KR20080062932A - Liquid crystal display device having image sensing function - Google Patents

Abstract

An LCD(Liquid Crystal Display) having an image sensing function is provided to make a size of photo TFTs installed in R and B pixel units bigger than a size of a photo TFT installed in a G pixel unit, thereby obtaining overall uniform images capable of light sensing even for a short time. A pixel area comprises pixels including RGB(Red, Green and Blue) sub pixels. First and second switching TFTs(Thin Film Transistors)(106,170) are respectively installed in the RGB sub pixels. First to third photo TFTs(140) are respectively installed within the RGB sub pixels. A size of the first and second photo TFT device disposed within the RGB sub pixel is bigger than a size of the third photo TFT device.

Description

Liquid crystal display with image sensing function {LIQUID CRYSTAL DISPLAY DEVICE HAVING IMAGE SENSING FUNCTION}

1 is a plan view showing a part of a TFT array substrate according to the prior art;

2 is a cross-sectional view taken along the line II-II of FIG.

3 is a cross-sectional view showing a photo sensing device according to the prior art.

Figure 4 is a schematic diagram comparing the channel width of the photo thin film transistor provided in each of the R, G, B pixel portion according to the prior art.

5 is a plan view schematically showing a liquid crystal display device having an image sensing function according to the present invention;

FIG. 6 is a cross-sectional view of the first thin film transistor portion taken along line VI-VI of FIG. 5.

FIG. 7 is a cross-sectional view of the photo thin film transistor and the first thin film transistor according to the X-ray line of FIG.

8 is a schematic diagram comparing the channel widths of the photo thin film transistors provided in each of the R, G, and B pixel portions of a liquid crystal display having an image sensing function according to the present invention;

-Code description of main parts of drawing-

102: gate line 104: data line

106: first TFT 108: gate electrode

110: source electrode 112: drain electrode

114: active layer 116: contact hole

118: pixel electrode 180: first storage capacitor

120: second storage capacitor 144: gate insulating film 150: protective film 140: photo TFT 170: first TFT 152: first driving voltage supply line 172: second storage lower electrode 174: second storage upper electrode

155: second contact hole 200: photo sensing element

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having an image sensing function having sensors of different sizes in each of red (R), green (G), and blue (B) pixel areas. It is about.

Conventional liquid crystal display devices display an image by adjusting the light transmittance of the liquid crystal using an electric field. To this end, the liquid crystal display includes a liquid crystal display panel in which liquid crystal cells are arranged in a matrix, and a driving circuit for driving the liquid crystal display panel.

The liquid crystal display panel includes a thin film transistor array substrate and a color filter array substrate facing each other, a spacer positioned to maintain a constant cell gap between the two substrates, and a liquid crystal filled in the cell gap.

The thin film transistor array substrate includes gate lines and data lines, a thin film transistor formed of a switch element at each intersection of the gate lines and data lines, a pixel electrode formed in a liquid crystal cell unit, and connected to the thin film transistor; It consists of the orientation film apply | coated on them.

The gate lines and the data lines receive signals from the driving circuits through the respective pad parts.

The thin film transistor supplies the pixel voltage signal supplied to the data line to the pixel electrode in response to the scan signal supplied to the gate line.

The color filter array substrate includes color filters formed in units of liquid crystal cells, a black matrix for distinguishing between color filters and reflecting external light, a common electrode for supplying a reference voltage to the liquid crystal cells in common, and an alignment layer applied thereon. It consists of.

The liquid crystal display panel is completed by separately manufacturing a thin film transistor array substrate and a color filter array substrate, and bonding the liquid crystal.

The liquid crystal display according to the related art will be described with reference to FIGS. 1 and 2 as follows.

1 is a plan view showing a part of a TFT array substrate according to the prior art, and FIG. 2 is a cross-sectional view taken along the line II-II of FIG.

1 and 2, a thin film transistor array substrate includes a gate line 2 and a data line 4 formed to intersect a gate insulating film 44 on a lower substrate 42, and a thin film formed at each intersection thereof. A transistor and a pixel electrode 19 formed in a cell region provided in a cross structure thereof are provided.

The TFT array substrate includes a storage capacitor 20 formed at an overlapping portion of the pixel electrode 18 and the previous gate line 2.

