JP2009104083A - Light guide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide capable of being manufactured in high productivity by a lamination process and forming a core by performing development without using any organic solvent. <P>SOLUTION: The light guide is formed of a clad and a core in the clad. The clad is manufactured by curing a curing film after laminating the curable film formed of an epoxy resin composition containing polyalkylene glycol diglycidyl ether, water-added bisphenol epoxy resin, solid bisphenol epoxy resin, phenoxy resin and a cation curing initiator. In addition, the core is manufactured by performing pattern exposure and development after laminating an optical curing film formed of an epoxy resin composition containing an epoxy resin having 3,4-epoxy cyclohexenyl skeleton, liquid-like bisphenol epoxy resin, solid bisphenol epoxy resin and an optical cation curing agent. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical waveguide formed of a polymer material.

  In addition to the need for high-speed processing of optical communications represented by the Internet, the need to realize high-speed processing and electromagnetic noise avoidance is increasing by adopting optical transmission in fields where large amounts of image information are transmitted within the device. ing. For this purpose, an in-device optical connection for transmitting light between LSIs and IC chips using light instead of conventional electric transmission is an important technology.

  In this field, the optical input / output unit of the waveguide is not a single mode waveguide having a cross-sectional diameter of 10 μm or less using a wavelength of 1.3 μm or 1.5 μm, as used in long-distance optical communication. A multimode waveguide having a cross-sectional diameter of 30 to 100 μm that facilitates alignment of the light receiving and emitting elements is optimal. In such a multimode waveguide, the loss of light is small, and mass production is excellent. There is a demand for practical use of a polymer waveguide that can be easily integrated.

  As a polymer material for producing such a polymer waveguide, a highly transparent thermoplastic resin or a curable resin that is cured by light or heat is used.

  However, when a thermoplastic resin such as acrylic resin, PET, or cycloolefin polymer is used (see, for example, Patent Document 1), the thermoplastic resin melts when a high temperature acts, and therefore cannot withstand soldering. Moreover, since the thermoplastic resin has low adhesive strength, it is difficult to produce an optical waveguide with high interlayer adhesion, and there is a problem that it is difficult to put it into practical use.

  On the other hand, since curable resins have high heat resistance and good interlayer adhesion, it is the mainstream to use curable resins as polymer materials.

  For example, in Patent Document 2, a liquid photocurable resin containing an oxetane resin, an epoxy resin, and a photopolymerization initiator is used as a polymer material for a cladding or a core, and this photocurable resin liquid is applied and formed. After that, a technique for manufacturing an optical waveguide by a method having a step of forming a core by performing pattern exposure and development is disclosed.

In Patent Document 3, a liquid photocurable epoxy resin containing a polyfunctional reactive oligomer and a photopolymerization initiator is used as a polymer material for cladding and core, and this photocurable epoxy resin liquid is applied. A technique for producing an optical waveguide by a method having a step of forming a core by pattern exposure and development after being formed is disclosed.
JP-A-1-302308 JP 2001-343539 A Japanese Patent No. 30603903

  However, as described in Patent Documents 2 and 3, when a liquid photocurable resin is used as a polymer material, a coating process for applying a photocurable resin liquid is required, which has a problem in productivity. It was. Further, in Patent Documents 2 and 3, it is necessary to perform development using an organic solvent in performing development after pattern exposure is performed on the coating layer of the photocurable resin liquid. There was also a problem that there was an adverse effect on the human body in the work environment.

  The present invention has been made in view of the above points, and can be manufactured with high productivity by a laminating process, and can be developed without using an organic solvent to form a core. An object of the present invention is to provide an optical waveguide with low loss.

  The optical waveguide according to the present invention is an optical waveguide formed from a clad and a core in the clad, wherein the clad is polyalkylene glycol diglycidyl ether, hydrogenated bisphenol type epoxy resin, solid bisphenol type epoxy resin, phenoxy resin, And a curable film formed by laminating a curable film formed of an epoxy resin composition containing a cationic curing initiator, and the core is an epoxy resin having a 3,4-epoxycyclohexenyl skeleton, It is produced by laminating a liquid bisphenol type epoxy resin, a solid bisphenol type epoxy resin, and a photocurable film formed of an epoxy resin composition containing a photocationic curing agent, and then pattern exposure and development. With features Is shall.

  According to the present invention, an optical waveguide can be formed with high productivity by a laminating process using a curable film for cladding and a photocurable film for core, and development is performed without using an organic solvent. Thus, the core can be formed, and the loss of light is small, and a flexible optical waveguide can be formed.

  The present invention is also characterized in that the epoxy resin composition forming the photocurable film for the core contains a phenoxy resin.

