KR20060132372A - Liquid crystal display device having image sensing function and method for fabricating thereof - Google Patents

Abstract

An LCD having an image sensing function and a manufacturing method thereof are provided to allow image input and output to an LCD by providing the LCD with a sensing device that can detect a document and an image. A gate line(102) and a data line(104) intersect each other on a substrate, and define a pixel region where a pixel electrode(118) is placed. A first thin film transistor(106) is placed at an intersection of the gate line and the data line. A photo thin film transistor(140) is placed at one region of the pixel region, and detects light from the outside. The photo thin film transistor includes a bottom gate electrode placed therein, and a top gate electrode placed at an upper portion thereof.

Description

Liquid Crystal Display Device Having Image Sensing Function And Method For Fabricating Thereof}

1 is a plan view showing a portion of a conventional TFT array substrate.

FIG. 2 is a cross-sectional view of the TFT array substrate illustrated in FIG. 1 taken along the line II ′. FIG.

3 is a cross-sectional view showing a conventional photo sensing device.

4 is a schematic view of a liquid crystal display device having an image sensing function according to the present invention.

FIG. 5 is a cross-sectional view taken along lines II ′ and II-II ′ of FIG. 4. FIG.

FIG. 6 is a circuit diagram schematically illustrating one pixel illustrated in FIG. 4.

FIG. 7 is a diagram illustrating a region, which is covered by a black matrix and an opening region, among pixels illustrated in FIG. 5;

8 is a cross-sectional view illustrating a photo sensing method according to a first embodiment of the present invention.

9 and 10 are circuit diagrams for describing in detail the photo sensing method according to the first embodiment of the present invention.

11 is a cross-sectional view for describing a photo sensing method according to a second embodiment of the present invention.

12 is experimental data showing the effect of the second embodiment of the present invention.

13 shows channel and photocurrent formation in bottom gate, top gate and double gate structures.

14A to 14E are flowcharts illustrating a method of manufacturing a liquid crystal display device having an image sensing function according to an exemplary embodiment of the present invention.

 <Description of Symbols for Main Parts of Drawings>

102: gate line 104: data line

106: first TFT 108: gate electrode

10, 110: source electrode 12, 112: drain electrode

14, 114: active layer 16,116: contact hole

18, 118: pixel electrode 180: first storage capacitor

120: second storage capacitor 44,144: gate insulating film

50,150: 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

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having an image sensing function capable of document, image scanning, and touch input, a manufacturing method thereof, and an image sensing method using the same.

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 a gate line and a data line, a thin film transistor formed of a switch element at each intersection of the gate lines and the data lines, a pixel electrode formed of a liquid crystal cell and connected to the thin film transistor, and the like. It consists of the applied alignment film. 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 then injecting and encapsulating a liquid crystal.

1 is a plan view illustrating a thin film transistor array substrate of a conventional liquid crystal display panel, and FIG. 2 is a cross-sectional view of the thin film transistor array substrate illustrated in FIG. 1 taken along the line II ′.

The thin film transistor array substrate shown in FIGS. 1 and 2 includes a gate line 2 and a data line 4 intersecting each other with a gate insulating film 44 interposed on the lower substrate 42, and a thin film formed at each intersection thereof. A transistor (Thin Film Transistor, hereinafter referred to as " TFT ") 6 and a pixel electrode 18 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. Here, the active layer 14 and the ohmic contact layer 48 are commonly 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 connected to 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 dielectric anisotropy and transmits the light incident through the pixel electrode 18 from the light source (not shown) toward the upper substrate.

The storage capacitor 20 is formed by the front gate line 2 and the pixel electrode 18. The gate insulating layer 44 and the passivation layer 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.

Such a conventional liquid crystal display device has only a display function and does not have a function of sensing and displaying an external image such as an external document or a content image such as an image.

FIG. 3 is a diagram illustrating a conventional image sensing device. (The elements included in a conventional TFT among the components in the image sensing device shown in FIG. 3 are the same as those of the TFTs shown in FIGS. 1 and 2. Reference numerals will be given.)

The image sensing device shown in FIG. 3 is a switch located 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. TFT 6 is provided.

The photo TFT 40 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 incident light 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, and the photo TFT 40 overlaps with the photo TFT 40. The storage upper electrode 74 is connected to the driving drain electrode 62. The storage capacitor 80 stores a 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 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 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.

