JP5038914B2 - Solution casting method - Google Patents

Description

  The present invention relates to a solution casting method for producing a film from a dope in which a polymer is dissolved in a solvent.

  In the solution casting method, a dope made by dissolving a polymer in a solvent is cast on a casting support to form a casting film, and the casting film is peeled off from the casting support and dried. Make a polymer film. The cast film, that is, the wet film peeled off from the cast support is dried while being conveyed. A driving roller and a non-driving so-called free roller that supports the wet film are arranged in the transport path of the wet film, and the wet film is transported by the drive roller and other transport means.

  Various optical devices such as a liquid crystal display using a polymer film are being made thinner and more multifunctional, and it is desired to make the polymer film thinner and smoother than ever. For this reason, the driving roller and the free roller slip with respect to the wet film being conveyed, and the wet film may be scratched or wrinkled. In particular, the wet film from peeling off from the support to entering the tenter often has a very high value such that the solvent content exceeds 100%, and there is a problem that it is particularly easy to slip. In addition, there is a problem in that a so-called surface projection that leaves a roller mark on the wet film may occur, resulting in a deterioration in product yield.

Various proposals have been made so far in order to carry out the conveyance stably and to prevent the generation of scratches. For example, a method of transporting a wet film in a non-contact manner immediately after a peeling roller when peeling a cast film from a support to a position port of a tenter has been proposed (for example, see Patent Document 1). In this method, a roller or the like is used as a conveying means that is not in contact with the surface exposed at the time of casting. Moreover, the solvent content rate at the time of peeling from a support body is set to 20 to 150%, and the Vickers hardness of the peeling roller and the transfer roller disposed in the transport path to the drying device is set to 500 to 800. (For example, patent document 2) is proposed. Furthermore, the solvent content of the wet film when contacting the transfer roller is 12 to 80%, and the pressure received from these rollers when the wet film comes into contact with the peeling roller or the transfer roller is 500 to 3000 Pa. There has been proposed a method (for example, see Patent Document 3) in which the contact time per wire is 0.01 to 0.72 seconds.
JP 2001-277267 A JP 2002-292658 A JP 2006-256184 A

  However, in the method described in Patent Document 1, there remains a problem that the higher the solvent content of the film to be conveyed, the more likely the film is wrinkled. In the method described in Patent Document 2, the holding force of the transfer roller is insufficient. The problem remains that the film slips on the transfer roller and the film is scratched. Further, in the method described in Patent Document 3, the contact time between the film and the transfer roller is too short and the holding force is not sufficient, so that the film extends in the transport direction and is long in the long direction (transport direction). There is a problem that extended wrinkles, so-called vertical wrinkles, occur.

  In order to apply tension in the width direction with the tenter, it is necessary to evaporate a large amount of solvent before the tenter is introduced. Therefore, a large amount of solvent is evaporated from the peeling position where the cast film is peeled off from the band to the tenter, but the additive is often vaporized as the solvent is evaporated in large amounts. When the vaporized additive adheres to the peripheral surface of the drive roller or free roller and solidifies, there is a problem that the slip phenomenon of the wet film is further promoted.

  In the above Patent Documents 1 and 2, the wet film is guided by the roller, although there is a certain effect that prevents the additive from adhering to the roll or does not adversely affect the transportability and the flatness of the wet film. The problem of scratches and wrinkles occurring on the surface has not been solved.

  The present invention has been made in view of the above problems, and prevents the slipping of the wet film from peeling to entering the tenter even if the additive adheres to the roller. It is an object of the present invention to provide a solution casting method for producing a polymer film having a thickness of 20 to 80 μm by preventing generated scratches, wrinkles and surface exposure.

In order to achieve the above object, the present invention provides a casting process in which a dope containing a polymer and a solvent is cast on a traveling band to form a casting film, and the casting film is formed by the solvent. Tenter drying to form a polymer film by drying the wet film while stretching it in the width direction by a tenter comprising a peeling step to remove the wet film into a wet film, and a drying means and a holding means for holding both sides of the wet film. And a pre-drying step of drying the wet film before entering the tenter, casting the dope so that the polymer film has a thickness of 20 to 80 μm, and the pre-drying step Then, the crests and troughs along the circumferential direction are alternately arranged in the axial direction, the crests and the troughs have a substantially semicircular cross section, and the pitch between the troughs and the crests is 0. .01mm or less 2 mm or less, a roller having a height from the bottom of the valley to the top of the peak of 0.01 mm to 1 mm, and supporting the wet film until the solvent content reaches 30%. It is configured as.

  It is preferable that the curvature radius of a trough part and the said peak part is 0.1 mm or more and 0.5 mm or less, and it is preferable to form the flat surface parallel to an axial direction in the vertex part of a peak part. The width of the flat surface in the axial direction is more preferably 0.05 mm or more and 0.5 mm or less.

