JP2006330138A - Display device and display driving method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display a moving image with a good display quality without blurring or blurring in a display device provided with a display panel corresponding to an active matrix type driving method, and corresponding to video data (display data). Provided are a display device capable of displaying image information with appropriate gradation and a display driving method thereof.
In one processing cycle period Tcyc, by applying a low-level power supply voltage Vsc to a display pixel EM, the light emission driving current is cut off from being supplied to an organic EL element OEL and the light emission operation is not performed. Tnem, the display pixel EM is set to the selected state, the write operation period Twrt for holding the voltage component according to the display data, and the voltage component held in the write operation period Twrt according to the display data And a light emission operation period Tem in which the light emission drive current is caused to flow through the organic EL element OEL to perform a light emission operation.
[Selection] Figure 5

Description

  The present invention relates to a display device and a display driving method thereof, and more particularly, to a display device including a display panel corresponding to an active matrix driving method and a display driving method thereof.

  2. Description of the Related Art In recent years, display devices that are thin and light and have low power consumption have been widely used as monitors and displays for personal computers and video equipment. In particular, a liquid crystal display device (LCD) is widely applied as a display device for portable devices (mobile devices) such as mobile phones, digital cameras, personal digital assistants (PDAs), and electronic dictionaries that have been popular in recent years.

  In addition, as a next-generation display device that follows such a liquid crystal display device, a self-luminous element such as an organic electroluminescence element (organic EL element), an inorganic electroluminescence element (inorganic EL element), or a light emitting diode (LED). Research and development for full-scale popularization of light-emitting element type display devices having a display panel in which optical elements (light-emitting elements) of a type are arranged in a matrix are also actively conducted.

  In particular, in a light emitting element type display device to which an active matrix type driving method is applied, a display response speed is faster than a liquid crystal display device, and there is no viewing angle dependency, and high brightness and high contrast are achieved. The display image quality can be increased, and a backlight is not required unlike a liquid crystal display device. Therefore, it is extremely applicable to portable devices that can be made thinner and lighter and consume less power. Has superior features.

Here, a drive control method in a liquid crystal display device or a light emitting element type display device will be briefly described with reference to the drawings.
FIG. 16 is a schematic configuration diagram showing the main part of an active matrix display device in the prior art. FIG. 17 is a timing chart schematically showing an example of a display driving method (hold type) of an active matrix display device in the prior art, and FIG. 18 is a diagram of an active matrix display device in the prior art. It is the timing chart which showed typically the other example (pseudo impulse type) of the display drive method. Here, in FIG. 17 and FIG. 18, for the sake of comparison with the later-described embodiment, for convenience, the display panel has a configuration in which display pixels of 12 rows (1st to 12th rows) are arranged. The display drive method was shown. In the figure, k is a positive integer. In addition, in order to clarify the video data writing operation and display operation and blanking data writing operation and display operation in each row, hatching is shown for convenience.

  First, in a display device to which a conventional cathode ray tube (CRT) is applied, as is well known, an electron beam is deflected inside the cathode ray tube and scanned while irradiating a fluorescent screen (screen). Among these, impulse-type display drive control is performed in which light emission is performed for a short time and nothing is displayed (light emission) until the electron beam is irradiated again in the next frame period.

  According to this, since the image information of the next frame period is displayed after the image information of the previous frame period disappears, it is difficult to visually recognize the afterimage in the moving image display operation, and a good display image quality is realized. However, there is a problem that flickering is likely to occur in a still image display operation without movement.

  On the other hand, an active matrix type display device such as a liquid crystal display device or a light emitting element type display device generally has a plurality of scanning lines SLp and data lines DLp arranged in the row and column directions as shown in FIG. A display panel 110P in which a plurality of display pixels EMp are two-dimensionally arranged, a scan driver 120P connected to each scan line SLp, and a data driver 130P connected to each data line DL. It has a configuration.

  For example, as shown in FIG. 17, the display drive control in the display device having such a configuration is performed by sequentially applying a scanning signal Ssel of a selection level to the scanning line SLp of each row from the scanning driver 120P. The display pixels EMp are sequentially set to the selected state, and in synchronization with the selection timing of each row, the gradation voltage Vpix corresponding to the video data (display data) of the row is applied from the data driver 130P to the data line DLp of each column. Thus, a voltage component based on the gradation voltage Vpix is held in each display pixel EMp (video data is written; video data writing operation).

  Thereby, gradation control according to the voltage component is performed in each display pixel EMp (specifically, the alignment state of the liquid crystal molecules is controlled in the liquid crystal display device, and the light emitting element type display device emits light. By controlling the light emission luminance of the element, a display operation (light emission operation) corresponding to the video data is executed, and desired image information is displayed on the display panel.

  Next, by sequentially applying the non-selection level scanning signal Ssel from the scanning driver 120P to the scanning line SLp, the display pixel EMp for each row is set to the non-selected state. At this time, the display pixel is written to each display pixel. By holding the video data (voltage component), the display operation corresponding to the video data is continued (video display operation). This display operation is continuously performed, for example, for one frame period until the next video data is written in the display pixels EMp in each row (hold type display drive control).

  In such a hold-type display driving method, unlike the above-described impulse-type display driving method, the display operation (light emission operation) corresponding to the video data is continued in most of one frame period. In the still image display operation, flickering hardly occurs. On the other hand, in the moving image display operation, the image information displayed in the previous frame period is easily recognized as an afterimage, and the image is displayed. There has been a problem that blurring and blurring of information occur and display image quality deteriorates.

  Therefore, in a liquid crystal display device or a light emitting element type display device, as a display driving method for improving the display image quality by suppressing blurring and blurring in the above-described moving image display operation, for example, as shown in FIG. In the period, in addition to the video data writing operation (video data writing period) and the video display operation (video display period) for the display pixels EMp in each row described above, each display pixel EMp is displayed with the lowest gradation (light emission operation). Or, in order to perform a non-display operation (non-light emission operation), an operation of supplying blanking data to each data line from the data driver and writing the blanking data to each display pixel (blanking data writing period), A method for executing a black display operation (black display period) based on the blanking data is known.

  As a result, a black display period of a certain period is inserted into one frame period, and a display state in which nothing is displayed (light emission) is set, so that the video display period is relatively shortened and applied to the cathode ray tube described above. A display driving method similar to the impulse type (which is referred to as “pseudo impulse type display driving method” for convenience) can be realized, and the display quality in the moving image display operation can be improved. Such a display device drive control method is described in detail, for example, in Patent Document 1 and the like.

JP 2004-264481 A (pages 17 to 18, FIG. 6)

  However, in the pseudo-impulse display driving method shown in the prior art, as shown in FIG. 18, the same as the writing period and the video display period of the video data supplied from the data driver within one frame period. Since it is necessary to set the blanking data writing period and black display period supplied from the data driver, the video data supplied from the data driver within one frame period as shown in FIG. Compared with the case where only the writing operation and the video display operation are performed and the black display operation is not performed, the time allocated to the video data writing operation is shortened, and the drive frequency (that is, the display device) related to the writing operation is reduced. Drive frequency) (need to write at high speed).

  In this way, when the video data (display data) writing period is shortened and the writing operation must be executed at high speed, the CR time due to the resistance component or capacitance component parasitic on the display panel (signal wiring, etc.) There is a problem in that signal delay occurs due to constants, and insufficient writing occurs, causing video data to be written to each display pixel to be insufficient, and gradation display according to video data cannot be performed properly. Had.

  Although not shown in FIGS. 17 and 18, when video data is written to each display pixel, a voltage component based on the video data remaining in the display pixel and remaining in the previous frame period is obtained. Since there is a need to shorten the time for reset operation that discharges and initializes (reset) and the rising operation of the signal level when setting the scan line of the row to the selected level, there is room for setting the operation timing. There is a problem that timing control becomes complicated and malfunctions are likely to occur.

  Accordingly, in view of the above-described various problems, the present invention can display a moving image with a good display quality free from blurring and blurring in a display device including a display panel that supports an active matrix driving method. An object of the present invention is to provide a display device capable of displaying image information with appropriate gradation corresponding to video data (display data) and a display driving method thereof.

  The invention according to claim 1 includes a display panel in which a plurality of display pixels are arranged in the vicinity of intersections of a plurality of scanning lines and a plurality of data lines arranged in the column direction. , A scanning drive unit that sequentially applies a scanning signal to the display pixels for each row of the display panel at a predetermined timing to set the selected state, and a level corresponding to display data for displaying desired image information. A data driving unit that generates a tone signal and sequentially supplies the gray level signal to the display pixels of the row set in the selected state, and the gradation supplied from the data driving unit to the display pixels for each row of the display panel A power source driving unit that applies a power source voltage for performing a display operation in a bias state corresponding to the display data based on a signal; and a timing control signal to supply the scanning driving unit and the Each of the data drive unit and the power supply drive unit at a predetermined timing, and at least during the period other than the period during which the display pixels for each row are displayed in a bias state corresponding to the display data. A drive control unit that performs a non-display operation by blocking application of the power supply voltage to the display pixels in the row by the drive unit.

  According to a second aspect of the present invention, in the display device according to the first aspect, the drive control unit performs the non-display operation by blocking the application of the power supply voltage to the display pixels of the respective rows. And a means for generating the timing control signal for supplying the gradation signal from the data driver to the display pixel.

  According to a third aspect of the present invention, in the display device according to the first or second aspect, the display device applies the display pixel for each row of the display panel to the display pixel for each row based on the gradation signal. It further includes a state setting control unit for applying a setting signal for canceling the set bias state corresponding to the display data and setting the bias state to a specific bias state.

  According to a fourth aspect of the present invention, in the display device according to the third aspect, the drive control unit performs the non-display operation by blocking the application of the power supply voltage to the display pixels of the respective rows. And a means for generating the timing control signal for supplying the setting signal to the display pixel from the state setting control unit.

  According to a fifth aspect of the present invention, in the display device according to any one of the first to fourth aspects, each display pixel includes a light emitting element and a light emission driving circuit that controls a light emitting operation of the light emitting element. The light emission drive circuit has at least a charge accumulation means for accumulating charges based on the gradation signal and a light emission drive having a predetermined current value based on a forward bias voltage corresponding to the amount of charge accumulated in the charge accumulation means. Emission control means for generating current and supplying it to the light emitting element; and writing control means for controlling a supply state of charge based on the gradation signal to the charge storage means. .

