Patent Publication Number: US-10781837-B2

Title: Joint structure and method of manufacturing joint structure

Description:
This application claims priority to Japanese Patent Application No. 2016-193992, filed on Sep. 30, 2016, the contents of which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     This invention relates to a joint structure comprising a light-absorbable member and a light-permeable member superposed to each other and joined to each other through a weld part formed in a boundary face or in the neighborhood of the boundary face and a method for manufacturing the joint structure. 
     RELATED ART 
     As a method for joining plural members has hitherto been known a joining method through laser beam irradiation. In recent years is noticed a laser transmission welding method in which heating is local and thermal damage to a product is small and an influence of a weld part on an appearance is small. This method is a method wherein a member having a permeability to a laser beam (light-permeable member) is used as a joining member and a member having an absorbability to a laser beam (light-absorbable member) is used as the other joining member and these members are superposed to each other and exposed to a laser beam from the light-permeable member at a pressurized state, whereby energy of the irradiated laser beam is absorbed by the light-absorbable member in the neighborhood of a boundary face thereof to cause heat generation, and the generated heat is transferred to the light-permeable member to fuse the both members, and finally the fused portions are cooled and solidified to join the both members to each other. 
     The laser transmission welding method has some important points. Among them, it is especially important that the members to be joined are surely adhered to each other by pressurization. If a gap is existent between the members to be joined, heat generated in the light-absorbable member by the laser beam irradiation is not well transferred to the light-permeable member, and hence poor welding such as upheaving, expanding, explosion or the like is caused by local temperature rising. 
     In general, the pressurization is attained by a method wherein a glass plate having a permeability to a laser beam is disposed onto the light-permeable member and a pressure is applied to the both members through the glass plate (see Patent Document 1). However, this method has a problem that the glass plate is contaminated with soot generated in the heating and fusion of the members to be joined or a vaporization ingredient of a flame retardant to increase an absorption rate of the glass plate to the laser beam and hence the glass plate itself is heated to cause breakage. Also, the laser beam is shielded by the contaminated glass plate so as not to reach to the light-absorbable member sufficiently and hence the decrease of welding strength is caused. 
     On the other hand, Patent Document 2 proposes a method of adhering the members to be joined to each other by sucking without using the glass plate. In the method of Patent Document 2, a groove portion is formed in one of the members to be joined and the both members are adhered to each other by depressurizing a space of the groove portion. In the welding through laser beam irradiation, however, thermal deformation is caused in one or both of the members to be joined or warping is caused in the members to be joined during the forming, and hence a gap is generated between the members to be joined to decrease an adhesiveness by sucking. 
     PATENT DOCUMENTS 
     
         
         Patent Document 1: JP-A-562-142092 
         Patent Document 2: WO2010-035696 
       
    
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the invention to provide a joint structure suitable for uniformly and surely adhering members to be joined to each other without using a glass plate and to provide a method of manufacturing a joint structure which is capable of uniformly and surely adhering members to be joined to each other without using a glass plate. 
     In order to solve the above problems, the invention provides a joint structure comprising a light-absorbable member having at least one opening portion and a light-permeable member superposed on the light-absorbable member so as to cover the opening portion, wherein an annular weld part is formed so as to enclose the opening portion and join the light-absorbable member and the light-permeable member, and the light-permeable member is formed into a thin sheet adhering to the light-absorbable member by deforming at a depressurized state of an interior of the opening portion before the formation of the annular weld part. 
     It is preferable that the light-permeable member is formed so as to have a thickness adhering to the light-absorbable member by deforming when the interior of the opening portion is depressurized to not less than −80 kPa but not more than −20 kPa as a gauge pressure before the formation of the annular weld part. 
     In the joint structure according to the invention, it is preferable that a dot-like weld part(s) joining the light-absorbable member and the light-permeable member is/are disposed at a position adjacent to the annular weld part. 
     Also, the invention provides a joint structure comprising a light-absorbable member having at least one opening portion and a light-permeable member superposed on the light-absorbable member so as to cover the opening portion, wherein an annular weld part is formed so as to enclose the opening portion and join the light-absorbable member and the light-permeable member, and the light-permeable member is provided outside the annular weld part with a thinned piece adhering to the light-absorbable member by deforming at a depressurized state of an interior of the opening portion before the formation of the annular weld part. 
     In this case, it is preferable that the thinned piece is formed to have a thickness adhering to the light-absorbable member by deforming when the interior of the opening portion is depressurized to not less than −80 kPa but not more than −20 kPa as a gauge pressure before the formation of the annular weld part. 
     In the joint structure according to the invention, the thinned piece is preferable to be formed along a peripheral edge part of the light-absorbable member. 
     In the joint structure according to the invention, it is preferable that a dot-like weld part(s) joining the light-absorbable member and the light-permeable member is/are disposed at a position adjacent to the annular weld part. 
     In order to solve the above problems, the invention is a method of manufacturing a joint structure which comprises superposing a light-permeable member onto a light-absorbable member having at least one opening portion so as to cover the opening portion, irradiating a laser beam from the side of the light-permeable member to form an annular weld part so as to enclose the opening portion to thereby join the light-absorbable member and the light-permeable member, wherein the light-permeable member is deformed at a state of depressurizing an interior of the opening portion before the formation of the annular weld part to form a thin sheet adhering to the light-absorbable member, and the interior of the opening portion is depressurized in the formation of the annular weld part to deform the light-permeable member and the laser beam is irradiated from the side of the light-permeable member at a state of adhering to the light-absorbable member. 
     In this case, it is preferable that the light-permeable member is formed in a thickness adhering to the light-absorbable member by deforming when the interior of the opening portion is depressurized to not less than −80 kPa but not more than −20 kPa as a gauge pressure before the formation of the annular weld part. 
     Furthermore, in order to solve the above problems, the invention is a method of manufacturing a joint structure which comprises superposing a light-permeable member onto a light-absorbable member having at least one opening portion so as to cover the opening portion, irradiating a laser beam from the side of the light-permeable member to form an annular weld part so as to enclose the opening portion to thereby join the light-absorbable member and the light-permeable member, wherein a thinned piece of the light-permeable member adhering to the light-absorbable member is formed outside the annular weld part by deforming at a state of depressurizing an interior of the opening portion before the formation of the annular weld part, and the interior of the opening portion is depressurized in the formation of the annular weld part to deform the thinned piece and the laser beam is irradiated from the side of the light-permeable member at a state of adhering to the light-absorbable member. 
