JP2001166166A - Polymer optical waveguide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer optical waveguide which has sufficient flexibility and is low in loss and high in reliability. SOLUTION: This polymer optical waveguide film is composed of a high polymer alone, has at least a core 4 and an upper clad 5 and lower clad 3 having the refractive index lower than the refractive index of the core and has a UV absorption layer 6 in the upper part of the upper clad 5 and the lower part of the lower clad 3. Accordingly, the polymer waveguide film maintains the sufficient optical waveguide characteristic before peeling of the substrate and there is an effect of greatly improving the deterioration in waveguide characteristics by irradiation with UV rays by adding the absorption layer to the film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer optical waveguide film, and more particularly, to optical interconnection, optical multiplexing, and the like.
The present invention relates to a low-loss polymer optical waveguide film having flexibility and being suitable for use in optical components such as demultiplexing.

[0002]

2. Description of the Related Art As an optical component or a base material of an optical fiber, inorganic materials such as quartz glass and multi-component glass having characteristics of small light propagation loss and a wide transmission band are widely used. Recently, a polymer-based material has also been developed and has been attracting attention as a material for an optical waveguide because it is superior in workability and price as compared with an inorganic material.
For example, a planar optical waveguide having a core-clad structure in which a polymer having excellent transparency such as polymethyl methacrylate (PMMA) or polystyrene is used as a core and a plastic having a lower refractive index than the core material is used as a cladding material. (Japanese Unexamined Patent Publication No. 3-188402)
issue). In addition, a planar optical waveguide using polyimide or polysiloxane, which is a transparent polymer having high heat resistance, has also been manufactured. Further, a characteristic of the polymer optical waveguide is that it can be formed to be easily bent. For polymer optical waveguides,
Providing sufficient flexibility and reducing propagation loss will enable flexible optical wiring and branching by making active use of the original flexible properties, making it fully applicable to optical interconnection. It is. However, conventionally, since the waveguide was formed on a thick polymer substrate such as a glass substrate, a silicon substrate, and an acrylic substrate due to manufacturing restrictions, the waveguide had little flexibility, and the flexibility was not actively utilized. is the current situation. In order to fabricate a polymer optical waveguide having sufficient flexibility, first, a relatively thin polymer optical waveguide is formed on a glass substrate, a silicon substrate, and a thick polymer substrate, and then the polymer optical waveguide portion is formed. What is necessary is just to separate from a board | substrate. However, if the adhesion between the substrate and the polymer is weakened from the beginning of the fabrication, the polymer may be separated from the substrate during the fabrication. Conversely, if the adhesion to the substrate is strengthened, subsequent peeling becomes difficult. During the fabrication of polymer optical waveguides, the adhesion to the substrate is strong, and it is desirable to easily detach from the substrate when peeling off the substrate after fabricating the waveguide, but such a method is not easy at present. It is. Another drawback inherent to polymer waveguides is that they have poor stability to ultraviolet light. That is, the reaction gradually deteriorates due to sunlight, such as oxidation or depolymerization.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a low-loss and high-reliability polymer optical waveguide having sufficient flexibility.

[0004]

SUMMARY OF THE INVENTION In general, the present invention relates to a polymer optical waveguide film,
In a polymer optical waveguide film composed of only a polymer and having at least a core and an upper clad and a lower clad having a lower refractive index than the core, an ultraviolet absorbing layer is provided above the upper clad and below the lower clad. Features.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. The polymer optical waveguide film of the present invention can be manufactured, for example, as follows. On a substrate having copper as an uppermost layer, an optical waveguide layer producing step of producing a polymer optical waveguide film having at least a clad and a core having a higher refractive index than the clad, and thereafter, immersed in a hydrochloric acid aqueous solution or a potassium hydroxide aqueous solution. Thus, the method includes a peeling step of peeling the polymer optical waveguide film from the substrate, and, following the peeling step, a protective layer forming step of forming an ultraviolet absorbing layer above and below the clad layer. As an example of a substrate having a copper thin film as the uppermost layer, there is a substrate in which a copper thin film having a thickness of several tens to several hundreds of nm is attached on a glass or silicon wafer by vapor deposition or sputtering.

In order to form the polymer film in close contact with the substrate, a spin coating method, a doctor blade method,
Alternatively, the free standing film can be mechanically adhered. In any case, since it is necessary to have an adhesive force that does not separate during the waveguide fabrication process, the above-mentioned polymer film is formed after coating an adhesion auxiliary agent such as a silane coupling agent on the substrate. Often do.

[0007] The concentration of hydrochloric acid is about 10 to 20%, and the substrate and the polymer waveguide film can be separated similarly to the aqueous potassium hydroxide solution. The aqueous potassium hydroxide solution penetrates between the substrate and the polymer optical waveguide film and acts to weaken the adhesion between them. In addition, if the edge of the polymer optical waveguide film is damaged and immersed in a hydrochloric acid solution, the solution permeates between the substrate and the polymer optical waveguide film in a short time, so that the film can be released very quickly. The polymer optical waveguide film separated from the substrate needs to be sufficiently washed with an aqueous solution of hydrochloric acid or potassium hydroxide with pure water.

