JPH10170738A - Polymer optical waveguide and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-loss optical waveguide having a low refractive index and high heat resistance, by using a racemic polymer produced from each specified epoxy compd. or epoxyacrylate compd. having asymmetric spirorings as the essential component for the optical core and/or optical clad. SOLUTION: A racemic polymer containing an epoxy compd. containing asymmetric spirorings expressed by the formula, or containing this epoxy compd. and an epoxyacrylate compd. obtd. from an acrylic acid and methacrylic acid as the essential component is used for the optical core and/or optical clad. In the formula, X represents a hydrogen, alkyl group, alkoxy group, nitro group or halogen group, m is an integer of 1 to 3, and n is an integer of 0 to 10. In the production method, each film to constitute the core and clad is formed by coating and hardening, and the core is formed by photolithography and/or reactive ion etching.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide using a polymer material, and relates to optical communication, optical information processing,
It can be used for various optical waveguides, optical waveguide devices, optical integrated circuits or optical wiring boards widely used in the field of micro-optics or other general optics.

[0002]

2. Description of the Related Art An optical waveguide is a special light that performs light multiplexing / demultiplexing, switching, and the like by confining light by forming a portion having a slightly higher refractive index than the surroundings on the surface of the substrate or directly below the substrate surface. Parts. Specific examples include an optical multiplexing / demultiplexing circuit, a frequency filter, an optical switch, an optical interconnection component, and the like that are useful in the field of communication and optical information processing. The features of optical waveguide devices are that, compared to optical fiber parts that are basically made by processing individual optical fibers, high performance can be realized compactly based on precisely designed waveguide circuits. That is, mass production is possible, and various types of optical waveguides can be integrated on one chip. To briefly review the history of the development of optical waveguides, it can be said that optical waveguide devices have been developed assuming introduction into optical fiber communication systems. In the 1970's, the early days of optical fiber communication, research was mainly on multi-mode optical waveguides compatible with multi-mode fiber, but in the 1980's, optical communication systems using single-mode fiber became mainstream. In line with this introduction, research and development of single mode optical waveguides has been activated. Advantages of the single-mode optical waveguide include easy control of guided light, advantage in miniaturization of the device, high optical power density, and suitability for high-speed operation. on the other hand,
With the rapid rise of multimedia, not only advanced computer communications but also offices and homes are increasingly motivated to distribute high-speed signals by light. As a result, multi-mode optical waveguide components have been attracting attention as low-cost optical components.
The multi-mode optical waveguide has advantages over the single-mode optical waveguide in that it is more suitable for mass production and that handling such as connection is much easier. Conventionally, as an optical waveguide material, an inorganic glass having excellent transparency and small optical anisotropy has been mainly used. However, inorganic glass has problems such as being heavy and easily broken and high production cost. Recently, instead of inorganic glass, it is extremely transparent in the visible region and has a communication wavelength of 1.3 μm and 1 μm. There is an increasing movement to manufacture optical waveguide components using a transparent polymer having a window of .55 μm. For polymer materials, it is easy to form a thin film by spin coating or dipping, etc.
It is suitable for producing a large-area optical waveguide. In addition, since a heat treatment step at a high temperature is not included during film formation, an optical waveguide can be manufactured on a substrate such as a plastic substrate, which is difficult to heat-treat at a high temperature, as compared with a case where an inorganic glass material such as quartz is used. There are advantages. Further, it is also possible to produce a substrate-free optical waveguide film utilizing the flexibility and toughness of a polymer. In addition, the fact that manufacturing is basically a low-temperature process and that it is easy to apply to replication, such as mass production using molds, has the potential for cost reduction compared to glass-based or semiconductor-based optical waveguides. high.
Therefore, it is expected that optical waveguide components such as an optical integrated circuit used in the field of optical communication and an optical wiring board used in the field of optical information processing can be manufactured in large quantities and at low cost using polymer optical materials. ing. As a polymer for an optical waveguide, various transparent polymers such as polymethyl methacrylate have been proposed, and research and development of the formation of an optical waveguide have been actively pursued. Conventionally, polymer optical materials have been considered to have problems in terms of environmental resistance such as heat resistance, but in recent years, heat resistance has been improved by incorporating an aromatic group such as a benzene ring or using an inorganic polymer. Improved materials have been reported (for example, JP-A-3-43423).

[0003]