     In this case, it is preferable that the thinned piece is formed in a thickness adhering to the light-absorbable member by deforming when the interior of the opening portion is depressurized to not less than −80 kPa but not more than −20 kPa as a gauge pressure before the formation of the annular weld part. 
     In the method of manufacturing the joint structure according to the invention, the thinned piece is preferable to be formed along a peripheral edge part of the light-absorbable member. 
     In the method of manufacturing the joint structure according to the invention, it is preferable that a laser beam are irradiated from the side of the light-permeable member after the superposition of the light-permeable member and the light-absorbable member and before the formation of the annular weld part to form a dot-like weld part(s) joining the light-permeable member and the light-absorbable member. 
     In the method of manufacturing the joint structure according to the invention, it is preferable that a suction port communicating with the opening portion and connecting to an external depressurizing device is formed in the light-absorbable member. 
     In the method of manufacturing the joint structure according to the invention, it is preferable that the suction port is fused and closed by irradiating a laser beam from the side of the light-permeable member after the formation of the annular weld part while keeping the interior of the opening portion at a depressurized state. 
     In the method of manufacturing the joint structure according to the invention, it is preferable that the interior of the opening portion is depressurized while feeding a purge gas to the interior of the opening portion. 
     In this case, the depressurization of the interior of the opening portion and the feed of the purge gas are conducted with a double pipe through the suction port. 
     In the method of manufacturing the joint structure according to the invention, it is preferable that an airtightness test of the annular weld part is performed by measuring a change of a pressure per unit time when the interior of the opening portion is kept at the depressurized state subsequent to the formation of the annular weld part or the interior of the opening portion is pressurized or the depressurization and pressurization are performed alternately. 
     In the method of manufacturing the joint structure according to the invention, it is preferable that the judgement on adhesion between the light-absorbable member and the light-permeable member, start of the formation of the annular weld part and end of the formation of the annular weld part is performed based on a change of a pressure obtained by always detecting a pressure inside the opening portion. 
     EFFECT OF THE INVENTION 
     In the manufacture of the joint structure according to the invention, the thin sheet-formed light-permeable member or the thinned piece formed in the light-permeable member can be deformed by depressurizing the interior of the opening portion to adhere to the light-absorbable member, whereby an excellent adhesiveness between the light-absorbable member and the light-permeable member by suction can be obtained. 
     According to the invention, therefore, the joint structure suitable for uniformly and surely adhering the members to be joined to each other can be provided without using a glass plate, and also there can be provided a method of manufacturing a joint structure which is capable of uniformly and surely adhering the members to be joined to each other without using a glass plate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of an embodiment of the joint structure according to the invention and  FIG. 1B  is a section view taken along a line A-A in  FIG. 1A .  FIG. 1C  is enlarged view of region I-C in  FIG. 1B . 
         FIG. 2A  is a perspective view of another embodiment of the joint structure according to the invention and  FIG. 2B  is a section view taken along a line B-B in  FIG. 2A .  FIG. 2C  is enlarged view of region II-C in  FIG. 2B . 
         FIG. 3A  is a perspective view of the other embodiment of the joint structure according to the invention and  FIG. 3B  is a section view taken along a line C-C in  FIG. 3A .  FIG. 3C  is enlarged view of region in  FIG. 3B . 
         FIGS. 4A and 4B  are section views of modification examples of a thinned piece in the joint structure shown in  FIGS. 3A and 3B . 
         FIG. 5A  is a plane view of a light-absorbable member used in the method of manufacturing an embodiment of the joint structure according to the invention and  FIG. 5B  is a section view taken along a line D-D shown in  FIG. 5A .  FIG. 5C  is enlarged view of region V-C in  FIG. 5B . 
         FIG. 6A  is a schematic view of a layout showing the method of manufacturing an embodiment of the joint structure according to the invention and  FIG. 6B  is a section view showing a suction adhering step thereof. 
         FIG. 7  is a schematic view illustrating a pressure control device and a laser beam irradiating device used in the method of manufacturing an embodiment of the joint structure according to the invention. 
         FIGS. 8A-8D  are section views illustrating the sequence of forming an annular weld part by irradiating a laser beam to an annular groove of a light-absorbable member in the method of manufacturing an embodiment of the joint structure according to the invention, respectively. 
         FIGS. 9A-9C  are section views illustrating another examples of an annular groove applicable to the method of manufacturing the joint structure according to the invention. 
         FIG. 10A  is a perspective view of an embodiment of the connector according to the invention and  FIG. 10B  is a section view thereof.  FIG. 10C  is enlarged view of region X-C from  FIG. 10B . 
         FIG. 11A  is a perspective view of an embodiment of the sensor according to the invention and  FIG. 11B  is a section view thereof.  FIG. 11C  is enlarged view of region XI-C from  FIG. 11B . 
     
    
    
     EMBODIMENTS FOR CARRYING OUT THE INVENTION 
     An embodiment of the invention will be described with reference to the drawings below. Moreover, similar members and portions shown in the drawings are represented by symbols added with a symbol “100” or “200”, and an explanation on overlapping portions is omitted. 
       FIGS. 1A, 1B, and 1C  show an embodiment of the joint structure  100  according to the invention, in which  FIG. 1A  is a perspective view and  FIG. 1B  is a section view taken along a line A-A in  FIG. 1A  and  FIG. 1C  is enlarged view of region I-C in  FIG. 1B . As shown in this figure, the joint structure  100  comprises a light-absorbable member  102  having an opening portion O and a light-permeable member  106  superposed with the light-absorbable member  102  so as to cover the opening portion O and joined to the light-absorbable member  102  through an annular weld part  104  enclosing the opening portion O. Moreover, the term “annular” means not only a circular form such as a ring but also a continuously closed form (endless form). Therefore, the annular form includes not only a circle and an ellipsoid but also a rectangle, a polygon and other closed forms. The weld part  104  is formed on a boundary face F between the light-permeable member  106  and the light-absorbable member  102 . As mentioned in detail later, the weld part  104  can be formed by irradiating a laser beam from the side of the light-permeable member  106  toward the light-absorbable member  102  to cause heat generation, fusing the light-absorbable member  102  as well as the light-permeable member  106  by the generated heat and solidifying the fused portions. 
