JP2012123253A - Optical waveguide and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable optical waveguide in which a transmission loss is small and a pulse signal is minimally blunted, and an electronic device including the same.SOLUTION: An optical waveguide 1 comprises a core layer 13. The core layer 13 includes: at least two cladding parts 15; and a core part 14 for transmitting light, which is adjacent to the two cladding parts 15, has an average refractive index higher than that of the cladding part 15, and has a refractive index lowering from a center portion thereof toward the cladding part 15. The core part 14 and the cladding part 15 are formed as follows: A layer including a (meth)acrylic polymer and a monomer having a refractive index different from the (meth)acrylic polymer is irradiated with active radiation so as to proceed a reaction of the monomer in an irradiated region. An unreacted portion of the monomer is thus diffused from an unirradiated region to the irradiated region, resulting in causing a difference in refractive index between the irradiated region and the unirradiated region. One of the irradiated region and the unirradiated region is used as the core part 14 and the other is used as the cladding part 15.

Description

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

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

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

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

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

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

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

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

  However, recently, there is an increasing demand for an optical waveguide with a large capacity, and further multi-channel and higher density are required. As the number of channels increases and the density increases, the pitch of the channel (core part) becomes narrower. Along with this, crosstalk (the leakage light from one channel interferes with adjacent channels) and pulse signals Faced with new challenges such as slowing of the pulse (spreading of the pulse signal).

JP 2006-276735 A

  An object of the present invention is to provide a highly reliable optical waveguide with small transmission loss and pulse signal dullness, and an electronic device including such an optical waveguide.

Such an object is achieved by the present inventions (1) to (11) below.
(1) An optical waveguide having a core layer for transmitting light,
The core layer is
At least two cladding portions;
Provided adjacent to the two cladding portions, the average refractive index is higher than the average refractive index of the cladding portion, and the refractive index is lower from the central portion toward the cladding portion, and transmits the light. With a core part,
A layer containing a (meth) acrylic polymer and a monomer having a refractive index different from that of the (meth) acrylic polymer is irradiated with active radiation, and within the irradiation region irradiated with the active radiation, By advancing the reaction, the unreacted monomer is diffused into the irradiated region from the unirradiated region that is not irradiated with the active radiation, and as a result, a refractive index difference is generated between the irradiated region and the unirradiated region. By generating the optical waveguide, one of the irradiated region and the non-irradiated region is used as the core portion, and the other is used as the clad portion.

  (2) The optical waveguide according to (1), wherein a refractive index of the clad portion decreases from a central portion toward the core portion.

  (3) In the refractive index distribution in a direction perpendicular to the thickness direction of the cross section of the core layer, the refractive index of the core part and the cladding part is continuously changed. Optical waveguide.

  (4) The refractive index distribution has at least two minimum values, at least one first maximum value, and at least two second maximum values smaller than the first maximum value, which are , The second maximum value, the minimum value, the first maximum value, the minimum value, and the second maximum value are arranged in this order, and the first maximum value is included in this region. The optical waveguide according to (3), wherein a region sandwiched between the two minimum values is the core portion, and a region on the second maximum value side from each minimum value is the cladding portion.

  (5) The optical waveguide according to (4), wherein the refractive index distribution is adjusted by setting at least one of the irradiation amount, irradiation time, irradiation depth, and irradiation interval of the active radiation.

  (6) The difference between the minimum value and the average refractive index of the cladding portion is 3 to 80% of the difference between the minimum value and the first maximum value, as described in (4) or (5) above. Optical waveguide.

  (7) The optical waveguide according to any one of (4) to (6), wherein a difference between the minimum value and the first maximum value is 0.005 to 0.07.

(8) When the horizontal axis represents the position in the direction perpendicular to the thickness direction of the cross section, and the vertical axis represents the refractive index in the cross section,
The refractive index distribution is substantially U-shaped convex in the vicinity of the first maximum value, and substantially U-shaped convex in the vicinity of the minimum value. (4) to (7) The optical waveguide according to any one of the above.

  (9) In the refractive index distribution, a width of a region where the refractive index in the vicinity of the first maximum value has a value equal to or larger than the average refractive index of the cladding portion is a [μm], and the vicinity of the minimum value. (4) thru | or (b) whose b is 0.01a-1.2a when the width | variety of the area | region where the refractive index in has a value less than the average refractive index of the said clad part is set to b [micrometer]. The optical waveguide according to any one of 8).

  (10) The light according to any one of (1) to (9), wherein the (meth) acrylic polymer has a main chain and a leaving group that is released from the main chain by irradiation with the active radiation. Waveguide.

  (11) An electronic apparatus comprising the optical waveguide according to any one of (1) to (10).

  According to the present invention, an optical waveguide capable of performing highly reliable optical communication even when a large-capacity optical signal is incident can be obtained by suppressing transmission loss and blunting of a pulse signal.

In addition, when a plurality of core portions are formed to make a multi-channel, an optical waveguide that can reliably suppress crosstalk is obtained.
Further, by using such an optical waveguide, a highly reliable electronic device can be obtained.

1 is a perspective view showing an embodiment of an optical waveguide of the present invention (partially cut out and shown through). In the XX sectional view shown in FIG. 1, an example of a refractive index distribution when the horizontal axis indicates the position in the width direction of the center line C1 of the core layer thickness and the vertical axis indicates the refractive index is schematically shown. FIG. It is a figure which shows an example of intensity distribution of the emitted light when light injects into one of the core parts of the optical waveguide shown in FIG. It is a figure for demonstrating the manufacturing method of the optical waveguide shown in FIG. It is a figure for demonstrating the manufacturing method of the optical waveguide shown in FIG. It is a figure for demonstrating the manufacturing method of the optical waveguide shown in FIG. It is a figure for demonstrating the manufacturing method of the optical waveguide shown in FIG. It is a figure for demonstrating the manufacturing method of the optical waveguide shown in FIG. It is a figure for demonstrating a mode that a refractive index difference arises between an irradiation area | region and an unirradiated area | region, and took the position of the width direction of the cross section of a layer on the horizontal axis, and took the refractive index of the cross section on the vertical axis | shaft. It is a figure which shows refractive index distribution at the time. The figure which cut out the part centering on the core part in the cross section of the optical waveguide of another structure, and an example of the refractive index distribution T on the centerline C2 which passes the center of the width direction of the core part of this cross section FIG. It is a perspective view which shows the die-coater which obtains a multicolor molded object. It is a longitudinal cross-sectional view which expands and shows a part of die-coater. It is a figure for demonstrating the manufacturing method of the optical waveguide shown in FIG. It is a figure for demonstrating the manufacturing method of the optical waveguide shown in FIG. It is a figure for demonstrating the manufacturing method of the optical waveguide shown in FIG. It is a figure which shows refractive index distribution when taking the refractive index of the cross section of the optical waveguide shown in FIG. 10 on a horizontal axis, and taking the position of the thickness direction of a cross section on the vertical axis | shaft.

  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 in a transparent manner), and FIG. 2 is a cross-sectional view taken along line XX shown in FIG. FIG. 3 schematically shows an example of the refractive index distribution when the position of the layer thickness in the center line C1 is taken in the width direction and the vertical axis indicates the refractive index. FIG. 3 shows the core of the optical waveguide shown in FIG. It is a figure which shows an example of intensity distribution of the emitted light when light injects into one of the parts. 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 11, a core layer 13 for transmitting light, and a clad layer 12 in this order from the lower side in FIG.

(Core layer)
Among these, the core layer 13 has a refractive index distribution in the surface direction. This refractive index distribution has a region having a relatively high refractive index and a region having a relatively low refractive index, whereby incident light can be confined and propagated in a region having a high refractive index.

  2A is a cross-sectional view taken along the line XX in FIG. 1, and FIG. 2B is a cross-sectional view taken along the center line C1 passing through the center in the thickness direction of the core layer 13 in the cross-sectional view taken along the line XX. It is a figure which shows an example of refractive index distribution typically.

  The core layer 13 has four local minimum values Ws1, Ws2, Ws3, and Ws4 as shown in FIG. 2B and five local maximums in a direction (width direction) perpendicular to the thickness direction of the cross section. The refractive index distribution W includes the values Wm1, Wm2, Wm3, Wm4, and Wm5. The five maximum values include a maximum value having a relatively high refractive index (first maximum value) and a maximum value having a relatively low refractive index (second maximum value).

  Among these, there are local maximum values Wm2 and Wm4 having a relatively 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.

  In the optical waveguide 1, as shown in FIG. 2, the portion between the minimum value Ws <b> 1 and the minimum value Ws <b> 2 includes the maximum value Wm <b> 2 having a relatively large refractive index, and thus becomes the core portion 14. Since the maximum value Wm4 is also included between Ws3 and the minimum value Ws4, the core portion 14 is formed. More specifically, the core portion 141 is defined between the minimum value Ws1 and the minimum value Ws2, and the core portion 142 is defined between the minimum value Ws3 and the minimum value Ws4.

