JP2003167561A - Display device and portable terminal device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device permitting to reduce power consumption of the entire device by reducing consumption current due to charge/discharge of, especially, signal lines, and to provide a portable terminal device using the same. <P>SOLUTION: In a liquid crystal display device mounted with memory built-in pixels, each pixel circuit 11 is provided with a pixel selection switch 24 permitting to write a picture data to a memory circuit 23 synchronizing with horizontal scanning so as to be able to control writing of the picture data to the memory circuit 23 in pixel units and hold the previous data in the memory circuit 23 as it is, without rewriting data to those pixels for which rewriting of memory data is not necessary. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device and a mobile terminal device using the same, and more particularly to a display device having a memory unit for each pixel and a mobile terminal device using the same as an output display unit.

[0002]

2. Description of the Related Art A display device, such as a liquid crystal display device, displays an image by changing the form of the molecular alignment of liquid crystals depending on the presence or absence of an electric field and controlling the transmission / blocking of light. In principle, this liquid crystal display device is a low power consumption display device that does not require much driving power and consumes less power. Personal Digital A
It is widely used as an output display unit of mobile terminal devices such as ssistants).

As described above, in a liquid crystal display device mounted on a mobile terminal device such as a mobile phone or a PDA, in order to use the battery for a long time with one charge, the drive voltage is lowered or the drive voltage is increased. Low power consumption is being promoted by lowering the frequency. In addition, in order to further reduce power consumption, there is also known a liquid crystal display device adopting a structure having a memory portion for each pixel as its pixel structure (see Japanese Patent Laid-Open No. 9-212140, etc.). ).

As described above, in a liquid crystal display device adopting a pixel structure having a memory section for each pixel, once the image data of a still image is written in the memory section of each pixel, the memory thereafter. Since it is sufficient to repeatedly drive the display of the pixel with the image data stored in the section, it is not necessary to charge and discharge the signal line each time, and theoretically, the power required for polarity reversal is consumed. Since this is all that is required, it is possible to further reduce power consumption.

[0005]

By the way, in a liquid crystal display device, as a method of writing a signal to a pixel, generally, a pixel is selected in a row unit by vertical scanning, and a pixel in the selected row is selected. For example, a line-sequential method in which signals for one line (for one row) are simultaneously written in row units or a dot-sequential method in which signals for one line are sequentially written in pixel units is adopted. These writing methods are also adopted in the case of the above-described liquid crystal display device having a pixel with a built-in memory.

Here, an advantage of the liquid crystal display device having a pixel with a built-in memory is that image data once written can be held in the memory portion and image display can be repeated using the held data. Despite these advantages,
In a conventional liquid crystal display device with a pixel with a built-in memory,
As described above, when writing the image data, a sequence has been adopted in which all the data (memory data) in the memory circuit is rewritten row by row.

As described above, in a liquid crystal display device which adopts a sequence for newly writing data, for example, when the previously written data and the currently written data are the same, it is not necessary to rewrite the memory data, but the data is rewritten. Since rewriting operation is performed even for unnecessary memory data, when continuous image data such as a moving image is input, unnecessary current consumption occurs due to charging / discharging the signal line, reducing power consumption of the entire device. Hinders Therefore, particularly when considering the application to mobile terminal devices such as mobile phones and PDAs, reduction of power consumption of the liquid crystal display device itself is an important problem to be solved in order to further reduce the power consumption of the mobile terminal device. Become.

The present invention has been made in view of the above problems. An object of the present invention is to reduce current consumption due to charge / discharge of a signal line and to reduce power consumption of the entire device. An object is to provide a display device and a mobile terminal device using the display device.

[0009]

In a display device according to the present invention, a plurality of pixel circuits including a memory portion are arranged in a matrix on a substrate, and each of the plurality of pixel circuits is wired in a column unit. The first selection switch for permitting the writing of the digital image signal supplied from the signal line to the memory unit in synchronization with the vertical scanning, and the writing of the digital image signal supplied from the signal line to the memory unit to the horizontal scanning It is configured to have a second selection switch that permits in synchronization.
This display device is used as an output display unit in a mobile terminal device such as a mobile phone or a PDA.

