JP2004117585A - Method for manufacturing optical waveguide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide at low cost an optical waveguide which is prevented from deteriorating in light propagation characteristic because of a locally left intermediate layer by efficiently removing an excessively dripped or applied core material. <P>SOLUTION: A method for manufacturing the optical waveguide which has a process of dripping or applying an excessive liquid core material 8 on a surface of a substrate clad 1 where a core groove 5 is formed where light is guided, a process of controlling the liquid level height of the core material 8 by pressing a cover clad 2 against the substrate clad 1, and a process of curing the dripped core material 8 uses the substrate clad 1 provided with a discharge groove 6 for discharging the excessive core material 8 between the substrate clad 1 and cover clad 2 from nearby the core groove 5 to an end of the substrate 1 or the cover clad 2 provided with the discharge groove from nearby the core groove 6 to an end of the cover clad 2. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing an optical waveguide. Specifically, the present invention relates to an optical waveguide in a waveguide type optical element or the like constituting an optical device used in the optical communication field and the optical information processing field.
[0002]
[Prior art]
In many cases, quartz glass or a dielectric crystal is used for manufacturing an optical splitter or the like, which is a planar optical waveguide, and its manufacturing method has mainly been a combination of a photolithography and a dry etching process. However, these production methods are not suitable for mass production because their processes are complicated and their equipment costs are high, and their material costs are also high. Therefore, in recent years, an optical waveguide using a polymer-based material has attracted attention.
[0003]
The optical waveguide has a core-clad planar light guide having a core material made of a polymer having excellent transparency such as PMMA (polymethyl methacrylate) or polystyrene, and a clad material made of a material having a lower refractive index than the core material. Wave paths have been proposed. FIG. 11 is a schematic perspective view of a planar optical waveguide having such a structure. In the drawings, 1 is a substrate clad, 2 is a cover clad, 3 is a core portion, 4 is an optical fiber, and 5 is a core groove. In order to fabricate this planar optical waveguide, for example, using a photoresist, a method of performing reactive ion etching after each or batch processing, or injection molding using a mold in which the core pattern of the optical waveguide is processed on the surface. A method of manufacturing a substrate clad excellent in mass productivity such as a hot embossing method of transferring a core pattern by pressing a mold against a polymer material in a molten state has been studied.
[0004]
For example, Japanese Unexamined Patent Publication (Kokai) No. 63-293509 discloses that, as shown in FIGS. 12 (a) to 12 (d), a core having a refractive index higher than that of a clad material is provided in a core groove 5 of a substrate clad 1 produced by these methods. The material (resin liquid) 8 is dropped, the cover clad 2 is placed thereon, and the core material 8 is pressed with a press plate 11 to control the liquid level of the core material 8 to a predetermined height. A method of manufacturing an optical waveguide (core portion 3) by curing the same is disclosed. In this method, the core material 8 between the cover clad 2 and the substrate clad 1 has a function of bonding the two, and the optical waveguide can be relatively easily manufactured.
[0005]
However, due to the undulation of the surface of the cover clad 2 or the substrate clad 1 due to the pressing, the resin pool 8a is likely to be generated locally, particularly at the edge of the core groove 5, as shown in FIG. At this time, since the outlet of the core material 8 is only the end face opening of the core groove 5 having a very small cross-sectional area (actually, the cross-sectional area is as small as 3 μm to 200 μm square). The resin accumulated in the pool 8a cannot be sufficiently discharged, and the local intermediate layer 9 remains as a result. The light γ leaks from the intermediate layer 9 and the light propagation characteristics are reduced.
[0006]
Japanese Patent Application Laid-Open No. 8-327842 discloses a method of forming a core-clad structure using a photocurable or thermosetting resin having a specific composition. In this method, after forming a lower clad having a core groove using a photocurable or thermosetting resin and a mold having a specific composition, the core material is poured into the core groove and cured, and overflows to the upper surface of the lower clad. After removing the excess core material, a resin having the same specific composition is flown again to form the upper clad.
[0007]
In this method, since the above-mentioned intermediate layer does not exist between the upper clad and the lower clad, there is almost no leakage of light γ, and the light propagation characteristics do not deteriorate.
[0008]
However, according to this method, since the excess core material is removed by an etching step after the core material is cured, the number of steps is increased, and the manufacturing cost is high.
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described problems of the related art, and has as its object to efficiently remove an excessively dripped or applied core material and to reduce light generated due to local residual intermediate layer. An object of the present invention is to provide an inexpensive optical waveguide that prevents the deterioration of propagation characteristics.
