JP5974483B2 - Optical waveguide, optical waveguide manufacturing method, and electronic apparatus - Google Patents

Description

The present invention relates to an optical waveguide, an optical waveguide manufacturing method, and an electronic apparatus.

  Conventionally, an optical waveguide is generally 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. A continuously changing graded index type has been proposed.

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

  Here, as a method for supplying the refractive index adjusting agent into the polymer substrate, Patent Document 1 includes methods such as coating, spraying, adhesion, dipping, and deposition.

  However, in the method of supplying the refractive index adjusting agent in this way, the supply amount is not uniform, and accordingly, an unintended bias occurs in the refractive index distribution in the polymer substrate. Further, since the work is complicated, it is difficult to increase the manufacturing efficiency of the optical waveguide.

  Recently, there has been a strong 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 portion) becomes narrower. Accordingly, the accuracy of the position where the refractive index adjusting agent is supplied must be increased. However, there is a limit to the improvement of the positional accuracy due to the characteristics of the work of supplying the substance, and it is not possible to deal with the production of a narrow pitch optical waveguide.

JP 2006-276735 A

An object of the present invention, the transmission loss is small, an electronic apparatus having multiple channels and densification readily optical waveguide, a method of manufacturing or mow optical waveguide can be manufactured optical waveguide, and the optical waveguide It is in.

Such an object is achieved by the present inventions (1) to (12) below.
(1) preparing a layer composed of a material obtained by dispersing a photopolymerizable monomer having a refractive index different from that of the polymer in a polymer having a softening point of 90 ° C. or higher;
The layer is partially irradiated with light, and the photopolymerizable monomer is moved and unevenly distributed, thereby causing a refractive index bias in the layer, a plurality of core portions, and both sides of each core portion A step of obtaining an optical waveguide having a plurality of side clad portions provided so as to be adjacent to the surface;
Have
The refractive index distribution W in the width direction in the cross section of the optical waveguide has two minimum values, one first maximum value, and two second maximum values smaller than the first maximum value. These have regions arranged in the order of the second maximum value, the minimum value, the first maximum value, the minimum value, and the second maximum value, and among the regions, the first maximum value When the region sandwiched between the two minimum values so as to include each core portion and the region on the second maximum side from each minimum value as the side cladding portion, each minimum value is: Less than the average refractive index in each of the side cladding portions, and the refractive index continuously changes throughout the refractive index distribution W,
The difference between the minimum value and the second maximum value is 10 to 40% of the difference between the minimum value and the first maximum value;
In the refractive index distribution W, the refractive index in the vicinity of the first maximum value is a [μm], which is the width of the portion having the average refractive index value in the cladding portion, and the refractive index in the vicinity of the minimum value. However, when the width having the value of the average refractive index in the cladding part is b [μm], b is 0.01a to 0.8a,
WCO / WCL satisfies the relationship of 0.1 to 5, where the average width of the plurality of core portions is WCO [μm] and the average width of the plurality of side cladding portions is WCL [μm]. An optical waveguide manufacturing method characterized by the above.

(2) The method for manufacturing an optical waveguide according to (1), wherein an average width WCL of the plurality of side surface cladding portions is 5 to 250 μm.

(3) The method for producing an optical waveguide according to (1) or (2), wherein the polymer has a Shore D hardness of 50 to 95.

(4) The polymer according to any one of (1) to (3), wherein the polymer is a (meth) acrylic resin, an epoxy resin, a silicone resin, a polyimide resin, a fluorine resin, or a polyolefin resin. Manufacturing method of optical waveguide.

(5) The method for producing an optical waveguide according to any one of (1) to (4), wherein the photopolymerizable monomer contains an unsaturated hydrocarbon in a molecular structure.

(6) In any one of the above (1) to (5), in the region corresponding to the cladding part in the refractive index distribution W, the second maximum value is located outside the vicinity of the interface with the core part. A method for producing an optical waveguide according to claim 1 .

(7) In the region corresponding to the cladding portion in the refractive index distribution W, the second maximum value is located at the center of the region, and the minimum value is calculated from the second maximum value. The method for manufacturing an optical waveguide according to any one of the above (1) to (6), wherein the refractive index is changed so as to continuously decrease toward.

(8) The refractive index difference between the minimum value and the first maximum value is 5.0 × 10 ^{−3 to} 7.0 × 10 ⁻² , and is described in any one of (1) to (7) above. Manufacturing method of the optical waveguide.

(9) When the horizontal axis represents the position of the cross section and the vertical axis represents the refractive index of the cross section,
The refractive index distribution W, the a substantially U-shaped projection on the first maximum value near the above (1) which has a substantially U-shaped downward convex at the minimum value near (8 The method for producing an optical waveguide according to any one of the above.

(10) The first maximum value includes a flat portion in which the refractive index is not substantially changed in the vicinity of the top portion;
The method for manufacturing an optical waveguide according to any one of (1) to (9) , wherein the flat portion has a length of 100 μm or less.

(11) An optical waveguide having a plurality of core portions and a plurality of side clad portions provided so as to be adjacent to both side surfaces of each core portion,
The refractive index distribution W in the width direction in the cross section of the optical waveguide has two minimum values, one first maximum value, and two second maximum values smaller than the first maximum value. These have regions arranged in the order of the second maximum value, the minimum value, the first maximum value, the minimum value, and the second maximum value, and among the regions, the first maximum value When the region sandwiched between the two minimum values so as to include each core portion and the region on the second maximum side from each minimum value as the side cladding portion, each minimum value is: Less than the average refractive index in each of the side cladding portions, and the refractive index continuously changes throughout the refractive index distribution W,
The difference between the minimum value and the second maximum value is 10 to 40% of the difference between the minimum value and the first maximum value;
In the refractive index distribution W, the refractive index in the vicinity of the first maximum value is a [μm], which is the width of the portion having the average refractive index value in the cladding portion, and the refractive index in the vicinity of the minimum value. However, when the width having the value of the average refractive index in the cladding part is b [μm], b is 0.01a to 0.8a,
When the average width of the plurality of core portions is WCO [μm] and the average width of the plurality of side cladding portions is WCL [μm], WCO / WCL satisfies the relationship of 0.1 to 5,
The refractive index distribution W is the photopolymerizability in a core layer composed of a material in which a structure derived from a photopolymerizable monomer having a refractive index different from that of the polymer is dispersed in a polymer having a softening point of 90 ° C. or higher. An optical waveguide formed on the basis of the concentration of a monomer-derived structure.
(12) An electronic apparatus comprising the optical waveguide according to (11) .

According to the present invention, it is possible to obtain an optical waveguide that has a small transmission loss and can be easily multi-channeled and densified.
Further, by using such an optical waveguide, a highly reliable electronic device can be obtained.

1 is a perspective view showing a first embodiment of an optical waveguide of the present invention (partially cut out and shown through). 1 is a diagram schematically showing an example of a refractive index distribution when the horizontal axis indicates the position of the core layer thickness in the center line C1 and the vertical axis indicates the refractive index in the XX sectional view shown in FIG. It is. It is a figure which shows an example of intensity distribution of the emitted light when light injects into one of the core parts of the optical waveguide shown in FIG. The figure which cut out a part centering on the core part of XX sectional drawing shown in FIG. 1, and the refractive index on center line C2 which passes the center of the width direction of the core part of XX sectional drawing It is a figure which shows an example of distribution T typically. It is a perspective view which shows 2nd Embodiment of the optical waveguide of this invention (a part is notched and it permeate | transmits and shows). FIG. 5 is a view in which a part of the core portion of the YY sectional view shown in FIG. It is a figure which shows an example of the upper refractive index distribution T typically. It is a figure which shows an example of intensity distribution of the emitted light in an output side end surface when light injects into one of the core parts of the optical waveguide shown in FIG. It is a perspective view which shows 3rd Embodiment of the optical waveguide of this invention (partially sees and shows). 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 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. It is a figure which shows refractive index distribution when taking the refractive index of the cross section of an optical waveguide on a horizontal axis, and taking the position of the thickness direction of a cross section on the vertical axis | shaft. It is a figure for demonstrating the method to measure the intensity distribution of the emitted light in the output side end surface of an optical waveguide. It is a figure which shows intensity distribution of the emitted light in the output side end surface of the optical waveguide obtained by Example 1, the comparative example 1, and the comparative example 2. FIG.

  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.

(First embodiment)
FIG. 1 is a perspective view showing a first embodiment of an optical waveguide of the present invention (partially cut out and shown in a transparent manner), and FIG. 2 is a horizontal axis of a cross-sectional view taken along line XX shown in FIG. FIG. 3 schematically shows an example of a refractive index distribution when the position of the thickness of the core layer on the center line C1 is taken and the vertical axis indicates the refractive index, and FIG. 3 shows the core portion 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 these. In the following description, the upper side in FIG. 1 is referred to as “upper” and the lower side is referred to as “lower”.

  The optical waveguide 1 shown in FIG. 1 functions as an optical wiring that transmits an optical signal from one end to the other end.

  The optical waveguide 1 is divided into a cladding layer 11, a core layer 13 and a cladding layer 12 from the lower side in FIG. Among these, the core layer 13 is formed with a refractive index distribution W having a refractive index biased in the width direction. This refractive index distribution W has a relatively high refractive index region (maximum value) and a low region (minimum value), so that incident light is confined and propagated in a high refractive index region. be able to. As a result, transmission loss and blunting of the pulse signal are suppressed, and highly reliable optical communication can be performed even when a large-capacity optical signal is incident.

  The maximum value includes a relatively high first maximum value and a relatively low second maximum value, and the minimum value is located across the first maximum value. Further, the core portion is positioned corresponding to the first maximum value, and the cladding portion is positioned corresponding to the second maximum value. As a result, a minimum value is located between the core part and the cladding part, and a large refractive index difference is formed between the first maximum value and the minimum value. Is difficult to leak. Further, since the second maximum value lower than the first maximum value is located in the cladding part, even if light leaks from the core part, the leaked light is confined in the cladding part. Thereby, crosstalk between core parts adjacent in the width direction is suppressed. As a result, even if a plurality of core portions are formed in the core layer 13 to be multi-channeled or the core portions 13 are narrowed to increase the density, the optical waveguide 1 can maintain high-quality optical communication. can do.

  Further, since the refractive index distribution W is formed by continuously changing the refractive index due to movement and uneven distribution of the photopolymerizable monomer as described above, the core layer 13 includes the core portion 14 and the core portion 13. There will be no clear structural interface with the side cladding 15. For this reason, problems such as peeling and cracks between the core portion 14 and the side clad portion 15 hardly occur, and the optical waveguide 1 is highly reliable.

Hereinafter, each part of the optical waveguide 1 will be described in detail.
(Core layer)
Among these, the core layer 13 is formed with a refractive index distribution W having a refractive index biased in the width direction, as described above.

  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 typically an example of the refractive index distribution W.

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

  Among these, the maximum value Wm2 and the maximum value Wm4 exist between the minimum value Ws1 and the minimum value Ws2, and between the minimum value Ws3 and the minimum value Ws4.

  In the optical waveguide 1, as shown in FIG. 2, since the maximum value Wm2 having a relatively large refractive index is located between the minimum value Ws1 and the minimum value Ws2, this region becomes the core portion 14. Similarly, since the local maximum value Wm4 is located between the local minimum value Ws3 and the local minimum value Ws4, the core portion 14 is formed. Here, a core portion 141 is defined between the minimum value Ws1 and the minimum value Ws2, and a 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. Here, the region on the left side of the minimum value Ws1 is the side cladding portion 151, the region between the minimum value Ws2 and the minimum value Ws3 is the side surface cladding portion 152, and the region on the right side of the minimum value Ws4 is the side surface cladding portion 153. .

  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.

  The optical waveguide 1 has a long and narrow band shape, and the refractive index distribution W as described above is maintained substantially the same in the entire longitudinal direction of the optical waveguide 1.

  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 core layer 13 shown in FIG. 1 is provided with two parallel core parts 141 and 142 and three side clad parts 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 refractive indexes of the core portions 141 and 142 are higher than the refractive indexes of the side cladding portions 151, 152, and 153, the core portions 141 and 142 and the side cladding portions 151, 152, and 153 It is possible to cause light reflection at the interface. 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 at the interface between the core part 14 and the clad part (the clad layers 11 and 12 and the side clad parts 15) and propagates to the other. By doing so, 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, each of the four minimum values Ws1, Ws2, Ws3, and Ws4 is less than the average refractive index WA in the adjacent side cladding portion 15. As a result, a region having a smaller refractive index than the side cladding portion 15 exists at the boundary between each core portion 14 and each side cladding portion 15. As a result, a steeper refractive index gradient is formed in the vicinity of each 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.

  Further, in the refractive index distribution W, since the refractive index has a maximum value and a minimum value, and the refractive index continuously changes, the speed of light increases with increasing distance from the center due to the property that the speed of light is inversely proportional to the refractive index. Therefore, it becomes difficult for a difference in propagation time for each optical path to occur. For this reason, the transmission waveform does not easily collapse, and for example, 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 as in the present embodiment, the core portion 14 and the side surface are generally limited due to the restrictions associated with the principle of forming a refractive index difference. Although the average refractive index difference from the clad portion 15 cannot be made sufficiently large, according to the present invention, since the maximum value and the minimum value are alternately arranged, the average refractive index of the core portion 14 and Even if the difference from the average refractive index of the side cladding 15 is small, light can be reliably confined in the core 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. That is, according to the present invention, since the core portion 14 and the side cladding portion 15 can be formed in the same layer, the optical waveguide 1 that is easy to manufacture and has high dimensional accuracy can be obtained.

  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. It is preferable. Thereby, in each core part 141 and 142, the probability that transmission light will gather in the center part of the width of core part 141 and 142 becomes high, and the probability that it will leak to side cladding parts 151, 152, and 153 becomes relatively low. As a result, the transmission loss of the core parts 141 and 142 can be further reduced.

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

  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.

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

  On the other hand, the maximum values Wm1, Wm3, and Wm5 of the refractive index distribution W are located in the side cladding portions 151, 152, and 153 as shown in FIG. It is preferable to be located other than 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.

  Note that the vicinity of the edges of the side cladding portions 151, 152, and 153 is a region having a distance of 5% of the width of the side cladding portions 151, 152, and 153 from the above-described edge portion to the inside.

  In addition, the local maximum values Wm1, Wm3, Wm5 are located at the center of the width of the side cladding portions 151, 152, 153, and the local minimum values Ws1, Ws2, Ws3, which are adjacent to the local maximum values Wm1, Wm3, Wm5. It is preferable that the refractive index continuously decreases toward Ws4. As a result, the maximum distances between the maximum values Wm2, Wm4 in the core portions 141, 142 and the maximum values Wm1, Wm3, Wm5 in the side cladding portions 151, 152, 153 are secured, and the maximum values Wm1, Since light can be reliably confined in the vicinity of Wm3 and Wm5, leakage of transmission light from the core portions 141 and 142 described above can be more reliably suppressed.

