JP2011170033A - Light emitting device and electronic apparatus, and method of driving pixel circuit - Google Patents

Abstract

A light-emitting device capable of obtaining a desired light emission amount while preventing deterioration of a light-emitting element is provided.
A pixel circuit is disposed between a capacitor and a light emitting element connected in series between a first power supply line and a second power supply line, and between a node ND and a data line. And a selection switch TSL. The drive circuit 20 sets the selection switch TSL to the on state in the writing period PW, while outputting the data potential VD to the data line 16, and sets the selection switch TSL to the off state in the light emission control period PEL. The voltage output to the first feeder 14 is changed over time so that the voltage across the light emitting element E increases with time, and after reaching the light emission threshold voltage Vth_el, a current flows through the light emitting element E to emit light. Change.
[Selection] Figure 4

Description

  The present invention relates to a light-emitting device, an electronic apparatus, and a pixel circuit driving method.

  In recent years, various light-emitting devices using light-emitting elements such as organic light-emitting diode (Organic Light Emitting Diode, hereinafter referred to as “OLED”) elements called organic EL (Electro Luminescent) elements and light-emitting polymer elements have been proposed (for example, patents). Reference 1).

  FIG. 16 is a diagram illustrating a configuration of a pixel circuit in the light emitting device disclosed in Patent Document 1. As shown in FIG. 16, the pixel circuit includes two switching elements SW1 and SW2, a capacitive element, and an OLED element. As shown in FIG. 17, in the writing period, the data potential VD corresponding to the specified gradation of the OLED element is output to the signal line 42. At this time, the switching element SW1 is set to the on state, while the switching element SW2 is set to the off state. As a result, the data potential output to the signal line 42 is written to the capacitor element via the switching element SW1. In the light emission period after the data writing period, as shown in FIG. 18, the switching element SW1 is set to the off state, while the switching element SW2 is set to the on state. Thereby, the electric charge accumulated in the capacitive element flows into the OLED element via the switching element SW2, and the OLED element emits light.

JP-A-8-54836

In the technique of Patent Document 1 described above, since the electric charge is discharged instantly during the light emission period, the discharge current that instantaneously flows into the light emitting element during the light emission period increases as the required light emission amount (time integral value of light emission luminance) increases. The value of becomes large, causing a problem that the light emitting element is deteriorated.
In view of the above circumstances, an object of the present invention is to provide a light emitting device that can obtain a desired light emission amount while preventing deterioration of a light emitting element.

  In order to solve the above problems, a light-emitting device according to the present invention includes a pixel circuit and a drive circuit that drives the pixel circuit, and the pixel circuit is interposed between a first power supply line and a second power supply line. Switching provided between a capacitor and a light emitting element connected in series, a node interposed between the capacitor and the light emitting element, and a data line for outputting a data potential corresponding to a specified gradation of the light emitting element And the driving circuit sets the switching element to the on state in the writing period, outputs the data potential to the data line, and sets the switching element to the off state in the light emission period after the writing period. On the other hand, the voltage output to the first feeder is changed with time so that the voltage across the light emitting element increases with time, and after reaching the light emission threshold voltage, current flows through the light emitting element to emit light. To change And features. The timing at which the light emitting element starts to emit light during the light emission period is determined according to the value of the data potential. In addition, when the designated gradation of the light emitting element designates a gradation other than the highest gradation (for example, white), the data potential is set to a value such that the voltage across the light emitting element is lower than the light emission threshold voltage. It is preferably set.

  In the present invention, after the voltage between both ends of the light emitting element, which increases with time in the light emission period, reaches the light emission threshold voltage, the light emitting element has a time change rate of the potential output to the first feeder. Current flows. In the light emission period, the timing at which the voltage across the light emitting element reaches the light emission threshold voltage is determined according to the value of the data potential written in the writing period. That is, the length of time during which light is emitted when a current flows through the light emitting element in the light emission period is determined according to the value of the data potential. Here, since the light emission amount of the light emitting element is represented by the time integral value of the current flowing through the light emitting element, the drive circuit needs a current having a value that does not deteriorate the light emitting element to obtain the desired light emission amount. By controlling the time rate of change of the potential output to the first power supply line and the data potential so as to flow through the light emitting element for a long time, a desired light emission amount can be obtained while preventing deterioration of the light emitting element. .

