JP2012181428A - Optical waveguide and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reliable optical waveguide with high transmission efficiency and high optical coupling efficiency relative to light-emitting/receiving elements, and an electronic apparatus having such an optical waveguide.SOLUTION: An optical waveguide 1 includes: a region in the vicinity of a light incident end part 1A thereof composed of an SI portion with a refractive index profile of a step index type on a line on a cross section; and regions not in the vicinity of the light incident end part 1A composed of a GI portion with a refractive index profile of a graded index type. A refractive index profile of a step index type refers to distribution in which a refractive index changes stepwise, and a refractive index profile of a graded index type refers to distribution which has a region with a high refractive index and regions adjoining the both side thereof with a low refractive index, in which the refractive index changes gradually. In addition, the optical waveguide 1 has a gradual decrement portion 6 in which a cross sectional area of a core portion 14 gradually decreases from the light incident end part 1A to a light emission end part 1B.

Description

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

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

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

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

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

  By replacing the electric wiring in the signal processing board with such an optical waveguide, it is expected that the problem of the electric wiring as described above is solved and the signal processing board can be further increased in throughput.

  Here, as the optical waveguide, conventionally, a step index type having a core portion having a constant refractive index and a clad portion having a constant refractive index lower than the core portion has been generally used. A graded index type with a continuously changing refractive index has been proposed.

  For example, Patent Document 1 proposes an optical waveguide in which a refractive index adjusting agent is diffused in a polymer substrate so that the refractive index is distributed concentrically in a cross section. According to such a graded index type optical waveguide, it is said that transmission loss can be reduced as compared with the step index type.

  However, the graded index type optical waveguide has a smaller cross-sectional area of the high refractive index portion corresponding to the core portion, and therefore, the optical coupling efficiency with the light emitting element that makes light incident is lower than the step index type optical waveguide. It is easy to become. For this reason, when aligning a light emitting element, high alignment precision is requested | required and the mounting ease is a problem.

JP 2006-276735 A

  An object of the present invention is to provide a highly reliable optical waveguide with high transmission efficiency and optical coupling efficiency with respect to a light receiving and emitting element, and an electronic device including such an optical waveguide.

Such an object is achieved by the present inventions (1) to (12) below.
(1) An optical waveguide having a core portion and a cladding portion adjacent to a side surface of the core portion,
When a line is drawn on the cross section, the refractive index distribution on the line has an SI part that is a step index type and a GI part that is a graded index type at any position in the longitudinal direction. And
An optical waveguide comprising a gradually decreasing portion in which the cross-sectional area of the core portion gradually decreases from the light incident side to the light emitting side of the optical waveguide.

  (2) The optical waveguide according to (1), wherein the SI part and the GI part are integrally connected at a connection part.

  (3) The refractive index distribution of the cross section in the connection portion is configured to gradually change from one of the step index type or the graded index type between one end and the other end of the connection portion. The optical waveguide according to (2).

  (4) The optical waveguide according to any one of (1) to (3), wherein the SI section is provided at a light incident end of the optical waveguide.

  (5) The optical waveguide according to any one of (1) to (4), wherein the GI unit is provided at a light emitting end of the optical waveguide.

  (6) The optical waveguide according to any one of (1) to (5), wherein a length of the GI part is longer than a length of the SI part.

  (7) The refractive index distribution in the GI portion includes two minimum values, one first maximum value, and two second maximum values smaller than the first maximum value, It includes 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, and the refractive index is continuously continuous as a whole. The optical waveguide according to any one of the above (1) to (6), which is a changing distribution.

  (8) The optical waveguide according to any one of (1) to (7), wherein the gradually decreasing portion is provided at an end of the optical waveguide.

(9) The optical waveguide has a strip shape,
When a line is drawn in the width direction of the optical waveguide on the cross section, the refractive index distribution W on the line has a step index type SI part and a graded index type GI part, respectively. At any position in the direction, and
When a line is drawn in the thickness direction of the optical waveguide on the cross section, the refractive index distribution T on the line is a step index type for the entire optical waveguide. The optical waveguide described.

(10) The optical waveguide has a strip shape,
When a line is drawn in the width direction and the thickness direction of the optical waveguide on the cross section, the refractive index distribution W in the width direction and the refractive index distribution T in the thickness direction on the line are step index types, respectively. And the GI part in which the refractive index distribution W and the refractive index distribution T are respectively graded index types, respectively, in any one of the positions in the longitudinal direction. The optical waveguide according to any one of the above.

  (11) The optical waveguide according to (9) or (10), wherein the gradually decreasing portion is formed by gradually decreasing the width of the core portion in plan view.

  (12) An electronic apparatus comprising the optical waveguide according to any one of (1) to (11).

  According to the present invention, it is possible to obtain an optical waveguide having high transmission efficiency and high optical coupling efficiency with respect to a light emitting / receiving element and the like and capable of performing highly reliable optical communication.

Further, by further optimizing the graded index type refractive index distribution, it is possible to further suppress the dullness of the pulse signal while further improving the transmission efficiency. Furthermore, when a plurality of core portions are formed to make a multi-channel, an optical waveguide that can reliably suppress crosstalk is obtained.
Further, by using such an optical waveguide, a highly reliable electronic device can be obtained.

1 is a perspective view showing a first embodiment of an optical waveguide of the present invention (partially cut out and shown through). It is the YY sectional view taken on the line shown in FIG. 3A is a cross-sectional view taken along the line X1-X1 of FIG. 1, and FIG. 3B is an example of the refractive index distribution W on the center line C1 drawn in the width direction of the cross-sectional view taken along the line X1-X1. FIG. 3C is a diagram schematically showing an example of the refractive index distribution T on the center line C2 drawn in the thickness direction of the X1-X1 line cross-sectional view. 4A is a cross-sectional view taken along the line X2-X2 of FIG. 1, and FIG. 4B is an example of the refractive index distribution W on the center line C3 drawn in the width direction of the cross-sectional view taken along the line X2-X2. FIG. 4C is a diagram schematically showing an example of the refractive index distribution T on the center line C4 drawn in the thickness direction of the X2-X2 line sectional view. It is a figure which shows intensity distribution of the emitted light when light injects into the core part of GI part. FIG. 2 is a plan view showing only one core portion in the optical waveguide shown in FIG. 1. It is another structural example of the gradual reduction part shown in FIG. It is another structural example of the gradual reduction part shown in FIG. It is another structural example of the gradual reduction part shown in FIG. 10A is a cross-sectional view taken along the line X2-X2 shown in FIG. 1 for the second embodiment, and FIG. 10B is a center line C4 drawn in the thickness direction of the cross-sectional view taken along the line X2-X2. It is a figure which shows an example of the upper refractive index distribution T typically. It is another structural example of the refractive index distribution T shown in FIG. It is sectional drawing which shows 3rd Embodiment of the optical waveguide of this invention. 13 is another configuration example of the gradual reduction unit shown in FIG. 12. 13 is another configuration example of the gradual reduction unit shown in FIG. 12. It is a figure for demonstrating the 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. It is a figure for demonstrating the 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. It is a figure for demonstrating the 1st manufacturing method of the optical waveguide shown in FIG. It is a figure for demonstrating a mode that a refractive index difference arises between an irradiation area | region and a non-irradiation area | region in the layer comprised with the composition for GI part formation, taking the position of the cross section of a layer on a horizontal axis, It is a figure which shows refractive index distribution when taking the refractive index of a surface on the vertical axis | shaft. It is a figure for demonstrating a mode that a refractive index difference arises between an irradiation area | region and a non-irradiation area | region in the layer comprised by the composition for SI part formation, taking the position of the cross section of a layer on a horizontal axis, It is a figure which shows refractive index distribution when taking the refractive index of a surface on the vertical axis | shaft. It is a figure for demonstrating the 3rd manufacturing method of the optical waveguide shown in FIG. It is a figure for demonstrating the manufacturing method of the optical waveguide shown in FIG. It is a figure for demonstrating the manufacturing method of the optical waveguide 1 shown in FIG.13 (c). It is a figure for demonstrating the manufacturing method of the optical waveguide 1 shown in FIG.13 (c). It is a figure for demonstrating the manufacturing method of the optical waveguide 1 shown in FIG.13 (c).

Hereinafter, the optical waveguide and the electronic device of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
<Optical waveguide>
<< First Embodiment >>
First, a first embodiment of the optical waveguide of the present invention will be described.

  FIG. 1 is a perspective view showing a first embodiment of the optical waveguide of the present invention (partially cut out and shown through), and FIG. 2 is a cross-sectional view taken along line YY shown in FIG. In the following description, the upper side in FIGS. 1 and 2 are exaggerated in the layer thickness direction (vertical direction in each figure).

  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. Here, as an example, a case where light is incident from the light incident end 1A of the optical waveguide 1 shown in FIG. 1 and light is emitted from the light emitting end 1B will be described.

  The optical waveguide 1 is formed by laminating a clad layer 11, a core layer 13, and a clad layer 12 in this order from the lower side in FIG. 1, and has an elongated strip shape.

  Further, in the core layer 13, two core portions 14 extending in parallel from the light incident end portion 1A to the light emitting end portion 1B are formed. In the core layer 13, a portion other than the core portion 14 is a side clad portion 15. In addition, a dense dot is attached | subjected to each core part 14 shown in FIG. 1, and a sparse dot is attached | subjected to each side clad part 15. FIG.

  In such an optical waveguide 1, the refractive index distribution is a step index type in the vicinity of the light incident end 1A. Specifically, in the vicinity of the light incident end portion 1A, when a line is drawn on the cross section, the refractive index distribution on the line changes in a step shape (step shape). In particular, the portions corresponding to the regions having a high refractive index are the core portions 14, and the portions corresponding to the regions having a relatively low refractive index are the cladding layers 11, 12 or the side cladding portions 15. In the present invention, the portion where the refractive index distribution is a step index type is provided at any position in the longitudinal direction of the optical waveguide 1 (in the vicinity of the light incident end 1A in this embodiment). The portion is referred to as an SI portion (reference numeral SI in FIGS. 1 and 2). In the present invention, the SI portion means that both the refractive index distribution W on the line drawn in the width direction of the optical waveguide 1 and the refractive index distribution T on the line drawn in the thickness direction are stepped. This means a distribution that has been changed into a step index distribution.

  On the other hand, the refractive index distribution of the optical waveguide 1 other than the vicinity of the light incident end 1A is a graded index type. Specifically, except for the vicinity of the light incident end 1A, when a line is drawn on the cross section, the refractive index distribution on the line is a region having a high refractive index and a region having a low refractive index adjacent to both sides thereof. And the refractive index is continuously changing. Then, based on this refractive index distribution, a portion corresponding to a region having a relatively high refractive index is each core portion 14, and a portion corresponding to a region having a relatively low refractive index is the cladding layer 11, 12 or the side cladding portion 15. It has become. In the present invention, the portion where the refractive index distribution is a graded index type is provided at any position in the longitudinal direction of the optical waveguide 1 (in the present embodiment, other than the vicinity of the light incident end 1A). This part is called a GI part (reference numeral GI in FIGS. 1 and 2). The GI portion in the present invention means that at least one or both of the refractive index distribution W on the line drawn in the width direction of the optical waveguide 1 and the refractive index distribution T on the line drawn in the thickness direction are on the transverse section. This means a distribution in which the above-described refractive index continuously changes, that is, a graded index distribution. Therefore, the GI portion includes a form in which either one of the refractive index distribution W and the refractive index distribution T is a step index type distribution. In the present embodiment, as an example, a description will be given of a form in which the refractive index distribution W is a graded index type distribution and the refractive index distribution T is a step index type distribution.

  Since the SI part and the GI part as described above are formed in one optical waveguide 1, the optical waveguide 1 has excellent optical coupling efficiency with a light emitting / receiving element, an optical fiber, or the like.

  In addition, the optical waveguide of the present invention has at least part of a gradually decreasing portion in which the cross-sectional area of the core portion 14 gradually decreases from the light incident side toward the light emitting side. With such a gradually decreasing portion, the cross sectional area of the core portion 14 on the light incident side is relatively large, and the cross sectional area of the core portion 14 on the light emitting side is relatively small. For this reason, the light emitted from the light emitting element can efficiently enter the large incident surface of the optical waveguide 1, while the light emitted from the small emitting surface of the optical waveguide 1 is narrowed down. Therefore, even if the area of the light receiving portion of the light receiving element is small, it can be made incident efficiently. Therefore, in addition to the SI portion and the GI portion described above, the optical waveguide 1 exhibits remarkable characteristics in the optical coupling efficiency with the light emitting / receiving element or the like by forming the gradually decreasing portion. It will be a thing. In the present embodiment, as an example, a form having a gradually decreasing portion configured so that the cross-sectional area gradually decreases over the entire length of the core portion 14 will be described.

Hereinafter, each part of the optical waveguide 1 will be described in detail.
As described above, the present embodiment has the SI portion located in the vicinity of the light incident end portion 1A and the GI portion located elsewhere.

(SI part)
Among these, in the SI portion, both the refractive index distribution W in the width direction and the refractive index distribution T in the thickness direction are distributions in which the refractive index changes stepwise (step index type distribution). The distribution in which the refractive index changes stepwise is a distribution having a region having a relatively high refractive index and a substantially constant value and a region having a relatively low refractive index and a substantially constant value. The incident light can be confined and propagated in a region having a high refractive index.

  3A is a cross-sectional view taken along the line X1-X1 of FIG. 1, and FIG. 3B is an example of the refractive index distribution W on the center line C1 drawn in the width direction of the cross-sectional view taken along the line X1-X1. FIG. 3C is a diagram schematically showing an example of the refractive index distribution T on the center line C2 drawn in the thickness direction of the X1-X1 line cross-sectional view.

  As described above, the refractive index distribution W shown in FIG. 3B has the relatively high refractive index regions W2 and W4 having a relatively high refractive index and a substantially constant value. It has low refractive index regions W1, W3, and W5 that take a certain value. The refractive index distribution W is distributed so that the low refractive index region W1, the high refractive index region W2, the low refractive index region W3, the high refractive index region W4, and the low refractive index region W5 are arranged in this order from the left side. For this reason, the low refractive index regions are adjacent to the left and right sides of the high refractive index region, and light is reflected at this interface. Therefore, the light incident on the high refractive index regions W2 and W4 is repeatedly reflected at the interfaces with the adjacent low refractive index regions W1, W3, and W5, and the light exit end 1A of the optical waveguide 1 exits the light exit end. The signal light can be propagated to the part 1B. Based on the magnitude relationship of the refractive indexes, the portions corresponding to the low refractive index regions W1, W3, and W5 are the side cladding portions 15, respectively, and the portions corresponding to the high refractive index regions W2 and W4 are the core portions 14, respectively. It becomes.

  On the other hand, as described above, the refractive index distribution T shown in FIG. 3C has a relatively high refractive index region T2 having a relatively high refractive index and a substantially constant value, and a relatively low refractive index and a substantially constant refractive index. It has low refractive index regions T1 and T3 having a constant value. The refractive index distribution T is distributed such that the low refractive index region T1, the high refractive index region T2, and the low refractive index region T3 are arranged in this order from the lower side. For this reason, the low refractive index regions are adjacent to the upper and lower sides of the high refractive index region, and light is reflected at this interface. Therefore, the light incident on the high refractive index region T2 is repeatedly reflected at the interface with the adjacent low refractive index regions T1 and T3, and the light incident end 1A of the optical waveguide 1 is directed to the light emitting end 1B. Signal light can be propagated. Based on the magnitude relationship of the refractive index, portions corresponding to the low refractive index regions T1 and T3 become the cladding layers 11 and 12, and a portion corresponding to the high refractive index region T2 becomes the core portion 14.

  The SI portion extends along the optical path of the optical waveguide 1, but the refractive index distribution and T as described above are set to be substantially the same distribution on the optical path of the SI portion.

  The refractive index of the core part 14 may be higher than the refractive index of the clad part (each clad layer 11, 12 and each side clad part 15), and the difference is not particularly limited, but 0.5% of the refractive index of the clad part. The above is preferable, and 0.8% or more is more preferable. On the other hand, the upper limit value may not be set, but is preferably about 5.5%. If the difference in refractive index is less than the lower limit, the effect of propagating light may be reduced, and even if the upper limit is exceeded, further increase in light transmission efficiency cannot be expected.

The refractive index difference is expressed by the following equation when the refractive index of the core portion 14 is n ₁ and the refractive index of the cladding portion is n ₂ .
Refractive index difference (%) = | n ₁ / n ₂ −1 | × 100

  Along with the refractive index distribution W as described above, the core layer 13 of the SI portion is provided with two long core portions 14 and three side clad portions 15 adjacent to the side surfaces of the core portions 14. It has been. Similarly, with the refractive index distribution T, the SI portion is provided with the core portion 14 and the cladding layers 11 and 12 adjacent to the upper and lower surfaces thereof.

