JP4613963B2 - Organic EL display device - Google Patents

Description

  The present invention relates to an organic EL display device using an electroluminescent (hereinafter, referred to as organic EL) element of an organic material as a light emitting element (electro-optical element) of a light emitting pixel.

  The organic EL element is a self-luminous light emitting element capable of obtaining a luminance of several hundred nits with a driving voltage of 10 V or less. An organic EL display device using the organic EL element as a light emitting element of a light emitting pixel has no viewing angle dependency and a high contrast ratio, and has a moving image display performance compared to a hold type display typified by a liquid crystal display device. Due to its excellent features, it is promising as a future flat panel display.

  However, a light-emitting element typified by an organic EL element has problems that device characteristics change or power consumption increases when it is continuously driven at a high voltage or a large current for high luminance. In general, in an organic EL display device, since pixels are usually driven under a certain condition, the light emission luminance and the contrast depend on the characteristics of the organic EL element. Similarly, the current power consumption depends on the characteristics of the organic EL element. Under these circumstances, in organic EL display devices, as with a display using a cathode ray tube, it is possible to cause the pixels to always emit light with sufficient brightness, resulting in a temperature increase due to changes in characteristics of the organic EL elements and an increase in power consumption. It is also difficult from the point of view.

  However, in an organic EL display device, it is possible to reproduce a relatively dark signal such as a movie without impairing the image quality because of its linear gradation characteristics and fast response speed. It is considered to be very important to control the luminance of the display according to the environment. For this reason, various technologies have been proposed in which the brightness of the surroundings is detected by a light receiving element and the light emission luminance is controlled by changing the drive voltage of the organic EL element according to the detection result (for example, Patent Document 1). , 2).

Japanese Patent Laid-Open No. 1-110077 JP 2002-062856 A

  However, all of the above prior arts employ a configuration in which a dedicated light-receiving element such as a phototransistor is provided outside the panel in order to detect ambient brightness, which increases costs by increasing the number of parts. For example, in the case of brightness detection with a phototransistor, brightness detection is performed by one point, and the position where brightness can be detected with respect to the display area of the surface is biased. There is a problem that it is difficult to accurately detect the ambient brightness environment.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an organic EL display device capable of accurately controlling the light emission luminance in accordance with the surrounding brightness environment. is there.

  In order to achieve the above object, in the present invention, in an organic EL display device having a display pixel region in which light-emitting pixels including organic EL elements are arranged in a matrix, brightness around the display pixel region is detected. As a light receiving element for this purpose, an organic EL element in a light receiving pixel region arranged in a matrix around the display pixel region on the same substrate as the display pixel region is used, or a matrix shape is used. The organic EL element of the second display pixel region or the organic EL element of the display pixel region that is arranged on the display and performs a specific image display, and based on the detection output of the organic EL element, the organic EL element of the display pixel region While controlling the light emission luminance, the organic EL element in the light receiving pixel region or the organic EL element in the second display pixel region is processed in the same process as the organic EL element in the display pixel region. It adopts a configuration to create in.

  In the organic EL display device having the above-described configuration, the same organic EL element as the light emitting pixel in the display pixel region functions as a light receiving element for detecting the brightness around the display pixel region. Even if no element is provided separately, ambient brightness can be detected, and luminance control of the light-emitting pixels can be performed based on the detection output. In addition, no special process is required even when the EL element is configured by a vapor deposition process. Therefore, the organic EL element in the light receiving pixel area or the organic EL element in the second display pixel area for performing a specific image display can be created in the same process as the organic EL element in the display pixel area.

  According to the present invention, in an organic EL display device having a display pixel area in which light emitting pixels including organic EL elements are arranged in a matrix, as a light receiving element for detecting the brightness around the display pixel area, A large number of organic EL elements in a light receiving pixel area arranged in a matrix around the display pixel area on the same substrate as the display pixel area or a specific image arranged in a matrix. By using the organic EL element in the second display pixel region for display or the organic EL element in the display pixel region, the ambient brightness can be detected without providing a separate light receiving element such as a phototransistor. It is possible to control the luminance of the light-emitting pixels based on the detection output, and even when an EL element is configured by a vapor deposition process, a special process is required. The organic EL device in the light-receiving pixel region or the organic EL element of the second display pixel area for a particular image display, can be created in an organic EL device in the same process of the display pixel area.