  For example, when the required light emission amount is large, the driving circuit sets the data potential output to the data line in the writing period to a value such that the voltage across the light emitting element is close to the light emission threshold voltage. In the driving circuit, the voltage between the both ends of the light emitting element increases with time during the light emission period, and a current of a value that does not deteriorate the light emitting element flows through the light emitting element after reaching the light emission threshold voltage. In addition, the potential output to the first feeder is changed with time. In this case, since the voltage between both ends of the light emitting element is set to a value close to the light emitting threshold voltage at the start point of the light emitting period, the voltage between both ends of the light emitting element reaches the light emitting threshold voltage after the light emitting period starts. It is possible to shorten the length of time to do. Therefore, a sufficient period can be secured for light emission during the light emission period when a current flows through the light emitting element. As a result, even when a required amount of light emission is large, a desired light emission amount can be obtained while preventing deterioration of the light emitting element.

  As a specific aspect of the light emitting device according to the present invention, the potential output to the first feeder line during the light emission period increases linearly or decreases linearly. That is, since the time change rate of the potential output to the first feeder line is constant during the light emission period, after the voltage across the light emitting element reaches the light emission threshold voltage during the light emission period, the light emission element is constant. Current flows. The product of the constant current value and the time length from the time when the voltage across the light emitting element reaches the light emitting threshold voltage to the end of the light emitting period (referred to as “light emitting time”) is the light emitting element Therefore, by dividing the desired light emission amount by a constant current value, the light emission time required to obtain the light emission amount can be defined accurately and easily. In addition, since the time change rate of the potential output to the first power supply line during the light emission period is constant, the value of the data potential necessary for obtaining the light emission time can be defined accurately and easily. That is, according to this aspect, the light emission amount can be controlled accurately and easily.

  As another mode of the light emitting device according to the present invention, a plurality of pixel circuits are arranged corresponding to each intersection of a plurality of scanning lines and a plurality of data lines, and the plurality of scanning lines are in units of a predetermined number. Divided into a plurality of blocks, the plurality of blocks correspond one-to-one with the plurality of first power supply lines, and the first power supply line corresponding to a certain block is commonly connected to the plurality of pixel circuits corresponding to the block. The driving circuit sequentially outputs a scanning signal for setting the switching element in the pixel circuit to the on state for each of the plurality of writing periods to one scanning line, and the pixel corresponding to the one scanning line. Each time a data potential corresponding to a specified gradation of the circuit is output to each data line and the writing period of the plurality of pixel circuits corresponding to each block is completed, the light emission period of the plurality of pixel circuits corresponding to the block Will start all at once Similarly, the potential output to the first power supply line corresponding to the block is changed over time. In this aspect, the first feeder is provided for each block. The drive circuit corresponds to the block so that the light emission periods of the plurality of pixel circuits corresponding to the block start all at once each time the writing period of the plurality of pixel circuits corresponding to the block ends. The potential output to the first power supply line is changed with time. In other words, the drive circuit controls the potential output to the first power supply line provided for each block, thereby driving (light-emitting) the pixel circuits for a plurality of rows belonging to the block. There is an advantage that the configuration and control are simplified as compared with the mode of driving the pixel circuit.

  The light emitting device according to the present invention is used in various electronic devices. A typical example of an electronic device is a device that uses a light-emitting device as a display device. Examples of the electronic apparatus according to the present invention include a personal computer and a mobile phone. However, the use of the light emitting device according to the present invention is not limited to image display. For example, the light emitting device of the present invention is also applied as an exposure device (optical head) for forming a latent image on an image carrier such as a photosensitive drum by irradiation of light.

  The present invention is also specified as a method of driving a pixel circuit. A driving method according to the present invention is a driving method of a pixel circuit including a capacitor element and a light emitting element connected in series between a first feeder line and a second feeder line. The potential of the node interposed between the light emitting element is set to a value corresponding to the specified gradation of the light emitting element, and the voltage across the light emitting element increases with time in the light emitting period after the writing period. Then, after reaching the light emission threshold voltage, the potential output to the first power supply line is changed with time so that a current flows through the light emitting element to emit light. The same effect as that of the light emitting device according to the present invention can be obtained by the above driving method.

