JP2011043537A - Pixel circuit, electro-optical device, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pixel circuit performing black display unboundedly similar to real black. <P>SOLUTION: This invention is a pixel circuit (P1) arranged corresponding to crossing of a scanning line (3) and a data line (6) crossed to the scanning line (3) and extended, and includes: an electro-optical element (8) having gradation in accordance with a data potential output to the data line; a first electrode (E1) connected to a first capacity line (30), and a capacitive element (C1) having a second electrode (E2) connected to the data line; a first switching element (Tr1) in which the switching element is arranged between the second electrode and the electro-optical element and becomes a conductive state during selection of the scanning line, thereby conducting these second electrode and electro-optical element; and a second switching element (Tr2) arranged between the second capacity line (31) and the electro-optical element. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pixel circuit, an electro-optical device, and an electronic apparatus including an organic EL (electro luminescent) element, a liquid crystal, and the like.

Conventionally, an electro-optical device including an organic EL element or the like as an electro-optical element has been provided. The electro-optical device includes various drive circuits for supplying a predetermined current or voltage to the organic EL element or the like. Such a drive circuit may include, for example, a capacitor element connected in parallel to the organic EL element. In this case, a data potential is supplied to the anode of the organic EL element and one electrode of the capacitor, and a reference potential is supplied to the cathode of the organic EL element and the other electrode of the capacitor, respectively. According to this, since the current supply caused by the electric charge corresponding to the data potential stored in the capacitor element can be performed to the organic EL element, the organic EL element can be driven, etc. It becomes possible.
As such an electro-optical device, for example, a device disclosed in Patent Document 1 is known.

JP 2000-122608 A

  Incidentally, the electro-optical device as described above has the following problems. That is, in order to make the light emission amount (time integration value of the light emission luminance) of the organic EL element a sufficient value, it is necessary to increase the amount of charge stored in the capacitor element. It needs to be a large value. However, the realization of such a large capacity value is inherently difficult due to the limitation of the physical area allowed for installation of each drive circuit. If it is assumed that a capacitive element having such a large capacitance value is provided, each drive circuit may have a very insane size, or such a simple case may be Although it is not assumed, it is necessary to provide a capacitive element for securing the capacitance value somewhere on the substrate outside the drive circuit. There is a risk that various problems such as hindering widening will occur.

In addition to the drive circuit having the above-described configuration, there is a drive circuit including a drive transistor for adjusting a current that should flow through the organic EL element between the organic EL element and the power source. In this case, the adjustment of the current (that is, the adjustment of the light emission luminance) is performed through adjustment of the magnitude of the data potential applied to the gate of the driving transistor.
According to this, although the difficulty of installing the capacitive element having the above-described large capacitance value does not occur, the power supply voltage is always applied to the source or drain of the driving transistor no matter what brightness the organic EL element emits light. Therefore, a new problem arises that wasteful power is consumed.

  In addition, the organic EL element has parasitic capacitance regardless of the difference in the drive circuit described above, but the organic EL element emits light of a predetermined gradation for a predetermined period. If the charge is stored in the parasitic capacitance, it is difficult to perform a true black display. This causes a so-called “black float” and adversely affects the image quality of the displayed image, such as causing a decrease in contrast.

An object of the present invention is to provide a pixel circuit, an electro-optical device, and an electronic apparatus that can solve at least a part of the problems described above.
It is another object of the present invention to provide a pixel circuit, an electro-optical device, and an electronic device that can solve the problems related to the pixel circuit, the electro-optical device, and the electronic device of this aspect.

  In order to solve the above-described problem, the pixel circuit of the present invention is a pixel circuit that is arranged corresponding to the intersection of a scanning line and a data line extending across the scanning line, and has a data potential output to the data line. An electro-optical element having a corresponding gradation, a first electrode connected to the first capacitor line, a capacitor element having a second electrode connected to the data line, the second electrode, and the electro-optical element Between the first switching element that conducts between the second electrode and the electro-optic element by being placed in a conduction state when the scanning line is selected, and between the second capacitance line and the electro-optic element. And a second switching element.

