WO2012026135A1 - 光導波路および電子機器 - Google Patents
光導波路および電子機器 Download PDFInfo
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- WO2012026135A1 WO2012026135A1 PCT/JP2011/004773 JP2011004773W WO2012026135A1 WO 2012026135 A1 WO2012026135 A1 WO 2012026135A1 JP 2011004773 W JP2011004773 W JP 2011004773W WO 2012026135 A1 WO2012026135 A1 WO 2012026135A1
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- refractive index
- optical waveguide
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- cladding
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
- G02B6/1221—Basic optical elements, e.g. light-guiding paths made from organic materials
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
- G02B6/028—Optical fibres with cladding with or without a coating with core or cladding having graded refractive index
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/13—Integrated optical circuits characterised by the manufacturing method
- G02B6/138—Integrated optical circuits characterised by the manufacturing method by using polymerisation
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/42—Coupling light guides with opto-electronic elements
- G02B6/4201—Packages, e.g. shape, construction, internal or external details
- G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
- G02B6/4214—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms the intermediate optical element having redirecting reflective means, e.g. mirrors, prisms for deflecting the radiation from horizontal to down- or upward direction toward a device
Definitions
- the present invention relates to an optical waveguide and an electronic device.
- optical waveguides have become widespread as means for guiding an optical carrier wave from one point to another point with respect to an optical communication technology for transferring data using the optical carrier wave.
- the optical waveguide has a linear core part and a clad part provided so as to cover the periphery thereof.
- Patent Document 1 describes an optical waveguide in which a refractive index adjusting agent is diffused in a polymer substrate so that the refractive index of a core portion is distributed concentrically in a cross section.
- the refractive index of the cladding part covering the periphery of the core part is constant.
- the core part is made of a material that is substantially transparent to the light of the optical carrier wave
- the cladding part is made of a material having a refractive index lower than that of the core part.
- crosstalk may occur between adjacent core portions.
- the present invention includes the following.
- a first cladding layer A core layer provided on the first clad layer and having a clad part, a first core part, a clad part, a second core part, and a clad part provided in the in-layer direction in this order;
- a second cladding layer provided on the core layer;
- the refractive index distribution W in the in-layer direction of the first core portion and the portion extending to the clad portion is continuously changed, and the first convex portion, the first concave portion, and the first concave portion Has a region lined up in the order of the two convex portions,
- the refractive index distribution W located in the first core portion has the first convex portion
- the refractive index distribution W located in the clad portion has the second convex portion having a maximum refractive index smaller than that of the first convex portion,
- the refractive index difference between the maximum value of the refractive index of the first core part and the maximum value of the refractive index of the first cladding layer is the maximum value of the refractive index of the first core part and the maximum value of the refractive index of the cladding part.
- the optical waveguide is larger than the refractive index difference.
- the second core layer is an optical waveguide having a third core portion located in an interlayer direction of the first core portion.
- the optical waveguide has a refractive index at the top of the first recess that is smaller than an average refractive index in the cladding.
- the refractive index distribution W is an optical waveguide having a top portion of the second convex portion in addition to the vicinity of the interface between the first core portion and the cladding portion.
- the refractive index distribution W has a top portion of the second convex portion at the center portion of the cladding portion, and is continuously refracted from the top portion of the second convex portion toward the first concave portion.
- the refractive index difference between the first core portion and the first cladding layer in the refractive index distribution T is the refractive index between the top of the first concave portion and the top of the first convex portion in the refractive index distribution W.
- optical waveguide In the optical waveguide according to any one of [1] to [9], Having a hole provided so as to cross the first core part and the first cladding layer, and an inner surface of the hole constitutes a reflection surface that reflects light transmitted through the core part; Optical waveguide. [11] In the optical waveguide according to any one of [1] to [10], The difference between the refractive index of the top of the first recess and the average refractive index of the cladding is 3 of the difference between the refractive index of the top of the first recess and the refractive index of the top of the first projection. Optical waveguide that is ⁇ 80%.
- a core layer comprising: a core portion; and side clad portions adjacent to both side surfaces of the core portion; An optical waveguide having a clad layer laminated on both sides of the core layer,
- the refractive index distribution W in the width direction of the cross section of the core layer has at least two minimum values, at least one first maximum value, and at least two second maximum values smaller than the first maximum value.
- FIG. 1 is a perspective view showing a first embodiment of an optical waveguide of the present invention (partially cut out and shown through).
- 1 is a diagram schematically showing an example of a refractive index distribution when the horizontal axis indicates the position of the core layer thickness in the center line C1 and the vertical axis indicates the refractive index. It is. It is a figure which shows an example of intensity distribution of the emitted light when light injects into one of the core parts of the optical waveguide shown in FIG.
- FIG. 1 is a sectional view taken along the line XX in FIG. 1, and a refractive index on the center line C2 passing through the center of the core part in the width direction of the line XX. It is a figure which shows an example of distribution T typically.
- FIG. 1st manufacturing method of the optical waveguide shown in FIG. It is a figure for demonstrating the 1st manufacturing method of the optical waveguide shown in FIG.
- FIG. 1st manufacturing method of the optical waveguide shown in FIG. It is a figure for demonstrating the 1st manufacturing method of the optical waveguide shown in FIG.
- FIG. 1st manufacturing method of the optical waveguide shown in FIG. It is a figure for demonstrating the 1st manufacturing method of the optical waveguide shown in FIG.
- FIG. 1st manufacturing method of the optical waveguide shown in FIG. It is a figure for demonstrating the 1st manufacturing method of the optical waveguide shown in FIG.
- FIG. 1 is a perspective view showing a first embodiment of the optical waveguide of the present invention (partially cut out and shown in a transparent manner), and FIG. 2 is a horizontal axis of the cross-sectional view taken along the line XX shown in FIG.
- FIG. 3 shows an example of the refractive index distribution when the position of the core layer in the center line is taken and the vertical axis indicates the refractive index.
- FIG. 3 shows one of the core portions of the optical waveguide shown in FIG. It is a figure which shows an example of intensity distribution of the emitted light when light injects.
- the upper side in FIG. 1 is referred to as “upper” and the lower side is referred to as “lower”.
- the thickness direction of the layers is exaggerated.
- the optical waveguide of the first embodiment includes a first cladding layer (cladding layer 11), a core layer (core layer 13), and a second cladding layer (cladding layer 12).
- the core layer (core layer 13) is provided on the clad layer 11, and the clad part, the first core part (core part 14), the clad part (clad part 15), and the second core provided in the in-layer direction. It has a part (core part 14) and a clad part in this order.
- the second cladding layer is provided on the core layer.
- the refractive index distribution W in the in-layer direction of the first core part (core part 14) and the part extending over the cladding part (clad part 15) is continuously changing, and the first convex part, It means one having a region arranged in the order of the first concave portion and the second convex portion.
- Such a refractive index distribution is referred to as a “W-type refractive index distribution”.
- the refractive index distribution W located in the first core portion has a first convex portion.
- the refractive index distribution W located in the cladding portion has a second convex portion having a maximum refractive index smaller than that of the first convex portion.
- the refractive index distribution T in the interlayer direction of the first cladding layer (cladding layer 11) and the first core portion (core portion 14) has, for example, a “step index type (hereinafter referred to as SI type) pattern.
- SI type refractive index distribution T means that the refractive index is substantially constant in each of the core layer and the cladding layer, and the refractive index is discontinuous at the boundary between the core layer and the cladding layer.
- the refractive index distribution P in the interlayer direction of the portion extending over the first cladding layer (cladding layer 11), the cladding portion (cladding portion 15) and the second cladding layer (cladding layer 12) is at least located in the first cladding layer. And the portion located in the cladding portion are different.
- the refractive index distribution P may change discontinuously.
- the refractive index distribution P has a refractive index pattern similar to that of the refractive index distribution T, for example. That is, in the refractive index distribution P, it is preferable that the region located in the cladding portion has the fifth convex portion.
- the fifth convex portion of the refractive index distribution P corresponds to the third convex portion of the refractive index distribution T.
- the maximum refractive index or the average refractive index of the region located in the cladding part is preferably higher than the maximum refractive index or the average refractive index located in the first cladding layer.
- the laminated structure of the first cladding layer having the refractive index distribution P, the cladding portion of the core layer, and the second cladding layer is composed of the first cladding layer having the refractive index distribution T and the core portion of the core layer. It can be formed in the same process as the laminated structure of the second cladding layer.
- the refractive index distribution P may be the same as the refractive index distribution T (for example, all of the six vertical and horizontal diagonal directions on the plane in the refractive index distribution extending from the core portion to the adjacent cladding portion (cladding) layer). May be different from each other).
- different refractive index distributions mean that (i) the repeated pattern of the shape of the refractive index distribution is different, or (ii) the shape of the refractive index distribution is the same pattern and the refractive index values are different. (However, manufacturing variations may be considered the same).
- the refractive index difference in the interlayer direction between the adjacent cladding portion and the cladding layer may be different from the refractive index difference in the in-layer direction between the adjacent first core portion and the cladding portion.
- the refractive index distribution P can be, for example, an SI type.
- the SI type refractive index distribution P means that the refractive index is substantially constant in each of the core layer and the cladding layer, and the refractive index is discontinuous at the boundary between the core layer and the cladding layer.
- the first effect is that high optical transmission characteristics can be realized.
- the first concave portion is formed at the end portion, so that the refractive index difference between the central portion and the end portion of the core portion becomes large.
- crosstalk between core parts adjacent in the in-layer direction is suppressed.
- Even if light leaks from the core portion, the leaked light can be confined to the second convex portion of the cladding portion. Thereby, crosstalk between core parts adjacent in the in-layer direction is suppressed.
- the second effect is that a light confinement effect is obtained in the interlayer direction of the clad portion.
- the refractive index changes from the cladding part to the cladding layer. For this reason, it becomes possible to confine light in a clad part or a clad layer.
- the third effect is that a design capable of reducing optical loss is possible depending on the usage mode. It is possible to design the refractive index distribution T in the interlayer direction to be different from the refractive index distribution W in the in-layer direction with the first core portion as a base point. For example, by making the refractive index difference in the interlayer direction larger than the refractive index difference in the in-layer direction, it is possible to reduce optical loss when the optical waveguide film is bent or rolled up in the extending direction of the optical waveguide. . This will be described in detail. If the film is bent in a predetermined direction, the film may be stretched and the refractive index difference may be reduced. On the other hand, even if the refractive index difference is reduced by increasing the refractive index difference in the direction in which the film is bent in advance, the optical loss can be reduced.
- the fourth effect is high design freedom.
- the optical waveguide of the present embodiment is obtained by laminating films, for example. For this reason, the thickness of the cladding layer is arbitrarily determined in relation to the thickness of the core layer. Further, since the thickness can be controlled, effects such as reduction of optical coupling loss can be enhanced.
- the refractive index distribution of the present embodiment is measured and specified from the cross section of the optical waveguide in the direction orthogonal to the extending direction of the optical waveguide (for example, the extending direction of the first core portion).
- the present invention is not limited to this mode, and may have five layers, seven layers or more.
- one or more second core layers may be stacked on the first core layer. Any core layer is preferably sandwiched between clad layers.
- the optical waveguide of the present embodiment is provided on the second cladding layer, and may include a second core layer that is a separate member from the core layer.
- the second core layer has a third core portion located in the interlayer direction of the first core portion.
- the optical waveguide of the present embodiment may include a plurality of core portions spaced in the in-layer direction and a plurality of core portions spaced in the interlayer direction.
- a plurality of core portions may be arranged in a lattice shape in the cross section of the optical waveguide.
- films are laminated. Since the positional deviation of the center of the core part in the interlayer direction is reduced, the optical coupling defect is reduced.
- the optical waveguide of this Embodiment forms a core part by energy irradiation, for example. Since the misalignment of the core part in the interlayer direction is reduced, the optical coupling defect is reduced.
- the refractive index distribution in the in-layer direction of the core layer may be such that a part of the region between at least two adjacent core parts is W-type, and regions located on both sides of the core part may be W-type, All the regions may be W-shaped.
- the W-type refractive index distribution repeated in the in-layer direction may be different for each repeating unit.
- the refractive index distribution in the interlayer direction of the core portion may be that the region extending at least between the core portion and the upper clad layer (or lower clad portion) is the refractive index distribution T, and the regions located on both sides of the core portion are the refractive index distribution. T may be sufficient, and refractive index distribution T may be repeated in all the area
- the refractive index distribution T repeated in the interlayer direction may be different for each repeating unit.
- the refractive index distribution in the interlayer direction of the cladding part may be different at least between the first cladding part and the cladding part, but between the first cladding part and the cladding part and between the second cladding part and the cladding part. May be different.
- the refractive index distribution P repeated in the interlayer direction may be different for each repeating unit.
- the difference in refractive index may be, for example, the difference between the maximum value of the first core part and the maximum value of the cladding part, or the difference between the average value of the first core part and the average value of the cladding part.
- Continuous changing the refractive index distribution means that, for example, a transition region in which the refractive index gradually changes is provided in a region near the interface between the cladding layer and the core layer.
- the function form representing the continuous change in the refractive index with respect to the thickness direction can take various forms, and examples thereof include a spline function and an exponential function. In the present embodiment, for example, the refractive index between the convex portion and the concave portion changes continuously.
- the convex portion (first convex portion to sixth convex portion) of the refractive index distribution has either an aspect in which the top portion has a maximum value or an aspect in which the top portion has a flat portion.
- the concave portions (first concave portion to third concave portion) of the refractive index distribution have both an aspect in which the top has a minimum value and an aspect in which the top has a flat portion.
- the first core portion is a region from the maximum value of the first convex portion to the minimum value of the first concave portion
- the cladding portion is a region from the minimum value of the first concave portion to the maximum value of the second concave portion. Also good. Moreover, it may replace with the maximum value or the minimum value, and may employ
- the width of the flat portion is not particularly limited, but for example, is preferably 100 ⁇ m or less, more preferably 20 ⁇ m or less, and even more preferably 10 ⁇ m or less.
- the refractive index distribution of the present embodiment is, for example, (1) a method of observing a refractive index-dependent interference fringe using an interference microscope (dual-beam interference microscope) and calculating the refractive index distribution from the interference fringe. Or (2) It becomes possible to measure by the refraction near field method (Refracted Near Field method; RNF).
- the refraction near field method can employ the measurement conditions described in JP-A-5-332880. In the embodiment, since the measurement is simple, a method using an interference microscope is preferable.
- an optical waveguide piece is obtained by slicing the optical waveguide in the cross-sectional direction of the optical waveguide. For example, the optical waveguide is sliced so that the length is 200 ⁇ m to 300 ⁇ m.
- a chamber filled with oil having a refractive index of 1.536 is created in a space surrounded by two glass slides.
- a measurement sample in which the optical waveguide piece is sandwiched in the space in the chamber and a blank sample in which the optical waveguide piece is not inserted are prepared.
- an interference fringe photograph in the cross-sectional direction of the optical waveguide fragment is obtained using an interference microscope.
- the refractive index distribution can be obtained by image analysis of the interference fringe photograph. For example, the optical path length of the interference microscope is changed to continuously acquire image data in which the place where the interference fringes are generated.
- the refractive index at each measurement point in the interlayer direction and the in-layer direction is calculated from a plurality of image data.
- the interval between the measurement points is not particularly limited, but is, for example, 2.5 ⁇ m.
- a maximum value exists in the convex portion of the refractive index distribution, and a minimum value exists in the concave portion.
- the top of the first convex portion is the maximum value Wm2
- the top of the second convex portion is the maximum value Wm3
- the top of the third convex portion is the maximum value Tm2
- the top of the fourth convex portion is The maximum value Tm3, the top of the first recess is the minimum value Ws2, and the top of the second recess is the minimum value Ts2.
- the optical waveguide 1 shown in FIG. 1 functions as an optical wiring that transmits an optical signal from one end to the other end.
- the optical waveguide 1 is formed by laminating a cladding layer 11, a core layer 13, and a cladding layer 12 in this order from the lower side in FIG.
- the core layer 13 has a refractive index distribution in the surface direction.
- This refractive index distribution has a region having a relatively high refractive index and a region having a relatively low refractive index, whereby incident light can be confined and propagated in a region having a high refractive index.
- FIG. 2A is a cross-sectional view taken along the line XX of FIG. 1
- FIG. 2B is a cross-sectional view taken along the center line C1 passing through the center of the core layer 13 in the thickness direction of the cross-sectional view taken along the line XX. It is a figure which shows an example of refractive index distribution typically.
- the core layer 13 includes four local minimum values Ws1, Ws2, Ws3, and Ws4 and five local maximum values Wm1, Wm2, Wm3, Wm4, and Wm5 as shown in FIG. 2B in the width direction. It has a refractive index distribution W.
- the five maximum values include a maximum value having a relatively high refractive index (first maximum value) and a maximum value having a relatively low refractive index (second maximum value).
- the portion between the minimum value Ws ⁇ b> 1 and the minimum value Ws ⁇ b> 2 includes the maximum value Wm ⁇ b> 2 having a relatively large refractive index, and thus becomes the core portion 14. Since the maximum value Wm4 is also included between Ws3 and the minimum value Ws4, the core portion 14 is formed. More specifically, the core portion 141 is defined between the minimum value Ws1 and the minimum value Ws2, and the core portion 142 is defined between the minimum value Ws3 and the minimum value Ws4.
- the region on the left side of the minimum value Ws1, the region between the minimum value Ws2 and the minimum value Ws3, and the region on the right side of the minimum value Ws4 are regions adjacent to both sides of the core portion 14, respectively.
- a region on the left side of the minimum value Ws1 is a side cladding portion 151
- a region between the minimum value Ws2 and the minimum value Ws3 is a side cladding portion 152
- a region on the right side of the minimum value Ws4 is a side cladding portion 153.
- the refractive index distribution W should have at least a region where the second maximum value, the minimum value, the first maximum value, the minimum value, and the second maximum value are arranged in this order. Note that this region is repeatedly provided according to the number of core portions.
- the refractive index distribution W has a second maximum value, a minimum value, and a first value. Local maximum values, local minimum values, second local maximum values, local minimum values, first local maximum values, local minimum values, second local maximum values, and the like. It is only necessary to have a region in which the maximum value of 1 and the second maximum value are alternately arranged.
- the plurality of local minimum values, the plurality of first local maximum values, and the plurality of second local maximum values are preferably substantially the same as each other, but the local minimum values are the first local maximum value and the second local maximum value.
- the values may be slightly different from each other. In that case, it is preferable that the amount of deviation is suppressed within 10% of the average value of the plurality of minimum values.
- the optical waveguide 1 has an elongated band shape, and the refractive index distribution W as described above is maintained substantially the same distribution in the entire longitudinal direction of the optical waveguide 1.
- the core layer 13 is formed with two long core portions 14 and three side cladding portions 15 adjacent to each side of the core portions 14. It will be.
- the optical waveguide 1 shown in FIG. 1 is provided with two parallel core portions 141 and 142 and three side cladding portions 151, 152, and 153 arranged in parallel.
- each core part 141 and 142 will be in the state surrounded by each side cladding part 151,152,153 and each cladding layer 11,12, respectively.
- the average refractive index of these two core parts 141 and 142 is higher than the average refractive index of the three side clad parts 151, 152, and 153, each core part 141, 142 and each side clad part 151. , 152, 153 can cause total reflection of light.
- a dense dot is attached
- the light incident on one end of the core portion 14 is totally reflected between the core portion 14 and the clad portion (the clad layers 11 and 12 and the side clad portions 15), By propagating, it can be taken out from the other end of the core part 14.
- a quadrangular shape such as a square or a rectangle, but this shape is not particularly limited.
- the shape may be a circle such as a triangle, a triangle, a pentagon, or a polygon such as a hexagon.
- the width and height of the core part 14 are not particularly limited, but are preferably about 1 to 200 ⁇ m, more preferably about 5 to 100 ⁇ m, and more preferably about 20 to 70 ⁇ m. More preferably.
- the four minimum values Ws1, Ws2, Ws3, and Ws4 are each less than the average refractive index WA in the side cladding portion 15.
- a region having a smaller refractive index than the side clad portion 15 exists between each core portion 14 and each side clad portion 15.
- a steeper refractive index gradient is formed in the vicinity of each local minimum value Ws1, Ws2, Ws3, and Ws4. This suppresses light leakage from each core portion 14, thereby reducing transmission loss.
