# US 9,520,411 B2 · Display device and electronic device including the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,520,411 B2 - Document ID: US9520411B2 - Status: Granted - Kind: B2 - Application number: 12/945,475 - Filed: 2010-11-12 - Published: 2011-05-19 - Granted: 2016-12-13 - Earliest claimed: 2009-11-13 - Assignees: Semiconductor Energy Laboratory Co., Ltd. - Applicants: Kei Takahashi; Shunpei Yamazaki - Inventors: Kei Takahashi; Shunpei Yamazaki - Web page: https://patentgrep.com/patent/US9520411B2 ## CPC - H10D 86/60: wherein the TFTs are in active matrices - G09G 3/3233: with pixel circuitry controlling the current through the light-emitting element - G09G 3/3266: Details of drivers for scan electrodes - H10D 86/423: {comprising semiconductor materials not belonging to the Group IV, e.g. InGaZnO} - H10K 59/1213: {the pixel elements being TFTs} - H10K 59/122: Pixel-defining structures or layers, e.g. banks - H10K 59/123: Connection of the pixel electrodes to the thin film transistors [TFT] - G09G 2300/0814: used for selection purposes, e.g. logical AND for partial update - G09G 2300/0842: forming a memory circuit, e.g. a dynamic memory with one capacitor - G09G 2310/0286: Details of a shift registers arranged for use in a driving circuit - G09G 2310/08: Details of timing specific for flat panels, other than clock recovery - H10D 30/6745: {Polycrystalline or microcrystalline silicon} - H10D 30/6755: {Oxide semiconductors, e.g. zinc oxide, copper aluminium oxide or cadmium stannate} - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES - G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00) - H10K: ORGANIC ELECTRIC SOLID-STATE DEVICES ## Abstract A display device includes a pixel portion including a plurality of pixels each including a first transistor, a second transistor, and a light-emitting element, in which a gate of the first transistor is electrically connected to a scan line, one of a source and a drain of the first transistor is electrically connected to a signal line, and the other of them is electrically connected to a gate of the second transistor; one of a source and a drain of the second transistor is electrically connected to a power supply line and the other of them is electrically connected to the light-emitting element, and the first transistor includes an oxide semiconductor layer. A period when the display device displays a still image includes a period in which output of a signal to all the scan lines in the pixel portion is stopped. ## Claims ### Claim 1 A display device comprising: a pixel portion comprising a plurality of pixels each including a first transistor, a second transistor, and a light-emitting element having a pair of electrodes, a driver circuit portion for driving the pixel portion; a signal generation circuit for generating a control signal for driving the driver circuit portion and an image signal supplied to the plurality of pixels; a memory circuit for storing image signals of respective frame periods; a comparison circuit for detecting a difference between image signals of successive frame periods among the image signals of the respective frame periods stored in the memory circuit by selectively reading out the image signals of successive frame periods stored in the memory circuit and comparing the image signals; a selection circuit for selecting and outputting the image signals of the successive frame periods when the comparison circuit detects the difference; and a display control circuit for supplying the control signal and the image signal output from the selection circuit to the driver circuit portion when the comparison circuit detects the difference, and stopping supply of the control signal to the driver circuit portion when the comparison circuit does not detect the difference, wherein a first gate of the first transistor is electrically connected to a scan line, one of a first source and a first drain of the first transistor is electrically connected to a signal line, and the other of the first source and the first drain of the first transistor is electrically connected to a second gate of the second transistor, wherein one of a second source and a second drain of the second transistor is electrically connected to a power supply line and the other of the second source and the second drain of the second transistor is electrically connected to one of the pair of electrodes of the light-emitting element, wherein the first transistor comprises a first oxide semiconductor layer a hydrogen concentration of which is 5×1019/cm3 or less, wherein a node between the second gate and the other of the first source and the first drain is configured to be supplied with a video signal that is an analog signal, wherein the node is configured to hold the video signal when the first transistor is off, wherein a period when the display device displays a still image includes a period when output of a signal to all the scan line in the pixel portion is stopped, wherein a carrier concentration of the first oxide semiconductor layer is less than 1×1014/cm3, wherein the first oxide semiconductor layer comprises indium, gallium, and