TFT substrate having data lines as touch driving electrode and common electrodes as touch sensing electrode and touch display panel using same

A TFT substrate for a touch display panel of reduced thickness defines a display area and a surrounding non-display area. The TFT substrate includes a first conductive layer on the substrate and a second conductive layer on the first conductive layer. In the display area, the first conductive layer includes data lines and the second conductive layer includes common electrodes. Each common electrode extends as a strip along a first direction. Each data line extends along a second direction. The first direction intersects the second direction. Each data line crosses the common electrodes. Each data line functions as a touch driving electrode and each common electrode functions as a touch sensing electrode.

FIELD

The subject matter herein generally relates to a thin film transistor (TFT) substrate and a touch display panel using the TFT substrate.

BACKGROUND

A touch display panel can include touch sensing structures. A conventional mutual capacitive touch display panel may include a plurality of touch driving electrodes and a plurality of touch sensing electrodes. However, the touch driving electrodes and the touch sensing electrodes are usually located on different layers, which does not reduce an overall thickness of the touch display panel. Therefore, there is room for improvement in the art.

DETAILED DESCRIPTION

A definition that applies throughout this disclosure will now be presented.

Referring toFIG. 1, an exemplary embodiment of a touch display panel100is an in-cell touch display panel. The touch display panel100includes a TFT substrate10, a color filter substrate60facing the TFT substrate10, a liquid crystal layer80between the TFT substrate10and the color filter substrate60, and a plurality of conventional photo spacers (not shown) for supporting a gap between the TFT substrate10and the color filter substrate60.

FIG. 2throughFIG. 3illustrate the TFT substrate10. As shown inFIG. 3, the TFT substrate10includes a substrate11, a TFT layer12on a surface of the substrate11, a first conductive layer13formed on a surface of the TFT layer12away from the substrate11, a second conductive layer14on a surface of the first conductive layer13away from the substrate11, and a third conductive layer16formed on a surface of the second conductive layer14away from the substrate11.

As shown inFIG. 3, the TFT substrate10further includes a first insulating material layer101between the first conductive layer13and the second conductive layer14, to insulate the first conductive layer13from the second conductive layer14. The TFT substrate10further includes a second insulating material layer103between the second conductive layer14and the third conductive layer16, to insulate the second conductive layer14from the third conductive layer16. The TFT substrate10further includes a planarization layer105on the second insulating material layer103which covers the third conductive layer16. The planarization layer105is electrically insulating.

The TFT layer12has a multilayer structure (not shown). The TFT layer12includes a plurality of TFTs124(as shown inFIG. 4). Each TFT124is conventional TFT in the art. As shown inFIG. 4, each TFT124includes a gate electrode1241, a source electrode1243, and a drain electrode1245.

Referring toFIG. 2andFIG. 3, the second conductive layer14is patterned to form a plurality of common electrodes20. The second conductive layer14is made of a transparent conductive material. As shown inFIG. 2, each common electrode20extends as a strip shape along a first direction D1shown inFIG. 2, and the plurality of common electrodes20is arranged in a row along the second direction D2shown inFIG. 2. The first direction intersects the second direction. In this exemplary embodiment, the first direction is perpendicular to the second direction. It is known that the common electrodes20are configured to cooperate with the pixel electrode137(shown inFIG. 4) to form an electric field (not shown). The electric field rotates the liquid crystal molecules (not shown) in the liquid crystal layer80. In this exemplary embodiment, the common electrodes20are also configured as touch sensing electrodes.

Referring toFIG. 2andFIG. 3, the third conductive layer16is patterned to form a plurality of connecting wires30. As shown inFIG. 2, each connecting wire30extends along the second direction D2shown inFIG. 2, and the plurality of connecting wires30is arranged in a row along the first direction D1shown inFIG. 2. Each connecting wire30crosses the plurality of common electrodes20.

As shown inFIG. 2, the TFT substrate10defines a display area110and a non-display area120surrounding the display area110. The plurality of common electrodes20is located in the display area110. As shown inFIG. 2, the TFT substrate10further includes a control circuit50located in the non-display area120. Each of the common electrodes20is electrically connected to the control circuit50by at least one connection wire30. The control circuit50is configured to receive touch signals from the common electrode20.

In this embodiment, as shown inFIG. 2, the plurality of connecting wires30is divided into a plurality of connecting wire groups300. The plurality of connecting wire groups300are arranged at intervals along the first direction. Each connecting wire group300includes at least one connecting wire30. In this embodiment, each connecting wire group300includes seven connecting wires30. Each connecting wire group300is electrically connected to one common electrode20and is electrically insulated from other common electrodes20. Therefore, a number of the connecting wire groups300is equal to a number of the common electrodes20. One end of each connecting wire set300is electrically coupled to the control circuit50, such that each common electrode20is electrically coupled to the control circuit50by one connecting wire group300.

The connecting wires30in each connecting wire group300are electrically connected in parallel, to reduce the overall resistance of the connecting wire group300. It can be understood that the number of the connecting wires30in each connection wire group300is not limited to seven, and may also be any number larger than one, such as two, three, or more.

