Electro phoretic display device including touch panel

Disclosed is an electro phoretic display (EPD) device capable of minimizing the whole thickness and weight by integrally including a photo-sensing touch panel and minimizing the number of lines such as a signal line. The EPD device includes first and second substrates facing each other, a plurality of gate lines, a plurality of common lines, and a driving voltage line formed on the first substrate in a first direction, an output line formed and a plurality of data lines defining pixel regions by crossing the gate lines in a second direction, pixel transistors formed at intersecting parts between the respective gate lines and the data lines, a pixel electrode formed at each pixel region, a sensing transistor formed between one of the common lines and the driving voltage line, an output transistor formed between one of the gate lines, adjacent to the sensing transistor, and the sensing transistor to transmit an output signal to the output line, a sensing capacitor formed between one of the common lines and a connection part between the sensing transistor and the output transistor, a common electrode formed over the entire surface of the second substrate, and an electro phoretic layer formed between the first and the second substrates.

This application claims the benefit of Korea Patent Application No. 10-2008-0128452 filed on Dec. 17, 2008, the entire contents of which is incorporated herein by reference for all purposes as if fully set forth herein.

BACKGROUND

1. Field of the Invention

The present disclosure relates to an electro phoretic display device, and more particularly, to an electro phoretic display device capable of minimizing the whole thickness and weight by integrally including a photo-sensing touch panel and minimizing the number of lines such as a signal line.

2. Discussion of the Related Art

An electro phoretic display (EPD) device refers to a type of flat panel display used for an E-book, comprising a pair of indication plates each equipped with a field generating electrode, and a micro capsule disposed between the pair of indication plates, the micro capsule containing electric ink having white and black pigment particles respectively electrified to positive or negative potentials.

The EPD device applies voltage to the two facing electrodes so that a potential difference is caused between opposite ends of the electrodes, accordingly moving the black and white electrified pigment particles respectively to the electrodes having opposite polarities and thereby displaying an image.

Such an EPD device is advantageous because it displays an image naturally as if being printed on paper because it has high reflectivity and contrast ratio while being relatively less subject to a viewing angle. Also, the EPD device is capable of maintaining the image without continuous application of a voltage owing to the bistability of black and white, and therefore power consumption can be reduced. Furthermore, in contrast to an LCD, the EPD device does not need a polarizing plate, an alignment layer, and an LCD and so on, thus being advantageous in terms of price competitiveness.

A display device, including the EPD device, as used for some applications require a touch input to operate the device. Thus, a touch screen panel has been mounted on a display panel.

Generally, the touch screen panel may be divided into a resistance type, a capacitor type, and a photo-sensing type, depending on the operating system. These days, the display device is structured by mounting the touch screen panel on the display panel and accordingly is used as a combined display and input device.

However, when the touch screen panel is applied to the conventional EPD device, some problems are incurred as follows.

The EPD device is structured in such a manner that electric ink is interposed between two substrates having a pixel electrode and a facing electrode of the pixel electrode, respectively, and a voltage difference is generated between the pixel electrode and the facing electrode. Therefore, the EPD device operates as ions in the electric ink are moved to corresponding polarities by the voltage difference.

In order to dedicatedly attach the touch screen panel on the EPD device, the touch screen panel and the EPD device need to be separately formed and attached, thereby increasing the whole thickness and the number of processes.

Furthermore, the overlapped structure of the two panels would deteriorate transmittance as a display device.

BRIEF SUMMARY

An EPD device including a touch panel, comprises: first and second substrates facing each other, a plurality of gate lines, a plurality of common lines, and a driving voltage line formed on the first substrate in a first direction, an output line and a plurality of data lines defining pixel regions by crossing the gate lines, wherein the output line and the data lines are formed in a second direction crossing the first direction, pixel transistors formed at intersecting parts between the respective gate lines and the data lines, a pixel electrode formed at each pixel region, a sensing transistor formed between one of the common lines and the driving voltage line, an output transistor formed between one of the gate lines, adjacent to the sensing transistor, and the sensing transistor to transmit an output signal to the output line, a sensing capacitor formed between one of the common lines and a connection part between the sensing transistor and the output transistor, a common electrode formed over the entire surface of the second substrate, and an electro phoretic layer formed between the first and the second substrates.

