JPH11198228A - Inline coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for coating water-based coating material or the like having good productivity and quality such as thickness irregularities during a film making process, a manufacturing method of a film employing the method, and also form a simultaneously biaxially orientated film that combines high quality and high productivity done by the method. SOLUTION: The inline coating method is featured such that after a molten resin film is allowed to be in close contact with a cooling medium to thereby be solidified by cooling and then a coating material is applied to the cooled film surface, simultaneously blaxial orientation is carried out at a high orientation speed of 10<4> %/min or more in both the longitudinal direction and lateral direction. Also, the film manufacturing method employs an inline-coating method. In addition, a simultaneously biaxially orientated film is obtained by the manufacture, and includes a coating material layer having a thickness of 0.005-0.5 μm on the film surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method which can be used in a process for producing a surface-modified biaxially stretched film made of a thermoplastic resin, and further relates to a simultaneous coating method using the coating method. The present invention relates to a method for producing an axially stretched film.

More specifically, the present invention relates to the above-mentioned coating method and a method for producing a simultaneously biaxially stretched film, which makes it possible to produce a good thermoplastic resin film at a particularly high speed and without surface modification unevenness.

[0003]

2. Description of the Related Art As a biaxial stretching method used for producing a film from a polyester resin which is a typical example of a thermoplastic resin, usually, a film is stretched in a width direction after stretching in a longitudinal direction.
A so-called sequential biaxial stretching method is usually performed.

[0004] In order to modify the surface of the film during the film forming process, a coating material is coated after stretching in the longitudinal direction, and this is coated with water or the like in a preheating zone in a tenter of a width stretching machine. A method of stretching the film in the width direction after drying the solvent has been adopted.

In the simultaneous biaxial stretching method in which the longitudinal direction and the width direction are simultaneously biaxially stretched, a coating material is coated before stretching and dried in a preheating zone in a tenter of the simultaneous biaxial stretching machine. After that, simultaneous biaxial stretching has been performed.

[0006]

However, in such surface modification by the sequential biaxial stretching method or the simultaneous biaxial stretching method, the productivity must be sacrificed.

That is, in the case of sequential biaxial stretching, in order to perform coating after stretching in the longitudinal direction, the coating speed must be high, and the coated coating liquid must be rapidly dried in a short time. For this reason, if the coating solution concentration is increased for a short time drying,
Quality problems such as coating streaks and surface defects are likely to occur. Conversely, if the concentration of the coating liquid is reduced, the coating liquid often uses water, so that drying takes a long time and productivity is sacrificed. As described above, it is difficult to perform coating in a film forming process that balances quality and productivity with the conventional method. The same is true in the case of the simultaneous biaxial stretching method, because it is necessary to coat the coating material thicker by the biaxial stretching ratio, it takes more time to dry the coating liquid than in the case of sequential biaxial stretching, Productivity was greatly sacrificed, and it was difficult to perform coating in a film-forming process that achieved both quality and productivity.

[0008] In view of the above, the present invention provides a coating method in a film forming process that achieves both quality and productivity.
It is an object of the present invention to provide a method for producing a simultaneously biaxially stretched film using the coating method.

Another object of the present invention is to provide a simultaneously biaxially stretched film which is excellent in both quality and productivity obtained by such a method.

[0010]

According to the coating method of the present invention, a molten resin film is brought into close contact with a cooling medium and solidified by cooling.
The present invention provides an in-line coating method in which, after coating a coating material on the cooled film surface, the film is simultaneously biaxially stretched in a longitudinal direction and a width direction at a high stretching speed of 10 ⁴ % / min or more. is there.

Further, the method for producing a simultaneous biaxially stretched film of the present invention is characterized in that the molten resin film is brought into close contact with a cooling medium to be cooled and solidified, and a coating material is coated on the surface of the cooled film. The stretching speed is 10 ⁴ %
A method for producing a simultaneous biaxially stretched film, characterized in that the film is subjected to simultaneous biaxial stretching in the longitudinal direction and the width direction at a high speed of at least / min.

