JP2011007886A - Method of manufacturing optical waveguide and die used for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical waveguide that prevents formation of a lower clad layer and a core groove from failing due to bubbles remaining in the lower clad layer, and to provide a die used for the method.SOLUTION: The method of manufacturing an optical waveguide uses soft lithography. The lower clad layer having the core groove and spacer grooves arranged in substantially parallel to each other at an interval on both sides of the core groove is formed on a substrate by using a second die (a projecting die) having a projecting part corresponding to the core groove and the spacer grooves. In the second die, a cross-sectional shape perpendicular to the longitudinal direction of the projection part corresponding to spacer groove has an inverted trapezoidal shape. The bottom end side of the projection part corresponding to spacer groove bottom face is shorter than the projection part upper end side corresponding to the spacer groove upper end face, and at least the sides of the projection corresponding to spacer groove are tilted on the side of the projection corresponding to core groove.

Description

  The present invention relates to an optical waveguide manufacturing method and a mold used therefor.

  Along with the practical application of optical communication systems, the technology related to optical waveguides as its basic configuration has attracted attention. An optical waveguide typically has a buried structure in which a core layer having a high refractive index is surrounded by a cladding layer having a low refractive index, or a core having a high refractive index on a lower cladding layer having a low refractive index. Forming a ridge structure with an upper cladding layer as an air layer, and the light incident on the core layer of the optical waveguide is the interface between the core layer and the cladding layer or the interface between the core layer and the air layer And propagates through the core layer while reflecting.

  As a method of manufacturing an optical waveguide, for example, a clad material is applied on a substrate and cured to form a lower clad layer, then a core material is applied onto the lower clad layer, and a mask is applied and cured. The core layer is formed by removing the uncured portion, or the core material is applied on the lower cladding layer and then cured, and then the patterned resist layer is formed, and the uncovered portion is removed. Thus, after forming the core layer, a method has been adopted in which a clad material is applied on the lower clad layer so as to embed the core layer and cured to form the upper clad layer.

In contrast to this method, a stamper method has recently been studied as a method for manufacturing an optical waveguide simply and inexpensively. For example, in Patent Documents 1, 2, and 3, a clad material is dropped on a glass substrate, a stamper mold having a pattern having the same shape as the core layer is pressed on the surface to form a core groove, and then the clad material is cured. Forming a lower cladding layer having a core groove, and then injecting and filling the core material into the core groove, curing the core material to form the core layer, and then embedding the core layer A method is disclosed in which a cladding material is dropped on a layer, a base substrate is adhered, and then the cladding material is cured to form an upper cladding layer.
JP 2006-227655 A Japanese Patent No. 3858899 Japanese Patent No. 3858995

  In this stamper method, when the stamper mold is brought into contact with the clad material, bubbles may be included between the clad material and the stamper mold, and the lower clad layer may be formed without the bubbles being discharged from the clad material. When bubbles are present in the lower cladding layer as described above, the thickness of the lower cladding layer is reduced and the light confinement effect becomes insufficient. In a severe case, the core groove is disconnected.

  Therefore, the present inventors tried to remove bubbles in the lower cladding material by forming the cladding material under reduced pressure after pressing the stamper mold against the cladding material, but in the conventionally used stamper mold, There has been a problem that even if such defoaming treatment is performed, bubbles in the clad material cannot be sufficiently removed.

  Under the circumstances described above, the problem to be solved by the present invention is a method of manufacturing an optical waveguide in which formation failure of the lower cladding layer and the core groove due to bubbles remaining in the lower cladding layer is unlikely to occur, and the optical waveguide is used for the method. To provide a mold.

  As a result of various studies, the inventors have found that there is a difference in the ease of bubbles in the cladding material depending on the shape of the lower cladding layer having the core groove, and the cross section perpendicular to the longitudinal direction of the lower cladding layer including the core groove. When the trapezoidal shape was found, it was found that bubbles in the lower cladding material were quickly removed by the defoaming treatment, and the present invention was completed.

That is, according to the present invention, the second mold having the respective protrusions corresponding to the core groove and the spacer grooves provided substantially in parallel with a space on both sides of the core groove is dropped on the substrate. Forming a lower clad layer on the substrate having a core groove and spacer grooves arranged substantially parallel to each other on both sides of the core groove; and injecting a core material into the core groove Filling the core material and curing the core material; injecting and filling the spacer groove with a clad material, and applying the clad material on the lower clad layer so as to embed the core layer And then curing the cladding material to form an upper cladding layer, and
As the second mold, the shape of the cross section perpendicular to the longitudinal direction of the convex portion corresponding to the spacer groove is an inverted base in which the lower end side of the convex portion corresponding to the bottom surface of the spacer groove is shorter than the upper end side of the convex portion corresponding to the upper end surface of the spacer groove. There is provided a method for manufacturing an optical waveguide characterized by using a shape having at least a side of a convex portion corresponding to a spacer groove on a core groove corresponding convex portion side.

  In the method of manufacturing an optical waveguide according to the present invention, the second mold has an angle formed between the oblique side of the spacer groove corresponding convex portion on the core groove corresponding convex portion side and the spacer groove corresponding convex upper end side corresponding to the spacer groove upper end surface. Is preferably 45 ° or less. Moreover, it is preferable that an interval (x) between the core groove and the spacer groove is equal to or less than the width of the core groove on the upper end surface of the lower cladding layer.

  Further, the present invention is a mold used in the above-described method for manufacturing an optical waveguide, and each recess or corresponding to a core groove and a spacer groove provided substantially in parallel with a space on both sides of the core groove. A concave portion corresponding to the spacer groove or having a cross-sectional shape perpendicular to the longitudinal direction of the convex portion, the concave portion corresponding to the bottom surface of the spacer groove, or the concave portion corresponding to the upper end surface of the spacer groove. Alternatively, a mold having an inverted trapezoidal shape shorter than the upper end side of the convex part, and at least a concave part corresponding to the core groove or a side of the concave part or convex part corresponding to the spacer groove on the convex part side is provided. To do.

  Furthermore, the present invention includes an optical waveguide obtained by the above manufacturing method.

  The method of manufacturing an optical waveguide according to the present invention includes a convex portion corresponding to each of the core groove and a spacer groove provided on both sides of the core groove with a space therebetween and arranged substantially in parallel, and corresponding to the spacer groove. Since the lower clad layer is formed on the substrate by using a second mold (convex mold) having an inverted trapezoidal shape in which the base corresponding to the bottom surface of the spacer is shorter than the upper side, the lower clad layer is formed in the lower clad material. An optical waveguide can be manufactured with a high yield, with less thickness reduction of the lower cladding layer and poor formation of the core groove due to the incorporated bubbles.

  In addition, according to the present invention, even when a low-rigidity substrate such as a film substrate is used, the lower clad layer in the portion located below the core layer has a substantially uniform thickness and is guided. An optical waveguide with a very small loss can be easily manufactured.

It is a schematic diagram which shows an example of the cross-sectional shape perpendicular | vertical to the longitudinal direction of the 2nd type | mold (convex type) of this invention. It is a schematic diagram which shows the cross-sectional shape perpendicular | vertical to the longitudinal direction of the conventional 2nd type | mold. It is typical process drawing for demonstrating the representative example of the manufacturing method of the optical waveguide by this invention. 3 is an optical micrograph of a lower clad layer produced in Example 1. 2 is an optical micrograph (enlarged view) of a lower clad layer produced in Example 1. FIG. 4 is an optical micrograph of a lower clad layer produced in Comparative Example 1. 2 is an optical micrograph (enlarged view) of a lower clad layer produced in Comparative Example 1. FIG. It is a schematic diagram which shows the effect | action of this invention. It is a schematic diagram which shows the subject of a prior art.

The method of manufacturing an optical waveguide according to the present invention has a convex portion corresponding to a core groove and spacer grooves provided substantially parallel to each other on both sides of the core groove by dropping a clad material on the substrate. Forming, on the substrate, a lower cladding layer having a core groove and spacer grooves arranged substantially parallel to each other on both sides of the core groove on the substrate using a second mold; Injecting and filling material, and curing the core material to form a core layer; injecting and filling the spacer groove with cladding material and filling the core layer on the lower cladding layer Applying a clad material and then curing the clad material to form an upper clad layer; and
As the second mold, the shape of the cross section perpendicular to the longitudinal direction of the convex portion corresponding to the spacer groove is an inverted base in which the lower end side of the convex portion corresponding to the bottom surface of the spacer groove is shorter than the upper end side of the convex portion corresponding to the upper end surface of the spacer groove. It has a shape, and at least the side of the convex portion corresponding to the spacer groove on the convex side corresponding to the core groove is used.

  FIG. 1 shows an example of a cross-sectional shape perpendicular to the longitudinal direction of the second mold of the present invention, and FIG. 2 shows a cross-sectional shape perpendicular to the longitudinal direction of a conventional mold. In addition, the 2nd type | mold which concerns on this invention is not limited to the aspect of FIG.

