JPWO2012039392A1 - Optical waveguide and electronic equipment - Google Patents

Abstract

The optical waveguide has a core layer and a clad layer provided on each surface thereof, and the core layer is provided with two parallel core portions and three parallel side clad portions provided alternately. Yes. When the optical waveguide is incident on the core portion CH1 at one end thereof, the intensity of the leaked light observed at the side clad portion CL2 at the other end of the optical waveguide is such that the leaked light observed at the core portion CH2 is observed. It is comprised so that it may become larger than intensity | strength. That is, the intensity distribution of the emitted light with respect to the position of the end face at the other end at this time is such a distribution that a maximum value is observed in each of the core part CH1 and the side cladding part CL2, and a minimum value is observed in the core part CH2. Yes.

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.

  In recent years, there has been a strong demand for an optical waveguide with a large capacity, and further multi-channel and higher density have been demanded. As the number of channels increases and the density increases, the pitch of the channels (core part) becomes narrower, and along with this, the occurrence of crosstalk (the leakage light from one channel interferes with the adjacent channels) increases. It has become a challenge.

JP 2006-276735 A

  An object of the present invention is to provide an optical waveguide capable of suppressing interference (crosstalk) between adjacent channels, and an electronic apparatus including the optical waveguide.

Such an object is achieved by the present inventions (1) to (9) below.
(1) An optical waveguide having a plurality of parallel core portions and a clad portion adjacent to at least both side surfaces of each core portion,
Among the plurality of core portions, a desired one is a core portion CH1, a portion adjacent to the core portion CH1 is a core portion CH2, and
Among the plurality of clad parts, a clad part CL1 is located between the core part CH1 and the core part CH2, and a clad part CL2 is located on the opposite side of the core part CH2 from the clad part CL1. When
An intensity of the leaked light that has entered the core part CH1 at one end of the optical waveguide and leaked from the optical signal observed at the clad part CL2 at the other end is observed at the core part CH2. An optical waveguide characterized by being configured to be larger than the intensity of light.

  (2) For the outgoing light observed at the end face of the other end of the optical waveguide, the intensity distribution with respect to the position of the end face has a maximum value in the clad portion CL2, and sets a minimum value smaller than the maximum value to the core portion. The optical waveguide according to (1), which is included in CH2.

  (3) The optical waveguide according to (2), wherein an intensity difference between the maximum value in the cladding portion CL2 and the minimum value in the core portion CH2 is 3 to 20 dB.

  (4) The optical waveguide according to (2) or (3), wherein the maximum value in the cladding part CL2 is −60 to −20 dB with respect to the intensity of the optical signal observed in the CH1.

  (5) An intensity difference between the maximum value in the clad part CL2 and the minimum value in the core part CH2 is g1, and the intensity of the optical signal observed in the core part CH1 and the minimum value in the core part CH2 The optical waveguide according to any one of (2) to (4), wherein g1 / g2 satisfies a relationship of 0.05 to 0.5, where g2 is a difference in strength with respect to.

  (6) The optical waveguide according to any one of (2) to (5), wherein the intensity distribution of the emitted light is continuously changing with respect to the position of the end face.

  (7) The optical waveguide according to any one of (1) to (6), wherein a width of each core portion is 20 to 200 μm.

(8) a first cladding layer;
A core layer provided on the first clad layer, in which a first core portion CH1, a first clad portion CL1, a second core portion CH2, and a second clad portion CL2 are formed in this order;
A second cladding layer provided on the core layer;
An optical waveguide having
When light incident on the first core portion CH1 at one end of the optical waveguide exits from the other end as outgoing light,
In the intensity distribution of the emitted light obtained in the region extending over the first core part CH1, the first cladding part CL1, the second core part CH2, and the second cladding part CL2, the second core part CH2 An optical waveguide characterized in that the intensity of the emitted light is smaller than the intensity of the emitted light in the second cladding part CL2.

  (9) An electronic apparatus comprising the optical waveguide according to any one of (1) to (8).

According to the present invention, an optical waveguide that can suppress crosstalk between adjacent channels can be obtained.
Further, by using such an optical waveguide, a highly reliable electronic device can be obtained.

FIG. 1 is a perspective view showing a first embodiment of an optical waveguide according to the present invention (partially cut out and shown through). FIG. 2 is a diagram illustrating an example of an intensity distribution of outgoing light when light is incident on one of the core portions of the optical waveguide shown in FIG. FIG. 3 is a diagram for explaining a method of measuring the intensity distribution of outgoing light on the outgoing side end face of the optical waveguide. 4 schematically illustrates an example of the refractive index distribution W when the horizontal axis indicates the position of the core layer thickness in the center line and the vertical axis indicates the refractive index in the cross-sectional view taken along the line XX in FIG. FIG. FIG. 5 is a perspective view showing a second embodiment of the optical waveguide of the present invention (shown partially cut away and transmitted). FIG. 6 is a diagram illustrating an example of an intensity distribution of outgoing light when light is incident on one of the core portions of the optical waveguide shown in FIG. FIG. 7 schematically shows an example of the refractive index distribution T when the horizontal axis represents the refractive index and the vertical axis represents the position in the center line of the width of the core portion in the YY sectional view shown in FIG. FIG. FIG. 8 is a diagram for explaining a first manufacturing method of the optical waveguide shown in FIG. FIG. 9 is a diagram for explaining a first manufacturing method of the optical waveguide shown in FIG. FIG. 10 is a diagram for explaining a first manufacturing method of the optical waveguide shown in FIG. FIG. 11 is a diagram for explaining a first manufacturing method of the optical waveguide shown in FIG. FIG. 12 is a diagram for explaining a first manufacturing method of the optical waveguide shown in FIG. FIG. 13 is a diagram for explaining a state in which a refractive index difference is generated between an irradiated region and an unirradiated region. The horizontal axis represents the position of the cross section of the layer, and the vertical axis represents the refractive index of the horizontal section. It is a figure which shows refractive index distribution at the time. FIG. 14 is a diagram for explaining a manufacturing method (third manufacturing method) of the optical waveguide shown in FIG. FIG. 15 is a perspective view showing a die coater for obtaining a multicolor molded body. 16 is an enlarged longitudinal sectional view showing a part of the die coater shown in FIG. FIG. 17 is a cross-sectional view showing another configuration example of the mixing unit. FIG. 18 is a diagram showing the intensity distribution of outgoing light on the outgoing side end face of the optical waveguides obtained in Example 1, Comparative Example 1 and Comparative Example 2.

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, the optical waveguide of the present invention will be described.

  FIG. 1 is a perspective view showing an embodiment of an optical waveguide according to the present invention (partially cut out and shown through), and FIG. 2 shows light incident on one of core portions of the optical waveguide shown in FIG. It is a figure which shows an example of intensity distribution of the emitted light at the time of doing. In the following description, the upper side in FIG. 1 is referred to as “upper” and the lower side is referred to as “lower”. In FIG. 1, the thickness direction of the layers (the vertical direction in each figure) is exaggerated.

  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.

Hereinafter, each part of the optical waveguide 1 will be described in detail.
The optical waveguide 1 is formed by laminating a clad layer (first clad layer) 11, a core layer 13 and a clad layer (second clad layer) 12 in this order from the lower side in FIG.
According to the optical waveguide 1 described later, interference (crosstalk) between adjacent channels is suppressed, and further multichanneling and higher density can be achieved.

Moreover, the optical waveguide 1 according to the present embodiment has high optical transmission characteristics (first effect).
The optical waveguide 1 according to the present embodiment has a refractive index distribution W as described later in the width direction (in-layer direction). In this refractive index distribution W, since the minimum value is located across the first maximum value, a large refractive index difference is formed between the core portion and the cladding portion. Thereby, it becomes difficult for light to leak from a core part. In addition, since the second maximum value smaller than the first maximum value is located in the cladding part, even if light leaks from the core part, the leaked light is confined to the second maximum value of the cladding part. . Thereby, crosstalk between core parts adjacent in the width direction is suppressed.

  Further, the optical waveguide 1 according to the present embodiment has a refractive index distribution T as described later in the thickness direction (interlayer direction). In this refractive index distribution T, a maximum value and a minimum value are alternately arranged, and for the maximum value, a first maximum value and a smaller second maximum value are alternately arranged (W-type distribution). It has become. With such a distribution, the light confinement effect in the core portion is much superior to that of the step index (SI) type. As a result, generation of optical transmission loss is effectively suppressed, and high optical transmission characteristics can be realized. The reason for this is not necessarily clear, but it is considered that light penetration from the core portion is effectively suppressed by the W-type refractive index distribution.

  Further, in the optical waveguide 1 according to the present embodiment, a certain light confinement effect is obtained also in the cladding layer based on the W-type refractive index distribution T (second effect). Therefore, in the optical waveguide 1, not only the light leaked in the width direction but also the light leaked in the thickness direction can be confined in the clad layer. Thereby, crosstalk can be reliably suppressed in both the width direction and the thickness direction.

Moreover, the optical waveguide 1 according to the present embodiment has a high degree of design freedom (third effect).
The optical waveguide 1 according to the present embodiment is formed by laminating films, for example. Among these, the thickness of the cladding layer can be arbitrarily determined in relation to the thickness of the core layer. Moreover, since the thickness can be strictly controlled, the effect of reducing the optical coupling loss can be maximized. Furthermore, when the optical waveguide 1 is bent, a compressive force is applied to the inner side of the bent portion and a tensile force is applied to the outer side, and the refractive index may change unintentionally accordingly. The optical waveguide 1 can be easily designed with different thicknesses of the clad layers sandwiching the core layer in consideration of such bending.

(Core layer)
Among these, the core layer 13 is formed with two core parts 14 arranged in parallel in the width direction and three side clad parts 15 arranged in parallel so as to sandwich each core part 14. 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.

  More specifically, the core layer 13 shown in FIG. 1 includes two core parts 141 (first core part CH1) and 142 (second core part CH2) in parallel and three side cladding parts 151 and 152 (in parallel). First clad portions CL1) and 153 (second clad portions CL2) are alternately provided. Thereby, each core part 141 and 142 will be in the state surrounded by each side cladding part 151,152,153 and each cladding layer 11,12, respectively. Here, the refractive indexes of the core portions 141 and 142 are higher than the refractive indexes of the side cladding portions 151, 152, and 153 and the refractive indexes of the cladding layers 11 and 12, respectively. And reflection of light can be caused at the interfaces between the side clad portions 151, 152, 153 and the clad layers 11, 12. Then, the light incident on one end portion of the core portion 14 is propagated to the other while being reflected at the interface between the core portion 14 and the clad portion (the clad layers 11 and 12 and the side clad portions 15). It can be taken out from the other end of the core part 14.

  The core portion 14 shown in FIG. 1 has a quadrilateral shape (rectangular shape) such as a square or a rectangle, but this shape is not particularly limited. For example, a perfect circle, an ellipse, or an oval The shape may be a circle such as a triangle, a triangle, a pentagon, or a polygon such as a hexagon.

  The width and height of the core part 14 (thickness of the core layer 13) are not particularly limited, but are preferably about 20 to 200 μm, more preferably about 25 to 100 μm, and 30 to 30 μm, respectively. More preferably, it is about 70 μm.

  Here, when light is incident on one desired end portion of the plurality of core portions 141 and 142 of the optical waveguide 1 shown in FIG. 1, the intensity distribution P1 of the emitted light at the other end portion is acquired. The intensity distribution shows a characteristic distribution.

  FIG. 2 is a diagram showing the intensity distribution P1 of the emitted light when light is incident on the core portion 141 of the optical waveguide 1 shown in FIG. 1, and the horizontal axis indicates the position in the width direction of the outgoing side end face of the core layer 13. It is a figure which shows an example of intensity distribution when taking and taking the intensity | strength of emitted light on the vertical axis | shaft.

  When light is incident on the core portion 141 (CH1), the intensity of the emitted light is highest at the central portion of the emission end of the core portion 141. And although the intensity | strength of emitted light becomes small as it leaves | separates from the center part of the core part 141, the core part 142 (CH2) adjacent to the core part 141 takes a small value locally. That is, the intensity distribution P1 of the emitted light in this case takes a maximum value Pm1 at the center of the exit end of the core part 141 (CH1) and takes a minimum value Ps1 at the core part 142 (CH2). According to the optical waveguide 1 in which the emitted light has such an intensity distribution, although the complete leakage of the light propagating through the core portion 141 cannot be prevented, the leakage light is suppressed from collecting in the core portion 142. “Crosstalk” in which leaked light interferes with the core part 142 can be reliably suppressed. As a result, the optical waveguide 1 can reliably prevent the occurrence of crosstalk even when the number of channels is increased and the density is increased.

  In the conventional optical waveguide, the intensity distribution P1 of the emitted light does not take the minimum value in the core portion adjacent to the core portion where the light is incident, but rather takes the maximum value. This local maximum value is crosstalk, and in the adjacent core portions, the crosstalk optical signal originally interferes with the optical signal propagating through the core portion. Such interference of optical signals has been a problem because it significantly deteriorated the quality of optical communication in the optical waveguide.

  On the other hand, in the optical waveguide of the present invention, as described above, the intensity distribution P1 of the emitted light takes the minimum value Ps1 in the adjacent core portion 142 (CH2), and thus the crosstalk as described above is suppressed. . As a result, according to the present invention, the optical waveguide 1 capable of realizing high-quality optical communication is obtained.

  Moreover, according to the optical waveguide 1 showing the intensity distribution P1 of the emitted light as described above, there is an advantage that the propagation loss and the blunting of the pulse signal are suppressed in addition to the suppression of the crosstalk as described above.

  Further, in the intensity distribution P1 of the emitted light, the leakage light of the core part 141 (CH1) is not collected in the core part 142 (CH2), but instead is adjacent to the core part 142 and located on the opposite side to the core part 142. It is preferable that the distribution reflects the fact that it has gathered in the side cladding portion 153 (CL2). That is, it is preferable that the intensity distribution P1 of the emitted light has a minimum value Ps1 in the core portion 142 (CH2) and a maximum value Pm2 in the side cladding portion 153 (CL2) as described above. The optical waveguide 1 having the intensity distribution P1 of the emitted light as described above intentionally collects the leaked light from the core part 141 that cannot be completely prevented in the side cladding part 153, resulting in leakage at the core part 142. Light concentration can be prevented. As a result, the optical waveguide 1 that can more reliably suppress crosstalk is obtained.

  In this case, the difference in intensity between the maximum value Pm2 in the side clad part 153 (CL2) and the minimum value Ps1 in the core part 142 (CH2) is based on the maximum value Pm1 in the core part 141 (CH1) described above. , Preferably about 3 to 20 dB, more preferably about 5 to 15 dB. If the difference in intensity between the maximum value Pm2 and the minimum value Ps1 is within the above range, the occurrence of crosstalk in the core portion 142 is surely prevented, so that the optical waveguide 1 can perform higher-quality optical communication. It can be done.

