JP5760628B2 - Optical waveguide, opto-electric hybrid board, and electronic equipment - Google Patents

Description

  The present invention relates to an optical waveguide, an opto-electric hybrid board, and an electronic device.

  In recent years, with the wave of computerization, wideband lines (broadband) capable of communicating a large amount of information at high speed have been spreading. Also, as devices for transmitting information to these broadband lines, transmission devices such as router devices and WDM (Wavelength Division Multiplexing) devices are used. In these transmission apparatuses, a large number of signal processing boards in which arithmetic elements such as LSIs and storage elements such as memories are combined are installed, and each line is interconnected.

  Each signal processing board has a circuit in which arithmetic elements, storage elements, etc. are connected by electrical wiring. However, with the increase in the amount of information to be processed in recent years, each board has a very high throughput. It is required to transmit. However, with the speeding up of information transmission, problems such as generation of crosstalk and high frequency noise and deterioration of electric signals are becoming apparent. For this reason, electrical wiring becomes a bottleneck, making it difficult to improve the throughput of the signal processing board. Similar problems are also becoming apparent in supercomputers and large-scale servers.

  On the other hand, an optical communication technique for transferring data using an optical carrier wave has been developed, and in recent years, an optical waveguide is becoming popular as a means for guiding the optical carrier wave from one point to another point. This optical waveguide has a linear core part and a clad part provided so as to cover the periphery thereof. The core part is made of a material that is substantially transparent to the light of the optical carrier wave, and the cladding part is made of a material having a refractive index lower than that of the core part.

  In the optical waveguide, light introduced from one end of the core portion is conveyed to the other end while being reflected at the boundary with the cladding portion. A light emitting element such as a semiconductor laser is disposed on the incident side of the optical waveguide, and a light receiving element such as a photodiode is disposed on the emission side. Light incident from the light emitting element propagates through the optical waveguide, is received by the light receiving element, and performs communication based on the flickering pattern of the received light or its intensity pattern.

  If the electrical wiring in the signal processing board is replaced by such an optical waveguide, it is expected that the problem of the electrical wiring as described above will be solved and the signal processing board can be further increased in throughput.

  By the way, when the electric wiring is replaced with an optical waveguide, an optical waveguide module that includes a light emitting element and a light receiving element and optically connects the light emitting element and the light receiving element is used.

  For example, Patent Document 1 discloses an optical interface having a printed circuit board, a light emitting element mounted on the printed circuit board, and an optical waveguide provided on the lower surface side of the printed circuit board. The optical waveguide and the light emitting element are optically connected through a through hole, which is a through hole for transmitting an optical signal, formed on the printed board. Further, mirrors for converting the optical path of the optical waveguide are formed at both ends of the optical waveguide.

  However, the optical interface as described above has a problem that the optical coupling loss is large in the optical coupling between the light emitting element and the optical waveguide or in the optical coupling between the light receiving element and the optical waveguide. Specifically, when the signal light emitted from the light emitting portion of the light emitting element passes through the through hole and enters the optical waveguide, the signal light radiates radially, so that all the signal light is incident on the mirror. I can't. Similarly, when the signal light propagating through the optical waveguide and reflected by the mirror passes through the through hole and enters the light receiving element, it is not possible to make all the signal light enter the light receiving element. For this reason, a part of the signal light does not contribute to the optical communication, resulting in an increase in optical coupling loss.

  In recent years, optical waveguides in which a plurality of core portions are laminated in the thickness direction have been developed. In such an optical waveguide, the core portion can be integrated at a high density, but the optical coupling loss is further increased in the optical coupling with the light emitting / receiving element. This is because, in an optical waveguide in which a plurality of core portions are stacked, the distance between the light emitting / receiving element placed on the optical waveguide and the mirror is inevitably increased, and the loss therebetween increases.

JP 2005-294407 A

  An object of the present invention is to provide an optical waveguide having high optical coupling efficiency with a light emitting / receiving element and capable of high-quality optical communication even when the density is increased, and a highly reliable opto-electric hybrid board including the optical waveguide, and To provide electronic equipment.

Such an object is achieved by the present inventions (1) to (10) below.
(1) a first core layer comprising a first side cladding portion adjacent to the first core portion and the first core portion, a cladding layer, a second adjacent to the second core portion and second core portion A laminated body including a portion in which a second core layer including a side clad portion is laminated in this order ;
A first optical path provided in each of the first core part and the second core part;
A light reflecting surface provided in the first core portion;
Connection points provided on the surface of the laminate;
A second optical path that optically connects the light reflecting surface and the connection point and intersects the first optical path;
A first low refractive index layer that is provided on the opposite side of the first optical path in the first core portion from the light reflecting surface so as to cross the first core portion and has a lower refractive index than the first core portion. When,
The one end side and the other end side of the first optical path in the second core part so as to sandwich the second optical path in the second core layer and across the second core part, respectively. A second low refractive index layer provided and having a refractive index lower than that of the second core portion;
I have a,
When the surface of the laminate is viewed in plan, the first low refractive index layer and one of the two second low refractive index layers are provided at the same position. Optical waveguide.

(2) The light reflecting surface is configured by a surface that obliquely crosses the first core portion,
Two said second other one of the low refractive index layer is an optical waveguide according to the above (1) that is disposed at a position where said light reflecting surface and the cladding layer meet.

(3) Furthermore, a light reflecting surface provided in the second core part;
A connection point provided on the surface of the laminate and optically connected to the light reflecting surface provided in the second core part;
Have
When the surface of the laminate is viewed in plan, the position of the light reflecting surface provided in the first core portion and the position of the light reflecting surface provided in the second core portion are different from each other. The optical waveguide according to (1) or (2) .

(4) The optical waveguide according to any one of (1) to (3) , wherein a thickness of the first low refractive index layer and a thickness of the second low refractive index layer are each 0.5 to 50 μm. .

(5) Each of the first core layer and the second core layer is manufactured by forming a refractive index difference between an active radiation irradiation region and a non-irradiation region. The optical waveguide according to any one of (4).
(6) The optical waveguide according to (5), wherein the first low refractive index layer and the second low refractive index layer are formed by the same exposure process.

(7) before SL of the first core portion, the width of the portion located above the light incident side of the low refractive index layer is smaller than the width of the portion located on the light emission side than the low-refractive index layer The optical waveguide according to any one of (1) to (6) above.
(8) The second low refractive index layer provided on one end side of the first optical path in the second core portion is used as one end side second low refractive index layer, and provided on the other end side of the first optical path. When the second low refractive index layer is a second low refractive index layer on the other end side,
An intermediate second low refractive index that is provided between the one end side second low refractive index layer and the other end side second low refractive index layer in the second core portion and has a refractive index lower than that of the second core portion. The optical waveguide according to any one of (1) to (7), further including a layer.

(9) An opto-electric hybrid board comprising the optical waveguide according to any one of (1) to (8) .

(10) An electronic apparatus comprising the opto-electric hybrid board according to (9) .

  According to the present invention, by providing a low refractive index layer having a lower refractive index than the core along the optical path between the light emitting / receiving element and the light reflecting surface, the optical coupling efficiency with the light receiving / emitting element is increased. An optical waveguide capable of high-quality optical communication even when the density is increased can be obtained.

  Further, according to the present invention, by providing such an optical waveguide, the S / N ratio of optical communication can be increased, and thus a highly reliable opto-electric hybrid board and electronic device can be obtained.

1 is an exploded perspective view showing a first embodiment of an optical waveguide of the present invention and an optical waveguide module including the optical waveguide module (partially shown). FIG. It is the YY sectional view taken on the line of FIG. FIG. 3 is a partially enlarged view of FIG. 2. FIG. 3 is a partially enlarged view of FIG. 2. FIG. 2 is a plan view showing a part of the optical waveguide shown in FIG. It is a disassembled perspective view which shows 2nd Embodiment of the optical waveguide of this invention, and an optical waveguide module containing the same (it shows partially transmitting). FIG. 7 is a plan view showing a part of the optical waveguide shown in FIG. It is a figure (sectional drawing) for demonstrating the method of manufacturing the optical waveguide shown in FIG. It is a figure (sectional drawing) for demonstrating the method of manufacturing the optical waveguide shown in FIG. It is a figure (sectional drawing) for demonstrating the method of manufacturing the optical waveguide shown in FIG. It is a figure (sectional drawing) for demonstrating the method of manufacturing the optical waveguide shown in FIG. It is a figure for demonstrating a mode that a refractive index difference arises between an irradiation area | region and a non-irradiation area | region, taking the position of the cross section of a layer on a horizontal axis, and refraction when taking the refractive index of a cross section on a vertical axis | shaft. It is a figure which shows rate distribution. It is sectional drawing which shows the optical waveguide obtained by the comparative example.

  Hereinafter, the optical waveguide, the opto-electric hybrid board and the electronic apparatus of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

<Optical waveguide and optical waveguide module>
<< First Embodiment >>
First, the first embodiment of the optical waveguide of the present invention and the optical waveguide module (the opto-electric hybrid board of the present invention) including the same will be described.

  FIG. 1 is an exploded perspective view showing a first embodiment of an optical waveguide of the present invention and an optical waveguide module including the optical waveguide, and FIG. 2 is a sectional view taken along line YY of FIG. 3 and 4 are partially enlarged views of FIG. In the following description, the upper side of FIGS. 1 to 4 is referred to as “upper” and the lower side is referred to as “lower”. Moreover, in FIGS. 2-4, in order to avoid that a figure becomes complicated, illustration of a support film and a cover film is abbreviate | omitted. In each figure, the vertical direction of the optical waveguide is emphasized.

  An optical waveguide 1 shown in FIG. 1 functions as an optical wiring that transmits signal light from one end to the other end. Here, as an example, signal light from the light incident end 1A shown in FIG. Will be described, and signal light is emitted from the light emitting end 1B.

  The optical waveguide 1 shown in FIG. 1 has a laminated body 12 in which a clad layer 111, a core layer 131, a clad layer 112, a core layer 132, and a clad layer 113 are laminated in this order from the lower side. It has a belt shape.

  As shown in FIGS. 1 and 2, two core portions 14 extending in parallel from the light incident end portion 1 </ b> A to the light emitting end portion 1 </ b> B are formed in the core layers 131 and 132, respectively. Four core portions 14 are formed in the entire waveguide 1. Of the core layers 131 and 132, the portion other than the core portion 14 is the side cladding portion 15. Note that dots are given to each core portion 14 shown in some drawings.

