Patent Publication Number: US-2016249413-A1

Title: Transparent planar heater

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This U.S. non-provisional patent application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2015-0025288, filed on Feb. 23, 2015, and 10-2015-0178462, filed on Dec. 14, 2015, the entire contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND 
     The inventive concepts relate to a transparent planar heater. 
     Since a planar heater generates heat by applying electricity, the planar heater does not generate air pollution, electromagnetic waves, noise, or the like and thus is used for various kinds of fields. 
     For example, the planar heater is used for a residential heating system for heating a floor of an apartment or a general house, an industrial heating system for an office or a working area, an industrial heating device for printing drying or painting drying, and a vehicle heating device for removing frost or moisture on a sunroof or window of a vehicle. 
     SUMMARY 
     Embodiments of the inventive concepts provide a transparent planar heater that prevents infrared rays and the like and improves heating uniformity. 
     The object of the present invention is not limited to the aforesaid, but other objects not described herein will be clearly understood by those skilled in the art from descriptions below. 
     An embodiment of the inventive concept provides a transparent planar heater including: a transparent substrate; a transparent heating layer disposed on the transparent substrate; and an electrode disposed on the transparent heating layer and electrically connected to the transparent heating layer. The transparent heating layer includes: a metal layer disposed on the transparent substrate, the metal layer being configured to receive an external power from the electrode, thereby generating heat; and a selective transmission layer disposed on the transparent substrate to block at least a portion of a wavelength region of an infrared rays region of light and transmit a portion of the wavelength region of the light. 
     In an embodiment, the metal layer may include at least one of gold (Au), platinum (Pt), silver (Ag), aluminum (Al), copper (Cu), zinc (Zn), TiN, TaN, tungsten (W), titanium (Ti), molybdenum (Mo), and chrome (Cr). 
     In an embodiment, the selective transmission layer may transmit at least a portion of a wavelength region of a visible rays region. 
     In an embodiment, the selective transmission layer may include at least one of indium tin oxide (ITO), an aluminum-doped zinc oxide (ZnO:Al), a gallium doped zinc oxide (ZnO:Ga), a boron-doped zinc oxide (ZnO:B), a fluorine-doped tin dioxide (SnO 2 :F), a tin dioxide (SnO2), InZnO, gold (Au), platinum (Pt), silver (Ag), aluminum (Al), molybdenum (Mo), and chrome (Cr). 
     In an embodiment, the transparent heating layer may further include a heat dissipation layer disposed on the metal layer and configured to uniformly release the heat generated from the metal layer. 
     In an embodiment, the heat dissipation layer may include at least one of gold (Au), platinum (Pt), silver (Ag), aluminum (Al), copper (Cu), zinc (Zn), nickel (Ni), TiN, TaN, tungsten (W), titanium (Ti), molybdenum (Mo), and chrome (Cr). 
     In an embodiment, the transparent heating layer may have a thickness of 10 nm to 200 nm. 
     In an embodiment, the transparent heating layer may further include a seed layer disposed between the transparent substrate and the metal layer. 
     In an embodiment, the transparent heating layer may further include a conductive oxide layer disposed between the metal layer and the electrode, and the metal layer may be disposed between the seed layer and the conductive oxide layer. 
     In an embodiment, the transparent planar heater may further include a transparent protective layer disposed on the transparent heating layer to cover the electrode. 
     In an embodiment, the transparent planar heater may further include a stress relaxation layer disposed below the transparent substrate to relax stress applied to the transparent substrate. 
     In an embodiment, the transparent heating layer has a pattern exposing a portion of the transparent substrate. 