- the optical waveguide 1 is obtained.
- the refractive index distribution W the refractive index continuously changes as a whole.
- the effect of confining light in the core portion 14 is further enhanced, so that transmission loss can be further reduced.
- the region closer to the center of the core portion 14 is transmitted. Since light propagates intensively, a difference in propagation time for each optical path is less likely to occur. For this reason, even when the transmission light includes a pulse signal, it is possible to suppress blunting of the pulse signal (spreading of the pulse signal). As a result, the optical waveguide 1 that can further improve the quality of optical communication is obtained.
- the maximum values Wm2 and Wm4 are located at the core portions 141 and 142 as shown in FIG. 2, but the core portions 141 and 142 are located at the center of the width. Yes.
- the probability that transmission light will gather in the center part of the width of core part 141 and 142 becomes high, and the probability that it will leak to side cladding parts 151, 152, and 153 becomes relatively low.
- the transmission loss of the core parts 141 and 142 can be further reduced.
- the central portion of the width of the core portion 141 is a region having a distance of 30% of the width of the core portion 141 on both sides from the midpoint between the minimum value Ws1 and the minimum value Ws2.
- the positions of the maximum values Wm2 and Wm4 be located at the center of the width of the cores 141 and 142 if possible, but the edge of the cores 141 and 142 (not necessarily the center) ( If it is located outside the vicinity of the portions that are in contact with the side clad portions 151, 152, and 153, a significant deterioration in characteristics can be avoided. That is, the transmission loss of the core parts 141 and 142 can be suppressed to some extent.
- the vicinity of the edge of the core part 141 is a region having a distance of 5% of the width of the core part 141 from the edge to the inside.
- the maximum values Wm1, Wm3, and Wm5 of the refractive index distribution W are located in the side cladding portions 151, 152, and 153 as shown in FIG. , 153 is preferably located outside the vicinity of the edge (portion in contact with the core portions 141 and 142).
- the local maximum values Wm2, Wm4 in the core portions 141, 142 and the local maximum values Wm1, Wm3, Wm5 in the side cladding portions 151, 152, 153 are sufficiently separated from each other.
- 142 can sufficiently reduce the probability that the transmitted light leaks into the side clad parts 151, 152, 153.
- the transmission loss of the core parts 141 and 142 can be reduced.
- the vicinity of the edge of the side cladding portions 151, 152, and 153 is a region having a distance of 5% of the width of the side cladding portions 151, 152, and 153 from the edge to the inside.
- the local maximum values Wm1, Wm3, and Wm5 are located at the center of the width of the side cladding portions 151, 152, and 153, and the local minimum values Ws1, Ws2 are adjacent to the local maximum values Wm1, Wm3, and Wm5. , Ws3, Ws4, it is preferable that the refractive index continuously decreases.
- the maximum distances between the maximum values Wm2, Wm4 in the core portions 141, 142 and the maximum values Wm1, Wm3, Wm5 in the side cladding portions 151, 152, 153 are secured, and the maximum values Wm1, Since light can be reliably confined in the vicinity of Wm3 and Wm5, leakage of transmission light from the core portions 141 and 142 described above can be more reliably suppressed.
- the local maximum values Wm1, Wm3, and Wm5 are smaller in refractive index than the local maximum values Wm2 and Wm4 located in the core portions 141 and 142 described above. Although it does not have, since the refractive index is higher than the surroundings, it has a slight light transmission property. As a result, the side clad parts 151, 152, and 153 have an effect of preventing transmission to other core parts by confining transmission light leaked from the core parts 141 and 142. That is, the presence of the maximum values Wm1, Wm3, and Wm5 can suppress crosstalk.
- the minimum values Ws1, Ws2, Ws3, and Ws4 are less than the average refractive index WA of the side cladding portion 15, but the difference is desirably within a predetermined range. Specifically, the difference between the minimum value Ws1, Ws2, Ws3, Ws4 and the average refractive index WA of the side cladding portion 15 is the minimum value Ws1, Ws2, Ws3, Ws4 and the maximum value Wm2 in the core portions 141, 142.
- the difference from Wm4 is preferably about 3 to 80%, more preferably about 5 to 50%, further preferably about 7 to 20% (for example, (WA ⁇ Ws1) / (Wm2 -Ws1) ⁇ 100 is preferably about 3 to 80%, more preferably about 5 to 50%, and even more preferably about 7 to 20% (hereinafter, "to" Unless otherwise stated, it means that the upper and lower limits are included)).
- the side clad portion 15 has a light transmission property necessary and sufficient for suppressing crosstalk.
- crosstalk can fully be suppressed by making the difference of minimum value Ws1, Ws2, Ws3, Ws4 and the average refractive index WA of the side cladding part 15 more than the said lower limit. By setting it to the upper limit value or less, it is possible to suppress a decrease in the light transmission performance of the core portions 141 and 142 due to the light transmission performance in the side cladding portion 15 being too large.
- the difference between the minimum values Ws1, Ws2, Ws3, Ws4 and the maximum values Wm1, Wm3, Wm5 is about 6 to 90% of the difference between the minimum values Ws1, Ws2, Ws3, Ws4 and the maximum values Wm2, Wm4. It is preferably about 10 to 70%, more preferably about 14 to 40%. As a result, the balance between the refractive index height of the side cladding portion 15 and the refractive index height of the core portion 14 is optimized, and the optical waveguide 1 has particularly excellent optical transmission properties and more reliably suppresses crosstalk. It will be possible.
- the difference in refractive index between the minimum values Ws1, Ws2, Ws3, and Ws4 and the maximum values Wm2 and Wm4 in the core portions 141 and 142 is preferably as large as possible, but is about 0.005 to 0.07.
- it is about 0.007 to 0.05, more preferably about 0.01 to 0.03 (for example, (Wm1-Ws1) / (Wm2-Ws1) ⁇ 100 is 0).
- 0.005 to 0.07 is preferable, 0.007 to 0.05 is more preferable, and 0.01 to 0.03 is still more preferable.
- the refractive index distribution W in the core portions 141 and 142 has a maximum value when the horizontal axis indicates the cross-sectional position of the core layer 13 and the vertical axis indicates the refractive index.
- the refractive index is continuously changing in the vicinity of Wm2 and the maximum value Wm4, it may have a substantially convex V shape (substantially linear except for the maximum value). It has an approximately U-shape that is convex upward (the entire vicinity of the maximum value is rounded).
- the refractive index distribution W has such a shape, the light confinement action in the core portions 141 and 142 becomes more remarkable.
- the refractive index distribution W has a shape in which the refractive index continuously changes in the vicinity of the minimum value Ws1, the vicinity of the minimum value Ws2, the vicinity of the minimum value Ws3, and the vicinity of the minimum value Ws4. If so, it may have a substantially convex V shape (substantially linear except for the maximum value), but preferably has a substantially U shape convex downward (the entire vicinity of the maximum value is rounded). It is said.
- the present inventors made light incident on one desired end portion of the plurality of core portions 141 and 142 of the optical waveguide 1 and acquired the intensity distribution of the emitted light at the other end portion. It was found that the intensity distribution is extremely useful for suppressing the crosstalk of the optical waveguide 1.
- FIG. 3 is a diagram showing the intensity distribution of the emitted light when light is incident on the core portion 141 of the optical waveguide 1.
- the intensity of the emitted light becomes the largest at the central part of the outgoing end of the core part 141.
- the intensity of the emitted light decreases as the distance from the central portion of the core portion 141 decreases.
- an intensity distribution that takes a minimum value in the core portion 142 adjacent to the core portion 141 is obtained. . Since the minimum value of the intensity distribution of the emitted light coincides with the position of the core part 142 in this way, the crosstalk in the core part 142 can be suppressed to be extremely small.
- An optical waveguide 1 that can reliably prevent the generation is obtained.
- the intensity distribution of the emitted light does not take the minimum value in the core portion adjacent to the core portion where the light is incident, but rather takes the maximum value, which causes a crosstalk problem. It was.
- the behavior of the intensity distribution of the emitted light in the optical waveguide of the present invention as described above is extremely useful for suppressing crosstalk.
- the refractive index distribution W has the minimum values Ws1, Ws2, Ws3, and Ws4, and is refracted.
- the characteristic refractive index distribution W in which the refractive index continuously changes throughout the refractive index distribution W, represents the intensity distribution of the emitted light, which conventionally had a maximum value in the core section 142, as the core section. For example, the side clad portion 153 adjacent to 142 is shifted. That is, the crosstalk is reliably suppressed by this shift.
- the intensity distribution of the emitted light as described above is not necessarily observed although the probability of being observed in the optical waveguide of the present invention is high, but the NA (numerical aperture) of the incident light and the cross-sectional area of the core portion 141 are not necessarily observed.
- the NA number of the incident light
- the cross-sectional area of the core portion 141 are not necessarily observed.
- a clear minimum value may not be observed, or the position of the minimum value may deviate from the core part 142. Even in such a case, crosstalk is sufficiently suppressed. Is done.
- the refractive index in the vicinity of the maximum values Wm2 and Wm4 is continuously equal to or higher than the average refractive index WA. Is a [ ⁇ m], and the width of the portion where the refractive index in the vicinity of the minimum values Ws1, Ws2, Ws3, and Ws4 is continuously less than the average refractive index WA is b [ ⁇ m].
- b is preferably about 0.01a to 1.2a, more preferably about 0.03a to 1a, and further preferably about 0.1a to 0.8a.
- the substantial widths of the minimum values Ws1, Ws2, Ws3, and Ws4 can exhibit the above-described functions and effects. That is, by setting b to be equal to or more than the lower limit value, it is possible to suppress the substantial width of the minimum values Ws1, Ws2, Ws3, and Ws4 from being too narrow and the effect of confining light in the core portions 141 and 142 from being reduced. On the other hand, by setting b to be equal to or less than the upper limit value, the substantial widths of the minimum values Ws1, Ws2, Ws3, and Ws4 are too wide, the width and pitch of the core portions 141 and 142 are limited, and transmission efficiency decreases. It is possible to prevent the increase in the number of channels and the increase in density.
- the average refractive index WA in the side cladding 15 can be approximated at the midpoint between the maximum value Wm1 and the minimum value Ws1, for example.
- the constituent material (main material) of the core layer 13 as described above is not particularly limited as long as it is a material that causes the above-described difference in refractive index, but specifically, acrylic resin, methacrylic resin, polycarbonate, polystyrene, epoxy
- acrylic resin methacrylic resin
- polycarbonate polycarbonate
- polystyrene epoxy
- quartz glass A glass material such as borosilicate glass can be used.
- the resin material may be a composite material obtained by combining materials having different compositions, and may contain an unpolymerized monomer.
- the norbornene-based polymer includes, for example, ring-opening metathesis polymerization (ROMP), combination of ROMP and hydrogenation reaction, polymerization by radical or cation, polymerization using a cationic palladium polymerization initiator, and other polymerization initiators (for example, It can be obtained by all known polymerization methods such as polymerization using nickel or other transition metal polymerization initiators).
- ROMP ring-opening metathesis polymerization
- combination of ROMP and hydrogenation reaction polymerization by radical or cation
- polymerization using a cationic palladium polymerization initiator for example, It can be obtained by all known polymerization methods such as polymerization using nickel or other transition metal polymerization initiators.
- the clad layers 11 and 12 constitute clad portions located at the lower and upper portions of the core layer 13, respectively.
- the average thickness of the clad layers 11 and 12 is preferably about 0.1 to 1.5 times the average thickness of the core layer 13 (the average height of each core portion 14). More preferably, the average thickness of the cladding layers 11 and 12 is not particularly limited, but it is usually preferably about 1 to 200 ⁇ m, and preferably about 5 to 100 ⁇ m. More preferably, it is about 10 to 60 ⁇ m. Thereby, the function as a clad part is suitably exhibited while preventing the optical waveguide 1 from becoming unnecessarily large (thickened).
- constituent material of the cladding layers 11 and 12 for example, the same material as the constituent material of the core layer 13 described above can be used, but a norbornene polymer is particularly preferable.
- the material when selecting the constituent material of the core layer 13 and the constituent materials of the clad layers 11 and 12, the material may be selected in consideration of the difference in refractive index between them. Specifically, in order to ensure total reflection of light at the boundary between the core portion 14 and the cladding layers 11 and 12, the material may be selected so that the refractive index of the constituent material of the core portion 14 is sufficiently large. As a result, a sufficient refractive index difference is obtained in the thickness direction of the optical waveguide 1, and light can be prevented from leaking from the respective core portions 14 to the cladding layers 11 and 12.
- the adhesiveness (affinity) between the constituent material of the core layer 13 and the constituent materials of the cladding layers 11 and 12 is high.
- the clad layers 11 and 12 may be provided as necessary, and either one or both may be omitted. In this case, the surface of the core layer 13 is exposed to the atmosphere (air), but since the refractive index of air is sufficiently low, the air can substitute for the functions of the cladding layers 11 and 12.
- the refractive index distribution T in the thickness direction of the optical waveguide 1 has a shape different from the refractive index distribution W in the width direction described above.
- FIG. 4A is a diagram in which a part centered on the core portion of the XX sectional view shown in FIG. 1 is cut out
- FIG. 4B is a diagram of the core portion of the XX sectional view. It is a figure which shows typically an example of the refractive index distribution T on the centerline C2 which passes the center of the width direction.
- FIG. 4B is a diagram illustrating an example of the refractive index distribution T when the horizontal axis indicates the refractive index and the vertical axis indicates the position on the center line C2.
- the optical waveguide 1 is formed by laminating the clad layer 11, the core layer 13, and the clad layer 12 in this order. Of the cross section, the optical waveguide 1 is refracted in the thickness direction passing through the core portion 14.
- the index distribution T has a shape in which the refractive index is substantially constant in each of the region (part) T1 corresponding to the core portion 14 and the region (part) T2 corresponding to each of the cladding layers 11 and 12. Further, the refractive index changes discontinuously at the boundary between the region T1 and the region T2. That is, the refractive index distribution T has a step index shape. Since such an optical waveguide 1 can be obtained by simply laminating the clad layer 11, the core layer 13, and the clad layer 12, there is an advantage that the manufacturability is high.
- the ratio of the refractive index difference between the refractive index n1 in the core portion 14 and the refractive index n2 in the cladding layer 11 and the cladding layer 12 is preferably as large as possible. Is preferably 0.5% or more, and more preferably 0.8% or more.
- the upper limit value may not be set, but is preferably about 5.5%. If the difference in refractive index is less than the lower limit, the effect of transmitting light may be reduced. On the other hand, even if the upper limit is exceeded, no further increase in light transmission efficiency can be expected.
- the ratio of the refractive index difference between the refractive index n1 and the refractive index n2 is expressed by the following equation.
- Refractive index difference ratio (%)
- the refractive index difference between the core portion 14 and the cladding layers 11 and 12 in the refractive index distribution T takes a value in a specific range based on a preferable range of the ratio of the refractive index difference.
- the difference in refractive index between the minimum values Ws1, Ws2, Ws3, Ws4 and the first maximum values Wm2, Wm4 in the refractive index distribution W is larger.
- n1-n2 may be larger than the refractive index difference between the minimum values Ws1, Ws2, Ws3, Ws4 and the first maximum values Wm2, Wm4 in the refractive index distribution W, but preferably 100. It is 5% or more, more preferably 101% or more, and still more preferably 102% or more. Thereby, the transmission loss in the thickness direction is necessary and sufficiently suppressed.
- the refractive index is substantially constant.
- the ratio of the refractive index deviation amount to the average refractive index in each of the regions T1 and T2. Is preferably 10% or less, and more preferably 5% or less.
- a support film 2 as shown in FIG. 1 may be laminated on the lower surface of the optical waveguide 1 as necessary.
- Support film 2 supports and reinforces the lower surface of the optical waveguide 1. Thereby, the reliability and mechanical characteristics of the optical waveguide 1 can be improved.
- the constituent material of the support film 2 examples include various resin materials such as polyethylene terephthalate (PET), polyolefin such as polyethylene and polypropylene, polyimide and polyamide, and metal materials such as copper, aluminum and silver. It is done. In the case of a metal material, a metal foil is preferably used as the support film 2.
- PET polyethylene terephthalate
- polyolefin such as polyethylene and polypropylene
- polyimide and polyamide polyimide and polyamide
- metal materials such as copper, aluminum and silver. It is done.
- a metal material a metal foil is preferably used as the support film 2.
- the average thickness of the support film 2 is not particularly limited, but is preferably about 5 to 200 ⁇ m, more preferably about 10 to 100 ⁇ m. Thereby, since the support film 2 has moderate rigidity, the optical waveguide 1 is reliably supported and the flexibility of the optical waveguide 1 is difficult to be hindered.
- the support film 2 and the optical waveguide 1 are bonded or bonded, and examples of the method include thermocompression bonding, bonding with an adhesive or a pressure sensitive adhesive, and the like.
- the adhesive layer examples include acrylic adhesives, urethane adhesives, silicone adhesives, and various hot melt adhesives (polyester and modified olefins).
- thermoplastic polyimide adhesive agents such as a polyimide, a polyimide amide, a polyimide amide ether, a polyester imide, a polyimide ether, are used preferably. Since the adhesive layer made of such a material is relatively flexible, even if the shape of the optical waveguide 1 changes, the change can be freely followed. As a result, it is possible to reliably prevent peeling due to the shape change.
- the average thickness of such an adhesive layer is not particularly limited, but is preferably about 1 to 100 ⁇ m, and more preferably about 5 to 60 ⁇ m.
- the cover film 3 protects the optical waveguide 1 and supports the optical waveguide 1 from above. Thereby, the optical waveguide 1 is protected from dirt and scratches, and the reliability and mechanical characteristics of the optical waveguide 1 can be improved.
- a constituent material of such a cover film 3 it is the same as the constituent material of the support film 2.
- resin materials such as polyethylene terephthalate (PET), polyolefin such as polyethylene and polypropylene, polyimide and polyamide
- Metal materials such as copper, aluminum, silver, are mentioned.
- a metal material a metal foil is preferably used as the cover film 3.
- a mirror is formed in the middle of the optical waveguide 1, light is transmitted through the cover film 3, so that the constituent material of the cover film 3 is preferably substantially transparent.
- the average thickness of the cover film 3 is not particularly limited, but is preferably about 3 to 50 ⁇ m, more preferably about 5 to 30 ⁇ m. By setting the thickness of the cover film 3 within the above range, the cover film 3 has sufficient light transmittance in optical communication, and has sufficient rigidity to reliably protect the optical waveguide 1.
- cover film 3 and the optical waveguide 1 are bonded or bonded, and examples of the method include thermocompression bonding, bonding with an adhesive or a pressure-sensitive adhesive, and the like. Of these, the adhesive described above can be used.
- the optical waveguide 1 composed of a laminate of the clad layer 11, the core layer 13, and the clad layer 12 has been described. However, these may be integrally formed.
- the number of the core parts 14 is not specifically limited, One or three or more may be sufficient. .
- the refractive index distribution W of the cross section of the optical waveguide 1 has two minimum values, and the minimum value is less than the average refractive index WA as described above. Yes, and it is sufficient that the refractive index continuously changes throughout the refractive index distribution W.
- the refractive index distribution W has accordingly.
- the number of local minimum values will increase to 6, 8, 10,.
- FIG. 5 is a perspective view showing a second embodiment of the optical waveguide of the present invention (partially shown).
- illustration of a part of core part 14 is abbreviate
- the second embodiment is the same as the first embodiment except that a mirror (reflection surface) 17 that changes the traveling direction of light propagating through the core unit 14 is provided.
- the mirror 17 is formed with a recess (hole) 170 having a V-shaped cross section so as to partially penetrate the optical waveguide 1 in the thickness direction, and is configured by a part of the side surface (inner surface) of the recess 170. Has been. This side surface is planar and is inclined 45 ° with respect to the axis of the core portion 14. The light propagating through the core portion 14 is reflected by the mirror 17, and the optical path is converted by 90 ° downward in FIG. Further, the light propagating from below in FIG. 5 is reflected by the mirror 17 and enters the core portion 14. That is, the mirror 17 has a function as an optical path conversion unit that converts an optical path of light propagating through the core unit 14.
- the processed surfaces of the clad layer 11, the core layer 13, and the clad layer 12 are exposed on the mirror 17, and the processed surface of the core portion 14 is located almost at the center of the mirror 17.