  In such an optical waveguide 1, a mirror (light reflecting surface) 1612 is provided at the light incident end 1 </ b> A of the core layer 131, and a mirror 1614 is provided at the light emitting end 1 </ b> B for each core part 14. . Further, a mirror 1611 is provided at the light incident end 1A of the core layer 132, and a mirror 1613 is provided at the light emitting end 1B for each core part 14, respectively. These mirrors 1611, 1612, 1613, 1614 convert the optical path of the optical waveguide 1 extending in the left-right direction in FIG. 2 to the outside of the optical waveguide 1. Specifically, the mirrors 1611 and 1612 shown in FIG. 2 change the optical path so that the optical path of the optical waveguide 1 is optically connected to the light emitting parts 711 and 721 of the light emitting elements 71 and 72 at the light incident end 1A, respectively. Convert 90 ° upward. Similarly, the mirrors 1613 and 1614 convert the optical path upward by 90 ° so that the optical path of the optical waveguide 1 is optically connected to the light receiving portions 731 and 741 of the light receiving elements 73 and 74 at the light emitting end 1B. Through such mirrors 1611, 1612, 1613, 1614, the signal light emitted from the light emitting elements 71, 72 is incident on the core portion 14 of the optical waveguide 1, and the signal light propagated through the core portion 14 is The light can be incident on the light receiving elements 73 and 74. As a result, optical communication is possible between the light emitting elements 71 and 72 and the light receiving elements 73 and 74.

  Here, as shown in FIG. 2, each core portion 14 is interrupted in the vicinity of the mirror 1612. The interrupted portion is made of a material having a refractive index lower than that of the core portion 14, and has a thin layer shape provided so as to cross the optical path. This portion is referred to as a low refractive index layer 145. The core portion 14 is also interrupted in the vicinity of the mirror 1614, and the interrupted portion is a low refractive index layer 145.

  Such a low refractive index layer 145 acts to return the signal light that would otherwise have been lost to the optical path by reflecting the signal light with the core portion 14. Therefore, by providing the low refractive index layer 145, for example, the incident efficiency of the signal light that is emitted from the light emitting element 72 and incident on the mirror 1612 is increased, and the signal light that is emitted from the mirror 1614 and incident on the light receiving element 74 is increased. Incident efficiency can be increased. That is, the optical coupling efficiency between the optical waveguide 1 and the light emitting / receiving element can be increased. Further, when the improvement in optical coupling efficiency is sacrificed to some extent, the allowable range of mutual alignment accuracy and surface accuracy of the mirrors 1612 and 1614 can be relaxed accordingly. For this reason, the mirrors 1612 and 1614 can be easily formed, and the optical waveguide 1 can be manufactured at low cost.

Hereinafter, each part of the optical waveguide 1 and the optical waveguide module 10 will be described in detail.
(Core layer)
As described above, the core layers 131 and 132 are each formed with the two core portions 14 and the side cladding portions 15.

  In the optical waveguide 1 shown in FIG. 2, for example, the signal light incident through the mirror 1611 is totally reflected at the interface between the core part 14 and the clad parts (the clad layers 112 and 113 and the side clad parts 15). It can be propagated to the other end.

  In order to cause total reflection at the interface between the core part 14 and the clad part, a difference in refractive index needs to exist at the interface. Although the refractive index of the core part 14 should just be larger than the refractive index of a clad part, and the difference is not specifically limited, It is preferable that it is 0.5% or more of the refractive index of a clad part, and it is 0.8% or more. Is more preferable. On the other hand, the upper limit value may not be set, but is preferably about 5.5%. If the difference in refractive index is less than the lower limit, the effect of transmitting light may be reduced, and even if the upper limit is exceeded, no further increase in light transmission efficiency can be expected.

The difference in refractive index is expressed by the following equation, where A is the refractive index of the core portion 14 and B is the refractive index of the cladding portion.
Refractive index difference (%) = | A / B-1 | × 100

  Moreover, in the structure shown in FIG. 1, although the core part 14 is formed in linear form by planar view, you may be curving, branching, etc. in the middle, The shape is arbitrary.

  The cross-sectional shape of the core portion 14 is generally a square such as a square or a rectangle (rectangle), but is not particularly limited, and is not limited to a circle, such as a perfect circle or an ellipse, a rhombus, a triangle, or a pentagon. A polygon such as

  The width and height of the core portion 14 are not particularly limited, but are preferably about 1 to 200 μm, more preferably about 5 to 100 μm, and still more preferably about 20 to 70 μm.

  The constituent materials (main materials) of the core layers 131 and 132 include acrylic resin, methacrylic resin, polycarbonate, polystyrene, epoxy resin, polyamide, polyimide, polybenzoxazole, polysilane, polysilazane, silicone resin, fluorine resin, In addition to various resin materials such as cyclic olefin resins such as polyurethane, benzocyclobutene resin and norbornene resin, glass materials such as quartz glass and borosilicate glass can be used. The resin material may be a composite material obtained by combining materials having different compositions, and may contain an unpolymerized monomer. In the core layers 131 and 132, although the main material is the same, a difference in refractive index between the core portion 14 and the side cladding portion 15 is developed due to the difference in the molecular structure of the material, the concentration of the additive, and the like. May be.

  Of these, norbornene resins are particularly preferable. Norbornene-based resins include, for example, ring-opening metathesis polymerization (ROMP), combination of ROMP and hydrogenation reaction, polymerization by radical or cation, polymerization using a cationic palladium polymerization initiator, and other polymerization initiators (for example, It can be obtained by all known polymerization methods such as polymerization using nickel or other transition metal polymerization initiators).

(Clad layer)
The clad layers 111, 112, 113 are located above and below the core layers 131, 132.

  The average thickness of the clad layers 111, 112, 113 is preferably about 0.1 to 1.5 times the average thickness of the core layers 131, 132 (average height of each core portion 14). More preferably, the average thickness of the clad layers 111, 112, and 113 is not particularly limited, but is usually preferably about 1 to 200 μm. More preferably, it is about 3-100 micrometers, and it is further more preferable that it is about 5-60 micrometers. Thereby, the function as a clad layer is suitably exhibited while preventing the optical waveguide 1 from becoming unnecessarily large (thickened).

  Moreover, as a constituent material of each cladding layer 111,112,113, the material similar to the constituent material of the core layers 131 and 132 mentioned above can be used, for example, but norbornene-type resin is especially preferable.

  Moreover, when selecting the constituent material of the core layers 131 and 132 and the constituent material of the clad layers 111, 112, and 113, the material may be selected in consideration of the difference in refractive index between them. Specifically, the refractive index of the constituent material of the core layer 131 is sufficiently larger than the refractive index of the cladding layers 111 and 112 in order to ensure total reflection of light at the boundary between the core layer 131 and the cladding layers 111 and 112. What is necessary is just to select a material so that it may become. Thereby, a sufficient refractive index difference is obtained in the thickness direction of the optical waveguide 1, and light can be prevented from leaking from the core portion 14 to the cladding layers 111 and 112.

  From the viewpoint of suppressing light attenuation, it is also important that the adhesiveness (affinity) between the constituent material of the core layer 131 and the constituent materials of the cladding layers 111 and 112 is high.

(Support film)
A support film 2 as shown in FIG. 1 may be laminated on the lower surface of the optical waveguide 1 as necessary.

  The support film 2 supports the lower surface of the optical waveguide 1 to protect and reinforce it. Thereby, the reliability and mechanical characteristics of the optical waveguide 1 can be improved.

  Examples of the constituent material of the support film 2 include various resin materials such as polyethylene terephthalate (PET), polyolefin such as polyethylene and polypropylene, polyimide and polyamide, and metal materials such as copper, aluminum and silver. It is done. In the case of a metal material, a metal foil is used as the support film 2.

  Moreover, although the average thickness of the support film 2 is not specifically limited, It is preferable that it is about 5-200 micrometers, and it is more preferable that it is about 10-100 micrometers. Thereby, since the support film 2 has moderate rigidity, while supporting the optical waveguide 1 reliably, it becomes difficult to inhibit the softness | flexibility of the optical waveguide 1. FIG.

  The support film 2 and the optical waveguide 1 are bonded or bonded, and examples of the method include thermocompression bonding, bonding with an adhesive or a pressure sensitive adhesive, and the like.

  Among these, as an adhesive layer, various hot-melt-adhesives (polyester type | system | group, modified olefin type | system | group) etc. are mentioned other than an acrylic adhesive, a urethane type adhesive agent, a silicone type adhesive agent, for example. Moreover, as a thing with especially high heat resistance, thermoplastic polyimide adhesive agents, such as a polyimide, a polyimide amide, a polyimide amide ether, a polyester imide, a polyimide ether, are used preferably. Since the adhesive layer made of such a material is relatively flexible, even if the shape of the optical waveguide 1 changes, the change can be freely followed. As a result, it is possible to reliably prevent peeling due to the shape change.

  The average thickness of such an adhesive layer is not particularly limited, but is preferably about 1 to 100 μm, and more preferably about 5 to 60 μm.

(Cover film)
On the other hand, you may make it laminate | stack the cover film 3 as shown in FIG. 1 on the upper surface of the optical waveguide 1 as needed.

  The cover film 3 protects the optical waveguide 1 and supports the optical waveguide 1 from above. Thereby, the optical waveguide 1 is protected from dirt and scratches, and the reliability and mechanical characteristics of the optical waveguide 1 can be improved.

  As a constituent material of such a cover film 3, it is the same as the constituent material of the support film 2. For example, in addition to various resin materials such as polyethylene terephthalate (PET), polyolefin such as polyethylene and polypropylene, polyimide and polyamide, Metal materials, such as copper, aluminum, silver, are mentioned. In the case of a metal material, a metal foil is used as the cover film 3. Further, when the optical path is set so as to penetrate the cover film 3, the constituent material of the cover film 3 is preferably substantially transparent.

  Moreover, although the average thickness of the cover film 3 is not specifically limited, It is preferable that it is about 3-50 micrometers, and it is more preferable that it is about 5-30 micrometers. By setting the thickness of the cover film 3 within the above range, the cover film 3 has sufficient light transmittance in optical communication, and has sufficient rigidity to reliably protect the optical waveguide 1.

  Note that the cover film 3 and the optical waveguide 1 are bonded or bonded, and examples of the method include thermocompression bonding, bonding with an adhesive or a pressure sensitive adhesive, and the like. Of these, the adhesive described above can be used.

(mirror)
Mirrors (light reflecting surfaces) 1611, 1612, 1613, and 1614 shown in FIG. 2 are formed by digging into the optical waveguide 1, and the inner wall surfaces of the recesses (spaces) 1601, 1602, 1603, and 1604 obtained thereby. Consists of part. A part of the inner wall surface includes a plane formed so as to cross the core portion 14 at an angle of 45 ° with respect to the optical path, and these planes become mirrors 1611, 1612, 1613, and 1614. The recesses 1601 and 1603 shown in FIG. 2 are formed over the cladding layer 111, the core layer 131, the cladding layer 112, and the core layer 132. The recesses 1602 and 1604 are formed over the cladding layer 111 and the core layer 131. Although omitted in FIG. 2, the support film 2 and the cover film 3 may also be applied. In addition, you may make it form a reflecting film in the mirrors 1611, 1612, 1613, and 1614 as needed. As the reflective film, a metal film such as Au, Ag, or Al is preferably used.