However, the conventional optical materials as described above have a drawback that the solvent resistance is low. In addition, there was a serious problem in processing called intermixing. The term "intermixing" as used herein means that when polymer films are laminated by a solution coating method, the surface of the lower layer is dissolved or swelled in the upper layer coating solution and the interface becomes uneven. When intermixing occurs, the waveguide shape becomes smaller than the design dimension, or the refractive index difference between the core and the clad changes, making it difficult to achieve a desired function as an optical waveguide. Therefore, in the field of optical waveguides in which the same material whose relative refractive index difference is controlled in the range of 0.3 to several% is often used as the core material and the cladding material, the lower cladding, the core,
In the process of sequentially forming the upper cladding,
As long as a coating method using the same or very similar solvent is used, suppression of intermixing has been a very difficult problem to be solved. Further, a material containing an aromatic group such as a benzene ring which is effective in improving heat resistance also has a disadvantage that it has a large birefringence, which is fatal for use in a single mode optical waveguide. In general, when a polymer thin film is formed using a material containing an aromatic group such as a benzene ring, the aromatic group such as a benzene ring is oriented in the thin film to exhibit birefringence. For this reason, the optical waveguide manufactured using the material has polarization dependency, and even if the intensity of the incident light is constant, its output characteristic fluctuates due to the fluctuation of the polarization plane, and actually, the output characteristic fluctuates. When used as an optical waveguide, there is a problem that the use is extremely limited. On the other hand, an inorganic polymer having no aromatic ring and excellent heat resistance has a drawback that it is not easy to form a thick film or to process it. That is, when the film is made thick, cracking is liable to occur, and in order to process the film by dry etching, it is necessary to use a special reaction gas, and there is a problem that there is no suitable mask material. The present invention has been made in view of such circumstances, and has as its object the purpose of polymer optics that has high solvent resistance, avoids intermixing, has excellent heat resistance, has low birefringence, and has excellent processability. An object of the present invention is to provide a low-loss optical waveguide having low birefringence and high heat resistance, which has never been obtained by using a material.

[0004]

SUMMARY OF THE INVENTION In summary of the present invention, the first invention of the present invention has the following structural formula (Formula 1):

[0005]

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Wherein X represents hydrogen, an alkyl group, an alkoxy group, a nitro group, or a halogen, m represents an integer of 1 to 3, and n represents an integer of 0 to 10. An optical core and / or a racemic polymer obtained by using an epoxy compound containing a spiro ring or an epoxy acrylate compound obtained from the epoxy compound and at least one selected from acrylic acid and methacrylic acid as essential components.
Alternatively, the present invention relates to a polymer optical waveguide which is used as an optical clad. Further, a second invention of the present invention is an invention relating to the method for producing a polymer optical waveguide of the first invention, wherein in the method for producing a polymer optical waveguide, the film forming the core and the cladding is formed. The core is formed by applying and curing each film, and a photolithography method and / or a reactive ion etching method and / or a photolocking method and / or a mold method are used in forming a core.

[0007] The present inventors photo-cure a flat and uniform thin film of a racemic mixture containing an epoxy compound or an epoxy acrylate compound containing an asymmetric spiro ring as an essential component, and thereby have a sufficient and sufficient resistance for producing an optical waveguide. We succeeded in obtaining solvent properties. In addition, it has been found that the film can be easily formed into a thick film by a simple method such as a spin coating method, and that a single-mode optical waveguide by dry etching and a multi-mode optical waveguide by photolithography can be easily processed. Further, they have found that heat resistance is remarkably improved by introducing an aromatic ring in which two benzene rings are mutually bonded at two substitution positions. At the same time, the optically active structure of the aromatic moiety has an asymmetric spiro ring structure in which the benzene ring is orthogonal in the molecule, reducing the birefringence at the molecular level and finally forming a racemic polymer. It has been found that the birefringence is further reduced at the bulk level. As a result, the birefringence of the film is reduced to a level of 1 × 10 ⁻⁴ even though the aromatic ring fraction is increased to ensure heat resistance, and the polarization of an optical waveguide manufactured using the material is reduced. We succeeded in suppressing the wave dependence below the allowable value. The racemic mixture containing an epoxy compound or an epoxy acrylate compound containing an asymmetric spiro ring as an essential component used in the present invention is photocurable, which means that the solvent resistance, the thick film-forming property, and the photolithography process described above are used. In addition, they found that they were very effective for duplication (mass production) using the die method.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The contents of the present invention will be specifically described below. The optical waveguide of the present invention has sufficient heat resistance and a low birefringence to function as an optical waveguide device because it is a main component of an epoxy compound or an epoxy acrylate compound which is an essential raw material of a polymer used as an optical waveguide material. Derived from an aromatic ring having an asymmetric spiro structure.
The asymmetric spiro aromatic ring is fixed such that the benzene rings at both ends of the molecular formula are almost orthogonal to each other by spiro moieties connecting the two, and as a result, birefringence is hardly generated at the molecular level. Further, the polymer for an optical waveguide device used in the present invention is obtained by polymerizing a racemic mixture containing an epoxy compound or an epoxy acrylate compound having an asymmetric spiro aromatic ring as an essential component by light or heat, The birefringence remaining at the molecular level is also canceled out to a negligible level by the racemic body of the optical waveguide material as a whole. Thus, the present invention makes it possible to provide an optical waveguide having no polarization dependence. Further, in the asymmetric spiro aromatic ring used in the present invention, the free rotation of the benzene ring at both ends of the molecule is extremely restricted as compared with a bisphenol compound which is a well-known aromatic ring for resin. As a result, the heat resistance represented by the glass transition temperature and the like is remarkably improved, and the temperature range for functioning as an optical waveguide device is sufficiently secured. Examples of the epoxy acrylate compound used in the first invention of the present invention include the following structural formula (Formula 2):

[0009]

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(Wherein, X represents hydrogen, an alkyl group, an alkoxy group, a nitro group, or a halogen. M represents an integer of 1 to 3, n represents an integer of 0 to 10. R represents hydrogen or An epoxy acrylate compound containing an asymmetric spiro ring represented by the following formula:

As a specific example of the polymer optical waveguide of the present invention, a non-aromatic compound or a part of an aromatic ring for adjusting the refractive index of the core and the clad is fluorinated. Characterized by containing a compound, characterized by satisfying the single-mode waveguide condition for light waves in the visible-near-infrared region, and multi-mode guided by light waves in the visible-near-infrared region One that satisfies the condition is exemplified.