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

[First Embodiment]
FIG. 1 is a front view showing an outline of the configuration of the organic EL display device according to the first embodiment of the present invention. As is clear from FIG. 1, the organic EL display device according to the present embodiment has a display pixel area 11 that performs image display on the front side thereof, and brightness around the display pixel area 11, that is, the display pixel area 11. The configuration includes a light receiving pixel area 12 for detecting illuminance and a batch area 13 for displaying a mark such as a brand name or a manufacturer name (“DISPLAY” in this example).

  The display pixel region 11 has a configuration in which scanning lines and data lines are arranged in a matrix, and light emitting pixels including organic EL elements are arranged at intersections thereof. The light emitting pixel has a configuration in which, for example, a polysilicon thin film transistor (TFT) is used as an active element, and an organic EL element is formed on a substrate on which the thin film transistor is formed. FIG. 2 shows an example of the circuit configuration of the light emitting pixel.

  As is apparent from FIG. 2, the light emitting pixel circuit has an organic EL element 21 whose anode is connected to, for example, the ground (GND), a drain connected to the cathode of the organic EL element 21, and a source connected to, for example, the negative power supply Vss. The TFT 22, the capacitor 23 connected between the gate of the TFT 22 and the negative power source Vss, the TFT 24 whose gate is connected to the scanning line 27, the drain is connected to the data line 28, and the drain is the source of the TFT 24, A configuration having a TFT 25 having a source connected to the negative power source Vss, a gate connected to the gate of the TFT 22, a drain connected to the drain of the TFT 25, a gate connected to the control line 29, and a source connected to the gate of the TFT 22. It has become.

  The light-emitting pixel circuit having the above configuration is a current writing type pixel circuit in which luminance information is written in the form of current. That is, luminance information is written as current through the data line 28 in the state where the scanning line 27 is selected. This current luminance information is taken into the pixel circuit by the TFT 24, converted into voltage luminance information by the TFT 25, and held in the capacitor 23.

  The TFT 22 converts the voltage luminance information held in the capacitor 23 into a current, and passes this current (drive current) through the organic EL element 21 to drive the organic EL element 21 to emit light. As a result, the organic EL element 21 emits light with luminance according to the written current luminance information. The written luminance information is held in the capacitor 23 even after the scanning line 27 is not selected. Therefore, the organic EL element 21 continues to emit light at a luminance corresponding to the held voltage luminance information.

  In this light emission state, when a light emission time control signal is given to the gate of the TFT 26 through the control line 29, the TFT 26 is turned on in response thereto. As a result, the voltage luminance information (charge) held in the capacitor 23 is discharged through the TFT 26. When the gate-source potential of the TFT 22 falls below the threshold value, the TFT 22 is turned off and supply of the drive current to the organic EL element 21 is stopped. As a result, the organic EL element 21 in the light emitting state shifts to the non-light emitting state. That is, the TFT 26 controls the light emission time of the organic EL element 21 by turning on / off according to the light emission time control signal given through the control line 29.

  Note that FIG. 2 merely shows an example of the light emitting pixel circuit, and the present invention is not limited to this. That is, the light emitting pixel circuit may be a current writing type pixel circuit having another circuit configuration, and is not limited to the current writing type, and a voltage writing type pixel circuit in which luminance information is written in the form of voltage is used. Is also possible.

  FIG. 3 is a cross-sectional view showing an example of the structure of the organic EL element. As can be seen from FIG. 3, the organic EL element has a first electrode (for example, an anode) 32 made of a transparent conductive film formed on a substrate 31 made of transparent glass or the like, and further has a hole transport layer thereon. 33, a light emitting layer 34, an electron transport layer 35, and an electron injection layer 36 are sequentially deposited to form an organic layer 37, and then a second electrode (for example, cathode) 38 made of metal is formed on the organic layer 37. It has become the composition. In the organic EL element 21 having such a configuration, by applying a DC voltage E between the first electrode 32 and the second electrode 38, light is emitted when electrons and holes are recombined in the light emitting layer 34. It has become.

