Patent Application
20140092027
1. Field of the Invention
The present invention relates to a touch panel and its production and, more particularly, to a simplified method for producing a touch panel, in which the conventional lamination process is omitted, and the touch panel produced thereby, in which the conventional drawback of image deterioration caused by the patterning of the transparent conductive layers is largely eliminated.
2. Description of the Prior Art
With the advancement of touch-screen technology in recent years, touch panels have been widely used in a broad variety of electronic devices, including mobile phones, personal digital assistants (PDAs), input interfaces of game consoles, and computer touch-screens. In the actual practice, a touch panel is typically combined with a liquid crystal display (LCD) device to constitute a touch screen adaptable to various electronic devices, through which a user can conveniently input data and instructions without relying upon a traditional input device, such as a keyboard or a computer mouse.
In general, the transparent conductive glass used in a touch panel is primarily composed of a transparent, non-conductive glass substrate, on which a transparent material with high electrical conductivity, typically a transparent metal oxide such as indium tin oxide (ITO), is coated to form a transparent conductive layer. The transparent conductive layer is etched into a predetermined electrode pattern in the form of, for example, a unidirectional electrode array.
Therefore, the transparent conductive layer contains a patterned region (which is formed with electrodes) and a non-patterned region (the etched-away portion). The non-patterned region is not provided with ITO, allowing light to directly penetrate therethrough to reach the glass substrate. Since the patterned and non-patterned regions have substantially different refractive indexes, the user would notice the presence of the etch lines at the junctions between the patterned and non-patterned regions. As a result, images displayed on the screen are deteriorated due to the occurrence of discontinuity, haziness, granulation and low resolution in the images.
In the case of fabrication of a bidirectional electrode array, it is traditionally made by laminating two transparent conductive films patterned with electrode patterns. During the lamination process, however, it is difficult to achieve stable bridging and precise registration between two transparent conductive films, resulting in decreased reliability and quality control of the touch panels thus fabricated.
An object of the invention is to provide a simplified method for producing a touch panel, in which the conventional lamination process is eliminated.
In order to achieve the object described above, the touch panel according to the invention comprises a plastic film substrate having a first surface and a second surface opposite to the first surface. The first surface is provided in sequence with a first undercoat layer, a second undercoat layer and a first patterned transparent conductive layer, and the first surface is further printed with a first patterned metal circuit layer along the periphery of the first patterned transparent conductive layer. The second surface is provided in sequence with a third undercoat layer, a fourth undercoat layer and a second patterned transparent conductive layer, and the second surface is further printed with a second patterned metal circuit layer along the periphery of the second patterned transparent conductive layer.
In a preferred embodiment, the plastic film substrate has a thickness ranging from 2 μm to 300 μm, more preferably from 2 μm to 200 μm.
Another object of the invention is to provide a method for producing a touch panel, comprising the steps of:
In a preferred embodiment, the method described above may further comprise a Step G intervening between the Step D and the Step E, wherein the Step G comprises annealing the first and second patterned transparent conductive layers, so as to have the layers crystallized.
In a preferred embodiment, the annealing Step G is performed at a temperature of 100˜200° C. for 30˜90 minutes.
In a preferred embodiment, the Step D comprises the sub-steps of:
In an alternative preferred embodiment, the Step D comprises the sub-steps of:
In a preferred embodiment, the undercoat layers and transparent conductive layers are formed in the Step C by using a dry process selected from the group consisting of vacuum evaporation, sputtering and ion plating, or by using a wet process.
In a preferred embodiment, the first and second patterned metal circuit layers are formed in Step E by screen printing of conductive silver paste onto the plastic film substrate.
In a preferred embodiment, the baking Step F is performed at a temperature of 100˜200° C.
According to the present invention, the following advantageous effects will be obtainable.
1. The invention involves direct formation of transparent conductive patterns on both sides of the plastic film substrate, whereby the lamination and precise registration operations required for the conventional methods are eliminated, and the touch panel thus produced has a reduced overall thickness compared to the conventional touch panels.
2. The invention successfully overcomes the drawback of image deterioration caused by the patterning of the transparent conductive layers and reduces the optical difference between the patterned regions and the non-patterned regions by adjusting the refractive indexes and thicknesses of the various thin layers that constitute the transparent conductive film.
3. The invention generally pertains to a sheet-by-sheet process and is superior over the conventional roll-to-roll processes in which the thin layers applied on the plastic film substrate (such as undercoat layers and patterned transparent conductive layers) tend to easily exfoliate due to the occurrence of uneven tension.
The above and other objects, features and effects of the invention will become apparent with reference to the following description of the preferred embodiments taken in conjunction with the accompanying drawing, in which:
The plastic film substrate used in the invention can be any type of plastic film that is transparent to light. The material from which the plastic film substrate is made is not critical under the spirit of the invention, which includes but is not limited to polyester resins, acetate resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, methacrylate resins, polyvinylchloride resins, polyvinylidine chloride resins, polystyrene resins, polyvinyl alcohol resins, polyarylate resins, and polyphenylene sulfide resins.
