JP3969646B2 - Solution casting method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a solution casting method andapparatusRelatedAndIn particular, polymer films used for optical applications, liquid crystal display devices, organic electroluminescence, polarizing plates, etc.TheManufacturingDoSolution casting methodAnd equipmentRelated tois there.
[0002]
[Prior art]
The high-functional polymer film as described above is generally produced by casting a dope on a support using a casting die, peeling it off from the support, and then winding it through a drying step. Yes. This is a typical film manufacturing method called a solution casting method. In this manufacturing method, after the film is peeled off from the support, in order to improve the flatness, mechanical strength, optical properties, etc. of the film, a device called a tenter that performs film width regulation and film stretching is provided. It is common to dry while transporting.
[0003]
The both ends of the film conveyed by the tenter device curl on the side close to the support, that is, on the peeling surface side. This is due to the fact that the release surface side has a higher solvent content than the anti-release surface side, and the shrinkage amount on the release surface side becomes larger due to drying. A member such as a tenter clip or a pin of the tenter device holds the part slightly inside the both side edges of the film, and regulates the width of the film by the running track and the running speed and applies tension in the stretching direction. ing. Therefore, the held inner portion does not curl due to the tension, but the outer portion of the held portion, that is, the outer end portion of the tenter clip or pin (hereinafter referred to as the ear portion) has a large curl. Will occur. This curled portion and phenomenon is generally called ear curl.
[0004]
When the film is detached from the tenter clip or the pin, the film is conveyed by a roller. However, the ear curl is broken on the roller, often resulting in conveyance failure. In addition, the ear curl may contact the roller unevenly, so that wrinkles may occur continuously or intermittently in the ear portion.
[0005]
Further, in the tenter device, both end portions of the film held by a tenter clip or a pin are in an extended state because the holding portion does not dry and shrink due to it. As a result, when the film released from the tenter clip or pin comes into contact with the roller, there is a difference between the tension applied to the center of the film and that applied to the ears, which may cause wrinkles on the roller. Connected.
[0006]
Therefore, a method of reducing the distance between the position where the film is removed from the tenter clip or pin (hereinafter referred to as “holding release point”) and the first contact roller after the holding release point is generally used as a method for suppressing the ear curl. It is considered valid. It is also generally effective to reduce the wrap angle of the driven or non-driven roller installed after the holding release point with respect to the film. In addition, regardless of the direction of the ear curl, the length of the roller after the holding release point is shorter than the width of the film so that the ear curl and the roller do not contact each other, or the ear curl is cut by a cutter, etc. There is also a method of cutting and removing by (for example, see Patent Document 1).
[0007]
[Patent Document 1]
JP-A-9-85680 (page 1-4, FIG. 1)
[0008]
On the other hand, in order to increase production efficiency, the film forming process is speeded up. As part of this, in the drying by the tenter device, there is a tendency that the drying temperature is increased to increase the drying speed.
[0009]
In liquid crystal display devices, organic electroluminescence, polarizing plates, and the like, there is an increasing demand for higher functionality of products. Therefore, it is necessary to make films used for these films thinner and thinner, and solution casting methods that propose thinning, polarizing plates using the same, liquid crystal display devices, and the like have been proposed (for example, Patent Document 2 and (See Patent Document 3).
[0010]
[Patent Document 2]
JP 2000-199819 A
[0011]
[Patent Document 3]
JP 2002-120244 A
[0012]
[Problems to be solved by the invention]
However, the method of reducing the distance between the holding release point and the roller has restrictions on the structure of the equipment, or the roller indicates the full width of the film, and the size of the diameter is limited. In many cases, the distance cannot be reduced until a sufficient effect is obtained.
[0013]
In addition, with regard to the small wrap angle of the roller, the frequency of occurrence of ear folds and wrinkles may be increased depending on the conveyance conditions, and the degree of freedom of roller placement is low due to equipment structure and equipment space restrictions. In some cases, a valid wrap angle cannot be set. Further, the method of shortening the length of the roller has a problem that the film conveyance tends to be unstable and cannot be applied to a portion that forms a boundary of each process, for example, a roller having a sealing function. The method of cutting and removing the ear curl has a problem in that it is difficult to apply a tension to the portion of the ear curl, so that stable cutting cannot be performed with sufficient cutting stress.