zinc, and wherein the first oxide semiconductor layer comprises a microcrystalline portion. ### Claim 2 (depends on 1) The display device according to claim 1, wherein the control signal is a high power supply potential, a low power supply potential, a clock signal, a start pulse signal, or a reset signal. ### Claim 3 (depends on 1) The display device according to claim 1, wherein the plurality of pixels each further comprises a luminous layer. ### Claim 4 (depends on 1) The display device according to claim 1, wherein a band gap of the first oxide semiconductor layer is 2 eV or more. ### Claim 5 (depends on 1) The display device according to claim 1, wherein the second transistor comprises a second oxide semiconductor layer a hydrogen concentration of which is 5×1019/cm3 or less. ### Claim 6 (depends on 1) The display device according to claim 1, wherein the second transistor comprises a polycrystalline silicon layer. ### Claim 7 (depends on 1) An electronic device comprising the display device according to claim 1. ### Claim 8 (depends on 7) The electronic device according to claim 7, wherein the electronic device is an electronic paper comprising operation keys. ### Claim 9 A display device comprising: a pixel portion comprising a plurality of pixels each including a first transistor, a second transistor, and a light-emitting element having a pair of electrodes; a driver circuit portion for driving the pixel portion; a signal generation circuit for generating a control signal for driving the driver circuit portion and an image signal to be supplied to the driver circuit portion; a memory circuit for storing image signals of respective frame periods; a comparison circuit for detecting and outputting a difference between image signals of successive frame periods among the image signals of the respective frame periods stored in the memory circuit by selectively reading out the image signals of successive frame periods stored in the memory circuit and comparing the image signals; a selection circuit for outputting the image signals to be supplied to the driver circuit portion in accordance with an output from the comparison circuit; and a display control circuit for controlling the control signal from the signal generation circuit and the image signal outputted from the selection circuit to the driver circuit portion in accordance with the output from the comparison circuit, wherein a first gate of the first transistor is electrically connected to a scan line, one of a first source and a first drain of the first transistor is electrically connected to a signal line, and the other of the first source and the first drain of the first transistor is electrically connected to a second gate of the second transistor, wherein one of a second source and a second drain of the second transistor is electrically connected to a power supply line and the other of the second source and the second drain of the second transistor is electrically connected to one of the pair of electrodes of the light-emitting element, wherein the first transistor comprises a first oxide semiconductor layer, wherein a node between the second gate and the other of the first source and the first drain is configured to be supplied with a video signal that is an analog signal, wherein the node is configured to hold the video signal when the first transistor is off, wherein a period when the display device displays a still image includes a period when output of a signal to all the scan lines in the pixel portion is stopped, wherein a carrier concentration of the first oxide semiconductor layer is less than 1×1014/cm3, wherein the first transistor comprises the first oxide semiconductor layer a hydrogen concentration of which is 5×1019/cm3 or less, wherein the first oxide semiconductor layer comprises indium, gallium, and zinc, and wherein the first oxide semiconductor layer comprises a microcrystalline portion. ### Claim 10 (depends on 9) The display device according to claim 9, wherein the plurality of pixels each further comprises a luminous layer. ### Claim 11 (depends on 9) The display device according to claim 9, wherein a band gap of the first oxide semiconductor layer is 2 eV or more. ### Claim 12 (depends on 9) The display device according to claim 9, wherein the second transistor comprises a second oxide semiconductor layer a hydrogen concentration of which is 5×1019/cm3 or less. ### Claim 13 (depends on 9) The display device according to claim 9, wherein the second transistor comprises a polycrystalline silicon layer. ### Claim 14 (depends on 9) An electronic device comprising the display device according to claim 9. ### Claim 15 (depends on 14) The electronic device according to claim 14, wherein the electronic device is an electronic paper comprising operation keys. ### Claim 16 (depends on 9) The display device according to claim 9, wherein the display control circuit is configured so as not to output the control signal to the driver circuit portion in accordance with the output from the comparison circuit. ### Claim 17 (depends on 9) The display device according to claim 9, wherein the control signal