JPH10250014A - Manufacture of ceramic green sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously manufacture a uniform thin film ceramic green sheet with high yield by coating at least one surface of a polyester film with ceramic slurry made of ceramic raw material, binder and solvent before crystal orientation is completed, drying it and orienting it. SOLUTION: The ceramic green sheet is obtained by coating at least one surface of a polyester film before crystal orientation is completed with ceramic slurry, drying it and orienting it. The slurry is obtained by mechanically dispersing or dissolving binder of organic polymer containing 100% of ceramic raw material and having characteristics of 20kg/cm of 100% modulus and 500% or more of elongation at break in solvent for holding the slurry itself stably in a dispersed state. The film before the orientation is completed is oriented uniaxially, for example, longitudinally or laterally of the unoriented film is used, it is dried in heattreating step of orienting or heat setting it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a ceramic green sheet, and more particularly to a method for producing a uniform thin ceramic green sheet.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable increase in the use of ceramic chip capacitors in accordance with miniaturization of electronic equipment. In particular, usage of mobile communication devices and the like has been remarkably increased due to miniaturization and low power consumption.

Conventionally, ceramic chip capacitors have
A slurry in which ceramic powder, a solvent, a binder, and other additives (eg, a plasticizer, a dispersant, and an antistatic agent) are uniformly dispersed by an appropriate mechanical dispersion method is applied to a carrier sheet by a casting method. Then, drying is performed to form a ceramic green sheet, the internal electrodes are printed on the sheet, and those cut to a predetermined size are laminated,
It was manufactured by sintering and attaching external electrodes. In particular, the accuracy of the thickness of the ceramic green sheet,
Since this greatly affects the electrical properties of the final chip capacitor, not only the preparation of the slurry but also the carrier sheet requires high quality, such as surface foreign matter, uniform flatness, and thickness uniformity, at the ceramic green sheet manufacturing stage. Accurate surface properties have been required. In addition, with the miniaturization of electronic devices, chip capacitors themselves have also been miniaturized, so the thickness of a single ceramic green sheet must be reduced to about a few μm, and the dispersion and application of slurry is more difficult than in the past. Demands have become stricter on the method and carrier sheet.

However, no matter how finely the manufacturing conditions are adjusted, the flow characteristics of the slurry change due to environmental conditions such as temperature and humidity in the coating process and the evaporation of the solvent, for example. It is difficult to stably produce a long time, and it is necessary to take some kind of correction means during the production, or there is a problem that the yield of the product is reduced.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to improve the disadvantages of the prior art and to provide a method for producing a uniform ceramic green sheet thin film.

[0006]

According to the present invention, at least one side of the polyester film before the crystal orientation is completed,
This is a method for producing a ceramic green sheet, which comprises applying a ceramic slurry comprising a ceramic raw material, a binder and a solvent, followed by drying and stretching.

In the present invention, the polyester constituting the polyester film is a linear saturated polyester synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof.
Specific examples of such polyester include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylene dimethylene) terephthalate, and polyethylene-2,6-
Naphthalate and the like, and a copolymer of these or a blend thereof with a small proportion of another resin are also included.
Of these, polyethylene terephthalate and polyethylene-2,6-naphthalate are preferred.

[0008] As the ceramic raw material in the present invention,
Dielectrics disclosed in known materials, for example, barium titanate, Pb (Mg _1/3 , Nb _2/3 ) O ₃ , Pb (Sm _1/2 ,
Nb _1/2 ) O ₃ , Pb (Zn _1/3 , Nb _2/3 ) O ₃ , PbT
hO ₃ , PbZrO _3, etc. (by Kiyoshi Okazaki, Ceramic Derivatives Engineering 4th Edition, Gakudensha), but are not particularly limited thereto, as long as the dielectric properties required for a ceramic chip capacitor can be obtained. I just need.

Examples of the binder in the present invention include polyurethane, urea resin, melamine resin, aqueous polymer-isocyanate, epoxy resin, vinyl acetate resin, and acrylic binders. Characteristics that are strong and can sufficiently follow the stretching of the film are required. In order to satisfy such characteristics, it is necessary that the binder has a 100% modulus of 20 kg / cm ² or less and a breaking elongation of 500% or more.

[0010] The 100% modulus and elongation at break of the binder are values obtained by conducting a tensile test on a binder formed into a film having a thickness of 0.2 mm and a width of 10 mm. It refers to the tensile strength when the elongation is 100%.

The composition ratio (ceramic raw material) / (binder) of the ceramic raw material and the binder is 70/30.
A range of ９５95/5 is preferred.

Next, as a solvent for dispersing or dissolving the ceramic raw material and the binder, any solvent such as an aqueous solvent or an organic solvent can be used, and any solvent can be used as long as the slurry itself can stably maintain a dispersed state. No restrictions.

Further, a dispersing agent is added to the slurry within a range that does not affect the electrical properties of the dried green sheet.
A plasticizer, an antistatic agent, an antifoaming agent and the like may be added.

In the present invention, the polyester film is
It can be manufactured by a conventionally known method. For example, a sequential biaxial stretching method and a simultaneous biaxial stretching method are preferably exemplified.