[0014]
In addition, the phenomenon such as the above-described ear curl or roll breakage, ear extension, wrinkle, etc., occurs more prominently or frequently with increasing drying temperature and film thickness in the tenter device. . This is because when the temperature of the film rises due to an increase in the drying temperature, or when the film thickness is thin, many films reduce their rigidity.
[0015]
Therefore, in order to prevent the occurrence of these phenomena, there is a problem that drying conditions are relaxed and film thinning is avoided, which restricts productivity and new product development.
[0016]
  The present invention has been made in view of the above problems, and is a solution casting method capable of suppressing the occurrence of ear folds, wrinkles, and the like caused by ear curls occurring at both side ends of the film after the holding release point.And equipmentThe purpose is to provide.
[0017]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention provides:The dope was cast on a support using a casting die, and the dope was peeled off as a polymer film. Then, the dope was transported and dried while holding both ends of the polymer film with a tenter, and the drying occurred. In the solution casting method for cutting and removing both side ends of the polymer film having an ear curl, the tenter was separated by a conveying roller consisting of a roller body having an equal diameter and both side ends having a smaller diameter than the roller body. Non-contacting the both side ends of the transport roller to both side ends of the polymer film, and supporting the central portion in the width direction of the polymer film excluding both side ends of the polymer film by the roller body, The portion of the polymer film that transports the polymer film and passes through both end portions of the transport roller is included in the portion to be cut and removed. Wherein the cutting removal Te.
[0018]
  The fluctuation range of the outer diameter of the roller body is preferably less than 0.01 mm. It is preferable that a difference in outer diameter between the roller main body and both end portions is 0.4 mm or more and 6.0 mm or less, and the outer diameter difference is provided by a curved or chamfered stepped process or a tapered process. . It is preferable that an equal-diameter conveying roller having an equal diameter over the entire width direction is provided on the upstream side or the downstream side of the conveying roller. It is preferable that the conveying roller and the equal-diameter conveying roller are alternately provided. It is preferable that the temperature of the polymer film when being transported by the transport roller is 40 ° C. or higher and the thickness of the polymer film is 25 μm or more and 160 μm or less.
[0019]
The effect is particularly high when the temperature of the film when conveyed by the conveying roller is 40 ° C. or more and the thickness T of the film is 25 μm or more and 160 μm or less. Furthermore, a cellulose acylate film is suitable as the film.
[0020]
Furthermore, the cellulose acylate film, the polarizing plate, and the liquid crystal display device of the present invention are characterized by being manufactured by the solution casting method.
[0021]
  The present invention also provides:The dope was cast on a support using a casting die, and the dope was peeled off as a polymer film. Then, the dope was transported and dried while holding both ends of the polymer film with a tenter, and the drying occurred. In the solution casting apparatus for cutting and removing both side ends of the polymer film having an ear curl, the polymer film is composed of a roller body having an equal diameter and both side ends having a smaller diameter than the roller body, and the tenter is detached. The both side ends and the both ends of the small diameter are brought into non-contact, and the center of the polymer film in the width direction excluding both ends of the polymer film is supported by the roller body, and the polymer film is conveyed. The part of the polymer film that passes through the conveying roller and both end portions of the conveying roller is included in the part to be cut and removed. Characterized in that it comprises a that cutting removal means. The fluctuation range of the outer diameter of the roller body is preferably less than 0.01 mm. It is preferable that a difference in outer diameter between the roller main body and both end portions is 0.4 mm or more and 6.0 mm or less, and the outer diameter difference is provided by a curved or chamfered stepped process or a tapered process. . It is preferable that an equal-diameter conveying roller having an equal diameter over the entire width direction is provided on the upstream side or the downstream side of the conveying roller. It is preferable that the conveying roller and the equal-diameter conveying roller are alternately provided.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a part of a solution casting process embodying the present invention. FIG. 1 shows a film transport process immediately after the film leaves the tenter, and is a plan view from above. The film 11 is dried while being stretched by the tenter 12 and being stretched. In the tenter 12, the tenter clip 13 travels according to the tenter track 14 and conveys the film 11 while holding both side ends of the film 11. A pin clip may be used instead of the tenter clip 13. Each tenter clip 13 is automatically controlled by a controller (not shown) to release the clip and release the holding of the film 11 when the holding releasing point P is reached. When the width 11 of the film 11 is determined and the holding release point P is passed, the film 11 is sent to a roller drying chamber (not shown), which is the next process, by the first conveying roller 17 and the second conveying roller 18, and as a product. It is wound up. Here, although the first conveying roller 17 has a smaller outer diameter than the second conveying roller 18, the present invention is not limited to this.