  According to this invention, it is possible to form an optical waveguide with a smaller light loss.

  The present invention is also characterized in that the epoxy resin composition forming the above-mentioned core photocurable film also contains an epoxy resin having a chemical structure of the formula (1).

  According to this invention, it is possible to form an optical waveguide with a smaller light loss.

  The present invention also provides 1,2-epoxy-4- (2-oxiranyl) cyclohexane of 2,2-bis (hydroxymethyl) -1-butanol as an epoxy resin composition for forming the curable film for cladding. It also contains an adduct.

  According to this invention, it is possible to form an optical waveguide with a smaller light loss.

  According to the present invention, an optical waveguide can be formed with high productivity by a laminating process using a curable film for cladding and a photocurable film for core, and development is performed without using an organic solvent. Thus, the core can be formed, and the loss of light is small, and a flexible optical waveguide can be formed.

  Hereinafter, the best mode for carrying out the present invention will be described.

  In the present invention, the curable film used to form the clad is an epoxy containing polyalkylene glycol diglycidyl ether, hydrogenated bisphenol type epoxy resin, solid bisphenol type epoxy resin, phenoxy resin, and cationic curing initiator. It is formed by a resin composition.

  By containing the above-mentioned polyalkylene glycol diglycidyl ether, excellent flexibility due to its molecular structure can be expressed in the cured product, and the optical waveguide can be easily made flexible by lowering the Tg of the cladding. In addition, the refractive index can be lowered, transparency can be increased, and light loss can be reduced. Moreover, the tack property (adhesiveness) of a curable film can be improved and the adhesiveness between layers can be improved. If the polyalkylene glycol diglycidyl ether content is too high, the Tg will be too low and the heat resistance will be lowered, or the tackiness will be too strong and handling problems will occur. The content of is preferably in the range of 5 to 20 mass% with respect to the total resin content.

  As this polyalkylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether and the like can be used.

  Also, by containing the above hydrogenated bisphenol type epoxy resin, the Tg of the clad can be lowered to make the optical waveguide flexible, and the refractive index can be lowered and the transparency can be increased. And light loss can be reduced. As this hydrogenated bisphenol-type epoxy resin, any one that is liquid at room temperature or solid at room temperature can be used, so that the tackiness of the curable film can be improved by using a liquid one, By using a solid material, the tackiness of the curable film can be lowered, and the tackiness of the curable film can be adjusted. The content of the hydrogenated bisphenol type epoxy resin is preferably in the range of 20 to 50% by mass with respect to the total resin content.

  Examples of the hydrogenated bisphenol type epoxy resin include hydrogenated bisphenol A type epoxy resin, hydrogenated bisphenol F type epoxy resin, hydrogenated bisphenol E type epoxy resin, and hydrogenated bisphenol S type epoxy resin.

  Moreover, by containing the solid bisphenol-type epoxy resin that is solid at room temperature (room temperature), the brittleness of the cured product can be suppressed and the toughness of the clad can be increased, and the Tg can be adjusted low. The optical waveguide can be easily made flexible, the refractive index can be lowered, the transparency can be increased, and the optical loss can be reduced. Moreover, it can also adjust so that the tackiness of a curable film may become low. The content of the solid bisphenol type epoxy resin is preferably in the range of 10 to 40% by mass with respect to the total resin content.

  As this solid bisphenol type epoxy resin, solid bisphenol A type epoxy resin, solid bisphenol F type epoxy resin, solid bisphenol E type epoxy resin, solid bisphenol S type epoxy resin and the like can be used.

  Also, by containing the above phenoxy resin, the brittleness of the cured product can be suppressed and the toughness of the clad can be increased, and the Tg can be adjusted to be low, and the optical waveguide can be easily made flexible. In addition, the refractive index can be lowered, transparency can be increased, and light loss can be reduced. Moreover, it can adjust so that the viscosity of the solvent solution (varnish) prepared when producing a curable film may become high, preparation of a curable film becomes easy, and tackiness of a curable film It is also possible to adjust so as to keep the value low. If the content of the phenoxy resin is too large, the thixotropy of the varnish becomes high and becomes unsuitable for coating properties when producing a curable film. Therefore, the content of the phenoxy resin is 10 to the total resin content. A range of 25% by weight is preferred.

  Moreover, by containing a cationic curing initiator as described above as a curing initiator for imparting curability to the epoxy resin composition, the transparency of the cladding can be increased, and light loss can be reduced. It can be done. This cationic curing agent includes a photocationic curing initiator that can initiate curing only by light, a thermal cationic curing initiator that can initiate curing only by heat, and a light / thermal cationic curing initiator that can initiate curing by both light and heat. However, any of these can be used, and in addition to using these alone, a plurality of them may be used in combination. Although content of a cationic hardening initiator is set as needed, generally the range of 0.5-2 mass% is preferable with respect to resin whole quantity.