     The light-absorbable member  102  has an absorption rate to a laser beam higher than that of the light-permeable member  106  and is composed mainly of a thermoplastic resin or a thermoplastic elastomer, which can be shaped by an injection molding or the like. It is preferable to have an absorption rate of not less than 10% to a laser beam selected from laser beams having a center of oscillation wavelength within a range of 193-10600 nm. As a laser are included, for example, a carbon dioxide laser (wavelength: about 10600 nm), Nd-YAG laser (wavelength: about 1064 nm), a green laser being a secondary harmonic of Nd—YVO 4  laser (wavelength: about 532 nm), a diode laser (wavelength: about 800 nm, 840 nm or 950 nm), an excimer laser (wavelength: about 193 nm) and so on. In order to adjust the absorption rate of the light-absorbable member  102 , a black coloring agent such as carbon black or the like, a pigment, a dyestuff and so on may be kneaded with the thermoplastic resin or a thermoplastic elastomer. 
     As the thermoplastic resin are included, for example, polyamide resin, polyethylene resin, polypropylene resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyphenyl ether resin, polystyrene resin, high-impact polystyrene resin, hydrogenated polystyrene resin, polyacryl styrene resin, ABS resin, AS resin, AES resin, ASA resin, SMA resin, polyalkyl methacrylate resin, polymethyl methacrylate resin, polycarbonate resin, polyester resin, polyphenylene sulfide, liquid crystal polymer and so on. As the thermoplastic elastomer are included, for example, styrene-based thermoplastic elastomer, olefinic thermoplastic elastomer, polyester-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, PVC-based thermoplastic elastomer and so on. The thermoplastic resin may be kneaded with glass fibers, minerals and the like as a reinforcing material. 
     In the illustrated example, the light-absorbable member  102  is mainly comprised of a peripheral wall  108  defining an opening portion O and a bottom wall  110  closing the lower end part of the peripheral wall  108 . The cross-sectional shape of the peripheral wall  108  is substantially rectangular, but is not limited thereto and may take any shape such as circular, ellipsoidal, trapezoidal, polygonal, gourd-shaped and the like. In the peripheral wall  108  is formed a suction port  112  communicating with the opening portion O so as to depressurize an interior of the opening portion O as mentioned later. The suction port  112  may be formed in the bottom wall  110  or a lower end of the peripheral wall  108  is opened without forming the bottom wall  110  and the opened port in the lower end is used as the suction port  112 . 
     The light-permeable member  106  has an absorption rate to a laser beam lower than that of the light-absorbable member  102  and is composed mainly of a thermoplastic resin or a thermoplastic elastomer, which may be formed by injection molding or the like. It is preferable to have an absorption rate to a laser beam selected from laser beams having a center of oscillation wavelength within a range of 193 nm-10600 nm lower than that of the light-absorbable member  102 . 
     As the thermoplastic resin constituting the light-permeable member  106  are included, for example, polyamide resin, polyethylene resin, polypropylene resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyphenyl ether resin, polystyrene resin, high-impact polystyrene resin, hydrogenated polystyrene resin, polyacryl styrene resin, ABS resin, AS resin, AES resin, ASA resin, SMA resin, polyalkyl methacrylate resin, polymethyl methacrylate resin, polycarbonate resin, polyester resin, polyphenylene sulfide, liquid crystal polymer and so on. As the thermoplastic elastomer are included, for example, styrene-based thermoplastic elastomer, olefinic thermoplastic elastomer, polyester-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, PVC-based thermoplastic elastomer and so on. Moreover, the thermoplastic resin may be kneaded with glass fibers, minerals and the like as a reinforcing material. Further, the thermoplastic resin or thermoplastic elastomer may be kneaded, for example, with a white pigment or a chromatic coloring agent of yellow, green, red or the like as long as it has an absorption rate lower than that of the light-absorbable member. 
     The light-permeable member  106  is formed into a thin sheet adhering at its peripheral edge portion to an upper end face of the peripheral wall  108  of the light-absorbable member  102  by deforming when an interior of the opening portion O is depressurized before the formation of the annular weld part  104 . Thus, when the light-permeable member  106  is superposed with the light-absorbable member  102 , even if a gap is produced between the upper end face of the peripheral wall  108  of the light-absorbable member  102  and the light-permeable member  106 , the interior of the opening portion O can be depressurized through the suction port  112  to adhere the light-permeable member  106  to the upper end face of the peripheral wall  108  of the light-absorbable member  102 , whereby an excellent adhesiveness by suction can be obtained between the mutual light-permeable member  106  and light-absorbable member  102  while preventing vacuum leakage. 
     In order to more surely establish the above, it is preferable that the light-permeable member  106  is deformed when the interior of the opening portion O is depressurized to not less than −80 kPa but not more than −20 kPa as a gauge pressure before the formation of the annular weld part  104  so as to have a thickness for the development of an easy deformability adhering to the light-absorbable member  102 . In order to ensure the adhesiveness by sufficient deformation, the thickness of the light-permeable member  106  is preferably 0.005 mm-0.2 mm, more preferably 0.01 mm-0.1 mm considering the formability. 
     In order that the light-permeable member  106  is adhered to the light-absorbable member  102  by deforming when the interior of the opening portion O is depressurized to not less than −80 kPa but not more than −20 kPa as a gauge pressure before the formation of the annular weld part  104 , it is preferable to select or control a material having a tensile elastic coefficient (Young&#39;s modulus) of 0.01-18 GPa. When the tensile elastic coefficient (Young&#39;s modulus) of the light-permeable member  106  exceeds 18 GPa, it is necessary to make the thickness very thinner for easily deforming in the depressurization of the opening portion O and hence it is difficult to shape the member as designed. For example, when the light-permeable member  106  is formed by injection molding, a resin is not flown into a thinned portion, which is a cause of poor formation. On the other hand, when the tensile elastic coefficient (Young&#39;s modulus) of the light-permeable member  106  is less than 0.01 GPa, the rigidity of the material itself becomes lower, and hence it is difficult to keep the shape of the member itself and it is difficult to place the member of the target shape in a target position. In order to balance the easy deformability, formability and positioning property of the light-permeable member  106  in a higher dimension, it is preferable to select or control the tensile elastic coefficient (Young&#39;s modulus) of the material for the light-permeable member  106  within a range of 6-10 GPa. The tensile elastic coefficient (Young&#39;s modulus) can be measured by placing a test specimen as described in JIS K7162 in a tension testing machine, drawing a stress-strain curve from stress and strain (deformation quantity) according to a definition of JIS K7161 and determining a gradient from the curve. In this case, if the stress-strain curve is not linear and it is difficult to determine the gradient therefrom, a secant modulus (a gradient of a straight line connecting a point of the stress-strain curve to an original point) or the like can be used instead of the Young&#39;s modulus. 
