Abstract:
The present invention discloses a conductive film including a substrate, a first hard coated layer, a second hard coated layer, a first refraction layer, a second refraction layer, and a transparent conductive layer, which are arranged in a predetermined order. The second hard coated layer has the silicon-based material accounting for certain percentages of the weight thereof, and the transparent conductive layer may cover parts of the second refraction layer. When a light enters into the transparent conductive layer/the second refraction layer with an incident angle, the light may be associated with a first reflectance/a second reflectance. The difference between the first reflectance and the second reflectance is designed to be lower than a first threshold value. Accordingly, the present invention may eliminate the display difference between an etched and a non-etched area of the conductive film and improve the visual quality.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a conductive film; in particular, to a conductive film that is capable of eliminating display difference between an etched and a non-etched area. 
         [0003]    2. Description of Related Art 
         [0004]    As the technology progresses, electronic devices have been widely utilized in people&#39;s daily lives. For the electronic devices to receive inputs from human operators, traditional input devices such as keypads/keyboards are usually employed. However, touch panels (or touch-screens) have been emerging to at least somewhat become the primary option of the input device in certain electronic devices including mobile phones and tablet computers. 
         [0005]    Applications of the touch panels include a variety of types such as resistive touch panel, capacitive touch panel, infrared touch panel, and ultrasonic-wave touch panel. 
         [0006]    The traditional touch panels generally have a thin and transparent metallic layer serving as a conductive film deposited on a glass substrate. When the conductive film is touched, a corresponding signal such as an input has been received or which location of the conductive film has been touched may be recorded. 
         [0007]    The thin and transparent metallic layer is manufactured through steps of lithography and etching process so as to form patterns of circuitry thereon. However, some traces will be formed after the completion of the etching process especially in the case where difference in reflection between the glass substrate and the transparent conductive layer is large enough to have a significant drop-off in terms of spectrum, which obscures the image to be displayed and undermines the quality of the display. 
       SUMMARY OF THE INVENTION 
       [0008]    The object of the present invention is to provide a conductive film having a hard coated layer. The thickness and the makeup of the hard coated layers may be adjusted to reduce the reflectance difference of different portions (i.e., the etched portion and the non-etched portion). The reduction may help eliminate the gap in the difference between those portions/areas. Therefore, the etched traces cannot be observed by the users so that the image quality of the conductive film is improved. 
         [0009]    In order to achieve the aforementioned objects, according to an embodiment of the present invention, a conductive film is provided. The conductive film includes a substrate, a first hard coated layer, a second hard coated layer, a first refraction layer, a second refraction layer, and a transparent conductive layer. The first hard coated layer may be disposed on the substrate and the second hard coated layer may be disposed on the first hard coated layer and made of a silicon-based material. The first refraction layer, the second refraction layer, and the transparent conductive layer are disposed on the second hard coated layer in a predetermined order. More specifically, the first refraction layer may be in contact with the second hard coated layer while the second refraction layer may be disposed on the first refraction layer with the transparent conductive layer disposed on the second refraction layer and partially covering the second refraction layer. When a light enters into the transparent conductive layer of the conductive film with an incident angle, the light may be associated with a first reflectance. When the light enters into the second refraction layer of the conductive film with the same incident angle, the light may be associated with a second reflectance. The difference between the first reflectance and the second reflectance could be lower than a first threshold value. 
         [0010]    In an embodiment of the present invention, the second hard coated layer may be one to two micrometers in thickness with the silicon-based material accounting for sixty to ninety percents of the weight thereof In addition, the thickness of the first hard coated layer may range between six to ten micrometers. The first refraction layer is in the range of 100 Å to 300 Å, and refractive index of the first refraction layer is in the range of 1.6 to 2.0. The thickness of the second refraction layer is in the range of 500 Å to 700 Å, and refractive index of the second refraction layer is in the range of 1.42 to 1.46. Moreover, the substrate is made of glass material, PET material, or a mixture of the glass and the PET materials, and the refractive index of the substrate may be at 1.52. 
         [0011]    To sum up, the conductive film of the present invention may lead to a reflectance and transmittance matching effect between the etched portion and the non-etched portion of the conductive film by properly selecting the thickness and the makeup of the hard coated layers to be within predetermined ranges. Therefore, the etched portion and the non-etched portion could be associated with similar reflection indexes so as to improve the image quality. 