  In such an SI portion, since the refractive index in the width direction and the thickness direction in the core portion 14 is substantially constant, the width of propagation of the signal light is wide and the thickness is also thick. For this reason, when the SI portion is exposed on the incident side end face, the light incident efficiency from the light emitting element to the optical waveguide 1 is increased. This is because the SI part has a large area through which signal light can propagate, so that the light-receiving area is larger than that of the GI part, and the light incident efficiency is relatively high. As a result, the optical coupling efficiency between the optical waveguide 1 and other optical elements can be increased.

  In addition, when the SI portion is exposed on the incident side end face, the area where the signal light from the light emitting element can be received is relatively large, so that the allowable amount of positional deviation of the light emitting element with respect to the optical waveguide 1 is further increased. be able to. In this case, when mounting the optical waveguide 1, high alignment accuracy is not required, so that mounting ease can be improved.

(GI Department)
In the GI portion, the refractive index distribution W in the width direction is a distribution in which the refractive index continuously changes (graded index type distribution), whereas the refractive index distribution T in the thickness direction has a stepped refractive index. It is a distribution that changes in a shape (step index type distribution).

  4A is a cross-sectional view taken along the line X2-X2 of FIG. 1, and FIG. 4B is an example of the refractive index distribution W on the center line C3 drawn in the width direction of the cross-sectional view taken along the line X2-X2. FIG. 4C is a diagram schematically showing an example of the refractive index distribution T on the center line C4 drawn in the thickness direction of the X2-X2 line sectional view.

  The refractive index distribution W shown in FIG. 4B is a distribution having a relatively high refractive index region and low regions adjacent to both sides thereof, and the refractive index continuously changing. Yes. In the cross-sectional view taken along the line X2-X2 shown in FIG. 4A, the portion corresponding to the region where the refractive index distribution W shown in FIG. 4B is high is the core portion 14, and the refractive index is low. A portion corresponding to the region is the side clad portion 15. The graded index type distribution may include a distribution in which the maximum value of the refractive index is located in the core portion 14 and the refractive index continuously decreases so as to draw a tail from both sides to the core portion 14. A distribution including a local minimum value or another local maximum value (a local maximum value smaller than the local maximum value) is also a type of graded index type distribution. Light incident on the core layer 13 having such a distribution is likely to concentrate in the vicinity of the maximum value. For this reason, the signal light propagating through the core portion 14 is more confined in the center portion, and leakage to the side clad portion 15 side is suppressed. As a result, the optical waveguide 1 with high transmission efficiency is obtained.

  The refractive index distribution W shown in FIG. 4B is a distribution that includes four local minimum values Ws1, Ws2, Ws3, and Ws4 and five local maximum values Wm1, Wm2, Wm3, Wm4, and Wm5. Further, 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).

  Among these, there are local maximum values Wm2 and Wm4 having a relatively high refractive index between the local minimum value Ws1 and the local minimum value Ws2, and between the local minimum value Ws3 and the local minimum value Ws4.

  In the GI portion, as shown in FIG. 4, since the maximum value Wm2 having a relatively high refractive index is located between the minimum value Ws1 and the minimum value Ws2, the portion corresponding to this region is the core portion. Similarly, since the local maximum value Wm4 is located between the local minimum value Ws3 and the local minimum value Ws4, the portion corresponding to this region also becomes the core portion 14. In FIG. 4, the core portion 141 is located between the minimum value Ws1 and the minimum value Ws2 in each core portion 14, and is positioned between the minimum value Ws3 and the minimum value Ws4. These are referred to as a core part 142.

  In addition, since 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 the side surfaces of the core part 14, this region. The portions corresponding to are side cladding portions 15. In FIG. 4, among the side clad portions 15, the side clad portion 151 is located on the left side of the minimum value Ws 1, and the side face is located between the minimum value Ws 2 and the minimum value Ws 3. The clad portion 152 is located on the right side of the minimum value Ws4 as the side clad portion 153.

  Thus, the refractive index distribution W has a region in which the second maximum value, the minimum value, the first maximum value, the minimum value, and the second maximum value are arranged in this order. In addition, this area | region is repeatedly provided according to the number of core parts. When there are two core portions 14 as in the present embodiment, the refractive index distribution W has the second maximum value, the minimum value, the first maximum value, the minimum value, the second maximum value, the minimum value, A local maximum value and a local minimum value are arranged alternately, such as a local maximum value, a local minimum value, and a second local maximum value, and the region where the first local maximum value and the second local maximum value are alternately arranged for the local maximum value. It only has to have. That is, the number of first local maximum values is set to the same number according to the number of core portions 14, and the number of second local maximum values and local minimum values is determined accordingly. For example, when the number of the core portions 14 is n, the refractive index distribution W may have n first maximum values, 2n minimum values, and n + 1 second maximum values. It should be noted that such a fixed rule for the maximum value and the minimum value does not need to be applied to the entire refractive index distribution W, and only needs to be applied to a part of the refractive index distribution W.

  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 value is the first local maximum value or the second local maximum value. As long as the relationship that the second maximum value is lower than the first maximum value and the second maximum value is lower than the first maximum value is maintained, 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 GI portion extends along the optical path of the optical waveguide 1, but the refractive index distribution W as described above is set to be substantially the same distribution on the optical path of the optical waveguide 1.

  Along with the refractive index distribution W as described above, the core layer 13 of the GI part is formed with two long core parts 14 and three side clad parts 15 adjacent to the side surfaces of these core parts 14. Will be.

  Since the average refractive index of the two core parts 141 and 142 is higher than the average refractive index of the three side clad parts 151, 152, and 153, the core parts 141 and 142 and the side clad parts 151, 152, and 153 It is possible to cause reflection of light at the interface with the.

  Here, the four minimum values Ws1, Ws2, Ws3, and Ws4 are each less than the average refractive index WA in the side clad portion 15. As a result, 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. As a result, a steeper refractive index gradient is formed in the vicinity of the boundary between each core portion 14 and each side clad portion 15, thereby reliably suppressing light leakage from each core portion 14. Become. As a result, transmission loss can be particularly reduced in the GI unit.

  Further, the refractive index distribution W changes continuously as a whole. As a result, the effect of confining light in the core portion 14 is further enhanced as compared with the SI portion, so that transmission loss can be further reduced.

  Furthermore, according to the refractive index distribution W as described above, since the signal light propagates intensively in a portion closer to the center of the core portion 14, a difference is hardly generated in the propagation time for each optical path. For this reason, even when a pulse signal is included in the signal light, blunting of the pulse signal (spreading of the pulse signal) can be suppressed. As a result, the quality of optical communication can be further improved in the GI unit.

  In addition, the refractive index continuously changing in the refractive index distribution W means that the curve of the refractive index distribution W is rounded at each part and is a differentiable curve.

  In addition, when the core portion 14 and the side cladding portion 15 are formed in the core layer 13 as in the present embodiment, generally, the average refraction of the core portion 14 is limited due to the restriction due to the principle of forming a refractive index difference. Although it is difficult to form a sufficient refractive index difference between the refractive index and the average refractive index of the side cladding portion 15, according to the present invention, even if the average refractive index difference is small, light is reliably transmitted to the core portion. Can be trapped in. For this reason, in the GI part manufactured by the method which forms the core part 14 and the side clad part 15 from the same layer, this invention exhibits the effect especially.

  Further, in the refractive index distribution W, the maximum values Wm2 and Wm4 are between the minimum values Ws1 and Ws2 (core portion 141) and between the minimum values Ws3 and Ws4 (core portion 142), as shown in FIG. However, among the core parts 141 and 142, it is preferable to be located in the center part of the width. Thereby, in each core part 141 and 142, the probability that signal light will gather in the center part of the width of core part 141 and 142 will become high, and the probability that it will leak to side cladding parts 151, 152, and 153 becomes relatively low. As a result, 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 position of the minimum value Ws1 and the position of the minimum value Ws2.

  In addition, the positions of the maximum values Wm2 and Wm4 are not necessarily the center, but if they are located in the vicinity of the edges of the cores 141 and 142 (near the interfaces with the side clad parts 151, 152, and 153). , A significant decline in properties is avoided. That is, the transmission loss of the core parts 141 and 142 can be suppressed to some extent.

  In addition, the edge part vicinity of the core part 141 is an area | region of 5% of the width | variety of the core part 141 inside the edge part mentioned above inside.

  On the other hand, in the refractive index distribution W, the maximum values Wm1, Wm3, and Wm5 are, as shown in FIG. Portion 152) is located on the right side (side clad portion 153) of the minimum value Ws4, but is particularly located near the edge of the side clad portions 151, 152, 153 (near the interface with the core portions 141, 142). It is preferable. As a result, 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 signal light leaks into the side clad parts 151, 152, 153. As a result, the transmission loss of the core parts 141 and 142 can be reduced.

  Note that the vicinity of the edges 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 above-described edge portion 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, respectively. , Ws3, Ws4, it is preferable that the refractive index continuously decreases. As a result, 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. Since light can be reliably confined in the vicinity of Wm1, Wm3, and Wm5, leakage of signal light from the core portions 141 and 142 described above can be more reliably suppressed.

  Further, the local maximum values Wm1, Wm3, and Wm5 are relatively smaller than the local maximum values Wm2 and Wm4 located in the core portions 141 and 142 described above. Since the refractive index is slightly higher than that of the surroundings, the side cladding portions 151, 152, and 153 have a slight light transmission property. As a result, the side clad parts 151, 152, 153 can confine the signal light leaked from the core parts 141, 142, and can prevent the leaked signal light from spreading to other core parts. To do. That is, the presence of the maximum values Wm1, Wm3, and Wm5 can suppress crosstalk between the core portions 14.

  Note that, as described above, 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. It is preferably about 3 to 80% of the difference from Wm4, more preferably about 5 to 50%, and still more preferably about 7 to 30%. As a result, the side clad portion 15 has a light transmission property necessary and sufficient for suppressing crosstalk. If the difference between the minimum value Ws1, Ws2, Ws3, Ws4 and the average refractive index WA of the side cladding 15 is below the lower limit, the light transmission in the side cladding 15 is too small and crosstalk is sufficient. If the value exceeds the upper limit, the light transmission property of the side cladding portion 15 is too large, and the light transmission properties of the core portions 141 and 142 may be adversely affected.

  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. Preferably, it is about 0.007 to 0.05, more preferably about 0.01 to 0.05. Thereby, the above-described difference in refractive index becomes necessary and sufficient for confining light in the core portions 141 and 142.

  Further, as shown in FIG. 4B, the refractive index distribution W in the core portions 141 and 142 is obtained when the horizontal axis indicates the position in the width direction of the cross section of the core layer 13 and the vertical axis indicates the refractive index. Any shape may be used as long as it continuously changes in the vicinity of the maximum value Wm2 and in the vicinity of the maximum value Wm4, but preferably has a substantially U-shape that is convex upward (the entire vicinity of the maximum value is rounded) Is done. When the refractive index distribution W has such a shape, the light confinement action in the core portions 141 and 142 becomes more remarkable.

  Further, as shown in FIG. 4B, the refractive index distribution W in the GI section has a refractive index continuously changing 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. However, it is preferably a substantially U-shape that protrudes downward (the entire vicinity of the minimum value is rounded).

  In the GI portion in which the refractive index distribution W as described above is formed, when light is incident on one of the plurality of core portions 141 and 142, leakage of light to the other core portion is suppressed. Is done. That is, crosstalk can be reliably suppressed in the GI unit.

  FIG. 5 is a diagram showing the intensity distribution of the emitted light when light is incident on the core part 141 of the GI part.

  When light is incident on the core part 141 of the GI part, the intensity of the emitted light is highest at the center of the emission end face 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. However, in the GI portion, an intensity distribution that takes a minimum value in the core portion 142 adjacent to the core portion 141 is obtained. As described above, in the GI portion, the minimum value of the intensity distribution of the emitted light coincides with the position of the core portion 142 adjacent to the core portion 141 where the light is incident, so that the crosstalk in the core portion 142 can be suppressed to be extremely small. . As a result, the GI unit can reliably prevent the occurrence of interference even when the number of channels is increased and the density is increased.

  Such an intensity distribution of the emitted light is considered to be caused by a characteristic distribution shape of the refractive index distribution W in the GI portion. That is, the refractive index distribution W has a characteristic distribution in which the refractive index distribution W has a minimum value and two adjacent maximum values having different heights, and the refractive index continuously changes as a whole. Therefore, the light leaking to the core part 142 in the prior art is shifted to the side clad part 153 etc. adjacent to the core part 142, and as a result, the minimum value of the intensity distribution is located in the core part 142. It is thought that it became. For this reason, crosstalk is suppressed in the GI part, and the optical waveguide 1 having this GI part can suppress the occurrence of crosstalk and improve the quality of optical communication.

  Even if the intensity distribution of the emitted light is shifted to the side clad portion 15, the light receiving element and the like are arranged in accordance with the position of the core portion 14, so that there is little possibility of causing interference and the quality of optical communication is deteriorated. I will not let you.

  The intensity distribution of the emitted light as described above is not necessarily observed if the refractive index distribution W is as described above. The NA (numerical aperture) of the incident light and the crossing of the core portion 141 are not necessarily observed. Depending on the area, the pitch of the core portions 141 and 142, etc., a clear minimum value may not be observed, or the position of the minimum value may deviate from the core portion 142. Even in such a case, crosstalk is sufficient. To be suppressed.

  Further, in the refractive index distribution W shown in FIG. 4B, when the average refractive index in the side cladding portion 15 is WA, the refractive index near the maximum values Wm2 and Wm4 is continuously equal to or higher than the average refractive index WA. Is a [μm], 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 [μm]. At this time, 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. As a result, the substantial widths of the minimum values Ws1, Ws2, Ws3, and Ws4 become necessary and sufficient for providing the above-described functions and effects. That is, when b is below the lower limit value, the substantial widths of the minimum values Ws1, Ws2, Ws3, and Ws4 are too narrow, and the action of confining light in the core portions 141 and 142 may be reduced. On the other hand, when b exceeds the upper limit value, the substantial widths of the local minimum values Ws1, Ws2, Ws3, and Ws4 are too wide, and the width and pitch of the core portions 141 and 142 are limited accordingly, and transmission is performed. There is a possibility that the efficiency may be lowered and the increase in the number of channels and the increase in density may be hindered.

  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.

  On the other hand, the refractive index distribution T shown in FIG. 4C is the same as the refractive index distribution T in the SI portion. That is, it has a high refractive index region T2 having a relatively high refractive index and a substantially constant value, and low refractive index regions T1 and T3 having a relatively low refractive index and a substantially constant value. . Then, a low refractive index region T1, a high refractive index region T2, and a low refractive index region T3 are distributed in this order from the lower side of FIG. The portions corresponding to the low refractive index regions T1 and T3 become the cladding layers 11 and 12, and the portions corresponding to the high refractive index region T2 become the core portion 14.

  In such a GI part, since the refractive index in the width direction of the core part 14 is higher in the center part, the width of propagation of the signal light is narrow, but the signal light tends to concentrate in the center part. For this reason, when the GI part is exposed at the output side end face, the light incident efficiency from the optical waveguide 1 to the light receiving element is increased. As a result, the optical coupling efficiency between the optical waveguide 1 and other optical elements can be increased.

  In the present specification, for convenience of explanation, the core layer 13 is described as being divided into the core portion 14 and the side clad portion 15, but as described above, the change in the refractive index distribution W is continuous. At the same time, the composition of the interface at each part also changes continuously. Therefore, the boundary between the layers is not clear, and the boundary may not be visually recognized.

(Connection between SI and GI)
The SI unit and the GI unit as described above are connected at the connection unit 5. The connecting portion 5 can be formed by a method in which the SI portion and the GI portion are separately manufactured and then combined with each other, but the SI portion and the GI portion are formed by a method in which the SI portion and the GI portion are integrally manufactured. preferable. Thereby, in the connection part 5, SI part and GI part will be connected integrally. As a result, the optical waveguide 1 having high mechanical strength of the connecting portion 5 and excellent optical coupling efficiency between the SI portion and the GI portion is obtained.

  Here, it is preferable that the refractive index distribution W and the refractive index distribution T in the connection portion 5 are connected so as to gradually change between the SI portion and the GI portion. Thereby, the transmission efficiency at the time of a signal light moving from SI part to GI part can be improved more. That is, if the refractive index distribution is connected discontinuously at the connection portion 5, the signal light may be scattered, reflected, or the like at that location, and the signal light may be attenuated. Therefore, when the optical waveguide 1 is manufactured by separately manufacturing the SI portion and the GI portion and bonding them, the optical coupling loss at the connection portion may be slightly increased although the effect of the present invention is obtained. is there.