  According to a sixth aspect of the present invention, in the display device according to the fifth aspect, the light emission control means provided in each display pixel has one end connected to the power supply line and the other end connected to the light emitting element. A conduction path through which the light emission drive current flows; and a control terminal connected to the charge storage unit and controlling a conduction state of the conduction path to control a supply state of the light emission drive current to the light emitting element. It is characterized by.

  According to a seventh aspect of the present invention, in the display device according to the sixth aspect, one end of the writing control means provided in each display pixel is connected to the data line to which the gradation signal is supplied, and the other end. Is connected to the control terminal of the light emission control means via the charge storage means and to the scan line to which the scan signal is applied, and based on the gradation signal to the charge storage means A control terminal for controlling the supply state of electric charge is provided.

  According to an eighth aspect of the present invention, in the display device according to any one of the fifth to seventh aspects, the light emission drive circuit has at least one end of a conduction path to which the power supply voltage is applied, and the other end of the conduction path. A first switch means connected to a connection contact with the light emitting element, a control terminal is connected to the scanning line, the power supply voltage is applied to one end of a conduction path, and the first terminal is connected to the other end of the conduction path. The second switch means to which the control terminal of the switch means is connected, the control terminal is connected to the scanning line, the data line is connected to one end of the conduction path, and the connection contact is connected to the other end of the conduction path A third switch means connected; and a capacitive element connected between a control terminal of the first switch means and the connection contact, wherein the light emission control means comprises the first switch means. The charge storage Means, characterized in that it is configured to include the capacitive element.

  According to a ninth aspect of the present invention, in the display device according to any one of the fifth to eighth aspects, the light emission driving circuit discharges the electric charge accumulated in the charge accumulation unit and applies no voltage to the light emission control unit. Or a bias control means for applying a reverse bias voltage.

  According to a tenth aspect of the present invention, in the display device according to the ninth aspect, the bias control means provided in each display pixel has one end connected to a scanning line to which the scanning signal is supplied and the other end emitting the light. A charge path connected to the control terminal of the control means for applying the scanning signal of a predetermined signal level to the control terminal of the light emission control means, and a bias line to which the setting signal is applied, A control terminal for controlling the discharge state of the charge accumulated in the accumulation means is provided.

According to an eleventh aspect of the present invention, in the display device according to the ninth or tenth aspect, the light emission driving circuit has a control terminal connected to the bias line, one end of a conduction path connected to the scan line, and the conduction path. And a switch terminal connected to a control terminal of the first switch means, and the bias control means includes the fourth switch means. To do.
According to a twelfth aspect of the present invention, in the display device according to any one of the fifth to eleventh aspects, at least the light emission control means provided in the light emission drive circuit includes an amorphous silicon thin film transistor. .

According to a thirteenth aspect of the present invention, in the display device according to any one of the fifth to twelfth aspects, the data driver causes the light emitting element to emit light at a predetermined luminance gradation as the gradation signal. Means is provided for generating a gradation current having a predetermined current value.
A fourteenth aspect of the present invention is the display device according to any one of the fifth to thirteenth aspects, wherein the light emitting element is an organic electroluminescence element.

  The invention according to claim 15 has a display panel in which a plurality of display pixels are arranged in the vicinity of intersections of a plurality of scanning lines and a plurality of data lines arranged in the column direction. A gradation corresponding to display data for displaying desired image information in synchronization with a timing of applying a scanning signal sequentially to the display pixels for each row of the display panel at a predetermined timing and setting the selected state. In a display driving method of a display device that displays a desired image information on the display panel by supplying a signal to display the display pixels in a bias state corresponding to the display data, the display pixels are arranged on the display panel. Sequentially setting the display pixels for each row to a selected state and supplying the grayscale signal; and displaying the display pixels in each row to which the grayscale signal is supplied as the display data. The display pixels in each row are used as the display data in a period including a step of sequentially performing a display operation in a bias state according to the above and a step of supplying the gradation signal to the display pixels in each row. And a non-display operation by cutting off the application of the power supply voltage for the display operation in a corresponding bias state.

  According to a sixteenth aspect of the present invention, in the display driving method of the display device according to the fifteenth aspect, each display pixel includes display driving means, and the display pixels in each row are displayed in a bias state corresponding to the display data. The step of operating is performed by applying a forward bias voltage corresponding to the gradation signal to the display driving means.

  According to a seventeenth aspect of the present invention, in the display driving method of the display device according to the fifteenth or sixteenth aspect, the display pixels in the respective rows are subjected to the step of performing the non-display operation of the display pixels in the respective rows. The method further includes the step of canceling the set bias state corresponding to the display data and setting the bias state to a specific bias state.

  According to an eighteenth aspect of the present invention, in the display driving method of the display device according to the seventeenth aspect, the bias state corresponding to the display data set in the display pixel of each row is canceled and set to a specific bias state. The step of performing is performed by applying no voltage or a reverse bias voltage to the display driving means.

  The invention according to claim 19 is the display driving method of the display device according to any one of claims 15 to 18, wherein each of the display pixels includes a light emitting element, and the display pixels in each of the rows correspond to the display data. The step of performing the display operation in the biased state is characterized in that the light emitting element of each display pixel is caused to perform a light emission operation at a luminance gradation corresponding to the display data.

  According to a twentieth aspect of the present invention, in the display driving method of the display device according to the nineteenth aspect, the step of supplying the gradation signal to the display pixels of each row uses the light emitting element as a predetermined value as the gradation signal. A gradation current having a predetermined current value for light emission operation at a luminance gradation is supplied.

  That is, in the display device and the display driving method thereof according to the present invention, a power supply driving unit (power supply driver) that applies a power supply voltage for performing display operation for each row of a plurality of display pixels arranged two-dimensionally on the display panel. In a display operation period (light emission operation period) in which display pixels in each row arranged on the display panel are displayed in a bias state corresponding to display data, a power supply voltage is applied to the display pixels in each row, In a non-display operation period including a writing operation period of a gradation signal (gradation current) corresponding to display data to the display pixels, control is performed so as to cut off the application of the power supply voltage to the display pixels in each row.

  As a result, the display pixels (light-emitting elements) in the row are not displayed (non-light-emitting operation) only by cutting off the application of the power supply voltage without performing the blanking data writing operation to the display pixels in each row. Therefore, it is possible to realize pseudo impulse type display drive control in which a display operation (light emission operation) is performed at a luminance gradation corresponding to display data only during a predetermined period in a predetermined one processing cycle period (one frame period). Can do.

  Here, the ratio of the non-display period (black insertion rate) in one processing cycle period (one frame period) is arbitrarily set by arbitrarily setting a period during which application of the power supply voltage to the display pixels in each row is cut off. Since it can be set to approximately 30% or more which can suppress blur and blur, a clear and good display image quality can be realized.

  Further, according to the display device and the display driving method according to the present invention, in order to display a moving image with clear display image quality, a black display operation (blanking data writing operation and display operation) is performed during one frame period. Thus, the display data writing operation period for the display pixels in each row is not shortened, and a sufficient writing time for each row can be secured. Therefore, it is possible to suppress a deterioration in display quality due to insufficient writing of display data and to realize appropriate gradation display according to display data. In addition, this allows a margin for timing control of various signals, so that the malfunction of the display device can be suppressed.

  Furthermore, according to the display device and the display driving method thereof according to the present invention, for example, an amorphous silicon thin film transistor is used as a light emission control unit or a display driving unit (a switching element for light emission driving) in each display pixel arranged in the display panel. When a circuit configuration comprising: is applied, no voltage (0 V) or reverse bias voltage is applied to the light emission control means and display drive means provided in each display pixel during the non-display operation period (reverse bias state) Therefore, deterioration of element characteristics (threshold voltage fluctuation; Vth shift) in the amorphous silicon thin film transistor is largely suppressed, and appropriate gradation display (appropriate luminance gradation) according to display data is achieved. The light emitting operation of the light emitting element can be realized.

Hereinafter, a display device and a display driving method thereof according to the present invention will be described in detail with reference to embodiments.
[First Embodiment]
<Display device>
First, a schematic configuration of a display device according to the present invention will be described with reference to the drawings.
FIG. 1 is a schematic block diagram showing a first embodiment of a display device according to the present invention. FIG. 2 shows a display panel and its peripheral circuits (scan driver, data) applied to the display device according to this embodiment. It is a principal part block diagram which shows an example of a driver and a power supply driver.

  In the embodiment described below, the display panel has a configuration in which a plurality of display pixels including light emitting elements are two-dimensionally arranged, and each display pixel has a luminance gradation corresponding to display data (video data). A light-emitting element type display device that displays image information by performing a light-emitting operation will be described. However, the present invention is not limited to this, and each display pixel has a level corresponding to display data as in a liquid crystal display device. It may be a display device that performs tone control (set to a bias state according to display data) and performs gradation display (display operation) of desired image information by transmitted light or reflected light.

  As shown in FIGS. 1 and 2, the display device 100 </ b> A according to the present embodiment includes a plurality of scanning lines SL and a plurality of data lines DL arranged so as to be orthogonal to each other in the outline, row, and column directions. A display panel 110 in which a plurality of display pixels EM each provided with a light emission drive circuit and a light emitting element, which will be described later, are arranged in the vicinity of each intersection, is connected to each scanning line SL of the display panel 110, and predetermined for each scanning line SL. By sequentially applying the scanning signal Vsel of the selection level (high level) at the timing of, the scanning driver (scanning drive unit) 120 that sets the display pixel EM for each row to the selected state, and the scanning line SL of each row in parallel. A power supply driver (power supply drive unit) 130 connected to a plurality of power supply lines VL and sequentially applying a power supply voltage Vsc at a predetermined timing for each power supply line VL; A data driver (data driving unit) 140 that is connected to each data line DL of the data line 110 and supplies a gradation signal (gradation current Idata) corresponding to display data to the display pixel EM via each data line DL; Based on a timing signal supplied from a display signal generation circuit 160 to be described later, at least the operation states of the scan driver 120, the power supply driver 130, and the data driver 140 are controlled to execute a predetermined image display operation on the display panel 110. Display data (luminance) based on a system controller (drive control unit) 150 that generates and outputs a scanning control signal, a power supply control signal, and a data control signal for output, and a video signal supplied from the outside of the display device 100A, for example. Gradation data) is generated and supplied to the data driver 140, and based on the display data. Extracting a timing signal for displaying predetermined image information to have the display panel 110 (the system clock, etc.), or is configured to include a display signal generating circuit 160 supplies the generated by the system controller 150.

