FIELD OF THE INVENTION 
       [0001]    The present invention relates to an electrothermal element, and more particularly to an electrothermal element with better infrared emissivity, which can be used as a heat source of heater and installed in the ceiling or mounted directly on the wall. 
       BACKGROUND OF THE INVENTION 
       [0002]    Heater is indispensable in many high latitude countries. Even in a subtropical country like Taiwan, people still need a heater to warm up the temperature in the room. The heaters available in the current market, depending on the way of heating, can be categorized in two different kinds, one is air type heater, and one is radiation type heater. To produce hot air, the air type heater heats the air around the thermal object, and with a fan, to spread the hot air allover the room. Typical air type heaters are ceramic heater, blade-type heater and kerosene radiant heater. The radiation type heater produces heat with the thermal element which is able to emit infrared radiation to warm up the target or the air in a room. The typical radiation type heaters include quartz-tube heater, tungsten lamp heater and halogen lamp heater. 
         [0003]    However, the typical disadvantages of air type heater are heating slowly and consuming electrical power, and some of products also exhausting oxygen and making noise. While the radiation type heater although is heating faster but life of product is usually short, and because it&#39;s consuming more oxygen, the ventilation become an issue. Other disadvantage of the radiation type heater is that it&#39;s emitting red light when operation, which causes disturbance to a sleeper. Normally, no matter which type heater being used, it&#39;s hard to match the interior decoration most time so as to become interference in interior design. 
       SUMMARY OF THE INVENTION 
       [0004]    In order to cure the disadvantages of traditional heaters described above, the present invention discloses an electrothermal element which is heating faster, without consuming oxygen, with no noise made by fan, occupying less space. The electrothermal element comprises a substrate, which is the main portion of the electrothermal element and can be an object of plate or board; an electrothermal layer, which has electrodes deposited thereon and produces heat and emits infrared radiation when connected electrically; a reflective layer for reflecting infrared radiation from one side of the electrothermal element; and an auxiliary layer which is high thermal conductive, for spreading the heat evenly and converting some portion of thermal energy into infrared radiation so as to enhance the emissivity of infrared radiation of the electrothermal element. 
         [0005]    In addition to the advantages described above, the electrothermal element of the present invention also has the following advantages.
   (1) Heating the target with the infrared radiation, which is much faster than the air type heater.   (2) Operating without fan so as to low down the noise.   (3) Comparing with the quartz-tube heater, tungsten lamp heater and halogen lamp heater, the operating temperature is low, without the problem of consuming oxygen, life of product is longer, and more safe.   (4) Without emitting visible light when in operation to cause interference to the sleeper.   (5) The electrothermal element itself is a thin plate or board which can be easily installed in the ceiling or on the wall, and occupying less space than the traditional stand heater.   (6) The electrothermal element of the present invention is employing the infrared radiation which enhance the ventilation of blood of human&#39;s body, that is, medical effect is excellent, therefore, the present invention is not limited to be used in winter time.   (7) The electrothermal element of the present invention radiates infrared radiation more efficient so as to consuming less electrical power to save energy.   
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The structure and the technical means adopted by the present invention to achieve the above and other objects can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings. 
           [0014]      FIG. 1  is a schematic cross-sectional view showing the electrothermal element according to a preferred embodiment of the present invention. 
           [0015]      FIG. 2  is a schematic top view showing the electrothermal layer according to a preferred embodiment of the present invention. 
           [0016]      FIG. 3  illustrates the transparent reflective layer formed with different doped ZnO films stacked alternatively according to a preferred embodiment of the present invention. 
           [0017]      FIG. 4A  is a schematic cross-sectional view showing the electrothermal element according to a preferred embodiment of the present invention. 
           [0018]      FIG. 4B  is a schematic cross-sectional view showing the electrothermal element according to a preferred embodiment of the present invention. 
           [0019]      FIG. 4C  is a schematic cross-sectional view showing the electrothermal element according to a preferred embodiment of the present invention. 
           [0020]      FIG. 4D  is a schematic cross-sectional view showing the electrothermal element according to a preferred embodiment of the present invention. 
           [0021]      FIG. 5A  is a schematic cross-sectional view showing the electrothermal element according to a preferred embodiment of the present invention. 
