JP2011221127A - Display device and driving method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving circuit of an organic EL display device having a high aperture ratio on a displaying unit and little luminance variation with temperature.SOLUTION: In a display device that includes a monitoring unit comprising an N-type transistor and an organic EL element thereon and a displaying unit comprising an N-type transistor and an organic EL element thereon, the monitoring unit detects threshold voltages of the N-type transistor at the gradation of black and the gradation of white, respectively. Video data being output to the N-type transistor in the displaying unit is compensated with the detected threshold voltage.

Description

  One embodiment of the present invention relates to a display device capable of controlling input of a video signal to a pixel with a driver circuit.

  In an active matrix display device, a selection transistor, a driving transistor, and a display element are provided in each of tens to millions of pixels arranged in a matrix. The active matrix type can flexibly cope with the increase in size and definition of the panel, and is becoming the mainstream of future display devices.

  As a typical driver circuit included in an active matrix display device, a scan line driver circuit and a signal line driver circuit are given. The scanning line driving circuit selects a plurality of pixels for each line or for each plurality of lines. Then, the video signal input to the pixels included in the selected line is controlled by the signal line driver circuit.

  FIG. 6 shows a prior art active matrix pixel structure having two NMOS transistors. A light-emitting element having an anode, an organic light-emitting material, and a cathode is formed on a substrate over which a driving transistor is formed. The light-emitting element is turned on when the driving transistor is turned on.

  In the circuit of FIG. 6, the current flowing between the source electrode and drain electrode of the driving transistor and the gate electrode is expressed by the number (1). In the number (1), the mobility is μ, the capacitance per unit area of the gate insulating film is Cox, the channel width is W, the channel length is L, the potential of the driving transistor is Vg, and the potential applied to the anode of the light emitting element is Va. The threshold voltage is Vth.

  The current between the anode and the cathode of the light emitting element is represented by the number (2). In the formula (2), the constant is A, the temperature is T, the voltage function is U, the voltage between the anode and the cathode of the light emitting element is V, the threshold voltage of the light emitting element is VthEL, the Boltzmann constant is kB, and the tunnel current is It. .

  Since the tunnel current It is sufficiently small, it can be ignored. Further, assuming that the cathode potential is Vcat, the voltage V between the anode and the cathode of the light emitting element can be expressed as V = Va−Vcat. When the light emitting element is not caused to emit light, the threshold voltage applied to the light emitting element is VthEL = Va−Vcat. At this time, when the video signal is set so that the potential required to energize the driving transistor is Va = Vcat + VthEL, the voltage Vg of the video signal is Vg = Va + Vth = Vcat + VthEL + Vth.

  Further, Va is determined from the number (2) with respect to the current required to obtain the luminance corresponding to a certain gradation. Further, the potential Vg of the video signal is determined from Va obtained from Equation (2) and Equation (1).

  The number (2) is temperature-dependent, and also in the number (1), the threshold voltages Vth and VthEL of the driving transistor are temperature-dependent, so that Vg also depends on the temperature. Therefore, even if the same video signal potential Vg is input to the driving transistor, the luminance of the panel also changes due to the influence of the temperature of the peripheral circuit at that time.

  In the circuit as shown in FIG. 6, the threshold voltage Vth of the driving transistor changes depending on the temperature. For this reason, the threshold voltage Vth of the driving transistor may cause a problem that the panel shines even in black display or does not shine sufficiently in white display. In order to correct the luminance variation of the driving transistor, for example, as in the invention of Patent Document 1, the number of transistors per pixel must be increased to increase the area of the capacitor. The aperture ratio of the display unit becomes very small.

