JP4367544B2 - Image display device - Google Patents

Description

  The present invention relates to an image display device capable of high-quality color display, and more particularly to an image display device capable of downsizing the device by downsizing the area of a pixel driving circuit.

Hereinafter, a conventional technique will be described with reference to FIG.
In recent years, research on so-called organic EL displays using organic EL (also known as OLED, Organic Light Emitting Diode) elements has been vigorously advanced. However, when this is made full color and gradation emission is made, the optical emission characteristics of each organic EL element corresponding to each RGB emission are different. Therefore, in order to obtain a predetermined luminance with a predetermined chromaticity, Each of the organic EL elements ideally needs an independent gradation driving current. Therefore, as in a conventional liquid crystal display drive circuit, when each RGB pixel is directly driven by a single drive circuit, problems such as the inability to obtain a desired color and difficulty in gradation control have occurred. It was.
FIG. 15 is a structural diagram of a simple matrix type organic EL display proposed to avoid such a problem.
Each organic EL element 202 connected to a plurality of data wirings 203 is provided in a matrix on the substrate 201, and each of the data wirings 203 has an organic EL element 202 with a different display color of RGB. Connected every time. One end of each data wiring 203 is connected to the extraction electrode 204 at the end of the substrate 201. An organic EL driving circuit 206 corresponding to each RGB color is connected to the extraction electrode 204 via a wiring rearrangement unit 205. Here, the wiring rearrangement means 205 is a multilayer wiring board configured using a resin multilayer build-up board, and the extraction electrodes 204 corresponding to each RGB color are connected to the organic EL driving circuit 206 corresponding to each RGB color. Have a role to play.
The operation of this conventional example will be briefly described below. Although not shown in the drawing, when a row of organic EL elements 202 to emit light is selected by a predetermined row scanning circuit, a display signal corresponding to the selected organic EL element is transmitted from the organic EL drive circuit 206 via the data wiring 203. Input to group 202. As a result, the organic EL element 202 in the selected row performs light emission display according to the display signal. The organic EL display displays an image by repeating the scanning of each row and the display signal input in this manner. In this conventional example, by introducing the wiring rearrangement means 205, each of the RGB organic EL elements 202 can be independently driven by the organic EL driving circuit 206 corresponding to each RGB color, thereby avoiding the above-mentioned problem. be able to. Such a conventional example is described in detail, for example, in Japanese Patent Laid-Open No. 2000-56732.

JP 2000-56732 A

  Currently, in the world of small- and medium-sized liquid crystal displays, a technique for integrally forming an analog signal driving circuit using a polycrystalline Si-TFT (Thin-Film-Transistor) on the same glass substrate as a pixel is being developed. This is because the cost of the analog signal drive circuit can be reduced and the seismic reliability of the display can be improved. In such a technique, the analog signal driving circuit includes a shift register, a latch circuit, a DA converter circuit, and the like. For details of this technique, for example, Proceedings of 2000 IEEE International Solid-State Circuits Conference (ISSCC 2000), pp.188-189.

  Now, in an organic EL display as well, if such an analog signal driving circuit using a polycrystalline Si-TFT can be integrally formed on the same glass substrate as a pixel, the cost can be reduced and the display can be reduced. It should be possible to improve seismic reliability. However, as described above in [Background Art], in an organic EL display, each organic EL element of each color ideally needs an independent gradation drive current. Therefore, if the analog signal driving circuit is configured on the glass substrate as in the above liquid crystal display, an independent analog signal driving circuit for RGB is required. As a result, the area of the analog signal drive circuit becomes three times that of the liquid crystal display even when the above-described wiring rearrangement means is used, and in view of the mounting area of the organic EL display, the display device can be downsized. It turns out to be an obstacle.

  In the above discussion, it is assumed that the analog signal driving circuit is integrally formed on the same glass substrate as the pixel using a polycrystalline Si-TFT. However, if the analog signal driving circuit is provided on the single crystal LSI, However, mounting three types of drive circuit LSIs on the display is clearly disadvantageous in terms of mounting area, and there are similar problems.

  The above problems can be solved by the following means.

    A display unit composed of two or more types of pixel groups having light emitting means of different main wavelengths, and an analog display signal generating means for generating an analog display signal for input to the pixel group using digital display data as an input; In an image display device having a display signal input means for inputting an analog display signal to a pixel group and a light emission drive means for driving the light emission means in each pixel according to the input analog display signal, the analog display signal Output digital display data that is not the same in correspondence with pixels having light emitting means of different main wavelengths with respect to the same digital display data, the number of output bits being larger than the number of input bits at the input part of the generation means Provide digital display data conversion means that can be converted into

  A display unit composed of two or more types of pixel groups having light emitting means of different main wavelengths, and an analog display signal generating means for generating an analog display signal for input to the pixel group using digital display data as an input; In an image display device having a display signal input means for inputting an analog display signal to the pixel group and a light emission drive means for driving the light emission means in each pixel according to the inputted analog display signal, an analog display is provided. The signal generating means is made to be able to output analog display signals that are not the same for the same digital display data, corresponding to pixels having light emitting means of different main wavelengths.

  A display unit composed of two or more types of pixel groups having light emitting means of different main wavelengths, and an analog display signal generating means for generating an analog display signal for input to the pixel group using digital display data as an input; In an image display device having in each pixel a display signal input means for inputting an analog display signal to the pixel group and a light emission drive means for driving the light emission means in accordance with the input analog display signal. The means corresponds to pixels having light emitting means having different main wavelengths with respect to the same analog display signal, so that the light emitting means can be driven with driving currents that are not the same.

