JP2011120987A - Die coating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a die coating apparatus which reduces the variation of a coating film in the width direction, and stabilizes the shape of the coating film. <P>SOLUTION: In a die head 100, a lip surface facing a web as a surface to be coated is composed of shim lip surfaces 20B located in the width directions to a discharge port 21, a die lip surface 11A located on an upstream side in conveyance direction, and a die lip surface 12A located on a downstream side thereof. The contact angle &beta; of the shim lip surfaces 20B is larger than the contact angle &alpha; of the die lip surface 12A. According to this, the shim lip surfaces 20B have the capillary force smaller than that of the die lip surface 12A, and more hardly get wet. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a die coating apparatus that applies a coating solution by a die coating method onto a continuously running belt-like support (hereinafter referred to as “web”). More specifically, the present invention relates to the structure of the die head of the die coating apparatus.

  2. Description of the Related Art Conventionally, a die coating apparatus that forms a coating film by applying a coating solution by a die coating method on a continuously running web is widely known. This die coating apparatus is used for manufacturing an electrode plate, for example, in manufacturing an electrode of a non-aqueous secondary battery.

  In the coating by the above-described die coating apparatus, the die head on which the discharge port for the coating liquid is formed is opposed to the web, and the coating liquid pushed out from the discharge port is applied onto the web. For example, as disclosed in Patent Document 1 and Patent Document 2, the die head has a configuration in which a pair of die blocks sandwich a shim in which a groove serving as a flow path for the coating liquid is formed.

JP 2007-330900 A JP 2004-275810 A

  However, the conventional die coating apparatus described above has the following problems. That is, as shown in FIG. 7, the coating liquid 30 pushed out from the discharge port 21 of the die head 90 spreads in the width direction of the web 40 (the direction perpendicular to the conveyance direction of the web 40, the horizontal direction in FIG. 7). A coating film is formed. That is, the width of the coating film is larger than the opening width of the shim 20. The spread of the coating solution 30 (W0 in FIG. 7) is considered to be due to the capillary force generated in the gap (G in FIG. 7) between the lip surface of the die head 90 and the surface of the web 40.

  If the gap G is always constant, the capillary force is also kept constant. Therefore, the spread W0 of the coating solution 30 is also constant, and the influence of the capillary force on the quality of the coating film is small. However, in practice, the gap G varies due to the eccentricity of the backup roll 50 and errors in assembling the die head. For this reason, the spread W0 of the coating liquid 30 also varies, which hinders stabilization of the shape of the coating film.

  The present invention has been made to solve the problems of the conventional die head described above. That is, the problem is to provide a die coating apparatus that reduces variations in the width direction of the coating film and stabilizes the shape of the coating film.

  A die coating apparatus for solving this problem is a die coating apparatus for applying a coating liquid onto a continuously running web, and the lip surface of the die head facing the web is connected to a discharge port of the coating liquid. The first surface, which is a surface area that is in contact with the discharge port and located downstream of the web direction of the discharge port, and the first surface area that is in contact with the discharge port and is located on both sides of the web of the discharge port in the width direction. The contact angle α with respect to the coating liquid on the first surface is smaller than the contact angle β with respect to the coating liquid on the second surface.

  That is, since the lip surface of the die head in the die coating apparatus of the present invention has a contact angle α of the first surface smaller than a contact angle β of the second surface, the first surface is compared with the second surface. Capillary force is large. That is, the second surface is less wettable and less affected by the capillary force than the first surface. Therefore, the coating liquid hardly spreads to the second surface side (width direction side) with respect to the discharge port, and actively flows to the first surface side (downstream side in the transport direction). From this, it can be expected that the width variation of the coating film is suppressed.

  In the die coating apparatus of the present invention, the contact angle ratio (β / α), which is the ratio of the contact angle α and the contact angle β, is preferably 2 or more. According to this configuration, the difference in wettability between the first surface and the second surface becomes clearer, and the coating liquid flows more actively downstream in the transport direction. Therefore, it is possible to further suppress the width variation of the coating film.

