JP2003195081A - Method of forming optical waveguide - Google Patents

Abstract

(57) Abstract: A method for easily manufacturing an optical waveguide mounted on an optical device such as an optical IC, an optical module, an LED, and an LD is provided. An optical waveguide comprising a lower cladding layer, a core portion, and an upper cladding layer, wherein at least one of the lower cladding layer and the core portion is formed using a dry film. .

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 an optical waveguide mounted on an optical device such as an optical IC, an optical module, an LED and an LD.

[0002]

2. Description of the Related Art Recently, an optical data link module, an optical I
Light emitting elements such as C, LEDs, and LDs, and light receiving elements such as photodiodes and phototransistors have been mounted, and it is required to connect these light emitting elements and light receiving elements with an optical waveguide even within the same substrate. . In order to meet such demands, a method of connecting elements by combining an optical fiber and an optical connector has been proposed. For example, as disclosed in Japanese Patent Laid-Open No. 29905/1993, on a wiring board. There has been proposed a method of embedding an optical fiber in the insulating film formed in the above.

[0003]

However, when an optical fiber is used, there is a risk that the optical fiber may be hooked, damaged or cut, and care must be taken in handling the optical fiber as well as the optical data bus and optical address. It is necessary to connect a large number of optical fibers in a bus etc., and it is very troublesome just to arrange them.
It had a problem of poor productivity. Further, fixing the optical fiber also makes the work of embedding it in a solder resist or the like very complicated. Furthermore, the wiring using the optical connector has a problem that it is difficult to save space. It is an object of the present invention to provide a method of manufacturing an optical waveguide, which enables efficient and easy formation of the optical waveguide.

[0004]

The present inventors have arrived at the present invention by earnestly examining a method for forming an optical waveguide in view of the problems of the prior art as described above. That is, the present invention is an optical waveguide comprising a lower clad layer, a core portion and an upper clad layer, wherein at least one of the lower clad layer and the core portion is formed using a dry film. It provides a method.

The dry film of the present invention comprises a base film such as polyethylene terephthalate and a resin layer formed on the base film. If necessary, a cover film such as polyethylene or polypropylene may be provided on the side opposite to the base film. Laminate as a protective film,
The resin layer may be sandwiched between the base film and the cover film.

In the above, the resin layer is a (meth) acrylic polymer, for example, (A) a (meth) acrylic polymer,
Examples thereof include a resin composition containing (B) a compound having two or more polymerizable reactive groups in the molecule and (C) a radiation polymerization initiator. In particular, a radiation-curable resin composition can be used for the dry film for forming the core portion. As the (A) (meth) acrylic polymer, an alkali-soluble copolymer obtained from a radically polymerizable compound having a carboxyl group and a radically polymerizable compound other than that, and a polymer represented by the following general formula (1) Is preferably used. General formula (1)

[Chemical 1] [R ₁ , R ₂ and R ₃ are hydrogen or an alkyl group having a carbon chain of 1 to 12, X is a group having a carboxyl group, Y is a group having a polymerizable group, Z is an organic group other than X and Y. is there]

In the present invention, the dry film can be produced by directly coating the composition containing the above-mentioned components (A) to (C) on the base film, but the dry film is dissolved in an organic solvent, followed by spin coating and dipping. Method, spray method, bar coating method, roll coating method, curtain coating method, gravure printing method, silk screen method, or a method of spraying the solvent using a dryer etc. after applying using a method such as an inkjet method Can be manufactured. In this case, as the organic solvent, the organic solvent used at the time of preparing the copolymer of the component (A) can be used, and particularly,
Solvents with low boiling points are preferred. These solvents may be used alone or in combination of two or more, and (A)
10 to 1 to 100 parts by weight of the total amount of the component (C)
It is preferable to set the value within the range of 50 parts by weight.

In the present invention, at least one of the lower clad layer and the core portion, preferably both of them, is formed of a dry film. The refractive index difference between the lower clad layer forming dry film and the core part forming dry film must be 0.1% or more.

In the present invention, the dry film resist is removed by removing the cover film from the substrate such that the base film is on top of the dry film resist while applying a normal pressure hot roll pressure bonding method, a vacuum heat roll pressure bonding method, a vacuum heat press pressure bonding method, or the like. Using the lamination method, the layers are laminated while applying appropriate heat and pressure. Then
In the case of the lower clad layer, it is cured by heat or radiation as it is. On the other hand, after stacking on the lower clad in the same manner as the lower clad layer, a phototool on which a desired optical waveguide pattern is drawn is placed on the base film, and the ultraviolet exposure method, visible light exposure method, laser exposure method is used. And so on,
The photosensitive resin layer is exposed through a photo tool. As a result, photopolymerization proceeds and cures in the exposed portion of the photosensitive resin layer, and the portion shielded by the pattern of the phototool (unexposed portion) remains uncured.

