JP2014195921A - Mold for molding lens for optical communication, lens for optical communication, and method for molding lens for optical communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold for molding a lens for optical communication capable of abating the generation of a weld attributed to the disparity of point arrival timings of one resin flow and another and unlikely to entail transfer defects; a lens for optical communication; and a method for molding a lens for optical communication.SOLUTION: A constitution wherein the area of an air escape unit configured on a first mold is greater on the gate GT side than on the side opposite the gate is provided.

Description

  The present invention is used for optical communication, for example, optical communication in which light from a light source that emits light, such as a semiconductor laser, is coupled to an optical fiber, or light from a light source that has passed through the optical fiber is coupled to a light receiving element such as a photodiode. The present invention relates to a mold for molding a lens for use, a lens for optical communication, and a method for forming a lens for optical communication.

  In optical communication or the like, a lens for optical coupling is used for efficient optical coupling between a light source or a light receiving element and an optical fiber. In conventional optical coupling lenses, a configuration in which a glass lens is mainly supported by stainless steel legs has been widely used, but in recent years, from the desire to reduce material costs and manufacturing process costs, Patent Literature As shown in FIG. 1, a resin-integrated leg-integrated lens has been developed that enables easy molding of a highly accurate aspherical surface and enables mass production.

  By the way, in general molding of a resin lens, a lens is molded by injecting and solidifying resin from a gate into a cavity formed by closing the first mold and the second mold. However, if air remains in the cavity when the resin is filled, the resin may not be filled and transfer failure may occur. For this reason, an air escape portion such as a minute gap is provided in a part of the mold, and as the resin is filled, the air in the cavity is discharged from the air escape portion to the outside, so that the gate enters the cavity. The filling efficiency of the inflowing resin is increased so that the shape of the cavity is transferred cleanly. In a leg-integrated lens for optical communication, if air is not exhausted from the cavity, the air is compressed as the resin fills, so-called gas burning occurs, and there is a risk that the transfer failure portion will turn brown. is there. Also, if transfer defects occur in the legs, the adhesion area when the lens is affixed to the substrate will become even smaller, even though the lens is originally small in diameter and small in adhesion area, and the sealing ability There is a risk that problems such as it becomes difficult to perform sealing in order to extend the lifetime of the optical element.

  On the other hand, the technique shown in Patent Document 2 is known as an application of the above-described air venting technique to a cup-shaped molded product that is not a leg-integrated lens for optical communication but has a similar shape. It has been. In Patent Document 2, there is a gate at a position where the apex portion of the cup is transferred, and by providing an air escape portion on the bottom surface of the cup that is the farthest from the gate, when resin is injected from the gate, A technique is disclosed in which air escapes from an air escape portion provided on the bottom surface of the cup.

JP 2007-183565 A JP 2004-299090 A

  Here, if the technique described in Patent Document 2 is simply applied to a leg-integrated lens for optical communication, a gate is arranged at the center of the optical surface of the molded lens, and the designed optical Since the surface shape is different, desired optical characteristics cannot be obtained. Therefore, in the leg-integrated lens for optical communication, it is conceivable that the gate is provided at a position where the outer periphery of the leg is transferred from the viewpoint of suppressing the influence on the optical characteristics and simplifying the mold structure.

  However, when the present inventor forms a leg-integrated lens for optical communication, a gate is provided at a position where the outer periphery of the leg is transferred, and an air escape portion is provided at a position where the position farthest from the gate on the bottom of the leg is transferred. When the resin was injection-molded with the resin, it was found that the appearance may be deteriorated, for example, a weld is formed in the vicinity of the leg on the side opposite to the gate of the lens to be molded. As a result of intensive research on this problem by the present inventors, when molding a leg-integrated lens for optical communication, the resin flows in from a gate provided at a position where the leg outer periphery is transferred. Turned out to be. More specifically, in FIG. 1, the cavity CV surrounded by the mold is composed of a lens cavity LC for transferring the lens part and a leg cavity SC for transferring the leg part, but via the gate GT. Part of the resin (A) that has flowed in from the side surface of the leg cavity SC crosses the axis of the lens cavity LC (the optical axis of the lens part to be transferred) and flows from above to the opposite side of the gate of the leg cavity SC. Then, it goes to the point P farthest from the gate. On the other hand, another part (B) of the resin that has flowed in from the side surface of the leg cavity SC through the gate GT goes around the leg cavity SC and goes to the point P farthest from the gate.

  At this time, if the movement distance of the resin flow A to the point P of B is compared, the movement distance of the B flow becomes longer. Further, when the speeds of the resin flows A and B are compared, since there is an air escape portion at the point P, the ease of air removal between the front end portion of the resin flow and the point P is the direction of the resin flow A. Is difficult to receive air resistance, is less resistant to resin flow because it passes through the lens cavity LC having a larger volume than the leg cavity SC, and the flow direction and flow A of the resin filled from the gate The flow of the resin A is faster due to the fact that the direction through the lens cavity LC is substantially the same. Therefore, the resin flow A reaches the point P farthest from the gate earlier than the resin flow B. After the resin flow A reaches the point P, it proceeds to face the resin flow B and merges with the resin flow B to fill the cavity CV with the resin. Since the flow A of the resin is merged so as to face B, a weld is generated at the merge point, causing a poor appearance.

  The present invention has been made in view of such problems, and a mold for molding a lens for optical communication that can reduce appearance defects such as weld without causing a transfer defect, and an optical communication An object of the present invention is to provide a lens and a method for forming a lens for optical communication.