In the display device having the above configuration or the portable terminal device using the display device as an output display unit, the first selection switch of each pixel circuit is selectively driven row by row by vertical scanning, so that the pixels of the selected row are selected. Allows writing of signals to the memory part of the circuit. On the other hand, the second selection switch is selectively driven on a column-by-column basis by horizontal scanning to allow writing of a signal to the memory unit of the pixel circuit of the selected column. As a result, by selectively driving the horizontal selection switch on a pixel-by-pixel basis, writing of a signal to the memory unit of each pixel circuit can be controlled on a pixel-by-pixel basis.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a display device, for example, a liquid crystal display device according to an embodiment of the present invention.

As is apparent from FIG. 1, in the liquid crystal display device according to the present embodiment, pixel circuits (hereinafter sometimes simply referred to as “pixels”) 11 having a pixel structure described later are arranged in a matrix of n rows and m rows. Pixel units 12 arranged in columns, vertical drive circuits 13 that selectively drive each pixel circuit 11 of the pixel units 12 in units of rows, and pixel circuits 11 in rows that are selectively driven by the vertical drive circuit 13 It is configured to have a horizontal drive circuit 14 which is selectively driven in units and which supplies an image signal to the selected pixel circuit 11.

With respect to the pixel array of n rows and m columns of the pixel portion 12, n scanning lines 15-1 to 15-n and m signal lines 16-1 to 16-m are arranged in a matrix. The pixel circuit 11 is arranged at the intersection. Further, for each of the pixel circuits 11, the pixel selection line 17-1 is provided for each column.
.About.17-m are wired along the signal lines 16-1 to 16-m. Here, the vertical drive circuit 13 and the horizontal drive circuit 14 have a so-called drive circuit integrated structure integrally formed on a substrate (hereinafter referred to as “liquid crystal display panel”) 18 on which the pixel portion 12 is formed. Has become.

The liquid crystal display panel 18 is, for example, a thin film transistor (Thin) which is a switching element of each pixel circuit 11.
A TFT substrate on which a film transistor (TFT) is formed,
It has a structure in which a counter substrate on which a color filter, a counter electrode, etc. are formed is overlapped, and a liquid crystal material is sealed between these substrates. Then, in the pixel portion 12, the TFT of each pixel circuit 11 in units of rows by the vertical drive circuit 13
Switching control and signal line 1 from the horizontal drive circuit 14
Image display is performed by controlling the orientation of the liquid crystal by applying a voltage based on the image signal supplied through 6-1 to 16-m and changing the light transmittance.

[First Circuit Example of Pixel Circuit] FIG. 2 is a circuit diagram showing a first circuit example of the pixel circuit, and shows only the circuit configuration of one pixel in the i-th row and the i-th column. The pixel circuit 11A according to the first circuit example has a configuration including a liquid crystal cell 21, a storage capacitor 22, a memory circuit 23, a pixel selection switch 24, and a row selection switch 25.

One ends of the liquid crystal cell 21 and the storage capacitor 22 are commonly connected to each other, and are also connected to the input / output ends of the memory circuit 23. The common voltage VCOM is applied to the other end of the liquid crystal cell 21, and 1 is applied to the other end of the storage capacitor 22.
A potential Cs whose polarity is inverted is applied every horizontal scanning period (or one field period). The pixel selection switch 24 and the row selection switch 25 are connected in series between the signal line 16-i and the input / output terminal of the memory circuit 23.

Specifically, one end of the pixel selection switch 24 is connected to the signal line 16-i, and a memory data rewrite permission signal (horizontal selection) supplied from the horizontal drive circuit 14 through the pixel selection line 17-i. Signal) hGATE
In response to the above, the circuit is turned on (closed), and the image data given from the horizontal drive circuit 14 through the signal line 16-i is passed to permit the rewriting of the data held in the memory circuit 23. The row selection switch 25 is
One end thereof is connected to the other end of the pixel selection switch 24, and the other end thereof is connected to the input / output end of the memory circuit 23. In response to the scan signal vGATE given from the vertical drive circuit 15 through the scan line 15-i. By turning on, pixels for which data rewriting is permitted are selected in row units.

