WO1994025954A1 - Apparatus for recovery of threshold voltage shift in amorphous silicon thin-film transistor device - Google Patents

Apparatus for recovery of threshold voltage shift in amorphous silicon thin-film transistor device Download PDF

Info

Publication number
WO1994025954A1
WO1994025954A1 PCT/GB1994/000467 GB9400467W WO9425954A1 WO 1994025954 A1 WO1994025954 A1 WO 1994025954A1 GB 9400467 W GB9400467 W GB 9400467W WO 9425954 A1 WO9425954 A1 WO 9425954A1
Authority
WO
WIPO (PCT)
Prior art keywords
display
voltage
time
threshold voltage
tft
Prior art date
Application number
PCT/GB1994/000467
Other languages
French (fr)
Inventor
Sywe Neng Lee
Dyi-Chung Hy
Original Assignee
Prime View Hk Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Prime View Hk Limited filed Critical Prime View Hk Limited
Priority to AU61500/94A priority Critical patent/AU6150094A/en
Publication of WO1994025954A1 publication Critical patent/WO1994025954A1/en

Links

Classifications

    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3648—Control of matrices with row and column drivers using an active matrix
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00—Command of the display device
    • G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
    • G09G2310/0243—Details of the generation of driving signals
    • G09G2310/0254—Control of polarity reversal in general, other than for liquid crystal displays
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/04—Maintaining the quality of display appearance
    • G09G2320/041—Temperature compensation
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/04—Maintaining the quality of display appearance
    • G09G2320/043—Preventing or counteracting the effects of ageing
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/04—Maintaining the quality of display appearance
    • G09G2320/043—Preventing or counteracting the effects of ageing
    • G09G2320/048—Preventing or counteracting the effects of ageing using evaluation of the usage time
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
    • G09G2330/02—Details of power systems and of start or stop of display operation
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3614—Control of polarity reversal in general