The mold according to claim 1 is a mold for injection-molding a resin-made optical communication lens that focuses a light beam emitted from a light source or an optical fiber,
The lens is a leg-integrated lens,
The lens is
A lens unit having a first optical surface and a second optical surface facing each other;
A cylindrical leg portion extending from the periphery of the lens portion toward the first optical surface in a substantially optical axis direction;
The mold has a first mold and a second mold facing each other,
The first mold forms the first optical surface of the lens portion, at least part of the outer peripheral surface of the leg portion, at least part of the inner peripheral surface of the leg portion, and the bottom surface of the leg portion. Having a transfer surface,
The second mold has a transfer surface that forms the second optical surface of the lens unit,
Forming a cavity for molding the lens part and the leg part by combining the first mold and the second mold;
The mold has a gate for allowing molten resin to flow into the cavity,
The gate communicates with a transfer surface forming the outer peripheral surface of the leg;
The position of the gate in the optical axis direction overlaps at least partially with the position of the cavity forming the lens portion in the optical axis direction,
The first mold has an air escape portion on a transfer surface that forms the outer peripheral surface of the leg portion of the lens and / or the lower portion of the inner peripheral surface or the bottom surface of the leg portion,
The first mold is perpendicular to a perpendicular drawn from the center of the gate portion to the optical axis and includes the optical axis, and the gate-side region and the gate-opposite region. The total area of the air bleed portion in the region on the opposite side of the gate is larger than the total area of the air bleed portion in the region on the gate side.

  When molding a resin-integrated leg-integrated lens for optical communication, the position of the gate for the resin to flow in communicates with the transfer surface forming the outer peripheral surface of the leg and forms the lens portion of the lens. Due to the fact that at least part of the cavity overlaps with the position in the optical axis direction, resin flows A and B are born as shown in FIG. According to the present invention, the area of the air bleed portion in the first mold is larger than the region on the opposite side of the gate. Since the area on the side is larger, the air in the flow direction of the resin flow B is easier to escape than the air in the flow direction of the resin flow A. That is, the air resistance received by the resin flow B is smaller than the air resistance received by the resin flow A. As a result, since the speed of the resin flow B is increased, the resin flow A reaches the point P farthest from the gate and does not face the resin flow B. Flow B can reach point P as an integral flow. That is, since the resin flows A and B reach the point P farthest from the gate at almost the same timing, the occurrence of welds at the flow merge point can be suppressed. As a matter of course, the resin flows between the resin flows A and B, that is, after flowing from the gate, passes through the vicinity of the outer periphery of the lens cavity toward the position where the opposite gate portion side of the leg bottom is transferred. It is added that the flow also moves in accordance with the flow of the resin flows A and B, and reaches the point P almost simultaneously with the timing at which the resin flows A and B reach the point P. In addition, since it has an air escape part, air in the cavity is exhausted from the air escape part, which suppresses gas burning, transfer failure, reduction in adhesion area based on them, and reduction in sealing ability be able to. Therefore, according to the present invention, it is possible to obtain a mold capable of manufacturing a lens for optical communication made of a resin capable of reducing appearance defects such as weld without causing defective transfer. Note that the point P does not mean only the point farthest from the gate in a strict sense, but also includes the vicinity of the point farthest from the gate.

  The mold according to claim 2 is characterized in that, in the invention according to claim 1, the air escape portion is one or a plurality of openings.

  According to a third aspect of the present invention, in the invention of the second aspect, the narrowest width of the opening is 0.002 mm to 0.070 mm.

  In a lens for optical communication, the dimensional accuracy of the outer periphery of the leg is strictly required, and the bottom surface of the leg is often used as an adhesion reference surface for bonding to the substrate. There is a request not to generate burrs on the bottom surface, but if the narrowest width of the opening of the air escape portion is 0.002 mm to 0.070 mm, the resin enters the opening when the resin flows in. Since it becomes difficult, generation | occurrence | production of a burr | flash can be reduced. Particularly preferably, the length is 0.005 mm to 0.020 mm. If there are a plurality of openings, the narrowest width in one opening may be within the above numerical range.

  According to a fourth aspect of the present invention, in the invention according to the first aspect, the air escape portion is formed of a porous member.

  By using a porous member as the air escape portion, it is not necessary to perform complicated processing such as making a hole in the mold. Further, by using a porous member, the area of the air escape portion can be increased without complicating the mold structure while suppressing the generation of burrs, and the resin flow can be easily adjusted. . Moreover, the strength of the entire mold is sufficiently ensured even in the injection molding in which excessive pressure is applied, by using the porous member as the air escape portion instead of the entire mold.

  The mold according to claim 5 is the invention according to claim 4, wherein the porous member is press-fitted into the first mold.

  By fixing the porous member by press-fitting, the structure can be simplified as compared with fixing with a screw or the like, and the porous member to be used can be reduced in size.

  The mold according to claim 6 is the invention according to claim 4 or 5, wherein the porous member has a porous diameter of 0.001 mm to 0.015 mm.

  If the diameter of the hole of a porous member is 0.001 mm-0.015 mm, it can suppress significantly that resin enters a hole, ie, generation | occurrence | production of a burr | flash can be suppressed.

  According to a seventh aspect of the present invention, in the invention according to any one of the first to sixth aspects, the air escape portion is provided so as to communicate with a transfer surface that forms the bottom surface of the leg portion. It is characterized by that.

  The mold structure can be simplified by providing the air escape portion so as to communicate with the transfer surface forming the bottom surface of the leg portion. Further, since the air escape portion and the leg cavity are substantially straight, it is possible to efficiently evacuate air.

  The mold according to claim 8 is the invention according to any one of claims 1 to 7, wherein the first mold is viewed from the second mold side, and the optical axis is the center and the mold is When a line segment connecting the optical axis and the center of the gate is used as a reference line, the air escape portion has an angle from the reference line of 90 ° to 150 ° and an area of −90 ° to −150 °. It is characterized by being.

