Touch panel

A touch panel has a substrate on which a first conductive layer, an insulating layer, a second conductive layer and a protective layer are formed in order. The second conductive layer and the first conductive layer form a touch-sensing area. The protective layer and the substrate have the same refractive index; and the first conductive layer, the insulating layer and the second conductive layer have the same refractive index so that the whole layered structure substantially has a symmetrical distribution of refractive indices, and leading to having optical characteristics of high transmittance and low reflectance.

This Application claims priority of Taiwan Patent Application No. 101225569, filed on Dec. 28, 2012 in the TIPO (Taiwan Intellectual Property Office), which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a touch panel, especially to a touch panel having a multi-layer structure in which layers of the structure are symmetrically distributed in accordance with refractive index.

2. Description of the Related Art

In recent years, many electronic devices, such as mobile phones and tablet personal computers, are equipped with a touch sensor function. A touch panel is used as an input/output interface where a user may slide his finger or a stylus on the touch panel to control an electronic device.

The touch sensing technologies used in the present touch panel may be different, wherein the capacitive touch sensing technology has become the most commonly used technology. With reference toFIGS. 1 and 2,FIG. 1is a structural schematic view of a conventional capacitive touch panel, andFIG. 2is a cross-sectional view taken along the line AA inFIG. 1. The conventional capacitive touch panel mainly includes a glass substrate9, a black matrix layer93, multiple first electrodes90, multiple second electrodes91, multiple first connecting wires98, multiple second connecting wires99and a protective layer94. The black matrix layer93is formed on the periphery region of a surface of the glass substrate9so as to form a shading area. The first electrodes90are formed on the surface of the glass substrate9and are arranged in a matrix manner and are connected in serial along an X-axis direction by multiple first conductive wires900. The second electrode91are formed on the surface of the glass substrate9and are arranged in a matrix manner, wherein the second electrodes91are respectively arranged between the first electrodes90, and the second electrodes91are connected in serial along a Y-axis direction by multiple second conductive wires910. The first electrodes90and the second electrodes91are connected to a peripheral control circuit respectively through the first connecting wires98and the second connecting wires99. The protective layer94covers the black matrix layer93, the first electrodes90, the second electrodes91, the first connecting wires98and the second connecting wires99. With reference toFIG. 2, in order to prevent the first conductive wire900and the second conductive wires910from being in contact with each other, multiple bridge insulation members92are disposed between the first conductive wires900and the second conductive wires910at the intersections of the first conductive wires900and the second conductive wires910, so that the first conductive wires900can be insulated from the second conductive wires910.

In the foregoing capacitive touch panel, the insulatedly-crossed first electrodes90and second electrodes91can produce capacitors and thereby form a touch-sensing area. When a user uses his finger to touch the surface of the capacitive touch panel, the capacitance of the capacitor at the touch point will be changed such that the peripheral control circuit connected to the first electrodes90and the second electrodes91can locate the position of the finger touch from the change of capacitance.

During the production process of the foregoing touch panel, the black matrix layer93is first formed on the surface of the glass substrate9, and then a transparent conductive layer is mounted on the surfaces of the glass substrate9and the black matrix layer93to form the first electrodes90and the second electrodes91through a patterning process. At this time the black matrix layer93at the periphery region has a thickness being larger than a thickness of the patterned transparent conductive layer in the touch-sensing area, and thereby creating a height difference at edges of the touch-sensing area. Thus, in the follow-up process of mounting the protective layer94, a thickness of the protective layer94may change at the edges of the touch-sensing area and then cause a rainbow mura phenomenon to occur at the edges of the touch-sensing area due to light interference.

Furthermore, the bridge insulation members92which are only mounted at intersections of the conductive wires do not contribute to the mechanical performance of the touch panel. Besides, since the bridge insulation members92are usually made from photoresists having a refractive index of about 1.5, the refractive index of the bridge insulation members92is lower than the refractive index of the first electrodes90and the second electrodes91, and thereby the conditions of refraction of light through the bridge insulation member92and through the electrodes are different, such that a user may easily see the outline of the wirings of the first electrodes90and the second electrode91.