  Further, since the region on the left side of the minimum value Ws1, the region between the minimum value Ws2 and the minimum value Ws3, and the region on the right side of the minimum value Ws4 are regions adjacent to both side surfaces, the side cladding portion 15 is provided. It becomes. More specifically, a region on the left side of the minimum value Ws1 is a side cladding portion 151, a region between the minimum value Ws2 and the minimum value Ws3 is a side cladding portion 152, and a region on the right side of the minimum value Ws4 is a side cladding portion 153. To do.

  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. It is only necessary to have a region in which the maximum value of 1 and the second maximum value are alternately arranged.

  The plurality of local minimum values, the plurality of first local maximum values, and the plurality of second local maximum values are preferably substantially the same as each other, but the local minimum values are the first local maximum value and the second local maximum value. 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.

  Further, the optical waveguide 1 has an elongated band shape, and the refractive index distribution W as described above is in the entire longitudinal direction of the optical waveguide 1 (cross section cut at an arbitrary position in the light propagation (transmission) direction). Almost the same distribution is maintained.

  Along with the refractive index distribution W as described above, the core layer 13 is formed with two long core portions 14 and three side clad portions 15 adjacent to both side surfaces of the core portions 14. The Rukoto.

  More specifically, the optical waveguide 1 shown in FIG. 1 is provided with two parallel core portions 141 and 142 and three side clad portions 151, 152, and 153 arranged in parallel. 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, since the average refractive index of these two core parts 141 and 142 is naturally higher than the average refractive index of the three side clad parts 151, 152, and 153, each core part 141 and 142 and each side clad. Light can be reflected in the vicinity of the interfaces with the portions 151, 152, and 153. In addition, a dense dot is attached | subjected to each core part 14 shown in FIG. 1, and a sparse dot is attached | subjected to each side clad part 15. FIG.

  In the optical waveguide 1, the light incident on one end of the core part 14 is reflected near the interface between the core part 14 and the clad part (the clad layers 11 and 12 and the side clad parts 15), and is reflected on the other side. By propagating, it can be taken out from the other end of the core part 14.

  1 has a quadrangular 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 each is preferably about 1 to 200 μm, more preferably about 5 to 100 μm, and about 20 to 70 μm. More preferably.

  Here, the four minimum values Ws1, Ws2, Ws3, and Ws4 are each less than the average refractive index WA in the side clad portion 15. As a result, a region having a smaller refractive index than the side clad portion 15 exists between each core portion 14 and each side clad portion 15. As a result, a steeper refractive index gradient is formed in the vicinity of each local minimum value Ws1, Ws2, Ws3, and Ws4. This suppresses light leakage from each core portion 14, thereby reducing transmission loss. The optical waveguide 1 is obtained.

  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.

  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.

  In addition, when the core portion 14 and the side cladding portion 15 are formed in the core layer 13, generally, the average of the core portion 14 and the side cladding portion 15 is limited due to the restrictions associated with the principle of forming a refractive index difference. The difference in refractive index cannot be made sufficiently large. In this case, light reflection in the vicinity of the interface between the core portion 14 and the side cladding portion 15 may not be performed efficiently, and light may not be reliably confined in the core portion 14. On the other hand, when the refractive index in the vicinity of the interface between the core portion 14 and the side cladding portion 15 is continuously changed as in this embodiment, even if the average refractive index difference between them is small. The light can be reliably confined in the core part 14. For this reason, in the optical waveguide 1 manufactured by the method of forming the core part 14 and the side clad part 15 from the same layer, the present invention particularly exhibits the effect.

  Further, in the refractive index distribution W, the maximum values Wm2 and Wm4 are located at the core portions 141 and 142 as shown in FIG. 2, but the core portions 141 and 142 are located at the center of the width. Yes. 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, the transmission loss of the core parts 141 and 142 can be further reduced.

  For example, 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. If it is located other than (in the vicinity of the interfaces with the side clad portions 151, 152, 153), a significant deterioration in characteristics is avoided. That is, the transmission loss of the core parts 141 and 142 can be suppressed to some extent.

  For example, the vicinity of the edge portion of the core portion 141 is a region having a distance of 5% of the width of the core portion 141 on the inner side from the interface (edge portion) with the core portions 141 and 142 of the side clad portions 151, 152, and 153. And

  On the other hand, the maximum values Wm1, Wm3, and Wm5 of the refractive index distribution W are located in the side cladding portions 151, 152, and 153 as shown in FIG. , 153 is preferably located outside the vicinity of the edge (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, the transmission loss of the core parts 141 and 142 can be reduced.

  For example, the vicinity of the edge of the side cladding portions 151, 152, 153 means that the side cladding portions 151, 152, 153 are inward from the interfaces (edges) with the core portions 141, 142 of the side cladding portions 151, 152, 153, A region having a distance of 5% of the width of 153 is assumed.

  In addition, the local maximum values Wm1, Wm3, and Wm5 are located at the center of the width of the side cladding portions 151, 152, and 153, so that the local maximum values Wm2 and Wm4 in the core portions 141 and 142 and the side cladding The separation distances from the regions of the maximum values Wm1, Wm3, and Wm5 in the portions 151, 152, and 153 are ensured to the maximum. For this reason, the probability that the transmission light in the core portions 141 and 142 leaks into the side cladding portions 151, 152, and 153 can be more reliably reduced.

  In addition, since the refractive index continuously decreases from the region of the maximum values Wm1, Wm3, Wm5 to the region of the adjacent minimum values Ws1, Ws2, Ws3, Ws4, the region of the maximum values Wm2, Wm4 Light can be confined more reliably in the vicinity.

  As described above, light can be transmitted through the core portions 141 and 142 while preventing loss of light.

  Furthermore, since the local maximum values Wm1, Wm3, and Wm5 are smaller than the local maximum values Wm2 and Wm4 located in the core portions 141 and 142, the side cladding portions 151, 152, and 153 are as high as the core portions 141 and 142. Although it has no optical transmission property, it has a slight optical transmission property because its refractive index is higher than the surroundings. 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, crosstalk can be suppressed by the presence of the regions of the maximum values Wm1, Wm3, and Wm5 in the side cladding portions 151, 152, and 153.

  Note that, as described above, the minimum values Ws1, Ws2, Ws3, and Ws4 are less than the average refractive index WA of the side cladding portion 15, but the difference is desirably within a predetermined range. Specifically, the difference between the minimum value Ws1, Ws2, Ws3, Ws4 and the average refractive index WA of the side cladding portion 15 is the minimum value Ws1, Ws2, Ws3, Ws4 and the maximum value Wm2 in the core portions 141, 142. It is preferably about 3 to 80% of the difference from Wm4, more preferably about 5 to 50%, and still more preferably about 7 to 30%. As a result, the side clad portion 15 has a light transmission property necessary and sufficient for suppressing crosstalk. If the difference between the minimum value Ws1, Ws2, Ws3, Ws4 and the average refractive index WA of the side cladding 15 is below the lower limit, the light transmission in the side cladding 15 is too small and crosstalk is sufficient. If the value exceeds the upper limit, the light transmission property of the side cladding portion 15 is too large, and the light transmission properties of the core portions 141 and 142 may be adversely affected.

  The difference 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 preferably about 0.005 to 0.07. It is more preferably about 0.007 to 0.05, and further preferably about 0.01 to 0.05. Thereby, the above-described difference becomes necessary and sufficient to confine light in the core portions 141 and 142.

  Further, as shown in FIG. 2B, the refractive index distribution W in the core portions 141 and 142 has a position in the direction (width direction) perpendicular to the thickness direction of the cross section of the core layer 13 on the horizontal axis. If the refractive index is taken on the vertical axis, the refractive index continuously changes in the vicinity of the maximum value Wm2 and the maximum value Wm4. It may be substantially linear), but is preferably substantially U-shaped 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. 2B, 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.

  Here, the inventor enters light at one end of a desired one of the plurality of core portions 141 and 142 of the optical waveguide 1 and acquires the intensity distribution of the emitted light at the other end. The inventors found that the intensity distribution is extremely useful for suppressing the crosstalk of the optical waveguide 1.

  FIG. 3 is a diagram illustrating the intensity distribution of the emitted light when light enters the core portion 141 of the optical waveguide 1.

  When light is incident on the core part 141, the intensity of the emitted light is highest at the center part of the emission end of the core part 141. The intensity of the emitted light decreases as the distance from the central portion of the core portion 141 decreases. However, according to the optical waveguide of the present invention, an intensity distribution that takes a minimum value in the core portion 142 adjacent to the core portion 141 is obtained. . Since the minimum value of the intensity distribution of the emitted light coincides with the position of the core part 142 in this way, the crosstalk in the core part 142 can be suppressed to be extremely small. An optical waveguide 1 that can reliably prevent the generation is obtained.

  In the conventional optical waveguide, the intensity distribution of the emitted light does not take the minimum value in the core portion adjacent to the core portion where the light is incident, but rather takes the maximum value, which causes a crosstalk problem. It was. On the other hand, the behavior of the intensity distribution of the emitted light in the optical waveguide of this embodiment is extremely useful for suppressing crosstalk.