  Further, the local maximum value Pm2 in the side clad part 153 (CL2) is preferably about −60 to −20 dB, more preferably about −50 to −30 dB with respect to the local maximum value Pm1 in the core part 141. If the intensity of the maximum value Pm2 is within the above range, the intensity of the minimum value Ps1 is optimized according to the intensity of the maximum value Pm2, and the occurrence of crosstalk in the core portion 142 is more reliably prevented. In addition, when the intensity of the maximum value Pm2 is less than the lower limit value, there is a possibility that the above-described action of collecting leakage light in the side cladding portion 153 becomes insufficient, and the occurrence of crosstalk cannot be sufficiently suppressed. On the other hand, when the intensity of the maximum value Pm2 exceeds the upper limit value, more than necessary leakage light gathers in the side cladding portion 153, and normal optical coupling between the core portions 141 and 142 and the light receiving element is prevented at the emission side end portion. There is a fear.

  The intensity difference between the local maximum value Pm2 in the side cladding part 153 (CL2) and the local minimum value Ps1 in the core part 142 (CH2) is g1, and the intensity of the optical signal observed in the core part 141 (CH1) and the core part 142 are determined. When the difference in strength from the minimum value Ps1 in (CH2) is g2, g1 / g2 preferably satisfies the relationship of 0.05 to 0.5, and satisfies the relationship of 0.1 to 0.4. Is more preferable. As a result, it is possible to more reliably achieve both a reduction in transmission loss and a reduction in pulse signal dullness and suppression of crosstalk. In addition, when g1 / g2 is less than the said lower limit, since the height of the maximum value Pm2 is too low, there is a possibility that the crosstalk cannot be sufficiently suppressed. On the other hand, when g1 / g2 exceeds the upper limit, more than necessary leakage light gathers in the side cladding portion 153, and normal optical coupling between the core portions 141 and 142 and the light receiving element may be hindered at the emission side end portion. is there.

  The intensity distribution P1 of the emitted light may be a discontinuously changed shape, but is preferably a continuously changed shape. If the intensity distribution P1 of the emitted light has such a shape, the occurrence of crosstalk can be prevented more reliably.

  Further, as described above, the width of the core portion 14 is preferably about 20 to 200 μm. However, by setting the width of the core portion 14 in such a range, light leaked into the side cladding portion 153 described above. The necessary and sufficient action is to collect the crosstalk, and the occurrence of crosstalk can be more reliably suppressed.

  The intensity distribution P1 of the emitted light as described above can be acquired as follows.

  FIG. 3 is a diagram for explaining a method of measuring the intensity distribution of outgoing light on the outgoing side end face of the optical waveguide.

  In the method shown in FIG. 3, first, the incident-side optical fiber 21 having a diameter of 50 μm is disposed so as to face one of the core portions 14 of the incident-side end face 1a of the optical waveguide 1 to be measured. The incident-side optical fiber 21 is connected to a light emitting element (not shown) for making light incident on the optical waveguide 1, and is arranged so that the optical axis thereof coincides with the optical axis of the core portion 14. Yes.

  On the other hand, an exit side optical fiber 22 having a diameter of 62.5 μm is disposed on the exit side end face 1b of the optical waveguide 1 so as to face the end surface 1b. The emission-side optical fiber 22 is connected to a light receiving element (not shown) for receiving the emitted light emitted from the optical waveguide 1, and its optical axis is the center in the thickness direction of the core layer of the optical waveguide 1. It is aligned with the line. The exit-side optical fiber 22 is configured to be able to scan the plane including this center line while maintaining a constant distance from the exit-side end face 1b.

  Then, the emission side optical fiber 22 is scanned while the light is incident on one of the core portions from the incident side optical fiber 21. Then, by measuring the intensity of the emitted light measured by the light receiving element with respect to the position of the emission side optical fiber 22, the intensity distribution P1 of the emitted light with respect to the position of the emission side end face 1b can be obtained.

  Here, the optical waveguide 1 showing the intensity distribution P1 of the emitted light as described above includes a region having a relatively high refractive index and a region having a relatively low refractive index in the width direction of the core layer 13, and has a continuous refractive index. It is obtained by forming a changed refractive index profile W. That is, in the optical waveguide 1 having the shape of the refractive index distribution W, the aforementioned intensity distribution P1 of the emitted light can be observed.

Hereinafter, an example of the refractive index distribution W will be described.
4A is a cross-sectional view taken along the line XX shown in FIG. 1, and FIG. 4B is a cross-sectional view taken along the line X-X of FIG. 4 where the horizontal axis indicates the position of the core layer thickness on the center line C1. It is a figure which shows an example of refractive index distribution W when taking and taking a refractive index on the vertical axis | shaft.

  The core layer 13 includes four local minimum values Ws1, Ws2, Ws3, and Ws4 and five local maximum values Wm1, Wm2, Wm3, Wm4, and Wm5 as shown in FIG. It has a refractive index distribution W. The five maximum values include a maximum value (first maximum value) Wm2 and Wm4 having a relatively high refractive index, and a maximum value (second maximum value) Wm1, Wm3 having a relatively low refractive index. Wm5 exists.

  Among these, there are local maximum values Wm2 and Wm4 having a relatively large refractive index between the minimum value Ws1 and the minimum value Ws2, and between the minimum value Ws3 and the minimum value Ws4, respectively. The values Wm1, Wm3, and Wm5 are local maximum values with relatively small refractive indexes.

  The minimum value Ws1 is on the boundary line between the side cladding part 151 and the core part 141, the minimum value Ws2 is on the boundary line between the core part 141 and the side cladding part 152, and the minimum value Ws3 is on the boundary line between the side cladding part 152 and the core part 142. The minimum value Ws4 is located on the boundary line between the core part 142 and the side clad part 153, respectively.

  The local maximum values Wm2, Wm4 are preferably located at the center of the core portions 141, 142, while the local maximum values Wm1, Wm3, Wm5 are positioned at the center of the side cladding portions 151, 152, 153. It is preferable.

  That is, the refractive index distribution W should have at least 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. Note that this region is repeatedly provided according to the number of core portions. When the number of core portions 14 is two as in the present embodiment, the refractive index distribution W has a second maximum value, a minimum value, and a first value. Local maximum values, local minimum values, second local maximum values, local minimum values, first local maximum values, local minimum values, second local maximum values, and the like. Any shape in which the maximum value of 1 and the second maximum value are alternately arranged may be used.

  The plurality of local minimum values, the plurality of first local maximum values, and the plurality of second local maximum values are preferably substantially the same as each other, but the local minimum values are the first local maximum value and the second local maximum value. As long as the relationship that the second maximum value is smaller than the first maximum value and the second maximum value is smaller 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.

  In addition, the optical waveguide 1 has an elongated strip shape, and the refractive index distribution W as described above is maintained substantially the same in the entire longitudinal direction of the optical waveguide 1.

  Here, each of the four minimum values Ws1, Ws2, Ws3, and Ws4 is less than the average refractive index WA in the adjacent side cladding portion 15. Thus, a region having a refractive index smaller than the average refractive index WA of the side cladding portion 15 exists between each core portion 14 and each side cladding portion 15. As a result, a steeper refractive index gradient is formed in the vicinity of each of the local minimum values Ws1, Ws2, Ws3, and Ws4, thereby suppressing light leakage from each of the core portions 14, thereby reducing transmission loss. Further, the optical waveguide 1 in which the occurrence of crosstalk is suppressed in the width direction is obtained.

  Further, the refractive index distribution W changes continuously as a whole. Thereby, compared with an optical waveguide having a step index type refractive index profile, the effect of confining light in the core portion 14 is further enhanced, so that transmission loss can be further reduced and occurrence of crosstalk can be further suppressed.

  Furthermore, according to the refractive index distribution W having the respective minimum values Ws1, Ws2, Ws3, and Ws4 as described above and the refractive index continuously changing, the region closer to the center of the core portion 14 is transmitted. Since light propagates intensively, a difference in propagation time for each optical path is less likely to occur. For this reason, even when the transmission light includes a pulse signal, it is possible to suppress blunting of the pulse signal (spreading of the pulse signal). As a result, the optical waveguide 1 that can further improve the quality of optical communication is obtained.

  Note that the refractive index continuously changing in the refractive index distribution W is a state in which the curve of the refractive index distribution W is rounded in each part and the curve is differentiable.

  Further, in the refractive index distribution W, the maximum values Wm2 and Wm4 are located in the core portions 141 and 142 as shown in FIG. 4, but the core portions 141 and 142 are located in the central portion of the width. It is preferable. Thereby, in each core part 141 and 142, the probability that transmission light will gather in the center part of the width of core part 141 and 142 becomes high, and the probability that it will leak to side cladding parts 151, 152, and 153 becomes relatively low. As a result, transmission loss of the core parts 141 and 142 can be further reduced and crosstalk can be further suppressed.

  The central portion of the width of the core portion 141 is a region having a distance of 30% of the width of the core portion 141 on both sides from the midpoint between the minimum value Ws1 and the minimum value Ws2.

  In addition, it is desirable that the positions of the maximum values Wm2 and Wm4 be located in the center of the width of the cores 141 and 142 if possible, but not necessarily in the center but in the vicinity of the edges of the cores 141 and 142. It suffices if it is located other than (in the vicinity of the interfaces with the side clad portions 151, 152, 153).

  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, the maximum values Wm1, Wm3, and Wm5 in the refractive index distribution W are located in the side cladding portions 151, 152, and 153 as shown in FIG. , 153 is preferably located outside the vicinity of the edge (near the interface with the cores 141 and 142). 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 transmitted light leaks into the side clad parts 151, 152, 153. As a result, transmission loss of the core parts 141 and 142 can be reduced and crosstalk can be further suppressed.

  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.

  In addition, the local maximum values Wm1, Wm3, Wm5 are located at the center of the width of the side cladding portions 151, 152, 153, and the local minimum values Ws1, Ws2, Ws3, which are adjacent to the local maximum values Wm1, Wm3, Wm5. It is preferable that the refractive index continuously decreases toward Ws4. 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, and the maximum values Wm1, Since light can be reliably confined in the vicinity of Wm3 and Wm5, leakage of transmission light from the core portions 141 and 142 described above can be more reliably suppressed.

  Furthermore, the local maximum values Wm1, Wm3, and Wm5 are smaller in refractive index than the local maximum values Wm2 and Wm4 located in the core portions 141 and 142 described above. Although it does not have, since the refractive index is higher than the surroundings, it has a slight light transmission property. As a result, the side clad parts 151, 152, and 153 have an effect of preventing transmission to other core parts by confining transmission light leaked from the core parts 141 and 142. That is, the presence of the maximum values Wm1, Wm3, and Wm5 makes it possible to more reliably suppress crosstalk.

  Note that the minimum values Ws1, Ws2, Ws3, and Ws4 are less than the average refractive index WA of the adjacent side cladding portions 15 as described above, 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 20%. 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 between the minimum values Ws1, Ws2, Ws3, Ws4 and the maximum values Wm1, Wm3, Wm5 is about 6 to 90% of the difference between the minimum values Ws1, Ws2, Ws3, Ws4 and the maximum values Wm2, Wm4. Is more preferable, about 10 to 70% is more preferable, and about 14 to 40% is further preferable. As a result, the balance between the refractive index height of the side cladding portion 15 and the refractive index height of the core portion 14 is optimized, and the optical waveguide 1 has particularly excellent optical transmission properties and more reliably suppresses crosstalk. It will be possible.

  The difference in refractive index between the minimum values Ws1, Ws2, Ws3, and Ws4 and the maximum values Wm2 and Wm4 in the core portions 141 and 142 is preferably as large as possible, but is about 0.005 to 0.07. Preferably, it is about 0.007 to 0.05, more preferably about 0.01 to 0.03. 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 has a maximum value when the horizontal axis indicates the position of the cross section of the core layer 13 and the vertical axis indicates the refractive index. If the refractive index is continuously changing in the vicinity of Wm2 and the maximum value Wm4, it may have a substantially convex V shape (substantially linear except for the maximum value). It has an approximately U-shape that is convex upward (the entire vicinity of the maximum value is rounded). 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 has a shape in which the refractive index continuously changes in the vicinity of the minimum value Ws1, the vicinity of the minimum value Ws2, the vicinity of the minimum value Ws3, and the vicinity of the minimum value Ws4. If so, it may have a substantially convex V shape (substantially linear except for the maximum value), but preferably has a substantially U shape convex downward (the entire vicinity of the maximum value is rounded). It is said.

  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.

  Each maximum value Wm1, Wm2, Wm3, Wm4, and Wm5 may be substantially U-shaped convex upward as described above, but the refractive index is not substantially changed near the top. May be included. Even if the refractive index distribution W has such a shape in the vicinity of the top of each local maximum value, the optical waveguide of the present invention exhibits the above-described actions and effects. Here, the flat portion where the refractive index does not substantially change is a region where the refractive index fluctuation is less than 0.001, and the refractive index continuously decreases on both sides thereof. Say.

  Although the length of a flat part is not specifically limited, Preferably it is 100 micrometers or less, More preferably, it is 20 micrometers or less, More preferably, you may be 10 micrometers or less.

  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 the case where the core layer 13 has the two core parts 14 was demonstrated in this embodiment, the number of the core parts 14 is not specifically limited, Three or more may be sufficient.

  When the number of core portions 14 increases to 3, 4, 5,..., The number of local minimum values of the refractive index distribution W is increased to 6, 8, 10,. do it.

  The constituent material (main material) of the core layer 13 as described above is not particularly limited as long as it is a material that causes the above-described difference in refractive index, but specifically, acrylic resin, methacrylic resin, polycarbonate, polystyrene, epoxy Cyclic ether resins such as polyamide resins and oxetane resins, polyamides, polyimides, polybenzoxazoles, polysilanes, polysilazanes, silicone resins, fluorine resins, polysilanes, polyurethanes, benzocyclobutene resins, norbornene resins, etc. In addition to various resin materials such as cyclic olefin 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).

(Clad layer)
The clad layers 11 and 12 constitute clad portions located at the lower and upper portions of the core layer 13, respectively.

  The average thickness of the clad layers 11 and 12 is preferably about 0.1 to 1.5 times the average thickness of the core layer 13 (average height of each core portion 14). More preferably, the average thickness of the clad layers 11 and 12 is not particularly limited, but is usually preferably about 1 to 300 μm, and preferably about 5 to 200 μm. More preferably, it is about 10 to 100 μm. Thereby, the function as a clad part is suitably exhibited while preventing the optical waveguide 1 from becoming unnecessarily large (thickened).

  Further, as the constituent material of the cladding layers 11 and 12, for example, the same material as the constituent material of the core layer 13 described above can be used, but a norbornene polymer is particularly preferable.

  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.

  The clad layers 11 and 12 may be provided as necessary, and either one or both may be omitted. In this case, the surface of the core layer 13 is exposed to the atmosphere (air), but since the refractive index of air is sufficiently low, the air can substitute for the functions of the cladding layers 11 and 12.

(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 the 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.

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

  FIG. 5 is a perspective view showing a second embodiment of the optical waveguide of the present invention (partially cut out and shown in a transparent manner), and FIG. 6 shows light in one of the core portions of the optical waveguide shown in FIG. It is a figure which shows an example of intensity distribution of the emitted light when radiates. In the following description, the upper side in FIG. 5 is referred to as “upper” and the lower side is referred to as “lower”. FIG. 5 exaggerates the thickness direction of the layers (the vertical direction in each figure).

