JP3469083B2 - Liquid crystal display device with image reading function and image reading method - Google Patents

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, which includes an active matrix panel provided with a thin film transistor (TFT) and a light receiving element such as 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 image display devices, many liquid crystal display devices have been used.
A liquid crystal display device including an active matrix panel having an FT has been actively researched because it can easily obtain higher image quality than a simple matrix liquid crystal display device.

On the other hand, in order to reduce the size of a document image reading device, the document can be read by contacting the two-dimensionally arranged image sensors without using a scanning mechanism of the document or the sensor unit. It is known to do so.

Further, by combining the image display device and the reading device as described above to display an image and read an original image or the like to obtain image data, it is possible to reduce the size of the entire device. Some have been proposed to improve operability.

This type of device is specifically, for example, as disclosed in Japanese Unexamined Patent Publication No. 4-282609, on the back surface side of a transparent substrate on which a TFT and a transparent pixel electrode in a liquid crystal display device are formed. A transparent substrate on which an image sensor is formed is arranged. Further, when reading an original image, all the pixels in the liquid crystal are set in a light-transmitting state, backlight light is irradiated over the entire surface of the original, and the original image is read by detecting the intensity of light reflected from the original. Has become.

[0006]

However, in the structure in which the transparent substrate on which the TFTs and the like are formed and the transparent substrate on which the image sensor is formed are arranged in an overlapping manner as described above, the backlight light and the reflected light from the original document are used. , The image visibility and reading characteristics are degraded. Further, when the original image is read by illuminating the entire surface of the original with the backlight light when reading the original image, the reflected light from the adjacent pixel in the original enters the image sensor, so that the adjacent pixels are read. There is a problem that the crosstalk between them becomes large and the resolution tends to decrease. This problem becomes more remarkable as the read pixel density increases.

Regarding the former problem, although the specific structure is not described in Japanese Patent Laid-Open No. 4-282609, even if the TFT and the image sensor are mounted on the same transparent substrate. Although there is a statement that it is good, in general, in the case of such a configuration, it is necessary to form a wiring pattern for controlling the display TFT as well as a wiring pattern for controlling the image sensor on the same substrate. The effective display area of the image is reduced and the visibility is also deteriorated.

Regarding the latter problem, for example, JP-A-5-219301 discloses an EL element, an LED,
Disclosed is a display reading apparatus in which a substrate having a self-luminous element such as a PDP and a substrate having a light receiving element are stacked, and a document image is read so that adjacent light emitting elements do not simultaneously emit light. However, even in this case, it is not possible to avoid deterioration of image visibility and reading characteristics due to stacking two substrates. Moreover,
Since it is difficult to form the above-described light emitting element on the substrate, there are problems that the manufacturing cost increases and the yield decreases.

In view of the above points, the present invention can reduce the size of the device, improve the operability, and reduce the manufacturing cost without deteriorating the visibility. An object of the present invention is to provide a liquid crystal display device with an image reading function capable of reducing crosstalk and improving the image reading resolution, and an image reading method using such a liquid crystal display device.

[0010]

A liquid crystal display device with an image reading function according to the present invention includes a plurality of source lines for transmitting image signals and a plurality of source lines for transmitting scanning signals, the plurality of source lines being provided in a direction intersecting the source lines. A gate line, a pixel electrode provided corresponding to each intersection of the source line and the gate line, a first transistor connected to the pixel electrode and connected to the source line and the gate line, A counter electrode provided to face the pixel electrode, a liquid crystal provided between the pixel electrode and the counter electrode, and a light-receiving element provided corresponding to each pixel electrode for detecting the amount of light reflected from the document are provided. In a liquid crystal display device with an image reading function, a second transistor connected to one end side of the light receiving element and connected to the source line and the gate line is further provided. Sensor, a line on the other end side connected to the other end of the light receiving element, a back light source that emits light for display and light for illuminating the original, and a single pixel when reading an image, Alternatively, for each set of pixels that are not adjacent to each other, the liquid crystal is in a translucent state, the light of the back light source is applied to the document, and the amount of light reflected from the document is detected by the light receiving element to read the document image. It is characterized by being configured in.

With this structure, an image can be displayed and read without providing a source line and a gate line dedicated to the second transistor connected to one end side of the light receiving element, so that an effective display area of the image. It is possible to reduce the size of the device, improve operability, and reduce the manufacturing cost without deteriorating the visibility due to the decrease in the number of pixels. Since the light from the unit does not enter, crosstalk can be reduced and the image reading resolution can be improved.

The non-adjacent pixel sets may be, for example, a set of pixels at intervals of one or more pixels, or may be adjacent to each other in a predetermined direction and perpendicular to the predetermined direction, depending on the read pixel density or the like. In addition, it may be set to a set of pixels at every 1 or more pixels.

Further, it is possible to display and read a color image by providing a color filter in which a region for transmitting light of a predetermined color is formed corresponding to each pixel electrode.

Further, by providing a plurality of back light sources for emitting lights of different colors, it is possible to illuminate the original with a plurality of colors of light for each pixel and detect the amount of reflected light. Color images can be read with density and resolution.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION (Embodiment 1) As a liquid crystal display device with an image reading function according to Embodiment 1 of the present invention, as shown in FIG. An example of a liquid crystal display device used after being used will be described.

(1) Overall Structure of Liquid Crystal Display Device In this liquid crystal display device, 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 described in detail later, a liquid crystal layer 14, A counter glass substrate 16 on which the transparent counter electrode 15 is formed and a 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.