The driving of the image sensing device having the structure will be briefly described. For example, a driving voltage of about 10 V is applied to the driving source electrode 60 of the photo TFT 40 and the gate electrode 8 is applied to the driving source electrode 60. For example, when a reverse bias voltage of about -5V is applied and light is sensed in the active layer 14, the photocurrent flowing from the driving source electrode 60 to the driving drain electrode 62 through the channel according to the sensed light amount (Photo) Current) pass is generated. Since the photocurrent path flows from the driving drain electrode 60 to the storage upper electrode 74, the storage lower electrode 72 is connected to the gate electrode 8 of the photo TFT 40, and thus the storage capacitor 80 receives a photocurrent. Charge is caused to be charged. As such, the charges charged in the storage capacitor 80 are transferred to the switch TFT 6 so that the image sensed by the photo TFT 40 can be read.

As such, the conventional liquid crystal display device has only a function for display, and a conventional image sensing device has only a function of sensing an image.

Accordingly, an object of the present invention is to provide a liquid crystal display and a method of manufacturing the same, which have an image sensing function capable of inputting an image such as a document, a fingerprint of a person, etc. and displaying the input image on the image.

Still another object of the present invention is to provide a liquid crystal display device and a method of manufacturing the same, which can improve the efficiency of light sensing.

In order to achieve the above object, a liquid crystal display device having an image sensing function according to the present invention includes a gate line and a data line which are formed to cross each other on a substrate and define a pixel region in which pixel electrodes are located; A first thin film transistor positioned at an intersection of the gate line and the data line; And a photo thin film transistor positioned in one region of the pixel region for sensing light from the outside, wherein the photo thin film transistor includes a bottom gate electrode positioned inside of the pixel region and a top gate electrode positioned on the upper portion thereof. It is characterized by including.

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 first storage capacitor and the integrated circuit to selectively supply the sensing signal to the integrated circuit.

A first driving voltage supply line formed in parallel with the gate line to supply a first driving voltage to the photo thin film transistor; 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 thin film transistor; And a sensing signal transfer line positioned parallel to the data line with the pixel region therebetween, and configured to transfer a sensing signal from the second thin film transistor to an integrated circuit.

The photo thin film transistor may include a gate insulating film formed to cover the bottom gate electrode; A first semiconductor pattern overlapping the first gate electrode with the gate insulating layer 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.

A first channel formed by the bottom gate electrode, the first source electrode and the first drain electrode; And a second channel provided by the top gate electrode, the first source electrode, and the first drain electrode.

When the photo thin film transistor senses light, a first photocurrent through the first channel is generated, and a second photocurrent through the second channel is generated.

The amount of photocurrent generated is proportional to the thickness of the first semiconductor pattern.

And a protective film formed to cover the photo TFT, wherein the top gate electrode is formed on the protective film and overlaps the first semiconductor pattern.

The same signal is supplied to the bottom gate electrode and the top gate electrode.

The pixel electrode and the top gate electrode are made of the same material.

A method of manufacturing a liquid crystal display panel according to the present invention includes a gate including a gate line having a bottom gate electrode of a photo thin film transistor, a second gate electrode of a first TFT, a bottom gate electrode, and a second gate electrode commonly connected on a substrate. Forming a pattern; Forming a gate insulating film on the substrate on which the gate pattern is formed; Forming a first semiconductor pattern overlapping the bottom gate electrode and a second semiconductor pattern overlapping the second gate electrode on the gate insulating layer; A data line intersecting the gate line with the gate insulating layer interposed therebetween, and a first source electrode, a first drain electrode, and a second semiconductor pattern, which are respectively connected to and face each other and face each other. Forming a photo TFT and a first TFT by forming a source / drain pattern including a second source electrode and a second drain electrode positioned to be visible; Forming a protective film having a hole exposing the second drain electrode of the first TFT; And forming a transparent electrode pattern including a pixel electrode connected to the second drain electrode through the hole and a top gate electrode overlapping the first semiconductor pattern with the passivation layer therebetween.

The forming of the gate pattern may include a first driving voltage supply line which is formed in parallel with the gate line to supply a first driving voltage to the photo TFT, is connected to the gate electrode, and is connected to the first driving voltage supply line; And forming second parallel driving voltage supply lines.