  The flow of the resin passing between the flow A and B of the resin, that is, the inflow from the gate, is due to the air escape portion being in the region of 90 ° to 150 ° and −90 ° to −150 ° from the reference line. After that, it is possible to reduce the air resistance that is received by the flow toward the transfer position passing through the vicinity of the outer periphery of the lens cavity and the side opposite to the gate portion on the leg bottom surface. Accordingly, since the resin flow passing between the resin flows A and B moves more reliably in accordance with the flow of the resin flows A and B, the resin flow passing between the resin flows A and B The resin flows A and B are not as separate flows but as a single flow, the certainty toward the point P is increased, and the occurrence of welds can be more reliably suppressed. As shown in FIG. 2, when the first mold is viewed from the second mold side, the segment connecting the optical axis OA and the center CN of the gate as the reference line BL when the optical axis is the center is used. The right side is + and the left side is-. For example, in FIG. 2, −150 degrees and +45 degrees are illustrated. In addition, an angle formed by a straight line obtained by extending the reference line to the side opposite to the gate and the reference line is expressed as 180 degrees or -180 degrees. The “gate center CN” refers to the center of the surface where the gate GT and the cavity CV intersect.

  The mold according to claim 9 is the optical axis according to any one of claims 1 to 8, wherein the first mold is viewed in the optical axis direction and from the side opposite to the leg portion. When the line segment connecting the optical axis and the center of the gate is used as a reference line, the air escape portion exists in the region of 150 ° to 180 ° and the region of −150 ° to −180 °. It is characterized by not.

  It is possible to suppress an increase in the speed of the resin flow A because the air escape portion does not exist in the region where the angle from the reference line is 150 ° to 180 ° or −150 ° to −180 °. Therefore, since the timing at which the resin flow reaches the point P is almost the same, it is possible to suppress the occurrence of welds and the appearance defect based thereon. Also, if the air escape portion is in the region of 150 ° to 180 ° and the region of −150 ° to −180 ° from the reference line, the resin flow A is the bottom surface of the leg cavity SC. It is conceivable that an air escape portion exists on the extension line of the flow toward the surface, and burrs are likely to occur due to the momentum of the resin flow, but the air escape portion is also in the region of 150 to 180 degrees- By not providing in the region of 150 degrees to -180 degrees, such a fear can be prevented.

  According to a tenth aspect of the present invention, in the invention according to any one of the first to ninth aspects, the air escape portion communicates with an air suction means.

  By connecting the air escape part to the air suction means, the air in the mold cavity can be extracted more quickly through the air escape part, the filling efficiency of the resin material is increased, and the flow of the resin is also controlled. It becomes even easier.

  An optical communication lens according to an eleventh aspect is formed from the mold according to any one of the first to tenth aspects.

The method for molding a lens for optical communication according to claim 12 includes a lens portion having a first optical surface and a second optical surface that face each other, and the first optical surface from the periphery of the lens portion in a substantially optical axis direction. An injection molding method of a resin-made lens for optical communication having a cylindrical leg portion extending on the optical surface side of
Forming a first mold having a first optical surface, a transfer surface forming at least a part of a peripheral surface of the leg portion and a bottom surface of the leg portion, and the second optical surface of the lens portion; A mold closing step of forming a cavity for molding the lens by closing the second mold having a transfer surface;
Filling the cavity with a resin through a gate communicating at least partially with the optical axis position of the lens portion and communicating with the transfer surface forming the outer periphery of the leg portion. A molding step of molding the lens by:
A mold opening step of opening the first mold and the second mold after the molding step;
A mold release step of releasing the molded product from the first mold or the second mold after the mold opening step;
Have
The transfer surface forming the outer peripheral surface of the leg portion and / or the lower portion of the inner peripheral surface or the bottom surface of the leg portion in the first mold has an air escape portion,
The first mold is perpendicular to a perpendicular drawn from the center of the gate portion to the optical axis and includes the optical axis, and the gate-side region and the gate-opposite region. And the total area of the air escape portion of the region on the opposite side of the gate is larger than the total area of the air escape portion of the region on the gate side,
In the molding step, the air in the cavity escapes from the air vent when the resin is filled.

  According to the above manufacturing method, since the area of the air escape portion in the first mold is larger in the region on the gate side than in the region on the opposite side of the gate, the leg-integrated lens for optical communication During molding, the flow of the resin flow B can be increased, and the resin flows A and B become an integrated flow, and it is possible to reach the point P farthest from the gate at almost the same timing. To do. Therefore, it is possible to suppress the occurrence of welds at the flow merge point.

  According to a thirteenth aspect of the present invention, there is provided a method for forming a lens for optical communication according to the twelfth aspect of the present invention, wherein the air escape portion is one or a plurality of openings.

  According to a fourteenth aspect of the present invention, there is provided a method for molding a lens for optical communication according to the twelfth aspect of the present invention, wherein the air escape portion is formed of a porous member.

  By using a porous member as the air escape portion, it is easy to increase the area through which air escapes, so that air can be more suitably discharged during the molding process.

  The method for molding a lens for optical communication according to claim 15 is the invention according to any one of claims 12 to 14, wherein the air escape portion communicates with a point slope forming a bottom surface of the leg portion. It is provided in.

  Since the air escape portion and the leg cavity can be made substantially straight, the air escapes more suitably during the molding process.

  The method for molding a lens for optical communication according to claim 16 is the invention according to any one of claims 12 to 15, wherein the first mold is moved from the direction opposite to the leg in the optical axis direction. As seen from the above, when the line segment connecting the optical axis and the center of the gate is the reference line, the air escape portion is an area whose angle from the reference line is 90 degrees to 150 degrees. And -90 degrees to -150 degrees.

  The flow of the resin passing between the flow A and B of the resin during the molding process is caused by the air escape portion being in the region where the angle from the reference line is 90 ° to 150 ° and −90 ° to −150 °. Since it can be made faster, the resin flow passing between the resin flows A and B and the resin flows A and B are not separated, but are more reliably directed to the point P as a single flow. Generation | occurrence | production can be suppressed more reliably.

  The method for molding a lens for optical communication according to claim 17 is the invention according to any one of claims 12 to 16, wherein the first mold is moved in the optical axis direction and from the side opposite to the leg portion. As seen, when the line segment connecting the optical axis and the center of the gate is used as a reference line, the air escape portion is also in the region of 150 ° to 180 °, −150 ° to −180 °. It does not exist even in the region of degrees.

  The absence of air vents in the region where the angle from the reference line is 150 ° to 180 ° or in the region of −150 ° to −180 ° increases the speed of the resin flow A during the molding process. Can be suppressed. Therefore, the timing at which the resin flows come together and reach the point P is almost the same, and the occurrence of welds and appearance defects based on the welds can be suppressed. Also, if the air escape portion is in the region of 150 ° to 180 ° and the region of −150 ° to −180 ° from the reference line, the resin flow A is the bottom surface of the leg cavity SC. It is conceivable that an air escape portion exists on the extension line of the flow toward the surface, and burrs are likely to occur due to the momentum of the resin flow, but the air escape portion is also in the region of 150 to 180 degrees- By not providing in the region of 150 degrees to -180 degrees, it is possible to prevent such a fear from occurring during the molding process.

  The method for molding a lens for optical communication according to claim 18 is characterized in that, in the invention according to any one of claims 12 to 17, the air escape portion communicates with air suction means.

  By connecting the air escape part to the air suction means, the air in the mold cavity can be extracted more quickly through the air escape part before or during the molding process, and filling the resin material Efficiency increases and control of the resin flow becomes even easier.

  According to the present invention, there is provided a mold for molding a lens for optical communication that can reduce appearance defects such as welds without causing defective transfer, a lens for optical communication, and a method for molding a lens for optical communication. Can be provided.

It is a figure for demonstrating the principle of this invention, and is a perspective view which shows typically the cavity in a metal mold | die. It is a figure for demonstrating the relationship between the reference line BL and an angle. It is an optical axis direction sectional view of an optical communication module using a lens concerning this embodiment. It is a perspective view shown in the state where the principal part of the optical communication module was disassembled. It is optical axis direction sectional drawing of the lens concerning this Embodiment. It is a figure which shows the manufacturing process of the lens of this Embodiment. It is a conceptual diagram which shows the position which projected the position and area of the porous member, the ventilation path, and the gate on the transfer surface. It is a figure which shows the metal mold | die concerning a modification. It is a figure for demonstrating the position of the air escape part in the metal mold | die concerning a modification. It is a figure which shows the modification of the structure of circular through-hole AM6 and pin AM7.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 3 is a sectional view in the optical axis direction of the optical communication module 10 according to the present embodiment. FIG. 4 is an exploded view of a main part of the optical communication module 10 to form an optical communication lens 20, a substrate 12, and a holder 30. It is a perspective view at the time. The substrate 12 supports the light source 15. Further, a light receiving element may be arranged instead of the light source 15. In the optical communication module 10 according to the present embodiment, a lens 20 is covered so as to surround the light source 15 supported by the substrate 12, and the bottom surface of the leg portion 21 of the lens 20 is bonded to the substrate by an adhesive. The holder 30 is disposed so as to cover the lens 20, and the end of the holder 30 is welded to the substrate 12, thereby forming the optical communication module 10. Hereinafter, each component will be described in detail.

  The substrate (also referred to as a stem) 12 is made of a ceramic material having a uniform thickness and has a disk shape. The size of the substrate 12 is sufficiently larger than the outer diameter of the holder 30 when viewed from the optical axis direction. In addition, the surface of the substrate 12 is plated with gold. And it has the rod-shaped terminal 11 for electric power feeding which penetrates the board | substrate 12. As shown in FIG. A chip mounting portion 13 is attached to the center of the substrate 12, and a laser chip (light source 15) is attached to a side surface of the chip mounting portion 13 via a heat sink 14, whereby the light source 15 is supported on the substrate 12. The light source 15 is connected to the terminal 11 via a wiring (not shown). The shape of the substrate 12 is not limited to a disk shape, and may be a polygonal shape or an elliptical shape.

  As a light source used for optical communication, a light emitting diode (LED), a laser diode (LD), a vertical cavity surface emitting laser (VCSEL), and the like are used. The wavelength used is generally about 1310 ± 15 nm or 1550 ± 15 nm for the single mode, and about 850 ± 15 nm for the multimode. In the case of using a light receiving element, PD (Photo Diode) or the like is used.

  Hereinafter, the lens 20 will be described in detail with reference to a cross-sectional view including the optical axis of the lens 20 of FIG.

The lens 20 includes a lens portion 22 and a cylindrical leg portion 21 extending from the periphery of the lens portion 22 in a substantially optical axis direction. The lens portion 22 and the leg portion 21 are integrally formed of resin. Molded. For example, it is molded by an injection molding method in which a molten resin is injected into a mold cavity and molded by cooling. The resin used for the lens for optical communication is not particularly limited as long as it has a good infrared transmittance. Acrylic resin, polycarbonate resin, polyester resin, cycloolefin resin, polysulfone resin, polyethersulfone Examples thereof include resins, polyimide resins, polyetherimide resins, polymethylpentene resins, silicone resins, and epoxy resins. Among these, it is preferable to use a cycloolefin resin from the viewpoint that the optical performance hardly changes due to moisture absorption. The shape of the lens 20 when viewed from the optical axis direction is preferably a circular shape, but may be a polygonal shape such as a quadrangle or an elliptical shape. Further, the size of the outer shape D of the lens for optical communication is generally 2 to 6 mm, and the total length H in the optical axis direction is 3 to 7 mm. In addition, the optical axis in this specification refers to the thickest part or the thinnest part of the lens part 22 or a straight line passing through the center of the lens part 22. In addition, in the present specification, when it is described as approximately XX, XX itself is also included. For example, the substantially optical axis direction includes the optical axis direction itself.
In addition, when it is referred to as a substantially optical axis direction, it indicates a direction in which the inclination from the optical axis is 2 degrees or less. In the present specification, the axis that forms the optical axis of the lens in the lens cavity is also referred to as the optical axis.

The lens unit 22 has two optical surfaces facing each other, that is, an optical surface S1 on the leg side (generally the light source side) and an optical surface S2 on the opposite side (generally the optical fiber side). The optical surface S1 and the optical surface S2 may be provided with a diffractive structure for improving temperature characteristics. Since resin lenses for optical communication are used in various temperature environments, the optical characteristics (particularly defocus characteristics) may change due to expansion or contraction of the lenses due to temperature changes. By providing a favorable diffractive structure, the influence on the optical characteristics due to the expansion or contraction of the lens can be reduced. In the case of providing a diffractive structure, if the diffractive structure is preferentially provided on an optical surface having a large effective diameter, the diffraction pitch can be increased and the manufacturability can be improved. Moreover, it is preferable that the optical surfaces S1 and S2 satisfy the following formula.
│SgFmax-SgFmin│ <0.05 (1)
However,
SgFmax: Maximum sag amount of the optical surface S2 (mm)
SgFmin: Minimum sag amount (mm) of the optical surface S2
The sag amount of the optical surface S2 represents the amount of displacement in the optical axis direction when a plane that passes through the intersection of the optical surface S2 and the optical axis and is perpendicular to the optical axis is used as a reference plane. Yes, the difference between the intersection point and the position closest to the optical fiber side is the maximum sag amount, and the difference between the intersection point and the position closest to the light source side is the minimum sag amount, and the range is the entire optical surface S2.

  By satisfying the expression (1), the difference between the most protruding amount (SgFmax) of the optical surface and the most retracted amount (SgFmin) becomes small, that is, the optical surface becomes close to a plane. When a diffractive structure is formed on a deep curved surface when considering the provision of an optical surface diffractive structure, in processing of a mold having a transfer surface for forming the diffractive structure, the expected angle of the surrounding transfer surface (with respect to the axis) (Inclination angle) is increased, and interference of the tool is likely to occur. However, by making the optical surface close to a flat surface, it becomes easier to form a diffractive structure, and the ease of manufacture can be improved. The “optical surface” refers to a region within a range (effective diameter) in which a light beam emitted from a light source or an optical fiber can pass.

  The periphery of the lens portion 22 is called a flange portion. The flange portion is a portion extending in the circumferential direction of the lens portion, and the shape of the flange portion is appropriately set within a range that does not significantly affect the optical performance of the lens and the yield at the time of injection molding. For example, the flange portion may have a protruding surface at a position (optical fiber side) higher in the optical axis direction than the vertex position of the optical surface S2, and a part of the flange portion may be a tapered surface. You may have a level | step difference from which the position of an axial direction differs. When the corner portion of the flange portion is a tapered surface inclined toward the leg side and in the outer peripheral direction, the taper surface can be used as a guide when covering the holder 30 described later, and at the time of injection molding Release properties are also improved. Further, when the flange portion has a projecting surface at a position higher in the optical axis direction than the apex position of the optical surface S2, it is handled or handled when the lens is formed and placed on a placement member such as a tray. Even when the optical surface S2 faces downward, there is an advantage that the projecting surface of the flange portion serves as a guard and the optical surface is not damaged. In addition, historical information on a manufacturing jig or the like on a part of the flange portion on the optical surface S2 side (specifically, in which mold is manufactured, when molding a plurality of lenses at a time, (Information on which cavity was molded), information on the position of the gate for injecting resin into the cavity formed by the mold, and information on the direction of the aberration and which customer product it was used to indicate Marking may be provided. It is preferable from the viewpoint of reducing the cost that the marking is not provided after the molding of the lens but is formed simultaneously with the injection molding of the lens by processing the mold. The shape and number of markings are not particularly limited, and a plurality of characters and hemispherical shapes can be selected as appropriate.

  The leg portion 21 has a cylindrical shape, and extends from the flange portion around the lens portion 22 to the first optical surface side in the substantially optical axis direction. The leg portion 21 preferably has a substantially cylindrical shape, but may have a polygonal cylindrical shape. Moreover, the optical axis direction length HS of the leg part 21 of the lens normally used for optical communication is 1 to 4 mm, and the leg width W is 0.2 mm to 0.6 mm. When the minimum value of the leg width is about 7 to 40% with respect to the length of the leg in the optical axis direction, not only the strength at the base of the leg but also the strength of the entire leg is increased. More preferably, it is 15 to 30%. If the width of the leg portion is less than or equal to the upper limit, the lens does not become too large, can be adapted to practical use, and can cope with downsizing. The lower portion of the leg means a height from the bottom of the leg to 30% of the total length H of the lens.

  The leg 21 exists so as to cover the light source 15, and is often joined to the substrate 12 by an adhesive on the bottom surface of the leg 21. Adhesives include thermosetting adhesives, hot melt adhesives, UV curable adhesives, anaerobic pressure sensitive adhesives, epoxy adhesives, etc., but UV curing has little effect on the lens during bonding. It is preferable to use an adhesive or an epoxy-based adhesive, and it is desirable to use a highly thixotropic adhesive that has a sufficient adhesive force between the metal and resin systems and does not spread liquid. Since the lens 20 having the leg 21 is made of resin and the substrate 12 is usually gold-plated, the bottom surface of the leg 21 is attached by an adhesive without being welded. Further, the bottom surface of the leg portion 21 may be used as an attachment reference surface when the optical axis of the lens portion 22 is positioned.

  As shown in FIG. 3, the holder 30 is made of a cylindrical stainless steel, and is attached to the outside of the lens 20 in the direction orthogonal to the optical axis with a slight gap. When the holder 30 is attached, the holder 30 is attached from above the lens 20 joined to the substrate 12 to which the light source is attached so that the inner periphery of the holder 30 and the outer periphery of the lens 20 are substantially fitted. The difference in the optical axis circumferential direction between the inner circumference of the holder 30 and the outer circumference of the lens 20 is preferably between 0.002 mm and 0.020 mm. When it is 0.002 mm or more, the holder 30 can be smoothly inserted into the lens 20, and when it is 0.020 mm or less, the holder 30 and the lens 20 can be substantially fitted. Moreover, when the corner | angular part of the flange part of the lens 20 is a taper surface, it becomes possible to insert the holder 30 smoothly. After the holder 30 is inserted, the portion in contact with the substrate 12 is welded, so that the holder 30 and the substrate 12 are joined to form an optical communication module. A cylindrical sleeve 31 having a smaller diameter is fixed to the end of the holder 30 opposite to the substrate 12, and a ferrule 32 into which the optical fiber FB is inserted is inserted therein. The optical fiber FB Is opposed to the lens portion 22. The holder 30 and the sleeve 31 may be integrated.