The film obtained by the present invention has a thickness of 0.005 to 0.5 μm on the film surface which realizes high productivity obtained by the above-described method and also realizes good quality.
m is a simultaneous biaxially stretched film having m coating material layers.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a molten resin is
It is a thermoplastic resin that exhibits fluidity when heated, and typical thermoplastic resins include polyethylene, polypropylene, various polyolefin resins such as polymethylpentene, nylon 6, and various polyamide resins such as nylon 66, Polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polymethylene terephthalate, polypropylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexylene dimethylene terephthalate, and as a copolymer component, for example, diethylene glycol And diol components such as neopentyl glycol and polyalkylene glycol, and adipic acid, sebacic acid, phthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid. Various polyester resins such as polyester obtained by copolymerizing a carboxylic acid component, other,
Polyacetal resin, polyphenylene sulfide resin and the like can be used. In particular, in the present invention, when a polyamide resin or a polyester resin is used, the effect is high and preferable. Among them, polyethylene-2,6-
Naphthalate and polyethylene terephthalate are particularly preferred, and polyethylene terephthalate is particularly preferred because it is inexpensive and therefore used in a wide variety of applications and has high application and application effects. Further, these resins may be homo resins, or may be copolymerized or blended resins. Furthermore, among these resins, there are various additives, for example, antioxidants, antistatic agents, crystal nucleating agents, inorganic particles, thickeners, heat stabilizers, lubricants, etc., which are added as appropriate. Is preferred. Typical additives include silicon dioxide, alumina, calcium carbonate, zirconium oxide, talc, kaolin, clips, barium sulfate, titanium oxide, cross-linked polystyrene resin, cross-linked polyester resin, and mixtures thereof. It should be used according to.

After applying a static charge to the above-mentioned thermoplastic resin melt film and bringing it into close contact with a cooling medium to cool and solidify the film, the coating material is wet-coated on the surface of the obtained film, to be slightly thicker. Specifically, although not particularly limited, according to the findings of the present inventors, preferably 3 to
After coating with a thickness of 30 μm, more preferably 5 to 20 μm, simultaneous biaxial stretching is performed in the machine direction and the width direction at a stretching speed of 10 ⁴ % / min or more, and further heat treatment is performed if necessary. . The simultaneous stretching speed is 1
0 ^4% / minute or more, preferably 3 × 10 ^4% / min or more, since the first high productivity and high quality film is obtained by further preferably simultaneous biaxial stretching at 10 ^5% / min or more high-speed is there.

In the present invention, the term "closely contacted" includes a case where the cooling medium and the film are in contact with each other (they move while being in contact with each other) enough to effectively perform the cooling treatment performed by the cooling medium. ). Also,
In the present invention, "high speed" refers to a simultaneous stretching speed of 10
^It means ⁴ % / min or more, and in the present invention, it is significant to perform simultaneous biaxial stretching at the high speed. According to the findings of the present inventors, in the simultaneous low-speed biaxial stretching method, after coating the coating material thickly on the film surface, to slowly evaporate the solvent such as water over time, The water and the like of the coating material are absorbed by the thermoplastic resin, and as a result, the glass transition temperature of the resin is partially lowered or partially crystallized, and the drawing tension curve is partially changed. In the stretching step, uneven stretching, that is, uneven thickness is caused, and surface defects are caused, which is not desirable.

Therefore, in the present invention, as described below,
The coating material is preferably coated as thick as 3 to 30 μm (wet thickness) on the film surface, but when the solvent such as water is evaporated quickly without taking time as much as possible, the solvent of the coating material becomes a thermoplastic resin. Is hardly absorbed by
Even if a small amount of solvent is absorbed and the glass transition temperature is partially lowered, simultaneous stretching in the longitudinal and width directions at a stretching speed of 10 ⁴ % / min or more is performed by simultaneous biaxial stretching. This results in a favorable effect that stretching unevenness is less likely to occur due to reduced properties. The simultaneous biaxial stretching temperature at this time is 100 ° C. lower than the boiling point of water.
Or less, preferably 90 ° C or less, more preferably 85 ° C
The following should be good. Of course, any suitable solvent can be used as desired, but from the viewpoints of versatility, productivity, recoverability, pollution problems, etc., those containing water as the main component are the most excellent. Of course, a small amount of a solvent such as alcohols or ketones may be added to this.

[0017] Coating thickness of the coating material (wet thickness)
Is not particularly limited as described above, but is preferably 3
-30 μm, more preferably 5-20 μm. In terms of the thickness of the coating material in a dry state without a solvent obtained by simultaneous biaxial stretching and heat treatment, it is preferably about 0.005 to 0.5 μm.

