JP2012212147A - Portable information device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress power consumption of a portable information device.SOLUTION: A plurality of storage circuits are arranged in a pixel and a digital video signals are stored for each pixel. When a still picture is displayed, the picture is written once and then information written to the pixel is the same, so the still picture can continuously be displayed by reading the signals stored in the storage circuits without inputting signals for each frame. Namely, when the still picture is displayed, at least one frame of signals are processed and then a source signal line driving circuit can be stopped thereafter, and with this, power consumption can greatly be reduced.

Description

  The present invention relates to a portable information device, and in particular, a portable phone, a PDA (Personal Digital Assistant), a portable personal computer, a portable game device, a portable navigation system, an electronic book, etc. having a flat display using EL, organic EL, and the like. It relates to an information device.

  In recent years, mobile phones have become popular due to the development of communication technology. In the future, more video transmission and more information transmission are expected. On the other hand, personal computers are also being produced with mobile-friendly products due to their light weight. A large number of information devices called personal digital assistants, beginning with electronic notebooks, have been produced and are becoming popular. In addition, with the development of EL display devices and the like, most of these portable devices are equipped with a flat display.

  As a more recent technology, active matrix display devices have begun to be used in these portable devices. In an active matrix display device, one TFT is arranged for each pixel, and the screen is controlled by the TFT. Such an active matrix display device has advantages such as higher resolution of images, improved image quality, and compatibility with moving images as compared with a passive matrix display device. Therefore, in the future, the display device of portable information equipment will change from a passive matrix type to an active matrix type.

  In addition, among active matrix display devices, display devices using low-temperature polysilicon have been commercialized in recent years. With the low-temperature polysilicon technology, in addition to the pixel TFT constituting the pixel, a driving circuit can be simultaneously formed in the peripheral portion of the pixel portion using the TFT. Therefore, an EL display device (a display device having an EL element) is indispensable for a display unit of a mobile device, which has greatly contributed to downsizing and low power consumption of the device, and whose application fields have been greatly expanded in recent years. It has become a device.

  FIG. 10 shows a block diagram of a conventional portable information terminal. Reference numeral 1204 denotes a power source. In the portable information terminal, it is required to extract information requested by the user as necessary. The information includes information stored in a storage device (DRAM 1209, flash memory 1210, etc.) in the portable information terminal, information stored in a memory card 1203 inserted into the portable information terminal, and via an external interface port 1205. Some can be obtained by connecting to external devices.

  A user's instruction input from the pen input tablet 1201 is read as electronic information in the detection circuit 1202. The electronic information is sent to the video signal processing circuit 1207 by the tablet interface 1218. The video signal processing circuit 1207 converts the read electronic information into image data based on the image format stored in the VRAM 1211 and sends the image data to the controller 1212. Here, the controller 1212 generates a signal for driving the display device 1213, drives the display device 1213, and performs display.

  FIG. 11 shows a block diagram of a conventional mobile phone. What is already illustrated in the portable information terminal shown in FIG.

  The cellular phone includes a transmission / reception circuit 1224 for transmitting / receiving radio waves, a voice processing circuit 1221 for processing received signals, a speaker 1223, a microphone 1222, a keyboard 1220 for inputting data, a display device 1213 for displaying, an EL controller 1212 for the display, It consists of storage devices (VRAM 1211, DRAM 1209, flash memory 1210, etc.).

  In the mobile phone shown in FIG. 11, the operations of the keyboard interface 1238, the video signal processing circuit 1207, the VRAM 1211, and the EL controller 1212 are the same as those in the mobile information terminal shown in FIG. The only difference is that the user's instructions are read as electronic information on the keyboard 1220.

  FIG. 12 shows a detailed configuration of the transmission / reception circuit 1224 in FIG. Electronic information including audio information is received by the antenna 1302. The filter 1303 extracts only necessary data from the electronic information and inputs the data to the amplifier 1305 via the switch 1304. Data input to the amplifier 1305 is amplified and input to the filter 1307. Data from which unnecessary information is cut by the filter 1303 is increased in frequency by the first frequency conversion circuit 1309 and input to the filter 1312.

  Data whose unnecessary information is cut by the filter 1312 is increased in frequency again by the second frequency conversion circuit 1313 and input to the filter 1316.

  Data from which unnecessary information is cut by the filter 1316 is amplified by the amplifier 1317 and input to the data demodulation circuit 1318.

  The data demodulating circuit 1318 solves the encoded data and inputs it to the CPU 1206.

  Conversely, data sent from the CPU is input to the data modulation circuit 1319 and encoded. The phase of the encoded data is adjusted by the orthogonal transformer 1315 and the frequency of the encoded data is increased, and the encoded data is input to the frequency converter circuit 1311.

  The data input to the frequency conversion circuit 1311 is input to the filter 1308 with the frequency increased. Data from which unnecessary information is cut by the filter 1308 is amplified by the amplifier 1306 and input to the filter 1303 via the switch 1304.

  Data from which unnecessary information is cut by the filter 1303 is transmitted by the antenna 1302.

  FIG. 13 shows a schematic diagram of a display device having an EL element driven by a conventional digital method. In the display device, a pixel portion 9003, a source signal line driver circuit 9001, and a gate signal line driver circuit 9002 are arranged.

  The pixel portion 9003 has a plurality of pixels 9004. The source signal line driver circuit 9001 includes a shift register circuit 9001-1, a latch circuit A9001-2, and a latch circuit B9001-3. The gate signal line driver circuit 9002 includes a shift register circuit 9002-1 and a buffer circuit 9002-1.

  FIG. 14 shows a circuit diagram of the pixel 9004. The pixel 9004 includes one source signal line 9005, one power supply line 9006, and one gate signal line 9007. The pixel 9004 includes a switching TFT 9008 and an EL driving TFT 9009. The gate electrode of the switching TFT 9008 is connected to the gate signal line 9007. One of the source region and the drain region of the switching TFT 9008 is connected to the source signal line 9005, and the other is connected to the gate electrode of the EL driving TFT 9009 and the capacitor 9010 included in each pixel.

