Patent Abstract:
A method of producing a touch screen includes feeding and laminating a roll of an adhesive sheet material to bond a sheet glass, a roll of a first sheet material having first electrodes, and a roll of a second sheet material having second electrodes; pinching and pressing the laminated sheet materials between a pair of press rollers to form a laminated body of the bonded sheet materials. When being fed, the sheet materials are cut off at a predetermined length corresponding to a lateral size of a rectangular touch screen, and thus the sheet materials can be provided in a predetermined size in one cutting process. Rolling the sheet materials reduces wrinkles and folds and eliminates a protection sheet for each sheet material, which is required in a case of stacking a plurality of planar sheets, thus facilitating cost reduction.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority under 35 U.S.C. §119 of Japanese Application No. 2011-139437 filed on Jun. 23, 2011, the disclosure of which is expressly incorporated by reference herein in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method of producing a touch screen, particularly a method of producing a capacitance touch screen having linear electrodes intersecting one another. 
         [0004]    2. Description of Related Art 
         [0005]    A conventional touch screen has two sheet materials, each of which includes a plurality of linear electrodes parallel to one another. A first sheet material is bonded to a sheet glass and a second sheet material is bonded thereto such that the linear electrodes of the second sheet material intersect the linear electrodes of the first sheet material in a plan view. 
         [0006]    Japanese Patent Laid-Open Publication No. 2009-064693A discloses a touch screen having a touch switch intermediate body for a capacitance touch switch produced by forming a base body portion in injection molding of a clear resin and bonding a clear conductive layer to a surface of the base body portion in in-mold forming to produce a clear conductive film. 
         [0007]    In the touch screen disclosed in Japanese Patent Laid-Open Publication No. 2009-064693A, work hours can be reduced by using an in-mold film to bond the clear conductive film to the base body portion in in-mold forming. A process is required, however, to cut the in-mold film to fit the size of the base body portion for bonding of the clear conductive film, concurrently with forming of the base body portion in injection molding. In addition, positioning is required again to laminate two base body portions. Thus, work hours are increased and processes are complicated in a case of application to a touch screen having intersecting electrodes in a plan view. 
         [0008]    Japanese Patent Laid-Open Publication No. 2010-262529A discloses a touch screen having a similar capacitance touch switch produced by screen printing or etching a metallic foil to form mesh electrodes on one surface of each of two substrates and by bonding and integrating the two substrates such that the mesh electrodes are provided opposite to each other through an adhesive layer. 
         [0009]    In the touch screen disclosed in Japanese Patent Laid-Open Publication No. 2010-262529A, work hours can be reduced by forming the mesh electrodes by printing or etching. However, positioning is required to laminate the two substrates, complicating a process. 
         [0010]    Japanese Patent Laid-Open Publication No. 2009-070191A discloses a touch screen having a capacitance sensor including very fine electrode groups, which is produced by bonding a pair of clear films each having a conductive film on one surface such that conductive films are provided outside and by etching the conductive films to form a plurality of electrode groups. 
         [0011]    In the touch screen disclosed in Japanese Patent Laid-Open Publication No. 2009-070191A, however, etching after bonding the pair of clear films requires protection of one of the films while etching the other, thus increasing work hours and complicating a process. 
       SUMMARY OF THE INVENTION 
       [0012]    In view of the circumstances above, a main advantage of the present invention is to provide a method of producing a touch screen in reduced work hours and a simplified process. 
         [0013]    An aspect of the present invention provides a method of producing a touch screen including a first sheet material having a plurality of linear first electrodes disposed in parallel to one another; a second sheet material having a plurality of linear second electrodes disposed in parallel to one another; and a laminated body provided by bonding the first sheet material onto the second sheet material such that the first electrodes and the second electrodes intersect with each other, the method including rolling the first sheet material and the second sheet material in directions in which the first electrodes and the second electrodes intersect with each other; providing an adhesive layer and a peel-off sheet covering the adhesive layer on at least one of the first sheet material and the second sheet material; feeding the rolled first sheet material and the rolled second sheet material; removing the peel-off sheet; and bonding the first sheet material and the second sheet material with the adhesive layer therebetween to form the laminated body. 
