JP7281366B2 - Green sheet manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing green sheets used for heater elements, sensor elements, ceramic capacitors, substrates for ceramic packages, and the like.

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

JP-A-6-285826 JP-A-9-76220

However, in the case of the carrier film described in Patent Document 1, since the carrier film has poor air permeability, although the slurry is dried from the upper surface in the drying oven, it is difficult to dry from the lower surface in contact with the carrier film, resulting in a long drying time. There is a problem.
Moreover, when the metal mesh described in Patent Document 2 is used for the carrier sheet, there is a problem that mesh traces are left on the dried green sheet.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a green sheet manufacturing method capable of reducing the drying load of the green sheet and suppressing surface defects of the green sheet.

In order to solve the above-mentioned problems, a method for producing a green sheet according to a first aspect of the present invention is a method for producing a green sheet, in which a breathable coated paper in which one side of a base paper is coated with a release agent is coated. The slurry of the green sheet is continuously applied to the upper surface of the coated paper, and the slurry of the green sheet is continuously coated on the upper surface of the coated paper, and the 2 The slurry is dried by heating at a position where the lower surface of the coated paper is exposed between two rolls.

According to this green sheet manufacturing method, the slurry is heated and dried at the position where the lower surface of the coated paper is exposed. Solvent evaporates through the underside of the coated paper. In this way, the slurry is dried also from the lower surface side, so that the drying load can be reduced and the drying time can be shortened.
Moreover, since the coated paper is smoother than the mesh, it is possible to suppress surface defects such as mesh marks on the dried green sheet.

A method for producing a green sheet according to a second aspect of the present invention is a method for producing a green sheet, wherein a breathable coated paper having one side of a base paper coated with a release agent is turned upward to have air permeability. The slurry of the green sheet is continuously applied to the upper surface of the coated paper by contacting it with a base and running continuously, and the slurry is heated and dried at a position where the lower surface of the base is exposed. It is characterized by

According to this green sheet manufacturing method, the slurry is heated and dried at the position where the lower surface of the coated paper is exposed. Solvent evaporates through the underside of the coated paper. In this way, the slurry is dried also from the lower surface side, so that the drying load can be reduced and the drying time can be shortened.
Moreover, since the coated paper is smoother than the mesh, it is possible to suppress surface defects such as mesh marks on the dried green sheet.
Furthermore, since the coated paper is supported in contact with the base, it does not need to be supported with high tension between the two rolls. For this reason, for example, when the slurry is applied thickly, it is not necessary to apply a high tension to the coated paper, so breakage of the coated paper can be suppressed.

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

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

In the green sheet manufacturing method of the present invention, a breathable second coated paper in which one side of a base paper is coated with a release agent is coated on the slurry coated on the upper surface of the coated paper. facing downward, running the slurry sandwiched between the coated paper and the second coated paper, further exposing the lower surface of the coated paper, and the upper surface of the second coated paper The slurry may be dried by heating at the 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 streaky scratches occur in the slurry due to transport rolls or the like during running. can be suppressed. In addition, by drying the slurry while both sides are covered with each coated paper, the drying speed on both sides becomes the same, and warping during drying is reduced compared to when only one side of the slurry is covered with coated paper. do.

In the method of manufacturing a green sheet according to claim 5, it is preferable that the slurry has a viscosity of 50 Pa·s or more during application when measured with a Brookfield viscometer at 25° C. and a rotation speed of 3 rpm.
According to this green sheet manufacturing method, the viscosity of the slurry is relatively high, and the thickness of the green sheet becomes more uniform by running the slurry while holding both sides of the slurry between coated papers.

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

1 is a diagram showing the configuration of a manufacturing apparatus used in a green sheet manufacturing method according to an embodiment of the first aspect of the present invention; FIG. 1 is a schematic cross-sectional view showing the configuration of coated paper; FIG. FIG. 6 is a diagram showing the configuration of a manufacturing apparatus used in the green sheet manufacturing method according to the embodiment of the second aspect of the present invention; FIG. 10 is a diagram showing the configuration of a manufacturing apparatus used in a green sheet manufacturing method according to an embodiment of the third aspect of the present invention; FIG. 8 is a diagram showing variations in the thickness of green sheets obtained when the viscosity of the slurry is changed in the third embodiment of the present invention.

Embodiments of the present invention will be described below.
FIG. 1 is a diagram showing a schematic configuration of a manufacturing apparatus 1 used in a green sheet manufacturing method 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 a coated paper 3.