When applied to a device such as a personal computer in which the display surface of an image is tilted, the cross-sectional shape around the image display area is L-shaped or U-shaped. It is also possible to provide a linear document guide or the like, or to rotate the display surface so that the display surface becomes 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 this liquid crystal, one having a negative dielectric anisotropy is used, and the polarization directions of the polarization filter layer 11 and the polarization filter layer 17 are parallel to each other, and Since the polarization directions of the polarization filter layers 11 and 17 are orthogonal to each other (crossed Nicols), the liquid crystal layer 14 (more specifically, the polarization filter layers 11 and 17 and the liquid crystal layer) when an electric field is applied. 14) is in a translucent state.

The transparent counter electrode 15 is set to a predetermined potential Vp, but in order to reduce the drive 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 does not necessarily have to be provided. However, by providing the touch panel unit 19, it is possible to confirm that the document is placed and to automatically display the image when the document placement is detected. To start scanning, or to detect the size of the placed document,
Image data corresponding to this can be obtained.

(2) Structure of Circuits Formed in Active Matrix Panel 13 As shown in FIG. 2, the active matrix panel 13 includes a display / reading section 21, a drive circuit section 31 arranged around the display / reading section 21. Drive circuit unit 31 and backlight 1
A control unit 71 for controlling the operation of No. 8 is provided. The control unit 71 may be provided outside the active matrix panel 13.

The display / reading section 21 is provided with a source line 22 and a gate line 23 in directions orthogonal to each other. In addition, 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 corresponding to each intersection with 3
6, and a TFT (D) 27 for the photodiode 25 is provided.

Here, the TFT (L) 26 is an n-channel T
While being formed in the FT, the TFT (D) 27 is formed as a p-channel TFT. That is, the gate line 23
By applying a positive voltage VL or a negative voltage VD to each of them, it is possible to independently control the ON state. Although the polarities of the TFT (L) 26 and the TFT (D) 27 may be opposite, in general, the transparent pixel electrode 2
It is easier to increase the display speed when the TFT (L) 26 connected to 4 is an n-channel.

Each of the above TFT (L) 26 and TFT (D)
The source electrodes 26a and 27a of
The gate electrodes 26b and 27b are connected to the gate line 23.

Further, the drain electrode 26 of the TFT (L) 26
c is connected to the transparent pixel electrode 24, while TFT (D)
The drain electrode 27c of 27 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 image quality, a capacitive element or the like is provided in parallel with the transparent pixel electrode 24 and the transparent counter electrode 15, or between each transparent pixel electrode 24 and the gate line 23 of the adjacent pixel. May have a capacity.

The drive circuit section 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 Vsynk input once every one vertical scanning period in synchronization with the horizontal synchronizing signal Hsynk which is also a vertical clock, and as a timing signal, the TFT control circuit 33. It is designed to output to.

The TFT control circuit 33 has a voltage of VL (positive) or VD (negative) according to the timing signal and a TFT selection signal instructing selection of the TFT (L) 26 or the TFT (D) 27. The driving pulse of the gate voltage Vg is sequentially output to each gate line 23, and T for each horizontal scanning line is output.
The FT (L) 26 and the TFT (D) 27 are turned on.

The shift register 34 sequentially shifts the pulse of the horizontal synchronizing signal Hsynk input once in each horizontal scanning period in synchronization with the horizontal clock Hck, fetches the display image data of each pixel, and reads the 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 is adapted to hold display image data for each pixel for one horizontal scanning line in response to a timing signal from the shift register 34.

The D / A converter 35b outputs the 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 the transparent pixel electrode 24 and the transparent counter electrode 15 are provided. And a predetermined charge is accumulated in the photodiode 25.

On the other hand, the reading circuit 36 comprises 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 exposure amount of the photodiode 25 by the reflected light from the original, and outputs the read image data for each pixel. More specifically, for example, the photodiode 25 is driven by a predetermined voltage (for example, 5 to 6 V) output from the D / A converter 35b in advance.
After the charge accumulated in the discharge is discharged by the exposure of the reflected light from the original, when the discharged charge is replenished, the amount of the charge required for the replenishment is detected, and the digital data corresponding to this is output. It is like this. It should be noted that the present invention is not limited to the detection of the amount of electric charge required for supplementing the electric charge as described above, and the voltage across the photodiode 25 after the discharge may be detected.

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, and the shift register 3
The signals are sequentially output according to the timing signal from 4.

(3) Specific Structure and Manufacturing Method of Active Matrix Panel 13 The active matrix panel 13 has a transparent pixel electrode 2 on a glass substrate 12 as shown in FIGS. 3 and 4, for example.
4, photodiode 25, TFT (L) 26, and T
The FT (D) 27 and the like are arranged and configured.

The photodiode 25 includes the semiconductor layer 2
It is composed of 5a and 25b.

Further, the TFT (L) 26 and the TFT (D)
27 is a source electrode 26a and 27a, a gate electrode 26b
27b, drain electrodes 26c and 27c, semiconductor layer 26
It is composed of d · 27d, ohmic layers 26e · 27e, and a gate insulating film 43. In FIG. 3, the gate insulating film 43 is omitted for convenience of illustration. The source electrodes 26a and 27a and the gate electrodes 26b and 27b are each formed by a convex portion formed on the source line 22 or the gate line 23.

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

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

(B) The chromium layer 41 is formed by etching.
Is patterned to form the gate electrodes 26b and 27b and the light shielding electrode 28. The gate electrode 26b / 2
7b configures the gate line 23 in a cross section (not shown). The light-shielding electrode 28 constitutes a wiring pattern on the anode side of the photodiode 25.

(C) 1 on the glass substrate 12 by sputtering
The ITO layer 42, which is a 00 nm transparent electrode, is deposited.