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

  Note that the minimum values Ws1, Ws2, Ws3, and Ws4 are less than the average refractive index WA of the adjacent side cladding portions 15 as described above, but the difference is desirably within a predetermined range. Specifically, the difference between the minimum value Ws1, Ws2, Ws3, Ws4 and the average refractive index WA of the side cladding portion 15 is the minimum value Ws1, Ws2, Ws3, Ws4 and the maximum value Wm2 in the core portions 141, 142. It is preferably about 3 to 80% of the difference from Wm4, more preferably about 5 to 50%, and still more preferably about 7 to 20%. As a result, the side clad portion 15 has a light transmission property necessary and sufficient for suppressing crosstalk. If the difference between the minimum value Ws1, Ws2, Ws3, Ws4 and the average refractive index WA of the side cladding 15 is below the lower limit, the light transmission in the side cladding 15 is too small and crosstalk is sufficient. If the value exceeds the upper limit, the light transmission property of the side cladding portion 15 is too large, and the light transmission properties of the core portions 141 and 142 may be adversely affected.

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

The refractive index 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 5.0 × 10 ^{−3 to} 7.0 ×. 10 is preferably about ^-2, more preferably from 7.0 × ¹⁰ -3 to 5.0 × ¹⁰ about ^-2, 1.0 × ¹⁰ -2 to 3.0 × ¹⁰ approximately ^-2 More preferably. Thereby, the above-described difference in refractive index becomes necessary and sufficient for confining light in the core portions 141 and 142.

  Further, as shown in FIG. 2B, the refractive index distribution W in the core portions 141 and 142 has a maximum value when the horizontal axis indicates the cross-sectional position of the core layer 13 and the vertical axis indicates the refractive index. If the refractive index is continuously changing in the vicinity of Wm2 and the maximum value Wm4, it may have a substantially convex V shape (substantially linear except for the vicinity of the maximum value). Is 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, according to the refractive index distribution W as described above, it is possible to obtain effects such as transmission loss reduction, pulse signal dullness reduction, crosstalk suppression, and the like. It has been found that the average width WCL of the side cladding part or the ratio of the average width WCO of the core part and the average width WCL of the side cladding part is greatly influenced. And when these factors existed in the predetermined range, it discovered that the above-mentioned effect became more remarkable and reliable, and came to complete this invention.

  That is, in the present invention, the ratio (WCO / WCL) between the average width WCO of the core portion 14 and the average width WCL of the side cladding portion 15 is in the range of 0.1-10. By optimizing the width ratio between the core portion 14 and the side clad portion 15, each effect described above can be enhanced. Therefore, for example, when WCO / WCL is less than the lower limit value, the average width of the core portion 14 becomes too narrow, so that crosstalk can be reduced, but transmission loss tends to increase, and the optical waveguide 1 can be downsized. Is disturbed. Further, when WCO / WCL exceeds the upper limit value, the average width of the side cladding portion 15 becomes too narrow, so that crosstalk increases, and further, the average width of the core portion 14 becomes too wide. Bluntness increases.

  Note that WCO / WCL is preferably about 0.1 to 5, more preferably about 0.2 to 4.

  On the other hand, in the present invention, the relationship that the average width WCL of the side cladding portion 15 is in the range of 5 to 250 μm is satisfied independently of or in addition to WCO / WCL. Thereby, each effect mentioned above can each be advanced. Therefore, for example, when WCL is less than the lower limit value, the average width of the side clad portion 15 becomes too narrow, and there is a possibility that the dullness of the pulse signal increases or the crosstalk increases. Moreover, when WCL is more than the upper limit value, the shape of the refractive index distribution W cannot be optimized, and transmission loss may increase. Furthermore, there is a possibility that miniaturization of the optical waveguide 1 becomes difficult.

  The average width WCL of the side cladding portion 15 is more preferably 10 to 200 μm, and further preferably 10 to 120 μm.

  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. This intensity distribution is the intensity distribution of the emitted light at the other end portion when light is incident on the end portion of the core portion 141 among the plurality of core portions 141 and 142 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, in the optical waveguide 1, an intensity distribution is obtained such that a minimum value is obtained in the core portion 142 adjacent to the core portion 141. As described above, the minimum value of the intensity distribution of the emitted light matches the position of the core part 142, so that the crosstalk in the core part 142 can be suppressed to be extremely small. As a result, it is possible to obtain the optical waveguide 1 that can reliably prevent the occurrence of interference even when the number of channels is increased and the density is increased.

  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 intensity distribution of the emitted light in the optical waveguide of the present invention as described above is extremely useful for suppressing crosstalk.

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

  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 is not necessarily observed although there is a high probability of being observed in the optical waveguide of the present invention. The NA (numerical aperture) of the incident light and the cross-sectional area of the core portion 141 are not necessarily observed. Depending on the pitches of the core parts 141 and 142, a clear minimum value may not be observed, or the position of the minimum value may deviate from the core part 142. Even in such a case, crosstalk is sufficiently suppressed. Is done.

Further, the refractive index distribution W shown in FIG. 2 (b), a case where the average refractive index of the side clad portion 15 was set to WA, the maximum value Wm2, the average refractive index Wm4 refractive index in the vicinity of consecutive W A portion Is a [μm], and the width of the portion where the refractive index in the vicinity of the minimum values Ws1, Ws2, Ws3, and Ws4 is continuously the average refractive index WA is b [μm]. At this time, b is preferably about 0.01a to 1.2a, more preferably about 0.03a to 1a, and further preferably about 0.1a to 0.8a. As a result, the substantial widths of the minimum values Ws1, Ws2, Ws3, and Ws4 become necessary and sufficient for providing the above-described functions and effects. That is, when b is below the lower limit value, the substantial widths of the minimum values Ws1, Ws2, Ws3, and Ws4 are too narrow, and the action of confining light in the core portions 141 and 142 may be reduced. On the other hand, when b exceeds the upper limit value, the substantial widths of the local minimum values Ws1, Ws2, Ws3, and Ws4 are too wide, and the width and pitch of the core portions 141 and 142 are limited accordingly, and transmission is performed. There is a possibility that the efficiency may be lowered and the increase in the number of channels and the increase in density may be hindered.

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

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

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

  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, Three or more may be sufficient.

  For example, when the number of the core portions 14 is one, the refractive index distribution W has two minimum values, and the minimum value is less than the average refractive index WA as described above, and the entire refractive index distribution W is The refractive index only needs to change continuously. When the number of core portions 14 increases to 3, 4, 5,..., The number of local minimum values of the refractive index distribution W is 6 accordingly. , 8, 10...

  The constituent material (main material) of the core layer 13 as described above is not particularly limited as long as the refractive index difference is generated as described above. For example, acrylic resin, methacrylic resin, polycarbonate, polystyrene, epoxy resin, Cyclic ether resin such as oxetane resin, polyamide, polyimide, polybenzoxazole, polysilane, polysilazane, silicone resin, fluorine resin, polyurethane, polyolefin resin, polybutadiene, polyisoprene, polychloroprene, PET and PBT Polyester, polyethylene succinate, polysulfone, polyether, various resin materials such as cyclic olefin resins such as benzocyclobutene resin and norbornene resin, and glass materials such as quartz glass and borosilicate glass It can be used. Note that the resin material may be a composite material in which materials having different compositions are combined.

  Among these, (meth) acrylic resins, epoxy resins, silicone resins, polyimide resins, fluorine resins, or polyolefin resins are preferable, and (meth) acrylic resins or epoxy resins are more preferable. Since these resin materials have high light transmittance, the optical waveguide 1 with particularly small transmission loss can be obtained.

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

  The average thickness of the cladding layers 11 and 12 is preferably about 0.05 to 1.5 times the average thickness of the core layer 13 (the average height of each core portion 14), and 0.1 to 1. 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 about 3 to 100 μm, respectively. More preferably, it is about 5 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 material of the cladding layers 11 and 12, for example, the same material as the constituent material of the core layer 13 described above can be used, but in particular, (meth) acrylic resin, epoxy resin, silicone resin, A polyimide resin or a fluorine resin is preferable, and a (meth) acrylic resin or an epoxy resin is more preferable.

  Further, when selecting the constituent material of the core layer 13 and the constituent materials of the clad layers 11 and 12, the material may be selected in consideration of the refractive index difference between them. Specifically, in order to reflect light reliably at the boundary between the core portion 14 and the cladding layers 11 and 12, the material may be selected so that the refractive index of the constituent material of the core portion 14 is sufficiently large. As a result, a sufficient refractive index difference is obtained in the thickness direction of the optical waveguide 1, and light can be prevented from leaking from the respective core portions 14 to the cladding layers 11 and 12.

  From the viewpoint of suppressing light attenuation, it is also important that the adhesiveness (affinity) between the constituent material of the core layer 13 and the constituent materials of the cladding layers 11 and 12 is high.

  On the other hand, the refractive index distribution T in the thickness direction of the optical waveguide 1 is not particularly limited as long as the refractive index of the core portion 14 is high and the refractive indexes of the cladding layers 11 and 12 are low (for example, step index type, gray level). However, it is preferable that the core portion 14 has a maximum value and has a minimum value near the boundary between the core portion 14 and the cladding layers 11 and 12.

  4A is a diagram in which a part centered on the core portion of the XX sectional view shown in FIG. 1 is cut out, and FIG. 4B is a diagram of the core portion of the XX sectional view. It is a figure which shows typically an example of the refractive index distribution T on the centerline C2 which passes the center of the width direction. FIG. 4B is a diagram illustrating an example of the refractive index distribution T when the horizontal axis indicates the refractive index and the vertical axis indicates the position on the center line C2.

  As described above, the optical waveguide 1 is divided into the clad layer 11, the core layer 13, and the clad layer 12. Of the transverse cross section, the refractive index distribution T in the thickness direction in the core portion 14 is the center. And local minimum values Ts1 and Ts2 positioned on both sides of the local 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, as shown in FIG. 4, a region between the local minimum value Ts <b> 1 and the local minimum value Ts <b> 2 includes the local 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 according to the number of core layers 13 stacked. For example, when two core layers 13 are provided via a cladding layer, in the refractive index distribution T, a minimum value and a maximum value are alternately displayed. Will be lined up. 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 strip shape, and the refractive index distribution T as described above is maintained substantially the same distribution in the entire longitudinal direction of the optical waveguide 1.

  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.

  Further, in the refractive index distribution T, since the refractive index continuously changes while having the above-described minimum values Ts1 and Ts2, the speed of light is inversely proportional to the refractive index. The distance from the center increases and the difference in propagation time for each optical path hardly occurs. For this reason, the transmission waveform does not easily collapse, and for example, even when the transmission light includes a pulse signal, it is possible to suppress blunting of the pulse signal (spreading of the pulse signal). As a result, the optical waveguide 1 that can further improve the quality of optical communication is obtained.

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

  Further, in the refractive index distribution T, the maximum value Tm is located in the core portion 14 as shown in FIG. 4, but is located in the center portion of the thickness among the core portions 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.

  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 in the vicinity of the interface). Thereby, the transmission loss of the core part 14 can be suppressed to some extent.

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

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

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

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

  As described above, when 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.

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

Further, the difference in refractive index between the minimum values Ts1 and Ts2 and the maximum value Tm in the core portion 14 is preferably as large as possible, but is about 5.0 × 10 ^{−3 to} 7.0 × 10 ^−2. Preferably, it is about 7.0 × 10 ^{−3 to} 5.0 × 10 ⁻² , and more preferably about 1.0 × 10 ^{−2 to} 5.0 × 10 ⁻² . Thereby, the above-described refractive index difference becomes necessary and sufficient for confining light in the core portion 14.

  Further, in the refractive index distribution T in the core portion 14, when the horizontal axis indicates the position of the cross section of the core portion 14 and the vertical axis indicates the refractive index, the refractive index continuously changes in the vicinity of the maximum value Tm. However, it may have a substantially V-shape that is convex upward (substantially linear except for the maximum value), but is preferably substantially U-shaped that is convex upward (the entire area near the maximum value is rounded). It is said). 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-shaped convex shape (substantially linear except for the maximum value) if the refractive index continuously changes in the vicinity of the minimum value Ts1 and the minimum value Ts2. However, it preferably has a substantially U-shape projecting downward (the entire vicinity of the maximum value is rounded).

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

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

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

  Moreover, although the average thickness of the support film 2 is not specifically limited, It is preferable that it is about 5-200 micrometers, and it is more preferable that it is about 10-100 micrometers. Thereby, since the support film 2 has moderate rigidity, the optical waveguide 1 is reliably supported and the flexibility of the optical waveguide 1 is difficult to be hindered.

  The support film 2 and the optical waveguide 1 are bonded or bonded, and examples of the method include thermocompression bonding, bonding with an adhesive or a pressure sensitive adhesive, and the like.

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

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

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

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

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

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

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

  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.

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

  FIG. 5 is a perspective view showing a second embodiment of the optical waveguide of the present invention (shown partially cut away and transmitted). In the following description, the upper side in FIG. 5 is referred to as “upper” and the lower side is referred to as “lower”.

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

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

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

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

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

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

  Here, in the optical waveguide 1 shown in FIG. 5, a refractive index distribution having a refractive index biased in the thickness direction is formed. 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.

Hereinafter, an example of the refractive index distribution T will be described.
6A is a diagram in which a part of the cross-sectional view taken along the line YY shown in FIG. 5 is cut out. FIG. 6B shows the center in the width direction of the core portion of the cross-sectional view taken along the line YY. It is a figure which shows typically an example of the refractive index distribution T on centerline C2 'which passes. FIG. 6B is a diagram schematically showing an example of a refractive index distribution when the horizontal axis indicates the refractive index and the vertical axis indicates the position in the thickness direction of the core portion of the cross section.

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

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

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

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

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

  The plurality of local minimum values, the plurality of first local maximum values, and the plurality of second local maximum values are preferably substantially the same as each other, but the local minimum values are the first local maximum value and the second local maximum value. As long as the relationship that the second maximum value is smaller than the first maximum value and the second maximum value is smaller than the first maximum value is maintained, the values may be slightly different from each other. In that case, it is preferable that the amount of deviation is suppressed within 10% of the average value of the plurality of minimum values.

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

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

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

  Further, the refractive index distribution T has the above-described local minimum values Ts1, Ts2, Ts3, and Ts4, and the refractive index continuously changes, so that the speed of light is inversely proportional to the refractive index. The speed of light increases with distance from the center, and a difference in propagation time for each optical path hardly occurs. For this reason, the transmission waveform does not easily collapse, and for example, even when the transmission light includes a pulse signal, it is possible to suppress blunting of the pulse signal (spreading of the pulse signal). As a result, the optical waveguide 1 that can further improve the quality of optical communication is obtained.

