Laser-welded article

Abstract

It is an object of the present invention to provide a laser-welded article that workpieces prepared simply can be easily unified by laser in one laser welding process without using complicated processes. Moreover, the laser-welded article has sufficient welding strength of the molded workpieces, and does not damage the resin property. The laser-welded article comprises: an integral construction of a single weakly laser-absorptive molded workpiece or plural weakly laser-absorptive molded workpieces, which is welded by exothermic through irradiating laser under butting at least a part of edge portions thereof, wherein the workpiece or the workpieces include a thermoplastic resin and a weakly laser absorbent to have an absorbance: a ranging from 0.07 to 3.0, and have abilities of absorbing at least partial beam of the laser and transmitting other partial beam of the laser.

1. A laser-welded article comprising:
 an integral construction of a single weakly laser-absorptive molded workpiece or a plurality of weakly laser-absorptive molded workpieces, which is welded by heat generated from irradiation with a laser through laser welding by melting of butted portions of the single weakly laser-absorptive molded workpiece, or laser welding by melting of butted portions of the plurality of weakly laser-absorptive molded workpieces, where at least a part of the edge portions of the workpiece or the workpieces are butted, with no overlapping of the butted portions, the laser generating rays having a wavelength ranging from 800 nm to 1600 nm, 
 wherein the workpiece or the workpieces have an absorbance “a” throughout the workpiece or the workpieces ranging, from 0.1 to 1.8 converted into an absorbance of the molded workpiece with 1 mm thickness, and have the ability of absorbing at least partial beam of the laser and transmitting another partial beam of the laser, the workpiece or the workpieces including: 
 a thermoplastic resin at least selected from the group consisting of polyamide resin, polycarbonate resin, polyphenylene sulfide resin, polybutylene terephthalate resin, and polypropylene resin, and 
 a weakly laser absorbent of nigrosine dye, where the content of the weakly laser absorbent ranges from 0.01 to 0.5 weight % against the thermoplastic resin. 
 
     
     
       2. The laser-welded article according to  claim 1 , wherein the integral construction of the single weakly laser-absorptive molded workpiece is welded while butting edge portions of the single weakly laser-absorptive molded workpiece. 
     
     
       3. The laser-welded article according to  claim 1 , wherein the integral construction of the plurality of weakly laser-absorptive molded workpieces is welded while butting edge portions of the plurality of weakly laser-absorptive molded workpieces. 
     
     
       4. The laser-welded article according to  claim 1 , wherein a ratio a 1 /a 2  defined by an absorbance “a 1 ” of a first workpiece of the plurality of weakly laser-absorptive molded workpieces and an absorbance “a 2 ” of a second workpiece ranges from 0.8 to 1.3. 
     
     
       5. The laser-welded article according to  claim 4 , wherein the ratio a 1 /a 2  is 1. 
     
     
       6. The laser-welded article according to  claim 1 , wherein at least one of C 1 L 1  and C 2 L 2  ranges from 0.01×10 −3  to 4.0×10 −3 , wherein
 C 1 L 1  is a product of a concentration C 1  (weight %) of the weakly laser absorbent of a first workpiece of the integral construction of the plurality of weakly laser-absorptive molded workpieces, and L 1  (cm) is a thickness of the first workpiece, and 
 C 2 L 2  is a product of a concentration C 2  (weight %) of the weakly laser absorbent of a second workpiece, and L 2  (cm) is a thickness of the second workpiece. 
 
     
     
       7. The laser-welded article according to  claim 1 , wherein the single weakly laser-absorptive molded workpiece or the plurality of weakly laser-absorptive molded workpieces have a thickness ranging from 200 to 5000 microns. 
     
     
       8. The laser-welded article according to  claim 1 , wherein the weakly laser absorbent has an absorption coefficient ε d  ranging from 1000 to 8000 (ml/g·cm). 
     
     
       9. The laser-welded article according to  claim 1 , wherein the thermoplastic resin is polyamide resin and the absorbance “a” ranges from 0.1 to 1.8. 
     
     
       10. The laser-welded article according to  claim 1 , wherein the thermoplastic resin is polycarbonate resin and the absorbance “a” ranges from 0.2 to 1.8. 
     