In another aspect of the present invention, a method for manufacturing an EPD device including a touch panel, comprises: preparing first and second substrates facing each other; forming a plurality of gate lines, a plurality of common lines and a driving voltage line in a first direction, first and second gate electrodes protruded from the gate lines, and sensing gate electrodes protruded from the common lines on a first substrate; forming first and second semiconductor layers respectively overlapping with the first and the second gate electrodes, and a third semiconductor layer overlapping with the sensing gate electrode; forming a data line and an output line in a second direction crossing the first direction, a source electrode protruded from the data line and a drain electrode at an interval from the source electrode on the first semiconductor layer, an output drain electrode protruded from the output line and an output source electrode at an interval from the output drain electrode on the second semiconductor layer, and a sensing source electrode and a sensing drain electrode separated from and corresponded to each other on the third semiconductor layer; forming a pixel electrode on each pixel region disposed on intersecting parts between the gate lines and the data lines; forming a common electrode on the entire surface of the second substrate; and forming an electro phoretic layer between the first and the second substrates.

FIG. 1is a circuit diagram of an electro phoretic display (EPD) device according to an embodiment of the present invention.

Although not shown, the EPD device comprises an EPD panel, a gate driving unit connected to the EPD panel, a data driving unit, a gray scale voltage generation unit connected to the data driving unit, a signal control unit controlling the above parts, and a photo-sensing unit detecting light varied according to a finger contact and the like and thereby determining the position.

In addition, the EPD device according to the embodiment comprises first and second substrates facing each other, and an electro phoretic layer (not shown) interposed between the first and the second substrates, including a micro capsule containing positive and negative ions, that is, opposite polarities.

The EPD panel in terms of an equivalent circuit as shown inFIG. 1comprises pluralities of gate lines101(101′) and data lines102defining pixel regions, and pixel transistors Tp formed at intersecting parts between the respective gate lines101and the data lines102. Optionally, a photo-sensing unit (T1, Cs and T2) is further provided at every n-number of pixels (n: natural number). In addition, common lines151are further formed at a lower part of each gate line101parallel with the gate line101.

The pixel transistor Tp is connected to an electro phoretic capacitor Cep formed between common electrodes (not shown) formed on the second substrate, and to a storage capacitor Cst formed between the pixel electrode and the common line151. The pixel transistor Tp is applied with signals from the gate driving unit and the data driving unit through the gate line101and the data line102.

The photo-sensing unit further comprises a driving voltage line Vdry121and an output line SL112. Additionally, a sensing transistor T1113is formed between the driving voltage line Vdry121and the common line Vcom151, an output transistor T2117is formed at a shear gate line Gn-1101and a drain terminal of the sensing transistor T1113, and a sensing capacitor Cs115is formed between the drain terminal of the sensing transistor T1113and the common line Vcom151.

Here, the drain terminal of the sensing transistor T1113is connected to one electrode of the sensing capacitor Cs115through a node N, and also connected to a source terminal of the output transistor T2117.

That is, the photo-sensing unit is formed among the shear gate line101, the driving voltage line121and the common line151. Density of the photo-sensing unit can be adjusted as necessary. The photo-sensing unit is structured by unit equivalent to or smaller than (unit pixel*n) a minimum area touchable at any case. For example, the photo-sensing unit may be formed at every green pixel, or at every n-number of pixels (n: natural number).

The photo-sensing unit periodically commands output of photo-sensing signals through the shear gate line Gn-1101, receives the photo-sensing signals accordingly output through the output line SL112, processes the signals, and outputs corresponding data to a central control unit (not shown) so that new image signals can be supplied to the EPD device in accordance with the data.

More specifically, the sensing transistor T1113is a 3-terminal device, of which a gate terminal is connected to the common line151, a source terminal is connected to the driving voltage line121and a drain terminal is connected to the node N.

The output transistor T2117is also a 3-terminal device, of which a gate terminal is connected to the shear gate line Gn-1101, a source terminal is connected to the node N, and a drain terminal is connected to the output line SL112.

In this case, when light is emitted to a channel unit semiconductor of the sensing transistor T1113, the channel unit semiconductor comprising amorphous silicon forms a photo current. The photo current is flowed to the sensing capacitor Cs115and the output transistor T2117by the driving voltage Vdrv applied to the driving voltage line121, and the sensing capacitor Cs115stores the current as a signal voltage. Here, an electrode on the other side of the sensing capacitor Cs115is applied with common voltage in connection with the common line151, and maintains a constant common voltage such that the sensing transistor T1113can be operated only by light, not being influenced by surrounding voltages.