The first semiconductor pattern includes a first channel formed by the bottom gate electrode, the first source electrode, and the first drain electrode, and a second channel formed by the top gate electrode, the first source electrode, and the first drain electrode. It characterized in that it comprises a channel.

When the photo thin film transistor senses light, a first photocurrent through the first channel is generated, and a second photocurrent through the second channel is generated.

The amount of photocurrent generated is proportional to the thickness of the first semiconductor pattern.

The same signal is supplied to the bottom gate electrode and the top gate electrode.

Other objects and advantages of the present invention in addition to the above object will be apparent from the description of the preferred embodiments of the present invention with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 4 to 14.

4 is a plan view illustrating a liquid crystal display device having an image sensing function according to a first exemplary embodiment of the present invention, and FIG. 5 is a cut-away view taken along lines II ′ and II-II ′ of FIG. 4, respectively. It is a cross section. In particular, FIGS. 4 and 5 illustrate a TFT array substrate of a liquid crystal display having an image sensing function. The color filter array substrate positioned with the TFT array substrate and the liquid crystal interposed therebetween includes a usual black matrix, color filter, and the like.

The TFT array substrate having the image sensing function shown in FIGS. 4 and 5 has a gate line 102 and a data line 104 formed to intersect on the lower substrate 142 with a gate insulating layer 144 interposed therebetween. The pixel switching TFTs (hereinafter referred to as " first TFTs ") 106 formed in each unit and the pixel electrodes 118 and pixel electrodes 118 formed in the cell regions provided in the intersecting structure are interposed therebetween. A read-out line 204 formed in parallel with the line 104 and a first line formed in parallel with the gate line 102 to supply the first and second driving voltages to the photo TFT 140. And 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. And a switching TFT (hereinafter referred to as a "second TFT") 170 formed in an intersection region of the substrate. Then, 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 ( And a second storage capacitor 120 (hereinafter, referred to as a “second storage capacitor”) formed at an overlapping portion of the 102. The second storage capacitor 120 shown in FIG. 2 is provided for convenience as a second storage capacitor 120 of the next pixel. Indicated.

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 protective film 150. The pixel electrode 118 generates a potential difference with a common electrode formed on an upper substrate (eg, a color filter array 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 dielectric anisotropy and transmits the light incident through the pixel electrode 118 from the light source (not shown) toward 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 above-described first TFT among the components of the TFT will be denoted by the same reference numerals as the components of the first TFT). 2, the gate electrode 108 connected to the driving voltage supply line 171 and the active layer 114 and the active layer 114 overlapping the gate electrode 108 with the gate insulating layer 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, and the driving source electrode 160. ) Is connected to the first driving voltage supply line 152 by a metal 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 serves to sense incident light by a predetermined image such as a document or a fingerprint of a person.

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 between 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 the charge due to the photocurrent generated in the photo TFT 140.

The second 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 in the present invention having the structure described above will be described with reference to the circuit diagram shown in FIG. 6.

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 on the active layer 114, the amount of light sensed is sensed. Accordingly, a photo current path that flows from the driving source electrode 160 to the driving drain electrode 162 via the channel is generated. The photocurrent path flows from the driving drain electrode 160 to the first storage upper electrode 174 and 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. In this way, the charge charged in the first storage capacitor 180 (photo TFT) is read by the read out IC through the second TFT 170 and the readout line 204.

In other words, the signal detected by the read-out integrated circuit according to the amount of light sensed by the photo TFT 140 is changed, so that an image such as a document, an image scan, or a touch input can be sensed. The sensed image may be transferred to the controller or the like or may be embodied in an image of the liquid crystal display panel according to a user's control.

Meanwhile, in the present invention, as shown in FIG. 7, the black matrix B of the color filter array substrate includes the pixel region A in which the pixel electrode 118 is positioned and the photo TFT 140 for sensing light. It is obscured by.

FIG. 8 is a cross-sectional view illustrating a process of sensing light by a liquid crystal display having an image sensing function according to a first embodiment of the present invention, and FIG. 9 is a circuit diagram illustrating a process of sensing external light incident on a photo TFT. 10 is a circuit diagram illustrating a process in which a sensed signal is detected by a readout integrated circuit (I.C).

