JP2011232786A - Optical waveguide structure and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical waveguide structure and an electronic apparatus with small optical loss in a reflection part.SOLUTION: The optical waveguide structure of this invention has an optical waveguide having a core part transmitting light and a clad part joined to an outer circumference of the core part, and a reflection part having an inclined face inclined with respect to a transmission direction of the light of the core part. The optical waveguide structure is processed for the improvement of the smoothness of the inclined face. Additionally, the electronic device of this invention uses the optical waveguide structure.

Description

  The present invention relates to an optical waveguide structure and an electronic device.

  In recent years, in order to cope with the speeding up of electronic devices, development of an optical / electric hybrid board using a mixture of electrical wiring and optical wiring has been performed. The optical wiring has an optical waveguide portion composed of a core portion and a cladding portion. In the optical waveguide part, it is possible to transmit an optical signal by transmitting light through the core part.

  In an optical / electrical hybrid substrate composed of an optical wiring having such an optical waveguide portion and an electrical wiring, the light transmitted through the optical wiring (core portion of the optical waveguide) is converted from an optical signal to an electrical signal by an optical device. Is converted into a signal. In this way, in order to transmit the light transmitted through the optical wiring to the optical device, the direction of the optical signal is changed by a reflection unit such as a mirror.

  Such a mirror is formed by forming a groove at a predetermined position of the optical wiring by dicing (for example, see Patent Document 1). However, when a mirror is formed by such a dicing process, there is a problem that light loss at the reflection surface of the mirror becomes large. Therefore, it has been necessary to improve the reflectance of light on the reflecting surface by evaporating aluminum, gold or the like on the reflecting surface.

JP 2000-304953 A

  An object of the present invention is to provide an optical waveguide structure and an electronic device that have a small optical loss at a reflection portion.

Such an object is achieved by the present invention described in the following (1) to (8).
(1) An optical waveguide having a core part for transmitting light and a clad part joined to the outer periphery of the core part, and a reflecting part having an inclined surface inclined with respect to the light transmission direction of the core part. An optical waveguide structure, which is subjected to a treatment for improving the smoothness of the inclined surface.
(2) The optical waveguide structure according to (1), wherein the process for improving the smoothness is a resin layer provided on the inclined surface.
(3) The optical waveguide structure according to (2), wherein a refractive index of the resin layer is equal to or higher than a refractive index of the core portion.
(4) The optical waveguide structure according to (3), wherein a difference between a refractive index of the resin layer and a refractive index of the core portion is 4% or less.
(5) The optical waveguide structure according to any one of (2) to (4), wherein the resin layer has a thickness of 0.1 to 10 μm.
(6) The optical waveguide structure according to any one of (2) to (5), wherein the resin layer is made of a resin composition containing an epoxy resin.
(7) The optical waveguide structure according to any one of (2) to (5), wherein the resin layer is made of a resin composition containing an acrylic resin.
(8) An electronic apparatus using the optical waveguide structure according to any one of (1) to (7).

ADVANTAGE OF THE INVENTION According to this invention, the optical waveguide structure and electronic device with a small optical loss in a reflection part can be obtained.
Moreover, when the process which improves the said smoothness is made into the resin layer provided in the said slope, the smoothness of a reflection part can be improved especially and, thereby, light loss can be reduced more.
Moreover, when norbornene-type resin is used as a material which comprises an optical waveguide, in addition to being able to improve the insulation and heat resistance of an optical waveguide structure more, a hygroscopic property can also be made low.

It is sectional drawing which shows typically an example of the optical waveguide structure of this invention. It is sectional drawing which expanded and showed the reflection part of the optical waveguide. It is sectional drawing which shows the formation method of a reflection part typically. It is sectional drawing which shows the formation method of a reflection part typically. It is sectional drawing which shows the formation method of a resin layer typically. It is a top view which shows an example of an optical waveguide.

Hereinafter, the optical waveguide structure of the present invention will be described in detail.
FIG. 1 is a cross-sectional view schematically showing an example of an optical waveguide structure. FIG. 2 is an enlarged cross-sectional view showing a reflection portion of the optical waveguide.
(Optical waveguide structure)
As shown in FIG. 1, in the optical waveguide structure 100, an optical device 2 and an electronic device 3 are provided on one surface side of an optical waveguide forming substrate 1 through terminal portions 4. The terminal portion 4 is sealed with a sealing resin 5. A light emitting / receiving unit 21 is provided at the lower part of the optical device 2 (lower part in FIG. 1).
An electrical wiring 6 is provided on the other surface side of the optical waveguide forming substrate 1, and the electrical wiring 6 and the terminal portion 4 are electrically connected via a plug 61 provided so as to penetrate the optical waveguide forming substrate 1. Connected.

(Optical waveguide substrate)
In the optical waveguide forming substrate 1, an insulating layer 11, an optical waveguide 12, and an insulating layer 13 are laminated in this order.
The optical waveguide 12 includes a core part 121 that transmits light and a clad part 122 joined to the outer periphery of the core part.
The optical waveguide forming substrate 1 is provided with a reflecting portion 7 that reflects light transmitted through the optical waveguide 12 below the light emitting / receiving portion 21 (lower portion in FIG. 1).

(Insulating layer)
The insulating layer 11 is provided in order to maintain insulation between the electrical wiring 6 and the electronic device 3 and the optical device 2.
Examples of the resin constituting the insulating layer 11 include a novolak type phenol resin such as a phenol novolak resin, a cresol novolak resin, and a bisphenol A novolak resin, an unmodified resole phenol resin, an oil modified by paulownia oil, linseed oil, walnut oil, and the like. Phenolic resins such as resol phenolic resins such as resol phenolic resins, bisphenol epoxy resins such as bisphenol A epoxy resin and bisphenol F epoxy resin, novolac epoxy resins such as novolac epoxy resin and cresol novolac epoxy resins, biphenyl type epoxy resins Such as epoxy resins, urea (urea) resins, melamine resins and other triazine ring resins, unsaturated polyester resins, bismaleimide resins, polyurethane resins, diallyl phthalates DOO resins, silicone resins, resins having a benzoxazine ring, cyanate ester resins, polyimide resins such as polyimide resin, polyamide resin, polyamide resins such as polyamide-imide resins.
Among these, it is particularly preferable to use at least one resin selected from polyimide resins and epoxy resins. Thereby, insulation can be improved more.