  In addition, the die head of the die coating apparatus of the present invention includes, for example, a pair of die blocks and a shim that is sandwiched between the pair of die blocks and has a groove serving as a flow path for the coating liquid. The die block forms a discharge port by sandwiching the shim groove, the first surface is the lip surface of the die block arranged on the downstream side in the web conveying direction, and the second surface is the lip surface of the shim This configuration is applicable.

  Further, the die head may be made of different materials on the first surface and the second surface. That is, the first surface and the second surface are different parts, and by forming each part with a different material, it is possible to form a lip surface with high accuracy and excellent durability.

  Further, the lip surface of the die head of the present invention has a third surface that is in contact with the discharge port and is located on the upstream side of the web direction of the discharge port in the web conveyance direction. Is preferably smaller than the contact angle β with respect to the coating solution on the second surface. With this configuration, the coating liquid has higher wettability on the third surface side (upstream side in the transport direction) than on the second surface side (width direction side) with respect to the discharge port. For this reason, it is possible to further suppress the variation in the width of the coating film.

  ADVANTAGE OF THE INVENTION According to this invention, the die coating apparatus which reduces the dispersion | variation in the width direction of a coating film and stabilizes the shape of a coating film is implement | achieved.

It is a figure which shows the outline | summary of the die coating apparatus concerning embodiment. It is an exploded view showing the outline composition of the die head concerning an embodiment. FIG. 3 is a perspective view showing a state in which the parts of the die head shown in FIG. 2 are superposed. It is a figure of the state which saw the web seeing the die head and the coating film from the backup roller side. It is width direction sectional drawing which shows schematic structure of the application | coating part of the die head concerning Embodiment. It is a graph which shows the relationship between contact angle ratio and width dispersion | variation. It is width direction sectional drawing which shows schematic structure of the application | coating part of the die head concerning the conventional form.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a die coating apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. In the following embodiment, the present invention is applied as a die coating apparatus used when manufacturing an electrode of a non-aqueous secondary battery.

[Configuration of die coating equipment]
FIG. 1 shows an outline of an application part of a die coating apparatus 200 of the present embodiment. The die coating apparatus 200 includes a coating liquid tank 31 that stores the coating liquid 30, a die head 100 that receives the coating liquid 30 and discharges the coating liquid 30, and a backup roller 50 that supports a web 40 that is an object to be coated. And. The die head 100 faces the backup roller 50 via the web 40.

  The web 40 continuously runs on the backup roller 50 while being wound around the backup roller 50. The backup roller 50 rotates following the continuous travel of the web 40. Note that the backup roller 50 may be rotationally driven, and the web 40 may continuously travel along with the rotation.

  The coating liquid 30 in the coating liquid tank 31 is supplied to the die head 100, and the coating liquid 30 is pushed out from a discharge port provided on the lip surface of the die head 100. That is, the die coating apparatus 200 applies the coating liquid 30 onto the continuously running web 40 while extruding the coating liquid 30 from the discharge port of the die head 100. Thereby, the coating film 41 is formed on the web 40.

The web 40 is a base material that serves as an electrode plate of a non-aqueous secondary battery. For example, an aluminum foil corresponds to the positive electrode, and a copper foil corresponds to the negative electrode. The coating liquid 30 corresponds to a positive electrode active material paste (for example, lithium nickelate (LiNiO ₂ )) or a negative electrode active material paste (for example, graphite).

[Die head configuration]
FIG. 2 shows a state in which the die head 100 of this embodiment is disassembled. FIG. 3 shows a state in which the die head 100 shown in FIG. 2 is assembled.

  The die head 100 according to the present embodiment includes a pair of die blocks 10 (hereinafter, a die block disposed on the upstream side in the conveyance direction of the web 40 is referred to as “die block 11”, and a die block disposed on the downstream side is referred to as “die block”. And a shim 20 sandwiched between the die blocks 11 and 12. The die block 11 is provided with a hole 15 penetrating the die block 11. This hole 15 serves as a receiving port for the coating liquid 30. Note that the receiving port for the coating liquid 30 may be provided in the die block 12.