  By producing a curable film from an epoxy resin composition prepared by combining the above resin components and curing initiator materials, and curing this curable film, a highly flexible and highly flexible cladding can be obtained. It can be manufactured with less mixing of voids at the time of laminating, and it is possible to obtain a clad of a flexible optical waveguide with a small optical loss.

  In the epoxy resin composition for producing a curable film for forming a clad, the above-described components are essential. In addition to the above-described components, 1,2-bis (hydroxymethyl) -1-butanol is 1,2- It is preferable to contain an epoxy-4- (2-oxiranyl) cyclohexane adduct. This is a transparent alicyclic epoxy that is liquid at room temperature, which can adjust the Tg of the cured product to be higher, can lower the refractive index of the cladding, and can increase transparency. Therefore, the optical loss can be reduced. The content of 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol is preferably in the range of 3 to 15% by mass with respect to the total resin content. . If it is less than 3% by mass, the effect of inclusion cannot be sufficiently obtained. Conversely, if it exceeds 15% by mass, the flexibility of the cured product is reduced, and the bending resistance of the cladding is reduced. It is not preferable in producing a flexible optical waveguide.

  The epoxy resin composition for producing a curable film for forming a clad further has a reactive double bond such as various epoxy resins, various oxetane resins, various acrylates and methacrylates within the range not impairing the gist of the present invention. It can contain compounds, various liquid or solid rubber-like substances, and can also contain sensitizers and surface conditioners (leveling agents, antifoaming agents, repellency inhibitors), etc. It is.

  Next, in the present invention, the photocurable film used to form the core is an epoxy resin having a 3,4-epoxycyclohexenyl skeleton, a liquid bisphenol type epoxy resin, a solid bisphenol type epoxy resin, and a photocation. It is formed with an epoxy resin composition containing a curing agent.

  By containing the epoxy resin having the 3,4-epoxycyclohexenyl skeleton, the transparency of the core can be increased and the optical loss can be reduced. Moreover, it can adjust so that tack property may become strong, and can obtain the photocurable film which has a quick cure rate in a hardening process, and also makes Tg high or low according to molecular structure. The Tg of the cured product can be adjusted. In addition, when a waveguide core is produced by pattern exposure and development of a photocurable film, both sides of the core are likely to be roughened by development, and light is scattered on both sides of the core, resulting in cladding. Easily escape and optical waveguide loss generally occurs, but by including an epoxy resin having a 3,4-epoxycyclohexenyl skeleton, the phenomenon that the refractive index of this side portion of the core is lower than the inside of the core is seen, The amount of light escaping from both side surfaces of the core to the cladding is reduced, and the optical waveguide loss can be reduced. The content of the epoxy resin having a 3,4-epoxycyclohexenyl skeleton is preferably in the range of 5 to 20% by mass with respect to the total resin content.

  Examples of the epoxy resin having a 3,4-epoxycyclohexenyl skeleton include 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexenecarboxylate, ε-caprolactone-modified 3,4-epoxycyclohexenylmethyl-3. ', 4'-epoxycyclohexanecarboxylate or the like can be used.

  Further, by containing the liquid bisphenol type epoxy resin that is liquid at room temperature, the brittleness of the cured product can be suppressed and the toughness of the core can be increased, and the Tg can be adjusted to be low. Flexibility is facilitated, the refractive index can be increased, transparency can be increased, and light loss can be reduced. Moreover, it can also adjust so that the tackiness of a curable film may become strong. The content of the liquid bisphenol-type epoxy resin is preferably in the range of 10 to 40% by mass with respect to the total resin content.

  As this liquid bisphenol type epoxy resin, liquid bisphenol A type epoxy resin, liquid bisphenol F type epoxy resin, liquid bisphenol E type epoxy resin, liquid bisphenol S type epoxy resin and the like can be used.

  Further, by containing the solid bisphenol type epoxy resin that is solid at room temperature, the brittleness of the cured product can be suppressed and the toughness of the core can be increased, and the Tg can be adjusted to be low. Flexibility is facilitated, the refractive index can be increased, transparency can be increased, and light loss can be reduced. Moreover, it can also adjust so that the tackiness of a curable film may become low. The content of the solid bisphenol type epoxy resin is preferably in the range of 40 to 80% by mass with respect to the total resin content.

