JP4894720B2 - Optical waveguide and photoelectric composite substrate - Google Patents

Description

  The present invention relates to an optical waveguide formed of a polymer material and a photoelectric composite substrate provided with the optical waveguide.

  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 a small loss, and an object of the present invention is to provide a photoelectric composite substrate having such an optical waveguide.

An optical waveguide according to claim 1 of the present invention is an optical waveguide formed of a clad and a core in the clad, and the clad is 1,2-epoxy of 2,2-bis (hydroxymethyl) -1-butanol. It is prepared by laminating and curing a curable film formed of an epoxy resin composition containing a 4- (2-oxiranyl) cyclohexane adduct, a bisphenol type epoxy resin, a phenoxy resin, and a cationic curing initiator. The core is an epoxy resin having a 3,4-epoxycyclohexenyl skeleton, and 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol , Novolac type epoxy resin, bisphenol type epoxy resin, having chemical structure of formula (1) Epoxy resin, and after laminating a photocurable film formed by epoxy resin composition containing a photo-cationic curing agent, and pattern exposure, the unexposed portions of the phenomenon process be removed using an aqueous flux cleaning agent It is what is produced by doing.

  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, an optical waveguide can be formed with a small loss of light.

  The invention of claim 2 is characterized in that, in claim 1, the epoxy resin composition forming the core photocurable film also contains a phenoxy resin.

  According to the present invention, in producing a core by exposing and developing a photocurable film, it is possible to reduce damage such as chipping and scratches generated in the core, and to form an optical waveguide with smaller light loss. It is something that can be done.

  Further, the invention of claim 3 is the epoxy resin composition for forming a clad curable film according to claim 1 or 2, which also contains an epoxy resin of formula (2), and as a cationic curing initiator, A cationic curing initiator and a photocationic curing initiator are used in combination.

  According to the present invention, a highly transparent clad can be formed, light loss can be further reduced, and a curable film for clad is exposed and cured to form the clad. In this case, even if there is a portion that cannot be irradiated with light, it can be thermally cured by heating, and the optical waveguide having a smaller light loss can be formed by improving the adhesion between the core and the clad.

  The invention of claim 4 is the cationic resin composition according to claim 1 or 2, wherein the epoxy resin composition forming the curable film for cladding also contains an epoxy resin having a 3,4-epoxycyclohexenyl skeleton. Only the photocationic curing initiator is used as the initiator.

  According to the present invention, a curable film for cladding is laminated on a core, and light is irradiated and heated to form a core in which light guided in the core does not easily escape to the cladding. In addition, an optical waveguide having a smaller light loss can be formed.

  A photoelectric composite substrate according to claim 5 of the present invention is characterized in that the optical waveguide according to any one of claims 1 to 4 is provided on a substrate having a circuit, as described above. It is possible to obtain a photoelectric composite substrate having an optical waveguide with a small loss of light.

  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, an optical waveguide can be formed with a small loss of light.

  Further, it is possible to obtain a photoelectric composite substrate having such an optical waveguide with a small light loss.

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

  In the present invention, the curable film used to form the cladding is 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol, bisphenol. It is formed by an epoxy resin composition containing a type epoxy resin, a phenoxy resin, and a cationic curing initiator.

  By including the 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol as described above, the refractive index of the cladding can be lowered and transparent. The optical loss can be increased, and the optical loss can be reduced. Moreover, it can adjust so that the tackiness of a curable film may be weakened, and also can adjust Tg of hardened | cured material high. If the content of 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol is too large, the curable film becomes brittle and the handleability is poor. Therefore, the content is preferably in the range of 30 to 70% by mass with respect to the total amount of the resin components.

