JP2017016017A - Optical waveguide and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical waveguide in which an optical path core does not collapse even when the optical path core is formed to have a larger height and a smaller width.SOLUTION: The optical waveguide includes an under clad layer 1, a linear optical path core 2 formed to protrude on a surface of the under clad layer 1, and a dummy core D for preventing the optical path core 2 from falling down, formed to protrude on the surface of the under clad layer 1 as spaced from the optical path core 2. The optical path core 2 and the dummy core D are formed by exposing a photosensitive resin layer for forming cores through a photomask having an opening pattern corresponding to the patterns of the optical path core 2 and the dummy core D to transfer the patterns, and then developing the resin layer by use of a developer.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical waveguide used in the fields of optical communication, optical information processing, position sensors, and other general optics, and a method for manufacturing the same.

  In general, an optical waveguide has a linear optical path core formed in a protruding pattern on the surface of an under cladding layer (see, for example, Patent Document 1).

  In the pattern formation of the optical path core, first, a photosensitive resin for core formation is applied to the surface of the undercladding layer to form the photosensitive resin layer. Next, the photosensitive resin layer is exposed to the pattern through a photomask having an opening pattern corresponding to the pattern of the optical path core, and the exposed portion is cured. And by developing using a developing solution, an unexposed part is dissolved and removed, The remaining said exposed part is formed in the core for optical paths of the said pattern.

Japanese Patent Laying-Open No. 2015-106035

  By the way, in an electro-optical device in which an optical waveguide is used, light emitted from the distal end surface of the optical path core is efficiently transmitted to the optical component when the optical waveguide and the optical component (optical element, lens, etc.) are connected. Therefore, it is known that it is advantageous to increase the height of the optical path core.

  Recently, as the above-mentioned electro-optical device is further reduced in size, it is required to reduce the width of the optical waveguide used therein. In order to realize this, it is necessary to narrow the width of the optical path core.

  However, as described above, when the height of the optical path core of the optical waveguide is increased and the width is narrowed, the optical path core may fall down after the development process. The fallen optical path core has a large light propagation loss.

  The present invention has been made in view of the above circumstances, and provides an optical waveguide in which the optical path core does not fall down even if the optical path core has a high height and a narrow width, and a method for manufacturing the same. Is the purpose.

  In order to achieve the above object, the present invention provides an undercladding layer, an optical path core protrudingly formed on the surface of the undercladding layer, and a gap between the undercladding layer and the optical path core. The first gist is an optical waveguide provided with a dummy core for preventing the collapse of the above-mentioned optical path core, which protrudes from the surface.

  The present invention also includes a step of preparing an undercladding layer, a step of forming a photosensitive resin layer for forming a core on the surface of the undercladding layer, a pattern of an optical path core, and a gap between the optical path core and the optical path core. A step of exposing the photosensitive resin layer to the pattern through a photomask formed with an opening pattern corresponding to the pattern of the dummy core for preventing the collapse of the optical path core formed with The second gist is a method for producing an optical waveguide comprising a developing step of dissolving and removing an unexposed portion using a developer and forming the remaining exposed portion on the optical path core and dummy core of the pattern. To do.

  In order to prevent the optical path core from falling down even if the optical path core is high in height and narrow in the optical waveguide, first, in the prior art, the optical path core Investigated the cause of the collapse of the core. As a result, it has been found that the cause is a load caused by the developer in the development process. That is, as described above, in the development process after exposing the photosensitive resin layer for core formation, the unexposed part is dissolved and removed with a developer, and the formed optical path core is then removed. The flow of the developer hits. Since the optical path core has a high height, the area receiving the flow is large, and the load applied to the optical path core is increased accordingly. In addition, since the optical path core is narrow, it is difficult to withstand the load. For this reason, the optical path core falls down as described above.

  In view of this, the inventors of the present invention, in the development process, in order to make the formed optical path core less susceptible to the flow of the developer, the dummy core is formed with a gap from the optical path core. Inspired to form protrusions on the surface. That is, when the photosensitive resin layer for forming the core is exposed to the pattern of the optical path core, at the same time, it is exposed to the pattern of the dummy core, and in the subsequent development process, along with the optical path core, the optical path core The dummy core is formed on both sides or one side. In other cases, when a plurality of optical path cores are formed in parallel and a gap between adjacent optical path cores and the optical path core is narrow (for example, less than 50 μm), the optical path core group including these optical path cores The dummy core is formed on the outside of the optical path core with a gap from the optical path cores on both sides of the optical path core group.

