Abstract:
This invention proposes a flexible electrical heating element comprising a substrate, a metal interlayer coating and a far-infrared emissive carbon film. The flexible electrical heating element utilizes a low-cost and environmental friendly vacuum coating technique to deposit the metal interlayer coating and the far-infrared emissive carbon film on the flexible and insulating substrate which can provide uniform heating, and the far-infrared emissive carbon film can emit far-infrared.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This present invention relates to a flexible electrical heating element, more particularly to a flexible electrical heating element and manufacturing method thereof. 
         [0003]    2. Description of the Prior Arts 
         [0004]    Conventional electrical heating products are usually built by stiff, fragile and inflexible heating element such as metal wires, carbon heater and ceramic radiator. They bring inconvenience and are dangerous to the user caused by non-uniformly localized heating, user un-friendliness and the ease for electrical breakdown when in the situation of inappropriate bending during service. The heating element made from conventional carbon fiber though get rid of the problems stated above, the carbonization process for manufacturing carbon fiber is environmental unfriendly and expensive. 
       SUMMARY OF THE INVENTION 
       [0005]    In order to improve drawbacks stated in the Prior Arts, this invention proposes a flexible electrical heating element comprising a substrate as an insulating material which could be a polymeric fiber fabric or a glass fiber fabric, a metal interlayer coating deposited on the fabric substrate, and a carbon film deposited as the out most layer with far-infrared emission capability, wherein the flexible electrical heating element utilizing a vacuum coating technique to successively deposit the metal interlayer coating and the far-infrared emissive carbon film. Moreover, this invention proposes a method of manufacturing a flexible electrical heating element utilizing the vacuum coating technique comprising the following steps: 
         [0006]    a. substrate cleaning, 
         [0007]    b. depositing the metal interlayer coating onto the substrate, 
         [0008]    c. depositing the far-infrared emissive carbon film by using hydrocarbon gas onto the metal interlayer coating, 
         [0009]    d. the flexible electrical heating element manufactured. 
         [0010]    An advantage of this invention is utilizing the vacuum coating clean process to evenly deposit the metal interlayer coating and the far-infrared emissive carbon film onto a flexible insulating material, particularly in form of fabric. The uniformly covered metal interlayer coating provides area heating and carbon film emits far-infrared. The flexible insulating substrate performs as the support to further prevent fracture, damage or unexpected disaster for inappropriate bending during service. In addition, the flexible electrical heating element is capable of revitalizing human tissues beneficial from the far-infrared emitted by the carbon film. Moreover, based on the demands, an antibiotic, electromagnetic shielding or any other functions can be built in by depositing additional functional coatings onto the carbon film by utilizing the vacuum coating technique successively. By utilizing the vacuum coating technique, it reduces manufacturing cost and avoids the complexity brought by the conventional manufacturing process to increase additional functions of the flexible electrical heating element. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  illustrates a flexible electrical heating element of the invention. 
           [0012]      FIG. 2  illustrates the steps of manufacturing method of this invention. 
           [0013]      FIG. 3  illustrates the heating effectiveness of the invented flexible heating element. 
           [0014]      FIG. 4  illustrates the far-infrared emissivity of the invented flexible heating element. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    Hereinafter, embodiments of this invention will be explained in detail with reference to the drawings; however, this invention is not limited thereto. 
         [0016]      FIG. 1  illustrates a flexible electrical heating element  1  of this invention comprising a substrate  10  as an insulating material, a metal interlayer coating  101  deposited on the fabric substrate  10 , and a far-infrared emissive carbon film  102  deposited as the out most layer with far-infrared emission capability, wherein the flexible electrical heating element  1  utilizing a vacuum coating technique to successively deposit the metal interlayer coating  101  and the far-infrared emissive carbon film  102 . The substrate  10  is an insulating material which can be a flexible board, a fiber bundles, a fiber fabric or a non-woven fabric; the preferred choice can be a polymeric fiber fabric or a glass fiber fabric. The metal interlayer coating  101  is heated when external voltage is applied and the metal interlayer coating  101  comprises refractory metals suitable to the vacuum coating technique, such as niobium (Nb), molybdenum (Mo), tantalum (Ta), tungsten (W), rhenium (Re), titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), hafnium (Hf), ruthenium (Ru), osmium (Os) or iridium (Ir) and an alloy therefrom, wherein tungsten (W), titanium (Ti) or the chromium (Cr) is preferred. The far-infrared emissive carbon film  102  is obtained onto the metal interlayer coating  101  by utilizing the vacuum coating technique, whilst employing hydrocarbon gas as the raw material to form the far-infrared emissive carbon film  102  on the flexible electrical heating element  1  with far-infrared emission capability. The hydrocarbon gas comprises acetylene (C 2 H 2 ), methane (CH 4 ) or ethane (C 2 H 6 ), wherein the acetylene (C 2 H 2 ) is preferred. Moreover, based on the demands, an antibiotic, electromagnetic shielding or any other functions can be built in by depositing additional functional coatings onto the far-infrared emissive carbon film  102  by utilizing the vacuum coating technique successively. The vacuum coating technique comprises the physical vapor deposition (PVD) technique or the chemical vapor deposition (CVD) technique, wherein the cathodic arc plasma system (CAPD) technique of the PVD families is preferred. 
         [0017]    Refer to  FIG. 2  and TABLE 1. TABLE 1 provides parameters for each state of coating process.  FIG. 2  illustrates the steps of manufacturing method of this invention comprising the substrate  10 , the metal interlayer coating  101 , and the far-infrared emissive carbon film  102  according to the parameters listed in the TABLE 1, the steps comprise as follows: 
         [0018]    a. substrate  10  cleaning, 
         [0019]    the substrate  10  which can be the insulating material comprising the flexible board, the fiber bundles, the fiber fabric or the non-woven fabric, the preferred choice can be a polymeric fiber fabric or a glass fiber fabric, 
         [0020]    b. depositing the metal interlayer coating  101  onto the substrate  10 , 
         [0021]    the refractory metals used in the metal interlayer coating  101  deposition comprising niobium (Nb), molybdenum (Mo), tantalum (Ta), tungsten (W), rhenium (Re), titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), hafnium (Hf), ruthenium (Ru), osmium (Os) or iridium (Ir), 
         [0022]    c. depositing the far-infrared emissive carbon film  102  by using hydrocarbon gas onto the metal interlayer coating  101 , 
         [0023]    the hydrocarbon gas comprising acetylene (C 2 H 2 ), methane (CH 4 ) or ethane (C 2 H 6 ) and the preferred choice which can be acetylene (C 2 H 2 ), 
         [0024]    d. the flexible electrical heating element  1  manufactured. 
         [0000]    
       