  Further, by containing the above bisphenol type epoxy resin, it is possible to reduce the brittleness of the cured product by adjusting the Tg of the cured product to be low, and to increase the transparency, and to reduce the optical loss. Can be reduced. As this bisphenol-type epoxy resin, any one that is liquid at normal temperature and solid at normal temperature can be used. Therefore, by using a liquid one, the tackiness of the curable film can be improved, and further solid By using a thing, the tackability of a curable film can be lowered | hung and the tackability of a curable film can be adjusted. The content of the bisphenol type epoxy resin is preferably in the range of 10 to 30% by mass with respect to the total resin content.

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

  Moreover, by containing said phenoxy resin, it can suppress the brittleness of hardened | cured material, can improve the toughness of a clad, can adjust Tg low, can raise a refractive index, and is transparent. Performance 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 | curing agent is set as needed, generally the range of 0.5-2 mass% is preferable with respect to resin whole quantity.

  A 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 laminated and cured to laminate a clad excellent in transparency. It can be manufactured with little mixing of voids at the time, and an optical waveguide cladding with low optical loss can be obtained.

  In the epoxy resin composition for producing a curable film for forming a clad, the above components are essential, but in addition to the above components, an epoxy resin of the formula (2) is preferably contained. In this case, it is preferable to use a thermal cationic curing initiator and a photocationic curing initiator in combination as the cationic curing initiator.

  The epoxy resin of the formula (2) is a trimethylolpropane type epoxy resin, which has extremely high transparency and can form a highly transparent clad to reduce the optical loss of the optical waveguide. In addition, when an epoxy resin of formula (2) is contained, even when a thermal cationic curing initiator is included as a cationic curing initiator in the epoxy resin composition, a curable film is prepared by applying an epoxy resin varnish. It is difficult to cure the resin during the drying process, and it is possible to obtain a curable film having a long usable life and excellent laminating properties. Moreover, the curable film produced with this epoxy resin composition by using together a thermal cationic curing initiator and a photocationic curing initiator as a cationic curing initiator of the epoxy resin composition containing the epoxy resin of Formula (2). When forming a clad by laminating from above the core and exposing to cure, there is a part that cannot be irradiated with light, and even if this part is insufficiently cured, this part is cured by heating and cured Insufficiency can be prevented, and the optical waveguide with less optical loss can be formed by improving the adhesion between the core and the clad (this will be described in detail later). The compounding quantity of the epoxy resin of Formula (2) has the preferable range of 3-25 mass% with respect to the resin component whole quantity. If the amount is less than 3% by mass, the effect of blending cannot be sufficiently obtained. Conversely, if the amount exceeds 25% by mass, the tackiness of the curable film becomes too strong, which is not preferable. Moreover, when using together a thermal cation curing initiator and a photocationic curing initiator, it is preferable to set the ratio so that a thermal cation curing initiator may be 20-80 mass%. If the thermal cation curing initiator is less than 20% by mass, thermal curing of the uncured part becomes insufficient, and conversely if the thermal cation curing initiator exceeds 80% by mass, photocuring is sufficiently performed. I can't do that.

  In addition to the above components, the epoxy resin composition for producing a curable film for forming a clad further contains an epoxy resin that is liquid at room temperature and has a plurality of 3,4-epoxycyclohexenyl structures in one molecule. Is preferred. In this case, it is preferable to use only a photocationic curing initiator as the cationic curing initiator.

  This epoxy resin having a 3,4-epoxycyclohexenyl skeleton is extremely high in transparency, can form a clad with high transparency and low refractive index, and produces an optical waveguide with low optical loss. Is something that can be done. Further, since it has a structure called internal epoxy, cationic curing is easy to proceed, and sufficient curing can be performed in a short time. Further, a curable film having a strong tackiness can be obtained, and the Tg can be increased or decreased depending on the molecular structure, and the Tg of the cured product can be adjusted. . Furthermore, when the epoxy resin composition contains the epoxy resin having the 3,4-epoxycyclohexenyl skeleton, when only the photocationic curing initiator is used as the cationic curing initiator, the curability produced with the epoxy resin composition is used. By laminating the film from above the core, exposing it to cure, and heating and after-curing to form the cladding, the waveguide loss of the optical waveguide becomes extremely low. Will be described later). The amount of the epoxy resin having a 3,4-epoxycyclohexenyl skeleton is preferably in the range of 5 to 50% by mass with respect to the total amount of the resin components.

