Abstract:
A method for manufacturing a resin molding that uses a laser beam can provide a high level of adhesion, an excellent appearance, and can include very strong welded portions. The method can include preparing a light-transmitting resin member having a protruding portion formed on a rear surface of the light-transmitting resin member and having an end surface, the protruding portion having both side surfaces having asymmetric inclination angles with respect to the normal of the end surface of the protruding portion. The method can also include arranging and pressing together the end surface of the protruding portion that is a welded region of the light-transmitting resin member, and a welded region of a corresponding light-absorbing resin member so that they are opposed to each other. A laser beam can be emitted from a laser light source to be incident on a surface of the light-transmitting resin member while the laser beam is refracted. The method can also include repeatedly irradiating the laser beam onto the welded regions to heat and fuse the entire welded regions to weld the light-transmitting resin member and the light-absorbing resin member while opposed to each other and pressed together, wherein the inclination angle of the side surface of the protruding member near the laser light source is equal to or more than a travel angle of the refracted laser beam.

Description:
This application claims the priority benefit under 35 U.S.C. §119 of Japanese Patent Application No. 2010-023103 filed on Feb. 4, 2010, which is hereby incorporated in its entirety by reference. 
     TECHNICAL FIELD 
     The presently disclosed subject matter relates to a method for manufacturing a resin molding. 
     BACKGROUND ART 
     Conventional vehicle lights can have a resin molding which includes a housing formed from a light-absorbing resin such as acrylonitrile styrene acrylate (ASA) and a lens that is formed from a light-transmitting resin such as a polymethylmethacrylate (PMMA) or a polycarbonate and is welded to the housing. 
     Japanese Patent Application Laid-Open No. 2000-294013 (corresponding to U.S. Pat. No. 6,592,239) proposes a laser welding method. In this method, a lens is pressed against a lamp body (housing) together and then the entire circumference of the lens is scanned with a laser beam using a robot with a laser beam to be incident on the lens, thereby heating and fusing the surface of the lamp body as well as fusing the ends of the seal support legs of the lens by means of the fusing heat of the lamp body. 
     Japanese Patent Application Laid-Open No. 2001-243811 (corresponding to U.S. Pat. No. 6,464,374) proposes a vehicle light wherein a front lens and a lamp body are directly bonded by means of laser welding. In this vehicle light, seal support legs which extend in the bonding direction are formed on the outer peripheral edge of the surface of the front lens while an abutment surface that makes contact with the end surface of the seal support legs is formed on the lamp body. A laser light receiving surface that guides a laser beam being incident from a direction diagonal to the bonding direction is formed protruding on the outer surface of the seal support legs. The laser light receiving surface is also formed as a flat surface slanting towards the bonding direction at the ends of the seal support legs such that the ends of the seal support legs are curved towards the outside extending in the bonding direction. 
     However, a method of welding a resin molding using a laser beam has not been fully developed as of yet. 
     A method for manufacturing a resin molding that uses a laser beam, has a high level of adhesion, an excellent appearance, and includes very strong welded portions is still highly demanded. 
     SUMMARY 
     The presently disclosed subject matter was devised in view of these and other problems and features and in association with the conventional art. According to an aspect of the presently disclosed subject matter, a method for manufacturing a resin molding is provided, the method including: 
     a) preparing a light-transmitting resin member having a protruding portion formed on a rear surface of the light-transmitting resin member and having an end surface, the protruding portion having both side surfaces having asymmetric inclination angles with respect to the normal of the end surface of the protruding portion; 
     b) arranging and pressing the end surface of the protruding portion that is a welded region of the light-transmitting resin member, and a welded region of a corresponding light-absorbing resin member so that they are opposed to each other, and then causing a laser beam emitted from a laser light source to be incident on a surface of the light-transmitting resin member while the laser beam is refracted; and 
     c) repeatedly irradiating the laser beam onto the welded regions to heat and fuse the entire welded regions to weld the light-transmitting resin member and the light-absorbing resin member while opposed to each other and pressed together, wherein 
     the inclination angle of the side surface of the protruding member near the laser light source is equal to or more than a travel angle of the refracted laser beam. 
