JPH11160729A - Liquid crystal display element with image reading function and image reading method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain miniaturization and reduction of production cost without lowering reliability or processing speed caused by sharing a vertical driver between a pixel transistor for image reading and a pixel transistor for signal reading. SOLUTION: A thin film transistor(TFT) (L) 26 connected to a transparent pixel electrode 24 is connected to a gate line 23a for signal reading and a TFT 27 connected to the cathode side of a photodiode 25 is connected to a gate line 23b for image reading respectively. These TFTs are constituted so as to control their ON/OFF states independently through different TFT control circuits 33a and 33b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device having an image reading function, comprising an active matrix panel provided with a light receiving element such as a thin film transistor (TFT) and a photodiode, and a liquid crystal layer, and such a liquid crystal. The present invention relates to an image reading method using a display device.

[0002]

2. Description of the Related Art In recent years, in order to reduce the size of an image display device, a display device using a liquid crystal is often used.
A liquid crystal display device including an active matrix panel having an FT can be easily obtained with high image quality as compared with a simple matrix type liquid crystal display device, and thus has been actively studied.

In addition, by combining the above-described image display device and reading device to display an image and to obtain image data by reading a document image or the like, it is possible to reduce the size of the entire device, There are also proposals for improving operability.

[0004] Specifically, this type of device is, as disclosed in, for example, Japanese Patent Application Laid-Open No. 4-282609, provided on the back side of a transparent substrate on which TFTs and transparent pixel electrodes are formed in a liquid crystal display device. It is configured by disposing a transparent substrate on which an image sensor is formed.

[0005]

However, if one vertical driver is used as described above, the first transistor and the second transistor must be set to be separately turned on as a price. As this method, the gate threshold voltage is set to be different between the first transistor and the second transistor, or
Channels and n-channels are used in combination, but problems remain in terms of reliability and processing speed.

In view of the above, the present invention provides a vertical driver in each of a signal readout circuit and an image readout circuit, and does not require a setting to turn on each transistor separately. Thus, a liquid crystal display device with an image reading function that is technically simple and highly reliable can be realized.

Further, by forming a vertical driver together with a horizontal driver and a pixel electrode by using polysilicon,
Even if the vertical driver is provided in each of the signal reading circuit and the image reading circuit, the liquid crystal display device with the image reading function as described above can be realized at low cost.

[0008]

In a liquid crystal display device with an image reading function according to the present invention, a vertical driver is provided in each of a signal reading circuit and an image reading circuit, and the setting is such that each transistor is separately turned on. It is set so that image input / output can be performed independently without the need for. With this configuration, it is possible to realize a liquid crystal display device with an image reading function that is technically simple, has high reliability, and has a high processing speed.

However, as described above, when it is desired to increase the number of vertical drivers from one to two, when a general-purpose IC or the like is used, the cost increases as the number of drivers increases. Therefore, like the horizontal driver and the pixel electrode, the vertical driver is formed of polysilicon,
In addition to reducing the cost of ICs, etc., even if it is desired to increase the number of drivers as described above, the cost does not increase in principle, so a low-cost and high-performance liquid crystal display device with an image reading function is required. Can be realized.

As a method for solving the above-mentioned problem, as disclosed in, for example, Japanese Patent Application Laid-Open No. 9-186312, one end of a light receiving element such as a photodiode is connected to a CC.
There is a method of connecting a D (charge coupled device) to read out the output of the light receiving element by a so-called interline transfer method using a scanning function of a CCD.

In this method, since a CCD is used on the image reading side, a vertical driver for image reading becomes unnecessary. Therefore, the setting for turning on the first transistor and the second transistor separately as described above is not necessary. Although it is a powerful method that can solve the above-mentioned problem because it is not necessary from the beginning, it is difficult to form a CCD at the same time using the same process as a pixel transistor and a drive circuit that controls them. In this case, it is necessary to provide a separate process for forming the CCD, which leads to an increase in the number of manufacturing steps. As a result, problems remain in manufacturing cost, yield, reliability, and the like.

