JP2007086223A - Optical waveguide and method for manufacturing optical waveguide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical waveguide that facilitates an optical connection with an optical fiber and can reduce optical loss, and to provide a method for manufacturing the optical waveguide. <P>SOLUTION: The optical waveguide has a holding member on an end face in the light guiding direction of the optical waveguide main body, the holding member to hold an optical fiber in such a manner that the end part in the light guiding direction of the optical fiber to be optically connected to the end face of the optical waveguide core is aligned at least coaxial to the end part in the light guiding direction of the optical waveguide core. The method for manufacturing the optical waveguide includes: a step of providing the end face in the light guiding direction of the optical waveguide main body with a holding member that can hold an optical fiber in such a manner that the end part in the light guiding direction of the optical fiber to be optically connected with the end face of the optical waveguide core is aligned at least coaxial to the end part in the light guiding direction of the optical waveguide core; and a step of optically connecting the end face of the optical waveguide core and the optical fiber held by the holding member, with a photosetting adhesive. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical waveguide and a method for manufacturing the optical waveguide.

  The optical waveguide manufacturing method includes (1) a method of impregnating a film with a monomer and selectively exposing the core portion to change the refractive index and bonding the film (selective polymerization method), and (2) a core layer and a cladding. A method of forming a clad portion by reactive ion etching after applying a layer (RIE method), (3) Photo exposure and development using an ultraviolet curable resin in which a photosensitive material is added to a polymer material. A method using a lithography method (direct exposure method), (4) a method using injection molding, (5) a method of changing the refractive index of the core part by exposing the core part after coating the core layer and the clad layer (photo A method using a bleaching method) has been proposed.

However, the selective polymerization method of (1) has a problem in film lamination, and the methods of (2) and (3) are expensive due to the use of a photolithography method, and the method of (4) is There is a problem in the accuracy of the obtained core diameter. Further, the method (5) has a problem that a sufficient difference in refractive index between the core layer and the clad layer cannot be obtained.
At present, the practical methods excellent in the performance of the optical waveguide are only the methods (2) and (3), but there is a problem of cost as described above. Any of the methods (1) to (5) is difficult to apply to forming a polymer waveguide on a flexible plastic substrate having a large area.

  In addition, as a method of manufacturing an optical waveguide, a polymer substrate material for a core is filled in a pattern substrate (clad) on which a groove pattern serving as a capillary is formed, and then cured to form a core layer, on which a planar surface is formed. A method of bonding a substrate (cladding) is known, but in this method, not only the capillary groove but also the entire surface of the pattern substrate and the flat substrate is thinly filled with a polymer precursor material and cured to form a core layer. As a result of the formation of a thin layer having the same composition as the above, there is a problem that light leaks through the thin layer.

As one method for solving this problem, Debit Hart uses a clamping jig to fix the pattern substrate on which a groove pattern serving as a capillary is formed and a flat substrate, and further, the contact portion between the pattern substrate and the flat substrate. After sealing with a resin, a method of manufacturing an optical waveguide by reducing the pressure and filling the capillary with a monomer solution (diallyl isophthalate) for the core was proposed (see Patent Document 1 below).
In this method, instead of using the polymer precursor material as the core forming resin material, the viscosity of the filling material is reduced by using a monomer, and the capillary is filled using the capillary phenomenon so that the monomer is not filled except the capillary. It is a method to do. Since this method uses a monomer as the core forming material, the volume shrinkage when the monomer is polymerized into a polymer is large, voids are likely to occur inside the core, and the light transmission loss of the optical waveguide increases. There is.
Further, this method is a complicated method in which the pattern substrate and the flat substrate are fixed with a clamp, or in addition, the contact portion is sealed with resin, and mass productivity is high. As a result, cost reduction cannot be expected. It cannot be applied to the production of an optical waveguide using a film having a thickness of the order of mm or 1 mm or less as the cladding.

  Recently, George M. Whitesides and others at Harvard University have proposed a method called capillary micromolding as one of the soft lithography as a new technology for creating nanostructures.

This is because a master substrate is made using photolithography, and the nanostructure of the master substrate is copied to a PDMS rubber mold using the adhesion and easy peelability of polydimethylsiloxane (PDMS). This is a method in which a liquid polymer is poured and solidified using a capillary phenomenon. The following non-patent document 1 describes detailed explanation articles.
Alternatively, a patent on capillary micromolding has been filed by Kim Enoch et al. Of George M. Whitesides group at Harvard University (see Patent Document 2).

  Even if the manufacturing method described in this patent is applied to the manufacture of an optical waveguide, since the core portion of the optical waveguide has a small cross-sectional area, it takes time to form the core portion and is not suitable for mass production. In addition, when the monomer solution is polymerized to become a polymer, the volume is changed, the core shape is changed, and the transmission loss is increased.

  B. Michel et al. Of the IBM Zurich Research Institute have proposed a high-resolution lithography technique using PDMS, and reported that this technique can achieve a resolution of several tens of nanometers. Detailed commentary articles are described in Non-Patent Document 2 below. In this way, soft lithography technology using PDMS and capillary micromolding are technologies that have recently attracted attention as nanotechnology mainly in the United States.

  However, when an optical waveguide is produced using the above-mentioned micromold method, the volume shrinkage during curing is reduced (thus, transmission loss is reduced), and the filling liquid ( It is impossible to reduce the viscosity of the monomer and the like. Therefore, if priority is given to reducing the transmission loss, the viscosity of the filling liquid cannot be reduced below a certain limit, the filling speed becomes slow, and mass production cannot be expected.

  The micromold method is based on the premise that a smooth and rigid substrate such as glass or a silicon wafer substrate is used as the substrate, and does not consider the use of a flexible film base material. As a result, the shape of the waveguide to be formed is distorted, and a waveguide having sufficient light propagation performance cannot be produced.

  On the other hand, the present inventors have already proposed a method in which a flexible film base material is also used as a clad base material and a polymer waveguide is formed on the film base material (see Patent Document 3 or Patent Document 4). . With this optical waveguide manufacturing method, flexible optical waveguides, which were impossible in the past, are precisely configured, all devices are made of the same type of material system, and the optical end face is obtained by a highly accurate cutting process, resulting in lower costs. It has become possible.

  Here, in recent years, in IC technology and LSI technology, in order to suppress signal delay and noise, and to improve integration, optical wiring is performed between equipment devices, between boards in equipment equipment, and in chips instead of metal wiring. Has been done. Specifically, an optical fiber is optically connected to the optical waveguide. For such optical connection, it is necessary to suppress the waveguide loss of light. As a technique applicable to such a purpose, for example, a technique of connecting a light emitting element and a light receiving element with an optical waveguide (For example, see Patent Documents 5 to 7).

  The optical wiring element described in Patent Document 5 includes an incident side mirror for causing light from the light emitting element to enter the core, and an emission side mirror for emitting light from the core to the light receiving element. A clad layer is formed in a concave shape at a position corresponding to an optical path from the light emitting element to the incident side mirror and from the output side mirror to the light receiving element, and the light from the light emitting element and the light from the output side mirror are converged. The optical wiring element described in Patent Document 6 is such that the light incident end face of the core is formed to be convex toward the light emitting element, and the light from the light emitting element is converged to suppress the waveguide loss. .

Further, Patent Document 7 describes an optoelectronic integrated circuit in which an optical waveguide circuit is directly assembled on a photoelectric fusion circuit substrate in which electronic elements and optical elements are integrated. A method of optically connecting an optical fiber to an optical waveguide using these techniques can be considered.
Japanese Patent No. 3151364 US Pat. No. 6,355,198 Japanese Patent Application No. 2003-58871 Japanese Patent Application No. 2003-58887 JP 2000-39530 A JP 2000-39531 A JP 2000-235127 A SCIENTIFIC AMERICAN SEPTEMBER 2001 (Nikkei Science December 2001 issue) IBM J. REV. & DEV. VOL. 45 NO. 5 SEPTEMBER 2001

  However, the techniques described in Patent Literature 5 and Patent Literature 6 have a complicated structure, and therefore, there is a problem that a very complicated process is required for the production. Moreover, in the technique described in the above-mentioned Patent Document 7, a photolithographic method with high cost is used for manufacturing an optical waveguide. Therefore, the optoelectronic integrated circuit is inevitably expensive.

  The present invention has been made to solve the above-described problems, and provides an optical waveguide capable of easily performing optical joining with an optical fiber and capable of reducing optical loss and an optical waveguide manufacturing method. Objective.

  The above-described problems are solved by providing the following optical waveguide and method for manufacturing the optical waveguide.

  That is, the optical waveguide of the present invention is an optical waveguide having an optical waveguide core made of a curable resin for core formation and a cladding layer surrounding the periphery of the optical waveguide core and having a refractive index smaller than that of the optical waveguide core. The optical waveguide end of the optical waveguide core and the optical waveguide end of the optical waveguide core are at least coaxial with the end surface of the optical waveguide core on the end surface of the optical waveguide body. A holding member capable of holding the optical fiber is provided.

In the optical waveguide of the present invention, the optical waveguide end of the optical fiber that is optically bonded to the end surface of the optical waveguide core and the optical waveguide end of the optical waveguide core are at least coaxial with the end surface of the optical waveguide. Since the holding member capable of holding the optical fiber is provided, when optically joining the end face of the optical waveguide core and the optical waveguide direction end of the optical fiber, the optical fiber is held by the holding member and then optically joined. With this configuration, the optical waveguide core and the optical fiber of the optical waveguide can be easily executed with high accuracy and reduced optical loss.
Accordingly, it is possible to provide an optical waveguide that can easily perform optical joining with an optical fiber and reduce optical loss.

  The holding member has a bent portion bent along the outer periphery of the optical fiber, and can hold the optical fiber in the bent portion. Thus, since the holding member holds the optical fiber by the bent portion bent along the outer periphery of the optical fiber, the optical fiber can be stably and easily held.

  The bent portion may be any shape that is bent along the outer periphery of the optical fiber, and may have an arc shape, a U shape, an arc shape, or the like.

  The holding member is an annular body having a hole having a shape along the outer periphery of the optical fiber, and the optical fiber can be held in the hole. For this reason, while being able to perform optical joining with an optical fiber easily, the optical waveguide which can reduce optical loss can be provided.

  Further, the holding member continuously decreases in inner diameter as it approaches the end face side of the optical waveguide main body in the optical waveguide direction, and the minimum inner diameter of the holding member is larger than the outer diameter of the optical fiber. It can be easily held on the holding member so that the optical fiber and the optical waveguide core are coaxial.

