JP2002140034A - Portable information device and its driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a portable information device with an LE display device which can be made low in power consumption when a still picture is displayed. SOLUTION: In the EL display device that the portable information device has, a plurality of storage circuits and a D/A converter are arranged in a pixel. When the EL display device displays a still picture, the EL display device and video display functions other than a control circuit which controls the EL display device are stopped to make the power consumption small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a portable information device. In particular, the present invention relates to a portable information device, such as a mobile phone, a PDA, a portable personal computer, a portable navigation system, and an electronic book, into which a display device using an organic EL element or the like is incorporated.

[0002] In this specification, an EL element refers to both an element utilizing light emission (fluorescence) from a singlet exciton and an element utilizing light emission (phosphorescence) from a triplet exciton. And

[0003]

2. Description of the Related Art In recent years, mobile phones have become widespread due to the development of communication technology. In the future, the transmission of moving images and the transmission of more information are expected. On the other hand, personal computers have been manufactured for mobile devices due to their light weight. A large number of information devices called personal digital assistants (PDAs) started with electronic notebooks have been produced and are becoming popular. Also, due to the development of EL display devices and the like, most of these portable information devices are equipped with flat displays.

In a more recent technology, there is a trend to use an active matrix type display device as an EL display device used for them.

In the active matrix type display device, an image is controlled by arranging one thin film transistor (hereinafter referred to as TFT) for each pixel. Such an active matrix display device has advantages over a passive matrix display device, such as higher definition, higher image quality, and compatibility with moving images. Therefore, it is expected that the EL display device of the portable information device will change from the passive matrix type to the active matrix type in the future.

[0006] Among active matrix display devices, display devices using low-temperature polysilicon have recently been commercialized. With low temperature polysilicon technology,
In addition to the pixel TFT that constitutes the pixel,
A driving circuit can be simultaneously formed using TFTs, which greatly contributes to miniaturization of the device and low power consumption. Along with this, an EL display device has become an indispensable device in a display section of a mobile device, etc., in which the application field has been remarkably expanding in recent years.

FIG. 15 is a block diagram of a conventional portable information terminal incorporating an EL display device.

[0008] In a portable information terminal, it is required that a user derive required information as needed. The information is first stored in a storage device (DRAM 1) in the portable information terminal.
509, flash memory 1510, etc.), those stored in a memory card 1503 inserted into a portable information terminal, and those that obtain information by connecting to an external device via an external interface port 1505. is there. These pieces of information are based on the user's instruction input from the pen input tablet 1501,
Processed by the CPU 1506 and the EL display device 1513
Performs display.

Specifically, a pen input doublet 1501
The input signal is detected by the detection circuit 1502 and input to the doublet interface 1518. This input signal is sent to the doublet interface 15
18 and input to the video signal processing circuit 1507 and the like. The CPU 1506 processes necessary data, converts the data into image data based on the image format stored in the VRAM 1511,
Send to 12. Here, the EL controller 1512 generates a signal for driving the EL display device 1513 and outputs the signal to the display device 1513.
Input to 13. Thus, the display device 1513 is driven to perform display.

FIG. 16 is a block diagram of a conventional portable telephone incorporating an EL display device. The mobile phone includes a transmission / reception circuit 1615 for transmitting and receiving radio waves, a voice processing circuit 1602 for performing voice processing on a received signal, a speaker 1614, a microphone 1608, and a keyboard 160 for inputting data.
1, a keyboard interface 1618 for processing a signal input from the keyboard 1601;

On the basis of a user's instruction input from a keyboard, a device stored in a storage device (DRAM 1609, flash memory 1610, etc.), a device stored in a memory card 1603 inserted into a portable information terminal, an external device Interface port 160
And the like obtained by connecting to an external device via the CPU 5
06, and the EL display device 1613 performs display.

More specifically, a signal input from a keyboard 1601 is processed by a keyboard interface 1618 and input to a video signal processing circuit 1607 and the like. The necessary data is processed by the CPU 1606, and
The image data is converted into image data based on the image format stored in the RAM 1611 and sent to the EL controller 1612. Here, the EL controller 1612 generates a signal for driving the EL display device 1613 and inputs the signal to the display device. Thus, the display device is driven to perform display.

FIG. 26 shows an example of the structure of the transmission / reception circuit 1615.

The transmitting / receiving circuit 1615 includes an antenna 260
2, filters 2603, 2607, 2608, 261
2, 2616, switch 2604, amplifier 2605, 2
606, 2617, the first frequency conversion circuit 2609, the second
A frequency conversion circuit 2613, a frequency conversion circuit 2611, oscillation circuits 2610 and 2614, an orthogonal converter 2615, a data demodulation circuit 2618, and a data modulation circuit 2619 are included.

Here, as a display device incorporated in the portable information terminal or the portable telephone, a conventional digital E-type is used.
The L display device will be described. The schematic diagram is shown in FIG. A pixel portion 1308 is provided at the center. A source signal line driver circuit 1301 for controlling a source signal line is provided above the pixel portion. The source signal line driver circuit 1301 includes a shift register circuit 1303, a first latch circuit 1304, a second latch circuit 1305,
A D / A converter (D / A conversion circuit) 1306, an analog switch 1307, and the like are provided. A gate signal line drive circuit 1 for controlling a gate signal line is provided on the left and right sides of the pixel portion.
302 is arranged. In FIG. 13, the gate signal line driving circuits 1302 are arranged on both the left and right sides of the pixel portion, but may be arranged on one side. However, it is desirable to dispose them on both sides in terms of drive efficiency and drive reliability.

The source signal line drive circuit 1301 has a configuration as shown in FIG. The drive circuit shown as an example in FIG. 14 has a horizontal resolution of 1024 pixels,
A source signal line driving circuit corresponding to the display of a 3-bit digital gradation signal, and a shift register circuit (SR) 140
1, a first latch circuit (LAT1) 1402, a second latch circuit (LAT2) 1403, a D / A converter (D
/ A) 1404 and the like. Although not shown in FIG. 14, a buffer circuit, a level shifter circuit, and the like may be provided as necessary.

The operation of the display device will be briefly described with reference to FIGS. First, a clock signal (S-CLK, S-CLKb) and a start pulse (S-SP) are input to a shift register circuit 1303 (denoted by SR in FIG. 14), and pulses (sampling pulses) are sequentially output. Subsequently, those pulses are input to a first latch circuit 1304 (denoted as LAT1 in FIG. 14), and hold the digital signals (Digital Data) input to the first latch circuit 1304, respectively. Here, D1 is the most significant bit (MSB:
Most Significant Bit), D3 is the least significant bit (LS)
B: Least Significant Bit). When the holding of the digital signal for one horizontal cycle is completed in the first latch circuit 1304, the first latch circuit 1330
04 is a latch signal (L
In response to the input of the “attach pulse”, the data is simultaneously transferred to the second latch circuit 1305 (denoted as LAT2 in FIG. 14).

Thereafter, the shift register circuit 1303 is again activated.
Operates to start holding digital signals for the next horizontal cycle. At the same time, the digital signal held by the second latch circuit 1305 is converted to an analog signal by a D / A converter 1306 (denoted as D / A in FIG. 14). This analog signal is input to the pixel via the source signal line. By repeating this operation, an image is displayed.

Subsequently, driving of the pixel portion 1308 will be described. FIG. 29 illustrates a part of the pixel portion 1308 in FIG. FIG. 29A shows a matrix of 3 × 3 pixels. A portion surrounded by a dotted frame 1900 is one pixel, and FIG. 29B is an enlarged view thereof. In FIG. 29B, reference numeral 1901 denotes a TFT which functions as a switching element when writing a signal to a pixel (hereinafter, referred to as a switching TFT). This switching TFT 1
Either an n-channel type or a p-channel type polarity may be used for 901. Reference numeral 1902 denotes a TFT that functions as an element (current control element) for controlling a current supplied to the EL element 1903 (hereinafter, referred to as an EL driving TFT).
It is. In the case where a p-channel type is used for the EL driving TFT 1902, it is arranged between the anode 1909 of the EL element 1903 and the power supply line 1907. As another configuration method, a cathode 1910 and a cathode electrode 190 of an EL element 1903 are used by using an n-channel TFT for an EL driving TFT 1902.
8 can also be arranged. But,
The operation of the TFT is such that the source ground is good and the EL element 1
903, the EL driving TFT 19
In general, a method of using a p-channel TFT for 02 and disposing an EL driving TFT 1902 between an anode 1909 of an EL element 1903 and a power supply line 1907 as shown in FIG. Many are adopted. 19
Reference numeral 04 denotes a storage capacitor for holding a signal (voltage) input from the source signal line 1906. One terminal of the storage capacitor 1904 in FIG.
7, but a dedicated wiring may be used. The gate electrode of the switching TFT 1901 is connected to the gate signal line 1905, one of the source region and the drain region is connected to the source signal line 1906, and the other is connected to the gate electrode of the EL driving TFT.

Next, the operation of the circuit of the active matrix type EL display device will be described with reference to FIG. First, when the gate signal line 1905 is selected, a voltage is applied to the gate electrode of the switching TFT 1901 and the switching TFT 1901 is turned on.
Then, a signal (voltage) of the source signal line 1906 is input to the storage capacitor 1904. The voltage of the storage capacitor 1904 is
Gate-source voltage V _{GS of} EL driving TFT 1902
Therefore, the current corresponding to the voltage of the storage capacitor 1904 is E
It flows to the L driving TFT 1902 and the EL element 1903.
As a result, the EL element 1903 turns on.

The luminance of the EL element 1903, that is, the EL element
The amount of current flowing through 1903 is the
V_GSIs controlled by V_GSIs the storage capacity 1904
Which is input to the source signal line 1906
Signal (voltage). That is, the source signal line 1906
By controlling the signal (voltage) input to the
The luminance of the L element 1903 is controlled. Finally, the gate signal
The line 1905 is deselected and the switching TFT
The gate of 1901 is closed and the switching TFT 190 is closed.
1 is turned off. At that time, the storage capacity 1904 stores
The accumulated charge is retained. Therefore, the EL driving TFT
V of 1902_GSIs held as it is, and V _GSDepending on the
The current flows through the EL element 19 via the EL driving TFT 1902.
Continue to 03.

Regarding the driving of the EL element, etc., SID99 Dige
st: P372: “Current Status andfuture of Light-Emi
tting Polymer Display Driven by Poly-Si TFT ”, ASI
A DISPLAY98: P217: “High Resolution Light Emitti
ng Polymer Display Drivenby Low Temperature Polysi
licon Thin Film Transistor with Integrated Drive
r ”, Euro Display99 Late News: P27:“ 3.8 Green O
LED with Low Temperature Poly-Si TFT ”etc.

[0023]

In the conventional portable information device as described above, when the incorporated display device displays an image, even if the image is a still image,
The same video data was continuously sent to the display device 60 times per second. That is, in FIG. 15, a portion surrounded by a broken line (the video signal processing circuit 1507 in the CPU 1506, V
RAM 1511, EL controller 1512, source signal line driving circuit and gate signal line driving circuit of EL display device 1513, pen input doublet 1501, detection circuit 15
02, the doublet interface 1518) continued to operate as long as the image was displayed. Also,
In FIG. 16, portions surrounded by broken lines (a video signal processing circuit 1607 in the CPU 1606, a VRAM 1611, an EL controller 1612, a source signal line driving circuit and a gate signal line driving circuit of an EL display device 1613, a keyboard 16
01, the keyboard interface 1618) continued to operate as long as the image was displayed.

Here, in a passive matrix type display device having a small number of pixels, there is a type in which a storage circuit is built in a driver IC or a controller of the display device and the VRAM is stopped. In a display device using such a large number of pixels, it is impractical to have a memory circuit in a driver or a controller from the viewpoint of chip size. Therefore, in the conventional portable information device, many circuits must continue to operate even when a still image is displayed, which hinders a reduction in power consumption.

In mobile devices, low power consumption is greatly desired. In addition, mobile devices
Although the driving circuit continues to operate even in the still image display as described above, despite the fact that the driving circuit is used in the still image mode (continue to display the still image) most of the time,
This is a drag on low power consumption.

Accordingly, an object of the present invention is to reduce the power consumption of a driving circuit at the time of displaying a still image in a device such as a portable information terminal or a portable telephone which requires low power consumption.