The polymer thin film required in the production process of the polymer optical waveguide of the present invention comprises a core material, a clad material,
That is, a mixture for an optical waveguide (hereinafter, collectively referred to as a monomer-containing material) containing an epoxy compound or an epoxy acrylate compound (hereinafter, referred to as a monomer) as a main component was applied to a desired thickness. Thereafter, it is obtained by photopolymerization or thermal polymerization of an epoxy group or an acryl group contained in the monomer. In order to cause the reaction to occur efficiently and sufficiently, it is desirable to add a polymerization initiator. The light or thermal polymerization can be suitably carried out by using various known initiators, formulations, and the like, but is preferably of a type that does not color the formed film as much as possible. Examples of a photopolymerization initiator that can be used for photopolymerization of an epoxy monomer include generally well-known onium salts and sulfonium salts. Examples of a photopolymerization initiator that can be used for photopolymerization of an epoxy acrylate monomer include benzoin, benzyl, benzoin methyl ether, benzoin isopropyl ether, and acetophenone. Examples of the thermal polymerization initiator include peroxides such as benzoyl peroxide, p-chlorobenzoyl peroxide, and diisopropyl peroxycarbonate, and azo compounds such as azobisisobutyronitrile.

A typical method of forming a film is a method in which a monomer-containing material is used as it is or dissolved in a solvent, applied on a substrate, a clad or a core, and then a cured film is obtained by light or heat. By dissolving in a solvent, the monomer-containing material becomes a fluid having an appropriate viscosity corresponding to the step of forming a thin film. Solvents used at this time include aromatics such as toluene, xylene, mesitylene and chlorobenzene, alcohols such as ethanol, n-propyl alcohol, i-propyl alcohol and butanol, acetone, methyl ethyl ketone, methyl isobutyl ketone and methyl isoamyl. Ketones such as ketones, esters such as ethyl acetate, butyl acetate, ethyl lactate, 2
-Cellosolves such as ethoxyethanol and 2-butoxyethanol, cellosolve acetates such as 2-ethoxyethyl acetate and 2-butoxyethyl acetate, dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether and diethylene glycol diethyl ether; Heterocycles such as ethers, tetrahydrofuran, N-methylpyrrolidone, and γ-butyrolactone are exemplified. By selecting the type of solvent and adjusting the solution concentration, the monomer-containing material can obtain an appropriate viscosity corresponding to the process of forming a thin film.

According to the present invention, when actually manufacturing an optical waveguide using the monomer-containing material, it is necessary to first adjust the refractive index of the monomer-containing material according to the waveguide mode condition required for the optical waveguide. is there. That is, at least two types of monomer-containing materials having a precisely controlled refractive index difference must be prepared as the core material and the clad material.
The refractive index is adjusted by adding a non-aromatic monomer or a monomer having a partially fluorinated aromatic ring as a component for reducing the refractive index. The magnitude of the relative refractive index difference is determined according to the mode of light to be guided and the dimensions of the core, but is generally in the range of 0.1% to 5%. For example, when the mode diameter of the single mode optical fiber and that of the guided light are matched, it is desirable that the shape of the core is a square of 8 μm square and the relative refractive index difference is 0.3%. In the case of a multi-mode optical waveguide having a size of about 40 μm square, a relative refractive index difference of about 1% is generally used to match the mode diameter with the multi-mode optical fiber. After adjusting the core material and the clad material on the basis of the monomer-containing material in this manner, FIG.
In order to fabricate a channel-type buried optical waveguide as schematically shown in FIG. FIG. 1 is a schematic diagram including an outline of a cross-sectional structure of a polymer optical waveguide. In FIG. 1, reference numeral 1 denotes a core,
2 means clad. First, a clad material is applied to a substrate and cured by light or heat to form a lower clad. Next, a core material is applied thereon by spin coating or the like. One of the great features of the optical waveguide of the present invention is that intermixing is completely suppressed by curing the film every time the film is formed. Next, after the core material is also cured by the same method as described above, a layer serving as an etching mask is formed on the core layer and processed into a waveguide pattern by photolithography or the like. As a material for the etching mask, an organic photoresist or a metal is used. Next, a desired waveguide pattern can be formed by reactive ion etching of the core layer through the etching mask. This method is particularly effective for producing a single mode optical waveguide. When the core has photoreactivity, a waveguide pattern can be formed by directly irradiating light through a mask and dissolving and removing a non-irradiated portion with a solvent. This method is particularly effective for producing a multimode optical waveguide. Finally, an upper cladding layer is applied and cured.