  As this solid bisphenol type epoxy resin, solid bisphenol A type epoxy resin, solid bisphenol F type epoxy resin, solid bisphenol E type epoxy resin, solid bisphenol S type epoxy resin and the like can be used.

  In addition, by containing a photocationic curing initiator as described above as a photocuring initiator for imparting photocurability to the epoxy resin composition, the transparency of the core can be increased and light loss is reduced. Is something that can be done. Although content of a photocationic hardening agent is set as needed, generally the range of 0.5-2 mass% is preferable with respect to resin whole quantity.

  A photo-curable film is produced from an epoxy resin composition prepared by combining the above resin components and curing initiator materials, and this curable film is subjected to pattern exposure and developed to provide excellent transparency and flexibility. A high-performance core can be produced with less mixing of voids during lamination, and a flexible optical waveguide core with low optical loss can be obtained. In addition, the photocurable film prepared from the above epoxy resin composition can be developed using a water-based flux cleaning agent as a developer, and it is not necessary to use an organic solvent for development. It is possible to avoid problems and adverse effects on the human body in the work environment.

  In the epoxy resin composition for producing a curable film for forming a core, the above components are essential, but it is preferable to contain a phenoxy resin in addition to the above components. By containing the phenoxy resin, the brittleness of the cured product can be suppressed, the toughness of the core can be increased, Tg can be adjusted to be low, and the optical waveguide can be easily made flexible. A refractive index can be increased, transparency can be increased, and light loss can be reduced. In particular, since the toughness of the core can be increased by suppressing the brittleness of the cured product in this way, physical damage such as chipping and scratching occurs on the edge of the core formed in a pattern by exposure and development. This can be prevented, and waveguide loss can be reduced. Moreover, it can adjust so that the viscosity of the solvent solution (varnish) prepared when producing a photocurable film may become high, preparation of a photocurable film becomes easy, and also a photocurable film It can also be adjusted to keep the tackiness of the sheet low. The content of the phenoxy resin is preferably in the range of 1 to 5% by mass with respect to the total resin content. If it is less than 1% by mass, the effect of containing the phenoxy resin cannot be sufficiently obtained. Conversely, if it exceeds 5% by mass, it becomes difficult to perform development with an aqueous flux cleaning agent. It is not preferable.

  Moreover, it is preferable to make the epoxy resin composition which produces the photocurable film for core formation contain the epoxy resin which has a chemical structure of said Formula (1) other than said component. By containing the epoxy resin having the chemical structure of the formula (1), a highly transparent core can be formed, and an optical waveguide with small optical loss can be formed. When the epoxy resin having the chemical structure of the formula (1) is not contained, depending on the composition of the epoxy resin composition, the transparency of the produced photocurable film is obscured due to the presence or absence of a benzene ring or a difference in molecular weight. The epoxy resin having the chemical structure of formula (1) forms a photocurable film because the transparency of the photocurable film is increased by containing the epoxy resin having the chemical structure of formula (1). The epoxy resin is thought to act as a compatibilizer between the epoxy resins, and due to this special action, the epoxy resin becomes a cured product without micro phase separation and the core is formed. It is considered that the optical waveguide loss can be reduced. As for content of the epoxy resin which has a chemical structure of Formula (1), 5-20 mass% is preferable with respect to resin whole quantity.

  Reactive double bonds such as various epoxy resins, various oxetane resins, various acrylates and methacrylates are further added to the epoxy resin composition for producing the photocurable film for core formation, as long as the gist of the present invention is not impaired. It can also contain various liquid or solid rubber-like substances, and can also contain sensitizers and surface conditioners (leveling agents, antifoaming agents, anti-repelling agents), etc. Is.

  In producing a curable film for cladding and a photocurable film for core using the epoxy resin composition described above, the epoxy resin composition is dissolved in a solvent to prepare a solvent solution (varnish). It can carry out by apply | coating with the coater on the surface of a peeling film, and drying this.

  Next, a method for producing an optical waveguide using the curable film for clad and the photocurable film for core will be described. Here, the refractive index of the clad curable film is lower than the refractive index of the core photocurable film.

  First, a clad curable film 1 is laminated on the surface of a flexible substrate 11 on which a circuit 11 such as a flexible printed wiring board is formed, as shown in FIG. By curing the clad curable film 1, an underclad 3a is laminated on the surface of the substrate 11 as shown in FIG.