Considering this point, the above solution is considered to be an effective means for realizing a low-cost and high-performance liquid crystal display device with an image reading function.

[0013]

(Embodiment 1) A liquid crystal display device with an image reading function according to Embodiment 1 of the present invention is installed such that the display surface of an image is substantially horizontal as shown in FIG. An example of a liquid crystal display device which is used in this manner will be described.

(1) Overall configuration of the liquid crystal display device. This liquid crystal display device includes a polarizing filter layer 11, an active matrix panel 13 in which a transparent pixel electrode 24 and the like are formed on a glass substrate 12, which will be described in detail later, a liquid crystal layer 14, and a counter glass substrate 16 in which a transparent counter electrode 15 is formed. , And the polarization filter layer 17 are laminated. Also,
A backlight 18 is provided below the polarization filter layer 11, and a touch panel unit 19 is provided above the polarization filter layer 17.

For example, when the present invention is applied to an apparatus such as a personal computer which uses an image display surface inclined, an L-shaped or U-shaped cross section is formed around the image display area. A document guide or the like having a linear shape may be provided, and the image may be rotated so that the display surface is substantially horizontal as shown in FIG.

The liquid crystal layer 14 is formed by enclosing a 90 ° twisted nematic liquid crystal in a predetermined gap provided between the active matrix panel 13 and the transparent counter electrode 15. As the liquid crystal, one having a negative dielectric anisotropy is used, and the polarization filter layer 11 and the polarization filter layer 17 are arranged such that the polarization direction of one of the polarization filter layers and the orientation direction of the liquid crystal are parallel to each other, and By arranging the polarization directions of the two polarization filter layers 11 and 17 in directions perpendicular to each other (crossed Nicols), the liquid crystal layer 14 (more specifically, the polarization filter layers 11 and 17 and the liquid crystal layer 14) is in a light transmitting state.

The transparent counter electrode 15 is set at a predetermined potential Vp. However, in order to reduce the driving voltage, the potential Vp may be inverted every horizontal scanning period or each field period. .

As the touch panel unit 19, various types such as a contact type and a capacitance type can be applied.
The touch panel unit 19 is not necessarily provided. However, by providing the touch panel unit 19, it is possible to confirm that the original is placed, and the image is automatically displayed when the placement of the original is detected. Scanning is started, or the size of the placed document is detected,
It is also possible to obtain image data corresponding to this.

(2) Configuration of Circuit Formed on Active Matrix Panel 13 As shown in FIG. 2, the active matrix panel 13 is provided with a display / read section 21 and a drive circuit section 31 arranged around the display / read section.

The display / read section 21 is provided with a source line 22 and a gate line 23 in directions orthogonal to each other. The source line 22 and the gate line 2
The transparent pixel electrode 24, the photodiode 25, and the TFT (L) 2 for the transparent pixel electrode 24 correspond to each intersection with the transparent pixel electrode 24.
6 and a TFT (D) 27 for the photodiode 25 are provided. Each of the above TFTs (L) 26 and TFT
(D) The source electrodes 26a and 27a of 27 are connected to the source line 22, and the gate electrodes 26b and 27b are connected to the gate lines 23a and 23b, respectively.

The drain electrode 26 of the TFT (L) 26
c is connected to the transparent pixel electrode 24 while the TFT (D)
The 27 drain electrode 27c is connected to the cathode side of the photodiode 25. The anode side of the photodiode 25 is grounded via the light-shielding electrode 28.
That is, the photodiode 25 is connected so that a reverse bias is applied.

In order to improve the display quality, a capacitive element or the like is provided in parallel with the transparent pixel electrode 24 and the transparent counter electrode 15, or a capacitor is provided between each transparent pixel electrode 24 and the gate line 23 of an adjacent pixel. May have a capacity.