  In the pre-drying step, the wet film having a solvent content in the range of 70 to 150% is preferably dried in a temperature range of 10 ° C. or more and less than 100 ° C. until the solvent content is in the range of 10 to 30%. In the pre-drying step, it is preferable to apply a tension of 10 N to 300 N per 1 m width in the transport direction of the wet film.

  According to the present invention, it is possible to provide a solution casting method for producing a polymer film having a thickness of 20 to 80 μm while preventing scratches, wrinkles, and surface exposure caused by conveyance by a roller.

[material]
As a dope raw material, a known polymer and solvent capable of producing a film by solution casting can be used. Among the polymers, cellulose acylate and cyclic polyolefin can be preferably used. Since any of these polymers is basically the same in the construction of the production equipment and the flow of the production method, the case where a cellulose acylate film is used as a polymer component will be described below as an example.

Among the cellulose acylates, the ratio of esterifying the hydroxyl group of cellulose with carboxylic acid, 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 and B are both acyl group substitution degrees, the acyl group in A is an acetyl group, and the acyl group in B has 3 to 22 carbon atoms. Among these, cellulose triacetate whose acyl group is an acetyl group is particularly preferable.
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 of the hydroxyl groups is substituted with acyl groups having 2 or more carbon atoms. Since the degree of substitution is 1 when esterification of one hydroxyl group in the glucose unit is 100%, in the case of cellulose acylate, the hydroxyl groups at the 2nd, 3rd and 6th positions are each 100% ester. The degree of substitution is 3.

  Here, the substitution degree of the acyl group at the 2-position of the glucose unit is DS2, the substitution degree of the acyl group at the 3-position is DS3, and the substitution degree of the acyl group at the 6-position is DS6. The total acyl group substitution degree 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. . Further, DS6 / (DS2 + DS3 + DS6) is preferably 0.28 or more, more preferably 0.30 or more, and further preferably 0.31 to 0.34.

  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 2.22 to 2.90, particularly preferably 2.40 to 2.88. DSB is preferably 0.30 or more, and particularly preferably 0.70 or more. Further, 20% or more of the DSB is preferably a substituent at the 6-position hydroxyl group, more preferably at least 25%, even more preferably 30% or more, and particularly preferably 33% 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.

  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 (eg, benzene, toluene, etc.), halogenated hydrocarbons (eg, dichloromethane, chloroform, chlorobenzene, etc.), alcohols (eg, methanol, ethanol, n-propanol, Examples thereof include 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.). Here, the dope is a polymer solution obtained by dissolving a polymer in a solvent.

  As the solvent, among the above compounds, a halogenated hydrocarbon having 1 to 7 carbon atoms is preferable, and dichloromethane is most preferable. And from the viewpoint of properties such as solubility of cellulose acylate, peelability from a cast film support, mechanical strength of the film, and optical properties of the film, one or several kinds of alcohols having 1 to 5 carbon atoms are used. Is preferably 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.

  Depending on the purpose, the dope may be added with various known additives such as a plasticizer, an ultraviolet absorber (UV agent), a deterioration preventing agent, a slipping agent, and a peeling accelerator. For example, as the plasticizer, phosphate plasticizers such as triphenyl phosphate and biphenyldiphenyl phosphate, phthalate plasticizers such as diethyl phthalate, and various known plasticizers such as polyester polyurethane elastomers are used. be able to.

  The same applies to additives such as solvents and plasticizers, deterioration inhibitors, ultraviolet absorbers, optical anisotropy control agents, dyes, matting agents, release agents, etc., paragraph [0196] of JP-A-2005-104148. To [0516] paragraphs, and these descriptions can also be applied to the present invention.

  The dope whose cellulose acylate density | concentration is 5 to 40 weight% is manufactured using the above raw material. The cellulose acylate concentration is more preferably in the range of 15% by weight to 30% by weight, and further preferably in the range of 17% by weight to 25% by weight. The concentration of the additive is preferably in the range of 1% by weight to 20% by weight with respect to the entire solid content.

  Regarding the production of the dope, the raw material dissolution method, filtration method, defoaming, and addition method are described in detail in paragraphs [0517] to [0616] of JP-A-2005-104148. The contents of can also be applied to the present invention.

[Film production method]
FIG. 1 is a schematic view showing a solution casting apparatus 10. However, the present invention is not limited to the solution casting apparatus 10. In the solution casting apparatus 10, a dope 11 in which cellulose acylate is dissolved in a solvent is cast to form a wet film 12 which is a cellulose acylate film containing the solvent, and the wet film 12 is conveyed. A first drying chamber 16 that dries while drying, a tenter 17 that holds both side ends of the wet film 12 exiting the first drying chamber 16 and dries while transporting the wet film 12, and both end portions of the wet film 12 A second drying chamber 21 which is a cellulose acylate film (hereinafter simply referred to as a film) 19 which is dried while transporting the wet film 12 and contains almost no solvent, and the film 19 is cooled. A cooling chamber 22 for reducing the amount of charge of the film 19 and a pair of knurling rollers for embossing the side ends. 6, is provided with a winding portion 27 for winding the film 19.