Hereafter, each said structure is demonstrated concretely.
(Display panel / Display pixel)
FIG. 3 is a circuit configuration diagram showing an example of a display pixel (light emission drive circuit) applied to the display device according to the present embodiment. In the present embodiment, light emission having a current value corresponding to display data is supplied to a light emitting element provided in each display pixel by supplying a gradation current having a current value corresponding to display data as a display pixel. The case where a circuit configuration (light emission drive circuit) corresponding to a drive control method of a current gradation designation method in which a drive current is supplied and a light emission operation (display operation) at a desired luminance gradation is provided will be described. However, the present invention is not limited to this. For example, by applying a gradation voltage having a voltage value corresponding to display data, a light emission driving current having a current value corresponding to display data is caused to flow to the light emitting element of each display pixel. In addition, a circuit configuration corresponding to a drive control method of a voltage gradation designation system that performs light emission operation at a desired brightness gradation may be provided.

  In the display panel 110 applied to the display device 100A according to the present embodiment, in a plurality of display pixels EM arranged in a two-dimensional array in the row and column directions, for example, first, light emission driving is performed on the display pixels EM for each row. The display pixels EM in each row are sequentially non-light-emitting (non-display operation) for a predetermined period by sequentially shutting off the application of the power supply voltage for each of the rows, and then the display data writing operation is sequentially executed. Each display pixel EM is controlled to sequentially emit light (display operation) at a predetermined luminance gradation.

  As a configuration for this, the display pixels EM arranged in the display panel 110 according to the present embodiment are roughly configured based on the scanning signal Vsel applied from the scanning driver 120 as shown in FIG. Is set to the selected state, the gradation signal (gradation current Idata) supplied from the data driver 140 in the selected state is fetched, and the light emission driving circuit DC1 that generates the light emission driving current according to the gradation signal; A configuration including a known organic EL element (light emitting element) OEL that emits light with a predetermined luminance gradation based on the light emission drive current supplied from the light emission drive circuit DC1 can be applied.

  Specifically, in the light emission drive circuit DC1 according to the present embodiment, as shown in FIG. 3, the gate terminal (control terminal) is on the scanning line SL, and the drain terminal and the source terminal (one end and the other end of the conduction path) are on. A thin film transistor (write control means, second switch means) Tr11 connected to a power supply line VL to which a predetermined power supply voltage Vsc is applied and a contact N11, and a gate terminal (control terminal) to the scanning line SL, a source terminal And the drain terminal (one end and the other end of the conduction path) are connected to the data line DL and the contact N12, respectively, the thin film transistor (write control means, third switch means) Tr12, and the gate terminal (control terminal) to the contact N11. , The drain terminal and the source terminal (one end and the other end of the conduction path) are connected to the power supply line VL and the contact (connection contact) N12, respectively, and the thin film transistor (light emission Control means, first switch means, display drive means) Tr13, and a capacitor (charge storage means, capacitive element) Cs connected between the contact N11 and the contact N12 (between the gate and source terminals of the thin film transistor Tr13). It has a configuration.

  The organic EL element OEL has an anode terminal connected to the contact N12 of the light emission drive circuit DC1 and a common voltage Vcom applied to the cathode terminal. Here, the common voltage Vcom includes a writing operation period in which a gradation signal (gradation current Idata) corresponding to display data is supplied to the display pixel EM (light emission drive circuit DC1), and an organic EL element (light emitting element). ) In the non-light emission operation period (non-display operation period) in which the OEL does not perform the light emission operation, the power supply voltage Vsc (= Vs) set to the low level is equal to or higher than the power supply voltage Vsc. In addition, a power supply voltage Vsc (= Ve) set to a high level in a light emission operation period (display operation period) in which a light emission drive current is supplied to the organic EL element (light emitting element) OEL and a light emission operation is performed at a predetermined luminance gradation. Is set to an arbitrary potential (for example, ground potential GND) that is lower than (Vs ≦ Vcom <Ve).

  Here, the capacitor Cs may be a parasitic capacitance formed between the gate and the source of the thin film transistor Tr13. In addition to the parasitic capacitance, a capacitor is further connected in parallel between the contact N11 and the contact N12. There may be. The thin film transistors Tr11 to Tr13 are not particularly limited. For example, the thin film transistors Tr11 to Tr13 are all formed of a single channel type thin film transistor (field effect transistor), whereby an n channel type amorphous silicon thin film transistor is formed. Can be applied.

  In this case, by applying an already established amorphous silicon manufacturing technology, it is possible to manufacture a light emission driving circuit composed of an amorphous silicon thin film transistor having uniform and stable element characteristics (such as electron mobility) by a relatively simple manufacturing process. it can. In the following description, a case where the thin film transistors Tr11 to Tr13 are all constituted by n-channel thin film transistors will be described as a configuration example of the light emission drive circuit DC1.

  In the above description, the light emitting element driven to emit light by the light emission driving circuit DC1 is the organic EL element OEL. However, the light emitting element in the present invention is not limited to the organic EL element OEL, and is a current control type light emitting element. Any other light emitting device such as a light emitting diode may be used. Furthermore, in the present embodiment, a case will be described in which image information is displayed by driving light emission of a current control type light emitting element by the light emission drive circuit DC1, but a voltage component corresponding to display data is generated and voltage control is performed. It may have a configuration for driving light emission of a type light emitting element or a circuit configuration for changing the alignment state of liquid crystal molecules.

(Scanning driver)
The scanning driver 120 applies a scanning signal Vsel of a selection level (high level in the above-described display pixel EM) to each scanning line SL based on a scanning control signal supplied from the system controller 150, thereby making each row The display pixel EM is set to the selected state. Specifically, the operation of applying the scanning signal Vsel to the scanning line SL of each row is executed at a timing that does not overlap with each other, thereby sequentially setting the display pixels EM for each row to the selected state.

  Here, for example, as shown in FIG. 2, the scan driver 120 corresponds to the scan line SL of each row based on a scan clock signal SCK and a scan start signal SST supplied as a scan control signal from a system controller 150 to be described later. A known shift register 121 that sequentially outputs shift signals to be output, and an output supplied as a scan control signal from the system controller 150 by converting the shift signal output from the shift register 121 to a predetermined signal level (on level) An output circuit unit (output buffer) 122 that outputs a scanning signal Vsel to each scanning line SL based on the control signal SOE is provided.

(Power supply driver)
Based on the power supply control signal supplied from the system controller 150, the power supply driver 130 applies the high-level power supply voltage Vsc (= Ve) to the power supply line VL of the row for the display pixels EM of each row only during the light emission operation period. The low-level power supply voltage Vsc (= Vs) is applied during an operation period (non-light emission operation (non-display operation) period including a writing operation period) other than the light emission operation (display operation) period. Here, the operation of applying the low-level power supply voltage Vsc is substantially equivalent to the operation of cutting off the supply of the power supply voltage Vsc to the display pixel EM (light emission drive circuit DC1).

  Here, for example, as illustrated in FIG. 2, the power supply driver 130 may be configured in each row based on the clock signal VCK and the start signal VST supplied as power supply control signals from the system controller 150, as in the scan driver 120 described above. A well-known shift register 131 that sequentially outputs a shift signal corresponding to the power supply line VL, and a shift signal converted into a predetermined voltage level (voltage values Ve and Vs) and output control signal VOE supplied as a power supply control signal. And an output circuit unit 132 that outputs the power supply voltage Vsc to each power supply line VL.

(Data driver)
FIG. 4 is a schematic block diagram illustrating an example of a data driver applicable to the display device according to the present embodiment. Note that the internal configuration of the data driver shown in FIG. 4 is merely an example of a configuration that can generate a gradation current having a current value corresponding to display data, and the present invention is not limited to this. It is not something.

  As shown schematically in FIGS. 1 and 2, the data driver 140 is based on a data control signal supplied from the system controller 150, and display data (digital data) supplied from a display signal generation circuit 160 described later. (Brightness gradation data) is fetched and held sequentially at a predetermined timing for each row, and a gradation current Idata having a current value corresponding to the gradation value of the display data is generated and selected during the writing operation period. The display pixels EM in the row set in the state are supplied all at once via the data lines DL.

  Specifically, as shown in FIG. 5, the data driver 140 is a shift register that sequentially outputs shift signals based on data control signals (shift clock signal CLK, sampling start signal STR) supplied from the system controller 150. A circuit 41, a data register circuit 42 for sequentially taking in display data D0 to Dm for one row supplied from the display signal generation circuit 160 based on the input timing of the shift signal, and a data control signal (data latch signal STB) Based on the data latch circuit 43 that holds the display data D0 to Dm for one row fetched by the data register circuit 42, and the gradation reference voltages V0 to VP supplied from the power supply means (not shown). Thus, the stored display data D0 to Dm are converted to a predetermined analog signal voltage (level). A D / A converter 44 for converting to a voltage Vpix), a gradation current Idata corresponding to display data converted to an analog signal voltage, and a data control signal (output enable signal OE) supplied from the system controller 150 The voltage / current conversion / gradation current supply circuit 45 that outputs the data to the data lines DL of the column corresponding to the display data at the same time can be applied.

(System controller)
The system controller 150 generates and outputs a scanning control signal, a power supply control signal, and a data control signal as timing control signals for controlling the operation state to at least the scanning driver 120, the power supply driver 130, and the data driver 140, respectively. Thus, each driver is operated at a predetermined timing to generate and output a scanning signal Vsel and a power supply voltage Vsc having a predetermined voltage level, and a gradation signal (gradation current Idata) corresponding to display data. Then, the drive control operation (non-light emission operation, writing operation, light emission operation) in each display pixel EM (light emission drive circuit DC1) is continuously executed, and predetermined image information based on the video signal is displayed on the display panel 110. Control (display drive control of the display device to be described later) is performed.

(Display signal generation circuit)
For example, the display signal generation circuit 160 extracts a luminance gradation signal component from a video signal supplied from the outside of the display device 100A, and converts the luminance gradation signal component from a digital signal for each row of the display panel 110. Is supplied to the data register circuit 42 of the data driver 140 as display data (luminance gradation data). Here, when the video signal includes a timing signal component that defines the display timing of image information, such as a television broadcast signal (composite video signal), the display signal generation circuit 160 displays the luminance gradation signal component. In addition to the function of extracting the timing signal component, the timing signal component may be extracted and supplied to the system controller 150. In this case, the system controller 150 generates control signals to be individually supplied to the scan driver 120, the power supply driver 130, and the data driver 140 based on the timing signal supplied from the display signal generation circuit 160. .

