JP2006349928A - Drive circuit and drive method for organic electroluminescence device - Google Patents

Abstract

Power consumption of a passive drive organic EL display device is reduced.
A scan electrode driving circuit applies a voltage (−Va) lower than a ground voltage to a selected scan electrode, and applies a voltage Vb higher than the ground voltage to the remaining scan electrodes. The data electrode drive circuit 12 applies the output side voltage Vc of the constant current source to the data electrode corresponding to the organic EL element to emit light, and applies the ground voltage to the remaining data electrodes. When a negative voltage (-Va) is applied to the selected scan electrode and line sequential driving is performed, the positive voltage Vb applied to the remaining scan electrodes can be lowered. Therefore, it is possible to reduce power consumption due to charging / discharging of the organic EL elements arranged in different rows and different columns from the organic EL elements to emit light.
[Selection] Figure 3

Description

  The present invention relates to a display device using an organic electroluminescence (hereinafter abbreviated as EL) element, and more particularly to a drive circuit and a drive method for a passive drive organic EL display device.

  In recent years, display devices using organic EL elements have been researched and developed as self-luminous elements. Among them, the passive drive organic EL display device has been put to practical use in a display device for the back surface of a mobile phone and the like because it has good visibility and is thin.

A driving circuit and a driving method of a conventional organic EL display device are disclosed in, for example, Patent Document 1 (see FIGS. 13 to 16). The organic EL display device includes a data electrode X ₁ to X _m, a scan electrode Y ₁ to Y _n, provided at the intersection of these electrodes organic EL element E _{1, 1} to E _m, and _n. One organic EL element is electrically equivalent to a parallel connection circuit of a diode and a capacitor. In FIGS. 13 to 16, the organic EL element that emits light is represented by a diode, and the organic EL element that does not emit light is represented by a capacitor.

The organic EL elements E _{1,1 to} E _{m, n} are driven by the scan electrode driving circuit 1 and the data electrode driving circuits 2a and 2b. Switches SY _{1 to} SY _n included in scan electrode drive circuit 1 switch the voltage applied to scan electrodes Y _{1 to} Y _n between power supply voltage Vcc and ground voltage (zero voltage). The switches SX _{1 to} SX _m included in the data electrode drive circuit 2 a switch whether to apply the output side voltage of the constant current source to the data electrodes X _{1 to} X _m . The switches SZ _{1 to} SZ _m included in the data electrode drive circuit 2b switch whether to apply a ground voltage to the data electrodes X _{1 to} X _m . The states of these three types of switches are switched by a control signal (not shown) output from a light emission control circuit (not shown). In general, the output-side voltage of the constant current source varies depending on the impedance of the organic EL element and the wiring resistance of the electrodes. Here, in order to simplify the explanation, the output-side voltage of the constant current source is always the power supply voltage Vcc. Is equal to

For example, when the organic EL elements E _1,1 and E _2,1 arranged in the first row are caused to emit light, and then the organic EL elements E _2,2 and E _3,2 arranged in the second row are caused to emit light The scan electrode driving circuit 1 and the data electrode driving circuits 2a and 2b operate as follows. The organic EL element E _{1, 1,} when the emit E _2,1, the switch SY ₁ the scanning electrode driving circuit 1 to the ground voltage side, the switch SY ₂ to SY _n is connected to the power source voltage Vcc side, the data electrode driving In the circuits 2a and 2b, the switches SX ₁ , SX ₂ , SZ _{3 to} SZ _m are turned on, and the other switches are turned off (see FIG. 13). At this time, since the anode voltages of the organic EL elements E _1,1 and E _2,1 are sufficiently higher than the cathode voltage, a current flows in the direction shown in FIG. As a result, the organic EL elements E _1,1 and E _2,1 emit light.

  Other organic EL elements are arranged in the same row as the organic EL elements that emit light (first group: G1) and arranged in the same column as any of the organic EL elements that emit light (second group: G2) and those arranged in different rows and different columns from the organic EL elements that emit light (third group: G3). In the organic EL elements in the first and second groups, the anode voltage matches the cathode voltage, and in the organic EL elements in the third group, the anode voltage is lower than the cathode voltage. For this reason, none of the organic EL elements in the first to third groups emit light. At this time, the voltage Vcc is applied to the organic EL elements in the third group in the reverse direction. Thereby, the organic EL elements in the third group are charged by the voltage Vcc.

Next, the switch SY ₁ to SY _n the scanning electrode driving circuit 1 is connected to the ground voltage side, the data electrode driving circuit 2a, the switch SX ₁ ~SX _m in 2b turned off, the switch SZ ₁ ~SZ _m is on State (see FIG. 14). Thereby, all the charges charged in the organic EL elements in the third group are discharged.

Then, when the light emission of organic EL element E _{2, 2,} E _3,2 is the switch SY ₂ the scanning electrode driving circuit 1 is the ground voltage side, the switch SY _1, SY ₃ to SY _n is the power source voltage Vcc side In the data electrode drive circuits 2a and 2b, the switches SX ₂ , SX ₃ , SZ ₁ , SZ _{4 to} SZ _m are turned on, and the other switches are turned off (see FIG. 15). With such a state of the switch is changed, the organic EL element E _{2, 2,} a current flows through several channels shown in FIG. 15 to E _3,2, the organic EL element E _{2, 2,} E _3,2 fast Is charged. Thereby, the organic EL elements E _2,2 and E _3,2 start to emit light in a short time, and the organic EL display device instantaneously shifts to a steady state shown in FIG. Line sequential driving is performed by the series of operations described above.

In addition to this, in Patent Document 2, in the organic EL display device having the same configuration as that shown in FIG. 13, a data electrode corresponding to an organic EL element that should not emit light has a predetermined value lower than the light emission start voltage of the organic EL element. It is disclosed to apply a voltage V _L of.
Japanese Patent No. 3314046 Japanese Patent No. 3609299

  In the organic EL display device disclosed in Patent Document 1, when voltage Vcc is applied to an organic EL element to emit light, organic EL elements arranged in a different row and different column from the organic EL elements that emit light (that is, the third group) The voltage Vcc is applied to the organic EL element in the reverse direction. For this reason, the organic EL elements in the third group are charged by the voltage Vcc. The charged charge is discharged when both the scan electrode and the data electrode are connected to the ground voltage.