First, the liquid crystal display shown in FIG. 8 includes a color filter array substrate facing the TFT array substrate on which the photo TFT 140 is formed with the liquid crystal 195 therebetween. A black matrix 254 for masking the second TFT 170 and the like and opening the pixel region and the photo TFT 140 is formed on the color filter array substrate, and a color filter 256 corresponding to the pixel region is formed.

In the liquid crystal display, as shown in FIG. 9, a driving voltage of about 10 V, for example, is applied from the first driving voltage supply line 152 to the driving source electrode 160 of the photo TFT 140. A reverse bias voltage of, for example, about −5 V is applied to the gate electrode 108 of the photo TFT 140 from the second driving voltage supply line 171 and light (eg, external light) is applied to the active layer 114. Is sensed, a photo current path is generated which flows from the driving source electrode 160 to the driving drain electrode 162 via the channel of the active layer 114 according to the sensed amount of light. 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 charge due to the photocurrent is charged at 180. Here, the maximum charge amount of the first storage capacitor 180 may be charged by a voltage difference of about 15V, for example, between the driving source electrode 160 and the gate electrode 108.

As such, while the photo TFT 140 senses light and charge is charged in the first storage capacitor 180, a gate low voltage, for example, -5 V is applied to the gate electrode 108 of the second TFT 170. The second TFT 170 maintains the turn-off state.

Thereafter, as shown in FIG. 10, the second TFT 170, which is supplied with a high voltage, for example, about 20 to 25 V, is supplied to the gate electrode 108 of the second TFT 170 while being turned on. The current path due to the charge charged in the storage capacitor 120 is read out via the source electrode 110, the active layer 114 channel, the drain electrode 112, and the lead-out line 204 of the second TFT 170. It is supplied to an integrated circuit (IC). The sensing signal by the current path supplied in this way is read by the readout integrated circuit IC.

As described above, the liquid crystal display having the image sensing function according to the present invention has not only a display function for realizing an image but also an imyce sensing capability, thereby inputting an external document, a touch, etc. You will have all the functions you can print.

FIG. 11 is a diagram illustrating a liquid crystal display device having an image sensing function according to a second embodiment of the present invention.

FIG. 11 shows the same components except that the top gate 185 is formed on the top layer of the photo TFT 140 and the thickness d1 of the active layer 114 is higher than that of FIGS. 4 and 5. Since the same components as in FIGS. 4 and 5 are given the same reference numerals, detailed description thereof will be omitted.

In FIG. 11, when the top gate 185 is further formed on the top layer of the photo TFT 140 and a reverse bias voltage of about −5 V is applied like the gate electrode 108 of the photo TFT 140, photocurrent generation is suddenly generated. Will increase. Furthermore, as the thickness of the active layer 114 is increased, the generation of photocurrent rapidly increases.

This effect is demonstrated by the experimental data shown in FIG.

In the experimental data shown in FIG. 12, the A curve indicates the thickness of the active layer 114 in the structure in which the top gate 195 is provided on the top layer of the photo TFT 140 (hereinafter referred to as a "double gate photo TFT"). It shows the generation efficiency of the photocurrent with increasing, and the B curve is the thickness d1 of the active layer 114 in the photo TFT 140 (hereinafter referred to as "bottom gate photo TFT") in the first embodiment of the present invention. It shows the generation efficiency of the photo current with increasing).

As can be seen in FIG. 12, when the light is sensed using the "double gate photo TFT", the contrast is about 36.6. When the light is sensed using the "bottom gate photo TFT," about 75.1 light current is generated. It shows efficiency.

Here, as the thickness of the active layer 114 is gradually increased, it can be seen that the generation of the photocurrent is greatly increased compared to the "bottom gate photo TFT" in the "double gate photo TFT" structure. As a result, when the thickness d1 of the active layer 114 is doubled, the photocurrent efficiency of about 210 is obtained in the "double gate photo TFT".

Through such experimental data, in the present invention, when the double gate photo TFT is employed and the thickness d1 of the active layer 114 is formed to be thick, the generation of photocurrent is increased, resulting in light sensing of the photo TFT 140. The efficiency can be increased.

This is believed to be due to the following principle.