  As a result, when the dummy core is formed on both sides of the optical path core, the flow of developer from both sides of the optical path core is received by the dummy core on both sides, and the optical path core is affected by the flow of developer. It became difficult to prevent the fall of the core for the optical path.

  On the other hand, when the dummy core is formed on one side of the optical path core, the flow of the developer from one side where the dummy core is formed is received by the dummy core on one side, and the optical path core receives the developer from the one side. It has been found that the optical path core is prevented from falling down due to the flow of the developer from one side, which is less affected by the flow. The flow of the developer from the other side where the dummy core is not formed is received by the optical path core, so the optical path core tries to fall down on the opposite side of the dummy core, but the optical path core falls down. In order to prevent this, the dummy core supported the optical path core, and after the development process was completed, it was also found that the optical path core returned to its original standing state by its own restoring force.

  Further, when the dummy core is formed on both sides of the optical path core group, the flow of the developer from both sides of the optical path core group is received by the dummy core on the both sides, and the optical path core group receives the flow of the developer. Less affected. Moreover, since the gap between the adjacent optical path cores and the optical path core is narrow in the optical path core group, the optical path cores in the optical path core group are much less susceptible to the flow of the developer. And found out that lodging was prevented.

  As described above, the present inventors have found that the dummy core formed with a gap from the optical path core acts to prevent the collapse of the optical path core, and have reached the present invention.

  The optical waveguide of the present invention has a gap with the optical path core, and a dummy core for preventing the collapse of the optical path core is formed on the surface of the under cladding layer. The fall of the optical path core can be prevented. Therefore, the optical waveguide of the present invention is free from light propagation loss due to the collapse of the optical path core, and can be a reliable optical waveguide with stable light propagation.

  And the manufacturing method of the optical waveguide of the present invention is such that the photosensitive resin layer for forming the core formed on the surface of the under cladding layer is subjected to pattern exposure so that the exposed portion is separated from the core for the optical path and the gap with the core for the optical path. Since the optical path core is formed in the dummy core for preventing the fall of the optical path core, the fall of the optical path core due to the flow of the developer in the development process can be prevented. Therefore, a reliable optical waveguide of the present invention with stable light propagation can be produced.

  In particular, when the optical path core height / width ratio (optical path core height / optical path core width) exceeds 2.5, the optical path core has a higher height. The width is narrower. For this reason, the optical propagation efficiency between the optical path core and the optical component is further improved, and the width of the optical waveguide can be reduced to further reduce the size of the electro-optical device using the optical waveguide.

  In addition, when the ratio of the optical path core height to the width (optical path core height / optical path core width) exceeds 2.5 as described above, the optical path core is likely to fall down. When the number of the optical path cores formed on the surface of the under cladding layer is one, and the number of the optical path cores is plural, the gap between the adjacent optical path cores and the optical path core is 50 μm or more. In this case, a gap of less than 50 μm from the optical path core is formed on both sides of the optical path core, and the ratio of the height to the width (dummy core height / dummy core width) is set to 2.5 or less. By setting and forming, the fall of the said core for optical paths can be prevented.

  Further, the ratio of the height and width of the optical path core (optical path core height / optical path core width) exceeds 2.5, and a plurality of the optical path cores are arranged in parallel, and the adjacent optical path core and optical path When the gap between the optical path cores is less than 50 μm, the optical path cores on both sides of the optical path core group are opened outside the optical path core group consisting of the optical path cores, and a gap of less than 50 μm is provided. By forming the dummy core with the ratio of height to width (dummy core height / dummy core width) set to 2.5 or less, it is possible to prevent the fall of the optical path core in the optical path core group. .

(A) is a top view which shows typically 1st Embodiment of the optical waveguide of this invention, (b) is the AA sectional drawing. (A)-(e) is explanatory drawing which shows the manufacturing method of the said optical waveguide typically. (A) is a top view which shows typically 2nd Embodiment of the optical waveguide of this invention, (b) is the BB sectional drawing. (A) is a top view which shows typically 3rd Embodiment of the optical waveguide of this invention, (b) is the CC sectional drawing.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1A is a plan view showing a first embodiment of the optical waveguide of the present invention, and FIG. The optical waveguide according to this embodiment includes an underclad layer 1, a single linear optical path core 2 protruding from the surface of the underclad layer 1, and optical paths on both sides of the optical path core 2. And a dummy core D for preventing the collapse of the optical path core 2 formed on the surface of the under cladding layer 1 with a gap S1 of less than 50 μm. The optical path core 2 has a ratio of the height H1 to the width W1 (optical path core height H1 / optical path core width W1) exceeding 2.5, and the dummy core D has a height H2 and a width W2. The ratio (dummy core height H2 / dummy core width W2) is set to 2.5 or less. The formation of the dummy core D for preventing the fall of the optical path core 2 is a major feature of the present invention. In this embodiment, an over clad layer 3 is formed on the surface of the under clad layer 1 in a state where the optical path core 2 and the dummy core D are covered.

