Coating device and coating method for sheet-like substrate

Abstract

To provide a coating device and a coating method which can form a thin coated film on a sheet-like substrate with high quality, even by using any coating liquid and even under any coating condition.SOLUTION: A coating device according to the present invention, which forms a coated film on a sheet-like substrate being continuously conveyed, comprises: a conveying mechanism for the sheet-like substrate; a die having a discharge surface on which a slit-shape discharge port for coating liquid extending in a width direction that is a direction of a width of the sheet-like substrate, which is arranged so that the discharge surface opposes to the sheet-like substrate; and an air nozzle, arranged at a position opposing to the die through the sheet-like substrate, which sprays air in a direction of the discharge surface, in which a spraying width, in the width direction on a surface of the sheet-like substrate, of air sprayed from the air nozzle is equal to 80% or more of a length in the width direction of the discharge port for the coating liquid.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a coating apparatus and a coating method for forming a coating film on a sheet-like substrate, and more particularly to a coating apparatus and a coating method capable of forming a high-quality coating film even if the coating film is thin. [Background technology]

[0002] Coating techniques for forming functional coating films on sheet-like substrates such as films, metal foils, paper, textiles, and nonwoven fabrics are used in various fields such as functional films, paper products, cloth products, membrane products, batteries, electrical appliances, and semiconductor materials. In particular, for applications requiring uniformity in the thickness of the coating film, a coating die having a slit-shaped outlet is preferably used. There are various types of coating devices using dies, but in the case of a thin coating film, an extrusion coating device that discharges a coating liquid while pressing the discharge surface of the die against the sheet-like substrate, as in Patent Document 1 and Patent Document 2, is disclosed. In the extrusion coating device, a certain thickness of liquid pool is maintained between the discharge surface of the die and the sheet-like substrate without being affected by uneven thickness of the sheet-like substrate or eccentricity of the transport roller due to the balance between the pressure of the coating liquid discharged from the die and the conveying tension of the sheet-like substrate, and a thin coating film can be stably formed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-36761 A [Patent Document 2] Patent No. 2754038 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the methods disclosed in Patent Documents 1 and 2, when the pressure of the coating liquid discharged from the die is extremely small relative to the conveying tension of the sheet-like substrate, specifically when the viscosity of the coating liquid is low, the thickness of the coating film is extremely thin, or the conveying speed of the sheet-like substrate is slow, a part of the liquid pool between the discharge surface of the die and the sheet-like substrate is crushed by the conveying tension of the sheet-like substrate, causing coating defects such as streaks, smudges, and uneven film thickness in the coating film. The conveying tension of the sheet-like substrate cannot be easily lowered from the viewpoint of preventing wrinkles, meandering, and collapse of the sheet-like substrate, and when the above-mentioned coating defects occur, the viscosity of the coating liquid and the coating conditions must be changed.

[0005] Therefore, the present invention provides a coating device and a coating method that are capable of forming a thin coating film with good quality on a sheet-like substrate regardless of the coating liquid and coating conditions. [Means for solving the problem]

[0006] [1] The coating device for a sheet-like substrate of the present invention that solves the above-mentioned problems is a coating device that forms a coating film on a continuously transported sheet-like substrate, The width direction of the sheet-like substrate is defined as the width direction. A conveying mechanism for the sheet-like substrate; a die having a discharge surface formed with a slit-shaped discharge port for a coating liquid extending in a width direction, the discharge surface being disposed so as to face the sheet-like substrate; and an air nozzle that is disposed at a position facing the die across the sheet-like substrate and that blows air in the direction of the discharge surface, wherein the width of the air blown from the air nozzle in the width direction on the surface of the sheet-like substrate is 80% or more of the width direction length of the discharge port of the coating liquid.

