Patent ID: 7863802

Claim:
A crystal element made of a double-rotation Y-cut plate, said crystal element comprising a crystal blank which is cut from a crystal of quartz, a principle plane of the crystal blank being orthogonal to a Yâ€³-axis, where a Y-axis and a Z-axis are rotated by an angle of Î± centering around an X-axis in the crystal of quartz to be designated as a Yâ€²-axis and a Zâ€²-axis, and the X-axis and the Yâ€²-axis are rotated by an angle of Î² centering around the Zâ€²-axis to be designated as an Xâ€²-axis and said Yâ€³-axis, wherein said crystal blank has mutually orthogonal two null stress-sensitivity axes and has emphasized vibration displacement in four regions radially divided from a center at which said null stress-sensitivity axes mutually intersect at a right angle, wherein a thickness of a center part at which said null stress-sensitivity axes mutually intersect at a right angle is increased, and a ridge line portion defining a quadrangular pyramid like shape from said center part toward an outer peripheral part of said crystal blank is formed, and wherein when a base opposing to a vertex angle of said quadrangular pyramid like shape is provided, a sectional thickness of said crystal blank along said base is larger in the central region of said crystal blank and becomes gradually smaller toward both ends of said crystal blank.