Patent ID: 8866567

Claim:
A quartz crystal unit comprising: a case having an open end; a quartz crystal resonator; and a lid; wherein the quartz crystal resonator comprises a quartz crystal tuning fork resonator having a quartz crystal tuning fork base, and first and second quartz crystal tuning fork tines connected to the quartz crystal tuning fork base, each of the quartz crystal tuning fork base and the first and second quartz crystal tuning fork tines having a thickness within a range of 0.05 mm to 0.18 mm, each of the first and second quartz crystal tuning fork tines having opposite main surfaces and a first side surface and a second side surface opposite the first side surface in the width direction, the first side surface of the first quartz crystal tuning fork tine confronting the second side surface of the second quartz crystal tuning fork tine; wherein at least one groove having a base portion and a plurality of surfaces including a first surface opposite the first side surface is formed in at least one of the opposite main surfaces of each of the first and second quartz crystal tuning fork tines so that a length of the at least one groove formed in the at least one of the opposite main surfaces of each of the first and second quartz crystal tuning fork tines is within a range of 20% to 78% of an overall length of the quartz crystal tuning fork resonator and less than 1.29 mm, the quartz crystal tuning fork resonator having a capacitance ratio r 1 of a fundamental mode of vibration and a capacitance ratio r 2 of a second overtone mode of vibration; wherein an electrode is disposed on at least one of the base portion and the first surface of the at least one groove formed in the at least one of the opposite main surfaces of each of the first and second quartz crystal tuning fork tines so that the electrode disposed on the at least one of the base portion and the first surface of the at least one groove formed in the at least one of the opposite main surfaces of the first quartz crystal tuning fork tine has an electrical polarity opposite to an electrical polarity of the electrode disposed on the at least one of the base portion and the first surface of the at least one groove formed in the at least one of the opposite main surfaces of the second quartz crystal tuning fork tine and the capacitance ratio r 2 of the second overtone mode of vibration of the quartz crystal tuning fork resonator is greater than 1500; wherein the quartz crystal tuning fork resonator is housed in the case; and wherein the lid is connected to the case to cover the open end of the case.