JP5866919B2 - Coating apparatus and coating method - Google Patents

Description

  The present invention relates to a coating apparatus that coats a coating solution using a die coater and a coating method thereof. More particularly, the present invention relates to a coating apparatus and a coating method for providing a coating liquid having a high solid content, a high viscosity, and a high thixotropy with a stable basis weight immediately after the start of coating.

  A method of coating a thick film using a die coater has been known in the past.For example, when creating a battery electrode plate, stably coating a thick film on a current collector, It is considered a relatively difficult technology. In particular, since a coating liquid having a high solid content and filled with particles at a high concentration has high thixotropic properties, it takes a very long time to stabilize the basis weight after coating. Accordingly, the basis weight is low immediately after the start of coating, and the basis weight increases with the passage of time, and it often follows the course of stabilization at a certain point.

Here, the “weight per unit area” is the weight or mass per unit area of the coating liquid. Therefore, the “weight per unit area” has a one-to-one correspondence with the “film thickness”. Therefore, the “weight per unit area” may be read as “film thickness”.
Here, conventionally, several means for solving the problem that it takes time until the basis weight is stabilized have been proposed. For example, Patent Document 1 discloses a method of detecting the internal pressure of a die coater and controlling the feed speed of a material to be coated. That is, when the internal pressure of the die coater is high, the amount of coating liquid discharged is large, so that the feed speed of the material to be coated is increased. When the internal pressure of the die coater is low, the feed speed of the material to be coated is decreased.

However, this coating method requires a complicated system that detects the internal pressure of the die coater and feeds it back to the motor. Also, unless the time lag until this feedback is considerably high, the timing of coating does not match well, and the thickness unevenness is amplified on the contrary, and stable coating cannot be performed. It is also difficult to increase the coating speed.
As another method, Patent Document 2 discloses a circulation system path that connects a pump and a tank used during non-coating, a coating system path through which a coating liquid flows from the pump used during coating to the die head, and a circulation system path and coating. There has been proposed a coating apparatus having a valve for switching between a work path and an opening / closing valve at both ends of a die head. With such a configuration, after the coating liquid is circulated and stabilized in the circulation system, the flow path is switched with a valve to start coating. This stabilizes the basis weight at the start of coating, and at the end of coating, opens the on-off valves at both ends of the die head to suddenly lower the internal pressure of the die coater, thereby stabilizing the coating end thickness. Have been described.

  However, if this is done with a coating solution with high thixotropy, the coating solution stops in the coating system path and the die head from the switching valve, so that the coating starts from a very high viscosity of the coating solution. End up. That is, since there are many coating liquids which do not flow immediately, the malfunction of not reaching the fabric weight required at the time of a coating start arises. Further, when the coating is completed, the on-off valves at both ends of the die head are opened to allow the coating liquid to escape, resulting in useless coating liquid.

  As another method, Patent Document 3 discloses that the circulation system in the coating apparatus of Patent Document 2 is eliminated, and the coating liquid is returned to the tank by switching from the open / close valve closed state at both ends of the die head to the open state at the end of coating. A method for eliminating the waste of the coating liquid has been proposed.

JP 2003-190862 A JP 2003-190861 A JP 2003-190863 A

  However, the coating apparatus described in Patent Document 3 also employs a method of detecting the internal pressure in the die head and controlling the feed speed of the material to be coated. Still exists. Moreover, since the method of controlling the speed of the coating material of patent document 1 is employ | adopted with respect to the problem of the fabric weight stabilization at the time of a coating start, a complicated feedback system is still required.

  The present invention has been made in order to solve the above-described problems, and does not require a complicated feedback system, and is stable from immediately after the start of coating even when a coating solution with high thixotropy filled with particles is used. An object of the present invention is to provide a coating apparatus and a coating method capable of obtaining a basis weight.

In order to solve the above problems, an aspect of the present invention includes a coating die head, a coating liquid supply apparatus that supplies a coating liquid to the coating die head, and the coating liquid that is supplied from the coating liquid supply apparatus. A coating liquid reflux control device for controlling the reflux of the liquid, and the coating liquid supply device supplies at least the volume of the coating die head when the coating liquid is refluxed before starting the coating. The coating liquid is supplied such that the coating liquid is refluxed and the supply pressure of the coating liquid to the coating die head exceeds the discharge pressure of the coating liquid from the coating die head at the time of coating; the discharge pressure of a coating device, characterized in discharge pressure der Rukoto satisfying the discharge amount of a given said coating liquid to a predetermined.

According to another aspect of the present invention, the coating die head is configured to supply the coating liquid from the coating liquid supply device through a coating liquid inlet provided at one end in the width direction when the coating liquid is applied. The coating apparatus is characterized in that the coating liquid is fed back to the coating liquid reflux control apparatus from a coating liquid reflux port provided at the other end.
In another aspect of the present invention, the coating liquid supply apparatus further includes a pressure gauge that is provided in at least one of the supply outlet of the coating liquid supply apparatus, the coating die head, and the coating liquid reflux control apparatus and measures an internal pressure. It is a construction device.