In this circuit example, the pixel selection switch 24 and the row selection switch 25 are connected in series in this order between the signal line 16-i and the input / output terminal of the memory circuit 23. The connection order may be exchanged with each other, and there is no difference in circuit operation. Further, as the pixel selection switch 24 and the row selection switch 25, for example, TFTs are used.

[Driving System] (Vertical Driving Circuit 13) The vertical driving circuit 13 is composed of, for example, a shift register, and the scanning signal vGATE.
Are sequentially output at a predetermined cycle, and are sequentially supplied to the pixel array of n rows and m columns through the scanning lines 15-1 to 15-n, whereby each pixel circuit 11 is selectively driven row by row.

(Horizontal drive circuit 14) Horizontal drive circuit 14
Is the memory circuit 2 of each pixel circuit 11 in the pixel section 12.
The image data to be written in 3 (hereinafter, may be abbreviated as "memory data") is processed in units of one line (one line), and the image data of the same line one field before is processed in pixel units. Perform comparison processing.

In this comparison process, the horizontal drive circuit 14
Judges that it is necessary to rewrite the memory data for the pixel in which the image data of the current field and the image data of the previous field are different, and supplies the image data to the pixel through the signal line 16-i, and the pixel selection line. 17-
A memory data rewrite permission signal hGATE is supplied through i. On the other hand, since it is not necessary to rewrite the memory data for the pixel in which the image data of the current field and the image data of the previous field are the same, the image data and memory data rewrite permission signal hG
Stop supplying ATE together.

Next, the operation of the liquid crystal display device having the above-described structure, which is equipped with the pixel circuit 11A according to the first circuit example, will be described with reference to FIG.
4 will be described with reference to the schematic diagram of FIG.

In the case of the present example, as shown in FIG. 3, in the i-th row, the memory data is rewritten for each pixel of the 1st column to the jth column and the kth column to the mth column, and the j + 1th column is rewritten. ~
For each pixel in the (k−1) th column, the memory data is not rewritten, and the data up to that point is retained as it is.
The operation of rewriting / holding the memory data in the i-th row will be specifically described below.

At the time of scanning the i-th row, the vertical drive circuit 13 makes the scanning signal vGATE (i) given to the i-th scanning line 15-i active (high level).
As a result, the row selection switch 25 is turned on (closed), so that the pixel circuits 11 for the first row of the i-th row are selected. At this time, the image data for one line to be written in the i-th row is input to the horizontal drive circuit 14. It is assumed that the horizontal drive circuit 14 has a built-in image memory, for example, and holds the image data of the previous field in the memory.

The horizontal drive circuit 14 compares the image data of the i-th row of the previous field held in the built-in memory with the image data of the i-th row of the current field to be written in pixel units. Then, it is determined that the memory data needs to be rewritten for the pixels having different data, and the memory data need not be rewritten for the same pixel. In the case of this example, the horizontal drive circuit 14 is
It is necessary to rewrite the memory data for each pixel of the j-th column and the k-th column to the m-th column, and it is not necessary to rewrite the memory data for each pixel of the j + 1-th column to the k-1th column.

Based on the result of the determination, the horizontal drive circuit 14 causes the signal lines 16-1 to 16-j corresponding to the pixels in the first column to the j-th column and the pixels in the k-th column to the m-th column. The image data is supplied to the signal lines 16-k to 16-m corresponding to, and the writing period of each pixel of the first column to the j-th column and the writing period of each pixel of the k-th column to the m-th column. The memory data rewrite permission signal hGATE is activated all the time.

As a result, in each of the pixel circuits of the 1st to jth columns and the kth to mth columns, the pixel selection switch 2 is used.
4 is turned on, the horizontal drive circuit 1 is connected through the signal lines 16-1 to 16-j and the signal lines 16-k to 16-m.
The image data supplied from 4 is the pixel selection switch 2
4 and the row selection switch 25, the memory circuit 23
Is supplied to. As a result, in each of the pixel circuits of the first column to the j-th column and the k-th column to the m-th column, the image data for the memory circuit 23 is rewritten.