  A display unit composed of two or more types of pixel groups having light emitting means of different main wavelengths, and an analog display signal generating means for generating an analog display signal for input to the pixel group using digital display data as an input; In an image display device having in each pixel a display signal input means for inputting an analog display signal to the pixel group and a light emission drive means for driving the light emission means in accordance with the input analog display signal. The means corresponds to a pixel having light emitting means of different main wavelengths so that the light emitting means can be driven in a driving period that is not the same.

  A display unit composed of two or more types of pixel groups having light emission means of different main wavelengths, an image signal processing means for generating digital display data, and a digital display data as an input for inputting to the pixel group Analog display signal generating means for generating an analog display signal, display signal input means for inputting the analog display signal to the pixel group, and light emission driving for driving the light emitting means in accordance with the input analog display signal In the image display device having the means in each pixel, the image signal processing means corresponds to a pixel having the number of bits larger than the number of input bits and having light emitting means having different main wavelengths for the same digital display data. To convert the output digital display data that are not identical to each other.

According to the present invention, it is possible to provide a more compact image display apparatus that can reduce the mounting area of the organic EL display while enabling desired color display and gradation control.

(First embodiment)
The first embodiment of the present invention will be described below with reference to FIGS.
First, the overall configuration of the present embodiment will be described with reference to FIG.

FIG. 1 is a configuration diagram of an organic EL display panel according to this embodiment. Pixels 2 each having RGB organic EL elements as pixel light emitters are arranged in a matrix on the display unit, and the pixels 2 are connected to each other via gate lines 7, signal lines 3, power supply lines 9, and the like. Yes. The gate line 7 extending in the row direction is connected to the shift register 8, the signal line 3 extending in the column direction is connected to the analog signal driving circuit 6, and the pixel 2, the shift register 8, and the analog signal driving circuit 6 are connected to the glass substrate 1. It is formed using polycrystalline Si TFT. The digital signal input terminal 16 is input to the digital display data conversion circuit 15, and the output of the digital display data conversion circuit 15 is input to the analog signal driving circuit 6 described above. In the analog signal driving circuit 6, digital display data is input to the digital signal line 14 and latched by the latch circuit 11 in accordance with the scanning of the shift register 10. The output of the latch circuit 11 is input to the DA conversion circuit 12, and the output of the DA conversion circuit 12 is output to the signal line 3. Note that the gradation voltage generation resistor 13 supplies analog gradation voltages of 256 gradations to the DA conversion circuit 12.

  Next, the operation of this embodiment will be described.

  The RGB 6-bit digital display data input to the digital signal input terminal 16 is converted into RGB 8-bit digital display data by the digital display data conversion circuit 15 and input to the analog signal drive circuit 6 provided on the glass substrate. Is done. The written RGB 8-bit digital display data is input to the digital signal line 14 in the analog signal driving circuit 6 and is latched by the latch circuit 11 for each 8-bit data of each pixel in accordance with the scanning of the shift register 10. The scanning of the shift register 10 is performed at a timing that makes a round for each horizontal scanning period, and when the writing to the latch circuit 11 is completed, the written RGB each 8 bits at the timing of the subsequent horizontal blanking period. The digital display data is input to the DA conversion circuit 12 all at once. The DA conversion circuit 12 selects one of the 256 gradation analog gradation voltages output from the gradation voltage generating resistor 13 in correspondence with the RGB 8-bit digital display data, and selects the selected analog gradation voltage. Has a function of writing to the signal line 3. At this time, the shift register 8 selectively scans the gate line 7 corresponding to the write data at a predetermined timing, and the pixel 2 in the scanned row is written to the signal line 3 in the corresponding column. Analog gradation voltage is written.

    Next, the pixel 2 having an organic EL element will be described.

    FIG. 2 is a structural diagram of the pixel 2. One end of the organic EL element 23 is dropped to a common ground voltage, and the other end is connected to the drain of the organic EL element driving TFT 22. The gate of the organic EL element driving TFT 22 is further connected to one end of the pixel input switch 21, and the other end of the pixel input switch 21 is connected to the signal line 3. The gate of the pixel input switch 21 is connected to the gate line 7. The source of the organic EL element driving TFT 22 is connected to the power supply line 9, and the power supply line 9 is commonly connected between the pixels as already shown in FIG. The organic EL element driving TFT 22 and the pixel input switch 21 are composed of polycrystalline Si TFTs.

  The operation of the pixel 2 will be described below. When the corresponding gate line 7 is selected by the shift register 8, the pixel input switch 21 of the pixel 2 is turned on, and the signal voltage, that is, the analog gradation voltage written in the signal line 3, is converted into the organic EL element driving TFT 22 Input to the gate. This analog gradation voltage is stored in the gate capacitance of the organic EL element driving TFT 22 even after the pixel input switch 21 is turned off, and the pixel input switch 21 of the pixel 2 is again set by the shift register 8 in the next frame scan. Holds until selected. Here, the organic EL element driving TFT 22 applies a corresponding analog signal current to the organic EL element 23 in accordance with the analog gradation voltage applied to the gate, and the organic EL element 23 emits light with a predetermined chromaticity in accordance with the signal current. As a result, gradation display corresponding to the signal voltage and the above-described analog gradation voltage is possible.

  The basic structure of the analog signal driving circuit 6 and the scanning of the pixel 2 as described above are not significantly different from the basic structure of the driving circuit of the liquid crystal display device and the scanning of the liquid crystal pixel already cited in the conventional example. Details of the digital display data conversion circuit 15 having a characteristic structure in the example will be described below.

