Patent Publication Number: US-2012026126-A1

Title: Capacitive touch screen

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2010-0072311, filed on Jul. 27, 2010, entitled “Capacitive Touch Screen”, which is hereby incorporated by reference in its entirety into this application. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a capacitive touch screen. 
     2. Description of the Related Art 
     With the development of the mobile communication technology, user terminals such cellular phones, PDAs, and navigations can serve as a display unit that simply displays character information as well as a unit for providing various and complex multi-media such as audio, moving picture, radio internet web browser, etc. Therefore, electronic information terminals having a limited size require a larger display screen, such that a display device using a touch screen has become the main focus. 
     The touch screen combines a screen and coordinate input units, thereby saving space as compared to a key input scheme according to the prior art. Therefore, a display apparatus recently developed uses a touch screen in order to more improve a screen size and user convenience. 
     The touch screen is classified into a resistive type and a capacitive type. The resistive touch screen includes a pair of base members that are spaced apart from each other by a spacer having an opening formed inside thereof and have resistive films formed on opposite surfaces, and sensing electrodes that are formed in outer regions of the resistive films to sense a change in voltage generated from the resistive films. The capacitive type is classified into a self capacitive touch screen and a mutual capacitive touch screen. The self capacitive touch screen includes a base member having a plurality of electrode patterns formed on one surface thereof and detects a change in capacitance generated from the electrode patterns when the touch screen is touched by an input unit from the outside to calculate coordinates of the touched points. In such a self capacitive touch screen having a single layer structure, each of the electrode patterns has unique coordinate information. In addition, the mutual capacitive touch screen includes a base member having a plurality of electrode patterns formed on opposite surfaces with different directionalities and a spacer spatially separating the electrode patterns, and detects a mutual change in capacitance generated from the electrode patterns separated and disposed when the touch screen is touched by an input unit from the outside to calculate the coordinates of the touched points. 
     Reviewing the touch screens according to the prior art, in the resistive touch screen, a conductive material is applied over the base member, thereby not causing a problem. However, in the capacitive touch screen, the electrode patterns are formed by patterning a conductive material with a unique color and the base member is made of a transparent material, thereby causing a visibility problem in that the electrode pattern is recognized distinctively from the base member. 
     Such a visibility problem is noticeable at the edge regions of the electrode patterns and it becomes more serious when the electrode pattern is made of a conductive polymer. The conductive polymer is advantageous in view of low manufacturing costs as compared to the known metal oxide such ITO but is disadvantageous in view of low transparency. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in an effort to provide a capacitive touch screen in which electrode patterns are made of a conductive polymer and a color of a base member corresponds to a unique color of the conductive polymer to reduce visibility of the electrode patterns, different from a capacitive touch screen according to the prior art in which a base member made of a transparent material is used in order to improve light transmittance. 
     A capacitive touch screen according to a preferred embodiment of the present invention includes: a base member; a plurality of electrode patterns formed on one surface of the base member and made of a conductive polymer; and electrode wirings connected to the electrode patterns and sensing a change in capacitance, wherein a color of the base member corresponds to a unique color of the conductive polymer. 
     Brightness of the base member corresponds to unique brightness of the electrode pattern or chroma of the base member corresponds to unique chroma of the electrode pattern. 
     The base member is a glass substrate or a film substrate. 
     The conductive polymer is any one of polythiophene, polypyrrole, polyaniline, polyacetylene and polyphenylene polymers. 
     The capacitive touch screen further includes a protective layer covering the electrode patterns and the electrode wirings. 
     A capacitive touch screen according to a preferred embodiment of the present invention includes: a base member; a plurality of electrode patterns formed on one surface of the base member and made of a conductive polymer; a compensation layer formed on one surface of the base member and having a color corresponding to a unique color of the conductive polymer; and electrode wirings connected to the electrode patterns and sensing a change in capacitance. 
     The compensation layer is formed over one surface of the base member and the electrode patterns are formed on the compensation layer. 
     Brightness of the compensation layer corresponds to unique brightness of the electrode pattern or chroma of the compensation layer corresponds to unique chroma of the electrode pattern. 
     The base member is a glass substrate or a film substrate. 