  The second mold used in the present invention corresponds to a convex portion 9 corresponding to the core groove and a spacer groove provided substantially in parallel with a space on both sides of the core groove, as shown in 6 of FIG. The cross-sectional shape of the convex portion 10 corresponding to the spacer groove is an inverted trapezoid whose bottom side 14 corresponding to the spacer groove bottom surface is shorter than the upper side 13. By using such a second mold, bubbles in the lower clad material are quickly removed, and an optical waveguide can be manufactured with a high yield.

  As shown in FIG. 6A, when the second mold 6 enters the cladding material 15 applied on the substrate 1, air is taken into the cladding material 15 and bubbles 18 are generated. Until the second mold 6 and the substrate 1 are brought into contact with each other, a force in the x direction is generated in the cladding material 15 due to the penetration of the second mold 6 (see FIG. 6B). That is, the force in the x direction is a force (flow) acting on the cladding material 15 due to the penetration of the core groove corresponding convex portion 9. On the other hand, the force in the y direction is a component of the force in the x direction parallel to the inclined side 16 of the spacer groove corresponding convex portion 10 on the core groove corresponding convex portion 9 side. It can also be considered that the resultant force in the substrate direction and the force that eliminates the cladding material in the x direction are combined. That is, when the second mold of the present invention in which the cross-sectional shape of the spacer groove-corresponding convex portion 10 is an inverted trapezoidal shape is used, the second mold 6 is pressed against the substrate 1, so Directional force acts, and the bubble 18 moves to the side 16. Thereafter, the force in the x direction and the y direction further acts on the bubble 18 that has reached the side 16, so that the bubble 18 moves along the side 16 as indicated by the arrow in FIG. Then, it is quickly discharged out of the lower cladding material. On the other hand, when the conventional second mold 6 ′ is used, although the force in the x and y directions is generated by the penetration of the second mold 6 ′ into the cladding material 15 ′ (FIG. 7), the bubbles 18 Even if a force in the y direction is applied to the second portion 6, the cross-sectional shape of the spacer groove corresponding convex portion 10 ′ of the second mold 6 ′ is rectangular and the side 16 ′ is perpendicular to the substrate 1. The bubbles 18 are difficult to move along. That is, a component parallel to the side 16 ′ is balanced by the balance between the force with which the lower cladding material derived from the penetration of the second mold 6 ′ is eliminated in the x direction, the force in the y direction, and the buoyancy acting on the bubbles 18. Appears to be zero. Therefore, when the second mold 6 ′ is used, it is considered that the bubbles 18 are difficult to be discharged outside the second mold 6 ′.

  The second mold according to the present invention will be described in more detail later in << Mold used in optical waveguide manufacturing method >>.

  First, the manufacturing method of this invention is demonstrated.

≪Method for manufacturing optical waveguide≫
An optical waveguide manufacturing method according to the present invention (hereinafter also referred to as “the manufacturing method of the present invention”) is obtained by dripping a clad material on a substrate and making the core groove and both sides of the core groove substantially spaced apart in parallel. Each having a convex portion corresponding to the spacer groove, and a cross-sectional shape perpendicular to the longitudinal direction of the convex portion corresponding to the spacer groove is an inverted trapezoid whose base corresponding to the bottom surface of the spacer groove is shorter than the upper side. After the second mold is placed, the clad material is hardened, the second mold is removed, and the core groove and the core groove are provided in parallel with a space on both sides of the core groove. Forming a lower cladding layer having a spacer groove formed; injecting and filling a core material into the core groove; and curing the core material to form a core layer; and cladding material in the spacer groove To fill and fill the core layer After the clad material is applied to the upper cladding layer, process and forming an upper clad layer by curing the cladding material; including.

  The manufacturing method of the present invention uses a soft lithography and has a second mold (convex mold) having convex portions corresponding to the core groove and spacer grooves that are provided in parallel with a space on both sides of the core groove. ) Is used to form a lower clad layer having a core groove and spacer grooves provided substantially parallel to each other on both sides of the core groove on the substrate. Soft lithography is a kind of stamper method, and is a method of transferring a lower clad layer using a second mold (convex mold) formed of a soft material such as silicone rubber or urethane rubber. .

  Hereinafter, representative examples of the production method of the present invention will be described in detail with reference to FIG. 3. However, the production method of the present invention is not limited to the following representative examples, and may be implemented with appropriate modifications. it can.

  First, as shown in FIG. 3 (a), for example, a metal or an alloy such as phosphor bronze is cut, and a recess 7 corresponding to the core groove, and a spacer groove provided substantially in parallel with a gap on both sides of the core groove. The first trapezoidal recess 5 is formed by forming the inverted trapezoidal recess 8 corresponding to the above.

  Next, for example, a curable silicone material such as a two-component curable polysiloxane is applied to the first mold 5 and cured, and then the first mold 5 is removed, and FIG. As shown, a second mold (convex) having a convex portion 9 corresponding to the core groove and a convex portion (spacer) 10 corresponding to the spacer groove provided on both sides of the core groove with a space therebetween. 6 is produced.

  Note that when the second mold 6 is manufactured, a release agent is applied on the first mold 5 so that the second mold 6 can be easily released from the first mold 5. Also good. A known release agent may be used as the release agent, and is not particularly limited.

  Next, as shown in FIG. 3B, after a suitable amount of the clad material 15 is dropped on the substrate 1, for example, on a stage having parallelism, a convex portion (spacer) 10 corresponding to the spacer groove is formed. The second mold 6 is brought close to the substrate 1 so as to come into contact with the substrate 1. At this time, before the convex portion (spacer) 10 corresponding to the spacer groove of the second mold 6 comes into contact with the substrate 1, the second mold 6 is temporarily stopped, and the defoaming process is performed by drawing a vacuum. It is preferable to remove bubbles from the cladding material 15. In addition, after the second mold 6 is placed on the substrate 1 so that the convex portions (spacers) 10 corresponding to the spacer grooves are in contact with the substrate 1 without dropping part or all of the cladding material 15, The gap between the substrate 1 and the second mold 6 may be filled by injecting the cladding material 15. At this time, the cladding material 15 is preferably injected under reduced pressure. In any case, it is preferable to press the second mold 6 against the substrate 1 so that the protrusions (spacers) 10 corresponding to the spacer grooves are in close contact with the substrate 1 as shown in FIG.

  As described above, since the surface of the spacer groove-corresponding protrusion 10 on the core groove-corresponding protrusion 9 side is inclined, the second mold 6 according to the present invention is caught in the cladding material by the defoaming process. The bubbles can be removed quickly.

  As the substrate 1, any known material can be used regardless of an inorganic material or an organic material. For example, a silicon substrate; a glass substrate such as quartz or pyrex (registered trademark); a metal such as Al or Cu. It is preferable to use a substrate; a metal oxide substrate; a resin substrate such as polyimide or polyetherketone; an organic-inorganic hybrid substrate. Among these, a resin substrate is preferable, and a film substrate made of a resin film is more preferable.

  The film substrate is not particularly limited as long as it is a resin film composed of a conventionally known optical waveguide material. Specifically, an epoxy resin, a polyimide resin, an acrylic resin, and a polyester resin are used. Examples of the resin film include resin, polystyrene resin, cycloolefin resin, polyethersulfone resin, polyetherketone resin, polyethernitrile resin, oxetane resin, silane resin, and silicone resin. . Of these resin films, considering the production of the opto-electric hybrid module, from the viewpoint of heat resistance (particularly heat resistance assuming soldering, specifically 200-250 ° C. heat resistance), a polyimide resin That is, a film composed of a polyimide film (including a halogenated polyimide film) is preferable. Moreover, when using a polyimide film as a film substrate, you may utilize a commercial item. As a commercial item of a polyimide film, the brand name "Kapton (trademark)" series of Toray DuPont Co., Ltd. is mentioned, for example.

  The thickness of the substrate 1 may be appropriately selected according to the use of the optical waveguide or the wavelength of light used when the opto-electric hybrid module is manufactured, and is not particularly limited, but preferably 5 μm. More preferably, it is 10 μm or more, preferably 100 μm or less, more preferably 50 μm or less. If the thickness of the substrate 1 is too small, the strength of the substrate may decrease. On the other hand, if the thickness of the substrate 1 is too large, the transparency of the substrate may decrease when an opto-electric hybrid module is manufactured.

  In the manufacturing method of the present invention, in addition to the convex portion 9 corresponding to the core groove, the second die 6 has a convex portion (spacer) corresponding to a spacer groove provided in parallel with a gap on both sides of the core groove. 10 is provided, the substrate 1 or the second mold 6 bends when the second mold 6 is placed on the substrate 1 even if a low rigidity substrate such as a film substrate is used. There is not, and the space | interval of the convex part 9 and the board | substrate 1 corresponding to a core groove | channel is hold | maintained substantially uniformly. In addition, by appropriately setting the depth of the spacer groove, that is, the height of the convex portion (spacer) 10 corresponding to the spacer groove, the thickness of the lower clad layer 2 at the lower portion of the core layer can be easily set. Can be controlled.

  Then, after the clad material 15 filled in the gap between the substrate 1 and the second mold 6 is cured, the second mold 6 is removed and, as shown in FIG. A lower cladding layer 2 having a core groove 11 and inverted trapezoidal spacer grooves 12 provided substantially parallel to each other at both sides of the core groove 11 is formed. The clad material 15 constituting the lower clad layer 2 is not particularly limited as long as it is a conventionally known optical waveguide material. For example, ultraviolet (or light) curable resin, thermosetting resin or the like is cured. Resin and thermoplastic resin. Of these resins, ultraviolet (or light) curable resins are preferred.

