Patent Publication Number: US-2015086708-A1

Title: Method of processing a substrate

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a touch panel technology, and particularly relates to a panel lamination method. 
     2. Description of the Prior Art 
     In today&#39;s various types of consumer electronic products, such as tablet PCs, personal digital assistant (PDA) devices, mobile phone devices, satellite navigation systems, video players, and other portable electronic products, touch panel components have been widely used as the man-machine interface to communicate the information. 
     Typically, a touch panel element includes a sensor substrate and protective cover. The sensor substrate is laminated with the protective cover using an optical adhesive film. However, the optical adhesive film used in the conventional bonding or lamination method is too thick, usually to a thickness of  25  microns. This limits the further thinning of the touch devices. 
     Therefore, a need remains in the art for an improved method of laminating or processing a panel or a substrate in order to achieve further thinning of the touch panel devices. 
     SUMMARY OF THE INVENTION 
     To solve the above problems and improve the quality of bonding, the present invention provides a method of processing a panel or substrate such that the thickness of a touch panel element can be further decreased. 
     According to one embodiment of the invention, a method of processing a substrate or panel is disclosed. A substrate having thereon an array of chips is provided. A mask layer is laminated on the substrate. The mask layer has a plurality of openings to reveal active areas of the chips respectively. A spray-coating process is then performed to form an adhesive film in the active areas. The mask layer is then stripped off. 
     According to the embodiments of the invention, the mask layer may comprise a releasable adhesive, a metal mask, or a combination thereof. 
     According to the embodiments of the invention, the spray-coating process may employ an adhesive material having a low viscosity that ranges between 10 centipoise (cps) and 3000 cps. 
     According to the embodiments of the invention, the adhesive material having a low viscosity may comprise epoxy resins, polyesters, or polymethyl methacrylate (PMMA). 
     According to the embodiments of the invention, the adhesive film may have a thickness that is smaller than 5 micrometers. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1-4  demonstrate a method of processing a panel or a substrate according to one embodiment of the invention. 
         FIGS. 5-7  depict various embodiments wherein the mask layer has different types or combinations to form different structural features in the adhesive film. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1-4  demonstrate a method of processing a panel or a substrate according to one embodiment of the invention. 
     First, as shown in  FIG. 1 , a substrate  10 , such as a sensor substrate of a touch panel device, is provided. A plurality of chips  11  in an array (in this example to 5×5 array arrangement) is provided on the substrate  10 . The chips  11  are separated from one another by a cutting lane  102 . 
     According to the embodiment of the invention, the aforesaid substrate  10  may comprise a transparent substrate and at least one sensor electrode layer (not shown), but not limited thereto. 
     The aforesaid transparent substrate may comprise a polyethylene terephthalate (PET) substrate or a glass substrate, but not limited thereto. 
     The aforesaid sensor electrode layer may comprise indium tin oxide (ITO) transparent electrode, but not limited thereto. 
     As can be seen in the enlarged area in  FIG. 1 , each of the chips  11  may comprise an active area  110 , a peripheral area  112  that surrounds the active area  110 , and a FPC (flexible printed circuit) bonding area  114 . The aforesaid active area may also be referred to as display area or effective area. 
     According to the embodiment of the invention, a plurality of gold fingers  114   a  may be disposed within the FPC bonding area  114 . 
     As shown in  FIG. 2 , a mask layer  20  is laminated onto the substrate  10 . The mask layer  20  may comprise a plurality of openings  210  to respectively expose the active areas  110  of the chips  11 . 
     The surfaces of the substrate  10  except for the active areas  110  are masked. More specifically, the cutting lanes  102 , the peripheral areas  112 , and the FPC bonding areas  114  are masked by the mask layer  20 . 
     According to the embodiment of the invention, the aforesaid mask layer  20  may comprise a releasable adhesive, a metal mask, or a combination thereof. 
     As shown in  FIG. 3 , a spray-coating process is carried out to form an adhesive film  30  onto the exposed active areas  110  that are not masked by the mask layer  20  by using a spray coating apparatus  300 . 
     According to the embodiment of the invention, to form the adhesive film  30 , the aforesaid spray-coating process employs an adhesive material having a low viscosity that ranges between 10 centipoise (cps) and 3000 cps. 
     According to the embodiment of the invention, the aforesaid adhesive material having a low viscosity may comprise epoxy resins, polyesters, or polymethyl methacrylate (PMMA). 
     According to the embodiment of the invention, the aforesaid adhesive film  30  has a solvent residue rate that is greater than 1%. 
     According to the embodiment of the invention, the aforesaid adhesive film  30  has a thickness that is smaller than  5  micrometers. 
     According to the embodiment of the invention, the aforesaid adhesive film  30  has a uniformity that is smaller than 10%. 
     According to the embodiment of the invention, the aforesaid adhesive film  30  has a surface roughness Ra that is greater than 0.01 micrometers, wherein Ra is center line average roughness. 
     According to the embodiment of the invention, the aforesaid adhesive film  30  has a surface profile variation of about 0.3 μm/mm. 
     As shown in  FIG. 4 , subsequently, the aforesaid mask layer  20  is removed, leaving the array pattern of the adhesive film  30  intact. At this point, it is understood that the adhesive film  30  is only formed within the active areas  110  of the chips  11 . The adhesive film  30  has a thickness of less than 5 micrometers. 
     According to the embodiments of the invention, the mask layer  20  may have different types or combinations to form different structural features in the adhesive film  30 , as shown in  FIGS. 5-7 . 
       FIG. 5  depicts an embodiment wherein the mask layer  20  is a releasable adhesive. After stripping the releasable adhesive, along the perimeter of each of the active areas  110 , a slope structure or a protrusion may be formed in the adhesive film  30 , wherein a twist angle θ may be greater than 15 degrees. 
       FIG. 6  depicts an embodiment wherein the mask layer  20  is a metal. Because the masked areas may not be tightly masked, splashing may occur during the spray-coating process. Colloidal particles may be deposited according to a Gaussian distribution from the active area  110  to the surrounding masked area. 
       FIG. 7  depicts an embodiment wherein the mask layer  20  is a combination of metal and releasable adhesive. An R angle may be seen along the perimeter of the adhesive film  30  within each of the active areas  110 . The aforesaid R angle may be greater than 0.1 mm. 
     After completing the steps of forming the patterned adhesive film  30  as set forth through  FIGS. 1-4 , the substrate  10  may then be laminated with another substrate. 
     The aforesaid another substrate may be a glass substrate including, but not limited to, a soda lime substrate, a cover glass, or a sapphire substrate. 
     Alternatively, the aforesaid another substrate may be a sheet substrate such as a PET film, an ITO film, or piezoelectric materials. 
     After the above-mentioned substrates are laminated and bonded together, a post treatment process such as UV curing, post-baking, or chemical strengthening treatments may be performed. Thereafter, a cutting process may be performed to singulate the plurality of chips  11 . 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.