JP2003145562A - Method for producing film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a film which is excellent in processability, resistant to curling in water, and suitable for the production of a polarizing plate. SOLUTION: In each of the roll drying parts 16 and 18 of an apparatus 10 for producing the film by the method, at least a part is a high temperature drying zone for supplying drying air of at least 115 deg.C for drying. In the zone, (1) the air is supplied from the support surface 26A side of the film 26, (2) the air is supplied from the air surface 26B side of the film 26 to control the flow velocity of the drying air to be blown to the film 26 to be 3 m/s or below, or (3) the air is supplied from both sides of the film 26. When the film 26 is immersed in water of 25 deg.C, the radius of curvature of the curled film 26 is at least 25 mm. When the film 26 is divided into two in the thickness direction, the plasticizer content ratio between the support surface 26A side and the air surface 26B side of the film 26 is 1.2-2.0.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a film manufacturing method, and more particularly to a film manufacturing method for manufacturing a cellulose acylate film used as a polarizing plate protective film by a solution film forming method.

[0002]

2. Description of the Related Art Cellulose acylate films (especially cellulose acetate films) have low birefringence and transparency, as well as appropriate moisture permeability. Therefore, the cellulose acylate film is suitable for a polarizing plate manufacturing process and is widely used as a polarizing plate protective film. In the polarizing plate manufacturing process, the cellulose acylate film is washed with water,
A polarizing plate is manufactured by bonding the polarizing film and then punching it.

By the way, a cellulose acylate film is usually produced by a solution casting method. That is, it is produced by casting a concentrated solution (dope) on a running endless support, drying the dope to give a self-supporting property, and then continuously stripping and further drying. The film produced by this solution casting method has good flatness, and
Since it has a small optical anisotropy, it is suitable as a polarizing plate protective film. However, when the dope is dried on the support, a concentration distribution of the solvent occurs in the thickness direction of the dope, which causes a problem that the hydrophobic plasticizer moves according to the solvent distribution. The hydrophobic plasticizer is blended in an appropriate amount with respect to the hydrophilic cellulose acylate in order to adjust the dimensional stability against humidity. Therefore, when the plasticizer moves and the difference in hydrophobicity occurs in the thickness direction, the degree of curling when the film absorbs water becomes large, and folds or wrinkles occur in the process of bonding with the polarizing film, or coating of the functional layer. In this case, various problems occur such as coating unevenness or contact during transport to generate dust. Further, there is a drawback that the completed polarizing plate is likely to be warped.

As a method of adjusting the degree of curl, Japanese Patent Publication No. 54-25682 discloses a method of blowing hot moist air having a dew point of 40 ° C. or more onto the surface to be curled. Further, in JP-A-4-281448, a solvent gas or 100 to 150 ° C. is applied to the surface to be curled.
The method of spraying water vapor is described. These methods are very effective as means for controlling curl under a specific atmosphere. However, in recent years, the drying temperature of the film must be increased more and more, and it has become impossible to sufficiently suppress the curl in high humidity, especially in water, only by these methods.

Further, Japanese Patent Laid-Open No. 2001-200098 describes a method of introducing a propionyl group or a butyryl group as a 6-position substituent of cellulose. With this method, curling in water can be reduced, but the problem of higher raw material cost compared to general cellulose acetate, and changes in film characteristics such as birefringence value and mechanical strength, which result in a suitable polarized light. There is a problem that the plate protective film cannot be manufactured.

Further, in order to prevent curling in water, it is known that peeling from the support with a very high volatile content of 150% or more based on the dry weight of the film and drying from both sides are effective. ing. Peeling with such a high volatile content can be achieved by cooling the temperature of the support to 10 ° C. or lower, as described in JP-B-5-17844. However, when the film thus produced is used as a polarizing plate protective film, there is a problem that chipping or peeling occurs at the edge portion during punching, and the yield is likely to be reduced.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is a film which is excellent in processability and has a small curl in water and which is suitable for manufacturing a polarizing plate. It is intended to provide a manufacturing method.