  The operation of the optical communication module 10 assembled to have the above-described components will be described. When power is supplied through the terminal 11, the light source 15 emits light, passes through the lens unit 22, passes through the refractive surface and / or the diffractive surface, and is focused on the end surface of the optical fiber 32. Will be propagated. Conversely, when receiving light from the optical fiber, the light from the end face of the optical fiber passes through the lens unit 22 and passes through the refracting surface and / or the diffracting surface and is focused on the light receiving element.

  FIG. 6 is a diagram showing a manufacturing process of a lens suitable for the above-described embodiment. 6 includes the optical axis of the lens molded by the mold and coincides with the plane passing through the center CN of the gate GT, and the gate side and the optical axis are easy to understand in FIG. Although the porous member PM as the air vent and the air passage AT leading to the outside are described at the position where the bottom surface of the leg portion on the side opposite to the gate is transferred across, the actual position at the position shown in FIG. A porous member and an air passage AT are disposed. In the following description, the first mold is assumed to be a movable mold MM, and the second mold is assumed to be a fixed mold FM. Here, the fixed mold FM has a transfer surface FM1 for transferring the optical surface S2, and a flat mating surface FM3 around the transfer surface FM1. On the other hand, the movable mold MM that is movable with respect to the fixed mold FM has a main mold AM and a nested mold (sub mold) BM. The main mold AM and the nested mold (sub mold) BM may be integrated, but are preferably separate from the viewpoint of mold fabrication. The main mold AM has a transfer surface AM1 for transferring the inner and outer circumferences of the leg portion 21, a transfer surface AM5 for transferring the bottom surface 21b of the leg portion 21, a central circular opening AM2, and a resin material from the outside. It has a gate GT and a flat mating surface AM4 facing the mating surface FM3. At this time, the depth HG of the length of the gate AM3 in the optical axis direction is preferably 0.8 mm to 2 mm. If the ratio of the length H in the optical axis direction of the lens to the depth HG of the gate is 2.5: 1 to 1.5: 1, the gate portion can be easily cut and the filling efficiency is increased. Therefore, it is preferable.

  Since the gate GT is formed by the rectangular cross-section groove formed on the mating surface AM4 of the movable mold MM and the mating surface FM3 with the fixed mold FM, the mating surface FM3 can be a simple flat surface. The mold structure is simplified. The gate GT communicates with a position where the outer peripheral surface of the leg portion 21 is transferred, and is provided toward the lens portion 22 so as not to face a position corresponding to the inner peripheral surface of the leg portion 21. That is, at least a part of the gate GT overlaps with the space (lens portion after molding) formed by the transfer surface FM1 and the transfer surface BM1 in the optical axis direction. Further, a part of the space formed by the transfer surface AM1 and the transfer surface AM5 is a portion for forming the leg portion. Moreover, it is preferable that the center position of a gate exists in the position of 70%-90% of the full length H of a lens from a leg part bottom face.

  The cylindrical nested BM is fitted to the circular opening AM2, is movable with respect to the main mold AM, and has a transfer surface BM1 for transferring the leg-side optical surface S1 at the tip.

  The air escape portion is provided on the transfer surface that forms the lower portion of the leg portion of the first mold, and the area of the air escape portion is larger than the side opposite to the gate (on the opposite gate portion side) across the optical axis. The gate side is larger. Here, the lower part of the leg means an area from the bottom of the leg to 50% (HS / 2) of the length of the leg. The air escape portion may be one or a plurality of openings, or may be a porous member. Examples of the shape of the opening include a substantially circular shape, a substantially annular shape, or a slit shape. Note that the area of the air escape portion is defined as the area of the air escape portion facing the cavity. When a porous member is used, the total area of the holes facing the cavity is defined as the area of the air vent.

  In the present embodiment, an air escape portion is provided on the bottom surface of the leg portion, and a porous member PM is employed as the air escape portion. Since the air vent portion is provided on the bottom surface of the leg portion, the leg cavity and the air vent portion can be made substantially straight, so that air is preferably released. The porous member PM is connected to the external space through the air passage AT. Of course, by connecting the air passage AT to an air suction means such as a vacuum generator, the efficiency of venting air from the cavity can be improved, and the flow of the resin can be more easily controlled.

  FIG. 7 shows the position and area of the porous member on the transfer surface of the mold that forms the bottom surface of the leg portion of the lens, and the position where the air passage AT and the gate GT are projected on the transfer surface in the present embodiment. It is a conceptual diagram. As shown in FIG. 7, the area of the porous member PM is configured such that the region on the gate side is larger than the region on the side opposite to the gate. In FIG. 7, the dotted line crossing the optical axis OA is a straight line passing through the optical axis OA and perpendicular to the line segment BL connecting the center CN of the gate and the optical axis OA. This is a boundary that separates the gate and the region on the opposite side (on the opposite gate side). In this embodiment, it is installed in the region of −140 degrees to −95 degrees, −80 degrees to +80 degrees, +95 degrees to +140 degrees, and the center of the ventilation path AT is −120 degrees and −60 degrees. , +60 degrees and +120 degrees. Since the area of the porous member PM, which is an air escape portion, is larger on the gate side than on the anti-gate side, the resin flow A through the lens cavity and the resin flow B through the leg cavity are close to an integrated flow. Thus, since the point P farthest from the gate is reached almost simultaneously, the possibility of welds can be reduced. Moreover, since air escapes from the air escape portion, it is possible to suppress gas burning, transfer failure, a decrease in the adhesion area based on them, a reduction in sealing ability, and the like. Furthermore, since the porous member is used as the air escape portion, it is easy to increase the area of the air escape portion, and the resin flow is easily adjusted. In addition, it is not necessary to perform complicated processing such as drilling holes in the mold, and the mold is not a porous member, but a part of the mold is a porous member. The strength as a whole is sufficiently ensured even in injection molding in which excessive pressure is applied. In this embodiment, the porous member on the side opposite to the gate portion and the porous member on the gate portion side are discontinuous, but the continuous structure, that is, all of -140 degrees to +140 degrees as the porous member. Also good. In this case, since the porous member can be a single member, the mold structure is simplified.