         
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Parameters 
                 Value 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Ion bombardment 
                 Argon (Ar) flow rate (sccm) 
                  50~100 
               
               
                   
                 Working pressure (Pa) 
                 0.5~1   
               
               
                   
                 Bombardment time (min) 
                 4~8 
               
               
                   
                 Substrate bias (−V) 
                 200~250 
               
               
                 Coating process for the 
                 Target material 
                 Metal 
               
               
                 metal interlayer coating 
                 Ar flow rate (sccm) 
                  50~100 
               
               
                 101 
                 Working pressure (Pa) 
                 0.5~1   
               
               
                   
                 Deposition time (min) 
                 4~8 
               
               
                   
                 Target current (A) 
                  60~100 
               
               
                 Coating process for the 
                 Target material 
                 Metal 
               
               
                 far-infrared emissive 
                 C 2 H 2  flow rate (sccm) 
                  50~200 
               
               
                 carbon film 102 
                 Working pressure (Pa) 
                 0.04~0.26 
               
               
                   
                 Deposition time (min) 
                 20~60 
               
               
                   
                 Target current (A) 
                 100~150 
               
               
                   
               
             
          
         
       
     
         [0025]    In step a., the substrate  10  is put into the CAPD to be cleaned by removing the surface contaminant for improving coating adhesion in accordance with the parameters of ion bombardment in the TABLE 1. In step b., the metal interlayer coating  101  is deposited by the refractory metals as a target on the substrate  10 , and tungsten (W), titanium (Ti) or chromium (Cr) as preferred refractory metals. In step c., the far-infrared emissive carbon film  102  by applying the hydrocarbon gas; afterwards, the flexible electrical heating element  1  is manufactured. 
         [0026]      FIG. 3  illustrates the heating effectiveness of the invented flexible heating element  1 , which is manufactured by cathodic arc plasma technique by adjusting the hydrocarbon gas flow rate and deposition time of the far-infrared emissive carbon film  102 , respectively.  FIG. 3(   a ) indicates that the less the C 2 H 2  flow rate is, the faster temperature rise of the flexible electrical heating element  1  is, wherein the C 2 H 2  flow rate preferably sets between 50 standard cubic centimeters per minute (sccm) to 200 sccm. Under a circumstance of constant voltage of 15 volt, when the C 2 H 2  flow rate respectively sets at 50 sccm and 150 sccm, temperature respectively rises to 100 Celsius degrees (° C.) and 40° C.  FIG. 3(   b ) indicates that under a circumstance of constant C 2 H 2  flow rate, the longer the deposition time is, the faster the temperature rise of the flexible electrical heating element  1  is, wherein the deposition time preferably sets between 20 minutes (min) to 60 min. Under a circumstance of constant voltage of 10 volt, when the deposition time respectively sets at 20 min and 30 min, the temperature respectively rises to over 50° C. and over 100° C.  FIG. 4  illustrates the far-infrared (FIR) emissivity of the invented flexible electrical heating element  1 , which is manufactured by cathodic arc plasma technique by adjusting the hydrocarbon gas flow rate and the deposition time of the far-infrared emissive carbon film  102 , respectively.  FIG. 4(   a ) indicates that far-infrared (FIR) emissivity increases as the C 2 H 2  flow rate increases. When the C 2 H 2  flow rate is 200 sccm, the far-infrared (FIR) emissivity reaches approximately 90%.  FIG. 4(   b ) indicates that the far-infrared (FIR) emissivity increases as the deposition time increases. When the deposition time increases from 30 min to 60 min, the far-infrared (FIR) emissivity increases over 80%. 
         [0027]    Adjustment of the coating parameters for the hydrocarbon gas can affect the heating efficiency (in terms of temperature rise) and the far-infrared emissivity. Hence, based on demands, this invention can adjust coating parameters to manufacture the flexible electrical heating element  1  in a low-cost method. 
         [0028]    This and other modification, as will occur to those skilled in the art, may be made in the exemplary embodiments shown without departing from the spirit of the invention and the exclusive use of all modification as come within the scope of the appended claims is contemplated.