- the refractive index is substantially constant in the region T1 (see FIG. 4) corresponding to the core portion 14 of the refractive index distribution T, the reflected light is constant regardless of which part the incident light enters. It is presumed that this is because of the characteristic, and as a result, the light reflectance is improved.
- the mirror 17 may be provided so as to traverse only the core portion 14, but as shown in FIG. 5A, each of the cladding layers 11, 12 and the side cladding portion 15 around the core portion 14 is provided. It is preferably provided so as to cross. Thereby, the effective area contributing to reflection in the mirror 17 is widened, and mirror loss is suppressed.
- a reflective film may be formed on the surface of the processed surface constituting the mirror 17.
- the reflective film include a metal film such as Au, Ag, and Al, and a film made of a material having a lower refractive index than the core portion 14.
- Examples of the method for forming the metal film include a physical vapor deposition method such as vacuum vapor deposition, a chemical vapor deposition method such as CVD, and a plating method.
- the optical waveguide of the present invention is a light emitting element or a light receiving element (both of which are optical fibers or the like). And the tolerance of misalignment with the end face is wide. This is because the refractive index distribution T in the thickness direction of the optical waveguide 1 has a region T1 in which the refractive index is substantially constant, so that the incident efficiency is almost equal at any position in the region T1. . Therefore, the optical waveguide 1 is easy to optically couple with the light emitting element and the light receiving element and has a small optical coupling loss.
- FIG. 5B shows another configuration example of the second embodiment.
- the core portion 14 does not reach the end face of the optical waveguide 1 at one end portion, and is interrupted in the middle.
- a side clad portion 15 is formed from the location where the core portion 14 is interrupted to the end face.
- a portion where the core portion 14 is interrupted is referred to as a core portion missing portion 16.
- the mirror 17 is formed in this core part lacking part 16.
- the processed surfaces of the cladding layer 11, the core layer 13, and the cladding layer 12 are exposed.
- the processed surface of the side cladding portion 15 is on the processed surface of the core layer 13. It will be exposed.
- both the processed surface of the core portion 14 and the processed surface of the side cladding portion 15 are exposed on the processed surface of the core layer 13.
- the mirror 17 shown in FIG. 5 (b) has uniform smoothness because the exposed surface of the core layer 13 is composed of only a single material. This is because a single material is processed at the time of processing, and the processing rate becomes uniform in the plane. For this reason, the mirror 17 has excellent reflection characteristics and has a small mirror loss.
- deletion part 16 is separated from the core part 14, the density
- FIGS. 6 to 10 are diagrams for explaining a first method of manufacturing the optical waveguide 1 shown in FIG.
- the upper side in FIGS. 6 to 10 is referred to as “upper” and the lower side is referred to as “lower”.
- the optical waveguide 1 is manufactured by preparing a clad layer 11, a core layer 13, and a clad layer 12, and laminating them.
- the first manufacturing method of the optical waveguide 1 is as follows: [1] After applying the core layer forming composition 900 on the support substrate 951 to form a liquid film, the support substrate 951 is placed on a level table to form the liquid film. While flattening, the solvent is evaporated (desolvent). Thereby, the layer 910 is obtained. [2] Next, a refractive index difference is generated by irradiating a part of the layer 910 with actinic radiation to obtain the core layer 13 in which the core part 14 and the side cladding part 15 are formed. [3] Next, the cladding layers 11 and 12 are laminated on both surfaces of the core layer 13 to obtain the optical waveguide 1.
- a core layer forming composition 900 is prepared.
- the core layer forming composition 900 contains a polymer 915 and an additive 920 (including at least a monomer in this embodiment).
- a composition 900 for forming a core layer is a material that causes a reaction of at least a monomer in the polymer 915 by irradiation with actinic radiation and changes the refractive index distribution accordingly. That is, in the core layer forming composition 900, the refractive index distribution changes due to the deviation in the abundance ratio of the polymer 915 and the monomer, and as a result, the core portion 14 and the side cladding portion 15 are formed in the core layer 13. It is a material that can be used.
- the core layer forming composition 900 is applied on the support substrate 951 to form a liquid film (see FIG. 6A). Then, the support substrate 951 is placed on the level table to flatten the liquid film and evaporate (desolvent) the solvent. Thereby, the layer 910 is obtained (see FIG. 6B).
- the support substrate 95 for example, a silicon substrate, a silicon dioxide substrate, a glass substrate, a polyethylene terephthalate (PET) film, or the like is used.
- a silicon substrate for example, a silicon substrate, a silicon dioxide substrate, a glass substrate, a polyethylene terephthalate (PET) film, or the like is used.
- PET polyethylene terephthalate
- Examples of the coating method for forming a liquid film include a doctor blade method, a spin coating method, a dipping method, a table coating method, a spray method, an applicator method, a curtain coating method, and a die coating method.
- the polymer (matrix) 915 exists substantially uniformly and randomly, and the additive 920 is substantially uniformly and randomly dispersed in the polymer 915. Thereby, the additive 920 is substantially uniformly and randomly dispersed in the layer 910.
- the average thickness of the layer 910 is appropriately set according to the thickness of the core layer 13 to be formed, and is not particularly limited, but is preferably about 5 to 300 ⁇ m, more preferably about 10 to 200 ⁇ m.
- the polymer 915 serves as a base polymer for the core layer 13.
- the polymer 915 has sufficiently high transparency (colorless and transparent) and is compatible with the monomer described later, and among them, the monomer can react (polymerization reaction or crosslinking reaction) as described later. There are preferably used those having sufficient transparency even after the monomer is polymerized.
- having compatibility means that the monomer is at least mixed and does not cause phase separation with the polymer 915 in the core layer forming composition 900 or the layer 910.
- Examples of such a polymer 915 include cyclic olefin resins such as norbornene resins and benzocyclobutene resins, acrylic resins, methacrylic resins, polycarbonates, polystyrenes, epoxy resins, polyamides, polyimides, polybenzoxazoles, Examples thereof include silicone resins and fluorine resins, and one or more of these can be used in combination (polymer alloy, polymer blend (mixture), copolymer, etc.).
- the core layer 13 having excellent optical transmission performance and heat resistance can be obtained.
- the cyclic olefin-based resin may be unsubstituted or may have hydrogen substituted with other groups.
- cyclic olefin resins examples include norbornene resins and benzocyclobutene resins.
- norbornene-based resin it is preferable to use a norbornene-based resin from the viewpoints of heat resistance and transparency. Moreover, since norbornene-type resin has high hydrophobicity, the core layer 13 which cannot produce the dimensional change by water absorption etc. can be obtained.
- the norbornene-based resin may be either one having a single repeating unit (homopolymer) or one having two or more norbornene-based repeating units (copolymer).
- a norbornene-based resin for example, (1) addition (co) polymer of norbornene type monomer obtained by addition (co) polymerization of norbornene type monomer, (2) addition copolymers of norbornene monomers with ethylene and ⁇ -olefins, (3) an addition polymer such as an addition copolymer of a norbornene-type monomer and a non-conjugated diene and, if necessary, another monomer; (4) a ring-opening (co) polymer of a norbornene-type monomer, and a resin obtained by hydrogenating the (co) polymer if necessary, (5) a ring-opening (co) polymer of a norbornene-type monomer and ethylene or ⁇ -olefins, and a resin obtained by hydrogenating the (co) polymer if necessary, (6) Ring-opening copolymers such as norbornene-type monomers and non-conjugated dienes, or other monomers,
- 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, it can be obtained by any known polymerization method such as polymerization using a polymerization initiator of nickel or another transition metal).
- ROMP ring-opening metathesis polymerization
- combination of ROMP and hydrogenation reaction polymerization by radical or cation
- polymerization using cationic palladium polymerization initiator cationic palladium polymerization initiator
- other polymerization initiators for example, it can be obtained by any known polymerization method such as polymerization using a polymerization initiator of nickel or another transition metal).
- norbornene resins are preferably those having at least one repeating unit represented by the following structural formula B, that is, addition (co) polymers. Since the addition (co) polymer is rich in transparency, heat resistance, and flexibility, for example, after the optical waveguide 1 is formed, an electrical component or the like may be mounted on the optical waveguide 1 via solder. This is because even in such a case, high heat resistance, that is, reflow resistance can be imparted to the optical waveguide 1.
- Such a norbornene-based polymer is suitably synthesized by using, for example, a norbornene-based monomer described later (a norbornene-based monomer represented by Structural Formula C described below or a crosslinkable norbornene-based monomer).
- the product when the optical waveguide 1 is incorporated into various products, the product may be used in an environment of about 80 ° C., for example. Even in such a case, an addition (co) polymer is preferable from the viewpoint of ensuring heat resistance.
- the norbornene-based resin preferably includes a norbornene repeating unit having a substituent containing a polymerizable group or a norbornene repeating unit having a substituent containing an aryl group.
- repeating unit of norbornene having a substituent containing a polymerizable group the repeating unit of norbornene having a substituent containing an epoxy group, the repeating unit of norbornene having a substituent containing a (meth) acryl group, and an alkoxysilyl group At least one of the repeating units of norbornene having a substituent containing is preferable.
- These polymerizable groups are preferable because of their high reactivity among various polymerizable groups.
- the norbornene-based resin preferably contains an alkylnorbornene repeating unit.
- the alkyl group may be linear or branched.
- the norbornene-based resin By including the repeating unit of alkyl norbornene, the norbornene-based resin has high flexibility, and therefore can provide high flexibility (flexibility).
- a norbornene-based resin containing a repeating unit of alkyl norbornene is preferable because it has excellent transmittance for light in a specific wavelength region (particularly, a wavelength region near 850 nm).
- norbornene-based resin containing the norbornene repeating unit as described above examples include hexyl norbornene homopolymer, phenylethyl norbornene homopolymer, benzyl norbornene homopolymer, hexyl norbornene and phenylethyl norbornene copolymer, hexyl norbornene. And a copolymer of benzylnorbornene and the like.
- R 1 represents an alkyl group having 1 to 10 carbon atoms
- a represents an integer of 0 to 3
- b represents an integer of 1 to 3
- p 1 / q 1 is 20 or less.
- the norbornene-based resin of the formula (1) can be produced as follows. (1) is obtained by dissolving norbornene having R 1 and norbornene having an epoxy group in the side chain in toluene and solution polymerization using Ni compound (A) as a catalyst.
- the manufacturing method of norbornene which has an epoxy group in a side chain is as (i) (ii), for example.
- R 1 is an alkyl group having 4 to 10 carbon atoms
- R 2 represents an alkyl group having 1 to 10 carbon atoms
- R 3 represents a hydrogen atom or a methyl group
- c represents an integer of 0 to 3
- the norbornene-based resin of the formula (2) is obtained by dissolving norbornene having R 2 and norbornene having acryl and methacryl groups in the side chain in toluene, and performing solution polymerization using the above-described Ni compound (A) as a catalyst. Obtainable.
- R 2 is an alkyl group having 4 to 10 carbon atoms and c is 1 from the viewpoint of achieving both flexibility and heat resistance.
- Compounds such as copolymers of butylbornene and 2- (5-norbornenyl) methyl acrylate, copolymers of hexylnorbornene and 2- (5-norbornenyl) methyl acrylate, decylnorbornene and 2- (5-norbornenyl) methyl acrylate And a copolymer thereof are preferred.
- R 4 represents an alkyl group having 1 to 10 carbon atoms
- each X 3 independently represents an alkyl group having 1 to 3 carbon atoms
- d represents 0 to 3 carbon atoms. Represents an integer, and p 3 / q 3 is 20 or less.
- the resin of the formula (3) can be obtained by dissolving norbornene having R 4 and norbornene having an alkoxysilyl group in the side chain in toluene, and solution polymerization using the above-described Ni compound (A) as a catalyst. it can.
- norbornene-based polymers represented by the formula (3) in particular, a compound in which R 4 is an alkyl group having 4 to 10 carbon atoms, d is 1 or 2, and X 3 is a methyl group or an ethyl group,
- R 5 represents an alkyl group having 1 to 10 carbon atoms
- a 1 and A 2 each independently represent a substituent represented by the following formulas (5) to (7). (However, they are not the same substituent at the same time, and p 4 / q 4 + r is 20 or less.)
- the resin of the formula (4) can be obtained by dissolving norbornene having R 5 and norbornene having A 1 and A 2 in the side chain in toluene, and solution polymerization using Ni compound (A) as a catalyst. it can.
- R 6 represents a hydrogen atom or a methyl group, and g represents an integer of 0 to 3.
- X 4 each independently represents an alkyl group having 1 to 3 carbon atoms, and h represents an integer of 0 to 3)
- norbornene-based resin represented by the formula (4) for example, any one of butyl norbornene, hexyl norbornene or decyl norbornene, 2- (5-norbornenyl) methyl acrylate, norbornenyl ethyl trimethoxysilane, Terpolymer with either triethoxysilyl norbornene or trimethoxysilyl norbornene, butyl bornene, hexyl norbornene or decyl norbornene, terpolymer of 2- (5-norbornenyl) methyl acrylate and methyl glycidyl ether norbornene, butylbornene, Either hexyl norbornene or decyl norbornene and methyl glycidyl ether norbornene, norbornenyl ethyltrimethoxysilane, triethoxysilylno Terpolymers, etc. with either
- R 7 represents an alkyl group having 1 to 10 carbon atoms
- R 8 represents a hydrogen atom, a methyl group or an ethyl group
- Ar represents an aryl group
- X 1 represents oxygen Represents an atom or a methylene group
- X 2 represents a carbon atom or a silicon atom
- i represents an integer of 0 to 3
- j represents an integer of 1 to 3
- p 5 / q 5 is 20 or less is there.
- the resin of the formula (8) is obtained by dissolving norbornene having R 7 and norbornene containing — (CH 2 ) —X 1 —X 2 (R 8 ) 3-j (Ar) j in the side chain in toluene, It can be obtained by solution polymerization using a compound as a catalyst.
- norbornene resins represented by the formula (8) those in which X 1 is an oxygen atom, X 2 is a silicon atom, and Ar is a phenyl group are preferable.
- R 7 is an alkyl group having 4 to 10 carbon atoms
- X 1 is an oxygen atom
- X 2 is a silicon atom
- Ar is a phenyl group
- R 7 is an alkyl group having 4 to 10 carbon atoms
- X 1 is a methylene group
- X 2 is a carbon atom
- Ar is Compounds in which R 8 is a hydrogen atom, i is 0, and j is 1, for example, a copolymer of butylbornene and phenylethylnorbornene, a copolymer of hexylnorbornene and phenylethylnorbornene, a copolymer of decylnorbornene and phenylethylnorbornene Etc. Further, the following may be used as the norbornene resin.
- R 10 represents an alkyl group having 1 to 10 carbon atoms
- R 11 represents an aryl group
- k is 0 or more and 4 or less.
- P 6 / q 6 is 20 or less. is there.
- p 1 / q 1 to p 3 / q 3 , p 5 / q 5 , p 6 / q 6 or p 4 / q 4 + r may be 20 or less, preferably 15 or less, About 0.1 to 10 is more preferable. Thereby, the effect including the repeating unit of multiple types of norbornene is exhibited.
- the polymer 915 may be an acrylic resin, a methacrylic resin, an epoxy resin, a polyimide, a silicone resin, a fluorine resin, or the like.
- acrylic resins and methacrylic resins include poly (methyl acrylate), poly (methyl methacrylate), poly (epoxy acrylate), poly (epoxy methacrylate), poly (amino acrylate), and poly (amino methacrylate).
- epoxy resin examples include alicyclic epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, biphenyl type epoxy resin having a biphenyl skeleton, naphthalene ring-containing epoxy resin, Dicyclopentadiene type epoxy resin having cyclopentadiene skeleton, phenol novolac type epoxy resin, cresol novolac type epoxy resin, triphenylmethane type epoxy resin, triphenylmethane type epoxy resin, aliphatic epoxy resin and triglycidyl isocyanurate, etc. Of these, one or more of these composite materials are used.
- the polyimide is not particularly limited as long as it is a resin obtained by ring-closing and curing (imidizing) a polyamic acid which is a polyimide resin precursor.
- the polyamic acid can be obtained, for example, as a solution by reacting tetracarboxylic dianhydride and diamine in an equimolar ratio in N, N-dimethylacetamide.
- examples of the tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and 2,2-bis (2,3-di ().
- examples of the diamine include m-phenylenediamine, p-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, and 3,3'-diaminodiphenyl.
- examples of the silicone resin include silicone rubber and silicone elastomer. These silicone resins are obtained by reacting a silicone rubber monomer or oligomer with a curing agent.
- silicone rubber monomer or oligomer examples include those containing a methylsiloxane group, an ethylsiloxane group, or a phenylsiloxane group.
- silicone rubber monomer or oligomer for example, those obtained by introducing a functional group such as an epoxy group, a vinyl ether group, or an acrylic group are preferably used in order to impart photoreactivity.
- the fluorine-based resin for example, a polymer obtained from a monomer having a fluorine-containing aliphatic ring structure, a polymer obtained by cyclopolymerizing a fluorine-containing monomer having two or more polymerizable unsaturated bonds, Examples thereof include a polymer obtained by copolymerizing a fluorine-containing monomer and a radical polymerizable monomer.
- fluorine-containing aliphatic ring structure examples include perfluoro (2,2-dimethyl-1,3-dioxole), perfluoro (4-methyl-1,3-dioxole), and perfluoro (4-methoxy-1,3-dioxole). ) And the like.
- fluorine-containing monomer examples include perfluoro (allyl vinyl ether), perfluoro (butenyl vinyl ether) and the like.
- radical polymerizable monomer examples include tetrafluoroethylene, chlorotrifluoroethylene, perfluoro (methyl vinyl ether) and the like.
- the refractive index of each part of the core layer 13 is determined according to the relative magnitude relationship between the refractive index of the polymer 915 and the refractive index of the monomer in each part and the existence ratio thereof, the polymer depends on the type of monomer used.
- the refractive index of 915 may be adjusted as appropriate.
- a monomer having an aromatic ring (aromatic group), a nitrogen atom, a bromine atom or a chlorine atom in the molecular structure is generally selected, A polymer 915 is synthesized (polymerized).
- a monomer having an alkyl group, a fluorine atom or an ether structure (ether group) is generally selected in the molecular structure, and the polymer 915 is synthesized ( Polymerization).
- norbornene-based resin having a relatively high refractive index those containing a repeating unit of aralkyl norbornene are preferable.
- Such norbornene-based resins have a particularly high refractive index.
- Examples of the aralkyl group (arylalkyl group) of the aralkylnorbornene repeating unit include benzyl group, phenylethyl group, phenylpropyl group, phenylbutyl group, naphthylethyl group, naphthylpropyl group, fluorenylethyl group, fluorene group, and the like. Examples thereof include a nylpropyl group, and a benzyl group and a phenylethyl group are particularly preferable.
- a norbornene-based resin having such a repeating unit is preferable because it has a very high refractive index.
- the polymer 915 as described above has a leaving group (leaving pendant group) that is branched from the main chain and at least a part of the molecular structure of which can be released from the main chain by irradiation with actinic radiation. Is preferred. Since the refractive index of the polymer 915 decreases due to the removal of the leaving group, the polymer 915 can form a refractive index difference depending on the presence or absence of irradiation with actinic radiation.
- Examples of the polymer 915 having such a leaving group include a polymer having at least one of an —O— structure, an —Si—aryl structure, and an —O—Si— structure in a molecular structure. Such a leaving group is released relatively easily by the action of a cation.
- the leaving group that causes a decrease in the refractive index of the resin by leaving at least one of the —Si-diphenyl structure and the —O—Si-diphenyl structure is preferable.
- examples of the polymer 915 having a leaving group in the side chain include polymers of monocyclic monomers such as cyclohexene and cyclooctene, norbornene, norbornadiene, dicyclopentadiene, dihydrodicyclopentadiene, tetracyclododecene,
- examples thereof include cyclic olefin resins such as polymers of polycyclic monomers such as cyclopentadiene, dihydrotricyclopentadiene, tetracyclopentadiene, dihydrotetracyclopentadiene and the like.
- one or more cyclic olefin resins selected from polymers of polycyclic monomers are preferably used. Thereby, the heat resistance of resin can be improved.
- polymerization forms known forms such as random polymerization and block polymerization can be applied.
- specific examples of the polymerization of norbornene monomers include (co) polymers of norbornene monomers, copolymers of norbornene monomers and other copolymerizable monomers such as ⁇ -olefins, A combined hydrogenated product corresponds to a specific example.
