Touch panel

This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 097103050 filed in Taiwan, Republic of China on Jan. 28, 2008, the entire contents of which are hereby incorporated by reference.

1. Field of Invention

The present invention relates to a touch panel and, in particular, to a touch panel with enhanced transmittance.

2. Related Art

Recently, touch panels have been widely applied to typical consumer electronic products such as a mobile communication, a digital camera, a digital music player (MP3), a personal digital assistant (PDA), a global positioning system (GPS), a hand-held personal computer (hand-held PC) or a novel ultra mobile personal computer (UMPC). In each of the above-mentioned electronic products, the touch panel is a touch screen combined with a display screen. However, the reflectance of the touch panel significantly influences the viewing quality for the user.

Referring to FIG. 1 , a conventional touch panel 1 mainly includes two transparent conductive films 11 A and 11 B disposed opposite to each other. The transparent conductive films 11 A and 11 B are separated by a plurality of spacers 12 with an air layer 13 formed between the transparent conductive films 11 A and 11 B. In addition, the touch panel 1 further includes a glass substrate 14 , a plastic substrate 15 and a hardened layer 16 . The glass substrate 14 is disposed on one side of the transparent conductive film 11 A, and the plastic substrate 15 and the hardened layer 16 are disposed on one side of the transparent conductive film 11 B. In addition, a display screen (not shown) can be connected to the glass substrate 14 to form a touch screen together with the touch panel 1 .

However, the typical material of the transparent conductive films 11 A and 1 B is indium tin oxide (ITO) having a refractive index of about 2. The air layer 13 has the refractive index of 1, and the difference between the refractive indices of the transparent conductive films 11 A and 11 B and the air layer 13 increases the reflectance and thus lower the transmittance. In addition, the difference between the refractive index of the outside air and the refractive indices of the glass substrate 14 , the plastic substrate 15 and the hardened layer 16 also increases the reflectance. FIG. 2 shows the relationship between the reflectance of the touch panel 1 and the incident light wavelength. As shown in FIG. 2 , the average reflectance of the touch panel 1 is about 20% and may reach as high as 40%. Consequently, both the transmittance and the contrast of the touch panel 1 are decreased and the display quality is thus influenced.

In view of the foregoing, an object of the present invention is to provide a touch panel having decreased reflectance so as to enhance the screen transmittance and contrast.

To achieve the above, the present invention discloses a touch panel including two transparent conductive films and at least one refractive index matching layer. The two transparent conductive films are disposed opposite to each other. The refractive index matching layer is disposed between the transparent conductive films.

In addition, the present invention also discloses a touch panel including a first transparent conductive film, a second transparent conductive film, at least one spacer, a transparent substrate and a refractive index matching layer. The first and second transparent conductive films are disposed opposite to each other and suspended by the spacer such that the first and second transparent conductive films are separated from each other. The transparent substrate is disposed on one side of the first transparent conductive film. The refractive index matching layer is disposed between the transparent substrate and the first transparent conductive film.

As mentioned above, the touch panel of the present invention has the refractive index matching layer disposed therein. The refractive index matching layer can reduce the difference between the refractive indices of the transparent conductive films and the refractive index of the air layer or between the refractive indices of the transparent conductive films and the refractive index of the transparent substrate. Thus, the present invention can enhance the transmittance and the contrast and thus the display quality.

The present invention will become more fully understood from the subsequent detailed description and accompanying drawings, which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 is a schematic illustration showing a conventional touch panel;

FIG. 2 shows the relationship between a reflectance of the touch panel of FIG. 1 and an incident light wavelength;

FIG. 3 is a schematic illustration showing a touch panel according to a first embodiment of the present invention;

FIG. 4 shows the relationship between a reflectance of the touch panel of FIG. 3 and an incident light wavelength;

FIG. 5 is a schematic illustration showing a touch panel according to a second embodiment of the present invention;

FIG. 6 shows the relationship between a reflectance of the touch panel of FIG. 5 and an incident light wavelength;

FIG. 7 is a schematic illustration showing a touch panel according to a third embodiment of the present invention; and

FIG. 8 shows the relationship between a reflectance of the touch panel of FIG. 7 and an incident light wavelength.

