JP2020179663A - Method for producing green sheet - Google Patents

Abstract

To provide a method for producing a green sheet capable of reducing the dry load of the green sheet and further suppressing surface defects of the green sheet.SOLUTION: A method for producing a green sheet 2 has a process where a coated face of gas permeable coated paper 3 obtained by coating one side of base paper 3a with a release agent 3b is turned up, the same is continuously run in a state where tension is applied to a space between two rolls 11, 12 separated in a running direction and support is performed, an upper face of the coated paper is continuously coated with a slurry 2x of the green sheet, and the slurry is heated and dried at a position in which a lower face of the coated paper is exposed in the space between the two rolls.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing a green sheet used for a heater element, a sensor element, a ceramic capacitor, a substrate for a ceramic package, and the like.

Conventionally, a method for producing a ceramic green sheet using a carrier sheet (film) has been known (see, for example, Patent Documents 1 and 2). This method is performed as follows. First, a slurry obtained by mixing and dispersing a raw material powder, a solvent and a binder material is continuously applied onto a traveling carrier sheet (Patent Document 1), or extruded onto the carrier sheet by an extrusion method. (Patent Document 2) Then, it is introduced into a drying furnace and heat-dried to produce a green sheet.

Japanese Unexamined Patent Publication No. 6-285826 Japanese Unexamined Patent Publication No. 9-76220

However, in the case of the carrier film described in Patent Document 1, since the carrier film has poor air permeability, the slurry dries from the upper surface in the drying furnace, but it is difficult to dry from the lower surface in contact with the carrier film, and the drying time becomes long. There is a problem.
Further, when the metal mesh described in Patent Document 2 is used for the carrier sheet, there is a problem that the green sheet after drying has mesh marks.

Therefore, an object of the present invention is to provide a method for producing a green sheet, which can reduce the drying load of the green sheet and suppress surface defects of the green sheet.

In order to solve the above problems, in the method for producing a green sheet according to the first aspect of the present invention, in the method for producing a green sheet, a coated surface of a breathable coated paper in which one side of a base paper is coated with a release agent is used. The green sheet slurry is continuously coated on the upper surface of the coated paper by applying tension between two rolls that are turned upward and separated in the traveling direction to support and continuously travel. The slurry is heat-dried at a position where the lower surface of the coated paper is exposed between the rolls.

According to this green sheet manufacturing method, the slurry is heated and dried at a position where the lower surface of the coated paper is exposed. Therefore, the slurry not only evaporates the solvent from the upper surface and dries, but also from the lower surface in contact with the coated paper. The solvent evaporates through the underside of the coated paper. In this way, since the slurry is also dried from the lower surface side, the drying load can be reduced and the drying time can be shortened.
Further, since the coated paper is smoother than the mesh, it is possible to suppress the occurrence of surface defects such as mesh marks on the green sheet after drying.

In the method for producing a green sheet according to the second aspect of the present invention, in the method for producing a green sheet, one side of the base paper is coated with a release agent so that the coated surface of the breathable coated paper faces upward and has breathability. It is brought into contact with the base and continuously run, the slurry of the green sheet is continuously coated on the upper surface of the coated paper, and the slurry is heated and dried at a position where the lower surface of the base is exposed. It is characterized by that.

According to this green sheet manufacturing method, the slurry is heated and dried at a position where the lower surface of the coated paper is exposed. Therefore, the slurry not only evaporates the solvent from the upper surface and dries, but also from the lower surface in contact with the coated paper. The solvent evaporates through the underside of the coated paper. In this way, since the slurry is also dried from the lower surface side, the drying load can be reduced and the drying time can be shortened.
Further, since the coated paper is smoother than the mesh, it is possible to suppress the occurrence of surface defects such as mesh marks on the green sheet after drying.
Further, since the coated paper is supported in contact with the base, it is not necessary to apply a high tension between the two rolls to support the coated paper. Therefore, for example, when the slurry is thickly coated, it is not necessary to apply high tension to the coated paper, so that the coated paper can be prevented from breaking.

In the method for producing a green sheet of the present invention, the method for molding the green sheet may be a doctor blade method.
According to this green sheet manufacturing method, it is easy to control the thickness of the green sheet to be constant.

In the method for producing a green sheet of the present invention, the base may be mesh, roller conveyor, floating, or felt.
According to this green sheet manufacturing method, a breathable base can be easily realized.

In the method for producing a green sheet of the present invention, a breathable second coated paper coated with a release agent on one side of the base paper is applied onto the coated surface of the slurry coated on the upper surface of the coated paper. The slurry is run in a state of being sandwiched between the coated paper and the second coated paper, and the lower surface of the coated paper is exposed and the upper surface of the second coated paper is exposed. The slurry may be heated and dried at a position where is exposed.
According to this green sheet manufacturing method, since the slurry is run while being sandwiched between the coated paper and the second coated paper, surface defects such as streaks and scratches occur on the slurry due to a transport roll or the like during running. Can be suppressed. In addition, by drying the slurry with both sides covered with coated paper, the drying speed of both sides becomes the same, and the warpage during drying is reduced compared to the case where only one side of the slurry is covered with coated paper. To do.