[0010]
[Means for Solving the Problems]
The method of manufacturing an optical waveguide according to the present invention includes a step of dripping or applying an excess liquid core material on a substrate clad surface having a core groove formed in a portion where light is guided, and pressing a cover clad against the substrate clad. A step of controlling the liquid level of the core material, and a method of manufacturing an optical waveguide having a step of curing the dropped core material, wherein a discharge groove for discharging excess core material between the substrate clad and the cover clad has a core. A substrate clad provided from the vicinity of the groove to the end face of the substrate clad or a cover clad provided from the vicinity of the core groove to the end face of the cover clad is used.
[0011]
In this case, it is preferable that a discharge hole communicating with the back side of the substrate clad or the back side of the cover clad is formed in the discharge groove.
[0012]
Further, in the present invention, in the step of controlling the liquid level, an elastic body having a lower elastic modulus than the press body that presses the cover clad may be interposed between the press body and the cover clad. In this case, a cushioning material having a lower coefficient of friction than the elastic body may be interposed between the elastic body and the cover clad.
[0013]
Further, in the present invention, in the step of controlling the liquid level, a portion for pressing the cover clad or the substrate clad may be moved or increased substantially in parallel with the discharge direction of the excess core material in the discharge groove.
[0014]
Further, in the present invention, the cover clad can be pressed against the substrate clad while being adsorbed on the press plate by the suction device. In this case, it is desirable to use a cover clad provided with a through hole.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. 1A and 1B are views showing an optical splitter obtained by the manufacturing method of the present invention, wherein FIG. 1A is a plan view thereof, and FIG. 1B is a sectional view taken along line AA of FIG. In this optical splitter, a core portion 3 as an optical waveguide is formed in a core groove 5 formed in a substrate clad 1, and a cover clad 2 is bonded to a surface of the substrate clad 1 on which a core groove 5 is formed. In this optical splitter, a large number of discharge grooves 6 having a substantially rectangular cross section extending from the vicinity of the core groove 5 to the end surface of the substrate clad 1 or the cover clad 2 are provided. The discharge groove 6 is provided for discharging the surplus core material 8 existing between the substrate clad 1 and the cover clad 2, and may be formed on the substrate clad 1 side as shown in FIG. Although not shown, it may be formed on the cover clad 2 side. In short, the substrate clad 1 and the cover clad 2 only need to form the discharge groove 6 having an opening on the end face of the clad. The position where the discharge groove 6 is provided is arbitrary as long as one end thereof is near the core groove 5 and the core material 8 overflowing from the core groove 5 flows into the discharge groove 6. However, the other end of the discharge groove 6 must be opened at the end face of the substrate clad 1 or the end face of the cover clad 2. Further, as shown in FIG. 1, the other end of the discharge groove 6 may be opened in another discharge groove 6. The shape of the discharge port (the cross-sectional shape of the discharge groove 6), the number and length of the discharge grooves 6, the disposing direction, the pitch between the discharge grooves 6, and the like are not limited. Further, the width and the depth of the discharge groove 6 are not particularly limited, but both the width and the depth are approximately 3 μm to 200 μm. The discharge groove 6 is formed simultaneously with the core groove 5 when the substrate clad 1 is formed. The same materials as those disclosed in JP-A-63-293509 are applied to the material of the substrate clad 1 and the cover clad 2, the structure of the core groove 5, the material of the core material 8, and the like. Is omitted.
[0016]
Next, a method for manufacturing the optical splitter will be described with reference to FIG. The manufacturing process is different from the process disclosed in JP-A-63-293509 only in that a discharge groove 6 is provided in the substrate clad 1 or the cover clad 2 to be used. Is the same. Prior to manufacture, a substrate clad 1 having a core groove 5 and a discharge groove 6 is prepared in advance. This is obtained, for example, by pressing the mold against the molten clad material using a mold in which the core pattern and the discharge groove pattern have been transferred to the surface. A sufficient amount of liquid core material 8 is poured into the core groove 5 of the substrate clad 1 so as to overflow the core groove 5 (FIG. 2A). Next, the cover clad 2 is arranged on the core material 8, and the liquid level of the core material 8 is controlled to a predetermined height by the press plate 11 (FIG. 2B). At this time, the core material 8 spreads in the gap between the substrate clad 1 and the cover clad 2 and excess core material 8 flows into the discharge groove 6. The core material 8 spread in the gap functions to bond the substrate clad 1 and the cover clad 2. Further, since one end of the discharge groove 6 is opened at the end face of the substrate clad 1, excess core material 8 flows into the discharge groove 6 smoothly, thereby preventing local resin reservoir from being formed. Next, the core material 8 is cured by irradiating ultraviolet rays from a UV lamp 12 or applying heat from the back surface of the substrate clad 1 while being pressed by the press plate 11 to form the core portion 3 (FIG. 2C). . Then, an optical splitter as shown in FIG. 1 is obtained (FIG. 2D).