As a detailed method for producing a polyester film, for example, in the case of a sequential biaxial stretching method, it can be produced under the following conditions. That is, after drying the polyester, a temperature of Tm to (Tm + 70) ° C. (however, Tm:
(Melting point of polyester) in an extruder, extruded from a die (e.g., T-die, I-die, etc.) onto a rotary cooling drum, quenched at 40 to 90 ° C to produce an unstretched film,
Then, the unstretched film was treated with (Tg-10) to (Tg + 7
0) Temperature of ° C (Tg: glass transition temperature of polyester)
At a magnification of 2.5 to 8.0 times in the longitudinal direction, and at a magnification of 2.5 to 8.0 times in the horizontal direction.
It can be manufactured by heat setting at a temperature of ２５０250 ° C. for 1 to 60 seconds.

The thickness of the polyester film is 5 to 250.
The range of μm is preferred. Further, as such a polyester film, it is preferable that the polyester film is oriented so that a value measured by a differential scanning calorimeter at a heating rate of 10 ° C./min of 4 cal / g or more in a nitrogen gas stream is 4 cal / g or more. .

The above slurry is applied to the polyester film before the crystal orientation is completed. Here, as the polyester film before the crystal orientation is completed,
(1) an unstretched film in which a polymer is melted to form a film as it is, (2) a uniaxially stretched film in which the unstretched film is oriented in either the longitudinal direction or the transverse direction,
(3) A stretched film oriented at a low magnification in two directions of a longitudinal direction and a transverse direction (a biaxially oriented film before being finally stretched again in a longitudinal direction or a transverse method to complete oriented crystallization), and the like. You. Among these, a uniaxially stretched film to which the above-mentioned slurry can be applied in the polyester film forming step is preferable, and a uniaxially stretched film oriented in the longitudinal direction is more preferable. The slurry can be applied by any method. For example, the roll coating method,
A gravure coating method, a kiss coating method and the like are preferable.

A function-imparting layer can be provided on the film before applying the slurry within a range that does not affect the dielectric properties of the ceramic green sheet. Examples of the function imparting layer include a release layer and an easily adhesive layer (primer layer).

The slurry applied to the polyester film before the completion of the crystal orientation by the above-mentioned method is dried by a heat treatment or another method and stretched. For example, when a uniaxially stretched film is used, drying is preferably performed in a heat treatment step in stretching or heat setting the film.

Coating film (ceramic green sheet) formed on polyester film before crystal orientation is completed
(Thickness after drying) can be freely selected,
It is preferably 0 μm.

Such unevenness in the thickness of the coating film is eliminated by drying and stretching, so that a green sheet having a uniform thickness can be obtained.

The green sheet obtained here is:
Processing steps such as electrode printing, laminating, and firing are performed, and the same steps as those in the related art can be used. Further, the polyester film used as the carrier sheet is separated from the ceramic green sheet in any of the above steps.

[0023]

The present invention will be described below in detail with reference to examples. In the examples, “parts” means “parts by weight”.

Example 1 Barium titanate was converted to an aqueous polyurethane dispersion (Superflex 300, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., with the properties of a binder alone (100% modulus 17 kg / cm ² , elongation at break 1230%)) The mixture was mixed and mechanically dispersed to prepare a ceramic slurry.

Next, polyethylene terephthalate having an intrinsic viscosity of 0.66 (35 ° C., in o-chlorophenol) was added to 2
After being melt-extruded on a rotary cooling drum maintained at 0 ° C. and quenched to prepare an unstretched film, the unstretched film was stretched 3.6 times in the machine direction at 90 ° C., and the slurry was 40 g / m ^2. (Wet) in a kiss coat method. Subsequently, the film was stretched 3.9 times in the horizontal direction at 105 ° C., and further heat-treated at 205 ° C. to obtain a ceramic green sheet laminate comprising a ceramic green sheet layer having a thickness of 2 μm and a polyester film having a thickness of 38 μm. The difference between the maximum value and the minimum value of the thickness of this ceramic green sheet in a width of 100 mm was 0.1 μm. Further, when the number of cracks on the surface of 1 cm ² arbitrarily selected was visually inspected, no cracks were observed.

Comparative Example 1 The same ceramic slurry as in Example 1 was applied to the surface of a 38 μm-thick biaxially stretched polyethylene terephthalate film by a kiss coating method so as to have a dry thickness of 2 μm, and a ceramic green sheet was laminated. I got a body. However, due to streaks generated during application,
The difference between the maximum value and the minimum value of the thickness at a width of 100 mm is 0.
Although the number of cracks on the randomly selected surface of 1 cm ² was small as large as 5 μm, crater-like surface defects occurred in the thick portion of the coating layer due to changes in drying conditions due to uneven thickness.

[0027]

According to the present invention, uniform thin film ceramic green sheets can be manufactured continuously and at a high yield.

Claims (5)

[Claims] 1. A method for producing a ceramic green sheet, comprising applying a ceramic slurry comprising a ceramic raw material, a binder and a solvent to at least one surface of a polyester film before completion of crystal orientation, followed by drying and stretching. 2. A binder having a 100% modulus of 2
The method for producing a ceramic green sheet according to claim 1, wherein the organic polymer is an organic polymer having characteristics of 0 kg / cm ² and elongation at break of 500% or more. 3. The ceramic according to claim 1, wherein the polyester film before completion of the crystal orientation is a uniaxially stretched polyester film obtained by orienting an unstretched film in one of a longitudinal direction and a transverse direction in sequential biaxial stretching. Green sheet manufacturing method. 4. The method for producing a ceramic green sheet according to claim 1, wherein the polyester film is a polyethylene terephthalate film. 5. The method according to claim 1, wherein the polyester film is a polyethylene-2,6-naphthalate film.