Here, the driving voltage line121is disposed parallel with the gate line101. The driving voltage line121is formed of the same metal and disposed on the same layer as the gate line101and the common line151at certain distances from the gate line101and the common line151. The output line112is formed of the same metal and on the same layer as the data line102. The photo-sensing unit is formed throughout the shear gate line101, the driving voltage line121, and the common line151adjoining them. Here, since the common line151and the shear gate line101have not only the EPD function but also a photo sensing function, on and off states of the sensing transistor113and the output transistor117are controlled by the common line151and the shear gate line101, respectively. Thus, the signal lines such as the gate line101and the common line151used for the EPD are also used for driving the photo-sensing unit. Therefore, at least two signal lines can be omitted from the EPD device, consequently improving the NA.

Hereinafter, the EPD device will be described in greater detail with reference to the drawings including plan views and sectional views.

FIG. 2is a plan view of the EPD device, andFIG. 3is a sectional view of a first substrate shown inFIG. 2, cut along lines I-I′, II-II′ and III-III′.

Referring toFIG. 2andFIG. 3, the EPD device according to the embodiment of the present invention comprises the pluralities of gate lines101and data lines102arranged on a first substrate100, intersecting to define pixel regions, the pixel transistors Tp formed at the intersectional parts between the gate lines101and the data lines102, the common lines151arranged parallel with the respective gate line101to pass through the pixel regions nearby, and the pixel electrodes104formed corresponding to the respective pixel regions. The common line151is formed of the same metal and on the same layer as the gate line101at a certain interval from the gate line101.

As shown inFIG. 3which is the sectional view cut along the line I-I′, the pixel transistor Tp comprises a gate electrode101aprotruded from the gate line101, a source electrode102aprotruded from the data line102to overlap the gate electrode101a, a drain electrode102bdistanced from the source electrode102a, and first semiconductor layers142(shown inFIG. 2) and 142aformed in contact with lower sides of the data line101and the source/drain electrodes102aand102b. A gate dielectric171is further formed on the first substrate100which includes the gate line101and the gate electrode101a. A passivation layer172is further formed on the first substrate100which includes the data line102and the source/drain electrodes102aand102b. The pixel electrode104is formed on the passivation layer172of each pixel region separately from every other pixel electrode104. The source electrode102ahas an E shape, and the drain electrode102balso has an E shape in facing engagement with the E-shape source electrode102a, being separated from the source electrode102a. Since the source electrode102ahas the E shape, width and length of a channel between the source electrode102aand the drain electrode102bare increased, thereby improving the operation performance of the pixel transistor Tp.

As aforementioned, the photo-sensing units are formed optionally at every n-number of pixels. The output line112is further provided adjacently parallel with the right data line102of the corresponding pixel. In addition, the driving voltage line121is further provided adjacently parallel with the shear gate line Gn-1and the common line151.

The sensing transistor T1and the sensing capacitor Cs of the photo-sensing unit are configured as shown inFIG. 2and the II-II′ line sectional view ofFIG. 3.

First, the sensing transistor T1comprises the sensing gate electrode151aprotruded from the common line151, the gate dielectric171formed on the first substrate100to cover the sensing gate electrode151a, a second semiconductor layer141forming an island and covering the sensing gate electrode151a, and a sensing source electrode132and a sensing drain electrode131formed on both sides of the second semiconductor layer141. Here, the sensing source electrode132having a layer form is electrically connected to the driving voltage line121disposed at the lower part thereof through a contact hole, and applied with the driving voltage signal Vdrv. That is, the source terminal of the sensing transistor Ts is connected with the driving voltage line121.

With respect to the sectional surface, the sensing drain electrode131includes the gate dielectric171interposed at a lower part thereof such that the sensing capacitor Cs is formed between the sensing drain electrode131and the common line151disposed at the lower part. The sensing drain electrode131operates as the node N in the circuit shown inFIG. 1. The node N is connected with the sensing drain electrode131of the sensing transistor T1, the electrode formed on one side of the sensing capacitor Cs, and further with the source electrode of the output transistor T2.

Here, the sensing capacitor Cs is defined to include the sensing drain electrode131corresponding to the node N, the common line151formed at the lower part, and the gate dielectric171interposed between the sensing drain electrode131and the line electrode151.