The present invention is not limited to the above-described method for producing an optical waveguide, and is particularly suitable for a mixture for an optical waveguide mainly containing an asymmetric spiro ring-containing monomer which is a feature of the present invention. The present invention provides a developed photo-locking method and mold method. The specific method is as follows. Photo-locking method, a step of dissolving an ultraviolet-curable resin solution containing an epoxy compound containing an asymmetric spiro ring as a main component and a monomer for refractive index control having a different refractive index from the ultraviolet-curable resin solution in a predetermined solvent, and Is applied on the clad and cured by ultraviolet light through a photomask, and the step of forming a core or clad by volatilizing and removing the monomer for refractive index control of the masked uncured portion, and the masked uncured portion And ultraviolet curing. Mold method, a step of forming a clad layer by applying an ultraviolet curable resin solution containing an epoxy compound containing an asymmetric spiro ring on a substrate,
Pressing a convex mold on the clad film to cure by light irradiation or heating to form a clad replica having a concave portion, and ultraviolet curing mainly containing an epoxy compound containing an asymmetric spiro ring in the concave portion. Encapsulating and curing a resin solution to form a core portion.

The generally known photo-locking method is to dissolve a polymer having excellent light transmittance and a monomer for controlling the refractive index having different refractive indexes (hereinafter referred to as a refractive index controlling monomer) in a predetermined solvent, This is applied on the cladding layer, and is cured by ultraviolet light through a photomask.
This is a method of forming a clad structure. When the refractive index control monomer has a lower refractive index than the base polymer, the non-mask portion becomes the clad and the mask portion becomes the core. The present invention is characterized in that a monomer-containing material, which is a feature of the present invention, is used in place of the light-transmitting polymer described above. However, after the refractive index controlling monomer is volatilized and removed, a process of curing the monomer-containing material once again is added. The merit of this photo-locking method is that the part where the refractive index control monomer is removed is not a conventional transparent polymer but a low molecular weight monomer-containing material. There is little physical disturbance, and physical and optical uniformity is kept high, so that transparency is excellent.

Next, a mold method using an asymmetric spiro ring-containing monomer will be described. A mold having a convex shape is pressed against a film made of a monomer-containing material, which is a feature of the present invention, and cured by light irradiation or heating to produce a resin replica having a concave shape. A monomer containing a monomer having a higher refractive index is sealed in the replica and cured to form a core. At this time, after the core portion protruding from the groove of the clad replica is removed by etching or the like, the above-mentioned monomer content for clad replica is applied and cured as an upper layer to form a buried optical waveguide. The monomer-containing material used in the present invention has advantages in that the density fluctuation is small as compared with other photocurable resins, and the refractive index fluctuation which is likely to occur in a mold method can be avoided.

The optical waveguide having the characteristics described above and manufactured by the method described above is excellent in solvent resistance, has a small intrinsic birefringence of the material, and further reduces the bulk birefringence by the racemic effect. As a result, when used as an optical waveguide, the polarization dependence of guided light is small, low-loss waveguide is realized, and heat resistance is excellent.

[0019]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Embodiment 1

[0021]

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Asymmetric spiro ring-containing epoxy compound represented by the above structural formula (Formula 3) 41.6 wt%, solvent 56.7 w
t%, photoinitiator 1.4wt%, leveling agent 0.3wt
%, And filtered through a filter having a pore size of 0.1 μm to prepare an ultraviolet-curable resin solution (A). Similarly, 41.6 wt% of an asymmetric spiro ring-containing epoxy mixture containing a fluorine-containing aliphatic cyclic epoxy compound, and 56.7 wt% of a solvent
%, Photoinitiator 1.4 wt%, leveling agent 0.3 wt%
Was mixed and filtered through a filter having a pore size of 0.1 μm to prepare an ultraviolet-curable resin solution (B). Both resin solutions have a relative refractive index difference (wavelength 1.3 μm) after film formation and curing.
(A) after film formation and curing to make m) 0.3%
The composition was previously prepared so that the refractive index of (B) would be 1.5464 and 1.5417, respectively. High refractive index resin solution (A) for core, low resin solution (B)
Was used for cladding. The production of an optical waveguide using the resin solutions (A) and (B) was performed according to the following steps. First, an ultraviolet curable resin solution (B) was dropped on a silicon wafer, and thinned by a spin coating method.
This was irradiated with a high-pressure mercury lamp (5400 mJ / cm ² ), and further heated at 110 ° C. for 10 minutes to be completely cured to obtain a lower clad. The film thickness after curing was 18 μm. Next, the resin film (A) was coated thereon. On this occasion,
No intermixing was observed between the resin film of (A) and the lower cladding layer. Subsequently, the resin film of (A) was irradiated with a high pressure mercury lamp (5400 mJ / cm ² ),
The core was completely cured by heating at 110 ° C. for 10 minutes. The film thickness was 8 μm as set. Next, by photolithography, 11 μm every 7 μm to 1 μm
Up to a linear mask pattern was formed. Next, the core layer other than the mask pattern was etched by reactive ion etching to form a core ridge. A part of this was taken out, and the cross-sectional shape structure was confirmed with an electron microscope. As a result, the etching was realized almost vertically, and the height was 8 μm.
It was confirmed that a core ridge having a width of 5 μm to 10 μm was formed. Finally, a resin solution (B) was applied on the core ridge, and cured in the same manner as in the case of the lower clad to form an optical waveguide having a buried channel structure. Both ends of the optical waveguide thus produced were cut off with a dicing saw to obtain a linear optical waveguide having a length of 5 cm. Microscopic observation of the cross section in the light transmission mode confirmed that only the core glowed brightly. Core diameter 8μm × 8
When an optical waveguide of μm was selected and the propagation loss was measured, 0.3 dB / cm at a wavelength of 1.3 μm and 1 d at a wavelength of 1.55 μm.
B / cm. At both communication wavelengths, the loss difference (polarization dependent loss) between the TE mode and the TM mode was very small. The waveguide was completely single mode. Furthermore,
The loss of this waveguide is 120 ° C. and 75 ° C.
It did not fluctuate for more than one month even under the condition of / 90% RH. Furthermore, in a directional coupler fabricated using the same pattern as the above-described linear waveguide using the directional coupler mask pattern, it was confirmed that the coupling lengths in the TE mode and the TM mode were substantially the same, and the directional coupler was used as an optical waveguide. In this case, too, no birefringence or very low birefringence was found.