The drive circuit 31 includes a shift register 3
2, a TFT control circuit 33, a shift register 34, a charging voltage output circuit 35, and a reading circuit 36 are provided.

The shift register 32 sequentially shifts the pulse of the vertical synchronizing signal Vsync, which is input once every one vertical scanning period, in synchronization with the horizontal synchronizing signal Hsync which is also a vertical clock, and provides a TFT control circuit 33a as a timing signal.
Output.

In response to the timing signal, the TFT control circuit 33a sequentially outputs a drive pulse of a gate voltage Vg having a voltage of VL to each signal reading gate line 23a, and outputs a TFT (L) 26 for each horizontal scanning line. Is turned on. In response to the timing signal, the TFT control circuit 33b outputs a gate voltage VD of VD.
The g drive pulse is sequentially output to each image reading gate line 23b, and the TFT (D) 27 for each horizontal scanning line is turned on.

The shift register 34 sequentially shifts the pulse of the horizontal synchronizing signal Hsync input once every horizontal scanning period in synchronization with the horizontal clock Hclk, captures display image data of each pixel, and reads read image data. Is output to the charging voltage output circuit 35 and the reading circuit 36.

The charging voltage output circuit 35 is provided with a line memory 35a and a D / A converter (digital-analog converter) 35b.

The line memory 35a holds display image data for each pixel for one horizontal scanning line in accordance with a timing signal from the shift register 34.

The D / A converter 35b outputs a source voltage Vs (for example, 0 to 6V) corresponding to the display image data held in the line memory 35a to the source line 22, and outputs the transparent pixel electrode 24 and the transparent counter electrode 15 , Or a predetermined charge is accumulated in the photodiode 25.

On the other hand, the reading circuit 36 is provided with an A / D converter (analog-digital converter) 36a and a line memory 36b.

The A / D converter 36a is connected to the source line 22, detects the amount of exposure of the photodiode 25 due to the reflected light from the document, and outputs read image data for each pixel. More specifically, for example, the photodiode 25 is controlled by a predetermined voltage (for example, 5 to 6 V) previously output from the D / A converter 35b.
After the charge accumulated in the document is discharged by exposure of the reflected light from the document, when the discharged charge is replenished, the amount of charge required for the replenishment is detected, and the corresponding digital data is output. It has become. It is to be noted that the voltage at both ends of the photodiode 25 after the above-described discharge may be detected, instead of detecting the amount of charge required for replenishing the charge.

The line memory 36b temporarily holds the read image data for each pixel for one horizontal scanning line output from the A / D converter 36a,
4 are sequentially output in response to the timing signal. The overall configuration of the liquid crystal display device is summarized below. Signal read gate line 23a, signal read vertical shift register 32a, signal read TF
The T control circuit 33a forms a vertical driver for signal reading, and controls the TFT (L) 26 which is a pixel transistor for signal reading.

Similarly, the image reading gate line 23
b, an image reading vertical shift register 32b and an image reading TFT control circuit 33b constitute an image reading vertical driver, and control a TFT (D) 27 which is an image reading pixel transistor.

Source line 22, shift register 34,
The line memory 35a and the D / A converter 35b constitute a horizontal driver for signal reading, and a TFT (L) which is a pixel transistor for signal reading.
26 is controlled.

Similarly, the source line 22, the A / D converter 36a, and the line memory 36b constitute a horizontal driver for image reading, and control a TFT (D) 27 which is a pixel transistor for image reading. doing.

(3) Specific configuration and manufacturing method of the active matrix panel 13. The active matrix panel 13 includes a transparent pixel electrode 2 on a glass substrate 12 as shown in FIGS.
4. Photodiode 25, TFT (L) 26, and T
FT (D) 27 and the like are arranged. The photodiode 25 includes semiconductor layers 25a and 25b.