[0007] The coating device for the sheet-like substrate of the present invention preferably has any one of the following aspects [2] to [5]. [2] The coating device for a sheet-like substrate according to [1] above, wherein the air blowing width is 90% or more and 110% or less of the length in the width direction of the discharge port of the coating liquid. [3] The coating device for a sheet-like substrate according to [1] or [2] above, wherein the air nozzle has a slit-shaped air outlet extending in the width direction. [4] The coating device for a sheet-like substrate according to any one of [1] to [3] above, wherein the die is installed at a position where the discharge surface does not come into contact with the sheet-like substrate when the blowing of air from the air nozzle to the sheet-like substrate is stopped. [5] The coating device for a sheet-like substrate according to any one of [1] to [4] above, further comprising a supply mechanism for supplying a coating liquid to the die, and a control section, wherein the control section controls the blowing of air from the air nozzle and the supply of the coating liquid from the supply mechanism, and controls so as to stop the blowing of air from the air nozzle for at least a part of the period during which the supply of the coating liquid is stopped while repeatedly starting and stopping the supply of the coating liquid from the supply mechanism.

[0008] [6] A coating method for a sheet-like substrate of the present invention that solves the above-mentioned problems is a coating method for forming a coating film on a continuously transported sheet-like substrate, comprising the steps of: The width direction of the sheet-like substrate is defined as the width direction. a die having a discharge surface on which a slit-shaped discharge port for a coating liquid extending in a width direction is formed, the discharge port for the coating liquid is disposed so as to face the sheet-like substrate; While discharging the coating liquid from a discharge port of the coating liquid onto the sheet-like substrate being transported, Air is blown onto the sheet-like substrate from the side opposite to the side on which the die is disposed, in the direction of the discharge surface of the die, so that the width of the blown air in the width direction on the surface of the sheet-like substrate is 80% or more of the width direction length of the discharge port of the coating liquid.

[0009] The coating method for the sheet-like substrate of the present invention is preferably any one of the following methods [7] to

[10] . [7] The method for coating a sheet-like substrate according to [6] above, wherein the air blowing width is from 90% to 110% of the length in the width direction of the discharge port of the coating liquid. [8] The method for applying to a sheet-like substrate according to [6] or [7] above, wherein air is blown in a slit pattern onto the sheet-like substrate. [9] The method for coating a sheet-like substrate according to any one of [6] to [8] above, wherein the discharge surface of the die does not come into contact with the sheet-like substrate when air is not being blown onto the sheet-like substrate.

[10] A coating method for intermittently forming a coating film on the sheet-like substrate according to any one of the above [6] to [9], comprising repeating start and stop of discharge of the coating liquid from the coating liquid discharge port, and stopping air blowing during at least a portion of the time when discharge of the coating liquid is stopped. Effect of the Invention

[0010] According to the coating device and coating method for a sheet-like substrate of the present invention, the pressure of the coating liquid discharged from the die and the blowing pressure of the air discharged from the air nozzle are balanced, forming a liquid pool of a certain thickness between the discharge surface of the die and the sheet-like substrate. Regardless of the coating liquid or coating conditions, by freely adjusting the blowing pressure of the air, it is possible to form a high-quality thin coating film on the sheet-like substrate without being affected by the transport tension of the sheet-like substrate. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an apparatus 100 for applying to a sheet-like substrate according to one embodiment of the present invention. [Diagram 2] 2 is an enlarged detailed cross-sectional view of the die 20 and the air nozzle 30 of FIG. 1. [Diagram 3] 3 is a detailed cross-sectional view of the die 20 and the air nozzle 30 in FIG. 2 as viewed from the X direction. [Figure 4] 2 is an enlarged detailed cross-sectional view of the die 20 and the air nozzle 30 of FIG. 1. [Diagram 5] FIG. 1 is a schematic cross-sectional view showing a coating device 101 for a sheet-like substrate according to another embodiment of the present invention. [Figure 6] FIG. 6 is an enlarged detailed cross-sectional view of the die 20 and the air nozzle 30 of FIG. 5. [Figure 7]FIG. 2 is a schematic cross-sectional view showing a coating device different from that of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A preferred embodiment of the present invention will be described below. Note that the following description is merely an example of an embodiment of the present invention, and the present invention should not be construed as being limited thereto, and various modifications are possible without departing from the scope of the present invention.