[0027]

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention uses the following means.

A plurality of storage circuits are arranged in pixels of a display device incorporated in a portable information device, and a digital signal is stored for each pixel. For still images, once you write,
After that, since the information written to the pixel is the same,
Even if a signal is not input for each frame, a still image can be displayed continuously by reading the signal stored in the storage circuit.

That is, when displaying a still image, at least one
After the signal processing operation for a frame is performed, the source signal line driving circuit, the image signal processing circuit, and the like can be stopped, and accordingly, the power consumption can be significantly reduced.

Hereinafter, the configuration of the portable information device of the present invention will be described.

According to the present invention, in a portable information device having an EL display device, the EL display device has a plurality of pixels, and each of the plurality of pixels has a plurality of storage circuits and a D / A converter. A portable information device is provided.

According to the present invention, in a portable information device having an EL display device, the EL display device has a plurality of pixels, and each of the plurality of pixels has n (n is a natural number of 2 or more) storage units. And a D / A converter that converts a digital signal stored in the n storage circuits into an analog signal.

According to the present invention, there is provided an EL display device, wherein the EL display device has a plurality of pixels and a power supply line, and each of the plurality of pixels has a TFT to which an analog signal is input to a gate electrode. And an EL element.
In a portable information device in which one of a source region and a drain region of the FT is connected to the power supply line and the other is connected to the EL element, each of the plurality of pixels is n (n is 2 A portable information device is provided, comprising: (the above natural numbers) storage circuits; and a D / A converter that converts digital signals stored in the n storage circuits into the analog signals.

According to the present invention, there is provided an EL display device, wherein the EL display device has a plurality of pixels and a power supply line, and each of the plurality of pixels has a TFT whose gate electrode receives an analog signal. And an EL element.
In a portable information device in which one of a source region and a drain region of the FT is connected to the power supply line and the other is connected to the EL element, each of the plurality of pixels is nxm (n and Is a natural number of 2 or more) storage circuits, and a D / A converter that converts n bits of digital signals stored in the n × m storage circuits into the analog signals. A portable information device is provided.

According to the present invention, there is provided an EL display device, wherein the EL display device has a plurality of pixels, each of which has an analog signal input to a gate electrode.
An FT, a power supply line, and an EL element;
In the portable information device, one of the source region and the drain region is connected to the power supply line, and the other is connected to the EL element.
n × m (n and a natural number of 2 or more) storage circuits;
A D / A converter for converting the n-bit digital signal stored in the n × m storage circuits into the analog signal, wherein each of the plurality of pixels stores the m-frame digital signal. A portable information device is provided.

In the portable information device, the EL display device has a source signal line, and the storage circuit and the D / A converter are arranged so as to overlap with the source signal line. Good.

The EL display device has a gate signal line, and the storage circuit and the D / A converter are arranged so as to overlap with the gate signal line. Good.

According to the present invention, there is provided an EL display device, wherein the EL display device has a plurality of pixels, and each of the plurality of pixels is a portable information device having an EL element. A source signal line and n (n is 2
The above (natural number) gate signal lines, power supply lines, and n
First TFTs, n storage circuits, and second TFTs
And a D / A converter, wherein the n first TFs are provided.
Each of the T gate electrodes is connected to any one of the n gate signal lines, one of a source region and a drain region is connected to the source signal line, and the other is connected to the source signal line. An output terminal of the n storage circuits is connected to an input terminal of the D / A converter, and an output terminal of the n storage circuits is connected to an input terminal of the D / A converter. A terminal is connected to a gate electrode of the second TFT, and one of a source region and a drain region of the second TFT is
A portable information device is provided, wherein the portable information device is connected to the power supply line and the other is connected to the EL element.

According to the present invention, there is provided an EL display device, wherein the EL display device has a plurality of pixels, and each of the plurality of pixels is a portable information device having an EL element. n (n is a natural number of 2 or more) source signal lines, gate signal lines, power supply lines, and n
First TFTs, n storage circuits, and second TFTs
And a D / A converter, wherein the n first TFs are provided.
T gate electrodes are each connected to the gate signal line, one of a source region and a drain region is each connected to a different one of the n source signal lines, and the other is each An output terminal of the n storage circuits is connected to an input terminal of the D / A converter, and an output terminal of the n storage circuits is connected to an input terminal of the D / A converter. A terminal is connected to a gate electrode of the second TFT, and one of a source region and a drain region of the second TFT is
A portable information device is provided, wherein the portable information device is connected to the power supply line and the other is connected to the EL element.

The EL display device has a source signal line driving circuit, and the source signal line driving circuit includes a shift register and a first latch for holding an n-bit digital signal by a sampling pulse from the shift register. A second latch circuit to which the n-bit digital signal held by the first latch circuit is transferred; and a 1-bit unit for transferring the n-bit digital signal transferred to the second latch circuit. And a switch for sequentially selecting and inputting to the source signal line.

The EL display device has a source signal line driving circuit, and the source signal line driving circuit has a shift register and a first latch for holding a 1-bit digital signal by a sampling pulse from the shift register. A portable information device may include a circuit and a second latch circuit to which the one-bit digital signal held in the first latch circuit is transferred.

The EL display device has a source signal line drive circuit, and the source signal line drive circuit includes a shift register and a latch circuit that holds an n-bit digital signal by a sampling pulse from the shift register. It may be a portable information device characterized by having.

The EL display device has a source signal line driving circuit, the source signal line driving circuit includes a shift register, a latch circuit for holding an n-bit digital signal by a sampling pulse from the shift register, The portable information device may include n switches for inputting the n-bit digital signal held in the latch circuit to the n source signal lines.

The storage circuit is a static type memory (S
(RAM), ferroelectric memory (FRAM) or dynamic memory (DRAM).

The portable information device may be characterized in that the storage circuit is formed on a glass substrate, a plastic substrate, a stainless steel substrate, or a single crystal wafer.

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

According to the present invention, an EL having a plurality of pixels
In the method for driving a portable information device in which a display device is incorporated, a digital signal is stored in a plurality of storage circuits included in each of the plurality of pixels, the stored digital signal is repeatedly read, and the repeatedly read digital signal is stored. The method of driving a portable information device is characterized in that the signals are converted into analog signals respectively and input to an EL element.

The plurality of pixels are arranged in a matrix, and of the plurality of pixels, only the stored digital signals of the plurality of storage circuits included in pixels in a specific row or pixels in a specific column are rewritten. A method for driving a portable information device, characterized in that:

According to the present invention, in a driving method of a portable information device incorporating an EL display device having a plurality of pixels and a source signal line driving circuit for inputting a video signal to the plurality of pixels, the plurality of pixels are A digital signal is stored in a plurality of storage circuits respectively, the stored digital signal is repeatedly read out, the repeatedly read out digital signal is converted into a corresponding analog signal, and input to an EL element. A method for driving a portable information device is provided, wherein the operation of the line driving circuit is stopped.

According to the present invention, an EL display device and a CPU
In the method for driving a portable information device comprising:
The display device includes a plurality of pixels and a first circuit that outputs a signal to the plurality of pixels, the CPU includes a second circuit that controls the first circuit, A digital signal is stored in a plurality of storage circuits each of which has a pixel, and the stored digital signal is repeatedly read out.
A method for driving a portable information device is provided, wherein the operation of the second circuit is stopped by converting the repeatedly read digital signal into a corresponding analog signal and inputting the converted analog signal to an EL element.

According to the present invention, an EL having a plurality of pixels
In the method for driving a portable information device in which a display device and a VRAM are incorporated, a digital signal is stored in a plurality of storage circuits respectively included in the plurality of pixels, and the stored digital signal is repeatedly read, and the readout is repeatedly performed. By converting a digital signal into a corresponding analog signal and inputting it to an EL element, the VRA
A method for driving a portable information device is provided, wherein the data read operation of M is stopped.

[0052] The driving method of the portable information device may be characterized in that a read operation is performed once in one frame period in the plurality of storage circuits.

The storage circuit is a static type memory (S
RAM), a ferroelectric memory (FRAM), or a dynamic memory (DRAM).

[0054] The method for driving a portable information device may be characterized in that the storage circuit is formed on a glass substrate, a plastic substrate, a stainless steel substrate, or a single crystal wafer.

[0055] The portable information device may be a portable telephone, a personal computer, a navigation system, a PDA or an electronic book, and may be a driving method of the portable information device.

[0056]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a display device of a portable information device according to the present invention will be described.

FIG. 1 shows the configuration of the present invention.
In the present invention, when a still image is displayed, the display device 2413
The video signal is stored in the storage circuit inside the pixel of
Display is performed by calling the stored video signal. Therefore, the video signal processing circuit 2407 and the VRAM 2
411, the source signal line driver circuit in the display device 2413 can be stopped.

The contents will be specifically described below. If input from the pen input tablet 2401 is not performed for a certain period of time, or if a signal input to change the image display from the external interface port 2405 is not performed for a certain period of time, the CPU 2406
Is determined to be the still image mode. CPU240
6 makes such a determination, the CPU 2406 performs the following operation. EL controller 2412
, The source signal line driving circuit of the display device 2413 is stopped. Specifically, the operation of the source signal line driving circuit can be stopped by stopping the supply of the start pulse, the clock signal, and the video data signal to the source signal line driving circuit. At this time, the gate signal line driving circuit does not stop, receives a signal, and performs an operation of transmitting data of the storage circuit to the EL driving TFT.

As described above, when reading out the signal held in the storage circuit by using the gate signal line driving circuit, E
The L controller 2412 includes a gate signal line driving circuit,
The clock signal, the start pulse, and the like continue to be supplied, and the gate signal line driver circuit continues to operate.

Generally, the gate signal line driving circuit is driven at a frequency of 1/100 or less as compared with the source signal line driving circuit. Therefore, even if the operation is not stopped, there is no problem in power consumption. Of course, the gate signal line driving circuit may be stopped. With such an operation, the display device 24
Reference numeral 13 denotes a state in which only the gate signal line drive circuit or both the source signal line drive circuit and the gate signal line drive circuit are stopped to perform display.

Next, the CPU 2406
Internal video signal processing circuit 2407 and VRAM 24
11 is stopped. As described above, the display device 2413
Since the display is performed using the video data stored in the internal storage circuit, there is no need to send new video data to the display device.
Video signal processing circuit 2407 to be processed, VRAM 2411
Etc. do not have to be working.

That is, the video signal processing circuit 2407, VR
The operation of the AM 2411 or the like can be stopped.

As described above, power reduction in the CPU 2406, power reduction in the VRAM 2411, and power reduction in the source signal line driving circuit are achieved.

When an input is made to the pen input tablet 2401 while the EL display device is displaying a still image, and the image displayed by the EL display device is changed by a video signal corresponding to this input, a pen input is used. Tablet interface 2418 from tablet detection circuit 2402
The CPU 2406 is instructed to change the display content through the CPU 2406, and the stopped VRAM 2
411, the video signal processing circuit 2407 is operated. The display device 241 is operated by the EL controller 2412.
A start pulse, a clock signal, and video data are supplied to the source signal line driving circuit No. 3 and the stopped source signal line driving circuit is operated to write a new video signal to the pixel.

As described above, if the parts (gate signal line drive circuit, EL controller 2412, pen input doublet 2401, detection circuit 2402, doublet interface 2418) enclosed by the broken line in FIG. The terminal can continue to display the still image.

FIG. 2 shows an example of a portable telephone using the present invention. The operation outline is almost the same as that of the portable information terminal of FIG. The difference from the portable information terminal is that, in the portable telephone, the input is performed by the keyboard 2501, and the input information is input to the CPU 2506 via the keyboard interface 2518 and the communication system of the telephone company. The information input to the antenna is amplified by the transmission / reception circuit 2515 and then input to the CPU 2506.

When displaying a still image, the video signal processing circuit 2507 and the VRAM
2511; the source signal line driver circuit and the like can be stopped.

As described above, in FIG. 2, the portions surrounded by broken lines (gate signal line driving circuit, EL controller 2512, keyboard 2501, keyboard interface 251)
If 8) is running, this mobile phone can continue to display still images.

Next, a display device included in the portable information device of the present invention will be described.

