Display panel inspecting method and display panel fabricating method
A method for inspecting a display panel in which pixels each including a drive transistor that passes a drive current when signal voltage is applied to the gate of the drive transistor, and a light-emitting element that emits light according to the flow of the drive current are arranged in rows and columns, includes: applying, across the gate and the source of the drive transistor, an initialization voltage less than or equal to the threshold voltage of the drive transistor; applying a power supply voltage to the drain of the drive transistor to which the initialization voltage is applied across the gate and the source; and determining, as a defective pixel with a current leak, a pixel having a light-emitting element that does not emit light when the power supply voltage is applied to the drain of the drive transistor and emits light after the elapse of a predetermined period.
1. A display panel inspecting method for inspecting a display panel in which pixels are arranged in rows and columns,
the pixels each including
a drive transistor that passes a drive current when a signal voltage reflecting an image signal is applied to a gate of the drive transistor, the drive current corresponding to the signal voltage;
a light-emitting element that emits light when the drive current flows through the light-emitting element, the light having a brightness corresponding to the drive current; and
at least one switching transistor having a source and a drain, the drain is connected to the gate of the drive transistor,
the display panel inspecting method comprising:
(A) applying an initialization voltage across the gate and a source of the drive transistor, the initialization voltage being less than or equal to a threshold voltage of the drive transistor;
(B) applying a power supply voltage for generating the drive current to one of the source and a drain of the drive transistor in a state where the initialization voltage is applied across the gate and the source of the drive transistor, or applying an inspecting voltage to the other of the source and the drain of the switch transistor or the gate of the switch transistor, the inspecting voltage, when applied to the gate of the drive transistor, causing a gate-source voltage of the drive transistor to be greater than or equal to the threshold voltage; and
(C) determining, as being a defective pixel with a current leak, a pixel, among the pixels, which has the light-emitting element that does not emit light at a moment when (B) is executed and emits light after an elapse of a predetermined period from the moment,
wherein the predetermined period is a period that is longer than one frame period.
2. The display panel inspecting method according to claim 1 ,
wherein the predetermined period is longer than one frame period in which all of the pixels are scanned.
3. The display panel inspecting method according to claim 1 ,
wherein the at least one switching transistor includes (i) a selection transistor having a source and a drain, the drain is connected to the gate of the drive transistor and the source is connected to a data line that transmits the signal voltage, and (ii) a reference transistor having a source and a drain, the drain is connected to the gate of the drive transistor and the source is connected to a reference power supply line for detecting the threshold voltage,
in (B), the power supply voltage is applied to the one of the source and the drain of the drive transistor in a state where the selection transistor and the reference transistor are placed in a non-conducting state and a voltage of the data line is set to a voltage with which the light-emitting element does not emit light, and
in (C), the drive transistor included in the pixel having the light-emitting element that does not emit light when the power supply voltage is applied to the one of the source and the drain of the drive transistor and emits light after the elapse of the predetermined period from when the power supply voltage is applied, is determined as being defective with the current leak.
4. The display panel inspecting method according to claim 1 ,
wherein the switch transistor includes a selection transistor having a source and a drain, one of which is connected to the gate of the drive transistor and the other of which is connected to a data line that transmits the signal voltage,
in (B), the selection transistor is placed in a conducting state by applying the inspecting voltage to the gate of the selection transistor in a state where the power supply voltage is applied to the one of the source or the drain of the drive transistor and a voltage of the data line is set to a voltage with which the light-emitting element does not emit light, and
in (C), the selection transistor included in the pixel having the light-emitting element that does not emit light when the inspecting voltage is applied to the gate of the selection transistor and emits light after the elapse of the predetermined period from when the inspecting voltage is applied, is determined as being defective with the current leak occurring between the source and the gate or between the drain and the gate.
5. The display panel inspecting method according to claim 4 ,
wherein in (B), the selection transistor is intermittently placed in the conducting state by continuously applying a pulse signal, as the inspecting voltage, to a gate of the selection transistor, the pulse signal having, as a pulse width, a period that is at least double one horizontal scanning period in row-by-row scanning.
6. The display panel inspecting method according to claim 1 ,
wherein the at least one switching transistor includes a reference transistor having a source and a drain, the drain is connected to the gate of the drive transistor and the source is connected to a reference power supply line different from a data line that transmits the signal voltage,
in (B), the reference transistor is placed in a conducting state by applying the inspecting voltage to a gate of the reference transistor in a state where the power supply voltage is applied to the one of the source or the drain of the drive transistor, and
in (C), the reference transistor included in the pixel having the light-emitting element that does not emit light when the inspecting voltage is applied to the gate of the reference transistor and emits light after the elapse of the predetermined period from when the inspecting voltage is applied, is determined as being defective with the current leak occurring between the source and the gate or between the drain and the gate.
7. The display panel inspecting method according to claim 6 ,
wherein in (B), the reference transistor is intermittently placed in the conducting state by continuously applying a pulse signal, as the inspecting voltage, to a gate of the reference transistor, the pulse signal having, as a pulse width, a period that is at least double one horizontal scanning period in row-by-row scanning.
8. The display panel inspecting method according to claim 1 ,
wherein the at least one switching transistor includes (i) a selection transistor having a source and a drain, the drain is connected to the gate of the drive transistor and the source is connected to a data line that transmits the signal voltage, and (ii) a reference transistor having a source and a drain, the drain is connected to the gate of the drive transistor and the source is connected to a reference power supply line for detecting the threshold voltage,
in (B), a voltage of the data line is set to the inspecting voltage in a state where the selection transistor and the reference transistor are placed in a non-conducting state and the power supply voltage is applied to the one of the source and the drain of the drive transistor, and
in (C), the selection transistor included in the pixel having the light-emitting element that does not emit light at a moment when the voltage of the data line is set to the inspecting voltage and emits light after the elapse of the predetermined period from the moment, is determined as being defective with the current leak occurring between the source and the drain.
9. The display panel inspecting method according to claim 1 ,
wherein the at least one switching transistor includes (i) a selection transistor having a source and a drain, the drain is connected to the gate of the drive transistor and the source is connected to a data line that transmits the signal voltage, and (ii) a reference transistor having a source and a drain, the drain is connected to the gate of the drive transistor and the source is connected to a reference power supply line for detecting the threshold voltage,
in (B), a voltage of the reference power supply line is set to the inspecting voltage in a state where the selection transistor and the reference transistor are placed in a non-conducting state and the power supply voltage is applied to the one of the source and the drain of the drive transistor, and
in (C), the reference transistor included in the pixel having the light-emitting element that does not emit light at a moment when the voltage of the reference power supply line is set to the inspecting voltage and emits light after the elapse of the predetermined period from the moment, is determined as being defective with the current leak occurring between the source and the drain.
10. A display panel fabricating method comprising:
forming, above a substrate:
a drive transistor that passes a drive current to a source and a drain when a signal voltage reflecting an image signal is applied to a gate of the drive transistor, the drive current corresponding to the signal voltage;
a light-emitting element that emits light when the drive current flows to the light-emitting element, the light having a brightness corresponding to the drive current; and
at least one switching transistor having one of a source and a drain, wherein the drain is connected to the gate of the drive transistor; and
the display panel inspecting method according to claim 1 .