JP7200038B2 - Film manufacturing method and film manufacturing apparatus - Google Patents

Description

The present invention relates to a film manufacturing method and a film manufacturing apparatus.

BACKGROUND ART A method of producing a resin film is known in which a coating liquid in which a resin is dissolved in an organic solvent is applied onto a substrate, and the coating film formed by the coating is dried. When a film is produced by such a method, uneven thickness of the film due to non-uniform coating may be a problem.

It is known that the use of a high boiling point solvent as an organic solvent for a coating solution reduces unevenness in the thickness of the coating film between coating and drying due to the surface tension of the coating solution. However, when the thickness of the coating film is large, a high boiling point solvent cannot be used to completely evaporate the solvent. As an example, when producing a film with a thickness of 80 μm, the thickness of the coating will be 400 μm or more.

Patent Document 1 below describes a step of applying the paint to one surface of the support while moving the support (base film) relative to the coating position of the paint, and applying the paint after the coating. and smoothing the coating surface at least by blowing gas. In Patent Document 1, it is said that the coating material immediately after coating can be made to flow by the fluid pressure of the gas, and streak-like surface roughness or the like generated on the coating surface can be smoothed out, thereby promoting the smoothing of the coating surface.

JP-A-10-263453

When the coating film is smoothed by the method described in Patent Document 1, thickness unevenness can be reduced, but fine ripples of height are formed on the surface of the film. In particular, when a thick film is formed, fine wind ripples are likely to occur, and are perceived as poor appearance when viewed with the human eye. Wind ripples that cause such poor appearance can be defects when the obtained film is used as an optical film.

An object of the present invention is to provide a film manufacturing method and a film manufacturing apparatus capable of reducing thickness unevenness and appearance defects.

(1) A film manufacturing method according to an aspect of the present invention comprises a step of applying a coating liquid to a strip-shaped substrate that is continuously conveyed in a longitudinal direction, and a step of applying a gas to the coating film formed by the coating. a step of smoothing the coating film by spraying; and a step of drying the coating film, wherein the impinging wind speed is the component of the wind speed of the gas in the direction perpendicular to the substrate at the surface position of the substrate. is 7 m/s or more, and the average change rate from the maximum value of the impinging wind speed is 0.25 m/(s mm) at 10 mm in the conveying direction of the base material at the position where the impinging wind speed is maximum. It is below.

(2) In the film manufacturing method of (1), it is preferable that the maximum impinging wind speed is 12 m/s or less.

(3) In the film manufacturing methods (1) and (2), it is preferable that the average temperature of the coating film when the gas is blown is 10° C. or higher and 40° C. or lower.

(4) In the film manufacturing method of (1) to (3), it is preferable that the coating film has an average thickness of 400 μm or more and 1000 μm or less.

(5) In the film manufacturing method of (1) to (4), the coating liquid may contain a resin and an organic solvent, and the gas may contain vaporized gas of the organic solvent.

(6) A film manufacturing apparatus according to an aspect of the present invention includes a conveying device that continuously conveys a strip-shaped substrate in a longitudinal direction, and a coating liquid that is applied to the substrate being conveyed by the conveying device. and a smoothing device for smoothing the coating film by blowing gas onto the coating film formed by the coating device, wherein the smoothing device is configured to spray the gas at a surface position of the base material. The maximum value of the impinging wind speed, which is the component of the wind speed in the direction perpendicular to the base material, is 7 m / s or more, and the maximum value of the impinging wind speed at a position where the impinging wind speed is maximum and 10 mm before and after the base material in the conveying direction. The gas is injected so that the average rate of change from 0.25 m/(s·mm) or less.

ADVANTAGE OF THE INVENTION According to this invention, the film manufacturing method and film manufacturing apparatus which can reduce thickness nonuniformity and appearance defect can be provided.

It is a mimetic diagram showing composition of a film manufacturing device concerning one embodiment of the present invention. 7 is a graph showing the distribution of impinging wind speeds in a prototype example.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of a film manufacturing apparatus according to one embodiment of the present invention.

The film manufacturing apparatus includes a conveying device 1 that continuously conveys a belt-shaped base material B in the longitudinal direction, a coating device 2 that applies a coating liquid P to the base material B being conveyed by the conveying device 1, a coating A smoothing device 3 for smoothing the coating film F formed by the device 2 by blowing a gas G onto the coating film F, and a drying device 4 for drying the coating film F smoothed by the smoothing device 3 are provided. By peeling off the coating film F dried by the drying device 4 from the substrate B, a product film is obtained.