The TFT (L) 26 and the TFT (D)
27 is a source electrode 26a / 27a, a gate electrode 26b
27b, drain electrodes 26c and 27c, semiconductor layer 26
d and 27d, ohmic layers 26e and 27e, and a gate insulating film 43. In FIG. 3, the gate insulating film 43 is omitted for convenience. The source electrodes 26a and 27a and the gate electrode 26
b and 27b are formed by convex portions formed on the source line 22 and the gate lines 23a and 23b, respectively.

The active matrix panel 13 as described above is manufactured, for example, as shown in FIG.

(A) 1 is formed on a glass substrate 12 by sputtering.
A 00 nm chromium layer 41 is deposited.

(B) The above chromium layer 41 is etched.
Is patterned to form a light-shielding electrode 28. The light-shielding electrode 28 forms a wiring pattern on the anode side of the photodiode 25.

(C) 1 is formed on the glass substrate 12 by sputtering.
An ITO layer 42 as a 00 nm transparent electrode is deposited.

(D) The ITO layer 42 is patterned by etching to form the transparent pixel electrode 24.

(E) 200 nm of SiNX (for example, Si3 N4) or SiO2 by plasma CVD
After the insulating film 29 is deposited, the portion above the light-shielding electrode 28 and the portion of the transparent pixel electrode 24 above the contact portion 24a with the drain electrode 26c are removed by etching.

(F) An amorphous silicon (a-Si) layer having a thickness of 100 nm is deposited by a plasma CVD method, and a polycrystalline silicon (p-Si) layer is formed by crystallization using an excimer laser. Pattern and T
Semiconductor layer 26d for FT (L) 26 and TFT (D) 27
27d, and semiconductor layer 2 for photodiode 25
5a is formed.

The semiconductor layers 26d and 27d are formed into an n-channel by implanting impurities such as phosphorus by ion implantation or ion shower, while the semiconductor layer 25a is implanted into a p-channel by implanting impurities such as boron. Form. Note that in this case, instead of selectively implanting impurities, the n-channel semiconductor layers 26d and 27d and the semiconductor layer 25a may be separately formed twice.

(G) 50 nm ohmic layers 26e and 27e are formed on the source and drain regions of the semiconductor layers 26d and 27d in the same manner as the semiconductor layers 26d. Also, n + p-S is formed on the semiconductor layer 25a.
The photodiode 25 is formed by forming the ohmic layer 25b of i.

(H) After depositing a 700 nm aluminum layer by sputtering, the aluminum layer is patterned by etching to form a source electrode 26a, 27a and a drain electrode 26c.
27c, and the TFT (L) 26 and the TFT (D) 27
Is configured.

The source electrodes 26a and 27a constitute a source line 22 in a cross section (not shown). The drain electrode 26c of the TFT (L) 26 is connected to the contact portion 24a of the transparent pixel electrode 24,
The drain electrode 27c of the FT (D) 27 is connected to the ohmic layer 25b of the photodiode 25.

(I) 300 nm made of SiNX (for example, Si3 N4) or SiO2 by plasma CVD
A gate insulating film 43 of 150 nm is deposited by sputtering.
After depositing an aluminum-zirconium alloy layer, the gate electrode 26b is patterned by etching.
27b is formed.

Finally, a passivation film 44 is formed above the gate electrodes 26b and 27b, the gate insulating film 43 and the like. Further, in the above, the pixel electrode portion has been specifically described.
It is assumed that it is made simultaneously with the above process.

The above device configuration is, for example, a gate device.
Although the so-called staggered type in which the gate electrode is formed above the polysilicon is described as an example, an inverted staggered type in which the gate electrode is formed below the polysilicon may be used. Furthermore, the details of the order, constituent materials, process conditions, and the like in the above manufacturing process are merely examples,
It is not limited to this.