[0023]
FIG. 2 shows a transport process of the film 11 by the first transport roller, and is a cross-sectional view seen from the traveling direction side of the film 11. Both end portions of the first conveying roller 17 have an outer diameter smaller than that of the central portion, and a stepped portion 17a is formed. The step size L1 is equal to one half of the difference between the outer diameter D1 of the central portion and the outer diameter D2 of the side end portion. It is set appropriately depending on the wrap angle of the conveying roller 17 and the like. Since the step size L1 is preferably in the range of 0.2 mm to 3.0 mm, the difference between the outer diameter D1 of the central portion and the outer diameter D2 of the side end portion is 0.4 mm or more and 6. 0 mm or less. By adopting this shape, the ear curl 11a can avoid contact with the first conveying roller 17, and can prevent the film 11 from being bent or wrinkled by contact pressure.
[0024]
The difference between the outer diameter D1 of the central portion and the outer diameter D2 of the side end portions is more preferably 1.0 mm or more and 5.0 mm or less, and most preferably 2.0 mm or more and 4.0 mm or less. . In addition, the corner of the stepped portion 17a has a curved shape, thereby preventing damage such as scratches to the film 11.
[0025]
The outer diameter D1 of the central part is 75.00 mm or more and 200.00 mm or less, and this value is substantially constant in the range of the length LC of the central part. Here, substantially substantially constant means that the fluctuation range is less than 0.01 mm. As a result, the film 11 has a constant contact pressure with the first conveying roller 17 in the width direction, and the tension in the advancing direction during conveyance is also kept constant in the width direction, thereby preventing the occurrence of wrinkles and the like. Is done. Further, the length LC of the central portion is set so that no step mark of the first conveying roller 17 remains in the range of the final product width of the film 11. For example, when the width W of the film 11 including the ear curl 11a is 1600 mm and the final product width is 1330 mm, it is preferable that the length LC of the central portion is approximately 1450 mm.
[0026]
In the present embodiment, the second conveying roller 18 (see FIG. 1) also has a stepped shape in which both end portions are reduced in diameter, like the first conveying roller 17. Thereby, the inhibitory effect of an ear break and a wrinkle can further be heightened. Further, the outer diameter of the central portion of the second conveying roller 18 is 70.00 mm or more and 150.00 mm or less, which is smaller than that of the first conveying roller, but the present invention is limited to this. It is not a thing.
[0027]
Further, in the case where the ear-cutting process for removing the ear curl 11a is incorporated in the solution film-forming process, at least one of the transport rollers transported to the ear-cut process is provided with a step similar to that of the first transport roller 17. It is preferable to have. For example, when the edge cutting process is incorporated immediately after the second conveying roller 18, at least one of the first conveying roller 17 and the second conveying roller 18 has the above-described step shape. However, if a plurality of such step-shaped conveying rollers are continued, the tension on the side end portion of the film 11 including the ear curl 11a is lowered, so that the cutting stress by a cutter or the like may not be sufficiently applied. . In such a case, it is effective to alternately arrange the step-shaped and non-step-shaped conveying rollers.