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

  Further, in the refractive index distribution T, the maximum values Tm2 and Tm4 are located in the core portions 141 and 143 as shown in FIG. 6, but the core portions 141 and 143 are located in the central portion of the thickness. ing. Thereby, in each core part 141 and 143, the probability that transmission light will gather in the center part of the thickness of core part 141 and 143 becomes high, and the probability that it leaks relatively to each cladding layer 11, 121, 122 becomes low. . As a result, the transmission loss of the core portions 141 and 143 can be further reduced and crosstalk can be further suppressed.

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

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

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

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

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

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

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

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

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

The refractive index difference between the local minimum values Ts1, Ts2, Ts3, Ts4 and the local maximum values Tm2, Tm4 in the core portions 141, 143 is preferably as large as possible, but is 5.0 × 10 ^{−3 to} 7.0 ×. 10 is preferably about ^-2, more preferably from 7.0 × ¹⁰ -3 to 5.0 × ¹⁰ about ^-2, 1.0 × ¹⁰ -2 to 5.0 × ¹⁰ approximately ^-2 More preferably. Thereby, the above-described difference in refractive index becomes necessary and sufficient for confining light in the core portions 141 and 143.

  Further, the refractive index distribution T in the core portions 141 and 143 is obtained when the horizontal axis indicates the position of the center line C2 ′ and the vertical axis indicates the refractive index (when FIG. 6 is rotated 90 ° counterclockwise). As long as the refractive index continuously changes in the vicinity of the maximum value Tm2 and the maximum value Tm4, it may have a substantially convex V shape (substantially linear except for the maximum value). Preferably, it has a substantially U-shape that is convex upward (the entire vicinity of the maximum value is rounded). When the refractive index distribution T has such a shape, the light confinement action in the core portions 141 and 143 becomes more remarkable.

  Further, as shown in FIG. 6B, the refractive index distribution T has a shape in which the refractive index continuously changes in the vicinity of the minimum value Ts1, the vicinity of the minimum value Ts2, the vicinity of the minimum value Ts3, and the vicinity of the minimum value Ts4. If so, it may have a substantially convex V shape (substantially linear except for the maximum value), but preferably has a substantially U shape convex downward (the entire vicinity of the maximum value is rounded). It is said.

Further, in the refractive index distribution T shown in FIG. 6B, when the average refractive index in each of the cladding layers 11, 121, 122 is TA, the refractive index in the vicinity of the maximum values Tm2, Tm4 is continuously average refractive index T. the width of a portion which is a and a [μm], the minimum value Ts1, Ts2, Ts3, the width of the portion having a refractive index of the average refractive index T a continuous in Ts4 near the b [μm]. At this time, b is preferably about 0.01a to 1.2a, more preferably about 0.03a to 1a, and further preferably about 0.1a to 0.8a. As a result, the substantial widths of the minimum values Ts1, Ts2, Ts3, and Ts4 become necessary and sufficient for providing the above-described functions and effects. That is, when b is below the lower limit value, the substantial widths of the minimum values Ts1, Ts2, Ts3, and Ts4 are too narrow, so that the effect of confining light in the core portions 141 and 143 may be reduced. On the other hand, when b exceeds the upper limit value, the substantial widths of the minimum values Ts1, Ts2, Ts3, and Ts4 are too wide, and accordingly, the thickness and pitch of the core portions 141 and 143 are limited, and transmission is performed. There is a possibility that the efficiency may be lowered and the increase in the number of channels and the increase in density may be hindered.

  The average refractive index TA in the cladding layer 11 can be approximated at the midpoint between the maximum value Tm1 and the minimum value Ts1.

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

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

  In the present embodiment, crosstalk can also be suppressed between the core portions 141 and 143 arranged in the thickness direction of the optical waveguide 1.

  Specifically, light is incident on one desired end among the plurality of cores 141, 142, 143, and 144 of the optical waveguide 1 shown in FIG. 5, and the intensity distribution P2 of the emitted light at the other end. , The intensity distribution shows a characteristic distribution suitable for suppressing crosstalk.

  FIG. 7 is a diagram showing the intensity distribution P2 of the emitted light on the exit side end surface when light is incident on the core portion 141 of the optical waveguide 1 shown in FIG. It is a figure which shows an example of intensity distribution when the position of a side end surface is taken.

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

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

(Third embodiment)
Next, a third embodiment of the optical waveguide of the present invention will be described.

  FIG. 8 is a perspective view showing a third embodiment of the optical waveguide of the present invention (partially shown). In addition, in order to make a figure legible, illustration of a part of core part 14 is abbreviate | omitted and illustration of the support film 2 and the cover film 3 is abbreviate | omitted.

  Hereinafter, the third embodiment of the optical waveguide will be described. However, the difference from the first embodiment will be mainly described, and the description of the same matters will be omitted. In FIG. 8, the same components as those of the first embodiment are denoted by the same reference numerals as those described above, and detailed description thereof is omitted.

  The third embodiment is the same as the first embodiment except that a mirror (reflection surface) 17 that changes the traveling direction of light propagating through the core portion 14 is provided.

  The mirror 17 is formed with a recess (hole) 170 having a V-shaped cross section so as to partially penetrate the optical waveguide 1 in the thickness direction, and is configured by a part of the side surface (inner surface) of the recess 170. Has been. This side surface is planar and is inclined 45 ° with respect to the axis of the core portion 14. The light propagating through the core portion 14 is reflected by the mirror 17, and the optical path is converted by 90 ° downward in FIG. Further, the light propagating from below in FIG. 8 is reflected by the mirror 17 and enters the core portion 14. That is, the mirror 17 has a function as an optical path conversion unit that converts an optical path of light propagating through the core unit 14.

  Further, the processed surfaces of the cladding layer 11, the core layer 13, and the cladding layer 12 are exposed on the mirror 17, and the processed surface of the core portion 14 is located almost at the center of the mirror 17.

  The mirror 17 may be provided so as to traverse only the core portion 14, but as shown in FIG. 8A, each of the cladding layers 11, 12 and the side surface cladding portion 15 around the core portion 14 is provided. It is preferably provided so as to cross. Thereby, the effective area contributing to reflection in the mirror 17 is widened, and mirror loss is suppressed.

  Further, as necessary, a reflective film may be formed on the surface of the processed surface constituting the mirror 17. Examples of the reflective film include a metal film such as Au, Ag, and Al, and a film made of a material having a lower refractive index than the core portion 14.

  Examples of the metal film forming method include physical vapor deposition such as vacuum vapor deposition, chemical vapor deposition such as CVD, and plating.

On the other hand, FIG. 8B shows another configuration example of the third embodiment.
In the optical waveguide 1 shown in FIG. 8B, the core portion 14 does not reach the end face of the optical waveguide 1 at one end portion, and is interrupted in the middle. A side clad portion 15 is formed from the location where the core portion 14 is interrupted to the end face. A portion where the core portion 14 is interrupted is referred to as a core portion missing portion 16.

  The mirror 17 is formed in the core portion defect portion 16. In such a mirror 17, the processed surfaces of the cladding layer 11, the core layer 13, and the cladding layer 12 are exposed. Of these, only the processed surface of the side cladding portion 15 is on the processed surface of the core layer 13. It will be exposed. On the other hand, in the case of FIG. 8A described above, both the processed surface of the core portion 14 and the processed surface of the side clad portion 15 are exposed on the processed surface of the core layer 13.

  As described above, the mirror 17 shown in FIG. 8B has uniform smoothness because the exposed surface of the core layer 13 is composed of only a single material. This is because a single material is processed at the time of processing, and the processing rate becomes uniform in the plane. For this reason, the mirror 17 has excellent reflection characteristics and has a small mirror loss.

  Moreover, since the core part defect | deletion part 16 is separated from the core part 14, it does not contain the density | concentration nonuniformity of the substance derived from the monomer explained in full detail behind. For this reason, variations in the reflection characteristics in the width direction as well as the thickness direction are reduced, and the mirror 17 has particularly excellent reflection characteristics.

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

  The optical waveguide 1 can be manufactured by sequentially forming a composition for forming the cladding layer 11, a composition for forming the core layer 13, and a composition for forming the cladding layer 12. However, it can also be produced by simultaneously extruding the three compositions into three layers. The latter method will be described below.

  FIGS. 9 and 10 are diagrams showing an apparatus used for manufacturing the optical waveguide 1, and FIGS. 11 to 13 are diagrams for explaining a method of manufacturing the optical waveguide 1 shown in FIG. In the following description, the upper side in FIGS. 11 to 13 is referred to as “upper” and the lower side is referred to as “lower”.

  In the manufacturing method of the optical waveguide 1, [1] First, two types of optical waveguide forming compositions 901 and 902 (first composition and second composition) are extruded on a support substrate 951 in layers. Layer 910 is obtained. [2] Next, a portion of the layer 910 is irradiated with actinic radiation to cause a difference in refractive index, 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.

  The optical waveguide forming compositions 901 and 902 each contain a polymer 915 and an additive 920 (including at least a monomer in the present embodiment), but the compositions thereof are 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 reaction occurs in the polymer 915 upon 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 changes due to the deviation in the ratio of the polymer 915 and the monomer, and as a result, the core portion 14 and the side cladding portion 15 are formed in the core layer 13. It is a material that can be used.

  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 determined by setting the composition of the polymer 915, the composition of the monomer, the abundance ratio of the polymer 915 and the monomer, and the like. It can be adjusted appropriately.

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

  Further, in the optical waveguide forming composition 901 and the optical waveguide forming composition 902, it is preferable that the compositions are set so that the monomer contents are substantially equal to each other. By setting in this way, the difference in monomer content between the optical waveguide forming composition 901 and the optical waveguide forming composition 902 becomes small, so that the diffusion movement of the monomer triggered by this is suppressed. The As described above, the diffusion movement of the monomer is useful in forming the refractive index difference. However, when the content difference is large, it may be unavoidable that the monomer moves in an undesirable direction. In the multicolor extrusion molding method to be described later, since the refractive index distribution in the thickness direction of the layer 910 can be freely formed, the diffusion movement of the monomer may be suppressed at least in the thickness direction. Rather, it is preferable that unintentional monomer diffusion transfer in the thickness direction is suppressed. By suppressing the unintended diffusion movement of the monomer, the optical waveguide 1 having the refractive index distribution T having the target shape can be reliably manufactured.

  When the monomer content is substantially equal, the conditions of the polymer 915 or the monomer may be different between the optical waveguide forming composition 901 and the optical waveguide forming composition 902. Specifically, the composition of the polymer 915 to be used is different between the optical waveguide forming composition 901 and the optical waveguide forming composition 902, and the molecular weight and the degree of polymerization are different even if the composition is the same. Good. 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 the optical waveguide forming composition 902 is extruded between these layers, thereby forming a multicolor molded body 914 having five layers at a time. To do. 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 object 901 is simultaneously extruded in this order from below, 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, from the lower side of FIG. 11A, the first molded layer 914a mainly composed of the optical waveguide forming composition 901, the optical waveguide forming composition 901, and the optical waveguide forming composition. A second molding layer 914b made of a mixture of 902, a third molding layer 914c mainly made of an optical waveguide forming composition 902, and a fourth molding made of a mixture of the optical waveguide forming composition 901 and the optical waveguide forming composition 902. A layer 914d, a fifth molded layer 914e mainly composed of the optical waveguide forming composition 901, a sixth molded layer 914f composed mainly of a mixture of the optical waveguide forming composition 901 and the optical waveguide forming composition 902, and mainly formed an optical waveguide. A seventh molded layer 914g made of the composition 902, an eighth molded layer 914h made of a mixture of the optical waveguide forming composition 901 and the optical waveguide forming composition 902, and mainly the optical waveguide Ninth shaping layer 914i comprising a forming composition 901, and which are 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.11 (b)).

  The obtained layer 910 includes a clad layer 11 formed from a layer lower than 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.

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

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

  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.

  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. 9 is a perspective view showing a die coater for obtaining a multicolor molded body 914, and FIG.

  As shown in FIG. 9, 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 systems of pipes for supplying the optical waveguide forming compositions 901 and 902 to the die head 810, respectively, and the first optical waveguide forming composition 902 is supplied to the die head 810. 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. 10, 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. 9 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 molded layer 914a, the second molded layer 914b, the third molded layer 914c, the fourth molded layer 914d, the fifth molded layer 914e, the sixth molded layer 914f, the seventh molded 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 as the support film 2. FIG.

  Further, the die coater 800 shown in FIG. 9 can form a layer 910 including one core layer 13, but if a plurality of core layers 13 are provided, the structure of the mixing unit 830 can be changed accordingly. Good. 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.

Next, the polymer 915 and the additive 920 will be described.
(polymer)
The polymer 915 is a base polymer for the optical waveguide 1.

  The polymer 915 has sufficiently high transparency (colorless and transparent) and is compatible with the monomer described later, and among them, the monomer can react (polymerization reaction or crosslinking reaction) as described later. There are preferably used those having sufficient transparency even after the monomer is polymerized.

  Here, “having compatibility” means that the monomer is at least mixed and does not cause phase separation with the polymer 915 in the optical waveguide forming compositions 901 and 902 or in the layer 910.

  Examples of such a polymer 915 include acrylic resins, methacrylic resins, polycarbonates, polystyrenes, cyclic ether resins such as epoxy resins and oxetane resins, polyamides, polyimides, polybenzoxazoles, polysilanes, polysilazanes, and silicones. Resin, fluorine resin, polyurethane, polyolefin resin, polybutadiene, polyisoprene, polychloroprene, polyester such as PET and PBT, polyethylene succinate, polysulfone, polyether, benzocyclobutene resin and norbornene resin, etc. These can be used in combination of one or more of them (polymer alloy, polymer blend (mixture), copolymer, etc.).

  Among these, (meth) acrylic resins, epoxy resins, silicone resins, polyimide resins, fluorine resins, or polyolefin resins are preferred, and (meth) acrylic resins or epoxy resins are preferred. A resin-based material is more preferable. By using these resins as the polymer 915, the optical waveguide 1 having excellent optical transmission performance can be obtained. Hereinafter, these resins will be described in detail.

((Acrylic polymer))
(Meth) acrylic polymers are acrylic monomers such as acrylic acid and acrylic esters, methacrylic monomers such as methacrylic acid and methacrylic esters, or derivatives thereof (for example, alkoxy derivatives, caprolactone derivatives, etc.) Is a polymer (including resin and rubber) obtained by polymerizing this raw material monomer.

  Therefore, as the (meth) acrylic polymer, a homopolymer obtained by polymerizing one of the raw material monomers, a copolymer obtained by polymerizing two or more different raw material monomers, the raw material monomer and another raw material monomer Examples thereof include copolymers formed by polymerization.

  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 superposed | polymerized. By doing so, an acrylic rubber is obtained.

  Examples of the raw material monomer include MMA monomer (manufactured by Kuraray or Mitsubishi Rayon), acrylate monomer (manufactured by Daicel Cytec), Blemmer (manufactured by NOF), acrylate monomer (manufactured by Nippon Shokubai), photocurability. Monomers / oligomers (manufactured by Shin-Nakamura Chemical Co., Ltd.) and the like can be mentioned.