1 is a block diagram of a light emitting device according to a first embodiment of the present invention. It is a circuit diagram of a pixel circuit. It is a figure for demonstrating the signal which a scanning line drive circuit and a data line drive circuit generate | occur | produce. 6 is a timing chart for explaining the operation of the light emitting device. It is a diagram for explaining the operation of the pixel circuit in the writing period. It is a figure for demonstrating operation | movement of the pixel circuit in the light emission control period. It is a figure for demonstrating the relationship between the designated gradation and the time length of the non-light-emission period and the light emission period. It is a block diagram of the light-emitting device which concerns on 2nd Embodiment of this invention. 6 is a timing chart for explaining the operation of the light emitting device. It is a circuit diagram of a pixel circuit concerning a modification of the present invention. It is a circuit diagram of a pixel circuit concerning a modification of the present invention. It is a circuit diagram of a pixel circuit concerning a modification of the present invention. It is a perspective view which shows the specific form of the electronic device which concerns on this invention. It is a perspective view which shows the specific form of the electronic device which concerns on this invention. It is a perspective view which shows the specific form of the electronic device which concerns on this invention. It is a figure which shows the structure of the conventional pixel circuit. It is a figure for demonstrating operation | movement of the conventional pixel circuit. It is a figure for demonstrating operation | movement of the conventional pixel circuit.

<A: First Embodiment>
FIG. 1 is a block diagram showing a schematic configuration of a light emitting device 100 according to the first embodiment of the present invention. The light emitting device 100 is mounted on an electronic device as a display device that displays an image. As shown in FIG. 1, the light emitting device 100 includes an element unit 10 in which a plurality of pixel circuits P are arranged, and a drive circuit 20 that drives each pixel circuit P. The drive circuit 20 includes a scanning line drive circuit 21, a data line drive circuit 23, and a potential generation circuit 25. The drive circuit 20 is distributed and mounted on a plurality of integrated circuits, for example. However, at least a part of the drive circuit 20 may be formed of a thin film transistor formed on the substrate together with the pixel circuit P.

  The element unit 10 crosses the X direction with m scanning lines 12 extending in the X direction and m first power supply lines 14 extending in the X direction in pairs with the respective scanning lines 12. N data lines 16 extending in the Y direction are formed (m and n are natural numbers). The plurality of pixel circuits P are arranged at the intersection of the pair of scanning lines 12 and first power supply lines 14 and the data lines 16 and arranged in a matrix of m rows × n columns. The scanning line driving circuit 21 outputs scanning signals GWR [1] to GWR [m] to each scanning line 12. The data line driving circuit 23 outputs data potentials VD [1] to VD [n] to the data lines 16 in accordance with the gradations designated for the pixel circuits P (hereinafter referred to as “designated gradations”).

  The potential generation circuit 25 generates a lamp potential Vrmp, which is a higher potential of the power supply, and a ground potential VCT, which is a lower potential of the power supply. The potential generation circuit 25 outputs the lamp potential Vrmp to each first power supply line 14. For convenience of explanation, the lamp potential output to the first feeder 14 in the i-th row is denoted as Vrmp [i]. On the other hand, the ground potential VCT is commonly supplied to the pixel circuits P via the second power supply line 18. In the present embodiment, the ground potential VCT is set to 0V.

  FIG. 2 is a circuit diagram of the pixel circuit P. In FIG. 2, only one pixel circuit P located in the j-th column (J = 1 to n) of the i-th row (i = 1 to m) is representatively shown. As shown in FIG. 2, the pixel circuit P includes a light emitting element E, a capacitive element C1, and a selection switch TSL.

  The light emitting element E and the capacitive element C1 are arranged in series on a path connecting the first power supply line 14 in the i-th row and the second power supply line 18 common to the pixel circuits P in each row. The light emitting element E is an OLED element in which a light emitting layer of an organic EL material is interposed between an anode and a cathode that face each other. The capacitive element C1 includes a first electrode L1 and a second electrode L2. The first electrode L1 is connected to the first feeder 14, while the second electrode L2 is connected to the light emitting element E.

  The selection switch TSL is interposed between the node ND interposed between the capacitive element C1 and the light emitting element E and the data line 16 in the j-th column, and establishes an electrical connection (conduction / non-conduction) between them. Control. As shown in FIG. 2, for example, an N-channel transistor (thin film transistor) is preferably employed. The gates of the selection switches TSL of the n pixel circuits P belonging to the i-th row are commonly connected to the i-th scanning line 12.

  Next, each signal generated by the scanning line driving circuit 21 and each signal generated by the data line driving circuit 23 will be described with reference to FIG. As shown in FIG. 3, the scanning line driving circuit 21 scans the scanning signals GWR [1] to GWR [m] in each of m horizontal scanning periods (H [1] to H [m]) in the vertical scanning period. Are sequentially set to the active level (high level) to sequentially select each scanning line 12 (n pixel circuits P in each row). The transition of the scanning signal GWR [i] to the high level means selection of the scanning line 12 in the i-th row. When the scanning signal GWR [i] transitions to a high level, the selection switches TSL of the n pixel circuits P belonging to the i-th row are simultaneously turned on. The data line driving circuit 23 generates data potentials VD [1] to VD [n] corresponding to one row (n) of pixel circuits P selected by the scanning line driving circuit 21 in each horizontal scanning period H. Output to each data line 16. The data potential VD [j] output to the data line 16 in the j-th column in the horizontal scanning period H [i] in which the i-th row is selected is supplied to the pixel circuit P located in the j-th column in the i-th row. On the other hand, the potential DATA [i, j] corresponds to the designated gradation (referred to as “designated gradation”).