JP-A-11-219146

  The threshold voltage of the driving transistor is easily affected by the temperature of the surrounding circuit. In particular, when the temperature of the light emitting element increases, the threshold voltage of the driving transistor decreases, and even when a video signal potential for black display is input, there is a possibility that the panel is lit and the panel is lit. It is an object of the present invention to provide a display device having a high aperture ratio in a display portion and having little change in luminance due to temperature and a driving method thereof without increasing the number of transistors per pixel or increasing the area of a capacitor. And

  According to one embodiment of the present invention, a monitor portion in which a monitor pixel is configured by a first light-emitting element and a first driving transistor that controls current of the first light-emitting element, and a second light-emitting element And a second driving transistor that controls the current of the second light emitting element, a display portion in which a display pixel is formed, and a first generated when a monitor current is passed through the first light emitting element. Detecting a voltage value of the driving transistor, and a voltage value detected by the detecting unit as a control signal, correcting a video signal for controlling light emission of the second light emitting element, A conversion circuit unit that outputs a corrected video signal to the gate terminal is included, and the pixel configuration of the monitor unit and the display unit is the same.

  According to one embodiment of the present invention, a first monitor unit in which a first monitor pixel includes a first light-emitting element and a first driving transistor that controls a current of the first light-emitting element; A second monitor unit in which a second monitor pixel is composed of a second light emitting element and a second driving transistor for controlling a current of the second light emitting element; and a third light emitting element And a third driving transistor for controlling the current of the third light-emitting element, a display portion in which a display pixel is configured, and when the first monitor current is passed through the first light-emitting element Detection for detecting the first voltage value of the first driving transistor generated and the second voltage value of the second driving transistor generated when the second monitor current is passed through the second light emitting element, respectively. And the first voltage and the second voltage are respectively input as control signals. A conversion circuit unit that corrects a video signal that controls light emission of the third light-emitting element and outputs the corrected video signal to the gate terminal of the third drive transistor; a first monitor unit; The pixel configuration of the monitor unit and the display unit is the same.

  In one embodiment of the present invention, the first voltage of the first driving transistor corresponding to the first monitor current input to the first organic EL element is detected, and the second voltage input to the first organic EL element is detected. The second voltage of the first driving transistor corresponding to the monitor current is detected, and the video data input to the second organic EL element is corrected using the first voltage and the second voltage.

  In one embodiment of the present invention, the correction is performed by obtaining a voltage threshold value in the first organic EL element and the first driving transistor from the first voltage and the second voltage, and correcting the threshold value.

  In one embodiment of the present invention, after detecting the first voltage, the second voltage is detected by switching a switch.

  In one embodiment of the present invention, the first voltage of the first driving transistor corresponding to the first monitor current input to the first organic EL element is detected, and the second voltage input to the second organic EL element is detected. The second voltage of the second driving transistor corresponding to the monitor current is detected, and the video data input to the third organic EL element is corrected using the first voltage and the second voltage.

  In one embodiment of the present invention, the correction is performed from the first voltage to the first threshold voltage of the first organic EL element and the first driving transistor, and from the second voltage to the second organic EL element and the second voltage. The second threshold value of the voltage in the driving transistor is obtained and corrected according to the first threshold value and the second threshold value.

  According to the present invention, a change in threshold voltage due to temperature can be corrected in a driving transistor and a light-emitting element, so that a display device having a wide usable temperature range can be provided.

  Further, according to one embodiment of the present invention, it is not necessary to form a new transistor in a display pixel or increase the area of a capacitor, so that the aperture ratio of the display portion can be increased. Therefore, a clear and high-definition display device can be provided.

  Further, the pixel in the monitor portion in one embodiment of the present invention has the same structure as the pixel in the display portion, and can be manufactured in the same process. Therefore, the conventional manufacturing method can be used as it is. it can. In addition, since the progress of the deterioration of the monitor unit 302 and the progress of the deterioration of the display unit 303 are equal, correction with high accuracy can be performed.

FIG. 9 is a flowchart of a driving method according to one embodiment of the present invention. FIG. 9 is a flowchart of a driving method according to one embodiment of the present invention. FIG. 10 is a block diagram of a display device of one embodiment of the present invention. FIG. 10 is a circuit diagram of a display device of one embodiment of the present invention. FIG. 10 is a circuit diagram of a display device of one embodiment of the present invention. The circuit diagram of the conventional display apparatus. 4A and 4B each illustrate an example of an electronic device provided with a display device of one embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, one form of the present invention can be implemented in many different modes, and it is possible for those skilled in the art to modify the form and details in various ways without departing from the spirit and scope of the present invention. Easy to understand. Therefore, the present invention is not construed as being limited to the description of this embodiment mode. Note that in the drawings described below, the same portions or portions having similar functions are denoted by the same reference numerals, and repetitive description thereof is omitted.