  In the upper end surface of the lower cladding layer 2, the width of the interval (x) between the core groove 11 and the spacer groove 12 is preferably equal to or less than the width of the core groove 11 (FIG. 3D). When the interval (x) between the core groove 11 and the spacer groove 12 is too wide, bubbles easily enter both sides of the core layer, and the bubbles are difficult to be discharged. Further, in the second mold 6, when the distance between the convex portion 9 corresponding to the core groove 11 and the convex portion 10 corresponding to the spacer groove 12 is wide, the second mold 6 is placed on the substrate 1. Since the second mold 6 is easily bent, the thickness of the lower clad layer 2 located below the core layer may not be formed substantially uniformly. On the other hand, the lower limit of the width of the interval (x) is not particularly limited, but if it is too narrow, the light confinement effect tends to decrease. The width of the interval (x) is preferably such that the depth (y) of the spacer groove 12 with respect to the interval (x) satisfies the following relationship.

  The ratio (y / x) of the depth (y) of the spacer groove 12 to the distance (x) between the core groove 11 and the spacer groove 12 on the upper end surface of the lower cladding layer 2 is preferably 1/1 or more, more preferably 2/1 or more, preferably 20/1 or less, more preferably 10/1 or less. If the ratio (y / x) is too small, bubbles easily enter both sides of the core layer, and the bubbles are difficult to be discharged. Further, in the second mold 6, the distance between the convex portion 9 corresponding to the core groove 11 and the convex portion 10 corresponding to the spacer groove 12 becomes large, and when the second die 6 is placed on the substrate 1. Since the second mold 6 is easily bent, the thickness of the lower clad layer 2 located below the core layer may not be made substantially uniform. On the other hand, if the ratio (y / x) is too large, a sufficiently thick core layer can be formed, but the distance (x) is reduced and the second mold is formed from the first mold. At the time of mold release, there is a risk that a mold release failure may occur due to insufficient strength of the interval (x) part.

  In the lower cladding layer 2, the depth of the spacer groove 12 is set to be substantially equal to the thickness of the lower cladding layer 2. The width (z) of the spacer groove 12 (FIG. 3 (d)) may be adjusted as appropriate according to the thickness of the lower cladding layer 2 and the like, and is not particularly limited. When the thickness is 1, it is preferably 2 or more, more preferably 5 or more, still more preferably 10 or more, and preferably 50 or less, more preferably 30 or less, still more preferably 20 or less. . If the width of the spacer groove 12 is too small with respect to the depth of the spacer groove 12, the width of the convex portion (spacer) 10 corresponding to the spacer groove 12 in the second mold 6 becomes small. When pressing against the substrate 1, the substrate 1 or the second mold 6 may bend. On the contrary, if the width of the spacer groove 12 is too large with respect to the depth of the spacer groove 12, there is a possibility that bubbles taken into the clad material 15 are difficult to be discharged.

  In the lower clad layer 2, the surface 17 of the lower clad layer 2 facing the spacer groove 12 is inclined upward (on the side opposite to the substrate) (FIG. 3D). The angle θ formed by the slope 17 of the lower cladding layer 2 and the bottom surface of the lower cladding layer 2 (the surface including the upper side 13 shown in FIG. 1) is preferably 45 ° or less. When θ exceeds 45 °, the slope of the lower cladding layer rises, and the y-direction component parallel to the side 16 becomes small, so that it is difficult to obtain the effect of removing bubbles in the lower cladding material.

  The thickness of the lower clad layer 2 may be appropriately selected according to the use of the optical waveguide, the wavelength of light to be used, and the like, and is not particularly limited, but preferably excluding the lower side of the core groove 11. It is 10 μm or more, more preferably 20 μm or more, and preferably 150 μm or less, more preferably 100 μm or less. If the thickness of the lower cladding layer 2 is too small, the core layer 3 having a sufficient thickness may not be formed. Conversely, if the thickness of the lower clad layer 2 is too large, the transparency of the lower clad layer 2 may be lowered when an opto-electric hybrid module is manufactured.

  The refractive index of the lower cladding layer 2 is not particularly limited as long as it is lower than the refractive index of the core layer 3. For example, the type and composition of the cladding material are selected within the range of 1.45 to 1.65. By doing so, it can be arbitrarily adjusted.

  In the case where the second mold 6 is formed of silicone rubber and the lower cladding layer 2 is formed of a thermosetting resin, a thermoplastic resin, or an ultraviolet (or light) curable resin, the second mold 6 is used. When the lower clad layer 2 is formed several tens of times using 6, the second mold 6 may be deteriorated due to heat, change with time, or the like. Further, after the lower cladding layer 2 is formed, it may be contaminated by the residue of the cladding material. In such a case, the first mold 5 to the second mold 6 may be produced again and used.

  After forming the lower cladding layer 2, as shown in FIG. 3E, the core material is injected and filled into the core groove 11, and the core material is cured to form the core layer 3. In FIG. 3E, only one core layer 3 is formed, but two or more core layers 3 may be formed depending on the use of the optical waveguide. The core layer 3 is formed in a straight line extending in a direction perpendicular to the paper surface, but may be formed in a predetermined pattern according to the use of the optical waveguide. The core material constituting the core layer 3 may be any conventionally known optical waveguide material as long as the refractive index is higher than that of the clad material constituting the lower clad layer 2 and the clad material constituting the upper clad layer 4, and is not particularly limited. Although not intended, for example, a curable resin such as an ultraviolet (or light) curable resin or a thermosetting resin may be used. Of these resins, ultraviolet (or light) curable resins are preferred.

  The thickness (depth) of the core layer 3 may be appropriately selected according to the use of the optical waveguide, the wavelength of light to be used, and the like, and is not particularly limited, but is preferably 5 μm or more, more preferably 10 μm. Further, it is preferably 100 μm or less, more preferably 50 μm or less. If the thickness of the core layer 3 is too small, the amount of light propagating through the core layer 3 may decrease. Conversely, if the thickness of the core layer 3 is too large, the thickness of the lower cladding layer 2 is increased. In other words, unnecessary portions of the lower clad layer 2 increase on both sides of the core layer 3 and the manufacturing cost may increase. Moreover, since the thickness of the lower clad layer 2 and the core layer 3 constituting the optical waveguide is increased, the thickness of the optical waveguide film formed on the substrate 1 may be increased.

  The core layer 3 preferably has a rectangular cross section perpendicular to the longitudinal direction, and most preferably has a square shape. That is, the aspect ratio (width / thickness) of the core layer 3 is preferably ½ or more, more preferably 2/3 or more, still more preferably 5/6 or more, and preferably 2/1 or less. More preferably, it is 3/2 or less, more preferably 6/5 or less. Most preferably, it is 1/1. If the aspect ratio of the core layer 3 is too small or too large, the cross-sectional shape perpendicular to the longitudinal direction of the core layer 3 becomes flat, so that light enters the core layer 3 or the core layer 3 In some cases, light loss may occur when light is emitted from the light source.

  The refractive index of the core layer 3 is not particularly limited as long as it is higher than the refractive indexes of the lower cladding layer 2 and the upper cladding layer 4, but is preferably in the range of 1.45 to 1.65, for example. It can be arbitrarily adjusted by selecting the type and composition of the core material.

  Next, as shown in FIG. 3 (f), after the cladding material is injected and filled in the spacer groove 12 and the cladding material is applied on the lower cladding layer 2 and the core layer 3 so as to embed the core layer 3. Then, the clad material is cured to form the upper clad layer 4. The clad material constituting the upper clad layer 4 may be the same as or different from the clad material constituting the lower clad layer 2, and is not particularly limited. For example, ultraviolet (or light) curing is performed. Curable resins such as curable resins and thermosetting resins, and thermoplastic resins. Of these resins, ultraviolet (or light) curable resins are preferred.

  The thickness of the upper cladding layer 4 from the upper end surface of the core layer to the upper end surface of the upper cladding layer 4 may be appropriately selected according to the use of the optical waveguide, the wavelength of light to be used, and the like, but is not particularly limited. The thickness is preferably 10 μm or more, more preferably 20 μm or more, and preferably 100 μm or less, more preferably 50 μm or less. If the thickness of the upper clad layer 4 is too small, the light confinement effect of the core is weakened, and light may escape from the upper clad, which may increase optical loss. On the contrary, if the thickness of the upper cladding layer 4 is too large, unnecessary portions increase and the manufacturing cost may increase.

  The refractive index of the upper cladding layer 4 is not particularly limited as long as it is lower than the refractive index of the core layer 3, but is preferably in the range of 1.45 to 1.65, for example. It can be arbitrarily adjusted by selecting the composition.

