Patent Publication Number: US-2021195697-A1

Title: Thin film heater and camera lens having the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No(s). 108146859 filed in Taiwan R.O.C. on Dec. 20, 2019, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     1. Technical Field 
     This present disclosure relates to a thin film heater and a vehicle camera lens having the thin film heater. 
     2. Related Art 
     Advanced driver assistance system (ADAS) is one of key technologies in the development of intelligent vehicles, and ADAS can be incorporated with image sensor. Through image recognition and radar feedback information, the situation outside the vehicle can be analyzed in real time to enable drivers to take proactive actions, thereby preventing traffic accidents. A conventional ADAS is capable of detecting certain objects and performing basic classification to remind risk and danger on the road and, in some cases, even slow down or stop the vehicle. The ADAS is suitable for monitoring blind spots, assisting lanes change and providing forward collision warning. 
     Generally, an ADAS includes multiple image sensors in order to achieve monitoring around all perspectives of the vehicle. Since the ADAS is a dominant tool for automatic driving, its system reliability is very important for drivers. The ADAS should work normally when one drives the vehicle in wet and cold environment. 
     SUMMARY 
     According to one embodiment of the present disclosure, a thin film heater includes a heat conductive layer, a heat insulation layer and a heat generation layer. The heat generation layer is disposed between the heat conductive layer and the heat insulation layer. The thermal conductivity of the heat conductive layer is greater than or equal to three times the thermal conductivity of the heat insulation layer. 
     According to another embodiment of the present disclosure, a camera lens, includes a cover glass and the aforementioned thin film heater. The thin film heater is in thermal contact with the cover glass. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a thin film heater according to a first embodiment of the present disclosure; 
         FIG. 2A  is a schematic view of a thin film heater according to a second embodiment of the present disclosure; 
         FIG. 2B  is a schematic view showing bent thin film heater in  FIG. 2A ; 
         FIG. 3  is a schematic view of a thin film heater according to a third embodiment of the present disclosure; 
         FIG. 4  is a schematic view of a thin film heater according to a fourth embodiment of the present disclosure; 
         FIG. 5  is a schematic view of a thin film heater according to a fifth embodiment of the present disclosure; 
         FIG. 6  is a schematic view of a thin film heater according to a sixth embodiment of the present disclosure; 
         FIG. 7  is a schematic view of a thin film heater according to a seventh embodiment of the present disclosure; 
         FIG. 8  is a schematic view of a thin film heater according to an eighth embodiment of the present disclosure; 
         FIG. 9  is a schematic view of a thin film heater according to a ninth embodiment of the present disclosure; 
         FIG. 10  is a schematic view of a thin film heater according to a tenth embodiment of the present disclosure; 
         FIG. 11  is a schematic view of a thin film heater according to an eleventh embodiment of the present disclosure; 
         FIG. 12  is a schematic view of a thin film heater according to a twelfth embodiment of the present disclosure; 
         FIG. 13  is a schematic view of a thin film heater according to a thirteenth embodiment of the present disclosure; and 
         FIG. 14  is a schematic view of a vehicle camera lens according to one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawings. 
     According to one embodiment of the present disclosure, thin film heater includes a heat conductive layer, a heat insulation layer and a heat generation layer. Please refer to  FIG. 1  showing a schematic view of a thin film heater according to a first embodiment of the present disclosure. In this embodiment, a thin film heater  1   a  includes a heat generation layer  10 , a heat conductive layer  20 , a heat insulation layer  30  and a patterned electrode  40 . 
     The heat generation layer  10  is made of, for example but not limited to, indium tin oxide (ITO), indium oxide (In 2 O 3 ), tin oxide (SnO 2 ), zinc oxide (ZnO), cadmium oxide (CdO), cadmium-indium oxide (CdIn 2 O 4 ), cadmium-tin oxide (Cd 2 SnO 4 ), tin-zinc oxide (Zn 2 SnO 4 ), aluminum doped zinc oxide (AZO), gallium doped zinc oxide (GZO), or indium doped zinc oxide (IZO), and heat generation layer  10  has a sheet resistance of 45±20Ω/□. The heat conductive layer  20  is made of, for example but not limited to, titanium oxide, aluminum oxide, magnesium oxide or silicon oxide, and the heat conductive layer  20  is disposed on one side of the heat generation layer  10 . The heat conductive layer  20  can be in thermal contact with any element (not shown in the drawings) needed to be heated, and heat generated by the heat generation layer  10  is transferred to the element by the heat conductive layer  20 . The element needed to be heated can be, for example, a cover glass in a vehicle camera lens or a car window. 