  The casting chamber 13 includes a casting die 31 that flows out of the dope 11 and a band 32 as a casting support. The casting die 31 is preferably a coat hanger type die. A temperature controller (not shown) for controlling the temperature of the casting die 31 is attached to the casting die 31 so that the temperature of the dope 11 is maintained at a predetermined temperature.

  The width of the casting die 31 is not particularly limited. In the present embodiment, the width is about 1.1 to 2.0 times the width of the film 19 that is the final product. Further, the casting die 31 is provided with a plurality of thickness adjusting bolts (heat bolts) for adjusting the gaps of the slits of the casting die 31 at predetermined intervals in the width direction in order to adjust the thickness of the beads when flowing out. It is preferred that The thickness of the film 19 after drying is adjusted to 20 to 80 μm by adjusting the size of the gap of the slit of the casting die 31 and the outflow amount of the dope.

  The band 32 is wound around a backup roller 33 that rotates in the circumferential direction, and continuously travels as the backup roller 33 rotates. The backup roller 33 is provided with drive means (not shown), and is rotated by this drive means. The width of the band 32 is not particularly limited, and in the present embodiment, it is in the range of 1.1 to 2.0 times the casting width of the dope 11. The band 32 has an average peripheral surface roughness of 0.01 μm or less, and is subjected to chrome plating or the like.

  The backup roller 33 has a flow path (not shown) through which the heat transfer medium passes. A heat transfer medium circulation device (not shown) is connected to the backup roller 33. The heat transfer medium circulation device controls the temperature of the heat transfer medium and circulates the heat transfer medium in the flow path. Supply. Thus, the peripheral surface temperature of the backup roller 33 is controlled so that the temperature of the band 32 in contact with the backup roller 33 becomes a predetermined value. The temperature of the band 32 is appropriately set according to the type of solvent, the type of solid component, the concentration of the dope 11 and the like.

  A casting bead is formed from the casting die 31 to the band 32, and a casting film 38 is formed on the band 32. A decompression chamber 36 is provided on the upstream side of the casting bead. The decompression chamber 36 sucks air upstream of the casting bead, thereby decompressing the upstream area with respect to the casting beat, and stabilizes the state of the casting bead.

  The pressure in the upstream area with respect to the bead is preferably 2000 Pa to 10 Pa lower than the downstream area. In order to keep the casting bead in a desired shape, it is preferable to attach a suction device (not shown) to the edge portion of the casting die 31 to suck both sides of the bead. This suction air volume is 1 L / min. ~ 100 L / min. It is preferable that it is the range of these.

  The casting chamber 13 has a temperature control device 37 for keeping the internal temperature at a predetermined value, and a condenser (not shown) for condensing and recovering the solvent evaporated from the dope 11 and the casting film 38. Are provided. A recovery device (not shown) for recovering the condensed and liquefied solvent is provided outside the casting chamber 13. The solvent recovered by the recovery device is regenerated and reused as a solvent for dope production.

  The casting chamber 13 includes a gas delivery unit (not shown) for sending out an inert gas and an exhaust duct (not shown) for discharging the air inside the casting chamber 13 to the outside. It is done. By replacing the internal air with an inert gas, the solvent gas concentration in the casting chamber 13 is set to 20% or less, more preferably 1 to 20%.

  The casting chamber 13 is provided with a peeling roller 45 that supports the wet film 12 in order to peel the casting film 38 from the band 32. The cast film 38 is dried until it becomes self-supporting, and then peeled off from the band 32. Having self-supporting means that the wet film is dried to the extent that it can be supported and conveyed in the first drying chamber 16.

  The cast film 38 can be supported and transported as the wet film 12 when the solvent content (hereinafter referred to as the solvent content) reaches 70%. In some cases, conveyance is possible. In this case, the wet film 12 may be introduced into the first drying chamber 16 even with a solvent content greater than 70%. The cast film 38 is more preferably peeled off after the solvent content is gradually reduced to 150% or less and before it becomes less than 70%, that is, in the range of 70% to 150%. . As a result, the casting film 38 is not peeled off on the band 32, and the first drying chamber 16 can be transported more satisfactorily without causing scratches or wrinkles on the wet film 12.

  The above-mentioned solvent content is a value based on the dry weight. Specifically, when the weight of the sampled sample is x and the weight after completely drying the sample is y, 100 × {(xy) / y} is a calculated value.