Note that the following optical waveguide manufacturing method can easily perform optical joining with an optical fiber, and can provide an optical waveguide manufacturing method capable of reducing optical loss.
Specifically, the method for producing an optical waveguide of the present invention comprises a step of preparing a rubber mold formed of a cured resin layer of a curable resin for forming a rubber mold and having a recess corresponding to the optical waveguide core, and the rubber mold A step of closely adhering the clad substrate, a step of filling the concave portion of the rubber mold to which the clad substrate is adhered, and a hardening resin for forming the optical waveguide core, and the filling of the filled optical waveguide core A step of forming an optical waveguide core by curing a functional resin, a step of peeling the rubber mold from the cladding substrate, and forming a cladding layer on the cladding substrate on which the optical waveguide core is formed A step of cutting the end portion of the optical waveguide core, an optical waveguide end portion of the optical fiber optically joined to the end face of the optical waveguide core, and an optical waveguide end portion of the optical waveguide core at least coaxially. As described above, the step of providing a holding member capable of holding the optical fiber on the end surface of the optical waveguide main body in the optical waveguide direction, and the end surface of the optical waveguide core and the optical fiber held by the holding member are made into a photocurable adhesive. And a step of optically bonding with a material.

In addition, the viscosity before hardening of the said photocurable adhesive is 30 mPa * s or more and 1000 mPa * s or less.
The refractive index of the photocurable adhesive is in the range of −7% to + 7% of the refractive index of the optical waveguide core.

  The photo-curing adhesive has a transmission loss of 1 dB or less with respect to light in a wavelength range of 500 nm to 900 nm.

  Further, the rubber mold has an inlet and an outlet for the optical waveguide core forming curable resin in the cured resin layer, and includes an injection port for press-fitting the optical waveguide core forming curable resin. And a reinforcing member for reinforcing the cured resin layer.

  The reinforcing member may be any one of a metal material, a ceramic material, and a plastic material, and the cured resin layer may be a silicone rubber. Further, the shear rubber hardness of the rubber mold forming curable resin of the rubber mold is in the range of 10 to 50.

  In the optical waveguide according to the present invention, the optical waveguide end of the optical fiber that is optically bonded to the end surface of the optical waveguide core and the optical waveguide end of the optical waveguide core are at least coaxial with the end surface of the optical waveguide body. A holding member capable of holding the optical fiber is provided. Further, the optical waveguide manufacturing method of the present invention is such that the optical waveguide end of the optical fiber optically joined to the end face of the optical waveguide core and the optical waveguide end of the optical waveguide core are at least coaxial. The step of providing a holding member capable of holding an optical fiber on the end surface of the optical waveguide main body in the optical waveguide direction and the end surface of the optical waveguide core and the optical fiber held by the holding member are optically bonded with a photo-curing adhesive. And a process. For this reason, it is possible to provide an optical waveguide capable of easily performing optical joining with an optical fiber, and to provide an optical waveguide capable of reducing optical loss and an optical waveguide manufacturing method.

The optical waveguide manufacturing method of the present invention is characterized by the following steps.
That is, the manufacturing method of the optical waveguide of the present invention is:
(1) preparing a rubber mold formed from a cured resin layer of a curable resin for forming a rubber mold and having a recess corresponding to the optical waveguide core;
(2) adhering a clad substrate to the rubber mold;
(3) filling the concave portion of the rubber mold to which the clad substrate is in close contact with a curable resin for forming an optical waveguide core;
(4) curing the filled optical waveguide core forming curable resin to form an optical waveguide core;
(5) peeling the rubber mold from the clad substrate;
(6) forming a cladding layer on the cladding substrate on which the optical waveguide core is formed;
(7) cutting the end of the optical waveguide core;
(8) A holding member capable of holding the optical fiber so that the optical waveguide direction end of the optical fiber to be optically bonded to the end face of the optical waveguide core and the optical waveguide direction end of the optical waveguide core are at least coaxial. Providing the optical waveguide body on the end face in the optical waveguide direction;
(9) A step of optically bonding the end face of the optical waveguide core and the optical fiber held by the holding member with a photocurable adhesive.

  One aspect of the optical waveguide manufacturing process of the present invention will be described. 1 (A) to 1 (G) are conceptual diagrams showing each step in the manufacturing method of the present invention, and FIG. 2 is a diagram in which a rubber mold is brought into close contact with a base material for cladding that is one area larger than the rubber mold. It is a perspective view which shows the state (process shown by FIG.1 (D)).

  FIG. 1A shows a cut surface obtained by cutting the master 10 on which the convex portion 12 corresponding to the optical waveguide core is formed at right angles to the longitudinal direction of the convex portion 12.

  Next, a cured resin layer 20a of a curable resin for forming a rubber mold is formed on the surface of the master 10 on which the convex portions 12 are formed. FIG. 1B shows a cut surface obtained by cutting the master 10 on which the cured resin layer 20a of the curable resin for rubber mold formation is cut at right angles to the longitudinal direction of the convex portion 12. FIG.

  Next, the cured resin layer 20a of the rubber mold-forming curable resin is peeled off from the master 10 to take a mold (not shown), and then the concave portions 22 corresponding to the convex portions 12 are exposed at both ends of the mold. By cutting, the entrance 22a (see FIG. 2) for filling the concave portion 22 with the optical waveguide core-forming curable resin, and the optical waveguide core-forming curable resin from the concave portion 22 corresponding to the convex portion 12. The discharge port 22b (see FIG. 2) for discharging is cut and formed to produce the rubber mold 20 (see FIG. 1 (C) and FIG. 2).

  A clad substrate 30 having a conductive pattern 31 formed thereon and having a slightly larger area than that of the rubber mold 20 is brought into close contact with the rubber mold 20 thus produced (AA cut surface in FIG. 2). Although the details of the clad substrate 30 will be described later, the clad substrate 30 has a first clad layer. The clad substrate 30 may be provided integrally with the first clad layer.

  Next, several drops of the optical waveguide core-forming curable resin 40a are dropped on the entrance 22a of the rubber mold 20, and the optical waveguide core-forming curing is applied to the recess 22 of the rubber mold 20 by capillary action and pressure reduction / pressure injection. Fill with functional resin. The optical waveguide core-forming curable resin is discharged from the discharge port 22b at the other end of the recess 22 (not shown). FIG. 1E shows a cross-sectional view of the rubber mold 20 in which the concave portion 22 is filled with a curable resin for forming an optical waveguide core, cut at right angles to the longitudinal direction of the concave portion.

  Next, the optical waveguide core 40 is formed by UV-curing the optical waveguide core-forming curable resin 40 a in the recess 22 of the rubber mold 20. The rubber mold 20 on which the optical waveguide core 40 is formed is peeled from the master 10. FIG. 1F shows a cut surface obtained by cutting an optical waveguide core 40 formed on a clad substrate 30 at a right angle to the longitudinal direction of the optical waveguide core.

  Furthermore, the optical waveguide 60 of the present invention is manufactured by forming the second cladding layer 50 of the optical waveguide core-forming curable resin on the formation surface of the optical waveguide core 40 of the cladding substrate 30. FIG. 1G shows a cut surface obtained by cutting the optical waveguide perpendicularly to the longitudinal direction of the optical waveguide core.

  FIG. 3 shows an example in which a film to be the second cladding layer is adhered to the base material for the cladding by the first cladding layer on which the optical waveguide core 40 is formed by an adhesive.

  FIGS. 3A to 3F are common to the steps shown in FIGS. 1A to 1F, and start from the master 10 and have the first clad layer. The process up to the step of forming the optical waveguide core 40 on the clad substrate 30 as the material is shown.

In FIG. 3G, the optical waveguide 60 obtained by the step of bonding the second clad layer (clad film) 52 to the formation surface of the optical waveguide core 40 of the clad substrate 30 using the adhesive layer 54. The cut surface which cut | disconnected this at right angles to the optical waveguide core longitudinal direction is shown.

  FIG. 4 shows an example in which a reinforcing member that reinforces the cured resin layer of the rubber mold is provided, and the conductive pattern 31 is provided on the side of the clad substrate 30 on which the optical waveguide core is formed. 4 (A) to 4 (F) are the same as the steps shown in FIGS. 3 (B) to 3 (G), and the conductive pattern 31 is formed by starting (omitting) the master 10. Up to the step of forming the optical waveguide core on the clad base material 30 will be shown. FIG. 4F shows an optical waveguide 60 obtained by bonding a second clad layer (clad film) 52 to the optical waveguide core forming surface of the clad substrate 30 using an adhesive layer 54. The cut surface cut | disconnected at right angles to the waveguide core longitudinal direction is shown. In this example, a light-transmitting top plate 24a such as a quartz plate, a glass plate, or a hard plastic plate is used in a rubber mold recess forming region (an irradiation region such as ultraviolet rays). In the present invention, since a rubber mold made of rubber is used, even when the conductive pattern 31 is provided on the side where the optical waveguide core 40 is formed as shown in FIG. 4, the conductive pattern 31 is not adversely affected. The optical waveguide core 40 can be formed.

  Next, as shown in FIG. 5, in order to make the end portion of the optical waveguide core 40 of the optical waveguide 60 of the present invention formed as described above into an optical end surface, it is cut by a dicer or the like, An optical waveguide direction end of an optical fiber 82 (see FIG. 5C) optically joined to an end surface of the optical waveguide core 40 on an optical waveguide direction end surface of the waveguide 60, an optical waveguide direction end of the optical waveguide core 40, The holding member 80 capable of holding the optical fiber 82 is bonded by a photo-curing adhesive so that the optical fiber 82 is at least coaxial.

As described above, the holding member 80 is configured such that the optical waveguide direction end of the optical fiber 82 optically joined to the end face of the optical waveguide core 40 and the optical waveguide direction end of the optical waveguide core 40 are at least coaxial. In addition, the shape is not particularly limited as long as the optical fiber 82 can be held, but any shape having a bent portion bent along the outer periphery of the optical fiber 82 may be used.
The bent portion is preferably arcuate along the outer periphery of the optical fiber 82.

  Specifically, as the holding member 80, an annular holding member 80A (FIG. 6A) having a hole portion 81A (corresponding to the bent portion) shaped along the outer periphery of the optical fiber 82, and the outer periphery of the optical fiber 82 A truncated cone-shaped holding member 80B (FIG. 6B) having a hole portion 81B having a shape extending along the axis.

  Further, the holding member 80 may be arcuate or U-shaped instead of being annular. Specifically, as shown in FIG. 6C, a holding member 80 </ b> C in which a bent portion bent along the outer periphery of the optical fiber 82 has an arc shape, and a U-shaped region having an arc-shaped region along the outer periphery of the optical fiber 82. A holding member 80E (see FIG. 6 (E)) having a letter shape and a holding member 80F having a shape provided so that the distance between both ends of the U-shaped holding member 80E is gradually separated (FIG. 6 (F)). ) And the like.

Note that when the holding member 80 is provided on the optical waveguide 60, the area of the end surface of the holding member 80 that contacts the optical waveguide 60 via a photocurable adhesive (detailed later) is the same as that of the holding member 80. The outer wall of the holding member 80 may be inclined with respect to the direction perpendicular to the end surface so as to be wider than the area of the end surface facing the end surface (see the holding member 80D in FIG. 6D).
By setting it as such a shape, the adhesive force of the optical waveguide 60 of the holding member 80 can be improved.

