JPH06294915A - Production of quartz optical waveguide - Google Patents

Abstract

PURPOSE:To provide a method to produce a quartz optical waveguide at a low cost with high productivity. CONSTITUTION:The production of quartz optical waveguide includes the following process. A lower clad substrate is formed by using a clad compsn. containing a quartz powder for the clad and an org. binder component. An ink compsn. containing a quartz powder for the core and a synthetic resin is applied on the lower clad substrate to form a precursor of an optical waveguide having desired pattern. The precursor of the optical waveguide is hardened, and the org. binder component and the synthetic resin are removed by pyrolysis. Then succeedingly, the quartz powder for the clad and the quartz powder for the core are calcined to convert the lower clad substrate and optical waveguide precursor into the lower clad and the optical waveguide, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a silica optical waveguide.

[0002]

2. Description of the Related Art A flame deposition method is generally used as a method for manufacturing a quartz optical waveguide. In this method, first, for example, a silica-based fine particle for the lower clad is deposited on a Si substrate to form a lower clad precursor having a desired thickness, and then a silica-based fine particle for the core is further deposited thereon. After forming a core precursor having a desired thickness, the whole is vitrified to form a lower clad and a core slab. Next, for example, photolithography is applied to this core slab to form an optical waveguide of a desired pattern, and then silica-based fine particles for the upper clad are deposited again on the optical waveguide by a flame deposition method to form an upper clad of a desired thickness. Forming a precursor,
This upper clad precursor is made into transparent glass and converted into an upper clad.

Thus, a silica type optical waveguide embedded between the lower clad and the upper clad is formed.

[0004]

By the way, in the case of the above-mentioned method, sophisticated techniques such as flame deposition and photolithography, and a complicated apparatus are required. Further, since there are a large number of steps as a whole and a high-level operation technique is required, there is a problem in terms of realization of high productivity, resulting in an increase in price of the obtained optical waveguide component.

An object of the present invention is to solve the above-mentioned problems in manufacturing a silica-based optical waveguide by using the flame deposition method and to provide a method for manufacturing a silica-based optical waveguide efficiently and therefore inexpensively. .

[0006]

In order to achieve the above-mentioned object, in the present invention, a step of forming a lower clad substrate using a clad composition containing a silica-based powder for clad and an organic binder component ( Hereinafter, referred to as a first step); a step of forming an optical waveguide precursor having a desired pattern by applying an ink composition containing a silica-based powder for a core and a synthetic resin on the lower clad substrate (hereinafter, referred to as a first step). 2 step); and, after the optical waveguide precursor is cured, the organic binder component and the synthetic resin are thermally decomposed and removed, and subsequently, the silica powder for cladding and the silica powder for core are fired. Accordingly, a step of converting the lower clad substrate and the optical waveguide precursor into a lower clad and an optical waveguide (hereinafter, referred to as a third step); A method for producing a silica-based optical waveguide, characterized in that, in the third step of the above method, after curing the optical waveguide precursor, the optical waveguide precursor is treated with a silica-based powder for cladding and an organic binder. Embedding a clad composition containing components to form an upper clad precursor (hereinafter referred to as step 3a); and
By thermally decomposing and removing the organic binder component and the synthetic resin, and subsequently firing the silica powder for the cladding and the silica powder for the core, the substrate for the lower cladding, the optical waveguide precursor, and the A method of manufacturing a silica-based optical waveguide, comprising: a step of converting the upper clad precursor into a lower clad, an optical waveguide, and an upper clad (hereinafter referred to as step 3b);

First, the first step is a step of molding a lower clad substrate, which is a precursor of the lower clad, by using a clad composition described later. The clad composition contains, as essential components, a silica-based powder for clad and an organic binder component for binding these powders during molding.
As the quartz-based powder, powder made of simple substance of quartz (SiO ₂ ), or powder in which quartz is doped with a predetermined amount of P component, B component, F component or the like is used. The latter powder has a softening point lower than that of a simple substance of quartz due to the action of the dope component. Therefore, the sintering temperature in the third step described later can be set low, and thermal deformation of the substrate during sintering can be suppressed, which is preferable.