[0008]

In order to achieve the above-mentioned object, the present invention comprises casting a concentrated solution on a support, peeling it off as a film, and blowing dry air to the film to dry it. In the film manufacturing method for manufacturing a film, a high temperature drying zone in which the temperature of the drying air is 115 ° C. or higher is provided, and the drying air of 115 ° C. or higher is in contact with the support in the high temperature drying zone. When the dry air of 115 ° C. or higher is blown from the support surface side, or from the air surface side opposite to the support surface, or from both the support surface side and the air surface side, In addition, the wind speed of the dry air on the air surface is set to 3 m / s or less.

The inventor of the present invention provides a film having a suitable heat dimensional stability by providing a high temperature drying zone in which a film peeled from a support is dried by blowing dry air at 115 ° C. or higher. I found a thing. Also, 1
It was found that when spraying dry air at 15 ° C or higher, the processability of the film and the curl in water change depending on the wind direction and speed of the dry air. Then, in order to produce a film having good processability and a small curl in water, dry air of 115 ° C. or higher is blown from the side of the support surface, or is blown from both the side of the support surface and the side of the air surface. It has been found that it may be applied or blown from the air surface side so that the wind speed on the air surface is 3 m / s or less. The present invention has been made on the basis of such knowledge, and provides a high temperature drying zone for blowing dry air at 115 ° C. or higher, and regulates the wind direction and velocity of the drying air in the high temperature drying zone as described above. By doing so, a film having excellent processability and having a small curl in water is produced. The film thus obtained is suitable for a manufacturing process of a polarizing plate, and a polarizing plate can be manufactured without causing breakage or chipping of the film.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the film manufacturing method according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram showing the overall construction of a manufacturing apparatus 10 using the present invention.

As shown in FIG. 1, the manufacturing apparatus 10 includes a casting unit 12, a tenter drying unit 14, and roll drying units 16 and 18.
It consists of

The casting part 12 has a pair of drums 20, 20.
Is provided, and an endless band (corresponding to a support) 22 is wound around the pair of drums 20, 20. The band 22 is made of, for example, stainless steel and has a mirror-finished surface. This band 22
Runs by rotating one of the pair of drums 20, 20 and circulates around the pair of drums 20, 20.

A dope extruded in a film form from a die 24 is cast on the orbiting band 22. In addition to cellulose acylate, a suitable amount of hydrophobic plasticizer is added to this dope. The dope cast on the band 22 is dried with, for example, hot air, and after being self-supporting to some extent, it is peeled from the band 22. Both ends of the peeled film 26 are fixed by clips or pins (not shown) in order to ensure flatness, and the film 26 is conveyed to the tenter drying unit 14. In the tenter drying unit 14, the film 26 is conveyed while being tensioned in the width direction, and is dried to some extent. Tenter drying section 1
After 4, the film 26 is further dried in roll dryers 16, 18.

In the roll dryers 16 and 18, the film 2
The film 26 is dried by blowing hot air (dry air) on the film 26 while the film 6 is conveyed by being wound on a plurality of rolls 32, 32, .... The film 26 thus dried is conveyed to the curl correction device 28 as needed, and solvent gas or water vapor is blown from the curl correction device 28 to the air surface 26B of the film 26 to adjust the curl of the film 26. It The curl-adjusted film 26 is rolled into a roll film 30.

The curl correction device 28 is used to form the film 26.
When water vapor is sprayed on the film 26, it is desirable to lower the temperature of the film 26 as long as the water vapor does not condense on the film 26. At this time, the temperature of the film 26 may be adjusted by the temperature of the room air supply, the cooling contact roll, or the temperature of the backup roll during processing.