  In FIG. 1 again, the light receiving pixel region 12 includes an organic EL element (not shown) having the same structure as the organic EL element 21 constituting the light emitting pixel around the display pixel region 11. Are arranged at a suitable interval. Here, the display pixel region 11 and the light-receiving pixel region 12 that are both formed of organic EL elements are formed simultaneously. As an example, the light emitting pixel and the light receiving pixel are simultaneously deposited by a CVD (Chemical Vapor Deposition) method. Similarly to the formation of the pixels, with respect to the protective glass 14 that protects the display pixel region 11, the light-emitting pixels and the light-receiving pixels can be bonded together using the same glass.

  The light receiving pixel region 12 has a detection circuit wiring independent of the display pixel region 11. Unlike the light emitting pixels, the light receiving pixels do not need to be driven by arranging three colors of R (red), G (green), and B (blue) in a matrix. However, in consideration of the manufacturing process, it is preferable that the light receiving pixel region 12 is also arranged in a matrix arrangement so as to be shared with the display pixel region 11. Further, the light receiving pixel region 12 is preferably as wide as possible in order to obtain sufficient detection sensitivity with respect to the brightness environment around the display pixel region 11.

  FIG. 4 shows an example of the circuit configuration of the light receiving pixel. As is clear from FIG. 4, the light receiving pixel circuit has an organic EL element 41, a detection resistor R11, a current detection amplifier 42, a detection resistor R12, an AD converter 43, and a light emission time setting circuit 44. For example, the organic EL element 41 is connected in series with the detection resistor R11 between the ground and the positive power supply Vdd and functions as a light receiving element. When the organic EL element 41 receives ambient light (light), a detection current Id corresponding to the amount of ambient light flows through the organic EL element 41 and the detection resistor R11.

  The current detection amplifier 42 has resistors R13 and R14 each having one end connected to both ends of the detection resistor R11, and a non-inverting (+) input terminal and an inverting (−) input terminal at each other end of the resistors R13 and R14. Each operational amplifier OP is connected to each other, and a bipolar transistor Q having a base connected to the output terminal of the operational amplifier OP and a collector connected to the non-inverting input terminal is provided. The detection resistor R12 is connected between the emitter of the transistor Q and the ground.

  In the circuit example of FIG. 4, the case where the number of the organic EL elements 41 is one is described as an example. However, actually, a large number of organic EL elements are arranged in the light receiving pixel region 12. Therefore, for these many organic EL elements, all the anodes may be commonly connected to the ground, and all the cathodes may be commonly connected to the detection resistor R11. Thereby, the average value of the brightness detected by a large number of organic EL elements can be detected by the detection resistor R11.

  Here, a specific configuration example of the light receiving pixel region 12 will be described. When the size of the display pixel area 11 (display size) is, for example, 15 inches, the light receiving pixel area 12 is, for example, 1 cm around the display pixel area 11. As the light receiving element (organic EL element) material, ITO (200 nm) is used for the anode electrode, CuPc (15 nm), α-NPD (45 nm), Alq3 (50 nm) is used for the organic material, and MgAg (100 nm) is used for the cathode electrode.

This is an example in which the same conditions are set as in the case where the organic EL element in the display pixel region 11 is created. In the light receiving element (organic EL element) formed under these conditions, the detection current Id in the dark place is almost zero, whereas the bias voltage is 7 V under general fluorescent lamp illumination (approximately 250 lux). The inventors of the present application have confirmed that a characteristic of 42 mA / m ² can be obtained.

Here, there is formed a light-receiving pixel region 12 by the respective outer circumference of 15 Display 1 cm, since the area of the light-receiving pixel region 12 at this time is ^{0.0114m 2, 42mA / m 2 ×} 0.0114m 2 = A detection current Id of 0.479 mA, that is, about 0.5 mA flows through the organic EL element 41 and the detection resistor R11. Therefore, if the resistance value of the detection resistor R11 is set to, for example, 100Ω and the current detection amplifier 42 is set to about 20 times, a detection current Id of about 0.5 mA can be obtained as a detection voltage Vd of about 1V by the detection resistor R12.