The weight average molecular weight of the (meth) acrylic polymer 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 such a (meth) acrylic polymer having a weight average molecular weight, compatibility with the monomer described later can be improved, and strength and flexibility of the core layer 13 can be improved.

  Here, 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 and the refractive index of the monomer and the abundance ratio in each part. 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.

  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. For example, the (meth) acrylic polymer 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 having such a chemical structure, the leaving group can be detached from the main chain by irradiation with the active radiation 930, and the refractive index thereof is changed.

  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 by leaving, at least one of -Si-diphenyl structure and -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 mass, and more preferably 20 to 60% by mass with respect to the total mass of the (meth) acrylic polymer. When the amount of the leaving group is within the above range, a (meth) acrylic polymer having an excellent refractive index modulation function (an effect of changing the refractive index difference) can be obtained, and the formed core layer 13 can be formed. Flexibility can also be improved.

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

  Furthermore, a (meth) acrylic polymer having an epoxy group can also be used. By using such a (meth) acrylic polymer, 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, examples of the raw material monomer include glycidyl (meth) acrylate, α-ethylglycidyl (meth) acrylate, α-propylglycidyl (meth) acrylate, and 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) acryl , 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, 3,4-epoxycyclohexylbutyl (meth) acrylate, etc. Can be used.

  Further, as the raw material monomer, for example, EBECRYL (manufactured by Daicel Cytec), Denacol acrylate (manufactured by Nagase ChemteX), Neopol (manufactured by Nippon Iupika) and the like can be used. Furthermore, as the (meth) acrylic polymer having an epoxy group, for example, Blemmer (manufactured by NOF Corporation) can be used.

  Moreover, a fluorine-containing (meth) acrylic polymer can also be used. As a raw material monomer for obtaining this polymer, for example, METHACRYLATES CAS No. 1799-84-4 (2- (perfluorobutyl) ethyl methacrylate) manufactured by Daikin Industries Ltd., Unimatec Cheminox and the like can be used.

  Furthermore, a maleimide-modified acrylic polymer can also be used. As this polymer, for example, Aron Tac (manufactured by Toagosei) or the like can be used, and as a raw material monomer, for example, Aronix (manufactured by Toagosei) or the like can be used.

  In addition, as (meth) acrylic polymer, Sumipex MHF (manufactured by Sumitomo Chemical), silicone graft (meth) acrylic polymer, Cymac US-352 (manufactured by Toagosei), UV curable (meth) acrylic polymer 8KX-018C (manufactured by Taisei Fine Chemical Co., Ltd.) can be used.

  In addition, as raw material monomers, terminal acrylic polyether, Denacol acrylate DA-931 (manufactured by Nagase ChemteX), terminal methacryl silicone oil, BY167-152C (manufactured by Toray Dow Corning), aqueous acrylate, RD-180 (Manufactured by Mutual Chemical Industries), ABE-300 as bisphenol A diacrylate, A-BPEF (above, Shin-Nakamura Chemical Co., Ltd.) as full orange acrylate, Miramer HR-3700 (manufactured by Toyo Chemicals), benzyl ( A (meth) acrylate (made by Hitachi Chemical Co., Ltd.) etc. can be used.

((Epoxy polymer))
Epoxy polymers are particularly used as a polymer in the present invention because they are highly transparent, have excellent light transmission properties, and have excellent heat resistance and adhesion. In addition, the epoxy-based polymer is compatible with the monomer described later, and among them, the monomer can react (polymerization reaction or crosslinking reaction) as described later, and is sufficient even after the monomer reacts. Those having transparency are preferably used.

  Here, “having compatibility” means that at least a monomer is mixed and does not cause phase separation with the epoxy-based polymer in the optical waveguide forming compositions 901 and 902 and the layer 910.

  Furthermore, the epoxy polymer is a norbornene epoxy monomer, a silicon-containing epoxy monomer, an alicyclic epoxy monomer, a bisphenol type epoxy monomer, a fluorinated epoxy monomer, an aliphatic epoxy monomer, a naphthalene ring-containing epoxy monomer, an aromatic ring-containing epoxy monomer. A polymer (including resin and rubber) obtained by polymerizing this raw material monomer using an epoxy monomer or a derivative thereof as a raw material monomer.

  Therefore, as an epoxy polymer, a homopolymer obtained by polymerizing one of the above raw material monomers, a copolymer obtained by polymerizing two or more different raw material monomers, and the above raw material monomer and another raw material monomer are polymerized. And the like.

  Among such raw material monomers, examples of the norbornene-based epoxy monomer include those represented by the following formula (1).

  In addition, the compound represented by Formula (1) is epoxy norbornene, For example, ProNBAS EpNB can be used as such a compound. In addition, HP-7200HHH manufactured by DIC can be used as the dicyclopentadiene type epoxy monomer.

  Moreover, as a silicon-containing epoxy monomer, what is represented by the following formula | equation (2) or Formula (3) is mentioned, for example.

  In addition, the compound represented by Formula (2) is (gamma) -glycidoxy propyl trimethoxysilane, As this compound, Toray Dow Corning Z-6040 can be used, for example. Moreover, the compound represented by Formula (3) is 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and as this compound, for example, E0327 manufactured by Tokyo Chemical Industry can be used. In addition, SF8413, BY16-839, and SF8421 manufactured by Toray Dow Corning can be used.

  Furthermore, as an alicyclic epoxy monomer, what is represented by the following formula | equation (4)-Formula (6) is mentioned, for example.

  The compound represented by the formula (4) 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 (5) is 1,2-epoxy-4-vinylcyclohexane. As this compound, for example, Celoxide 2000 manufactured by Daicel Chemical Industries, Ltd. can be used. Further, the compound represented by the formula (6) is 1,2: 8,9 diepoxy limonene, and as this compound, for example, (Celoxide 3000 manufactured by Daicel Chemical Industries, Ltd.) can be used. In addition, Celoxide 2081 manufactured by Daicel Chemical Industries, Ltd. can also be used.

  Examples of the bisphenol type epoxy monomer include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, and those represented by the following formula (7).

In addition, as a compound represented by Formula (7), specifically, for example, bisphenoxyethanol fluorenediglycidyl ether (in Formula (7), n = 1, and R _{1 to} R ₆ are all hydrogen atoms) Bisphenol fluorenediglycidyl ether (in formula (7), n = 0, R _{1 to} R ₆ are all hydrogen atoms), and the like. In addition, YS-128S and YD-020G manufactured by Nippon Steel Chemical Co., Ltd. can be used as bis A type epoxy monomers, and ST-3000 and ST-4000D manufactured by Nippon Steel Chemical Co., Ltd. can be used as hydrogenated bis A type epoxy monomers. .

  Furthermore, as a fluorinated epoxy monomer, what is represented by the following formula | equation (8) is mentioned, for example. In addition, Daikin Industries 'EPOXIDES CAS No.74328-56-6 (1,6-bis (2', 3'-epoxypropyl) -perfluoro-n-hexane), EPOXIDES CAS No.791-22-0 (1, 4-bis (2 ′, 3′-epoxypropyl) -perfluoro-n-butane) can also be used.

  Moreover, as an aliphatic epoxy monomer, what is represented by the following formula | equation (9) is mentioned, for example. In addition, Denasel EX-850L and Denacol EX-216L manufactured by Nagase ChemteX can be used as the polyfunctional aliphatic epoxy monomer.

  Furthermore, as a naphthalene ring containing epoxy monomer, what is represented by the following formula | equation (10) is mentioned, for example.

［式（７）中、Ｒ_１〜Ｒ_４は、それぞれ独立して、水素原子または炭素数１〜６のアルキル基である。また、Ｒ_５、Ｒ_６は、それぞれ独立して、水素原子またはメチル基である。さらに、各ｎは、それぞれ独立して、０〜１０の整数を表わす。］

[In Formula (7), R < ₁ > -R < ₄ > is a hydrogen atom or a C1-C6 alkyl group each independently. R ₅ and R ₆ are each independently a hydrogen atom or a methyl group. Further, each n independently represents an integer of 0 to 10. ]

［式（８）中、ｎは、２〜１０の整数を表わす。］

[In Formula (8), n represents the integer of 2-10. ]

［式（９）中、ｎは、２〜１０の整数を表わす。］

[In formula (9), n represents an integer of 2 to 10. ]

［式（１０）中、Ｒは、水素原子、炭素数１〜４のアルキル基、またはフェニル基を表わす。］

[In Formula (10), R represents a hydrogen atom, a C1-C4 alkyl group, or a phenyl group. ]

  In addition to the above, as an epoxy polymer or raw material monomer, Epicoat (manufactured by Japan Epoxy Resin), phenoxy resin YP series, novolac type epoxy resin YDCN series (above, manufactured by Nippon Steel Chemical Co., Ltd.), Ogsol EG (Osaka Gas) Chemical), Biphenyl type epoxy resin YX-4000H (Mitsubishi Chemical), Rica Resin (Nippon Nippon Chemical Co., Ltd.), Silicone modified epoxy (Shin-Etsu Chemical or Toray Dow Corning), Denacol (Nagase ChemteX), Fluorine Epoxy (made by Daikin Industries), ARUFON UG-4000, 4035, 4040 (made by Toagosei), Aron Oxetane OXT-213, 221, 211 (made by Toagosei) and the like can be used.

  When the epoxy polymer is a copolymer obtained by polymerizing the raw material monomer and another raw material monomer, the other raw material monomer is not particularly limited as long as it is of a different type from the raw material monomer, For example, what is illustrated with the monomer contained in the additive 920 mentioned later can be used.

The weight average molecular weight of the epoxy-based polymer is not particularly limited, is preferably from 2 × ¹⁰ 4 ~3 × ¹⁰ about ^5, more preferably 3 × ¹⁰ 4 ~2 × ¹⁰ about ^5. By using an epoxy-based polymer having such a weight average molecular weight, compatibility with a monomer described later can be enhanced, and strength and flexibility of the core layer 13 can be improved.

  Here, the refractive index of each part of the core layer 13 is determined according to the relative size relationship between the refractive index of the epoxy polymer and the refractive index of the monomer and the abundance ratio in each part. 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 epoxy polymer.

  Also, 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 epoxy polymer. For example, the epoxy polymer 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 an epoxy polymer having such a chemical structure, the leaving group can be detached from the main chain by irradiation with actinic radiation 930, and its refractive index changes.

  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 epoxy-based polymer by leaving, at least one of -Si-diphenyl structure and -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 based on the total weight of the epoxy polymer. When the amount of the leaving group is within the above range, an epoxy polymer having an excellent refractive index modulation function (an effect of changing the refractive index difference) can be obtained, and the flexibility of the core layer 13 to be formed can be improved. Improvements can also be made.

  Such an epoxy-based polymer having a leaving group can be easily obtained by polymerizing the raw material monomer described above and a monomer having a leaving group introduced into the raw material monomer.

  Furthermore, an epoxy-based polymer having an epoxy group can also be used. By using such an epoxy polymer, it becomes possible to form the core layer 13 having excellent adhesion to the cladding layers 11 and 12.

((Silicone polymer))
Silicone polymers are used as the polymers in the present invention because they are particularly highly transparent, have excellent light transmission properties, and have excellent heat resistance, light stability, and electrical insulation. In addition, the silicone polymer has compatibility with the monomer described later, and among them, the monomer can react (polymerization reaction or crosslinking reaction) as described later, and is sufficient even after the monomer reacts. Those having transparency are preferably used.

  Here, “having compatibility” means that the monomer is at least mixed and does not cause phase separation with the silicone polymer in the optical waveguide forming compositions 901 and 902 and the layer 910.

  Furthermore, the silicone-based polymer is a polymer (including resin and rubber) obtained by polymerizing (hydrolyzing / condensing or condensing) this raw material monomer using organoalkoxysilane or a derivative thereof as a raw material monomer.

  Therefore, as a silicone polymer (polyorganosiloxane), a homopolymer obtained by polymerizing one of the above raw material monomers, a copolymer obtained by polymerizing two or more different raw material monomers, the above raw material monomer and other raw material monomers And a copolymer obtained by polymerizing and the like.

  The organoalkoxysilane used as a raw material monomer (silicone monomer) is not particularly limited, and examples thereof include those represented by the following formula (11).

［式（１１）中、Ｒ^１、Ｒ^３は、それぞれ独立して、一価の有機基である。また、Ｒ^２は、アルキル基またはアルコキシアルキル基である。さらに、ｍは、０または１であり、ｎは、０〜３の整数を表わす。］

[In Formula (11), R ¹ and R ³ are each independently a monovalent organic group. R ² is an alkyl group or an alkoxyalkyl group. Furthermore, m is 0 or 1, and n represents an integer of 0 to 3. ]

In formula (11), R ¹ and R ³ (monovalent organic group) are each independently an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, vinyl Group, alkenyl group such as allyl group, aryl group such as phenyl group and tolyl group, aralkyl group such as naphthyl group and phenethyl group, halogenated alkyl group, halogenated aryl group and carbon atoms in these organic groups Examples thereof include a nitrogen atom, an oxygen atom, a silicon atom, a sulfur atom, a phosphorus atom, or an atomic group containing these atoms.

R ² is specifically an alkyl group such as a methyl group, an ethyl group, a propyl group, or a butyl group, a methoxymethyl group, an ethoxymethoxy group, a propoxymethoxy group, a methoxyethoxy group, an ethoxyethoxy group, or a propoxyethoxy group. And an alkoxyalkyl group such as a butoxyethoxy group.

  Specific examples of the organoalkoxysilane represented by the above formula (11) include isopropyltrimethoxysilane, neopentyltrimethoxysilane, allyltrimethoxysilane, 4-vinylphenyltrimethoxysilane, and trimethylsilylmethyl. Trimethoxysilane, isobutyltriethoxysilane, ethynyltrimethoxysilane, diethynyldimethoxysilane, 4-vinylphenyltriethoxysilane, trimethylsilylmethyltriethoxysilane, isopropyltripropoxysilane, cyclopentyltriisopropoxysilane, neopentylriboxysilane, Isopropylmethyldimethoxysilane, methylneopentyldimethoxysilane, cyclohexylmethyldimethoxysilane, methylcyclopentyldimeth Sisilane, allylmethyldimethoxysilane, (4-chlorophenyl) methyldimethoxysilane, ethylpropyldimethoxysilane, ethylisopentyldimethoxysilane, ethylneopentyldimethoxysilane, ethylcyclopentyldimethoxysilane, phenylethyldimethoxysilane, ethyl-3,3,3 -Trifluoropropyldimethoxysilane, butylpropyldimethoxysilane, sec-butylpropyldimethoxysilane, pentylpropyldimethoxysilane, hexylpropyldimethoxysilane, 3-chloropropylpropyldimethoxysilane, 3-bromopropylpropyldimethoxysilane, isopropyl-sec-butyl Dimethoxysilane, isopropylcyclopentyldimethoxysilane, isopropylvinyldimethoxy Run, cyclopentylisobutyldimethoxysilane, dihexyldimethoxysilane, dicyclopentyldimethoxysilane, bis (trimethylsilylmethyl) dimethoxysilane, 3,3,3-trifluoropropylhexyldimethoxysilane, sec-butylmethyldiethoxysilane, ethylpropyldiethoxysilane , Ethyl-tert-butyldiethoxysilane, dipropyldiethoxysilane, diisopropyldiethoxysilane, diisopropylbutylethoxysilane, dicyclopentyldiethoxysilane, 4-methoxyphenylvinyldiethoxysilane, isobutyldimethylmethoxysilane, tert-butyldimethyl Methoxysilane, (4-chlorophenyl) dimethylmethoxysilane, dimethyl-2-thienylmethoxysilane, Propylmethoxysilane, tributylmethoxysilane, isobutyldimethylethoxysilane, allyldimethylethoxysilane, triethylethoxysilane, phenyldiethylethoxysilane, dipropylisobutylethoxysilane, diphenylmethylethoxysilane, allyldimethylpropoxysilane, triethylpropoxysilane, diphenylmethyl Butoxysilane, 1,4-bis (methyldimethoxysilyl) phenylene, 2-aminoethylaminomethyltrimethoxysilane, 3-aminopropyldimethylethoxysilane, 2- (2-aminoethylthioethyl) triethoxysilane, β- ( 3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltriethoxysilane, and the like.