The TFT 6 includes a gate electrode 8 connected to the gate line 2, a source electrode 10 connected to the data line 4, a drain electrode 12 connected to the pixel electrode 18, The active layer 14 overlaps the gate electrode 8 and forms a channel between the source electrode 10 and the drain electrode 12.

The active layer 14 is formed to overlap the data line 4, the source electrode 10, and the drain electrode 12, and further includes a channel portion between the source electrode 10 and the drain electrode 12.

An ohmic contact layer 48 for ohmic contact with the data line 4, the source electrode 10, and the drain electrode 12 is further formed on the active layer 14.

The active layer 14 and the ohmic contact layer 48 are referred to as a semiconductor pattern 45.

The TFT 6 causes the pixel voltage signal supplied to the data line 4 to be charged and held in the pixel electrode 18 in response to the gate signal supplied to the gate line 2.

The pixel electrode 18 is in contact with the drain electrode 12 of the TFT 6 through the contact hole 16 penetrating the protective film 50.

The pixel electrode 18 generates a potential difference from the common electrode formed on the upper substrate (not shown) by the charged pixel voltage.

Due to this potential difference, the liquid crystal positioned between the TFT array substrate and the color filter array substrate is rotated by the dielectric anisotropy, and the light incident through the pixel au from the light source (not shown) is transmitted to the upper substrate.

The storage capacitor 20 is formed by the front gate electrode 2 and the pixel electrode 18. The gate insulating film 44 and the passivation film 50 are positioned between the gate line 2 and the pixel electrode 18.

The storage capacitor 20 helps the pixel voltage charged in the pixel electrode 18 to be maintained until the next pixel voltage is charged.

The liquid crystal display device according to the related art has only a display function and does not have a function of sensing and displaying an external image such as a content image such as an external document or an image.

A conventional image sensing device capable of sensing such an external image will be described with reference to FIGS. 3 and 4 as follows.

3 is a cross-sectional view showing a photo sensing device according to the prior art.

4 is a plan view illustrating an arrangement state of R, G, and B pixels of a photo sensing device according to the related art.

Referring to FIG. 3, the image sensing device according to the related art is opposite to the photo TFT 40 with the photo TFT 40, the storage capacitor 80 connected to the photo TFT 40, and the storage capacitor 80 interposed therebetween. And a switch TFT 60 positioned in the direction.

The photo TFT 50 is electrically connected to the active layer 14 and the active layer 14 overlapping the gate electrode 8 with the gate electrode 8 formed on the substrate 42 and the gate insulating film 44 interposed therebetween. The driving source electrode 60 and the driving drain electrode 62 facing the driving source electrode 60 are provided.

The active layer 14 is formed to overlap the driving source electrode 60 and the driving drain electrode 62 and further includes a channel portion between the driving source electrode 60 and the driving drain electrode 62.

An ohmic contact layer 48 for ohmic contact with the driving source electrode 60 and the driving drain electrode 62 is further formed on the active layer 14.

The photo TFT 40 serves to sense light incident by a predetermined image such as a document or a fingerprint of a person.

The storage capacitor 80 overlaps the storage lower electrode 72 with the storage lower electrode 72 and the insulating layer 44 connected to the gate electrode 8 of the photo TFT 40 interposed therebetween. A storage upper electrode 74 connected to the driving drain electrode 62 of the 40 is provided.

The storage capacitor 80 stores the charge due to the photocurrent generated in the photo TFT 40.

The switching TFT 6 includes a gate electrode 8 formed on the substrate 42, a source electrode 10 connected to the storage upper electrode 74, a drain electrode 12 facing the source electrode 10, and An active layer 14 overlapping the gate electrode 8 and forming a channel between the source electrode 910 and the drain electrode 12 is provided.

The active layer 14 is formed to overlap the source electrode 10 and the drain electrode 12 and further includes a channel portion between the source electrode 10 and the drain electrode 12.

An ohmic contact layer 48 for ohmic contact with the source electrode 10 and the drain electrode 12 is further formed on the active layer 14.

As described above, the image sensing device according to the related art has the following problems.

In the image sensing device according to the related art, the size of the sensor TFT and the storage capacitance corresponding to the R, G, and B pixels are kept the same. In particular, as shown in FIG. 4, the channel widths W1, W2, and W3 of the sensor TFTs 40 provided in each of the R, G, and B pixels have the same size.