  In addition, since the porous member PM is provided in a region where the angle from the reference line BL is 90 degrees to 150 degrees and a region where the angle is −90 degrees to −150 degrees, the resin passing between the flow A and B of the resin Since the flow can be made faster, the resin flow passing between the resin flows A and B and the resin flows A and B have a higher certainty toward the point P as one flow rather than as separate flows, The generation of welds can be more reliably suppressed. Further, since there is no air escape portion in the region where the angle from the reference line is 150 ° to 180 ° or in the region where the angle is −150 ° to −180 °, the increase in the speed of the resin flow A is suppressed. It is possible to prevent the occurrence of welds with more certainty, and to eliminate the possibility of large burrs caused by the momentum of the resin. In addition, you may give the role of a ventilation path to a porous member by extending a porous member to external space. Further, the porous member according to the present embodiment is fixed to the mold by press-fitting. Furthermore, since the average porous diameter of the porous member is 0.007 mm, the occurrence of burrs can be suppressed.

  The manufacturing process of the lens suitable for the above-described embodiment will be described. First, as shown in FIG. 6A, the mating surfaces FM3 and AM4 are brought into close contact with each other so that the movable mold is fixed to the fixed mold FM. A clamping process for clamping the MM is performed. In this state, a molding process for injecting molten resin into the internal cavity via the gate GT is started. At this time, since the area of the air escape portion in the gate side region is larger, it passes through the lens cavity. Since the resin flow A and the resin flow B passing through the leg cavities reach the point P farthest from the gate almost at the same time, the possibility of welds can be reduced. After the resin is filled, the molding process is completed by cooling and solidifying the resin in a state where a predetermined pressure is applied.

  Thereafter, as shown in FIG. 6B, after the resin is cooled, the movable mold MM is displaced so as to be integrally moved away from the fixed mold FM, and the mold release process is started.

  Next, as shown in FIG. 6C, the mold release process is completed by relatively moving the nested mold BM so as to protrude from the main mold AM. By the releasing step, the optical surface of the lens 20 that is a molded product is pushed out by the transfer surface BM1. Thereafter, the molded product is removed from the transfer surface BM1, but since the gate part GA solidified in the gate GT is connected to the molded product, this is cut (C) in the step shown in FIG. The cut surface GC is formed by polishing the cut surface. Thus, the lens 20 can be obtained. However, if the cut surface has an acceptable shape, polishing is not necessarily required. Therefore, a lens manufactured by the manufacturing method using the mold is a lens that does not have a defective appearance such as a transfer defect or a weld.

  FIG. 8 is a schematic cross-sectional view of a mold according to another embodiment, but parts not particularly described are the same as those of the embodiment shown in FIGS.

  The air escape portion of the present embodiment has a plurality of substantially annular openings. More specifically, the movable mold MM has a circular through hole AM6 so as to communicate with the transfer surface forming the outer peripheral surface of the lower portion of the lens leg, and a pin AM7 inserted so as to slide on the AM6. An annular opening formed by the pin AM7 and the circular through hole AM6 is an air vent. In FIG. 8, for easy understanding, the circular through hole AM6 and the pin AM7 are shown on the schematic cross-sectional view of FIG. 8, but actually, the circular through hole AM6 and the pin are located at the position shown in FIG. AM7 is arranged. Here, the length of the narrowest width of the gap between the circular through hole AM and the pin, that is, the length in the diameter direction of the gap between the circular through hole and the pin is 0.002 mm to 0.006 mm. As the resin flows in, the resin does not easily enter the opening, and the generation of burrs can be reduced. Further, the width of the opening can be adjusted by inserting a pin.

  FIG. 9 is a conceptual diagram for easily explaining the positional relationship between the bottom surface of the lens leg and AM6 and AM7 in the present embodiment. In the present embodiment, the air vent is not provided in the region on the side opposite to the gate, and the circular through hole AM6 and the pin are arranged so that the center of the opening comes in the −45 ° and + 45 ° regions of the gate side region. AM7 is arranged. In addition, the diameter of the pin AM in FIG. 9 is 0.05 mm.

  Note that the shape of the circular through hole AM6 pin AM7 has a burr escape structure as shown in FIG. 10 within a range that does not affect the release yield, thereby affecting the outer shape of the lens even if a burr occurs. No shape.

  The present invention is not limited to the embodiments described in the specification, and other embodiments and modifications are apparent to those skilled in the art from the embodiments and ideas described in the present specification. It is.

  For example, the main mold AM may be divided into a plane perpendicular to the optical axis and a plane passing through the lower part of the leg portion, and a gap (slit) generated on the divided surface may be used as the air vent portion. The adjustment of the slit width (area of the air escape portion) at this time can be easily adjusted by making the position of the dividing surface in the optical axis direction different between the gate side and the opposite gate side.

  Further, in addition to the air escape portion of the present invention, in the mold, air venting may be performed by providing a minute gap between the mating surfaces AM4 and FM3 on the opposite side from the gate.