  Specific examples of the curable resin and the thermoplastic resin used in the present invention include, for example, an epoxy resin, a polyimide resin, an acrylic resin, a polystyrene resin, a cycloolefin resin, a polyethersulfone resin, and a polyetherketone resin. Examples thereof include resins, polyether nitrile resins, oxetane resins, silane resins, and silicone resins. These resins may be used alone or in combination of two or more. These resins may be a solution type dissolved in a solvent or a solventless type containing no solvent, but a solventless type is more preferable. Furthermore, when these resins are used as the curable resin, a curing agent or a crosslinking agent can be used in combination.

  When a curable resin having a low viscosity is used as the cladding material or the core material among the curable resins such as ultraviolet (or light) curable resin and thermosetting resin, the liquid curable resin is used as the substrate 1 and the second material. After filling the gap with the mold 6 and the core groove 11 provided in the lower clad layer 2, or filling the spacer groove 12 provided in the lower clad layer 2 and coating on the lower clad layer 2. Thereafter, the lower clad layer 2, the core layer 3, and the upper clad layer 4 are formed by curing with ultraviolet rays (or light) or heat. In addition, when using a thermoplastic resin, or when using a resin having a high viscosity among curable resins such as an ultraviolet (or light) curable resin and a thermosetting resin, it is heated to be in a fluid state or a melt state. After filling the resin into the gap between the substrate 1 and the second mold 6 and the core groove 11 provided in the lower cladding layer 2, or after filling the spacer groove 12 provided in the lower cladding layer 2, and After coating on the lower clad layer 2, the thermoplastic resin is cooled by cooling, and the curable resin is cured by ultraviolet rays (or light) or heat to be cured by the lower clad layer 2, the core layer 3, and the upper clad. Layer 4 is formed. From the viewpoint of working efficiency, the viscosity of each material during filling is preferably 0.0001 Pa · s or more, more preferably 0.001 Pa · s or more, and preferably 100 Pa · s or less, more preferably 50 Pa · s or less. If the viscosity of each material at the time of filling is too low, it takes a long time to cure, so the work efficiency may be reduced. On the other hand, if the viscosity of each material during filling is too high, the handleability is deteriorated, so that the working efficiency may be lowered, or air may enter and a defective portion may be generated.

  Thus, as shown in FIG. 3 (f), the lower cladding layer 2 formed on the substrate 1, the core layer 3 formed in the core groove 11 of the lower cladding layer 2, and the core layer 3 are embedded. An optical waveguide having the lower cladding layer 2 and the upper cladding layer 4 formed on the core layer 3 is obtained.

  In the above description, the method of manufacturing one optical waveguide using the master mold (first mold 5) shown in FIG. 3A has been described. However, a master mold (corresponding to a plurality of optical waveguides) A plurality of optical waveguides can also be manufactured using the first mold. In this case, at the stage where the lower clad layer 2 is formed on the substrate 1, for example, by dicing, it is cut into individual chips, and thereafter, individual optical waveguides may be manufactured in the same manner as described above.

  According to the manufacturing method of the present invention, the bubbles in the lower clad material 15 are quickly discharged out of the lower clad material 15, so that poor formation of the lower clad layer 2 and the core groove 11 is unlikely to occur, and light is produced with high yield. Waveguides can be manufactured. In addition, an optical waveguide having a substantially uniform thickness in which the lower clad layer 2 located below the core layer 3 is controlled and having a very small waveguide loss can be easily manufactured.

  Furthermore, if a resin mold (second mold 6) shown in FIG. 3B is attached to the roll surface, optical waveguides can be mass-produced in the manner of intaglio printing.

  In addition, since the obtained optical waveguide has the lower clad layer 2, the core layer 3, and the upper clad layer 4 formed on the substrate 1, if a substrate with electric wiring is used as the substrate 1, the light emitting element and By cutting the portion on which the light receiving element is mounted into a V shape by using, for example, a dicing saw and forming a 45 ° mirror, the opto-electric hybrid module can be easily manufactured.

  Further, in the manufacturing method of the present invention, the master mold (first mold 5) shown in FIG. 3A corresponds to the optical fiber fixing groove in series with the recess 7 corresponding to the core groove (in the direction perpendicular to the paper surface). If the concave portion to be provided is provided, an optical waveguide substrate with an optical fiber fixing groove can be obtained.

  A weir is preferably provided between the optical fiber fixing groove and the core groove, but the weir is formed of a clad material constituting the lower cladding layer, and has an appropriate thickness (optical fiber fixing groove and core groove). Therefore, there is no problem in the transmission and reception of optical signals between the core of the optical fiber mounted in the optical fiber fixing groove and the core layer formed in the core groove.

  The thickness of the weir is preferably 5 μm or more and 50 μm or less. If the thickness of the weir is too small, the weir may not be transferred cleanly when forming the lower clad layer using the second mold (convex mold) having a recess corresponding to the weir. Conversely, if the thickness of the weir is too large, the transmission loss of the optical signal between the core of the optical fiber mounted in the optical fiber fixing groove and the core layer formed in the core groove may increase. The height of the weir (that is, the height from the bottom surface of the core groove) may be set as appropriate according to the outer diameter, core diameter, etc. of the optical fiber mounted in the optical fiber fixing groove, and is particularly limited. It is not a thing.

  Moreover, it is preferable that the upper end surface part of the core groove is lower than the upper end surface part of the optical fiber fixing groove. The step between the upper end surface portion of the optical fiber fixing groove and the upper end surface portion of the core groove preferably corresponds to the thickness of the upper cladding layer.

<UV curable epoxy resin>
As the clad material and the core material used in the production method of the present invention, among the curable resin and the thermoplastic resin as described above, an epoxy resin is preferable, and a UV curable epoxy resin is more preferable. Examples of the UV curable epoxy resin include an epoxy resin containing a polyglycidyl compound having a polyalkylene glycol chain and at least two glycidyl groups, a bisphenol type epoxy resin, and an alicyclic epoxy resin. When it is desired to obtain a flexible optical waveguide having flexibility, an epoxy resin containing a polyglycidyl compound having a polyalkylene glycol chain and at least two glycidyl groups is particularly suitable. When it is not necessary to provide it, a bisphenol type epoxy resin or an alicyclic epoxy resin is suitable.

  In the polyglycidyl compound having a polyalkylene glycol chain and at least two glycidyl groups, the oxyalkylene group constituting the polyalkylene glycol chain is preferably 2 or more carbon atoms, more preferably 3 or more carbon atoms, preferably It is an oxyalkylene group having 12 or less carbon atoms, more preferably 8 or less carbon atoms, and most preferably 4 carbon atoms. These oxyalkylene groups may be either linear or branched, and may have a substituent. Further, these oxyalkylene groups may all be the same oxyalkylene group or may be a combination of different types of oxyalkylene groups.

  Specific examples of the polyglycidyl compound having a polyalkylene glycol chain and at least two glycidyl groups include polyethers such as polyethylene ether glycol, polypropylene ether glycol, polytetramethylene ether glycol, and polypentamethylene ether glycol. Diglycidyl ether of polyol: copoly (tetramethylene · neopentylene) ether diol, copoly (tetramethylene · 2-methylbutylene) ether diol, copoly (tetramethylene · 2,2-dimethylbutylene) ether diol, copoly (tetramethylene · 2) , 3-dimethylbutylene) ether diol and other copolyether polyol diglycidyl ethers; trimethylolpropane triglycidyl ether and the like Triglycidyl ether of aliphatic polyols; and the like. Of these polyglycidyl compounds, diglycidyl ether of polyether polyol is preferred, and diglycidyl ether of polytetramethylene ether glycol is particularly preferred.

  The polyglycidyl compound as described above is prepared by a conventionally known method such as diols such as ethylene glycol, 1,4-butanediol, neopentyl glycol, and 1,6-hexanediol, and aliphatic triols such as glycerin and trimethylolpropane. Can be produced by subjecting the terminal hydroxy group to epichlorohydrin after dehydration condensation if necessary.

  The diglycidyl ether of polytetramethylene ether glycol has the following formula (1):

[Wherein n is an integer of 1 to 30]
The number average molecular weight of the polytetramethylene ether glycol is preferably 200 or more and preferably 2,000 or less. Such a diglycidyl ether of polytetramethylene ether glycol can be obtained by a conventionally known production method. More specifically, after reacting polytetramethylene ether glycol and epichlorohydrin in the presence of a catalyst to obtain a chlorohydrin ether body, the chlorohydrin ether body is dehydrohalogenated such as sodium hydroxide. It can be obtained by a two-step method in which the reaction is carried out to cause ring closure. At this time, if the number average molecular weight of the polytetramethylene ether glycol is too low, the flexibility of the epoxy resin film may be lowered. On the other hand, when the number average molecular weight of polytetramethylene ether glycol is too high, the diglycidyl ether of polytetramethylene ether glycol becomes a solid, and the handleability may deteriorate. In addition, the number average molecular weight of polytetramethylene ether glycol can be calculated | required in standard polystyrene conversion by the gel permeation chromatography (GPC) method.

  The diglycidyl ether of polytetramethylene ether glycol may be synthesized by the above production method, but a commercially available product can also be used. Examples of commercially available diglycidyl ether of polytetramethylene ether glycol include trade names “jER (registered trademark) YL7417” and “jER (registered trademark) YL7217” manufactured by Japan Epoxy Resin Co., Ltd.