Therefore, it is necessary to provide a touch panel to overcome the problems existing in the conventional technology.

SUMMARY OF THE INVENTION

In view of the shortcomings of the conventional technology, the main objective of the invention is to provide a touch panel having a multi-layer structure in which layers are symmetrically distributed in accordance with refractive index. The touch panel has optical characteristics of high transmittance and low reflection and prevents the occurrence of rainbow mura phenomenon.

In order to achieve the foregoing object of the present invention, the present invention provides a touch panel having a substrate, a first conductive layer, an insulating layer, a second conductive layer and a protective layer. The substrate has a first refractive index. The first conductive layer has a second refractive index and is patterned and formed on the substrate. The insulating layer has a third refractive index and covers the first conductive layer. The second conductive layer has a fourth refractive index and is patterned and formed on the insulating layer to constitute a touch-sensing area with the first conductive layer. The protective layer has a fifth refractive index and covers the second conductive layer. The first refractive index and the fifth refractive index fall between 1.5 and 1.6, the second refractive index, the third refractive index and the fourth refractive index fall between 1.7 and 2.2, so that a multi-layer structure constituted by at least the substrate, the first conductive layer, the insulating layer, the second conductive layer and the protective layer has a symmetrical distribution of refractive index.

Layers being symmetrically distributed in accordance with refractive index contribute to achievement of optical characteristics of high transmittance and low reflection. And the insulating layer can buffer the effects of stress between the substrate and the electrode layer so as to provide the touch-sensing structure with a better mechanical performance.

The present invention further provide a touch panel having a substrate, a first conductive layer, an insulating layer, a shading layer, a second conductive layer and a protective layer. The first conductive layer is patterned and formed on the substrate. The insulating layer covers the first conductive layer. The shading layer is formed on the substrate, surrounds the first conductive layer and correspondingly covers a periphery of the insulating layer to provide a shading area. The second conductive layer is patterned and formed on the insulating layer to constitute a touch-sensing area with the first conductive layer. The protective layer covers the second conductive layer and the shading layer.

Since the shading layer correspondingly covers the peripheral region of the insulating layer, which means the shading layer is formed after forming the insulating layer, and the thickness of the insulating layer is substantially equal to or larger than the thickness of the shading layer, the thickness of the shading layer will taper towards the edges of the substrate. After forming the second conductive layer and the protective layer, the thickness of the protective layer will also taper towards the edges of the substrate along with the shading layer, which means the thickness of the protective layer will only change within the shading area. Thus, the protective layer can maintain a consistent thickness within the touch-sensing area to prevent the occurrence of rainbow mura phenomenon.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The foregoing objects, features and advantages adopted by the present invention can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings. Furthermore, the directional terms described in the present invention, such as upper, lower, front, rear, left, right, inner, outer, side and etc., are only directions referring to the accompanying drawings, so that the used directional terms are used to describe and understand the present invention, but the present invention is not limited thereto.

With reference toFIGS. 3A to 3C,FIG. 3Ais a schematic view of electrode pattern arrangement of a touch panel according to a preferred embodiment of the present invention, andFIGS. 3B and 3Care cross-sectional views respectively taken along the line AA′ and BB′ inFIG. 3A. The touch panel mainly has a substrate1, a first conductive layer10, an insulating layer11, a second conductive layer13, a shading layer12(e.g. a black matrix layer) and a protective layer14.

The substrate1in this embodiment is a transparent glass and has a first refractive index. The first refractive index falls between 1.5 and 1.6, such as 1.5.