Further, it is preferable that the particle size of these quartz-based powders is small. The reason is that the larger the particle size is, the higher the temperature of sintering and vitrification becomes, so that the substrate is more likely to be thermally deformed during the third step, as described above. Usually 0.05
It is preferable that the particle diameter is about 1.0 μm. on the other hand,
The organic binder component may be any as long as it can be easily pyrolyzed and removed in the third step described later, and does not produce a pyrolysis residue, such as polyvinyl alcohol, polyvinyl butyral, methyl cellulose, Thermoplastic resins such as carboxymethyl cellulose and ethylene oxide can be mentioned.

The composition for clad can be used in the form of slurry, paste or mixed powder depending on the molding method. For example, when a slurry-like clad composition is used, the lower clad substrate can be molded by casting the slurry into a mold having a desired shape, dehydrating the mold, and then releasing the mold. Further, when the paste is viscous, the paste can be applied by, for example, a doctor blade method to form a film, which can be used as a lower clad substrate. This doctor blade method can also be applied to the above-mentioned slurry.

Further, in the case of using the mixed powder, the quartz-based powder and the organic binder component are uniformly kneaded, and then the kneaded product is filled in a mold of a desired shape and pressed under a desired pressure to form the mixture. You can Further, the quartz powder for clad and the synthetic resin used in the second step described later are uniformly kneaded, and the kneaded product is applied onto a smooth base material to form a substrate for the lower clad. You can also

The second step is a step of forming an optical waveguide precursor having a desired pattern on the lower clad substrate molded in the first step as described above by using the ink composition described later. The ink composition contains, as essential components, a silica-based powder for the core and a synthetic resin that fixes these powders.

As the silica-based powder for the core, for example, a simple substance of silica is doped with a predetermined amount of a component such as Ge so that the silica-based powder has a larger refractive index than that of the glass by the silica-based powder for the clad described above. What has been used is used. Further, the particle size of the silica-based powder for the core is preferably small for the same reason as in the case of the silica-based powder for the clad, but further, the pattern of the pattern mask used at the time of pattern drawing of the optical waveguide precursor described later. It must be smaller than the width or the width of the formed optical waveguide precursor. Therefore, the particle size is usually 1.0μ.
It is preferable to use those of m or less.

On the other hand, as the synthetic resin in the ink composition, as in the case of the clad composition, one that is easily decomposed by heat in the third step and does not generate impurities such as pigments or decomposition residues is selected. To be done. As a preferable example, a type that is cured by heat treatment after application, a type that is cured by oxidative polymerization, a curing type that is a two-component reaction type, or a type that is cured by light irradiation can be mentioned. If it ’s a type,
It does not matter what kind of resin such as acrylic resin, epoxy resin, vinyl resin, etc.

Further, in the case of this ink composition, the above-mentioned silica-based powder for core and the above-mentioned synthetic resin are contained as essential components, but an appropriate amount of auxiliary agents such as an organic stabilizer, a defoaming agent and a surfactant are further contained. May be. The optical waveguide precursor is formed as follows. That is, on the clad substrate obtained in the first step, a pattern mask in which the pattern of the optical waveguide to be formed is cut out is placed in close contact, and the above-mentioned ink composition is roll-printed thereon, for example. After that, the pattern mask is removed.

An optical waveguide precursor made of the above ink composition is drawn in a predetermined pattern on the lower clad substrate. The ink composition undergoes heat shrinkage when it is sintered in the third step described below. Therefore, it is necessary to determine the width and thickness of the pattern of the pattern mask in consideration of this heat shrinkage amount.

Further, when this pattern mask is used in which the entrance end and the exit end of the optical waveguide to be formed are made wider than the path width of the optical waveguide, it is formed as shown in FIG. Further, since the entrance end 1a and the exit ends 1b, 1b of the optical waveguide 1 are wider than the core 1c, the coupling efficiency can be increased when an optical fiber (not shown) is coupled thereto, which is preferable.