     In the joint structure  100  of the embodiment, dot-like weld parts  114  joining the light-absorbable member  102  and the light-permeable member  106  are arranged in a position adjacent to the annular weld part  104  as shown in  FIG. 1A , whereby the joining strength between the light-absorbable member  102  and the light-permeable member  106  is more increased. 
     The dot-like weld parts  114  can be formed by irradiating a laser beam from the side of the light-permeable member  106  toward the light-absorbable member  102  in the same manner as in the case of the annular weld part  104 . When the light-permeable member is substantially rectangular, the dot-like weld parts  114  are preferable to be formed adjacent to a corner portion. In this case, the dot-like weld parts  114  suppress warping of the light-permeable member  106  due to thermal deformation effectively in the formation of the annular weld part  104 , whereby a more excellent adhesiveness between the light-permeable member  106  and the light-absorbable member  102  by suction can be obtained together with the adhesion effect by the easy deformation of the thin-sheet light-permeable member  106  during the depressurization inside the opening portion O. 
     In the joint structure  100 , a ratio of an area S 2  of a portion at the side of the light-absorbable member  102  (a portion below a boundary face F, which is called as a “second portion” hereinafter) to an area S 1  of a portion at the side of the light-permeable member  106  (a portion above a boundary face F, which is called as a “first portion” hereinafter) in the annular weld part  104  is within a range of 12-35 viewing a section perpendicular to the extending direction of the annular weld part  104  as shown by an enlarged view in  FIG. 1B . When the ratio is less than 12, there is a fear of causing a separation starting a boundary to the annular weld part  104  when a force peeling the light-permeable member  106  from the light-absorbable member  102  is applied (boundary separation) or a separation of at least a part of a portion of the weld part  104  at the side of the light-absorbable member  102  at a state of integrally uniting to the light-permeable member  106 . Also, this separation is difficult to be inspected non-destructively in an industrial production. When the ratio of area S 2  to area S 1  is not less than 12, the separation is hardly caused in the weld part  104 , and the light-permeable member  106  or the light-absorbable member  102  itself is broken when a force peeling the light-permeable member  106  from the light-absorbable member  102  is applied (member breakage), so that it is enough to control strengths of the members  102  and  106  when the welding strength is designed or set and hence the structure can be manufactured stably. On the other hand, when the ratio exceeds 35, it is necessary to increase a power or prolong an irradiation time for arriving a laser beam at a deeper position of the light-absorbable member  102 , and hence there is a fear of exposing thermal influence to the light-permeable member  106  (upheaving, bubbling, melting on the surface, carbonization due to burning, discoloring) or thermal influence to the light-absorbable member  102  (carbonization due to burning, bubbling). In order to realize the avoidance of these thermal influences and the suppression and prevention of the separation in the weld part  104  in a higher dimension, the ratio of S 2  to S 1  is preferable to be a range of 19-26. 
     When the ratio of the area S 2  of the portion at the side of the light-permeable member to the area S 1  of the portion at the side of the light-absorbable member in the weld part  104  is made to the above range, the thermal influence to the light-permeable member  106  associated with the formation of the annular weld part  104  can be made small to suppress thermal strain of the light-permeable member  106  while ensuring the joining strength, and hence the more excellent adhesiveness between the light-permeable member  106  and the light-absorbable member  102  by suction can be obtained together with the adhesion effect by the easy deformation of the thin sheet-like light-permeable member  106  during the depressurization inside the opening portion O. 
     Moreover, the weld part  104  having the above ratio of area S 2  to area S 1  can be formed by the method of manufacturing the joint structure as mentioned later with reference to  FIGS. 8A-8D . In the calculation of the areas S 1  and S 2 , the range (boundary) of the weld part  104  can be judged by cutting the joint structure  100  in a direction perpendicular to the extending direction of the weld part  104  to prepare a test specimen and observing a section thereof with an optical microscope or an electron microscope or confirming a tomographic image thereof with an X-ray CT. 
     When the light-permeable member  106  is produced by injection molding, convex warping toward the lower face side or toward the upper face side of the light-permeable member  106  may be generated resulting from the position of a gate, flowing of the molten resin, non-uniform cooling after the take-out from a mold and the like. The convex warping toward the lower face side is unfavorable because a gap is caused between the peripheral edge portion of the light-permeable member  106  and the upper end face of the peripheral wall  108  of the light-absorbable member  102  when the light-permeable member  106  is superposed on the light-absorbable member  102 . In this embodiment, therefore, a concave portion  116  having a reduced thickness is formed in the lower face of the light-permeable member  106  (face at the side of the light-absorbable member  102 ) over not less than 50% of the inner region of the annular weld part  104 , whereby the warping direction is induced into a direction of forming convex toward the upper face side. When the forming region of the concave portion  116  is less than 50% of the inner region of the annular weld part  104 , there is a fear that a force enough to induce warping of the light-permeable member  106  as a whole cannot be obtained with respect to shrinking of the resin material causing the warping. In order to prevent the warping quantity from excessively increasing, it is preferable to make the depth of the concave portion  116  not more than 50% of the thickness. If the depth of the concave portion  116  exceeds 50% of the thickness, the rigidity of the light-permeable member  106  is decreased to cause torsion as to the shrink of the resin material causing the warping, so that a gap is generated between the light-permeable member  106  and the light-absorbable member  102  in the adhesion by suction to make adhesiveness poor and hence there is a fear of causing position shift or poor welding (excessive temperature rise or unmelting due to non-transfer of heat). 
     Another embodiment of the joint structure  200  according to the invention will be described with reference to  FIGS. 2A, 2B and 2C . The joint structure  200  is different from the joint structure  100  in a point that plural opening portions O are formed in the light-absorbable member  202 . 
     The light-absorbable member  202  is provided with a peripheral wall  208 , a bottom wall  210  closing a lower end part of the peripheral wall  208 , and a top wall  218  communicating to an upper end part of the peripheral wall  208 , and plural slits  220  extending in the same direction are formed in the top wall  218  to define opening portions O. The top wall  218  can control flexural deformation of the light-permeable member  206  when shock or load is applied to the upper face of the light-permeable member  206  from exterior to prevent a light-permeable member  206  or weld parts  204 , and  214  from breaking. Since the top wall  218  acts as a beam, it can reinforce the peripheral wall  208  of the light-absorbable member  202 . 