  When the silicone polymer is a copolymer obtained by polymerizing the raw material monomer (organoalkoxysilane) and another raw material monomer, the other raw material monomer may be of a different type from the raw material monomer, Although it does not specifically limit, For example, what is illustrated with the monomer contained in the additive 920 mentioned later can be used.

The weight average molecular weight of the silicone-based polymer is not particularly limited, is preferably from 2 × ¹⁰ 4 ~3 × ¹⁰ about ^5, more preferably 3 × ¹⁰ 4 ~2 × ¹⁰ about ^5. By using a silicone-based polymer 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, the refractive index of each part of the core layer 13 is determined in accordance with the relative magnitude relationship between the refractive index of the silicone-based polymer and the refractive index of the monomer and the abundance ratio in each part. Therefore, the refractive index of each part of the core layer 13 can be adjusted by appropriately selecting the type of monomer used and the type of silicone polymer.

  Further, as described above, the silicone-based polymer is obtained by hydrolysis / condensation or condensation of an organoalkoxysilane or a derivative thereof. Therefore, in the molecular structure, an —O— structure, an —Si-aryl structure is included. And at least one of —O—Si— structures. Therefore, the portion having such a structure functions as a leaving group that is released from the main chain by actinic radiation 930 described later, and the refractive index can be changed by the elimination of the leaving group from the main chain. Therefore, also from this point, the refractive index difference between the core portion 14 and the side cladding portion 15 can be adjusted.

  The leaving group that causes a decrease in the refractive index of the silicone polymer upon leaving is preferably at least one of -Si-diphenyl structure and -O-Si-diphenyl structure.

  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, more preferably 20 to 60% by weight based on the total weight of the silicone polymer. When the amount of the leaving group is within the above range, a silicone polymer having an excellent refractive index modulation function (effect of changing the refractive index difference) can be obtained, and the flexibility of the core layer 13 to be formed can be improved. Improvements can also be made.

  In addition, when the thing which has an epoxy group is used as a silicone type polymer, it becomes possible to form the core layer 13 excellent in adhesiveness with respect to the cladding layers 11 and 12. FIG.

((Polyimide polymer))
The polyimide polymer is particularly high in transparency, has excellent light transmission properties, and further has excellent heat resistance, light stability, mechanical properties, adhesion, and electrical insulation. Used as In addition, the polyimide-based polymer is compatible with the monomer described later, and among them, the monomer can react (polymerization reaction or crosslinking reaction) as described later, and is sufficient even after the monomer reacts. Those having transparency are preferably used.

  Here, “having compatibility” means that the monomer is at least mixed and does not cause phase separation with the polyimide polymer in the optical waveguide forming compositions 901 and 902 and the layer 910.

  Furthermore, a polyimide-type polymer is a polymer containing the polyimide (oligomer) formed by heating and hardening (imidation) the polyamic acid obtained by making tetracarboxylic anhydride and diamine react.

  Therefore, as the polyimide polymer, a homopolymer obtained by polymerizing one kind of the above polyimide, a block copolymer obtained by polymerizing two or more kinds of the above polyimide, a block copolymer obtained by polymerizing the above polyimide and another oligomer, etc. Is mentioned.

  Although it does not specifically limit as a tetracarboxylic anhydride and diamine used in order to obtain such a polyimide, For example, the following are mentioned.

  That is, examples of the tetracarboxylic acid anhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and 2,2-bis (2,3-dicarboxyphenyl). ) Propane dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone Those having no fluorine atom in the molecule such as acid dianhydride, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, 4,4-bis (3,4- Dicarboxytrifluorophenoxy) tetrafluorobenzene dianhydride, 1,4-bis (3,4-dicarboxytrifluorophenoxy) tetrafluorobenzene dianhydride, Fluoromethyl) bimellitic dianhydride, di (trifluoromethyl) pyromellitic dianhydride, di (heptafluoropropyl) pyromellitic dianhydride containing fluorine atoms in the molecule Of these, one or two or more of these can be used in combination.

  Examples of the diamine include m-phenylenediamine, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, bis (3-aminophenyl) sulfide, and (3-aminophenyl) (4-aminophenyl). Sulfide, bis (3-aminophenyl) sulfoxide, (3-aminophenyl) (4-aminophenyl) sulfoxide, bis (4-aminophenyl) sulfone, (3-aminophenyl) (4-aminophenyl) sulfone, 3, 4′-diaminobenzophenone, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 4,4′-bis (3-aminophenoxy) biphenyl, bis [4- (4-Aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) ) Phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfoxide, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, 4,4 '-Diamino-5,5'-diphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 3,4'-diamino-4,5'-dibiphenoxybenzophenone, 3,3'-diamino-4- Biphenoxybenzophenone, such as those containing no fluorine atom in the molecule, 2,2′-bis (trifluoromethyl) -4,4′-diaminobiphenyl, 2-trifluoromethyl-4,4′- Diaminodiphenyl ether, 2′-trifluoromethyl-3,4′-diaminodiphenyl ether, 2,2-bis (3-aminopheny ) -1,1,1,3,3,3-hexafluoropropane, 1,3-bis (3-aminophenoxy) -4-trifluoromethylbenzene, 1,3-bis (3-amino-5- Trifluoromethylphenoxy) benzene, 1,3-bis (3-amino-5-trifluoromethylphenoxy) -5-trifluoromethylbenzene, 1,4-bis (4-amino-2-trifluoromethylphenoxy) benzene , 2,2-bis [4- (3-aminophenoxy) phenyl) -1,1,1,3,3,3-hexafluoropropane and the like containing a fluorine atom in the molecule, etc. One or more of these can be used in combination.

  In addition, when the polyimide-based polymer is a block copolymer obtained by polymerizing the polyimide (oligomer) and another oligomer, the other oligomer is not particularly limited as long as it is of a type different from the polyimide, For example, at least one of (meth) acrylic oligomers, epoxy oligomers, and silicone oligomers (organosiloxane oligomers) can be used.

The weight average molecular weight of the polyimide-based polymer is not particularly limited, is preferably from 2 × ¹⁰ 4 ~1 × ¹⁰ about ^6, more preferably 2 × ¹⁰ 5 ~4 × ¹⁰ about ^5. By using a polyimide polymer 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, the refractive index of each part of the core layer 13 is determined in accordance with the relative magnitude relationship between the refractive index of the polyimide-based polymer and the refractive index of the monomer in each part and the existence ratio thereof. Therefore, the refractive index of each part of the core layer 13 can be adjusted by appropriately selecting the type of monomer used and the type of polyimide-based polymer.

  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 polyimide polymer. For example, the polyimide polymer 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 a polyimide polymer having such a chemical structure, the leaving group can be detached from the main chain by irradiation with actinic radiation 930, and its refractive index changes.

  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 polyimide-based polymer by leaving, at least one of the -Si-diphenyl structure and the -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, more preferably 20 to 60% by weight based on the total weight of the polyimide polymer 915. When the amount of the leaving group is within the above range, the polyimide polymer 915 having an excellent refractive index modulation function (an effect of changing the refractive index difference) can be obtained, and the flexibility of the core layer 13 to be formed is provided. Can also be improved.

  Such a polyimide-based polymer having a leaving group can be easily obtained by, for example, using this as a block copolymer obtained by polymerizing the above polyimide (oligomer) and an organosiloxane oligomer as another oligomer.

((Fluoropolymer))
The fluorine-based polymer is particularly used as a polymer in the present invention because it has high transparency, excellent light transmission properties, and excellent mechanical properties and moisture absorption resistance. In addition, the fluorine-based polymer is compatible with the monomer described later, and among them, the monomer can react (polymerization reaction or crosslinking reaction) as described later, and is sufficient even after the monomer reacts. Those having transparency are preferably used.

  Here, “having compatibility” means that at least the monomer is mixed and does not cause phase separation with the fluoropolymer in the optical waveguide forming compositions 901 and 902 or in the layer 910.

  Further, the fluorine-based polymer is a polymer containing a fluorine atom in its molecular structure. In the present invention, the fluorine-based polymer includes an aliphatic ring structure, an imide ring structure, a triazine ring structure, a benzoxazole structure, and It has at least one kind of ring structure among aromatic ring structures, and preferably contains a fluorine atom in the structure. Among these, a polymer having an aliphatic ring structure as a main chain is particularly preferable. Thereby, the layer 910 obtained from the optical waveguide forming compositions 901 and 902 can have a more uniform film thickness.

  A polymer having an aliphatic ring structure as a main chain (hereinafter sometimes referred to as “fluorinated aliphatic ring structure polymer”) is a monomer having a ring structure containing a fluorine atom, a fluorine atom and two or more fluorine atoms. A monomer having a polymerizable unsaturated bond can be used as a raw material monomer to polymerize this raw material monomer.

  Therefore, the fluorine-containing aliphatic ring structure polymer includes a homopolymer obtained by polymerizing one of the raw material monomers, a copolymer obtained by polymerizing two or more different raw material monomers, the raw material monomer and other raw material monomers. And the like.

  In the present specification, the fluorine-containing aliphatic ring structure polymer is mainly composed of a plurality of aliphatic ring structures, and one or more carbon atoms constituting this aliphatic ring structure. A fluorine atom or an atomic group containing a fluorine atom is bonded.

  Specific examples of such a fluorinated alicyclic polymer include those having structural units (repeating units) as listed in the following formulas (12) to (16) in the main chain.

［上記各式中、ｌは０〜５、ｍは０〜４、ｎは０〜１、ｌ＋ｍ＋ｎは１〜６、ｏ、ｐ、ｑは、それぞれ独立して、０〜５、ｏ＋ｐ＋ｑは１〜６であり、Ｒ^１、Ｒ^２およびＲ^３は、それぞれ独立して、Ｆ、Ｃｌ、ＣＦ_３、Ｃ_２Ｆ_５、Ｃ_３Ｆ_７またはＯＣＦ_３であり、Ｘ^１およびＸ^２は、それぞれ独立して、ＦまたはＣｌである。］

[In the above formulas, l is 0-5, m is 0-4, n is 0-1, 1 + m + n is 1-6, o, p, q are each independently 0-5, o + p + q is 1-6. 6, R ¹ , R ² and R ³ are each independently F, Cl, CF ₃ , C ₂ F ₅ , C ₃ F ₇ or OCF ₃ , and X ¹ and X ² are each independently F or Cl. ]

  In order to obtain the fluorine-containing aliphatic ring structure polymer having such a configuration, examples of the monomer (monomer) having a ring structure containing a fluorine atom include perfluoro (2,2-dimethyl-1,3-dioxole). , Perfluoro (2-methyl-1,3-dioxole), perfluoro (2-ethyl-2propyl-1,3-dioxole), perfluoro (2,2-dimethyl-4methyl-1,3-dioxole), etc. Those having perfluorodioxoles in which a fluorine-substituted alkyl group such as a fluorine atom, a trifluoromethyl group, a pentafluoroethyl group or a heptafluoropropyl group is bonded to a dioxole ring member carbon, or perfluoro (4-methyl-2 -Methylene-1,3-dioxolane), perfluoro (2-methyl-1,4-dioxin) and the like Such as those comprising a fluorine alicyclic structure and the like, can be used singly or in combination of two or more of them.

  Moreover, as a monomer (monomer) provided with a fluorine atom and two or more polymerizable unsaturated bonds, for example, perfluoro (3-oxa-1,5-hexadiene), perfluoro (3-oxa-1,6- Heptadiene), perfluoro (4-methyl-3-oxa-1,6-heptadiene), perfluoro (4-chloro-3-oxa-1,6-heptadiene), perfluoro (4-methoxy-3-oxa-1,6) -Heptadiene), perfluoro (5-methyl-3-oxa-1,6-heptadiene), and the like, and one or more of these can be used in combination.

  In addition, the fluorine-containing aliphatic ring structure polymer uses, as a raw material monomer, both a monomer having a ring structure containing a fluorine atom and a monomer having a fluorine atom and two or more polymerizable unsaturated bonds, These can also be obtained by copolymerizing them.

  Further, when the fluorine-containing aliphatic ring structure polymer is a copolymer obtained by polymerizing the above raw material monomer and another raw material monomer, examples of the other raw material monomer include tetrafluoroethylene, chlorotrifluoroethylene, perfluoro In addition to radically polymerizable monomers such as (methyl vinyl ether), those exemplified as monomers contained in the additive 920 described later can be used.

The weight average molecular weight of the fluorine-based polymer is not particularly limited, is preferably from 2 × ¹⁰ 4 ~3 × ¹⁰ about ^5, more preferably 3 × ¹⁰ 4 ~2 × ¹⁰ about ^5. By using such a fluorine-based polymer having 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, 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 fluorine-based polymer and the refractive index of the monomer and the abundance ratio in each part. Therefore, the refractive index of each part of the core layer 13 can be adjusted by appropriately selecting the type of monomer used and the type of fluoropolymer.

  Also, 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 fluoropolymer. For example, the fluorine-based polymer 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 fluorine-based polymer having such a chemical structure, the leaving group can be detached from the main chain by irradiation with actinic radiation 930, and its refractive index changes.

  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 fluoropolymer upon leaving, at least one of a -Si-diphenyl structure and an -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 fluoropolymer. When the amount of the leaving group is within the above range, a fluorine-based polymer having an excellent refractive index modulation function (an effect of changing the refractive index difference) can be obtained, and the flexibility of the core layer 13 to be formed can be improved. Improvements can also be made.

  In addition, such a fluorine-based polymer having a leaving group can be easily obtained by polymerizing the raw material monomer described above and a monomer having a leaving group introduced into the raw material monomer.