     The heat insulation layer  30 , for example but not limited to, silicon oxide or tantalum nitride disposed on another side of the heat generation layer  10 , such that the heat generation layer  10  is between the heat conductive layer  20  and the heat insulation layer  30 . The heat insulation layer  30  has lower thermal conductivity than the heat generation layer  10 , and it is favorable for most amount of heat generated by the heat generation layer  10  being transferred via the heat conductive layer  20 , such that the thin film heater  1   a  enjoys single directional heat conduction. In one embodiment, the thermal conductivity of the heat conductive layer  20  is greater than or equal to three times the thermal conductivity of the heat insulation layer  30 ; thus, the heat generated by the heat generation layer  10  tends to flow through the heat conductive layer  20  more easily, and does not tend to flow toward the heat insulation layer  30 . The thermal conductivity of the heat conductive layer  20  can be greater than or equal to 30.0 W/mK, and the thermal conductivity of the heat insulation layer  30  can be less than or equal to 10 W/mK. For example, in this embodiment, the thermal conductivity of the heat conductive layer  20  is from 30.0 W/mK to 90.0 W/mK, and the thermal conductivity of the heat insulation layer  30  is from 0.84 W/mK to 10.0 W/mK. 
     The patterned electrode  40 , for example but not limited to, a metal pad disposed on the surface of the heat generation layer  10 . The patterned electrode  40  may include electrically conductive material such as gold, silver, copper, aluminum, cast iron, steel, graphite, brass, red copper, copper-silver alloy and aluminum alloy. The patterned electrode  40  can be connected with external power source (not shown in the drawings) for introducing electric current into the heat generation layer  10 , thereby achieving electric heating to the heat generation layer  10 . 
     According to one embodiment of the present disclosure, thin film heater further includes a protective layer and a substrate. Please refer to  FIG. 2A  and  FIG. 2B .  FIG. 2A  is a schematic view of a thin film heater according to a second embodiment of the present disclosure, and  FIG. 2B  is a schematic view showing bent thin film heater in  FIG. 2A . In this embodiment, a thin film heater  1   b  includes a heat generation layer  10 , a heat conductive layer  20 , a heat insulation layer  30 , a patterned electrode  40 , a substrate  50  and a protective layer  60 . As to the heat generation layer  10 , the heat conductive layer  20 , the heat insulation layer  30  and the patterned electrode  40 , any description of these elements can be referred to the aforementioned content related to the thin film heater  1   a  in  FIG. 1 , and such description is not repeated hereafter. 
     The substrate  50  is made of, for example but not limited to, polyimide (PI). In one embodiment, the substrate  50  can be made of colorless polyimide (CPI). The substrate  50  is disposed on one side of the heat conductive layer  20 , and the heat conductive layer  20  is located between the heat generation layer  10  and the substrate  50 . The substrate  50  can be taken as a base for deposition of the heat conductive layer  20  during fabrication of the thin film heater  1   b . The protective layer  60  is, for example but not limited to, a hard coating (HC) disposed on one side of the heat insulation layer  30 , and the heat insulation layer  30  is located between the heat generation layer  10  and the protective layer  60 . 
     In this embodiment, the thickness of the heat insulation layer  30  is less than or equal to four times of the thickness of the heat conductive layer  20 . A total thickness of the heat insulation layer  30  and the protective layer  60  can be less than or equal to four times of a total thickness of the heat conductive layer  20  and the substrate  50 . Therefore, the thin film heater  1   b  can be bent (as shown in  FIG. 2B ) to be applicable to a curved heated object. 
