JP2006023375A - Optical waveguide manufacturing method and the optical waveguide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method with which a high-quality optical waveguide can be easily manufactured, and to provide the optical waveguide formed thereby. <P>SOLUTION: The optical waveguide manufacturing method includes a forming step, in which a core layer 11 formed on a support base is cut in a prescribed shape, with the support base 10 left uncut and with the unnecessary parts of the cut core layer 11 removed; a coating step, in which the surface of the support base 10 and the core layer 11 are coated with material having a refractive index lower than that of the core layer 11; and a separating step, in which the support base 10 and the coating layer 12 are cut in the circumference of the core layer 11 precut in the prescribed shape and are then cut off dividedly by each core layer 11. The optical waveguide 1 is manufactured using this method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical waveguide manufacturing method and an optical waveguide, and more particularly to an optical waveguide manufacturing method used in various optical communication components and an optical waveguide obtained thereby.

  With the development of optical communication technology in recent years, development of a high-performance optical waveguide is desired as a basic element constituting optical communication components such as an optical switch and an optical multiplexer / demultiplexer. An optical waveguide generally has a basic structure in which a core layer and an upper cladding layer are sequentially formed on a substrate directly or via a lower cladding layer. As a material for the core layer, inorganic materials such as quartz glass are mainly used as in the case of optical fibers because of its advantages such as low light propagation loss. Recently, however, it is excellent in workability and cost. Studies on polymer optical waveguides using organic materials such as synthetic resins have been underway.

  For example, Patent Document 1 mentions a plastic optical waveguide using polymethyl methacrylate (PMMA), polystyrene (PS), polycarbonate (PC), polyimide (PI), or the like. Also, from the viewpoint of excellent heat resistance, various studies have been made on polymer optical waveguides using specific polyimide resins (see Patent Document 2).

As a method for manufacturing such a polymer optical waveguide, a method of forming a core layer using a direct exposure method, a reactive ion etching method, a photo bleaching method, or the like is known (for example, described in Patent Document 3). .
JP-A-6-347658 (paragraph [0002] etc.) JP 2001-108854 A (paragraphs [0005], [0006], etc.) JP 2004-109927 A (paragraph [0002] etc.)

  However, the above-mentioned conventional manufacturing method is expensive because it uses photolithography, and has various difficulties such as not being able to ensure a sufficient difference in refractive index, and is easier to manufacture and has a desired It has been desired to realize a technique capable of obtaining an optical waveguide having high performance.

  Accordingly, an object of the present invention is to provide an optical waveguide manufacturing method capable of easily manufacturing a high-quality optical waveguide, and an optical waveguide obtained thereby.

In order to solve the above-described problems, the optical waveguide manufacturing method of the present invention cuts the core layer formed on the supporting base material into a predetermined shape, leaving the supporting base material. A molding process to remove unnecessary parts,
A coating step of coating the surface of the support substrate and the core layer using a material having a refractive index lower than that of the core layer;
And a separation step of cutting the support base material and the coating layer around the core layer cut into the predetermined shape and separating the core layer into the core layers.

  In the production method of the present invention, it is preferable that the core layer is cut by punching with a blade mold generally called a half cut. In addition, it is also preferable that at least one of the forming step, the covering step, and the separating step is continuously performed using a roll-to-roll method. Thus, by cutting only the core layer portion while leaving the support base material, it is possible to apply a roll-to-roll system.

  The optical waveguide of the present invention is manufactured by the above-described optical waveguide manufacturing method of the present invention, and in particular, the refractive index of the core layer is from the center in the thickness direction. It is preferable that it decreases continuously toward the front and back.

  In the optical waveguide of the present invention, the core layer may have one or more incident portions and one or more exit portions, and in particular, the shape of the core layer may be one incident portion and It can be made into a strip shape having one emitting part.

  According to the present invention, by adopting the above-described configuration, a high-quality optical waveguide can be easily manufactured as compared with the prior art, and the cost is excellent. In addition, when the coating process is continuously performed using a roll-to-roll method, mass production becomes possible, so that productivity can be improved.

