JP2013107316A - Biaxially oriented polyester film excellent in secondary processability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially oriented polyester film excellent in secondary processability such as printing and coating, which can achieve stable secondary processing without troubles since there is less slackness on the film in the secondary processing, and does not need condition adjustment of a coater especially when the film is a slit roll corresponding to the rim end of a mill roll with the wide width as a film.SOLUTION: The biaxially oriented polyester film is a sequentially biaxially oriented polyester film made of polyester resin which practically primarily consists of polyethylene terephthalate, in which the film is rolled out from a surface of the roll made of the film, and the slack ratio when longitudinally measured is 0.04% or less, wherein the slack ratio is (the maximum value-the minimum value)÷the average value×100.

Description

  The present invention relates to a biaxially oriented polyester film excellent in secondary processability such as printing, coating, and lamination. Specifically, when performing precise functional coating such as antistatic coating, mold release coating, and antireflection coating, biaxial orientation has stable processing suitability without causing slack flapping, meandering, and wrinkles. It relates to a polyester film.

  Conventionally, biaxially oriented polyester films are widely used as various industrial base films because of their excellent transparency, dimensional stability, and chemical resistance. Such a biaxially oriented polyester film is generally stretched in the longitudinal direction between rolls having different rotation speeds, then stretched in the width direction with the film end held in the tenter, and heat-set in the tenter. Manufactured by an axial stretching method and once wound up as a wide and long mill roll. However, in the width direction of the obtained film, the film length in the longitudinal direction is short at the end of the mill roll, and the film length in the longitudinal direction is different in the width direction such that the film length in the longitudinal direction is long at the center. It has been conventionally known that this occurs. This can be confirmed by observing at the exit of the tenter that the central portion is more slack than the end position in the width direction. This phenomenon is particularly prominent at the end of the mill roll, and the difference in film length in the width direction tends to be small at the center. Therefore, when slitting from the mill roll to obtain a slit roll, the slit roll corresponding to the edge of the mill roll has a large difference in the film length in the longitudinal direction, particularly in the width direction. A tension is not applied to a portion that is long in the longitudinal direction, and sagging occurs, causing a phenomenon of meandering and fluttering during film travel. Further, when the sagging is large, there is a problem that wrinkles or creases occur.

  On the other hand, a technique is known in which the difference in length between the center and the end of the mill roll is reduced, and the film is flattened. For example, a technique has been known in which a biaxially oriented polyester film heat-set after biaxial stretching is gradually cooled at a cooling rate of 100 ° C. or less per second to improve the flatness of the film and reduce sagging (for example, (See Patent Document 1). However, such a conventional technique has a problem that a desired film cannot be obtained.

  Further, a technique has been known in which the rail width on the end side that is slack according to the degree of sagging at the end is adjusted so as to be uniform without sagging on the left and right (see, for example, Patent Document 2). However, such conventional technology does not solve the slack of the slit roll corresponding to the end of the wide mill roll. Furthermore, in order to adjust the rail width, the physical property values of the film such as the heat shrinkage ratio are changed, and there is a problem that the target film cannot be obtained.

  In addition, when cooling after heat treatment with a tenter, at least 120 ° C. or more and 160 ° C. or less of air is blown at a wind speed of 2 m / s or more at a speed of 2 m / s over 3 seconds, and then the ambient temperature is 35 ° C. or more and 80 ° C. or more. There has been known a technique in which slack that improves film flatness is reduced by passing through a second chamber controlled to be equal to or lower than 2 ° C. over 2 seconds (see, for example, Patent Document 3). However, such a conventional technique has a problem that a desired film cannot be obtained.

  Moreover, the technique of suppressing the bowing phenomenon and reducing the thermal contraction rate difference of the width direction by heating the position of 30-1000 mm before the longitudinal stretch point of the edge part of a polyester film with a far infrared heater or a near infrared heater was known. (For example, refer patent document 4 etc.). However, this conventional technique has a problem that the end heating position is narrow and is not effective in improving the sag.