  The thickness of the insulating layer 11 is not particularly limited because it is appropriately set depending on the application, but in the case of a flexible circuit, for example, 10 to 40 μm is preferable, and 15 to 35 μm is particularly preferable. Thereby, in the state which maintained insulation, it can also be excellent in flexibility.

The insulating layer 13 is provided to maintain insulation between the electrical wiring 6 and the electronic device 3 and the optical device 2.
The insulating layer 11 and the insulating layer 13 may be made of the same resin or different resins.
As the resin constituting the insulating layer 13, for example, a novolac type phenol resin such as a phenol novolak resin, a cresol novolak resin, a bisphenol A novolak resin, an unmodified resole phenol resin, an oil modified by paulownia oil, linseed oil, walnut oil, etc. Phenolic resins such as resol phenolic resins such as resol phenolic resins, bisphenol epoxy resins such as bisphenol A epoxy resin and bisphenol F epoxy resin, novolac epoxy resins such as novolac epoxy resin and cresol novolac epoxy resins, biphenyl type epoxy resins Such as epoxy resins, urea (urea) resins, melamine resins and other triazine ring resins, unsaturated polyester resins, bismaleimide resins, polyurethane resins, diallyl phthalates DOO resins, silicone resins, resins having a benzoxazine ring, cyanate ester resins, polyimide resins such as polyimide resin, polyamide resin, polyamide resins such as polyamide-imide resins.
Among these, it is particularly preferable to use at least one resin selected from polyimide resins and epoxy resins. Thereby, insulation can be improved more.

  The thickness of the insulating layer 13 may be the same as or different from the thickness of the insulating layer 11. Specifically, for example, in the case of a flexible circuit, 10 to 40 μm is preferable, and 15 to 35 μm is particularly preferable. Thereby, in the state which maintained insulation, it can also be excellent in flexibility.

(Optical waveguide)
The optical waveguide 12 includes a core part 121 that transmits light and a clad part 122 joined to the outer periphery of the core part.

(Core part)
Examples of the material constituting the core part 121 include resin materials such as cyclic olefin resins such as acrylic resins, epoxy resins, polyimide resins, benzocyclobutene resins, and norbornene resins. Among these, norbornene resins (particularly, addition polymers of norbornene resins) are preferable. Thereby, it is excellent in insulation and heat resistance. Furthermore, the hygroscopicity can be lowered as compared with the case where other resins are used.

Moreover, as a constituent material of the core part 121, a material whose refractive index changes by irradiation with actinic radiation or by further heating is preferable. Preferable examples of such materials include those composed mainly of a resin composition containing a cyclic olefin resin such as a benzocyclobutene resin or a norbornene resin, and a norbornene resin (particularly a norbornene resin attached). Those containing (polymerized) (as the main material) are particularly preferred. In this case, the region irradiated with actinic radiation finally becomes the core part 121, and the other part constitutes the cladding part 122.
Examples of the active radiation used for the exposure include active energy rays such as visible light, ultraviolet light, infrared light, and laser light, electron beams, and X-rays. An electron beam can be irradiated with an irradiation dose of, for example, about 50 to 2,000 KGy.

  Examples of the norbornene-based resin include (1) addition (co) polymers of norbornene monomers obtained by addition (co) polymerization of norbornene monomers, and (2) norbornene monomers and ethylene or α-olefins. Addition copolymers, (3) addition polymers such as addition copolymers of norbornene-type monomers with non-conjugated dienes, and other monomers as required, (4) ring-opening (co) weights of norbornene-type monomers And a hydrogenated resin of the (co) polymer if necessary, (5) a ring-opening copolymer of a norbornene-type monomer and ethylene or α-olefins, and, if necessary, the (co) polymer Hydrogenated resin, (6) Ring-opening copolymer of norbornene-type monomer and non-conjugated diene, or other monomer, and hydrogenating the (co) polymer as necessary Ring-opening polymers such as the above polymers. Examples of these polymers include random copolymers, block copolymers, and alternating copolymers.

  These norbornene resins include, for example, ring-opening metathesis polymerization (ROMP), combination of ROMP and hydrogenation reaction, polymerization by radical or cation, polymerization using cationic palladium polymerization initiator, other polymerization initiators (for example, , Polymerization using nickel or other transition metal polymerization initiators) and the like.

  Among these, as the norbornene-based resin, one having a repeating unit represented by the following formula (1), that is, an addition (co) polymer is preferable. Thereby, transparency, heat resistance (specifically, heat resistance during solder reflow) and flexibility are excellent.

  Among the norbornene-based resins as described above, those having at least one selected from hexyl group, decyl group, epoxy group and diphenylmethylsilyloxy group in the side chain are preferable. Thereby, in particular, the light transmittance in the wavelength region of 850 nm can be improved.

  For example, an antioxidant, a refractive index adjuster, a plasticizer, a thickener, a reinforcing agent, a sensitizer, a leveling agent, an antifoaming agent, an adhesion aid, and a flame retardant are added to the constituent material of the core 121. An agent may be included. Addition of an antioxidant has the effect of improving high temperature stability, improving weather resistance, and suppressing light deterioration. Examples of such an antioxidant include phenols such as monophenols, bisphenols, and triphenols, and aromatic amines. Further, the resistance to bending can be further increased by adding a plasticizer, a thickener, and a reinforcing agent.

  The content of additives typified by the antioxidant (the total in the case of two or more) is preferably about 0.5 to 40% by weight, and 3 to 30% by weight with respect to the entire constituent material of the core part 121. The degree is more preferable. If the content is the lower limit, the function of the additive may not be fully exhibited. If the content exceeds the upper limit, depending on the type and characteristics of the additive, the light transmitted through the core part 121 (transmission light) is transmitted. The rate may decrease.