According to the present invention, when the capacitive element and the electro-optic element are conducted when the first switching element is conducted, when the electro-optic element is, for example, an organic EL element, the charge stored in the capacitive element (this charge) Current corresponding to the data potential output to the data line) flows through the organic EL element, and the organic EL element emits light with a gradation corresponding to the charge (that is, organic EL). The element is driven). In this case, the present invention does not require the drive transistor that causes the increase in power consumption as described above. Therefore, the power consumption can be reduced as compared with the drive circuit having such a configuration. Can do.
In the present invention, in particular, a second switching element is provided between the electro-optic element and the second capacitance line. As a result, if the second capacitor line has an appropriate potential and the second switching element becomes conductive at an appropriate timing, the charge stored in the electro-optic element or its parasitic capacitance is extracted (in other words, In other words, it is possible to discharge the electro-optical element. Therefore, according to the present invention, it is possible to avoid a state in which an extra charge is stored in the electro-optical element. When the electro-optical element is an organic EL element, it is not limited to true black. Near black display (almost complete non-light emission) can be performed.

  In order to solve the above-described problem, an electro-optical device according to an embodiment of the present invention includes a plurality of pixel circuits arranged corresponding to intersections of a plurality of scanning lines and a plurality of data lines, and a driving period in each unit period. A scanning line driving circuit that sequentially selects one scanning line, and a driving period in the unit period for each writing period that is a period in the unit period and before the driving period is started. A data line driving circuit that outputs a data potential corresponding to the gradation data of the pixel circuit corresponding to the selected scanning line to each data line, and each of the plurality of pixel circuits includes the data An electro-optical element having a gradation corresponding to a potential; a first electrode connected to a first capacitor line; a capacitor element having a second electrode connected to the data line; the second electrode; Arranged between the optical element and the A first switching element that conducts between the second electrode and the electro-optic element by being in a conducting state when selecting a line; and a second capacitance line and the electro-optic element, and other than the driving period. And a second switching element that is in a conductive state for a predetermined period within the time zone.

According to the present invention, since the above-described “pixel circuit” according to the present invention is included, substantially the same operational effects as the operational effects achieved thereby are exhibited.
Further, according to the present invention, in order to drive one pixel circuit or one electro-optical element included therein, a plurality of pixel circuits connected to one data line corresponding to the pixel circuit are included. A plurality of capacitive elements included can be used. Therefore, in the present invention, it is not necessary to increase the capacitance value of each capacitive element in this case.
As described above, according to the present invention, the installation area can be enlarged as expected when a capacitive element having a large capacitance value is provided, or the like. There is no need to worry about inconveniences.

In the electro-optical device according to the aspect of the invention, the second switching element selection line connected to all the second switching elements included in each of the plurality of pixel circuits, and the second switching for selecting the second switching element selection line. An element selection line driving circuit may be further provided.
According to this aspect, when the second switching element (hereinafter, abbreviated as “second SW”) selection line drive circuit selects the second SW selection line, all of the second SW included in the electro-optical device is It becomes a conduction state all at once. That is, in this aspect, the above-described discharge for the electro-optical element is performed simultaneously for all the electro-optical elements.
According to this, it becomes possible to simplify the processing mode as compared with, for example, the case where the electro-optical element is discharged for each group including a predetermined number of second SWs, or such control for each group. Therefore, the configuration can be simplified (for example, it is not necessary to install a shift register for the second SW selection line). Such an effect contributes to more effective realization of discharge for the electro-optic element.

Alternatively, in the electro-optical device according to the aspect of the invention, among the second switching elements included in each of the plurality of pixel circuits, the plurality of second switching elements corresponding to one of the scanning lines may correspond to each group. And a plurality of second switching element selection lines, and a second switching element selection line driving circuit that sequentially selects the plurality of second switching element selection lines.
According to this aspect, the second SW selection line driving circuit sequentially selects the plurality of second SW selection lines, so that a group of the plurality of second SWs corresponding to each one of the second SW selection lines is sequentially arranged for each group. It becomes a conductive state. In other words, in this aspect, the above-described discharge of the electro-optical element is sequentially performed for each scanning line or for each second SW selection line.
According to this, compared with the case where discharge is performed for all of the electro-optical elements at once, for example, the discharge can be suitably performed after the electro-optical elements that require discharge are accurately selected.

In the electro-optical device according to the aspect of the invention, the second switching element is repeatedly in a conductive state with a predetermined interval while the plurality of unit periods are repeatedly visited. The predetermined interval is one length of the unit period. You may comprise so that it may be defined on the basis of thickness.
According to this aspect, preferably, the above-described electro-optical element can be discharged every unit period, so that the operational effect (particularly, the effect related to true black display) according to the present invention is achieved. Played more effectively.
In this aspect, the “predetermined interval” only needs to be defined as “reference to one length of the unit period”. For example, in some cases, the second switching element is activated every time the unit period is visited twice. It includes a case where the second switching element becomes conductive every time the unit period comes K times (K is an appropriate positive integer), or more generally, when it becomes conductive.