     The presently disclosed subject matter can provide a manufacturing method of a resin molding that can effectively eliminate gaps by means of uniformly irradiating a laser beam onto the welded regions. 
     In the method for manufacturing a resin molding, the inclination angle of the side surface of the protruding member near the laser light source may be over 0° and equal to or less than 40°. 
     In the method for manufacturing a resin molding, the side surface of the protruding member near the laser light source can be a curved surface. 
     In the method for manufacturing a resin molding, in the above step c) the laser beam can be scanned using a Galvano scanner. 
     In the method for manufacturing a resin molding, in the above step c) when an angle of incidence of the laser beam on the welded region is varied depending on a position where the laser beam is incident, a scanning speed of the laser beam can be varied to equalize heating temperatures within the welded region. 
     In the method for manufacturing a resin molding, in the above step c) when an angle of incidence of the laser beam on the welded region is varied depending on a position where the laser beam is incident due to a single laser beam utilized, a plurality of laser beams can be utilized to equalize heating temperatures within the welded region. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       These and other characteristics, features, and advantages of the presently disclosed subject matter will become clear from the following description with reference to the accompanying drawings, wherein: 
         FIGS. 1A to 1D  are a diagram showing a welding process by means of repeated irradiation of a laser beam, a perspective view of an irradiated workpiece, a temperature chart with respect to the laser irradiation time, and a cross sectional view illustrating how the welded ribs are formed in a light-transmitting resin member, respectively; 
         FIGS. 2A to 2C  are cross sectional views showing a case where the side surface of the welded rib is inclined with respect to the welded surface during the welding process which is accomplished by means of repeated irradiation of a laser beam; 
         FIGS. 3A to 3C  are plan views and a cross-sectional view showing a welding process accomplished by means of repeated irradiation of a laser beam onto a two-dimensional welded region; and 
         FIGS. 4A and 4B  are a diagram and a cross sectional view showing a welding process accomplished by means of repeated irradiation of a laser beam onto a three-dimensional welded region, and  FIG. 4C  is a diagram showing a modified example of the welding process accomplished by means of repeated irradiation of a laser beam onto a three-dimensional welded region. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     A description will now be made below to a method for manufacturing a resin molding of the presently disclosed subject matter with reference to the accompanying drawings in accordance with exemplary embodiments. 
     When a light-transmitting (clear) resin member and a light-absorbing (light-absorbing, opaque) resin member are arranged to be opposite to each other and pressed together making contact with each other and a laser beam is irradiated from the light-transmitting resin member side, the laser beam can pass through the light-transmitting resin member to reach the light-absorbing resin member. When the laser beam is absorbed by the light-absorbing resin member, the light-absorbing resin member can be heated, softened and then fused. Because the light-transmitting resin member makes contact with the light-absorbing resin member under pressure, the heat of the light-absorbing resin member can be conducted to the light-transmitting resin member especially at the contact region. Therefore, the light-transmitting resin member can be softened thereby increasing the contact region and eventually fusing the light-transmitting resin member as well. Both members can then be fused and welded (adhered) together. 
     In general, for a resin molding such as a vehicle light, a laser beam is scanned while continuously welding resin members under pressure along the peripheries where the members are pressed to make contact with each other. The inventors investigated a welding method that repeatedly irradiates a laser beam during a high-speed scan along a welded region set to the periphery of a workpiece and almost simultaneously heats and fuses the entire welded region so as to weld the resin members together. A Galvano scanner can be one exemplary means that allows a laser beam to be scanned at a high speed. 