  Hereinafter, although 2nd Embodiment of an optical waveguide is described, it demonstrates centering around difference with 1st Embodiment, The description is abbreviate | omitted about the same matter. In FIG. 5, the same components as those of the first embodiment are denoted by the same reference numerals as those described above, and detailed description thereof is omitted.

  The second embodiment is the same as the first embodiment except that it has two stacked core layers 13. That is, the optical waveguide 1 shown in FIG. 5 is formed by laminating five layers of the clad layer 11, the core layer 13, the clad layer 121, the core layer 13, and the clad layer 122 in this order from the lower side.

  Of these, the two core layers 13 have two core portions 14 arranged in parallel in the width direction and three side clad portions 15 arranged in parallel so as to sandwich each core portion 14, as in the first embodiment. Is formed.

  More specifically, of the two core layers 13 shown in FIG. 5, the lower core layer 131 includes two parallel core portions 141 and 142 and three parallel side cladding portions 151, 152, and 153. It is provided alternately. As a result, the core portions 141 and 142 are surrounded by the side clad portions 151, 152, and 153 and the clad layers 11 and 121, respectively.

  On the other hand, the upper core layer 132 is also alternately provided with two parallel core portions 143 and 144 and three side clad portions 154, 155 and 156 in parallel. Thereby, each core part 143, 144 will be in the state surrounded by each side cladding part 154, 155, 156 and each cladding layer 121, 122, respectively.

  In FIG. 5, the core portions 141 and 143 located on the left side of the core layers 131 and 132 are provided at the same position in the width direction of the optical waveguide 1. Similarly, the core parts 142 and 144 located on the right side of the core layers 131 and 132 are provided at the same position in the width direction of the optical waveguide 1.

  Here, light is incident on one desired end portion of the plurality of core portions 141, 142, 143, and 144 of the optical waveguide 1 shown in FIG. 5, and the intensity distribution P2 of the emitted light at the other end portion is obtained. The intensity distribution shows a characteristic distribution.

  FIG. 6 is a diagram showing the intensity distribution P2 of the outgoing light on the outgoing side end surface when light is incident on the core portion 141 of the optical waveguide 1 shown in FIG. It is a figure which shows an example of intensity distribution when the position of a side end surface is taken.

  When light is incident on the core portion 141 (CH1), the intensity of the emitted light is highest at the central portion of the emission end of the core portion 141. The intensity of the emitted light decreases as the distance from the central portion of the core portion 141 decreases, but takes a locally small value in the core portion 143 (CH2) adjacent in the thickness direction of the core portion 141. That is, the intensity distribution P2 of the emitted light in this case takes the maximum value Pm1 at the center of the emission end of the core part 141 (CH1) and takes the minimum value Ps1 at the core part 143 (CH2). According to the optical waveguide 1 in which the emitted light has such an intensity distribution, although the complete leakage of the light propagating through the core portion 141 cannot be prevented, the leakage light is suppressed from collecting in the core portion 143. “Crosstalk” in which leaked light interferes with the core portion 143 can be reliably suppressed. As a result, even if the optical waveguide 1 is multi-channeled and densified not only in the width direction but also in the thickness direction, the occurrence of crosstalk can be reliably prevented.

  Moreover, according to the optical waveguide 1 showing the intensity distribution P2 of the emitted light as described above, there is an advantage that the propagation loss and the blunting of the pulse signal are suppressed in addition to the suppression of the crosstalk as described above.

  Further, in the intensity distribution P2 of the emitted light, the leakage light of the core part 141 (CH1) is not collected in the core part 143 (CH2), but instead is adjacent to the core part 143 and located on the opposite side to the core part 141. It is preferable that the distribution reflects the collection in the cladding layer 122. That is, it is preferable that the intensity distribution P2 of the emitted light has a minimum value Ps1 in the core portion 143 (CH2) and a maximum value Pm2 in the cladding layer 122 (CL2) as described above (see FIG. 6). . In the optical waveguide 1 having the intensity distribution P2 of the emitted light, the leakage light from the core part 141 that cannot be completely prevented is intentionally collected in the cladding layer 122. As a result, the leakage light in the core part 143 is obtained. Can be prevented. As a result, an optical waveguide 1 that can more reliably suppress crosstalk in the thickness direction is obtained.

  In this case, the intensity difference between the maximum value Pm2 in the cladding layer 122 (CL2) and the minimum value Ps1 in the core part 143 (CH2) is based on the maximum value Pm1 in the core part 141 (CH1) described above. It is preferably about 3 to 20 dB, and more preferably about 5 to 15 dB. If the difference in intensity between the maximum value Pm2 and the minimum value Ps1 is within the above range, the occurrence of crosstalk in the core portion 143 is surely prevented, so that the optical waveguide 1 performs higher-quality optical communication. It can be done.

  In addition, the maximum value Pm2 in the cladding layer 122 (CL2) is preferably about −60 to −20 dB, more preferably about −50 to −30 dB with respect to the maximum value Pm1 in the core portion 141. If the intensity of the maximum value Pm2 is within the above range, the intensity of the minimum value Ps1 is optimized according to the intensity of the maximum value Pm2, and the occurrence of crosstalk in the core portion 143 is more reliably prevented. When the intensity of the maximum value Pm2 is less than the lower limit, the above-described effect of collecting leakage light in the cladding layer 122 may be insufficient, and the occurrence of crosstalk may not be sufficiently suppressed. When the intensity of the maximum value Pm2 exceeds the upper limit, more than necessary leakage light gathers in the cladding layer 122, and normal optical coupling between the cores 141 and 143 and the light receiving element may be hindered at the emission side end. is there.

  The intensity difference between the maximum value Pm2 in the cladding layer 122 (CL2) and the minimum value Ps1 in the core part 143 (CH2) is g3, and the intensity of the optical signal observed in the core part 141 (CH1) and the core part 143 ( When the strength of the minimum value Ps1 in CH2) is g4, it is preferable that g3 / g4 satisfies the relationship of 0.05 to 0.5, and more preferably satisfies the relationship of 0.1 to 0.4. preferable. As a result, it is possible to more reliably achieve both a reduction in transmission loss and a reduction in pulse signal dullness and suppression of crosstalk. In addition, when g3 / g4 is less than the lower limit, the height of the maximum value Pm2 is too low, and thus crosstalk may not be sufficiently suppressed. On the other hand, when g3 / g4 exceeds the upper limit, more than necessary leakage light collects in the cladding layer 122, and normal optical coupling between the cores 141 and 143 and the light receiving element may be hindered at the emission side end. .

  The intensity distribution P2 of the emitted light may be a shape that changes discontinuously, but is preferably a shape that changes continuously. If the intensity distribution P2 of the emitted light has such a shape, the occurrence of crosstalk can be prevented more reliably.

  Further, as described above, the height of the core portion 14 is preferably about 20 to 200 μm. However, when the height of the core portion 14 is set in such a range, the core portion 14 leaks into the cladding layer 122 described above. The action of collecting light is necessary and sufficient, and the occurrence of crosstalk can be more reliably suppressed.

  The intensity distribution P2 of the emitted light as described above can be obtained by the same method as the intensity distribution P1 of the emitted light described above.

  Here, the optical waveguide 1 showing the intensity distribution P2 of the emitted light as described above includes a region having a relatively high refractive index and a region having a relatively low refractive index in the thickness direction of the optical waveguide 1 and has a continuous refractive index. It is obtained by forming a refractive index profile T changed to That is, in the optical waveguide 1 having the shape of the refractive index distribution T, the aforementioned intensity distribution P2 of the emitted light can be observed.

Hereinafter, an example of the refractive index distribution T will be described.
7A is a diagram in which a part of the YY line cross-sectional view shown in FIG. 5 is cut out, and FIG. 7B shows the center in the width direction of the core portion of the YY cross-sectional view. It is a figure which shows typically an example of the refractive index distribution T on the centerline C2 to pass. FIG. 7B is a diagram schematically illustrating an example of a refractive index distribution when the horizontal axis indicates the refractive index and the vertical axis indicates the position in the thickness direction of the core portion of the cross section.

  The optical waveguide 1 has a refractive index distribution T including four minimum values Ts1, Ts2, Ts3, Ts4 and five maximum values Tm1, Tm2, Tm3, Tm4, Tm5 as shown in FIG. Have. Further, the five maximum values include a maximum value (first maximum value) Tm2 and Tm4 having a relatively large refractive index, and a maximum value (second maximum value) Tm1, Tm3 having a relatively small refractive index. Tm5 exists.

  Among these, there are local maximum values Tm2 and Tm4 having a relatively large refractive index between the local minimum value Ts1 and the local minimum value Ts2, and between the local minimum value Ts3 and the local minimum value Ts4, respectively. The values Tm1, Tm3, and Tm5 are maximum values with relatively small refractive indexes.

  The minimum value Ts1 is on the boundary line between the cladding layer 11 and the core part 141, the minimum value Ts2 is on the boundary line between the core part 141 and the cladding layer 121, and the minimum value Ts3 is the boundary between the cladding layer 121 and the core part 143. On the line, the local minimum value Ts4 is located on the boundary line between the core part 143 and the cladding layer 122, respectively.

  The local maximum values Tm2 and Tm4 are preferably located in the central portions of the core portions 141 and 143, while the local maximum values Tm1, Tm3, and Tm5 are located in the central portions of the cladding layers 11, 121, and 122. It is preferable.

  That is, the refractive index distribution T only needs to have at least 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. This region is repeatedly provided according to the number of core layers stacked. When the number of core layers 13 is two as in this embodiment, the refractive index distribution T has a second maximum value and a minimum value. Value, first local maximum value, local minimum value, second local maximum value, local minimum value, first local maximum value, local minimum value, second local maximum value, and the like. The value may be a shape in which the first maximum value and the second maximum value are alternately arranged.

  The plurality of local minimum values, the plurality of first local maximum values, and the plurality of second local maximum values are preferably substantially the same as each other, but the local minimum values are the first local maximum value and the second local maximum value. As long as the relationship that the second maximum value is smaller than the first maximum value and the second maximum value is smaller 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 optical waveguide 1 has an elongated strip shape, and the refractive index distribution T as described above is maintained substantially the same in the entire longitudinal direction of the optical waveguide 1.

  Here, the four minimum values Ts1, Ts2, Ts3, and Ts4 are less than the average refractive index TA in the adjacent cladding layers 11, 121, and 122, respectively. As a result, a region having a smaller refractive index than the average refractive index TA of each cladding layer 11, 121, 122 exists between each core portion 14 and each cladding layer 11, 121, 122. As a result, a steeper refractive index gradient is formed in the vicinity of each local minimum value Ts1, Ts2, Ts3, and Ts4. This suppresses light leakage from each core portion 14, thereby reducing transmission loss. In addition, the optical waveguide 1 in which the occurrence of crosstalk is suppressed in the thickness direction is obtained.

  Further, the refractive index distribution T continuously changes in refractive index as a whole. Thereby, compared with an optical waveguide having a step index type refractive index profile, the effect of confining light in the core portion 14 is further enhanced, so that transmission loss can be further reduced and occurrence of crosstalk can be further suppressed.

  Further, according to the refractive index distribution T having the respective minimum values Ts1, Ts2, Ts3, and Ts4 as described above and the refractive index continuously changing, the region closer to the center of the core portion 14 is transmitted. Since light propagates intensively, a difference in propagation time for each optical path is less likely to occur. For this reason, even when the transmission light includes a pulse signal, it is possible to suppress blunting of the pulse signal (spreading of the pulse signal). As a result, the optical waveguide 1 that can further improve the quality of optical communication is obtained.

  Note that the refractive index continuously changing in the refractive index distribution T is a state in which the curve of the refractive index distribution T is rounded at each part and the curve is differentiable.

  Further, in the refractive index distribution T, the maximum values Tm2 and Tm4 are located in the core portions 141 and 143 as shown in FIG. 7, but the core portions 141 and 143 are located in the central portion of the thickness. ing. Thereby, in each core part 141 and 143, the probability that transmission light will gather in the center part of the thickness of core part 141 and 143 becomes high, and the probability that it leaks relatively to each cladding layer 11, 121, 122 becomes low. . As a result, the transmission loss of the core portions 141 and 143 can be further reduced and crosstalk can be further suppressed.

  The central portion of the thickness of the core portion 141 is a region at a distance of 30% of the thickness of the core portion 141 on both sides from the midpoint between the minimum value Ts1 and the minimum value Ts2.

  Further, it is desirable that the positions of the local maximum values Tm2 and Tm4 be located at the center of the thickness of the cores 141 and 143 if possible, but the edge of the cores 141 and 143 is not necessarily the center. It suffices to be located outside the vicinity (near the interface with each cladding layer 11, 121, 122).

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

  On the other hand, the maximum values Tm1, Tm3, and Tm5 of the refractive index distribution T are located in the cladding layers 11, 121, and 122 as shown in FIG. , 122 is preferably located outside the vicinity of the edge (near the interface with the cores 141, 143). As a result, the local maximum values Tm2, Tm4 in the core portions 141, 143 and the local maximum values Tm1, Tm3, Tm5 in the respective cladding layers 11, 121, 122 are sufficiently separated from each other. , 143 can sufficiently reduce the probability that the transmitted light leaks into the cladding layers 11, 121, 122. As a result, transmission loss of the core parts 141 and 143 can be reduced and crosstalk can be further suppressed.

  The vicinity of the edge of each cladding layer 11, 121, 122 is a region having a distance of 5% of the thickness of each cladding layer 11, 121, 122 inside from the edge described above.

  The local maximum values Tm1, Tm3, and Tm5 are located at the center of the thickness of each of the cladding layers 11, 121, and 122, and the local minimum values Ts1, Ts2, and Ts3 that are adjacent to the local maximum values Tm1, Tm3, and Tm5. , It is preferable that the refractive index continuously decreases toward Ts4. Thereby, the separation distances between the maximum values Tm2, Tm4 in the core portions 141, 143 and the maximum values Tm1, Tm3, Tm5 in the respective cladding layers 11, 121, 122 are ensured to the maximum, and the maximum values Tm1, Since light can be reliably confined in the vicinity of Tm3 and Tm5, the leakage of the transmission light from the core parts 141 and 143 can be more reliably suppressed.

  Furthermore, since the local maximum values Tm1, Tm3, and Tm5 have a refractive index smaller than the local maximum values Tm2 and Tm4 located in the core portions 141 and 143, the high optical transmission characteristics of the core portions 141 and 143 are high. Although it does not have, since the refractive index is higher than the surroundings, it has a slight light transmission property. As a result, each of the clad layers 11, 121, and 122 has a function of preventing transmission to other core portions by confining transmission light leaked from the core portions 141 and 143. In other words, the presence of the maximum values Tm1, Tm3, and Tm5 can more reliably suppress crosstalk.