(Embodiment 1)
In the first embodiment, an example in which the video signal Vg of the driving transistor of the display unit is corrected using two monitor units will be described. FIG. 1 is a flowchart for correcting a video signal input to a driving transistor using a driving circuit according to an embodiment of the present invention.

  In FIG. 1, the process starts from step 100 and proceeds to step 101. In 101, the potential Vcat is applied to the cathodes of the light emitting elements of the first monitor unit and the second monitor unit.

  In step 102, the first monitor section detects the potential VL of the video signal in the black gradation corresponding to the potential of the cathode Vcat of the light emitting element given in step 101. In the present invention, the black gradation is the lowest gradation in the display device. In step 103, using the potential VL detected in step 102, the potential VgL of the driving transistor of the monitor unit corrected in the black gradation is calculated.

  In step 104, the second monitor section detects the potential VH of the video signal in the white gradation with respect to the potential Vcat of the electrode of the light emitting element given in step 101. In the present invention, the white gradation is the highest gradation in the display device. In step 105, using the potential VH detected in step 104, the potential VgH of the driving transistor of the monitor unit corrected in the white gradation is calculated.

  In step 106, VgL calculated in step 103 and VgH calculated in step 105 are input to the display unit to correct the threshold voltage of the driving transistor in the display unit, and the process ends in step 107.

  Through steps 100 to 107 described above, the correction value calculated using the potentials detected by the two monitor units can be reflected on the display unit. Note that since the temperature of the light-emitting element changes with time, the operation may be repeated according to the flowchart of FIG. 1 during the display time.

  By using the structure of this embodiment mode, it is not necessary to form a new transistor in the display portion or increase the area of the capacitor, so that the threshold voltage due to temperature can be reduced in the driving transistor without reducing the aperture ratio. Can be corrected. Accordingly, a display device having a wide temperature application range can be provided.

  Furthermore, since the monitor portion in one embodiment of the present invention has the same structure as the display portion and can be manufactured in the same process, a conventional manufacturing method can be used as it is. In addition, since the progress of the deterioration of the monitor unit 302 and the progress of the deterioration of the display unit 303 are equal, correction with high accuracy can be performed.

(Embodiment 2)
In the second embodiment, an example in which the video signal Vg of the driving transistor of the display unit is corrected using one monitor unit will be described. FIG. 2 is a flowchart for correcting a video signal input to a driving transistor using a driving circuit according to an embodiment of the present invention.

  In FIG. 2, the process starts from step 200 and proceeds to step 201. In 201, the potential Vcat is applied to the cathode of the light emitting element of the monitor unit.

  In step 202, the monitor unit detects the potential VL of the video signal necessary for the light emitting element in the black gradation with respect to the potential of the cathode Vcat of the light emitting element given in step 201. In step 203, using the VL detected in step 202, the potential VgL of the driving transistor of the monitor unit corrected in the black gradation is calculated.

  Next, in step 204, the video signal having the potential VL in the black gradation is switched to the video signal having the potential VH in the white gradation in the monitor unit.

  In step 205, the monitor unit detects the potential VH of the video signal necessary for the light emitting element in white gradation with respect to the cathode potential Vcat of the light emitting element given in step 201. In step 206, using the VH detected in step 205, the potential VgH of the driving transistor of the monitor unit at the corrected white gradation is calculated.

  In step 207, the video signal reflecting VgL calculated in step 203 and VgH calculated in step 206 is input to the display unit, thereby correcting the threshold voltage Vth of the driving transistor of the display unit in black and white gradations. And the process ends at step 208.

  According to this flowchart, correction values calculated from a plurality of potentials detected by one monitor unit can be reflected on the display unit. Note that since the temperature of the light-emitting element changes with time, the operation may be repeated according to the flowchart of FIG. 2 during the display time.

  By using this configuration, the area of the monitor unit can be reduced, and the display device can be downsized.