  Instead of the band 32 and the backup roller 33, a drum that rotates in the circumferential direction can be used as a casting support. In this case, the casting film 38 is cooled to be gelled to have self-supporting property. By performing drying together with cooling, the timing of peeling off the casting film 38 can be made earlier than when the band 32 and the backup roller 33 are used. Moreover, when using a drum, the casting film can be cooled and dried so that the timing of stripping can be further advanced and the production efficiency can be further improved. When the drum is used as a casting support, the stripping timing is preferably when the solvent content of the casting membrane is in the range of 100 to 250%.

  The first drying chamber 16 is provided with a blower duct 46 for blowing dry air and a guide roller 48 for guiding the wet film 12 to the tenter 17. Details of the guide roller 48 will be described later with reference to another drawing. In the first drying chamber 16, the wet film 12 is dried to such an extent that the tenter 17 can be gripped as described later. The extent to which gripping is possible is usually that the solvent content of the wet film 12 is 30% or less. As shown in FIG. 1, the casting chamber 13 and the first drying chamber 16 are continuously provided in the transport direction, and the casting film 38 is introduced into the first drying chamber 16 as the wet film 12 as soon as it is peeled off. And dried. In this case, the solvent content at the time of stripping and the solvent content at the introduction of the first drying chamber 16 can be regarded as the same value.

  In the first drying chamber 16, it is more preferable to dry the wet film 12 until the solvent content is in the range of 10 to 30%. Since the casting film 38 is preferably peeled off when the solvent content is in the range of 70% to 150% as described above, the wet film 12 is the first while the solvent content decreases from 70% to 30%. Drying in the drying chamber 16 is preferable. And the timing of the stripping from the band 32 is 150% or less and an A value in a range higher than 70%, and a B value in a range of 10% or more and less than 30% in the first drying chamber 16. In some cases, the first drying chamber 16 dries while the A value reaches the B value. In the case where the additive is contained in the wet film, in the first drying chamber 16 where the solvent content of the wet film 12 changes greatly in this way, the additive is vaporized together with the solvent and adheres to the guide roller 48. Although often solidified, by supporting or transporting the wet film 12 with a guide roller 48 described later, it can be transported satisfactorily without slipping, and scratches and wrinkles caused by the slip can be prevented. Then, the surface film is prevented and the wet film 12 does not become uneven due to the additive adhered to the surface of the guide roller 48 and solidified.

  In the first drying chamber 16, even if the solvent content is reduced to 20%, the drying may be further advanced, and it is more preferable that the drying is advanced to a range of 10 to 30%. Even when the solvent content is less than 30%, the effect of preventing the generation of scratches and wrinkles is further enhanced by supporting or transporting the wet film 12 by a guide roller 48 described later.

  The air may be blown from the air duct 46 so as to blow directly onto the wet film 12, or instead of blowing directly onto the wet film 12, the first drying is performed so that the solvent gas concentration around the wet film 12 is not saturated. Air may be vented to circulate the interior of the chamber 16.

  The temperature of the wet film 12 is adjusted mainly by the air from the air duct 46. A preferable temperature range of the wet film 12 in the first drying chamber 16 is 10 ° C. or more and less than 100 ° C., more preferably 50 ° C. or more and less than 100 ° C. When the temperature is lower than 10 ° C., the drying efficiency is poor, and it is necessary to increase the length of the conveyance path of the first drying chamber 16 as compared with the case of 10 ° C. or higher. Moreover, if it is 100 degreeC or more, the wet film 12 may deform | transform. In order to set the temperature of the wet film 12 in the range of 10 ° C. or more and less than 100 ° C., the temperature of the dry air from the air duct 46 is preferably in the range of 20 ° C. to 120 ° C.

  Since the wet film 12 contains a solvent, when the temperature changes, the frictional force with the contacting film tends to change. However, by using a guide roller 48 described later, even if the wet film 12 is set in a wide temperature range of 10 ° C. to less than 100 ° C., it can be transported satisfactorily without slipping, Wrinkles do not occur. Therefore, even if this is set so that the temperature of the wet film 12 changes from the upstream side to the downstream side of the conveyance path of the first drying chamber 16, there is an effect that the conveyance can be performed satisfactorily.

  The first drying chamber 16 is provided with a gas delivery unit (not shown) that sends out an inert gas. By replacing the internal air with an inert gas, the solvent gas concentration in the first drying chamber 16 is set to 20% or less, more preferably 1 to 20%.

  It is preferable that a draw tension is applied to the wet film 12 conveyed in the first drying chamber 16. The draw tension is a tension in the transport direction of the wet film 12. Thereby, sagging of the wet film 12 can be prevented. The free roller that supports the wet film 12 to which the draw tension is applied and guides it to the downstream side is preferably a guide roller 48 described later. Thereby, it is possible to prevent the wet film 12 from being scratched or wrinkled, and this effect is particularly great when the draw tension of the wet film 12 is 10 to 300 N / m. The value of the draw tension means a force applied per 1 m in the width direction of the wet film 12. Therefore, when the width of the wet film 12 is n (0 <n, unit; m), the range in which the effect of the guide roller 48 is particularly large is n × 10 (N) to n × 300 (N). .