Definitions

  • the present invention relates generally to a threshold voltage shift recovery apparatus associated with amorphous silicon (a-Si:H) thin-film transistor (TFT) devices. More particularly the invention is directed towards a-Si:H TFT devices used in an LCD display such as data driver and scan driver circuits or in pixel switching elements.
  • a-Si:H TFT devices used in an LCD display such as data driver and scan driver circuits or in pixel switching elements.
  • Amorphous silicon TFT's have been widely used in active matrix LCD displays because of their good switching characteristics.
  • the threshold voltage, V th shifting during operation shows instability of the amorphous silicon and hence factors such as temperature and applied voltage can cause its character to change during use of the LCD display. Studies have shown that the time dependence of this threshold voltage shift is due to gate bias voltage. Threshold voltage shift is accelerated when the devices are operated under increasingly higher temperature conditions.
  • Threshold voltage, V th can be defined, when plotted in graphic form, as the voltage, V g/ of the gate of a TFT along an abscissa intersected by a plot of the sguare root of the TFT drain current, Ids along the ordinate axis.
  • V g a gate voltage, V g , that is greater than the V th is necessary to give enough current to drive the TFT pixel elements of the LCD display.
  • the shifting of V th over time, and accelerated with increased temperature reduces the effective driving voltage between the gate and source and also reduces the source drain current, Ids, which results in the degrading of the LCD TFT display performance.
  • V th the threshold value
  • a threshold voltage shift of 6-to-7 volts may occur when a positive 40 volts DC is applied to the TFT gate for approximately 15 hours at 25°C, as shown in FIG. 1.
  • a V th shift of approximately 5 volts may occur when a 30 volt AC pulse with a 50% duty cycle is applied to the TFT gate for approximately 88 hours, as shown in FIG. 2.
  • the direction of the threshold voltage shift depends on the sign of the voltage between the gate and source of a given TFT.
  • a negative threshold voltage shifting occurs when a negative DC voltage is applied to the TFT gate for a period of time.
  • V th shift an approximately negative 2.3 voltage shift of V th is shown when a negative 20 volts is applied to a TFT gate.
  • the equation commonly used to describe the V th shift, ⁇ V th can be expressed as:
  • a voltage shift of about 4 volts has been observed in a TFT-LCD after approximately 10,000 hours of operation at 80°C.
  • a ⁇ V th of less than 2 volts is required during the lifetime of the display.
  • the TFTs are under constant high temperature and the ⁇ V th will be more pronounced in a shorter period of time.
  • Other applications in which a significant ⁇ V th will be achieved include aviation and automobile applications.
  • V g is necessary to produce enough current to drive the pixel or other elements of the display due to the low mobility of the a-Si TFTs.
  • V th reduces the effective driving voltage between the gate and source and thereby reduces the source drain current. Ids, resulting in a degradation of performance. Therefore, it is highly desirable to maintain a low V th during the lifetime of the display.
  • V th There are several known methods for reducing and/or slowing down the shifting of the threshold voltage, V th .
  • One known method uses high temperature annealing to slow down the threshold voltage shifting by, for example, baking an LCD display in a high temperature oven for a fixed period of time.
  • ⁇ V th Another method to control ⁇ V th is to reduce the applied gate voltage, V g , since ⁇ V th is proportional to V g .
  • V g the applied gate voltage
  • ⁇ V th is proportional to V g .
  • a high gate voltage is necessary to produce enough current to drive other elements due to the low mobility of the amorphous silicon TFTs. Therefore, a lower gate voltage results in a significant reduction in the performance of the LCD display.
  • the third method uses a negative biased voltage to "drive back" a positive shifting V th .
  • This method utilizes applying a gate voltage to a scan line of TFT's while the line is not activated.
  • This method requires complicated analysis in order to minimize the shift of V th because there are practical limits to the magnitude and duration of the applied negative gate voltage. This is because, for each frame, each scan line has to turn ON within 1/60 of a second. This makes the required circuitry very complex in order to have the V th shifted properly.
  • an object of the present invention to provide an apparatus for an improved recovery of the threshold voltage shifting of an amorphous silicon TFT-LCD display.
  • the present invention provides an apparatus for recovering a threshold voltage, V th , of thin-film amorphous silicon transistors deposited on a substrate of a display and a gate voltage, V g , is applied to each of the transistors during use causing V th to increase with time, the apparatus comprising: detection means operably coupled to the display for detecting when the display is not in use; and, voltage generation means operably coupled to said detection means for generating a voltage, V g ' , of opposite polarity with respect to V g when the display is not in use, and wherein, said voltage, V g ', is applied to the gates of the transistors of the display only when it is not in use for causing V th to decrease with time thereby maintaining an effective driving voltage for the transaction of the display. An effective driving voltage for the pixel elements of the LCD display is thereby maintained.
  • FIG. 1 is a graph of the threshold voltage shift of a TFT relative to an applied gate voltage
  • FIG. 2 is a graph of the threshold voltage shift of a TFT after 88 hours of operation
  • FIG. 3 is a graph of the threshold voltage recovery of a TFT after a negative 20 volts has been applied for 16 hours.
  • FIG. 4 is a block diagram of an apparatus for controlling the V th in accordance with the present invention.
  • FIG. 2 a typical threshold voltage shift is shown for an amorphous silicon transistor after approximately 88 hours of 30 VAC being applied to the gate. As can be seen in FIG. 2, V th has shifted approximately 5 volts during this
  • FIG. 3 is a graph of the threshold voltage recovery provided by the present invention.
  • FIG. 3 illustrates the recovery of V th to within approximately 0.9 volts of the initial V th after a negative 20 volts was applied to the TFT gates for approximately 16 hours during the time the
  • TFT-LCD display was turned OFF.
  • the threshold voltage can be fully recovered to the original V th if a longer time and/or a higher negative voltage is applied to the gates.
  • the magnitude of the negative DC voltage and the time duration of this negative voltage applied to the gate of the TFT device can be designed according to the display application.
  • FIG. 4 discloses a block diagram of a recovery circuit of the invention.
  • a TFT glass substrate 10 is shown with thin-film transistors 12 deposited thereon.
  • a voltage generator circuit 16 is connected to the gates of TFTs 12.
  • a timer, temperature sensor and detection circuit 18 is connected to temperature sensor 14 and voltage generator circuit 16 for controlling the operation of circuit 16.
  • a circuit 20 is provided for indicating to detection circuit 18 when TFTs 12 are being used.
  • Circuit 20 includes a normally open relay 22 and an ON/OFF switch 24.
  • switch 24 When switch 24 is turned ON, this causes normally open relay 22 to close, thereby enabling detection circuit 18 to activate a timer to begin measuring the use of the LCD display. Also, detection circuit 18 senses when relay 22 is open. Circuit 18 then enables circuit 16 to apply a voltage, V , to the gates of TFTs 12 only when it senses that the LCD display is in the OFF state so as to cause V th to shift in a direction opposite of that caused by V g during the time the LCD display is in the ON state.
  • V voltage
  • the voltage, V g ', applied to the gates of the amorphous silicon transistors 12 can be simply applied for a fixed period of time and at a fixed magnitude to constantly offset the voltage threshold shaft wnenever the LCD is in the OFF state.
  • the novel method of the present invention requires the steps of detecting when the LCD display is in the OFF state and applying a negative voltage to the gates of the TFT transistors only during their OFF state to recover the threshold voltage shift that occurred during the ON state of the LCD display.
  • the method also includes the step of applying a constant value negative voltage to the gates of the TFT transistors during the OFF state of the LCD display for a predetermined period of time.
  • the method further includes the step of applying a negative voltage to the gates of the TFT transistors for a period of time according to the eguation
  • the novel method and apparatus uses a self-generated negative voltage signal in the LCD display units and applies the negative voltage signal to the gate of an amorphous silicon TFT only when the LCD display is turned OFF or is not being used. This method and apparatus will recover the threshold shift of the devices and thus enhance the operation and prolong the useful life of the display.
  • the appropriate voltage and the needed time of application of the voltage to the LCD display in its OFF state can be calculated by circuit 18 which includes the temperature of substrate 10 in order to more accurately calculate the required magnitude and time duration of the voltage V g ' , to be applied to transistors 12. Such calculations may be necessary in an application such as HD-TV projection where the TFT's are exposed to relatively high temperatures.

Abstract

An apparatus is provided for recovery of a threshold voltage, Vth, of thin-film amorphous silicon transistors (12) deposited on a substrate (10) and a gate voltage is applied to each of the transistors (12) during use, causing Vth to shift with time. The apparatus detect when the LCD display (10) is not being used, generates a voltage Vg', of opposite polarity with respect to Vg when the LCD display is not being used, and applies Vg' to the gates of the transistors (12) of the LCD display (10) for causing Vth to shift in a direction opposite to that caused by Vg, thereby maintaining an effective driving voltage for the transistor (12) of the LCD display (10).

