Display device and method for correcting signal voltage using determined threshold voltage shift

1. A display device, comprising:

a display including light-emitting pixels each of which includes a light-emitting element and a drive transistor, the drive transistor including a gate electrode, a source electrode and a drain electrode, and being configured to supply a current to the light-emitting element to cause the light-emitting element to emit light;

a signal line driving circuit configured to supply a signal voltage applied between the gate electrode and the source electrode of the drive transistor;

a memory that stores correction data including a representative drive transistor threshold voltage deterioration curve, characteristics of the drive transistor of each light-emitting pixel, and an accumulated stress of the drive transistor of each light-emitting pixel; and

a control circuit configured to

calculate, using the correction data stored in the memory, an amount of threshold voltage shift of the drive transistor on the basis of an amount of deterioration of a threshold voltage of the drive transistor during a deterioration period in which the signal voltage is kept at a value that is not zero and an amount of recovery of the threshold voltage of the drive transistor during a recovery period in which the signal voltage is kept at zero;

refer to a representative deterioration curve that shows a relationship between an application time of the signal voltage and the amount of threshold voltage shift in a case where the signal voltage is a predetermined reference voltage;

store, as an accumulated converted time, a value of the application time that corresponds to the amount of threshold voltage shift on the representative deterioration curve;

convert a duration of the deterioration period into a converted time that is a time required for deteriorating the threshold voltage of the drive transistor by the amount of deterioration in a case where the signal voltage is the reference voltage;

calculate the accumulated converted time at an end of the deterioration period by adding the converted time to the accumulated converted time at a start of the deterioration period;

calculate the amount of threshold voltage shift at the end of the deterioration period by calculating a value of the amount of threshold voltage shift that corresponds to the accumulated converted time at the end of the deterioration period on the representative deterioration curve; and

correct the signal voltage in accordance with the amount of threshold voltage shift.

2. The display device according to claim 1 ,

wherein the control circuit is configured to:

calculate the amount of threshold voltage shift at an end of the recovery period by subtracting the amount of recovery from the amount of threshold voltage shift at a start of the recovery period; and

calculate the accumulated converted time at the end of the recovery period by calculating a value of the application time that corresponds to the amount of threshold voltage shift at the end of the recovery period on the representative deterioration curve.

3. The display device according to claim 1 ,

wherein the control circuit is configured to:

convert the duration t d of the deterioration period into the converted time t d _ ref in accordance with the following equation:

t

d

⁢

⁢

_

⁢

⁢

ref

=

(

V

gs

⁢

⁢

_

⁢

⁢

ref

-

V

th

⁢

⁢

0

+

V

offset

V

gs

⁢

⁢

_

⁢

⁢

d

-

V

th

⁢

⁢

0

+

V

offset

)

-

α

β

⁢

t

d

where t d _ ref is the converted time, V gs _ ref is the reference voltage, V gs _ d is the signal voltage, V th0 is the threshold voltage of the drive transistor before application of the signal voltage, and α, β, and V offset are predetermined constants; and

calculate the amount of deterioration ΔV th _ d in accordance with the following equations:

Δ

⁢

⁢

V

th

⁢

⁢

_

⁢

⁢

d

=

A

⁡

(

V

gs

⁢

⁢

_

⁢

⁢

ref

-

V

th

⁢

⁢

0

+

V

offset

)

α

⁢

t

d

⁢

⁢

_

⁢

⁢

ref

β

and

A

=

A

0

⁢

exp

(

-

E

a

kT

)

where A 0 is a constant, E a is activation energy of the threshold voltage shift, k is a Boltzmann constant, and T is temperature.

4. A display device, comprising:

a display including light-emitting pixels each of which includes a light-emitting element and a drive transistor, the drive transistor including a gate electrode, a source electrode and a drain electrode, and being configured to supply a current to the light-emitting element to cause the light-emitting element to emit light;

a signal line driving circuit configured to supply a signal voltage applied between the gate electrode and the source electrode of the drive transistor;

a memory that stores correction data including a representative drive transistor threshold voltage deterioration curve, characteristics of the drive transistor of each light-emitting pixel, and an accumulated stress of the drive transistor of each light-emitting pixel; and

a control circuit configured to

calculate, using the correction data stored in the memory, an amount of threshold voltage shift of the drive transistor on the basis of an amount of deterioration of a threshold voltage of the drive transistor during a deterioration period in which the signal voltage is kept at a value that is not zero and an amount of recovery of the threshold voltage of the drive transistor during a recovery period in which the signal voltage is kept at zero;

calculate the amount of recovery ΔV th _ r in accordance with the following equations:

