JP2016012005A - Optical waveguide, opto-electric hybrid board, and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical waveguide capable of preventing the occurrence of crosstalk in association with optical path conversion and performing high-quality optical communication, and a photoelectric hybrid substrate and an electronic apparatus that include the optical waveguide.SOLUTION: An optical waveguide 1 comprises a core layer 13 and a cavity part 170A. The core layer 13 is formed with: a long core part 14; a side clad part 15 provided to surround an end part 141 of the core part 14; and a low refractive index part 16 provided between the end part 141 and the side clad part 15 and having a refractive index lower than that of the side clad part 15. The cavity part 170A (light reflection part) is provided in a portion of the core layer 13, includes an inclined surface 171 (boundary surface) being in oblique contact with an optical axis C1 of the core part 14, and reflects light transmitted in the core part 14 on the inclined surface 171. In a planar view of the core layer 13, an end 141a in a longitudinal direction of the end part 141 of the core part 14 is located inside the cavity part 170A, and the low refractive index part 16 overlaps with an outer edge of the cavity part 170A.

Description

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

  In recent years, optical waveguides are becoming popular as a means for guiding an optical signal 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 light, 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.

  When such an optical waveguide replaces, for example, the electrical wiring in the signal processing board, problems specific to electrical signals such as generation of high-frequency noise and deterioration of the electrical signal are eliminated, and the signal processing board can be further increased in throughput. It is expected to be.

  When replacing electrical wiring with an optical waveguide, it is necessary to perform mutual conversion between an electrical signal and an optical signal. Therefore, an optical device including a light emitting element, a light receiving element, and an optical waveguide that optically connects between them. Waveguide modules have been developed.

  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.

  In the optical interface as described above, it is necessary to change the optical path with a mirror formed in the optical waveguide so that the signal light emitted from the light emitting portion of the light emitting element enters the core portion of the optical waveguide.

  As such a mirror, for example, a mirror that converts the optical path of the core part by forming a hollow part by removing a part of the core part and using the inner wall surface of the hollow part as a reflecting surface is known. ing.

JP 2005-294407 A

  In recent years, the number of core portions formed in one optical waveguide tends to increase, and the interval between the parallel core portions is also narrowed. However, as a result, when the optical path is converted by the mirror, a phenomenon that light enters the adjacent mirror or core portion easily occurs. Such a phenomenon is called crosstalk and is one of the causes of lowering the S / N ratio of optical communication.

  An object of the present invention is to provide an optical waveguide capable of suppressing the occurrence of crosstalk due to optical path conversion and performing high-quality optical communication, and an opto-electric hybrid board and an electronic apparatus including the optical waveguide. .

Such an object is achieved by the present inventions (1) to (7) below.
(1) A long core part, a side clad part provided so as to surround at least one end part of the core part, and adjacent to the end part in at least a short direction of the core part. A core layer formed between the end portion and the side clad portion, and a low refractive index portion having a lower refractive index than the side clad portion;
A light reflecting portion provided in a part of the core layer, the light reflecting portion being located at a boundary between the light reflecting portion and the core layer, the boundary surface being obliquely in contact with the optical axis of the core portion; A light reflecting portion configured such that light propagating through the portion is reflected at the boundary surface;
Have
In a plan view of the core layer as viewed from the thickness direction, the end in the longitudinal direction of the core portion among the ends is located inside the light reflecting portion, and the low refractive index portion and the An optical waveguide characterized by overlapping an outer edge of a light reflecting portion.

  (2) The optical waveguide according to (1), wherein the light reflecting portion is made of a low refractive index material having a refractive index lower than that of the core portion.

  (3) The optical waveguide according to (1) or (2), wherein the light reflecting portion includes a cavity provided in a part of the core layer.

(4) The core part includes a wide part having a relatively wide width, and a narrow part having a relatively narrow width adjacent to the wide part in the longitudinal direction of the core part. ,
The optical waveguide according to any one of (1) to (3), wherein the end portion overlaps part or all of the wide portion in the plan view.

  (5) The light guide according to any one of (1) to (4), wherein a difference between a maximum refractive index of the side cladding portion and a minimum refractive index of the low refractive index portion is 0.002 to 0.05. Waveguide.

  (6) An opto-electric hybrid board comprising the optical waveguide according to any one of (1) to (5) above.

  (7) An electronic apparatus comprising the optical waveguide according to any one of (1) to (5).

  ADVANTAGE OF THE INVENTION According to this invention, the optical waveguide which can suppress generation | occurrence | production of the crosstalk accompanying optical path conversion and can perform high quality optical communication is obtained.

  In addition, according to the present invention, a highly reliable opto-electric hybrid board and electronic apparatus having such an optical waveguide can be obtained.

It is a perspective view which shows 1st Embodiment of the optical waveguide of this invention. It is a figure which sees through and shows the outline of a light reflection part and a core part among the optical waveguides shown in FIG. FIG. 3A is a plan view of the optical waveguide shown in FIG. 1, and FIG. 3B is a cross-sectional view taken along line AA of FIG. It is a figure which emphasizes and shows a light reflection part with a thick line among the optical waveguides shown in FIG. It is a top view which shows 1st Embodiment of the optical waveguide of this invention, Comprising: It is a figure for demonstrating the effect of this invention. 6A is a cross-sectional view of the core layer in the cross-sectional view taken along the line BB in FIG. 3, and FIG. 6B is an example of a refractive index distribution in the core layer. It is a perspective view which shows 2nd Embodiment of the optical waveguide of this invention, Comprising: It is a figure which sees through and shows the outline of a light reflection part and a core part. FIG. 8A is a plan view of the optical waveguide shown in FIG. 7, and FIG. 8B is a cross-sectional view taken along the line AA in FIG. FIG. 9A is a plan view showing a third embodiment of the optical waveguide of the present invention, and FIG. 9B is a cross-sectional view taken along line AA in FIG. 9A. It is a top view which shows 4th Embodiment of the optical waveguide of this invention. It is a top view which shows 5th Embodiment of the optical waveguide of this invention. It is a top view which shows 6th Embodiment of the optical waveguide of this invention. It is a top view which shows 7th Embodiment of the optical waveguide of this invention. FIG. 14A is a plan view showing an eighth embodiment of the optical waveguide of the present invention, and FIG. 14B is a cross-sectional view taken along line AA of FIG. It is a longitudinal cross-sectional view which shows embodiment of the opto-electric hybrid board | substrate of this invention. 6 is a plan view showing an optical waveguide obtained in Comparative Example 1. FIG. 10 is a plan view showing an optical waveguide obtained in Comparative Example 2. FIG. 10 is a plan view showing an optical waveguide obtained in Comparative Example 3. FIG.

  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>
<< First Embodiment >>
First, a first embodiment of the optical waveguide of the present invention will be described.

  FIG. 1 is a perspective view showing a first embodiment of an optical waveguide according to the present invention. FIG. 2 is a perspective view showing the outline of the light reflecting portion and the core portion in the optical waveguide shown in FIG. FIG. 3A is a plan view of the optical waveguide shown in FIG. 1, and FIG. 3B is a cross-sectional view taken along line AA of FIG. FIG. 4 is a diagram showing a light reflecting portion highlighted in a thick line in the optical waveguide shown in FIG. FIG. 5 is a plan view showing the first embodiment of the optical waveguide of the present invention, and is a view for explaining the effect of the present invention. In the following description, the lower side in FIG. 3B is referred to as “lower”, and the upper side in FIG. 3B is referred to as “upper”.

  An optical waveguide 1 shown in FIG. 1 has a band shape, and transmits an optical signal between a light incident portion and a light emitting portion to perform optical communication.

  As shown in FIG. 3B, the optical waveguide 1 includes a laminate 10 in which a clad layer 11, a core layer 13, and a clad layer 12 are laminated from below. In the core layer 13, a long core portion 14 and a side clad portion 15 provided adjacent to the side surface are formed. 2 and 3, the core portion 14 and the side cladding portion 15 that are visible when the core layer 13 is seen through the cladding layer 12 are illustrated.

  The width and height (the thickness of the core layer 13) of the core part 14 are not particularly limited, but are preferably about 1 to 200 μm, more preferably about 5 to 100 μm. Thereby, it is possible to increase the density of the core part 14 while increasing the transmission efficiency of the core part 14. That is, since the number of core portions 14 that can be laid per unit area can be increased, large-capacity optical communication can be performed even in a small area.

  Further, the refractive index distribution in the width direction and the refractive index distribution in the thickness direction of the optical waveguide 1 may be so-called step index (SI) type distributions in which the refractive index changes discontinuously, respectively. May be a so-called graded index (GI) type distribution in which the values continuously change.

  Further, the core portion 14 may be linear or curved in plan view. Furthermore, the core part 14 may branch on the way or may mutually cross | intersect.

  Furthermore, the cross-sectional shape of the core portion 14 is not particularly limited, and may be a circle such as a perfect circle, an ellipse, or an oval, or a polygon such as a triangle, a rectangle, a pentagon, or a hexagon. By being (rectangular shape), the core part 14 of the stable quality can be manufactured efficiently.

  On the other hand, the cladding layer 11 is provided below the core layer 13, and the cladding layer 12 is provided above the core layer 13.

  The average thickness of the cladding layers 11 and 12 is preferably about 0.05 to 1.5 times the average thickness of the core layer 13, and more preferably about 0.1 to 1.25 times. Specifically, the average thickness of the cladding layers 11 and 12 is preferably about 1 to 200 μm, more preferably about 3 to 100 μm, and further preferably about 5 to 60 μm. Thereby, the function as a clad part is ensured while preventing the optical waveguide 1 from becoming thicker than necessary.