If a pattern mask is used in which a plurality of patterns of optical waveguides to be formed in one mask are cut out as the pattern mask, the ink composition is pattern-printed to form one lower clad. A plurality of optical waveguide precursors can be formed on the substrate at one time, and the optical waveguide can be manufactured with high productivity, which is useful. Next, in the third step, the lower clad substrate and the optical waveguide precursor formed in the above steps are vitrified.

In that case, first, the synthetic resin which is the binder component of the optical waveguide precursor is completely cured. As the curing method, an appropriate method such as heat treatment, oxidative polymerization, or light irradiation is selected according to the curing type of the synthetic resin used. After the optical waveguide precursor is completely cured, the organic binder component in the lower clad substrate and the synthetic resin in the optical waveguide precursor are thermally decomposed to remove them as a gas.

The temperature at this time varies depending on the kinds of the organic binder component and the synthetic resin used, but if it is about 600 ° C., it can be removed almost completely by thermal decomposition. The atmosphere of the thermal decomposition treatment may be an inert gas atmosphere or an oxygen-containing atmosphere. Further, when the organic binder component or the synthetic resin contains metal impurities and the like, it is useful to adopt an atmosphere containing chlorine or a chlorine compound because these metal impurities can be removed at the same time.

Then, by heating the whole at a higher temperature, the silica-based powder for the clad and the silica-based powder for the core are sintered to form transparent glass. The treatment temperature may be higher than the temperature at which these silica powders vitrify, but if a too high temperature is applied, the silica powder may be softened and the shrinkage rate may vary depending on the location. Therefore, the optical waveguide and the lower clad substrate after sintering may be deformed.

Therefore, it is preferable to set the treatment temperature to the lowest vitrification temperature. Further, it is preferable to perform the vitrification treatment with a heat-resistant holding plate sandwiching the lower clad substrate and the optical waveguide precursor from above and below while applying a slight pressure. The holding plate used in this latter method is preferably made of a material that does not fuse with the silica-based powder, for example, a material obtained by vapor-depositing carbon on the surface of high-density carbon, quartz, or heat-resistant ceramics such as alumina or zirconia. It is preferable that the surface is made as smooth as possible so as to prevent releasability after sintering and generation of fine irregularities on the surface of the optical waveguide after sintering.

Quartz powder constituting the lower clad substrate,
All of the silica-based powders constituting the optical waveguide precursor are vitrified, and the lower clad of transparent glass and the optical waveguide located thereon are integrally manufactured. In the third step described above, after the curing of the optical waveguide precursor is completed, the above-described clad composition is buried again as an upper clad precursor (step 3a), and then the entire organic binder is added. By thermally decomposing the components and the synthetic resin and sintering the silica-based powder (step 3b), an optical waveguide embedded between the lower clad and the upper clad can be formed.

[0023]

Examples of the invention

Example 1 67 parts by weight of pure water and 3 parts by weight of polyvinyl alcohol were added to 100 parts by weight of the silica-based powder for clad having a maximum particle size of 1.0 μm and an average particle size of 0.5 μm, and the mixture was stirred to be used for the clad. A composition (slurry) was prepared.

This slurry was cast into a plaster mold,
A plate having a length of 100 mm, a width of 100 mm, and a thickness of 2 mm was formed and dried at a temperature of 100 ° C. to form a lower clad substrate. On the other hand, 40 wt.% Of silica-based UV-curable acrylic resin-based screen ink was doped with Ge to have a relative refractive index difference of 0.3% with respect to quartz, and had a maximum particle size of about 1 μm. % Dispersion to prepare an ink composition.

A pattern mask having a plane size of 100 mm in length and 100 mm in width and having 64 Y-shaped patterns drawn therein was prepared. The Y-shaped pattern drawn on this pattern mask is designed to be about 1.4 times as large as the pattern size of the optical waveguide to be formed, and the pattern at the positions corresponding to the incident end and the outgoing end. As shown in FIG. 1, the size is about twice as large as other parts.