  Next, the operation of the drive circuit 20 (the drive method of the pixel circuit P) will be described with reference to the pixel circuit P in the i-th row and the j-th column, with reference to FIG. In FIG. 4, a period from when the scanning signal GWR [i] changes to the high level until it changes again to the high level is referred to as one field period (1V). One field period 1V is divided into a writing period PW and a light emission control period PEL. The writing period PW corresponds to one horizontal scanning period H, and the scanning signal GWR [i] is set to a high level in the writing period PW, while being set to a low level in the light emission control period PEL. Hereinafter, the operation of the pixel circuit P in the j-th column belonging to the i-th row will be described by dividing it into a writing period PW and a light emission control period PEL.

(A) Write period PW
As shown in FIG. 4, when the writing period PW starts, the driving circuit 20 (scanning line driving circuit 21) sets the scanning signal GWR [i] to a high level. Therefore, as shown in FIG. 5, the selection switch TSL is turned on. When the selection switch TSL is turned on, the data line 16 and the node ND are brought into conduction. As a result, the potential Va [i, j] of the node ND changes to the data potential VD [j] output to the data line 16 in the jth column. The data potential VD [j] is the potential DATA [i, j] corresponding to the designated gradation of the pixel circuit P located in the i-th row and the j-th column.

  In this embodiment, the data potential VD [j] output to the data line 16 in the writing period PW is a voltage between both ends of the light emitting element E (voltage between the node ND and the second feeder line 18). It is set to a value lower than the threshold voltage Vth_el. Therefore, as shown in FIG. 4, the potential Va [i, j] (DATA [i, j]) of the node ND in the writing period PW is lower than the light emission threshold voltage Vth_el. Therefore, in the writing period PW, no current flows through the light emitting element E and the light emitting element E enters a non-light emitting state. As shown in FIG. 4, the drive circuit 20 (potential generation circuit 25) sets the lamp potential Vrmp [i] to be output to the first feeder 14 to the reference potential Vref.

(B) Light emission control period PEL
As shown in FIG. 4, when the light emission control period PEL starts, the drive circuit 20 (scan line drive circuit 21) sets the scan signal GWR [i] to a low level. Therefore, as shown in FIG. 6, since the selection switch TSL transitions to the OFF state, the node ND is in an electrically floating state, and its potential Va [i, j] is lower than the light emission threshold voltage Vth_el. , j].

  The drive circuit 20 (potential generation circuit 25) causes the voltage across the light emitting element E to increase with time, and after reaching the light emission threshold voltage Vth_el, a current flows through the light emitting element E to emit light. In addition, the lamp potential Vrmp [i] output to the first feeder 14 is changed over time. More specifically, it is as follows. As shown in FIG. 4, the potential generation circuit 25 changes the lamp potential Vrmp [i] output to the first feeder 14 from the start point ts to the end point te of the light emission control period PEL with a time change rate RX (RX = dVrmp / dt). ) To increase linearly. That is, in the present embodiment, the lamp potential Vrmp [i] is a voltage signal having a ramp waveform (sawtooth waveform). As a result, the potential of the first electrode L1 of the capacitive element C1 also rises linearly at the time change rate RX.

As described above, since the node ND is in an electrically floating state, the potential of the node ND (that is, the potential of the second electrode L2) Va [i, j] rises in conjunction with the potential of the first electrode L1. At this time, the time change rate of the potential Va [i, j] of the node ND is equal to the time change rate RX of the lamp potential Vrmp [i]. When the potential Va [i, j] at the node ND reaches the light emission threshold voltage Vth_el, the current Iel from the first power supply line 14 flows to the light emitting element E through the capacitive element C1. As a result, the light emitting element E enters a light emitting state. When the capacitance of the capacitive element C1 is denoted by Cp and the charge accumulated in the capacitive element C1 is denoted by Q, the current Iel flowing through the light emitting element E after the potential Va [i, j] of the node ND reaches the light emission threshold voltage Vth_el is Is represented by the following formula (1).
Iel = dQ / dt = Cp × dVrmp / dt = Cp × dRX / dt (1)

