JP2507532B2 - Manufacturing method of ceramic green sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a ceramic green sheet, and more particularly to a method for manufacturing a wide ceramic green sheet with high yield.

[Conventional technology]

The ceramic green sheet is manufactured by the doctor blade method. The doctor blade method is a dam having a doctor blade placed on a carrier film, which is a slurry prepared by adding a solvent to an inorganic powder such as a ceramic main material and a sintering aid, an organic binder, and an organic material such as a plasticizer. The carrier film is moved in a certain direction, the slurry is passed through the gap between the doctor blade and the carrier film to apply a certain thickness on the carrier film, and the solvent is evaporated by drying to solidify the green sheet. Is the way to do it.

Here, as the drying method, it takes 10 to 15 hours for natural drying as described in "New manufacturing method of fine ceramics and process automation technology" issued by Realize Co., Ltd. on November 1, 1985. Therefore, in terms of productivity and quality, forced drying is performed. The forced drying is a method in which hot air is applied to the slurry film coated on the carrier film to gradually dry it, and a drying furnace is used.

In the drying of the green sheet, prevention of film cracking is an important issue from the aspects of productivity and quality.
Regarding the film cracking, as described in the above-mentioned document,
For example, in the case of a drying furnace having a furnace length of 20 m, the drying ends 7 to 8 m from the entrance, so the temperature and wind speed conditions up to this point are important and it is necessary to avoid sudden drying. It is important to raise the temperature gently from the inlet at room temperature and adjust the outlet and inlet of hot air to make the wind speed uniform in the width direction.

[Problems to be Solved by the Invention]

However, when obtaining a wide and large-area green sheet, it is difficult to make the temperature and wind speed uniform in the width direction, uneven drying is likely to occur, and the occurrence rate of film cracks increases. Furthermore, even if the temperature and wind speed can be set uniformly in the width direction, the concentration of the solvent generated by evaporation is higher in the central part than in the parts near both ends in the width direction, so the solvent evaporates. As a result, the green sheet contracts earlier at the edges than at the center. As a result, there is a problem that a crack is generated from the central portion which is finally dried.

An object of the present invention is to provide a method for manufacturing a wide green sheet without causing cracks during drying.

[Means for solving the problem]

In the method for manufacturing a ceramic green sheet by the doctor blade method, in the drying step of drying the ceramic green sheet by evaporating the solvent from the slurry coated on the carrier film, the width direction of the ceramic green sheet from both ends. Is achieved by a method of manufacturing a ceramic green sheet in which the central portion is dried first. Further, the drying may be performed by increasing the wind speed in the central portion from both ends in the width direction of the ceramic green sheet, and by drying the temperature in the central portion from both ends in the width direction of the ceramic green sheet. You may do it.

[Action]

The shrinkage of the green sheet due to drying occurs when the organic binder dissolved in the solvent shrinks due to the evaporation of the solvent and attracts the inorganic particles such as the ceramic main material and the sintering aid. Therefore, for example, when the drying progresses from the end in the width direction of the green sheet, the undried region is left in the central portion at the end. The binding force of the organic binder is weaker in the undried portion swollen with the solvent than in the dried portion, so that in the central portion, the stress generated by the contraction from both sides causes cracking. For this reason, in the present invention, since the drying shrinkage is performed from the central portion toward both ends by the above configuration, the undried portion having a weak bonding force becomes the end portion, and the stress generated by the shrinkage can be released to the end portion. The occurrence of cracks can be prevented.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.

<Example 1> Fig. 1 shows Example 1 of an apparatus for carrying out the method for producing a ceramic green sheet of the present invention.

Here, the components of the slurry used in the production of the green sheet of this example and the production method will be described. Alumina (90 parts by weight) was used as the main component, and talc (6 parts by weight) and clay (4 parts by weight) were added as sintering aids. Organic matter is
PVB (5 parts by weight) as a binder and DBP as a plasticizer
(2 parts by weight) was used. A mixed solution (40 parts by weight) of trichloroethylene, tetrachloroethylene, and n-butanol was added to these raw materials as an organic solvent and mixed for 24 hours, and then a slurry having a viscosity of 15,000 cps was prepared by vacuum defoaming.

The apparatus used in this example supplies the slurry 2 to a dam 4 having a doctor blade 3 placed on a carrier film 5 as shown in FIG. 1, and conveys the carrier film 5 together with the conveyor belt 6 as shown in FIG. Move it in the direction of the arrow,
Slurry 2 with doctor blade 3 and carrier film 5
In a so-called doctor blade method, in which the green sheet 1 is manufactured by coating the carrier film 5 with a certain thickness by passing through the gap and evaporating the solvent in the drying furnace 8.
Hot air outlet 7a 3m from the entrance inside the drying furnace with a total length of 20m
~ 7e is installed.