  Next, the core photocurable film 2 is laminated on the surface of the underclad 3 a, and a mask 13 in which the core pattern slit 12 is formed as shown in FIG. By irradiating possible light, the core photocurable film 2 is exposed in a core pattern. After the exposure, the core photocurable film 2 is developed to remove the unexposed portion of the core photocurable film 2, thereby exposing the exposed and photocured core 4. It is formed on the surface of the underclad 3a in a pattern shape as in 1 (d). Here, in the present invention, development can be performed using an aqueous flux cleaner as a developer. In addition to the light exposure using the mask 13 as described above, the exposure can also be performed by a direct drawing method in which a laser beam is scanned and irradiated in a pattern shape.

  Thereafter, the clad curable film 1 is laminated, overlaid on the under clad 3a so as to cover the core 4 as shown in FIG. By curing, an overclad 3b is laminated and formed as shown in FIG.

  In this manner, the optical waveguide A in which the core 4 is embedded in the clad 3 composed of the under clad 3a and the over clad 3b can be formed on the surface of the substrate 10. The optical waveguide A is formed flexibly, and a photoelectric composite flexible wiring board can be obtained by using a flexible printed wiring board having the circuit 11 as the substrate 10.

  In producing the optical waveguide A as described above, the clad 3 and the core 4 can be produced by a laminating process in which the clad curable film 1 and the core photocurable film 2 are laminated. The optical waveguide A can be manufactured with high productivity without the need for a simple process. The clad 3 and the core 4 can be formed with a uniform and high-precision thickness by the clad curable film 1 and the core photocurable film 2.

  In addition, when developing the core photocurable film 2 to form the core 4 as shown in FIG. 1D, the developer acts on the underclad 3a, and the underclad 3a swells with the developer, The underclad 3a and the core 4 may be delaminated, but contains a 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol. By forming the underclad 3a using the curable film 1 for clad produced with the epoxy resin composition, such swelling and delamination can be prevented. Thus, swelling and delamination can be prevented because 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol is multifunctional. It is thought that it originates in the chemical structural formula that it is an alicyclic epoxy resin and is an external epoxy which is not glycidyl ether type.

  Next, the present invention will be specifically described with reference to examples.

(Preparation of curable film for clad and photocurable film for core)
The following were used as each material.
(1) Polyalkylene glycol diglycidyl ether / polypropylene glycol diglycidyl ether: “PG207N” manufactured by Toto Kasei Co., Ltd.
(2) Epoxy resin having 3,4-epoxycyclohexenyl skeleton, 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexene carboxylate: “Celoxide 2021P” manufactured by Daicel Chemical Industries, Ltd.
Ε-caprolactone-modified 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate: “Celoxide 2081” manufactured by Daicel Chemical Industries, Ltd.
(3) Hydrogenated bisphenol type epoxy resin / Liquid hydrogenated bisphenol A type epoxy resin: “YX8000” manufactured by Japan Epoxy Resin Co., Ltd.
Solid hydrogenated bisphenol A type epoxy resin: “YL7170” manufactured by Japan Epoxy Resin Co., Ltd.
(4) Solid bisphenol type epoxy resin / solid bisphenol A type epoxy resin: “Epicoat 1006FS” manufactured by Japan Epoxy Resin Co., Ltd.
Solid bisphenol F type epoxy resin: “Epicoat 4007” manufactured by Japan Epoxy Resin Co., Ltd.
(5) Liquid bisphenol type epoxy resin / Liquid bisphenol F type epoxy resin: “Epicron 830S” manufactured by Dainippon Ink & Chemicals, Inc.
・ Liquid bisphenol A epoxy resin: “Epicron 850S” manufactured by Dainippon Ink and Chemicals, Inc.
(6) Phenoxy resin, “YP50” manufactured by Toto Kasei Co., Ltd.
(7) Epoxy resin of formula (1), “VG-3101” manufactured by Mitsui Chemicals, Inc.
(8) 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol and “EHPE3150” manufactured by Daicel Chemical Industries, Ltd.
(9) Light cationic curing initiator, Ltd. ADEKA "SL-170" (SbF ₆ ^- sulfonium salt)
(10) thermal cationic curing initiator, available from Sanshin Chemical Industry Co., Ltd. "SI-150L" (SbF ₆ ^- sulfonium salt)
(11) Surface conditioner “F470” manufactured by Dainippon Ink & Chemicals, Inc.
(12) Solvent / Toluene / MEK
The above materials were weighed in a glass container according to the composition shown in Table 1, dissolved at 60 ° C. under reflux, and then filtered through a PTFE membrane filter having an opening of 1 μm to prepare a varnish. And this varnish is apply | coated to the surface of a mold release film (Teijin DuPont PET film "OX-50") using the multi-coater of the comma coater head made from Hirano Techseed, and this is dried, and thickness is 10 micrometers and thickness. A curable film 1 for cladding having a thickness of 50 μm and a photocurable film 2 for core having a thickness of 40 μm were prepared.

