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US 4,062,626 AGranted
Liquid crystal display device
AssigneeHitachi, Ltd.
InventorsHideaki Kawakami, Yutaka Yoneda, Yoshiharu Nagae, Masaaki Kitazima
Life of this patent
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Abstract
A liquid crystal display device in which an electronic switch having a double threshold characteristic is combined with each of a plurality of liquid crystal cells, and an ac signal voltage and an ac bias voltage are applied to one and the other terminals respectively of the combined circuit of the liquid crystal cells and electronic switches. In the device, the electronic switches are turned on or off depending on the relation between the phase of the signal voltage and that of the bias voltage so that the liquid crystal cells can be excited for display by the voltage applied thereacross in response to the turn-on of the electronic switches.
Claims17
A liquid crystal display device comprising:
- a series circuit of a liquid crystal cell and an electronic switch, said electronic switch having a double threshold characteristic in which the resistance of said electronic switch is changed over from a high level to a low level when the absolute value of a voltage applied thereacross exceeds a predetermined value;
- means for applying an ac signal voltage to one end of said series circuit;
- and
- means for applying an ac bias voltage to the other end of said series circuit,
- whereby said electronic switch is controlled depending on the relation between the phase of said as signal voltage and that of said ac bias voltage so that said liquid crystal cell is excited for display when the resistance of said electronic switch takes the low level.
2 more elements
A liquid crystal display device comprising:
- a liquid crystal cell;
- means for applying an ac signal voltage to said liquid crystal cell through an electronic switch having a double threshold characteristic in which the resistance of said electronic switch is changed over from a high level to a low level when the absolute value of a voltage applied thereacross exceeds a predetermined value;
- and
- means for applying an ac bias voltage to said liquid crystal cell through a load resistor,
- whereby said electronic switch is controlled depending on the relation between the phase of said ac signal voltage and that of said ac bias voltage so that said liquid crystal cell is excited for display when the resistance of said electronic switch takes the low level.
2 more elements
A liquid crystal display device comprising:
- first and second control terminals;
- a series circuit of a liquid crystal cell and an electronic switching device connected in series between said first and second control terminals, said electronic switching device having an applied voltage versus current flow characteristic defining the effective resistance of said switching device such that the effective resistance of said switching device presents a relatively high impedance value upon the application thereacross of a voltage the absolute value of which is less than a prescrived threshold value, and presents a relatively low impedance value upon the application of a voltage thereacross being at least equal to said prescribed threshold value;
- means for applying an ac signal voltage to said first control terminal;
- means for applying an ac bias voltage to said second control terminal;
- and
- means for controlling the phase of said ac bias voltage with respect to the phase of said ac signal voltage such that
- for out-of-phase conditions of said ac bias an ac signal voltages, the absolute value of the resultant voltage across said switching device is at least equal to said prescribed threshold value and a relatively low impedance is presented by said switching device, so that said liquid crystal cell is excited by the voltage between said first and second control terminals, and
- for in-phase conditions of said ac bias and ac signal voltages, the absolute value of the resultant voltage across said switching device is less than said prescribed threshold value, and a relatively high impedance is presented by said switching device, so that said liquid crystal cell is prevented from being excited by the voltage between said first and second terminals.
5 more elements
A liquid crystal display device comprising:
- first, second, and third terminals;
- a liquid cyrstal cell connected between said second terminal and a source of reference potential;
- an electronic switching device connected between said first and second terminals, said electronic switching device having an applied voltage versus current flow characteristic defining the effective resistance of said switching device such that the effective resistance of said switching device presents a relatively high impedance value upon the application thereacross of a voltage, the absolute value of which is less than a prescribed threshold value, and presents a relatively low impedance vaue upon the application of a voltage thereacross being at least equal to said prescribed threshold value;
- a resistance element connected between said second and third terminals;
- means for applying an ac signal voltage to said first terminal;
- means for applying an ac bias voltage to said third terminal;
- and
- means for controlling the phase of said ac bias voltage with respect to the phase of said ac signal voltage such that
- for out-of-phase conditions of said ac bias and ac signal voltage, the absolute value of the resultant voltage across said switching device is at least equal to said prescribed threshold value and a relatively low impedance is presented by said switching device, so that said liquid crystal cell is excited by the voltage between said second terminal and said source of reference potential, and
- for in-phase conditions of said ac bias and ac signal voltages, the absolute value of the resultant voltage across said switching device is less than said prescribed threshold value, and a relatively high impedance is presented by said switching device, so that said liquid crystal cell is prevented from being excited by the voltage between said second terminal and said source of reference potential.
7 more elements
Dependencies are inferred from the claim text.