  This detection voltage Vd is converted into, for example, 4-bit digital data by the AD converter 43. Here, a case where 4-bit AD conversion is performed is described as an example, but it is not limited to 4-bit. A larger number of bits enables finer control, so a larger number is desirable. The digitized data is given to the light emission time setting circuit 44.

  The light emission time setting circuit 44 has, for example, a correspondence table between the detection voltage Vd and the light emission time of the light emitting pixel as a reference table (LUT), and the digital corresponding to the detection voltage Vd supplied from the AD converter 43 according to the reference table. The light emission time of the light emitting pixel (organic EL element 21) in one field period is determined from the data. This light emission time control can be realized by turning on / off the TFT 26 through the control line 29 in FIG. 2 by a light emission time control signal in which the light emission time is set for each field period by the light emission time setting circuit 44.

As an actual value of the light emission time, when the refresh rate is a signal of 60 Hz, when the organic EL element 21 emits light for the entire time of one field, it is about 16.67 ms, which is 100%. Further, the organic EL element 21 at this time is designed so that a light emission luminance of about 300 cd / m ² can be obtained with a light emission time of 50% at a constant current value.

Here, when the periphery of the display pixel region 11 is dark and the detection current Id by the organic EL element 41 as a light receiving element is small, the light emission time setting circuit 44 determines the light emission time of the light emitting pixel (organic EL element 21) according to the reference table. The length is set short, for example, 25% as shown in FIG. Thereby, the maximum luminance of the display is controlled to 150 cd / m ^2, and the brightness of the display screen is limited, so that a display image can be viewed with appropriate brightness even in a dark environment.

On the contrary, when the periphery of the display pixel region 11 is bright and the detection current Id by the organic EL element 41 is large, the light emission time setting circuit 44 sets the light emission time of the light emitting pixel (organic EL element 21) long according to the reference table. As shown in FIG. 5A, for example, 50%. As a result, the maximum brightness of this display is controlled to 300 cd / m ^2, and the display emits light at twice the brightness as compared to the brightness in the dark environment, so that the display image can be viewed with the optimum brightness even in the bright environment. Can do.

  Note that the control of the light emission time according to the brightness environment around the display pixel region 11 described above is merely an example, and the variable range of control can be set larger.

  As described above, in the organic EL display device according to the first embodiment, the same organic EL element as the light emitting pixel in the display pixel region 11 is used as the light receiving element for detecting the brightness around the display pixel region 11. As a result, brightness can be detected without providing a special light-receiving element such as a phototransistor, so that it is possible to display images optimally according to the ambient brightness environment at low cost and to deposit EL elements. Even when it is configured by a process, it can be created at the same time without requiring any special process.

  Then, by controlling the luminance of the light emitting pixels in the display pixel region 11 according to the surrounding brightness environment, the following effects can be obtained. First, it is possible to suppress a temperature rise due to wasteful power consumption and to minimize changes in characteristics of the light emitting pixels. In addition, considering personal use television in the bedroom, it is possible to set the light emission brightness with optimal control according to the brightness environment of each situation, whether watching at night or watching in the morning or noon. The image quality is not impaired. Furthermore, even in an in-vehicle display typified by car navigation, the same effect as that of a conventional liquid crystal display device controlling the light emission luminance by controlling the backlight can be easily realized by the organic EL display device. Become.

  Further, as described above, it is known that the organic EL element has a high response speed. By using the organic EL element with a high response speed as a light receiving element, a change in ambient brightness can be detected quickly. This can be reflected in the control of the light emission luminance of the organic EL element 21. In particular, since a large number of organic EL elements 41 in the light receiving pixel region 12 are arranged around the display pixel region 11, the ambient brightness received by the display screen can be accurately detected. More accurate brightness control according to the environment can be realized.

  In the above embodiment, the case where the light emission luminance according to the brightness around the display pixel region 11 is controlled by controlling the light emission time of the organic EL element 21 has been described as an example. Since the brightness of the organic EL element 21 is a function of input data, the light emission brightness of the organic EL element 21 is also controlled by controlling the drive current of the organic EL element 21 as described above. It is possible to control.

