JP2020181120A - Optical waveguide, optical module, and electronic apparatus - Google Patents

Abstract

To provide an optical waveguide which suppresses the adhesive included in an adhesive layer that secures a cover layer from oozing out and with which the cover layer hardly peels off, and a high-reliability optical module and electronic apparatus equipped with this optical waveguide.SOLUTION: An optical waveguide 1 comprises: a core layer 13 including a core part 14; a first clad layer 12 and a second clad layer 11 laminated one on top of another via the core layer; a cavity part 160 penetrating the first clad layer and reaching the core part; and a first face 101 and a second face mutually having a surface-reverse relationship. The cavity part includes a lightguide part which opens in the first face and where the optical path of the core part is converted by the inner face of the cavity part, a cover layer 191 covering the opening of the cavity part and provided on the first face, and an adhesive layer 192 provided between the first face and the cover layer, the thickness of which being 25 μm or less and the adhesive force being 0.3 N/10 mm or greater.SELECTED DRAWING: Figure 3

Description

The present invention relates to optical waveguides, optical modules and electronic devices.

In optical communication using an 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 clad portion. A light emitting element such as a semiconductor laser is arranged on the incident side of the optical waveguide, and a light receiving element such as a photodiode is arranged on the exit side. The light incident from the light emitting element propagates through the optical waveguide and is received by the light receiving element.

When the optical waveguide and the light emitting element and the light receiving element are photocoupled, the optical path of the core portion is converted through a mirror formed in the middle of the core portion of the optical waveguide, and the light path is guided to the outside of the optical waveguide. Structures to be combined are being studied.

For example, Patent Document 1 discloses an optical waveguide having a core portion and a cavity portion provided in the core portion. The inclined surface located on the inner surface of this cavity functions as a mirror that converts the optical path of the core portion.

Further, Patent Document 1 discloses that a cover layer is provided so as to close the hollow portion. This makes it possible to protect the mirror.

JP-A-2015-197457

In the optical waveguide described in Patent Document 1, a bonding layer made of an adhesive or the like is used to fix the cover layer. In general, adhesives develop adhesive strength by curing. Therefore, shrinkage is accompanied during curing, and this curing shrinkage may deform the vicinity of the mirror covered by the cover layer. If the mirror is deformed, the loss may increase in the optical coupling through the mirror.

Therefore, it is considered to use an adhesive instead of the adhesive. The pressure-sensitive adhesive can fix the cover layer by the adhesive force. However, since the adhesive does not cure as significantly as the adhesive, it may flow even after the cover layer is fixed. For this reason, the adhesive may seep out and adhere to the mirror located on the inner surface of the cavity. Then, the reflection efficiency of the mirror is lowered. On the other hand, if an attempt is made to suppress exudation, there is a concern that the adhesive strength will decrease.

An object of the present invention is an optical waveguide that suppresses exudation of the adhesive contained in the pressure-sensitive adhesive layer that fixes the cover layer and that makes it difficult for the cover layer to peel off, and a highly reliable optical module provided with such an optical waveguide. To provide electronic devices.

Such an object is achieved by the present invention of the following (1) to (6).
(1) A core layer including a core portion, a first clad layer and a second clad layer laminated via the core layer, and a cavity portion that penetrates the first clad layer and reaches the core portion. A light guide portion having a first surface and a second surface having a front and back relationship with each other, the cavity portion opens to the first surface, and the optical path of the core portion is converted by the inner surface of the cavity portion. When,
A cover layer provided on the first surface and covering the opening of the cavity,
An adhesive layer provided between the first surface and the cover layer, having a thickness of 25 μm or less and an adhesive strength of 0.3 N / 10 mm or more.
An optical waveguide characterized by having.

(2) The light guide unit is
A first protective layer provided on the opposite side of the first clad layer from the core layer,
A second protective layer provided on the side of the second clad layer opposite to the core layer,
Have,
The optical waveguide according to (1) above, wherein the cavity portion also penetrates the first protective layer.

(3) The optical waveguide according to (1) or (2) above, wherein the cover layer is made of a polyimide resin as a main material.

(4) The optical waveguide according to any one of (1) to (3) above, wherein the pressure-sensitive adhesive layer is mainly made of a silicone resin.

(5) The optical waveguide according to any one of (1) to (4) above,
An optical element optically connected to the inner surface of the cavity,
An optical module characterized by having.

(6) An electronic device including the optical waveguide according to any one of (1) to (4) above.

According to the present invention, it is possible to obtain an optical waveguide that suppresses exudation of the pressure-sensitive adhesive from the pressure-sensitive adhesive layer that fixes the cover layer and that the cover layer is not easily peeled off.

Further, according to the present invention, a highly reliable optical module can be obtained.
Further, according to the present invention, a highly reliable electronic device can be obtained.

It is sectional drawing which shows the optical module which concerns on embodiment. It is a top view which shows the part of the optical module shown in FIG. 1 excluding the housing and the receptacle. It is a partially enlarged perspective view of the optical waveguide shown in FIG. FIG. 2 is a cross-sectional view taken along the line AA of FIG.

Hereinafter, the optical waveguide, the optical module, and the electronic device of the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.

1. 1. Optical Module First, the optical waveguide according to the embodiment and the optical module according to the embodiment will be described.