  The capacitor 9010 is provided to hold the gate voltage (potential difference between the gate electrode and the source region) of the EL driving TFT 9009 when the switching TFT 9008 is in a non-selected state (off state).

  One of a source region and a drain region of the EL driving TFT 9009 is connected to the power supply line 9006 and the other is connected to the EL element 9011. The power supply line 9006 is connected to the capacitor 9010.

  The EL element 9011 includes an anode, a cathode, and an EL layer provided between the anode and the cathode. In the case where the anode is connected to the source region or drain region of the EL driving TFT 9009, the anode serves as a pixel electrode and the cathode serves as a counter electrode. On the contrary, when the cathode is connected to the source region or drain region of the EL driving TFT 9009, the cathode serves as the pixel electrode and the anode serves as the counter electrode.

  A counter potential is applied to the counter electrode of the EL element 9011. The power supply line V is given a power supply potential. The power supply potential and the counter potential are supplied by a power supply provided in an external IC of the display device.

  A clock signal (CK) and a start pulse (SP) are input to the shift register circuit 9001-1 included in the source signal line driver circuit 9001. The shift register circuit 9001-1 sequentially generates timing signals based on the clock signal (CK) and the start pulse (SP), and sequentially supplies the timing signals to the latch circuit A 9001-2.

  The latch circuit A9001-2 has a plurality of latches for storing digital video signals. When the timing signal is input, the latch circuit A 9001-2 sequentially captures and holds the digital video signal in each latch.

  The time until writing of the digital video signal to all the latches of the latch circuit A9001-2 is called a line period. Actually, a period obtained by adding a horizontal blanking period to the line period may be called a line period.

  After the end of one line period, a latch signal (Latch Signal) is supplied to the latch circuit B9001-3. At this moment, the digital video signals written and held in the latch circuit A9001-2 are sent all at once to the latch circuit B9001-3, and are written and held in all the latches of the latch circuit B9001-3.

  Based on the timing signal from the shift register circuit 9001-1, the digital video signal is sequentially written again to the latch circuit A9001-2 that has finished sending the digital video signal to the latch circuit B9001-3.

  During the second line period, the digital video signals written and held in the latch circuit B 9001-3 are sequentially supplied to the source signal line 9005.

  On the other hand, when a clock signal (CLK) and a start pulse signal (SP) are input to the shift register circuit 9002-1 in the gate signal line driver circuit 9002, a selection signal for controlling switching of the switching TFT 9008 is generated. The selection signal is buffered and amplified in the buffer circuit 9002-2 and input to the gate signal line 9007.

  The switching TFT 9008 is turned on by the selection signal input to the gate signal line 9007, and the digital video signal input to the source signal line is input to the gate electrode of the EL driving TFT 9009 through the switching TFT. .

  Switching of the EL driving TFT is controlled by information of 1 or 0 included in the digital video signal input to the gate electrode of the EL driving TFT 9009. When the EL driving TFT is in an off state, the potential of the power supply line 9006 is not applied to the pixel electrode included in the EL element 9011, and thus the EL element does not emit light. When the EL driving TFT is on, the potential of the power supply line 9006 is applied to the pixel electrode included in the EL element 9011 and the EL element emits light.

  One image is displayed by performing the above operation in each pixel.

  In the conventional information terminal device as described above, when the display screen is displayed, even if the screen is a still screen, the same video data is continuously sent to the display device 60 times per second. It was. In other words, the video signal processing circuit 1207, the VRAM 1211, the controller 1212, and the display signal 1213 included in the CPU 1206 operate as long as display is performed as long as display is performed.

  In some passive display devices with a small number of pixels, a memory is built in a driver IC or an EL controller of the display device and the VRAM is stopped. A display device using a large number of pixels such as an active matrix. Then, it is unrealistic to have a memory in the driver or the controller from the viewpoint of the chip size. Therefore, in the conventional information terminal device, even when displaying a still image, many circuits must continue to operate, which hinders reduction in power consumption.

  In portable information terminals, low power consumption is highly desired. In addition, in this mobile device, although it is mostly used in the still image mode, the drive circuit continues to operate even when displaying a still image as described above. This is a drag on power consumption.

  In view of the above-described problems, an object of the present invention is to reduce power consumption of a driving circuit when a still image is displayed by using a novel circuit.

  In order to solve the above-described problems, the present invention uses the following means.

A plurality of storage circuits are arranged in the pixel, and a digital video signal is stored for each pixel.
In the case of a still image, once writing is performed, the information written to the pixels thereafter is the same. Therefore, by reading the signal stored in the storage circuit without inputting the signal every frame, Can be displayed continuously. In other words, when displaying a still image, it is possible to stop the source signal line drive circuit after performing a signal processing operation for at least one frame, thereby greatly reducing power consumption. Is possible.

  The configuration of the EL display device of the present invention will be described below.

  According to the present invention, in the portable information device having a display device and its controller, the display device has a plurality of pixels each including a memory circuit and an EL element, and when the display device displays a still image, the display device A portable information device is provided that stops video display functions other than the controller.

  According to the present invention, in the portable information device having the display device and the controller thereof, the display device has a plurality of pixels each including a memory circuit, an EL element, and a TFT for controlling a current flowing through the EL element, and the display device When displaying a still image, a portable information device is provided that stops video display functions other than the display device and the controller.

  The controller may be a clock generation circuit of a display device.

  According to the present invention, in the portable information device having a display device, the display device has a plurality of pixels each including a memory circuit and an EL element, and when the display device displays a still image, a signal having video information is displayed. There is provided a portable information device that is not input to the display device from the outside of the display device.