[0028]
Note that the first and second conveying rollers 17 and 18 having a step shape in the present embodiment may be driving rollers or non-driving rollers, which are appropriately selected. Furthermore, although the object which makes a level | step difference was made into the two of the 1st and 2nd conveyance rollers 17 and 18 here, this invention is not limited about this number, For example, for many conveyance to an ear cutting process A roller may be the target.
[0029]
Further, when contacting the first conveying roller 17 and the second conveying roller 18 having a stepped shape, when the temperature of the film 11 is 40 ° C. or more and the thickness T is 25 μm or more and 160 μm or less, The expression of the wrinkle prevention effect is particularly high. Here, the thickness T of the film 11 is a thickness at the time of contact with the first and second transport rollers 17 and 18, and means a wet film thickness. When the thickness T of the film 11 is less than 25 μm, there is a problem that the rigidity of the film 11 is too low and the suppression of the ear folding becomes temporary, and when it is 160 μm or more, the first conveying roller In addition to 17 and the second conveying roller 18, there may be a case where it is necessary to sufficiently suppress the ear folds and wrinkles by increasing the number of pass rollers having the same shape.
[0030]
Furthermore, it is effective not only when the film 11 has a single-layer structure but also when it has a laminated structure using a sequential casting method or a co-casting method. The laminated structure is particularly effective when the wet film thickness is 25 μm or more and 160 μm or less in all layers.
[0031]
FIG. 3 is a cross-sectional view of the first conveying roller 27 as another embodiment, as viewed from the traveling direction side of the film 21. However, the other side end (not shown) has the same shape. In the first conveying roller 27 of the present embodiment, only the passing position of the ear curl 21a is reduced in diameter, and the outer diameter of the end of the passing position remains equal to the outer diameter D1 of the central portion. Also here, the step size L1 is preferably 0.2 mm or more and 3.0 mm or less, as in the above embodiment, so that the difference between the outer diameter D1 of the central portion and the outer diameter D2 of the small diameter portion is set to 0. 0. 4 mm or more and 6.0 mm or less. Even with this shape, the ear curl 21a can avoid contact with the first conveying roller 27, so that the ear 21 is prevented from being folded or wrinkled by the contact pressure.
[0032]
As described above, with respect to the shape of the first conveying roller 27, by reducing the diameter only in a range sufficient for the ear curl 21a to avoid contact, it is possible to obtain an effect of preventing the occurrence of ear folding and wrinkles. Further, the corner of the stepped portion 27a is a chamfered shape instead of the curved shape in the above embodiment, thereby preventing the film 21 from being similarly damaged. Further, the first conveying roller 27 may be used as the second conveying roller 18.
[0033]
FIG. 4 is a cross-sectional view of one end portion of a first conveying roller as still another embodiment. However, the other side end (not shown) has the same shape. Here, the first conveying roller 37 has a shape in which the side end portion is gradually reduced in diameter (tapered) instead of the step shape in each of the above-described embodiments.
[0034]
The taper amount L2 in the taper portion 37a is preferably 0.2 mm or more and 3.0 mm or less similarly to the step size L1. However, the taper amount L2 also needs to be set as appropriate depending on the state of the ear curl 31a, the wrap angle with respect to the film 31, and the like. Further, the taper amount L2 at this time is an amount in a range from the innermost side of the tapered shape to a position where the side edge of the film 31 passes, and is an amount in a range to the side edge of the roller 37 as shown in FIG. Absent. Therefore, the outer diameter at the position through which the side edge of the film 31 passes is D2, and the difference between this value and the outer diameter D1 of the central portion is in the range of 0.4 mm to 6.0 mm. If it is larger than 6.0 mm, the generation rate of wrinkles increases, and if it is smaller than 0.4 mm, the expression of the effect of preventing the ear folds and wrinkles decreases. The outer diameter difference is more preferably 1.0 mm or greater and 5.0 mm or less, and most preferably 2.0 mm or greater and 4.0 mm or less.