In the present invention, the film is subjected to a surface activation treatment, for example, a treatment such as a corona discharge treatment, an ozone treatment, an ultraviolet treatment, a sand mat treatment, and a chemical treatment before coating the coating material. This is preferable because a more uniform coating can be achieved.

The biaxial stretching in the present invention refers to an operation of stretching biaxially in the longitudinal direction and the width direction to give a molecular orientation in the biaxial direction. The biaxial stretching method must be a simultaneous biaxial stretching method of simultaneously stretching in the longitudinal direction and the width direction. Simultaneous biaxial stretching refers to stretching in the longitudinal direction of the film to simultaneously give orientation in the biaxial direction of the width direction.Using a simultaneous biaxial tenter, the film is conveyed while holding both ends of the film with clips, This is a method of stretching in the longitudinal direction and the width direction. Of course, it is sufficient if there is a portion in which the stretching in the longitudinal direction and the stretching in the width direction are simultaneously stretched temporally. At the same time, or a method of further stretching independently in the width direction or the longitudinal direction after the simultaneous biaxial stretching, and in the present invention, a method of re-stretching after the simultaneous biaxial stretching is particularly preferable. The film temperature during each of these stretching steps is preferably maintained at a temperature not lower than the glass transition temperature of the polyester film and not higher than 100 ° C., which is the boiling point of water. Moreover, the simultaneous biaxial stretching method is the same as that of the simultaneous biaxial tenter because the stretching speed in each of these directions can be as high as 10 ⁴ % / min or more, and the stretching direction and the stretching ratio can be freely changed. It is preferable to use a system in which the clips are individually driven by a linear motor system. Conventional simultaneous biaxial stretching methods include a screw method in which a clip is placed in a groove of a screw to increase a clip interval, and a pantograph method in which a clip interval is increased using a pantograph. However, in such a method, the film forming speed must be lower than 10 ⁴ % / min. Therefore, when the coated film is stretched while being dried, stretching unevenness becomes large, and further, such as stretching ratio, etc. There was a major problem, such as difficulty in changing the conditions.However, using a linear drive tenter that independently controls each clip using the principle of a linear motor and adjusts the clip spacing, The speed can be increased more than the conventional sequential biaxial stretching method, and as a result, not only a film having a uniform thickness can be obtained without deterioration in thickness unevenness even if simultaneous biaxial stretching is performed after coating, It is possible to adopt any stretching method and format. For example, in order to form a film having a strong orientation in the longitudinal direction, it may be stretched in multiple stages in each stretching direction, or may be further stretched in the longitudinal direction or the width direction after simultaneous biaxial stretching. After stretching, a film with good dimensional stability and a film with no unevenness of physical properties (no bowing) in the width direction can be relaxed to return dimensions in the length direction and / or width direction in the heat treatment process after stretching. Can be. That is, various excellent films can be formed with high productivity by using the linear drive tenter of the clip which can individually control each clip.
In order to achieve such a free stretching mode, there are special end portions such as making the thickness of the end portion of the film about two to three times thicker than the center portion, or making the molecular weight of the end portion higher than that of the center portion. It is also effective to make the film into a thin film.

The magnification of the simultaneous biaxial stretching varies depending on the type of the resin, but is usually 2 to 12 in each direction.
It is about twice. After stretching, it is often effective to carry out a relaxation heat treatment (heat setting) in order to remove the distortion, but at this time, instead of performing the heat treatment immediately after the stretching, once the stretched film is stretched, Heat treatment after cooling to a glass transition temperature Tg or lower can provide a film having uniform physical properties in the width direction. Note that, as the temperature of the heat treatment, various temperatures from the stretching temperature to the vicinity of the melting point of the resin are taken according to the application.

It is relatively easy to make the main axis of orientation of the simultaneously biaxially stretched film thus obtained exist in the longitudinal direction and the width direction, and to produce a film in which the orientation is balanced in both axes.

Next, the method for producing the film of the present invention will be described by taking an example of a polyester resin, but the present invention is not necessarily limited to this.