Description

APPARATUS FOR RECOVERY OF THRESHOLD VOLTAGE SHIFT IN AMORPHOUS SILICON THIN-FILM TRANSISTOR DEVICE.
The present invention relates generally to a threshold voltage shift recovery apparatus associated with amorphous silicon (a-Si:H) thin-film transistor (TFT) devices. More particularly the invention is directed towards a-Si:H TFT devices used in an LCD display such as data driver and scan driver circuits or in pixel switching elements. Amorphous silicon TFT's have been widely used in active matrix LCD displays because of their good switching characteristics. However, the threshold voltage, Vth, shifting during operation shows instability of the amorphous silicon and hence factors such as temperature and applied voltage can cause its character to change during use of the LCD display. Studies have shown that the time dependence of this threshold voltage shift is due to gate bias voltage. Threshold voltage shift is accelerated when the devices are operated under increasingly higher temperature conditions.
Threshold voltage, Vth, can be defined, when plotted in graphic form, as the voltage, Vg/ of the gate of a TFT along an abscissa intersected by a plot of the sguare root of the TFT drain current, Ids along the ordinate axis. In LCD display operations a gate voltage, Vg, that is greater than the Vth is necessary to give enough current to drive the TFT pixel elements of the LCD display. The shifting of Vth over time, and accelerated with increased temperature, reduces the effective driving voltage between the gate and source and also reduces the source drain current, Ids, which results in the degrading of the LCD TFT display performance.
Therefore, it is very important and desirable to maintain the threshold value, Vth, during the lifetime of the LCD display since the shifting of Vth results in the inability of V to properly open or close the pixel TFTs. For example, within c e amorphous silicon TFT, a threshold voltage shift of 6-to-7 volts may occur when a positive 40 volts DC is applied to the TFT gate for approximately 15 hours at 25°C, as shown in FIG. 1. A Vth shift of approximately 5 volts may occur when a 30 volt AC pulse with a 50% duty cycle is applied to the TFT gate for approximately 88 hours, as shown in FIG. 2. The direction of the threshold voltage shift depends on the sign of the voltage between the gate and source of a given TFT. A negative threshold voltage shifting occurs when a negative DC voltage is applied to the TFT gate for a period of time. For example, in FIG. 1, an approximately negative 2.3 voltage shift of Vth is shown when a negative 20 volts is applied to a TFT gate. The equation commonly used to describe the Vth shift, ΔVth, can be expressed as:
ΔVth = A exp(-Ea/kT) (log t)V
where A is a constant, k is the Boltzmann constant, T is the absolute temperature of the TFT and t is the amount of time a bias Vg has been applied to the gate of the TFT. The values of activation energy, Ea, and parameters α and β are best obtained through experimentation through the well-known method of least square fitting, because the parameters depend on the properties of the amorphous silicon sample and the insulator used in the display.
The above equation clearly shows the dependence of Vth on temperature, time, and gate voltage. One of the theories to explain this phenomenon is to attribute the ΔVth to charge trapping in the nitride. Another theory is the creation of meta-stable Si-dangling bonds in the accumulation layer of the amorphous silicon film.
A voltage shift of about 4 volts has been observed in a TFT-LCD after approximately 10,000 hours of operation at 80°C. In general, to maintain a sufficient driving current, a ΔVth of less than 2 volts is required during the lifetime of the display. In critical applications such as projection TV, the TFTs are under constant high temperature and the ΔVth will be more pronounced in a shorter period of time. Other applications in which a significant ΔVth will be achieved include aviation and automobile applications. In TFT-LCD display operations a high gate voltage, Vg, is necessary to produce enough current to drive the pixel or other elements of the display due to the low mobility of the a-Si TFTs. The shifting of Vth reduces the effective driving voltage between the gate and source and thereby reduces the source drain current. Ids, resulting in a degradation of performance. Therefore, it is highly desirable to maintain a low Vth during the lifetime of the display. There are several known methods for reducing and/or slowing down the shifting of the threshold voltage, Vth. One known method uses high temperature annealing to slow down the threshold voltage shifting by, for example, baking an LCD display in a high temperature oven for a fixed period of time. However, it is impractical and expensive to anneal a TFT-LCD display after it has been assembled.
Another method to control ΔVth is to reduce the applied gate voltage, Vg, since ΔVth is proportional to Vg. However, a high gate voltage is necessary to produce enough current to drive other elements due to the low mobility of the amorphous silicon TFTs. Therefore, a lower gate voltage results in a significant reduction in the performance of the LCD display.
The third method uses a negative biased voltage to "drive back" a positive shifting Vth. This method utilizes applying a gate voltage to a scan line of TFT's while the line is not activated. This method requires complicated analysis in order to minimize the shift of Vth because there are practical limits to the magnitude and duration of the applied negative gate voltage. This is because, for each frame, each scan line has to turn ON within 1/60 of a second. This makes the required circuitry very complex in order to have the Vth shifted properly.
It is, therefore, an object of the present invention to provide an apparatus for an improved recovery of the threshold voltage shifting of an amorphous silicon TFT-LCD display.
It is a further object of the present invention to provide a simple and easily implemented apparatus to reduce the shifting of the threshold voltage. it is a still further object of the present invention to provide an apparatus for recovering the threshold voltage shift while the TFT-LCD display is OFF and not being used.
The present invention provides an apparatus for recovering a threshold voltage, Vth, of thin-film amorphous silicon transistors deposited on a substrate of a display and a gate voltage, Vg, is applied to each of the transistors during use causing Vth to increase with time, the apparatus comprising: detection means operably coupled to the display for detecting when the display is not in use; and, voltage generation means operably coupled to said detection means for generating a voltage, Vg' , of opposite polarity with respect to Vg when the display is not in use, and wherein, said voltage, Vg', is applied to the gates of the transistors of the display only when it is not in use for causing Vth to decrease with time thereby maintaining an effective driving voltage for the transaction of the display. An effective driving voltage for the pixel elements of the LCD display is thereby maintained.
These and other objects of the present invention will be more clearly understood in connection with the accompanying drawings in which: Fig. 1 is a graph of the threshold voltage shift of a TFT relative to an applied gate voltage; FIG. 2 is a graph of the threshold voltage shift of a TFT after 88 hours of operation;
FIG. 3 is a graph of the threshold voltage recovery of a TFT after a negative 20 volts has been applied for 16 hours; and
FIG. 4 is a block diagram of an apparatus for controlling the Vth in accordance with the present invention.
In FIG. 2 a typical threshold voltage shift is shown for an amorphous silicon transistor after approximately 88 hours of 30 VAC being applied to the gate. As can be seen in FIG. 2, Vth has shifted approximately 5 volts during this
88 hours of use.
FIG. 3 is a graph of the threshold voltage recovery provided by the present invention. FIG. 3 illustrates the recovery of Vth to within approximately 0.9 volts of the initial Vth after a negative 20 volts was applied to the TFT gates for approximately 16 hours during the time the
TFT-LCD display was turned OFF. The threshold voltage can be fully recovered to the original Vth if a longer time and/or a higher negative voltage is applied to the gates.
The magnitude of the negative DC voltage and the time duration of this negative voltage applied to the gate of the TFT device can be designed according to the display application.
FIG. 4 discloses a block diagram of a recovery circuit of the invention. A TFT glass substrate 10 is shown with thin-film transistors 12 deposited thereon. A temperature sensor 14, which is preferably a thermocouple, diode or resistive sensor, is shown within substrate 10 and can be deposited either directly on substrate 10 or attached within the display such that the sensor is adjacent to substrate 10. A voltage generator circuit 16 is connected to the gates of TFTs 12. A timer, temperature sensor and detection circuit 18 is connected to temperature sensor 14 and voltage generator circuit 16 for controlling the operation of circuit 16. A circuit 20 is provided for indicating to detection circuit 18 when TFTs 12 are being used. Circuit 20 includes a normally open relay 22 and an ON/OFF switch 24. When switch 24 is turned ON, this causes normally open relay 22 to close, thereby enabling detection circuit 18 to activate a timer to begin measuring the use of the LCD display. Also, detection circuit 18 senses when relay 22 is open. Circuit 18 then enables circuit 16 to apply a voltage, V , to the gates of TFTs 12 only when it senses that the LCD display is in the OFF state so as to cause Vth to shift in a direction opposite of that caused by Vg during the time the LCD display is in the ON state.
During use of the invention, the voltage, Vg', applied to the gates of the amorphous silicon transistors 12 can be simply applied for a fixed period of time and at a fixed magnitude to constantly offset the voltage threshold shaft wnenever the LCD is in the OFF state.
The novel method of the present invention requires the steps of detecting when the LCD display is in the OFF state and applying a negative voltage to the gates of the TFT transistors only during their OFF state to recover the threshold voltage shift that occurred during the ON state of the LCD display. The method also includes the step of applying a constant value negative voltage to the gates of the TFT transistors during the OFF state of the LCD display for a predetermined period of time.
In an alternate embodiment, the method further includes the step of applying a negative voltage to the gates of the TFT transistors for a period of time according to the eguation
ΔVth = A exp(-Ea/kT) (log t)V.
Thus, there has been disclosed a novel method and apparatus relating to the threshold voltage shift recovery that is associated with amorphous silicon TFT devices.
Particularly when the devices are used in the LCD display in the data driver and the scan driver circuits or in the pixel switching elements. The novel method and apparatus uses a self-generated negative voltage signal in the LCD display units and applies the negative voltage signal to the gate of an amorphous silicon TFT only when the LCD display is turned OFF or is not being used. This method and apparatus will recover the threshold shift of the devices and thus enhance the operation and prolong the useful life of the display. However, in a more sophisticated application, the appropriate voltage and the needed time of application of the voltage to the LCD display in its OFF state can be calculated by circuit 18 which includes the temperature of substrate 10 in order to more accurately calculate the required magnitude and time duration of the voltage Vg' , to be applied to transistors 12. Such calculations may be necessary in an application such as HD-TV projection where the TFT's are exposed to relatively high temperatures.