(Clad part)
The material constituting the clad portion 122 is not particularly limited as long as the refractive index is lower than that of the material constituting the core portion 121. Specific examples include resin materials such as cyclic olefin resins such as acrylic resins, epoxy resins, polyimide resins, and norbornene resins. Among these, norbornene resins (particularly, addition polymers of norbornene resins) are preferable. Thereby, it is excellent in insulation and heat resistance. Furthermore, the hygroscopicity can be lowered as compared with the case where other resins are used.

  For example, in the case of an addition polymer of norbornene resin, the refractive index can be adjusted depending on the type of the side chain. Specifically, the refractive index can be adjusted as appropriate by providing an alkyl group, an aralkyl group, a halogenated alkyl group, a silyloxy group, or the like in the side chain of the norbornene-based resin addition polymer. A difference in refractive index with the constituent material can be generated.

  In particular, a combination of a norbornene resin addition polymer as a material constituting the core part 121 and a norbornene resin addition polymer as a material constituting the cladding part 122 is preferable. Thereby, especially heat resistance and toughness can be improved.

  Specifically, the norbornene-based resin (addition polymer thereof) constituting the clad part 122 preferably has a linear aliphatic group in the side chain. Thereby, folding resistance can be improved. Examples of the linear aliphatic group include a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group.

(Manufacture of optical waveguide)
The optical waveguide 12 as described above includes, for example, “a method of providing a core in a pre-formed recess and covering the periphery thereof with a clad material”, “ultraviolet light on a laminate formed of a clad layer, a core layer, and a clad layer, etc. It can be obtained by a known method such as “a method of forming a core part by irradiating the activation energy of 2 to change the structure of a part of the core layer”.

(Reflection part)
The optical waveguide forming substrate 1 can be obtained by bonding the optical waveguide 12 obtained by the above method and the insulating layer 11 or the like.
As shown in FIG. 2, the reflecting portion 7 has an inclined surface 71 formed by providing a space having a triangular cross section from the lower surface side of the optical waveguide forming substrate 1 as described above.
The inclined surface 71 is inclined with respect to the light transmission direction of the core portion 121. Thereby, for example, as indicated by an arrow A in FIG. 2, the light transmitted through the core unit 121 is reflected, and the light transmission direction can be changed.
The present invention is characterized in that the inclined surface 71 is subjected to a process for improving the smoothness of the inclined surface 71. In a reflection part such as a mirror formed in a conventional optical waveguide, a minute unevenness is formed on the surface in order to form a reflection surface by dicing, and thereby light is scattered on the reflection surface, etc. In some cases, the optical loss increased. For this reason, there are cases where the optical signal cannot be sufficiently transmitted to the light emitting and receiving unit.
The present inventors investigated this cause and found that the loss of light can be further reduced by improving the smoothness of the inclined surface 71 of the reflecting portion 7 as a countermeasure.

  As a process for improving the smoothness of the inclined surface 71, a method of forming the resin layer 72 as shown in FIG. Thereby, since the resin is buried in the minute unevenness of the inclined surface, the inclined surface becomes substantially smooth.

  The refractive index of the resin layer 72 is not particularly limited, but is preferably the same as the refractive index of the core part 121 or the refractive index of the resin layer 72 is higher than the refractive index of the core part 121. Thereby, the conversion of the light transmission direction can be made more accurate. In addition, light can be prevented from entering the resin layer 72.

  When the refractive index of the core part 121 and the refractive index of the resin layer 72 are different, the difference is not particularly limited, but is preferably 4% or less (excluding 0), particularly 0.1% or less. It is preferable. When the refractive index is within the above range, the flexibility of light propagating through the optical waveguide 12 is particularly excellent.

  Although the thickness of the resin layer 72 is not specifically limited, It is preferable that it is 0.1-10 micrometers, and it is especially preferable that it is 1-5 micrometers. If the thickness is less than the lower limit value, the effect of reducing the optical loss may be reduced. If the thickness exceeds the upper limit value, the light transmitted through the core part 121 is not reflected by the inclined surface 71 and is transmitted to the resin layer 72. May end up.

  Examples of the resin constituting the resin layer 72 include bisphenol type epoxy resins such as bisphenol A epoxy resin and bisphenol F epoxy resin, novolac type epoxy resins such as novolac epoxy resin and cresol novolac epoxy resin, and epoxy type such as biphenyl type epoxy resin. Examples of the resin composition include a thermosetting resin such as a resin, and a thermoplastic resin such as a cyclic polyolefin resin such as an acrylic resin, a polyolefin resin, and a norbornene resin. Among these, a resin composition containing at least one of an epoxy resin and an acrylic resin is preferable. Thereby, the smoothness of the inclined surface 71 can be further improved. In addition, when an epoxy resin is used, the adhesion between the resin layer 72 and the inclined surface 71 can be improved.

  In particular, when the material constituting the optical waveguide 12 is a norbornene resin, the resin constituting the resin layer 72 is not particularly limited, but an acrylic resin represented by the following formula (2), and represented by the following formula (3). It is preferable to use an acrylic resin or an epoxy resin represented by the following formula (4).

  By using the acrylic resin or the epoxy resin represented by the above formulas, the difference in thermal expansion coefficient between the core portion 121 and the resin layer 72 can be reduced, thereby improving the heat resistance. .

  Moreover, when using acrylic resin shown by the said Formula (2) or (3), it is preferable to use a refractive index regulator. Thereby, the difference in refractive index between the norbornene resin and the acrylic resin can be reduced.

  The refractive index adjusting agent is not particularly limited as long as it has compatibility with the acrylic resin represented by the formula (2) or (3) and is lower than the refractive index of the acrylic resin. . Specific examples include bisphenol A acrylate, bisphenol F acrylate, aliphatic acrylate, and alicyclic acrylate. Among these, a refractive index adjuster of bisphenol A acrylate represented by the following formula (5) is preferable.