Hereinafter, preferred embodiments of the present invention will be described in detail.
1A to 1D show an example of a manufacturing process of the optical waveguide of the present invention. As shown in the figure, in the present invention, when manufacturing an optical waveguide, first, the core layer 11 formed on the support base material 10 as shown in FIG. It cut | disconnects in a shape, and the unnecessary part of the cut | disconnected core layer 11 is removed (a shaping | molding process (refer the figure (b))). Next, as shown in FIG. 3C, the surfaces of the support base 10 and the core layer 11 are coated using a material having a lower refractive index than that of the core layer 11 (coating step). Thereafter, the support base material 10 and the coating layer 12 are cut around the core layer 11 cut into a predetermined shape, and are cut into each core layer 11 to obtain a desired shape as shown in FIG. The optical waveguide 1 can be obtained (separation step).

  The cutting of the core layer 11 in the molding step can be performed using, for example, punching with a Thomson blade mold, laser cutting, slitting with a rotary blade, or the like, but only the core layer 11 is cut leaving the support substrate 10. As long as it can be used, there is no particular limitation. Especially, it is preferable to cut | disconnect by punching with a Thomson blade type | mold, and, thereby, a smooth cut surface can be obtained. In the case of punching with a Thomson blade mold, it is necessary to control the vertical width of the blade with precision so as not to cut the support base material. In the case of laser cutting, it is necessary to devise so that the output is precisely controlled and the cutting speed is adjusted so that only the desired portion is left without cutting the supporting base material.

  In addition, the molding step, the covering step, and the separation step according to the present invention can all be performed continuously using a roll-to-roll method, and preferably all the manufacturing steps are continuously performed using a roll-to-roll method. This can contribute to the improvement of productivity. Specifically, as shown in FIG. 5A, first, a support base material 10 made of a polymer film having flexibility is unwound from a roll 21, and is applied onto the support base material 10 in a coating part A. The core layer 11 is applied and dried (or cured) in the dried (cured) part B. In order to obtain the core layer 11 with a desired thickness or to form a GI-type core layer 11 described later, the core layer 11 is further laminated through the coating part C and the drying (curing) part D. In the illustrated example, the coating / drying (curing) process is performed twice in total, but may be repeated three or more times according to the target core layer 11 and is not limited.

  After the core layer 11 is formed, the core layer 11 is cut at the punched portion E as the molding step. Of the core layer 11 cut into a predetermined shape while leaving the support base material 10, unnecessary portions are wound up and removed by the roll 22. Subsequently, in the coating part F, the surface of the support base material 10 and the core layer 11 is covered with a material having a lower refractive index than the core layer 11, and drying (or curing) is performed by the drying (curing) part G. The covering layer 12 is formed. Thereafter, the support base material 10 and the coating layer 12 are cut by the punched portion H, and the optical waveguide 1 having a desired shape can be obtained. In addition, the cutting method as the separation step in the punched portion H is not particularly limited, and can be performed in the same manner as the molding step in the punched portion E described above. Finally, the unnecessary support substrate 10 and coating layer 12 after cutting are wound up by the roll 23.

  As shown in FIG. 1D, an optical waveguide of the present invention obtained by such a series of steps has a core layer 11 and an upper clad layer having a lower refractive index than the core layer 11 ( The covering layer) 12 has a structure formed in order, and the signal light is incident-propagated-emitted through the core layer 11.

Even if the core layer 11 according to the present invention is an SI (step index) type having a uniform refractive index, a refractive index distribution exists in the core layer, and the refractive index of the core layer is the central portion in the thickness direction. Although it may be a GI (graded index) type continuously decreasing from the front to the back, a GI type is preferred. GI type optical waveguides are known to have low loss over a wide wavelength range and suitable for high-speed and large-capacity transmission because the propagation time is constant regardless of the path of the light beam. By doing so, a higher performance optical waveguide can be obtained. More preferably, when the refractive index of the central portion A in the thickness direction of the core layer 11 shown in the figure is n _A and the refractive indexes of the front and back surfaces B and B ′ are n _B and n _B ′ (see FIG. 1D). ), The core layer 11 is formed so that the refractive index continuously changes in a substantially quadratic curve shape in the thickness direction as shown in FIG. As a result, a high-performance optical waveguide with lower transmission loss can be obtained.