  Note that since the monitor portion in one embodiment of the present invention has the same structure as the display portion and can be manufactured in the same process, a conventional manufacturing method can be used as it is. In addition, since the progress of the deterioration of the monitor unit 302 and the progress of the deterioration of the display unit 303 are equal, correction with high accuracy can be performed.

  In this example, a structure of a display device according to one embodiment of the present invention will be described. FIG. 3 shows a block diagram of the display device as an example.

  The display device illustrated in FIG. 3 includes a panel 1000 including a monitor unit 1001 and a display unit 1002, and a drive circuit unit 1100 including a detection unit 1101 and a conversion circuit unit 1102. The detection unit 1101 and the conversion circuit unit 1102 may be formed on separate substrates or may be formed on the same substrate.

  Panel 1000 is electrically connected to a monitor current input from the outside. The monitor unit 1001 and the detection unit are electrically connected via a connection terminal. The detection unit 1101 and the conversion circuit unit 1102 are electrically connected. Further, the conversion circuit portion 1102 and the display portion 1002 are also electrically connected through a connection terminal.

  This will be described with reference to the block diagram of FIG. First, a potential is given to the monitor unit from a monitor current input from the outside, and the detection unit 1101 detects the drive potential of the light emitting element and the driving transistor in the monitor unit. The detected driving potential is input to the conversion circuit unit 1102 as a control signal, and the video signal input to the display unit is corrected using the value. The corrected video signal is input to the gate terminal of the driving transistor connected to the light emitting element of the display portion 1002.

  As the panel 1000 changes with temperature, the required potential also changes. That is, the video signal output to the display unit 1002 is corrected using the potential detected by the monitor unit 1001. By continuing to correct the video signal during the driving period, the video signal in which the optimum potential value is always reflected can be input to the display portion.

  In this example, a more specific structure of the driver circuit included in the display device of one embodiment of the present invention will be described. FIG. 4 shows a circuit diagram of the drive circuit as an example. The driver circuit illustrated in FIG. 4 is electrically connected to a panel 300 including a monitor unit 301, a monitor unit 302, and a display unit 303. The driver circuit includes at least switches 311 to 314, a capacitor 325, a buffer 327, and a conversion circuit 315.

  The display portion 303 uses an active matrix pixel structure including an N-type driving transistor, an N-type selection transistor, and a light-emitting element. The monitor unit 301 and the monitor unit 302 only need to have at least an N-type driving transistor and a light-emitting element, and the selection transistor is not necessarily provided. In the final product, the monitor unit does not function as a display unit. Therefore, a light shielding film is formed on the entire monitor portion.

  Transistors are also used for the switches 311 to 314. Note that as the transistor, a single crystal semiconductor layer, a thin film transistor including a non-single-crystal semiconductor layer typified by amorphous silicon, polycrystalline silicon, microcrystalline (also referred to as semi-amorphous) silicon, or the like is used. I can do it. Alternatively, an oxide semiconductor layer such as IZO may be used.

  As a structure of the transistor, a top gate type, a bottom gate type, or the like can be used. Note that as the bottom-gate transistor, a channel etch type, a channel protection type, or the like can be used.

  The monitor current input from the outside and the source electrode or the drain electrode of the driving transistor of the monitor unit 301 are electrically connected through the switch 311 and the connection terminal of the panel and the driving circuit. Note that the potential given from the monitor current input from the outside is higher than the threshold value of the driving transistor. The capacitor 325 and the gate electrode of the driving transistor of the monitor unit 301 are electrically connected through the switch 312. The capacitor 325 is connected to the buffer 327, and the potential stored in the capacitor 325 is input to the conversion circuit 315.

  In addition, the source or drain electrode of the driving transistor of the monitor unit 302 is electrically connected to the monitor current input from the outside for applying a white gradation potential through the switch 313. The capacitor 326 and the gate electrode of the driving transistor in the monitor unit 302 are electrically connected through the switch 314. The capacitor 326 is connected to the buffer 328, and the potential stored in the capacitor 326 is input to the conversion circuit 315 as a control signal.

