JP2007086122A - Optical distribution member and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical distribution member which is easy in manufacturing, low in propagation loss, and can have a large refractive index between a core part and a cladding layer without restricting the selection of both of the core part and the cladding layer material and corresponds to a low-temperature process for using a glass epoxy substrate for an electric wiring plate as a substrate. <P>SOLUTION: The optical wiring member has a metal layer having a groove, the core part formed along the groove, and the cladding layer having a smaller refractive index than the core part formed between the core part and the metal layer. Its manufacturing method is provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical wiring member that can be applied to an optical waveguide used for optical connection between devices that perform optical signal transmission or in a wiring board inside the device.

  With the advancement of IT due to the progress of broadband such as FTTH (Fiber to the Home), the light of interconnection between devices / devices in devices that perform high-speed and large-capacity signal processing such as routers. Transmission is progressing.

  In addition, advances in LSI technology have increased the information processing speed and integration scale, and the performance of microprocessors and the capacity of memory chips have increased rapidly. Along with this, various electronic devices such as personal computers using these functions, information appliances mainly using video information such as hard disk recorders and DVD recorders have appeared on the market.

  Therefore, in signal transmission over a relatively short distance such as between boards in a device or between chips in a board, which has been performed by conventional electrical signals, (1) For high speed, CR (C: Signal capacitance due to wiring capacitance, R: wiring resistance) time constant becomes a problem, and (2) EMI (Electromagnetic Interference) noise and crosstalk between channels are a problem for increasing the density of electrical wiring. Therefore, it has become difficult to further increase the speed and density.

  Therefore, as one of the techniques for solving these problems, there is an optical wiring (optical interconnection) technique. The optical wiring can be applied to various places such as between devices, between boards in the device, or between chips in the board. It is useful to use a flexible optical wiring material for optical connection between devices and between boards straddling movable parts in the device. Devices that have board-to-board connections that straddle the movable part include foldable mobile phones and notebook computers.

  Such an optical signal transmission system includes a light emitting element for converting an electric signal into an optical signal, a light receiving element for converting the optical signal into an electric signal, and an electric signal transmission / reception for controlling the light emitting element and the light receiving element. In addition, an IC or the like is required for power supply, power supply to these elements is also required, and electrical wiring is also required for the optical interconnection system.

  There are various forms of optical wiring, but an optical waveguide called a channel type that has a core part that is a path for light and a cladding layer that has a lower refractive index than the core part that surrounds it is currently the mainstream. It has become. The channel type has low optical energy loss and high reliability. In the single mode propagation type, the diameter of the core is about 1 to several μm, but in the multimode propagation type, it is several tens of μm.

  Examples of the optical waveguide material include quartz and glass used as materials for optical fibers and optical elements, and these materials have good optical characteristics such as transmittance and high reliability. However, since these inorganic materials need to be processed at a high temperature and the productivity is not high, recently there has been an increase in the use of polymer materials for optical waveguides.

  As a method of forming an optical waveguide using a polymer material, a method of exposing and developing after forming a photosensitive optical waveguide material (see Patent Document 1), and masking the formed material with a resist Etching by RIE (Reactive Ion Etching) (refer to Patent Document 2), Photobleaching method using polysilane as a material after forming a material that changes the refractive index by exposure and then selectively exposing (see Patent Document 3) ), A stamping method in which the pattern of the core portion is formed by a mold (see Patent Document 4). FIG. 3 schematically shows a cross-sectional shape of an optical waveguide manufactured by these methods. In this figure, reference numeral 1 is a substrate, reference numeral 3 is a first cladding layer, reference numeral 4 is a core portion, and reference numeral 5 is a second cladding layer. As shown in the figure, a structure in which the entire core portion is covered with the first and second cladding layers is called a channel type. There is also an optical waveguide structure called a ridge type in which the second cladding layer does not exist.

  The photo bleaching method uses the characteristics of a material whose refractive index changes by light irradiation. When using a material whose refractive index decreases by exposure, only the portion corresponding to the cladding layer is exposed and exposed by exposure. When using a material with an increased refractive index, only the portion corresponding to the core portion is exposed. In this method, since the cladding layer and the core portion start from the same film, the adhesion between the two is better than other methods.

  In the stamping method, a mold having a concave portion to be a core part mold is prepared in advance, and the mold is pushed into the film of the core part forming material, or the core part forming material is applied on the mold and molded. In this method, the film is adhered to a separately formed cladding layer.

In addition, there is a technique in which a surface treatment is performed on the first cladding layer and the core part is self-formed by surface tension (see Patent Document 5). In the method of forming the core portion by surface tension, the interface between the core portion and the cladding layer is smooth.
JP 2005-221556 A (Claims) JP 2001-166166 A (page 3) JP 2004-333883 A (Claims) JP 2004-78084 A (Claims) JP 2003-21740 A (Claims)

  However, conventional optical waveguide forming methods using polymer materials have many problems. In particular, when a multimode optical waveguide having a large core portion diameter is manufactured, if a photosensitive material is used for the cladding layer, it is necessary to dig a polymer material to a depth of several tens of μm, which is the diameter of the core portion. A lot of time is spent on development. In addition, there is a limit to smoothing the interface of the polymer material formed by development, and the boundary between the core portion and the cladding layer is not smooth, so that the waveguide light scattering increases and the light propagation loss increases. . In addition, in RIE etching, in addition to spending a lot of time for etching, the interface between the core portion and the cladding layer becomes rough, and since it is a vacuum process, the production cost is high.