  When the refractive index distribution is gradually changed in the connection portion 5, the length of the connection portion 5 is appropriately set according to the total length of the optical waveguide 1. Specifically, it is preferably about 0.5 to 20% of the total length of the optical waveguide 1, and more preferably about 1 to 15%. By setting the length of the connecting portion 5 within the above range, the rate of change in the refractive index distribution at the connecting portion 5 becomes relatively gradual, so that the decrease in the optical coupling between the SI portion and the GI portion is reliably suppressed. It is possible to prevent the connection portion 5 from becoming too long and adversely affecting the overall transmission efficiency of the optical waveguide 1.

  1 and 2, the length of the GI portion is configured to be longer than the length of the SI portion. Thereby, it can prevent that the transmission efficiency of the whole optical waveguide 1 falls. This is because the SI part has high incident efficiency of signal light, but the transmission efficiency is inferior to that of the GI part. Therefore, if at least the vicinity of the light incident end 1A is the SI part, the other part is the GI part. This is because it is effective from the viewpoint of overall transmission efficiency. Specifically, the length of the SI portion is preferably about 0.5 to 20% of the entire optical waveguide 1, and more preferably about 1 to 15%. By making the length of the SI part within the above range, the signal light incident efficiency in the SI part, the signal light transmission efficiency in the GI part, and the coupling efficiency with other optical devices can be highly compatible. .

  As described above, the optical waveguide of the present invention includes both the SI part and the GI part, so that the transmission efficiency and the optical coupling efficiency with other optical elements can be highly compatible.

  In both the SI part and the GI part, in FIG. 1, the core part 14 is linearly formed in a plan view, but may be curved, branched or the like in the middle, and its shape is arbitrary.

  Further, the cross-sectional shape of the core portion 14 shown in FIG. 1 is not limited to a square or a rectangle such as a rectangle as shown in FIG. Polygons such as pentagons and hexagons may be used.

  The width and height of the core part 14 (thickness of the core layer 13) are not particularly limited, but each is preferably about 1 to 200 μm, more preferably about 5 to 100 μm, and about 20 to 70 μm. More preferably.

  In the SI part and the GI part as described above, as the constituent material (main material) of the core layer 13, acrylic resin, methacrylic resin, polycarbonate, polystyrene, epoxy resin, polyamide, polyimide, polybenzoxazole, polysilane, polysilazane, In addition to various resin materials such as silicone resins, fluorine resins, polyurethane, cyclic olefin resins such as benzocyclobutene resins and norbornene resins, glass materials such as quartz glass and borosilicate glass can be used. The resin material may be a composite material obtained by combining materials having different compositions, and may contain an unpolymerized monomer.

  Of these, norbornene resins are particularly preferable. 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).

  On the other hand, in the SI part and the GI part, examples of the constituent material of the cladding layers 11 and 12 include the same material as the constituent material of the core layer 13 described above, and a norbornene-based polymer is particularly preferably used.

  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 (average height of each core portion 14). More preferably, the average thickness of the cladding layers 11 and 12 is not particularly limited, but is usually preferably about 1 to 200 μm and about 5 to 100 μm. It is more preferable that the thickness is about 10 to 60 μm. Thereby, the function as a clad part is suitably exhibited while preventing the optical waveguide 1 from becoming unnecessarily large (thickened).

  Further, 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 refractive index difference between them. Specifically, in order to reflect light reliably 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.

  From the viewpoint of suppressing light attenuation, it is also important that 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. By using the same constituent materials for both, the adhesion at the interface can be enhanced.

  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). However, since the refractive index of air is sufficiently low, the air substitutes for the functions of the cladding layers 11 and 12, and the signal light Propagation is possible.

(Gradual reduction part)
The optical waveguide 1 also has a gradually decreasing portion 6 configured so that the cross-sectional area gradually decreases over the entire length of the core portion 14.

FIG. 6 is a plan view showing only one of the core portions of the optical waveguide 1 shown in FIG.
The cross-sectional area of the gradually decreasing portion 6 is the largest at the light incident end 1A and the smallest at the light emitting end 1B. Then, from the light incident end 1A to the light exit end 1B, the cross-sectional area changes so as to have a constant reduction rate.

  As a pattern in which the cross-sectional area gradually decreases, the thickness of the core portion 14 is constant and the width gradually decreases, the case where the width of the core portion 14 is constant and the thickness gradually decreases, and the core portion 14 The case where both the width and the thickness of the core portion 14 gradually decrease can be mentioned. Here, the case where the thickness of the core portion 14 is constant and the width gradually decreases will be described.

  As shown in FIG. 6, when the width of the core portion 14 at the light incident end portion 1A is p1, and the width of the core portion 14 at the light emission end portion 1B is p2, p2 is preferably 0.1 to 0.1 of p1. About 0.9 times, more preferably about 0.2 to 0.8 times p1. Thereby, the optical coupling efficiency between the optical waveguide 1 and the light emitting / receiving element can be further increased.

  In addition, although p2 is suitably set according to the magnitude | size of the light-receiving part of a light receiving element, it is preferable that it is about 5-1000 micrometers as an example, and it is more preferable that it is about 10-500 micrometers.

  Moreover, p1 and p2 are set according to the thickness of the core part 14. Specifically, when the thickness of the core portion 14 is 1, p1 and p2 are each preferably about 0.5 to 2, and more preferably about 0.75 to 1.5. If p1 and p2 are within the above ranges, the aspect ratio of the entrance surface and the exit surface of the core portion 14 does not become too flat, so that it is possible to prevent the optical coupling efficiency with respect to the light emitting / receiving element from being significantly lowered.

  Further, the angle α1 formed by the boundary line between the core part 14 and the side cladding part 15 and the end surface at the light incident end part 1A, and the boundary line between the core part 14 and the side cladding part 15 at the light emitting end part 1B. The angle α2 formed by the end face is preferably not less than 45 degrees and less than 90 degrees, more preferably not less than 50 degrees and not more than 89 degrees. Thereby, the probability that light leaks from the core portion 14 to the side cladding portion 15 can be further reduced. Note that the angles between the boundary line between the core portion 14 and the side cladding portion 15 and the end face are α1 and α2 which are 90 degrees or less.

  The shape of the gradually decreasing portion 6 is preferably symmetrical with respect to a center line C that passes through the center of the width of the core portion 14 and is parallel to the extending direction of the core portion 14. Thereby, the intensity distribution of the signal light emitted from the emission end is also a line-symmetric distribution with respect to the center line. As a result, the deviation of the intensity of the signal light can be suppressed, and the optical coupling efficiency with the light receiving element can be further increased compared to the case where the signal light is not line symmetric.

  The boundary line between the core part 14 and the side cladding part 15 may be a straight line or a curved line, but preferably does not include a discontinuous shape. If it does not include a discontinuous shape, that is, if the boundary line is a smooth shape, unintended reflection or scattering of signal light can be suppressed, and a decrease in transmission efficiency can be suppressed.

Here, another configuration example of the gradual reduction unit 6 will be described.
7 to 9 are other configuration examples of the gradual reduction unit 6 shown in FIG. 7 and 8 are plan views showing only one of the core parts, and FIG. 9 is a plan view showing two of the core parts.

  The gradually decreasing portion 6 shown in FIG. 7 is the same as the gradually decreasing portion 6 shown in FIG. 6 except that only a part in the longitudinal direction of the core portion 14 is gradually reduced.

  Specifically, the optical waveguide 1 shown in FIG. 7 is provided with two gradually decreasing portions 6, one of which is provided in the vicinity of the light incident end 1 </ b> A and the other one is the light emitting end 1 </ b> B. It is provided in the vicinity. Further, the width is constant between the two gradually decreasing portions 6.

  Note that the position of the gradually decreasing portion 6 provided in the vicinity of the light incident end portion 1A may not coincide with the position of the SI portion described above, but preferably coincides. As a result, when signal light propagates from the SI part to the GI part, the incident characteristics to the GI part are improved by the effect of the gradual reduction part 6, so that the connectivity between the SI part and the GI part is particularly good. As a result, the transmission efficiency of the entire optical waveguide 1 can be further increased.

  The gradually decreasing portion 6 shown in FIG. 8 is the same as the gradually decreasing portion 6 shown in FIG. 7 except that the boundary line between the core portion 14 and the side cladding portion 15 is curved.

Each of these curves is a parabola that opens toward the light incident end 1 </ b> A side, and the focal point of the parabola is located at substantially the center in the width direction of the core part 14. For this reason, the signal light reflected at the boundary line between the core portion 14 and the side cladding portion 15 is collected near the focal point, and as a result, leakage of light to the side cladding portion 15 side is suppressed. The Further, in the gradual decrease portion 6 provided in the vicinity of the light emitting end portion 1B, the emitted light is narrowed down by collecting the signal light. As a result, the optical coupling efficiency for the light receiving element can be further increased.
Even with such an optical waveguide 1, the same operations and effects as those of the optical waveguide 1 shown in FIG. 1 can be obtained.

  The gradually decreasing portion 6 shown in FIG. 9 is the same as the gradually decreasing portion 6 shown in FIG. 6 except that the direction in which the cross-sectional area decreases in the two core portions 14 is different from each other.

  That is, the core portion 141 is configured so that the cross-sectional area gradually decreases from the left to the right in FIG. 9, whereas the core portion 142 conversely crosses from the right to the left in FIG. 9. The area is configured to gradually decrease. By arranging the gradually decreasing portion 6 in this way, it is possible to prevent the distance between the core portion 141 and the core portion 142 from significantly increasing or decreasing. That is, if the direction in which the cross-sectional area decreases is the same, there are places where the separation distance is small and large, so there is a risk that crosstalk may occur in smaller places, but the direction in which the cross-sectional area decreases If it is reversed, the change in the separation distance can be reduced, and the occurrence of crosstalk can be suppressed.

  In this case, if the direction in which light is incident is reversed between the core part 141 and the core part 142, the same operations and effects as those of the optical waveguide 1 shown in FIG. 1 can be obtained.

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

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

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

  Moreover, although the average thickness of the support film 2 is not specifically limited, It is preferable that it is about 5-200 micrometers, and it is more preferable that it is about 10-100 micrometers. Thereby, since the support film 2 has moderate rigidity, 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.

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

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

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

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

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

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

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

  In the present embodiment, 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.

  Moreover, although this embodiment demonstrated the case where the core layer 13 had the two core parts 14, the number of the core parts 14 is not specifically limited, One or three or more may be sufficient. .

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

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

  In the first embodiment described above, in the GI portion, only the refractive index distribution W on the line drawn in the width direction on the cross section is a graded index type distribution, and the refractive index distribution T on the line drawn in the thickness direction is In this embodiment, both the refractive index distribution W and the refractive index distribution T are graded index distributions in the GI portion. The rest is the same as in the first embodiment.

  10A is a cross-sectional view taken along the line X2-X2 shown in FIG. 1 for the second embodiment, and FIG. 10B is a center line C4 drawn in the thickness direction of the cross-sectional view taken along the line X2-X2. It is a figure which shows an example of the upper refractive index distribution T typically.

  The refractive index distribution T shown in FIG. 10B is different from the refractive index distribution T shown in FIG. Hereinafter, this distribution will be particularly described.

10 the refractive index distribution T shown in (b), the thickness of the substantially centrally located and the high refractive index region T _H whose refractive index is substantially constant, the high refractive index region T _H in the thickness direction of the GI section located on both sides of the direction, the refractive index area T _M in which the refractive index is continuously reduced toward both sides in the thickness direction, positioned on both sides in the thickness direction of the medium refractive index region T _M, And a low refractive index region T _L having a substantially constant refractive index. That is, of the refractive index distribution T, the refractive index of the high refractive index region T _H is relatively high, the refractive index of the low refractive index region T _L is relatively lower than the high refractive index region T _H, the medium refractive index region in T _M, and low refractive index region T _L refractive index so as to connect the refractive index of the high refractive index region T _H is continuously changed.

In such a refractive index distribution T, the core portion 14 corresponds to the high refractive index region T _H and the middle refractive index region T _M , and each cladding layer 11 corresponds to the low refractive index region T _L. 12.

In other words, the core unit 14 includes a high refractive index layer corresponding to the high refractive index region T _H, is constituted by an intermediate layer corresponding to the intermediate refractive index area T _M, the cladding layers 11 and 12, respectively And a low refractive index layer corresponding to the low refractive index region _TL .

In the GI portion having such a refractive index distribution T, in the middle refractive index region _TM , the light incident on the core portion 14 is propagated while gradually changing its optical path toward the central axis side of the core portion 14. The behavior is shown. For this reason, the incident light propagates along the central axis of the core portion 14 and hardly leaks to the clad layers 11 and 12 side. As a result, in the GI unit having such a refractive index distribution T, transmission loss is suppressed.

Here, in the refractive index distribution T shown in FIG. 10, the high refractive index region _TH is located at the center of the core portion 14 in the thickness direction. Thereby, the probability that the light propagating through the core part 14 gathers at the center part in the thickness direction of the core part 14 is high, and the probability of leaking into the clad layers 11 and 12 is relatively lower. As a result, the transmission loss of the core unit 14 can be further reduced.

  Further, such a refractive index distribution T has an effect of reliably preventing the occurrence of crosstalk between the layers (between the optical waveguides) particularly in the optical waveguide formed by laminating a plurality of the optical waveguides 1 described above. Bring. Specifically, when light is incident on the first-layer core portion 14, the light is reliably prevented from entering the second-layer core portion 14 and causing interference. Therefore, the GI portion shown in FIG. 10 facilitates the increase in the number of channels and the increase in density in the thickness direction.

  In addition, the center part of the area | region corresponding to the core part 14 is an area | region of the distance of 30% of the thickness of the core part 14, on both sides from the middle point of the thickness direction of the core part 14.

The position of the high refractive index region T _H may not necessarily be the center of the region corresponding to the core portion 14, in addition to near the edge of the core portion 14 (the vicinity of the interface between the cladding layers 11 and 12) If it is located, the characteristic deterioration is avoided. Thereby, the transmission loss of the core part 14 can be suppressed to some extent.

  In addition, the edge part vicinity of the core part 14 is an area | region of 5% of the thickness of the core part 14 inside from the edge part mentioned above inside.

Also, of the refractive index distribution T, the ratio of the refractive index difference between the refractive index n _L in the refractive index n _H in the high refractive index region T _H, the low refractive index region T _{L (cladding} layer 11 and the cladding layer 12) ( proportion to the refractive index _{n L),} the more as large as possible good, preferably is not less than 0.5% of the refractive index of the cladding layers 11 and 12, 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.

In addition, the ratio of the refractive index difference between the refractive index n _H and the refractive index n _L is expressed by the following equation.
Refractive index difference ratio (%) = | n _H / n _L −1 | × 100

Further, in the high refractive index region _TH and the low refractive index region _TL , the refractive index is substantially constant. Specifically, the deviation from the average refractive index in each region is 10% or less of the average refractive index. It is preferable that it is 5% or less.

  Based on the refractive index distribution T as described above, the optical waveguide 1 is divided into three layers: a clad layer 11, a core layer 13 (core portion 14), and a clad layer 12.

  In the present specification, for convenience of explanation, the optical waveguide 1 is divided into the above three layers. However, as described above, the change in the refractive index distribution T is continuous, and at the same time, at the interface of the three layers. Since the composition also changes continuously, the boundaries between the layers are not clear, and the boundaries may not be visually identifiable.

(Other configuration examples)
Further, the refractive index in the high refractive index region _{TH and} the refractive index in the low refractive index region _TL may not be constant, and the entire refractive index distribution T may be continuously changed.
FIG. 11 shows another configuration example of the refractive index profile T shown in FIG.

  Hereinafter, the refractive index distribution T shown in FIG. 10 will be described. The GI portion shown in FIG. 11 is the same as the GI portion shown in FIG. 10 except that the shape of the refractive index distribution T is different.

  The refractive index distribution T shown in FIG. 11 has a local maximum value Tm located at the center thereof and local minimum values Ts1 and Ts2 positioned on both sides of the local maximum value Tm. For convenience of explanation, of the local minimum values shown in FIG. 11, the local minimum value located below the local maximum value Tm is Ts1, and the local minimum value located above is Ts2.

  In the optical waveguide 1, as shown in FIG. 11, a region between the local minimum value Ts 1 and the local minimum value Ts 2 includes the local maximum value Tm, and this region becomes the core portion 14.

  On the other hand, the region below the minimum value Ts1 becomes the cladding layer 11, and the region above the minimum value Ts2 becomes the cladding layer 12.

  That is, the refractive index distribution T has a region where the minimum value, the maximum value, and the minimum value are arranged in this order.

  This region is repeatedly provided according to the number of stacked optical waveguides 1. For example, when two optical waveguides 1 are stacked, in the refractive index distribution T, four minimum values and three maximum values are alternately arranged. It becomes. In this case, it is preferable that the relatively large first maximum value and the relatively small second maximum value are alternately arranged. That is, the second maximum value, the minimum value, the first maximum value, the minimum value, the second maximum value, the minimum value, the first maximum value,... It is preferable to line up like this.