In this case, the sensor of the G pixel, which has the highest transmittance, has a high amount of sensing light even in a short time, but the sensor of the R and G pixels, which have a relatively low transmittance, does not have a large amount of sensing when the scan time is short. You will see a dark image as a whole.

That is, in the conventional LCD integrated liquid crystal display device, especially a color scanner integrated liquid crystal display device, one photo sensor is formed for each of the R, G, and B sub-pixels, and the combined amount of sensing light can be used to obtain a color scan image. .

In this case, however, if the scan time is short, the green sensor with high light transmittance can sense enough, but the R and B pixel sensors with low light transmittance have insufficient time to sense, so that the sensed image has a green color. The picture quality is dark overall.

For example, if the scan time is T2, the difference in charging voltage of the R, G, and B sensors is not large, and the color difference of the scanned image is not large. However, if the scan time is as short as T1, the G sensor is well charged. , Charging of B sensor is not enough.

Accordingly, the present invention has been made to solve the above problems of the prior art, an object of the present invention is to charge even during a short scan time by increasing the size of the sensor of the color filter unit having a low transmittance than the sensor size of the color filter unit having a high transmittance The present invention provides a liquid crystal display having an image sensing function capable of improving a scanned image.

According to an aspect of the present invention, there is provided a liquid crystal display device having an image sensing function, the pixel area including pixels including red, blue, and green subpixels; A first switching TFT and a second switching TFT in each of the red, blue, and green subpixels; First, second, and third photo TFTs respectively provided in the red, blue, and green subpixels; And the size of the first and second photo TFT elements located in the red and blue subpixels is larger than the size of the third photo TFT elements located in the green subpixels.

Hereinafter, a liquid crystal display having an image sensing function according to the present invention will be described in detail with reference to the accompanying drawings.

6 is a plan view schematically illustrating a liquid crystal display having an image sensing function according to the present invention.

FIG. 7 is a cross-sectional view of the first thin film transistor unit taken along the line VII-VII of FIG. 6.

8 is a cross-sectional view of the photo thin film transistor unit and the first thin film transistor unit along the line VII-VII of FIG. 6.

9 is a plan view illustrating an arrangement state of R, G, and B pixels of a liquid crystal display having an image sensing function according to the present invention.

10 is a plan view comparing the channel widths of the thin film transistors provided in each of the R, G, and B pixel parts of the liquid crystal display having the image sensing function according to the present invention.

6 and 7, a TFT array substrate having an image sensing function according to the present invention includes a gate line 102 and a data line 104 with a gate insulating film 144 interposed on a lower substrate 142. The pixel switching element (hereinafter referred to as a first TFT ") 106 formed at each intersection thereof, and the data line (120) between the pixel electrode 118 and the pixel electrode 118 formed in the cell region provided in the intersection structure. A read-out line 204 formed in parallel with the 104 and a gate line 102 in parallel with each other to supply the first and second driving voltages to the photo TFT 140; The photo TFT 140, the gate line 102 and the lead out line 204 formed at the intersection of the second driving voltage supply lines 152 and 171, the first driving voltage supply line 152 and the lead out line 204. A switching TFT (hereinafter referred to as " second TFT ") formed at the intersection of the < RTI ID = 0.0 >

A photo sensing storage capacitor (hereinafter referred to as a “first storage capacitor”) 180 positioned between the photo TFT 140 and the second TFT 170, the pixel electrode 118 and the previous gate line. A pixel storage capacitor (hereinafter referred to as "second storage capacitor") formed in the overlapping portion of 102 is provided.

The second storage capacitor 120 in the drawing shows the second storage capacitor 120 of the next pixel for convenience.

The first TFT 106 includes a gate electrode 108 connected to the gate line 102, a source electrode 110 connected to the data line 104, and a drain electrode 112 connected to the pixel electrode 118. And an active layer 114 overlapping the gate electrode 108 and forming a channel between the source electrode 110 and the drain electrode 112.

The active layer 114 is formed to overlap the data line 104, the source electrode 110, and the drain electrode 112, and further includes a channel portion between the source electrode 110 and the drain electrode 112.

An ohmic contact layer 148 for ohmic contact with the data line 104, the source electrode 110, and the drain electrode 112 is further formed on the active layer 114.

Here, the active layer 114 and the ohmic contact layer 148 are commonly referred to as a semiconductor pattern 145.