(4) Operation at the time of image display. After the pulse of the horizontal synchronizing signal Hsync is input to the shift register 34 and display image data for each pixel is input to the line memory 35a in synchronization with the horizontal clock Hclk, the line memory 35a The display image data is sequentially held, and the D / A converter 35b outputs a voltage corresponding to each display image data to each source line 22.

After the pulse of the vertical synchronizing signal Vsync is input to the shift register 32, the vertical clock Vclk
When the (horizontal synchronization signal Hsync) is input, the TFT control circuit 33a outputs a drive pulse of the voltage VL to the gate line 23a corresponding to the first horizontal scanning line.

Then, each TFT (L) 26 connected to the gate line 23a is turned on, and is output from the D / A converter 35b between each transparent pixel electrode 24 and the transparent counter electrode 15. Electric charges corresponding to the voltage are accumulated to form an electric field. That is, a portion of the liquid crystal layer 14 corresponding to each transparent pixel electrode 24 rotates the plane of polarization of light from the backlight 18 to be in a transmissive state with a luminance according to each display image data. This state is maintained until a drive pulse is applied again to the same gate line 23a in the next field.

As described above, the voltage corresponding to the display image data is not output to each source line 22 at the same time, but is output sequentially for each pixel in one horizontal scanning line in synchronization with the horizontal clock Hclk or the like. You may do so.

Thereafter, each time the horizontal synchronization signal Hsync is input, the same operation is performed for each horizontal scanning line, whereby an image for one screen is displayed.

(5) Operation at the time of reading an image. When an image reading switch (not shown) is operated in a state where the original is placed on the liquid crystal display device and the placement of the original is detected by the touch panel unit 19, the original image is displayed as shown in Table 1 below. Reading is performed.

[0058]

[Table 1]

(A) The liquid crystal layer 14 in a portion corresponding to all the pixels is made to be in a light transmitting state by the same operation as in the image display.

That is, the gate voltage Vg = VL is output from the TFT control circuit 33a to the gate line 23a and
When the FT (L) 26 is turned on, the D / A converter 35b outputs the source voltage Vs =
VsLmax is output to the source line 22, charges are accumulated between the transparent pixel electrode 24 and the transparent counter electrode 15, and the liquid crystal layer 14 enters a light transmitting state.

(B) When the image is displayed, the gate voltage Vg
A predetermined charge is accumulated in the photodiode 25 by an operation in which the source voltage Vs differs.

That is, a gate voltage Vg = VD is output from the TFT control circuit 33b to the gate line 23b to turn on the TFT (D) 27, and a predetermined source applied to the photodiode 25 as display image data. Data corresponding to the voltage Vs = VsD is input to the line memory 35a, and the predetermined source voltage Vs = VsD is output from the D / A converter 35b to the source line 22. Then, the photodiode 25 is in a state where a reverse bias is applied, and a predetermined charge is accumulated.

The backlight 18 is turned off at least up to this point. (C) Next, when the backlight 18 is turned on for a predetermined time, the light emitted from the backlight 18 is applied to the document via the liquid crystal layer 14, and the photodiode 25 is exposed by the reflected light.

Therefore, in the photodiode 25, charges canceling the accumulated charges are generated in accordance with the amount of incident light, and the accumulated charges are reduced. That is, the higher the brightness (lower density) of the document image, the more the stored charge decreases, while the lower the brightness (high density), the less the stored charge.

(D) After the backlight 18 is turned off,
Similarly to the above (b), the gate voltage Vg = VD is output from the TFT control circuit 33b to the gate line 23b,
FT (D) 27 is turned on. In this case,
The output of the D / A converter 35b of the charging voltage output circuit 35 is kept in a high impedance state.

The A / D converter 36a outputs the read image data to the line memory 36b according to the reduction amount of the charge stored in the photodiode 25, and the line memory 36b outputs one horizontal scanning line for each pixel. The read image data is temporarily held, and the read image data is sequentially output according to a timing signal from the shift register 34.