Referring toFIG. 3, the second insulating material layer103is located on the first insulating material layer101and covers the common electrodes20. The third conductive layer16forming the plurality of connecting wires30is located on the second insulating material layer103. Some of the connecting wires30in the plurality of connecting wires30are electrically coupled to the common electrodes20by via holes104. Each via hole104extends through the second insulating material layer103. In this exemplary embodiment, three connecting wires30in each connecting wire group300are electrically coupled to the corresponding one common electrode20. It can be understood that the number of the connection wires30in each connection wire group300electrically coupled to a common electrode20is not limited to three, and may also be one, two or more. At least one connection wire30must be electrically coupled to the corresponding one common electrode20.

Referring toFIG. 3andFIG. 4, the first conductive layer13is patterned to form a plurality of data lines132. As shown inFIG. 4, each data line132extends along the second direction D2shown inFIG. 4, and the plurality of data lines132is arranged at intervals along the first direction D1shown inFIG. 4. Since each common electrode20extends along the first direction D1, each data line132intersects and crosses the plurality of common electrodes20. It is known that the data lines132are configured to transmit data signals to the source electrodes of the TFTs. In this exemplary embodiment, the data lines132are also configured as touch driving electrodes.

As shown inFIG. 3, the first insulating material layer101is located on the TFT layer12and completely covers the plurality of data lines132. The second conductive layer14forming the common electrodes20is located on the first insulating material layer101.

As shown inFIG. 4, the TFT substrate10further includes a plurality of scan lines134. Each scan line134extends along the first direction D1shown inFIG. 4, and the plurality of scan lines134is arranged at intervals along the second direction D2shown inFIG. 4. It is to be understood that the scan lines134and the data lines132are not located at a same layer, the scan lines134being formed by conductive layers other than the first conductive layer13. The plurality of scan lines134is insulated from the plurality of data lines132. The scan lines134and the data lines132intersect with each other to define pixel units136. At least one TFT124and a pixel electrode137are located in each pixel unit136. The gate electrode1241of one of the at least one TFT124is electrically coupled to one scan line134, a source electrode1243of the one of the at least one TFT124is electrically coupled to one data line132, and a drain electrode1245of the one of the at least one TFT124is electrically coupled to a pixel electrode137.

As described above, each connecting wire30extends along the second direction D2shown inFIG. 2, and each data line132extends along the second direction D2shown inFIG. 4, the connecting wires30and the data lines132always being parallel. In this exemplary embodiment, a number of the connection wires30is equal to a number of the data lines132. Referring toFIG. 3, in this exemplary embodiment, the connecting wires30and the data lines132are made of conductive material. A projection of each connecting wire30on the substrate11overlaps a projection of one data line132on the substrate11, thus the connecting wires have no effect on the aperture ratio.

As shown inFIG. 4, the TFT substrate10further includes a demultiplexer138in the non-display area120. The demultiplexer138is located between the plurality of data lines132and the control circuit50. Each data line132is electrically coupled to the control circuit50by the demultiplexer138. The demultiplexer138has three selection terminals, RSW, GSW, and BSW. The demultiplexer138outputs signals to all of the data lines132according to the signals of the selection terminals RSW, GSW, and BSW. Data signals or touch driving signals can be applied to the data lines132by the control circuit5and the demultiplexer138. Several adjacent data lines132may be used as one touch driving electrode.

The touch display panel100adopts a time-division driving method. During a display period, display driving signals (e. g. a common electrode voltage) are applied to the common electrodes20, and a data signals are applied to the data lines132. During a touch sensing period, touch driving signals are applied to the data lines132. The common electrodes20receive the touch sensing signals and transmit the touch sensing signals to the control circuit50by the connecting wires30.

The drive-time sequence of the TFT substrate10is shown inFIG. 5. The TFT substrate10is driven in a plurality of frame times. Each frame time includes a display period T1and a touch sensing period T2. During the display period T1, the control signals of the three selection terminals RSW, GSW, and BSW of the demultiplexer138are sequentially alternating pulse signals. Data voltage signals are applied to the data lines132, and each common electrode20receives a direct current voltage (common electrode voltage), each of the scan lines134receiving the scan signal in sequence. During the touch sensing period T2, the control signals of the three selection terminals RSW, GSW, and BSW of the demultiplexer138are all switched to a direct current voltage (high potential voltage), and touch driving signals (pulse signal voltages) are applied to the data lines132. Each common electrode20receives a voltage which is different from the common electrode voltage (e. g. higher than the common electrode voltage in this exemplary embodiment), and scan signals stop being applied to the scan lines134.

During the touch sensing period T2, each data line132functions as a touch driving electrode and each common electrode20functions as a touch sensing electrode, each data line132and one common electrode20forming a first mutual capacitor. Each data line132also cooperates with one connecting wire30that overlaps the data line132to form a second mutual capacitor. Each common electrode20cooperates with a connecting wires30that is not electrically coupled to the common electrode20to form a parasitic capacitor.

The TFT substrate10does not need to set additional electrodes functioning as the touch driving electrode and the touch sensing electrodes, thus thickness the TFT substrate can be effectively reduced.