  In the photo bleaching method, since the refractive index difference is expressed with one kind of material, it is difficult to increase the refractive index difference between the core portion and the cladding layer. The relative refractive index difference Δn in a material that can be used at present is about 0.03. When such a relative refractive index difference is small, the shape of the optical waveguide draws a curve, and the waveguide light is the core when the radius of curvature is small. It is easy to leak from the portion through the cladding layer to the outside, or when a plurality of core portions are close to each other, crosstalk in which guided light interferes easily occurs. In addition, since polysilane used for photobleaching has a curing temperature as high as 300 ° C. or higher, the selection range of materials used for the peripheral member of the optical waveguide is reduced. Here, the relative refractive index difference Δn is given by “(refractive index of core portion−refractive index of cladding layer) / refractive index of core portion”.

  Since the stamping method is cured with the shape fixed by the mold, internal stress is generated in the polymer material, or the cured core part needs to be peeled off from the mold with low stress. Therefore, it is necessary to select the interfacial treatment agent and treatment method to be applied to the mold in advance.

  In the method of forming the core portion with surface tension, the core portion is fixed at a predetermined position only by controlling the affinity of the interface, and therefore it is necessary to finely optimize the surface treatment method depending on the material used. Further, since the surface treatment agent is provided in the cladding layer, the optical waveguide must be designed in consideration of the refractive index of the surface treatment agent, and precise control of the manufacturing process is required.

  In addition, when a material having a high hygroscopic property is used as the optical waveguide material, a change in the refractive index due to the moisture absorption deteriorates the optical characteristics. Therefore, it is necessary to separately provide a barrier layer around the optical waveguide.

  That is, the present invention relates to an optical wiring having a metal layer having a groove, a core portion formed along the groove, and a cladding layer having a refractive index smaller than that of the core portion formed between the core portion and the metal layer. According to another aspect of the present invention, a groove is formed in the metal layer, and then a cladding layer having a refractive index smaller than that of the core portion is formed along the bottom and side surfaces of the groove. It is a manufacturing method of the optical wiring member which forms a core part in contact with the said cladding layer in the hollow part of the existing cladding layer.

  According to the optical wiring member of the present invention, the optical waveguide can be easily manufactured, and the interface between the core portion and the cladding layer can be smoothed, so that the optical waveguide has excellent optical characteristics with less guided light scattering. Is obtained. Furthermore, since the range of materials that can be used is wide, it can be designed so that the refractive index difference between the core portion and the cladding layer is large, and the confinement effect of guided light can be increased. Further, since a material that can be cured at a relatively low temperature such as an epoxy resin can be used, an optical waveguide can be formed on a glass epoxy substrate generally used as an electric wiring board.

  A cross-sectional view of the optical wiring member in the present invention is schematically shown in FIG. A first cladding layer 3, a core portion 4, and a second cladding layer 5 are sequentially stacked on a groove formed in the metal layer 2 on the substrate 1. However, the second cladding layer 5 is not always necessary. Preferably, by providing the second cladding layer, it is possible to cover the core portion where the guided light is mainly propagated, and therefore, the light propagation characteristics are not easily influenced by the surrounding atmosphere such as humidity. When the second cladding layer is provided, it is sufficient that at least a part of the surface of the core part is covered, and it is more preferable that the entire surface of the core part is covered with the second cladding layer. Even if a part of the core part is exposed to the outside air, since the refractive index of air is 1, it is smaller than the refractive index of the core part, and the effect of confining the propagating light in the core part can be obtained.

  As shown in FIG. 1, the bottom surface 10 of the groove formed in the metal layer may be formed of the first cladding layer (in a state where the groove penetrates the metal layer), and as shown in FIG. Further, the bottom surface portion 10 of the groove may be formed of a metal layer (a state where the groove does not penetrate the metal layer). In the configuration of the optical wiring member of the present invention, the core portion and the portion made of the first and second cladding layers function as an optical waveguide, and the metal layer having the groove forms the optical waveguide at a predetermined position. It has a function as a mold for. In addition, the metal layer can also be used as an electrical wiring or an environmental barrier layer that suppresses moisture absorption of the optical waveguide. Moreover, the strength of the optical wiring member including the optical waveguide can be increased by using the substrate.

1 and 2 show a form in which the metal layer 2 is formed on the substrate 1, the substrate 1 is not necessarily required in the present invention. When the substrate is used, the material is not particularly limited, and examples thereof include a metal substrate, a ceramic substrate, a glass substrate, a quartz substrate, an inorganic substrate such as a silicon wafer, a plastic film, a glass epoxy substrate, and the like.

  In the present invention, the metal layer is not particularly limited, and examples thereof include a metal foil and those formed on a substrate by sputtering or plating. A material used for the metal layer is not particularly limited, and a material containing copper, aluminum, chromium, gold, silver, stainless steel, nickel, titanium, tungsten, or the like can be used. The metal layer can be patterned and used as an electric wiring. In this case, copper or an alloy containing copper, which has low electric resistance and high versatility as an electric circuit material, can be preferably used. When using copper foil, the well-known rolling foil for circuit boards, electrolytic foil, etc. can be used.