FIG. 1 is a cross-sectional view showing an optical module according to an embodiment. FIG. 2 is a plan view showing a portion of the optical module shown in FIG. 1 excluding the housing and the receptacle. In each figure of the present application, the three axes orthogonal to each other are the X-axis, the Y-axis, and the Z-axis. Further, in the following description, the tip end side of the Z axis is also referred to as "upper" and the proximal end side is also referred to as "lower".

The optical module 1000 (optical module according to the embodiment) shown in FIG. 1 includes an optical waveguide 1 (the optical waveguide according to the embodiment), an electric substrate 2, and a light emitting element 31 (optically connected to the optical waveguide 1). It has an optical element), a control element 4, a lens array 5, a receptacle 61, and a housing 7. In such an optical module 1000, the light emitted from the light emitting element 31 is output to the optical fiber 9 via the optical waveguide 1. Therefore, the optical module 1000 according to the present embodiment functions as an optical transmitter.

The electric substrate 2 shown in FIG. 1 includes an insulating substrate 21, a conductive layer 22 provided on the upper surface of the insulating substrate 21, and a contact 23.

Further, a light emitting element 31 and a control element 4 are mounted on the upper surface of the electric substrate 2 shown in FIG. These elements and the conductive layer 22 are electrically connected via a bonding wire (not shown). The connection structure is not limited to the bonding wire, and may be replaced by another structure such as flip chip bonding.

Examples of the light emitting element 31 include a surface emitting laser (VCSEL), a light emitting diode (LED), and an organic EL element.
Further, examples of the control element 4 include a driver IC and the like.

In addition to the above-mentioned elements, a light receiving element such as a photodiode or a phototransistor, a CPU (central arithmetic processing device), an MPU (microprocessor unit), an LSI, an IC, a RAM, a ROM, and a capacitor are placed on the electric substrate 2. , Coil, resistor, diode and other various electronic components may be mounted. Further, a light receiving element may be used instead of the light emitting element 31. In that case, the optical module 1000 functions as an optical receiver. Further, by using the light emitting element 31 and the light receiving element together, the optical module 1000 functions as an optical transmitter / receiver.

Further, a contact 23 electrically connected to the conductive layer 22 is provided at the left end of the electric substrate 2 shown in FIG. The portion provided with the contact 23 is inserted into and fitted to the electric connector 82 attached to the right end of the electric wiring 81 shown in FIG. As a result, the electric board 2 and the electric wiring 81 are electrically connected via the electric connector 82. As a result, an external electrical connection is made to the optical module 1000.

On the other hand, the optical waveguide 1 shown in FIGS. 1 and 2 has a sheet shape. The core portion 14 formed inside the optical waveguide 1 serves as a light guide path. In FIG. 2, the core portion 14 is shown through.

Further, an MT type optical connector 62 is attached to the right end of the optical waveguide 1. The MT type optical connector 62 is inserted from the left side of the receptacle 61. That is, an MT type receiving portion 611 is formed on the left side of the receptacle 61, and an MT type optical connector 62 is inserted into the MT type receiving portion 611.

The MT-type receiving unit 611 and the MT-type optical connector 62 may be replaced with members that can be fitted to each other and satisfy different connector standards.

Further, the optical waveguide 1 is formed with a reflecting portion 16. The optical path P1 extending in the left-right direction of FIG. 1 via the reflecting portion 16 is converted into an optical path P2 extending in the vertical direction of FIG. The optical path 1 and the light emitting element 31 are optically connected by the optical path P2. The optical paths P1 and P2 shown in FIG. 1 show an example of a path through which light propagates, respectively.

The lens array 5 is provided between the optical waveguide 1 and the electric substrate 2. The lens array 5 shown in FIG. 1 has a container-like shape having a bottom portion 51 at the top and an opening at the bottom, and has a bottom portion 51 and a wall portion 52 erected downward from the edge of the bottom portion 51. , Is equipped. Then, the lower surface of the wall portion 52 is joined to the upper surface of the electric substrate 2, and the optical waveguide 1 is joined to the upper surface of the bottom portion 51. As a result, an internal space 53 surrounded by the bottom portion 51, the wall portion 52, and the electric substrate 2 is formed. Further, the above-mentioned light emitting element 31 and the control element 4 are housed in the internal space 53. As a result, the light emitting element 31 and the control element 4 can be protected from the external environment, foreign matter adhesion, and the like. The lens array 5 is not limited to the above configuration, and the internal space 53 may be partially open, for example.

The lens array 5 has light transmission and can pass through the optical path P2. Further, a lens 54 is formed on the bottom portion 51. The lens 54 is, for example, a convex lens, and can focus the light propagating in the optical path P2 at a target position.

The lens array 5 may include a diffraction grating, a polarizer, a prism, a filter, and the like in addition to the lens 54.

An MPO-type receiving unit 612 is formed on the right side of the receptacle 61. An MPO-type optical connector 92 attached to the left end of the optical fiber 91 is inserted and fitted into the MPO-type receiving unit 612. As a result, the optical fiber 91 and the optical waveguide 1 are optically connected. As a result, an external optical connection is made to the optical module 1000.

The MPO-type receiving unit 612 and the MPO-type optical connector 92 may be replaced with members that can be fitted to each other and satisfy different connector standards. Further, the optical waveguide 1 and the optical fiber 91 may be directly connected without using the receptacle 61 or the MPO type optical connector 92.

The housing 7 is a box-shaped member that houses all parts except the electric wiring 81, the electric connector 82, the optical fiber 91, and the MPO type optical connector 92. By housing in such a housing 7, each part can be protected from the external environment, and the reliability and portability of the optical module 1000 can be improved.

