JP2008185670A - Organic electroluminescence display device, control method of organic electroluminescence display device, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain smooth image display by suppressing an image persistence phenomenon induced by difference in luminance degradation caused by the temperature in an organic EL element. <P>SOLUTION: A degradation amount in the emission luminance of each display pixel is detected by an emission luminance change detection unit 508 based on the detection output of each light receiving element in a light receiving element group 38, as well as a change amount in temperature in each pixel is detected by a temperature change detection unit 511 based on the detection output of a temperature detection unit 40 that uses the same organic EL element as in the pixel as a detection element. The emission luminance of the organic EL element is controlled so that the degradation amount of the luminance caused by the temperature of the organic EL element is fixed by reflecting the degradation amount in luminance of each display pixel on the change amount in temperature in each pixel by a data normalization processing unit 512. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic EL (Electro Luminescence) display device, a control method for an organic EL display device, and an electronic apparatus.

  In recent years, panel-type display devices (displays) using self-luminous elements such as light-emitting diodes (LEDs), laser diodes (LD), and organic EL elements as display elements have been developed. In this type of display device, generally, a screen portion (display panel) is configured by arranging a large number of self-light-emitting elements in a matrix, and each element is selectively made to emit light according to a video signal, thereby displaying an image. Is done.

  As a display medium, a display plays a big role in our daily life, as represented by a television receiver, a computer monitor, a portable information terminal, and the like. With the development of the Internet, the importance of displays as human interfaces is increasing. Under such circumstances, there is a demand for a high-resolution, high-speed display that is easy on the eyes, easy to see on a high-definition screen, and can be clearly displayed without delay in moving images.

  A display device using a self-light emitting element is thinner than a display device using a non-self light emitting element, for example, a liquid crystal display device using liquid crystal (LCD; (Liquid Crystal Display), because a backlight is unnecessary. The organic EL display device using an organic EL element has a wide viewing angle, high visibility, and a response speed of the element. Has been attracting attention in recent years.

  On the other hand, the organic EL element has a problem of deterioration over time such that each organic layer is deteriorated due to heat generated by light emission, the light emission luminance is lowered, and light emission itself is unstable. In addition, organic EL elements exhibit light-emitting diode characteristics, and the current flowing through the device increases proportionally with increasing temperature. As a result, the organic EL element has a proportional relationship with the emission luminance, and thus tends to promote device degradation. .

  As a countermeasure, conventionally, a luminance relationship due to a rise in temperature is suppressed by suppressing the amount of current flowing through the device by using a proportional relationship between the amount of current and light emission luminance (for example, Patent Document 1). reference).

  In addition, a temperature sensor is arranged near the pixel at the intersection of the scanning line and the data line, and the voltage level of the driving voltage for driving the scanning line is controlled in accordance with the change in the ambient temperature detected by the temperature sensor. Even when the temperature changes, uniform and bright display is performed (for example, see Patent Document 2).

JP 2003-323152 A JP 2003-157050 A

  However, in the conventional technique described in Patent Document 1, since the amount of current flowing through the device is suppressed, there is a problem in that light emission luminance decreases due to control of the amount of current and a good image display cannot be provided. .

  On the other hand, the temperature dependence of light emission luminance-applied voltage characteristics varies depending on the device. Therefore, when the emission luminance is controlled using only the detection output of the temperature sensor as in the prior art described in Patent Document 2, the change caused by the temperature of the emission luminance-applied voltage characteristics of each device (organic EL element). There are problems such as not being able to cope with the difference.

  In addition, as described above, the organic EL element exhibits a light emitting diode characteristic, and has a temperature characteristic in which the light emission luminance varies depending on the temperature. When light is emitted with a certain luminance, the higher the temperature of the organic EL element, the more easily the relative luminance is degraded. Specifically, as shown in FIG. 22, if the horizontal axis is the driving time, the vertical axis is the relative luminance, and the relative luminance when the driving time is 0 is 1, the relative luminance increases as the driving time increases. In addition to deterioration, the luminance deterioration curve varies depending on the temperature.

  If there is a difference in relative luminance at different temperatures throughout the display area, this difference in relative luminance appears as a so-called burn-in phenomenon to the human eye. That is, a burn-in phenomenon occurs due to a difference in luminance deterioration due to the temperature of the device.

  It is difficult to correct the difference in relative luminance degradation caused by temperature by simply suppressing the amount of current flowing through the device or controlling it using only the detection output of the temperature sensor. Even if the conventional techniques described in Patent Documents 1 and 2 are used, it is not possible to suppress the image sticking phenomenon that occurs due to the difference in relative luminance degradation caused by the temperature of the organic EL element.

  Therefore, the present invention has a display device capable of suppressing a burn-in phenomenon caused by a difference in luminance deterioration due to temperature of the organic EL element and realizing a smooth image display, a control method for the display device, and the display device. An object is to provide electronic equipment.

  In order to achieve the above object, according to the present invention, in an organic EL display device in which a plurality of pixels including an organic EL element formed between a pair of substrates are arranged, one of the pair of substrates has an organic A light receiving element is arranged corresponding to each EL element, and the light receiving element detects leakage light of the organic EL element to detect the luminance of each organic EL element, and the deterioration of the relative luminance of the organic EL element is reduced. On the other hand, the temperature of the organic EL element is detected on the basis of the generated current-applied voltage characteristics of the detection element using a detection element composed of the same element as the EL element, and the deterioration of the relative luminance is reflected in the detection result. Thus, the light emission luminance of the organic EL element is controlled so that the luminance deterioration amount due to the temperature of the organic EL element becomes constant.

  In the organic EL display device having the above-described configuration and the electronic device using the display device, the temperature of each organic EL element is determined based on the generated current-applied voltage characteristics of the detection element using a detection element made of the same element as the organic EL element. And the deterioration of relative luminance of the organic EL element is detected using the luminance information of each organic EL element, and not only the temperature information of each organic EL element but also the deterioration information of the relative luminance of the organic EL element is obtained. By using and controlling the light emission luminance of each organic EL element, it is possible to suppress the image sticking phenomenon that occurs due to the difference in luminance deterioration due to the temperature of the organic EL element.

  According to the present invention, the luminance due to the temperature of the organic EL element is controlled by controlling the light emission luminance of the organic EL element using not only the temperature information of each organic EL element but also the deterioration information of the relative luminance of the organic EL element. Since the image sticking phenomenon that occurs due to the difference in deterioration can be suppressed, a smooth image display can be realized.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Panel configuration)
FIG. 1 is a block diagram showing a panel configuration of an active matrix organic EL display device according to an embodiment of the present invention.

  As shown in FIG. 1, the organic EL display device 10 according to the present embodiment includes a pixel array unit 11 in which pixels (PXLC) 20 are two-dimensionally arranged in a matrix (matrix shape), and the pixel array unit 11. A driving circuit that is arranged in the periphery and drives each pixel 20 to emit light, such as a writing scanning circuit 12, a power supply scanning circuit 13, and a horizontal driving circuit 14, is provided.

  The pixel array unit 11 is provided with scanning lines 15-1 to 15-m and power supply lines 16-1 to 16-m for each pixel row with respect to the pixel array of m rows and n columns, and for each pixel column. In addition, signal lines 17-1 to 17-n are wired.

  The pixel array unit 11 is usually formed on a transparent insulating substrate such as a glass substrate, and has a flat (flat) panel structure. Each pixel 20 of the pixel array unit 11 can be formed using an amorphous silicon TFT (Thin Film Transistor) or a low-temperature polysilicon TFT.

  When the pixel 20 is formed using the low-temperature polysilicon TFT, the writing scanning circuit 12, the power supply scanning circuit 13, and the horizontal driving circuit 14 are also mounted on the display panel (substrate) 18 that forms the pixel array unit 11. be able to.

  The writing scanning circuit 12 includes a shift register or the like, and sequentially supplies scanning signals WS1 to WSm to the scanning lines 15-1 to 15-m when writing video signals to the respective pixels 20 of the pixel array unit 11. 20 is line-sequentially scanned line by line.

  The power supply scanning circuit 13 is configured by a shift register or the like, and is synchronized with the line sequential scanning by the write scanning circuit 12 and switched between a first potential Vccp and a second potential Vini lower than the first potential Vccp. DS1 to DSm are supplied to the power supply lines 16-1 to 16-m. Here, the second potential Vini is a potential sufficiently lower than the offset voltage Vofs given from the horizontal drive circuit 14.

  The horizontal drive circuit 14 appropriately selects one of the signal voltage Vsig and the offset voltage Vofs of the video signal according to the luminance information supplied from a signal supply source (not shown), and the signal lines 17-1 to 17-. For example, data is written all at once to each pixel 20 of the pixel array unit 11 via n. That is, the horizontal drive circuit 14 employs a line-sequential writing drive mode in which the input signal voltage Vsig is written all at once in a row (line) unit.