  In this embodiment, since the time change rate RX of the lamp potential Vrmp is constant, the time from when the potential Va [i, j] of the node ND reaches the light emission threshold voltage Vth_el to the end point te of the light emission control period Pel. In the period, a constant current Iel continues to flow through the light emitting element E. Further, the temporal change rate RX of the lamp potential Vrmp is set to such a value that the current Iel flowing through the light emitting element E does not deteriorate the light emitting element E. In FIG. 4, the period from the start point ts of the light emission control period PEL until the potential Va [i, j] of the node ND reaches the light emission threshold voltage Vth_el (the voltage between both ends of the light emitting element E becomes the light emission threshold voltage). The period until reaching the non-light-emitting period Pf. On the other hand, a period from when the potential Va [i, j] of the node ND reaches the light emission threshold voltage Vth_el to the end point te of the light emission control period PEL is referred to as a light emission period PL. In the present embodiment, the temporal change rate of the potential Va [ij] of the node ND that increases with time from the start of the light emission control period PEL until the voltage across the light emitting element E reaches the light emission threshold voltage Vth_el is constant. Therefore, the time lengths of the non-light emitting period Pf and the light emitting period PL are determined according to the potential Va [i, j] of the node ND set in the writing period PW.

  Here, the light emission amount of the light emitting element E is represented by the product of the current Iel (constant value) flowing through the light emitting element E and the time length of the light emission period PL. Since the light emission luminance of the light emitting element E is a value corresponding to the current Iel flowing through the light emitting element E, it can be said that the light emission amount of the light emitting element E is a time integral value of the light emission luminance. In the present embodiment, the light emission amount required for the light emitting element E becomes larger as the designated gradation is higher (closer to “white” which is the highest gradation). The drive circuit 20 (for example, the data line drive circuit 23) controls the value of the data potential VD [j] in accordance with the specified gradation of the light emitting element E, thereby variably setting the time length of the light emission period PL. Expresses the specified gradation. For example, when the designated gradation of the light emitting element E is “white” which is the highest gradation, it is necessary to set the time length of the light emission period PL to a value sufficiently larger than the time length of the non-light emission period Pf. In this case, as shown in FIG. 7, the driving circuit 20 uses the data potential VD [j] output to the data line 16 in the writing period PW as the potential Va [i, j] of the node ND (both ends of the light emitting element E). Is set to a value that is close to the light emission threshold voltage Vth_el. Thereby, the time length of the non-light emission period Pf (the period from the start point ts of the light emission control period PEL until the potential Va [i, j] of the node ND reaches the light emission threshold voltage Vth_el) can be sufficiently shortened. Thus, the time length of the light emission period PL, which is the remaining period of the light emission control period PEL, can be set to a value sufficiently larger than the time length of the non-light emission period Pf. Thereby, even when the designated gradation of the light emitting element E is “white” which is the maximum gradation (when the required light emission amount is large), it is possible to express a desired gradation while preventing the light emitting element E from deteriorating. That's it. Note that when the designated gradation is “white”, which is the highest gradation, the light emitting element E emits light over the entire light emission control period PEL (that is, the time length of the non-light emission period Pf is zero). May be. In this aspect, when the designated gradation is “white” which is the highest gradation, the value of the data potential VD [j] output to the data line 16 in the writing period PW is the potential Va [i, j of the node ND. ] Is set to a value that exceeds the light emission threshold voltage Vth_el.

  Further, for example, when the designated gradation of the light emitting element E is “black” which is the lowest gradation, the light emission amount required for the light emitting element E is zero, so the time length of the light emission period PL needs to be zero. . In this case, as shown in FIG. 7, the drive circuit 20 increases the data potential VD [j] output to the data line 16 in the writing period PW to a node ND that increases with time after the light emission control period PEL starts. Is set to a value such that the potential Va [ij] reaches the light emission threshold voltage Vth_el at the end point te of the light emission control period PEL. As a result, the entire light emission control period PEL is set as the non-light emission period Pf. That is, the time length of the light emission period PL becomes zero, and a “black” gradation can be expressed. Further, for example, when the designated gradation of the light emitting element E is “gray” which is an intermediate gradation, as shown in FIG. 7, the drive circuit 20 outputs the data potential VD [j output to the data line 16 in the writing period PW. ] Is set to a value such that the time length of the light emission period PL becomes a time length necessary for obtaining a desired light emission amount. Thereby, a desired gradation can be expressed while suppressing deterioration of the light emitting element E.