[0013] FIG. 1 is a schematic cross-sectional view showing a coating device 100 for a sheet-like substrate according to one embodiment of the present invention. The sheet-like substrate 1 is unwound from an unwinding device 10 and transported through transport rollers 11 to 14 toward a winding device 15 in the direction of the arrow in FIG. 1. A coating liquid is applied to the surface of the sheet-like substrate 1 by a die 20, and the coating liquid is solidified by a post-treatment device 90 as necessary to form a coating film. An air nozzle 30 is installed at a position facing the die 20 across the sheet-like substrate 1, and air is blown toward the discharge surface of the die 20. A coating liquid supplying device 21 is connected to the die 20, and an air supplying device 31 is connected to the air nozzle 30.

[0014] FIG. 2 is a detailed cross-sectional view of the die 20 and the air nozzle 30 in FIG. 1, which are enlarged. The coating liquid discharged from the die 20 forms a liquid pool 23 between the discharge surface 22 of the die 20 and the surface of the sheet-like substrate 1, and is then applied to the sheet-like substrate 1 to become the coating film 2. Furthermore, air is blown from the air nozzle 30 toward the die discharge surface 22 in the direction of the dashed line in FIG. 2, and the sheet-like substrate 1 is pressed toward the die discharge surface 22 by the air blowing pressure P3 acting on the back surface of the sheet-like substrate 1. At this time, the thickness of the liquid pool 23, that is, the size of the gap between the die discharge surface 22 and the surface of the sheet-like substrate 1, is determined by the balance between the pressure P2 of the coating liquid discharged from the die 20 and the air blowing pressure P3. Specifically, when the air blowing pressure P3 is increased, the sheet-like substrate 1 approaches the die discharge surface 22, and the thickness of the liquid pool 23 becomes thinner. At this time, the coating liquid discharged from the die 20 is applied by passing through a narrow liquid pool 23, so the pressure with which the coating liquid presses the sheet-like substrate 1, i.e., the pressure P2 of the coating liquid discharged from the die 20, increases, and the sheet-like substrate 1 moves to a position where it is ultimately balanced with the air blowing pressure P3. Conversely, if the air blowing pressure P3 is weakened, the thickness of the liquid pool 23 increases due to the opposite mechanism to the above.

[0015] The pressure P2 of the coating liquid discharged from the die 20 is proportional to the viscosity of the coating liquid and the flow rate of the coating liquid discharged from the die 20. Therefore, the lower the viscosity of the coating liquid, the thinner the thickness of the coating film 2, and the slower the conveying speed of the sheet-like substrate 1, the lower the pressure P2 of the coating liquid, so that the thickness of the liquid pool 23 becomes thinner and more likely to be crushed, and coating defects such as streaks, smudges, and uneven film thickness tend to occur in the coating film 2. However, according to the coating device 100 of the present invention, by appropriately adjusting the air blowing pressure P3, it is possible to maintain the thickness of the liquid pool 23 and prevent the above-mentioned coating defects.

[0016] FIG. 3 is a detailed cross-sectional view of the die 20 and the air nozzle 30 in FIG. 2 as viewed from the X direction. The die 20 is formed with a slit-shaped discharge port 24 with the width direction of the sheet-like substrate 1 as the longitudinal direction, and the coating liquid is discharged from the discharge port 24 within a range of width W2. Air is blown from the air nozzle 30 in the direction of the dashed line in FIG. 3. At this time, the air blowing width W3 on the back surface of the sheet-like substrate 1 (the lower surface in FIG. 3) is preferably 80% or more of the coating liquid discharge width W2 from the viewpoint of forming a liquid pool 23 of uniform thickness across the width direction of the sheet-like substrate 1, and more preferably 90% or more. The air blowing width W3 may be wider than the coating liquid discharge width W2, but if air is blown into an area without a liquid pool 23, there is a concern that the sheet-like substrate 1 will bend in the width direction and collide with the die 20, so the air blowing width W3 is preferably 110% or less of the coating liquid discharge width W2.