  The shape of the recess is not particularly limited as long as it includes a mirror. In FIG. 2, the recess is provided in the middle of the optical waveguide 1, but it may be provided at the end of the optical waveguide 1. Specifically, mirrors 1611, 1612, 1613, and 1614 may be formed on a cut surface obtained by obliquely cutting off the end of the optical waveguide 1. By providing a recess in the middle of the optical waveguide 1, the mirror is exposed to the inside of the recess and it is easy to prevent the intrusion of external light, so that the stability is excellent.

  Note that the recess 1601 shown in FIG. 2 is formed by digging each layer located below the cladding layer 113. Of the inner wall surface of the recess 1601, the exposed surface of the core layer 132 is a mirror 1611. The recess 1602 is formed by digging each layer located below the cladding layer 112. Of the inner wall surface of the recess 1602, the exposed surface of the core layer 131 is a mirror 1612.

  Further, the recess 1603 shown in FIG. 2 is formed by digging each layer positioned below the cladding layer 113. Of the inner wall surface of the recess 1603, the exposed surface of the core layer 132 is a mirror 1613. The recess 1604 is formed by digging each layer positioned below the cladding layer 112. Of the inner wall surface of the recess 1604, the exposed surface of the core layer 131 is a mirror 1614.

  As described above, the optical waveguide 1 shown in FIG. 2 has a recess formed including a layer on which a mirror is to be formed and a layer below the mirror. Therefore, after laminating each layer, it is dug together. All mirrors can be formed by processing. That is, in the structure of the optical waveguide 1 shown in FIG. 2, once the processing reference position for the core portion 14 is determined at the time of digging, the reference position is used until all the mirrors are formed thereafter. Therefore, it can be said that the structure can minimize the positional deviation between the mirrors. On the other hand, when each core layer is subjected to a process of digging only the core layer, each layer must be laminated while the mirrors are aligned after the core layer is digged. However, it is disadvantageous in that the positional deviation between the mirrors is likely to occur.

  Therefore, the optical waveguide 1 shown in FIG. 2 has high positional accuracy between mirrors, and is aligned with high accuracy with respect to a light receiving / emitting device including a plurality of light emitting units and light receiving units in one element, It can be combined with high efficiency.

  The mirror can be replaced with other optical path conversion means such as a bent waveguide.

(Light emitting element and light receiving element)
The light emitting elements 71 and 72 shown in FIG. 2 have element main bodies 710 and 720, light emitting portions 711 and 721 and electrodes 712 and 722 provided on the lower surface thereof. Specific examples of such light emitting elements 71 and 72 include a semiconductor laser such as a surface emitting laser (VCSEL), a light emitting diode (LED), and the like.

  On the other hand, the light receiving elements 73 and 74 shown in FIG. 2 have element main bodies 730 and 740, light receiving portions 731 and 741 and electrodes 732 and 742 provided on the lower surface thereof. Specific examples of such light receiving elements 73 and 74 include photodiodes.

  In addition, as the light emitting elements 71 and 72 and the light receiving elements 73 and 74, for example, BGA (Ball Grid Array) type or LGA (Land Grid Array) type elements having package specifications are used. FIG. 2 shows a surface-mount type element as an example.

  An electrical wiring 77 is provided on the upper surface of the optical waveguide 1. The light emitting elements 71 and 72 and the light receiving elements 73 and 74 are electrically and mechanically connected to the electric wiring 77 by bumps 78 made of various solders, various brazing materials and the like.

  An underfill (sealing material) 79 is filled in the gap between the optical waveguide 1 and the light emitting elements 71 and 72 and the gap between the optical waveguide 1 and the light receiving elements 73 and 74, respectively. Thereby, the incident efficiency when the signal light emitted from the light emitting elements 71 and 72 enters the optical waveguide 1, and the incident efficiency when the signal light emitted from the optical waveguide 1 enters the light receiving elements 73 and 74, respectively. Can be increased. At the same time, the light emitting elements 71 and 72 and the light receiving elements 73 and 74 can be protected from vibration, external force, foreign matter adhesion, and the like.

  The constituent material of the underfill 79 is not particularly limited as long as it is a transparent material, and examples thereof include an epoxy resin, a polyester resin, a polyurethane resin, and a silicone resin.

  Further, in FIG. 2, the light emitting elements 71 and 72 and the light receiving elements 73 and 74 are illustrated as being placed on the optical waveguide 1, but as described above, between the optical waveguide 1 and each element. The cover film 3 may be inserted.

(Low refractive index layer)
As described above, the optical waveguide 1 includes the laminated body 12 in which the core layers 131 and 132 and the clad layers 111, 112, and 113 are alternately laminated.

  In each of the core layers 131 and 132, two core portions 14 are formed. On the optical path of each core portion 14, mirrors 1611, 1612, 1613, and 1614 are formed. Assuming that the central axis of the optical path in each core portion 14 is the first optical path, this first optical path is connected to each light emitting / receiving element via each connection point 121 on the surface of the laminate 12 by each mirror. Has been converted. The central axis of the optical path connecting each mirror and each light emitting / receiving element is the second optical path. In other words, in this specification, the central axis of the optical path extending in the left-right direction in each core portion 14 in FIG. 2 is defined as the first optical path, and the central axis of the optical path orthogonal to the first optical path is defined as the second optical path. To do.

  Here, the second optical path that passes through the mirror 1612 and the connection point 121 intersects the first optical path in the core portion 14 formed in the core layer 132. Similarly, the second optical path passing through the mirror 1614 and the connection point 121 intersects the first optical path in the core portion 14 formed in the core layer 132.

  Conventionally, when two optical paths intersect in the core portion, signal light is mixed or lost at the intersection, leading to problems such as optical communication interference and a decrease in S / N ratio. For this reason, it is necessary to arrange the optical paths so as not to intersect as much as possible, and there is a restriction on the arrangement pattern of the optical waveguides. However, in an optical waveguide in which a plurality of core layers are laminated, it is inevitable that the optical paths are crossed, which hinders higher density.

  Therefore, in the present invention, when two optical paths intersect in the core portion 14, for example, when the second optical path intersects the first optical path, the second optical path crosses the first optical path and the second optical path The low refractive index layer 145 is arranged so as to extend along the optical path. By disposing the low refractive index layer 145, the core part 14 is interrupted in the middle. In FIG. 2, for example, two low refractive index layers 145 are disposed so as to cross the core portion 14 of the core layer 132 along the second optical path connecting the light emitting portion 721 of the light emitting element 72 and the mirror 1612. Further, for example, three low refractive index layers 145 are arranged so as to cross the core portion 14 of the core layer 132 along the second optical path connecting the mirror 1614 and the light receiving portion 741 of the light receiving element 74.

  As described above, these low refractive index layers 145 have an effect of suppressing the crossing and loss of signal light at the intersection of the first optical path and the second optical path. Hereinafter, this operation will be described with reference to FIGS.

  FIG. 3 is a partially enlarged view of the vicinity of the mirror 1612 in FIG. Arrows L 1, L 2, and L 3 shown in FIG. 3 are examples of light traces of signal light emitted from the light emitting unit 721 of the light emitting element 72.

  The signal light emitted from the light emitting portion 721 toward the outside from the end portion of the mirror 1612 like the light trace L1 has been lost without being incident on the mirror 1612 in the prior art, but the low refractive index layer 1451. By providing (145), the signal light is reflected at the interface between the core portion 14 and the low refractive index layer 1451 of the core layer 132 shown in FIG. The Similarly, the signal light emitted like the light trace L2 is reflected at the interface between the core portion 14 of the core layer 132 and the low refractive index layer 1452 (145), and its path is set so that it can enter the mirror 1612. Be changed. As a result, as indicated by light traces L1 and L2 in FIG. 3, this signal light is reflected by the mirror 1612 and propagates in the extending direction of the core portion 14 (the right side in FIG. 3). Can be used as signal light.

  Further, a part (the low refractive index layer 1451) of the low refractive index layer 145 shown in FIG. 3 extends not only in the core layer 132 but also in the core layer 131. The light trace L3 is incident on the mirror 1612 by being reflected by the extending portion. And it propagates toward the right side of the core part 14.

  Note that these signal lights need to pass through the low refractive index layer 1451 after being reflected by the mirror 1612, but the signal light reflected by the mirror 1612 is incident on the low refractive index layer 1451 at a large incident angle. Therefore, it is transmitted with almost no reflection.

  Similarly, the signal light propagating through the first optical path of the core portion 14 of the core layer 132 needs to pass through the low refractive index layers 1451 and 1452, but the signal light propagating through the core portion 14 has its propagation angle. Is substantially parallel to the first optical path or at an angle close thereto, so that it is incident on the low refractive index layers 1451 and 1452 at a large incident angle, and is transmitted with almost no reflection.

  From the above, by providing the low refractive index layer 145 along the second optical path, the transmission efficiency of the second optical path can be improved without impairing the transmission efficiency in the first optical path intersecting the second optical path. Can be increased. That is, the optical coupling efficiency between the optical waveguide 1 and the light emitting element 72 can be increased. As a result, the S / N ratio of the entire optical waveguide module 10 is improved, and the quality of optical communication can be improved.

  Further, the low refractive index layer 1451 provided along the second optical path that connects the light emitting portion 721 of the light emitting element 72 and the mirror 1612 may be provided so as to interfere with the mirror 1612, or at a slightly separated position. Preferably, as shown in FIG. 3, the position where the mirror 1612 intersects the boundary surface between the core portion 14 of the core layer 131 and the clad layer 111 (intersection point M1 shown in FIG. 3) may be provided. Is provided. This position corresponds to the edge of the mirror 1612. By providing the low refractive index layer 1451 at this position, the amount of light that cannot be incident on the mirror 1612 and is lost is minimized, and the optical coupling efficiency is maximized. be able to.

  Even when the low refractive index layer 1451 is provided at a position other than the intersection M1, it is preferable that the position where the low refractive index layer 1451 is provided is in the vicinity of the mirror 1612. The vicinity of the mirror 1612 is a range where the mirror 1612 is provided and a range corresponding to a distance of 50% or less of the thickness of the core portion 14 from the intersection M1. If the low refractive index layer 1451 is located within this range, the above-described effects can be reliably obtained. Further, as will be described later, a plurality of low refractive index layers 1451 may be provided in the vicinity of the mirror 1612. In this case also, each low refractive index layer 1451 is preferably provided within the above range.