  In the present invention, by using the above manufacturing method, the optical waveguide 1 having a structure in which the core layer 11 has one or more incident portions and one or more output portions can be easily obtained. 2A to 2C show examples of suitable configurations of the optical waveguide of the present invention. For example, in the example shown in FIG. 2A, the core layer 11 is formed in a strip shape having one incident portion 13a and one emission portion 14a. Moreover, in the figure (b), the core layer 11 is formed in the shape which has the one incident part 13b and the two output parts 14b, and in the example of the figure (c), the core layer 11 is respectively It is formed in a shape having two incident portions 13c and emission portions 14c. Of course, three or more incident portions and / or emission portions may be provided, and the core layer can be appropriately formed according to the application, and is not limited to the illustrated example.

  The material of the core layer 11 is not particularly limited, and various monomers (including solutions) and oligomers (including solutions) such as ultraviolet (UV) curable, electron beam (EB) curable, and thermosetting types. From the viewpoint of required properties as a core layer such as transparency and heat resistance, the polymer solution can be appropriately selected and used in combination.

（式中、Ｒ¹は水素原子またはメチル基を表し、Ｒ²は炭素数８〜２０のアルキル基を表す）で表される化合物、ジ（メタ）アクリルエステル、トリ（メタ）アクリルエステル、さらには、スチレン、ジビニルベンゼン等のスチレン系モノマーなどを挙げることができる。 Among these monomers, for example, acrylic acid, methacrylic acid and their lower alcohol esters, the following general formula (1),

(Wherein R ¹ represents a hydrogen atom or a methyl group, and R ² represents an alkyl group having 8 to 20 carbon atoms), a di (meth) acryl ester, a tri (meth) acryl ester, May include styrene monomers such as styrene and divinylbenzene.

  Examples of the lower alcohol of the lower alcohol ester of acrylic acid and methacrylic acid include monohydric alcohols having 1 to 5 carbon atoms, preferably 1 to 3 carbon atoms, more preferably methanol.

Moreover, in the compound represented by the general formula (1), R ² representing a higher alkyl group having 8 to 20 carbon atoms preferably has 10 to 16 carbon atoms, more preferably 12 to 14 carbon atoms. The higher alkyl group R ² may be a single alkyl group or a mixed alkyl group, but is most preferably a mixed alkyl group having 12 and 13 carbon atoms. In this case, the ratio of the alkyl group having 12 carbon atoms and the alkyl group having 13 carbon atoms, that is, the ratio of dodecyl (meth) acrylate and tridecyl (meth) acrylate is usually 20:80 to 80:20, and particularly preferably 40:60 to 60:40.

において、ｎが１〜１５、特に１〜１０のものが好ましい。 Di (meth) acrylic esters include diesters of ethylene glycol and (meth) acrylic acid, diesters of polyethylene glycol and (meth) acrylic acid, diols having 3 to 6 carbon atoms in the alkyl chain, and (meth) acrylic acid. And a diester. Examples of tri (meth) acrylic esters include triesters of triols having 3 to 6 carbon atoms in the alkyl chain and (meth) acrylic acid. In addition, as polyethyleneglycol which comprises diester of polyethyleneglycol and (meth) acrylic acid, the following general formula (2),

In which n is 1 to 15, particularly 1 to 10.

  As a method for forming a layer by polymerizing or copolymerizing the above monomers, a curing method using heat or light is generally used, but is not particularly limited. In general, in the case of thermosetting, t-butyl hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, dimyristyl peroxydicarbonate, t-butyl peroxyacetate, t- Polymerization initiators such as organic peroxides such as butyl peroxy (2-ethylhexanoate) and cumyl peroxy octoate, azo compounds such as azobisisobutyronitrile and azobiscyclohexanenitrile are added, and 50 to A method of polymerizing at 120 ° C. for 1 to 20 hours can be employed. In addition, as a polymerization initiator in the case of photocuring, ketal compounds such as benzyl methyl ketal and acetophenone diethyl ketal, ketone compounds such as α-hydroxyketone, Michler's ketone, α-hydroxycyclohexyl phenyl ketone, and benzophenones such as benzophenone A compound, a metallocene compound such as metallocene, a benzoin compound such as benzoin isopropyl ether, and the like are preferably used.

