Optical waveguide manufacturing method

Abstract

To provide a manufacturing method for an optical waveguide that can efficiently manufacture an optical waveguide with high pitch accuracy in a core part, in which a size of at least one of an irradiation region and a non-irradiation region can be set suitably in consideration of deformation of a core layer that is caused due to a clad formation layer.SOLUTION: A manufacturing method for an optical waveguide includes the steps of: preparing a core formation layer and a clad formation layer; obtaining a core layer including a plurality of core parts corresponding to non-irradiation regions and a side-surface clad part existing between the core parts and corresponding to irradiation regions by irradiating a part of the core formation layer with an active radiation; and obtaining an optical waveguide having the core layer and a clad layer by stacking the clad formation layer on the core layer and heating them. A size of at least one of the irradiation region and the non-irradiation region is adjusted in accordance with the time passed after the manufacture of the clad formation layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an optical waveguide. [Background technology]

[0002] Patent Document 1 discloses a method for manufacturing an optical waveguide, including the steps of forming a lower cladding layer on a polyimide laminate, forming a core layer on the lower cladding layer, forming a core pattern from the core layer, forming an upper cladding layer on the core pattern, and cutting out a straight optical waveguide. The core pattern forming step includes spin-coating a fluorinated polyamic acid solution onto the lower cladding layer, heating it at 300°C or higher to form a core layer, forming a core pattern from the core layer using a photoresist, and dry-etching the core pattern to obtain a core ridge. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-103738 Summary of the Invention [Problem to be solved by the invention]

[0004] Optical waveguides made of such organic materials are prone to dimensional changes due to the characteristics of organic materials. In particular, when the manufacturing process of an optical waveguide involves a resin curing reaction, the reaction rate can change due to various external factors. As a result, the dimensional accuracy of the core ridge after heating decreases, and the accuracy of the spacing between cores in the final optical waveguide decreases.

[0005] The object of the present invention is to provide a method for manufacturing an optical waveguide that can appropriately set the size of at least one of the irradiated area and the non-irradiated area in anticipation of deformation of the core layer caused by the cladding forming layer, and that can efficiently manufacture optical waveguides with high pitch accuracy of the core portion. [Means for solving the problem]

[0006] These objects can be achieved by the present invention as set forth in (1) to (6) below. (1) preparing a core forming layer and a cladding forming layer; A part of the core forming layer is irradiated with active radiation, and a non-irradiated area is and line up in the specified direction obtaining a core layer including a plurality of core portions and side clad portions located between the core portions and corresponding to the irradiation region; a step of laminating the cladding layer on the core layer and heating the resulting layer to obtain an optical waveguide having the core layer and the cladding layer; and Depending on the time elapsed since the production of the cladding layer, In the direction in which the core portions are arranged A method for manufacturing an optical waveguide, comprising adjusting the size of at least one of the irradiated region and the non-irradiated region.

[0007] (2) The elapsed time is the number of days stored at room temperature, The method for manufacturing an optical waveguide according to (1) above, wherein the correction factor when adjusting the size is y and the number of days of storage at room temperature is x, the correction factor is set so as to satisfy the following correction formula (1). y=x A (1) [In the correction formula (1), A is 0.00015 to 0.00045.]

[0008] (3) The method for producing an optical waveguide according to (1) or (2) above, wherein the cladding layer has a thickness of 1 to 200 μm.

[0009] (4) The optical waveguide is the core layer; a first clad layer and a second clad layer, which are the clad layers stacked on both sides of the core layer; Equipped with the core layer is provided on a substrate before the step of obtaining the optical waveguide; The step of obtaining the optical waveguide includes: laminating the cladding layer on the core layer to obtain a laminate; peeling the substrate from the laminate; laminating the cladding layer on the core layer and heating the cladding layer to obtain the optical waveguide; The method for producing an optical waveguide according to any one of (1) to (3) above, comprising:

[0010] (5) The optical waveguide is a first cover layer laminated on the first clad layer on the opposite side of the core layer; a second cover layer laminated on the second clad layer on the opposite side of the core layer; The method for manufacturing an optical waveguide according to (4) above, further comprising:

[0011] (6) The method for producing an optical waveguide according to any one of (1) to (5) above, wherein the film thickness of the optical waveguide is 50 to 300 μm. [Effects of the Invention]

[0012] According to the present invention, optical waveguides having core portions with high pitch accuracy can be efficiently manufactured. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a plan view showing an optical waveguide manufactured by a method for manufacturing an optical waveguide according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] 5A to 5C are process diagrams illustrating a method for manufacturing an optical waveguide according to an embodiment. [Figure 4]4 is a diagram for explaining a method for manufacturing the optical waveguide shown in FIG. 3, and is an enlarged view of a part of the optical waveguide shown in FIG. 2. FIG. [Figure 5] 4 is a diagram for explaining a method for manufacturing the optical waveguide shown in FIG. 3, and is an enlarged view of a part of the optical waveguide shown in FIG. 2. FIG. [Figure 6] 4 is a diagram for explaining a method for manufacturing the optical waveguide shown in FIG. 3, and is an enlarged view of a part of the optical waveguide shown in FIG. 2. FIG. [Figure 7] FIG. 10 is a scatter plot showing the correlation between the number of days that a clad film having a second clad layer is stored at room temperature and the pitch of the core portion. [Figure 8] FIG. 8 is a scatter plot showing the correlation between the number of days that a clad film having a second clad layer is stored at room temperature and the correction factor required to correct the shrinkage of the core layer shown in FIG. 7. [Figure 9] 1 is a graph showing how the pitch of the core portion changes when the number of days of storage at room temperature of a clad film having a first clad layer and a clad film having a second clad layer are the same and different from each other. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for manufacturing an optical waveguide according to the present invention will now be described in detail with reference to preferred embodiments shown in the accompanying drawings.

[0015] Fig. 1 is a plan view showing an optical waveguide manufactured by a method for manufacturing an optical waveguide according to an embodiment, and Fig. 2 is a cross-sectional view taken along line AA in Fig. 1.

[0016] In each drawing of the present application, three mutually orthogonal axes are set as the X-axis, Y-axis, and Z-axis, and are indicated by arrows. The tip end of the arrow is referred to as the "plus side," and the base end is referred to as the "minus side." Furthermore, the tip end of the arrow representing the Z-axis is referred to as the "upper side," and the base end is referred to as the "lower side."

[0017] 1.Optical waveguide The optical waveguide 1 shown in FIGS. 1 and 2 is sheet-shaped and has a laminated structure in which a first cover layer 18, a first cladding layer 11, a core layer 13, a second cladding layer 12, and a second cover layer 19 are laminated in this order. Each layer of the laminated structure extends along the XY plane. As will be described later, the optical waveguide 1 is a long resin film with its major axis along the X axis and is flexible. Therefore, the optical waveguide 1 can be used even when bent, for example, along the Z axis.