       FIG. 1A  is a diagram that schematically shows the configuration of a laser beam welding apparatus using a Galvano scanner. Assume an xyz orthogonal coordinate system. The xy plane, for example, forming a horizontal plane, that includes a reference plane for supporting the workpiece. An optical system  13  can be arranged to adjust the focal point with respect to a laser beam  12  emitted from the end of an optical fiber  11  connected to a laser oscillator. The focal point adjustment optical system  13  can include a movable lens that can adjust the focal point on the optical path. A first Galvano mirror  14  can be arranged with respect to the laser beam emitted from the focal point adjustment optical system  13  so that the laser beam can scan the work surface in the x-direction, for example. A second Galvano mirror  15  can be arranged with respect to the laser beam reflected by the first Galvano minor  14  so that the laser beam can scan the work surface in the y-direction, for example. 
     A control unit  16  can control the Galvano mirrors  14  and  15  and the focal point adjustment optical system  13 . An emitted laser beam  12   s  can perform an xy scan within a two-dimensional plane by means of the Galvano minors  14  and  15 . In addition, the focal length can be controlled, so that the focal point can be moved in the z direction by means of adjusting the focal point adjustment optical system  13 . In other words, the focusing position of the laser beam can be scanned three-dimensionally. If the scanning is only in two dimensions, a scanning head with a fe lens can be used instead of the focal point adjustment optical system  13 . Galvano mirrors are lightweight allowing high-speed scanning, and accordingly, are suitable for this purpose. 
       FIG. 1B  is a schematic diagram showing a repeated laser welding process on a workpiece that has a two-dimensional welded region arranged within the xy plane. A lens  22  formed from a light-transmitting resin can be arranged opposite to a container-shaped housing  21  formed from a light-absorbing resin so as to close the opening of the housing  21 . The lower surface of the lens  22  and the upper surface of the housing  21  are brought into contact under pressure with each other by a pressure P along the z-direction. The laser beam  12   s  can pass through the lens  22  from above in the z-direction, thereby irradiating the upper surface of the housing  21 . The laser beam  12   s  can have a beam diameter corresponding to the width of the welded region  27 , for example. The irradiation position is repeatedly scanned along the welded region  27  by means of driving the Galvano minors. In the configuration of  FIG. 1A , the first Galvano mirror  14  may scan the x-direction and the second Galvano minor  15  may scan the y-direction. 
       FIG. 1C  is a graph schematically showing time variations of temperature in the laser irradiation position. The temperature rises for a single laser beam irradiation and starts to fall after the completion of the irradiation. Before cooling to the temperature before the irradiation, the next laser beam is irradiated and the temperature rises again. The average temperature gradually rises by means of the repeated laser beam irradiation. If the position within the welded region changes, similar temperature changes will occur in the form of slightly shifted timing. The entire welded region can be heated almost uniformly and almost at the same time for obvious reasons. 
     Normally, there are fine irregularities, which occur during the molding, existing on the surfaces of the housing  21  and the lens  22 . Because of this, localized gaps may exist between the resin members. If the entire welded region is in a fused state, both of the resins will melt and blend together and the gaps will effectively disappear due to the pressure thereby making it possible to obtain a strong welding. 
     Since the laser light source is fixed during the welding process using the Galvano scanner, the laser beam can be incident by an angle (angle of incidence) with respect to the normal of the surface of the lens. 
       FIG. 1D  is a cross-sectional view showing the workpiece having a protruding portion (for example, a rib)  23  for welding, formed on the rear surface of the lens  22 . Namely, a rib  23  with a height of h can be formed on the rear surface of the lens  22  and can have an inner side surface  23   a  and an outer side surface  23   b . Then, the laser beam  12   s  with a certain beam diameter can be irradiated onto the workpiece. A laser beam  12   s   1  or one portion of the laser beam  12   s  can be incident on the surface of the lens  22  at an angle of incidence θ 1  and enters, and is refracted by a refraction angle θ 2 . The refracted light can travel through the lens  22  and the rib  23  and reach the welded region  27 . In contrast, after a laser beam  12   s   2  (one portion of the laser beam  12   s ) is incident on the surface of the lens  22 , it can be emitted into the atmosphere from the rear surface of the lens  22  and can be incident again on the side surface  23   a  of the rib  23  while the optical path changes. Therefore, the laser beam does not reach a predetermined irradiation position within the welded region  27 . For this reason, the laser beam  12   s  causes a shadow  28  to occur where it is not irradiated on the inner peripheral side of the welded region  27 . 