Moreover, it is preferable to use a refractive index adjuster also when using the epoxy resin represented by the formula (4). Thereby, the difference in refractive index between the norbornene resin and the epoxy resin can be reduced.
The refractive index modifier for the epoxy resin represented by the formula (4) is also particularly limited as long as it has compatibility with the epoxy resin and is lower than the refractive index of the epoxy resin. Not. Specific examples include bisphenol A type epoxy, bisphenol F type epoxy, cyclohexene oxide, and aliphatic epoxy. Among these, a refractive index adjuster of a cyclohexene oxide compound represented by the following formula (6) is preferable.

  The content of such a refractive index adjusting agent is appropriately determined according to the refractive index of the norbornene-based resin and the refractive index of the refractive index adjusting agent to be used. 90% by weight is preferable, and 40 to 60% by weight is particularly preferable. When the content of the refractive index adjusting agent is within the above range, the refractive index matching with the core is particularly excellent.

The resin composition preferably contains a diluent such as an organic solvent in order to facilitate the formation of the resin layer 72 in addition to the resin. Thereby, the resin layer 72 can be easily thinned.
Examples of the organic solvent include propylene glycol ether solvents such as propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether and propylene glycol monoethyl ether, and alcohol solvents such as isopropanol. Among these organic solvents, a solvent that is a poor solvent for the material constituting the optical waveguide 12 is particularly preferable. Thereby, it can prevent that the inclined surface 71 is swollen with a solvent.

  The content of the organic solvent is preferably 50 to 95% by weight, and particularly preferably 70 to 90% by weight, based on the total amount including the resin composition. When the content is within the above range, the resin layer 72 can be made thinner and the film smoothed after solvent volatilization can be facilitated.

  In addition to the resin component and the organic solvent, the resin composition may contain other additives such as a curing agent, a curing catalyst, a leveling agent, an antifoaming agent, an adhesion assistant, and an antioxidant.

  As described above, the optical waveguide structure of the present invention has been described. However, the present invention is not limited to this, and for example, the insulating layers 11 and 13 may be omitted. Further, as a method for improving the smoothness of the inclined surface 71, in addition to the formation of the resin layer 72, physical polishing, a solvent (in this case, a good solvent is preferable for the material constituting the optical waveguide 12), etc. Examples include a polishing method such as chemical polishing using, a cutting method using dry etching, and a method using a laser. Further, the resin layer 72 may be formed after polishing.

Next, the formation method of the reflection part 7 and the resin layer 72 is demonstrated.
First, a method for forming the reflective portion 7 will be described.
The method for forming the reflecting portion 7 of the present invention will be briefly described. As shown in FIG. 3, the reflecting portion 7 of the optical waveguide 12 including the core portion 121 and the clad portion 122 joined to the outer periphery of the core portion 121. The reflecting portion 7 is formed by irradiating the portion 7 'forming the laser 8 with the laser 8 and removing the constituent material of the optical waveguide 12 in the irradiated portion. Thus, since the reflection part 7 can be formed by irradiation of the laser 8, it becomes easy to form the reflection part 7 in an arbitrary pattern at an arbitrary position. Therefore, the pattern of the optical wiring can be easily formed.

Next, a method for forming the reflecting portion 7 will be specifically described with reference to FIG.
First, the laser 8 is irradiated through the mask 81, and the optical waveguide 12 is moved in the horizontal direction (A direction) with respect to the laser 8 (the laser 8 and the mask 81 do not move). At that time, since the irradiation time of the laser 8 irradiated to each part of the optical waveguide 12 changes, the reach of the laser 8 to the optical waveguide 12 in the depth direction is different, and the constituent material of the optical waveguide 12 is changed in the depth direction. In this way, the inclined surface 71 is formed by continuous removal (FIG. 4).

When the optical waveguide 12 is irradiated with the laser 8 at a certain size, the constituent material of the optical waveguide 12 in the irradiated portion (irradiated portion) 82 is removed to a predetermined depth.
Next, since the optical waveguide 12 moves in the horizontal direction, the irradiated portion 82 irradiated by the laser 8 moves in the horizontal direction. Here, since the size of the irradiated portion 82 irradiated with the laser 8 does not change, the laser 8 is not irradiated on the left side (left side in FIG. 4) of the irradiated portion 82 due to the movement of the optical waveguide 12, and the optical waveguide. No further material constituting 12 will be removed.
On the other hand, since the laser 8 is still irradiated in the vicinity of the center of the irradiated portion 82, the material constituting the optical waveguide 12 is removed deeper than the left portion.
The right part of the irradiated portion 82 is a portion where the laser 8 is newly irradiated by the movement of the optical waveguide 12. Therefore, the material constituting the optical waveguide 12 is removed for the time when the laser 8 is newly irradiated.

  Similarly, since the optical waveguide 12 continuously moves in the horizontal direction, the position of the irradiation portion 82 continuously changes by a certain length. Thereby, a difference arises in the time when the laser 8 is irradiated. Due to this difference, a space having a triangular cross section with the longest portion irradiated with the laser 8 as a vertex is formed, and an inclined surface 71 is formed by one side thereof.

  The moving speed of the optical waveguide 12 is not particularly limited, but is preferably moved at a speed of 10 to 100 μm / s, and more preferably moved at a speed of 40 to 60 μm / s. Thereby, the smoothness of the inclined surface 71 can be improved.

Examples of the laser 8 include an excimer laser such as ArF and KrF, a YAG laser, and a CO ₂ laser.

  Although the irradiation energy of the laser 8 is not specifically limited, 1-10 mJ is preferable and 5-7 mJ is especially preferable. Within the above range, the constituent material of the optical waveguide 12 can be removed in a short time. Although the frequency at the time of irradiation of the laser 8 is not particularly limited, 50 to 300 Hz is preferable, and 200 to 250 Hz is particularly preferable. When the frequency is within the above range, the smoothness of the processed surface is particularly excellent.