[0018] As shown in FIG. 1, nine elongated core portions 14 extending along the X-axis and side clad portions 15 adjacent to the side surfaces of each core portion 14 are formed in the core layer 13. Therefore, the side clad portions 15 are adjacent to both side surfaces of each core portion 14 in the Y-axis direction. As shown in FIG. 2, the first clad layer 11 is adjacent to the lower surface of each core portion 14, and the second clad layer 12 is adjacent to the upper surface of each core portion 14. This stably maintains a sufficiently large refractive index difference between the core portions 14 and the clad portions (the side clad portions 15, the first clad layer 11, and the second clad layer 12), thereby increasing the transmission efficiency of the core portions 14. Note that the core portions 14 may branch midway within the core layer 13 or may intersect with other core portions 14 midway.

[0019] The number of core portions 14 provided in the core layer 13 is not particularly limited, and may be, for example, about 1 to 100. The total length of the optical waveguide 1 along the X axis is not particularly limited, but is preferably about 10 to 3000 mm. Furthermore, the total width of the optical waveguide 1 along the Y axis is not particularly limited, but is more preferably about 2 to 200 mm.

[0020] The film thickness of the core layer 13 along the Z axis is not particularly limited, but is preferably about 1 to 200 μm, more preferably about 5 to 100 μm, and even more preferably about 10 to 70 μm, which ensures the optical properties and mechanical strength required for the core layer 13.

[0021] The film thickness along the Z-axis of each of the first cladding layer 11 and the second cladding layer 12 is preferably about 1 to 200 μm, more preferably about 3 to 100 μm, and even more preferably about 5 to 50 μm. This ensures that the first cladding layer 11 and the second cladding layer 12 have the optical properties and mechanical strength required. Furthermore, when the first cladding layer 11 and the second cladding layer 12 are formed from the cladding-forming layer, excessive cure shrinkage of the cladding-forming layer can be prevented, and this influence on the core layer 13 can be prevented.

[0022] The optical waveguide 1 has an end face 101 located on the negative side of the X axis and an end face 102 located on the positive side of the X axis. The end faces 101 and 102 each function as a light input / output surface.

[0023] An optical connector (not shown) may be attached to at least one of the ends of the optical waveguide 1. The optical connector can be used to fix the optical waveguide 1 to other optical components and to optically connect the end faces 101 and 102 to other optical components. The optical waveguide 1 may also have a mirror that changes the optical path of light passing through the core 14. By changing the optical path via the mirror, the core 14 can be optically connected to an optical component provided outside the optical waveguide 1.

[0024] The first cover layer 18 is laminated on the lower surface of the first cladding layer 11. The second cover layer 19 is laminated on the upper surface of the second cladding layer 12. This makes it possible to improve the mechanical properties and durability of the optical waveguide 1.

[0025] The film thickness of the optical waveguide 1 along the Z axis is preferably 50 to 300 μm, more preferably 60 to 200 μm, and even more preferably 70 to 150 μm, which can increase the flexibility of the optical waveguide 1 while ensuring sufficient mechanical strength of the optical waveguide 1.

[0026] Each part of the optical waveguide 1 will be described in more detail below. 2. Optical waveguide manufacturing method Next, a method for manufacturing an optical waveguide according to an embodiment will be described below. In the following description, a method for manufacturing the optical waveguide 1 shown in FIGS.

[0027] Fig. 3 is a process diagram for explaining a method for manufacturing an optical waveguide according to an embodiment. Fig. 4 to Fig. 6 are diagrams for explaining a method for manufacturing the optical waveguide shown in Fig. 3, and are enlarged views of a part of the optical waveguide shown in Fig. 2.

[0028] The method for manufacturing the optical waveguide 1 shown in FIG. 3 includes a preparation step S102, a core layer formation step S104, and a cladding layer formation step S106.

[0029] In the preparation step S102, a core forming layer 160 and a cladding forming layer 170 are prepared. In the core layer formation step S104, a part of the core forming layer 160 is irradiated with active radiation R to obtain a core layer 13 including a core portion 14 and a side cladding portion 15. In the cladding layer formation step S106, the cladding forming layer 170 is laminated on the core layer 13 and heated to obtain an optical waveguide 1.

[0030] In the method for manufacturing the optical waveguide 1 according to this embodiment, the size of at least one of the irradiation region 301 to be irradiated with the active radiation R and the non-irradiation region 302 is adjusted depending on the time that has elapsed since the cladding forming layer 170 was manufactured.

[0031] With this configuration, it is possible to adjust the size of at least one of the irradiated region 301 and the non-irradiated region 302 in anticipation of deformation of the core layer 13 caused by the cladding forming layer 170. As a result, even if the core layer 13 is deformed, it is possible to make the size of at least one of the core portion 14 and the side cladding portion 15 closer to the desired size. As a result, it is possible to efficiently manufacture the optical waveguide 1 shown in FIG. 2, in which the pitch P of the core portion 14 is highly accurate.

[0032] Each step will be explained below in order. 2.1. Preparation process In the preparation step S102, the core forming layer 160 and the cladding forming layer 170 are prepared.

[0033] In this embodiment, as shown in FIG. 4(a), a core film 200 having a substrate 100 and a core forming layer 160 laminated on the upper surface of the substrate 100 is prepared.

[0034] In this embodiment, as shown in Fig. 5(f), a clad film 402 is prepared, which has a second cover layer 19 and a clad-forming layer 170 laminated on the lower surface of the second cover layer 19. Similarly, as shown in Fig. 6(i), a clad film 401 is prepared, which has a first cover layer 18 and a clad-forming layer 170 laminated on the upper surface of the first cover layer 18.

[0035] 2.1.1. Core film As described above, the core film 200 is a laminate of the substrate 100 and the core-forming layer 160. The core film 200 is in the form of a film, and may be in the form of a sheet or a roll that can be wound up.

[0036] Examples of methods for forming the core-forming layer 160 include a method in which a varnish-like core-forming resin composition is applied to the substrate 100 and then dried, and a method in which a resin film is laminated on the substrate 100.

[0037] The resin composition can be applied by using various coaters such as a spin coater, a die coater, a comma coater, or a curtain coater, or by a printing method such as screen printing.

[0038] In the method of laminating a resin film, a film-like resin film prepared from a varnish-like core-forming resin composition is laminated using, for example, roll lamination, vacuum roll lamination, flat plate lamination, vacuum flat plate lamination, atmospheric pressure press, vacuum press, etc.

[0039] The core film 200 may include a plurality of regions corresponding to the optical waveguides 1 so that a plurality of optical waveguides 1 can be finally cut out. In this case, by adding a step of cutting out the optical waveguides 1, the optical waveguides 1 can be manufactured more efficiently.

[0040] 2.1.1.1. Base material For example, a resin film is used for the substrate 100. Examples of materials that can be used for the substrate 100 include polyolefins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene, and polypropylene, fluororesins such as polyimide, polyamide, polyetherimide, polyamideimide, and polytetrafluoroethylene (PTFE), polycarbonate, polyethersulfone, polyphenylene sulfide, and liquid crystal polymers.

[0041] If necessary, the substrate 100 may be subjected to a release treatment or the like to facilitate separation of the core layer 13 from the substrate 100.