  In addition, when the holding member 80 is provided on the optical waveguide 60, the area of the end surface of the holding member 80 that comes into contact with the optical waveguide 60 via a photocurable adhesive (described later in detail) The inner wall of the holding member 80 may be inclined with respect to the direction perpendicular to the end face so as to be wider than the area of the end face facing the end face.

Similarly, when the holding member 80 is formed in an annular shape, the inner peripheral diameter is continuously reduced as it approaches the joint end face side with the optical waveguide 60, and the minimum inner peripheral diameter of the holding member 80 is the optical fiber 82. You may make it prepare so that it may become larger than the outer periphery diameter.
By adopting such a shape, the optical fiber 82 is held by the holding member 80, and the optical fiber 82 can be easily guided to the optical waveguide core 40 when the optical waveguide core 40 and the optical fiber 82 are optically joined. it can.

  As shown in FIG. 5C, when the optical fiber 82 is optically bonded to the optical waveguide core 40 of the optical waveguide 60, the optical waveguide direction end of the optical fiber 82 is held at the bent portion of the holding member 80, and The end surface in the optical waveguide direction is brought into contact with the end surface of the optical waveguide core 40.

  Further, the optical fiber 82 and the optical waveguide core 40 are optically bonded by inserting a photo-curing adhesive into the gap between the optical fiber 82 and the optical waveguide core 40 held by the holding member 80 and irradiating with light.

  As described above, since the optical waveguide 60 of the present invention includes the holding member 80, there is little loss of bonding light when the optical waveguide core 40 and the optical fiber 82 are optically bonded, and the connection work is simple and an expensive apparatus is required. An optical waveguide 60 can be provided.

Below, the manufacturing method of the optical waveguide by this invention is demonstrated in order of a process.
(1) Step of preparing rubber mold The production of the rubber mold in the step of preparing the rubber mold is preferably performed using a master having a convex portion corresponding to the optical waveguide core. However, the present invention is not limited to this. Absent. In the following, a method using the master will be described.

(Preparation of master)
A conventional method such as a photolithography method or an RIE method can be used without particular limitation for producing a master having a convex portion corresponding to the optical waveguide core. Further, the method (Japanese Patent Application No. 2002-10240) for producing an optical waveguide by the electrodeposition method or the photo-deposition method previously filed by the present applicant can also be applied to produce the master. The size of the convex portion corresponding to the optical waveguide core formed on the master is generally about 5 μm to 500 μm, preferably about 40 μm to 200 μm, and is appropriately determined according to the use of the optical waveguide. For example, in the case of a single mode optical waveguide, an optical waveguide core of about 10 μm square is generally used, and in the case of a multimode optical waveguide, an optical waveguide core of about 40 μm to 150 μm square is generally used. Depending on the case, an optical waveguide having a larger optical waveguide core portion of about several hundred μm is also used.

(Production of rubber mold)
As described above, the rubber mold has a composite laminated structure in which a light-cured portion is composed of a rigid substrate having a rubber layer for forming a rubber mold and a similar concave portion corresponding to a convex portion of a light-transmitting optical waveguide core. Apply or inject a rubber mold-forming curable rubber resin to the rubber surface on which the convex portions corresponding to the core are formed, and if necessary, perform a curing process such as heat treatment to cure the resin rubber. The cured rubber layer is then peeled off from the master. Further, the rubber mold has an entrance for filling the concave portion corresponding to the convex portion with the curable resin for forming the optical waveguide core, and an outlet for discharging the resin from the concave portion corresponding to the convex portion. Although formed, the formation method is not particularly limited. Protrusions corresponding to the entrance and discharge ports can be provided in advance on the master, but as a simple method, for example, after forming the rubber mold rubber layer on the master with a rubber mold forming curable rubber liquid There is a method in which the mold is peeled and the mold is taken out, and then the inlet and outlet are formed by cutting both ends of the mold so that the concave portion is exposed. By using a rubber material with a rubber hardness of 5 to 40 and a soft property, the rubber material formed by the molding master of the optical waveguide core increases the molding property of peeling after the optical waveguide core is formed by the soft rubber elasticity, We will give precise optical waveguide core forming ability. For the rubber layer, it is possible to select an appropriate value of the rubber thickness that can maintain the molding accuracy with respect to vibrations and pressure changes during the injection of the optical waveguide core material with high accuracy.

  It is also effective to provide through holes communicating with the rubber mold recess at both ends of the recess. The through-hole on the entrance side can be used as a liquid (resin) reservoir, and the through-hole on the discharge side can be connected to the vacuum suction device by inserting a vacuum suction pipe into it. Further, it is also possible to connect the curable resin liquid for forming the optical waveguide core to the injection pipe through the entrance side through hole and pressurize and inject the resin liquid. Depending on the pitch of the recesses, the through-holes may be provided corresponding to the respective recesses, or one through-hole communicating with each recess may be provided.

  The thickness of the cured rubber layer is appropriately determined in consideration of handleability as a rubber mold, but generally the thickness of the entire rubber layer is 5 μm to 5 mm, more preferably 30 μm to 700 μm. . Due to this thickness, rubber hardness (elasticity) and low surface energy, deformation and releasability at the time of peeling can be made appropriate, interface fracture from the molded optical waveguide core can be suppressed after photocuring, and the optical waveguide core can be reduced by molding the optical waveguide core. Surface smoothness can be maintained. The smoothness (Ra) is 100 nm or less, and if it is optimized, a smoothness of 40 nm or less can be achieved. This surface smoothness value can sufficiently suppress light leakage if the surface roughness is one fifth or less of the wavelength of the light used, and more preferably if the surface roughness is one tenth or less of the light wavelength. The amount of leakage is a characteristic that can be almost reduced.

  In this sense, the rubber hardness (rubber elasticity) of the rubber material, the thickness, and the surface energy value of the rubber mold are mutually related, and are important control characteristic values depending on the required molding accuracy. By satisfying these requirements, the manufacturing process is such that a waveguide can be easily and partially formed even on a substrate having an electronic device or electronic circuit in the vicinity thereof.

Further, the master may be subjected to a release treatment such as application of a release agent in advance to promote peeling from the rubber mold.
As the curable resin for forming a rubber mold, the cured product can be easily peeled from the master, has a certain level of mechanical strength and dimensional stability as a rubber mold (repeatedly used), and has a hardness that maintains a concave shape ( Hardness) and good adhesion to the clad substrate. Various additives can be added to the curable resin for forming a rubber mold as necessary.

  When the curable resin for rubber mold formation is in an uncured state, it can be applied or cast onto the surface of the master, and the projections corresponding to the individual optical waveguide cores formed on the master can be accurately copied. Therefore, it is preferable to have a certain appropriate viscosity, for example, about 500 to 7000 mPa · s. (Note that “the curable resin for forming a rubber mold” used in the present invention also includes those that become a rubber-like body having elasticity after curing.) In addition, a solvent is used to adjust the viscosity to other members. It may be added to the extent that it does not adversely affect.

  The rubber mold forming curable resin is a silicone rubber (silicone elastomer) or a silicone resin in terms of peelability, mechanical strength / dimensional stability, hardness, and adhesion to the clad substrate. An organopolysiloxane is preferably used. The curable organopolysiloxane preferably contains a methylsiloxane group, an ethylsiloxane group, or a phenylsiloxane group in the molecule. The curable organopolysiloxane may be a one-component type or a two-component type used in combination with a curing agent, and may be a thermosetting type or a room temperature curable type (for example, cured with moisture in the air). The other) (further ultraviolet curing or the like) may be used.

  The curable organopolysiloxane is preferably in a rubbery state after curing, which is usually referred to as a liquid silicone rubber (“liquid” includes those having a high viscosity such as a paste). The two-part type used in combination with a curing agent is preferable. Among them, the addition type liquid silicone rubber cures uniformly in a short time on the surface and the inside, and at that time, a by-product is formed. It is preferably used because it has no or little, excellent releasability and low shrinkage.

  Among the liquid silicone rubbers, liquid dimethylsiloxane rubber is particularly preferable from the viewpoint of adhesion, peelability, strength and hardness controllability. In addition, a cured product of liquid dimethylsiloxane rubber generally has a refractive index as low as about 1.43, so that a rubber mold made therefrom can be used as it is as a clad layer without being peeled off from the clad substrate. . In this case, it is necessary to devise such that the rubber mold, the filled optical waveguide core forming resin, and the clad substrate are not peeled off.

  The viscosity of the liquid silicone rubber is from the viewpoint of accurately copying the convex portion corresponding to the optical waveguide core and facilitating defoaming by reducing the mixing of bubbles, and from the viewpoint of forming a rubber mold having a thickness of several millimeters. , About 500 to 7000 mPa · s is preferable, and about 2000 to 5000 mPa · s is more preferable. If it is 500 mPa · s or less, the injection efficiency is too good, and it may enter between the clad substrate and the rubber interface of the rubber mold, resulting in deterioration of the shape accuracy. Moreover, even if the injection assisting means is exhausted when the pressure is 7000 mPa · s or more, the injection speed does not increase, the mold taking accuracy is hindered, and the productivity is lowered.

  Furthermore, the surface energy of the rubber surface in contact with the optical waveguide core material of the rubber mold is in the range of 7 dyn / cm to 30 dyn / cm, preferably 12 dyn / cm to 21 dyn / cm. This is preferable from the viewpoint of the penetration speed of the curable resin for forming the optical waveguide core. If it is 7 dyn / cm or less, the penetration rate of the photocured optical waveguide core material liquid into the fine mouth becomes slow, which causes a problem in productivity. If it is 30 dyn / cm or more, the surface of the cured molded product may be damaged due to adhesion of the surface when the rubber mold is peeled off, and the surface smoothness may be greatly reduced.

  The share rubber hardness of the surface rubber layer of the rubber mold is 10 to 50, preferably 15 to 30 from the viewpoint of mold taking performance, maintaining the shape of the recess, and peelability. If it is 10 or less, the mold accuracy is lowered, causing a problem in reproducibility of the shape, and if it is 50 or more, there is a case where the surface of the molded product is damaged because proper elasticity does not appear when the mold is peeled from the rubber mold.

  The rubber layer surface roughness (Ra) of the rubber mold is 0.5 μm or less, preferably 0.1 μm or less, more preferably 0.05 μm or less. Loss can be greatly reduced. The surface roughness is required to be 1/5 or less of the wavelength of the light to be used. When the surface roughness is 1/10 or less, the waveguide loss due to the surface roughness of the optical waveguide core of the light is almost negligible.