In the above example, the liquid crystal layer 14 having a negative dielectric anisotropy is used, and the polarization filter layers 11 and 17 are connected to each other by the polarization direction of one of the polarization filter layers and the orientation of the liquid crystal. Directions are parallel to each other, and
An example has been described in which the liquid crystal layer 14 is in a light-transmitting state when an electric field is applied by arranging the polarization directions of the polarizing filter layers 11 and 17 in directions perpendicular to each other (crossed Nicols). Uses a positive liquid crystal, and arranges the polarization filter layer 11 and the polarization filter layer 17 such that the alignment direction of the liquid crystal and the polarization directions of the two polarization filter layers 11 and 17 are parallel to each other (paranicol). It is the same as above.

When the electric field acts as described above, the liquid crystal layer 1
4 is configured to be in a light-transmitting state, the voltage V applied to the transparent pixel electrode 24 and the photodiode 25 is
sLmax and VD can be set equal. In particular, when these source voltages Vs are directly supplied from a predetermined voltage source without using the D / A converter 35b, the number of types of voltage sources is reduced and the circuit is reduced. There is an advantage that simplification of the process becomes easy.

On the other hand, a twisted nematic liquid crystal having a negative dielectric anisotropy of 90 ° was used, and the polarization filter layer 1 was used.
1 and the polarization filter layer 17 are arranged so that the polarization directions are parallel (paranicol), or a liquid crystal having a positive dielectric anisotropy is used and the polarization filter layer 1 is used.
1 and the polarization filter layer 17 may be arranged in a direction (crossed Nicols) in which the polarization directions are orthogonal to each other. That is, in this case, the liquid crystal layer 14 is in a light-transmitting state when no electric field is applied, so that the source voltage Vs = V
Vs = VsLmin may be applied instead of sLmax to discharge the charge accumulated between the transparent pixel electrode 24 and the transparent counter electrode 15.

Although the backlight 18 is extinguished except at the time of exposure, the backlight 18 may be kept lit if sufficient charge can be accumulated in the photodiode 25 even in the lit state. However, in this case, each T
Since the discharge starts as soon as the FT (D) 27 is turned off, each photo is read out with the same delay time from the time when the FT (D) 27 is turned off, or the liquid crystal layer 14 is temporarily set to a light-shielding state. Although it is necessary to make the exposure time of the diode 25 the same, accurate control of the exposure time becomes easier as compared with the case where the backlight 18 is turned on and off.

Further, as shown in the following (Table 2), after accumulating charges in the photodiode 25, the liquid crystal layer 14
May be in a light-transmitting state. Also in this case, if the light blocking effect of the liquid crystal layer 14 is sufficient, the backlight 18 may be kept on. However, in that case, it is necessary to make the exposure time of each photodiode 25 the same as described above. On the other hand, when electric charges are accumulated in the photodiode 25 with the backlight 18 turned off, if there is not much influence of light transmitted from the back of the placed document, the photodiode 25 as shown in the table is used. When accumulating charges in the liquid crystal layer 14
Need not always be kept in the light-shielded state.

[0072]

[Table 2]

The light receiving element is not limited to the photodiode 25, and various charge storage type light receiving elements can be applied.

The display and reading of the image are not limited to being performed over the entire screen, and the display and reading of the image may be performed simultaneously by dividing the display area and the reading area. In other words, when the backlight 18 is configured to be always lit as described above, or when the backlight 18 is turned off for a short time, the image display operation is performed for each region.
Alternatively, by performing an image reading operation, display and reading of an image can be performed.

Further, the image reading area may be set in advance, or the area where the placement of the document is detected by the touch panel unit 19 may be set as the reading area.

[0076]

The present invention is embodied in the form described above and has the following effects. That is, by providing a vertical driver in each of the signal readout circuit and the image readout circuit, and enabling the image input / output without the necessity of setting to turn on each transistor separately, technically, A simple, highly reliable, high processing speed liquid crystal display device with an image reading function can be realized.