In the electro-optical device according to the aspect of the invention, after the driving period, there is a period in which the first switching element is still in a conductive state, and in the period, there is a period in which the second switching element is in a conductive state. You may comprise as follows.
According to this aspect, each capacitive element corresponding to the data line connected to the first switching element (via the second electrode of the capacitive element) through the first and second switching elements that are both in a conductive state. It is possible to discharge the stored charge. In this case, naturally, the above-described electro-optical element is also discharged at the same time.
As described above, according to this aspect, not only the electro-optical element but also each capacitive element is discharged at the same time, so that it is possible to efficiently carry out initialization, so to speak, regarding each of these elements. It is.

The electro-optical device according to the aspect of the invention may be configured such that there is a period in which the second switching element is in a conductive state within the writing period.
According to this aspect, the electro-optical element is prevented from being driven while the electric charge corresponding to the data potential is being stored in the capacitive element (that is, during writing). This is because, in the present invention, one end of the first switching element is connected to the electro-optical element, and the electro-optical element is connected to one end of the second switching element. This is because the first switching element and the second capacitor line which are in the non-conductive state can be short-circuited if the conductive state is established. As a result, a leak current or the like that may be generated in the first switching element escapes to the second capacitance line, and thus it is possible to avoid the transition of the electro-optical element to an unnecessary driving state.

In the electro-optical device according to the aspect of the invention, the potential of the second capacitance line may be the potential of the electrode on the side opposite to the first switching element of the pair of electrodes constituting the electro-optical element, You may comprise so that it may be smaller than the sum with the threshold voltage for driving an electro-optical element.
According to this aspect, since the potential drop between the electro-optic element and the second capacitance line can be made relatively large, the above-described discharge of the electro-optic element can be performed more effectively.

Moreover, in order to solve the above-described problems, an electronic apparatus according to the present invention includes the various electro-optical devices described above.
Since the electronic apparatus according to the present invention includes the various electro-optical devices described above, it is possible to display a black image that is as close as possible to a true black display. As a result, it is possible to display a higher quality image. It is.

1 is a block diagram illustrating an electro-optical device according to a first embodiment of the invention. FIG. FIG. 2 is a circuit diagram illustrating details of a unit circuit and a data potential generation unit surrounding the electro-optical device of FIG. 1. 3 is a timing chart for explaining the operation of the electro-optical device of FIGS. 1 and 2. FIG. 4 is an explanatory diagram (part 1: writing operation) for visually expressing charging and discharging of the capacitive element (C1) and discharging of the electro-optical element (8) in the electro-optical device operating according to FIG. 3; FIG. 4 is an explanatory diagram (part 2; light emission operation) for visually expressing charging and discharging of the capacitive element (C1) and discharging of the electro-optical element (8) in the electro-optical device operating according to FIG. FIG. 4 is an explanatory diagram (part 3; initialization operation) for visually expressing charging and discharging of the capacitive element (C1) and discharging of the electro-optical element (8) in the electro-optical device operating according to FIG. 3; FIG. 6 is a circuit diagram illustrating details of a unit circuit and a data potential generation unit included in an electro-optical device according to a second embodiment of the invention. 8 is a timing chart for explaining the operation of the electro-optical device in FIG. 7. FIG. 9 is an explanatory diagram (initialization operation) for visually expressing charging and discharging of the capacitive element (C1) and discharging of the electro-optical element (8) in the electro-optical device operating according to FIG. It is a perspective view which shows the electronic device to which the organic electroluminescent apparatus which concerns on this invention is applied. It is a perspective view which shows the other electronic device to which the organic EL apparatus which concerns on this invention is applied. It is a perspective view which shows the further another electronic device to which the organic EL apparatus which concerns on this invention is applied.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. In addition to FIGS. 1 and 2 mentioned here, in each drawing referred to below, the ratio of dimensions of each part may be appropriately different from the actual one.