[0017]
As described above, according to the present invention, the intermediate layer 9 existing in the conventional method is not formed, and an optical waveguide with less light leakage can be easily obtained. In particular, since the discharge groove 6 can be formed at the same time as the core groove 5, the number of manufacturing steps does not increase, and the discharge groove 6 does not require precision such as mirror finishing of the groove inner surface unlike the core groove 5. In addition, the manufacturing cost can be suppressed almost as before.
[0018]
Further, the substrate clad 1 shown in FIG. 3 can be used. The substrate clad 1 is provided with a discharge hole 7 that extends from the bottom surface of the discharge groove 6 to the back surface (non-bonding surface) of the substrate clad 1. The discharge hole 7 is for discharging the core material 8 discharged into the discharge groove 6 to the back side of the substrate clad 1. The width of the discharge hole 7 may be smaller than the width of the discharge groove 6, but is substantially the same as the width of the discharge groove 6, and its length (length in the disposing direction of the discharge groove 6) is arbitrary. Specifically, the length is set to 10 to 100 μm, but is not limited to this range. Further, the shape may be arbitrary, such as a rectangular cylindrical hole, a cylindrical hole, or a pyramidal hole. Needless to say, when the discharge groove 6 is provided in the cover clad 2, the discharge hole 7 is provided so as to communicate with the back surface (non-bonding surface) of the cover clad 2.
[0019]
If only the discharge groove 6 is provided, if the core material 8 does not flow sufficiently in the disposing direction, a resin pool may be formed and the intermediate layer 8 may be formed. However, in the second embodiment, the discharge hole is not provided. The core material 8 flows also in the press direction through 7 and the core material 8 is discharged more quickly.
[0020]
Furthermore, in the present invention, as in the third embodiment shown in FIG. The press plate 11 is provided with a plurality of suction holes 15 for sucking the cover clad 2, and the cover clad 2 is sucked on the entire surface of the press plate 11 by vacuum evacuation. As a result, the undulation of the cover clad 2 generated at the time of pressing is reduced along the press plate 11 and flatness is secured. Thus, an optical splitter in which the resin pool is further reduced and light loss due to the intermediate layer 9 is small can be manufactured.
[0021]
FIG. 5 is an explanatory diagram showing a manufacturing method according to a fourth embodiment of the present invention. In this method, an elastic body 16 having a lower elastic modulus than the press plate 11 is interposed between the press plate 11 and the cover clad 2 and pressed. Since the surface of the substrate clad 1 (the bonding surface with the cover clad 2) actually has micro unevenness and inclination, the cover clad 2 may not sufficiently adhere to the substrate clad 1 in some cases. Therefore, if an elastic body 16 having a lower elastic modulus than the press plate 11 is interposed, the press pressure is evenly applied to the cover clad 2. As a result, the cover clad 2 uniformly adheres to the substrate clad 1, and the formation of the intermediate layer 9 due to the variation in the degree of adhesion is further suppressed. Examples of the elastic body 16 include a rubber material such as silicon rubber. The hardness is preferably 30 to 90 according to JIS-K6253 (based on the durometer type A test), and the elastic modulus is preferably 10 to 100 kg / cm2. A preferable one is selected depending on the relationship with the substrate clad 1.
[0022]
FIG. 6 shows a manufacturing method according to a fifth embodiment of the present invention. In this method, a cushioning material 17 having a lower coefficient of friction than the elastic body 16 is provided between the elastic body 16 and the cover clad 2. Intervene. Here, the coefficient of friction refers to the coefficient of friction between the press plate 11 and the coefficient of friction lower than the elastic body 16 means that the coefficient of friction between the press plate 11 and the cushioning material 17 is equal to the coefficient of friction between the press plate 11 and the cover clad 2. Means smaller than the coefficient of friction. As the cushioning material 17, for example, a sheet or a film such as a Teflon (registered trademark) sheet or a glass sheet having a thickness of about 100 μm is preferably used. Further, not only the sheet material but also a lubricating liquid can be used as the cushioning material 17 and disposed between the elastic body 16 and the cover clad 2.