     Particularities of other embodiments are included in the detailed description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The accompanying drawings are included to provide a further understanding of the inventive concept, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the inventive concept and, together with the description, serve to explain principles of the inventive concept. In the drawings: 
         FIG. 1  is an exploded perspective view of a transparent planar heater according to an embodiment of the inventive concept; 
         FIG. 2  is a cross-sectional view of the transparent planar heater of  FIG. 1 ; 
         FIG. 3A  is a graph illustrating resistance of a metal layer according to a thickness of the metal layer of  FIG. 1 ; 
         FIG. 3B  is a graph illustrating a transmittance of the metal layer according to the thickness of the metal layer of  FIG. 1 ; 
         FIG. 4  is a graph illustrating a transmittance according to a wavelength of light transmitted through a selective transmission layer of  FIG. 1 ; 
         FIG. 5  is a cross-sectional view of a transparent planar heater according to an embodiment of the inventive concept; 
         FIG. 6  is a view of the bent transparent planar heater of  FIG. 1 ; 
         FIG. 7  is a perspective view illustrating a portion of constituents of a transparent planar heater according to an embodiment of the inventive concept; and 
         FIG. 8  is a plan view illustrating a portion of constituents of the transparent planar heater of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     Advantages and features of the inventive concepts, and implementation methods thereof will be clarified through following embodiments described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Further, the present invention is only defined by scopes of claims. Like reference numerals refer to like elements throughout. 
     In the following description, the technical terms are used only for explaining a specific exemplary embodiment while not limiting the present invention. The terms of a singular form may include plural forms unless referred to the contrary. The meaning of ‘comprises’ and/or ‘comprising’ specifies a component, a step, an operation and/or an element does not exclude other components, steps, operations and/or elements. 
     The object of the present invention is not limited to the aforesaid, but other objects not described herein will be clearly understood by those skilled in the art from descriptions below. Terms as defined in a commonly used dictionary should be construed as having the same meaning as in an associated technical context, and unless defined apparently in the description, the terms are not ideally or excessively construed as having formal meaning. 
     Hereinafter, a transparent planar heater according to exemplary embodiments of the inventive concept will be described in detail with reference to the accompanying drawings. 
       FIG. 1  is an exploded perspective view of a transparent planar heater according to an embodiment of the inventive concept.  FIG. 2  is a cross-sectional view of the transparent planar heater of  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , a transparent planar heater  10  according to an embodiment of the inventive concept may transmit light. The transparent planar heater  10  may generate heat. Accordingly, the transparent planar heater  10  may be used for moisture removal, heating, drying, and the like. For example, although the transparent planar heater  10  may be provided to various kinds of windows to remove frost and moisture generated in the windows, an embodiment of the inventive concept is not limited thereto. 
     Referring to  FIG. 1 , the transparent planar heater  10  may include a transparent substrate  100 , a transparent heating layer  200 , and an electrode  300 . The transparent planar heater  10  may include a transparent protective layer  400 . According to an embodiment of the inventive concept, the transparent planar heater  10  has a structure in which the transparent substrate  100 , the transparent heating layer  200 , the electrode  300 , and the transparent protective layer  400  are sequentially laminated. 
     The transparent substrate  100  may be made of transparent glass or transparent plastic. Accordingly, light may be transmitted through the transparent substrate  100 . The transparent substrate  100  may have a flat plate shape or a curved shape having a curvature. 
     According to an embodiment of the inventive concept, the transparent substrate  100  may be a flat plate shaped substrate made of a glass material. The transparent substrate  100  may include an alkali-free glass material, an alkali-silica-based glass material, and a quartz glass material. Also, a transparent oxide or amorphous silicon may be deposited on the transparent substrate  100 . 
     The transparent substrate  100  may have a thickness of about 1 μm to about 10,000 μm. Here, the thickness may represent a vertical height of the transparent substrate  100 . 
     The transparent heating layer  200  may be disposed on the substrate. The transparent heating layer  200  may transmit light. The transparent heating layer  200  may be electrically connected to the electrode  300 . Accordingly, the transparent heating layer  200  may receive an external power from the electrode  300  to generate heat. 