<Driving control method of display pixel (light emission driving circuit)>
Next, in the present embodiment, a drive control method for the display pixels (see FIG. 3) constituting the display panel described above will be described.
FIG. 5 is a timing chart showing a drive control method (non-light emitting operation, writing operation, light emitting operation) in the display pixel applied to the display device according to the present embodiment. 6 is a conceptual diagram showing a non-light emission operation and a writing operation in the display pixel (light emission drive circuit) according to the present embodiment, and FIG. 7 is a diagram in the display pixel (light emission drive circuit) according to the present embodiment. It is a conceptual diagram which shows light emission operation | movement.

  In the drive control operation in the display pixel EM (light emission drive circuit DC1) according to the present embodiment, as shown in FIG. 5, the display pixel EM connected to the scan line SL is selected within a predetermined one processing cycle period Tcyc. And the gradation current Idata having a current value corresponding to the display data is supplied, whereby the display is provided between the gate and the source (capacitor Cs) of the light emission driving thin film transistor Tr13 provided in the light emission driving circuit DC1. Light emission having a current value corresponding to display data based on a write operation period Twrt for holding a voltage component corresponding to data and a voltage component held between the gate and source of the thin film transistor Tr13 in the write operation period Twrt. A light emission operation period (display operation period) Tem in which a drive current is caused to flow through the organic EL element OEL to perform a light emission operation at a predetermined luminance gradation, and the light emission operation In a period other than the interval Temp (a period including the write operation period Twrt), the supply of the power supply voltage Vsc to the display pixel EM (light emission drive circuit DC1) is cut off (a low-level power supply voltage Vsc is applied). Is set to include a non-light emission operation period (non-display operation period) Tnem in which the light emission drive current is not supplied to the organic EL element OEL and the light emission operation is not performed (Tcyc ≧ Tem + Tnem, Tnem ≧ Twrt). ).

  Here, the write operation period Twrt, the light emission operation period Tem, and the non-light emission operation period Tnem set during one processing cycle period Tcyc are performed after the non-light emission operation, as shown in FIG. May be executed continuously, or the writing operation is executed at an arbitrary timing in the non-light emitting operation period (in the middle of the non-light emitting operation period), and the light emitting operation is executed after the end of the light emitting operation period. It may be a thing.

  The one processing cycle period Tcyc according to the present embodiment is set to a period required for the display pixel EM to display image information for one pixel in one frame (one screen) image, for example. That is, as described in the display driving method of the display device described later, when one frame image is displayed on the display panel 110 in which a plurality of display pixels EM are two-dimensionally arranged in the row direction and the column direction, the one processing cycle is performed. The period Tcyc is set to a period required for the display pixels EM for one row to display an image for one row of images of one frame.

(Non-display operation period)
First, in the non-light emission operation period (non-display operation period) Tnem, as shown in FIGS. 5 and 6A, a scan signal Vsel of a non-selection level is applied from the scan driver 120 to the scan line SL. Thus, the display pixel EM is set to a non-selected state, and a low-level power supply voltage Vsc (= Vs) is applied from the power supply driver 130 to the power supply line VL. Further, the gradation current Idata is not supplied from the data driver 140 to the data line DL.

  As a result, the thin film transistors Tr11 and Tr12 provided in the light emission driving circuit DC1 are set in an off state, and therefore, the electrical connection between the gate terminal (contact N11; one end side of the capacitor Cs) of the thin film transistor Tr13 and the power supply line VL is established. In addition to being interrupted, the electrical connection between the source terminal (contact N12; the other end of the capacitor Cs) of the thin film transistor Tr13 and the data line DL is also set in an interrupted state.

  Here, as described in the display driving method of the display device to be described later, the drive control operation in each display pixel is repeatedly executed with one processing cycle period Tcyc (one frame period Tfr) as a cycle. The voltage component written based on the display data in the previous processing cycle period is held between the gate and source of Tr13 of the thin film transistor (at both ends of the capacitor Cs) at the start of the period Tnem. Tr13 is in an on state.

  Therefore, a low level (ground potential GND or lower) power supply voltage Vsc (= Vs) applied to the power supply line VL is applied to the anode terminal (contact N12) of the organic EL element OEL via the thin film transistor Tr13. Therefore, the reverse bias voltage is applied to the organic EL element OEL with respect to the potential Vcom (ground potential GND) of the cathode terminal, so that the light emission drive current does not flow and light emission. No operation is performed (non-light emission operation).

(Write operation period)
Next, in the write operation period Twrt set during the non-light emission operation period Tnem, as shown in FIGS. 5 and 6A, the scan driver 120 applies a selection level (high level) to the scan line SL. ) Is applied to set the display pixel EM to the selected state, and in synchronization with the selection timing, the data driver 140 applies the data to the data line DL according to the display data (negative polarity). A gradation current Idata having a current value is supplied. In the write operation period Twrt, similarly to the non-light emission operation period Tnem, the low-level power supply voltage Vsc (= Vs) is applied from the power supply driver 130 to the power supply line VL.

  As a result, the thin film transistors Tr11 and Tr12 provided in the light emission drive circuit DC1 are turned on, and the low-level power supply voltage Vsc is applied to the gate terminal (contact N11; one end side of the capacitor Cs) of the thin film transistor Tr13 through the thin film transistor Tr11. At the same time, the source terminal (contact N12; the other end of the capacitor Cs) of the thin film transistor Tr13 is electrically connected to the data line DL via the thin film transistor Tr12.

  Here, the gradation current Idata having a negative current value is supplied to the data line DL, whereby the operation of drawing the gradation current Idata from the data line DL toward the data driver 140 is performed. A voltage level lower than the power supply voltage Vsc is applied to the source terminal (contact N12; the other end of the capacitor Cs) of the thin film transistor Tr13.

  Thus, the potential difference is generated between the contacts N11 and N12 (between the gate and the source of the thin film transistor Tr13), so that the thin film transistor Tr13 is turned on, and the thin film transistor Tr13, the contact N12, the thin film transistor Tr12, and the data line DL are connected from the power supply line VL. As a result, a write current Ia corresponding to the gradation current Idata flows in the direction of the data driver 140.

  At this time, a charge corresponding to the potential difference generated between the contacts N11 and N12 (between the gate and source of the thin film transistor Tr13) is accumulated in the capacitor Cs and held as a voltage component (in FIG. 5, both ends of the capacitor Cs). (See potential Vc). Further, the power supply line VL is controlled so that a low level (ground potential GND or lower) power supply voltage Vsc (= Vs) is applied and the write current Ia flows in the direction of the data line DL. Since the potential applied to the anode terminal (contact N12) of the organic EL element OEL is lower than the potential Vcom (ground potential GND) of the cathode terminal, a reverse bias voltage is applied to the organic EL element OEL. No light emission drive current flows through the EL element OEL, and no light emission operation is performed (non-light emission operation).

(Display operation period)
Next, in the light emission operation period (display operation period) Tem after the write operation period Twrt or the non-light emission operation period (non-display operation period) Tnem including the write operation period Twrt, FIG. 5 and FIG. As shown, the display pixel EM is set to a non-selected state by applying a low level scanning signal Vsel to the scanning line SL from the scanning driver 120, as in the non-light emitting operation period Tnem described above. In synchronization with the non-selection timing, the supply of the gradation current Idata from the data driver 130 is cut off, and the operation of drawing the gradation current Idata is stopped. In the light emission operation period Temp, a high level power supply voltage Vsc (= Ve) is applied from the power supply driver 130 to the power supply line VL.

  As a result, the thin film transistors Tr11 and Tr12 provided in the light emission drive circuit DC1 are turned off, and the application of the power supply voltage Vsc to the gate terminal (contact N11; one end side of the capacitor Cs) of the thin film transistor Tr13 is cut off. Since the application of the voltage level due to the drawing operation of the gradation current Idata to the source terminal (contact N12; the other end side of the capacitor Cs) of Tr13 is cut off, the capacitor Cs has the write operation period Twrt described above. The accumulated charge is retained.

  In this manner, the potential difference between the contacts N11 and N12 (between the gate and source of the thin film transistor Tr13; both ends of the capacitor Cs) is maintained, and the thin film transistor Tr13 maintains the on state. In addition, since the power supply voltage Vsc higher than the common voltage Vcom (ground potential GND) is applied to the power supply line VL, the potential applied to the anode terminal (contact N12) of the organic EL element OEL is the cathode terminal. It becomes higher than the potential (ground potential).

  Therefore, a predetermined light emission drive current Ib flows in the forward bias direction from the power supply line VL to the organic EL element OEL via the thin film transistor Tr13 and the contact N12, and the organic EL element OEL emits light. Here, the voltage component (the potential Vc across the capacitor Cs) held by the capacitor Cs corresponds to a potential difference when the write current Ia corresponding to the gradation current Idata is passed through the thin film transistor Tr13. The light emission drive current Ib flowing has a current value (Ib≈Ia) equivalent to the write current Ia.

  In the display pixel EM, the light emission drive current Ib is transmitted through the thin film transistor Tr13 during the light emission operation period Tem based on the voltage component corresponding to the display data (gradation current Idata) written in the write operation period Twrt. The organic EL element OEL continues to operate to emit light at a luminance gradation corresponding to the display data.

  As described above, according to the display pixel EM (light emission drive circuit DC1) according to the present embodiment, in the writing operation period Twrt, the gradation current Idata (writing data) specifying the current value corresponding to the display data (luminance gradation) is written. The current Ia) is forcibly passed between the drain and source of the drive transistor Tr13, and the organic EL element (light emitting element) based on the voltage component between the gate and source of the drive transistor Tr13 held according to the current value. ) By controlling the light emission drive current Ib that flows to the OEL, it is possible to apply a drive control method of a current gradation designation system that performs light emission operation at a predetermined luminance gradation.

  Further, according to the display pixel EM according to the present embodiment, the grayscale current corresponding to the display data is obtained by the single light emission driving transistor (thin film transistor Tr13) constituting the light emission driving circuit DC1 provided in each display pixel EM. Realizing both a function of converting the current level of Idata to a voltage level (current / voltage conversion function) and a function of supplying a light emission drive current Ib having a predetermined current value to the organic EL element OEL (light emission drive function) Therefore, desired light emission characteristics can be stably realized over a long period of time without being affected by variations in operation characteristics of each transistor constituting the light emission drive circuit DC and changes with time.