  The size of the optical waveguide 12 irradiated with the laser 8 is not particularly limited because it depends on the size of the reflecting portion 7 to be formed, but is preferably 80 to 200 μm × 80 to 200 μm square, particularly 100 to 150 μm. × 100 to 150 μm square is preferable. Thereby, the fine reflection part 7 can be formed.

(Formation of resin layer)
Thus, the angle of the inclined surface 71 of the reflection part 7 obtained can be suitably adjusted by adjusting the moving speed of the optical waveguide 12, and the energy density of the laser 8 to irradiate, for example. In particular, when the angle of the inclined surface 71 is in the vicinity of 45 degrees, it is preferable that the angle is slightly lower than 45 degrees.

  In the present embodiment, the inclined surface 71 is formed by moving the optical waveguide 12, but the inclined surface 71 may be formed by moving the laser 8 (and the mask 81). Such an inclined surface 71 can change the traveling direction of light propagating through the optical waveguide 12. The method of forming the inclined surface 71 by the laser 8 as described above is superior in surface smoothness compared to the conventional method of forming the inclined surface by dicing, but requires lower light loss. It is preferable to perform a process for improving the smoothness described later. Thereby, the optical loss in the inclined surface 71 (reflecting part 7) can be reduced more.

Next, the formed inclined surface 71 is processed to improve the smoothness. Thereby, the smoothness of the inclined surface 71 can be improved and light loss can be reduced.
Here, a method for forming the resin layer 72 as a process for improving the smoothness of the inclined surface 71 will be described.
As shown in FIG. 5, a resin layer 72 (not shown) is finally formed in a portion where the constituent material of the optical waveguide 12 is removed by irradiation of the laser 8 (a portion in the vicinity where the inclined surface 71 is formed). Resin composition 72 'is dropped.

  Then, the resin layer 72 is formed by removing (volatilizing) the solvent in the resin composition 72 ′. Examples of the conditions for removal include a method of treating at 50 to 200 ° C. for 5 to 60 minutes. Thus, the resin layer 72 having a thickness of about 1 to 10 μm can be formed by removing the solvent. Thereby, the smoothness of the inclined surface 71 can be improved.

When resin which comprises resin composition 72 'is a photocurable resin, you may irradiate light, such as an ultraviolet-ray. The irradiation energy is not particularly limited, but is preferably 100~3,000mJ / cm ^2, particularly 2,000~2,500mJ / cm ² is preferred. Thereby, the crosslinking degree of photocuring resin can fully be improved.

  When the resin constituting the resin layer 72 is a thermosetting resin, the resin layer 72 is cured. As curing conditions, for example, 100 to 180 ° C. × 1 to 10 minutes are preferable, and 120 to 150 ° C. × 2 to 8 minutes are particularly preferable. Thereby, the heat resistance of the resin layer 72 can be improved.

  As described above, in the optical waveguide 12 of the present invention, since the reflecting portion 7 can be formed in an arbitrary pattern at an arbitrary position, the optical waveguide 12 with improved flexibility of optical wiring and an optical waveguide using the same A structure can be obtained.

In the conventional method of forming the reflection portion by dicing, it is difficult to provide the reflection portion at an arbitrary position when the optical wiring is a thin line.
On the other hand, in the optical waveguide structure of the present invention, the reflection portion 7 can be formed by using the laser 8, so that the reflection portion 7 can be easily formed in an arbitrary pattern at an arbitrary position. The degree of freedom of optical wiring can be improved.
For example, as shown in FIG. 6, the optical waveguide 12 has five reflecting portions 7a corresponding to the five core portions 121 on one end side (right side in FIG. 6), three reflecting portions 7b on the center portion, and the other end. It has two reflection parts 7c in the part. Thereby, a signal from a substrate (not shown) can be transmitted through the core part 121, and a part of the signal can be received and transmitted by the reflecting part 7b, and the rest can be transmitted by the reflecting part 7c. Can be received and transmitted.

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example and a comparative example, this invention is not limited to this.
Example 1
1. Production of Optical Waveguide / Catalyst Precursor C1: Synthesis of Pd (OAc) ₂ (P (Cy) ₃ ) _{2 In} a two-necked round bottom flask equipped with a funnel, Pd (OAc) ₂ (5.00 g, 22.3 mmol) And a red-brown suspension consisting of CH ₂ Cl ₂ (30 mL) was stirred at −78 ° C. Cy represents a cyclohexyl group, and Ac represents an acetyl group.
A funnel was charged with a CH ₂ Cl ₂ solution (30 mL) of P (Cy) ₃ (13.12 mL (44.6 mmol)) and added dropwise to the stirred suspension over 15 minutes. As a result, the color gradually changed from reddish brown to yellow.
After stirring at −78 ° C. for 1 hour, the suspension was warmed to room temperature, stirred for an additional 2 hours, and diluted with hexane (20 mL).
The yellow solid was then filtered in air, washed with pentane (5 × 10 mL) and dried in vacuo to give a primary collection.
The secondary collection was separated by cooling the filtrate to 0 ° C., washed and dried as above.
The yield was 15.42 g (88%). The NMR data was as follows. 1H-NMR (δ, CD ₂ Cl ₂ ): 1.18-1.32 (brm, 18H, Cy), 1.69 (brm, 18H, Cy), 1.80 (brm, 18H, Cy) _{), 1.84 (s, 6H,} CH 3), 2.00 (br d, 12H, Cy), 31P-NMR (δ, CD 2 Cl 2): 21.2 (s). Hereinafter, the obtained primary collection and secondary collection were used as catalyst precursor C1.