  Note that the minimum values Ts1, Ts2, Ts3, and Ts4 are less than the average refractive index TA of each of the cladding layers 11, 121, and 122 as described above, but the difference is desirably within a predetermined range. . Specifically, the difference between the minimum values Ts1, Ts2, Ts3, and Ts4 and the average refractive index TA of each of the cladding layers 11, 121, and 122 is the difference between the minimum values Ts1, Ts2, Ts3, and Ts4 and the core portions 141 and 143. The difference between the maximum values Tm2 and Tm4 is preferably about 3 to 80%, more preferably about 5 to 50%, and still more preferably about 7 to 30%. As a result, each of the clad layers 11, 121, and 122 has a light transmission property that is necessary and sufficient to suppress crosstalk. In addition, when the difference between the minimum values Ts1, Ts2, Ts3, and Ts4 and the average refractive index TA of each of the cladding layers 11, 121, and 122 is less than the lower limit value, the light transmission property in each of the cladding layers 11, 121, and 122 is high. There is a possibility that the crosstalk cannot be sufficiently suppressed due to being too small, and when the upper limit is exceeded, the optical transmission in each of the clad layers 11, 121, 122 is too large, and the core portions 141, 143 There is a risk of adversely affecting optical transmission.

  The difference between the minimum values Ts1, Ts2, Ts3, Ts4 and the maximum values Tm1, Tm3, Tm5 is about 6 to 90% of the difference between the minimum values Ts1, Ts2, Ts3, Ts4 and the maximum values Tm2, Tm4. Is more preferable, about 10 to 70% is more preferable, and about 14 to 40% is further preferable. As a result, the balance between the refractive index height of the cladding layer and the refractive index height of the core is optimized, and the optical waveguide 1 has particularly excellent optical transmission properties and can more reliably suppress crosstalk. It becomes.

  The difference in refractive index between the minimum values Ts1, Ts2, Ts3, and Ts4 and the maximum values Tm2 and Tm4 in the core portions 141 and 143 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 143.

  Further, the refractive index distribution T in the core portions 141 and 143 has a position of the center line C2 on the horizontal axis and a refractive index on the vertical axis (when FIG. 7 is rotated 90 ° counterclockwise). In the vicinity of the maximum value Tm2 and the vicinity of the maximum value Tm4, as long as the refractive index continuously changes, it may have a substantially convex V shape (substantially linear except for the maximum value). Preferably, it has a substantially U-shape projecting upward (the entire vicinity of the maximum value is rounded). When the refractive index distribution T has such a shape, the light confinement action in the core portions 141 and 143 becomes more remarkable.

  Further, as shown in FIG. 7B, the refractive index distribution T has a shape in which the refractive index continuously changes in the vicinity of the minimum value Ts1, the vicinity of the minimum value Ts2, the vicinity of the minimum value Ts3, and the vicinity of the minimum value Ts4. If so, it may have a substantially convex V shape (substantially linear except for the maximum value), but preferably has a substantially U shape convex downward (the entire vicinity of the maximum value is rounded). It is said.

  Further, in the refractive index distribution T shown in FIG. 7B, when the average refractive index in each of the cladding layers 11, 121, 122 is TA, the refractive index in the vicinity of the maximum values Tm2, Tm4 is continuously average refractive index TA. The width of the above portion is a [μm], and the width of the portion where the refractive index in the vicinity of the minimum values Ts1, Ts2, Ts3, and Ts4 is continuously less than the average refractive index TA 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 Ts1, Ts2, Ts3, and Ts4 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 Ts1, Ts2, Ts3, and Ts4 are too narrow, so that the effect of confining light in the core portions 141 and 143 may be reduced. On the other hand, when b exceeds the upper limit value, the substantial widths of the minimum values Ts1, Ts2, Ts3, and Ts4 are too wide, and accordingly, the thickness and pitch of the core portions 141 and 143 are limited, 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 TA in the cladding layer 11 can be approximated at the midpoint between the maximum value Tm1 and the minimum value Ts1.

  Each maximum value Tm1, Tm2, Tm3, Tm4, and Tm5 may be substantially U-shaped convex upward as described above, but the refractive index does not substantially change in the vicinity of the top. May be included. Even if the refractive index distribution T has such a shape in the vicinity of the top of each local maximum value, the optical waveguide of the present invention exhibits the above-described functions and effects. Here, the flat portion where the refractive index does not substantially change is a region where the refractive index fluctuation is less than 0.001, and the refractive index continuously decreases on both sides thereof. Say.

  Although the length of a flat part is not specifically limited, Preferably it is 100 micrometers or less, More preferably, it is 20 micrometers or less, More preferably, you may be 10 micrometers or less.

<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. 8-12 is a figure for demonstrating the manufacturing method (1st manufacturing method) of the optical waveguide 1 shown in FIG. 1, respectively. In the following description, the upper side in FIGS. 8 to 12 is referred to as “upper” and the lower side is referred to as “lower”.

  The optical waveguide 1 is manufactured by preparing a clad layer 11, a core layer 13, and a clad layer 12, and laminating them.

The first manufacturing method of the optical waveguide 1 is as follows: [1] After applying the core layer forming composition 900 on the support substrate 951 to form a liquid film, the support substrate 951 is placed on a level table to form the liquid film. While flattening, the solvent is evaporated (desolvent). Thereby, the layer 910 is obtained.
[2] Next, a refractive index difference is generated by irradiating a part of the layer 910 with actinic radiation to obtain the core layer 13 in which the core part 14 and the side cladding part 15 are formed. [3] Next, the cladding layers 11 and 12 are laminated on both surfaces of the core layer 13 to obtain the optical waveguide 1.

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

  The composition 900 for forming a core layer contains a polymer 915 and an additive 920 (in this embodiment, at least a monomer is included). Such a composition 900 for forming a core layer is a material that causes a reaction of at least a monomer in the polymer 915 by irradiation with actinic radiation and changes the refractive index distribution accordingly. That is, in the core layer forming composition 900, the refractive index distribution changes due to the deviation in the abundance ratio of the polymer 915 and the monomer, and as a result, the core portion 14 and the side cladding portion 15 are formed in the core layer 13. It is a material that can be used.

  Next, the core layer forming composition 900 is applied onto the support substrate 951 to form a liquid film (see FIG. 8A). Then, the support substrate 951 is placed on the level table to flatten the liquid film and evaporate (desolvent) the solvent. Thereby, the layer 910 is obtained (see FIG. 8B).

  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 resulting layer 910, the polymer (matrix) 915 is present substantially uniformly and randomly, and the additive 920 is substantially uniformly and randomly dispersed in the polymer 915. Thereby, the additive 920 is substantially uniformly and randomly dispersed in the layer 910.

  The average thickness of the layer 910 is appropriately set according to the thickness of the core layer 13 to be formed, and is not particularly limited, but is preferably about 5 to 300 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 core layer forming composition 900 or the layer 910.

  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 and fluorine resins, and one or more of these can be used in combination (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 norbornene repeating units containing such a polymeric group is used, both flexibility and heat resistance can be achieved.

  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 containing 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 resin containing the repeating unit 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 containing the repeating unit represented by the formula (1), particularly, R ₁ is an alkyl group having 4 to 10 carbon atoms from the viewpoint of achieving both flexibility and heat resistance. And a compound in which a and b are each 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.

（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.)

A norbornene-based resin containing a repeating unit of the formula (2) is prepared by dissolving norbornene having R ₂ and norbornene having an acrylic and methacrylic group in the side chain in toluene, and using the Ni compound (A) described above as a catalyst. It can be obtained by polymerization.

Among the norbornene-based resins containing the repeating unit represented by the formula (2), in particular, R ₂ is an alkyl group having 4 to 10 carbon atoms from the viewpoint of achieving both flexibility and heat resistance, and c Are compounds such as butyl norbornene and 2- (5-norbornenyl) methyl acrylate copolymer, hexyl norbornene and 2- (5-norbornenyl) methyl acrylate copolymer, decyl norbornene and 2- (acrylic acid 2- ( Copolymers with 5-norbornenyl) methyl are 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 containing the repeating unit of the formula (3) is obtained by dissolving norbornene having R ₄ and norbornene having an alkoxysilyl group in the side chain in toluene, and performing solution polymerization using the above-described Ni compound (A) as a catalyst. Can be obtained at

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 containing the repeating unit of the formula (4) is obtained by dissolving norbornene having R ₅ and norbornene having A ₁ and A ₂ in the side chain in toluene, and performing solution polymerization using Ni compound (A) as a catalyst. Can be obtained at

（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)

  In addition, as norbornene-type resin containing the repeating unit represented by Formula (4), for example, any of butyl norbornene, hexyl norbornene, or decyl norbornene, 2- (5-norbornenyl) methyl acrylate, and norbornenyl ethyl A terpolymer with either trimethoxysilane, triethoxysilyl norbornene or trimethoxysilyl norbornene, any of butyl norbornene, hexyl norbornene or decyl norbornene, 2- (5-norbornenyl) methyl acrylate and methyl glycidyl ether norbornene Terpolymer, butyl norbornene, hexyl norbornene or decyl norbornene, methyl glycidyl ether norbornene, norbornenyl ethyl trimethoxysilane , Terpolymers, etc. and either triethoxysilyl 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 containing the repeating unit of the formula (8) includes norbornene having R ₇ and norbornene containing — (CH ₂ ) _i —X ₁ —X ₂ (R ₈ ) _{3 -j} (Ar) _j in the side chain. It can be obtained by dissolving in toluene and solution polymerization using a Ni compound as a catalyst.

Of the norbornene resins containing the repeating unit 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, polysilane, 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 cyclopentadiene skeleton, phenol novolac type epoxy resin, cresol novolac type epoxy resin, triphenylmethane type epoxy resin, triphenylmethane type epoxy resin, aliphatic epoxy resin, triglycidyl isocyanurate, etc. Of these, one or more of these 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.

  Any polysilane may be used as long as the main chain is a polymer composed only of Si atoms. The main chain may be linear or branched. And in addition to Si atom, organic substituents, such as a hydrogen atom, a hydrocarbon group, and an alkoxy group, have couple | bonded with Si atom in polysilane.

  Among these, examples of the hydrocarbon group include an aliphatic hydrocarbon group having 1 to 10 carbon atoms which may be substituted with a halogen, an aromatic hydrocarbon group having 6 to 14 carbon atoms, and the like.

  Specific examples of the aliphatic hydrocarbon group include a chain hydrocarbon group such as methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group, decyl group, trifluoropropyl group, and nonafluorohexyl group, Examples thereof include alicyclic hydrocarbon groups such as a cyclohexyl group and a methylcyclohexyl group.

  Specific examples of the aromatic hydrocarbon group include a phenyl group, a p-tolyl group, a biphenyl group, and an anthracyl group.

  As an alkoxy group, a C1-C8 thing is mentioned, Specifically, a methoxy group, an ethoxy group, a phenoxy group, an octyloxy group etc. are mentioned.

  As the polyurethane, any polymer may be used as long as it is a polymer containing a urethane bond (—O—CO—NH—) in the main chain. And a urethane-urea copolymer containing a urethane bond and a urea bond (—NH—CO—NH—, —NH—CO—N═, or —NH—CO—N <) in the main chain, etc. Also good.

  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.

  Further, the polymer 915 as described above has a leaving group (leaving pendant group) that is branched from the main chain and at least a part of the molecular structure of which can be released from the main chain by irradiation with actinic radiation. Is preferred. That is, since the refractive index of the polymer 915 is lowered by the leaving group leaving, the polymer 915 can form a refractive index difference depending on whether or not the irradiation with active radiation is performed.

  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 in the polymer 915 having a leaving group in the side chain, and more preferably 20 to 60% by weight. preferable. When the content is within the above range, both flexibility and refractive index modulation function (effect of changing the refractive index difference) are particularly excellent.

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

(Additive)
Additive 920 contains 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 including at least one norbornene skeleton represented by the following structural formula A, 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 core layer forming composition 900 is preferably 0.01% by weight or more, more preferably 0.5% by weight or more, and 1% by weight or more. Is more preferable. In addition, it is preferable that an upper limit is 5 weight% or less.

  In addition, the additive 920 includes a catalyst precursor, a co-catalyst, an antioxidant, an ultraviolet absorber, a light stabilizer, a silane coupling agent, a coating surface improver, a thermal polymerization inhibitor, a leveling agent, and a surfactant. , Colorants, storage stabilizers, plasticizers, lubricants, fillers, inorganic particles, anti-aging agents, wettability improvers, antistatic agents, and the like.

  The layer 910 containing the polymer 915 and the additive 920 as described above has a predetermined refractive index due to the action of the additive 920 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. 9).

  Below, the case where what has a refractive index lower than the polymer 915 is used as a monomer 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. 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.

  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. 9, 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 0.1~9J / cm ^2, more preferably about ^{0.2~6J / cm 2, 0.2~3J / 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. 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. 13 is a diagram for explaining a state in which a refractive index difference is generated between the irradiated region 925 and the non-irradiated region 940. The horizontal axis indicates the position of the cross section of the layer 910, and the refractive index of the horizontal section indicates the vertical index. It is a figure which shows refractive index distribution when it takes on an axis | 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. 13 (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 all at once, but gradually move from a portion close to the irradiated region 925 and outward from the center of the unirradiated region 940 to compensate for this. Monomer migration also occurs. As a result, as shown in FIG. 13A, the high refractive index portion H is located on the non-irradiated region 940 side and the low refractive index portion L is located on the irradiated region 925 side across the boundary between the irradiated region 925 and the unirradiated region 940. Is formed. Since the high refractive index portion H and the low refractive index portion L are formed in accordance with the diffusion movement of the monomer as described above, they are necessarily constituted by smooth curves. Specifically, the high refractive index portion H has, for example, a substantially U shape that is convex upward, and the low refractive index portion L has, for example, a substantially U shape that is convex downward.

  The refractive index of the polymer obtained by polymerizing the monomers as described above is almost the same as the refractive index of the monomer before polymerization (the difference in refractive index is about 0 to 0.001). As the polymerization proceeds, the refractive index decreases according to the amount of the monomer and the amount of the substance derived from the monomer. Therefore, the shape of the refractive index distribution W can be controlled by appropriately adjusting the amount of monomer or polymerization initiator relative to the polymer.

  On the other hand, in the unirradiated region 940, the monomer is not polymerized because the polymerization initiator is 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 the 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. Thereby, the refractive index distribution W which the optical waveguide of this invention has is formed.

  The polymer 915 preferably has a leaving group as described above. This leaving group is released upon irradiation with actinic radiation 930 and decreases the refractive index of the polymer 915. Therefore, when the irradiation region 925 is irradiated with the actinic radiation 930, the above-described diffusion movement of the monomer is started, the leaving group is released from the polymer 915, and the refractive index of the irradiation region 925 decreases from before the irradiation. (See FIG. 13B).

  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. 13B is obtained. Note that the change in the refractive index in FIG. 13A and the change in the refractive index in FIG. 13B occur almost simultaneously. Such a refractive index change further expands this refractive index difference.

  In addition, the refractive index difference and the shape of the refractive index distribution to be formed can be controlled by adjusting the irradiation amount of the active radiation 930. For example, the refractive index difference can be enlarged by increasing the irradiation amount. Can do. Further, the layer 910 may be dried before the irradiation with the active radiation 930, but the shape of the refractive index distribution can be controlled by adjusting the degree of drying at that time. For example, by increasing the degree of drying, the diffusion transfer amount of the monomer can be suppressed.

  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 above principle, the core layer 13 having the refractive index distribution W is obtained (see FIG. 10).

  In the refractive index distribution W, there are minimum values Ws1, Ws2, Ws3, and Ws4 converted from the low refractive index portion L (see FIG. 4B), and these minimum values are the core portion 14 and the side cladding portion. 15 is located at the interface.