  In the present embodiment, the digital display data input to the digital signal input terminal 16 has an RGB 6-bit information amount. However, the digital display data input to the analog signal drive circuit 6 via the digital display data conversion circuit 15 is RGB each 8 bits, and the analog signal drive circuit 6 can output 256 gradation analog gradation voltages corresponding to 8 bits. is there. This is because the digital display data conversion circuit 15 is provided with a correction function for the light emission characteristic of the organic EL element 23 having different characteristics for each RBG with respect to the signal voltage input to the organic EL element driving TFT 22. is there.

  FIG. 3 schematically shows the light emission characteristics of the organic EL elements 23 of each RBG with respect to the input signal voltage for the purpose of explanation. Here, the signal voltage is a 3-bit digital value and the light emission gradation is plotted as 2 bits, but the characteristics themselves are shown as a continuous curve. As shown in the figure, the RGB organic EL elements 23 start to emit light with different signal voltages, and the emission luminance increases with different slopes with respect to the signal voltages. For example, B is the signal voltage gradation (001), G and R start to emit light at the signal voltage gradation (011), G has a steep gradient of G, R follows this, and B is the smoothest. It is. At this time, if the same signal voltage is applied to the R, G, B pixels as the signal voltage gradation in order to display a colorless gray scale from black to white, B will be applied at low luminance (001). Only emits pure blue, and at high luminance (111), G exhibits a green-white color coordinated.

  On the other hand, in this embodiment, the digital display data conversion circuit 15 corrects the digital display data as schematically shown in the conversion table of FIG. For example, when the input digital display data to the digital display data conversion circuit 15 is B (00), G (00), R (00), B (001), G (011), R Converts digital display data of (011) to B (11), G (11), R (11), B (111), G (110), R (111) Convert and output digital display data. As a result, regardless of the value of the input digital display data input to the digital display data conversion circuit 15, the present embodiment can display a desired color at a constant color temperature.

  In this embodiment, the display color temperature can be changed in real time by rewriting the data conversion table of the digital display data conversion circuit 15 or referring to a different conversion data table. This function can be used, for example, when performing adaptive display according to the ambient light of the display or when adjusting the color temperature in accordance with the deterioration of the organic EL element 23. Alternatively, it is also possible to arbitrarily convert the color temperature setting between the text sentence display area and the natural image display area on the display screen. In this case, it is generally preferable to set the color temperature of the text sentence display area to a higher temperature than the natural image display area in order to improve the readability of the display screen.

  In this embodiment, the analog signal driving circuit 6 is composed of a polycrystalline Si TFT simultaneously with the pixel 2, but the present invention is not limited to such a structure, and the pixel peripheral circuit such as the analog signal driving circuit 6 is used. The part may be realized by a single crystal LSI and mounted on a substrate. Even in this case, it is obvious that there is no need to make separate analog signal driving circuits 6 for RGB, which is an advantage in terms of mounting cost.

In addition, the RGB light emission characteristics of the organic EL element 23 shown in the present example are changed by changing the organic EL material, but it is obvious that the application of the present invention is not specified to a specific organic EL material. is there. In this embodiment, the input digital display data to the digital display data conversion circuit 15 is set to 6 bits, and the output digital display data is set to 8 bits. However, the present invention can be applied regardless of the number of bits of these digital display data. .
(Second embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to FIG.
FIG. 5 is a configuration diagram of an organic EL display panel according to the second embodiment.
The overall configuration and operation of this embodiment are basically the same as those of the first embodiment except that the digital display data conversion circuit 15 is not provided and the structure of the analog signal driving circuit 36 is partially changed. The configuration and operation are the same. Therefore, in order to avoid duplication, description of the whole structure and its operation | movement is abbreviate | omitted, and it demonstrates below focusing on the said change point which is the characteristics of a present Example.

  In this embodiment, the digital signal input terminal 16 is directly input to the analog signal driving circuit 36. In the analog signal driving circuit 36, the digital display data is input to the digital signal line 14 and is latched by the latch circuit 31 according to the scanning of the shift register 10. The output of the latch circuit 31 is input to the DA conversion circuit 32, and the output of the DA conversion circuit 32 is output to the signal line 3. Note that the gradation voltage generation resistor 33 supplies an analog gradation voltage of 160 gradations to the DA conversion circuit 32.

  Next, the operation of the analog signal driving circuit 36 will be described.

  The RGB 6-bit digital display data input to the digital signal input terminal 16 is input to the analog signal drive circuit 36 provided on the glass substrate 1. The written RGB 6-bit digital display data is input to the digital signal line 14 in the analog signal driving circuit 36 and is latched by the latch circuit 31 for each 6-bit data of each pixel in accordance with the scanning of the shift register 10. The scanning of the shift register 10 is performed at a timing that makes a round for each horizontal scanning period, and when writing to the latch circuit 31 is completed, the written RGB 6 bits each at the timing of the subsequent horizontal blanking period. The digital display data is input to the DA conversion circuit 32 all at once. The DA converter circuit 32 is designed with different DA conversion characteristics for the R DA converter circuit (RD / A), G DA converter circuit (GD / A), and B DA converter circuit (BD / A). The D / A conversion circuit 32 corresponding to each RGB selects one of the 160 gradation analog gradation voltages output from the gradation voltage generation resistor 33 in correspondence with each RGB 6-bit digital display data, It has a function of writing the selected analog gradation voltage to the signal line 3.

