JP2016175007A - Coating applicator and application method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating applicator which stably holds a bead and stably forms a uniform coating film even when a transfer speed of a base material is increased and a coat thickness of a coating film is reduced.SOLUTION: A coating applicator of the invention includes: a slit die 10 having a discharge slit 13 for discharging a coating liquid; and a decompression unit 20 provided at the upstream side of the slit die 10. The decompression unit 20 includes: a decompression slit 21 provided adjacent to the discharge slit 13; and a decompression chamber 22 connected with the decompression slit 21. A distance L between an upstream side end part 13a of an opening surface of the discharge slit 13 and a downstream side end part 21b of an opening surface 21a of the decompression slit 21 is shorter than 1.0 mm. An opening width W of the decompression slit 21 is smaller than 1.0 mm.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a coating apparatus including a slit die having a discharge slit, and a coating method.

  In a coating apparatus equipped with a conventional slit die, the coating liquid supplied from the supply port is spread in the horizontal direction by the manifold, and the coating liquid pushed out from the manifold is discharged from the discharge slit to be applied to the surface of the substrate. A film is formed. Here, in order to stably form a uniform coating film, it is necessary to stably hold the bead formed between the slit die and the base material by the coating liquid ejected from the ejection slit.

  However, if the relative speed between the slit die and the substrate is increased, the beads cannot be stably held, and a uniform coating film cannot be stably formed. Therefore, as a countermeasure, a vacuum chamber is added upstream of the slit die (opposite to the substrate transport direction), and the upstream side of the bead is decompressed by this vacuum chamber, thereby stably holding the beads. A method is known (for example, Patent Document 1).

  However, in order to generate a uniform negative pressure on the upstream side of the bead, it is necessary to provide a certain degree of decompression chamber, and as a result, there is a problem that the entire coating apparatus is increased in size.

  Therefore, Patent Document 2 discloses a coating apparatus in which a recess is formed on the upstream side of the discharge slit, and a decompression chamber is formed in a part of the recess by mounting an adjustment block in the recess. Is disclosed. As a result, the decompression chamber can be easily configured, and by adjusting the mounting position of the adjustment block, the opening width of the decompression chamber (opening width of the decompression slit) can be set according to the type of coating solution and the thickness of the coating film The optimum value can be set in consideration of the above.

Japanese Patent Laid-Open No. 1-213641 JP 2008-23405 A

  However, when forming a coating film using the coating apparatus described in Patent Document 2, the relative speed (coating speed) between the slit die and the substrate is increased, and the thickness of the coating film to be formed is reduced. Accordingly, there is a problem that even if the mounting position of the adjustment block is adjusted, the beads cannot be stably held, and it becomes difficult to stably form a uniform coating film. In particular, when a thin coating film is formed using a coating solution having a low viscosity (for example, 30 mPa · s or less), this problem becomes significant.

  The present invention has been made to solve the above-mentioned problems, and its main purpose is to increase the relative speed (coating speed) between the slit die and the substrate and to reduce the thickness of the coating film to be formed. However, an object of the present invention is to provide a coating apparatus and a coating method capable of stably holding a bead and forming a uniform coating film stably.

  A coating apparatus according to the present invention includes a slit die having a discharge slit for discharging a coating liquid, and a decompression unit provided on the upstream side of the slit die, and the decompression unit is provided adjacent to the discharge slit. The decompression slit and the decompression chamber connected to the decompression slit, and the distance between the upstream edge of the discharge slit opening surface and the downstream edge of the decompression slit opening surface is 1.0 mm. The opening width of the decompression slit is less than 1.0 mm.

  A coating method according to the present invention is a coating method in which a coating film is formed on a substrate by discharging a coating liquid from a discharge slit using the above-described coating apparatus, and the coating is discharged from the discharge slit. The upstream bead (upstream meniscus) of the liquid bead is controlled to be positioned at the downstream edge of the opening surface of the decompression slit.

  According to the present invention, even if the relative speed (coating speed) between the slit die and the substrate is increased and the coating film to be formed is thin, the bead can be held stably and a uniform coating film can be formed. It is possible to provide a coating apparatus and a coating method that can be stably formed.