  In FIG. 1, an electro-optical device 10 is a device used in various electronic devices as a means for displaying an image, and a pixel array unit 100 in which a plurality of unit circuits (pixel circuits) P1 are arranged in a planar shape. The scanning line driving circuit 200 and the data line driving circuit 300 are included. In FIG. 1, the scanning line driving circuit 200 and the data line driving circuit 300 are illustrated as separate circuits, but a configuration in which a part or all of these circuits are a single circuit is also employed. The

As shown in FIG. 1, the pixel array unit 100 is provided with m scanning lines 3 extending in the X direction and n data lines 6 extending in the Y direction orthogonal to the X direction ( m and n are natural numbers). Each unit circuit P <b> 1 is arranged at a position corresponding to the intersection of the scanning line 3 and the data line 6. Therefore, these unit circuits P1 are arranged in a matrix of m rows × n columns.
Further, as shown in FIG. 1, the pixel array unit 100 is provided with one selection line 32 extending in parallel with the extending direction of the scanning line 3. In the first embodiment, the selection line 32 is connected to all of the unit circuits P1, more precisely all of the second transistors Tr2 described later included in each unit circuit P1.

A scanning line driving circuit 200 shown in FIG. 1 is a circuit for selecting a plurality of unit circuits P1. The scanning line driving circuit 200 generates scanning signals G [1] to G [m] that are sequentially activated and outputs them to each of the m scanning lines 3. The transition to the active state of the scanning signal G [i] supplied to the scanning line 3 in the i-th row (i is an integer satisfying 1 ≦ i ≦ m) is the selection of the n unit circuits P1 belonging to the i-th row. Means.
Further, the scanning line driving circuit 200 generates a selection signal GC that becomes active at an appropriate timing, and outputs the selection signal GC to the selection line 32. Details of the timing will be described later with reference to FIG.
The “scanning line driving circuit 200” of the first embodiment is an element having both characteristics of the “scanning line driving circuit” and the “second switching element selection line driving circuit” according to the present invention.

The data line driving circuit 300 shown in FIG. 1 has data potentials VD [1] to VD corresponding to the gradation data of n unit circuits P1 corresponding to the scanning lines 3 selected by the scanning line driving circuit 200. [n] is generated and output to each data line 6. Hereinafter, the data potential VD output to the data line 6 in the j-th column (j is an integer satisfying 1 ≦ j ≦ n) may be referred to as VD [j].
In order to realize such an operation, the data line driving circuit 300, as shown in FIG. 2, includes a data potential generator 301, a switching transistor 302, and a switching transistor control wiring for supplying a control signal to its gate. (Hereinafter abbreviated as “SW wiring”) 303. The SW wiring 303 outputs a control signal SEL that transitions between the active state and the inactive state while appropriately synchronizing with the transition between the active state and the inactive state of each of the scanning signals G [1] to G [m]. Is done.

FIG. 2 is a circuit diagram showing a detailed electrical configuration of each unit circuit P1.
As shown in FIG. 2, each unit circuit P1 includes an electro-optic element 8, a capacitive element C1, a first transistor Tr1, and a second transistor Tr2.
The electro-optical element 8 is an OLED (Organic Light Emitting Diode) element in which a light emitting layer of an organic EL material is interposed between an anode and a cathode. As shown in FIG. 2, a constant potential is supplied to the first transistor Tr1. It is arranged between the constant potential lines. Here, the anode is provided for each unit circuit P1 and is an individual electrode controlled for each unit circuit P1, and the cathode is a common electrode provided in common for the unit circuit P1. The cathode is connected to a constant potential line to which a constant potential is supplied. The anode may be a common electrode and the cathode may be an individual electrode.
As shown in FIG. 2, the electro-optic element 8 has a parasitic capacitance 8C. When a predetermined potential difference is applied between the anode and the cathode of the electro-optic element 8, a certain charge is stored in the electro-optic element 8 or a parasitic capacitance 8C that can be regarded as equivalent to this.

The capacitive element C1 is a means for holding the data potential VD [j] supplied from the data line 6. As shown in FIG. 2, the capacitive element C <b> 1 includes a first electrode E <b> 1 connected to the capacitive line 30 (an example of the “first capacitive line” in the present invention) and a second electrode E <b> 2 connected to the data line 6. And having.
Note that the capacitor line 30 to which the fixed potential is supplied is commonly connected to each unit circuit P1.