  The plurality of minimum values and the plurality of maximum values are preferably substantially the same as each other, but 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 a plurality of minimum values.

  Here, the minimum values Ts1 and Ts2 are less than the average refractive index TA in the cladding layers 11 and 12, respectively. As a result, a region having a smaller refractive index than the clad layers 11 and 12 exists between the core portion 14 and the clad layers 11 and 12. As a result, a steeper refractive index gradient is formed in the vicinity of the local minimum values Ts1 and Ts2, thereby reliably suppressing light leakage from the respective core portions 14 to the respective cladding layers 11 and 12. It becomes. As a result, a GI unit with particularly small transmission loss is obtained.

  Further, the refractive index distribution T continuously changes in refractive index as a whole. As a result, the effect of confining light in the core portion 14 is further enhanced as compared with the SI portion having a refractive index distribution in which the refractive index changes stepwise, and therefore transmission loss can be further reduced.

  Furthermore, according to the refractive index distribution T having the respective minimum values Ts1 and Ts2 as described above and the refractive index continuously changing, the transmission light is concentrated in a region closer to the center of the core portion 14. Therefore, 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 quality of optical communication can be further improved in the GI unit.

  In addition, the refractive index continuously changing in the refractive index distribution T means that the curve of the refractive index distribution T is rounded at each part and is a differentiable curve.

  Further, in the refractive index distribution T, the maximum value Tm is located at the center of the thickness of the core portion 14 as shown in FIG. Thereby, in the core part 14, the probability that signal light will gather in the center part of the thickness of the core part 14 will become high, and the probability that it will leak to each clad layer 11 and 12 relatively becomes low. As a result, the transmission loss of the core parts 141 and 142 can be further reduced.

  The central portion of the thickness of the core portion 14 is a region having a distance of 30% of the thickness of the core portion 14 on both sides from the midpoint between the minimum value Ts1 and the minimum value Ts2.

  In addition, even if the position of the maximum value Tm is not necessarily the central portion, if the position is near the edge portion of the core portion 14 (near the interface with each of the cladding layers 11 and 12), the significant deterioration in characteristics can be avoided. . That is, the transmission loss of the core unit 14 can be suppressed to some extent.

  In addition, the edge part vicinity of the core part 14 is an area | region of 5% of the thickness of the core part 14 inside from the edge part mentioned above inside.

  On the other hand, in the refractive index distribution T, the refractive index of each cladding layer 11 and 12 changes so as to be the highest except for the vicinity of the interface with the core portion 14 and the lowest in the vicinity of the interface with the core portion 14. As a result, the maximum value Tm in the core portion 14 and the high refractive index region in each of the cladding layers 11 and 12 are sufficiently separated from each other. The probability of leaking into the layers 11, 12 can be made sufficiently low. As a result, the transmission loss of the core unit 14 can be reduced.

  Note that the vicinity of the interface with the core portion 14 in each of the cladding layers 11 and 12 is a region having a distance of 5% of the thickness of each of the cladding layers 11 and 12 inward from the interface.

  Further, the average refractive index TA in each of the cladding layers 11 and 12 can be approximated at the midpoint between the minimum values Ts1 and Ts2 and the maximum value in each of the cladding layers 11 and 12.

  As described above, when a plurality of optical waveguides 1 are stacked, a relatively large first maximum value is located in the core portion, and a relatively small second maximum value is located in the cladding layer. Will be. In this case, it is preferable that the second maximum value is located at the center of the thickness of the cladding layer. Thereby, the separation distance between the first maximum value located in the core portion and the second maximum value located in the cladding layer is ensured to the maximum, and the light leaking from the core portion can be It becomes possible to confine in the clad layer so as not to enter the core portion. Thereby, even when the several optical waveguide 1 is laminated | stacked, the crosstalk between layers can be suppressed reliably.

  As described above, the minimum values Ts1 and Ts2 are less than the average refractive index TA of each of the cladding layers 11 and 12, but the difference between the two is preferably within a predetermined range. Specifically, the difference between the minimum values Ts1 and Ts2 and the average refractive index TA of the cladding layers 11 and 12 is about 3 to 80% of the difference between the minimum values Ts1 and Ts2 and the maximum value Tm in the core portion 14. It is preferably about 5 to 50%, more preferably about 7 to 30%. As a result, each of the cladding layers 11 and 12 has a light transmission property necessary and sufficient to suppress crosstalk. When the difference between the minimum values Ts1 and Ts2 and the average refractive index TA of each of the cladding layers 11 and 12 is less than the lower limit value, the optical transmission in each of the cladding layers 11 and 12 is too small, and crosstalk is sufficient. If the value exceeds the upper limit, the light transmission properties of the clad layers 11 and 12 may be too large, and the light transmission properties of the core portion 14 may be adversely affected.

  Further, the difference in refractive index between the minimum values Ts1 and Ts2 and the maximum value Tm in the core portion 14 is preferably as large as possible, but is preferably about 0.005 to 0.07, preferably 0.007 to 0.00. It is more preferably about 05, and further preferably about 0.01 to 0.05. Thereby, the above-described refractive index difference becomes necessary and sufficient for confining light in the core portion 14.

  Further, in the refractive index distribution T in the core portion 14, when the horizontal axis indicates the position of the cross section of the core portion 14 and the vertical axis indicates the refractive index, the refractive index continuously changes in the vicinity of the maximum value Tm. However, it is preferably formed in a substantially U shape (the entire vicinity of the maximum value is rounded) that is upwardly convex (convex to the right in FIG. 11). When the refractive index distribution T has such a shape, the light confinement action in the core portion 14 becomes more remarkable.

  Further, the refractive index distribution T may be a shape in which the refractive index continuously changes in the vicinity of the minimum value Ts1 and the minimum value Ts2, but is preferably convex downward (convex to the left in FIG. 11). The shape is substantially U-shaped (the entire vicinity of the maximum value is rounded).

«Third embodiment»
Next, a third embodiment of the optical waveguide of the present invention will be described.
FIG. 12 is a cross-sectional view showing a third embodiment of the optical waveguide of the present invention.

  Hereinafter, the third embodiment will be described, but the description will focus on the differences from the first embodiment, and the description of the same matters will be omitted.

  The third embodiment is the same as the first embodiment except that the gradually decreasing portion 6 is configured by gradually reducing the thickness of the core portion 14.

  In the gradually decreasing portion 6 shown in FIG. 12, the thickness gradually decreases from the light incident end portion 1A to the light emitting end portion 1B.

  As shown in FIG. 12, when the thickness of the core portion 14 at the light incident end portion 1A is q1, and the thickness of the core portion 14 at the light exit end portion 1B is q2, q2 is preferably 0. About 1 to 0.9 times, more preferably about 0.2 to 0.8 times q1. Thereby, the optical coupling efficiency between the optical waveguide 1 and the light emitting / receiving element can be further increased.

  In addition, although q2 is suitably set according to the magnitude | size of the light-receiving part of a light receiving element, it is preferable that it is about 5-1000 micrometers as an example, and it is more preferable that it is about 10-500 micrometers.

  At the light incident end 1A, the angle β1 formed by the boundary line between the core part 14 and the cladding layers 11 and 12 and the end face, and at the light emitting end part 1B, the boundary line between the core part 14 and the cladding layers 11 and 12 And β2 are preferably 45 degrees or more and less than 90 degrees, and more preferably 50 degrees or more and 89 degrees or less. Thereby, the probability that light leaks from the core portion 14 to the cladding layers 11 and 12 can be further reduced. In addition, the angle between the boundary line between the core portion 14 and the cladding layers 11 and 12 and the end face is defined as β1 and β2 which are 90 degrees or less.

Here, another configuration example of the gradual reduction unit 6 will be described.
FIGS. 13 and 14 are other configuration examples of the gradual reduction unit 6 shown in FIG.

  The gradual decrease unit 6 shown in FIG. 13 is the same as the gradual decrease unit 6 shown in FIG. 12 except that it is provided in a part of the core portion 14 in the longitudinal direction.

  Specifically, the optical waveguide 1 shown in FIG. 13A is provided with two gradually decreasing portions 6, one of which is provided in the vicinity of the light incident end 1 </ b> A, and the other one is a light emitting portion. It is provided in the vicinity of the end 1B. Further, the thickness is constant between the two gradually decreasing portions 6.

  Note that the position of the gradually decreasing portion 6 provided in the vicinity of the light incident end portion 1A may not coincide with the position of the SI portion described above, but preferably coincides. As a result, when signal light propagates from the SI part to the GI part, the incident characteristics to the GI part are improved by the effect of the gradual reduction part 6, so that the connectivity between the SI part and the GI part is particularly good. As a result, the transmission efficiency of the entire optical waveguide 1 can be further increased.

  The optical waveguide 1 shown in FIG. 13B is the same as the optical waveguide 1 shown in FIG. 13A except that the thicknesses of the cladding layers 11 and 12 are partially different. That is, in FIG. 13B, according to the change in the thickness of the gradually decreasing portion 6 provided in the core portion 14, the thickness of each of the cladding layers 11 and 12 is changed so as to cancel the change. Thereby, the total thickness of the optical waveguide 1 shown in FIG. 13B is constant as a whole.

  Even with such an optical waveguide 1, the same operations and effects as those of the optical waveguide 1 shown in FIG.

  Moreover, since such an optical waveguide 1 has uniform bending rigidity as a whole, the optical waveguide 1 is excellent in handleability and mountability.

  In such an optical waveguide 1, even when the core portion 14 (core layer 13) is thin, the clad layers 11 and 12 compensate for this, so that a decrease in mechanical strength is prevented. Is done. Thereby, it is possible to prevent the optical waveguide 1 from being damaged when the optical waveguide 1 and the light emitting / receiving element are assembled.

  The optical waveguide 1 shown in FIG. 13C is shown in FIG. 13A except that only the lower surface of the core part 14 (core layer 13) is displaced so that the thickness of the core part 14 is partially different. Similar to the optical waveguide 1. In such an optical waveguide 1, the thickness of the upper cladding layer 12 is constant, while the thickness of the lower cladding layer 11 is partially different.

  Even with such an optical waveguide 1, the same operations and effects as those of the optical waveguide 1 shown in FIG.

  The optical waveguide 1 shown in FIG. 13D is the same as the optical waveguide 1 shown in FIG. 13A except that the position of the gradually decreasing portion 6 is different. That is, in FIG. 13 (a), the gradually decreasing portions 6 are provided in the vicinity of the light incident end portion 1A and in the vicinity of the light emitting end portion 1B, respectively, whereas in FIG. It is different in that it moves slightly inward from the part.

  Even with such an optical waveguide 1, the same operations and effects as those of the optical waveguide 1 shown in FIG.

  The optical waveguide 1 shown in FIG. 14A is the same as the optical waveguide 1 shown in FIG. 13A except that the boundary line between the core portion 14 and each of the cladding layers 11 and 12 in the gradually decreasing portion 6 is curved. It is.

  Each of these curves is a parabola that opens toward the light incident end 1 </ b> A side, and the focal point of the parabola is located at substantially the center in the thickness direction of the core part 14. For this reason, the signal light reflected by the boundary line between the core portion 14 and each of the cladding layers 11 and 12 is collected in the vicinity of the focal point, and as a result, the light beams to the respective cladding layers 11 and 12 side are concentrated. Leakage is suppressed.

  Even with such an optical waveguide 1, the same operations and effects as those of the optical waveguide 1 shown in FIG.

  The optical waveguide 1 shown in FIGS. 14B, 14C, and 14D is similar to FIGS. 13B, 13C, and 13C except that the boundary line is curved as described above. This is the same as the optical waveguide 1 shown in FIG. 13D, and the same operations and effects as these are obtained.

<Optical waveguide manufacturing method>
Next, an example of a method for manufacturing the optical waveguide 1 described above will be described.
≪First manufacturing method≫
First, the 1st method (1st manufacturing method) which manufactures 1st Embodiment of the optical waveguide of this invention is demonstrated.

  FIGS. 15-19 is a figure for demonstrating the 1st manufacturing method of the optical waveguide 1 shown in FIG. 1, respectively. In the following description, the upper side in FIGS. 15 to 19 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] A SI film forming composition 901 and a GI area forming composition 902 are respectively applied on a support substrate 951 to form a liquid film, and then this support substrate 951 is used. Is placed on a level table to flatten the liquid film and evaporate (desolve) the solvent. 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.

Hereinafter, each process will be described sequentially.
[1] First, an SI part forming composition 901 and a GI part forming composition 902 are prepared.
Among these, the composition 902 for GI part formation contains the polymer 915 and the additive 920 (In this embodiment, it contains a monomer at least.). In such a GI part forming composition 902, upon irradiation with actinic radiation, at least monomer reaction occurs in the GI part forming composition 902, and the monomer moves accordingly, and the refractive index distribution is changed. It is a material to make. That is, in the GI part forming composition 902, the refractive index distribution changes due to the deviation in the ratio of the polymer 915 and the monomer, and as a result, the core part 14 and the side cladding part 15 are formed in the core layer 13. It is a material that can be used.

  On the other hand, the SI part-forming composition 901 includes a polymer 915 whose molecular structure changes due to irradiation with actinic radiation and whose refractive index changes. Moreover, the additive 920 is included as needed. The SI part forming composition 901 is a material in which the molecular structure of the polymer 915 is changed by irradiation with actinic radiation, and the refractive index is changed accordingly. That is, the SI portion forming composition 901 causes a difference in the molecular structure of the polymer 915 depending on whether or not the irradiation of active radiation or the amount of irradiation is large. As a result, the core portion 14 and the side cladding portion 15 are included in the core layer 13. It is a material that can be formed.

  Next, the prepared SI part forming composition 901 and the prepared GI part forming composition 902 are respectively applied onto the support substrate 951 to form a liquid film. When applying, the SI part forming composition 901 and the GI part forming composition 902 are respectively supplied to adjacent positions on the support substrate 951 (see FIG. 15A). At this time, the SI part forming composition 901 and the GI part forming composition 902 may be in contact with each other, but it is preferable to supply the SI part forming composition 901 and the GI part forming composition 902 so as not to contact each other. Thereby, the range which both mix can be adjusted easily.

  Thereafter, the blades 905 are scanned as indicated by arrows to spread the supplied compositions 901 and 902 (see FIG. 15B). The blade 905 scans the supplied SI part forming composition 901 while spreading it on the side of the GI part forming composition 902 supplied adjacently. As a result, part of the SI part forming composition 901 is mixed with the GI part forming composition 902, and both form one liquid film. Thereafter, 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. 15C). In the layer 910, the part where the SI part forming composition 901 and the GI part forming composition 902 are mixed together finally becomes the connection part 5. The connection portion 5 formed in this way is obtained by integrally connecting the SI portion and the GI portion.

  Examples of the blade 905 include a doctor blade, various squeegees, various rollers, and the like.

In addition, the blade 905 may be reciprocated a plurality of times in the portion to be the connection portion 5, but it is preferable that the SI portion forming composition 901 and the GI portion forming composition 902 are not so uniform. As a result, the connecting portion 5 is likely to have a continuous gradient in the mixing ratio of the two compositions, and finally, the refractive index distribution gradually changes from one end of the connecting portion 5 to the other end. A structure is formed. From this point of view, the number of scans of the blade 905 is preferably 3 or less, more preferably 2 or less.
The scanning direction of the blade 905 may be opposite to the above direction.

  The scanning direction of the blade 905 is preferably a direction parallel to the extending direction of the core portion 14 (the propagation direction of the signal light) in the optical waveguide 1 as described above, but other directions, for example, The direction orthogonal to the extending direction of the core part 14 may be sufficient.

  For the support substrate 951, for example, a silicon substrate, a silicon dioxide substrate, a glass substrate, a polyethylene terephthalate (PET) film, or the like is used.

  Examples of the coating method for forming the 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.

  In the obtained layer 910, the polymer (matrix) 915 is substantially uniformly and randomly present, and the additive 920 in the GI part forming composition 902 is substantially uniform with respect to the polymer 915. Randomly distributed.

  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 μm, and more preferably about 10 to 200 μm.

(polymer)
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.

  Here, “having compatibility” means that the monomer is at least mixed and does not cause phase separation with the polymer 915 in the SI part forming composition 901, the GI part forming composition 902, and the layer 910. That means.

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

  Among these, those mainly composed of cyclic olefin resins are preferable. By using a cyclic olefin resin as the polymer 915, 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.

  Examples of the cyclic olefin resins include norbornene resins and benzocyclobutene resins.

  Among these, 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).