  In addition, together with the above monomers, one or more of phosphoric acid esters, aromatic carboxylic acid esters, aliphatic carboxylic acids, aliphatic carboxylic acid esters, glycols and glycol (meth) acrylates may be blended and used. From the point of preventing white turbidity when left for a long time under high temperature and high humidity.

  Examples of the polymer include polyester resins such as (meth) acrylic resin (ester of (meth) acrylic acid), polycarbonate (PC), polyethylene terephthalate (PET), polybutylene terephthalate (PBT) (crystal, non-crystalline). Crystal), polyethersulfone, polynorbornene, epoxy resin, for example, bisphenol A type, novolak type epoxy resin and polyaminoamide, modified polyaminoamide, modified aromatic polyamine, modified aliphatic polyamine, modified alicyclic polyamine, phenol Cured products with active hydrogen such as polyaryl, polyimide (PI), polycarbodiimide, polyetherimide, polyamideimide, polyesterimide, polyamide (PA), polystyrene (PS), acrylonitrile -Styrene copolymers such as styrene copolymer (AS), methyl methacrylate-styrene copolymer (MS, MMA-St), styrene-butadiene block copolymer (SBS), acrylonitrile-butadiene-styrene copolymer (ABS) Resins (among others, SBS and ABS have the advantage of excellent impact resistance), polyarylene ethers such as polyphenylene ether, polyarylate (PAR), polyacetal, polyphenylene sulfide, polysulfone, polyether ether ketone and polyether ketone ketone Polyether ketones, polyvinyl alcohol, polyvinyl pyrrolidone, styrene-ethylene-butadiene-styrene block polymer (SEBS), vinylidene fluoride resin, hexafluoropropylene resin, hexafluoro Etc. can be mentioned fluorine-based resin such as acetone resins, among others, (meth) acrylic resin is preferable.

  Other transparent resins include polyvinyl chloride (PVC), cycloolefin polymer (trade name: Arton (JSR Co., Ltd.), Zeonex (Nippon Zeon Co., Ltd., etc.), polypropylene (PP), polyethylene (PE), Examples include triacetyl cellulose (TAC) resin, polyether sulfone (PES), phenol resin, polysulfone (PSF) resin, etc. Among them, styrene resins, particularly those starting from monomers or low molecular weight materials MS resin, (meth) acrylic resin, and epoxy resin.

  In addition to copolymers of acrylic acid, methacrylic acid and their lower alcohol esters and styrenic monomers, transparent resins using monomers in which some or all of the above-described monomers are replaced with fluorine atoms, etc. Can also be used.

  The core layer 11 can be formed according to a conventional method using the above-described various materials. In particular, when the core layer 11 is a GI type, for example, the following method can be suitably used. That is, first, a solution in which two or more kinds of organic materials having different refractive indexes are dissolved is prepared, and two or more kinds, preferably three kinds or more, and more preferably four kinds or more solutions are obtained. The layers are coated and laminated so that the refractive index increases sequentially from the lowest. After applying the solution with the highest refractive index, the refractive index in the core layer 11 can be continuously reduced as described above by further applying and laminating the refractive index sequentially. it can.

For example, a solution in which four types of organic materials having different refractive indexes are dissolved is prepared, and as shown in FIG. Sequentially, seven layers indicated by reference numerals 11d, 11c, 11b, 11a, 11b, 11c, and 11d are formed. If the refractive index of each layer 11a~11d respectively and n _a ~n _d, they satisfy the relation: _{n d <n c <n b} <n a. Therefore, as the number of types of solutions increases, a refractive index gradient with higher continuity can be formed.

  Such solutions having different refractive indexes can be suitably prepared by using two or more types of organic materials having different refractive indexes and changing the mixing ratio of these organic materials. In addition, the refractive index can be adjusted by using an additive that does not cause a problem in required performance such as light transmittance. Such a combination of organic materials can be appropriately selected from the above-described materials of the core layer 11 from the viewpoint of compatibility and the like which are problematic when mixed.

  Further, the above-mentioned solution has a refractive index difference of 0.1 or more, particularly 0.1 to 1.0 after the solvent is removed between the solution having the highest refractive index and the solution having the lowest refractive index. It is preferable to adjust so that it may become inside. Thereby, in the obtained core layer 11, the refractive index difference between the central portion in the thickness direction and the front and back surfaces can be secured to 0.1 or more, particularly within a range of 0.1 to 1.0, By reducing the transmission loss, the utilization efficiency of incident light can be further improved.