By the way, the above-mentioned roll drying sections 16 and 1
8 is a high temperature drying zone in which at least a part thereof is blown with drying air of 115 ° C. or higher. In the high temperature drying zone, dry air of 115 ° C. or higher is supplied by any of the following methods. That is, dry air is supplied to
6 is sprayed from the support surface 26A side. Air surface 26B
Dry air is blown from the side of the air surface 26B so that the wind speed at 3 m / s or less becomes. Dry air is blown from both the support surface 26A and the air surface 26B. The direction of blowing the dry air is not particularly limited, but in order to prevent dust in the process from being taken up and attached to the film, the air supply port (not shown) should be on the ceiling side and the exhaust port (not shown). (Not shown) is preferably provided on the floor side for downflow. Therefore, the manufacturing apparatus 10 shown in FIG. 1 is suitable for supplying air by the method of, for example, by providing an air supply port on the ceiling surface of the roll drying unit 16 and an exhaust port on the floor surface, Dry air of 115 ° C or higher is used as the support surface 26A.
Downflow from the side.

The exhaust ports of the high temperature drying zone may be provided on both ends of the film 26 in the longitudinal direction, or may be provided on both the ceiling surface and the floor surface before and after the air supply position.

Further, the roll drying sections 16 and 18 may be provided not only with a high temperature drying zone but also with a low temperature drying zone for blowing dry air of less than 115 ° C. The method of supplying air in the low-temperature drying zone is not limited to the above-described methods (1), and may be supplied by methods other than (1). Furthermore, if all of the roll drying sections 16 and 18 are used as the low temperature drying zone, the thermal dimensional stability of the film 26 will be deteriorated, so it is advisable to provide the high temperature drying zone in any step until winding.

The film 26 thus dried and manufactured is used, for example, as a protective film of a polarizing plate in the manufacturing process of the polarizing plate. In the manufacturing process of the polarizing plate, the film 26 is washed with water, attached to the polarizing film, and then punched to manufacture the polarizing plate.

Next, the operation of the manufacturing apparatus 10 configured as described above will be described.

Since the manufacturing apparatus 10 is provided with the high temperature drying zone in which the drying air is 115 ° C. or more, the film 26 can be dried quickly and the film 26 having good thermal dimension stability can be obtained. Obtainable. However, since dry air of 115 ° C or higher has a high drying capacity,
Depending on the wind direction and speed of the dry air, the curl in water may become large. However, in the present embodiment, 1
Since the wind direction and speed of the dry air of 15 ° C. or higher are regulated by the method (1) to (3), the thermal dimensional stability of the film 26 can be improved while preventing the curl in water from increasing.

That is, in the method (1), since dry air is blown to the side of the support surface 26A containing a large amount of plasticizer to dry it, even if dry air of 115 ° C. or higher is blown to the film 26, the underwater curl does not increase.

In the method (1), dry air of 115 ° C. or more is blown to the air surface 26B side having less plasticizer. However, when the air speed on the air surface 26B is set to 3 m / s or less, abrupt drying occurs. Was prevented. As a result, the curl in water that causes defective manufacturing of the polarizing plate does not deteriorate.

Further, in the method (1), dry air of 115 ° C. or higher is blown to the air surface 26B side having less plasticizer, but since dry air of 115 ° C. or higher is blown to the support surface 26A side as well. The film 26 is dried substantially evenly on both sides. Therefore, the underwater curl does not increase.

As described above, by spraying dry air at 115 ° C. or higher by any one of the above methods, the film 26 can be dried without increasing the curl in water. The film 26 thus obtained has the following characteristics regarding curl characteristics and plasticizer distribution. That is, 25
The curvature radius of the curl when immersed in water at ℃ is 25 mm or more, and when the film 26 is divided into two in the thickness direction, the plasticizer content of the support surface 26A and the air surface 26B obtained by gas chromatography or the like. Ratio is 1.2 ~
It has the characteristic of being 2.0.

The radius of curvature in water at 25 ° C. is 25 mm
The film 26 having the above characteristics has a very small curl when washed with water, for example, and is suitable for a step of laminating with a polarizing film. That is, since the curl at the time of washing with water is very small, the film 26 after washing with water can be easily attached to the polarizing film, and at the same time, the produced polarizing plate can be prevented from warping.