Example 2 An ultraviolet-curable resin solution (A) containing a chiral spiro ring-containing epoxy compound as a main component used in Example 1 was used for a core so that the relative refractive index difference between the core and the core during curing was 1%. Was prepared for cladding. The refractive indices at a wavelength of 850 nm after curing of the films prepared from both resin solutions were 1.5528 and 1.53, respectively.
73. Thus, the relative refractive index difference between the two was 1% as set. The above resin solutions (A) and (B ')
The fabrication of an optical waveguide using was performed according to the following steps. First, an ultraviolet curable resin solution (B ') was dropped on a silicon wafer, and thinned by a spin coating method. This was irradiated with a high-pressure mercury lamp (5400 mJ / cm ² ), and further heated at 110 ° C. for 10 minutes to be completely cured to obtain a lower clad. The film thickness after curing was 40 μm. Then
On top of this, (A) so that the thickness after curing becomes 40 μm.
Was coated. At this time, no intermixing was observed between the resin film of (A) and the lower cladding layer. Non-contact with the resin film produced in this way,
A photomask capable of forming a linear pattern having a width of 40 μm was mounted and irradiated with a high-pressure mercury lamp (7500 mJ / c).
m ² ). The uncured portion was removed by wet etching to produce a core ridge having a width and a height of 40 μm. The core ridge fabricated in this manner was fabricated by photolithography and reactive ion etching.
The shape was the same as a core ridge for a multimode optical waveguide of 0 μm × 40 μm. Finally, overcladding was performed using a resin solution (B '). Thermal curing after photocuring was performed for 20 minutes to form a buried channel structure. Both ends of the optical waveguide thus produced were cut off with a dicing saw to obtain a multimode linear optical waveguide having a length of 5 cm. When the near-field pattern was observed in the light transmission mode at a wavelength of 850 nm, it was observed that only the core portion glowed brightly in a pattern unique to multimode waveguide. Further, when the light propagation loss at this wavelength was measured, it was 0.2 dB / cm. Furthermore, the loss of this waveguide is 120 ° C. and 75 ° C./90%
It did not fluctuate for more than one month even under RH conditions. In this embodiment, the solution (B ') prepared for cladding contains an asymmetric spiro ring-containing epoxy compound in an amount of 20 wt% based on all solutes. However, even a clad material containing no asymmetric spiro ring-containing epoxy compound,
If even the relative refractive index difference is kept at an appropriate value of about 1%,
It was confirmed that there was no significant change in the performance of the finally completed multimode optical waveguide.

Embodiment 3

[0025]

