CN100511371C - Display device and electronic device - Google Patents

Display device and electronic device Download PDF

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Publication number
CN100511371C
CN100511371C CNB2005100737019A CN200510073701A CN100511371C CN 100511371 C CN100511371 C CN 100511371C CN B2005100737019 A CNB2005100737019 A CN B2005100737019A CN 200510073701 A CN200510073701 A CN 200510073701A CN 100511371 C CN100511371 C CN 100511371C
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China
Prior art keywords
photocell
display device
transistor
electrode
light emitting
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CNB2005100737019A
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CN1700286A (en
Inventor
早川昌彦
山崎优
安藤由香里
宮川惠介
小山润
纳光明
安西彩
山崎舜平
瀬尾哲史
安部宽子
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Semiconductor Energy Laboratory Co Ltd
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Semiconductor Energy Laboratory Co Ltd
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    • Y02B20/42—

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  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Electroluminescent Light Sources (AREA)

Abstract

A display device where the influence of variations in current of the light emitting element due to changes in ambient temperature and changes with time can be suppressed. The display device of the invention has a light emitting element, a driving transistor connected in series to the light emitting element, a monitoring light emitting element, a limiter transistor connected in series to the monitoring light emitting element, a constant current source for supplying a constant current to the monitoring light emitting element, and a circuit for outputting a potential equal to an inputted potential. A first electrode of the light emitting element is connected to an output terminal of the circuit through the driving transistor, and a first electrode of the monitoring light emitting element is connected to an input terminal of the circuit through the limiter transistor. The channel length L 1 and the channel width W 1 of the driving transistor, and the channel length L 2 and the channel width W 2 of the limiter transistor satisfy L 1 /W 1 :L 2 /W 2 =1:2 to 1:10.

Description

Display device and electronic installation
Technical field
The present invention relates to have the display device and the television equipment of light generating device.
The invention further relates to the electronic installation that uses display device with light generating device.
Background technology
In recent years, active development has the display device of the photocell that is generally EL (electroluminescence), and advantage such as high image quality by utilizing photocell, wide viewing angle, and the thickness that has reduced and quality and be expected to be widely used.
Photocell is characterized as its resistance (internal resistance) and changes with environment temperature (hereinafter referred to as environment temperature).Especially, resistance reduces when temperature surpasses room temperature, and when temperature resistance increase during less than room temperature.The such feature of photocell is shown in the curve among Figure 10 A, and Figure 10 A illustrates the voltage-to-current feature of photocell and the relation between the temperature.Photocell also has such feature, and promptly its electric current reduces in time.The such feature of photocell is shown in the curve of Figure 10 B, and Figure 10 B illustrates the voltage-to-current feature of photocell and the relation between the time.
Summary of the invention
The aforementioned feature of photocell causes the variation that brightness changes or changes in time with environment temperature.Consider the explanation of front, the present invention proposes a kind of display device, wherein changes owing to environment temperature and the influence of the variation of the electric current of the photocell that change in time causes can be suppressed.
Consider previous reasons, the invention provides a kind of display device, it has the function of proofreading and correct the environment temperature change and proofreaies and correct the function that changes in time (below be referred to as calibration function).
Display device of the present invention has photocell, drives the transistor that is connected serially to photocell, monitors photocell, and series connection is used to supply constant current source and the buffering amplifier of constant current to monitor photocell to monitor the limit transistor of photocell.First electrode of photocell is connected to the outlet terminal of buffer amplifier by driving transistors.Monitor that first electrode of photocell is connected to the input end of buffer amplifier through limit transistor.The channel length (L2) and the channel width (W2) of the channel length of driving transistors (L1) and channel width (W1) and limit transistor satisfy L1/W1:L2/W2=1:2 to 1:10.Limit transistor is conducting always.
Display device of the present invention has photocell, monitors photocell, is connected serially to the AC transistor that monitors photocell, is used to supply constant current to the constant current source that monitors photocell, buffer amplifier.First electrode of photocell is electrically connected to the output terminal of buffer amplifier.Monitor first electrode of photocell, an input end that is connected to buffer amplifier in the transistorized gate electrode of AC and AC transistorized source electrode and the drain electrode.Another of AC transistorized source electrode and drain electrode is connected to AC power supplies.
Display device of the present invention has photocell, monitor photocell, be used to supply constant current to monitor the constant current source of photocell, buffer amplifier, be connected to the capacitor of the input end of buffer amplifier, be provided in photocell first electrode and the buffering amplifier output terminal between first switch, be provided in first electrode of photocell and the second switch between the AC power supplies, be provided in to monitor first electrode of photocell and the 3rd switch between the buffering amplifier input terminal, and be provided in to monitor first electrode of photocell and the 4th switch between the AC power supplies.
Display device of the present invention has and is used to apply forward bias to photocell with monitor that it is conducting state and second switch and the 4th switch are the control circuit of nonconducting state that photocell makes first switch and the 3rd switch simultaneously.Display device of the present invention further has control circuit, and it is used to apply reversed bias voltage to photocell with monitor that it is nonconducting state and second switch and the 4th switch are conducting state that photocell makes first switch and the 3rd switch simultaneously.
Display device of the present invention has photocell, monitors photocell, is connected serially to the current source transistor that monitors photocell, buffer amplifier.First electrode of photocell is electrically connected to the output terminal of buffer amplifier.Monitor first electrode and the source electrode of current source transistor and an input end that is connected to buffer amplifier in the drain electrode of photocell.The gate electrode of current source transistor is connected to first power supply, and another of the source electrode of current source transistor and drain electrode is connected to second source.Current source transistor works in the zone of saturation.
Display device of the present invention has photocell, monitor photocell, be used to supply constant current to the constant current source that monitors photocell, buffer amplifier and the resistor that is provided in to monitor first electrode of photocell and cushions the amplifier input terminal centre.First electrode of photocell is electrically connected to the output terminal of buffer amplifier.
Display device of the present invention has photocell, and switching transistor monitors photocell, is connected serially to the positively biased transistor that monitors photocell, is used to supply constant current to constant current source that monitors photocell and buffering amplifier.First electrode of photocell is electrically connected to the output terminal of buffer amplifier.Monitor that first electrode of photocell is connected to the input end of buffer amplifier.The transistorized gate electrode of the gate electrode of switching transistor and positively biased is connected to gate line.In positively biased transistorized source electrode and the drain electrode one is connected to the input end of buffer amplifier and another is connected to the positively biased power supply.
Display device of the present invention has the pixel region that comprises a plurality of pixels, source electrode driver, first grid driver and second grid driver.Each pixel has photocell, is used for the first transistor that the control of video signal inputs to pixel, is used to control the light emission of photocell or the transistor seconds of non-light emission (non-light emission).Capacitor has and is formed at the first and second transistorized gate electrodes with first conductive layer on one deck, be formed at the source electrode of the first transistor and transistor seconds and drain electrode wiring with one deck second conductive layer, and be formed at insulation course between first conductive layer and second conductive layer.
Display device of the present invention has the pixel region that comprises a plurality of pixels, source electrode driver, first grid driver and second grid driver.Each pixel has photocell, is used for the first transistor that the control of video signal inputs to pixel, the capacitor that is used to control the light emission or the non-photoemissive transistor seconds of photocell and is used to keep vision signal.Capacitor has and is formed at and the source electrode of the first transistor and drain electrode wiring first conductive layer with one deck, is formed at and the pixel electrode of photocell second conductive layer with one deck, is formed at the insulation course between first conductive layer and second conductive layer.
The invention provides a kind of display device that has demonstration white light emitting elements (photocell of emission white light) and monitor white light emitting elements.The change of environment temperature and change are in time monitored by the supervision white light emitting elements, and its bearing reaction is on the electrical source voltage that shows white light emitting elements.
More specifically, show that white light emitting elements monitors that with constant voltage driving work white light emitting elements works with constant-current driving.In constant voltage driving, constant voltage is applied to photocell, yet in constant-current driving, constant current is supplied to photocell.When monitoring that white light emitting elements is worked with constant-current driving, the change of environment temperature and change in time are as shown in the potential difference of supervision white light emitting elements.Such change is reflected in the electrical source voltage that shows white light emitting elements the change of recoverable environment temperature and change in time in monitoring the white light emitting elements potential difference.
The invention provides a kind of display device, wherein white light emitting elements has 45% to 80% dutycycle, and monitors that white light emitting elements has 45% to 100% dutycycle.The dutycycle of white light emitting elements is all average duty ratios that are provided in white light emitting elements in the pixel region.Dutycycle is a light period to light period and the non-light emissioning cycle ratio as the write cycle when all incoming video signal display white.
The invention provides a kind of display device, wherein white light emitting elements at the total magnitude of current of some cycle less than monitoring total magnitude of current in the white light emitting elements.
In this mode, the load of white light emitting elements is different from the load that monitors on the white light emitting elements, and considers brightness decay based on the quantity of electric charge that flows through white light emitting elements.Therefore, can carry out permanent brightness and drive, wherein the amount of the electric charge in the amount of electric charge and the supervision white light emitting elements is compared in the white light emitting elements, and the brightness of correction white light emitting elements is constant.
Display device of the present invention has white light emitting elements, is connected serially to the driving transistors of white light emitting elements, monitors white light emitting elements, be connected serially to the limit transistor that monitors white light emitting elements, be used to supply constant current to the constant current source that monitors white light emitting elements, buffer amplifier, and nonferrous layer.First electrode of white light emitting elements is connected to the output terminal of buffer amplifier through driving transistors.Monitor that first electrode of white light emitting elements is connected to the input end of buffer amplifier through limit transistor.The channel length (L2) and the channel width (W2) of the channel length of driving transistors (L1) and channel width (W1) and limit transistor satisfy L1/W1:L2/W2=1:2 to 1:10.Provide white light emitting elements so that overlap with nonferrous layer.Limit transistor is always open-minded.
Display device of the present invention has white light emitting elements, monitors white light emitting elements, is connected serially to the AC transistor that monitors white light emitting elements, is used to supply constant current to the constant current source that monitors white light emitting elements, buffer amplifier, and nonferrous layer.First electrode of white light emitting elements is electrically connected to the output terminal of buffer amplifier.Monitor first electrode of white light emitting elements, an input end that is connected to buffer amplifier in the transistorized gate electrode of AC and AC transistorized source electrode and the drain electrode.In AC transistorized source electrode and the drain electrode another is connected to AC power supplies.Provide white light emitting elements to overlap with nonferrous layer.
Display device of the present invention has white light emitting elements, monitor white light emitting elements, be used to supply constant current to the constant current source that monitors white light emitting elements, buffer amplifier, nonferrous layer, be connected to the input end of buffer amplifier, be provided in white light emitting elements first electrode and the buffering amplifier output terminal between first switch, be provided in first electrode of white light emitting elements and the second switch between the AC power supplies, be provided in to monitor first electrode of white light emitting elements and the 3rd switch between the buffering amplifier input terminal, be provided in to monitor first electrode of white light emitting elements and the 4th switch between the AC power supplies.Provide white light emitting elements to overlap with nonferrous layer.