     According to one embodiment of the present disclosure, a heat isolation layer is disposed on one side the heat generation layer facing toward the heat insulation layer. Please refer to  FIG. 3  showing a schematic view of a thin film heater according to a third embodiment of the present disclosure. In this embodiment, a thin film heater  1   c  includes a heat generation layer  10   c , a heat conductive layer  20 , a heat insulation layer  30 , a patterned electrode  40 , a substrate  50  and a protective layer  60 . As to these elements mentioned above, any description can be referred to the aforementioned content related to the thin film heater in  FIG. 1  and  FIG. 2A , and such description is not repeated hereafter. 
     In this embodiment, the heat generation layer  10   c  is located between the heat conductive layer  20  and the heat insulation layer  30 , and a recess  130  is formed on the surface of the heat generation layer  10   c  facing toward the heat insulation layer  30 , and a heat isolation layer  130 ″ is disposed in the recess  130 . The heat isolation layer  130 ″ includes medium with low thermal conductivity, such as air, inorganic porous material (e.g., foam glass and calcium silicate), foam organic polymer (e.g., polyurethane (PU) with fluorocarbon gas, foam rubber, foam polyurethane), aerogel, hollow glass particles, rock wool, glass fibers and porous silicone. It is worth noting that the present disclosure is not limited to these exemplary heat isolation layer. In this embodiment, the patterned recess  130  is formed on the surface of the heat generation layer  10   c , and the recess  130  in  FIG. 3  has multiple channels  131  communicated with each other. The heat isolation layer  130 ″ is favorable for increasing heat resistance between the heat insulation layer  30  and the heat generation layer  10   c  so as to prevent heat generated by the heat generation layer  10   c  from being transferred into the heat insulation layer  30 . The recess is not limited to the specific examples mentioned above. In other embodiments, multiple independent recesses can be formed on the surface of the heat generation layer, and the heat isolation layer is disposed in each recess. 
     It is worth noting that the present disclosure is not limited to the heat isolation layer in  FIG. 3 . Please refer to  FIG. 4  showing a schematic view of a thin film heater according to a fourth embodiment of the present disclosure. In this embodiment, a thin film heater  1   d  includes a heat generation layer  10   d , a heat conductive layer  20 , a heat insulation layer  30 , a patterned electrode  40 , a substrate  50  and a protective layer  60 . As to these elements mentioned above, any description can be referred to the aforementioned content related to the thin film heaters  1   a ,  1   b  in  FIG. 1  and  FIG. 2A , and such description is not repeated hereafter. In this embodiment, the heat generation layer  10   d  is disposed between the heat conductive layer  20  and the heat insulation layer  30 , and the heat generation layer  10   d  has a rough surface  140  facing toward the heat insulation layer  30 . A heat isolation layer  140 ″ is disposed on the rough surface  140 ; one or more gaps are formed between the rough surface  140  and the heat insulation layer  30 , and the heat isolation layer  140 ″ is disposed in the gap. The heat isolation layer  140 ″ includes medium with low thermal conductivity, such as air, inorganic porous material, foam organic polymer, aerogel, hollow glass particles, rock wool, glass fibers and porous silicone. 
     According to one embodiment of the present disclosure, the heat isolation layer is disposed between the protective layer and the heat generation layer. Please refer to  FIG. 5  showing a schematic view of a thin film heater according to a fifth embodiment of the present disclosure. In this embodiment, thin film heater  1   e  includes a heat generation layer  10 , a heat conductive layer  20 , a heat insulation layer  30   e , a patterned electrode  40 , a substrate  50  and a protective layer  60 . As to these elements mentioned above, any description can be referred to the aforementioned content related to the thin film heaters in  FIG. 1  and  FIG. 2A , and such description is not repeated hereafter. In this embodiment, the heat insulation layer  30   e  is disposed on one side of the heat generation layer  10 , and the heat insulation layer  30   e  has a through-hole structure  310  penetrating through the heat insulation layer  30   e . The heat isolation layer  310 ″ is disposed in the through-hole structure  310 . The through-hole structure  310  includes multiple through holes  311 , and the heat isolation layer  310 ″ in the through-hole structure  310  is located between the protective layer  60  and the heat generation layer  10 . The heat isolation layer  310 ″ includes medium with low thermal conductivity, such as air, inorganic porous material, foam organic polymer, aerogel, hollow glass particles, rock wool, glass fibers and porous silicone. The through holes  311  of the through-hole structure  310  are communicated with each other in this embodiment, but the present disclosure is not limited thereto. In other embodiments, multiple independent through holes can be formed in the heat insulation layer, and the heat isolation layer is disposed in each through hole. 