  Here, the DA conversion circuit 32 in this embodiment also serves as the digital display data conversion circuit 15 in the first embodiment. That is, for the same 6-bit digital display data, different analog gradation voltages corresponding to each color of RGB are output to the signal line 3, so that in this embodiment as well, as in the first embodiment, the input digital display is performed. It is possible to display a desired color at a constant color temperature regardless of the data value.

In this embodiment, the RGB arrangement in the pixel area employs a stripe arrangement in the column direction. Thus, the DA conversion circuit 32 corresponding to a different display color is arranged for each signal line 3, but the present invention is not limited to such a color arrangement, for example, the DA conversion circuit 32 and the signal line. If a changeover switch between 3 is provided, other color arrangements can be supported.
In this embodiment, the configuration of the main analog signal driving circuit 36 such as the shift register 10 and the latch circuit 31 is the same in RGB, and 160 gradation analog gradation voltages are output from the same gradation voltage generating resistor 33. In this respect, a reduction in area that is different from the concept of independently having different drive circuits for RGB as in the conventional example is realized.
In this embodiment, the pixel peripheral circuit portion such as the analog signal driving circuit 46 may be realized by a single crystal LSI and mounted on the substrate.
In this embodiment, the analog gradation voltage is set to 160 gradations, but since this is determined by the number of analog gradation voltages that can be used in common between RGB, the organic EL used for RGB emission is used. It goes without saying that the number of gradations should be optimally designed in advance depending on the type of element 23 and the display color selected.
(Third embodiment)
Hereinafter, the third embodiment of the present invention will be described with reference to FIGS.
FIG. 6 is a configuration diagram of an organic EL display panel according to the third embodiment.
The overall configuration and operation of the present embodiment are the same except that the digital display data conversion circuit 15 is not present, the structure of the analog signal driving circuit 46 is partially changed, and the structure of the pixel 44 is changed. Basically, it is the same as the overall configuration and operation of the first embodiment. Therefore, in order to avoid duplication, description of the whole structure and its operation | movement is abbreviate | omitted, and it demonstrates below focusing on the said change point which is the characteristics of a present Example.

  In this embodiment, the digital signal input terminal 16 is directly input to the analog signal driving circuit 46. In the analog signal driving circuit 46, the digital display data is input to the digital signal line 14, and is latched by the latch circuit 41 according to the scanning of the shift register 10. The output of the latch circuit 41 is input to the DA conversion circuit 42, and the output of the DA conversion circuit 42 is output to the signal line 3. Note that the gradation voltage generation resistor 43 supplies 64 analog gradation voltages corresponding to 6 bits to the DA conversion circuit.

    Next, the operation of the analog signal driving circuit 46 will be described.

The RGB 6-bit digital display data input to the digital signal input terminal 16 is input to an analog signal driving circuit 46 provided on the glass substrate 1. The written RGB 6-bit digital display data is input to the digital signal line 14 in the analog signal driving circuit 46 and is latched by the latch circuit 41 for each 6-bit data of each pixel in accordance with the scanning of the shift register 10. The scanning of the shift register 10 is performed at a timing that makes a round for each horizontal scanning period, and when writing to the latch circuit 41 is completed, the written RGB each 6 bits at the timing of the subsequent horizontal blanking period. The digital display data is input to the DA conversion circuit 42 all at once. The DA conversion circuit 42 selects one of the 64 gradation analog gradation voltages output from the gradation voltage generating resistor 43 in correspondence with the 6-bit digital display data, and signals the selected analog gradation voltage. Has the function of writing to line 3.
As described above, the analog signal driving circuit 46 of the present embodiment writes the same analog gradation voltage for the same 6-bit digital display data to all the pixels 44 regardless of the RGB display color. It has a function.
Next, the structure of the pixel 44 in the present invention will be described with reference to FIG.
FIG. 7 is a configuration diagram of the pixel 44 in the present embodiment. Here, the structures of the pixels 44R, 44G, and 44B corresponding to the three display colors of RGB are also shown. One end of the organic EL elements 23R, G, B is dropped to a common ground voltage, and the other end is connected to the drains of the organic EL element driving TFTs 22R, G, B. The gates of the organic EL element driving TFTs 22R, G, and B are further connected to one end of the pixel input switch 21, and the other end of the pixel input switch 21 is connected to the signal line 3. The gate of the pixel input switch 21 is connected to the gate line 7. The sources of the organic EL element driving TFTs 22R, G, and B are connected to the power supply line 9, and the power supply line 9 is commonly connected between the pixels as already shown in FIG. The organic EL element driving TFTs 22R, G, B and the pixel input switch 21 are composed of polycrystalline Si TFTs.

  The operation of the pixels 44R, G, B will be described below. When the corresponding gate line 7 is selected by the shift register 8, the pixel input switches 21 of the pixels 44R, G, and B are turned on, and the signal voltage written in the signal line 3 and the analog gradation voltage are organic. Input to the gates of EL element drive TFT22R, G, B. This analog gradation voltage is stored in the gate capacitance of the organic EL element driving TFTs 22R, G, B even after the pixel input switch 21 is turned off, and the pixels 44R, G, B are again scanned in the next frame. This is held until the input switch 21 is selected by the shift register 8. Here, the organic EL element driving TFT22R, G, B gives a corresponding signal current to the organic EL elements 23R, G, B according to the analog gradation voltage applied to the gate, and the organic EL elements 23R, G, B Light emission is displayed with a predetermined chromaticity according to the current. As a result, gradation display corresponding to the signal voltage and the above-described analog gradation voltage is possible.