  In FIG. 3, the low refractive index layer is not only at the intersection M1 but also at a position where the mirror 1612 intersects the boundary surface between the core portion 14 of the core layer 131 and the cladding layer 112 (intersection M2 shown in FIG. 3). 145 (1452) is provided. This position is also a position corresponding to the edge of the mirror 1612. That is, the low refractive index layer 145 is provided on both one end side (right side) and the other end side (left side) of the first optical path in the core layer 132 so as to sandwich the second optical path in the vicinity of the intersection. ing. As a result, the second optical path is sandwiched between the two low refractive index layers 145, and signal light crossing and loss at the intersection are particularly suppressed. As a result, the transmission efficiency in the second optical path, that is, the optical coupling efficiency between the light emitting portion 721 of the light emitting element 72 and the mirror 1612 can be particularly increased. The fragment F of the core portion 14 sandwiched between the two low refractive index layers 145 propagates the signal light along the first optical path and propagates the signal light along the second optical path. That is, the fragment F functions as a waveguide in the vertical direction of FIG. 3 by confining the signal light propagating along the second optical path inside.

  The extending direction of the low refractive index layer 145 is appropriately set according to the second optical path connecting the light emitting element 72 and the mirror 1612. Specifically, it is preferably set in a direction that forms an angle of 80 to 100 ° with respect to the extending direction (optical path) of the core portion 14 of the optical waveguide 1, and is set in a direction that forms an angle of 85 to 95 °. More preferably. In the case of FIG. 3, since the angle of the mirror 1612 with respect to the first optical path is 45 ° and the second optical path is orthogonal to the first optical path, the extension of the low refractive index layer 145 accordingly. The direction is also set to a direction orthogonal to the first optical path (a direction parallel to the second optical path). The angle of the second optical path with respect to the first optical path is preferably about 80 to 100 ° as in the extending direction of the low refractive index layer 145, but is 90 ° from the viewpoint of optical coupling efficiency. Is more preferable. This is because the optical path length of the second optical path can be minimized. In this case, there is also an advantage that the light emitting element 72 can be easily placed.

  Furthermore, when the extending direction of the low refractive index layer 145 is orthogonal to the first optical path, there is an advantage that the exposure process is facilitated when an exposure process is involved in manufacturing the optical waveguide 1. This is because when the low refractive index layer 145 is formed for each of the plurality of core layers 131 and 132, it can be formed by one exposure.

  On the other hand, FIG. 4 is a partially enlarged view around the mirror 1614 in FIG. Arrows L4, L5, and L6 shown in FIG. 4 are examples of light traces of the signal light that propagates through the core portion 14 of the core layer 131, is reflected by the mirror 1614, and then enters the light receiving element 74.

  The signal light that has propagated through the core portion 14 enters the mirror 1614, is reflected, and then travels toward the light receiving portion 741 of the light receiving element 74. When reflected at an angle such as the light trace L4, the signal light is Conventionally, the light is not incident on the light receiving portion 741, but is lost. However, by providing the low refractive index layer 1453 (145), the signal light is low in the core portion 14 of the core layer 132 shown in FIG. The path is changed so that the light is reflected at the interface with the refractive index layer 1453 and can enter the light receiving portion 741. Similarly, the signal light reflected at an angle such as the light trace L5 is reflected at the interface between the core portion 14 of the core layer 132 and the low refractive index layer 1455 (145), and the path thereof is made incident on the light receiving portion 741. Is changed. As a result, loss light can be used as signal light.

  Further, a part of the low refractive index layer 145 shown in FIG. 4 (low refractive index layers 1453 and 1454) extends not only in the core layer 132 but also in the core layer 131. The light trace L6 is incident on the light receiving portion 741 by being reflected by the extending portion, and thereby the amount of light incident on the light receiving portion 741 can be increased.

  In addition, in order for the signal light that has propagated through the core portion 14 to enter the mirror 1614, it is necessary to pass through the low refractive index layers 1453 and 1454, but the signal light that has propagated through the core portion 14 has its propagation angle. Is substantially parallel to or close to the optical path of the core 14, the light is incident on the low refractive index layers 1453 and 1454 at a large incident angle and is transmitted without being substantially reflected.

  Similarly, the signal light propagating through the first optical path of the core portion 14 of the core layer 132 needs to pass through the low refractive index layers 1453, 1454, and 1455, but passes through almost without being reflected.

  From the above, by providing the low refractive index layer 145 along the second optical path, the transmission efficiency of the second optical path can be improved without impairing the transmission efficiency in the first optical path intersecting the second optical path. Can be increased. That is, the optical coupling efficiency between the optical waveguide 1 and the light receiving element 74 can be increased. As a result, the S / N ratio of the entire optical waveguide module 10 is improved, and the quality of optical communication can be improved.

  In addition, the low refractive index layer 1453 provided along the second optical path that connects the mirror 1614 and the light receiving portion 741 of the light receiving element 74 may be provided so as to interfere with the mirror 1614 or at a slightly separated position. Preferably, as shown in FIG. 4, the position where the mirror 1614 and the boundary surface between the core portion 14 of the core layer 131 and the cladding layer 111 intersect (intersection M3 shown in FIG. 4) may be provided. Is provided. By providing at this position, it is possible to minimize the amount of light that cannot be incident on the light receiving portion 741, and to maximize optical coupling efficiency.

  Even when the low-refractive-index layer 1453 is provided at a position other than the intersection M3, the position where the low refractive index layer 1453 is provided is preferably in the vicinity of the mirror 1614. The vicinity of the mirror 1614 is a range in which the mirror 1614 is provided and a range corresponding to a distance of 50% or less of the thickness of the core portion 14 from the intersection M3. If the low refractive index layer 1453 is positioned within this range, the above-described effects can be reliably obtained.

  In FIG. 4, the low refractive index layer is not only at the intersection M3 but also at a position where the mirror 1614 and the boundary surface between the core portion 14 of the core layer 131 and the cladding layer 112 intersect (intersection M4 shown in FIG. 4). 145 (1455) is provided. That is, the low refractive index layer 145 is provided on both one end side (right side) and the other end side (left side) of the first optical path in the core layer 132 with the second optical path interposed therebetween. As a result, the second optical path is sandwiched between the two low refractive index layers 145, and signal light crossing and loss at the intersection are particularly suppressed. As a result, the transmission efficiency in the second optical path, that is, the optical coupling efficiency between the mirror 1614 and the light receiving portion 741 of the light receiving element 74 can be particularly increased.

  Further, in FIG. 4, a low refractive index layer 145 (1454) is also provided at a position where it interferes with the mirror 1614. Thus, three low refractive index layers 145 are provided in the vicinity of the second optical path that connects the mirror 1614 and the light receiving portion 741 of the light receiving element 74. By increasing the number of low refractive index layers 145 in this way, the probability of converting lost light into signal light increases, so that the optical coupling efficiency can be increased accordingly.

  The number of the low refractive index layers 145 is not particularly limited, and may be four or more. This is the same not only on the light emitting side but also on the light incident side.

  In the above description, the vicinity of the mirrors 1612 and 1614 has been particularly described. However, the low refractive index layer 145 is provided not only in the vicinity of the mirrors 1612 and 1614 but also in the vicinity of the mirrors 1611 and 1613. Thereby, also in the 2nd optical path which connects the light emitting element 71 and the mirror 1611, and the 2nd optical path which connects the mirror 1613 and the light receiving element 73, optical coupling efficiency can be improved. The second optical path is not limited to the optical path connecting the mirror and the light emitting / receiving element. For example, an optical path connecting a light emitting element and a light receiving element provided on both sides of the core portion may be the second optical path. Even in such a case, since the second optical path can be set freely without avoiding the core portion, the degree of freedom in designing the optical waveguide module can be increased.

  The thickness of the low refractive index layer 145 as described above is not particularly limited as long as it can cause light reflection at the interface between the core portion 14 and the low refractive index layer 145, but is preferably about 0.5 to 50 μm. More preferably, it is about 1 to 20 μm. By setting the thickness of the low refractive index layer 145 within the above range, light can be reliably reflected at the interface, and loss when signal light passes through the low refractive index layer 145 can be suppressed.

  The refractive index of the low refractive index layer 145 is not particularly limited as long as it is lower than the refractive index of the core portion 14, but is preferably equal to the refractive index of the side cladding portion 15. Thereby, when forming the core part 14 and the side surface clad part 15 in the core layers 131 and 132, the low refractive index layer 145 can be formed, without adding an extra process.

  Moreover, the same pattern is formed in the core layer 131 and the core layer 132 shown in FIG. For this reason, the exposure process at the time of forming each core layer is sufficient, and the manufacturing process can be simplified.

  The magnitude relationship between the refractive index of the core portion 14 and the refractive index of the low refractive index layer 145 is set in the same manner as the above-described magnitude relationship between the refractive index of the core portion and the refractive index of the cladding portion.

(Gradual increase)
FIG. 5 is a plan view showing a part of the optical waveguide 1 shown in FIG. 1 (the cover film 3 and the clad layer 113).

  The width in plan view of the core portion 14 formed in the core layers 131 and 132 may be uniform over the entire length, but as shown in FIG. 5, the width from the light incident end portion 1A toward the light emitting end portion 1B. It is preferable that the (outer diameter) gradually increases. In particular, in the core part 14 divided into three near the mirror 1612, the width on the right side (light emission end part 1B side) is wider than the width on the left side of the low refractive index layer 1451. preferable. Further, although not shown in FIG. 5, it is preferable that the width on the right side is wider than the width on the left side of the low refractive index layer 1452. Thereby, the probability that the signal light emitted from the light emitting element 72 and reflected by the mirror 1612 is incident on the core part 14 can be increased, and the transmission efficiency is improved. Similarly, in the core part 14 divided into four near the mirror 1614, the width on the right side is wider than the width on the left side (light incident end 1A side) from the low refractive index layer 1453. Is preferred. Further, although not shown in FIG. 5, it is preferable that the width on the right side is wider than the width on the left side of the low refractive index layer 1454, and the width on the right side is larger than the width on the left side of the low refractive index layer 1455. The width is preferably wider. Thereby, the probability that the signal light propagating through the core portion 14 enters the mirror 1614 can be increased, and the transmission efficiency can be improved.

  As an example of the rate of increase in the width, when the width before the increase is 1, the width after the increase is preferably about 1.02 to 1.50, and is about 1.05 to 1.40. More preferred.

  Although not shown in FIG. 5, it is preferable that the above configuration is also provided in the vicinity of the mirror 1611 and the vicinity of the mirror 1613.

  Thus, in the optical waveguide 1, the transmission efficiency is improved by gradually increasing the width from the light incident end 1 </ b> A toward the light exit end 1 </ b> B. Although FIG. 5 shows an example in which the width gradually increases in steps, the width may increase continuously.

  In the optical waveguide 1 shown in FIG. 5, the cross-sectional shape of the core portion 14 is rectangular (quadrangle). However, in the case of a circular shape or the like, it is preferable that the outer diameter of the core portion 14 is gradually increased.