It is sectional drawing which showed typically the structure of the coating device in one Embodiment of this invention. It is an expanded sectional view of the part shown by A of FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment. Moreover, it can change suitably in the range which does not deviate from the range which has the effect of this invention.

  FIG. 1 is a cross-sectional view schematically showing a configuration of a coating apparatus according to an embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view of a portion indicated by A in FIG. In addition, the arrow X shown in FIG.1 and FIG.2 shows the conveyance direction of the base material 30. FIG. In the following description, the direction opposite to the conveyance direction X of the base material 30 is referred to as “upstream side”, and the same direction as the conveyance direction X is referred to as “downstream side”. Moreover, FIG.1 and FIG.2 exaggerated and showed a part of structure of the coating device, and does not show an actual dimension.

  The coating apparatus in this embodiment forms a coating film on the surface of the substrate 30 conveyed in the X direction. As shown in FIG. 1, a slit die 10 having a discharge slit 13 for discharging a coating liquid, And a decompression unit 20 provided on the upstream side of the slit die 10.

  The slit die 10 is composed of an upstream block 17 and a downstream block 16, and a shim plate (not shown) is disposed between the upstream block 17 and the downstream block 16, or the upstream block and The discharge slit 13 is formed by providing a step in the downstream block. The upstream block 17 has an upstream lip 12 at the tip, and the downstream block 16 has a downstream lip 11 at the tip.

  The slit die 10 is formed with a manifold 14 for spreading the coating liquid supplied from a supply port (not shown) in the width direction of the coating film (direction perpendicular to the transport direction X of the base material 30). . The coating liquid pushed out from the manifold 14 is discharged from the discharge slit 13, thereby forming a coating film 50 on the surface of the substrate 30.

  As shown in FIG. 1, the decompression unit 20 provided on the upstream side of the slit die 10 includes a decompression slit 21 provided adjacent to the ejection slit 13 and a decompression chamber connected to the decompression slit 21. 22. Here, the decompression slit 21 and the decompression chamber 22 are configured by disposing the decompression block 23 on the base material 30 side of the upstream block 17. The decompression chamber 22 is provided with a plurality of suction holes 24, and the decompression chamber 22 is connected to a vacuum pump (not shown) via an exhaust passage 15 formed in the upstream block 17.

  As shown in FIG. 2, the coating liquid ejected from the ejection slit 13 is applied to the surface of the base material 30 while forming a bead 40 between the slit die 10 and the base material 30. Is formed. At this time, the upstream side of the bead 40 is decompressed by decompressing the decompression slit 21 through the decompression chamber 22 with a vacuum pump.

  By the way, if the conveyance speed (coating speed) of the base material 30 is increased and the coating film 50 to be formed is made thinner, even if the upstream side of the bead 40 is decompressed by the decompression slit 21, the bead 40. Cannot be held stably, and as a result, there arises a problem that it is difficult to stably form a uniform coating film. In particular, when the viscosity of the coating solution is lowered, the holding of the beads 40 becomes unstable, and it becomes difficult to stably form a uniform coating film.

  The inventors of the present application have examined the cause of such a problem, and have obtained the following knowledge.

That is, as shown in FIG. 2, on the upstream side of the bead 40, the air flows in the order of the decompression slit 21, the decompression chamber 22, and the exhaust path 15 from the gap between the decompression block 23 and the base material 30. At this time, the reduced pressure required to stably hold the bead 40 increases as the conveyance speed (application speed) of the base material 30 increases. Therefore, in such a case, by narrowing the distance D ₁ of the between the decompression block 23 and the base 30, to be given a sufficiently pressure loss, be performed under reduced pressure on the upstream side of the bead 40 sufficiently It becomes impossible to hold the beads 40 stably.

  Further, since the pressure reduction on the upstream side of the bead 40 is performed through the pressure reducing slit 21, the pressure reducing pressure on the upstream side of the bead 40 is reduced from the gap between the pressure reducing block 23 and the base material 30 to the pressure reducing slit 21 and the pressure reducing pressure. It is substantially controlled by the magnitude of the dynamic pressure (the speed of the airflow) when air flows in the order of the chamber 22 and the exhaust passage 15.