Further, the film 26 having the characteristic that the plasticizer content ratio is 1.2 to 2.0 is suitable for both the laminating step with the polarizing film and the punching step. That is, when the plasticizer content ratio is as small as less than 1.2,
When punching, chipping or peeling occurs at the edge part, but by setting the plasticizer content ratio to 1.2 or more, the workability at punching is improved, and punching is performed without chipping or peeling. be able to. Further, when the plasticizer content ratio exceeds 2.0, curling in water becomes large and folds and wrinkles occur in the laminating step, but the plasticizer content ratio should be 2.0 or less. As a result, the curl in water becomes small, and the film can be reliably attached to the polarizing film without being bent or wrinkled.

A more preferable range of the plasticizer content ratio is 1.3 to 1.8, and more preferably 1.4 to 1.8.
It is 1.7.

The plasticizer content ratio is influenced not only by the method of supplying dry air, but also by the volatile matter when the film 26 is peeled from the band 22. For example, this peeled volatile matter is based on the dry weight of the film. If it is 150% or more, the plasticizer content ratio tends to be less than 1.2, which is not preferable. Therefore, the stripped volatile matter needs to be smaller than 150%. The peeled volatile matter is preferably 120% or less, and 10
0% is more preferable, and 80% or less is further preferable. However, when the peeled volatile content is 25% or less, productivity is remarkably impaired and the plasticizer amount difference between the support surface / air surface becomes too large, so 25% or more is preferable.

As described above, according to the manufacturing apparatus 10 of the present embodiment, it is possible to manufacture the film 26 which has a small curl in water and is excellent in punching workability. Therefore, it is possible to manufacture the film 26 suitable for the manufacturing process of the polarizing plate in which the film 26 is washed with water and bonded to the polarizing film and punched, and the yield can be improved in the manufacturing process of the polarizing plate. it can.

The above-mentioned manufacturing apparatus 10 is 115 ° C.
This is an example suitable for supplying high-temperature dry air by the method, but when supplying the air by the method, the manufacturing apparatus 34 shown in FIG. 2 is preferable. The manufacturing apparatus 34 shown in FIG.
The film 26 that has passed through the tenter drying unit 14 is turned upside down and introduced into the roll drying units 16 and 18. The roll dryers 16 and 18 are provided with a high-temperature drying zone, a ceiling surface side of the high-temperature drying zone is provided with an inlet (not shown) for dry air of 115 ° C. or higher, and an exhaust port (not shown) is provided on the floor. (Illustration) is provided. Therefore, 115 ° C
The above dry air is downflowed and blown to the air surface 26B side of the film 26. At that time, the air surface 26
By controlling the wind speed at B to 3 m / s or less, it is possible to prevent the underwater curl from increasing.

Further, FIGS. 1 and 2 show examples of the manufacturing apparatuses 10 and 34 provided with the band type casting portion 12, but FIG.
As shown in FIG. 3, a manufacturing apparatus 3 having a drum-shaped casting portion 38
The present invention may be applied to 6. That is, a rotating drum 40 is installed in the casting unit 38, and the dope extruded from the die 24 is cast onto the surface of the drum 40.
The cast dope is peeled after it has self-supporting property by cooling, and is introduced into the tenter drying section 42 as the film 26. The introduced film 26 is dried to some extent and then introduced into the roll drying units 16 and 18. Even in this case, by providing the roll drying sections 16 and 18 with the high temperature drying zone, it is possible to manufacture the film 26 which has a small curl in water and is excellent in punching workability.

[0034]

EXAMPLES As Examples 1 and 2 and Comparative Examples 1 and 2, films having different characteristics were produced, saponified, and then polarizing plates were produced using the films. less than,
The production conditions of each film, the dope preparation conditions, the saponification treatment conditions, and the polarizing plate preparation conditions are shown. (Film Manufacturing Conditions of Example 1) The film 26 was manufactured by casting the dope A using the manufacturing apparatus 10 of FIG. That is, the dope A is extruded from the die 24 and the band 22
After being cast on the surface and dried until it becomes self-supporting, the film 26 is peeled off from the band 22, and the tenter drying section 14
Introduced. At this time, the volatile matter at the time of peeling was 66%.