  When using a UV curable epoxy resin containing the polyglycidyl compound, a reactive diluent such as a bisphenol type epoxy resin, an alicyclic epoxy resin, or oxetane is used as necessary for adjusting the refractive index and viscosity. You may mix | blend. However, an epoxy resin having a lower viscosity is preferable because it is excellent in handleability.

  Examples of the bisphenol type epoxy resin include bisphenol A type epoxy resin, diglycidyl ether of bisphenol A-alkylene oxide adduct, bisphenol F type epoxy resin, diglycidyl ether of bisphenol F alkylene oxide adduct, and bisphenol AD type epoxy resin. Bisphenol S type epoxy resin, tetramethyl bisphenol A type epoxy resin, tetramethyl bisphenol F type epoxy resin, halogenated bisphenol type epoxy resin (for example, fluorinated bisphenol type epoxy resin, chlorinated bisphenol type epoxy resin, brominated Bisphenol type epoxy resin). These bisphenol type epoxy resins may be used alone or in combination of two or more. Of these bisphenol-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, brominated bisphenol A-type epoxy resins, and brominated bisphenol F-type epoxy resins are preferred from the viewpoint of easy availability and handling. . As commercial products of these bisphenol type epoxy resins, for example, trade names “jER (registered trademark) 828EL” (bisphenol A type epoxy resin) and “jER (registered trademark) 5050” (brominated) manufactured by Japan Epoxy Resin Co., Ltd. Bisphenol A type epoxy resin).

  The blending amount of the bisphenol type epoxy resin may be appropriately adjusted so that the epoxy resin film obtained from the UV curable epoxy resin has a desired refractive index, and is not particularly limited. When the total of the removed UV curable epoxy resin composition is 100% by mass, the blending amount of the polyglycidyl compound, the bisphenol type epoxy resin, and the alicyclic epoxy resin is 0% by mass to 70% by mass of the polyglycidyl compound. The total of the mass% (more preferably 5 mass% to 60 mass%) and the bisphenol type epoxy resin and the alicyclic epoxy resin is 30 mass% to 100 mass% (more preferably 40 mass% to 95 mass%). Is preferred. When the compounding quantity of a polyglycidyl compound exceeds 70 mass%, the cure rate of a film may become slow or the intensity | strength of the obtained film may be insufficient. Moreover, if the addition amount of a polyglycidyl compound is 5 mass% or more, the film provided with intensity | strength and flexibility can be obtained.

  Examples of the alicyclic epoxy resin include 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate and its ε-caprolactone modified product (manufactured by Daicel Chemical Industries, Ltd., trade name “Celoxide (registered trademark)”. ) 2081 "), 1,2-epoxy-vinylcyclohexene, bis (3,4-epoxycyclohexylmethyl) adipate, 1-epoxyethyl-3,4-epoxycyclohexane, limonene diepoxide, 3,4-epoxycyclohexylmethanol, Dicyclopentadiene diepoxide, oligomer-type cycloaliphatic epoxy resin (manufactured by Daicel Chemical Industries, Ltd., trade names “Epolide (registered trademark) GT300”, “Epolide (registered trademark) GT400”, “EHPE (registered trademark) 3150”) Such as me Epoxy resin obtained by oxidizing tin, hydrogenated bisphenol A type epoxy resin, hydrogenated bisphenol F type epoxy resin, hydrogenated biphenol type epoxy resin, hydrogenated phenol novolak type epoxy resin, hydrogenated cresol novolak type epoxy resin Examples thereof include an epoxy resin obtained by directly hydrogenating an aromatic epoxy such as a hydrogenated naphthalene type epoxy resin or an epoxy resin obtained by hydrogenating a polyhydric phenol and then reacting with epichlorohydrin. These alicyclic epoxy resins may be used alone or in combination of two or more. Among these alicyclic epoxy resins, 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate and its ε-caprolactone modified product, since it is easily available and has low viscosity and excellent workability. Hydrogenated bisphenol A type epoxy resins and hydrogenated bisphenol F type epoxy resins are preferred.

  The compounding quantity of an alicyclic epoxy resin is not specifically limited, What is necessary is just to adjust suitably so that UV curable epoxy resin may have a desired refractive index.

In order to cure the UV curable epoxy resin, a photocationic polymerization initiator is blended with the UV curable epoxy resin. Examples of the cationic photopolymerization initiator include metal fluoroboron complex salts and boron trifluoride complex compounds as described in US Pat. No. 3,379,653; described in US Pat. No. 3,586,616. Bis (perfluoroalkylsulfonyl) methane metal salts such as: aryldiazonium compounds as described in US Pat. No. 3,708,296; described in US Pat. No. 4,058,400 Aromatic onium salts of group VIa elements such as: aromatic onium salts of group Va elements as described in US Pat. No. 4,069,055; described in US Pat. No. 4,068,091 Dicarbonyl chelates of group IIIa-Va elements; thiopyrylium salts as described in US Pat. No. 4,139,655; US Pat. MF ₆ as described in JP 4,161,478 ^- anion (wherein, M is phosphorus, are selected from antimony and arsenic) VIb element in the form of; U.S. Pat. No. 4,231,951 Arylsulfonium complex salts as described in US Pat. No. 4,256,828; aromatic iodonium complex salts and aromatic sulfonium complex salts as described in US Pat. R. Bis [4- (Journal of Polymer Science, Polymer Chemistry Edition], Vol. 22, p. 1789 (1984) by Watt et al. Diphenylsulfonio) phenyl] sulfide-bis-hexafluorometal salts (eg, phosphates, arsenates, antimonates, etc.); mixed ligand metal salts of iron compounds; silanol-aluminum complexes; . These photocationic polymerization initiators may be used alone or in combination of two or more. Of these photocationic polymerization initiators, arylsulfonium complex salts, aromatic iodonium complex salts of halogen-containing complex ions or aromatic sulfonium complex salts, and aromatic onium salts of Group II, Group V and Group VI elements are preferred. Some of these salts are, for example, trade names “CPI-6976”, “CPI-6969” (above, manufactured by Aceto Chemical), trade name “FX-512” (manufactured by 3M Company), trade name “UVR”. -6990 "," UVR-6974 "(manufactured by Union Carbide Corporation), trade names" UVE-1014 "," UVE-1016 "(manufactured by General Electric Company), trade names" KI-85 ". "(Degussa Aktiengesellschaft), trade names" SP-150 "," SP-170 "(above, manufactured by ADEKA Corporation), trade names" Sun-Aid (registered trademark) SI-60L "," Sun-Aid (registered trademark) ) SI-80L "," Sun-Aid (registered trademark) SI-100L "," Sun-Aid (registered trademark) SI-11 " Commercial products such as “0L” and “Sun-Aid (registered trademark) SI-180L” (manufactured by Sanshin Chemical Industry Co., Ltd.) can be obtained.

  Of these photocationic polymerization initiators, onium salts are preferred because of their excellent handleability and balance between latency and curability, and diazonium salts, iodonium salts, sulfonium salts, and phosphonium salts are particularly preferred. Is preferred.

  The blending amount of the cationic photopolymerization initiator may be appropriately adjusted according to the blending amount of the epoxy resin component to be cured, and is not particularly limited, but is preferably based on 100 parts by mass of the total epoxy resin component. Is 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, further preferably 1 part by mass or more, preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and further preferably 5 parts by mass. Or less.

  The UV curable epoxy resin has an appropriate molecular weight such as a polyglycidyl compound having a polyalkylene glycol chain and at least two glycidyl groups as raw materials, and a bisphenol type epoxy resin or an alicyclic epoxy resin blended as necessary. By selecting, the viscosity can be adjusted within a range of 10 mPa · s or more and 100,000 mPa · s or less at a temperature of 23 ° C. without using a solvent.

Since the UV curable epoxy resin is in a liquid state at room temperature, the second mold is placed on the substrate and injected and filled in an appropriate amount into the gap, or alternatively, an appropriate amount is dropped on the substrate and the second mold is placed. Or after filling and filling the core groove, or after filling the spacer groove and filling the core layer so as to embed the core layer, for example, integration of irradiation amount (exposure energy) 0.01 J / cm ² or more, is cured by irradiation with 10J / cm ² or less of ultraviolet, the lower cladding layer, the cured epoxy resin film constituting the core layer or the upper clad layer is obtained It is done.

≪Mold used for optical waveguide manufacturing process≫
The mold of the present invention used in the method of manufacturing an optical waveguide according to the present invention has a concave portion or a convex portion corresponding to a core groove and a spacer groove provided on both sides of the core groove with a space therebetween. The shape of the cross section perpendicular to the longitudinal direction of the convex portion corresponding to the spacer groove is an inverted trapezoid whose lower end side of the convex portion corresponding to the bottom surface of the spacer groove is shorter than the upper end side of the convex portion corresponding to the upper end surface of the spacer groove. Further, at least a side of the spacer groove corresponding convex portion on the core groove corresponding convex portion side is inclined.

  As described above, in the manufacturing method of the present invention, the lower cladding layer having the core groove and the spacer grooves provided on both sides of the core groove with a space therebetween is formed on the substrate using soft lithography. A representative example of the master mold (first mold) used at this time is indicated by reference numeral 5 in FIG. 3A, and a resin mold (second mold) produced from the master mold (first mold) is shown. A typical example is indicated by reference numeral 6 in FIGS. 1 and 3B.