FIG. 25 shows a structure of a source signal line driver circuit and some pixels in a display device having a pixel having a memory circuit. This circuit corresponds to a 3-bit digital gradation signal, and includes a shift register circuit 201, a first latch circuit 202, a second latch circuit 203, a bit signal selection switch 204, and a pixel 20.
5 Reference numeral 210 denotes a signal supplied directly from the gate signal line driving circuit or the outside, and will be described later together with a description of a pixel.

FIG. 24 shows the circuit configuration of the pixel 205 in FIG. 25 in detail. This pixel is
It corresponds to a 3-bit digital gradation, and includes an EL element (114), a storage capacitor (Cs), and a storage circuit (105 to 1).
07) and a D / A converter (D / A: 111), EL
It has a driving TFT (115), a power supply line (112), and the like. 101 is a source signal line, 102 to 104 are gate signal lines for writing, and 108 to 110 are T lines for writing.
FT.

FIG. 3 is a timing chart for the display device shown in FIG. The display device corresponds to a 3-bit digital gradation signal and is intended for a VGA device.
The driving method will be described with reference to FIGS. 3, 24 and 25. Note that the reference numerals in FIGS. 3, 24 and 25 are used as they are (the figure numbers are omitted).

Referring to FIG. 25 and FIGS. 3 (A) and (B). In FIG. 3A, each frame period is represented by α, β, γ.
This will be described. First, the circuit operation in the section α will be described.

As in the case of the conventional digital driving circuit, a clock signal (S-
CLK, S-CLKb) and start pulse (S-S
P) is input, and sampling pulses are sequentially output. Subsequently, the sampling pulse is supplied to the first latch circuit 2
02 (LAT1) and a digital signal (Digital D) also input to the first latch circuit 202.
ata) is held. This period is referred to as a dot data sampling period in this specification. The dot data sampling period for one horizontal period is
These periods are indicated by 1 to 480 in FIG. The digital signal is 3 bits, and D1 is MSB (Most Sig).
nificant Bit), D3 is LSB (Least Significant Bi)
t). When the holding of the digital signal for one horizontal cycle is completed in the first latch circuit 202, the digital signal held by the first latch circuit 202 during the retrace period is the input of the latch signal (Latch Pulse). , Are simultaneously transferred to the second latch circuit 203 (LAT2).

Subsequently, according to the sampling pulse output from the shift register circuit 201 again, the operation of holding the digital signal for the next horizontal cycle is performed.

On the other hand, the digital signal transferred to the second latch circuit 203 is written to a storage circuit arranged in a pixel. As shown in FIG. 3B, the dot data sampling period of the next row is divided into I, II, and III, and
The digital signal held in the latch circuit is output to the source signal line. At this time, the bit signal selection switch 2
04 is selectively connected so that the signal of each bit is sequentially output to the source signal line.

In the period I, the write gate signal line 10
2, a pulse is input, the TFT 108 is turned on, and a digital signal is written to the storage circuit 105. Then, the period
In II, a pulse is input to the write gate signal line 103, the TFT 109 is turned on, and a digital signal is written to the storage circuit 106. Finally, in a period III, a pulse is input to the write gate signal line 104 and the TFT 1
10 conducts, and a digital signal is written to the storage circuit 107.

Thus, the processing of the digital signal for one horizontal period is completed. The period in FIG. 3B is a period indicated by an asterisk in FIG. 3A. By performing the above operation up to the final stage, digital signals for one frame are written to the storage circuits 105 to 107.

The written digital signal is converted into an analog signal by the D / A converter 111 and input to the gate electrode of the EL driving TFT 115. A current corresponding to the analog signal is input from the power supply line 112 to the EL element 114 via the EL driving TFT 115. Thus, the luminance of the EL element 114 is changed to express a gradation. Here, since it is 3 bits, the luminance is 0 to 7
The above eight steps are obtained.

The above operation is repeated to continuously display the image. Here, when displaying a still image,
After the digital signals are once stored in the storage circuits 105 to 107 in the first operation, the digital signals stored in the storage circuits 105 to 107 may be repeatedly read in each frame period.

The digital signal stored in the storage circuit is repeatedly read out for each frame period, and the D / A 11
The operation of converting into an analog signal in 1 may be controlled using a DAC controller.

Alternatively, each output of the storage circuit is input to the D / A 111 via a reading TFT (not shown). By operating the read TFT on / off, the digital signal stored in the storage circuit may be repeatedly read for each frame period.

At this time, an operation of inputting a signal to a read gate signal line (not shown) to which the gate electrode of the read TFT is connected is performed using a read gate signal line driving circuit (not shown). Do.

Therefore, while the still image is being displayed, the driving of the source signal line driving circuit in the EL display device can be stopped.

Further, writing of a digital signal to the storage circuit or reading of a digital signal from the storage circuit can be performed for each gate signal line. That is, the source signal line drive circuit is operated only for a short period,
A display method such as rewriting only a part of the screen can be adopted.

Further, in this embodiment, three storage circuits are provided in one pixel, and a function of storing a 3-bit digital signal for one frame is provided. However, the present invention is limited to this number. do not do. That is, in order to store n (n is a natural number of 2 or more) bits of digital signals for m (m is a natural number of 2 or more) frames, one pixel has n × m storage circuits. Just do it.

As described above, the digital signal is stored using the storage circuit mounted in the pixel, and when displaying a still image, the digital signal stored in the storage circuit is repeated in each frame period. Used. Thus, a still image can be displayed continuously without driving the source signal line driving circuit. Therefore, it is possible to greatly contribute to lower power consumption of the EL display device.

As for the source signal line driving circuit,
Due to the problem of the arrangement of the latch circuit and the like that increases with the number of bits, it is not always necessary to integrally form the circuit on the insulator, and a part or all of the circuit may be externally provided.

Further, in the source signal line driving circuit shown in this embodiment, a latch circuit corresponding to the number of bits is arranged, but it is also possible to arrange and operate only one bit. In this case, the digital signal from the upper bit to the lower bit may be input to the latch circuit in series.

In the present invention, as described above, it is also possible to rewrite a signal for each gate signal line. In this case, it is desirable to use a decoder as the gate signal line driving circuit. FIG. 23 illustrates an example in which a decoder is used as a gate signal line driver circuit.

In the case of using a decoder, Japanese Patent Laid-Open No.
The circuit disclosed in 101669 may be used.

Further, partial rewriting can be performed by using the same in the source signal line driving circuit.

With such a configuration, the portable information device of the present invention can reduce the number of parts that continue to operate during the display of a still image and reduce power consumption.

[0094]

Embodiments of the present invention will be described below.

[Example 1] In this example, the storage circuit and the D / A converter in the circuit of the pixel portion of the EL display device included in the portable information device of the present invention, which were shown in the embodiment, are specifically described as transistors. An example of the configuration using the above will be shown, and its operation will be described.

FIG. 8 shows an example in which the D / A converter 111 is actually constituted by a circuit, which is similar to the pixel shown in FIG. As the D / A converter 111, a D / A converter that selects a plurality of gradation voltage lines was used. The same parts as those in FIG. 24 are denoted by the same reference numerals.

When processing a 3-bit digital signal,
There are eight gradation voltage lines, each of which is connected to a switch TFT. Outputs from the storage circuits 105 to 107 selectively drive the switch TFT via a decoder. Accordingly, a gray scale voltage corresponding to the digital signal input from the storage circuit is input to the gate electrode of the EL driving TFT 115.

In the figure, the reference numerals assigned to the respective parts denote the parts shown in FIG.
24 are given the same reference numerals as in FIG. The memory circuits 105 to 107 are provided with write selection TFTs 108 to 110, respectively, and are controlled by storage circuit selection signal lines (write gate signal lines) 102 to 104.

In FIG. 8, the storage circuits 105 to 1
The output from each of 07 is composed of the signal stored in the storage circuit and an inverted signal of the signal.

FIG. 4 shows an example of a storage circuit. A portion indicated by a dotted frame 450 is a storage circuit (in FIG. 8,
451).
Denotes a writing TFT (each portion indicated by 108 to 110 in FIG. 8). Although a static memory (Static RAM: SRAM) using a flip-flop is used for the memory circuit 450 shown here, the memory circuit is not limited to this structure.

The circuit shown in FIG. 8 in this embodiment can be driven according to the timing chart shown in FIG. 3 in the embodiment. The circuit operation will be described with reference to FIGS. 3 and 8 are used as they are (the figure numbers are omitted).

Referring to FIGS. 3A and 3B, FIG. FIG. 3 (A)
In the following description, each frame period will be described as α, β, and γ. First, the circuit operation in the section α will be described.

The driving method from the shift register circuit to the second latch circuit is the same as that shown in the embodiment, so that it is followed.

In the period I, the write gate signal line 10
2, a pulse is input, the TFT 108 is turned on, and a digital signal is written to the storage circuit 105. Then, the period
In II, a pulse is input to the write gate signal line 103, the TFT 109 is turned on, and a digital signal is written to the storage circuit 106. Finally, in a period III, a pulse is input to the write gate signal line 104 and the TFT 1
10 conducts, and a digital signal is written to the storage circuit 107.

Thus, the processing of the digital signal for one horizontal period is completed. The period in FIG. 3B is a period indicated by an asterisk in FIG. 3A. By performing the above operation up to the final stage, digital signals for one frame are written to the storage circuits 105 to 107.

The written digital signal is converted into an analog signal by the D / A converter 111 and input to the gate electrode of the EL driving TFT 115. A current corresponding to the analog signal is input from the power supply line 112 to the EL element 114 via the EL driving TFT 115. Thus, the luminance of the EL element 114 is changed to express a gradation. Here, since a 3-bit digital signal is input, eight levels of luminance from 0 to 7 can be obtained.

As described above, display for one frame period is performed. On the other hand, on the drive circuit side, digital signal processing in the next frame period is simultaneously performed.

An image is displayed by repeating the above procedure. Note that when displaying a still image, when writing of a digital signal of a certain frame to the storage circuit is completed, the source signal line driving circuit is stopped, and the signal written to the same storage circuit is output every frame. Read and display.

At this time, although not shown in FIG.
The output of each storage circuit of each pixel is input to the D / A via the read TFT, and the read TFT is
, The signal of the storage circuit can be repeatedly read every frame period. As a circuit for operating the reading TFT, a circuit having a known configuration can be used freely.

Further, a signal input to the storage circuit is always input to the D / A circuit, and a corresponding analog signal is output to the liquid crystal element to display a still image. In this case, the pixel continues to display at the same luminance until the writing TFT is selected and information is newly written to the storage circuit. In this driving method, the above-described read TFT and the like are not required.

According to such a method, power consumption during display of a still image can be greatly reduced.

[Embodiment 2] In this embodiment, an example in which the second latch circuit of the source signal line drive circuit is omitted by writing data to the storage circuit of the pixel portion in a dot-sequential manner will be described.

FIG. 5 is a diagram showing an E using a pixel having a storage circuit.
3 shows a configuration of a source signal line driver circuit and some pixels in an L display device. This circuit corresponds to a 3-bit digital gradation signal, and includes a shift register circuit 501, a latch circuit 502, and a pixel 503. Reference numeral 510 denotes a signal supplied directly from the gate signal line driving circuit or the outside, and will be described later together with a description of the pixel.

FIG. 6 is a detailed diagram of the circuit configuration of the pixel 503 shown in FIG. Similar to the first embodiment, it corresponds to a 3-bit digital gradation signal, and includes an EL element 614, a storage circuit (605 to 607), and a D / A converter (D / A / D converter).
A: 611). 601 is the first bit (M
SB, a source signal line for a second bit signal, 603, a source signal line for a third bit (LSB) signal, 604, a gate signal line for writing, and 608.
Reference numerals 610 denote writing TFTs.

FIG. 7 is a timing chart for driving the circuit shown in this embodiment. This will be described with reference to FIGS.

The operations from the shift register circuit 501 to the latch circuit (LAT1) 502 are performed in the same manner as in the embodiment and the first embodiment. As shown in FIG. 7B, immediately after the completion of the first-stage latch operation, writing of the pixel into the storage circuit is started. Write gate signal line 60
4, a pulse is input to the write TFTs 608-61.
0 is turned on, and writing to the storage circuit is enabled. The digital signal for each bit held in the latch circuit 502 is simultaneously written via three source signal lines 601 to 603.

When the digital signal held in the latch circuit in the first stage is written in the storage circuit, the digital signal is held in the latch circuit in the next stage in accordance with the subsequent sampling pulse. In this way,
Writing to the storage circuit is sequentially performed.