  In Table 1, among the epoxy resin compositions for producing the clad curable film 1, the compositions satisfying the requirements of claim 1 are “cladding example composition 1” to “cladding example composition 3”. The composition that does not satisfy the requirement of “Clad Comparative Example Composition 1” is displayed, and among the epoxy resin compositions for producing the core photocurable film 2, the composition that satisfies the requirement of claim 1 is designated as “Core Example Composition 1”. To “core example composition 4”, and the composition not satisfying the requirements of claim 1 is indicated as “core comparative example composition 1”.

  And the refractive index and Tg (glass transition temperature) of said curable film 1 for a clad and the photocurable film 2 for a core were measured, and a result is shown in Table 1.

The refractive index was measured as follows. A pressure-type vacuum laminator is formed on the smooth surface of a 30 mm × 10 mm × 4 mm thick high refractive index glass plate (refractive index of 1.6) using a film prepared in the same manner as described above so as to have a thickness of 80 μm on the surface of the release film. (Nichigo-Morton Co., Ltd. “V-130”) is laminated at 60 ° C. and 0.2 MPa, and is exposed by irradiating with ultra-high pressure mercury lamp at ² J / cm ² under ultraviolet light. After peeling off the release film, heat treatment was performed at 150 ° C. for 1 hour. And it grind | polished in order to make the surface of a film smooth, and the refractive index of the film was measured with the refractive index measuring apparatus made from Atago.

The Tg was measured as follows. In the same manner as described above, a film prepared to have a thickness of 80 μm on the surface of the release film was exposed by irradiating with ultraviolet light under a condition of ² J / cm ² with an ultrahigh pressure mercury lamp, and heat treatment at 100 ° C. for 5 minutes. Then, the release film was peeled off, and only the film was heat-treated at 150 ° C. for 1 hour. This cured film was cut into a size of 5 mm × 50 mm, and measured using a viscoelasticity spectrometer (“DMS200” manufactured by Seiko Denshi Kogyo Co., Ltd.) as the peak temperature of the complex elastic modulus (E ″) as Tg. did.

(Example 1)
Using a flexible double-sided copper-clad laminate ("FELIOS (R-F775)" manufactured by Matsushita Electric Works Co., Ltd.) in which a 12-μm-thick copper foil is laminated on both sides of a 25-μm-thick polyimide film, patterning is performed on the copper foil on one side. The circuit board 11 was formed and the copper foil on the other side was etched and removed, thereby producing a flexible board 10 as shown in FIG. 2A composed of a flexible printed wiring board having an outer size of 130 mm × 130 mm. . A strong adhesive surface of a re-peeling type double-sided adhesive tape 17 (“No. 7692” manufactured by Teraoka Seisakusho Co., Ltd.) is applied to the entire surface of a glass plate 16 having a size of 140 mm × 140 mm × thickness 2 mm. The surface of the double-sided adhesive tape 17 on which the circuit 11 of the flexible substrate 10 is formed is laminated with a vacuum laminator “V-130”. The flexible substrate 10 was temporarily bonded to the glass plate 16 as shown in FIG.

Next, a 10 μm-thick curable film 1 for clad having the “cladding example composition 1” is used, and the curable film 1 for clad is vacuum-bonded on the surface of the flexible substrate 10 on which the circuit 11 is not formed. A laminator “V-130” was laminated as shown in FIG. Then, the curable film 1 for cladding is irradiated with ultraviolet light under the condition of ² J / cm ^{2 with} an ultra-high pressure mercury lamp, and the release film is peeled off, followed by heat treatment at 150 ° C. for 30 minutes, and oxygen plasma treatment. The underclad 3a which the curable film 1 for hardening hardened | cured was formed.

Next, the core photocurable film 2 having a thickness of 40 [mu] m was used as the “core example composition 1”. The core photocurable film 2 was applied to the surface of the underclad 3a with a vacuum laminator “V-130”. Lamination was performed as shown in FIG. 2 (d) under the same conditions as above. Then, a negative mask 13 formed with a linear pattern of slits 12 having a width of 40 μm and a length of 120 mm is superimposed on the surface of the core photocurable film 2 and exposed by irradiating ultraviolet light with a super high pressure mercury lamp under the condition of ³ J / cm ^2. And the part corresponding to the slit 12 of the photocurable film 1 was photocured.