Synthesis of core polymer (P1) Polymer P1: Synthesis of hexylnorbornene (HxNB) / diphenylmethylnorbornenemethoxysilane (diPhNB) copolymer HxNB (8.94 g, 0.05 mol), diPhNB (16.1 g, 0.05 mol) , 1-hexene (4.2 g, 0.05 mol) and toluene (142.0 g) were mixed in a 250 mL sealam bottle and heated to 120 ° C. in an oil bath to form a solution.
To this solution, [Pd (PCy ₃ ) ₂ (O ₂ CCH ₃ ) (NCCH ₃ )] tetrakis (pentafluorophenyl) borate (hereinafter abbreviated as “Pd1446”) (5.8 × 10 ⁻³ g, 4 0.0 × 10 ⁻⁶ mol) and N, N-dimethylanilinium tetrakis (pentafluorophenyl) borate (hereinafter abbreviated as “DANFABA”) (3.2 × 10 ⁻³ g, 4.0 × 10 ^{− 6} mol) was added in the form of a concentrated dichloromethane solution, respectively.
After the addition, the resulting solution was maintained at 120 ° C. for 6 hours. When methanol was added dropwise to the vigorously stirred mixture, the copolymer precipitated. The precipitated copolymer was collected by filtration and vacuum dried in an oven at 80 ° C. The weight after drying was 12.0 g (yield: 48%). When the molecular weight of the obtained copolymer was measured by GPC method (gel permeation chromatography method) using THF as a solvent (polystyrene conversion), it was Mw = 16,196 and Mn = 8,448. When the composition of the copolymer was measured by 1H-NMR, it was 1H-NMR: 54/46 = HxNB / diPhNB copolymer. Hereinafter, the HxNB / diPhNB copolymer was designated as polymer P1.
The refractive index of the polymer P1 (copolymer) (the refractive index was measured by the prism coupling method, hereinafter the same) was 633 nm, 1.5569 in the TE mode, and 1.5555 in the TM mode. .

-Preparation of core part varnish (V1) Hexylnorbornene (42.03g, 0.24mol) and dimethylbis (norbornenemethoxy) silane (7.97g, 0.026mol) were weighed and put into a glass bottle.
Ciba IRGANOX 1076 (0.5 g) and Ciba IRGAFOS 168 (0.125 g) were added to the monomer solution as an antioxidant to obtain a monomer antioxidant solution.
In a solution (30.0 g) of the above polymer P1 dissolved in mesitylene so as to be 10 wt%, a monomer antioxidant solution (3.0 g) and the catalyst precursor C1 (4.94 × 10 ⁻⁴ g, 6.29 × 10 ⁻⁷ mol, in 0.1 mL of methylene chloride), RHODORSIL PHOTOINITIATOR 2074 (2.55 × 10 ⁻³ g, 2.51 × 10 ⁻⁶ mol, methylene chloride) as a photoacid generator (co-catalyst) In 0.1 mL of chloride) was added to prepare varnish V1.
This varnish V1 was used after being filtered with a 0.2 μm pore filter. Hereinafter, Ciba IRGANOX 1076 was referred to as “IRGANOX 1076”, Ciba IRGAFOS 168 as “IRGAFOS 168”, and RHODORSIL PHOTOINITIATOR 2074 as “RHODORSIL 2074”.

Synthesis of Cladding Polymer (P2) Polymer P2: Synthesis of Decylnorbornene (DeNB) / Methyl Glycidyl Ether Norbornene (AGENB) Copolymer DeNB (16.4 g, 0.07 mol), AGENB (5.41 g, 0.03 mol) and Toluene (58.0 g) was added to the sealum bottle in the dry box. This solution was stirred in an oil bath at 80 ° C.
To this solution was added a toluene solution (5 g) of (η6-toluene) Ni (C ₆ F ₅ ) ₂ (0.69 g, 0.0014 mol).
After the addition, the resulting mixture was maintained at room temperature for 4 hours. Toluene solution (87.0 g) was added to the reaction solution. When methanol was added dropwise to the vigorously stirred reaction mixture, the copolymer precipitated.
The precipitated copolymer was collected by filtration and vacuum dried in an oven at 60 ° C. The weight after drying was 17.00 g (yield: 87%). When the molecular weight of the obtained copolymer was measured by GPC method using THF as a solvent (in terms of polystyrene), it was Mw = 75,000 and Mn = 30,000.
When the composition of the copolymer was measured by 1H-NMR, it was 1H-NMR: 77/23 = DeNB / AGENB copolymer. Hereinafter, DeNB / AGENB copolymer was designated as polymer P2.
The refractive index of the polymer P2 (copolymer) was 1.5153 in the TE mode and 1.5151 in the TM mode at a wavelength of 633 nm.

-Preparation of clad varnish (V2) IRGANOX 1076 (0.05 g) and IRGAFOS 168 (1. g) were used as antioxidants in a solution (16.7 g) of the above polymer P2 dissolved in toluene so as to be 30 wt%. 25 × 10 ⁻² g) and RHODORSIL 2074 (0.1 g in 0.5 mL of methylene chloride) were added as a photoacid generator to prepare varnish V2.
This varnish V2 was used after being filtered with a 0.2 μm pore filter.

-Formation of optical waveguide Filtered varnish V1 was poured onto a glass substrate as a core layer forming material, and spread to a substantially constant thickness with a doctor blade. The glass substrate was then placed on a ventilated horizontal platform overnight to evaporate the solvent and form a substantially dry solid film.
The film was irradiated with UV light (wavelength: 365 nm) through a photomask (irradiation amount = 3 J / cm ² ), then heated in an oven at 85 ° C. for 30 minutes and further at 150 ° C. for 60 minutes. Thereby, a core layer (single-layer optical waveguide) was obtained. In addition, the pattern of the core part was able to be confirmed visually after the 1st heating.
Two clad layers having an average thickness of 50 μm were formed using varnish V2 as a clad layer forming material. The core layer was sandwiched between the two clad layers, and heated in an oven at 150 ° C. for 1 hour while applying a pressure of 10 MPa. Thereby, an optical waveguide was obtained.
The optical waveguide was linear with a core width of 50 μm, a core interval of 250 μm, 12 cores, and a core length of 10 cm. The refractive index of the core portion was 1.555, and the refractive index of the cladding portion was 1.542.