This pattern mask was placed in intimate contact with the lower clad substrate and the ink composition was roll-printed on the lower clad substrate to remove the pattern mask. On the lower clad substrate, 64 optical waveguide precursors each having a path width of 14 μm and a thickness of 14 μm (a path width of 20 μm and a thickness of 20 μm at the end) were formed. After irradiating these optical waveguide precursors with ultraviolet rays to perform a curing treatment, the precursors were again put into a plaster mold, and the slurry was cast from above.

The green molded body taken out from the mold is heated to a temperature of 1
After drying at 00 ° C for 3 hours, the temperature is 30 in N ₂ atmosphere.
A thermal decomposition treatment was carried out by heating at 0 ° C. and then at a temperature of 500 ° C. in an O ₂ atmosphere. Then, the upper and lower surfaces of the obtained plate,
It was sandwiched between carbon plates, and in that state, heat treatment was performed at 1400 ° C. in a He atmosphere to make the whole transparent vitrified.

64 Y-shaped optical waveguides each having a path width of 10 μm and a road height of 10 μm, each end having a road width of 15 μm and a road height of 15 μm and expanding in a trumpet shape have a lower clad with a thickness of 50 μm and a thickness of 800 μm. A plate body embedded between the upper clads was obtained. By cutting this plate for each optical waveguide, 64 thick film optical waveguide components could be manufactured at the same time.

Example 2 Polyvinyl butyl alcohol (1.0 parts by weight), phosphoric acid (1% by weight) and boron were added to 100 parts by weight of silica powder for cladding having a maximum particle size of 1.0 μm and an average particle size of 0.5 μm. Acid 3
20 parts by weight of pure water containing 20% by weight, 20 parts by weight of ethanol, and 2 parts by weight of dibutyl phthalate (plasticizer) were mixed to prepare a clad composition (paste).

A green sheet having a length of 100 mm, a width of 100 mm and a thickness of 1 mm was formed as a lower clad substrate by the doctor blade method using this paste. On the other hand, B, P, Ge should have a relative refractive index difference of 0.3% with respect to quartz.
40% by weight of a silica-based powder for cores having a maximum particle diameter of 1.0 μm and dispersed in a UV-curable acrylic resin-based screen ink to prepare an ink composition.

Further, a pattern mask having a plane size of 100 mm in length and 100 mm in width and having 64 Y-shaped patterns drawn therein was prepared. The Y-shaped pattern drawn on this pattern mask is designed to be about 1.4 times as large as the pattern size of the optical waveguide to be formed, and the pattern at the positions corresponding to the incident end and the outgoing end. The size is about twice as large as other parts.

This pattern mask was placed in intimate contact with the lower clad substrate, and the above ink composition was roll-printed on it to remove the pattern mask. On the lower clad substrate, 64 optical waveguide precursors each having a path width of 14 μm and a thickness of 14 μm (a path width of 20 μm and a thickness of 20 μm at the end) were formed. These optical waveguide precursors were coated with the above ink composition by the same doctor blade method to form an upper clad precursor having a thickness of 300 μm.

Then, after carrying out a thermal decomposition treatment under the same conditions as in Example 1, the temperature was 1300 ° C. in a He atmosphere.
The whole was made into a vitrified material by sintering at. Road width 10μ
m, road height 10 μm, each end has road width 15 μm, road height 15
64 Y-shaped optical waveguides having a trumpet shape with a thickness of 500 μm and a lower clad with a thickness of 500 μm and a thickness of 150 μm.
A plate embedded between the upper clads of μm was obtained.

This plate is cut into individual optical waveguides, and 6
It was possible to simultaneously manufacture four thick film optical waveguide components. Example 3 3 parts by weight of methylcellulose was added to 100 parts by weight of silica-based powder for cladding, which was doped with 2% by weight of B, 0.5% by weight of P, had a maximum particle size of 1.0 μm and an average particle size of 0.2 μm. Part, pure water 22 parts by weight, SN sweatshirt 366 (trade name,
0.3 part by weight of a surfactant manufactured by San Nobuco Co., Ltd. was uniformly mixed to prepare a clad composition (plastic mixture).

