JP7503466B2 - Film manufacturing method and film manufacturing apparatus - Google Patents

Description

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

A method for producing a resin film is known in which a coating solution in which a resin is dissolved in an organic solvent is applied to a substrate, and the coating film formed by the coating is dried. When producing a film by this method, it may be necessary to produce a coating film that is 40 μm or thicker and has an excellent appearance in order to obtain the required functionality.

It is known that using a low-viscosity coating fluid reduces the appearance defects of the coating film from coating to drying due to the surface tension of the coating fluid. However, if the viscosity is low, the coating film will flow after coating and a thick film cannot be maintained. On the other hand, if the viscosity is increased to obtain a thick film, the effects of coating unevenness (streaks, step unevenness) caused by bead defects in the coated area become more pronounced, making it impossible to obtain a coating film with a good appearance.

The following Patent Document 1 describes a coating film forming method that includes a step of applying paint to one side of a support (base film) while moving the support relative to the paint application position, and a step of smoothing the paint-applied surface by blowing at least a gas after the application. Patent Document 1 claims that blowing gas onto the coating film immediately after application stops the flow and makes it possible to smooth the coated surface.

JP 2004-261791 A

The method described in Patent Document 1 can be used to obtain a film with a smooth coating, but when applied to a coating with a thick wet film, wind ripples are generated on the coating surface, which are recognized by the human eye as a defective appearance. Such wind ripples that cause a defective appearance become defects when the obtained film is used as an optical film.

The objective of the present invention is to provide a method and apparatus for manufacturing thick films that reduces appearance defects.

After extensive research, the inventors have discovered that the following configuration provides a thick film manufacturing method and film manufacturing device that reduces appearance defects.

(1) A method for producing a film, comprising the steps of:
A coating step of applying a coating liquid containing a solvent-soluble resin and a solvent onto a support by using a coating means to form a coating film;
The method includes a film thickening step of increasing the viscosity of the coating film by blowing gas onto the coating film, and a step of drying the coating film,
the maximum value of the collision wind speed, which is a component of the wind speed of the gas in the direction perpendicular to the substrate at the surface position of the substrate in the thickening step of increasing the viscosity of the coating film by blowing the gas, is 2.0 m/s or more and 7.0 m/s or less;
A film manufacturing method, wherein an average rate of change from the maximum collision wind speed in a range 10 mm before and after, in the transport direction of the substrate, a position where the collision wind speed is maximum is 0.25 m/(s·mm) or less.

(2) The film manufacturing method described in (1), characterized in that the viscosity of the coating liquid is 1 to 50 cP.

(3) A film manufacturing method according to (1) or (2), characterized in that the temperature of the gas blown is 15 to 35°C.

(4) A film manufacturing method according to any one of (1) to (3), in which the average thickness of the coating film is 80 μm or more and 200 μm or less.

(5) A conveying device that continuously conveys a strip-shaped base material in a longitudinal direction;
a coating device that applies a coating liquid to the substrate being transported by the transport device;
a film thickening device that increases the viscosity of the coating film formed by the coating device by blowing gas onto the coating film,
The thickening device is a film manufacturing device that blows gas so that the maximum value of the collision wind speed, which is the component of the gas wind speed at the surface position of the substrate in the direction perpendicular to the substrate, is 2.0 m/s or more and 7.0 m/s or less, and the average rate of change from the maximum value of the collision wind speed 10 mm before and after the conveying direction of the substrate at the position where the collision wind speed is maximum is 0.25 m/(s·mm) or less.

The present invention provides a method and apparatus for manufacturing thick films that reduces appearance defects.

1 is a schematic diagram showing a configuration of a film manufacturing apparatus according to an embodiment of the present invention. 13 is a graph showing the distribution of impingement wind speed in a prototype example.

Hereinafter, an embodiment 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 strip-shaped substrate B (support) in the longitudinal direction, a coating device 2 that applies a coating liquid P to the substrate B being conveyed by the conveying device 1, a film-thickening device 3 that increases the viscosity of the coating film F by spraying gas G onto the coating film F formed by the coating device 2, and a drying device 4 that dries the coating film F thickened by the film-thickening device 3.

As shown in the figure, the conveying device 1 can be configured to continuously convey a long strip-shaped substrate by a plurality of conveying rollers. In this case, the conveying device 1 may be configured to unwind and convey the substrate B wound on a reel, and to wind the substrate B onto another reel after peeling off the product film formed by drying the coating film F.