Here, the point to be noted in the present embodiment is that the channel dimensions of the organic EL element driving TFTs 22R, G, and B are as shown in the figure, respectively (gate width / gate length) = W / L = 5/40, It is different in 5/20, 5/10 and RGB. As described above, the role of the organic EL element driving TFT 22 is to apply a corresponding signal current to the organic EL element 23 in accordance with the analog gradation voltage applied to the gate, thereby causing the organic EL element 23 to emit light. Therefore, if the channel dimensions are different, it becomes possible to give different signal currents to the organic EL element 23 even for the same analog gradation voltage, and in this embodiment as well, light emission between RGB of the organic EL element 23 is possible. It is possible to reduce the difference in characteristics and display a desired color at a constant color temperature regardless of the value of the input digital display data.
This embodiment can be applied only by changing the channel dimensions of the organic EL element driving TFT, and is easier to apply than the other embodiments. However, since the present embodiment simply adjusts the ratio of the signal current applied to the organic EL element 23 to a constant value between RGB, it corrects even offsets and subtle differences in characteristic curves between RGB in the organic EL element. It is not possible. Therefore, it is desirable to combine this embodiment with other means such as the first and second embodiments.
In this example, the channel dimensions of the organic EL element driving TFT22R, G, B were (gate width / gate length) = W / L = 5/40, 5/20, 5/10, respectively. It is obvious that each change should be made by changing the organic EL material. It is clear that the application of the present invention is not specific to a specific organic EL material, and the setting of the channel dimensions needs to be optimized depending on the specifications of the material and display color.
(Fourth embodiment)
Hereinafter, a fourth embodiment of the present invention will be described with reference to FIG.
The overall configuration and operation of the present embodiment are basically the same as the overall configuration and operation of the third embodiment except that the structure of the pixel 48 is changed. Therefore, in order to avoid duplication, description of the whole structure and its operation | movement is abbreviate | omitted, and it demonstrates below focusing on the said change point which is the characteristics of a present Example.
The structure of the pixel 48 in the present invention will be described with reference to FIG.
FIG. 8 is a configuration diagram of the pixel 48 in the present embodiment. Here, the structures of the pixels 48R, 48G, and 48B corresponding to the three display colors of RGB are also shown. One end of the organic EL elements 23R, G, B is dropped to a common ground voltage, and the other end is connected to the drain of the organic EL element driving TFT 22. The gate of the organic EL element driving TFT 22 is further connected to one end of the pixel input switch 21, and the other end of the pixel input switch 21 is connected to the signal line 3. The gate of the pixel input switch 21 is connected to the gate line 7. The source of the organic EL element driving TFT 22 is connected to the power supply line 9, but the source resistors 49R and 49G are provided between the pixels 48R and 48G corresponding to R and G, respectively. The power supply line 9 is commonly connected between the pixels as already shown in FIG. The organic EL element driving TFT 22 and the pixel input switch 21 are composed of polycrystalline Si TFTs, and the source resistors 49R and 49G are composed of the same polycrystalline Si thin film as the channel layer of the TFT.

  The operation of the pixels 48R, G, B will be described below. When the corresponding gate line 7 is selected by the shift register 8, the pixel input switches 21 of the pixels 48R, G, and B are turned on, and the signal voltage that has been written to the signal line 3 and the analog gradation voltage are organic. Input to the gate of the EL element driving TFT 22. This analog gradation voltage is stored in the gate capacitance of the organic EL element driving TFT 22 even after the pixel input switch 21 is turned off, and the pixel input switches 21 of the pixels 48R, G, and B are again turned on in the next frame scan. This is held until selected by the shift register 8. Here, the organic EL element driving TFT 22 gives a corresponding signal current to the organic EL elements 23R, G, B in accordance with the analog gradation voltage applied to the gate, and the organic EL elements 23R, G, B have a predetermined value in accordance with the signal current. Light emission display with chromaticity. As a result, gradation display corresponding to the signal voltage and the above-described analog gradation voltage is possible.