Claims

1. An apparatus for recovering a threshold voltage, Vth, of thin-film amorphous silicon transistors (12) deposited on a substrate (10) of a display and a gate voltage, Vg, is applied to each of the transistors during use causing Vth to increase with time, the apparatus comprising: detection means (18) operably coupled to the display for detecting when the display is not in use; and, voltage generation means (16) operably coupled to the detection means for generating a voltage, Vg', of opposite polarity with respect to Vg when the display is not in use, wherein, the voltage, Vg', is applied to the gates of the transistors of the display only when it is not in use for causing Vth to decrease with time thereby maintaining an effective driving voltage for the transaction of the display.
2. An apparatus according to claim l, wherein: the detection means (16) includes means for detecting the amount of time the display (10) is in use; and the voltage, Vg'( is applied to the transistor gates
(12) only when the display is not in use for an amount of time and at a magnitude proportional to the amount of time the display was in use.
3. An apparatus according to claim 2, wherein: the detection means (16) includes means for detecting the temperature of the display (10) during its time of use; and the voltage, V ', is applied for an amount of time and at a magnitude proportional to the temperature of the display during its time of use.
4. An apparatus according to claim 3, wherein the temperature detection means (16) includes a temperature sensor (14) deposited on the display substrate (10) .
5. An apparatus according to claim 3, wherein the temperature detection means (16) includes a temperature sensor adjacent the display substrate.
6. An apparatus according to claim 5, wherein the temperature sensor (14) is one taken from the group consisting of thermocouple, diode and resistance sensors.
7. An apparatus according to claim 1, wherein the voltage generation (18) means includes a battery power supply.
8. An apparatus according to any one of the preceding claims, wherein the display (10) is an LCD.
PCT/GB1994/000467 1993-04-30 1994-03-10 Apparatus for recovery of threshold voltage shift in amorphous silicon thin-film transistor device WO1994025954A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU61500/94A AU6150094A (en) 1993-04-30 1994-03-10 Apparatus for recovery of threshold voltage shift in amorphous silicon thin-film transistor device