The first TFT 106 allows the pixel voltage signal supplied to the data line 104 to be charged and held in the pixel electrode 118 in response to the gate signal supplied to the gate line 102.

The pixel electrode 118 is connected to the drain electrode 112 of the TFT 106 through the first contact hole 116 penetrating the passivation layer 150.

The pixel electrode 118 generates a potential difference with a common electrode formed on an upper substrate (for example, a color filter array substrate) not shown by the charged pixel voltage.

This potential difference causes the liquid crystal located between the TFT array substrate and the color filter array substrate to rotate due to dielectric anisotropy, and transmits light incident through the pixel electrode 118 from a light source (not shown) to the upper substrate.

The second storage capacitor 120 is formed by the front gate line 102 and the pixel electrode 118. The gate insulating layer 144 and the passivation layer 150 are positioned between the gate line 102 and the pixel electrode 118.

The second storage capacitor 120 helps to maintain the pixel voltage charged in the pixel electrode 118 until the next pixel voltage is charged.

The photo TFT 140 (hereinafter, the components having the same functions as those of the first TFT among the components of the TFT will be denoted by the same reference numerals as the components of the first TFT). The gate electrode 108 to which the driving voltage supply line 171 is connected and the active layer 114 and the active layer 114 overlapping the gate electrode 108 with the gate insulating film 144 therebetween are electrically connected to each other. A driving source electrode 160 connected to the driving voltage supply line 152 and a driving drain electrode 162 facing the driving source electrode 160 are provided.

Here, the photo TFT 140 includes a second contact hole 155 through which the first driving voltage supply line 152 is partially exposed through the passivation layer 150 and the gate insulating layer 144. 160 is connected to the first driving voltage supply line 152 by the transparent electrode pattern 154 formed on the second contact hole 155.

The active layer 114 is formed to overlap the driving source electrode 160 and the driving drain electrode 162 and further includes a channel portion between the driving source electrode 160 and the driving drain electrode 162.

An ohmic contact layer 148 for ohmic contact with the driving source electrode 160 and the driving drain electrode 162 is further formed on the active layer 114.

The photo TFT 140 senses incident light by a predetermined image such as a document or a human fingerprint.

The first storage capacitor 180 overlaps the first storage lower electrode 172 with the first storage lower electrode 172 and the insulating layer 144 interposed therebetween with the gate electrode 108 of the photo TFT 140 interposed therebetween. And a storage upper electrode 174 connected to the driving drain electrode 162 of the photo TFT 140.

The first storage capacitor 180 stores a charge due to the photocurrent generated in the photo TFT 140.

The first TFT 170 includes a gate electrode 108 formed on the substrate 142, a source electrode 110 connected to the second storage upper electrode 174, and a drain electrode 112 facing the source electrode 110. And an active layer 114 overlapping the gate electrode 108 and forming a channel between the source electrode 110 and the drain electrode 112.

The active layer 114 is formed to overlap the source electrode 110 and the drain electrode 112, and further includes a channel portion between the source electrode 110 and the drain electrode 112.

An ohmic contact layer 148 for ohmic contact with the source electrode 110 and the drain electrode 112 is further formed on the active layer 114.

The operation process of the image sensing device according to the present invention having such a structure will be described as follows.

First, when the first driving voltage is applied to the driving source electrode 160 of the photo TFT 140 and the second driving voltage is applied to the gate electrode 108, and a predetermined light is sensed by the active layer 114, the sensing is sensed. According to the amount of light, a photocurrent path flowing to the driving drain electrode 162 via a channel is generated in the driving source electrode 160.

The photocurrent path flows from the driving drain electrode 160 to the first storage upper electrode 174 and at the same time the first storage lower electrode 172 is connected to the gate electrode 108 of the photo TFT 140. The photo TFT is charged with the charge by the photocurrent.

As such, the charge charged in the first storage capacitor 180 is read by the readout IC through the second TFT 170 and the readout line 204. That is, since the signal detected by the readout integrated circuit according to the amount of light sensed by the photo TFT 140 is changed, it is possible to sense an image such as a document, an image scan, a touch input, or the like. The sensed image may be transmitted to the controller or the like or may be embodied in an image of the liquid crystal display panel according to a user's adjustment.

On the other hand, the photo TFT provided in each pixel portion in the liquid crystal display having the image sensing function according to the present invention will be described with reference to FIG.

In the liquid crystal display having the image sensing function according to the present invention, a plurality of R, G, and B subpixels are provided to constitute a unit pixel.