The first conductive layer10is patterned and formed on the substrate1. With further reference toFIG. 3A, the first conductive layer10is a transparent conductive film (e.g. indium tin oxide) made after performing exposure, development and etching steps. In this embodiment, the first conductive layer10includes multiple bar-shaped bridging structures101which are not connected with each other and are arranged in a matrix manner. The first conductive layer10has a second refractive index being larger than the foregoing first refractive index and may fall between 1.7 and 2.2. Each of the bridging structures101is used to connect two adjacent first electrodes132, so that a plurality of the first electrodes132can be electrically connected along a first direction (e.g. X-axis direction).

The insulating layer11fully covers the first conductive layer10and has multiple through holes15. In more detail, the insulating layer11is fully coated on the first conductive layer10and the substrate1to cover the bridging structures101, wherein each of the bridging structures101has two ends which respectively correspond to one of the through holes15. It is worth noting that the so-called “the insulating layer11is fully coated” means that the insulating layer11is formed into an entire film structure which covers the bridging structures101at the same time instead of being formed into multiple separated structures. In this embodiment, the insulating layer11is made of high refractive index photoresist and therefore has a third refractive index which may fall between 1.7 and 2.2. Preferably the third refractive index is substantially equal to the second refractive index.

The second conductive layer13is patterned and formed on the insulating layer11and thereby forms a touch-sensing area (area “C” as shown inFIG. 3A) with the first conductive layer10. The touch-sensing area may be substantially equal to the insulating layer11in size and shape. With reference toFIG. 3BandFIG. 3C, in this embodiment, the second conductive layer13is also a transparent conductive film (e.g. indium tin oxide) made after performing exposure, development and etching steps and includes multiple first electrodes132, multiple second electrodes130and multiple second conductive wires131. The first electrodes132and the second electrodes130are arranged in a matrix manner (as shown inFIG. 3A). As shown inFIG. 3C, two adjacent ones of the first electrodes132which are adjacent in an X-axis direction are electrically connected to each other via two adjacent corresponding through holes15and a corresponding bridging structure101of the first conductive layer10. Besides, each of the second conductive wires131connects two adjacent ones of the second electrodes130and crosses a corresponding bridging structure101so that the second electrodes130are connected in serial in a second direction (e.g. Y-axis direction). In this embodiment, the second conductive layer13has a fourth refractive index which falls between 1.7 and 2.2 and is preferably substantially equal to the second refractive index.

The shading layer12is formed on the substrate1and surrounds the first electrodes132and the second electrodes130of the second conductive layer13. The shading layer12covers a periphery of the insulating layer11and provides a shading area (area “D” as shown inFIG. 3A). The shading area is used to surround the touch-sensing area so as to shade the first connecting wires134and the second connecting wires135which are connected to the first electrodes132and second electrodes130. It is worth noting that in this embodiment the shading layer12covers the periphery of the insulating layer11, and the second conductive layer13covers a periphery of the shading layer12. With reference toFIG. 3A, the first electrodes132and the second electrodes130are connected to a peripheral control circuit respectively through the first connecting wires134and the second connecting wires135, respectively, wherein the first connecting wires134and the second connecting wires135are mounted on the shading layers12and may be made of the same transparent electrically conductive material as the second conductive layer13or metallic material.

Furthermore, the touch panel of the present invention further includes a protective layer14. The protective layer14is transparent and covers the second conductive layer13, the insulating layer11and the shading layer12. The protective layer14has a fifth refractive index which falls between 1.5 and 1.6 and is preferably substantially equal to the first refractive index.