((Polyolefin polymer))
Examples of the polyolefin polymer include ethylene, propylene, 1-butene, cis-2-butene, trans-2-butene, isobutene, 1-pentene, 2-pentene, 2-methyl-1-butene, and 3-methyl-1. -Monoolefin monomers such as butene, 2,3-dimethyl-2-butene, 1-butene, 1-hexene, 1-octene, 1-nonene, 1-decene, allene, methylallene, butadiene, 2,3 -Polymers (including resins and rubbers) obtained by polymerizing raw material monomers using diene monomers such as dimethylbutadiene, 1,3-pentadiene, 1,4-pentadiene, chloroprene and 1,5-hexadiene. .)

  The polyolefin-based polymer includes a homopolymer obtained by polymerizing one of the raw material monomers, a copolymer obtained by mixing two or more different raw material monomers, and the raw material monomer and another raw material monomer. And the like.

  Further, other raw material monomers to be polymerized with the above raw material monomers are not particularly limited. For example, styrene, α-methyl styrene, o-methyl styrene, p-methyl styrene, m-methyl styrene, o-ethyl styrene, p -Aromatic vinyl monomers such as t-butylstyrene, chlorostyrene, chloromethylstyrene, bromostyrene, (meth) acrylonitrile, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, (meth ) Vinyl monomers such as butyl acrylate, allyl (meth) acrylate, N-phenylmaleimide, N-methylmaleimide, butyl acetate, vinyl acetate, isopropenyl acetate, vinyl chloride and vinyl ether.

  Examples of the polymer obtained by polymerizing the above raw material monomers include polystyrene, styrene-butadiene copolymer, vinyl acetate or a hydrolyzate thereof, polyvinyl alcohol, polyacetal, polybutyral, polyvinyl chloride, vinyl chloride / vinyl acetate copolymer. Examples include coalescence.

  Another raw material monomer may be a monomer having a chemical structure that is partially photoisomerized or photodimerized by irradiation with actinic radiation 930. In a polyolefin-based polymer having such a chemical structure, irradiation with actinic radiation 930 causes photoisomerization or photodimerization, and its refractive index changes. Photoisomerization is a phenomenon in which cis-trans isomerization, photo-Fries rearrangement, and decarboxylation are caused by irradiation with actinic radiation, and photodimerization is a phenomenon in which bonds are formed between adjacent double bonds. .

  Examples of such a chemical structure for photoisomerization or photodimerization include N = N group such as azobenzene group, azonaphthalene group, aromatic heterocyclic azo group, bisazo group, formazan group, maleimide group, indene group, C = C groups such as coumarin groups, cinnamate groups, polyene groups, stilbene groups, stilbazole groups, stilbazolium groups, cinnamoyl groups, hemithioindigo groups, chalcone groups, aromatic Schiff bases, and aromatic hydrazone structures. Examples thereof include C═O groups such as N group, benzophenone group and anthraquinone group, ester groups such as allyl ester group, acylphenol structure and the like, and at least one of them is used. In particular, at least one of an azobenzene group, a maleimide group, a coumarin group, a cinnamoyl group, and an indene group is preferably used.

  Examples of the compound having the above chemical structure include, for example, Imilex (manufactured by Nippon Shokubai), aliphatic bismaleimide (manufactured by DMI), Aronix (manufactured by Toagosei), bismaleimides (manufactured by Kay Aikasei), methylcinnamate (Inoue Fragrance Factory), 2-methoxyhexyl paramethoxycinnamate and the like.

(Additive)
In the present embodiment, the additive 920 includes a monomer in both the optical waveguide forming composition 901 and the optical waveguide forming composition 902. In the present embodiment, the additive 920 in the optical waveguide forming composition 901 further includes a polymerization initiator, while the additive 920 in the optical waveguide forming composition 902 includes a polymerization initiator. Not.

((monomer))
The monomer (photopolymerizable monomer) reacts in the irradiated region by irradiation with actinic radiation, which will be described later, to form a reaction product, and the monomer diffuses and moves with it, so that the layer 910 has an irradiated region and an unirradiated region. It is a compound that can cause a difference in refractive index between them.

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

  By the way, the difference in refractive index generated between the irradiated region and the non-irradiated region is generated based on the difference between the refractive index of the polymer 915 and the refractive index of the monomer. Therefore, the monomer contained in the additive 920 is the polymer 915. Is selected in consideration of the magnitude relationship with the refractive index.

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

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

  The minimum value of the refractive index distribution W corresponds to a region where the refractive index of the irradiated region is reduced in the layer 910 due to the reaction of the monomer (generation of a reaction product), and the region where the refractive index of the irradiated region is increased is refracted. The maximum value of the rate distribution W corresponds.

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

  Such a monomer is not particularly limited as long as it is a compound having a polymerizable portion in the molecular structure, and the monomers mentioned as the raw material of the polymer 915 are used. For example, acrylic acid (methacrylic acid) Monomers, epoxy monomers, oxetane monomers, norbornene monomers, vinyl ether monomers, styrene monomers, photodimerization monomers, and the like can be used, and one or more of these can be used in combination.

  Among these monomers, by using the same type of monomer as the polymer 915, the monomer can be more uniformly dispersed in the polymer 915. Therefore, the characteristics of the optical waveguide forming compositions 901 and 902 should be homogenized. Can do.

  Further, unsaturated hydrocarbons are particularly preferably used as the polymerizable portion. A compound containing an unsaturated hydrocarbon easily causes a polymerization reaction such as radical polymerization or cationic polymerization, and is suitable as a monomer used in the present invention.

  Here, as the acrylic acid (methacrylic acid) -based monomer and epoxy-based monomer, the same monomers as those cited as the raw material of the 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, by using such a monomer, it is possible to shorten the time for forming the core layer 13 and hence the time for manufacturing the optical waveguide 1.

  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.

  Examples of vinyl ether monomers include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, n-pentyl vinyl ether, n-hexyl vinyl ether, and n-octyl. Examples thereof include alkyl vinyl ethers such as vinyl ether, n-dodecyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexyl vinyl ether, and cycloalkyl vinyl ethers, and one or more of these can be used in combination.

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

  Further, examples of the photodimerization monomer include monomers having a chemical structure that can be photodimerized as described above, and specifically, 4,4′-diphenylmethane bismaleimide, bis- (3-ethyl-5-methyl-4-methyl). Maleimidophenyl) methane, 2,2′-bis- [4- (4-maleimidophenoxy) phenyl] propane and the like can be mentioned, and one or two of these can be used in combination.

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

  Further, 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, -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.

  As the monomer having an oxetanyl group, for example, Aron oxetane (manufactured by Toagosei Co., Ltd.) can be used.

  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 mass or more and 50 parts by mass or less, and more preferably 2 parts by mass or more and 40 parts by mass or less with respect to 100 parts by mass of the polymer 915. Thereby, the refractive index modulation between the core part 14 and the side clad part 15 can be caused more reliably.

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

  Further, the optical waveguide forming composition 901 may contain a monomer, while the optical waveguide forming composition 902 may contain no monomer. In this case, in each of the cladding layers 11 and 12, the monomer diffusion movement in the layer does not occur, so that the refractive index in each of the cladding layers 11 and 12 can be made uniform.

((Polymerization initiator))
The polymerization initiator acts on the monomer with irradiation of actinic radiation and promotes the reaction of the monomer.

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

  Examples of the radical polymerization initiator include benzophenones and acetophenones. Specifically, Irgacure 651, Irgacure 184 (above, manufactured by BASF Japan) and the like can be mentioned.

  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. Specifically, Adekaoptomer SP-170 (manufactured by ADEKA), Sun-Aid SI-100L (manufactured by Sanshin Chemical Industry), Rhodorsil 2074 (manufactured by Rhodia Japan) and the like can be mentioned.

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

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

  In addition, various crosslinking agents can be used. For example, carbodilite V-02-L2 (manufactured by Nisshinbo Chemical Co., Ltd.) can be used as a crosslinking agent for aqueous (meth) acrylates for crosslinking of (meth) acrylic monomers.

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

  In the present embodiment, as described above, the additive 920 in the optical waveguide forming composition 901 includes a polymerization initiator, while the additive 920 in the optical waveguide forming composition 902 is a polymerization initiator. Therefore, the monomer polymerization reaction is accelerated only in the core layer 13, and the monomer polymerization reaction is not accelerated in the cladding layers 11 and 12. Therefore, in the cladding layers 11 and 12, the change in the refractive index is suppressed, and the refractive index within the layer can be made relatively uniform.

  However, the addition of the polymerization initiator is not limited to the above case, and both the optical waveguide forming composition 901 and the optical waveguide forming composition 902 may contain a polymerization initiator. In this case, since it is preferable to suppress the polymerization reaction of the monomer as much as possible in the cladding layers 11 and 12, the types and addition amounts of the polymerization initiators included in the optical waveguide forming composition 901 and the optical waveguide forming composition 902 are different. You can make it. Specifically, a polymerization initiator contained in the optical waveguide forming composition 902 is used as the polymerization initiator contained in the optical waveguide forming composition 901 which is highly reactive with the wavelength of the actinic radiation 930 described later. As described above, those having low reactivity with respect to the wavelength of actinic radiation 930 described later may be used. When the same type of polymerization initiator is used, the amount added to the optical waveguide forming composition 902 may be less than that of the optical waveguide forming composition 901.

  Furthermore, a photoacid generator may be used as the polymerization initiator contained in the optical waveguide forming composition 901, and a thermal acid generator may be used as the polymerization initiator contained in the optical waveguide forming composition 902. Thereby, with the irradiation of the active radiation 930, the polymerization reaction of the monomer is promoted mainly only in the core layer 13 and the refractive index distribution W is formed. On the other hand, the polymerization reaction of the monomer is performed in the cladding layers 11 and 12. Not promoted. After the refractive index profile W is formed, heat is applied to the layer 910 to accelerate the monomer polymerization reaction in the cladding layers 11 and 12 in this case. As a result, in the layer 910, the refractive index distribution T in the thickness direction is fixed.

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

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 is preferably 0.01% by mass or more, more preferably 0.5% by mass or more in the optical waveguide forming compositions 901 and 902, and more preferably 1% by mass or more. More preferably. In addition, it is preferable that an upper limit is 5 mass% or less.

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

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

  [2] Next, a mask (masking) 935 in which an opening (window) 9351 is formed is prepared, and the layer 910 is irradiated with active radiation 930 through the mask 935 (see FIG. 12).

  Below, the case where what has a refractive index lower than the polymer 915 is used as a monomer is demonstrated to an example. Correspondingly, in the optical waveguide forming compositions 901 and 902 used to form the layer 910, the composition of the polymer 915 is (refractive index of the optical waveguide forming composition 901)> (optical waveguide The refractive index of the forming composition 902 is set so as to satisfy the relationship. 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.

  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. The opening 9351 has 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. 12, the opening (window) 9351 of the mask 935 is shown by partially removing the mask along the pattern of the irradiation region 925 of the active radiation 930. However, the quartz glass, the PET base material, etc. In the case of using the photomask manufactured in (1), it is also possible to use a photomask provided with a shielding portion of active radiation 930 made of a shielding material made of metal such as chromium. In this mask, the part other than the shielding part is the window (transmission part).

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

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

The irradiation dose of the actinic radiation 930 is preferably in the range of about 0.1~9J / cm ^2, more preferably about ^{0.2~6J / cm 2, 0.2~3J / cm} 2 of about More preferably.

  When the layer 910 is irradiated with the active radiation 930 through the mask 935, the polymerization initiator is activated in the 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 polymer 915 and the monomer are appropriately selected so that a difference in refractive index occurs between them, the refractive index between the irradiated region 9253 and the non-irradiated region 9403 of the core layer 13 is increased with the diffusion and movement of the monomer. There is a difference. 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.

  FIG. 14 is a diagram for explaining a state in which a difference in refractive index occurs between the irradiated region 9253 and the non-irradiated region 9403 of the core layer 13, and the horizontal axis indicates the position in the width direction of the cross section of the layer 910. It is a figure which shows refractive index distribution when taking the refractive index of a cross section on the vertical axis | shaft.

  In this embodiment, since a monomer having a refractive index smaller than that of the polymer 915 is used as the monomer, the refractive index of the unirradiated region 9403 increases and the refractive index of the irradiated region 9253 decreases as the monomer diffuses and moves ( FIG. 14 (a)).

  It is considered that the monomer diffusion movement is caused by the consumption of the monomer in the irradiation region 9253 and the concentration gradient of the monomer formed accordingly. For this reason, the monomers in the entire unirradiated region 9403 do not move toward the irradiated region 9253 all at once, but gradually move from a portion close to the irradiated region 9253, and outward from the center of the unirradiated region 9403 to compensate for this. Monomer migration also occurs. As a result, as shown in FIG. 14A, the high refractive index portion H on the non-irradiated region 9403 side and the low refractive index portion L on the irradiated region 9253 side across the boundary between the irradiated region 9253 and the non-irradiated region 9403. 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 (difference in refractive index is about 0 to 0.001). As the polymerization proceeds, the refractive index decreases according to the amount of the monomer and the amount of the substance derived from the monomer. Therefore, the shape of the refractive index distribution W can be controlled by appropriately adjusting the amount of monomer or polymerization initiator relative to the polymer.

  On the other hand, in the unirradiated region 9403, since the polymerization initiator is not activated, the polymerization of the monomer is not promoted.

  In addition, in the irradiation region 9253, the ease of monomer diffusion transfer gradually decreases as the polymerization of the monomer proceeds. As a result, in the irradiated region 9253, the closer to the unirradiated region 9403, the higher the concentration of the monomer, and the lower the refractive index. As a result, the distribution shape of the low refractive index portion L formed in the irradiated region 9253 tends to be asymmetrical, and the gradient on the non-irradiated region 9403 side becomes steeper. Thereby, the refractive index distribution W which the optical waveguide of this invention has is formed.

  The polymer 915 preferably has a leaving group as described above. This leaving group is released upon irradiation with actinic radiation 930 and decreases the refractive index of the polymer 915. Therefore, when the irradiation region 9253 is irradiated with the actinic radiation 930, the above-described diffusion and movement of the monomer is started, the leaving group is released from the polymer 915, and the refractive index of the irradiation region 9253 decreases from before the irradiation. (See FIG. 14B).

  Since this decrease in refractive index occurs uniformly in the entire irradiation region 9253, the above-described difference in refractive index between the high refractive index portion H and the low refractive index portion L is further enlarged. As a result, a refractive index distribution W shown in FIG. 14B is obtained. Note that the refractive index change in FIG. 14A and the refractive index change in FIG. 14B occur almost simultaneously. Such a refractive index change further expands this refractive index difference.