     The transparent heating layer  200  may have a thickness of about 10 nm to about 500 nm The transparent heating layer  200  may include a metal layer  220 , a selective transmission layer  230 , and a seed layer  210 . According to an embodiment of the inventive concept, the transparent heating layer  200  may have a structure in which the seed layer  210 , the metal layer  220 , and the selective transmission layer  230  are sequentially laminated. 
     The seed layer  210  may be disposed on the transparent substrate  100 . The seed layer  210  may have a thickness of about 5 nm to about 200 nm The seed layer  210  may improve thin-film quality including crystallizability of the metal layer  220 . Accordingly, the transparent planar heater  10  may be improved in electrical conductivity and optical transmittance. 
     The seed layer  210  may include at least one of indium tin oxide (ITO), an aluminum doped zinc oxide (ZnO:Al), a gallium doped zinc oxide (ZnO:Ga), a boron doped zinc oxide (ZnO:B), a zinc oxide containing tin (ZnsnO), a fluorine doped tin dioxide (SnO 2 :F), a tin dioxide (SnO2), InZnO, a vanadium pentoxide (V 2 O5), an aluminum oxide (Al 2 O 3 ), a silicon dioxide (SiO 2 ), a titanium dioxide (TiO 2 ), AlTiO, ZnO. Accordingly, the seed layer  210  may prevent the metal layer  220  from being oxidized. The seed layer  210  may transmit light. 
     The seed layer  210  may be formed by one of evaporation, sputtering, chemical vapor deposition (CVD), atomic layer deposition (ALD), pulsed laser deposition (PLD), molecular beam epitaxy (MBE), sol-gel, spray, and printing. 
     The metal layer  220  may be disposed above the transparent substrate  100 . Here, the disposition above the transparent substrate  100  may represent that the metal layer  220  contacts or is spaced apart from an upper portion of the transparent substrate  100 . According to an embodiment of the inventive concept, the metal layer  220  may be spaced apart from the transparent substrate  100 . The metal layer  220  may be disposed on the seed layer  210  disposed between the metal layer  220  and the transparent substrate  100 . 
     The metal layer  220  may be electrically connected to the electrode  300  to receive an external power (not shown). When the metal layer  220  receives the external power, the metal layer  220  may generate heat. The metal layer  220  may have a large sized area. 
     The metal layer  220  may include at least one of gold (Au), platinum (Pt), silver (Ag), aluminum (Al), copper (Cu), zinc (Zn), TiN, TaN, tungsten (W), titanium (Ti), molybdenum (Mo), and chrome (Cr). 
     The metal layer  220  may be formed by one of evaporation, sputtering, chemical vapor deposition (CVD), atomic layer deposition (ALD), pulsed laser deposition (PLD), molecular beam epitaxy (MBE), sol-gel, spray, and printing. 
     The metal layer  220  may use nano-level particles to improve heating characteristics and transparency. The metal layer  220  may have a flat plate shape having a thickness of about 1 nm to about 50 nm The transparent planar heater  10  may adjust the thickness of the metal layer  220  to control a heating amount. This will be described in detail in  FIG. 3A . 
     The selective transmission layer  230  may be disposed above the transparent substrate  100 . According to an embodiment of the inventive concept, the selective transmission layer  230  may be spaced apart from an upper portion of the transparent substrate  100 . The selective transmission layer  230  may be disposed on the metal layer  220  disposed between the transparent substrate  100  and the selective transmission layer  230 . Alternatively, according to another embodiment, the selective transmission layer  230  may be disposed between the seed layer  210  and the metal layer  220 . 
     The selective transmission layer  230  may include at least one of indium tin oxide (ITO), an aluminum doped zinc oxide (ZnO:Al), a gallium doped zinc oxide (ZnO:Ga), a boron doped zinc oxide (ZnO:B), a fluorine doped tin dioxide (SaO 2 :F), a tin dioxide (SnO2), InZnO, gold (Au), platinum (Pt), silver (Ag), aluminum (Al), molybdenum (Mo), and chrome (Cr). 