As such a norbornene-based resin, for example,
(1) addition (co) polymer of norbornene type monomer obtained by addition (co) polymerization of norbornene type monomer,
(2) an addition copolymer of a norbornene monomer and ethylene or α-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 α-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, and polymers obtained by hydrogenating the copolymer as necessary. Examples of these polymers include random copolymers, block copolymers, and alternating copolymers.

  These norbornene resins include, for example, ring-opening metathesis polymerization (ROMP), combination of ROMP and hydrogenation reaction, polymerization by radical or cation, polymerization using cationic palladium polymerization initiator, other polymerization initiators ( For example, it can be obtained by any known polymerization method such as polymerization using a polymerization initiator of nickel or another transition metal).

  Among these, the norbornene-based resin is preferably an addition (co) polymer having at least one repeating unit represented by the following structural formula B. 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).

  Further, 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.

  Among them, 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.

  As the 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.

  Moreover, if the thing containing 2 or more types of repeating units of norbornene containing such a polymeric group is used, both flexibility and heat resistance can be aimed at.

  On the other hand, by including a norbornene repeating unit having a substituent containing an aryl group, dimensional change due to water absorption can be more reliably prevented by the extremely high hydrophobicity derived from the aryl group.

  Further, the norbornene-based resin preferably includes an alkylnorbornene repeating unit. The alkyl group may be linear or branched.

  By including the repeating unit of alkyl norbornene, the norbornene-based resin has high flexibility, and thus can provide high flexibility (flexibility).

  A norbornene-based resin containing an alkylnorbornene repeating unit is also preferable because of its excellent transmittance with respect to light in a specific wavelength region (particularly, a wavelength region near 850 nm).

  Specific examples of the norbornene-based resin including the norbornene repeating unit as described above 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.

  Therefore, as the norbornene-based resin, those represented by the following formulas (1) to (4) and (8) to (10) are preferable.

（式（１）中、Ｒ_１は、炭素数１〜１０のアルキル基を表し、ａは、０〜３の整数を表し、ｂは、１〜３の整数を表し、ｐ_１／ｑ_１が２０以下である。）

(In Formula (1), 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, and 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.

In addition, the manufacturing method of norbornene which has an epoxy group in a side chain is as (i) (ii), for example.
(I) Synthesis of norbornene methanol (NB—CH ₂ —OH) CPD (cyclopentadiene) and α-olefin (CH ₂ ═CH—CH ₂ —OH) produced by cracking of DCPD (dicyclopentadiene) are heated under high temperature and high pressure. React.

(Ii) Synthesis of epoxy norbornene It is formed by the reaction of norbornene methanol and epichlorohydrin.

  In formula (1), when b is 2 or 3, epichlorohydrin in which the methylene group is an ethylene group, a propylene group or the like is used.

Among the norbornene-based resins represented by the formula (1), from the viewpoint that both flexibility and heat resistance can be achieved, in particular, R ₁ is an alkyl group having 4 to 10 carbon atoms, and a and A compound in which each b is 1, for example, a copolymer of butyl norbornene and methyl glycidyl ether norbornene, a copolymer of hexyl norbornene and methyl glycidyl ether norbornene, a copolymer of decyl norbornene and methyl glycidyl ether norbornene, or the like is preferable.

（式（２）中、Ｒ_２は、炭素数１〜１０のアルキル基を表し、Ｒ_３は、水素原子またはメチル基を表し、ｃは、０〜３の整数を表し、ｐ_２／ｑ_２が２０以下である。）

(In Formula (2), 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, and p ₂ / q _2. Is 20 or less.)

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 Ni compound (A) described above as a catalyst. Obtainable.

Among the norbornene-based resins represented by the formula (2), 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 butyl norbornene and 2- (5-norbornenyl) methyl acrylate, copolymers of hexyl norbornene and 2- (5-norbornenyl) methyl acrylate, decyl norbornene and 2- (5-norbornenyl) acrylate A copolymer with methyl is preferred.

（式（３）中、Ｒ_４は、炭素数１〜１０のアルキル基を表し、各Ｘ_３は、それぞれ独立して、炭素数１〜３のアルキル基を表し、ｄは、０〜３の整数を表し、ｐ_３／ｑ_３が２０以下である。）

(In Formula (3), 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, and 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.

Among the 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, For example, a copolymer of butylnorbornene and norbornenylethyltrimethoxysilane, a copolymer of hexylnorbornene and norbornenylethyltrimethoxysilane, a copolymer of decylnorbornene and norbornenylethyltrimethoxysilane, butylnorbornene and triethoxysilyl Copolymer of norbornene, copolymer of hexyl norbornene and triethoxysilyl norbornene, copolymer of decyl norbornene and triethoxysilyl norbornene, copolymer of butyl norbornene and trimethoxysilyl norbornene, hex Copolymer of norbornene and trimethoxysilyl norbornene, copolymers, etc. of decyl norbornene and trimethoxysilyl norbornene are preferred.

（式（４）中、Ｒ_５は、炭素数１〜１０のアルキル基を表し、Ａ_１およびＡ_２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、ｐ_４／（ｑ_４＋ｒ）が２０以下である。）

(In formula (4), R ₅ represents an alkyl group having 1 to 10 carbon atoms, and 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.

（式（５）中、ｅは、０〜３の整数を表し、ｆは、１〜３の整数を表す。）

(In formula (5), e represents an integer of 0 to 3, and f represents an integer of 1 to 3.)

（式（６）中、Ｒ_６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。）

(In formula (6), R ₆ represents a hydrogen atom or a methyl group, and g represents an integer of 0 to 3.)

（式（７）中、Ｘ_４は、それぞれ独立して、炭素数１〜３のアルキル基を表し、ｈは、０〜３の整数を表す。）

(Equation (7) in, _{X 4} each independently represents an alkyl group having 1 to 3 carbon atoms, h is. Represents an integer of 0 to 3)

  As the 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, terpolymer of butyl norbornene, hexyl norbornene or decyl norbornene, 2- (5-norbornenyl) methyl acrylate and methyl glycidyl ether norbornene, butyl Norbornene, hexyl norbornene or decyl norbornene and methyl glycidyl ether norbornene, norbornenyl ethyl trimethoxysilane, triethoxysilane Terpolymers, etc. with either the norbornene-or trimethoxysilyl norbornene.

（式（８）中、Ｒ_７は、炭素数１〜１０のアルキル基を表し、Ｒ_８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、Ｘ_１は、酸素原子またはメチレン基を表し、Ｘ_２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、ｐ_５／ｑ_５が２０以下である。）

(In formula (8), 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, and X ₁ represents oxygen. 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, and 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 ) _i -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 Ni compound as a catalyst.

Of the 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.

Further, particularly from the viewpoint of flexibility, heat resistance and refractive index control, 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 Compounds in which ₈ is a methyl group, i is 1 and j is 2, for example, a copolymer of butylnorbornene and diphenylmethylnorbornenemethoxysilane, a copolymer of hexylnorbornene and diphenylmethylnorbornenemethoxysilane, decylnorbornene and diphenylmethylnorbornenemethoxysilane And a copolymer thereof are preferred.
Specifically, it is preferable to use the following norbornene resin.

（式（９）におけるＲ_７、ｐ_５、ｑ_５、ｉは、式（８）と同じである。）

(R ₇ , p ₅ , q ₅ , and i in formula (9) are the same as in formula (8).)

From the viewpoint of flexibility, heat resistance, and refractive index control, in Formula (8), R ₇ is an alkyl group having 4 to 10 carbon atoms, X ₁ is a methylene group, X ₂ is a carbon atom, and Ar is A compound having a phenyl group, R ₈ is a hydrogen atom, i is 0, and j is 1, for example, a copolymer of butylnorbornene and phenylethylnorbornene, a copolymer of hexylnorbornene and phenylethylnorbornene, a decylnorbornene and phenylethylnorbornene It may be a copolymer or the like.
Further, the following may be used as the norbornene resin.

（式（１０）において、Ｒ_１０は、炭素数１〜１０のアルキル基を表し、Ｒ_１１は、アリール基を示し、ｋは０以上、４以下である。ｐ_６／ｑ_６は２０以下である。）

(In Formula (10), R ₁₀ represents an alkyl group having 1 to 10 carbon atoms, R ₁₁ represents an aryl group, and k is 0 or more and 4 or less. P ₆ / q ₆ is 20 or less. is there.)

_{Further, p 1 / q 1 ~p 3} / q 3, p 5 / q 5, p 6 / q 6 or _{p 4 / (q 4 + r} ) may or if 20 or less, 15 or less Preferably, about 0.1-10 is more preferable. Thereby, the effect including the repeating unit of multiple types of norbornene is exhibited.

  On the other hand, the polymer 915 may be an acrylic resin, a methacrylic resin, an epoxy resin, a polyimide, a silicone resin, a fluorine resin, polyurethane, or the like as described above.

  Among these, examples of 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). , Polyacrylic acid, polymethacrylic acid, poly (isocyanate acrylate), poly (isocyanate methacrylate), poly (cyanate acrylate), poly (cyanate methacrylate), poly (thioepoxy acrylate), poly (thioepoxy methacrylate) , Poly (allyl acrylate), poly (allyl methacrylate), acrylate / epoxy acrylate copolymer (copolymer of methyl methacrylate and glycidyl methacrylate), styrene / epoxy Acrylate copolymer and the like, these one or more composite material is used.

  Examples of the epoxy resin 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 a cyclopentadiene skeleton, phenol novolac type epoxy resin, cresol novolac type epoxy resin, triphenylmethane type epoxy resin, aliphatic epoxy resin and triglycidyl isocyanurate, etc. One or more composite materials are used.

  Further, 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.

  As the polyamic acid, for example, it can be obtained as a solution by reacting tetracarboxylic dianhydride and diamine in an equimolar ratio in N, N-dimethylacetamide.

  Among these, examples of the tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2-bis (2,3-di Carboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3- Hexafluoropropane dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) And sulfonic acid dianhydrides.

  On the other hand, 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. Sulfone, 2,2-bis (4-aminophenoxyphenyl) propane, 2,2-bis (4-aminophenoxyphenyl) hexafluoropropane, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 2,4-diaminotoluene, 2,6-diaminotoluene, diaminodiphenylmethane, 4,4′-diamino-2,2-dimethylbiphenyl, 2,2-bis (trifluoromethyl)- 4,4′-diaminobiphenyl and the like can be mentioned.

  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.

  Examples of the silicone rubber monomer or oligomer include those containing a methylsiloxane group, an ethylsiloxane group, or a phenylsiloxane group.

  Moreover, as a silicone rubber monomer or oligomer, in order to provide photoreactivity, 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 addition, as 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.

  Examples of the fluorinated aliphatic ring structure include perfluoro (2,2-dimethyl-1,3-dioxole), perfluoro (4-methyl-1,3-dioxole), and perfluoro (4-methoxy-1,3-dioxole). ) And the like.

  Moreover, as a fluorine-containing monomer, perfluoro (allyl vinyl ether), perfluoro (butenyl vinyl ether) etc. are mentioned, for example.

  Examples of the radical polymerizable monomer include tetrafluoroethylene, chlorotrifluoroethylene, perfluoro (methyl vinyl ether), and the like.

  In addition, since 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.

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

  As the norbornene-based resin having a relatively high refractive index, a resin containing a repeating unit of aralkylnorbornene is 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.

  In addition, the polymer 915 included in the SI part-forming composition 901 is particularly a detachable group (detachable pendant) that is branched from the main chain and at least a part of its molecular structure can be released from the main chain upon irradiation with actinic radiation. Group). 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. The GI part forming composition 902 may also include a polymer 915 having a leaving group.

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

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

  Here, 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. Among these, one or more cyclic olefin resins selected from polymers of polycyclic monomers are preferably used. Thereby, the heat resistance of resin can be improved.

  In addition, as polymerization forms, known forms such as random polymerization and block polymerization can be applied. For example, specific examples of polymerization of norbornene type monomers include (co) polymers of norbornene type monomers, copolymers of norbornene type monomers and other copolymerizable monomers such as α-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. (In particular, norbornene-based resins) are preferable (that is, addition polymers of norbornene-based compounds). Thereby, it is excellent in transparency, heat resistance, and flexibility.

Further, as the norbornene resin having a leaving group in the side chain, for example, in the norbornene resin represented by the formula (8), X ₁ is an oxygen atom, X ₂ is a silicon atom, and Ar is a phenyl group. Some are listed.

In the formula (3), there are cases where the Si—O—X ₃ part of the alkoxysilyl group is eliminated.

  For example, when the norbornene-based resin of the formula (9) is used, it is presumed that the reaction proceeds as follows by the acid generated from the photoacid generator (denoted as PAG). Here, only the part of the leaving group is shown, and the case where i = 1 is described.

Furthermore, in addition to the structure of the formula (9), the side chain may have an epoxy group. By using such a thing, there exists an effect that the core layer 13 excellent in adhesiveness with respect to the cladding layers 11 and 12 and a base material can be formed.
Specific examples include the following.

（式（３１）において、ｐ_７／（ｑ_７＋ｒ_２）は、２０以下である。）

(In the formula (31), p ₇ / (q ₇ + r ₂ ) is 20 or less.)

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.

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

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

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

(Additive)
The additive 920 added to the GI part forming composition 902 includes a monomer and a polymerization initiator. Further, the additive 920 added to the SI part forming composition 901 can have the same composition as the GI part forming composition 902 except that it does not contain a monomer and a polymerization initiator.

((monomer))
The monomer reacts in the irradiation region of the actinic radiation to form a reactant by irradiation with actinic radiation 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.

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

  By the way, 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.

  Specifically, in the layer 910, when it is desired that the refractive index of the irradiated region be high, a polymer 915 having a relatively low refractive index and a monomer having a high refractive index with respect to the polymer 915 are included. Used in combination. On the other hand, when it is desired that the refractive index of the irradiated region be low, a polymer 915 having a relatively high refractive index and a monomer having a low refractive index with respect to the polymer 915 are used in combination.

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

  And, when the refractive index of the irradiated region decreases in the layer 910 due to the monomer reaction (reactant generation), when the portion forms a minimum value of the refractive index distribution W and the refractive index of the irradiated region increases, This portion constitutes the maximum value of the refractive index distribution.

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

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

  Among these, it is preferable to use a monomer or oligomer having a cyclic ether group such as an oxetanyl group or an epoxy group, or a norbornene monomer as the monomer. By using a monomer or oligomer having a cyclic ether group, the cyclic ether group is likely to be opened, so that a monomer capable of reacting quickly can be obtained. Further, by using a norbornene-based monomer, the core layer 13 (optical waveguide 1) having excellent optical transmission performance and excellent heat resistance and flexibility can be obtained.

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

  As the monomer having an oxetanyl group and the oligomer having an oxetanyl group, those selected from the following formulas (11) to (20) are preferable. By using 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.

（式（１８）においてｎは０以上、３以下である。）

(In formula (18), n is 0 or more and 3 or less.)

  Among the monomers and oligomers as described above, compounds represented by the formulas (13), (15), (16), (17), and (20) are used from the viewpoint of securing a difference in refractive index from the polymer 915. It is preferable.

  Furthermore, in consideration of the difference in refractive index from the polymer 915 resin, the low molecular weight, the high mobility of the monomer, and the fact that the monomer does not easily volatilize, it is expressed by the equations (20) and (15). It is particularly preferred to use the compounds

  Moreover, as a compound which has an oxetanyl group, the compound represented by the following formula | equation (32) and a formula (33) can be used. As a compound represented by Formula (32), Toagosei Co., Ltd. trade name TESOX etc., and as a compound represented by Formula (33), Toagosei Co., Ltd. trade name OX-SQ etc. can be used.

（式（３３）において、ｎは１または２である）

(In formula (33), n is 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.

  As 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. Especially, it is preferable to use the alicyclic epoxy monomer represented by Formula (36)-(39) from a viewpoint that the distortion energy of an epoxy ring is large and is excellent in reactivity.

  In addition, the compound represented by Formula (34) is epoxy norbornene. As such a compound, for example, EpNB manufactured by Promeras Corporation can be used. The compound represented by the formula (35) is γ-glycidoxypropyltrimethoxysilane. As this compound, for example, Z-6040 manufactured by Toray Dow Corning Silicone can be used. Moreover, the compound represented by Formula (36) is 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and as this compound, for example, E0327 manufactured by Tokyo Chemical Industry can be used.

  Furthermore, the compound represented by the formula (37) is 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexenecarboxylate, and as this compound, for example, Celoxide 2021P manufactured by Daicel Chemical Industries, Ltd. is used. can do. Further, the compound represented by the formula (38) is 1,2-epoxy-4-vinylcyclohexane, and as this compound, for example, Ceroxide 2000 manufactured by Daicel Chemical Industries, Ltd. can be used.

  Furthermore, the compound represented by the formula (39) is 1,2: 8,9 diepoxy limonene. As this compound, for example, (Celoxide 3000 manufactured by Daicel Chemical Industries, Ltd.) can be used.