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

(E) 400 nm of SiN _x (eg Si ₃ N ₄ ) or SiO _{2 formed by} plasma CVD method
After depositing the gate insulating film 43, the portion above the light shielding electrode 28 and the portion above the contact portion 24a of the transparent pixel electrode 24 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, a polycrystalline silicon (p-Si) layer is formed by crystallization using an excimer laser, and then etching is performed. Patterning, T
Semiconductor layer 26d for FT (L) 26 and TFT (D) 27
27d, and the semiconductor layer 2 for the photodiode 25
5a is formed.

The semiconductor layer 26d is implanted with an impurity such as phosphorus by ion implantation or ion shower to form an n-channel, while the semiconductor layer 27d and the semiconductor layer 25a are implanted with an impurity such as boron. Form in p-channel. In this case, instead of selectively implanting impurities, the n-channel semiconductor layer 26d and p
The semiconductor layer 27d and the semiconductor layer 25a of the channel are
It may be divided into several times and made separately.

(G) Similar to the semiconductor layers 26d ..., 50 nm ohmic layers 26e and 27e are formed on the source and drain regions of the semiconductor layers 26d and 27d. In addition, 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, patterning is performed by etching to form source electrodes 26a and 27a and drain electrodes 26c and 26c.
27c is formed, and TFT (L) 26 and TFT (D) 27 are formed.
Make up.

The source electrodes 26a and 27a constitute the 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, while T
The drain electrode 27c of the FT (D) 27 is connected to the ohmic layer 25b of the photodiode 25.

Finally, the passivation film 44 is formed above the source electrode 26a, the drain electrode 26c, the semiconductor layer 26d and the like.

In the above manufacturing method, the display / reading section 21 has been mainly described, but particularly when the polycrystalline silicon process is used as described above, the transistors and wirings forming the drive circuit section 31 are also included. , It is also easy to build in the same process at the same time. On the other hand, when using the amorphous silicon process,
The driver circuit 3 is mounted by directly mounting the driver IC on the glass substrate 12 or by using a flexible substrate.
1 may be configured.

(4) Operation during image display When the pulse of the horizontal synchronizing signal Hsynk is input to the shift register 34, the display image data for each pixel is input to the line memory 35a in synchronization with the horizontal clock Hck. ,
The line memory 35a sequentially holds display image data for one horizontal scanning line, 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 Vsynk is input to the shift register 32, the vertical clock Vck
(Horizontal synchronization signal Hsynk) is input and TFT
TF for instructing the control circuit 33 to select the TFT (L) 26
When the T selection signal is input, the TFT control circuit 33
The voltage V is applied to the gate line 23 corresponding to the horizontal scanning line.
Outputs L (positive) drive pulse.

Therefore, each TFT (L) 26 connected to the gate line 23 is turned on, and the D / A converter 35b outputs between each transparent pixel electrode 24 and the transparent counter electrode 15. An electric field is formed by accumulating charges according to the voltage. That is, the liquid crystal layer 14 in the portion corresponding to each transparent pixel electrode 24 rotates the polarization plane of the light from the backlight 18, and becomes a translucent state with the brightness corresponding to each display image data. This state is maintained until the drive pulse is applied again to the same gate line 23 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 sequentially output to each pixel in one horizontal scanning line in synchronization with the horizontal clock Hck or the like. You may do it.

Thereafter, the same operation is performed for each horizontal scanning line every time the horizontal synchronizing signal Hsynk is input, so that an image for one screen is displayed.

(5) Operation during image reading When a document is placed on the liquid crystal display device and the placement of the document is detected by the touch panel unit 19, when an image reading switch (not shown) is operated, the following table 1 The original image is read as described below.

[Table 1] (A) By the same operation as that at the time of displaying the image, as shown in FIG. 6A, the liquid crystal layer 14 in the portion corresponding to every other pixel P1 in the vertical and horizontal directions is set in the light-transmitting state, while the pixel P1 The liquid crystal layer 14 in the portion corresponding to the adjacent pixel P2 is shielded from light.

That is, the TFT control circuit 33 has a TFT
(L) The TFT selection signal for instructing the selection of 26 is input,
From the TFT control circuit 33, gate voltage Vg = VL (positive)
Are sequentially output to each gate line 23, and each TFT (L)
26 are sequentially turned on, and the gate voltage V
In synchronization with the output of g, the source voltage Vs corresponding to the maximum brightness is supplied from the D / A converter 35b to the pixel P1.
= VsLmax, the source voltage Vs = VsLmin corresponding to the lowest luminance is output to the source line 22 for the pixel P2, and the charge is accumulated or discharged between the transparent pixel electrode 24 and the transparent counter electrode 15. , The liquid crystal layer 14 of the pixel P1
Only the light is transparent.

(B) Gate voltage Vg when the above image is displayed
And the source voltage Vs is different, the pixel P1
Predetermined charges are accumulated in the photodiode 25 corresponding to.

In other words, the TFT control circuit 33 has a TFT
(D) The TFT selection signal instructing the selection of 27 is input,
From the TFT control circuit 33, the gate voltage Vg = VD (negative)
Is output to the gate line 23 to turn on the TFT (D) 27, and as display image data, data corresponding to a predetermined source voltage Vs = VsD applied to the photodiode 25 is input to the line memory 35a. , D
From the A / A converter 35b, the predetermined source voltage Vs
= VsD is output to the source line 22. Therefore, the photodiode 25 is in a state in which a reverse bias is applied, and predetermined charges are accumulated.

The backlight 18 is turned off by at least this point.

Here, the charge may be similarly stored in the photodiode 25 corresponding to the pixel P2 to simplify the control. On the other hand, by storing the charges only in the pixel P1, the time required to store the charges can be shortened. More specifically, the latter is connected to, for example, the odd-numbered or even-numbered gate lines 23 instead of the shift register 32, and receives the vertical synchronization signal Vsynk whose phase is shifted by a half cycle when an image is displayed. It suffices to provide two shift registers and input the vertical synchronizing signal Vsynk to only one shift register when accumulating charges in the photodiode 25.