This mixture was filled in a cylindrical mold having a diameter of 100 mm, press-molded at a pressure of 5 kg / cm ² and dried at 100 ° C. to form a disk sheet having a diameter of 100 mm and a thickness of 1.3 mm. On the other hand, B, P and Ge are doped so that the relative refractive index difference with respect to quartz is 0.3%, and the maximum particle size is 1.0 μm.
The silica-based powder for core, which is m, was dispersed in an evaporation-drying type epoxy resin ink in an amount of 30% by weight to prepare an ink composition.

The pattern mask used in Example 1 was closely placed on the upper disk pattern, the ink composition was roll-printed on the pattern mask, the pattern mask was removed, and the optical waveguide precursor was formed on the disk pattern. Printed.
The formed optical waveguide precursor was dried and cured at a temperature of 80 ° C., and then the above mixture was placed thereon and press-molded to form an upper clad precursor having a thickness of 0.8 mm.

After the whole was dried at a temperature of 80 ° C., a thermal decomposition treatment was carried out under the same conditions as in Example 1, and further a sintering treatment was carried out at a temperature of 1300 ° C. in a He atmosphere to make the whole into a transparent glass. 64 Y-shaped optical waveguides having a track width of 10 μm and a road height of 10 μm, and each end having a track width of 15 μm and a road height of 15 μm and expanding in a trumpet shape, a lower clad with a thickness of 650 μm and an upper clad with a thickness of 400 μm. A plate embedded between the two was obtained.

This plate is cut into individual optical waveguides, and 6
It was possible to simultaneously manufacture four thick film optical waveguide components. Example 4 Example 2 was applied to a Si substrate having a diameter of 127 mm (5 inches).
Under the conditions, a green sheet with a thickness of 0.2 mm is formed, an optical waveguide precursor is formed, the optical waveguide precursor is cured, an upper clad precursor with a thickness of 0.2 mm is formed, a thermal decomposition treatment, and a sintering treatment are performed. Each optical waveguide was cut.

An element was obtained in which the thick film optical waveguide component of Example 2 was integrated on a Si substrate.

[0040]

As is apparent from the above description, the method of the present invention is a low cost and high productivity silica optical waveguide without using expensive equipment and advanced operation technology as in the prior art. Can be manufactured. Further, by expanding the diameters of the entrance end and the exit end during the formation of the optical waveguide precursor, it is possible to obtain a silica-based optical waveguide that is easily coupled with an optical fiber and has improved coupling efficiency.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a silica-based optical waveguide manufactured by the method of the present invention.

[Explanation of symbols]

 1 silica-based optical waveguide 1a, 1b end of silica-based optical waveguide 1c waveguide

Front page continued (72) Inventor Kazuaki Yoshida 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (2)

[Claims] 1. A step of forming a lower clad substrate using a clad composition containing a silica-based powder for clad and an organic binder component; a quartz-based powder for a core and a synthetic resin on the lower clad substrate. A step of forming an optical waveguide precursor having a desired pattern by applying an ink composition containing; and curing the optical waveguide precursor, then thermally decomposing and removing the organic binder component and the synthetic resin, and subsequently, Baking the silica-based powder for clad and the silica-based powder for core to convert the substrate for lower cladding and the optical waveguide precursor into a lower cladding and an optical waveguide, respectively. A method for manufacturing a silica-based optical waveguide. 2. A step of molding a substrate for lower clad by using a composition for clad containing a silica based powder for cladding and an organic binder component; a silica based powder for core and a synthetic resin on the substrate for lower cladding. Forming an optical waveguide precursor having a desired pattern by applying an ink composition containing: an optical waveguide precursor is cured, and then the optical waveguide precursor is clad containing quartz powder for cladding and an organic binder component. Burying with the composition for forming an upper clad precursor; and thermally decomposing and removing the organic binder component and the synthetic resin, and subsequently firing the quartz powder for cladding and the quartz powder for core. By doing so, the lower clad substrate, the optical waveguide precursor,
And a step of converting the upper clad precursor into a lower clad, an optical waveguide, and an upper clad, respectively.