  The refractive index distribution W has a certain correlation with the monomer-derived structure concentration in the core layer 13. Therefore, it is possible to indirectly specify the refractive index distribution W of the optical waveguide 1 by measuring the concentration of the monomer-derived structure.

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

  Further, since the intensity distribution P of the light emitted from the optical waveguide 1 has a certain correlation with the refractive index distribution W, the refractive index distribution W is indirectly specified by using this. can do.

  In addition, for example, (1) a method of observing a refractive index dependent interference fringe using a dual-beam interference microscope and calculating a refractive index distribution from the interference fringe, (2) a refractive near field method ( It is possible to measure directly by means of a refractionated near field method (RNF). Among these, the refractive near field method can employ the measurement conditions described in, for example, JP-A-5-332880. On the other hand, the interference microscope is preferably used in that the refractive index distribution can be easily measured.

  Hereinafter, an example of a procedure for measuring the refractive index distribution using an interference microscope will be described. First, the optical waveguide is sliced in the cross-sectional direction (width direction) to obtain an optical waveguide fragment. For example, the optical waveguide is sliced so that the length is 200 to 300 μm. Next, a chamber filled with oil having a refractive index of 1.536 is produced in a space surrounded by two glass slides. And a measurement sample part and a blank sample part which does not put an optical waveguide fragment are produced by inserting an optical waveguide fragment in a space in the chamber. Next, using an interference microscope, the measurement sample portion and the blank sample portion are respectively irradiated with the light divided into two, and then the transmitted light is integrated to obtain an interference fringe photograph. Since the interference fringes are generated with the refractive index distribution (phase distribution) of the optical waveguide fragment, the refractive index distribution W in the width direction of the optical waveguide is obtained by image analysis of the obtained interference fringe photograph. Can do. In addition, when acquiring the refractive index distribution W, the accuracy of the refractive index distribution W can be improved by image analysis of a plurality of interference fringe photographs. When obtaining a plurality of interference fringe photographs, it is only necessary to change the optical path length by moving the prism in the interference microscope to obtain photographs having different interference fringe spacings and interference fringe spots. Further, when image analysis is performed on the interference fringe photograph, for example, analysis points may be set at intervals of 2.5 μm.

  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.

  [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. 11).

  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. 12A )reference).

  Then, as indicated by an arrow in FIG. 12A, 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. 12B).

  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.

  In the above description, the case where the core layer 13 and the clad layers 11 and 12 are stacked after the core layer 13 is irradiated with the active radiation 930 to form the core part 14 and the side clad part 15 has been described. The core layer 13 and the clad layers 11 and 12 may be stacked before 930 irradiation, and then the active radiation 930 may be irradiated.

  Further, the core layer 13 may be laminated in a plurality of layers via a cladding layer. Also in this case, if the layer is irradiated before being irradiated with the active radiation 930, the core part 14 and the side clad part 15 can be collectively formed on the plurality of core layers 13, so that the manufacturing process can be performed. Simplification can be achieved. Further, in this case, there is almost no displacement of the core portion 14 between the plurality of core layers 13. Therefore, the optical waveguide 1 with extremely high dimensional accuracy can be obtained as compared with the case where the core portions 14 and the side cladding portions 15 are formed on the core layers 13 and then laminated. Such an optical waveguide 1 has a particularly high optical coupling efficiency when optically coupling with a light emitting / receiving element or the like.

(Second manufacturing method)
Next, a first method (second manufacturing method) for manufacturing the first 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 core layer forming composition 900 is different.

The second method of manufacturing the optical waveguide 1 is as follows: [1] After applying the core layer forming composition 900 on the support substrate 951 to form a liquid film, the support substrate 951 is placed on a level table to form the liquid film. While flattening, the solvent is evaporated (desolvent). Thereby, the layer 910 is obtained.
[2] Next, after irradiating a part of the layer 910 with actinic radiation, the layer 910 is subjected to a heat treatment to cause a refractive index difference, and the core layer 13 having the core portion 14 and the side cladding portion 15 is formed. obtain. [3] Next, the cladding layers 11 and 12 are laminated on both surfaces of the core layer 13 to obtain the optical waveguide 1.

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

  FIG. 14 is a diagram for explaining a manufacturing method (third manufacturing method) of the optical waveguide 1 shown in FIG. In the following description, the upper side in FIG. 14 is referred to as “upper” and the lower side is referred to as “lower”.

  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 the formation method of the layer 910 containing the polymer 915, the additive 920, and the like is different.

  The third method of manufacturing the optical waveguide 1 is as follows: [1] Two types of optical waveguide forming compositions 901 and 902 (first composition and second composition) are extruded on a support substrate 951 in layers. 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. And the optical waveguide 1 is obtained.

Hereinafter, each process will be described sequentially.
[1] First, optical waveguide forming compositions 901 and 902 are prepared.

  The optical waveguide forming compositions 901 and 902 each contain a polymer 915 and an additive 920 (including at least a monomer in this embodiment), but the compositions are different.

  Of the two types of compositions, the optical waveguide forming composition 901 is mainly a material for forming the core layer 13 and is the same material as the core layer forming composition 900 described above.

  On the other hand, the optical waveguide forming composition 902 is mainly a material for forming the cladding layers 11, 121, and 122, and is composed of a material having a lower refractive index than the optical waveguide forming composition 901.

  The difference in refractive index between the optical waveguide forming composition 901 and the optical waveguide forming composition 902 is determined by setting the composition of the polymer 915, the composition of the monomer, the abundance ratio of the polymer 915 and the monomer, and the like. It can be adjusted appropriately.

  For example, when the refractive index of the monomer is lower than that of the polymer 915, the content of the monomer in the composition is higher in the optical waveguide forming composition 902 than in the optical waveguide forming composition 901. On the other hand, when the refractive index of the monomer is higher than that of the polymer 915, the content of the monomer in the composition is higher in the optical waveguide forming composition 901 than in the optical waveguide forming composition 902. In other words, the composition of the polymer 915 and the additive 920 in each of the optical waveguide forming compositions 901 and 902 is appropriately selected according to the refractive indexes of the polymer 915 and the monomer.

  Further, in the optical waveguide forming composition 901 and the optical waveguide forming composition 902, it is preferable that the compositions are set so that the monomer contents are substantially equal to each other. By setting in this way, the difference in monomer content between the optical waveguide forming composition 901 and the optical waveguide forming composition 902 becomes small, so that the diffusion movement of the monomer triggered by this is suppressed. The Although the diffusion movement of the monomer is useful in forming the refractive index difference as described above, it may be unavoidable to move in an undesirable direction. Further, since it is possible to form a refractive index distribution in the thickness direction of the layer 910 by a multicolor extrusion molding method described later, there is no problem even if the diffusion movement of the monomer is suppressed at least in the thickness direction, Rather, it is preferable that unintentional monomer diffusion transfer in the thickness direction is suppressed. By suppressing the unintended diffusion movement of the monomer, the optical waveguide 1 having the refractive index distribution T having the target shape can be reliably manufactured.

  When the monomer content is substantially equal, the conditions of the polymer 915 or the monomer may be different between the optical waveguide forming composition 901 and the optical waveguide forming composition 902. Specifically, the composition of the polymer 915 to be used is different between the optical waveguide forming composition 901 and the optical waveguide forming composition 902, and the molecular weight and the degree of polymerization are different even if the composition is the same. Good. By using the thing of the same composition, since compatibility becomes high mutually, it becomes easy to mix compositions. Thereby, the continuity of the refractive index distribution T can be improved.

  Also, when different compositions are used, the polymer 915 has the same basic composition, but the presence or absence of a leaving group (reaction medium) may be changed. For example, it is preferable that the polymer 915 contained in the optical waveguide forming composition 901 contains a leaving group, while the polymer 915 contained in the optical waveguide forming composition 902 does not contain a leaving group. As a result, separation of the leaving group occurs only in the core layer 13, and a refractive index difference is formed in the layer, and in the cladding layers 11, 121, and 122, separation of the leaving group does not occur. The refractive index does not change, and the refractive indexes of the cladding layers 11, 121, and 122 can be made relatively uniform. In this case, the addition of the additive 920 (monomer, polymerization initiator, etc.) can be omitted in both the optical waveguide forming composition 901 and the optical waveguide forming composition 902.

  On the other hand, when at least the additive 920 described above in the optical waveguide forming composition 901 contains a monomer, the polymer 915 contained in each of the optical waveguide forming compositions 901 and 902 does not necessarily contain a leaving group. It does not have to be.

  In addition, the monomers contained between the optical waveguide forming composition 901 and the optical waveguide forming composition 902 may be the same or different. In addition, since the mutual movement of a mutual monomer arises reliably by using the thing of the same composition, the refractive index distribution T mentioned above can be clarified more. As a result, the optical waveguide 1 having excellent characteristics can be obtained.

  Further, the optical waveguide forming composition 901 may contain a monomer, while the optical waveguide forming composition 902 may contain no monomer. In this case, in each of the cladding layers 11 and 12, no monomer diffusion movement occurs in the layer, so that the refractive index in each of the cladding layers 11, 121, and 122 can be made uniform.

  Further, the composition of the monomer used, that is, the refractive index may be varied. In this way, the optical waveguide forming composition 901 and the optical waveguide forming composition 902 have substantially the same monomer content, and a refractive index difference is formed between the two while suppressing the diffusion movement of the monomer. can do.

  The additive 920 in the optical waveguide forming composition 901 may contain a polymerization initiator, while the additive 920 in the optical waveguide forming composition 902 may not contain a polymerization initiator. In this case, the monomer polymerization reaction is accelerated only in the core layer 13, and the monomer polymerization reaction is not accelerated in the cladding layers 11, 121, and 122. Therefore, in the cladding layers 11, 121, and 122, a change in refractive index is suppressed, and the refractive index within the layer can be made relatively uniform.

  However, the addition of the polymerization initiator is not limited to the above case, and both the optical waveguide forming composition 901 and the optical waveguide forming composition 902 may contain a polymerization initiator. Even in this case, it is preferable to suppress the polymerization reaction of the monomer as much as possible in the cladding layers 11, 121, and 122. Therefore, the types and additions of the polymerization initiators included in the optical waveguide forming composition 901 and the optical waveguide forming composition 902 What is necessary is just to make it differ. Specifically, for example, a polymerization initiator that is highly reactive with respect to the wavelength of the active radiation 930 is used as the polymerization initiator contained in the optical waveguide forming composition 901, and the polymerization initiator contained in the optical waveguide forming composition 902 is used. As for a thing with low reactivity with respect to the wavelength of actinic radiation 930, it may be used. When the same type of polymerization initiator is used, the amount added to the optical waveguide forming composition 902 may be less than that of the optical waveguide forming composition 901.

  Furthermore, a photoacid generator may be used as the polymerization initiator contained in the optical waveguide forming composition 901, and a thermal acid generator may be used as the polymerization initiator contained in the optical waveguide forming composition 902. Thereby, the polymerization reaction of the monomer is promoted mainly in the layer of the core layer 13 with the irradiation of the active radiation 930, and the refractive index distribution W is formed. On the other hand, the polymerization of the monomer is performed in the cladding layers 11, 121, and 122. The reaction is not promoted. After the refractive index profile W is formed, heat is applied to the layer 910 to accelerate the monomer polymerization reaction in the cladding layers 11, 121, and 122. As a result, in the layer 910, the refractive index distribution T in the thickness direction is fixed.

  Examples of the thermal acid generator include sulfonium salt type compounds such as triphenylsulfonium trifluoromethanesulfonic acid and triphenylsulfonium nonafluorobutanesulfonic acid, diphenyliodonium trifluoromethanesulfonic acid, and diphenyliodonium nonafluorobutanesulfonic acid. Examples thereof include iodonium salt type compounds, phosnium salt type compounds such as pentaphenylphosnium trifluoromethanesulfonic acid, pentaphenylphosnium nonafluorobutanesulfonic acid, and the like.

  Next, the optical waveguide forming compositions 901 and 902 are formed in layers on the support substrate 951 by a multicolor extrusion molding method.

  In the multicolor extrusion molding method, the optical waveguide forming composition 901 is extruded in five layers, and at the same time, the optical waveguide forming composition 902 is extruded between each of these layers, thereby laminating nine layers. A formed body 914 is formed in a lump. Specifically, in the multicolor molded body 914, since the optical waveguide forming composition 901, 902, 901, 902, 901, 902, 901, 902, 901 is extruded in this order from the bottom, the composition At the boundary between objects, the optical waveguide forming composition 901 and the optical waveguide forming composition 902 are slightly turbid. Therefore, in the vicinity of the boundary between the compositions, a part of the optical waveguide forming composition 901 and a part of the optical waveguide forming composition 902 are mixed, and the mixing ratio continuously changes along the thickness direction. A region is formed. As a result, the multicolor molded body 914 has a high refractive index at the position where the optical waveguide forming composition 901 is extruded, and has a low refractive index at the position where the optical waveguide forming composition 902 is extruded. Between the layers, the refractive index continuously changes.

  Note that the shape of the refractive index distribution T in the thickness direction in the layer 910 can be freely adjusted by varying the amounts of the optical waveguide forming compositions 901 and 902 to be extruded in each layer.

  And the solvent in the obtained multicolor molded object 914 is evaporated (desolvation), and the layer 910 is obtained (refer FIG.14 (b)).

  The obtained layer 910 is a laminate in which the clad layer 11, the core layer 131, the clad layer 121, the core layer 132, and the clad layer 122 are laminated in this order from below, and has a refractive index distribution T in the thickness direction. It will be a thing.

  In the resulting layer 910, the polymer (matrix) 915 is present substantially uniformly and randomly, and the additive 920 is substantially uniformly and randomly dispersed in the polymer 915. Thereby, the additive 920 is substantially uniformly and randomly dispersed in the layer 910.

  The average thickness of the layer 910 is appropriately set according to the thickness of the optical waveguide 1 to be formed and is not particularly limited, but is preferably about 10 to 500 μm, and more preferably about 20 to 300 μm.

  By the way, the multicolor molded body 914 for obtaining such a layer 910 is manufactured using a die coater (multicolor extrusion molding apparatus) 800 as described below. In addition, in order to avoid that a figure becomes complicated, in the following description, it demonstrates using the figure simplified so that the number of layers to carry out extrusion molding may decrease.

  FIG. 15 is a perspective view showing a die coater for obtaining a multicolor molded body 914, and FIG. 16 is an enlarged longitudinal sectional view showing a part of the die coater.

  As shown in FIG. 15, the die coater 800 includes a die head 810 including an upper lip portion 811 and a lower lip portion 812 provided below the upper lip portion 811.

  The upper lip portion 811 and the lower lip portion 812 are each formed of a long block body and are overlapped with each other. A hollow manifold 820 is formed on the mating surfaces. The width of the manifold 820 is continuously expanded so as to increase toward the right side of the die head 810. On the other hand, the thickness of the manifold 820 is continuously reduced so as to decrease toward the right side of the die head 810. At the right end of the manifold 820, the width of the cavity is the maximum and the thickness is the minimum, and the slit 821 is formed.