In the tenter drying section 14, the dry air of 130 ° C. is supplied from both sides of the film 26,
The maximum wind speed of the dry air blown onto was set to 3.0 m / s. Further, in the roll drying unit 16, the support surface 2
Air surface 26B by supplying 120 ° C dry air from the 6A side
The air was exhausted from the side, and in the roll drying section 18, dry air of 140 ° C. was supplied from the side of the support surface 26A of the film 26 and exhausted from the side of the air surface 26B. At this time, the maximum velocity of the drying air blown on the film 26 in each of the roll drying units 16 and 18 was 5.0 m / s. Next, the air surface 26B of the film 26 dried by the roll dryers 16 and 18 was blown with steam at 145 ° C. at a rate of 3 g / m ^{2 by} the curl correction device 28, and then the film 26 was wound. The film 26 thus produced had a film thickness of 79 μm and a curl radius of curvature in water at 25 ° C. of 33 mm. Further, the plasticizer content ratio when the film 26 is divided into two in the thickness direction (support surface 26A side / air surface 26B side).
Was 1.63. (Film manufacturing conditions of Example 2) Using the manufacturing apparatus 34 of FIG. 2, the dope A was cast and the film 26 was manufactured. That is, the dope A is extruded from the die 24 and the band 22
After being cast on the surface and dried to have self-supporting property, the film 26 was peeled off and introduced into the tenter drying section 14. At this time, the volatile matter at the time of peeling was 70%.

In the tenter drying section 14, dry air at 110 ° C. is supplied from both sides of the film 26 to remove the film 26.
The maximum air velocity of the dry air blown onto was set to 10.0 m / s. In the roll drying unit 16, the air surface 2
Drying air of 120 ° C is supplied from the 6B side to support surface 26
Exhaust from the A side, and in the roll drying unit 18, the film 26
Dry air of 130 ° C. was supplied from the air surface 26B side and was exhausted from the air surface 26B side. At this time, the maximum speed of the drying air blown onto the film 26 in each of the roll drying units 16 and 18 was 1.5 m / s. Next, the air surface 26B of the film 26 dried by the roll drying units 16 and 18 was sprayed with steam at 145 ° C. at a rate of 8 g / m ^{2 on} the air surface 26B of the film 26, and then the film 26 was wound. The film thickness of the film 26 thus produced was 79 μm, and the curl radius of curvature in water at 25 ° C. was 35 mm. Further, the plasticizer content ratio when the film 26 is divided into two in the thickness direction (support surface 26A side / air surface 26B side).
Was 1.61. (Film Manufacturing Conditions of Comparative Example 1) Using the manufacturing apparatus 34 shown in FIG. 2, the film 26 was manufactured by casting the dope A. That is, the dope A is extruded from the die 24 and the band 22
After being cast on the surface and dried to have self-supporting property, the film 26 was peeled off and introduced into the tenter drying section 14. At this time, the volatile matter at the time of peeling was 70%.

In the tenter drying section 14, the dry air of 110 ° C. is supplied from both sides of the film 26 to remove the film 26.
The maximum air velocity of the dry air blown onto was set to 10.0 m / s. In the roll drying unit 16, the air surface 2
Drying air of 120 ° C is supplied from the 6B side to support surface 26
Exhaust from the A side, and in the roll drying unit 18, the film 26
Dry air of 130 ° C. was supplied from the side of the air surface 26B, and was exhausted from the side of the support surface 26A. At this time, the maximum velocity of the drying air blown onto the film 26 in each of the roll drying units 16 and 18 was 7.0 m / s. Next, the air surface 26B of the film 26 dried by the roll drying units 16 and 18 was sprayed with steam at 145 ° C. at a rate of 8 g / m ^{2 on} the air surface 26B of the film 26, and then the film 26 was wound. The film 26 thus produced had a film thickness of 79 μm and a curl radius of curvature in water at 25 ° C. of 25 mm. Further, the plasticizer content ratio when the film 26 is divided into two in the thickness direction (support surface 26A side / air surface 26B side).
Was 1.67. (Film Manufacturing Conditions of Comparative Example 2) The film 26 was manufactured by casting the dope B using the manufacturing apparatus 36 shown in FIG. That is, the dope B was extruded from the die 24, cast on the drum 40 having a surface temperature of −3 ° C., and when it had self-supporting property, it was peeled off as the film 26 and introduced into the tenter drying section 42. At this time, the volatile content at the time of peeling is 270%
Met.