(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 only through the liquid crystal layer 14 in the pixel P1 portion, and the reflected light causes the light to be reflected. Photodiode 2 of pixel P1
5 is exposed.

Therefore, in the photodiode 25, a charge that cancels the accumulated charge is generated according to the amount of incident light, and the accumulated charge amount decreases. That is, the higher the lightness (the density is lower) of the original image, the more the stored charge amount is reduced, while the part having the low lightness (the higher density) is not reduced much.

As described above, the liquid crystal layer 1 in the portion of the pixel P1
By irradiating the original with the backlight light only through 4, the reflected light from the adjacent pixels in the original image does not enter the photodiode 25, so that the crosstalk with the adjacent pixels is reduced and the resolution is reduced. Is improved.

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

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

Here, regarding the pixel P2, indefinite image data is output, but the image data is output for all the pixels, and the pixel P1 is output by the subsequent data processing.
May be extracted, or the TFT control circuit 33 may output a drive pulse only to the gate line 23 corresponding to the pixel P1 or only the pixel P1 may be read by the reading circuit 36. The above A / D conversion, image data holding, and output may be selectively performed.

(E) The operations of (a) to (d) are repeated for each of the three pixels adjacent to the pixel P1, whereby the original image of all the pixels is read.

In the above example, as shown in FIG. 6A, the original image is read for every other set of pixels P1, but FIG. 6 ( b)
It is also possible to reduce the crosstalk with the adjacent pixels by reading every group of pixels P1 every two or more pixels as shown in FIG.
Further, as shown in FIG. 6C, the reading operation may be repeated for each pixel P1. In this case, since the reading operation is repeated many times, it takes a little longer to read the entire original image. However, even if the pixel density is high, crosstalk with other pixels is almost prevented and the resolution is surely increased. Can be done easily. Further, as shown in FIGS. 6D and 6E, reading may be performed for each group of pixels for one line along one source line 22 or gate line 23, or as shown in FIGS.
Alternatively, as shown in FIG. 5, the reading may be performed for each group of pixels corresponding to a plurality of lines along the source line 22 or the gate line 23. In these cases, since crosstalk in the direction perpendicular to the source line 22 or the gate line 23 is prevented, the resolution can be increased to some extent and the reading speed can be relatively increased.

In the above example, the liquid crystal layer 14 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 polarization filter layer and the alignment of the liquid crystal. The directions are parallel to each other, and
By arranging the polarization directions of the polarization filter layers 11 and 17 in directions orthogonal to each other (crossed Nicols), an example in which the liquid crystal layer 14 is in a translucent state when an electric field is applied has been described. Is used, and the polarization filter layer 11 and the polarization filter layer 17 are arranged so that the alignment direction of the liquid crystal and the polarization directions of both polarization filter layers 11 and 17 are parallel to each other (paranicols). The same is true.

When the electric field acts in this way, the liquid crystal layer 1
4 is configured to be in a translucent state, the voltage V applied to the transparent pixel electrode 24 and the photodiode 25 is
It is also possible to set sLmax and VD equal to each other. Especially, in the case where these source voltages Vs are directly supplied from a predetermined voltage source without using the D / A converter 35b, the type of the voltage source is reduced and the circuit is reduced. There are advantages such as simplification of.

On the other hand, a twisted nematic liquid crystal having a negative dielectric anisotropy of 90 ° is used, and the polarization filter layer 1 is used.
1 and the polarization filter layer 17 are arranged so that the polarization directions are parallel to each other (paranicols), or liquid crystal having positive dielectric anisotropy is used, and the polarization filter layer 1
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, since the liquid crystal layer 14 is in a translucent state when no electric field is applied, the source voltage Vs = V
Instead of sLmax, Vs = VsLmin may be applied to discharge the electric charge accumulated between the transparent pixel electrode 24 and the transparent counter electrode 15.

Although the example in which the backlight 18 is turned off except during the exposure is shown, it may be left on when the photodiode 25 can sufficiently accumulate electric charges even in the lighting state. However, in this case, each T
Discharge starts as soon as the FT (D) 27 is turned off. Therefore, the liquid crystal layer 14 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 once put in a light-shielded state. Although it is necessary to make the exposure times of the diodes 25 the same, accurate control of the exposure time becomes easier than when the backlight 18 is turned on and off.

Further, for each set of pixels which are not adjacent to each other, the liquid crystal layer 14 may be set in the light transmitting state after the charges are accumulated in the photodiode 25 as shown in Table 2 below. Also in this case, if the liquid crystal layer 14 has a sufficient light shielding effect, the backlight 18 may be left on. However, in that case, it is necessary to make the exposure time of each photodiode 25 the same as in the above case. On the other hand, in the case where 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 surface of the placed document, as shown in the table, the photodiode 25 It is not always necessary to keep the liquid crystal layer 14 in a light-shielded state when accumulating charges in the liquid crystal display device.

[Table 2]

The constituent materials, the order of the steps in the manufacturing process, the process conditions, etc. are merely examples.
It is not limited to these.