Further, since the vertical driver is formed simultaneously with the horizontal driver and the pixel electrode using polysilicon, the vertical driver can be provided separately at a signal reading circuit and an image reading circuit at a low cost. In addition, a liquid crystal display device with an image reading function having the above advantages can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an external configuration of a liquid crystal display device with an image reading function.

FIG. 2 is an explanatory diagram showing a circuit configuration of an active matrix panel 13.

FIG. 3 is a plan view showing a specific configuration of an active matrix panel 13;

FIG. 4 is a sectional view taken along arrows AA and BB of FIG. 3;

FIG. 5 is an explanatory view showing a method of manufacturing the active matrix panel 13.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Polarization filter layer 12 Glass substrate 13 Active matrix panel 14 Liquid crystal layer 15 Transparent counter electrode 16 Counter glass substrate 17 Polarization filter layer 18 Backlight 19 Touch panel unit 21 Display / read section 22 Source line 23a Signal read gate line 23b Image read Gate line 24 Transparent pixel electrode 25 Photodiode 26 TFT (L) 27 TFT (D) 28 Light-shielding electrode 31 Drive circuit unit 32a Vertical shift register for signal readout 32b Vertical shift register for image readout 33a TFT control circuit for signal readout 33b Image reading TFT control circuit 34 Horizontal shift register 35 Charge voltage output circuit 35a Line memory 35b D / A converter 36 Reading circuit 36a A / D converter 36b Line memory

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H04N 1/04 107 H04N 5/66 102B 5/66 102 H01L 29/78 614

Claims (4)

[Claims] 1. A plurality of source lines for transmitting an image signal, a plurality of gate lines provided in a direction intersecting the source lines and transmitting a scanning signal, and a plurality of source lines and a gate line. A pixel electrode provided corresponding to each intersection, a first transistor connected to each pixel electrode and connected to a source line and a gate line, and provided opposite to the pixel electrode. The counter electrode, the liquid crystal provided between the pixel electrode and the counter electrode, and the charge held in advance corresponding to each pixel electrode are discharged by the reflected light from the document, and reflected from the document. In a liquid crystal display device having an image reading function provided with a light receiving element for detecting a light amount, the liquid crystal display device is further connected to one end of the light receiving element, and is connected to the source line and the gate.
A second transistor connected to the first transistor and a driving circuit connected to and controlling the first transistor and the second transistor to form the first transistor and the second transistor. A liquid crystal display device with an image reading function, which is formed simultaneously with the same process as in the above. 2. The image reading function according to claim 1, wherein the first transistor, the second transistor, and a transistor constituting a driving circuit for controlling the first transistor and the second transistor are formed using a polysilicon process. With liquid crystal display element. 3. The image reading function according to claim 1, wherein among the driving circuits formed simultaneously with the first and second transistors, not only a vertical driver but also a horizontal driver are formed at the same time. Liquid crystal display element. 4. A plurality of source lines for transmitting an image signal, a plurality of gate lines provided in a direction intersecting the source lines and transmitting a scanning signal, and a plurality of source lines and a gate line. A pixel electrode provided corresponding to each intersection, a first transistor connected to each pixel electrode and connected to a source line and a gate line, and provided opposite to the pixel electrode. The counter electrode, the liquid crystal provided between the pixel electrode and the counter electrode, and the charge held in advance corresponding to each pixel electrode are discharged by the reflected light from the document, and reflected from the document. In a liquid crystal display device having an image reading function provided with a light receiving element for detecting a light amount, the liquid crystal display device is further connected to one end of the light receiving element, and is connected to the source line and the gate.
A second transistor connected to the first and second transistors, and a drive circuit connected to the first transistor and the second transistor for controlling the transistors is provided separately without sharing a vertical driver. An image reading method for a liquid crystal display device with an image reading function, characterized by comprising: