JP5436937B2 - Manufacturing method of resin molded products - Google Patents

Description

  The present invention relates to a method for producing a resin molded product.

  For example, a vehicle lamp has a resin molded product in which a housing made of a light-absorbing resin such as acrylonitrile styrene acrylate (ASA) and a lens made of a translucent resin such as polymethyl methacrylate (PMMA) or polycarbonate are welded. There are many cases.

  In Japanese Patent Laid-Open No. 10-310676, a hot plate is sandwiched between a lens and a housing, the lens and the housing are heated and melted by the hot plate, and the hot plate is removed to weld the lens and the housing. The resin composition for housing which can be controlled is proposed.

  Japanese Patent Laid-Open No. 2001-243812 presses a lens and a lamp body (housing), enters a laser beam from the lens side using a robot, heats and melts the surface of the lamp body, and melts the lamp body to heat the lens side. In laser welding in which the tip of the seal leg is also melted and the laser beam is scanned over the entire circumference of the lens, a method is proposed in which the joint surface is tilted so that the laser beam is incident obliquely. By placing an elastic light guide having substantially the same refractive index as the lens material on the lens surface, the light refraction effect disappears and the light is not condensed, and the light reaches the entire welded joint surface, thereby increasing the bonding strength. It describes.

  Japanese Patent Application Laid-Open No. 2004-349123 arranges an elastic light guide and a flat transparent base material on the lens surface including a case where the surface of the lens combined with the housing is a curved surface, and applies a compression load. A method in which the elastic light guide and the lens are brought into close contact with each other, laser light is incident from the transparent substrate side, and the contact portion between the lens and the housing is heated and melted through the elastic light guide and the lens to weld the housing and the lens. suggest.

Japanese Patent Laid-Open No. 10-310676 JP 2001-243812 A JP 2004-349123 A

  The method of welding resin molded products using laser light has not been sufficiently developed.

  A method for producing a resin molded product including a welded portion having high adhesion, excellent appearance, and high bonding strength using laser light is desired.

According to one aspect of the present invention,
The first welding region of the translucent resin member and the second welding region of the light-absorbing resin member are arranged to face each other,
Apply pressure between the light-transmitting resin member and the light-absorbing resin member so as to be in a pressurized state in contact with each other,
An optical system including a focus adjustment optical system capable of adjusting a focal position of an input laser beam and a galvano mirror capable of scanning a laser beam emitted from the focus adjustment optical system in a two-dimensional direction is prepared. ,
A laser beam is incident from the translucent resin member, irradiated onto the welding line of the second welding region of the light absorbing resin member, and the focal position of the laser beam with respect to the second welding region is adjusted by the focus adjusting optical system. However, the laser beam is scanned two-dimensionally by the galvano mirror, the irradiation line on the second welding region is repeatedly irradiated, the entire welding line is simultaneously heated, softened and melted, and the translucent resin member is also softened and melted. , Welding the light-transmitting resin member and the light-absorbing resin member;
A method of manufacturing a resin molded product, wherein the light-transmitting resin member is a lens, the light-absorbing resin member is a housing, the welding region has a three-dimensional structure, and the laser beam is incident on the welding region There is provided a method for manufacturing a resin molded product, in which the incident angle varies depending on the position, and the scanning speed of the laser beam varies depending on the position to average the heating temperature.

  Since the entire welding line is heated at the same time, it is easy to obtain strong welding, and a gap hardly remains between the light-transmitting resin member and the light-absorbing resin member.

and 1A to 1E are a diagram side view, a plan view, a graph, and a diagram showing a case where welding is performed by irradiating a welding region (two-dimensional structure) arranged on a plane with a laser beam. 2A to 2E are graphs showing changes in volume with respect to the temperature of the light-absorbing resin, cross-sectional views showing changes in the opposing resin member due to repeated laser beam irradiation, and graphs showing changes in the temperature of the light-absorbing resin with respect to the time of repeated laser beam irradiation. It is. 3A and 3B are a schematic perspective view and a sectional view showing welding by repeated laser irradiation on a three-dimensional welding region, and FIGS. 3C and 3D are a sectional view and a diagram showing a modification. 4A to 4C are a side view of a laser welding apparatus, a top view of a welding region, a cross-sectional view of the welding region, and a temperature distribution showing considerations made by the present inventors for laser welding using a robot.

  When a light-transmitting (transparent) resin member and a light-absorbing (light-absorbing, opaque) resin member are opposed to and brought into contact with each other in a pressurized state, and the laser beam is irradiated from the light-transmitting resin member side, the laser beam is translucent resin It penetrates the member and reaches the light absorbing resin member. When the laser beam is absorbed by the light absorbing resin member, the light absorbing resin member is heated, softened, and further melted. Since the translucent resin member is in contact with the light-absorbing resin member under pressure, the heat of the light-absorbing resin member is also transmitted to the translucent resin member. Therefore, the translucent resin member is also softened and melted. Both members are in a molten state and are welded. The present inventors examined a laser welding method using a robot.

  FIG. 4A is a side view showing a configuration of a laser welding apparatus using a robot. A converging optical system 102 including an expander and a condenser lens is connected to the tip of the optical fiber 101 connected to the laser light source, and a converging laser beam 103 is emitted. The converging optical system 102 is held by the robot 104 and controls the three-dimensional position of the converging optical system and the traveling direction of the laser beam six-dimensionally. The gantry 105 supports the robot 104 and supports the housing jig 106. The jig 106 supports a housing 108 made of a light absorbing resin. A lens 109 made of a translucent resin is disposed on the housing 108 so as to face the housing 108. The lens 109 and the housing 108 are held in a pressurized state.

  The robot 104 positions the converging optical system 102 at a predetermined start point, emits a laser beam 103, and irradiates the housing 108 through the lens 109. The surface portion of the housing 108 irradiated with the laser beam absorbs the laser beam and is heated, softened, and melted. The lens 109 in contact with the heated housing 108 is also heated.

  As shown in FIG. 4B, the welding region 110 set at the peripheral edge of the lens 109 has a normal loop shape. Laser irradiation is started from the start point, the converging optical system is moved along the loop by the robot 104, and the welding process is completed after one round.

  As shown in FIG. 4C, with the progress of the laser beam, a fusion region 111 and softening (glass transition) regions 112 and 113 before and after the fusion region 111 are formed in the welding region 110 of the housing 108 (and the lens 109). In the melting region, the resin of the lens and the housing are melted and slightly crushed. In the case of laser welding, the height of the collapsed region is about 0.1 mm or less.

  In many cases, the surface of the resin member has irregularities such as a protruding region or a weld line. An uneven area on the upper surface of the housing is indicated by 108r, and an uneven area on the lower surface of the lens is indicated by 109r. Usually, the protruding step is about 0.2 mm. In the region where the laser beam has not yet passed, the resin is a solid phase and the protruding step is not collapsed. In the vicinity of the protruding step, the contact between the lens and the housing is hindered, and a gap can be formed. If the gap does not disappear, good welding may not be performed. Even if the laser beam makes one round of the welded region, a region that is not welded remains, and there is a possibility that a welded state without airtightness may be obtained.

  Such local welding failure is considered to be because heating and melting by laser irradiation are locally performed in the welding region. If the entire welding region can be heated and melted as in hot plate welding, local welding defects will be improved.

  The present inventors examined using a laser beam to scan the laser beam at high speed in order to heat and melt the entire welding region. If the welding area is repeatedly irradiated with a laser beam and the next irradiation is performed before cooling, the temperature of the irradiation area will increase. However, such high-speed scanning may be difficult using a robot. There is a galvano scanner as a configuration capable of high-speed scanning with a laser beam.

  FIG. 1A is a diagram schematically showing a configuration of a laser beam welding apparatus using a galvano scanner. A focus adjusting optical system 13 is arranged for the laser beam 12 emitted from the tip of the optical fiber 11 connected to the laser oscillator. The focus adjustment optical system includes a movable lens and can adjust the focus position on the optical path. A first galvano mirror 14 is arranged for the laser beam emitted from the focus adjustment optical system 13 and performs, for example, x-direction scanning within the processing surface. A second galvano mirror 15 is arranged with respect to the laser beam reflected by the first galvano mirror 14 and performs, for example, a y-direction scan within the processing surface.

  The control device 16 controls the galvano mirrors 14 and 15 and the focus adjustment optical system 13. The emitted laser beam 12 s can be two-dimensionally scanned in the xy plane by the galvano mirrors 14 and 15, and can be moved in the z direction by controlling the focal length by adjusting the focus adjusting optical system 13. . That is, the focusing position of the laser beam can be scanned three-dimensionally. Galvanomira is lightweight and can be scanned at high speed.