  In this embodiment, a capacitor and a buffer are used as a configuration for storing and outputting a potential to be detected. However, the configuration is not limited to this configuration, and a configuration having an equivalent function may be used as appropriate. Further, the potential for giving the white gradation is always given from the monitor current input from the outside, and the capacitor 326 and the buffer 328 are not necessarily required because the potential does not need to be accumulated. However, it is preferable to provide a capacity and a buffer so that the progress of the deterioration of the monitor unit 302 and the progress of the deterioration of the display unit 303 become equal.

  A driving method will be described using the circuit of FIG. First, a potential Vcat is applied to the cathode of the light emitting element of the panel.

  First, a description will be given of obtaining the potential VL in the black gradation. When the switch 311 and the switch 312 are turned on, in the monitor unit 301, the potential applied to the anode of the light emitting element is close to the sum of the cathode potential Vcat and the threshold voltage VthEL of the light emitting element. After that, by turning off the switch 312, the potential VL that gives a black gradation to the light emitting element is stored in the capacitor 325 with respect to the cathode potential Vcat of the light emitting element.

  The potential VL stored in the capacitor 326 is input to the conversion circuit 315 as a control signal through the buffer 327. In the conversion circuit 315, the video signal corrected using the potential VL is output to the gate terminal of the driving transistor connected to the light emitting element of the display portion 303.

  As the threshold voltage VthEL of the light emitting element changes with temperature, the required black gradation potential VL also changes. In this embodiment, since the cathode potential Vcat of the light emitting element is fixed, it is necessary to appropriately correct the black gradation potential VL.

  That is, the video signal output to the display unit 303 is corrected using the potential VL detected by the monitor unit 301. By continuously correcting the potential VL in the black gradation during the driving period, a video signal that always reflects the optimum potential VL value can be input to the display portion.

  Next, a description will be given of obtaining the potential VH in the white gradation. The switches 313 and 314 are turned on, and a current corresponding to white gradation is supplied to the monitor unit 302. When a certain time has elapsed, in the monitor unit 302, the potential VH applied to the anode of the light emitting element becomes a constant value with respect to the current corresponding to the white gradation. After that, by turning off the switch 314, the potential VH that gives white gradation to the light emitting element is determined with respect to the cathode potential Vcat of the light emitting element.

  Since the potential VH also depends on the temperature, it is necessary to appropriately correct the video signal input to the display unit 303 according to the temperature change. Therefore, by correcting the video signal input to the display unit 303 using the value of VH detected by the monitor unit 302 during the driving period, an appropriate potential can always be applied to the display unit.

  In this example, a more specific structure of the driver circuit included in the display device of one embodiment of the present invention will be described. FIG. 5 shows a circuit diagram of the drive circuit as an example. The driver circuit illustrated in FIG. 5 is electrically connected to a panel 400 including a monitor unit 401 and a display unit 403. In addition, the driver circuit includes at least switches 410 to 418 and a conversion circuit 430.

  As in Embodiment 2, the display portion 403 uses an active matrix pixel structure including an N-type driving transistor, an N-type driving transistor, and a light-emitting element. In addition, it is only necessary that at least an N-type driving transistor and a light-emitting element be formed in the monitor portion 401, and a selection transistor is not necessarily provided. In the final product, the monitor unit does not function as a display unit. Therefore, a light shielding film is formed on the entire monitor portion.

  The switch 410 electrically connects a monitor current input from the outside for applying a white gradation potential and a source electrode or a drain electrode of a driving transistor of the monitor unit 401 via a connection terminal between the panel and the driving circuit. Connect to.

  The gate electrode of the driving transistor of the monitor unit 401 and the capacitors 421 to 424 are electrically connected through switches 411 to 414, respectively. The capacitors 421 to 424 are connected to the buffers 425 to 428, respectively, and potentials stored in the capacitors are input to the conversion circuit 430.

  In this embodiment, a capacitor and a buffer are used as a configuration for storing and outputting a potential to be detected. However, the configuration is not limited to this configuration, and a configuration having an equivalent function may be used as appropriate.