     
       11. The laser-welded article according to  claim 1 , wherein the thermoplastic resin is polypropylene resin and the absorbance “a” ranges from 0.1 to 0.8. 
     
     
       12. The laser-welded article according to claim 1, wherein the tensile stress strength of the prepared laser-welded article is 50N or more in accordance with Japanese Industrial Standard K-7113-1995. 
     
     
       13. A laser-welded article comprising:
 an integral construction of a single weakly laser-absorptive molded workpiece or a plurality of weakly laser-absorptive molded workpieces, which is welded by heat generated from irradiation with a laser through laser welding by melting of butted portions of the single weakly laser-absorptive molded workpiece, or laser welding by melting of butted portions of the plurality of weakly laser-absorptive molded workpieces, where at least a part of the edge portions of the workpiece or the workpieces are butted, with no overlapping of the butted portions, the laser generating rays having a wavelength ranging from 800 nm to 1600 nm,   wherein the workpiece or the workpieces have an absorbance “a” throughout the workpiece or the workpieces ranging, from 0.1 to 1.8 converted into an absorbance of the molded workpiece with 1 mm thickness, and have the ability of absorbing at least partial beam of the laser and transmitting another partial beam of the laser, the workpiece or the workpieces including:   a thermoplastic resin at least selected from the group consisting of polyamide resin, polycarbonate resin, polyphenylene sulfide resin, polybutylene terephthalate resin, and polypropylene resin, and   a weakly laser absorbent of nigrosine dye selected from the group consisting of C.I. Solvent Black 5 and C.I. Solvent Black 7,   where the content of the weakly laser absorbent ranges from 0.01 to 0.5 weight % against the thermoplastic resin.   
     
     
       14. The laser-welded article according to claim 13, wherein the integral construction of the single weakly laser-absorptive molded workpiece is welded while butting edge portions of the single weakly laser-absorptive molded workpiece. 
     
     
       15. The laser-welded article according to claim 13, wherein the integral construction of the plurality of weakly laser-absorptive molded workpieces is welded while butting edge portions of the plurality of weakly laser-absorptive molded workpieces. 
     
     
       16. The laser-welded article according to claim 13, wherein a ratio a 1 /a 2  defined by an absorbance “a 1 ” of a first workpiece of the plurality of weakly laser-absorptive molded workpieces and an absorbance “a 2 ” of a second workpiece ranges from 0.8 to 1.3. 
     
     
       17. The laser-welded article according to claim 13, wherein at least one of C 1 L 1  and C 2 L 2  ranges from 0.01×10 −3  to 4.0×10 −3 , wherein
 C 1 L 1  is a product of a concentration C 1  (weight %) of the weakly laser absorbent of a first workpiece of the integral construction of the plurality of weakly laser-absorptive molded workpieces, and L 1  (cm) is a thickness of the first workpiece, and 
 C 2 L 2  is a product of a concentration C 2  (weight %) of the weakly laser absorbent of a second workpiece, and L 2  (cm) is a thickness of the second workpiece. 
 
     
     
       18. The laser-welded article according to claim 13, wherein the single weakly laser-absorptive molded workpiece or the plurality of weakly laser-absorptive molded workpieces have a thickness ranging from 200 to 5000 microns. 
     
     
       19. The laser-welded article according to claim 13, wherein the weakly laser absorbent has an absorption coefficient ε d  ranging from 1000 to 8000 (ml/gcm). 
     
     
       20. The laser-welded article according to claim 13, wherein the thermoplastic resin is polyamide resin and the absorbance “a” ranges from 0.1 to 1.8. 
     
     
       21. The laser-welded article according to claim 13, wherein the thermoplastic resin is polycarbonate resin and the absorbance “a” ranges from 0.2 to 1.8. 
     
     
       22. The laser-welded article according to claim 13, wherein the thermoplastic resin is polypropylene resin and the absorbance “a” ranges from 0.1 to 0.8. 
     
     
       23. The laser-welded article according to claim 16, wherein the ratio a 1 /a 2  is 1.