Patent Publication Number: US-2016230272-A1

Title: Evaporation source heating device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of manufacture of organic electroluminescent devices, and in particular to an evaporation source heating device. 
     2. The Related Arts 
     An organic electroluminescent device is a self-luminous device, which has advantages, including low voltage, wide view angle, fast response, and good temperature adaptation and is believed to be of great prospects of application among flat panel displays and is even considered the next flat panel displaying technology succeeding to plasma display panels (PDPs) and liquid crystal displays (LCDs). 
     Based on the molecular weights of the organic electroluminescent materials used, the organic electroluminescent devices are classified as small molecule organic electroluminescent devices (such as organic light-emitting diode, OLED) and large molecule organic electroluminescent devices (such as polymer light-emitting diode, PLED). Due the difference in molecular weight, the two kinds of organic electroluminescent devices are of manufacturing processes that are quite different. OLED is generally made through a thermal evaporation process, while PLED is made through a spin-coating or inkjet printing process. 
     An OLED generally comprises a substrate, an ITO based transparent anode formed on the substrate, a hole injection layer (HIL) formed on the transparent anode, a hole transport layer (HTL) formed on the hole injection layer, an emissive layer (EML) formed on the hole transport layer, an electron transport layer (ETL) formed on the emissive layer, an electron injection layer (EIL) formed on the electron transport layer, and a cathode formed on the electron injection layer. To increase efficiency, the emissive layer generally adopts a host/guest doping system. 
     The manufacture process of OLED is thermal evaporation, where an organic material is heated in a vacuum condition (E −5  pa), allowing a sublimating organic material or a melting organic material to vaporize in a high temperature and deposit on a substrate carrying a TFT (Thin-Film Transistor) structure or an anode structure. Heretofore, the mainstream evaporation sources include point evaporation source and line evaporation source. The point evaporation source is generally used in a pilot line or an early-stage mass production line. Since the material utilization and film thickness homogeneity achieved with a line evaporation source are superior to those of a point evaporation source, most of the recently established mass production lines adopt line evaporation sources. However, the point evaporation source occupies a small amount of space and a number of point evaporation sources can be arranged in a single film-coating chamber, allowing deposition of a number of materials therein, thereby making it suitable for pilot lines. 
     The difference between the evaporation temperature and the decomposition temperature of an organic material is generally small. A crucible of a point evaporation source often has a great temperature difference in the interior thereof (top hot and bottom cold). If a great amount of material is deposited, the material is hard to reach a stable thermal balance condition, making the evaporation speed unstable. Increasing temperature to make the material thermally balance often cause potential risk of decomposition of the material in the top part. If the amount of material deposited is small, in a condition of high evaporation rate, the temperature of the upper part of the crucible often exceeds the decomposition temperature of the material, so that the vaporized material, when passing through this area, is susceptible to decomposition. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an evaporation source heating device, which comprises a plurality of metal barrels arranged between a heating element and a crucible so that through a process of transmitting heat from the heating element through the plurality of metal barrels in a step by step manner, the crucible is uniformly heated and the result of evaporation deposition is ensured. 
     To achieve the above object, the present invention provides an evaporation source heating device, which comprises: a base, a housing coupled to the base, a heating element arranged inside the housing, a plurality of metal barrels arranged inside the heating element and mounted to the base, and a crucible arranged inside the metal barrels. 
     The base is received in the housing and the base comprises a plurality of recesses formed therein. The plurality of metal barrels is respectively mounted in the plurality of recesses. 
     The metal barrels are cylindrical and the recesses are circular recesses. 
     The circular recesses are concentric. 
     The metal barrels have heights that are substantially equal to or less than a height of the housing. 
     The base is made of a metal or a thermal insulation ceramic material. 
     The metal barrels are made of metal plates. 
     The metal plates have thicknesses of 0.01 mm-10 cm. 
     The metal plates are made of materials of aluminum, aluminum alloys, titanium, titanium alloys, or materials having excellent thermal conductivities. 
     The heating element comprises a heating resistance wire. 
     The present invention also provides an evaporation source heating device, which comprises: a base, a housing coupled to the base, a heating element arranged inside the housing, a plurality of metal barrels arranged inside the heating element and mounted to the base, and a crucible arranged inside the metal barrels; 
     wherein the base is received in the housing and the base comprises a plurality of recesses formed therein, the plurality of metal barrels being respectively mounted in the plurality of recesses; 
     wherein the metal barrels are cylindrical and the recesses are circular recesses; 
     wherein the circular recesses are concentric; 
     wherein the metal barrels have heights that are substantially equal to or less than a height of the housing; 
     wherein the base is made of a metal or a thermal insulation ceramic material; 
     wherein the metal barrels are made of metal plates; 
     wherein the metal plates have thicknesses of 0.01 mm-10 cm; 
     wherein the metal plates are made of materials of aluminum, aluminum alloys, titanium, titanium alloys, or materials having excellent thermal conductivities; and 
     wherein the heating element comprises a heating resistance wire. 
     The efficacy of the present invention is that the present invention provides an evaporation source heating device, which comprises a plurality of metal barrels arranged between a heating element and a crucible. The plurality of metal barrels is mounted on a base. During heating, through a process of transmitting the heat from the heating element through the plurality of metal barrels in a step by step manner, the heat is transmitted to the crucible. Since the metal barrels have excellent properties of heat conduction, distribution of heat thereon is generally uniform, allowing the crucible to be uniformly heated and ensuring the result of evaporation deposition. Further, the number of the metal barrels can be increased or decreased according to practical needs in order to adjust the transfer and balance of temperature through the metal barrels and thus controlling the temperature difference of the crucible. 