  On the other hand, when the decompression chamber is arranged upstream of the bead 40, the decompression pressure on the upstream side of the bead 40 is substantially controlled by the magnitude of the static pressure in the decompression chamber. Therefore, when the pressure reducing slit 21 is disposed upstream of the bead 40 and the pressure is reduced, when the air flows into the pressure reducing slit 21 through the gap between the pressure reducing block 23 and the base material 30, the air current is disturbed. The dynamic pressure varies.

As described above, when the conveyance speed (coating speed) of the base material 30 is increased, the reduced pressure required to stably hold the bead 40 is increased. Therefore, it is preferable to provide a sufficient pressure loss by reducing the distance D ₁ of the between the decompression block 23 and the substrate 30. However, when the gap (distance D ₁ ) between the decompression block 23 and the base material 30 is reduced, air having a relatively high flow velocity flows into the decompression slit 21 having a large opening width from the small gap (distance D ₁ ). The air current is likely to be disturbed, and it becomes difficult to control the dynamic pressure. As a result, the reduced pressure on the upstream side of the bead 40 becomes unstable, and it becomes difficult to hold the bead 40 stably. Furthermore, this phenomenon tends to be promoted as the viscosity of the coating solution decreases.

In order to reduce the turbulence of the airflow for depressurizing the bead 40 as described above, it is preferable to reduce the opening width W of the depressurization slit 21 as shown in FIG. Thereby, when air flows into the slit 21 for decompression from the gap between the decompression block 23 and the substrate 30 (distance D ₁ between the decompression block 23 and the substrate 30), turbulence of the airflow occurs. Can be reduced.

The optimum range of the opening width W of the decompression slit 21 is preferably set to less than 1.0 mm. When the opening width W is 1.0 mm or more, the main flow of air flowing into the pressure reducing slit 21 from the gap between the pressure reducing block 23 and the base material 30 (distance D ₁ between the pressure reducing block 23 and the base material 30). The distance between (center) and the meniscus 40 a on the upstream side of the bead 40 is increased, that is, the decompression position is separated from the bead 40. As a result, the upstream meniscus 40a of the bead 40 becomes unstable, and the upstream meniscus 40a vibrates or retracts downstream (the pinning position of the upstream meniscus 40a on the upstream lip surface 12a is downstream ( Retreat in the direction of arrow X).

Further, as described above, it is preferable that the distance D ₁ of the between the decompression block 23 and the substrate 30 is small, the opening width W is 1.0mm or more, the distance D ₁ and the opening width W Since the difference becomes large, the airflow is likely to be disturbed in the decompression slit 21. As a result, the reduced pressure on the upstream side of the bead 40 becomes unstable, and it becomes difficult to hold the bead 40 stably. Furthermore, this phenomenon is promoted as the viscosity of the coating solution is lowered. Therefore, by setting the opening width W of the decompression slit 21 to less than 1.0 mm, the bead 40 can be stably held even when the viscosity of the coating solution is 30 mPa · s or less.

On the other hand, when the coating film is applied using the slit die, as shown in FIG. 2, the upstream meniscus 40a of the bead 40 is connected to the downstream edge 21b (the upstream lip 12 of the upstream lip 12) of the opening surface 21a of the decompression slit 21. It is preferable that application conditions and the like are set so as to be positioned (to be pinned) at the upstream edge of the lip surface 12a. In other words, the application conditions (for example, gap (slits) and slits) are determined depending on the wet film thickness of the coating film and the physical properties (surface tension and viscosity) of the coating liquid so that the pinning position of the upstream meniscus 40a of the bead 40 is the downstream edge 21b. The distance D ₂ ) between the die 10 and the substrate 30 and the coating speed) are set.

  Then, under the application conditions, the reduced pressure is controlled so that the upstream meniscus 40 a of the bead 40 can be positioned (pinned) on the downstream edge 21 b of the opening surface 21 a of the reduced pressure slit 21.

  If the upstream meniscus 40a of the bead 40 is not positioned (pinned) at the downstream edge 21b, the bead 40 becomes unstable, and the appearance of the coating film (unevenness of coating and abnormal film thickness) tends to occur.