<Display drive method of display device>
Next, a display driving method (image information display operation) in the display device according to the present embodiment will be described.
FIG. 8 is a timing chart schematically showing an example of the display driving method of the display device according to the present embodiment. In the present embodiment, for convenience of explanation, it is assumed that display pixels of 12 rows (n = 12; 1st to 12th rows) are arranged on the display panel for convenience. To do. In the figure, k is a positive integer, and the hatched portions indicated by the cross mesh in each row in the figure represent the display data writing operation period described above, and the hatched portions indicated by dots are , Each represents the above-described light emitting operation period.

  In the display driving method of the display device 100A according to the present embodiment, first, the display pixel EM is not operated for display on the display pixel EM (light emission drive circuit DC1) for each row arranged in the display panel 110 (organic EL element). A non-light emission operation is performed (not causing the OEL to perform a light emission operation), and the gradation current Idata corresponding to the display data is set at an arbitrary timing during the non-light emission operation period Tnem (in the present embodiment, just before the end of the non-light emission operation period Tnem). The writing operation for writing is sequentially executed for each row, and then the light emission operation is sequentially performed at a predetermined luminance gradation corresponding to the display data (gradation current), whereby image information for one screen of the display panel 110 is displayed. . Here, the operation timing is controlled so that at least the write operation periods Twrt in each row do not overlap (in time).

  Specifically, first, as shown in FIG. 8, in the non-light emission operation period Tnem (displayed in white in the figure) within one frame period Tfr, as shown in FIG. By applying the non-selection level (low level) scanning signal Vsel to the scanning lines SL in 110 specific rows (for example, i-th row; 1 ≦ i ≦ 12), the display pixels EM in the i-th row. Is set to the non-selected state. Further, the gray scale current Idata is not supplied from the data driver 140 to each data line DL (the gray scale current Idata is not supplied).

  Then, in synchronization with this timing, the low-level power supply voltage Vsc (= Vs) is applied from the power supply driver 130 to the i-th power supply line VL, as shown in FIG. Further, since no potential difference is generated between the drain and source of the light emission driving thin film transistor Tr13 in each display pixel EM of the i row, the light emission driving current Ib does not flow in the direction of the organic EL element OEL via the thin film transistor Tr13. The i rows of display pixels EM are set to a non-light emitting state (non-light emitting operation).

  Next, as shown in FIG. 8, in the writing operation period Twrt (indicated by a cross mesh in the figure) set within the non-light emitting operation period Tnem, as shown in FIG. By applying the scanning signal Vsel of the selection level (high level) to the i-th scanning line SL of the panel 110, the i-th display pixel EM is set to the selected state. In the write operation period Twrt, the low-level power supply voltage Vsc (= Vs) is applied from the power supply driver 130 to the i-th power supply line VL.

  Then, in synchronization with the selection timing, the gradation current Idata having a current value corresponding to the display data of the i row is supplied from the data driver 140 to each data line DL, as shown in FIG. As described above, the write current Ia corresponding to the gradation current Idata flows through the light emission drive circuit DC of each display pixel EM in the i row, and between the gate and source terminals (both ends of the capacitor Cs) of each thin film transistor Tr13. The voltage component Vdata corresponding to the gradation current Idata is held (charge is accumulated).

Here, in the write operation period Twrt, similarly to the non-light emission operation period Tnem described above, the low-level power supply voltage Vsc (=) with respect to the i-th power supply line VL in which the write operation is performed. Vs) is applied, no potential difference is generated between the drain and source of the light emission driving thin film transistor Tr13 in each display pixel EM, so that no light emission drive current flows in the direction of the organic EL element OEL via the thin film transistor Tr13. The i rows of display pixels EM are set to a non-light emitting state (non-light emitting operation).
The non-light-emitting operation including such a writing operation is sequentially performed with respect to the display pixels EM arranged on the display panel 110 while shifting the timing for each row. In particular, the writing operations in each row do not overlap with each other in time. Are executed sequentially.

  Next, as shown in FIG. 8, in the light emission operation period Tem (indicated by dot hatching in the figure), as shown in FIG. 5, i rows of scan lines from the scan driver 120 where the non-light emission operation period Tnem has ended. By applying a non-selection level (low level) scanning signal Vsel to SL, each display pixel EM in the i row is set to a non-selection state. Further, the supply of the gradation current Idata from the data driver 140 to each data line DL is interrupted.

Then, in synchronization with this timing, the high-level power supply voltage Vsc (= Ve) is applied from the power supply driver 130 to the i-th power supply line VL, as shown in FIG. Since a potential difference is generated between the drain and the source of the light emission driving thin film transistor Tr13 in each display pixel EM in the row, based on the voltage component charged in each display pixel EM (between the gate and source of the light emission driving thin film transistor Tr13). The light emission drive current Ib corresponding to the display data (gradation current Idata) is supplied to the organic EL element OEL, and the light emission operation is performed with a predetermined luminance gradation.
Such a light emitting operation is performed at different timings for each display pixel EM in the row where the above-described writing operation (or non-light emitting operation including the writing operation) is completed for the display pixels EM arranged in the display panel 110. It is executed sequentially.

  That is, for a plurality of display pixels EM arranged two-dimensionally on the display panel 110, a non-light emitting operation period Tnem having a predetermined length is set for each row during one frame period Tfr. It is possible to realize pseudo impulse type display drive control in which each display pixel EM emits light at a luminance gradation corresponding to display data (gradation current Idata) only for a certain period. Here, the length of the non-light emission operation period Tnem or the light emission operation period Tem set in one frame period Tfr is, for example, a timing control signal from the system controller 150 to the scan driver 120, the power supply driver 130, and the data driver 140. Can be arbitrarily set by a scanning control signal, a power supply control signal, and a data control signal.

  Therefore, in the timing chart shown in FIG. 8, by setting the ratio (black insertion rate) of the non-display period due to the non-light emission operation (including the write operation) in one frame period Tfr to 50%, for example, Since half of the image information (display screen) displayed on the display panel 110 can be displayed black (not displayed), it is necessary for human vision to clearly view a moving image without blurring or blurring. Therefore, a black insertion rate of approximately 30% or more can be realized, and a moving image can be displayed with good display image quality. The black insertion rate (ratio of non-display period) in one frame period Tfr is not limited to the above-described 50%, and is preferably an arbitrary numerical value of 30% or more, but is 30% or less. It may be a numerical value.

  In this case, similarly to the display driving method shown in the conventional technique (see FIG. 17), the display pixels EM of all the rows (for 12 rows) of the display panel 110 are used for the entire time of one frame period Tfr. Since the sequential writing operation can be executed, the writing operation period Twrt () in each row is used to execute the blanking data writing operation and the black display operation as in the display driving method shown in FIG. (Corresponding to the video data writing period in the prior art) is not shortened, the writing time of each row can be sufficiently secured, and the deterioration of display quality due to insufficient writing of display data is suppressed. Thus, it is possible to realize appropriate gradation display according to the display data. In addition, this allows a margin for timing control of various signals, so that the malfunction of the display device can be suppressed.

  In the present embodiment, for convenience of explanation, as shown in the timing chart of FIG. 8, after performing a non-light emitting operation (non-display operation) including a writing operation period in one frame period Tfr, Although the case where the light emitting operation (display operation) is performed has been described, after performing the writing operation not accompanied by the light emitting operation of the organic EL element OEL (display operation of the display pixel EM), the light emitting operation of a predetermined length is performed. Then, even when the non-light emission operation is executed thereafter, the control operation is substantially the same.

[Second Embodiment]
Next, a second embodiment of the display device and the display driving method according to the present embodiment will be described with reference to the drawings.
FIG. 9 is a main part configuration diagram showing an example of a display panel and its peripheral circuits (scan driver, data driver, power supply driver, bias control driver) applied to the display device according to the second embodiment. FIG. 10 is a circuit configuration diagram showing an example of a display pixel (light emission drive circuit) applied to the display device according to the present embodiment. Here, about the structure equivalent to 1st Embodiment mentioned above (refer FIGS. 1-3), the same or equivalent code | symbol is attached | subjected and the description is simplified.

  In the first embodiment described above, as shown in FIG. 3, the light emission driving circuit DC1 provided in each display pixel EM has a circuit configuration including a plurality of single channel type thin film transistors. In this case, Although it has been explained that an amorphous silicon thin film transistor having a simple manufacturing process and uniform device characteristics (electron mobility) can be applied, the amorphous silicon thin film transistor generally generates a threshold voltage fluctuation (Vth shift) due to driving history. It is known that it is easy to do.

  Therefore, when an amorphous silicon thin film transistor is applied as the light emission driving switching element (thin film transistor Tr13), the current value of the light emission drive current Ib supplied to the organic EL element OEL is changed to display data due to the variation of the threshold voltage. And the light emission operation (display operation) at an appropriate luminance gradation cannot be performed, and the display image quality may be deteriorated.

  Therefore, in the present embodiment, in the one frame period Tfr described above, each display pixel EM has a non-light emitting operation period (non-display operation period) other than the light emitting operation (display operation) that causes the threshold voltage to vary. The gate-source voltage (the potential Vc across the capacitor Cs) of the switching element for driving light emission (thin film transistor Tr23) is set to 0 V (no voltage) or negative voltage (reverse bias voltage), and the threshold value of the switching element is set. It has a configuration that suppresses voltage fluctuations.

  As shown in FIG. 9, the display device 100B according to the present embodiment specifically has a display in which a plurality of display pixels EM are two-dimensionally arranged in the row and column directions, as in the first embodiment described above. A scanning driver (scanning drive unit) 120 that sequentially applies a selection level (high level) scanning signal Vsel to the panel 110 and each scanning line SL of the display panel 110 to set the display pixel EM for each row to a selected state. And a power supply driver (power supply driver) 130 for sequentially applying a power supply voltage Vsc to a power supply line VL arranged in parallel with the scanning line SL of each row, and a gradation signal (gradation current Idata) corresponding to display data. A data driver (data driving unit) 140 that supplies the display pixel EM via each data line DL, a scanning control signal and power control for executing a predetermined image display operation in the display panel 110 In accordance with a system controller (drive control unit) 150 that generates and outputs a data control signal, display data (luminance gradation data) is generated and supplied to the data driver 140 based on an externally supplied video signal. And a bias signal (setting signal) Vbs having a predetermined voltage level on the display pixels EM of each row via a bias line BL arranged in parallel with the scanning line SL of each row. And a bias control driver (state setting control unit) 170 for applying.