In the tenter drying unit 42, dry air of 80 to 130 ° C. is supplied from both sides of the film 26, and the maximum speed of the dry air blown onto the film 26 is 10.0 m /
s. In the roll drying unit 16, 120 ° C. dry air is supplied from the support surface 26A side and exhausted from the air surface 26B side. Was air-supplied and exhausted from the air surface 26B side. At this time, the maximum velocity of the drying air blown onto the film 26 in each of the roll drying units 16 and 18 was 7.0 m / s. Next, the air surface 2 of the film 26 dried by the roll dryers 16 and 18
6B, curl corrector 28 with steam at 145 ° C. 3 g /
After spraying in an amount of m ² , it was wound up. The film 26 thus manufactured has a film thickness of 79 μm,
The curl radius of curvature in water at 100C was 100 mm.
Further, the plasticizer content ratio (support surface 26A side / air surface 26B side) when the film 26 is divided into two in the thickness direction is:
It was 1.08. Preparation of Dope A Cellulose triacetate (substitution degree 2.8) 89.3% by weight, triphenylphosphate 7.1% by weight, biphenyldiphenylphosphate 3.6% by weight Solid content 100 parts by weight As opposed to
A silica fine particle dispersion liquid was appropriately added, and further, a mixed solvent of 87% by weight of dichloromethane and 13% by weight of methanol was appropriately added and dissolved by stirring to prepare a dope. The solid content concentration of the dope was 19.0%. Preparation of Dope B Cellulose triacetate (substitution degree 2.8) 89.5% by weight, triphenylphosphate 7.0% by weight, biphenyldiphenylphosphate 3.5% by weight Solid content 100 parts by weight As opposed to
A mixed solvent consisting of 82% by weight of methylene chloride, 15% by weight of methanol and 3% by weight of n-butanol was appropriately added and dissolved by stirring to prepare a dope having a solid content concentration of 23.0%. (Saponification treatment) The produced film 26 was heated at 50 ° C for 1.5
After treating with N and NaOH aqueous solution for 180 seconds, it was neutralized, washed with water and dried to saponify the surface. (Production of Polarizing Plate) PVA film (75 made by Kuraray Co., Ltd.)
μm), iodine 0.3 g / l, potassium iodine 18.0
Immerse in g / l aqueous solution at 25 ℃, and add 80g boric acid.
/ L, potassium iodide 30g / l, zinc chloride 10g /
It was stretched 5.0 times in an aqueous solution at 50 ° C. 60 ° C
After drying for 5 minutes at PVA (PVA manufactured by Kuraray Co., Ltd.)
-117H) Using a 4% aqueous solution as an adhesive, the film 26 that has been subjected to a fighting treatment is washed with water to remove dust on the surface, and then continuously sandwiched with a stretched PVA film with a nip roll to apply pressure to both surfaces. Further, it was dried at 80 ° C. to obtain a polarizing plate. The film immersion time in the dyeing solution was appropriately adjusted so that the transmittance of the polarizing plate was 42 ± 0.5%, and the polarization degree of the obtained polarizing plate was 99.7 to 99.9%. (Punching of Polarizing Plate) A circular punching blade having a diameter of 30 mm was applied to the polarizing plate, and the blade was hit with a hammer to punch the polarizing plate to which the film 26 was attached.

Table 1 shows the results of producing a polarizing plate under the above conditions.

[0040]

[Table 1] As can be seen from Table 1, in Comparative Example 1, the dry air of 115 ° C. or higher was blown onto the air surface 26B at a wind velocity higher than 3 m / s, so that the obtained film 26 had a radius of curvature of 2 in water.
It was very small at 2 mm, and when it was washed with water, it was greatly curled toward the support surface 26A. Therefore, the handling property in the laminating step was deteriorated, and the film 26 was broken on the transport path roll in the production of the polarizing plate. In addition, since the polarizing plate manufactured by using the film 26 of Comparative Example 1 has a large warp, it was difficult to attach it to glass in manufacturing the polarizing plate.