     The conductive polymer is any one of polythiophene, polypyrrole, polyaniline, polyacetylene and polyphenylene polymers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a capacitive touch screen according to a first preferred embodiment of the present invention; 
         FIG. 2  is a cross-sectional view of the capacitive touch screen of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view showing a modified example of the capacitive touch screen of  FIGS. 1 and 2 ; 
         FIG. 4  is a plan view showing another modified example of the capacitive touch screen of  FIGS. 1 and 2 ; 
         FIG. 5  is a plan view of a capacitive touch screen according to a second preferred embodiment of the present invention; 
         FIG. 6  is a cross-sectional view of the capacitive touch screen of  FIG. 5 ; and 
         FIG. 7  is a cross-sectional view showing a modified example of the capacitive touch screen of  FIGS. 5 and 6 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Various features and advantages of the present invention will be more obvious from the following description with reference to the accompanying drawings. 
     The terms and words used in the present specification and claims should not be interpreted as being limited to typical meanings or dictionary definitions, but should be interpreted as having meanings and concepts relevant to the technical scope of the present invention based on the rule according to which an inventor can appropriately define the concept of the term to describe most appropriately the best method he or she knows for carrying out the invention. 
     The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. In the specification, in adding reference numerals to components throughout the drawings, it is to be noted that like reference numerals designate like components even though components are shown in different drawings. Further, when it is determined that the detailed description of the known art related to the present invention may obscure the gist of the present invention, the detailed description thereof will be omitted. 
     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is a plan view of a capacitive touch screen according to a first preferred embodiment of the present invention,  FIG. 2  is a cross-sectional view of the capacitive touch screen of  FIG. 1 , and  FIGS. 3 and 4  show modified examples of the capacitive touch screen of  FIGS. 1 and 2 . Hereinafter, a capacitive touch screen (hereinafter, referred to as a touch screen) according to the present embodiment will be described with reference to these figures. 
     A touch screen  100  according to the present embodiment uses a base member  110  including pigment to reduce visibility of electrode patterns  120  having a unique blue color. 
     The base member  110  may include the electrode patterns  120  formed on one surface thereof and may use a glass substrate or a film substrate. Among others, the film substrate may be made of polyethyleneterephthalate (PET), polymethylmethacrylate (PMMA), polypropylene (PP), polyethylene (PE), polyethylenenaphthalate (PEN), polycarbonate (PC), polyethersulfone (PES), polyimide (PI), polyvinyl alcohol (PVA), cyclic olefin copolymer (COC), styrene polymer, and so on, but is not particularly limited thereto. 
     The plurality of electrode patterns  120  formed on the base member  110  are made of a conductive polymer. The conductive polymer may adopt an organic compound, such as polythiophene, polypyrrole, polyaniline, polyacetylene, polyphenylene, or the like. In particular, among the polythiophene, poly-3,4-ethylenedioxythiophene/polystyrenesulfonate (PEDOT/PSS) compound is most preferable and at least one of the organic compounds may be mixed. 
     As shown in  FIGS. 1 and 2 , when the touch screen  100  is a self capacitive type, the plurality of electrode patterns  120  are separately formed and have unique coordinate values. The electrode patterns shown in  FIGS. 1 and 2  may be modified to have a rectangular shape or another polygonal shape. 
     In addition, electrode wirings  130  connected to the electrode patterns  120  are formed on the base member  110 . The electrode wiring  130  connected to the electrode pattern  120  may be made of a conductive material (for example, silver (Ag) paste) and be disposed to be collected at one side of the base member  110 . 
     The conductive polymer configuring the electrode pattern  120  has a unique color. At this time, the unique color may be partially different depending on the component of the conductive polymer but is generally tinged with blue. The unique color of the electrode pattern  120  may be defined by a L*a*b color system distinguishing colors by brightness, color, and chroma. 
     First, in order to reduce visibility of the electrode patterns  120  formed on the base member  110 , it is preferable that the color of the base member  110  corresponds to the unique color of the electrode pattern  120 . Even though the color of the base member  110  is not completely the same as the color of the electrode pattern  120 , if it is recognized as the color corresponding thereto, the electrode pattern  120  and the base member  110  may be recognized as a single member, such that the visibility of the electrode pattern  120  is reduced. 
     In addition, when the brightness or the chroma of the base member  110  corresponds to the unique brightness or the unique chroma of the electrode pattern  120 , the visibility of the electrode pattern  120  is further reduced. When the brightness or the chroma is the same on the assumption that the colors are the same among the three factors distinguishing the colors, the colors of the base member  110  and the electrode pattern  120  become more alike to each other. When both the brightness and the chroma are the same, the colors of the base member  110  and the electrode pattern  120  become the same. 
     The base member  110  is manufactured by including pigment so that the color of the base member  110  such as a glass substrate and a film substrate corresponds to the unique color of the electrode pattern  120  made of the conductive polymer. As the pigment, colored inorganic pigment, organic pigment, dyes, or the like may be used. 