  According to the present invention, in the portable information device having a display device, the display device includes a plurality of pixels each including a memory circuit, an EL element, and a TFT for controlling a current flowing through the EL element, and the display device is a still image. A portable information device is provided in which a signal having video information is not input to the display device from the outside of the display device.

  According to the present invention, in the portable information device having a display device and a CPU, the display device has a plurality of pixels each including a memory circuit and an EL element, and when the display device displays a still image, There is provided a portable information device characterized in that the video display function is stopped.

  According to the present invention, in the portable information device having a display device and a CPU, the display device has a plurality of pixels each including a memory circuit, an EL element, and a TFT for controlling a current flowing through the EL element, and the display device When a still image is displayed, a portable information device is provided in which the video display function of the CPU is stopped.

  According to the present invention, in the portable information device having a display device and a VRAM, the display device has a plurality of pixels each including a memory circuit and an EL element, and when the display device displays a still image, the VRAM A portable information device is provided that stops calling stored data.

  According to the present invention, in the portable information device having a display device and a VRAM, the display device has a plurality of pixels each including a memory circuit, an EL element, and a TFT for controlling a current flowing through the EL element, and the display device When displaying a still image, a portable information device is provided that stops calling data stored in the VRAM.

  According to the present invention, in the portable information device having a display device, the display device has a plurality of pixels each including a memory circuit and an EL element, and when the display device displays a still image, the source of the display device A portable information device characterized by stopping the signal line driver circuit is provided.

  According to the present invention, in the portable information device having a display device, the display device includes a plurality of pixels each including a memory circuit, an EL element, and a TFT for controlling a current flowing through the EL element, and the display device is stationary. When displaying an image, a portable information device is provided in which the source signal line driver circuit of the display device is stopped.

  The storage circuit may be called once per frame period.

  According to the present invention, in the portable information device having a display device, the display device includes a plurality of pixels, the plurality of pixels includes a memory circuit and an EL element, and a specific row among the plurality of pixels. Alternatively, a portable information device including means for rewriting data stored in a memory circuit included in a column of pixels is provided.

  According to the present invention, in the portable information device having a display device, the display device includes a plurality of pixels, and the plurality of pixels include a memory circuit, an EL element, and a TFT for controlling a current flowing through the EL element. A portable information device comprising means for rewriting data stored in a memory circuit included in a pixel in a specific row or column among the plurality of pixels is provided.

  The portable information device may be a mobile phone, a personal computer, a navigation system, a PDA, or an electronic book.

  By storing digital video signals using a plurality of storage circuits arranged inside each pixel, the digital video signals stored in the storage circuit are repeatedly used in each frame period when displaying a still image. When the still image is continuously displayed, the source signal line driver circuit can be stopped. Therefore, it can greatly contribute to the reduction of power consumption of the entire EL display device.

The block diagram which shows the structure of the portable information terminal of this invention. 1 is a block diagram illustrating a configuration of a mobile phone according to the present invention. FIG. 6 is a pixel circuit diagram of a display device of the present invention. FIG. 6 is a block diagram of a driver circuit of a display device of the present invention. The top view and sectional drawing of the display apparatus of this invention. 1 is an external view of a mobile phone having the configuration of the present invention. 1 is an external view of a mobile phone having the configuration of the present invention. 1 is an external view of a mobile phone having the configuration of the present invention. 1 is an external view of a mobile phone having the configuration of the present invention. The block diagram which shows the structure of the conventional portable information terminal. The block diagram which shows the structure of the conventional mobile telephone. The block diagram which shows the structure of a transmission / reception circuit. The block diagram of the conventional display apparatus. FIG. 6 is a pixel circuit diagram of a conventional display device. The figure which shows the response time of a triplet EL material. FIG. 6 is a top view of a pixel of a display device of the present invention.

FIG. 1 shows the configuration of the present invention. In the present invention, when a still image is displayed, display is performed by storing a video signal in a storage circuit inside a pixel of the display device 2213 and calling the stored video signal. Therefore, it is possible to display a still image without driving the source signal line driver circuit in the video signal processing circuit 2107, the VRAM 2111, and the display device 2213 among the internal circuits of the CPU 2106 that have been operated conventionally. Become. Note that information required by the user as needed can be extracted from the external device via the external interface port 2105.
In addition, information stored in the memory card 2103 inserted into the portable information terminal can be extracted. Reference numeral 2104 denotes a power source.

  The contents will be specifically described below.

  When the input from the pen input tablet 2101 is not performed for a certain period of time, or when the signal input that requires the video display to be changed from the external input terminal is not performed for a certain period of time, the CPU 2106 determines that the still image mode is set.

  When the CPU 2106 makes such a determination, the CPU 2106 performs the following operation. The source signal line driver circuit of the display device 2213 is stopped via the EL controller 2112. Specifically, the operation of the source signal line driver circuit can be stopped by stopping the supply of the start pulse, clock signal, and video data signal to the source signal line driver circuit. At this time, the gate signal line driver circuit does not stop but receives a signal supply and supplies data of a memory circuit provided in a pixel portion in the display device 2213 to a pixel electrode of each pixel.

  Since the gate signal line driving circuit is generally driven at a frequency of 1/100 or less as compared with the source signal line driving circuit, there is no problem in terms of power consumption even if the operation is not stopped. Of course, the gate signal line driving circuit may be stopped. By such an operation, the display device performs display by stopping only the gate signal line driver circuit or both signal line driver circuits.

  Next, the CPU 2106 stops the signal processing circuit inside the CPU 2106 and the VRAM 2111. As described above, since the display device 2213 performs display using the video data stored in the internal storage circuit, there is no need to newly send video data to the display device 2213 when displaying a still image. . Therefore, the video signal processing circuit 2107 for generating and processing video data, the tablet interface 2118, the VRAM 2111, and the like do not have to operate. Further, it is not necessary to access storage circuits such as the DRAM 2109 and the flash memory 2110 that hold information requested by the user.