On the other hand, in Example 2, dry air of 115 ° C. or higher was blown onto the air surface 26B at a wind speed of 3 m / s or lower, so that the obtained film 26 is easy to handle in the bonding step. The physical properties were well balanced with punching workability.

In Example 1, dry air at 115 ° C. or higher is blown from the side of the support surface 26A or from both sides, so that the handling properties and punching workability in the laminating process are well balanced. showed that.

On the other hand, in Comparative Example 2, the exfoliated volatile matter was 270.
%, The obtained film 26 had a plasticizer content ratio of 1.08, which was extremely small, and the processability was deteriorated.
Therefore, in the punching process, peeling from the polarizing film was observed at several places on the circumference of the punching edge.

In the above test, the radius of curvature in water was measured by cutting the completed film 26 into a width of 35 mm and a length of 3 mm, immersing the film 26 in water at 25 ° C. for 30 minutes, and then reading the radius of curvature.

When the weight (g) of the film sample was A and the weight (g) of the film sample after drying for 1 hour in an 115 ° C. air thermostat was B, the volatile content ( %) = (A−B) / B × 100.

The plasticizer content ratio is such that the film 26 is scraped from either surface with a double-edged razor, etc. until the film thickness is halved, the uncut parts of the film are dissolved in chloroform, and the amount of the plasticizer is determined by gas chromatography. The graph was analyzed. This was performed on both sides, and the value of the plasticizer content on the support surface 26A side was divided by the value of the plasticizer content on the air surface 26B side. A Shimadzu GC-14A gas chromatograph was used for the analysis, and OV-17 was used as the column packing material.
Was analyzed at a column temperature of 280 ° C.

[0047]

As described above, according to the film manufacturing method of the present invention, the film peeled from the support is provided with a high temperature drying zone for blowing dry air of 115 ° C. or more to dry the film, In the drying zone, dry air of 115 ° C or higher is blown from the support surface side, from both the support surface side and the air surface side, or from the air surface side so that the wind speed on the air surface is 3 m / s or less. Therefore, it is possible to produce a film having excellent processability and having a small curl in water. The film thus obtained is
It is suitable for the manufacturing process of a polarizing plate, and a polarizing plate can be manufactured without causing breakage or chipping of the film.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing the overall configuration of a manufacturing apparatus using the present invention.

FIG. 2 is a conceptual diagram showing an overall configuration of a manufacturing apparatus provided with a high temperature drying zone different from that in FIG.

FIG. 3 is a conceptual diagram showing the overall configuration of a casting apparatus different from that in FIG.

[Explanation of symbols]

10 ... Manufacturing apparatus, 12 ... Casting section, 14 ... Tenter drying section, 16, 18 ... Roll drying section, 20 ... Drum, 22 ...
Band, 24 ... Die, 26 ... Film, 26A ... Support surface, 26B ... Air surface, 28 ... Curl correction device, 30 ... Roll film, 32 ... Roll, 34 ... Manufacturing device, 36 ...
Manufacturing equipment, 38 ... Casting section, 40 ... Drum, 42 ... Tenter drying section

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Claims (2)

[Claims] 1. A film production method for producing a film by casting a concentrated solution on a support, peeling it off as a film, and blowing the film with dry air to dry the film. Of 115 ° C. or higher is provided, and in the high temperature drying zone, the dry air of 115 ° C. or higher is supplied from the side of the support surface which is in contact with the support, or the side of the air surface opposite to the support surface. From
Alternatively, while blowing from both the support surface side and the air surface side and blowing the dry air of 115 ° C. or higher from the air surface side, the wind speed of the dry air on the air surface is set to 3 m / s or less. A film manufacturing method characterized by the above. 2. The film according to claim 1, wherein after drying the film with the dry air, steam at 100 to 150 ° C. is blown to the air side of the film to wind the film. Production method.