Memory element and display device
View Patent ↗The present invention provides a memory element includes a thin film transistor configured to have a semiconductor thin film and a pair of gate electrodes that vertically sandwich the semiconductor thin film with intermediary of insulating films therebetween, and a capacitor configured to be connected to a first gate electrode of the pair of gate electrodes, wherein data is stored in the capacitor connected to the first gate electrode, and data stored in the capacitor is read out by controlling a second gate electrode of the pair of gate electrodes.
1. A memory element comprising:
a thin film transistor having a semiconductor thin film and a pair of gate electrodes that vertically sandwich the semiconductor thin film with insulating films between each of the gate electrodes and the semiconductor thin film, the thin film transistor having a source and a drain;
a capacitor connected to a first gate electrode of the pair of gate electrodes; and
a switch electrically interposed between the drain of the thin film transistor and the capacitor,
wherein,
the capacitor is configured to store data, and the data that is stored in the capacitor is configured to be read out by controlling a second gate electrode of the pair of gate electrodes.
2. The memory element according to claim 1 , wherein:
the source of the thin film transistor is an input current terminal and corresponds to a data input side and the drain of the thin film transistor is an output current terminal and corresponds to a data output side,
in data writing, the second gate electrode is controlled in a state in which the switch is in an on-state, to thereby write data supplied from the input current terminal to the capacitor, and
in data reading, the second gate electrode is controlled in a state in which the switch is in an off-state, to thereby read out data written to the capacitor to the output current terminal.
3. The memory element according to claim 2 , wherein:
a threshold voltage of the thin film transistor changes due to application of a voltage that is dependent upon data written to the capacitor to the first gate electrode, and
the data stored in the capacitor is read out by controlling the second gate electrode and by regarding a change of the threshold voltage as a change between an on-state and an off-state of the thin film transistor.
4. A display device including rows of gate lines, columns of data lines, and pixels disposed at intersections of the gate lines and the data lines, each of the pixels including a memory element and an electro-optical element, each memory element storing data supplied from a respective data line and reading out data in accordance with a signal supplied from a respective gate line, the electro-optical element offering luminance dependent upon the stored data, each memory element comprising:
a thin film transistor having a semiconductor thin film and a pair of gate electrodes that vertically sandwich the semiconductor thin film with insulating films between each of the gate electrodes and the semiconductor thin film, the thin film transistor having a source and a drain;
a capacitor connected to a first gate electrode of the pair of gate electrodes, and
a switch electrically interposed between the drain of the thin film transistor and the capacitor,
wherein,
the capacitor is configured to store data, and the data that is stored in the capacitor is configured to be read out by controlling a second gate electrode via the respective gate line.
5. The display device according to claim 4 , wherein:
the source of the thin film transistor is an input current terminal connected to the data line and the drain of the thin film transistor is an output current terminal connected to the electro-optical element,
in data writing, the second gate electrode is controlled via the respective gate line in a state in which the switch is in an on-state, to thereby write data supplied from the input current terminal to the capacitor, and
in data reading, the second gate electrode is controlled via the respective gate line in a state in which the switch is in an off-state, to thereby read out data written to the capacitor to the output current terminal.
6. The display device according to claim 5 , wherein the switch is formed of a thin film transistor and is shielded from external light for prevention of data leakage.
7. The display device according to claim 4 , wherein:
the pixel includes a plurality of memory elements that are connected in series to each other between the data line and the electro-optical element, the memory elements are controlled in a time-division manner via a plurality of gate lines each corresponding to a respective one of the memory elements, to thereby write multi-bit data corresponding to multiple grayscales, and time-division driving of the electro-optical element is carried out in accordance with written multi-bit data, to thereby control luminance of the electro-optical element based on multiple grayscales.
8. The display device according to claim 4 , wherein:
the pixel is subjected to area division into a plurality of regions,
each of the regions includes the electro-optical element and the memory element, and
multi-bit data is written to a plurality of memory elements disposed in a plurality of regions, to thereby control luminance of the pixel based on multiple grayscales in accordance with the written multi-bit data.