(Pixel circuit)
FIG. 2 is a circuit diagram illustrating a specific configuration example of the pixel (pixel circuit) 20. As shown in FIG. 2, the pixel 20 includes a current-driven electro-optical element, for example, an organic EL element 21, whose light emission luminance changes according to a current value flowing through the device, and the organic EL element 21 includes In addition, the driving transistor 22, the writing transistor 23, the storage capacitor 24, and the auxiliary capacitor 25 are provided.

  Here, N-channel TFTs are used as the drive transistor 22 and the write transistor 23. However, the combination of the conductivity types of the driving transistor 22 and the writing transistor 23 here is only an example, and is not limited to these combinations.

  The organic EL element 21 has a cathode electrode connected to a common power supply line 19 wired in common to all the pixels 20. The drive transistor 22 has a source connected to the anode electrode of the organic EL element 21 and a drain connected to the power supply line 16 (16-1 to 16-m).

  The writing transistor 23 has a gate connected to the scanning line 15 (15-1 to 15-m), a source connected to the signal line 17 (17-1 to 17-n), and a drain connected to the gate of the driving transistor 22. Has been. The storage capacitor 24 has one end connected to the gate of the drive transistor 22 and the other end connected to the source of the drive transistor 22 (the anode electrode of the organic EL element 21).

  The auxiliary capacitor 25 has one end connected to the source of the driving transistor 22 and the other end connected to the cathode electrode (common potential supply line 19) of the organic EL element 21. The auxiliary capacitor 25 is connected in parallel to the organic EL element 21 to compensate for the capacity shortage of the organic EL element 21. That is, the auxiliary capacitor 25 is not an essential component, and the auxiliary capacitor 25 can be omitted when the capacity of the organic EL element 21 is sufficient.

  In the pixel 20 having such a configuration, the writing transistor 23 is supplied from the horizontal driving circuit 14 through the signal line 17 by being turned on in response to the scanning signal WS applied from the writing scanning circuit 12 to the gate through the scanning line 15. The input signal voltage Vsig or the offset voltage Vofs of the video signal corresponding to the luminance information is sampled and written into the pixel 20. The written input signal voltage Vsig or offset voltage Vofs is held in the holding capacitor 24.

  When the potential DS of the power supply line 16 (16-1 to 16-m) is at the first potential Vccp, the drive transistor 22 is supplied with current from the power supply line 16 and is held in the storage capacitor 24. By supplying the organic EL element 21 with a drive current having a current value corresponding to the voltage value of the input signal voltage Vsig, the organic EL element 21 is driven by current.

(Circuit operation)
Next, the circuit operation of the organic EL display device 10 according to the present embodiment will be described with reference to the timing chart of FIG.

  In the timing chart of FIG. 3, with a common time axis, the change in potential (scanning signal) WS of the scanning line 15 (15-1 to 15-m) at 1H (H is the horizontal scanning time), the power supply line 16 ( 16-1 to 16-m), and changes in the gate potential Vg and the source potential Vs of the driving transistor 22 are shown. Until time t2, the waveform of the potential (scanning signal) WS of the scanning line 15 is indicated by a one-dot chain line, and the potential DS of the power supply line 16 is indicated by a dotted line so that the two can be identified. After time t3, both are indicated by solid lines.

<Light emission period>
In the timing chart of FIG. 3, before the time t1, the organic EL element 21 is in a light emission state (light emission period). In this light emission period, the potential DS of the power supply line 16 is at the high potential Vccp (first potential), and the drive current (drain-source current) Ids is supplied from the power supply line 16 to the organic EL element 21 through the drive transistor 22. Therefore, the organic EL element 21 emits light with a luminance corresponding to the drive current Ids.

<Threshold correction preparation period>
Then, at time t1, a new field of line sequential scanning is entered, and the potential DS of the power supply line 16 transitions from the high potential Vccp to a potential Vini (second potential) that is sufficiently lower than the offset voltage Vofs of the signal line 17. The source potential Vs of the drive transistor 22 also starts to decrease toward the low potential Vini.

  Next, at time t2, the scanning signal WS is output from the writing scanning circuit 12, and the potential WS of the scanning line 15 shifts to the high potential side, so that the writing transistor 23 becomes conductive. At this time, since the offset voltage Vofs is supplied from the horizontal drive circuit 14 to the signal line 17, the gate potential Vg of the drive transistor 22 becomes the offset voltage Vofs. Further, the source potential Vs of the drive transistor 22 is at a potential Vini that is sufficiently lower than the offset voltage Vofs.

  Here, the low potential Vini is set so that the gate-source voltage Vgs of the drive transistor 22 is larger than the threshold voltage Vth of the drive transistor 22. As described above, the threshold potential correcting operation for correcting (cancelling) the variation of the threshold voltage Vth for each pixel by initializing the gate potential Vg of the driving transistor 22 to the offset voltage Vofs and the source potential Vs to the low potential Vini, respectively. Is ready.

<Threshold correction period>
Next, when the potential DS of the power supply line 16 is switched from the low potential Vini to the high potential Vccp at time t3, the source potential Vs of the drive transistor 22 starts to rise. Eventually, the gate-source voltage Vgs of the drive transistor 22 becomes the threshold voltage Vth of the drive transistor 22, and a voltage corresponding to the threshold voltage Vth is written into the storage capacitor 24.

  Here, for convenience, a period during which a voltage corresponding to the threshold voltage Vth is written to the storage capacitor 24 is referred to as a threshold correction period. In this threshold value correction period, the organic EL element 21 is cut off so that the current supplied from the drive transistor 22 flows exclusively to the storage capacitor 24 side and not to the organic EL element 21 side. As described above, the potential Vcath of the common power supply line 34 is set.

  Next, at time t4, the potential WS of the scanning line 15 shifts to the low potential side, so that the writing transistor 23 is turned off. At this time, the gate of the driving transistor 22 is in a floating state, but the driving transistor 22 is in a cutoff state because the gate-source voltage Vgs is equal to the threshold voltage Vth of the driving transistor 22. Therefore, the drain-source current Ids does not flow.

<Writing period / mobility correction period>
Next, at time t5, the potential of the signal line 17 is switched from the offset voltage Vofs to the signal voltage Vsig of the video signal. Subsequently, at time t6, the potential WS of the scanning line 15 transitions to the high potential side, whereby the writing transistor 23 becomes conductive and the signal voltage Vsig of the video signal is sampled.

  By sampling the input signal voltage Vsig by the write transistor 23, the gate potential Vg of the drive transistor 22 becomes the input signal voltage Vsig. At this time, since the organic EL element 21 is initially in a cut-off state (high impedance state), the drain-source current Ids of the drive transistor 22 flows into the combined capacitance of the capacitance component of the organic EL element 21 and the auxiliary capacitor 25. Thus, charging of the combined capacity is started.

  Due to the charging of the combined capacitance, the source potential Vs of the drive transistor 22 starts to rise, and the gate-source voltage Vgs of the drive transistor 22 eventually becomes Vsig + Vth−ΔV. That is, the increase ΔV of the source potential Vs is subtracted from the voltage (Vsig + Vth) held in the holding capacitor 24, in other words, acts to discharge the charged charge of the holding capacitor 24, and negative feedback is applied. It will be. Therefore, the increase ΔV of the source potential Vs becomes a feedback amount of negative feedback.

  As described above, the drain-source current Ids flowing through the drive transistor 22 is negatively fed back to the gate input of the drive transistor 22, that is, the gate-source voltage Vgs, so that the drain-source current Ids of the drive transistor 22 is reduced. Mobility correction is performed to cancel the dependence on the mobility μ, that is, to correct the variation of the mobility μ for each pixel.

  More specifically, since the drain-source current Ids increases as the signal voltage Vsig of the video signal increases, the absolute value of the feedback amount (correction amount) ΔV of negative feedback also increases. Therefore, the mobility correction according to the light emission luminance level is performed. Further, when the signal voltage Vsig of the video signal is constant, the absolute value of the feedback amount ΔV of the negative feedback increases as the mobility μ of the driving transistor 22 increases, so that variation in the mobility μ for each pixel is removed. Can do.

<Light emission period>
Next, at time t7, the potential WS of the scanning line 15 transitions to the low potential side, so that the writing transistor 23 is turned off (off). As a result, the gate of the drive transistor 22 is disconnected from the signal line 17. At the same time, the drain-source current Ids starts to flow through the organic EL element 21, whereby the anode potential of the organic EL element 21 rises according to the drain-source current Ids.

  The increase in the anode potential of the organic EL element 21 is nothing but the increase in the source potential Vs of the drive transistor 22. When the source potential Vs of the drive transistor 22 rises, the gate potential Vg of the drive transistor 22 also rises in conjunction with the bootstrap operation of the storage capacitor 24.