After that, the base film 1 is peeled off, and the uncured portion is removed using a developer such as an aqueous sodium carbonate solution, an aqueous sodium phosphate solution, an aqueous potassium carbonate solution. A small amount of antifoaming agent or surfactant may be added to the developer. Further, the removal of the unexposed portion is generally performed by spraying a developer with a spray method.
It can also be carried out by a dipping method of dipping in a developer. By removing the unexposed portion, a clad layer is formed under the core portion according to the pattern of the photo tool 8.

Next, an upper clad layer is formed. In the present invention, the upper clad layer is preferably made of the same resin layer as the lower clad layer. The upper clad layer can be formed by using a dry film, but can be formed by applying a coating solution containing a resin component and an organic solvent to the lower clad layer and the core portion and curing the coating by heat or radiation.

[0012]

EXAMPLES The present invention will be specifically described below with reference to examples. Preparation Example 1 of Copolymer (A) 1 After replacing a flask equipped with a dry ice / methanol reflux device with nitrogen, 1.3 g of 2,2′-azobisisobutyronitrile as a polymerization initiator and lactic acid as an organic solvent were used. 53.8 g of ethyl was charged and stirred until the polymerization initiator was dissolved. Subsequently, 6.7 g of methacrylic acid, 15.7 g of dicyclopentanyl methacrylate and 9.0 of styrene.
After charging g and 13.5 g of n-butyl acrylate, gentle stirring was started. After that, increase the temperature of the solution to 8
The temperature was raised to 0 ° C., and polymerization was carried out at this temperature for 4 hours. Then, the reaction product was dropped into a large amount of hexane to solidify the reaction product. Further, the coagulated product was redissolved in tetrahydrofuran of the same weight and coagulated again with a large amount of hexane. This redissolution-coagulation operation was performed three times in total, and the obtained coagulated product was vacuum dried at 40 ° C. for 48 hours to obtain the target copolymer A-1.

Preparation Example 2 of Copolymer (A) After replacing the flask equipped with a dry ice / methanol reflux vessel with nitrogen, 0.5 g of 2,2'-azobisdimethylvaleronitrile as a polymerization initiator and an organic solvent were used. Then, 54.3 g of ethyl lactate was charged and stirred until the polymerization initiator was dissolved. Subsequently, 4.5 g of methacrylic acid, 9.0 g of dicyclopentanyl methacrylate, 20.4 g of methyl methacrylate, and 1 of n-butyl acrylate.
After charging 1.3 g, gentle stirring was started. Then, the temperature of the solution was raised to 80 ° C., and polymerization was carried out at this temperature for 4 hours. Then, the reaction product was dropped into a large amount of hexane to solidify the reaction product. Further, the coagulated product was redissolved in tetrahydrofuran of the same weight and coagulated again with a large amount of hexane. This redissolution-coagulation operation was performed three times in total, and the obtained coagulated product was vacuum dried at 40 ° C. for 48 hours to obtain the target copolymer A-2.

Preparation Example 3 of Copolymer (A) After a flask equipped with a dry ice / methanol reflux was replaced with nitrogen, 1.3 g of 2,2'-azobisisobutyronitrile was used as a polymerization initiator. 53.8 g of ethyl lactate was charged as a solvent, and the mixture was stirred until the polymerization initiator was dissolved. Subsequently, 6.7 g of methacrylic acid and isobol
Nyl methacrylate 15.7 g, styrene 9.0 g,
And after charging 13.5 g of n-butyl acrylate ,
The stirring was started gently. Then, the temperature of the solution was raised to 80 ° C., and polymerization was carried out at this temperature for 4 hours. Then, the reaction product was dropped into a large amount of hexane to solidify the reaction product. Further, the coagulated product was redissolved in tetrahydrofuran of the same weight and coagulated again with a large amount of hexane. This re-dissolution-coagulation operation was performed three times in total, and the obtained coagulated product was vacuum dried at 40 ° C. for 48 hours to obtain the target copolymer A.
-3 was obtained.

Preparation of radiation curable dry film J-1 Polymerization reactive polyfunctional acrylate (manufactured by Toagosei Co., Ltd., M810) was added to 32.0 parts by weight of the above-mentioned copolymer A-1.
0), 10.0 parts by weight, trimethylolpropane triacrylate, 6.5 parts by weight, and Irgcure. 369 (Ciba Specialty
Chemicals Co., Ltd.) 3.0 parts by weight, ethyl lactate 48.
5 parts by weight were added and mixed to obtain a uniform solution. Then, this solution was added to a polyethylene terephthalate film (film thickness: 5
(0 μm) by spin coating and then dried at 100 ° C. for 15 minutes to obtain a radiation curable dry film J-1 having a film thickness of 55 μm.