         [0014]    According to the present invention, the width of the rolled sheet materials is provided so as to correspond to the longitudinal length of a rectangular touch screen, for example, and the sheet materials are cut at a predetermined length corresponding to the lateral size of the rectangular touch screen when fed out. Thus, the sheet materials in a predetermined size can be provided in one cutting process. Furthermore, rolling the sheet materials reduces wrinkles and folds compared to a case where sheet materials are stacked in flat piles. In addition, it is unnecessary to provide the rolled sheet materials with a protection sheet for each sheet material, which is required in a case of stacking a plurality of planar sheets to feed one by one, thus facilitating cost reduction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein: 
           [0016]      FIG. 1  schematically illustrates a production overview of a touch screen according to an embodiment of the present invention; 
           [0017]      FIGS. 2A to 2C  are each cross-sectional views of a main portion illustrating a sheet material for adhesion, a first sheet material, and a second sheet material, respectively; 
           [0018]      FIGS. 3A and 3B  are each plan views illustrating the first sheet material and the second sheet material, respectively; 
           [0019]      FIGS. 4A and 4B  are each partial cross-sectional views illustrating a state in which the sheet materials are laminated and bonded and a state in which a second electrode lead is exposed, respectively; 
           [0020]      FIG. 5  is a plan view illustrating an enlarged portion of the touch screen; and 
           [0021]      FIG. 6  is a view illustrating a second embodiment in a similar manner to  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0022]    The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description is taken with the drawings making apparent to those skilled in the art how the forms of the present invention may be embodied in practice. 
         [0023]    The embodiments of the present invention are described in detail below with reference to the drawings. 
         [0024]      FIG. 1  schematically illustrates a production overview of a touch screen according to the embodiment of the present invention. Three rolls R 1 , R 2 , and R 3  are prepared as materials of a touch screen as shown in  FIG. 1 . The upper roll R 1  in the drawing is a rolled adhesive sheet material  1  for bonding a sheet glass described herein after. With reference to  FIG. 2A , front and rear surfaces of the adhesive sheet material  1  are each covered by a sheet separator  1   a  to prevent the rolled adhesive sheet material  1  from adhering in an overlapping portion. 
         [0025]    The middle roll R 2  in  FIG. 1  is a rolled first sheet material  2 . With reference to  FIG. 2B , the first sheet material  2  has, in a laminated state, a sheet base material  2   a  composed of a flexible clear plastic, for example; a fixing layer  2   b  composed of an adhesive agent, for example, provided on an upper surface in the drawing of the sheet base material  2   a;  a plurality of linear first electrodes  3  fixed by the fixing layer  2   b;  and an adhesive layer  2   c  composed of an adhesive agent provided on a rear surface in the drawing of the sheet base material  2   a.    
         [0026]    The first electrodes  3  are provided in parallel to one another and extend in a front/back direction of a paper surface of the drawing. The plurality of first electrodes  3  are covered by an electrode protection film  2   d.  A lower surface in the drawing of the adhesive layer  2   c  is covered by a sheet separator  2   e  that serves as a peel-off sheet. The first sheet material  2  is preferably rolled such that the first electrodes  3  are provided inside. With the first electrodes  3  provided outside, in contrast, a tensile load is exerted on the first electrodes  3 , thus possibly leading to disconnection. Conversely, with the first electrodes  3  provided inside, a load in a compression direction is exerted on the first electrodes  3 , thus unlikely to be disconnected. 
         [0027]    The first electrodes  3  of the first sheet material  2  extend one by one in a direction orthogonal to a feeding direction (left/right direction in the drawing) of the first sheet material  2  and are provided in parallel to one another in a plan view as shown in  FIG. 3A . First electrode groups  31 , each of which is composed of the first electrodes  3  in a number corresponding to a range of the size of a touch screen as a product, are continuously provided with predetermined intervals in between in the feeding direction. A first electrode lead  3   a  having a flat terminal shape is provided in an upper portion in the drawing of each of the first electrodes  3  for electrical connection with an external circuit (not show in the drawing). 
         [0028]    The lower roll R 3  in  FIG. 1  is a rolled second sheet material  4 . With reference to  FIG. 2C , the second sheet material  4  has, in a laminated state, a sheet base material  4   a  composed of a flexible clear plastic, for example; a fixing layer  4   b  composed of an adhesive agent, for example, provided on an upper surface in the drawing of the sheet base material  4   a ; and a plurality of linear second electrodes  5  fixed by the fixing layer  4   b.  The plurality of second electrodes  5  extend in the left/right direction in the drawing and are provided in parallel to one another. The plurality of second electrodes  5  are covered by an electrode protection film  4   c . Similar to the first sheet material  2 , the second sheet material  4  is rolled such that the second electrodes  5  are provided inside. 