  As described above, the drive circuit 20 causes the constant current Iel having a value that does not deteriorate the light emitting element E to flow through the light emitting element E for a time length necessary to obtain a desired light emission amount (gradation). In addition, the time change rate RX of the lamp potential Vrmp and the data potential VD [j] are controlled. Accordingly, there is an advantage that a desired light emission amount can be obtained while preventing the light emitting element E from being deteriorated.

<B: Second Embodiment>
FIG. 8 is a block diagram of the light emitting device 100 according to the second embodiment of the present invention. In the second embodiment, the m scanning lines 12 are divided into m / 3 blocks B (B [1] to B [m / 3]) in units of three adjacent lines. Further, in the present embodiment, a plurality (m / 3) of first feed lines 14 (14 [1] to 14 [m / 3]) corresponding to a plurality (m / 3) of blocks B in a one-to-one relationship. Extends in the X direction. The first power supply line 14 [k] corresponding to the kth (1 ≦ k ≦ m / 3) block B [k] is commonly connected to the plurality of pixel circuits P belonging to the block B [k]. . Further, the lamp potential Vrmp output to the first feeder 14 [k] corresponding to the kth block B [k] is denoted as Vrmp [k]. Since the configuration of the pixel circuit P is the same as that of the first embodiment, detailed description thereof is omitted.

  Next, the operation of the light emitting device 100 according to this embodiment will be described. The operations of the scanning line driving circuit 21 and the data line driving circuit 23 are the same as those in the first embodiment. That is, the scanning line driving circuit 21 sequentially selects one scanning line 12 for each of a plurality of horizontal scanning periods H (for each of a plurality of writing periods PW), while the data line driving circuit 23 selects a selected scanning line. The data potential VD (VD [1] to VD [j]) corresponding to the specified gradation of the pixel circuit P corresponding to the line 12 is output to each data line 16. Hereinafter, the operation of the drive circuit 20 will be described with reference to FIG. 9 while paying attention to the first block B [1].

  In FIG. 9, the scanning signal GWR [1] output to the first scanning line 12 selected first among the three scanning lines 12 belonging to the first block B [1] is set to the high level. A period from the transition to the scanning signal GWR [1] transitioning to the high level again is referred to as one field period (1V). In the present embodiment, one field period 1V is divided into a block writing period PBW and a block light emission control period PBEL.

  As shown in FIG. 9, the block writing period PBW includes the writing period PW [1] of the pixel circuit P corresponding to the scanning line 12 in the first row and the pixel corresponding to the scanning line 12 in the second row. The circuit P includes a writing period PW [2] and a writing period PW [3] of the pixel circuit P corresponding to the scanning line 12 in the third row. Since the operation of the drive circuit 20 in each writing period PW (PW [1] to PW [3]) is the same as that in the first embodiment, detailed description thereof is omitted here. In short, in the block writing period PBW, each pixel circuit P belonging to the first block B [1] is written with the data potential VD corresponding to the designated gradation of the pixel circuit P, and the written data The potential VD is held by the capacitive element C1. In the block writing period PBW, the drive circuit 20 (for example, the potential generation circuit 25) outputs the ramp potential Vrmp [i] to be output to the first power supply line 14 [1] corresponding to the first block B [1]. Is set to the reference potential Vref. When the writing period PW [3] of the pixel circuit P corresponding to the scanning line 12 in the third row ends, the writing periods PW of the plurality of pixel circuits P belonging to the first block B [1] end. As a result, the block writing period PBW ends.

  When the block writing period PBW ends and the block light emission control period PBEL starts, the drive circuit 20 (potential generation circuit 25) causes the light emission control periods of the plurality of pixel circuits P belonging to the first block B [1]. The ramp potential Vrmp [1] output to the first power supply line 14 [1] corresponding to the block B [1] is changed with time so that PEL starts all at once. Specifically, as shown in FIG. 9, the potential generation circuit 25 applies the lamp potential Vrmp [1] to be output to the first power supply line 14 [1] from the start point ts2 to the end point te2 of the block light emission control period PEL over time. Increase linearly at the rate of change RX. As a result, the voltage across the light emitting elements E of each pixel circuit P belonging to the first block B [1] (potential Va at the node ND) increases all at once and reaches the light emission threshold voltage Vth_el. , A constant current Iel flows through the light emitting element E to emit light. As described in the first embodiment, the constant current Iel continues to flow through the light emitting element E of each pixel circuit P for a time length corresponding to the value of the data potential VD written in the writing period PW. The gradation specified in the pixel circuit P is expressed.

