Touch panel for display device and method of fabricating the same

A touch panel for a display device and a method of fabricating the same are disclosed. The touch panel for the display device includes upper and lower substrates, first and second transparent electrodes on opposing surfaces of the upper and lower substrates, a plurality of metal electrodes in a circumference of the first and second transparent electrodes, and a flexible printed cable having a plurality of signal applying lines extended from the upper and lower substrates to a rear side of the display device for applying signal voltages to the metal electrodes, wherein the flexible printed cable is bent at a corner of the upper and lower substrates from a top to a bottom of the display device, and has a first part extended from the corner of the display device and a second part extended from the first part and the first and second parts being perpendicular to each other.

This application claims the benefit of the Korean Patent Application No. P2002-087769 filed on Dec. 31, 2002, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a touch panel, and more particularly, to a touch panel for a display device and a method of fabricating the same. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for preventing an electrostatic discharge.

2. Discussion of the Related Art

In order to efficiently use various electronic devices, touch panels have been widely used to input signals on display surfaces without additional remote controllers or other input devices. The touch panels have been widely integrated with display surfaces of flat display devices such as electronic calculators, liquid crystal display (LCD) devices, plasma display panel (PDP) devices, electroluminescence (EL) devices, and cathode ray tubes (CRTs). By integrating the touch panels with display devices, a user can select desired information while watching an image displayed on the display device.

Depending upon a sensing method when a user touches a display surface, the touch panels may be classified into a resistive type, an electromagnetic type, a capacitor type, an infrared type, and a light sensor type.

Among the various type touch panels, the resistive type touch panel includes an upper transparent substrate having an upper electrode, and a lower transparent substrate having a lower electrode. The lower and upper transparent substrates are bonded to each other at a constant interval. Accordingly, if the surface of the upper transparent substrate is touched at a predetermined point using input means, e.g., a finger, a pen, and etc., the upper electrode formed on the upper transparent substrate is electrically connected to the lower electrode formed on the lower transparent substrate. A voltage change by a resistance value or a capacitance value of the touched point is then detected and output along with a location defined by coordinates of the touched point.

The related art analog resistive type touch panel will be described with reference to the accompanying drawings.FIG. 1is a block diagram illustrating how a signal is applied for the operation of the related art touch panel. As shown inFIG. 1, a touch panel100is positioned on an LCD device130having a backlight140, in which transparent electrodes are formed on opposing surfaces of lower and upper substrates, and metal electrodes are formed for providing signal voltages to the transparent electrodes according to the X-axis and Y-axis directions. Then, the electrodes are connected to a touch panel controller110for applying the signal voltages to the metal electrodes of the touch panel100, or reading the voltage of a touching point. Also, the touch panel controller110is connected to a micro-computer120for controlling the entire system including a display device.

Hereinafter, a touch panel for an LCD device according to the related art will be described with reference to the accompanying drawings.

FIG. 2is a plane view schematically illustrating the related art touch panel.FIGS. 3A and 3Bare plane views illustrating metal electrodes and signal applying line application on respective upper and lower substrates ofFIG. 2.FIG. 4is a cross-sectional view taken along line IV-IV ofFIG. 2.FIG. 5is a cross-sectional view taken along line V-V ofFIG. 2.FIG. 6is a cross-sectional view taken along line VI-VI ofFIG. 2.

As mentioned above, the related art touch panel for the display device is used as a means for inputting signals on the display surface of the LCD device. Referring toFIG. 2, the related art touch panel for the display device includes a viewing area corresponding to the display surface of the display device, and a dead space region20corresponding to the circumference of the viewing area surrounding the viewing area. With this configuration, the upper and lower transparent substrates are bonded to each other through an insulating adhesive provided in the dead space region20. That is, rectangular upper and lower PET (polyethylene terephtalate) substrates1and2corresponding to the display surface of the display device are formed to face into each other, and then first and second transparent electrodes3and4are respectively formed on the upper and lower PET substrates1and2. Then, the upper and lower PET substrates1and2are bonded to each other by the insulating adhesive provided in the dead space region20at a predetermined interval.