     The selective transmission layer  230  may have a thickness of about 5 nm to about 300 nm. When the selective transmission layer  230  increases in thickness, resistance of the selective transmission layer  230  with respect to current flowing from the electrode  300  to the metal layer  220  may increase. 
     For example, when the thickness of the selective transmission layer  230  increases, a migration distance of the current flowing from the electrode  300  to the metal layer  220  may increase. As the migration distance of the current increases, the resistance of the selective transmission layer  230  may increase. Accordingly, the thickness of the selective transmission layer  230  may be adjusted within a range of about 5 nm to about 300 nm in consideration of resistance, purpose of usage, and process variables. 
     The selective transmission layer  230  may be formed by one of evaporation, sputtering, chemical vapor deposition (CVD), atomic layer deposition (ALD), pulsed laser deposition (PLD), molecular beam epitaxy, sol-gel, spray, and printing. 
     The selective transmission layer  230  may block a portion of light and transmit a portion of light. This will be described in detail later in  FIG. 4 . 
     The electrode  300  may be disposed on the transparent heating layer  200 . The electrode  300  may be connected to an external power through a wire (not shown). The electrode  300  may be electrically connected to the transparent heating layer  200  and provide the external power to the transparent heating layer  200 . 
     The electrode  300  may be a transparent conductive material. The electrode  300  may include a first electrode  310  disposed on one side of the transparent heating layer  200  and a second electrode  320  disposed on the other side of the transparent heating layer  200 . 
     The electrode  300  may include at least one of indium tin oxide (ITO), an aluminum doped zinc oxide (ZnO:Al), a gallium doped zinc oxide (ZnO:Ga), a boron doped zinc oxide (ZnO:B), a fluorine doped tin dioxide (SaO 2 :F), a tin dioxide (SnO2), InZnO, gold (Au), platinum (Pt), silver (Ag), aluminum (Al), copper (Cu), zinc (Zn), TiN, TaN, tungsten (W), titanium (Ti), molybdenum (Mo), and chrome (Cr). 
     The transparent protective layer  400  may be disposed on the transparent heating layer  200 . The transparent protective layer  400  may cover the electrode  300  disposed on the transparent heating layer  200 . Accordingly, the transparent protective layer  400  may protect the transparent heating layer  200  and the electrode  300  against external shock or a chemical material. Also, the transparent protective layer  400  may have insulation effects. 
     The transparent protective layer  400  may include a insulation material having excellent heat transfer and heat capacity characteristics. For example, the transparent protective layer  400  may include at least one of an aluminum oxide (Al 2 O 3 ), a silicon dioxide (SiO 2 ), a titanium dioxide (TiO 2 ), AlTiO, a zinc oxide (ZnO), a vanadium pentoxide (V 2 O5), a zirconium dioxide (ZrO 2 ), and a hafnium dioxide (HfO 2 ). 
     The transparent protective layer  400  may be formed by one of evaporation, sputtering, chemical vapor deposition (CVD), atomic layer deposition (ALD), pulsed laser deposition (PLD), molecular beam epitaxy (MBE), sol-gel, spray, and printing. 
       FIG. 3A  is a graph illustrating resistance of the metal layer according to the thickness of the metal layer.  FIG. 3B  is a graph illustrating a transmittance of the metal layer according to the thickness of the metal layer. 
     Referring to  FIGS. 3A and 3B , according to an embodiment of the inventive concept, when the thickness of the metal layer (see reference numeral  220  in  FIG. 2 ) increases, resistance with respect to current flowing to the metal layer  220  may decrease. That is, the resistance of the metal layer  220  is inversely proportional to the thickness of the metal layer  220 . 
     For example, when a voltage applied to the metal layer  220  is constant, a heating value of the metal layer  220  is inversely proportional to the resistance. Since the resistance of the metal layer  220  is inversely proportionally to the thickness of the metal layer  220 , the heating value of the metal layer  220  may be proportional to the thickness of the metal layer  220 . Thus, the heating value that is desirable to the transparent planar heater  10  may be realized through adjusting the thickness of the metal layer  220 . The reason is that the resistance of the metal layer  220  is adjusted by adjusting the thickness of the metal layer  220 . 