  Next, the release film was peeled off from the photocurable film 1, and then heat treated at 140 ° C. for 2 minutes, and further adjusted to 55 ° C. as a developing solution (Arakawa Chemical Industries, Ltd. “Pine Alpha ST”). −100SX ”), the unexposed portion of the photo-curable film 1 is dissolved and removed, further washed with water and air blown, and then dried at 100 ° C. for 10 minutes, whereby FIG. The core 4 was formed as shown in (e). Further, the surface state of the underclad 3a after the development processing was visually observed, and the appearance of the core 4 was observed with a stereomicroscope. The results are shown in Table 2.

Next, as shown in FIG. 2 (f), micromirrors 19 for deflecting the guided light by 90 ° were formed at 10 mm from both ends of the core 4. That is, first, using a rotating blade with a cutting blade apex angle of 90 ° (“# 5000” blade manufactured by Disco Corporation), the rotational speed is 10000 rpm and the moving speed is 0.1 mm / s. The V-groove 20 having a depth of 50 μm is processed by moving the position across the position, and then a solution obtained by diluting the varnish of “Clad Example Composition 3” 50 times with a solvent of toluene: MEK = 3: 7 is prepared. By thinly applying to the V-groove 20 with a brush, drying at 100 ° C. for 30 minutes, and then exposing to ultra-high pressure mercury lamp by irradiating with ultraviolet light under the condition of 1 J / cm ² , and further performing heat treatment at 120 ° C. for 10 minutes, The V groove 20 was smoothed. After that, a micromask 19 was formed on the surface of the V groove 20 with a gold thin film having a thickness of 1000 mm by covering the surface of the V groove 20 with a metal mask having only the V groove 20 opened.

Next, the film of “clad example composition 1” was used as the curable film 1 for clad having a thickness of 50 μm, and this curable film for clad 1 from above the core 4 was heated at 80 ° C. with a vacuum laminator “V-130”. Lamination was performed under the condition of 0.3 MPa as shown in FIG. And after heat-treating at 120 ° C. for 30 minutes, ultraviolet light is irradiated onto the curable film for cladding 1 under the condition of ² J / cm ² with an ultra-high pressure mercury lamp, and after further removing the release film, heat-treat at 150 ° C. for 30 minutes, The clad curable film 1 was cured to form an overclad 3b.

  After the surface of the over clad 3b formed on the core 4 in this way was subjected to oxygen plasma treatment, the coverlay film 21 (“Halogen-free coverlay film R-CAES” manufactured by Matsushita Electric Works Co., Ltd .: polyimide, thickness 125 μm, The adhesive layer (15 μm thick) is laminated on the surface of the over clad 3b with a vacuum laminator “V-130” at 120 ° C. and 0.3 MPa as shown in FIG. 2 (h), and heated at 160 ° C. for 1 hour to cure. I let you.

  Then, as shown in FIG. 2 (i), the core 4 is embedded in the clad 3 composed of the under clad 3a and the over clad 3b by peeling off the glass plate 16 from the weak adhesive surface of the double-sided adhesive tape 17 and cutting it out with a router. A photoelectric composite flexible wiring board B having a configuration in which the optical waveguide A formed therein is provided on the surface of the flexible substrate 10 with the circuit 11 was obtained. In this photoelectric composite flexible wiring board B, the optical path of the guided light that enters and exits the optical waveguide A is indicated by an arrow in FIG.

(Examples 2 to 10, Comparative Examples 1 to 3)
A photoelectric composite flexible wiring board B was obtained in the same manner as in Example 1 except that the clad curable film 1 and the core photocurable film 2 were used in the combinations shown in Table 2.

  With respect to the photoelectric composite flexible wiring boards B of Examples 1 to 10 and Comparative Examples 1 to 3 obtained as described above, the optical loss was measured and the flex resistance was measured. The results are shown in Table 2.

The optical loss was measured as follows. On the surface of the flexible substrate 10 of the photoelectric composite flexible wiring board B, the end of the optical fiber having a core diameter of 10 μm and NA of 0.21 is passed through silicone oil matching oil at a position corresponding to the micromirror 19 at one end of the core 4. And the end of the optical fiber having a core diameter of 200 μm and NA of 0.4 at the portion corresponding to the micromirror 19 at the other end of the core 4 is connected via matching oil, and the light from the LED light source of 850 nm wavelength Was incident on the optical waveguide A from an optical fiber having a core diameter of 10 μm and NA of 0.21, and the power (P ₁ ) of light emitted through the optical fiber having a core diameter of 200 μm and NA of 0.4 was measured with a power meter. On the other hand, the power (P ₀ ) of light in a state where the optical waveguide A is not interposed by abutting the end faces of both optical fibers was measured with a power meter. Then, from the equation of _{-10log (P 1 / P 0)} , to determine the insertion loss of the optical waveguide A with micromirrors 19 arranged in the photoelectric composite flexible wiring board B. The results are shown in the column of “Optical waveguide insertion loss (1)” in Table 2.