  Although the detailed reason why such an intensity distribution is obtained in the optical waveguide of the present embodiment is not clear, one reason is that the refractive index distribution W has minimum values Ws1, Ws2, Ws3, and Ws4, and The characteristic refractive index distribution W that the refractive index continuously changes in the entire refractive index distribution W is the intensity distribution of the emitted light, which conventionally had a maximum value in the core portion 142. For example, the side cladding portion 153 adjacent to the portion 142 is shifted. That is, the crosstalk is reliably suppressed by this shift.

  Even if the intensity distribution of the emitted light is shifted to the side clad portion 15, the light receiving element and the like are arranged in accordance with the position of the core portion 14, so that there is almost no risk of interference and the quality of optical communication is deteriorated. I will not let you.

  The intensity distribution of the emitted light as described above has a high probability of being observed in the optical waveguide of the present embodiment, but is not necessarily observed, and the NA (numerical aperture) of the incident light or the crossing of the core portion 141 is not necessarily observed. Depending on the area, the pitch of the core parts 141, 142, etc., a clear minimum value may not be observed or the position of the minimum value may deviate from the core part 142. It is suppressed.

  In the refractive index distribution W shown in FIG. 2B, when the average refractive index in the side cladding portion 15 is WA, the refractive index in the vicinity of the maximum values Wm2 and Wm4 is continuously equal to or higher than the average refractive index WA. The width of the region 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 width of the region of the minimum values Ws1, Ws2, Ws3, and Ws4 becomes necessary and sufficient to exhibit the above-described functions and effects. That is, when b is less than the lower limit value, the substantial width of the region of the minimum values Ws1, Ws2, Ws3, and Ws4 is too narrow, so that the effect of confining light in the core portions 141 and 142 may be reduced. is there. On the other hand, when b exceeds the upper limit, the area of the minimum values Ws1, Ws2, Ws3, and Ws4 is too wide, and accordingly, the width and pitch of the core portions 141 and 142 are limited. There is a possibility that the transmission efficiency is lowered and the increase in the number of channels and the increase in density are hindered.

  The average refractive index WA in the side cladding 15 can be approximated at the midpoint between the maximum value Wm1 and the minimum value Ws1, for example.

  In the present invention, the core layer 13 (the core portion 14 and the side clad portion 15) as described above is configured with a (meth) acrylic polymer as a base polymer. In particular, the core portion 14 is composed of a polymer obtained by reacting a (meth) acrylic polymer with a different monomer, or a mixture of a (meth) acrylic polymer and a polymer obtained by polymerizing the monomer. ing. The constituent material of the core layer 13 may contain the unreacted (unpolymerized) monomer. The materials as described above will be described in detail later.

(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 refractive index of the cladding layers 11 and 12 is lower than the average refractive index of the core portions 141 and 142 included in the core layer 13.

  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 200 μm, and preferably about 5 to 100 μm. More preferably, it is about 10 to 60 μm. Thereby, the function as a clad part is suitably exhibited while preventing the optical waveguide 1 from becoming unnecessarily large (thickened).

  Further, as the constituent materials of the cladding layers 11 and 12, for example, acrylic resin, methacrylic resin, polycarbonate, polystyrene, epoxy resin, polyamide, polyimide, polybenzoxazole, polysilane, polysilazane, silicone resin, fluorine resin, In addition to various resin materials such as cyclic olefin-based resins such as benzocyclobutene-based resins and norbornene-based resins, examples thereof include glass materials such as quartz glass and borosilicate glass. A combination of more than one species can be used.

  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 in the vicinity of the interface 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 shape change.

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

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

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

  As a constituent material of such a cover film 3, it is the same as the constituent material of the support film 2. For example, in addition to various resin materials such as polyethylene terephthalate (PET), polyolefin such as polyethylene and polypropylene, polyimide and polyamide, Metal materials, such as copper, aluminum, silver, are mentioned. In the case of a metal material, a metal foil is preferably used as the cover film 3. Further, when a mirror is formed in the middle of the optical waveguide 1, light is transmitted through the cover film 3, so that the constituent material of the cover film 3 is preferably substantially transparent.

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

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

  In the present embodiment, the optical waveguide 1 composed of a laminate of the clad layer 11, the core layer 13, and the clad layer 12 has been described. However, these may be integrally formed.

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

  For example, when the number of the core portions 14 is one, the refractive index distribution W of the cross section of the optical waveguide 1 has two minimum values, and the minimum value is less than the average refractive index WA as described above. Yes, and it is sufficient that the refractive index continuously changes throughout the refractive index distribution W. When the core portion 14 increases to 3, 4, 5,..., The refractive index distribution W has accordingly. The number of local minimum values will increase to 6, 8, 10,.

  Further, in the present embodiment, in the core portion 14 of the core layer 13, the refractive index continuously decreases from the central portion toward the side cladding portion 15, and the refraction in the side cladding portion 15. Although the case where the rate is continuously reduced from the center toward the core 14 has been described, the change in the refractive index may be stepwise.

  Further, in the present embodiment, the case where the refractive index of the side cladding portion 15 of the core layer 13 is lowered from the center portion toward the core portion 14 has been described. The configuration may be substantially constant.

  Note that the core layer 13 having the above-described configuration is provided with at least one of the irradiation amount, irradiation time, irradiation depth, and irradiation interval of the active radiation irradiated in the step [2] in the manufacturing method of the optical waveguide 1 described later. Can be obtained by appropriately setting.

<Optical waveguide manufacturing method>
Next, an example of a method for manufacturing the optical waveguide 1 described above will be described.

  4-8 is a figure for demonstrating the manufacturing method of the optical waveguide 1 shown in FIG. 1, respectively. In the following description, the upper side in FIGS. 4 to 8 is referred to as “upper” and the lower side is referred to as “lower”.

  In this embodiment, the optical waveguide 1 is manufactured by preparing a clad layer 11, a core layer 13, and a clad layer 12, and laminating them.

  More specifically, the optical waveguide 1 is manufactured by [1] applying a core layer forming composition 900 on a support substrate 951 to form a liquid film, and then placing the support substrate 951 on a level table. The liquid film is flattened and 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 core layer forming composition 900 contains a (meth) acrylic polymer 915 and an additive 920 (including at least a monomer in the present embodiment). In such a core layer forming composition 900, upon irradiation with actinic radiation, at least monomer reaction occurs in the (meth) acrylic polymer 915 (core layer forming composition 900), and accordingly, the refractive index distribution is changed. It is a material that causes change. That is, in the core layer forming composition 900, the refractive index distribution changes due to the deviation in the ratio of the (meth) acrylic polymer 915 and the monomer. It is a material that can be formed.

  Next, the core layer forming composition 900 is applied onto the support substrate 951 to form a liquid film (see FIG. 4A). 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. 4B).

  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 (meth) acrylic polymer (matrix) 915 is present substantially uniformly and randomly, and the additive 920 is substantially uniform in the (meth) acrylic polymer 915 and Randomly distributed. 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.

((Meth) acrylic polymer)
The (meth) acrylic polymer 915 is a base polymer for the core layer 13.

  The (meth) acrylic polymer 915 is particularly used as a polymer in the present invention because of its high transparency and light transmission properties. In addition, the (meth) acrylic polymer 915 is compatible with the monomer described later, and among them, the monomer can be reacted (polymerization reaction or crosslinking reaction) as described later, and after the monomer has reacted. Also, those having sufficient transparency are preferably used.

  Here, “having compatibility” means that at least a monomer is mixed and phase separation with the (meth) acrylic polymer 915 does not occur in the core layer forming composition 900 or the layer 910.

  Furthermore, the (meth) acrylic polymer 915 includes acrylic acid monomers such as acrylic acid and acrylic acid esters, methacrylic acid monomers such as methacrylic acid and methacrylic acid esters, or derivatives thereof (for example, alkoxy derivatives, A polymer (including resin and rubber) obtained by polymerizing the raw material monomer using a caprolactone derivative or the like) as a raw material monomer.

  Therefore, the (meth) acrylic polymer 915 includes a homopolymer obtained by polymerizing one kind of the above raw material monomers, a copolymer obtained by polymerizing two or more different kinds of the above raw material monomers, And a copolymer obtained by polymerizing the above.

  Examples of such raw material monomers include monofunctional (meth) acrylate, bifunctional (meth) acrylate, trifunctional or higher polyfunctional (meth) acrylate, and the like.

  Examples of monofunctional (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, and s-butyl. (Meth) acrylate, t-butyl (meth) acrylate, butoxyethyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, heptyl (meth) acrylate, octyl heptyl (meth) ) Acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate Rate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-chloro-2- Aliphatic (meth) acrylates such as hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cyclopentyl (meth) acrylate, dicyclopentanyl (meth) Acrylate, dicyclopentenyl (meth) acrylate, isobornyl (meth) acrylate, 3-methyl-3-oxetanylmethyl (meth) acrylate, 1-adamantyl (meth) acrylate Cycloaliphatic (meth) acrylates such as salt, phenyl (meth) acrylate, nonylphenyl (meth) acrylate, p-cumylphenyl (meth) acrylate, o-biphenyl (meth) acrylate, 1-naphthyl (meth) acrylate, 2-naphthyl (meth) acrylate, benzyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-hydroxy-3- (o-phenylphenoxy) propyl (meth) acrylate, 2-hydroxy-3 -(1-naphthoxy) propyl (meth) acrylate, aromatic (meth) acrylate such as 2-hydroxy-3- (2-naphthoxy) propyl (meth) acrylate, 2-tetrahydrofurfuryl (meth) acrylate, N- (Meth) acryloyloxye And heterocyclic (meth) acrylates such as tilhexahydrophthalimide and 2- (meth) acryloyloxyethyl-N-carbazole.