  At this time, the increase amount of the gate potential Vg is equal to the increase amount of the source potential Vs. Therefore, the gate-source voltage Vgs of the drive transistor 22 is kept constant at Vsig + Vth−ΔV during the light emission period. At time t8, the potential of the signal line 17 is switched from the signal voltage Vsig of the video signal to the offset voltage Vofs.

(Panel structure)
Next, the panel structure of the display panel 18 in the organic EL display device 10 according to the present embodiment will be described.

<Panel structure of top emission type organic EL display device>
FIG. 4 is a cross-sectional view of an essential part showing an outline of the panel structure of the top emission type organic EL display device.

  As shown in FIG. 4, the top emission organic EL display device 10 </ b> A includes a support substrate 31 and a counter substrate 32, and the organic EL element 21 is provided so as to be sandwiched between the substrates 31 and 32. It has become. The support substrate 31 is appropriately selected from a transparent substrate such as quartz or glass, a silicon substrate, or the like.

  Here, the above-described active matrix method is adopted as the driving method of the organic EL display device 10A. However, the driving method of the organic EL display device 10A is not limited to the active matrix method, and the present invention can be applied even when the passive matrix method is adopted.

  On the support substrate 31, for each pixel 20 including the organic EL element 21, a circuit element that drives the organic EL element 21, specifically, the drive transistor 22, the write transistor 23, the storage capacitor 24, and the auxiliary capacitor 25 described above. Is formed.

  Further, on the support substrate 11, a drive circuit that is disposed around the pixel array unit 11 and drives each pixel 20 to emit light, specifically, the above-described write scanning circuit 12, power supply scanning circuit 13, and horizontal drive circuit 14. Etc. are formed.

  The organic EL element 21 is a current-driven electro-optical element whose emission luminance changes according to the value of a current flowing through the device. The organic EL element 21 is arranged in a matrix (matrix) in the display area at the center of the main surface of the support substrate 31. Two-dimensional arrangement. Each of these organic EL elements 21 emits light of, for example, each of R (red), G (green), and B (blue), and is arranged in a display area according to a predetermined arrangement format.

  An element isolation insulating layer 33 that separates the organic EL elements 21 is formed between the organic EL elements 21. The scanning lines 15 and the power supply lines 16 described above are wired in the element isolation insulating layer 33 for each pixel row.

  The organic EL element 21 is an organic layer (electron layer) including a lower electrode (anode electrode) 34 arranged on the support substrate 31 for each organic EL element 21 and a light emitting layer that is formed on the lower electrode 34 and emits light of each color. Transport layer, light-emitting layer, hole transport layer / hole injection layer) 35, an upper electrode that is formed in a solid film shape so as to cover each organic layer 35 and element isolation insulating layer 33 and serves as a common electrode for each organic EL element 21 (Cathode electrode) 36 are sequentially stacked.

  Although the lower electrode 34 is an anode electrode and the upper electrode 36 is a cathode electrode here, the lower electrode 34 may be a cathode electrode and the upper electrode 36 may be an anode electrode. Further, a transparent material film 37 made of, for example, silicon nitride is provided between the upper electrode 36 and the counter substrate 32.

  On the surface side of the counter substrate 32, a light receiving element 38 is located at a position between the organic EL elements 21, that is, a position facing the element isolation insulating layer 33 where the scanning lines 15 and the power supply lines 16 are wired. The number corresponding to the organic EL elements 21 is arranged. Specifically, the light receiving element 38 is provided in a state of embedding a recess 32 a formed on the surface side of the counter substrate 32. The recess 32a is formed by etching or the like before the support substrate 31 and the counter substrate 32 are arranged to face each other.

  Here, an arrangement structure is adopted in which the light receiving element 38 is embedded in a recess 32a formed on the surface side of the counter substrate 32. However, a recess is formed on the organic EL element 21 side of the counter substrate 32, and the recess is formed in the recess. It is also possible to adopt an arrangement structure in which the light receiving element 38 is embedded, or an arrangement structure in which a recess is formed on the counter substrate 32 side of the transparent material film 37 and the light receiving element 38 is embedded in the recess.

  The light receiving element 38 is a high-sensitivity light receiving sensor (visible light sensor) formed of, for example, an amorphous silicon semiconductor, detects the leaked light of the organic EL element 21 in a corresponding relationship, performs photoelectric conversion, and performs electricity according to the amount of light received. Generate a signal. The correspondence relationship between the organic EL element 21 and the light receiving element 38 will be described later.

  The light receiving element 38 is not limited to a high sensitivity light receiving sensor formed of an amorphous silicon semiconductor, and a known light receiving sensor capable of generating an electric signal according to the amount of received light can be used. However, by using a highly sensitive light receiving sensor as the light receiving element 38, there is an advantage that leakage light having a light amount of about 20% with respect to the light emission intensity of the organic EL element 21 can be detected as described later.

  In addition, since the organic EL element can have a function as a light receiving element because of its structure, the organic EL element can also be used as the light receiving element 38. By using the organic EL element as the light receiving element 38, the organic EL element 21 and the light receiving element 38 can be formed by the same process, which is advantageous in terms of the manufacturing process.

  The light receiving element 38 has a light amount leakage of about 20% with respect to the emission intensity of the organic EL element 21 due to the arrangement relationship with respect to the organic EL element 21 determined by the pixel arrangement pitch and the film thickness of the upper electrode 36 and the transparent material film 37. Light can be detected. As described above, if the light receiving element 38 can receive about 20% of the light emission intensity of the organic EL element 21, control described later based on the light reception output of the light receiving element 38 can be sufficiently realized.

  Further, as shown in the plan view of FIG. 5, the light receiving elements 38 are arranged between the organic EL elements 21 adjacent in plan view in the scanning direction. Then, when scanning the pixel row by the writing scanning circuit 12 described above, when the organic EL element 21 in a certain pixel row is selected, one light receiving element 38 adjacent to the organic EL element 21 in the selected row is This corresponds to monitoring leakage light of the organic EL element 21. This correspondence is the correspondence between the organic EL element 21 and the light receiving element 38 described above.

  Specifically, the organic EL element 21 in a certain pixel row and one light receiving element 38 adjacent to the organic EL element 21 in the scanning direction are paired and correspond to the organic EL element 21 in the same period as the scanning period of the organic EL element 21. The light receiving element 38 in the monitoring area monitors the leaked light of the organic EL element 21.

  Due to this timing relationship, even if there are two organic EL elements 21 adjacent to both the front and rear sides in the scanning direction with respect to one light receiving element 38, the light receiving element 38 has a light leakage amount from one organic EL element 21. Can be received, and leakage of light from the other organic EL element 21 can be prevented. Here, the cross-sectional view taken along the line AA ′ of FIG. 5 is the cross-sectional configuration diagram of FIG. 4.

  As described above, a panel module (corresponding to the display panel 18 in FIG. 1) of the so-called top emission type organic EL display device 10A that extracts light emitted from the organic layer 35 of the organic EL element 21 from the counter substrate 32 side is configured.

  Here, the top emission organic EL display device 10A has been described as an example, but the present invention is not limited to application to the top emission organic EL display device 10A, and light emission from the organic layer 35 of the organic EL element 21 is performed. The present invention can also be applied to a so-called bottom emission organic EL display device that extracts light from the support substrate 31 side. The structure of the panel module of the bottom emission type organic EL display device will be described below.

<Panel structure of bottom emission type organic EL display device>
FIG. 6 is a cross-sectional view of an essential part showing an outline of the panel structure of the bottom emission type organic EL display device. In FIG. 6, the same parts as those in FIG.

  As shown in FIG. 6, in the case of the bottom emission type organic EL display device 10B, since the emitted light from the organic layer 35 is extracted from the support substrate 31 side, the upper electrode 36 is formed of a reflective material, and the lower electrode 34 is formed of a transparent material. Here, the lower electrode 34 is disposed in a state corresponding to each organic EL element 21 on a planarization insulating film (not shown) provided in a state of covering the TFT disposed on the support substrate 31.

  The light receiving element 38 is disposed on the planarization insulating film between the lower electrodes 34 so as to be separated from the adjacent lower electrodes 34. Further, in order to detect leakage light of the organic EL element 21 by the light receiving element 38, the element isolation insulating layer 33 arranged so as to cover the light receiving element 38 is made of a transparent material.

  The above point is that the panel module of the bottom emission type organic EL display device 10B is structurally different from the panel module of the top emission type organic EL display device 10A. It is basically the same as the 10A panel module.

(Temperature detector)
The panel module of the top emission organic EL display device 10A or the bottom emission organic EL display device 10B according to the present embodiment described above includes the pixel 20 in addition to the light receiving element 38 that detects leakage light of the organic EL element 21. Using the same element as the organic EL element 21 (that is, the organic EL element) as a detection element, a temperature detection unit that detects the temperature of the organic EL element 21 is provided.