     Because there is no heat generated due to the light absorption of the light-absorbing resin member in the shadow located in the welded region, significant variations in the temperature that can be reached are present within the welded region as schematically illustrated in the figure. When the resin member in the shadow does not reach a fused state due to the lack of heat, effective elimination of gaps by means of pressure will not occur resulting in the possibility of poor welding. This shadow region becomes wider as the angle of incidence θ 1  of the laser beam  12   s  increases or as the height h of the rib  23  becomes higher. Therefore, there may be constraints on the design and manufacture of workpieces. 
     In order to ensure welding strength due to an effective gap elimination, the entire welded region can be uniformly irradiated with a laser beam and variations in the temperature reached can be controlled. The inventors investigated the structure of a workpiece effective for obtaining a uniform temperature in the welded region during the welding process using the Galvano scanner. For example, the occurrence of shadows in the welded region can be prevented from occurring by leaning the side surfaces of the rib toward the light source. 
       FIG. 2A  is a diagram in which virtual xyz coordinate axes are set during the laser welding process using the Galvano scanner. The optical system shown here can be configured such that the reflection on a Galvano minor is straightforwardly achieved. It is possible to consider the laser beam incident position on the first Galvano minor  14  as the position of a virtual light source and also to consider the laser beam  12   s  scanning the irradiation position along the welded region  27   a  by means of rotating the Galvano minors  14  and  15 . The position of the virtual light source can be set on the z axis and the welded region  27   a  can be set within the xy plane. The surface of the lens  22  can be formed by a plane parallel to the xy plane. The laser beam  12   s  that has a certain beam diameter can be discharged from the virtual light source at a height of D from the surface of the lens  22 . The laser beam can be incident on a lens irradiation surface  70 , positioned at a distance of L from the z axis (horizontal distance), at an angle of incidence θ 1  and after being refracted at an angle of refraction θ 2 , the refracted light travels through the lens  22  and the rib  23  irradiating the welded surface  27   a  (which is a contact surface of the rib  23  and the housing  21 ) at an angle almost equal to the angle of refraction θ 2  (travel angle). The inner side surface  23   a  of the rib  23  can be slanted with respect to the normal of the welded surface  27   a  at an angle φ. At this time, if the inclination angle φ is equal to or more than the travel angle of the refracted light, the laser beam  12   s  that is incident on the lens  22  will not be emitted into the atmosphere but can uniformly reach the welded surface  27   a.    
     The refraction angle or the travel angle θ 2  of the refracted light is associated with D and L and the refractive indices of the atmosphere and the lens. 
     θ 1  can be represented by the following equation based on D and L:
 
tan θ1= L/D.  
 
     In addition, from the Pythagorean theorem, the following equation can be formed,
 
sin θ1 =L/√ ( L   2   +D   2 )  (equation 1).
 
     Furthermore, if the refractive index n 1  of the atmosphere and the refractive index n 2  of the lens  22  are considered, the angle of incidence θ 1  and the angle of refraction θ 2  are associated according to Snell&#39;s law and represented by the following equation:
 
 n 1×sin θ1 =n 2×sin θ2  (equation 2).
 
     From equation 1 and equation 2,
 
 n 1×( L /√/( L   2   +D   2 ))= n 2×sin θ2
 
     and to clarify θ2,
 
θ2=sin −1 (( n 1 /n 2)×( L /√/( L   2   +D   2 )))  (equation 3).