  Examples of the bifunctional (meth) acrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and polyethylene glycol di ( (Meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetrapropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,3 -Butanediol di (meth) acrylate, 2-methyl-1,3-propanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, ne Pentyl glycol di (meth) acrylate, 3-methyl-1,5-pentanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 2-butyl-2-ethyl-1,3-propanediol Fats such as di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, glycerin di (meth) acrylate, tricyclodecane dimethanol (meth) acrylate Alicyclic (meth) acrylate, cyclohexanedimethanol (meth) acrylate, tricyclodecane dimethanol (meth) acrylate, hydrogenated bisphenol A di (meth) acrylate, hydrogenated bisphenol F di (meth) acrylate ( (Meth) acrylate, bispheno Such as aromatic A (meth) acrylate such as di- (meth) acrylate, bisphenol F di (meth) acrylate, bisphenol AF di (meth) acrylate, fluorene type di (meth) acrylate, and isocyanuric acid di (meth) acrylate And heterocyclic (meth) acrylates.

  Examples of the trifunctional or higher polyfunctional (meth) acrylates include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, and pentaerythritol tetra (meth) acrylate. And aliphatic (meth) acrylates such as dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and heterocyclic (meth) acrylates such as isocyanuric acid tri (meth) acrylate.

  In addition, although it does not specifically limit as another raw material monomer superposed | polymerized with the said raw material monomer, For example, an acrylonitrile etc. are mentioned, When acrylic acid (methacrylic acid) type monomer is selected as said raw material monomer, these are polymerized. By doing so, an acrylic rubber is obtained.

The weight average molecular weight of the (meth) acrylic polymer 915 is not particularly limited, but is preferably about 2 × 10 ^{4 to} 3 × 10 ⁵ , and more preferably about 3 × 10 ⁴ to 2 × 10 ^5. . By using the (meth) acrylic polymer 915 having such a weight average molecular weight, compatibility with the monomer described later can be enhanced, and strength and flexibility of the core layer 13 can be improved.

  Here, in the present invention, 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 (meth) acrylic polymer 915 and the refractive index of the monomer in each part, and the abundance ratio thereof. . Therefore, the refractive index of each part of the core layer 13 can be adjusted by appropriately selecting the type of monomer to be used and the type of the (meth) acrylic polymer 915.

  In addition, the refractive index difference between the core portion 14 and the side cladding portion 15 can be easily adjusted by designing the structure of the (meth) acrylic polymer 915. For example, the (meth) acrylic polymer 915 is designed to have a chemical structure having a main chain and a leaving group that is released from the main chain by actinic radiation 930 described later. In the (meth) acrylic polymer 915 having such a chemical structure, the refractive index is changed by detaching the leaving group from the main chain by irradiation with the active radiation 930.

  Examples of such a leaving group include those 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 sufficiently cleaved from the main chain by the action of actinic radiation 930 and easily separated from the main chain, but the molecular structure can be cleaved more easily by utilizing the action of a cation.

  Among these, as the leaving group that causes a decrease in the refractive index of the (meth) acrylic polymer 915 by leaving, at least one of a -Si-diphenyl structure and a -O-Si-diphenyl structure is preferable.

  Moreover, as another leaving group, the substituent which has an acetophenone structure at the terminal is mentioned, for example. The molecular structure of this leaving group is sufficiently cleaved by the action of actinic radiation 930 and is easily detached from the main chain, but the molecular structure is more easily cleaved using the action of free radicals.

  The amount (number) of the leaving group is not particularly limited, but is preferably 10 to 80% by weight, and more preferably 20 to 60% by weight with respect to the total weight of the (meth) acrylic polymer 915. When the amount of the leaving group is within the above range, the (meth) acrylic polymer 915 having an excellent refractive index modulation function (an effect of changing the refractive index difference) can be obtained, and the core layer 13 to be formed can be formed. Flexibility can also be improved.

  The (meth) acrylic polymer 915 having such a leaving group can be easily obtained by polymerizing the raw material monomer described above and a monomer having a leaving group introduced into this raw material monomer.

  Furthermore, a (meth) acrylic polymer 915 having an epoxy group can also be used. By using the (meth) acrylic polymer 915, it is possible to form the core layer 13 having excellent adhesion to the cladding layers 11 and 12.

  When obtaining this (meth) acrylic polymer 915, the raw material monomers include, for example, glycidyl (meth) acrylate, α-ethylglycidyl (meth) acrylate, α-propylglycidyl (meth) acrylate, α-butylglycidyl (meth). Acrylate, 2-methylglycidyl (meth) acrylate, 2-ethylglycidyl (meth) acrylate, 2-propylglycidyl (meth) acrylate, 3,4-epoxybutyl (meth) acrylate, 3,4-epoxyheptyl (meth) acrylate , Α-ethyl-6,7-epoxyheptyl (meth) acrylate, o-vinylbenzyl glycidyl ether, m-vinylbenzyl glycidyl ether, p-vinylbenzyl glycidyl ether, 3,4-epoxycyclohexylmethyl (meth) A combination of one or more of chlorate, 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, 3,4-epoxycyclohexylbutyl (meth) acrylate, etc. Can be used.

(Additive)
The additive 920 includes a monomer as an essential component, and includes a monomer and a polymerization initiator in the present embodiment.

((monomer))
The monomer reacts in the active radiation irradiation region to form a reaction product by irradiation with actinic radiation described later, and the unreacted monomer diffuses and moves from the non-irradiation region to which the active radiation is not irradiated to the irradiation region. Thus, in the layer 910, the compound can cause a refractive index difference between the irradiated region and the unirradiated region.

  As a reactant of the monomer, a polymer formed by polymerizing the monomer in the (meth) acrylic polymer 915 (polymer), a crosslinked structure in which the monomer crosslinks the (meth) acrylic polymer 915, and Examples thereof include at least one of branched structures in which the monomer is polymerized into the (meth) acrylic polymer 915 and branched from the (meth) acrylic polymer 915.

  By the way, the refractive index difference generated between the irradiated region and the non-irradiated region is included in the additive 920 because it is generated based on the difference between the refractive index of the (meth) acrylic polymer 915 and the refractive index of the monomer. The monomer is selected in consideration of the magnitude relationship with the refractive index of the (meth) acrylic polymer 915.

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

  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.

  When the refractive index of the irradiated region in the layer 910 decreases due to the monomer reaction (reactant generation), the minimum value of the refractive index distribution W is obtained in the portion, and the refractive index of the irradiated region increases. In this part, the maximum value of the refractive index distribution is obtained.

  As the monomer, those having high compatibility with the (meth) acrylic polymer 915 and having a refractive index difference with the (meth) acrylic polymer 915 of 0.01 or more are preferably used.

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

  In addition, in this invention, if acrylic acid (methacrylic acid) type monomers are used among these, since compatibility with the (meth) acrylic-type polymer 915 which is a base polymer is high, the acryl from an unirradiated area to an irradiated area | region is carried out. The diffusion of the acid (methacrylic acid) monomer is performed more smoothly. For this reason, the formation time of the core layer 13 can be shortened, and thus the production time of the optical waveguide 1 can be shortened.

  Further, since the compatibility is high, the acrylic acid (methacrylic acid) monomer is more uniformly dispersed in the (meth) acrylic polymer 915, so that there is little variation in characteristics in the obtained core portions 141 and 142. There are also advantages.

  As the acrylic acid (methacrylic acid) monomer, the same raw material monomers as those mentioned for the (meth) acrylic polymer 915 can be used.

  Further, since the ring opening of the cyclic ether group is likely to occur, a monomer or oligomer having a cyclic ether group such as an oxetanyl group and an epoxy group can react rapidly. Therefore, the use of such a monomer can also shorten the formation time of the core layer 13 and, in turn, the production time of the optical waveguide 1.

  Furthermore, by using a norbornene-based monomer, it is possible to obtain the core layer 13 (optical waveguide 1) having excellent optical transmission performance and excellent heat resistance and flexibility.

  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 the core layer 13 having excellent transparency near the wavelength of 850 nm and high flexibility and heat resistance can be formed. 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, they are represented by the formulas (13), (15), (16), (17), and (20) from the viewpoint of ensuring a refractive index difference with the (meth) acrylic polymer 915. It is preferable to use a compound.

  Furthermore, considering the point that the refractive index difference with the (meth) acrylic polymer 915 is large, the molecular weight is small, the monomer mobility is high, and the monomer is not easily volatilized, the equations (20) and (15) It is particularly preferred to use a compound represented by

  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.

  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^１〜Ｒ^４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^１およびＲ^２のいずれか一方、Ｒ^３およびＲ^４のいずれか一方は存在しない。］

[Wherein, a represents a single bond or a double bond, R ^{1 to} R ⁴ 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 ¹ and R ² or one of R ³ and R ⁴ 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 ¹ and R ² , R ³ and R ⁴ may each be an alkylidenyl group having 1 to 10 carbon atoms (C _{1 to} C ₁₀ ).