  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.

  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, 1,2-bis (hydroxymethyl) -1-butanol. , 2-epoxy-4- (2-oxiranyl) cyclohexane adduct, novolac-type epoxy resin, bisphenol-type epoxy resin, epoxy resin having the chemical structure of formula (1), and photocationic curing agent Is formed.

  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 tackiness may be strengthened, 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 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol as described above, the transparency of the core can be increased. Optical loss can be reduced. Moreover, while adjusting so that the tackiness of a photocurable film may be weakened, it can adjust so that Tg of hardened | cured material may be raised. If the content is too large, the photocurable film becomes brittle and the handleability is reduced, so that 1,2-epoxy-4- (2-oxiranyl) of 2,2-bis (hydroxymethyl) -1-butanol The content of the cyclohexane adduct is preferably in the range of 5 to 50% by mass with respect to the total resin content.

  Moreover, by containing said novolak-type epoxy resin, transparency of a core can be made high and optical loss can be reduced. Moreover, while adjusting so that the tackiness of a photocurable film may be weakened, it can adjust so that Tg of hardened | cured material may be raised. The blending amount is preferably in the range of 10 to 50% by mass with respect to the total resin content. If it exceeds 50% by mass, the cured product becomes brittle, the compatibility with other resins decreases, the transparency decreases, and the oxidative coloring at the reflow temperature increases, which is not preferable.

  Moreover, by containing said bisphenol-type epoxy resin, Tg of hardened | cured material can be adjusted low, the brittleness of hardened | cured material can be reduced, and a refractive index can be made high, and transparency is made high. The light loss can be reduced. As this bisphenol type epoxy resin, any one that is liquid at normal temperature and solid at normal temperature can be used. Therefore, the tackiness of the photocurable film can be improved by using a liquid one, and solid The tackiness of the photocurable film can be lowered and the tackiness of the photocurable film can be adjusted. The content of the bisphenol type epoxy resin is preferably in the range of 30 to 60% by mass with respect to the total resin content.

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

  Further, by containing an epoxy resin having the chemical structure of the above 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.

  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 photocurable film is produced from an epoxy resin composition prepared by combining the above resin components and curing initiator materials, and the photocurable film is exposed to a pattern and developed to provide excellent transparency, and A highly flexible core can be produced with little 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, the Tg can be adjusted to a lower value, and the refractive index can be increased and transparent. Performance 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.

  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, an example of a method for producing an optical waveguide using the curable film for cladding 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 transparent temporary substrate 11 that transmits light such as ultraviolet rays, and the clad curable film 1 is cured by irradiation with light such as ultraviolet rays or by heating, as shown in FIG. The under clad 3a is laminated on the surface of the temporary 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 (c). 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, as shown in FIG. 1D, V grooves 14 are cut at both ends of the core 4 in the longitudinal direction, and micromirrors 15 are formed on the surface of the V grooves 14 by vapor deposition of gold or the like.

  Next, the clad curable film 1 is laminated and overlaid on the underclad 3a so as to cover the core 4 as shown in FIG.

  Then, a rigid substrate 7 on which a circuit 6 such as a printed wiring board is formed is superimposed on the surface of the curable film 1 for clad as shown in FIG. 1 (f), and light is irradiated to the curable film 1 for clad through a transparent temporary substrate 11. Then, the curable film for cladding 1 is cured to form the upper cladding 3b, and then the temporary substrate 11 is peeled off as shown in FIG.

  Thus, 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, and a rigid circuit in which a circuit 6 such as a printed wiring board is formed. A photoelectric composite substrate B in which the optical waveguide A is provided on the surface of the substrate 7 can be obtained.

  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 in a uniform and highly accurate thickness by the clad curable film 1 and the core photocurable film 2.