As illustrated, the conveying device 1 can be configured as a belt conveyer-like device in which an endless loop-shaped base material B is stretched between two rollers 11 and circulated and conveyed. Further, the conveying device 1 may be configured to continuously convey a long strip-shaped base material by a plurality of conveying rollers. In this case, the conveying device 1 unwinds and conveys the base material B wound on the reel, and winds the base material B after peeling off the product film formed by drying the coating film F on another reel. may be configured to take

The coating device 2 applies the coating liquid P to the surface of the substrate B uniformly. Specifically, examples of the coating device 2 include a die coater, a knife coater, a bar coater, and a gravure coater.

Although not particularly limited, in the illustrated example, the coating device 2 is configured to have a die 21 that discharges the coating liquid P supplied from a tank (not shown) over the entire width of the substrate B.

The coating liquid P applied to the substrate B by the coating device 2 may contain a resin that is the main component of the product film to be manufactured and an organic solvent that dissolves the resin.

The resin contained in the coating liquid P is not particularly limited, but highly transparent acrylic resins, polycarbonates, and the like are preferably used when the obtained film is used for optical purposes.

As the organic solvent contained in the coating liquid P, for example, low boiling point solvents such as dichloromethane and methyl ethyl ketone are preferable. By using such a low boiling point solvent, it becomes relatively easy to completely volatilize the organic solvent so that it does not remain in the product film even when a product film having a relatively large thickness is produced.

In order to form a relatively thick film, the viscosity of the coating liquid P must be increased. When the viscosity of the coating liquid P increases, unevenness in thickness and poor appearance of the coating film F are likely to occur.

The lower limit of the average thickness of the coating film F formed by the coating device 2 (average thickness at the time of smoothing by the smoothing device 3) is preferably 400 µm, more preferably 600 µm. On the other hand, the upper limit of the average thickness of the coating film F formed by the coating device 2 is preferably 1000 μm, more preferably 800 μm. When the average thickness of the coating film F formed by the coating device 2 is equal to or greater than the lower limit, thickness unevenness and appearance defects are likely to occur in the coating film F, so the smoothing device 3 is effective in suppressing thickness unevenness and appearance defects. become conspicuous. Further, when the average thickness of the coating film F formed by the coating device 2 is equal to or less than the upper limit, the smoothing device 3 can sufficiently suppress unevenness in thickness and poor appearance.

The lower limit of the average temperature in the region where the gas G is sprayed by the smoothing device 3 on the coating film F formed by the coating device 2 (the spraying region described later) is preferably 10°C, more preferably 15°C. On the other hand, the upper limit of the average temperature of the coating film F formed by the coating device 2 is preferably 40°C, more preferably 30°C. By making the average temperature of the coating film F formed by the coating device 2 equal to or higher than the lower limit, cooling is not required, so increases in equipment cost and running cost of the coating device 2 can be suppressed. In addition, by setting the average temperature of the coating film F formed by the coating device 2 to be equal to or lower than the upper limit, the organic solvent in the coating film F is evaporated and smoothed before being smoothed by the smoothing device 3 after coating. It is thought that it is possible to prevent the inhibition of the transformation.

The smoothing device 3 reduces thickness unevenness of the coating F by blowing the gas G perpendicularly onto the coating F formed by the coating device 2 . Thickness unevenness of the coating film F is likely to be formed such that a portion of the coating film F having a large thickness or a portion having a small thickness extends like a streak in the conveying direction of the substrate B. In addition, when the viscosity of the coating liquid is high, the thickness unevenness of the coating film F is such that the part where the thickness of the coating film F is large or the part where the thickness is small crosses the base material B in the width direction (the direction perpendicular to the conveying direction mark). It is often formed like this.

The smoothing device 3 has a nozzle 31 that injects a gas G that is blown onto the coating film F. As shown in FIG. The gas G jetted from the nozzle 31 preferably contains a vaporized organic solvent. Specifically, the smoothing device 3 can be configured to spray the gas G, which is a mixture of air and an organic solvent, from the nozzle 31 onto the coating F. Since the gas G sprayed onto the coating film F contains an organic solvent, the drying of the coating film F progresses and the viscosity increases before the spraying of the gas G by the smoothing device 3 ends, and the thickness of the coating film F decreases. Hindering uniformity and surface smoothing can be suppressed. Therefore, the smoothing device 3 may have a tank for storing the organic solvent, a device for vaporizing the organic solvent, an ejector for introducing the organic solvent into the air, and the like. Further, the smoothing device 3 may suck the air containing the organic solvent evaporated from the coating film formed by the coating device 2 and supply the air to the nozzle 31 . Thereby, the consumption of the organic solvent can be suppressed.

The nozzle 31 has a slit-shaped outlet extending in a direction perpendicular to the conveying direction of the base material B and parallel to the surface of the base material B (parallel to the width direction of the base material B). is tapered toward the outlet (the width of the flow path in the lateral direction of the outlet decreases toward the outlet).