The above operation is repeated until the last stage, and one horizontal period ends.

This is repeated for all horizontal periods 1 to 480.

Thus, the display period of the first frame is completed. In the section β, the processing of the digital signal in the next frame is performed.

The period shown in FIG. 7B corresponds to the period indicated by ** in FIG. 7A.

By repeating the above procedure, an image is displayed. Note that when displaying a still image, when writing of a digital signal of a certain frame to the storage circuit is completed, the source signal line driving circuit is stopped, and the signal written to the same storage circuit is output every frame. Read and display. With such a method, power consumption during the display of a still image can be significantly reduced. Furthermore, the number of latch circuits can be halved as compared with the circuit shown in the embodiment, and it is possible to contribute to downsizing of the entire device by saving space in circuit arrangement.

[Embodiment 3] In this embodiment, Embodiment 2
An example of an EL display device using a method of performing writing to a storage circuit in a pixel by line-sequential driving by applying the circuit configuration of an EL display device in which the second latch circuit is omitted, which is described in FIG.

FIG. 17 shows an example of a circuit configuration of a source signal line driving circuit of the EL display device shown in this embodiment. This circuit corresponds to a 3-bit digital gradation signal, and includes a shift register circuit (SR) 1701, a latch circuit (LAT1) 1702, and a switch circuit (SW) 170.
3. It has a pixel 1704. Reference numeral 1710 denotes a signal supplied directly from the gate signal line driving circuit or the outside.
Since the circuit configuration of the pixel may be the same as that of the second embodiment, FIG. 6 is referred to as it is.

FIG. 18 is a timing chart for driving the circuit shown in this embodiment. This will be described with reference to FIGS. 6, 17 and 18.

The operation from when the sampling pulse is output from the shift register circuit 1701 until the latch circuit 1702 holds the digital signal in accordance with the sampling pulse is the same as in the first and second embodiments. In this embodiment, since the switch circuit 1703 is provided between the latch circuit 1702 and the storage circuit in the pixel 1704, even if the holding of the digital signal in the latch circuit is completed, writing to the storage circuit is immediately performed. Does not start. Until the end of the dot data sampling period, the switch circuit 1
Reference numeral 703 remains closed, during which the latch circuit keeps holding the digital signal.

As shown in FIG. 18B, when the holding of the digital signal for one horizontal period is completed, the latch signal (Latch Pulse) is input during the retrace period, and the switch circuits 1703 are simultaneously opened. , Latch circuit 17
The digital signal held in the pixel
4 is written to the storage circuit. The operation in the pixel 1704 relating to the writing operation at this time and the operation in the pixel 1704 relating to the reading operation at the time of display in the next frame period may be the same as in the second embodiment. Omitted.

The period shown in FIG. 18B corresponds to the period shown in FIG.
, Which corresponds to the period indicated by the mark.

With the above method, line-sequential write driving can be easily performed even in the source signal line driving circuit in which the second latch circuit is omitted.

[Embodiment 4] In this embodiment, the D shown in FIG.
An example of a pixel using a structure different from that of the / A converter is shown. FIG. 9 shows a circuit diagram thereof. The same parts as those in FIG. 8 are denoted by the same reference numerals.

In this method, a gray scale voltage line is selected in a manner similar to that shown in FIG. 8, but in FIG. 8, the number of elements is large, and the area occupied by elements in a pixel is large. For this reason, in FIG. 9, the switches are connected in series, and the number of elements is reduced by also serving as a decoder and a switch.

In FIG. 9, the storage circuits 105 to 1
The output from each of 07 is composed of a signal stored in the storage circuit and an inverted signal of the signal.

This embodiment can be implemented by freely combining with Embodiments 1 to 3.

[Embodiment 5] In this embodiment, an example of a pixel using a structure different from the D / A converter shown in FIGS. 8 and 9 will be described. FIG. 20 shows a circuit diagram thereof. 8 and 9 are denoted by the same reference numerals.

In the D / A converters shown in FIGS. 8 and 9, since the gray scale voltage lines are used, wiring is required for the number of gray scales, which is not suitable for increasing the number of gray scales. For this reason, in FIG. 20, the reference voltage is divided by a combination of the capacitors C1 to C3 to generate a gradation voltage. In such a capacity division method, since a gray scale is created by the ratio of the capacitors C1 to C3, various gray scales can be expressed.

A D / A converter of such a capacity division system is described in AMLCD99 Digest of Technical Papers, p.

This embodiment can be implemented by freely combining with Embodiments 1 to 3.

[Embodiment 6] In this embodiment, an example of a pixel using a different structure from the D / A converter shown in FIGS. 8, 9 and 20 will be described. FIG. 21 shows a circuit diagram thereof. 8, 9 and 20 are denoted by the same reference numerals.

FIG. 21 shows a further simplification of the D / A converter shown in FIG. Capacity C1-C
3. Of the two electrodes, the electrode not connected to the EL element is connected to _VL at the time of reset, and is connected to either _VH or _VL at the time of non-reset. It can be composed only of.

In FIG. 21, the storage circuits 105 to 105
The output from each of 107 is constituted by the signal stored in the storage circuit and the inverted signal of the signal.

This embodiment can be implemented by freely combining with Embodiments 1 to 3.

[Embodiment 7] In this embodiment, an example of a source signal line drive circuit having a structure different from that of the embodiment shown in FIG. 25 will be described.

As shown in FIG. 22, the latch circuit of the source signal line drive circuit has only one bit, and the source signal line drive circuit is operated at triple speed instead. Data is input to the source signal line driving circuit in the order of bit data, second bit data, and third bit data,
An effect similar to that of the source signal line driving circuit of FIG. 25 shown in the embodiment can be obtained.

In this method, a circuit for sequentially exchanging data is required outside, but the size of the source signal line driving circuit can be reduced.

[Embodiment 8] In this embodiment, the TFTs of the pixel portion of the EL display device of the portable information device of the present invention and the drive circuit portions (source signal line drive circuit, gate signal line drive circuit) provided around the pixel portion are provided. Will be described at the same time. However, for the sake of simplicity, a CMOS circuit, which is a basic unit for the drive circuit unit, is illustrated.

First, as shown in FIG. 10A, oxidation is performed on a substrate 5001 made of glass such as barium borosilicate glass represented by Corning # 7059 glass or # 1737 glass, or aluminoborosilicate glass. A base film 5002 made of an insulating film such as a silicon film, a silicon nitride film, or a silicon oxynitride film is formed.
For example, a plasma CVD method SiH _4, NH _3, N ₂ silicon oxynitride film 5002a made from O 10 to 2
00 [nm] (preferably 50 to 100 [nm]) is formed, similarly SiH _4, N ₂ O hydrogenated silicon oxynitride film 5002b made from 50 to 200 [nm] (preferably 100
１５０150 [nm]). Although the base film 5002 has a two-layer structure in this embodiment, the base film 5002 may have a single-layer structure or a structure in which two or more insulating films are stacked.

Each of the island-shaped semiconductor layers 5003 to 5006 is formed of a crystalline semiconductor film formed by using a semiconductor film having an amorphous structure by a laser crystallization method or a known thermal crystallization method.
The thickness of the island-shaped semiconductor layers 5003 to 5006 is 25 to 8
It is formed with a thickness of 0 [nm] (preferably 30 to 60 [nm]). The material of the crystalline semiconductor film is not limited, but is preferably formed of silicon or a silicon germanium (SiGe) alloy.

In order to form a crystalline semiconductor film by a laser crystallization method, a pulse oscillation type or continuous emission type excimer laser, a YAG laser, or a YVO ₄ laser is used.
In the case of using these lasers, it is preferable to use a method in which laser light emitted from a laser oscillator is linearly condensed by an optical system and irradiated on a semiconductor film. The crystallization conditions are appropriately selected by the practitioner. When an excimer laser is used, the pulse oscillation frequency is 30 [Hz], and the laser energy density is 100 to 400 [mJ / cm ² ] (typically, 2
00 to 300 [mJ / cm ² ]). When a YAG laser is used, the second harmonic is used, the pulse oscillation frequency is set to 1 to 10 [kHz], and the laser energy density is set to 30.
0 to 600 [mJ / cm ² ] (typically 350 to 500 [mJ / c]
m ² ]). And a width of 100 to 1000 [μm],
For example, a laser beam condensed linearly at 400 [μm] is irradiated over the entire surface of the substrate, and the superposition rate (overlap rate) of the linear laser beam at this time is set to 80 to 98 [%].

Next, island-like semiconductor layers 5003 to 5006
Is formed to cover the gate insulating film 5007. The gate insulating film 5007 is formed by a plasma CVD method or a sputtering method.
It is formed of an insulating film containing silicon with a thickness of 40 to 150 [nm]. In this embodiment, a silicon oxynitride film is formed with a thickness of 120 [nm]. Needless to say, the gate insulating film is not limited to such a silicon oxynitride film, and another insulating film containing silicon may be used as a single layer or a stacked structure. For example, when a silicon oxide film is used, TEOS (Tetraethyl Orthosilicat
e) and O ₂ were mixed, the reaction pressure was 40 [Pa], and the substrate temperature was 30.
It can be formed by discharging at a high frequency (13.56 [MHz]) and a power density of 0.5 to 0.8 [W / cm ² ] at 0 to 400 [° C.]. The silicon oxide film thus manufactured can obtain favorable characteristics as a gate insulating film by subsequent thermal annealing at 400 to 500 [° C.].

[0150] Then, a first conductive film 5008 and a second conductive film 5009 for forming a gate electrode are formed over the gate insulating film 5007. In this embodiment, the first conductive film 5008 is formed of Ta to a thickness of 50 to 100 [nm],
A second conductive film 5009 is formed with W to a thickness of 100 to 300 [nm].

The Ta film is formed by a sputtering method by sputtering a Ta target with Ar. in this case,
When an appropriate amount of Xe or Kr is added to Ar, the internal stress of the Ta film can be relaxed and the film can be prevented from peeling. Also, α
The phase Ta film has a resistivity of about 20 [μΩcm] and can be used as a gate electrode, but the β phase Ta film has a resistivity of about 180 [μΩcm] and is not suitable for a gate electrode. . In order to form an α-phase Ta film, tantalum nitride having a crystal structure close to the Ta α-phase is formed on a Ta base with a thickness of about 10 to 50 [nm]. Can be easily obtained.

When a W film is formed, it is formed by a sputtering method using W as a target. Alternatively, it can be formed by a thermal CVD method using tungsten hexafluoride (WF ₆ ). In any case, it is necessary to lower the resistance in order to use it as a gate electrode.
[μΩcm] or less is desirable. The resistivity of the W film can be reduced by enlarging the crystal grains. However, when there are many impurity elements such as oxygen in W, the crystallization is inhibited and the resistance is increased. From this, in the case of using the sputtering method, a W target having a purity of 99.9999 [%] is used, and a W film is formed by giving sufficient consideration so as not to mix impurities from the gas phase during film formation. Resistivity 9-20
[μΩcm] can be realized.

In this embodiment, the first conductive film 500
8 was Ta, and the second conductive film 5009 was W. However, there is no particular limitation, and any of Ta, W, Ti, Mo, Al, and Cu was used.
Alternatively, it may be formed of an element selected from the above, or an alloy material or a compound material containing the element as a main component. Also,
A semiconductor film typified by a polycrystalline silicon film doped with an impurity element such as phosphorus may be used. As a desirable example of another combination other than this embodiment, a combination in which the first conductive film 5008 is formed of tantalum nitride (TaN) and the second conductive film 5009 is W, Is formed of tantalum nitride (TaN), the second conductive film 5009 is made of Al, the first conductive film 5008 is made of tantalum nitride (TaN), and the second conductive film 5009 is made of Cu. No.

Next, a mask 5010 made of a resist is formed, and a first etching process for forming electrodes and wirings is performed. In this embodiment, ICP (Inductively Coupled)
d Plasma: Inductively coupled plasma) etching method,
CF ₄ and Cl ₂ are mixed as an etching gas, and RF (13.56 [MH]) of 500 [W] is applied to the coil-type electrode at a pressure of 1 [Pa].
z]) Power is supplied to generate plasma. 100 [W] RF (13.56 [MH] also on the substrate side (sample stage)
z]) Apply power and apply a substantially negative self-bias voltage. When CF ₄ and Cl ₂ are mixed, the W film and Ta
The film is etched to the same extent.