  Furthermore, as the monomer, 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.

  Monomers having an oxetanyl group and oligomers having an oxetanyl group have a slow initiation reaction but a fast growth reaction. On the other hand, 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.

  Specifically, when 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. When the ratio of the combination 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. When 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. Among these, 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. By using these second monomers, the reactivity between the first monomer and the polymer 915 can be improved, whereby the heat resistance of the waveguide can be improved while maintaining transparency.

  Specific examples of 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). Examples thereof include compounds and compounds of the above formulas (34) to (39).

  The norbornene-based monomer is a generic term for monomers containing at least one norbornene skeleton represented by the following structural formula D, and examples thereof include compounds represented by the following structural formula C.

［式中、ａは、単結合または二重結合を表し、Ｒ_１２〜Ｒ_１５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、Ｒ_１２およびＲ_１３のいずれか一方、Ｒ_１４およびＲ_１５のいずれか一方は存在しない。］

[Wherein, a represents a single bond or a double bond; R _{12 to} R ₁₅ each independently represents a hydrogen atom, a substituted or unsubstituted hydrocarbon group, or a functional substituent; Represents an integer of 0 to 5; 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 (hydrocarbyl 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, C 4-12 (C ₄ -C ₁₂ ) cycloalkenyl group, C 6-12 (C ₆ -C ₁₂ ) aryl group, C 7-24 (C ₇ -C ₂₄ ) aralkyl group In addition, 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 ).

  In addition, examples of monomers other than the above, for example, 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.

  Specific examples include 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, and 2-butoxyethyl (meth) acrylate.

  Examples of 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, and n-octyl. Examples thereof include alkyl vinyl ethers such as vinyl ether, n-dodecyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexyl vinyl ether, and cycloalkyl vinyl ethers, and one or more of these can be used in combination.

  Moreover, as a styrene-type monomer, styrene, divinylbenzene, etc. are mentioned, for example, These 1 type or 2 types can be used in combination.

  In addition, the combination of these monomers and the polymer 915 mentioned above is not specifically limited, Any combination may be sufficient.

  Further, at least a part of 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. Thereby, the refractive index modulation between the core and the clad is possible, and there is an effect that both flexibility and heat resistance can be achieved.

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

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

  Examples of the radical polymerization initiator include benzophenones and acetophenones.

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

  In particular, when a monomer having a cyclic ether group is used as the monomer, the following cationic polymerization initiator (photoacid generator) is preferably used.

  For example, sulfonium salts such as triphenylsulfonium trifluoromethanesulfonate, tris (4-t-butylphenyl) sulfonium-trifluoromethanesulfonate, diazonium salts such as p-nitrophenyldiazonium hexafluorophosphate, ammonium salts, phosphonium salts, diphenyliodonium Trifluoromethanesulfonate, iodonium salts such as (triccumyl) iodonium-tetrakis (pentafluorophenyl) borate, quinonediazides, diazomethanes such as bis (phenylsulfonyl) diazomethane, 1-phenyl-1- (4-methylphenyl) sulfonyloxy- Sulfones such as 1-benzoylmethane and N-hydroxynaphthalimide-trifluoromethanesulfonate Esters, disulfones such as diphenyldisulfone, tris (2,4,6-trichloromethyl) -s-triazine, 2- (3.4-methylenedioxyphenyl) -4,6-bis- (trichloromethyl)- Compounds such as triazines such as s-triazine are used as photoacid generators. These photoacid generators may be used alone or in combination.

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

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

  Among these, the sensitizer increases the sensitivity of the polymerization initiator to light and is suitable for the function of reducing the time and energy required for the activation (reaction or decomposition) of the polymerization initiator and for the activation of the polymerization initiator. It has a function of changing the wavelength of light to a wavelength.

  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. For example, 9,10-dibutoxyanthracene (CAS No. 76275) is selected. 14-4) anthracenes, xanthones, anthraquinones, phenanthrenes, chrysene, benzpyrenes, fluoranthenes, rubrenes, pyrenes, indanthrines, thioxanthen-9-ones (Thioxanthen-9-ones) and the like, and these can be used alone or as a mixture.

  Specific examples of the sensitizer include, for example, 2-isopropyl-9H-thioxanthen-9-one, 4-isopropyl-9H-thioxanthen-9-one, 1-chloro-4-propoxythioxanthone, phenothiazine. Or a mixture thereof.

  The content of the sensitizer in the GI part forming composition 902 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.

  In addition to the above, as additive 920, SI part forming composition 901 and GI part forming composition 902 include a catalyst precursor, a co-catalyst, an antioxidant, an ultraviolet absorber, a light stabilizer, a silane cup, and the like. Ring agent, coating surface improver, thermal polymerization inhibitor, leveling agent, surfactant, colorant, storage stabilizer, plasticizer, lubricant, filler, inorganic particles, degradation inhibitor, wettability improver, antistatic agent, etc. May be included.

  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 that is uniformly dispersed in the polymer 915.

  [2] Next, 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. 16).

  Below, the case where what has a refractive index lower than the polymer 915 is used as a monomer contained in the composition 902 for GI part formation is demonstrated to an example.

  That is, in the example shown here, the irradiation region 925 of the active radiation 930 is mainly the side cladding portion 15.

  Therefore, in the example shown here, 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. Therefore, when forming the core portion 14 whose width is gradually decreased, the opening 9351 whose width is gradually increased to form the side cladding portion 15 whose width is gradually increased accordingly. A mask 935 in which is formed may be used. In addition, since 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 in the GI portion.

  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. Among these, it is particularly preferable to use a photomask or a stencil mask. This is because a fine pattern can be formed with high accuracy, and handling is easy, which is advantageous in improving productivity.

  Further, in FIG. 16, the opening (window) 9351 of the mask 935 is shown by partially removing the mask along the pattern of the irradiation region 925 of the active radiation 930. However, the quartz glass, the PET base material, etc. In the case of using the photomask manufactured in (1), it is also possible to use a photomask provided with a shielding portion of active radiation 930 made of a shielding material made of metal such as chromium. In this mask, the part other than the shielding part is the window (transmission part).

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

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

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

  When the layer 910 is irradiated with the active radiation 930 through the mask 935, the polymerization initiator is activated in the irradiated region 925 in the portion of the layer 910 that includes the GI part forming composition 902. 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. As described above, since 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. 20 is a diagram for explaining a state in which a refractive index difference occurs between the irradiated region 925 and the non-irradiated region 940 in the layer 910 composed of the GI part forming composition 902. It is a figure which shows refractive index distribution when taking the position of a surface on a horizontal axis, and taking the refractive index of a cross section on the vertical axis | shaft.

  In this embodiment, since a monomer having a smaller refractive index than that of the polymer 915 is used as the monomer, 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. 20 (a)).

  It is considered that the monomer diffusion movement is caused by the consumption of the monomer in the irradiation region 925 and the concentration gradient of the monomer formed accordingly. For this reason, the monomers in the entire unirradiated region 940 do not move toward the irradiated region 925 at the same time, but gradually move from a portion close to the irradiated region 925. Monomer migration also occurs. As a result, as shown in FIG. 20A, 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.

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

  In addition, in the irradiation region 925, the ease of monomer diffusion transfer gradually decreases as the polymerization of the monomer proceeds. As a result, in the irradiated region 925, the closer to the unirradiated region 940, the higher the monomer concentration, and the greater the amount of decrease in refractive index. As a result, 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.

  Further, the polymer 915 may have a leaving group as described above. This leaving group is released upon irradiation with actinic radiation 930 and decreases the refractive index of the polymer 915. Therefore, when the irradiation region 925 is irradiated with the active radiation 930, in the layer 910 composed of the GI part forming composition 902, the above-described monomer diffusion movement is started and the leaving group is detached from the polymer 915. In addition, the refractive index of the irradiation region 925 decreases before irradiation (see FIG. 20B).

  Since the decrease in the refractive index occurs uniformly in the entire irradiation region 925, the difference in refractive index 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. 20B is obtained. Note that the change in the refractive index in FIG. 20A and the change in the refractive index in FIG. 20B occur almost simultaneously, and the refractive index distribution W is formed. Although the refractive index distribution is exaggerated in FIG. 20A, the refractive index difference between the high refractive index portion H and the low refractive index portion L accompanying the actual diffusion movement of the monomer is relatively small. This refractive index difference is sufficiently expanded by the refractive index change in FIG. 20B, and a graded index type refractive index distribution W is formed.

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

  Next, the layer 910 is subjected to heat treatment. In this heat treatment, the monomer in the irradiation region 925 irradiated with light is further polymerized. On the other hand, in this heating step, the monomer in the 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, and more preferably about 40 to 160 ° C.

  Further, the heating time is preferably set so that the polymerization reaction of the monomer in the irradiation region 925 is almost completed. Specifically, the heating time is preferably about 0.1 to 2 hours, preferably 0.1 to 1 hour. More preferred is the degree.

Note that this heat treatment may be performed as necessary and may be omitted.
Based on the principle as described above, the GI portion of the core layer 13 is obtained (see FIG. 17).

  In the refractive index distribution W of the GI portion, there are minimum values Ws1, Ws2, Ws3, and Ws4 converted from the low refractive index portion L (see FIG. 4B), and the position of these minimum values is the core portion. 14 corresponds to the interface between the side clad portion 15 and the side clad portion 15.

  In addition, the refractive index distribution W in the GI portion has a certain correlation with the monomer-derived structure concentration. Therefore, it is possible to indirectly specify the refractive index distribution W of the GI part by measuring the concentration of the monomer-derived structure.

  The concentration of the structure can be measured using, for example, FT-IR, TOF-SIMS line analysis, surface analysis, or the like.

  Furthermore, the refractive index distribution W can be indirectly specified even if the intensity distribution of the emitted light from the GI portion has a certain correlation with the refractive index distribution W.

  Of course, the refractive index distribution W of the GI portion can be directly specified by a refraction near field method, a differential interference method, or the like.

  In addition, when a monomer having a higher refractive index than that of the polymer 915 is used as the monomer, the refractive index of the movement destination increases with the diffusion movement of the monomer. The irradiation area 940 may be set.

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

  On the other hand, in the layer 910 composed of the SI part forming composition 901, the leaving group is detached from the polymer 915 with the irradiation of the active radiation 930, and the refractive index of the irradiation region 925 decreases from before the irradiation.

  FIG. 21 is a diagram for explaining a state in which a refractive index difference occurs between the irradiated region 925 and the non-irradiated region 940 in the layer 910 composed of the SI part forming composition 901, and the crossing of the layer 910. It is a figure which shows refractive index distribution when taking the position of a surface on a horizontal axis, and taking the refractive index of a cross section on the vertical axis | shaft.

In the irradiation region 925, the leaving group in the polymer 915 is released with the irradiation of the active radiation 930, and thereby the refractive index of the polymer 915 is lowered (see FIG. 21). As a result, the low refractive index portion L is formed in the irradiated region 925 of the layer 910, and the high refractive index portion H is formed in the non-irradiated region 940. The low refractive index portion L becomes the side cladding portion 15, and the high refractive index portion H becomes the core portion 14.
The SI part of the core layer 13 is obtained by the principle as described above.

The refractive index distribution W in the SI portion has a certain correlation with the concentration of the leaving group. Therefore, it is possible to indirectly specify the refractive index distribution W of the SI part by measuring the concentration of the leaving group.
The above-described various analytical methods can be used to measure the concentration of the leaving group.

  [3] Next, the cladding layers 11 and 12 are laminated on both surfaces of the core layer 13. Thereby, the optical waveguide 1 is obtained.

  For this, first, the clad layer 11 (12) is formed on the support substrate 952 (see FIG. 18).

  As a method for forming the clad layer 11 (12), 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.

  Next, 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 cladding layer 11 is formed and the support substrate 952 on which the cladding layer 12 is formed (FIG. 19A )reference).

  Then, as indicated by the arrow in FIG. 19A, pressure is applied from the upper surface side of the support substrate 952 on which the cladding layer 12 is formed, and the cladding layers 11 and 12 and the core layer 13 are pressure-bonded.

  Thereby, the clad layers 11 and 12 and the core layer 13 are joined and integrated (see FIG. 19B).

  Next, the support substrate 952 is peeled off and removed from the cladding layers 11 and 12, respectively. Thereby, the optical waveguide 1 is obtained.

  Thereafter, if necessary, the support film 2 is laminated on the lower surface of the optical waveguide 1 and the 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.

«Second manufacturing method»
Next, a second method (second manufacturing method) for manufacturing the second embodiment of the optical waveguide of the present invention will be described.

  Hereinafter, the second manufacturing method will be described, but the description will focus on differences from the first manufacturing method, and description of similar matters will be omitted.

  The second manufacturing method is the same as the first manufacturing method except that the composition of the GI part forming composition 902 is different.

  The second manufacturing method of the optical waveguide 1 is as follows: [1] A SI film forming composition 901 and a GI area forming composition 902 are respectively applied on a supporting substrate 951 to form a liquid film, and then the supporting substrate 951. Is placed on a level table to flatten the liquid film and evaporate (desolve) the solvent. 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.

Hereinafter, each process will be described sequentially.
[1] First, an SI part forming composition 901 and a GI part forming composition 902 are prepared.

  The GI part forming composition 902 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, cross-linking 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. .

  As the catalyst precursor (procatalyst), 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. Thereby, 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.

  As such a catalyst precursor, a catalyst precursor containing (mainly) at least one of the compounds represented by the following formulas (Ia) and (Ib) is preferably used.

［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。］

[In the formulas Ia and Ib, 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. In Formula Ib, 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, and a and b , 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. Here, Cp represents a cyclopentyl group, and Cy represents a cyclohexyl group.

  The catalyst precursor represented by the formula Ib is preferably a compound in which p and r are each selected from integers of 1 and 2.

Typical catalyst precursors according to such formula Ib include Pd (OAc) ₂ (P (Cy) ₃ ) ₂ . Here, Cy represents a cyclohexyl group, and Ac represents an acetyl group.

  These 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).

  In the state where the activation temperature is lowered (active latent state), the catalyst precursor 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 cocatalyst 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).

  As the cocatalyst (cocatalyst), 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.

Examples of the weak coordination anion include tetrakis (pentafluorophenyl) borate ion (FABA ⁻ ), hexafluoroantimonate ion (SbF ₆ ⁻ ), and the like.

  Examples of the cocatalyst (photoacid generator or photobase generator) 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.

  As a commercial product of such a promoter, for example, “RHODORSIL (registered trademark, the same applies hereinafter) PHOTOINITIATOR 2074 (CAS No. 178233-72-2) available from Rhodia USA, Cranberry, NJ "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. 87709-41-9)" available from Midori Chemical Co., Tokyo, Japan, available from Toyo Ink Manufacturing Co., Ltd., Tokyo, Japan "TAG-371 (CAS No. 193957-53-8 “TTBPS-TPFPB (tris (4-tert-butylphenyl) sulfonium tetrakis (pentapentafluorophenyl) borate)”, available from Toyo Gosei Co., Ltd., Tokyo, Midori Chemical Industries, Tokyo, Japan Examples thereof include “NAI-105 (CAS No. 85342-62-7)” available from a corporation.

  When RHODORSIL PHOTOINITIATOR 2074 is used as a co-catalyst, ultraviolet rays (UV light) are preferably used as actinic radiation (chemical rays) to be described later, and mercury lamps (high pressure mercury lamps) are preferred as ultraviolet irradiation means. Used for. Thereby, ultraviolet rays (active radiation) having sufficient energy of less than 300 nm can be supplied to the layer 910, and RHODOLSIL PHOTOINITIATOR 2074 can be efficiently decomposed to generate the above-described cation and WCA.

[2]
[2-1] Next, as in the first manufacturing method, the layer 910 is irradiated with the active radiation 930 through the mask 935.

  In the irradiation region 925, 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).

  These cations and weakly coordinating anions cause a change (decomposition) in the molecular structure of the catalyst precursor existing in the irradiation region 925, and change this into an active latent state (latent active state).

  Here, 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. A catalyst precursor that is in a state where a monomer reaction cannot be caused in 925.

  Therefore, even after irradiation with the active radiation 930, if the layer 910 is stored at, for example, about −40 ° C., the state can be maintained without causing a monomer reaction. For this reason, the core layer 13 can be obtained by preparing a plurality of layers 910 after irradiation with the active radiation 930 and subjecting them to a heat treatment described later, which is highly convenient.

  In addition to the change in the molecular structure of the catalyst precursor as described above, the leaving group is released from the polymer 915 as in the first production method. Thereby, a refractive index difference is generated between the irradiated region 925 and the non-irradiated region 940 of the layer 910.

[2-2] Next, the layer 910 is subjected to heat treatment (first heat treatment).
Thereby, in the irradiation region 925, the catalyst precursor in the active latent state is activated (becomes active), and monomer reaction (polymerization reaction or cross-linking reaction) occurs.