A through hole is provided in a part of the housing 7, and a portion of the electric substrate 2 provided with the contact 23 protrudes from the through hole. As a result, the electric connector 82 can be easily attached to the contact 23. Similarly, the MPO type receiving portion 612 of the receptacle 61 is exposed from a through hole provided in a part of the housing 7. As a result, the optical fiber 91 can be easily connected to the optical module 1000 simply by inserting the MPO type optical connector 92 into the MPO type receiving unit 612.

Examples of the constituent material of the housing 7 include metal materials such as stainless steel, aluminum alloy, and titanium alloy, as well as various resin materials and various ceramic materials. Further, the housing 7 may be provided as needed or may be omitted. In that case, the mold resin may be provided so as to cover the lens array 5 and the optical waveguide 1. The mold resin may be provided so as to fill the inside of the housing 7.

2. Optical Waveguide Next, the optical waveguide 1 will be described.

FIG. 3 is a partially enlarged perspective view of the optical waveguide shown in FIG. FIG. 4 is a cross-sectional view taken along the line AA of FIG.

As shown in FIGS. 3 and 4, the optical waveguide 1 according to the present embodiment has a light guide portion 100 having a laminated body 10 and a recess 160 (cavity portion) provided in the laminated body 10, and a light guide portion 100. It has a cover layer 191 provided on the upper surface 101 (first surface) of the above surface and covering the opening of the recess 160, and an adhesive layer 192 provided between the upper surface 101 and the cover layer 191. ..

Of these, the laminated body 10 includes a lower protective layer 17, a clad layer 11, a core layer 13, a clad layer 12, and an upper protective layer 18, which are laminated in order from the bottom. Further, as shown in FIG. 3, the core layer 13 includes a long core portion 14 extending along the Y axis and a side clad portion provided adjacent to the side surface of the core portion 14 in the X-axis direction. It is equipped with 15.

Further, as shown in FIGS. 1 and 4, the recess 160 included in the light guide unit 100 includes a reflection unit 16 that mutually converts between the optical path P1 and the optical path P2 by light reflection. As shown in FIG. 4, the reflecting portion 16 is a part of the inner surface of the recess 160 that opens to the upper surface 101 of the light guide portion 100 having the upper surface 101 and the lower surface 102 (second surface) and penetrates the core layer 13. is there. That is, the reflective portion 16 is an interface between the recess 160, which is a hollow portion, and the core layer 13. In the reflecting unit 16, the optical path P1 and the optical path P2 can be mutually converted by reflection based on the difference in refractive index.

Hereinafter, each part of the optical waveguide 1 will be described in more detail.
2.1 Core layer The side surface of the core portion 14 formed in the core layer 13 shown in FIG. 3 is surrounded by the side surface clad portions 15 and the clad layers 11 and 12. The refractive index of the core portion 14 is higher than that of the side clad portion 15 and the clad layers 11 and 12. As a result, light can be confined and propagated in the core portion 14. The side surface clad portion 15 and any one or both of the clad layers 11 and 12 may be integrated.

In the core layer 13, the refractive index distribution in the plane orthogonal to the optical path P1 may be any distribution, for example, a so-called step index (SI) type distribution in which the refractive index changes discontinuously. , The so-called graded index (GI) type distribution in which the refractive index changes continuously may be used.

Further, the cross-sectional shape of the core portion 14 by a plane orthogonal to the optical path P1 is not particularly limited, and is not particularly limited, and is a circle such as a perfect circle, an ellipse, or an oval, a polygon such as a triangle, a quadrangle, a pentagon, or a hexagon, and other variations. It may be in shape.

Further, the average thickness of the core layer 13 is not particularly limited, but is preferably about 1 to 200 μm, more preferably about 5 to 100 μm, and even more preferably about 10 to 70 μm. As a result, the thickness of the optical waveguide 1 can be reduced while suppressing a decrease in the transmission efficiency of the optical waveguide 1.

Examples of the constituent material (main material) of the core layer 13 include acrylic resin, methacrylic resin, polycarbonate, polystyrene, cyclic ether resin such as epoxy resin and oxetane resin, polyamide, polyimide, polybenzoxazole, and the like. Polysilane, polysilazane, silicone resin, fluorine resin, polyurethane, polyolefin resin, polybutadiene, polyisoprene, polychloroprene, polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polyethylene succinate, polysulfone, poly Examples thereof include various resin materials such as ether and cyclic olefin resin. Among these, examples of the cyclic olefin-based resin include benzocyclobutene-based resins and norbornene-based resins. As the resin material, a composite material in which materials having different compositions are combined is also used.

2.2 Clad layer The average thickness of the clad layers 11 and 12 is preferably about 1 to 200 μm, more preferably about 3 to 100 μm, and even more preferably about 5 to 60 μm. As a result, the functions as the clad layers 11 and 12 are ensured while preventing the optical waveguide 1 from becoming thicker than necessary.

Further, as the constituent materials of the clad layers 11 and 12, for example, the same materials as the constituent materials of the core layer 13 described above can be used, but in particular, (meth) acrylic resin, epoxy resin, silicone resin, and the like. It is preferably at least one selected from the group consisting of a polyimide resin, a fluorine resin, a polyolefin resin and a cyclic olefin resin.