  The clad layers 11 and 12 may be provided as necessary and may be omitted. Even in this case, for example, outside air functions as a cladding layer.

  The optical waveguide 1 is provided with a recess 170 formed by removing a part thereof. That is, the optical waveguide 1 includes the laminated body 10 and the concave portion 170 formed thereon. The concave portion 170 shown in FIG. 1 is located in the middle of the longitudinal direction of the core portion 14. A part of the inner side surface of the recess 170 is an inclined surface 171 that is in contact with the optical axis C <b> 1 (see FIG. 3B) of the core portion 14 while being inclined. That is, the inner surface of the portion corresponding to the core layer 13 (the portion included in the extension of the core layer 13) of the recess 170 is the inclined surface 171. The inclined surface 171 can be said to be a boundary surface between the concave portion 170 and the core portion 14.

  Further, the inside of the recess 170 is hollow. In other words, it can be said that the concave portion 170 is filled with air having a refractive index lower than that of the core portion 14. Therefore, when the portion corresponding to the core layer 13 in the recess 170 is defined as “cavity 170A”, the constituent material of the recess 170 and the constituent material of the core portion 14 are defined at the boundary surface between the cavity 170A and the core portion 14. Reflection of light occurs based on the difference in refractive index. As a result, the inclined surface 171 including the boundary surface in the surface functions as a mirror that converts the optical path of the core portion 14. That is, the inclined surface 171 can change the propagation direction by, for example, reflecting the light that enters from the right end of FIG. Therefore, it can be said that the hollow portion 170A is a “light reflecting portion”. In FIG. 4, the outline of the cavity 170A (light reflecting portion) is indicated by a thick line, and the space of the cavity 170A (light reflecting portion) is indicated by oblique lines intersecting each other.

  As shown in FIG. 3B, the vertical cross-sectional shape of the recess 170 is a trapezoid whose upper base is longer than the lower base. In addition, this longitudinal cross-sectional shape is not specifically limited, For example, a triangle, a parallelogram, etc. may be sufficient.

  The inclined surface 171 is a flat surface continuously formed from the cladding layer 12 through the core layer 13 to the middle of the cladding layer 11 as shown in FIGS. Further, another inclined surface 172 is provided at a position facing the inclined surface 171 in the inner surface of the recess 170. Similar to the inclined surface 171, the inclined surface 172 is a flat surface continuously formed from the cladding layer 12 through the core layer 13 to the middle of the cladding layer 11.

  On the other hand, two surfaces of the inner surface of the recess 170 that are substantially parallel to the optical axis of the core portion 14 are upright surfaces 173 and 174 that are substantially perpendicular to the upper surface of the cladding layer 12, respectively.

  The two inclined surfaces 171 and 172 and the two upright surfaces 173 and 174 as described above constitute the inner surface of the recess 170.

  Further, the shape of the opening of the recess 170 is rectangular as shown in FIG. The shape of the opening is not particularly limited, and may be, for example, other quadrilaterals (including trapezoids, parallelograms, etc.), pentagons, hexagons, and oval shapes. It may be.

  In addition, the line segment (ridge line) formed by the contact between the inclined surface 171 and the inclined surface 172 and the upper surface of the cladding layer 12 corresponds to the short side of the opening forming the rectangle of the recess 170. On the other hand, the upright surface 173 and the line segment (ridge line) formed by contacting the upright surface 174 and the upper surface of the cladding layer 12 correspond to the long sides of the opening forming the rectangle of the recess 170, respectively.

  As described above, the inclined surface 171 is in contact with the optical axis of the core portion 14 while being inclined, but the optical axis conversion direction changes according to the inclination angle of the inclined surface 171. For this reason, the inclination angle of the inclined surface 171 is appropriately set according to the position of an optical component that is provided outside the optical waveguide 1 and optically connected to the core portion 14.

  For example, light propagating from the right to the left in the core portion 14 along the optical axis C <b> 1 shown in FIG. 3B is reflected downward by the inclined surface 171. Then, the reflected light can be incident on an optical component (not shown) provided below the inclined surface 171.

  However, when a plurality of core portions 14 are adjacent to each other in the optical waveguide 1, for example, as shown in FIG. 5, two core portions 14 are provided in the core layer 13 via the side clad portion 15. In the case where they are present, the inclined surfaces 171 provided corresponding to the respective core portions 14 are adjacent to each other via the side clad portion 15. In such a case, when the density of the core portions 14 is increased, the distance between the inclined surfaces 171 is naturally shortened. As a result, there is a problem that the light reflected by the inclined surface 171 is likely to enter the adjacent inclined surface 171 and the core portion 14, and crosstalk is likely to occur.

  Therefore, the present inventor has intensively studied a method for suppressing the occurrence of crosstalk accompanying such optical path conversion. In the core layer 13, a low refractive index portion 16 having a refractive index lower than that of the side cladding portion 15 is provided between the core portion 14 and the side cladding portion 15, and in plan view, particularly in the core layer 13. It has been found that by optimizing the positional relationship between the corresponding cavity portion 170A, the core portion 14 and the low refractive index portion 16, occurrence of crosstalk associated with optical path conversion can be suppressed, and the present invention is completed. It came to.

  That is, in the present invention, when the optical waveguide 1 is viewed in plan as shown in FIG. 3A (when the core layer 13 is viewed in plan from the thickness direction), the core of the end portion 141 of the core portion 14 is the core. An end 141a in the longitudinal direction (left-right direction in FIG. 3) of the portion 14 is configured to be located inside the hollow portion 170A (light reflecting portion). In this way, by configuring the longitudinal end 141a of the core portion 14 to be located inside the cavity portion 170A, the outer edge of the cavity portion 170A indicated by a thick line in FIG. A relatively long distance from the end portion 141 of the portion 14 can be ensured. When a stress change occurs in the optical waveguide 1, the stress change based on the expansion and contraction in the longitudinal direction is usually more dominant than the short side direction. Therefore, the outer edge and the end of the cavity portion 170 </ b> A in the longitudinal direction of the core portion 14. Securing the distance from the portion 141 is effective in minimizing the influence of the stress change on the reflection characteristics of the inclined surface 171. By suppressing the stress change at the end portion 141 in this manner, it is possible to suppress the deformation of the inclined surface 171 and to prevent the inclined surface 171 from reflecting light in an unintended direction. As a result, it is possible to suppress the occurrence of crosstalk accompanying the optical path conversion.

  At the same time, in the present invention, when the optical waveguide 1 is viewed in plan, the low refractive index portion 16 adjacent in the short direction of the end portion 141 and the outer edge of the cavity portion 170A overlap each other. As described above, by providing the low refractive index portion 16 between the core portion 14 and the side clad portion 15, the end portion 141 has a low refractive index having a lower refractive index than the conventional one on both sides in the short direction. The state is sandwiched between the walls of the rate portion 16. In such a state, even if light is about to enter the inclined surface 171 from an unintended external optical component (for example, an optical component installed in accordance with an adjacent core part), the light is inclined to the inclined surface 171. It becomes difficult to enter. Similarly, even when light propagating through the core portion 14 is reflected in an unintended direction by the inclined surface 171, the light hardly enters the adjacent inclined surface 171. As a result, it is possible to suppress the occurrence of crosstalk accompanying the optical path conversion. 3 to 5, dense dots are attached to the core portion 14 and sparse dots are attached to the low refractive index portion 16.

  Although depending on the formation method, the side clad part 15 and the low refractive index part 16 have a lower refractive index than the core part 14, but their mechanical strength is often higher than that of the core part 14. Therefore, the above-described longitudinal end 141a is positioned inside the cavity 170A and the low refractive index portion 16 is overlapped with the outer edge of the cavity 170A. Since it is equivalent to corresponding to a region having high strength, it is useful to have the above positional relationship also from the viewpoint of enhancing resistance to stress change. In addition, by providing the low refractive index portion 16, an effect of weakening the influence of the stress change is also expected. For this reason, coupled with the above-described action of suppressing the occurrence of stress change, the inclined surface 171 is more difficult to deform, and the occurrence of crosstalk accompanying the optical path conversion can be more reliably suppressed.

  Furthermore, by configuring the low refractive index portion 16 and the outer edge of the cavity portion 170 </ b> A to overlap, many areas of the inclined surface 171 are occupied by the cross section of the core portion 14. For this reason, for example, when the concave portion 170 (hollow portion 170A) is formed by machining, laser processing, or the like, and the inclined surface 171 is obtained, variations in processing rate due to differences in constituent materials are less likely to occur. As a result, an inclined surface 171 with higher surface accuracy can be obtained, which contributes to increasing the light reflection efficiency on the inclined surface 171.

  As described above, according to the present invention, it is possible to obtain an optical waveguide capable of performing high-quality optical communication in which occurrence of crosstalk accompanying optical path conversion is suppressed and a decrease in S / N ratio is suppressed.

  The end portion 141 of the core portion 14 refers to one end in the longitudinal direction of the core portion 14 and a portion in the vicinity thereof. Specifically, it indicates a range of a length L1 along the longitudinal direction of the core portion 14 from the longitudinal end 141a of the core portion 14 shown in FIG. The end portion 141 of the core portion 14 is defined as a portion having a distance of the thickness t of the core portion 14 from the end 141 a in the longitudinal direction of the core portion 14. Since the end portion 141 is close to a portion adjacent to the inclined surface 171, if the change of the stress distribution reaches this portion, there is a possibility that the reflection characteristics on the inclined surface 171 are greatly affected. Therefore, according to the present invention, it is possible to minimize a decrease in reflection characteristics on the inclined surface 171 by suppressing a change in stress generated in the end portion 141 of the core portion 14.

