JP5576317B2 - Sheet forming apparatus and sheet forming method - Google Patents

Description

  The present invention relates to a sheet forming apparatus and a sheet forming method using a doctor blade method.

  In the electronic parts industry, electronic parts of laminated ceramics in which ceramic layers are laminated are widely used. Such a laminated ceramic is obtained by producing a green sheet using a slurry in which a ceramic powder and a resin-based composition such as a molding aid are mixed, and firing the green sheet laminate. The green sheet is generally produced by a doctor blade method.

  The slurry used to make the green sheet may use an organic solvent or water as a solvent, but it will chew a lot of bubbles in the slurry mixing process etc. and remain as it is without breaking until the green sheet is made. There is. When such a slurry containing bubbles is made into a sheet, defects such as pinholes frequently occur. The defoaming process that removes bubbles in the slurry is passed before the sheeting process, but fine bubbles in the slurry cannot be completely removed. Occurs and the yield decreases.

  On the other hand, in the green sheet forming method by the doctor blade method, a baffle plate whose upper end protrudes from the slurry reservoir portion is installed in the slurry reservoir portion of the slurry dam of the sheet forming apparatus to remove bubbles in the slurry. Has been proposed (see, for example, Patent Document 1). FIG. 2 is a schematic cross-sectional view of a conventional sheet forming apparatus. In the conventional sheet forming apparatus 20, a baffle plate 28 whose upper end protrudes from the slurry liquid level is installed in the slurry reservoir 27, and fine bubbles in the slurry are lifted and removed above the baffle plate.

JP 2003-112309 A

  However, in the method described in Patent Document 1, since the flow of slurry is blocked by the plate, a portion where the slurry is retained is generated in the reservoir, and the bubbles trapped by the baffle plate do not progress and the bubbles accumulate on the upper surface of the slurry reservoir. . In the slurry in which bubbles are accumulated in this way, solidification of the slurry components occurs, and the generated solid matter is precipitated. In addition, solid matter that has not settled is transported to the doctor blade part, caught on the blade to form uneven thickness of the green sheet, and further passes through the blade and becomes a protrusion of the green sheet, resulting in a new defect Will be generated.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a sheet forming apparatus and a sheet forming method capable of removing bubbles from a slurry and forming a uniform green sheet.

  (1) In order to achieve the above object, a sheet forming apparatus according to the present invention is a sheet forming apparatus using a doctor blade method, and a slurry dam for storing ceramic slurry, and the flow of the slurry in the slurry dam. A screen fixing unit that fixes the mesh screen in an upward inclination with respect to a direction, and a doctor blade that applies a slurry that has passed through the mesh screen onto a carrier film to form a green sheet.

  Thus, the sheet forming apparatus of the present invention forms a mesh screen inclined in the slurry dam and forms a green sheet with the slurry that has passed through the mesh screen. As a result, bubbles rise on the surface of the screen and break up on the slurry surface. As a result, bubbles can be removed from the slurry and a uniform green sheet can be formed.

  (2) Further, in the sheet forming apparatus of the present invention, the screen fixing unit fixes the mesh screen with an upward inclination of 45 ° or less. In this way, by installing a gently inclined mesh screen, bubbles rise on the surface of the screen and are easily broken on the slurry surface.

  (3) Moreover, the sheet forming method of the present invention is a sheet forming method using a doctor blade method, in which a mesh screen is fixed in a slurry dam with an upward inclination with respect to the flow direction of the slurry, and ceramics. And the step of allowing the mesh screen to permeate, and the step of applying the slurry permeated through the mesh screen on a carrier film to form a green sheet. Thereby, bubbles can be removed from the slurry and a uniform green sheet can be formed.

  (4) Moreover, the sheet forming method of the present invention is characterized in that the mesh screen to be fixed has an opening of 150 μm or less. Thereby, foam can be removed without retaining the slurry.

  (5) Further, in the sheet forming method of the present invention, the ceramic particle diameter in the introduced slurry is 1 μm or less, and the viscosity of the introduced slurry is 1000 mPa / s or more and 6000 mPa / s or less. It is characterized by. Even for such a slurry that tends to cause non-uniformity of the green sheet, bubbles can be removed and a uniform green sheet can be formed.