  As the monomer reaction proceeds, the monomer concentration in the irradiation region 925 gradually decreases. As a result, 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.

As a result, a refractive index profile similar to that in the first manufacturing method is formed in the layer 910.
Although the heating temperature in this heat processing is not specifically limited, It is preferable that it is about 30-80 degreeC, and it is more preferable that it is about 40-60 degreeC.

  The heating time is preferably set so that the reaction of the monomer in the irradiation region 925 is almost completed. Specifically, the heating time is preferably about 0.1 to 2 hours, and 0.1 to 1 hour. More preferred is the degree.

Next, second heat treatment is performed on the layer 910.
As a result, 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.

  In this way, by reacting the monomers remaining in the respective regions 925 and 940, the core portion 14 and the side clad portion 15 obtained can be stabilized.

  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 about 80 to 90 ° C. Is more preferable.

  The heating time is preferably about 0.5 to 2 hours, more preferably about 0.5 to 1 hour.

Next, 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., 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 core layer 13 is obtained through the above steps.

  For example, when a sufficient refractive index difference is obtained between the core portion 14 and the side cladding portion 15 in a state before the second heat treatment or the third heat treatment, After the second heat treatment or the third heat treatment may be omitted.

  [3] Next, as in the first manufacturing method, the cladding layers 11 and 12 are laminated on both surfaces of the core layer 13. Thereby, the optical waveguide 1 is obtained.

≪Third manufacturing method≫
Next, a third method (third manufacturing method) for manufacturing the first embodiment of the optical waveguide of the present invention will be described.
FIG. 22 is a diagram for explaining a third manufacturing method of the optical waveguide 1 shown in FIG.

  Hereinafter, the third manufacturing method will be described, but the description will focus on the differences from the first manufacturing method, and description of similar matters will be omitted.

  The third manufacturing method is the same as the first manufacturing method, except that one type of core layer forming composition 900 is used, and the core layer 13 is formed by partial heat treatment.

The third 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, the part of the layer 910 where the SI part is to be formed is heated, and the monomer of the layer 910 is volatilized and removed. [3] 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 portion 14 and the side cladding portion 15 are formed. [4] Next, the cladding layers 11 and 12 are laminated on both surfaces of the core layer 13 to obtain the optical waveguide 1.

Hereinafter, each process will be described sequentially.
[1] First, a core layer forming composition 900 is prepared.

The core layer forming composition 900 used in the third manufacturing method is the same as the GI part forming composition 902 used in the first manufacturing method, except that the polymer 915 must have a leaving group. is there.
Next, the layer 910 is formed using the core layer forming composition 900.

  [2] Next, heat treatment is performed on the portion 911 of the layer 910 where the SI portion is to be formed (see FIG. 22). Thereby, the monomer is volatilized and removed from the heat-treated portion 911. As a result, since the monomer content in the portion 911 is small, the diffusion and movement of the monomer does not occur, and a continuous distribution of the refractive index is not formed.

  The heating temperature in the heat treatment is appropriately set according to the composition of the monomer, but as an example, it is preferably more than 100 ° C., more preferably 110 to 200 ° C., and further preferably 120 to 180 ° C. preferable. As a result, the monomer can be volatilized and removed without altering the polymer 915 or the like.

  Further, the heating time is preferably about 0.1 to 2 hours, and more preferably about 0.1 to 1 hour.

  As a result of removing the monomer, the monomer content is preferably less than half by weight, and more preferably less than one third.

  Examples of the heating method include heating with a Peltier element, an electric heater, etc., infrared irradiation, etc. Among them, heating with a Peltier element is preferably used. In this heating method, the heating range and the heating temperature can be controlled very strictly, so that the amount of monomer removal can be controlled to a high degree. As a result, finally, the SI portion can be reliably formed.

  Moreover, although it may be made to heat-process the same conditions as the whole about the part 911 which heat-processes, you may make it make conditions differ partially. For example, if the heating temperature is gradually lowered or the heating time is gradually shortened as the portion of the portion 911 is closer to the portion where the GI portion is to be formed, the monomer removal amount can be gradually reduced. it can. As a result, finally, the change in the refractive index distribution at the connection portion 5 between the SI portion and the GI portion can be made continuous.

  [3] Next, as in the first manufacturing method, the layer 910 is irradiated with the active radiation 930 through the mask 935.

  When the layer 910 is irradiated with the actinic radiation 930 through the mask 935, the portion 911 in the layer 910 where the SI portion is to be formed contains almost no monomer, and thus the reaction of leaving group leaving from the polymer 915 is dominant. This causes a refractive index difference between the irradiated region 925 and the non-irradiated region 940. That is, since the monomer hardly moves and diffuses, the refractive index distribution between the irradiated region 925 and the non-irradiated region 940 is a stepped distribution. As a result, the portion 911 where the SI portion is to be formed becomes the SI portion of the core layer 13.

  On the other hand, in the layer 910 other than the portion 911 where the SI portion is to be formed, the monomer is contained, so that the diffusion of the monomer occurs. As a result, this portion becomes the GI portion of the core layer 13.

  [4] Next, as in the first manufacturing method, the cladding layers 11 and 12 are laminated on both surfaces of the core layer 13. Thereby, the optical waveguide 1 provided with SI part and GI part is obtained.

<< Fourth Manufacturing Method >>
Next, a method for manufacturing the second embodiment of the optical waveguide of the present invention (fourth manufacturing method) will be described.

  FIG. 23 is a diagram for explaining a method of manufacturing the optical waveguide 1 shown in FIG. In the following description, the upper side in FIG. 23 is referred to as “upper” and the lower side is referred to as “lower”.

  Hereinafter, although the 4th manufacturing method is explained, it explains focusing on difference with the 1st manufacturing method, and omits the explanation about the same matter.

  In the fourth production method, except that the clad layer forming composition, the core layer forming composition, and the clad layer forming composition are molded in multiple colors so as to be extruded in three layers, and this is irradiated with actinic radiation. Is the same as in the first manufacturing method.

  The fourth manufacturing method of the optical waveguide 1 is as follows: [1] Multicolor molding on a support substrate 951 so that the cladding layer forming composition, the core layer forming composition, and the cladding layer forming composition are extruded in three layers. Thus, a liquid film is formed and dried to obtain a layer 912. [2] Next, the part of the layer 912 where the SI part is to be formed is heated, and the monomer of the layer 912 is volatilized and removed. [3] Next, a refractive index difference is generated by irradiating a part of the layer 912 with actinic radiation to form the core part 14 and the side cladding part 15. Thereby, the optical waveguide 1 is obtained.

Hereinafter, each process will be described sequentially.
[1] First, three compositions are simultaneously extruded onto the support substrate 951 so that the composition 9121 for forming the clad layer, the composition 9122 for forming the core layer, and the composition 9123 for forming the clad layer are arranged in this order from the bottom. The liquid film 9120 is multicolor molded (see FIG. 23A). At this time, the extrusion conditions are changed in the middle of the multicolor molding, and the composition is divided into a portion where no mixing of the composition between layers occurs and a portion where the composition occurs. As a result, it is possible to form a state in which the respective compositions are not mixed in a part of the liquid coating 9120 and the respective compositions are mixed in the other part. The former part finally becomes the SI part, and the latter part finally becomes the GI part.

  That is, as shown in FIG. 23 (a), in the portion that finally becomes the GI portion, on the upper surface of the support substrate 951, a liquid coating 9120a made of only the cladding layer forming composition 9121 and the cladding layer forming composition are formed. A liquid coating 9120b formed by mixing the product 9121 and the core layer forming composition 9122, a liquid coating 9120c consisting only of the core layer forming composition 9122, a core layer forming composition 9122, and a cladding layer forming composition. A liquid film 9120 obtained by laminating a liquid film 9120d formed by mixing 9123 and a liquid film 9120e formed only by the cladding layer forming composition 9123 is obtained.

  In order to control the mixing of the composition, for example, the fluidity of the composition is changed by changing the viscosity of the composition or the compatibility of each other in the middle, thereby facilitating mutual diffusion. A method of adjusting, a method of adjusting whether or not to operate a mechanism for forcibly mixing the compositions at the time of extrusion, and the like are used.

  Thereafter, the liquid coating 9120 is dried to obtain a layer 912. More specifically, the clad layer 11 is mainly formed from the liquid film 9120a, the core layer 13 is mainly formed from the liquid films 9120b, 9120c, and 9120d, and the clad layer 12 is mainly formed from the liquid film 9120e (FIG. 23). (See (b)).

  [2] Next, as in the third manufacturing method, a heat treatment is performed on the portion 911 of the layer 912 where the SI portion is to be formed (see FIG. 23B). Thereby, the monomer is volatilized and removed from the heat-treated portion 911. As a result, since the monomer content in the portion 911 is small, the diffusion and movement of the monomer does not occur, and a continuous distribution of the refractive index is not formed.

  [3] Next, as in the first manufacturing method, the layer 912 is irradiated with the active radiation 930 through the mask 935.

  When the layer 912 is irradiated with the active radiation 930 through the mask 935, the portion 911 of the layer 912 formed from the core layer forming composition 9122 contains almost no monomer. The reaction in which the leaving group is detached from the polymer 915 becomes dominant, and this causes a refractive index difference between the irradiated region 925 and the unirradiated region 940. That is, since the monomer hardly moves and diffuses, the refractive index distribution between the irradiated region 925 and the non-irradiated region 940 is a stepped distribution. As a result, the part 911 where the SI part is to be formed becomes a part of the SI part.

On the other hand, among the layers formed from the core layer forming composition 9122 of the layer 912, the monomer other than the portion 911 where the SI portion is to be formed contains the monomer, so that the monomer is diffused and transferred. As a result, this part becomes a part of the GI part.
The optical waveguide 1 is obtained as described above.

  The obtained optical waveguide 1 has an SI part and a GI part. In the GI part, both the refractive index distribution W in the width direction and the refractive index distribution T in the thickness direction continuously change in refractive index. Will be. In such an optical waveguide 1, the transmission efficiency in the GI portion is particularly high, so that the transmission efficiency of the entire optical waveguide 1 can be further increased, and the optical coupling efficiency with other optical elements at the light emitting end portion. Can be further enhanced.

«Fifth manufacturing method»
Next, a method (fifth manufacturing method) for manufacturing the third embodiment of the optical waveguide of the present invention will be described.

  24 to 26 are views for explaining a method of manufacturing the optical waveguide 1 shown in FIG. In the following description, the upper side in FIGS. 24 to 26 is referred to as “upper” and the lower side is referred to as “lower”. 24 to 26 are drawn so as to pass through the core layer 13 and the clad layers 11 and 12, and in FIGS. 25 and 26, dots are given to regions corresponding to the core portion 14.

  Hereinafter, the fifth manufacturing method will be described, but the description will focus on differences from the first manufacturing method, and description of similar matters will be omitted.

  First, as shown in FIG. 24A, a lower clad layer base material 11 'is prepared. A predetermined step is formed on the upper surface of the lower clad layer base material 11 ′ in accordance with a change in the thickness of the core layer 13 (core portion 14) to be manufactured. Here, a case where the optical waveguide 1 shown in FIG. 13C is manufactured will be described as an example. In the optical waveguide 1 shown in FIG. 13C, the gradually decreasing portions 6 are provided at the left end portion and the right end portion, respectively. Therefore, the upper surface of the lower clad layer base material 11 ′ moves up and down according to the thickness change of the core layer 13, while the lower surface is a horizontal smooth surface. The lower clad layer base material 11 ′ has a first surface 111 whose upper surface is gradually lowered to the left toward the left end portion at a position slightly moved to the right side from the left end surface in the longitudinal direction. And the second surface 112 that gradually increases to the left. Further, at a position slightly moved to the left side from the right end surface in the longitudinal direction, a third surface 113 whose upper surface gradually increases to the right toward the right end, and then gradually decreases to the right. And a fourth surface 114 that is lowered. Of these, the degree of inclination of the upper surfaces of the first surface 111 and the third surface 113 respectively corresponds to the degree of inclination of the lower surface of the gradually decreasing portion 6 of the core layer 13 shown in FIG. . On the other hand, the degree of inclination of the upper surfaces of the second surface 112 and the fourth surface 114 is the same as that obtained by inverting the first surface 111 and the third surface 113, respectively. Moreover, the upper surfaces other than these surfaces are horizontal surfaces.

  Next, similarly to the first manufacturing method, the layer 910 is obtained using the SI part forming composition 901 and the GI part forming composition 902 (see FIG. 24B).

  Next, the layer 910 is selectively irradiated with light. At this time, as shown in FIG. 24C, a mask M having an opening formed thereon is arranged above the layer 910, and light is irradiated to the layer 910 through this opening. Thereby, a refractive index difference is generated between the irradiated region and the non-irradiated region. Here, the region irradiated with light becomes the side cladding portion 15 and the non-irradiated region becomes the core portion 14 (see FIG. 25D).

  Next, the obtained laminated body of the layer 910 and the lower clad layer base material 11 ′ is cut along two cut surfaces S shown in FIG. The two cut surfaces S are the boundary line between the first surface 111 and the second surface 112 provided on the upper surface of the lower clad layer base material 11 ′, and the third surface 113 and the fourth surface It is a surface along each boundary line with the surface 114. By cutting the laminated body along the cut surface S, a laminated body of the lower clad layer 11 and the core layer 13 is obtained (see FIG. 25F).

  Next, as shown in FIG. 26 (g), the clad layer 12 is pasted on the core layer 13. Through the above steps, the optical waveguide 1 shown in FIG.

  In the above description, the method for manufacturing the optical waveguide 1 shown in FIG. 13C has been described. However, when necessary, when the layer 910 is dried, the upper surface of the layer 910 is formed (for example, machining, mold) It may be dried while pushing). Thereby, the upper surface of the layer 910 can be moved up and down, and the optical waveguide 1 shown in FIGS. 13A, 13B, and 13D or the optical waveguide 1 shown in FIG. 14 can be manufactured. .

  Further, the order of the steps is not limited to the above, and for example, the base material for forming the cladding layer 12 may be attached and then cut along the cut surface S.

<Electronic equipment>
The optical waveguide of the present invention as described above has high optical coupling efficiency with other optical elements (such as light receiving and emitting elements), and 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.

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

  In addition, the optical waveguide of the present invention has little 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.

  Although the optical waveguide and the electronic device of the present invention have been described above, the present invention is not limited to this, and for example, an arbitrary component may be added to the optical waveguide.

  For example, the optical waveguide may be formed with an optical path conversion unit such as a mirror that converts the optical path.

  In addition, the method for producing the optical waveguide of the present invention is not limited to the above-described method. For example, 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). Or other methods such as photodimerization method).

  In these methods, since 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.

  In each of the above embodiments, the SI portion is disposed in the vicinity of the light incident end of the optical waveguide, and the GI portion is disposed in other portions. However, the positions of the SI portion and the GI portion are limited to this position. Not. For example, the effect of the present invention can be obtained even when the GI portion is disposed in the center portion in the longitudinal direction of the optical waveguide and the SI portions are disposed in the vicinity of the light incident end portion and the light emitting end portion.

Next, examples of the present invention will be described.
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.

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

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

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

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

(2) Manufacture of SI part formation composition With respect to the obtained polymer # 1, 40 g of mesitylene, 0.01 g of antioxidant Irganox 1076 (manufactured by Ciba Geigy), 0.01 g of polymerization initiator (photoacid generator) Rhodorsil Photoinitiator 2074 (Rhodia, CAS # 178233-72-2) (1.36E-2g in 0.1 mL of ethyl acetate) was added and dissolved uniformly, and then filtered through a 0.2 μm PTFE filter to obtain a clean SI part. A forming composition was obtained.

(3) Manufacture of GI part forming composition A cyclohexyloxetane monomer (first monomer represented by the formula (20), manufactured by Toa Gosei CHOX, CAS # 483303-25-) was obtained from the obtained SI part forming composition. 9, molecular weight 186, boiling point 125 ° C./1.33 kPa) 2 g was added and dissolved uniformly, followed by filtration with a 0.2 μm PTFE filter to obtain a clean GI part forming composition.

(4) Production of optical waveguide (production of lower clad layer)
A photosensitive norbornene resin composition (Avatrel 2000P varnish manufactured by Promeras Co., Ltd.) was uniformly applied on a silicon wafer with a doctor blade, and then placed in a dryer at 45 ° C. for 15 minutes. After completely removing the solvent, the entire coated surface was irradiated with 100 mJ of ultraviolet light and heated in a dryer at 120 ° C. for 1 hour to cure the coating film, thereby forming a lower clad layer. The formed lower clad layer had a thickness of 20 μm and was colorless and transparent.