The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements.

First Embodiment

FIG. 3 is a schematic illustration showing a touch panel 2 according to the first embodiment of the present invention. Referring to FIG. 3 , the touch panel 2 includes two transparent conductive films 21 A and 21 B and a refractive index matching layer 27 . The transparent conductive films 21 A and 21 B are disposed opposite to each other. The material of the transparent conductive films 21 A and 21 B includes, for example but not limited to, indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), zinc oxide (ZnO), tin oxide (SnO 2 ) or combinations thereof.

The refractive index matching layer 27 is disposed between the transparent conductive films 21 A and 21 B, and is an elastic insulating layer for replacing the conventional air layer. The material of the refractive index matching layer 27 includes silicone, epoxy or combinations thereof. The refractive index matching layer 27 can also be a liquid refractive index matching layer, and is made of the material preferably including liquid silicone, liquid epoxy or combinations thereof. In addition, the refractive index matching layer 27 can be formed of a material with a single refractive index or formed of multiple materials with different refractive indices.

The refractive index of the refractive index matching layer 27 is smaller than that of each of the transparent conductive films 21 A and 21 B. For example, if the transparent conductive films 21 A and 21 B are made of indium tin oxide (ITO) having the refractive index of about 2, the refractive index of the refractive index matching layer 27 may range from 1 to 2 and preferably from 1.3 to 1.7. The above-mentioned design is to decrease the reflectance, which is caused by the differences between the refractive index of the middle air layer and the refractive indices of the transparent conductive films 21 A and 21 B.

In addition, the transparent conductive films 21 A and 21 B must contact with each other so that the touch panel can work. Thus, the refractive index matching layer 27 can serve as a buffer layer between the transparent conductive films 21 A and 21 B, so that the lifetime of the touch panel 2 is lengthened.

In this embodiment, the refractive index matching layer 27 further includes at least one spacer 22 disposed inside the refractive index matching layer 27 . The transparent conductive films 21 A and 21 B are suspended by the spacer 22 to separate the transparent conductive films 21 A and 21 B from each other.

The touch panel 2 further includes a first transparent substrate 24 A disposed on one side of the transparent conductive film 21 A, and a second transparent substrate 24 B disposed on one side of the transparent conductive film 21 B. Each of the first and second transparent substrates 24 A and 24 B is a glass substrate or a plastic substrate. The plastic substrate can be made of polyethelyne (PE), polycarbonate (PC) or polyethylene terephthalate (PET). In addition, the second transparent substrate 24 B can include a hardened layer 26 for protecting the touch panel 2 .

FIG. 4 shows the relationship between a reflectance of the touch panel 2 and an incident light wavelength. As shown in FIG. 4 , the average reflectance of the touch panel 2 is about 10% and may reach the value smaller than 20%.

Second Embodiment

Referring to FIG. 5 , a touch panel 3 according to the second embodiment of the present invention includes two transparent conductive films 21 A and 21 B and two refractive index matching layers 37 A and. 37 B. The difference between the touch panel 3 and the touch panel 2 of the first embodiment is in that the refractive index matching layers 37 A and 37 B of the touch panel 3 are respectively disposed between the spacer 22 and the transparent conductive film 21 A and between the spacer 22 and the transparent conductive film 21 B. The refractive index matching layers 37 A and 37 B are suspended by the spacer 22 , and therefore the refractive index matching layers 37 A and 37 B are separated from each other to form an air layer 38 therebetween. In addition, the refractive index matching layers 37 A and 37 B have the electroconductive property, and the material thereof may include a transparent conductive material or a material having lower refractive index and obtained by mixing the transparent conductive material with the transparent dielectric material. For example, the transparent conductive material can include indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), zinc oxide (ZnO), tin oxide (SnO 2 ) or combinations thereof. The transparent dielectric material may be silicon dioxide, cryolite or magnesium fluoride (MgF 2 ). In the manufacturing process, the refractive index matching layer 37 A and the first transparent conductive film 21 A can be coated in one batch, and the refractive index matching layer 37 B and the second transparent conductive film 21 B can be coated in one batch.