  When a driving roller is disposed in the conveyance path of the first drying chamber 16, the draw tension of the wet film 12 traveling upstream from the driving roller can be adjusted by adjusting the rotational speed of the driving roller. it can. If a guide roller 48 to be described later is used as the drive roller, it can be conveyed more satisfactorily without slipping or wrinkling, and without causing slippage or wrinkles. The draw tension per meter in the width direction of the wet film 12 is preferably in the range of 10 to 300 N. In the case of such a draw tension, the guide roller compared to a conventional suction roller, for example. 48 has a particularly high effect. If the tension of the wet film 12 is less than 10 N / m, a so-called conveyance failure may occur in which the wet film 12 is slack and cannot be transported. If the tension is greater than 300 N / m, the wet film 12 extends in the transport direction and becomes longitudinal. Wrinkles may occur.

  A plurality of guide rollers 48 may be provided in the first drying chamber 16. Note that all of the plurality of rollers provided in the conveyance path of the first drying chamber 16 may be the guide rollers 48, or only some of them may be the guide rollers 48. Of the plurality of rollers, the driving roller is more preferably the guide roller 48, but a free-rotating roller is more preferably the guide roller 48.

  Both ends of the wet film 12 sent to the tenter 17 are held by holding means (not shown), and are conveyed by movement of the holding means. And it dries during this conveyance. Examples of the holding means include a clip that holds the side portion of the wet film 12 and a plurality of pins that pierce and hold the side portion. When the band 32 is used as a casting support and the casting film 38 is peeled off after part of the solvent is evaporated, the holding means in the tenter 17 is preferably a clip, while the drum is used as the casting support. When the cast film that has been used and peeled off with little evaporation of the solvent is peeled off, a pin is preferable as the holding means in the tenter 17. In the tenter 17, the wet film 12 is dried at a temperature of 120 ° C. or higher and 180 ° C. or lower.

  After the wet film 12 is dried by the tenter 17, both end portions thereof are cut and removed by the ear clip device 18. The separated both end portions are sent to the crusher 51 by a cutter blower (not shown). By the crusher 51, the side end portion is crushed into chips. This chip is reused for dope production.

  On the other hand, the wet film 12 from which both end portions have been cut off is sent to the second drying chamber 21 and further dried while being conveyed. Although the internal temperature of the 2nd drying chamber 21 is not specifically limited, It is preferable to set it as 60-140 degreeC. As with the first drying chamber 16, it is more preferable that a guide roller 48 is provided in the conveyance path of the second drying chamber 21. Thereby, even if the temperature of the wet film 12 is a high temperature of, for example, 100 ° C. or higher, the wet film 12 can be stably conveyed without slipping, and it is possible to prevent the wet film 12 from being scratched, wrinkled, or the like. it can. Further, the guide roller 48 does not press the foreign matter against the wet film 12, and the wet film 12 is not uneven. When the guide roller 48 is used, there is an effect that there is no surface projection.

  Note that all of the plurality of rollers provided in the conveyance path of the second drying chamber 21 may be the guide rollers 48, or only some of them may be the guide rollers 48. Of the plurality of rollers, the driving roller is more preferably the guide roller 48, but a so-called free roller that is free rotating is more preferably the guide roller 48.

  The dried film 19 is preferably cooled to approximately room temperature in the cooling chamber 22.

  The static eliminator 23 is a so-called forced static eliminator such as a static eliminator, and makes the voltage of the film 19 a predetermined range. It is preferable to neutralize the film 19 so that the charged voltage is −3 kV to +3 kV. The position of the static eliminating device 23 is not limited to the downstream side of the cooling chamber 22.

  The knurling imparting roller pair 26 imparts knurling to both side ends of the film 19 by embossing. The embossing is preferably performed so that the height of the unevenness at the knurled portion is 1 μm to 200 μm.

  Inside the winding unit 27, a winding device 52 for winding the film 19 and a press roller 53 for controlling the tension at the time of winding are provided.

  In FIG. 2, the guide roller 48 includes a roller main body 48a and shaft portions 48b fitted to both ends of the roller main body 48a. The roller body 48a conveys the wet film 12 while supporting it on the outer peripheral surface thereof. In addition, as a material of the roller main body 48a and the shaft portion 48b, a material excellent in corrosion resistance, for example, aluminum, iron, stainless steel, carbon fiber reinforced plastic (CFRP), or the like is used.

  In FIG. 3, a trough 60 and a crest 61 having a substantially semicircular cross section are formed along the circumferential direction on the circumferential surface of the roller body 48a. The troughs 60 and the crests 61 are alternately arranged in the axial direction. The valley portion 60 and the mountain portion 61 are processed and formed with high precision by, for example, a precision lathe using a cutting tool.