The first transistor Tr1 is an N-channel type and is a switching element that conducts between the second electrode E2 of the capacitive element C1 and the electro-optic element 8 by being conducted when the scanning line 3 is selected. As shown in FIG. 2, the source of the first transistor Tr1 is connected to the anode of the electro-optical element 8, and the drain thereof is connected to the second electrode E2 of the capacitive element C1.
The gate of the first transistor Tr1 is connected to the scanning line 3, and when the scanning signal G [i] transitions to the active state, the first transistor Tr1 is turned on, and the second electrode E2 and the electro-optic element 8 are in conduction. On the other hand, when the scanning signal G [i] transitions to the inactive state, the first transistor Tr1 is turned off, and the second electrode E2 and the electro-optic element 8 are turned off.

The second transistor Tr <b> 2 is an N-channel type, and performs switching when the selection line 32 is selected, thereby switching the constant potential line 31 (an example of the “second capacitance line” in the present invention) and the electro-optic element 8. It is an element. As shown in FIG. 2, the source of the second transistor Tr <b> 2 is connected to the anode of the electro-optic element 8, and the drain thereof is connected to the constant potential line 31.
The gate of the second transistor Tr2 is connected to the selection line 32, and when the selection signal GC transits to the active state, the second transistor Tr2 is turned on, and the constant potential line 31 and the electro-optical element 8 become conductive. When the scanning signal G [i] transitions to the inactive state, the first transistor Tr1 is turned off, and the constant potential line 31 and the electro-optical element 8 are brought out of conduction. In the first embodiment, as described above, since all of the second transistors Tr2 are connected to one selection line 32, the transition between the conduction state and the non-conduction state is all the second transistors Tr2. It is performed all at once.

  The potential of the constant potential line 31 is VCT, the potential on the cathode side of the electro-optical element 8 (that is, the potential of a constant potential line connected to the cathode and not the constant potential line 31) is VSS, and When the light emission threshold voltage is Vth, it is preferable that VCT <VSS + Vth be established between them. The reason will be described later.

Next, the operation or action of the electro-optical device 10 according to the first embodiment will be described with reference to FIGS. 3 to 6 in addition to FIGS. 1 and 2 already referred to.
As shown in FIG. 3, each unit period 1T in one vertical scanning period (1V) includes a writing period Pw from the start of the unit period 1T until a predetermined period elapses, and after the elapse of the writing period Pw. Drive period Pd and an initialization period Ph after the elapse of the drive period Pd. In this embodiment, the initialization period Ph is a period from the end point of the drive period Pd to the end point of the unit period 1T.

  The scanning line driving circuit 200 shown in FIG. 1 sequentially selects one scanning line 3 for each driving period Pd in each unit period 1T. For example, in the i-th unit period 1T within one vertical scanning period (1V), the scanning line 3 of the i-th row is selected by setting the scanning signal G [i] to the active level.

The data line driving circuit 300 shown in FIG. 1 corresponds to each scanning line 3 selected by the scanning line driving circuit 200 in the driving period Pd in the unit period 1T for each writing period Pw in each unit period 1T. A data potential VD corresponding to the gradation data of the electro-optic element 8 in the unit circuit P1 is output to each data line 6. For example, in the writing period Pw in the i-th unit period 1T in one vertical scanning period (1V), the data potential VD [corresponding to the gradation data of each of the n unit circuits P1 in the i-th row. 1] to VD [n] are output to each data line 6.
Hereinafter, focusing on each unit circuit P1 in the i-th row, the operation for driving the electro-optical element 8 will be described by being divided into a writing period Pw, a driving period Pd, and an initialization period Ph.

(A) Writing period Pw
In the writing period Pw, charges corresponding to the data potential VD corresponding to the gradation data of the unit circuit P1 belonging to the i-th row are charged (accumulated) in the capacitor element C1 in each unit circuit P1. For example, the charge corresponding to the data potential VD [j] corresponding to the gradation data of the unit circuit P1 in the i-th row and the j-th column is the m capacitive elements C1 connected to the data line 6 in the j-th column. The battery is charged in parallel. At this time, the control signal SEL in the active state is output to the SW wiring 303 (see FIG. 3), and the switching transistor 302 is turned on.