Under the above-mentioned etching conditions, the shape of the resist mask is made appropriate, so that the end portions of the first conductive layer and the second conductive layer are tapered due to the effect of the bias voltage applied to the substrate side. Become. The angle of the tapered portion is 15 to 45 °. In order to perform etching without leaving a residue on the gate insulating film, the etching time may be increased by about 10 to 20%. Since the selectivity of the silicon oxynitride film to the W film is 2 to 4 (typically 3), the exposed surface of the silicon oxynitride film is etched by about 20 to 50 [nm] by over-etching. become. Thus, by the first etching process, the first conductive layer and the second conductive layer
Conductive layers 5011 to 5016 (first conductive layer 50
11a to 5016a and second conductive layers 5011b to 501
6b) is formed. At this time, in the gate insulating film 5007, a region which is not covered with the first shape conductive layers 5011 to 5016 is etched to a thickness of about 20 to 50 [nm] to form a thinned region. (FIG. 10B)

Then, a first doping process is performed to add an impurity element imparting n-type. The doping may be performed by an ion doping method or an ion implantation method. The condition of the ion doping method is that the dose is 1 × 10 ^{13 to} 5 × 10
¹⁴ [atoms / cm ² ] and an acceleration voltage of 60 to 100 [keV]. An element belonging to Group 15 of the periodic table, typically phosphorus (P) or arsenic (As) is used as the n-type impurity element. Here, phosphorus (P) is used. In this case, the conductive layers 5011 to 5015 serve as a mask for the impurity element imparting n-type, and are self-aligned in the first impurity region 50.
17 to 5025 are formed. First impurity region 501
For 7 to 5025, 1 × 10 ²⁰ to 1 × 10 ²¹ [atoms / cm ³ ]
Is added in the concentration range of n.
(FIG. 10B)

Next, as shown in FIG. 10C, a second etching process is performed without removing the resist mask. Using CF ₄ , Cl ₂ and O _{2 as an} etching gas,
The film is selectively etched. At this time, the second shape conductive layers 5026 to 5031 are formed by the second etching process.
(First conductive layers 5026a to 5031a and second conductive layers 5026b to 5031b) are formed. At this time, in the gate insulating film 5007, the second shape conductive layer 50 is formed.
The area not covered by 26 to 5031 is further 20 to 50 [n
m] to form a thinned region.

The etching reaction of the W film or the Ta film by the mixed gas of CF ₄ and Cl ₂ can be inferred from the generated radical or ion species and the vapor pressure of the reaction product.
Comparing the vapor pressures of fluorides and chlorides of W and Ta, W
WF ₆ is extremely high and other WC
l ₅ , TaF ₅ and TaCl ₅ are comparable. Therefore, C
With the mixed gas of F ₄ and Cl ₂ , both the W film and the Ta film are etched. However, when an appropriate amount of O ₂ is added to this mixed gas, CF ₄ and O ₂ react to form CO and F, and a large amount of F radicals or F ions are generated. As a result, the etching rate of the W film having a high fluoride vapor pressure increases. On the other hand, in Ta, the increase in the etching rate is relatively small even if F increases. Further, since Ta is more easily oxidized than W, the surface of Ta is oxidized by adding O ₂ .
Since the oxide of Ta does not react with fluorine or chlorine,
The etching rate of the a film decreases. Therefore, the W film and Ta
It is possible to make a difference in the etching rate with the film, and it is possible to make the etching rate of the W film larger than that of the Ta film.

Then, a second doping process is performed as shown in FIG. In this case, the dose is lower than that of the first doping process, and n is set as a condition of a high acceleration voltage.
Doping with an impurity element for giving a mold. For example, the acceleration voltage is set to 70 to 120 [keV], and 1 × 10 ¹³ [atoms / cm]
² ], a new impurity region is formed inside the first impurity region formed in the island-shaped semiconductor layer in FIG. Doping is performed in the second shape conductive layer 5026.
To 5030 are used as masks for the impurity elements, and doping is performed so that the impurity elements are also added to regions below the first conductive layers 5026a to 5030a. Thus, third impurity regions 5032 to 5036 are formed. The concentration of phosphorus (P) added to third impurity regions 5032 to 5036 depends on that of first conductive layers 5026 a to 5026 a to 5 a.
030a has a gentle concentration gradient according to the thickness of the tapered portion. Note that the first conductive layers 5026a to 503
In the semiconductor layer overlapping the tapered portion of Oa, the impurity concentration is slightly reduced from the end of the tapered portion of the first conductive layers 5026a to 5030a toward the inside, but is substantially the same.

A third etching process is performed as shown in FIG. This is performed using a reactive ion etching method (RIE method) using CHF ₆ as an etching gas. Third
Of the first conductive layers 5026a to 5026a-5
031a is partially etched to form the first portion.
The region where the conductive layer overlaps with the semiconductor layer is reduced. By the third etching treatment, the third shape conductive layer 5037 is formed.
To 5042 (first conductive layers 5037a to 5042a and second conductive layers 5037b to 5042b). At this time, in the gate insulating film 5007, a region that is not covered with the third shape conductive layers 5037 to 5042 is two more.
A region that is etched and thinned by about 0 to 50 [nm] is formed.

By the third etching process, third impurity regions 5032 to 5036 overlap with first conductive layers 5037a to 5041a.
32a to 5036a, and second impurity regions 5032b to 5036 between the first impurity region and the third impurity region.
b is formed.

Then, as shown in FIG.
The island-shaped semiconductor layer 5004 forming the channel type TFT has the first
4th impurity region 5043-of the conductivity type opposite to the conductivity type of
Form 5048. The third shape conductive layer 5038b is
Used as a mask for impurity elements.
Form a pure region. At this time, the n-channel TFT is
The island-shaped semiconductor layers 5003, 5005, 5006 and
And the wiring portion 5042 is entirely covered with a resist mask 5200.
Cover. The impurity regions 5043 to 5048
Phosphorus is added at different concentrations, but diborane
(B_TwoH₆) Formed by the ion doping method using
The impurity concentration is 2 × 10 ²⁰~ 2 × 10
^{twenty one}[atoms / cm^Three].

Through the above steps, impurity regions are formed in the respective island-shaped semiconductor layers. Third overlapping with the island-shaped semiconductor layer
The conductive layers 5037 to 5041 each having the shape described above function as gate electrodes. 5042 functions as an island-shaped source signal line.

After removing the resist mask 5200, a step of activating the impurity element added to each island-shaped semiconductor layer is performed for the purpose of controlling the conductivity type. This step is performed by a thermal annealing method using a furnace annealing furnace.
In addition, a laser annealing method or a rapid thermal annealing method (RTA method) can be applied. In the thermal annealing method, the oxygen concentration is 400 to 700 in a nitrogen atmosphere of 1 [ppm] or less, preferably 0.1 [ppm] or less.
In this embodiment, the heat treatment is performed at 500 ° C. for 4 hours.
However, when the wiring material used for the third shape conductive layers 5037 to 5042 is weak to heat, activation is performed after an interlayer insulating film (mainly containing silicon) is formed to protect the wiring and the like. It is preferred to do so.

Further, a heat treatment is carried out at 300 to 450 ° C. for 1 to 12 hours in an atmosphere containing 3 to 100% of hydrogen to hydrogenate the island-like semiconductor layer. In this step, dangling bonds in the semiconductor layer are terminated by thermally excited hydrogen. As another means of hydrogenation, plasma hydrogenation (using hydrogen excited by plasma) may be performed.

Next, as shown in FIG.
Of the interlayer insulating film 5055 from the silicon oxynitride film to 100
It is formed with a thickness of about 200 [nm]. After a second interlayer insulating film 5056 made of an organic insulating material is formed thereon, the first interlayer insulating film 5055, the second interlayer insulating film 5056,
And a contact hole is formed in the gate insulating film 5007, and each wiring (including a connection wiring and a signal line) 5057 is formed.
After patterning 5062 and 5064, the pixel electrode 5063 in contact with the connection wiring 5062 is formed by patterning.

As the second interlayer insulating film 5056, a film made of an organic resin is used. As the organic resin, polyimide, polyamide, acrylic, BCB (benzocyclobutene), or the like can be used. In particular, since the second interlayer insulating film 5056 has a strong meaning of flattening, acrylic having excellent flatness is preferable. In this embodiment, an acrylic film is formed with a thickness that can sufficiently flatten a step formed by a TFT. Preferably, it is 1 to 5 [μm] (more preferably, 2 to 4 [μm]).

The contact holes are formed by dry etching or wet etching, and n-type impurity regions 5017, 5018, 5021, 5023 to 5025 are formed.
Alternatively, a contact hole reaching the p-type impurity regions 5043 to 5048, a contact hole reaching the wiring 5042, a contact hole reaching the power supply line (not shown), and a contact hole reaching the gate electrode (not shown) are formed. .

In addition, wiring (including connection wiring and signal line) 5
057 to 5062 and 5064, the Ti film is 100 [n].
m], an aluminum film containing Ti is 300 [nm], and a Ti film 1
A laminate film having a three-layer structure in which 50 nm is continuously formed by a sputtering method and patterned into a desired shape is used. Of course,
Other conductive films may be used.

In this embodiment, an MgAg film having a thickness of 110 [nm] was formed as the pixel electrode 5063, and patterning was performed. Contact is established by arranging the pixel electrode 5063 so as to be in contact with and overlap with the connection wiring 5062. This pixel electrode 5063 serves as a cathode of the EL element.
(FIG. 12 (A))

Next, as shown in FIG. 12B, an insulating film containing silicon (a silicon oxide film in this embodiment) is formed to a thickness of 500 [nm], and is formed at a position corresponding to the pixel electrode 5063. An opening is formed, and a third interlayer insulating film 5065 functioning as a bank is formed. When the opening is formed, a tapered side wall can be easily formed by using a wet etching method. Care must be taken because if the side wall of the opening is not sufficiently smooth, deterioration of the EL layer due to the step will become a significant problem.

Next, the EL layer 5066 and the anode (opposite electrode) 5067 are continuously formed by using a vacuum deposition method without opening to the atmosphere. Note that the thickness of the EL layer 5066 is 80 to 2
00 [nm] (typically 100 to 120 [nm]), anode 50
67 was formed of an ITO film.

In this step, an EL layer and an anode are sequentially formed on a pixel corresponding to red, a pixel corresponding to green, and a pixel corresponding to blue. However, since the EL layer has poor resistance to a solution, it must be formed individually for each color without using a photolithography technique. Therefore, it is preferable to hide a portion other than a desired pixel by using a metal mask and selectively form an EL layer and an anode only at a necessary portion.

That is, first, a mask for hiding all pixels other than pixels corresponding to red is set, and a red light emitting EL layer is selectively formed using the mask. Next, a mask for hiding all pixels other than pixels corresponding to green is set, and a green light-emitting EL layer is selectively formed using the mask. Next, a mask for covering all pixels other than the pixel corresponding to blue is similarly set, and an EL layer for emitting blue light is selectively formed using the mask. Note that all the masks are described herein as being different, but the same mask may be used again.

Here, a method of forming three types of EL elements corresponding to RGB was used. However, a method of combining a white light emitting EL element and a color filter, a blue or blue-green light emitting EL element and a phosphor (fluorescent light) were used. (A color conversion layer: CCM) or a method in which an EL element corresponding to RGB is overlapped with a cathode (pixel electrode) using a transparent electrode.

Note that a known material can be used for the EL layer 5066. As a known material, it is preferable to use an organic material in consideration of a driving voltage. For example, a four-layer structure including a hole injection layer, a hole transport layer, a light emitting layer, and an electron injection layer may be used as the EL layer.

Next, an anode 5067 is formed using a metal mask on a pixel having a switching TFT in which a gate electrode is connected to the same gate signal line (a pixel on the same line).

In this embodiment, as the anode 5067, I
Although TO was used and MgAg was used as the cathode 5063,
The present invention is not limited to this. Anode 5067 and cathode 5
Other known materials may be used as 063.

Lastly, a passivation film 5068 made of a silicon nitride film is formed to a thickness of 300 [nm]. By forming the passivation film 5068, the EL layer 50
66 can be protected from moisture and the like, and the reliability of the EL element can be further improved.