  Examples of the substituted hydrocarbon group include those in which some or all of the hydrogen atoms of the hydrocarbon group are substituted with halogen atoms, that is, halohydrocarbyl groups, perhalohydrocarbyl groups. Or halogenated hydrocarbon groups such as perhalocarbyl groups.

Moreover, as a functional substituent, for example, — (CH ₂ ) _n —CH (CF ₂ ) ₂ —O—Si (Me) ₃ , — (CH ₂ ) _n —CH (CF ₃ ) ₂ —O—CH ₂ —O—CH ₃ , — (CH ₂ ) _n —CH (CF ₃ ) ₂ —O—C (O) —O—C (CH ₃ ) ₃ , — (CH ₂ ) _n —C (CF ₃ ) ₂ — OH, — (CH ₂ ) _n —C (O) —NH ₂ , — (CH ₂ ) _n —C (O) —Cl, — (CH ₂ ) _n —C (O) —O—R ⁵ , — ( ^{_{CH 2) n-O-R}} 5, - (CH 2) n -O-C (O) -R 5, - (CH 2) n -C (O) -R 5, - (CH 2) n -O —C (O) —OR ⁵ , — (CH ₂ ) _n —Si (R ⁵ ) ₃ , — (CH ₂ ) _n —Si (OR ⁵ ) ₃ , — (CH ₂ ) _n —O—Si (R ⁵⁾ ) ₃ and-(C _{H 2) n -C (O)} -OR 6 , and the like.

Here, in each of the formulas above, each, n is an integer of 0, ^{R 5} are each independently a hydrogen atom, a linear or branched C 1 to 20 _(C 1 -C ₂₀₎ alkyl group, a linear or branched halogenated or perhalogenated alkyl group having a carbon number 1 to 20 _(C 1 _{-C 20)} linear or branched C 2 to 10 _(C 2 ~ alkenyl group of C _10), a linear or branched alkynyl group having 2 to 10 carbon atoms _(C 2 _{~C 10),} a cycloalkyl group having 5 to 12 carbon atoms _(C 5 _{~C 12),} to 6 carbon atoms -14 (C ₆ -C ₁₄ ) aryl group, C 6-14 (C ₆ -C ₁₄ ) halogenated or perhalogenated aryl group or C 7-24 (C ₇ -C ₂₄ ) aralkyl group Represents.

Incidentally, the hydrocarbon group represented by R ⁵ represents the same hydrocarbon groups as those represented by R ¹ to R ^4. As represented by R ^{1 to} R ⁴ , the hydrocarbon group represented by R ⁵ may be halogenated or perhalogenated.

  In addition, the norbornene-based monomer has a norbornene-based moiety (norbornene-based double bond) represented by the structural formula A in place of the monomer represented by the structural formula C or together with the monomer represented by the structural formula C. A crosslinkable norbornene-based monomer can also be used. This crosslinkable norbornene-based monomer is a compound capable of causing a crosslinking reaction in the presence of a catalyst precursor.

  As the crosslinkable norbornene-based monomer, there are a compound having a continuous polycyclic ring system and a compound having a linked multicyclic ring system.

  Examples of the continuous polycyclic ring-based compound (continuous polycyclic ring-based crosslinkable norbornene-based monomer) include compounds represented by the following structural formula D.

［式中、Ｙは、メチレン（−ＣＨ_２−）基を表し、ｍは、０〜５の整数を表わす。ただし、ｍが０である場合、Ｙは、単結合である。］

[Wherein Y represents a methylene (—CH ₂ —) group, and m represents an integer of 0 to 5. However, when m is 0, Y is a single bond. ]

  For simplicity, norbornadiene is considered to be included in a continuous polycyclic ring system and includes a polymerizable norbornene double bond.

  On the other hand, examples of the linked polycyclic ring-based compound (linked polycyclic ring-based crosslinkable norbornene-based monomer) include compounds represented by the following structural formula E.

［式中、ａは、それぞれ独立して、単結合または二重結合を表し、ｍは、それぞれ独立して、０〜５の整数を表し、Ｒ^９は、それぞれ独立して二価の炭化水素基、二価のエーテル基または二価のシリル基を表す。また、ｎは、０または１である。］

[Wherein, a independently represents a single bond or a double bond; m independently represents an integer of 0 to 5; and R ⁹ independently represents a divalent hydrocarbon. Represents a group, a divalent ether group or a divalent silyl group. N is 0 or 1. ]

Specific examples of the divalent hydrocarbon group (hydrocarbyl group) include an alkylene group represented by the general formula:-(C _d H _2d )-(d is preferably an integer of 1 to 10). And a divalent aromatic group (aryl group).

The divalent alkylene group is preferably a linear or branched alkylene group having 1 to 10 carbon atoms (C _{1 to} C ₁₀ ), such as a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, Examples include a hexylene group, a heptylene group, an octylene group, a nonylene group, and a decylene group.

  The branched alkylene group is one in which a main chain hydrogen atom is substituted with a linear or branched alkyl group.

On the other hand, the divalent aromatic group is preferably a divalent phenyl group or a divalent naphthyl group.
The divalent ether group is a group represented by —R ¹⁰ —O—R ¹⁰ —.
Here, R ¹⁰ independently represents the same as R ⁹ .

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

  In addition, monomers other than the above, for example, 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. Examples thereof include alkyl vinyl ethers such as vinyl ether, n-octyl 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.

  Further, examples of the photodimerization monomer include 4,4′-diphenylmethane bismaleimide, bis- (3-ethyl-5-methyl-4-maleimidophenyl) methane, 2,2′-bis- [4- (4- Maleimidophenoxy) phenyl] propane and the like, and one or two of them can be used in combination.

  In addition, the combination of these monomers and the (meth) acrylic-type polymer 915 mentioned above is not specifically limited, Any combination may be sufficient.

  Further, as the monomer, the above-mentioned various monomers, that is, monomers such as acrylic acid (methacrylic acid) monomer, epoxy monomer, oxetane monomer, norbornene monomer, vinyl ether monomer, styrene monomer, photodimerization monomer, and the like are the same. -Two or more types may be used in combination regardless of non-same type. Among these combinations, it is preferable to use two or more of 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 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, between the irradiated region and the unirradiated region A difference in refractive index can be reliably generated.

  Specifically, the monomer represented by the formula (20) is referred to as a “first monomer”, and the formula (11), the formula (12), the formula (15), the formula (18), the formula (19), and the formula (34) are used. When the combination of one or more of the monomers represented by (39) is referred to as a “second monomer”, it is preferable to use the first monomer and the second monomer together, When 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. 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 is a monomer having an oxetanyl group different from the monomer represented by the formula (20) or a monomer having an epoxy group. By using such a second monomer, the reactivity between the first monomer and the (meth) acrylic polymer 915 can be improved, thereby improving the heat resistance of the optical waveguide 1 while maintaining transparency. Can be made.

  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 (meth) acrylic polymer 915. preferable. Thereby, the refractive index modulation between the core part 14 and the side clad part 15 is made possible, and there is an effect that both the flexibility and the heat resistance of the obtained optical waveguide 1 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 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 exclusively used for acrylic acid (methacrylic acid) monomers and styrene monomers, cationic polymerization initiators are exclusively used for epoxy monomers, oxetane monomers, and vinyl ether monomers, and only for norbornene monomers. Those containing a catalyst and a catalyst precursor are preferably used.

  In addition, when the (meth) acrylic polymer 915 has a leaving group, these polymerization initiators act on the leaving group and also exhibit a function of promoting the leaving from the main chain.

  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 addition, when using the monomer which has a cyclic ether group as a monomer, the following cationic polymerization initiators (photoacid generator) are used preferably.

  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 catalyst precursor (second substance) contained in the polymerization initiator used for the norbornene monomer is a substance capable of initiating the reaction (polymerization reaction, crosslinking reaction, etc.) of the norbornene monomer. It is a substance whose activation temperature changes due to the action of the activated promoter (first substance).

  As such a catalyst precursor, for example, those containing (mainly) at least one of the compounds represented by the following formulas (Ia) and (Ib) are 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).

  The cocatalyst (first substance) 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 promoter (photoacid generator or photobase generator) include tetrakis (pentafluorophenyl) borate and hexafluoroantimonate represented by the following structural formula F, and tetrakis (pentafluorophenyl). ) Gallates, aluminates, antimonates, other borates, gallates, carboranes, halocarboranes and the like.

  The content of the polymerization initiator is preferably 0.01 parts by weight or more and 0.3 parts by weight or less with respect to 100 parts by weight of the (meth) acrylic polymer 915, and 0.02 parts by weight or more and 0.2 parts by weight or less. It is more preferable that the amount is not more than parts. Thereby, there exists an effect of a reactive improvement.

  In this embodiment, the additive 920 includes a polymerization initiator in addition to the monomer. However, when the reactivity of the monomer is extremely high, the addition of the polymerization initiator to the additive 920 is omitted. May be.

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 to these, 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, an interface. Activators, colorants, storage stabilizers, plasticizers, lubricants, fillers, inorganic particles, deterioration inhibitors, wettability improvers, antistatic agents, and the like may be included.