Further, in order to measure the optical loss only in the portion of the optical waveguide A of the photoelectric composite flexible wiring board B, the micromirrors 19 at both ends of the photoelectric composite flexible wiring board B are cut off as shown in FIG. An optical waveguide A having a length of 100 mm and 40 μm × 40 μm of the end face of the core 4 exposed at both ends is formed, and an optical fiber is connected to each end face of the core 4 in the same manner as described above. The optical power (P ₁ ) emitted through the optical waveguide A and the optical power (P ₀ ) without the optical waveguide A being measured are measured, and the optical waveguide A is calculated from the calculation formula of −10 log (P ₁ / P ₀ ). The insertion loss of was determined. The results are shown in the column of “Optical waveguide insertion loss (2)” in Table 2.

  The measurement of bending resistance was performed as follows. A bending test in which the photoelectric composite flexible wiring board B is repeatedly bent at a 90 ° angle alternately with a radius of curvature of 2 mm is performed 100,000 times. The same measurement was performed to measure the insertion loss. Then, before and after the bending test, a case where the loss increment was 1 dB or less was evaluated as “◯”, and a case where it exceeded 1 dB was evaluated as “X”.

  As can be seen in Table 2, the curable film for cladding of “Clad Example Composition 1” to “Clad Example Composition 3” and the core light of “Core Example Composition 1” to “Core Example Composition 4” In each example using a combination of curable films, the loss of the optical waveguide was small and the bending resistance was high.

  Further, in Example 1, Example 5, and Example 8 using the core photocurable film of “Core Example Composition 1”, chipping may occur in part of the edge portion of the core during development. Although the loss of the optical waveguide is slightly worse, Examples 2 to 4 using the core photocurable films of “Core Example Composition 2” to “Core Example Composition 4” containing phenoxy resin. In Examples 6, 7, 9, and 10, there was no such chipping in the core, and the optical waveguide loss was small. Furthermore, in Example 4 and Example 10, since the core photocurable film of “core example composition 4” containing the epoxy resin of formula (1) is used, the compatibility of the resin is increased and the transparency is increased. As a result, the optical waveguide loss is further improved.

  Further, in Examples 1 to 4 using the curable film for clad of “Clad Example Composition 1”, swelling may occur on the surface of the underclad after development, which adversely affects the characteristics of the optical waveguide. “Clad Example Composition 2”, “Clad Implementation”, which may contain 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol In Examples 5 to 10 using the curable film for cladding of “Example composition 3”, such swelling phenomenon did not occur.

  The difference between “Clad Example Composition 2” and “Clad Example Composition 3” is that the former uses a photocationic curing initiator and a thermal cationic curing initiator together, and the latter uses a photocationic curing initiator alone. However, in all of Examples 5 to 10 using these curable films for cladding, the same loss characteristics of the optical waveguide are obtained, and it is necessary to cure by heating or light irradiation. It is confirmed that it can be properly used as needed for the processing step, for example, when it is necessary that the curing does not start by heating before.

FIG. 1 shows a process of manufacturing an optical waveguide in an example of an embodiment of the present invention, and (a) to (f) are sectional views. The manufacturing process in an Example is shown, (a) thru | or (i) are sectional drawings, respectively. It is sectional drawing of an optical waveguide for measuring the insertion loss (2) of an optical waveguide.

Explanation of symbols

1 Curable curable film 2 Core photocurable film 3 Clad 4 Core

Claims (4)

  In an optical waveguide formed from a clad and a core in the clad, the clad contains polyalkylene glycol diglycidyl ether, hydrogenated bisphenol-type epoxy resin, solid bisphenol-type epoxy resin, phenoxy resin, and cationic curing initiator. It is produced by laminating a curable film formed of an epoxy resin composition and then curing, and the core is an epoxy resin having a 3,4-epoxycyclohexenyl skeleton, a liquid bisphenol type epoxy resin, a solid bisphenol An optical waveguide, which is produced by laminating a photocurable film formed of an epoxy resin composition containing a type epoxy resin and a photocationic curing agent, followed by pattern exposure and development.   The optical waveguide according to claim 1, wherein the epoxy resin composition forming the core photocurable film also contains a phenoxy resin. The optical waveguide according to claim 1 or 2, wherein the epoxy resin composition forming the photocurable film for the core also contains an epoxy resin having a chemical structure of the formula (1).

  The epoxy resin composition forming the curable film for cladding also contains a 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol. The optical waveguide according to any one of claims 1 to 3, wherein

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