  As described above, power reduction in the CPU 2106, power reduction in the VRAM 2111, and power reduction in the source signal line driver circuit are achieved.

  When a signal is input again from an external input terminal such as the pen input tablet 2101, the detection circuit 2102 of the pen input tablet 2101 instructs the CPU 2106 to change the display content. Then, the CPU 2106 operates the stopped VRAM 2111, tablet interface 2118, and video signal processing circuit 2107. Then, a start pulse, a clock signal, and video data can be supplied to the source signal line driver circuit of the display device 2213 through the EL controller 2112, and a new video signal can be written into the pixel.

  FIG. 2 is an example of a mobile phone using the present invention. The outline of the operation is almost the same as that of the portable information terminal of FIG. Unlike a portable information terminal, in a mobile phone, input is performed by a keyboard, and external data is input to an antenna via a communication system of a telephone company and amplified by a transmission / reception circuit shown in FIG. After that, it is controlled by the CPU and sent to the display device. In the case of displaying a still image, the video signal processing circuit, the VRAM, the source signal line driver circuit, and the like can be stopped as in the portable information terminal.

  Examples of the present invention will be described below.

  In this embodiment, a structure of a mobile phone having the structure of the present invention will be described.

  FIG. 2 shows a block diagram of the mobile phone of this embodiment. Those already illustrated in the portable information terminal shown in FIG.

  The cellular phone includes a transmission / reception circuit 2124 for transmitting and receiving radio waves, an audio processing circuit 2121 for processing audio signals received, a speaker 2123, a microphone 2122, a keyboard 2120 for inputting data, a display device 2113 for display, an EL controller 2112, It consists of storage devices (VRAM 2111, DRAM 2109, flash memory 2110, etc.).

  In the mobile phone shown in FIG. 2, operations of the keyboard interface 2138, the video signal processing circuit 2107, the VRAM 2111 and the EL controller 2112 are the same as those in the mobile information terminal shown in FIG. The only difference is that the user's instructions are read as electronic information on the keyboard 2120. Data from the outside is input to the antenna via the communication system of the telephone company, amplified by the transmission / reception circuit 2224 shown in FIG. 2, then controlled by the CPU 2106, and sent to the display device 2213.

  If the input from the keyboard 2220 is not performed for a certain period of time or the signal input that requires the video display to be changed from the external input terminal is not performed for a certain period of time, the CPU 2106 determines that the still image mode is set.

  When the CPU 2106 makes such a determination, the CPU 2106 performs the following operation. The source signal line driver circuit of the display device 2213 is stopped via the EL controller 2112. Specifically, the operation of the source signal line driver circuit can be stopped by stopping the supply of the start pulse, clock signal, and video data signal to the source signal line driver circuit. At this time, the gate signal line driver circuit does not stop but receives a signal supply and supplies data of a memory circuit provided in a pixel portion in the display device 2213 to a pixel electrode of each pixel.

  Since the gate signal line driving circuit is generally driven at a frequency of 1/100 or less as compared with the source signal line driving circuit, there is no problem in terms of power consumption even if the operation is not stopped. Of course, the gate signal line driving circuit may be stopped. By such an operation, the display device performs display by stopping only the gate signal line driver circuit or both signal line driver circuits.

  Next, the CPU 2106 stops the signal processing circuit inside the CPU 2106 and the VRAM 2111. As described above, since the display device 2213 performs display using the video data stored in the internal storage circuit, there is no need to newly send video data to the display device 2213 when displaying a still image. . Therefore, the video signal processing circuit 2107 that generates and processes video data, the keyboard interface 2138, the VRAM 2111, and the like do not have to operate. Further, it is not necessary to access storage circuits such as the DRAM 2109 and the flash memory 2110 that hold information requested by the user.

  As described above, power reduction in the CPU 2106, power reduction in the VRAM 2111, and power reduction in the source signal line driver circuit are achieved.

  In addition, when a signal is input again from an external input terminal such as the keyboard 2220, the keyboard 2220 instructs the CPU 2106 to change the display contents. Then, the CPU 2106 operates the stopped VRAM 2111, keyboard interface 2138, and video signal processing circuit 2107. Then, a start pulse, a clock signal, and video data can be supplied to the source signal line driver circuit of the display device 2213 through the EL controller 2112, and a new video signal can be written into the pixel.

  In this embodiment, a detailed structure of a pixel portion included in a display device used in the present invention will be described.

  A plurality of pixels are arranged in a matrix in the pixel portion. An enlarged view of the pixel 704 of this embodiment is shown in FIG. The pixel 704 is provided with a switching TFT 705, an EL driving TFT 706, an SRAM 707, and an EL element 708 sandwiching the EL between the counter electrode and the pixel electrode.

  A gate electrode of the switching TFT 705 is connected to the gate signal line 709. One of the source region and the drain region of the switching TFT 705 is connected to the source signal line 710, and the other is connected to the input side of the SRAM 707.

  The SRAM 707 has two p-channel TFTs and two n-channel TFTs, and the source region of the p-channel TFT is connected to the high voltage side power supply line 711 and is maintained at the voltage Vddh. The source region of the n-channel TFT is connected to the low voltage side power supply line 712 and is kept at the voltage Vss. Note that Vddh> Vss. One p-channel TFT and one n-channel TFT are paired, and two pairs of p-channel TFT and n-channel TFT exist in one SRAM.

  The drain regions of the paired p-channel TFT and n-channel TFT are connected to each other. The gate electrodes of the paired p-channel TFT and n-channel TFT are connected to each other. The drain regions of one pair of p-channel and n-channel TFTs are maintained at the same potential as the gate electrodes of the other pair of p-channel and n-channel TFTs. The drain region of one pair of p-channel and n-channel TFTs is an input side for receiving an input signal (Vin), and the drain region of the other pair of p-channel and n-channel TFTs is an output signal. This is the output side where (Vout) is output.