[0017] The shape of the air outlet of the air nozzle 30 may be any shape that can apply a uniform air blowing pressure to the back surface of the sheet-like substrate 1, and examples thereof include a slit shape with the width direction of the sheet-like substrate 1 as the longitudinal direction, and a porous shape with a plurality of holes arranged in the width direction of the sheet-like substrate 1. However, if the distance between the air nozzle 30 and the sheet-like substrate 1 is close, coating streaks may occur in the coating film 2 according to the hole pitch when the outlet of the air nozzle 30 is porous. If the distance between the air nozzle 30 and the sheet-like substrate 1 is far, even if the outlet of the air nozzle 30 is porous, the air discharged from each hole spreads before reaching the sheet-like substrate 1, and the effect of the hole pitch is reduced. However, since the distance between the air nozzle 30 and the sheet-like substrate 1 is far, the air blowing pressure P3 acting on the back surface of the sheet-like substrate 1 is reduced, and the range of coating conditions that can be balanced with the pressure P2 of the coating liquid discharged from the die 20 is narrowed. If the outlet of the air nozzle 30 is slit-shaped, air can be blown uniformly across the width of the sheet-like substrate 1 even if the distance between the air nozzle 30 and the sheet-like substrate 1 is close, so it is more preferable that the outlet of the air nozzle 30 be slit-shaped.

[0018] FIG. 4 is a detailed cross-sectional view of the die 20 and the air nozzle 30 in a state where the blowing of air from the air nozzle 30 to the sheet-like substrate 1 in FIG. 1 is stopped. In a state where the blowing of air to the sheet-like substrate 1 is stopped, the conveying path of the sheet-like substrate 1 is on a tangent line connecting the outer circumference of the conveying roller 11 and the conveying roller 12. At this time, as shown in FIG. 4, the die 20 is preferably installed at a position where the discharge surface 22 does not contact the sheet-like substrate 1. This is because, when the discharge of the coating liquid from the die 20 is stopped, the blowing of air from the air nozzle 30 is also stopped, so that the discharge surface 22 of the die and the sheet-like substrate 1 are separated from each other, and scratches and coating liquid stains are not generated in the area of ​​the sheet-like substrate 1 where the coating film is not formed. The distance C between the discharge surface 22 of the die and the sheet-like substrate 1 may be determined in consideration of the state of the coating liquid stains on the discharge surface 22 of the die and the fluttering of the conveying sheet-like substrate 1, but is preferably about 5 mm or less, more preferably 1 mm or less.

[0019] The post-treatment device 90 in Fig. 1 is only required to be installed when solidification of the coating film is required, and does not have to be installed for products in which the coating film is wound in a liquid state, such as varnish-impregnated prepreg. The post-treatment device 90 may be selected according to the properties of the coating film, and examples of the post-treatment device include a hot air dryer, an infrared ray irradiation device, a UV irradiation device, and a coagulation tank.

[0020] FIG. 5 is a schematic cross-sectional view showing a coating apparatus 101 for a sheet-like substrate according to another embodiment of the present invention. Except that a control device 40 is connected to the coating liquid supply device 21 and the air supply device 31, the coating apparatus 100 is the same as the coating apparatus 100 in FIG. 1. FIG. 6 is a detailed cross-sectional view of an enlarged die 20 and an air nozzle 30 when a coating film 2 is intermittently formed on a sheet-like substrate 1 using the coating apparatus 101 in FIG. 5. According to the coating apparatus 101 of the present invention, in an area where a coating film 2 is to be formed on the sheet-like substrate 1, the control device 40 controls the coating liquid supply device 21 and the air supply device 31 so that the coating liquid is discharged from the die 20 and the air is blown from the air nozzle 30 at the same time as shown in FIG. 6(A), and conversely, in an area where the coating film 2 is not to be formed on the sheet-like substrate 1, the control device 40 controls the coating liquid supply device 21 and the air supply device 31 so that the coating liquid is discharged from the die 20 and the air is blown from the air nozzle 30 as shown in FIG. 6(B), thereby making it possible to intermittently form a coating film 2 on the sheet-like substrate 1. 6(B), by stopping the blowing of air from the air nozzle 30, the sheet-like substrate 1 quickly moves away from the discharge surface 22 of the die, so that the liquid at the coating end of the coating film 2 can be reliably drained, and intermittent coating with good appearance can be performed. The supply of the coating liquid to the die 20 and the supply of air to the air nozzle 30 do not necessarily have to be started or stopped at the same time, and may be performed with a time difference depending on the formation status of the coating film 2. However, from the viewpoint of reliably draining the liquid at the coating end of the coating film 2 as described above, it is preferable to stop the supply of air to the air nozzle 30 for at least a part of the time when the supply of the coating liquid to the die 20 is stopped. EXAMPLES

[0021] Specific examples of the present invention and comparative examples different from the present invention are shown below. However, the present invention should not be interpreted as being limited to the examples shown below, and various modifications are possible within the scope of the object and effect of the present invention.