     Referring to  FIG. 3B , as the metal layer  220  increases in thickness, the metal layer  220  decreases in transmittance. That is, the transmittance of the metal layer  220  is inversely proportional to the thickness of the metal layer  220 . 
     When the thickness of the metal layer  220  increases, the transmittance and resistance of the metal layer  220  may decrease and the heating value of the metal layer  220  may increase. Accordingly, the thickness of the metal layer  220  may be adjusted within a range of about 1 nm to about 50 nm in consideration of a transmittance, resistance, purpose of usage, and process variables. 
       FIG. 4  is a graph illustrating a transmittance according to a wavelength of light transmitted through the selective transmission layer of  FIG. 1 . 
     As described above, the selective transmission layer (see reference numeral  230  in  FIG. 2 ) may block a portion of light and transmit a portion of light. That is, the selective transmission layer  230  may block a predetermined wavelength region of the light and transmit the rest wavelength region of the light. 
     For example, the light transmitted through the selective transmission layer  230  may be reflected by a light incident surface (not shown) and a light emitting surface (not shown). Accordingly, the light transmitted through the selective transmission layer  230  may be interfered with the light reflected by the selective transmission layer  230 . Since interference phenomenon of a light occurs, the light in a predetermined wavelength region may be blocked by the selective transmission layer  230 , and the light in the rest wavelength region may be transmitted through the selective transmission layer  230 . 
     Referring to  FIG. 4 , according to an embodiment of the inventive concept, the selective transmission layer  230  may decrease in transmittance as a wavelength of light increases. In detail, according to an embodiment of the inventive concept, the selective transmission layer  230  may block at least a portion of the wavelength region of an infrared rays region of the incident light. Accordingly, the selective transmission layer  230  may block infrared rays or control a transmission amount of the infrared rays. Here, the infrared rays region may include a wavelength range of about 780 nm to about 3 mm. Accordingly, the transparent planar heater (see reference numeral  10  in  FIG. 1 ) may have heat insulation effects that efficiently prevent infrared rays. 
     In general, the infrared rays is a kind of electromagnetic waves having a wavelength greater than that of red visible rays. The infrared rays may have thermal action greater than that of visible rays or ultraviolet rays. Also, the heater may transmit radiant heat in a form of infrared rays. 
     The selective transmission layer  230  may block at least a portion of a wavelength region of the infrared rays of light to prevent the radiant heat generated from an inner space of the transparent planar heater (see reference numeral  10  in  FIG. 2 ) from being released to the outside of the transparent planar heater  10 . Also, the selective transmission layer  230  may prevent the radiant heat generated in an outer space of the transparent planar heater  10  from being introduced into the inner space of the transparent planar heater  10 . Accordingly, the selective transmission layer  230  may serve as an heat-insulating material. 
     The selective transmission layer  230  may transmit at least a portion of a wavelength region of the visible rays region. Here, the visible rays region may include a wavelength range of about 380 nm to about 780 nm. 
       FIG. 5  is a cross-sectional view of a transparent planar heater according to an embodiment of the inventive concept.  FIG. 6  is a view of the bent transparent planar heater of  FIG. 1 . 
     For simplicity of explanation, components that are substantially the same as the example described with reference to  FIGS. 1 to 4  will not be provided. 
     Referring to  FIGS. 5 and 6 , according to an embodiment of the inventive concept, a transparent planar heater  11  may include a transparent substrate  100 , a transparent heating layer  201 , an electrode  300 , a transparent protective layer  400 , and a stress relaxation layer  500 . 