In addition, as shown inFIG. 2and the line sectional view ofFIG. 3, the output transistor T2comprises the output gate electrode101bprotruded from the shear gate line Gn-1101to correspond to the photo-sensing unit, the gate dielectric171covering the output gate electrode101b, a third semiconductor layer143aforming an island covering the output gate electrode101b, an output source electrode112boverlapping with the third semiconductor layer143aand having an E shape, and a drain electrode112aprotruded from the output line112and arranged in facing engagement with the E-shape output source electrode112b, being separated from the output source electrode102b.

At the node N, the output source electrode112band the sensing drain electrode131are integrally interconnected.

The passivation layer172is further formed over the entire surface of the first substrate100including the sensing transistor T1, the sensing capacitor Cs and the output transistor T2. The pixel electrode104is formed on the passivation layer172of each pixel region.

As shown in the drawings, the pixel electrode104may be in the form of a single layer comprising a reflective electrode or a double layer comprising a transparent electrode and a reflective electrode.

Hereinafter, the operation of the above structured photo-sensing unit will be explained.

The driving voltage, for example 10˜15V, is applied to the source electrode of the sensing transistor T1113through driving voltage line121. Additionally, a voltage of 0V is applied to gate electrode of the sensing transistor T1113through the common line151. Therefore, when a predetermined light is sensed at the semiconductor layer of the sensing transistor T1, a path of a photo current is formed, flowing from the source electrode of the sensing T1to the drain electrode through the channel, according to intensity of the sensed light. The photo current flows to the sensing capacitor Cs115through the drain electrode of the sensing transistor T1. According to this, the sensing capacitor Cs between the driving voltage line121and the common line151is electrified with electric charges by the photo current. Thus, the charges electrifying the sensing capacitor Cs are passed through the output transistor T2and the output line112, and amplified and read at a read-out IC (not shown) connected to the output line112. Touch input is detected in accordance with the amplified photo current value.

In other words, touch input images can be sensed by the signals detected by the read-out IC in connection with the output line112varied according to the intensity of the light sensed by the sensing transistor T1. The sensed images may be transmitted to the control unit or implemented on a screen of the EPD panel according to a user's control.

Hereinafter, a manufacturing method for the EPD device will be explained.

FIG. 4AthroughFIG. 4Fare plan views illustrating the manufacturing processes of the EPD device according to the embodiment of the present invention. Herein, the photo-sensing unit is formed at every “n” pixels (“n” is a natural number).

As shown inFIG. 4A, a first metal is vapor-deposited on the first substrate100and then selectively removed, thereby forming the gate line101in a first direction including the gate electrodes101afor each pixel. In addition, the common line151is formed in the first direction at an interval from the gate line101. Simultaneously, the driving voltage line121is formed in the first direction at an upper part of the common line151to correspond to the photo-sensing unit. In addition, the EPD device further comprises the sensing gate electrode151aprotruded from the common line151toward the photo-sensing unit, and the output gate electrode101bprotruded along with the sensing gate electrode101afrom the shear gate line Gn-1passing through the photo-sensing unit.

Next, the gate dielectric171(FIG. 3) is formed on the first substrate100including the gate line101, the gate electrode101a, the sensing gate electrode151a, the driving voltage line121, the common line151and the output gate electrode101b.

Afterward, as shown inFIG. 4B, a semiconductor layer is vapor-deposited on the upper part of the gate dielectric171(FIG. 3) and selectively patterned, accordingly forming semiconductor layers142and143in a second direction crossing the first direction to define the pixel region along with the gate line101, and the first to the third semiconductor layers142a,141and143arespectively overlapping with the gate electrode101a, the sensing gate electrode151aand the output gate electrode101b.

Referring toFIG. 4C, the gate dielectric171is selectively removed so that the driving voltage line121is partly exposed corresponding to the photo-sensing unit. Accordingly, a gate hole133is formed.

Next, as shown inFIG. 4D, a second metal is vapor-deposited on the gate dielectric171that includes the semiconductor layers142and143having the gate hole133and the first to third semiconductor layers142a,141and143a, and then overlapped on the semiconductor layers142and143, thereby forming the data line102in the second line to define the pixel region by crossing the gate line101, and also forming the output line112adjacent to the photo-sensing unit. The source electrode102aoverlaps the first to the third semiconductor layers142a,141and143a. Especially, the source electrode102ais protruded between the respective pixels from the data line102so as to overlap the semiconductor layer pattern142a. Furthermore, there are also provided the drain electrode102bformed at an interval from the source electrode102a, the output source electrode112aprotruded from the output line112to overlap with the semiconductor layer pattern143a, the output drain electrode112bformed at an interval from the output source electrode112a, and the sensing source electrode132and the sensing drain electrode131formed on both sides of the semiconductor layer pattern141.