is a high power supply potential, a low power supply potential, a clock signal, a start pulse signal, or a reset signal. ### Claim 18 A display device comprising: a pixel portion comprising a plurality of pixels each including: a first transistor; a second transistor; and a light-emitting element comprising a pair of electrodes and an electroluminescence layer therebetween; a driver circuit portion for driving the pixel portion; a signal generation circuit for generating a control signal for driving the driver circuit portion and an image signal; a memory circuit comprising a frame memory configured to store the image signal; and a display control circuit configured to switch between supply and stop of the image signal and the control signal to the driver circuit portion, wherein one of a source and a drain of the first transistor is electrically connected to a gate of the second transistor, wherein one of a second source and a second drain of the second transistor is electrically connected to one of the pair of electrodes of the light-emitting element, wherein the first transistor comprises a first oxide semiconductor layer, wherein a carrier concentration of the first oxide semiconductor layer is less than 1×1014/cm3, wherein the first transistor comprises the first oxide semiconductor layer a hydrogen concentration of which is 5×1019/cm3 or less, wherein the first oxide semiconductor layer comprises indium, gallium, and zinc, and wherein the first oxide semiconductor layer comprises a microcrystalline portion. ### Claim 19 (depends on 18) The display device according to claim 18, wherein the control signal comprises at least any one of a high power supply potential, a low power supply potential, a clock signal, a start pulse signal, and a reset signal. ### Claim 20 (depends on 18) The display device according to claim 18, wherein the plurality of pixels each further comprises a luminous layer. ### Claim 21 (depends on 18) The display device according to claim 18, wherein a band gap of the first oxide semiconductor layer is 2 eV or more. ### Claim 22 (depends on 18) The display device according to claim 18, wherein the second transistor comprises a second oxide semiconductor layer a hydrogen concentration of which is 5×1019/cm3 or less. ### Claim 23 (depends on 18) The display device according to claim 18, wherein the second transistor comprises a polycrystalline silicon layer. ### Claim 24 (depends on 18) An electronic device comprising the display device according to claim 18. ### Claim 25 (depends on 24) The electronic device according to claim 24, wherein the electronic device is an electronic paper comprising operation keys. ### Claim 26 A display device comprising: a pixel portion comprising a plurality of pixels each comprising a first transistor, a second transistor, and a light-emitting element; a driver circuit portion for driving the pixel portion; a display control circuit for controlling supply of an image signal to the driver circuit portion, wherein a gate of the first transistor is electrically connected to a scan line, wherein one of a source and a drain of the first transistor is electrically connected to a signal line, wherein the other of the source and the drain of the first transistor is electrically connected to a gate of the second transistor, wherein one of a source and a drain of the second transistor is electrically connected to a power supply line and the other of the source and the drain of the second transistor is electrically connected to the light-emitting element, wherein the first transistor comprises a first oxide semiconductor layer comprising a channel formation region of the first transistor, wherein a carrier concentration of the first oxide semiconductor layer is less than 1×1014/cm3, wherein the first transistor comprises the first oxide semiconductor layer a hydrogen concentration of which is 5×1019/cm3 or less, wherein the first oxide semiconductor layer comprises indium, gallium, and zinc, and wherein the first oxide semiconductor layer is crystalline. ### Claim 27 (depends on 26) The display device according to claim 26, wherein the first oxide semiconductor layer comprises a microcrystalline portion. ### Claim 28 (depends on 26) The display device according to claim 26, wherein the plurality of pixels each further comprises a luminous layer. ### Claim 29 (depends on 26) The display device according to claim 26, comprising a signal generation circuit for generating a control signal for driving the driver circuit portion and an image signal. ### Claim 30 (depends on 26) The display device according to claim 26, comprising a memory circuit comprising frame memory configured to store an image signal. ### Claim 31 (depends on 26) The display device according to claim 26, wherein a band gap of the first oxide semiconductor layer is 2 eV or more. ### Claim 32 (depends on 26) The display device according to claim 26, wherein the second transistor comprises a second oxide semiconductor layer. ### Claim 33 (depends on 26) The display device according to claim 26, wherein the second transistor comprises a polycrystalline silicon layer.