- These cyclic olefin resins can be produced by a known polymerization method.
- the polymerization methods include an addition polymerization method and a ring-opening polymerization method, and among them, the cyclic olefin resin obtained by the addition polymerization method.
- norbornene-based resins are preferable (that is, addition polymers of norbornene-based compounds). Thereby, it is excellent in transparency, heat resistance, and flexibility.
- X 1 is an oxygen atom
- X 2 is a silicon atom
- Ar is a phenyl group.
- the side chain may have an epoxy group.
- the compound represented by the formula (31) includes, for example, hexyl norbornene, diphenylmethyl norbornene methoxysilane (norbornene containing —CH 2 —O—Si (CH 3 ) (Ph) 2 in the side chain) and epoxy norbornene in toluene. It can be obtained by dissolving and solution polymerization using a Ni compound as a catalyst.
- examples of another leaving group include a substituent having an acetophenone structure at the terminal. This leaving group is released relatively easily by the action of free radicals.
- the content of the leaving group is not particularly limited, but is preferably 10 to 80% by weight in the polymer 915 having a leaving group in the side chain, and more preferably 20 to 60% by weight. preferable. When the content is within the above range, both flexibility and refractive index modulation function (effect of changing the refractive index difference) are particularly excellent.
- the width of changing the refractive index can be expanded by increasing the content of the leaving group.
- Additive 920 contains a monomer and a polymerization initiator.
- the monomer reacts in the irradiation region of the actinic radiation to form a reactant by irradiation with actinic radiation described later, and the monomer diffuses and moves with it, so that the layer 910 is refracted between the irradiation region and the non-irradiation region. It is a compound that can cause a rate difference.
- a polymer (polymer) formed by polymerizing the monomer in the polymer 915 As a reaction product of the monomer, a polymer (polymer) formed by polymerizing the monomer in the polymer 915, a cross-linked structure in which the monomer cross-links the polymers 915, and a polymer 915 obtained by polymerizing the monomer to the polymer 915. At least one of the branched structures branched from.
- the difference in refractive index generated between the irradiated region and the non-irradiated region is generated based on the difference between the refractive index of the polymer 915 and the refractive index of the monomer. Therefore, the monomer contained in the additive 920 is the polymer 915. Is selected in consideration of the magnitude relationship with the refractive index.
- a polymer 915 having a relatively low refractive index and a monomer having a high refractive index with respect to the polymer 915 are included. Used in combination.
- a polymer 915 having a relatively high refractive index and a monomer having a low refractive index with respect to the polymer 915 are used in combination.
- those having compatibility with the polymer 915 and having a refractive index difference with the polymer 915 of 0.01 or more are preferably used.
- Such a monomer is not particularly limited as long as it is a compound having a polymerizable site, and examples thereof include norbornene monomers, acrylic acid (methacrylic acid) monomers, epoxy monomers, oxetane monomers, and vinyl ether monomers. , A styrene monomer, etc., and one or more of these can be used in combination.
- a monomer or oligomer having a cyclic ether group such as an oxetanyl group or an epoxy group, or a norbornene monomer as the monomer.
- a monomer or oligomer having a cyclic ether group the cyclic ether group is likely to be opened, so that a monomer capable of reacting quickly can be obtained.
- the core layer 13 (optical waveguide 1) having excellent optical transmission performance and excellent heat resistance and flexibility can be obtained.
- the molecular weight (weight average molecular weight) of the monomer having a cyclic ether group or the molecular weight (weight average molecular weight) of the oligomer is preferably 100 or more and 400 or less, respectively.
- the monomer having an oxetanyl group and the oligomer having an oxetanyl group those selected from the group of the following formulas (11) to (20) are preferable.
- these there is an advantage that transparency in the vicinity of a wavelength of 850 nm is excellent and both flexibility and heat resistance are possible. These may be used alone or in combination.
- n is 0 or more and 3 or less.
- compounds represented by the following formulas (32) and (33) can be used as the compound having an oxetanyl group.
- the compound represented by the formula (32) trade name TOSOX manufactured by Toagosei Co., Ltd.
- trade name OX-SQ manufactured by Toagosei Co., Ltd. trade name OX-SQ manufactured by Toagosei Co., Ltd.
- n 1 or 2
- examples of the monomer having an epoxy group and the oligomer having an epoxy group include the following.
- the monomer and oligomer having an epoxy group are polymerized by ring-opening in the presence of an acid.
- the monomer having an epoxy group and the oligomer having an epoxy group those represented by the following formulas (34) to (39) can be used.
- the compound represented by the formula (34) is epoxy norbornene, and as such a compound, for example, EpNB manufactured by Promeras Corporation can be used.
- the compound represented by the formula (35) is ⁇ -glycidoxypropyltrimethoxysilane, and as this compound, for example, Z-6040 manufactured by Toray Dow Corning Silicone can be used.
- the compound represented by the formula (36) is 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane. As this compound, for example, E0327 manufactured by Tokyo Chemical Industry can be used.
- the compound represented by the formula (37) is 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexenecarboxylate, and for example, Celoxide 2021P manufactured by Daicel Chemical Industries, Ltd. is used. can do.
- the compound represented by the formula (38) is 1,2-epoxy-4-vinylcyclohexane, and as this compound, for example, Celoxide 2000 manufactured by Daicel Chemical Industries, Ltd. can be used.
- the compound represented by the formula (39) is 1,2: 8,9 diepoxy limonene.
- this compound for example, (Celoxide 3000 manufactured by Daicel Chemical Industries, Ltd.) can be used.
- a monomer having an oxetanyl group, an oligomer having an oxetanyl group, a monomer having an epoxy group, and an oligomer having an epoxy group may be used in combination.
- the monomer having an oxetanyl group and the oligomer having an oxetanyl group have a slow initiation reaction for initiating polymerization but a fast growth reaction.
- a monomer having an epoxy group and an oligomer having an epoxy group have a fast initiation reaction for initiating polymerization, but have a slow growth reaction. Therefore, by using a monomer having an oxetanyl group, an oligomer having an oxetanyl group, a monomer having an epoxy group, and an oligomer having an epoxy group, when irradiated with light, the light irradiated portion and the unirradiated portion A difference in refractive index can be reliably generated.
- the monomer represented by the formula (20) is “first monomer” and the monomer containing the component B is “second monomer”, it is preferable to use the first monomer and the second monomer in combination.
- the ratio of the combined use is defined by (weight of second monomer) / (weight of first monomer), it is preferably about 0.1 to 1, more preferably about 0.1 to 0.6. preferable.
- the combined ratio is within the above range, the balance between the reactivity of the monomer and the heat resistance of the optical waveguide 1 is improved.
- the monomer corresponding to the second monomer includes a monomer having an oxetanyl group different from the monomer represented by the formula (20) and a monomer having a vinyl ether group.
- a monomer having an oxetanyl group different from the monomer represented by the formula (20) at least one of an epoxy compound (particularly an alicyclic epoxy compound) and a bifunctional oxetane compound (a monomer having two oxetanyl groups) is preferably used.
- the second monomer include the compound of the above formula (15), the compound of the above formula (12), the compound of the above formula (11), the compound of the above formula (18), and the above formula (19). And compounds of the above formulas (34) to (39).
- norbornene-based monomer is a generic term for monomers containing at least one norbornene skeleton represented by the following structural formula A, and examples thereof include compounds represented by the following structural formula C.
- R 12 to R 15 each independently represents a hydrogen atom, a substituted or unsubstituted hydrocarbon group, or a functional substituent, An integer of 0 to 5 is represented. However, when a is a double bond, either one of R 12 and R 13 or one of R 14 and R 15 does not exist. ]
- Examples of the unsubstituted hydrocarbon group include, for example, a linear or branched alkyl group having 1 to 10 carbon atoms (C 1 to C 10 ), a linear or branched carbon number of 2 -10 (C 2 -C 10 alkenyl group, linear or branched alkynyl group having 2 to 10 carbon atoms (C 2 -C 10 ), cycloalkyl having 4 to 12 carbon atoms (C 4 -C 12 ) Group, a cycloalkenyl group having 4 to 12 carbon atoms (C 4 to C 12 ), an aryl group having 6 to 12 carbon atoms (C 6 to C 12 ), and an aralkyl group having 7 to 24 carbon atoms (C 7 to C 24 )
- R 12 and R 13 , R 14 and R 15 may each be an alkylidenyl group having 1 to 10 carbon atoms (C 1 to C 10 ).
- acrylic acid (methacrylic acid) monomers include acrylic acid, methacrylic acid, acrylic acid ester, methacrylic acid ester, acrylic acid amide, methacrylic acid amide, acrylonitrile, and the like. These can be used alone or in combination of two or more.
- vinyl ether monomers include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, n-pentyl vinyl ether, n-hexyl vinyl ether, n-octyl.
- alkyl vinyl ethers or cycloalkyl vinyl ethers such as vinyl ether, n-dodecyl vinyl ether, 2-ethylhexyl vinyl ether, and cyclohexyl vinyl ether, and one or more of these can be used in combination.
- examples of the styrene monomer include styrene and divinylbenzene, and one or two of these can be used in combination.
- the monomer may be oligomerized as described above.
- the addition amount of these monomers is preferably 1 part by weight or more and 50 parts by weight or less, and more preferably 2 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the polymer.
- the polymerization initiator acts on the monomer with irradiation of actinic radiation to promote the reaction of the monomer, and is added as necessary in consideration of the reactivity of the monomer.
- the polymerization initiator to be used is appropriately selected according to the type of monomer polymerization reaction or crosslinking reaction.
- radical polymerization initiators are preferably used exclusively for acrylic acid (methacrylic acid) monomers and styrene monomers
- cationic polymerization initiators are preferably used exclusively for epoxy monomers, oxetane monomers, and vinyl ether monomers.
- radical polymerization initiators examples include benzophenones and acetophenones.
- examples of the cationic polymerization initiator include Lewis acid generating type such as diazonium salt, Bronsted acid generating type such as iodonium salt and sulfonium salt.
- the following cationic polymerization initiator photoacid generator
- photoacid generator photoacid generator
- sulfonium salts such as triphenylsulfonium trifluoromethanesulfonate, tris (4-t-butylphenyl) sulfonium-trifluoromethanesulfonate, diazonium salts such as p-nitrophenyldiazonium hexafluorophosphate, ammonium salts, phosphonium salts, diphenyliodonium Iodonium salts such as trifluoromethanesulfonate, (triccumyl) iodonium-tetrakis (pentafluorophenyl) borate, quinonediazides, diazomethanes such as bis (phenylsulfonyl) diazomethane, 1-phenyl-1- (4-methylphenyl) sulfonyloxy- Sulfos such as 1-benzoylmethane, N-hydroxynaphthalimide-trifluoromethanes, di
- the content of the polymerization initiator is preferably 0.01 parts by weight or more and 0.3 parts by weight or less, more preferably 0.02 parts by weight or more and 0.2 parts by weight or less with respect to 100 parts by weight of the polymer. . Thereby, there exists an effect of a reactive improvement.
- the sensitizer increases the sensitivity of the polymerization initiator to light and is suitable for the function of reducing the time and energy required for the activation (reaction or decomposition) of the polymerization initiator and for the activation of the polymerization initiator. It has a function of changing the wavelength of light to a wavelength.
- Such a sensitizer is appropriately selected according to the sensitivity of the polymerization initiator and the peak wavelength of absorption of the sensitizer, and is not particularly limited.
- 9,10-dibutoxyanthracene (CAS No. 76275) is selected. 14-4)), anthracenes, xanthones, anthraquinones, phenanthrenes, chrysenes, benzpyrenes, fluoranthenes, rubrenes, pyrenes, indanthrines, thioxanthen-9-ones (Thioxanthen-9-ones) and the like, and these can be used alone or as a mixture.
- sensitizer examples include, for example, 2-isopropyl-9H-thioxanthen-9-one, 4-isopropyl-9H-thioxanthen-9-one, 1-chloro-4-propoxythioxanthone, and phenothiazine. Or a mixture thereof.
- the content of the sensitizer in the core layer forming composition 900 is preferably 0.01% by weight or more, more preferably 0.5% by weight or more, and 1% by weight or more. Is more preferable. In addition, it is preferable that an upper limit is 5 weight% or less.
- the additive 920 includes a catalyst precursor, a co-catalyst, an antioxidant, an ultraviolet absorber, a light stabilizer, a silane coupling agent, a coating surface improver, a thermal polymerization inhibitor, a leveling agent, and a surfactant. , Colorants, storage stabilizers, plasticizers, lubricants, fillers, inorganic particles, anti-aging agents, wettability improvers, antistatic agents, and the like.
- the layer 910 containing the polymer 915 and the additive 920 as described above has a predetermined refractive index due to the action of the additive 920 dispersed uniformly in the polymer 915.
- a mask (masking) 935 in which an opening (window) 9351 is formed is prepared, and the layer 910 is irradiated with active radiation 930 through the mask 935 (see FIG. 7).
- the irradiation region 925 of the active radiation 930 is mainly the side cladding portion 15.
- an opening (window) 9351 equivalent to the pattern of the side cladding portion 15 to be formed is mainly formed in the mask 935.
- This opening 9351 forms a transmission part through which the active radiation 930 to be irradiated passes.
- the pattern of the core part 14 and the side clad part 15 is determined based on the refractive index distribution W formed according to irradiation of the active radiation 930, the pattern of the opening 9351 and the pattern of the side clad part 15 are completely There is a case in which there is a slight deviation between the two patterns.
- the mask 935 may be formed in advance (separately formed) (for example, plate-shaped) or may be formed on the layer 910 by, for example, a vapor deposition method or a coating method.
- Preferred examples of the mask 935 include a photomask made of quartz glass or a PET base material, a stencil mask, a metal thin film formed by a vapor deposition method (evaporation, sputtering, etc.), etc.
- a photomask or a stencil mask it is particularly preferable to use a photomask or a stencil mask. This is because a fine pattern can be formed with high accuracy, and handling is easy, which is advantageous in improving productivity.
- the opening (window) 9351 of the mask 935 is shown by partially removing the mask along the pattern of the irradiation region 925 of the active radiation 930.
- the quartz glass, the PET base material, etc. it is also possible to use a photomask provided with a shielding portion of active radiation 930 made of a shielding material made of metal such as chromium.
- the part other than the shielding part is the window (transmission part).
- the actinic radiation 930 to be used is not particularly limited as long as it can cause a photochemical reaction (change) with respect to the polymerization initiator and can release the leaving group contained in the polymer 915.
- visible light In addition to ultraviolet light, infrared light, and laser light, electron beams, X-rays, and the like can also be used.
- the actinic radiation 930 is appropriately selected depending on the kind of the sensitizer when it contains a polymerization initiator, a leaving group, and a sensitizer, and is not particularly limited, but has a wavelength of 200 to 450 nm. It is preferable to have a peak wavelength in the range. As a result, the polymerization initiator can be activated relatively easily and the leaving group can be removed relatively easily.
- the dose of the active radiation 930 is preferably about 0.1 to 9 J / cm 2 , more preferably about 0.2 to 6 J / cm 2, and about 0.2 to 3 J / cm 2. More preferably.
- the polymerization initiator When the layer 910 is irradiated with the active radiation 930 through the mask 935, the polymerization initiator is activated in the irradiated region 925. Thereby, the monomer is polymerized in the irradiation region 925. When the monomer is polymerized, the amount of monomer in the irradiated region 925 decreases, and accordingly, the monomer in the unirradiated region 940 diffuses and moves to the irradiated region 925.
- the polymer 915 and the monomer are appropriately selected so that a difference in refractive index is generated between them, a refractive index difference is generated between the irradiated region 925 and the non-irradiated region 940 as the monomer diffuses and moves.
- FIG. 11 is a diagram for explaining a state in which a difference in refractive index occurs between the irradiated region 925 and the non-irradiated region 940.
- the horizontal axis indicates the position of the cross section of the layer 910, and the refractive index of the horizontal section indicates the vertical index. It is a figure which shows refractive index distribution when it takes on an axis
- the refractive index of the unirradiated region 940 becomes higher and the refractive index of the irradiated region 925 becomes lower as the monomer diffuses and moves ( (See FIG. 11 (a)).
- the diffusion movement of the monomer occurs due to the consumption of the monomer in the irradiation region 925 and the concentration gradient of the monomer formed accordingly. For this reason, the monomers in the entire unirradiated region 940 do not move toward the irradiated region 925 all at once, but gradually move from a portion close to the irradiated region 925 and outward from the center of the unirradiated region 940 to compensate for this. Monomer migration also occurs. As a result, as shown in FIG.
- the high refractive index portion H on the non-irradiated region 940 side and the low refractive index portion L on the irradiated region 925 side across the boundary between the irradiated region 925 and the non-irradiated region 940. Is formed. Since the high refractive index portion H and the low refractive index portion L are formed in accordance with the diffusion movement of the monomer as described above, they are necessarily constituted by smooth curves. Specifically, the high refractive index portion H has, for example, a substantially U shape that is convex upward, and the low refractive index portion L has, for example, a substantially U shape that is convex downward.
- the refractive index of the polymer obtained by polymerizing the monomers as described above is almost the same as the refractive index of the monomer before polymerization (the difference in refractive index is about 0 to 0.001). As the polymerization proceeds, the refractive index decreases according to the amount of the monomer and the amount of the substance derived from the monomer. Therefore, the shape of the refractive index distribution W can be controlled by appropriately adjusting the amount of monomer with respect to the polymer.
- the monomer is not polymerized because the polymerization initiator is not activated.
- the ease of monomer diffusion transfer gradually decreases as the polymerization of the monomer proceeds.
- the distribution shape of the low refractive index portion L formed in the irradiated region 925 is likely to be asymmetrical left and right, and the gradient on the non-irradiated region 940 side becomes steeper. Thereby, the refractive index distribution W which the optical waveguide of this invention has is formed.
- the polymer 915 preferably has a leaving group as described above. This leaving group is released upon irradiation with actinic radiation 930 and decreases the refractive index of the polymer 915. Therefore, when the irradiation region 925 is irradiated with the actinic radiation 930, the above-described diffusion movement of the monomer is started, the leaving group is released from the polymer 915, and the refractive index of the irradiation region 925 decreases from before the irradiation. (See FIG. 11B).
- This decrease in the refractive index occurs uniformly in the entire irradiation region 925, so that the refractive index difference between the high refractive index portion H and the low refractive index portion L described above is further enlarged. As a result, a refractive index distribution W shown in FIG. 11B is obtained. Note that the change in refractive index in FIG. 11A and the change in refractive index in FIG. 11B occur almost simultaneously. Such a refractive index change further expands the refractive index difference.
- the refractive index of the core layer after energy irradiation is adjusted by appropriately adjusting the components of the core layer before energy irradiation, the irradiation amount of energy irradiation, or the degree of drying of the core layer before energy irradiation.
- the shape of the distribution can be controlled.
- the refractive index difference and the shape of the refractive index distribution to be formed can be controlled by adjusting the dose of the active radiation 930. For example, the refractive index difference can be enlarged by increasing the irradiation amount.
- the shape of the refractive index distribution can be controlled by adjusting the content and irradiation amount of the photoacid generator.
- the layer 910 may be dried before the irradiation with the active radiation 930, but the shape of the refractive index distribution can be controlled by adjusting the degree of drying at that time. For example, by increasing the degree of drying, the diffusion transfer amount of the monomer can be suppressed. Also, by increasing the drying temperature, the amount of diffusion can be increased and the refractive index distribution can be controlled.
- the layer 910 is subjected to heat treatment.
- the monomer in the irradiation region 925 irradiated with light is further polymerized.
- the monomer in the unirradiated region 940 is volatilized. Thereby, in the unirradiated region 940, the monomer is further reduced, the refractive index is increased, and the refractive index is close to that of the polymer 915.
- the heating temperature in this heat treatment is not particularly limited, but is preferably about 30 to 180 ° C, more preferably about 40 to 160 ° C.
- the heating time is preferably set so that the polymerization reaction of the monomer in the irradiation region 925 is almost completed.
- the heating time is preferably about 0.1 to 2 hours, preferably 0.1 to 1 hour. More preferred is the degree.
- the refractive index distribution W there are minimum values Ws1, Ws2, Ws3, and Ws4 converted from the low refractive index portion L (see FIG. 2B), and the positions of these minimum values are the core portion 14 and the side surface. This corresponds to the boundary with the clad portion 15.