The above operation is the same for the other blocks B. In short, the driving circuit 20 starts the light emission control periods PEL of the plurality of pixel circuits P corresponding to the block B all at once when the writing periods PW of the plurality of pixel circuits P corresponding to the blocks B are all completed. As described above, the lamp potential Vrmp output to the first power supply line 14 corresponding to the block B is changed over time.
That is, the drive circuit 20 controls the lamp potential Vrmp output to the first power supply line 14 provided for each block B, thereby driving the pixel circuits P for a plurality of rows belonging to the block B together (light emission). Therefore, there is an advantage that the configuration and control are simplified compared to the first embodiment in which the pixel circuit P is driven in units of rows.

<C: Modification>
The present invention is not limited to the above-described embodiments, and for example, the following modifications are possible. Also, two or more of the modifications shown below can be combined.

(1) Modification 1
The configuration of the pixel circuit P is not limited to that shown in FIG. For example, the configuration of the pixel circuit P may be the mode shown in FIG. 10, the first electrode L1 of the capacitive element C1 is connected to the light emitting element E, while the second electrode L2 of the capacitive element C1 is connected to the second feeder line 18 with each of the embodiments described above. Is different. Also in this mode, in the light emission control period PEL, the drive circuit 20 linearly increases the lamp potential Vrmp output to the first power supply line 14 at the time change rate RX, so that the voltage between both ends of the light emitting element E changes over time. After reaching the light emission threshold voltage Vth_el, the constant current Iel flows through the light emitting element E.

  Further, for example, the configuration of the pixel circuit P may be the mode shown in FIG. In the aspect of FIG. 11, the potential generation circuit 25 outputs the higher potential VEL of the power supply to the second power supply line 18, while outputting the lamp potential Vrmp that is the lower potential of the power supply to each first power supply line 14. This is different from the above-described embodiments. In this aspect, in the light emission control period PEL, the drive circuit 20 linearly decreases the lamp potential Vrmp [i] output to the first feeder 14 with the time change rate RX, so After the voltage increases with time and reaches the light emission threshold voltage Vth_el, a constant current Iel flows through the light emitting element E. Furthermore, the embodiment of FIG. 11 can be modified as shown in FIG.

(2) Modification 2
In each of the above-described embodiments, the potential output to the first power supply line 14 in the light emission control period PEL increases linearly, but is not limited thereto, and is output to the first power supply line 14 in the light emission control period PEL. The mode of the potential change to be made is arbitrary. For example, the waveform of the potential output to the first power supply line 14 in the light emission control period PEL may be curved. In short, the potential output to the first power supply line 14 during the light emission control period PEL is such that the voltage across the light emitting element E increases with time, and after reaching the light emission threshold voltage Vth_el, a current is supplied to the light emitting element E. Any material that changes with time so that light flows and emits light may be used.

  However, as in each of the above-described embodiments, if the time change rate of the potential output to the first feeder 14 in the light emission control period PEL is constant, the voltage across the light emitting element E in the light emission control period PEL. After reaching the light emission threshold voltage Vth_el, a constant current flows through the light emitting element E. Therefore, by dividing the desired light emission amount by the constant current value, the time length of the light emission period PL required to obtain the light emission amount can be accurately and easily specified. In addition, since the time change rate of the potential output to the first feeder 14 in the light emission control period PEL is constant, the value of the data potential VD necessary for obtaining the time length of the light emission period PL is also accurate and easy. Can be prescribed. That is, according to this aspect, the light emission amount can be controlled accurately and easily.

(3) Modification 3
In each of the above-described embodiments, the temporal change rate RX of the lamp potential Vrmp output to the first feeder 14 in the light emission control period PEL is constant. However, the present invention is not limited to this. For example, the lamp potential Vrmp It is also possible to adopt a mode in which the time change rate is variably set. For example, if the light emission of the element unit 10 continues and the panel temperature rises, the luminance characteristics of the light emitting element E of each pixel circuit P also change. Therefore, it is possible to variably set the time change rate of the lamp potential Vrmp so that the luminance of the light emitting element E becomes a desired value even when the panel temperature changes.

(4) Modification 4
The light emitting element E may be an OLED element, an inorganic light emitting diode, or an LED (Light Emitting Diode). In short, all elements that emit light in response to the supply of electric energy (application of electric field or supply of current) can be used as the light-emitting elements of the present invention.

<D: Application example>
Next, an electronic apparatus using the light emitting device according to the present invention will be described. FIG. 13 is a perspective view illustrating a configuration of a mobile personal computer that employs the light emitting device 100 according to the embodiment described above as a display device. The personal computer 2000 includes a light emitting device 100 as a display device and a main body 2010. The main body 2010 is provided with a power switch 2001 and a keyboard 2002. Since the light emitting device 100 uses an OLED element as the light emitting element E, it is possible to display an easy-to-see screen with a wide viewing angle.