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An asymmetric spiro ring-containing epoxy acrylate compound represented by the above structural formula (Formula 4): 49.7 wt%,
49.7 wt% of a solvent, 0.4 wt% of a photoinitiator, and 0.2 wt% of a thermal initiator were mixed and filtered with a filter having a pore diameter of 0.1 μm to prepare an ultraviolet-curable resin solution (C). Similarly, 49.7 wt% of an asymmetric spiro ring-containing epoxy acrylate mixture containing a fluorine-containing aliphatic cyclic epoxy acrylate compound, 49.7 wt% of a solvent, 0.4
wt% and 0.2 wt% of a thermal initiator were mixed, and the mixture was similarly filtered through a filter having a pore diameter of 0.1 μm to prepare an ultraviolet curable resin solution (D). In order to make the relative refractive index difference (wavelength 1.3 μm) of both the resin solutions after film formation and curing 0.3%, the refractive indices of (C) and (D) after film formation and curing are 1 respectively. .5
The composition was previously adjusted to be 411 or 1.5365. The resin solution (C) having a high refractive index was used for the core, and the resin solution (D) having a low refractive index was used for the clad.
The production of an optical waveguide using the resin solutions (C) and (D) was performed according to the following steps. First, an ultraviolet curable resin solution (D) was dropped on a silicon wafer, and thinned by a spin coating method. This is irradiated with a high pressure mercury lamp (540
0 mJ / cm ² ), and further heated at 120 ° C. for 1 hour to completely cure, thereby forming a lower clad. Film thickness after curing is 1
It was 8 μm. Next, a resin film (C) was coated thereon. At this time, no intermixing was observed between the resin film (C) and the lower cladding layer.
Subsequently, the resin film of (C) was irradiated with a high pressure mercury lamp (1920
mJ / cm ² ) and completely cured by heating at 120 ° C. for 1 hour to obtain a core layer. The film thickness was 8 μm as set. Next, by photolithography, the width from 7 μm to 1
A linear mask pattern of up to 11 μm was formed every μm. Next, the core layer other than the mask pattern was etched by reactive ion etching to form a core ridge. A part of this was taken out, and the cross-sectional structure was confirmed by an electron microscope. As a result, it was confirmed that etching was realized almost vertically, and a core ridge having a height of 8 μm and a width of 5 μm to 13 μm was formed. Finally, a resin solution (D) was applied on the core ridge, and cured in the same manner as in the case of the lower clad to form an optical waveguide having a buried channel structure. Both ends of the optical waveguide thus produced were cut off with a dicing saw to obtain a linear optical waveguide having a length of 5 cm. Microscopic observation of the cross section in the light transmission mode confirmed that only the core glowed brightly. An optical waveguide having a core diameter of 8 μm × 8 μm was selected, and the propagation loss was measured.
It was 1 dB / cm at 5 μm. At both communication wavelengths,
The loss difference (polarization dependent loss) between the TE mode and the TM mode was very small. The waveguide was completely single mode. Furthermore, the loss of this waveguide even at 120 ° C.
Also, it did not fluctuate for more than one month under the conditions of 75 ° C / 90% RH. Furthermore, in a directional coupler fabricated using the same pattern as the above-described linear waveguide using the directional coupler mask pattern, it was confirmed that the coupling lengths in the TE mode and the TM mode were substantially the same, and the directional coupler was used as an optical waveguide. In this case, too, no birefringence or very low birefringence was found.

Example 4 The UV-curable resin solution (C) containing the asymmetric spiro ring-containing epoxy acrylate compound as a main component used in Example 3 was used for a core, and the relative refractive index difference from the core during curing was 1%. The epoxy acrylate ultraviolet curing resin solution (D ') prepared as described above was prepared for cladding. The refractive indices at a wavelength of 850 nm after curing of the films prepared from both resin solutions were 1.5366 and 1.5212, respectively. in this way,
The relative refractive index difference between the two was 1% as set. The production of an optical waveguide using the above resin solutions (C) and (D ′)
This was performed according to the following steps. First, an ultraviolet curable resin solution (D ') was dropped on a silicon wafer, and thinned by a spin coating method. This was irradiated with a high-pressure mercury lamp (1920
mJ / cm ² ), and further heated at 120 ° C. for 1 hour to completely cure, thereby forming a lower clad. Film thickness after curing is 40
μm. Then, the thickness after curing is 40
The resin film (C) was coated to a thickness of μm. At this time, no intermixing was observed between the resin film (C) and the lower cladding layer. A photomask capable of forming a linear pattern having a width of 40 μm in a non-contact manner with the resin film thus produced was mounted, and irradiated with a high-pressure mercury lamp (4100 mJ / cm ² ). The uncured portion was removed by wet etching to produce a core ridge having a width and a height of 40 μm. The core ridge manufactured in this manner had a shape equivalent to that of a 40 μm × 40 μm multi-mode optical waveguide core ridge manufactured by photolithography and reactive ion etching. Finally, overcladding was performed using a resin solution (D '). Thermal curing after photocuring was performed for 90 minutes to form a buried channel structure. Both ends of the optical waveguide thus manufactured were cut off with a dicing saw, and the length of the optical waveguide was 5 mm.
cm of a multimode linear optical waveguide was obtained. Wavelength 850
When the near-field pattern was observed in the light transmission mode of nm, it was observed that only the core portion glows brightly with a pattern unique to multimode waveguide. Further, when the light propagation loss at this wavelength was measured, it was 0.2 dB / cm or less. Furthermore, the loss of this waveguide did not fluctuate at 120 ° C. or 75 ° C./90% RH for more than one month. In this example, the solution (D ') prepared for cladding was prepared by adding an asymmetric spiro ring-containing epoxy acrylate compound in an amount of 20 wt% based on the total solute.
include. However, even if the clad material does not contain any asymmetric spiro ring-containing epoxy acrylate compound, even if the relative refractive index difference is maintained at an appropriate value of about 1%, the performance of the finally obtained multimode optical waveguide is large. No change was observed.