     According to one embodiment of the present disclosure, the thin film heater includes a heat transfer structure. Please refer to  FIG. 6  showing a schematic view of a thin film heater according to a sixth embodiment of the present disclosure. In this embodiment, thin film heater  1   f  includes a heat generation layer  10 , a heat conductive layer  20   f , a heat insulation layer  30 , a patterned electrode  40 , a substrate  50  and a protective layer  60 . As to these elements mentioned above, any description can be referred to the aforementioned content related to the thin film heaters  1   a ,  1   b  in  FIG. 1  and  FIG. 2A , and such description is not repeated hereafter. In this embodiment, a thin film heater if further includes a heat transfer structure  70  disposed in the heat conductive layer  20   f . The heat transfer structure  70  is a patterned metal layer extending into the heat conductive layer  20   f . The heat transfer structure  70  penetrates through the heat conductive layer  20   f  and contacts the heat generation layer  10  and the substrate  50 . A configuration including the heat conductive layer  20   f  and the heat transfer structure  70  is favorable for enhancing thermal conductivity, such that heat generated by the heat generation layer  10  is transferred toward the substrate  50  more easily via the heat conductive layer  20   f  and the heat transfer structure  70 . It is worth noting that the present disclosure is not limited to the heat transfer structure in  FIG. 6 . In other embodiments, the heat transfer structure may include multiple metal nanowires or metal nanoparticles dispersed in heat conductive layer or spread on the surface of the heat conductive layer. The heat transfer structure  70  is made of, for example but not limited to, gold, silver, copper, aluminum, aluminum ally, manganese, graphite or carbon fiber. Moreover, the heat transfer structure  70  may be in a form of, for example, pillar, sheet, scale, sphere, powder, long fiber, short fiber, whisker crystal, nanowire or nanoparticle. 
     According to one embodiment of the present disclosure, the heat transfer structure extends from the heat conductive layer into the substrate. Please refer to  FIG. 7  showing a schematic view of a thin film heater according to a seventh embodiment of the present disclosure. In this embodiment, a thin film heater  1   g  includes a heat generation layer  10 , a heat conductive layer  20   g , a heat insulation layer  30 , a patterned electrode  40 , a substrate  50   g , a protective layer  60  and a heat transfer structure  70   g . As to these elements mentioned above, any description can be referred to the aforementioned content related to the thin film heaters  1   b , if in  FIG. 2A  and  FIG. 6 , and such description is not repeated hereafter. The heat transfer structure  70   g  is disposed in the heat conductive layer  20   g . In this embodiment, the heat transfer structure  70   g  is a patterned metal layer extending into the heat conductive layer  20   g . The heat transfer structure  70   g  penetrates through the heat conductive layer  20  and further extends from the heat conductive layer  20   g  into the substrate  50   g , such that an effect of the heat transfer structure  70   g  to the enhancement of thermal conductivity is more obvious. 
     According to one embodiment of the present disclosure, the heat transfer structure is disposed in the substrate. Please refer to  FIG. 8  showing a schematic view of a thin film heater according to an eighth embodiment of the present disclosure. In this embodiment, a thin film heater  1   h  includes a heat generation layer  10 , a heat conductive layer  20 , a heat insulation layer  30 , a patterned electrode  40 , a substrate  50   h , a protective layer  60  and a heat transfer structure  70   h . As to these elements mentioned above, any description can be referred to the aforementioned content related to the thin film heaters  1   b , if in  FIG. 2A  and  FIG. 6 , and such description is not repeated hereafter. In this embodiment, the heat transfer structure  70   h  is disposed in the substrate  50   h . The heat transfer structure  70   h  penetrates through the substrate  50   h  and contacts the heat conductive layer  20 . The heat transfer structure  70   h  extends into the substrate  50   h  so as to be favorable for transferring heat from the heat conductive layer  20  toward the substrate  50   h.    