Since the polymer material for forming the cladding layer and the core portion of the present invention functions as an optical waveguide for confining and propagating light in the core portion, the first cladding layer having a refractive index n1 and the refractive index n the core portion is _c, the refractive index of the second cladding layer (where used) is _{n 2 that, n} 1 <n _c, and may be a polymer material that satisfies the relationship of _n 2 _{<n c.} A UV curable resin, a thermoplastic resin, a thermosetting resin, an aramid resin, or the like that satisfies the above relationship can be used.

  The thermoplastic resin is flexible, and an optical wiring member having high flexibility is easily obtained. In addition, it is preferable because internal strain caused by a difference in linear expansion coefficient from a hard material such as a metal layer can be reduced in a heating process at the time of manufacturing an optical wiring member. The thermoplastic resin used in the present invention is not particularly limited, but PMMA (polymethyl methacrylate), polycarbonate, polystyrene, polyetherimide, cycloolefin, polyphenylene ether, polyphenylene sulfide, polyether sulfone and the like are preferable.

  Thermosetting resins have the characteristics of having high heat resistance and mechanical strength. The thermosetting resin used in the present invention is not particularly limited, but polyimide, fluorinated polyimide, deuterated polyimide, polynorbornene, epoxy resin, epoxy-novolak resin, cyanate resin, BT (bismaleimide / triazine) resin, benzocyclobutene Fluorinated benzocyclobutene, polysiloxane, deuterated polysiloxane, alkyl-substituted siloxane, silicone resin, deuterated silicone resin, fluorinated polyether, polyfluoromethacrylate and the like are preferable.

  The UV curable resin used in the present invention is not particularly limited, but a UV curable epoxy resin, a UV curable acrylic resin, a UV curable halogenated acrylic resin, and the like are preferable.

  In addition, an aramid resin, a fluorinated aramid resin, a sulfonated aramid resin, or the like can also be used.

If necessary, an inorganic filler may be added to the cladding layer of the optical waveguide or the polymer material for the core portion. By adding an inorganic filler, the temperature dependence of the refractive index of the core part or cladding layer to be formed and the linear expansion coefficient can be reduced. Further, it is preferable that the inorganic filler has a smaller particle size and the refractive index of the inorganic filler is close to the refractive index of the polymer material mixed, because an increase in guided light scattering due to the addition of the inorganic filler can be suppressed. Although it does not specifically limit as an inorganic filler, It is preferable that it is at least 1 sort (s) chosen from the material containing any coupling | bonding of a Si-O bond, Mg-O bond, and Al-O bond. A material having a Si—O bond, a Mg—O bond, and an Al—O bond is chemically stable, and therefore, a material having a large energy gap in a solid state, that is, a transparent material is often used. Further, many of these materials have a solid-state refractive index between 1.4 and 1.8 which is the refractive index region of the polymer material. For example, there are SiO ₂ , Al ₂ O ₃ , MgO, MgAl ₂ O ₄ , Al and Si, Mg and Al, Mg and Si, Ti and Si double oxides and solid solutions, and further, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Ag, In, Sn, Sb, Te, Cs, Ba, Hf, Ta, W, Re, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and other oxides are dissolved. Can be used. As other double oxides, CaSiO ₃ , ZrSiO ₄ , BaCrO ₄ , ZnCrO _{4 and the} like can be used. Metal sulfates can also be preferably used as the inorganic filler, and examples thereof include barium sulfate, calcium sulfate, and strontium sulfate. As barium sulfate, precipitated barium sulfate is preferred because it is easy to obtain one having a small particle size. As other inorganic substances, carbonates such as barium carbonate and calcium carbonate, and fluorides such as magnesium fluoride, sodium fluoride, barium fluoride, calcium fluoride, strontium fluoride, and lithium fluoride can be used. In addition to these inorganic substances, if the refractive index is in the range of 1.4 to 2.4, they can be used alone or in combination of two or more.

In order to form the optical wiring member of the present invention, first, a groove in which the optical waveguide (core part) is accommodated is formed in the metal layer, and the first cladding layer is formed along the bottom surface and side surface of the groove. Next, a core portion is formed on the depression of the first cladding layer located in the groove of the metal layer. Preferably, the second cladding layer is continuously formed so that the first cladding layer and the second cladding layer continuously cover the entire core portion. The first cladding layer and the second cladding _{layer, n} 1 <n _c, and may be _{n 2 <n n 1 = n} 2 If the relationship fulfills a _c, a and in the same material Alternatively, different materials may be used.

  The greater the relative refractive index difference Δn in the present invention, the greater the effect of confining the light propagating to the core. Δn is preferably 0.04 or more and 0.4 or less. When Δn is 0.04 or more, the effect of confining the propagation light to the core portion is increased, and even when the optical waveguide is bent with a small radius of curvature, the leakage of the propagation light to the outside of the optical waveguide can be reduced or eliminated. . When Δn is larger than 0.4, a polymer material having an extremely high refractive index is used as the core material, and a material having an extremely low refractive index is used as the cladding layer. Narrow.