  In addition, in manufacturing the photoelectric composite substrate B by joining the optical waveguide A to the rigid substrate 7 of the printed wiring board as described above, after laminating the curable film for cladding 1 as shown in FIG. As shown in FIG. 1 (f), a substrate 7 is placed on the clad curable film 1, and then the clad curable film 1 is irradiated with light to be cured, whereby the clad curable film 1 forms the upper clad 3b. At the same time, bonding to the substrate 7 can be performed simultaneously. At this time, since the rigid substrate 7 does not transmit light, the entire surface of the curable film for cladding 1 is irradiated by irradiating light from the light-transmitting transparent temporary substrate 11 side as shown in FIG. It can be cured in a short time. However, the micro mirror 15 is provided on the core 4 as described above, and the curable film 1 for clad cannot be sufficiently exposed in the shadowed portion of the micro mirror 15, and the curing becomes insufficient. Therefore, in this case, the epoxy resin composition for producing the curable film for cladding 1 contains the epoxy resin of the formula (2) as described above, and a thermal cation curing initiator as a cation curing initiator, What uses a photocationic curing initiator together is used. And in this thing, after irradiating light to the curable film 1 for clad and photocuring with the effect | action of a photocationic curing initiator, it heats to the temperature which can be hardened | cured with a thermal cation curing initiator, and aftercure. Thus, the portion of the light guide that is not sufficiently exposed and not sufficiently cured can be thermally cured to prevent insufficient curing, and the adhesiveness between the core 4 and the clad 3 can be improved, and the light loss can be reduced. Can be formed, and reflow resistance and heat cycle resistance can be improved.

Further, when the core photocurable film 2 is developed after pattern exposure to develop the core 4 as shown in FIG. 1 (c), both sides of the core 4 are easily roughened by development. Light is scattered on both side surfaces of the light 4 so that the light can easily escape to the clad 3, which may cause a large optical waveguide loss. Therefore, in this case, the epoxy resin composition for producing the curable film for cladding 1 contains an epoxy resin having a 3,4-epoxycyclohexenyl skeleton as described above, and light as a cation curing initiator. What mix | blended only the cationic hardening initiator is used. Then, the clad curable film 1 is laminated from above the core 4 as shown in FIG. 1 (e), exposed to light and exposed, and then heated and after-cured, so that light is emitted from both sides of the core 4. It is possible to prevent the occurrence of a large optical waveguide loss due to escape to the cladding 3. This is because the 3,4-epoxycyclohexenyl structure is likely to cause an interaction (infiltration or molecular diffusion) into the resin phase of the core 4, so that the core 4 in contact with the epoxy resin having the 3,4-epoxycyclohexenyl structure. This is probably because the surface layers of both surfaces have a lower refractive index than the inside of the core 4. The heating conditions of the after cure after this light irradiation are preferably 120 to 150 ° C. and about 30 to 90 minutes.

  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) Epoxy resin having 3,4-epoxycyclohexenyl skeleton, 3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexene carboxylate: “Celoxide 2021P” manufactured by Daicel Chemical Industries, Ltd.
(2) 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol and “EHPE3150” manufactured by Daicel Chemical Industries, Ltd.
(3) 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 4005P” manufactured by Japan Epoxy Resin Co., Ltd.
・ Liquid bisphenol A epoxy resin: “Epicron 850S” manufactured by Dainippon Ink and Chemicals, Inc.
・ Liquid bisphenol F type epoxy resin: “Epicron 835” manufactured by Dainippon Ink & Chemicals, Inc.
(4) Epoxy resin of formula (1), “VG-3101” manufactured by Mitsui Chemicals, Inc.
(5) Novolac type epoxy resin / solid novolac type epoxy resin: “EPPN201” manufactured by Nippon Kayaku Co., Ltd.
(6) Phenoxy resin, “YP50” manufactured by Toto Kasei Co., Ltd.
(7) Epoxy resin of formula (2), trimethylolpropane type epoxy resin: “Epototo YH300” manufactured by Toto Kasei Co., Ltd.
(8) Light cationic curing initiator, Ltd. ADEKA "SL-170" (SbF ₆ ^- sulfonium salt)
(9) thermal cationic curing initiator, available from Sanshin Chemical Industry Co., Ltd. "SI-150L" (SbF ₆ ^- sulfonium salt)
(10) Surface conditioner “F470” manufactured by Dainippon Ink & Chemicals, Inc.
(11) 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 2 ”, and a composition not satisfying the requirements of claim 1 is indicated as“ Core Comparative Example Composition 1 ”.