(Embodiment 2) Active matrix panel 13 constituting a liquid crystal display device with an image reading function
As another example, the TFT (L) 26 and the TFT (D) 27 are formed on the light shielding electrode 28, and the semiconductor layer 26 is formed.
An example in which a staggered TFT in which the gate electrodes 26b and 27b are provided above the d and 27d is used will be described. Note that, hereinafter, components having the same functions as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIGS. 7 and 8, a light shielding electrode 28 is formed on the glass substrate 12, and TFT (L) 2 is formed on the light shielding electrode 28 with an insulating film 29 made of, for example, SiO ₂ interposed therebetween.
6 or the semiconductor layers 26d and 27d of the TFT (D) 27 are formed. The semiconductor layer 25a of the photodiode 25 is directly formed on the light-shielding electrode 28 as in the first embodiment, and the light-shielding electrode 28 constitutes the anode side wiring pattern.

Above the semiconductor layers 26d and 27d, ohmic layers 26e and 27e, source electrodes 26a and 27a,
And the drain electrodes 26c and 27c are formed, and the gate electrodes 26b and 2 are further disposed via the gate insulating film 43.
7b is formed.

By constructing the wiring pattern of the photodiode 25 with the light-shielding electrode 28 in this way, a liquid crystal display device having an image reading function can be manufactured in the same process as a normal liquid crystal display device. Can be easily reduced.

(Embodiment 3) The TFT (L) 26 and the TFT (D) 27 are both formed as an n-channel TFT, and the threshold voltage VL0 of the gate of the TFT (L) 26 is the TFT.
An example in which (D) 27 is set to be higher than the threshold voltage VD0 of the gate will be described.

That is, when the gate voltage Vg with VD0 <Vg <VL0 is applied to the gate line 23, T
When only the FT (D) 27 is turned on and the gate voltage Vg with VL0 <Vg is applied, the TFT (L)
26 and the TFT (D) 27 are both turned on. Such a threshold voltage can be set by various known methods such as adjusting the concentration of impurities such as phosphorus when they are implanted into the semiconductor layers 26d and 27d.

TFT (L) 26 and TFT as described above
The liquid crystal display device with an image reading function provided with (D) 27 reads the original image as shown in Table 3 below.

[Table 3] (A) When the gate voltage Vg with VL0 <Vg is output to the gate line 23, the TFT (L) 26 is turned on, and the source voltage Vs = VsLmax or VsLmax output to the source line 22 at that time. , Charges are accumulated between the transparent pixel electrode 24 and the transparent counter electrode 15,
Alternatively, the liquid crystal layer 14 in the portion corresponding to the pixel P1 for reading the image is discharged to be in the light-transmitting state, while the other pixel P
The liquid crystal layer 14 in the portion corresponding to 2 is shielded from light.

At this time, the TFT (D) 27 is also turned on and the photodiode 25 similarly accumulates electric charge by the source voltage Vs = VsLmax. Therefore, VsLma
When setting x = VsD, the following photodiode 2
It is possible to omit the step of accumulating the electric charge in only 5.

(B) When the gate voltage Vg with VD0 <Vg <VL0 is output to the gate line 23, the TFT (D) 2
Since only 7 is turned on, the source voltage Vs = V
A voltage VsD different from sLmax causes a predetermined charge to be stored in at least the photodiode 25 corresponding to the pixel P1 for reading an image, as in the first embodiment.

The backlight 18 is turned off at least by this point.

(C) Next, the gate voltage Vg with Vg <VD0 is output to the gate line 23, and both the TFT (L) 26 and the TFT (D) 27 are turned off.
When the backlight 18 is turned on for a predetermined time, the light emitted from the backlight 18 is applied to the original through the liquid crystal layer 14, and the photodiode 25 is exposed by the reflected light, so that the photodiode 25 has the same density as the original image. The amount of accumulated charge is accordingly.

(D) After the backlight 18 is turned off,
Similar to (b) above, the gate voltage Vg with VD0 <Vg <VL0 is output to the gate line 23, and the TFT (D) 27
Only the ON state is turned on, and the read image data is obtained.

Also in the third embodiment, as described in the first embodiment, the exposure time of each photodiode 25 is made the same by reading the image data at the same timing as the charge accumulation. As a result, the backlight 18 may be kept on.

In the structure of the third embodiment, the TFT (D) 27 is always turned on when an image is displayed, that is, the TFT (L) 26 is turned on. If the potential on the anode side of the photodiode 25 is set to the ground potential, only a reverse bias voltage is applied to the photodiode 25, and almost no current flows, so there is almost no effect on the display image.

If the reverse bias voltage is applied to the photodiode 25 in this manner, the polarity of the source voltage Vs is changed every horizontal scanning period in order to prevent flicker when displaying an image and to improve the image quality. It is also possible to apply a known method of inverting each source line 22 or inverting each source line 22 adjacent to each other. That is, in this case, each photodiode 25 of each pixel is connected so as to be reverse biased according to the applied source voltage Vs, or as shown in FIG. 9, when the source voltage Vs is positive or negative. However, the photodiode 2 should be reverse biased.
5 may be connected.

By applying a negative voltage to the anode side of the photodiode 25, it is possible to contribute to the improvement of the response speed of display.

Further, as shown in FIG. 10, if the changeover switch 51 is provided so that the source voltage Vs is applied to the anode side of the photodiode 25 at the time of displaying the image, theoretically, the influence on the displayed image is exerted. You can eliminate them all. In this case, if the wiring connected to the anode side of the photodiode 25 is provided independently for each source line 22, or if all the wiring on the anode side is common, the charging voltage output circuit 35 is used. Therefore, the source voltage Vs may be alternately applied to each source line 22 while the other source lines 22 are in a high impedance state.

Further, in each of the above-described embodiments, an example in which the transparent counter electrode 15 is formed on the counter glass substrate 16 is shown, but the present invention is not limited to this, and as shown schematically in FIG. Transparent pixel electrode 24 and transparent counter electrode 1 on the substrate
And a so-called in-plane switching system (I
It can be similarly applied to a PS) liquid crystal display device. In this case, the transparent counter electrode 15 may be used as the wiring on the anode side of the photodiode 25.