[0042] 2.1.1.2. Core-forming resin composition The core-forming resin composition may be, for example, a composition containing a polymer, a monomer, a polymerization initiator, and the like.

[0043] Polymers Examples of polymers include acrylic resins, methacrylic resins, polycarbonate, polystyrene, cyclic ether resins such as epoxy resins and oxetane resins, polyamide, polyimide, polybenzoxazole, polysilane, polysilazane, silicone resins, fluorine-containing resins, polyurethane, polyolefin resins, polybutadiene, polyisoprene, polychloroprene, polyesters such as PET and PBT, polyethylene succinate, polysulfone, polyether, cyclic olefin resins such as benzocyclobutene resins and norbornene resins, and phenoxy resins. One or more of these may be combined and used as a polymer alloy, polymer blend (mixture), copolymer, etc.

[0044] Among these, acrylic resins, phenoxy resins, and cyclic olefin resins are preferably used as the polymer.

[0045] Examples of acrylic resins include polymers of acrylic compounds containing one or more selected from the group consisting of monofunctional acrylates, polyfunctional acrylates, monofunctional methacrylates, polyfunctional methacrylates, urethane acrylates, urethane methacrylates, epoxy acrylates, epoxy methacrylates, polyester acrylates, and urea acrylates. The acrylic resins may have a polyester skeleton, a polypropylene glycol skeleton, a bisphenol skeleton, a fluorene skeleton, a tricyclodecane skeleton, a dicyclopentadiene skeleton, or the like.

[0046] Examples of phenoxy resins include those containing bisphenol A, bisphenol A type epoxy compounds or derivatives thereof, and bisphenol F, bisphenol F type epoxy compounds or derivatives thereof as copolymerization component units.

[0047] The polymer content is, for example, preferably 15% by mass or more, more preferably 40% by mass or more, and even more preferably 60% by mass or more of the total solid content of the core-forming resin composition. This improves the mechanical properties of the core layer 13. Furthermore, the polymer content in the core-forming resin composition is preferably 95% by mass or less, more preferably 90% by mass or less of the total solid content of the core-forming resin composition. This improves the optical properties of the core layer 13.

[0048] The total solid content of the core-forming resin composition refers to the nonvolatile content in the composition, ie, the remainder excluding volatile components such as water and solvent.

[0049] Monomer The monomer is not particularly limited as long as it is a compound having a polymerizable site in its molecular structure, but examples thereof include acrylic acid (methacrylic acid)-based monomers, epoxy-based monomers, oxetane-based monomers, norbornene-based monomers, vinyl ether-based monomers, styrene-based monomers, and photodimerization monomers, and one or more of these may be used in combination.

[0050] Among these, acrylic acid (methacrylic acid)-based monomers or epoxy-based monomers are preferably used as the monomer.

[0051] Examples of acrylic acid (methacrylic acid)-based monomers include compounds having two or more ethylenically unsaturated groups, and bifunctional or trifunctional or higher functional (meth)acrylates. Specific examples include aliphatic (meth)acrylates, alicyclic (meth)acrylates, aromatic (meth)acrylates, heterocyclic (meth)acrylates, and their ethoxylated, propoxylated, ethoxylated propoxylated, and caprolactone-modified derivatives. Furthermore, the monomers may have a bisphenol skeleton, a urethane skeleton, or the like in the molecule.

[0052] Examples of epoxy-based monomers include alicyclic epoxy compounds, aromatic epoxy compounds, and aliphatic epoxy compounds.

[0053] The monomer may be a photopolymerizable monomer that reacts to generate a reaction product in an irradiated region upon irradiation with active radiation such as visible light, ultraviolet light, infrared light, laser light, electron beams, or X-rays. The monomer may be capable of moving in an in-plane direction perpendicular to the film thickness in the core forming layer 160 upon irradiation with active radiation, and may cause a refractive index difference between an irradiated region and a non-irradiated region in the resulting core layer 13.

[0054] The content of the monomer is preferably 1 part by mass or more and 70 parts by mass or less, and more preferably 10 parts by mass or more and 60 parts by mass or less, relative to 100 parts by mass of the polymer, which makes it possible to more reliably form the refractive index difference, i.e., to more reliably cause refractive index modulation.

[0055] 2.1.1.2.3. Polymerization initiator The polymerization initiator is appropriately selected depending on the type of polymerization reaction or crosslinking reaction of the monomer. Examples of the polymerization initiator that can be used include radical polymerization initiators such as acrylic acid (methacrylic acid) monomers and styrene monomers, and cationic polymerization initiators such as epoxy monomers, oxetane monomers, and vinyl ether monomers.

[0056] Examples of the radical polymerization initiator include benzophenones, acetophenones, etc. Specific examples include Irgacure (registered trademark) 651, Irgacure 819, Irgacure 2959, and Irgacure 184 (all manufactured by IGM Japan LLC).

[0057] Examples of cationic polymerization initiators include Lewis acid generators such as diazonium salts, and Bronsted acid generators such as iodonium salts and sulfonium salts. Specific examples include ADEKA OPTOMER SP-170 (manufactured by ADEKA Corporation), SAN-AID SI-100L (manufactured by Sanshin Chemical Industry Co., Ltd.), and Rhodorsil 2074 (manufactured by Rhodia Japan Co., Ltd.).

[0058] The content of the polymerization initiator is preferably 0.01 to 5 parts by mass, and more preferably 0.05 to 3 parts by mass, relative to 100 parts by mass of the polymer, which allows the monomer to react quickly without deteriorating the optical and mechanical properties of the core layer 13.

[0059] Other The core-forming resin composition may further contain, for example, a crosslinking agent, a sensitizer (photosensitizer), a catalyst precursor, a cocatalyst, an antioxidant, an ultraviolet absorber, a light stabilizer, a silane coupling agent, a coating surface improver, a thermal polymerization inhibitor, a leveling agent, a surfactant, a colorant, a storage stabilizer, a plasticizer, a lubricant, a filler, inorganic particles, an antidegradant, a wettability improver, an antistatic agent, and the like.

[0060] Solvents The above-mentioned components are added to a solvent and stirred to obtain a varnish-like core-forming resin composition. The obtained composition may be subjected to filtration using a PTFE filter with a pore size of 0.2 μm, for example. Alternatively, the obtained composition may be subjected to mixing using various mixers.

[0061] Examples of solvents contained in the core-forming resin composition include organic solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, ethyl acetate, cyclohexane, heptane, cyclohexane, cyclohexanone, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol dimethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, cellosolve-based solvents, carbitol-based solvents, anisole, and N-methylpyrrolidone, and one or a mixture of two or more of these solvents can be used.

[0062] 2.1.2.Clad film As described above, clad film 401 is a laminate of first cover layer 18 and clad forming layer 170. As described above, clad film 402 is a laminate of second cover layer 19 and clad forming layer 170. Clad films 401 and 402 are in the form of a film, and may be in the form of a sheet or a roll that can be wound up.

[0063] Examples of methods for forming the cladding layer 170 include a method in which a varnish-like cladding resin composition is applied onto the cover layer and then dried, and a method in which a resin film is laminated onto the cover layer.