  The shim 20 is provided with a straight slit 22. When the die blocks 11 and 12 sandwich the shim 20 by the slit 22, a gap is formed in the die head 100. This gap serves as a flow path for the coating liquid 30. The flow path is continuous with the hole 15 of the die block 11, and the received coating liquid 30 is poured therein. Further, the flow path (slit 22) reaches one side of the shim 20, and the discharge port 21 serving as the discharge port for the coating liquid 30 is formed by sandwiching the die blocks 11 and 12. The shape of the slit 22 is not limited to a straight shape, and may be a tapered shape, for example.

  In the die head 100, the surface on which the discharge port 21 is formed becomes a lip surface facing the web 40. The lip surface is constituted by a die lip surface 11A that is a tip surface of the die block 11, a die lip surface 12A that is a tip surface of the die block 12, and a shim lip surface 20B that is a tip surface of the shim 20. The shim lip surface 20 </ b> B is divided by the discharge port 21 and is disposed at both ends of the discharge port 21. The discharge port 21 has a rectangular shape surrounded by the die lip surfaces 11A and 12A and the shim lip surfaces 20B and 20B, and is in contact with the lip surfaces 11A, 20B, 12A and 20B.

  FIG. 4 shows a state in which the die 40 and the coating film 41 are seen through the web 40 as seen from the backup roller 50 side. The die head 100 is disposed so that the width direction of the discharge port 21 (the facing direction of the shim lip surfaces 20B and 20B at both ends of the discharge port 21) and the width direction of the web 40 are parallel. Then, the continuous running of the web 40 and the discharge of the coating liquid 30 by the die head 100 are performed at the same time, whereby the coating film 41 is formed on the web 40 on the downstream side of the portion facing the die head 100.

  Further, the die head 100 uses different materials for the die block and the shim 20. Specifically, the die block 10 uses a material that has better wettability with respect to the coating solution 30 than the shim 20. That is, the contact angle α of the die lip surfaces 11A and 12A with respect to the coating solution 30 is made of a material that is smaller than the contact angle β of the shim lip surface 20B with respect to the coating solution 30.

[Coating film width variation]
Next, the mechanism for suppressing the width variation of the coating film 41 in the die head 100 of this embodiment will be described.

  As in the die head 100 of this embodiment, the contact angle α of the surface area (die lip surface 12A) on the downstream side in the transport direction with respect to the discharge port 21 in the lip surface, and the surface area on both sides in the width direction with respect to the discharge port 21 By making it smaller than the contact angle β of the shim lip surface 20B, as shown in FIG. 5, it can be expected that the spread of the coating liquid 30 in the width direction (W1 in FIG. 5) is suppressed (that is, this embodiment). W1 in FIG. 5 <W0 in FIG. 7 which is a conventional form).

That is, the amount of spread in the width direction of the coating liquid 30 is based on the capillary force acting between the lip surface of the die head 100 and the web 40. This capillary force h is obtained by the following equation (1).
h = 2T cos θ / ρgr (1)
In Equation (1), T is the surface tension, θ is the contact angle, ρ is the density, g is the acceleration of gravity, and r is the inner diameter (here, the gap between the lip surface of the die head 100 and the web 40 (G in FIG. 6)). Respectively.

  As can be seen from the equation (1), the capillary force h greatly varies depending on the value of cos θ. That is, the greater the cos θ, the stronger the capillary force h. Therefore, for the shim lip surface 20B, a material having a weak capillary force h, that is, a large contact angle θ is used. Thereby, the coating liquid 30 is difficult to spread in the width direction from the discharge port 21. Further, when the capillary force h is weak, the fluctuation amount of the capillary force h accompanying the fluctuation of the inner diameter r (gap G) is also small.