  However, it is preferable to control the light emission time of the organic EL element 21, more specifically, in the active matrix type, by controlling the time during which one pixel emits light during one field period and adjusting the light emission luminance, contrast and gradation There is an advantage that light emission luminance can be adjusted without degrading image quality performance such as performance.

  In the above embodiment, it is assumed that ambient brightness detection and emission luminance control are always performed, and emission luminance is linearly controlled according to the ambient brightness. For example, it is represented by car navigation. As described above, the control method of switching to several stages including the two-stage switching between the day mode and the night mode is an effective method depending on the application. These switching operations may be performed by the light emission time setting circuit 44 of FIG.

[Second Embodiment]
FIG. 6 is a front view showing an outline of the configuration of the organic EL display device according to the second embodiment of the present invention. In FIG. 6, the same parts as those in FIG. As is clear from FIG. 6, the organic EL display device according to the present embodiment has a display pixel region 11 that performs image display and a frame 15 that holds the display pixel region on the front side thereof. Has a configuration in which a batch area 13 for displaying a mark such as a brand name and a manufacturer name (in this example, “DISPLAY”) is provided as a second display pixel area.

  As in the case of the first embodiment, the display pixel region 11 has a configuration in which scanning lines and data lines are arranged in a matrix and light emitting pixels including organic EL elements are arranged at intersections thereof. The frame portion of the batch area 13 is transparent, and characters are displayed by organic EL elements. The organic EL element in the batch area 13 functions as a light emitting element that displays an image of characters and the like, and also functions as a light receiving element. It is well known that an organic EL element also has a function as a light receiving element.

  The light emitting / receiving pixels in the batch area 13 are formed simultaneously with the light emitting pixels in the display pixel area 11. For example, the light emitting pixels in the display pixel region 11 and the light emitting / light receiving pixels in the batch region 13 are simultaneously deposited by the CVD method. In the batch area 13, the organic EL element has both functions of a light emitting element and a light receiving element, and therefore has circuit wiring independent of the display pixel area 11. Further, unlike the light emitting pixels in the display pixel region 11, the light emitting / receiving pixels in the batch region 13 do not need to be driven by arranging three colors of RGB in a matrix. However, when the character portion emits white light, it is necessary to drive by arranging three colors of RGB in a matrix like the light emitting pixels in the display pixel region 11.

  FIG. 7 is a circuit diagram showing an example of the circuit configuration of the light emitting / receiving pixels in the batch area 13. As is apparent from FIG. 7, the light emitting / receiving pixel circuit includes an organic EL element 51, a changeover switch 52 for switching the organic EL element 51 to function as a light emitting element or a light receiving element, and an organic EL element. A configuration having a pixel drive circuit 53 that drives the light emitting element 51 when it functions as a light emitting element, and a detection circuit 54 that detects a current Id that flows through the organic EL element 51 when the organic EL element 51 functions as a light receiving element; It has become.

  In this circuit example, the case where there is one organic EL element 51 is taken as an example, but in reality, a large number of organic EL elements are arranged in the batch area 13 according to the characters to be displayed, and the character portion When light is emitted in white, the number of organic EL elements is further increased. Therefore, for these many organic EL elements, all the anodes may be commonly connected to the ground, and the fixed contact B side of the changeover switch 52 may be commonly connected.

  The pixel drive circuit 53 includes a drive transistor TFT connected between the negative power source Vss and one fixed contact A of the changeover switch 52, a resistor R21 connected between the negative power source Vss and the gate of the transistor TFT, The capacitor C is connected in parallel with the resistor R21, and the resistor R22 is connected between the gate of the transistor TFT and the ground.

  The detection circuit 54 has the same configuration as the light receiving pixel circuit (see FIG. 4) of the first embodiment. However, the end of the detection resistor R11 on the ground side is connected to the other fixed contact B of the changeover switch 52.

  Next, the circuit operation of the light emitting / receiving pixel circuit having the above configuration will be described. When the organic EL element 51 is normally used for light emission, that is, when characters are displayed by the organic EL element 51 in the batch region 13, the changeover switch 52 is switched to the fixed contact A side, and the constant current source When the organic EL element 51 is driven with a constant current (normal light emission current In) by the pixel driving circuit 53 comprising the above, the organic EL element 51 is in a light emitting state.