Thus, an EL display panel having a structure as shown in FIG. 12B is completed. In the manufacturing process of the EL display panel in this embodiment,
Due to the circuit configuration and process, a source signal line is formed by Ta and W, which are materials forming the gate electrode, and a gate signal line is formed by Al, which is a wiring material forming the source and drain electrodes. However, different materials may be used.

The TFT in the active matrix type EL display device manufactured by the above-described process has a top gate structure, but a TFT having a bottom gate structure.
This embodiment can be easily applied to TFTs having other structures.

In this embodiment, a glass substrate is used. However, the present invention is not limited to a glass substrate, but may be implemented by using a material other than a glass substrate, such as a plastic substrate, a stainless steel substrate, or a single crystal wafer. It is possible.

By the way, the EL display panel of this embodiment exhibits extremely high reliability and can improve the operating characteristics by arranging the TFT having the optimum structure not only in the pixel portion but also in the drive circuit portion. In the crystallization step, N
It is also possible to increase the crystallinity by adding a metal catalyst such as i. Thus, the driving frequency of the source signal line driving circuit can be increased to 10 MHz or more.

First, a TFT having a structure in which hot carrier injection is reduced so as not to reduce the operation speed as much as possible,
N-channel type TF of CMOS circuit forming drive circuit section
Used as T. In addition, as the drive circuit here,
It includes a shift register, a buffer, a level shifter, a latch in line-sequential driving, a transmission gate in point-sequential driving, and the like.

In the case of this embodiment, the activity of the n-channel TFT is
The conductive layer is between the source region, the drain region, and the gate insulating film.
Overlap LDD region that overlaps with the gate electrode
(L _OVRegion), with the gate electrode sandwiching the gate insulating film
Offset LDD areas (L_OFFArea) and
Including a channel forming region.

Also, a p-channel type TFT of a CMOS circuit
Since there is almost no concern about deterioration due to hot carrier injection, it is not necessary to provide an LDD region. Needless to say, it is also possible to provide an LDD region similarly to the n-channel type TFT and take measures against hot carriers.

In addition, when a CMOS circuit in which current flows bidirectionally in the channel formation region, that is, a CMOS circuit in which the roles of the source region and the drain region are exchanged is used in the driver circuit, n In the channel type TFT, it is preferable to form an LDD region on both sides of the channel formation region so as to sandwich the channel formation region. An example of such a transmission gate is a transmission gate used for dot sequential driving. Further, in the case where a CMOS circuit in which off-state current needs to be suppressed as low as possible is used in the driver circuit, the n-channel TFT forming the CMOS circuit preferably has an L _OV region. As such an example,
A transmission gate used for point-sequential driving is exemplified.

Actually, when the structure shown in FIG. 12B is completed, a protective film (laminate film, ultraviolet curable resin film, etc.) with high airtightness and low degassing or a transparent film is provided so as not to be further exposed to the outside air. It is preferable to package (enclose) with an optical sealing material. At this time, the reliability of the EL element is improved by setting the inside of the sealing material to an inert atmosphere or disposing a hygroscopic material (for example, barium oxide) inside.

When the airtightness is improved by processing such as packaging, a connector (flexible printed circuit: FPC) for connecting terminals routed from elements or circuits formed on the substrate to external signal terminals. To complete the product. Such a state in which the product can be shipped is referred to as an EL display device in this specification.

According to the steps shown in this embodiment, the EL
The number of photomasks required for manufacturing a display device can be reduced. As a result, the process can be shortened, which can contribute to a reduction in manufacturing cost and an improvement in yield.

[Embodiment 9] In this embodiment, an example in which an EL display device of a portable information device of the present invention is manufactured will be described with reference to FIGS.

FIG. 19A is a top view of an EL display device, FIG. 19B is a cross-sectional view taken along line AA ′ of FIG. 19A, and FIG. 13) is a sectional view taken along line BB ′ of FIG.

[0193] The pixel portion 400 provided over the substrate 4001
2, the source signal line driving circuit 4003, and the first and second
A sealing material 4009 is provided so as to surround the gate signal line driving circuits 4004a and 4004b. 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. Accordingly, the pixel portion 4002, the source signal line driver circuit 4003, and the first and second gate signal line driver circuits 4004a and 4004b are each composed of a substrate 4001, a sealant 4009, and a sealant 4008.
, And is sealed with the filler 4210.

The pixel portion 4 provided on the substrate 4001
002, the source signal line driver circuit 4003, and the first and second gate signal line driver circuits 4004a and 4004b have a plurality of TFTs. In FIG. 19B, typically, the source signal line driving circuit 4 formed on the base film 4010 is formed.
The drive TFT 4201 included in 003 (here, an n-channel TFT and a p-channel TFT are illustrated)
And a pixel TFT (TFT for controlling current to an EL element: EL driving TFT) 4202 included in the pixel portion 4002
Is illustrated.

In this embodiment, a p-channel TFT and an n-channel TFT manufactured by a known method are used as the driving TFT 4201, and a p-channel TFT manufactured by a known method is used as the EL driving TFT 4202. Used.

Drive TFT 4201 and EL drive TFT
An interlayer insulating film (planarizing film) 4301 is formed over the 4202, and a pixel electrode (anode) 4203 electrically connected to the drain region 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. Further, a material obtained by adding gallium to the transparent conductive film may be used.

An insulating film 4302 is formed on the pixel electrode 4203, and the insulating film 4302 is
An opening is formed on 3. In this opening, an EL (electroluminescence) layer 4204 is formed on the pixel electrode 4203. For the EL layer 4204, a known organic EL material or inorganic EL material can be used. As the organic EL material, there are a low-molecular (monomer) material and a high-molecular (polymer) material, and either 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.

On the EL layer 4204, a cathode 4205 made of a light-shielding conductive film (typically, a conductive film containing aluminum, copper, or silver as a main component or a laminated film of these and another conductive film) is provided. It is formed. In addition, the cathode 4205
It is desirable to remove moisture and oxygen existing at the interface between the EL layer 4204 and oxygen as much as possible. Therefore, it is necessary to devise a method in which 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 made possible by using a multi-chamber type (cluster tool type) film formation apparatus. A predetermined voltage is applied to the cathode 4205.

As described above, the pixel electrode (anode) 42
03, an EL element 4303 comprising an EL layer 4204 and a cathode 4205 is formed. Then, a protective film 4209 is formed over the insulating film 4302 so as to cover the EL element 4303. The protective film 4209 is effective in preventing oxygen, moisture, and the like from entering the EL element 4303.

A wiring 4005a is connected to the power supply line, and is electrically connected to the source region of the EL driving TFT 4202. Leading wiring 4005a
Is electrically connected to the FPC wiring 4333 of the FPC 4006 via the anisotropic conductive film 4300 through the space between the sealant 4009 and the substrate 4001.

As the sealing material 4008, a glass material, a metal material (typically, a stainless steel material), a ceramic material, and a plastic material (including a plastic film) can be used. FRP as plastic material
(Fiberglass-Reinforced Pl
aics) plate, PVF (polyvinyl fluoride)
A film, a mylar film, a polyester film, or an acrylic resin film can be used. Further, 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 direction of light emission 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.

As the filler 4210, an ultraviolet curable resin or a thermosetting resin can be used in addition to an inert gas such as nitrogen or argon, and PVC (polyvinyl chloride), acrylic, polyimide, epoxy resin, silicone Resin, PVB (polyvinyl butyral) or E
VA (ethylene vinyl acetate) can be used. In this embodiment, nitrogen was used as the filler.

In order to expose the filling material 4210 to a hygroscopic substance (preferably barium oxide) or a substance capable of adsorbing oxygen, the substrate 400
A concave portion 4007 is provided on the one surface, and a hygroscopic substance or a substance 4207 capable of adsorbing oxygen is arranged. Then, the hygroscopic substance or the substance 4207 capable of adsorbing oxygen is held in the concave part 4007 by the concave part cover material 4208 so that the hygroscopic substance or the substance 4207 capable of adsorbing oxygen is not scattered. Note that the concave portion cover member 4208 has a fine mesh shape and is configured to allow air and moisture to pass therethrough and not allow a hygroscopic substance or a substance 4207 capable of adsorbing oxygen to pass therethrough. By providing the hygroscopic substance or the substance 4207 which can adsorb oxygen, deterioration of the EL element 4303 can be suppressed.

As shown in FIG. 19C, the pixel electrode 42
Simultaneously with the formation of 03, a conductive film 4203a is formed so as to be in contact with the lead wiring 4005a.

The anisotropic conductive film 4300 has a conductive filler 4300a. Substrate 4001 and F
By thermocompression bonding with the PC 4006, the conductive film 4203a on the substrate 4001 and the FPC wiring 4333 on the FPC 4006 are electrically connected by the conductive filler 4300a.

[Embodiment 10] In this embodiment, an example is shown in which an EL display device of downward light emission, which emits light emitted from an EL element to the pixel substrate side, is used as the EL display device of the portable information device of the present invention. Is shown.

If the design rule is set to 1 μm and the pixel pitch is set to about 100 ppi, the storage circuit and the D / A converter inside the pixel can be arranged below the source signal line, and the aperture ratio is reduced. Can be solved. Thereby, the present invention can be applied to the case where the upper light emitted from the EL element is emitted in the opposite direction to the pixel substrate side.
The present invention can be applied not only to the L display device but also to an EL display device that emits light downward.

FIG. 30 schematically shows a top view of a pixel of the EL display device having the above structure and emitting light downward.

Reference numeral 3301 denotes a pixel; 3302 to 3304, storage circuits; 3305, a D / A converter (described as D / A in the figure); 3306, a pixel electrode; and 3307, a source signal line. As the pixel electrode 3306, a transparent electrode is used. Note that power supply lines, counter electrodes, color filters, storage capacitors, and the like are not shown. Here, the storage circuits 3302-3
304 and the D / A converter 3305 are formed below the source signal line 3307.

Although not shown, the source signal line 33
It is also possible to dispose these storage circuits 3302 to 3304 and the D / A converter 3305 and the like below the gate signal line instead of below 07.

[Embodiment 11] EL of information terminal equipment of the present invention
In the pixels of the display device, a static memory (Static RAM: SRAM) is used as a storage circuit, but the storage circuit is not limited to the SRAM. The storage circuit applicable to the pixel of the EL display device of the information terminal device of the present invention includes a dynamic RAM (Dynamic RAM:
DRAM) and the like.

Further, although not particularly shown, a ferroelectric memory (Ferroelectric RAM:
It is also possible to configure a pixel of the EL display device of the information terminal device of the present invention using FRAM). FRAM is SR
It is a non-volatile memory having a writing speed equivalent to that of an AM or a DRAM. By utilizing the characteristics such as a low writing voltage, it is possible to further reduce the power consumption of the EL display device of the information terminal device of the present invention. In addition, the configuration is possible by using a flash memory or the like.

[Embodiment 12] In an EL display device included in a portable information device of the present invention, an external light emitting quantum efficiency is drastically improved by using an EL material capable of utilizing phosphorescence from a triplet exciton for emission. be able to. This allows
The power consumption, the life, and the weight of the EL element can be reduced.

[0216] Here, a report is shown in which the triplet exciton is used to improve the external light emission quantum efficiency. (T.Tsutsui, C.Adac
hi, 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 in the above paper is shown below.

[0218]

Embedded image

(MABaldo, DFO'Brien, Y. You, A. Shou
stikov, S. Sibley, METhompson, SRForrest, Nature
395 (1998) p.151.)

The EL materials (P
The molecular formula of (t complex) is shown below.

[0221]

Embedded image

(MABaldo, S. Lamansky, PEBurrrows,
METhompson, SRForrest, Appl.Phys.Lett., 75 (199
9) p.4.) (T.Tsutsui, M.-J.Yang, M.Yahiro, K.Nakamu
ra, T.Watanabe, T.tsuji, Y.Fukuda, T.Wakimoto, S.Ma
yaguchi, Jpn.Appl.Phys., 38 (12B) (1999) L1502.)

The EL materials (I
The molecular formula of (r complex) is shown below.

[0224]

Embedded image

Next, characteristics of an EL material capable of utilizing phosphorescence from triplet excitons for light emission will be described.

In the EL display device of the portable information device of the present invention, DC was applied to the power supply line and ON / OFF was switched by the arbitrary waveform generator, and the response time was measured. ON
Period (selection period), OFF period (non-selection period, voltage 0V)
Was 250 μs each.