  Further, not only the shim lip surface 20B side is not easily wetted, but also the wettability is different between the shim lip surface 20B and the die lip surface 12A. Specifically, a material in which the contact angle θ of the shim lip surface 20B is larger than the contact angle θ of the die lip surface 12A is used so that the capillary force acting in the width direction is weaker than the capillary force acting in the transport direction. As a result, the coating liquid 30 is more likely to spread in the transport direction from the discharge port 21 than in the width direction. In this way, it is expected that the spread in the width direction and the variation thereof are suppressed by positively flowing the coating liquid 30 discharged from the discharge port 21 in the transport direction.

  As a method for controlling the contact angle θ, different materials are used for the die block 10 and the shim 20 in this embodiment, but the present invention is not limited to this. For example, a water-repellent coating process may be performed on the shim lip surface 20B. Further, the roughening process may be performed on the shim lip surface 20B. The water repellent coating treatment has a problem that its performance deteriorates due to cleaning of the lip surface, etc., and its durability is low. In addition, it is difficult to form surface irregularities with high precision in the roughening treatment. A method of differentiating the contact angle θ depending on the material is preferable because these problems do not occur.

[Example]
Subsequently, an experimental result of examining the width variation of the coating film 41 will be described. In this experiment, the contact angle ratio between the shim lip surface 20B and the die lip surfaces 11A and 12A (the contact angle β of the shim lip surface / the contact angle α of the die lip surface) is obtained, and the relationship between the contact angle ratio and the width variation of the coating film 41. investigated.

In this experiment, stainless steel (SUS304) was used for the die block 10, and several samples of the shim 20 were prepared and experimented in order to change the contact angle ratio. In this experiment, the physical properties of the coating solution 30 and the configuration of the die coating apparatus 200 are as follows.
Surface tension T = 0.035 to 0.075 N / m
Density ρ = 1.3 to 1.7 g / cm ³
Inner diameter r = 30-100 μm
The value of the inner diameter r means the gap G between the lip surface of the die head 100 and the web 40.

The experimental results are shown in Table 1 below. In this experiment, shims having the same shape made of SUS304, PET, PFA, and PTFE were prepared as the shim 20 samples. “PET-1” and “PET-2” mean that two samples were tested with the same material. The same applies to “PTFE-1” and “PTFE-2”.

  “Contact angle α” and “Contact angle β” are static contact angles with respect to the coating film 30 obtained by a general contact angle meter. “Width variation” means that the coating film 41 is formed for each sample, the width of the coating film 41 is measured at a plurality of points, the standard deviation is obtained based on the measured values, and the contact angle ratio is 1 ( That is, the standard deviation of each sample when the standard deviation of stainless steel (SUS304) is used as 100 for the shim 20 is shown. In other words, when the value of “width variation” is smaller than 100, it means that the width of the coating film 41 is more stable than that using the stainless steel for the shim 20. It means that the width of is stable. FIG. 6 is a graph of the experimental results in Table 1, with the horizontal axis representing the contact angle ratio and the vertical axis representing the width variation of the coating film 41.

  According to the result of this experiment, when the contact angle ratio is larger than 1, that is, when the contact angle β of the shim lip surface 20B is larger than the contact angle α of the die lip surface 12A, the width variation is compared with that when the contact angle ratio is 1. Small. Therefore, it can be seen that the width of the coating film 41 is stable. Furthermore, when the contact angle ratio is 2 or more, the width variation is significantly smaller than when the contact angle ratio is about 1.4. Therefore, it can be seen that the width of the coating film 41 is remarkably stabilized. That is, it can be seen that if the contact angle ratio is larger than 1, there is an effect of suppressing the width variation, and further, if the contact angle ratio is 2 or more, the width variation can be remarkably suppressed.

