Heater and method of manufacturing same

Abstract

A heater includes a plate-shaped substrate having a heating surface for heating an object to be heated and a heater element provided in the substrate or on a surface thereof. A central axis C 2 of a circumscribed circle of the resistant heater element and a central axis C 1 of the substrate are not on the same axis and there is a gap between these two axes. In a method of manufacturing the heater, a central axis C 1 of a resistant heater is specified, thermal uniformity of the heating surface of a preliminary substrate is evaluated, and a central axis C 2 of the substrate is specified. The central axis C 2 is specified at a position where the thermal uniformity of the heating surface is superior to a case where the central axis C 2 of the substrate is located on the central axis C 1 . Then a substrate having the central axis C 2 is formed by subjecting the preliminary substrate to grinding processing.

What is claimed is:  
     
         1 . A heater comprising: 
 a plate-shaped substrate including a heating surface which heats an object to be heated; and    a resistant heater element provided in the substrate or on a surface thereof,    wherein a central axis C 2  of a circumscribed circle of the resistant heater element and a central axis C 1  of the substrate are not on the same axis and there is a gap between these two axes.    
     
     
         2 . The heater according to  claim 1 , wherein distance and direction of the gap are set so as to improve thermal uniformity on the heating surface compared to a case where the central axes C 1  and C 2  are on the same axis.  
     
     
         3 . The heater according to  claim 1 , wherein the gap is within a range of 0.05 mm to 10 mm.  
     
     
         4 . The heater according to  claim 1 , wherein the gap is within a range of 0.01 mm to 8 mm.  
     
     
         5 . The heater according to  claim 1 , wherein the resistant heater element includes one or a plurality of heater element units and the circumscribed circle is a circumscribed circle relative to a projected shape of all the heater element units onto the heating surface.  
     
     
         6 . The heater according to  claim 5 , wherein a planar shape of the substrate is any one of a substantial circle and a substantial regular polygon, and the projected shape thereof is any one of a substantial circle and a substantial regular polygon.  
     
     
         7 . The heater according to  claim 1 , wherein the substrate includes at least any one of ceramics selected from the group consisting of aluminum nitride, silicon carbide, silicon nitride and aluminum oxide as a main component, and the resistant heater element is made of at least one of metals selected from the group consisting of molybdenum, tungsten and platinum.  
     
     
         8 . The heater according to  claim 1 , wherein the resistant heater element has any one of shapes selected from the group consisting of a line shape, a band shape, a mesh shape and a film shape.  
     
     
         9 . A method of manufacturing a heater, comprising: 
 forming a plate-shaped preliminary substrate which has a resistant heater element in the substrate or on a surface thereof and includes a heating surface on one side thereof for heating an object to be heated;    specifying a position of a central axis C 1  of the resistant heater element provided in the preliminary substrate;    evaluating thermal uniformity of the heating surface of the preliminary substrate;    specifying a position of a central axis C 2  of the substrate at a position where the heat uniformity of the heating surface is superior to the case where the central axis C 2  of the substrate is on the central axis C 1 , based on results of the thermal uniformity evaluation; and    forming the substrate having the central axis C 2  by subjecting the preliminary substrate to grinding processing.    
     
     
         10 . The method according to  claim 9 , wherein the position of the central axis C 2  of the substrate is specified so as to set a gap between the central axis C 2  and the central axis C 1  of the resistant heater element to be within a range of 0.005 mm to 10 mm.  
     
     
         11 . The method according to  claim 9 , wherein the position of the central axis C 2  of the substrate is specified so as to set a gap between the central axis C 2  and the central axis C 1  of the resistant heater element to be within a range of 0.01 mm to 8 mm.  
     
     
         12 . The method according to  claim 9 , wherein the central axis C 1  of the resistant heater element is specified based on an X-ray photographed image of the resistant heater element.  
     
     
         13 . The method according to  claim 9 , wherein, in the thermal uniformity evaluation of the heating surface, a temperature distribution on the heating surface of the preliminary substrate is measured by use of an infrared thermometer.  
     
     
         14 . The method according to  claim 9 , wherein the preliminary substrate includes at least one of ceramics selected from the group consisting of aluminum nitride, silicon carbide, silicon nitride and aluminum oxide as a main component, and the resistant heater element is made of at least one of metals selected from the group consisting of molybdenum, tungsten and platinum.  
     
     
         15 . The method according to  claim 9 , wherein the preliminary substrate formation comprises: 
 molding a ceramic body having the resistant heater element embedded therein and    sintering the molded ceramic body.    
     
     
         16 . The method according to  claim 15 , wherein the step of sintering is performed by hot-pressing.