First, a raw material pellet containing a necessary additive in a polymerization step of a polyester resin or an extruder process is prepared, and the raw material is dried in hot air, in a vacuum, or in a vent extruder. In the above, melting at a temperature not lower than the melting point Tm of the resin and not higher than the thermal decomposition temperature Tb, or cooling the molten resin once after melting at a temperature equal to or higher than the melting point Tm of the resin, for example, in the second stage of a tandem extruder or the like After cooling, the resin is supercooled to a melting point Tm or lower and a crystallization temperature Tmc or higher. The resin is made to flow while the thermally decomposed or gelled product of the resin is kept as small as possible, and foreign substances are removed through a multi-stage filter. Then, the film is further connected to a gear pump or the like to make the resin extrusion amount uniform, and after forming into a desired shape with a die, a film having good thickness uniformity can be obtained. By making the supercooled state in this way, not only is the film containing less foreign matter such as oligomers and thermal decomposition products, but also the melt discharged from the die is less affected by external vibrations such as air and sound waves. There is also an advantage that a film having a good thickness unevenness can be obtained.

An electrostatic charge is applied to the sheet-like film discharged from the die, and the sheet-like film is brought into close contact with the cast drum and cooled and solidified. At this time, if an extremely thin water film or water droplet of about 0.1 μm is interposed on the drum, the adhesion to the drum is further improved, and a completely amorphous film having a more uniform thickness is obtained. It is preferred. In addition, the shape of the thermoplastic resin film is adjusted such that the thickness of the end portion is reduced to about three times the thickness of the central portion by adjusting the gap between the bases or the like to improve the stretchability or to improve the film forming yield. good. Further, the stretching property is further stabilized by increasing the molecular weight only at the end of the film, but for this purpose, a raw material having a molecular weight higher than the molecular weight at the central part is supplied by using another extruder, and the extruder is fed before or at the base. The co-extrusion is performed so that the film is laminated only on the edge of the film. Stretching from an amorphous state is preferred, but if necessary, some crystallinity, that is, a crystallinity of 0.5 to 15
(%) Is preferable because it is possible to obtain a film having good thermal dimensional stability and good slipperiness. The thickness unevenness in the longitudinal direction of the cast film before stretching is as small as 7% or less, preferably 5% or less.

By subjecting the unstretched film to various surface activation treatments such as corona discharge treatment, ozone treatment, ultraviolet treatment, sand mat treatment, and chemical treatment, the next coating treatment can be performed uniformly. Can be. The surface of the treated film is coated with a coating material such as a water-based material, and it is important that the coating thickness is larger than the required coating thickness after stretching by almost the same simultaneous biaxial stretching ratio. The thickness is preferably about 3 to 30 μm as described above. If the film with such a thick coating material is not evaporated as quickly as possible, taking as little time as possible, such as water, the water of the coating material is partially absorbed by the thermoplastic resin. In addition, stretching may be uneven. For this purpose, an auxiliary heating device such as a powerful infrared / far infrared heater may be installed in the preheating zone.
Further, even if a small amount of water is absorbed and the glass transition temperature of the resin film partially decreases, the stretching speed is reduced to 10 ^4.
When the simultaneous biaxial stretching is performed in the longitudinal direction and the width direction at a high speed of at least% / min, the temperature dependency of the simultaneous biaxial stretching tension is reduced, so that uneven stretching is less likely to occur. In addition, the simultaneous biaxial stretching temperature at this time is 100 ° C. or lower, preferably 90 ° C. or lower, which is lower than the boiling point of water, and more preferably 85 ° C. or lower, since the temperature dependency of the simultaneous biaxial stretching tension is reduced. Is also good.

The unstretched film is subjected to a simultaneous biaxial tenter for simultaneous biaxial stretching at a high speed. At this time, the stretching may be simply started and ended simultaneously in the longitudinal direction and the width direction. Before and after biaxial stretching, stretching in advance in the longitudinal direction and / or width direction may be performed, or re-stretching after simultaneous biaxial stretching may be performed. In particular, when the film is stretched again in the longitudinal direction after the simultaneous biaxial stretching, the film shape in the vicinity of the edge becomes linear, and not only the edge cut ratio decreases, but also the strength is strong in the longitudinal direction (for example, 14 kg / mm as F5 value). ² or more), which is preferable because the film has good flatness and small thickness unevenness.