(Production of core layer)
The SI part forming composition was placed on a part of the lower cladding layer, and the GI part forming composition was placed at a position slightly away from the SI part forming composition. The supply amount of the GI part forming composition was slightly larger than that of the SI part forming composition. In addition, the supply positions of the two are separated so that they do not come into contact with each other even if they spread due to their own weight.

  Next, the SI part-forming composition and the GI part-forming composition were uniformly spread by a doctor blade. At this time, the doctor blade was scanned so as to spread the SI part forming composition on the GI part forming composition side. Then, after scanning up to the entire length of the optical waveguide to be formed, the scanning direction was reversed and returned to the scanning start position. This reciprocating scan was performed once again to form a liquid film.

Next, the obtained liquid film was put into a dryer at 45 ° C. for 15 minutes. After the solvent was completely removed, a photomask was pressed and selectively irradiated with ultraviolet rays at 1000 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 photomask was provided with an opening so that a gradually decreasing portion was formed over the entire length of the core portion.

(Preparation of upper clad layer)
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 μm 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. The formed optical waveguide has eight core portions formed in parallel. Further, the maximum width of the mask shielding portion was 50 μm, and the maximum width of the opening was 80 μm. The thickness of the optical waveguide was 200 μm.
Moreover, the length of the connection part was about 1 cm, and the length of the SI part was about 5 mm.

(Evaluation of refractive index distribution)
Then, with respect to the cross section of the obtained optical waveguide, the refractive index distribution on the line drawn in the width direction and the thickness direction is measured by the refractive near field method, and the refractive index distribution W in the width direction and the refractive index in the thickness direction are measured. Distribution T was obtained. Tables 1 and 2 show the parameters of the obtained refractive index distribution.

(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 6)
Except that the molar ratio of each structural unit of polymer # 1 was changed to 10 mol% for the hexylnorbornene structural unit and 90 mol% for the diphenylmethylnorbornenemethoxysilane structural unit as the polymer, the same as in Example 1. Thus, an optical waveguide was obtained.

(Example 7)
In addition to reducing the irradiation amount of ultraviolet rays to 500 mJ / cm ² , as a polymer, the molar ratio of each structural unit of polymer # 1 was changed to 20 mol% for the hexylnorbornene structural unit and 80 mol% for the diphenylmethylnorbornenemethoxysilane structural unit. An optical waveguide was obtained in the same manner as in Example 1 except that was used.

(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 GI part forming composition was manufactured by the method shown below.

  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), bifunctional oxetane monomer (shown by the formula (15), Toa Gosei Manufactured by DOX, CAS # 18934-00-4, molecular weight 214, boiling point 119 ° C./0.67 kPa) 2 g, photoacid generator Rhodorsil Photoinitiator 2074 (manufactured by Rhodia, CAS # 178233-72-2) (1.36E-2g, In 0.1 mL of ethyl acetate) and uniformly dissolved, followed by filtration with a 0.2 μm PTFE filter to obtain a clean GI part forming composition.

(Example 14)
An optical waveguide was obtained in the same manner as in Example 1 except that the GI part forming composition was manufactured by the method shown below.

  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), alicyclic epoxy monomer (shown by the formula (37), Daicel) Chemical, Celoxide 2021P, CAS # 2386-87-0, molecular weight 252, boiling point 188 ° C./4 hPa) 2 g, photoacid generator Rhodorsil Photoinitiator 2074 (Rhodia, CAS # 178233-72-2) (1.36E-2 g, In 0.1 mL of ethyl acetate) and uniformly dissolved, followed by filtration with a 0.2 μm PTFE filter to obtain a clean GI part forming composition.

(Example 15)
An optical waveguide was obtained in the same manner as in Example 1 except that the GI part forming composition was manufactured by the method shown below.

  10 g of the purified polymer # 1 was weighed into a 100 mL glass container, 40 g of mesitylene, 0.01 g of antioxidant Irganox 1076 (manufactured by Ciba Geigy), cyclohexyloxetane monomer (shown by the formula (20), manufactured by Toagosei Co., Ltd. (CHOX) 1 g, alicyclic epoxy monomer (manufactured by Daicel Chemical Industries, Celoxide 2021P), 1 g, photoacid generator Rhodorsil Photoinitiator 2074 (manufactured by Rhodia, CAS # 178233-72-2) (1.36E-2 g, in 0.1 mL of ethyl acetate) ) And uniformly dissolved, followed by filtration with a 0.2 μm PTFE filter to obtain a clean GI part forming composition.

(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.

  First, 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 molecular weight of this polymer was Mw = 110,000 and Mn = 50,000 by GPC measurement. 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 three compositions of the clad layer forming composition, the core layer forming composition, and the clad layer forming composition are extruded onto the substrate so that they are arranged in this order from the bottom, so that a three-layer liquid film is formed in multiple colors. An optical waveguide was obtained in the same manner as in Example 1 except that. In addition, when forming the SI portion, the multi-color molding apparatus has a low viscosity so that the respective compositions do not mix with each other, and when forming the GI portion, the multi-color molding apparatus has a high viscosity so that the respective compositions are mixed with each other. The condition of the composition to be supplied to was changed. Thereby, a continuous refractive index distribution was obtained also in the thickness direction of the GI part.

(Example 18)
First, as the GI part forming composition, the above-described SI part forming composition was used.
The mask used when exposing the region where the SI part is to be formed is different from the mask used when exposing the region where the GI part is to be formed.

  That is, the photomask for forming the GI portion is irradiated with ultraviolet rays using an opening corresponding to the region where the side clad portion is to be formed, and the ultraviolet transmittance is gradually reduced around the opening. did. Thereby, a continuous distribution was formed in the integrated light quantity of ultraviolet rays. The integrated amount of ultraviolet light corresponds to the amount of the leaving group that is released from the polymer by irradiation with ultraviolet light, and corresponds to the amount of decrease in the refractive index that accompanies the elimination of the leaving group. Therefore, the transmittance distribution of the photomask is set according to the shape of the refractive index distribution to be finally formed.

  An optical waveguide was obtained in the same manner as in Example 1 except that the composition for forming a GI part as described above was used and a photomask as described above was used for forming the GI part.

  In the obtained optical waveguide, the refractive index of the side clad portion was substantially constant, while the refractive index of the core portion continuously decreased from the central portion toward the periphery.

(Example 19)
A core layer and an upper clad layer were formed in the same manner as in Example 1 except that a lower clad layer base material as shown in FIG. 24 was used to form the lower clad layer. Note that a photomask having an opening set so that the width of the core is constant was used. Then, unnecessary portions were cut and removed to obtain an optical waveguide.

  The obtained optical waveguide had a gradually decreasing portion in which the width of the core portion was constant and the thickness gradually decreased.

(Example 20)
An optical waveguide was obtained in the same manner as in Example 19 except that a photomask having an opening set so that the width of the core portion gradually decreased was used.

  The obtained optical waveguide had a gradually decreasing portion in which both the width and thickness of the core portion were gradually decreased.

(Comparative Example 1)
An optical waveguide was obtained in the same manner as in Example 1 except for the following.

First, after forming the lower clad layer, the SI part forming composition was applied thereon, exposed and heated to obtain a core layer. At the time of exposure, a photomask having an opening set so that the width of the core is constant was used.
Thereafter, an optical waveguide was obtained by forming an upper cladding layer.

  In the obtained optical waveguide, the refractive index distribution W in the width direction and the refractive index distribution T in the thickness direction are stepwise distributions in the entire optical waveguide. Further, the refractive index distribution W and the refractive index distribution T were substantially the same as the refractive index distribution W and the refractive index distribution T in the SI part of Example 1.

(Comparative Example 2)
An optical waveguide was obtained in the same manner as in Comparative Example 1 except that a photomask having an opening set so that the width of the core portion gradually decreased was used.

(Comparative Example 3)
In the same manner as in Comparative Example 1 except that the entire core layer is exposed using a photomask whose transmittance is continuously changed so that the exposure amount is continuously changed during exposure. Got. At the time of exposure, a photomask having an opening set so that the width of the core is constant was used.

  Further, in the obtained optical waveguide, the refractive index of the side cladding portion is substantially constant, while the refractive index of the core portion continuously decreases from the central portion toward the periphery. Further, the refractive index distribution W was substantially the same as the refractive index distribution W in the GI part of Example 18, and the refractive index distribution T was substantially the same as the refractive index distribution T in the SI part of Example 1.

(Comparative Example 4)
An optical waveguide was obtained in the same manner as in Comparative Example 3 except that a photomask having an opening set so that the width of the core portion gradually decreased was used.

2. Evaluation 2.1 Refractive Index Distribution of Optical Waveguide Regarding the cross section of the SI portion of the obtained optical waveguide, the refractive index distribution on the line drawn in the width direction was measured by a refractive near field method. In addition, since 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 two high refractive index regions W2, W4 and three low refractive index regions W1, W3, W5 were alternately arranged as shown in FIG.

  And from the obtained refractive index distribution W, the average value of each low refractive index area | region W1, W3, W5 and the average value of each high refractive index area | region W2, W4 were calculated | required.

  On the other hand, the refractive index distribution T on the line drawn in the thickness direction for the cross section of the SI portion was also measured in the same manner.

  Further, regarding the cross section of the GI portion of the obtained optical waveguide, the refractive index distribution on the line drawn in the width direction was measured by a refractive near field method. In addition, since 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.

  Then, from the obtained refractive index distribution W, each minimum value Ws1, Ws2, Ws3, Ws4 and each maximum value Wm1, Wm2, Wm3, Wm4, Wm5 were obtained, and an average refractive index WA in the cladding part was obtained.

  In the refractive index distribution W, the average value of the width a [μm] 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 higher than the average refractive index WA, and The average value of the width b [μm] of the portion where the refractive index in the vicinity of each minimum value Ws1, Ws2, Ws3, Ws4 has a value less than the average refractive index WA was measured.

  As a result, the refractive index distribution W of the GI portion obtained in each example had a continuous change in refractive index as a whole.

  On the other hand, the refractive index distribution T on the line drawn in the thickness direction of the cross section of the GI portion was also measured in the same manner.

2.2 Transmission loss and insertion loss of an optical waveguide Light emitted from an 850 nm VCSEL (surface emitting laser) is introduced into an optical waveguide obtained via an optical fiber of 50 μmφ, and received by the optical fiber of 200 μmφ, and the light intensity Was measured. The cutback method was used for the measurement. When the measured values were plotted with the longitudinal direction of the optical waveguide taken on the horizontal axis and the insertion loss on the vertical axis, the measured values were arranged on a straight line. Therefore, the transmission loss of the optical waveguide was calculated from the slope of the straight line. The transmission loss obtained in this way is the transmission loss (unit: dB / cm) of the optical waveguide itself.

  On the other hand, the insertion loss measured for the optical waveguide having a length of 10 cm includes the transmission loss of the optical waveguide itself and the coupling loss between the optical waveguide and the optical fiber. Therefore, relative values of the loss loss of the optical waveguides obtained in each of the examples and the comparative examples were obtained when the loss loss of the optical waveguide obtained in Comparative Example 1 was set to 1.

2.3 Retention of pulse signal waveform A pulse signal having a pulse width of 1 ns was incident on the obtained optical waveguide from a laser pulse light source, and the pulse width of the emitted light was measured.

  And the relative value when the measured value of the optical waveguide obtained by the comparative example 1 was set to 1 was calculated about the pulse width of the measured emitted light, and this was evaluated according to the following evaluation criteria.

<Evaluation criteria for pulse width>
A: Relative value of pulse width is less than 0.5 B: Relative value of pulse width is 0.5 or more and less than 0.8 Δ: Relative value of pulse width is 0.8 or more and less than 1 ×: The relative value of the pulse width is 1 or more. Table 3 shows the evaluation results of 2.2 and 2.3.

  As is clear from Table 3, it is recognized that the optical waveguide obtained in each example has suppressed transmission loss, insertion loss and blunting of the pulse signal, respectively, as compared with the optical waveguide obtained in each comparative example. It was. In particular, the insertion loss was superior to the optical waveguides obtained in the respective comparative examples. This is because the SI section has a wide cross-sectional area that can be incident on the basis of the shape of the refractive index distribution, so that it can receive all the signal light from the optical fiber, while the GI section has high transmission efficiency and emission. Because the convergence at the time is high, the signal light can be incident on the optical fiber for receiving light without fail, so that the optical waveguide provided with the SI part and the GI part can achieve both effects. Conceivable.

  Further, when the refractive index distribution is a continuous distribution in which the minimum value and the maximum value are alternately arranged as shown in FIG. 4B, the transmission loss and insertion loss of the optical waveguide can be particularly suppressed. . In addition, when the distribution is continuous not only in the width direction of the optical waveguide but also in the thickness direction, the tendency is remarkable.

  Further, it has been clarified that the insertion loss is reduced by providing the gradual reduction portion. In particular, not only the width and thickness of the core portion but also a gradually decreasing portion in which both are gradually reduced can be used to particularly reduce the insertion loss.

DESCRIPTION OF SYMBOLS 1 Optical waveguide 1A Light incident edge part 1B Light emission edge part 11, 12 Cladding layer 11 'Base material for lower clad layers 111 1st surface 112 2nd surface 113 3rd surface 114 4th surface 13 Core layer DESCRIPTION OF SYMBOLS 14 Core part 141,142 Core part 15 Side surface clad part 151,152,153 Side surface clad part 2 Support film 3 Cover film 5 Connection part 6 Gradual reduction part 900 Core layer formation composition 901 SI part formation composition 902 GI part formation Composition 905 Blade 910, 912 layer 911 Part where SI part is to be formed 9120 Liquid coating 9120a, 9120b, 9120c, 9120d, 9120e Liquid coating 9121, 9123 Clad layer forming composition 9122 Core layer forming composition 915 Polymer 920 Additive 930 Actinic radiation 935 Mask (masking)
9351 opening (window)
925 Irradiated region 940 Unirradiated region 951, 952 Support substrate W, T Refractive index distribution WA Average refractive index W1, W3, W5 Low refractive index region W2, W4 High refractive index region Ws1, Ws2, Ws3, Ws4 Minimal values Wm1, Wm2, Wm3, Wm4, Wm5 average refractive index at the maximum value TA cladding layer T1, T3 low refractive index region T2 high refractive index region Ts1, Ts2 minimum value Tm maximum value T _L low-refractive-index region T _M in refractive index Region _TH High Refractive Index Region C, C1, C2, C3, C4 Centerline H High Refractive Index Part L Low Refractive Index Part a, b Width SI SI Part GI GI Part M Mask S Cut Surface

Claims (12)

An optical waveguide having a core part and a clad part adjacent to a side surface of the core part,
When a line is drawn on the cross section, the refractive index distribution on the line has an SI part that is a step index type and a GI part that is a graded index type at any position in the longitudinal direction. And
An optical waveguide comprising a gradually decreasing portion in which the cross-sectional area of the core portion gradually decreases from the light incident side to the light emitting side of the optical waveguide.   The optical waveguide according to claim 1, wherein the SI part and the GI part are integrally connected at a connection part.   The refractive index distribution of the cross section in the said connection part is comprised so that it may change gradually from one side of a step index type or a graded index type between the one ends of the said connection part between other ends. The optical waveguide described.   The optical waveguide according to claim 1, wherein the SI portion is provided at a light incident end of the optical waveguide.   The optical waveguide according to claim 1, wherein the GI portion is provided at a light emitting end portion of the optical waveguide.   The optical waveguide according to claim 1, wherein a length of the GI part is longer than a length of the SI part.   The refractive index distribution in the GI portion has two minimum values, one first maximum value, and two second maximum values smaller than the first maximum value, and the second It includes a region where the local maximum value, the local minimum value, the first local maximum value, the local minimum value, and the second local maximum value are arranged in this order, and the refractive index continuously changes as a whole. The optical waveguide according to claim 1, wherein the optical waveguide has a distribution.   The optical waveguide according to claim 1, wherein the gradually decreasing portion is provided at an end of the optical waveguide. The optical waveguide has a strip shape,
When a line is drawn in the width direction of the optical waveguide on the cross section, the refractive index distribution W on the line has a step index type SI part and a graded index type GI part, respectively. At any position in the direction, and
9. The light according to claim 1, wherein when a line is drawn in the thickness direction of the optical waveguide on the cross section, the refractive index distribution T on the line is a step index type throughout the optical waveguide. Waveguide. The optical waveguide has a strip shape,
When a line is drawn in the width direction and the thickness direction of the optical waveguide on the cross section, the refractive index distribution W in the width direction and the refractive index distribution T in the thickness direction on the line are step index types, respectively. And the refractive index distribution W and the refractive index distribution T each having a graded index type GI portion at any position in the longitudinal direction. The optical waveguide described.   The optical waveguide according to claim 9 or 10, wherein the gradually decreasing portion is formed by gradually decreasing the width of the core portion in plan view.   An electronic apparatus comprising the optical waveguide according to claim 1.

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