JP-A 51-102073 JP 54-73873 A JP 9-277373 A JP 2002-172696 A

In addition, after film formation by the above technology, the film that came out of the tenter can be rolled up as a mill roll without sacrificing productivity, and the mill roll film can be matched to the width and length requested by the customer. Even when slitting and winding up as a slit roll, it becomes possible to wind up without any trouble as well, and even if normal slit functional coating is performed using this slit roll, the film meanders and flutters Such a phenomenon did not occur, and there were no subtle coating irregularities or scratches.
However, even when using a slit roll that can be wound up without any troubles, if a precise functional coating is applied, phenomena such as wobbling or flapping of the film may occur. It has been found that it causes a wound. When such a phenomenon occurs, secondary processing is performed while adjusting tension, roll angle, position, etc., or the use is abandoned.
It has also been found that this phenomenon is more likely to occur closer to the end of the mill roll.

  As a result of examining these unprecedented phenomena in detail, the present inventors have been able to wind the slit roll without meandering, but those slit from the end of the mill roll are in the longitudinal direction in the width direction. Since the film lengths were slightly different, film sagging occurred during running, and it was determined that these phenomena occurred.

  The present invention has been made against the background of such prior art problems. That is, the object of the present invention is that there is little sagging of the film during running of the film in the secondary processing, so there is no trouble due to this, and secondary processing can be performed stably. In particular, to provide a biaxially oriented polyester film excellent in secondary workability such as printing, coating and laminating, which eliminates the need for condition adjustment of the coater even when there is a slit roll corresponding to the edge of a wide mill roll as a film. It is in.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have completed the present invention. That is, according to the first invention of the present invention, it is a sequential biaxially stretched film substantially made of a polyester resin mainly composed of polyethylene terephthalate, and the film is unwound from the surface layer of the roll made of the film, and the longitudinal direction The biaxially oriented polyester film is characterized in that the sag rate is 0.04% or less. In this case, it is preferable to heat the end of the film immediately before stretching in the longitudinal direction when forming a sequential biaxially stretched film made of a polyester resin containing polyethylene terephthalate as a main component.

  According to a second aspect of the present invention, the biaxially oriented polyester according to the first aspect, wherein the maximum value of the principal axis orientation angle measured by a microwave transmission type molecular orientation meter is 20 degrees or more. It is a film.

  According to a third invention of the present invention, in the first and second inventions, the orientations of the principal axis orientation angles measured by the microwave transmission type molecular orientation meter are all the same direction. It is an oriented polyester film.

  According to the present invention, in the biaxially oriented polyester film excellent in secondary processability such as printing, coating, laminating, since there is little sag during film running in the secondary process, fluttering and meandering due to sag due to it, wrinkles, etc. Stable secondary processing is possible without any trouble such as In particular, even if a slit roll corresponding to the edge of the wide mill roll is used as the film, it is possible to make it unnecessary to adjust the conditions of a secondary processing machine such as a printing machine or a coater.

  The polyester used in the present invention is a polyester such as polyethylene terephthalate, polybutylene terephthalate, or polyethylene naphthalate, and may be a mixture or copolymer polyester thereof. As the polyester, a polyester composition containing additives such as an organic or inorganic lubricant, an antioxidant, a heat stabilizer, an ultraviolet absorber, and an antistatic agent is used as long as the effects of the present invention are not impaired. be able to.

  The polyester in the present invention is supplied to a known melt-extrusion apparatus represented by an extruder, and is heated and melted at a temperature equal to or higher than the softening point of the polyester. The melted composition is extruded from a slit-shaped die such as a T-die, and is brought into close contact with a cooling roll and solidified by cooling to obtain a substantially non-oriented polyester film (hereinafter referred to as CA original fabric). The resin may be extruded as a single layer or a laminate. Then, the uniaxially stretched film extended | stretched to the longitudinal direction continuously is obtained by supplying CA original fabric between several rolls. That is, by passing a plurality of rolls set to low peripheral speed rotation (hereinafter referred to as roll groups) and a roll group set to high peripheral speed rotation, the film is tensioned by the speed difference of each roll group in the longitudinal direction. Stretch.