  As shown in FIG. 3A, the first die 5 has a recess 7 corresponding to the core groove and a recess 8 corresponding to a spacer groove provided on both sides of the core groove so as to be substantially parallel to each other. . Examples of the material constituting the first mold 5 include organic materials (for example, permanent resist, polymethyl methacrylate, epoxy resin, etc.) and inorganic materials (for example, metal or alloy such as phosphor bronze, quartz glass, etc.). . As a method for producing the first mold 5, in the case of an organic material, for example, photolithography, cutting, and the like can be given. In the case of an inorganic material, for example, cutting, etching, air blasting, bonding and the like can be mentioned. Of these materials and production methods, inorganic materials and cutting are particularly suitable in view of durability as a master mold (first mold).

  In the first mold 5, the shape of the cross section perpendicular to the longitudinal direction of the concave portion 8 corresponding to the spacer groove is such that the lower end side of the concave portion corresponding to the spacer groove bottom surface is shorter than the upper end side of the concave portion 8 corresponding to the spacer groove upper end surface. It has an inverted trapezoidal shape, and at least the side of the spacer groove-corresponding recess 8 on the core groove-corresponding recess 7 side is inclined. Therefore, the shape of the cross section perpendicular to the longitudinal direction of the spacer groove-corresponding recess 8 may be an inverted one-sided trapezoidal shape shown in FIG. It may be trapezoidal. Preferably, it is an inverted single trapezoid shape. The angle θ formed by the side of the spacer groove-corresponding recess 8 on the core groove-corresponding recess 7 side and the extended line of the bottom side of the spacer groove-corresponding recess 8 is preferably 45 ° or less.

  Further, in the convex portion corresponding to the lower cladding layer, the interval (x) between the concave portion 7 corresponding to the core groove and the concave portion 8 corresponding to the spacer groove is equal to or less than the width of the concave portion 7 corresponding to the core groove. Is preferred.

  Furthermore, the ratio (y / x) of the depth (y) of the recess 8 corresponding to the spacer groove to the interval (x) between the recess 7 corresponding to the core groove and the recess 8 corresponding to the spacer groove is preferably 1 / 1 or more, more preferably 2/1 or more, and preferably 20/1 or less, more preferably 10/1 or less.

  In the first mold 5 shown in FIG. 3A, only one recess 7 corresponding to the core groove is formed, but two or more are formed depending on the use of the optical waveguide. It may be. Moreover, although the recessed part 7 corresponding to a core groove is formed in the linear form extended in the orthogonal | vertical direction with respect to a paper surface, it may be formed in the predetermined pattern shape according to the use etc. of an optical waveguide. Further, the first mold 5 shown in FIG. 3A is configured to manufacture one optical waveguide, but may be configured to manufacture a plurality of optical waveguides.

  Although not shown in FIG. 3A, in the first mold 5, an optical fiber is connected in series (in a direction perpendicular to the paper surface) to the recess 7 corresponding to the core groove depending on the use of the optical waveguide. A recess corresponding to the fixed groove may be formed. Further, when the core material is injected into the core groove and filled, the core material does not enter the optical fiber fixing groove, so that the gap between the concave part 7 corresponding to the core groove and the concave part corresponding to the optical fiber fixing groove is between It is preferable that a convex portion corresponding to the weir is formed. Furthermore, it is preferable that the upper end surface portion of the recess 7 corresponding to the core groove is lower than the upper end surface portion of the recess corresponding to the optical fiber fixing groove.

  As shown in FIG. 1 and FIG. 3B, the second mold 6 includes a convex portion 9 corresponding to the core groove and a convex portion corresponding to a spacer groove provided substantially parallel to the both sides of the core groove. Part (spacer) 10. The material constituting the second mold 6 is not particularly limited as long as it can be molded using the first mold 5. For example, ultraviolet (or light) curable resin, heat ( Or two-part) curable resins such as curable resins and thermoplastic resins. For example, in the case of using a curable resin, the second mold 6 can be produced by pouring the curable resin into the first mold 5 so that the concave portion formed in the first mold 5 is filled and curing the curable resin. When a thermoplastic resin is used, the thermoplastic resin heated to be in a fluidized or melted state is placed on the side of the first mold 5 where the recess is formed, or the first resin The second mold 6 can be manufactured by pouring the mold 5 so as to fill the concave portion and cooling it while applying pressure as necessary.

  Of the materials constituting the second mold 6, a silicone material is particularly suitable because the peelability of the lower clad layer to be formed is improved. Of the silicone materials, a curable silicone rubber oligomer or monomer that becomes a silicone rubber or silicone resin after curing, or a curable silicone material such as a curable silicone resin oligomer or monomer, is preferred, and a curable polysiloxane. Is particularly preferred. As the curable silicone material, what is called liquid silicone is usually used. However, since it is excellent in peelability of the formed lower clad layer and excellent in mechanical strength, it is a two-component used in combination with a curing agent. A mixed type is preferred. If a low-viscosity curable silicone material is used, it is excellent in workability such as removal of bubbles entrained during the production of the mold, and a precise pattern of the transfer pattern can be obtained. Furthermore, the curable polysiloxane may be either a one-component curable type or a two-component curable type, and may be either a thermosetting type or a room temperature curable type.

  Specific examples of the curable silicone material include those containing alkyl siloxane, alkenyl siloxane, alkyl alkenyl siloxane, polyalkyl hydrogen siloxane and the like. In particular, a two-component mixed system of an alkyl alkenyl siloxane and a polyalkyl hydrogen siloxane, which has a low viscosity and is room temperature curable, is preferable from the viewpoint of peelability and curability.

  In the second mold 6, the shape of the cross section perpendicular to the length direction of the convex portion 10 corresponding to the spacer groove is such that the lower end side 14 of the convex portion 10 corresponding to the bottom surface of the spacer groove is the upper end side of the spacer groove convex portion 10. The shape is an inverted trapezoid shorter than 13, and at least the side 16 of the spacer groove corresponding convex portion 10 on the core groove corresponding convex portion 9 side is inclined. In other words, the shape of the cross section perpendicular to the length direction of the convex portion 10 may be an inverted one-sided trapezoidal shape as shown in FIG. A corner trapezoid may be used. The oblique side 16 of the spacer groove convex portion 10 preferably has an angle θ formed by the oblique side 16 and the spacer groove corresponding convex portion upper end side 13 shown by a dotted line in FIG. If the angle θ formed by the oblique side of the spacer groove convex portion 10 and the upper end side of the spacer groove is 45 ° or less, bubbles in the cladding material are quickly removed out of the cladding material.

  Moreover, it is preferable that the distance (x) between the convex portion 9 corresponding to the core groove and the convex portion 10 corresponding to the spacer groove is equal to or less than the width of the convex portion corresponding to the core groove.

  Furthermore, the ratio (y / x) of the height (y) of the convex portion 10 corresponding to the spacer groove to the interval (x) between the convex portion 9 corresponding to the core groove and the convex portion 10 corresponding to the spacer groove is preferably Is 1/1 or more, more preferably 2/1 or more, and is preferably 20/1 or less, more preferably 10/1 or less.

  In the second mold 6 shown in FIG. 1 and FIG. 3 (b), only one convex portion 9 corresponding to the core groove is formed, but depending on the use of the optical waveguide, etc. More than that may be formed. Moreover, although the convex part 9 corresponding to a core groove | channel is formed in the linear form extended in the orthogonal | vertical direction with respect to the paper surface, it may be formed in the predetermined pattern shape according to the use etc. of an optical waveguide. Further, the second mold 6 shown in FIGS. 1 and 3B is configured to manufacture one optical waveguide, but may be configured to manufacture a plurality of optical waveguides. Good.

  Although not shown in FIGS. 1 and 3 (b), in the second mold 6, depending on the use of the optical waveguide, etc., the projections 9 corresponding to the core grooves are in series (a direction perpendicular to the paper surface). ) May be formed with protrusions corresponding to the optical fiber fixing grooves. Further, when the core material is injected and filled into the core groove, the gap between the convex portion 9 corresponding to the core groove and the convex portion corresponding to the optical fiber fixing groove is prevented so that the core material does not enter the optical fiber fixing groove. It is preferable that a recess corresponding to the weir is formed. Furthermore, it is preferable that the lower end surface portion of the convex portion 9 corresponding to the core groove is lower than the lower end surface portion of the convex portion corresponding to the optical fiber fixing groove.

  The reason for forming the core groove and the spacer grooves provided on both sides of the core groove with a gap on the lower clad layer using the second mold manufactured from the first mold is as follows. When forming a core groove and a spacer groove provided on both sides of the core groove with a gap in the lower cladding layer, using a first die (convex shape) having a convex portion corresponding to each groove, When the lower clad layer is formed, when the first mold (convex mold) and the lower clad layer are poorly releasable, a mold chipping or the like occurs and the dimensional accuracy decreases. Further, even if a release agent is applied to improve the releasability between the first mold (convex type) and the lower cladding layer, there is a problem that it is difficult to remove the release agent. Therefore, in order to form the lower clad layer, it is advantageous to produce a second mold (convex mold) made of resin using the first mold (concave mold) which is the master mold and use this. It is.