  In the present invention, as described above, when the optical waveguide 1 is viewed in plan, the end 141a in the longitudinal direction of the end 141 of the core 14 may be inside the cavity 170A. When the portion 170A is in such a positional relationship, the core portion 14 is exposed on the inclined surface 171. Therefore, the inclined surface 171 includes a boundary surface where the core portion 14 having a higher refractive index than that of the side cladding portion 15 and air are adjacent, that is, a boundary surface between portions having a sufficiently large refractive index difference. It has sufficient reflection characteristics.

  Therefore, according to the present invention, it is possible to suppress a decrease in the reflection characteristics on the inclined surface 171 when the temperature changes, and to secure a sufficient refractive index difference on the inclined surface 171 to obtain a high reflection characteristic. be able to. As a result, the optical waveguide 1 can be connected with high optical coupling efficiency when optically connected to an external optical component.

  In the present invention, when the optical waveguide 1 is viewed in plan, the end 141a in the longitudinal direction of the end portion 141 of the core portion 14 is located inside the cavity portion 170A and adjacent to the short side direction of the end portion 141. The matching low refractive index portion 16 only needs to overlap the outer edge of the cavity portion 170A (see the thick line in FIG. 4). For example, how far the end 141a in the longitudinal direction is located inside the cavity portion 170A, etc. The optimization of the positional relationship between the end 141 and the cavity 170A is also considered.

  Specifically, in the longitudinal direction of the core part 14, the shortest distance between the longitudinal end 141a of the core part 14 and the outer edge (contour) of the cavity part 170A is L2 (see FIG. 3), and the maximum length of the cavity part 170A is set. When the thickness is L3 (see FIG. 3), the shortest distance L2 is preferably about 5 to 90% of the maximum length L3, more preferably about 7 to 85%, and about 10 to 70%. More preferably. By setting the ratio of the shortest distance L2 to the maximum length L3 in this way, at least the influence of the stress change on the inclined surface 172 side does not easily reach the end portion 141 of the core portion 14. For this reason, the fall of the reflective characteristic in the inclined surface 171 can be suppressed more reliably. If the shortest distance L2 is less than the lower limit value, depending on the dimensions of each part, the above-described effects may be limited. On the other hand, if the shortest distance L2 exceeds the upper limit value, depending on the dimensions of each part. Can not secure a sufficient space for the inclined surface 171, and the inclination angle of the inclined surface 171 may be limited.

  The shortest distance L2 is a hollow portion located on the distal end side of the end portion 141 of the core portion 14 (on the left side from the end portion 141 in FIG. 3) in the longitudinal direction of the core portion 14 when the optical waveguide 1 is viewed in plan view. It is the shortest distance between the outer edge of 170A and the end 141a in the longitudinal direction of the end 141. The maximum length L3 is the length of the longest portion that the cavity 170A can take in the longitudinal direction of the core portion 14 when the optical waveguide 1 is viewed in plan.

Here, the core part 14 is a part having a higher refractive index than the side clad part 15 and the clad layers 11 and 12. The difference in refractive index between the clad part and the core part 14 is preferably 0.3% or more, and more preferably 0.5% or more. The upper limit value is not particularly set, but is preferably about 5.5%. The refractive index difference is expressed by the following equation when the refractive index of the core portion 14 is A and the refractive index of the cladding portion is B.
Refractive index difference (%) = | A / B-1 | × 100

  On the other hand, the low refractive index portion 16 is a portion having a refractive index lower than that of the side cladding portion 15. The difference between the lowest refractive index of the low refractive index portion 16 and the highest refractive index of the side cladding portion 15 is not particularly limited, but is preferably about 0.002 to 0.05, and is about 0.005 to 0.03. It is more preferable that By setting the refractive index difference in this way, the above-described effect when the low refractive index portion 16 is provided is more reliably exhibited. That is, when the difference between the lowest refractive index of the low refractive index portion 16 and the highest refractive index of the side cladding portion 15 is less than the lower limit value, the refractive index difference is too small, so that the interval between adjacent core portions 14 is narrow. For example, the effect of providing the low refractive index portion 16 as described above may be reduced. On the other hand, when the value exceeds the upper limit, the effect as described above is not affected, but depending on the shape of the core portion 14 in plan view, the spatial uniformity of the refractive index difference is reduced. There is a risk of inconveniences such as individual differences becoming large.

  The low-refractive-index part 16 should just be provided in the position which adjoins at least the edge part 141 in a transversal direction, but in the optical waveguide 1 shown in FIG. It is provided between the clad part 15. For this reason, the refractive index difference between the core portion 14 and the low refractive index portion 16 becomes larger than when the low refractive index portion 16 is not provided, and the transmission loss of the core portion 14 can be reduced.

  6A is a cross-sectional view of the core layer in the cross-sectional view taken along the line BB in FIG. 3, and FIG. 6B is an example of a refractive index distribution in the core layer. In the example of the refractive index distribution shown in FIG. 6, the refractive index distribution is formed so as to gradually increase toward the center of the core portion 14. Further, in the low refractive index portion 16 adjacent to the core portion 14, a refractive index distribution is formed so as to gradually decrease toward the center. Further, in the side clad portion 15, the refractive index is substantially constant.

  In such a refractive index distribution, the refractive index is distributed so as to change gently between the core portion 14 and the low refractive index portion 16 and between the low refractive index portion 16 and the side cladding portion 15. Yes. For this reason, the degree of change in structure or physical properties is moderate at these interfaces, which is also effective from the viewpoint of suppressing the stress change described above.

  The core layer 13 having such a refractive index distribution can be manufactured by, for example, a nanoimprint method, a direct drawing method, a direct exposure self-forming method, or the like. Among these, in the direct drawing method, radiation is locally irradiated toward a film having a refractive index modulation ability capable of forming a refractive index difference between an exposed region and a non-exposed region by irradiation of radiation such as light, By forming the refractive index difference, the core part 14, the side cladding part 15 and the low refractive index part 16 are formed.

  Examples of the principle of refractive index modulation include monomer diffusion, photobleaching, photoisomerization, photodimerization, and the like, and one or a combination of two or more of these is used. Of these, monomer diffusion is particularly preferably employed as the principle of refractive index modulation. In monomer diffusion, light is irradiated (exposed) partially to a film made of a material in which a photopolymerizable monomer having a refractive index different from that of the polymer is dispersed in the polymer to polymerize the photopolymerizable monomer. Along with the occurrence, the photopolymerizable monomer is moved and unevenly distributed, thereby causing a refractive index bias in the coating. Thereby, a refractive index difference arises between the exposure area | region and non-exposure area | region of a film, and the core part 14, the side clad part 15, and the low refractive index part 16 can be formed.

  In addition, as a material which produces a monomer diffusion, the photosensitive resin composition etc. which were described in Unexamined-Japanese-Patent No. 2010-090328 are mentioned, for example. In the monomer diffusion, the photopolymerizable monomer may be unevenly distributed between the core portion 14 and the side surface clad portion 15 in the process of movement of the photopolymerizable monomer. In this case, by using a photopolymerizable monomer having a refractive index lower than that of the polymer, a region having a lower refractive index than the side cladding portion 15 between the core portion 14 and the side cladding portion 15, that is, a low refractive index portion. 16 is formed. Therefore, according to the monomer diffusion, the core layer 13 can be efficiently formed in a desired pattern.

  On the other hand, in the case of refractive index modulation based on the principles of photobleaching, photoisomerization, and photodimerization, it is possible to adjust the amount of change in refractive index according to the amount of irradiated light (radiation dose). In photobleaching, the molecular structure in the material is cleaved by light irradiation, and the leaving group is detached from the main chain. Thereby, the refractive index of the material can be changed. In photoisomerization and photodimerization, light irradiation causes photoisomerization or photodimerization of the material, and the refractive index of the material changes.

  Examples of the material that causes photobleaching include core film materials described in JP-A-2009-145867.

  Examples of materials that cause photoisomerization include norbornene resins described in JP-A-2005-164650.

  Moreover, as a material which produces photodimerization, the photosensitive resin composition etc. which were described in Unexamined-Japanese-Patent No. 2011-105791 are mentioned, for example.

  Further, a refractive index difference may be formed by diffusing the refractive index adjusting agent in the polymer and continuously changing the concentration of the refractive index adjusting agent. Examples of a method for supplying the refractive index adjusting agent into the polymer include methods such as coating, spraying, adhesion, dipping, and deposition. When supplying the refractive index adjusting agent by such a supply method, an arbitrary refractive index distribution can be formed by adjusting the supply amount for each region. In addition, as a refractive index regulator, what was described in Unexamined-Japanese-Patent No. 2006-276735 is mentioned, for example.

  In addition, although the low refractive index part 16 shown in FIG. 3 has comprised strip | belt shape in planar view, it is preferable that the width | variety is about 2 to 60% of the width | variety of the core part 14, and is about 5 to 50%. More preferably. By setting the width of the low refractive index portion 16 within the above range, the optical waveguide 1 can be stably manufactured while exhibiting the above-described effects by the low refractive index portion 16. That is, when the width of the low refractive index portion 16 is less than the lower limit value, the width of the low refractive index portion 16 becomes insufficient, so that the effect may be limited depending on the width of the core portion 14. On the other hand, when the width of the low refractive index portion 16 exceeds the upper limit, the width of the low refractive index portion 16 is too wide, so that the refractive index of the low refractive index portion 16 is likely to be unstable and the manufacturability is lowered. At the same time, since it is necessary to widen the interval between the core portions 14 by the amount of the low refractive index portion 16, the formation density of the core portions 14 may be reduced.