  The optimum range of the distance L between the upstream edge 13a of the opening surface of the discharge slit 13 and the downstream edge 21b of the opening surface 21a of the decompression slit 21 is, as described above, the upstream meniscus of the bead 40. 40a is preferably designed to be positioned (pinned) at the downstream edge 21b of the opening surface 21a of the decompression slit 21. From this viewpoint, for example, when the wet film thickness at the time of applying the coating film is 20 μm or less, the distance L is preferably set to less than 1.0 mm.

  If the distance L is 1.0 mm or more, the upstream meniscus 40a of the bead 40 cannot be positioned (pinned) at the downstream edge 21b of the opening surface 21a of the decompression slit 21, and the downstream side of the lip surface 12a. Move backward (in the direction of arrow X). Such beads are easily affected by external factors (for example, minute fluctuations in the surface condition of the substrate, minute fluctuations in reduced pressure, etc.), and the beads are not formed stably, resulting in uniform A coating film cannot be formed.

  As described above, the coating apparatus according to the present invention includes the slit die 10 having the ejection slit 13 for discharging the coating liquid, and the decompression unit 20 provided on the upstream side of the slit die 10. Includes a decompression slit 21 provided adjacent to the ejection slit 13 and a decompression chamber 22 connected to the decompression slit 21. Here, the distance L between the upstream edge 13a of the opening surface of the ejection slit 13 and the downstream edge 21b of the opening surface 21a of the decompression slit 21 is set to be less than 1.0 mm, and the decompression slit 21 The opening width W is preferably set to less than 1.0 mm. With such a configuration, the bead 40 can be stably held even when the conveyance speed (coating speed) of the base material 30 is increased and the coating film to be formed is made thin. A stable coating film can be stably formed.

  In this embodiment, by reducing the opening width W of the decompression slit 21 to less than 1.0 mm, the turbulence of the airflow in the decompression slit 21 has been reduced, but as shown in FIG. You may make it incline toward the upstream toward the decompression chamber 22. As a result, the air that has flowed into the decompression slit 21 can quickly diffuse in the decompression slit 21. As a result, since the turbulence of the airflow in the decompression slit 21 can be reduced, the bead 40 can be stably held.

  The inclination angle θ of the decompression slit 21 is appropriately determined depending on the size of the opening width W of the decompression slit 21 and the like, but is set in a range of 30 to 60 ° with respect to the opening surface 21a of the decompression slit 21. It is preferable. Airflow can be effectively diffused at an inclination angle in this range.

  In the present embodiment, the decompression slit 21 and the decompression chamber 22 can be configured by disposing the decompression block 23 on the base member 30 side of the upstream block 17, so that the decompression unit 20 can be downsized. This can reduce the size of the coating apparatus.

The volume of the decompression chamber 22 is not particularly limited, but is 0.002 m ³ per 1 m in the width direction of the decompression slit 21 (direction perpendicular to the transport direction X) in order to reduce the size of the coating apparatus. It is preferable that it is less than. Furthermore, from the above viewpoint, 0.001 m ³ or less is preferable. On the other hand, if the volume of the decompression chamber 22 becomes too small, air flow is likely to be disturbed in the decompression unit 20, so the lower limit of the volume of the decompression chamber 22 is perpendicular to the width direction of the decompression slit 21 (conveying direction X). Per direction length) is preferably 0.0001 m ³ or more.

  Further, as shown in FIG. 1, the decompression chamber 22 is provided with a plurality of suction holes 24. In order to decompress the decompression chamber 22 uniformly in the width direction, the number of suction holes 24 is reduced. It is preferable to provide four or more slits per 1 m in the width direction of the slit 21 for use. Thereby, the pressure reduction pressure in the width direction (direction orthogonal to the conveyance direction X) of the pressure reduction slit 21 can be made uniform. The upper limit of the number of suction holes 24 is not particularly limited, but is preferably 12 or less per 1 m in the width direction of the decompression slit 21 from the viewpoint of downsizing the coating apparatus.

  A coating method according to another embodiment of the present invention is characterized in that the coating film 50 is formed on the substrate 30 by discharging the coating liquid from the discharge slit 13 using the above-described coating apparatus. Here, the upstream meniscus 40 a of the bead 40 of the coating liquid discharged from the discharge slit 13 is controlled to be positioned (pinned) at the downstream edge 21 b of the opening surface 21 a of the decompression slit 21. preferable.