Display device of the present invention has and is used to supply positive bias-voltage to white light emitting elements and the control circuit that monitors white light emitting elements and makes first switch and the 3rd switch be in conducting state simultaneously and second switch and the 4th switch are in nonconducting state.Display device of the present invention further has and is used to apply reversed bias voltage to white light emitting elements with monitor the control circuit of white light emitting elements, makes first switch and the 3rd switch be in nonconducting state simultaneously and second switch and the 4th switch are in conducting state.Provide white light emitting elements to overlap with nonferrous layer.
Display device of the present invention has white light emitting elements, monitors white light emitting elements, is connected serially to the current source that monitors white light emitting elements, buffer amplifier, nonferrous layer.First electrode of white light emitting elements is electrically connected to the output terminal of buffer amplifier.Monitor first electrode and the source electrode of current source transistor and an input end that is connected to buffer amplifier in the drain electrode of white light emitting elements.The gate electrode of current source transistor is connected to first power supply.The source electrode of current source transistor and in the drain electrode another are connected to second source.Provide white light emitting elements to overlap with nonferrous layer.Current source transistor works in the zone of saturation.
Display device of the present invention has white light emitting elements, monitor white light emitting elements, be used to supply constant current to the constant current source that monitors white light emitting elements, buffer amplifier, nonferrous layer and the resistor that is provided in to monitor first electrode of white light emitting elements and cushions amplifier input terminal.First electrode of white light emitting elements is electrically connected to the output terminal of buffer amplifier.Provide white light emitting elements to overlap with nonferrous layer.
Display device of the present invention has white light emitting elements, and switching transistor monitors white light emitting elements, is connected serially to the positively biased transistor that monitors white light emitting elements, is used to supply constant current to the constant current source that monitors white light emitting elements, buffer amplifier, and nonferrous layer.First electrode of white light emitting elements is electrically connected to the output terminal of buffer amplifier.Monitor that first electrode of white light emitting elements is connected to the input end of buffer amplifier.The transistorized gate electrode of the gate electrode of switching transistor and positively biased is connected to gate line.An input end that is connected to buffer amplifier in positively biased transistorized source electrode and the drain electrode, and another is connected to the positively biased power supply.Provide white light emitting elements to overlap with nonferrous layer.
The present invention with aforementioned structure can provide the influence of the variation of the photocell electric current that display device wherein causes owing to the change of environment temperature and change in time to be suppressed.
Description of drawings
Fig. 1 is the view that display device configurations of the present invention is shown.
Each is the view that display device configurations of the present invention is shown for Fig. 2 A and Fig. 2 B.
Fig. 3 is the view that the layout of display device of the present invention is shown.
Fig. 4 is the view that display device configurations of the present invention is shown.
Each is the sequential chart that the operation of display device of the present invention is shown for Fig. 5 A and Fig. 5 B.
Each is the view that display device configurations of the present invention is shown for Fig. 6 A and Fig. 6 B.
Each is the view of panel that a kind of mode of display device of the present invention is shown for Fig. 7 A and Fig. 7 B.
Each is the view of panel that a kind of mode of display device of the present invention is shown for Fig. 8 A and Fig. 8 B.
Each is the view that the example of the electronic installation that uses display device of the present invention is shown for Fig. 9 A to Fig. 9 F.
Each is the figure that the temperature profile of photocell and feature in time are shown for Figure 10 A and 10B.
Figure 11 A and Figure 11 B are the figures that photocell time-varying current and time dependent brightness are shown respectively.
Figure 12 is the view that the configuration of display device of the present invention is shown.
Figure 13 is the view that the configuration of display device of the present invention is shown.
Figure 14 is the view that the configuration of display device of the present invention is shown.
Figure 15 is the view that the configuration of display device of the present invention is shown.
Figure 16 is the view that the configuration of display device of the present invention is shown.
Figure 17 is the view that the configuration of display device of the present invention is shown.
Figure 18 is the view of panel that a kind of mode of display device of the present invention is shown.
Figure 19 is the view that the configuration of display device of the present invention is shown.
Each is the view that the configuration of display device of the present invention is shown for Figure 20 A and Figure 20 B.
Figure 21 is the view that the configuration of display device of the present invention is shown.
Figure 22 is the view that the configuration of display device of the present invention is shown.
Figure 23 is the view that the configuration of display device of the present invention is shown.
Figure 24 is the view that the configuration of display device of the present invention is shown.
Figure 25 is the view that the configuration of display device of the present invention is shown.
Figure 26 is the figure that the current density-voltage characteristic of photocell is shown.
Figure 27 is the figure that the current density-voltage characteristic of photocell is shown.
Figure 28 is the figure that the variation of n and s is shown.
Embodiment
Though the present invention illustrates fully that in the mode of embodiment and embodiment be appreciated that for a person skilled in the art, multiple change and modification are obvious with reference to the accompanying drawings.Therefore, unless such change and modification depart from the category that the present invention limits, they should be interpreted as being included in the scope of the present invention.In the structure of noting the following describes of the present invention, components identical is represented by identical identification number in institute's drawings attached.
[embodiment 1]
Display device of the present invention has photocell 13 and monitors photocell 66, and they all are provided on the substrate 20.Photocell 13 with monitor that photocell 66 is formed down identical creating conditions by identical technology, and have identical feature or essentially identical feature with in time change about the change of environment temperature.
Display device of the present invention has constant current source 105 and buffering amplifier 110.These circuit can be formed at photocell 13 substrate 20 identical with monitoring photocell 66 on, or be formed on the another kind of substrate.
The pixel region 40 that is provided on the substrate 20 comprises a plurality of pixels of settling with matrix.Each pixel has photocell 13 and at least two transistors.In this embodiment, the driving transistors 12 that is connected serially to photocell 13 only is shown.Driver (first grid driver 41, second grid driver 42 and source electrode driver 43 are this illustrate) also is provided on the substrate 20 and controls light emission or the emission of non-light and the brightness of each pixel.One in two electrodes of photocell 13 is connected to relative power supply 18, and another is connected to the output terminal of buffer amplifier 110 through driving transistors 12.
One or more supervision photocells 66 are provided on the substrate 20.One in two electrodes of supervision photocell 66 is connected to relative power supply 18, and another is connected to the input end of buffer amplifier 110 through limit transistor 111.
The monitoring circuit 64 that comprises one or more supervision photocells 66 can be provided in pixel region 40 or other zone.Yet monitoring circuit 64 preferably is provided in the zone of non-pixel region 40 and does not show so that do not influence image.
Constant current is supplied to from constant current source 105 and monitors photocell 66.When environment temperature changes and changes when this state occurs in time, monitor that the resistance of photocell 66 self also changes.Therefore, monitor photocell 66 because constant current is provided to, potential difference changes between two electrodes of supervision photocell 66.
In the situation of aforementioned structure, the electromotive force of an electrode that is connected to the supervision photocell 66 of relative power supply 18 does not change, and monitors that the electromotive force of another electrode (being called first electrode here) of photocell 66 changes, and this electrode is connected to constant current source 105.The electromotive force of the change of first electrode of supervision photocell 66 is provided to buffer amplifier 110.
Monitor that the electromotive force of an electrode of photocell 66 inputs to the input end of buffer amplifier 110.Be supplied to first electrode of photocell 13 through driving transistors 12 from the electromotive force of the output terminal output of buffering amplifier 110.
In structure shown in the drawings, the inverting terminal and the output terminal of buffer amplifier 110 are connected to each other.The input end of buffer amplifier 110 is connected to first electrode that monitors photocell 66 and the output terminal of buffer amplifier 110 is connected to first electrode of photocell 13.
Provide buffer amplifier 110 so that prevent potential change.Therefore, also can adopt other circuit to replace buffer amplifier 110 as long as it can prevent potential change.Just, when the electromotive force of an electrode that monitors photocell 66 transfers to photocell 13, be used to prevent that the circuit of potential change is provided in to monitor between photocell 66 and the photocell 13.Such circuit is not limited to aforementioned buffer amplifier 110, can adopt the circuit of any configuration.
Aforementioned buffer amplifier 110 is the circuit that are used to prevent potential change, and can be described as the circuit that is used to export the electromotive force that equals to import electromotive force.
First kind of architectural feature of display device of the present invention is to have to be connected serially to the limit transistor 111 (referring to Fig. 1) that monitors photocell 66.
The gate electrode of limit transistor 111 is connected to power supply 112.Limit transistor 111 is open-minded, and the electromotive force of limit transistor 111 is opened in power supply 112 supplies.One in the source electrode of limit transistor 111 and the drain electrode is connected to first electrode that monitors photocell 66, and another is connected to the input end of buffer amplifier 110.
Limit transistor 111 is provided flows through monitors transmitted element 66 so that prevent overcurrent.Even monitor that the anode and the negative electrode of photocell 66 are short circuits, limit transistor 111 prevents to monitor photocell 66 because overcurrent flows through the damage that short circuit partly causes.
Monitor photocell 66 in order to prevent that overcurrent from flowing through, the channel length (L2) and the channel width (W2) of the channel length of driving transistors 12 (L1) and channel width (W1) and limit transistor 111 satisfy L1/W1:L2/W2=1:2 to 1:10.
Driving transistors 12 or limit transistor 111 are not transistors but corresponding to the transistor of two series connection.In some cases, the channel length of driving transistors 12 or limit transistor 111 and channel width are respectively corresponding to total channel length of two serial transistors and total channel width.
In being shown in the structure of accompanying drawing, limit transistor 111 is p channel transistors, but the present invention is not limited to this, and the N channel transistor also can use.
In being shown in the structure of accompanying drawing, monitor that the number of photocell 66 is identical with the number of a photocell 13 that is listed as in the pixel region 40, but the present invention is not limited to this.At least requiring provides to monitor a photocell 66.
Second kind of structure of display device of the present invention is with reference to Figure 12 explanation.Being characterized as of second kind of structure has the AC transistor 113 that is connected serially to supervision photocell 66.
The gate electrode of AC transistor 113 is connected to the input end of buffer amplifier 110 through switch 116.The gate electrode of AC transistor 113 also is connected to AC power supplies 115 through switch 117.One in the source electrode of AC transistor 113 and the drain electrode is connected to AC power supplies 114, and another is connected to first electrode that monitors photocell 66.Provide AC transistor 113 so that apply reversed bias voltage to monitoring photocell 66.
When reversed bias voltage was applied to supervision photocell 66, switch 116 turn-offed so that buffer amplifier 110 is not electrically connected to and monitors photocell 66.In addition, switch 117 is opened and the electromotive force of AC power supplies 115 is supplied to AC transistor 113, thereby AC transistor 113 is open-minded.Then the relative size between the electromotive force of the electromotive force of power supply 18 and AC power supplies 114 is to set arbitrarily relatively.By applying reversed bias voltage to monitoring photocell 66, electric current is applied to the anode of supervision photocell 66 and the short circuit part of negative electrode partly, thereby can insulate the short circuit part.Therefore, can proofread and correct owing to monitor the defective that the short circuit of photocell 66 partly causes.