Accordingly, if a predetermined portion of the upper PET substrate1is touched with a pen or a finger, the first and second transparent electrodes3and4are also electrically connected to each other at the predetermined portion, so that a voltage, varied by a resistance or a resistance value of the touching point, is detected and output. In order to detect the voltage output by the resistance value or the capacitance value at the predetermined portion, a signal applying line is connected to apply a voltage to the first and second transparent electrodes3and4, and to read the voltage value varied by the touching point. The signal applying line is connected to the first and second transparent electrodes3and4in the dead space region20.

The related art touch panel for the display device will be explained in more detail with reference to the plane and cross-sectional views described below.

Referring toFIGS. 3A and 3B, andFIGS. 4 to 6, the transparent upper and lower PET substrates1and2are formed to have a size and a shape corresponding to the display surface of the display device. The first and second transparent electrodes3and4are formed on each opposing surface of the upper and lower PET substrates1and2. Then, metal electrodes (e.g., Ag paste) are formed in the dead space region20. Referring toFIG. 3A, first and second metal electrodes5aand5bare formed in the dead space region20at the left and right sides of the upper PET substrate to be connected to the first transparent electrode3. The first and second metal electrodes5aand5bare connected to first and second signal applying lines5cand5ddirectly connected to external power sources Vcc and Vss for applying voltage signals from the external.

Herein, as shown inFIGS. 4 and 5, the first and second metal electrodes5aand5bare electrically connected to the transparent electrode3, so that the first and second metal electrodes5aand5bare directly formed on the transparent electrode3. However, the second signal applying line5dis electrically connected to the second metal electrode5b, as shown inFIG. 4, and electrically insulated from the transparent electrode3. In this respect, a first insulating layer10ais formed between the transparent electrode3and the electrode having the second signal applying line5d. As shown in the second signal applying line5d, the first signal applying line5cis directly connected to the first metal electrode5afor applying the voltage signal, and an insulating layer is formed between the transparent electrode3and the electrode having the first signal applying line5c.

Accordingly, the first and second signal applying lines5cand5dare bonded to flexible printed cable (FPC)7at one portion of the substrate by a conductive adhesive8a, so that the external voltage signals are applied to the first and second metal electrodes5aand5bthrough the first and second signal applying lines5cand5d. Also, as shown inFIG. 3B, third and fourth metal electrodes6aand6bare formed in the dead space region20at the lower and upper sides of the lower PET substrate2to be connected to the transparent electrode4, and third and fourth signal applying lines6cand6dare formed in the dead space region20at the left side of the lower PET substrate2to be electrically connected the third and fourth metal electrodes6aand6bto the FPC7. Referring toFIG. 4, as shown in the first and second signal applying lines5cand5d, a second insulating10bis formed between the transparent electrode4and the signal applying line6cto electrically insulate the signal applying line6cfrom the transparent electrode4. Also, the FPC7is connected to the third and fourth metal electrodes6aand6bin the dead space region20through the third and fourth signal applying lines6cand6d.

The first and second signal applying lines5cand5dare printed on the upper surface of the FPC7, and the third and fourth signal applying lines6cand6dare printed on the lower surface of the FPC7. As shown inFIG. 6, the first, second, third, and fourth signal applying lines5c,5d,6c, and6dare bonded by the conductive adhesives8aand8b. The first to fourth signal applying lines5c,5d,6c, and6dprinted on the upper and lower surfaces of the FPC7output the voltage to the transparent electrode3or4when applying the power supply voltage Vcc and the ground voltage GND to the first to fourth metal electrodes5a,5b,6a, and6bof the transparent electrode3or4, or electrically connecting the upper and lower transparent electrodes3and4to each other at a predetermined portion.