With reference toFIGS. 3A to 3C, it can be seen that the bridging structures101of the first conductive layer10are covered by the insulating layer11and the size of the bridging structures101is far smaller than the entire insulating layer11. When the insulating layer11and the first conductive layer10has substantially the same refractive index, the bridging structures101of the first conductive layer10can be seen as a part of the insulating layer, optically, or the optical effect provided by the bridging structures101can be ignored within the touch-sensing area. In other words, when discussing the refractive indices and the transmittance of the layers in the touch panel, as shown inFIG. 4, the multi-layer structure within the range of the touch-sensing area can be simplified as only containing the substrate1, the insulating layer11, the second conductive layer13and the protective layer14, wherein as mentioned above the substrate1has the first refractive index between 1.5 and 1.6, the insulating layer11has the third refractive index between 1.7 and 2.2, the second conductive layer13has the fourth refractive index between 1.7 and 2.2 and the protective layer14has the fifth refractive index between 1.5 and 1.6. In one embodiment, the protective layer14may be designed to have substantially the same refractive index as the substrate1, that is, the first refractive index may be substantially equal to the fifth refractive index; and the insulating layer11may be designed to have substantially the same refractive index as the second conductive layer13, that is the third refractive index may be substantially equal to the fourth refractive index. For example, the protective layer14and the substrate1have the same refractive index of 1.6, and the insulating layer11and the second conductive layer13have the same refractive index of 2.0, that is, compared with the protective layer14and the substrate1, the insulating layer11and the second conductive layer13have a higher refractive index. Therefore, the refractive indices of the layers in the multi-layer structure inFIG. 4from the first layer to the last layer are listed as follows: 1.6 (low refractive index), 2 (high refractive index), 2 (high refractive index), 1.6 (low refractive index). With respect to an imaginary symmetrical center line S of the overall layered structure of the touch panel, which is also a boundary line between the insulating layer11and the second conductive layer13in this embodiment, it can be seen that the multi-layer structure of the touch panel constituted by the substrate, the first conductive layer, the insulating layer, the second conductive layer and the protective layer has a symmetrical distribution of refractive index. Thus, compared with the conventional technologies partially forming the insulating layer and bridging members that cause a mismatch between refractive indices and lead to poor optical performance, the present invention using the fully-coated and high refractive index insulating layer11to constitute a touch-sensing structure with other layers, so that the touch panel can have a multi-layer structure that has a symmetrical distribution of refractive index, thereby achieving improved optical characteristics of high transmittance and low reflection and therefore the outline of the wirings of the first conductive layers10and the second conductive layers13(including the first electrodes132and the second electrodes130) will not be obvious to the eyes of the user.

Although the embodiment is described with a four-layer structure, however, the present invention can be carried out by other multi-layer structure as long as layers in the multi-layer structure are designed to have a symmetrical distribution of refractive index with respect to a center line of the multi-layer structure.

Since the insulating layer11is fully-coated, the insulating layer can buffer the effects of stress between the substrate1and the first conductive layer10and the second conductive layer13to provide the touch-sensing structure with a better mechanical performance.

Besides, since the shading layer12is formed on the insulating layer11, the insulating layer11will have a thickness equal to or larger than the thickness of the shading layer12. Thus after forming the protective layer14, the surface of the protective layer14locating at the boundary between the insulating layer11and shading layer12will be substantially parallel to the surface of the substrate1, as shown inFIG. 3B. In other words, comparingFIG. 2withFIG. 3B, it is worth noting that the protective layer14above the boundary between the second conductive layer13and the shading layer12does not have a concave portion, and the thickness of the protective layer14only changing within the shading area, such as tapering in a direction towards the edges of the substrate1, will not affect the optical performance of the touch panel within the range of the touch-sensing area, thereby the touch panel can maintain consistency of conditions for refraction and reflection within the range of the touch-sensing area, so as to avoid rainbow mura phenomenon.

With regard to a manufacturing method of the touch panel of the present invention, please refer toFIGS. 5A to 5G. The manufacturing method includes a step of providing a substrate1as shown inFIG. 5A, a step of forming a first conductive layer10as shown inFIG. 5B, a step of forming an insulating layer11as shown inFIG. 5C, a step of forming a shading layer12as shown inFIG. 5D, a step of forming a second conductive layer13as shown inFIG. 5Eand a step of forming a protective layer14as shown inFIGS. 5F and 5G.