  As an arrangement position of the temperature detection unit on the panel, the inside of the pixel 20 or the peripheral part of the pixel array unit 11 (outside the display area) can be considered. When provided in the periphery of the pixel array unit 11, it is preferably provided corresponding to at least one of the pixel row and the pixel column of the pixel array unit 11 in order to more accurately detect the temperature of the organic EL element 21. However, the arrangement is not limited to this example.

  This temperature detection unit uses the same organic EL element as the organic EL element 21 of the pixel 20 as a detection element, and utilizes the temperature dependency of the generated current-applied voltage characteristic (IV characteristic) of the organic EL element. The temperature of the organic EL element 21 of the pixel 20 is detected.

  FIG. 7 shows the temperature dependence of the generated current-applied voltage characteristic (A) and the emission luminance-applied voltage characteristic (B) of the organic EL element. As is clear from the figure, the temperature of the organic EL element in a state where an applied voltage having a certain voltage value is applied to the organic EL element and the generated current I1 emits light when the temperature of the organic EL element is 30 ° C. When the temperature rises to 45 ° C. and further to 60 ° C., the generated current I changes from I1 to I2 (I1 <I2) and further to I3 (I2 <I3) as the temperature rises. In other words, the organic EL element has a diode characteristic in which the generated current-applied voltage characteristic shifts to the low voltage side as the temperature rises.

  On the other hand, when the organic EL element is driven at a constant current, the temperature change ΔT and the voltage shift amount ΔV of the organic EL element are expressed as a correlated function as shown in FIG. Accordingly, the temperature change ΔT can be detected by detecting the voltage shift amount ΔV of the organic EL element.

  And since the detection element of a temperature detection part is the same organic EL element as the organic EL element 21 of the pixel 20, and shows the temperature dependence of the same generated current-applied voltage characteristic, the organic EL of the pixel 20 is detected by the temperature detection part. The temperature of the element 21 can be detected.

  As will be described later, the temperature information of the organic EL element 21 detected by the temperature detection unit is not affected by the difference in the generated current-applied voltage characteristics caused by the temperature of each organic EL element 21, and the organic EL element 21 is not affected by the difference. This is used for optimal brightness control for each element 21. Details thereof will be described later.

<Example of arrangement in a pixel>
FIG. 9 is a circuit diagram illustrating a circuit example of the temperature detection unit in the case of being arranged in the pixel 20. As shown in FIG. 9, the temperature detection unit 40 </ b> A according to this circuit example includes a temperature information detection unit 41 and a level adjustment unit 42.

  The temperature information detection unit 41 has the same configuration as that of the organic EL element 21 of the pixel 20 and includes an organic EL element 411 having a cathode electrode grounded, and a load resistor 412 connected between the organic EL element 411 and the power source Vdd. ing.

  Here, as the load resistor 412, for example, a TFT in which the source is connected to the power supply Vdd, the drain is connected to the anode electrode of the organic EL element 411, and a constant voltage Vb is applied to the gate is used.

  The level adjustment unit 42 includes a resistor 421 having one end connected to the anode electrode (the drain of the TFT) of the organic EL element 411, an operational amplifier 422 having a non-inverting (+) input end connected to the other end of the resistor 421, The differential amplifier has a resistor 423 connected between the inverting (−) input terminal of the operational amplifier 422 and the ground, and a resistor 424 connected between the output terminal and the inverting input terminal of the operational amplifier 422.

  In the temperature detection unit 40A having the above-described configuration, the temperature information detection unit 41 detects the voltage V-EL across the organic EL element 411 as the temperature information of the organic EL element 411 and thus the temperature information of the organic EL element 21 of the pixel 20. To do. The level adjustment unit 42 amplifies the detection voltage V-EL of the temperature information detection unit 41 by a predetermined magnification and outputs the amplified voltage as temperature information of the organic EL element 21.

  As described above, by arranging the temperature detection unit 40A in each of the pixels 20 of the pixel array unit 11, the aperture ratio of the pixel 20 is reduced, but the temperature of the organic EL element 21 of each pixel 20 is detected more accurately. be able to.

<Example of arrangement outside the display area>
FIG. 10 is a circuit diagram showing a circuit example of the temperature detection unit when arranged outside the display area (peripheral part of the pixel array unit 11). In FIG. 10, the same parts as those in FIG. Show. The temperature detection unit 40B according to this circuit example includes a level adjustment unit 43 having a configuration different from that of the level adjustment unit 42 in addition to the temperature information detection unit 41.

  The level adjustment unit 43 includes an ADC (analog-digital converter) 431, a memory 432 such as a ROM, and a DAC (digital-analog converter) 433. In the memory 432, for example, linear data corresponding to the amplification factor of the level adjustment unit 42 is stored in advance.

  In the temperature detection unit 40B having the above configuration, the level adjustment unit 43 converts the detection voltage V-EL of the temperature information detection unit 41 into digital data by the ADC 431, and a predetermined magnification based on the linear data stored in the memory 432. After being converted into the digital data amplified in step (3), it is output as temperature information of the organic EL element 21 via the DAC 433.

  As described above, by arranging the temperature detection unit 40B outside the display area (peripheral part of the pixel array unit 11), the temperature detection accuracy of the organic EL element 21 is lowered as compared with the case where each pixel 20 is arranged. However, it can be arranged smartly at low cost without reducing the aperture ratio of the pixel 20 and without changing the configuration of the pixel array unit 11.

(Control part)
The organic EL display device 10 including the display panel (panel module) 18 in which the temperature detection unit 40 (40A / 40B) described above is disposed includes a control unit described below in addition to the display panel 18. Thus, the display drive control of the display panel 18 is performed under the control of the control unit.

  FIG. 11 is a block diagram illustrating an example of a configuration of a control unit that performs display drive control of the display panel 18.

  As shown in FIG. 11, the control unit 50 includes a level control unit 501, a relative level adjustment unit 502, a memory unit 503, a division unit 504, an A / D (analog / digital) conversion unit 505, a memory unit 506, and a multiplication unit 507. , Relative luminance deterioration detection unit 508, A / D conversion unit 509, memory unit 510, temperature change detection unit 511, data normalization processing unit 512, voltage division calculation unit 513, voltage division result comparison calculation unit 514, voltage division ratio control The configuration includes a unit 515 and a calculation selection control unit 516.

  The control unit 50 performs display drive control (emission drive control of the organic EL element 21) of each pixel 20 of the pixel array unit 11 in the display panel 18 according to the input digital video signal, while the display panel 18 The relative luminance deterioration amount is monitored based on the detection signal of each light receiving element of the provided light receiving element group 38, and the temperature change of each pixel is monitored based on the detection signal of the temperature detecting unit 40 provided in the display panel 18. Based on these monitoring results, drive control (emission luminance control) of the organic EL element 21 is performed so that the luminance deterioration amount due to the temperature characteristics of the organic EL element 21 is constant (uniform).

  In the control unit 50, the digital video signal is supplied to the memory unit 503 via the level control unit 501 and the relative level adjustment unit 502, and after the gradation value of each display pixel is stored in the memory unit 503, the display panel 18. To be supplied. The functions of the level control unit 501 and the relative level adjustment unit 502 will be described later.

  In the display panel 18, as described above, each pixel 20 of the pixel array unit (display unit) 11 in which the pixels 20 are two-dimensionally arranged in a matrix is placed in row units by the write scanning circuit 12 and the power supply scanning circuit 13. And the display data corresponding to the digital video signal is written to each pixel of the selected row from the horizontal drive circuit 14, so that the organic EL element 21 of each pixel 20 has a gradation corresponding to the digital video signal. Light emission driving is performed.

  When the organic EL element 21 of each pixel 20 emits light in order by this row scanning display drive, each light receiving element 38 receives the leaked light of each organic EL element 21 in a corresponding relationship, photoelectrically converts it, and receives the light. Output as a voltage value according to the amount. The voltage value output from the light receiving element 38 is supplied to the division unit 504.

  The division unit 504 performs arithmetic processing for dividing the voltage value output from the light receiving element 38 by the gradation value given from the memory unit 503 via the multiplication unit 507. Here, if the light emission intensity (light emission luminance) of the display pixel is strong (if it is bright), the gradation is high, and conversely if the light emission intensity is low (if it is dark), the gradation is low. From the division result, the state of luminance of the display pixel (whether it is high luminance or low luminance) can be recognized. The division result is converted into digital data by the A / D conversion unit 505 and stored in the memory unit 506.

  The multiplication unit 507 performs a 20% multiplication process on the gradation value of each display pixel stored in the memory unit 503. Here, the multiplication process of 20% is performed on the gradation value of the display pixel, as described above, the amount of the leaked light received by the light receiving element 38 is about 20% of the light emitting amount of the organic EL element 21. Therefore, the voltage value from the light receiving element 38 to be subjected to the division operation and the gradation value from the memory unit 503 are made to correspond to (align).