In addition, charge accumulation between the transparent pixel electrode 24 and the transparent counter electrode 15 and the photodiode 25 at the time of reading an image is different from that at the time of normal image display.
Since the same voltage is applied to all pixels, drive pulses may be simultaneously output to all gate lines 23 to accumulate charges.

Further, the light receiving element is not limited to the photodiode 25, and various charge storage type light receiving elements can be applied. Further, the original image can be similarly read by using a photosensor other than the charge storage type. In this case, the step of accumulating charges prior to exposure is not necessary, and an A / D converter 36a that detects the voltage across the light-receiving element or that detects the current flowing through the light-receiving element may be used. Can be used.

The display and reading of the image are not limited to those performed over the entire surface of the screen, and the display and the reading may be separately performed so that the image can be displayed and read at the same time. That is, when the backlight 18 is always lit as described above, or when the backlight 18 is set to be off for a short time, the image display operation is performed for each area.
Alternatively, an image can be displayed and read by performing an image reading operation. Further, the image reading area may be set in advance, or the area in which the placement of the document is detected by the touch panel unit 19 may be set as the reading area.

(Embodiment 4) An example of a liquid crystal display device capable of displaying and reading a color image will be described.

In this liquid crystal display device, as shown in FIG. 12, between the counter glass substrate 16 and the transparent counter electrode 15,
A micro color filter 6 in which a region for transmitting red, green, or blue light is formed corresponding to each transparent pixel electrode 24.
1 is provided. Other configurations are the same as those of the monochrome liquid crystal display device (Embodiment 1, Embodiment 2, or Embodiment 3).

With this structure, a color image is displayed and read by the same operation as that of the monochrome liquid crystal display device. That is, when red, blue, or green image data is input as display image data, a color image is displayed by additive color mixing. Further, for each transparent pixel electrode 24, the red, blue, or green light is applied to the original through the micro color filter 61, and the reflected light amount corresponding to each color component in the original image is detected. The image data of is read.

Even when such a color liquid crystal display device is constructed, the TFT (L) 26 and the TFT (D) 27 are formed by the common source line 22 and gate line 23, as in the monochrome liquid crystal display device. Controlled,
Since a gate line or the like dedicated to the TFT (D) 27 is not required, it is possible to increase the effective display area of an image and obtain high visibility. Further, as described in the first embodiment, every one or more pixel groups, every one pixel group, every one line pixel group, every one or more line pixel group. Crosstalk between adjacent pixels can be reduced by irradiating light from the backlight 18 and reading the original image.

In this liquid crystal display device, each 3
One pixel (color pixel) of a predetermined color is formed by the additive color mixture of the light transmitted through the one transparent pixel electrode 24. Therefore, when the pixel density of the pixel (single pixel) corresponding to each transparent pixel electrode 24 is the same as the pixel density in the monochrome liquid crystal display device (for example, the transparent pixel electrode 24
Of the same size), the pixel density of the color pixels (substantially display and read pixel density) becomes 1/3 of the pixel density in the monochrome liquid crystal display device.

(Embodiment 5) Even if the pixel density of color pixels is equal to the pixel density of a single pixel, that is, even if the size of the transparent pixel electrode 24 is the same as that of a monochrome liquid crystal display device, An example of a liquid crystal display device in which the same pixel density of color pixels as that of the liquid crystal display device is obtained will be described.

In this liquid crystal display device, as shown in FIG. 13, the backlight 18 comprises monochromatic light sources 18a to 18c for emitting monochromatic light of red, blue or green, respectively. These monochromatic light sources 18a to 18c are controlled to be turned on and off independently by a control unit (not shown). Other configurations are the same as those of the monochrome liquid crystal display device.

The operation for displaying an image and the operation for reading an image will be described below.

(1) Operation during image display The red, blue, and green monochromatic light sources 18a to 18c are sequentially and selectively lighted, and in each lighting period, based on red, blue, or green display image data, respectively. Then, the same display operation as that of the monochrome image display device is performed. That is, the red, blue, and green components are displayed in time division for each single pixel, and a color image is displayed by the visual afterimage effect. In this way, by displaying the image of each color in a time division manner by the monochromatic light sources 18a to 18c, one single pixel can be made to act as a color pixel, and the pixel density of the color pixel is made equal to the pixel density of the single pixel. be able to.

(2) Operation during image reading Red, blue, and green monochromatic light sources 18a to 18c are sequentially used, and the same reading operation as that of the monochrome liquid crystal display device is performed for each monochromatic light source 18a. Thus, the image data of each color component in the original image is read. More specifically, first, the red monochromatic light source 1
8a is used, red light is applied to the original through the transparent pixel electrodes 24 for each set of pixels that are not adjacent to each other, and the amount of reflected light according to the red component in the original image is detected.
Next, the blue monochromatic light source 18b is used to read the image of the blue component, and the green monochromatic light source 18c is used to read the image of the green component. In this way, the color image data is read by repeating the reading operation three times for the monochromatic light sources 18a to 18c. In this way, since the images of the red, blue, and green components are read for each single pixel by sequentially using the monochromatic light sources 18a to 18c, the pixel density is three times as high as that when the micro color filter is used. You can read a color image with.

Instead of reading each pixel group which is not adjacent to each other for each color of light, red, blue and green lights are sequentially radiated and read for each pixel group. May be repeated for the number of pixel sets.