As mentioned above, the first to fourth signal applying lines5c,5d,6c, and6dare bonded to the FPC7by the conductive adhesives8aand8b, and the upper and lower substrates1and2are bonded to each other in the dead space region without the FPC7by an insulating adhesive9.

A method for electrically bonding the first to fourth signal applying lines5c,5d,6c, and6dto the FPC7will now be explained in detail. First, the conductive adhesive8ais positioned below the first and second signal applying lines5cand5dbonded to the upper surface of the FPC7, and the conductive adhesive8bis positioned on the third and fourth signal applying lines6cand6dbonded to the lower surface of the FPC7. Next, the insulating adhesive9is deposited in the dead space region20except for the portion of the dead space region occupied by the FPC7. Subsequently, only the portion of the FPC7on which the conductive adhesive is formed is heated at a temperature of approximately 100° C., and pressed by the external force. Thus, the FPC7is bonded to the first to fourth signal applying lines5c,5d,6c, and6d, and the lower and upper substrates1and2are bonded to each other.

The operation of the touch panel for the display device according to the related art will be explained as follows.

If the surface of the upper substrate1is touched at the predetermined portion with a pen or a finger, the first and second transparent electrodes3and4become electrically connected to each other at the predetermined portion. Accordingly, the power supply voltage (Vcc) and the ground voltage (GND) are applied to the right and left sides of the first transparent electrode3formed on the upper PET substrate1through the two signal applying lines5cand5dprinted on the upper surface of the FPC7and the metal electrodes5aand5b. A voltage, having a value varied by a resistance value or a capacitance value specific to the touch point, is then outputted through the second transparent electrode4of the lower PET substrate2and the metal electrodes6aand6b, and the two signal applying lines6cand6dprinted on the lower surface of the FPC7, so that the X-axis coordinates are detected.

Next, the power supply voltage Vcc and the ground voltage GND are applied to the upper and lower sides of the second transparent electrode4formed on the lower PET substrate2through the two signal applying lines6cand6dprinted on the lower surface of the FPC7and the metal electrodes6aand6b. Then, the voltage value is then output at the touching point by the first transparent electrode3and the metal electrodes5aand5bof the upper PET substrate1, so that the Y-axis coordinates are detected. Accordingly, the X-Y coordinates of the touching point are detected.

FIG. 7illustrates an FPC, to which a signal applying line of the related art touch panel is bonded, to the rear side of a lower substrate in a display device.FIG. 8is an expanded view ofFIG. 7illustrating a contact hole of the FPC.FIG. 9is a cross-sectional view taken along line IX-IX ofFIG. 8.

As mentioned above, as shown inFIG. 7, the FPC7and the first to fourth signal applying lines5c,5d,6c, and6dbonded to the upper and lower surfaces of the FPC7are bent to the side of the touch panel, and pass through the rear side60of an LCD panel integrated with the touch panel, so that the FPC7passes through a driver IC51connected to a printed circuit board (PCB). In this case, as shown inFIG. 8, the driver IC51may be in direct contact with the third and fourth signal applying lines6cand6dbonded to the lower surface of the FPC7among the signal applying lines bonded to the FPC7, thereby causing a short-circuit of the driver IC51. Especially, when performing a shock test for preventing an electrostatic discharge (ESD), a short-circuit of the driver IC is generated.

As shown inFIG. 8, the FPC7passing through the PCB50is connected to a touch panel controller (not shown) to input and output the signal voltage to the transparent electrode of the touch panel. A through-hole55is formed in the FPC7to facilitate a connection to the touch panel controller, so that the third and fourth signal applying lines6cand6dof the lower surface of the FPC7are formed to the upper surface of the FPC7. However, as shown inFIG. 9of a cross-sectional view taken along line IX-IX ofFIG. 8for illustrating a portion prior to forming the through-hole55, the first and second signal applying lines5cand5dare formed on the upper surface of the FPC7, and the third and fourth signal applying lines6cand6dare formed on the lower surface of the FPC7. As a result, the third and fourth signal applying lines6cand6dformed on the lower surface of the FPC7may be in contact with the driver IC.