  The optical waveguide is manufactured as follows.

  First, as shown in FIG. 2A, the under cladding layer 1 is prepared. Examples of the under cladding layer 1 include those obtained by curing a photosensitive resin or a thermosetting resin, or a resin film. The height of the under cladding layer 1 is set within a range of 10 to 500 μm, for example.

  Next, as shown in FIG. 2B, a photosensitive resin for forming a core is applied to the surface of the under cladding layer 1 to form one photosensitive resin layer 2A.

  Next, as shown in FIG. 2C, an opening pattern corresponding to the pattern of the optical path core 2 and the dummy core D (see FIG. 2D) is formed above the photosensitive resin layer 2A. One exposure mask M is positioned. Then, the photosensitive resin layer 2A is exposed through the exposure mask M. Thereafter, the photosensitive resin layer 2A is heat-treated as necessary. Thereby, the exposed portion of the photosensitive resin layer 2A is cured.

  Subsequently, as shown in FIG. 2D, development is performed using a developer to dissolve and remove the unexposed portion of the photosensitive resin layer 2A (see FIG. 2C). The exposed portion is left on the surface of the under cladding layer 1. Thereafter, if necessary, the remaining exposed portion is subjected to heat treatment, and the developer remaining in the remaining exposed portion is removed. Then, the remaining exposed portions are formed on the optical path core 2 and the dummy core D having the above pattern. The optical path core 2 and the dummy core D are formed at the same time and are formed at the same height H1 (H2). The height H1 (H2) is set within a range of 10 to 100 μm, for example. The width W1 of the optical path core 2 is set, for example, within a range of 3 to 39 μm, and the width W2 of the dummy core D is set, for example, to 5 μm or more.

  In the developing process, a developer flow occurs. In this embodiment, the dummy core D is formed on both sides of the optical path core 2, and therefore the developer flow from both sides of the optical path core 2. Is received by the dummy cores D on both sides, and the optical path core 2 is less susceptible to the flow of the developer. As a result, the ratio of the height H1 and the width W1 of the optical path core 2 (optical path core height H1 / optical path core width W1) exceeds 2.5, and the optical path core 2 tends to fall down. However, the fall of the optical path core 2 is prevented. As described above, it is a major feature of the present invention that the dummy core D prevents the optical path core 2 from falling down.

  Then, as shown in FIG. 2E, a photosensitive resin or a thermosetting resin for forming an over clad layer is formed on the surface of the under clad layer 1 so as to cover the optical path core 2 and the dummy core D. After coating, it is cured and formed on the overcladding layer 3. The height of the over clad layer 3 from the top surface of the optical path core 2 is set, for example, within a range of 1 to 1000 μm. In this way, the optical waveguide can be produced.

  FIG. 3A is a plan view showing a second embodiment of the optical waveguide of the present invention, and FIG. 3B is a BB cross-sectional view thereof. In the optical waveguide of this embodiment, a plurality of optical path cores 2 formed on the surface of the under cladding layer 1 are adjacent to each other in the first embodiment shown in FIGS. A gap S2 between the optical path core 2 and the optical path core 2 is set to 50 μm or more. The dummy core D for preventing the fall of the optical path core 2 is formed on both sides of each optical path core 2 with a gap S1 less than 50 μm from the optical path core 2. Other parts are the same as those of the first embodiment, and the same reference numerals are given to the same parts. Then, the same operations and effects as the first embodiment are obtained.

  In the first and second embodiments, the dummy core D is formed on both sides of the optical path core 2. However, the dummy core D may be formed only on one side of the optical path core 2. In this case, since the optical path core 2 receives the flow of the developer from the other side where the dummy core D is not formed, the optical path core 2 tends to fall on the opposite side of the dummy core D. The dummy core D supports the optical path core 2 so that the optical path core 2 does not fall down. After the development process is completed, the optical path core 2 returns to the original standing state by its own restoring force.