In FIG. 1, a green sheet manufacturing apparatus 1 includes twin rolls for unwinding a strip-shaped coated paper 3 from an unwinding roll (not shown) and then supporting and running the paper while applying tension. 11 and a take-up roll 12, a substantially box-shaped liquid reservoir 5 placed on the coated paper 3 to store the slurry (sludge liquid) 2x, and a doctor blade (not shown) attached to the right side plate of the liquid reservoir 5. and a drying furnace 4.
A longitudinally elongated opening is provided in the right bottom portion of the liquid reservoir 5 so that the upper surface of the coated paper 3 positioned below the liquid reservoir 5 is continuously coated with the slurry 2x. On the other hand, the width of the coated paper 3 is wider than the opening of the liquid reservoir 5 so that both ends of the coated paper 3 are not coated with the slurry 2x. The slurry 2x is obtained by mixing and dispersing a raw material powder, a solvent and a binder material, and the raw material powder is alumina powder, for example.
The doctor blade adjusts the thickness of the slurry 2x while scraping off excess slurry 2x on the coated paper 3. - 特許庁The slurry 2x whose thickness is adjusted by the doctor blade is introduced into the drying furnace 4 together with the coated paper 3, and after the slurry 2x is heated and dried, it is taken out from the drying furnace 4 as the green sheet 2.

As shown in FIG. 2, the coated paper 3 is air permeable by coating one side of a base paper 3a with a silicone release agent (layer) 3b, and the release agent 3b side is the coated surface. The base paper 3a can be formed, for example, by making pulp. The release agent is not limited to silicone, and may be fluorine-based release agent such as PTFE.
In addition, a filler 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.
By applying the slurry 2 x with the coated surface of the coated paper 3 facing upward, the coated paper 3 can be easily peeled off from the green sheet 2 .

Here, as shown in FIG. 1, the twin rolls 11 sandwich the coated paper 3 from above and below, and the take-up roll 12 winds the coated paper 3 together with the green sheet 2 after the slurry 2x has been coated and dried. . Therefore, the coated paper 3 is supported under tension between the twin roll 11 and the take-up roll 12, which are spaced apart in the running direction (horizontal direction in FIG. 1), and is continuously run.
The twin roll 11 and the take-up roll 12 correspond to "two rolls" in the claims.

A drying furnace 4 is placed directly above the position where the lower surface 3r of the coated paper 3 is exposed between the twin rolls 11 and the winding roll 12, and heats and dries the slurry 2x at this position.
As a result, as shown by the arrow in FIG. 1, the slurry 2x is not only dried by evaporating the solvent from the upper surface of the slurry 2x in the drying furnace 4, but also from the lower surface in contact with the coated paper 3 through the lower surface 3r of the coated paper 3. The solvent evaporates. In this way, the slurry 2x is also dried from the lower surface side, so 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.
Moreover, since the coated paper 3 is smoother than the mesh, it is possible to suppress surface defects such as mesh marks on the dried green sheet.

The coated paper 3 has a thickness of 100 to 300 μm, and the slurry 2x has a thickness of 70 to 800 μm.
Alternatively, the dried green sheet 2 may be separated before being wound onto the winding roll 12, and only the coated paper 3 may be wound and reused.

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

As shown in FIG. 3, in the manufacturing apparatus 1B, a permeable base (roller conveyor) 20 is arranged between the twin roll 11 and the take-up roll 12. It touches the top and is made to run continuously.
The roller conveyor 20 is a device in which a plurality of rotating rollers are arranged and fixed in parallel in a predetermined frame while being spaced apart in the axial direction, and an object to be conveyed is placed thereon 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 spaced apart in the axial direction, and this gap has air permeability.
As a result, as shown by the arrows in FIG. 3, the slurry 2x is not only dried by evaporating the solvent from the upper surface of the slurry 2x in the drying furnace 4, but also from the lower surface of the coated paper 3, which is in 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 the drying load can be reduced and the drying time can be shortened.
In addition, in the second mode, the coated paper 3 is supported in contact with the roller conveyor 20, so that the tension between the twin rolls 11 and the take-up roll 12 is high as in the first mode. It is not necessary to hang and support. Therefore, for example, when the slurry 2x is applied thickly, it is not necessary to apply a high tension to the coated paper 3, so breakage of the coated paper 3 can be suppressed.

As the air-permeable base, mesh or felt can be used in addition to the 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 retain its shape. In addition, a floating mechanism may be employed, or a transport device combining these may be used.

Next, referring to FIG. 4, a method of 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 a green sheet manufacturing method according to an embodiment of the third aspect of the present invention.