In the method for producing a green sheet according to claim 5, the viscosity of the slurry at the time of coating is preferably 50 Pa · s or more when measured with a B-type viscometer at 25 ° C. and a rotation speed of 3 rpm.
According to this method for producing a green sheet, the viscosity of the slurry is relatively high, and the thickness of the green sheet becomes more uniform by running the slurry while sandwiching both sides of the slurry with each coated paper.

According to the present invention, the drying load of the green sheet can be reduced, and the surface defects of the green sheet can be suppressed.

It is a figure which shows the structure of the manufacturing apparatus used in the manufacturing method of the green sheet which concerns on embodiment of 1st Embodiment of this invention. It is a schematic cross-sectional view which shows the structure of the coated paper. It is a figure which shows the structure of the manufacturing apparatus used in the manufacturing method of the green sheet which concerns on embodiment of the 2nd aspect of this invention. It is a figure which shows the structure of the manufacturing apparatus used in the manufacturing method of the green sheet which concerns on embodiment of the 3rd aspect of this invention. It is a figure which shows the variation of the thickness of the green sheet obtained when the viscosity of the slurry was changed in the 3rd aspect of this invention.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a diagram showing a schematic configuration of a manufacturing apparatus 1 used in the method for manufacturing a green sheet according to an embodiment of the first aspect of the present invention, and FIG. 2 is a schematic cross-sectional view showing the configuration of coated paper 3.

In FIG. 1, the green sheet manufacturing apparatus 1 is a double roll in which a roll-shaped and strip-shaped coated paper 3 is unwound from an unwinding roll (not shown), and then supported and run while applying tension. 11 and a take-up roll 12, a substantially box-shaped liquid reservoir 5 placed on coated paper 3 to store slurry (slurry) 2x, and a doctor blade (not shown) attached to the right side plate of the liquid reservoir 5. And a drying furnace 4.
An elongated opening in the longitudinal direction is provided at the bottom of the right side of the liquid reservoir 5, and the slurry 2x is continuously applied to the upper surface of the coating paper 3 located below the liquid reservoir 5. On the other hand, the width of the coated paper 3 is wider than the opening of the liquid reservoir 5, so that the slurry 2x is not coated on both ends of the coated paper 3. The slurry 2x is a mixture and dispersion of a raw material powder, a solvent and a binder material, and the raw material powder is, for example, alumina powder.
The doctor blade adjusts the thickness of the slurry 2x while scraping off the excess slurry 2x on the coated paper 3. The slurry 2x whose thickness has been adjusted by the doctor blade is introduced into the drying oven 4 together with the coated paper 3, and after the slurry 2x is heated and dried, it becomes a green sheet 2 and is taken out from the drying oven 4.

As shown in FIG. 2, the coated paper 3 has a silicone release agent (layer) 3b coated on one side of the base paper 3a to have breathability, and the release agent 3b side is the coated surface. The base paper 3a can be formed by, for example, papermaking pulp. The release agent is not limited to silicone, and may be a fluorine-based release agent such as PTFE.
Further, a sealing agent may be provided in advance on the surface of the base paper 3a so that the release agent 3b does not soak into the base paper 3a too much.
Then, by coating the slurry 2x with the coated surface of the coated paper 3 as the upper surface, the coated paper 3 can be easily peeled off from the green sheet 2.

Here, as shown in FIG. 1, the twin roll 11 sandwiches the coated paper 3 from above and below, and the winding roll 12 coats the slurry 2x and winds the dried coated paper 3 together with the green sheet 2. .. Therefore, the coated paper 3 is supported by applying tension between the twin rolls 11 and the take-up rolls 12, which are separated from each other in the traveling direction (left-right direction in FIG. 1), and is continuously traveled.
The twin roll 11 and the take-up roll 12 correspond to "two rolls" in the claims.

Then, the drying furnace 4 is placed directly above the position where the lower surface 3r of the coated paper 3 is exposed between the twin roll 11 and the winding roll 12, and the slurry 2x is heated and dried at this position.
As a result, as shown by the arrow in FIG. 1, the slurry 2x not only dries by evaporating the solvent from the upper surface in the drying furnace 4, but also passes through the lower surface 3r of the coated paper 3 from the lower surface in contact with the coated paper 3. The solvent evaporates. In this way, since the slurry 2x is also dried from the lower surface side, the drying load can be reduced and the drying time can be shortened. The slurry is not limited to an aqueous system and may be an organic solvent.
Further, since the coated paper 3 is smoother than the mesh, it is possible to suppress the occurrence of surface defects such as mesh marks on the green sheet after drying.