  In this case, the longitudinal draw ratio is preferably 2 times or more, particularly preferably 2.5 times or more. If it is less than 2 times, the thickness unevenness in the vertical direction becomes a problem, and if the stretch ratio in the width direction is continuously increased, it becomes easy to tear in one direction, and the elongation at break and the strength become unbalanced. May occur. In order to enable stable production, the upper limit of the longitudinal draw ratio is about 4.5 times, particularly 4 times from a practical aspect, but is not particularly limited.

  The temperature during stretching in the longitudinal direction is preferably from 80 to 140 ° C, particularly preferably from 100 to 120 ° C. If it is less than 80 degreeC, extending | stretching temperature will be too low and the extending | stretching residue will generate | occur | produce and become a problem. In addition, the stretching stress is large, and the motor load of the rotating roll increases, which may cause a problem that the motor specification upper limit is exceeded. Further, when the temperature exceeds 140 ° C., the unstretched film raw material is fused to a rotating roll when stretched in the longitudinal direction, or the film meanders after longitudinal stretching and breaks off from the clip in the subsequent width stretching. However, there is no particular limitation.

In general, the CA original fabric after extrusion of the polyester resin is easily gripped with a clip by making the end portion thicker than the central portion. In the present invention, when stretching in the longitudinal direction, the film immediately before the stretching section between the final roll of the roll group set to low peripheral speed rotation and the first roll of the roll group set to high peripheral speed rotation. It is preferable to provide means for heating the end. A means for heating the film end is disposed, and the position where the film is substantially heated is preferably a position closer to the center than a position away from the end face of the CA original fabric by a distance corresponding to 12% of the CA original fabric width, more preferably 15 %, And more preferably 20%. If the position is closer to the end than the above position, the effect of improving sag may not be obtained.
Further, the substantially heating position is preferably a position closer to the end than a position corresponding to 33% of the width of the original fabric from the end surface of the CA original fabric, more preferably 30%, and even more preferably 25%. If the above is exceeded, the sagging improvement effect may be saturated or the sagging improving effect may be lost. Conventionally, there has been known a method of heating more strongly only at the thickened end portion in order to reduce bowing, but in order to reduce sagging, heating is performed not only on the thickened portion but also on the flat portion inside the thickened portion. is necessary. For this reason, it is presumed that it is necessary to improve the sag by making the shrinkage stress in the longitudinal direction in the width direction of the film after uniaxial stretching as uniform as possible.

  The heating means for the film end may be located on one or both sides of the front and back surfaces of the film.

  As the heating means of the film end, various heat sources such as hot air, rolls and part rolls that can be installed by dividing a desired temperature and width, and a near infrared heater, a far infrared heater, and the like can be used. Moreover, you may install a shielding board in the center part of the elongate heater which can heat the whole film to the width direction, It does not specifically limit.

The upper limit of the end film temperature at the end of the film is preferably 10 ° C. (vs. center), more preferably 7 ° C. (vs. center), and even more preferably 5 ° C. (vs. Center). If the above is exceeded, the film itself may soften and stick to the roll. The lower limit of the end film temperature is preferably 2 ° C. (vs. center), more preferably 3 ° C. (vs. center), and further preferably 4 ° C. (vs. center). . Below the above, the effect of improving the sag resulting in the present invention may not be obtained.
The central part here means a position having the same distance from both end faces of the film.

  The biaxially oriented polyester film of the present invention may be either one-stage stretching or multi-stage stretching that stretches in two or more stages as a means for stretching in the longitudinal direction, and is not particularly limited.

  The uniaxially stretched film obtained by the above method obtains a biaxially oriented film using a transverse stretching apparatus that performs normal preheating, width direction stretching, heat setting, and cooling. At this time, since the biaxially oriented polyester film is affected by the transverse stretching conditions and the heat setting conditions, the conditions can be appropriately selected by known methods to obtain desired physical properties. Preferably, the above stretching conditions can be performed in the following steps. For example, preheating is performed at a temperature not lower than the melting point and not higher than the melting point of the polymer composition constituting the resin composition. Moreover, as a draw ratio, in the case of biaxial stretching, the area magnification after extending | stretching is 2-30 times with respect to the area before extending | stretching, Preferably it is 9-16 times. The thickness of the biaxially oriented polyester film of the present invention is 12 μm to 250 μm, but is not particularly limited.