Next, as shown inFIG. 4E, the passivation layer172is formed on the entire surface of the gate dielectric171including the data line102, the source electrode and the drain electrode102aand102b, the output source electrode112a, the output drain electrode112band the source pattern and the drain pattern131and132. After that, a contact hole136is formed to expose predetermined parts of the upper part of the drain electrode102b.

Referring toFIG. 4F, next, the pixel electrode is vapor-deposited on the entire surface including the contact hole136and then selectively removed so that the pixel electrodes are formed corresponding to the respective pixel regions. As described above, the pixel electrode104may be a double layer comprising a transparent electrode and a reflective electrode or a single layer comprising a reflective electrode. Therefore, light emitted by an electro-phoretic micro capsule (not shown) formed between the first substrate100and the second substrate (not shown) facing each other can be reflected from the pixel electrode104and output to the outside.

Hereinafter, the structure of the first substrate, that is, a lower substrate of the EPD device, and the second substrate facingly mounted to the first substrate will be explained in detail.

FIG. 5is a sectional view of the EPD device, cut along the line I-I′ ofFIG. 2.

As shown inFIG. 5, the EPD device comprises the pixel transistor Tp formed on the first substrate100and the sensing capacitor Cs, the sensing transistor T1and the output transistor T2constituting the photo-sensing unit, which are explained above withFIG. 2toFIG. 4F. In addition, the EPD device comprises a common electrode210formed through the entire surface of the second substrate200facing the first substrate100. Also, an electro phoretic layer including the micro capsule300is formed between the pixel electrode104and the common electrode210of the first and the second substrates100and200. As the electro phoretic layer is electrophoresed by voltage application, negative charges and positive charges in the micro capsule300can be separately arranged.

The electro phoretic layer comprises a plurality of the micro capsules300, and a binder binding the micro capsules300. Each of the micro capsules300contains white ink particles310electrified to negative (−) or positive (+) potential, black ink particles320electrified by the opposite potential to the white ink particles310, and a transparent dielectric. For instance, if the white ink particles310are electrified to positive potential (+), the black ink particles320are electrified to negative potential (−).

As external light emitted from the outside is directly reflected by the white ink particles310, a white image is displayed.

More specifically, as shown in the drawings, when a negative voltage (−) is applied to the pixel electrode104with respect to the common voltage Vcom applied to the common electrode210, the white ink particles310having the positive charges are moved toward the first substrate100whereas the black ink particles320having the negative charges are moved toward the common electrode210of the second substrate200. Accordingly, a black image is visualized.

On the other hand, when a positive voltage (+) is applied to the pixel electrode104with respect to the common voltage Vcom, the black ink particles320having the negative charges are moved toward the first substrate100whereas the white ink particles310having the positive charges are moved toward the second substrate200. Accordingly, a white image is visualized.

As apparent from the above description, the EPD device according to any one of the above-described embodiment of the present invention has following advantages.

First of all, since a photo-sensing circuit unit functioning as a touch panel is formed on a substrate having a TFT, an in-cell type touch panel can be implemented in the EPD device.

Second, the photo-sensing circuit unit comprises a photo-sensing transistor, an output transistor detecting a signal corresponding to sensing by the photo-sensing transistor, and a sensing capacitor, while omitting two signal lines by utilizing part of signal lines connected to the photo-sensing transistor and the output transistor as a shear gate line and a common line. Such omission of the signal lines is effective in increasing NA, reducing weight of the device and simplifying the processes.

Third, since the signal lines are omitted and simplified as above, an installment space for the photo-sensing circuit unit can be secured even when implementing a high definition EPD device. Accordingly, the in-cell type touch recognition can be achieved in the high definition EPD device.

Fourth, the photo-sensing circuit unit is disposed at an overlapping position between the shear gate line and the common line so that a power line for driving the sensing transistor lies parallel with the gate line. Thus, non-operational areas generated at connection parts of the signal lines are minimized, thereby preventing deterioration of NA and image quality.