  The distance between adjacent bottom points 60a of the valley part 60 and the distance between adjacent vertexes 61a of the peak part 61, that is, the pitches Pv and Pm of the valley part 60 and the peak part 61 are 0.01 mm or more and 2 mm or less. ing. If the pitches Pv and Pm are less than 0.01 mm, lathe processing becomes difficult, and even if it is possible, the manufacturing cost is increased and it becomes very expensive. On the other hand, if the pitches Pv and Pm are larger than 2 mm, slipping or surface projection occurs.

  The height Hv-m from the bottom point 60a to the apex 61a is 0.01 mm or more and 1 mm or less. When the height Hv-m is less than 0.01 mm, the effect of removing the air layer between the wet film 12 is lost, and slipping is likely to occur. If the height Hv-m is larger than 1 mm, lathe processing becomes difficult, and even if it can, the manufacturing cost is increased and the cost becomes very expensive.

  The distance from the center Ov of the circle forming the cross section of the valley 60 to the bottom point 60a and the distance from the center Om of the circle forming the cross section of the peak 61 to the apex 61a, that is, of the valley 60 and the peak 61 The curvature radii Rv and Rm are 0.1 mm or more and 0.5 mm or less. When the curvature radii Rv and Rm are less than 0.1 mm, the contact area with the wet film 12 becomes small, and slipping may occur. When the curvature radii Rv and Rm are larger than 0.5 mm, the height Hv-m is lowered and slipping may occur.

  In FIG. 4, a flat surface 70 parallel to the axial direction is formed at the apex 61 a portion of the peak portion 61. The flat surface 70 is formed by, for example, polishing the apex 61a portion of the peak portion 61 with a polishing machine after forming the valley portion 60 and the peak portion 61. A width Wf of the flat surface 70 in the axial direction is 0.05 mm or more and 0.5 mm or less. When the width Wf is less than 0.05 mm, a portion that cannot be polished depending on the processing accuracy of the peak portion 61 occurs. If the width Wf is larger than 0.5 mm, the valleys 60 and the peaks 61 cannot be formed at the pitch defined above.

  As explained above, it has valleys 60 and peaks 61 that are alternately formed on the circumferential surface along the circumferential direction, and have a substantially semicircular cross section, and the pitches Pv and Pm of valleys 60 and peaks 61 are as follows. Since the height Hv-m from the bottom 60a of the valley portion 60 to the apex 61a of the peak portion 61 is 0.01 mm or more and 2 mm or less, the wet film 12 is conveyed using the guide roller 48 having a height of 0.01 mm or more and 1 mm or less. Even if the solidified additive is adhered to the guide roller 48, the air layer between the wet film 12 is effectively removed, and the guide roller 48 is caused to frictional force such that the wet film 12 does not slip. To touch. Therefore, it is possible to prevent the generation of scratches and pulling wrinkles. Further, there is no occurrence of area projection due to the valley portion 60 and the mountain portion 61.

  Since the flat surface 70 is formed at the apex 61a portion of the peak portion 61 and the width Wf in the axial direction is set to 0.05 mm or more and 0.5 mm or less, the frictional force can be further increased, and the streaks formed by the flat surface 70 are formed. There is no area projection.

  The pitches Pv and Pm are more preferably 0.3 mm or more and 0.5 mm or less. The height Hv-m is more preferably 0.02 mm or more and 0.1 mm or less.

  The curvature radii Rv and Rm are more preferably 0.2 mm or more and 0.4 mm or less. The width Wf is more preferably 0.1 mm or greater and 0.3 mm or less.

  The width of the wet film 12 is more preferably 1800 mm or more and 2500 mm or less. Normally, the larger the width of the wet film 12, the more easily the scratches and wrinkles are caused by the slip, but the effect of using the guide roller 48 is sufficiently confirmed even in the wet film 12 having a width in the range of 1800 mm to 2500 mm. Is done.

  In the above preferable ranges of numerical values relating to the pitches Pv and Pm, the height Hv-m, the curvature radii Rv and Rm, the width Wf, and the width of the wet film, the above-described effects are particularly large.

  It should be noted that the guide roller 48 has a good effect both when applied to a drive roller that is rotationally driven by a motor (not shown) and when applied to a free roller to which a drive source is not connected.

  As described above, according to the present invention, the wet film contains a solvent and is heated to accelerate drying. However, according to the present invention, when a film of 20 to 80 μm is to be formed, the guide roller Since 48 is used, the wet film can be guided without slipping, and scratches, pulling wrinkles, and surface exposure do not occur in the wet film.