  As a method of forming a groove for providing an optical waveguide in a metal layer, a method of etching the metal layer while masking portions other than the portion where the groove is formed with a photoresist can be cited. When the metal layer is formed on the substrate, the entire metal layer in the groove may be removed by etching. When there is no substrate and only a metal layer, if the groove is formed so as not to penetrate the metal layer, the coating liquid leaks from the bottom surface of the groove when the material for forming the first cladding layer is applied. Can be prevented.

  In addition, as another method of forming the groove in the metal layer, a method of forming a metal material in a portion other than the portion that becomes the groove, or the like can be given. According to this method, a groove having a shape penetrating the metal layer is formed. As a method for selectively forming the metal layer in a portion other than the groove, for example, a semi-additive method or a full additive method in which the metal wiring of the electric circuit board is formed by plating can be applied. The semi-additive method is a method in which a base metal layer for supplying electric charge is formed on a substrate by sputtering or the like, and a portion where the groove is formed is masked with a photoresist, and then plating is grown to a portion other than the groove by electrolytic plating. is there. The full additive method is a method in which a catalyst such as palladium is applied to a portion other than the portion where the groove is formed on the substrate, and the plating is grown to the portion other than the groove by electroless plating.

  In addition, there are a method of performing groove processing with a laser and a mechanical grinding method using a dicing blade. However, since the laser or dicing blade method is a one-dimensional linear process formation, the etching or plating method can form grooves on the two-dimensional surface at one time, whereas the optical waveguide pattern can be formed in a large area with high density. In the case of forming, it is inferior from the viewpoint of productivity.

  In the present invention, since the groove is formed in the metal layer as a mold for forming the optical waveguide, the groove shape is such that the side surface of the groove is perpendicular to the bottom surface in the cross-sectional shape, or the top surface of the groove is more than the bottom surface of the groove. It is preferable to incline so that it may spread. The angle formed between the side surface and the bottom surface of the groove is an angle indicated by A in FIGS. 1 and 2, and the angle A is preferably 30 ° or more and 90 ° or less. When the angle A is 30 ° or more, the material of the core portion is easily localized at the groove position, and when the angle A is 90 ° or less, the width of the upper surface portion of the groove is wider than the bottom surface portion. The cladding layer and the core portion can be easily formed in the groove without any gap.

  Next, the preferable range about the depth of the groove | channel formed in a metal layer is described. Here, the depth of the groove is the length of a perpendicular line extending from the upper surface of the metal layer to the bottom surface of the groove formed in the metal layer, and is the length indicated by d in FIG. 1 or FIG. The depth of the groove formed in the metal layer may be deep enough to embed the optical waveguide. However, as will be described later, the material used for the core portion has a large self-aggregation force even if the groove is shallow. If it can be easily localized in the groove, the groove does not need to be deep enough to embed the core part sufficiently. If the groove is too shallow, when the material for forming the first cladding layer is applied, the concave shape of the groove due to the leveling of the surface is not reflected on the surface of the first cladding layer, or the first cladding Even if a dent is formed on the surface of the layer, the depth of the groove may be 10 μm or more because the core forming material may not be localized in the groove because it is shallow. preferable. On the other hand, if the groove is too deep, it takes a long time to form the groove, which is not economical. Therefore, the groove depth is preferably 200 μm or less.

  In the present invention, as shown in FIG. 1, the first cladding layer is formed along the side surface of the groove provided in the metal layer, and the core is formed in the depression of the first cladding layer existing at the groove position. The material for forming the part is localized by gravity, self-cohesive force, wettability with the first cladding layer, or the like. Localization as used herein refers to a phenomenon in which the material for forming the core portion is concentrated in the depressions of the first cladding layer.

  The first cladding layer formed on the grooved metal layer is coated with a material for forming the first cladding layer using a spin coater, screen printing, blade coater, die coater, etc., and then dried. Obtained by solidification. The core part to be formed in the depression of the first cladding layer is coated with a material for forming the core part on the first cladding layer using a spin coater, screen printing, blade coater, die coater, etc., and dried. The method of solidifying is mentioned. Moreover, you may apply | coat by the inkjet method or the dispenser method.

  In order for the core part to fit in the depression of the first cladding layer, it is important to control the wettability of the first cladding layer and the core part forming material and the fluidity of the core part forming material. . By changing the amount and viscosity of the core part forming material to be applied and controlling the fluidity, the core part forming material can be simply applied onto the first cladding layer without specifically aiming at the recessed part. It is also possible to embed a material for forming the core portion in an optimal shape in the depression on the first cladding layer. If the wettability of both is too good, when the material for forming the core part is applied, the material for forming the core part spreads not only in the recessed part of the first cladding layer but also in the part other than the recessed part. If the wettability is too bad, the adhesiveness between the first cladding layer and the core portion is deteriorated, and the material for forming the core portion is not embedded in the depression of the first cladding layer. As a method for controlling the paintability when the paintability between the first cladding layer and the material for forming the core is not optimal, a method of improving the paintability by irradiating the surface of the first cladding layer with UV light. Is mentioned. In the case of irradiating UV, the paintability of both can be controlled by changing the amount of transmitted UV light with a mask at the groove and other portions.

  If the material for forming the core spreads to other parts than the dents, the excess core can be removed by blowing air or nitrogen gas onto the substrate surface, sucking with vacuum, wiping with dust-free cloth or buffing, etc. The forming material can be removed.