  The concave portion 170 may be filled with a material having a lower refractive index than the core portion 14 (low refractive index material) as necessary. Even in this case, the inclined surface 171 reflects light based on the refractive index difference between the constituent material of the recess 170 and the constituent material of the core portion 14. In addition, when the low refractive index material is solid, it is possible to prevent foreign matter from entering the recess 170 or to make it difficult for the external environment of the optical waveguide 1 to directly affect the vicinity of the recess 170. The weather resistance of 1 can be improved.

  The low refractive index material is appropriately selected according to the refractive index of the core portion 14 and is not limited at all. Examples thereof include various resin materials such as silicone resins, polyolefin resins, and polyester resins. The lower the refractive index of the low refractive index material, the better as it is lower than the refractive index of the core portion 14, and it is preferable to be lower than 0.01. In the present specification, the low refractive index material includes a gas such as air.

  In addition, a material having light reflectivity, for example, a metallic material having a metallic luster, or the like may be formed on the inclined surface 171 as necessary. In this case, the recess 170 may be filled with various materials, and the refractive index of the material is not particularly limited.

  Examples of the metal material include simple substances or compounds of metals such as aluminum, silver, and nickel.

  Since the concave portion 170 is hollow, the refractive index difference between adjacent materials on the inclined surface 171 can be maximized compared to the case where the concave portion 170 is filled with some solid material. The reflection efficiency at 171 can be particularly increased.

  The inclined surface 171 is appropriately set according to the position of the optical component optically connected to the core portion 14 as described above. When the lower surface of the core layer 13 is used as the reference surface, the inclined surface 171 and the inclined surface are inclined. The angle formed by the surface 171 is preferably about 30 to 60 °, and more preferably about 40 to 50 °. By setting the tilt angle within the above range, it is possible to efficiently convert the optical path of the core portion 14 on the tilted surface 171 and to suppress the loss accompanying the optical path conversion.

  The angle formed between the reference surface and the inclined surface 172 is not particularly limited, but is preferably about 20 to 90 °, and more preferably the same as the inclined angle of the inclined surface 171. As a result, when stress is generated in the vicinity of the recess 170, the stress is less likely to be unevenly distributed, and the occurrence of problems due to stress concentration can be particularly suppressed. The angle formed by the reference surface and the inclined surfaces 171 and 172 refers to the angle on the side opposite to the concave portion 170 side among the angles formed by the reference surface and the inclined surfaces 171 and 172.

  On the other hand, the angle formed between the reference surface and the upright surfaces 173 and 174 is preferably about 60 to 90 °, more preferably about 70 to 90 °, and still more preferably about 80 to 90 °. By setting the angle formed by the reference surface and the upright surfaces 173 and 174 within the above range, it is possible to particularly suppress the stress applied to the interface between the cladding layer 11 and the core layer 13. In each figure, it is shown as approximately 90 °. In addition, the angle formed by the reference surface and the upright surfaces 173 and 174 refers to the angle on the side opposite to the concave portion 170 among the angles formed by the reference surface and the upright surfaces 173 and 174.

  Moreover, since the recessed part 170 provided with the upright surfaces 173 and 174 can suppress the width | variety to the minimum, when the several recessed part 170 is formed adjacently, the space | interval can be minimized. Therefore, keeping the angle formed by the reference surface and the upright surfaces 173 and 174 within the above range is useful in that the concave portions 170 can be arranged at a high density even with respect to the core portions 14 provided at a narrow pitch. is there. Further, by keeping the angle formed by the reference surface and the upright surfaces 173 and 174 within the above range, the stress concentration due to the difference in the physical properties of the materials constituting the layers in the vicinity of the upright surfaces 173 and 174 can be particularly suppressed. The reliability can be particularly improved.

  The maximum depth of the recess 170 is appropriately set from the thickness of the laminated body 10 and is not particularly limited, but is preferably 1 to 500 μm from the viewpoint of mechanical strength and flexibility of the optical waveguide 1. And more preferably about 5 to 400 μm. The concave portion 170 only needs to reach at least the core layer 13 and does not have to reach the cladding layer 11.

  Moreover, it is preferable that the pitch of the core part 14 is about 3-500 micrometers, and it is more preferable that it is about 5-300 micrometers. Thereby, the optical waveguide 1 in which the core portions 14 are integrated with high density can be obtained while sufficiently suppressing the crosstalk between the core portions 14.

  The constituent materials (main materials) of the core layer 13 and the cladding layers 11 and 12 as described above are, for example, acrylic ether, methacrylic resin, polycarbonate, polystyrene, cyclic ether resin such as epoxy resin and oxetane resin. , Polyamide, polyimide, polybenzoxazole, polysilane, polysilazane, silicone resin, fluorine resin, polyurethane, polyolefin resin, polybutadiene, polyisoprene, polychloroprene, polyester such as PET and PBT, polyethylene succinate, polysulfone, poly Various resin materials such as ethers and cyclic olefin resins such as benzocyclobutene resins and norbornene resins can be used. In addition, as cyclic olefin resin, what was described in Unexamined-Japanese-Patent No. 2010-090328 is used, for example.

  Further, the resin material may be a composite material in which materials having different compositions are combined. Since these are relatively easy to process, they are suitable as constituent materials for the core layer 13 and the clad layers 11 and 12 in which the concave portions 170 are formed.

  In addition, the edge part 141 mentioned above should just be applied to at least one edge part of the longitudinal direction of the core part 14, and may be applied to both edge parts. Further, the end portion 141 described above may be applied to one end portion of the core portion 14, and a connector or the like may be attached to the other end portion and connected to an external optical component via the connector.

  In addition, when a plurality of core portions are formed in the optical waveguide 1 and at least one of the core portions is the above-described core portion 14, occurrence of crosstalk due to optical path conversion is suppressed between adjacent inclined surfaces.

  The number of core portions formed in one optical waveguide 1 is not particularly limited, but is, for example, about 2 to 100.

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

  FIG. 7 is a perspective view showing a second embodiment of the optical waveguide of the present invention, and is a view seen through the outlines of the light reflecting portion and the core portion. FIG. 8A is a plan view of the optical waveguide shown in FIG. 7, and FIG. 8B is a cross-sectional view taken along the line AA in FIG. In the following description, the lower side in FIG. 8B is referred to as “lower”, and the upper side in FIG. 8B is referred to as “upper”. In FIG. 8, dense dots are attached to the core portion 14 and sparse dots are attached to the low refractive index portion 16.

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

  The optical waveguide 1 according to the second embodiment is the same as the optical waveguide 1 according to the first embodiment except that the shape of the core portion 14 in plan view is different.

  That is, in the optical waveguide 1 shown in FIGS. 7 and 8, the width of the end portion 141 of the core portion 14 in plan view is wider than the width of the portion adjacent to the end portion 141 in the longitudinal direction of the core portion 14. Here, the end portion 141 shown in FIGS. 7 and 8 is referred to as a “wide portion 145”, and a portion adjacent to the wide portion 145 is a portion having a relatively narrow width than the wide portion 145. " In other words, in the present embodiment, the entire end portion 141 of the core portion 14 corresponds to the wide width portion 145. In FIG. 8A, the clad layer 12 is shown so as to pass through.

  In such an optical waveguide 1, the wide width portion 145 (end portion 141) functions as an incident portion where light enters the core portion 14 or an emission portion where light from the core portion 14 is emitted. On the other hand, the narrow portion 146 has a function of propagating light incident on the core portion 14. As in the present embodiment, by providing the wide portion 145 having a relatively wide width and the narrow portion 146 having a relatively narrow width with respect to the core portion 14, the light entrance / exit efficiency with respect to the core portion 14 can be improved. Both transmission efficiency can be achieved. That is, since the wide portion 145 where the light is incident has a wide incident surface, it is easy to receive even diffused light, and light reception leakage is easily reduced. Further, since the narrow portion 146 is provided so as to be adjacent to the wide portion 145, the light emitted from the wide portion 145 is also emitted without being diffused so much that the optical coupling efficiency with respect to external optical components is significantly reduced. Can be suppressed. On the other hand, since the propagation angle is small in the narrow width portion 146, it is possible to suppress the occurrence of so-called higher-order modes, and it is easy to reduce the leaked light leaking from the core portion 14 to the low refractive index portion 16. For this reason, the transmission efficiency at a longer distance can be increased. Therefore, by providing the wide portion 145 and the narrow portion 146, the optical waveguide 1 in which high optical coupling efficiency and high transmission efficiency with respect to an external optical component are compatible is obtained.

  The width of the wide portion 145 (the length in the short direction) is preferably about 1.01 to 5 times the width of the narrow portion 146, and more preferably about 1.05 to 3 times. . As a result, the balance between the width of the wide portion 145 and the width of the narrow portion 146 is optimized, so that it is possible to suppress a decrease in transmission efficiency in the narrow portion 146 while maintaining the optical coupling efficiency in the wide portion 145. it can. Further, when a plurality of core portions 14 are formed in the optical waveguide 1, the formation density is difficult to decrease. Therefore, when the width of the wide portion 145 is less than the lower limit value, the meaning of providing the wide portion 145 is diminished, and thus the optical coupling efficiency may be insufficiently improved. On the other hand, if the width of the wide portion 145 exceeds the upper limit, depending on the width of the narrow portion 146, the difference in width between the wide portion 145 and the narrow portion 146 becomes too large, and transmission loss is likely to occur. At the same time, the width of the wide portion 145 becomes too wide, and the density at which the core portion 14 can be formed may be reduced.