     A concave portion  216  of the light-permeable member  206  has an effect of controlling the warping direction and quantity of the light-permeable member  206  as mentioned above. In addition to this, a gap is kept between the light-permeable member  206  and the top wall  218 . As a result, when the opening portion O is depressurized, the light-permeable member  206  can be contacted with the top wall  218  to prevent the decrease of an area receiving a negative pressure. If the area receiving the negative pressure is decreased, the light-permeable member  206  cannot be deformed sufficiently under a vacuum pressure, and there is a fear of damaging an adhesiveness between the light-permeable member  206  and the light-absorbable member  202  by suction. From a viewpoint of the prevention thereof, the forming region of the concave portion  216  formed in the light-permeable member  206  is preferable to be not less than 50% of an interior region of the annular weld part  204 . 
     Even in the joint structure  200  according to the embodiment, a ratio of an area S 2  of a portion at the side of the light-absorbable member  202  to an area S 1  of a portion at the side of the light-permeable member  206  in the annular weld part  204  viewing a section perpendicular to an extending direction thereof is within a range of 12-35, preferably 19-26 like the aforementioned joint structure  100 . 
     The other embodiment of the joint structure  300  according to the invention will be described with reference to  FIGS. 3A, 3B, and 3C . The joint structure  300  is provided with a light-permeable member  306  and a light-absorbable member  302 . The light-absorbable member  302  has a peripheral wall  308 , a bottom wall  310  closing a lower end part of the peripheral wall  308 , and a top wall  318  communicating to an upper end part of the peripheral wall  308 . Plural slits  320  extending in the same direction are formed in the top wall  318  to define opening portions O. The joint structure  300  is different from the joint structures  100  and  200  in a point that a thinned piece  324  adhering to an upper face end of a peripheral wall  308  of a light-absorbable member  302  is formed by deforming a light-permeable member  306  at a position outside an annular weld part  304  before the formation of the annular weld part  304  when an interior of an opening portion O is at a depressurized state. Thus, even when a gap is caused between the the upper end face of the peripheral wall  308  of the light-absorbable member  302  and the light-permeable member  306  in the superposition between the light-permeable member  306  and the light-absorbable member  302 , the thinned piece  324  of the light-permeable member  306  can be drawn and adhered to the upper end face of the peripheral wall  308  of the light-absorbable member  302  when the interior of the opening portion O is depressurized through a suction port  312 , so that vacuum breakage due to air leakage can be prevented and also an excellent adhesiveness between the light-permeable member  306  and the light-absorbable member  302  by suction can be obtained. 
     To this end, the thinned piece  324  is preferable to be formed in a thickness developing the easy deformability for adhering to the light-absorbable member  302  by deforming when the interior of the opening portion O is depressurized to not less than −80 kPa but not more than −20 kPa as a gauge pressure before the formation of the annular weld part  304 . In order to ensure the adhesiveness by sufficient deformation, the thickness of the thinned piece is preferably 0.005 mm-0.2 mm, and more preferably 0.01 mm-0.1 mm in view of the formability. 
     In the example of  FIGS. 3A   3 B, and  3 C, the thinned piece  324  is formed in a horizontal direction from the lower end of the peripheral portion of the light-permeable member  306  along the upper end face of the peripheral wall  308  of the light-absorbable member  302 . Alternatively, it may be hanged down from the lower end of the peripheral portion of the light-permeable member  306  along the outer face of the peripheral wall  308  as shown in  FIG. 4A  or an annular groove  326  is formed in the upper end face of the peripheral wall  308  of the light-absorbable member  302  and the thinned piece  324  may be hanged down from the lower face of the light-permeable member  306  so as to insert into the annular groove  326  as shown in  FIG. 4B . 
     Even in the joint structure  300 , the annular weld part  304  is preferable to have a ratio of an area S 2  of a portion at the side of the light-absorbable member  302  to an area S 1  of a portion at the side of the light-permeable member  306  viewing a section perpendicular to the extending direction thereof within a range of 12-35, more preferably 19-26 like the joint structures  100  and  200 . 
     Next, the method of manufacturing the joint structure according to the invention will be described with reference to  FIGS. 5A, 5B, 6A, 6B, 7, 8A-8D, and 9A-9C . Here, the method of manufacturing the joint structure  100  shown in  FIGS. 1A, 1B, and 1C  are described as an example. This manufacturing method can be applied to the manufacture of the joint structures  200  and  300  shown in  FIGS. 2A, 2B, 3A, 3B, 4A and 4B . 
     The first step is a step of providing members. A light-absorbable member  102  and a light-permeable member  106  are provided in this step. The material and basic structure of each of the light-absorbable member  102  and the light-permeable member  106  in the joint structure  100  are previously described with reference to  FIGS. 1A, 1B, and 1C  so that their overlapping explanations are omitted here. 
       FIGS. 5A, 5B and 5C  show the light-absorbable member  102  before the joining to the light-permeable member  106 , wherein  FIG. 5A  is a plane view,  FIG. 5B  is a section view taken along a line D-D of  FIG. 5A , and  FIG. 5C  is enlarged view of region V-C in FIG. B. As shown in this figure, an annular groove  130  is previously formed in an upper end face of a peripheral wall  108  of the light-absorbable member  102  (face contacting to the light-permeable member  106 ) and at a predetermined site of forming an annular weld part  104 . The width of the annular groove  130  is preferable to be made larger than a diameter of a laser beam to be irradiated, for example, 0.1 mm-3 mm. When the width of the annular groove  130  is less than 0.1 mm, a width of the annular weld part  104  to be formed therein cannot be ensured sufficiently, and hence there is a fear that the welding strength is decreased and an airtightness or the like cannot be maintained due to the penetration of air, water and dust by exterior force or change of pressure. When the width of the annular groove  130  exceeds 3 mm, there is a fear that a portion other than the annular weld part  104  is thermally influenced and deformed by heat in the welding or an excessive strain is retained by heat shrinkage in the solidification of the annular weld part  104  to cause deformation. Also, the depth of the annular groove  130  (distance from a boundary face F to a groove bottom) is preferable to be not less than L/20 (mm) but not more than L (mm) when L is the width (mm) of the annular groove  130 . Thus, as mentioned later with reference to  FIGS. 8A-8D , a laser beam can be irradiated to the annular groove  130  to sufficiently expand a molten pool generated in the groove bottom, while heat generated therein can be well transferred to the light-permeable member  106  to thereby form a good weld part  104 . Moreover, the depth of the annular groove  130  is preferable to be not less than L/10 (mm) but not more than L/3 (mm) in view of ensuring the strength and airtightness of the weld part  104 . For example, the annular groove  130  can have a width L of 0.3 mm and a depth of 0.05 (=L/6) mm. If the depth of the annular groove  130  is as small as less than L/20 (mm), the expanded molten pool contacts with the light-permeable member  106  just after the irradiation of the laser beam to the bottom of the annular groove  130 , while heat is dispersed, so that the molten pool cannot be widened in a lateral direction sufficiently and hence there is a fear that the welding becomes poor (a part of the annular groove  130  is left). If the depth of the annular groove  130  is too large exceeding L (mm), the molten pool generated in the bottom of the annular groove  130  cannot arrive at the light-permeable member  106  though it is expanded, and hence there is a fear that carbonization due to burning and/or discoloration is caused to bring about the poor welding. In the illustrated example, the sectional shape of the annular groove  130  is rectangular, but may be semi-circular or semi-ellipsoidal. Furthermore, at least one communication groove  132  communicating the annular groove  130  to an interior of an opening portion O ( 4  grooves per each side in the illustrated example) are previously formed in the upper end face of the peripheral wall  108 . 