  The SRAM is designed to hold Vin and output Vout that is a signal obtained by inverting Vin. That is, when Vin is Hi, Vout is a Lo signal corresponding to Vss, and when Vin is Lo, Vout is a Hi signal corresponding to Vddh.

  The output side of the SRAM 707 is connected to the gate electrode of the EL driving TFT 706. The source region of the EL driving TFT 706 is connected to the power supply line 713, and the drain region is connected to the pixel electrode included in the EL element 708.

  The switching TFT 705 is turned on by a selection signal input to the gate signal line 709. The digital video signal input to the source signal line 710 is input as Vin to the input side of the SRAM 707 via the switching TFT 705.

  The input digital video signal is held until the next digital video signal is input. SRAM requires less time for writing a digital video signal than DRAM, and can write data at high speed.

  The digital video signal has 1 or 0 information, and the digital video signal input to the SRAM 707 is output with the information inverted. For example, when a digital video signal having 1 information is input to the SRAM 707, a digital video signal having 0 information is output from the output side of the SRAM 707 as Vout. Conversely, when a digital video signal having 0 information is input to the SRAM 707, a digital video signal having 1 information is output as Vout from the output side of the SRAM 707.

  The digital video signal output from the output side of the SRAM 707 is input to the gate electrode of the EL driving TFT 706. The EL driving TFT 706 is turned on or off in accordance with 1 or 0 information included in the digital video signal input to the gate electrode.

  When the EL driving TFT 706 is turned off, the power supply potential of the power supply line 713 is not applied to the pixel electrode of the EL element 708, and thus the EL element 708 does not emit light. On the other hand, when the EL driving TFT 706 is turned on, the power supply potential of the power supply line 713 is applied to the pixel electrode of the EL element 708, so that the EL element 708 emits light.

  Similarly, by inputting a digital video signal to all pixels, it is selected whether or not the EL element of each pixel emits light.

  When all bits of digital video signals are input to all pixels, one image is displayed. Gray scale display may be performed by controlling the length of light emitted from the EL elements of each pixel during one frame period, or the area of a pixel having a light emitting EL element with a plurality of pixels as one unit. Gradation display may be performed by controlling.

  In the present invention, by providing the SRAM in the pixel, the digital video signal input to the pixel can be more reliably held until the next digital video signal is input. That is, it is possible to prevent the charge held in the gate electrode of the EL driving TFT from being reduced by the leakage current of the switching TFT, and to prevent the emission luminance of the EL element from being lowered.

  Note that since a volatile memory can be formed using a TFT, it can be formed at the same time as a switching TFT and an EL driving TFT.

  In the present invention, the holding capacitor does not have to be provided actively. When the storage capacitor is not provided, the time for inputting the digital video signal to the pixel can be shortened. Therefore, even if the number of pixels of the EL display increases, the length of the writing period can be suppressed.

  Note that this embodiment can be freely combined with the configuration shown in Embodiment 1.

  In this embodiment, a driver circuit for a display device used in the present invention will be described. FIG. 4A is a block diagram of a source signal line driver circuit.

  The source signal line driver circuit includes a shift register circuit 761, a latch circuit A 762, a latch circuit B 763, and a D / A conversion circuit 764.

  A clock signal (CK) and a start pulse (SP) are input to the shift register circuit 761 included in the source signal line driver circuit. The shift register circuit 761 sequentially generates timing signals based on the clock signal (CK) and the start pulse (SP), and sequentially supplies the timing signals to the latch circuit A762.

  The latch circuit A 762 includes a plurality of latches that store digital video signals. When the timing signal is input, the latch circuit A 762 sequentially captures and holds the digital video signal in each latch.

  The time until writing of the digital video signal to all the latches of the latch circuit A 762 is completed is called a line period. Actually, a period obtained by adding a horizontal blanking period to the line period may be called a line period.

  After the end of one line period, a latch signal (Latch Signal) is supplied to the latch circuit B763. At this moment, the digital video signals written and held in the latch circuit A 762 are sent all at once to the latch circuit B 763 and written and held in all the latches of the latch circuit B 763.

  Based on the timing signal from the shift register circuit 761, the digital video signal is sequentially written again in the latch circuit A 762 that has finished sending the digital video signal to the latch circuit B 763.

  During the second line period, the digital video signals written and held in the latch circuit B 763 are sequentially supplied to the source signal lines.

  FIG. 4B is a block diagram of the gate signal line driver circuit. The gate signal line driver circuit includes a shift register circuit 766 and a buffer circuit 767. When the clock signal (CLK) and the start pulse signal (SP) are input to the shift register circuit 766 in the gate signal line driver circuit, a selection signal for controlling the switching of the pixel TFT is generated. The selection signal is buffered and amplified in the buffer circuit 767 and input to the gate signal line.

  Note that this embodiment can be implemented by being freely combined with Embodiment 1 or Embodiment 2.

  In this embodiment, an example in which an EL display device is manufactured using the present invention will be described with reference to FIGS.

  FIG. 5A is a top view of an EL display device formed by sealing a TFT substrate provided with an EL element with a sealing material, and FIG. 5B is a top view of FIG. 5A. FIG. 5C is a cross-sectional view taken along the line BB ′ of FIG. 5A.

  A sealant 4009 is provided so as to surround the pixel portion 4002, the source signal line driver circuit 4003, and the first and second gate signal line driver circuits 4004a and 4004b provided over the substrate 4001. Further, a sealing material 4008 is provided over the pixel portion 4002, the source signal line driver circuit 4003, and the first and second gate signal line driver circuits 4004a and 4004b. Therefore, the pixel portion 4002, the source signal line driver circuit 4003, and the first and second gate signal line driver circuits 4004 a and 400 b are sealed with the filler 4210 by the substrate 4001, the sealant 4009, and the sealant 4008. ing.