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

FIG. 34 shows a driving waveform of a signal input to the power supply line and an optical response waveform indicating 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 waveform. The photomultiplier uses a negative output type, and applied a voltage of 0 V to 6 V. At this time, the response time was 33 μs.

As described above, if the phosphorescence emission from the triplet exciton can be used, it is possible in principle to realize a higher external emission quantum efficiency three to four times higher than the case where the fluorescence emission from the singlet exciton is used. .

[Embodiment 13] In this embodiment, an external view of a portable information terminal of the present invention will be described. FIG. 31 shows a portable information terminal having the structure of the present invention, where 2701 is a display panel and 2702 is an operation panel. The display panel 2701 and the operation panel 2702 are connected to each other by a connection portion 270.
3 are connected. The surface of the connection portion 2703 on which the display portion 2704 of the display panel 2701 is provided and the operation key 2706 of the operation panel 2702
Can be arbitrarily changed.

[0231] The display panel 2701 has a display portion 2704. The portable information terminal shown in FIG. 31 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 270.
5 is output. An EL display device is used for the display portion 2704.

The display portion 2704 has an aspect ratio of 16:
9, 4: 3, etc. can be arbitrarily selected. Display 2
The size of 704 is desirably about 1 inch to 4.5 inches diagonally.

The operation panel 2702 has an operation key 270
6, a power switch 2707 and a voice input unit 2708. Although the operation key 2706 and the power switch 2707 are provided separately in FIG. 31, a configuration in which the power switch 2707 is included in the operation key 2706 may be employed.
In the voice input unit 2708, voice is input.

In FIG. 31, the display panel 2701 has the audio output unit 2705 and the operation panel 2702 has the audio input unit 2708, but the present embodiment is not limited to this configuration. The display panel 2701 is a voice input unit 27
08, and the operation panel 2702 is
5 may be provided. Further, both the audio output unit 2705 and the audio input unit 2708 may be provided on the display panel 2701, or the audio output unit 2705 and the audio input unit 2708 may be provided.
708 may be provided on the operation panel 2702.

FIG. 32 shows an example in which the operation key 2706 of the portable information terminal shown in FIG. 31 is operated with the index finger. FIG. 33 shows an example in which the operation key 2706 of the portable information terminal shown in FIG. 31 is operated with the thumb. Note that the operation keys 2706 are provided on the operation panel 2702.
May be provided on the side surface. The operation can be performed with only one index finger or one thumb.

[Embodiment 14] In this embodiment, an electronic apparatus to which the portable information device of the present invention is applied will be described with reference to FIGS.
7 will be described.

A personal computer is a portable information device of the present invention. FIG. 28A illustrates a personal computer, which includes a main body 2801, an image input portion 2802, a display portion 2803, a keyboard 2804, and the like. Display unit 28
As 03, by using an EL display device having a memory circuit for each pixel, low power consumption of a personal computer can be realized.

There is a navigation device as a portable information device of the present invention. FIG. 28B illustrates a navigation device, which includes a main body 2811, a display portion 2812, and a speaker portion 281.
3, a storage medium 2814, an operation switch 2815, and the like. By using an EL display device having a memory circuit for each pixel as the display portion 2812, low power consumption of the navigation device can be realized.

[0239] An electronic book is a portable information device of the present invention. FIG. 28C illustrates an electronic book, which includes a main body 2851, a display portion 2852, a storage medium 2853, and operation switches 285.
4. Mini disk (MD) including antenna 2855
And DVD (DigitalVersatile Dis)
The data stored in c) and the data received by the antenna are displayed. By using an EL display device having a memory circuit for each pixel as the display portion 2652, power consumption of the electronic book can be reduced.

A portable telephone is a portable information device of the present invention. FIG. 27A illustrates a mobile phone, which includes a display panel 29.
01, operation panel 2902, connection unit 2903, display unit 2904, audio output unit 2905, operation keys 2906, power switch 2907, audio input unit 2908, antenna 2
909, CCD light receiving section 2910, external input port 201
1 and so on. By using an EL display device having a memory circuit for each pixel as the display portion 2904, low power consumption of the mobile phone can be realized.

There is a PDA as a portable information device of the present invention. FIG. 27B shows a PDA, which includes a display portion and a pen input doublet 3004, operation keys 3006, a power switch 3007, an external input port 3011, and an input pen 301.
2 etc. are included. By using an EL display device including a memory circuit for each pixel as the display portion 3004, low power consumption of the PDA can be realized. [Embodiment 15] In this embodiment, in an EL display device having pixels having the same configuration as that shown in FIG. 20, a signal held in a storage circuit of each pixel and input to a D / A converter is converted. To convert the analog signal to
FIG. 3 shows a case where control is performed using a DAC controller.
6 will be described.

In this embodiment, the operation of converting the signal held in the storage circuit of each pixel and input to the D / A converter into a corresponding analog signal and outputting the analog signal from the D / A converter is stored. This operation will be referred to as a circuit read operation.

As a configuration of the DAC controller, a circuit having a known configuration can be used freely.

In FIG. 36, the pixel is a writing TF
T108 to 110, storage circuits 105 to 107, a source signal line 101, a power supply line 112, a write gate signal line 102 to 104, and a D / A converter 400
, An EL driving TFT 115, an EL element 114, and a storage capacitor CS.

One of the source region and the drain region of the writing TFTs 108 to 110 is connected to the source signal line 10.
1 and the other one is a storage circuit 105-
107 inputs. T for writing
The gate electrodes of the FTs 108 to 110 are connected to the write gate signal lines 102 to 104, respectively. The outputs of the storage circuits 105 to 107 are connected to the inputs in1 to in3 of the D / A converter 400, respectively. The output out of the D / A converter 400 is connected to the gate electrode of the EL driving TFT 115 and one electrode of the storage capacitor Cs. One of a source region and a drain region of the EL driving TFT 115 is connected to the power supply line 112, and the other is connected to one electrode of the EL element 114. EL drive TFT 1 of storage capacitor Cs
The 15 side not connected to the gate electrode is connected to the power supply line 112.

The D / A converter 400 includes NAND circuits 441 to 443 and inverters 444 to 446 and 46.
1, switches 447a to 449a, switches 447b to
449b, a switch 460, capacitors C1 to C3, a reset signal line 452, a low-voltage gradation power line 453, a high-voltage gradation power line 454, and an intermediate-voltage gradation power line 455.

The operation until the digital signals are stored in the storage circuits 105 to 107 is described in the embodiment mode and the first embodiment.
Since the operation is the same as that shown in FIG.

Hereinafter, the operation of D / A converter 400 will be described.

The switch 460 is turned on by the signal res input to the reset signal line 452, and the potentials of the capacitors C1 to C3 connected to the out terminal are
It is fixed to the potential V _M of the intermediate pressure side gradation power line 455. Further, the potential of the high-voltage gradation power supply line 454 is set equal to the potential _VL of the low-voltage gradation power supply line 453. At this time, even if a digital signal is input to in1 to in3, no signal is written to the capacitors C1 to C3.

Thereafter, the signal r on the reset signal line 452
es changes, the switch 460 is turned off, and the capacitance C
The fixing of the potentials on the out terminal side of 1 to C3 is released. Then, the potential of the high voltage side gray scale power supply line 454 is changed to the potential V _L values different V _H of the low voltage side gray scale power supply line 453. At this time, according to the signals input to the terminals in1 to in3, the NAND
The outputs of the circuits 441 to 443 change, and the switches 447 to
In each of 449, one of the two switches is turned on, and the potential V _H of the high-voltage side gray scale power supply line or the potential of the low-voltage side gray scale power supply line _VL becomes the capacitance C1 to C3.
Are applied to the electrodes.

Here, the values of the capacitors C1 to C3 are set corresponding to each bit. For example, C1: C2:
C3 is set to be 1: 2: 4.

The voltages applied to the capacitors C1 to C3 change the potentials of the capacitors C1 to C3 on the out terminal side, and change the output potential. In other words, the input in1 to in
An analog signal corresponding to the digital signal of No. 3 is output from the out terminal.

The signal res input to the reset signal line 452 and the potential of the high-side gradation power supply line 454
By controlling with the C controller, the output of the analog signal with respect to the input digital signal from the D / A converter 400 can be controlled.

After the digital signal is once written in the storage circuit of the pixel, the above operation is repeated using a DAC controller, and the operation of reading the digital signal held in the storage circuit is repeated to display a still image. be able to.

At this time, the operation of the source signal line driver circuit and the gate signal line driver circuit can be stopped.

In FIG. 36, a pixel having a configuration in which three storage circuits are arranged has been described as an example, but the present invention is not limited to this. In general, the present invention can be applied to an EL display device having a pixel in which n (n is a natural number of 2 or more) memory circuits are arranged in each pixel.

As the DAC controller, a circuit having a known configuration can be used freely.

[Embodiment 16] In this embodiment, an example of the structure of a pixel of the present invention will be described with reference to FIG.

In FIG. 35, the same parts as those in FIG. 24 are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 35, storage circuits 105 to 107
Are input to the D / A 111 via the reading TFTs 121 to 123, respectively. Here, the gate electrodes of the reading TFTs 121 to 123 are connected to the reading gate signal line 124.

In the pixel having the configuration shown in FIG. 35, the operation of writing a signal to each of the storage circuits 105 to 107 is the same as that in the embodiment and the example, and the description is omitted here.

When displaying a still image, the storage circuit 105
After the digital signals are stored in the memory circuits 10 to 107, the read TFTs 121 to 123 are turned on by inputting a signal to the read gate signal line 124.
The digital signals held at 5 to 107 are input to the D / A 111. Here, when each pixel has a reading TFT as in this embodiment, inputting the digital signal held in the storage circuits 105 to 107 to the D / A 111 is referred to as a signal reading operation of the storage circuit. I do.

Turning on the read TFTs 121 to 123
By switching off and repeating the read operation,
Still images can be displayed.

Here, the read operation is performed by selecting a read gate signal line. The read gate signal line 124 can be driven by using a read gate signal line driving circuit.

As the configuration of the read gate signal line drive circuit, a known gate signal line drive circuit or the like can be used freely.

In FIG. 35, a pixel having a configuration in which three memory circuits are arranged has been described as an example. However, the present invention is not limited to this. In general, the present invention can be applied to an EL display device having a pixel in which n (n is a natural number of 2 or more) memory circuits are arranged in each pixel.

[Embodiment 17] In this embodiment, the EL of the present invention is used.
FIG. 37 illustrates a structure of a pixel of the display device.

In FIG. 37, the same parts as those in FIG. 24 are denoted by the same reference numerals, and description thereof will be omitted.

Storage circuits 141a to 143a and storage circuits 141b to 143b are arranged for each pixel.

The selection switch 151 is a writing TFT.
The connection between the storage circuit 108 and the storage circuit 141a or the storage circuit 141b is selected. The selection switch 152 is used for writing T
FT109 and storage circuit 142a or storage circuit 142b
Choose a connection with. The selection switch 153 is connected to the writing TFT 110 and the storage circuit 143 a or the storage circuit 14.
Select the connection with 3b.

The selection switch 154 selects the connection between the D / A 111 and the storage circuit 141a or 141b. The selection switch 155 selects the connection between the D / A 111 and the storage circuit 142a or 142b.
The selection switch 156 is connected to the D / A 111 and the storage circuit 143.
a or the connection with the storage circuit 143b is selected.

The storage circuits 141a to 141a are selected by the selection switches 151 to 153 and the selection switches 154 to 156.
3a and a storage circuit 141.
It is possible to select whether to store a digital signal in b to 143b. Further, a case where a digital signal is input to the D / A 111 from the storage circuits 141a to 143a and a case where the digital signal is input to the D / A 111 from the storage circuits 141b to 143b.
1 can be selected.

In each pixel, an operation of inputting a digital signal to each selected storage circuit and an operation of reading a digital signal held in each selected storage circuit are the same as those in the embodiment mode and the first embodiment. Description is omitted because there is.

The pixel stores a 3-bit digital signal for one frame period using the storage circuits 141a to 143a, and uses the storage circuits 141b to 143b to store a 3-bit digital signal for a frame period different from the frame period. The minute signal can be stored.