  When the second mold is made of a transparent and flexible material such as silicone rubber, the lower cladding layer is formed even if the groove is narrow and deep like the spacer groove. Clear transfer is possible without depending on the hardness of the clad material. Therefore, the selection range of the clad material constituting the lower clad layer is wide, and when ultraviolet (or light) curable resin is used, ultraviolet (or light) is transmitted when the ultraviolet (or light) is cured. In addition, there is an advantage that it is not necessary to limit the material constituting the substrate for forming the lower cladding layer to a transparent material.

  If the mold of the present invention is used, an optical waveguide having a substantially uniform thickness in which the lower cladding layer in the lower part of the core layer is controlled using soft lithography and having a very small waveguide loss. Can be easily produced.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples, and appropriate modifications are made within a range that can meet the purpose described above and below. Any of these can be carried out and are included in the technical scope of the present invention.

  First, preparation of a UV curable epoxy resin used as a cladding material and a core material in Examples and Comparative Examples will be described.

<< Preparation of UV curable epoxy resin (1) >>
48 parts by mass of polytetramethylene glycol diglycidyl ether (manufactured by Japan Epoxy Resin Co., Ltd., trade name “jER (registered trademark) YL7417”; number average molecular weight 700 to 800), ε-caprolactone-modified 3,4-epoxycyclohexylmethyl- 30 parts by mass of 3 ′, 4′-epoxycyclohexanecarboxylate (manufactured by Daicel Chemical Industries, Ltd., trade name “Celoxide (registered trademark) 2081”), bisphenol A type epoxy resin (manufactured by Japan Epoxy Resins Co., Ltd., trade name “jER”) (Registered trademark) 828EL ") 18 parts by mass, 4 parts by mass of triarylsulfonium hexafluorophosphate (manufactured by Aceto Chemical, trade name" CPII-6992 ") which is a photopolymerization initiator, Product name Were mixed with Awatori Rentaro (registered trademark) "), was prepared UV-curable epoxy resin (1) used as a cladding material.

<< Preparation of UV curable epoxy resin (2) >>
Polytetramethylene glycol diglycidyl ether (manufactured by Japan Epoxy Resin Co., Ltd., trade name “jER (registered trademark) YL7417”; number average molecular weight 700-800) 9 parts by mass, bisphenol A type epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd.) , 43.5 parts by mass of a trade name “jER (registered trademark) 828EL”), 43.5 parts by mass of a brominated bisphenol A type epoxy resin (manufactured by Japan Epoxy Resin Co., Ltd., trade name “jER (registered trademark) 5050”), A photopolymerization initiator, triarylsulfonium hexafluorophosphate (trade name “CPI-6992”, manufactured by Aceto Chemical Co., Ltd.), 4 parts by mass, a rotating / revolving mixer (Sinky Co., Ltd., trade name “Netaro Awatori” (Registered trademark) ”) and used as a core material A UV curable epoxy resin (2) was prepared.

  Next, examples and comparative examples in which optical waveguides are actually manufactured will be described.

<< Production of optical waveguide >>
<Example 1>
In this example, the lower cladding layer of the flexible optical waveguide was produced.

  1-1) The surface of phosphor bronze (thickness 10 mm) is cut, and a recess having a width of 50 μm and a depth of 50 μm corresponding to the core groove, and a reverse cross-section provided side by side with a space of 10 μm on both sides of the recess. A concave portion corresponding to the one-sided spacer groove was formed to produce a first die (concave shape) as shown in FIG. In this first mold, in the cross section perpendicular to the longitudinal direction, the angle formed by the side of the spacer groove recess located on the core groove side and the extension line of the lower end of the recess corresponding to the bottom surface of the spacer groove is 45 °, The width corresponding to the bottom surface of the spacer groove was 2 mm, and the depth was 75 μm. In FIG. 3A, the recess 8 corresponding to the spacer groove is drawn with a width smaller than the depth due to space limitations.

  1-2) A two-component curing type in which a first mold is placed on a glass substrate (thickness 2 mm) with a gap therebetween, and air bubbles are not sandwiched between the glass substrate and the first mold. Silicone rubber (made by Toray Dow Corning Co., Ltd., trade name “SILPOT 184”) is injected and filled, and allowed to stand at room temperature for 24 hours to cure, and then a second mold made of silicone rubber (convex type) ) Was produced. As shown in FIGS. 1 and 3B, the obtained second mold corresponds to the core groove and the inverted trapezoidal spacer groove provided on both sides of the core groove so as to be spaced substantially parallel to each other. It had each convex part. In FIG. 1 and FIG. 3B, the convex portion 10 corresponding to the spacer groove is drawn with a width smaller than the height due to space limitations.

  1-3) On a polyimide film as a film substrate (trade name “Kapton (registered trademark) H type” manufactured by Toray DuPont Co., Ltd .; thickness 25 μm), a UV curable epoxy resin (1) is used as a cladding material. After the appropriate amount was dropped, the second mold was brought close to the film substrate so that the convex portions (spacers) corresponding to the spacer grooves contacted the film substrate on a stage having parallelism. Before the second mold spacer contacted the film substrate, the second mold was temporarily stopped and vacuum was applied to perform defoaming to remove bubbles from the cladding material.

  Next, as shown in FIG. 3C, the second mold was pressed onto the film substrate so that the spacer of the second mold was in close contact with the film substrate. In this state, after being cured by UV irradiation from the second mold side, the second mold is removed and the core groove and both sides of the core groove are formed on the film substrate as shown in FIG. A lower cladding layer having a spacer groove provided in parallel with a gap therebetween is formed. The thickness of the lower clad layer was equal to the depth of the spacer groove, and was 75 μm (the thickness below the core groove was 25 μm). In FIG. 3C, the convex portion 10 corresponding to the spacer groove is drawn with a width smaller than the height due to space limitations. In FIG. 3D, the spacer groove 12 is drawn with a width smaller than the depth due to space limitations. When the refractive index of the lower clad layer was measured using a prism coupler (product name “SPA-4000”, manufactured by Cylon Technology Inc.), the refractive index at a wavelength of 830 nm was 1.50.

In the step 1-3), the UV curable epoxy resin is cured at an illuminance of 10 mW / cm ² using an exposure machine (trade name “MA-60F” manufactured by Mikasa Co., Ltd.) using a high-pressure mercury lamp as a light source. The test was performed for 15 minutes, that is, with an exposure energy of 9 J / cm ² .

  When the obtained lower clad layer was observed with a microscope ("VH-8000", manufactured by Keyence Corporation, magnification of 250 times), as shown in FIG. 4, a core continuous in the longitudinal direction of the lower clad layer was formed on the substrate. A groove and a spacer groove substantially parallel to the core groove were formed at intervals on both sides of the core groove.

<Comparative Example 1>
In this comparative example, the lower clad layer of the flexible optical waveguide was produced.

  In Example 1, the concave portion corresponding to the core groove has a rectangular shape, and the cross-sectional shape of the concave portion corresponding to the spacer groove provided substantially parallel with a gap on both sides of the concave portion corresponding to the core groove is a rectangular shape. A flexible optical waveguide was produced in the same manner as in Example 1 except that the second mold (convex mold) shown in FIG. The width corresponding to the spacer groove in the second mold was 1.5 mm and the depth was 75 μm. In FIG. 2, the convex portion 10 ′ corresponding to the spacer groove is drawn with a width smaller than the thickness due to space limitations.

  When the obtained lower cladding layer was observed with a microscope in the same manner as in Example 1, the core groove and the spacer groove were connected as shown in FIG. In an optical waveguide formed from such a lower cladding layer, it is expected that the core layer will be disconnected due to bubbles remaining in the cladding material.

<Example 2>
In this example, an optical waveguide was produced using the lower clad layer produced in Example 1.

  2-1) The film substrate on which the lower clad layer obtained in Example 1 was formed was placed on a hot plate, and UV curable epoxy was used as a core material at both ends of the core groove formed in the lower clad layer. Resin (2) was dropped, and the core material was filled in the entire core groove using capillary action. When the filling of the core material was completed, the heating was stopped and UV irradiation was performed to cure, thereby forming a core layer having a width of 50 μm and a thickness of 50 μm in the core groove as shown in FIG. In FIG. 3E, the spacer groove 12 is drawn with a width smaller than the depth due to space limitations. When the refractive index of the core layer was measured using a prism coupler (product name “SPA-4000”, manufactured by Cylon Technology Inc.), the refractive index at a wavelength of 830 nm was 1.58.

  2-2) An appropriate amount of UV curable epoxy resin (1) was dropped as a clad material on the lower clad layer on which the core layer was formed, and a glass substrate subjected to a release treatment was placed. Next, before the gap between the lower cladding layer and the glass substrate reaches a desired value, a vacuum is applied to perform defoaming treatment. When bubbles are completely absent, the glass substrate is moved to the desired value. Adhered. In this state, UV irradiation was performed from the glass substrate side and cured to form an upper clad layer having a thickness of 25 μm, thereby obtaining a flexible optical waveguide as shown in FIG. In FIG. 3F, the hardened material of the cladding material filling the spacer groove 12 is drawn smaller in width than the thickness due to space limitations. When the refractive index of the upper cladding layer was measured using a prism coupler (product name “SPA-4000”, manufactured by Cylon Technology Inc.), the refractive index at a wavelength of 830 nm was 1.50.