  Also in the present embodiment, when the optical waveguide 1 is viewed in plan, the longitudinal end 141a of the end portion 141 of the core portion 14 is located inside the cavity portion 170A, and the short side direction of the end portion 141 Is adjacent to the outer edge of the cavity 170A. Thereby, when the optical waveguide 1 and an external optical component are optically connected, it is possible to suppress the occurrence of crosstalk accompanying the optical path conversion on the inclined surface 171. As a result, the optical waveguide 1 having a high S / N ratio and capable of performing high-quality optical communication is obtained.

  In addition, also in 2nd Embodiment, the effect | action and effect similar to 1st Embodiment are acquired. That is, when a plurality of core portions are formed in the optical waveguide 1 and at least one of the core portions is the above-described core portion 14, the occurrence of crosstalk associated with optical path conversion is suppressed between adjacent inclined surfaces.

«Third embodiment»
Next, a third embodiment of the optical waveguide of the present invention will be described.

  FIG. 9A is a plan view showing a third embodiment of the optical waveguide of the present invention, and FIG. 9B is a cross-sectional view taken along line AA in FIG. 9A. In the following description, the lower side in FIG. 9B is referred to as “lower”, and the upper side in FIG. 9B is referred to as “upper”. In FIG. 9, dense dots are attached to the core portion 14 and sparse dots are attached to the low refractive index portion 16.

  Hereinafter, the third embodiment will be described. In the following description, differences from the first and second embodiments will be mainly described, and description of similar matters will be omitted.

  The optical waveguide 1 according to the third embodiment is the same as the optical waveguide 1 according to the first and second embodiments except that the shape of the concave portion 170 in plan view is different.

  That is, in the optical waveguide 1 shown in FIG. 9, the shape of the opening of the concave portion 170 is rounded in a plan view. More specifically, the opening of the recess 170 shown in FIG. 9 has a rectangular shape with rounded corners. Since the opening of the recess 170 has such a rounded shape, when the temperature around the optical waveguide 1 changes, the change in the stress distribution in the vicinity of the opening is further suppressed. For this reason, the amount of change in the stress distribution spreading to the core portion 14 can be reduced, and the decrease in the light reflection efficiency on the inclined surface 171 can be further suppressed.

  9, the cross-sectional shape of the concave portion 170 at the interface between the cladding layer 12 and the core layer 13, the cross-sectional shape of the concave portion 170 at the interface between the core layer 13 and the cladding layer 11, and the bottom surface of the concave portion 170. Each of the shapes is preferably rounded. Thereby, the change in stress distribution can be further suppressed at each interface and bottom surface. As a result, a decrease in light reflection efficiency on the inclined surface 171 can be further suppressed.

  Note that the minimum curvature radii of the opening shape, the cross-sectional shape, and the bottom surface shape of the concave portion 170 are each preferably about 1 to 500 μm, more preferably about 3 to 400 μm, and further about 10 to 350 μm. preferable. Thereby, the fall of the light reflection efficiency in the inclined surface 171 can be suppressed more fully. If the minimum radius of curvature of the opening shape or the like exceeds the upper limit value, the area of the opening or the like becomes too large, and the formation density when forming the plurality of recesses 170 may be reduced.

  Also in the third embodiment, the same operation and effect as in the first and second embodiments can be obtained. That is, when a plurality of core portions are formed in the optical waveguide 1 and at least one of the core portions is the above-described core portion 14, the occurrence of crosstalk associated with optical path conversion is suppressed between adjacent inclined surfaces.

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

  FIG. 10 is a plan view showing a fourth embodiment of the optical waveguide of the present invention. In FIG. 10, dense dots are attached to the core portion 14, and sparse dots are attached to the low refractive index portion 16.

  Hereinafter, although 4th Embodiment is described, in the following description, it demonstrates centering around difference with 1st-3rd embodiment, The description is abbreviate | omitted about the same matter.

  The optical waveguide 1 according to the fourth embodiment is the same as the optical waveguide 1 according to the first to third embodiments except that the number of core portions 14 and the shape of the concave portion 170 in plan view are different.

  That is, the optical waveguide 1 shown in FIG. 10 includes two core portions 14. Each core part 14 includes a wide part 145 and a narrow part 146. Further, the end portion 141 of the core portion 14 and the wide width portion 145 coincide with each other.

  On the other hand, the optical waveguide 1 is configured so that the longitudinal ends 141a of the end portions 141 of the two core portions 14 are located inside the cavity portion 170A shown in FIG. . That is, one hollow portion 170 </ b> A is provided so as to straddle the end portions 141 of the plurality of core portions 14.

  Further, the optical waveguide 1 is configured such that the low refractive index portion 16 adjacent in the short direction of the end portion 141 overlaps the outer edge of the cavity portion 170A in the plan view.

  According to such an optical waveguide 1, when optically connected to an external optical component, optical signals interfere with each other between the two inclined surfaces 171, that is, crosstalk due to optical path conversion occurs. Can be suppressed. As a result, the optical waveguide 1 having a high S / N ratio and capable of performing high-quality optical communication is obtained.

  Moreover, in this embodiment, the optical path conversion of the several core part 14 is borne in one cavity part 170A. For this reason, the inclination angle, surface roughness, and the like of the inclined surface 171 are easily aligned for each core portion 14, and variations in the optical path conversion angle for each core portion 14 are suppressed. As a result, the optical coupling efficiency with respect to an external optical component in each core portion 14 can be made uniform, and the reliability of the optical waveguide 1 can be further improved. In addition, since the number of times of forming the cavity 170A is reduced, the manufacturing process of the optical waveguide 1 can be simplified.

In addition, the number of the core parts 14 which one cavity part 170A straddles is not specifically limited, Three or more may be sufficient.
Moreover, also in 4th Embodiment, the effect | action and effect similar to 1st-3rd embodiment are acquired.

«Fifth embodiment»
Next, a fifth embodiment of the optical waveguide of the present invention will be described.

  FIG. 11 is a plan view showing a fifth embodiment of the optical waveguide of the present invention. In FIG. 11, dense dots are attached to the core portion 14, and sparse dots are attached to the low refractive index portion 16.

  Hereinafter, although 5th Embodiment is described, in the following description, it demonstrates centering around difference with 1st-4th embodiment, The description is abbreviate | omitted about the same matter.

  The optical waveguide 1 according to the fifth embodiment is the same as the optical waveguide 1 according to the fourth embodiment except that the shape of the end portion 141 (wide portion 145) of the core portion 14 is different in plan view.

  That is, the optical waveguide 1 shown in FIG. 11 also includes two core portions 14 as in the optical waveguide 1 shown in FIG. 10, but the end portions 141 of the two core portions 14 are connected to each other. Is different. Thereby, compared with 2nd Embodiment, the width | variety of this edge part 141 (wide part 145) can be expanded more. As a result, the entrance / exit efficiency in the wide portion 145 is increased, and the optical coupling efficiency with respect to an external optical component can be further increased.

  Similarly to the above embodiments, the optical waveguide 1 is configured such that the end 141a in the longitudinal direction of the end 141 is located inside the cavity 170A shown in FIG.

  Further, the optical waveguide 1 is configured such that the low refractive index portion 16 adjacent in the short direction of the end portion 141 overlaps the outer edge of the cavity portion 170A in the plan view.

  According to such an optical waveguide 1, when optically connected to an external optical component, optical signals interfere with each other between the inclined surface 171 and an adjacent inclined surface (not shown). That is, it is possible to suppress the occurrence of crosstalk accompanying the optical path change. As a result, the optical waveguide 1 having a high S / N ratio and capable of performing high-quality optical communication is obtained.

Furthermore, many regions of the inclined surface 171 are occupied by the cross section of the core portion 14. For this reason, when the recessed part 170 is formed by, for example, machining or laser processing, variations in the processing rate due to differences in constituent materials are less likely to occur. As a result, the inclined surface 171 with higher surface accuracy is obtained, which contributes to increasing the light reflection efficiency on the inclined surface 171.
In addition, also in 5th Embodiment, the effect | action and effect similar to 1st-4th embodiment are acquired.

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

  FIG. 12 is a plan view showing a sixth embodiment of the optical waveguide of the present invention. In FIG. 12, dense dots are attached to the core portion 14, and sparse dots are attached to the low refractive index portion 16.

  Hereinafter, the sixth embodiment will be described. In the following description, differences from the first to fifth embodiments will be mainly described, and description of similar matters will be omitted.

  The optical waveguide 1 according to the sixth embodiment is the same as the optical waveguide 1 according to the third embodiment except that the shape of the wide portion 145 of the core portion 14 is different in plan view.

  That is, the wide portion 145 shown in FIG. 12 is longer in the longitudinal direction of the core portion 14 than the wide portion 145 shown in FIG. For this reason, in the plan view of the optical waveguide 1, a part of the wide portion 145 protrudes outward from the outline of the cavity 170A. However, even in this case, the end 141a in the longitudinal direction of the end portion 141 of the core portion 14 is located inside the cavity portion 170A, and is adjacent to the short direction of the end portion 141. The rate portion 16 overlaps the outer edge of the cavity portion 170A. In other words, in the present embodiment, the end portion 141 overlaps a part of the wide width portion 145, and although the end portion 141 (a part of the wide width portion 145) is located inside the cavity portion 170A, the wide width portion The other part of 145 protrudes outside the cavity 170A. For this reason, also in this embodiment, the same operation and effect as the third embodiment can be obtained.

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

  FIG. 13 is a plan view showing a seventh embodiment of the optical waveguide of the present invention. In FIG. 13, dense dots are attached to the core portion 14, and sparse dots are attached to the low refractive index portion 16.