 
     From equation 3, θ 2  is associated with the height D from the surface of the lens to be irradiated by the laser beam up to the light source, the distance L from the light source projected onto the surface of the lens up to the laser irradiation position, and the refractive indices of the atmosphere and the lens n 1  and n 2 . 
     During an actual welding process, if the virtual light source position can be determined for the workpiece in advance, the D and L can be determined. Even further, the refractive index of the light-transmitting resin member used for a common vehicle light, such as PMMA, is already known. Therefore, it is possible to estimate the travel angle of the refracted light on the basis of equation 3. If an inclination is formed equal to or more than the travel angle derived from equation 3 on the side surface of the rib of the entire periphery of the lens, the laser beam can almost be uniformly irradiated onto the welded region. If a laser beam with a beam diameter thermally uniform is irradiated onto the welded region, there will not be any significant variations in the temperature reached thereby making adhesion possible while effectively eliminating gaps. 
     As shown in  FIG. 2B , when the lens irradiation surface  70  is not parallel to the welded surface  27   a , the travel angle of the refracted light can be derived by adding the angle of inclination θ 3  of the lens irradiation surface  70  with respect to the welded surface  27   a , to the angle of refraction θ 2  at the lens irradiation surface  70 . In other words, the laser beam  12   s  can be uniformly irradiated onto the welded surface  27   a  by the inclination angle φ of the side surface  23   a  of the rib  23  being equal to or more than the travel angle (θ 2 +θ 3 ) of the refracted light. The angle of refraction θ 2  at the lens irradiation surface  70  can be derived from equation 3 based on a height D′ up to the light source on a second orthogonal coordinate system (not shown) corresponding to an x′ y′ plane and a distance L′ up to the lens irradiation surface. 
     The side surface  23   a  of the rib  23  leaning with respect to the welded region  27   a  is not limited to being a flat surface. As shown in  FIG. 2C , the side surface  23   a  of the rib  23  can be a curved surface. 
     Hereinafter, an exemplary embodiment of the welding process using a Galvano scanner on a workpiece that has a side surface of a rib leaning with respect to the welded region will be described. 
       FIG. 3A  is a plan view of a workpiece that has a two-dimensional welded region as seen from above in the z axis. A scan head  31  can be arranged above the inside of circular-band shaped welded region at, for example, the center position in the z direction. The scan head  31  can include an optical system for adjusting the focal point, an x Galvano minor, a y Galvano mirror, and a controller such as shown in  FIG. 1A . The laser beam  12   s  that has a beam diameter emitted from the scan head  31  can be repeatedly scanned in a loop. After setting up the workpiece, a laser beam irradiation can be received multiple times at the same position during a period of time in which the temperature of the resin member to be fused increases to a temperature at which a fused state can be achieved. For example, a laser beam irradiation can be received multiple times at the same position until the resin portion at the same position reaches the softening temperature (glass transition temperature) and a further laser beam irradiation can be received multiple times until reaching a fused state. The laser beam can use, for example, a YAG second or third harmonic laser, a semiconductor laser, a fiber laser, or the like. The laser beam spot diameter can be from 1 mm to 5 mm, for example. When the diameter of the laser beam is not sufficient for the width of the welded region, multiple welded lines which change positions in the radial direction can be set or a laser beam irradiation can be irradiated multiple times onto each welded line. 
       FIG. 3B  is a cross sectional view taken along line IIIB-IIIB in  FIG. 3A . A lens  22  formed from a light-transmitting resin can be arranged opposite to a housing  21  formed from a light-absorbing resin so as to close the opening of the housing  21 . A rib  23  can be formed on the rear surface of the lens  22  and the inner side surface  23   a  of the rib  23  can be inclined at an angle φa equal to or more than the travel angle of the refracted light with respect to the normal of the welded region  27 . The lower surface of the rib  23  and the upper surface of the housing  21  are brought into contact with each other under pressure by a pressure P along the z direction. The laser beam  12   s  can pass through the lens  22  and the rib  23 , thereby irradiating the welded region  27  where the lower surface of the rib  23  is in contact with the upper surface of the housing  21 . The laser beam  12   s  can be irradiated onto the welded region  27  without causing a shadow according to the inclination angle φa of the inner side surface  23   a  of the rib  23 . By means of continuously forming the inclined inner side surface  23   a  of the rib  23  extending over the entire periphery of the lens  22 , the laser beam can be uniformly irradiated onto the entire welded region. As a result, variations in the temperature reached can be relieved, gaps effectively eliminated, and a strong adhesion obtained. 
