenance part by a tenter. It is the schematic of the tenter used in this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Film manufacturing equipment 13 Tenter 20 Film 21 Dope 32 Casting drum 33 Casting film 36 Peeling roller

Claims (7)

A step of casting a dope containing cellulose acylate and a solvent on a support that runs endlessly to form a cast film; and
From the support as a peel Engineering shall be the stripping wet film the casting film,
The internal temperature is adjusted by the drying air that is arranged in order from the upstream side in the moving direction of the pins that convey the wet film by moving while holding both side ends of the wet film, and the temperature is adjusted and supplied. The internal temperature of the first drying area of the tenter composed of one drying area, the second drying area, and the third drying area is set to 50 ° C. or more and 80 ° C. or less, and the width of the wet film guided from the peeling step is set. A first drying step of drying by conveying the wet film while being narrowed by the pin in the first drying region ;
The internal temperature of the second drying region is set higher than the internal temperature of the first drying region by 30 ° C. or more and 100 ° C. or less, and the width of the wet film is maintained by the pins in the second drying region. A second drying step of drying by conveying the wet film ;
A third drying step in which the internal temperature of the third drying region is 125 ° C. or higher and lower than 140 ° C., and the wet film is dried by conveying the wet film while the width of the wet film is widened by the pins in the third drying region ; A method for producing a cellulose acylate film, comprising: 2. The cellulose acylate film according to claim 1, wherein the wet film is heated at a temperature rising time per second of 3 ° C. to 5 ° C. between the first drying step and the second drying step. Production method. 3. The method for producing a cellulose acylate film according to claim 1, wherein the wet film having a residual solvent amount of 20% by weight or more is sent to the second drying region. The method for producing a cellulose acylate film according to any one of claims 1 to 3, wherein an internal temperature of the second drying region is 115 ° C or higher and lower than 130 ° C. The method for producing a cellulose acylate film according to any one of claims 1 to 4, wherein the widening ratio in the third drying step is 0.1% or more and less than 5.0%. The dope is claims 1, characterized in that it comprises a retardation increasing agent represented by the chemical formula 1 in a proportion of less than 3.0 wt% 0.1 wt% or more based on the total amount of said doped 5 The manufacturing method of the cellulose acylate film as described in any one.

The surface temperature of the support is not more 10 ° C. or less -10 ° C. or more, any one claims 1 to 6, characterized in that stripping made to have a self-supporting and gelled by cooling the casting film The manufacturing method of the cellulose acylate film of description.

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