JPH07187803A - Production of green sheet - Google Patents

Abstract

PURPOSE:To obtain a green sheet which is free from variations in film thickness after drying and has a uniform thickness even if there is a variation in the thickness of the green sheet (slurry state) before drying. CONSTITUTION:The device of this process is provided with a mechanism for controlling the green sheet to the specified thickness by a pair of rollers 6 which rotate to press the green sheet (slurry state) 4a on a carrier film 3 coated from a doctor blade 1 from above and below within a drying furnace 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a green sheet such as a laminated ceramic capacitor, and more particularly to controlling the thickness of the green sheet.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIG.

In Japanese Patent Laid-Open No. 3-106605, a semi-dry strip-shaped green is obtained by continuously drawing a slurry 2 containing a raw material powder, a solvent and a binder material from a fixed gap and forcibly heating it. A manufacturing method for forming the sheet 4b is disclosed.

This is a relatively viscous sludge 2 made by dispersing a raw material powder, a solvent and a binder material is continuously applied from a predetermined gap of a doctor blade 1 provided on a carrier film 3, A strip-shaped undried green sheet 4a having a thickness and a predetermined width is formed. Next, the carrier film 3 and the undried green sheet 4a on the carrier film 3 move in the drying furnace 5 as they are, during which a part of the solvent in the slurry is forcibly vaporized and diffused to provide some flexibility. The green sheet 4c having a belt-shaped solid substance having a cake shape is formed.

[0005]

A laminated ceramic capacitor 13 is one of the products using the green sheet 4c thus manufactured. In the monolithic ceramic capacitor 13, it is important that the thickness of the green sheet 4c is uniform because the film thickness of the green sheet 4c determines product quality such as electric capacity and insulation.

However, in the above conventional method, it is difficult to accurately align the gap of the doctor blade 1 with the carrier film 3 in parallel, and the thickness of the undried green sheet 4a continuously drawn from the gap also changes with time. Therefore, the thickness of the green sheet 4c after drying is 1 μm.
There will be variations around m. In the multilayer ceramic capacitor 13, the green sheet 4 cut into a predetermined size
In order to obtain the laminate 11 by printing the internal electrode 10 on c and stacking a plurality of sheets, the film thickness difference of the green sheet 4c (see FIG.
Due to (b), the green sheets 4c are obliquely displaced and stacked, and the positions of the internal electrodes 10 are also displaced (FIG. 5 (b)), resulting in a laminated body 11. When this laminated body 11 was cut into a chip shape, a chip 12 as shown in FIG. 6B was obtained, and the distance of the dielectric layer from the internal electrode 10 to the end face of the capacitor was insufficient, resulting in insulation failure.

Further, some air bubbles may be present in the undried green sheet 4a pulled out from the doctor blade 1, and it remains as pinholes 9 in the green sheet 4c even after the dried green sheet 4c is formed, and the laminated ceramic The insulating property, which is the withstand voltage of the capacitor 13, was significantly deteriorated.

In the trend toward miniaturization and high capacity of the monolithic ceramic capacitor 13, it is desired to reduce the thickness of the green sheet and increase the number of layers, and the above-mentioned two problems of the inclination of the laminate and the insulating property are especially 20 μm or less of the green. The influence is remarkable when the thickness of the sheet 4c is large.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing a green sheet which solves the above-mentioned conventional drawbacks.

In the method for producing a green sheet according to the present invention, a doctor blade having a certain gap is provided on a carrier film, and a raw material powder, a solvent and a binder material are mixed and dispersed from the gap to continuously apply a slurry. Then, the coated slurry is dried in a drying oven,
In the step of forming the green sheet, the green sheet on the carrier film is rolled by a pair of rollers in a drying oven that press and rotate the carrier film and the green sheet from above and below. Further, it is characterized in that the upper roller of the pair of rollers is in contact with both ends of the carrier film, and protrusions corresponding to the thickness of the green sheet are provided. Further, it is characterized in that it has a plurality of rows of the above-mentioned pair of rollers and rolls in stages.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic perspective view of a green sheet forming apparatus according to a first embodiment of the present invention, and its structure will be described. Although not shown, the carrier film 3
Roll-to-roll, that is, the carrier film 3 wound into a roll is pulled out, conveyed from left to right, and wound into a roll. First, the doctor blade 1 is arranged on the carrier film 3 pulled out from the unwinding roll. The doctor blade 1 has a tank shape without a bottom for storing the sludge 2. The side plate on the rear end side of the carrier film 3 in the conveying direction moves up and down so that a certain gap is formed when the doctor blade is placed on the carrier film 3. It has become. A drying furnace 5 is arranged next to the carrier film conveying direction. The left and right sidewalls of the drying oven 5 have openings through which the carrier film 3 passes, and the drying oven 5 supports the carrier film 3 so that it does not bend. The film thickness adjusting roller 6 is provided in the same horizontal position as the support for supporting the carrier film 3.
b is provided with a film thickness adjusting roller 6a above the carrier film 3 with the carrier film 3 interposed therebetween. These film thickness adjusting rollers 6a, 6b
Are rotated in the same direction at a speed synchronized with the conveyance of the carrier film 3, and the interval between both rollers has an arbitrary parallelism of 1.
It can be set below μm. Further, the drying oven 5 has zones in which several temperatures can be set so that a stepwise dry state can be obtained in the transport direction of the carrier film 3. The carrier film 3 exiting the drying oven 5 is
It is wound into a roll.