Δ

⁢

⁢

V

th

⁢

⁢

_

⁢

⁢

r

=

Δ

⁢

⁢

V

th

⁢

⁢

_

⁢

⁢

ini

⁢

exp

⁢

{

-

(

t

r

τ

)

γ

}

and

τ

=

τ

0

⁢

exp

⁡

(

E

τ

kT

)

where ΔV th _ ini is the amount of threshold voltage shift at the start of the recovery period, t r is a duration of the recovery period, τ 0 is a coefficient, E τ is activation energy of a time constant τ of escape of a carrier from a gate insulating film of the drive transistor, k is a Boltzmann constant, T is temperature, and γ is a predetermined constant; and

correct the signal voltage in accordance with the amount of threshold voltage shift.

5. A method for driving a display device including a display, which includes light-emitting pixels each of which includes a light-emitting element and a drive transistor, the drive transistor including a gate electrode, a source electrode and a drain electrode, and being configured to supply a current to the light-emitting element to cause the light-emitting element to emit light; a memory that stores correction data, and a signal line driving circuit configured to supply a signal voltage applied between the gate electrode and the source electrode of the drive transistor, the method comprising:

accessing the memory that stores the correction data, which includes a representative drive transistor threshold voltage deterioration curve, characteristics of the drive transistor of each light-emitting pixel, and an accumulated stress of the drive transistor of each light-emitting pixel;

calculating, using the correction data stored in the memory, an amount of threshold voltage shift of the drive transistor on the basis of an amount of deterioration of a threshold voltage of the drive transistor during a deterioration period in which the signal voltage is kept at a value that is not zero and an amount of recovery of the threshold voltage of the drive transistor during a recovery period in which the signal voltage is kept at zero;

referring to a representative deterioration curve that shows a relationship between an application time of the signal voltage and the amount of threshold voltage shift in a case where the signal voltage is a predetermined reference voltage;

storing, as an accumulated converted time, a value of the application time that corresponds to the amount of threshold voltage shift on the representative deterioration curve;

converting a duration of the deterioration period into a converted time that is a time required for deteriorating the threshold voltage of the drive transistor by the amount of deterioration in a case where the signal voltage is the reference voltage;

calculating the accumulated converted time at an end of the deterioration period by adding the converted time to the accumulated converted time at a start of the deterioration period;

calculating the amount of threshold voltage shift at the end of the deterioration period by calculating a value of the amount of threshold voltage shift that corresponds to the accumulated converted time at the end of the deterioration period on the representative deterioration curve; and

correcting the signal voltage in accordance with the amount of threshold voltage shift.

6. The method for driving a display device according to claim 5 , the method further comprising:

calculating the amount of threshold voltage shift at an end of the recovery period by subtracting the amount of recovery from the amount of threshold voltage shift at a start of the recovery period; and

calculating the accumulated converted time at the end of the recovery period by calculating a value of the application time that corresponds to the amount of threshold voltage shift at the end of the recovery period on the representative deterioration curve.

7. The method for driving a display device according to claim 5 , the method further comprising:

converting the duration t d of the deterioration period into the converted time t d _ ref in accordance with the following equation:

t

d

⁢

_

⁢

ref

=

(

V

gs

⁢

_

⁢

ref

-

V

th

⁢

⁢

0

+

V

offset

V

gs

⁢

_

⁢

d

-

V

th

⁢

⁢

0

+

V

offset

)

-

α

β

⁢

t

d

where t d _ ref is the converted time, V gs _ ref is the reference voltage, V gs _ d is the signal voltage, V th0 is the threshold voltage of the drive transistor before application of the signal voltage, and α, β, and V offset are predetermined constants; and

calculating the amount of deterioration ΔV th _ d in accordance with the following equations:

Δ

⁢

⁢

V

th

⁢

_

⁢

d

=

A

⁡

(

V

gs

⁢

_

⁢

ref

-

V

th

⁢

⁢

0

+

V

offset

)

α

⁢

t

d

⁢

_

⁢

ref

β

and

A

=

A

0

⁢

exp

⁡

(

-

E

a

kT

)

where A 0 is a constant, E a is activation energy of the threshold voltage shift, k is a Boltzmann constant, and T is temperature.