     The second step is a step of arranging the light-permeable member  106  on the light-absorbable member  102  so as to cover the opening portion O as shown in  FIG. 6A . 
     The third step is a step of adhering the superposed light-absorbable member  102  and light-permeable member  106  to each other by suction, wherein the adhesion by suction is performed by depressurizing the interior of the opening portion O. As a state after the superposition of the light-permeable member  106  and the light-absorbable member  102  is shown in a left of  FIG. 6B , a gap may be formed between the light-permeable member  106  and the light-absorbable member  102  due to warping in the formation of the light-permeable member  106  or thermal deformation in the welding through a laser beam as mentioned later. However, since the light-permeable member  106  is formed into a thinned sheet, when the interior of the opening portion O is depressurized, the peripheral edge portion of the light-permeable member  106  can be deformed so as to direct to the upper end face of the peripheral wall  108  and adhered thereto as shown in a right of  FIG. 6B . 
     The depressurization in the interior of the opening portion O can be performed with an external pressure-controlling device D as shown in  FIG. 7  and through a suction port  112  previously formed in the light-absorbable member  102 . 
     The pressure-controlling device D is comprised mainly of a depressurization device D 1 , a pressurization device D 2 , a controller D 3  and a double pipe P connected to the suction port  112 . 
     The depressurization device D 1  comprises a vacuum pump for sucking and discharging air inside the opening portion O and an electric leak valve (not shown). In a suction line L 1  of the depressurization device D 1  is disposed a pressure sensor PG 1 , whereby a pressure inside the opening portion O can be detected during the depressurization. 
     The pressurization device D 2  comprises a pressurized tank and a feed valve for feeding a purge gas of air or an inert gas such as nitrogen, argon or the like (not shown). In a feed line L 2  of the pressurization device D 2  is disposed a pressure sensor PG 2 , whereby a pressure inside the opening portion O can be detected during the pressurization. 
     The controller D 3  is constructed by PLC (programmable logic controller), a personal computer or the like, which adjusts an opening degree of the feed valve and the leak valve. Also, the controller D 3  is connected to the pressure sensors PG 1  and PG 2 , and the feed valve and leak valve can be controlled based on signals detected by the pressure sensors PG 1  and PG 2 . 
     The double pipe P is comprised of a suction pipe p 1  arranged outside and a feed pipe p 2  arranged inside. The suction pipe p 1  is communicated with the interior of the opening portion O and the depressurization device D 1  to suck air from the interior of the opening portion O. The feed pipe p 2  is communicated with the interior of the opening portion O and the pressurization device D 2  to feed a purge gas to the interior of the opening portion O. Moreover, an outer pipe of the double pipe P may be the feed pipe and an inner pipe thereof may be the suction pipe (not shown). As shown in the figure, however, when the suction pipe p 1  is arranged outside, gas generated in the welding can be removed efficiently. 
     The fourth step is a joining step wherein a laser beam LB is irradiated from the side of the light-permeable member  106  toward the upper end face of the peripheral wall  108  of the light-absorbable member  102  at a state of adhering the light-absorbable member  102  and the light-permeable member  106  by suction to form an annular weld part  104  and dot-like weld parts  114  in the boundary face F between the light-absorbable member  102  and the light-permeable member  106  or in the vicinity thereof (see  FIGS. 1A, 1B, and 1C ) to thereby join the light-absorbable member  102  and the light-permeable member  106  to each other. 
     Even in the joining step, the interior of the opening portion O is maintained at a depressurized state, but it is preferable to feed a purge gas to the interior of the opening portion O through the feed pipe p 2  at least during the formation of the annular weld part  104 . In this case, air flow can be generated inside the opening portion O, whereby soot generated in the welding or vaporization ingredient of a flame retardant can be discharged and removed efficiently through the suction pipe p 1  toward exterior. 
     In the formation of the weld parts  104  and  114 , dot-like weld parts  114  are first formed and thereafter the annular weld part  104  is formed. It is because the light-permeable member  106  is temporarily joined to the light-absorbable member  102  through the dolt-like weld parts  114  being relatively small in the thermal load to the light-permeable member  106  and then thermal deformation of the light-permeable member  106  is suppressed in the formation of the annular weld part  104  being relatively large in the thermal load to prevent vacuum breakage due to air leakage resulted from this thermal deformation. Since the pressure receiving area to vacuum is decreased with the advance of the formation of the annular weld part  104 , it is preferable to arrange three or more dot-like weld parts  114  so as to form a plane for supplementing the decreased quantity of the pressure. In this example, four dot-like weld parts are formed adjacent to each corner portion of the light-permeable member  106 . 
     The dot-like weld parts  114  are formed by irradiating a laser beam LB to the upper end face of the peripheral wall  108  of the light-absorbable member  102  at a state of stopping an optical head H ( FIG. 7 ) above the light-permeable member  106 . The dot-like weld parts  114  are preferable to have a diameter of about 0.3 mm-0.7 mm, more preferably about 0.5 mm. The annular weld part  104  is formed by irradiating a laser beam LB to the upper end face of the peripheral wall  108  while moving the optical head H along the peripheral wall  108  of the light-absorbable member  102  above the light-permeable member  106 . The width of the annular weld part  104  is preferably about 0.3 mm-0.7 mm, more preferably about 0.5 mm. As an oscillator of the laser beam LB can be used, for example, a fiber laser (wavelength: 1070 nm), a YAG laser (wavelength: 1064 nm), a semiconductor laser (wavelength: 808 nm, 840 nm or 940 nm), a CO 2  laser (wavelength: 10600 nm) and so on. 