     In  FIG. 2A  through  FIG. 8 , the protective layer  60  is disposed in one side of the heat insulation layer  30 , but the present disclosure is not limited thereto. Please refer to  FIG. 9  showing a schematic view of a thin film heater according to a ninth embodiment of the present disclosure. In this embodiment, a thin film heater  1   i  includes a heat generation layer  10 , a heat conductive layer  20 , a heat insulation layer  30 , a patterned electrode  40 , a substrate  50  and a protective layer  60 . As to these elements mentioned above, any description can be referred to the aforementioned content related to the thin film heaters  1   a ,  1   b  in  FIG. 1  and  FIG. 2A , and such description is not repeated hereafter. 
     In this embodiment, the heat insulation layer  30  is disposed between the heat generation layer  10  and the substrate  50 , and the substrate  50  is disposed between the heat insulation layer  30  and the protective layer  60 . Herein, the substrate  50  is taken as a base for deposition of the heat insulation layer  30  during fabrication of the thin film heater  1   i . 
     According to one embodiment of the present disclosure, a heat isolation layer is provided between the substrate and the heat generation layer. Please refer to  FIG. 10  showing a schematic view of a thin film heater according to a tenth embodiment of the present disclosure. In this embodiment, a thin film heater  1   j  includes a heat generation layer  10 , a heat conductive layer  20 , a heat insulation layer  30   j , a patterned electrode  40 , a substrate  50  and a protective layer  60 . As to these elements mentioned above, any description can be referred to the aforementioned content related to the thin film heaters  1   b ,  1   i  in  FIG. 2A  and  FIG. 9 , and such description is not repeated hereafter. In this embodiment, the heat insulation layer  30   j  has a through-hole structure  310  penetrating through the heat insulation layer  30   j , and the heat isolation layer  310 ″ is disposed in the through-hole structure  310 . The heat isolation layer  310 ″ is located between the substrate  50  and the heat generation layer  10 . The function of the heat isolation layer  310 ″ can be referred to the aforementioned content related to the thin film heaters  1   c ,  1   e  in  FIG. 3  and  FIG. 5 , and such description is not repeated hereafter. 
     Please refer to  FIG. 11  showing a schematic view of a thin film heater according to an eleventh embodiment of the present disclosure. In this embodiment, a thin film heater  1   k  includes a heat generation layer  10 , a heat conductive layer  20   k , a heat insulation layer  30 , a patterned electrode  40 , a substrate  50  and a protective layer  60 . As to these elements mentioned above, any description can be referred to the aforementioned content related to the thin film heaters  1   b ,  1   i  in  FIG. 2A  and  FIG. 9 , and such description is not repeated hereafter. In this embodiment, thin film heater  1   k  further includes a heat transfer structure  70   k . The heat transfer structure  70   k  is a patterned metal layer extending into the heat conductive layer  20   k . The heat transfer structure  70   k  penetrates through the heat conductive layer  20   k  and contacts one side of the heat generation layer  10  away from the heat insulation layer  30 . Examples and function of the heat transfer structure  70   k  can be referred to the thin film heaters  1   f ,  1   g  in  FIG. 6  and  FIG. 7 , and such description is not repeated hereafter. 
     Please refer to  FIG. 12  showing a schematic view of a thin film heater according to a twelfth embodiment of the present disclosure. In this embodiment, a thin film heater 1 m includes a heat generation layer 10 m, a heat conductive layer  20 , a heat insulation layer  30 , a patterned electrode  40 , a substrate  50  and a protective layer  60 . As to these elements mentioned above, any description can be referred to the aforementioned content related to the thin film heaters  1   b ,  1   i  in  FIG. 2A  and  FIG. 9 , and such description is not repeated hereafter. In this embodiment, a recess  130  is formed on the surface of the heat generation layer 10 m facing toward the heat insulation layer  30 , and a heat isolation layer  130 ″ is disposed in the recess  130 . 