[0035]
By tapering the end portions on both sides in this way, it is possible to obtain an effect close to the step shape in each of the embodiments. The taper is advantageous in that it is less likely to leave marks or scratches on the film 31 than the stepped shape, but even in this case, no taper-shaped marks remain in the width range of the final product of the film 31. Thus, it is necessary to set the length LC (see FIG. 2) of the central portion, and it is preferable that the portion passing through the tapered portion 37a is cut and removed in a later step. Further, the tapered first conveying roller 37 can be used as the second conveying roller 18.
[0036]
The materials of the first conveying rollers 17, 27, and 37 in each of the above embodiments are all metals, and aluminum (Al) is hard chrome plated, but plastic may be used as necessary. The step shape and the taper shape can be processed by cutting or plating thickness adjustment. However, the structure, material, and shape processing method of the first transport rollers 17, 27, 37 and the second transport roller 18 are not limited to these.
[0037]
About the said 1st conveyance rollers 17, 27, 37, you may use 2 or more types together in one solution casting apparatus. In this case, the arrangement order of the pass roller shapes can be set as appropriate.
[0038]
Moreover, as the films 11, 21, and 31 that can be produced in the present invention, a cellulose acylate film is preferable, and among them, a cellulose triacetate film is most preferable, but is not limited thereto. In other words, the polymer or the precursor as the main component of the films 11, 21, 31 may be any material that can be doped by using a solvent. Examples thereof include various polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate, various polyolefins such as polyethylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyamide, and polyimide. In the case of cellulose triacetate, the raw materials are those of cotton linter and wood pulp, and in this embodiment, cotton linters are used alone. A mixture may be used.
[0039]
About dope, it is preferable to make the viscosity in the temperature at the time of casting into the range of 5-100 mPa * s. The casting speed of the dope or the conveying speed of the films 11, 21, 31 can be generally applied in a region of 100 m / min or less. In addition, the present invention is more effective for manufacturing systems that are generally difficult to form into a film, such as when the transport speed of the film 11 is high or when the thickness T of the film is very thin.
[0040]
In the present invention, various known solvents can be used as the solvent for the dope used for film formation. For example, in addition to various halogenated hydrocarbons, alcohols, ethers, esters, ketones and the like can be used alone or in combination.
[0041]
Furthermore, in the present invention, various additives may be appropriately contained in the films 11, 21, 31. As additives, plasticizers, ultraviolet absorbers, dyes, optically anisotropic compounds, matting agents and the like are common.
[0042]
Furthermore, the present invention also includes a polarizing plate and a liquid crystal display device comprising the cellulose acylate film produced by the above solution casting method as constituent elements. The polarizing plate of the present invention has a cellulose acylate film such as cellulose triacetate prepared by the solution casting method of each of the above embodiments on both surfaces of a polarizing film made of a polyvinyl alcohol (PVA) film as a protective film. Obtained by pasting together. The polarizing film is obtained by dyeing a polyvinyl alcohol-based film. As the dyeing method, a gas phase adsorption method and a liquid phase adsorption method are generally used, and both can be applied. Dyeing was performed by phase adsorption.
[0043]
For dyeing by liquid phase adsorption, iodine is used here, but the present invention is not limited to this. The polyvinyl alcohol film was immersed in an iodine / potassium iodide (KI) aqueous solution with an immersion time of 30 seconds to 5000 seconds. In this case, the aqueous solution preferably has an iodine concentration of 0.1 g / liter to 20 g / liter and a potassium iodide concentration of 1 g / liter to 100 g / liter. Moreover, it is preferable that the temperature of the aqueous solution at the time of immersion is set to the range of 5 degreeC or more and 50 degrees C or less.
[0044]
The liquid phase adsorption method is not limited to the above immersion method, and a known method such as a method of applying iodine or other dye solution to a polyvinyl alcohol film or a method of spraying may be applied. Dyeing may be performed before or after the polyvinyl alcohol film is stretched, but the polyvinyl alcohol film is appropriately swelled and easily stretched by being dyed, so that the stretching step It is particularly preferable to provide a dyeing step before the step.