  Then, the transparency, refractive index, and Tg (glass transition temperature) of the clad curable film 1 and the core photocurable film 2 were measured, and the results are shown in Table 1.

  Transparency is evaluated by collecting each material in a glass container at a predetermined blending amount, stirring and dissolving under reflux, and then visually confirming it. "△", the thing which becomes cloudy was determined to be "x".

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.

  In Table 1, the clad curable films of “Clad Example Composition 1” to “Clad Example Composition 3” and the Core Photocurable Films of “Core Example Composition 1” to “Core Example Composition 2” In any case, an optical waveguide having excellent transparency, excellent flexibility and tackiness, and a cured product having a high glass transition temperature and excellent heat resistance can be produced.

  On the other hand, the curable film for clad of “Clad Comparative Example Composition 1” is transparent, but has poor flexibility, low tackiness, high softening temperature, and high viscosity during melting. The optical waveguide is manufactured by the laminating process, such as powder falling from the surface, chipping and cracking of the film during handling, poor adhesion after lamination, and poor filling of the lower side of the core when over clad is formed on the core. Problems are likely to occur.

  Moreover, the photocurable film for cores of “Core Comparative Example Composition 1” has a problem of transparency because it has a slightly whitened state due to poor compatibility of the blended materials.

Example 1
An ultraviolet transparent transparent polycarbonate plate is used as the temporary substrate 11, and a 10 μm thick clad curable film 1 having the “cladding example composition 1” is used. Using a pressure-type vacuum laminator (“V-130” manufactured by Nichigo Morton Co., Ltd.), lamination was performed as shown in FIG. Then, the cladding curable film 1 is irradiated with ultraviolet light under a condition of ² J / cm ^{2 with} an ultra-high pressure mercury lamp, exposed, and after peeling off the release film, heat treatment is performed at 140 ° C. for 30 minutes, and oxygen plasma treatment is further performed. Then, the clad curable film 1 was cured to form an underclad 3a.

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 under the same conditions as above as shown in FIG. 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 2 for cores was photocured.

  Next, after peeling off the release film from the photocurable film 2 for the core, a heat treatment was performed at 140 ° C. for 2 minutes, and a water-based flux cleaning agent adjusted to 55 ° C. as a developer (“Pine Alpha ST-100SX ") is developed with an ultrasonic cleaner to dissolve and remove the unexposed portion of the core photocurable film 2, and further washed with water and air blown. Was dried for 10 minutes to form the core 4 as shown in FIG. Further, the appearance of the core 4 after the development processing was observed with a stereomicroscope. The results are shown in Table 2.

Next, as shown in FIG. 1D, micromirrors 15 for deflecting the guided light by 90 ° were formed at 10 mm from both ends of the core 4. That is, first, a rotating blade having a cutting blade apex angle of 90 ° (“# 5000” blade manufactured by Disco Corporation) was used, and the rotational speed was 10,000 rpm and the moving speed was 0.1 mm / s. The V-groove 14 having a depth of 50 μm was processed by moving the position across the position, and then a solution obtained by diluting the varnish of “Clad Example Composition 1” 50 times with a solvent of toluene: MEK = 3: 7 By thinly applying to the V-groove 14 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 surface of the V groove 14 was smoothed. Thereafter, gold was vacuum-deposited by covering a metal mask in which only the portion of the V-groove 14 was opened, thereby forming a micromirror 15 with a 1000-thick gold thin film on the surface of the V-groove 14.