  Here, the multiplication unit 507 performs the multiplication process of 20% on the gradation value from the memory unit 503, but by performing the multiplication process five times on the voltage value from the light receiving element 38. In addition, the voltage value from the light receiving element 38 to be subjected to the division operation in the division unit 504 can be associated with the gradation value from the memory unit 503.

  The relative luminance deterioration detection unit 508 determines, from the data stored in the memory unit 506, a pixel that emits light at the highest luminance on one display screen or a luminance near the high luminance display pixel, and a pixel that emits light at the lowest luminance or a luminance near the low luminance. Recognized as a luminance display pixel, for each of the high luminance display pixel and the low luminance display pixel, the amount of deterioration in relative luminance in a predetermined driving period is determined based on the gradation value provided from the memory unit 503 via the multiplication unit 507. To detect.

  As described above, the organic EL element 21 exhibits a light emitting diode characteristic and has a temperature characteristic in which the light emission luminance varies depending on the temperature. When the light is emitted at a certain luminance, the light emission luminance (brightness) deteriorates as the temperature increases. Specifically, as the driving time becomes longer, the relative luminance deteriorates and the luminance deterioration curve varies depending on the temperature. In addition, the deterioration characteristic of the relative luminance due to temperature is different between the high luminance display pixel and the low luminance display pixel, and as is apparent from FIG. 12, the characteristic (A) of the high luminance display pixel is higher than that of the low luminance display pixel. Deterioration is more remarkable than characteristic (B).

  The temperature detector 40 (40A / 40B) in the display panel 18 detects the temperature of each organic EL element 21 during the non-display period of the display pixel and outputs it as a voltage value. The voltage value output from the temperature detection unit 40 is converted into digital data by the A / D conversion unit 509 and stored in the memory unit 510.

  The temperature change detection unit 511 includes a characteristic shift detection unit 5111, a shift amount calculation unit 5112, and a temperature change calculation unit 5113. The temperature change detection unit 511 is based on saved data about the detected temperature stored in the memory unit 510 (for example, a predetermined period (for example, A temperature change in one frame period) is detected for each organic EL element 21.

  In this temperature change detection unit 511, the characteristic shift detection unit 5111 is based on the temperature information detected by the temperature detection unit 40, that is, based on the stored data regarding the detected temperature stored in the memory unit 510, as shown in FIG. From the relationship between the change ΔT and the voltage shift amount ΔV, the presence or absence of a characteristic shift of the generated current-applied voltage characteristic (see FIG. 7A) of the organic EL element exhibiting temperature dependence is detected.

  When the characteristic shift detector 5111 detects a characteristic shift, the shift amount calculator 5112 calculates a shift amount in a predetermined period (for example, one frame period), that is, a shift voltage value, from the data stored in the memory unit 510. The temperature change calculation unit 5113 calculates the temperature change amount (temperature change estimated value) of the organic EL element 21 from the shift voltage value calculated by the shift amount calculation unit 5112.

  The data normalization processing unit 512 has a numerical correlation data table indicating the correspondence between luminance and temperature, and for each temperature change of each pixel (organic EL element 21) detected by the temperature change detection unit 511, The relative luminance deterioration for each of the high luminance display pixel and the low luminance display pixel detected by the relative luminance deterioration detection unit 508 is reflected, and the temperature change corresponding to the relative luminance deterioration of the high luminance display pixel is reflected. The first voltage value (hereinafter referred to as “the relative luminance deterioration amount of the high luminance display pixel”) ΔLa and the second voltage value corresponding to the temperature change amount reflecting the relative luminance deterioration amount of the low luminance display pixel It is normalized (converted) to ΔLb (hereinafter referred to as “relative luminance degradation of low luminance display pixel”).

  The voltage division calculation unit 513 divides the relative luminance degradation amount ΔLa of the high luminance display pixel normalized by the data normalization processing unit 512 by the relative luminance degradation amount ΔLb of the low luminance display pixel for each pixel. This division ratio (division coefficient) ΔLa / ΔLb is a ratio between the temperature change reflecting the relative luminance deterioration of the high luminance display pixel and the temperature change reflecting the relative luminance deterioration of the low luminance display pixel. Therefore, it represents the degree of image sticking phenomenon that occurs due to the difference in luminance degradation due to temperature. Hereinafter, the division result ΔLa / ΔLb is referred to as a temperature characteristic image sticking correlation coefficient.

  The voltage division result comparison operation unit 514 performs image sticking that occurs due to a difference in luminance degradation due to temperature based on the temperature characteristic image sticking correlation coefficient ΔLa / ΔLb that is a result of division by the voltage division operation unit 513 for each pixel. Determine the extent of the phenomenon.

  Here, a correspondence relationship between the temperature difference ΔT between the high luminance display pixel and the low luminance display pixel and a critical point at which a seizure phenomenon occurs (hereinafter, referred to as a “seizure critical point”) will be described. Note that the seizure critical point (numerical value) corresponds to a predetermined reference value in the claims.

  As an example, as shown in FIG. 13, when the temperature difference ΔT is 5 ° C., the critical point for occurrence of seizure is 1.53. This indicates that the critical point at which the seizure phenomenon occurs at a temperature difference of 5 ° C. is 1.53, and at the temperature difference of 5 ° C., the temperature characteristic seizure correlation coefficient ΔLa / ΔLb is less than the critical point ( If ΔLa / ΔLb <1.53), it means that no seizure phenomenon occurs.

  Similarly, the seizure critical point is 1.45 when ΔT = 10 ° C., the seizure critical point is 1.40 when ΔT = 15 ° C., and the seizure critical point is when ΔT = 20 ° C. 1.36, the critical point of seizure generation is 1.31 when ΔT = 25 ° C., the critical point of seizure generation is 1.24 when ΔT = 30 ° C., and the critical point of seizure generation when ΔT = 35 ° C. Is 1.19 and ΔT = 40 ° C., the critical point for occurrence of seizure is 1.12.

  That is, ΔLa / ΔLb <1.45 at a temperature difference of 10 ° C., ΔLa / ΔLb <1.40 at a temperature difference of 15 ° C., ΔLa / ΔLb <1.36 at a temperature difference of 29 ° C., and ΔLa / ΔLb <at a temperature difference of 25 ° C. 1.31, ΔLa / ΔLb <1.24 at a temperature difference of 30 ° C., ΔLa / ΔLb <1.19 at a temperature difference of 35 ° C., and seizure phenomenon at ΔLa / ΔLb <1.12 at a temperature difference of 40 ° C. Will not.

  Therefore, the voltage division result comparison calculation unit 514 performs the following comparison calculation process. That is, in a certain pixel, when the temperature change of the organic EL element 21 is, for example, 15 ° C., the temperature characteristic seizure correlation coefficient is obtained from the correspondence relationship between the temperature difference ΔT and the seizure critical point. If ΔLa / ΔLb is 1.40 or more, that is, whether or not seizure occurs, and if it is 1.40 or more, the extent of seizure, that is, the seizure critical point (1.40). ) Is calculated.

  The voltage division ratio control unit 515 calculates, for each pixel, a control value for preventing the image sticking phenomenon from occurring based on the determination result of the degree of the image sticking phenomenon occurring by the voltage division result comparison operation unit 514. Specifically, when it is determined that the seizure phenomenon occurs in the voltage division result comparison operation unit 514 and a difference is calculated with respect to the seizure critical point, a control value corresponding to the difference is calculated. This control value is a luminance correction value for correcting the signal level of the input digital signal so that the deterioration of the relative luminance due to the temperature characteristics of the organic EL element 21 is constant (uniform).

  Here, it is assumed that the voltage division calculation unit 513, the voltage division result comparison calculation unit 514, and the voltage division ratio control unit 515 incorporate a correspondence table indicating the correspondence relationship between the calculated voltage value and the luminance. Thus, when performing luminance correction, it is possible to inquire for each circuit unit how much luminance value the calculated voltage value corresponds to, so that smooth correction is possible.

  Based on the brightness correction value (control value) of each pixel calculated by the voltage division ratio control unit 515, the calculation selection control unit 516 performs high brightness when the correction target pixel is a high brightness display pixel. Selection control is performed to determine whether or not to correct the signal level (luminance level) for the display pixel. Based on the selection result by the calculation selection control unit 516, the level control unit 501 performs correction control according to the luminance correction value calculated by the voltage division ratio control unit 515 with respect to the signal level of the high luminance display pixel. Do.

  Here, it is assumed that the voltage division calculation unit 513, the voltage division result comparison calculation unit 514, and the voltage division ratio control unit 515 incorporate a correspondence table indicating the correspondence relationship between the calculated voltage value and the luminance. Thus, when performing luminance correction, it is possible to inquire for each circuit unit how much luminance value the calculated voltage value corresponds to, so that smooth correction is possible.