[0045]
It is also preferable to dye with a dichroic dye instead of iodine. Examples of dichroic dyes include azo dyes, stilbene dyes, pyrazolone dyes, triphenylmethane dyes, quinoline dyes, oxazine dyes, thiazine dyes, anthraquinone dyes, and other dye compounds. it can. Water-soluble dye compounds are most preferable. Further, it is preferable that a hydrophilic functional group such as a sulfonic acid group, an amino group, or a hydroxyl group is introduced into the molecule of these dichroic dyes.
[0046]
In the production process of a polarizing film by stretching a dyed polyvinyl alcohol film, a compound that crosslinks polyvinyl alcohol is used. Specifically, a polyvinyl alcohol film is immersed in a crosslinking agent solution in the pre-stretching step or the stretching step to contain a crosslinking agent. It may be applied instead of dipping. The polyvinyl alcohol film is sufficiently hardened by the inclusion of the crosslinking agent, and as a result, appropriate orientation is imparted. In addition, as a crosslinking agent of polyvinyl alcohol, boric acids are most preferable, but are not limited thereto.
[0047]
For the adhesive between the obtained polarizing film and the cellulose triacetate film, various known adhesives that can be used for bonding the polarizing film and the protective film can be used. Among these, an aqueous solution of a polyvinyl alcohol polymer or a boron compound containing a modified polyvinyl alcohol having an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group or the like is preferable. This adhesive is preferably applied so that the thickness after drying is 0.01 μm or more and 10 μm or less, and more preferably 0.05 μm or more and 5 μm or less. Furthermore, an antireflection layer, an antiglare layer, a slippage imparting layer, an easy adhesion layer or the like can be imparted to the surface of the cellulose triacetate film layer imparted to the polyvinyl alcohol layer as a protective film.
[0048]
Further, an antireflection film provided with an antireflection layer on the above polarizing plate is obtained, and this is used as one side of the surface protective film, twisted nematic (TN), super twisted nematic (STN), vertical alignment (VA). Thus, a transmissive, reflective, or transflective liquid crystal display device in a mode such as in-plane switching (IPS) or optically compensated bend cell (OCB) is obtained. Further, an optical compensation film such as a viewing angle widening film for improving the viewing angle of the liquid crystal display device, a retardation plate, and the like can be used in combination. When used in a transmissive or transflective liquid crystal display device, it is used in combination with a commercially available brightness enhancement film (a polarized light separating film having a polarization selective layer, such as D-BEF manufactured by Sumitomo 3M Co., Ltd.). In addition, a display device with higher visibility can be obtained.
[0049]
【Example】
[Example 1]
A cellulose triacetate film was formed by a solution casting method. Both end portions of the first conveying roller 17 and the second conveying roller 18 following the tenter 12 are stepped. The width W of the film 11 was 1600 mm, the thickness T of the film 11 when contacting the first conveying roller 17 was 80 μm, and the temperature of the film 11 was 45 to 80 ° C. The cellulose triacetate film contains triphenyl phosphate (TPP) as a plasticizer.
[0050]
The first conveying roller 17 has an outer diameter D1 at the center of 150.00 mm and a length LC of 1450 mm. As for this roller 17, the side edge part including the site | part which corresponds to the width of each 75 mm in the right-and-left edge part of the film 11 is made small in diameter. The outer diameter D2 of both end portions of the reduced diameter is 148.50 mm, and the step size L1 is 0.75 mm. The corner of the stepped portion 17a is a curved surface having a curvature radius R of 0.5 mm.
[0051]
The second conveying roller 18 has the same shape, and has an outer diameter at the center of 100.00 mm and a length of 1450 mm. As for this roller 18, the side edge part including the site | part which corresponds to the width of each 75 mm in the right-and-left edge part of the film 11 is made small in diameter. The outer diameter of the both side end portions that have been reduced in diameter is 98.50 mm, and the size of the step is 0.75 mm. The corners of the stepped portions were curved surfaces with a curvature radius R of 0.5 mm.
[0052]
As a result of the present example, the ear curl 11a was stably conveyed until the ear-cutting process without being bent or wrinkled in the conveyance process by the first and second conveyance rollers 17 and 18. As a result, the wound product had no surface failure and the quality was very good.