The lower limit of the maximum value of the impinging wind speed, which is the component of the wind speed of the gas G at the surface position of the base material B in the direction perpendicular to the base material B, is preferably 7 m/s, more preferably 8 m/s. On the other hand, the upper limit of the maximum value of impinging wind speed is preferably 12 m/s, more preferably 10 m/s. The thickness of the coating film F can be made sufficiently uniform by setting the maximum value of the impinging wind speed to be equal to or higher than the lower limit. Further, by setting the maximum value of the impinging wind speed to be equal to or less than the upper limit, formation of wind ripples on the surface of the coating film F can be suppressed. The impingement wind speed is a value measured by an anemometer placed at a position where the base material B is conveyed in a state where the base material B is not present.

The average change rate from the maximum value of the impinging wind speed at 10 mm forward and backward in the conveying direction of the base material B at the position where the impinging wind speed is the maximum (average value of the value obtained by dividing the amount of change in the maximum wind speed by the distance of 10 mm, hereinafter, before and after the peak) The lower limit of the average rate of change) is preferably 0.02 m/(s·mm), more preferably 0.05 m/(s·mm). On the other hand, the upper limit of the average rate of change before and after the peak is preferably 0.25 m/(s·mm), more preferably 0.20 m/(s·mm). By making the average rate of change before and after the peak equal to or higher than the lower limit, it is possible to prevent the range in which the gas G collides from becoming too large while keeping the maximum value of the impinging wind speed sufficiently high. In addition, by setting the average rate of change before and after the peak to be equal to or less than the above upper limit, wind ripples are formed on the surface of the coating film F by suppressing the forward and backward movement of the coating film F caused by the difference in wind force before and after the conveying direction of the base material B. can be suppressed.

The lower limit of the length of the substrate B in the conveying direction (hereinafter referred to as the length of the sprayed region) in the region where the impingement wind speed is 1 m/min or more, as the sprayed region where the gas G is substantially sprayed, is preferably 10 mm, 50 mm is more preferred, and 80 mm is even more preferred. On the other hand, the upper limit of the sprayed region length is preferably 10 mm, more preferably 50 mm. By making the length of the sprayed region equal to or greater than the lower limit, it is possible to suppress the formation of ripples on the coating film due to collision of the gas G with a locally high impingement wind speed. Further, by setting the length of the sprayed area to the upper limit or less, it is possible to prevent the gas particles from dispersing to make the thickness uniform and to prevent an unnecessary increase in energy consumption.

The drying device 4 is a device that dries the coating film F to form a resin film. As a method for drying the coating film F, a method of promoting vaporization of the organic solvent in the coating film F by hot air, radiant heat, or the like can be used.

As is clear from the above description, the film manufacturing apparatus according to one embodiment of the present invention includes a conveying device 1 that continuously conveys a strip-shaped base material B in the longitudinal direction, and a base material B that is conveyed by the conveying device 1. and a smoothing device 3 for smoothing the coating film F formed by the coating device 2 by blowing a gas G onto the coating film F. The impingement wind speed, which is the component of the wind speed of the gas G in the direction perpendicular to the base material, at the surface position of the base material B has a maximum value of 7 m/s or more, and the impingement wind speed is 10 mm before and after the position where the maximum impingement wind speed is the maximum value. The gas G is injected so that the average rate of change from the maximum impinging wind speed is 0.25 m/s or less. According to this film manufacturing apparatus, since the maximum value of the impinging wind speed is large, the thickness unevenness of the coating film F, which is relatively thick, can be reduced. It is possible to suppress the formation of fine wind ripples on the surface of and reduce the appearance defect.

Moreover, the film manufacturing apparatus of this embodiment is an apparatus which implements the film manufacturing method of one embodiment of the present invention. That is, the film manufacturing method of one embodiment of the present invention includes a step of applying a coating liquid P to a strip-shaped base material B that is continuously conveyed in the longitudinal direction (coating step), and a coating formed by the coating. A step of smoothing the coating film F by blowing the gas G onto the film F (smoothing step) and a step of drying the coating film F (drying step), The maximum value of the impinging wind speed, which is the component in the direction perpendicular to the base material B at, is 7 m / s or more, and the maximum value of the impinging wind speed at 10 mm before and after the conveying direction of the base material B at the position where the impinging wind speed is maximum. The average rate of change is 0.25 m/(s·mm) or less. According to this film manufacturing method, since the maximum value of the impinging wind speed is large, the thickness unevenness of the relatively thick coating film can be reduced, and the average rate of change is small, so that fine wind ripples are formed on the surface of the coating film. It is possible to reduce appearance defects by suppressing the occurrence of scratches.

In the film manufacturing method of one embodiment of the present invention, it is preferable that the maximum impinging wind speed is 12 m/s or less. Thereby, the formation of fine wind ripples on the surface of the coating film F can be suppressed more reliably.