[Experiment 1] to [Experiment 3]
Dope 11 was made with the following composition.
Cellulose triacetate (degree of acetylation = 60.7%) 100 parts by weight Plasticizer a (triphenyl phosphate) 8 parts by weight Plasticizer b (biphenyl diphenyl phosphate) 4 parts by weight Matting agent (fine particles of silicon dioxide, average particle diameter) 15nm, Mohs hardness about 7)
0.03 part by weight Solvent component 1 (dichloromethane) 594 parts by weight Solvent component 2 (methanol) 66 parts by weight

  Of the plurality of guide rollers 48 in the first drying chamber 16 of the solution casting apparatus 10, one of the most upstream side and one of the most downstream side was used as a drive roller. The former is called a first drive roller, and the latter is called a second drive roller. The plurality of guide rollers 48 arranged in the conveyance path between the first drive roller and the second drive roller are all free rollers. The wrap angle of the wet film 12 at the guide roller 48 in the first transfer chamber 16 was 90 °. Then, the rotational speed of the second drive roller is made larger than the rotational speed of the first drive roller, and the tension in the transport direction of the wet film 12 between the first drive roller and the second drive roller is the width of the wet film 12. It was set to 80N / m in the direction. The conveyance speed of the wet film 12 was 10 m / min. Note that the driving roller and the free roller disposed on the conveyance path other than the first drying chamber 16 are all guide rollers 48.

  As the guide roller 48, a roller body 48 a made of stainless steel (without plating) having a diameter of 300 mm and a surface length of 1000 mm was prepared by fitting a shaft portion 48 b so that the distance between the shafts was 1500 mm. The roller body 48a was formed with valleys 60 and peaks 61 so as to have a pitch Pv, Pm 0.5 mm, a height Hv-m 0.04 mm, a curvature radius Rv 0.4 mm, and Rm 0.4 mm.

  The dope 11 was flowed out from the casting die 36 so that the thickness of the dried film 19 was 40 μm, and a casting film 38 was formed on the band 32. The position where the casting film 38 is peeled off from the band 32 is the first position, the inlet of the wet film 12 in the first drying chamber 16 is the second position, and the outlet of the wet film 12 in the first drying chamber 16 is the third position. . Then, the air sent to the dope 11, the inside of the casting chamber 13, the band 32, and the casting film 38 so that the solvent content of the wet film 12 at the first position and the second position is 100% by weight. Each temperature with dry air from a duct (not shown) was adjusted.

  Then, Experiment 1 to Experiment 3 were carried out with the solvent content at the third position and the temperatures of the wet film 12 at the second position and the third position as values shown in Table 1. The first drying chamber 16 is provided with a blower duct 46 for blowing out air and an exhaust duct (not shown) for letting indoor gas out of the room. The humidity and temperature of the air from the blower duct 46 are adjusted. As a result, the solvent content at the third position and the temperature of the wet film 12 at the third position were adjusted.

  In Table 1, "A" in the "Roller" column means the guide roller 48, "P1" in the "Solvent Content" column and "Film Temperature" column is the first position, and "P2" is The second position, “P3”, means the third position.

  It was visually evaluated whether the film 19 obtained in Experiment 1 to Experiment 3 of Example 1 had scratches, pulling wrinkles, and surface projection. If no scratches, wrinkles, or surface prints are confirmed, “◎”, but scratches, wrinkles, or surface prints are confirmed, but these levels are very small and should be used without problems for liquid crystal displays. “○” indicates the case where scratches can be made, and “X” indicates that it is difficult to use on a liquid crystal display or the like because scratches, pulling wrinkles, and surface projection are confirmed. This evaluation result is shown in the “Evaluation Result” column of Table 1.

[Comparative Experiment 1] and [Comparative Experiment 2]
The guide roller 48 in the first drying chamber 16 in Experiment 1 was replaced with a so-called flat roller having a smooth peripheral surface, and this was designated as Comparative Experiment 1. Further, the guide roller 48 of the first drying chamber 16 was replaced with a so-called concave roller whose outer diameter continuously decreased from the end in the longitudinal direction toward the center, and this was designated as comparative experiment 2. Note that the driving roller and the free roller disposed on the conveyance path other than the first drying chamber 16 are all guide rollers 48 as in Experiments 1 to 3. Other conditions and the evaluation method are the same as those in Experiments 1 to 3. In Table 1, “B” in the “Roller” column means a flat roller, and “C” means a concave roller.

[Experiment 1] to [Experiment 3]
As the guide roller 48, a roller body 48 a made of stainless steel (without plating) having a diameter of 300 mm and a surface length of 1000 mm was prepared by fitting a shaft portion 48 b so that the distance between the shafts was 1500 mm. The roller body 48a was formed with valleys 60 and peaks 61 so as to have a pitch Pv, Pm 1.0 mm, a height Hv-m 0.5 mm, a curvature radius Rv 0.4 mm, and Rm 0.4 mm.