[0022] [Example 1] A coating film was formed on a sheet-like substrate 1 using the coating apparatus 100 of the present invention shown in FIG. 1. A PET film having a thickness of 38 μm and a width of 250 mm was used as the sheet-like substrate. A polyvinyl alcohol (PVA) aqueous solution adjusted to a viscosity of 200 mPa·s was used as the coating liquid to be applied to the sheet-like substrate. A stainless steel slot die having a discharge width of 100 mm was used as the die 20, and a syringe pump was used as the coating liquid supply device 21. A resin air nozzle having an air blowing width of 100 mm, a discharge port having a diameter of 1 mm, and a multi-hole shape with a hole pitch of 3 mm was used as the air nozzle 30. A device consisting of a compressor, a pressure tank, a regulator, a globe valve, and a flow meter was used as the air supply device 31. A hot air drying device with a temperature controlled to 100°C was used as the post-processing device 90.

[0023] The conveying speed of the sheet-like substrate was 5 m / min, the conveying tension of the sheet-like substrate was 60 N / m, the thickness of the coating film applied to the sheet-like substrate before drying was 5 μm, the distance C between the die discharge surface and the sheet-like substrate when no air was being blown was 1 mm, the distance between the air nozzle and the sheet-like substrate was 10 mm, and the amount of air discharged from the air nozzle was adjusted in the range of 20 to 100 L / min.

[0024] The coating film formed in this example was a film of uniform thickness over a width of 100 mm, had no coating defects such as streaks, and had a good appearance.

[0025] [Comparative Example 1] As a coating method different from that of the present invention, a coating film was formed by a slot die coating method in which a die 20 was placed close to a conveying roller 11, as shown in Fig. 7(A). The configuration and coating conditions were the same as those of Example 1, except that the location of the die 20 was different and that the air nozzle 30 was not used. The distance between the discharge surface 22 of the die and the surface of the sheet-like substrate 1 was 50 μm. The coating film formed in this example had intermittent streaks, and a coating film of uniform thickness could not be formed. When the distance between the discharge surface of the die and the surface of the sheet-like substrate was further reduced, a part of the discharge surface of the die rubbed against the sheet-like substrate, causing the sheet-like substrate to break and become unfeasible to convey.

[0026] [Comparative Example 2] As a coating method different from that of the present invention, as shown in Fig. 7(B), a coating film was formed by an extrusion coating method in which coating was performed while pressing the discharge surface 22 of a die into the sheet-like substrate 1. The same configuration and coating conditions were used as in Example 1, except that the location of the die 20 was different and that the air nozzle 30 was not used. The depth to which the discharge surface 22 of the die was pressed into the sheet-like substrate 1 was adjusted in the range of 0.1 to 5 mm. The coating film formed in this example had a uniform thickness at both ends in the width direction, but had streak-like coating defects in the center in the width direction.

[0027] [Example 2] In Example 1 of the present invention, the distance between the air nozzle 30 and the sheet-like substrate was changed to 2 mm, and a coating film was formed. The coating film formed in this example had slight thickness irregularities at a pitch of 3 mm in the width direction, but was a film of almost uniform thickness over a width of 100 mm.