  According to the present invention, it is possible to remove bubbles from the slurry and form a uniform green sheet.

It is a model cross-sectional view of the sheet forming apparatus of the present invention. It is a model cross-sectional view of the conventional sheet forming apparatus.

  Next, embodiments of the present invention will be described with reference to the drawings.

(Configuration of sheet forming device)
FIG. 1 is a schematic cross-sectional view of the sheet forming apparatus 10. As shown in FIG. 1, the sheet forming apparatus 10 is an apparatus using a doctor blade method, and includes a slurry introducing unit 1, a slurry dam 2, a screen fixing unit 3, and a doctor blade 4. The slurry introduction unit 1 introduces a ceramic slurry 9. The slurry 9 to be introduced is prepared by adding a forming aid such as a solvent, a binder dispersant, and an antifoaming agent to the ceramic powder, followed by mixing and vacuum degassing.

  The ceramic particle diameter in the introduced slurry is 1 μm or less, and the viscosity of the introduced slurry 9 is effective if it is 1000 mPa / s or more and 6000 mPa / s or less. Even for the slurry 9 that easily causes non-uniformity of the green sheet 6, the bubbles can be removed and the uniform green sheet 6 can be formed.

  In addition, as a solvent, you may use an organic solvent or water. For example, even in the slurry 9 such as alcohol, it is possible to exclude bubbles mixed in after defoaming. However, the present invention is particularly effective for aqueous slurry. For the slurry 9 using an organic solvent as a solvent, it is required to take an exposure measure so as not to adversely affect the human body and take an explosion-proof measure to protect it from high flammability. In order to avoid these problems, water-based slurry using water as a solvent is sometimes used. However, when water is used as a solvent, the surface tension is higher than that of an organic solvent system, and many bubbles are generated in a process such as slurry mixing. bite. In the aqueous slurry, bubbles in the slurry 9 are not easily broken.

  The slurry dam 2 has a structure for storing the introduced slurry 9, and the stored slurry 9 is supplied to the doctor blade 4. By adjusting the introduction of the slurry 9 and the supply to the doctor blade 4, the liquid level of the slurry 9 can be kept constant.

  The screen fixing unit 3 fixes the mesh screen in an upward inclination with respect to the flow direction of the slurry 9 in the slurry dam 2. The reason for fixing by inclining is to prevent bubbles in the slurry 9 from drifting to the liquid surface. By tilting the mesh screen 7, the foam rises on the screen surface, and it is possible to promote foam breakage due to drying. Thereby, bubbles can be removed from the slurry 9 and a uniform green sheet 6 can be formed.

  As a specific structure of the screen fixing part 3, the following insertion slits can be considered. First, a mesh screen plate is prepared by cutting through the metal plate and pasting the mesh screen 7. In the slurry dam 2, an insertion slit for inserting the mesh screen plate into the slurry dam 2 in an oblique direction is provided as the screen fixing portion 3. In this way, the mesh screen plate can be easily fixed. The screen fixing part 3 preferably fixes the mesh screen with an upward inclination of 45 ° or less. In this way, by installing the gently inclined mesh screen 7, the bubbles rise on the screen surface and are easily broken on the surface of the slurry 9. The inclination angle may be changed according to the flow rate of the slurry 9.

  The mesh screen 7 to be fixed preferably has an opening of 150 μm or less. Thereby, foam can be removed without retaining the slurry 9. By providing a means for removing bubbles such as a mesh screen 7 in the slurry dam 2, it is possible to prevent the slurry 9 from being formed into a sheet while containing fine bubbles, and to prevent the occurrence of pinhole defects. .

  The doctor blade 4 applies the slurry 9 that has passed through the mesh screen 7 on the carrier film 5 while adjusting the thickness to a certain value. The applied slurry 9 is dried on the carrier film 5 to form a sheet. In this way, the green sheet 6 is formed.

