JP4310855B2 - Method and apparatus for producing ceramic green sheet - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for producing a ceramic green sheet, in which a ceramic slurry is coated with high accuracy using a die coater method to obtain a green sheet having a stable film thickness.
[0002]
[Prior art]
Conventionally, a ceramic green sheet is used when manufacturing a multilayer ceramic capacitor, a ceramic multilayer substrate, or the like. In order to create a ceramic green sheet, a ceramic raw material powder having a required composition and a binder solution are mixed with each other to obtain a ceramic slurry, and then the ceramic slurry is formed into a sheet to obtain a ceramic green sheet. . Among sheet forming methods, the die coater method has a feature that the coating film thickness of the ceramic slurry can be controlled with high accuracy.
[0003]
In the die coater method, as shown in FIG. 1, a die head 3 having a nozzle port 3a is disposed at a position facing a backup roll 2 for supporting a traveling substrate (carrier film) 1, and the substrate In this method, a gap is provided between 1 and the die head 3, the ceramic slurry 4 is discharged from the nozzle port 3 a of the die head 3 to the gap, and the substrate 1 is formed into a sheet.
[0004]
[Problems to be solved by the invention]
However, even if the sheet is formed by the die coater method, a phenomenon occurs in which the film thickness varies periodically in the sheet length direction. One of the causes of this film thickness variation is considered to be a variation in coating speed (base material traveling speed). Variations in coating speed occur due to uneven rotation of the motor that drives the backup roll and carrier film transport roll, uneven tension on the carrier film, and the like. In order to suppress the film thickness fluctuation, it is only necessary to reduce the fluctuation amount of the coating speed, but this has a limit. Therefore, there is a need for a coating apparatus that can suppress film thickness variation even when the coating speed varies.
[0005]
FIG. 2 shows a flow of the ceramic slurry 4 discharged from the nozzle port 3a between the upstream lip 3b and the downstream lip 3c and formed into a sheet.
In Fig. 2, 1) shows the coating speed, 2) shows the upstream free surface position, 3) shows each change in film thickness, and when the coating speed 1) increases, the upstream free surface position 2) moves downstream. However, the film thickness 3) becomes thin.
[0006]
The film thickness is given by the outflow amount / coating speed from the downstream lip 3c. If the flow rate from the downstream lip 3c does not change at the same rate when the coating speed changes, the film thickness fluctuates. When the gap Hu between the upstream lip 3b and the substrate 1 and the gap Hd between the downstream lip 3c and the substrate 1 are substantially the same as in the prior art, when the coating speed 1) fluctuates, The outflow amount from the downstream lip 3c cannot be dealt with immediately, resulting in a time lag between the change in the coating speed and the outflow amount, so that the film thickness 3) fluctuates greatly. It was.
[0007]
Accordingly, an object of the present invention is to provide a method and apparatus for manufacturing a ceramic green sheet that can keep the film thickness fluctuation of the ceramic green sheet small even when the coating speed fluctuates.
[0008]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the invention according to claim 1 is directed to a coated surface that is continuously run from a nozzle port between an upstream lip and a downstream lip that are spaced apart from each other. In a method for producing a ceramic green sheet in which a ceramic green sheet is formed by discharging ceramic slurry,
The relationship between the distance Hu between the upstream lip and the surface to be coated and the distance Hd between the downstream lip and the surface to be coated
5> Hu / Hd ≧ 1.3
Provided is a manufacturing method characterized by being set to be
[0009]
As for the film thickness fluctuation of the ceramic green sheet, the fluctuation of the outflow amount from the downstream lip cannot immediately respond to the fluctuation of the coating speed, and the time between the fluctuation of the coating speed and the fluctuation of the outflow amount This happens because a shift occurs. In order to reduce the influence of this deviation, the amount of movement of the upstream free surface may be reduced. As a means for this, in the present invention, the gap Hu of the upstream lip is set to be 1.3 times or more the gap Hd of the downstream lip. That is, when Hu / Hd <1.3, the volume of the space formed between the upstream lip and the surface to be coated is small, and the upstream free surface moves greatly due to fluctuations in the coating speed. On the other hand, if Hu / Hd ≧ 1.3, the volume of the space formed between the upstream lip and the surface to be coated becomes relatively large, and the movement of the upstream free surface with respect to fluctuations in the coating speed. Can be reduced. However, when Hu / Hd ≧ 5, when the pressure at the center of the upstream lip and the downstream lip changes, the position of the upstream free surface moves too much upstream, and dripping easily occurs. Possible causes of such a pressure change include a change in flow rate due to a change in viscosity of the slurry before and after the application, and a change in gap due to thermal expansion of the backup roll due to a temperature change. Therefore, by setting Hu / Hd within the above range, even if the coating speed fluctuates, film thickness fluctuation is suppressed, and problems such as liquid dripping are also eliminated.
[0010]