  Furthermore, at the time of coating formation of the GI core layer, it is preferable to coat and form the upper layer using a solvent in which the layer coated and formed immediately before can be dissolved. That is, after forming the previous layer, when forming the next layer, the drying speed is adjusted so that the surface of the previously formed layer is dissolved by the solvent of the next layer. Thereby, the mutual diffusion of the layer materials in contact with each other at the interface between the respective layers can be promoted, and the continuity of the refractive index change of the core layer 11 can be further increased. For the same reason, when using a curable material, first coat the first layer, then crosslink to a dry, cured, semi-cured state, and then apply the second layer. Regarding the second layer, it is preferable to perform drying or curing after allowing time for the first layer material and the second layer material to interdiffuse in the vicinity of the interface. Thereafter, by coating all the layers in the same manner, mutual diffusion occurs at the interface of each layer, and an extremely smooth refractive index change can be realized, and the core layer 11 having the most excellent continuity is formed. can do.

  The method for applying the solution is not particularly limited, and an appropriate method such as gravure printing, doctor blade, bar coater, spin coating, dipping, spray coating or the like can be used. Further, the solvent is not particularly limited, and can be appropriately selected from conventional organic solvents such as acetone, methyl ethyl ketone (MEK), ethyl acetate, cellosolve, dioxane, tetrahydrofuran (THF), benzene, cyclohexanone, and the like. .

  The material for forming the upper cladding layer 12 can be appropriately selected from commonly used materials and has flexibility such as plastic and elastomer and can be molded into a desired shape. In addition, a material having a low refractive index can be preferably used. Specifically, for example, polyethylene, polypropylene, polyamide, polystyrene, acrylonitrile-butadiene-styrene (ABS) resin, polymethyl methacrylate, polycarbonate, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyethylene-vinyl acetate copolymer, Polyvinyl alcohol, polyethylene-polyvinyl alcohol copolymer, fluororesin, silicone resin, natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer, butyl rubber, halogenated butyl rubber, chloroprene rubber, acrylic rubber, ethylene-propylene- Examples thereof include diene terpolymer (EPDM), acrylonitrile-butadiene copolymer, fluororubber, and silicone rubber.

  Among these, silicone polymers and fluorine polymers having a low refractive index are particularly preferable. Specifically, silicone polymers such as polydimethylsiloxane polymer, polymethylphenylsiloxane polymer, fluorosilicone polymer, polytetrafluoroethylene (PTFE), Tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFE), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-ethylene copolymer (ETFE), polyvinylidene fluoride, polyvinyl fluoride, vinylidene fluoride-trifluoroethylene chloride copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoride ethylene Terpolymer, tetrafluoroethylene-propylene rubbers, and fluorine-based thermoplastic elastomers. These materials can be used alone or in admixture of two or more. Note that the same material may be used when providing the lower cladding layer. In the present invention, the upper and lower clad layers in the thickness direction are not necessarily required, and the object can be achieved if there are clad layers on both sides.

  The supporting base material 10 can be appropriately selected from conventionally known materials and is not particularly limited. For example, a silicon substrate, a quartz substrate, a metal foil, a glass plate, A molecular film or the like can be used.

  In the present invention, the structure of the optical waveguide is not limited to the illustrated example, and may be a suitable structure such as a planar type, a slab type, a ridge type, a lens type, and an embedded type.

Hereinafter, the present invention will be described specifically by way of examples.
Example An optical waveguide was prepared using a styrene monomer having a refractive index of 1.59 after heat curing and a methyl methacrylate monomer having a refractive index of 1.49. A polyethylene terephthalate (PET) film having a thickness of 100 μm was used as the supporting substrate.

  First, as a monomer preparation, M solution was prepared by adding 1% by weight of benzoin isopropyl ether as a photopolymerization initiator to methyl methacrylate monomer. Similarly, benzoin isopropyl ether as a photopolymerization initiator for styrene monomer. S solution was obtained by adding 1% by weight. Next, mixed solutions (1) to (5) shown in Table 1 below were prepared using the M solution and the S solution.