     A process of forming the annular weld part  104  in which a ratio of an area of the second portion S 2  to an area of the first portion S 1  in  FIGS. 1A, 1B and 1C  are set to 12-35 by irradiating the laser beam LB to the annular groove  130  previously formed in the upper end face of the peripheral wall  108  of the light-absorbable member  102  will be described with reference to  FIGS. 8A-8D . 
     When a laser beam is irradiated from the side of the light-permeable member  106  toward the bottom of the annular groove  130  at a state of adhering the light-absorbable member  102  and the light-permeable member  106  to each other by suction as shown in  FIG. 8A , the bottom of the annular groove  130  is melted by heat generation to start bubbling in a molten pool as shown in  FIG. 8B . By continuously irradiating the laser beam is grown bubbles to grow the molten pool as shown in  FIG. 8C . In this case, the molten pool of the light-absorbable member  102  is not immediately contacted with the light-permeable member  106  due to the presence of the annular groove  130 , so that the molten pool can be grown till sufficient width and depth are obtained. In  FIG. 8D  is shown a state that the irradiation of the laser beam is stopped to complete the formation of the annular weld part  104  after the arrival of the molten pool at the light-permeable member  106 . 
     In this example, communication grooves  132  communicating the annular groove  130  to the opening portion O are disposed in the upper end face of the peripheral wall  108  of the light-absorbable member  102 , so that soot generated in the process of forming the annular weld part  104  and vaporization ingredient v of a flame retardant are sucked and discharged into the opening portion O through the annular groove  130  and the communication grooves  132  and finally discharged to exterior through the suction pipe p 1 . 
     The fifth step is a step of inspecting an airtightness by conducting an airtight test of the annular weld part  104  in which a pressure change per unit time is measured by keeping the depressurized state inside the opening portion O, pressurizing the interior of the opening portion O or alternately performing the depressurization and the pressurization. The pressure inside the opening portion O is measured by the pressure sensors PG 1  and PG 2  shown in  FIG. 7 , and the pressure change per unit time is calculated in the controller D 3  and can be output to or displayed in exterior if necessary. Alternatively, the airtight test of the annular weld part  104  can be performed by arranging a flow rate sensor (not shown) in the suction line L 1  or the feed line L 2  to measure a change of a flow rate per unit time. 
     The sixth step (not shown) is a step of closing the suction port  112  by irradiating a laser beam LB from the side of the light-permeable member  106  to the interior of the suction port  112  or surrounding thereof while keeping the depressurized state inside the opening portion O after the formation of the annular weld part  104 . Thus, the interior of the opening portion O can be closed while keeping vacuum inside the opening portion O. Of course, the suction port  112  may be at an opened state. 
     According to the method of manufacturing the joint structure according to the embodiment, the opening portion O is formed in the light-absorbable member  102 , and the light-absorbable member  102  is adhered to the light-permeable member  106  by suction by depressurizing the interior of the opening portion O, so that the use of the glass plate for adhering both the members  102  and  106  to each other under a pressure is useless and the aforementioned various problems resulted from the use of the glass plate can be solved. 
     Also, the light-permeable member  106  can be deformed easily by depressurizing the interior of the opening portion O, so that even if the gap is generated between the light-permeable member  106  and the light-absorbable member  102  in the superposition, the gap can be closed with the light-permeable member  106  by depressurizing the interior of the opening portion O and the excellent adhesiveness by suction can be obtained. 
     Furthermore, since the dot-like weld parts  114  are formed for temporary joining prior to the formation of the annular weld part  104 , thermal deformation of the light-permeable member  106  can be suppressed on the way of forming the annular weld part  104  and also the decrease of the adhesiveness by suction due to the thermal deformation can be prevented. 
     Since the annular groove  130  is formed on the upper end face of the peripheral wall  108  of the light-absorbable member  102  and the annular weld part  104  is formed by irradiating the laser beam LB to the annular groove  130 , a high joining strength can be obtained by the formation of weld part  104  having sufficient width and depth, and also thermal influence upon the light-permeable member  106  can be made small to suppress thermal deformation of the light-permeable member  106  in the welding process and the decrease of adhesiveness by suction due to the thermal deformation can be prevented. 
     Since the communication grooves  132  communicating the annular groove  130  to the opening portion O are disposed in the upper end face of the peripheral wall  108  of the light-absorbable member  102 , soot generated during the formation of the annular weld part  104  and vaporization ingredient v of a flame retardant can be sucked into the opening portion O through the annular groove  130  and the communication grooves  132  and finally discharged to exterior through the suction pipe p 1 . 
     Since the depressurization in the opening portion O is performed while feeding the purge gas to the interior of the opening portion O, air flow can be generated in the opening portion O to discharge and remove the soot and the vaporization ingredient v efficiently. 
     When the airtightness test of the annular weld part  104  is performed by keeping the depressurized state of the opening portion O after the formation of the annular weld part  104 , pressurizing the interior of the opening portion O, or alternately performing the depressurization and the pressurization to measure a change of pressure or flow rate per unit time, the manufacturing installation can be simplified and the manufacturing time can be shortened largely. 
     When the pressure in the opening portion O is always detected by the pressure sensor PG 1  and the adhesion between the light-absorbable member  102  and the light-permeable member  106 , the start of forming the annular weld part  104  and the end of forming the annular weld part  104  are judged based on the pressure change detected, it is possible to shorten working time in the usual production and early handling in the abnormal state. 
     The invention is described with reference to the illustrated examples. However, it is not limited to these embodiments and various modifications and additions may be performed within a scope described in claims. In the method of manufacturing the joint structure of the above embodiments, for example, the bottom of the annular groove  130  is illustrated to be flat, but an elevated portion  134  may be provided on the groove bottom as shown in  FIG. 9A . Also, the number of the annular groove  130  is not limited to one. For example, two adjoining grooves may be disposed and integrally united in the welding to form a wider weld part  104  as shown in  FIG. 9B , or an annular groove  136  may be disposed at the side of the light-permeable member  106  as shown in  FIG. 9C . 
     EXAMPLE 
     Example 1 
     An example of applying the invention to a connector will be described.  FIGS. 10A, 10B, and 10C  show a connector using the joint structure  200  of  FIGS. 2A, 2B and 2C , in which  FIG. 2A  is a perspective view,  FIG. 2B  is a section view along a fitting direction X, and  FIG. 2C  is enlarged view of region II-C in  FIG. 2B . In this figure, the corresponding member or portion is represented by adding ‘ to the symbol, and the overlapping explanation is omitted. 