  As the laser oscillator, for example, a YAG second to third harmonic laser oscillator, a semiconductor laser, a fiber laser, or the like can be used. If only two-dimensional scanning is used, a scan head having an fθ lens can be used instead of the focus adjustment optical system.

  FIG. 1B is a cross-sectional view schematically illustrating a workpiece having a welding region arranged in a two-dimensional plane. A lens 22 is formed oppositely on the container-shaped housing 21 so as to close the opening of the housing 21. The case where the welding rib 23 is formed on the lower surface of the lens 22 is shown. The rib 23 is not an essential component. A translucent pressure plate 25 is disposed on the lens 22, and the lower surface of the lens 22 and the upper surface of the housing 21 are brought into pressure contact with pressure P. The laser beam 12 s passes through the translucent pressure plate 25 and the lens 22 and irradiates the upper surface of the housing 21 in contact with the rib 23. The irradiation position is scanned along the rib (welding region) by driving the galvano mirror. A plane on which the welding region is arranged is defined as an xy plane. In the configuration of FIG. 1A, the first galvano mirror 14 performs scanning in the x direction, and the second galvano mirror 15 performs scanning in the y direction.

  FIG. 1C shows an example of the shape of the two-dimensional welding region 27. It is the loop shape illustrated by circular strip shape. The laser beam is irradiated by repeatedly scanning the loop. The same position is subjected to laser beam irradiation a plurality of times from the time when the workpiece is set to the time when the resin member to be welded reaches the molten state from the temperature at the time of installation. For example, the laser beam irradiation is performed a plurality of times until the same portion reaches the softening temperature (glass transition temperature), and further, the laser beam irradiation is performed a plurality of times until the molten metal is melted. It is also possible to suppress foaming by gradually raising the temperature of the light-absorbing resin.

  As a test piece, a sample having a length of one round of the welding line at the center in the width direction of the circular belt-like welded region was formed, and test irradiation was performed. The lens was made of PMMA and the housing was made of ASA. The temperature was measured with a thermocouple sandwiched between the lens and the housing. The laser output was 200 W, the scanning speed was 4 m / sec, and 20 continuous laser beam irradiations were performed. The scanning time for one round is 37.5 msec. In the actual product, it may be assumed that one round of the welding line exceeds 1 m. Therefore, in this test, a test was performed that imitates the welding process in a part of the actual product by inserting a certain interval after irradiation of one round of the welding line. In this test, an insertion of about 0.8 seconds was performed as an interval.

  FIG. 1D is a graph showing the time change of the measured temperature ts. For one laser beam irradiation, the temperature rises, for example, by about 40 ° C., and starts decreasing after the end of irradiation. Before the temperature is lowered to the temperature before irradiation, the next laser beam is irradiated and the temperature rises. The average temperature gradually increases due to repeated laser beam irradiation. When the average temperature is increased, the temperature rise due to the single laser beam irradiation is reduced, and the overall shape is convex upward. When the position in the welding region is changed, it is considered that the same temperature change occurs with the timing slightly shifted. It is clear that the entire weld zone can be heated almost uniformly at the same time. In addition, although the temperature which a thermocouple showed was shown as it was, after a test, the lens and the housing were broken and the thermocouple was taken out. In the destructive test, the lens and the housing are well welded, and it is assumed that the actual reached temperature is higher than the illustrated temperature and has reached 240 ° C. or higher.

  FIG. 1E is a diagram showing an optical system in which the reflection in the galvano mirror is replaced by straight travel. The laser beam incident position on the first galvano mirror 14 can be considered as the position of the virtual light source. The laser irradiation position is scanned in a two-dimensional plane by the rotation of the galvano mirrors 14 and 15. When the position in the xy plane of the virtual light source is aligned with the center of the circular belt-like welded region, the incident angle θ is constant at any position of the circular belt-like welded region. When constant speed scanning is performed, the incident energy per time is constant at any position in the circular welded region.

  In addition, when the shape of the welding region becomes a shape that greatly changes the distance from the virtual light source, the incident angle changes and the irradiation area also changes. If constant velocity scanning is performed, the incident energy per area per unit time will change depending on the position, and the ultimate temperature will also change. In such a case, it is preferable to control the scanning speed according to the incident angle or the distance from the virtual light source, to lower the scanning speed at a position where the incident energy density is low, and to equalize the temperature in the welding region. Such control can be performed via the control device 16.