- the refractive index distribution W has a certain correlation with the monomer-derived structure concentration in the core layer 13. Therefore, it is possible to indirectly specify the refractive index distribution W of the optical waveguide 1 by measuring the concentration of the monomer-derived structure.
- the concentration of the structure can be measured using, for example, FT-IR or TOF-SIMS line analysis, surface analysis, or the like.
- the refractive index distribution W can be indirectly specified even if the intensity distribution of the emitted light from the optical waveguide 1 has a certain correlation with the refractive index distribution W.
- the refractive index distribution W can be directly specified by a refraction near field method, a differential interference method, or the like.
- the refractive index of the movement destination increases with the diffusion movement of the monomer.
- the irradiation area 940 may be set.
- the use of the mask 935 may be omitted.
- the clad layers 11 and 12 are laminated on both surfaces of the core layer 13. Thereby, the optical waveguide 1 is obtained.
- the clad layer 11 (12) is formed on the support substrate 952 (see FIG. 9).
- a varnish (cladding layer forming composition) containing a clad material is applied and cured (solidified), and a curable monomer composition is applied and cured (solidified). Any method may be used.
- the core layer 13 is peeled from the support substrate 951, and the core layer 13 is sandwiched between the support substrate 952 on which the clad layer 11 is formed and the support substrate 952 on which the clad layer 12 is formed (FIG. 10A). )reference).
- the clad layers 11 and 12 and the core layer 13 are joined and integrated (see FIG. 10B).
- the support substrate 952 is peeled off and removed from the cladding layers 11 and 12, respectively. Thereby, the optical waveguide 1 is obtained.
- a support film 2 is laminated on the lower surface of the optical waveguide 1 and a cover film 3 is laminated on the upper surface.
- the core layer 13 may be formed not on the support substrate 951 but on the cladding layer 11. Further, the clad layer 12 may be formed by applying a material on the core layer 13 instead of being laminated on the core layer 13.
- the second manufacturing method is the same as the first manufacturing method except that the composition of the core layer forming composition 900 is different.
- the second method of manufacturing the optical waveguide 1 is as follows: [1] After applying the core layer forming composition 900 on the support substrate 951 to form a liquid film, the support substrate 951 is placed on a level table to form the liquid film. While flattening, the solvent is evaporated (desolvent). Thereby, the layer 910 is obtained. [2] Next, after irradiating a part of the layer 910 with actinic radiation, the layer 910 is subjected to a heat treatment to cause a refractive index difference, and the core layer 13 having the core portion 14 and the side cladding portion 15 is formed. obtain. [3] Next, the cladding layers 11 and 12 are laminated on both surfaces of the core layer 13 to obtain the optical waveguide 1.
- a core layer forming composition 900 is prepared.
- the core layer forming composition 900 used in the second production method contains a catalyst precursor and a cocatalyst instead of the polymerization initiator.
- the catalyst precursor is a substance capable of initiating a monomer reaction (polymerization reaction, crosslinking reaction, etc.), and is a substance whose activation temperature changes due to the action of a promoter activated by light irradiation. Due to this change in the activation temperature, a difference occurs in the temperature at which the monomer reaction starts between the light irradiation region 925 and the non-irradiation region 940, and as a result, the monomer can be reacted only in the irradiation region 925. .
- any compound may be used as long as the activation temperature changes (increases or decreases) with irradiation of actinic radiation, and in particular, irradiation with actinic radiation. Along with this, the activation temperature decreases.
- the core layer 13 optical waveguide 1 can be formed by heat treatment at a relatively low temperature, and unnecessary heat is applied to the other layers, so that the characteristics (optical transmission performance) of the optical waveguide 1 are deteriorated. Can be prevented.
- a catalyst precursor containing (mainly) at least one of the compounds represented by the following formulas (Ia) and (Ib) is preferably used.
- E (R) 3 represents a neutral electron donor ligand of group 15, respectively, E represents an element selected from group 15 of the periodic table, and R represents , Represents a moiety containing a hydrogen atom (or one of its isotopes) or a hydrocarbon group, and Q represents an anionic ligand selected from carboxylate, thiocarboxylate and dithiocarboxylate.
- LB represents a Lewis base
- WCA represents a weakly coordinating anion
- a represents an integer of 1 to 3
- b represents an integer of 0 to 2
- p and r represent numbers that balance the charge of the palladium cation and the weakly coordinated anion.
- Typical catalyst precursors according to Formula Ia include Pd (OAc) 2 (P (i-Pr) 3 ) 2 , Pd (OAc) 2 (P (Cy) 3 ) 2 , Pd (O 2 CCMe 3 ) 2 (P (Cy) 3 ) 2 , Pd (OAc) 2 (P (Cp) 3 ) 2 , Pd (O 2 CCF 3 ) 2 (P (Cy) 3 ) 2 , Pd (O 2 CC 6 H 5 ) 3 (P (Cy) 3 ) 2 may be mentioned, but is not limited thereto.
- Cp represents a cyclopentyl group
- Cy represents a cyclohexyl group.
- the catalyst precursor represented by the formula Ib is preferably a compound in which p and r are selected from integers of 1 and 2, respectively.
- Typical catalyst precursors according to such formula Ib include Pd (OAc) 2 (P (Cy) 3 ) 2 .
- Cy represents a cyclohexyl group
- Ac represents an acetyl group.
- catalyst precursors can efficiently react with a monomer (in the case of a norbornene-based monomer, an efficient polymerization reaction, a crosslinking reaction, etc. by an addition polymerization reaction).
- the catalyst precursor in a state where the activation temperature is lowered (active latent state), has an activation temperature lower by about 10 to 80 ° C. (preferably about 10 to 50 ° C.) than the original activation temperature. Is preferred. Thereby, the refractive index difference between the core part 14 and the side clad part 15 can be produced reliably.
- Such a catalyst precursor includes (mainly) one containing at least one of Pd (OAc) 2 (P (i-Pr) 3 ) 2 and Pd (OAc) 2 (P (Cy) 3 ) 2. Is preferred.
- the co-catalyst is a substance that can be activated by irradiation with actinic radiation to change the activation temperature of the catalyst precursor (procatalyst) (the temperature at which the monomer reacts).
- any compound can be used as long as it has a molecular structure that changes (reacts or decomposes) when activated by irradiation with actinic radiation.
- a compound (photoinitiator) that decomposes upon irradiation with actinic radiation and generates a cation such as a proton or other cation and a weakly coordinated anion (WCA) that can be substituted with a leaving group of the catalyst precursor ( (Mainly) is preferably used.
- weakly coordinating anions examples include tetrakis (pentafluorophenyl) borate ion (FABA ⁇ ), hexafluoroantimonate ion (SbF 6 ⁇ ), and the like.
- cocatalyst examples include tetrakis (pentafluorophenyl) gallium in addition to tetrakis (pentafluorophenyl) borate and hexafluoroantimonate represented by the following formula: Acid salts, aluminates, antimonates, other borates, gallates, carboranes, halocarboranes and the like.
- PHOTOINITIATOR 2074 (CAS No. 178233-72-2) available from Rhodia USA, Cranberry, New Jersey.
- TAG-372R ((dimethyl (2- (2-naphthyl) -2-oxoethyl) sulfonium tetrakis (pentafluorophenyl) borate: CAS No. 193957) available from Toyo Ink Manufacturing Co., Ltd., Tokyo, Japan” -54-9)
- MPI-103 CAS No.
- UV light ultraviolet rays
- actinic radiation actinic radiation
- mercury lamp high pressure mercury lamp
- the layer 910 is irradiated with the active radiation 930 through the mask 935.
- the co-catalyst reacts (bonds) or decomposes by the action of the active radiation 930 to release (generate) cations (protons or other cations) and weakly coordinated anions (WCA).
- the catalyst precursor in the active latent state (or the latent active state) has an activation temperature lower than the original activation temperature, but there is no temperature increase, that is, at about room temperature, the irradiation region.
- the optical waveguide 1 (for example, the core layer 13) can be obtained by preparing a plurality of layers 910 after the irradiation with the active radiation 930 and subjecting them to a heat treatment to be described later. Is expensive.
- the leaving group is detached from the polymer 915 as in the first production method. This creates a refractive index difference between the irradiated region 925 and the unirradiated region 940 of the layer 910.
- the layer 910 is subjected to heat treatment (first heat treatment).
- first heat treatment first heat treatment
- the catalyst precursor in the active latent state is activated (becomes active), and monomer reaction (polymerization reaction or cross-linking reaction) occurs.
- the monomer concentration in the irradiation region 925 gradually decreases.
- a difference in monomer concentration occurs between the irradiated region 925 and the unirradiated region 940, and the monomer diffuses from the unirradiated region 940 and collects in the irradiated region 925 in order to eliminate this.
- a refractive index profile similar to that in the first manufacturing method is formed in the layer 910.
- the heating temperature in this heat treatment is not particularly limited, but is preferably about 30 to 80 ° C., more preferably about 40 to 60 ° C.
- the heating time is preferably set so that the reaction of the monomer in the irradiation region 925 is almost completed.
- the heating time is preferably about 0.1 to 2 hours, preferably 0.1 to 1 hour. More preferred is the degree.
- second heat treatment is performed on the layer 910.
- the catalyst precursor remaining in the unirradiated region 940 and / or the irradiated region 925 is activated (activated) directly or with activation of the cocatalyst, thereby causing the regions 925 and 940 to be activated.
- the remaining monomer is reacted.
- the heating temperature in the second heat treatment is not particularly limited as long as it can activate the catalyst precursor or the cocatalyst, but is preferably about 70 to 100 ° C., and is preferably about 80 to 90 ° C. Is more preferable.
- the heating time is preferably about 0.5 to 2 hours, and more preferably about 0.5 to 1 hour.
- the layer 910 is subjected to a third heat treatment. Thereby, reduction of the internal stress which arises in the core layer 13 obtained, and the further stabilization of the core part 14 and the side clad part 15 can be aimed at.
- the heating temperature in the third heat treatment is preferably set to 20 ° C. or more higher than the heating temperature in the second heat treatment, specifically, preferably about 90 to 180 ° C., and preferably 120 to 160 ° C. More preferred is the degree.
- the heating time is preferably about 0.5 to 2 hours, more preferably about 0.5 to 1 hour.
- the clad layers 11 and 12 are laminated on both surfaces of the core layer 13. Thereby, the optical waveguide 1 is obtained.
- the mirror 17 shown in FIG. 5 it digs into a part of obtained optical waveguide 1, and this forms the recessed part 170 which makes the mirror 17 an inner wall surface.
- the digging process for the optical waveguide 1 can be performed by, for example, a laser processing method, a dicing method using a dicing saw, or the like.
- the optical waveguide of the present invention as described above is excellent in optical transmission efficiency and long-term reliability. For this reason, by providing the optical waveguide of the present invention, a highly reliable electronic device (electronic device of the present invention) capable of performing high-quality optical communication between two points can be obtained.
- Examples of the electronic device including the optical waveguide of the present invention include electronic devices such as a mobile phone, a game machine, a router device, a WDM device, a personal computer, a television, and a home server. In any of these electronic devices, it is necessary to transmit a large amount of data at high speed between an arithmetic device such as an LSI and a storage device such as a RAM. Therefore, by providing such an electronic device with the optical waveguide of the present invention, problems such as noise and signal degradation peculiar to electrical wiring are eliminated, and a dramatic improvement in performance can be expected.
- the amount of heat generated in the optical waveguide portion is greatly reduced compared to electrical wiring. For this reason, the electric power required for cooling can be reduced and the power consumption of the whole electronic device can be reduced.
- the optical waveguide of the present invention has small transmission loss and pulse signal dullness, and interference does not easily occur even when the number of channels is increased and the density is increased. For this reason, an optical waveguide having high density and a small area and high reliability can be obtained. By mounting the optical waveguide, the reliability of electronic equipment can be improved and the size can be reduced.
- optical waveguide and the electronic device of the present invention have been described above.
- present invention is not limited to this, and for example, an arbitrary component may be added to the optical waveguide.
- a transmission device such as a router device or a WDM (Wavelength Division Multiplexing) device is used as a device for transmitting information to a broadband line (broadband) capable of communicating a large amount of information at high speed.
- a broadband line broadband line
- a large number of signal processing boards in which arithmetic elements such as LSIs and storage elements such as memories are combined are installed, and each line is interconnected.
- the optical waveguide of the present embodiment has excellent optical transmission characteristics such as few optical defects and reduced crosstalk. As a result, it is possible to suppress the occurrence of crosstalk, high frequency noise, deterioration of electric signals, and the like as information transmission is accelerated. Therefore, information can be transmitted with high throughput in each signal processing board. In addition, information can be transmitted with high throughput even by a super computer or a large-scale server.
- the method for producing the optical waveguide of the present invention is not limited to the above-described method.
- a method of cutting a molecular bond by irradiation with actinic radiation and changing a refractive index (photo bleach method), a core layer is formed.
- a method in which a photocrosslinkable polymer having an unsaturated bond capable of photoisomerization or photodimerization is contained in the composition to be formed, and this is irradiated with actinic radiation to change the molecular structure and change the refractive index (photoisomerization).
- photoisomerization photocrosslinkable polymer having an unsaturated bond capable of photoisomerization or photodimerization
- other methods such as photodimerization method).
- the amount of change in the refractive index can be adjusted according to the irradiation amount of the active radiation, the irradiation amount of the active radiation applied to each part of the layer according to the shape of the target refractive index distribution W is set. By making them different, a core layer having a refractive index distribution W can be formed.
- Example 1 Production of optical waveguide (Example 1) (1) Synthesis of norbornene-based resin having a leaving group In a glove box filled with dry nitrogen in which the water and oxygen concentrations are both controlled to 1 ppm or less, 7.2 g (40.1 mmol) of hexylnorbornene (HxNB) Then, 12.9 g (40.1 mmol) of diphenylmethylnorbornenemethoxysilane was weighed into a 500 mL vial, 60 g of dehydrated toluene and 11 g of ethyl acetate were added, and the top was sealed with a silicon sealer.
- HxNB hexylnorbornene
- Ni catalyst represented by the following chemical formula (A) and 10 mL of dehydrated toluene are weighed in a 100 mL vial, put a stirrer chip, tightly plugged, and thoroughly agitate the catalyst. Dissolved in.
- the molar ratio of each structural unit in polymer # 1 was 50 mol% for the hexylnorbornene structural unit and 50 mol% for the diphenylmethylnorbornenemethoxysilane structural unit, as determined by NMR.
- composition for forming core layer 10 g of the purified polymer # 1 was weighed into a 100 mL glass container, and 40 g of mesitylene, 0.01 g of antioxidant Irganox 1076 (manufactured by Ciba Geigy), cyclohexyl oxetane monomer (formula) 1st monomer shown in (20), Toagosei Co., Ltd.
- the core layer-forming composition was uniformly applied on the lower clad layer with a doctor blade, and then placed in a dryer at 55 ° C. for 10 minutes. After the solvent was completely removed, a photomask was pressed and selectively irradiated with ultraviolet rays at 1300 mJ / cm 2 . The mask was removed, and heating was performed at 150 ° C. in a dryer for 1.5 hours. It was confirmed that a very clear waveguide pattern appeared after heating. Moreover, formation of the core part and the side clad part was confirmed.
- the formed optical waveguide has eight core portions formed in parallel. The width of the core portion was 50 ⁇ m, the width of the side cladding portion was 80 ⁇ m, and the thickness of the core layer was 50 ⁇ m.
- a dry film in which Avatrel 2000P is laminated in advance on a polyethersulfone (PES) film so as to have a dry thickness of 20 ⁇ m is bonded to the above core layer, and put into a vacuum laminator set at 140 ° C. for thermocompression bonding. It was. Thereafter, 100 mJ was irradiated on the entire surface and heated in a dryer at 120 ° C. for 1 hour to cure Avatrel 2000P to form an upper clad layer to obtain an optical waveguide. A length of 10 cm was cut out from the obtained optical waveguide.
- PES polyethersulfone
- the refractive index distribution W of the width direction was acquired using the interference microscope along the centerline of the thickness direction.
- the refractive index distribution W has a plurality of minimum values and maximum values, were those in which the refractive index continuously changed.
- a method for measuring a refractive index distribution using an interference microscope will be described.
- the optical waveguide was sliced in the cross-sectional direction of the optical waveguide to obtain an optical waveguide fragment.
- the optical waveguide was sliced so that the length was 200 ⁇ m to 300 ⁇ m.
- a chamber filled with oil having a refractive index of 1.536 was created in a space surrounded by two glass slides.
- a measurement sample in which the optical waveguide fragment was sandwiched in the space in the chamber and a blank sample without the optical waveguide fragment were prepared.
- using an interference microscope to obtain an interference fringe photograph of the cross-sectional direction of the optical waveguide fragments.
- the interference fringe photograph was subjected to image analysis to obtain a refractive index distribution.
- the image analysis of the interference fringe photograph was performed as follows. First, change the optical path length of the interference microscope, and the image data with different locations that can fringes continuously acquired.
- the refractive index at each measurement point in the interlayer direction and the in-layer direction was calculated from a plurality of image data. In this example, the interval between measurement points was 2.5 ⁇ m.
- a refractive index distribution T in the thickness direction was obtained using an interference microscope along the center line passing through the center of the width of the core portion in the vertical direction.
- the refractive index distribution T changes at a substantially constant value in the region corresponding to the core portion, and also at a substantially constant value lower than the refractive index of the region corresponding to the core portion in the region corresponding to each cladding layer. It changed. That is, the refractive index distribution in the thickness direction of the obtained optical waveguide was a so-called step index type.
- Example 2 An optical waveguide was obtained in the same manner as in Example 1 except that the irradiation amount of ultraviolet rays was increased to 1500 mJ / cm 2 .
- Example 3 While increasing the irradiation amount of ultraviolet rays to 2000 mJ / cm 2 and changing the molar ratio of each structural unit of polymer # 1 to 40 mol% for the hexyl norbornene structural unit and 60 mol% for the diphenylmethyl norbornene methoxysilane structural unit as the polymer An optical waveguide was obtained in the same manner as in Example 1 except that was used.
- Example 4 The amount of UV irradiation was reduced to 500 mJ / cm 2 and the polymer molar ratio of each structural unit of polymer # 1 was changed to 45 mol% for hexylnorbornene structural units and 55 mol% for diphenylmethylnorbornenemethoxysilane structural units.
- An optical waveguide was obtained in the same manner as in Example 1 except that was used.
- Example 5 Except that the molar ratio of each structural unit of polymer # 1 was changed to 30 mol% for the hexylnorbornene structural unit and 70 mol% for the diphenylmethylnorbornenemethoxysilane structural unit as the polymer, the same as in Example 1. Thus, an optical waveguide was obtained.
- Example 8 In addition to reducing the amount of UV irradiation to 300 mJ / cm 2 and changing the molar ratio of each structural unit of polymer # 1 to 40 mol% for the hexylnorbornene structural unit and 60 mol% for the diphenylmethylnorbornenemethoxysilane structural unit as the polymer An optical waveguide was obtained in the same manner as in Example 1 except that was used.
- Example 9 In addition to reducing the amount of UV irradiation to 500 mJ / cm 2 , the polymer has a molar ratio of each structural unit of polymer # 1 changed to 30 mol% for hexylnorbornene structural units and 70 mol% for diphenylmethylnorbornenemethoxysilane structural units.
- An optical waveguide was obtained in the same manner as in Example 1 except that was used.
- Example 10 In addition to reducing the irradiation amount of ultraviolet rays to 100 mJ / cm 2 and changing the molar ratio of each structural unit of polymer # 1 to 60 mol% for the hexyl norbornene structural unit and 40 mol% for the diphenylmethylnorbornene methoxysilane structural unit as the polymer An optical waveguide was obtained in the same manner as in Example 1 except that was used.
- Example 11 In addition to increasing the irradiation amount of ultraviolet rays to 1500 mJ / cm 2 , as a polymer, the molar ratio of each structural unit of polymer # 1 was changed to 10 mol% for the hexyl norbornene structural unit and 90 mol% for the diphenylmethyl norbornene methoxysilane structural unit. An optical waveguide was obtained in the same manner as in Example 1 except that was used.
- Example 12 In addition to increasing the irradiation amount of ultraviolet rays to 3000 mJ / cm 2 , as a polymer, the molar ratio of each structural unit of polymer # 1 was changed to 5 mol% for the hexylnorbornene structural unit and 95 mol% for the diphenylmethylnorbornenemethoxysilane structural unit.