  The pixel portion 4002, the source signal line driver circuit 4003, and the first and second gate signal line driver circuits 4004a and 4004b provided over the substrate 4001 include a plurality of TFTs. In FIG. 5B, typically, a driving TFT (here, an n-channel TFT and a p-channel TFT are illustrated) 4201 formed over the base film 4010 and included in the source signal line driver circuit 4003; An EL driving TFT (TFT for controlling current to the EL element) 4202 included in the pixel portion 4002 is illustrated.

  In this embodiment, a p-channel TFT or an n-channel TFT manufactured by a known method is used as the driving TFT 4201, and a p-channel TFT manufactured by a known method is used as the EL driving TFT 4202. Further, the pixel portion 4002 is provided with a storage capacitor (not shown) connected to the gate of the EL driving TFT 4202.

  An interlayer insulating film (planarization film) 4301 is formed over the driving TFT 4201 and the EL driving TFT 4202, and a pixel electrode (anode) 4203 electrically connected to the drain of the EL driving TFT 4202 is formed thereon. As the pixel electrode 4203, a transparent conductive film having a large work function is used. As the transparent conductive film, a compound of indium oxide and tin oxide, a compound of indium oxide and zinc oxide, zinc oxide, tin oxide, or indium oxide can be used. Moreover, you may use what added the gallium to the said transparent conductive film.

  An insulating film 4302 is formed over the pixel electrode 4203, and an opening is formed over the pixel electrode 4203 in the insulating film 4302. In this opening, an EL (electroluminescence) layer 4204 is formed on the pixel electrode 4203. A known organic EL material or inorganic EL material can be used for the EL layer 4204. The organic EL material includes a low molecular (monomer) material and a high molecular (polymer) material, either of which may be used.

  As a method for forming the EL layer 4204, a known vapor deposition technique or coating technique may be used. The EL layer may have a stacked structure or a single layer structure by freely combining a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, or an electron injection layer.

  Over the EL layer 4204, a cathode 4205 made of a light-shielding conductive film (typically a conductive film containing aluminum, copper, or silver as its main component or a stacked film of these with another conductive film) is formed. . In addition, it is preferable to remove moisture and oxygen present at the interface between the cathode 4205 and the EL layer 4204 as much as possible. Therefore, it is necessary to devise such that the EL layer 4204 is formed in a nitrogen or rare gas atmosphere and the cathode 4205 is formed without being exposed to oxygen or moisture. In this embodiment, the above-described film formation is possible by using a multi-chamber type (cluster tool type) film formation apparatus. The cathode 4205 is given a predetermined voltage.

  As described above, an EL element 4303 including the pixel electrode (anode) 4203, the EL layer 4204, and the cathode 4205 is formed. A protective film 4303 is formed over the insulating film 4302 so as to cover the EL element 4303. The protective film 4303 is effective in preventing oxygen, moisture, and the like from entering the EL element 4303.

  Reference numeral 4005a denotes a lead wiring connected to the power supply line, which is electrically connected to the source region of the EL driving TFT 4202. The lead wiring 4005 a passes between the sealant 4009 and the substrate 4001 and is electrically connected to the FPC wiring 4301 included in the FPC 4006 through the anisotropic conductive film 4300.

As the sealing material 4008, a glass material, a metal material (typically a stainless steel material), a ceramic material, or a plastic material (including a plastic film) can be used. Plastic materials include FRP (Fiberglass-Reinforced Plastics) plate, PVF (polyvinyl fluoride)
A film, mylar film, polyester film or acrylic resin film can be used. A sheet having a structure in which an aluminum foil is sandwiched between PVF films or mylar films can also be used.

  However, when the emission direction of light from the EL element is directed toward the cover material, the cover material must be transparent. In that case, a transparent material such as a glass plate, a plastic plate, a polyester film or an acrylic film is used.

  Further, as the filler 4103, in addition to an inert gas such as nitrogen or argon, an ultraviolet curable resin or a thermosetting resin can be used. PVC (polyvinyl chloride), acrylic, polyimide, epoxy resin, silicone resin, PVB (Polyvinyl butyral) or EVA (ethylene vinyl acetate) can be used. In this example, nitrogen was used as the filler.

  Further, in order to expose the filler 4103 to a hygroscopic substance (preferably barium oxide) or a substance capable of adsorbing oxygen, a recess 4007 is provided on the surface of the sealing material 4008 on the substrate 4001 side to adsorb the hygroscopic substance or oxygen. A possible substance 4207 is placed. In order to prevent the hygroscopic substance or the substance 4207 capable of adsorbing oxygen from scattering, the concave part cover material 4208 holds the hygroscopic substance or the substance 4207 capable of adsorbing oxygen in the concave part 4007. Note that the concave cover material 4208 has a fine mesh shape, and is configured to allow air and moisture to pass therethrough but not a hygroscopic substance or a substance 4207 capable of adsorbing oxygen. By providing the hygroscopic substance or the substance 4207 capable of adsorbing oxygen, deterioration of the EL element 4303 can be suppressed.

  As shown in FIG. 5C, the conductive film 4203a is formed so as to be in contact with the lead wiring 4005a at the same time as the pixel electrode 4203 is formed.

  The anisotropic conductive film 4300 has a conductive filler 4300a. By thermally pressing the substrate 4001 and the FPC 4006, the conductive film 4203a on the substrate 4001 and the FPC wiring 4301 on the FPC 4006 are electrically connected by the conductive filler 4300a.

  Note that this embodiment can be implemented by being freely combined with Embodiments 1 to 3.

  In the present invention, by using an EL material that can use phosphorescence from triplet excitons for light emission, the external light emission quantum efficiency can be dramatically improved. This makes it possible to reduce the power consumption, extend the life, and reduce the weight of the EL element.

Here, a report of using triplet excitons to improve the external emission quantum efficiency is shown.
(T. Tsutsui, C. Adachi, S. Saito, Photochemical Processes in Organized Molecular Systems, ed. K. Honda, (Elsevier Sci. Pub., Tokyo, 1991) p.437.)