Since the downstream lip gap Hd has a correlation with the film thickness, it is determined exclusively according to the film thickness. On the other hand, the gap Hu of the upstream lip is related to the film thickness variation as described above. Therefore, by setting the gaps Hd and Hu within the above range, a sheet having a desired film thickness and little film thickness variation in the sheet length direction can be formed.
[0011]
As in claim 3, when Hu / Hd = 1.5, the fluctuation amount of the film thickness accompanying the fluctuation of the coating speed (3%) can be reduced to almost zero. Therefore, it is possible to form a sheet with extremely high accuracy.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 3 shows an example of a die coater type coating apparatus according to the present invention. The same parts as those in FIG.
A supply device 5 for supplying the ceramic slurry 4 is provided at the rear portion of the die head 3, and the ceramic slurry 4 is continuously supplied from the supply device 5 to the nozzle port 3 a of the die head 3. An upstream lip 3b is provided on the upstream side of the nozzle port 3a, and a downstream lip 3c is provided on the downstream side. The distance Hu between the upstream lip 3b and the surface to be coated, the downstream lip 3c and the surface to be coated, The relationship with the distance Hd of
5> Hu / Hd ≧ 1.3
It is set to become.
[0013]
The coated surface is not limited to the surface of the carrier film 1, and may be a metal surface, a green sheet surface, a printed electrode surface, or the like. The back surface of the surface to be coated is not limited to the backup roll 2 and may be a flat plate. The supply device 5 may be a volumetric type such as a gear pump or a pressure control type such as an air pressurization tank.
[0014]
In this example, each condition was set as follows.
Film thickness: 50 μm or less Gap Hu of the upstream lip: 100 μm or less Gap Hd of the downstream lip: 77 μm or less Coating speed: 0.2 to 1.0 m / s
Coating speed fluctuation: ± 1-6% (Sine fluctuation: Frequency 100Hz or less)
Flow rate of ceramic slurry: 6 × 10 ^{−6 to} 3 × 10 ⁻⁵ m ² / s
Nozzle opening gap W: 0.1 to 0.5 mm
Viscosity of ceramic slurry: 0.05 to 1.0 Pas
[0015]
FIG. 4 shows changes in the film thickness fluctuation amount when Hu / Hd is changed when each condition is set as described above and the film thickness fluctuation quantity of Hu / Hd = 1 is set to 1.
As can be seen from FIG. 4, when Hu / Hd ≧ 1.3, the film thickness fluctuation amount is 0.2 or less, and the film thickness fluctuation is greatly reduced. In particular, when Hu / Hd = 1.5, the film thickness variation amount was almost 0, and a remarkable effect was obtained.
In FIG. 4, the data of Hu / Hd> 3 is not shown, but it has been experimentally confirmed that even in a region exceeding 3, a film thickness variation amount equivalent to that when Hu / Hd = 3 can be obtained. It was.
However, when Hu / Hd ≧ 5, a problem occurs for a reason different from the film thickness fluctuation. That is, when the flow rate or the gap changes with time, the pressure changes and the upstream free surface moves too far upstream from the balanced position, and liquid dripping may occur.
For the above reason, 5> Hu / Hd ≧ 1.3.
[0016]
FIG. 3 illustrates an example in which the die head 3 is close to the surface to be coated 1 from the side. However, the present invention is a type in which the die head is close to the surface to be coated from above or a type in which the die head is close from below. The same applies to the apparatus, and the direction of the die head is not limited.
[0017]
【The invention's effect】
As apparent from the above description, according to the present invention, the ratio of the distance Hu between the upstream lip and the surface to be coated and the distance Hd between the downstream lip and the surface to be coated is less than 5 and 1.3 or more. Therefore, even if the coating speed fluctuates, the film thickness fluctuation of the ceramic green sheet can be kept small, and the occurrence of dripping can be prevented. Therefore, it is possible to realize a highly accurate method for manufacturing a ceramic green sheet with a small film thickness variation.
[Brief description of the drawings]
FIG. 1 is a side view of a general die coater type coating apparatus.
FIG. 2 is an enlarged view showing a flow of a slurry to be formed into a sheet.
FIG. 3 is a side view of an apparatus for producing a ceramic green sheet according to the present invention.
FIG. 4 is a graph showing a relationship between a ratio of a gap Hu of an upstream lip and a gap Hd of a downstream lip and a film thickness variation amount.
[Explanation of symbols]
1 Surface to be coated (carrier film)
2 Backup roll 3 Die head 3a Nozzle port 3b Upstream lip 3c Downstream lip 4 Ceramic slurry

Claims (3)

A ceramic green sheet for forming a ceramic green sheet by discharging ceramic slurry from a nozzle opening between an upstream lip and a downstream lip arranged at intervals to a coated surface to be continuously run supported on the back side. In the manufacturing method,
The relationship between the distance Hu between the upstream lip and the surface to be coated and the distance Hd between the downstream lip and the surface to be coated
5> Hu / Hd ≧ 1.3
The manufacturing method characterized by setting so that it may become. A ceramic green sheet for forming a ceramic green sheet by discharging ceramic slurry from a nozzle opening between an upstream lip and a downstream lip arranged at intervals to a coated surface to be continuously run supported on the back side. In manufacturing equipment,
The relationship between the distance Hu between the upstream lip and the surface to be coated and the distance Hd between the downstream lip and the surface to be coated
5> Hu / Hd ≧ 1.3
A manufacturing apparatus characterized by being set to be The manufacturing apparatus according to claim 2, wherein Hu / Hd = 1.5.

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