         [0029]    The second electrodes  5  of the second sheet material  4  extend one by one in the feeding direction (left/right direction in the drawing) of the second sheet material  4  and are provided in parallel to one another in a plan view as shown in  FIG. 3B . Second electrode groups  51 , each of which is composed of the second electrodes  5  having an extending length corresponding to a range of the size of a touch screen as a product, are continuously provided with predetermined intervals in between in the feeding direction. A second electrode lead  5   a  having a flat terminal shape is provided in a right portion in the drawing of each of the second electrodes  5  for electrical connection with an external circuit (not show in the drawing). 
         [0030]    The electrodes  3  and  5  are formed by etching a copper foil, for example, such that a mesh pattern including continuous rhombic meshes extends in a belt shape (not shown in the drawing). Since the electrodes are provided in such a mesh pattern, conductivity is maintained as a whole (one piece) even if a portion is disconnected. 
         [0031]    The sheet materials  1 ,  2 , and  4  are fed from the three rolls R 1  to R 3 , respectively, configured as above. The sheet materials  2  and  4  are vertically laminated such that the electrode groups  31  and  51  overlap in a plan view, and then the adhesive sheet material  1  is laminated onto the first sheet material  2 . Before each of the sheet is laminated, the sheet separator  1   a  on the first sheet material  2  side is removed from the adhesive sheet material  1 , the electrode protection film  2   d  and the sheet separator  2   e  are removed from the first sheet material  2 , and the electrode protection film  4   c  is removed from the second sheet material  4  by a peeler (not shown in the drawing). The laminated sheet materials  1 ,  2 , and  4  are pinched between a pair of pressure rollers  6   a  and  6   b  as shown in  FIG. 1 , for example. 
         [0032]    The sheet materials  1 ,  2 , and  4  are pressed between the pair of pressure rollers  6   a  and  6   b  and are fed. Then, as shown in  FIG. 4A , the adhesive sheet material  1  covering the first electrodes  3  is bonded onto the first sheet material  2 , and the second sheet material  4  is bonded to the lower surface of the first sheet material  2  in a state where the second electrodes  5  are covered by the adhesive layer  2   c.  Thus, a laminated body of the sheet materials  1 ,  2 , and  4  is provided as a touch screen material  7  integrated into one sheet. The touch screen material  7  is cut at a predetermined length in a feeding direction by cutters  8   a  and  8   b  disposed at predetermined intervals in the next process. The length corresponds to the length of a range in which the electrode groups  31  and  51  are disposed and may be a lateral width of a touch screen as a product, for example. 
         [0033]    As indicated with a dashed two-dotted line in  FIG. 3A , in a case where the feeding direction of the adhesive sheet material  1  is the lateral width direction of the touch screen as a product, a longitudinal width B 1  orthogonal to the lateral width is shorter by a predetermined length than a longitudinal width B 2  of the first sheet material  2 . Aligning the ends of the adhesive sheet material  1  and the first sheet material  2  opposite to the first electrode lead  3  side as shown in  FIG. 4A  for lamination allows exposure of a portion of the first electrode lead  3   a  at the end of the first electrode  3 . 
         [0034]    Subsequently, the touch screen material  7  is cut by a cutter  8   c  at a position for a predetermined length to the left from the right end in  FIG. 4A  for a depth where the second electrodes  5  are exposed. Then, the right end portions of the adhesive sheet material  1  and the first sheet material  2  are cut off. The cutter  8   c  preferably has an L shape, as shown in the drawing, composed of a main portion and a blade for cutting, the main portion being pressed against the front surface of the sheet separator  1   a , for example. In this case, a length (cutting depth) C of the blade of the cutter  8   c  is slightly shorter than a length D from the front surface of the sheet separator  1   a  to the second electrode lead  5   a  (C&lt;D). It is preferred that the blade edge be set so as not to reach the second electrode lead  5   a  even if the adhesive sheet material  1  and the fixing layer  2   b  are elastically deformed due to the pressing force of the main body of the cutter  8   c.  Thus, as shown in  FIG. 4B , the adhesive sheet material  1  and the first sheet material  2  are cut off for a predetermined length L from the right end in the drawing of the second sheet material  3  and a portion of the second electrode lead  5   a  at the end of the second electrode  5  is exposed. 
         [0035]    As a guide to position the cutter  8   c,  guiding perforations  12  may be provided, for example, as shown in  FIG. 3A . This allows easy and highly accurate positioning for cutting in a cutting process by the cutter  8   c.    