- An optical waveguide was obtained in the same manner as in Example 1 except that was used.
- Example 13 An optical waveguide was obtained in the same manner as in Example 1 except that the core layer forming composition was manufactured by the method shown below.
- Example 14 An optical waveguide was obtained in the same manner as in Example 1 except that the core layer forming composition was manufactured by the method shown below.
- Example 15 An optical waveguide was obtained in the same manner as in Example 1 except that the core layer forming composition was manufactured by the method shown below.
- 10 g of the purified polymer # 1 is weighed into a 100 mL glass container, 40 g of mesitylene, 0.01 g of an antioxidant Irganox 1076 (manufactured by Ciba Geigy), cyclohexyl oxetane monomer (shown by Formula 20, CHOX manufactured by Toagosei Co., Ltd.) 1 g, 1 g of alicyclic epoxy monomer (manufactured by Daicel Chemical Industries, Celoxide 2021P), photoacid generator Rhodorsil Photoinitiator 2074 (manufactured by Rhodia, CAS # 178233-72-2) (1.36E-2 g in 0.1 mL of ethyl acetate) And then uniformly dissolved, followed by filtration with a 0.2 ⁇ m PTFE filter to obtain a clean composition for forming a core layer.
- an antioxidant Irganox 1076 manufactured by Ciba Geigy
- Example 16 An optical waveguide was obtained in the same manner as in Example 1 except that the polymer synthesized by the method shown below was used.
- a polymer was synthesized in the same manner as in Example 1 except that 10.4 g (40.1 mmol) of phenyldimethylnorbornenemethoxysilane was used instead of 12.9 g (40.1 mmol) of diphenylmethylnorbornenemethoxysilane.
- the structural unit of the obtained polymer is shown in the following formula (103).
- the molar ratio of each structural unit was 50 mol% for the hexylnorbornene structural unit and 50 mol% for the phenyldimethylnorbornenemethoxysilane structural unit, as determined by NMR.
- Example 17 The core layer-forming composition was prepared by the following method, and the core layer-forming composition was uniformly applied on the lower clad layer with a doctor blade, and then a dryer at 60 ° C. An optical waveguide was obtained in the same manner as in Example 1 except that the optical waveguide was added for 10 minutes.
- Example 18 Except with reduced irradiation of the ultraviolet to 500 mJ / cm 2, thereby obtaining the optical waveguide in the same manner as in Example 15.
- a core layer forming composition in which the cyclohexyloxetane monomer was omitted from polymer # 1 was applied thereon, and then exposed and heated to obtain a core layer. Thereafter, an optical waveguide was obtained by forming an upper cladding layer.
- the refractive index of the core part was almost constant, and the refractive index of the side cladding part was also almost constant. That is, the refractive index distribution W in the width direction of the core layer of the obtained optical waveguide is a so-called step index type.
- Comparative Example 2 An optical waveguide was obtained in the same manner as in Comparative Example 1 except that exposure was performed using a photomask whose transmittance was continuously changed so that the exposure amount was continuously changed during exposure.
- the refractive index of the side cladding portion was almost constant, while the refractive index of the core portion continuously decreased from the central portion toward the periphery. That is, the refractive index distribution of the core layer of the obtained optical waveguide is a so-called graded index type.
- Comparative Example 3 An optical waveguide was obtained in the same manner as in Comparative Example 1 except that exposure was performed using a photomask whose transmittance was continuously changed so that the exposure amount was continuously changed during exposure.
- the refractive index distribution has a plurality of minimum values and maximum values, and the refractive index of the core portion continuously decreases from the central portion toward the periphery, reaching a minimum value.
- the refractive index continuously increased as the distance from the minimum value increased.
- the shape of the refractive index distribution was substantially V-shaped, and the change in the refractive index in the vicinity thereof was discontinuous.
- the refractive index distribution was measured by the refractive near field method along the center line in the thickness direction. A refractive index profile in the width direction was obtained.
- the obtained refractive index distribution has the same refractive index distribution pattern repeated for every core part, a part was cut out from the obtained refractive index distribution, and this was made into the refractive index distribution W.
- the shape of the refractive index distribution W was a shape in which four minimum values and five maximum values were alternately arranged as shown in FIG.
- each local minimum value Ws1, Ws2, Ws3, Ws4 and each local maximum value Wm1, Wm2, Wm3, Wm4, Wm5 were obtained, and an average refractive index WA in the cladding part was obtained.
- the width a [ ⁇ m] of the portion where the refractive index in the vicinity of the maximum values Wm2 and Wm4 formed in the core portion has a value equal to or greater than the average refractive index WA, and each minimum value
- the width b [ ⁇ m] of the portion where the refractive index in the vicinity of Ws1, Ws2, Ws3, and Ws4 has a value less than the average refractive index WA was measured.
- the refractive index distribution was measured using an interference microscope under the above conditions along the center line passing through the center of the width of the core portion in the vertical direction, and the optical waveguide A refractive index distribution T in the thickness direction of the transverse section of the waveguide was obtained.
- the refractive index distribution W of the optical waveguide obtained in each example had a continuous change in the refractive index as a whole.
- the refractive index distribution T of the optical waveguide obtained in each example was a step index type. Further, in the examples, the refractive index distribution P over the first cladding layer, the cladding portion, and the cladding layer was SI type.
- the refractive index distribution W of the optical waveguide obtained in Comparative Example 1 was a step index type as described above, and the refractive index distribution T was also a step index type.
- the refractive index distribution W of the optical waveguide obtained in Comparative Example 2 was a graded index type, while the refractive index distribution T was a step index type.
- the refractive index distribution W of the optical waveguide obtained in Comparative Example 3 has a refractive index discontinuously changing between the core portion and the side cladding portion, while the refractive index distribution T has a step index. It was a mold.
- the refractive index distribution W of the optical waveguide obtained in Reference Example 1 is the same shape as the refractive index distribution W of the optical waveguide obtained in each example, while the clad layer is omitted.
- the refractive index distribution T was not measured.
- FIG. 12 is a diagram for explaining a method of measuring the intensity distribution of the outgoing light on the outgoing side end face of the optical waveguide.
- the incident-side optical fiber 21 having a diameter of 50 ⁇ m is disposed so as to face one of the core portions 14 of the incident-side end face 1a of the optical waveguide 1 to be measured.
- the incident-side optical fiber 21 is connected to a light emitting element (not shown) for making light incident on the optical waveguide 1, and is arranged so that the optical axis thereof coincides with the optical axis of the core portion 14. Yes.
- an output side optical fiber 22 having a diameter of 62.5 ⁇ m was disposed so as to face the end surface 1b.
- the emission-side optical fiber 22 is connected to a light receiving element (not shown) for receiving the emitted light emitted from the optical waveguide 1, and its optical axis is the center in the thickness direction of the core layer of the optical waveguide 1. It is aligned with the line.
- the exit-side optical fiber 22 is configured to be able to scan the plane including this center line while maintaining a constant distance from the exit-side end face 1b.
- the light exiting optical fiber 22 is scanned while light is incident on one of the core portions from the light incident side optical fiber 21. Then, by measuring the intensity of the emitted light measured by the light receiving element with respect to the position of the emission side optical fiber 22, the intensity distribution of the emitted light with respect to the position of the emission side end face 1b can be obtained.
- FIG. 13 shows the intensity distribution of the emitted light measured as described above.
- FIG. 13 representatively shows the intensity distribution of the emitted light measured by the optical waveguides obtained in Example 1, Comparative Example 1, and Comparative Example 2.
- the crosstalk was sufficiently suppressed in all the optical waveguides obtained in Example 1. Further, in the optical waveguide obtained in Example 1, the intensity of the emitted light in the core portion 14 adjacent to the core portion 14 (the core portion 14 in the center of FIG. 13) where light is incident is adjacent to the core portion 14. It was confirmed that the intensity of the emitted light was smaller than that of the side clad portion 15 located on the side opposite to the core portion 14 where the light was incident. This is because, in the optical waveguide obtained in Example 1, the side cladding portion 15 has a maximum value smaller than the core portion 14 and the refractive index distribution continuously changes.
- the light receiving elements connected to the optical waveguide are each core portion 14. Are connected so as to face the end surface of the light-emitting side, and are not connected to the side clad portion 15. Therefore, even if light gathers in the side cladding part 15, crosstalk does not occur and interference is suppressed.
- the maximum value of the intensity distribution of the emitted light is located in the core portion 14 adjacent to the core portion 14 where the light is incident, and the leaked light is observed. (Crosstalk).
- a recess having a V-shaped cross section was formed by laser processing on the vicinity of one end of the obtained optical waveguide. Thereby, the mirror shown in FIG. 5 was formed for each optical waveguide.
- the mirror loss is measured by the mirror loss measurement method specified in 4.6.3 of the JPCA (Japan Electronic Circuits Association) standard and the optical waveguide test method (JPCA-PE02-05-01S). did.
- the output side optical fiber is aligned with the vertical end face of the optical waveguide, and the incident side optical fiber is set at a position optically connected to the core portion of the optical waveguide via a mirror. Then, light is incident on the optical waveguide from the incident side optical fiber, and the light intensity detected by the output side optical fiber is defined as P1 (dBm).
- the mirror loss (dB) was calculated from P0-P1. As a result, in each of the optical waveguides obtained in each of the examples and the comparative examples, the mirror loss was suppressed to a small value, whereas in the optical waveguide obtained in the reference example, the mirror loss was large.
- the photosensitive resin composition F1 was uniformly applied on the lower clad with a doctor blade, and then placed in a dryer at 50 ° C. for 10 minutes. After completely removing the solvent, a photomask on which a linear pattern with a line of 50 ⁇ m and a space of 50 ⁇ m is drawn is pressure-bonded and irradiated with ultraviolet rays using a parallel exposure machine so that the irradiation dose is 500 mJ / cm 2. did. After that, the mask was removed, and when it was put in an oven at 150 ° C. for 30 minutes and taken out, it was confirmed that a clear waveguide pattern appeared. The thickness of the obtained core layer was 50 ⁇ m.
- Example B (1) Polymer synthesis 20.0 g of methyl methacrylate, 30.0 g of benzyl methacrylate, and 450 g of methyl isobutyl ketone were charged into a separable flask, mixed with stirring, and then replaced with nitrogen gas to obtain a monomer solution. On the other hand, 0.25 g of azobisisobutyronitrile as a polymerization initiator was dissolved in 10 g of methyl isobutyl ketone and replaced with nitrogen gas to obtain an initiator solution. Thereafter, the monomer solution was heated to 80 ° C. while stirring, and the initiator solution was added to the monomer solution using a syringe. The mixture was heated and stirred at 80 ° C. for 1 hour and then cooled to obtain a polymer solution.
- the photosensitive resin composition C1 was uniformly applied on the lower clad with a doctor blade, and then placed in a dryer at 50 ° C. for 10 minutes. After completely removing the solvent, a photomask on which a linear pattern with a line of 50 ⁇ m and a space of 50 ⁇ m was drawn was pressure-bonded and irradiated with ultraviolet rays using a parallel exposure machine so that the irradiation dose was 500 mJ / cm 2 . . After that, when the mask was removed, and it was taken out for 30 minutes in a nitrogen dryer at 150 ° C., it was confirmed that a clear waveguide pattern appeared. The thickness of the obtained core layer was 50 ⁇ m.
- Example C First, a polymer A2 synthesized in the same manner as (1) of Example B was obtained except that 2- (perfluorohexyl) ethyl methacrylate was used instead of benzyl methacrylate. Thereafter, an optical waveguide was obtained in the same manner as in Example B except that the polymer A2 was used instead of the polymer A1.
- Comparative Example 4 (1) Synthesis of norbornene-based resin having a leaving group In a glove box filled with dry nitrogen in which the water and oxygen concentrations are both controlled to 1 ppm or less, 7.2 g (40.1 mmol) of hexylnorbornene (HxNB) ), 12.9 g (40.1 mmol) of diphenylmethylnorbornenemethoxysilane was weighed into a 500 mL vial, 60 g of dehydrated toluene and 11 g of ethyl acetate were added, and the top was sealed with a silicon sealer.
- HxNB hexylnorbornene
- Ni catalyst represented by the following formula (4) and 10 mL of dehydrated toluene are weighed in a 100 mL vial, put a stirrer chip, and tightly plugged. Dissolved in.
- 1 mL of the Ni catalyst solution represented by the chemical formula (A) is accurately weighed with a syringe, quantitatively injected into the vial bottle in which the two types of norbornene are dissolved, and stirred at room temperature for 1 hour, a marked increase in viscosity is observed. confirmed.
- the stopper was removed, 60 g of tetrahydrofuran (THF) was added, and the mixture was stirred to obtain a reaction solution.
- THF tetrahydrofuran
- a norbornene-based resin A (polymer # 1) having a leaving group in the side chain was obtained by heating and drying for 12 hours.
- the diphenylmethylnorbornenemethoxysilane structural unit was 50 mol%.
- the refractive index was 1.55 (measurement wavelength: 633 nm) by Metricon.
- the present embodiment includes the following.
- the refractive index of the top part of the first recess may be smaller than the average refractive index in the cladding part.
- the refractive index distribution W may have the top of the second convex portion in addition to the vicinity of the boundary between the first core portion and the cladding portion.
- the refractive index distribution W has a top portion of the second convex portion at the center portion of the cladding portion, and the refractive index continuously decreases from the top portion of the second convex portion toward the first concave portion. You may have a region.
- the refractive index difference between the first core portion and the first cladding layer in the refractive index distribution T may be larger than the refractive index difference between the top of the first concave portion and the top of the first convex portion in the refractive index distribution W.
- the refractive index of the top portion the maximum value or the refractive index of the central portion of the flat portion can be used.
- the top of the third convex portion in the refractive index distribution T may be located at the center of the core portion.
- the maximum value of the third convex portion may be larger than the maximum value of the first convex portion.
- the refractive index distribution T has a top portion of the third convex portion at the center of the core portion, and the refractive index continuously decreases from the top portion of the third convex portion toward the second concave portion. You may have.
- the refractive index distribution T located in the first cladding layer has a maximum value of the refractive index in a region other than the vicinity of the boundary between the first cladding layer and the first core portion, and in the vicinity of the boundary between the first cladding layer and the core portion.
- the refractive index difference between the refractive index of the top of the second concave portion and the average refractive index of the cladding layer is 3 of the refractive index difference between the refractive index of the top of the second concave portion and the refractive index of the top of the third convex portion. It may be up to 80%.
- the refractive index difference between the refractive index of the top of the second concave portion and the refractive index of the top of the third convex portion may be 0.005 to 0.07.
- the difference between the refractive index of the top of the first recess and the average refractive index of the cladding is 3 to 80% of the difference between the refractive index of the top of the first recess and the refractive index of the top of the first projection. There may be.
- the refractive index difference between the refractive index of the top of the first concave portion and the refractive index of the top of the first convex portion may be 0.005 to 0.07.
- the width of the portion where the refractive index of the first convex portion has a value greater than or equal to the average refractive index of the cladding portion is a [ ⁇ m]
- the refractive index of the first concave portion is the cladding.
- the present embodiment includes the following. (1) a core layer comprising a core portion and side clad portions adjacent to both side surfaces of the core portion; An optical waveguide having a clad layer laminated on both sides of the core layer,
- the refractive index distribution W in the width direction of the cross section of the core layer has at least two minimum values, at least one first maximum value, and at least two second maximum values smaller than the first maximum value.
- the refractive index distribution T in the thickness direction of the cross section of the optical waveguide has a substantially constant refractive index in each of a region corresponding to the core portion and a region corresponding to the cladding layer, and the core portion and the An optical waveguide characterized in that the refractive index changes discontinuously at the interface with the cladding layer.
- the second maximum value is located at the center of the region, and the minimum value is determined from the second maximum value.
- the difference between the minimum value and the average refractive index in the side cladding portion is 3 to 80% of the difference between the minimum value and the first maximum value.
- the refractive index distribution W has a substantially U shape that protrudes upward in the vicinity of the first maximum value, and a substantially U shape that protrudes downward in the vicinity of the minimum value.
- the width of the portion where the refractive index in the vicinity of the first maximum value has a value equal to or greater than the average refractive index in the side cladding portion is a [ ⁇ m]
- the refractive index difference between the core portion and the cladding layer in the refractive index distribution T is greater than the refractive index difference between the minimum value and the first maximum value in the refractive index distribution W (1) Thru
- the above has a hole provided so as to cross the core part and the cladding layer, and a reflection surface configured to reflect light transmitted through the core part is configured by the inner surface of the hole (The optical waveguide according to any one of 1) to (9).