[0064] The resin composition can be applied by using various coaters such as a spin coater, a die coater, a comma coater, or a curtain coater, or by a printing method such as screen printing.

[0065] In the method of laminating a resin film, a film-like resin film prepared from a varnish-like clad-forming resin composition is laminated using, for example, roll lamination, vacuum roll lamination, flat plate lamination, vacuum flat plate lamination, atmospheric pressure pressing, vacuum pressing, etc.

[0066] 2.1.2.1.Cover Layer The thickness of first cover layer 18 and second cover layer 19 is not particularly limited, but is preferably about 1 to 200 μm, more preferably about 3 to 100 μm, and even more preferably about 5 to 50 μm. If the thickness of each cover layer is within the above range, the ability of first cover layer 18 and second cover layer 19 to protect core layer 13 and the like can be ensured, while adverse effects of optical waveguide 1 becoming too thick, such as a decrease in the flexibility of optical waveguide 1, can be suppressed.

[0067] The film thicknesses of the first cover layer 18 and the second cover layer 19 may be different from each other, but are preferably the same. This makes it possible to suppress warping of the optical waveguide 1 due to differences in film thickness. Note that "the same film thickness" means that the difference in film thickness is 5 μm or less.

[0068] Examples of the main material of the first cover layer 18 and the second cover layer 19 include materials containing various resins such as polyolefins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene, and polypropylene, fluororesins such as polyimide, polyamide, polyetherimide, polyamideimide, and polytetrafluoroethylene (PTFE), polycarbonate, polyethersulfone, polyphenylene sulfide, and liquid crystal polymers.

[0069] The main materials of the first cover layer 18 and the second cover layer 19 may be different from each other, but are preferably the same from each other, which makes it possible to suppress warping of the optical waveguide 1 due to differences in the main materials.

[0070] The elastic modulus of the first cover layer 18 and the second cover layer 19 is preferably 1 to 12 GPa, more preferably 2 to 11 GPa, and even more preferably 3 to 10 GPa. The elastic modulus is the tensile modulus.

[0071] 2.1.2.2. Cladding-forming resin composition The above-mentioned resin composition for forming the cladding may be, for example, a composition containing a polymer, a monomer, a polymerization initiator, and the like.

[0072] Polymers Examples of polymers include acrylic resins, methacrylic resins, polycarbonate, polystyrene, cyclic ether resins such as epoxy resins and oxetane resins, polyamide, polyimide, polybenzoxazole, polysilane, polysilazane, silicone resins, fluorine-containing resins, polyurethane, polyolefin resins, polybutadiene, polyisoprene, polychloroprene, polyesters such as PET and PBT, polyethylene succinate, polysulfone, polyether, cyclic olefin resins such as benzocyclobutene resins and norbornene resins, and phenoxy resins. One or more of these may be combined and used as a polymer alloy, polymer blend (mixture), copolymer, etc.

[0073] Among these, acrylic resins, phenoxy resins, and cyclic olefin resins are preferably used as the polymer.

[0074] Examples of acrylic resins include polymers of acrylic compounds containing one or more selected from the group consisting of monofunctional acrylates, polyfunctional acrylates, monofunctional methacrylates, polyfunctional methacrylates, urethane acrylates, urethane methacrylates, epoxy acrylates, epoxy methacrylates, polyester acrylates, and urea acrylates. The acrylic resins may have a polyester skeleton, a polypropylene glycol skeleton, a bisphenol skeleton, a fluorene skeleton, a tricyclodecane skeleton, a dicyclopentadiene skeleton, or the like.

[0075] Examples of phenoxy resins include those containing bisphenol A, bisphenol A type epoxy compounds or derivatives thereof, and bisphenol F, bisphenol F type epoxy compounds or derivatives thereof as copolymerization component units.

[0076] The polymer may also contain a thermosetting resin, if necessary, such as an amino resin, an isocyanate compound, a blocked isocyanate compound, a maleimide compound, a benzoxazine compound, an oxazoline compound, a carbodiimide compound, a cyclocarbonate compound, a polyfunctional oxetane compound, an episulfide resin, or an epoxy resin.

[0077] The polymer content is preferably 15% by mass or more, more preferably 40% by mass or more, and even more preferably 60% by mass or more, of the total solid content of the cladding-forming resin composition. This improves the mechanical properties of the first cladding layer 11 and the second cladding layer 12. The polymer content in the cladding-forming resin composition is preferably 95% by mass or less, more preferably 90% by mass or less, of the total solid content of the cladding-forming resin composition. This improves the optical properties of the first cladding layer 11 and the second cladding layer 12.

[0078] The total solid content of the cladding-forming resin composition refers to the nonvolatile content in the composition, ie, the remainder excluding volatile components such as water and solvent.

[0079] Monomers The monomer is not particularly limited as long as it is a compound having a polymerizable site in its molecular structure, but examples thereof include acrylic acid (methacrylic acid)-based monomers, epoxy-based monomers, oxetane-based monomers, norbornene-based monomers, vinyl ether-based monomers, styrene-based monomers, and photodimerization monomers, and one or more of these may be used in combination.

[0080] Among these, acrylic acid (methacrylic acid)-based monomers or epoxy-based monomers are preferably used as the monomer.

[0081] Examples of acrylic acid (methacrylic acid)-based monomers include compounds having two or more ethylenically unsaturated groups, and bifunctional or trifunctional or higher functional (meth)acrylates. Specific examples include aliphatic (meth)acrylates, alicyclic (meth)acrylates, aromatic (meth)acrylates, heterocyclic (meth)acrylates, and their ethoxylated, propoxylated, ethoxylated propoxylated, and caprolactone-modified derivatives. Furthermore, the monomers may have a bisphenol skeleton, a urethane skeleton, or the like in the molecule.

[0082] Examples of epoxy-based monomers include alicyclic epoxy compounds, aromatic epoxy compounds, and aliphatic epoxy compounds.

[0083] The content of the monomer is preferably 1 part by mass or more and 70 parts by mass or less, and more preferably 10 parts by mass or more and 60 parts by mass or less, relative to 100 parts by mass of the polymer.

[0084] 2.1.2.2.3. Polymerization initiator The polymerization initiator is appropriately selected depending on the type of polymerization reaction or crosslinking reaction of the monomer. Examples of the polymerization initiator that can be used include radical polymerization initiators such as acrylic acid (methacrylic acid) monomers and styrene monomers, and cationic polymerization initiators such as epoxy monomers, oxetane monomers, and vinyl ether monomers.

[0085] Examples of the radical polymerization initiator include benzophenones, acetophenones, etc. Specific examples include Irgacure 651, Irgacure 819, Irgacure 2959, and Irgacure 184 (all manufactured by IGM Japan LLC).

[0086] Examples of cationic polymerization initiators include Lewis acid generators such as diazonium salts, and Bronsted acid generators such as iodonium salts and sulfonium salts. Specific examples include ADEKA OPTOMER SP-170 (manufactured by ADEKA Corporation), SAN-AID SI-100L (manufactured by Sanshin Chemical Industry Co., Ltd.), and Rhodorsil 2074 (manufactured by Rhodia Japan Co., Ltd.).