  Power proportional to the square of the power supply voltage Vcc is consumed by charging and discharging in the organic EL elements in the third group. However, charging / discharging in the organic EL elements in the third group is unrelated to the light emission of the organic EL elements. As described above, in the organic EL display device disclosed in Patent Document 1, power proportional to the square of the power supply voltage Vcc is obtained by charging / discharging the organic EL elements arranged in a different row and different column from the organic EL elements that emit light. Is wasted.

Patent Document 2 discloses, as one solution to this problem, applying a predetermined voltage V _L lower than the light emission start voltage of the organic EL element to the data electrode corresponding to the organic EL element that should not emit light. Has been. However, depending on the characteristics of the organic EL element and the configuration of the organic EL display device, a method other than the method disclosed in Patent Document 2 may be preferable.

  Therefore, an object of the present invention is to provide a driving circuit and a driving method for an organic EL element that can reduce power consumption unrelated to light emission by a method different from the conventional one.

1st invention is a drive circuit of the organic electroluminescent element which drives the organic electroluminescent element provided in the intersection of several scanning electrode and several data electrode,
A scan electrode driving circuit that applies a first voltage lower than the ground voltage to the selected scan electrode among the scan electrodes, and applies a second voltage higher than the ground voltage to the remaining scan electrodes; ,
Among the data electrodes, a data electrode corresponding to an organic electroluminescence element to emit light is applied with a third voltage, and a data electrode driving circuit for applying a ground voltage to the remaining data electrodes.

According to a second invention, in the first invention,
The data electrode driving circuit applies a ground voltage to all the data electrodes before applying the third voltage,
In the meantime, the scan electrode driving circuit applies the first voltage to the selected scan electrode and applies a ground voltage to the remaining scan electrodes.

According to a third invention, in the second invention,
The scan electrode driving circuit includes a switch that switches a voltage applied to the scan electrode to the first voltage, the second voltage, and a ground voltage,
The data electrode driving circuit includes a switch for switching a voltage applied to the data electrode between the third voltage and a ground voltage.

According to a fourth invention, in the first invention,
Before applying the third voltage, the data electrode driving circuit does not apply a specific voltage to the data electrode corresponding to the organic electroluminescence element to emit light among the data electrodes, and the remaining data electrodes Is characterized in that a ground voltage is applied.

A fifth invention is the fourth invention,
The scan electrode drive circuit includes a switch that switches a voltage applied to the scan electrode between the first voltage and the second voltage,
The data electrode driving circuit includes a switch for switching whether to apply the third voltage, a ground voltage, or neither the third voltage nor the ground voltage to the data electrode. It is characterized by that.

According to a sixth invention, in the first invention,
Before applying the third voltage, the data electrode driving circuit applies a fourth voltage to the data electrode corresponding to the organic electroluminescence element to emit light among the data electrodes, and the remaining data. A ground voltage is applied to the electrodes.

A seventh invention is the sixth invention, wherein
The scan electrode drive circuit includes a switch that switches a voltage applied to the scan electrode between the first voltage and the second voltage,
The data electrode driving circuit includes a switch for switching a voltage applied to the data electrode to the third voltage, the fourth voltage, and a ground voltage.

In an eighth aspect based on the first aspect,
An absolute value of the first voltage is smaller than a light emission start voltage of the organic electroluminescence element.

A ninth invention is an organic electroluminescence element driving method for driving an organic electroluminescence element provided at an intersection of a plurality of scanning electrodes and a plurality of data electrodes,
Applying a first voltage lower than the ground voltage to the selected scan electrode among the scan electrodes, and applying a second voltage higher than the ground voltage to the remaining scan electrodes;
A step of applying a third voltage to the data electrode corresponding to the organic electroluminescence element to emit light, and applying a ground voltage to the remaining data electrodes.

A tenth invention is the ninth invention,
Prior to applying the third voltage, the method further comprises applying the first voltage to the selected scan electrode and applying a ground voltage to the remaining scan electrodes and all the data electrodes.

In an eleventh aspect based on the ninth aspect,
Before applying the third voltage, a specific voltage is not applied to the data electrodes corresponding to the organic electroluminescence elements to be lit among the data electrodes, and a ground voltage is applied to the remaining data electrodes. The method further includes a step.

In a twelfth aspect based on the ninth aspect,
Before applying the third voltage, the fourth voltage is applied to the data electrode corresponding to the organic electroluminescence element to emit light, and the ground voltage is applied to the remaining data electrodes. Further comprising the step of:

  According to the first or ninth invention, the organic EL elements arranged in different rows and different columns from the organic EL elements that emit light are charged by the second voltage. Therefore, by reducing the second voltage, it is possible to reduce power consumption unrelated to light emission and reduce power consumption of the organic EL display device.

  According to the second, third, or tenth aspect of the invention, when switching the scanning electrode to be selected, it is possible to reduce power consumption unrelated to light emission while discharging the charge charged in the organic EL element. .

  According to the fourth, fifth, or eleventh invention, it is possible to reduce power consumption unrelated to light emission at a lower cost.

  According to the sixth, seventh, or twelfth invention, power consumption unrelated to light emission can be reduced while causing the organic EL element to emit light in a short time.

  According to the eighth aspect, the organic EL element that should not emit light can be prevented from emitting light.