Each of the R, G, and B subpixels is provided with a photo TFT 140 that functions to sense an image.

Among the R, G, and B subpixels, the photo TFT 140 of the G pixel having the highest transmittance has a high amount of sensing light even in a short time, but the photo TFT 140 of the R and G pixels having a relatively low transmittance has a scan time. If it is short, the amount of sensing is not large. After scanning, the color image becomes green and shows a dark image as a whole.

Therefore, in the present invention, the size of the photo TFT provided in the R and B pixel portions having a lower transmittance than that of the G pixels is formed larger than that of the photo TFT provided in the G pixel portion. That is, the size adjustment of the photo TFT is made possible by adjusting the channel width W. FIG. That is, as shown in FIG. 8, of the sensor TFTs 140 provided in each of the R and B pixels among the channel widths W1, W2, and W3 of the sensor TFTs 140 provided in the R, G, and B pixels, respectively. The channel widths W1 and W3 have a larger value than the channel width W2 of the sensor TFT 140 provided in the B pixel.

On the other hand, the size of the photo TFT is formed differently, but the size of the switching TFT and the display TFT provided in the remaining R, G, and B pixel portions are kept the same.

Since the size of the photo TFT provided in the R and B pixel parts having a lower transmittance than the G pixel is formed larger than the size of the photo TFT provided in the G pixel part, uniform light sensing is possible even for a short time, thereby making the overall uniformity. One image can be obtained.

On the other hand, while described above with reference to a preferred embodiment of the present invention, those skilled in the art various modifications of the present invention without departing from the spirit and scope of the invention described in the claims below And can be changed.

As described above, the liquid crystal display having the image sensing function according to the present invention has the following effects.

The liquid crystal display having an image sensing function according to the present invention forms a photo TFT having a transmittance lower than that of a G pixel because the size of the photo TFT provided in the R and B pixel portions is larger than that of the photo TFT provided in the G pixel portion. Even light can be sensed even during time, so that an overall uniform image can be obtained.

Claims (7)

 A pixel region including pixels including red, blue, and green subpixels; A first switching TFT and a second switching TFT in each of the red, blue, and green subpixels; First, second, and third photo TFTs respectively provided in the red, blue, and green subpixels; And And the size of the first and second photo TFT elements located in the red and blue subpixels is larger than the size of the third photo TFT elements located in the green subpixels. The liquid crystal display of claim 1, wherein a channel width of the first and second photo TFT elements is larger than a channel width of the third photo TFT. The liquid crystal display of claim 1, wherein the first switching TFT and the second switching TFT of each of the red, blue, and green subpixels have the same size. The LCD device of claim 1, further comprising: a color filter array substrate on which color filters corresponding to each of the red, blue, and green subpixels are formed; A thin film transistor array substrate facing the color filter array substrate with a liquid crystal interposed therebetween, wherein the photo sensing element is formed; The thin film transistor array substrate Gate lines and data lines formed on the substrate to cross each other and defining respective sub-pixel regions; A first thin film transistor positioned at an intersection of the gate line and the data line; And a pixel electrode connected to the first thin film transistor. The method of claim 4, wherein the photo TFT device A photo thin film transistor for sensing the light; A first storage capacitor for storing a signal sensed by the photo thin film transistor; An integrated circuit for detecting the sensing signal stored in the first storage capacitor; And a second thin film transistor positioned between the second storage capacitor and the integrated circuit to selectively supply the sensing signal to the integrated circuit. The semiconductor device of claim 5, further comprising: a first driving voltage supply line formed in parallel with the gate line to supply a first driving voltage to the photo TFT; A second driving voltage supply line formed in parallel with the first driving voltage supply line to supply a second driving voltage to the photo TFT; And a sensing signal transfer line positioned parallel to the data line with the pixel region therebetween, the sensing signal transfer line for transferring a sensing signal from the second thin film transistor to an integrated circuit. Device. The method of claim 6, wherein the photo TFT is A first gate electrode formed on the substrate and connected to the second driving voltage supply line; A gate insulating film formed to cover the first gate electrode; A first semiconductor pattern overlapping the first gate electrode with the gate insulating film interposed therebetween; A first source electrode in contact with the first semiconductor pattern and electrically connected to the first driving voltage supply line; And a first drain electrode facing the first source electrode.

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