  FIG. 14 shows a configuration of a mobile phone that employs the light emitting device 100 according to the embodiment described above as a display device. The cellular phone 3000 includes a plurality of operation buttons 3001, scroll buttons 3002, and the light emitting device 100. By operating the scroll button 3002, the screen displayed on the light emitting device 100 is scrolled.

  FIG. 15 shows a configuration of a personal digital assistant (PDA) that employs the light emitting device 100 according to the embodiment described above as a display device. The information portable terminal 4000 includes a plurality of operation buttons 4001, a power switch 4002, and the light emitting device 100. When the power switch 4002 is operated, various types of information such as an address book and a schedule book are displayed on the light emitting device 10.

  Electronic devices to which the light emitting device according to the present invention is applied include those shown in FIGS. 13 to 15, digital still cameras, televisions, video cameras, car navigation devices, pagers, electronic notebooks, electronic papers, calculators. , Word processors, workstations, videophones, POS terminals, printers, scanners, copiers, video players, devices equipped with touch panels, and the like. Further, the use of the light emitting device 100 according to the present invention is not limited to the display of images. For example, the light emitting device 100 of the present invention is also used as an exposure device that forms a latent image on a photosensitive drum by exposure in an electrophotographic image forming apparatus.

DESCRIPTION OF SYMBOLS 10 ... Element part, 12 ... Scanning line, 14 ... 1st feed line 14 ... Data line, 18 ... 2nd feed line, 20 ... Drive circuit, 21 ... Scan line drive circuit, 23 ... Data line driving circuit, 100... Light emitting device, C1 .capacitor element, E... Light emitting element, GWR... Scanning signal, ND ....... node, TSL ... selection switch, P. ON period, PEL: light emission control period, Pf: non-light emission period, PL: light emission period, VD: data potential.

Claims (7)

A pixel circuit; and a drive circuit that drives the pixel circuit;
The pixel circuit includes:
A capacitive element and a light emitting element connected in series between the first feeder line and the second feeder line;
A switching element provided between a node interposed between the capacitive element and the light emitting element and a data line to which a data potential corresponding to a specified gradation of the light emitting element is output;
The drive circuit is
In the writing period, the switching element is set to an on state, while the data potential is output to the data line,
In the light emission period after the writing period, the switching element is set to an off state, while the voltage between both ends of the light emitting element increases with time, and after the light emission threshold voltage is reached, the light emission Changing the potential output to the first feeder line over time so that a current flows through the element to emit light;
A light emitting device characterized by that. The potential output to the first feeder line during the light emission period increases linearly or decreases linearly.
The light-emitting device according to claim 1. The timing at which the light emitting element starts to emit light in the light emission period is determined according to the value of the data potential.
The light-emitting device according to claim 1 or 2. A plurality of the pixel circuits corresponding to each intersection of a plurality of scanning lines and a plurality of the data lines;
The plurality of scanning lines are divided into a plurality of blocks having a predetermined number as a unit,
The plurality of blocks have a one-to-one correspondence with the plurality of first power supply lines, and the first power supply line corresponding to a certain block is commonly connected to the plurality of pixel circuits corresponding to the block,
The drive circuit is
For each of the plurality of writing periods, a scanning signal for setting the switching element in the pixel circuit to an ON state is sequentially output to one scanning line, and a designated floor of the pixel circuit corresponding to the one scanning line is output. The data potential corresponding to the key is output to each data line,
Each time the writing period of the plurality of pixel circuits corresponding to each block ends, the light emission period of the plurality of pixel circuits corresponding to the block starts all at once. Change the potential output to one feeder line over time,
The light-emitting device according to claim 1, wherein the light-emitting device is a light-emitting device. The data potential is set to a value such that a voltage across the light emitting element is lower than a light emission threshold voltage.
The light emitting device according to claim 1, wherein the light emitting device is a light emitting device.   An electronic apparatus comprising the light emitting device according to claim 1. A driving method of a pixel circuit including a capacitor element and a light emitting element connected in series between a first feeder line and a second feeder line,
In a writing period, a potential of a node interposed between the capacitor and the light emitting element is set to a value according to a specified gradation of the light emitting element.
In the light emission period after the writing period, the voltage across the light emitting element increases with time, and after reaching the light emission threshold voltage, a current flows through the light emitting element to emit light, Changing the potential output to the first feeder line over time;
A driving method of a pixel circuit.

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