(First embodiment)
1 to 4 are diagrams showing the configuration and operation of the organic EL display device according to the first embodiment of the present invention. As shown in FIGS. 1 to 4, the organic EL display device includes m data electrodes X _{1 to} X _m , n scan electrodes Y _{1 to} Y _n , and (m × n) organic EL elements. E _{1,1 to} E _{m, n} . Scan electrodes Y _{1 to} Y _n are provided in parallel to each other, and data electrodes X _{1 to} X _m are provided in parallel to each other and orthogonal to scan electrodes Y _{1 to} Y _n . The data electrodes X _{1 to} X _m and the scan electrodes Y _{1 to} Y _n intersect at (m × n) locations, and the organic EL elements E _{1,1 to} E _{m, n} are (m × n) intersections, respectively. Provided.

The drive circuit for the organic EL elements E _{1,1 to} E _{m, n} includes a scan electrode drive circuit 11 and a data electrode drive circuit 12. The scan electrode drive circuit 11 includes three switches SD _j , SU _j , SG _j for each scan electrode Y _j (j is an integer from 1 to n; hereinafter the same), and these switches are used to scan electrodes. Drive _Yj . The switch SD _j switches whether the scan electrode Y _j is connected to a voltage (−Va) lower than the ground voltage (zero voltage). The switch SU _j switches whether the scan electrode Y _j is connected to a voltage Vb higher than the ground voltage. The switch SG _j switches whether the scan electrode Y _j is connected to the ground voltage.

The data electrode driving circuit 12 includes two switches DU _i and DD _i for each data electrode X _i (i is an integer of 1 to m; hereinafter the same), and the data electrode X _i is connected using these switches. To drive. The switch DU _i switches whether the data electrode X _i is connected to the output side voltage of the constant current source. The switch DD _i switches whether the data electrode X _i is connected to the ground voltage.

Scan electrode driver circuit 11, the voltage applied to the scan electrodes Y ₁ to Y _n by switching between the voltage (-Va) to the voltage Vb and the ground voltage, from among the scan electrodes Y ₁ to Y _n 1 The number of scan electrodes is selected. Thereby, the organic EL elements for one row are selected. The data electrode drive circuit 12 switches the voltage applied to the data electrodes X _{1 to} X _m between the output side voltage of the constant current source and the ground voltage. Thereby, one row of display data is supplied to the selected one row of organic EL elements. The scan electrode driving circuit 11 and the data electrode driving circuit 12 operate as described above for each row of the organic EL elements E _{1,1 to} E _{m, n} , so that the organic EL display device performs screen display.

Hereinafter, among the scan electrodes Y _{1 to} Y _n , the scan electrode selected by the scan electrode driving circuit 11 is referred to as “selected scan electrode”, and the remaining scan electrodes are referred to as “non-selected scan electrodes”. Among the data electrodes X _{1 to} X _m , the data electrode corresponding to the organic EL element to emit light is referred to as “lighting data electrode”, and the remaining data electrodes are referred to as “non-lighting data electrodes”. The organic EL element provided at the intersection of the selected scanning electrode and the lighting data electrode emits light, and the other organic EL elements do not emit light. Organic EL elements that do not emit light are classified into the following three groups.
First group: arranged in the same row as the organic EL elements emitting light Second group: arranged in the same column as any of the organic EL elements emitting light Third group: different and different from the organic EL elements emitting light Those arranged in columns

The states of the switches included in scan electrode drive circuit 11 and data electrode drive circuit 12 change as follows. First, in the scan electrode driving circuit 11, one of the switches SD _{1 to} SD _n corresponding to the selected scan electrode and the one of the switches SG _{1 to} SG _n corresponding to the non-selected scan electrode are turned on, and the other switches Is turned off. At this time, in the data electrode driving circuit 12, the switches DD _{1 to} DD _m are turned on, and the switches DU _{1 to} DU _m are turned off. In the next scanning electrode driving circuit 11, to that corresponding to the selected scanning electrodes of the switches SD ₁ to SD _n, which corresponds to the non-selected scanning electrodes of the switches SU ₁ to SU _n and is turned on, other The switch is turned off. At this time, in the data electrode driving circuit 12, one of the switches DU _{1 to} DU _m corresponding to the lighting data electrode and the one of the switches DD _{1 to} DD _m corresponding to the non-lighting data electrode are turned on. The switch is turned off.

For example, when the organic EL elements E _1,1 and E _2,1 arranged in the first row are caused to emit light and then the organic EL elements arranged in the second row are caused to emit light, the scanning electrode driving circuit 11 and The data electrode drive circuit 12 operates as follows. When the organic EL elements E _1,1 and E _2,1 are caused to emit light, the scanning electrode Y ₁ is a selective scanning electrode, the scanning electrodes Y _{2 to} Y _n are non-selecting scanning electrodes, and the data electrodes X ₁ and X ₂ are lighting data electrodes. The data electrodes X _{3 to} X _m are non-lighting data electrodes. Further, the organic EL elements other than the organic EL elements E _1,1 and E _2,1 are classified into first to third groups G1 to G3 as shown in FIG.

In order to cause the organic EL elements E _1,1 and E _2,1 to emit light, first, in the scan electrode driving circuit 11, the switches SD ₁ and SG _{2 to} SG _n are turned on, and the other switches are turned off. In the data electrode driving circuit 12, the switches DD _{1 to} DD _m are turned on, and the switches DU _{1 to} DU _m are turned off (see FIG. 1). In the state shown in FIG. 1, the organic EL elements E _{1,1 to} E _{m, n} do not emit light.

Next, in the scan electrode driving circuit 11, the switches SG _{2 to} SG _n are changed to the off state, and the switches SU _{2 to} SU _n are changed to the on state. At this time, in the data electrode driving circuit 12, the switches DD ₁ and DD ₂ are turned off, and the switches DU ₁ and DU ₂ are turned on. As a result, the scanning electrode driving circuit 11, the switch SD _1, SU ₂ ~SU _n is turned on, the other switches are turned off. In the data electrode driving circuit 12, switches _{DU 1, DU 2, DD 3} ~DD m is turned on, the other switches are turned off (see Figure 2). In the state shown in FIG. 2, the organic EL elements E _1,1 and E _2,1 emit light, and the other organic EL elements do not emit light.