  Based on the brightness correction value (control value) of each pixel calculated by the voltage division ratio control unit 515, the calculation selection control unit 516 performs high brightness when the correction target pixel is a high brightness display pixel. Selection control is performed to determine whether or not to correct the signal level (luminance level) for the display pixel. Based on the selection result by the calculation selection control unit 516, the level control unit 501 performs correction control according to the luminance correction value calculated by the voltage division ratio control unit 515 with respect to the signal level of the high luminance display pixel. Do.

<Relative level adjustment unit>
Next, a specific configuration of the relative level adjustment unit 502 will be described. The relative level adjustment unit 502 includes a still image determination unit 5021, a changeover switch 5022, and a level adjustment unit 5023.

As shown in FIG. 14, for example, the still image determination unit 5021 includes a frame memory 50211, an arithmetic circuit 50212, and a determination circuit 50213. The still image determination unit 5021 includes the video signal level V1N of the Nth frame and the previous frame stored in the frame memory 50211. Using the video signal level V1 (N-1) of the (N-1) th frame, the arithmetic circuit 50212 [{V1N-V1 (N-1)} / V1 (N-1)] * 100
The calculation circuit determines whether or not the calculation result is 70% or less of the video signal level V1 (N-1) of the (N-1) th frame. Judged as a still image. Naturally, when it exceeds 70%, it becomes a moving image.

  The changeover switch 5022 normally supplies the input digital video signal directly to the memory unit 503, and when the determination result of the still image determination unit 5021 is a still image, the input digital video signal is converted to the level adjustment unit 5023. To the memory unit 503. The level adjustment unit 5023 multiplies the signal level of the video signal when it is determined as a still image by, for example, 100 times.

  Here, the reason why the signal level of the video signal is multiplied by 100 when it is determined as a still image is as follows. In other words, as described above, the relative luminance deterioration detection unit 508 detects the amount of deterioration of the relative luminance during a predetermined driving period. The brightness level varies. The change in the luminance level of the still image in one frame period is as extremely small as about 1/100 compared to the change in the luminance level of the moving image in one frame period.

  Therefore, when it is determined that the image is a still image, the relative luminance deterioration detection unit 508 performs a weak signal level transition between the previous and next frames by performing a multiplication process of about 100 times on the signal level of the video signal. (Brightness change) can be easily detected. However, the numerical value of 100 is merely an example, and is not limited to this, and it is sufficient that the magnification is at least enough to detect a weak signal level transition between the preceding and succeeding frames.

  Regarding the adjustment of the signal level at the time of still image, a correspondence table between the signal level at the time of still image and the corresponding luminance value is built in the level adjustment unit 5023 in advance, and this correspondence table is used to adjust the signal level at the time of still image. It is also possible to adopt a configuration in which the signal level is set to a luminance value corresponding to the signal level.

  In the organic EL display device 10 according to the present embodiment having the above-described configuration, the organic EL element 21 used as the light emitting element has a deterioration in the organic layer 35 (see FIGS. 4 and 6) due to heat generated by light emission and the like. It has a problem of deterioration over time such as a decrease in light emission and unstable light emission. Further, as described above, the organic EL element exhibits light emitting diode characteristics (see FIG. 7), and the current flowing through the device increases in proportion to the temperature rise, and as a result, is proportional to the light emission luminance.

  As described above, in an organic EL display device using an organic EL element as a light emitting element, the organic EL element is a self-luminous element. And in the present condition that the light emission luminance changes as the temperature of the device rises and the method of the change differs for each device, the organic EL display device 10 according to the present embodiment adopts the following configuration. It is a feature.

  That is, the organic EL display device 10 according to the present embodiment corresponds to each of the organic EL elements 21 on one of the pair of substrates 31 and 32, specifically, on the counter substrate 32 side on the light extraction side. The light receiving element 38 is arranged, and the light receiving element 38 detects leakage light of the organic EL element 21 to detect the luminance of each organic EL element 21, and from the same element (organic EL element) as the organic EL element 21. The temperature change of each organic EL element 21 is detected on the basis of the generated current-applied voltage characteristic of the detection element, and the deterioration of relative luminance is reflected in the temperature change to thereby detect the organic EL element. The light emission luminance of the organic EL element 21 is controlled so that the deterioration of the relative luminance due to the temperature 21 is constant.

  In the luminance control by the control unit 50 according to the present embodiment, as specific control, relative luminance deterioration is detected by the relative luminance deterioration detection unit 508 for each of the high luminance display pixel and the low luminance display pixel, and the organic EL The temperature change detection unit 511 detects the temperature change of each element 21, and the detected temperature change is a high-brightness display pixel that reflects the relative brightness deterioration of each of the high-brightness display pixel and the low-brightness display pixel. Is normalized (converted) by the data normalization processing unit 512 to the relative luminance degradation amount ΔLa and the relative luminance degradation amount ΔLb of the low luminance display pixel, and the relative luminance degradation amount obtained by the temperature correction is performed. Luminance correction is controlled based on the temperature characteristic burn-in correlation coefficient ΔLa / ΔLb, which is the result of dividing ΔLa and the relative luminance degradation ΔLb.

  In this way, the deterioration of relative luminance of the organic EL element 21 is detected using the luminance information of each organic EL element 21, and not only the temperature information of each organic EL element 21 but also the deterioration of the relative luminance of the organic EL element 21 is detected. By controlling the light emission luminance of each organic EL element 21 based on the information, it is possible to suppress the image sticking phenomenon that occurs due to the difference in luminance deterioration due to the temperature of the organic EL element 21, thereby realizing a smooth image display. .

  In particular, an element having a generated current-applied voltage characteristic (see FIG. 7) showing the same temperature dependence as the organic EL element 21 as a detection element of the temperature detection unit 40 that detects the temperature of the organic EL element 21, that is, an organic EL element By using 411, the light emission luminance-applied voltage characteristics of these organic EL elements 21 and 411 are similarly voltage-shifted according to the temperature change, so that the temperature of the organic EL element 21 is changed from the voltage shift amount of the organic EL element 411. The amount of change can be accurately detected and reflected in the luminance control of the organic EL element 21, and the luminance change due to the temperature change can be corrected with high accuracy. In addition, the temperature detection organic EL element 411 can be formed by the same process as the organic EL element 21 of the pixel 20.

  Note that the control unit 50 configured as described above includes a pixel array unit (display unit) 11 in which the pixels 20 are arranged in a matrix, and peripheral drive circuits (a write scanning circuit 12, a power supply scanning circuit 13, and a horizontal drive). The circuit 14) may be mounted on the display panel 18 or may be provided outside the display panel 18.

  Here, each component of the control unit 50 in the organic EL display device 10 according to the present embodiment, that is, a level control unit 501, a relative level adjustment unit 502, a memory unit 503, a division unit 504, an A / D conversion unit 505, a memory Unit 506, multiplication unit 507, relative luminance deterioration detection unit 508, A / D conversion unit 509, memory unit 510, temperature change detection unit 511, data normalization processing unit 512, voltage division calculation unit 513, voltage division result comparison calculation unit As for 514, voltage division ratio control unit 515 and calculation selection control unit 516, a computer device that performs each function such as information storage processing, signal processing, and calculation processing by executing a predetermined program is used like a personal computer. It can be realized by software configuration.

  However, the present invention is not limited to the implementation by software configuration, and can also be implemented by a hardware configuration or a combined configuration of hardware and software.

(Control method)
Next, a processing procedure of the control method of the organic EL display device 10 according to the present embodiment having the above-described configuration (the control method of the organic EL display device according to the present invention) will be specifically described with reference to the flowchart of FIG. The process by this control method is corresponded to the process performed under control by the control part 50 of FIG. Note that this series of processing is executed in units of pixels in synchronization with the scan cycle.

  Here, as an example, as shown in FIG. 16, when the initial temperature of the organic EL element 21 is 30 ° C., the relative luminance of the high luminance display pixel (A) is La (= 1.0), and the low luminance. The relative luminance of the display pixel (B) is set to Lb (= 1.0), and the temperature of the high luminance display pixel in the display state after the elapse of a predetermined driving period t rises to 60 ° C., and the high luminance at this time The relative luminance of the display pixel deteriorates by 6% from the initial value La (ΔLa = La × 6%), the temperature of the low luminance display pixel rises to 45 ° C., and the relative luminance of the low luminance display pixel at this time is the initial value. The brightness correction control in the case of 4% deterioration (ΔLa = La × 4%) as compared with Lb will be described as an example.

  Note that the control method is the same for both still images and moving images, and therefore, here, a description will be given of common control for still images / moving images.