The clad layers 11 and 12 may be provided as needed or may be omitted. At this time, for example, if the core layer 13 is exposed to the outside air (air), the outside air functions as the clad layers 11 and 12.

2.3 Protective layer In the optical waveguide 1 shown in FIGS. 3 and 4, the lower protective layer 17 and the upper protective layer 18 protect the core layer 13 and the clad layers 11 and 12, and the core portion 14 is caused by the external environment or the like. It is possible to suppress a decrease in transmission efficiency.

Examples of the constituent materials of the lower protective layer 17 and the upper protective layer 18 include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyolefins such as polyethylene and polypropylene, polyimide resins, polyamide resins, and cyclic olefins. Examples thereof include materials containing various resins such as resins.

The average thickness of the lower protective layer 17 and the upper protective layer 18 is not particularly limited, but is preferably about 5 to 500 μm, and more preferably about 10 to 400 μm.

Further, the lower protective layer 17 and the upper protective layer 18 may have the same configuration or different configurations from each other.

The lower protective layer 17 and the upper protective layer 18 may be provided as needed, and at least one of them may be omitted.

2.4 Recessed light guide unit 100 includes a recess 160 penetrating the core layer 13 as described above. The reflecting portion 16 provided on the inner surface of the recess 160 is a surface of the core portion 14 that is inclined with respect to the optical path P1. The angle formed by the optical path P1 and the optical path P2 can be adjusted according to the inclination angle of the reflecting portion 16.

The recess 160 shown in FIG. 4 has a triangular shape when viewed from the X-axis direction. Then, as shown in FIG. 4, the reflective portion 16 is a flat surface continuously formed from the upper protective layer 18 through the clad layer 12 and the core layer 13 to the clad layer 11. The shape of the recess 160 as viewed from the X-axis direction is not limited to the shape shown in FIG. 4, and may be any shape. Further, the reflecting portion 16 is not limited to a flat surface, and may be a curved surface.

The inclination angle of the reflecting portion 16 is not particularly limited, but when the lower surface of the laminated body 10 shown in FIG. 4 is used as a reference plane, the angle formed by the reference plane and the reflecting portion 16 on the optical path P1 side is about 30 to 60 °. It is preferably about 40 to 50 °, and more preferably about 40 to 50 °. By setting the inclination angle within the above range, the optical path P1 of the core portion 14 can be efficiently converted in the reflecting portion 16, and the loss due to the optical path conversion can be suppressed.

The position of the deepest portion of the recess 160 is not particularly limited, but may be at least on the side of the protective layer 17 below the core layer 13.

Further, in the present embodiment, the recess 160 is a hollow portion, but the recess 160 may be filled with a material having a refractive index lower than that of the core portion 14, and a metal film is formed on the reflection portion 16. You may.

On the tip side of the optical waveguide 1 in the Y-axis direction, the core portion 14 is exposed at the end surface of the core layer 13. The exposed surface of the core portion 14 is the light entrance / exit surface 140. Therefore, in the optical waveguide 1 according to the present embodiment, the optical path P1 extends between the reflection portion 16 and the light entrance / exit surface 140.

The optical path P1 may be optically connected to the optical fiber 91 via a reflection portion (not shown) instead of the light entrance / exit surface 140 provided on the end surface of the core layer 13.

Further, in the optical waveguide 1 shown in FIG. 2, four core portions 14 are formed in the core layer 13. A recess 160 is provided corresponding to each core portion 14. The recesses 160 may be individually provided corresponding to the four core portions 14, or one recess 160 may be provided so as to straddle the four core portions 14. Further, the positions of the recesses 160 provided corresponding to the core portions 14 in the Y-axis direction are the same in FIG. 2, but may be offset from each other.

The number of core portions 14 formed in the core layer 13 is not particularly limited, and may be 1 to 3 or 5 or more.

2.5 Cover layer The optical waveguide 1 according to the present embodiment has a cover layer 191 provided on the upper surface 101 via an adhesive layer 192. The cover layer 191 is provided so as to cover the recess 160. As a result, the reflective portion 16 can be protected from the intrusion of foreign matter and the external environment. As a result, it is possible to suppress a decrease in the light reflectance of the reflecting unit 16, and it is possible to suppress a loss due to optical path conversion.

The average thickness of the cover layer 191 is not particularly limited, but is preferably about 5 to 500 μm, more preferably about 10 to 400 μm, and even more preferably about 15 to 50 μm. As a result, since the cover layer 191 has sufficient mechanical strength, the periphery of the recess 160 can be sufficiently reinforced. Therefore, it is possible to minimize the deterioration of the mechanical properties of the optical waveguide 1 due to the provision of the recess 160.

The constituent material of the cover layer 191 includes, for example, various resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyolefins such as polyethylene and polypropylene, polyimide resins, polyamide resins, and cyclic olefin resins. Materials can be mentioned.

Of these, the cover layer 191 is preferably made of a polyimide resin as a main material. Since the polyimide resin has a relatively high elastic modulus and a high thermal decomposition temperature, it has sufficient durability against external forces and the external environment. Therefore, the cover layer 191 containing the polyimide-based resin can more reliably protect the reflective portion 16. Specifically, the heat resistance of the optical waveguide 1 can be increased. Further, when the constituent material of the upper protective layer 18 contains a polyimide resin, a difference in thermal expansion is less likely to occur between the upper protective layer 18 and the cover layer 191. Therefore, the generation of thermal stress can be suppressed, the deformation of the reflecting portion 16 due to stress concentration can be suppressed, and the increase in loss due to optical path conversion can be suppressed. The main material means that the polyimide-based resin occupies 50% by mass or more of the constituent materials of the cover layer 191. The content of the polyimide-based resin is preferably 90% by mass or more.