FIG. 37 shows a circuit for storing a 3-bit digital signal for two frames, but this embodiment is not limited to this. Generally, the present invention can be applied to an EL display device having pixels capable of storing n (n is a natural number of 2 or more) digital signals for m (m is a natural number of 2 or more) frames.

[0276]

In a portable information device incorporating an EL display device, digital signals are stored using a plurality of storage circuits disposed inside each pixel. When displaying a still image, the digital signal stored in the storage circuit in each frame period is used repeatedly. Thus, the source signal line driving circuit and the like can be stopped when a still image is displayed continuously. In addition, a circuit such as a video signal processing circuit that processes a signal input to the EL display device can be stopped when a still image is continuously displayed, so that the portable information device consumes less power. It greatly contributes to electric power.

[Brief description of the drawings]

FIG. 1 is a block diagram of a portable information terminal of the present invention having a plurality of storage circuits therein.

FIG. 2 is a block diagram of a mobile phone of the present invention having a plurality of storage circuits therein.

FIG. 3 is a diagram showing a timing chart for performing display using pixels of the EL display device of the portable information device of the present invention.

FIG. 4 is a circuit diagram of a storage circuit included in a pixel of an EL display device included in the portable information device of the present invention.

FIG. 5 is a diagram illustrating a circuit configuration example of a source signal line driver circuit without a second latch circuit.

6 is a detailed circuit diagram of a pixel of the EL display device of the portable information device of the present invention driven by the source signal line driving circuit of FIG.

FIG. 7 is a diagram showing a timing chart for performing display using the circuits shown in FIGS. 5 and 6;

FIG. 8 is a diagram showing a D of the EL display device of the portable information device of the present invention
The figure which shows the structure of an / A converter.

FIG. 9 shows D of the EL display device of the portable information device of the present invention.
The figure which shows the structure of an / A converter.

FIG. 10 illustrates an example of a manufacturing process of an EL display device of a portable information device of the present invention.

FIG. 11 is a diagram illustrating an example of a manufacturing process of an EL display device of a portable information device of the present invention.

FIG. 12 illustrates an example of a manufacturing process of an EL display device of a portable information device of the present invention.

FIG. 13 is a diagram simply showing the overall circuit configuration of a conventional EL display device of a portable information device.

FIG. 14 is a diagram showing a circuit configuration example of a source signal line driving circuit of an EL display device of a conventional portable information device.

FIG. 15 is a block diagram of a conventional portable information terminal.

FIG. 16 is a block diagram of a conventional mobile phone.

FIG. 17 illustrates a circuit configuration example of a source signal line driver circuit without a second latch circuit.

18 is a diagram showing a timing chart for performing display using the circuit shown in FIG. 17;

19A and 19B are a top view and a cross-sectional view of an EL display device of a portable information device according to the present invention.

FIG. 20 is a diagram showing a configuration of a D / A converter of an EL display device of a portable information device according to the present invention.

FIG. 21 is a diagram illustrating a configuration of a D / A converter of an EL display device of a portable information device according to the present invention.

FIG. 22 is a diagram illustrating a circuit configuration example of a source signal line driver circuit including a latch circuit for 1-bit processing.

FIG. 23 illustrates an example of a gate signal line driver circuit using a decoder.

FIG. 24 is a diagram illustrating a configuration of a pixel of an EL display device of a portable information device of the present invention.

FIG. 25 illustrates a circuit configuration example of a source signal line driver circuit.

FIG. 26 is a block diagram of a transmission / reception unit of a mobile phone.

FIG. 27 is a diagram showing an application example of the portable information device of the present invention.

FIG. 28 is a diagram showing an application example of the portable information device of the present invention.

FIG. 29 illustrates a configuration example of a pixel portion of a conventional active matrix EL display device.

FIG. 30 is a top view of a pixel of the EL display device of the portable information device of the present invention.

FIG. 31 is a diagram showing an example of a portable information terminal of the present invention.

FIG. 32 illustrates an example of a portable information terminal according to the present invention.

FIG. 33 is a diagram showing an example of a portable information terminal of the present invention.

FIG. 34: EL using phosphorescence from triplet excitons
The figure which shows the characteristic of a material.

FIG. 35 is a diagram showing a configuration of a pixel of an EL display device of a portable information device of the present invention.

FIG. 36 is a diagram showing a structure of a pixel of an EL display device of a portable information device of the present invention.

FIG. 37 is a diagram showing a configuration of a pixel of an EL display device of a portable information device of the present invention.

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Claims (25)

[Claims] 1. A portable information device having an EL display device, wherein the EL display device has a plurality of pixels, each of which has a plurality of storage circuits and a D / A.
A portable information device having a converter. 2. A portable information device having an EL display device, wherein the EL display device has a plurality of pixels, each of which has n (n is a natural number of 2 or more) storage circuits. A D / A converter for converting digital signals stored in the n storage circuits into analog signals. 3. An EL display device, comprising: a plurality of pixels; a power supply line; each of the plurality of pixels having a TFT to which an analog signal is input to a gate electrode; One of a source region and a drain region of the TFT,
In the portable information device connected to the power supply line and the other is connected to the EL element, the plurality of pixels each include n (n is a natural number of 2 or more) storage circuits; And a D / A converter for converting a digital signal stored in the storage circuit into the analog signal. 4. An EL display device, wherein the EL display device has a plurality of pixels and a power supply line, each of the plurality of pixels having a TFT to which an analog signal is input to a gate electrode; One of a source region and a drain region of the TFT,
A portable information device connected to the power supply line and the other connected to the EL element, wherein each of the plurality of pixels includes n × m (n and a natural number of 2 or more) storage circuits; A portable information device, comprising: a D / A converter that converts a digital signal of n bits stored in the nxm storage circuits into the analog signal. 5. An EL display device, comprising: a plurality of pixels; each of the plurality of pixels having a TFT to which an analog signal is input to a gate electrode; a power supply line; One of a source region and a drain region of the TFT,
A portable information device connected to the power supply line and the other connected to the EL element, wherein each of the plurality of pixels includes n × m (n and a natural number of 2 or more) storage circuits; A D / A converter for converting the n-bit digital signal stored in the n × m storage circuits into the analog signal, wherein each of the plurality of pixels stores the m-frame digital signal. A portable information device characterized by the above-mentioned. 6. The EL display device according to claim 1, wherein the EL display device has a source signal line, and the storage circuit and the D / A converter overlap the source signal line. A portable information device which is arranged. 7. The EL display device according to claim 1, wherein the EL display device has a gate signal line, and the storage circuit and the D / A converter overlap with the gate signal line. A portable information device which is arranged. 8. A portable information device having an EL display device, wherein the EL display device has a plurality of pixels, wherein the plurality of pixels each have an EL element. A line, n (n is a natural number of 2 or more) gate signal lines, a power supply line, n first TFTs, n storage circuits, a second TFT,
A gate electrode of each of the n first TFTs is connected to a different one of the n gate signal lines, and one of a source region and a drain region is Each is connected to the source signal line, and the other is connected to one of the n different input terminals of the n storage circuits, and the output terminals of the n storage circuits are respectively connected to the D / A
The input terminal of the D / A converter is connected to the input terminal of the converter, and the output terminal of the D / A converter is the second TFT.
One of a source region and a drain region of the second TFT is connected to the power supply line, and the other is connected to the EL.
A portable information device which is connected to an element. 9. A portable information device having an EL display device, wherein the EL display device has a plurality of pixels, and each of the plurality of pixels has an EL element. n is a natural number of 2 or more) source signal lines, a gate signal line, a power supply line, n first TFTs, n storage circuits, a second TFT,
A gate electrode of each of the n first TFTs is connected to the gate signal line; and one of a source region and a drain region is one of the n source signal lines. , And the other is connected to any one of the n input terminals of the n storage circuits, and the output terminals of the n storage circuits are respectively connected to the D / A
The input terminal of the D / A converter is connected to the input terminal of the converter, and the output terminal of the D / A converter is the second TFT.
One of a source region and a drain region of the second TFT is connected to the power supply line, and the other is connected to the EL.
A portable information device which is connected to an element. 10. The EL display device according to claim 8, wherein the EL display device has a source signal line driving circuit, wherein the source signal line driving circuit is a shift register and an n-bit digital signal by a sampling pulse from the shift register. , A second latch circuit to which the n-bit digital signal held by the first latch circuit is transferred, and the n-bit signal transferred to the second latch circuit. Digital signal of 1
A portable information device comprising: a switch for sequentially selecting bits by bit and inputting the selected signal to the source signal line. 11. The EL display device according to claim 8, wherein the EL display device has a source signal line drive circuit, wherein the source signal line drive circuit is a shift register and a 1-bit digital signal generated by a sampling pulse from the shift register. And a second latch circuit to which the 1-bit digital signal held by the first latch circuit is transferred. 12. The EL display device according to claim 9, wherein the EL display device has a source signal line driving circuit, wherein the source signal line driving circuit is a shift register and an n-bit digital signal by a sampling pulse from the shift register. And a latch circuit for holding the information. 13. The EL display device according to claim 9, wherein the EL display device includes a source signal line driving circuit, wherein the source signal line driving circuit is configured to shift a shift register and an n-bit digital signal by a sampling pulse from the shift register. A portable information device, comprising: a latch circuit that holds the latch signal; and n switches that input the n-bit digital signal held by the latch circuit to the n source signal lines. 14. The memory according to claim 1, wherein the storage circuit is a static memory (SRAM), a ferroelectric memory (FRAM), or a dynamic memory (DRAM). Portable information device. 15. The storage circuit according to claim 1, wherein the storage circuit is provided on a glass substrate, a plastic substrate,
A portable information device formed on a stainless steel substrate or a single crystal wafer. 16. The portable information device according to claim 1, wherein the portable information device is a mobile phone, a personal computer, a navigation system, a PDA, or an electronic book. 17. A driving method of a portable information device incorporating an EL display device having a plurality of pixels, wherein a digital signal is stored in a plurality of storage circuits respectively provided in the plurality of pixels, and the stored digital signal is stored in the storage circuit. A method for driving a portable information device, comprising repeatedly reading, converting the repeatedly read digital signal into a corresponding analog signal, and inputting the analog signal to an EL element. 18. The storage device according to claim 17, wherein the plurality of pixels are arranged in a matrix, and among the plurality of pixels, the storage of the plurality of storage circuits included in a pixel in a specific row or a pixel in a specific column. A method for driving a portable information device, characterized in that only a digital signal obtained is rewritten. 19. A driving method for a portable information device incorporating an EL display device having a plurality of pixels and a source signal line driving circuit for inputting a video signal to the plurality of pixels, wherein each of the plurality of pixels has A digital signal is stored in a plurality of storage circuits, the stored digital signal is repeatedly read, the repeatedly read digital signal is converted into a corresponding analog signal, and input to an EL element. A method for driving a portable information device, wherein the operation of a circuit is stopped. 20. A method for driving a portable information device having an EL display device and a CPU, wherein the EL display device has a plurality of pixels and a first circuit for outputting a signal to the plurality of pixels. The CPU has a second circuit that controls the first circuit, stores a digital signal in a plurality of storage circuits included in each of the plurality of pixels, repeatedly reads the stored digital signal, A method for driving a portable information device, wherein the operation of the second circuit is stopped by converting a digital signal repeatedly read into a corresponding analog signal and inputting the analog signal to an EL element. 21. An EL display device having a plurality of pixels;
In a method for driving a portable information device incorporating a RAM, a digital signal is stored in a plurality of storage circuits respectively included in the plurality of pixels, the stored digital signal is repeatedly read, and the repeatedly read digital signal is corresponded. A data reading operation of the VRAM is stopped by converting the signals into analog signals to be input to EL elements, respectively. 22. The driving method of a portable information device according to claim 17, wherein a read operation is performed once in one frame period in the plurality of storage circuits. 23. The memory device according to claim 17, wherein the storage circuit is a static memory (SRAM), a ferroelectric memory (FRAM), or a dynamic memory (DRAM). Of driving a portable information device. 24. The storage circuit according to claim 17, wherein the storage circuit is provided on a glass substrate, a plastic substrate,
A method for driving a portable information device, wherein the method is formed on a stainless steel substrate or a single crystal wafer. 25. The drive of a portable information device according to claim 17, wherein the portable information device is a mobile phone, a personal computer, a navigation system, a PDA or an electronic book. Method.