  Moreover, it is preferable that the rubber material for rubber molds and the light transmissive substrate have a light transmittance of 50% / mm or more in the ultraviolet light region and / or the visible region. In particular, it is necessary to have a light transmittance of 50% / mm or more with respect to light having a wavelength of 365 nm. More preferably, the rubber material of the 80% / mm rubber mold is light transmissive in the visible region because the rubber mold is used as a base material for cladding in the following (step of adhering the substrate with the clad layer to the rubber mold). Positioning can be easily performed, and it can be observed that the curable resin for forming the optical waveguide core is filled into the rubber mold recesses in the following step (3), so that the completion of filling can be easily confirmed. Because it is possible. In addition, it is preferable that the rubber mold is light transmissive in the ultraviolet region. When the ultraviolet curable resin is used as the curable resin for forming the optical waveguide core, the ultraviolet curing is efficiently performed through the rubber mold. Therefore, the transmittance of the rubber mold in the ultraviolet light region (350 nm to 400 nm) is preferably 50% or more.

  Liquid silicone rubber, which becomes a silicone rubber after curing, is excellent in conflicting properties such as adhesion to the clad substrate and peelability, and has the ability to copy nanostructures. Silicone rubber and clad If the substrate for adhesion is brought into close contact, even the ingress of liquid can be prevented. A rubber mold using such a silicone rubber copies the master with high accuracy and adheres well to the clad substrate. Therefore, the resin for forming the optical waveguide core is efficiently only in the recess between the rubber mold and the clad substrate. The clad base material and the rubber mold can be easily peeled off. Therefore, an optical waveguide whose shape is maintained with high accuracy can be manufactured very simply from this rubber mold.

  When the cured resin layer, especially the cured resin layer has rubber elasticity, a part of the cured resin layer, that is, a part other than the part that copies the convex portion of the master can be replaced with another rigid material. The handling property and the compatibility with the change in the injection pressure of the optical waveguide core material during injection are improved.

(2) Step of closely adhering a clad substrate to a rubber mold As a clad substrate used in the present invention, a substrate having a high ultraviolet light transmittance such as a glass substrate, a ceramic substrate, or a plastic substrate is used without limitation. It is done. In particular, a plastic substrate is preferable for processability. In addition, in the case of a base material having an appropriate refractive index, it may be left as it is. However, in order to control the refractive index, a material obtained by depositing a refractive index control resin coat or a plurality of inorganic materials on the base material by a PVD method is also used. .

The refractive index of the cladding layer must be less than 1.55, and more preferably less than 1.51. In particular, the refractive index of the cladding layer needs to be smaller than the refractive index of the optical waveguide core by 0.01 or more. This is caused by the fact that the refractive index of the core material of the trunk optical fiber is larger than 1.47. Further, as a characteristic of the clad layer, in the smoothness at the core contact surface, the surface roughness (Ra) is 0.1 μm or less, and more preferably 0.07 μm or less, the connection light loss can be reduced. .
In addition, it is preferable to have excellent adhesion to a rubber mold, and when both are brought into close contact with each other, no void is formed except for the rubber mold recess. In addition, when the clad substrate is not very good in adhesion to the rubber mold and / or the optical waveguide core, the adhesion to the rubber mold or the like is performed by treatment with an ozone atmosphere or ultraviolet irradiation treatment with a wavelength of 300 nm or less. It is preferable to improve.

  Among plastic substrates, optical waveguides using flexible film substrates can be used as couplers, optical wiring between boards, optical demultiplexers, and the like. The film base material has optical properties such as refractive index, light transmittance, mechanical strength, surface smoothness, heat resistance, adhesion to a rubber mold, flexibility depending on the use of the optical waveguide to be produced. (Flexibility) and the like are selected.

Examples of the material for the film base include acrylic resins (polymethyl methacrylate, etc.), alicyclic acrylic resins, styrene resins (polystyrene, acrylonitrile / styrene copolymers, etc.), olefin resins (polyethylene, polypropylene, ethylene Propylene copolymer, etc.), alicyclic olefin resin, vinyl chloride resin, vinylidene chloride resin, vinyl alcohol resin, vinyl butyral resin, arylate resin, fluorine-containing resin, polyester resin (polyethylene terephthalate, polyethylene naphthalate) Phthalate, etc.), polycarbonate resin, cellulose di- or triacetate, amide resin (aliphatic, aromatic polyamide, etc.), imide resin, sulfone resin, polyether sulfone resin, polyether ether ketone resin, polyphenyle Sulfide resins, polyoxymethylene-based resin or a blend of the resin, and the like.
As the alicyclic acrylic resin, OZ-1000, OZ-1100 (manufactured by Hitachi Chemical Co., Ltd.) or the like in which an aliphatic cyclic hydrocarbon such as tricyclodecane is introduced into an ester substituent is used.

  The alicyclic olefin resins include those having a norbornene structure in the main chain, and those having a norbornene structure in the main chain and an alkyloxycarbonyl group in the side chain (alkyl groups having 1 to 6 carbon atoms or cycloalkyl). And those having a polar group such as a group). Among them, an alicyclic olefin resin having a norbornene structure in the main chain and a polar group such as an alkyloxycarbonyl group in the side chain as described above has a low refractive index (refractive index is around 1.50, and is an optical waveguide core. The optical waveguide according to the present invention has excellent optical characteristics such as a high refractive index and a high optical transparency, excellent adhesion to a rubber mold, and excellent heat resistance. Suitable for making.

The thickness of the film base material is appropriately selected in consideration of flexibility, rigidity, ease of handling, etc., and is generally preferably about 0.03 mm to 0.5 mm.
The smoothness of the film substrate surface needs to be Ra 10 μm or less, more preferably 1 μm or less, and still more preferably 0.1 μm or less. When the smoothness of the surface of the film substrate is Ra 10 μm or more, the shape forming accuracy of the optical waveguide core waveguide to be formed is lowered and the propagation loss of light is increased, which makes it difficult to use. Even when an undercoat layer is provided, if the smoothness of the surface of the film substrate is Ra 10 μm or more, the undercoat layer often has a large problem in film properties and smoothness.

  The conductive pattern is formed by coating a conductive layer on the entire surface or part of the clad base material on the optical waveguide non-forming portion, PVD method, or foil adhesion method. Etching method, laser heating scanning method, electric discharge machining method, etc.). As an electronic circuit conductive layer, one layer or a composite thin film layer such as a metal such as chromium, copper, aluminum, gold, molybdenum, nickel, silver, platinum, iron, titanium, zinc, tungsten, bell, or an alloy containing such a metal. In addition, a conductive metal compound, a thin film obtained by adding a conductive fine powder such as carbon black to a polymer material, or the like is used. In particular, the conductive pattern of the electronic circuit is gold, copper, aluminum, molybdenum, nickel that is suitable for wire bonding and flip chip mounting to enable mounting of electrical continuity with each electronic device and light control device. And their alloys are particularly good.

The thickness of the conductive layer is suitably about 0.05 μm to 30 μm. More preferably, a thickness of 0.2 μm to 2 μm is appropriate.
The conductive pattern is preferably provided on the non-formation surface of the optical waveguide core of the clad substrate, and can be laminated.

(3) The step of filling the concave portion of the rubber mold with the clad base material in close contact with the curable resin for forming the optical waveguide core In order to fill the concave portion of the rubber mold with the curable resin for forming the core, the rubber mold is filled with the rubber mold. A slightly larger size of the clad film is brought into close contact, and a small amount of core-forming curable resin is dripped into the entrance of the recess to fill it using the capillary phenomenon, or the core-forming curable resin is pressure-filled into the recess. The discharge port of the concave portion can be filled by vacuum suction or by performing both pressure filling and vacuum suction. As described above, when the through hole is provided at the end of the recess, the entrance side through hole can be filled with resin and filled with pressure, or a vacuum suction tube can be inserted into the discharge side through hole to perform vacuum suction.

  In addition, when the pressure filling and the vacuum suction are used in combination, it is more preferable to synchronize them, and the pressure is increased stepwise in the pressure filling and the pressure is reduced stepwise in the vacuum suction. However, it is preferable from the viewpoint of reciprocal law in which the curable resin for forming an optical waveguide core is injected at a higher speed while the rubber mold is stably fixed.

  The pressure filling and / or vacuum suction is preferably performed at a static pressure. By performing with static pressure, pulsation can be prevented. The static pressure can be expressed by providing a space in the middle of the pressure filling and / or decompression suction device and the entry part or the discharge part, or by using a height difference in the case of pressure filling. it can.

  As the curable resin for forming the optical waveguide core, resins such as radiation curable, electron beam curable, and thermosetting can be used, and among them, ultraviolet curable resins and thermosetting resins are preferably used. In particular, high-temperature processes in substrates with a mixture of electronic components and elements, optical components and elements often affect the performance degradation and durability of the components. Since it is only an injection process at room temperature, it is possible to perform an additional process after manufacturing an electronic circuit or an optical circuit in order to perform all processes, particularly a mold-making process, at room temperature or under 120 ° C. Does not adversely affect circuit board performance.

  As the ultraviolet curable resin or thermosetting resin for forming the optical waveguide core, an ultraviolet curable or thermosetting monomer, an oligomer, or a mixture of a monomer and an oligomer is preferably used. In particular, the mixing of the oligomer helps the curing speed and improves the accuracy of the shape.

In addition, an epoxy-based, polyimide-based, or acrylic-based ultraviolet curable resin is preferably used as the ultraviolet curable resin.
The curable resin for forming the optical waveguide core is filled in the gap formed between the rubber mold and the film base (the concave portion of the rubber mold), so that the curable resin for forming the optical waveguide core can be used. It is necessary to have a sufficiently low viscosity. The uncured viscosity of the curable resin is 50 mPa · s to 2000 mPa · s, desirably 100 mPa · s to 1000 mPa · s, more preferably 300 mPa · s to 700 mPa · s. This is preferable from the viewpoint of good core shape and low optical loss. If it is less than 50 mPa · s, it may get into unnecessary gaps between the rubber mold and the substrate with the clad layer, resulting in moldability and shape variation, and the characteristics may be impaired. Decreases.

  Further, in order to reproduce the original shape of the convex portion corresponding to the optical waveguide core formed on the master with high accuracy, it is necessary that the volume change before and after curing of the curable resin is small. For example, a decrease in volume causes a large waveguide loss. Therefore, the curable resin desirably has a volume change as small as possible, and is desirably 10% or less, preferably 0.01% to 4%. Lowering the viscosity using a solvent is preferably avoided if possible because the volume change before and after curing is large. In particular, a material system with a volume of 0.01% or less or volume expansion reduces the peeling efficiency from the rubber mold and causes surface degradation such as surface breakage when peeling from the rubber mold, resulting in reduced surface smoothness and optical waveguide. Loss increases, which is not preferable.

  In order to reduce the volume change (shrinkage) after curing of the curable resin for forming an optical waveguide core, a polymer can be added to the curable resin. The polymer is preferably compatible with the curable resin for forming the optical waveguide core and does not adversely affect the refractive index, elastic modulus, and transmission characteristics of the resin. In addition to reducing the volume change by adding a polymer, the viscosity and the glass transition point of the cured resin can be highly controlled. Examples of the polymer include acrylic, methacrylic acid, and epoxy polymers, but are not limited thereto.