  Another aspect of the present invention is a coating method using the above-described coating apparatus, wherein the coating liquid supply pressure to the coating die head in the coating liquid supply apparatus is set before the start of coating. The coating die head is allowed to reflux while maintaining a discharge pressure that satisfies a predetermined predetermined coating liquid discharge amount, and the coating liquid reflux amount is limited or stopped at the start of coating. The coating method is characterized by discharging the coating liquid.

  According to the coating apparatus and the coating method according to an aspect of the present invention, a complicated feedback system is not required, and even when a coating solution with high thixotropy filled with particles is used, immediately after the start of coating. Thus, it is possible to obtain a coating film having a stable basis weight.

It is a figure which shows the structural example of the coating apparatus which concerns on one Embodiment of this invention. It is a figure which shows another structural example of the coating apparatus which concerns on one Embodiment of this invention. It is a figure which shows the specific structural example of the coating apparatus which concerns on one Embodiment of this invention.

  FIG. 1 is a diagram illustrating a configuration example of a coating apparatus according to the present embodiment. The coating apparatus 1 includes a coating die head (hereinafter referred to as “coating head”) 2, a coating liquid supply apparatus 3, and a coating liquid reflux control apparatus 4. The coating liquid supply device 3 supplies the coating liquid to the coating head 2. The coating head 2 performs coating by discharging a coating liquid. The coating liquid reflux control device 4 is for refluxing the coating liquid to the coating liquid supply device 3 when coating is not performed.

  The feature of the coating apparatus according to the present embodiment is that the discharge port of the coating head 2 is closed by some means until just before the start of coating, and the internal pressure of the coating head 2 has a desired coating amount. The coating liquid supply device 3 is set so that the coating liquid is recirculated through the coating liquid recirculation control device 4 while maintaining an internal pressure equal to or higher than the internal pressure of the coating head 2 to be obtained. As a result, the coating liquid inside the coating head 2 always flows and is kept at the same or high pressure as at the time of coating. Therefore, even when the coating liquid has a high thixotropic property, the viscosity of the coating liquid is high. The flow characteristics of the coating liquid are reduced, and are maintained almost the same as during coating.

  Therefore, it is possible to discharge the coating liquid in a desired discharge amount from the moment when the discharge port of the coating head 2 is opened at the start of coating. As means for closing the discharge port of the coating head 2, a method of providing a shutter in the coating head 2, a method of blocking the discharge port with a tape or the like, and pressing the discharge port against the back roll via a buffer holding material or the like. Examples include, but are not limited to, any method.

FIG. 2 is a diagram illustrating another configuration example of the coating apparatus according to the present embodiment. As shown in FIG. 2, pressure gauges 6 to 8 may be installed so that the pressure at the set place can be constantly measured. As shown in FIG. 2, the pressure gauge can be installed at any or all of the supply outlet (outlet) of the coating liquid supply apparatus 3, the inside of the coating head 2, the inlet or the inside of the coating liquid reflux control apparatus 4. is there.
In addition, the coating head 2 used in the coating apparatus 1 of the present embodiment has a central shape as the shape for the purpose of always refluxing the coating liquid via the coating liquid reflux controller 4 except during coating. For example, the liquid is fed from the coating liquid input port provided at one end in the width direction, and is provided at the other end in the width direction as a shape to be fed from the width direction rather than the so-called T die shape. It is easier to design and more preferable when the shape is a shape that recirculates from the coating liquid reflux port (outflow port). However, the present invention is not limited to this.

FIG. 3 is a diagram illustrating a specific configuration example of the coating apparatus according to the present embodiment. The coating apparatus 1 includes a coating head 11, a pump 12, a flow path valve 13, a tank recirculation valve 14, a die recirculation valve 15, a coating liquid tank 16, and a die head internal pressure gauge 17. FIG. 3 shows an example of the configuration, and the present invention is not limited to this.
In the configuration of FIG. 3, the coating head 11 corresponds to the coating die head 2 of FIG. The pump 12 and the coating liquid tank 16 correspond to the coating liquid supply device 3 in FIG. The flow path valve 13, the tank recirculation valve 14, and the die recirculation valve 15 correspond to the coating liquid recirculation control device 4 of FIG.