  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.

  After releasing the release film from the clad cured film 1, the printed wiring board substrate 7 (made of “R1766” manufactured by Matsushita Electric Works Co., Ltd.) on which the inner layer circuit 6 is formed is connected to the circuit 6 and the core 4. Were aligned using a vacuum laminator “V-130” under the conditions of 80 ° C. and 0.2 MPa as shown in FIG.

Thereafter, as shown in FIG. 1 (f), ultraviolet light is irradiated from the temporary substrate 11 side with an ultrahigh pressure mercury lamp under the condition of 1 J / cm ² , and the curable film for cladding 1 is exposed and photocured. Further, after-curing by heating at 140 ° C. for 1 hour, the overclad 3b was formed and the substrate 7 was adhered. At this time, the state of the over clad 3b was visually observed. The results are shown in Table 2.

  Then, the optical waveguide A formed by burying the core 4 in the clad 3 composed of the under clad 3a and the over clad 3b by peeling and removing the temporary substrate 11 as shown in FIG. A photoelectric composite substrate B laminated and integrated with the substrate 7 of the printed wiring board was obtained.

  A printed wiring board can be further laminated on the photoelectric composite substrate B in multiple layers. That is, the copper foil 18 on one side of the double-sided copper clad laminate 17 having a thickness of 60 μm was removed by etching off and the light inlet / outlet 19 was processed by a router. Further, the copper foil 18 on one side of the other double-sided copper clad laminate 20 having a thickness of 60 μm was removed by etching off. Then, as shown in FIG. 2A, while aligning the light inlet / outlet 19 and the micromirror 15 of the laminated plate 17, the etch-off surface of the laminated plate 17 is adhered to the adhesive layer 22 ("Nikka Flex" manufactured by Nikkan Kogyo Co., Ltd.). SAFV40 (D) ") is overlaid on the surface of the underclad 3a of the optical waveguide A, and the etch-off surface of the laminated plate 20 is overlaid on the surface of the substrate 7 with the adhesive layer 22 interposed between 170 ° C and 1.8 MPa. The laminated plates 17 and 20 were bonded by heating and pressing under conditions.

  Next, through the process of through-hole 20, copper plating treatment, formation of outer layer circuit 21 in a predetermined pattern by etching copper foil 18, formation of solder resist, gold plating treatment, silk printing, etc., the process of FIG. Thus, a rigid photoelectric composite substrate B having an optical waveguide A in which micromirrors 15 are formed at both ends of a core 4 having a total length of 100 mm and having circuits 6 and 21 formed in multiple layers was obtained. The optical path of the optical waveguide A is indicated by an arrow in FIG.

(Examples 2-4, Comparative Examples 1-2)
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. In the case of Comparative Example 1 using the “Clad Comparative Example Composition 1” as the curable film 1 for cladding, lamination in the process of FIG. 1A is performed at 90 ° C. and 0.2 MPa. Lamination in the step of FIG. 1 (e) was performed under conditions of 110 ° C. and 0.3 MPa.

  About the photoelectric composite board | substrate B of Examples 1-4 and Comparative Examples 1-2 which were obtained as mentioned above, the measurement of light loss and evaluation of heat cycle performance were performed. The results are shown in Table 2.