  As described above, the optical waveguide 1 has the low refractive index layer 145 provided so as to extend along the second optical path that intersects the first optical path in the core portion 14. Thus, the crossing and loss of signal light can be suppressed, and the optical coupling efficiency with the light emitting / receiving element can be increased. Further, when the improvement in optical coupling efficiency is sacrificed to some extent, the tolerance of alignment accuracy and surface accuracy (processing accuracy) of the mirrors 1612 and 1614 is relaxed.

  In the optical waveguide 1, each second optical path is connected to each connection point 121 on the upper surface of the optical waveguide 1 by each mirror 1611, 1612, 1613, 1614. The first optical path can be accessed from the upper surface side of the optical waveguide 1. For this reason, the optical coupling is easily realized only by mounting the light emitting / receiving element on the upper surface of the optical waveguide 1. Moreover, in the optical waveguide 1, as described above, even if the first optical path and the second optical path cross each other, the transmission efficiency and the optical coupling efficiency are not easily lowered, so that the degree of freedom in designing the optical path is high. For example, when the optical waveguide 1 is viewed from the top, as shown in FIG. 5, the core portion 14 formed in the core layer 131 is hidden behind the core portion 14 formed in the core layer 132 and directly viewed. I can't. In the conventional optical waveguide, it was not possible to directly access the core part hidden behind from the upper surface side, but in the optical waveguide 1, since the first optical path and the second optical path can be crossed, By simply shifting the position of the connection point 121 along the first optical path, it is possible to access the hidden core part from the upper surface side. These effects do not change even when the number of core layers is increased. For this reason, the optical waveguide 1 can be highly easily densified and can be easily mounted.

<< Second Embodiment >>
Next, a second embodiment of the optical waveguide of the present invention will be described.

  FIG. 6 is an exploded perspective view showing a second embodiment of the optical waveguide of the present invention and an optical waveguide module including the optical waveguide module (partially shown).

  Hereinafter, although 2nd Embodiment etc. are described, in the following description, it demonstrates centering around difference with 1st Embodiment etc., The description is abbreviate | omitted about the same matter.

  This embodiment is the same as the first embodiment except that it has a mating hole 18 for an optical fiber connector that opens on the upper surface. Further, the optical waveguide module 10 shown in FIG. 6 is replaced with a surface-mounted light emitting / receiving element, an optical fiber connector such as a light emitting optical fiber connector 75 and a light receiving optical fiber connector 76, an optical fiber 70 connected thereto, 1 is the same as the optical waveguide module 10 shown in FIG.

  The light-emitting optical fiber connector 75 shown in FIG. 6 has a connector main body 751, four through holes 752 that penetrate the connector main body 751, and two engagement pins 753 that protrude from the lower surface of the connector main body 751. . Further, an optical fiber 70 is inserted into each through-hole 752, and the end face of each optical fiber 70 is configured to be exposed on the lower surface of the connector main body 751.

  Similarly, the optical fiber connector for receiving light 76 shown in FIG. 6 has a connector main body 761, four through holes 762 that penetrate the connector main body 761, and two mating pins 763 that protrude from the lower surface of the connector main body 761. doing. Further, the optical fibers 70 are inserted into the respective through holes 762, and the end surfaces of the optical fibers 70 are configured to be exposed on the lower surface of the connector main body 761.

  On the other hand, the optical waveguide 1 shown in FIG. 6 has four mating holes 18 on its upper surface. These mating holes 18 are configured to be mated with the mating pins 753 and 763 described above. By this mating, the optical fiber connector for light emission 75 and the optical fiber connector for light reception 76 are fixed to the optical waveguide 1 and Alignment can be performed.

  In addition, each through-hole 752 provided in the optical fiber connector 75 for light emission is formed so that the end surface of each optical fiber 70 inserted in each overlaps with the connection point 121 connected to the mirrors 1611 and 1612 of the optical waveguide 1. Yes. Similarly, each through-hole 762 provided in the optical fiber connector for light reception 76 is formed so that the end face of each optical fiber 70 inserted into each of the through holes 762 overlaps with the connection point 121 connected to the mirrors 1613 and 1614 of the optical waveguide 1. ing.

  According to the optical waveguide 1 having such a configuration, the same operation and effect as in the first embodiment can be obtained, and the optical fiber (only by engaging the engagement pins 753 and 763 of each connector with the engagement hole 18. Since the optical coupling with the light emitting / receiving element) can be performed, the optical coupling and the release thereof can be easily performed.

  FIG. 7 is a plan view showing a part of the optical waveguide 1 shown in FIG. 6 (the cover film 3 and the clad layer 113).

  In many cases, the light-emitting optical fiber connector 75 and the light-receiving optical fiber connector 76 are arranged so that the end faces of the optical fibers are line-symmetric with respect to the mating pins. For this reason, it is preferable that the optical waveguide 1 is also arranged so that the connection point 121 has a line-symmetrical positional relationship with respect to the mating hole 18 in accordance therewith. That is, it is preferable that a mirror and a low refractive index layer are disposed so as to satisfy this positional relationship. Thereby, the optical waveguide 1 can be connected to a general-purpose optical fiber connector.

  The arrangement of the optical fibers in the light-emitting optical fiber connector 75 and the light-receiving optical fiber connector 76 is not limited to the lattice-like arrangement as shown in FIG. 6. For example, the positions of adjacent optical fibers are mutually along the longitudinal direction of the optical waveguide 1. The arrangement may be shifted. In this case, the arrangement of the mirror and the low refractive index layer formed in the optical waveguide 1 is also adjusted accordingly.

<Optical waveguide manufacturing method>
Next, an example of a method for manufacturing the optical waveguide 1 will be described. Here, a method for manufacturing the optical waveguide 1 shown in FIG. 2 is taken as an example.

  FIGS. 8-11 is a figure (sectional drawing) for demonstrating the method to manufacture the optical waveguide shown in FIG. 2, respectively.

  The optical waveguide 1 removes a laminated body 12 in which a clad layer 111, a core layer 131, a clad layer 112, a core layer 132, and a clad layer 113 are laminated in this order, and a part of the laminated body 12 from below. And have recesses 1601, 1602, 1603, and 1604 formed.

  In such an optical waveguide 1, after each layer is manufactured individually and a recess is formed in each layer, a method of stacking the layers or after manufacturing each layer individually and stacking the layers to obtain a laminate Although manufactured by a method of forming a recess in the laminate, the latter method will be described here.

  Hereinafter, the manufacturing method of the optical waveguide, [1] a step of manufacturing a base material for forming a laminate, [2] a step of forming a refractive index difference by irradiating a part of the base material with active radiation, [3] The process for forming the recess will be described separately.

  [1] The base material 960 for forming the laminate is manufactured by, for example, a method in which the layers 911 and 912 are individually formed on the support substrate, and then separated from the support substrate and bonded to each other. .

  Specifically, each layer-forming composition 901, 902 is applied onto a support substrate 951 to form a liquid film, and then the liquid film is homogenized and volatile components are removed (see FIG. 8).

  Examples of the coating method include a doctor blade method, a spin coating method, a dipping method, a table coating method, a spray method, an applicator method, a curtain coating method, and a die coating method.

  In order to remove volatile components in the liquid film, a method of heating the liquid film, placing the liquid film under reduced pressure, or spraying a dry gas is used. Thereby, the layers 911 and 912 are obtained.

  Next, the layers 911 and 912 are peeled from the support substrate 951 and stacked. Thereby, the base material 960 shown in FIG. 9 is obtained. Note that the base material 960 can also be formed by removing the volatile components after sequentially coating the compositions 901 and 902 on the support substrate 951.

  Examples of the composition for forming the layers 911 and 912 include solutions (dispersions) obtained by dissolving or dispersing the constituent materials of the respective layers in various solvents.

  Among these, the composition 901 for forming the core layer includes a polymer 915 and an additive 920 such as a monomer and a polymerization initiator. In the layers 911 and 912 formed from such a composition, the monomer reacts by irradiation with actinic radiation, and accordingly, the abundance ratio of the polymer 915 and the monomer is biased, so that the active radiation irradiation region and the non-irradiation are not irradiated. A refractive index difference can be formed between the regions. Therefore, by using such a composition 901, the core part 14 and the side cladding part 15 can be formed in the core layers 131 and 132.

  On the other hand, the composition 902 for forming the cladding layer is mainly composed of the constituent material of the cladding layer described above, and has a lower refractive index than the highest refractive index included when a refractive index difference occurs in the core layer. The composition is used. Note that the composition 902 for forming the clad layer does not contain the monomer as described above, and therefore, no refractive index difference is formed even when irradiated with actinic radiation.

Therefore, the base material 960 for manufacturing the optical waveguide 1 is obtained by alternately laminating the layers 911 formed from the composition 901 and the layers 912 formed from the composition 902.
Here, the components of the composition 901 for forming the core layer will be described.

(polymer)
The polymer 915 serves as a base polymer for the core layer.

  The polymer 915 has sufficiently high transparency (colorless and transparent) and is compatible with the monomer described later, and among them, the monomer can react (polymerization reaction or crosslinking reaction) as described later. There are preferably used those having sufficient transparency even after the monomer is polymerized.

  Here, “having compatibility” means that the monomer is at least mixed and does not cause phase separation with the polymer 915 in the composition 901 or the layer 911.

  Examples of such a polymer 915 include cyclic olefin resins such as norbornene resins and benzocyclobutene resins, acrylic resins, methacrylic resins, polycarbonates, polystyrenes, epoxy resins, polyamides, polyimides, polybenzoxazoles, Examples thereof include silicone resins, polyurethanes, fluorine resins, and the like, and one or two or more of these can be used (polymer alloy, polymer blend (mixture), copolymer, etc.).

  Among these, those mainly composed of cyclic olefin resins are preferable. By using a cyclic olefin resin as the polymer 915, a core layer having excellent optical transmission performance and heat resistance can be obtained.

  As cyclic olefin resin, what was described in Unexamined-Japanese-Patent No. 2010-090328 is used, for example.

  Note that the refractive index of each part of the core layer is determined according to the relative magnitude relationship between the refractive index of the polymer 915 and the refractive index of the monomer in each part and the abundance ratio thereof, so that the polymer 915 depends on the type of monomer used. You may make it adjust the refractive index of this suitably.

  For example, in order to obtain a polymer 915 having a relatively high refractive index, a monomer having an aromatic ring (aromatic group), a nitrogen atom, a bromine atom or a chlorine atom in the molecular structure is generally selected, A polymer 915 is synthesized (polymerized). On the other hand, in order to obtain a polymer 915 having a relatively low refractive index, a monomer having an alkyl group, a fluorine atom or an ether structure (ether group) is generally selected in the molecular structure, and the polymer 915 is synthesized ( Polymerization).

  Further, the polymer 915 as described above has a leaving group (leaving pendant group) that is branched from the main chain and at least a part of the molecular structure of which can be detached from the main chain upon irradiation with actinic radiation. Also good. Since the refractive index of the polymer 915 decreases due to the removal of the leaving group, the polymer 915 can form a refractive index difference depending on the presence or absence of irradiation with actinic radiation.