  The method of forming the second cladding layer after forming the first cladding layer and the core portion is in accordance with the method of forming the first cladding layer.

  According to the manufacturing method of the present invention, when the material for forming the first cladding layer and the core portion is applied, each surface uses a liquid or solution-like polymer material, so that the surface tension is smooth. It becomes a shape. In addition, since the shape of the core portion is secured by the groove of the metal layer, it is not necessary to perform processing such as etching on the formed first cladding layer or core portion, and the surface of each region is smooth. Kept. Therefore, the interface between the cladding layer and the core portion is very clear. On the other hand, in the conventional method of producing the core part by development or etching, the interface of the core part becomes rough, and in particular, in the photo bleaching method, the interface between the core part and the cladding layer tends to be blurred. The optical waveguide obtained by the present invention is more useful because an optical waveguide having a smooth interface has superior optical characteristics such as a deterioration in waveguide mode and a small optical propagation loss. In addition, since the etching of the metal layer in the present invention can be performed in a shorter time compared to the etching and development of the polymer material, the productivity of the manufacturing method of the present invention is high.

  After forming the second cladding layer, a metal layer (hereinafter referred to as a surface metal layer) may be further formed on the surface thereof. Examples of the method for forming the metal layer include metal foil lamination, sputtering, and plating. The surface metal layer may be used as a barrier layer that prevents moisture from entering the optical waveguide, or may be patterned and used as an electrical wiring.

  When the metal layer is formed on the substrate as a starting material for producing the optical wiring member in the present invention, it is also possible to remove the substrate after forming the second cladding layer. When the substrate and the metal layer are bonded with a weakly adhesive force such as a removable adhesive, the substrate may be peeled off as it is, and when it is firmly bonded, the substrate may be dissolved and removed by etching. When a substrate having no flexibility is used, it is preferable to remove the substrate to increase the flexibility of the optical wiring member and to increase the degree of freedom of routing as the optical wiring member.

  After peeling off the substrate, the metal layer originally formed on the substrate (hereinafter referred to as the lower metal layer) may be used as a barrier layer for preventing moisture from entering the optical waveguide, similar to the surface metal layer described above. Then, it may be patterned and used as electric wiring. However, when the lower metal layer is used as the barrier layer, it is preferable to leave the metal layer on the bottom surface of the groove without penetrating the lower metal layer when forming the groove in the lower metal layer.

  Various kinds of devices such as incorporating photoelectric conversion elements or passive optical components on the surface or inside of the optical wiring member of the present invention, forming electric wiring, or bonding the optical wiring member of the present invention to another substrate, etc. An optical wiring board suitable for the purpose can be manufactured. Examples of the photoelectric conversion element include a laser and a photodetector. Among these elements, using a surface-emitting laser that emits or receives light on the element surface instead of the end face, or a surface-receiving type photodetector, it is easy to reduce the spread of light during light propagation and to increase the signal intensity. It is preferable because the mounting structure of the light emitting / receiving portion can be easily simplified. Moreover, a mirror and a lens can be incorporated as needed for optical coupling between the light emitting / receiving element and the optical waveguide. For example, the mirror can be formed by cutting the end face of the optical waveguide at 45 ° with a dicing blade or the like. In addition, passive optical circuits such as an optical multiplexer / demultiplexer, a wavelength filter, and a wavelength multiplexer may be formed in the optical wiring board.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

The measurement method and conditions for each characteristic are as follows.
<Refractive index>
Measurement was performed at 25 ° C. using a prism coupler device 2010 manufactured by Metricon and a dedicated P-1 prism.
<Light propagation loss>
It was measured by the cutback method according to the JPCA standard (JPCA-PE02-05-01S-2004).

Example 1
A photoresist layer is formed on a glass epoxy copper clad laminate “Nicaplex” L-6504C (manufactured by Nikkan Kogyo Co., Ltd.) in which a copper foil with a thickness of 70 μm is bonded to a glass epoxy substrate with a thickness of 0.8 mm. After exposure and development, striped openings having a width of 100 μm and a pitch of 1 mm shown in FIG. 4 were formed in the resist. The portion indicated by reference numeral 6 in FIG. 4 is a resist formation portion, and the portion indicated by reference numeral 7 is a resist opening. Next, the substrate was immersed in an iron chloride etching solution, and the copper foil in the portion exposed to the photoresist opening was etched while stirring the solution to form a groove. When the cross-sectional shape of the groove after etching was observed with FE-SEM (Field Emission-Scanning Electron Microscope) S-4800 (manufactured by Hitachi High-Technologies Corporation), the groove depth was 70 μm and penetrated the copper foil. The width of the upper surface portion of the groove is 120 μm, the width of the bottom surface portion of the groove is 70 μm, the angle between the side surface and the bottom surface of the groove (angle A shown in FIG. 1) is 70 °, and the upper portion is open. It became. Etching was performed for 8 minutes.

  After removing the resist, as a resin composition for forming the first cladding layer, liquid epoxy resin “EPO-TEC” # 314 (manufactured by Epoxy Technology Co., Ltd.) is applied with a spin coater, and an oven is applied. After being used and dried at 80 ° C. for 5 minutes in the air, it was cured by heating at 150 ° C. for 1 hour in nitrogen. The thickness of the obtained first cladding layer was 20 μm, and the refractive index at a wavelength of 850 nm was 1.51.