Examples of the coated paper 3 include those having a thickness of 100 to 300 μm, and examples of the slurry 2x include those having a thickness of 70 to 800 μm.
Further, the dried green sheet 2 may be separated before being wound on the winding roll 12, and only the coated paper 3 may be wound and reused.

Next, with reference to FIG. 3, a method for producing a green sheet according to an embodiment of the second aspect of the present invention will be described. FIG. 3 shows a manufacturing apparatus 1B used in the method for manufacturing a green sheet according to the second embodiment of the present invention. In the green sheet manufacturing apparatus 1B, the same components as those in the embodiment of the first aspect are designated by the same reference numerals as those in FIG. 1, and detailed description thereof will be omitted.

As shown in FIG. 3, in the manufacturing apparatus 1B, a base (roller conveyor) 20 having air permeability is arranged between the twin rolls 11 and the take-up roll 12, and the coated paper 3 is a roller conveyor 20. It touches the top and runs continuously.
The roller conveyor 20 is a device in which a plurality of rotating rollers are vertically spaced apart from each other in a predetermined frame and fixed in parallel, and a conveyed object is placed on the roller conveyor 20 and moved.

In the manufacturing apparatus 1B, the drying furnace 4 is placed directly above the position where the lower surface of the roller conveyor 20 is exposed, and the slurry 2x is heated and dried at this position. In the roller conveyor 20, each rotating roll is axially separated, and this gap has air permeability.
As a result, as shown by the arrow in FIG. 3, not only the solvent evaporates from the upper surface of the slurry 2x in the drying furnace 4 to dry it, but also the lower surface 3r of the coated paper 3 comes into contact with the coated paper 3. And the solvent evaporates through the gaps of the roller conveyor 20. Therefore, as in the embodiment of the first aspect of the present invention, the slurry 2x is also dried from the lower surface side, so that the drying load can be reduced and the drying time can be shortened.
Further, in the second aspect, since the coated paper 3 is contacted and supported on the roller conveyor 20, a high tension is applied between the double roll 11 and the take-up roll 12 as in the first aspect. It is not necessary to hang it and support it. Therefore, for example, when the slurry 2x is thickly coated, it is not necessary to apply high tension to the coated paper 3, so that the coated paper 3 can be prevented from breaking.

As the base having air permeability, a mesh or felt can be used in addition to the above roller conveyor. In the case of felt, it is preferable to support the lower side of the felt with a frame or the like in order to maintain the shape. In addition, a floating mechanism may be adopted, or a transport device in which these may be mixed may be adopted.

Next, with reference to FIG. 4, a method for manufacturing a green sheet using the second coated paper 3x will be described.
FIG. 4 is a diagram showing a schematic configuration of a manufacturing apparatus 1C used in the method for manufacturing a green sheet according to an embodiment of a third aspect of the present invention.

In FIG. 4, the green sheet manufacturing apparatus 1C winds the roll-shaped and strip-shaped coated paper 3 from the unwinding roll R1 and then supports and runs the double roll 15 and the winding while applying tension. A strip-shaped second coated paper 3x unwound from the unwinding roll R2, a substantially box-shaped liquid reservoir 7 for storing the slurry (slurry) 2x, and a drying furnace 4 are provided. There is. The drying furnace 4 and the take-up roll 12 are the same as those of the green sheet manufacturing apparatus 1. The second coated paper 3x has the same structure as that of the coated paper 3, and one side of the base paper is coated with a release agent to have breathability (FIG. 2).
A discharge nozzle 7s is provided in the liquid reservoir 7, and the slurry 2x of the liquid reservoir 7 is continuously coated on the upper surface of the coated paper 3 which is unwound from the unwinding roll R1 and travels slightly upward. It is designed to do.

Here, the unwinding roll R2 is arranged above the unwinding roll R1 so as to substantially face the unwinding roll R1, and the second coated paper 3x unwound from the unwinding roll R2 is slightly downward. It travels toward and is introduced into the twin roll 15 and combined with the coated paper 3.
At this time, the second coated paper 3x is covered on the upper surface of the coated paper 3 with the coated surface facing down, and the slurry 2x is covered with the coated paper 3 and the second by the double roll 15. The roll 12 winds the dried coated paper 3 together with the green sheet 2 while running in a state of being sandwiched between the coated paper 3x of 2. Therefore, the coated paper 3 is supported by applying tension between the twin rolls 15 and the take-up rolls 12, which are separated from each other in the traveling direction (left-right direction in FIG. 4), and is continuously traveled.
The twin roll 15 and the take-up roll 12 correspond to "two rolls" in the claims.