Preferred are polyester resins, polycarbonate resins and polyolefin resins. Advantageously, the plastic film substrate has a thickness ranging from 2 μm to 300 μm, preferably from 2 μm to 200 μm.
Step A: providing a plastic film material.
Step B: cutting the plastic film material to obtain a sheet-like plastic film substrate 11 as shown in
Step C: forming undercoat layers and transparent conductive layers on the plastic film substrate 11 through a dry process, such as vacuum evaporation, sputtering and ion plating, or through a wet process, such as coating, whereby the plastic film substrate 11 comprises a first surface 111, on which a first undercoat layer 12, a second undercoat layer 13 and a first transparent conductive layer 21 are formed in sequence as shown in
Step D: patterning the first and second transparent conductive layers 21, 22 into a first patterned transparent conductive layer and a second patterned transparent conductive layer, respectively. The Step D comprises the following sub-Steps. In Step D-1, a temporary protective film 23 is applied over the second transparent conductive layer 22, as shown in
Step E: forming a first patterned metal circuit layer 18 and a second patterned metal circuit layer 19 on the plastic film substrate 11 along the peripheries of the first and second patterned transparent conductive layers 14, 17 using a printing process, as shown in
Step F: baking the resultant device at a temperature of 100˜200° C. to cure the first and second patterned metal circuit layers 18, 19.
The method described above may further comprise a Step G intervening between the Step D and the Step E, which comprises annealing the first and second patterned transparent conductive layers at a temperature of 100˜200° C. for about 30˜90 minutes, so as to have the layers crystallized.
Alternatively, the Step D described above comprises the following sub-Steps. In Step D-10, a temporary protective film is applied over the second transparent conductive layer. In Step D-20, the plastic film substrate is supported on a support member, with the second transparent conductive layer facing downwardly. In Step D-30, a first patterned etching-resistant layer is formed over the first transparent conductive layer. In Step D-40, the first transparent conductive layer is etched to remove the regions thereof unprotected by the first patterned etching-resistant layer, thereby forming a first patterned transparent conductive layer. In Step D-50, the first patterned etching-resistant layer is removed and a temporary protective film is applied over the first patterned transparent conductive layer. In Step D-60, the plastic film substrate is reversed with respective to the support member with the first patterned transparent conductive layer facing downwardly. In Step D-70, the temporary protective film applied over the second transparent conductive layer is removed. In Step D-80, a second patterned etching-resistant layer is formed over the second transparent conductive layer. In Step D-90, the second transparent conductive layer is etched to remove the regions thereof unprotected by the second patterned etching-resistant layer, thereby forming a second patterned transparent conductive layer. In Step D-100, the second patterned etching-resistant layer is removed to reveal both of the first and second patterned transparent conductive layers.
It is worthwhile to note that the method disclosed herein involves direct formation of transparent conductive patterns on both sides of the plastic film substrate, whereby the lamination and precise registration operations required for the conventional methods are eliminated. As such, the method disclosed herein is not only simplified as compared to the conventional methods but adapted to produce a touch panel with reduced overall thickness as compared to the conventional devices. Moreover, the method disclosed herein generally pertains to a sheet-by-sheet process and is superior over the conventional roll-to-roll processes in which the thin layers applied on the plastic film substrate (such as undercoat layers and patterned transparent conductive layers) tend to easily exfoliate due to the occurrence of uneven tension.
In addition, the first and second undercoat layers 12, 13 have refractive indexes of N1 and N2, respectively, and have thicknesses of T1 and T2, respectively, and the first patterned transparent conductive layer 14 has a refractive index of n1 and a thicknesses of t1, wherein n1≧N1>N2 and T2>t1>T1. The third and fourth undercoat layers 15, 16 have refractive indexes of N3 and N4, respectively, and have thicknesses of T3 and T4, respectively, and the second patterned transparent conductive layer 17 has a refractive index of n2 and a thicknesses of t2, wherein n2≧N3>N4 and T4>t2>T3. Therefore, the drawback of image deterioration caused by the patterning of the transparent conductive layers may be overcome and the optical difference between the patterned regions and the non-patterned regions may be reduced by adjusting the refractive indexes and thicknesses of the various thin layers that constitute the transparent conductive film.
In conclusion, the touch panel disclosed herein can surely achieve the intended objects and effects of the invention by virtue of the processing steps described above. While the invention has been described with reference to the preferred embodiments above, it should be recognized that the preferred embodiments are given for the purpose of illustration only and are not intended to limit the scope of the present invention and that various modifications and changes, which will be apparent to those skilled in the relevant art, may be made without departing from the spirit of the invention and the scope thereof as defined in the appended claims.
