JPH0688616B2 - How to store green sheets - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Use of the Invention] The present invention is used as a material for electronic parts, substrates for electronic parts, machine parts, blade base materials, baking base plates, sintered bodies with complex shapes, solid electrolyte membranes and the like. Regarding how to save green sheets.

BACKGROUND OF THE INVENTION Green sheets are widely used as a material for electronic parts such as ceramic capacitors and ceramic multilayer wiring boards, and have a powder composition for improving formability, uniformity, machinability and printability. Many studies have been carried out on the production method thereof, such as binders and solvents. However,
The green sheet obtained in this way is less flexible and brittle due to residual solvent and plasticizers such as phthalates gradually evaporating during storage, resulting in reduced strength and plasticity depending on conditions. Adhesion of the surface of the green sheets increases due to bleeding of the agent, and the green sheets may be bonded to each other. Especially methylcellulose,
A green sheet made of a mixture of a water-soluble binder such as polyvinyl alcohol or a water-soluble (meth) acrylic resin and a plasticizer such as glycerin becomes very brittle due to moisture and cannot be used.

The storability that does not change or deteriorate the characteristics in a specific environment is one of the important performances required for green sheets, but for the preservation of green sheets, a little consideration is given to storing it in a closed container such as a tea box. (Molding of fine ceramics and organic materials: Katsuyoshi Saito, published in August 1985, publisher: CMC Co., Ltd.).

[Object of the Invention] An object of the present invention is to provide a storage method in which the characteristics of the green sheet are slightly changed with time or are not deteriorated, particularly, a storage method of the green sheet during long-term storage or transportation.

[Outline of the Invention] The present invention is to package a green sheet using a polymer barrier film, and particularly to put the green sheet in a bag-shaped polymer barrier film, depressurize the inside of the bag, and then seal the film. Alternatively, after the pressure is reduced, an inert gas is filled, and then the film is sealed.

Here, the barrier film referred to in the present invention is a film of a barrier material, which is defined as a general term for materials used for suppressing permeation of water, oil, water vapor, gas, etc. in "paper pulp term" of JIS-P0001. belongs to.

As the material of the barrier film, low density polyethylene,
Medium / high density polyethylene, linear low density polyethylene, biaxially oriented polyester, polypropylene, polyvinyl chloride, vinyl chloride / vinylidene chloride copolymer, vinylidene chloride / acrylic ester copolymer, ethylene / vinyl alcohol copolymer, Examples thereof include polyvinyl alcohol, polychlorotrifluoroethylene, and the like. These single films or single films are laminated / laminated, coated, surface-treated, multilayer extruded, etc., or a combination thereof is applied. The thing (composite film) is used. In particular, those obtained by subjecting the above-mentioned polymer film to vacuum vapor deposition of aluminum or laminated to an aluminum foil (aluminum laminated film) are preferably used.

The gas barrier properties of these polymer barrier films have a water vapor transmission rate of 10 g / m ² · 24 hr or less, preferably 2 g / m ² · 24 hr.
Below, oxygen permeability is 50cc / m ² · 24hr or less, preferably 5cc
/ m ² · 24hr or less is suitable. The toluene, the transmittance of the organic solvents such as methyl ethyl ketone 10g / m ² · 24hr or less,
It is preferably 2 g / m ² · 24 hr or less.

The water vapor permeability was measured by the moisture permeability test method (JIZ Z 0208) of the moisture-proof packaging material, and the oxygen permeability was measured by the gas permeability of the plastic film for food packaging (JIS Z 1707). The organic solvent transmittance was measured according to JIS Z 0208.

Green sheets packaged using these polymer barrier films include oxides such as alumina, alumina-glass, zirconia and ferrite, nitrides and carbides such as silicon nitride, aluminum nitride and silicon carbide, barium titanate and titanate. Polyvinyl butyral resin on ceramic powder composed of lead zirconate (PZT), YBa ₂ Cu ₃ O _{7-x and} other belovskite type complex oxides, complex oxides such as cordierite, mullite and spinel, and mixtures thereof, ( Casting the slurry obtained by kneading (meth) acrylic acid-based resin, methylcellulose, etc. as a binder, adding phthalates, plasticizers such as glycerin, polyethylene glycol, etc. if necessary, on a polymer film such as PET This is a green sheet obtained by post-drying. The sheet is in a state of being attached to the PET film or in a state of being peeled off from the PET film.

The object of the present invention can be achieved by packaging these green sheets with the polymer barrier film, but the green sheets are put into a bag-shaped polymer barrier film, and the inside of the bag is depressurized by an aspirator, a vacuum pump or the like. The film is then sealed by thermocompression using a policyr or the like or depressurized, and then nitrogen gas, helium gas, argon gas, carbon dioxide gas, nitrogen / oxygen mixed gas (oxygen concentration 10
It is more effective to enclose a dry inert gas (e.g. below%) and then seal. When reducing the pressure, the pressure inside the bag should be less than 760 mmHg at room temperature, preferably 100 mmHg.
When the inert gas is introduced, the pressure inside the bag should be more than 100 mmHg at room temperature, preferably more than 500 mmHg.