12 is a view showing channels and photocurrent paths in a bottom gate TFT, a top gate TFT, and a double gate TFT in which a bottom gate and a top gate are mixed.

First, in the bottom gate TFT, a channel C is formed in a region adjacent to the bottom gate electrode 108, and a photocurrent path D is formed to pass through the channel C. The top gate TFT is a top gate electrode 185. The channel E is formed in the region adjacent to the photoelectric path, and the photocurrent path F is formed to pass through the channel E.

In the double gate TFT having both of these characteristics, channels C and E are formed in the region adjacent to the bottom gate electrode 108 and the region adjacent to the top gate electrode 185, respectively. Two photocurrent paths D and F passing through are formed. As a result, the amount of photocurrent generated increases.

Hereinafter, a method of manufacturing a thin film transistor array substrate of a liquid crystal display panel having an image sensing function according to the present invention will be described in detail with reference to FIGS. 14A to 14E.

First, as the gate metal layer is formed on the lower substrate 142 through a deposition method such as a sputtering method, and then the gate metal layer is patterned by a photolithography process and an etching process, as shown in FIG. 14A, the gate line 102, The gate electrode 108 of the first TFT 106, the gate electrode 108 of the second TFT 170, the first driving voltage supply line 152, the first storage lower electrode 172 of the first storage capacitor, and Gate patterns including the second driving voltage supply line 171 are formed. Here, the second driving voltage supply line 171 is integrated with the first storage lower electrode 172 of the first storage capacitor 180.

The gate insulating layer 144 is formed on the lower substrate 142 on which the gate patterns are formed through a deposition method such as PECVD or sputtering. An amorphous silicon layer and an n + amorphous silicon layer are sequentially formed on the lower substrate 142 on which the gate insulating layer 144 is formed.

Subsequently, the amorphous silicon layer and the n + amorphous silicon layer are patterned by a mask photolithography process and an etching process so that the semiconductor patterns 145 of the first and second TFTs 106 and 170 and the photo TFT 140 are shown in FIG. 14B. Is formed. Here, the semiconductor pattern 145 is formed of a double layer of the active layer 114 and the ohmic contact layer 148. Here, the active layer 114 is formed to a thicker thickness (d1) than in the prior art. For example, when the thickness of the conventional active layer 114 is about 1700 kPa, the thickness d1 of the active layer 114 in the present invention is about 3400 kPa.

After the source / drain metal layer is sequentially formed on the lower substrate 142 on which the semiconductor pattern 145 is formed, the data line 104 as shown in FIG. 14C using a photolithography process and an etching process using a mask, Source electrodes 110, drain electrodes 112 of the first and second TFTs 106 and 170, driving source electrodes 160 and driving drain electrodes 162 of the photo TFT 140, and driving drains of the photo TFT 140. Source / drain patterns including the first storage upper electrode 174 connected to the electrode 162 are formed.

Subsequently, after the passivation layer 150 is entirely formed on the gate insulating layer 144 on which the source / drain patterns are formed, it is patterned by a photolithography process and an etching process. A first contact hole 116 exposing the drain electrode 112 of the 106 and a second contact hole 155 exposing the first driving voltage supply line 152 are formed.

After the transparent electrode material is entirely deposited on the passivation layer 150 by a deposition method such as sputtering, the transparent electrode material is patterned through a photolithography process and an etching process, so that the pixel electrode 118 and the first electrode as shown in FIG. A transparent electrode pattern including a metal pattern 154 for electrically connecting the driving voltage supply line 152 and the driving source line 160 and the top gate 185 of the photo TFT 140 is formed. The pixel electrode 118 is electrically connected to the drain electrode 112 through the contact hole 116. In addition, the pixel electrode 118 is formed to overlap the front gate line 102 with the gate insulating layer 144 and the passivation layer 150 interposed therebetween, thereby forming the second storage capacitor 120.

By such a series of manufacturing processes, it is possible to form a TFT array substrate of a liquid crystal display device having a photo-sensing function.

As described above, a liquid crystal display having an image sensing function, a method of manufacturing the same, and an image sensing method using the same include a sensing element capable of sensing a document, an image, etc. in a liquid crystal display capable of realizing only an image. By doing so, not only an image or the like can be input using a single liquid crystal display device, but also the input image can be embodied in the image as needed. In particular, by adding an image sensing function to the liquid crystal display device, the input and output of the image into the liquid crystal display device are possible, which has a great advantage in terms of cost and volume.