Preparation of Radiation-Curable Dry Film J- 2 Based on 27.7 parts by weight of the above-mentioned copolymer A-2, a polyfunctional acrylate having polymerization reactivity (M81 manufactured by Toagosei Co., Ltd.).
00) in 16.6 parts by weight, trimethylolpropane triacrylate in 11.1 parts by weight, and Irgcure. 369 (manufactured by Ciba Specialty Chemicals) 3.0 parts by weight, ethyl lactate 4 parts
1.6 parts by weight were added and mixed to obtain a uniform solution. Subsequently, this solution was applied onto a polyethylene terephthalate film (film thickness: 50 μm) by spin coating, and then 10
A radiation-curable dry film J-2 having a film thickness of 55 μm was obtained by drying at 0 ° C. for 15 minutes.

Example 1 (1) Formation of Optical Waveguide Formation of Lower Clad Layer The radiation-curable dry film J-2 was transferred onto the surface of a silicon substrate by a normal pressure heat roll pressure bonding method (temperature: 80 ° C.). Then, prebaking was performed using a hot plate under the conditions of 120 ° C. and 10 minutes. Then, a coating film made of the radiation-curable dry film J-2 was coated with a wavelength of 365 nm and an illuminance of 200
It was irradiated with an ultraviolet ray of mW / cm 2 for 5 seconds to be radiation-cured. Then, this cured film was post-baked under the condition of 200 ° C. for 1 hour to form a lower clad layer having a thickness of 50 μm. When the refractive index (measurement wavelength: 824 nm) of the lower clad layer thus formed was measured,
It was 1.50.

Formation of core part Next, the radiation curable dry film J-1 was transferred onto the lower clad layer by the atmospheric pressure heat roll pressure bonding method (temperature: 80 ° C.) and 120 ° C. using a hot plate. It was prebaked under the condition of 10 minutes. Thereafter, the coating film having a thickness of 50 μm made of the radiation curable dry film J-1 was irradiated with ultraviolet rays having a wavelength of 365 nm and an illuminance of 200 mW / cm 2 for 5 seconds through a photomask having a line pattern having a width of 50 μm, The coating was radiation cured. Next, PEB was performed on the irradiated coating film at 100 ° C. for 1 minute.
Then, 1.8% of the substrate having the radiation-cured coating film
Tetramethylammonium hydroxide aqueous solution (TMA
The unexposed portion of the coating film was dissolved by immersing it in a developing solution containing H). Then, post-baking was performed under the condition of 200 ° C. for 1 hour to form a core portion having a line-shaped pattern with a width of 50 μm. Further, the refractive index (measuring wavelength 824 nm) of this core portion was measured and found to be 1.52.
It was to be noted that the rectangular core portion at this stage (line width of about 50 μm) was accurately formed.

Formation of Upper Clad Layer Next, the J-2 solution before dry film preparation (before spin coating) is applied on the upper surface of the lower clad layer having a core portion by a spin coater, and 120 is applied using a hot plate.
Prebaking was carried out under the conditions of 10 ° C. and 10 minutes. Then, a coating film made of J-2 has a wavelength of 365 nm and an illuminance of 200 mW / cm.
50 μm thick by irradiating with 2 ultraviolet rays for 5 seconds
The upper clad layer of was formed. Then, the upper clad layer was post-baked at 200 ° C. for 6 hours.
Refractive index of the formed upper clad layer (measurement wavelength 824n
When m) was measured, it was 1.50. The obtained optical waveguide had the structure shown in FIG. Results In the above method, both core height and core width are 50 ± 5
A μm shape was formed. In addition, light having a wavelength of 824 nm was made incident from one end of the obtained optical waveguide. Then, the waveguide loss per unit length was measured by the cutback method by measuring the amount of light emitted from the other end, and it was 0.3.

[0020]

According to the method of manufacturing an optical waveguide of the present invention,
The optical elements can be efficiently connected, there is no fear of damaging the optical waveguide, and even a complicated optical waveguide pattern can be easily formed.

[0021]

[Brief description of drawings]

FIG. 1 shows a sectional view of an optical waveguide obtained in Example 1.

Continued front page    (72) Inventor Tomohiro Utaka             2-11-21 Tsukiji, Chuo-ku, Tokyo J             Within SRL Co., Ltd. F term (reference) 2H047 KA04 PA01 PA02 PA15 PA22                       PA24 PA28 QA05 TA42 TA43                       TA44

Claims (3)

[Claims] 1. An optical waveguide comprising a lower clad layer, a core part and an upper clad layer, wherein at least one of the lower clad layer and the core part is formed by using a dry film. Method. 2. The method of manufacturing an optical waveguide according to claim 1, wherein the upper clad layer is coated with a coating liquid containing a radiation curable resin or a thermosetting resin and an organic solvent and cured. 3. The method of manufacturing an optical waveguide according to claim 1, wherein the dry film is made of a radiation curable resin.