     This connector  200 ’ is a receptacle connector fixed to a substrate in an electronic device such as mobile device, information device or the like and connected to another connector (not shown) by inserting in a fitting direction X. This is comprised mainly of a housing  202 ′ as a light-absorbable member  202 , plural contacts  203  extended in the fitting direction X and arranged in a direction perpendicular to the fitting direction X, and a thin sheet-formed cover  206 ′ as a light-permeable member  206  sealed so as to cover an opening portion O′ of the housing  202 ′. 
     The housing  202 ′ is made from a light-absorbable and insulating thermoplastic resin and provided with a peripheral wall  208 ′ having a fitting port  212 ′ for inserting the other connector, a bottom wall  210 ′ and a top wall  218 ′. 
     In the top wall  218 ′ of the housing  202 ′ are formed a plurality of slits  220 ′ along the fitting direction X, and the opening portion O′ is defined by these slits  220 ′. In each of the slits  220 ′ is arranged the contact  203 . The forward end of the each contact  203  is protruded downward from the inner face of the top wall  218 ′ for connecting to the other connector, while the posterior end thereof is exposed from the housing  202 ′ for connecting to the substrate of the electronic device or the other printed circuit board. 
     The cover  206 ′ is superposed to the housing  202 ′ so as to cover the opening portion O′ of the housing  202 ′ and joined to the upper end face of the peripheral wall  208 ′ over the whole periphery through an annular weld part  204 ′ formed so as to enclose the slits  220 ′ in a bundle. Thus, a root of penetrating air, soot or water from a fitting port  212 ′ through the slits  220 ′ into the interior of the electronic device is blocked by the cover  206 ′ and the annular weld part  204 ′. Also, four dot-like weld parts  214 ′ are formed outside the annular weld part  204 ′ and adjacent to corner parts of the cover  206 ′. 
     In the connector  200 ′, the annular weld part  204 ′ has a ratio of an area S 2 ′ of a portion at the side of the housing  202 ′ to an area S 1 ′ of a portion at the side of the cover  206 ′ viewing from a section perpendicular to the extending direction within a range of 12-35, preferably 19-26. The symbol F′ in  FIG. 10B  represents a boundary face between the housing  202 ′ and the cover  206 ′. 
     The connector  200 ′ can be manufactured by the method described with reference to  FIGS. 5A, 5B, 6A, 6B, 7, and 8A-8D  using the fitting port  212 ′ as a suction port  212 . 
     Example 2 
     An example of applying the invention to a sensor will be described.  FIGS. 11A, 11B, and 11C  show a sensor using the joint structure  300  shown in  FIG. 4A , in which  FIG. 4A  is a perspective view and  FIG. 4B  is a section view. 
     The sensor  300 ′ may be all types of acceleration sensor, vibration sensor, angular velocity sensor, distance sensor, position sensor and so on. The sensor  300 ′ is comprised mainly of a chassis  302 ′ as a light-absorbable member  302 , and a cover  306 ′ as a light-permeable member  306  sealed so as to cover an opening portion O′ of the chassis  302 ′. A detector body (sensor chip, not shown) is housed in the interior of the chassis  302 ′. 
     The chassis  302 ′ is made from a light-absorbable thermoplastic resin and provided with a peripheral wall  308 ′ defining the opening portion O′ and protruding a suction cylinder  312 ′ forward and a bottom wall  310 ′. 
     The cover  306 ′ is placed on the peripheral wall  308 ′ of the chassis  302 ′ so as to cover the opening portion O′ of the chassis  302 ′ and joined thereto over the whole periphery through dot-like weld parts  314 ′ and annular weld part  304 ′. In the peripheral edge part of the cover  306 ′ is hanged down a thinned piece  324 ′ along the outer face of the peripheral wall  308 ′. The thinned piece  324 ′ is formed so as to draw and adhere to the peripheral wall  308 ′ when the interior of the opening portion O′ is depressurized through the suction cylinder  312 ′. 
     In the sensor  300 ′, the annular weld part  304 ′ has a ratio of an area S 2 ′ of a portion at the side of the chassis  302 ′ to an area S 1 ′ of a portion at the side of the cover  306 ′ viewing from a section perpendicular to the extending direction within a range of 12-35, preferably 19-26. The symbol F′ in  FIG. 11B  represents a boundary face between the chassis  302 ′ and the cover  306 ′. 
     The sensor  300 ′ can be manufactured by the method described with reference to  FIGS. 5A, 5B, 6A, 6B, 7, 8A-8D  using the suction cylinder  312 ′ as a suction port  312 . 
     Moreover, the base end part of the suction cylinder  312 ′ is opened, but the opening of the base end part of the suction cylinder  312 ′ may be closed by irradiating a laser beam to the vicinity of the opened base end part of the suction cylinder  312 ′ from the cover  306 ′ at a state of keeping the depressurization of the opening portion O′ after the formation of the annular weld part  304 ′ according to the sixth step of the manufacture method described above. Thus, the interior of the sensor  300 ′ can be closed at a state of keeping vacuum. 
     INDUSTRIAL APPLICABILITY 
     According to the invention, the joint structure suitable for adhering mutual members to be joined to each other uniformly and surely is provided without using a glass plate, and also the method of manufacturing a joint structure, which is capable of adhering mutual members to be joined to each other uniformly and surely, can be provided without using a glass plate. 
     DESCRIPTION OF REFERENCE SYMBOLS 
     
         
         
           
               100 ,  200 ,  300  joint structure 
               102 ,  202 ,  302  light-absorbable member 
               104 ,  204 ,  304  annular weld part 
               106 ,  206 ,  306  light-permeable member 
               108 ,  208 ,  308  peripheral wall 
               112 ,  212 ,  312  suction port 
               114 ,  214 ,  314  dot-like weld part 
               130  annular groove 
               132  communication groove 
               324  thinned piece 
             D pressure control device 
             D 1  depressurization device 
             D 2  pressurization device 
             D 3  controller 
             F boundary face 
             H optical head 
             L 1  suction line 
             L 2  feed line 
             O opening portion 
             PGL PG 2  pressure sensor 
             S 1  area of first portion of annular weld part (at the side of light-permeable member) 
             S 2  area of second portion of annular weld part (at the side of light-absorbable member)