  The layer 910 containing the (meth) acrylic polymer 915 and the additive 920 as described above has a predetermined refractive index due to the action of the additive 920 uniformly dispersed in the (meth) acrylic polymer 915. is doing.

  [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. 5).

  In the following, a monomer having a refractive index lower than that of the (meth) acrylic polymer 915 is used as a monomer, and a (meth) acrylic polymer 915 having a refractive index that is lowered by the separation is used as a leaving group. The case will be described as 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. 5, 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 capable of causing the reaction of the monomer to progress, and can further cause a photochemical reaction (change) to the polymerization initiator, and is included in the (meth) acrylic polymer 915. Any material capable of releasing the leaving group may be used. For example, in addition to visible light, ultraviolet light, infrared light, and laser light, an electron beam, X-ray, or the like can 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 reaction of the monomer can surely proceed, the polymerization initiator can be activated relatively easily, and the leaving group can be removed relatively easily.

  At this time, by setting at least one of the irradiation amount, irradiation time, irradiation depth, and irradiation interval of the active radiation 930, the target refractive index distribution W can be obtained in the obtained core layer 13.

The 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, at about 0.2~3J / cm ² More preferably.

  The irradiation depth of the active radiation 930 can be, for example, the central portion in the thickness direction of the layer 910, and the active radiation 930 is continuously applied to the layer 910, for example.

  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 (meth) acrylic polymer 915 and the monomer are appropriately selected so that a difference in refractive index is generated between them, the refractive index is refracted between the irradiated region 925 and the unirradiated region 940 as the monomer diffuses and moves. A rate difference occurs.

  FIG. 9 is a diagram for explaining a state in which a difference in refractive index occurs between the irradiated region 925 and the non-irradiated region 940, where the horizontal axis represents the position in the width direction of the cross section of the layer 910 and the refraction of the cross section. It is a figure which shows refractive index distribution when a rate is taken on a vertical axis.

  In this embodiment, since a monomer having a refractive index smaller than that of the (meth) acrylic polymer 915 is used as the monomer, the refractive index of the unirradiated region 940 increases with the diffusion of the monomer, and the refractive index of the irradiated region 925 is increased. The rate is low (see FIG. 9A).

  It is considered that the monomer diffusion movement is caused by the consumption of the monomer in the irradiated region 925 and the monomer concentration difference between the irradiated region 925 and the unirradiated region 940 formed accordingly. For this reason, the monomers in the entire unirradiated region 940 do not move toward the irradiated region 925 at the same time, but gradually move from a portion close to the irradiated region 925. Monomer migration also occurs. As a result, as shown in FIG. 9A, the high refractive index portion H on the non-irradiated region 940 side and the low refractive index portion L on the irradiated region 925 side across the boundary between the irradiated region 925 and the non-irradiated region 940. Is formed. Since the high refractive index portion H and the low refractive index portion L are formed in accordance with the diffusion movement of the monomer as described above, they are necessarily constituted by smooth curves. Specifically, the high refractive index portion H has, for example, a substantially U shape that is convex upward, and the low refractive index portion L has, for example, a substantially U shape that is convex downward.

  The refractive index of the polymer obtained by polymerizing the monomers as described above is almost the same as the refractive index of the monomer before polymerization (the difference in refractive index is about 0 to 0.001). As the polymerization proceeds, the refractive index decreases according to the amount of the monomer and the amount of the reactant derived from the monomer.

  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 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.

  As the (meth) acrylic polymer 915, those having a leaving group as described above can be used. When such a (meth) acrylic polymer 915 is used, the leaving group is detached with the irradiation of the active radiation 930 and the refractive index of the (meth) acrylic polymer 915 is lowered. 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 (meth) acrylic polymer 915, and the refractive index of the irradiation region 925 is the irradiation index. It will fall from the front (refer FIG.9 (b)).

  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. 9B is obtained. The change in the refractive index in FIG. 9A and the change in the refractive index in FIG. 9B occur almost at the same time, and the refractive index distribution W is formed. In FIG. 9A, the refractive index distribution is exaggerated, but the refractive index difference between the high refractive index portion H and the low refractive index portion L accompanying the actual diffusion movement of the monomer is relatively small. The refractive index difference is sufficiently expanded by the refractive index change in FIG. 9B, and the refractive index distribution W of the optical waveguide of the present invention is formed.

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

  Next, the layer 910 is subjected to heat treatment. In this heat treatment, the monomer in the irradiation region 925 irradiated with light is further polymerized. On the other hand, in this heating step, the monomer in the unirradiated region 940 is volatilized. Thereby, in the unirradiated region 940, the amount of monomers is further reduced, the refractive index is increased, and the refractive index is close to that of the (meth) acrylic 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. 6).

  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. 2B), and the positions of these minimum values are the core portion 14 and the side surface. This corresponds to the interface with the clad portion 15.

  The refractive index distribution W has a certain correlation with the concentration (amount) of the reactant derived from the monomer 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 reactant derived from this monomer.

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

  Furthermore, the refractive index distribution W can be indirectly specified even if the intensity distribution of the emitted light from the optical waveguide 1 has a certain correlation with the refractive index distribution W.

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

  In addition, when using a monomer having a higher refractive index than the (meth) acrylic polymer 915, the refractive index of the movement destination increases with the diffusion movement of the monomer, contrary to the above, and accordingly, The irradiation area 925 and the non-irradiation area 940 may be set. Further, in this case, it is preferable to use a (meth) acrylic polymer 915 having a leaving group whose refractive index increases by leaving.

  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 cladding layer 11 (12) is formed on the support substrate 952 (see FIG. 7).

  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. 8A )reference).

  8A, 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. 8B).

  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.

Next, another configuration example of the optical waveguide 1 will be described.
FIG. 10 is a diagram in which a part of the cross section of an optical waveguide having another configuration centered on the core portion is cut out, and the refractive index on the center line C2 passing through the center in the width direction of the core portion of the cross section. It is a figure which shows an example of distribution T typically.

  In the following, the optical waveguide 1 shown in FIG. 10 will be described, but the description will focus on the differences from the optical waveguide 1 shown in FIG. 1, and the description of the same matters will be omitted.

  In the optical waveguide 1 shown in FIG. 10, the refractive index of the core portion 14 of the core layer 13 decreases from the central portion toward the side cladding portion 15, and the vertical direction (cladding layer 11, It is lower toward 12).

  In the present embodiment, a refractive index distribution T is formed in the optical waveguide 1 in the thickness direction passing through the core portion 14 in the cross section thereof. Specifically, the refractive index distribution T has a maximum value Tm located at the center thereof, and minimum values Ts1 and Ts2 located on both sides of the maximum value Tm. Note that the minimum value positioned below the maximum value Tm is Ts1, and the maximum value positioned above the maximum value Tm is Ts2.

  In the optical waveguide 1 of the present embodiment, as shown in FIG. 10, the region between the minimum value Ts1 and the minimum value Ts2 includes the maximum value Tm.

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

  That is, the refractive index distribution T only needs to have at least a region in which the minimum value, the maximum value, and the minimum value are arranged in this order.

  This region is repeatedly provided in accordance with the number of core layers 13 stacked. For example, when two core layers 13 are provided, in the refractive index distribution T, the minimum value and the maximum value are alternately arranged. Become. In this case, it is preferable that the relatively large first maximum value and the relatively small second maximum value are alternately arranged. In other words, the second maximum value, the minimum value, the first maximum value, the minimum value, the second maximum value, the minimum value, the first maximum value, and the like may be 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. If 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 a plurality of minimum values.

  Further, the optical waveguide 1 has an elongated band shape, and the refractive index distribution T as described above is in the entire longitudinal direction of the optical waveguide 1 (cross section cut at an arbitrary position in the light propagation (transmission) direction). Almost the same distribution is maintained.

  Here, the minimum value Ts1 is less than the average refractive index TA in the cladding layer 11, and the minimum value Ts2 is less than the average refractive index TA in the cladding layer 12. As a result, a region having a smaller refractive index than the clad layers 11 and 12 exists between the core portion 14 and the clad layers 11 and 12. As a result, a steeper refractive index gradient is formed in the vicinity of the local minimum values Ts1 and Ts2, thereby suppressing light leakage from the respective core portions 14 to the respective cladding layers 11 and 12. An optical waveguide 1 with low loss 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.

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

  The refractive index continuously changing in the refractive index distribution T means that the curve of the refractive index distribution T is rounded in each part, and the slope of the tangent line of the refractive index distribution T changes abruptly. It does not contain.

  Further, in the refractive index distribution T, the maximum value Tm is located in the core portion 14 as shown in FIG. 10, but is located in the center portion of the thickness of the core portion 14. Thereby, in the core part 14, the probability that transmission light will gather in the center part of the thickness of the core part 14 will become high, and the probability that it will leak to each clad layer 11 and 12 relatively becomes low. As a result, the transmission loss of the core parts 141 and 142 can be further reduced.