On the other hand, for the signal lines 16-j + 1 to 16-k-1 corresponding to the pixels in the j + 1th column to the k-1th column,
The horizontal drive circuit 14 stops the supply of the image data and makes the memory data rewrite permission signal hGATE inactive (low level) over the writing period of each pixel in the j + 1th column to the k−1th column. As a result, in each of the pixel circuits in the (j + 1) th column to the (k-1) th column, the pixel selection switch 2
Since 4 is turned off (open), the image data is not rewritten in the memory circuit 23, and the data up to that point is retained in the memory circuit 23 as it is.

Thereafter, the i + 1th line, the i + 2nd line, ..., N
In each scanning period of the row, the control of writing / holding image data to / from the memory circuit 23 is sequentially executed in the same sequence. Note that when the image data for one line is exactly the same as the previous field and the current field, it is not necessary to write the memory data for all the pixels in that row. Stops the supply of image data to all pixels, and outputs the memory data rewrite enable signal hGAT.
All you have to do is make E inactive.

As described above, in the liquid crystal display device having the pixels with the built-in memory, each pixel circuit 11 is provided with the pixel selection switch 24 for permitting the writing of the image data to the memory circuit 23 in synchronization with the horizontal scanning. Since the writing of the image data to the memory circuit 23 can be controlled on a pixel-by-pixel basis, the pixel that does not need rewriting of the memory data is not rewritten, and the data up to that point is retained in the memory circuit 23 as it is. It can be realized in units.

As a result, even when continuous image data such as a moving image is input, the memory data is not rewritten for the pixels having the same image data as the previous field, and the sequence for holding the memory data is maintained. By adopting this, it is not necessary to write the image data to the memory circuit 23 in that pixel, so that the power consumption can be reduced by the current consumption associated with the writing. In particular, by stopping the supply of image data to the pixels that do not rewrite the memory data, the current consumption due to the charging and discharging of the signal line corresponding to that pixel is eliminated, further reducing the power consumption of the entire device. it can.

In the case of a still image, as a matter of course, it is only necessary to retain the memory data as it is, and it is not necessary to rewrite the memory data in units of fields. Therefore, in principle, the current consumption due to the charging / discharging of the signal line is eliminated. You can

[Second Circuit Example of Pixel Circuit] FIG. 5 is a circuit diagram showing a second circuit example of the pixel circuit. In the figure, the same parts as those in FIG. 2 are designated by the same reference numerals.

Pixel circuit 11A according to the first circuit example described above
In the configuration, the image data input from the signal line 16-i through the pixel selection switch 24 and the row selection switch 25 is directly supplied to the liquid crystal cell 21 and the storage capacitor 22 and stored in the memory circuit 23. Was there. Then, not only digital image data but also analog image signals can be supported.

On the other hand, in the pixel circuit 11B according to the second circuit example, the image data input via the pixel selection switch 24 and the row selection switch 25 is temporarily stored in the memory circuit 23, and then the data is read. By reading out to the liquid crystal cell 21 and the storage capacitor 22 via the reading buffer 26, a path for writing the image data in the memory circuit 23 and a path for reading the image data from the memory circuit 23 are separated. Then, it cannot deal with analog image signals, but only with digital image data.

As described above, the path for writing the image data to the memory circuit 23 and the path for reading the image data from the memory circuit 23 are separated from each other, and the data read buffer 26 is provided on the read side path. In the pixel circuit 11B, the influence of the pixel potential of the liquid crystal cell portion on the data in the memory circuit 23 can be eliminated, and the memory data can be prevented from being rewritten under the influence of the pixel potential. Can have a large margin.

Also in the liquid crystal display device having a pixel with a built-in memory, which has the data reading buffer 26, by providing the pixel selection switch 24 in each pixel circuit 11, writing of image data to the memory circuit 23 is performed on a pixel-by-pixel basis. Since control is possible, a control sequence for rewriting / holding image data for the memory circuit 23 can be realized in pixel units.

[Third Circuit Example of Pixel Circuit] FIG. 6 is a circuit diagram showing a third circuit example of the pixel circuit. In the figure, the same parts as those in FIG. 5 are designated by the same reference numerals.

In the pixel circuit 11C according to the third circuit example, in addition to the configuration of the pixel circuit 11B according to the second circuit example,
The configuration has a write switch 27 connected between the signal line 16-i and the common connection point of the liquid crystal cell 21 and the storage capacitor 22. The write switch 27 is a switch for writing an analog image signal, and is composed of, for example, a thin film transistor, and is connected from the vertical scanning circuit 13 to the second
Second scanning signal v supplied via the scanning line 28-i of
Driven by GATE2.