  The refractive index of the cured product of the curable resin for forming the optical waveguide core is preferably in the range of 1.20 to 1.60, more preferably in the range of 1.4 to 1.6, and the refractive index of the cured product is within the above range. In some cases, two or more types of resins having different refractive indexes are used.

Further, in this step, it is desirable to reduce the pressure of the entire system (about 0.1 Pa to 200 Pa) in order to promote the filling of the curable resin for forming the optical waveguide core into the rubber mold recess due to the capillary phenomenon.
In order to further promote the filling, it is also effective means to lower the viscosity by heating the curable resin for forming the optical waveguide core filled from the entrance of the rubber mold in addition to the pressure reduction of the system. It is.

(4) Step of curing the filled optical waveguide core forming curable resin to form the optical waveguide core The cured optical waveguide core forming curable resin is cured. In order to cure the ultraviolet curable resin, an ultraviolet lamp, an ultraviolet LED, a UV irradiation device or the like is used. In order to cure the thermosetting resin, means for accelerating curing such as heating in an oven is also effective. As described above, the temperature condition at the time of curing is preferably a room temperature condition near room temperature or 120 ° C. or less.

(5) Step of peeling the rubber mold from the clad base material After the step of curing the optical waveguide core forming curable resin, the rubber mold is peeled from the clad base material. Further, the rubber mold used in the steps (1) to (3) can be used as it is for the cladding layer as long as the conditions such as the refractive index are satisfied. Use as a layer. In this case, the rubber mold is preferably subjected to ozone treatment in order to improve the adhesion between the rubber mold and the optical waveguide core material.

(6) Step of forming a clad layer on the clad substrate on which the optical waveguide core is formed A clad layer is formed on a film substrate on which the optical waveguide core is formed. For example, the clad base material used in the step 2) is used in the same manner), a layer cured by applying a curable resin for clad, a solvent solution of a polymer material is applied and dried. Examples thereof include a polymer film obtained.

  As the curable resin for cladding, an ultraviolet curable resin or a thermosetting resin is preferably used. For example, an ultraviolet curable or thermosetting monomer, an oligomer, or a mixture of a monomer and an oligomer is used.

  In order to reduce the volume change (shrinkage) after curing of the curable resin for forming a clad, the polymer has compatibility with the resin and does not adversely affect the refractive index, elastic modulus and transmission characteristics of the resin (for example, Methacrylic acid or epoxy) can be added to the resin.

  When a film is used as the clad layer, it is bonded using an adhesive. At this time, it is desirable to select a material whose refractive index is close to that of the film. As the adhesive to be used, an ultraviolet curable resin is preferably used. For example, an ultraviolet curable monomer, an oligomer, or a mixture of a monomer and an oligomer is used. Thereby, a clad layer having a refractive index is formed.

In order to reduce the volume change (shrinkage) after curing of the ultraviolet curable resin, a polymer similar to the polymer added to the cladding layer can be added. A photo-curing material is most suitable because a photo-curing resin has a smaller volume change at the time of curing and thus has higher accuracy.
The difference in refractive index between the clad substrate and the clad layer is preferably small, and the difference is within 0.1, preferably within 0.05, more preferably within 0.001, and most preferably no difference. This is preferable from the viewpoint of light confinement.

  In the method for producing an optical waveguide according to the present invention, in particular, a liquid silicone resin that is cured as a curable resin for forming a rubber mold and becomes a rubbery state, in particular, a liquid dimethylsiloxane solution, and a norbornene structure as a base material for cladding is used as a main chain. The combination using an alicyclic olefin resin having a side chain and a polar group such as an alkyloxycarbonyl group has particularly high adhesion between the two, there is no deformation of the rubber mold concave structure, and the concave structure is not broken. Even if the area is very small (for example, a rectangle of 10 μm × 10 μm), the concave portion can be quickly filled with the curable resin.

  In the method for producing an optical waveguide of the present invention, it is preferable that the cured resin layer is reinforced with a reinforcing member in the step of preparing the rubber mold shown in (1) above. Further, the reinforcing member is provided with an injection port (see 24b indicated by an imaginary line in FIG. 10A) for press-fitting the curable resin for forming the optical waveguide core. An injection tube is inserted and connected to the inlet. It is preferable to provide a plurality of injection ports so that the pressurized state is uniform at the entry portion (filling port) of each recess. Further, an exhaust port (see FIG. 5) on the side opposite to the injection port of the reinforcing member (the side on which the optical waveguide core resin is discharged from the concave portion of the rubber mold) so that the filling speed can be further increased by reducing the pressure inside the rubber mold. 10 (A) 24c shown by the phantom line) is provided, and a vacuum deaeration tube is inserted and connected to the concave discharge side so as to be vacuum suctioned. It is preferable to provide a plurality of exhaust ports so that the decompressed state is not biased on the discharge side of the rubber mold recess.

  As described above, in order to increase the filling speed, the curable resin for forming the optical waveguide core is pressurized and filled from the entrance portion of the rubber mold, or if the discharge side of the concave portion of the rubber mold is sucked under reduced pressure, Even when a pressure change occurs, by providing a reinforcing member, displacement between the rubber mold and the clad substrate may occur, or vibration may occur in the entire or part of the rubber mold and the rubber mold may be deformed. Further, it is possible to prevent the adhesion with the clad substrate from being impaired, and the filling speed can be increased without sacrificing the accuracy of the optical waveguide core shape.

A case where a rubber mold provided with a reinforcing member is used will be described with reference to the drawings. FIG. 7A shows a perspective view in which a rubber mold provided with a reinforcing member 24 is closely attached to a clad substrate 30. In FIG. 7A, reference numeral 24 denotes a reinforcing member, and a rubber mold recess forming region (an irradiation region such as ultraviolet rays) has a structure in which the reinforcing member is cut out. Reference numerals 26a and 26b denote injection pipes, reference numerals 28a and 28b denote vacuum deaeration pipes, respectively, and reference numeral 90 denotes both of the reinforcing member 24 and the clad base material 30 so as not to cause a slight displacement. It is a screw for fixing. Reference numeral 20 a denotes a cured resin layer of a rubber mold, and this portion is not covered with the reinforcing member 24.
FIG. 7B is a cross-sectional view taken along the line AA in FIG. 7A, and 22 indicates a rubber mold recess.

  8 (A) and 8 (B) show an example using a rubber mold having a reinforcing member similar to that in FIG. 7, and the clad base material is placed so that the clad base material and the rubber mold are not positioned. A holding member 92 having a holding portion (concave portion) to be held is used, which is also effective particularly when a flexible film is used as a clad substrate. Further, in this example, a light-transmitting substrate 24a such as a quartz plate, a glass plate, or a hard plastic plate is used for a rubber mold recess forming region (irradiation region such as ultraviolet rays), and a shape similar to the recess of the optical waveguide core in advance. Then, a groove portion having a shape slightly larger than the shape of the optical waveguide core is molded, and a rubber mold portion of a rubber material is produced along the groove using a master of the optical waveguide core. This makes it possible to eliminate the instability of the rubber mold due to vibrations and deformations due to the concave portion of the rigid body close to the elastic characteristics, which is a drawback of the rubber material, and to obtain highly accurate molding performance.

The aspect of the rubber mold provided with the reinforcing member is not limited to the above.
For example, as shown in FIGS. 9A and 9B, a fitting groove (not shown) for fixing the rubber mold to the holding member 92 is provided, and the fitting groove is provided in the reinforcing member of the rubber mold. It is also possible to provide a fitting member (not shown) having a shape that fits into the fitting groove 29 and fit the fitting member 29 into the fitting groove 93 to be fixed.

The reinforcing member is made of a metal material, a ceramic material, a hard plastic material, or a composite material thereof, and a thickness of about 1 mm to 40 mm is appropriate.
In the method for manufacturing the optical waveguide 60 of the present invention, in order to increase the filling speed as described above, the curable resin for forming the optical waveguide core is pressurized and filled from the entrance of the rubber mold, or in addition, the rubber mold recess is discharged. When vacuuming is performed on the side, if a pressure change occurs under pressure or reduced pressure, the rubber mold and the clad base material will be displaced, or vibration will occur in the whole or part of the rubber mold, causing the rubber mold to deform. Or the adhesion to the clad substrate may be impaired. However, the provision of the reinforcing member eliminates the problems as described above, and the filling speed can be increased without sacrificing the accuracy of the optical waveguide core shape.

  When a plurality of optical waveguide cores are formed on a clad substrate, it is preferable to provide a gap for pressure relaxation in the cured resin layer of the rubber mold provided with the reinforcing member as described above. The void portion means a common space that communicates with all the entrance portions of the entrance portion (filling port of the curable resin for forming the optical waveguide core) at one end portion of the plurality of recesses of the rubber mold. Moreover, it is preferable to provide the space | gap part connected to all the discharge parts of the discharge part in the other end part of the several recessed part of a rubber mold in addition to the said space | gap. By providing the gap portion in the entry portion, the injection pressure does not act directly on the entry portion, and the injection pressure for each entry portion is relaxed and made uniform. Further, by providing the discharge part gap, the suction negative pressure can be relaxed and made uniform, and the injection of the resin into each recess of the rubber mold is made uniform.

Next, the process of introducing an optical element into the intermediate waveguide portion of the manufactured optical waveguide 60 will be described with reference to FIGS.
FIG. 11 is a schematic diagram illustrating an example of mounting an optical element on an optical waveguide. In this example, a planar optical element has a bottom surface (the widest surface) in a space formed by cutting the optical waveguide core 62. Inserted. 11A shows the manufactured waveguide substrate (in the state where the optical waveguide core portion 62 is sandwiched between the clad portions 64, the same applies hereinafter), and FIG. 11B shows the space 66 formed in the waveguide substrate 61. 11C is a perspective view showing a state in which the optical waveguide 60 in which the space 66 is formed and the rigid substrate 70 are bonded, and FIG. 11D is a perspective view showing a state in which the optical element 80 is fitted in the space 66. .

  FIG. 12 is a schematic view showing another example of mounting the optical element on the optical waveguide. In this example, the plate-like optical element faces the side of the groove formed by cutting the optical waveguide core 62. Inserted. 12A shows a waveguide substrate installed on the substrate, FIG. 12B shows a state in which grooves are formed in the waveguide substrate 61, and FIG. 12C shows an optical waveguide 60 in which grooves 68 are formed. FIG. 12D is a perspective view showing the state in which the optical element 80 is fitted in the groove 68.

  11 and 12 show an example in which the optical element 80 is inserted into one optical waveguide core part 62. In the present invention, a plurality of optical waveguide core parts are provided for one optical element. May be present. Further, the shape of the optical waveguide core portion may be not only a linear shape but also a curved shape (curvature radius of 1 mm or more).