2. Formation of Reflecting Section The optical waveguide 12 produced above was attached using a glass substrate as a support, and fixed to a sample holder of an excimer laser (wavelength: 193 nm, device name: ProMaster (OPTEC)) with a vacuum chuck. The laser intensity is set to 7 mJ, the laser oscillation frequency is set to 250 Hz, the opening of the stainless steel mask for cutting the laser light is set to 1 mm × 1 mm, the moving speed of the processing table is set to 45 μm / s, and the moving distance to the processing table is set to 150 μm. The center line of the core was processed. As a result of observing the processed cross section (reflecting portion) with a microscope, the region of the upper clad layer and the core layer where the resin was removed was an isosceles triangle, and the apex angle was approximately 90 °.

3. Smoothing treatment (formation of resin layer)
Weigh 10 g of bisphenoxyethanol fluorene acrylate, 0.3 g of IRGACURE651 (CIBA SPECIALITY CHEMICALS) as a photopolymerization initiator, dissolve in 90 g of propylene glycol monomethyl ether, filter with a 0.02 μm pore filter, and coat An agent was used. This coating agent is applied to a glass substrate by spin coating, put in a clean oven at 50 ° C. for 30 minutes, exposed to 3 J / cm ² with an ultra-high pressure mercury lamp, and then put in an oven at 85 ° C. for 10 minutes. And the refractive index was measured, and it was 1.60 at a wavelength of 850 nm. The above coating agent was dropped onto the groove processed part (reflective part) of the optical waveguide with a syringe, and the coating agent other than the groove part was removed with a silicon rubber squeegee.
This waveguide was placed in a clean oven at 50 ° C. for 30 minutes, exposed to 3 J / cm ² with an ultrahigh pressure mercury lamp, and then placed in an oven at 85 ° C. for 10 minutes.
When the groove portion was observed with a microscope, the coating portion of the core portion was smooth. The thickness of the resin layer was 5 μm.
This optical waveguide and a polyimide film with a copper foil were laminated to obtain an optical waveguide structure.

(Example 2)
The resin layer was formed in the same manner as in Example 1 except for the following.
0.15 g of bisphenol A-type epoxy 5 g, 3,4-epoxycyclohexenylmethyl-3′4′-epoxycyclohexene carboxylate 5 g, and adekatopomer SP170 (Asahi Denka Kogyo Co., Ltd., hereinafter abbreviated as SP-170) were weighed. The same procedure as in Example 1 was performed except that a solution dissolved in 45 g of propylene glycol monomethyl ether was used as a coating agent. The refractive index of the resin layer was 1.55 at a wavelength of 850 nm. When coating was performed in the same manner as in Example 1 and observed with a microscope, the coating portion of the core portion was smooth. The thickness of the resin layer was 5 μm.

(Example 3)
The resin layer was formed in the same manner as in Example 1 except for the following.
0.15 g of bisphenol A type epoxy 10 g, 3,4-epoxycyclohexenylmethyl-3′4′-epoxycyclohexenecarboxylate 10 g, Adekaoptomer SP170 (Asahi Denka Kogyo Co., Ltd., hereinafter abbreviated as SP-170), The same procedure as in Example 1 was performed except that a solution dissolved in 30 g of propylene glycol monomethyl ether was used as a coating agent. The refractive index of the resin layer was 1.55 at a wavelength of 850 nm. When coating was performed in the same manner as in Example 1 and observed with a microscope, the coating portion of the core portion was smooth, but the shape was curved and the groove portion was oval. The thickness of the resin layer was 10 μm.

Example 4
The resin layer was formed in the same manner as in Example 1 except for the following.
2.5 g of bisphenol A type epoxy, 2.5 g of 3,4-epoxycyclohexenylmethyl-3′4′-epoxycyclohexene carboxylate, Adekaoptomer SP170 (Asahi Denka Kogyo Co., Ltd., hereinafter abbreviated as SP-170) The same procedure as in Example 1 was carried out except that 15 g was weighed and dissolved in 95 g of propylene glycol monomethyl ether as a coating agent. The refractive index of the resin layer was 1.55 at a wavelength of 850 nm. When coating was performed in the same manner as in Example 1 and observation was performed with a microscope, buffer stripes were observed in the coating portion of the core portion, and steps having a period of 0.5 to 1 μm were observed on the core. The thickness of the resin layer was 0.5 μm.

(Example 5)
The optical waveguide was the same as Example 1 except that the following was used.
As a cladding layer forming material, a varnish containing a branched polysilane having an aliphatic hydrocarbon group is applied on a glass substrate that has been subjected to a release treatment, dried at 80 ° C. for 20 minutes, and an average thickness of 50 μm. A clad layer was formed.
Next, a varnish containing a branched polyphenylsilane having an aromatic hydrocarbon group having a refractive index higher than that of the branched polysilane is applied as a material for forming a core layer thereon, at 80 ° C. for 20 minutes. Dried. Thereafter, the core is exposed to an ultra-high pressure mercury lamp through a photomask provided with a shielding portion at the core portion, and is heat-treated at 250 ° C. A layer was formed. On top of that, the same polysilane varnish as described above was applied as a clad layer forming material and heat-treated at 300 ° C. to form a clad layer having an average thickness of 50 μm. The optical waveguide was produced as described above. The optical waveguide was linear with a width of 0.5 cm and a length of 10 cm. The refractive index of the core part was 1.475, and the refractive index of the clad part was 1.415.

(Example 6)
The optical waveguide was the same as Example 1 except that the following was used.
As a clad layer forming material, a UV curable epoxy resin varnish (E3129 manufactured by NTT-AT) is spin-coated on a release-treated glass substrate and then cured by UV irradiation to obtain a clad layer having an average thickness of 50 μm. Formed. Next, a UV curable epoxy resin (E3135 manufactured by NTT-AT) having a refractive index higher than that of the UV curable epoxy resin is spin-coated thereon as a core layer forming material, and the core is directly formed by photolithography. The part (width 50 μm × thickness 50 μm) was patterned. Thereafter, the same UV curable epoxy resin varnish as described above was spin-coated as a cladding layer forming material, and then cured by UV irradiation to form a cladding layer having an average thickness of 50 μm. The optical waveguide was produced as described above. The optical waveguide was linear with a width of 0.5 cm and a length of 10 cm. The refractive index of the core portion was 1.532 and the refractive index of the cladding portion was 1.512.