[0087] The content of the polymerization initiator is preferably 0.01 to 5 parts by mass, and more preferably 0.05 to 3 parts by mass, per 100 parts by mass of the polymer, which allows the monomers to react quickly without deteriorating the optical and mechanical properties of the first cladding layer 11 and the second cladding layer 12.

[0088] Other The clad-forming resin composition may further contain, for example, a crosslinking agent, a sensitizer (photosensitizer), a catalyst precursor, a cocatalyst, an antioxidant, an ultraviolet absorber, a light stabilizer, a silane coupling agent, a coating surface improver, a thermal polymerization inhibitor, a leveling agent, a surfactant, a colorant, a storage stabilizer, a plasticizer, a lubricant, a filler, inorganic particles, an antidegradant, a wettability improver, an antistatic agent, and the like.

[0089] Solvents The above-mentioned components are added to a solvent and stirred to obtain a varnish-like clad-forming resin composition. The obtained composition may be subjected to filtration using a PTFE filter with a pore size of 0.2 μm, for example. Alternatively, the obtained composition may be subjected to mixing using various mixers.

[0090] Examples of the solvent contained in the resin composition for forming the cladding include organic solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, ethyl acetate, cyclohexane, heptane, cyclohexane, cyclohexanone, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol dimethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, cellosolve-based solvents, carbitol-based solvents, anisole, and N-methylpyrrolidone, and one or a mixture of two or more of these solvents can be used.

[0091] The clad-forming resin composition for forming the first clad layer 11 and the clad-forming resin composition for forming the second clad layer 12 may be the same as or different from each other.

[0092] 2.2. Core layer formation process In the core layer formation step S104, the core layer 13 is formed from the core formation layer 160. Specifically, a part of the core formation layer 160 is irradiated with active radiation R to obtain the core layer 13 including a plurality of core portions 14 corresponding to the non-irradiated regions 302 and side cladding portions 15 located between the core portions 14 and corresponding to the irradiated regions 301.

[0093] 4(b) is used to set the irradiation region 301 and the non-irradiation region 302. By irradiating the active radiation R through the photomask 303, the irradiation region 301 and the non-irradiation region 302 can be set according to the mask pattern of the photomask 303.

[0094] Instead of using the photomask 303, a direct imaging exposure machine 304 may be used. In FIG. 4(c), the actinic radiation R is irradiated by the direct imaging exposure machine 304. Examples of the direct imaging exposure machine 304 include exposure machines that can select an irradiation area using various spatial light modulators, such as a reflective spatial light modulator such as a digital micromirror device (DMD) or a transmissive spatial light modulator such as a liquid crystal display (LCD). By using such a direct imaging exposure machine 304, it is possible to set the irradiation area 301 and the non-irradiation area 302 without using a photomask 303. This allows the sizes of the irradiation area 301 and the non-irradiation area 302 to be adjusted without changing the photomask 303, thereby reducing the manufacturing cost and improving the efficiency of the optical waveguide 1.

[0095] 4(b) and 4(c) show the polymer 131 and the monomer 132 contained in the core forming layer 160. In the core forming layer 160 before being irradiated with actinic radiation R, the monomer 132 is distributed almost uniformly in the polymer 131. Note that here, the monomer 132 and the structure derived from the monomer 132 have a lower refractive index than the polymer 131.

[0096] After irradiation with actinic radiation R, the core forming layer 160 is heated. This heating activates the polymerization initiator present in the irradiated region 301, causing the reaction of the monomer 132 to proceed. This causes a difference in concentration of the monomer 132, which in turn causes the monomer 132 to move. As a result, as shown in FIG. 5(d), the concentration of the monomer 132 in the irradiated region 301 increases, while the concentration of the monomer 132 in the non-irradiated region 302 decreases. As a result, the refractive index of the irradiated region 301 decreases due to the influence of the monomer 132, and the refractive index of the non-irradiated region 302 increases due to the influence of the polymer 131. As a result, a core layer 13 including a core portion 14 and a side cladding portion 15 is obtained, as shown in FIG. 5(e).

[0097] The heating conditions for the core forming layer 160 include, for example, a heating temperature of 100 to 200° C. and a heating time of 10 to 180 minutes.

[0098] The refractive index may change due to the evaporation of the monomer 132 or the change in the molecular structure of the polymer 131 as a result of this heating.

[0099] The above describes a method for forming the core layer 13 by irradiating the core-forming resin composition with active radiation R. However, the method for forming the core layer 13 is not limited to the above method. For example, photolithography, replication, etc. may also be used. Photolithography is a method for forming the core portion 14 and the side clad portion 15 using materials with different refractive indices by combining exposure, development, and etching techniques. Replication is a method for forming the core portion 14 by pressing a mold having a core pattern against a resin film, and then forming the side clad portion 15. Furthermore, the core-forming layer 160 before or after irradiation with active radiation R may be subjected to a surface treatment, as necessary. Examples of surface treatments include plasma treatment, corona treatment, ultraviolet irradiation treatment, and electron beam irradiation treatment.

[0100] 2.3. Cladding layer formation process In the cladding layer forming step S106, the first cladding layer 11 and the second cladding layer 12 are laminated on the core layer 13, and the substrate 100 is peeled off, thereby obtaining the optical waveguide 1.

[0101] In this embodiment, as shown in Fig. 5(f), the clad film 402 is laminated on the upper surface of the core layer 13. Then, the obtained laminate is heated. As a result, the core layer 13 and the clad film 402 are bonded together as shown in Fig. 6(g). As a result, the second clad layer 12 covering the core layer 13 is obtained. The heating conditions at this time include, for example, a heating temperature of 100 to 200°C and a heating time of 10 to 180 minutes.

[0102] After peeling the substrate 100 from the core layer 13 as shown in FIG. 6(h), a clad film 401 is laminated on the lower surface of the core layer 13 as shown in FIG. 6(i). The resulting laminate is then heated. This bonds the core layer 13 and the clad film 401 together. As a result, a first clad layer 11 covering the core layer 13 is obtained. Heating conditions at this time include, for example, a heating temperature of 100 to 200°C and a heating time of 10 to 180 minutes. Preferably, the heating temperature is set to a higher temperature or a longer time than the heating conditions used to form the second clad layer 12. In this manner, the optical waveguide 1 shown in FIG. 2 is obtained.

[0103] 2.4. Adjustment of the irradiated and non-irradiated areas Here, the adjustment of the irradiated region 301 and the non-irradiated region 302 in the core layer forming step S104 will be described.

[0104] As described above, in this embodiment, the size of at least one of the irradiated region 301 and the non-irradiated region 302 is adjusted depending on the time that has elapsed since the cladding forming layer 170 was manufactured.

[0105] The cladding forming layer 170 may be manufactured in advance and stored in the form of cladding films 401, 402. In this case, when the cladding layer forming step S106 is performed, the required amount is cut out from the stored cladding films 401, 402 and used. In this case, the elapsed time since the manufacturing of the cladding films 401, 402 used in the cladding layer forming step S106 is not constant, but a large amount of the cladding films 401, 402 can be manufactured in advance, which makes it easier to improve manufacturing efficiency.