Provide capacitor 126 to apply the electromotive force that reversed bias voltage is kept the input end of buffer amplifier 110 when monitoring photocell 66 with box lunch.Yet the present invention is not limited to capacitor 126, and other can keep the circuit of the electromotive force of buffer amplifier 110 input ends also can adopt.
On the other hand, when positive bias-voltage was applied to supervision photocell 66, switch 116 was opened and switch 117 shutoffs.
In being shown in the structure of accompanying drawing, AC transistor 113 is p channel transistors, but the present invention is not limited to this, and the N channel transistor also can adopt.Further, though the gate electrode of AC transistor 113 is connected to the input end of buffer amplifier 110, the present invention is not limited to this.The open/close state of control circuit with control AC transistor 113 can independently be provided.
Aforementioned second kind of structure can free and aforementioned first kind of textural association.
The third structure of display device of the present invention will illustrate with reference to Figure 13.Being characterized as of the third structure has the capacitor 126 that is connected to buffer amplifier 110 input ends, be provided in photocell 13 first electrode and the buffering amplifier 110 output terminal between first switch 121, be provided in first electrode of photocell 13 and the second switch 122 between the AC power supplies 125, the 3rd switch 123 between the input end that is provided in to monitor photocell 66 and cushion amplifier 110, be provided in to monitor first electrode of photocell 66 and the 4th switch 124 between the AC power supplies 125, and be provided in constant current source 105 and the buffering amplifier 110 input end between the 5th switch 128.For first switch 121, second switch 122, the three switches, 123, the four switches 124 and the 5th switch 128 have the known elements of switching function, go into transistor and may be utilized.
When reversed bias voltage was applied to photocell 13 and monitors photocell 66, control circuit 127 made first switch, 121, the three switches 123 and the 5th switch 128 be in nonconducting state, and second switch 122 and the 4th switch 124 are in conducting state.Then, the relative size between the electromotive force of the electromotive force of power supply 18 and AC power supplies 125 is any setting relatively.As mentioned above, by applying reversed bias voltage to photocell 13 and supervision photocell 66, the short circuit part that can insulate is also proofreaied and correct because the defective that short circuit partly causes.
On the other hand, when positive bias-voltage is applied to photocell 13 and monitors photocell 66, first switch, 121, the three switches 123 during control short circuit 127, be in conducting state with the 5th switch 128, and second switch 122 and the 4th switch 124 are in nonconducting state.
The electromotive force that the input end of buffer amplifier 110 is provided when providing capacitor 126 to apply reversed bias voltage to photocell 13 and supervision photocell 66 with box lunch.Yet the present invention is not limited to capacitor 126, and other can keep the circuit of the input end of buffer amplifier 110 also can adopt.
Aforementioned the third structure can be free with aforementioned first and second kinds of structures in a combination.
The 4th kind of structure of display device of the present invention will illustrate with reference to Figure 14.Being characterized as of the 4th kind of structure has current source transistor 134 but not constant current source 105.
Current source transistor 134 is connected serially to and monitors photocell 66, and its gate electrode is connected to power supply 135.One in the source electrode of current source transistor 134 and the drain electrode is connected to first electrode that monitors photocell 66, and another is connected to power supply 133.
Current source transistor 134 works in the zone of saturation so that as current source.Therefore, the electromotive force of power supply 133 is grid-source voltages with adjustment current source transistor 134 of setting arbitrarily.For operating current source transistor 134 in the zone of saturation, the channel length L of current source transistor 134 is preferably set to 2 to 100 to the ratio (L/W) of channel width W.
In being shown in the structure of accompanying drawing, current source transistor 134 is p channel transistors, but the present invention is not limited to this, and the N channel transistor also can adopt.
Aforementioned the 4th kind of structure can be free and aforementioned first a kind of combination in the third structure.
The 5th kind of structure of display device of the present invention will illustrate with reference to Figure 15.Being characterized as of the 5th kind of structure has the input end that is provided in buffer amplifier 110 and monitors resistor 140 between the photocell 66.Resistor 140 can be variohm or fixed resister.
Resistor 140 is provided so as to be adjusted at some cycle (as, a frame period) monitor between the electric current total amount of the electric current total amount of photocell 66 and photocell 13 poor.
Normally work if monitor photocell 66 usefulness constant current sources 105, monitor that the dutycycle of photocell 66 is 100%.Therebetween, the dutycycle of photocell 13 is about 70%, even white image is shown on the whole screen, and if consider luminous ratio then it is lower than 70%.In other words, at normal manipulation mode, monitor that photocell 66 change in time is faster than photocell 13 change progress in time.
Therefore,, provide resistor 140, thereby monitor that in some cycle the electric current total amount in photocell 66 and the photocell 13 equates so that monitor constantly that at some the current value of photocell 66 is lower than the current value of photocell 13 according to the 5th kind of structure.As a result of, change in time is with identical speed progress, so see that with the angle of change in time electrical source voltage can proofread and correct more accurately.
Aforementioned the 5th kind of structure can be free with aforementioned first to the 4th kind of structure in one or more combinations.
The 6th kind of structure of display device of the present invention will illustrate with reference to Figure 17.The 6th kind of architectural feature is to have the positively biased transistor 132 that series value monitors photocell 66.The gate electrode of positively biased transistor 132 is connected to and is included in switching transistor 11 in the pixel 10 with the gate line of delegation.One in the source electrode of positively biased transistor 132 and the drain electrode is connected to first electrode that monitors photocell 66, and another is connected to positively biased power supply 131.Provide positively biased transistor 132 so that apply positive bias-voltage to monitoring photocell 66.
When positive bias-voltage was applied to supervision photocell 66, positively biased transistor 132 was open-minded, and the relative size of the electromotive force of the electromotive force of relative power supply 18 and positively biased power supply 131 is to set arbitrarily.
By applying positively biased monitoring voltage photocell 66, electric current is applied to the short circuit part that monitors photocell 66 partly, thus insulation short circuit part.Therefore, can proofread and correct owing to monitor the defective that the short circuit of photocell 66 partly causes.
In aforementioned structure, except positively biased transistor 132 also provides limit transistor 111.Aforementioned the 6th kind of structure can be free with aforementioned first to the 5th kind of structure in one or more combinations.
According in aforementioned first to the 6th kind of structure one or more, electrical source voltage can be proofreaied and correct according to the change of environment temperature and change in time.In addition, according to the present invention, need not user's operation just can carry out correction.Therefore, correction can continue to the terminal user at device provisioning, and this is expected to the life-span of extension fixture.
In the situation that colour shows, the electroluminescence layer with different emission can be formed in each pixel, and usually, corresponding to red (R), green (G), and the electroluminescence layer of blue (B) every kind of color is formed in each pixel.In such circumstances, provide at least corresponding to redness, the supervision photocell 66 of green and blue every kind of color, constant current source 105 and buffering amplifier 110, and can be according to every kind of color correction electrical source voltage.
[embodiment 2]
The example of display device of the present invention illustrates with reference to the accompanying drawings.Display device of the present invention has a plurality of pixels 10, each pixel all comprises a plurality of elements, and they are provided in such zone, and (x is a natural number to source electrode line Sx here, 1=x=m) (to be natural number, 1=y=n) intersected with each other and insulator is placed in (referring to Fig. 2 A) between them with gate lines G y.Pixel 10 has photocell 13, capacitor 16 and two transistors.One of them transistor is to be used for the switching transistor 11 that the control of video signal inputs to pixel 10, and another is light emission or the non-photoemissive driving transistors 12 that is used to control photocell 13.Switching transistor 11 and driving transistors 12 are field effect transistors, and each all has gate electrode, three terminals of source electrode and drain electrode.
The gate electrode of switching transistor 11 is connected to gate lines G y, and one in its source electrode and the drain electrode is connected to source electrode line Sx, and another is connected to the gate electrode of driving transistors 12.In the source electrode of driving transistors 12 and the drain electrode one is connected to power lead Vx, and (x is a natural number, and 1=x=m), and another is connected to the pixel electrode of photocell 13.The comparative electrode of photocell 13 is connected to relative power supply 18.Capacitor 16 is provided between the gate electrode and source electrode of driving transistors 12.
The conductivity of switching transistor 11 and driving transistors 12 is unrestricted, and can use N channel transistor and p channel transistor.In being shown in the structure of accompanying drawing, switching transistor 11 is N channel transistors, and driving transistors 12 is p channel transistors.The electromotive force of the electromotive force of power lead Vx and relative power supply 18 is also unrestricted, but different electromotive force be applied to power lead Vx with relative power supply 18 in case apply positive bias-voltage or reversed bias voltage to photocell 13.
Display device of the present invention with aforementioned structure is characterized as has two transistors in pixel 10.According to aforementioned structure, the transistor size of layout in each pixel 10 can reduce.The wiring that the less just minimizing of the transistorized number of layout in each pixel 10 will be settled causes high aperture ratio, high resolving power, and high yield.When realized high aperture than the time, the brightness of photocell can reduce with the increase of light emitting area.Just, the current density of photocell reduces.Therefore, driving voltage can reduce, and this causes low power consumption.In addition, the reliability of photocell 13 can improve with lower driving voltage.
Display device of the present invention is characterised in that driving transistors 12 works in the range of linearity.Therefore, can make the driving voltage of photocell 13 be lower than the situation that driving transistors works in the zone of saturation, cause lower power consumption.
The semiconductor that is included in switching transistor 11 and the driving transistors 12 can be with any amorphous semiconductor (amorphous silicon), crystallite semiconductor, and poly semiconductor (polysilicon) and organic semiconductor form.Crystallite semiconductor can be used silane gas (SiH 4) and fluorine gas (F 2) or silane gas and hydrogen formation, or after forming film with aforementioned gas, form by laser emission.
Each gate electrode of switching transistor 11 and driving transistors 12 forms individual layer or stack layer with conductive material.For example, preferably adopt the stacked structure of tungsten (W) and tungsten nitride (WN), molybdenum (Mo), aluminium (Al), and the stacked structure of molybdenum (Mo), or the stacked structure of molybdenum (Mo) and molybdenum nitride (MoN).
The conductive layer (source electrode and drain electrode wiring) that is connected to the extrinsic region (source electrode and drain electrode) of switching transistor 11 and driving transistors 12 is to form as individual layer or stack layer with conductive material.For example, preferably adopt titanium (Ti), silicated aluminum (Al-Si), and the stacked structure of titanium (Ti), molybdenum (Mo), silicated aluminum (Al-Si), and the stacked structure of molybdenum (Mo), or molybdenum nitride (MoN), silicated aluminum (Al-Si), and molybdenum nitride (MoN).Replacedly, a kind of acieral also can adopt in nickeliferous alumina-base material or nickeliferous and carbon and the silicon.