Further, as necessary, fillers, antioxidants, ultraviolet absorbers, colorants, storage stabilizers, plasticizers, lubricants, deterioration inhibitors, antistatic agents and the like are added to the constituent materials of the cover layer 191. You may. For example, the coefficient of thermal expansion of the cover layer 191 can be adjusted by adding a filler.

Further, the tensile strength of the cover layer 191 is preferably about 200 to 800 MPa, more preferably about 250 to 750 MPa. By setting the tensile strength of the cover layer 191 within the above range, the optical waveguide 1 having sufficient durability can be obtained.

The tensile strength of the cover layer 191 is measured in accordance with the tensile property test method specified in JIS K 7127 (ASTM D882). The tensile strength is a measured value at 25 ° C. for a test piece having an average thickness of 25 μm.

The elastic modulus of the cover layer 191 is preferably about 3000 to 12000 MPa, more preferably about 4000 to 11000 MPa. By setting the elastic modulus of the cover layer 191 within the above range, the periphery of the recess 160 can be sufficiently reinforced. Therefore, it is possible to minimize the deterioration of the mechanical properties of the optical waveguide 1 due to the provision of the recess 160.

The elastic modulus of the cover layer 191 is measured according to the test method for tensile properties specified in JIS K 7127 (ASTM D882). The elastic modulus is a measured value at 25 ° C. for a test piece having an average thickness of 25 μm.

In addition, the test result of the bending resistance MIT of the cover layer 191 is preferably 10,000 times or more, and more preferably 20,000 times or more. As a result, a highly reliable optical waveguide 1 can be obtained.

The heat shrinkage of the cover layer 191 is preferably about 0.01 to 0.2%. As a result, the optical waveguide 1 with less deformation such as warpage can be obtained.

Further, the coefficient of thermal expansion of the cover layer 191 is not particularly limited, but the coefficient of linear expansion is preferably about 5 to 25 ppm / ° C., and more preferably about 7 to 20 ppm / ° C. As a result, the optical waveguide 1 with less thermal deformation can be obtained.

The coefficient of thermal expansion of the cover layer 191 is preferably about the same as the coefficient of thermal expansion of the upper protective layer 18. The same degree means that the difference between the two is 2 ppm / ° C or less. As a result, the difference in thermal expansion between the cover layer 191 and the upper protective layer 18 is less likely to occur, so that the occurrence of deformation and warpage of the reflective portion 16 can be suppressed to be particularly small.

Further, as shown in FIG. 4, when the total length of the light guide portion 100 in the Y-axis direction is L1 and the total length of the cover layer 191 in the Y-axis direction is L2, the total length L2 is a length that can cover the recess 160. If it is more than that, it is preferably shorter than the total length L1, and more preferably 0.1% or more and 50% or less of the total length L1. This makes it possible to visually determine the presence or absence of the cover layer 191. That is, when the total length L2 of the cover layer 191 is the same as the total length L1 of the light guide unit 100, it may be difficult to determine the presence or absence of the cover layer 191. However, if it is shorter than the total length L1, the edge of the cover layer 191 is Since it is easy to identify by visual inspection or tactile sensation, it becomes easy to determine the presence or absence of the cover layer 191. As a result, the inspection work of the optical waveguide 1 can be efficiently performed, and the front and back sides of the optical waveguide 1 can be easily discriminated without incident light on the optical waveguide 1. Therefore, the work of attaching the optical waveguide 1 to the lens array 5 described above can be efficiently performed.

2.6 Adhesive layer The optical waveguide 1 according to the present embodiment has an adhesive layer 192. By fixing the cover layer 191 to the upper protective layer 18 via the pressure-sensitive adhesive layer 192, the cover layer 191 can be fixed without using an adhesive. As a result, it is possible to prevent the reflection portion 16 from being deformed due to curing shrinkage, and it is possible to suppress an increase in loss due to optical path conversion.

On the other hand, since the pressure-sensitive adhesive layer 192 does not cure as significantly as the adhesive, there is a possibility that the pressure-sensitive adhesive layer 192 will flow over time after the cover layer 191 is fixed. Specifically, the adhesive contained in the adhesive layer 192 may seep out. In the example shown in FIG. 4, the adhesive exuded from the pressure-sensitive adhesive layer 192 attached to the upper surface 101 of the light guide unit 100 may move from the upper surface 101 to the reflecting portion 16. When such exudation and movement of the pressure-sensitive adhesive occurs, the pressure-sensitive adhesive may adhere to the reflective portion 16 and reduce the reflectance of the reflective portion 16.

Therefore, the present inventor has made extensive studies on the composition of the pressure-sensitive adhesive layer 192. When the thickness of the pressure-sensitive adhesive layer 192 is 25 μm or less and the pressure-sensitive adhesive strength of the pressure-sensitive adhesive layer 192 is 0.3 N / 10 mm or more, the pressure-sensitive adhesive exudes without impairing the function of the cover layer 191. We have found that it is possible to suppress the above, and have completed the present invention.