When a predetermined time elapses after the switch state changes as shown in FIG. 2, the organic EL display device enters a steady state shown in FIG. Even in the state shown in FIG. 3, the organic EL elements E _1,1 and E _2,1 emit light, and the other organic EL elements do not emit light.

When the organic EL elements arranged in the second row are caused to emit light, the scanning electrode Y ₂ is a selected scanning electrode, and the scanning electrodes Y ₁ , Y _{3 to} Y _n are non-selected scanning electrodes. First, in the scanning electrode driving circuit 11, the switch _{SD 2, SG 1, SG 3} ~SG n is turned on, the other switches are turned off. In the data electrode drive circuit 12, the switches DD _{1 to} DD _m are turned on, and the switches DU _{1 to} DU _m are turned off (see FIG. 4). In the state shown in FIG. 4, the organic EL elements E _{1,1 to} E _{m, n} do not emit light. Thereafter, the same processing as in the first line is performed.

In the state shown in FIG. 1, a voltage (−Va) is applied to the selected scan electrode Y ₁ , and a ground voltage is applied to the non-selected scan electrodes Y _{2 to} Y _n and the data electrodes X _{1 to} X _m . For this reason, in the m organic EL elements corresponding to the selected scanning electrode Y ₁ , the anode voltage is higher than the cathode voltage by Va. Therefore, m organic EL elements corresponding to the selected scanning electrode Y ₁ are charged by the voltage Va. However, a voltage whose absolute value is smaller than the light emission start voltage Vth of the organic EL element is used as the voltage (−Va) so that the organic EL element does not emit light even when the voltage at both ends becomes Va. Therefore, in the state shown in FIG. 1, the organic EL elements E _{1,1 to} E _{m, n} do not emit light.

In the state shown in FIG. 2, a voltage (−Va) is applied to the selected scanning electrode Y ₁ , a voltage Vb is applied to the non-selected scanning electrodes Y _{2 to} Y _n , and a ground voltage is applied to the non-lighting data electrodes X _{3 to} X _m. The output data terminals of the constant current source are connected to the lighting data electrodes X ₁ and X ₂ . Since the current flowing through the constant current source is constant, the voltages of the lighting data electrodes X ₁ and X ₂ immediately after the switch state is changed as shown in FIG. 2 are n organic ELs corresponding to the lighting data electrodes. The value shown in the following formula (1) is obtained by capacitive coupling of the element.
Vb ′ = {(n−1) / n} × (Vb + Va) −Va (1)
Thus, the voltage Vb ′ of the lighting data electrodes X ₁ and X ₂ immediately after the change of the switch state becomes substantially equal to the voltage Vb. On the other hand, even after the switch state changes, the voltages of the non-lighting data electrodes X _{3 to} X _m remain at the ground voltage.

The reason why only the organic EL elements E _1,1 and E _2,1 emit light in the state shown in FIG. 2 is as follows. In the organic EL elements E _1,1 and E _2,1 , since the voltage Vb ′ is applied to the anode side and the voltage (−Va) is applied to the cathode side, the voltage at both ends is (Vb ′ + Va). Here, a voltage such that the voltage (Vb ′ + Va) is larger than the light emission start voltage Vth is used as the voltage Vb. Therefore, the organic EL elements E _1,1 and E _2,1 emit light.

In the organic EL elements in the first group (organic EL elements arranged in the same row as the organic EL elements E _1,1 and E _2,1 ), the anode side has a ground voltage and the cathode side has a voltage (−Va). Is applied, the voltage at both ends becomes Va. As described above, since the absolute value of the voltage (−Va) is smaller than the light emission start voltage Vth, the organic EL elements in the first group do not emit light.

In the organic EL elements in the second group (organic EL elements arranged in the same column as any of the organic EL elements E _1,1 and E _2,1 ), the voltage Vb ′ is on the anode side and the voltage Vb is on the cathode side. Is applied, the voltage at both ends becomes (Vb′−Vb). Since the voltage (Vb′−Vb) is negative and smaller than the light emission start voltage Vth, the organic EL elements in the second group do not emit light.

In the organic EL elements in the third group (organic EL elements arranged in a different row and different column from the organic EL elements E _1,1 and E _2,1 ), the ground voltage is on the anode side and the voltage Vb is on the cathode side. Is applied, the voltage at both ends becomes −Vb. Since the voltage (−Vb) is negative and smaller than the light emission start voltage Vth, the organic EL elements in the third group do not emit light.

The output side voltage of the constant current source in the steady state shown in FIG. The reason why only the organic EL elements E _1,1 and E _2,1 emit light in the state shown in FIG. 3 is as follows. In the organic EL elements E _1,1 and E _2,1 , since the voltage Vc is applied to the anode side and the voltage (−Va) is applied to the cathode side, the voltage at both ends is (Vc + Va). Here, a current source in which the voltage (Vc + Va) is larger than the light emission start voltage Vth is used as the constant current source in the data electrode driving circuit 12. Therefore, the organic EL elements E _1,1 and E _2,1 emit light with a predetermined luminance corresponding to the current supplied from the constant current source.

  The same voltage as in FIG. 2 is applied to the anode side and the cathode side of the organic EL elements in the first and third groups. For this reason, the organic EL elements in the first and third groups do not continue to emit light.

  In the organic EL elements in the second group, since the voltage Vc is applied to the anode side and the voltage Vb is applied to the cathode side, the voltage at both ends becomes (Vc−Vb). Here, a voltage such that the voltage (Vc−Vb) is smaller than the light emission start voltage Vth is used as the voltage Vb. For this reason, the organic EL elements in the second group do not emit light.

  As described above, according to the drive circuit according to the present embodiment (that is, the scan electrode drive circuit 11 and the data electrode drive circuit 12), a voltage higher than the light emission start voltage Vth is applied to the organic EL element to emit light. A voltage lower than the light emission start voltage Vth can be applied to the organic EL element. Therefore, a desired organic EL element can be made to emit light correctly.