Next, the operation will be described with reference to FIG. When the slurry 2 is put into the doctor blade 1 and the carrier film 3 is conveyed in the above state, the undried green sheet 4a is coated on the carrier film 3 by the gap of the doctor blade 1. The green sheet 4a enters the drying furnace 5 and is dried at a set temperature gradient, but the surface of the green sheet 4 is slightly dried and the film thickness adjusting roller 6a arranged at a drying position where the sheet does not adhere even if it comes into contact with the roller. 6b
Then, the green sheet is rolled and pressed to be rolled. In this way, the green sheet 4c having a variation of 0.5 μm or less and a uniform thickness can be obtained.

FIG. 2 is a schematic perspective view showing a second embodiment of the present invention.

In the second embodiment, the protrusions 7 having a height corresponding to the thickness of the green sheet 4 are provided at both ends of the film thickness adjusting roller 6a which is in contact with the green sheet 4. Compared with the first embodiment in which the thickness of the green sheet can be adjusted by changing the gap between the rollers, the height of the protrusions 7 determines the versatility of the thickness, but since the carrier film 3 can be rolled firmly, it can be rolled. Moreover, the thickness of the green sheet can be made uniform.

FIG. 3 is a schematic perspective view showing a third embodiment of the present invention.

In the third embodiment, the rollers b of the first and second embodiments are installed in a plurality of rows in the drying furnace 5.
The green sheet 4c having a large variation in film thickness has an advantage that rolling correction can be carried out stepwise.

[0018]

As described above, according to the method for manufacturing a green sheet of the present invention, the setting is made when the green sheet is in the dry oven 4b (only the surface of the green sheet is dry) in the drying oven 5. Since the green sheet 4b is rolled by the pair of rollers 6 having a gap corresponding to the film thickness, even if the undried green sheet 4a pulled out from the doctor blade 1 does not have a uniform thickness, the dried green sheet 4c Keeps the film thickness of submicron constant,
The oblique stacking caused by the film thickness difference in the subsequent stacking process is improved.

Further, since the discharge amount of the sludge 2 is drawn thicker than the target film thickness from the doctor blade 1, even if the pinhole 9 or the like occurs, it is rolled by the roller 6 and the number of pinholes is reduced. It has a great effect on product quality.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a green sheet forming apparatus showing a first embodiment of the present invention.

FIG. 2 is an enlarged perspective view of the roller rolling unit of FIG.

FIG. 3 is a schematic perspective view of a green sheet forming apparatus showing a third embodiment of the present invention.

4A is a perspective view of a green sheet having a uniform film thickness; FIG. 4B is a perspective view of a green sheet having a film thickness difference; and FIG. 4C is a perspective view of a green sheet having pinholes.

FIG. 5A is a cross-sectional view of a laminated body without oblique lamination. FIG. 5B is a cross-sectional view of a laminated body that is obliquely laminated.

FIG. 6 (a) is a cross-sectional view of what is cut into a desired shape from FIG. 4 (a), and FIG. 6 (b) is a cross-sectional view of what is cut into a desired shape from FIG.

FIG. 7 is a perspective view showing an outline of a conventional green sheet forming apparatus.

FIG. 8A is a perspective view of a raw chip of a monolithic ceramic capacitor, and FIG. 8B is a monolithic ceramic capacitor having external electrodes formed thereon.

[Explanation of symbols]

 1 Doctor blade 2 Sludge liquid 3 Carrier film 4a Green sheet (slurry state) 4b Green sheet (dry state) 4c Green sheet 5 Drying oven 6a Film thickness adjusting roller (upper side) 6b Film thickness adjusting roller (lower side) 7 Upper roller protrusion Part 8 Film thickness 9 Pinhole 10 Internal electrode 11 Laminated body 12 Chip 13 External electrode forming chip

Claims (3)

[Claims] 1. A doctor blade having a fixed gap provided on a carrier film, the raw material powder, a solvent, and a binder material are mixed and dispersed through the gap to continuously apply the slurry, and the coating is performed. In the step of drying the sludge through a drying oven to form a green sheet, a pair of rollers that press and rotate the carrier film and the green sheet from above and below in the drying oven are used to remove the green sheet on the carrier film. A method for producing a green sheet, which comprises rolling. 2. The method for producing a green sheet according to claim 1, wherein the upper roller of the pair of rollers is provided in contact with both ends of the carrier film and provided with protrusions having a thickness of the green sheet. 3. The method for producing a green sheet according to claim 1, wherein the roller has a plurality of rows and is rolled stepwise.