Here, what should be noted in the present embodiment is that the source resistors 49R and 49G are provided as described above, and the values thereof are different in R, G, and B. Here, the pixel 48B is not provided with a source resistance, but this should be interpreted as a resistance value of 0 MΩ. As described above, the role of the organic EL element driving TFT 22 is to apply a corresponding signal current to the organic EL element 23 in accordance with the analog gradation voltage applied to the gate, thereby causing the organic EL element 23 to emit light. Therefore, if the source resistance value is different, it becomes possible to give different signal currents to the organic EL element 23 even for the same analog gradation voltage. Thus, it is possible to display a desired color at a constant color temperature regardless of the value of the input digital display data.
This embodiment can also be applied with only slight changes in the pixels, and is easier to apply than the other embodiments. However, since the present embodiment also simply adjusts the fixed resistance value, it is not possible to correct even the offset between RGB and subtle characteristic curve differences in the organic EL element. Similarly to the third embodiment, this embodiment is preferably combined with other means such as the first and second embodiments.
In this embodiment, the resistance values of the source resistors 49R and 49G are 10 MΩ and 5 MΩ, respectively. However, it is obvious that these values should be changed by changing the organic EL material. It is clear that the application of the present invention is not limited to a specific organic EL material, and the setting of the source resistance needs to be optimized including the pixel 48B depending on the specifications of the material and display color.
(Fifth embodiment)
Hereinafter, the fifth embodiment of the present invention will be described with reference to FIGS.
FIG. 9 is a configuration diagram of an organic EL display panel according to the fifth embodiment.
The overall configuration and operation of the present embodiment are basically the same as the overall configuration of the third embodiment except that the structure of the pixel 51 is changed and a lighting switch shift register is newly added. And the operation is the same. Therefore, in order to avoid duplication, description of the whole structure and its operation | movement is abbreviate | omitted, and it demonstrates below focusing on the said change point which is the characteristics of a present Example.
As shown in FIG. 9, the pixel 51 in the present invention is provided with a lighting scanning line 53 extending from the lighting switch shift register 52 in parallel with the gate line 7.
The structure of the pixel 51 in the present invention will be described with reference to FIG.
FIG. 10 is a configuration diagram of the pixel 51 in the present embodiment. Here, the structures of the pixels 51R, 51G, and 51B corresponding to the three display colors of RGB are also shown. One end of the organic EL elements 23R, G, B is dropped to a common ground voltage, and the other end is connected to the drain of the organic EL element driving TFT 22. Here, for the pixels 51R and 51G, lighting switches 54R and 54G are provided between the organic EL elements 23R and G and the organic EL element driving TFT22. The gates of the organic EL element driving TFTs 22R, G, and B are further connected to one end of the pixel input switch 21, and the other end of the pixel input switch 21 is connected to the signal line 3. The gate of the pixel input switch 21 is connected to the gate line 7. The sources of the organic EL element driving TFTs 22R, G, and B are connected to the power supply line 9, and the power supply line 9 is commonly connected between the pixels as already shown in FIG. Note that the organic EL element driving TFTs 22R, G, B, the pixel input switch 21, and the lighting switches 54R, 54G are composed of polycrystalline Si TFTs.

  The operation of the pixels 51R, G, B will be described below. When the corresponding gate line 7 is selected by the shift register 8, the pixel input switches 21 of the pixels 51R, G, and B are turned on, and the signal voltage, that is, the analog gradation voltage written to the signal line 3, is organic. Input to the gate of the EL element driving TFT 22. This analog gradation voltage is stored in the gate capacitance of the organic EL element driving TFT 22 even after the pixel input switch 21 is turned off, and the pixel input switches 21 of the pixels 51R, G, and B are again turned on in the next frame scan. This is held until selected by the shift register 8. Here, the organic EL element driving TFT 22 gives a corresponding signal current to the organic EL elements 23R, G, B in accordance with the analog gradation voltage applied to the gate, and the organic EL elements 23R, G, B have a predetermined value in accordance with the signal current. Light emission display with chromaticity. As a result, gradation display corresponding to the signal voltage and the above-described analog gradation voltage is possible.

  Here, what should be noted in the present embodiment is that the lighting switches 54R and 54G are provided as described above, and the values thereof are different for R, G, and B. Here, the lighting switch 54 is not provided in the pixel 51B, but this should be interpreted that the lighting switch 54 is always on in the pixel 51B. As described above, the role of the organic EL element driving TFT 22 is to apply a corresponding signal current to the organic EL element 23 in accordance with the analog gradation voltage applied to the gate, thereby causing the organic EL element 23 to emit light. However, by introducing the lighting switch 54 here, the lighting period of the organic EL element 23 can be limited to the ON period of the lighting switch 54. This will be described below with reference to FIGS.

FIG. 11 is a diagram showing the write scanning timing to the pixel defined by the pixel input switch 21 and the lighting switch scanning timing defined by the lighting switches 54R and 54G. The horizontal axis represents the time axis, the vertical axis represents the scanning position in the pixel row, the upper end is the first pixel row, and the lower end is the last pixel row. In the figure, a solid line shows a state in which writing scanning to a pixel is sequentially performed from the first pixel row to the last pixel row over each frame period. Here, the two types of dotted lines indicate the scanning timing of the lighting switches 54R and 54G, and the lighting switches 54R and 54G are turned on and off, respectively, as illustrated. From the figure, since the ON period of the lighting switch 54R is limited to about ½ of the frame period, the lighting period of the R pixel is similarly limited, and the ON period of the lighting switch 54G is about 3 of the frame period. Since it is limited to about / 4, the lighting period of the G pixel is similarly limited, and it is understood that the lighting period of the B pixel is about the same as the frame period.

12 shows a specific drive timing chart of the lighting switches 54G and 54R together with that of the pixel input switch 21. FIG. Here, for the sake of simplification, the operation of the pixel in the first row is shown, but actually, it is not always necessary to arrange RGB in the first row as described later. However, the operation timing of the pixels arranged in other rows is the same as the timing between the pulses, only the time axis is shifted parallel to the frame period. FIG. 12 should be understood as a simplified drawing for purposes of illustration. As described in FIG. 11, the pixel input switch 21 is temporarily turned on at the beginning of the frame period, so that the signal voltage, that is, the analog gradation voltage written in the signal line 3, is changed to the organic EL element driving TFT22. Write to the gate. At this time, the lighting switches 54G and 54R are also turned on at the same timing, so that the organic EL elements 23R, G, and B are turned on all at once (of course, when an analog gradation voltage of “non-lighting” is written to the pixel) This is not the case) Next, when about half of the frame period has elapsed, the lighting switch 54R is turned off, and the organic EL element 23R is forcibly entered into a non-lighting state. Next, when about 3/4 of the frame period has elapsed, the lighting switch 54G is turned off, and the organic EL element 23G is forcibly entered into the non-lighting state. On the other hand, the organic EL element 23B is kept lit throughout the frame period.