  FIG. 2A is a graph showing the relationship of ASA resin volume to temperature. The vertical axis represents volume and the horizontal axis represents temperature. From room temperature to a certain temperature range, the volume gradually increases almost linearly with temperature. When the weighted deflection temperature (thermal deformation temperature) is exceeded, the volume increase rate increases, and after the glass transition temperature (softening temperature), the transition is made to a more steep, almost linear volume increase rate. The ASA used is a general grade, the deflection temperature under load is about 95 ° C., and 240 ° C. belongs to the fluid region.

  2B-2D show the expected change in weld area. FIG. 2B shows a state before softening, and a local gap exists between the housing 21 and the lens 22 due to the protruding steps of the housing 21 and the lens 22. FIG. 2C shows a state before the melting past the softening point, the entire welding region can be deformed, the resin is flattened by pressurization, and the gap between the housing 21 and the lens 22 is reduced. FIG. 2D shows a molten state, and the entire welding line is in a molten state (at least a combination of a softened state and a molten state), so that the gap between the housing 21 and the lens 22 disappears, and the molten resins 21 and 22 are replaced. They are expected to melt together and disappear. It is easy to obtain a strong weld, and there will be little gap left between the housing and the lens.

  FIG. 2E is a graph schematically showing a temporal change in temperature. The solid line shows the temperature change due to repeated laser beam irradiation. From time t0 to t1, the average temperature rises by repeating the laser beam irradiation while repeating the temperature rise and fall as in FIG. 1D. From time t1 to t2, at least in a state where the temperature is raised, the light absorbing resin is in a molten state and both resin members are pushed in. Welding is completed at time t2, and the temperature is lowered by natural heat dissipation.

For comparison, a change in temperature in the case where laser irradiation is performed for one round along the welding line by a robot is indicated by a broken line. By the laser beam irradiation, the temperature of the light absorbing resin rises to the melting temperature all at once. Even if the resin is in a molten state at the irradiation position, the laser beam is not yet irradiated at other positions, or the temperature is lowered and the resin is in a solid phase. Therefore, the indentation of the resin is limited and it will be difficult to completely eliminate the local gap.

  According to repeated laser beam irradiation on the same welding line, the entire welding line is simultaneously heated, softened, and melted, so that both resin members are pushed in and local gaps are also effectively eliminated.

  FIG. 3A is a diagram schematically showing laser beam welding by three-dimensional scanning. A laser beam emitted from the laser oscillator 10 is introduced into the scan head 31 via the optical fiber 12. The scan head 31 includes the focus adjustment optical system, x galvano mirror, y galvano mirror, and control device shown in FIG. 1A. A housing 21 made of light-absorbing resin is disposed on the jig 36. The welding area of the housing has a three-dimensional configuration that does not fit in a two-dimensional plane. A lens 22 made of a translucent resin having a welding region that matches the welding region of the housing 21 is disposed on the housing 21 so as to face both the welding regions. The lens 22 and the housing 21 are pressurized with a pressure P in a direction in contact with each other.

  The scan head 31 scans the laser beam 12s along the welding region and repeatedly irradiates it. The position in the two-dimensional xy plane is controlled by the galvano mirrors 14 and 15, and the focal length in the z direction is controlled by the focus adjustment optical system to maintain a constant focus state.

  FIG. 3B shows an example of a focused state. The converging laser beam 12 s is in a so-called rear pin state having a focal position behind the welding region 27. By defocusing from the welded region, melting occurs in a wide area of the welded region to obtain a strong bond.

  As an example, a vehicle rear combination lamp having a three-dimensional structure was welded. A lens formed of a light-transmitting resin member and a housing formed of a light-absorbing resin member are welded in a three-dimensional structure welding region. The length of one round of the welding area was 1 m, the laser output was 150 W, the scanning speed was 10 m / sec, and the total irradiation length was 200 m (200 rounds). As a result of destructive inspection after welding, peeling did not occur over the entire length, indicating that the material was in a material destruction mode and that strong welding was possible.

  In the welding region having a three-dimensional structure, the incident angle changes and the irradiation area also changes. The incident angle on the surface of the light absorbing resin member may be about 60 degrees. Compared to the case of normal incidence, the irradiation area at an incident angle of 60 degrees is doubled. When ribs are used, it is desirable to have a margin in the rib width. The rib width is preferably 2 mm to 3 mm. Further, the rib height is preferably 0.5 mm or more for melting. If the total rib height is melted, the rib height is preferably 1 mm or less in order to suppress irradiation energy (laser output). In this case, the rib height is preferably 0.5 mm to 1 mm. For example, stable and good welding was obtained with a rib width of 3 mm and a rib height of 0.5 mm.