     The heat isolation layer can work with heat transfer structure to make the improvement of heat conduction more obvious. Please refer to  FIG. 13  showing a schematic view of a thin film heater according to a thirteenth embodiment of the present disclosure. In this embodiment, a thin film heater  1   n  includes a heat generation layer  10   n , a heat conductive layer  20   n , a heat insulation layer  30 , a patterned electrode  40 , a substrate  50 , a protective layer  60  and a heat transfer structure  70   n . As to these elements mentioned above, any description can be referred to the aforementioned content related to the thin film heaters  1   a ,  1   b ,  1   k  in  FIG. 1 ,  FIG. 2A  and  FIG. 11 , and such description is not repeated hereafter. In this embodiment, a recess  130  is formed on the surface of the heat generation layer  10   n  facing toward the heat insulation layer  30 , and a heat isolation layer  130 ″ is disposed in the recess  130 . Furthermore, the heat transfer structure  70   n  is a patterned metal layer extending into the heat conductive layer  20   n . The heat transfer structure  70   n  penetrates through the heat conductive layer  20   n  and contacts the heat generation layer  10   n . Therefore, the thin film heater  1   n  includes the heat isolation layer  130 ″ as well as the heat transfer structure  70   n  in this embodiment, such that heat generated by the heat generation layer  10   n  is transferred toward the heat conductive layer  20   n  more easily; also, it is favorable for preventing heat from being transferred toward the heat insulation layer  30 , thereby achieving single directional heat conduction. 
     According to the present disclosure, the aforementioned features of the thin film heater can be utilized in numerous combinations so as to achieve corresponding effects. 
     The thin film heater disclosed in the disclosure is applicable to vehicle camera lens.  FIG. 14  is a schematic view of a vehicle camera lens according to one embodiment of the present disclosure. In this embodiment, a camera lens  2  includes a cover glass  21 , a thin film heater  22  and an optical sensor  23 . The cover glass  21 , for example but not limited to, is a tempered glass plate exposing to outside, and the cover glass  21  is configured to prevent moisture or impact by external forces on optical elements. The thin film heater  22  can be considered as a thin film heater disclosed in any one of aforementioned embodiments, and the thin film heater  22  is in thermal contact with the cover glass  21 . The optical sensor  23  is disposed on one side of the thin film heater  22  opposite to the cover glass  21 . External light can travel through the cover glass  21  and thin film heater  22  to reach the optical sensor  23 . 
     When the optical sensor  23  is provided for receiving visible light, each layer of the thin film heater  22  can be made of material which visible light is able to pass through. In detail, take the thin film heater  1   a  in  FIG. 1  and as example, the heat generation layer  10 , the heat conductive layer  20  and the heat insulation layer  30  are made of visible-light transmittable material, or these layers have small thickness to allow transmittance of visible light. In contrast, when the optical sensor  23  is provided for receiving non-visible light, each layer of the thin film heater  22  can be made of opaque material. Specifically, when the optical sensor  23  is provided for receiving infrared light, the heat generation layer  10 , the heat conductive layer  20  and the heat insulation layer  30  of the thin film heater  1   a  in  FIG. 1  are made of infrared-light transmittable material. 
     According to the present disclosure, the thin film heater includes a multilayer structure containing heat conductive layer, heat insulation layer and heat generation layer. The heat conductive layer has a higher thermal conductivity than the heat insulation layer; more specifically, the thermal conductivity of the heat conductive layer is greater than or equal to three times that of the heat insulation layer. Therefore, most amount of heat generated by the heat generation layer is transferred via the heat conductive layer  20 , such that it is favorable for single directional heat conduction of the thin film heater. 
     Furthermore, according to the present disclosure, the camera lens applicable to vehicle includes cover glass and thin film heater in thermal contact with each other. When the moisture/water vapor existing in wet and cold environment condenses onto the cover glass, the thin film heater heats the cover glass to remove condensed water or moisture/water vapor. Since the thin film heater enjoys single directional heat conduction, heat flows to the cover glass via the heat conductive layer more easily so as to improve the efficiency of moisture/water vapor removal. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure. It is intended that the specification and examples be considered as exemplary embodiments only, with a scope of the disclosure being indicated by the following claims and their equivalents.