(How to use the sheet forming equipment)
First, the mesh screen 7 is fixed in the slurry dam 2 with an upward inclination with respect to the flow direction of the slurry 9. The mesh screen 7 is installed in the slurry dam 2 so as to protrude from the slurry liquid surface and have an upward slope in the flow direction of the slurry 9. Thereby, the fine bubbles in the slurry 9 can be trapped by the mesh screen 7 without retaining the flow of the slurry 9. The trapped bubbles are pushed out above the inclined mesh screen 7 by the force floating above the bubbles and the flow of the slurry 9. Since the bubbles thus separated from the liquid surface are broken as needed by drying, the generation of solid matter in the slurry dam 2 can be suppressed.

  Next, a ceramic slurry 9 is introduced and permeated through the mesh screen 7. And the slurry 9 which permeate | transmitted the mesh screen 7 is apply | coated on the carrier film 5, and it is made to dry, and the green sheet 6 is formed.

(Example)
Sheet forming was actually performed using the sheet forming apparatus 10 having the above configuration. A 50 mesh (aperture 109 μm) was used as the mesh screen 7, and the inclination angle was fixed at 30 °. To the slurry 9, PZT powder having an average particle size of 0.7 μm (particle size distribution meter: LA920, manufactured by HORIBA, Ltd.) was mixed as ceramics. The slurry formulation (weight ratio) was powder 100, water 20, dispersant 2, defoamer 0.5, and binder 10. The film feed speed was 1 m / min.

  Table 1 is a table showing the defect rates of the comparative examples and the examples. The embodiment is a green sheet 6 formed using a sheet forming apparatus 10 equipped with an inclined mesh screen 7. The comparative example is a green sheet formed using a sheet forming apparatus equipped with a conventional baffle plate as a countermeasure against bubbles and a green sheet formed under the same conditions without taking countermeasures against bubbles. All the green sheets were formed with a thickness of 50 μm.

The pinhole defect rate, the sheet thickness unevenness defect rate, and the protrusion defect rate were verified for each of the green sheets of Examples, Comparative Examples with Bubble Countermeasures, and Comparative Examples without Bubble Countermeasures. The defect rate was obtained by cutting the green sheet into a predetermined size and then applying the cut sheet to an inspection device to identify the number of causes and the cause.

  As shown in Table 1, in the example, a ceramic green sheet free from pinhole defects and free from defects such as uneven thickness of the green sheet and mixing of protrusions could be formed. On the other hand, about the comparative example, although the difference occurred in the defective rate by the presence or absence of foam countermeasures, none of the results reached the examples. In particular, it was found that the sheet thickness nonuniformity defect rate and the protrusion defect rate are significantly effective as compared with the comparative example with a countermeasure against bubbles. As described above, it has been proved that by providing an inclined mesh screen in the slurry dam, pinholes can be prevented and uneven thickness of the green sheet and mixing of protrusions can be suppressed.

DESCRIPTION OF SYMBOLS 1 Slurry introduction part 2 Slurry dam 3 Screen fixing | fixed part 4 Doctor blade 5 Carrier film 6 Green sheet 7 Mesh screen 9 Slurry 10 Sheet forming apparatus

Claims (5)

A sheet forming apparatus using a doctor blade method,
A slurry dam for storing ceramic slurry;
In the slurry dam, a screen fixing part for fixing the mesh screen with an upward inclination with respect to the flow direction of the slurry,
A sheet forming apparatus comprising: a doctor blade that applies a slurry that has passed through the mesh screen onto a carrier film to form a green sheet.   The sheet forming apparatus according to claim 1, wherein the screen fixing unit fixes the mesh screen with an upward inclination of 45 ° or less. A sheet forming method using a doctor blade method,
In the slurry dam, a step of fixing the mesh screen with an upward inclination with respect to the flow direction of the slurry;
Introducing a ceramic slurry and allowing the mesh screen to pass through;
Applying the slurry that has passed through the mesh screen onto a carrier film to form a green sheet.   The sheet forming method according to claim 3, wherein the mesh screen to be fixed has an opening of 150 μm or less.   The ceramic particle diameter in the introduced slurry is 1 µm or less, and the viscosity of the introduced slurry is 1000 mPa / s or more and 6000 mPa / s or less. Sheet forming method.

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