Accordingly, the related art touch panel for the display device has the following disadvantages.

In the related art touch panel for the display device, the FPC is formed to apply the signal to the metal electrodes on the transparent electrode. When the FPC is bent to the bottom of the LCD device, some of the signal applying lines bonded to the FPC may be in direct contact with the driver IC of the LCD device, so that the driver IC may be damaged during a shock test for preventing an electrostatic discharge (ESD).

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a touch panel for a display device and a method of fabricating the same that substantially obviate one or more of problems due to limitations and disadvantages of the related art.

Another object of the present invention is to provide a touch panel for a display device and a method of fabricating the samethat prevents an electrostatic discharge generated when a flexible printed cable (FPC) with bonded signal applying lines is bent, so that the signal applying lines bonded to the FPC are in direct contact with a driver IC of a display device.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a touch panel for a display device having a driver IC includes upper and lower substrates, first and second transparent electrodes on opposing surfaces of the upper and lower substrates, a plurality of metal electrodes in a circumference of the first and second transparent electrodes, and a flexible printed cable having a plurality of signal applying lines extended from the upper and lower substrates to a rear side of the display device for applying signal voltages to the metal electrodes, wherein the flexible printed cable is bent at a corner of the upper and lower substrates from a top to a bottom of the display device, and has a first part extended from the corner of the display device and a second part extended from the first part and the first and second parts being perpendicular to each other.

The flexible printed cable has a plurality of through-holes before the flexible printed cable overlaps the driver IC. The signal applying lines of the lower surface of the flexible printed cable are disposed on the upper surface of the flexible printed cable.

Also, the flexible printed cable extends through the driver IC of the display device to be connected to a printed circuit board.

The signal applying lines for applying signals to the metal electrodes on the upper substrate are printed on the upper surface of the flexible printed cable, and the signal applying lines for applying signals to the metal electrodes on the lower substrate are printed on the lower surface of the flexible printed cable.

The metal electrodes include first and second metal electrodes being electrically connected to the first transparent electrode in the circumference of the first transparent electrode along the X-axis direction, and third and fourth metal electrodes being electrically connected to the second transparent electrode in the circumference of the upper and lower sides on the second transparent electrode along the Y-axis direction.

Also, the first, second, third, and fourth metal electrodes are connected to the first, second, third, and fourth signal applying lines.

The display device is an LCD device.

In another aspect of the present invention, a method of fabricating a touch panel for a display device having a driver IC includes forming upper and lower substrates, forming first and second transparent electrodes on opposing surfaces of the upper and lower substrates, forming a plurality of metal electrodes in a circumference of the first and second transparent electrodes, and forming a flexible printed cable having a plurality of signal applying lines extended from the upper and lower substrates to a rear side of the display device for applying signal voltages to the metal electrodes, wherein the flexible printed cable is bent at a corner of the upper and lower substrates from a top to a bottom of the display device, and has a first part extended from the corner of the display device and a second part extended from the first part and the first and second parts being perpendicular to each other.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A touch panel according to the present invention will be described with reference to the accompanying drawings.

FIGS. 10A and 10Bare plane views illustrating metal electrodes and signal applying lines on respective upper and lower substrates of a touch panel according to the present invention.FIG. 11is a cross-sectional view taken along line XI-XI ofFIGS. 10A and 10B.

The touch panel according to the present invention has the same structure as that of the related art except for the locations of signal applying lines. Accordingly, in the touch panel according to the present invention, upper and lower substrates of PET films are formed to face into each other where a viewing area and a non-viewing area (dead space region) are formed thereon. The non-viewing area is the circumference of the viewing area and surrounds the viewing area. Then, transparent electrodes are formed on the opposing surfaces of the upper and lower substrates, and a plurality of electrodes are formed in the non-viewing area (dead space region) of the transparent electrodes.