  When the display is turned on or when it is desired to detect ambient brightness intentionally, the changeover switch 52 is switched to the fixed contact B side. This switching may be performed manually or automatically. When the ambient brightness is constantly monitored, the AD converter 43, the light emission time setting circuit 44, and the vertical scanning timing of the display are synchronized with each other for a time of several tens of μs, that is, not visually recognizable. By switching the changeover switch 52 quickly, it is possible to always detect ambient brightness.

  The current at the time of detection flows through the detection resistor R11 as the brightness detection current Id. The subsequent detection operation is the same as that of the light receiving pixel circuit of the first embodiment. That is, the brightness detection current Id is amplified by the current detection amplifier 42, and thus appears as a detection voltage Vd at both ends of the detection resistor R12. This detection voltage Vd is converted into, for example, 4-bit digital data by the AD converter 43. The light emission time setting circuit 44 determines the light emission time of the light emitting pixels (organic EL element 21) in one field from the digital data corresponding to the detection voltage Vd supplied from the AD converter 43 according to the reference table (LUT).

Here, when the periphery of the display pixel region 11 is dark and the detection current Id by the organic EL element 51 as the light receiving element is small, the light emission time setting circuit 44 determines the light emission time of the light emitting pixel (organic EL element 21) according to the reference table. Set short, for example, 25%. Thereby, the maximum luminance of the display is controlled to 150 cd / m ^2, and the brightness of the display screen is limited, so that a display image can be viewed with appropriate brightness even in a dark environment.

On the contrary, when the periphery of the display pixel region 11 is bright and the detection current Id by the organic EL element 51 is large, the light emission time setting circuit 44 sets the light emission time of the light emitting pixel (organic EL element 21) long according to the reference table. For example, 50%. As a result, the maximum brightness of this display is controlled to 300 cd / m ^2, and the display emits light at twice the brightness as compared to the brightness in the dark environment, so that the display image can be viewed with the optimum brightness even in the bright environment. Can do.

  Note that the control of the light emission time according to the brightness environment around the display pixel region 11 described above is merely an example, and the variable range of control can be set larger.

  As described above, in the organic EL display device according to the second embodiment, in addition to the effects of the organic EL display device according to the first embodiment, the organic EL elements in the batch region 13 are arranged around the display pixel region 11. In addition, since it is not necessary to provide a dedicated light receiving pixel region, it is possible to detect the surrounding brightness without any special restriction on the appearance of the display.

[Third Embodiment]
The organic EL display device according to the third embodiment of the present invention has the same basic external configuration as the organic EL display device according to the second embodiment (see FIG. 6). The difference is that in the organic EL display device according to the second embodiment, the organic EL elements in the batch region 13 are also used as light receiving elements for detecting the ambient brightness, whereas the third embodiment In the organic EL display device according to the above, the light emitting pixels in the display pixel region 11 are also used as light receiving elements for detecting the surrounding brightness.

  In the organic EL display device according to the present embodiment, the driving of the organic EL element (corresponding to the organic EL element 21 in FIG. 2) in the display pixel region 11 is switched between light emission and light reception within the vertical scanning timing. The organic EL element as a light emitting element has a function as a light receiving element. Specifically, in an active matrix organic EL display device that determines light emission luminance by controlling the light emission time in one field period, the light emission time is set to 25% to 50% as shown in the timing chart of FIG. Since it is common to do this, the non-light emitting time is assigned to the light receiving period. In this case, a period of 75% to 50% can be secured as the light receiving period, and the organic EL element is excellent in responsiveness, so that ambient brightness can be reliably detected.

  FIG. 8 is a circuit diagram showing an example of the circuit configuration of the light emitting / receiving pixels when the organic EL element in the display pixel region 11 is also used as a light receiving element. One or more light emitting / receiving pixel circuits according to this configuration example are provided for each of the three RGB colors.

  Specifically, the R (red) light emission / light reception pixel circuit includes an organic EL element 61R, a changeover switch 62R that switches between the organic EL element 61R and the organic EL element 61R. A pixel driving circuit 63R that drives the EL element 61R according to an input signal when it functions as a light emitting element, and a detection that detects a current Id that flows through the organic EL element 61R when the organic EL element 61R functions as a light receiving element. The circuit 64R is included.