         [0012]    In order to further the understanding regarding the present invention, the following embodiments are provided along with illustrations to facilitate the disclosure of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  shows a schematic diagram of a conductive film according to an embodiment of the present invention. 
           [0014]      FIG. 2  shows a stereogram of the conductive film according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    The aforementioned illustrations and following detailed descriptions are exemplary for the purpose of further explaining the scope of the present invention. Other objectives and advantages related to the present invention will be illustrated in the subsequent descriptions and appended drawings. 
         [0016]    Referring to  FIG. 1  and  FIG. 2 ,  FIG. 1  shows a schematic diagram of a conductive film according to an embodiment of the present invention, and  FIG. 2  shows a stereogram of the conductive film according to an embodiment of the present invention. A conductive film  1  of the present invention includes a substrate  10 , a first hard coated layer  12 , a second hard coated layer  14 , a first refraction layer  16 , a second refraction layer  18 , and a transparent conductive layer  20 . 
         [0017]    In one implementation, the substrate  10  is made of glass and PET (polyethylene terephthalate) materials. For example, the substrate  10  can be made of acetylcellulose-based films such as diacetylcellulose films, triacetylcellulose films and acetylcellulose butyrate films, polycarbonate-based films, cyclic olefin-based films, acrylic resin-based films, polyester-based films such as polyethylene terephthalate films, polybutylene terephthalate films and polyethylene naphthalate films, polysulfone-based films, polyether sulfone-based films, polyether ether ketone-based films, polyimide-based films, and polyether imide-based films. In terms of light transmitting capability, mechanical property, lower water absorption, endurance to heat and tough weather condition, triacetylcellulose films, polycarbonate-based films, cyclic polyolefin-based films, acrylic resin-based films and polyethylene terephthalate films may be more desirable with acetylcellulose-based films, polycarbonate-based films, cyclic polyolefin-based films, acrylic resin-based films and polyester-based films may separate themselves from others in the same categories. 
         [0018]    In practice, when the substrate  10  is made of glass and PET materials, a refractive index of the substrate may be at 1.52. Of course, person skilled in the art can choose from other materials to prepare compounds serving as the substrate  10  with the refractive index around 1.52. The thickness of the substrate  10  in one implementation is lower than 300 μm. Besides, the first hard coated layer  12 , the second hard coated layer  14 , the first refraction layer  16 , and the second refraction layer  18  may be disposed on one surface of the substrate  10 , and an adhesive layer  22 , for bonding the conductive film  1  to other devices, may be disposed on a surface of the substrate  10  that is opposite to the surface where the first hard coated layer  12 , the second hard coated layer  14 , the first refraction layer  16 , and the second refraction layer  18  are placed with respect to the substrate  10 . In one implementation, the adhesive layer  22  is made of materials with superior optical characteristics such as an acrylic adhesive, a urethane adhesive or a silicone adhesive. 
         [0019]    The first hard coated layer  12  may be in contact with the substrate  10  when disposed on the substrate  10 . The second hard coated layer  14  may be disposed on the first hard coated layer  12  with the first refraction layer  16  placed between the second refraction layer  18 , which is in contact with the transparent conductive layer, and the second hard coated layer  14 . In other words, arrangement of the first hard coated layer  12 , the second hard coated layer  14 , the first refraction layer, and the second refraction layer  18  may be in terms of a predetermined order. The first refraction layer  16  may be a metallic oxide layer which is made of titanium oxide, ITO, tantalum oxide tin oxide, or combinations of any two of the aforementioned. The second refraction layer  18  may be a siloxane-based polymer layer which is made of inorganic silica-based compounds or polyorganosiloxane-based compounds or mixtures of these compounds. 
         [0020]    It is worth noting that the thickness of the first hard coated layer  12  may range between six to ten micrometers. And the first hard coated layer  12  may be with no silicon-based material but with carbon and hydrogen. On the other hand, the second hard coated layer  14  may have the silicon-based material accounting for sixty to ninety percents of the weight thereof. The second hard coated layer  14  may be one to two micrometers in thickness. It is also worth noting that carbon, hydrogen, SiO 2  and TiO 2  may also be part of the second hard coated layer  14 . 
         [0021]    As to the first hard coated layer  12  and the second hard coated layer  14 , no limitation concerning weight percentages of the carbon, hydrogen, SiO 2  and TiO 2 , so long as the conductive film  1  may pass the endurance test. 