Referring toFIG. 10A, the transparent electrode (not shown) is formed at the rear side on the upper substrate of the touch panel, and first and second metal electrodes250aand250bare formed at both sides of the upper substrate along the X-axis direction to be connected to the transparent electrode. Then, first and second signal applying lines270aand270bare connected to the first and second metal electrodes250aand250bfor applying signal voltages to the first and second metal electrodes250aand250b. Also, as shown inFIG. 10B, the transparent electrode (not shown) is formed on the lower substrate, and third and fourth metal electrode260aand260bare formed at both sides of the lower substrate along the Y-axis direction to be connected to the transparent electrode. Then, third and fourth signal applying lines270cand270dare connected to the third and fourth metal electrodes260aand260bfor applying signal voltages to the third and fourth metal electrodes260aand260b.

As shown inFIGS. 10A and 10B, a flexible printed cable (FPC)400is in contact with the lower surface of the upper substrate, and the upper surface of the lower substrate, so that the first and second signal applying lines270aand270bare printed on the upper surface of the FPC400, and the third and fourth signal applying lines270cand270dare printed on the lower surface of the FPC400. Also, the FPC400is formed to correspond to one side of the dead space region between the upper and lower substrates, and the upper and lower substrates are bonded to each other by both-sided adhesive.

Before bending the FPC400to the bottom of the display device as one body, a cross-sectional view of the FPC400will be described with reference toFIG. 11. Referring toFIG. 11, the first and second signal applying lines270aand270bconnected to the first and second metal electrodes (not shown) on the upper substrate are bonded to the upper surface of the FPC400, and the third and fourth signal applying lines270cand270dconnected to the third and fourth metal electrodes (not shown) are bonded to the lower surface of the FPC400.

FIG. 12illustrates a bent signal applying line after bonding the touch panel to the display device. As shown inFIG. 12, the upper and lower substrates are bonded to each other. Then, the FPC400is connected to one side of the dead space region in the touch panel100, and the touch panel100is mounted on the display device200such as an LCD device. In this case, the signal applying line is completely bonded to the FPC400, and then the FPC400of the film type that can be easily bent extends over the rear side of the display device200along the side of the touch panel100and the display device200to be connected to a touch panel controller (not shown) formed at the lower side of the display device200.

FIG. 13illustrates a bonded signal applying line when the FPC of the touch panel according to the present invention is bent to the rear bottom of a display device.FIG. 14is a cross-sectional view taken along line XIV-XIV ofFIG. 13.

As shown inFIG. 13, when the FPC400formed at one side of the touch panel passes over the rear side of the lower substrate of the display device200, the FPC400is bent in a “┐” shape to be connected to the touch panel controller. The FPC400overlaps a driver IC510and a PCB500. As shown in the drawings, a through-hole65is formed in the FPC400prior to overlapping the FPC400and the driver IC510, so that the third and fourth signal applying lines270cand270dformed on the lower surface of the FPC400extend over the upper surface of the FPC400.

Accordingly, as shown inFIG. 14, the cross-section of the FPC400having the through-hole65on the external PCB500prior to overlapping the driver IC510and the signal applying lines270a,270b,270c, and270dare positioned on the upper surface of the FPC400. In such a case, a contact hole of the FPC400must not be formed at a portion where a case top surrounds the touch panel and the LCD panel. If the contact hole of the FPC400overlaps the portion forming the case top, a short-circuit may be generated between a metal material of the case top and the FPC400.

As mentioned above, the touch panel for the display device according to the present invention has the following advantages.

In the touch panel for the display device according to the present invention, the FPC is connected to one side of the touch panel. That is, the signal applying lines extend over the upper surface of the FPC by the through-hole to be connected to the touch panel controller. In this case, the through-hole is formed before the FPC overlaps the driver IC, thereby preventing the driver IC from being connected to the signal applying line during a shock test for preventing an electrostatic discharge. As a result, a voltage resisting margin can be reinforced in the present invention.