  First, a digital video signal for image display is captured (step S11), the gradation value indicated by the signal level of the video signal is stored (step S12), and then the digital video signal is input to the display panel 18. (Step S13). Thereby, in the display panel 18, display driving of pixels is performed based on the digital input signal, and the organic EL elements 21 of the respective pixels 20 emit light.

  When the organic EL element 21 emits light, the corresponding light receiving element 19 receives the leaked light from the organic EL element 21, and outputs an electric signal corresponding to the amount of received light, that is, a voltage value corresponding to the light emission luminance. At the same time, the temperature detector 40 provided in the display panel 18 detects the temperature of the organic EL element 21 and outputs a voltage value corresponding to the detected temperature.

  Thus, when the display panel 18 is in the display driving state, a voltage value (luminance voltage value) corresponding to the light emission luminance output from the light receiving element 19 is captured (step S14), and this luminance voltage value is obtained in step S12. Divide by the stored gradation value (step S15), convert to digital data, and store (step S16).

  Next, for each of the high-luminance display pixel and the low-luminance display pixel, the deterioration of the light emission luminance during a predetermined driving period is detected based on the gradation value stored in step S12 (step S17).

  Note that the gradation value used for the division process in step S15 and the detection of the luminance degradation in step S17 is actually the amount of light received by the light receiving element 19 is equal to the amount of light emitted by the light emitting element 13. It is about 20%, and in order to correspond to the voltage value from the light receiving element 19, 20% division processing is performed.

  Next, a voltage value (temperature voltage value) corresponding to the temperature of the pixel 20 including the organic EL element 21 output from the temperature detection unit 40 is captured (step S18), and a temperature change is detected for each pixel (step S19). ).

  In addition, each process of steps S14 to S17 for detecting the luminance change amount for each of the high luminance display pixel and the low luminance display pixel, and each process of steps S18 and S19 for detecting the temperature change amount for each pixel. The processing order may be reversed, and both detection processes may be performed in parallel.

  Next, based on the numerical correlation data table indicating the correspondence between the brightness and the temperature, the temperature change of each pixel is converted into the brightness deterioration for each of the high brightness display pixel and the low brightness display pixel detected in step S17. Normalized (converted) to the corresponding voltage value (relative luminance degradation of the high luminance display pixel) ΔLa and voltage value (relative luminance degradation of the low luminance display pixel) ΔLb corresponding to the temperature change of the low luminance display pixel. (Step S20).

  Here, when the relative luminance deterioration of the high luminance display pixel due to the temperature change from 30 ° C. to 60 ° C. after the elapse of the predetermined driving period t is 6%, the relative luminance deterioration ΔLa of the high luminance display pixel is For example, when the relative luminance deterioration of the low-luminance display pixel is 4%, which is normalized to a voltage value of 4.8 V and the temperature change from 30 ° C. to 45 ° C. after a predetermined driving period has elapsed, It is assumed that the relative luminance degradation ΔLb is standardized as a voltage value of 3.2 V, for example.

  Next, the relative luminance degradation ΔLa of the high luminance display pixel is divided by the relative luminance degradation ΔLa of the low luminance display pixel (step S21), and then the temperature difference ΔT between the high luminance display pixel and the low luminance display pixel is ΔT. Based on the temperature characteristic seizure correlation coefficient ΔLa / ΔLb, which is a division result when ≧ 15 ° C. (= 60 ° C.−45 ° C.), the correspondence between the temperature difference and seizure critical point shown in FIG. Then, the degree of occurrence of the image sticking phenomenon due to the difference in deterioration of the relative luminance due to temperature is determined (step S22).

  In this example, the temperature characteristic burn-in correlation coefficient ΔLa / ΔLb is ΔLa / ΔLb = 4.8 V / 3.2 V = 1.50. From the correspondence relationship in FIG. Since the temperature difference ΔT with respect to the display pixel is equal to or higher than the critical point (1.40) at which image sticking occurs when the temperature difference is 15 ° C., it is determined that the image sticking phenomenon occurs due to the difference in relative luminance degradation due to temperature. Then, a process for calculating the degree of occurrence of seizure phenomenon, that is, the difference between the temperature characteristic seizure correlation coefficient ΔLa / ΔLb and the seizure critical point is performed.

  Here, in order to reduce the temperature characteristic image sticking correlation coefficient ΔLa / ΔLb to less than 1.40, that is, to decrease it by a value exceeding 0.10, the relative luminance degradation amount ΔLb of the low-luminance display pixel is reduced to about It may be set to 3.43 V or higher, or the relative luminance degradation ΔLa of the high luminance display pixel may be set to about 4.48 V or lower.

  For this purpose, the signal level of the low luminance display pixel is amplified by about 0.23 V (= 3.43 V-3.2 V) or more, or the signal level of the high luminance display pixel is about 0.32 V (= 4.48 V-4). .8V) or more is selected.

  Such processing is executed in each processing step of steps S23 to S25. That is, the luminance correction value for keeping the temperature characteristic image sticking correlation coefficient ΔLa / ΔLb in the range of 1.0 to 1.4 (in the above example, 0.23 V / high luminance display pixel with respect to the low luminance display pixel). 0.32V) is calculated for each pixel (step S23), and then correction by signal level amplification is performed on the low luminance display pixel or correction by attenuation of the signal level on the high luminance display pixel (Step S24), and then, based on the selection result, the luminance correction is performed by performing amplification control or attenuation control on the signal level (luminance level) of each pixel of the digital video signal (step S25). ).

  Through the series of processes described above, the deterioration of relative luminance is detected for each of the high luminance display pixel and the low luminance display pixel, and the temperature difference ΔT between the high luminance display pixel and the low luminance display pixel is detected. The temperature correction is performed by converting the relative luminance deterioration amount ΔLa of the high luminance display pixel corresponding to the deterioration amount of the relative luminance for each display pixel and the relative luminance deterioration amount ΔLb of the low luminance display pixel. Luminance correction is performed so that the temperature characteristic image sticking correlation coefficient ΔLa / ΔLb, which is the result of dividing the obtained relative luminance deterioration ΔLa, ΔLb, is less than the critical point for image sticking.

  In this luminance correction control, control is performed such that the deterioration of relative luminance due to the temperature of the organic EL element 21 becomes constant. Therefore, the luminance correction control occurs due to the difference in deterioration of the relative luminance due to the temperature of the organic EL element 21. The seizure phenomenon can be suppressed. As a result, smooth image display can be realized.

  In the above embodiment, the organic EL display device 10 including the organic EL elements 21 that emit RGB colors has been described as an example. However, the present invention is not limited to this, and emits white light. The present invention can also be applied to an organic EL display device including a light emitting element.

  Further, in the above embodiment, the description has been made on the assumption that the light leakage amount of each of the organic EL elements 21 is uniformly monitored by the corresponding light receiving elements 38, but red light, green light, blue light or Since the light emission intensity (light emission brightness) differs for each light emitting element that emits white light, level control is performed for each emission color so that the relative levels are aligned, or the amount of light leakage is monitored. It is also possible to limit the types of luminescent colors to be limited by the initial setting.

  In the above embodiment, the pixel 20 has two transistors, that is, the drive transistor 22 and the write transistor 23, and has a circuit configuration that controls the light emission period of the organic EL element 21 by switching the potential DS of the power supply line 16. Although an example has been described, the present invention is not limited to this.

[Application example]
The organic EL display device 10 according to the present invention described above includes various electronic devices shown in FIGS. 17 to 21, for example, electronic devices such as digital cameras, notebook personal computers, mobile terminal devices such as mobile phones, and video cameras. The present invention can be applied to display devices for electronic devices in various fields that display video signals input to the video signal or video signals generated in the electronic device as images or videos. An example of an electronic device to which the present invention is applied will be described below.

  The organic EL display device according to the present invention includes a module-shaped one with a sealed configuration. For example, a display module formed by being attached to a facing portion such as transparent glass on the pixel array portion (display portion) is applicable. The transparent facing portion may be provided with a color filter, a protective film, and the like, and further, the above-described light shielding film. Note that the display module may be provided with a circuit unit for inputting / outputting a signal and the like from the outside to the pixel array unit, an FPC (flexible printed circuit), and the like.

  FIG. 17 is a perspective view showing a television to which the present invention is applied. The television according to this application example includes a video display screen unit 101 including a front panel 102, a filter glass 103, and the like, and is created by using the display device according to the present invention as the video display screen unit 101.

  18A and 18B are perspective views showing a digital camera to which the present invention is applied. FIG. 18A is a perspective view seen from the front side, and FIG. 18B is a perspective view seen from the back side. The digital camera according to this application example includes a light emitting unit 111 for flash, a display unit 112, a menu switch 113, a shutter button 114, and the like, and is manufactured by using the display device according to the present invention as the display unit 112.