[0053]
[Example 2]
Both the first and second transport rollers 17 and 18 of Example 1 were tapered as shown in FIG. The outer diameter at the film side edge of the transport roller after processing into a tapered shape was 148.00 mm. About other conditions, it implemented similarly to Example 1. FIG.
[0054]
As a result of this example, the ear curl 11a was stably transported without being bent or wrinkled in the transport process by the first and second transport rollers subjected to the taper processing. As a result, the wound product had no surface failure and the quality was good.
[0055]
Example 3
Example 1 except that the size D1 of the step between the first and second transfer rollers 17 and 18 is 3.50 mm, and the outer diameter D2 of the side end is 143.00 mm and 93.00 mm, respectively. It carried out similarly. As a result of this example, weak wrinkles were sporadically scattered in the ear curl portion 11a, but this did not remain as a deformation and did not enter the product, so that a good product was obtained.
[0056]
[Comparative Example 1]
The first and second conveying rollers 17 and 18 were carried out in the same manner as in Example 1 except that both the steps and the tapered rollers 17 and 18 had a uniform diameter. The outer diameter of the first conveying roller is 150 mm, and the outer diameter of the second conveying roller is 100 mm. As a result of this comparative example, the ear curl 11a was bent by the first conveying roller, and sagging occurred in the film 11 on the upstream side of the second conveying roller. As a result, a conveyance failure occurred and the film 11 was cut.
[0057]
From the results of Examples 1 to 3 and Comparative Example 1, it can be seen that ear folding and wrinkles can be prevented by reducing the diameter of both end portions of the transport roller and transporting the film without contacting the ear curl. . As a result, the film can be stably conveyed, and a good product free from surface defects can be obtained.
[0058]
Example 4
An aqueous solution with an iodine concentration of 0.3 g / liter and potassium iodide of 18.0 g / liter was set at 25 ° C., and a polyvinyl alcohol film (thickness, Kuraray Co., Ltd.) having a film thickness of 75 μm was immersed therein. Piled up. Further, this film was stretched 5.0 times in an aqueous solution at 50 ° C. with a boric acid concentration of 80 g / liter and a potassium iodide concentration of 30 g / liter to obtain a polarizing film. The cellulose triacetate films 11 and 31 obtained in Examples 1 to 3 were each treated with a 1.5N sodium hydroxide (NaOH) aqueous solution at 50 ° C. for about 180 seconds, neutralized, and then washed with water. And bonded to the front and back of the polarizing film. A 4% aqueous solution of polyvinyl alcohol (trade name; PVA-117H, manufactured by Kuraray Co., Ltd.) was used as an adhesive. This was dried in an air constant temperature bath at 80 ° C. for about 30 minutes to obtain two types of polarizing plates.
[0059]
Using a spectrophotometer, the parallel transmittance Yp and the row transmittance Yc in the visible region were determined for the three types of polarizing plates obtained, and the degree of polarization PY was determined based on the following equation.
PY = {(Yp−Yc) / (Yp + Yc)}^1/2× 100 (%)
[0060]
As a result of this example, the polarization degree PY was 99.6% or more in any of the polarizing plates constituted by using the films 11 and 31 produced from Examples 1 to 3, and there was no unevenness. It can be seen that the film obtained by the solution casting method can be suitably used for a polarizing plate.
[0061]
Example 5
The viewing-side polarizing plate of the liquid crystal display device of the notebook computer on which the transmission type TN liquid crystal display device was mounted was replaced with the two types of produced polarizing plates. In addition, this liquid crystal display device has the polarization separation film (brand name; D-BEF, Sumitomo 3M Co., Ltd. product) which has a polarization selection layer between the backlight and a liquid crystal cell.
[0062]
As a result of this example, all of the three types of liquid crystal display devices obtained had no luminance unevenness and had very high display quality. This shows that the film obtained by the solution casting method of the present invention is suitable as a liquid crystal display device.