  The guide roller 48 was used in place of the guide rollers 48 of Experiment 1 to Experiment 3 of Example 1, and these experiments were designated Experiments 1 to 3 of Example 2. Other conditions are the same as those of Experiments 1 to 3 in Example 1. Evaluation was performed in the same manner as in Example 1. The evaluation results are shown in Table 2.

[Comparative Experiment 3]
As a guide roller, a roller body 48a made of stainless steel (no plating) having a diameter of 300 mm and a surface length of 1000 mm was prepared by fitting the shaft portion 48b so that the distance between the shafts was 1500 mm. In the roller body, valleys and peaks were formed so as to have a pitch Pv, Pm 0.001 mm, a height Hv-m 0.005 mm, a curvature radius Rv 0.4 mm, and Rm 0.4 mm. The other conditions were the same as in Experiment 1 of Example 1. This experiment was designated as comparative experiment 3 and was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2.

[Comparison Experiment 4]
As a guide roller, a roller body 48a made of stainless steel (no plating) having a diameter of 300 mm and a surface length of 1000 mm was prepared by fitting the shaft portion 48b so that the distance between the shafts was 1500 mm. Then, valleys and peaks were formed on the roller body so as to have a pitch Pv, Pm 3.0 mm, a height Hv-m 2.0 mm, a curvature radius Rv 0.4 mm, and Rm 0.4 mm. The other conditions were the same as in Experiment 1 of Example 1. This experiment is referred to as comparative experiment 4, and the evaluation results are shown in Table 2.

  In Experiment 1 to Experiment 3 of Example 1, the wet film 12 and the film 19 were not slipped by the guide roller 48. Moreover, there was no occurrence of cutouts due to valleys and mountains. The film 19 was free from scratches and wrinkles. On the other hand, in Comparative Experiments 1 and 2, the solvent content at the third position was 60%, and the amount of solvent evaporation in the first drying chamber was reduced compared to 40% and 20%. However, slippage occurred from the adhesion of the additive to the roller, and the conveyance was not good. For this reason, the films obtained in Comparative Experiments 1 and 2 had scratches and wrinkles, and surface projections and irregularities as traces of solidified additive were confirmed. Further, from Experiments 1 to 3 and Comparative Experiments 3 and 4 of Example 2, the pitches of the peaks and valleys and the height from the bottom of the valleys to the peak of the peaks are within the scope of the present invention. It can be seen that a greater effect can be obtained.

  From the above results, it can be seen that according to the present invention, there is no slip of the wet film with the roller, and scratches, wrinkles, and surface exposure are prevented, and good conveyance can be achieved. Thereby, the film obtained is smooth without scratches or wrinkles.

It is the schematic of solution casting apparatus. It is a perspective view which shows the structure of a web guide roller. It is an expanded partial sectional view which shows the surface shape of a web guide roller. It is an expanded partial sectional view which expands and shows the surface shape of a web guide roller further.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Solution casting apparatus 11 Dope 12 Wet film 16 1st drying chamber 17 Tenta 32 Band 38 Casting film 48 Web guide roller 60 Valley part 60a Bottom point 61 Peak part 61a Vertex 70 Flat surface

Claims (6)

A casting process in which a dope containing a polymer and a solvent is cast on a traveling band to form a casting film, and a peeling process in which the casting film is peeled off in a state containing the solvent to form a wet film. And a tenter drying step of drying the wet film while stretching it in the width direction by a tenter comprising a drying means and a holding means for holding both sides of the wet film to form a polymer film, and the step before entering the tenter In a solution casting method having a pre-drying step of drying a wet film,
Casting the dope so that the thickness of the polymer film is 20 to 80 μm,
In the pre-drying step, crests and troughs along the circumferential direction are alternately provided in the axial direction, the crests and troughs have a substantially semicircular cross section, and the troughs and crests The roller having a pitch of 0.01 mm to 2 mm and a height from the bottom of the valley to the peak of the peak of 0.01 mm to 1 mm, the wetness until the solvent content reaches 30% A solution casting method characterized by supporting a film.   The solution casting method according to claim 1, wherein radii of curvature of the valley and the peak are 0.1 mm or more and 0.5 mm or less.   The solution casting method according to claim 1, wherein a flat surface parallel to the axial direction is formed at an apex portion of the peak portion.   The solution casting method according to claim 3, wherein a width of the flat surface in the axial direction is 0.05 mm or more and 0.5 mm or less.   In the pre-drying step, the wet film having a solvent content in the range of 70 to 150% is dried in a temperature range of 10 ° C. or more and less than 100 ° C. until the solvent content is in the range of 10 to 30%. 5. The solution casting method according to any one of claims 1 to 4, wherein the solution casting method is performed.   6. The solution casting method according to claim 1, wherein in the pre-drying step, a tension of 10 N to 300 N per 1 m of width is applied in the transport direction of the wet film.

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