According to the present invention, blocking and holding of organic solvents and water (water vapor), permeation of oxygen gas, prevention of invasion, blocking of light and ultraviolet rays,
Heat shield etc. is done and the characteristics at the time of green sheet preparation are long term,
Especially, it is retained even during transportation. Furthermore, since it is non-chargeable, it is difficult for dust and the like to adhere to it, and it has the effect of preventing accidents and increasing safety.

[Examples] Hereinafter, the present invention will be specifically described with reference to Examples and the like, but the present invention is not limited thereto.

Reference Example 1 A polyvinyl butyral resin as a binder and a plasticizer as a ceramic powder in which 96% by weight of alumina (average particle diameter 1 to 2 μm) and 4% by weight of a frit composed of calcia, magnesia, and silica as a sintering aid were added. After dibutyl phthalate and toluene as a solvent were added and kneaded, the mixture was cast on a PET film, dried, and then peeled from the PET film to obtain an alumina green sheet having a thickness of 0.45 mm.

Reference Example 2 After adding water-soluble methacrylic resin as a binder, glycerin as a plasticizer, and water as a solvent to barium titanate (average particle size 0.5 μm) and drying in the same manner as in Reference Example 1, the thickness was 0.08 mm. A barium titanate green sheet was obtained. In this case, the green sheet was kept attached to the PET film without peeling from the PET film.

Example 1 A bag-shaped aluminum vapor-deposited biaxially stretched polyester film (trade name Lumirror manufactured by Toray, film thickness 25 μ, water vapor transmission rate 0.8 g / m ² · 24 hr, oxygen transmission rate 1.1 cc / m ² · 24 hr,
The two alumina green sheets obtained in Reference Example 1 were placed in respective bags with a vapor permeability of toluene of 0.5 g / m ² · 24 hr), and the pressure was reduced to 50 mmHg by a rotary pump. One of them is sealed with a policyr, and the other has a pressure in the bag of 760 mmHg.
Nitrogen gas was introduced until and then sealed.

Leave the two bags in a normal room, and after 1 week, 1 month, 3 months, 6 months, take out each green sheet and roll it onto a glass rod of 30 mmφ for flexibility. The tensile strength of the green sheet was measured by a strength tester. The results are summarized in Table-1 and Figure-1.

Example 2 The barium titanate green sheet obtained in Reference Example 2 was used and tested in the same manner as in Example 1. The results are summarized in Table-1 and Figure-1.

Comparative Example 3 Bag made of polymer barrier composite film made of ethylene and vinyl alcohol random copolymer (Kuraray's trade name Eval-E type, film thickness 30 μm, water vapor transmission rate 15 g / m ² · 24 hr, oxygen transmission rate The same test as in Example 1 was conducted using 3 cc / m ² · 24 hr and methyl ethyl ketone permeability of 0.1 g / m ² · 24 hr).

As a result, since the water vapor transmission rate was high, as shown in Table 1, the flexibility became slightly inferior after 6 months.

Example 4 The barium titanate green sheet obtained in Reference Example 2 was wrapped in the film used in Example 1, and the overlapping portion of the film was sealed with cellophane tape and tested in the same manner.

Comparative Example 1 The green sheet obtained in Reference Example 1 was placed in a tea box and tested in the same manner as in Example 1.

Comparative Example 2 The green sheet obtained in Reference Example 2 was wound into a cylinder having an outer diameter of about 8 cm while being attached to a PET film, the tip was fixed with cellophane tape, and left in a room as in Example 1. Tested

[Brief description of drawings]

FIG. 1 is a graph showing the change over time in the tensile strength of the green sheet. A is the time-dependent change of the tensile strength under the condition A of Example 1, B is the time-dependent change of the tensile strength under the condition B of Example 1, and G is the time-dependent change of the tensile strength under the condition G of Comparative Example 1. Represent each.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-61-164967 (JP, A) JP-A-61-152576 (JP, A) JP-A-56-151675 (JP, A) Actual development Sho-61- 144062 (JP, U) Actually opened 52-132934 (JP, U)

Claims (3)

[Claims] 1. A green sheet obtained by using a ceramic powder has a water vapor transmission rate of 10 g / m ² · 24 hr or less and an oxygen transmission rate of 50.
Packaging using at least one polymer barrier film selected from a single film, a composite film and an aluminum laminated film, which has characteristics of cc / m ² · 24 hr or less and organic solvent permeability of 10 g / m ² · 24 hr or less. A method of storing green sheets characterized by. 2. The storage method according to claim 1, wherein the green sheet is put in a bag-shaped polymer barrier film, the inside of the bag is depressurized, and then the film is sealed. 3. The green sheet is placed in a bag-shaped polymer barrier film, the bag is depressurized, an inert gas is sealed therein, and then the film is sealed. Storage method.