  On the first cladding layer, a naphthalene-based epoxy resin “Epiclon” HP-4032D (manufactured by Dainippon Ink & Chemicals, Inc.) and 4-ethyl-2-propylene as a resin composition for forming a core with a spin coater. A solution in which methylimidazole (curing accelerator) and cyclohexanone (solvent) were mixed at a weight ratio of 100: 2: 150 was applied, and the resin composition applied to portions other than the grooves with air was removed. Next, the resin composition for forming a core part applied on the groove was dried in an atmosphere at 80 ° C. for 5 minutes using an oven, and then heated and cured at 180 ° C. for 1 hour in nitrogen to form a core part. When the cross section of the obtained core part was observed with FE-SEM, the core part was localized in the hollow part of the 1st cladding layer, and the cross-sectional shape was a circle with a diameter of 35 micrometers. When a single film of the resin composition for forming the core part was separately prepared and its refractive index was measured, it was 1.61 at a wavelength of 850 nm.

  Further, a liquid epoxy resin “EPO-TECH” # 314 (manufactured by Epoxy Technology Co., Ltd.) is applied on the first cladding layer and the core portion with a spin coater, and 80% in the atmosphere using an oven. After drying at 5 ° C. for 5 minutes, a second cladding layer was formed by heating in nitrogen at 150 ° C. for 1 hour to cure. The thickness of the obtained second cladding layer was 20 μm.

  When the optical propagation loss at a wavelength of 850 nm of the optical wiring member thus obtained was measured, it was as good as 0.1 dB / cm. The relative refractive index difference Δn given by (refractive index of core portion−refractive index of cladding layer) / refractive index of core portion was 0.062. The temperature dependency of the refractive index of the cladding layer was −70 ppm / ° C., and the temperature dependency of the refractive index of the core portion was −52 ppm / ° C.

Examples 2-3
A sample was prepared and evaluated in the same manner as in Example 1 except that the etching time when forming the groove in the copper foil and the stirring conditions of the liquid were changed so that the cross-sectional shape of the groove as shown in Table 1 was obtained. . Table 1 shows the evaluation results.

Example 4
A copper layer having a thickness of 100 nm was formed by sputtering on a polyimide film “Kapton 100EN” (manufactured by Toray DuPont Co., Ltd.) having a thickness of 25 μm. Next, a photoresist layer was formed on the copper layer, and the resist was processed into stripes having a width of 100 μm and a pitch of 1 mm shown in FIG. 5 by exposure and development. Reference numeral 6 in FIG. 5 is a resist forming portion, and reference numeral 7 is a resist opening. Using the copper layer formed by the sputtering as an electrode, electrolytic plating was performed in a copper sulfate plating solution, and a copper film having a thickness of 18 μm was formed on the copper layer formed by sputtering. After removing the resist, the shape of the groove formed in the copper film was observed with an FE-SEM. The width of the upper surface portion was 90 μm, the width of the bottom surface portion was 100 μm, and the angle formed between the side surface and the bottom surface of the groove ( The angle A) shown in FIG. 1 was 105 °.

  After removing the resist, a first cladding layer, a core portion, and a second cladding layer were formed and evaluated in the same manner as in Example 1. Table 1 shows the evaluation results. However, in some places on the optical wiring member, the first cladding layer was not sufficiently contained in the groove, and the core portion existing thereon protruded from the groove.

Example 5
Example 1 except that a copper-clad polyimide film (manufactured by Toray Industries, Inc.) in which a 35 μm-thick copper foil was bonded to a 25 μm-thick polyimide film was used instead of the glass epoxy copper-clad laminate. Samples were prepared and evaluated. Table 1 shows the evaluation results. The obtained optical wiring member was highly flexible and could be bent freely.

Example 6
The width shown in FIG. 6 by a dicing apparatus DFD-6240 (manufactured by Disco Corporation) on a copper-clad polyimide film (manufactured by Toray Industries, Inc.) in which a copper foil having a thickness of 35 μm is bonded to a polyimide film having a thickness of 25 μm. Striped grooves with a pitch of 1 mm at 200 μm were formed. Reference numeral 9 in FIG. 6 is a groove. When the cross-sectional shape of the groove was observed with an FE-SEM, the groove depth was 35 μm and penetrated through the copper foil, the top surface width was 200 μm, the bottom surface width was 50 μm, and the side surface of the groove Had an inclination of 25 ° and an open top.

  After forming the groove, the first cladding layer, the core portion, and the second cladding layer were formed and evaluated in the same manner as in Example 1. Table 1 shows the evaluation results. However, the cross-sectional shape of the core portion was a shape close to an ellipse, with both side surfaces protruding from the recessed portion of the first cladding layer and extending laterally. The obtained optical wiring member was highly flexible and could be bent freely.

Example 7
A copper-clad polyimide film in which a 9 μm-thick copper foil is bonded on a 25 μm-thick polyimide film instead of a glass epoxy copper-clad laminate is the same as in Example 1 except that a product made by Toray Industries, Inc. is used. Samples were prepared and evaluated, and the evaluation results are shown in Table 1. However, the cross-sectional shape of the core part is a shape close to an ellipse, with both side surfaces protruding from the recessed portion of the first cladding layer and extending laterally. The obtained optical wiring member was highly flexible and could be bent freely.

