JPH09314017A - Coating method and coating device - Google Patents

Abstract

(57) An object of the present invention is to provide a coating method and an apparatus for forming a coating film (coat layer) having a uniform and good appearance on a high speed running film. SOLUTION: When a coating liquid is continuously applied to one surface (A) of a running film and then the other surface (B) is continuously coated with a coating liquid by a die coater, the coating is performed by the die coater. A reverse rotation roll having a smooth surface, which rotates in the reverse direction with respect to the film running direction, is brought into contact with the surface (A) of the running film downstream of the position, and the film thickness of the coating liquid is not changed on the rotating roll. Characteristic coating method and apparatus thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method and an apparatus therefor, and more specifically, it can be applied to a high-speed off-line coating to a running film or a high-speed in-line coating in a film manufacturing process, and has a uniform and good appearance. The present invention relates to a coating method for forming a (coat layer) and its apparatus.

[0002]

2. Description of the Related Art A film (including a sheet) such as a plastic film is coated for the purpose of imparting functions such as easy adhesion, easy slippage, gas barrier property, moistureproof property, antistatic property, and ink receiving property. Is commonly done. Known coaters used for this purpose include, for example, a gravure coater, a kiss roll coater, a reverse roll coater, a slide coater, a curtain coater, a knife coater, and an extrusion die coater.

The roll coater measures the coating liquid at intervals between the rolls, and the gravure roll measures the coating liquid in the size of the roll mesh, and the coating liquid film after the measurement is transferred by the rolls. However, in such a normal roll coater, the coating liquid is exposed to air, and the property tends to change due to drying. Further, when the coating liquid film is transferred from roll to roll or roll to film, a streak pattern is likely to occur due to the disturbance of the liquid pool. For this reason, there are many restrictions on the coating conditions, and this streak pattern is unavoidable especially in high-speed coating.

A die coater has been proposed as a means for compensating for the drawbacks of the roll coater. If a die coater is used, even at high speed coating of 200 m / min or more, a coated surface free of streak defects can be obtained, and the productivity is greatly improved. However, since the die coater controls the coating thickness by the minute gap between the running film and the die tip, wrinkles on the film, tension distribution in the width direction disturbing the flatness, and the film vibrating. Then, there is a problem that coating unevenness occurs.

Therefore, in order to prevent wrinkles and slack from occurring in the film, in JP-A-63-283783, a pair of rolls sandwiches only the uncoated portion of the end portion of the running film immediately after coating, and the outer side in the width direction. A method of providing a cross guider for applying a tension toward the head has been proposed. However, the wrinkles and slacks near the film edge can be removed by the cross guider, but there is a problem that the effect does not reach the central part, and there is no effect of suppressing the vibration at the central part of the film. As a method for preventing film vibration, Japanese Patent Laid-Open No. 62-247861 proposes a method of absorbing film vibration by gas without contacting the film. However, it is difficult to correct wrinkles and irregularities in the flatness of the film by this method.

[0006]

DISCLOSURE OF THE INVENTION As a result of intensive studies made by the present inventors to solve the above problems, a method and apparatus for cutting film vibration and die coating while maintaining the flatness of the film. Has been developed and the present invention has been achieved.

[0007]

That is, the present invention is as follows. When the coating liquid is continuously applied to one surface (A) of the running film and then the coating liquid is continuously applied to the other surface (B) by a die coater, the coating film is downstream from the coating position by the die coater. A coating film characterized in that the surface (A) of the running film on the side is brought into contact with a reverse rotation roll having a smooth surface which rotates in the reverse direction with respect to the film running direction, and the coating liquid film thickness is not changed on the rotation roll. Method and 2. A coating device for continuously coating the coating liquid on one surface (A) of the running film and then continuously coating the coating liquid on the other surface (B) with a die coater. A smooth reverse rotation roll having a surface which can come into contact with the surface (A) of the running film on the downstream side of the position and which rotates reversely with respect to the running direction of the film is provided, and the coating film thickness on the rotating roll is changed. The coating device is characterized by having no means.