The process of introducing the optical element into the waveguide middle portion of the optical waveguide will be described.
<Process for producing space or groove for installing optical element>
In the optical waveguide completed as described above, an optical waveguide core part as a waveguide is formed on a film or a rigid substrate as a cladding base material, and further on the cladding base material so as to cover the optical waveguide core part. An upper cladding layer is formed. In this step, in order to insert an optical element in the middle of the optical waveguide, a space or a groove is formed so as to cut the optical waveguide core portion in the intermediate portion in the waveguide direction of the optical waveguide core portion.

  Here, for example, as shown in FIG. 11 (D), the above-mentioned space refers to one side of the waveguide substrate 61 so that the planar optical element 80 can be inserted in the middle of the optical waveguide core 62 in a flat position. This refers to a punched portion produced in a wide area so as to cut the optical waveguide core portion 62 from. Further, the groove is, for example, as shown in FIG. 12D, so that a plate-like optical element can be inserted in the middle of the optical waveguide core portion 62 with its side face directed, A cutting portion that is manufactured in a small area so as to cut the optical waveguide core portion 62 from the above. Unlike the space 66, the groove 68 may reach the end in the direction intersecting the waveguide direction of the optical waveguide 60.

  It should be noted that both the space and the groove need only be produced so as to cut the optical waveguide core portion 62, and do not necessarily need to be produced so as to penetrate the waveguide substrate 61. However, as will be described later, in particular, when the space 66 is formed and the planar optical element 80 or the like is inserted into this space, from the viewpoint of ensuring the alignment accuracy between the optical waveguide core portion 62 and the optical element 80. It is preferable to produce so that it may penetrate.

  In order to form the intermediate space or groove of the optical waveguide core 62 so as to cut the optical waveguide core 62, a punching method (a method using a die punching, a Thomson blade, a push cutting blade or the like) or a cutting method (laser beam) is used. Scanning, precision needle scanning, etc.), and further, cutting methods (methods using dry etching, wet etching, machining, etc.) can be used. Among these, in particular, the method of producing a cutting groove by using a dicer device for cutting a wafer can obtain the optical surface accuracy of the end waveguide surface (the surface roughness Ra is Ra <100 nm). preferable.

  In the present invention, it is preferable that the size is slightly larger than the optical element 80 in which the space 66 or the groove 68 is provided. The reason for this is that when an optical element 80 is inserted as will be described later, if an air layer exists between the cut end portion of the optical waveguide core portion 62 and the optical element optical path portion, the optical loss increases. This is because it is preferable to fill the optical adhesive.

  Specifically, it is preferable to create a space 66 or a groove 68 having a length in the waveguide direction that is 3 μm to 5 mm longer than the length in the waveguide direction of the optical element 80 to be installed, and in the waveguide direction that is 20 μm to 1 mm longer. More preferably, the space 66 or the groove 68 having a length is formed. If it is less than 3 μm, not only is it difficult to fit the optical element 80, but it may also be difficult to fill the optical adhesive. If it exceeds 5 mm, the optical loss may increase even if the optical adhesive is filled.

  In the present invention, in the step of creating the space or groove, as shown in FIG. 11B, the space or groove is formed so as to penetrate to the clad substrate, and the optical element is inserted before inserting the optical element. As shown in (C), it is preferable to adhere a rigid substrate 70 as a base material to the surface of the waveguide substrate 61 opposite to the surface on which the optical waveguide core portion 62 of the clad base material is formed. By providing the base material in this manner and installing the optical element thereon (FIG. 11D), the position in the height direction (the thickness direction of the waveguide substrate) between the optical waveguide core part 62 and the optical element optical path part. The alignment can be performed with high accuracy.

  The material of the rigid base material 70 is not particularly limited, such as glass, metal, and ceramic, but the arithmetic average roughness Ra of the surface is preferably in the range of 20 nm to 2 μm, and in the range of 0.1 to 0.5 μm. More preferably. If Ra exceeds 2 μm, sufficient surface accuracy may not be obtained even if a base material is provided. In addition, it is difficult for a surface where Ra is less than 20 nm to be expensive in practice.

  On the other hand, as shown in FIG. 11B, in the case where a groove is formed with a certain angle θ with respect to the waveguide substrate 61 using a dicer blade 65 or the like, the cladding substrate constituting the waveguide substrate 61 is particularly configured. In order to fix and stabilize the waveguide substrate 61 itself when the material is a film or the like, a support body 75 may be provided on the waveguide substrate 61 from the beginning as shown in FIG.

<Step of inserting and positioning an optical element>
In this step, an optical element to be installed is prepared, and the optical element is inserted and positioned in the produced space or groove. In the present invention, since the optical waveguide is a polymer, the end surface of the optical waveguide core section cut at the time of producing the space can be used as it is as an optical end surface with little connection loss. In addition, in the case of an optical waveguide made of a normal hard inorganic material, it is difficult to insert because the optical element to be inserted is also hard, but in the case of an optical waveguide, the waveguide is somewhat elastic so that it can be inserted easily. can do.

  In this case, when the optical element is inserted into the produced space or groove, the optical element is positioned so that the maximum gap width between the optical path portion of the optical element and the end surface of the cut optical waveguide core portion is 0.4 mm or less. It is preferable to set it to 0.15 mm or less.

The maximum gap width refers to a length at which the optical path portion and the end face of the optical waveguide core portion are located farthest when an optical element is installed in a space or a groove. If the maximum gap width exceeds 0.4 mm, the optical loss may increase even if an optical adhesive is filled in the gap as described later.
The deviation width in the height direction between the optical waveguide core portion and the optical element optical path portion is preferably within ± 10% of the optical waveguide core diameter.

  Examples of the optical elements used in the present invention include active optical elements such as optical switches, optical filters, optical reflectors, diffraction gratings, and passive optical elements such as optical lenses. Among these, optical filters and optical lenses Any one or more of an optical mirror, an optical switch, a light emitting element, and a light receiving element are preferably used.

  In addition, it is preferable to use an element mounting substrate when inserting the optical element from the viewpoint of supporting the inserted optical element and increasing positioning accuracy. As the element mounting substrate, a quartz substrate, a silicon wafer, a highly smooth film, or the like can be used.

<The process of optically joining the optical path portion of the optical element and the optical waveguide core portion>
This step is a step of optically joining the optical path portion of the inserted optical element and the optical waveguide core portion. The optical joining can be performed with the optical element inserted, but it is preferable to fix the optical element positioned by any method in order to prevent displacement. In the state where the optical element is inserted, the gap between the optical element and the optical waveguide core part is an air layer, so that the difference in refractive index between the optical waveguide core part and the optical loss is large. Therefore, in the present invention, the difference in refractive index from the optical waveguide core portion is within ± 0.2, more preferably ± 0, in a minute space between the optical path portion of the optical element inserted and installed and the optical waveguide core portion. It is preferable to fill the optical adhesive having a refractive index within 0.05.

In particular, in the present invention, the optical waveguide core is an organic type made of a polymer material, and the optical adhesive usually used is also an organic type. Therefore, the compatibility is good when the two are brought into close contact with each other, and the refractive index difference is small. Therefore, the optical loss when optically bonded can be reduced as compared with the case of an inorganic optical waveguide core. Moreover, since the organic type has similar expansion / contraction characteristics due to heat, the mechanical strength of the joint can be increased.
The refractive index difference is more preferably within ± 0.1, further preferably within ± 0.03, and particularly preferably within ± 0.01.

  Further, as the optical adhesive, it is necessary to use a material having a refractive index difference within ± 0.1 with respect to the optical waveguide core portion and having a light transmittance of 90% / mm or more in the used wavelength region. Most preferable for reducing optical loss.

  The optical adhesive may be any of photocuring and thermosetting (including room temperature curing), and is an adhesive such as organic solvent dispersibility and organic solvent solubility. It is preferable that the filled portion can be solidified by heat treatment, drying, or the like. In particular, the use of a photo-curing adhesive that is processed near room temperature during curing is effective in terms of bonding dimension accuracy. As a result, optical connection can be made, loss of optical characteristics can be reduced, and stable optical performance can be obtained. Also, the mechanical strength can be expressed as the adhesive is solidified.

  The optical adhesive is preferably an epoxy, polyimide, acrylic ultraviolet curable resin, thermosetting resin, or the like similar to the curable resin for forming an optical waveguide core.

  Through the processes described above, it is possible to mount optical elements with functionality easily and inexpensively on the optical waveguide, and it is possible to mount optical modules, optical interconnections, optical circuit boards, media converters, opto-networks. Units and the like can be provided on a single board at low cost.

(7) The step of cutting the end portion of the optical waveguide core In the optical waveguide of the present invention, the optical waveguide core end of the optical waveguide core is cut to the optical waveguide end portion so that the optical waveguide core has an optical waveguide direction end portion. An end face is formed.
As a method for cutting the end portion of the optical waveguide core, a cutting method (a method using laser beam scanning, precision needle scanning, etc.), a cutting method (a method using dry etching, wet etching, machining, or the like) can be used. . Among these, in particular, the method of producing a cutting groove by using a dicer device for cutting a wafer can obtain the optical surface accuracy of the end waveguide surface (the surface roughness Ra is Ra <100 nm). preferable.

(8) A holding member capable of holding the optical fiber so that the optical waveguide direction end of the optical fiber to be optically bonded to the end surface of the optical waveguide core and the optical waveguide direction end of the optical waveguide core are at least coaxial. Steps provided on the end face of the optical waveguide main body in the optical waveguide direction As the holding member of the present invention, a material having a characteristic that enables high-precision molding such as a polymer material, a ceramic material, and a metal material is used without limitation. In particular, it is preferable to use a polymer material from the viewpoint of cost and molding accuracy.

  The method of providing the holding member on the end face of the optical waveguide in the direction of the optical waveguide is a photocurable adhesive, a thermosetting adhesive, a two-component mixed adhesive, a diluting solvent adhesive, a hydrolytic adhesive, and a hot melt adhesive. The holding member is attached to the optical waveguide so that the optical fiber can be held at least coaxially with the optical waveguide end of the optical fiber to be optically joined and the optical waveguide core end of the optical waveguide core. Adhere to the end face in the optical waveguide direction

  The position for providing the holding member so that the optical fiber can be held so as to be coaxial with the optical waveguide direction end of the optical fiber to be optically joined and the optical waveguide direction end of the optical waveguide core is an optical alignment center. Can be determined by the device. In addition, as a method for confirming the installation so as to be coaxial, the accuracy can be confirmed by optical propagation evaluation.

  The holding member used in this step is selected such that the inner wall (inner circumference) of the holding member has a shape along the outer circumference of the optical fiber to be optically bonded to the optical waveguide core.

(9) The step of optically bonding the end face of the optical waveguide core and the optical fiber held by the holding member with a photocurable adhesive material In this step, an optical fiber to be optically bonded to the optical waveguide core is prepared. The optical fiber is inserted into the bent portion or hole of the holding member provided on the end face of the optical waveguide in the optical waveguide direction by the step (8).