After simultaneous biaxial stretching, the film is cooled to a temperature lower than the glass transition point of the resin constituting the film, preferably to a temperature lower than the glass transition point of -10 ° C., and then heat-treated for imparting thermal dimensional stability. Is preferred. If heat treatment is performed at the same temperature immediately after stretching, the softened film in the heat treatment process is drawn into the stretching process due to the stress during stretching and the heat shrinkage stress, causing a bowing phenomenon, and the refractive index ellipsoid of the film is distorted, As a result, a physical property distribution in the width direction occurs. Therefore, in order to avoid these bowing phenomena, after the biaxial stretching, the resin is once cooled to a temperature lower than the glass transition point of the resin, a hard part is provided between the stretching step and the heat treatment step, and the heat treatment is performed after separating the respective steps. , The bowing phenomenon can be suppressed.

Further, it is preferable to perform a relaxation treatment for reducing the dimensions during and after the heat treatment, because higher thermal dimensional stability can be obtained. However, if the heat treatment temperature is too high or the heat treatment with too much relaxation rate is performed to pursue thermal dimensional stability, properties such as strength and flatness are undesirably reduced.

The film thus obtained is gradually cooled to room temperature and wound up by a winder to obtain a product.

According to a preferred embodiment of the present invention, after simultaneous biaxial stretching, the coating material thickness is 0.005 to 0.5 μm.
The surface modified film having the coating material layer can be generally wound into a film at a high speed range of a winding speed of 150 to 1000 m / min. In the conventional method, the winding speed is 60 to 120 m / min. At most, such a high-speed film formation is extremely useful in terms of productivity.

According to the present invention, it is possible to realize film formation at an ultra-high speed of 400 to 1000 m / min, which was conventionally considered difficult.

The film obtained according to the present invention is not limited to a heat-sensitive transfer receiving paper, but also a heat-sensitive stencil material, a capacitor material, a heat-sensitive transfer ribbon material, a magnetic tape material, a packaging material, and the like. It can be widely used for various applications and is effective.

[0033]

[Method of evaluating physical property values] Thermal characteristics: As a differential scanning calorimeter, a robot DSC “RD” manufactured by Seiko Electronics Industry Co., Ltd.
C220 ”and a disk station“ SSC / 5200 ”made by the company as a data analyzer, and about 10 mg of the sample was placed on an aluminum pan at 300 ° C. for 5 minutes.
The mixture was melted and held for 1 minute, quenched and solidified with liquid nitrogen, and then heated from room temperature at a rate of temperature increase of 20 ° C./minute. The peak temperature of the glass transition point observed at this time is Tg, the start temperature of the melting endothermic peak is Tmb, the peak temperature is Tm, and the peak end temperature is T.
me. After 5 mg of the sample was melted and held at 300 ° C. for 5 minutes, the temperature was lowered at a temperature lowering rate of 20 ° C./min. At this time, the start temperature of the temperature-reducing crystallization exothermic peak observed was Tcb, the peak temperature was Tc, and the peak end temperature was Tce.

2. Thickness unevenness in the longitudinal direction of the film: Film thickness nest tester “KG601” manufactured by Anritsu Corporation
A "and an electronic micrometer" K306C "
The thickness of a film sampled 30 mm wide and 10 m long in the longitudinal direction of the film is continuously measured. The transport speed of the film was 3 m / min. Maximum thickness T at 10m length
From the maximum (μm) and the minimum value Tmin (μm), R = Tmax−Tmin was calculated, and from R and the average thickness Tave (μm) having a length of 10 m, the thickness unevenness (%) was calculated as R / Tave × 100.

3. Birefringence: The retardation Rd of the film was determined by a polarizing microscope equipped with a Berek compensator. Rd was divided by the thickness of the film to obtain a birefringence.

4. Crystallinity: A density gradient tube is prepared using an aqueous solution of sodium bromide, and the density of the film at 25 ° C. is measured. From this density d, the crystallinity (%) = (d−da) / (dc−da) × 10
0 was set.

Here, da is an amorphous density, dc is a perfect crystal density, and in the case of polyethylene terephthalate, da = 1.335 and dc = 1.455 g / cm ³ from literature values.

5. Young's modulus, F5 value: Orientec Co., Ltd. automatic film strength and elongation measuring device Model AM
The measurement was performed using F / RTA-100 at a sample width of 10 mm, a sample length of 100 mm, and a tensile speed of 300 mm / min.

6. Heat shrinkage: Sampling a film into a width of 10 mm and a length of 220 mm.
Two 00 mm points are marked. The interval between these two points is accurately measured and is set to L0 (mm). Next, the sample is left in a hot air oven heated to 150 ° C. for 30 minutes, taken out, and left to reach room temperature. When the sample has cooled completely, measure the interval between the two points again,
(Mm). Here, the heat shrinkage rate was set as heat shrinkage rate (%) = (L0−L) / L0 × 100.