Example 8
Instead of a glass epoxy copper clad laminate, a 50 μm thick copper foil (made by Furukawa Circuit Foil Co., Ltd.) on a 1 mm thick copper plate is a releasable adhesive “SK Dyne” 1495 (manufactured by Soken Chemical Co., Ltd.) The sample was prepared and evaluated in the same manner as in Example 1 except that the substrate bonded through the above was used. Table 1 shows the evaluation results. Furthermore, the optical wiring member was peeled from the copper plate. The light propagation loss at a wavelength of 850 nm was as good as 0.1 dB / cm, unchanged from that before peeling. The optical waveguide substrate after peeling was highly flexible and could be bent freely.

Example 9
Instead of a glass epoxy copper clad laminate, a 210 μm thick copper foil (manufactured by Furukawa Circuit Foil Co., Ltd.) on a 1 mm thick copper plate is a releasable adhesive “SK Dyne” 1495 (manufactured by Soken Chemical Co., Ltd.) The sample was prepared and evaluated in the same manner as in Example 1 except that the substrate bonded through the above was used. Table 1 shows the evaluation results. Furthermore, the optical wiring member was peeled from the copper plate. The light propagation loss at a wavelength of 850 nm was as good as 0.1 dB / cm, unchanged from that before peeling.

Example 10
As a resin composition for forming a core part, a 20% by weight dimethylacetamide solution of an aramid resin obtained by polymerizing 9,9-bis (4-amino-3-fluorophenyl) fluorene and 2chloro-terephthalic acid dichloride was used. A sample was prepared and evaluated in the same manner as in Example 1 except that the heating condition was changed from 150 ° C. to 180 ° C. Table 1 shows the evaluation results. A single film of the resin composition for forming the core part was separately prepared and its refractive index was measured. As a result, it was 1.64 at a wavelength of 850 nm. Δn was 0.079.

Example 11
A sample was prepared in the same manner as in Example 1 except that the following resin compositions for forming the first and second cladding layers and the resin composition for forming the core portion were used. Table 1 shows the evaluation results. The temperature dependency of the refractive index of the cladding layer was −42 ppm / ° C., and the temperature dependency of the refractive index of the core portion was −44 ppm / ° C.

Resin composition for forming first and second cladding layers Organosilica sol having an average particle diameter of 12 nm dispersed in γ-butyrolactone in liquid epoxy resin “EPO-TECH” # 314 (manufactured by Epoxy Technology) For the first and second cladding layers, OSCAL-103 (manufactured by Catalytic Chemical Industry Co., Ltd.) is mixed using a ball mill so that the volume ratio after curing is epoxy resin: silica = 57: 43. A resin composition was obtained.

Resin composition for forming core part Using bead mill “Ultra Apex Mill” UAM-05 (manufactured by Kotobuki Industries Co., Ltd.), 17.4 parts by weight of barium sulfate BF-40 (manufactured by Sakai Chemical Industry Co., Ltd.) A dispersion was obtained by mixing and dispersing with 69 parts by weight of N, N-dimethylacetamide and 0.9 parts by weight of the dispersant “Disperbyk” 111 (manufactured by Big Chemie Japan Co., Ltd.). The dispersion and the naphthalene-based epoxy resin “Epicron” HP-4032D (manufactured by Dainippon Ink & Chemicals, Inc.) and the curing accelerator 2 so that the volume ratio after curing is epoxy resin: barium sulfate = 73: 27 Ethyl-4-methylimidazole was mixed using a ball mill to obtain a resin composition for forming a core part. The mixing ratio of the liquid epoxy resin and the curing accelerator was 100: 2 by weight.

Comparative Example 1
<Photo bleaching method>
In a yellow room where ultraviolet rays were blocked, a mixture of 400 ml of toluene and 10 g of sodium was stirred at high speed to disperse sodium. Polymerization was performed by adding 40 g of phenylmethyldichlorosilane and 4 g of tetrachlorosilane to this and stirring for 3 hours. The obtained sample was precipitated in ethanol to obtain branched polysilane.

  A first cladding is formed on a glass epoxy copper clad laminate “Nicaplex” L-6504C (manufactured by Nikkan Kogyo Co., Ltd.) in which a copper foil having a thickness of 70 μm is bonded to a glass epoxy substrate having a thickness of 0.8 mm. As a resin composition for layer formation, liquid epoxy resin “EPO-TECH” # 314 (manufactured by Epoxy Technology) was applied with a spin coater and dried in an atmosphere at 80 ° C. for 5 minutes. Thereafter, it was cured by heating in nitrogen at 150 ° C. for 1 hour. The thickness of the obtained first cladding layer was 20 μm, and the refractive index at a wavelength of 850 nm was 1.51.

  Next, polysilane obtained by the above method, silicone resin 3074 (manufactured by Dow Corning Toray), BTTB (3,3 ′, 4,4′-tetra- (t-butylperoxycarbonyl) benzophenone ) (Manufactured by Nippon Oil & Fats Co., Ltd.), a resin composition in which toluene is mixed at a weight ratio of 100: 50: 15: 100 is applied onto the first cladding layer with a spin coater, and then in the atmosphere using an oven. Drying was performed at 80 ° C. for 5 minutes to form a resin layer having a thickness of 30 μm. The obtained resin layer has a photobleaching property in which the refractive index is lowered by exposure.