[0063]
【The invention's effect】
  As described above, the solution casting method of the present inventionAnd equipmentThus, it is possible to prevent the occurrence of edge folding, wrinkles and the like due to the ear curl at both ends of the film after the tenter is detached. As a result, the film is continuously and stably conveyed, and a film as a good product can be obtained. The obtained film is further suitably used as a component of a polarizing plate or a liquid crystal display device.
[Brief description of the drawings]
FIG. 1 is a plan view from above showing a film transport process from a tenter to a transport roller in a solution casting method embodying the present invention.
FIG. 2 is a cross-sectional view seen from the film traveling direction side in a transporting process by a transporting roller embodying the present invention.
FIG. 3 is a cross-sectional view of only one end portion of a transport process using a transport roller according to another embodiment.
FIG. 4 is still another embodiment, and is a cross-sectional view of only one end portion of a transport process using a transport roller.
[Explanation of symbols]
11 film
11a Ear curl
12 Tenter
17 First transfer roller
17a Stepped part
18 Second transfer roller
21 films
27 First transfer roller
27a Stepped part
31 films
37 First transfer roller
37a Taper part
D1 Outer diameter of center
Outer diameter of D2 side end
L1 Step size
L2 Taper amount
LC center length
P Hold release point
T film thickness
W Film width

Claims (11)

The dope was cast on a support using a casting die, and the dope was peeled off as a polymer film. Then, the dope was transported and dried while holding both ends of the polymer film with a tenter, and the drying occurred. In the solution casting method for cutting and removing both side ends of the polymer film having an ear curl ,
By means of a conveying roller consisting of a roller body having an equal diameter and both end portions having a smaller diameter than the roller body , the both end portions of the conveying roller are brought into non-contact with both end portions of the polymer film from which the tenter has been detached. , Supporting the center of the polymer film in the width direction excluding both side ends of the polymer film with the roller body, and transporting the polymer film,
A solution casting method comprising cutting and removing a portion of the polymer film that passes through both end portions of the conveying roller in the portion to be cut and removed . The solution casting method according to claim 1, wherein the fluctuation range of the outer diameter of the roller body is less than 0.01 mm . The difference in outer diameter between the roller body and the end portions on both sides is set to 0.4 mm or more and 6.0 mm or less, and the outer diameter difference is provided by curved or chamfered step processing or taper processing. The solution casting method according to claim 1 or 2. The solution casting method according to any one of claims 1 to 3 , further comprising an equal-diameter conveying roller having an equal diameter over the entire width direction on the upstream side or the downstream side of the conveying roller . The solution casting method according to claim 4, wherein the conveying roller and the equal-diameter conveying roller are alternately provided.   The temperature of the polymer film when being transported by the transport roller is 40 ° C or more, and the thickness of the polymer film is 25 µm or more and 160 µm or less. Solution casting method. The dope was cast on a support using a casting die, and the dope was peeled off as a polymer film. Then, the dope was transported and dried while holding both ends of the polymer film with a tenter, and the drying occurred. In the solution casting apparatus for cutting and removing both side ends of the polymer film having an ear curl ,
It consists of a roller body having an equal diameter and both end portions having a smaller diameter than that of the roller body. The both end portions of the polymer film from which the tenter is detached and the both end portions having a small diameter are not in contact with each other. A roller for transporting the polymer film , supporting the central portion in the width direction of the polymer film excluding the end by the roller body ,
A solution casting apparatus comprising: a cutting and removing unit that includes a portion of the polymer film that passes through both end portions of the conveying roller in a portion to be cut and removed . 8. The solution casting apparatus according to claim 7, wherein a fluctuation range of the outer diameter of the roller body is less than 0.01 mm . The difference in outer diameter between the roller body and the end portions on both sides is set to 0.4 mm or more and 6.0 mm or less, and the outer diameter difference is provided by curved or chamfered step processing or taper processing. The solution casting apparatus according to claim 7 or 8. 10. The solution casting apparatus according to claim 7 , further comprising an equal-diameter conveying roller having an equal diameter over the entire width direction on the upstream side or the downstream side of the conveying roller . The solution casting apparatus according to claim 10, wherein the transport roller and the equal-diameter transport roller are alternately provided.

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