In the film manufacturing method of one embodiment of the present invention, the average temperature of the coating film F when the gas G is blown is preferably 10° C. or higher and 40° C. or lower. As a result, drying of the coating film F is suppressed, so that thickness unevenness and poor appearance can be reduced more reliably.

In the film manufacturing method of one embodiment of the present invention, the average thickness of the coating film F is preferably 400 μm or more and 1000 μm or less. Thus, when the thickness of the coating film is large, the effect of suppressing unevenness in thickness and poor appearance is particularly remarkable.

In the film manufacturing method of one embodiment of the present invention, the coating liquid may contain a resin and an organic solvent, and the gas G may contain vaporized gas of the organic solvent. In this way, by blowing the gas G containing the organic solvent contained in the coating liquid onto the coating film, drying of the coating film can be suppressed, and thickness unevenness and poor appearance can be suppressed more reliably.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various changes and modifications are possible.

In the film manufacturing apparatus according to the present invention, the drying device is not essential, and the coating film may be naturally dried.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these Examples.

Polycarbonate (PC), polymethyl methacrylate (PMMA) or polyimide (PI) was dissolved in an organic solvent to adjust the viscosity to 100P, and the coating liquid was applied to the substrate conveyed at a speed of 2.0m/min by a die coater. After coating, gas (mixture of air and gas obtained by vaporizing the organic solvent used in the coating liquid) is blown to the coating film by varying the impingement wind speed distribution in the substrate conveying direction in the smoothing device. A film was prepared by drying the smoothed material, and the thickness and appearance of the obtained film were evaluated.

The thickness is measured using a thickness measuring device "TOF-5R01" manufactured by Yamabun Denki Co., Ltd., and the maximum deviation from the average value (difference between the maximum or minimum value and the average value) is 2% or less of the average value. Those with a maximum deviation of more than 2% were evaluated as "good", and those with a maximum deviation of more than 2% were evaluated as "bad". The appearance was evaluated as "good" when wind ripples were not visually recognized in reflection and projection using a light source, and as "poor" when wind ripples were visually observed.

The wind speed distribution of the gas impinging on the coating film was measured using an anemometer "Anemomaster 6162" manufactured by Nippon Kanomax Co., Ltd. in the absence of the base material. Measured as directional wind speed (impinging wind speed).

Fig. 2 shows the distribution of the measured impinging wind speed, and Table 1 below shows the type of resin used, the maximum value of the impinging wind speed, the average change rate before and after the peak, and the evaluation results of thickness unevenness and appearance quality. show.

From this result, when the maximum value of the impinging wind speed is a certain value and the average change rate of the impinging wind speed before and after the peak is a certain value or more, the thickness unevenness of the obtained film is small, and it is caused by wind ripples. It was confirmed that no appearance abnormality occurred.

REFERENCE SIGNS LIST 1 conveying device 2 coating device 3 smoothing device 4 drying device 11 conveying roller 21 die 31 nozzle B base material F coating film G gas P coating liquid

Claims (6)

A step of applying a coating liquid to a strip-shaped base material that is continuously conveyed in the longitudinal direction;
A step of smoothing the coating film by blowing gas onto the coating film formed by the coating;
a step of drying the coating film;
with
The maximum value of the impinging wind speed, which is the component of the wind speed of the gas in the direction perpendicular to the base material at the surface position of the base material, is 7 m / s or more,
A method for manufacturing a film, wherein an average rate of change from the maximum value of the impinging wind speed is 0.25 m/(s·mm) or less at a position where the impinging wind speed is maximum, 10 mm before and after the base material in the conveying direction. 2. The method of manufacturing a film according to claim 1, wherein the maximum impinging wind speed is 12 m/s or less. The film manufacturing method according to claim 1 or 2, wherein the average temperature of the coating film when the gas is blown is 10°C or higher and 40°C or lower. The film manufacturing method according to any one of claims 1 to 3, wherein the coating film has an average thickness of 400 µm or more and 1000 µm or less. The coating liquid contains a resin and an organic solvent,
5. The film manufacturing method according to any one of claims 1 to 4, wherein the gas contains vaporized gas of the organic solvent. a conveying device for continuously conveying a strip-shaped base material in the longitudinal direction;
a coating device that applies a coating liquid to the base material being transported by the transport device;
a smoothing device for smoothing the coating film formed by the coating device by blowing gas onto the coating film;
with
The smoothing device has a maximum impinging wind speed of 7 m/s or more, which is a component of the wind speed of the gas in a direction perpendicular to the base material at the surface position of the base material, and is located at a position where the impinging wind speed is maximum. A film manufacturing apparatus for injecting the gas so that an average rate of change from the maximum value of the impinging wind speed in 10 mm forward and backward in the conveying direction of the substrate is 0.25 m/(s·mm) or less.

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