  Similarly, the G (green) light emitting / receiving pixel circuit has an organic EL element 61G, a changeover switch 62G, a pixel driving circuit 63G, and a detection circuit 64G, and the B (blue) emitting / receiving pixel circuit is also organic. An EL element 61B, a changeover switch 62B, a pixel drive circuit 63B, and a detection circuit 64B are provided. Since a large number of organic EL elements are arranged for each of RGB in the display pixel region 11, all the anodes are commonly connected to the ground for the large number of organic EL elements, and a changeover switch is used. What is necessary is just to connect the 52 fixed contact B side in common.

  The changeover switches 62R, 62G, and 62B are switched to the fixed contact A side when the light emission time control signal is active, and are switched to the fixed contact B side when the light emission time control signal is inactive. As the pixel drive circuits 63R, 63G, and 63B, those having the same configuration as the pixel circuit of the first embodiment (see FIG. 2) are used. Further, as the detection circuits 64R, 64G, and 64B, those having the same configuration as the light receiving pixel circuit (see FIG. 4) of the first embodiment are used. However, in the detection circuits 64R, 64G, and 64B, the detection resistor R11, the current detection amplifier 42, the detection resistor R12, and the AD converter 43 are provided for each color, but the light emission time setting circuit 44 is provided for each color in common. Will be.

  Next, the circuit operation of the light emitting / receiving pixel circuit having the above configuration will be described. First, when the light emission time control signal is active, the changeover switches 62R, 62G, and 62B are switched to the fixed contact A side. Accordingly, the pixel drive circuits 63R, 63G, and 63B drive the organic EL elements 61R, 61G, and 61B to emit light according to the input data (luminance data). At this time, the light emission time in one field period of the organic EL elements 61R, 61G, and 61B is generally set to 25% to 50% as is apparent from the timing chart of FIG.

  Next, when the light emission time control signal is inactive, that is, when the pixel is in a non-light emission state, the changeover switches 62R, 62G, and 62B are switched to the fixed contact B side. Accordingly, the organic EL elements 61R, 61G, and 61B that have functioned as light emitting elements so far function as light receiving elements. Then, for all pixels for each color, currents IdR, IdG, and IdB flow to detection resistors R11R, R11G, and R11B for each color according to the ambient brightness.

  The subsequent detection operation is the same as that of the light receiving pixel circuit of the first embodiment. That is, the brightness detection currents IdR, IdG, and IdB for each color are amplified by the current detection amplifiers 42R, 42G, and 42B, and appear as detection voltages VdR, VdG, and VdB at both ends of the detection resistors R12R, R12G, and R12B. . These detection voltages VdR, VdG, VdB are converted into, for example, 4-bit digital data by the AD converters 43R, 43G, 43B and supplied to the light emission time setting circuit 44.

  In the light emission time setting circuit 44, calculation is performed in accordance with the characteristics of the organic EL elements 61R, 61G, and 61B for RGB. For example, as is apparent from the light reception characteristics of the organic EL element shown in FIG. 9, the light reception output level of the organic EL element is data of 1/2 for blue and 1/6 for green with respect to red. Therefore, the light reception data that is more averaged can be obtained by performing the calculation of double the blue light reception data and 6 times the green light reception data.

  In addition, in order to detect a general white level, the wavelength level to be detected can be matched by calculating so that R: G: B = 3: 6: 1. The light emission time setting circuit 44 determines the light emission time of the light emitting pixels (organic EL elements 61R, 61G, 61B) in one field period according to the reference table (LUT) based on the result obtained by the above calculation.

Here, when the periphery of the display pixel region 11 is dark and the detection currents IdR, IdG, and IdB due to the organic EL elements 61R, 61G, and 61B are small, the light emission time setting circuit 44 follows the reference table to determine the light emission pixels (organic EL elements 61R, 61R, 61G, 61B) is set to a short emission time, for example, 25%. Thereby, the maximum luminance of the display is controlled to 150 cd / m ^2, and the brightness of the display screen is limited, so that a display image can be viewed with appropriate brightness even in a dark environment.