  A driving method using the circuit of FIG. 5 will be described. First, a potential Vcat is applied to the cathode of the light emitting element of the panel.

  The capacitors 423 and 424 are used when detecting the black gradation potential VL. The capacitors 421 and 422 are used when detecting the white gradation potential VH.

  First, a method for obtaining the black gradation potential VL1 will be described. The switches 413 and 418 are turned on. In the monitor unit 401, the potential applied to the anode of the light emitting element is close to the sum of the cathode potential Vcat and the threshold voltage VthEL of the light emitting element. At this time, the switches 411, 412 and 415 connected to the capacitors 421 and 422 used for detecting the white gradation potential VH are off and the switch 416 is on.

  Thereafter, the switch 418 is turned on, the switch 413 is turned off, and at the same time, the switch 410 and the switch 411 are turned on. Then, with respect to the cathode potential Vcat of the light emitting element, the capacitor 423 acquires the potential VL1 that gives the light emitting element a black gradation, and at the same time, the capacitor 421 stores the white gradation potential VH1.

  When the switch 411 is turned off and the switch 415 and the switch 417 are turned on, the potential VH1 and the potential VL1 stored in the capacitor 421 and the capacitor 423 are input to the conversion circuit 430 through the buffers 425 and 427, respectively. .

  In the conversion circuit 430, a video signal corrected using the potential VL1 and the potential VH1 is output to the display portion 403, and the change in black and white gradation due to the temperature change of the display portion is corrected.

  Further, the switch 410 and the switch 418 are turned off and the switch 414 is turned on while the switch 417 is turned on. At this time, the switches 411 and 412 connected to the capacitors 421 and 422 used for detecting the white gradation potential VH are turned off, the switch 415 is kept on, and the switch 416 is turned off.

  After that, when the switch 417 is turned on and the switch 414 is turned off, the black gradation potential VL2 corresponding to the threshold voltage VthEL changed by the influence of temperature is stored in the capacitor 424. At the same time, by turning on the switch 410 and the switch 412, the potential VH 2 of white gradation is stored in the capacitor 422.

  When the switch 412 is turned off and the switch 416 and the switch 418 are turned on, the potential VH2 and the potential VL2 stored in the capacitor 422 and the capacitor 424 are supplied to the conversion circuit 430 as control signals through the buffers 426 and 428, respectively. Entered.

  In the conversion circuit 430, the video signal corrected using the potential VL2 and the potential VH2 is output to the gate terminal of the driving transistor connected to the light emitting element of the display portion 403, and black and white gradations due to the temperature change of the display portion. Correction of changes in

  As the threshold voltage VthEL of the light emitting element changes with temperature, the required black gradation potential VL also changes. In this embodiment, since the cathode potential Vcat of the light emitting element is fixed, it is necessary to appropriately correct the black gradation potential VL.

  By repeating the above driving method during the driving period, it becomes possible to continue correcting the potential VH and the potential VL in the white and black gradations. Therefore, a video signal that reflects the values of the optimum potential VL and potential VH can always be given to the display portion.

  Since the display device according to one embodiment of the present invention is a self-luminous type, it is superior in visibility in a bright place and has a wide viewing angle as compared with a liquid crystal display. Therefore, it can be used for display portions of various electronic devices. In addition, when using this invention for the display part of an electronic device, a monitor part is light-shielded so that it cannot recognize from the outside.

  As an electronic device using the display device according to one embodiment of the present invention, a video camera, a digital camera, a goggle type display (head mounted display), a navigation system, an acoustic playback device (car audio, audio component, etc.), a notebook personal computer, Reproducing a recording medium such as a game machine, a portable information terminal (mobile computer, cellular phone, portable game machine or electronic book), an image reproducing device (specifically, a digital video disc (DVD)), And a device provided with a display capable of displaying the image). In particular, it is desirable to use a light-emitting device for a portable information terminal that often has an opportunity to see a screen from an oblique direction because the wide viewing angle is important. Specific examples of these electronic devices are shown in FIGS.