In the present invention, in the step (7), the optical waveguide core is cut so that the optical waveguide end face of the optical waveguide core is the optical end face. Therefore, the end face of the optical waveguide core cut in the cutting step is As it is, it can be used as an optical end face with little connection loss.
Further, by using a polymer as the optical waveguide core, the end face of the optical waveguide core cut during the cutting step can be used as it is as an optical end face with little connection loss. That is, it can be said that the holding member as in the present invention is suitable for use in a polymer optical waveguide using a polymer as an optical waveguide core.

  When the optical fiber is held by the holding member, the optical fiber is held by the holding member so that the maximum gap width between the optical waveguide end face (core end face) of the optical fiber and the optical end face of the optical waveguide core of the optical waveguide is 0.4 mm or less. It is preferable to hold, and it is more preferable to hold it to be 0.15 mm or less.

  Here, the maximum gap width indicates a length at which the optical waveguide end face of the optical fiber and the optical end face of the optical waveguide core are at a maximum allowable position when the optical fiber is held on the holding member. If the maximum gap width exceeds 0.4 mm, the bonding loss may increase even if the gap is filled with an optical adhesive as described later.

  The optical fiber held by this holding member and the optical end face of the optical waveguide core are -7 of the refractive index of the optical waveguide core in the gap between the optical waveguide end face of the optical fiber and the optical end face of the optical waveguide core of the optical waveguide. % Of the refractive index within the range of + 10% or less, more preferably −3% or more and + 5% or less, and still more preferably a photocurable adhesive having a refractive index within the range of −2% or more and + 3% or less. To do.

  In particular, in the present invention, the optical waveguide core is an organic type made of a polymer material, and the optical adhesive usually used is also an organic type. Therefore, the compatibility is good when the two are brought into close contact with each other, and the refractive index difference is small. Therefore, the optical loss when optically bonded can be reduced as compared with the case of an inorganic optical waveguide core. Moreover, since the organic type has similar expansion / contraction characteristics due to heat, the mechanical strength of the joint can be increased.

  As such a photo-curing type adhesive, it is an adhesive having organic solvent dispersibility, organic solvent solubility, etc., which can solidify the filled part by light irradiation, heat treatment, drying, etc. after filling. It is preferable that In particular, the use of a photo-curing adhesive that is processed near room temperature during curing is effective in terms of bonding dimension accuracy. As a result, optical connection can be made, loss of optical characteristics can be reduced, and stable optical performance can be obtained. Also, the mechanical strength can be expressed as the adhesive is solidified.

As the photocurable adhesive, an epoxy-based, polyimide-based, acrylic-based ultraviolet curable resin, thermosetting resin, or the like similar to the curable resin for forming an optical waveguide core is preferably used.
As the ultraviolet curable resin or thermosetting resin for forming the optical waveguide core, an ultraviolet curable or thermosetting monomer, an oligomer, or a mixture of a monomer and an oligomer is preferably used. In particular, the mixing of oligomers can aid in the speed of curing and help improve shape accuracy.

In addition, an epoxy-based, polyimide-based, or acrylic-based ultraviolet curable resin is preferably used as the ultraviolet curable resin.
This photo-curing adhesive is filled in the gap formed between the optical fiber and the optical waveguide core, so that the viscosity when uncured is 30 mPa · s to 1000 mPa · s in consideration of insertion into a narrow gap. Desirably, it is preferably 100 mPa · s to 500 mPa · s, more preferably 150 mPa · s to 350 mPa · s.
If it is less than 30 mPa · s, there is a problem that the adhesive agent leaks from the adhesion gap and does not stay in the necessary part. If it is more than 1000 mPa · s, there is a problem that it takes a long time for the liquid to enter the narrow gap.

  In addition, the photo-curing adhesive filled in the gap formed between the optical fiber and the optical waveguide core has a transmission loss of 1 dB for light in the wavelength range of 500 nm to 900 nm from the viewpoint of propagation loss characteristics of the transmitted light. What has the following characteristics is preferable. As the photocurable adhesive having such characteristics, for example, an epoxy UV adhesive, an acrylic UV adhesive, a polyimide UV adhesive, a silicone UV adhesive, or the like can be used.

  In this step, after filling the gap between the optical fiber held by the holding member and the optical waveguide core with the photocurable adhesive as described above, the adhesive is cured to obtain the optical fiber and the optical waveguide. It is possible to provide an optical waveguide that can easily perform optical joining with a core and reduce optical loss.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

<Production of rubber mold>
Five ridges (width: 50 μm, height: 50 μm, pitch: 250 μm, length: 50 mm) made of an ultraviolet curable polymer material having a square cross section were formed on a quartz substrate by a photolithography process, and an optical waveguide core master was produced. .
Reinforcement member (made of aluminum with a thickness of 1.5 mm) that is provided with an opening that transmits ultraviolet rays and that has three inlets and three exhaust ports, is similar to a 2 mm-thick quartz transparent rigid substrate Concave portions (width: 100 μm, height: 100 μm, pitch: 500 μm, length: 50 mm, 5 pieces) were formed on a transparent rigid substrate by a photolithography process and a hydrofluoric acid etching process, and integrated with a reinforcing member. Next, this reinforcing member was placed on the core master.

  Next, a mixture of a thermosetting liquid dimethylsiloxane rubber (manufactured by Dow Corning Asia Co., Ltd .: SYLGARD 184, viscosity 1000 mPa · s) and its curing agent is poured from the opening of the reinforcing member and heated at 130 ° C. for 20 minutes to rubber. The material was cured. The physical properties of the rubber material at this time were rubber hardness: 20, surface energy: 0.00018 N / cm, and average rubber thickness: 200 μm.

  After the rubber material is cured, the cured rubber, a transparent rigid substrate and a reinforcing member, which are integrated, are peeled off from the master, and have a recess corresponding to the protrusion corresponding to the optical waveguide core. A rubber mold was produced in which an inlet for filling the resin and an outlet for discharging the resin from the recess were formed.

<Formation of optical waveguide core and cladding layer>
The rubber mold was pressed and adhered to Arton film (JSR Co., Ltd., refractive index 1.51). An injection pipe and a vacuum deaeration pipe were connected to each inlet and each outlet of the rubber mold reinforcing member. An ultraviolet curable resin (manufactured by JSR: epoxy-based UV curable adhesive) having a viscosity of 1100 mPa · s was injected from the pressure injection tube into the concave portion of the rubber mold through a pressure adjustment controller at a pressure of 20 kPa. Further, at the discharge port of the rubber mold, a vacuum suction of −50 kPa by static pressure was performed using a diaphragm suction pump (maximum suction pressure: −3500 kPa) through a vacuum deaeration pipe. In 40 seconds from the start of vacuum suction, the rubber mold recess was filled with the ultraviolet curable resin.

Next, the pressure injection tube and the vacuum deaeration tube are removed from the rubber mold, and the core-forming curable resin is cured by irradiation with UV light having a light intensity of 50 mW / cm ² from the exposure opening of the rubber mold for 10 minutes. It was. When the rubber mold was peeled off, an optical waveguide core having a refractive index of 1.54 was formed on the ARTON film.

  Furthermore, the UV curable resin (manufactured by JSR Co., Ltd .: acrylic UV curable adhesive) whose refractive index after curing is 1.51, the same as that of ARTON film, is applied to the entire surface of the ARTON film on which the optical waveguide core is formed. After that, UV light having a light intensity of 50 mW / cm 2 was irradiated for 10 minutes to be cured by ultraviolet rays (film thickness after curing: 20 μm). By these steps, a flexible optical waveguide was obtained. The average waveguide loss of this optical waveguide was 0.12 dB / cm.

  Next, with respect to the produced polymer waveguide, the length of the optical waveguide core of the optical waveguide is set so as to cross the optical waveguide core with respect to the optical waveguide direction by using a dicer apparatus equipped with a 0.5 mm thick dicer blade. The optical end face was formed by cutting at an angle of 90 degrees with respect to the direction.

  next. An arc-shaped holding member having an inner diameter of a connection end face of 130 μm and an outer diameter of 300 μm on an end face in the optical waveguide direction of the optical waveguide, the inner diameter of the end face facing the connection end face being 400 μm and an outer diameter of 800 μm, the optical waveguide direction A holding member having a length of 1 mm (distance between the connection end surface and the end surface facing the connection end surface) was bonded using a UV curable epoxy adhesive.

  The holding member is bonded to a position where the optical fiber can be held so that the connecting end of the optical fiber and the connecting end of the optical waveguide core are coaxial when the holding member holds the optical fiber. This position adjustment is prepared by performing active alignment with a high-precision optical alignment device.

A GI multimode optical fiber having a core diameter of 50 μm and a numerical aperture NA of 0.21 was inserted into a holding member provided in the optical waveguide, and inserted to a position where it abutted against the optical end face of the optical waveguide core.
A UV curable optical adhesive having a refractive index of 1.531 that transmits 90% / mm of light having a wavelength of 0.85 μm and a viscosity of 250 Pa · s before curing is provided in the gap between the optical end face of the optical waveguide core and the optical fiber. After the injection, UV light having a wavelength of 360 nm was irradiated from the Arton film side to cure the UV curable optical adhesive.

Through the above steps, an optical waveguide in which the optical fiber held by the holding member was optically connected to the optical waveguide core was produced.
When light having a wavelength of 0.850 μm was introduced from the optical fiber into the optical waveguide core, the connection loss between the optical waveguide core and the optical fiber was 0.52 dB.
Further, the time spent for the joining work was measured by setting the bonding process of the holding member as the work start time and the fiber installation / joining process as the work end time, and it was 4.5 minutes.

  In addition, when a mechanical force was applied to the optically connected optical fiber using a tensile evaluation device, the optical fiber was not optically bonded to the end of the optical waveguide and did not leave, and as a mechanical force, a polymer waveguide As a result of applying tensile stress to a unit width of 100 g / cm, the junction loss was also unchanged at 0.52 dB as described above.

[Comparative Example 1]
An optical waveguide was prepared and optically connected to the optical fiber in the same manner as in Example 1 except that the optical fiber and the optical waveguide core of the optical waveguide were manually connected without providing a holding member in the optical waveguide. .

When light having a wavelength of 0.850 μm was introduced from the optical fiber prepared in Comparative Example 1 into the optical waveguide core, the connection loss between the optical waveguide core and the optical fiber was 0.96 dB. Further, the time spent for the joining work was measured with the bonding process of the holding member as the work start time and the fiber installation / joining process as the work end time, and it was 19 minutes.
In addition, when a mechanical force was applied to the optically connected optical fiber using a tensile evaluation device, the polymer waveguide was subjected to tensile stress on a unit width of 100 g / cm. Occurred and became unusable.