In the first embodiment, there is a period during which the active state selection signal GC is output to the selection line 32 within the writing period Pw (see FIG. 3). As a result, the second transistor Tr2 is turned on, the electro-optical element 8 and the constant potential line 31 are short-circuited, and the charge stored in the parasitic capacitance 8C parasitic on the electro-optical element 8 is discharged. In the first embodiment, since the selection line 32 is connected to all the second transistors Tr <b> 2 in the pixel array unit 100, this discharge is performed simultaneously for all the electro-optical elements 8. This prevents the leakage current of the first transistor Tr1 from flowing into the electro-optic element 8 during the writing period Pw and causing unexpected light emission.
FIG. 4 visually represents the above state. Referring to FIG. 3, a period labeled “FIG. 4” corresponds to FIG.

(B) Driving period Pd
In the drive period Pd, the output terminal of the data line drive circuit 300 is set to the high impedance state by outputting the control signal SEL in the inactive state to the SW wiring 303. After that, as shown in FIG. 3, the scanning signal G [i] transitions to a high level. As a result, the first transistor Tr1 in each unit circuit P1 belonging to the i-th row is turned on, and each unit circuit P1 belonging to the i-th row is connected to the data line 6 corresponding to each unit circuit P1. Charges charged in the writing period Pw are supplied from the plurality of capacitive elements C1. For example, in the electro-optic element 8 in the unit circuit P1 in the i-th row and the j-th column, the charges charged in the writing period Pw from the m capacitive elements C1 connected to the data line 6 in the j-th column. It will be supplied all at once. As a result, the electro-optical element 8 in each of the unit circuits P1 belonging to the i-th row emits light with a gradation corresponding to the data potential VD.
At this time, before the high-level scanning signal G [i] is output to the i-th scanning line 3, the inactive selection signal GC is output to the selection line 32. As a result, the second transistor Tr2 is turned off, and the constant potential line 31 and the electro-optic element 8 are placed in a non-conductive state.
FIG. 5 visually represents the above state (note that FIG. 5 shows an example in which the electro-optical element 8 belonging to the second row emits light). Referring to FIG. 3, a period labeled “FIG. 5” corresponds to FIG.

(C) Initialization period Ph
In the initialization period Ph, the active state selection signal GC is output to the selection line 32 while the on state of the first transistor Tr1 in the driving period Pd is maintained. As a result, the second transistor Tr2 is turned on while the conductive state between the electro-optical element 8 and each capacitive element C1 is maintained, and the electro-optical element 8 and the constant potential line 31 are short-circuited.
FIG. 6 visually represents the above state. Referring to FIG. 3, the period labeled “FIG. 6” corresponds to FIG. The first transistor Tr1 in which the ON state is maintained corresponds to the electro-optical element 8 that has emitted light until immediately before (belonging to the second row in FIG. 6; see the flow from FIG. 5 to FIG. 6). First, the electric charge stored in the parasitic capacitance 8 </ b> C of the electro-optical element 8 is discharged toward the constant potential line 31. Further, the charges stored in the plurality of capacitive elements C1 corresponding to the respective data lines 6 are also discharged toward the constant potential line 31 through the first transistor Tr1.
According to the operation as described above, during the initialization period Ph, the “initialization” of the electro-optic element 8 and each capacitive element C1 that have emitted light immediately before is performed (although the selection lines 32 are all second). Since it is connected to the transistor Tr2, the parasitic capacitance 8C of the electro-optic element 8 that is not involved in light emission is also discharged again (see FIG. 6).
At this time, if the above-described relationship of VCT <VSS + Vth is established, the above-described initialization or discharge is more effectively performed. This is the reason why this relational expression is preferable.

The electro-optical device 10 or the unit circuit P1 as described above has the following effects.
First, according to the first embodiment, when one electro-optical element 8 emits light, all of the capacitive elements C1 connected to the data line 6 corresponding to the electro-optical element 8 (m capacitive elements). The charges stored in C1) are used. Thereby, although it is not necessary to increase the capacitance value of each capacitive element C1, it is possible to ensure sufficient light emission luminance.
In addition, according to the first embodiment, the “driving transistor” as described in the section “Problems to be solved by the invention” is not used for the light emission of the electro-optical element 8, so that useless power is consumed. There is no risk of suffering from the problem of being done.

  Furthermore, according to the first embodiment, each unit circuit P1 includes the second transistor Tr2, and the electro-optic element 8 and the capacitive element C1 using the unit transistor P2 are initialized. The occurrence of a situation in which extra charge is stored in the parasitic capacitance 8C is previously avoided. Therefore, according to this embodiment, it is possible to perform true black display or display a higher quality image with a high contrast ratio.