As for casting conditions, the width of the dam 4 is 1 m, and the gap between the doctor blade 3 and the carrier film 5 is 0.5 m.
m, the conveyor belt 6 and the carrier film 5 are conveyed at a speed of 0.3 m / min.
It was set to 120 ° C.

First, when the hot air outlets 7a to 7e are closed and the method of the present invention is not used, cracks occur around 2m behind the hot air outlets 7a to 7b (5m from the inlet), and the sheet yield is 30%. there were.

In addition, all the hot air outlets blow air at room temperature of 23 ℃,
When the wind speed in the width direction is set to be uniform at 0.3 m / sec (measured 0.2 m in front of the hot air outlet), the crack generation position moves 0.5 m forward (near 4.5 m from the inlet). The cracks were slightly reduced, but the yield was 45%.

Then, the drying method which is the feature of the present invention, that is, the method in which the drying proceeds from the central portion to the both ends in the width direction, was performed. The air volume from the hot air outlet is increased by 7c to 7a, and
7c to reduce the wind speed at the center to a maximum of 0.35 m / sec and the end at a minimum of 0.25 m / sec, and set to form a gentle wind velocity curve between them (in front of the hot air outlet) (Measurement at the position of 0.2 m) No cracks occurred, yield 10
A green sheet was obtained at 0%.

<Embodiment 2> FIG. 2 shows Embodiment 2 of an apparatus for carrying out the method for manufacturing a ceramic green sheet of the present invention.

Other than the inside of the drying furnace 8 in FIG. 2, the other components are the same as in FIG. In this embodiment, the total length of the four zones is 20.
A wind speed control plate 9 was installed at the boundary of the zone of the drying furnace 8 of m. Normally, hot air is sucked and exhausted independently in each zone of the drying furnace, so a pressure difference occurs between each zone and a large wind flow occurs on the green sheet at the boundary, which may cause cracking. Often becomes. Therefore, in this embodiment, a wind speed control plate 9 is installed at the boundary portion (4 m from the entrance) between the first zone and the second zone where cracks frequently occur, so that the gap between the green sheet and the green sheet is larger in the central portion than in both end portions. The wind velocity generated here was set to be maximum in the central portion (central portion 0.4 m / sec, end portion 0.35 m / sec), and under the same casting conditions as in Example 1 (the warm air outlet in FIG. 1). 7a to 7e are removed), cracks are reduced and the yield is 30%
From 90% to 90%.

<Embodiment 3> FIG. 3 shows Embodiment 3 of an apparatus for carrying out the method for manufacturing a ceramic green sheet according to the present invention.

In Example 1 and Example 2, an example using a method in which the drying speed at the central portion in the drying furnace 8 is maximized at the central portion in the width direction so that the drying speed at the central portion is faster than at both ends, is shown. In Example 3, the drying speed is controlled by providing a temperature distribution in the width direction of the sheet.

Other than the inside of the drying furnace 8 in FIG. 3, the other components are the same as those in FIGS. 1 and 2. In the drying oven 8, a heating plate 10 having a heater 11 therein was fixed to the lower part of a conveyor belt 6 that conveys green sheets. The fixed position is 1m in total length from 2.5m behind the artificial to 3.5m.

By energizing the heater 11 and controlling the heating amount, the surface temperature of the carrier film 5 in the state without the green sheet 1 becomes the maximum value of 35 ° C at the central part and the minimum value of 28 ° C at the end parts, and the temperature is moderate during I set it to be a curve. The temperature above the carrier film is 25 ° C, which is close to room temperature (23 ° C).

Here, when the green sheets were manufactured under the casting conditions of Example 1 and Example 2, the occurrence of cracks was reduced compared to the case where the heater was not heated, and the yield was 30%.
It improved to 95%.

〔The invention's effect〕

According to the present invention, the stress generated by drying and shrinking from the center of the width is released to both ends of the width, so that even a wide green sheet can suppress cracking due to drying and produce a high-yield green sheet. You can

[Brief description of drawings]

FIGS. 1, 2 and 3 are perspective views showing different embodiments of the present invention. 1 ... Green sheet, 2 ... Slurry 3 ... Doctor blade, 7 ... Temperature outlet 8 ... Drying furnace, 9 ... Wind speed control plate 10 ... Heating plate

Claims (3)

(57) [Claims] 1. A method of manufacturing a ceramic green sheet by a doctor blade method, which comprises a drying step of evaporating a solvent from a slurry coated on a carrier film to dry the ceramic green sheet. A method for manufacturing a ceramic green sheet, which comprises first drying the central portion of the ceramic green sheet. 2. The method according to claim 1, wherein the drying is performed by increasing the wind speed in the central portion of the ceramic green sheet from both ends in the width direction. 3. The method according to claim 1, wherein the drying is performed by raising the temperature of the central portion of the ceramic green sheet to be higher than that of both ends in the width direction.