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US5568893A 1993-04-30 1993-04-30
US055,688 1993-04-30

Publications (1)

Publication Number Publication Date
WO1994025954A1 true WO1994025954A1 (en) 1994-11-10

Family

ID=21999534

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1994/000467 WO1994025954A1 (en) 1993-04-30 1994-03-10 Apparatus for recovery of threshold voltage shift in amorphous silicon thin-film transistor device

Country Status (5)

Country Link
JP (1) JPH06347753A (en)
CN (1) CN1122165A (en)
AU (1) AU6150094A (en)
TW (1) TW241357B (en)
WO (1) WO1994025954A1 (en)

Cited By (39)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0731441A2 (en) * 1995-03-06 1996-09-11 THOMSON multimedia A liquid crystal display driver with threshold voltage drift compensation
EP0731443A1 (en) * 1995-03-06 1996-09-11 THOMSON multimedia An amplifier with pixel voltage compensation for a display
WO2003017241A2 (en) * 2001-08-15 2003-02-27 Ignis Innovation Inc. Integrated multiplexer/de-multiplexer for active-matrix display/imaging arrays
WO2004039059A1 (en) * 2002-10-24 2004-05-06 Sharp Kabushiki Kaisha Image reading device and image reading method
US6872974B2 (en) * 2001-11-20 2005-03-29 International Business Machines Corporation Low threshold voltage instability amorphous silicon field effect transistor structure and biasing for active matrix organic light-emitting diodes
WO2005073951A1 (en) * 2004-01-29 2005-08-11 Koninklijke Philips Electronics N.V. Active matrix display device
EP1843316A2 (en) * 2006-04-04 2007-10-10 Samsung Electronics Co., Ltd. Display device and driving method thereof
US7714810B2 (en) 2003-05-19 2010-05-11 Seiko Epson Corporation Electro-optical apparatus and method of driving the electro-optical apparatus
US8497823B2 (en) 2002-01-24 2013-07-30 Semiconductor Energy Laboratory Co., Ltd. Semiconductor device and method of driving the semiconductor device
US8890220B2 (en) 2001-02-16 2014-11-18 Ignis Innovation, Inc. Pixel driver circuit and pixel circuit having control circuit coupled to supply voltage
US8901579B2 (en) 2011-08-03 2014-12-02 Ignis Innovation Inc. Organic light emitting diode and method of manufacturing
USRE45291E1 (en) 2004-06-29 2014-12-16 Ignis Innovation Inc. Voltage-programming scheme for current-driven AMOLED displays
US9070775B2 (en) 2011-08-03 2015-06-30 Ignis Innovations Inc. Thin film transistor
US9134825B2 (en) 2011-05-17 2015-09-15 Ignis Innovation Inc. Systems and methods for display systems with dynamic power control
US9153172B2 (en) 2004-12-07 2015-10-06 Ignis Innovation Inc. Method and system for programming and driving active matrix light emitting device pixel having a controllable supply voltage
US9373645B2 (en) 2005-01-28 2016-06-21 Ignis Innovation Inc. Voltage programmed pixel circuit, display system and driving method thereof
US9385169B2 (en) 2011-11-29 2016-07-05 Ignis Innovation Inc. Multi-functional active matrix organic light-emitting diode display
US9472138B2 (en) 2003-09-23 2016-10-18 Ignis Innovation Inc. Pixel driver circuit with load-balance in current mirror circuit
US9502653B2 (en) 2013-12-25 2016-11-22 Ignis Innovation Inc. Electrode contacts
US9606607B2 (en) 2011-05-17 2017-03-28 Ignis Innovation Inc. Systems and methods for display systems with dynamic power control
US9633597B2 (en) 2006-04-19 2017-04-25 Ignis Innovation Inc. Stable driving scheme for active matrix displays
US9792870B2 (en) 2012-05-28 2017-10-17 Panasonic Liquid Crystal Display Co., Ltd. Liquid crystal display device
US9818376B2 (en) 2009-11-12 2017-11-14 Ignis Innovation Inc. Stable fast programming scheme for displays
US9842889B2 (en) 2014-11-28 2017-12-12 Ignis Innovation Inc. High pixel density array architecture
US9934725B2 (en) 2013-03-08 2018-04-03 Ignis Innovation Inc. Pixel circuits for AMOLED displays
US9952698B2 (en) 2013-03-15 2018-04-24 Ignis Innovation Inc. Dynamic adjustment of touch resolutions on an AMOLED display
US10089924B2 (en) 2011-11-29 2018-10-02 Ignis Innovation Inc. Structural and low-frequency non-uniformity compensation
US10163996B2 (en) 2003-02-24 2018-12-25 Ignis Innovation Inc. Pixel having an organic light emitting diode and method of fabricating the pixel
US10176752B2 (en) 2014-03-24 2019-01-08 Ignis Innovation Inc. Integrated gate driver
US10204540B2 (en) 2015-10-26 2019-02-12 Ignis Innovation Inc. High density pixel pattern
US10373554B2 (en) 2015-07-24 2019-08-06 Ignis Innovation Inc. Pixels and reference circuits and timing techniques
US10410579B2 (en) 2015-07-24 2019-09-10 Ignis Innovation Inc. Systems and methods of hybrid calibration of bias current
US10586491B2 (en) 2016-12-06 2020-03-10 Ignis Innovation Inc. Pixel circuits for mitigation of hysteresis
US10657895B2 (en) 2015-07-24 2020-05-19 Ignis Innovation Inc. Pixels and reference circuits and timing techniques
US10714018B2 (en) 2017-05-17 2020-07-14 Ignis Innovation Inc. System and method for loading image correction data for displays
US10867569B2 (en) 2017-03-23 2020-12-15 Panasonic Liquid Crystal Display Co., Ltd. Display device
US10971078B2 (en) 2018-02-12 2021-04-06 Ignis Innovation Inc. Pixel measurement through data line
US10997901B2 (en) 2014-02-28 2021-05-04 Ignis Innovation Inc. Display system
US11025899B2 (en) 2017-08-11 2021-06-01 Ignis Innovation Inc. Optical correction systems and methods for correcting non-uniformity of emissive display devices