         [0022]    In practice, by properly selecting the thickness and the refractive index of the first hard coated layer  12 , the second hard coated layer  14 , the first refraction layer  16 , and the second refraction layer  18 , the etched traces in the conductive film  1  formed over the course of the etching process may not be observable by human eyes, and the difference in color display may be minimized. In one implementation, when the thickness of the first refraction layer  16  is in the range of 100 Å to 300 Å, and the refractive index thereof is in the range of 1.6 to 2.0 and the thickness of the second refraction layer  18  is in the range of 500 Å to 700 Å, and the refractive index of the second refraction layer  18  is in the range of 1.42 to 1.46 the etched traces in the conductive film  1  formed over the course of the etching process and the difference in the color display may not be observable. 
         [0023]    Since the transparent conductive layer  20  may be disposed on the second refraction layer  18 , the transparent conductive layer  20  may be the outer-most layer of the conductive film  1 . After the etching process, only predetermined areas of the transparent conductive layer  20  may be etched to form specific patterns and the transparent conductive layer  20  at the predetermined areas may be entirely etched away. Other areas of the transparent conductive layer  20  may continue overlapping the second refraction layer  16 . In one implementation, the transparent conductive layer  20  may be made of SnO2, ZnO2, In2O3, or ITO, and the thickness of the transparent conductive layer  20  may range from 150 Å to 250 Å. More specifically, the thickness of the transparent conductive layer  20  may be 180 Å when the transparent conductive layer  18  is made of ITO. 
         [0024]    A refractive index of the transparent conductive layer  20  may be in the range of 1.9 to 2.1. Moreover, since the transparent conductive layer  20  may be associated with high conductivity the grounding process for the conductive film  1  may be simplified, increasing the yield in the manufacturing process. Also because of the conductivity of the transparent conductive layer  20 , the electrode may be formed efficiently on the transparent conductive layer  20 . Therefore, the present invention may be applicable to the touch panel. In practice, in order to prevent the etched traces from being observed, the thickness and the refractive index of the transparent conductive layer  20  shall be selected with the refractive index and the thickness of the first hard coated layer  12 , the second hard coated layer  14 , the first refraction layer  16 , and the second refraction layer  18  taken into account. 
         [0025]    When a light enters into both the transparent conductive layer  20  and the second refraction layer  18  of the conductive film  1  with an incident angle, the light may be associated with a first reflectance R 1 . On the other hand, when the light only enters into the second refraction layer  18  with the same incident angle rather than into the transparent conductive layer  20  the light may be associated with a second reflectance R 2 . The difference between the first reflectance (R 1 ) and the second reflectance (R 2 ) may be lower than a first threshold value, which in one implementation is 0.5. Under this arrangement the difference in the reflectance is relatively small so that the etched traces may become not observable. 
         [0026]    Further, when the light penetrates the transparent conductive layer  20  and the second refraction layer  18  of the conductive film  1  with the incident angle, the light may be associated with a first transmittance T 1 . And when the light only penetrates the second refraction layer  18  with the same incident angle, the light may be associated with a second transmittance T 2 . The difference between the first transmittance (T 1 ) and the second transmittance (T 2 ) may be lower than a second threshold value, which in one implementation may be lower than 0.5. In ensuring the relatively small difference in the transmittance between the light penetrating both the transparent conductive layer  20  and the second refraction layer  18  and the light penetrating the second refraction layer  18  only, the conductive film  1  according to the present invention may cause the etched traces formed over the course of the etching process not to be observed by the users since the light travels straight forward and when the difference in the light transmittance between T 1  and T 2  is relatively small enough regardless of whether the light enters into the conductive film  1  from one surface of the substrate  10  and passes through the transparent conductive layer  20  and/or the second refraction layer  18  or from the opposite (back) surface of the substrate  10 . 
         [0027]    The conductive film  1  may be attached to the light-emitting surface of a display device using the adhesive layer  22 . The display device may include LCD, CRT, touch panel, or other electric devices having the aforementioned display devices. In this case, the users may not be interfered with said etched traces while watching images through the conductive film  1  of the present invention. 
         [0028]    It is worth noting that by having two hard coated layers incorporated the conductive film of the present invention may further enhance optical performances of the conductive film in terms of light uniformity. 
         [0029]    The descriptions illustrated supra set forth simply the preferred embodiments of the present invention; however, the characteristics of the present invention are by no means restricted thereto. All changes, alternations, or modifications conveniently considered by those skilled in the art are deemed to be encompassed within the scope of the present invention delineated by the following claims.