  FIG. 4A is a plan view showing a third embodiment of the optical waveguide of the present invention, and FIG. 4B is a sectional view taken along the line CC in FIG. The optical waveguide of this embodiment has a plurality of optical path cores 2 formed on the surface of the under cladding layer 1, and the gap S2 between the adjacent optical path cores 2 and the optical path core 2 is less than 50 μm. A plurality of optical path cores 2 are formed in parallel. Then, on the outside of the optical path core group 20 composed of the optical path cores 2, a clearance S1 of less than 50 μm is formed between the optical path cores 2 on both sides of the optical path core group 20 to prevent the optical path core 2 from falling down. The dummy core D is formed. Other parts are the same as those of the first embodiment, and the same reference numerals are given to the same parts.

  In this embodiment, since the dummy core D is formed on both sides of the optical path core group 20, the flow of the developer from both sides of the optical path core group 20 is received by the dummy core D on both sides, and the optical path The core group 20 is less susceptible to the flow of the developer. In addition, in the optical path core group 20, the gap S2 between the adjacent optical path cores 2 and the optical path core 2 is narrow (less than 50 μm). Therefore, the optical path core 2 in the optical path core group 20 is developed. Since it is much less susceptible to the influence of the liquid flow, the fall of the optical path core 2 is prevented.

  The optical waveguide of each of the above embodiments can be employed as an optical waveguide used for an opto-electric hybrid board, a position sensor and the like.

  In each of the above embodiments, the over clad layer 3 that covers the optical path core 2 and the dummy core D is formed. However, the over clad layer 3 may be formed as an air clad.

  Next, examples will be described together with comparative examples. However, the present invention is not limited to the examples.

[Formation material of under clad layer and over clad layer]
Component a: 100 parts by weight of an epoxy resin (manufactured by ADEKA, EP4080E).
Component b: 2 parts by weight of a photoacid generator (manufactured by Sun Apro, CPI101A).
By mixing these components a and b, a material for forming the under cladding layer and the over cladding layer was prepared.

[Material for forming optical path core and dummy core]
Component c: 75 parts by weight of an epoxy resin (manufactured by Daicel, EHPE3150).
Component d: 25 weight part of epoxy resins (manufactured by Tohto Kasei Co., Ltd., KI-3000-4).
Component e: 1 part by weight of a photoacid generator (manufactured by ADEKA, SP170).
Component f: 50 parts by weight of ethyl lactate (manufactured by Wako Pure Chemical Industries, Ltd., solvent).
The components for forming the optical path core and the dummy core were prepared by mixing these components cf.

[Example 1]
Using the respective forming materials, the optical waveguides shown in FIGS. 1A and 1B were produced in the same manner as in the first embodiment. The dimensions, elastic modulus, and refractive index of the optical waveguide core of the optical waveguide are shown in Table 1 below. The gap between the optical path core and the dummy core was 20 μm.

[Example 2]
In Example 1 above, the gap between the optical path core and the dummy core was set to 40 μm. The other parts were the same as in Example 1 above.

Example 3
Using the respective forming materials, optical waveguides shown in FIGS. 3A and 3B were produced in the same manner as in the second embodiment. The dimensions, elastic modulus, and refractive index of the optical path core of the optical waveguide were the same as in Example 1 (see Table 1 above). Further, the gap between the optical path core and the dummy core was 20 μm, and the gap between the adjacent optical path core and the optical path core was 500 μm.

Example 4
Using the respective forming materials, optical waveguides shown in FIGS. 4A and 4B were produced in the same manner as in the third embodiment. The dimensions, elastic modulus, and refractive index of the optical path core of the optical waveguide were the same as in Example 1 (see Table 1 above). The gap between the optical path core and the dummy core on both sides of the optical path core group was 20 μm, and the gap between the adjacent optical path core and optical path core in the optical path core group was 40 μm.

[Comparative Example 1]
In Example 1 described above, a dummy core was not formed as Comparative Example 1. The other parts were the same as in Example 1 above.

[Comparative Example 2]
In Example 2 described above, no dummy core was formed as Comparative Example 2. The other parts were the same as in Example 2 above.

[Comparative Example 3]
In Example 3 described above, no dummy core was formed as Comparative Example 3. The other parts were the same as in Example 3 above.