  FIG. 7A illustrates a light-emitting device, which includes a housing 3001, a support base 3002, a display portion 3003, speaker portions 3004, a video input terminal 3005, and the like. The display device according to one embodiment of the present invention can be used for the display portion 3003. Since the light-emitting device is a self-luminous type, a backlight is not necessary and a display portion thinner than a liquid crystal display can be obtained. Note that the display device according to one embodiment of the present invention includes all information display devices for personal computers, TV broadcast reception, advertisement display, and the like.

  FIG. 7B illustrates a digital still camera, which includes a main body 3101, a display portion 3102, an image receiving portion 3103, operation keys 3104, an external connection port 3105, a shutter button 3106, and the like. The display device according to one embodiment of the present invention can be used for the display portion 3102.

  FIG. 7C illustrates a laptop personal computer, which includes a main body 3201, a housing 3202, a display portion 3203, a keyboard 3204, an external connection port 3205, a pointing device 3206, and the like. The display device in one embodiment of the present invention can be used for the display portion 3203.

  FIG. 7D shows a mobile computer, which includes a main body 3301, a display portion 3302, a switch 3303, operation keys 3304, an infrared port 3305, and the like. The display device according to one embodiment of the present invention can be used for the display portion 3302.

  FIG. 7E illustrates a portable image reproducing device (specifically, a DVD reproducing device) provided with a recording medium, which includes a main body 3401, a housing 3402, a display portion 3403, a display portion 3404, and a recording medium (DVD or the like). A reading unit 3405, an operation key 3406, a speaker unit 3407, and the like are included. Although the display portion 3403 mainly displays image information and the display portion 3404 mainly displays character information, the display device in one embodiment of the present invention can be used for the display portion 3403 and the display portion 3404. Note that an image reproducing device provided with a recording medium includes a home game machine and the like.

  FIG. 7F illustrates a goggle type display (head mounted display), which includes a main body 3501, a display portion 3502, and an arm portion 3503. The display device according to one embodiment of the present invention can be used for the display portion 3502.

  FIG. 7G illustrates a video camera, which includes a main body 3601, a display portion 3602, a housing 3603, an external connection port 3604, a remote control receiving portion 3605, an image receiving portion 3606, a battery 3607, an audio input portion 3608, operation keys 3609, and the like. . The display device in one embodiment of the present invention can be used for the display portion 3602.

  Here, FIG. 7H illustrates a mobile phone, which includes a main body 3701, a housing 3702, a display portion 3703, an audio input portion 3704, an audio output portion 3705, operation keys 3706, an external connection port 3707, an antenna 3708, and the like. The display device in one embodiment of the present invention can be used for the display portion 3703. Note that the display portion 3703 can suppress power consumption of the mobile phone by displaying white characters on a black background.

  If the light emission luminance of the organic light emitting material is increased, the light including the output image information can be enlarged and projected by a lens or the like and used in a front type or rear type projector.

  In addition, the electronic devices often display information distributed through electronic communication lines such as the Internet and CATV (cable television), and in particular, opportunities to display moving image information are increasing. Since the organic light emitting material has a very high response speed, the light emitting device is preferable for displaying moving images.

  In addition, since the light emitting device consumes electric power in the light emitting device, it is desirable to display information so that the area of the light emitting portion is minimized. Therefore, when a light emitting device is used for a display unit mainly including character information, such as a portable information terminal, particularly a mobile phone or a sound reproduction device, it is driven so that character information is formed by the light emitting part with the non-light emitting part as the background. It is desirable to do.

  As described above, the applicable range of one embodiment of the present invention is so wide that the present invention can be used for electronic devices in various fields.