In FIG. 4, the green sheet manufacturing apparatus 1C includes a twin roll 15 and a winding roll 15 for supporting and running while applying tension after unwinding a roll-shaped strip-shaped coated paper 3 from an unwinding roll R1. Equipped with a take-up roll 12, a strip-shaped second coated paper 3x unwound from an unwinding roll R2, a substantially box-shaped reservoir 7 for storing slurry (sludge liquid) 2x, and a drying oven 4. there is The drying oven 4 and the winding roll 12 are the same as those of the green sheet manufacturing apparatus 1 . The second coated paper 3x has a structure similar to that of the coated paper 3, with one side of the base paper being coated with a release agent and having air permeability (FIG. 2).
A discharge nozzle 7s is provided in the liquid reservoir 7, and the slurry 2x in the liquid reservoir 7 is continuously applied by a pump to the upper surface of the coated paper 3 which is unwound from the unwinding roll R1 and travels slightly upward. It is designed to

Here, the unwinding roll R2 is disposed 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 positioned slightly below. Then, it is introduced into the double roll 15 and combined with the coated paper 3. - 特許庁
At this time, the second coated paper 3x is placed on the slurry 2x coated on the upper surface of the coated paper 3 with the coated surface facing downward, and the slurry 2x is applied to the coated paper 3 and the second coated paper 3x by the twin rolls 15. 2, and the winding roll 12 winds up the dried coated paper 3 together with the green sheet 2. - 特許庁Therefore, the coated paper 3 is supported under tension between the twin roll 15 and the take-up roll 12, which are spaced apart in the running direction (horizontal direction in FIG. 4), and is continuously run.
The twin roll 15 and the take-up roll 12 correspond to "two rolls" in the claims.

Then, the slurry 2x is sandwiched between the coated paper 3 and the second coated paper 3x and introduced into the drying furnace 4. After the slurry 2x is dried by heating, it becomes the green sheet 2 and becomes the drying furnace 4. taken out from
Here, in the drying furnace 4, the slurry 2x is dried at the position where the lower surface 3r of the coated paper 3 is exposed and the upper surface 3rx of the second coated paper 3x is exposed.
After drying, the second coated paper 3x is wound by the winding roll R3 before the green sheet 2 is wound by the winding roll 12. Rewind only.

According to the green sheet manufacturing method of the third aspect, the slurry 2x is run while being sandwiched between the coated paper 3 and the second coated paper 3x. It is possible to suppress the occurrence of surface defects such as scratches.
In addition, by drying the slurry 2x with both sides covered with the coated papers 3 and 3x, the drying speed of both sides of the slurry 2x becomes equal, compared to the case where only one side of the slurry 2x is covered with the coated paper. , to reduce warpage during drying.

In the green sheet manufacturing method of the third aspect, when measured with a Brookfield viscometer at 25 ° C. and a rotation speed of 3 rpm, the viscosity at the time of coating of the slurry 2x is preferably 50 Pa s or more, and the viscosity is 100 Pa s. s or more is more preferable.
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 the slurry 2x 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 silicone peeling is performed on one side of the base paper as the coated paper 3 and the second coated paper 3x. FIG. 4 shows variations in the thickness of a green sheet 2 produced by the method of producing a green sheet according to the third embodiment using the apparatus of FIG. 4 using silicone paper coated with an agent.
As is clear from FIG. 5, when the slurry 2x is taken out during coating of the slurry 2x and the viscosity measured at 25° C. with a Brookfield viscometer is 50 Pa·s or more, the variation in the thickness of the green sheet 2 is reduced. , was found to be more uniform. For the B-type viscosity, any viscometer may be used as long as it is a B-type viscometer. 4 was used.

It goes without saying that the present invention is not limited to the above-described embodiments, but extends to various modifications and equivalents within the spirit and scope of the present invention. In the method of manufacturing the green sheet of the third aspect, separate heating furnaces may be provided above and below the coated paper 3 side and the second coated paper 3x side for heating and drying.

2 green sheet 2x green sheet slurry 3 coated paper 3a base paper 3b release agent 3r underside of coated paper 3x second coated paper 3rx underside of second coated paper 4 drying oven 11, 12, 15 two roll 20 base

Claims (6)

In the green sheet manufacturing method,
The air-permeable coated paper coated with a release agent on one side of the base paper has its coated surface facing upward, and is supported by applying tension between two rolls spaced apart in the running direction to run continuously,
The slurry of the green sheet is continuously applied to the upper surface of the coated paper, and the slurry is dried by heating at a position between the two rolls where the lower surface of the coated paper is exposed. Green sheet manufacturing method. In the green sheet manufacturing method,
The air permeable coated paper coated with a release agent on one side of the base paper faces upward, is brought into contact with the air permeable base, and is continuously run,
A method for producing a green sheet, characterized by continuously coating the upper surface of the coated paper with the slurry of the green sheet, and heating and drying the slurry at the position where the lower surface of the base is exposed. 3. The method of manufacturing a green sheet according to claim 1, wherein the method of forming the green sheet is a doctor blade method. 3. The method of manufacturing a green sheet according to claim 2, wherein the base is mesh, roller conveyor, floating, or felt. On top of the slurry coated on the upper surface of the coated paper, a second breathable coated paper in which one side of the base paper is coated with a release agent is covered with the coated surface facing downward, and the slurry is applied as described above. The slurry is traveled while 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, characterized in that: 6. The method for producing a green sheet according to claim 5, wherein the slurry has a viscosity of 50 Pa.s or more when coated with a Brookfield viscometer at 25[deg.] C. and a rotation speed of 3 rpm.

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