7. Intrinsic viscosity [η] of polyester: 25
At ゜ C, the value was determined by the following formula using o-chlorophenol as a solvent.

[Η] = lm [ηsp / c] The specific viscosity ηsp is obtained by subtracting 1 from the relative viscosity ηr. c is the concentration, and the unit is dl / g.

[0042]

The present invention will now be described more specifically with reference to examples and comparative examples.

Example 1 As the thermoplastic resin, polyethylene terephthalate (PET) having intrinsic viscosities of 0.65 and 0.72 was used. DSC
When the thermal properties of polyethylene terephthalate having an intrinsic viscosity of 0.65 were measured using Tg, Tg: 69 ° C., Tm: 2
Thermal properties of polyethylene terephthalate having 55 ° C., Tc: 188 ° C., and intrinsic viscosity 0.72 are as follows: Tg: 69 ° C., Tm:
256 ° C, Tc: 190 ° C. Each polyethylene terephthalate pellet was vacuum dried at 180 ° C. for 3 hours. First, a raw material having an intrinsic viscosity of 0.65 is supplied to a 90 mm tandem extruder, and is uniformly melted at 285 ° C. in a first-stage extruder. Cooled uniformly to 260 ° C. After this melt was supplied in a fixed amount by a gear pump, the melt was passed through a sintering filter for removing foreign substances of 5 μm or more and introduced into a T-die die.

On the other hand, a polyethylene terephthalate (PET) raw material having an intrinsic viscosity of 0.72 is also used.
After drying the raw material in the same manner as the PET raw material of No. 65, the raw material was fed to a 40 mm extruder, melted at 285 ° C., and cooled to 265 ° C.
A fixed amount of the PET melt sheet having an intrinsic viscosity of 0.65 was laminated in three layers in the width direction only at both ends of a 660 mm width of the PET melt sheet with a width of 35 mm, and a melt having a film width of about 730 mm was discharged.

In the molten film extruded from the die,
A surface temperature of 65 ° C. while applying a static charge of 12,000 V
0.1μm formed on the surface layer by the condensation method
It was picked up at a high speed of 100 m / min on a mirror casting drum whose entire surface was covered with fine water droplets having a diameter of not more than the diameter, and rapidly cooled and solidified. The die lip gap was adjusted so that the average thickness at the film edge of the cast film thus obtained was 2.5 times the thickness at the center. The intrinsic viscosity [η _e ] at the edge is 0.68, and the intrinsic viscosity [η _c ] at the center of the film.
Was 0.62. The thickness unevenness in the longitudinal direction / width direction was 3% / 4%, the birefringence was 0, and the crystallinity was 2%.

The unstretched film thus obtained is subjected to a corona discharge treatment as a surface activation treatment, and a water-based coating material having excellent adhesiveness (terephthalic acid as an acidic component,
1,3 isophthalic acid pentasulfate sodium salt, adipic acid,
A water-soluble copolymerized polyester having a Tg of 0 ° C. and comprising ethylene glycol, diethylene glycol, and polyethylene glycol having a molecular weight of 4000 as a diol component is added to water.
Wt% dissolved) was coated with a No. 8 metering bar. The coating wet thickness at this time was 15 μm.

At this time, it was found that, unless the water used for coating was evaporated as quickly as possible, the water of the coating material was partially absorbed by the polyester film, resulting in uneven stretching. For this purpose, most of the water is dried in the preheating zone where an auxiliary heating device consisting of a powerful far-infrared heater is installed in the preheating zone of the simultaneous biaxial stretching tenter. The glass transition temperature Tg of the film is partially lowered, and as a result, the optimum stretching temperature differs in the portion of the film to be stretched. Otherwise, thickness unevenness will increase. For this purpose, using a simultaneous biaxial stretching machine in which each clip moves at high speed by linear drive, the simultaneous biaxial stretching speed is 7 × 10 ⁴ % / min, and the stretching direction and width are 85 ° C. The film was simultaneously biaxially stretched 4.5 times in each direction. Further, the film was stretched 1.3 times in the longitudinal direction and the width direction at 100 ° C. at 3 × 10 ⁴ % / min. After that, once cooled to 65 ° C, heat treated at 225 ° C in the same tenter, then gradually cooled down to room temperature while uniformly relaxing both axes by 5%, and cooled to room temperature. Winding, coating material thickness 0.1μm
And a biaxially oriented film having a total thickness of 8 μm was obtained. Table 1 shows the conditions of the film formation and the obtained characteristics.