The optical loss was measured as follows. At the light inlet / outlet 19 of the photoelectric composite substrate B, the end of the optical fiber having a core diameter of 10 μm and NA of 0.21 is connected to a portion corresponding to the micromirror 15 at one end of the core 4 through matching oil of silicone oil. The end of the optical fiber having a core diameter of 200 μm and NA of 0.4 is connected to the portion corresponding to the micromirror 15 at the other end of the core 4 through matching oil, and the light from the 850 nm wavelength LED light source is core diameter of 10 μm. The power (P ₁ ) of light emitted from an optical fiber having an NA of 0.21 and entering the optical waveguide A and having a core diameter of 200 μm and an optical fiber having an 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 of only the optical waveguide A portion of the photoelectric composite substrate B, the outer portions including the micromirrors 15 at both ends of the photoelectric composite substrate B are cut off, the length is 100 mm, and both ends are 40 μm. An optical waveguide A in which the end face of the core 4 of 40 μm is exposed is formed, and an optical fiber is connected to each end face of the core 4 in the same manner as described above, and the power of light emitted through the optical waveguide A (P ₁ ) and the light power (P ₀ ) in the state where the optical waveguide A is not interposed, and the insertion loss of the optical waveguide A was determined from the calculation formula of −10 log (P ₁ / P ₀ ). The results are shown in the column “Loss of optical waveguide (2)” in Table 2.

  The heat cycle property was evaluated as follows. First, with respect to the photoelectric composite substrates B obtained in Examples 1 to 4 and Comparative Examples 1 and 2, “optical waveguide insertion loss (1)” was measured in the same manner as described above, and then −55 ° C. and 125 ° C. A 300-cycle liquid-phase heat cycle test was conducted, and “optical waveguide insertion loss (1)” was measured in the same manner as described above for the photoelectric composite substrate B after the test. And the increase of insertion loss before and after the test was obtained.

  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 2” Each of the examples using a combination of curable films had small optical waveguide loss and good heat cycle performance.

  On the other hand, in Comparative Example 1 using a combination of the curable film for cladding of “Comparative Example 1 for Cladding” and the photocurable film for cores of “Core Example Composition 1”, the curable film for cladding from above the core. When forming an overclad by laminating, the curable film for clad has poor flexibility and is difficult to adapt to the shape of the core, resulting in poor filling properties around the core and an air layer, resulting in a large loss Met. In addition, since the filling property around the core is poor as described above, the heat cycle performance is greatly reduced.

  In Comparative Example 2 using a combination of the curable film for cladding of “Clad Example Composition 1” and the photocurable film for core of “Core Comparative Example Composition 1”, the problem in manufacturing the optical waveguide is Although there was no, since the transparency of the photocurable film for cores was bad, a loss occurred greatly.

An example of the process of manufacture of the photoelectric composite substrate concerning this invention is shown, (a) thru | or (g) are sectional drawings, respectively. An example of the process of manufacture of the photoelectric composite substrate concerning this invention is shown, (a) (b) is sectional drawing, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Curable curable film 2 Core photocurable film 3 Clad 4 Core 6 Circuit 7 Substrate

Claims (5)

In the optical waveguide formed from the clad and the core in the clad, the clad is 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol, It is produced by laminating a curable film formed of an epoxy resin composition containing a bisphenol type epoxy resin, a phenoxy resin, and a cationic curing initiator and then curing, and the core is 3,4-epoxy Epoxy resin having cyclohexenyl skeleton, 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol, novolac type epoxy resin, bisphenol type epoxy resin, formula Epoxy resin having chemical structure (1) and photocationic curing After laminating a photocurable film formed by epoxy resin composition containing, by pattern exposure, the unexposed portions intended to be produced by the phenomenon process be removed using an aqueous flux cleaning agent An optical waveguide characterized by being.

  The optical waveguide according to claim 1, wherein the epoxy resin composition forming the core photocurable film also contains a phenoxy resin. The epoxy resin composition forming the curable film for clad also contains the epoxy resin of the formula (2), and as the cationic curing initiator, a thermal cationic curing initiator and a photocationic curing initiator are used in combination. The optical waveguide according to claim 1, wherein the optical waveguide is characterized in that:

  The epoxy resin composition for forming a curable film for cladding also includes an epoxy resin having a 3,4-epoxycyclohexenyl skeleton, and is characterized by using only a photocationic curing initiator as a cationic curing initiator. The optical waveguide according to claim 1 or 2.   5. A photoelectric composite substrate, wherein the optical waveguide according to claim 1 is provided on a substrate having a circuit.

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