Second Embodiment
Hereinafter, a second embodiment according to the present invention will be described with reference to FIGS. The second embodiment is characterized by the configuration of the selection line that determines conduction / non-conduction of the second transistor Tr2, and the other features are the same as the configuration and operation or action of the first embodiment. It is the same. Therefore, hereinafter, the difference will be mainly described, and the description of other points will be simplified or omitted as appropriate.

In the second embodiment, the configuration relating to the control of the second transistor Tr2 is different. That is, as shown in FIG. 7, m selection lines 34 are provided so as to correspond to each of the m scanning lines 3. The i-th selection line 34 is connected to the second transistor Tr2 included in the n unit circuits P1 belonging to the i-th row.
The selection signals GC [1] to GC [m] generated in the scanning line driving circuit 200 in the active state or inactive state are output to the m selection lines 34, respectively.

The electro-optical device having such a configuration operates or acts as shown in FIG.
That is, when the writing operation related to the unit circuit P1 belonging to the first row is performed and the light emitting operation of the electro-optical element 8 included in the unit circuit P1 is performed, the selection line 34 in the first row is subsequently activated. When the state selection signal GC [1] is output, the second transistors Tr2 included in the n unit circuits P1 belonging to the first row are turned on. As a result, the electro-optical elements 8 belonging to the first row are discharged. In this case, the discharge from the electro-optical elements 8 belonging to the other rows is different from the first embodiment. It is not.
Thereafter, the same operation is performed from the second line onward.
FIG. 9 visually represents the above state (note that FIG. 9 shows an example in which discharge is performed on the electro-optical element 8 belonging to the second row).
As described above, in the second embodiment, the electro-optical element 8 is discharged sequentially for each scanning line 3 or for each selection line 34.

According to such a form, the effect of reducing wasteful power consumption becomes even more effective. This is because, in general, it is considered that the electro-optical element 8 or its parasitic capacitance 8C is most in need of discharge in the electro-optical element 8 that has emitted light until just before, and the other electro-optical elements 8 are For the time being, it can be ignored. That is, the second transistor Tr2 corresponding to the electro-optical element 8 does not need to be driven by force. Actually, in FIG. 6 representing the initialization operation of the first embodiment, the discharge of the electro-optic elements 8 belonging to the first row and the i-th row is not necessarily performed.
Thus, according to the second embodiment, as is clear from the comparison between FIGS. 9 and 6, the second transistor Tr2 that does not need to be driven for the time being is driven under the unnecessary circumstances. In the sense that there is no wasteful power is not consumed.

However, in the second embodiment, in order to enjoy such an effect, it takes time to install m selection lines 34 and sequentially drive them. The first embodiment is superior to the second embodiment in the sense that such effort is unnecessary. Further, in the first embodiment, since only one selection line 32 needs to be provided, there is also an advantage that a corresponding narrow frame can be realized.
As described above, the advantages and disadvantages of the first and second embodiments cannot be determined. If it is necessary to select one of the two, it is only necessary to select a mode suitable for the occasion after considering various circumstances in addition to the above-mentioned circumstances.

While the embodiments according to the present invention have been described above, the electro-optical device according to the present invention is not limited to the above-described embodiments, and various modifications can be made.
In each of the embodiments described above, (c) in the initialization period, there is an example in which there is a period in which the second transistor Tr2 is also in the on state, as in the period in which the first transistor Tr1 is in the on state (FIG. 6 or FIG. 9), the present invention is not limited to such a form. In each of the above embodiments, (a) the example in which the second transistor Tr2 is turned on in the writing period (see FIG. 4) has been described. However, the present invention is not limited to such a form. . In the present invention, the minimum requirement is that “when a certain electro-optical element 8 is driven, the second transistor Tr2 corresponding to the electro-optical element 8 to be driven is turned on. It must not be ". As long as this is observed, it is basically possible to perform the initialization operation or the write operation described in the above embodiments at an arbitrary timing.