  Based on the bias control signal supplied from the system controller 150, the bias control driver 170 applies the bias signal Vbs to the bias line BL of the row for the display pixels EM of each row only during a specific period in the non-light emission operation period Tnem. In the non-light emission operation period Tnem excluding the write operation period Twrt, 0V (no voltage is applied between the gate and the source of the thin film transistor Tr13 provided in each display pixel EM (light emission drive circuit DC2). ) Or applying a reverse bias voltage) to a no-field state or a reverse bias state (a specific bias state).

  Here, for example, as shown in FIG. 9, the bias control driver 170 applies a clock signal BCK and a start signal BST supplied as a bias control signal from the system controller 150 in the same manner as the scan driver 120 and the power supply driver 130 described above. Based on a known shift register 171 that sequentially outputs a shift signal corresponding to the bias line BL of each row, and based on an output control signal BOE that is converted into a predetermined voltage level and supplied as a bias control signal. And an output circuit unit 172 that outputs a bias signal Vbs to each bias line BL.

  The system controller 150 generates and outputs a bias control signal as a timing control signal for controlling the operation state to the bias control driver 170, whereby the scan driver 120 and the power supply driver 130 described in the first embodiment, In addition to the data driver 140, the bias control driver 170 is operated at a predetermined timing, and the scanning signal Vsel and the power supply voltage Vsc having a predetermined voltage level, the gradation signal (gradation current Idata) corresponding to the display data, and the bias signal Vbs is generated and output to the display panel 110, and drive control operations (non-light emission operation, reverse bias setting operation, writing operation, light emission operation) in each display pixel EM (light emission drive circuit DC2) are continuously executed. , Control for displaying predetermined image information based on the video signal on the display panel 110 (display described later) Performs location display drive control).

Further, for example, as shown in FIG. 10, the display pixels EM arranged in the display panel 110 according to this embodiment have display data similar to the configuration shown in the first embodiment (see FIG. 3). A light emission driving circuit DC2 that takes in a corresponding gradation signal (gradation current Idata) and generates a light emission driving current, and an organic EL element (light emitting element) that emits light at a predetermined luminance gradation based on the light emission driving current. In particular, the light emission drive circuit DC2 applied to the display pixel EM according to this embodiment includes a gate in addition to the thin film transistors Tr11 to Tr13 and the capacitor Cs described in the first embodiment. A thin film transistor (bi-directional transistor) having a terminal (control terminal) connected to the bias line BL and a drain terminal and a source terminal (one end and the other end of the conduction path) connected to the scanning line SL and the contact N11, respectively. (Ass control means, fourth switch means) Tr14.
Here, as described above, the thin film transistors Tr11 to Tr14 are configured by applying amorphous silicon thin film transistors having a simple manufacturing technique and uniform element characteristics (such as electron mobility).

Next, a drive control method for display pixels (see FIG. 10) applied to the display panel according to the present embodiment will be described.
FIG. 11 is a timing chart showing a drive control method (reverse bias setting operation, non-light emission operation, writing operation, light emission operation) in the display pixel applied to the display device according to the present embodiment. FIG. 12 is a conceptual diagram showing a reverse bias setting operation and a non-light emission operation in the display pixel (light emission drive circuit) according to this embodiment, and FIG. 13 is a display pixel (light emission drive circuit) according to this embodiment. It is a conceptual diagram which shows the writing operation | movement and light emission operation | movement in FIG. Here, the description of the drive control operation equivalent to that in the first embodiment will be simplified.

  As shown in FIG. 11, the drive control operation in the display pixel EM (light emission drive circuit DC2) according to the present embodiment is performed within a predetermined one processing cycle period Tcyc (for example, one frame period Tfr). Non-light emitting operation period in which the supply of the light emission driving current to the organic EL element OEL is cut off by cutting off the supply of the power supply voltage Vsc to the drive circuit DC2) (applying the low level power supply voltage Vsc) (Non-display operation period) Tnem and the non-light emission operation period Tnem are executed, and by applying a bias signal Vbs via the bias line BL, the light emission drive thin film transistor Tr13 provided in the light emission drive circuit DC2 No electric field where 0V (no voltage) or reverse bias voltage is applied by discharging (residual) charge held between the gate and source (capacitor Cs) The reverse bias setting period Tbs for setting the state or the reverse bias state and the display pixel EM that is executed during the non-light emission operation period Tnem and connected to the scanning line SL is set to the selected state, and the current value according to the display data Is supplied to the gate-source (capacitor Cs) of the thin film transistor Tr13 for light emission driving provided in the light emission driving circuit DC2 so that the voltage component corresponding to the display data is held. Based on a voltage component held between the gate and source of the thin film transistor Tr13 during the operation period Twrt and the write operation period Twrt, a light emission drive current Ib having a current value corresponding to display data is passed through the organic EL element OEL. , And a light emission operation period (display operation period) Tem that performs light emission operation at a predetermined luminance gradation (Tcyc ≧ Tem + Tne). m, Tnem ≧ Tbs + Twrt).

  Here, the reverse bias setting period Tbs and the writing operation period Twrt set during the non-light emitting operation period Tnem are set at the start and end of the non-light emitting operation period Tnem, respectively, as shown in FIG. The reverse bias setting period Tbs and the writing operation period Twrt may be performed so that the reverse bias setting operation and the writing operation are executed at an arbitrary timing of the non-light emitting operation period (in the middle of the non-light emitting operation period). May be set.

(Non-emission operation period)
First, in the non-light emitting operation period Tnem, as shown in FIGS. 11 and 12A, a scanning signal Vsel of a non-selection level is applied from the scanning driver 120 to the scanning line SL to thereby display the display pixel EM. In addition to setting the non-selected state, a low-level power supply voltage Vsc (= Vs) is applied from the power supply driver 130 to the power supply line VL. Further, the gradation current Idata is not supplied from the data driver 140 to the data line DL.

  As a result, the thin film transistors Tr11 and Tr12 provided in the light emission drive circuit DC2 are set in an off state, so that the electrical connection between the gate terminal (contact N11; one end side of the capacitor Cs) of the thin film transistor Tr13 and the power supply line VL is established. In addition to being interrupted, the electrical connection between the source terminal (contact N12; the other end of the capacitor Cs) of the thin film transistor Tr13 and the data line DL is also set in an interrupted state. In the non-light emitting operation period Tnem, during a period other than the reverse bias setting period Tbs, which will be described later, the bias control driver 170 applies a low level bias signal Vbs to the bias line BL, and the thin film transistor Tr14 is turned off. By setting, the electrical connection between the gate terminal (contact N11; one end side of the capacitor Cs) of the thin film transistor Tr13 and the scanning line SL is cut off.

  Here, similarly to the non-display operation period shown in the first embodiment, the drive control operation in each display pixel is repeatedly executed with one processing cycle period Tcyc (one frame period Tfr) as a cycle. The voltage component written based on the display data in the previous processing cycle period is held between the gate and source of Tr13 of the thin film transistor (both ends of the capacitor Cs) at the start of the non-light emitting operation period Tnem. The thin film transistor Tr13 is in an on state.

  Therefore, a low level (ground potential GND or lower) power supply voltage Vsc (= Vs) applied to the power supply line VL is applied to the anode terminal (contact N12) of the organic EL element OEL via the thin film transistor Tr13. Since the potential is equal to or less than the potential Vcom (ground potential GND) of the cathode terminal, a reverse bias voltage is applied to the organic EL element OEL, and the organic EL element OEL is driven to emit light. No current flows and no light emission operation is performed (non-light emission operation).

(Reverse bias setting period)
Next, in the reverse bias setting period Tbs set during the non-light emitting operation period Tnem, as shown in FIGS. 11 and 12B, the bias control driver 170 applies a high level bias to the bias line BL. A signal Vbs is applied.

  As a result, the thin film transistor Tr14 provided in the light emission drive circuit DC2 is turned on, so that the gate terminal (contact N11; one end side of the capacitor Cs) of the thin film transistor Tr13 is set to a non-selection level (low level; Vsn). Since the voltage level of the scanning signal Vsel is set, the voltage level (= Vsn) based on the scanning signal Vsel of the non-selection level is set between the gate and source of the thin film transistor Tr13 (both ends of the capacitor Cs). Therefore, a difference from the potential of the contact N12 occurs.

  Here, as described above, the voltage component written based on the display data in the previous processing cycle period is held in the capacitor Cs at the start of the non-light emitting operation period Tnem, and the thin film transistor Tr13. 11 is in the ON state, as shown in FIG. 11, when the reverse bias setting operation is executed at the start of the non-light emitting operation period Tnem, the contact N12 (the other end of the capacitor Cs) is connected to the contact N12 via the thin film transistor Tr13. The power supply voltage Vsc (= Vs) applied to the power supply line VL is applied.

  Therefore, a difference (Vsn−Vs) between the scanning signal Vsel (= Vsn) at the non-selection level and the low-level power supply voltage Vsc (= Vs) is present between the gate and source of the thin film transistor Tr13 (both ends of the capacitor Cs). The voltage is applied and held (see the potential Vc across the capacitor Cs in FIGS. 11 and 12B). Here, at least the voltage level of the scanning signal Vsel (= Vsn) at the non-selection level is set to be equal to or lower than the low-level power supply voltage Vsc (= Vs), whereby the gate-source region of the thin film transistor Tr13 is set. Can be set to 0 V (no electric field state) or a reverse bias state.

  When the reverse bias setting operation is executed at the start of the non-light emission operation period Tnem, the reverse bias voltage (Vsn−Vs) is held between the gate and source of the thin film transistor Tr13 (both ends of the capacitor Cs), During the non-light emitting operation period Tnem, the non-electric field state or the reverse bias state is continuously maintained.

  Thereby, since the thin film transistor Tr13 is controlled to be surely turned off, the potential applied to the anode terminal (contact N12) of the organic EL element OEL is equal to or less than the potential Vcom (ground potential GND) of the cathode terminal. Thus, a reverse bias voltage is applied to the organic EL element OEL, and no light emission drive current flows through the organic EL element OEL, and no light emission operation is performed (non-light emission operation).