As described above, in this embodiment, it becomes possible to give different lighting periods to the organic EL element 23 even with respect to the same analog gradation voltage. The light emission characteristic difference between them can be reduced, and a desired color can be displayed at a constant color temperature regardless of the value of the input digital display data.
This embodiment has an advantage that the lighting period ratio of each organic EL element 23 can be changed from the outside by the control of the lighting switch 54. However, since the present embodiment merely adjusts the lighting period ratio of the organic EL element 23 between RGB, it is not possible to correct even the offset or subtle characteristic curve difference between RGB in the organic EL element.
Therefore, it is desirable to combine this embodiment with other means such as the first and second embodiments.
In this embodiment, the lighting period ratios of the pixels R, G, and B are set to 1/2, 3/4, and 1 times of the frame period, respectively. However, this value should be changed by changing the organic EL material. It is clear. It is clear that the application of the present invention is not specific to a specific organic EL material, and the setting of the lighting period ratio needs to be optimized depending on the specifications of the material and display color.
Further, as shown in FIG. 9, in this embodiment, the RGB pixel array is set in the row direction stripe direction. Such a color arrangement has the advantage that the layout of the lighting scanning lines 53 can be simplified, but the application of the present invention is not limited to such a pixel arrangement.
(Sixth embodiment)
Hereinafter, the sixth embodiment of the present invention will be described with reference to FIG.
FIG. 13 is a configuration diagram of an organic EL display panel according to the sixth embodiment.
The overall configuration and operation of the present embodiment are basically the same as the overall configuration and operation of the third embodiment except that the power supply line 59 is separated for each RGB pixel. Therefore, in order to avoid duplication, description of the whole structure and its operation | movement is abbreviate | omitted, and it demonstrates below focusing on the said change point which is the characteristics of a present Example.

As described in the third embodiment, the organic EL element driving TFT 22 provided in each pixel gives the corresponding signal current to the organic EL element 23 according to the analog gradation voltage applied to the gate, and the organic EL element 23 Emits light with a predetermined chromaticity according to the signal current. As a result, it is possible to display a gradation corresponding to the signal voltage, that is, the analog gradation voltage, but in the present embodiment, here, the power supply line 59R for supplying the source voltage to the organic EL element driving TFT22, G and B are separated for each pixel of RGB, and different drive voltages are applied to each. Thus, in this embodiment, even when the same analog gradation voltage is applied to the pixel, the driving conditions of the organic EL element driving TFT 22R, G, B are modulated by the difference between the power supply lines 59R, G, B driving voltage. Thus, the signal currents for driving the organic EL elements 23R, G, and B are different from each other. Accordingly, also in this embodiment, the difference in RGB light emission characteristics of the organic EL element 23 can be reduced, and a desired color can be displayed at a constant color temperature regardless of the value of the input digital display data. This embodiment has an advantage that the signal current of each organic EL element 23, that is, the luminance can be changed only by changing the power supply lines 59R, G, B drive voltage from the outside. However, since the present embodiment merely adjusts the signal current characteristic applied to the organic EL element 23 between RGB, it cannot correct even the slight difference in characteristic curve between RGB in the organic EL element. Therefore, it is desirable to combine this embodiment with other means such as the first and second embodiments.
(Seventh embodiment)
Hereinafter, the seventh embodiment of the present invention will be described with reference to FIG.
FIG. 14 is a block diagram of a moving image (digital television) playback device 100 according to the seventh embodiment.
In addition to text data, compressed image data or the like is input to the wireless input interface circuit 101 as moving image data based on the MPEG standard, and the output of the wireless input interface circuit 101 is an I / O (Input / Output) circuit 102. To the data bus 103. In addition to this, a microprocessor 104 for decoding and controlling MPEG signals, a display panel controller 105 incorporating a DA converter, a frame memory 106, and the like are connected to the data bus 103. Further, the output of the display panel controller 105 is input to the organic EL display panel 110, and the organic EL display panel 1 is provided with a pixel matrix 111, a shift register 7, an analog signal driving circuit 6, and the like. Note that the moving image playback apparatus 100 is further provided with a secondary battery 107. Here, the organic EL display panel 110 has the same configuration and operation as the organic EL display panel provided on the glass substrate 1 described in the first embodiment, so the internal configuration and The description of the operation is omitted here.
The operation of the seventh embodiment will be described below. First, the wireless input interface circuit 101 captures image data or the like compressed according to a command from the outside, and transfers this data to the microprocessor 104 and the frame memory 106 via the I / O circuit 102. In response to a command operation from the user, the microprocessor 104 drives the entire moving image playback apparatus 100 as necessary, and performs decoding of decoded image data, signal processing, and information display. The image data subjected to signal processing here is temporarily stored in the frame memory 106 as necessary.
When the microprocessor 104 issues a display command, image data is input from the frame memory 106 to the organic EL display panel 110 via the display panel controller 105 according to the instruction, and the pixel matrix 111 is input. Displayed image data in real time. The display panel controller 105 outputs predetermined timing pulses necessary for displaying an image at the same time. It should be noted that 6-bit RGB image data is stored in the frame memory 106. This digital display data is once converted into 8-bit RGB digital display data by the microprocessor 104 and then displayed on an organic EL display. It is input to the panel 110. That is, in this embodiment, the microprocessor 104 also serves as the digital display data conversion circuit 15 in the first embodiment, and thus, dedicated hardware components such as the digital display data conversion circuit 15 are provided. Can be omitted. The organic EL display panel 110 uses these signals to display display data generated from 8-bit image data on the pixel matrix 111 in real time, as described in the first embodiment. Here, the secondary battery 107 supplies power for driving the entire moving image playback apparatus 100.