           [0022]      FIG. 5B  is a schematic cross-sectional view showing the electrothermal element according to a preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    Please refer to  FIG. 1 , which is the first embodiment of the present invention. In  FIG. 1 , the present invention discloses an electrothermal element  1  which comprises a substrate  100  in shape of board or plate, and the substrate  100  can be made of the materials of glass, micro-crystal glass, ceramic or carbon fiber. A reflective layer  400  is deposited on the substrate  100  for reflecting the infrared radiation; the layer can be made of high conductivity metals like gold, silver, copper or aluminum. An auxiliary layer  300  is deposited on the reflective layer  400  for increasing the thermal uniformity of the electrothermal element  1  and also convert the thermal energy of the electrothermal element  1  itself into infrared radiation, which decreases the temperature of the electrothermal element  1  so as to decrease the un-stability of the electrothermal element  1  caused by the temperature, and increase the emissivity of infrared, also stop the aging of the electrothermal element  1  caused by the ion permeation from the substrate (or other layers) to the electrothermal element  1 . The auxiliary layer  300  has the properties of high thermal conductivity and emitting infrared radiation, which can be made of diamond, diamond powder, diamond-like film or diamond-like carbon (DLC) film. An electrothermal layer  200  is deposited on the auxiliary layer  300  which produces heat and emits infrared when being connected electrically, and the electrothermal layer  200  can be made of conductive metal oxides like tin oxide (SnO 2 ), indium tin oxide (ITO) or zinc oxide (ZnO). An electrode  210  is deposited on the electrothermal layer  200  for being connected electrically. The value of electric resistance of the electrothermal layer  200  can be determined by changing the thickness of the layer or by changing the resistivity of the material in production process, or by etching pattern  220  on the electrothermal layer  200  to form an electrical layout. A protective layer  500  is deposited on the electrothermal layer  200 , which can be transparent or non-transparent, for protecting the electrothermal layer  200  from the air, also protecting the object or people from electrical shock. The protective layer  500  can be made of polymeric materials, or the materials used in the auxiliary layer  300  like diamond, diamond powder, diamond-like film or diamond-like carbon (DLC) film so the layer can function as both the protective layer  500  and the auxiliary layer  300 . 
         [0024]    As described above, the electrothermal layer  200  produces heat and emits infrared when being connected electrically, the auxiliary layer  300  increases the thermal uniformity and also converts the thermal energy of the electrothermal element itself into infrared radiation, and the reflective layer  400  reflects the infrared radiation efficiently, so, most infrared radiation emits from a first side  11  of the electrothermal element. Because of the advantages described above, the electrothermal element of the present invention is easily installed in the ceiling or on the wall and occupies less space, or can be integrated with the interior design, and the temperature generated by the electrothermal element&#39;s is low when in operation, other advantages includes no oxygen consumption and no noise made by fan. 
         [0025]    The structure of the second embodiment of the present invention has the similar structure of the first embodiment of the present invention. Please refer to  FIG. 1 , which is showing the second embodiment of the present invention, in which the reflective layer  400  is replaced with a transparent and conductive material, such as, transparent conductive films including SnO 2 , ITO, or ZnO, and in this embodiment, ZnO film is used. More particularly, according to the optical theory, the light is reflected at the interface of different materials with different refractive indices. For infrared light, the refractive index of ZnO film is significantly affected by doping levels. A transparent reflective layer  400  (shown in  FIG. 3 ) which is transparent in visible light, but high-reflecting in infrared light can be prepared by alternatively stacking different doped ZnO films, such as intrinsic ZnO  410  and doped ZnO  420 . So that, the reflective layer  400  made of different transparent conductive materials, the electrothermal element of the present invention can be an electrothermal element with high transparent index in visible light. 
         [0026]    The structure of the third embodiment of the present invention is based on the similar structure of the first embodiment of the present invention, but forming a pattern layer (not shown) on a side  11  of the electrothermal element by printing or sticking to improve the looking of the electrothermal element in order to match the style of interior design when the electrothermal element is installed in the ceiling or on the wall. The pattern layer can be used with thermochromic materials whose color is subjected to the temperature, that is, the temperature change of the electrothermal element will also change the color of the out-looking of the electrothermal element, such feature can be used as an indication of operation or scenario expression. More, the pattern layer can function as a protective layer when the pattern layer is made of insulating material, and when the electrothermal element is transparent with respect to visible light, the pattern layer can be deposited on a second side  12  of the electrothermal element. 