Next, a bar coater was used to form the core layer. First, after coating the solution (1) with a thickness of 1 μm on a PET film as a supporting substrate, the film coated with the solution (1) was irradiated with ultraviolet rays of 1000 mJ / cm under an atmosphere substituted with nitrogen. ² Irradiation was performed to cure the coating film of the solution (1). Next, the solution (2) was applied to the cured film of the solution (1) with a bar coater to a thickness of 1 μm, and the cured film (1) was sufficiently swollen with the solution (2), and then similarly. The coating film of the solution (2) was cured by irradiating ultraviolet rays with 1000 mJ / cm ² in an atmosphere substituted with nitrogen. Thereafter, the solutions (3) to (5) were sequentially applied / cured in the same manner to form a cured film.

Thereafter, coating / curing was repeated in the order of decreasing refractive index with the solutions (4), (3), (2), and (1), thereby forming each cured film. Finally, a total of 9 layers of coated / cured films so far are irradiated with ultraviolet rays of 5000 mJ / cm ² in a nitrogen-substituted atmosphere, and all the layers are cured almost completely, whereby the core layer Formed.

  The obtained core layer is punched into a strip of 5 mm width, leaving the PET film as the supporting substrate, and the solution (1) is applied to the step formed between the supporting substrate and the clad layer. did. The optical waveguide of the example was manufactured as described above.

Comparative Examples 1-3
As Comparative Examples 1 and 2, optical waveguides each having a core layer formed of only the solution (1) or (5) were produced. In addition, 1 μm thick sheets of the solutions (1) to (5) are respectively prepared, and these sheets are sequentially stacked so that the center in the thickness direction has the highest refractive index to form a nine-layer structure. The optical waveguide of Comparative Example 3 was manufactured by pressing.

  The optical characteristics of the optical waveguides produced in the above examples and comparative examples 1 to 3 were compared. The results were evaluated for light transmission loss and incident and outgoing waveforms (time difference between incoming and outgoing signals). The results are shown in Table 2 below.

  As shown in Table 2 above, it was confirmed that the optical transmission loss was equivalent in both the example and the comparative example. On the other hand, a result of measuring a signal width when a signal having a width of 250 ps is incident and emitted, and a time difference between input and output signals is compared with the optical waveguide of the example in which there is almost no difference. In the first and second SI-type waveguides, signal degradation still occurred. In Comparative Example 3, it was found that the performance was substantially improved. However, when an interface having a different refractive index was generated, the mode dispersion was slightly generated, and the signal was deteriorated.

(A)-(d) is a schematic sectional drawing which shows the flow of the process in the manufacturing method of this invention. (A)-(c) is the top view and side view which show the suitable structural example of the optical waveguide of this invention. It is a graph which shows the refractive index change of the thickness direction in a core layer. (A) And (b) is a schematic sectional drawing which shows one structural example of the optical waveguide of this invention. (A) is explanatory drawing of the manufacturing process using a roll toe roll system, (b) is a top view which shows the flow of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical waveguide 10 Support base material 11 Core layer 12 Upper clad layer (coating layer)
13, 13a, 13b, 13c Incident part 14, 14a, 14b, 14c Emitter 21, 22, 23 Roll

Claims (7)

The core layer formed on the supporting base material is cut into a predetermined shape while leaving the supporting base material, and a molding step for removing unnecessary portions of the cut core layer;
A coating step of coating the surface of the support substrate and the core layer using a material having a refractive index lower than that of the core layer;
And a separation step of cutting the support base material and the coating layer around the core layer cut into the predetermined shape and cutting the support base material and the coating layer for each core layer.   The method for manufacturing an optical waveguide according to claim 1, wherein the core layer is cut by cutting with a blade die.   The method for producing an optical waveguide according to claim 1, wherein at least one of the forming step, the covering step, and the separation step is continuously performed using a roll-to-roll method.   An optical waveguide manufactured by the method for manufacturing an optical waveguide according to claim 1.   The optical waveguide according to claim 4, wherein the refractive index of the core layer continuously decreases from the center in the thickness direction toward the front and back.   The optical waveguide according to claim 4 or 5, wherein the core layer has one or more incident portions and one or more emission portions.   The optical waveguide according to claim 4 or 5, wherein the shape of the core layer is a strip shape having one incident portion and one exit portion.

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