Fig. 3 illustrates the layout of the pixel 10 with aforementioned structure.Be switching transistor 11 shown in this layout, driving transistors 12, capacitor 16 and corresponding to the conductive layer 19 of the pixel electrode of photocell 13.Fig. 2 B illustrates along the cross-sectional structure of the line A-B-C of this layout.Switching transistor 11, driving transistors 12, photocell 13, capacitor 16 are provided in to have on the substrate 20 as glass and quartzy insulating surface.
Light-emitting layer 13 has the conductive layer 19 corresponding to pixel electrode, electroluminescence layer 33 and corresponding to the stacked structure of the conductive layer 34 of comparative electrode.If conductive layer 19 and 34 all transmits light, photocell 13 is launched light (two emission) on the direction of conductive layer 19 and conductive layer 34.Therebetween, if in conductive layer 19 and 34 one transmission light and another stops light, photocell 13 is only at the direction of conductive layer 19 or the direction emission light (top-emission or bottom emission) of conductive layer 34.Fig. 2 B illustrates photocell 13 and carries out cross-sectional structure in the situation of bottom emission.
Capacitor 16 is provided between the gate electrode and source electrode of driving transistors 12, and keeps the grid-source voltage of driving transistors 12.Capacitor 16 by be formed at the gate electrode of switching transistor 11 and driving transistors 12 with the conductive layer 22a of one deck and 22b (below be generically and collectively referred to as conductive layer 22), corresponding to the source electrode of driving transistors 12 and the conductive layer 26 of drain electrode wiring, the insulation course between conductive layer 22 and conductive layer 26 constitutes.
Capacitor 16 is also by corresponding to the source electrode of driving transistors 12 and the conductive layer 26 of drain electrode wiring, is formed at pixel electrode with photocell 13 with the conductive layer on one deck 36, and the insulation course between conductive layer 26 and conductive layer 36 constitutes.Shown in the layout among Fig. 3, conductive layer 35 is connected to conductive layer 36.
According to aforementioned structure, capacitor 16 can obtain enough big electric capacity to keep the grid-source voltage of driving transistors 12.Capacitor 16 is provided in to constitute below the conductive layer of power lead, therefore, because capacitor 16 makes the reduction of aperture ratio be prevented.In addition,, can reduce grid leakage current, cause lower power consumption because the gate insulating film of switching transistor 11 and driving transistors 12 is not to be used for capacitor 16.
Thickness corresponding to the conductive layer 24 to 27 of the source electrode of switching transistor 11 and driving transistors 12 and drain electrode wiring is respectively 500 to 2000 nanometers, preferred 500 to 1300 nanometers.When each thickness of conductive layer 24 to 27 increases by this way, because source electrode line Sx and power lead Vx are made of conductive layer 24 to 27, so can suppress the influence of voltage drop.Notice that the thickness that conductive layer 24 to 27 increases reduces the cloth line resistance, and the thickness increase of conductive layer 24 to 27 causes too much being difficult to accurately become pattern and forming flat surface.In other words, consider the influence of cloth line resistance, become the difficulty and the surface irregularity of pattern, each thickness of conductive layer 24 to 27 can be determined in aforementioned range.
Being characterized as of display device of the present invention also has the insulation course 28 and 29 that covers switching transistor 11 and driving transistors 12 (below be generically and collectively referred to as first insulation course 30) and is formed at second insulation course 31 on first insulation course 30.Conductive layer 19 corresponding to pixel electrode is formed on second insulation course 31.If second insulation course 31 is not provided, be formed on the layer identical corresponding to the conductive layer 24 to 27 of source electrode and drain electrode wiring, and therefore, the zone that is used to form conductive layer 19 is restricted to the zone of non-conductive layer 24 to 27 with conductive layer 19.Wherein, when providing second insulation course 31, the zone that is occupied by conductive layer 19 increases, and causes high aperture ratio.This structure is effectively, particularly for top-emission.High aperture is than increasing light emitting area, and this causes lower driving voltage and power consumption.
First insulation course 30 and second insulation course 31 by inorganic material as, monox and silicon nitride, organic material such as polyimide and acrylic acid.First insulation course 30 and second insulation course 31 can be made by same material or different materials.As insulating layer material, the material of siloxy group comprises that the organic functional group (as alkyl or aromatic hydrocarbons) that contains hydrogen at least is as substituting group.Replacedly, fluorin radical also can be used as substituting group.Further replacedly, fluorin radical and hydrogeneous at least organic functional group can be used as substituting group.
Second insulation course 31 can be formed by the organic material that can make some thickness reduce the bottom out-of-flatness.If second insulation course 31 is formed by organic material, preferred the 3rd insulation course 37 is formed by nitride, this nitride (silicon nitride particularly) as barrier film so that prevent degassing.
Bank layer (being also referred to as insulation course) 32 can be formed by organic material or inorganic material.Yet because provide light to launch organic 13 electroluminescence layer so that contacting 32 with bank layer contacts, bank layer 32 preferably has the shape that radius-of-curvature continuously changes, so that do not form pinprick etc. in the electroluminescence layer.In addition, bank layer 32 is preferably formed by the material that stops light, thereby limits the border between the pixel.
Display device of the present invention also has pixel region 40, and a plurality of here aforementioned pixels 10 are settled with matrix, first grid driver 41, second grid driver 42 and source electrode driver 43 (referring to Fig. 4).First grid driver 41 and second grid driver 42 are placed, so that face with each other and pixel region 40 is placed between them, or are placed in four limits of pixel region 40 one.
Source electrode driver 43 has impulse output circuit 44, latch 45 and selection circuit 46.Latch 45 comprises first latch 47 and second latch 48.Select circuit 46 to comprise transistor 49 and analog switch 50.For each row corresponding to source electrode line Sx provide transistor 49 and analog switch 50.The inversion signal of WE (write and wipe) signal takes place in phase inverter 51, if the inversion signal of WE signal is supplied with from the outside, then phase inverter 51 must not provide.
The gate electrode of transistor 49 is connected to selects signal wire 52, and one in source electrode and the drain electrode is connected to source electrode line Sx, and another is connected to power supply 53.Analog switch 50 is provided between second latch 48 and the source electrode line Sx.In other words, the input node of analog switch 50 is connected to second latch 48, and output node is connected to source electrode line Sx.One in two Control Node of analog switch 50 is connected to selection signal wire 52, and another is connected to selection underscore 52 through phase inverter 51.The electromotive force of power supply 53 turn-offs the driving transistors 12 that is included in the pixel 10.If driving transistors 12 is N channel transistors, the electromotive force of power supply 53 is set at the L level, yet if driving transistors 12 is p channel transistors, the electromotive force of power supply 53 is set at the H level.
First grid driver 41 has impulse output circuit 54 and selects circuit 55.Second grid driver 42 has impulse output circuit 56 and selects circuit 57. Select circuit 55 and 57 to be connected to each and select signal wire 52, but the selection circuit 57 that is included in the second grid driver 42 is connected to selection signal wire 52 through phase inverter 58.Just, anti-phase WE signal selects signal wire 52 to input to selection circuit 55 and 57 through each.
In the selection circuit 55 and 57 each all has three-state buffer.The input node of three-state buffer is connected to impulse output circuit 54 or impulse output circuit 56, and Control Node is connected to selection signal wire 52.The output node of three-state buffer is connected to gate lines G y.Three-state buffer is in running order when the signal that sends from selection signal wire 52 is the H level, and three-state buffer is in floating state when the signal that sends from selection signal wire 52 is the L level.
Be included in the impulse output circuit 44 in the source electrode driver 43, impulse output circuit 54 in first grid driver 41, the impulse output circuit 56 in second grid driver 42 is corresponding to the shift register that is made of a plurality of flip-flop circuits or decoder circuit.If decoder circuit is as impulse output circuit 44,54 and 56, source electrode line Sx or gate lines G y can select at random.When source electrode line Sx or gate lines G y can select at random, the pseudo-contour of the inhibition that can in the situation that adopts time gray scale method, generate.
The configuration of source electrode driver 43 is not limited to foregoing, and level translator and impact damper can additionally be provided.The configuration of first grid driver 41 and second grid driver 42 also is not limited to foregoing, and level translator and impact damper can additionally be provided.And, source electrode driver 43, first grid driver 41 and second grid driver 42 can comprise holding circuit.
Being characterized as of display device of the present invention also has power control circuit 63.Power control circuit 63 has and is used to supply power to photocell 13 power circuits 61 and control circuit 62.Power circuit 61 is connected to the pixel electrode and the power lead Vx of photocell 13 through determining transistor 12.Relative power supply 18 in the power circuit 61 is connected to the comparative electrode of photocell 13 through power lead Vx.
When positive bias-voltage be supplied to photocell 13 with supply of current to wherein and when making it luminous, power lead Vx and relatively the electric potential difference between the power supply 18 be set so that the electromotive force of power lead Vx is higher than the electromotive force of relative power supply 18.Wherein, when reversed bias voltage was applied to photocell 13, the electric potential difference between power lead Vx and the relative power supply 18 was set so that the electromotive force of power lead Vx is lower than the electromotive force of relative power supply 18.Such power settings is to make from prearranged signals to the power circuit 61 of control circuit 62 by supply.
According to the present invention, be applied to photocell 13 by using power control circuit 63 reversed bias voltages, thereby photocell 13 deterioration in time can be suppressed and reliability is improved.In photocell 13, the initial imperfection of anode and negative electrode short circuit may be because the deposition of foreign material, owing to the male or female pin hole that causes of out-of-flatness a little, and the out-of-flatness of electroluminescence layer and taking place.In having the pixel of such initial imperfection, can go wrong so that light emission and the emission of non-light are carried out not according to signal, therefore and the almost all electric current part and the whole element that flow through short circuit do not launched light, or some pixel launches light improperly or do not launch light, causes the defective demonstration of image.Yet because reversed bias voltage can be applied to photocell, electric current is supplied to the short circuit part between anode and the negative electrode partly according to the present invention, and short circuit partly produces heat.As a result of, the short circuit part can be oxidized or the insulation of carbonization one-tenth.Therefore, even initial imperfection occurs, this defective can be corrected and image can be shown in high quality.The such insulation of attention initial imperfection was preferably carried out before the display device shipment.Except initial imperfection, the defective of anode and negative electrode short circuit can pass in time and take place.Such defective is also referred to as gradual defective.Yet according to the present invention, reversed bias voltage can periodically be applied to photocell.Therefore, even gradual defective occurs, defective can be corrected, and image can show in high quality.Notice that reversed bias voltage can any sequential be applied to photocell 13.
As previously described, being characterized as also to have of display device of the present invention comprises the supervision short circuit 64 that monitors photocell 66, comprises the supervision control short circuit 65 of constant current source, buffer amplifier etc.The customized configuration of monitoring circuit 64 and supervision control circuit 65 are illustrated in the embodiment 1, and therefore, it illustrates in this omission.According to the present invention with aforementioned structure, because changing and change in time the variation of current value in the photocell that causes, environment temperature can be suppressed, cause improved reliability.