10 Optical communication module 11 Terminal 12 Substrate (stem)
13 Chip mounting portion 14 Heat sink 15 Light source 20 Lens 21 Leg portion 21b Leg bottom surface 22 Lens portion 30 Holder 31 Sleeve 32 Ferrule A Resin flow AM Main mold AM1 Transfer surface AM2 Circular opening AM3 Transfer surface AM4 Matching surface AM5 Transfer surface AM6 Circular through-hole AM7 Pin AT Air passage B Resin flow BL Reference line BM Nested BM1 Transfer surface CN Gate center CV Cavity D Lens outline FB Optical fiber FM Fixed mold FM1 Transfer surface FM3 Matching surface GA Gate part GT Gate H Lens total length HG Gate depth HS Leg length LC Lens cavity MM Movable mold OA (AX) Optical axis P Point farthest from gate PM Porous member S1 First optical surface S2 Second optical surface SC Leg cavity W Leg width

Claims (18)

A mold for injection molding a resin-made lens for optical communication that focuses a light beam emitted from a light source or an optical fiber,
The lens is a leg-integrated lens,
The lens is
A lens unit having a first optical surface and a second optical surface facing each other;
A cylindrical leg portion extending from the periphery of the lens portion toward the first optical surface in a substantially optical axis direction;
The mold has a first mold and a second mold facing each other,
The first mold forms the first optical surface of the lens portion, at least part of the outer peripheral surface of the leg portion, at least part of the inner peripheral surface of the leg portion, and the bottom surface of the leg portion. Having a transfer surface,
The second mold has a transfer surface that forms the second optical surface of the lens unit,
Forming a cavity for molding the lens part and the leg part by combining the first mold and the second mold;
The mold has a gate for allowing molten resin to flow into the cavity,
The gate communicates with a transfer surface forming the outer peripheral surface of the leg;
The position of the gate in the optical axis direction overlaps at least partially with the position of the cavity forming the lens portion in the optical axis direction,
The first mold has an air escape portion on a transfer surface that forms the outer peripheral surface of the leg portion of the lens and / or the lower portion of the inner peripheral surface or the bottom surface of the leg portion,
The first mold is perpendicular to a perpendicular drawn from the center of the gate portion to the optical axis and includes the optical axis, and the gate-side region and the gate-opposite region. And the total area of the air bleed portion in the region on the opposite side of the gate is larger than the total area of the air bleed portion in the region on the gate side.   The mold according to claim 1, wherein the air escape portion is one or a plurality of openings.   3. The mold according to claim 2, wherein the narrowest width of the opening is 0.002 mm to 0.070 mm.   The mold according to claim 1, wherein the air escape portion is formed of a porous member.   The mold according to claim 4, wherein the porous member is press-fitted into the first mold.   The mold according to claim 4 or 5, wherein a diameter of the hole of the porous member is 0.001 mm to 0.015 mm.   The mold according to claim 1, wherein the air escape portion is provided so as to communicate with a transfer surface forming the bottom surface of the leg portion.   When the first mold is viewed in the optical axis direction and from the second mold side, a line segment that is centered on the optical axis and that connects the optical axis and the center of the gate is used as a reference line. The mold according to any one of claims 1 to 7, wherein the air escape portion is in an area of 90 to 150 degrees and an area of -90 to -150 degrees with respect to the reference line. .   When the first mold is viewed from the optical mold direction and the second mold side, and a line segment that is centered on the optical axis and connects the optical axis and the center of the gate is used as a reference line, The mold according to any one of claims 1 to 8, wherein the air escape portion does not exist in a region of 150 to 180 degrees or in a region of -150 to -180 degrees.   The mold according to claim 1, wherein the air escape portion communicates with air suction means.   A lens for optical communication, which is molded from the mold according to any one of claims 1 to 10. A lens portion having a first optical surface and a second optical surface facing each other, and a cylindrical leg portion extending from the periphery of the lens portion toward the first optical surface in a substantially optical axis direction; An injection molding method for a resin-made optical communication lens having
Forming a first mold having a first optical surface, a transfer surface forming at least a part of a peripheral surface of the leg portion and a bottom surface of the leg portion, and the second optical surface of the lens portion; A mold closing step of forming a cavity for molding the lens by closing the second mold having a transfer surface;
Filling the cavity with a resin through a gate communicating at least partially with the optical axis position of the lens portion and communicating with the transfer surface forming the outer periphery of the leg portion. A molding step of molding the lens by:
A mold opening step of opening the first mold and the second mold after the molding step;
A mold release step of releasing the molded product from the first mold or the second mold after the mold opening step;
Have
The transfer surface forming the outer peripheral surface of the leg portion and / or the lower portion of the inner peripheral surface or the bottom surface of the leg portion in the first mold has an air escape portion,
The first mold is perpendicular to a perpendicular drawn from the center of the gate portion to the optical axis and includes the optical axis, and the gate-side region and the gate-opposite region. And the total area of the air escape portion of the region on the opposite side of the gate is larger than the total area of the air escape portion of the region on the gate side,
In the molding step, when the resin is filled, the air in the cavity escapes from the air vent part.   The mold according to claim 12, wherein the air escape portion is one or a plurality of openings.   The method for molding a lens for optical communication according to claim 12, wherein the air escape portion is formed of a porous member.   The method for molding a lens for optical communication according to claim 12, wherein the air escape portion is provided so as to communicate with a transfer surface forming a bottom surface of the leg portion.   When the first mold is viewed in the optical axis direction and from the second mold side, a line segment that is centered on the optical axis and that connects the optical axis and the center of the gate is used as a reference line. The optical communication according to any one of claims 12 to 15, wherein the air escape portion is in an area of 90 to 150 degrees and an area of -90 to -150 degrees with respect to the reference line. Lens molding method.   When the first mold is viewed from the optical mold direction and the second mold side, and a line segment that is centered on the optical axis and connects the optical axis and the center of the gate is used as a reference line, The lens for optical communication according to any one of claims 12 to 16, wherein the air escape portion does not exist in a region of 150 to 180 degrees or in a region of -150 to -180 degrees. Method.   The method for molding a lens for optical communication according to claim 12, wherein the air escape portion communicates with air suction means.

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