  The die head 810 can extrude the optical waveguide forming compositions 901 and 902 supplied from the left side of the manifold 820 while forming the optical waveguide forming compositions 901 and 902 from the slit 821 to the right side. That is, the width and thickness of the multicolor molded body 914 are determined according to the shape of the slit 821.

  A mixing unit 830 is provided on the left side of the die head 810. The mixing unit 830 is configured by combining two systems of pipes for supplying the optical waveguide forming compositions 901 and 902 to the die head 810, respectively, and the first optical waveguide forming composition 901 is supplied to the die head 810. Supply pipe 831 and a second supply pipe 832 for supplying the optical waveguide forming composition 902 to the die head 810.

  In addition, the optical waveguide forming compositions 901 and 902 supplied from the first supply pipe 831 and the second supply pipe 832 merge at the connection portion 835 responsible for connection with the die head 810, and to the manifold 820 of the die head 810. Supplied with. Note that the second supply pipe 832 is branched into two in the middle, and is connected to the upper layer portion and the lower layer portion of the connection portion 835, respectively. On the other hand, the first supply pipe 831 is connected to the middle layer portion of the connection portion 835. That is, in the connection portion 835, the flow of one layer composed of the optical waveguide forming composition 901 is merged so as to be sandwiched between the upper and lower two layers of flow composed of the optical waveguide forming composition 902. That is, the die coater 800 can form a multicolor molded body 914 formed by laminating three layers of the optical waveguide forming compositions 902, 901, and 902 from below.

  Further, the mixing unit 830 has a plurality of pins 836 provided at the junction of the first supply pipe 831 and the second supply pipe 832. These pins 836 have a long cylindrical shape, and are arranged so that the axes thereof and the extending directions of the first supply pipe 831 and the second supply pipe 832 are substantially orthogonal. In FIG. 16, three pins 836 are provided between the upper layer portion and the middle layer portion of the connection portion 835 and between the lower layer portion and the middle layer portion. The number of pins 836 is not particularly limited, but is preferably 2 or more, more preferably about 3 to 10. Further, the pin 836 can be replaced with another structure (for example, mesh, punching metal, etc.) as long as it can cause turbulent flow between the optical waveguide forming compositions 901 and 902.

  On the right side of the die head 810, a transport unit 840 that transports the multicolor molded body 914 that has been subjected to multicolor extrusion molding is provided. The transport unit 840 includes a roller 841 and a transport film 842 that moves along the roller 841. The transport film 842 is transported from the lower side of FIG. 15 to the right side by the rotation of the roller 841. At that time, the multicolor molded body 914 is stacked on the roller 841. Thereby, it can convey to the right side, hold | maintaining the shape of the multicolor molded object 914. FIG.

Next, the operation of the die coater 800 will be described.
When the optical waveguide forming compositions 901 and 902 are simultaneously supplied to the mixing unit 830, a three-layer laminar flow is formed at the connection portion 835. When the optical waveguide forming compositions 901 and 902 merge at the connecting portion 835, the flow of the optical waveguide forming compositions 901 and 902 is disturbed by the action of the plurality of pins 836 provided in the merge portion. This disturbance obscures the boundary between the laminar flows, and a region where the optical waveguide forming composition 901 and the optical waveguide forming composition 902 are mixed is formed at the boundary.

  The laminar flow thus formed is expanded in the width direction and compressed in the thickness direction in the manifold 820 of the die head 810. As a result, the multicolor molded body 914 as described above is formed. By using such a multicolor molded body 914, the optical waveguide 1 having the refractive index distribution T in the thickness direction described above is finally obtained.

  In addition, although the multicolor molded object 914 is formed on the conveyance film 842, this conveyance film 842 can also be utilized as the support substrate 951 mentioned above as it is.

  Further, the die coater 800 shown in FIG. 15 can form a layer 910 including one core layer 13, but when a plurality of core layers 13 are provided, the structure of the mixing unit 830 can be changed accordingly. That's fine. Specifically, the first supply pipe 831 is branched according to the number of layers of the core layer 13, and each layer of the optical waveguide forming composition 901 extruded from each first supply pipe 831 is sandwiched. The number of branches of the second supply pipe 832 may be increased. If it does in this way, 2nd Embodiment of the optical waveguide mentioned above can be manufactured.

  FIG. 17 is a cross-sectional view showing another configuration example of the mixing unit 830. In FIG. 17, in order to avoid complication, the tube axes of the first supply pipe 831 and the second supply pipe 832 are schematically shown by lines, and each composition is provided in each of the supply pipes 831 and 832. The starting point for injecting is indicated by ●. Further, the flow of the optical waveguide forming composition 901 is indicated by a solid line arrow, the flow of the optical waveguide forming composition 902 is indicated by a broken line arrow, and the mixture of the optical waveguide forming composition 901 and the optical waveguide forming composition 902 is obtained. Each flow is indicated by a dashed-dotted arrow.

  The first supply pipe 831 shown in FIG. 17 is branched into three from the starting point 831a. Among these, the central branch pipe 8311 extends straight in the direction of the die head 810.

  On the other hand, a branch pipe 8312 branched from the start point 831a extends diagonally above the central branch pipe 8311, and a branch pipe 8313 branched from the start point 831a extends diagonally below the central branch pipe 8311. doing.

  A first starting point 832a of the second supply pipe 832 is provided at a position slightly above the central branch pipe 8311. A branch pipe 8321 branched from the first start point 832a extends upward. The branched branch pipe 8322 extends downward.

  Among these, the branch pipe 8322 extended downward is joined to the center branch pipe 8311 at the junction J1.

  Further, the branch pipe 8321 extending upward is configured to merge with the branch pipe 8312 described above at the mixing point M1. Before the mixing point M1, the branch pipe 8321 and the branch pipe 8312 are aggregated in the collecting pipe 8331. The collecting pipe 8331 is located at the junction J2 located on the die head 810 side (front end side) with respect to the branch pipe 8322. It joins the central branch pipe 8311.

  On the other hand, a second starting point 832b of the second supply pipe 832 is provided at a position slightly below the central branch pipe 8311, and the branch pipe 8323 branched from the second start point 832b is located above. Further, a branched branch pipe 8324 extends downward.

  Among these, the branch pipe 8323 extending upward joins the central branch pipe 8111 at the junction J1.

  Further, the branch pipe 8324 extending downward is configured to join the branch pipe 8313 described above at the mixing point M2. Before the mixing point M2, the branch pipe 8323 and the branch pipe 8324 are aggregated in the collecting pipe 8332, and this collecting pipe 8332 is at a junction J2 located on the die head 810 side (front end side) with respect to the branch pipe 8323. It joins the central branch pipe 8311.

  Moreover, the above-mentioned pin 836 is provided at each mixing point M1, M2 and each junction point J1, J2 (not shown). At each mixing point M1, M2, the arrangement and number of pins 836 are set so that the optical waveguide forming composition 901 and the optical waveguide forming composition 902 are completely mixed. On the other hand, the arrangement and number of pins 836 are set so that the optical waveguide forming composition 901 and the mixture are partially mixed at each junction J1 and J2.

  Here, the optical waveguide forming composition 901 is injected into the start point 831a of the first supply pipe 831, while the first start point 832a and the second start point 832b of the second supply pipe 832 are optically guided. A waveguide forming composition 902 is injected.

  The optical waveguide forming composition 901 constitutes the central layer of the multicolor molded body 914 via the central branch pipe 8311.

  On the other hand, the composition 902 for forming an optical waveguide is joined via the branch pipe 8322 and the branch pipe 8323 so as to sandwich the center layer.

Further, the mixture of the optical waveguide forming composition 901 and the optical waveguide forming composition 902 sandwiches the layer composed of the optical waveguide forming composition 902 through the second supply pipe 832. Join.
As described above, the multicolor molded body 914 is molded.

  By using such a mixing unit 830, for example, when the refractive index of the optical waveguide forming composition 901 is higher than the refractive index of the optical waveguide forming composition 902, the above-described second embodiment of the optical waveguide can be manufactured. A multicolor molded body 914 can be molded.

  Further, the supply conditions of the optical waveguide forming composition 901 from the first supply pipe 831, for example, the inner diameter of the first supply pipe 831, the merging angle of the first supply pipe 831 with respect to the second supply pipe 832, unit Supply amount per time, supply pressure, viscosity, temperature, and the like, and supply conditions of the optical waveguide forming composition 902 from the second supply pipe 832, for example, the inner diameter of the second supply pipe 832, the first supply pipe The occupancy rate of each composition in the multicolor molded body 914 is changed by appropriately setting the merging angle of the second supply pipe 832 with respect to 831, the supply amount per unit time, the supply pressure, the viscosity, the temperature, and the like. can do. Thereby, finally, the shape of the refractive index distribution T of the optical waveguide 1 can be freely changed.

  The multicolor extrusion molding method and the die coater are examples of a method and an apparatus for producing a multicolor molded body 914, and may be a multicolor molding method and a multicolor molding apparatus that can cause turbidity of the composition between layers. For example, various methods (apparatus) such as an injection molding method (apparatus) can be used.

  [2] Thereafter, the active radiation 930 is irradiated in the same manner as in the first production method. Thereby, a refractive index distribution W is formed in the core layer 13. Then, the optical waveguide 1 having the refractive index distribution W in the width direction and the refractive index distribution T in the thickness direction is obtained.

  The layer 910 obtained from the multicolor molded body 914 includes core layers 131 and 132. Therefore, when the layer 910 is irradiated with the actinic radiation 930, the core portion 14 and the side cladding portion 15 can be collectively formed on the plurality of core layers 131 and 132 by one irradiation. For this reason, the optical waveguide 1 having the plurality of core layers 131 and 132 can be manufactured with fewer steps. Further, in this case, there is almost no displacement of the core portion 14 between the plurality of core layers 131 and 132. Therefore, the optical waveguide 1 with extremely high dimensional accuracy can be obtained. Such an optical waveguide 1 has a particularly high optical coupling efficiency when optically coupling with a light emitting / receiving element or the like.

<Electronic equipment>
The optical waveguide of the present invention as described above is excellent in optical transmission efficiency and long-term reliability while suppressing crosstalk. 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.

  Further, the optical waveguide of the present invention has small transmission loss and pulse signal dullness, and interference does not easily occur even when the number of channels is increased and the density is increased. For this reason, an optical waveguide having high density and a small area and high reliability can be obtained. By mounting the optical waveguide, the reliability of electronic equipment can be improved and the size can be reduced.

  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.

  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.

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) Production of composition for forming core layer 10 g of the purified polymer # 1 was weighed into a 100 mL glass container, and 40 g of mesitylene, 0.01 g of antioxidant Irganox 1076 (manufactured by Ciba Geigy), cyclohexyl oxetane monomer (formula) (20), Toa Gosei CHOX, CAS # 483303-25-9, molecular weight 186, boiling point 125 ° C./1.33 kPa) 2 g, polymerization initiator (photoacid generator) Rhodosil Photoinitiator 2074 (manufactured by Rhodia, CAS # 178233-72-2) (2.5E-2 g in 0.1 mL of ethyl acetate) was dissolved uniformly, and then filtered through a 0.2 μm PTFE filter to obtain a clean core layer forming composition. Obtained.

(3) 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 55 ° C. for 10 minutes. After completely removing the solvent, the entire coated surface was irradiated with 80 mJ of ultraviolet light and heated in a dryer at 120 ° C. for 1 hour to cure the coating film to form 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 core layer-forming composition was uniformly applied on the lower clad layer with a doctor blade, and then placed in a dryer at 55 ° C. for 10 minutes. After the solvent was completely removed, a photomask was pressed and selectively irradiated with ultraviolet rays at 1300 mJ / cm ² . The mask was removed, and heating was performed at 150 ° C. in a dryer for 1.5 hours. It was confirmed that a very clear waveguide pattern appeared after heating. Moreover, formation of the core part and the side clad part was confirmed. The formed optical waveguide has eight core portions formed in parallel. The width of the core portion was 50 μm, the width of the side cladding portion was 80 μm, and the thickness of the core layer was 50 μm.

(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.

(Evaluation of refractive index distribution)
And about the cross section of the core layer of the obtained optical waveguide, the refractive index distribution W of the width direction was acquired with the interference microscope along the centerline of the thickness direction. As a result, the refractive index distribution W had a plurality of minimum values and maximum values, and the refractive index changed continuously.

  On the other hand, regarding the cross section of the optical waveguide, a refractive index distribution T in the thickness direction was obtained by an interference microscope along a center line passing through the center of the width of the core portion in the vertical direction. As a result, the refractive index distribution T was a so-called step index (SI) type.

(Example 2)
An optical waveguide was obtained in the same manner as in Example 1 except that the irradiation amount of ultraviolet rays was increased to 1500 mJ / cm ² .

(Example 3)
While increasing the irradiation amount of ultraviolet rays to 2000 mJ / cm ² and changing the molar ratio of each structural unit of polymer # 1 to 40 mol% for the hexyl norbornene structural unit and 60 mol% for the diphenylmethyl norbornene methoxysilane structural unit as the polymer An optical waveguide was obtained in the same manner as in Example 1 except that was used.

Example 4
The amount of UV irradiation was reduced to 500 mJ / cm ² and the polymer molar ratio of each structural unit of polymer # 1 was changed to 45 mol% for hexylnorbornene structural units and 55 mol% for diphenylmethylnorbornenemethoxysilane structural units. An optical waveguide was obtained in the same manner as in Example 1 except that was used.

(Example 5)
Except that the molar ratio of each structural unit of polymer # 1 was changed to 30 mol% for the hexylnorbornene structural unit and 70 mol% for the diphenylmethylnorbornenemethoxysilane structural unit as the polymer, the same as in Example 1. Thus, an optical waveguide was obtained.

(Example 6)
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 7)
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 8)
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 9
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 10)
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 11)
An optical waveguide was obtained in the same manner as in Example 1 except that the core layer forming composition was manufactured by the method shown below.

  10 g of the purified polymer # 1 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) (2.5E-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 composition for forming a core layer.

(Example 12)
An optical waveguide was obtained in the same manner as in Example 1 except that the core layer forming composition was manufactured by the method shown below.

  10 g of the purified polymer # 1 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 Rhodosil Photoinitiator 2074 (Rhodia, CAS # 178233-72-2) (2.5E-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 composition for forming a core layer.

(Example 13)
An optical waveguide was obtained in the same manner as in Example 1 except that the core layer forming composition was manufactured by the method shown below.

  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 (Daicel Chemical, Celoxide 2021P) 1 g, photoacid generator Rhodorsil Photoinitiator 2074 (Rhodia, CAS # 178233-72-2) (2.5E-2 g, in ethyl acetate 0.1 mL) ) And uniformly dissolved, followed by filtration with a 0.2 μm PTFE filter to obtain a clean composition for forming a core layer.

(Example 14)
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 15)
While changing the drying conditions of the lower clad layer and the core layer before ultraviolet irradiation to 60 ° C. × 10 minutes and using the core layer forming composition manufactured by the method shown below, An optical waveguide was obtained in the same manner as in Example 1.

  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) 2 g, photoacid generator Rhodorsil Photoinitiator 2074 (manufactured by Rhodia, CAS # 178233-72-2) (2.72E-2 g in 0.1 mL of ethyl acetate) was added and dissolved uniformly, and then 0.2 μm of PTFE was added. Filtration through a filter gave a clean core layer forming composition.