Note being shown in the structure among Fig. 1 to 17, monitor that control circuit 65 comprises constant current source 105 and buffering amplifier 110.In the structure in being shown in Figure 12, monitor that control circuit 65 comprises constant current source 105, buffer amplifier 110, switch 116 and 117 and capacitor 126.In being shown in the structure of Figure 13, monitor that control circuit 65 comprises constant current source 105, buffer amplifier 110, the first switches 121, second switch 122, the three switches 123, the four switches 124, capacitor 126, control circuit 127 and the 5th switch 128.In being shown in the structure of Figure 14, monitor that control circuit 65 comprises buffer amplifier 110.In being shown in the structure of Figure 15, monitor that control circuit 65 comprises constant current source 105, buffer amplifier 110 and resistor 140.
Operation with display device of the present invention of aforementioned structure will illustrate with reference to the accompanying drawings.At first, the operation of source electrode driver will be with reference to figure 5A explanation.Clock signal (hereinafter referred to as SCK), clock inversion signal (hereinafter referred to as SCKB), and initial pulse (hereinafter referred to as SSP) is input to impulse output circuit 44, sampling pulse is exported to first latch 47 by the sequential with these signals.First latch 47 that data input to wherein keeps first vision signal that is listed as to the end with the sampling pulse sequential of importing.When the latch pulse inputed to second latch 48, the vision signal that remains on first latch 47 was transferred to second latch 48 simultaneously.
When supposition L level WE signal in period T 1 from selecting signal wire 52 transmission, and the H level signal selects circuit 46 in the following manner in each cycling in period T 2 transmission.Each cycle of period T 1 and T2 is corresponding to half of horizontal scanning period, and period T 1 is called as the first subphylum selection cycle (subgate selection period) and period T 2 is called as the second subphylum selection cycle.
In period T 1 (the first subphylum selection cycle), L level WE signal is from selecting signal wire 52 transmission, and transistor 49 is open-minded, and analog switch 50 is in nonconducting state.A plurality of then signal wire S1 are electrically connected to power supply 53 to the transistor 49 of Sn through being provided in each row.Just, signal wire S1 equals the electromotive force of power supply 53 to the electromotive force of Sn.
At this moment, the switching transistor 11 that is included in the pixel 10 is open-minded, and the electromotive force of power supply 53 transfers to the gate electrode of driving transistors 12 through switching transistor 11.Therefore, the electrode that flows through of driving transistors 12 shutoffs and photocell 13 has identical electromotive force.Just, do not have electric current to flow through two electrodes of photocell 13, thereby do not have the light emission.In this mode, the electromotive force of power supply 53 is transferred to the gate electrode of driving transistors 12 and no matter inputs to the state of the vision signal of video line, and therefore driving transistors 12 turn-offs and two electrodes of photocell 13 have same potential.Such operation is called erase operation.
In period T 2 (the second subphylum selection cycle), H level WE signal is from selecting signal wire 52 transmission, and transistor 49 turn-offs, and analog switch 50 is in conducting state.Then, for row, the vision signal that remains in second latch 48 transfers to signal wire S1 simultaneously to Sn.At this moment, the switching transistor 11 that is included in the pixel 10 is open-minded, and vision signal transfers to the gate electrode of driving transistors 12 through switching transistor 11.Therefore, according to the vision signal of input, driving transistors 12 is opened or is turn-offed, and two of photocell 13 electrodes have different electromotive forces or identical electromotive force thus.More particularly, when driving transistors 12 was opened, two electrodes of photocell 13 have different electromotive forces and electric current flows through wherein, just, and photocell 13 emission light.Notice that identical electric current flows through photocell 13 and flows between the anode of driving transistors 12 and drain electrode.
On the other hand, when driving transistors 12 turn-offed, two electrodes of photocell 13 had identical electromotive force and do not have electric current and flow through wherein, and just, photocell 13 is not launched light.In this mode, according to vision signal, driving transistors 12 is opened or is turn-offed, and two electrodes of photocell 13 have different electromotive forces or same potential.Such operation is called as write operation.
The operation of first grid driver 41 and second grid driver 42 will illustrate below.Clock signal (G1CK), clock inversion signal (G1CKB) and initial release (G1SP) are input to impulse output circuit 54, and pulse is that sequential with these signals exports to successively and selects circuit 55.Clock signal (G2CK), clock inversion signal (G2CKB) and initial release (G2SP) are input to impulse output circuit 56, and pulse is that sequential with these signals exports to successively and selects circuit 57.Fig. 5 B illustrates and is supplied to i, j, and k and p are capable, and (k and p are natural numbers for i, j, 1=i, j, k, selection circuit 55 p=n) and 57 pulse electromotive force.
When supposition L level WE signal transmits from selection signal wire 52 in period T 1, and H level WE signal is in period T 2 transmission, be similar to the operation of source electrode driver 43, selection circuit 55 in the first grid driver 41 and the selection circuit 57 in the second grid driver 42 are worked in each cycle in the following manner.In the sequential chart of Fig. 5 B, (being natural number, electromotive force 1=y=n) represented by Gy41, represented by Gy42 and receive from the electromotive force of the gate line of second grid driver 42 to receive gate lines G y from first grid driver 41.Obviously Gy41 represents identical wiring with Gy42.
At period T 1 (the first subphylum selection cycle), L level WE signal is from selecting signal wire 52 transmission.Therefore L level WE signal transfers to the selection circuit 55 in the first grid driver 41, selects circuit 55 to be in floating state thereby make.On the other hand, anti-phase WE signal, just H level WE signal is input to the selection circuit 57 of second grid driver 42, thereby selects circuit 57 in running order.Just, select circuit 57 transmission H level signals (row selection signal) to have the electromotive force identical with the H level signal to the capable gate lines G i of i down to gate lines G i.In other words, the capable gate lines G i of i is selected by second grid driver 42.
As a result of, the switching transistor 11 that is included in the pixel 10 is open-minded.Then, the electromotive force that is included in the power supply 53 in the anode driver 43 is transferred to the gate electrode of driving transistors 12, thereby driving transistors 12 is turned off and two electrodes of light emission anode 13 have identical electromotive force.Just, carry out the wherein not radiative erase operation of photocell 13 in this cycle.
At period T 2 (the second subphylum selection cycle), H level WE signal is from selecting signal wire 52 transmission.Therefore, H level WE signal is input to the selection circuit 55 of first grid driver 41, thereby selects circuit 55 in running order.Just, select the circuit 55 capable gate lines G i of transmission H level signal to the i so that gate lines G i has the electromotive force identical with the H level signal.In other words, the capable gate lines G i of i is selected by first grid driver 41.
As a result of, the switching transistor 11 that is included in the pixel 10 is open-minded.Then, vision signal second latch 48 from source electrode driver 43 transfers to the gate electrode of driving transistors 12, thus driving transistors 12 open or turn-off, and two electrodes of photocell 13 have different electromotive forces or identical electromotive force.Just, carry out wherein photocell 13 luminous or not radiative write operations in this cycle.Wherein, the L level signal is input to the selection circuit 57 in the second grid driver 42, and selects circuit 57 to be in floating state.
As previously described, gate lines G y is selected in period T 1 (the first subphylum selection cycle) by second grid driver 42, and is selected in period T 2 (the second subphylum selection cycle) by first grid driver 41.Just, gate line is controlled with complimentary fashion by first grid driver 41 and second grid driver 42.Erase operation is an execution in the first and second subphylum selection cycles, and write operation was carried out in another cycle.
Select in the cycle of the capable gate lines G i of i at first grid driver 41, second grid driver 42 is not worked (selecting circuit 57 to be in floating state), or the transmission row selection signal is to the capable gate line of non-i.Similarly, in the cycle of the capable gate lines G i of first grid driver 42 transmission row selection signal to the i, first grid driver 41 is in floating state, or the transmission row selection signal is to the capable gate line of non-i.
According to the present invention who carries out aforementioned operation, can force and turn-off photocell 13, cause the dutycycle that increases.Further, photocell 13 can not be provided for the TFT of releasing capacitor 16 electric charges and be compelled to turn-off, and this causes high aperture ratio.When realizing high duty ratio, the brightness of photocell can increase with light emitting area and reduce.Just, driving voltage can reduce and therefore reduce power consumption.
The present invention is not limited to aforementioned embodiments, and wherein the grid selection cycle is divided into two cycles.The grid selection cycle can be divided into the three or more cycles.
[embodiment 3]
The following describes the example of image element circuit, this image element circuit can be applied to display device of the present invention.Fig. 6 A illustrates image element circuit, and wherein erasing transistor 91 and erase gate polar curve Ry are added in the pixel 10 (pixel comprises three TFTs) that is shown in Fig. 2 A.This erasing transistor 91 can force the electric current that stops in the photocell 13.Therefore, do not wait for that the signal that will write all pixels 10 begins light period or begin light period immediately after beginning write cycle.Therefore, dutycycle can be increased, and mobile image can be shown in high quality especially.
Fig. 6 B illustrates image element circuit, and the driving transistors 12 that wherein is shown in the pixel 10 of Fig. 6 A is omitted, and additionally provide transistor 92 and 93 and power lead Vax (x is a natural number, 1=x=m) (pixel comprises four TFTs).Power lead Vax is connected to power supply 94.According to this structure, the gate electrode of transistor 92 is connected to the power lead Vax of permanent electromotive force, thereby the electromotive force of the gate electrode of transistor 92 is fixed and transistor 92 works in the zone of saturation.Wherein, transistor 93 works in the range of linearity, comprises that the vision signal of launching data about the light emission or the non-light of pixel 10 is input to the gate electrode of transistor 93.Have little source electrode-drain voltage because work in the transistor 93 of the range of linearity, changing a little of the grid-source voltage of transistor 93 do not influence the current value that flows through photocell 13.Therefore, the current value that flows through photocell 13 is determined by the transistor 92 that works in the zone of saturation.According to the present invention, can suppress the brightness inequality that causes owing to the variation in the feature of transistor 92 and increase picture quality with aforementioned structure.
As another kind of image element circuit, wherein be shown in the image element circuit (pixel comprises a TFT) that switching transistor 11 is omitted in the pixel 10 of Fig. 2 A and also can adopt.In this case, this class of operation is carried out like that like passive matrix display.
Replacedly, use the image element circuit of current mirror also can use.
Analog video signal or digital video signal can be used in the display device of the present invention.If use digital video signal, vision signal can be voltage or electric current.Just, the vision signal that inputs to pixel in the light emission of photocell can be constant voltage or constant current.When vision signal was constant voltage, constant voltage is applied to photocell or photocell is flow through in constant current.When vision signal was constant current, constant voltage is applied to photocell or photocell is flow through in constant current.When constant voltage is applied to photocell, carry out constant voltage driving.Wherein, when photocell is flow through in constant current, carry out constant-current driving.According to constant-current driving, constant current flow through and no matter the resistance of photocell change.Display device of the present invention can adopt constant voltage driving or constant-current driving, but the voltage vision signal preferably is used in the display device of the present invention.
