Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2001-11-13
2003-06-24
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S409000
Reexamination Certificate
active
06582820
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composite plate-like metal titanate and a production method thereof.
2. Related Art
A metal titanate such as barium titanate, strontium titanate, calcium titanate, and the like has widely been used as a material having dielectric, piezoelectric properties and industrially produced by mass production.
Conventionally, as the metal titanate, granular and fibrous ones have been proposed. Among them, since a fibrous metal titanate is capable of not only providing dielectric property to synthetic resin but also improving mechanical strength without deteriorating the molding workability of the resin by being mixed with the resin, it has been applied to a variety of uses, for example, as an antenna material, a capacitor material, a layered circuit substrate material, a connector material, and the like which are required to be dielectric.
However, although such a fibrous metal titanate does not deteriorate the molding workability of the synthetic resin as described above, it has the following problems attributed to the fibrous shape. That is, although it can improve the dielectric property as compared with a granular one in the case the longitudinal direction of the fiber is same as the direction of an electric field, it cannot improve the dielectric property so much as compared with a granular one in the case the diameter direction of the fiber is same as the direction of an electric field. Also, the fibrous metal titanate is not sufficient in the reinforcing capability to the force applied in the torsional direction.
On the other hand, a plate-like dielectric material has a characteristic of improving the dielectric constant regardless of the direction of an electric field owing to the intrinsic property of the shape. As such a plate-like dielectric material, Japanese Patent Laid Open No. Hei 10-95617 (1998) proposes plate-like substances of metal oxides such as magnesium, calcium, strontium, barium and the like and in an experiment example 3, plate-like alkaline earth metal salts were produced by mixing plate-like titanium oxide and alkaline earth metal hydroxides and hydrothermally treating the resulting mixtures. However, since the hydrothermal reaction was carried out while controlling the mole ratio of titanium and an alkaline earth metal to be 1/1 in the method, the strength of the obtained plate-like substance itself was deteriorated and, for example, the product was mixed with synthetic resin, some or all of the plate-like substance was broken by the external stress applied at the time of mixing or kneading to make it impossible to obtain desired mechanical strength and dielectric property.
SUMMARY OF THE INVENTION
Inventors of the present invention have enthusiastically investigated to solve the above described problems and consequently succeed in obtaining an innovative composite plate-like metal titanate having high strength itself and excellent in dielectric property and complete the present invention.
That is, the present invention relates to a composite plate-like metal titanate in which a surface of crystalline metal titanate having a composition expressed in MO.TiO
2
(wherein M denotes a divalent metal) is partially or entirely coated with amorphous and/or crystalline TiO
2
and relates to a production method thereof.
According to the present invention, a composite plate-like metal titanate having high strength as compared with that of a conventional one and excellent in dielectric property can be provided by mixing a plate-like titanium oxide compound with one or more of metal compounds selected from oxides, hydroxides, inorganic acid salts, and organic acid slats of a divalent metal element M in Ti>M by mole ratio and carrying out heating treatment of the mixture at 500° C. to 1,400° C.
The reason why the composite plate-like metal titanate of the present invention has high strength itself has not been made clear yet, however, it is supposed that amorphous and/or crystalline TiO
2
works as a matrix in some or all of its surface as described above.
The composite plate-like metal titanate of the present invention is a plate-like substance in which a surface of crystalline metal titanate having a composition expressed in MO.TiO
2
(wherein M denotes a divalent metal) is partially or entirely wrapped with amorphous and/or crystalline TiO
2
.
In this case, although the divalent metal denoted with M is not particularly restricted, examples are alkaline earth metals such as barium, strontium, calcium, magnesium and the like; elements such as manganese, zinc, copper, lead, cobalt, nickel and the like belonging to the fourth period in a periodic table; and elements such as silver, tin, molybdenum, niobium, zirconium and the like belonging to fifth period in a periodic table. Among them, preferable are alkaline earth metals and elements such as lead belonging to fourth period in a periodic table and especially preferable are alkaline earth metals. The divalent metal denoted with M is not necessarily to be a single type but may be a mixture of two or more metals.
Among composite plate-like metal titanates of the present invention, especially preferable are composite plate-like alkaline earth metal titanates such as composite plate-like barium titanate, composite plate-like strontium titanate and composite plate-like calcium titanate and composite plate-like lead titanate.
In this specification, the term, plate-like, includes flaky, scaly, micaceous shapes and the like.
The composite plate-like metal titanate of the present invention has the average major axial size of generally about 0.5 to 100 &mgr;m, preferably 1 to 20 &mgr;m; the average minor axial size of generally about 0.2 to 100 &mgr;m, preferably 0.5 to 20 &mgr;m; the average thickness of generally about 0.01 to 10 &mgr;m, preferably 0.05 to 5 &mgr;m according to the observation by a scanning type electron microscope. Also, the ratio (the average particle diameter/the average thickness) of the average particle diameter measured by a laser diffraction type particle size distribution meter and the average thickness measured by a scanning type electron microscope is about 3 to 100, preferably about 5 to 50.
The composite plate-like metal titanate of the present invention can be produced by mixing plate-like titanium oxide with one or more of metal salts selected from oxides, hydroxides, inorganic acid salts, and organic acid slats of a divalent metal element M in Ti>M by mole ratio and heating the mixture at 500° C. to 1,400° C.
In the above description, the preferable mole ratio of Ti and M, M:Ti=1:(1.02 to 1.67). If the ratio of Ti is too high, the dielectric dissipation factor becomes high and therefore it is not preferable, whereas if the ratio of Ti is too low, the strength of the aimed product become insufficient and therefore it is not preferable. Especially, if a low dielectric dissipation factor is required, it is preferable that M:Ti=1:(1.03 to 1.11).
Further, the preferable range of heating temperature is 600° C. to 1,100° C. If the heating treatment temperature is lower than 600° C., the crystallinity of MO.TiO
2
is inferior and if it is higher than 1,100° C., crystal growth of titanium oxide of matrix takes place and the dielectric dissipation factor is increased and at the same time the resulting product becomes a plate-like substance with a low strength and therefore it is not preferable.
According to the production method, a composite plate-like metal titanate with approximately even shape within a narrow dispersion of the particle distribution is obtained.
The plate-like titanium oxide, one of the raw materials, is not particularly restricted and can be produced according to known methods disclosed in, for example, Japanese Patent Publication No. Hei 6-88786 (1994), Japanese Patent Laid Open No. Hei 5-221795 (1993), Japanese Patent Laid Open No. Hei 10-95617 (1998), Japanese Patent Application No. Hei 11-158086 (1999).
One of the examples is a method comprising a step of acid treating a lepido
Aki Minoru
Matsunaga Harue
Tanaka Tomohiro
Yagi Toshiaki
Kiliman Leszek
Otsuka Chemical Co. Ltd.
Townsend & Banta
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