Abstract
Description
[1]
第1クラッド層と、
前記第1クラッド層上に設けられており、層内方向に設けられたクラッド部、第1コア部、クラッド部、第2コア部、及びクラッド部をこの順番で有するコア層と、
前記コア層上に設けられた第2クラッド層と、
を備え、
前記コア層のうち前記第1コア部、及び前記クラッド部に亘る部分の層内方向の屈折率分布Wが、連続的に変化していて、第1の凸部、第1の凹部、及び第2の凸部の順で並ぶ領域を有しており、
前記第1コア部に位置する前記屈折率分布Wは、前記第1の凸部を有しており、
前記クラッド部に位置する前記屈折率分布Wは、前記第1の凸部よりも屈折率の最大値が小さい前記第2の凸部を有しており、
前記第1クラッド層及び前記第1コア部に亘る部分の層間方向の屈折率分布Tが、前記第1クラッド層と前記第1コア部との界面において不連続的に変化している、光導波路。
[2]
[1]に記載の光導波路において、
前記第1クラッド層、前記クラッド部及び前記第2クラッド層に亘る部分の層間方向の屈折率分布Pが、前記第1クラッド層に位置する部分と前記クラッド部に位置する部分とで相異なる、
光導波路。
[3]
[1]または[2]に記載の光導波路において、
前記第1クラッド層、前記第1コア部に亘る部分の層間方向の屈折率分布Tが、前記屈折率分布Wと相異なる、光導波路。
[4]
[1]から[3]のいずれか1項に記載の光導波路において、
前記第1コア部の屈折率の最大値と前記第1クラッド層の屈折率の最大値との屈折率差は、第1コア部の屈折率の最大値と前記クラッド部の屈折率の最大値との屈折率差よりも、大きい、光導波路。
[5]
[1]から[4]のいずれか1項に記載の光導波路において、
前記第2クラッド層上に設けられた、前記コア層と別部材の第2コア層を備え、
前記第2コア層は、前記第1コア部の層間方向に位置する第3コア部を有する、光導波路。
[6]
[1]から[5]のいずれか1項に記載の光導波路において、
前記第1の凹部の頂部の屈折率は、前記クラッド部における平均屈折率より小さい、光導波路。
[7]
[1]から[6]のいずれか1項に記載の光導波路において、
前記屈折率分布Wは、前記第1コア部と前記クラッド部の界面近傍以外に前記第2の凸部の頂部を有する、光導波路。
[8]
[1]から[7]のいずれか1項に記載の光導波路において、
前記屈折率分布Wは、前記クラッド部の中心部に前記第2の凸部の頂部を有しており、前記第2の凸部の前記頂部から前記第1の凹部に向かって連続的に屈折率が低下している領域を有する、光導波路。
[9]
[1]から[8]のいずれか1項に記載の光導波路において、
前記屈折率分布Tにおける前記第1コア部と前記第1クラッド層との屈折率差は、前記屈折率分布Wにおける前記第1の凹部の頂部と前記第1の凸部の頂部との屈折率差より大きい、光導波路。
[10]
[1]から[9]のいずれか1項に記載の光導波路において、
前記第1コア部および前記第1クラッド層を横切るように設けられた空孔を有し、該空孔の内面により、前記コア部を伝送される光を反射する反射面が構成されている、光導波路。
[11]
[1]から[10]のいずれか1項に記載の光導波路において、
前記第1の凹部の頂部の屈折率と前記クラッド部における平均屈折率との差は、前記第1の凹部の頂部の屈折率と前記第1の凸部の頂部の屈折率との差の3~80%である、光導波路。
[12]
[1]から[11]のいずれか1項に記載の光導波路において、
前記第1の凹部の頂部の屈折率と前記第1の凸部の頂部の屈折率との屈折率差は、0.005~0.07である、光導波路。
[13]
[1]から[12]のいずれか1項に記載の光導波路において、
前記屈折率分布Wにおいて、前記第1の凸部の屈折率が、前記クラッド部における平均屈折率以上の値を有している部分の幅をa[μm]とし、前記第1の凹部の屈折率が、前記クラッド部における平均屈折率未満の値を有している幅をb[μm]としたとき、bは、0.01a~1.2aである、光導波路。
[14]
コア部と、該コア部の両側面に隣接する側面クラッド部と、を備えるコア層と、
該コア層の両面にそれぞれ積層されたクラッド層と、を有する光導波路であって、
前記コア層の横断面の幅方向の屈折率分布Wは、少なくとも2つの極小値と、少なくとも1つの第1の極大値と、前記第1の極大値より小さい少なくとも2つの第2の極大値と、を有し、これらが、第2の極大値、極小値、第1の極大値、極小値、第2の極大値の順で並ぶ領域を有しており、この領域のうち、前記第1の極大値を含むように前記2つの極小値で挟まれる領域が前記コア部、前記各極小値から前記第2の極大値側の領域が前記側面クラッド部であり、
前記各極小値は、前記クラッド部における平均屈折率未満であり、かつ、前記屈折率分布全体で屈折率が連続的に変化しており、
前記光導波路の横断面の厚さ方向の屈折率分布Tは、前記コア部に対応する領域および前記クラッド層に対応する領域のそれぞれで、屈折率がほぼ一定であり、かつ前記コア部と前記クラッド層との界面で屈折率が不連続的に変化していることを特徴とする光導波路。
[15]
[1]から[14]のいずれか1項に記載の光導波路を備えることを特徴とする電子機器。
まず、本発明の光導波路について説明する。
(第1実施形態)
図1は、本発明の光導波路の第1実施形態を示す(一部切り欠いて、および透過して示す)斜視図、図2は、図1に示すX-X線断面図について、横軸にコア層の厚さの中心線における位置をとり、縦軸に屈折率をとったときの屈折率分布の一例を示す図、図3は、図1に示す光導波路のコア部の1つに光を入射したときの出射光の強度分布の一例を示す図である。なお、以下の説明では、図1中の上側を「上」、下側を「下」という。また、図1は、層の厚さ方向(各図の上下方向)が誇張して描かれている。
第1の実施の形態の光導波路は、第1クラッド層(クラッド層11)、コア層(コア層13)、第2クラッド層(クラッド層12)を備える。コア層(コア層13)は、クラッド層11上に設けられており、層内方向に設けられたクラッド部、第1コア部(コア部14)、クラッド部(クラッド部15)、第2コア部(コア部14)、及びクラッド部をこの順番で有する。第2クラッド層は、コア層上に設けられる。
コア部の層内方向の屈折率分布では、端部に第1の凹部が形成されるので、コア部の中心部と端部と屈折率差が大きくなる。これにより、層内方向に隣接するコア部の間のクロストークが抑制される。また、コア部から光が漏れ出したとしても、漏れ光は、クラッド部の第2の凸部に閉じこめられ得る。これにより、層内方向に隣接するコア部の間のクロストークが抑制される。
第1コア部を基点として、層間方向の屈折率分布Tは、層内方向の屈折率分布Wに対して、異ならせる設計が可能である。たとえば、層間方向の屈折率差を、層内方向の屈折率差よりも大きくすることにより、光導波路のフィルムを光導波路の延在方向に折り曲げる、または巻き上げるときにおける光損失を低減させることができる。詳細に説明する。フィルムを所定方向に曲げると、フィルムが引き延ばされて、屈折率差が小さくなることがある。これに対して、予め、フィルムを曲げる方向の屈折率差を大きくすることにより、屈折率差が小さくなったとしても、光損失を低減することができる。
本実施の形態の光導波路は、たとえば、フィルムを積層して得られるものである。このため、クラッド層の厚さは、コア層の厚さとの関係で任意に決定される。また、厚み制御が出来るので、光結合損失の低減などの効果を高めることができる。
本実施の形態の屈折率分布は、光導波路の延在方向(例えば、第1コア部の延在方向)に対して直交する方向の光導波路の断面から、測定及び特定されるものである。
第1コア部は、第1の凸部の極大値から第1の凹部の極小値までの領域とし、クラッド部は、第1の凹部の極小値から第2の凹部の極大値までの領域としてもよい。また、極大値又は極小値に代えて、頂部の平坦部の中央部を採用してもよい。
光導波路1は、図1中の下側からクラッド層11、コア層13およびクラッド層12をこの順で積層してなるものである。
このうち、コア層13には、面方向において屈折率分布が形成されている。この屈折率分布は、相対的に屈折率の高い領域と低い領域とを有しており、これにより入射された光を屈折率の高い領域に閉じ込めて伝搬することができる。
クラッド層11および12は、それぞれ、コア層13の下部および上部に位置するクラッド部を構成するものである。
屈折率差の割合(%)=|n1/n2-1|×100
光導波路1の下面には、必要に応じて、図1に示すような支持フィルム2を積層するようにしてもよい。
一方、光導波路1の上面には、必要に応じて、図1に示すようなカバーフィルム3を積層するようにしてもよい。
次に、本発明の光導波路の第2実施形態について説明する。
図5(b)に示す光導波路1では、その一方の端部において、コア部14が光導波路1の端面まで到達せず、途中で途切れている。そして、コア部14が途切れた箇所から端面までは、側面クラッド部15が形成されている。なお、このコア部14が途切れた部分を、コア部欠損部16とする。
次に、上述した光導波路1の製造方法の一例について説明する。
(第1の製造方法)
まず、光導波路1の第1の製造方法について説明する。
[1]まず、コア層形成用組成物900を用意する。
ポリマー915は、コア層13のベースポリマーとなるものである。
(1)ノルボルネン型モノマーを付加(共)重合して得られるノルボルネン型モノマーの付加(共)重合体、
(2)ノルボルネン型モノマーとエチレンやα-オレフィン類との付加共重合体、
(3)ノルボルネン型モノマーと非共役ジエン、および必要に応じて他のモノマーとの付加共重合体のような付加重合体、
(4)ノルボルネン型モノマーの開環(共)重合体、および必要に応じて該(共)重合体を水素添加した樹脂、
(5)ノルボルネン型モノマーとエチレンやα-オレフィン類との開環(共)重合体、および必要に応じて該(共)重合体を水素添加した樹脂、
(6)ノルボルネン型モノマーと非共役ジエン、または他のモノマーとの開環共重合体、および必要に応じて該(共)重合体を水素添加したポリマーのような開環重合体が挙げられる。これらの重合体としては、ランダム共重合体、ブロック共重合体、交互共重合体等が挙げられる。
R1を有するノルボルネンと、側鎖にエポキシ基を有するノルボルネンとをトルエンに溶かし、Ni化合物(A)を触媒として用いて溶液重合させることで(1)を得る。
DCPD(ジシクロペンタジエン)のクラッキングにより生成したCPD(シクロペンタジエン)とαオレフィン(CH2=CH-CH2-OH)を高温高圧下で反応させる。
ノルボルネンメタノールとエピクロルヒドリンとの反応により生成する。
(式(4)中、R5は、炭素数1~10のアルキル基を表し、A1およびA2は、それぞれ独立して、下記式(5)~(7)で表される置換基を表すが、同時に同一の置換基であることはない。また、p4/q4+rが20以下である。)
(式(6)中、R6は、水素原子またはメチル基を表し、gは、0~3の整数を表す。)
(式(8)中、R7は、炭素数1~10のアルキル基を表し、R8は、水素原子、メチル基またはエチル基を表し、Arは、アリール基を表し、X1は、酸素原子またはメチレン基を表し、X2は、炭素原子またはシリコン原子を表し、iは、0~3の整数を表し、jは、1~3の整数を表し、p5/q5が20以下である。)
具体的には、以下のようなノルボルネン系樹脂を使用することが好ましい。
さらに、ノルボルネン系樹脂として、次のようなものを使用してもよい。
具体例として以下のようなものが挙げられる。
添加剤920は、モノマーおよび重合開始剤を含んでいる。
モノマーは、後述する活性放射線の照射により、活性放射線の照射領域において反応して反応物を形成し、それとともにモノマーが拡散移動することで、層910において照射領域と未照射領域との間に屈折率差を生じさせ得るような化合物である。
[式中、aは、単結合または二重結合を表し、R12~R15は、それぞれ独立して、水素原子、置換もしくは無置換の炭化水素基、または官能置換基を表し、mは、0~5の整数を表す。ただし、aが二重結合の場合、R12およびR13のいずれか一方、R14およびR15のいずれか一方は存在しない。]
重合開始剤は、活性放射線の照射に伴ってモノマーに作用し、モノマーの反応を促すものであり、モノマーの反応性を考慮し、必要に応じて添加される。
また、活性放射線930の照射量を調整することにより、形成される屈折率差および屈折率分布の形状を制御することができる。例えば、照射量を多くすることで、屈折率差を拡大することができる。また、光酸発生剤の含有量と照射量とを調整することにより、屈折率分布の形状を制御することができる。また、活性放射線930の照射前に層910を乾燥させてもよいが、その際の乾燥の程度を調整することにより、屈折率分布の形状を制御することもできる。例えば、乾燥の程度を大きくすることで、モノマーの拡散移動量を抑えることができる。また、乾燥温度を高めることにより、拡散量を増加させて、屈折率分布を制御することができる。
以上のような原理で、屈折率分布Wを有するコア層13が得られる(図8参照)。
次に、光導波路1の第2の製造方法について説明する。
[1]まず、コア層形成用組成物900を用意する。
[式Ia、Ib中、それぞれ、E(R)3は、第15族の中性電子ドナー配位子を表し、Eは、周期律表の第15族から選択される元素を表し、Rは、水素原子(またはその同位体の1つ)または炭化水素基を含む部位を表し、Qは、カルボキシレート、チオカルボキシレートおよびジチオカルボキシレートから選択されるアニオン配位子を表す。また、式Ib中、LBは、ルイス塩基を表し、WCAは、弱配位アニオンを表し、aは、1~3の整数を表し、bは、0~2の整数を表し、aとbとの合計は、1~3であり、pおよびrは、パラジウムカチオンと弱配位アニオンとの電荷のバランスをとる数を表す。]
[2-1]次に、第1の製造方法と同様に、マスク935を介して層910に活性放射線930を照射する。
これにより、照射領域925内では、活性潜在状態の触媒前駆体が活性化して(活性状態となって)、モノマーの反応(重合反応や架橋反応)が生じる。
その結果、層910には、第1の製造方法と同様の屈折率分布が形成される。
これにより、未照射領域940および/または照射領域925に残存する触媒前駆体を、直接または助触媒の活性化を伴って、活性化させる(活性状態とする)ことにより、各領域925、940に残存するモノマーを反応させる。
これにより、得られるコア層13に生じる内部応力の低減や、コア部14および側面クラッド部15の更なる安定化を図ることができる。
以上の工程を経て、光導波路1(たとえばコア層13)が得られる。
上述したような本発明の光導波路は、光伝送効率および長期信頼性に優れたものである。このため、本発明の光導波路を備えることにより、2点間で高品質の光通信を行い得る信頼性の高い電子機器(本発明の電子機器)が得られる。
1.光導波路の製造
(実施例1)
(1)離脱性基を有するノルボルネン系樹脂の合成
水分および酸素濃度がいずれも1ppm以下に制御され、乾燥窒素で満たされたグローブボックス中において、ヘキシルノルボルネン(HxNB)7.2g(40.1mmol)、ジフェニルメチルノルボルネンメトキシシラン12.9g(40.1mmol)を500mLバイアル瓶に計量し、脱水トルエン60gと酢酸エチル11gを加え、シリコン製のシーラーを被せて上部を密栓した。
精製した上記ポリマー#1 10gを100mLのガラス容器に秤量し、これにメシチレン40g、酸化防止剤Irganox1076(チバガイギー社製)0.01g、シクロヘキシルオキセタンモノマー(式(20)で示した第1モノマー、東亞合成製 CHOX、CAS#483303-25-9、分子量186、沸点125℃/1.33kPa)2g、重合開始剤(光酸発生剤) RhodorsilPhotoinitiator 2074(Rhodia社製、CAS# 178233-72-2)(2.50E-2g、酢酸エチル0.1mL中)を加え均一に溶解させた後、0.2μmのPTFEフィルターによりろ過を行い、清浄なコア層形成用組成物を得た。
(下側クラッド層の作製)
シリコンウエハー上に感光性ノルボルネン樹脂組成物(プロメラス社製 Avatrel2000Pワニス)をドクターブレードにより均一に塗布した後、45℃の乾燥機に15分間投入した。溶剤を完全に除去した後、塗布された全面に紫外線を80mJ照射し、乾燥機中120℃で1時間加熱して、塗膜を硬化させて、下側クラッド層を形成させた。形成された下側クラッド層は、厚みが20μmであり、無色透明であった。
上記下側クラッド層上にコア層形成用組成物をドクターブレードによって均一に塗布した後、55℃の乾燥機に10分間投入した。溶剤を完全に除去した後、フォトマスクを圧着して紫外線を1300mJ/cm2で選択的に照射した。マスクを取り去り、乾燥機中150℃で1.5時間の加熱を行った。加熱後、非常に鮮明な導波路パターンが現れているのが確認された。また、コア部および側面クラッド部の形成が確認された。なお、形成した光導波路は、コア部が8本並列に形成されたものである。また、コア部の幅を50μm、側面クラッド部の幅を80μm、コア層の厚さを50μmとした。
ポリエーテルスルホン(PES)フィルム上に、予め乾燥厚み20μmになるようにAvatrel2000Pを積層させたドライフィルムを、上記コア層に貼り合わせ、140℃に設定された真空ラミネーターに投入して熱圧着を行った。その後、紫外線を100mJ全面照射し乾燥機中120℃で1時間加熱して、Avatrel2000Pを硬化させて、上側クラッド層を形成させ、光導波路を得た。
なお、得られた光導波路から、長さ10cm分を切り出した。
そして、得られた光導波路のコア層の横断面について、その厚さ方向の中心線に沿って干渉顕微鏡を使用して、幅方向の屈折率分布Wを取得した。その結果、屈折率分布Wは、複数の極小値および極大値を有し、屈折率が連続的に変化したものであった。
以下、干渉顕微鏡を使用した屈折率分布の測定方法を示す。
まず、光導波路の断面方向に光導波路をスライスして、光導波路断片を得た。光導波路の長さが200μm~300μmとなるように、スライスした。次いで、2つのスライドガラスで囲まれた空間に、屈折率1.536のオイルで充填したチャンバーを作成した。このチャンバー内の空間に、光導波路断片を挟み込んだ測定サンプルと、光導波路断片を入れていないブランクサンプルを作成した。次いで、干渉顕微鏡を使用して、光導波路断片の断面方向の干渉縞写真を得た。この後、干渉縞写真を画像解析して、屈折率分布を得た。ここで、干渉縞写真の画像解析は、次のように行った。まず、干渉顕微鏡の光路長を変更して、干渉縞の出来る場所を変えた画像データを連続的に取得した。複数の画像データから、層間方向及び層内方向の各測定ポイントの屈折率を算出した。本実施例では、測定ポイントの間隔は、2.5μmとした。
紫外線の照射量を1500mJ/cm2に高めた以外は、実施例1と同様にして光導波路を得た。
紫外線の照射量を2000mJ/cm2に高めるとともに、ポリマーとして、ポリマー#1の各構造単位のモル比を、ヘキシルノルボルネン構造単位が40mol%、ジフェニルメチルノルボルネンメトキシシラン構造単位が60mol%に変更したものを用いるようにした以外は、実施例1と同様にして光導波路を得た。
紫外線の照射量を500mJ/cm2に減らすとともに、ポリマーとして、ポリマー#1の各構造単位のモル比を、ヘキシルノルボルネン構造単位が45mol%、ジフェニルメチルノルボルネンメトキシシラン構造単位が55mol%に変更したものを用いるようにした以外は、実施例1と同様にして光導波路を得た。
ポリマーとして、ポリマー#1の各構造単位のモル比を、ヘキシルノルボルネン構造単位が30mol%、ジフェニルメチルノルボルネンメトキシシラン構造単位が70mol%に変更したものを用いるようにした以外は、実施例1と同様にして光導波路を得た。
紫外線の照射量を300mJ/cm2に減らすとともに、ポリマーとして、ポリマー#1の各構造単位のモル比を、ヘキシルノルボルネン構造単位が40mol%、ジフェニルメチルノルボルネンメトキシシラン構造単位が60mol%に変更したものを用いるようにした以外は、実施例1と同様にして光導波路を得た。
紫外線の照射量を500mJ/cm2に減らすとともに、ポリマーとして、ポリマー#1の各構造単位のモル比を、ヘキシルノルボルネン構造単位が30mol%、ジフェニルメチルノルボルネンメトキシシラン構造単位が70mol%に変更したものを用いるようにした以外は、実施例1と同様にして光導波路を得た。
紫外線の照射量を100mJ/cm2に減らすとともに、ポリマーとして、ポリマー#1の各構造単位のモル比を、ヘキシルノルボルネン構造単位が60mol%、ジフェニルメチルノルボルネンメトキシシラン構造単位が40mol%に変更したものを用いるようにした以外は、実施例1と同様にして光導波路を得た。
紫外線の照射量を1500mJ/cm2に高めるとともに、ポリマーとして、ポリマー#1の各構造単位のモル比を、ヘキシルノルボルネン構造単位が10mol%、ジフェニルメチルノルボルネンメトキシシラン構造単位が90mol%に変更したものを用いるようにした以外は、実施例1と同様にして光導波路を得た。
紫外線の照射量を3000mJ/cm2に高めるとともに、ポリマーとして、ポリマー#1の各構造単位のモル比を、ヘキシルノルボルネン構造単位が5mol%、ジフェニルメチルノルボルネンメトキシシラン構造単位が95mol%に変更したものを用いるようにした以外は、実施例1と同様にして光導波路を得た。
コア層形成用組成物として、以下に示す方法で製造されたものを用いるようにした以外は、実施例1と同様にして光導波路を得た。
コア層形成用組成物として、以下に示す方法で製造されたものを用いるようにした以外は、実施例1と同様にして光導波路を得た。
コア層形成用組成物として、以下に示す方法で製造されたものを用いるようにした以外は、実施例1と同様にして光導波路を得た。