  Hereinafter, the seventh embodiment will be described. In the following description, differences from the first to sixth embodiments will be mainly described, and description of similar matters will be omitted.

  The optical waveguide 1 according to the seventh embodiment is configured such that the width of the concave portion 170 (length in the short direction) gradually decreases from the opening of the concave portion 170 toward the bottom surface. On the other hand, the optical waveguide 1 according to the third embodiment is configured such that the width of the concave portion 170 becomes constant from the opening of the concave portion 170 toward the bottom surface.

  That is, in the recess 170 shown in FIG. 9, the inner surface is divided into inclined surfaces 171 and 172 and upright surfaces 173 and 174, whereas in the recess 170 shown in FIG. In correspondence with the upright surfaces 173 and 174 in FIG. 9, inclined surfaces 173 ′ and 174 ′ are provided. Such a recess 170 shown in FIG. 13 is useful from the viewpoint of manufacturing efficiency because it is relatively easy to form.

  In addition, also in such 7th Embodiment, the effect | action and effect similar to 1st-6th Embodiment are acquired.

<< Eighth Embodiment >>
Next, an eighth embodiment of the optical waveguide of the present invention will be described.

  FIG. 14A is a plan view showing an eighth embodiment of the optical waveguide of the present invention, and FIG. 14B is a cross-sectional view taken along line AA of FIG. In FIG. 14, in FIG. 13, dense dots are attached to the core portion 14, and sparse dots are attached to the low refractive index portion 16.

  Hereinafter, the eighth embodiment will be described. In the following description, differences from the first to seventh embodiments will be mainly described, and description of similar matters will be omitted.

  In the optical waveguide 1 (FIG. 9) according to the third embodiment described above, the inclined surface 172 is provided so as to face the inclined surface 171 in plan view, whereas the optical waveguide 1 according to the eighth embodiment ( In FIG. 14), an upright surface 172 ′ is provided corresponding to the inclined surface 172. Such a concave portion 170 shown in FIG. 14 is useful from the viewpoint of manufacturing efficiency because the processing amount is small when forming the concave portion 170.

  In addition, also in such 8th Embodiment, the effect | action and effect similar to 1st-7th Embodiment are acquired.

<Opto-electric hybrid board>
Next, an embodiment of the opto-electric hybrid board according to the present invention will be described.

FIG. 15 is a longitudinal sectional view showing an embodiment of the opto-electric hybrid board according to the present invention.
An opto-electric hybrid board 100 shown in FIG. 15 has an optical waveguide 1, an electric wiring board 5 laminated thereon, and an adhesive layer 90 that is interposed between them and adheres them. Hereinafter, the configuration of each part of the opto-electric hybrid board 100 will be sequentially described.

  The optical waveguide 1 shown in FIG. 15 includes a support film 2 provided below the laminate 10 and a cover film 3 provided above the laminate 10 in addition to the laminate 10. By providing these films, the laminate 10 can be protected from the external environment and external force, and the reliability of the optical waveguide 1 can be further increased.

  Examples of the constituent material of the support film 2 and the cover film 3 include various resin materials such as polyethylene terephthalate (PET), polyolefin such as polyethylene and polypropylene, polyimide, and polyamide.

  Moreover, although the average thickness of the support film 2 and the cover film 3 is not specifically limited, It is preferable that it is about 5-500 micrometers, and it is more preferable that it is about 10-400 micrometers. Thereby, the laminated body 10 can be more reliably protected from external force and an external environment.

  The electrical wiring board 5 shown in FIG. 15 has a multilayer board 50 having a core board 51 and build-up layers 52 laminated on both surfaces thereof, and a through hole 53 penetrating the multilayer board 50. .

  Examples of the constituent material of the core substrate 51 include various resin materials such as polyimide resins, polyamide resins, epoxy resins, various vinyl resins, and polyester resins such as polyethylene terephthalate resins. In addition, paper, glass cloth, resin film, etc. are used as a base material, and this base material is impregnated with a resin material such as a phenol resin, a polyester resin, an epoxy resin, a cyanate resin, a polyimide resin, or a fluorine resin. In addition to insulating substrates used for composite copper-clad laminates such as glass cloth / epoxy copper-clad laminates, glass nonwoven fabrics / epoxy copper-clad laminates, polyetherimide resin substrates, polyethers It may be a heat-resistant / thermoplastic organic rigid substrate such as a ketone resin substrate or a polysulfone resin substrate, or a ceramic rigid substrate such as an alumina substrate, an aluminum nitride substrate, or a silicon carbide substrate.

  The core substrate 51 is formed with through wirings that electrically connect the build-up layers 52 laminated on both surfaces thereof.

  On the other hand, the buildup layer 52 is formed by alternately laminating insulating layers 521 and conductor layers 522. The conductor layer 522 is patterned to form electrical wiring. Insulating layer 521 is formed with through wiring that connects the electrical wirings provided on both surfaces thereof.

  Each of the conductor layer 522 and the through wiring is made of a conductive material such as a simple metal such as copper, aluminum, nickel, chromium, zinc, tin, gold, silver, or an alloy containing these metal elements. .

  The insulating layer 521 is made of a silicon compound such as silicon oxide or silicon nitride, a resin material such as a polyimide resin or an epoxy resin, or the like.

  In this way, an electrical circuit that extends not only in the plane direction but also in the thickness direction can be constructed in the buildup layer 52, and the density of the electrical circuit can be increased.

  In addition, although such a multilayer substrate 50 may be formed by what kind of construction method, it is formed by various buildup construction methods, such as an additive method, a semi-additive method, and a subtractive method, as an example.

  The electrical wiring board provided in the opto-electric hybrid board of the present invention is not limited to the one including the multilayer board such as the electrical wiring board 5 described above. For example, the multilayer board is a single-layer electrical wiring board (rigid board). It may be replaced, or may be replaced with various flexible substrates such as a polyimide substrate, a polyester substrate, and an aramid film substrate. The multilayer substrate 50 can be replaced with a coreless multilayer substrate that does not include the core substrate 51. In the case of a flexible substrate, since the substrate itself has sufficient light transmittance, the through hole 53 that functions as an optical through hole may not be formed.

  Further, the electrical wiring substrate 5 shown in FIG. 15 has a solder resist layer 54 provided on the upper surface of the multilayer substrate 50. In the solder resist layer 54, an opening is formed at a connection portion with the conductor layer 522.

  The solder resist layer 54 is made of various resin materials and includes an inorganic filler as necessary. The average thickness of the solder resist layer 54 is not particularly limited, but is preferably about 10 to 100 μm, and more preferably about 20 to 50 μm.

  The optical / electrical hybrid substrate 100 is obtained by bonding the optical waveguide 1 and the electric wiring substrate 5 as described above through the adhesive layer 90.

  Further, by mounting the optical element 6 on the opto-electric hybrid board 100, an optical module 1000 is obtained. The optical element 6 shown in FIG. 15 has an element body 60, a light emitting / receiving portion 61 and a terminal 62 provided on the lower surface of the element body 60, and a bump 63 provided so as to protrude downward from the terminal 62. ing. The light emitting / receiving unit refers to a light receiving unit, a light emitting unit, or a unit having both functions.

  The optical element 6 is disposed such that the optical axis of the light emitting / receiving unit 61 and the optical axis of the core unit 14 coincide with each other via the inclined surface 171. Thereby, the optical waveguide 1 and the optical element 6 are optically connected, and the optical signal propagating through the optical waveguide 1 is received by the optical element 6, or the optical signal emitted from the optical element 6 is incident on the optical waveguide 1. You can do it.

  Further, the bump 63 is connected to the conductor layer 522. Thereby, the optical element 6 is mechanically fixed, the terminal 62 of the optical element 6 and the conductor layer 522 are electrically connected, and the operation of the optical element 6 can be controlled from the electric wiring board 5 side. Has been.

  Examples of the optical element 6 include a light emitting element such as a surface emitting laser (VCSEL), a light emitting diode (LED), and an organic EL element, and a light receiving element such as a photodiode (PD, APD).

  Further, an electric element (not shown) may be mounted on the opto-electric hybrid board 100 shown in FIG. Examples of the electric element include IC, LSI, RAM, ROM, capacitor, coil, resistor, and diode.

  Note that since the adhesive layer 90 is on the optical path, the adhesive layer 90 preferably has translucency. Examples of the constituent material of the adhesive layer 90 include resin materials such as an epoxy resin, an imide resin, a silicone resin, a phenol resin, and a urea resin.

  In such an opto-electric hybrid board 100 and the optical module 1000, when the light emitting / receiving unit 61 and the core unit 14 are optically connected via the inclined surface 171, the cross associated with the optical path conversion between the adjacent inclined surfaces. The occurrence of talk can be suppressed. Thereby, the fall of the S / N ratio in optical communication can be suppressed, and high quality optical communication can be realized. Therefore, the opto-electric hybrid board 100 and the optical module 1000 are highly reliable.

<Electronic equipment>
In the optical waveguide according to the present invention as described above, the occurrence of crosstalk accompanying the optical path conversion is suppressed. 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 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 electric wiring are eliminated, and the performance of the electronic device is dramatically improved. It can contribute to cost reduction.

  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.

  As described above, the optical waveguide, the opto-electric hybrid board and the electronic device of the present invention have been described, but the present invention is not limited to this, for example, the optical waveguide and the opto-electric hybrid board according to each embodiment described above, Arbitrary components may be added.