Then, the slurry 2x is introduced into the drying furnace 4 in a state of being sandwiched between the coated paper 3 and the second coated paper 3x, and after the slurry 2x is heated and dried, it becomes a green sheet 2 and becomes a drying furnace 4 Taken from.
Here, in the drying furnace 4, the lower surface 3r of the coated paper 3 is exposed, and the slurry 2x is dried at a position where the upper surface 3rx of the second coated paper 3x is exposed.
Further, after drying, before winding the green sheet 2 on the take-up roll 12, the second coated paper 3x is taken up by the take-up roll R3, so that the take-up roll 12 is the coated paper 3 and the green sheet 2. Take up only.

According to the method for producing a green sheet according to the third aspect, the slurry 2x is run in a state of being sandwiched between the coated paper 3 and the second coated paper 3x, so that the slurry 2x is streaked by a transport roll or the like during running. It is possible to suppress the occurrence of surface defects such as scratches.
Further, by drying with both sides of the slurry 2x covered with the coated papers 3 and 3x, the drying speeds of both sides of the slurry 2x become the same, as compared with the case where only one side of the slurry 2x is covered with the coated paper. , Warpage during drying is reduced.

In the method for producing a green sheet according to the third aspect, when measured with a B-type viscometer at 25 ° C. and a rotation speed of 3 rpm, the viscosity of the slurry 2x at the time of coating is preferably 50 Pa · s or more, and the viscosity is 100 Pa · s. It is more preferably s or more.
In this way, the viscosity of the slurry 2x is relatively high, and the thickness of the green sheet 2 becomes more uniform by running while sandwiching both sides of the slurry 2x between the coated papers 3 and 3x.
In FIG. 5, the viscosities of the slurry 2x (including alumina powder, solvent and binder material) are set to 15 Pa · s and 170 Pa · s, respectively, and the silicone is peeled off on one side of the base paper as the coated paper 3 and the second coated paper 3x, respectively. The variation in the thickness of the green sheet 2 produced by the method for producing a green sheet according to the third aspect using the silicone paper coated with the agent is shown.
As is clear from FIG. 5, when the slurry 2x at the time of coating the slurry 2x is taken out and the viscosity measured at 25 ° C. by a B-type viscometer is 50 Pa · s or more, the variation in the thickness of the green sheet 2 is reduced. , Found to be more uniform. As the B-type viscosity, any viscometer can be used as long as it is a B-type viscometer, but in this embodiment, the B-type viscometer TV-10 manufactured by Toki Sangyo Co., Ltd., Rotor No. It was measured using 4.

It goes without saying that the present invention is not limited to the above embodiments and extends to various modifications and equivalents included in the ideas and scope of the present invention. In the method for producing a green sheet according to the third aspect, separate heating furnaces may be provided on the upper and lower sides of the coated paper 3 side and the second coated paper 3x side for heating and drying.

2 Green sheet 2x Green sheet slurry 3 Coating paper 3a Base paper 3b Release agent 3r Bottom surface of coating paper 3x Second coating paper 3rx Bottom surface of second coating paper 4 Drying furnaces 11, 12, 15 Two Roll 20 base

Claims (6)

In the method of manufacturing green sheets
The coated surface of the breathable coated paper coated with a release agent on one side of the base paper is turned upward, and tension is applied between two rolls separated in the traveling direction to support and continuously travel.
The upper surface of the coated paper is continuously coated with the slurry of the green sheet, and the slurry is heated and dried at a position where the lower surface of the coated paper is exposed between the two rolls. How to make a green sheet. In the method of manufacturing green sheets
Breathable coated paper coated with a release agent on one side of the base paper The coated side of the paper is turned upward and brought into contact with the breathable base to run continuously.
A method for producing a green sheet, which comprises continuously coating the upper surface of the coated paper with the slurry of the green sheet, and heating and drying the slurry at a position where the lower surface of the base is exposed. The method for producing a green sheet according to claim 1 or 2, wherein the method for forming the green sheet is a doctor blade method. The method for manufacturing a green sheet according to claim 2, wherein the base is a mesh, a roller conveyor, a floating, or felt. On top of the slurry coated on the upper surface of the coated paper, a breathable second coated paper coated with a release agent on one side of the base paper is covered with the coated surface facing down, and the slurry is covered. The slurry is run while being sandwiched between the coated paper and the second coated paper, and the slurry is heated and dried at a position where the lower surface of the coated paper is exposed and the upper surface of the second coated paper is exposed. The method for producing a green sheet according to any one of claims 1 to 4, wherein the green sheet is produced. The method for producing a green sheet according to claim 5, wherein the viscosity of the slurry at the time of coating is 50 Pa · s or more when measured with a B-type viscometer at 25 ° C. and a rotation speed of 3 rpm.

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