(Write operation period)
Next, in the write operation period Twrt set during the non-light emission operation period Tnem, as shown in FIGS. 11 and 13A, the scan driver 120 applies a selection level (high level) to the scan line SL. ) Is applied to set the display pixel EM to the selected state, and in synchronization with the selection timing, the data driver 140 applies the data to the data line DL according to the display data (negative polarity). A gradation current Idata having a current value is supplied. In the write operation period Twrt, similarly to the non-light emission operation period Tnem, the low-level power supply voltage Vsc (= Vs) is applied from the power supply driver 130 to the power supply line VL. To the bias line BL is applied with a low level bias signal Vbs.

  As a result, the thin film transistor Tr14 provided in the light emission drive circuit DC2 is set in an OFF state, and thus the electrical connection between the gate terminal (contact N11; one end side of the capacitor Cs) of the thin film transistor Tr13 and the scanning line SL is cut off. As in the write operation period shown in the first embodiment described above, the thin film transistors Tr11 to Tr13 are turned on and the power supply line VL to the thin film transistor Tr13, the contact N12, the thin film transistor Tr12, and the data line DL are set. The write current Ia corresponding to the gradation current Idata flows in the direction of the data driver 140 via the.

  Therefore, charges corresponding to the potential difference caused by the write current Ia are accumulated between the gate and source of the transistor Tr13 of the thin film transistor (both ends of the capacitor Cs) and are held as the voltage component Vdata (in FIG. 11, the capacitor Cs (See both-end potential Vc). At this time, a reverse bias voltage is applied to the organic EL element OEL, the light emission drive current does not flow, and the light emission operation is not performed (non-light emission operation).

(Light emission operation period)
Next, in the light emission operation period Tem after the write operation period Twrt or the non-light emission operation period Tnem including the write operation period Twrt, as shown in FIG. 11 and FIG. Similar to the operation period Tnem, the low-level scanning signal Vsel is applied from the scanning driver 120 to the scanning line SL to set the display pixel EM in a non-selected state, and in synchronization with the non-selection timing, The supply of the gradation current Idata from the data driver 130 is interrupted, and the drawing operation of the gradation current Idata is stopped. Similarly to the non-light emitting operation period Tnem, the bias control driver 170 applies a low level bias signal Vbs to the bias line BL. On the other hand, in the light emission operation period Tem, the high-level power supply voltage Vsc (= Ve) is applied from the power supply driver 130 to the power supply line VL.

  As a result, the thin film transistors Tr11, Tr12, Tr14 provided in the light emission driving circuit DC2 are turned off, so that the capacitor Cs has the above write operation as in the light emission operation period described in the first embodiment. The charge (voltage component Vdata) accumulated in the period Twrt is held, and the thin film transistor Tr13 is kept on. Further, by applying a high level power supply voltage Vsc (= Ve) to the power supply line VL, the potential of the anode terminal (contact N12) of the organic EL element OEL becomes higher than the potential of the cathode terminal (ground potential).

  Therefore, a predetermined light emission drive current Ib (≈Ia) flows in the forward bias direction from the power supply line VL to the organic EL element OEL through the thin film transistor Tr13 and the contact N12, and the organic EL element OEL displays display data during the light emission operation period Temp. The operation of emitting light at a luminance gradation corresponding to (gradation current Idata) is continued.

Here, the display pixel (light emission drive circuit) having the above-described circuit configuration and the threshold voltage variation suppression effect (Vth shift amount suppression effect) by the drive control method will be specifically described.
FIG. 14 is an experimental result showing a variation amount (Vth shift amount) of the threshold voltage when the switching element (thin film transistor) for driving light emission is set in the reverse bias state in the display pixel according to the present embodiment. Here, when an n-channel amorphous silicon thin film transistor applied as a switching element for driving light emission is continuously turned on by applying a forward bias voltage between the gate and the source (shown by a dotted line in the figure). When the reverse bias voltage (for example, −30 V) is applied and set in the reverse bias state (shown by a solid line in the figure) for only 1/5 of the driving operation period, the threshold voltage with respect to the passage of time An example of the result of measuring the change tendency of the amount of fluctuation is shown.

  As shown in FIG. 14, when a forward bias voltage is continuously applied to the thin film transistor, as shown by a dotted line in the figure, the amount of change in threshold voltage (Vth as the time elapses (horizontal axis)). (Shift amount) shows a tendency to increase significantly (about 2 V after 250 hours), but when a reverse bias voltage is applied to the thin film transistor for a certain period of time, as shown by the solid line in the figure, It has been found that the fluctuation amount of the threshold voltage tends to be significantly suppressed with respect to the course (horizontal axis) (about 0.6 V after 250 hours).

  Such a threshold voltage variation suppressing effect (Vth shift amount suppressing effect) is obtained by setting a reverse bias state for a certain period during the driving operation period in the element structure of the amorphous silicon thin film transistor, thereby forming a gate insulating film. Charge introduction into the nitride film is performed in a relatively shallow region, and the introduction into the deep region is suppressed, and further, the charge trapped in the nitride film is set by setting the reverse bias state. Is believed to be due to the release of.

  Therefore, even when an amorphous silicon thin film transistor is used as a light emission driving switching element provided in each display pixel EM (light emission drive circuit DC2), fluctuation in threshold voltage (Vth shift) due to drive history is suppressed. Therefore, the organic EL element OEL can be supplied with the light emission drive current Ib having a current value corresponding to the display data, and the light emission operation (display operation) can be performed with an appropriate luminance gradation. The display image quality can be improved.

<Display drive method of display device>
Next, a display driving method (image information display operation) in the display device according to the present embodiment will be described.
FIG. 15 is a timing chart schematically showing an example of the display driving method of the display device according to the present embodiment. Here, the description of the control method equivalent to that of the first embodiment will be simplified. In addition, hatched portions indicated by diagonal lines in each row in the figure each represent the above-described display data reverse bias setting period.

  In the display driving method of the display device 100B according to the present embodiment, first, the display pixel EM is not caused to perform display operation on the display pixels EM (light emission driving circuit DC2) for each row arranged in the display panel 110 (organic EL element). A non-light emission operation is performed (without causing the OEL to perform a light emission operation), and each display pixel EM (light emission drive circuit DC2) at an arbitrary timing during the non-light emission operation period Tnem (simultaneously with the start of the non-light emission operation period Tnem in this embodiment). ), A reverse bias setting operation for applying a reverse bias voltage to the light emission driving switching element (thin film transistor Tr13) provided in FIG. Thereafter, the write operation for writing the gradation current Idata corresponding to the display data is sequentially executed for each row at an arbitrary timing during the non-light emission operation period Tnem (in the present embodiment, just before the end of the non-light emission operation period Tnem). Thereafter, the image information for one screen of the display panel 110 is displayed by sequentially causing the light emission operation with a predetermined luminance gradation corresponding to the display data (gradation current). Here, the operation timing is controlled so that at least the write operation periods Twrt in each row do not overlap (in time).

  Specifically, first, as shown in FIG. 15, in the reverse bias setting period Tbs (indicated by hatching in the figure) set in synchronization with the start timing of the non-light emitting operation period Tnem within one frame period Tfr. 11, a non-selection level (low level) scanning signal Vsel is applied to the scanning line SL in a specific row (for example, the i-th row; 1 ≦ i ≦ 12) of the display panel 110. As a result, the display pixels EM in the i-th row are set to a non-selected state.

  In synchronism with this timing, a low-level power supply voltage Vsc (= Vs) is applied to the power line VL of the i row, and a bias signal Vbs is applied to the bias line BL of the i row. By applying the voltage, as shown in FIG. 12B, a reverse bias voltage is applied between the gate and the source of the light emission driving thin film transistor Tr13 in each display pixel EM of the i row (reverse bias setting operation). Therefore, the thin film transistor Tr13 is turned off, the light emission drive current Ib does not flow in the direction of the organic EL element OEL, and the display pixels EM in the i row are set in a non-light emission state (non-light emission operation).

  Further, in the non-light emission operation period Tnem (indicated by white in the drawing) after the reverse bias setting period Tbs ends, the reverse bias voltage applied between the gate and the source of the thin film transistor Tr13 is held by the reverse bias setting operation described above. As a result, the thin film transistor Tr13 maintains an off state, the light emission drive current Ib does not flow in the direction of the organic EL element OEL, and the display pixels EM in the i row continue to be in a non-light emission state (non-light emission operation). .

  Next, as shown in FIG. 15, in the writing operation period Twrt (indicated by a cross mesh in the figure) set in synchronization with the end timing of the non-light emitting operation period Tnem, as shown in FIG. By applying a selection level (high level) scanning signal Vsel to the i-th scanning line SL, the i-th display pixel EM is set to the selected state. Further, a low-level power supply voltage Vsc (= Vs) is applied to the i-th power supply line VL.

  Then, in synchronization with this selection timing, the gradation current Idata having a current value corresponding to the display data of the i row is supplied to each data line DL, as shown in FIG. A voltage component corresponding to the gradation current Idata is held (charge is accumulated) between the gate and source terminals of the thin film transistor Tr13 of each display pixel EM (light emission drive circuit DC) in the i row (both ends of the capacitor Cs).

The non-light-emitting operation including such a writing operation is sequentially performed with respect to the display pixels EM arranged on the display panel 110 while shifting the timing for each row. In particular, the writing operations in each row do not overlap with each other in time. Are executed sequentially.
Next, as shown in FIG. 15, in the light emission operation period Tem (displayed by dot hatching in the figure), each display pixel EM in the i row is set to a non-selected state, and the gradation current to each data line DL is set. Idata supply is cut off.

Then, in synchronization with this timing, a high-level power supply voltage Vsc (= Ve) is applied to the i-th power supply line VL, so that each display as shown in FIG. Based on the voltage component charged in the pixel EM (between the gate and the source of the thin film transistor Tr13 for light emission drive), the light emission drive current Ib corresponding to the display data (gradation current Idata) passes through the thin film transistor Tr13 and the organic EL element OEL. The light emission operation is performed at a predetermined luminance gradation.
Such a light emitting operation is performed at different timings for each display pixel EM in the row where the above-described writing operation (or non-light emitting operation including the writing operation) is completed for the display pixels EM arranged in the display panel 110. It is executed sequentially.

  That is, for a plurality of display pixels EM arranged two-dimensionally on the display panel 110, a non-light emitting operation period Tnem having a predetermined length is set for each row during one frame period Tfr. It is possible to realize pseudo impulse type display drive control in which each display pixel EM emits light at a luminance gradation corresponding to display data (gradation current Idata) only for a certain period. As a result, the moving image can be clearly displayed without blurring or blurring.