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
TW573290B (en) 2000-04-10 2004-01-21 Sharp Kk Driving method of image display apparatus, driving apparatus of image display apparatus, and image display apparatus
JP2001337650A (en) * 2000-05-24 2001-12-07 Canon Inc Liquid crystal display equipment with built-in memory means
JP3990167B2 (en) * 2002-03-04 2007-10-10 Ｎｅｃ液晶テクノロジー株式会社 Liquid crystal display device driving method and liquid crystal display device using the driving method
TWI254898B (en) * 2003-10-02 2006-05-11 Pioneer Corp Display apparatus with active matrix display panel and method for driving same
KR20050080318A (en) * 2004-02-09 2005-08-12 삼성전자주식회사 Method for driving of transistor, and driving elementusing, display panel and display device using the same
KR101172498B1 (en) * 2005-06-01 2012-08-10 삼성전자주식회사 Method for manufacturing liquid crystal display apparatus, liquid crystal display apparatus and aging system
CN100388342C (en) * 2005-06-06 2008-05-14 友达光电股份有限公司 Active type display device driving method

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4319237A (en) * 1979-02-14 1982-03-09 Matsushita Electric Industrial Co., Ltd. Brightness adjusting circuit of liquid crystal matrix panel for picture display

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4319237A (en) * 1979-02-14 1982-03-09 Matsushita Electric Industrial Co., Ltd. Brightness adjusting circuit of liquid crystal matrix panel for picture display

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Y.FUJIMOTO: "Study of the Vth shift of the thin-film transistor by the bias temperature stress test", IBM JOURNAL OF RESEARCH AND DEVELOPMENT, vol. 36, no. 1, January 1992 (1992-01-01), NEW YORK US, pages 76 - 82 *

