| 摘要 |
PROBLEM TO BE SOLVED: To impart an improve strength and a gloss of high-class feeling by forming a dial mode of alumina ceramic that has a crystal diameter in a specified range and a specified void diameter. SOLUTION: The average grain diameter of an alumina raw material powder is set to approximately 0.1-0.5μm, and a grain size distribution is set to shape range. Water is added to a raw material power to form a slurry, which is injected into a forming mold in a specific shaped. The then forming mold is rotated and a raw material powder is formed by a centrifugal force of approximately 3,000 G or higher, and the forming body is backed at a relatively low temperature of approximately 1,200-1,300 deg.C. A sintered body thus obtained becomes a fine crystal with a crystal particle diameter of approximately 1.0μm or less, thus reducing an average void diameter to approximately 0.5μm or less and hence achieving a bending resistance of approximately 700 MPa or higher and a glass with high-class feeling. As a result, crackes due to a shock when the watch is dropped or hit against a hard object can be prevented.
|