[0106] However, it has been found that the pitch P of the core portions 14 changes as the time elapsed since the production of the clad films 401 and 402 changes. The pitch P of the core portions 14 refers to the distance between the optical axes of the core portions 14 when the core portions 14 are lined up along the Y axis as shown in Figure 2.

[0107] Therefore, the present inventors conducted extensive research into the relationship between the time T elapsed since the production of the clad films 401, 402 and the pitch P of the core portions 14. They found that there is a correlation between the two, and that by setting the irradiation range of the actinic radiation R based on this correlation, the pitch P can be made to approach a desired value, which led to the completion of the present invention.

[0108] Specifically, there is a negative correlation between the elapsed time T and the pitch P, and as the elapsed time T of the clad films 401, 402 increases, the core layer 13 shrinks (deforms) along the Y axis due to the clad films 401, 402, and the pitch P decreases.

[0109] Therefore, in this embodiment, when manufacturing an optical waveguide 1 using clad films 401, 402 with a long elapsed time T, the size of at least one of the irradiated region 301 and the non-irradiated region 302 is set large according to the elapsed time T, in anticipation of shrinkage of the core layer 13 due to the clad films 401, 402. This allows the pitch P to approach a target value. As a result, an optical waveguide 1 with a high accuracy in the pitch P of the core portion 14 can be efficiently manufactured.

[0110] The relationship between the elapsed time T and the pitch P also varies depending on the temperature at which the clad films 401, 402 are stored. For example, when the clad films 401, 402 are stored at a low temperature below room temperature, the change in the pitch P is likely to be kept within an acceptable range even if the elapsed time T is long. In contrast, when the clad films 401, 402 are stored at a temperature above room temperature, the change in the pitch P becomes more apparent as the elapsed time T increases.

[0111] Therefore, the elapsed time T may be the number of days stored at room temperature, which is the number of days the pitch P has been left at room temperature. In other words, given that the effect of the elapsed time T on the pitch P is small below room temperature, particularly at temperatures below 10°C, the number of days stored at room temperature may be particularly taken into consideration as the elapsed time T.

[0112] FIG. 7 is a scatter plot showing the correlation between the number of days that a clad film 402 having a second clad layer 12 can be stored at room temperature and the pitch P of the core region 14. In FIG. 7, measured data is represented by dots. The number of days that a clad film 402 can be stored at room temperature is the number of days that have elapsed since the clad film 402 was removed from a refrigerator and began to be stored at room temperature. The temperature inside the refrigerator is 10°C or lower. Room temperature refers to a temperature between 15 and 30°C.

[0113] As shown by the dashed line in Fig. 7, there is a negative correlation between the number of days stored at room temperature and the pitch P, and the longer the number of days the clad films 401, 402 are stored at room temperature, the shorter the pitch P. Note that if the storage temperature is lower than room temperature, the slope of the dashed line is expected to be gentler than in Fig. 7.

[0114] In this embodiment, when the irradiation region 301 and the non-irradiation region 302 are set in the core layer formation step S104, the size of at least one of these regions is corrected by multiplying the original size by a correction factor. By adjusting the size of the irradiation region 301, etc. using the correction factor, even if the core layer 13 is deformed due to the clad films 401 and 402, the pitch P after deformation can be made closer to the target value.

[0115] Fig. 8 is a scatter plot showing the correlation between the number of days x that a clad film 402 having a second clad layer 12 is stored at room temperature and the correction factor y required to correct the shrinkage of the core layer 13 shown in Fig. 7. In Fig. 8, the measured data are indicated by dots.

[0116] As shown in FIG. 8, there is a positive correlation between the number of days x stored at room temperature and the correction factor y, and as the number of days x stored at room temperature increases, the correction factor y required for correction also increases.

[0117] In this case, it is preferable to set the correction magnification y so as to satisfy the following correction formula (1). y=x A (1) [In the above correction formula (1), A is 0.00015 to 0.00045.]

[0118] The correction magnification y expressed by the above correction formula (1) is a magnification for correcting the length in the Y-axis direction of at least one of the irradiation region 301 and the non-irradiation region 302. In Fig. 8, the curve expressed by the above correction formula (1) when A = 0.00015 is shown by a dashed line, and the curve expressed by the above correction formula (1) when A = 0.00045 is shown by a broken line.

[0119] As shown in Fig. 8, the actual measurement data falls within the range of the above correction formula (1). Therefore, by using the above correction formula (1), the correction factor y can be calculated more accurately, taking into account the influence of storage at room temperature. As a result, it is possible to efficiently manufacture optical waveguides 1 with improved accuracy in the pitch P of the core portions 14.

[0120] It is preferable to correct both the length of the irradiated region 301 along the Y axis and the length of the non-irradiated region 302 along the Y axis using a common correction magnification y, but they may be corrected using different correction magnifications y, or only one of them may be corrected. In addition, in the above correction formula (1), it is particularly preferable that A is 0.00020 to 0.00040. Furthermore, correction formula (1) is only an example and is not limited to this. For example, instead of correction formula (1), an equation obtained by adding an arbitrary coefficient to formula (1) may be used.

[0121] The relationship between the time T elapsed since the production of the clad films 401 and 402 and the pitch P of the core portion 14 has been explained above, but in the above-mentioned production method, the influence of the number of days of storage at room temperature on the clad film 401 is not as great as that on the clad film 402. The reason for this is thought to be that the above-mentioned production method employs an order in which the clad film 402 is first laminated onto the core layer 13, and then the clad film 401 is laminated thereon.

[0122] Therefore, when the number of days for which the clad film 401 and the clad film 402 are stored at room temperature differ, the number of days for which the clad film 402 is stored at room temperature should be given priority, and the size of the irradiation area 301 and the like should be adjusted based on that.

[0123] 9 is a graph showing how the pitch P of the core region 14 changes when the number of days of room temperature storage of the clad film 401 having the first clad layer 11 and the clad film 402 having the second clad layer 12 are the same and different from each other. In the example of FIG. 9, the target value of the pitch P is 2750 μm.

[0124] Sample No. 1 is an example in which both clad films 401 and 402 were stored at room temperature for a short period of time.

[0125] Sample No. 2 is an example in which both clad films 401 and 402 were stored at room temperature for a long period of time.

[0126] Sample No. 3 is an example in which clad film 401 has a long shelf life at room temperature and clad film 402 has a short shelf life at room temperature.

[0127] Sample No. 4 is an example in which clad film 401 has a short shelf life at room temperature and clad film 402 has a long shelf life at room temperature.

[0128] 9, when the pitch P of these four samples is compared, when the clad film 402 is stored at room temperature for a long period of time, the amount of change in pitch P from the target value of 2750 μm is larger than when the clad film 401 is stored at room temperature for a long period of time. In contrast, when the clad film 402 is stored at room temperature for a short period of time, the amount of change in pitch P from the target value of 2750 μm is smaller regardless of the clad film 401's storage period at room temperature.