100 step 101 step 102 step 103 step 104 step 105 step 106 step 107 step 200 step 201 step 202 step 203 step 204 step 205 step 206 step 207 step 208 step 300 panel 301 monitor unit 302 monitor unit 303 display unit 311 switch 312 switch 313 Switch 314 Switch 315 Conversion circuit 325 Capacity 326 Capacity 327 Buffer 328 Buffer 400 Panel 401 Monitor section 403 Display section 410 Switch 411 Switch 412 Switch 413 Switch 414 Switch 415 Switch 416 Switch 417 Switch 418 Switch 421 Capacity 422 Capacity 423 Capacity 424 Capacity 425 Buffer 426 bar F 427 Buffer 428 Buffer 430 Conversion circuit 1000 Panel 1001 Monitor unit 1002 Display unit 1100 Drive circuit unit 1101 Detection unit 1102 Conversion circuit unit 3001 Case 3002 Support base 3003 Display unit 3004 Speaker unit 3005 Video input terminal 3101 Main body 3102 Display unit 3103 Image receiving Unit 3104 operation key 3105 external connection port 3106 shutter button 3201 main body 3202 case 3203 display unit 3204 keyboard 3205 external connection port 3206 pointing device 3301 main unit 3302 display unit 3303 switch 3304 operation key 3305 infrared port 3401 main unit 3402 case 3403 display unit 3404 Display unit 3405 Recording medium (DVD etc.) reading unit 3406 Operation key 3407 Speaker unit 35 01 Main body 3502 Display unit 3503 Arm unit 3601 Main unit 3602 Display unit 3603 Case 3604 External connection port 3605 Remote control reception unit 3606 Image receiving unit 3607 Battery 3608 Audio input unit 3609 Operation key 3701 Main unit 3702 Display unit 3704 Audio input unit 3705 Audio Output unit 3706 Operation key 3707 External connection port 3708 Antenna

Claims (7)

A monitor unit in which a monitor pixel is constituted by a first light emitting element and a first driving transistor for controlling a current of the first light emitting element;
A display unit in which a display pixel is constituted by a second light emitting element and a second driving transistor for controlling a current of the second light emitting element;
A detector for detecting a voltage value of the first driving transistor generated when a monitor current is passed through the first light emitting element;
The voltage value detected by the detection unit is input as a control signal, the video signal for controlling the light emission of the second light emitting element is corrected, and the corrected video signal is output to the gate terminal of the second driving transistor. A conversion circuit unit,
A display device, wherein the monitor unit and the display unit have the same pixel configuration. A first monitor unit in which a first monitor pixel is constituted by a first light emitting element and a first driving transistor for controlling a current of the first light emitting element;
A second monitor unit in which a second monitor pixel is constituted by a second light emitting element and a second driving transistor for controlling a current of the second light emitting element;
A display unit in which a display pixel is configured by a third light emitting element and a third driving transistor for controlling a current of the third light emitting element;
A first voltage value of the first driving transistor generated when a first monitor current is supplied to the first light emitting element, and a second monitor current is supplied to the second light emitting element. A detection unit for detecting a second voltage value of the second driving transistor that occurs at times; and
The first voltage and the second voltage are respectively input as control signals, the video signal for controlling the light emission of the third light emitting element is corrected, and the video is corrected to the gate terminal of the third driving transistor. A conversion circuit unit that outputs a signal,
The display device, wherein the first monitor unit, the second monitor unit, and the display unit have the same pixel configuration. Detecting the first voltage of the first driving transistor corresponding to the first monitor current input to the first organic EL element;
Detecting a second voltage of the first driving transistor corresponding to a second monitor current input to the first organic EL element;
A method for driving a display device, wherein video data input to a second organic EL element is corrected using the first voltage and the second voltage. In claim 3,
In the correction, a threshold value of a voltage in the first organic EL element and the first driving transistor is obtained from the first voltage and the second voltage, and the correction is performed according to the threshold value. Device driving method. In claim 3 or 4,
A method for driving a display device, wherein the second voltage is detected by switching a switch after detecting the first voltage. Detecting the first voltage of the first driving transistor corresponding to the first monitor current input to the first organic EL element;
Detecting a second voltage of the second driving transistor corresponding to the second monitor current input to the second organic EL element;
A method for driving a display device, wherein video data input to a third organic EL element is corrected using the first voltage and the second voltage. In claim 6,
In the correction, the first threshold voltage of the first organic EL element and the first driving transistor from the first voltage and the second organic EL element and the second driving voltage from the second voltage are corrected. A driving method of a display device, characterized in that a second threshold value of a voltage in a transistor is obtained and corrected according to the first threshold value and the second threshold value.