Further, similarly to the monochrome liquid crystal display device, the TFT (L) 26 and the TFT (D) 27 are controlled by the common source line 22 and gate line 23, and the gate line dedicated to the TFT (D) 27 is provided. It is possible to increase the effective display area of an image and obtain high visibility by not requiring the above, but even when a gate line dedicated to the TFT (D) 27 is provided, the effect of increasing the pixel density is not achieved. Obtained in the same way. Moreover, even if the pixel density is high as described above, each monochromatic light source 1 is set for each group of pixels that are not adjacent to each other.
By reading the original image by irradiating the light of 8a to 18c, it is possible to surely reduce the crosstalk between adjacent pixels and increase the resolution.

(Embodiment 6) An example of a liquid crystal display device having a micro color filter and having a high reading pixel density will be described.

In this liquid crystal display device, as shown in FIG. 14, between the counter glass substrate 16 and the transparent counter electrode 15,
A display area 6 for transmitting a red, green, or blue light corresponding to each transparent pixel electrode 24 to display a color image.
The micro color filter 61 is provided with 1a and an illumination area 61b for transmitting light of all colors and illuminating the original.

In the transparent counter electrode 15, the areas corresponding to the display area 61a or the illumination area 61b of the micro color filter 61 are connected to the display counter electrode 15a and the illumination counter electrode 15b, respectively. It is divided. The illumination counter electrode 15b is connected to the display counter electrode 15a or is in a high impedance state by a switch 62 controlled by a control circuit (not shown). It should be noted that the potential may not be necessarily connected to the display counter electrode 15a but may be maintained at a predetermined potential.

On the other hand, as shown in FIGS. 15 and 16, the transparent pixel electrode 24 formed on the glass substrate 12 is the transparent pixel electrode 2 in the monochrome liquid crystal display device.
As in the case of 4, the display pixel electrode 24a connected to the TFT (L) 26 and the illumination pixel electrode 24b connected to the source line 22 are divided.

Further, the backlight 18 is provided with monochromatic light sources 18a to 18c for emitting red, blue, or green monochromatic light, respectively, as in the fifth embodiment.

The other structure is the same as that of the monochrome liquid crystal display device.

The operation for displaying an image and the operation for reading an image will be described below.

(1) Operation during image display During image display, red, blue, and green monochromatic light sources 18a ...
18c is turned on at the same time and acts as a white light source. Further, the switch 62 is opened so that the illumination counter electrode 15b is kept in a high impedance state, and the illumination counter electrode 15b and the illumination pixel electrode 24b are irrespective of the potential of the illumination pixel electrode 24b, that is, the potential of the source line 22. The electric charge is prevented from being accumulated during the period, and the light from the backlight 18 is controlled to be always shielded. The liquid crystal layer 1
When a normally white liquid crystal display device in which light is transmitted when no voltage is applied to 4 is configured,
The illumination counter electrode 15b is not in a high impedance state, and a predetermined voltage having a sufficiently large absolute value may be applied.

In this state, a color image is displayed by performing the same operation as in the fourth embodiment.
That is, each display pixel electrode 24a and liquid crystal layer 1 has the same operation as that of the fourth embodiment except that the light incident on the illumination pixel electrode 24b in the pixel is always shielded.
4, and the display area 6 of the micro color filter 61
A color image is displayed by the additive color mixture of the light passing through 1a.

In this liquid crystal display device, the aperture ratio is slightly reduced because the portion of the pixel electrode for illumination 24b in the pixel is in the light shielding state, but the liquid crystal display device of the fifth embodiment displays by time division. On the other hand, since each single pixel always emits light according to the image data, the frame period can be set to a desired length without causing flicker.

(2) Operation at the time of image reading At the time of reading an image, as shown in Tables 4 to 6 below, an operation different from the operation of the monochrome liquid crystal display device in the following points is performed. However, as for the illumination of the original, the red, blue, and green monochromatic light sources 18a to 18c are sequentially used, as in the fifth embodiment.

[Table 4]

[Table 5]

[Table 6]

That is, in the steps of accumulating charges between the transparent pixel electrode 24 and the transparent counter electrode 15 in Tables 1 to 3 above, the source voltage Vs = VsLmin is output to the source line 22 and the display pixel electrode 24a. The electric charge between the display counter electrode 15a and the display counter electrode 15a is discharged, and the display pixel electrode 24a portion of the pixel is shielded. As a result, the action of transmitting only red, blue, or green light of the display area 61a in the micro color filter 61 does not affect the reading of the image.

In the step in which the photodiode 25 is exposed by the light reflected from the original, the counter electrode 15b for illumination is switched to the counter electrode 15a for display through the switch 62.
The source voltage Vs = VsLmax corresponding to the maximum luminance is applied to the illumination pixel electrode 24b via the source line 22, and the portion of the illumination pixel electrode 24b in the group of pixels not adjacent to each other is transparent. It becomes a state.
Therefore, the illumination area 61 of the micro color filter 61
Since b is designed to transmit light of all colors as described above, any one of red, blue and green monochromatic light sources 18a
The monochromatic light emitted from .about.18c is also applied to the document as it is. Therefore, as in the fifth embodiment, red,
The blue and green monochromatic light sources 18a to 18c are sequentially used, and the same reading operation as that of the monochrome liquid crystal display device is performed for each monochromatic light source 18a.
Image data of each color component in the original image is read.

As described above, when displaying an image, a color image is displayed by the additive color mixture of three single pixels using a micro color filter, while at the time of reading the image, red, blue, and Green monochromatic light source 1
By reading the components of each color using 8a to 18c, the original image can be read with a pixel density three times that at the time of display.

[0125]

The present invention is carried out in the form as described above, and has the following effects.

That is, when the read pixel density is high by reading the original image by setting the liquid crystal in the transmissive state and irradiating the original with the light of the backlight for each single pixel or for each set of pixels that are not adjacent to each other. However, there is an effect that crosstalk between adjacent pixels can be reduced and the resolution can be increased.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing a circuit configuration of an active matrix panel 13 according to the first embodiment.