[0129] Based on the above results, it can be seen that the influence of clad film 402, which is laminated on core layer 13 first, is more dominant than the influence of clad film 401, which is laminated on core layer 13 later.

[0130] Depending on the manufacturing method, both clad films 401 and 402 may have a strong effect on pitch P. For example, this may occur when clad films 401 and 402 are simultaneously laminated to core layer 13. In this case, any calculated value, such as the average value of the number of days of room temperature storage of clad films 401 and 402, may be calculated and applied to the number of days of room temperature storage described above.

[0131] As described above, in this embodiment, the irradiation area 301 and the like are adjusted based on the effect that the elapsed time T from the time of production of the clad films 401, 402 has on the pitch P of the core portion 14. As described above, there are several possible mechanisms by which the elapsed time T of the clad films 401, 402 affects the pitch P, but one mechanism is that the rate of the curing reaction in the clad forming layer 170 decreases as the elapsed time T increases.

[0132] Assuming that the rate of the curing reaction does not decrease even if the elapsed time T is long, when the cladding forming layer 170 laminated on the core layer 13 is heated, the cladding forming layer 170 quickly cures and bonds to the core layer 13. Therefore, shrinkage of the core layer 13 should be suppressed.

[0133] On the other hand, if it is assumed that the rate of the curing reaction is slowing down, the curing of the cladding layer 170 is delayed, and it is thought that the shrinkage of the core layer 13 due to heating progresses before the cladding layer 170 is bonded to the core layer 13. It is also thought that the longer the elapsed time T of the cladding films 401, 402, the greater the change in the pitch P of the core portion 14, which coincides with the actual phenomenon.

[0134] As described above, the method for manufacturing an optical waveguide according to this embodiment includes a preparation step S102, a core layer formation step S104, and a cladding layer formation step S106. In the preparation step S102, the core-forming layer 160 and the cladding layer 170 are prepared. In the core-layer formation step S104, a portion of the core-forming layer 160 is irradiated with active radiation R to obtain a core layer 13 including a plurality of core portions 14 corresponding to the non-irradiated region 302 and side cladding portions 15 located between the core portions 14 and corresponding to the irradiated region 301. In the cladding layer formation step S106, the cladding layer 170 is laminated on the core layer 13 and heated to obtain an optical waveguide 1 including the core layer 13, the first cladding layer 11, and the second cladding layer 12. In the core-layer formation step S104, the size of at least one of the irradiated region 301 and the non-irradiated region 302 is adjusted depending on the elapsed time T from the time of manufacturing the cladding layer 170.

[0135] With this configuration, it is possible to appropriately set the size of at least one of the irradiated region 301 and the non-irradiated region 302 in anticipation of deformation of the core layer 13 caused by the cladding films 401, 402 including the cladding forming layer 170. This makes it possible to efficiently manufacture optical waveguides 1 with a high precision in the pitch P of the core portions 14.

[0136] The optical waveguide 1 manufactured in this embodiment includes a core layer 13, and a first cladding layer 11 and a second cladding layer 12 laminated on both sides of the core layer 13. The core layer 13 is provided on a substrate 100 before the step of obtaining the optical waveguide 1, i.e., the cladding layer forming step S106. The cladding layer forming step S106 includes the steps of laminating a cladding forming layer 170 on the core layer 13 to obtain a laminate, peeling the substrate 100 from the laminate, and laminating the cladding forming layer 170 on the core layer 13 and heating the laminate to obtain the optical waveguide 1.

[0137] This configuration provides an optical waveguide 1 having a structure in which a core layer 13 is sandwiched between the first cladding layer 11 and the second cladding layer 12. In such an optical waveguide 1, the difference in refractive index between the core layer 13 and the first cladding layer 11 and the second cladding layer 12 is stable, so that an optical waveguide 1 with low transmission loss can be efficiently manufactured.

[0138] The optical waveguide 1 manufactured in this embodiment further includes a first cover layer 18 and a second cover layer 19. The first cover layer 18 is laminated on the first cladding layer 11 on the side opposite to the core layer 13. The second cover layer 19 is laminated on the second cladding layer 12 on the side opposite to the core layer 13.

[0139] With this configuration, the first cladding layer 11, the second cladding layer 12, and the core layer 13 can be protected by the first cover layer 18 and the second cover layer 19. This increases the durability of the optical waveguide 1. It also improves operability when laminating the first cladding layer 11 and the second cladding layer 12 onto the core layer 13. Specifically, even if the first cladding layer 11 and the second cladding layer 12 are very thin, supporting them with the first cover layer 18 and the second cover layer 19 improves grippability, portability, and the like.

[0140] Although the method for manufacturing an optical waveguide according to the present invention has been described above based on the illustrated embodiments, the present invention is not limited to these.

[0141] For example, the method for manufacturing an optical waveguide of the present invention may be obtained by adding any desired step to the above-described embodiment. [Example]

[0142] Next, specific examples of the present invention will be described. 3. Fabrication of Optical Waveguides 3.1. Preparation of core film 3.1.1. Polymer synthesis Hexylnorbornene (HxNB, 7.2 g, 40.1 mmol) and diphenylmethylnorbornenemethoxysilane (diPhNB, 12.9 g, 40.1 mmol) were weighed into a 500 mL vial in a dry box, and 60 g of dehydrated toluene and 11 g of ethyl acetate were added. The vial was then sealed with a silicone sealer.

[0143] Next, 1.56 g (3.2 mmol) of Ni catalyst and 10 mL of dehydrated toluene were weighed into a 100 mL vial, a stirrer tip was inserted, and the vial was sealed. The catalyst was thoroughly stirred to completely dissolve. 1 mL of this Ni catalyst solution was accurately measured with a syringe and injected into the vial containing the two norbornenes. The mixture was stirred at room temperature for 1 hour, resulting in a significant increase in viscosity. At this point, the stopper was removed, and 60 g of tetrahydrofuran (THF) was added and stirred to obtain a reaction solution.

[0144] Next, 9.5 g of acetic anhydride, 18 g of hydrogen peroxide (30% concentration), and 30 g of ion-exchanged water were added to a 100 mL beaker and stirred to prepare an aqueous solution of peracetic acid. Next, the entire amount of this aqueous solution was added to the reaction solution and stirred for 12 hours to carry out the reduction treatment of Ni.

[0145] Next, the reaction solution was transferred to a separatory funnel, and after removing the lower aqueous layer, 100 mL of a 30% aqueous solution of isopropyl alcohol was added and vigorously stirred. After allowing to stand and allowing the two layers to separate completely, the aqueous layer was removed. This water washing process was repeated three times, and the oil layer was then dropped into a large excess of acetone to reprecipitate the resulting polymer. The polymer was then separated from the filtrate by filtration and dried in a vacuum oven at 60°C for 12 hours to obtain the polymer.

[0146] The molar ratio of each structural unit in the obtained polymer was identified by NMR measurement, and as a result, it was found that the hexylnorbornene structural unit was 50 mol % and the diphenylmethylnorbornenemethoxysilane structural unit was 50 mol %.