On the other hand, when the periphery of the display pixel region 11 is bright and the detection currents IdR, IdG, and IdB due to the organic EL elements 61R, 61G, and 61B are large, the light emission time setting circuit 44 follows the reference table and the light emission pixels (organic EL elements 61R, 61R, 61G, 61B) is set to a long time, for example, 50%. As a result, the maximum brightness of this display is controlled to 300 cd / m ^2, and the display emits light at twice the brightness as compared to the brightness in the dark environment, so that the display image can be viewed with the optimum brightness even in the bright environment. Can do.

  Note that the control of the light emission time according to the brightness environment around the display pixel region 11 described above is merely an example, and the variable range of control can be set larger.

  As described above, in the organic EL display device according to the third embodiment, in addition to the function and effect of the organic EL display device according to the first embodiment, the organic EL element in the display pixel region 11 is replaced with the display in the display pixel region 11. Since it is also used as a light receiving element for detecting ambient brightness, it is not necessary to provide a special light receiving element outside the panel, so the light emission luminance can be controlled according to the ambient brightness condition without changing the appearance. In addition to being able to perform the measurement, it is possible to observe the brightness of the surroundings on average, unlike the observation using a single point such as a phototransistor.

  Further, since the R, G, and B organic EL elements have light receiving characteristics similar to the respective light emitting characteristics, the R, G, and B detected values are electrically corrected in accordance with the light receiving characteristics to emit light. By controlling brightness, it is possible to detect ambient brightness in a wide wavelength band without being affected by light of a specific wavelength, and to control stable emission brightness. It is possible to display a good image according to the brightness environment.

It is a front view which shows the outline of a structure of the organic electroluminescence display which concerns on 1st Embodiment of this invention. It is a circuit diagram which shows an example of the circuit structure of a light emission pixel. It is sectional drawing which shows an example of the structure of an organic EL element. It is a circuit diagram which shows an example of the circuit structure of the light reception pixel in the organic electroluminescence display which concerns on 1st Embodiment. It is a timing chart which shows the luminance control by light emission time. It is a front view which shows the outline of a structure of the organic electroluminescence display which concerns on 2nd Embodiment of this invention. It is a circuit diagram which shows an example of the circuit structure of the light emission / light reception pixel in the organic electroluminescence display which concerns on 2nd Embodiment. It is a circuit diagram which shows an example of the circuit structure of the light emission / light reception pixel in the organic electroluminescence display which concerns on 3rd Embodiment. It is a characteristic view which shows the light reception characteristic of each organic EL element of R, G, B.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Display pixel area | region, 12 ... Light-receiving pixel area | region, 13 ... Batch area | region, 14 ... Protective glass, 15 ... Frame, 21, 41, 51, 61R, 61G, 61B ... Organic EL element, 42, 42R, 42G, 42B ... Current detection amplifier, 43, 43R, 43G, 43B ... AD converter, 44 ... Light emission time setting circuit, 52, 52R, 52G, 52B ... Changeover switch, 53, 53R, 53G, 53B ... Pixel drive circuit, 54, 54R, 54G 54B ... Detection circuit

Claims (3)

A first display pixel region in which light-emitting pixels including organic EL elements are arranged in a matrix;
A second display pixel region which is formed on the same substrate as the first display pixel region and performs a specific image display by an organic EL element;
Switching means for causing the organic EL element in the second display pixel region to function as a light emitting element or a light receiving element;
Control means for controlling the light emission luminance of the organic EL element in the first display pixel area based on the light reception output of the organic EL element in the second display pixel area when functioning as a light receiving element by switching the switching means And
The organic EL elements in the second display pixel region are arranged in a matrix and are created in the same process as the organic EL elements in the first display pixel region ,
The switching means performs a switching operation in synchronization with the vertical scanning timing of the first display pixel region.
Organic EL display device. The control means controls a light emission time of the organic EL element in the first display pixel region.
The organic EL display device according to 請 Motomeko 1. The second display pixel area displays a mark including a brand name and a manufacturer name.
The organic EL display device according to claim 1.

Images