  Examples of the polymer 915 having such a leaving group include a polymer having at least one of an —O— structure, an —Si—aryl structure, and an —O—Si— structure in a molecular structure. Such a leaving group is released relatively easily by the action of a cation.

  Among these, as the leaving group that causes a decrease in the refractive index of the resin by leaving, at least one of the -Si-diphenyl structure and the -O-Si-diphenyl structure is preferable.

  Specific examples of the polymer 915 having a leaving group in the side chain include those described in JP 2010-090328 A.

  On the other hand, examples of another leaving group include a substituent having an acetophenone structure at the terminal. This leaving group is released relatively easily by the action of free radicals.

  The content of the leaving group is not particularly limited, but is preferably 10 to 80% by weight, more preferably 20 to 60% by weight in the polymer 915 having a leaving group in the side chain. . When the content is within the above range, both flexibility and refractive index modulation function (effect of changing the refractive index difference) are particularly excellent.

  For example, the width for changing the refractive index can be expanded by increasing the content of the leaving group.

(Additive)
Additive 920 contains a monomer and a polymerization initiator.

((monomer))
The monomer reacts in the irradiation region of the actinic radiation to form a reactant by irradiation with actinic radiation, which will be described later, and the monomer diffuses and moves with it, so that the layer 911 is refracted between the irradiation region and the non-irradiation region. It is a compound that can cause a rate difference.

  As a reaction product of the monomer, a polymer (polymer) formed by polymerizing the monomer in the polymer 915, a cross-linked structure in which the monomer cross-links the polymers 915, and a polymer 915 obtained by polymerizing the monomer to the polymer 915. At least one of the branched structures branched from.

  By the way, since the refractive index difference generated between the irradiated region and the non-irradiated region is generated based on the difference between the refractive index of the polymer 915 and the refractive index of the monomer, the monomer contained in the additive 920 is the polymer 915. Is selected in consideration of the magnitude relationship with the refractive index.

  Specifically, in the layer 911, when it is desired that the refractive index of the irradiated region be high, a polymer 915 having a relatively low refractive index and a monomer having a high refractive index with respect to the polymer 915 are added. Used in combination. On the other hand, when it is desired that the refractive index of the irradiated region be low, a polymer 915 having a relatively high refractive index and a monomer having a low refractive index with respect to the polymer 915 are used in combination.

  Note that “high” or “low” in the refractive index does not mean an absolute value of the refractive index but means a relative relationship between certain materials.

  When the refractive index of the irradiated region in the layer 911 decreases due to the monomer reaction (reactant generation), the portion becomes the side cladding portion and the low refractive index layer of the core layer, and the refractive index of the irradiated region increases. In this case, the portion becomes the core portion of the core layer.

  As the monomer, a monomer having compatibility with the polymer 915 and having a refractive index difference with the polymer 915 of 0.01 or more is preferably used.

  Such a monomer is not particularly limited as long as it is a compound having a polymerizable site, and examples thereof include norbornene monomers, acrylic acid (methacrylic acid) monomers, epoxy monomers, oxetane monomers, and vinyl ether monomers. , A styrene monomer, etc., and one or more of these can be used in combination.

  Among these, it is preferable to use a monomer or oligomer having a cyclic ether group such as an oxetanyl group or an epoxy group, or a norbornene monomer as the monomer. By using a monomer or oligomer having a cyclic ether group, the cyclic ether group is likely to be opened, so that a monomer capable of reacting quickly can be obtained. Moreover, by using a norbornene-based monomer, a core layer (optical waveguide 1) having excellent optical transmission performance and excellent heat resistance and flexibility can be obtained.

  Among these, the molecular weight (weight average molecular weight) of the monomer having a cyclic ether group or the molecular weight (weight average molecular weight) of the oligomer is preferably 100 or more and 400 or less, respectively.

  Examples of the monomer having an oxetanyl group and the oligomer having an oxetanyl group include those described in JP 2010-090328 A. Among these, those represented by the following formula (20) are particularly preferable.

  Examples of the monomer having an epoxy group and the oligomer having an epoxy group include those described in JP 2010-090328 A.

  The addition amount of these monomers is preferably 1 part by weight or more and 50 parts by weight or less, and more preferably 2 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the polymer. Thereby, refractive index modulation can be performed, and there is an effect that both flexibility and heat resistance can be achieved.

((Polymerization initiator))
The polymerization initiator acts on the monomer with irradiation of actinic radiation to promote the reaction of the monomer, and is added as necessary in consideration of the reactivity of the monomer.

  The polymerization initiator to be used is appropriately selected according to the type of monomer polymerization reaction or crosslinking reaction. For example, radical polymerization initiators are preferably used exclusively for acrylic acid (methacrylic acid) monomers and styrene monomers, and cationic polymerization initiators are preferably used exclusively for epoxy monomers, oxetane monomers, and vinyl ether monomers.

  Examples of the radical polymerization initiator include benzophenones and acetophenones.

  On the other hand, examples of the cationic polymerization initiator include a Lewis acid generating type such as a diazonium salt, and a Bronsted acid generating type such as an iodonium salt and a sulfonium salt.

  In particular, when a monomer having a cyclic ether group is used as the monomer, the following cationic polymerization initiator (photoacid generator) is preferably used. Specifically, what was described in Unexamined-Japanese-Patent No. 2010-090328 is mentioned.

  The content of the polymerization initiator is preferably 0.01 parts by weight or more and 0.3 parts by weight or less, more preferably 0.02 parts by weight or more and 0.2 parts by weight or less with respect to 100 parts by weight of the polymer. . Thereby, there exists an effect of a reactive improvement.

In addition, when the reactivity of a monomer is remarkably high, you may abbreviate | omit addition of a polymerization initiator.
Further, the additive 920 may contain a sensitizer and the like in addition to the monomer and the polymerization initiator.

  Among these, the sensitizer increases the sensitivity of the polymerization initiator to light and is suitable for the function of reducing the time and energy required for the activation (reaction or decomposition) of the polymerization initiator and for the activation of the polymerization initiator. It has a function of changing the wavelength of light to a wavelength. Specifically, what was described in Unexamined-Japanese-Patent No. 2010-090328 is mentioned.

  The content of the sensitizer in the composition 901 is preferably 0.01% by weight or more, more preferably 0.5% by weight or more, and further preferably 1% by weight or more. In addition, it is preferable that an upper limit is 5 weight% or less.

  In addition to the above as additive 920, composition 901 includes a catalyst precursor, a cocatalyst, an antioxidant, an ultraviolet absorber, a light stabilizer, a silane coupling agent, a coating surface improver, and a thermal polymerization inhibitor. , Leveling agents, surfactants, colorants, storage stabilizers, plasticizers, lubricants, fillers, inorganic particles, deterioration inhibitors, wettability improvers, antistatic agents, and the like.

  The layer 911 obtained from the composition 901 as described above has a predetermined refractive index due to the action of the additive 920 that is uniformly dispersed in the polymer 915. Then, the refractive index is partially modulated by irradiation with actinic radiation, which will be described later, and the refractive index is biased.

  [2] Next, a mask (masking) 935 in which an opening (window) 9351 is formed is prepared, and the base material 960 is irradiated with active radiation 930 through the mask 935 (see FIG. 10).

  Hereinafter, the case where a monomer having a refractive index lower than that of the polymer 915 is used as the monomer contained in the composition 901 will be described as an example.

  That is, in the example shown here, the irradiation region 925 of the active radiation 930 is mainly the side clad portion and the low refractive index layer.

  Therefore, in the example shown here, the mask 935 is mainly formed with openings (windows) 9351 equivalent to the patterns of the side cladding portion and the low refractive index layer to be formed. This opening 9351 forms a transmission part through which the active radiation 930 to be irradiated passes.

  The mask 935 may be formed in advance (separately formed) (for example, plate-shaped) or formed on the base material 960 by, for example, a vapor deposition method or a coating method.

  Preferred examples of the mask 935 include a photomask made of quartz glass or a PET base material, a stencil mask, a metal thin film formed by a vapor deposition method (evaporation, sputtering, etc.), etc. Among these, it is particularly preferable to use a photomask or a stencil mask. This is because a fine pattern can be formed with high accuracy, and handling is easy, which is advantageous in improving productivity.

  Further, in FIG. 10, the opening (window) 9351 of the mask 935 is shown by partially removing the mask along the pattern of the irradiation region 925 of the active radiation 930. However, the quartz glass, the PET base material, etc. In the case of using the photomask manufactured in (1), it is also possible to use a photomask provided with a shielding portion of active radiation 930 made of a shielding material made of metal such as chromium. In this mask, the part other than the shielding part is the window (transmission part).

  The actinic radiation 930 to be used is not particularly limited as long as it can cause a photochemical reaction (change) with respect to the polymerization initiator and can release the leaving group contained in the polymer 915. For example, visible light, In addition to ultraviolet light, infrared light, and laser light, electron beams, X-rays, and the like can also be used.

  Among these, the actinic radiation 930 is appropriately selected depending on the type of the sensitizer when it contains a polymerization initiator, a leaving group type, and a sensitizer, and is not particularly limited, but has a wavelength of 200 to 450 nm. It is preferable to have a peak wavelength in the range. As a result, the polymerization initiator can be activated relatively easily and the leaving group can be removed relatively easily.

The irradiation dose of the actinic radiation 930 is preferably in the range of about 0.05~9J / cm ^2, more preferably about ^{0.1~6J / cm 2, 0.1~3J / cm} 2 of about More preferably.

  When the base material 960 is irradiated with the active radiation 930 through the mask 935, the following phenomenon occurs in the layer 911 formed of the composition 901 in the base material 960. First, the polymerization initiator is activated in the irradiated region 925 of the layer 911. Thereby, the monomer is polymerized in the irradiation region 925. When the monomer is polymerized, the amount of the monomer in the irradiated region 925 decreases, and accordingly, the monomer in the non-irradiated region 940 diffuses and moves to the irradiated region 925. As described above, since the polymer 915 and the monomer are appropriately selected so that a difference in refractive index occurs between them, a difference in refractive index occurs between the irradiated region 925 and the non-irradiated region 940 as the monomer diffuses and moves.

  FIG. 12 is a diagram for explaining a state in which a refractive index difference is generated between the irradiated region 925 and the non-irradiated region 940 in the base material 960. The horizontal cross-sectional position of the layer 911 is taken along the horizontal axis. It is a figure which shows refractive index distribution when taking the refractive index of this on the vertical axis | shaft.

  In this embodiment, since a monomer having a refractive index smaller than that of the polymer 915 is used as the monomer, the refractive index of the non-irradiated region 940 increases and the refractive index of the irradiated region 925 decreases as the monomer diffuses and moves ( FIG. 12 (a)).