  Hereinafter, the effect which the drive circuit concerning this embodiment has is explained. According to the drive circuit according to the present embodiment, the voltage Va, the voltage (Vc−Vb), and the voltage (−Vb) are applied to the organic EL elements in the first to third groups, respectively. The organic EL elements in the first to third groups are charged by these three kinds of voltages, and the charged charges are discharged when the scanning electrode to be selected is switched.

  When considering the power consumption in the organic EL display device according to the present embodiment, the first group includes at most one row of organic EL elements, and the second and third groups include (n-1) rows. Since the organic EL element is not included, when n is sufficiently large, the influence of charging / discharging in the organic EL element in the first group may be ignored. Further, since the voltage Vb is almost the same as the voltage Vc in order to reduce power consumption, the influence of charging / discharging in the organic EL elements in the second group can be ignored. Accordingly, the power consumed by the organic EL display device according to the present embodiment regardless of the light emission is the organic EL elements in the third group (that is, the organic EL elements arranged in different rows and different columns from the organic EL elements that emit light). It can be said that this is due to charge / discharge of the EL element).

  In the organic EL display device according to the present embodiment, power proportional to the square of the voltage Vb is consumed by charge and discharge in the organic EL elements in the third group. On the other hand, in the organic EL display device described in Patent Document 1, this value is proportional to the square of the power supply voltage Vcc. As can be seen by comparing the voltages applied to the organic EL elements to emit light, the voltage (Vc + Va) in this embodiment corresponds to the voltage Vcc described in Patent Document 1. Considering that the voltage Vb is almost the same as the voltage Vc, Vcc = Vc + Va = Vb + Va. Therefore, the voltage Vb in this embodiment can be made lower than the voltage Vcc described in Patent Document 1.

  Thus, the drive circuit for the organic EL element according to the present embodiment reduces power consumption unrelated to light emission by performing line sequential driving by applying a voltage lower than the ground voltage to the selected scan electrode, The power consumption of the organic EL display device can be reduced.

  Further, in the drive circuit described in Patent Document 2, three switches and scan electrodes are provided for each data electrode in order to switch the voltage applied to the data electrode in three ways and the voltage applied to the scan electrode in two ways. Two switches per piece are required. On the other hand, in the drive circuit according to the present embodiment, two switches per data electrode are used to switch the voltage applied to the data electrode in two ways and the voltage applied to the scan electrode in three ways. And two switches per scan electrode.

  Therefore, the total number of switches required when m data electrodes and n scanning electrodes are (3m + 2n) in Patent Document 2 is (2m + 3n) in this embodiment. . In the case of performing color display, m> n is satisfied because the three organic EL elements (corresponding to red, green, and blue, respectively) constituting one pixel are arranged in the direction in which the scanning electrodes extend. As described above, when m> n, including the case of performing color display, the drive circuit according to the present embodiment can be configured with fewer switches than the drive circuit described in Patent Document 2.

(Second Embodiment)
5 to 8 are diagrams showing the configuration and operation of an organic EL display device according to the second embodiment of the present invention. The drive circuit for the organic EL element according to the present embodiment includes a scan electrode drive circuit 21 and a data electrode drive circuit 22. Among the constituent elements of the present embodiment, the same constituent elements as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.

Scan electrode driving circuit 21 for each scanning electrode Y _j includes two switches SD _j, SU _j, to drive the scanning electrode Y _j with these switches. Data electrode driving circuit 22 includes two switches DU _i, the DD _i for each of the data electrodes X _i, drives the data electrodes X _i with these switches.

The scan electrode driving circuit 21 switches one voltage from the scan electrodes Y _{1 to} Y _n by switching the voltage applied to the scan electrodes Y _{1 to} Y _n between the voltage (−Va) and the voltage Vb. Select an electrode. The data electrode drive circuit 22 connects the data electrodes X _{1 to} X _m to the output side voltage of the constant current source, connects to the ground voltage, or connects to the output side voltage and the ground voltage of the constant current source. Switch to either not.

The states of the switches included in scan electrode drive circuit 21 and data electrode drive circuit 22 change as follows. First, in the scanning electrode driving circuit 21, to that corresponding to the selected scanning electrodes of the switches SD ₁ to SD _n, which corresponds to the non-selected scanning electrodes of the switches SU ₁ to SU _n and is turned on, the other switches Is turned off. At this time, in the data electrode drive circuit 22, the switches corresponding to the non-lighting data electrodes among the switches DD _{1 to} DD _m are turned on, and the other switches are turned off. Next, the state of the switches included in the scan electrode driving circuit 21 remains the same, and in the data electrode driving circuit 22, the switch corresponding to the lighting data electrode among the switches DU _{1 to} DU _m and the non-switching among the switches DD _{1 to} DD _n . The one corresponding to the lighting data electrode is turned on, and the other switches are turned off.

For example, when the organic EL elements E _1,1 and E _2,1 arranged in the first row are caused to emit light, and then the organic EL elements E _2,2 and E _3,2 arranged in the second row are caused to emit light The scan electrode drive circuit 21 and the data electrode drive circuit 22 operate as follows. The organic EL element E _{1, 1,} in order to emit E _2,1 is the first scan electrode drive circuit 21, the switch SD _1, SU ₂ ~SU _n are turned on, the other switches are turned off . In the data electrode drive circuit 22, the switches DD _{3 to} DD _m are turned on, and the other switches are turned off (see FIG. 5). In the state shown in FIG. 5, the organic EL elements E _1,1 and E _2,1 emit light, and the other organic EL elements do not emit light.

Next, in the data electrode drive circuit 22, the switches DU ₁ and DU ₂ are changed to the on state while the state of the switch included in the scan electrode drive circuit 21 is not changed. As a result, the scanning electrode driving circuit 21, the switch SD _1, SU ₂ ~SU _n are turned on, the other switches are turned off. In the data electrode driving circuit 22, switches _{DU 1, DU 2, DD 3} ~DD m is turned on, the other switches are turned off (see Figure 6). Even in the state shown in FIG. 6, the organic EL elements E _1,1 and E _2,1 emit light, and the other organic EL elements do not emit light.