That is, the thickness of the pressure-sensitive adhesive layer 192 according to the present embodiment is 25 μm or less. When the thickness of the pressure-sensitive adhesive layer 192 exceeds the upper limit value, the amount of the pressure-sensitive adhesive contained in the pressure-sensitive adhesive layer 192 increases, and the seepage of the pressure-sensitive adhesive cannot be suppressed within an allowable range. Then, the amount of the adhesive that flows to the reflective portion 16 will seep out.

The thickness of the pressure-sensitive adhesive layer 192 is an average value when 10 points or more are measured on the observation image by observing the cross section of the pressure-sensitive adhesive layer 192 after being attached to the light guide unit 100.

The thickness of the pressure-sensitive adhesive layer 192 is preferably 5 μm or more and 20 μm or less, and more preferably 7 μm or more and 15 μm or less. If the thickness of the pressure-sensitive adhesive layer 192 is less than the lower limit, it may be difficult to form the pressure-sensitive adhesive layer 192 uniformly.

On the other hand, the pressure-sensitive adhesive layer 192 according to the present embodiment has an adhesive strength of 0.3 N / 10 mm or more. When the adhesive strength of the pressure-sensitive adhesive layer 192 is less than the lower limit value, the adhesive strength of the pressure-sensitive adhesive layer 192 becomes insufficient, and the cover layer 191 cannot be sufficiently fixed. Therefore, when the optical waveguide 1 is bent or the like, the cover layer 191 is released from being fixed, and the cover layer 191 is peeled off. Then, the function of the cover layer 191 is deteriorated, and there is a possibility that foreign matter adheres to the reflective portion 16 or the reflective portion 16 is affected by the external environment.

As for the adhesive strength of the pressure-sensitive adhesive layer 192, a cover layer 191 having a width of 10 mm with the pressure-sensitive adhesive layer 192 attached to the entire surface is used as a test piece, and after this test piece is attached to a polyimide film, a 90 ° peel adhesive strength measuring device is used. Is measured using.

The adhesive strength of the pressure-sensitive adhesive layer 192 is preferably 1.0 N / 10 mm or more and 4.0 N / 10 mm or less, and more preferably 1.7 N / 10 mm or more and 3.5 N / 10 mm or less. If the adhesive strength of the pressure-sensitive adhesive layer 192 exceeds the upper limit value, the adhesive strength of the pressure-sensitive adhesive layer 192 is too strong, which may make it difficult to reattach the cover layer 191.

As described above, in the optical waveguide 1 according to the present embodiment, the core layer 13 including the core portion 14, the clad layer 12 (first clad layer) and the clad layer 11 (first clad layer) laminated via the core layer 13 are laminated. (2 clad layer), a recess 160 (hollow portion) that penetrates the clad layer 12 and reaches the core portion 14, an upper surface 101 (first surface) and a lower surface 102 (second surface) that have a front-back relationship with each other. The light guide portion 100 is provided on the upper surface 101, and the recess 160 is provided on the upper surface 101, and the light path P1 of the core portion 14 is converted by the reflecting portion 16 included in the inner surface of the recess 160. A pressure-sensitive adhesive layer 192 provided between the cover layer 191 covering the opening and the upper surface 101 and the cover layer 191 and having a thickness of 25 μm or less and an adhesive strength of 0.3 N / 10 mm or more. Have.

According to such an optical waveguide 1, an adhesive layer 192 is used to fix the cover layer 191. The pressure-sensitive adhesive layer 192 is useful in that it does not undergo significant curing shrinkage unlike an adhesive, and the cover layer 191 can be fixed with sufficient adhesive strength. At the same time, the pressure-sensitive adhesive is less likely to seep out from the pressure-sensitive adhesive layer 192, so that adhesion to the reflective portion 16 can be suppressed. As a result, the cover layer 191 is more reliably fixed to prevent foreign matter and the like from entering the recess 160, while suppressing the exuded adhesive from adhering to the reflective portion 16 and reflecting light from the reflective portion 16. It is possible to suppress the decrease in the rate. As a result, the loss due to the optical path conversion in the reflecting unit 16 can be suppressed.

Further, the optical module 1000 according to the present embodiment is a light emitting element 31 (optical element) optically connected to the optical waveguide 1 according to the present embodiment and the reflecting portion 16 included in the inner surface of the recess 160 (cavity portion). ) And.

According to such an optical module 1000, the cover layer 191 fully exerts its function, and the adhesive exuded from the adhesive layer 192 is hard to adhere to the reflective portion 16, so that the reflection is reflected. It is possible to suppress the loss due to the optical path conversion in the unit 16. As a result, a highly reliable optical module 1000 can be realized.

Examples of the constituent material of the pressure-sensitive adhesive layer 192 include silicone-based resin, polyvinyl chloride-based resin, polyester-based resin, elastomer-based resin, rubber-based resin, acrylic-based resin, polyvinyl ether-based resin, and the like. One or a mixture of two or more of the above is used. Further, any additive may be added to the pressure-sensitive adhesive layer 192, if necessary.

Of these, the pressure-sensitive adhesive layer 192 is preferably made of a silicone-based resin as a main material. Silicone-based resins have good heat resistance and are not easily denatured even when heated. Therefore, even when the optical waveguide 1 is used in an environment where the temperature changes greatly, it is possible to suppress the seepage of the pressure-sensitive adhesive from the pressure-sensitive adhesive layer 192. The main material means that the silicone-based resin occupies 50% by mass or more of the constituent materials of the pressure-sensitive adhesive layer 192, and the content of the silicone-based resin is preferably 90% by mass or more.

