Joined unit of glass base members, airtight envelope, and method for producing glass structural unit

Abstract

A joined unit of glass base members is provided, comprising first and second glass base members and a joining member which extends along opposing surfaces of the first and second glass base members, wherein glass base member is elastically deformed while being depressed in an internal direction of the glass base member in the vicinity of an end portion in a widthwise direction of the joining member, a boundary surface between the elastically deformed glass base member and the joining member and a surface of the elastically deformed glass base member, which are disposed in the vicinity of the end portion in the widthwise direction of the joining member, are positioned on an internal side of the glass base member, and an area, in which a residual stress is a compressive stress, is formed in the vicinity of the end portion in the widthwise direction of the joining member.

1 . A joined unit of glass base members, comprising:
 a first glass base member;   a second glass base member; and   a joining member which joins the first glass base member and the second glass base member, which is capable of providing a viscosity that has a negative temperature coefficient, and which extends at a predetermined width along opposing surfaces of the first glass base member and the second glass base member, wherein:   at least one of the first glass base member and the second glass base member is elastically deformed while being depressed in an internal direction of the glass base member in the vicinity of an end portion in a widthwise direction of the joining member;   a boundary surface between the elastically deformed glass base member and the joining member and a surface of the elastically deformed glass base member, which are disposed in the vicinity of the end portion in the widthwise direction of the joining member, are positioned on an internal side of the glass base member as compared with a boundary surface between the elastically deformed glass base member and the joining member which is disposed in the vicinity of a central portion in the widthwise direction of the joining member; and   an area, in which a residual stress in a thickness direction of the joining member is a compressive stress, is formed in the vicinity of the end portion in the widthwise direction of the joining member.   
     
     
         2 . The joined unit of glass base members according to  claim 1 , wherein:
 an area, in which a residual stress in the thickness direction of the joining member is a compressive stress, is formed at the central portion in the widthwise direction of the joining member; and   an area, in which a residual stress in the thickness direction of the joining member is a tensile stress, is formed adjacently to the area which is formed at the central portion in the widthwise direction of the joining member to provide the compressive stress and the area which is formed at the end portion in the widthwise direction of the joining member to provide the compressive stress.   
     
     
         3 . An airtight envelope comprising:
 a first glass base member;   a second glass base member; and   a joining member which joins the first glass base member and the second glass base member, which is capable of providing a viscosity that has a negative temperature coefficient, and which extends at a predetermined width along opposing surfaces of the first glass base member and the second glass base member, wherein:   at least one of the first glass base member and the second glass base member is elastically deformed while being depressed in an internal direction of the glass base member in the vicinity of an end portion in a widthwise direction of the joining member;   a boundary surface between the elastically deformed glass base member and the joining member and a surface of the elastically deformed glass base member, which are disposed in the vicinity of the end portion in the widthwise direction of the joining member, are positioned on an internal side of the glass base member as compared with a boundary surface between the elastically deformed glass base member and the joining member which is disposed in the vicinity of a central portion in the widthwise direction of the joining member; and   an area, in which a residual stress in a thickness direction of the joining member is a compressive stress, is formed in the vicinity of the end portion in the widthwise direction of the joining member.   
     
     
         4 . The airtight envelope according to  claim 3 , wherein:
 an area, in which a residual stress in the thickness direction of the joining member is a compressive stress, is formed at the central portion in the widthwise direction of the joining member; and   an area, in which a residual stress in the thickness direction of the joining member is a tensile stress, is formed adjacently to the area which is formed at the central portion in the widthwise direction of the joining member to provide the compressive stress and the area which is formed at the end portion in the widthwise direction of the joining member to provide the compressive stress.   
     
     
         5 . A method for producing a glass structural unit, including joining a first glass base member and a second glass base member for forming at least a part of the glass structural unit together with the first glass base member, the method comprising:
 a step of arranging a joining member between the first glass base member and the second glass base member so that the joining member is brought in contact with both of the first glass base member and the second glass base member, the joining member being capable of providing a viscosity which has a negative temperature coefficient, and the joining member extending at a predetermined width along opposing surfaces of the first glass base member and the second glass base member;   a step of pressing the joining member in a thickness direction of the joining member; and   a first joining step of radiating a first local heating light beam onto the joining member via the first glass base member so that a radiation position is moved in a direction in which the joining member extends, heating and melting the joining member in an entire region in a widthwise direction, and then cooling the joining member to a temperature of not more than a softening point, wherein:   the following expressions are fulfilled by a velocity of movement v (m/s) of the radiation position brought about by the first local heating light beam and a beam diameter φ (m) of the first local heating light beam provided that d (m) represents a thickness of the first glass base member, a (m 2 /s) represents a thermal diffusivity of the first glass base member, and w (m) represents the width of the joining member:
   φ/ v <( d/ 8) 2 /(12 a )   (Expression 1)
 
   φ>w   (Expression 2)
 
   
     
     
         6 . The method for producing the glass structural unit according to  claim 5 , further comprising:
 a second joining step of radiating a second local heating light beam onto the joining member cooled to the temperature of not more than the softening point in the first joining step so that a radiation position is moved in the direction in which the joining member extends, heating and melting only a central portion of the joining member interposed between both side portions in the widthwise direction of the joining member so that the both side portions are not softened, and then cooling the heated and melted central portion of the joining member to a temperature of not more than the softening point.   
     
     
         7 . The method for producing the glass structural unit according to  claim 6 , wherein the second local heating light beam is radiated so that the radiation position, which is brought about by the second local heating light beam, follows the radiation position which is brought about by the first local heating light beam. 
     
     
         8 . The method for producing the glass structural unit according to  claim 5 , further comprising:
 a second joining step of radiating a second local heating light beam onto the joining member prior to the radiation of the first local heating light beam in the first joining step so that a radiation position is moved in the direction in which the joining member extends, successively heating and melting parts in the widthwise direction of the joining member in the direction in which the joining member extends, thereafter cooling the heated and melted parts of the joining member to a temperature of not more than the softening point, and successively forming partially joined portions in partial areas in the widthwise direction of the joining member in the direction in which the joining member extends, wherein:   the second local heating light beam is radiated so that the radiation position, which is brought about by the first local heating light beam, follows the radiation position which is brought about by the second local heating light beam.   
     
     
         9 . The method for producing the glass structural unit according to  claim 8 , wherein the second local heating light beam is radiated so that the partially joined portions are formed continuously in the direction in which the joining member extends. 
     
     
         10 . The method for producing the glass structural unit according to  claim 8 , wherein the first local heating light beam is radiated during a period in which a temperature of the joining member fulfills a range of −0.1≦(T 2 −25)/(T sf −25)≦1 at each of positions of the joining member provided that T 2  represents the temperature of the joining member and T sf  represents the softening point of the joining member. 
     
     
         11 . The method for producing the glass structural unit according to  claim 8 , wherein the first local heating light beam is radiated during a period in which the viscosity of the joining member is not more than 10 18  (Pa·sec) at each of positions of the joining member. 
     
     
         12 . The method for producing the glass structural unit according to  claim 8 , wherein the first local heating light beam is radiated during a period in which the viscosity of the joining member is not more than 10 13.5  (Pa·sec) at each of positions of the joining member.