Comparative Example 1 The clip driving method used in Example 1 was changed from linear driving to a normal pantograph simultaneous biaxial stretching machine, and the casting speed was reduced to 31 m / min. as 3 × 10 ^3% / min was simultaneously biaxially stretched at a low rate, 10 ³ further 100 ° C. in the longitudinal direction and the width direction
A film was formed in the same manner as in Example 1 except that the film was stretched 1.3 times at% / min.

The results of the film forming property and quality of the biaxially stretched film thus obtained are shown in Table 1. However, when the film is stretched at a low speed in such a manner, the absorbed water adversely affects the stretchability. It can be seen that only bad films can be obtained.

[0050]

[Table 1]

[0051]

According to the present invention, as a method for modifying the surface of a thermoplastic resin film, an in-line coating material such as an aqueous material is coated in-line during the film forming process, and then the stretching speed is adjusted to 10 ^4.
By performing simultaneous biaxial stretching at a high speed of at least% / min, a film having excellent thickness uniformity can be obtained. Moreover, not only can such a high-quality film be obtained, but also a film production method excellent in productivity can be provided, which is a very effective method in practice.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29L 9:00

Claims (14)

[Claims] 1. A molten resin film is brought into close contact with a cooling medium to be cooled and solidified, and after coating a coating material on the surface of the cooled film, a stretching speed is 10 ⁴ % / min or more at a high speed in a longitudinal direction and a width direction. In-line coating method characterized by simultaneous biaxial stretching. 2. The in-line coating method according to claim 1, wherein the solvent constituting the coating material is mainly water. 3. The film surface is subjected to an activation treatment before coating.
Inline coating method as described. 4. The simultaneous biaxial stretching is performed at a stretching temperature of 100 ° C.
4. The in-line coating method according to claim 1, wherein the in-line coating method is performed as follows. 5. The coating thickness of a coating material (wet thickness)
Is 3 to 30 μm.
The inline coating method according to 2, 3 or 4. 6. The simultaneous biaxial stretching is performed by using a tenter device having a clip, and the clip is driven by a linear motor system.
Inline coating method according to 2, 3, 4 or 5. 7. A molten resin film is brought into close contact with a cooling medium to be cooled and solidified, and a coating material is coated on the surface of the cooled film. Thereafter, the film is stretched at a stretching speed of 10 ^4.
A method for producing a simultaneous biaxially stretched film, wherein the film is subjected to simultaneous biaxial stretching in the longitudinal direction and the width direction at a high speed of at least% / min. 8. The method for producing a simultaneous biaxially stretched film according to claim 7, wherein the film is a polyester film. 9. The method for producing a simultaneously biaxially stretched film according to claim 7, wherein a surface activation treatment is applied to the surface of the film before coating the coating material. 10. The simultaneous biaxial stretching, wherein the stretching speed is 3 × 10 ^4.
9. The method according to claim 7, wherein the step is performed at a high speed of at least% / min.
Or the method for producing a simultaneous biaxially stretched film according to 9. 11. The simultaneous twin film according to claim 7, wherein the coating thickness (dry thickness) of the coating material after the simultaneous biaxial stretching is 0.005 to 0.5 μm. A method for producing an axially stretched film. 12. The coating thickness (wet thickness) of the coating material before the simultaneous biaxial stretching is applied is 3 to 30 μm, and the coating thickness (dry thickness) of the coating material after the simultaneous biaxial stretching.
Is from 0.005 to 0.5 μm, the method for producing a simultaneously biaxially stretched film according to claim 7, 8, 9 or 10. 13. A winding speed of 150 to 1 after simultaneous biaxial stretching.
13. The method for producing a simultaneous biaxially stretched film according to claim 6, wherein the film is wound at 000 m / min. 14. The method of claim 6, 7, 8, 9, 10, 11, 1.
It is obtained by the method for producing a simultaneous biaxially stretched film described in 2 or 13, and has a thickness of 0.005 to 0.5 μm on the film surface.
m. A simultaneous biaxially stretched film comprising a m coating material layer.