         [0036]    As described above, the sheet materials  1 ,  2 , and  4  are fed from the rolled rolls R 1  to R 3 , respectively, and are laminated and bonded. With the adhesive agent previously integrated to either of the first sheet material  2  or the second sheet material  4  (first sheet material  2  in the embodiment), pressing the laminated sheet materials  1 ,  2 , and  4  fed from the rolls R 1  to R 3 , respectively, by the pair of press rollers  6   a  and  6   b  readily bonds the sheet materials  1 ,  2 , and  4 . This simplifies a bonding process in which sheet materials are laminated sheet by sheet in order and each of the sheet materials is positioned for bonding. In addition, pressing by the pair of press rollers  6   a  and  6   b  for bonding prevents bubbles from forming between the bonded surfaces, thus improving the yield and reducing the production cost. 
         [0037]    Thus, the sheet materials  1 ,  2 , and  4  are bonded in a laminated state and thereby the touch screen material  7  is provided that functions as a capacitance touch screen in which the electrodes  3  and  5  are provided opposite to each other with predetermined distances such that a plurality of intersections are provided in a plan view. The electrode leads  3   a  and  5   a  are exposed as described above. 
         [0038]    After the touch screen material  7  is provided, a sheet glass  9  is placed and bonded to the adhesive sheet material  1  as shown in  FIG. 4B . The sheet glass  9  is prepared in advance in the size of a touch screen as a product. In the case of bonding the sheet glass  9 , the sheet glass  9  is bonded later as described above. In a case of a touch screen to which a flexible clear material is bonded instead of the sheet glass  9 , the clear material may be inserted concurrently in the pinching process of the sheet materials  1 ,  2 , and  4  between the pair of the press rollers  6   a  and  6   b , thus further streamlining the process. 
         [0039]    With reference to  FIG. 5 , which schematically illustrates an enlarged portion of the touch screen  10  produced in the process above, the first electrode leads  3   a  are disposed in parallel on one side and the second electrode leads  5   a  are disposed in parallel on another side having one corner of a rectangle therebetween. The electrode leads  3   a  and  5   a  are electrically connected to an external controller  11  through lead wires. 
         [0040]    In the laminated structure of the embodiment above, the first electrodes  3  are provided on the upper side and the second electrodes  5  are provided on the lower side. The laminated structure, however, is not limited to above. A laminated structure may have the first electrodes  3  on the lower side and the second electrodes  5  on the upper side. In this case, a portion in which the first electrode leads  3   a  are covered by the second sheet material  4  may be cut off in a similar manner to the cutting by the cutter  8   c.    
         [0041]    The electrode leads  3   a  and  5   a  are disposed such that they are arranged along two sides with one corner of the rectangular touch screen  1  therebetween. Alternatively, the electrodes may be disposed along opposing sides, as shown in  FIG. 6 , for example, as a second embodiment. In  FIG. 6 , the first sheet material  2  is laminated onto the second sheet material  4 , and the sheet glass  9  is laminated onto the first sheet material  2 , similar to the embodiment above. The first electrode leads  3   a  are disposed in parallel along the upper side in the drawing, similar to the embodiment above, while the second electrode leads  5   a  are disposed in parallel along the lower side in the drawing, opposite to the side along which the first electrode leads  3   a  are disposed. 
         [0042]    As shown in  FIG. 6 , longitudinal widths B 2 , B 4 , and B 9  of the sheet materials  2  and  4  and the sheet glass  9 , respectively, are defined such that the longitudinal width B 2  of the first sheet material  2  laminated onto the second sheet material  4  is shorter than the longitudinal width B 4  of the second sheet material  4  to expose portions of the second electrode leads  5   a  and such that the longitudinal width B 9  of the sheet glass  9  is shorter than the longitudinal width B 2  of the first sheet material  2  to expose portions of the first electrode leads  3   a.  The adhesive sheet material  1  has the same longitudinal width as the sheet glass  9 . Thus, the electrode leads  3   a  and  5   a  are exposed in a state in which the sheet materials  2  and  4  and the sheet glass  9  are laminated, eliminating the process to partially cut by the cutter  8   c  in the embodiment above. 
         [0043]    Eliminating the cutting process in the second embodiment facilitates cost reduction. However, a transmission path to the second electrode lead  5   a  of the second electrode  5  is longer than that in the first embodiment as shown in  FIG. 6 . Thus, the layout may be appropriately selected according to a purpose of use. Specifically, in a case where high transmission efficiency is required, short transmission paths to the electrode leads  3   a  and  5   a  of the electrodes  3  and  5 , respectively, are prioritized as shown in  FIG. 5 , while in the case where it is unnecessary to consider an impact of reduced transmission efficiency, the second embodiment is employed. 
         [0044]    It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to exemplary embodiments, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular structures, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims. 
         [0045]    The present invention is not limited to the above described embodiments, and various variations and modifications may be possible without departing from the scope of the present invention.

Technology Classification (CPC): 6