That is, the pixel circuit 11 according to the second circuit example.
In the case of B, the configuration is such that only digital image data can be supported, whereas the pixel circuit 11 according to the third circuit example
In the case of C, the configuration is such that it can handle both digital image data and analog image signals. Here, the analog image signal is directly applied to the liquid crystal cell section through the write switch 27, and the digital image data is temporarily stored in the memory circuit 23 through the pixel selection switch 24 and the row selection switch 25, and then the data is stored. It is supplied to the liquid crystal cell section through the read buffer 26.

In this way, the data reading buffer 2
Even in a liquid crystal display device having a built-in memory, which has 6 and is compatible with an analog image signal, each pixel circuit 1
By providing the pixel selection switch 24 in FIG. 1, writing of image data into the memory circuit 23 can be controlled in pixel units, so that a control sequence of rewriting / holding image data in the memory circuit 23 can be realized in pixel units. .

[Fourth Circuit Example of Pixel Circuit] FIG. 7 is a circuit diagram showing a fourth circuit example of the pixel circuit. In the figure, the same parts as those in FIG. 6 are designated by the same reference numerals.

In the pixel circuit 11D according to the fourth circuit example, in addition to the configuration of the pixel circuit 11C according to the third circuit example,
Output terminal of memory circuit 23 and data read buffer 2
The data read switch 29 is connected to the input terminal 6 of the data read circuit 6. The data read switch 29 is a switch for reading image data from the memory circuit 23, and is made of, for example, a thin film transistor, and the data read control line 30 is provided from the vertical scanning circuit 13.
Data read control signal drG supplied via -i
Driven by ATE.

In this example, a data read switch 29 is provided between the output end of the memory circuit 23 and the liquid crystal cell section.
The data read buffer 26 and the data read buffer 26 are connected in that order, but the connection order may be interchanged with each other, and there is no difference in circuit operation.

As described above, in the liquid crystal display device equipped with the pixel with the built-in memory, which is compatible with the analog image signal and has the data reading buffer 26 and the data reading switch 29, each pixel circuit 11 has a pixel. By providing the selection switch 24, the writing of the image data to the memory circuit 23 can be controlled on a pixel-by-pixel basis, so that the control sequence of rewriting / holding the image data on the memory circuit 23 can be realized on a pixel-by-pixel basis.

In the above embodiment, the case where the present invention is applied to the liquid crystal display device using the liquid crystal cell as the display element of the pixel circuit has been described as an example. However, the present invention is not limited to the application to the liquid crystal display device. The present invention can be applied to all display devices including a memory unit for each pixel, such as an EL display device using an electroluminescence (liquid crystal display; EL) element as a display element of a pixel circuit.

[Application Example] FIG. 8 is an external view showing the outline of the configuration of a mobile terminal device according to the present invention, for example, a mobile phone.

The mobile phone according to the present example has a speaker unit 32, an output display unit 33, and an operation unit 3 on the front side of the device casing 31.
4 and the microphone section 35 are arranged in this order from the upper side. In the mobile phone having such a configuration, a liquid crystal display device is used for the output display unit 33, and as the liquid crystal display device, the liquid crystal display device according to the above-described embodiment, that is, the liquid crystal display device having a pixel with a built-in memory is used.

As described above, in the mobile phone using the liquid crystal display device having the pixels with a built-in memory as the output display section 83, the writing of the image data to each memory section of the pixel circuit can be controlled on a pixel-by-pixel basis. ,
Since it is not necessary to write image data to the memory portion in the pixels that do not need to be rewritten, and the power consumption can be reduced accordingly, it is possible to prolong the usage time for one charge of the battery which is the main power source.

Here, the case where the present invention is applied to a mobile phone has been described as an example, but the present invention is not limited to this, and the present invention can be applied to all mobile terminal devices such as a child device of a parent-child phone and a PDA.