[0023]
In the fourth embodiment, the elastic body 16 is used to apply the press stress uniformly to the entire surface of the cover clad 2. In this process, the elastic body 16 is deformed by the press stress and the cover clad 2 is deformed. Spread all over. However, if the coefficient of friction of the elastic body 16 is large, the deformation at the time of pressing is hindered, and stress may be concentrated on the end of the elastic body 16 and may not be uniformly pressed. Therefore, in the present embodiment, a cushioning material 17 having a low friction coefficient is interposed between the elastic body 16 and the cover clad 2 to cause the elastic body 16 to deform corresponding to the pressing stress. As a result, the stress is reliably applied evenly, and the liquid level control at the time of pressing can be accurately performed without causing local resin pooling.
[0024]
Next, a manufacturing method according to a sixth embodiment is shown in FIG. In this method, in the step of controlling the liquid level, the portion pressing the cover clad 2 is moved or increased substantially in parallel with the discharge direction of the excess core material 8 in the discharge groove 6. For this purpose, as shown in FIG. 7, for example, between the press plate 11 and the cover clad 2, an elastic body 16 made of a so-called kamaboko-shaped rubber material having one surface formed in an R shape may be used. it can. The elastic body 16 is used in such a manner that the R-shaped surface is pressed against the cover clad 2, but it is also effective to use a flat portion for the cover clad 2. The curvature of the R-shaped surface may be made according to the size of the cover clad 2 and the like. For example, if the cover clad 2 has a width of 10 mm and a length of 40 mm, the thickness is 3 mm, the width is 5 to 15 mm, and the length is Silicon rubber having a curvature of 35 mm and R10 to 30 mm in the longitudinal direction is used. Of course, as shown in FIG. 8, instead of the elastic body 16, a press plate 11 having a similar shape may be used to move the pressed portion.
[0025]
That is, as the pressing proceeds, the pressing pressure gradually moves from the thick central portion to both sides, or the area to be pressed expands to both sides. As shown in FIG. 9, the discharge grooves 6 are stressed except for the discharge grooves 6 a connecting the discharge grooves 6 so that the excess core material 8 is discharged by the stress that moves or increases with the press. Are arranged in parallel with the moving direction of. With such a method, the core material 8 can be easily discharged.
[0026]
In each of the above methods, in order to discharge the core material 8, a stress distribution and time during which a pressing stress is applied become a problem, and it may be difficult to control the liquid level of the core material 8. Therefore, in the seventh embodiment shown in FIG. 10, the cover clad 2 provided with the core material suction holes 2 a which are the through holes, and the through holes 18 are also provided at positions communicating with the core material suction holes 2 a of the cover clad 2. The provided press plate 11 is used. The core material suction holes 2 a of the cover clad 2 need only be located on the core grooves 5, and may be located on the discharge grooves 6.
[0027]
In this manner, by performing the vacuum evacuation and pressing, the excess core material 8 near the core material suction hole 2a is discharged from the core material suction hole 2a of the cover clad 2, and the other excess core material 8 is discharged. It is quickly discharged from the groove 6. For this reason, when only the discharge groove 6 is provided, the core material 8 in the peripheral portion (a region away from the discharge groove 6) tends to remain, which is a resistance at the time of discharge. However, if such a method is adopted, The core material 8 serving as the resistance is also quickly discharged, and the core portion 3 can be manufactured with high accuracy.
[0028]
As described above, in the present invention, since the discharge groove 6 extending from the vicinity of the core groove 5 to the end face of the substrate clad 1 or the cover clad 2 is provided, the excess core material 8 is pressed together with the cover clad 2 and discharged. The resin is pushed out into the groove 6, and the formation of the resin pool can be substantially prevented. Thereby, light loss due to the intermediate layer 9 is reduced, and light propagation characteristics can be improved.
[0029]
【The invention's effect】
According to the present invention, a discharge groove for discharging excess core material between the substrate clad and the cover clad is provided from the vicinity of the core groove to the end surface of the substrate clad. , The number of openings through which excess core material generated when the cover clad is pressed is discharged increases. Therefore, the surplus core material does not locally accumulate, and the formation of an intermediate layer made of the core material between the cover clad and the substrate clad is prevented. In addition, since the discharge groove can be molded simultaneously with the core groove, the number of manufacturing steps does not increase, and the discharge groove does not require accuracy as in the case of the core groove. In this way, an optical waveguide with less light leakage can be relatively easily manufactured at a relatively low cost.