  The molecular formula of the EL material (coumarin dye) reported by the above paper is shown below.

  (M.A.Baldo, D.F.O'Brien, Y.You, A.Shoustikov, S.Sibley, M.E.Thompson, S.R.Forrest, Nature 395 (1998) p.151.)

  The molecular formula of the EL material (Pt complex) reported by the above paper is shown below.

  (MABaldo, S. Lamansky, PEBurrrows, METhompson, SRForrest, Appl.Phys.Lett., 75 (1999) p.4.) (T.Tsutsui, M.-J.Yang, M.Yahiro, K .Nakamura, T.Watanabe, T.tsuji, Y.Fukuda, T.Wakimoto, S.Mayaguchi, Jpn.Appl.Phys., 38 (12B) (1999) L1502.)

  The molecular formula of the EL material (Ir complex) reported by the above paper is shown below.

  As described above, if phosphorescence emission from triplet excitons can be used, in principle, it is possible to realize an external emission quantum efficiency that is 3 to 4 times higher than that in the case of using fluorescence emission from singlet excitons.

  Note that this embodiment can be freely combined with Embodiments 1 to 4.

  In this embodiment, an external view of a portable information terminal of the present invention will be described. FIG. 6 shows a portable information terminal having the configuration of the present invention, 2701 is a display panel, and 2702 is an operation panel. The display panel 2701 and the operation panel 2702 are connected at a connection portion 2703. In the connection portion 2703, the angle θ between the surface of the display panel 2701 on which the display portion 2704 is provided and the surface of the operation panel 2702 on which the operation key 2706 is provided can be arbitrarily changed.

  The display panel 2701 has a display portion 2704. 6 has a function as a telephone, the display panel 2701 has an audio output unit 2705, and audio is output from the audio output unit 2705. An EL display is used for the display portion 2704.

  The aspect ratio of the display portion 2704 can be arbitrarily selected such as 16: 9, 4: 3. The size of the display portion 2704 is desirably about 1 inch to 4.5 inches diagonal.

  The operation panel 2702 has operation keys 2706, a power switch 2707, and a voice input unit 2708. In FIG. 6, the operation key 2706 and the power switch 2707 are provided separately, but the operation key 2706 may include the power switch 2707. The voice input unit 2708 inputs voice.

  In FIG. 6, the display panel 2701 has an audio output unit 2705 and the operation panel 2702 has an audio input unit 2708, but this embodiment is not limited to this configuration. The display panel 2701 may have a voice input unit 2708 and the operation panel may have a voice output unit 2705. Further, both the audio output unit 2705 and the audio input unit 2708 may be provided on the display panel 2701, and both the audio output unit 2705 and the audio input unit 2708 may be provided on the operation panel 2702.

  7 shows an example in which the operation key 2706 of the portable information terminal shown in FIG. 6 is operated with the index finger. FIG. 8 shows an example in which the operation key 2706 of the portable information terminal shown in FIG. 6 is operated with the thumb. Note that the operation key 2706 may be provided on a side surface of the operation panel 2702. The operation can be performed with only one index finger of the hand or the thumb.

  Note that this embodiment can be freely combined with Embodiments 1 to 5.

  In the present embodiment, a portable information terminal having a mobile phone different from that shown in the sixth embodiment will be described. FIGS. 9A and 9B are external views of the portable information terminal of this embodiment. FIG. 9A is a top view and FIG. 9B is a side view.

  Reference numeral 2901 denotes a display panel, and 2902 denotes an operation panel. The display panel 2901 and the operation panel 2902 are connected at a connection portion 2903. In the connection portion 2903, the angle between the surface on which the display portion 2904 of the display panel 2901 is provided and the surface on which the operation key 2906 is provided on the operation panel 2902 can be arbitrarily changed.

  The display panel 2901 has a display portion 2904. The portable information terminal shown in FIG. 9 has a function as a telephone, the display panel 2901 has an audio output unit 2905, and audio is output from the audio output unit 2905. An EL display device having the structure of the present invention is used for the display portion 2904.

  The operation panel 2902 includes operation keys 2906, a power switch 2907, and a voice input unit 2908. Although the operation key 2906 and the power switch 2907 are separately provided in FIG. 9, the operation key 2906 may include the power switch 2907. Voice is input in the voice input unit 2908.

  Further, an image can be taken into the portable information terminal from the CCD light receiving unit 2910 as electronic information.

  Reference numeral 2911 denotes an external connection port, which can take in data from the outside. Reference numeral 2909 denotes an antenna.

  In FIG. 9, the display panel 2901 has an audio output unit 2905 and the operation panel 2902 has an audio input unit 2908, but this embodiment is not limited to this configuration. The display panel 2901 may have an audio input unit 2908 and the operation panel may have an audio output unit 2905. Further, both the audio output unit 2905 and the audio input unit 2908 may be provided on the display panel 2901, and both the audio output unit 2905 and the audio input unit 2908 may be provided on the operation panel 2902.

  In the portable information terminal shown in FIG. 9, the operation keys 2906 each have an LED, a liquid crystal, an EL, or the like. One or more characters, symbols, numbers, and the like are displayed on each operation key 2906 by the LED, liquid crystal, EL, or the like included in each operation key 2906. In the portable information terminal of this embodiment, the user can change the direction of the image displayed on the display unit 2904 and the direction of the image such as characters, numbers, and symbols displayed on the operation keys 2906 as appropriate. is there.

  FIG. 9A shows the direction of the image displayed on the display portion 2904 and the characters, numbers, and symbols displayed on the operation keys 2906 when the display panel 2901 and the operation panel 2902 are arranged in the horizontal direction. The direction of the image is the original direction when viewed from the user side.

  Although not shown, when the display panel 2901 and the operation panel 2902 are arranged in the vertical direction, the direction of the image displayed on the display unit 2904 and the characters, numbers, and characters displayed on the operation keys 2906 are displayed. The direction of the image such as a symbol may be in the original direction when viewed from the user side.