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

  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 monomer from the irradiation region 9251 in the cladding layer 11 and the irradiation region 9252 in the cladding layer 12 in the irradiation region 925. 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 and movement of the monomer. In this region, the composition of the polymer 915 is set so that the refractive index is originally 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, the leaving group is detached as in the irradiation region 9253 in the core layer 13, and the refractive index of the 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. 13). Such an optical waveguide 1 partially irradiates actinic radiation 930 to a layer 910 composed of a composition for forming an optical waveguide in which a monomer is dispersed in a polymer 915, thereby diffusing and moving the monomer. Thus, the layer 910 has a refractive index distribution W that causes a refractive index bias. Further, such an optical waveguide 1 can be formed by simply irradiating a part of the active radiation 930 and has a high transmission efficiency. Therefore, the width and pitch of the core part 14 and the side cladding part 15 can be reduced. Even if it is narrow, high-quality optical communication is possible. Therefore, the optical waveguide 1 can be easily multi-channeled and highly densified.

  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. This corresponds to the interface between the side cladding 15 and the side cladding 15.

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

  The Shore D hardness of the polymer 915 is preferably about 50 to 95, more preferably about 55 to 90, and further preferably about 60 to 85. The polymer 915 having such hardness contributes to the formation of a sufficient refractive index difference by reliably diffusing and moving the monomer while providing the optical waveguide 1 with necessary and sufficient flexibility and bending resistance. Therefore, the obtained optical waveguide 1 has sufficient flexibility and mechanical strength suitable for bending use, and has excellent optical characteristics even in a bent state.

  Similarly, the Rockwell hardness of the polymer 915 is preferably about 50 to 125 on the M scale, more preferably about 60 to 115, and still more preferably about 70 to 110.

  In addition, the softening point of the polymer 915 is preferably 90 ° C. or higher, and more preferably 100 to 130 ° C. Thereby, the obtained optical waveguide 1 can reliably form the refractive index distribution W and can maintain the formed refractive index distribution W for a long period of time, and prevents disconnection even when used in a bent state. It has sufficient mechanical strength. Therefore, the optical waveguide 1 has excellent optical characteristics and high reliability. The softening point of the polymer 915 is the glass transition temperature or melting point of the polymer 915, and when both are present, it indicates the lower one.

  Note that the irradiation with the active radiation 930 may be performed in an inert gas atmosphere such as a nitrogen atmosphere or an argon atmosphere as necessary. Thereby, the oxidation and modification of the polymer 915 and the monomer can be suppressed, and the optical waveguide 1 having higher optical characteristics can be obtained.

  On the other hand, as shown in FIG. 15A, 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 Since the above monomer diffuses and moves to the irradiation region 9253, the refractive index of the region corresponding to the core portion 14 also increases in the refractive index distribution T ′ in the thickness direction of the core portion 14. On the other hand, since the refractive index does not change in the clad layers 11 and 12 positioned above and below the core portion 14, the refractive index difference between the core portion 14 and the upper and lower clad layers 11 and 12 increases as a result. It will be.

  Based on the principle as described above, the optical waveguide 1 having a refractive index distribution T having a large refractive index difference between the maximum value and the minimum value is obtained (see FIG. 15B). If the refractive index distribution T ′ has already realized a refractive index distribution shape that is sufficiently effective, the above-described change from the refractive index distribution T ′ to the refractive index distribution T is omitted. May be.

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

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

  The monomer-derived structure refers to a structure formed by reaction of an unreacted monomer or a monomer such as a monomer, an oligomer obtained by reacting the monomer, and a polymer obtained by reacting the monomer.

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

  Further, the refractive index distribution W and the refractive index distribution T can be obtained by utilizing the fact that the intensity distribution of the emitted light from the optical waveguide 1 has a certain correlation with the refractive index distribution W or the refractive index distribution T. It can be specified indirectly.

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

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

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

  Next, heat treatment is performed on the layer 910 as necessary. In this heat treatment, the monomer in the irradiated region 9253 of the core layer 13 irradiated with light is further polymerized.

  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.
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.

  Further, when the layer 910 is formed so as to include a plurality of core layers 13, when the active radiation 930 is irradiated on the layer 910, the core portions 14 and the side cladding portions 15 are collectively applied to the plurality of core layers 13 by one irradiation. Can be formed. For this reason, the optical waveguide 1 having a plurality of core layers 13 can be manufactured with a small number of steps. In this case, the core portion 14 can hardly be displaced between the plurality of core layers 13. Therefore, the optical waveguide 1 with extremely high dimensional accuracy can be obtained. Such an optical waveguide 1 has a particularly high optical coupling efficiency when optically coupling with a light emitting / receiving element or the like.

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

  Examples of the electronic device including the optical waveguide of the present invention include electronic devices such as a mobile phone, a game machine, a router device, a WDM device, a personal computer, a television, and a home server. In any of these electronic devices, it is necessary to transmit a large amount of data at high speed between an arithmetic device such as an LSI and a storage device such as a RAM. Therefore, by providing such an electronic device with the optical waveguide of the present invention, problems such as noise and signal degradation peculiar to electrical wiring are eliminated, and a dramatic improvement in performance can be expected.

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

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

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

  In addition, the method for producing the optical waveguide of the present invention is not limited to the above method. For example, a method of cutting molecular bonds by irradiation with actinic radiation to change the refractive index (photo bleach method), and forming a core layer A composition comprising a photocrosslinkable polymer having an unsaturated bond capable of photoisomerization or photodimerization, and irradiating with active radiation to change the molecular structure and change the refractive index (photoisomerization method) A method such as a photodimerization method can also be used.

  In these methods, since the amount of change in the refractive index can be adjusted according to the irradiation amount of the active radiation, the irradiation amount of the active radiation applied to each part of the layer according to the shape of the target refractive index distribution W is set. By making them different, a core layer having a refractive index distribution W can be formed.

Next, examples of the present invention will be described.
1. Optical waveguide manufacturing

Example 1
(1) Production of Cladding Layer Forming Resin Composition Daicel Chemical Industries, Ltd. Alicyclic Epoxy Resin, Celoxide 2081 20 g, ADEKA Co., Ltd. Cationic Polymerization Initiator, Adekaoptomer SP-170 0.6 g A solution was prepared by stirring and mixing 80 g of methyl isobutyl ketone.

  Subsequently, the obtained solution was filtered through a PTFE filter having a pore size of 0.2 μm to obtain a clean and colorless and transparent resin composition E1 for forming a cladding layer.

(2) Production of photosensitive resin composition As an epoxy polymer, phenoxy resin manufactured by Nippon Steel Chemical Co., Ltd., 20 g of YP-50S, 5 g of Celoxide 2021P manufactured by Daicel Chemical Industries, Ltd. as a monomer, and a polymerization initiator Adekaoptomer SP-170 (0.4 g) manufactured by ADEKA Co., Ltd. was charged into 80 g of methyl isobutyl ketone, and dissolved by stirring to prepare a solution.

  Subsequently, the obtained solution was filtered with a PTFE filter having a pore size of 0.2 μm to obtain a clean and colorless photosensitive resin composition F1.

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

(4) Production of core layer After the photosensitive resin composition F1 was uniformly applied by a doctor blade on the produced lower clad layer, it was put into a dryer at 50 ° C for 10 minutes. After completely removing the solvent to form a film, a photomask having a linear pattern of lines (core portion width) and spaces (cladding portion width) drawn on the entire surface was pressure-bonded onto the obtained film. Then, ultraviolet rays were irradiated from above the photomask with a parallel exposure machine. The cumulative amount of ultraviolet light was 800 mJ / cm ² .

  Next, the photomask was removed and placed in an oven at 150 ° C. for 30 minutes. Upon removal from the oven, it was confirmed that a clear waveguide pattern appeared on the coating. Table 1 shows the average width WCO of the core portion and the average width WCL of the side cladding portion. Further, the thickness of the obtained core layer was 50 μm, and the number of core portions was eight.

(5) Production of upper clad layer On the produced core layer, the clad layer forming resin composition E1 was applied in the same manner as in (3) to obtain a colorless and transparent upper clad layer having a thickness of 10 µm. An optical waveguide was obtained as described above.

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

(Examples 2-9)
The composition of the polymer, the composition and content of the monomer, and the cumulative amount of ultraviolet light are set as shown in Table 1, and the average width WCO of the core portion and the average width WCL of the side cladding portions are the values shown in Table 1, respectively. An optical waveguide was obtained in the same manner as in Example 1 except that the photomask pattern was set as described above.

(Example 10)
(1) Synthesis of (meth) acrylic polymer 20.0 g of methyl methacrylate (MMA), 30.0 g of benzyl methacrylate (BzMA), and 450 g of methyl isobutyl ketone were put into a separable flask and mixed with stirring. To prepare a monomer solution.

  On the other hand, 0.25 g of azobisisobutyronitrile as a polymerization initiator was dissolved in 10 g of methyl isobutyl ketone and then substituted with nitrogen gas to prepare an initiator solution.

  And the said initiator solution was added to the said monomer solution using the syringe, stirring the said monomer solution in the state heated at 80 degreeC. The mixture was stirred at 80 ° C. for 1 hour and then cooled to prepare a polymer solution. Thereafter, 5 L of isopropanol was prepared in a beaker, and the polymer solution was dropped into the beaker while stirring at room temperature with a stirrer. After completion of dropping, the mixture was further stirred for 30 minutes, and then the precipitated polymer was taken out and dried at 60 ° C. under reduced pressure for 8 hours in a vacuum dryer. Thereby, acrylic polymer A1 was obtained.

(2) Manufacture of resin composition for forming clad layer 20 g of aqueous acrylate resin solution RD-180 manufactured by Kyoyo Chemical Industry Co., Ltd., 20 g of isopropanol, and Nisshinbo Chemical Co., Ltd. Carbodilite V-02-L2 4 g was stirred and mixed to prepare a solution.

  Subsequently, the obtained solution was filtered with a PTFE filter having a pore size of 0.2 μm to obtain a clean, colorless and transparent resin composition B1 for forming a cladding layer.

(3) Production of photosensitive resin composition 20 g of synthesized acrylic polymer A1, 5 g of cyclohexyl methacrylate as a monomer, 0.4 g of Irgacure 651 manufactured by BASF Japan Ltd. as a polymerization initiator, in 80 g of methyl isobutyl ketone The solution was stirred and dissolved to prepare a solution.

  Subsequently, the obtained solution was filtered with a PTFE filter having a pore size of 0.2 μm to obtain a clean and colorless photosensitive resin composition C1.

(4) Production of lower clad layer The clad layer-forming resin composition B1 was uniformly applied onto a polyimide film having a thickness of 25 µm by a doctor blade, and then placed in a dryer at 80 ° C for 10 minutes. After completely removing the solvent, it was further put into an oven at 150 ° C. for 10 minutes and cured to obtain a colorless and transparent lower clad layer having a thickness of 10 μm.

(5) Production of core layer After the photosensitive resin composition C1 was uniformly applied by a doctor blade on the produced lower clad layer, it was put into a dryer at 50 ° C for 10 minutes. After completely removing the solvent to form a film, a photomask having a linear pattern of lines and spaces drawn on the entire surface was pressure-bonded onto the obtained film. Then, ultraviolet rays were irradiated from above the photomask with a parallel exposure machine. The cumulative amount of ultraviolet light was 700 mJ / cm ² .

  Next, the photomask was removed and placed in an oven at 150 ° C. for 30 minutes. Upon removal from the oven, it was confirmed that a clear waveguide pattern appeared on the coating. Table 1 shows the average width WCO of the core portion and the average width WCL of the side cladding portion. Further, the thickness of the obtained core layer was 50 μm, and the number of core portions was eight.

(6) Production of upper clad layer On the produced core layer, the clad layer-forming resin composition B1 was applied in the same manner as in (4) to obtain a colorless and transparent upper clad layer having a thickness of 10 µm. An optical waveguide was obtained as described above.

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

(Examples 11 to 13)
The composition and content of the monomer and the integrated light quantity of ultraviolet rays are set as shown in Table 2, and the photomask is set so that the average width WCO of the core portion and the average width WCL of the side cladding portions are the values shown in Table 2, respectively. An optical waveguide was obtained in the same manner as in Example 10 except that the above pattern was set.

(Comparative Example 1)
(1) Synthesis of norbornene-based resin having a leaving group In a glove box filled with dry nitrogen in which the water and oxygen concentrations are both controlled to 1 ppm or less, 7.2 g (40.1 mmol) of hexylnorbornene (HxNB) Then, 12.9 g (40.1 mmol) of diphenylmethylnorbornenemethoxysilane was weighed into a 500 mL vial, 60 g of dehydrated toluene and 11 g of ethyl acetate were added, and the top was sealed with a silicon sealer.

  Next, 1.56 g (3.2 mmol) of Ni catalyst and 10 mL of dehydrated toluene were weighed in a 100 mL vial, and a stirrer chip was placed and sealed, and the catalyst was thoroughly stirred to dissolve completely.

  When 1 mL of this Ni catalyst solution was accurately weighed with a syringe, and quantitatively injected into the vial bottle in which the two kinds of norbornene were dissolved and stirred at room temperature for 1 hour, a marked increase in viscosity was confirmed. At this point, the stopper was removed, 60 g of tetrahydrofuran (THF) was added, and the mixture was stirred to obtain a reaction solution.

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

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

(2) Production of composition for forming core layer 10 g of the purified polymer # 1 was weighed into a 100 mL glass container, and 40 g of mesitylene, 0.01 g of an antioxidant Irganox 1076 (manufactured by Ciba Geigy), and a polymerization initiator (light) Acid generator) Rhodorsil Photoinitiator 2074 (manufactured by Rhodia, CAS # 178233-72-2) (0.01 g in 0.1 mL of ethyl acetate) was added and dissolved uniformly, and then filtered through a 0.2 μm PTFE filter. A clean composition for forming a core layer was obtained. In addition, this composition differs from the photosensitive resin composition as described in each Example by the point in which a monomer is not contained. On the other hand, the polymer # 1 has a function of releasing a leaving group upon irradiation with actinic radiation, and a so-called photobleaching phenomenon occurs. The polymerization initiator is expressed as PI 2074 in Table 1.

(3) Manufacture of the composition for forming a clad layer The molar ratio of each structural unit of the purified polymer # 1 was changed to hexylnorbornene structural unit 80 mol% and diphenylmethylnorbornenemethoxysilane structural unit 20 mol%, respectively. A cladding layer forming composition was obtained in the same manner as the core layer forming composition except that it was used in place of polymer # 1.

(4) Production of lower clad layer The clad layer forming composition was uniformly applied onto a polyimide film having a thickness of 25 µm by a doctor blade, and then placed in a dryer at 50 ° C for 10 minutes. After completely removing the solvent, the entire surface was irradiated with UV light by a UV exposure machine to cure the applied composition. As a result, a colorless and transparent lower cladding layer having a thickness of 10 μm was obtained. The integrated light quantity of ultraviolet rays was 1300 mJ / cm ² .