[0030]
Further, in this method, by forming a discharge hole in the discharge groove to the back side of the substrate clad or the back side of the cover plate, excess core material can be discharged quickly.
[0031]
Further, in the step of controlling the liquid level, an elastic body having a lower elastic modulus than the press body for pressing the cover clad is interposed between the press body and the cover clad, so that the cover clad can be more planarized. And the resin pool can be further reduced.
[0032]
In this case, if a cushioning material having a lower friction coefficient than the elastic body is further interposed between the elastic body and the cover clad, the elastic body is smoothly deformed, and the stress concentration on the end of the cover clad is reduced. As a result, excess core material can be easily discharged.
[0033]
Further, in the step of controlling the liquid level, if the portion for pressing the cover clad or the substrate clad is moved or increased substantially in parallel with the discharge direction of the excess core material in the discharge groove, discharge by the press is easy. Done in
[0034]
Further, by pressing the cover clad against the substrate clad while adsorbing the press clad on the press plate by the suction device, the cover clad is more pressure-bonded to the substrate clad more planarly, and the formation of the resin pool is further reduced.
[0035]
In this case, by using the cover clad provided with the through hole, the excess core material is efficiently discharged, and an ideal optical waveguide without light loss is formed.
[Brief description of the drawings]
FIGS. 1A and 1B are diagrams showing an optical splitter which is an optical waveguide obtained by a manufacturing method of the present invention, wherein FIG. 1A is a plan view thereof, and FIG. 1B is a sectional view taken along line AA of FIG. 2 (a) to 2 (d) are explanatory views showing a method for manufacturing the optical waveguide shown in FIG.
3A and 3B are views showing a substrate clad used in a second embodiment, wherein FIG. 3A is a perspective view and FIG. 3B is a cross-sectional view.
FIG. 4 is an explanatory diagram showing a manufacturing method according to a third embodiment.
FIG. 5 is an explanatory diagram illustrating a manufacturing method according to a fourth embodiment.
FIG. 6 is an explanatory diagram showing a manufacturing method according to a fifth embodiment.
FIG. 7 is an explanatory diagram illustrating a manufacturing method according to a sixth embodiment.
FIG. 8 is an explanatory view showing a manufacturing method which is another method of the sixth embodiment.
FIG. 9 is a plan view of a substrate clad used in a sixth embodiment.
FIG. 10 is an explanatory diagram illustrating a manufacturing method according to a seventh embodiment.
FIG. 11 is a schematic perspective view of an optical splitter that is an example of an optical waveguide.
FIG. 12 is an explanatory diagram showing a method for manufacturing the optical splitter of the above.
FIG. 13 is an explanatory diagram showing a problem in the manufacturing method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Substrate clad 2 Cover clad 3 Core part 5 Core groove 6 Discharge groove 8 Core material 9 Intermediate layer 11 Press plate 15 Press plate suction hole

Claims (7)

A step of dripping or applying excess liquid core material to the surface of the substrate clad where the core groove 5 is formed in a portion where light is guided, and pressing a cover clad against the substrate clad to control the liquid level of the core material And a method of manufacturing an optical waveguide having a step of curing the dropped core material,
A cover provided with a discharge groove for discharging excess core material between the substrate clad and the cover clad, from the vicinity of the core groove to the end face of the substrate clad or from the vicinity of the core groove to the end face of the cover clad. A method for manufacturing an optical waveguide, comprising using a clad. 2. The method according to claim 1, wherein the discharge groove has a discharge hole communicating with a back side of the substrate clad or a back side of the cover clad. 3. 2. The step of controlling the liquid level, wherein an elastic body having a lower elastic modulus than the press body pressing the cover clad is interposed between the press body and the cover clad or below the substrate clad. 3. The method for manufacturing an optical waveguide according to item 1. 4. The method according to claim 3, wherein a buffer having a lower coefficient of friction than the elastic body is further provided between the elastic body and the cover clad or between the elastic body and the substrate clad. 2. The light guide according to claim 1, wherein in the step of controlling the liquid level, a portion pressing the cover clad or the substrate clad is moved or increased substantially in parallel with the discharge direction of the excess core material in the discharge groove. 3. Waveguide manufacturing method. The method for manufacturing an optical waveguide according to claim 1, wherein the cover clad is pressed against the substrate clad while being adsorbed on the press plate by a suction device. 7. The method according to claim 6, wherein a cover clad provided with a through hole is used.

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