(Example 16)
An optical waveguide was obtained in the same manner as in Example 15 except that the irradiation amount of ultraviolet rays was reduced to 500 mJ / cm ² .

(Comparative Example 1)
An optical waveguide was obtained in the same manner as in Example 1 except for the following.
First, after forming a lower clad layer, a core layer forming composition in which the cyclohexyloxetane monomer was omitted from polymer # 1 was applied thereon, and then exposed and heated to obtain a core layer.
Thereafter, an optical waveguide was obtained by forming an upper cladding layer.

  In the obtained optical waveguide, the refractive index of the core part was almost constant, and the refractive index of the side cladding part was also almost constant. That is, the refractive index distribution W of the core layer of the obtained optical waveguide is a so-called step index type.

(Comparative Example 2)
An optical waveguide was obtained in the same manner as in Comparative Example 1 except that exposure was performed using a photomask whose transmittance was continuously changed so that the exposure amount was continuously changed during exposure.

  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. That is, the refractive index distribution W of the core layer of the obtained optical waveguide was a so-called graded index (GI) type.

  Table 1 shows the manufacturing conditions and Table 2 shows the parameters of the refractive index distribution W of the core layer for the optical waveguides obtained in the above examples and comparative examples.

(Example 17)
(1) Production of Composition for Forming Optical Waveguide (First Composition) 10 g of the polymer # 1 purified in Example 1 was weighed into a 100 mL glass container, and 40 g of mesitylene and an antioxidant Irganox 1076 (Ciba Geigy) 0.01 g, cyclohexyl oxetane monomer (monomer represented by formula (20), manufactured by Toa Gosei CHOX, CAS # 483303-25-9, molecular weight 186, boiling point 125 ° C./1.33 kPa) 2 g, polymerization initiator (light Acid generator) Rhodorsil Photoinitiator 2074 (manufactured by Rhodia, CAS # 178233-72-2) (2.5E-2 g in 0.1 mL of ethyl acetate) was added and dissolved uniformly, and then filtered through a 0.2 μm PTFE filter. And a clean composition for forming an optical waveguide was obtained.

(2) Production of Composition for Forming Optical Waveguide (Second Composition) The molar ratio of each structural unit of polymer # 1 purified in Example 1 was determined as follows: hexyl norbornene structural unit 80 mol%, diphenylmethylnorbornene methoxysilane structure A composition for forming an optical waveguide was obtained in the same manner as in the first composition, except that each unit was changed to 20 mol%, instead of the polymer # 1.

(3) Manufacture of Optical Waveguide First, a mixing unit was prepared in which the structure of the mixing unit shown in FIG. 16 was changed to increase the number of branches of the first supply pipe and the second supply pipe.

And by this die coater, multicolor extrusion molding was performed on a polyethersulfone (PES) film using the produced optical waveguide forming composition. Thus, the first composition is the first layer, the third layer, the fifth layer, the seventh layer, and the ninth layer, and the second composition is the second layer, the fourth layer, the sixth layer, and the eighth layer. A multicolored molded product was obtained as a layer. This was put into a dryer at 55 ° C. for 10 minutes, and the solvent was completely removed to obtain a film for forming an optical waveguide having a refractive index distribution T as shown in FIG. Next, a photomask was pressure-bonded to the optical waveguide forming film, and ultraviolet rays were selectively irradiated at 2000 mJ / cm ² . The mask was removed, and heating was performed at 150 ° C. for 1.5 hours in a dryer. After heating, a clear waveguide pattern appeared, and it was confirmed that a core portion and a side cladding portion were formed. Thereafter, a length of 10 cm was cut out from the obtained optical waveguide. The formed optical waveguide includes two core layers, and each core layer has eight core portions formed in parallel. Further, the width of the core portion was 50 μm, the width of the side cladding portion was 80 μm, and the thickness of the optical waveguide was 100 μm.

(Evaluation of refractive index distribution)
And about the cross section of the core layer of the obtained optical waveguide, the refractive index distribution W of the width direction was acquired with the interference microscope along the centerline of the thickness direction. As a result, the refractive index distribution W had a plurality of minimum values and maximum values, and the refractive index changed continuously.

  On the other hand, regarding the cross section of the optical waveguide, a refractive index distribution T in the thickness direction was obtained by an interference microscope along a center line passing through the center of the width of the core portion in the vertical direction. As a result, the refractive index distribution T, like the refractive index distribution W, had a plurality of minimum values and maximum values, and the refractive index changed continuously.

(Example 18)
An optical waveguide was obtained in the same manner as in Example 17 except that the irradiation amount of ultraviolet rays was increased to 2500 mJ / cm ² .

(Example 19)
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 17 except that was used.

(Example 20)
In addition to reducing the irradiation amount of ultraviolet rays to 1000 mJ / cm ² and changing the molar ratio of each structural unit of polymer # 1 to 45 mol% for the hexylnorbornene structural unit and 55 mol% for the diphenylmethylnorbornenemethoxysilane structural unit as the polymer An optical waveguide was obtained in the same manner as in Example 17 except that was used.

(Example 21)
As the polymer, except that the molar ratio of each structural unit of the polymer # 1 was changed to 30 mol% for the hexylnorbornene structural unit and 70 mol% for the diphenylmethylnorbornenemethoxysilane structural unit, the same as in Example 17. Thus, an optical waveguide was obtained.

(Example 22)
In addition to reducing the irradiation amount of ultraviolet rays to 700 mJ / cm ² , as a polymer, the molar ratio of each structural unit of polymer # 1 was changed to 40 mol% for the hexyl norbornene structural unit and 60 mol% for the diphenylmethyl norbornene methoxysilane structural unit. An optical waveguide was obtained in the same manner as in Example 17 except that was used.

(Example 23)
In addition to reducing the amount of ultraviolet irradiation to 1000 mJ / cm ² and changing the molar ratio of each structural unit of polymer # 1 to 30 mol% for the hexylnorbornene structural unit and 70 mol% for the diphenylmethylnorbornenemethoxysilane structural unit as the polymer An optical waveguide was obtained in the same manner as in Example 17 except that was used.

(Example 24)
In addition to reducing the irradiation amount of ultraviolet rays to 300 mJ / cm ² and changing the molar ratio of each structural unit of polymer # 1 as a polymer to 60 mol% for hexylnorbornene structural units and 40 mol% for diphenylmethylnorbornenemethoxysilane structural units An optical waveguide was obtained in the same manner as in Example 17 except that was used.

(Example 25)
In addition to increasing the irradiation amount of ultraviolet rays to 2500 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 17 except that was used.

(Example 26)
In addition to increasing the irradiation amount of ultraviolet rays to 4000 mJ / cm ² and changing the molar ratio of each structural unit of polymer # 1 to 5 mol% for the hexyl norbornene structural unit and 95 mol% for the diphenylmethylnorbornene methoxysilane structural unit as the polymer An optical waveguide was obtained in the same manner as in Example 17 except that was used.

(Example 27)
An optical waveguide was obtained in the same manner as in Example 17 except that the composition manufactured by the method shown below was used as the composition for forming an optical waveguide (first composition).

  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) (2.5E-2 g, In 0.1 mL of ethyl acetate) was added and dissolved uniformly, followed by filtration with a 0.2 μm PTFE filter to obtain a clean optical waveguide forming composition.

(Example 28)
An optical waveguide was obtained in the same manner as in Example 17 except that the composition manufactured by the method shown below was used as the composition for forming an optical waveguide (first composition).

  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 Rhodosil Photoinitiator 2074 (Rhodia, CAS # 178233-72-2) (2.5E-2 g, In 0.1 mL of ethyl acetate) was added and dissolved uniformly, followed by filtration with a 0.2 μm PTFE filter to obtain a clean optical waveguide forming composition.

(Example 29)
An optical waveguide was obtained in the same manner as in Example 17 except that the composition manufactured by the method shown below was used as the composition for forming an optical waveguide (first composition).

  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), cyclohexyl oxetane monomer (shown by formula 20, CHOX manufactured by Toagosei Co., Ltd.) 1 g, 1 g of alicyclic epoxy monomer (manufactured by Daicel Chemical Industries, Celoxide 2021P), photoacid generator Rhodosil Photoinitiator 2074 (manufactured by Rhodia, CAS # 178233-72-2) (2.5E-2 g, in ethyl acetate 0.1 mL) After addition and uniform dissolution, filtration was performed with a 0.2 μm PTFE filter to obtain a clean composition for forming an optical waveguide.

(Example 30)
An optical waveguide was obtained in the same manner as in Example 17 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 31)
The same as Example 17 except that the composition for forming an optical waveguide (third composition) synthesized by the following method was used instead of the composition for forming an optical waveguide (second composition). Thus, an optical waveguide was obtained.
(1) Synthesis of Oxetane-Based Resin 50 g of cyclohexyl oxetane monomer (monomer represented by the above formula (20), manufactured by Toa Gosei CHOX, CAS # 483303-25-9, molecular weight 186, boiling point 125 ° C./1.33 kPa) Weighed into a bull flask bottle, put 50 g of mesitylene and sealed.

  Next, 0.40 g (0.5 mmol) of a catalyst represented by the following chemical formula (D) was placed in a 100 mL vial in a glove box whose moisture and oxygen concentrations were both controlled to 1 ppm or less and filled with dry nitrogen. Ethyl acetate (20 mL) was weighed, a stirrer chip was inserted and sealed, and the catalyst was thoroughly stirred to completely dissolve it.

  When 12.5 mL of the catalyst solution represented by the following chemical formula (D) is accurately weighed with a syringe, quantitatively injected into the flask in which the oxetane monomer is dissolved, and stirred at 60 ° C. for 1 and a half hours, a marked increase in viscosity occurs. As a result, a reaction solution was obtained.

  The reaction solution and 50 g of an ion exchange resin (manufactured by Organo Corp., EG-290-HG) were added and stirred for 30 minutes, and the catalyst was removed by filtration to obtain a polymer solution.

(2) Production of optical waveguide forming composition (third composition) Subsequently, an optical waveguide forming composition (third composition) was added in the same manner as the first composition, except that 3 g of the obtained polymer solution was added. Product).

(Example 32)
An optical waveguide was obtained in the same manner as in Example 31 except that the irradiation amount of ultraviolet rays was reduced to 1000 mJ / cm ² .

(Reference Example 1)
An optical waveguide was obtained in the same manner as in Example 17 except that the setting of the mixing unit used in Example 17 was changed.

  In the obtained optical waveguide, the refractive index distribution T in the thickness direction was a so-called graded index type.

(Reference Example 2)
In the mixing unit used in Example 17, an optical waveguide was obtained in the same manner as in Example 17 except that the mixing pin was omitted.

  In the obtained optical waveguide, the refractive index distribution T in the thickness direction was a so-called step index type.

  Table 3 shows the manufacturing conditions and Table 4 shows the parameters of the refractive index distribution T of the core layer for the optical waveguides obtained in the above Examples and Reference Examples.

2. Evaluation (Examples 1 to 16 and Comparative Examples 1 and 2)
2.1 Intensity distribution of emitted light from optical waveguide The intensity distribution of the emitted light when light was incident on one of the eight cores was measured on the exit side end face of the obtained optical waveguide.

The intensity distribution of the emitted light was measured by the method shown in FIG.
And the intensity distribution of the acquired emitted light is shown in FIG. FIG. 18 representatively shows the intensity distribution of the emitted light measured with the optical waveguides obtained in Example 1, Comparative Example 1, and Comparative Example 2. The intensity distribution of the emitted light was obtained by making the light incident on the central core portion 14 (CH1) in FIG. 18 and observing the emitted light at that time.

  As is clear from FIG. 18, it was confirmed that the crosstalk in the width direction was sufficiently suppressed in the optical waveguide obtained in Example 1. Moreover, in the optical waveguide obtained in Example 1, the intensity of the emitted light in the core portion 14 (CH2) adjacent in the width direction of the core portion 14 (CH1) where the light is incident is adjacent to the core portion 14. It was recognized that the intensity of the emitted light is smaller than the intensity of the emitted light at the side cladding part 15 (CL2) located on the opposite side of the core part 14 (CH1) where the light is incident, and there is a minimum value of the intensity of the emitted light at CH2. . Therefore, it became clear that the optical waveguide obtained in Example 1 can prevent interference between channels.

  Further, in the optical waveguide obtained in Example 1, it was confirmed that a part of the emitted light gathered in the side cladding part 15 and that the maximum value of the intensity of the emitted light exists in CL2. Normally, the light receiving element connected to the optical waveguide is connected so as to face the emission side end face of each core part 14 and is not connected to the side clad part 15. Therefore, even if light collects in the side cladding portion 15, crosstalk does not occur.

  Further, in the intensity distribution of the emitted light, the central core portion 14 (CH1) in FIG. 18, the core portion 14 (CH2) adjacent thereto in the first layer, and the side cladding portion 15 (between them) ( Table 5 shows the presence / absence of maximum and minimum values in CL1) and side cladding 15 (CL2) located on the opposite side of CH2 from CH1.

  Further, regarding the intensity distribution of the emitted light, the intensity difference between the maximum value at CL2 and the minimum value at CH2 and the intensity ratio of the maximum value at CL2 to the maximum value at CH1 are measured, and are shown in Table 5.

  As is apparent from Table 5, it was recognized that the same intensity distribution of emitted light as in Example 1 was obtained even in the optical waveguides obtained in other examples. That is, in the optical waveguides obtained in the respective examples, it has been clarified that the intensity distribution of the emitted light has a maximum value in CH1 and CL2 and a minimum value in CH2. Therefore, in the optical waveguides obtained in the embodiments, crosstalk is suppressed and interference between channels is prevented.

  On the other hand, in the optical waveguides obtained in Comparative Examples 1 and 2, as shown in FIG. 18, the intensity distribution of the emitted light is maximized in the core portion 14 (CH2) adjacent to the core portion 14 (CH1) where the light is incident. The value was found to be located. That is, crosstalk has occurred in these optical waveguides.

2.2 Refractive Index Distribution of Optical Waveguide With respect to the cross section of the core layer of the obtained optical waveguide, the refractive index distribution was measured with an interference microscope along the center line in the thickness direction. 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 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 greater than the average refractive index WA, and each minimum value The width b [μm] of the portion where the refractive index in the vicinity of Ws1, Ws2, Ws3, and Ws4 has a value less than the average refractive index WA was measured.

  As a result, the refractive index distribution W of the optical waveguide obtained in each example had a continuous change of the refractive index in the whole.

  On the other hand, the refractive index distribution W of the optical waveguide obtained in Comparative Example 1 was a step index type as described above.

  The refractive index distribution W of the optical waveguide obtained in Comparative Example 2 was a graded index type as described above.

2.3 Transmission loss of optical waveguide Light emitted from an 850 nm VCSEL (surface emitting laser) was introduced into an optical waveguide obtained via a 50 μmφ optical fiber, and received by a 200 μmφ optical fiber to measure the light intensity. . 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 was calculated from the slope of the straight line.

2.4 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 (step index type optical waveguide) obtained in Comparative Example 1 is set to 1 is calculated for the measured pulse width of the emitted light, and this is used as the following evaluation criteria. Therefore, it was evaluated.