Cited By (74)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0731441A2 (en) * 1995-03-06 1996-09-11 THOMSON multimedia A liquid crystal display driver with threshold voltage drift compensation
EP0731443A1 (en) * 1995-03-06 1996-09-11 THOMSON multimedia An amplifier with pixel voltage compensation for a display
EP0731441A3 (en) * 1995-03-06 1996-10-02 Thomson Multimedia Sa
US5701136A (en) * 1995-03-06 1997-12-23 Thomson Consumer Electronics S.A. Liquid crystal display driver with threshold voltage drift compensation
AU709232B2 (en) * 1995-03-06 1999-08-26 Thomson Multimedia S.A. Amplifier with pixel voltage compensation for a display
US8890220B2 (en) 2001-02-16 2014-11-18 Ignis Innovation, Inc. Pixel driver circuit and pixel circuit having control circuit coupled to supply voltage
WO2003017241A3 (en) * 2001-08-15 2003-05-22 Ignis Innovation Inc Integrated multiplexer/de-multiplexer for active-matrix display/imaging arrays
US7573452B2 (en) 2001-08-15 2009-08-11 Ignis Innovation Inc. Integrated multiplexer/de-multiplexer for active-matrix display/imaging arrays
WO2003017241A2 (en) * 2001-08-15 2003-02-27 Ignis Innovation Inc. Integrated multiplexer/de-multiplexer for active-matrix display/imaging arrays
US6872974B2 (en) * 2001-11-20 2005-03-29 International Business Machines Corporation Low threshold voltage instability amorphous silicon field effect transistor structure and biasing for active matrix organic light-emitting diodes
US11121203B2 (en) 2002-01-24 2021-09-14 Semiconductor Energy Laboratory Co., Ltd. Semiconductor device and method of driving the semiconductor device
US9450036B2 (en) 2002-01-24 2016-09-20 Semiconductor Energy Laboratory Co., Ltd. Semiconductor device and method of driving the semiconductor device
US8994622B2 (en) 2002-01-24 2015-03-31 Semiconductor Energy Laboratory Co., Ltd. Semiconductor device and method of driving the semiconductor device
US8497823B2 (en) 2002-01-24 2013-07-30 Semiconductor Energy Laboratory Co., Ltd. Semiconductor device and method of driving the semiconductor device
US10355068B2 (en) 2002-01-24 2019-07-16 Semiconductor Energy Laboratory Co., Ltd. Semiconductor device and method of driving the semiconductor device
WO2004039059A1 (en) * 2002-10-24 2004-05-06 Sharp Kabushiki Kaisha Image reading device and image reading method
US7388184B2 (en) 2002-10-24 2008-06-17 Sharp Kabushiki Kaisha Image reading device and image reading method
US10163996B2 (en) 2003-02-24 2018-12-25 Ignis Innovation Inc. Pixel having an organic light emitting diode and method of fabricating the pixel
US8130176B2 (en) 2003-05-19 2012-03-06 Seiko Epson Corporation Electro-optical apparatus and method of driving the electro-optical apparatus
US8188943B2 (en) 2003-05-19 2012-05-29 Seiko Epson Corporation Electro-optical apparatus and method of driving the electro-optical apparatus
US7714810B2 (en) 2003-05-19 2010-05-11 Seiko Epson Corporation Electro-optical apparatus and method of driving the electro-optical apparatus
US8643573B2 (en) 2003-05-19 2014-02-04 Seiko Epson Corporation Electro-optical apparatus and method of driving the electro-optical apparatus
US10089929B2 (en) 2003-09-23 2018-10-02 Ignis Innovation Inc. Pixel driver circuit with load-balance in current mirror circuit
US9472138B2 (en) 2003-09-23 2016-10-18 Ignis Innovation Inc. Pixel driver circuit with load-balance in current mirror circuit
US7804476B2 (en) 2004-01-29 2010-09-28 Tpo Hong Kong Holding Limited Active matrix display device
CN100452165C (en) * 2004-01-29 2009-01-14 统宝香港控股有限公司 Active matrix display device
WO2005073951A1 (en) * 2004-01-29 2005-08-11 Koninklijke Philips Electronics N.V. Active matrix display device
USRE45291E1 (en) 2004-06-29 2014-12-16 Ignis Innovation Inc. Voltage-programming scheme for current-driven AMOLED displays
USRE47257E1 (en) 2004-06-29 2019-02-26 Ignis Innovation Inc. Voltage-programming scheme for current-driven AMOLED displays
US9153172B2 (en) 2004-12-07 2015-10-06 Ignis Innovation Inc. Method and system for programming and driving active matrix light emitting device pixel having a controllable supply voltage
US9373645B2 (en) 2005-01-28 2016-06-21 Ignis Innovation Inc. Voltage programmed pixel circuit, display system and driving method thereof
US9728135B2 (en) 2005-01-28 2017-08-08 Ignis Innovation Inc. Voltage programmed pixel circuit, display system and driving method thereof
US7965263B2 (en) 2006-04-04 2011-06-21 Samsung Electronics Co., Ltd. Display device and driving method thereof
EP1843316A3 (en) * 2006-04-04 2009-04-08 Samsung Electronics Co., Ltd. Display device and driving method thereof
EP1843316A2 (en) * 2006-04-04 2007-10-10 Samsung Electronics Co., Ltd. Display device and driving method thereof
US9633597B2 (en) 2006-04-19 2017-04-25 Ignis Innovation Inc. Stable driving scheme for active matrix displays
US10453397B2 (en) 2006-04-19 2019-10-22 Ignis Innovation Inc. Stable driving scheme for active matrix displays
US10127860B2 (en) 2006-04-19 2018-11-13 Ignis Innovation Inc. Stable driving scheme for active matrix displays
US9818376B2 (en) 2009-11-12 2017-11-14 Ignis Innovation Inc. Stable fast programming scheme for displays
US10685627B2 (en) 2009-11-12 2020-06-16 Ignis Innovation Inc. Stable fast programming scheme for displays
US10249237B2 (en) 2011-05-17 2019-04-02 Ignis Innovation Inc. Systems and methods for display systems with dynamic power control
US9134825B2 (en) 2011-05-17 2015-09-15 Ignis Innovation Inc. Systems and methods for display systems with dynamic power control
US9606607B2 (en) 2011-05-17 2017-03-28 Ignis Innovation Inc. Systems and methods for display systems with dynamic power control
US9224954B2 (en) 2011-08-03 2015-12-29 Ignis Innovation Inc. Organic light emitting diode and method of manufacturing
US8901579B2 (en) 2011-08-03 2014-12-02 Ignis Innovation Inc. Organic light emitting diode and method of manufacturing
US9070775B2 (en) 2011-08-03 2015-06-30 Ignis Innovations Inc. Thin film transistor
US9818806B2 (en) 2011-11-29 2017-11-14 Ignis Innovation Inc. Multi-functional active matrix organic light-emitting diode display
US10453904B2 (en) 2011-11-29 2019-10-22 Ignis Innovation Inc. Multi-functional active matrix organic light-emitting diode display
US10079269B2 (en) 2011-11-29 2018-09-18 Ignis Innovation Inc. Multi-functional active matrix organic light-emitting diode display
US10089924B2 (en) 2011-11-29 2018-10-02 Ignis Innovation Inc. Structural and low-frequency non-uniformity compensation
US9385169B2 (en) 2011-11-29 2016-07-05 Ignis Innovation Inc. Multi-functional active matrix organic light-emitting diode display
US10147379B2 (en) 2012-05-28 2018-12-04 Panasonic Liquid Crystal Display Co., Ltd. Liquid crystal display device
US9940890B2 (en) 2012-05-28 2018-04-10 Panasonic Liquid Crystal Display Co., Ltd. Liquid crystal display device
US9792870B2 (en) 2012-05-28 2017-10-17 Panasonic Liquid Crystal Display Co., Ltd. Liquid crystal display device
US10424263B2 (en) 2012-05-28 2019-09-24 Panasonic Liquid Crystal Display Co., Ltd. Liquid crystal display device
US9934725B2 (en) 2013-03-08 2018-04-03 Ignis Innovation Inc. Pixel circuits for AMOLED displays
US9952698B2 (en) 2013-03-15 2018-04-24 Ignis Innovation Inc. Dynamic adjustment of touch resolutions on an AMOLED display
US9831462B2 (en) 2013-12-25 2017-11-28 Ignis Innovation Inc. Electrode contacts
US9502653B2 (en) 2013-12-25 2016-11-22 Ignis Innovation Inc. Electrode contacts
US10997901B2 (en) 2014-02-28 2021-05-04 Ignis Innovation Inc. Display system
US10176752B2 (en) 2014-03-24 2019-01-08 Ignis Innovation Inc. Integrated gate driver
US9842889B2 (en) 2014-11-28 2017-12-12 Ignis Innovation Inc. High pixel density array architecture
US10170522B2 (en) 2014-11-28 2019-01-01 Ignis Innovations Inc. High pixel density array architecture
US10410579B2 (en) 2015-07-24 2019-09-10 Ignis Innovation Inc. Systems and methods of hybrid calibration of bias current
US10657895B2 (en) 2015-07-24 2020-05-19 Ignis Innovation Inc. Pixels and reference circuits and timing techniques
US10373554B2 (en) 2015-07-24 2019-08-06 Ignis Innovation Inc. Pixels and reference circuits and timing techniques
US10204540B2 (en) 2015-10-26 2019-02-12 Ignis Innovation Inc. High density pixel pattern
US10586491B2 (en) 2016-12-06 2020-03-10 Ignis Innovation Inc. Pixel circuits for mitigation of hysteresis
US10867569B2 (en) 2017-03-23 2020-12-15 Panasonic Liquid Crystal Display Co., Ltd. Display device
US10714018B2 (en) 2017-05-17 2020-07-14 Ignis Innovation Inc. System and method for loading image correction data for displays
US11025899B2 (en) 2017-08-11 2021-06-01 Ignis Innovation Inc. Optical correction systems and methods for correcting non-uniformity of emissive display devices
US11792387B2 (en) 2017-08-11 2023-10-17 Ignis Innovation Inc. Optical correction systems and methods for correcting non-uniformity of emissive display devices
US10971078B2 (en) 2018-02-12 2021-04-06 Ignis Innovation Inc. Pixel measurement through data line
US11847976B2 (en) 2018-02-12 2023-12-19 Ignis Innovation Inc. Pixel measurement through data line