Next, specific examples of the present invention will be described.
1. Production of optical waveguide (Example 1)
(1) Synthesis of norbornene-based resin In a glove box whose moisture and oxygen concentrations are both controlled to 1 ppm or less and filled with dry nitrogen, 7.2 g (40.1 mmol) of hexylnorbornene (HxNB), diphenylmethylnorbornenemethoxy 12.9 g (40.1 mmol) of silane 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 and 10 mL of dehydrated toluene were weighed in a 100 mL vial, and a stirrer chip was placed and sealed, and the catalyst was thoroughly stirred to dissolve completely.

  When 1 mL of this Ni catalyst solution was accurately weighed with a syringe, and quantitatively injected into the vial bottle in which the two kinds of norbornene were dissolved and stirred at room temperature for 1 hour, a marked increase in viscosity 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) Production of composition for forming core layer 10 g of the above-mentioned polymer # 1 was weighed into a 100 mL glass container, and 40 g of mesitylene, 0.01 g of antioxidant Irganox 1076 (manufactured by Ciba Geigy), cyclohexyloxetane monomer (Toa) Synthetic CHOX, CAS # 483303-3-25-9, molecular weight 186, boiling point 125 ° C./1.33 kPa) 2 g, polymerization initiator (photoacid generator) Rhodosil Photoinitiator 2074 (manufactured by Rhodia, CAS # 178233-72-2) ( 0.025 g in 0.1 mL of ethyl acetate) was added and dissolved uniformly, and then filtered through a 0.2 μm PTFE filter to obtain a clean composition for forming a core layer.

(3) Manufacture of the composition for forming a clad layer The molar ratio of each structural unit of the purified polymer # 1 was changed to hexylnorbornene structural unit 80 mol% and diphenylmethylnorbornenemethoxysilane structural unit 20 mol%, respectively. A cladding layer forming composition was obtained in the same manner as the core layer forming composition except that it was used in place of polymer # 1.

(4) Production of first clad layer The clad layer-forming composition produced in (3) was uniformly applied with a doctor blade on the base film on which the release layer was formed, and then applied to a dryer at 50 ° C. Added for a minute. After completely removing the solvent, the entire surface was irradiated with UV light by a UV exposure machine to cure the applied composition. As a result, a colorless and transparent first cladding layer having a thickness of 10 μm was obtained. The cumulative amount of ultraviolet light was 500 mJ / cm ² .

(5) Preparation of core layer After apply | coating a core layer resin composition uniformly with a doctor blade on the base film in which the mold release layer was formed, it injected | thrown-in to 45 degreeC drying machine for 5 minutes. After completely removing the solvent to form a film, a photomask having a linear pattern of lines and spaces drawn on the entire surface was pressure-bonded onto the obtained film. Then, ultraviolet rays were irradiated from above the photomask with a parallel exposure machine. The cumulative amount of ultraviolet light was 800 mJ / cm ² .

  Next, the photomask was removed and placed in an oven at 150 ° C. for 20 minutes. Upon removal from the oven, it was confirmed that a clear waveguide pattern appeared on the coating. The thickness of the obtained core layer was 50 μm, and the number of core portions was 8.

  Here, a plurality of core layers were prepared, and a refractive index distribution was obtained with an interference microscope for one of the cross sections. As a result, a refractive index distribution as shown in FIG. 6 was observed in the cross section of the core layer. Therefore, the region where the refractive index distribution curve shows the maximum is the core portion, the region located on both sides of the region where the refractive index distribution curve shows the minimum is the low refractive index portion, and the low refractive index portion The dimension of each part was calculated | required by making the area | region located on the opposite side to a core part side into a side cladding part the area | region where a refractive index is higher than a low refractive index part. As a result, the width of the core portion was 50 μm, and the width of the low refractive index portion was 10 μm. The difference between the lowest refractive index of the low refractive index portion and the highest refractive index of the side cladding portion is shown as “refractive index difference” in the table.

(6) Preparation of second clad layer On the base film on which the release layer is formed, a clad layer forming composition is applied in the same manner as in (4), and a colorless and transparent second clad layer having a thickness of 10 μm is formed. Obtained.

(7) Manufacture of laminated body Next, a core layer was stacked on the first cladding layer. Then, the base film attached to the core layer was peeled off.

  Next, the second cladding layer was overlaid on the core layer. Then, the base film attached to the second cladding layer was peeled off.

  Thereafter, the first cladding layer, the core layer, and the second cladding layer were pressurized, and the layers were pressure-bonded to each other. This obtained the laminated body.

(8) Formation of recessed part Next, the cavity part (light reflection part) was formed in the both ends of the core part by laser processing, respectively. Thereby, an optical waveguide having a total length of 10 cm was obtained. The shape of the formed cavity is as shown in FIGS. Moreover, the dimension of each part based on the positional relationship of a cavity part and a core part is as showing below.

<Dimensions of each part based on the positional relationship between the cavity and the core>
・ Length L1: 50 μm
・ Shortest distance L2: 100 μm
・ Maximum length L3: 150 μm

(Example 2)
When producing the core layer, an optical waveguide was obtained in the same manner as in Example 1 except that the photomask used to irradiate ultraviolet rays was changed to form the core part having the shape shown in FIGS. . In addition, the dimension of the edge part of a core part was 50 micrometers of widths of the wide part, 70 micrometers of wide parts, and 50 micrometers of narrow parts. Moreover, the low refractive index part was formed so that the core part might be surrounded, and the width | variety of the low refractive index part was 20 micrometers. Furthermore, the shape of the laser processing mask used for producing the hollow portion was also changed in accordance with the change in the shape of the core portion.

(Example 3)
An optical waveguide was obtained in the same manner as in Example 2 except that the shape of the laser processing mask was changed to form the cavity having the shape shown in FIG. The minimum curvature radius of the shape of the laser processing mask was 20 μm.

(Examples 4 to 8)
The optical waveguide was formed in the same manner as in Example 3 except that the dimensions of the core part, the dimensions of each part based on the positional relationship between the cavity part and the core part, and the corresponding drawings were as shown in Tables 1 and 2. Obtained.

Example 9
An optical waveguide was obtained in the same manner as in Example 3 except that the recess was filled with a silicone material. A silicone material having a refractive index smaller by about 0.1 than that of the core portion was used.

(Example 10)
(1) Manufacture of composition for forming clad layer Daicel Chemical Industries, Ltd. alicyclic epoxy resin, Celoxide 2081 20 g, ADEKA Co., Ltd. cationic polymerization initiator, Adekaoptomer SP-170 0.6 g, A solution was prepared by stirring and mixing 80 g of methyl isobutyl ketone.

  Subsequently, the obtained solution was filtered with a PTFE filter having a pore size of 0.2 μm to obtain a clean and colorless composition for forming a clad layer.

(2) Manufacture of photosensitive resin composition As an epoxy polymer, phenoxy resin manufactured by Nippon Steel Chemical Co., Ltd., 20 g of YP-50S, 5 g of Celoxide 2021P manufactured by Daicel Chemical Industries, Ltd. as a photopolymerizable monomer, and polymerization As an initiator, 0.2 g of Adekaoptomer SP-170 manufactured by ADEKA Corporation was put into 80 g of methyl isobutyl ketone, and dissolved by stirring to prepare a solution.

  Subsequently, the obtained solution was filtered with a PTFE filter having a pore size of 0.2 μm to obtain a clean, colorless and transparent photosensitive resin composition.

(3) Production of lower clad layer The clad layer-forming composition was uniformly applied onto a polyimide film having a thickness of 25 µm by a doctor blade, and then placed in a dryer at 50 ° C for 10 minutes. After the solvent was completely removed, the entire surface was irradiated with ultraviolet rays with a UV exposure machine to cure the applied resin composition. As a result, a colorless and transparent lower cladding layer having a thickness of 10 μm was obtained. The cumulative amount of ultraviolet light was 500 mJ / cm ² .

(4) Production of core layer The photosensitive resin composition was uniformly applied by a doctor blade on the produced lower clad layer, and then placed in a dryer at 40 ° C for 10 minutes. After completely removing the solvent to form a film, ultraviolet rays were irradiated by a maskless exposure apparatus so as to draw a linear pattern of lines and spaces on the obtained film. The integrated light quantity of ultraviolet rays was 1300 mJ / cm ² .

  Next, the exposed film was placed in an oven at 150 ° C. for 30 minutes. Upon removal from the oven, it was confirmed that a plurality of clear waveguide patterns appeared on the coating. The thickness of the obtained core layer was 50 μm, and the number of core portions was 8.

  Here, a plurality of core layers were prepared, and a refractive index distribution was obtained with an interference microscope for one of the cross sections. As a result, a refractive index distribution as shown in FIG. 6 was observed in the cross section of the core layer. Therefore, the region where the refractive index distribution curve shows the maximum is the core portion, the region located on both sides of the region where the refractive index distribution curve shows the minimum is the low refractive index portion, and the low refractive index portion The dimension of each part was calculated | required by making the area | region located on the opposite side to a core part side into a side cladding part the area | region where a refractive index is higher than a low refractive index part. As a result, the width of the core portion was 50 μm, and the width of the low refractive index portion was 20 μm.

(5) Production of upper clad layer A clad layer-forming composition was applied on the produced core layer in the same manner as in (3) to obtain a colorless and transparent upper clad layer having a thickness of 10 μm.

(6) Formation of recessed part Next, the cavity part (light reflection part) was formed in the both ends of the core part by laser processing, respectively. Thereby, an optical waveguide having a total length of 10 cm was obtained. The shape of the formed cavity is as shown in Table 2. Table 2 also shows the dimensions of each part based on the positional relationship between the cavity part and the core part.