     In this case, in a touch screen  100 ′ a protective layer  140  that covers electrode patterns  120  and electrode wirings  130  is stacked on a base member  110 , as shown in  FIG. 3 . The protective layer  140  may be made of the same material as the base member  110  and be stacked on the base member  110  by an optically clear adhesive. The protective layer  140  functions as dielectrics generating capacitance when the touch screen is touched by an input unit. 
     As shown in  FIG. 4 , the touch screen  100 ″ may be implemented according to a mutual capacitive type. The mutual capacitive touch screen  100 ″ also has a configuration similar to that of the self capacitive touch screen. 
     However, as shown in  FIG. 4 , a plurality of electrode patterns  120 ′ are formed in parallel, having directionality, wherein each of the electrode patterns  120 ′ has a rectangular bar shape. In addition, another base member as shown in  FIG. 4  is disposed to be spaced apart from the base member by a spacer, such that the electrode patterns have a two-layer structure. 
     The electrode patterns formed on another base member are generally formed to be longitudinal to the electrode patterns shown in  FIG. 4 . The electrode patterns are not limited to have a bar shape but may be modified. 
     In the mutual capacitive touch screen  100 ″, the electrode pattern is also made of a conductive polymer and the base member  110  has a color corresponding to the unique color of the conductive polymer, thereby reducing visibility of the electrode pattern. 
       FIG. 5  is a plan view of a capacitive touch screen according to a second preferred embodiment of the present invention,  FIG. 6  is a cross-sectional view of the capacitive touch screen of  FIG. 5 , and  FIG. 7  shows a modified example of the capacitive touch screen of  FIGS. 5 and 6 . Hereinafter, a capacitive touch screen (hereinafter, referred to as a touch screen) according to the present embodiment will be described with reference to these figures. 
     In a touch screen  200  according to the present embodiment, a color of a base member  210  does not correspond to a unique color of an electrode pattern but a compensation layer  215  having a color corresponding to the unique color of the electrode pattern  220  is formed on one surface of the base member  210 , different from the touch screen as shown in  FIGS. 1 to 4 . The touch screen  200  can be more simply manufactured, while obtaining the same effects, as compared to the case in which the color of the base member is changed by adding pigment to the base member. 
     As shown in  FIGS. 5 and 6 , the compensation layer  215  having a color corresponding to the unique color of the electrode pattern  220  made of a conductive polymer is formed on one surface of the base member  210  on which the electrode pattern  220  is formed. The compensation layer  215  is formed by applying pigment to a region on which the electrode patterns  220  are not formed. 
     In addition, it is more preferable that the brightness or the chroma of the compensation layer  215  corresponds to the unique brightness or the unique chroma of the electrode pattern  220 , in order to reduce visibility of the electrode pattern  220 . The color, brightness, and chroma of the compensation layer  215  are determined by pigment. 
     The base member  210  of the touch screen  200  as shown in  FIGS. 5 and 6  may also be configured of a film substrate or a glass substrate. In addition, the touch screen  200  may be modified according to a mutual capacitive type as described with reference to  FIG. 4 . 
       FIG. 7  shows a modified example of the touch screen of  FIGS. 5 and 6 . A compensation layer  215 ′ of a touch screen  200 ′ shown in  FIG. 7  is formed over one surface of the base member  210  and electrode patterns  220  are formed on the compensation layer  215 ′. 
     As compared with the touch screen shown in  FIGS. 5 and 6 , the touch screen  200 ′ has a structure in which the compensation layer  215 ′ is disposed between the electrode pattern  220  and the base member  210 . The touch screen  200 ′ forms the compensation layer  215 ′ on one surface of the base member  210  and then forms the electrode patterns  220 , such that it can be simply manufactured. Different from the touch screen shown in  FIGS. 5 and 6 , the touch screen  200 ′ previously prevents the possibility of pigment to be applied to the electrode pattern  220 . 
     According to the present invention, the electrode patterns are made of the conductive polymer, making it possible to lower manufacturing costs of the touch screen. 
     In addition, the present invention uses the base member having a color corresponding to a unique color of the electrode pattern, thereby making it possible to solve the visibility problem in that the electrode pattern is recognized distinctively therefrom. 
     In addition, the present invention can obtain equivalent effects, without controlling the refractive index in order to improve visibility, different from the prior art. 
     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Accordingly, such modifications, additions and substitutions should also be understood to fall within the scope of the present invention.