In order to cause the organic EL elements E _2,2 and E _3,2 to emit light, first, in the scan electrode driving circuit 21, the switches SD ₂ , SU ₁ , SU _{3 to} SU _n are turned on, and the other switches are turned off. It becomes a state. In the data electrode drive circuit 22, the switches DD ₁ and DD _{4 to} DD _m are turned on, and the other switches are turned off (see FIG. 7). In the state shown in FIG. 7, the organic EL elements E _2,2 and E _3,2 emit light, and the other organic EL elements do not emit light.

Next, in the data electrode drive circuit 22, the switches DU ₂ and DU ₃ are changed to the on state while the state of the switches included in the scan electrode drive circuit 21 is not changed. As a result, the scanning electrode driving circuit 21, the switch _{SD 2, SU 1, SU 3} ~SU n are turned on, the other switches are turned off. In the data electrode driving circuit 22, switches _{DU 2, DU 3, DD 1} , DD 4 ~DD m are turned on, the other switches are turned off (see Figure 8). Even in the state shown in FIG. 8, the organic EL elements E _2,2 and E _3,2 emit light, and the other organic EL elements do not emit light.

In the state shown in FIG. 5, the voltage to the selected scanning electrodes Y ₁ (-Va), the non-selected scanning electrodes Y ₂ to Y _n to the voltage Vb, the ground voltage is applied to the non-lighting data electrodes X ₃ to X _m The lighting data electrodes X ₁ and X ₂ are in a floating state. The voltage Vb ′ of the lighting data electrodes X ₁ and X _{2 in} the state shown in FIG. 5 has a value represented by the following equation (2) due to capacitive coupling of n organic EL elements corresponding to each lighting data electrode.
Vb ′ = {(n−1) / n} × (Vb + Va) −Va (2)
As in the first embodiment, the voltage Vb ′ is substantially equal to the voltage Vb.

The reason why only the organic EL elements E _1,1 and E _2,1 emit light in the state shown in FIG. 5 is the same as that in the state shown in FIG. That is, the voltage at both ends of the organic EL elements E _1,1 and E _2,1 is (Vb ′ + Va), but the voltage Vb is such a voltage that the voltage (Vb ′ + Va) is larger than the light emission start voltage Vth. Is used. The voltage at both ends of the organic EL elements in the first group is Va, but the voltage Va is smaller than the light emission start voltage Vth. The voltage at both ends of the organic EL elements in the second group is (Vb′−Vb), but the voltage (Vb′−Vb) is negative and smaller than the light emission start voltage Vth. The voltage across the organic EL elements in the third group is −Vb, but the voltage (−Vb) is negative and smaller than the emission start voltage Vth. From the above, the organic EL elements E _1,1 and E _2,1 emit light, but the organic EL elements in the first to third groups do not emit light.

The reason why only the organic EL elements E _1,1 and E _2,1 emit light in the state shown in FIG. 6 is the same as in the state shown in FIG. That is, if the output side voltage of the constant current source in FIG. 6 is Vc, the voltages at both ends of the organic EL elements E _1,1 and E _2,1 are (Vc + Va), but the constant current in the data electrode drive circuit 22 is constant. As the source, a current source whose voltage (Vc + Va) is larger than the light emission start voltage Vth is used. The same voltage as in FIG. 5 is applied to the anode side and the cathode side of the organic EL elements in the first and third groups. The voltage across the organic EL elements in the second group is (Vc−Vb), and the voltage Vb is such that the voltage (Vc−Vb) is smaller than the emission start voltage Vth. From the above, the organic EL elements E _1,1 and E _2,1 emit light with a predetermined luminance corresponding to the current supplied from the constant current source, and the organic EL elements in the first to third groups do not emit light. .

The reason why only the organic EL elements E _2,2 and E _3,2 emit light in the states shown in FIGS. 7 and 8 is the same as described above, and thus the description thereof is omitted here.

As described above, the drive circuit according to the present embodiment (that is, the scan electrode drive circuit 21 and the data electrode drive circuit 22) has the same voltage as that of the first embodiment with respect to the organic EL elements E _{1,1 to} Em _{, n} . Is applied. Therefore, according to the drive circuit according to the present embodiment, as in the first embodiment, it is possible to reduce power consumption unrelated to light emission and reduce power consumption of the organic EL display device.

  Further, in the drive circuit according to the present embodiment, in order to switch between two voltages applied to the data electrodes and two voltages applied to the scan electrodes, there are m data electrodes and n scan electrodes. The total number of switches required in this case is (2n + 2m). Therefore, according to the drive circuit according to the present embodiment, the above-described effects can be achieved at a lower cost than in the past.

(Third embodiment)
9 to 12 are diagrams showing the configuration and operation of an organic EL display device according to the third embodiment of the present invention. The drive circuit for the organic EL element according to the present embodiment includes a scan electrode drive circuit 21 and a data electrode drive circuit 32. Among the constituent elements of the present embodiment, the same constituent elements as those of the first or second embodiment are denoted by the same reference numerals, and the description thereof is omitted.

Data electrode driving circuit 32 includes three switches DU _i, DD _i, the DS _i for each of the data electrodes X _i, drives the data electrodes X _i with these switches. The switch DS _i switches whether to connect the data electrode X _i to a predetermined voltage Vd. Generally, the voltage Vd is almost the same as the output side voltage Vc of the constant current source in the steady state. Data electrode driving circuit 32 switches between a voltage applied to the data electrodes X ₁ to X _m of the output-side voltage Vc and the voltage Vd and a ground voltage of the constant current source.