Each of the refractive index matching layers 37 A and 37 B can be a single layer or a composite layer. When the refractive index matching layer 37 A or 37 B is a composite layer, many configurations can be adopted. For example, the first refractive index matching layer 37 A or 37 B is composed of alternately stacked high and low refractive index layers, wherein the refractive indices of a portion of the high refractive index layers may be greater than the refractive indices of the transparent conductive films 21 A and 21 B.

In addition, the air layer 38 may also be replaced with the refractive index matching layer 27 of the first embodiment. That is, the refractive index matching layer 27 , such as elastic insulating layer or liquid refractive index matching layer, is formed between the refractive index matching layers 37 A and 37 B. Herein, the detailed descriptions of the property and the material of the refractive index matching layer 27 will be omitted.

FIG. 6 shows the relationship between a reflectance of the touch panel of FIG. 5 and an incident light wavelength. As shown in FIG. 6 , the average reflectance of the touch panel 3 is about 15%.

Third Embodiment

As shown in FIG. 7 , a touch panel 4 according to the third embodiment of the present invention is different from the tough panel 3 of the second embodiment in that the first transparent conductive film 41 A and the second transparent conductive film 41 B are suspended by the spacer 22 of the touch panel 4 , and therefore the first transparent conductive film 41 A is separated from the second transparent conductive film 41 B. In the third embodiment, a refractive index matching layer 47 A is disposed between the transparent substrate 24 A and the first transparent conductive film 41 A, and a refractive index matching layer 47 B is disposed between the transparent substrate 24 B and the second transparent conductive film 41 B. In the manufacturing process, the refractive index matching layer 47 A and the first transparent conductive film 41 A can be coated on the transparent substrate 24 A in one batch, and the refractive index matching layer 47 B and the second transparent conductive film 41 B can be coated on the transparent substrate 24 B in one batch. Each of the refractive index matching layers 47 A and 47 B can be a single layer or a composite layer consisting of alternately stacked high and low refractive index layers. The material of each of the refractive index matching layers 47 A and 47 B includes, for example but not limited to, niobium oxide, titanium oxide, tantalum oxide, zirconium oxide, silicon oxide, magnesium oxide or combinations thereof.

When each of the refractive index matching layers 47 A and 47 B is a single layer, the refractive indices of the refractive index matching layers 47 A and 47 B respectively range between the refractive indices of the first transparent conductive film 41 A and the transparent substrate 24 A and between the refractive indices of the second transparent conductive film 41 B and the transparent substrate 24 B. In addition, when each of the refractive index matching layers 47 A and 47 B is a composite layer, many configurations can be adopted. For example, films having high and low refractive indices are arranged alternately. Herein, the refractive index of one portion of the materials of the refractive index matching layers 47 A and 47 B can be greater than the refractive index of each of the first and second transparent conductive films 41 A and 41 B or each of the transparent substrates 24 A and 24 B. The object of the above-mentioned design is to decrease the reflectance caused by the differences between the refractive indices of the first and second transparent conductive films 41 A and 41 B and the refractive indices of the transparent substrates 24 A and 24 B and the middle air layer 38 .

In addition, the air layer 38 of the third embodiment may also be replaced by the refractive index matching layer 27 of the first embodiment. Herein, the detailed descriptions of the property and the material of the refractive index matching layer 27 will be omitted.

FIG. 8 shows the relationship between a reflectance of the touch panel of FIG. 7 and an incident light wavelength. As shown in FIG. 8 , the average reflectance of the touch panel 4 is about 10% and can reach the value smaller than 20%.

In summary, the touch panel of the present invention has the refractive index matching layer disposed therein. The refractive index matching layer can serve as the refractive index buffer layer, so that the differences between the refractive indices of the transparent conductive films and the refractive index of the air layer or between the refractive indices of the transparent conductive films and the refractive index of the transparent substrate can be decreased. Thus, the present invention can enhance the transmittance and the contrast and thus the display quality.

Although the present invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the present invention.