Hereinafter, the coating method at the time of coating with the coating apparatus 1 is demonstrated using FIG.
(1) First, after the coating liquid is introduced into the coating liquid tank 16, the flow path valve 13 and the die reflux valve 15 are closed, and the tank reflux valve 14 is opened. In this state, the pump 12 is started and the coating liquid is fed. As a result, the pipe from the coating liquid tank 16 to the pump 12 and the tank recirculation valve 14 is filled with the coating liquid. Next, the discharge port of the coating head 11 is closed, the flow path valve 13 is opened, the tank recirculation valve 14 is closed, and the die recirculation valve 15 is opened. The liquid feeding by the pump 12 is continued as it is, so that the inside of the coating head 11 is sufficiently filled with the coating liquid, and the coating liquid is sufficiently returned to the tank 16 through the die reflux valve 15.

(2) Next , the discharge port of the coating head 11 is opened, coating is performed by changing the discharge amount of the pump 12, and the pressure value of the die head internal pressure gauge 17 is read. Further, the basis weight at this time is measured. As a result of coating under some discharge conditions, if a coating film with a desired basis weight is obtained, the value of the die head internal pressure gauge 17 at this time is recorded. Here, this value is assumed to be “P”. When the pressure value P is obtained, close the flow path valve 13, recirculates the coating liquid to the coating liquid tank 16 without passing through the coating head 11 to open the tank reflux valve 1 4. Here, a pressure gauge is attached to the coating head 11 (die head internal pressure gauge 17), but a place corresponding to this may be provided, for example, near the inlet of the coating head 11.

(3) Next, the discharge port of the coating head 11 is closed again, the flow path valve 13 is opened, the tank recirculation valve 14 is closed, and the die recirculation valve 15 is opened. In this state, the liquid is fed from the pump 12, and the die head internal pressure (internal pressure of the coating head 11, the same applies hereinafter) at this time is supplied while maintaining the pressure P or higher. As a result, the coating liquid in the coating head 11 always flows while maintaining the required discharge pressure, and a desired amount of coating liquid is discharged from the coating head 11 immediately after the start of coating. A stable coating film can be obtained.
Here, the conventional operation in which the process (3) is not performed after the process (2) is as follows. That is, after the processes (1) and (2) are completed, the following operation (4) is performed.

  (4) After setting the discharge amount of the pump 12 to a pump discharge amount at which an appropriate die head internal pressure is obtained, the flow path valve 13 is opened, the tank recirculation valve 14 and the die recirculation valve 15 are closed, and coating is performed. Start. If coating is performed in this state, it is expected that a coating film having a desired weight per unit area can be obtained. However, since the coating liquid in the coating head 11 is actually stopped before the coating is started, reflow is not possible. It takes time to start. Therefore, even if the discharge amount of the pump 12 is made appropriate, the pressure loss in the liquid feeding pipe and the coating head 11 becomes very large, and the discharge amount from the discharge port of the coating head 11 is more than expected. Get smaller. As time passes, the coating liquid that has stopped flowing gradually starts to flow, so that the desired basis weight is finally obtained, but according to the experiment of the inventor of the present invention, the coating liquid having a large thixotropic property Then, it took about 10 to 20 minutes until the basis weight was stabilized.

[Experiment 1]
Hereinafter, experiments conducted by the inventors of the present invention will be described.
<Coating device>
The configuration of the coating apparatus was almost similar to that shown in FIG. The difference is that the pressure gauge 17 is measured not at the coating head 11 but at the inlet of the coating head 11. Further, a 20 L tank was used as the coating liquid tank 16 and a MONO pump (manufactured by Hyojin Equipment Co., Ltd.) was used as the pump 12 with a maximum coating liquid discharge rate of 2 L / min. The pressure gauge was attached to the inlet of the coating head 11 via a corneal pressure gauge via a T-shaped tube. The coating head 11 was a die head having a width of 300 mm, and the shim had an opening width of 200 mm and a thickness of 150 μm. Ball valves were used for the flow path valve 13, the tank recirculation valve 14, and the die recirculation valve 15, respectively.

<Coating liquid>
As a coating liquid, a slurry prepared by composition of lithium manganate: polyvinylidene fluoride: conductive auxiliary agent: N-methylpyrrolidone at a composition ratio of 52: 7: 1: 40 was used. The coating solution viscosity measured with a B-type viscometer at 10 rpm was about 8000 mPa · s.
<Base material>
As the coating substrate, a polyethylene terephthalate (PET) film having a thickness of 50 μm was used.
<Coating operation>
First, when the pressure at which the required weight per unit area was obtained was determined, the pressure value (hereinafter referred to as “P1”) by a corneal pressure gauge provided immediately before the coating liquid inlet of the coating head 11 was 0.25 MPa. Thus, a necessary basis weight of 100 g / m 2 was obtained.