[0051]

As described above, according to the present invention,
In a display device equipped with a pixel with a built-in memory, each pixel circuit is provided with a selection switch that permits writing of image data to the memory unit in synchronization with horizontal scanning. Writing can be controlled on a pixel-by-pixel basis, and since it is not necessary to write image data to the memory portion in pixels that do not need to be rewritten, the current consumption can be reduced, so that the power consumption of the entire device can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of an overall configuration of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a first circuit example of a pixel circuit.

FIG. 3 is a conceptual diagram showing a control sequence for rewriting / holding memory data.

FIG. 4 is a timing chart for explaining a control sequence for rewriting / holding memory data.

FIG. 5 is a circuit diagram showing a second circuit example of a pixel circuit.

FIG. 6 is a circuit diagram showing a third circuit example of the pixel circuit.

FIG. 7 is a circuit diagram showing a fourth circuit example of the pixel circuit.

FIG. 8 is an external view showing a schematic configuration of a mobile phone according to the present invention.

[Explanation of symbols]

11, 11A, 11B, 11C, 11D ... Pixel circuit, 1
2 ... Pixel part, 13 ... Vertical drive circuit, 14 ... Horizontal drive circuit, 18 ... Liquid crystal display panel, 21 ... Liquid crystal cell, 22 ... Storage capacitor, 23 ... Memory circuit, 24 ... Pixel selection switch, 25 ... Row selection Switch, 26 ... Data read buffer, 27 ... Write switch, 29 ... Data read switch

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/20 680 G09G 3/20 680T 3/30 3/30 J H04M 1/00 H04M 1/00 AF term (reference) 2H093 NA16 NC13 NC15 NC27 NC34 NC35 NC40 ND39 ND49 ND52 ND53 ND58 NE07 5C006 AA01 AF42 AF43 AF51 AF53 AF69 BB16 BC03 BC06 BC11 BC20 BF09 BF24 FA47 5C080 AA06 AA10 BB05 DD26 EE19 FF11 JJ02 JJ03 JJ04 KK07 KK47 5K027 AA11 BB17 FF22 MM15 MM17

Claims (11)

[Claims] 1. A plurality of pixel circuits including a memory portion are arranged in a matrix on a substrate, and each of the plurality of pixel circuits includes a digital image signal supplied from a signal line wired in a column unit. A first selection switch for permitting writing to the memory unit in synchronization with vertical scanning, and a second selection switch for permitting writing of the digital image signal supplied from the signal line into the memory unit in synchronization with horizontal scanning. A display device having a switch. 2. The display device according to claim 1, wherein the first and second selection switches are connected in series with each other between the signal line and the memory section. 3. Vertical drive means for selectively driving the first selection switches in the plurality of pixel circuits in row units, and selectively driving the second selection switches in the plurality of pixel circuits in pixel units, The display device according to claim 1, further comprising a horizontal driving unit that supplies a write signal to the pixel circuit. 4. The horizontal driving means stops the supply of a write signal to the pixel circuit when the second selection switch is in a non-selected state.
Display device described. 5. The display device according to claim 1, wherein the display element of the pixel circuit is a liquid crystal cell. 6. The display device according to claim 1, wherein the display element of the pixel circuit is an electroluminescence element. 7. A first selection switch as the output display section, which permits writing to the memory section and a digital image signal supplied from a signal line wired in a column unit in synchronization with vertical scanning. And a plurality of pixel circuits each having a second selection switch for permitting writing of the digital image signal supplied from the signal line to the memory unit in synchronization with horizontal scanning, are arranged in a matrix on the substrate. A mobile terminal device using the display device. 8. The display device includes a vertical driving unit that selectively drives the first selection switches in the plurality of pixel circuits in row units, and the second selection switches in the plurality of pixel circuits in pixel units. The mobile terminal device according to claim 7, further comprising a horizontal driving unit that selectively drives the pixel circuit and supplies a write signal to the pixel circuit. 9. The horizontal driving means stops the supply of a write signal to the pixel circuit when the second selection switch is in a non-selected state.
The portable terminal device described. 10. The mobile terminal device according to claim 7, wherein the display device is a liquid crystal display device using a liquid crystal cell as a display element of the pixel circuit. 11. The mobile terminal device according to claim 7, wherein the display device is an electroluminescence display device using an electroluminescence element as a display element of the pixel circuit.