  As described above in detail, in the die coating apparatus 200 of the present embodiment, the lip surface of the die head 100 is the shim lip surface 20B (an example of the second surface) positioned in the width direction with respect to the discharge port 21, and the transport direction. The die lip surface 11A (an example of the third surface) located on the upstream side and the die lip surface 12A (an example of the first surface) located on the downstream side are configured such that the contact angle of the shim lip surface 20B is the die lip surfaces 11A, 12A. Is larger than the contact angle. For this reason, the shim lip surface 20B is weaker in wettability than the die lip surfaces 11A and 12A. For this reason, the coating liquid 30 does not easily spread on the shim lip surface 20B side (width direction side) with respect to the discharge port 21, but actively flows to the die lip sides 11A and 12A (downstream side in the transport direction). From this, it can be expected that the width variation of the coating film 41 is suppressed.

  Note that this embodiment is merely illustrative and do not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the application of the present die coating apparatus is not limited to the manufacturing process of an electrode plate for a secondary battery, but can be widely applied to applications for forming a coating film by a die coating method.

  In the embodiment, the same material is used for the upstream die block 11 and the downstream die block 12 of the die head 100, but different materials may be used. For example, the same material as the shim 20 may be used for the upstream die block 11. Further, a material having better wettability than the die block 12 may be used for the die block 11. That is, it is sufficient that at least the contact angle of the die block 12 on the downstream side is smaller than the contact angle of the shim 20. When the coating liquid 30 is more actively flown in the transport direction, it is desirable to use a material having a contact angle smaller than that of the shim 20 for both the die blocks 11 and 12 as in the embodiment. .

  In the embodiment, the die head 100 has a structure in which the three parts of the die block 11, 12, and shim 20 are overlapped, and the lip surface is aligned with each part to form the three surfaces of the die lip surfaces 11A, 12A and the shim lip surface 20B. It is distinct but not limited to this. For example, all of them are integrated, and a part of the lip surface may be surface-processed to distinguish the regions at both ends in the width direction of the discharge port from the upstream region and the downstream region in the transport direction.

  In the embodiment, the discharge port 21 is formed by a single plate-like shim 20. However, the present invention is not limited to this. For example, a plurality of shim plates having slits may be prepared and overlapped.

11 (upstream) die block 11A (upstream) die lip surface 12 (downstream) die block 12A (downstream) die lip surface 20 shim 20B shim lip surface 21 outlet 30 coating liquid 40 web 41 coating film 50 backup Roller 100 Die head 200 Die coating device

Claims (5)

In die coating equipment that applies coating liquid onto a continuously running web,
The lip surface of the die head facing the web is
A discharge port for the coating liquid;
A first surface that is in contact with the discharge port and is a surface region located downstream of the discharge port in the web conveyance direction;
A second surface that is in contact with the discharge port and is a surface region located on both sides of the web in the width direction of the discharge port;
Have
A die coating apparatus, wherein a contact angle α of the first surface with respect to the coating solution is smaller than a contact angle β of the second surface with respect to the coating solution. In the die coating apparatus according to claim 1,
A die coating apparatus, wherein a contact angle ratio (β / α), which is a ratio of the contact angle α and the contact angle β, is 2 or more. In the die coating apparatus according to claim 1 or 2,
The die head is
A pair of die blocks;
A shim that is sandwiched between the pair of die blocks and has a groove that serves as a flow path for the coating solution;
With
The pair of die blocks form the discharge port by sandwiching the shim groove,
The first surface is a lip surface of the die block disposed on the downstream side in the web conveyance direction;
The die coating apparatus, wherein the second surface is a lip surface of the shim. In the die coating apparatus according to claim 3,
A die coating apparatus, wherein the first surface and the second surface are made of different materials. In the die coating apparatus according to any one of claims 1 to 4,
The lip surface of the die head facing the web is
A third surface that is in contact with the discharge port and is a surface region located upstream of the discharge port in the web conveyance direction;
A die coating apparatus, wherein a contact angle γ of the third surface with respect to the coating solution is smaller than a contact angle β of the second surface with respect to the coating solution.

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