ポリマーとして、以下に示す方法で合成されたものを用いるようにした以外は、実施例1と同様にして光導波路を得た。
コア層形成用組成物として、以下に示す方法で製造されたものを用いた点、及び下側クラッド層上にコア層形成用組成物をドクターブレードによって均一に塗布した後、60℃の乾燥機に10分間投入した点以外は、実施例1と同様にして光導波路を得た。
紫外線の照射量を500mJ/cm2に減らした以外は、実施例15と同様にして光導波路を得た。
下記のようにした以外は、実施例1と同様にして光導波路を得た。
その後、上側クラッド層を形成することにより、光導波路を得た。
露光の際に、露光量が連続的に変化するよう、透過率が連続的に変化したフォトマスクを用いて露光するようにした以外は、比較例1と同様にして光導波路を得た。
露光の際に、露光量が連続的に変化するよう、透過率が連続的に変化したフォトマスクを用いて露光するようにした以外は、比較例1と同様にして光導波路を得た。
クラッド層の積層を省略し、コア層のみで光導波路を構成するようにした以外は、実施例1と同様にして光導波路を得た。
2.1 光導波路の屈折率分布
得られた光導波路のコア層の横断面について、その厚さ方向の中心線に沿って屈折ニアフィールド法により屈折率分布を測定し、コア層の横断面の幅方向の屈折率分布を得た。なお、得られた屈折率分布は、コア部ごとに同様の屈折率分布パターンが繰り返されているので、得られた屈折率分布から一部を切り出し、これを屈折率分布Wとした。屈折率分布Wの形状は、図2に示すような、4つの極小値と5つの極大値とが交互に並んだ形状であった。
850nmVCSEL(面発光レーザー)より発せられた光を50μmφの光ファイバーを経由して得られた光導波路に導入し、200μmφの光ファイバーで受光を行って光の強度を測定した。なお、測定にはカットバック法を採用した。光導波路の長手方向を横軸にとり、挿入損失を縦軸にとって測定値をプロットしたところ、測定値は直線上に並んだ。そこで、その直線の傾きから伝送損失を算出した。
得られた光導波路に対して、レーザーパルス光源からパルス幅1nsのパルス信号を入射し、出射光のパルス幅を測定した。
◎:パルス幅の相対値が0.5未満である
○:パルス幅の相対値が0.5以上0.8未満である
△:パルス幅の相対値が0.8以上1未満である
×:パルス幅の相対値が1以上である
以上、2.2および2.3の評価結果を表1に示す。
得られた光導波路の出射側端面について、8つのコア部のうちの一方に光を入射したときの出射光の強度分布を測定した。
なお、出射光の強度分布の測定は、以下のようにして行った。
得られた光導波路の一方の端部近傍に対して、レーザー加工法により、横断面がV字状をなす凹部を形成した。これにより、各光導波路に対して図5に示すミラーを形成した。
その結果、各実施例および各比較例で得られた光導波路では、いずれもミラー損失が小さく抑えられていたのに対し、参考例で得られた光導波路では、ミラー損失が大きかった。
3.1 光導波路の製造
(実施例A)
(1)クラッド溶液の製造
ダイセル化学工業(株)製セロキサイド2081 20g、(株)ADEKA社製アデカオプトマーSP-170 0.6g、メチルイソブチルケトン80gを撹拌混合し、0.2μm孔径のPTFEフィルターでろ過して清浄で無色透明なクラッド溶液E1を得た。
新日鐵化学(株)製YP-50S 20gと、ダイセル化学工業(株)製セロキサイド2021P 5gと、(株)ADEKA製アデカオプトマーSP-170 0.2gと、をメチルイソブチルケトン80g中に投入し撹拌溶解し、0.2μm孔径のPTFEフィルターでろ過して清浄で無色透明な感光性樹脂組成物F1を得た。
厚み25μmのポリイミドフィルム上に前記クラッド溶液E1をドクターブレードにより均一に塗布した後、50℃の乾燥機に10分間投入した。溶媒を完全に除去した後、UV露光機で全面に紫外線を500mJ/cm2となるように照射し、硬化させて無色透明な下層クラッドを形成した。得られたクラッド層の厚みは10μmであった。
前記下層クラッド上に前記感光性樹脂組成物F1をドクターブレードにて均一に塗布した後、50℃の乾燥機に10分間投入した。溶剤を完全に除去した後に、ラインが50μm、スペースが50μmの直線パターンが全面に描かれたフォトマスクを圧着し、平行露光機を用いて照射量が500mJ/cm2となるように紫外線を照射した。その後、マスクを取り去り、150℃のオーブンに30分間投入して取り出すと鮮明な導波路パターンが現れているのが確認された。得られたコア層の厚みは50μmであった。
前記コア層上に前記クラッド溶液E1を用いて下層クラッドと同様の条件にて上層クラッドを形成した。得られた上層クラッドの厚みは10μmであった。
(1)ポリマーの合成
セパラブルフラスコにメタクリル酸メチル20.0g、ベンジルメタクリレート30.0g、およびメチルイソブチルケトン450gを投入し、撹拌混合したのち、窒素ガスで置換してモノマー溶液を得た。一方、重合開始剤としてアゾビスイソブチロニトリル0.25gをメチルイソブチルケトン10gに溶解し、窒素ガスで置換して開始剤溶液を得た。その後、前記モノマー溶液を撹拌しながら80℃に加熱し前記開始剤溶液をシリンジを用いてモノマー溶液に添加した。そのまま80℃で1時間加熱撹拌したのちに冷却し重合体溶液を得た。
互応化学工業(株)製の水性アクリレート樹脂溶液RD-180 20g、イソプロパノール20g、および日清紡ケミカル(株)製カルボジライトV-02-L2 0.4gを撹拌混合し、0.2μm孔径のPTFEフィルターでろ過して清浄で無色透明なクラッド溶液B1を得た。
(1)の方法で得られたポリマーA1 20gと、メタクリル酸シクロヘキシル5gと、BASFジャパン(株)製イルガキュア651 0.2gと、をメチルイソブチルケトン80g中に投入し撹拌溶解し、0.2μm孔径のPTFEフィルターでろ過して清浄で無色透明な感光性樹脂組成物C1を得た。
厚み25μmのポリイミドフィルム上に前記クラッド溶液B1をドクターブレードにより均一に塗布した後、80℃の乾燥機に10分間投入した。溶媒を完全に除去した後、さらに150℃のオーブンに10分間投入し硬化させて無色透明な下層クラッドを形成した。得られたクラッド層の厚みは10μmであった。
前記下層クラッド上に前記感光性樹脂組成物C1をドクターブレードにて均一に塗布した後、50℃の乾燥機に10分間投入した。溶剤を完全に除去した後に、ライン50μm、スペースが50μmの直線パターンが全面に描かれたフォトマスクを圧着し、平行露光機を用いて照射量が500mJ/cm2となるように紫外線を照射した。その後、マスクを取り去り、150℃の窒素乾燥機に30分間投入して取り出すと鮮明な導波路パターンが現れているのが確認された。得られたコア層の厚みは50μmであった。
前記コア層上に前記クラッド溶液B1を用いて下層クラッドと同様の条件にて上層クラッドを形成した。得られた上層クラッドの厚みは10μmであった。
まず、ベンジルメタクリレートの代わりに2-(パーフルオロヘキシル)エチルメタクリレートを用いたこと以外は実施例Bの(1)と同様にして合成されたポリマーA2を得た。
以下、ポリマーA1に代えてポリマーA2を用いるようにした以外は、実施例Bと同様にして光導波路を得た。
(光導波路の伝送損失)
850nmVCSEL(面発光レーザー)より発せられた光を50μm径の光ファイバーを経由し、実施例A~C得られた光導波路に導入し、200μm径の光ファイバーで受光して光の強度を測定した。そして、カットバック法により伝送損失を測定した。その後、導波路長を横軸にとり、挿入損失を縦軸にプロットすると測定値は直線上に並び、その傾きから各光導波路の伝搬損失はいずれも0.05dB/cmと算出することができた。
また、実施例A~Cにおいて、屈折率分布のパラメーターを1.の実施例と同様にして変更したところ、2.と同じ傾向の評価結果が得られた。
実施例A~Cで得られた光導波路について、2.3と同様の方法でパルス信号の波形の保持性を評価したところ、いずれもパルス信号の鈍りが小さいことが認められた。
また、実施例A~Cにおいて、屈折率分布のパラメーターを1.の実施例と同様にして変更したところ、2.と同じ傾向の評価結果が得られた。
(1)脱離性基を有するノルボルネン系樹脂の合成
水分および酸素濃度がいずれも1ppm以下に制御され、乾燥窒素で充満されたグローブボックス中において、ヘキシルノルボルネン(HxNB)7.2g(40.1mmol)、ジフェニルメチルノルボルネンメトキシシラン12.9g(40.1mmol)を500mLバイアル瓶に計量し、脱水トルエン60gと酢酸エチル11gを加え、シリコン製のシーラーを被せて上部を密栓した。
次に、100mLバイアルビン中に下記式(4)で表わされるNi触媒1.56g(3.2mmol)と脱水トルエン10mLを計量し、スターラーチップを入れて密栓し、触媒を十分に撹拌して完全に溶解させた。
この化学式(A)で表わされるNi触媒溶液1mLをシリンジで正確に計量し、上記2種のノルボルネンを溶解させたバイアル瓶中に定量的に注入し室温で1時間撹拌したところ、著しい粘度上昇が確認された。この時点で栓を抜き、テトラヒドロフラン(THF)60gを加えて撹拌を行い、反応溶液を得た。
100mLビーカーに無水酢酸9.5g、過酸化水素水18g(濃度30%)、イオン交換水30gを加えて撹拌し、その場で過酢酸水溶液を調製した。次にこの水溶液全量を上記反応溶液に加えて12時間撹拌してNiの還元処理を行った。
次に、処理の完了した反応溶液を分液ロートに移し替え、下部の水層を除去した後、イソプロピルアルコールの30%水溶液を100mL加えて激しく撹拌を行った。静置して完全に二層分離が行われた後で水層を除去した。この水洗プロセスを合計で3回繰り返した後、油層を大過剰のアセトン中に滴下して生成したポリマーを再沈殿させ、ろ過によりろ液と分別した後、60℃に設定した真空乾燥機中で12時間加熱乾燥を行うことにより、側鎖に脱離性基を有するノルボルネン系樹脂A(ポリマー#1)を得た。ノルボルネン系樹脂Aの分子量は、GPC測定によりMw=10万、Mn=4万、ノルボルネン系樹脂A中の各構造単位のモル比は、NMRによる同定により、ヘキシルルボルネン構造単位が50mol%、ジフェニルメチルノルボルネンメトキシシラン構造単位が50mol%であった。また屈折率はメトリコンにより1.55(測定波長;633nm)であった。
精製したノルボルネン系樹脂A10gを100mLのガラス容器に秤量し、これにメシチレン40g、酸化防止剤Irganox1076(チバガイギー社製)0.01g、シクロヘキシルオキセタンモノマー(式(20)で示した第1モノマー、東亜合成製 CHOX、CAS#483303-25-9、分子量186、沸点125℃/1.33kPa)2g、光酸発生剤RhodorsilPhotoinitiator 2074(Rhodia社製、CAS# 178233-72-2)(1.36E-2g、酢酸エチル0.1mL中)を加え均一に溶解させた後、0.2μmのPTFEフィルターによりろ過を行い、清浄なコア層用の感光性樹脂組成物ワニスV1を調製した。
(下層クラッドの作製)
シリコンウエハ上に感光性ノルボルネン樹脂組成物(プロメラス社製 Avatrel2000Pワニス)をドクターブレードにより均一に塗布した後、45℃の乾燥機に15分間投入した。溶剤を完全に除去した後、塗布された全面に紫外線を100mJ照射し、乾燥機中120℃で1時間加熱して、塗膜を硬化させて、下層クラッドを形成させた。形成された下層クラッドは、厚みが20μmであり、無色透明であり、屈折率は1.52(測定波長;633nm)であった。
上記下層クラッド上に、調製して得られた上述の感光性樹脂組成物ワニスV1をドクターブレードによって均一に塗布した後、45℃の乾燥機に15分間投入した。溶剤を完全に除去した後、フォトマスクを圧着して紫外線を500mJ/cm2で選択的に照射した。マスクを取り去り、乾燥機中45℃で30分間、85℃で30分間、150℃で1時間と三段階で加熱を行った。加熱後、非常に鮮明な導波路パターンが現れたコア層が確認された。
ポリエーテルスルホン(PES)フィルム上に、予め乾燥厚み20μmになるように感光性ノルボルネン樹脂組成物(プロメラス社製 Avatrel2000Pワニス)を積層して上層クラッド用フィルムを得た。
下層クラッド層上に形成したコア層と、上述の上層クラッド用フィルムとを、貼り合わせて、140℃に設定された真空ラミネーターに投入して熱圧着を行った後、紫外線を100mJ全面照射し乾燥機中120℃で1時間加熱して、Avatrel2000Pを硬化させて、上層クラッドを形成させ、光導波路を得た。
比較例4の光導波路のコア層の層内方向の屈折率分布は、W型ではないことを確認した。
屈折率分布Wは、第1コア部とクラッド部の境界近傍以外に第2の凸部の頂部を有してもよい。
屈折率分布Wは、クラッド部の中心部に第2の凸部の頂部を有しており、第2の凸部の頂部から第1の凹部に向かって連続的に屈折率が低下している領域を有してもよい。屈折率分布Tにおける第1コア部と第1クラッド層との屈折率差は、屈折率分布Wにおける第1の凹部の頂部と第1の凸部の頂部との屈折率差より大きくてもよい。ここで、頂部の屈折率としては、極大値又は平坦部の中央部の屈折率を用いることができる。
第1コア部および第1クラッド層を横切るように設けられた空孔を有し、該空孔の内面により、前記コア部を伝送される光を反射する反射面が構成されてもよい。
屈折率分布Tにおける第3の凸部の頂部は、コア部の中心部に位置してもよい。
第3の凸部の最大値は、第1の凸部の最大値より大きくてもよい。
屈折率分布Tは、コア部の中心に第3の凸部の頂部を有しており、第3の凸部の頂部から第2の凹部に向かって連続的に屈折率が低下している領域を有してもよい。
第1クラッド層に位置する屈折率分布Tは、第1クラッド層と第1コア部との境界近傍以外の領域に屈折率の最大値を有し、第1クラッド層とコア部との境界近傍に位置する領域に屈折率の最小値を有しており、かつ、当該最大値を示す部分から当該最小値を示す部分まで連続的に屈折率が低下している領域を有してもよい。
第2の凹部の頂部の屈折率とクラッド層における平均屈折率との屈折率差は、第2の凹部の頂部の屈折率と第3の凸部の頂部の屈折率との屈折率差の3~80%であってもよい。
第2の凹部の頂部の屈折率と第3の凸部の頂部の屈折率との屈折率差は、0.005~0.07であってもよい。
第1の凹部の頂部の屈折率とクラッド部における平均屈折率との差は、第1の凹部の頂部の屈折率と第1の凸部の頂部の屈折率との差の3~80%であってもよい。
第1の凹部の頂部の屈折率と第1の凸部の頂部の屈折率との屈折率差は、0.005~0.07であってもよい。
屈折率分布Wにおいて、第1の凸部の屈折率が、クラッド部における平均屈折率以上の値を有している部分の幅をa[μm]とし、第1の凹部の屈折率が、クラッド部における平均屈折率未満の値を有している幅をb[μm]としたとき、bは、0.01a~1.2aであってもよい。
(1) コア部と、該コア部の両側面に隣接する側面クラッド部と、を備えるコア層と、
該コア層の両面にそれぞれ積層されたクラッド層と、を有する光導波路であって、
前記コア層の横断面の幅方向の屈折率分布Wは、少なくとも2つの極小値と、少なくとも1つの第1の極大値と、前記第1の極大値より小さい少なくとも2つの第2の極大値と、を有し、これらが、第2の極大値、極小値、第1の極大値、極小値、第2の極大値の順で並ぶ領域を有しており、この領域のうち、前記第1の極大値を含むように前記2つの極小値で挟まれる領域が前記コア部、前記各極小値から前記第2の極大値側の領域が前記側面クラッド部であり、
前記各極小値は、前記クラッド部における平均屈折率未満であり、かつ、前記屈折率分布全体で屈折率が連続的に変化しており、
前記光導波路の横断面の厚さ方向の屈折率分布Tは、前記コア部に対応する領域および前記クラッド層に対応する領域のそれぞれで、屈折率がほぼ一定であり、かつ前記コア部と前記クラッド層との界面で屈折率が不連続的に変化していることを特徴とする光導波路。
前記屈折率分布Wは、前記第1の極大値近傍において上に凸の略U字状をなし、前記極小値近傍において下に凸の略U字状をなしている上記(1)ないし(5)のいずれかに記載の光導波路。
Claims (15)
- 第1クラッド層と、
前記第1クラッド層上に設けられており、層内方向に設けられたクラッド部、第1コア部、クラッド部、第2コア部、及びクラッド部をこの順番で有するコア層と、
前記コア層上に設けられた第2クラッド層と、
を備え、
前記コア層のうち前記第1コア部、及び前記クラッド部に亘る部分の層内方向の屈折率分布Wが、連続的に変化していて、第1の凸部、第1の凹部、及び第2の凸部の順で並ぶ領域を有しており、
前記第1コア部に位置する前記屈折率分布Wは、前記第1の凸部を有しており、
前記クラッド部に位置する前記屈折率分布Wは、前記第1の凸部よりも屈折率の最大値が小さい前記第2の凸部を有しており、
前記第1クラッド層及び前記第1コア部に亘る部分の層間方向の屈折率分布Tが、前記第1クラッド層と前記第1コア部との界面において不連続的に変化している、光導波路。 - 請求項1に記載の光導波路において、
前記第1クラッド層、前記クラッド部及び前記第2クラッド層に亘る部分の層間方向の屈折率分布Pが、前記第1クラッド層に位置する部分と前記クラッド部に位置する部分とで相異なる、
光導波路。 - 請求項1または2に記載の光導波路において、
前記第1クラッド層、前記第1コア部に亘る部分の層間方向の屈折率分布Tが、前記屈折率分布Wと相異なる、光導波路。 - 請求項1から3のいずれか1項に記載の光導波路において、
前記第1コア部の屈折率の最大値と前記第1クラッド層の屈折率の最大値との屈折率差は、前記第1コア部の屈折率の最大値と前記クラッド部の屈折率の最大値との屈折率差よりも、大きい、光導波路。 - 請求項1から4のいずれか1項に記載の光導波路において、
前記第2クラッド層上に設けられた、前記コア層と別部材の第2コア層を備え、
前記第2コア層は、前記第1コア部の層間方向に位置する第3コア部を有する、光導波路。 - 請求項1から5のいずれか1項に記載の光導波路において、
前記第1の凹部の頂部の屈折率は、前記クラッド部における平均屈折率より小さい、光導波路。 - 請求項1から6のいずれか1項に記載の光導波路において、
前記屈折率分布Wは、前記第1コア部と前記クラッド部の界面近傍以外に前記第2の凸部の頂部を有する、光導波路。 - 請求項1から7のいずれか1項に記載の光導波路において、
前記屈折率分布Wは、前記クラッド部の中心部に前記第2の凸部の頂部を有しており、前記第2の凸部の前記頂部から前記第1の凹部に向かって連続的に屈折率が低下している領域を有する、光導波路。 - 請求項1から8のいずれか1項に記載の光導波路において、
前記屈折率分布Tにおける前記第1コア部と前記第1クラッド層との屈折率差は、前記屈折率分布Wにおける前記第1の凹部の頂部と前記第1の凸部の頂部との屈折率差より大きい、光導波路。 - 請求項1から9のいずれか1項に記載の光導波路において、
前記第1コア部および前記第1クラッド層を横切るように設けられた空孔を有し、該空孔の内面により、前記コア部を伝送される光を反射する反射面が構成されている、光導波路。 - 請求項1から10のいずれか1項に記載の光導波路において、
前記第1の凹部の頂部の屈折率と前記クラッド部における平均屈折率との差は、前記第1の凹部の頂部の屈折率と前記第1の凸部の頂部の屈折率との差の3~80%である、光導波路。 - 請求項1から11のいずれか1項に記載の光導波路において、
前記第1の凹部の頂部の屈折率と前記第1の凸部の頂部の屈折率との屈折率差は、0.005~0.07である、光導波路。 - 請求項1から12のいずれか1項に記載の光導波路において、
前記屈折率分布Wにおいて、前記第1の凸部の屈折率が、前記クラッド部における平均屈折率以上の値を有している部分の幅をa[μm]とし、前記第1の凹部の屈折率が、前記クラッド部における平均屈折率未満の値を有している幅をb[μm]としたとき、bは、0.01a~1.2aである、光導波路。 - コア部と、該コア部の両側面に隣接する側面クラッド部と、を備えるコア層と、
該コア層の両面にそれぞれ積層されたクラッド層と、を有する光導波路であって、
前記コア層の横断面の幅方向の屈折率分布Wは、少なくとも2つの極小値と、少なくとも1つの第1の極大値と、前記第1の極大値より小さい少なくとも2つの第2の極大値と、を有し、これらが、第2の極大値、極小値、第1の極大値、極小値、第2の極大値の順で並ぶ領域を有しており、この領域のうち、前記第1の極大値を含むように前記2つの極小値で挟まれる領域が前記コア部、前記各極小値から前記第2の極大値側の領域が前記側面クラッド部であり、
前記各極小値は、前記クラッド部における平均屈折率未満であり、かつ、前記屈折率分布全体で屈折率が連続的に変化しており、
前記光導波路の横断面の厚さ方向の屈折率分布Tは、前記コア部に対応する領域および前記クラッド層に対応する領域のそれぞれで、屈折率がほぼ一定であり、かつ前記コア部と前記クラッド層との界面で屈折率が不連続的に変化していることを特徴とする光導波路。 - 請求項1から14のいずれか1項に記載の光導波路を備えることを特徴とする電子機器。
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US20130170803A1 (en) | 2013-07-04 |
JP2012068632A (ja) | 2012-04-05 |
TWI490573B (zh) | 2015-07-01 |
TW201219867A (en) | 2012-05-16 |
CN103080798A (zh) | 2013-05-01 |
CN103080798B (zh) | 2015-09-16 |
US9151888B2 (en) | 2015-10-06 |
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