Examples of the pressure-sensitive adhesive composed of a silicone-based resin include a peroxide-curing type pressure-sensitive adhesive and an addition reaction-curing type pressure-sensitive adhesive, but any type of silicone-based pressure-sensitive adhesive can be used. Often, other silicone-based adhesives may be used.

Further, the silicone-based pressure-sensitive adhesive preferably contains both silicone rubber and silicone resin as its constituent components. By using silicone rubber, elasticity can be imparted to the pressure-sensitive adhesive layer 192. As a result, the pressure-sensitive adhesive layer 192 can absorb the thermal stress generated between the cover layer 191 and the upper protective layer 18. Moreover, the adhesive strength can be enhanced by using a silicone resin. Therefore, the balance between elasticity and adhesive force can be improved by appropriately changing the ratio of silicone rubber and silicone resin.

The mass ratio of the silicone rubber to the silicone resin is not particularly limited, but is preferably 100: 100 to 100: 250, and more preferably 100: 130 to 100: 200. This makes it difficult for excess adhesive to seep out while ensuring the required adhesive strength.

Further, as described above, the light guide unit 100 includes an upper protective layer 18 (first protective layer) and a clad layer 11 provided on the opposite side of the clad layer 12 (first clad layer) from the core layer 13. It has a lower protective layer 17 (second protective layer) provided on the side opposite to the core layer 13 of the (second clad layer), and the recess 160 also penetrates the upper protective layer 18. By having such an upper protective layer 18 and a lower protective layer 17, the core layer 13 and the clad layers 11 and 12 can be protected from external forces and the external environment. Thereby, the reliability of the optical waveguide 1 can be further improved. Further, since the distance between the upper surface 101 and the core layer 13 becomes longer, the distance when the adhesive exuded from the adhesive layer 192 moves from the upper surface 101 to the reflecting portion 16 on the inner surface of the recess 160 also becomes longer. As a result, even if the pressure-sensitive adhesive exudes from the pressure-sensitive adhesive layer 192, it becomes difficult for the pressure-sensitive adhesive to reach the reflective portion 16. Therefore, it is possible to suppress a decrease in the light reflectance of the reflecting unit 16.

3. 3. Electronic device The optical waveguide 1 as described above has an effect of suppressing exudation of the adhesive contained in the adhesive layer 192 fixing the cover layer 191 and making it difficult for the cover layer 191 to peel off. Therefore, in the optical waveguide 1, the loss due to the optical path conversion in the reflecting unit 16 can be reduced, and a high S / N ratio (signal-to-noise ratio) can be realized in optical communication.

The electronic device according to the embodiment is not particularly limited as long as it is an electronic device provided with the above-mentioned optical waveguide 1, but for example, a smartphone, a tablet terminal, a mobile phone, a game machine, a router device, a WDM device, a personal computer, a television, and the like. Examples include electronic devices such as servers and supercomputers. By providing the optical waveguide 1, a highly reliable electronic device can be obtained.

The optical waveguide, the optical module, and the electronic device of the present invention have been described above based on the illustrated embodiments, but the present invention is not limited thereto.

For example, in the above embodiment, the lens is arranged between the optical waveguide and the light emitting / receiving element, but this lens may be provided as needed or may be omitted.

Further, as the electric substrate, a resin substrate such as a rigid substrate or a flexible substrate is often used, but a ceramic substrate, a glass substrate, or the like may be used.

Next, specific examples of the present invention will be described.
1. 1. Fabrication of optical waveguide (Experimental Example 1)
First, the optical waveguide shown in FIG. 4 was produced. Specifically, after laminating two clad layers with a core layer sandwiched between them, two protective layers (upper protective layer and lower protective layer) were laminated so as to sandwich them to obtain a laminated body. The manufacturing conditions of the laminated body are as follows.

-Core layer constituent material: Cyclic olefin resin-Core layer thickness: 50 μm
-Constituent material of clad layer: Cyclic olefin resin-Clad layer thickness: 5 μm
-Constituent material of each protective layer: Polyimide-based resin-Thickness of each protective layer: 25 μm

Next, a recess was formed in the laminated body using a dicing blade to obtain a light guide portion. The side surface shape of the recess was substantially triangular, and the shape of the reflective portion was a substantially flat surface. The inclination angle of the reflecting portion was set to 45 °.

Next, a cover layer with an adhesive layer was prepared and attached so as to cover the recess. An optical waveguide was obtained as described above.
The manufacturing conditions of the pressure-sensitive adhesive layer and the cover layer are as follows.

・ Main material of cover layer: Polyimide resin ・ Thickness of cover layer: 25 μm
-Main material of adhesive layer: Silicone resin-Thickness of adhesive layer: 10 μm
-Adhesive strength of the adhesive layer: 0.3N / 10mm

(Experimental Examples 2-8)
An optical waveguide was obtained in the same manner as in Experimental Example 1 except that the manufacturing conditions of the optical waveguide were changed as shown in Table 1.

In Table 1, among the above-mentioned experimental examples, those corresponding to the present invention are referred to as "Examples", and those not corresponding to the present invention are referred to as "Comparative Examples".