[0028] [Example 3] A coating film was formed under the same conditions as in Example 1, except that the shape of the outlet of the air nozzle 30 was changed to a slit shape and the distance between the air nozzle 30 and the sheet-like substrate was set to 2 mm, the same as in Example 2. The coating film formed in this example was a uniform film with a width of 100 mm, had no coating defects such as streaks, and had a good appearance. [Industrial Applicability]

[0029] The coating device and coating method for sheet-like substrates of the present invention can be widely used in a variety of applications, such as functional films, paper products, fabric products, membrane products, batteries, electrical appliance parts, and semiconductor parts. [Explanation of symbols]

[0030] 1. Sheet-shaped substrate 2 Coating film 10 Unwinding device 11 to 14 Conveyor roller (conveyor mechanism) 15 Winding device 20 Die 21 Coating liquid supply device (supply mechanism) 22 Die discharge surface 23 Liquid pool 24 Die outlet 30 Air nozzle 31 Air supply device 40 Control device (control unit) 90 Aftertreatment device 100-101 Coating device of the present invention C Distance between the die discharge surface and the surface of the sheet-like substrate P2 Pressure of the coating fluid discharged from the die P3 Air pressure on the back side of the sheet substrate W2 Discharge width of coating liquid W3 Air blowing width on the back side of the sheet substrate

Claims

1. A coating apparatus for forming a coating film on a sheet-like substrate that is continuously conveyed, The width direction of the sheet-like substrate is defined as the width direction. A conveying mechanism for the sheet-like substrate; a die having a discharge surface formed with a slit-shaped discharge port for a coating liquid extending in a width direction, the discharge surface being disposed so as to face the sheet-like substrate; an air nozzle that is disposed at a position facing the die with the sheet-like substrate interposed therebetween and that blows air in the direction of the discharge surface, the air nozzle having a width in the width direction on the surface of the sheet-like substrate of the air blown from the air nozzle being 80% or more of a length in the width direction of a discharge port of the coating liquid; The coating device for a sheet-like substrate has the following features.

2. 2. The coating device for a sheet-like substrate according to claim 1, wherein the air blowing width is 90% or more and 110% or less of the length of the coating liquid discharge port in the width direction.

3. The coating device for a sheet-like substrate according to claim 1 , wherein the air nozzle has a slit-shaped air outlet extending in the width direction.

4. The coating device for a sheet-like substrate according to claim 1, wherein the die is installed in a position where the discharge surface does not come into contact with the sheet-like substrate when the blowing of air from the air nozzle to the sheet-like substrate is stopped.

5. A supply mechanism and a control unit for supplying a coating liquid to the die, The control unit is a control unit for controlling the blowing of air from the air nozzle and the supply of the coating liquid from the supply mechanism; repeating supply and stop of the coating liquid from the supply mechanism, and controlling so as to stop the blowing of air from the air nozzle during at least a part of the time when the supply of the coating liquid is stopped; An apparatus for applying a coating material to a sheet-like substrate according to claim 1.

6. A coating method for forming a coating film on a continuously transported sheet-like substrate, comprising the steps of: The width direction of the sheet-like substrate is defined as the width direction. A die having a discharge surface on which a slit-shaped coating liquid discharge port extending in the width direction is formed is disposed so that the discharge port for the coating liquid faces the sheet-like substrate; While discharging a coating liquid from a discharge port of the coating liquid onto the sheet-like substrate being transported, Air is blown onto the sheet-like substrate from the side opposite to the side where the die is disposed, in the direction of the discharge surface of the die, so that the width of the blowing in the width direction on the surface of the sheet-like substrate is 80% or more of the width direction length of the discharge port of the coating liquid. A method for applying a coating to a sheet-like substrate.

7. The method for coating a sheet-like substrate according to claim 6, wherein the width of the air blowing is from 90% to 110% of the length in the width direction of the discharge port of the coating liquid.

8. The method for applying a coating material to a sheet-like substrate according to claim 6 , wherein air is blown in a slit shape onto the sheet-like substrate.

9. The method for coating a sheet-like substrate according to claim 6 , wherein the discharge surface of the die does not come into contact with the sheet-like substrate when air is not being blown onto the sheet-like substrate.

10. A coating method for intermittently forming a coating film on the sheet-like substrate, comprising: repeating discharge and stopping of the coating liquid from the discharge port of the coating liquid, and stopping the air blowing during at least a part of the period during which the discharge of the coating liquid is stopped; The method for coating a sheet-like substrate according to claim 6.

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