     For better understanding of the features and technical contents of the present invention, reference will be made to the following detailed description of the present invention and the attached drawings. However, the drawings are provided for the purposes of reference and illustration and are not intended to impose undue limitations to the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The technical solution, as well as beneficial advantages, of the present invention will be apparent from the following detailed description of an embodiment of the present invention, with reference to the attached drawings. In the drawings: 
         FIG. 1  is a perspective view showing an evaporation source heating device according to an embodiment of the present invention; 
         FIG. 2  is a cross-sectional view showing the evaporation source heating device of  FIG. 1 ; 
         FIG. 3  is a top plan view of a base of the evaporation source heating device of  FIG. 1 ; and 
         FIG. 4  is a perspective view of the base of the evaporation source heating device of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     To further expound the technical solution adopted in the present invention and the advantages thereof, a detailed description is given to a preferred embodiment of the present invention and the attached drawings. 
     Referring to  FIGS. 1-4 , the present invention provides an evaporation source heating device  10 , which comprises a base  20 , a housing  80  coupled to the base  20 , a heating element  60  arranged inside the housing  80 , a plurality of metal barrels  40  arranged inside the heating element  60  and mounted to the base  20 , and a crucible  90  arranged inside the metal barrels  40 . The base  20  is received in the housing  80 . The base  20  comprises a plurality of concentric circular recesses  21  formed therein. The metal barrels  40  are cylindrical barrels. The plurality of metal barrels  40  is respectively mounted in the plurality of recesses  21 . The heating element  60  comprises a heating resistance wire. 
     In the instant embodiment, the base  20  comprises four concentric circular recesses  21 , which are respectively designated  21   a,    21   b,    21   c,  and  21  d from the inside to the outside. The plurality of metal barrels  40  comprises three barrels, which are respective a first layer (the outermost layer) metal barrel  40   a,  a second layer (the middle layer) metal barrel  40   b,  and a third layer (the innermost layer) metal barrel  40   c.  The first-layer metal barrel  40   a,  the second-layer metal barrel  40   b,  and the third-layer metal barrel  40   c  are respectively mounted in the recesses  21   a,    21   b,  and  21   c.  The crucible  90  is arranged at a center of the third-layer metal barrel  40   c  and is mounted in and located above the innermost recess  21   d  of the base  20 . Further, according to the present invention, the number of the recesses  21  formed in the base  20  and the number of the metal barrels  40  mounted on the base  20  can be adjusted according to practical needs in order to achieve the best result of heating the crucible  90  contained in the evaporation source heating device  10 . 
     When the heating element  60  starts heating, heat is transmitted through the first-layer metal barrel  40   a  to propagates step by step into the second-layer metal barrel  40   b  and the third-layer metal barrel  40   c  and then to the crucible  90  to achieve heating of the crucible  90 . In a vacuum condition, the heat emitting from the heating element  60  of the evaporation source heating device  10  takes the form of thermal radiation that heats the metal barrels  40 . Since the thermal energies emitting from different parts of the heating element  60  may be different, there may be a great temperature difference occurring in the first-layer metal barrel  40   a.  Due to the excellent thermal conductivity of metal, when the first-layer metal barrel  40   a  irradiates heat toward the second-layer metal barrel  40   b,  the thermal energy of a high temperature part thereof is also conducted to a low temperature part thereof so that the temperature difference between different parts of the first-layer metal barrel  40   a  becomes less and thus, the temperature difference that might occur in the second-layer metal barrel  40   b  may be even less. And, the difference of temperature in the third-layer metal barrel  40   c  is substantially zero. Thus, when the heat is transmitted to the crucible  90  that is located in the interior, the crucible  90  may receive the heat that shows substantially no temperature difference in different parts thereof so that the crucible  90  can be heated uniformly. In other words, with the arrangement of the metal barrels  40 , the non-uniform distribution of heat from the heating element  60  is converted into heat of uniform distribution to be transmitted to the crucible  90 , thereby achieving no temperature difference inside the crucible  90 . 
     The metal barrels  40  may have heights that are substantially equal to or less than a height of the housing  80 , allowing the metal barrels  40  not to project outside the housing  80 . In the instant embodiment, the height of the first-layer metal barrel  40   a  is greater than a height of the crucible  90 ; the height of the second-layer metal barrel  40   b  is less than the height of the first-layer metal barrel  40   a;  and the height of the third-layer metal barrel  40   c  is less than the height of the second-layer metal barrel  40   b  and substantially equal to the crucible  90 . As a feasible alternative, the heights of the metal barrels  40  may be made equal to or close to the height of the crucible  90 . The number of the recesses  21  formed in the base  20  and the number of the metal barrels  40  mounted in the recesses  21  can be increased or decreased according to a desired result of heating. 
     The base  20  may be made of metal, thermal insulation ceramics, or other materials. 
     The metal barrels  40  are made of metal plates and the metal plates have thicknesses of 0.01 mm-10 cm. The metal plates are made of materials of aluminum, aluminum alloys, titanium, titanium alloys, or other metals having excellent thermal conductivities. 
     In summary, the present invention provides an evaporation source heating device, which comprises a plurality of metal barrels arranged between a heating element and a crucible. The plurality of metal barrels is mounted on a base. During heating, through a process of transmitting the heat from the heating element through the plurality of metal barrels in a step by step manner, the heat is transmitted to the crucible. Since the metal barrels have excellent properties of heat conduction, distribution of heat thereon is generally uniform, allowing the crucible to be uniformly heated and ensuring the result of evaporation deposition. Further, the number of the metal barrels can be increased or decreased according to practical needs in order to adjust the transfer and balance of temperature through the metal barrels and thus controlling the temperature difference of the crucible. 
     Based on the description given above, those having ordinary skills of the art may easily contemplate various changes and modifications of the technical solution and technical ideas of the present invention and all these changes and modifications are considered within the protection scope of right for the present invention.