  The light-absorbing resin member is irradiated with the laser beam through the translucent resin member. The surface of the translucent resin member also forms an optical interface and causes reflection. When the incident angle on the surface of the translucent resin member exceeds 70 degrees, the incident efficiency into the resin member is greatly lowered and often cannot be put into practical use.

  FIG. 3C shows a mode in which the translucent pressure plate 25 is arranged via the elastic translucent member 33 conforming to the surface shape of the translucent resin member 22 and a laser beam is incident from the translucent pressure plate 25. The elastic translucent member 33 is made of, for example, a transparent silicone resin. Regarding the elastic translucent member, reference can be made to the disclosure of FIGS. 1 and 2 and paragraphs 0007 to 0013 of JP-A No. 2004-349123.

  The correspondence when the range of the incident angle exceeds 70 degrees will be described below.

  FIG. 3D shows a mode in which a plurality of laser beams are simultaneously irradiated from a plurality of scan heads 31a and 31b. The scan heads 31a and 31b may receive a laser beam from another laser light source or a laser beam obtained by dividing a laser beam from one laser light source. By dividing the irradiation region, the laser irradiation region scanned by one scan head is limited, and the incident angle can be reduced and the laser irradiation region can be enlarged.

  Although the embodiments have been described above, the present invention is not limited to these embodiments. For example, the combination of the translucent resin member and the light absorbing resin member is not limited to the lens and the housing. You may make a showcase for small valuables such as jewelry. Various other uses are possible. It will be apparent to those skilled in the art that various modifications, substitutions, improvements, combinations, and the like can be made.

11 Laser head,
12 Laser light,
13 Focus adjustment optical system,
14 First Galvano Milola,
15 Second Galvanomira,
21 light-absorbing resin member,
22 translucent resin member,
23 Ribs,
25 translucent pressure plate,
27 welding area,
101 optical fiber,
102 convergent optical system,
103 laser light,
104 robot,
105 frame,
106 jig,
108 housing,
109 lenses,
110 welding area,
111 melting region,
112 glass region,
113 glass region.

Claims (6)

The first welding region of the translucent resin member and the second welding region of the light-absorbing resin member are arranged to face each other,
Apply pressure between the light-transmitting resin member and the light-absorbing resin member so as to be in a pressurized state in contact with each other,
An optical system including a focus adjustment optical system capable of adjusting a focal position of an input laser beam and a galvano mirror capable of scanning a laser beam emitted from the focus adjustment optical system in a two-dimensional direction is prepared. ,
A laser beam is incident from the translucent resin member, irradiated onto the welding line of the second welding region of the light absorbing resin member, and the focal position of the laser beam with respect to the second welding region is adjusted by the focus adjusting optical system. However, the laser beam is scanned two-dimensionally by the galvano mirror, the irradiation line on the second welding region is repeatedly irradiated, the entire welding line is simultaneously heated, softened and melted, and the translucent resin member is also softened and melted. , Welding the light-transmitting resin member and the light-absorbing resin member;
A method of manufacturing a resin molded product, wherein the light-transmitting resin member is a lens, the light-absorbing resin member is a housing, the welding region has a three-dimensional structure, and the laser beam is incident on the welding region A method of manufacturing a resin molded product, in which an incident angle varies depending on a position, and a scanning speed of the laser beam varies depending on the position, and the heating temperature is averaged.   2. The method of manufacturing a resin molded product according to claim 1, wherein a focused state when the laser beam is incident from the translucent resin member is a state having a focal position behind the first and second welding regions. .   The method for producing a resin molded article according to claim 1 or 2, wherein, at the same position of the welding line, the light-absorbing resin member is irradiated with the laser beam a plurality of times before reaching the glass transition temperature.   The resin molding according to any one of claims 1 to 3, wherein, at the same position of the welding line, the light-absorbing resin member receives a plurality of times of laser beam irradiation from the temperature at the time of installation until reaching the molten state. Product manufacturing method.   The said 2nd welding area | region will be in a molten state when repeatedly irradiating the said laser beam on the said 2nd welding area | region, Intrusion arises between the said 1st, 2nd welding area | region. The manufacturing method of the resin molded product of description. The said translucent resin member has a rib in the said light absorption resin member opposing surface, The said rib has a width of 2 mm-3 mm, and a height of 0.5 mm-1 mm, The any one of Claims 1-5. Manufacturing method for resin molded products.

Images