Also Published As

Publication number Publication date
TW241357B (en) 1995-02-21
CN1122165A (en) 1996-05-08
AU6150094A (en) 1994-11-21
JPH06347753A (en) 1994-12-22

Similar Documents

Publication Publication Date Title
WO1994025954A1 (en) Apparatus for recovery of threshold voltage shift in amorphous silicon thin-film transistor device
KR101166424B1 (en) Thin film transistor circuit, light emitting display apparatus, and driving method thereof
US8907876B2 (en) Pixel circuit, image display apparatus, driving method therefor and driving method of electronic device
Chiang et al. Electrical instability of hydrogenated amorphous silicon thin-film transistors for active-matrix liquid-crystal displays
KR101138272B1 (en) Thin-film transistor circuit, driving method thereof, and light-emitting display apparatus
Lee et al. A new poly-Si TFT current-mirror pixel for active matrix organic light emitting diode
JP2003302936A (en) Display device, oled panel, device and method for controlling thin film transistor, and method for controlling oled display
US9244315B2 (en) Active matrix display device
CN109949759B (en) Scanning signal compensation method, scanning signal compensation circuit and display
KR100316432B1 (en) Method and apparatus for real-time on-off contrast ratio optimization in liquid crystal displays
WO1997032297A1 (en) Method and system for the reduction of off-state current in field-effect transistors
US9460653B2 (en) Flat panel display
US11112628B2 (en) Liquid crystal display device including common electrode control circuit
Ibaraki et al. Threshold voltage instability of a-Si: H TFTs in liquid crystal displays
WO2000023848A1 (en) Ferroelectric liquid crystal display, and its driving method
Lebrun et al. 15.4: Invited Paper: Design of integrated Drivers with Amorphous Silicon TFTs for Small Displays. Basic Concepts
Oh et al. A novel gate driver circuit for depletion‐mode a‐IGZO TFTs
US20060289535A1 (en) Method of driving organic light-emitting element, display panel for driving the same and display device having the same
WO2019015184A1 (en) Threshold voltage regulator circuit and liquid crystal display device
Kuo et al. Thin film transistors as driving devices for attached devices
Lemmi et al. The leakage currents of amorphous silicon thin-film transistors: Injection currents, back channel currents and stress effects
Guo et al. P‐6: Reliability of Low Temperature Poly‐Si Thin Film Transistor
Han et al. P‐40: High Reliability Gate Driver Using Reverse Bias Method with Oxide TFTs
Zhang et al. Degradation Behaviors of Driving Thin-Film Transistors in Active-Matrix Organic Light-Emitting Diode Displays
Jung et al. Driving method compensating for the hysteresis of polycrystalline silicon thin-film transistors for active-matrix organic light-emitting diode displays

Legal Events

Date Code Title Description
WWE Wipo information: entry into national phase

Ref document number: 94191947.1

Country of ref document: CN

AK Designated states

Kind code of ref document: A1

Designated state(s): AT AU BB BG BR BY CA CH CN CZ DE DK ES FI GB HU JP KP KR KZ LK LU LV MG MN MW NL NO NZ PL PT RO RU SD SE SI SK TT UA UZ VN

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FR GB GR IE IT LU MC NL PT SE BF BJ CF CG CI CM GA GN ML MR NE SN TD TG

DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
121 Ep: the epo has been informed by wipo that ep was designated in this application
REG Reference to national code

Ref country code: DE

Ref legal event code: 8642

122 Ep: pct application non-entry in european phase
NENP Non-entry into the national phase

Ref country code: CA