  It is considered that the monomer diffusion movement is caused by the consumption of the monomer in the irradiation region 925 and the concentration gradient of the monomer formed accordingly. For this reason, the monomers in the entire non-irradiated region 940 do not move toward the irradiated region 925 all at once, but gradually move from a portion close to the irradiated region 925 and outward from the center of the non-irradiated region 940 to compensate for this. Monomer migration also occurs. As a result, as shown in FIG. 12A, the high refractive index region H on the non-irradiation region 940 side and the low refractive index region L on the irradiation region 925 side across the boundary between the irradiation region 925 and the non-irradiation region 940. Is formed. Since the high refractive index region H and the low refractive index region L are formed in accordance with the diffusion movement of the monomer as described above, they are necessarily constituted by smooth curves. Specifically, the high refractive index region H has, for example, a substantially U shape that protrudes upward, and the low refractive index region L has, for example, a substantially U shape that protrudes downward.

  The refractive index of the polymer obtained by polymerizing the monomers as described above is almost the same as the refractive index of the monomer before polymerization (the difference in refractive index is about 0 to 0.001). As the polymerization proceeds, the refractive index decreases according to the amount of the monomer and the amount of the substance derived from the monomer.

  On the other hand, in the non-irradiated region 940, the monomer is not polymerized because the polymerization initiator and the monomer are not activated.

  In addition, in the irradiation region 925, the ease of monomer diffusion transfer gradually decreases as the polymerization of the monomer proceeds. As a result, in the irradiated region 925, the closer to the non-irradiated region 940, the higher the monomer concentration, and the greater the amount of decrease in the refractive index. As a result, the distribution shape of the low refractive index region L formed in the irradiation region 925 is likely to be asymmetrical left and right, and the gradient on the non-irradiation region 940 side becomes steeper.

  Further, the polymer 915 may have a leaving group as described above. This leaving group is released upon irradiation with actinic radiation 930 and decreases the refractive index of the polymer 915. Therefore, when the irradiation region 925 is irradiated with the actinic radiation 930, in the layer 911, the diffusion movement of the monomer described above is started, the leaving group is released from the polymer 915, and the refractive index of the irradiation region 925 is equal to that before irradiation. (See FIG. 12B).

  Since this decrease in refractive index occurs uniformly in the entire irradiation region 925, the above-described difference in refractive index between the high refractive index region H and the low refractive index region L is further expanded. As a result, a graded index type refractive index distribution W shown in FIG. 12B is obtained. The graded index type refractive index distribution refers to a distribution having a maximum value of the refractive index and continuously decreasing so that the refractive index is tailed on both sides of the maximum value.

  Note that, in the core layer manufactured using the composition 901, the refractive index distribution of the core portion is a graded index type. Such a distribution has a stronger confinement effect of signal light propagating through the core portion than a step index type distribution in which the refractive index changes stepwise. For this reason, a core part with high transmission efficiency is obtained.

  In addition, the refractive index difference to be formed can be controlled by adjusting the irradiation amount of the active radiation 930. For example, the refractive index difference can be increased by increasing the irradiation amount.

  In addition, the formation of the refractive index difference as described above occurs simultaneously with one irradiation of the active radiation 930 in the plurality of layers 911 included in the base material 960. For this reason, it is not necessary to individually irradiate the plurality of layers 911, and the manufacturing process can be greatly simplified. In particular, in each of the above embodiments, the patterns formed on each core layer are the same except for the presence or absence of a mirror. For this reason, it can be said that each embodiment is a structure suitable for forming simultaneously by one irradiation. Furthermore, since the positional relationship between the layers of the patterns formed between the layers 911 is almost completely the same, the positional deviation is extremely small compared with the case of individually irradiating, and the optical coupling efficiency between the layers can be improved.

  On the other hand, the formation of the refractive index difference as described above does not occur in the layer 912 formed from the composition 902.

  Next, the base material 960 is subjected to heat treatment. In this heat treatment, the monomer in the irradiation region 925 irradiated with light is further polymerized. On the other hand, in this heating step, the monomer in the non-irradiated region 940 is volatilized. Thereby, in the non-irradiated region 940, the monomer is further reduced, the refractive index is increased, and the refractive index is close to that of the polymer 915.

  The heating temperature in this heat treatment is not particularly limited, but is preferably about 30 to 180 ° C, and more preferably about 40 to 160 ° C.

Further, the heating time is preferably set so that the polymerization reaction of the monomer in the irradiation region 925 is almost completed. Specifically, the heating time is preferably about 0.1 to 2 hours, preferably 0.1 to 1 hour. More preferred is the degree.
Note that this heat treatment may be performed as necessary and may be omitted.

  Based on the principle as described above, in the base material 960, a portion having a relatively high refractive index and a portion having a low refractive index are formed in the layer 911. As a result, the layer 911 becomes the core layer 131 and the core layer 132, and the layer 912 becomes the respective clad layers 111, 112, and 113, and the laminated body 12 in which these are laminated is obtained (see FIG. 11).

  In the case where a monomer having a higher refractive index than that of the polymer 915 is used, the refractive index of the movement destination becomes higher with the diffusion movement of the monomer, contrary to the above. The irradiation area 940 may be set.

  In addition, when light having high directivity such as laser light is used as the active radiation 930, the use of the mask 935 may be omitted.

[3] Next, recesses 1601, 1602, 1603, and 1604 are formed in the laminate 12.
These recesses 1601, 1602, 1603, and 1604 are formed by digging that removes a part from the lower surface side of the laminate 12. This digging process can be performed by, for example, a laser processing method, a dicing method using a dicing saw, or the like. In each of the above-described embodiments, since the concave portion is formed so that all the concave portions can be formed together after the stacked body 12 is formed, the reference position can be determined once when performing the digging process. For example, the reference position can be continuously used until all the recesses are formed. Therefore, the interval between the recesses can be reproduced with high accuracy, and the occurrence of optical coupling loss due to positional deviation can be suppressed.
The optical waveguide 1 is obtained as described above.

<Electronic equipment>
The optical waveguide of the present invention as described above has high optical coupling efficiency with other optical elements (light emitting / receiving elements and the like). For this reason, by providing the optical waveguide of the present invention, a highly reliable electronic device (electronic device of the present invention) capable of performing high-quality optical communication between two points can be obtained.

  Examples of the electronic device including the optical waveguide of the present invention include electronic devices such as a mobile phone, a game machine, a router device, a WDM device, a personal computer, a television, and a home server. In any of these electronic devices, it is necessary to transmit a large amount of data at high speed between an arithmetic device such as an LSI and a storage device such as a RAM. Therefore, by providing such an electronic device with the optical waveguide of the present invention, problems such as noise and signal degradation peculiar to electrical wiring are eliminated, and a dramatic improvement in performance can be expected.

  In addition, the amount of heat generated in the optical waveguide portion is greatly reduced compared to electrical wiring. For this reason, the electric power required for cooling can be reduced and the power consumption of the whole electronic device can be reduced.

  The optical waveguide, the opto-electric hybrid board, and the electronic device according to the present invention have been described above. However, the present invention is not limited to this, and for example, an arbitrary component may be added to the optical waveguide. .

  In addition, the method for producing an optical waveguide is not limited to the above-described ones. For example, a method in which molecular bonds are cut by irradiation with actinic radiation to change the refractive index (photo bleaching method), a composition is photoisomerized or photodimerized. Use a method such as a method (photoisomerization method or photodimerization method) that contains a photocrosslinkable polymer having an unsaturated bond and irradiates it with actinic radiation to change the molecular structure and change the refractive index. You can also.

Further, the refractive index distribution of the optical waveguide may be a step index type distribution or the like.
Further, the form of the optical waveguide does not have to be a laminated structure as described in each of the above embodiments, and may be a structure in which a tubular clad portion is provided so as to cover the core portion, for example.

Next, examples of the present invention will be described.
1. Optical waveguide manufacturing

Example 1
(1) Synthesis of norbornene-based resin having a leaving group In a glove box where both moisture and oxygen concentrations are controlled to 1 ppm or less and filled with dry nitrogen, 7.2 g (40.1 mmol) of hexylnorbornene (HxNB) ), 12.9 g (40.1 mmol) of diphenylmethylnorbornenemethoxysilane was weighed into a 500 mL vial, 60 g of dehydrated toluene and 11 g of ethyl acetate were added, and the top was sealed with a silicon sealer.

  Next, 1.56 g (3.2 mmol) of Ni catalyst represented by the following chemical formula (A) and 10 mL of dehydrated toluene are weighed in a 100 mL vial, put a stirrer chip, tightly plugged, and thoroughly agitate the catalyst. Dissolved in.

  When 1 mL of the Ni catalyst solution represented by the following chemical formula (A) is accurately weighed with a syringe and quantitatively injected into the vial bottle in which the above two types of norbornene are dissolved and stirred at room temperature for 1 hour, a marked increase in viscosity occurs. Was confirmed. At this point, the stopper was removed, 60 g of tetrahydrofuran (THF) was added, and the mixture was stirred to obtain a reaction solution.

  In a 100 mL beaker, 9.5 g of acetic anhydride, 18 g of hydrogen peroxide (concentration 30%) and 30 g of ion-exchanged water were added and stirred to prepare an aqueous solution of peracetic acid on the spot. Next, the total amount of this aqueous solution was added to the above reaction solution and stirred for 12 hours to reduce Ni.

  Next, the treated reaction solution was transferred to a separatory funnel, the lower aqueous layer was removed, and then 100 mL of a 30% aqueous solution of isopropyl alcohol was added and vigorously stirred. The aqueous layer was removed after standing and completely separating the two layers. After repeating this water washing process three times in total, the oil layer was dropped into a large excess of acetone to reprecipitate the polymer produced, separated from the filtrate by filtration, and then in a vacuum dryer set at 60 ° C. Polymer # 1 was obtained by heating and drying for 12 hours. The molecular weight distribution of the polymer # 1 was Mw = 100,000 and Mn = 40,000 by GPC measurement. The molar ratio of each structural unit in polymer # 1 was 50 mol% for the hexylnorbornene structural unit and 50 mol% for the diphenylmethylnorbornenemethoxysilane structural unit, as determined by NMR.

(2) Manufacture of composition (2-1) Manufacture of composition for core layer formation 10 g of the above-mentioned polymer # 1 was weighed into a 100 mL glass container, and 40 g of mesitylene and an antioxidant Irganox 1076 (manufactured by Ciba Geigy) ) 0.01 g, cyclohexyl oxetane monomer (monomer represented by the formula (20), manufactured by Toa Gosei CHOX, CAS # 483303-25-9, molecular weight 186, boiling point 125 ° C./1.33 kPa) 2 g, polymerization initiator (photoacid) Generating Agent) Rhodorsil Photoinitiator 2074 (manufactured by Rhodia, CAS # 178233-72-2) (1.36E-2 g in 0.1 mL of ethyl acetate) was added and dissolved uniformly, and then filtered through a 0.2 μm PTFE filter. A clean photosensitive resin composition was obtained.