2. Evaluation of optical waveguide 2.1 Evaluation of peeling resistance Next, regarding the optical waveguide obtained in each experimental example, the portion where the protective layer and the cover layer are fixed (hereinafter referred to as “fixed portion”) , An evaluation test of peel resistance was conducted. Specifically, a cut line was made from the cover layer side to the fixed portion. The cut line was set so as to penetrate the cover layer and the adhesive layer and reach the protective layer. The line of cut line was a straight line and a curved line with a radius of 1 mm (a perfect circle).

Next, the circumference of the cut line was observed with an optical microscope from the cover layer side. Then, the presence or absence of air bubbles generated when the protective layer and the cover layer were peeled off was inspected, and the inspection results were evaluated against the following evaluation criteria.

(Evaluation criteria for peel resistance)
A: No bubbles were found B: No bubbles were found on the straight cut line, but bubbles were found on the curved cut line C: At least bubbles were found on the straight cut line. It is shown in Table 1.

2.2 Evaluation of Adhesive Adhesion to Reflective Part Next, for the optical waveguides obtained in each experimental example, the cover layer was forcibly peeled off from the light guide part.

Next, in each experimental example, 96 reflecting parts were observed with an optical microscope. Then, the presence or absence of deposits on the reflective portion was inspected, and the inspection results were evaluated against the following evaluation criteria.

(Evaluation criteria for deposits on reflective parts)
A: The number of reflective parts with deposits is 0. B: The number of reflective parts with deposits is 1 or 2. C: The number of reflective parts with deposits is. Table 1 shows the evaluation results of 3 or more.

As shown in Table 1, in the optical waveguide corresponding to the example, both the peeling resistance of the cover layer and the difficulty of adhering the adhesive to the reflective portion were evaluated as A or B, which were good. there were. On the other hand, in the optical waveguide corresponding to the comparative example, either the peeling resistance of the cover layer or the difficulty of adhering the adhesive to the reflective portion was evaluated as C, which was poor. The deposit adhering to the reflective portion was an adhesive.

From the above results, it was confirmed that according to the present invention, it is possible to realize a pressure-sensitive adhesive layer in which the cover layer is hard to peel off and the pressure-sensitive adhesive is hard to seep out.

1 Optical waveguide 2 Electrical substrate 4 Control element 5 Lens array 7 Housing 9 Optical fiber 10 Laminated body 11 Clad layer 12 Clad layer 13 Core layer 14 Core part 15 Side clad part 16 Reflection part 17 Lower protective layer 18 Upper protective layer 21 Insulation Substrate 22 Conductive layer 23 Contact 31 Light emitting element 51 Bottom 52 Wall 53 Internal space 54 Lens 61 Receptacle 62 MT type optical connector 81 Electrical wiring 82 Electrical connector 91 Optical fiber 92 MPO type optical connector 100 Light guide 101 Top surface 102 Bottom surface 140 Light input Exit surface 160 Recessed 191 Cover layer 192 Adhesive layer 611 MT type receiving part 612 MPO type receiving part 1000 Optical module L1 Full length L2 Full length P1 Optical path P2 Optical path

Such an object is achieved by the present invention of the following (1) to (7) .
(1) A core layer including a core portion, a first clad layer and a second clad layer laminated via the core layer, and a cavity portion that penetrates the first clad layer and reaches the core portion. A light guide portion having a first surface and a second surface having a front and back relationship with each other, the cavity portion opens to the first surface, and the optical path of the core portion is converted by the inner surface of the cavity portion. When,
A cover layer provided on the first surface and covering the opening of the cavity,
An adhesive layer provided between the first surface and the cover layer, which is mainly made of a silicone resin, has a thickness of 25 μm or less, and has an adhesive strength of 1.0 N / 10 mm or more.
An optical waveguide characterized by having.

(4) The silicone-based resin contains silicone rubber and silicone resin as constituents.
The optical waveguide according to any one of (1) to (3) above , wherein the mass ratio of the silicone rubber to the silicone resin in the silicone-based resin is 100: 130 to 100: 200 .
(5) The optical waveguide according to any one of (1) to (4) above, wherein the total length of the cover layer is shorter than the total length of the light guide portion.

(6) The optical waveguide according to any one of (1) to (5 ) above,
An optical element optically connected to the inner surface of the cavity,
An optical module characterized by having.

(7) An electronic device including the optical waveguide according to any one of (1) to (5 ) above.

Claims (6)

The core layer including the core portion, the first clad layer and the second clad layer laminated via the core layer, and the cavity portion that penetrates the first clad layer and reaches the core portion are on the front and back sides of each other. A light guide portion having a first surface and a second surface having a relationship, the cavity portion opens to the first surface, and the optical path of the core portion is converted by the inner surface of the cavity portion.
A cover layer provided on the first surface and covering the opening of the cavity,
An adhesive layer provided between the first surface and the cover layer, having a thickness of 25 μm or less and an adhesive strength of 0.3 N / 10 mm or more.
An optical waveguide characterized by having. The light guide unit
A first protective layer provided on the opposite side of the first clad layer from the core layer,
A second protective layer provided on the side of the second clad layer opposite to the core layer,
Have,
The optical waveguide according to claim 1, wherein the cavity portion also penetrates the first protective layer. The optical waveguide according to claim 1 or 2, wherein the cover layer is made of a polyimide resin as a main material. The optical waveguide according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive layer is made of a silicone-based resin as a main material. The optical waveguide according to any one of claims 1 to 4.
An optical element optically connected to the inner surface of the cavity,
An optical module characterized by having. An electronic device comprising the optical waveguide according to any one of claims 1 to 4.

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