  The portable information terminal of the present invention can switch the direction of an image displayed on the display unit 2904 and the direction of an image such as letters, numbers, and symbols displayed on the operation keys 2906 in accordance with the convenience of the user. is there.

  Note that although FIG. 9 illustrates the case where the direction of the image displayed on the display unit 2904 and the direction of the image such as characters, numbers, and symbols displayed on the operation keys 2906 are always the same, the present invention is not limited to this. . The direction of the image displayed on the display unit 2904 and the direction of the image such as characters, numbers, and symbols displayed on the operation keys 2906 may be different.

  Note that the characters, numbers, and symbols displayed by the operation keys shown in FIG. 9 are examples, and the portable information terminal of the present invention is not limited to these characters, numbers, and symbols.

Further, the direction of the image displayed on the display unit 2904 and the direction of the image such as characters, numbers, and symbols displayed on the operation keys 2906 are displayed on the surface of the connection unit 103 having the display unit 2904 and the operation. A configuration may be adopted in which switching is automatically performed according to the angle between the panel 2902 and the surface having the operation keys 2906.
These configurations are described in detail in Japanese Patent Application No. 2000-080973.

  With the above configuration, the portable information terminal of the present invention can be made more convenient for the user.

  Note that this embodiment can be freely combined with Embodiments 1 to 5.

  In this example, characteristics of an EL material that can use phosphorescence from triplet excitons for light emission used in the present invention will be described.

  In the display device of the present invention, DC application and ON-OFF were switched to a power supply line by an arbitrary waveform generator, and response time was measured. The ON period (selection period) and the off period (non-selection period, voltage 0 V) were each 250 μs.

  As an optical system for measuring the light emission luminance of the EL element, a photomultiplier was installed in a microscope and a microscope barrel, and the output of the photomultiplier was measured with an oscilloscope. In this specification, the response time is defined as the rise of the switch from the non-selected state to the selected state and the fall of the switch from the selected state to the non-selected state. Specifically, the time required for the change in the optical response following the switch of the drive waveform to change to 90% with respect to the full response was defined as the response time.

  FIG. 15 shows a driving waveform of a signal input to the power supply line and an optical response waveform that means the light emission luminance of the EL element at the time of measurement. The top is the drive waveform and the bottom is the optical response. The photomultiplier uses a negative output type, and a voltage of 0V to 6V was applied. At this time, the response time was 33 μs.

  As described above, if phosphorescence emission from triplet excitons can be used, in principle, it is possible to realize an external emission quantum efficiency that is 3 to 4 times higher than that in the case of using fluorescence emission from singlet excitons.

  This embodiment can be implemented by freely combining with Embodiments 1-7.

  In this embodiment, an example in which a memory circuit provided in a pixel portion is disposed under a source signal line will be described.

  FIG. 16 is a top view of a pixel of a bottom-illuminated EL display device. The pixel 801 is a region including one of the source signal lines 804, the gate signal line 803, and one of the power supply lines 805, and has a pixel electrode 801. Although not shown in FIG. 16, the pixel 800 includes a switching TFT and an EL driving TFT.

  If the design rule is 1 μm and the pixel pitch is about 100 ppi, the memory circuit used in the present invention can be arranged under the source signal line 804, and not only the top-illuminated type but also the bottom-illuminated type EL display device Can also be applied.

  In addition, a memory circuit can be provided below the gate signal line 803 instead of the source signal line 804.

  In addition, the structure of a present Example can be implemented in combination freely with the structure described in Examples 1-8.

Claims (9)

A CPU, a pixel, and a source signal line driver circuit;
The pixel includes a circuit and an EL element.
The circuit has a function of storing a video signal,
The portable information device according to claim 1, wherein the CPU has a function of stopping the source signal line driver circuit when an input from an input tablet using a pen is not performed for a certain period of time. A CPU, a pixel, and a source signal line driver circuit;
The pixel includes a circuit and an EL element.
The circuit has a function of storing a video signal,
The CPU has a function of stopping a start pulse, a clock signal, and a video signal to the source signal line driving circuit when an input from an input tablet using a pen is not performed for a certain period of time. Portable information device. In claim 1 or claim 2,
A gate signal line driving circuit;
The portable information device according to claim 1, wherein the CPU has a function of preventing the gate signal line driver circuit from being stopped when an input from the input tablet is not performed for a predetermined time. In claim 1 or claim 2,
A gate signal line driving circuit;
The portable information device according to claim 1, wherein the CPU has a function of stopping the gate signal line driving circuit when an input from the input tablet is not performed for a predetermined time. In any one of Claims 1 thru | or 4,
The pixel is electrically connected to a first wiring;
The source signal line driver circuit is electrically connected to the first wiring;
The portable information device, wherein the first wiring has a region overlapping with the circuit. In claim 3 or claim 4,
The pixel is electrically connected to a first wiring;
The gate signal line driver circuit is electrically connected to the first wiring;
The portable information device, wherein the first wiring has a region overlapping with the circuit. In any one of Claims 1 thru | or 6,
Having a detection circuit;
The detection circuit has a function of issuing an instruction to change the display contents to the CPU when an input from the input tablet is performed. In any one of Claims 1 thru | or 7,
A first substrate provided with the pixel and the source signal line driver circuit;
A second substrate on the first substrate,
The second substrate has a recess on the first substrate side,
The recess has a region overlapping with the source signal line drive circuit,
A portable information device, wherein the concave portion is provided with a substance having a function of adsorbing water or oxygen. In any one of Claims 1 thru | or 8,
An FPC, routing wiring, and a conductive film on the routing wiring,
The conductive film has the same material as the electrode of the EL element,
The routing wiring is electrically connected to the pixel,
The portable information device characterized in that the routing wiring is electrically connected to the wiring of the FPC.

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