(2-2) Manufacture of the composition for clad layer formation As the composition for clad layer formation, the photosensitive norbornene resin composition (Avatrel 2000P varnish by Promeras) was prepared.

(3) Manufacture of optical waveguide (manufacture of base material)
A composition for forming a clad layer was uniformly applied on a polyethersulfone (PES) film by a doctor blade, and then placed in a dryer at 45 ° C. for 15 minutes to form a clad layer forming layer. The formed cladding layer forming layer had a thickness of 5 μm and was colorless and transparent.

  Next, the core layer forming composition was uniformly applied on the formed clad layer forming layer with a doctor blade, and then placed in a dryer at 45 ° C. for 15 minutes to completely remove the solvent.

  The base material for manufacturing the optical waveguide was obtained by alternately coating the clad layer forming layer and the core layer forming layer as described above. The core layer forming layer had a thickness of 50 μm.

  The refractive index of the core part is 1.55, the refractive index of the cladding part (average of the refractive index of the side cladding part and the refractive index of the cladding layer) is 1.53, and the refractive index of the low refractive index layer is 1.54. Met.

(exposure)
Next, a photomask was pressed on the upper surface of the base material, and ultraviolet rays were selectively irradiated at 500 mJ / cm ² . The mask was removed, and heating was performed at 150 ° C. in a dryer for 1.5 hours. Note that a photomask having an opening corresponding to a low refractive index region such as a low refractive index layer or a side cladding portion shown in FIG. 5 was used. Thereby, the laminated body for manufacturing an optical waveguide was obtained. In the core layer in the obtained laminate, the width of the side cladding portion was 80 μm, and the thickness of the low refractive index layer was 5 μm. The width of the core portion was 45 μm in the vicinity of the light incident end, 50 μm in the intermediate portion, and 55 μm in the vicinity of the light emitting end so as to gradually expand along the light traveling direction.

(Concave processing)
Subsequently, the recessed part shown in FIG. 2 was formed with respect to the laminated body by laser processing. Thereby, the optical waveguide with a mirror shown in FIG. 2 was obtained. In addition, the length of the obtained optical waveguide was 10 cm, and the length between mirrors was made the same about any optical waveguide mentioned later.

(Example 2)
An optical waveguide was obtained in the same manner as in Example 1 except that the low refractive index layer located near the mirrors 1611 and 1612 at the light incident end was omitted.

(Example 3)
An optical waveguide was obtained in the same manner as in Example 1 except that the low refractive index layer located in the vicinity of the mirrors 1613 and 1614 at the light exit end was omitted.

Example 4
An optical waveguide was obtained in the same manner as in Example 1 except that the number of the low refractive index layers 145 in the low refractive index layers provided in the vicinity of the mirror 1614 in FIG. Note that the low refractive index layer 1454 that interferes with the mirror 1614 is reduced.

(Example 5)
An optical waveguide was obtained in the same manner as in Example 1 except that the thickness of the low refractive index layer was changed to 1 μm.

(Example 6)
An optical waveguide was obtained in the same manner as in Example 1 except that the thickness of the low refractive index layer was changed to 10 μm.

(Example 7)
An optical waveguide was obtained in the same manner as in Example 1 except that the thickness of the low refractive index layer was changed to 20 μm.

(Example 8)
An optical waveguide was obtained in the same manner as in Example 1 except that the thickness of the low refractive index layer was changed to 25 μm.

Example 9
An optical waveguide was obtained in the same manner as in Example 1 except that the thickness of the low refractive index layer was changed to 0.5 μm.

(Example 10)
An optical waveguide was obtained in the same manner as in Example 1 except that the width of the core portion was constant at 50 μm.

(Comparative example)
An optical waveguide was obtained in the same manner as in Example 1 except that the formation of the low refractive index layer was omitted. A cross-sectional view of the obtained optical waveguide is shown in FIG. In the optical waveguide 8 shown in FIG. 13, the clad layer 811, the core layer 831, the clad layer 812, the core layer 832, and the clad layer 813 are laminated in this order from the lower side. The core part and side clad part of the same conditions as the optical waveguide obtained in 1 are formed. Further, similarly to the optical waveguide obtained in the first embodiment, recesses 841, 842, 843, and 844 are formed corresponding to the respective core portions. A part of the inner wall surface of these recesses 841, 842, 843, and 844 constitutes a mirror.

2. Evaluation of optical waveguide 2.1. Evaluation of insertion loss of optical waveguide Light emitted from an 850 nm VCSEL (surface emitting laser) is introduced into the optical waveguide obtained in the example and the comparative example via an optical fiber of 50 μmφ, and received by an optical fiber of 200 μmφ. The light intensity was measured. The insertion loss method was used for the measurement. And the relative value when the insertion loss of the optical waveguide obtained by the comparative example was set to 1 was calculated | required, and this was evaluated according to the following evaluation criteria. For the evaluation, an optical path passing through the mirror 1612 and the mirror 1614 shown in FIG. 2 was used.

<Evaluation criteria for insertion loss>
AA: The relative value of insertion loss is less than 0.3 A: The relative value of insertion loss is 0.3 or more and less than 0.5 B: The relative value of insertion loss is 0.5 or more and less than 0.7 C: Relative value of insertion loss is 0.7 or more and less than 0.9 D: Relative value of insertion loss is 0.9 or more and less than 1 E: Relative value of insertion loss is 1 or more

2.2. Evaluation of Transmission Loss of Optical Waveguide After evaluating the insertion loss, the optical waveguide transmission loss (unit: dB / cm) was measured by the cut-back method by cutting off the vicinity of the mirror of the optical waveguide and making them all the same length.
The results are shown in Table 1.

  As is clear from Table 1, it was confirmed that the optical waveguides obtained in each example had a lower insertion loss than the optical waveguides obtained in the comparative examples.

  The transmission loss was almost the same except for the optical waveguides obtained in Examples 1, 7, 8, 10 and the comparative example. The transmission loss of the optical waveguides obtained in Examples 7, 8, 10 and the comparative example was about 20% larger than those of the other optical waveguides. In addition, the transmission loss of the optical waveguide obtained in Example 1 was about 20% smaller than the other ones.

  From the above results, even when the difference in transmission loss is subtracted, the optical waveguide obtained in each example has a lower loss at the coupling portion with the optical fiber than the optical waveguide obtained in the comparative example. It is guessed. Therefore, it has been clarified that the optical waveguide obtained in each example has high optical coupling efficiency with respect to the light receiving and emitting elements.

DESCRIPTION OF SYMBOLS 1 Optical waveguide 10 Optical waveguide module 111,112,113 Clad layer 12 Laminated body 121 Connection point 131,132 Core layer 14 Core part 145,1451,1452,1453,1454,1455 Low refractive index layer 15 Side surface clad part 1601,1602 , 1603, 1604 Recess 1611, 1612, 1613, 1614 Mirror 18 Interlocking hole 70 Optical fiber 71, 72 Light emitting element 710, 720 Element main body 711, 721 Light emitting part 712, 722 Electrode 73, 74 Light receiving element 730, 740 Element main body 731, 741 Light-receiving portion 732, 742 Electrode 75 Light-emitting optical fiber connector 751 Connector main body 752 Through hole 753 Mating pin 76 Light-receiving optical fiber connector 761 Connector main body 762 Through hole 763 Mating pin 77 Electrical wiring 78 Bump 79 Underfill 8 Optical waveguide 811, 812, 813 Clad layer 831, 832 Core layer 841, 842, 843, 844 Recess 901, 902 Composition 911, 912 Layer 915 Polymer 920 Additive 925 Irradiation region 930 Active Radiation 935 Mask 9351 Opening 940 Non-irradiation area 951 Support substrate 960 Base material 2 Support film 3 Cover film 1A Light incident end 1B Light exit end M1, M2, M3, M4 Intersection L1, L2, L3, L4, L5, L6 Light trace F Fragment H High refractive index region L Low refractive index region W Refractive index distribution

Claims (10)

A first core layer comprising a first core part and a first side cladding part adjacent to the first core part, a cladding layer, a second core part and a second side cladding part adjacent to the second core part And a second core layer including a laminate including a portion laminated in this order;
A first optical path provided in each of the first core part and the second core part;
A light reflecting surface provided in the first core portion;
Connection points provided on the surface of the laminate;
A second optical path that optically connects the light reflecting surface and the connection point and intersects the first optical path;
A first low refractive index layer that is provided on the opposite side of the first optical path in the first core portion from the light reflecting surface so as to cross the first core portion and has a lower refractive index than the first core portion. When,
The one end side and the other end side of the first optical path in the second core part so as to sandwich the second optical path in the second core layer and across the second core part, respectively. A second low refractive index layer provided and having a refractive index lower than that of the second core portion;
Have
When the surface of the laminate is viewed in plan, the first low refractive index layer and one of the two second low refractive index layers are provided at the same position. Optical waveguide. The light reflecting surface is configured by a surface that obliquely crosses the first core portion,
2. The optical waveguide according to claim 1, wherein the other one of the two second low-refractive index layers is provided at a position where the light reflecting surface and the cladding layer intersect. Furthermore, a light reflecting surface provided in the second core part;
A connection point provided on the surface of the laminate and optically connected to the light reflecting surface provided in the second core part;
Have
When the surface of the laminate is viewed in plan, the position of the light reflecting surface provided in the first core portion and the position of the light reflecting surface provided in the second core portion are different from each other. Item 3. The optical waveguide according to Item 1 or 2.   4. The optical waveguide according to claim 1, wherein a thickness of the first low refractive index layer and a thickness of the second low refractive index layer are 0.5 to 50 μm, respectively.   The first core layer and the second core layer are each manufactured by forming a refractive index difference between an active radiation irradiation region and a non-irradiation region. The optical waveguide according to item 1.   The optical waveguide according to claim 5, wherein the first low refractive index layer and the second low refractive index layer are formed by the same exposure process.   2. The width of a portion of the first core portion located on the light incident side from the low refractive index layer is smaller than a width of a portion located on the light emission side of the low refractive index layer. 7. The optical waveguide according to any one of 6 above. The second low refractive index layer provided on one end side of the first optical path in the second core portion is used as one end side second low refractive index layer, and the second low refractive index layer is provided on the other end side of the first optical path. When the second low refractive index layer is the other end side second low refractive index layer,
An intermediate second low refractive index that is provided between the one end side second low refractive index layer and the other end side second low refractive index layer in the second core portion and has a refractive index lower than that of the second core portion. The optical waveguide according to claim 1, further comprising a layer.   An opto-electric hybrid board comprising the optical waveguide according to claim 1.   An electronic apparatus comprising the opto-electric hybrid board according to claim 9.

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