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

Although not limited to this, in the illustrated example, the coating device 2 is configured to have a die 21 that ejects 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 can contain a resin that is the main component of the functional film to be formed and an organic solvent that dissolves this resin.

The resin contained in the coating liquid P is not particularly limited, but for example, when the resulting film is to be used for optical purposes, acrylic resin, epoxy resin, urethane resin, silicone resin, etc. are preferably used.

The weight average molecular weight of the resin contained in the coating liquid P is preferably 500 to 20,000, more preferably 2,000 to 14,000, and even more preferably 3,000 to 12,000. When the weight average molecular weight of the resin is equal to or greater than the lower limit, volatilization of the resin can be suppressed in the coating film F formed by the coating device 2. When the weight average molecular weight of the resin is equal to or less than the upper limit, excessive increase in viscosity of the coating liquid P can be suppressed, and a thick film with reduced appearance defects can be obtained by the film thickening device 3.

The viscosity of the coating liquid P is preferably 1 to 50 cP, more preferably 5 to 35 cP, and even more preferably 10 to 20 cP. When the viscosity is equal to or higher than the lower limit, the effect of thickening the coating film F formed by the coating device 2 with the film thickening device 3 can be sufficiently obtained. When the viscosity of the coating liquid P is equal to or lower than the upper limit, the film thickening device 3 can obtain a thick film with reduced appearance defects.

The solid content concentration of the coating liquid P is preferably 30 to 70%, more preferably 40 to 60%, and even more preferably 45 to 55%. When the solid content concentration is equal to or higher than the lower limit, the coating film F formed by the coating device 2 does not become excessively thick, and the thickening device 3 can obtain a thick film with reduced appearance defects. When the solid content concentration of the coating liquid P is equal to or lower than the upper limit, the leveling effect can be fully exerted, and the thickening device 3 can obtain a thick film with reduced appearance defects.

The organic solvent contained in the coating liquid P is not particularly limited, but for example, solvents such as toluene, methyl isoethyl ketone, and propylene glycol monomethyl ether are preferred. By using a solvent in such a boiling point range, it is desirable from the standpoint of reducing the amount of residual organic solvent and equipment costs even when manufacturing a product film with a relatively large thickness.

To prevent poor appearance, it is necessary to reduce the viscosity of the coating liquid P in the coating area. If the viscosity of the coating liquid P is low, it becomes difficult to form a thick film, but the thickening device 3 makes it possible to coat a thick film while preventing poor appearance.

The lower limit of the average thickness of the coating film F formed by the coating device 2 is preferably 80 μm, more preferably 120 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 200 μm, more preferably 160 μm. If the average thickness of the coating film F formed by the coating device 2 is equal to or greater than the lower limit, it is difficult to maintain the thickness of the coating film F, and appearance defects are likely to occur, so the effect of obtaining a thick film with reduced appearance defects by the film thickening device 3 becomes significant. Also, if the average thickness of the coating film F formed by the coating device 2 is equal to or less than the upper limit, the film thickening device 3 can obtain a thick film with reduced appearance defects.

The lower limit of the average temperature (gas temperature) of the coating film F formed by the coating device 2 in the area where the gas G is sprayed by the thickening device 3 (spraying area described later) is preferably 15°C, more preferably 20°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 35°C, more preferably 25°C. By setting the average temperature of the coating film F formed by the coating device 2 to the lower limit or higher, cooling is not required, so that the increase in the 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 the upper limit or lower, it is thought that it is possible to prevent a large amount of organic solvent in the coating film F from evaporating when maintaining the thick film in the thickening device 3 after coating, which inhibits smoothing by subsequent leveling.

The film thickening device 3 maintains the thickness of the coating film F by blowing gas G perpendicularly onto the coating film F formed by the coating device 2.

The film-thickening device 3 has a nozzle 31 that sprays gas G onto the coating film F. The nozzle 31 has a slit-shaped outlet that extends perpendicular to the conveyance direction of the substrate B and parallel to the surface of the substrate B (parallel to the width direction of the substrate B), and the flow path immediately before the outlet tapers toward the outlet, with the dimension of the flow path narrowing (the short side direction of the outlet of the flow path) decreasing toward the outlet.