The present invention will be described below with reference to the drawings. FIG. 1 is an explanatory view of a coating apparatus showing one embodiment of the present invention. Although the drawing shows a case where the film is applied to both sides of the film with a die coater, the present invention is not limited to this form and can be applied to a case where one side is applied with a die coater. That is, this is a case where the die coater 3 is changed to another coater. FIG. 2 is an explanatory view of a coating device by a conventional method using a cross guider.

In FIG. 1, reference numeral 1 is a traveling film, 2,
2'is a guide roll, 3, 3'is a die coater, 4 is a reverse rotation roll, 5 is a cleaning liquid, 6 is a cleaning liquid pan, 7,
7'is the coating film, 8 and 8'is the liquid separation edge of the die, d,
The d'is the distance from the liquid release edge of the die coater to the film center of the roll closest to the film of the roll closest to the liquid release edge of the die which is in contact with the film during coating.

The running film 1 is not particularly limited depending on the material, but a plastic film is preferable. Examples of the plastic film include polyolefin film (for example, polyethylene film, polypropylene film, etc.), polyester film (for example, polyethylene terephthalate film, polyethylene-2,6-naphthalate film, etc.), polyamide film (for example, nylon 6 film, nylon 66 film, etc.). ), Polyetheretherketone film, polycarbonate film and the like. Among these, polyester film, particularly polyethylene terephthalate film and polyethylene-2,6-naphthalate film are preferable.

The thickness of the running film 1 is preferably in the range of 5 to 800 μm, particularly preferably in the range of 10 to 200 μm. The traveling speed of the traveling film is preferably 5 to 1000 m / min, particularly 10 to 35
The optimum value is 0 m / min.

In the present invention, the coating liquid has functional properties on the film surface, such as adhesiveness (including easy adhesion, heat sealing property), easy slippage (running property), antistatic property, conductivity, abrasion resistance, Scratch resistance, weather resistance, mold releasability, chemical resistance (including water resistance, solvent resistance), easy printability, drop resistance, stain resistance, writing ability,
Any coating solution may be used as long as it is a surface processing coating liquid that imparts light-shielding properties, waterproof properties, gas barrier properties, and the like. As these coating liquids, those conventionally known or used can be used. The viscosity of the coating liquid is 1 to 200
Centipoise (cp), more preferably 1.1 to 20 cp.

The guide rolls 2, 2'may be general-purpose guide rolls usually used in a plastic film transport system. The surface is preferably chrome-plated, but may be any surface-treated or non-surface-treated as long as it does not affect the film.

The die coaters 3 and 3'uniformly spread the coating liquid sent from a coating liquid supply system (not shown) in the film width direction within the manifold (however, it is narrower than the film width) and have a constant width. The film is extruded through the slits to the opposing traveling film 1 and is weighed to a certain thickness by the gap between the traveling film and the liquid separating edge of the die lip on the downstream side of the traveling film. This gap can be adjusted by the running speed and tension of the film and the amount of coating liquid discharged from the die.

As the reverse rotation roll 4, for example, an applicator roll of a roll coater can be used as it is. It is preferable that the surface in contact with the running film is hard chrome plated. The main purpose of this roll is to guide the running film 1 from the surface side coated with the coating liquid, and this roll has no means for changing the thickness of the coating liquid film.
For example, it is not necessary to use this roll as a gravure roll or to provide a measuring means such as a doctor knife. The surface speed (Vgr: m / min) of the reverse rotating roll 4 is 0. 0 with respect to the speed (Vf: m / min) of the running film.
The speed is preferably 2Vf≤Vgr≤3.0Vf, and more preferably 0.4Vf≤Vgr≤1.5Vf. The rotation direction is the reverse direction with respect to the traveling film 1.