  For the biaxially oriented polyester film of the present invention, depending on the purpose, for example, surface treatment by a conventionally known method such as corona discharge treatment, plasma treatment, ozone treatment, chemical treatment, anchor treatment using a known anchor treatment agent, etc. May be given. The antistatic coating agent is not particularly limited as long as it is an alkylsulfonic acid, glycerin ester, polyglycerin ester, or the like, and can impart antistatic properties. The coating method is a conventionally known method such as a reverse roll coating method, a roll knife coating method, a die coating method, or a gravure coating method, and is not particularly limited. Furthermore, it may be a coating by in-line coating.

  The lower limit of the mill roll width formed of the biaxially oriented polyester film of the present invention is preferably 3000 mm, more preferably 4000 mm, and even more preferably 5000 mm. When it is less than the above, the film length in the longitudinal direction is short at the end of the mill roll in the width direction of the film, and the film length in the longitudinal direction is different in the width direction such that the film length in the longitudinal direction is long at the center. The phenomenon may become difficult to express. The upper limit of the mill roll width is preferably 9000 mm, more preferably 7000 mm, and further preferably 6000 mm. If the above is exceeded, the difference in the length in the longitudinal direction between the end portion of the mill roll and the central portion may be too large, and the productivity may deteriorate, but the mill roll width is not particularly limited.

  The lower limit of the slit roll width slit from the mill roll comprising the biaxially oriented polyester film of the present invention is preferably 500 mm, more preferably 700 mm, and even more preferably 1300 mm. If it is less than the above, the difference in the film length in the longitudinal direction in the width direction becomes small, and sagging may hardly occur. The upper limit of the slit roll width is preferably 2500 mm, more preferably 2200 mm, and further preferably 1800 mm. If the above is exceeded, the effect of the biaxially oriented polyester film of the present invention may not be obtained, but the slit roll width slit from the mill roll is not particularly limited.

  The lower limit of the slit roll length slit from the mill roll made of the biaxially oriented polyester film of the present invention is preferably 500 m, and more preferably 2000 m. If it is less than the above, it is likely to be affected by the core portion of the slit roll, and the effect of the biaxially oriented polyester film of the present invention may not be obtained, but the length of the slit roll is not particularly limited.

  Sequential biaxially stretched film made of a polyester resin containing polyethylene terephthalate as a main component of the present invention, and the sag rate when unrolled from the surface layer of the slit roll made of the film and measured in the longitudinal direction is Preferably it is 0.04% or less, and the lower limit of the sag rate is preferably 0%. Sag occurs, causing a phenomenon of meandering and fluttering during film travel. When the sag ratio exceeds 0.04%, sag occurs during film running during secondary processing, and film meandering, fluttering, and wrinkling may occur.

  In the prior art, improvement of sagging prevention with a mill roll wound with a film immediately after film formation was the main focus, and the problem of sagging with the mill roll was almost solved. Therefore, the fine slack is stretched, and the normal functional coating is caused by the fact that the slack referred to in the present invention is not visible and the film that is stored after winding is slightly wound even if the slack is large. It is considered that problems in secondary processing such as these did not become obvious. However, it has been found that problems arise in secondary processing such as more precise functional coatings.

The principal axis orientation angle of the biaxially oriented polyester film of the present invention measured with a microwave transmission type molecular orientation meter is preferably 20 degrees or more, more preferably 25 degrees or more, and further preferably 28 degrees or more. . Above 20 degrees, the effect of the present invention is particularly remarkable.
The upper limit of the main axis orientation angle is not particularly limited in the present invention, but the upper limit is preferably 45 degrees, more preferably 40 degrees, and still more preferably 38 degrees. If it exceeds 45 degrees, problems such as distortion may occur at the time of heat shrinkage in the drying process after coating in the secondary processing. Moreover, it is preferable that the directions of the principal axis orientation angles in the full width direction of the film are all in the same direction.