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

  In addition, it is desirable that the position of the maximum value Tm be located in the center of the thickness of the core portion 14 if possible. However, even if it is not necessarily the center portion, the vicinity of the edge of the core portion 14 (each cladding layer 11). , 12 near the interface), a significant deterioration in characteristics can be avoided. That is, the transmission loss of the core unit 14 can be suppressed to some extent.

  For example, the vicinity of the edge portion of the core portion 14 is a region having a distance of 5% of the thickness of the core portion 14 inward from the interface between the cladding layers 11 and 12 of the core portion 14.

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

  For example, the vicinity of the interface between the cladding layers 11 and 12 and the core portion 14 is a region having a distance of 5% of the thickness of each cladding layer 11 and 12 inward from the interface.

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

  As described above, when the plurality of core layers 13 are stacked, the relatively large first maximum value is located in the core portion, and the relatively small second maximum value is located in the cladding layer. Will be. In this case, it is preferable that the second maximum value is located at the center of the thickness of the cladding layer. Thereby, the separation distance between the first maximum value located in the core portion and the second maximum value located in the cladding layer is ensured to the maximum, and the light leaking from the core portion can be It becomes possible to confine in the clad layer so as not to enter the core portion. Thereby, even when the several core layer 13 is laminated | stacked, the crosstalk between layers can be suppressed reliably.

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

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

  Further, the refractive index distribution T in the optical waveguide 1 is such that the refractive index is continuous in the vicinity of the maximum value Tm when the vertical axis indicates the position in the thickness direction of the cross section of the optical waveguide 1 and the horizontal axis indicates the refractive index. However, it may be substantially V-shaped convex to the right (substantially linear except for the maximum value), but is preferably substantially U-shaped convex to the right (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 portion 14 becomes more remarkable.

Further, the refractive index distribution T has a substantially V-shape that is convex to the left if the refractive index continuously changes in the vicinity of the minimum value Ts1 and the minimum value Ts2 (almost linear except for the maximum value). However, it is preferably substantially U-shaped convex to the left (the entire vicinity of the maximum value is rounded).
The optical waveguide 1 shown in FIG. 10 as described above can be manufactured as follows.

  13-15 is a figure for demonstrating the manufacturing method of the optical waveguide 1 shown in FIG. 10, respectively. In the following description, the upper side in FIGS. 13 to 15 is referred to as “upper” and the lower side is referred to as “lower”.

  The optical waveguide 1 is manufactured by [1 ′] extruding two types of optical waveguide forming compositions 901 and 902 (first composition and second composition) onto a support substrate 951 in layers. Layer 910 is obtained. [2 '] Next, a refractive index difference is generated by irradiating a part of the layer 910 with actinic radiation, whereby the optical waveguide 1 is obtained.

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

  Each of the optical waveguide forming compositions 901 and 902 contains the above-described (meth) acrylic polymer 915 and an additive 920 (in this embodiment, at least a monomer). The composition is slightly different.

  Of the two types of compositions, the optical waveguide forming composition 901 is a material mainly for forming the core layer 13, and at least active monomer in the (meth) acrylic polymer 915 by irradiation with actinic radiation. This is a material that causes a change in the refractive index distribution. That is, in the optical waveguide forming composition 901, the refractive index distribution is changed due to the deviation of the abundance ratio of the (meth) acrylic polymer 915 and the monomer. As a result, the core portion 14 and the side cladding portion 15 are included in the core layer 13. It is a material that can be formed.

  On the other hand, the optical waveguide forming composition 902 is mainly a material for forming the cladding layers 11 and 12 and is made of a material having a lower refractive index than that of 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 the composition of the (meth) acrylic polymer 915, the composition of the monomer, the (meth) acrylic polymer 915 and the monomer, respectively. By adjusting the abundance ratio, etc., it can be adjusted as appropriate.

  For example, when the refractive index of the monomer is lower than that of the (meth) acrylic 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 (meth) acrylic 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 (meth) acrylic polymer 915 and the additive 920 in each of the optical waveguide forming compositions 901 and 902 is appropriately selected according to each refractive index of the (meth) acrylic polymer 915 and the monomer. ing.

  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. In the multicolor extrusion molding method to be described later, the refractive index distribution in the thickness direction of the layer 910 can be formed. Therefore, the diffusion movement of the monomer may be suppressed at least in the thickness direction. It is preferable that the unintended diffusion transfer of the monomer in the vertical 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 for the (meth) acrylic 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 (meth) acrylic 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 polymerization degree are different even with the same composition. You can make it. 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.

  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 three layers, and at the same time, the optical waveguide forming composition 902 is extruded between these layers, thereby forming a multicolor molded body in which five layers are laminated. 914 is formed at once. Specifically, in the multicolor molded body 914, an optical waveguide forming composition 901, an optical waveguide forming composition 902, an optical waveguide forming composition 901, an optical waveguide forming composition 902, and an optical waveguide forming composition. Since the objects 901 are extruded in this order from the bottom, the optical waveguide forming composition 901 and the optical waveguide forming composition 902 are slightly turbid at the boundary between the compositions. 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, in the multicolor molded body 914, the first molded layer 914a made of the optical waveguide forming composition 901, the optical waveguide forming composition 901, and the optical waveguide forming composition 902 are shown from the lower side of FIG. A second molding layer 914b made of a mixture, a third molding layer 914c made of an optical waveguide forming composition 902, a fourth molding layer 914d made of a mixture of the optical waveguide forming composition 901 and the optical waveguide forming composition 902, optical A fifth molding layer 914e made of the waveguide forming composition 901, a sixth molding layer 914f made of a mixture of the optical waveguide forming composition 901 and the optical waveguide forming composition 902, and a seventh molding made of the optical waveguide forming composition 902. The molded layer 914g, the eighth molded layer 914h made of a mixture of the optical waveguide forming composition 901 and the optical waveguide forming composition 902, and the optical waveguide forming composition 901 It becomes ninth molded layer 914i becomes to have been laminated in this order.

  And the solvent in the obtained multicolor molded object 914 is evaporated (desolvation), and the layer 910 is obtained (refer FIG.13 (b)).

  The obtained layer 910 includes a clad layer 11 formed from a layer below the center portion of the third molding layer 914c and a seventh portion above the center portion of the third molding layer 914c from the lower side of FIG. This is a laminate of the core layer 13 formed from the layer below the center of the molding layer 914g and the clad layer 12 formed from the layer above the center of the seventh molding layer 914g.

  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.

  FIG. 11 is a perspective view showing a die coater for obtaining a multicolor molded body 914, and FIG. 12 is an enlarged longitudinal sectional view showing a part of the die coater.

  As shown in FIG. 11, the die coater 800 has 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 three lines of piping for supplying the optical waveguide forming compositions 901 and 902 to the die head 810, respectively. Supply pipe 831, and a second supply pipe 832 and a third supply pipe 833 that supply the optical waveguide forming composition 901 to the die head 810.

  In addition, the optical waveguide forming compositions 901 and 902 supplied from the first supply pipe 831, the second supply pipe 832, and the third supply pipe 833 merge at the connection portion 835 that is responsible for connection with the die head 810. , And supplied to the manifold 820 of the die head 810. Note that the second supply pipe 832 is branched into two in the middle, and is connected to the uppermost layer portion and the lowermost layer portion of the connection portion 835, respectively. On the other hand, the third supply pipe 833 is connected to the middle layer portion of the connection portion 835. Further, the first supply pipe 831 is also branched into two in the middle, between the uppermost layer portion and the middle layer portion (upper layer portion) of the connection portion 835 and between the lowermost layer portion and the middle layer portion (lower layer). Part).

  That is, in the connection part 835, the flow of one layer composed of the optical waveguide forming composition 901 is merged so as to be sandwiched between the two upper and lower layer flows composed of the optical waveguide forming composition 902. The outside is merged so as to be sandwiched between two upper and lower layers composed of the optical waveguide forming composition 901.

  At this time, the flow rate of the second supply pipe 832 connected to the uppermost layer and the lowermost layer is set to be smaller than that of the third supply pipe 833. Thereby, the first molding layer 914a and the ninth molding layer 914i are sufficiently thinner than the fifth molding layer e, and the refractive index of the lowermost layer portion and the lowermost layer portion is higher than the refractive index of the middle layer portion. Can be prevented.

  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. 12, these pins 836 are connected between the uppermost layer portion and the upper layer portion of the connection portion 835, between the upper layer portion and the middle layer portion, between the middle layer portion and the lower layer portion, and between the lower layer portion and the uppermost layer portion. Each is provided between the lower layer and the like. 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. 11 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 five-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, as described above, the first molding layer 914a, the second molding layer 914b, the third molding layer 914c, the fourth molding layer 914d, the fifth molding layer 914e, the sixth molding layer 914f, the seventh molding layer 914g, A multicolor molded body 914 in which the eighth molded layer 914h and the ninth molded layer 914i are laminated in this order from below 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. 11 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 number of branches of the first supply pipe 831, the second supply pipe 832, and the third supply pipe 833 may be increased according to the number of core layers 13.

  The multicolor extrusion molding method and the die coater are examples of a method and an apparatus for producing a multicolor molded body 914. If the method and the apparatus can cause turbidity of the composition between layers, for example, an injection molding method is used. Various methods (apparatus) such as (apparatus), coating method (apparatus), and printing method (apparatus) can also be used.