The reverse rotation roll 4 is used as an edge gripping tool when the coating liquid applied by the die coater 3 is spread on the back surface (front surface B) of the running film 1 or when the dryer after coating grips the film edge. In order to prevent the undried coating liquid from adhering, a step is provided at the end of the roll, that is, the outer diameter of both end portions of the roll is 2 to 20 mm smaller than the outer diameter of the central portion, and the central portion is the center of the roll. From the end to the end of the range a (mm) defined by the following formula,
It is preferable that the coating liquid does not spread to the edge of the running film.

[0017]

## EQU00002 ## (Wdc / 2) .ltoreq.a.ltoreq. (Wdc / 2) +50 (mm) where Wdc is the coating width (mm) in the die coater 3.

Reverse rotating roll 4 or cleaning liquid pan 6
Has a structure capable of moving up and down, and the surface of the rotary roll 4 is immersed in the cleaning liquid 5 when not coated. This prevents the coating liquid adhering to the surface of the reverse rotation roll 4 from drying and solidifying, becoming foreign matter when adhering again, and adhering to the traveling film 1 to be transferred to cause a defect.
Also, even if a reverse rotating roll is applied to the film when there is no liquid film on the running film when starting the coating, the cleaning liquid remaining on the roll surface acts as a lubricant, so that the coating start can be smoothed. You can

The cleaning liquid 5 is preferably one containing water as a main component and a slight amount of a surfactant added. A commercially available liquid detergent may be used as the surfactant.

In the present invention, the coater for applying the coating liquid on one surface (A) of the running film is optional,
From the viewpoint of high-speed coating property, a die coater as shown in FIG. 1 is preferable. Examples of other coaters include a gravure coater, a kiss roll coater, a reverse roll coater, and a slide coater.

In the coating method of the present invention, the coating liquid is continuously coated on one surface (A) of the running film, and then the coating liquid is continuously coated on the other surface (B) by a die coater. At this time, the surface of the running film on the downstream side of the coating position by the die coater (A) is brought into contact with a reverse rotating roll having a smooth surface which reversely rotates in the film running direction,
Further, it is characterized in that the coating liquid film thickness is not changed on the rotating roll. The distance (d) between the liquid separating edge of the die coater that applies the coating liquid on the surface (B) of the running film by this coating and the center line perpendicular to the film of the reverse rotation roll.
Is preferably 5 to 100 mm, and the surface rotation speed of the reverse rotation roll is preferably 0.2 to 3 times the film traveling speed (m / min). Further, it is preferable to provide a non-coating area having a width of 5 to 100 mm at both end portions of the running film.

Before continuous coating, the reverse rotary roll is rotated and washed while the surface is immersed in the cleaning liquid, the rotary roll is separated from the cleaning liquid at the time of coating, and the cleaning liquid remaining on the surface of the rotary roll is removed. Is used as a lubricant when it comes into contact with the surface (A) of the running film, and after application is completed, the reverse rotation is rotated and washed while the surface is immersed in the washing liquid, and the coating liquid on the roll surface is prevented from drying. Preferably. In the coating on one surface (A) of the running film, the surface (B) of the running film is provided on the downstream side of the position where the surface (A) is applied and before the coating liquid is applied to the film surface (B). It is preferable to bring the rotating roll into contact with (1). The rotating roll is rotated in the same direction as the normal running direction of the film.

[0023]

EXAMPLES The present invention will be described in more detail with reference to examples.

[Embodiment 1] In the coating apparatus shown in FIG. 1, a die coater having a coating width of 1000 mm and a reverse rotating roll having a large roll diameter at the central portion of 1020 mm were used, and both d and d ′ were 50 mm. Set the die coater, and set the upper and lower die coaters (3, 3 ') to 1
0 cp of water-based emulsion coating liquid was supplied. Thickness 200
A polyethylene terephthalate film having a width of 1100 mm and a width of 1100 mm was coated on both surfaces of the film while running at a speed of 100 m / min. A dryer (not shown) for holding the edge portion of the running film and drying and solidifying the coating liquid film with hot air was installed on the downstream side of the coating device. If there is no coating machine, the center of the running film at the coating position is about 50
The vibration was about 2 mm at Hz.