The states of the switches included in scan electrode drive circuit 21 and data electrode drive circuit 32 change as follows. First, in the scanning electrode driving circuit 21, to that corresponding to the selected scanning electrodes of the switches SD ₁ to SD _n, which corresponds to the non-selected scanning electrodes of the switches SU ₁ to SU _n and is turned on, the other switches Is turned off. In this time, the data electrode driving circuit 32, to that corresponding to the lighting data electrodes of the switches DS ₁ to DS _m, which corresponds to the non-lighting data electrodes of the switches DD ₁ Dd _m and is turned on, other The switch is turned off. Then the state of the switch included in the scan electrode driving circuit 21 as it is, the data electrode driving circuit 32, to that corresponding to the lighting data electrodes of the switches DU ₁ to DU _m, among the switches DD ₁ Dd _n non The one corresponding to the lighting data electrode is turned on, and the other switches are turned off.

For example, when the organic EL elements E _1,1 and E _2,1 arranged in the first row are caused to emit light, and then the organic EL elements E _2,2 and E _3,2 arranged in the second row are caused to emit light The scan electrode drive circuit 21 and the data electrode drive circuit 32 operate as follows. The organic EL element E _{1, 1,} in order to emit E _2,1 is the first scan electrode drive circuit 21, the switch SD _1, SU ₂ ~SU _n are turned on, the other switches are turned off . In the data electrode driving circuit 32, the switch _{DS 1, DS 2, DD 3} ~DD m is turned on, the other switches are turned off (see Figure 9). In the state shown in FIG. 9, the organic EL elements E _1,1 and E _2,1 emit light, and the other organic EL elements do not emit light.

Next, in the data electrode driving circuit 32, the switches DS ₁ and DS ₂ change to the off state and the switches DU ₁ and DU ₂ change to the on state while maintaining the state of the switches included in the scan electrode driving circuit 21. As a result, the scanning electrode driving circuit 21, the switch SD _1, SU ₂ ~SU _n are turned on, the other switches are turned off. In the data electrode driving circuit 22, switches _{DU 1, DU 2, DD 3} ~DD m is turned on, the other switches are turned off (see Figure 10). Even in the state shown in FIG. 10, the organic EL elements E _1,1 and E _2,1 emit light, and the other organic EL elements do not emit light.

The organic EL element E _{2, 2,} in order to emit E _3,2 is the first scan electrode drive circuit 21, the switch _{SD 2, SU 1, SU 3} ~SU n is turned on, other switches are turned off It becomes. In the data electrode driving circuit 32, a switch _{DS 2, DS 3, DD 1} , DD 4 ~DD m are turned on, the other switches are turned off (see Figure 11). In the state shown in FIG. 11, the organic EL elements E _2,2 and E _3,2 emit light, and the other organic EL elements do not emit light.

Next, in the data electrode driving circuit 32, the switches DS ₂ and DS ₃ are changed to the off state and the switches DU ₂ and DU ₃ are changed to the on state while maintaining the state of the switches included in the scan electrode driving circuit 21. As a result, the scanning electrode driving circuit 21, the switch _{SD 2, SU 1, SU 3} ~SU n are turned on, the other switches are turned off. In the data electrode driving circuit 32, switches _{DU 2, DU 3, DD 1} , DD 4 ~DD m are turned on, the other switches are turned off (see Figure 12). Even in the state shown in FIG. 12, the organic EL elements E _2,2 and E _3,2 emit light, and the other organic EL elements do not emit light.

In the state shown in FIG. 9, the voltage to the selected scanning electrodes Y ₁ (-Va), the non-selected scanning electrodes Y ₂ to Y _n to the voltage Vb, lighting data electrode X _1, the voltage Vd to X _2, the non-lighting data the electrode X ₃ to X _m ground voltage is applied.

The reason why only the organic EL elements E _1,1 and E _2,1 emit light in the state shown in FIG. 9 is almost the same as that in the state shown in FIG. That is, the voltage at both ends of the organic EL elements E _1,1 and E _2,1 is (Vd + Va), but the voltage Vd is such that the voltage (Vd + Va) is greater than the light emission start voltage Vth. . The voltage at both ends of the organic EL elements in the first group is Va, but the voltage Va is smaller than the light emission start voltage Vth. The voltage across the organic EL elements in the second group is (Vd−Vb), and the voltage Vb is such that the voltage (Vd−Vb) is smaller than the light emission start voltage Vth. The voltage across the organic EL elements in the third group is −Vb, but the voltage (−Vb) is negative and smaller than the emission start voltage Vth. From the above, the organic EL elements E _1,1 and E _2,1 emit light, but the organic EL elements in the first to third groups do not emit light.

The reason why only the organic EL elements E _1,1 and E _2,1 emit light in the state shown in FIG. 10 is the same as in the state shown in FIG. That is, if the output side voltage of the constant current source in FIG. 10 is Vc, the voltage at both ends of the organic EL elements E _1,1 and E _2,1 is (Vc + Va), but the constant current in the data electrode drive circuit 32 is constant. As the source, a current source whose voltage (Vc + Va) is larger than the light emission start voltage Vth is used. The same voltage as in FIG. 9 is applied to the anode side and the cathode side of the organic EL elements in the first and third groups. The voltage across the organic EL elements in the second group is (Vc−Vb), and the voltage Vb is such that the voltage (Vc−Vb) is smaller than the emission start voltage Vth. From the above, the organic EL elements E _1,1 and E _2,1 emit light with a predetermined luminance corresponding to the current supplied from the constant current source, and the organic EL elements in the first to third groups do not emit light. .

The reason why only the organic EL elements E _2,2 and E _3,2 emit light in the state shown in FIGS. 11 and 12 is the same as described above, and thus the description thereof is omitted here.

As described above, the drive circuit (that is, the scan electrode drive circuit 21 and the data electrode drive circuit 32) according to the present embodiment is the first implementation for the organic EL elements E _{1,1 to} E _{m, n in} the steady state. Apply the same voltage as the form. Therefore, according to the drive circuit according to the present embodiment, as in the first and second embodiments, it is possible to reduce power consumption unrelated to light emission and to reduce power consumption of the organic EL display device.