<Application>
Next, an electronic apparatus to which the electro-optical device 10 according to the above embodiment is applied will be described.
FIG. 10 is a perspective view illustrating a configuration of a mobile personal computer using the electro-optical device 10 according to the above-described embodiment as an image display device. The personal computer 2000 includes an electro-optical device 10 as a display device and a main body 2010. The main body 2010 is provided with a power switch 2001 and a keyboard 2002.
FIG. 11 shows a mobile phone to which the electro-optical device 10 according to the above embodiment is applied. A cellular phone 3000 includes a plurality of operation buttons 3001, scroll buttons 3002, and the electro-optical device 10 as a display device. By operating the scroll button 3002, the screen displayed on the electro-optical device 10 is scrolled.
FIG. 12 shows a portable information terminal (PDA: Personal Digital Assistant) to which the electro-optical device 10 according to the above embodiment is applied. The information portable terminal 4000 includes a plurality of operation buttons 4001, a power switch 4002, and the electro-optical device 10 as a display device. When the power switch 4002 is operated, various types of information such as an address book and a schedule book are displayed on the electro-optical device 10.

  As electronic devices to which the organic EL device according to the present invention is applied, in addition to those shown in FIGS. 10 to 12, a digital still camera, a television, a video camera, a car navigation device, a pager, an electronic notebook, electronic paper, a calculator, Examples include a word processor, a workstation, a videophone, a POS terminal, a video player, and a device equipped with a touch panel.

DESCRIPTION OF SYMBOLS 10 ... Electro-optical device, 100 ... Pixel array part, 200 ... Scanning line drive circuit, 300 ... Data line drive circuit, 301 ... Data potential generation part, 302 ... Switching transistor, 303 ... Switching Transistor control wiring, P1 ... Pixel circuit, 8 ... Electro-optic element, 3 ... Scanning line, 30 ... Capacitance line, 31 ... Constant potential line, 32,34 ... Select line, 6 ... Data line , C1... Capacitance element, E1... First electrode, E2... Second electrode, Tr1... First transistor, Tr2.

Claims (9)

A pixel circuit arranged corresponding to an intersection of a scan line and a data line extending across the scan line,
An electro-optical element having a gradation according to a data potential output to the data line;
A capacitive element having a first electrode connected to the first capacitor line and a second electrode connected to the data line;
A first switching element that is disposed between the second electrode and the electro-optical element and is electrically connected when the scanning line is selected, thereby electrically connecting the second electrode and the electro-optical element;
A second switching element disposed between a second capacitance line and the electro-optic element;
A pixel circuit comprising: A plurality of pixel circuits arranged corresponding to intersections of the plurality of scanning lines and the plurality of data lines;
A scanning line driving circuit for sequentially selecting one scanning line for each driving period in each unit period;
Gradation data of the pixel circuit corresponding to the scanning line selected in the driving period in the unit period for each writing period in the unit period and before the driving period is started. A data line driving circuit that outputs a data potential corresponding to each of the data lines;
With
Each of the plurality of pixel circuits is
An electro-optic element having a gradation according to the data potential;
A capacitive element having a first electrode connected to the first capacitor line and a second electrode connected to the data line;
A first switching element that is disposed between the second electrode and the electro-optical element and is electrically connected when the scanning line is selected, thereby electrically connecting the second electrode and the electro-optical element;
A second switching element that is disposed between the second capacitance line and the electro-optic element and is in a conductive state for a predetermined period in a time zone other than the driving period;
An electro-optical device comprising: A second switching element selection line connected to all of the second switching elements included in each of the plurality of pixel circuits;
A second switching element selection line driving circuit for selecting the second switching element selection line;
The electro-optical device according to claim 2, further comprising: Among the second switching elements included in each of the plurality of pixel circuits, a plurality of second switching elements arranged to correspond to each group of the plurality of second switching elements corresponding to the one scanning line. A selection line,
A second switching element selection line driving circuit for sequentially selecting the plurality of second switching element selection lines;
The electro-optical device according to claim 2, further comprising: The second switching element is
While the plurality of unit periods are repeatedly visited, the conductive state is repeatedly established with a predetermined interval,
The predetermined interval is
Determined based on the length of one unit period,
The electro-optical device according to claim 2, wherein After the driving period, there is a period in which the first switching element is still in a conductive state,
Within the period, there is a period during which the second switching element is conductive.
The electro-optical device according to claim 2, wherein Within the writing period,
There is a period during which the second switching element is in a conductive state.
The electro-optical device according to claim 2, wherein The potential of the second capacitance line is
Less than the sum of the potential of the electrode on the opposite side of the first switching element of the pair of electrodes constituting the electro-optic element and the threshold voltage for driving the electro-optic element;
The electro-optical device according to claim 2, wherein The electro-optical device according to claim 2 is provided.
An electronic device characterized by that.

Images