     When the shape of the welded region is a circular band and the light source is arranged at the center of the circular welded region, the inclination direction of the side surface of the rib will be equal to the irradiation direction of the laser beam. When the shape of the welded region is not a circular band or when the position of the virtual light source is shifted from above the center position of the welded region, it is possible for the side surface of the rib not to be in the irradiation direction of the laser beam but to lean in the direction of the width of the welded region. A description thereof will be next described. 
       FIG. 3C  is a top view showing the welded region in an oval-band shape arranged parallel to the xy plane. A scan head  31  is arranged above the inside of the oval-band shaped welded region  27 , for example, above the center of gravity in the z direction. For this case, the inner side surface of the rib on the laser irradiation position  70   a  is formed leaning in the direction of the arrow  73  with respect to the normal Lb of the outer peripheral of the welded region or namely, leaning in the direction of the width of the welded region. By means of forming the inclined inner side surface of the rib in the direction of the width of the welded region of the entire periphery of the lens, the laser beam can be uniformly irradiated onto the entire welded region. As a result, variations in the temperature reached can be relieved, gaps effectively eliminated, and a strong adhesion obtained. 
     If the shape of the welded region significantly changes the distance from the virtual light source, the angle of incidence will change and the irradiation surface area will also change. If the laser beam is scanned at a constant speed, the incident energy per unit time and per unit area will change depending on the position and the temperature reached will also change. For this type of case, the scanning speed can be controlled depending on the angle of incidence or the distance from the virtual light source. The scanning speed can be reduced at a position where the incident energy density lowers, and accordingly, the temperature inside the welded region can be equalized. This type of control can be performed through the control unit  16  as shown in  FIG. 1A . 
     The position of the light source is not limited to being above the inside of the welded region. Even if the light source is arranged above the outside of the welded region, it is possible to obtain effects similar to the exemplary embodiment when the side surface of the rib on the side where the light source is arranged is inclined. 
     If the refractive index of each medium is an already known value, the angle of inclination of the side surface of the rib can be derived by the height from the surface of the lens to be irradiated by the laser beam up to the light source and the distance from there up to the light source projected onto the surface of the lens. Therefore, even if the welded region has a three-dimensional structure, the effects according to the presently disclosed subject matter can be obtained. 
       FIG. 4A  is a diagram schematically showing laser beam welding using three-dimensional scanning. The laser beam emitted from the laser oscillator  10  can be introduced into a scan head  31  through an optical fiber  12 . For example, a housing  21 , formed from a light-absorbing resin, can be arranged in a jig  36  supported on a horizontal plane. The welded region of the housing  21  has a three-dimensional structure that does not fit into a two-dimensional plane. A lens  22  can have a welded region that is compatible with the welded region of the housing  21  and can be formed from a light-transmitting resin. The lens  22  can be arranged on the opposite housing  21  where both the welded regions of the housing  21  and the lens  22  are brought into contact with each other. The lens  22  and the housing  21  can be pressurized by a pressure P in the direction where that makes close contact with each other. The scan head  31 , which is arranged above the inside of a loop-shaped welded region such as above the center of gravity in the z direction, can scan the welded region with the laser beam  12   s  and repeatedly irradiate the welded region with the laser beam  12   s . Galvano mirrors  14  and  15  can control the position of the laser beam inside the two-dimensional plane and the focal point distance in the z direction can be controlled by a focal point adjustment optical system to maintain a constant focused state. 