Electroluminescence layer is by forming from the radiative material of single excited state (hereinafter referred to as the light-emitting material that singly excites) or from the radiative material of triplet excited state (hereinafter referred to as triple light-emitting materials that excite).For example, red in emission, in the photocell of green and green light, its brightness reduces half in the relative short time red light radiated element is formed by triple light-emitting materials that excite, and all the other zones are formed by the light-emitting material that singly excites.Triple light-emitting materials have such advantage, and material has good illumination efficiency and consumes lower-wattage to obtain identical brightness.
Replacedly, red light radiated element and green light radiated element can be formed by triple light-emitting materials that excite, and blue colour light emitting element can be formed by the light-emitting material that singly excites.When the green light radiated element with high visuality is formed by triple light-emitting materials that excite, can further realize low power consumption.As triple excitation light emission examples of material, the metal complex as impurity is arranged, have the metal complex of the 3rd transition series elements platinum as central metal, have the metal complex of indium as central metal, or the like.Further, electroluminescence layer can be by low molecular weight material, any formation in middle molecular weight material and the high molecular weight material.
The structure that photocell can adopt forward (forward) to pile up, anode wherein, electroluminescence layer, negative electrode are with this sequence stack, or the structure of oppositely piling up, negative electrode wherein, electroluminescence layer and anode are with this sequence stack.The male or female of photocell can be formed by the tin indium oxide (ITO) of transmission light, is added with the ITO of monox, and indium zinc oxide (IZO) mixes up gallium the is arranged zinc paste (GZO) of (Ga), or the like.
Photocell also can adopt such structure, and wherein a plurality of electroluminescence layers and charge generating layer are stacked between anode and the negative electrode, as anode, and electroluminescence layer, charge generating layer ..., electroluminescence layer, charge generating layer, ..., electroluminescence layer, negative electrode is with this sequence stack.Such element is also referred to as cascaded elements.Charge generating layer mixes up the organic compound that lithium is arranged by inorganic semiconductor such as metal or molybdena, or the like form.
When carrying out colored the demonstration with the panel with photocell, the electroluminescence layer with different emission band can be provided in each pixel.Usually, provide green (G), and the electroluminescence layer of blue (B) every kind of color corresponding to red (R).In such circumstances, can provide corresponding to redness, the supervision photocell 66 of green and blue every kind of color is thought every kind of color correction electrical source voltage.At this moment, can increase colour purity and can prevent that pixel portion has minute surface (dazzling (glare)) by wave filter (nonferrous layer) is provided, the wave filter of this transmission special wavelength band is positioned at the light emitting side of photocell.Ring-type polarizer that wave filter (nonferrous layer) can omit conventional need etc. is provided, and can eliminates from the loss of the light of electroluminescence layer emission.Further, the change of the color that occurs when deflection is seen pixel region just can reduce.
Electroluminescence layer can have such structure, its emission monochrome or white light.If the use white light emitting material, the wave filter that transmission has special wavelength light is provided in the light emitting side of photocell, thereby can carry out colored the demonstration.
[embodiment 4]
Photocell changes in time at the starting stage rapid progress and along with the time slows down gradually.Therefore, in using the display device of photocell, preferably carry out initial aging technique, wherein initially change in time brightness adjustment at photocell (as, before the display device shipment) occur in before in all photocells.
When initial rapid the change in time when taking place in advance of photocell by so initial aging technique, change after this not rapid progress in time, this reduces owing to change phenomenon such as the image aging (burn-in) that causes in time.
Initial aging technique is by only carrying out at some cycle exciting light radiated element, and preferably is higher than used voltage usually by applying.In view of the above, initially change at short notice in time and take place, and initial aging technique can be finished at once.
If display device of the present invention is worked with rechargeable battery, preferably when charging, carry out the technology of luminous or all pixels of glistening not in the display device of using, show its contrast counter-rotating of relative normal picture image (as, standby demonstration etc.) technology, check by sampling video signal and illumination or flash of light pixel and with the technology of the pixel of low frequencies light, or the like.Carry out aforementioned technology so that reduce image aging in the cycle when display device is not used, it is called as sudden strain of a muscle row's technology (flashout process), difference between the brightest point of aging image and the darkest point can be set at Pyatyi gray scale or lower, more preferably one-level gray scale or lower.In order to reduce image aging, except aforementioned technology, still image can reduce as much as possible.
[embodiment 5]
Panel as the display device of a kind of mode of the present invention is explained, comprising pixel region 40 being arranged, first grid driver 41, second grid driver 42 and source electrode driver 43.Pixel region 40 with a plurality of pixels is provided in (referring to Fig. 7 A) on the substrate 20, and wherein each pixel all comprises photocell 13, first grid driver 41, second grid driver 42, source electrode driver 43 and junctional membrane 407.Junctional membrane 407 is connected to external circuit (IC chip).
Fig. 7 B is the viewgraph of cross-section along the line A-B of panel.Fig. 7 B illustrates the driving transistors 12 that is formed in the pixel region 40, photocell 13 and capacitor 16 and be formed at the cmos circuit 410 of source electrode driver 43.
Provide encapsulant 408 in the periphery of pixel region 40, first grid driver 41, second grid driver 42, source electrode driver 43.Photocell 13 usefulness encapsulants 408 and relative substrate 406 sealings.Carry out sealing technology so that protection photocell 13 is avoided moisture damage.In this Implementation Modes, cladding material (by glass, pottery, plastics, manufacturings such as metal) is used for sealing, but thermosetting resin or UV light-cured resin and high block film such as metal oxide and nitride also can use.Element on substrate 20 preferably forms by compare the crystalline semiconductor (polysilicon) that has excellent specific property at aspects such as mobilities with amorphous semiconductor.Panel with aforementioned structure can reduce the number of the exterior I Cs that will connect, causes the size that reduces, weight, and thickness.
Figure 18 is the viewgraph of cross-section along panel C-D line, it illustrates driving transistors 12, photocell 13 and be provided in the capacitor 16 of pixel region 40, be provided in the cmos circuit 412 of first grid driver 41 and be provided in the cmos circuit 411 of second grid driver 42.Panels feature shown in the drawings is to provide encapsulant 408 so that overlapping first grid driver 41 and second grid driver 42.This structure realizes narrower frame.
In the aforementioned structure that is shown in Fig. 7 A and 7B and Figure 18, the pixel electrode transmission light of the photocell 13 and comparative electrode of photocell 13 stops light.Therefore, photocell 13 is carried out bottom emission.
As the structure that is different from aforementioned structure, a kind of like this structure is arranged, wherein the pixel electrode of photocell 13 stops light and the comparative electrode transmission light (referring to Fig. 8 A) of photocell 13.In this case, photocell 13 is carried out top-emission.
As the structure that is different from aforementioned structure, such structure is arranged, wherein the pixel electrode of photocell 13 and comparative electrode all transmit light (referring to Fig. 8 B).In this case, photocell 13 is carried out two emissions.
In two situations of launching of bottom emission, the conductive layer (source electrode and drain electrode wiring) that is connected to the extrinsic region of driving transistors 12 is preferably formed by the aluminium (Al) with low emissive material such as molybdenum combination.Especially, Mo, the stacked structure of Al-Si and Mo, or MoN, the stacked structure of Al-Si and MoN waits also and can adopt.As a result of, can prevent from the photo-emission source utmost point and the drain electrode wiring of photocell emission, so light can escape into the outside.Display device of the present invention can adopt any bottom emission, top-emission and two emission.
Pixel region 40 also can be made of TFT, and it is formed on the insulating surface and has the channel part that is formed by amorphous semiconductor (amorphous silicon), and first grid driver 41, second grid driver 42 and source electrode driver 43 can be made of the IC chip.The IC chip can be fixed on the substrate 20 or be fixed on the junctional membrane 407 that is connected to substrate 20 by COG.Amorphous semiconductor is easy to be formed at by CVD does not need crystallization steps on the big substrate, therefore not cheap panel is provided.Further, when conductive layer is to discharge (being typically ink ejecting method) by droplet to form, can realize more cheap panel.
[embodiment 6]
The electronic installation that provides the pixel region that comprises photocell comprises televisor (being also referred to as TV or television receiver), digital camera, digital video camera, mobile phone (being also referred to as mobile phone or cell phone), portable data assistance such as PDA, portable game machine, the monitor of computing machine, computing machine, audio dubbing device such as onboard audio are identical, provide recording medium copying image device such as family game machine etc.Their concrete examples will be with reference to figure 9A to the 9F explanation.
Portable data assistance comprises main body 9201, display part 9202 grades (referring to Fig. 9 A).The display device that is shown in the embodiment 1 to 5 can be applied to display part 9202.According to the present invention, therefore the electrical source voltage that is supplied to photocell can provide display device with monitoring that photocell proofreaies and correct, wherein since the change of environment temperature and the influence that changes electric current variation in the photocell that causes in time can be suppressed.
Digital video camera comprises display part 9701, display part 9702 grades (referring to Fig. 9 B).The display device that is shown in the embodiment 1 to 5 can be applied to display part 9701.According to the present invention, therefore the electrical source voltage that is supplied to photocell can provide display device with monitoring that photocell proofreaies and correct, wherein since the change of environment temperature and the influence that changes electric current variation in the photocell that causes in time can be suppressed.
Portable data assistance comprises main body 9101, display part 9102 grades (referring to Fig. 9 C).The display device that is shown in the embodiment 1 to 5 can be applied to display part 9102.According to the present invention, therefore the electrical source voltage that is supplied to photocell can provide display device with monitoring that photocell proofreaies and correct, wherein since the change of environment temperature and the influence that changes electric current variation in the photocell that causes in time can be suppressed.
Portable television comprises main body 9301, display part 9302 grades (referring to Fig. 9 D).The display device that is shown in the embodiment 1 to 5 can be applied to display part 9302.According to the present invention, therefore the electrical source voltage that is supplied to photocell can provide display device with monitoring that photocell proofreaies and correct, wherein since the change of environment temperature and the influence that changes electric current variation in the photocell that causes in time can be suppressed.But such televisor widespread use is to the undersized portable terminal person who is incorporated into as mobile phone, middle-sized portable terminal device and large scale terminal (as being of a size of 40 inches or bigger).
Portable computer comprises main body 9401, display part 9402 grades (referring to Fig. 9 E).The display device that is shown in the embodiment 1 to 5 can be applied to display part 9402.According to the present invention, therefore the electrical source voltage that is supplied to photocell can provide display device with monitoring that photocell proofreaies and correct, wherein since the change of environment temperature and the influence that changes electric current variation in the photocell that causes in time can be suppressed.
Televisor comprises main body 9501, display part 9502 grades (referring to Fig. 9 F).The display device that is shown in the embodiment 1 to 5 can be applied to display part 9502.According to the present invention, therefore the electrical source voltage that is supplied to photocell can provide display device with monitoring that photocell proofreaies and correct, wherein since the change of environment temperature and the influence that changes electric current variation in the photocell that causes in time can be suppressed.
If aforementioned electronic is used rechargeable battery, the minimizing of their life-span with power consumption increases, thereby can save the electric charge of rechargeable battery.