<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 5 shows the evaluation results of 2.3 and 2.4.

  As is apparent from Table 5, it was confirmed that the transmission loss and the blunting of the pulse signal were suppressed in the optical waveguides obtained in the respective examples as compared with the optical waveguides obtained in the respective comparative examples.

3. Evaluation (Examples 17 to 32 and Reference Examples 1 and 2)
3.1 Intensity Distribution of Emitted Light from Optical Waveguide The intensity distribution of the emitted light when light was incident on one of the 16 core portions was measured on the exit side end face of the obtained optical waveguide.

  The intensity distribution of the emitted light was measured by the method shown in FIG. 3 in each of the two core layers. Note that the intensity distribution of the emitted light was obtained by making the light incident on the central core portion 14 (CH1) of the first core layer and observing the emitted light at that time.

  In the intensity distribution of the emitted light, the core portion 14 (CH1) where light is incident, the core portion 14 (CH2) adjacent to the core portion 14 in the thickness direction, and the cladding layer 121 (CL1) positioned therebetween Table 6 shows the presence or absence of maximum and minimum values in the clad layer 122 (CL2) located on the opposite side of CH2 from CH1.

  Further, regarding the intensity distribution of the emitted light, the intensity difference between the maximum value at CL2 and the minimum value at CH2 and the intensity ratio of the maximum value at CL2 to the maximum value at CH1 are measured and shown in Table 6.

  As can be seen from Table 6, the intensity distributions of the emitted light in the optical waveguides obtained in the respective examples are all taken to have maximum values in CH1 and CL2, and minimum values in CH2. . Therefore, it was recognized that the optical waveguides obtained in the respective examples all suppressed crosstalk and prevented interference between channels.

  On the other hand, in the optical waveguides obtained in Reference Examples 1 and 2, the maximum value of the intensity distribution of the emitted light is located in the core portion 14 (CH2) adjacent to the core portion 14 (CH1) where the light is incident. It was recognized that That is, crosstalk has occurred in these optical waveguides.

3.2 Refractive Index Distribution of Optical Waveguide Regarding the cross section of the core layer of the obtained optical waveguide, the refractive index distribution was measured with an interference microscope along the center line in the thickness direction. In addition, since the same refractive index distribution pattern was repeated for every core part, the obtained refractive index distribution was partly cut out from the obtained refractive index distribution, and this was made into the refractive index distribution T. The shape of the refractive index distribution T 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 T, each minimum value Ts1, Ts2, Ts3, Ts4 and each maximum value Tm1, Tm2, Tm3, Tm4, Tm5 were obtained, and an average refractive index TA in the cladding layer was obtained.

  In the refractive index distribution T, the width a [μm] of the portion where the refractive index in the vicinity of the maximum values Tm2 and Tm4 formed in the core portion has a value equal to or greater than the average refractive index TA, and each minimum value. The width b [μm] of the portion where the refractive index in the vicinity of Ts1, Ts2, Ts3, and Ts4 has a value less than the average refractive index TA was measured.

  As a result, the refractive index distribution T of the optical waveguide obtained in each example had a continuous change of the refractive index in the whole.

  On the other hand, the refractive index distribution T of the optical waveguide obtained in Reference Example 1 was a graded index type as described above.

  The refractive index distribution T of the optical waveguide obtained in Reference Example 2 was a step index type as described above.

3.3 Transmission loss of optical waveguide Light emitted from an 850 nm VCSEL (surface emitting laser) was introduced into an optical waveguide obtained via an optical fiber of 50 μmφ, and received by a 200 μmφ optical fiber to measure the light intensity. . 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 was calculated from the slope of the straight line.

3.4 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.

  Then, with respect to the measured pulse width of the emitted light, a relative value is calculated when the measured value of the optical waveguide (step index type optical waveguide) obtained in Reference Example 1 is set to 1, and this is used as the following evaluation criteria. Therefore, it was evaluated.

<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 6 shows the evaluation results of 3.3 and 3.4.

  As is apparent from Table 6, it was confirmed that the transmission loss and the bluntness of the pulse signal were suppressed in the optical waveguides obtained in the respective examples as compared with the optical waveguides obtained in the respective reference examples.

In addition, about the optical waveguide manufactured by changing the conditions of Example 1 as follows, sufficient characteristics were not acquired.
-UV irradiation dose in the production of the lower cladding layer: 100 mJ
-UV irradiation dose in preparation of core layer: 500 mJ / cm ²
・ Drying conditions of the lower clad layer and core layer before irradiation with ultraviolet rays: 45 ° C. × 15 minutes ・ Amount of polymerization initiator added to the core layer: 1.36E-2g

4). Other Example 4.1 Production of Optical Waveguide (Example A)
(1) Manufacture of Clad Solution Daicel Chemical Industries Co., Ltd. Celoxide 2081 20 g, ADEKA Co., Ltd. Adekaoptomer SP-170 0.6 g, and methyl isobutyl ketone 80 g were stirred and mixed, and a 0.2 μm pore size PTFE filter. To obtain a clean, colorless and transparent clad solution E1.

(2) Production of photosensitive resin composition 20 g of YP-50S manufactured by Nippon Steel Chemical Co., Ltd. 5 g of Celoxide 2021P manufactured by Daicel Chemical Industries, Ltd. Adekaoptomer SP-170 manufactured by ADEKA Co., Ltd. 0.2 g Were added to 80 g of methyl isobutyl ketone, dissolved by stirring, and filtered through a PTFE filter having a pore size of 0.2 μm to obtain a clean, colorless and transparent photosensitive resin composition F1.

(3) Production of lower layer clad The clad solution E1 was uniformly applied onto a polyimide film having a thickness of 25 μm by a doctor blade, and then placed in a dryer at 50 ° C. for 10 minutes. After completely removing the solvent, the entire surface was irradiated with UV light at 500 mJ / cm ² with a UV exposure machine and cured to form a colorless and transparent lower clad. The thickness of the obtained cladding layer was 10 μm.

(4) Formation of core layer, patterning of core region and clad region The photosensitive resin composition F1 was uniformly applied on the lower clad with a doctor blade, and then placed in a dryer at 50 ° C. for 10 minutes. After completely removing the solvent, a photomask on which a linear pattern with a line of 50 μm and a space of 50 μm is drawn is pressure-bonded and irradiated with ultraviolet rays using a parallel exposure machine so that the irradiation dose is 500 mJ / cm ² did. After that, the mask was removed, and when it was put in an oven at 150 ° C. for 30 minutes and taken out, it was confirmed that a clear waveguide pattern appeared. The thickness of the obtained core layer was 50 μm.

(5) Formation of upper clad An upper clad was formed on the core layer using the clad solution E1 under the same conditions as the lower clad. The thickness of the obtained upper cladding was 10 μm.

(Example B)
(1) Polymer synthesis 20.0 g of methyl methacrylate, 30.0 g of benzyl methacrylate, and 450 g of methyl isobutyl ketone were charged into a separable flask, mixed with stirring, and then replaced with nitrogen gas to obtain a monomer solution. On the other hand, 0.25 g of azobisisobutyronitrile as a polymerization initiator was dissolved in 10 g of methyl isobutyl ketone and replaced with nitrogen gas to obtain an initiator solution. Thereafter, the monomer solution was heated to 80 ° C. while stirring, and the initiator solution was added to the monomer solution using a syringe. The mixture was heated and stirred at 80 ° C. for 1 hour and then cooled to obtain a polymer solution.

  Next, 5 L of isopropanol was prepared in a beaker, and the polymer solution was dropped while stirring with a stirrer at room temperature. After completion of the dropping, the mixture was further stirred for 30 minutes, and then the precipitated polymer was taken out and dried in a vacuum dryer at 60 ° C. for 8 hours under reduced pressure to obtain a polymer A1.

(2) Manufacture of clad solution 20 g of aqueous acrylate resin solution RD-180 manufactured by Kyoyo Chemical Industry Co., Ltd., 20 g of isopropanol, and 0.4 g of Carbodilite V-02-L2 manufactured by Nisshinbo Chemical Co., Ltd. were stirred and mixed. Filtration through a PTFE filter having a pore size of 2 μm gave a clean, colorless and transparent clad solution B1.

(3) Production of photosensitive resin composition 20 g of polymer A1 obtained by the method of (1), 5 g of cyclohexyl methacrylate, and 0.2 g of Irgacure 651 manufactured by BASF Japan Ltd. in 80 g of methyl isobutyl ketone The solution was stirred and dissolved, and filtered through a PTFE filter having a pore size of 0.2 μm to obtain a clean, colorless and transparent photosensitive resin composition C1.

(4) Preparation of lower layer clad The clad solution B1 was uniformly applied with a doctor blade on a polyimide film having a thickness of 25 μm, and then placed in a dryer at 80 ° C. for 10 minutes. After completely removing the solvent, it was further put into an oven at 150 ° C. for 10 minutes to be cured to form a colorless and transparent lower clad. The thickness of the obtained cladding layer was 10 μm.

(5) Formation of core layer, patterning of core region and clad region The photosensitive resin composition C1 was uniformly applied on the lower clad with a doctor blade, and then placed in a dryer at 50 ° C. for 10 minutes. After completely removing the solvent, a photomask on which a linear pattern with a line of 50 μm and a space of 50 μm was drawn was pressure-bonded and irradiated with ultraviolet rays using a parallel exposure machine so that the irradiation dose was 500 mJ / cm ² . After that, when the mask was removed, and it was taken out for 30 minutes in a nitrogen dryer at 150 ° C., it was confirmed that a clear waveguide pattern appeared. The thickness of the obtained core layer was 50 μm.

(6) Formation of upper clad An upper clad was formed on the core layer under the same conditions as the lower clad using the clad solution B1. The thickness of the obtained upper cladding was 10 μm.

(Example C)
First, a polymer A2 synthesized in the same manner as (1) of Example B was obtained except that 2- (perfluorohexyl) ethyl methacrylate was used instead of benzyl methacrylate.
Thereafter, an optical waveguide was obtained in the same manner as in Example B except that the polymer A2 was used instead of the polymer A1.

4.2 Evaluation (Transmission loss of optical waveguide)
Light emitted from an 850 nm VCSEL (surface emitting laser) was introduced into the optical waveguide obtained in Examples A to C via a 50 μm diameter optical fiber, received by a 200 μm diameter optical fiber, and the light intensity was measured. And the transmission loss was measured by the cutback method. Thereafter, when the waveguide length is plotted on the horizontal axis and the insertion loss is plotted on the vertical axis, the measured values are arranged on a straight line, and the propagation loss of each optical waveguide can be calculated as 0.05 dB / cm from the slope. .
In Examples A to C, the refractive index distribution parameters were set to 1. When changed in the same manner as in Example 1, 2. And 3. The evaluation result of the same tendency was obtained.

(Pulse signal waveform retention)
The optical waveguides obtained in Examples A to C were evaluated for the retention of the waveform of the pulse signal by the same method as in 2.3. As a result, it was found that the bluntness of the pulse signal was small.
In Examples A to C, the refractive index distribution parameters were set to 1. When changed in the same manner as in Example 1, 2. And 3. The evaluation result of the same tendency was obtained.

  According to the present invention, since interference (crosstalk) between adjacent channels can be suppressed, a highly reliable optical waveguide capable of high-quality optical communication can be obtained. In addition, according to the present invention, a highly reliable electronic device can be obtained. Therefore, the present invention has industrial applicability.

DESCRIPTION OF SYMBOLS 1 Optical waveguide 1a Incident side end surface 1b Outgoing side end surface 11, 12, 121, 122 Clad layer 13, 131, 132 Core layer 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 800 Die coater (multicolor extrusion molding equipment)
810 Die head 811 Upper lip portion 812 Lower lip portion 820 Manifold 821 Slit 830 Mixing unit 831 First supply tube 832 Second supply tube 835 Connection portion 836 Pin 831a Start point 8311, 8312, 8313 Branch tube 832a First start point 832b First start point 832b 2 starting point 8321, 8322, 8323, 8324 Branch pipe 8331, 8332 Collecting pipe M1, M2 Mixing point J1, J2 Confluence 840 Conveying section 841 Roller 842 Conveying film 900 Core layer forming composition 901, 902 Optical waveguide forming composition Material 910 Layer 914 Multicolor molding 915 Polymer 920 Additive 930 Actinic radiation 935 Mask (masking)
9351 opening (window)
925 Irradiation area 940 Non-irradiation area 951, 952 Support substrate 21 Incident side optical fiber 22 Emission side optical fiber C1, C2 Center line W Refractive index distribution WA Average refractive index T in the clad part T Refractive index distribution TA Average refractive index H in the clad layer High refraction Index part L Low refractive index part P1, P2 Intensity distribution of emitted light

Claims (9)

An optical waveguide having a plurality of parallel core portions and a cladding portion adjacent to at least both side surfaces of each core portion,
Among the plurality of core portions, a desired one is a core portion CH1, a portion adjacent to the core portion CH1 is a core portion CH2, and
Among the plurality of clad parts, a clad part CL1 is located between the core part CH1 and the core part CH2, and a clad part CL2 is located on the opposite side of the core part CH2 from the clad part CL1. When
An intensity of the leaked light that has entered the core part CH1 at one end of the optical waveguide and leaked from the optical signal observed at the clad part CL2 at the other end is observed at the core part CH2. An optical waveguide characterized by being configured to be larger than the intensity of light.   Regarding the emitted light observed at the end face of the other end of the optical waveguide, the intensity distribution with respect to the position of the end face has a maximum value in the clad portion CL2, and a minimum value smaller than the maximum value in the core portion CH2. The optical waveguide according to claim 1.   3. The optical waveguide according to claim 2, wherein a difference in strength between the maximum value in the cladding part CL <b> 2 and the minimum value in the core part CH <b> 2 is 3 to 20 dB.   4. The optical waveguide according to claim 2, wherein the maximum value in the clad portion CL <b> 2 is −60 to −20 dB with respect to the intensity of the optical signal observed in the CH <b> 1.   The intensity difference between the local maximum value in the cladding part CL2 and the local minimum value in the core part CH2 is g1, and the intensity between the optical signal observed in the core part CH1 and the local minimum value in the core part CH2 The optical waveguide according to any one of claims 2 to 4, wherein g1 / g2 satisfies a relationship of 0.05 to 0.5 when the difference is g2.   6. The optical waveguide according to claim 2, wherein the intensity distribution of the emitted light continuously changes in intensity with respect to the position of the end face.   The optical waveguide according to any one of claims 1 to 6, wherein each core portion has a width of 20 to 200 µm. A first cladding layer;
A core layer provided on the first clad layer, in which a first core portion CH1, a first clad portion CL1, a second core portion CH2, and a second clad portion CL2 are formed in this order;
A second cladding layer provided on the core layer;
An optical waveguide having
When light incident on the first core portion CH1 at one end of the optical waveguide exits from the other end as outgoing light,
In the intensity distribution of the emitted light obtained in the region extending over the first core part CH1, the first cladding part CL1, the second core part CH2, and the second cladding part CL2, the second core part CH2 An optical waveguide characterized in that the intensity of the emitted light is smaller than the intensity of the emitted light in the second cladding part CL2.   An electronic apparatus comprising the optical waveguide according to claim 1.

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