(5) Preparation of core layer After apply | coating the core layer resin composition uniformly with a doctor blade on the produced lower clad layer, it injected | thrown-in to the 50 degreeC drying machine for 10 minutes. After completely removing the solvent to form a film, a photomask on which a linear pattern of lines (core part width) 50 μm and space (cladding part width) 75 μm was drawn on the entire surface was pressure-bonded onto the obtained film. . Then, ultraviolet rays were irradiated from above the photomask with a parallel exposure machine. The integrated light quantity of ultraviolet rays was 1300 mJ / cm ² .

  Next, the photomask was removed and placed in an oven at 150 ° C. for 30 minutes. Upon removal from the oven, it was confirmed that a clear waveguide pattern appeared on the coating. The thickness of the obtained core layer was 50 μm. The number of core portions was eight.

(6) Production of upper clad layer On the produced core layer, the clad layer-forming resin composition E1 was applied in the same manner as in (3) to obtain a colorless and transparent upper clad layer having a thickness of 10 µm. An optical waveguide was obtained as described above.

(7) Evaluation of refractive index distribution And about the cross section of the core layer of the obtained optical waveguide, the refractive index distribution of the width direction was acquired with the interference microscope. As a result, the refractive index distribution was a so-called step index (SI) type distribution.

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

  In the obtained optical waveguide, the refractive index of the side clad portion was substantially constant, while the refractive index of the core portion continuously decreased from the central portion toward the periphery. That is, the refractive index distribution of the core layer of the obtained optical waveguide was a so-called graded index (GI) type.

(Comparative Example 3)
The optical waveguide was formed in the same manner as in Comparative Example 1 except that exposure (graded exposure) was performed using a photomask whose transmittance was continuously changed so that the exposure amount continuously changed during exposure. Obtained.

  In the obtained optical waveguide, the refractive index distribution has a plurality of minimum values and maximum values, and the refractive index of the core portion continuously decreases from the central portion toward the periphery, reaching a minimum value. In the side cladding portion, the refractive index continuously increased as the distance from the minimum value increased. At the minimum value, the shape of the refractive index distribution was V-shaped, and the change in the refractive index in the vicinity thereof was discontinuous.

(Comparative Examples 4 and 5)
Except that the average width WCO of the core part, the average width WCL of the side cladding part, and the UV exposure amount at the time of forming the core layer are changed to the values shown in Table 1, respectively, except that the photomask pattern and the UV irradiation conditions are changed. In the same manner as in Examples 1 and 2, optical waveguides were obtained.

(Comparative Examples 6 and 7)
Optical waveguides in the same manner as in Examples 10 and 11, except that the photomask pattern was changed so that the average width WCO of the core portion and the average width WCL of the side cladding portions were values shown in Table 2, respectively. Got.

  Tables 1 and 2 show the manufacturing conditions for the optical waveguides obtained in the above examples and comparative examples.

2. Evaluation 2.1 Refractive Index Distribution of Optical Waveguide With respect to the cross section of the core layer of the obtained optical waveguide, the refractive index distribution is measured by an interference microscope along the center line in the thickness direction, and the width of the cross section of the core layer is measured. A refractive index profile in the direction was obtained. In addition, since the obtained refractive index distribution has the same refractive index distribution pattern repeated for every core part, a part was cut out from the obtained refractive index distribution, and this was made into the refractive index distribution W.

  Of the refractive index distribution W, the shape of the distribution of “W type” in Tables 1 and 2 was a shape in which four local minimum values and five local maximum values were alternately arranged as shown in FIG. From this W-type refractive index distribution W, each minimum value Ws1, Ws2, Ws3, Ws4 and each maximum value Wm1, Wm2, Wm3, Wm4, Wm5 were obtained, and an average refractive index WA in the cladding part was obtained.

Further, in this W-shaped refractive index distribution W, it is formed in the core portion maximal value Wm2, WM4 refractive index in the vicinity of the width a of the portion having a mean refractive index W A [[mu] m], and The width b [μm] of the portion where the refractive index in the vicinity of each local minimum value Ws1, Ws2, Ws3, Ws4 has the value of the average refractive index WA was measured.
The above measurement results are shown in Tables 3 and 4.

  As a result, the refractive index distribution W in the width direction of the optical waveguides obtained in each of the examples and the comparative examples 4 to 7 was continuously changed in refractive index as a whole.

  The refractive index distribution W in the width direction of the optical waveguide obtained in Comparative Example 1 was a step index type. Further, the refractive index distribution W in the width direction of the optical waveguide obtained in Comparative Example 2 was a graded index type. Further, the refractive index distribution W in the width direction of the optical waveguide obtained in Comparative Example 3 has a plurality of minimum values and maximum values, and the refractive index is discontinuous between the core portion and the side cladding portion. Had changed.

  On the other hand, the refractive index distribution T in the thickness direction of the optical waveguide obtained in each example and each comparative example was a step index type.

2.2 Transmission loss of optical waveguide Light emitted from an 850 nm VCSEL (surface emitting laser) is introduced into the optical waveguide obtained in each example and each comparative example via a 50 μmφ optical fiber, and the emitted light is 200 μmφ. The light was received by an optical fiber and the light intensity was measured. Note that the cutback method was used to measure the transmission loss. Then, when the measured values were plotted with the longitudinal direction of the optical waveguide taken on the horizontal axis and the insertion loss on the vertical axis, the measured values were arranged on a straight line. Therefore, the transmission loss was calculated from the slope of the straight line.

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

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

<Evaluation criteria for pulse width>
A: Relative value of pulse width is less than 0.5 B: Relative value of pulse width is 0.5 or more and less than 0.8 Δ: Relative value of pulse width is 0.8 or more and less than 1 ×: The relative value of the pulse width is 1 or more. Tables 5 and 6 show the evaluation results of 2.2 and 2.3.

  As is clear from Tables 5 and 6, it is recognized that the transmission loss and the blunting of the pulse signal are suppressed in the optical waveguides obtained in the respective examples as compared with the optical waveguides obtained in the respective comparative examples. It was.

  In addition, since the composition for core layer formation in which the photobleaching phenomenon used in the comparative example 1 can adjust the modulation amount of the refractive index according to the irradiation light amount, the integrated light amount gradually increases. An attempt was made to form the refractive index profile W using a photomask set to change. When the refractive index distribution was evaluated as described above for the obtained optical waveguide, a high refractive index region and a low refractive index region were confirmed, but the change in refractive index was not as continuous as in each example. . In addition, the obtained optical waveguide had a larger transmission loss than the respective examples, and the retention of the pulse signal waveform was also low.

2.4 Intensity Distribution of Emitted Light from Optical Waveguide Further, the intensity distribution of the emitted light when the light was incident on one of the eight core portions was measured on the end face on the emission side of the obtained optical waveguide.
The intensity distribution of the emitted light was measured as follows.

  FIG. 16 is a diagram for explaining a method of measuring the intensity distribution of outgoing light on the outgoing side end face of the optical waveguide.

  In the method shown in FIG. 16, first, the incident-side optical fiber 21 having a diameter of 50 μm is arranged so as to face one of the core portions 14 of the incident-side end face 1a of the optical waveguide 1 to be measured. The incident-side optical fiber 21 is connected to a light emitting element (not shown) for making light incident on the optical waveguide 1, and is arranged so that the optical axis thereof coincides with the optical axis of the core portion 14. Yes.

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

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

  FIG. 17 shows the intensity distribution of the emitted light measured as described above. FIG. 17 representatively shows the intensity distribution of the emitted light measured with the optical waveguides obtained in Example 1, Comparative Example 1, and Comparative Example 2.

  As is clear from FIG. 17, it was confirmed that the crosstalk was sufficiently suppressed in the optical waveguide obtained in Example 1. Further, in the optical waveguide obtained in Example 1, the intensity of the emitted light in the core portion 14 adjacent to the core portion 14 (the core portion 14 in the center of FIG. 17) where light is incident is adjacent to the core portion 14. It was confirmed that the intensity of the emitted light was smaller than that of the side clad portion 15 located on the side opposite to the core portion 14 where the light was incident. This is because, in the optical waveguide obtained in Example 1, the side cladding portion 15 has a maximum value smaller than the core portion 14 and the refractive index distribution continuously changes. Conventionally, it is assumed that light that leaks into the adjacent core portion 14 and becomes “crosstalk” gathers in the side cladding portion 15 and consequently prevents the occurrence of crosstalk. . Therefore, in the optical waveguide obtained in Example 1, it is possible to prevent interference between channels.

  In the optical waveguide obtained in Example 1, it was observed that a part of the emitted light was collected in the side clad portion 15. Usually, the light receiving elements connected to the optical waveguide are each core portion 14. Are connected so as to face the end surface of the light-emitting side, and are not connected to the side clad portion 15. Therefore, even if light gathers in the side cladding part 15, crosstalk does not occur and interference is suppressed.

  Although not shown, the crosstalk in the width direction was sufficiently suppressed in the optical waveguides obtained in the other examples as in the first example.

  On the other hand, in the optical waveguides obtained in Comparative Examples 1 and 2, the local maximum value of the intensity distribution of the emitted light is located in the core portion 14 adjacent to the core portion 14 where the light is incident. Crosstalk was observed.

  Although not shown, crosstalk was also observed in the optical waveguide obtained in Comparative Example 3.

DESCRIPTION OF SYMBOLS 1 Optical waveguide 1a Incident side end surface 1b Outgoing side end surface 11, 12 Cladding layer 13 Core layer 14 Core part 141, 142, 143, 144 Core part 15 Side surface clad part 151, 152, 153, 154, 155, 156 Side surface clad part 16 Core part defect part 17 Mirror 170 Concave part 2 Support film 3 Cover film 800 Die coater (multicolor extrusion molding device)
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 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 914g seventh molded layer 914h Eighth molding layer 914i Ninth molding layer 915 Polymer 920 Additive 930 Actinic radiation 935 Mask (masking)
9351 opening (window)
925 Irradiation area 9251, 9252, 9253 Irradiation area 940 Non-irradiation area 9403 Non-irradiation area 951 Support substrate 21 Incident side optical fiber 22 Emission side optical fiber C1, C2 Center line W Refractive index distribution WA Average refractive index T, T ′ Refraction Index distribution H High refractive index part L Low refractive index part

Claims (12)

Preparing a layer composed of a material in which a photopolymerizable monomer having a refractive index different from that of the polymer is dispersed in a polymer having a softening point of 90 ° C. or higher;
The layer is partially irradiated with light, and the photopolymerizable monomer is moved and unevenly distributed, thereby causing a refractive index bias in the layer, a plurality of core portions, and both sides of each core portion A step of obtaining an optical waveguide having a plurality of side clad portions provided so as to be adjacent to the surface;
Have
The refractive index distribution W in the width direction in the cross section of the optical waveguide has two minimum values, one first maximum value, and two second maximum values smaller than the first maximum value. These have regions arranged in the order of the second maximum value, the minimum value, the first maximum value, the minimum value, and the second maximum value, and among the regions, the first maximum value When the region sandwiched between the two minimum values so as to include each core portion and the region on the second maximum side from each minimum value as the side cladding portion, each minimum value is: Less than the average refractive index in each of the side cladding portions, and the refractive index continuously changes throughout the refractive index distribution W,
The difference between the minimum value and the second maximum value is 10 to 40% of the difference between the minimum value and the first maximum value;
In the refractive index distribution W, the refractive index in the vicinity of the first maximum value is a [μm], which is the width of the portion having the average refractive index value in the cladding portion, and the refractive index in the vicinity of the minimum value. However, when the width having the value of the average refractive index in the cladding part is b [μm], b is 0.01a to 0.8a,
WCO / WCL satisfies the relationship of 0.1 to 5, where the average width of the plurality of core portions is WCO [μm] and the average width of the plurality of side cladding portions is WCL [μm]. An optical waveguide manufacturing method characterized by the above.   The method for manufacturing an optical waveguide according to claim 1, wherein an average width WCL of the plurality of side clad portions is 5 to 250 μm.   The method for producing an optical waveguide according to claim 1, wherein the polymer has a Shore D hardness of 50 to 95.   The optical waveguide according to any one of claims 1 to 3, wherein the polymer is a (meth) acrylic resin, an epoxy resin, a silicone resin, a polyimide resin, a fluorine resin, or a polyolefin resin. Method.   The method for manufacturing an optical waveguide according to claim 1, wherein the photopolymerizable monomer contains an unsaturated hydrocarbon in a molecular structure.   6. The device according to claim 1, wherein in the region corresponding to the cladding portion in the refractive index distribution W, the second maximum value is located outside the vicinity of the interface with the core portion. Manufacturing method of optical waveguide.   In the refractive index distribution W, in the region corresponding to the cladding portion, the second maximum value is located at the center of the region, and the second maximum value is directed toward the minimum value. 7. The method for manufacturing an optical waveguide according to claim 1, wherein the refractive index is changed so as to continuously decrease. 8. The optical waveguide according to claim 1, wherein a difference in refractive index between the minimum value and the first maximum value is 5.0 × 10 ^{−3 to} 7.0 × 10 ⁻² . Production method. When taking the position of the cross section on the horizontal axis and the refractive index on the cross section on the vertical axis,
9. The refractive index distribution W 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 downward in the vicinity of the minimum value. An optical waveguide manufacturing method according to claim 1. The first maximum value includes a flat portion in which the refractive index is not substantially changed in the vicinity of the top portion,
The method for manufacturing an optical waveguide according to claim 1, wherein a length of the flat portion is 100 μm or less. An optical waveguide having a plurality of core portions and a plurality of side clad portions provided so as to be adjacent to both side surfaces of each core portion,
The refractive index distribution W in the width direction in the cross section of the optical waveguide has two minimum values, one first maximum value, and two second maximum values smaller than the first maximum value. These have regions arranged in the order of the second maximum value, the minimum value, the first maximum value, the minimum value, and the second maximum value, and among the regions, the first maximum value When the region sandwiched between the two minimum values so as to include each core portion and the region on the second maximum side from each minimum value as the side cladding portion, each minimum value is: Less than the average refractive index in each of the side cladding portions, and the refractive index continuously changes throughout the refractive index distribution W,
The difference between the minimum value and the second maximum value is 10 to 40% of the difference between the minimum value and the first maximum value;
In the refractive index distribution W, the refractive index in the vicinity of the first maximum value is a [μm], which is the width of the portion having the average refractive index value in the cladding portion, and the refractive index in the vicinity of the minimum value. However, when the width having the value of the average refractive index in the cladding part is b [μm], b is 0.01a to 0.8a,
When the average width of the plurality of core portions is WCO [μm] and the average width of the plurality of side cladding portions is WCL [μm], WCO / WCL satisfies the relationship of 0.1 to 5,
The refractive index distribution W is the photopolymerizability in a core layer composed of a material in which a structure derived from a photopolymerizable monomer having a refractive index different from that of the polymer is dispersed in a polymer having a softening point of 90 ° C. or higher. An optical waveguide formed on the basis of the concentration of a monomer-derived structure. An electronic apparatus comprising the optical waveguide according to claim 11 .

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