[Comparative Example 4]
In Example 4 described above, no dummy core was formed as Comparative Example 4. The other parts were the same as in Example 4 above.

  As a result of producing the optical waveguides of Examples 1 to 4 and Comparative Examples 1 to 4, in Comparative Examples 1 to 3, the optical path core was overlaid after the development process for forming the optical path core. In Example 4, the optical path cores on both sides of the optical path core group were lying down. On the other hand, in Examples 1-4, there was no above-mentioned lodging of the core for optical paths. From this, it can be seen that the dummy core formed in Examples 1 to 4 prevents the fall of the optical path core.

  The optical waveguide of the present invention and the manufacturing method thereof can be used when the optical path core is prevented from falling down even if the optical path core is high in height and narrow in width.

1 Under cladding layer 2 Optical path core D Dummy core

Claims (8)

  An under-cladding layer, an optical path core protruding from the surface of the under-cladding layer, and the optical path core protruding from the surface of the under-cladding layer with a gap from the optical path core. An optical waveguide comprising a dummy core for preventing overfall.   There is one optical path core projecting on the surface of the under cladding layer, and the ratio of the optical path core height to the width (optical path core height / optical path core width) exceeds 2.5. The dummy core is formed on both sides of the optical path core with a gap of less than 50 μm from the optical path core, and the dummy core height to width ratio (dummy core height / dummy core width) is 2. The optical waveguide according to claim 1, wherein the optical waveguide is set to 5 or less.   There are a plurality of the optical path cores protruding from the surface of the under cladding layer, and the gap between the adjacent optical path cores and the optical path core is 50 μm or more. The ratio (optical path core height / optical path core width) exceeds 2.5, and the dummy core is formed on both sides of each optical path core with a gap of less than 50 μm from the optical path core. The optical waveguide according to claim 1, wherein a ratio of the height and width of the dummy core (dummy core height / dummy core width) is set to 2.5 or less.   A plurality of the optical path cores protruding from the surface of the under cladding layer are arranged in parallel, and a gap between adjacent optical path cores and the optical path core is less than 50 μm, and the height of the optical path core The width ratio (optical path core height / optical path core width) exceeds 2.5, and the dummy core is disposed outside the optical path core group including the plurality of optical path cores. 2. The optical path core on both sides of the optical path is formed with a gap of less than 50 μm, and the ratio of the height and width of the dummy core (dummy core height / dummy core width) is set to 2.5 or less. Optical waveguide.   A process of preparing an underclad layer, a process of forming a photosensitive resin layer for forming a core on the surface of the underclad layer, a pattern of an optical path core, and a state with a gap from the optical path core The step of exposing the photosensitive resin layer to the pattern through a photomask having an opening pattern corresponding to the dummy core pattern for preventing the collapse of the optical path core, and using a developer, A method for producing an optical waveguide, comprising: a development step of dissolving and removing an unexposed portion and forming the remaining exposed portion on an optical path core and a dummy core of the pattern.   The optical path core formed on the surface of the undercladding layer is one, and the ratio of the height and width of the optical path core (optical path core height / optical path core width) exceeds 2.5, The dummy core is formed on both sides of the optical path core with a gap of less than 50 μm from the optical path core, and the ratio of the dummy core height to the width (dummy core height / dummy core width) is 2.5 or less. The method for producing an optical waveguide according to claim 5, wherein   There are a plurality of the optical path cores formed on the surface of the under cladding layer, the gap between the adjacent optical path cores and the optical path core is 50 μm or more, and the ratio of the height and width of the optical path core ( (Optical path core height / optical path core width) exceeds 2.5, and the dummy core is formed on both sides of each optical path core with a gap of less than 50 μm from the optical path core. 6. The method of manufacturing an optical waveguide according to claim 5, wherein a ratio between the height and the width of the dummy core (dummy core height / dummy core width) is set to 2.5 or less.   A plurality of the optical path cores formed on the surface of the under cladding layer are arranged in parallel, and a gap between adjacent optical path cores and the optical path core is less than 50 μm, and the height and width of the optical path core The ratio (the height of the optical path core / the width of the optical path core) exceeds 2.5, and the dummy core is disposed outside the optical path core group including the plurality of optical path cores on both sides of the optical path core group. 6. The optical waveguide according to claim 5, wherein the optical path core is formed with a gap of less than 50 μm, and the ratio of the height and width of the dummy core (dummy core height / dummy core width) is set to 2.5 or less. The manufacturing method.

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