The lower limit of the maximum collision wind speed, which is the component of the wind speed of the gas G at the surface position of the substrate B in the direction perpendicular to the substrate B, is preferably 2.0 m/s, more preferably 3.0 m/s, and even more preferably 3.8 m/s. On the other hand, the upper limit of the maximum collision wind speed is preferably 7.0 m/s, more preferably 6.0 m/s, and even more preferably 5.4 m. By setting the maximum collision wind speed to the lower limit or higher, the thickness of the coating film F can be sufficiently maintained. In addition, by setting the maximum collision wind speed to the upper limit or lower, wind ripples on the surface of the coating film F and scattering of the coating film can be suppressed. The collision wind speed is a value measured by an anemometer placed at a position where the substrate B is transported without the substrate B.

The lower limit of the average rate of change from the maximum value of the collision wind speed at 10 mm forward and backward in the conveying direction of the substrate B at the position where the collision wind speed is maximum (the average value of the value obtained by dividing the change in the maximum wind speed by the distance of 10 mm forward and backward, hereinafter referred to as the average rate of change before and after the peak) is preferably 0.02 m/(s·mm), more preferably 0.04 m/(s·mm), and even more preferably 0.06 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), and even more preferably 0.15 m/(s·mm). By setting the average rate of change before and after the peak to the lower limit or more, it is possible to prevent the range where the gas G collides from becoming too large while making the maximum value of the collision wind speed sufficiently large. In addition, by setting the average rate of change before and after the peak to the upper limit or less, 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 substrate B is suppressed, and the formation of wind ripples on the surface of the coating film F can be suppressed.

The drying device 4 is a device that dries the coating film F to form a resin film. The method of drying the coating film F can be a method that promotes the evaporation of the organic solvent in the coating film F by using hot air, radiant heat, etc.

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 substrate B in the longitudinal direction, a coating device 2 that applies a coating liquid P to the substrate B being conveyed by the conveying device 1, and a thickening device 3 that thickens the coating film F formed by the coating device 2 by blowing gas G onto the coating film F. The thickening device 3 injects gas G so that the maximum value of the collision wind speed, which is the component of the wind speed of the gas G at the surface position of the substrate B in the direction perpendicular to the substrate, is 2.0 m/s or more and 7.0 m/s or less, and the average rate of change from the maximum value of the collision wind speed 10 mm before and after the position where the collision wind speed is maximum is 0.25 m/s or less. According to this film manufacturing apparatus, the thickness of the coating film can be maintained by keeping the maximum value of the collision wind speed within a predetermined range, and the small average rate of change before and after the peak of the collision wind speed suppresses the formation of wind ripples on the surface of the coating film F, thereby reducing appearance defects.

The film manufacturing apparatus of this embodiment is an apparatus for carrying out 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 process (coating process) of applying a coating liquid P to a strip-shaped substrate B continuously transported in the longitudinal direction, a process (thickening process) of thickening the coating film F formed by coating by blowing gas G onto the coating film F, and a process (drying process) of drying the coating film F, in which the maximum value of the collision wind speed, which is the component of the wind speed of the gas G in the direction perpendicular to the substrate B at the substrate B surface position, is 2.0 m/s or more, and the average rate of change from the maximum value of the collision wind speed at 10 mm before and after the transport direction of the substrate B at the position where the collision wind speed is maximum is 0.25 m/(s·mm) or less. According to this film manufacturing method, the thickness of the coating film can be maintained by keeping the maximum value of the collision wind speed within a predetermined range, and the small average rate of change suppresses the formation of wind ripples on the surface of the coating film, thereby reducing appearance defects.

In one embodiment of the film manufacturing method, it is preferable that the average temperature of the coating film F when the gas G is sprayed is 15°C or more and 35°C or less. This prevents the coating film F from drying excessively, making it possible to obtain a thick film with reduced appearance defects.

In one embodiment of the film manufacturing method, it is preferable that the average thickness of the coating film F is 80 μm or more and 200 μm or less. In this way, when the coating film is thick, the effect of obtaining a thick film with reduced appearance defects becomes particularly remarkable.