Before the start of coating, the reverse rotation roll 4 was lowered downward and immersed in the cleaning liquid 5 at 10 m / min.
Was rotated at the surface speed of. When the rotating roll 4 is moved upward at the start of coating, the excess cleaning liquid drops by gravity,
A film of the cleaning liquid was formed on the roll surface. In this state, the reverse rotation roll 4 was brought into contact with the film, but the rotation was stable. Before the surface liquid of the roll was exhausted, a coating film was formed on the lower surface (A surface) by the die coater 3, and the coating state was directly transferred. After that, coating was started by the die coater 3'on the upper surface (B surface), and the surface speed of the reverse rotation roll 4 was increased to 110 m / min.

During the coating, the running film 1 between the guide roll 2 and the guide roll 2'had no wrinkles, slack and vibration, and the coating by the die coater 3 was performed stably. Similarly, the running film 1 between the guide roll 3'and the reverse rotation roll 4 was free from wrinkles, slack and vibration, and the coating by the die coater 3'was carried out stably. The coating film on both sides of the film downstream of the reverse rotation roll 4 has no streaks,
It was good.

After that, the coating was once terminated to change the coating liquid. At that time, the coating films on both surfaces of the film downstream of the reverse rotation roll 4 were good with no streaks.

After that, the coating was once terminated to change the coating liquid. At that time, lower the reverse rotation roll 4 downward,
The roll surface was rotated while being immersed in the cleaning liquid. The coating liquid on the surface of the rotating roll was dissolved in the cleaning liquid, and the roll surface was almost clean. About 1 hour later, even when coating was started again, the surface of the reverse rotation roll remained wet with the cleaning liquid, and coating was started as it was, but there was no trouble such as foreign matter adhering to the film, and it was stable. It was possible to apply.

Comparative Example 1 Coating was carried out in exactly the same manner as in Example 1 except that the reverse rotation roll 4 was lowered downward so that the roll surface did not come into contact with the running film. The running film behind the guide rolls 2'is vibrated by the hot air dryer, and the coating film 7'on the upper die coater 3'has a streak called transverse stripes in the direction perpendicular to the film running direction. Seen in. Further, since the dryer is of a type that grabs the edge of the film, the central part of the film hangs down slightly due to its own weight, and the thickness of the coating film 7'is thinner toward the end part.

In this coating, the coating film 7 on the lower surface had no problem, but the coating film 7'on the upper surface was not at a level that could be commercialized.

[Comparative Example 2] Double-sided coating was carried out in exactly the same manner as in Example 1 except that a reverse rotating roll was not used and a coating device having cross guiders 24, 24 'provided at that position was used. The traveling film 21 behind the guide rolls 22 'had its vibration suppressed by the effect of the cross guider in the area of about 30 cm near the end, but in the center, the vibration was seen by the hot air dryer, and the die coater 23 on the upper surface. In the central part of the coating film 7 ', the horizontal streaks were generated. Also, the sagging in the center of the film is not as great as in Comparative Example 1,
The thickness of the coating film 25 'was thinner toward the edge of the film.

In this coating, the coating film 25 on the lower surface had no problem, but the coating film 25 'on the upper surface was not at a level that could be commercialized.

[Embodiments 2 and 3] With the coating equipment and coating conditions of Embodiment 1, the distance d between the liquid separation edge of the die coater and the center line of the guide roll 2'and the reverse rotation roll 4,
d ', the speed Vgr of the reverse rotation roll was changed and coating was performed.

Table 1 shows the results.