Next, although an example of the manufacturing method of this invention film is demonstrated, this is a specific example to the last, and does not restrain the content of this invention.
The physical properties, characteristics measurement and evaluation methods used in the present invention are described below.

(1) Sag rate In a slit roll wound up to a diameter of 600 mm or more, first, a surface layer of the slit roll is prepared so as to obtain a clean surface layer without wrinkles, winding deviation, air accumulation, dents, and pressing. Subsequently, a hole is made in the slit roll surface layer at a pitch of 50 mm in the width direction from the end of the slit roll to the extent that several films are penetrated with a needle such as a thumbtack, and the longitudinal direction (roll circumferential direction) from the surface layer of the slit roll. In order to obtain a needle hole interval of 3 m or more, the entire film width is sampled without wrinkles. Thereafter, the distance between the needle holes in the longitudinal direction of the obtained sample was measured with a measure without applying unnecessary tension except that the sample was flat on a flat table. The length of the needle hole in the longitudinal direction is measured at 3m or more, the scale of the measure is read to the order of 0.1mm, the sag rate is calculated from the maximum value, the minimum value and the average value according to the following formula. The figures are rounded off.

  Sag rate = (maximum value−minimum value) ÷ average value × 100

(2) Main axis orientation angle The main axis orientation angle was measured using a microwave molecular orientation meter using a sample cut out with a dimension of 140 mm in the longitudinal direction and 100 mm in the width direction as a measurement sample. As a microwave molecular orientation meter, a molecular orientation meter MOA-6004 of Oji Scientific Instruments Co., Ltd. was used. The largest value in the full width direction of the slit roll was determined as the maximum value.

(3) Intrinsic viscosity 0.1 g of a chip sample is precisely weighed and dissolved in 25 ml of a mixed solvent of phenol / tetrachloroethane = 6/4 (mass ratio), and 0.4 g / dl at 30 ° C. using an Ostwald viscometer. The flow time of a solution having a concentration of 5 was measured, and the Huggins constant was calculated from the time ratio on the assumption that the constant of Huggins was 0.38. In addition, the measurement was performed 3 times and the average value was calculated | required.

(4) Secondary processing suitability Using a 3-head coater manufactured by Okazaki Kikai Co., Ltd., silicon coating was performed at an unwinding tension of 200 N / m and a speed of 100 m / min. The state of fluttering and wrinkling due to meandering and sagging during film running was observed, and the evaluation was classified as follows as the suitability for secondary processing.
○: Stable processing is possible without any problem.
Δ: Some adjustment of conditions such as tension and roll parallelism is necessary, but it can be processed somehow.
×: Even if the conditions are adjusted, the meandering, sagging or wrinkles do not converge and the processing is stopped.

(5) Film temperature Using CT-SF15-C3 (compact and high-precision non-contact thermometer) of optris, the central part in the width direction of the CA raw fabric and the film end are the measurement position at the central position of the heating width. did. Also, the thermometer is installed immediately after the film passes from the low-speed rotating final roll in the longitudinal stretching apparatus, or when a heating means device such as an IR heater is installed, immediately after the film passes through the heating means device, The film temperature was measured at a distance of 200 mm.