Example 5 A multi-mode optical waveguide having an asymmetric spiro ring-containing epoxy resin as a core and a clad as obtained in Example 2 is more easily mass-produced by a mold method specifically described below. I was able to. In the same manner as in Example 2, an ultraviolet-curable resin solution (A) containing an asymmetric spiro ring-containing epoxy compound as a main component was used for the core, and when cured, the relative refractive index difference from the core was 1
% Of an epoxy-based UV-curable resin solution (B ') prepared for cladding. The fabrication of the multimode optical waveguide using the resin solutions (A) and (B ′) by a mold method was performed according to the following steps. A resin solution (B ′) was spin-coated on a smooth glass substrate, and a thick film having a thickness of 60 μm was applied. Here, a convex mold (40 μm in height, 40 μm in width, 6 cm in length) was pressed while applying pressure, and irradiated with a high-pressure mercury lamp (8000 mJ / cm ² ) from the back surface of the glass substrate. Then, while pressing the mold, the mixture is heated at 110 ° C. for 15 minutes to be completely cured, and the concave lower clad (the concave portion has a depth of 40 μm and a width of 40 mm)
μm, length 6 cm). Next, the core resin solution (A) was injected into the recess, and the core was formed by photocuring again with a high-pressure mercury lamp. At this time, no intermixing was observed between the concave lower cladding and the core. After photo-curing the core, a resin solution (B ') was spin-coated thereon with a thickness of 20 μm. This was completely cured by light and heat to form an upper clad layer. As a result, a multimode optical waveguide having a buried channel structure was obtained. This optical waveguide is 5 cm by a dicing saw.
When the near-field pattern was observed in a light transmission mode with a wavelength of 850 nm, it was confirmed that only the core portion glowed brightly in a pattern unique to multimode waveguide. Further, when the light propagation loss at this wavelength was measured, it was 0.2 dB / cm. Furthermore, the loss of this waveguide is 120 ° C. and 75 ° C./90% RH.
Did not fluctuate for more than one month. Furthermore,
Using a mold for a single-mode optical waveguide processed with high precision, an attempt was made to produce an optical waveguide equivalent to the asymmetric spiro ring-containing epoxy single-mode optical waveguide obtained in Example 1. Except for being slightly inferior to 1, an optical waveguide having almost the same performance was produced.

Example 6 A multimode optical waveguide having an asymmetric spiro ring-containing epoxy acrylate resin as a core and a clad as obtained in Example 4 was obtained by a mold method specifically described below.
Furthermore, mass production could be performed more easily. In the same manner as in Example 4, an ultraviolet-curable resin solution (C) containing an asymmetric spiro ring-containing epoxy acrylate compound as a main component was prepared for the core, and was adjusted so that the relative refractive index difference with the core upon curing was 1%. The epoxy acrylate ultraviolet curable resin solution (D ') was prepared for cladding. Resin solutions (C) and (D ')
Of multi-mode optical waveguides by using the die method
This was performed according to the following steps. A resin solution (D ′) was spin-coated on a smooth glass substrate, and a thick film having a thickness of 60 μm was applied. Here, a convex mold (40 μm in height, 40 μm in width, 6 cm in length) is pressed while applying pressure,
High-pressure mercury lamp irradiation from the back of the glass substrate (5000 mJ /
cm ² ). Then, while pressing the mold, 120
C. for 1 hour for complete curing to produce a concave lower clad (recess depth 40 .mu.m, width 40 .mu.m, length 6 cm). Next, a core resin solution (C) was injected into the concave portion, and the core was formed by photocuring again with a high-pressure mercury lamp. At this time, no intermixing was observed between the concave lower cladding and the core. After the core portion was light-cured, it was spin-coated thereon with a resin solution (D ′) having a thickness of 20 μm. This was completely cured by light and heat to form an upper clad layer. As a result, a multimode optical waveguide having a buried channel structure was obtained. This optical waveguide is cut into a length of 5 cm by a dicing saw, and a wavelength of 8 cm is cut out.
Observation of the near-field pattern in the light transmission mode of 50 nm confirmed that only the core portion glows brightly with a pattern unique to multimode waveguide. Further, when the light propagation loss at this wavelength was measured, it was 0.2 dB / cm. Furthermore, the loss of this waveguide did not fluctuate at 120 ° C. or 75 ° C./90% RH for more than one month. Further, using a mold for a single mode optical waveguide processed with high precision, an optical waveguide equivalent to the asymmetric spiro ring-containing epoxy acrylate single mode optical waveguide obtained in Example 3 was produced, and an optical waveguide loss was attempted. However, except that it was slightly inferior to Example 3, an optical waveguide having almost the same performance could be produced.

Example 7 The ultraviolet-curable resin solution (A) containing the asymmetric spiro ring-containing epoxy acrylate compound as the main component used in Example 4 was added to
A methacrylate monomer was added and dissolved. When the methacrylate monomer is not added and when it is added,
The methacrylate monomer amount was adjusted and added so that the relative refractive index difference (wavelength 850 nm) of the finally cured film became 1%. The preparation of a multimode optical waveguide by the photo-locking method using the above-mentioned preparation liquid was performed according to the following steps. Spin coating the above prepared solution on a silicon substrate,
This was irradiated with a high-pressure mercury lamp and further heated to be completely cured to obtain a lower clad. Next, the above-mentioned preparation liquid was spin-coated for the core. A positive photomask was mounted in a non-contact manner, and a high-pressure mercury lamp was selectively irradiated. Next, this thin film was vacuum-dried while being heated to 60 ° C. Thereby, the methacrylate monomer in the masked unirradiated portion was removed, and the methacrylate monomer was fixed in the film only in the irradiated portion. Next, without a mask, the portion having only the asymmetric spiro ring-containing epoxy acrylate compound was cured by irradiation with a high-pressure mercury lamp to form a core-clad structure. As described above, the relative refractive index difference of 1% between the unirradiated portion (core) and the irradiated portion (cladding) was realized within an error range with respect to the setting. Further, the above-mentioned preparation liquid was applied thereon, and cured as in the case of forming the lower clad to form the upper clad. Through these operations, a multimode optical waveguide having a buried channel structure was manufactured. This optical waveguide is cut into a length of 5 cm by a dicing saw, and a wavelength of 85 cm.
Observation of the near-field pattern in a light transmission mode of 0 nm confirmed that only the core portion glows brightly with a pattern unique to multimode waveguide. Further, when the light propagation loss at this wavelength was measured, it was 0.2 dB / cm. Furthermore, the loss of this waveguide even at 120 ° C.
Also, it did not fluctuate for more than one month under the conditions of 75 ° C / 90% RH.