     The transparent planar heater  11  may include a flexible or curved substrate. The transparent heating layer  201  may have a thickness of about 10 nm to about 200 nm. Since the transparent heating layer  201  has a small thickness of about 10 nm to about 200 nm, the transparent heating layer  201  may be flexibly bent or disposed on the curved transparent substrate  100 . According to an embodiment of the inventive concept, the transparent planar layer  201  may have a thickness of about 150 nm. 
     The transparent planar heater  201  may include a seed layer  210 , a metal layer  220 , a heat dissipation layer  240 , a selective transmission layer  230 , and a conductive oxide layer  250 . 
     The conductive oxide layer  250  may be disposed on the selective transmission layer  230 . The conductive oxide layer  250  may prevent the metal layer  220  from being oxidized together with the seed layer  210 . For example, the metal layer  220  may be disposed between the seed layer  210  and the conductive oxide layer  250  to prevent the metal layer  220  from being oxidized. 
     The conductive oxide layer  250  may include at least one of indium tin oxide (ITO), an aluminum doped zinc oxide (ZnO:Al), a gallium doped zinc oxide (ZnO:Ga), a boron doped zinc oxide (ZnO:B), a fluorine doped tin dioxide (SnO 2 :F), a tin dioxide (SnO2), InZnO, a vanadium pentoxide (V 2 O5), an aluminum oxide (Al 2 O 3 ), a silicon dioxide (SiO 2 ), a titanium dioxide (TiO 2 ), and AlTiO. 
     The conductive oxide layer  250  may be formed by one of evaporation, sputtering, chemical vapor deposition (CVD), atomic layer deposition (ALD), pulsed laser deposition (PLD), molecular beam epitaxy (MBE), sol-gel, spray, and printing. 
     The metal layer  220  may be disposed between the seed layer  210  and the conductive oxide layer  250 . The metal layer  220  may have a large sized area. Also, the electrodes  300  providing a power to the metal layer  220  may be disposed on both ends of the metal layer  220 , respectively. Accordingly, the metal layer  220  having a large sized area may have heating amounts that are different between a middle portion and the both end portions thereof. 
     Also, the metal layer  220  may have an uneven top surface. That is, the top surface of the metal layer  220  may have an uneven portion (not shown) upwardly protruding. An area on which the uneven portion is disposed may have a thickness that is greater than that of an area on which the uneven portion is not disposed. Accordingly, the area on which the uneven portion is disposed may have a heating value that is greater than that of the area on which the uneven portion is not disposed. The heat dissipation layer  240  may be disposed on the metal layer  220 . For example, the heat dissipation layer  240  may have a bottom surface contacting the metal layer  220  to absorb heat and a top surface releasing the absorbed heat in an upward direction. 
     The heat dissipation layer  240  may have an area corresponding to that of the metal layer  220 . The heat dissipation layer  240  may absorb heat generated from the metal layer  220  to uniformly radiate the heat. Accordingly, the transparent planar heater  11  having a large sized area may uniformly generate heat in an almost entire area thereof. 
     The heat dissipation layer  240  may have a thickness of about 1 nm to about 20 nm. When the heat dissipation layer  240  increases in thickness, heating uniformity of the transparent planar heater  11  may be improved. 
     For example, while heat absorbed to the bottom surface of the heat dissipation layer  240  is upwardly transferred, the absorbed heat may be thermally conducted to the entire area of the heat dissipation layer  240 . When the thickness of the heat dissipation layer  240  increases, a time in which the heat absorbed to the heat dissipation layer  240  is thermally conducted to the entire area of the heat dissipation layer  240  may increase. Accordingly, when the thickness of the heat dissipation layer  240  increases, the heating uniformity of the transparent planar heater  11  may be improved. 
     Also, when the thickness of the heat dissipation layer  240  increases, a migration distance of current flowing from the electrode  300  to the metal layer  220  may increase. As the migration distance of current increases, resistance between the electrode  300  and the metal layer  220  may increase. Thus, the thickness of the heat dissipation layer  240  may be adjusted in a range of about 1 nm to about 20 nm in consideration of resistance, heating uniformity efficiency, purpose of usage, and process variables. 