Example 1
Polyethylene terephthalate pellets (intrinsic viscosity 0.62 dl / g) containing 0.1% by weight of a sufficiently dried inorganic lubricant are supplied to an extruder, melted at 285 ° C., extruded into a film form from a T die, and a direct current high voltage Was applied to the cooling roll and solidified by cooling to obtain a substantially non-oriented polyester film (hereinafter referred to as CA original fabric) having a thickness of 350 μm. This substantially non-oriented polyester film was led to a longitudinal stretching apparatus comprising a group of rolls set to low-speed rotation and a roll group set to high-speed rotation. In the longitudinal stretching apparatus described above, a roll provided with a dielectric heating device that enables the low-speed rotation final roll to set a temperature in the width direction and a width at which the temperature becomes desired is used. By adjusting the temperature of the roll equipped with the dielectric heating device and the heating width to both ends of the CA raw fabric, the heating width of both ends of the CA raw fabric is 15% vs. CA raw fabric width, + 7 ° C. (vs. center) Then, the film was stretched 3.5 times at 90 ° C. in the longitudinal direction. Next, the film was stretched 4.2 times in the transverse direction in a tenter, and then heat treated at 225 ° C. while performing a 3% relaxation treatment to obtain a biaxially oriented polyester film having a thickness of 25 μm. The biaxially oriented polyester film described above is once wound on a long and wide mill roll having a width of 5000 mm and a length of 10,000 m, and then a slit roll having a width of 1300 mm and a length of 2000 m is set from the end edge to a width of 100 mm. Obtained.

(Example 2)
By adjusting the heating width of both ends of the CA raw fabric of the roll equipped with the dielectric heating device and the temperature of the heating width, the heating width of both ends of the CA raw fabric is set to 20% with respect to the CA original fabric width, + 5 ° C. ( After heating so as to be in the center), a slit roll made of a biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the film was stretched 3.2 times at 100 ° C. in the longitudinal direction.

(Example 3)
A slit roll made of a biaxially oriented polyester film was obtained in the same manner as in Example 1 except that it was heat-treated at 235 ° C. while performing 5% relaxation treatment after transverse stretching with a tenter.

Example 4
Extruded in a film form from a T-die and electrostatically adhered to a cooling roll using an electrode to which a direct current high voltage was applied, and cooled and solidified to obtain a substantially non-oriented polyester film (hereinafter referred to as CA original fabric) having a thickness of 1100 μm. A slit roll made of a biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the thickness was 75 μm.

(Comparative Example 1)
Example except that the low-speed rotation final roll of the longitudinal stretching apparatus does not use a roll equipped with a dielectric heating device that allows the temperature and the width to be the temperature to be set as desired in the width direction, and does not heat. In the same manner as in Example 1, a slit roll made of a biaxially oriented polyester film was obtained.

(Comparative Example 2)
By adjusting the heating width to both ends of the CA original fabric of the roll equipped with the dielectric heating device of the longitudinal stretching apparatus and the temperature of the heating width, the heating width of both ends of the CA original fabric is 7% vs. CA original fabric width. The slit roll which consists of a biaxially-oriented polyester film was obtained like Example 1 except having heated so that it might become +7 degreeC (vs. center).

(Comparative Example 3)
Without using a roll equipped with a dielectric heating device for the low-speed rotation final roll of the longitudinal stretching device, a near-infrared heater (IR heater) is placed at both ends so that the width of the near-infrared heater (IR heater) is 5% versus the CA raw fabric width. A slit roll made of a biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the CA raw fabric end was heated to + 7 ° C. (vs. center).

  The results are shown in Table 1.

  The biaxially oriented polyester film excellent in secondary processability of the present invention relates to a biaxially oriented polyester film excellent in secondary processability such as printing, coating, and laminating, and includes an antistatic coating, a release coating, and an antireflection coating. When performing precise functional coatings such as coatings, it can be used in a wide range of application fields because it provides stable processability without fluttering, meandering, and wrinkles. It is important to contribute to

Claims (3)

A sequential biaxially stretched film made of a polyester resin containing polyethylene terephthalate as a main component. The sag rate when measured in the longitudinal direction is 0.04% when the film is unwound from the surface layer of a roll made of the film. A biaxially oriented polyester film characterized by:
Sag rate = (maximum value−minimum value) ÷ average value × 100   The biaxially oriented polyester film according to claim 1, wherein the maximum value of the principal axis orientation angle measured by a microwave transmission type molecular orientation meter is 20 degrees or more. 3. The biaxially oriented polyester film according to claim 1, wherein the orientation directions of the principal axis orientation angles measured with a microwave transmission type molecular orientation meter are all the same direction.