(Example 7)
The same procedure as in Example 1 was performed except that the reflective portion was smoothed as follows.
The optical waveguide was placed in a chamber of a plasma asher (OPM-EM-1000, manufactured by Tokyo Ohka Kogyo Co., Ltd.), and smoothed for 5 minutes at an O ₂ flow rate of 200 sccm and a high frequency output of 400 W.
Before the plasma treatment, a step with a period of 0.5 to 1 μm was observed on the surface of the groove processing part (reflection part), but after the treatment, there was no periodic pattern as described above and it was smooth.

(Example 8)
The reflective portion was formed in the same manner as in Example 1 except for the following.
A dicing blade (NBC-ZH226J-D-T4B-SE, manufactured by Disco) is attached to the spindle of a dicing saw (DAD321, manufactured by Disco), and the optical waveguide is set in a direction perpendicular to the line direction of the core. Cutting was performed at 2 mm / s. When the cross section was observed, the surface of the lower cladding and the cut surface were 45 °. On the cut surface, grooves with a period of 1 μm were observed in the blade rotation direction.
Coating was performed under the same conditions using the same coating agent as in Example 1 (resin layer was formed). When the coated surface was observed with a microscope, it was smooth. The thickness of the resin layer was 5 μm.

(Comparative Example 1)
The reflective portion was formed as follows, and the same procedure as in Example 1 was performed except that the smoothing process was not performed.
A dicing blade (NBC-ZH226J-D-T4B-SE, manufactured by Disco) is attached to the spindle of a dicing saw (DAD321, manufactured by Disco), and the optical waveguide is set in a direction perpendicular to the line direction of the core. Cutting was performed at 2 mm / s. When the cross section was observed, the surface of the lower cladding and the cut surface were 45 °. On the cut surface, grooves with a period of 1 μm were observed in the blade rotation direction.

The following evaluation was performed about the optical waveguide structure obtained by each Example and the comparative example. The evaluation items are shown together with the contents. The obtained results are shown in Table 1.
1. Light loss Light with a wavelength of 850 nm generated from a laser diode is input to the end of this waveguide through an optical fiber, and the output is detected using the optical fiber on the opposite side of the groove, and the optical loss is evaluated by the following equation. did.
Total optical loss (dB) =-10 log (Pn / P0)
Where Pn is the value measured on the opposite side of the reflector, and P0 is the measured output of the light source at the end of the optical fiber before coupling the optical fiber to the waveguide end.

2. Heat resistance The heat resistance of the optical waveguide structure was evaluated by observing its appearance twice through a reflow process (260 ° C. to 15 seconds, maximum 265 ° C.).
(Double-circle): There was no abnormality, such as a swelling and peeling, in a groove processing part (reflection part).
○: Peeling occurred in addition to the product portion around the groove processed portion (reflecting portion).
(Triangle | delta): The swelling and peeling of a magnitude | size of less than 1 mm generate | occur | produced in the product part of the groove process part (reflection part).
X: Abnormalities such as swelling and peeling having a size of 1 mm or more occurred in the product portion of the groove processed portion (reflecting portion).

3. Flexibility The flexibility of the optical waveguide structure was evaluated with a hinge evaluation open / close tester (evaluation was performed with n = 10). Each code is as follows.
A: All samples had no increase in resistance or disconnection after 50,000 times or more.
◯: There was no increase in resistance or disconnection in 7 to 9 samples even after 50,000 times or more.
(Triangle | delta): There was no raise of resistance and a disconnection in 50,000 times or more in the sample of 3-6 sheets.
X: Less than 50,000 samples had resistance increase and disconnection in less than 2 samples.

4). Hygroscopicity The hygroscopicity of the optical waveguide structure was evaluated according to JIS-K7209 by the weight difference between before and after the 5 cm × 5 cm film of the optical waveguide structure was treated at 85 ° C./85% humidity for 168 hours. (Evaluation was performed with n = 10 sheets).
(Double-circle): The moisture absorption rate of all the samples was less than 0.2%.
A: The moisture absorption rate of 7 to 9 samples was less than 0.2%.
Δ: The moisture absorption rate of 3 to 6 samples was less than 0.2%.
X: The moisture absorption rate of the sample of 2 or less sheets was 0.2% or more.

As is apparent from Table 1, it was shown that the optical waveguide structures obtained in Examples 1 to 8 had a small optical loss at the reflecting portion.
Moreover, it was shown that Examples 1-5 are excellent also in heat resistance especially.
Moreover, it was shown that Examples 1-4 are excellent also in the flexibility.
Moreover, Examples 1-4 showed that hygroscopicity was especially low.

  It was confirmed that an electronic device such as a cellular phone using the optical waveguide structure obtained in this way also operates normally.

  The optical waveguide structure of the present invention is useful for various electronic devices such as servers, mobile phones, and PDAs, holograms, displays, and the like.

DESCRIPTION OF SYMBOLS 1 Optical waveguide formation board | substrate 100 Optical waveguide structure 11 Insulating layer 12 Optical waveguide 121 Core part 122 Cladding part 13 Insulating layer 2 Optical device 21 Light emitting / receiving part 3 Electronic device 4 Terminal part 5 Sealing resin 6 Electrical wiring 61 Plug 7 Reflecting part 7 'portion 7a reflecting portion 7b reflecting portion 7c reflecting portion 71 inclined surface 72 resin layer 72' resin composition 8 laser 81 mask 82 irradiated portion

Claims (2)

An optical waveguide having a core part for transmitting light and a clad part joined to the outer periphery of the core part;
A reflection part having an inclined surface inclined with respect to the light transmission direction of the core part, and an optical waveguide structure comprising:
An optical waveguide structure that is subjected to a treatment for improving the smoothness of the inclined surface.   An electronic device using the optical waveguide structure according to claim 1.

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