       FIG. 4B  is a cross-sectional view schematically showing a welded region with a three-dimensional structure. The lens  22  can be arranged so as to close the opening of the housing  21 . A rib  24  can be formed on one side of the rear surface of the lens  22  and the inner side surface  24   a  of the rib  24  can be inclined at an angle φb equal to or more than the travel angle of the refracted light with respect to the normal of the welded surface  27   b . Another rib  25  can be formed on another side of the rear surface of the lens  22  and the inner side surface  25   a  of the rib  25  can be inclined at an angle φc equal to or more than the travel angle of the refracted light with respect to the normal of the welded surface  27   c . The laser beam  12   s  can pass through the irradiation surfaces  70   b  and  70   c  and the ribs  24  and  25  on the lens  22  and irradiate the welded surfaces  27   b  and  27   c  (contact surface between the ribs  24  and  25  and the housing  21 ). Because the height of the irradiation surface  70   b  is greater than the irradiation surface  70   c  by ΔD with respect to the light source, if the distance up to the light source is symmetric, the inclination angle φb will be smaller than the inclination angle φc. The inclination angles φb and φc allow the laser beam to be uniformly irradiated without causing shadows on the welded surface. As far as other welded surfaces in the welded region are concerned, if the inner side surface of the lens is formed at an angle equal to or more than the travel angle of the refracted light, the laser beam will be uniformly irradiated onto the entire welded region. In conjunction with this, if the scanning speed of the Galvano minors and the focal point adjustment optical system can be controlled, the heating and fusing will be almost simultaneous while variations in the temperature reached will be relieved thereby making it possible to obtain an even stronger welding. 
     Since an optical interface can be formed on the surface of the light-transmitting resin member, when the laser beam is irradiated, the beam will be incident on the light-transmitting resin member and simultaneously be reflected. As the angle of incidence towards the light-transmitting resin member becomes larger, the reflected components of the laser beam will become larger and more noticeable. If the angle of incidence towards the surface of the light-transmitting resin member exceeds 70°, the incidence efficiency will drop greatly and will not be suitable for practical use in many cases. Because the refractive index for air of PMMA (which is commonly used as a light-transmitting resin member of a vehicle light) is approximately 1.49, the refractive angle corresponding to an angle of incidence of 70° will be approximately 40° according to equation 2. This suggests that if the inclination angle of the side surface of the rib is approximately 40° with respect to a reference plane, the conditions will be fulfilled. 
     When an angle of incidence towards the surface of the light-transmitting resin member is equal to or more than 70°, it is possible to use multiple laser light sources. 
       FIG. 4C  shows a mode in which multiple laser beams are simultaneously irradiated from multiple scan heads  31   a  and  31   b . The scan heads  31   a  and  31   b  can also receive a laser beam from a separate laser light source or a laser beam can be received that has been divided from laser beams from one laser light source. By means of dividing the irradiation region, the laser irradiation region to be scanned by one scan head is limited thereby lowering the angle of incidence and making it possible to expand the laser irradiation region. 
     Although the foregoing was described from specific exemplary embodiments, the presently disclosed subject matter is not limited to these. For example, a combination of a light-transmitting resin member and a light-absorbing resin member is not limited to a lens and a housing. It can also be prepared for a showcase for jewelry and other small valuables and various other structures that benefit from a clear lens welded to a base housing. 
     The shape of the welded region is not limited to the shape shown in the above exemplary embodiments. If the travel angle of the refracted light can be estimated from geometric parameters in each welded surface with an arbitrary shape, it would be possible to determine the angle of inclination of the side surface of a rib that allows the welded region to be uniformly irradiated by the laser beam. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the presently disclosed subject matter without departing from the spirit or scope of the presently disclosed subject matter. Thus, it is intended that the presently disclosed subject matter cover the modifications and variations of the presently disclosed subject matter provided they come within the scope of the appended claims and their equivalents. All related art references described above are hereby incorporated in their entirety by reference.