  With the configuration and operation as described above, in this embodiment as well as in the first embodiment, a desired color can be obtained at a constant color temperature regardless of the value of the digital display data stored in the frame memory 106. It was possible to display.

  Also in the present embodiment, the display color temperature is changed in real time by rewriting the data conversion table when the 8-bit digital display data of each RGB is generated by the microprocessor 104 or by referring to a different conversion data table. It is possible. This function can be used, for example, when performing adaptive display according to the ambient light of the display or when adjusting the color temperature in accordance with the deterioration of the organic EL element 23. Alternatively, it is also possible to arbitrarily convert the color temperature setting between the text sentence display area and the natural image display area on the display screen. In this case, it is generally preferable to set the color temperature of the text sentence display area to a higher temperature than the natural image display area in order to improve the readability of the display screen.

  In this embodiment, the analog signal driving circuit 6 is composed of a polycrystalline Si TFT simultaneously with the pixel matrix 111 and the shift register 7. However, the present invention is not limited to such a structure, and the analog signal driving circuit 6 The pixel peripheral circuit portion such as the above may be realized by a single crystal LSI and mounted on a substrate. Even in this case, it is obvious that there is no need to make separate analog signal driving circuits 6 for RGB, which is an advantage in terms of mounting cost.

  Further, the RGB light emission characteristics of the organic EL element 23 corresponding to FIG. 3 are changed by changing the organic EL material, but it is obvious that the application of the present invention is not specified to a specific organic EL material. . In this embodiment, the conversion of the digital display data in the microprocessor 104 is set from 6 bits to 8 bits. However, it goes without saying that the present invention can be applied regardless of the number of bits before and after the conversion of these digital display data. .

The block diagram of the organic electroluminescence display panel which is a 1st Example. FIG. 3 is a structural diagram of a pixel in the first embodiment. The light emission characteristic schematic diagram of the organic EL element in a 1st Example. The digital display data conversion table schematic diagram in a 1st Example. The block diagram of the organic electroluminescent display panel which is a 2nd Example. The block diagram of the organic electroluminescent display panel which is a 3rd Example. The pixel block diagram in a 3rd Example. The pixel block diagram in a 4th Example. The block diagram of the organic electroluminescent display panel which is a 5th Example. The pixel block diagram in a 5th Example. The pixel scanning timing diagram in the fifth embodiment. The drive timing diagram of the lighting switch in a 5th Example. The block diagram of the organic electroluminescence display panel which is a 6th Example. The block diagram of the moving image reproduction apparatus which is a 7th Example. FIG. 6 is a structural diagram of a simple matrix type organic EL display using a conventional technique.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 2 ... Pixel, 3 ... Signal line, 6 ... Analog signal drive circuit, 7 ... Gate line, 8 ... Shift register, 9 ... Power supply line, 10 ... Shift register, 11 ... Latch circuit, 12 ... DA conversion Circuit: 13 ... gradation voltage generating resistor, 14 ... digital signal line, 15 ... digital display data conversion circuit, 16 ... digital signal input terminal.

Claims (2)

  A pixel matrix comprising pixels arranged in a matrix;
  A signal line extending in a column direction of the pixel matrix;
  Gate lines extending in the row direction of the pixel matrix;
  A lighting scanning line extending in a row direction of the pixel matrix;
  An analog signal driving circuit that scans the signal line and writes a signal voltage to the signal line;
  A shift register that scans the gate line;
  A lighting switch shift register that scans the lighting scanning line and controls the lighting period of each pixel;
  A pixel having a first organic EL element that emits light in the first color includes a first organic EL element, a first pixel input transistor, a first drive transistor, and a first lighting transistor,
  The source / drain path of the first driving transistor, the source / drain path of the first lighting transistor, and both ends of the first organic EL element are connected in series between a power supply line and the ground,
  The gates of the first pixel input transistors in the same row of the pixel matrix are connected to the same gate line;
  The source / drain path of the first pixel input transistor in the same column of the pixel matrix is connected between the gate of the first driving transistor and the same signal line,
  The gates of the first lighting transistors of the pixels in the same row of the pixel matrix are connected to the same lighting scanning line;
  The pixel having the second organic EL element that emits light of the second color has a second organic EL element, a second pixel input transistor, and a second drive transistor,
  The source / drain path of the second driving transistor and both ends of the second organic EL element are connected in series between the power line and the ground,
  The gates of the second pixel input transistors in the same row of the pixel matrix are connected to the same gate line;
  The source / drain path of the second pixel input transistor in the same column of the pixel matrix is connected between the gate of the second drive transistor and the same signal line,
  An image display device, wherein organic EL elements of pixels in the same row of the pixel matrix emit light of the same color.   The image display device according to claim 1,
  A pixel having a third organic EL element that emits light in the third color includes a third organic EL element, a third pixel input transistor, a third drive transistor, and a third lighting transistor.
  The source / drain path of the third driving transistor, the source / drain path of the third lighting transistor, and both ends of the third organic EL element are connected in series between a power supply line and the ground,
  The gates of the third pixel input transistors in the same row of the pixel matrix are connected to the same gate line;
  The source / drain path of the third pixel input transistor in the same column of the pixel matrix is connected between the gate of the third driving transistor and the same signal line,
  An image display device, wherein gates of the first and third lighting transistors of pixels in the same row of the pixel matrix are connected to the same lighting scanning line.

Images