  Further, the drive circuit according to the present embodiment applies a predetermined voltage Vd to the data electrodes in advance. Thereby, the time until the voltage applied to the organic EL element to emit light reaches the light emission start voltage can be shortened, and the organic EL element can emit light in a short time.

  In addition, in the drive circuit according to the present embodiment, the same number of switches as the drive circuit described in Patent Document 2 are used to switch the voltage applied to the data electrode in three ways and the voltage applied to the scan electrode in two ways. Needed. However, in Patent Document 2, in order to cause the organic EL element to emit light in a short time, a process of resetting all charges accumulated in the organic EL element is performed. In the present embodiment, such a process is performed. Not. Therefore, according to the drive circuit according to the present embodiment, the luminance can be increased by eliminating the reset period and extending the period during which the organic EL element emits light, as compared with the drive circuit described in Patent Document 2. it can.

1 is a diagram showing an organic EL display device according to a first embodiment of the present invention. FIG. 2 is a continuation diagram of FIG. 1. FIG. 3 is a continuation diagram of FIG. 2. FIG. 4 is a continuation diagram of FIG. 3. It is a figure which shows the organic electroluminescence display which concerns on the 2nd Embodiment of this invention. FIG. 6 is a continuation diagram of FIG. 5. FIG. 7 is a continuation diagram of FIG. 6. FIG. 8 is a continuation diagram of FIG. 7. It is a figure which shows the organic electroluminescence display which concerns on the 3rd Embodiment of this invention. FIG. 10 is a continuation diagram of FIG. 9. FIG. 11 is a continuation diagram of FIG. 10. FIG. 12 is a continuation diagram of FIG. 11. It is a figure which shows the conventional organic EL display apparatus. FIG. 14 is a continuation diagram of FIG. 13. FIG. 15 is a continuation diagram of FIG. 14. FIG. 16 is a continuation diagram of FIG. 15.

Explanation of symbols

11, 21 ... scan electrode driving circuit 12, 22, 32 ... data electrode driving circuit E _1,1 ~E _{m, n} ... organic EL element X ₁ to X _m ... data electrodes Y ₁ to Y _n ... scan electrodes SD ₁ ~ SD _n , SU _{1 to} SU _n , SG _{1 to} SG _n ... Switches DD _{1 to} DD _m , DU _{1 to} DU _m , DS _{1 to} DS _m ... Switches in the data electrode driving circuit

Claims (12)

A driving circuit for an organic electroluminescence element that drives an organic electroluminescence element provided at an intersection of a plurality of scanning electrodes and a plurality of data electrodes,
A scan electrode driving circuit that applies a first voltage lower than the ground voltage to the selected scan electrode among the scan electrodes, and applies a second voltage higher than the ground voltage to the remaining scan electrodes; ,
The data electrode includes a data electrode driving circuit that applies a third voltage to the data electrode corresponding to the organic electroluminescence element to emit light and applies a ground voltage to the remaining data electrode. Drive circuit for electroluminescence element. The data electrode driving circuit applies a ground voltage to all the data electrodes before applying the third voltage,
2. The drive according to claim 1, wherein the scan electrode driving circuit applies the first voltage to the selected scan electrode and applies the ground voltage to the remaining scan electrodes during the period. circuit. The scan electrode driving circuit includes a switch that switches a voltage applied to the scan electrode to the first voltage, the second voltage, and a ground voltage,
The drive circuit according to claim 2, wherein the data electrode drive circuit includes a switch that switches a voltage applied to the data electrode between the third voltage and a ground voltage.   Before applying the third voltage, the data electrode driving circuit does not apply a specific voltage to the data electrode corresponding to the organic electroluminescence element to emit light among the data electrodes, and the remaining data electrodes The drive circuit according to claim 1, wherein a ground voltage is applied to the drive circuit. The scan electrode drive circuit includes a switch that switches a voltage applied to the scan electrode between the first voltage and the second voltage,
The data electrode driving circuit includes a switch for switching whether to apply the third voltage, a ground voltage, or neither the third voltage nor the ground voltage to the data electrode. The drive circuit according to claim 4, wherein:   Before applying the third voltage, the data electrode driving circuit applies a fourth voltage to the data electrode corresponding to the organic electroluminescence element to emit light among the data electrodes, and the remaining data. The drive circuit according to claim 1, wherein a ground voltage is applied to the electrodes. The scan electrode drive circuit includes a switch that switches a voltage applied to the scan electrode between the first voltage and the second voltage,
The drive according to claim 6, wherein the data electrode driving circuit includes a switch that switches a voltage applied to the data electrode to the third voltage, the fourth voltage, and a ground voltage. circuit.   2. The drive circuit according to claim 1, wherein an absolute value of the first voltage is smaller than a light emission start voltage of the organic electroluminescence element. A driving method of an organic electroluminescence element, driving an organic electroluminescence element provided at an intersection of a plurality of scanning electrodes and a plurality of data electrodes,
Applying a first voltage lower than the ground voltage to the selected scan electrode among the scan electrodes, and applying a second voltage higher than the ground voltage to the remaining scan electrodes;
An organic electroluminescence device comprising: applying a third voltage to a data electrode corresponding to the organic electroluminescence device to emit light among the data electrodes, and applying a ground voltage to the remaining data electrodes Driving method.   The method further includes applying the first voltage to the selected scan electrode and applying a ground voltage to the remaining scan electrodes and all the data electrodes before applying the third voltage. The driving method according to claim 9.   Before applying the third voltage, a specific voltage is not applied to the data electrodes corresponding to the organic electroluminescence elements to be lit among the data electrodes, and a ground voltage is applied to the remaining data electrodes. The driving method according to claim 9, further comprising a step.   Before applying the third voltage, the fourth voltage is applied to the data electrode corresponding to the organic electroluminescence element to emit light, and the ground voltage is applied to the remaining data electrodes. The driving method according to claim 9, further comprising the step of:

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