<Production of rubber mold>
After a UV curable thick film resist solution (manufactured by Micro Chemical Co., Ltd., SU-8) is applied to a silicon wafer substrate by a spin coating method, it is pre-baked in a heating oven at 80 ° C., exposed through a photomask with a high-pressure mercury lamp, After the development process, 10 fine convex portions (width: 80 μm, height: 80 μm, pitch: 1 mm, length: 100 mm) having a square cross section were formed and post-baked at 120 ° C. One end of each of the convex portions thus produced is made of a pressure relief gap having a height of 2 mm, a width (direction perpendicular to the convex portion) of 10 mm, and a longitudinal length of the substrate of 20 mm and a rectangular cross section. Protrusions were formed and used as core masters.

  Next, an aluminum reinforcing member as shown in FIG. 8 (A) is prepared, the opening for exposure is made of quartz glass, and a transparent rigid substrate made of acrylic with a thickness of 2 mm has the same pitch as the core master, Recesses having a similar shape (width: 150 μm, height: 150 μm, pitch: 1 mm, length: 100 mm, 10) were formed on the transparent rigid substrate by a photolithography process and an etching process and integrated with the reinforcing member.

  A core master is set, and a thermosetting silicone rubber oligomer (manufactured by Dow Corning Asia Co., Ltd .: SYLGARD184, dimethylpolysiloxane) is placed on the core master so that one end in the longitudinal direction of the convex portion is partially exposed. It applied so that the edge part of a certain cavity part preparation convex part might be covered. From above, the integrated reinforcing member was pressed and fixed. Thereafter, it was cured by heating at 135 ° C. for 18 minutes to integrate the silicone rubber and the reinforcing member. The thickness of the cured silicone rubber layer was 5 mm.

  Subsequently, this was peeled off from the master and a rubber mold was obtained. The silicone rubber layer of the rubber mold was formed with 80 μm square recesses, core entry curable resin entry and exit portions, and voids. The rubber hardness of the surface rubber layer was 30.

<Formation of optical waveguide core and cladding layer>
The rubber mold was pressed and adhered to the non-formed surface of the electronic circuit portion of Arton Film (manufactured by JSR Corporation, refractive index: 1.51, thickness: 250 μm). An injection pipe and a vacuum deaeration pipe were connected to each inlet and each outlet of the rubber mold reinforcing member. The injection tube was connected to a pressurized tank containing a core-forming curable resin, and a nitrogen cylinder was directly connected to the pressurized tank so that the resin could be injected by static pressure. The vacuum deaeration pipe is connected to a vacuum pump via a pressure control mechanism and a vacuum tank, so that vacuum suction is performed with a static pressure whose pressure is adjusted.

  Next, an ultraviolet curable resin (manufactured by JSR Co., Ltd .: UV curable optical adhesive) having a viscosity of 500 mPa · s is placed in the concave portion of the rubber mold while performing suction by static pressure in synchronization with pressurization by static pressure. Pressure decompression was injected.

After completion of filling, the injection tube and the vacuum deaeration tube were removed from the rubber mold, and UV light having a light intensity of 80 mW / cm 2 was irradiated for 8 minutes through a quartz window of the rubber mold to cure the core-forming curable resin.
When the rubber mold was peeled off, an optical waveguide core having a refractive index of 1.53 was formed on the ARTON film.

  Next, a thermosetting resin (JSR Co., Ltd. product: UV curable optical adhesive) having a refractive index after curing of 1.51 is applied to the entire surface of the ARTON film on which the optical waveguide core is formed. Then, it was cured by heating to obtain a flexible optical waveguide. The average waveguide loss of this optical waveguide was 0.13 dB / cm.

  Next, using the dicer apparatus provided with a 0.5 mm thick dicer blade on the produced polymer waveguide substrate, the optical waveguide core of the optical waveguide is crossed with respect to the optical waveguide direction. An optical end face was formed by cutting at an angle of 90 degrees with respect to the longitudinal direction.

  next. An annular holding member (with the same shape as the holding member 80B in FIG. 6B) having an inner diameter of 130 μm and an outer diameter of 750 μm on the end face in the optical waveguide direction of the optical waveguide and facing the connection end face A holding member having an inner diameter of 500 μm and an outer diameter of 1000 μm and a length in the optical waveguide direction (distance between the connection end face and the end face facing the connection end face) of 2 mm was bonded.

  The holding member is bonded to a position where the optical fiber can be held so that the connecting end of the optical fiber and the connecting end of the optical waveguide core are coaxial when the holding member holds the optical fiber. This position adjustment is prepared by active alignment using an automatic optical alignment device.

As a specific bonding method, a GI type multimode optical fiber having a core diameter of 50 μm and a numerical aperture NA0 / 21 is inserted into a holding member provided in the optical waveguide, and inserted to a position where it abuts against the optical end face of the optical waveguide core. .
UV curable optical adhesive having a refractive index of 1.525 that transmits 90% / mm of light having a wavelength of 0.85 μm, and a viscosity of 0.4 Pa · s before curing into the gap between the optical end face of the optical waveguide core and the optical fiber. After the agent was injected, UV light having a wavelength of 360 nm was irradiated from the Arton film side (directly above) to cure the UV curable optical adhesive. By this operation, the optical fiber was fixed to the optical end of the optical waveguide core.

Through the above steps, an optical waveguide in which the optical fiber held by the holding member was optically connected to the optical waveguide core was produced.
When light having a wavelength of 0.850 μm was introduced from the optical fiber into the optical waveguide core, the connection loss between the optical waveguide core and the optical fiber was 0.48 dB.
Further, the time spent for the joining work was measured with the bonding process of the holding member as the work start time and the fiber installation / joining process as the work end time, and it was 3.5 minutes.

  In addition, when a mechanical force is applied to the optically connected optical fiber using active alignment using an automatic optical alignment device, the optical fiber remains optically bonded to the end of the optical waveguide and is not detached. The junction loss after applying a large force was 0.48 dB as described above.

  As shown in the first and second embodiments, the optical waveguide end of the optical waveguide optically joined to the end surface of the optical waveguide core on the end surface of the optical waveguide in the optical waveguide direction, and the optical waveguide direction of the optical waveguide core A holding member having a bent portion bent along the outer periphery of the optical fiber is provided so that the optical fiber can be held so that the end portion is at least coaxial, and the optical fiber and the optical waveguide core held by the holding member As shown in Comparative Example 1, the connection loss between the optical waveguide core and the optical fiber can be reduced as compared with the case where the optical fiber and the optical waveguide core are optically bonded without providing a holding member. In addition, optical joining with an optical fiber could be easily performed with a simple configuration.

It is a conceptual diagram which shows the one aspect | mode of the manufacturing method of the optical waveguide of this invention. It is a perspective view which shows the state which contact | adhered the rubber mold to the base material for a clad. It is a conceptual diagram which shows another aspect of the manufacturing method of the optical waveguide of this invention. It is a conceptual diagram which shows another aspect of the manufacturing method of the optical waveguide of this invention. It is a conceptual diagram which shows the process of optically joining an optical fiber to the optical waveguide of this invention. It is a schematic diagram which shows the holding member provided in the optical waveguide of this invention. It is a conceptual diagram for demonstrating the optical waveguide core material filling process using the rubber mold provided with the reinforcement member. It is a conceptual diagram for demonstrating the other optical waveguide core material filling process using the rubber mold provided with the reinforcement member. It is a conceptual diagram for demonstrating the other optical waveguide core material filling process using the rubber mold provided with the reinforcement member. It is a figure which shows the example which provided the space | gap for stress relaxation in the cured resin layer of a rubber mold. It is a conceptual diagram which shows an example of the manufacturing method of the optical waveguide provided with the optical element. It is a conceptual diagram which shows an example of the other manufacturing method of the optical waveguide provided with the optical element.

Explanation of symbols

60 Optical waveguide 80, 80A, 80B, 80C, 80D, 80E, 80F Holding member

Claims (13)

An optical waveguide having an optical waveguide core made of a curable resin for forming a core, and a cladding layer surrounding the optical waveguide core and having a refractive index smaller than that of the optical waveguide core,
The optical fiber so that the optical waveguide end of the optical fiber to be optically joined to the end surface of the optical waveguide core and the optical waveguide end of the optical waveguide core are at least coaxial with the end surface of the optical waveguide main body in the optical waveguide direction. An optical waveguide comprising a holding member capable of holding the optical waveguide.   The optical waveguide according to claim 1, wherein the holding member has a bent portion bent along the outer periphery of the optical fiber, and the optical fiber can be held in the bent portion.   The optical waveguide according to claim 2, wherein the bent portion has an arc shape.   The optical waveguide according to claim 1, wherein the holding member is an annular body having a hole having a shape along the outer periphery of the optical fiber, and the optical fiber can be held in the hole.   5. The light guide according to claim 4, wherein the holding member continuously decreases in inner diameter as it approaches the end face side of the optical waveguide body in the optical waveguide direction, and the minimum inner diameter of the holding member is larger than the outer diameter of the optical fiber. Waveguide. A step of preparing a rubber mold formed of a cured resin layer of a curable resin for rubber mold formation and having a recess corresponding to the optical waveguide core;
Adhering a clad substrate to the rubber mold; and
Filling the concave portion of the rubber mold with which the clad substrate is in close contact with a curable resin for forming an optical waveguide core; and
Curing the filled curable resin for forming an optical waveguide core to form an optical waveguide core; and
Peeling the rubber mold from the clad substrate;
Forming a clad layer on the clad substrate on which the optical waveguide core is formed;
Cutting the end of the optical waveguide core;
An optical waveguide is provided with a holding member capable of holding the optical fiber so that the optical waveguide direction end of the optical fiber optically joined to the end face of the optical waveguide core and the optical waveguide direction end of the optical waveguide core are at least coaxial. Providing on the end face of the main body in the optical waveguide direction;
Optically bonding the end face of the optical waveguide core and the optical fiber held by the holding member with a photo-curing adhesive; and
A method for manufacturing an optical waveguide, comprising:   The method for producing an optical waveguide according to claim 6, wherein the viscosity of the photocurable adhesive before curing is 30 mPa · s or more and 1000 mPa · s or less.   The optical waveguide manufacturing method according to claim 6 or 7, wherein a refractive index of the photocurable adhesive is in a range of -7% to + 7% of a refractive index of the optical waveguide core. Method.   9. The method of manufacturing an optical waveguide according to claim 6, wherein the photocurable adhesive has a transmission loss of 1 dB or less with respect to light in a wavelength range of 500 nm to 900 nm. .   The rubber mold has an inlet and an outlet for the optical waveguide core forming curable resin in the cured resin layer, and has an injection port for press-fitting the optical waveguide core forming curable resin. The method for manufacturing an optical waveguide according to claim 6, further comprising a reinforcing member for reinforcing the layer.   The method of manufacturing an optical waveguide according to claim 10, wherein the reinforcing member is made of any one of a metal material, a ceramic material, and a plastic material.   The method for manufacturing an optical waveguide according to claim 6, wherein the cured resin layer is made of silicone rubber.   The method for producing an optical waveguide according to any one of claims 6 to 12, wherein the shear rubber hardness of the rubber mold forming curable resin of the rubber mold is in a range of 10 to 50. .

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