FIG. 3 is a plan view showing a specific configuration of the active matrix panel 13 of the first embodiment.

4 is a cross-sectional view taken along arrows AA and BB of FIG.

FIG. 5 is an explanatory diagram showing the manufacturing method of the active matrix panel 13 of the first embodiment.

FIG. 6 is an explanatory diagram showing an arrangement of pixels from which a document image is read in one exposure process in the liquid crystal display device with an image reading function according to the first embodiment.

FIG. 7 is a plan view showing a specific configuration of the active matrix panel 13 of the second embodiment.

8 is a sectional view taken along the line AA and the line BB of FIG.

FIG. 9 is a modification of the liquid crystal display device with an image reading function according to the third embodiment (another connection example of the photodiode 25).
It is a circuit diagram showing.

FIG. 10 is a circuit diagram showing another modification of the liquid crystal display device with an image reading function of the third embodiment (an example in which a source voltage is applied to the anode side of the photodiode 25).

FIG. 11 is an explanatory diagram showing an example of a case where an in-plane switching type liquid crystal display device is configured.

FIG. 12 is a perspective view showing an external configuration of a liquid crystal display device with an image reading function according to a fourth embodiment.

FIG. 13 is a perspective view showing an external configuration of a liquid crystal display device with an image reading function according to a fifth embodiment.

FIG. 14 is a perspective view showing an external configuration of a liquid crystal display device with an image reading function according to a sixth embodiment.

FIG. 15 is a plan view showing a specific configuration of the active matrix panel 13 of the sixth embodiment.

16 is a cross-sectional view taken along arrows AA and BB of FIG.

[Explanation of symbols]

11 Polarizing filter layer 12 glass substrates 13 Active matrix panel 14 Liquid crystal layer 15 Transparent counter electrode 15a Display counter electrode 15b Counter electrode for illumination 16 Opposite glass substrate 17 Polarization filter layer 18 backlight 18a Red monochromatic light source 18b Blue monochromatic light source 18c Green monochromatic light source 19 Touch panel unit 21 Display / reading section 22 Source line 23 gate lines 24 Transparent pixel electrode 24a display pixel electrode 24b Illumination pixel electrode 25 photodiode 26 TFT (L) 27 TFT (D) 28 Light-shielding electrode 31 Drive circuit section 32 shift register 33 TFT control circuit 34 shift register 35 Charge voltage output circuit 35a line memory 35b D / A converter 36 Reading circuit 36a A / D converter 36b line memory 61 Micro Color Filter 61a display area 61b Illumination area 62 switch 71 control unit P1 pixel P2 pixel

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H04N 1/028 H04N 1/028 Z 1/19 1/04 102 (72) Inventor Shinzaburo Ishikawa 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita (56) References Japanese Patent Laid-Open No. 7-261932 (JP, A) Japanese Patent Laid-Open No. 8-160382 (JP, A) Actually developed 63-128539 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02F 1/133 550 G02F 1/13 505 G02F 1/1335 505 G09F 9/35 302 G09G 3/36 H04N 1/028 H04N 1/19

Claims (2)

(57) [Claims] 1. A pixel electrode, a counter electrode provided so as to face the pixel electrode, a liquid crystal provided between the pixel electrode and the counter electrode, and a liquid crystal provided corresponding to each pixel electrode. In a liquid crystal display device with an image reading function equipped with a light receiving element that detects the amount of reflected light, further, a display area for transmitting light of a predetermined color corresponding to each pixel and transmitting light of all colors are transmitted. And a back light source that includes a plurality of light sources that emit white light when they are turned on at the same time and that emits light of different colors. While the liquid crystal in the part corresponding to the illumination area of the filter is shielded, the liquid crystal in the part corresponding to the display area is set to the light-transmitting state according to the image signal, and The light source is turned on and a color image is displayed by the additive color mixture of the light transmitted through the display areas of each color in the color filter. When reading the original image, all pixels correspond to the display area of the color filter. While the liquid crystal in the part is shielded, the liquid crystal in the part corresponding to the illumination area is set in the light-transmitting state for each single pixel or a group of pixels not adjacent to each other, and the above-mentioned back light sources are sequentially selected. The color image is read by illuminating the original document with the light of each color through the illumination area of the color filter and detecting the reflected light amount of the light of each color from the original document. Characteristic liquid crystal display with image reading function. 2. A pixel electrode, a counter electrode provided so as to face the pixel electrode, a liquid crystal provided between the pixel electrode and the counter electrode, and a liquid crystal provided corresponding to each pixel electrode. A light-receiving element for detecting the amount of reflected light, a color filter corresponding to each pixel, a display area for transmitting light of a predetermined color, and an illumination area for transmitting light of all colors, respectively. An image reading method using a liquid crystal display device with an image reading function, which includes a back light source that emits light of different colors and emits white light when turned on at the same time. While the liquid crystal in the portion corresponding to the illumination area is set to the light-shielded state, the liquid crystal in the portion corresponding to the display area is set to the light-transmitting state according to the image signal, and all the above-mentioned back light sources are turned on. A step of displaying a color image by an additive color mixture of light transmitted through the display areas of each color in the color filter, and for all pixels, while making the liquid crystal in the portion corresponding to the display area of the color filter a light-shielding state, For each single pixel or for each set of pixels that are not adjacent to each other, the liquid crystal in the portion corresponding to the illumination area is set in the light-transmitting state, and the back light sources are sequentially turned on to selectively emit light of each color. An image reading method, comprising: irradiating an original through an illumination area in a color filter and detecting a reflected light amount of each color light from the original to read a color image.