[embodiment 7]
The cross-sectional structure of carrying out the colored display device that shows will illustrate with reference to the accompanying drawings.More specifically, use the cross-sectional structure and the nonferrous layer of the display device of white light emitting elements to be described, this white light emitting elements emission white light.What illustrate below is the cross-sectional structure of three pixels located adjacent one another.
Driving transistors 12, the photocell 13 (hereinafter referred to as white light emitting elements 13) and the capacitor 16 of emission white light are provided in (referring to Figure 22) on the substrate 20.White light emitting elements 13 is carried out top-emission.Also provide the bank layer 31 that stops light.The bank layer 32 that stops light is by the stirring carbon granule, metallic particles, and pigment, colorants etc. also filter them if desired, and spin coating forms then.Add in the organic material if note carbon granule or metallic particles, can add surfactant or spreading agent so that they are evenly mixed.
Nonferrous layer 711 to 713 is provided on the relative substrate 406, and usually corresponding to redness, green, or blue.
When providing white light emitting elements 13 to be fixed on the relative substrate 406 with convenient substrate 20 and nonferrous layer 711 to 713 overlap.More particularly, provide white light emitting elements 13 so that the light emitting side is faced nonferrous layer 711 to 713.So aforementioned structure, the white light of launching from white light emitting elements 13 becomes redness, green, or blue, thus colour display device obtained.
Wherein the structure of the display device of white light emitting elements 13 execution bottom emission is with reference to Figure 23 explanation.In this case, as shown in drawings, nonferrous layer 714 provides as intermediate insulating layer to 716.Replacedly, nonferrous layer 714 to 716 can be provided between substrate 20 and driving transistors 12 or the capacitor 16.In this case, consider the heat resistance characteristic that nonferrous layer is bad, the active layer of driving transistors 12 preferably by amorphous semiconductor but not poly semiconductor form.As a result of, nonferrous layer 714 to 716 can prevent the damage that causes owing to the thermal treatment in the poly semiconductor manufacturing step.
Wherein white light emitting elements 13 is carried out the structure of two display device of launching with reference to Figure 24 explanation.The structure that is shown in Figure 24 is the combination that is shown in the structure of Figure 22 and 23.Provide chromatograph 711 to 716 so that clamp white light emitting elements 13, so white light emitting elements 13 is launched light in an opposite direction.
The electroluminescence layer of photocell is by vapour deposition, spin coating, and ink ejecting methods etc. form.Yet the electroluminescence layer with different wave length band can not accurately form with preceding method.Therefore, in this case, be necessary to increase distance between the different pixels and the distance between the embankment.Wherein, if white light emitting elements such use the shown in the structure as described above will not form different electroluminescence layers, this is favourable because require distance and the distance between the embankment that increases between the pixel and can not realize high resolving power.In addition, because color filter is used in the liquid crystal indicator, can utilize the technology of liquid crystal indicator and not development new technologies.
Transversely the width of the bank layer between the pixel 32 only requires that width is enough wide to be formed at wiring under it with covering, and 7.5 to 27.5 microns especially, more preferably 10 to 25 microns (referring to Figure 25).Bank layer 32 narrower width allow higher aperture ratio.High aperture is than increasing light emitting area, and this causes lower driving voltage and power consumption.
Can repeat pixel electrode and comparative electrode, to reflect and escape into neighborhood pixels from the light of white light emitting elements emission according to the light emergence angle.Further, in the viewing area that comprises a plurality of pixels of settling, because glitter (glare) of pixel electrode and comparative electrode occurs when pixel shows black with matrix.In order to prevent such glittering, blooming is fixing in some cases, but the cost height.
Yet according to aforementioned structure, bank layer 32 is formed by the material that stops light.If bank layer 32 stops light, it absorbs unnecessary light with the border between the clear qualification pixel, but so display of high resolution images.In addition, stop that the dielectric film of light reduces reflection of incident light, and can prevent to glitter.Therefore, no longer need blooming,, cause size, the reducing of thickness and weight as polarizing coating.
Comprise that triple excitation light emission materials of metal complex etc. can be used for the electroluminescence layer 13 of white light emitting elements 13.As triple excitation light emission examples of material, known metal complex as impurity is arranged, have the metal complex of the 3rd transition series elements platinum as central metal, have the metal complex of indium as central metal, or the like.Triple excitation light emission materials are not limited to these compounds, and also can belong to the compound of periodic table the 8th family to the 10 family's elements as central metal with having aforementioned structure and having.
The photocell of emission white light can be made of two or three light-emitting layer that comprises blue electroluminescent layer.Replacedly, white light emitting elements can be by piling up functional layer such as hole injection/transport layer arbitrarily, hole transport layer, electronics injection/transport layer, electron transport layer, light-emitting layer, electronic barrier layer and hole blocking layer and form.Further, the mixed connection of mixed layer or these layers also can form.These embodiments can with the aforementioned embodiments independent assortment.
[embodiment 8]
The invention provides a kind of display device that has white light emitting elements and monitor white light emitting elements, wherein the dutycycle of white light emitting elements is 45% to 80% and monitor that the dutycycle of white light emitting elements is 45% to 100%.
The dutycycle of white light emitting elements provides in the average duty ratio of all white light emitting elements of pixel region.Dutycycle is a light period to light period and the non-light period ratio as the write cycle when all incoming video signals show white lights.
The invention provides display device, wherein in some cycle white light emitting elements total electricity less than the total electricity that monitors in the white light emitting elements.
In this mode, make the load of white light emitting elements different, and consider brightness decay based on the amount of the electric charge that flows through white light emitting elements with the load that monitors white light emitting elements.Therefore, can carry out permanent brightness and drive, wherein the quantity of electric charge in the white light emitting elements is compared with the quantity of electric charge in monitoring white light emitting elements, and the brightness of white light emitting elements is corrected as constant.
The following describes the principle that drives (driving) according to permanent brightness of the present invention hereinafter referred to as CL.The photocell that is used to describe has such structure, wherein contains the film that the EL organic material takes place and is sandwiched between the pair of electrodes.
The electric current that flows through the film that contains organic generation EL material (below be also referred to as organic film) is called as the electric current (TCLC) of catching the electric charge restriction and is expressed from the next, wherein J is a current density, V is a voltage, and S is the value by the structures shape of material and photocell, and n is 2 or bigger value.
J＝S·V n...(1)
Following formula can obtain by rewriting formula (1).
logJ＝nlogV+logS...(2)
The current-voltage feature that formula (2) expression is represented by logarithm, it is that the straight line of n is represented by slope.The logS value is more little, and straight line is high more to the voltage side skew.
Figure 26 is the figure that photocell exemplary currents density-voltage characteristic is shown.This element has anode, DNTPD, NPB, Alq:C6, Alq, CaF 2And the stacked structure of Al.This figure illustrates the feature of original state, at room temperature keep this after 1000 hours feature and at room temperature use the feature of constant-current driving after 1000 hours.
As shown in figure 26, at room temperature be offset to the higher voltage side than initial characteristics with the current density-voltage characteristic of the photocell of constant-current driving after 1000 hours.Similarly, at room temperature kept 1000 hours and do not have the current density-voltage characteristic of the photocell of streaming current to be offset to higher voltage side.
Figure 27 describes the double-log figure that aforementioned three types of current density-voltage characteristics obtain by basis at the formula (2) of the current density regions that can obtain practical brightness.In the figure of Figure 27, current density-voltage characteristic is at 1 to 100mA/cm 2Current density draw, wherein can obtain 100 to 10000cd/m 2Brightness.In the figure of Figure 27, current density-feature is that the straight line of n is represented by slope.
Figure 28 illustrates by the n of Figure 27 acquisition and the change of S.The characteristic change that the figure indication of Figure 28 is represented with parameter n and S based on formula (2).The value of S does not change when photocell remains on room temperature, and sharply reduces when electric current is supplied to photocell.On the other hand, the value of n not only reduces but also works as photocell at room temperature to keep identical hourage also to reduce when electric current is supplied to photocell.The speed that the speed fundamental sum that reduces when electric current is supplied to photocell reduces when not having electric current to be supplied to wherein is identical.Just, n is such parameter, and it reduces fully in time and no matter whether is supplied with electric current.
The result illustrates n can be by the function representation of following formula (3) as the time.
n＝f(t)...(3)
The diode characteristics that the value of the n that the indication diode characteristics sharply changes illustrates photocell changes (value of n reduces and slope descends) and supply of current no matter whether in time.
On the one hand, S remains on the parameter that room temperature changes hardly and just change when photocell when electric current is supplied to wherein.Irrelevant with the time but value S that change in time can be expressed as the total charge dosage Q function of (electric current * time), and can obtain following formula.
S＝g(Q)...(4)
Because reduce during the worthwhile electric current supply value photocell of S, g (Q) is considered to the monotone decreasing function.Can think that the value of S is the threshold value of diode characteristics.Therefore, can explain like this that the threshold shift of the diode characteristics of photocell is to higher voltage side when electric current is supplied to wherein.
From formula (1), (3), (4) see, monitor that the current density-voltage characteristic of photocell and the current density-voltage characteristic of display light radiated element can be represented by the formula, wherein Jo is the current density (constant) that monitors photocell, and Jp is the current density of pixel, Qm monitors total charge dosage in the photocell, Qp is a total charge dosage in the pixel, and V is an electric charge, and t is the time.
Jo＝g(Qm)·V f(t)...(5)
Jp＝g(Qp)·V f(t)...(6)
From formula (5) and (6), the current density, J p in the pixel can be expressed from the next.
Jp＝Jo·g(Qp)/g(Qm)...(7)
Because g (Q) is the monotone decreasing function, the value of Jo and Jp differs from one another when monitoring that photocell has different electric current with the display light radiated element.For example, flow through and monitor that the photocell current ratio flows through the electric current of display light radiated element more (that is, Qm〉Qp), Jp is always greater than Jo.
Should be taken into account following situation and drive with the brightness that keeps the display light radiated element constant so that carry out CL ideally.At first, following formula can be that L and current efficiency obtain during for η in the brightness of pixel.
L＝η·Jp...(8)
When initial brightness is L 0With initial current density be J 0The time, current efficiency η represents by following degradation curve, wherein k is a rate constant and β is the parameter of the initial degraded of indication.
η＝(L 0/Jo)·exp{-(k·t)β}...(9)
As a result of, following formula (10) can obtain from formula (8) and (9).
L＝Jp·(L 0/Jo)·exp{-(k·t)β}...(10)
In order to keep brightness constant, should satisfy L=L 0(constant).Therefore, work as L=L 0During substitution formula (10), can obtain following formula (11).
Jp＝Jo·exp{(k·t)β}...(11)
Just, CL drives and can realize by the value that increases Jp according to formula (11).At last, can be from the formula (12) below formula (7) and (11) acquisition.
g(Qp)/g(Qm)＝exp{(k·t)β}...(12)
Therefore, CL drive can be by controlling Qp and Qm in case g (Qp)/g (Qm) near exp{ (kt) β realize.
The quantity of electric charge in the photocell considers when brightness decay is based on, the quantity of electric charge and monitor during the quantity of electric charge is compared in the photocell and carry out the CL driving in the display light radiated element, and the brightness of display light radiated element is corrected as constant.