  In this case, similarly to the display driving method shown in the conventional technique (see FIG. 17), the display pixels EM of all the rows (for 12 rows) of the display panel 110 are used for the entire time of one frame period Tfr. Since the sequential writing operation can be executed, the writing operation period Twrt in each row is not shortened, a sufficient writing time can be secured, and the display caused by insufficient writing of display data. An appropriate gradation display according to the display data can be realized by suppressing the deterioration of quality.

  Furthermore, in the non-light emission operation period Tnem, a reverse bias voltage can be applied to the light emission driving switching element (thin film transistor Tr13) provided in each display pixel EM to set the reverse bias state. Even when an amorphous silicon thin film transistor is applied, the threshold voltage fluctuation (Vth shift) can be greatly suppressed, and the organic EL element OEL can be operated to emit light with an appropriate luminance gradation according to display data. it can.

1 is a schematic block diagram showing a first embodiment of a display device according to the present invention. FIG. 2 is a main part configuration diagram illustrating an example of a display panel and peripheral circuits (scan driver, data driver, power supply driver) applied to the display device according to the first embodiment. It is a circuit block diagram which shows an example of the display pixel (light emission drive circuit) applied to the display apparatus which concerns on 1st Embodiment. It is a schematic block diagram which shows an example of the data driver applicable to the display apparatus which concerns on 1st Embodiment. 6 is a timing chart showing a drive control method (non-light emitting operation, writing operation, light emitting operation) in a display pixel applied to the display device according to the first embodiment. It is a conceptual diagram which shows the non-light-emission operation | movement and the writing operation | movement in the display pixel (light emission drive circuit) which concerns on 1st Embodiment. It is a conceptual diagram which shows the light emission operation | movement in the display pixel (light emission drive circuit) which concerns on 1st Embodiment. 3 is a timing chart schematically showing an example of a display driving method of the display device according to the first embodiment. It is a principal part block diagram which shows an example of the display panel applied to the display apparatus which concerns on 2nd Embodiment, and its peripheral circuit (a scanning driver, a data driver, a power supply driver, a bias control driver). It is a circuit block diagram which shows an example of the display pixel (light emission drive circuit) applied to the display apparatus which concerns on 2nd Embodiment. 10 is a timing chart showing a drive control method (reverse bias setting operation, non-light emitting operation, writing operation, light emitting operation) in a display pixel applied to the display device according to the second embodiment. It is a conceptual diagram which shows the reverse bias setting operation | movement and non-light emission operation | movement in the display pixel (light emission drive circuit) which concerns on 2nd Embodiment. It is a conceptual diagram which shows the write-in operation | movement and light emission operation | movement in the display pixel (light emission drive circuit) which concerns on 2nd Embodiment. FIG. 11 is an experimental result showing a variation amount (Vth shift amount) of a threshold voltage when a switching element (thin film transistor) for driving light emission is set in a reverse bias state in the display pixel according to the second embodiment. 6 is a timing chart schematically showing an example of a display driving method of the display device according to the second embodiment. It is a schematic block diagram which shows the principal part of the active matrix type display apparatus in a prior art. It is the timing chart which showed typically an example (hold type | mold) of the display drive method of the active matrix type display apparatus in a prior art. 10 is a timing chart schematically showing another example (pseudo-impulse type) display driving method of an active matrix type display device in the prior art.

Explanation of symbols

100A, 100B Display device 110 Display panel 120 Scan driver 130 Power supply driver 140 Data driver 150 System controller 160 Display signal generation circuit 150 Bias control driver EM Display pixel DC1, DC2 Light emission drive circuit SL Scan line VL Power line DL Data line BL Bias line Tr11 to Tr14 Thin film transistor Cs Capacitor OEL Organic EL element

Claims (20)

In a display device having a display panel in which a plurality of display pixels are arranged in the vicinity of intersections of a plurality of scanning lines arranged in a row direction and a plurality of data lines arranged in a column direction,
A scanning drive unit that sequentially applies a scanning signal to the display pixels for each row of the display panel at a predetermined timing, and sets the selection state;
A data driver that generates gradation signals according to display data for displaying desired image information and sequentially supplies the gradation signals to the display pixels in the row set in the selected state;
A power supply driving unit that applies a power supply voltage for causing the display pixels in each row of the display panel to perform a display operation in a bias state according to the display data based on the gradation signal supplied from the data driving unit; ,
By supplying a timing control signal, each of the scanning drive unit, the data drive unit, and the power supply drive unit is operated at a predetermined timing, and at least the display pixels in each row are in accordance with the display data. A drive control unit that performs non-display operation by blocking application of the power supply voltage to the display pixels in the row by the power supply drive unit during a period other than the period during which display operation is performed in a bias state;
A display device comprising: The drive control unit supplies the grayscale signal from the data driving unit to the display pixels in the row during a period in which application of the power supply voltage to the display pixels in each row is cut off to perform a non-display operation. 2. The display device according to claim 1, further comprising means for generating the timing control signal. The display device eliminates a bias state corresponding to the display data, which is set for the display pixel of each row based on the gradation signal, on the display pixel for each row of the display panel, and performs a specific bias. The display device according to claim 1, further comprising a state setting control unit that applies a setting signal for setting the state. The drive control unit supplies the setting signal from the state setting control unit to the display pixels in the row during a period in which the application of the power supply voltage to the display pixels in each row is cut off to perform a non-display operation. 4. The display device according to claim 3, further comprising means for generating the timing control signal. Each display pixel includes a light emitting element and a light emission driving circuit that controls a light emitting operation of the light emitting element,
The light emission drive circuit has at least a charge accumulation means for accumulating charges based on the gradation signal and a light emission drive having a predetermined current value based on a forward bias voltage corresponding to the amount of charge accumulated in the charge accumulation means. Emission control means for generating current and supplying it to the light emitting element; and writing control means for controlling a supply state of charge based on the gradation signal to the charge storage means. The display device according to claim 1. The light emission control means provided in each display pixel has one end connected to the power supply line and the other end connected to the light emitting element, and is connected to a conduction path through which the light emission driving current flows and to the charge storage means. The display device according to claim 5, further comprising a control terminal that controls a conduction state of the conduction path to control a supply state of the light emission driving current to the light emitting element. The write control means provided in each display pixel has one end connected to the data line to which the gradation signal is supplied and the other end connected to the control terminal of the light emission control means via the charge storage means. A conductive terminal connected to the scanning line to which the scanning signal is applied; and a control terminal for controlling a charge supply state based on the gradation signal to the charge storage unit. The display device according to claim 6. The light emission drive circuit includes at least a first switch means in which the power supply voltage is applied to one end of a conduction path, and a connection contact with the light emitting element is connected to the other end of the conduction path, and a control terminal is the scanning A second switch means connected to the line, the power supply voltage being applied to one end of the conduction path, and the control terminal of the first switch means being connected to the other end of the conduction path; A third switch means having one end of a conduction path connected to the data line, and the other end of the conduction path connected to the connection contact; a control terminal of the first switch means; and the connection contact And a capacitive element connected between
The said light emission control means is comprised including the said 1st switch means, and the said electric charge storage means is comprised including the said capacitive element, The said any one of Claim 5 thru | or 7 characterized by the above-mentioned. Display device. The light emission driving circuit further includes bias control means for discharging a charge stored in the charge storage means and applying no voltage or reverse bias voltage to the light emission control means. The display device according to claim 5. The bias control means provided in each display pixel has one end connected to a scanning line to which the scanning signal is supplied and the other end connected to the control terminal of the light emission control means, so that the predetermined signal level of the bias control means is provided. A conduction path for applying a scanning signal to the control terminal of the light emission control means; and a control terminal connected to a bias line to which the setting signal is applied and for controlling a discharge state of the charge accumulated in the charge accumulation means. The display device according to claim 9. In the light emission drive circuit, a control terminal is connected to the bias line, one end of a conduction path is connected to the scanning line, and a control terminal of the first switch means is connected to the other end of the conduction path. The switch means is further provided,
The display device according to claim 9 or 10, wherein the bias control means includes the fourth switch means. The display device according to claim 5, wherein at least the light emission control means provided in the light emission drive circuit is configured by an amorphous silicon thin film transistor. The data driver includes means for generating a gray-scale current having a predetermined current value for causing the light-emitting element to emit light at a predetermined luminance gradation as the gray-scale signal. Item 13. The display device according to any one of Items 5 to 12. The display device according to claim 5, wherein the light emitting element is an organic electroluminescence element. A display panel in which a plurality of display pixels are arranged in the vicinity of intersections of a plurality of scanning lines arranged in a row direction and a plurality of data lines arranged in a column direction. A scanning signal is sequentially applied to the display pixels for each row, and in synchronization with the timing for setting the selected state, a gradation signal corresponding to display data for displaying desired image information is supplied. In a display driving method of a display device for causing a display pixel to perform a display operation in a bias state according to the display data and displaying the desired image information on the display panel,
Supplying the gradation signals by sequentially setting the display pixels for each row arranged in the display panel to a selected state;
Sequentially displaying the display pixels in each row to which the gradation signal is supplied in a bias state corresponding to the display data;
A power supply voltage for causing the display pixels for each row to perform a display operation in a bias state corresponding to the display data in a period including a period of executing the step of supplying the gradation signal to the display pixels for each row. Shutting off the application and performing a non-display operation;
A display driving method for a display device, comprising: Each display pixel includes display driving means,
The step of causing the display pixels in each row to perform a display operation in a bias state corresponding to the display data is performed by applying a forward bias voltage corresponding to the gradation signal to the display driving unit. The display driving method of the display device according to claim 15. During the period of executing the step of non-displaying the display pixels for each row, the bias state corresponding to the display data set for the display pixels in each row is canceled and set to a specific bias state. The display driving method of the display device according to claim 15, further comprising a step. The step of eliminating the bias state corresponding to the display data and setting to a specific bias state set in the display pixel of each row applies a non-voltage or a reverse bias voltage to the display driving means. The display driving method of the display device according to claim 17, wherein the display driving method is performed by the following. Each display pixel includes a light emitting element,
The step of causing the display pixels in each row to perform a display operation in a bias state corresponding to the display data causes the light emitting elements of the display pixels to perform a light emission operation with a luminance gradation corresponding to the display data. Item 19. A display driving method for a display device according to any one of Items 15 to 18. The step of supplying the gradation signal to the display pixels in each row supplies, as the gradation signal, a gradation current having a predetermined current value for causing the light emitting element to emit light at a predetermined luminance gradation. 20. A display driving method for a display device according to claim 19, wherein:

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