Furthermore, in the present invention, the generation of photocurrent can be increased by introducing a double gate structure in the light sensing thin film transistor. As a result, the light sensing efficiency of the photo sensing element can be improved.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (16)

A gate line and a data line formed on the substrate to cross each other and defining a pixel area in which the pixel electrode is located; A first thin film transistor positioned at an intersection of the gate line and the data line; A photo thin film transistor positioned in one region of the pixel region for sensing light from the outside; The photo thin film transistor is And a top gate electrode positioned at an upper portion thereof and a bottom gate electrode positioned at an upper portion thereof, the liquid crystal display having an image sensing function. The method of claim 1, 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 first storage capacitor and the integrated circuit to selectively supply the sensing signal to the integrated circuit. The method of claim 2, A first driving voltage supply line formed in parallel with the gate line to supply a first driving voltage to the photo thin film transistor; 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 thin film transistor; And a sensing signal transfer line positioned to be parallel to the data line with the pixel area therebetween, and configured to transfer a sensing signal from the second thin film transistor to an integrated circuit. Device. The method of claim 3, wherein The photo thin film transistor is A gate insulating film formed to cover the bottom gate electrode; A first semiconductor pattern overlapping the first gate electrode with the gate insulating layer 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. The method of claim 4, wherein In the first semiconductor pattern A first channel provided by the bottom gate electrode, the first source electrode and the first drain electrode; And a second channel provided by the top gate electrode, the first source electrode, and the first drain electrode. The method of claim 5, When the photo thin film transistor senses light, And a first photocurrent passing through the first channel, and a second photocurrent passing through the second channel. The method of claim 6, The amount of photocurrent generated is proportional to the thickness of the first semiconductor pattern, the liquid crystal display having an image sensing function. The method of claim 6, A protective film formed to cover the photo TFT, And the top gate electrode is formed on the passivation layer and overlaps the first semiconductor pattern. The method according to claim 1 or 8, And the same signal is supplied to the bottom gate electrode and the top gate electrode. The method of claim 1, The pixel electrode and the top gate electrode of the liquid crystal display device having an image sensing function, characterized in that the same material. Forming a gate pattern including a bottom gate electrode of a photo thin film transistor, a second gate electrode of a first TFT, a bottom gate electrode, and a gate line connected to the second gate electrode on a substrate; Forming a gate insulating film on the substrate on which the gate pattern is formed; Forming a first semiconductor pattern overlapping the bottom gate electrode and a second semiconductor pattern overlapping the second gate electrode on the gate insulating layer; A data line intersecting the gate line with the gate insulating layer interposed therebetween, and a first source electrode, a first drain electrode, and a second semiconductor pattern, which are respectively connected to and face each other and face each other. Forming a photo TFT and a first TFT by forming a source / drain pattern including a second source electrode and a second drain electrode positioned to be visible; Forming a protective film having a hole exposing the second drain electrode of the first TFT; And forming a transparent electrode pattern including a pixel electrode connected to the second drain electrode through the hole and a top gate electrode overlapping the first semiconductor pattern with the passivation layer therebetween. A method of manufacturing a liquid crystal display device having a sensing function. The method of claim 11, Forming the gate pattern A first driving voltage supply line formed in parallel with the gate line to supply a first driving voltage to the photo TFT; And forming a second driving voltage supply line connected to the gate electrode and in parallel with the first driving voltage supply line. The method of claim 12, In the first semiconductor pattern And a first channel provided by the bottom gate electrode, the first source electrode, and the first drain electrode, and a second channel provided by the top gate electrode, the first source electrode, and the first drain electrode. A method of manufacturing a liquid crystal display device having an image sensing function. The method of claim 13, When the photo thin film transistor senses light, A first photocurrent is generated via the first channel, and a second photocurrent is generated via the second channel. The method of claim 14, The amount of generation of the photocurrent is in proportion to the thickness of the first semiconductor pattern manufacturing method of a liquid crystal display device having an image sensing function. The method of claim 11, The bottom gate electrode and the top gate electrode is supplied with the same signal characterized in that the manufacturing method of the liquid crystal display device having an image sensing function.

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