     The heat dissipation layer  240  may include at least one of gold (Au), platinum (Pt), silver (Ag), aluminum (Al), copper (Cu), zinc (Zn), nickel (Ni), TiN, TaN, tungsten (W), titanium (Ti), molybdenum (Mo), and chrome (Cr). 
     The heat dissipation layer  240  may be formed by one of evaporation, sputtering, chemical vapor deposition (CVD), atomic layer deposition (ALD), pulsed laser deposition (PLD), molecular beam epitaxy (MBE), sol-gel, spray, and printing. 
     The stress relaxation layer  500  may be disposed below the transparent substrate  100 . The stress relaxation layer  500  may include a transparent material. For example, the stress relaxation layer  500  may include at least one of indium tin oxide (ITO), an aluminum doped zinc oxide (ZnO:Al), a gallium doped zinc oxide (ZnO:Ga), a boron doped zinc oxide (ZnO:B), a fluorine doped tin dioxide (SnO 2 :F), a tin dioxide (SnO2), InZnO, a vanadium pentoxide (V 2 O5), an aluminum oxide (Al 2 O 3 ), a silicon dioxide (SiO 2 ), a titanium dioxide (TiO 2 ), and AlTiO. 
     The stress relaxation layer  500  may have a thickness of about 10 nm to about 500 nm. The stress relaxation layer  500  may be formed by one of evaporation, sputtering, chemical vapor deposition (CVD), atomic layer deposition (ALD), sol-gel, spray, and printing. 
     Referring to  FIG. 6 , when the transparent substrate is bent by an external force, stress may be generated in the transparent substrate  100 . When great stress is applied to the transparent substrate  100 , the transparent substrate  100  may be damaged. The stress relaxation layer  500  may absorb the stress applied to the transparent substrate  100 . 
     For example, when a force is applied in a downward direction to both ends of the transparent substrate  100 , a moment acts on the both ends of the transparent substrate  100 . Accordingly, the stress is applied to the both ends of the transparent substrate  100  to deform the transparent substrate  100 . At least a portion of the stress applied to the both ends of the transparent substrate  100  may be absorbed through the stress relaxation layer  500 . The stress relaxation layer  500  may absorb the stress generated in the transparent substrate  100  to prevent or reduce the damage of the transparent substrate  100 . 
       FIG. 7  is a perspective view illustrating a portion of constituents of a transparent planar heater according to an embodiment of the inventive concept.  FIG. 8  is a plan view illustrating a portion of constituents of the transparent planar heater of  FIG. 7 . 
     For simplicity of description, description for components that are substantially the same as those of the embodiment that was described with reference to  FIGS. 1 and 6  will not be provided. 
     Referring to  FIGS. 7 and 8 , according to an embodiment of the inventive concept, a transparent heating layer  202  may include a pattern P exposing a portion of the transparent substrate  100 . 
     Although the transparent heating layer  202  includes a stripe pattern P, an embodiment of the inventive concept is not limited thereto. For example the transparent heating layer  202  may include various kinds of patterns such as a wave pattern, a zigzag pattern, a circular pattern, a diamond pattern, and a grid pattern. Thus, the transparent planar heater  12  may generate heat only on a portion in which the pattern is disposed. 
     The transparent planar heater according to the embodiment of the inventive concept has at least one of the following effects. 
     Infrared rays and/or ultraviolet rays may be prevented. When the transparent planar heater has a large sized area, the degradation in the uniformity of the generated heat may be prevented. Also, the transparent planar heater may be used for various purposes because it is transparent. 
     The object of the present invention is not limited to the aforesaid, but other objects not described herein will be clearly understood by those skilled in the art from descriptions below. 
     Although the exemplary embodiments of the present invention have been described, it is understood that the present invention should not be limited to these exemplary embodiments but various changes and modifications can be made by one ordinary skilled in the art within the spirit and scope of the present invention as hereinafter claimed.