[embodiment 1]
The test result of the display device of the present invention of at room temperature working in this embodiment, will be with reference to figure 11A and 11B explanation.Figure 11 A illustrates the feature that the electric current of photocell (260 hours) changes in time, and Figure 11 B illustrates the feature that the brightness of photocell (260 hours) changes in time.In the figure of Figure 11 A and 11B, sample A is the panel with calibration function of the present invention, yet sample B and sample C are the samples that does not have calibration function.Sample A and B be with constant voltage driving and sample C constant-current driving.
In the figure of Figure 11 A and 11B, the horizontal ordinate express time (hour).Among Figure 11 A ordinate represent actual current standardized value (%) and among Figure 11 B ordinate represent the standardized value (%) of intrinsic brilliance.
In all samples, monitor that the dutycycle of photocell is 100%, however the dutycycle of photocell about 64%.Monitor that photocell has identical total electricity but the momentary current difference with photocell.
The electric current that Figure 11 A illustrates sample A tends to increase in time, and the electric current of sample B significantly fluctuates and tends to and reduces in time, and the electric current of sample C fluctuates hardly and remain constant behind certain hour substantially.
The reason that the electric current of sample A tends to increase in time is that photocell has 64% dutycycle because the supervision photocell has 100% dutycycle, and monitors that changing in time of photocell is faster than the progress of change in time of photocell.
The brightness that Figure 11 B illustrates sample A is fluctuateed hardly and is remained unchanged substantially behind certain hour, and the brightness of sample B is significantly fluctuateed and tended to and reduces in time, and the brightness of sample C is fluctuateed hardly but similar sample B tends to reduce in time.
Can find out from the result who is shown in Figure 11 A and 11B, can find to use sample A of the present invention to have permanent brightness but the increase electric current.This is because change in time makes progress more quickly by electric current increase+Δ.Just, since the electric current increases+Δ that causes of calibration function no better than because reducing in time of causing of time change.Therefore, use the brightness of sample A of the present invention to remain unchanged substantially.
Consider aforementioned operation, the display device of the present invention with calibration function can be described as permanent brightness display device, and display device of the present invention has permanent brightness.
Driving method with display device of the present invention of calibration function can be described as permanent brightness driving method (permanent lightness method, permanent brightness method, lightness control method, control brightness method, or bright control method).According to this driving method, as mentioned above, because the electric current that causes of calibration function increases and owing to change in time that the electric current that causes reduces to be to obtain in advance, and photocell is the driven when equaling to reduce to equate with increase.
Being used to carry out the speed that the voltage of permanent brightness driving method raises is described as follows.
When permanent brightness driving method is at original intensity L 0And current density, J 0Carry out, the current efficiency η that reduces in time is by the formulate of following function as time t.
η(t)＝L 0/J 0×f(t)...(1)
Known f (t) can be represented by following exponential function.
f(t)＝exp{-(t/α)β}...(2)
Notice that α is the parameter of the medium and long-term degradation of indication and β is the parameter of the initial degraded of indication, it can obtain by experiment.
Wherein, if current density, J t change (that is, J=J (t)) in time, brightness L can be expressed from the next.
L＝η(t)×J(t)...(3)
Therefore, in the situation of carrying out permanent brightness driving, work as L=L 0When (constant) satisfies, following formula (4) will be satisfied in formula (3).
L 0＝η(t)×J(t)...(4)
By formula (4) being replaced to obtain following formula to formula (1).
J(t)＝J 0/f(t)...(5)
Formula (5) illustrates such phenomenon, and is constant in order to keep brightness, considers that current efficiency reduction current density will be progressively from J 0Increase.This be because formula (2) f (t) is shown is the monotone decreasing function.
Usually, the power of current density and voltage (x level power), and the formula below therefore obtaining, wherein x is that C is a constant by the power of element decision.
J(t)＝C×V x(t)...(6)
Therefore, following formula is by replacing formula (6) in formula (5) and considering that formula (2) obtains.
V(t)＝Const.×[exp(t/α)β] 1/x...(7)
Formula (7) illustrates voltage and how to change to carry out permanent brightness driving.Const. be by initial current density J 0With constant x (Const.=(J 0/ C) 1/x) decision.Permanent brightness drives and can realize by considering that voltage raises.
[embodiment 2]
The present invention also can be applied to the display device of carrying out constant-current driving.
In this embodiment, the level of Gai Bianing detects with a plurality of supervision photocells in time, and vision signal or electrical source voltage are based on that the result of detection proofreaies and correct, thus the change in time of proofreading and correct photocell.Such situation illustrates with reference to Figure 19.
This embodiment uses a plurality of (at least two) to monitor photocell, monitors photocell 1001 and 1002 and wherein provide two.Constant current is supplied to photocell 1001 from constant current source 1003, and is supplied to other photocell 1002 from the constant current of constant current source 1004.
When the electric current from constant current source 1003 supply is different from from the electric current of constant current source 1004 supplies, the total amount that flows through the electric current that monitors photocell 1001 and 1002 differs from one another.Therefore, in monitoring photocell 1001 and 1002, change in time with different speed progress.
Monitor that photocell 1001 and 1002 is connected to computing circuit 1005, it calculates the electric potential difference (voltage difference) between an electrode that monitors photocell 1001 and an electrode that monitors photocell 1002.
The voltage that is calculated by computing circuit 1005 is provided to vision signal generation circuit 1006.In vision signal generation circuit 1006, the vision signal that is supplied to each pixel is based on from the voltage correction of computing circuit 1005 supplies.According to aforementioned structure, the change in time of recoverable photocell.
In the pixel that is shown in Fig. 6 B, the gate electrode of transistor 92 is connected to the power lead Vax of permanent electromotive force, thereby transistor 92 works in the zone of saturation, and emission of the light of photocell 13 or the emission of non-light are controlled by horizontal signal.In this case, vision signal does not have the electromotive force of correction and power lead Vax to change according to the voltage from computing circuit 1005 supplies.Power lead Vax is connected to power circuit 1007, and it is based on the electromotive force of the voltage correction power lead Vax that supplies from computing circuit 1005.
According to the display device with aforementioned structure embodiment, correction can be carried out according to change in time.
Be preferred for preventing the circuit of potential fluctuation,, provide in monitoring between photocell 1001 and the computing circuit 1005 and monitoring between photocell 1002 and the computing circuit 1005 as buffer amplifier.
As pixel with the configuration that is used to carry out the contrast current drives, use the pixel of the current mirror circuit that is shown in Figure 20 A, use the another kind configuration that is shown in Figure 20 B etc. also can adopt.
Pixel with current mirror circuit has transistor 1011 to 1014, capacitor 1015, photocell 1016 (referring to Figure 20 A).Current mirror circuit is made of transistor 1013 and 1014.The electric current that flows through photocell 1016 equals the electric current that flows through between the source electrode of transistor 1014 and drain electrode.The electric current that flows through between the source electrode of each transistor 1013 and 1014 and drain electrode is decided by to remain on the electric charge in the capacitor 1015.Pixel with another kind of configuration has transistor 1021 to 1024, capacitor 1025 and photocell 1026 (referring to Figure 20 B).
[embodiment 3]
Use passive matrix display device of the present invention to show with reference to Figure 21.Passive matrix display device has the pixel portion 501 that is formed on the substrate, column signal line drive circuit 502 and be placed in pixel portion 501 the periphery row signal line drive circuit 503 and be used to control the controller 540 and the row signal line drive circuit 503 of column signal line drive circuit 502.Pixel portion 501 has x row and is placed in signal wire C1 on the column direction to Cx, is placed in y row signal line L1 on the line direction to Ly and a plurality of photocell (x and y are natural numbers) that is placed in the matrix.Column signal line drive circuit 502 and row signal line drive circuit 503 are that the LS1 chip constitutes and is connected to the pixel portion 501 that is formed on the substrate through FPC.Monitoring circuit 541 provide in the same substrate of pixel portion 501 on.
The simple to operate of passive matrix display device is described as follows.At first, select the row signal line L1 of first row.More particularly, row signal line L1 is connected to earth potential through switch 512.Then, when the switch 508 to 511 of column signal line drive circuit 502 is in conducting state, be provided to the photocell 524 to 527 that is placed in first row from the electric current of constant current source 504 to 507.The gray scale demonstration is realized by the time span that the magnitude of current electric current that is supplied to 507 from constant current source 504 is supplied to photocell 524 to 527.When switch 508 to 511 is in nonconducting state and row signal line L1 is connected to Vcc through switch 512, reversed bias voltage is supplied to the photocell 524 to 527 of first row.Such operation is repeated to last column from first row.
Figure 16 illustrates the configuration of the example of column signal line drive circuit 502.Constant pressure source 601 has function and use that constant voltage takes place and has the constant pressure source such as the bandgap regulator of little temperature coefficient.The voltage that takes place from constant pressure source 601 passes through operational amplifier 602, and transistor 603 and resistor 604 are converted to the constant current with little temperature coefficient.The electric current of conversion instead is supplied to column signal line C1 to Cx through switch 610 to 613 partially and by the current mirror circuit copy then, and this current mirror circuit is made of transistor 605 to 609.
Display device according to this embodiment, input to column signal line drive circuit 502 video data or from the voltage that constant pressure source 601 takes place be with monitoring circuit 541 according to temperature change and the correction of change in time, thereby prevent the influence of temperature change and change in time.
The application based on May 21st, 2004 in the Jap.P. 2004-152624 of Jap.P. office application and on June 29th, 2004 the Jap.P. 2004-191833 in the application of Jap.P. office, their whole contents are included in herein by reference.

Claims (8)

1. display device, it comprises:
First photocell;
Be connected serially to the first transistor of this first photocell;
Second photocell;
Be connected serially to the transistor seconds of this second photocell;
Be used to supply the constant current source of constant current to the second photocell; With
The circuit that is used for output potential, the electromotive force of output equals to input to the electromotive force of described circuit;
Wherein first electrode of this first photocell is connected to the output terminal of this circuit by the first transistor;
Wherein first electrode of this second photocell is electrically connected to the input end of circuit by this transistor seconds,
Wherein the channel length L2 of the channel length L1 of the first transistor and channel width W1 and transistor seconds and channel width W2 satisfy L1/W1:L2/W2=1:2 to 1:10.
2. display device as claimed in claim 1, wherein circuit is a buffer amplifier.
3. display device as claimed in claim 1, wherein second electrode of second electrode of first photocell and second photocell remains on constant potential.
4. display device as claimed in claim 1, wherein first photocell and second photocell are provided on the same substrate.
5. display device as claimed in claim 1, wherein the first transistor is a driving transistors.
6. display device as claimed in claim 1, wherein transistor seconds is a limit transistor.
7. display device as claimed in claim 1, wherein second photocell is to monitor photocell.
8. electronic installation that comprises display device as claimed in claim 1.
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CN102867483B (en) * 2004-05-21 2015-01-28 株式会社半导体能源研究所 Display device and electronic device

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