         [0027]    The forth embodiment of the present invention is shown in  FIG. 4A . In  FIG. 4A , the present invention discloses an electrothermal element  1  which comprises a substrate  100  in shape of board or plate, and can be made of the materials of glass, micro-crystal glass, ceramic or carbon fiber. A auxiliary layer  300  is deposited on the substrate  100  for increasing the thermal uniformity of the electrothermal element  1  and also convert the thermal energy of the electrothermal element  1  itself into infrared radiation, which decreases the temperature of the electrothermal element  1  so as to decrease the un-stability of the electrothermal element  1  caused by the temperature, and increase the emissivity of infrared, also stop the aging of the electrothermal element  100  caused by the ion permeation from the substrate (or other layers) to the electrothermal element  1 . The auxiliary layer  300  is high thermal conductive and emitting infrared radiation, which can be made of diamond, diamond powder, diamond-like film or diamond-like carbon (DLC) film. An electrothermal layer  200  is deposited on the auxiliary layer  300  which produces heat and emits infrared when being connected electrically, and the electrothermal layer  200  can be made of conductive metal oxides like SnO 2 , ITO, or ZnO. An electrode  210  is deposited on the electrothermal layer  200  for being connected electrically, and the etching pattern  220  is made on the electrothermal layer  200  for adjusting the value of electric resistance. A reflective layer  400  is deposited on the electrothermal layer  200  for reflecting the infrared radiation; the layer can be made of metals with high conductivity like gold, silver, copper or aluminum. More, the reflective layer  400  can be made to be transparent as illustrated in the second embodiment of the present invention, in which the electrothermal element is a transparent element with respect to visible light. Further, in this forth embodiment, the electrothermal element also comprises a back plate  800  that can be made of the materials of glass, micro-crystal glass, ceramic or carbon fiber. With an adhesive layer  700 , such as PVB or EVA, the back plate  800  can be combined with the substrate  100 . Otherwise, the back plate  800  and the adhesive layer  700  can be replaced together with a protective layer as described in the first embodiment (shown in  FIG. 4B ). 
         [0028]    The fifth embodiment of the present invention is shown in  FIG. 4C , and the structure thereof is similar to that in the forth embodiment of the present invention. In  FIG. 4C , the auxiliary layer  300  is deposited on surface  11  of the substrate  100 . Since the auxiliary layer  300  is made of diamond, diamond powder, diamond-like film or diamond-like carbon (DLC) film, which not only has the advantages like lowing down temperature, increasing thermal uniformity of the electrothermal element and increasing the emissivity of infrared, but also can function as a protective layer to protect the surface  11  of the substrate  100 . Moreover, the back plate  800  and the adhesive layer  700  both can be replaced with a protective layer as described in the first embodiment (shown in  FIG. 4D ). 
         [0029]    The sixth embodiment of the present invention is based on the forth and fifth embodiment of the present invention (shown in  FIG. 4A ,  4 B,  4 C and  4 D), further forming a pattern layer on the surface  11  of the electrothermal element by printing or sticking to improve the looking of the electrothermal element in order to match the style of interior design when the electrothermal element is installed on the ceiling or on the wall. The pattern layer can be used with thermochromic materials whose color is subjected to the temperature, that is, the temperature change of the electrothermal element will also change the color of the out-looking of the electrothermal element, and such feature can be used as an indication of operation or scenario expression. Moreover, the pattern layer can function as a protective layer when the pattern layer is made of insulating material, and when the electrothermal element is transparent with respect to visible light, the pattern layer can be deposited on the surface  12  of the electrothermal element. 
         [0030]    The seventh embodiment of the present invention is shown in  FIG. 5A . In FIG.  5 A, the auxiliary layer  300 , the electrothermal layer  200  and a reflecting cover  600  cover on the substrate  100 . The reflective cover  600  can be made of a metal plate or a metal cover, or a cover which of the inner side coated with metals. The function of the reflecting cover  600  is to reflect the infrared and providing protection. The materials of the reflecting cover is made by high conductivity metals, such as gold, silver, copper or aluminum. Moreover, the auxiliary layer is deposited on the surface  11  (as shown in  FIG. 5B ) of the electrothermal element. Since the auxiliary layer is made of diamond, diamond powder, diamond-like film or diamond-like carbon (DLC) film, which not only has the advantages like lowing down temperature, increasing thermal uniformity of the electrothermal element and increasing the emissivity of infrared, but also can function as a protective layer to protect the surface of the substrate. Furthermore, a pattern layer can be formed on the surface  11  of the electrothermal element by printing or sticking to improve the out-looking of the electrothermal element in order to match the style of interior design when the electrothermal element is installed on the ceiling or on the wall. The pattern layer can be used with thermochromic materials whose color is subjected to the temperature, that is, the temperature change of the electrothermal element will also change the color of the out-looking of the electrothermal element, and such feature can be used as an indication of operation or scenario expression. 
         [0031]    The present invention has been described with some preferred embodiments thereof and it is understood that many changes and modifications in the described embodiments can be carried out without departing from the scope and the spirit of the invention that is intended to be limited only by the appended.
The present invention proposes an electrothermal element which comprises a substrate, a reflective layer, an electrothermal layer, and an auxiliary layer. The electrothermal layer can emit infrared radiation which is reflected by the reflective layer and enable infrared radiation emitted from one side of the electrothermal element. The auxiliary layer can increase the thermal uniformity of the electrothermal element and also convert the thermal energy of the electrothermal element itself into infrared radiation. It not only improves overall infrared emissivity of the electrothermal element but also reduces the temperature of the electrothermal element. This invention offers an effectively and rapidly warming up solution at selected local regions, no oxygen consumption and fan noise problems, and the electrothermal element can replace the traditional ceiling or be mounted directly on the wall, to solve the disadvantage of requiring space of the conventional electric heating device.