  Note that the (meth) acrylic polymer 915 contained between the optical waveguide forming composition 901 and the optical waveguide forming composition 902 may have the same chemical structure or a different chemical structure. In addition, since the compatibility of each becomes high by using the thing of the same chemical structure, it becomes easy to mix compositions. Thereby, the continuity of the refractive index distribution T can be improved.

  [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. 14).

  Hereinafter, a case where a monomer having a refractive index lower than that of the (meth) acrylic polymer 915 is used as the monomer, and a (meth) acrylic polymer 915 whose refractive index is lowered by separation as the leaving group will be described as an example. Correspondingly, in the optical waveguide forming compositions 901 and 902 used to form the layer 910, the composition of the (meth) acrylic polymer 915 is (the refractive index of the optical waveguide forming composition 901). )> (Refractive index of the optical waveguide forming composition 902). As a result, in the layer 910, the refractive index has the highest refractive index at the center in the thickness direction, there are local minimum values between the front and back surfaces of the layer 910, and the refractive index continuously changes. A rate distribution is formed.

  When the layer 910 is irradiated with the active radiation 930 through the mask 935, the polymerization initiator is activated in the irradiation region 9253 in the core layer 13 in the irradiation region 925. Thereby, the monomer is polymerized in the irradiation region 9253. When the monomer is polymerized, the amount of monomer in the irradiated region 9253 decreases, and accordingly, in the unirradiated region 940, the monomer in the unirradiated region 9403 in the core layer 13 diffuses and moves to the irradiated region 9253. As described above, since the (meth) acrylic polymer 915 and the monomer are appropriately selected so that a difference in refractive index occurs between them, the irradiated region 9253 and the unirradiated region 9403 of the core layer 13 are accompanied by the diffusion movement of the monomer. A refractive index difference occurs between the two. On the other hand, since the irradiation regions 9251 and 9252 in the cladding layers 11 and 12 do not contain a polymerization initiator, the polymerization reaction of the monomer is suppressed. Therefore, in this embodiment, it is preferable that the irradiation amount of the active radiation 930 is set so that the polymerization reaction of the monomers in the irradiation regions 9251 and 9252 in the cladding layers 11 and 12 does not occur.

  At this time, based on the principle shown in FIG. 9 described above, a refractive index difference is generated between the irradiated region 9253 and the non-irradiated region 9403 of the core layer 13, and a refractive index distribution W is formed.

  In the present embodiment, in the irradiation region 9253, not only the diffusion movement of the monomer from the unirradiated region 9403 in the core layer 13 but also the irradiation region 9251 in the cladding layer 11 and the irradiation in the cladding layer 12 in the irradiation region 925. Diffusion transfer of monomers from region 9252 also occurs. As a result, the refractive index further decreases in the irradiation region 9253. On the other hand, in the irradiation region 9251 and the irradiation region 9252, the refractive index increases with the diffusion movement of the monomer. In this region, however, the monomer content is set so that the refractive index is lowered. Even if this rises, the function of the optical waveguide 1 is not impaired.

Further, in the irradiation region 9251 in the cladding layer 11 and the irradiation region 9252 in the cladding layer 12, as in the irradiation region 9253 in the core layer 13, the leaving group is detached and the refractive index of the (meth) acrylic polymer 915 is lowered. . As a result, the refractive index further decreases in the irradiation region 9251 and the irradiation region 9252.
Based on the principle as described above, the optical waveguide 1 having the refractive index distribution W is obtained (see FIG. 9).

  On the other hand, as shown in FIG. 16A, a refractive index distribution T ′ is formed in the layer 910 before irradiation with the active radiation 930 in the thickness direction. As described above, the refractive index distribution T ′ is formed by using the optical waveguide forming composition 901 and the optical waveguide forming composition 902 having different refractive indexes and obtaining the layer 910 by the multicolor molding method. It has been done.

  Here, when the layer 910 is irradiated with the active radiation 930 through the mask 935, if there is a difference in monomer content between the optical waveguide forming composition 901 and the optical waveguide forming composition 902, the unirradiated region 9403 In the refractive index distribution T ′ in the thickness direction of the portion to be the core portion 14 of the core layer 13, the refractive index of the region corresponding to the portion to be the core portion 14 is diffused and transferred to the irradiation region 9253. Becomes higher. On the other hand, since the refractive index does not change in the cladding layers 11 and 12 positioned above and below the portion to be the core portion 14, as a result, between the obtained core portion 14 and the upper and lower cladding layers 11 and 12. The difference in refractive index will increase.

  Based on the principle as described above, the optical waveguide 1 having the refractive index distribution T having a large refractive index difference between the maximum value and the minimum value can be obtained (see FIG. 16B).

Thus, the optical waveguide 1 is obtained.
Thereafter, if necessary, the optical waveguide 1 is peeled from the support substrate 951, 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.

<Electronic equipment>
The optical waveguide 1 as described above is excellent in optical transmission efficiency and long-term reliability. For this reason, by providing the optical waveguide 1, a highly reliable electronic device (electronic device of the present invention) capable of performing high-quality optical communication between two points is 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.

DESCRIPTION OF SYMBOLS 1 Optical waveguide 11, 12 Clad layer 13 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 apparatus)
810 Die head 811 Upper lip part 812 Lower lip part 820 Manifold 821 Slit 830 Mixing unit 831 First supply pipe 832 Second supply pipe 833 Third supply pipe 835 Connection part 836 Pin 840 Conveyance part 841 Roller 842 Conveyance film 900 Core Layer forming composition 901, 902 Optical waveguide forming composition 910 Layer 914 Multicolor molded body 914a First molded layer 914b Second molded layer 914c Third molded layer 914d Fourth molded layer 914e Fifth molded layer 914f Sixth molded layer Layer 914g seventh molding layer 914h eighth molding layer 914i ninth molding layer 915 (meth) acrylic polymer 920 additive 930 actinic radiation 935 mask (masking)
9351 opening (window)
925 Irradiated region 9251, 9252, 9253 Irradiated region 940 Unirradiated region 9403 Unirradiated region 951, 952 Support substrate C1, C2 Center line W Refractive index distribution WA Average refractive index T, T 'Refractive index distribution H High refractive index Part L Low refractive index part

Claims (11)

An optical waveguide having a core layer for transmitting light,
The core layer is
At least two cladding portions;
Provided adjacent to the two cladding portions, the average refractive index is higher than the average refractive index of the cladding portion, and the refractive index is lower from the central portion toward the cladding portion, and transmits the light. With a core part,
A layer containing a (meth) acrylic polymer and a monomer having a refractive index different from that of the (meth) acrylic polymer is irradiated with active radiation, and within the irradiation region irradiated with the active radiation, By advancing the reaction, the unreacted monomer is diffused into the irradiated region from the unirradiated region that is not irradiated with the active radiation, and as a result, a refractive index difference is generated between the irradiated region and the unirradiated region. By generating the optical waveguide, one of the irradiated region and the non-irradiated region is used as the core portion, and the other is used as the clad portion.   The optical waveguide according to claim 1, wherein a refractive index of the clad portion decreases from a central portion toward the core portion.   3. The optical waveguide according to claim 2, wherein in the refractive index distribution in a direction perpendicular to the thickness direction of the cross section of the core layer, the refractive index of the core portion and the cladding portion is continuously changed.   The refractive index distribution has at least two local minimum values, at least one first local maximum value, and at least two second local maximum values less than the first local maximum value. , A local maximum value, a local minimum value, a first local maximum value, a local minimum value, and a second local maximum value are arranged in this order, and the two local areas include the first local maximum value. The optical waveguide according to claim 3, wherein a region sandwiched between local minimum values is the core portion, and a region on the second local maximum side from each local minimum value is the cladding portion.   5. The optical waveguide according to claim 4, wherein the refractive index distribution is adjusted by setting at least one of the irradiation amount, irradiation time, irradiation depth, and irradiation interval of the active radiation.   6. The optical waveguide according to claim 4, wherein a difference between the minimum value and an average refractive index of the cladding portion is 3 to 80% of a difference between the minimum value and the first maximum value.   The optical waveguide according to claim 4, wherein a difference between the minimum value and the first maximum value is 0.005 to 0.07. When the horizontal axis represents the position in the direction perpendicular to the thickness direction of the cross section, and the vertical axis represents the refractive index in the cross section,
8. The refractive index distribution according to claim 4, wherein the refractive index distribution has a substantially U shape that is convex upward in the vicinity of the first maximum value, and a substantially U shape that is convex in the vicinity of the minimum value. An optical waveguide according to 1.   In the refractive index distribution, the width of a region where the refractive index in the vicinity of the first maximum value has a value equal to or larger than the average refractive index of the cladding portion is a [μm], and the refractive index in the vicinity of the minimum value. 9, wherein b is 0.01 a to 1.2 a, where b [μm] is a width of a region having a value less than the average refractive index of the cladding portion. The optical waveguide described.   The optical waveguide according to claim 1, wherein the (meth) acrylic polymer has a main chain and a leaving group that is released from the main chain by irradiation with the active radiation.   An electronic apparatus comprising the optical waveguide according to claim 1.

Images