[0031]

As described above, the optical waveguide comprising the asymmetric spiro ring-containing polymer of the present invention has excellent solvent resistance,
In addition, the polarization dependence is small, and further low-loss waveguide is realized,
Excellent heat resistance. Further, by using the method for manufacturing an optical waveguide described in the present invention, it is possible to mass-produce desired optical waveguides at low cost. Therefore, the present invention is applicable to various optical waveguide devices (optical switches, optical filters, etc.), optical integrated circuits, optical wiring boards, and the like used in the fields of optical communication, optical information processing, micro-optics, and other general optics. Widely applicable.

[Brief description of the drawings]

FIG. 1 is a schematic diagram including an outline of a cross-sectional structure of a polymer optical waveguide.

[Explanation of symbols]

 1: core, 2: clad

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Saburo Imamura 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Atsushi Otsuji 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui East (72) Inventor Rihoko Suzuki 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd. (72) Inventor Tatsunobu Urakami 1190 Kasama-cho, Sakae-ku, Yokohama, Kanagawa Mitsui Toatsu Chemicals Inside the company (72) Inventor Toshihiro Motojima 3-2-5 Kasumigaseki, Chiyoda-ku, Tokyo Mitsui Toatsu Chemical Co., Ltd. (72) Inventor Keisuke Takuma 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd. Inside

Claims (8)

[Claims] 1. The following structural formula (Formula 1): (Wherein, X represents hydrogen, an alkyl group, an alkoxy group, a nitro group, or a halogen, m is an integer of 1 to 3, and n is 0 to 0)
Or an epoxy compound containing an asymmetric spiro ring represented by the formula (1) or an epoxy acrylate compound obtained from the epoxy compound and at least one selected from acrylic acid and methacrylic acid. A polymer optical waveguide, wherein a polymer is used as an optical core and / or an optical clad. 2. The epoxy acrylate compound according to claim 1, wherein the epoxy acrylate compound has the following structural formula (Formula 2): (Wherein, X represents hydrogen, an alkyl group, an alkoxy group, a nitro group, or a halogen, m is an integer of 1 to 3, and n is 0 to 0)
Represents an integer of 10. R represents hydrogen or a methyl group) and is an epoxy acrylate compound containing an asymmetric spiro ring, and a racemic polymer obtained using the compound as an essential component is used as an optical core and / or an optical clad. A polymer optical waveguide, characterized in that: 3. The polymer optical waveguide according to claim 1, wherein the polymer optical waveguide contains a non-aromatic compound for adjusting the refractive index of the core and the clad or a compound in which a part of an aromatic ring is fluorinated. Molecular optical waveguide. 4. The polymer optical waveguide according to claim 1, wherein the polymer optical waveguide satisfies a single-mode waveguide condition for light waves in the visible-near-infrared region. 5. The polymer optical waveguide according to claim 1, wherein the polymer optical waveguide satisfies a multimode waveguide condition for light waves in the visible-near-infrared region. 6. The following structural formula (Formula 1): (Wherein, X represents hydrogen, an alkyl group, an alkoxy group, a nitro group, or a halogen, m is an integer of 1 to 3, and n is 0 to 0)
Or an epoxy compound containing an asymmetric spiro ring represented by the formula (1) or an epoxy acrylate compound obtained from the epoxy compound and at least one selected from acrylic acid and methacrylic acid. In a method for producing a polymer optical waveguide using a polymer as an optical core and / or an optical clad,
The film forming the core and the clad is applied and cured for each film formation, and the core is formed by using a photolithography method and / or a reactive ion etching method and / or a photo locking method and / or a mold method. Characteristic method for producing a polymer optical waveguide. 7. The photo-locking method according to claim 6, wherein
A step of dissolving a UV curable resin solution containing an epoxy compound containing an asymmetric spiro ring as a main component, and a monomer for controlling the refractive index having a different refractive index from the UV curable resin solution in a predetermined solvent, and applying this on a clad; UV curing through a photomask, forming a core or clad by volatilizing and removing the refractive index control monomer of the masked uncured portion, and UV curing the masked uncured portion. A method for producing a polymer optical waveguide, comprising: 8. The method according to claim 6, wherein an ultraviolet curable resin solution containing an epoxy compound containing an asymmetric spiro ring is applied to a substrate to form a clad film, and the clad film is formed on the substrate. A step of forming a clad replica having a concave portion by pressing a convex mold by light irradiation or heating and enclosing an ultraviolet curable resin solution mainly containing an epoxy compound containing an asymmetric spiro ring in the concave portion, Curing the core to form a core portion.