  FIG. 19 is a perspective view showing a notebook personal computer to which the present invention is applied. A notebook personal computer according to this application example includes a main body 121 including a keyboard 122 that is operated when characters and the like are input, a display unit 123 that displays an image, and the like. It is produced by using.

  FIG. 20 is a perspective view showing a video camera to which the present invention is applied. The video camera according to this application example includes a main body 131, a lens 132 for shooting an object on a side facing forward, a start / stop switch 133 at the time of shooting, a display unit 134, and the like. It is manufactured by using such a display device.

  FIG. 21 is a perspective view showing a mobile terminal device to which the present invention is applied, for example, a mobile phone, in which (A) is a front view in an opened state, (B) is a side view thereof, and (C) is closed. (D) is a left side view, (E) is a right side view, (F) is a top view, and (G) is a bottom view. The mobile phone according to this application example includes an upper housing 141, a lower housing 142, a connecting portion (here, a hinge portion) 143, a display 144, a sub display 145, a picture light 146, a camera 147, and the like. And the sub display 145 is manufactured by using the display device according to the present invention.

It is a block diagram which shows the panel structure of the organic electroluminescence display which concerns on one Embodiment of this invention. 3 is a circuit diagram illustrating a specific configuration example of a pixel (pixel circuit) 20. FIG. It is a timing chart with which it uses for operation | movement description of the organic electroluminescence display which concerns on one Embodiment of this invention. It is principal part sectional drawing which shows the outline of the panel structure of a top emission type organic electroluminescence display. It is a top view which shows the positional relationship of an organic EL element and a light receiving element. It is principal part sectional drawing which shows the outline of the panel structure of a bottom emission type organic electroluminescence display. It is a figure which shows the temperature dependence of the generation electric current-applied voltage characteristic and light emission brightness-applied voltage characteristic of an organic EL element. It is a figure which shows the relationship between the temperature variation (DELTA) T of an organic EL element, and voltage shift amount (DELTA) V. It is a circuit diagram which shows the circuit example of the temperature detection part in the case of arrange | positioning in a pixel. It is a circuit diagram which shows the circuit example of the temperature detection part in the case of arrange | positioning outside a display area. It is a block diagram which shows an example of a structure of a control part. It is a figure which shows the difference of deterioration of the relative luminance by the temperature cause in a high-intensity display pixel (A) and a low-intensity display pixel (B). It is explanatory drawing about the correspondence of temperature change (temperature difference) (DELTA) T and a seizure critical point. It is a block diagram which shows an example of a structure of a still image determination part. It is a flowchart which shows the process sequence of the control method of the organic electroluminescent display apparatus by this invention. It is a figure which shows the relative luminance degradation amount of a high-intensity display pixel and a low-intensity display pixel. It is a perspective view which shows the television to which this invention is applied. It is the perspective view which shows the digital camera to which this invention is applied, (A) is the perspective view seen from the front side, (B) is the perspective view seen from the back side. 1 is a perspective view showing a notebook personal computer to which the present invention is applied. It is a perspective view which shows the video camera to which this invention is applied. It is a perspective view showing a cellular phone to which the present invention is applied, (A) is a front view in an open state, (B) is a side view thereof, (C) is a front view in a closed state, (D) Is a left side view, (E) is a right side view, (F) is a top view, and (G) is a bottom view. It is a figure which shows the luminance degradation by the temperature origin of an organic EL element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10, 10A, 10B ... Organic EL display device, 11 ... Pixel array part, 12 ... Write scanning circuit, 13 ... Power supply scanning circuit, 14 ... Horizontal drive circuit, 15-1 to 15-m ... Scanning line, 16-1 -16-m: power supply line, 17-1 to 17-n: signal line, 18: display panel (panel module), 20: pixel, 21,411: organic EL element, 22: drive transistor, 23: write transistor , 24 ... holding capacity, 25 ... auxiliary capacity, 31 ... support substrate, 32 ... counter substrate, 33 ... element isolation insulating layer, 34 ... lower electrode, 35 ... organic layer, 36 ... upper electrode, 37 ... transparent material film, 38 Light receiving element 40, 40A, 40B Temperature detection unit 41 Temperature information detection unit 42, 43 Level adjustment unit 50 Control unit 501, Level control unit 502 Relative level adjustment unit 503, 5 6, 510 ... memory unit, 504 ... division unit, 505, 509 ... A / D conversion unit, 507 ... multiplication unit, 508 ... relative luminance degradation detection unit, 511 ... temperature change detection unit, 512 ... data normalization processing unit, 513: Voltage division calculation unit, 514 ... Voltage division result comparison calculation unit, 515 ... Voltage division ratio control unit, 516 ... Calculation selection control unit

Claims (7)

A pixel array unit in which a plurality of pixels including an organic EL element formed between a pair of substrates are disposed;
A light receiving element group disposed on one of the pair of substrates corresponding to each of the organic EL elements, and detecting and photoelectrically converting leakage light of the organic EL elements;
A relative luminance deterioration detection unit that detects a deterioration in relative luminance of the organic EL element based on an input signal to the organic EL element and a detection signal of each light receiving element of the light receiving element group;
A temperature detection unit that detects a temperature of the organic EL element based on a generated current-applied voltage characteristic of the detection element using a detection element made of the same element as the organic EL element;
The amount of luminance deterioration due to the temperature of the organic EL element is made constant by reflecting the amount of deterioration of the relative luminance detected by the relative luminance deterioration detection unit in the detection result of the temperature detection unit. An organic EL display device comprising: a control unit that controls emission luminance. The organic EL display device according to claim 1, wherein the temperature detection unit is disposed in each of the pixels. The organic EL display device according to claim 2, wherein the temperature detection unit is disposed in a peripheral portion of the pixel array unit. The controller is
Based on the detection signal of each light receiving element of the light receiving element group, the high luminance display pixel and the low luminance display pixel are identified, and the relative luminance in a predetermined driving period is determined for each of the high luminance display pixel and the low luminance display pixel. A relative luminance deterioration detection unit for detecting deterioration,
A temperature change detection unit for detecting a temperature change in a predetermined period of each organic EL element based on a detection signal of the temperature detection unit;
The relative luminance degradation for each of the high luminance display pixel and the low luminance display pixel detected by the relative luminance degradation detection unit with respect to the temperature variation for each of the organic EL elements detected by the temperature variation detection unit. And a standardization processing unit that reflects
2. The organic EL device according to claim 1, wherein the light emission luminance of the organic EL element is controlled based on a processing result of the normalization processing unit so that a luminance deterioration amount due to temperature of the organic EL device becomes constant. Display device. The controller is
The normalization processing unit uses the first voltage value corresponding to the temperature change reflecting the luminance change of the high luminance display pixel as the temperature change corresponding to the luminance change of the low luminance display pixel. A division operation unit for dividing by the second voltage value;
A comparison operation unit that compares the division result of the division operation unit with a predetermined reference value;
A division ratio control unit that calculates a luminance correction value based on a comparison result of the comparison operation unit;
The display device according to claim 4, further comprising: a level control unit that controls a signal level of the input signal based on a luminance correction value of each of the organic EL elements calculated by the division ratio control unit. A method for controlling an organic EL display device in which a plurality of pixels including an organic EL element formed between a pair of substrates are arranged,
A leakage light detection step of detecting leakage light of the organic EL element by each light receiving element of the light receiving element group arranged corresponding to each of the organic EL elements on one of the pair of substrates;
A relative luminance deterioration detecting step for detecting a deterioration in relative luminance of the organic EL element based on an input signal to the organic EL element and a detection signal of each light receiving element of the light receiving element group;
A temperature detection step of detecting a temperature of the organic EL element based on a generated current-applied voltage characteristic of the detection element using a detection element made of the same element as the organic EL element;
The organic EL element so that the amount of luminance deterioration due to the temperature of the organic EL element is constant by reflecting the amount of deterioration of the relative luminance detected in the relative luminance deterioration detecting step with respect to the detection result in the temperature detecting step. And a control step for controlling the light emission luminance of the organic EL display device. A pixel array unit in which a plurality of pixels including an organic EL element formed between a pair of substrates are disposed;
A light receiving element group disposed on one of the pair of substrates corresponding to each of the organic EL elements, and detecting and photoelectrically converting leakage light of the organic EL elements;
A relative luminance deterioration detection unit that detects a deterioration in relative luminance of the organic EL element based on an input signal to the organic EL element and a detection signal of each light receiving element of the light receiving element group;
A temperature detection unit that detects a temperature of the organic EL element based on a generated current-applied voltage characteristic of the detection element using a detection element made of the same element as the organic EL element;
The amount of luminance deterioration due to the temperature of the organic EL element is made constant by reflecting the amount of deterioration of the relative luminance detected by the relative luminance deterioration detection unit in the detection result of the temperature detection unit. An electronic apparatus comprising: an organic EL display device including a control unit that controls light emission luminance.

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