[0035]

[Table 1]

[0036]

EFFECT OF THE INVENTION In the die coating method, the film is completely vibrated and wrinkled at the coating position by contacting a reverse rotary roll from the opposite coating surface side, and the positional relationship between the die and the rotary roll is specified. Can be removed. As a result, a high-quality coating surface without coating spots or coating streaks can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view showing one coating device of the present invention.

FIG. 2 is an explanatory diagram showing a conventional coating device using a cross guider. [Explanation of reference symbols] 1,21 Traveling film 2,2 ', 22,22' Guide roll 3,3 ', 23,23' Die coater 4 Reverse rotation roll 5 Cleaning liquid 6 Cleaning liquid pan 7,7 ', 25,25' Coating film 8,8 'Die release edge d, d'Distance between die coater release edge and center line perpendicular to film Vf Velocity of running film Vgr Reverse rotation roll

Claims (12)

[Claims] 1. When the coating liquid is continuously applied to one surface (A) of the running film and then the coating liquid is continuously applied to the other surface (B) with a die coater, the die coater is used. Do not contact the surface (A) of the running film on the downstream side of the coating position with a reverse rotating roll that rotates in the reverse direction with respect to the film running direction and has a smooth surface, and do not change the coating liquid film thickness on the rotating roll. A coating method characterized by: 2. The distance (d) between the liquid separating edge of the die coater for applying the coating liquid on the surface (B) of the running film and the center line perpendicular to the film of the reverse rotation roll is 5
The coating method according to claim 1, wherein the coating method is about 100 mm. 3. The surface rotation speed of the reverse rotation roll is
0.2 to 3 times the film running speed (m / min)
The coating method according to claim 1, wherein 4. The running film has 5 to 100 m on both side edges.
The coating method according to claim 1, wherein a non-coated area having a width of m is provided. 5. Prior to continuous coating, a reverse rotating roll is rotated and washed while the surface is immersed in a cleaning liquid, the rotating roll is separated from the cleaning liquid at the time of coating, and the cleaning liquid remaining on the surface of the rotating roll is removed. The coating method according to claim 1, which is used as a lubricant when the rotating roll is brought into contact with the surface (A) of the running film. 6. After the coating is finished, the reverse rotation roll is rotated and washed with the surface immersed in the cleaning liquid, and
The coating method according to claim 1, which prevents the coating liquid on the roll surface from drying. 7. The coating method according to claim 1, wherein the surface (A) of the running film is coated with a coating liquid with a die coater. 8. A rotating roll is brought into contact with the surface (B) of the running film on the downstream side of the position where the coating liquid is applied to the film surface (A) and before the coating liquid is applied to the film surface (B). The coating method according to claim 7. 9. The distance between the liquid separating edge of the die coater for applying the coating liquid on the surface (A) of the running film and the center line (contacting the surface (B) of the running film and perpendicular to the film of the rotating roll ( 9. d) is 5 to 100 mm.
Coating method. 10. A coating device for continuously coating a coating liquid on one surface (A) of a running film, and then continuously coating the coating liquid on the other surface (B) with a die coater, The surface of the running film (A) on the downstream side of the coating position by the die coater can be contacted, and a smooth reverse rotation roll having a surface that rotates in the opposite direction to the film running direction is provided, and the coating liquid on the rotation roll is provided. A coating apparatus having no means for changing the film thickness. 11. The distance (d) between the liquid separating edge of the die coater for applying the coating liquid on the surface (B) of the running film and the center line perpendicular to the film of the reverse rotation roll is 5 to 100 mm. The coating device according to claim 10. 12. The outer diameter of both end portions of the reverse rotation roll is smaller than the outer diameter of the central portion by 2 to 20 mm, and the central portion has a distance a (mm defined from the center of the roll toward the end portion by the following formula). The coating device according to claim 10, which is in the range of (4). ## EQU00001 ## (Wdc / 2) .ltoreq.a.ltoreq. (Wdc / 2) +50 (mm) Here, Wdc is the coating width (mm) of the coating liquid on the film surface (A).