Next, the flow path valve 13 and the tank recirculation valve 14 were switched, the flow path valve 13 was closed, and the coating liquid was recirculated without passing through the coating head 11. Further, a tape was applied to the coating liquid discharge port of the coating head 11 to prevent the coating liquid from being discharged, and the ball valve of the die reflux valve 15 was opened to ensure a circulation path for the coating liquid. Then, the flow path valve 13 and the tank recirculation valve 14 are switched, the tank recirculation valve 14 is closed and the flow path valve 13 is opened, whereby the coating liquid is recirculated through the coating head 11, and the pressure value P1 of the pressure gauge Was adjusted to 0.25 MPa, and the coating liquid was circulated.
Ten minutes later, the cover tape of the die head coating liquid discharge port was peeled off, and the ball valve of the die reflux valve 15 was closed to start coating. The coating was carried out for 30 minutes as it was.

<Evaluation>
The coating weight per unit area of the coating portion was measured at an elapsed time of 0 minutes, 10 minutes, 20 minutes, and 30 minutes.
[Experiment 2]
The same operation as in Experimental Example 1 was performed except that the pressure value P1 of the pressure gauge was set to 0.3 MPa.
[Comparative Example 1]
The same operation as in Experimental Example 1 was performed except that the pressure value P1 of the pressure gauge was set to 0.2 MPa.
[Comparative Example 2]
The pressure value P1 of the pressure gauge was set to 0.2 MPa, and the following points were changed in the coating operation in the same manner as in Experimental Example 1 for the coating apparatus, the coating liquid, and the coating substrate.

<Coating operation>
First, the flow path valve 13 and the die recirculation valve 15 are closed, and the tank recirculation valve 14 is opened so that the coating liquid flows back to the tank side without passing through the coating head 11, and then the pump 12 is started. Liquid was sent. Next, the flow path valve 13 and the tank recirculation valve 14 are switched, the tank recirculation valve 14 is closed and the flow path valve 13 is opened, so that the coating liquid is flowed to the coating head 11 side and the coating is started. . When coating was performed while changing the number of revolutions of the pump 12 and the basis weight was measured, the required basis weight was obtained at a pump speed of 42 rpm. This 42 rpm was maintained, and the coating was performed for 30 minutes with the flow path set to the coating head 11 side.

<Evaluation>
The evaluation of the experiment was performed in the same manner as in Experimental Example 1.
<Evaluation results>
Table 1 below shows the evaluation results of the above experiments.

  From the above evaluation results, the necessary coating weight was obtained from the beginning in Experiments 1 and 2 in which the coating was started after the pressure value P1 was maintained at a necessary pressure (0.25 MPa) or more. It can be seen that Comparative Examples 1 and 2 that did not perform the test had an insufficient basis weight at the initial stage, and it took 10 to 20 minutes to stabilize the basis weight.

  INDUSTRIAL APPLICABILITY The present invention can be used in a process in which ink having high thixotropy filled with particles is applied with a die coater. For example, it is very effective for applications in which a thick film is applied, such as electrode plate coating for lithium ion batteries.

1 ... coating device 2 ... coating die head (coating head)
DESCRIPTION OF SYMBOLS 3 ... Coating liquid supply apparatus 4 ... Coating liquid reflux control apparatus 6-8 ... Pressure gauge 11 ... Coating head 12 ... Pump 13 ... Flow path valve 14 ... Tank reflux valve 15 ... Die reflux valve 16 ... Coating liquid tank 17 ... Die head internal pressure gauge

Claims (4)

A coating die head;
A coating liquid supply device for supplying a coating liquid to the coating die head;
A coating liquid reflux control device for controlling the reflux of the coating liquid supplied from the coating liquid supply device;
Have
The coating liquid supply device circulates at least the volume of the coating liquid larger than the volume of the coating die head when the coating liquid is refluxed before starting coating, and the supply pressure of the coating liquid to the coating die head Supply the coating liquid so as to exceed the discharge pressure of the coating liquid from the coating die head at the time of coating ,
Wherein the discharge pressure of the coating liquid, coating and wherein the discharge pressure der Rukoto satisfying the discharge amount of a given said coating liquid to a predetermined.   The coating die head receives supply of the coating liquid from the coating liquid supply port provided at one end in the width direction when the coating liquid is applied, and is provided at the other end. The coating apparatus according to claim 1, wherein the coating liquid is refluxed from the coating liquid reflux port to the coating liquid reflux control apparatus.   The coating apparatus according to claim 1, further comprising a pressure gauge that is provided in at least one of a supply outlet of the coating liquid supply apparatus, the coating die head, and the coating liquid reflux control apparatus to measure an internal pressure. . A coating method using the coating apparatus according to any one of claims 1 to 3,
Before starting the coating, the coating liquid is circulated while maintaining the supply pressure of the coating liquid to the coating die head in the coating liquid supply apparatus higher than a discharge pressure that satisfies a predetermined discharge amount of the coating liquid. And
A coating method, wherein at the start of coating, the amount of reflux of the coating liquid is limited or stopped and the coating liquid is discharged from the coating die head.

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