[0147] 3.1.2. Preparation of Core-Forming Resin Composition 10 g of the above polymer was weighed into a 100 mL glass container, and 40 g of mesitylene, antioxidant Irganox 1076 (manufactured by BASF, 0.01 g), cyclohexyloxetane monomer (manufactured by Toagosei Co., Ltd., CHOX, 2 g), and polymerization initiator (photoacid generator) Rhodorsil (registered trademark) Photoinitiator 2074 (manufactured by Rhodia, 0.0125 g, dissolved in 0.1 mL of ethyl acetate) were added thereto and dissolved uniformly. The mixture was then filtered through a 0.2 μm PTFE filter to prepare a varnish-like core-forming resin composition.

[0148] 3.1.3. Preparation of the core-forming layer The core-forming resin composition was uniformly applied to a 100 μm-thick PET film that had been subjected to a release treatment using a doctor blade, and then placed in a dryer at 40°C for 5 minutes. The solvent was completely removed to form a coating. This resulted in a core film with a 40 μm-thick core-forming layer.

[0149] 3.2. Exposure process The core film was irradiated with ultraviolet light in a pattern including parallel linear irradiation regions using a direct imaging exposure machine. The core film was then placed in an oven and heated at 160°C for 60 minutes. This resulted in a core layer including linear core portions. The cumulative amount of ultraviolet light was 1300 mJ / cm. 2 It was decided.

[0150] 3.3. Preparation of clad film 3.3.1. Preparation of clad-forming resin composition A varnish-like resin composition for forming a clad was prepared by adding 2-undecylmethylimidazole (C11Z, manufactured by Shikoku Chemicals Corporation, 0.06 g) to and mixing with a norbornene-based resin composition containing a cyclic olefin-based resin (20 wt % 2-heptanone solution of Avatrel (registered trademark) 2590 manufactured by Promerus, 10 g).

[0151] 3.3.2. Preparation of cladding layer The cladding resin composition was uniformly applied with a doctor blade to a 25 μm thick polyimide film (Kapton 100ENC, manufactured by DuPont-Toray Co., Ltd.) and a 25 μm thick polyimide film (Upilex 25SGA, manufactured by Ube Industries, Ltd.), and then dried for 15 minutes in a dryer at 45° C. This produced two cladding films each having a 6 μm thick cladding-forming layer.

[0152] 3.4. Fabrication of optical waveguide Two clad films were cooled in a refrigerator with an internal temperature of 5°C and then placed at 22°C (room temperature) for a specified number of days. A clad film made from a 25 μm-thick polyimide film (Kapton 100ENC, manufactured by DuPont-Toray Co., Ltd.) left at room temperature was then fixed by adsorption to a bonding device. Meanwhile, a core film with a core layer formed thereon was subjected to plasma treatment and then fixed by adsorption to the bonding device. The plasma treatment involved exposing the core film to an atmosphere of 10 Pa and oxygen introduced at 100 mL / min using a plasma device. The clad-forming layer of the clad film was then laminated onto the core film to obtain a laminate. The laminate was then thermocompressed using a laminator. The resulting bonded body was placed in an oven and heated at 160°C for 30 minutes. The bonded body was then gradually cooled to room temperature.

[0153] Next, a clad film made of a 25 μm thick polyimide film (Upilex 25SGA manufactured by Ube Industries) that had been left at room temperature was adsorbed and fixed to a lamination device. Meanwhile, the substrate was peeled off from the core film on which the core layer had been formed. After corona treatment was applied to the peeled surface, the clad-forming layer of the clad film was laminated on the peeled surface of the core layer to obtain a laminate. The laminate was then thermocompressed using a laminator. The resulting pressed body was placed in an oven and heated at 180°C for 120 minutes to obtain an optical waveguide.

[0154] Then, a plurality of optical waveguides were manufactured by the above method while varying the number of days for which the clad film was stored at room temperature.

[0155] 4.Evaluation of optical waveguides The core pitch of the fabricated optical waveguides was measured. The measured pitch and the number of days the cladding film used to fabricate the optical waveguides had been stored at room temperature were plotted on an orthogonal coordinate system. This resulted in the scatter diagram shown in Figure 7.

[0156] As shown in Fig. 7, a negative correlation was observed between the number of days the cladding film was stored at room temperature and the core pitch, as indicated by the dashed line in Fig. 7. Therefore, by utilizing this correlation, it was found that optical waveguides with highly accurate core pitches can be efficiently manufactured by adjusting the size of at least one of the irradiated and non-irradiated regions depending on the time elapsed since the production of the cladding film having a cladding-forming layer. [Explanation of symbols]

[0157] 1 Optical waveguide 11 First cladding layer 12 Second cladding layer 13 Core layer 14 Core section 15 Side cladding 18 First Cover Layer 19 Second Cover Layer 100 Base material 101 End face 102 End face 131 Polymer 132 Monomer 160 Core cambium 170 Cladding layer 200 core film 301 Irradiation area 302 Non-irradiated area 303 Photomask 304 Direct imaging exposure machine 401 Clad Film 402 Clad Film Pitch R active radiation S102 Preparation process S104 Core layer formation process S106 Cladding layer formation process x number of days stored at room temperature y correction factor

Claims

1. providing a core forming layer and a cladding forming layer; irradiating a portion of the core-forming layer with active radiation to obtain a core layer including a plurality of core portions corresponding to non-irradiated regions and aligned in a predetermined direction, and side clad portions positioned between the core portions and corresponding to the irradiated regions; a step of laminating the cladding layer on the core layer and heating the resulting layer to obtain an optical waveguide having the core layer and the cladding layer; and A method for manufacturing an optical waveguide, characterized in that the size of at least one of the irradiated area and the non-irradiated area in the direction in which the core portions are arranged is adjusted depending on the elapsed time from the time of manufacturing the cladding forming layer.

2. The elapsed time is the number of days stored at room temperature, 2. The method for manufacturing an optical waveguide according to claim 1, wherein the correction factor when adjusting the size is y and the number of days of storage at room temperature is x, and the correction factor is set so as to satisfy the following correction formula (1): y=x Ａ (1) [In the correction formula (1), A is 0.00015 to 0.00045.]

3. 3. The method for manufacturing an optical waveguide according to claim 1, wherein the cladding layer has a thickness of 1 to 200 μm.

4. The optical waveguide is the core layer; a first clad layer and a second clad layer, which are the clad layers laminated on both sides of the core layer; Equipped with the core layer is provided on a substrate before the step of obtaining the optical waveguide; The step of obtaining the optical waveguide includes: laminating the cladding layer on the core layer to obtain a laminate; peeling the substrate from the laminate; laminating the cladding layer on the core layer and heating the cladding layer to obtain the optical waveguide; The method for manufacturing an optical waveguide according to any one of claims 1 to 3, comprising:

5. The optical waveguide is a first cover layer laminated on the first clad layer on the opposite side of the core layer; a second cover layer laminated on the second clad layer on the opposite side of the core layer; The method for manufacturing an optical waveguide according to claim 4 , further comprising:

6. 6. The method for manufacturing an optical waveguide according to claim 1, wherein the film thickness of the optical waveguide is 50 to 300 μm.

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