In the above steps 2-1) to 2-2), the UV curable epoxy resin is cured using an exposure machine (trade name “MA-60F” manufactured by Mikasa Co., Ltd.) using a high-pressure mercury lamp as a light source. The test was carried out at 10 mW / cm ² for 15 minutes, that is, with an exposure energy of 9 J / cm ² .

  2-3) About the obtained flexible optical waveguide, using an optical fiber connected to an LED light source having a wavelength of 850 nm at the other end, light having a wavelength of 850 nm is incident on one end of the core layer, and the amount of light is incident on the other end of the core layer. When the intensity of light propagating through the core layer was measured by bringing an optical fiber connected to a meter into contact, the waveguide loss was a very small value of 0.1 dB / cm.

  When the optical waveguide was bent at ± 90 degrees with a radius of 1 mm, no fold lines or cracks were generated, and a good appearance was shown.

  Further, when 10 optical waveguides were produced by repeating the same steps as in Examples 1 and 2, the waveguide loss of any of the optical waveguides was 0.1 dB / cm.

<Comparative Example 2>
In this comparative example, a flexible optical waveguide was produced using the lower cladding layer obtained in Comparative Example 1.

  In Example 2, except that the film substrate on which the lower cladding layer obtained in Comparative Example 1 was formed was used, a flexible optical waveguide was produced in the same manner as in Example 2, and the light propagating in the core layer Attempts were made to measure the intensity of light, but light was not guided, and the waveguide loss could not be measured.

  Further, when 10 optical waveguides were produced by repeating the same steps as in Comparative Examples 1 and 2, a result of a waveguide loss of 0.1 dB / cm was obtained for the 2 flexible optical waveguides. In the remaining eight flexible optical waveguides, light was not guided and the waveguide loss could not be measured. In these flexible optical waveguides, the core groove is disconnected, and bubbles in the lower clad material are not removed when the lower clad layer is formed, and it is considered that a core groove formation defect has occurred in the lower clad layer.

≪Evaluation≫
As described above, the lower cladding layer of the first embodiment and the flexible optical waveguide of the second embodiment have the convex portions corresponding to the core groove and the spacer grooves provided substantially parallel to each other on both sides of the core groove. And a convex shape corresponding to the spacer groove has a reverse trapezoidal shape (second die) whose bottom side corresponding to the bottom surface of the spacer groove is shorter than the upper side. In addition, a lower cladding layer having a core groove and a spacer groove provided in parallel with a gap on both sides of the core groove is formed, so that a convex portion (spacer) corresponding to the spacer groove having an inverted trapezoidal cross section exists. As a result, the bubbles were quickly discharged from the clad material, the core groove was not formed poorly, and the optical waveguide could be manufactured with good yield. In addition, the presence of the convex portion (spacer) corresponding to the spacer groove allows the film substrate or the convex mold to be supported and held substantially in parallel without being bent, so that the portion located below the core layer is The thickness of the lower cladding layer can be controlled, and as a result, the waveguide loss is very small. Furthermore, since the thickness of the lower clad layer, the core layer, and the upper clad layer is uniform in the flexible optical waveguide of Example 2, no fold lines or cracks are generated even when bent at ± 90 degrees with a radius of 1 mm. Showed good appearance.

  On the other hand, the lower clad layer of Comparative Example 1 and the flexible optical waveguide of Comparative Example 2 correspond to the core groove and the spacer groove provided substantially parallel to each other on both sides of the convex portion corresponding to the core groove. Although each convex portion has a rectangular cross-sectional shape perpendicular to the longitudinal direction of the spacer groove convex portion, bubbles in the lower cladding material are difficult to be discharged, resulting in poor formation of the core groove. The layer break occurred, and the optical waveguide could not be manufactured with a high yield.

  Thus, in the method of manufacturing an optical waveguide, each of the protrusions corresponding to the core groove and the spacer groove provided substantially parallel to the both sides of the core groove is provided, and the protrusion corresponds to the spacer groove. Using a convex mold (second mold) whose cross-sectional shape is an inverted trapezoid whose bottom corresponding to the bottom of the spacer groove is shorter than the upper side, the core groove is spaced on both sides of the core groove on the substrate. If a lower cladding layer having spacer grooves arranged substantially parallel to each other is formed, bubbles in the lower cladding material that lead to breakage of the core groove can be quickly discharged, so that an optical waveguide can be manufactured with a high yield. Further, if the second mold according to the basic shape invention is used, the thickness of the lower clad layer in the portion located below the core layer can be easily controlled even when a substrate having low rigidity such as a film substrate is used. It can be seen that a high-performance optical waveguide with very low waveguide loss can be obtained easily.

  The method of manufacturing an optical waveguide according to the present invention and the mold used therefor can efficiently discharge bubbles in the lower cladding material that lead to breakage of the core layer, and even if a substrate having low rigidity such as a film substrate is used, the core layer The lower cladding layer in the lower portion has a controlled and substantially uniform thickness, and enables an optical waveguide with very low waveguide loss to be easily manufactured with a high yield. When manufacturing an optical waveguide, the manufacturing cost can be significantly reduced. Therefore, the present invention makes a great contribution in various optical fields and electronic equipment fields where application of high performance optical waveguides with very small waveguide loss is expected.

1 Substrate 2 Lower cladding layer 3 Core layer 4 Upper cladding layer 5 First mold (concave)
6,6 'second mold (convex)
7 Concave part corresponding to the core groove 8 Concave part corresponding to the spacer groove 9, 9 ′ Convex part corresponding to the core groove 10, 10 ′ Convex part corresponding to the spacer groove (spacer)
DESCRIPTION OF SYMBOLS 11 Core groove 12 Spacer groove 13 Upper side corresponding to spacer groove bottom face 14 Base side corresponding to spacer groove bottom face 15 Cladding material 16 Oblique side of spacer groove corresponding convex part 16 'Side of convex part corresponding to spacer groove
17 Slope of lower cladding layer 18 Bubble

Claims (6)

On the substrate, a clad material is dropped, and a second mold having respective convex portions corresponding to a core groove and spacer grooves provided substantially parallel to each other at both sides of the core groove is used. Forming a lower clad layer having a core groove and spacer grooves provided substantially parallel to each other on both sides of the core groove;
Injecting and filling a core material into the core groove and curing the core material to form a core layer;
Injecting and filling the spacer material with the cladding material and applying the cladding material on the lower cladding layer so as to embed the core layer, and then curing the cladding material to form the upper cladding layer Including, and
As the second mold, the shape of the cross section perpendicular to the longitudinal direction of the convex portion corresponding to the spacer groove is an inverted base in which the lower end side of the convex portion corresponding to the bottom surface of the spacer groove is shorter than the upper end side of the convex portion corresponding to the upper end surface of the spacer groove. A method of manufacturing an optical waveguide, wherein the optical waveguide has a shape and at least the side of the spacer groove-corresponding convex portion on the core groove-corresponding convex side is inclined.   The angle between the oblique side of the spacer groove corresponding convex portion on the core groove corresponding convex portion side and the spacer groove corresponding convex upper end side corresponding to the spacer groove upper end surface in the second mold is 45 ° or less. The manufacturing method as described.   The manufacturing method according to claim 1 or 2, wherein an interval (x) between the core groove and the spacer groove is equal to or less than a width of the core groove on the upper end surface of the lower cladding layer. A mold used for a method of manufacturing an optical waveguide including a step of forming a lower cladding layer having a core groove and a spacer groove provided substantially parallel to each other on both sides of the core groove on a substrate,
Each recess corresponding to a core groove and a spacer groove provided substantially parallel to each other on both sides of the core groove;
The shape of the cross section perpendicular to the longitudinal direction of the concave portion corresponding to the spacer groove is an inverted trapezoid whose lower end side of the concave portion corresponding to the spacer groove bottom surface is shorter than the upper end side of the concave portion corresponding to the spacer groove upper end surface, and
A mold characterized in that at least the side of the concave portion corresponding to the spacer groove on the concave side corresponding to the core groove is inclined. A mold used for a method of manufacturing an optical waveguide including a step of forming a lower cladding layer having a core groove and a spacer groove provided substantially parallel to each other on both sides of the core groove on a substrate,
Each of the convex portions corresponding to the core groove and spacer grooves provided substantially parallel to each other with a space on both sides of the core groove,
The shape of the cross section perpendicular to the longitudinal direction of the convex portion corresponding to the spacer groove is an inverted trapezoid in which the lower end side of the convex portion corresponding to the bottom surface of the spacer groove is shorter than the upper end side of the convex portion corresponding to the upper end surface of the spacer groove. ,and,
The mold | type characterized by the side of the convex part corresponding to the spacer groove | channel on the convex part side corresponding to a core groove | channel being inclined at least.   The optical waveguide obtained by the manufacturing method in any one of Claims 1-3.