In order to form a core part in this resin layer, ultraviolet rays with a wavelength of 300 nm were irradiated at 4 J / cm ² through a photomask that shields a 30 μm-wide linear pattern. Subsequently, in order to solidify the resin layer, heating was performed at 300 ° C. for 1 hour in nitrogen, and the glass epoxy substrate decomposed beyond the heat resistance limit. For this reason, an optical waveguide could not be produced.

Comparative Example 2
<Method using photosensitive material>
As a resin composition for forming a first cladding layer on a glass substrate, a liquid epoxy resin “EPO-TEK” # 314 (epoxy technology (manufactured by EPOXY TECHNOLOGY)) is applied with a spin coater and air is used in an oven. The film was dried at 80 ° C. for 5 minutes and then heated and cured in nitrogen at 150 ° C. for 1 hour.The thickness of the obtained first cladding layer was 20 μm, and the refractive index at a wavelength of 850 nm was 1.51. Met.

A resin composition obtained by mixing an alicyclic epoxy resin “Celoxide” 2021P (manufactured by Daicel Chemical Industries, Ltd.) and a cationic photopolymerization initiator SP-170 (manufactured by Asahi Denka Kogyo Co., Ltd.) at a weight ratio of 70: 4, The coating was applied on the first cladding layer with a spin coater and dried in an atmosphere at 80 ° C. for 5 minutes using an oven to form a resin layer having a thickness of 30 μm. The obtained resin layer was irradiated with ultraviolet light having a wavelength of 365 nm at 750 mJ / cm ² through a photomask that transmits only a linear pattern having a width of 30 μm, and then developed in ethyl acetate to remove unexposed portions. Then, it heated at 150 degreeC in nitrogen for 1 hour, solidified, and formed the core part which has a cross-sectional shape of 30 micrometers x 30 micrometers. The refractive index of the core portion at a wavelength of 850 nm was 1.56.

  Next, a second cladding layer was formed on the first cladding layer and the core portion by the same material and method as that used to form the first cladding layer.

  The optical propagation loss at a wavelength of 850 nm of the optical waveguide obtained in this way was measured and found to be 1.5 dB / cm, and the attenuation of the guided light was large.

Comparative Example 3
<Stamping method>
A liquid epoxy resin “EPO-TEK” # 314 (Epoxy Technology (manufactured by EPOXY TECHNOLOGY)) was applied on a glass substrate as a resin composition for forming a first cladding layer using a spin coater, and an oven was used. After drying in the air at 80 ° C. for 5 minutes, the film was cured by heating in nitrogen at 150 ° C. for 1 hour, and the resulting first cladding layer had a thickness of 20 μm and a refractive index of 1. 51.

  Next, on the first cladding layer, a naphthalene-based epoxy resin “Epicron” HP-4032D (manufactured by Dainippon Ink & Chemicals, Inc.) and 4-ethyl as a resin composition for forming a core with a spin coater. A solution in which 2-methylimidazole (curing accelerator) and cyclohexanone (solvent) were mixed at a weight ratio of 100: 2: 150 was applied. Next, a mold having a linear groove with a width of 30 μm and a depth of 30 μm was pressed from the top of the coating, and in this state, dried in an atmosphere at 80 ° C. for 5 minutes and then heated in nitrogen at 180 ° C. for 1 hour. The resin was cured. When the mold was peeled from the substrate, a part of the core portion forming material formed inside the groove of the mold was not released from the mold, but was peeled off from the first cladding layer together with the mold. Further, a part of the material for forming the core part which has been released from the mold and remained on the first cladding layer has a cross-sectional shape which is distorted compared to the groove shape of the mold due to the shrinkage stress of the resin. Therefore, a sample that can be evaluated as an optical waveguide could not be produced.

Sectional view of the optical wiring member of the present invention Sectional drawing of the optical wiring member of another aspect of this invention Sectional view of optical wiring member in the prior art Photoresist pattern for forming grooves used in Example 1 by etching Photoresist pattern for forming grooves used in Example 4 by plating Groove pattern formed by the dicing apparatus of Example 6

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Metal layer 3 1st cladding layer 4 Core part 5 2nd cladding layer 6 Resist formation part 7 Resist opening part 8 Metal layer 9 Groove 10 Bottom face part of groove

Claims (5)

The optical wiring member which has a metal layer which has a groove | channel, a core part formed along the said groove | channel, and a cladding layer with a refractive index smaller than the core part formed between a core part and a metal layer. The optical wiring member according to claim 1, wherein at least a part of the surface of the core portion is covered with a cladding layer. The optical wiring member according to claim 1, wherein in the cross-sectional shape of the groove, the width of the upper surface portion of the groove is wider than the width of the bottom surface portion of the groove, and the angle formed between the side surface of the groove and the bottom surface of the groove is 30 ° or more and 90 ° or less. The optical wiring member according to claim 1, wherein the depth of the groove is 10 μm or more and 200 μm or less. Grooves are formed in the metal layer, and then a cladding layer having a refractive index smaller than that of the core portion is formed along the bottom and side surfaces of the groove, and the cladding is formed in the depression of the cladding layer existing at the groove position of the metal layer. An optical wiring member manufacturing method for forming a core portion in contact with a layer.