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

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

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

A reaction vessel was charged with 100 parts by weight of β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 0.12 parts by weight of magnesium chloride, 11 parts by weight of water, and 11 parts by weight of propylene glycol monomethyl ether, and the mixture was stirred at 130°C for 3 hours, and then degassed under reduced pressure at 60°C to obtain a siloxane resin. 100 parts by weight of the above siloxane resin, 2 parts by weight of a propylene carbonate solution of triarylsulfonium.SbF6 salt, 0.2 parts by weight of a xylene/isobutanol solution of polyether-modified polydimethylsiloxane, and propylene glycol monomethyl ether were mixed. A coating solution containing 100 parts by weight of glycol monomethyl ether and adjusted to a viscosity of 10 cP was applied to a substrate conveyed at a speed of 2.0 m/min by a die coater so that the wet film thickness immediately after coating was 150 μm. In a thickening device, the blower, valve, nozzle, and coating distance were controlled to vary the distribution of the impingement wind speed in the substrate conveying direction as shown in Figure 2, and the thickened film was blown onto the coating film to be dried by heating at 120 ° C for 2 minutes. Thereafter, the coating film was cured by irradiating it with ultraviolet light at a wavelength of 250 to 390 nm using a high-pressure mercury lamp so that the integrated light amount was 1000 mJ/cm ² , to obtain a coated film. The film thickness and appearance of the obtained film were evaluated.

Thickness was measured using a thickness measuring device "TOF-5R01" manufactured by Yamabun Denki Co., Ltd., and a value with an average of 75 μm or more and a maximum deviation from the average (the difference between the maximum or minimum value and the average) of 2% or less of the average was rated "good", while a value with an average of less than 75 μm or a maximum deviation of more than 2% was rated "poor". For appearance, when visually inspected by reflection and projection using a light source, a value with no visible wind ripples was rated "good", and a value with visible wind ripples was rated "poor".

The wind speed distribution of the gas colliding with the coating was measured in the absence of the substrate using an anemometer "Anemomaster 6162" manufactured by Kanomax Japan, as the wind speed perpendicular to the substrate (collision wind speed) at each position on the surface along which the substrate was being transported.

Figure 2 shows the distribution of the measured impact wind speed, and Table 1 below shows the type of resin used, the maximum impact wind speed and the average rate of change before and after the peak, as well as the evaluation results of the film thickness and appearance.

From these results, it was confirmed that when the maximum collision wind speed is within a certain range and the average rate of change around the peak of the collision wind speed is below a certain level, the thickness of the resulting film is good and no abnormal appearance due to wind ripples occurs.

REFERENCE SIGNS LIST 1 Conveying device 2 Coating device 3 Thickening device 4 Drying device 11 Conveying roller 21 Die 31 Nozzle B Substrate F Coating film G Gas P Coating liquid

Claims (5)

A method for producing a film, comprising the steps of:
A coating step of applying a coating liquid containing a solvent-soluble resin and a solvent onto a support by using a coating means to form a coating film;
The method includes a film thickening step of increasing the viscosity of the coating film by blowing gas onto the coating film, and a step of drying the coating film,
the maximum value of the collision wind speed, which is a component of the wind speed of the gas in the direction perpendicular to the substrate at the surface position of the substrate in the thickening step of increasing the viscosity of the coating film by blowing the gas, is 2.0 m/s or more and 7.0 m/s or less;
A film manufacturing method, wherein an average rate of change from the maximum collision wind speed in a range 10 mm before and after, in the transport direction of the substrate, a position where the collision wind speed is maximum is 0.25 m/(s·mm) or less. The film manufacturing method described in claim 1, characterized in that the viscosity of the coating liquid is 1 to 50 cP. The film manufacturing method according to claim 1 or 2, characterized in that the temperature of the gas blown is 15 to 35°C. The film manufacturing method according to any one of claims 1 to 3, wherein the average thickness of the coating film is 80 μm or more and 200 μm or less. A conveying device that continuously conveys a strip-shaped base material in a longitudinal direction;
a coating device that applies a coating liquid to the substrate being transported by the transport device;
a film thickening device that increases the viscosity of the coating film formed by the coating device by blowing gas onto the coating film,
The thickening device is a film manufacturing device that blows gas so that the maximum value of the collision wind speed, which is the component of the gas wind speed at the surface position of the substrate in the direction perpendicular to the substrate, is 2.0 m/s or more and 7.0 m/s or less, and the average rate of change from the maximum value of the collision wind speed 10 mm before and after the conveying direction of the substrate at the position where the collision wind speed is maximum is 0.25 m/(s·mm) or less.

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