  In addition, the coating method in this embodiment can be suitably used when the viscosity of the coating solution is 30 mPa · s or less and the wet film thickness during coating of the coating film is 20 μm or less. Furthermore, the coating method in the present embodiment is suitable when the viscosity of the coating solution is 20 mPa · s or less, and is suitable when the wet film thickness during coating of the coating film is 10 μm or less.

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible.

  For example, in the above embodiment, the base material 30 is preferably transported in the X direction while being supported by a backup roller (not shown). However, the base material 30 can be transported without using the backup roller.

  In the above embodiment, the suction hole 24 and the exhaust path 15 are formed in the upstream block 17, but the suction hole 24 and the exhaust path 15 may be provided at the bottom of the decompression block 23.

  Moreover, the viscosity of the coating liquid in this embodiment is measured with a B-type viscometer (Brookfield viscometer) at a coating liquid temperature of 23 ° C.

Further, in FIG. 2, the distance _{D 2} between the lip surface 11a, a base material 30 of the downstream lip 11, in view of the thin film coating (coating in a wet thickness of 20μm or less), preferably 200μm or less, 100 [mu] m The following is more preferable, and 50 μm or less is particularly preferable. The lower limit is preferably 15 μm or more, and particularly preferably 20 μm or more.

The distance _{D 1} of the between the lip surface 23a and the base 30 of the vacuum block 23, as mentioned above, is preferably smaller, specifically, preferably 200μm or less, more preferably 100μm or less, 50 [mu] m The following are particularly preferred: The lower limit is preferably 15 μm or more, and particularly preferably 20 μm or more.

Also, the lip surface 11a of the downstream lip 11, the distance _{D 2} between the substrate 30, the distance _{D 1} of the between the lip surface 23a and the base 30 of the vacuum block 23 is the same it may be, the distance _{D 1,} may be greater than the distance _{D 2.} The configuration of the coating apparatus (design), distance D ₂ and the distance D ₁ is preferably the same.

  The decompression block 23 disposed on the base material 30 side of the upstream block 17 may be formed integrally with the upstream block 17.

10 Slit die
11 Downstream lip
12 Upstream lip
12a Lip surface
13 Discharge slit
13a Upstream edge
14 Manifold
15 Exhaust passage
16 Downstream block 17 Upstream block 20 Pressure reducing unit
21 Slit for decompression
21a Open surface
21b Downstream edge
22 decompression chamber
23 Block for decompression
24 Suction hole
30 base material
40 beads
40a upstream meniscus
50 Coating film

Claims (7)

A slit die having a discharge slit for discharging the coating liquid;
A coating apparatus comprising a decompression unit provided on the upstream side of the slit die,
The decompression unit is
A decompression slit provided adjacent to the ejection slit;
A decompression chamber connected to the decompression slit,
The distance between the upstream edge of the opening surface of the discharge slit and the downstream edge of the opening surface of the decompression slit is less than 1.0 mm,
An opening width of the decompression slit is a coating apparatus having a width of less than 1.0 mm.   The coating apparatus according to claim 1, wherein the decompression slit is inclined toward the upstream side toward the decompression chamber.   The coating apparatus according to claim 2, wherein an inclination angle of the decompression slit is in a range of 30 to 60 ° with respect to an opening surface of the decompression slit. The volume of the decompression chamber, the per unit length 1m in the width direction of the pressure reducing slit is less than 0.002 m ^3, coating apparatus according to any one of claims 1 to 3. The decompression chamber includes a plurality of suction holes for decompressing the decompression chamber,
The number of the said suction holes is a coating device in any one of Claims 1-4 which is 4 or more per 1 m of the width direction of the said slit for pressure reduction. A coating method for forming a coating film on a substrate by discharging a coating liquid from the discharge slit using the coating apparatus according to any one of 1 to 5,
A coating method in which an upstream meniscus of the bead of the coating liquid ejected from the ejection slit is controlled so as to be positioned at a downstream edge of the opening surface of the decompression slit. The viscosity of the coating solution is 30 mPa · s or less,
The coating method according to claim 6, wherein a wet film thickness at the time of applying the coating film is 20 μm or less.

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