(Comparative Example 1)
An optical waveguide was obtained in the same manner as in Example 10 except that the positional relationship between the hollow portion and the core portion became the relationship shown in FIG. However, in forming the core layer, the low refractive index portion was not formed by changing the formation conditions and adjusting the amount of movement of the photopolymerizable monomer.

(Comparative Example 2)
An optical waveguide was obtained in the same manner as in Example 10 except that the positional relationship between the hollow portion and the core portion became the relationship shown in FIG. However, in forming the core layer, the low refractive index portion was not formed by changing the formation conditions and adjusting the amount of movement of the photopolymerizable monomer.

  The optical waveguide 9 shown in FIG. 16 and FIG. 17 is different from that of the hollow portion 970A and the end portion 941 of the core portion 94 in that the optical waveguide 9 shown in FIG. Same as 1. As shown in FIGS. 16 (a) and 17 (a), the optical waveguide 9 has an end 941a in the longitudinal direction of the core portion 94 out of the end portion 941 of the core portion 94 positioned outside the cavity portion 970A. doing. That is, the longitudinal end 941a of the core portion 94 shown in FIG. 16 is located on the left side of the cavity portion 970A, while the longitudinal end 941a of the core portion 94 shown in FIG. 17 is on the right side of the cavity portion 970A. Is located.

(Comparative Example 3)
An optical waveguide was obtained in the same manner as in Example 10 except that the positional relationship between the hollow portion and the core portion became the relationship shown in FIG.

  The optical waveguide 9 shown in FIG. 18 is the same as the optical waveguide 1 shown in FIG. 3 except that the positional relationship between the cavity portion 970A and the end portion 941 of the core portion 94 is different. That is, the optical waveguide 9 shown in FIG. 18 includes a side clad part 95 corresponding to the side clad part 15 shown in FIG. 3 and a low refractive index part 96 corresponding to the low refractive index part 16. In the short direction of the end portion 941 shown in FIG. 18, the outer edge of the cavity portion 970A overlaps the core portion 94, not the low refractive index portion.

2. 2.1 Evaluation of optical waveguide 2.1 Evaluation of crosstalk accompanying optical path conversion Of the optical waveguides obtained in each example and each comparative example, an incident side optical fiber having a diameter of 50 μm is used in accordance with the inclined surface of one end. Arranged. The incident-side optical fiber is connected to a light-emitting element for allowing light to enter the optical waveguide, and the optical axis thereof coincides with the optical axis of the optical fiber.

  On the other hand, an outgoing side optical fiber having a diameter of 50 μm was arranged at the other end of the optical waveguide in accordance with the inclined surface. The emission-side optical fiber is connected to a light receiving element for receiving light emitted from the optical waveguide, and the optical axis of the optical fiber coincides with the optical axis of the optical fiber.

  In evaluating the crosstalk, first, light was incident on one of the eight core portions. Next, the light intensity of the emitted light was measured at the core portion adjacent to the core portion where the light was incident. This emitted light is considered to contain leakage light due to crosstalk accompanying optical path conversion and leakage light due to crosstalk accompanying light propagation. Therefore, a test piece was prepared by cutting off the end of the core, and only leakage light due to crosstalk accompanying light propagation was measured. Then, the light intensity of the leaked light due to the crosstalk accompanying the light propagation was subtracted from the light intensity of the emitted light, and the light intensity of the leaked light due to the crosstalk accompanying the optical path conversion was calculated.

  Next, the intensity ratio of the light intensity of the leaked light due to the crosstalk accompanying the calculated optical path change with respect to the light intensity of the incident light was evaluated according to the following evaluation criteria.

<Evaluation criteria for strength ratio>
A: The intensity ratio is -30 [dB] or less B: The intensity ratio is more than -30 [dB] to -25 [dB] or less C: The intensity ratio is more than -25 [dB] to -20 [dB] or less Yes D: Intensity ratio is over -20 [dB] to -15 [dB] or less E: Intensity ratio is over -15 [dB] to -10 [dB] or less F: Intensity ratio is over -10 [dB] The above evaluation results are shown in Tables 1 and 2.

2.2 Evaluation of Insertion Loss and Mirror Loss About the optical waveguides obtained in each of the examples and comparative examples, “Testing method of polymer optical waveguide (JPCA-PE02-05- 01S-2008) ”, the insertion loss of the optical path through the inclined surface (mirror) was measured in accordance with the method for measuring the insertion loss of 4.6.1.

  Next, for the optical waveguides obtained in each Example and each Comparative Example, the light propagation loss was measured in accordance with the method for measuring the light propagation loss per unit length of 4.6.2 in the above test method.

  As a result, it was confirmed that the optical propagation loss was almost the same in each of the optical waveguides obtained in each example and each comparative example.

  Since the insertion loss of the optical waveguide is considered to be the sum of the light propagation loss and the mirror loss, the mirror loss was obtained for the optical waveguides obtained in the respective examples and the comparative examples. The obtained mirror loss was evaluated according to the following evaluation criteria.

<Evaluation criteria for mirror loss>
A: Mirror loss is small (less than 0.5 dB)
B: Mirror loss is slightly small (0.5 dB or more and less than 1.0 dB)
C: Mirror loss is slightly large (1.0 dB or more and less than 1.5 dB)
D: Mirror loss is large (1.5 dB or more and less than 2 dB)
E: Mirror loss is very large (2dB or more)
The above evaluation results are shown in Tables 1 and 2.

2.3 Evaluation of durability against temperature The optical waveguides obtained in the examples and the comparative examples were subjected to a temperature cycle test. The test conditions of the temperature cycle test are as shown below.

<Test conditions for temperature cycle test>
-Temperature: -60 to 150 ° C
・ Number of cycles: 500 cycles (30 minutes each for high temperature and low temperature)
・ Evaluation characteristics: Insertion loss

  Next, the insertion loss was compared before and after the test. And the increment of the insertion loss after a test was evaluated according to the following evaluation criteria. In addition, when the optical propagation loss per unit length was measured for the specimen after the test, there was almost no change from before the test, so most of the increase in insertion loss is considered to be due to an increase in mirror loss. It is done.

<Evaluation criteria for increment of insertion loss by temperature cycle test>
A: The increment is very small (less than 0.2 dB)
B: Small increment (0.2 dB or more and less than 0.5 dB)
C: Increment is slightly small (0.5 dB or more and less than 1.0 dB)
D: Slightly large increment (1.0 dB or more and less than 1.5 dB)
E: The increment is large (1.5 dB or more and less than 2 dB)
F: The increment is very large (2 dB or more)
The above evaluation results are shown in Tables 1 and 2.

  As is clear from Tables 1 and 2, it was confirmed that in the optical waveguides obtained in the respective examples, the occurrence of crosstalk accompanying the optical path conversion was suppressed.

  In addition, in the optical waveguide obtained in each example, mirror loss and increase in mirror loss when subjected to a temperature cycle test are suppressed, and the reliability of optical connection with external optical components is reduced. It was found to be expensive.

DESCRIPTION OF SYMBOLS 1 Optical waveguide 2 Support film 3 Cover film 5 Electrical wiring board 6 Optical element 9 Optical waveguide 10 Laminated body 11 Cladding layer 12 Cladding layer 13 Core layer 14 Core part 15 Side surface clad part 16 Low refractive index part 50 Multilayer board 51 Core board 52 Build-up layer 53 Through-hole 54 Solder resist layer 60 Element body 61 Light emitting / receiving portion 62 Terminal 63 Bump 90 Adhesive layer 94 Core portion 95 Side cladding portion 96 Low refractive index portion 100 Opto-electric hybrid board 141 End portion 141a Longitudinal end 141b Edge 145 in short direction Wide portion 146 Narrow portion 170 Recess 170A Cavity 171 Inclined surface 172 Inclined surface 172 ′ Upright surface 173 Upright surface 173 ′ Inclined surface 174 Upright surface 174 ′ Inclined surface 521 Insulating layer 522 Conductor layer 941 End 941a Longitudinal end 970A Cavity 1000 Optical module C1 Optical axis

Claims (7)

The long core part, a side clad part provided so as to surround at least one end part of the core part, and the end part adjacent to the end part in at least the short direction of the core part And a core layer in which a low refractive index portion having a lower refractive index than the side cladding portion is provided,
A light reflecting portion provided in a part of the core layer, the light reflecting portion being located at a boundary between the light reflecting portion and the core layer, the boundary surface being obliquely in contact with the optical axis of the core portion; A light reflecting portion configured such that light propagating through the portion is reflected at the boundary surface;
Have
In a plan view of the core layer as viewed from the thickness direction, the end in the longitudinal direction of the core portion among the ends is located inside the light reflecting portion, and the low refractive index portion and the An optical waveguide characterized by overlapping an outer edge of a light reflecting portion.   The optical waveguide according to claim 1, wherein the light reflecting portion is made of a low refractive index material having a refractive index lower than that of the core portion.   The optical waveguide according to claim 1, wherein the light reflecting portion is configured by a cavity provided in a part of the core layer. The core part includes a wide part having a relatively wide width, and a narrow part having a relatively narrow width adjacent to the wide part in the longitudinal direction of the core part.
The optical waveguide according to any one of claims 1 to 3, wherein the end portion overlaps part or all of the wide portion in the plan view.   The optical waveguide according to any one of claims 1 to 4, wherein a difference between a maximum refractive index of the side clad portion and a minimum refractive index of the low refractive index portion is 0.002 to 0.05.   An opto-electric hybrid board comprising the optical waveguide according to claim 1.   An electronic apparatus comprising the optical waveguide according to any one of claims 1 to 5.

Images