The step of forming the first conductive layer10is to first form a transparent conductive film on a surface of the substrate1and then perform exposure, development and etching processes to pattern the transparent conductive film so as to obtain multiple bridging structures101arranged in a matrix manner as the first conductive layer10.

The step of forming the insulating layer11is to perform a full-coating process to fully coat the insulating layer11on the first conductive layer10and the substrate1, and then perform exposure, development and etching processes for the insulating layer11to define the shape of the insulating layer11and multiple through holes15.

The step of forming the shading layer12is to form the shading layer12on the insulating layer11and the substrate1so that the shading layer12surrounds the first conductive layer10and the insulating layer11and correspondingly covers a periphery of the insulating layer11to provide a shading area.

The step of forming the second conductive layer13is to form another electrically conductive film on the substrate1and the shading layer12and then perform exposure, development and etching processes to pattern the electrically conductive film so as to obtain multiple first electrodes132and multiple second electrodes130as the second conductive layer13, wherein the second conductive layer13is partially formed inside the through holes15so that the adjacent first electrodes132of the second conductive layer13can be connected to each other through the corresponding through holes15and the corresponding bridging structure101of the first conductive layer10.

The step of forming the protective layer14is to form the protective layer14so that the protective layer14covers the second conductive layer13, the insulating layer11and the shading layer12.

With further reference toFIG. 6A,FIG. 6Ais a cross-sectional view of the touch panel according to another preferred embodiment of the present invention. The touch panel inFIG. 6Ais similar to the touch panel of the embodiment inFIG. 3Aand has a substrate1, a conductive layer10′, an insulating layer11, a shading layer12and a protective layer14. The substrate1has a first refractive index between 1.5 and 1.6. The conductive layer10′ is formed on the substrate1and is patterned to provide a touch-sensing area. With further reference toFIG. 6B, the conductive layer10′ may include multiple bar-shaped electrodes arranged side by side at intervals, and the conductive layer10′ has a second refractive index between 1.7 and 2.2. The insulating layer11is fully coated on the conductive layer10′ and has a third refractive index substantially the same as the second refractive index, such as falling between 1.7 and 2.2. The shading layer12is formed on the insulating layer11and the substrate1, surrounds the conductive layer10′ and correspondingly covers a periphery of the insulating layer11, so as to provide a shading area. The protective layer14covers the conductive layer10′, the insulating layer11and the shading layer12, wherein the protective layer14has a fourth refractive index substantially the same as the first refractive index, such as between 1.5 and 1.6. Similarly, in this embodiment, with reference to FIG.7, a multi-layer structure constituted by the substrate1, the conductive layer10′, the insulating layer11and the protective layer14also has a symmetrical distribution of refractive index. Thus, the touch-sensing structure of this embodiment can also achieve improved optical characteristics of high transmittance and low reflection.

Also, since the shading layer12is formed on the insulating layer11, the insulating layer11will have a thickness equal to or larger than the thickness of the shading layer12. Thus after forming the protective layer14, the surface of the protective layer14locating at the boundary between the insulating layer11and shading layer12will be substantially parallel to the surface of the substrate1, as shown inFIG. 3B. In other words, comparingFIG. 2withFIG. 6, it is worth noting that the protective layer14above the boundary between the second conductive layer13and the shading layer12does not have a concave portion, and the thickness of the protective layer14only changing within the shading area, such as tapering in a direction towards the edges of the substrate1, will not affect the optical characteristics of the touch panel with the range of the touch-sensing area, thereby the touch panel can maintain consistency of conditions for refraction and reflection within the range of the touch-sensing area, so as to avoid rainbow mura phenomenon.

By the above description, the touch panel of the present invention uses multiple layers being symmetrically distributed in accordance with refractive index to form its touch-sensing structure and adjusts the order of forming the shading layer, so that the overall structure can have a better mechanical performance and provide improved optical characteristics to avoid the occurrence of rainbow mura phenomenon.