Further, by adding an ultraviolet absorbing layer to the flexible polymer optical waveguide device obtained by the above-mentioned method, there is an effect of remarkably improving the deterioration of the waveguide characteristics due to the ultraviolet irradiation.

Hereinafter, the present invention will be described in detail with reference to the drawings. First, the above current problems will be described more specifically. FIG. 1 shows a configuration of a polymer optical waveguide fabricated on a substrate. 1 is a substrate, which is a polymer film support. Therefore, no thermal deformation is observed during the manufacturing process of the waveguide, and specific examples include mirror-finished metal, glass, and silicon wafer. Reference numeral 2 denotes a copper sputtering layer which is a feature of the present invention, that is, is not found in the prior art. Reference numeral 3 denotes a lower clad layer, which is formed by forming a solution-type transparent polymer dissolved in a solvent to a desired thickness on a substrate by spin coating. Reference numeral 4 denotes a core layer of the polymer optical waveguide, and it is necessary to use a material having a refractive index slightly higher than that of the cladding. After forming the core layer polymer to a desired thickness on the lower cladding layer by spin coating, a core portion is formed by photolithography, reactive ion etching, or the like. Thereafter, the same polymer as the lower clad layer is spin-coated to a desired thickness to form an upper clad layer 5. Thereafter, the polymer optical waveguide portion is peeled off from the substrate to form a film-shaped polymer optical waveguide. In a photo process for producing a core, in a resist development step, the substrate must be immersed in a developer. Therefore, an adhesive force that does not separate between the substrate and the lower clad layer during immersion in the developer is required. After the immersion in the developer, there is also a step of cleaning the substrate with distilled water. During this step, the lower clad must not be separated from the substrate. According to the present invention, the problem of the related art is solved by providing the layer denoted by reference numeral 2. FIG. 2 is a conceptual diagram of a polymer waveguide with an ultraviolet absorbing layer according to the present invention. In FIG. 2, reference numerals 3 to 5 have the same meaning as in FIG. 1, and 6 denotes an ultraviolet absorbing layer.

As described above, according to the present invention, a highly stable polymer optical waveguide film having a relatively large area and flexibility can be provided.

[0011]

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

Example 1 Copper was sputtered on a silicon substrate by 100%.
It is formed on the order of nm. An embedded polymer optical waveguide was formed on this substrate. A copolymer of deuterated polymethyl methacrylate and fluorinated methacrylate (molar ratio = 96.5: 3.5) was used as the cladding layer polymer, and deuterated polymethyl methacrylate was used as the core layer polymer. . Each of the polymers was dissolved in a mixed solution of chlorobenzene and xylene to form a solution. A cladding layer polymer was spin-coated to a thickness of about 25 μm on a silicon substrate with copper. After the bake drying treatment, the core layer polymer was spin-coated to a thickness of about 8 μm. Next, by photolithography and dry etching, a width of 8 μm and a height of 8 μm
Was processed into a linear pattern having a rectangular cross section. Finally,
A buried waveguide was prepared by spin coating a cladding polymer to a thickness of 25 μm. This waveguide is immersed in hydrochloric acid (hydrogen chloride 2).
0%) to separate the polymer waveguide portion from the substrate. Loss measurement results at a wavelength of 1.31 μm of the polymer optical waveguide film having peeled flexibility and the polymer optical waveguide attached to the substrate before peeling (waveguide length:
50 mm, including coupling loss) are shown in Table 1.

[0013]

[Table 1]

Since the results are almost the same, even if the polymer optical waveguide is separated from the substrate by the method of the present invention, the characteristics of the polymer optical waveguide are not adversely affected. It was proved to be effective as a method for producing. Further, the loss due to the bending (radius of curvature: 50 mm) of the separated polymer waveguide was 1.6 dB, and no remarkable change was observed.

Example 2 An embedded optical waveguide similar to that of Example 1 was fabricated on a silicon substrate to which copper had adhered. This waveguide was immersed in a 10% aqueous solution of potassium hydroxide to release the polymer optical waveguide film from the substrate. Table 1 shows the loss measurement results (wavelength: 50 mm, including coupling loss) at a wavelength of 1.31 μm of the polymer optical waveguide film having peeled flexibility and the polymer optical waveguide attached to the substrate before peeling. It is shown in FIG.

[0016]

[Table 2]

Since the results of the two methods are almost the same, even if they are separated from the substrate by the method of the present invention, the characteristics of the polymer optical waveguide are not adversely affected. It was proved to be effective as a method for producing.

Embodiment 3 Another embodiment of the present invention will be described with reference to FIG. A flexible waveguide with an ultraviolet protection film was manufactured by laminating the ultraviolet absorbing layers 6 above and below the flexible polymer optical waveguide of Example 1. A flexible waveguide protected by a transparent material such as a polyethylene film and a flexible waveguide protected by an ultraviolet absorbing layer were produced, and the waveguide characteristics at a wavelength of 1.3 μm after irradiation with ultraviolet light of 350 nm for 100 hours were compared. The loss (including the coupling loss) of the 50 mm waveguide increased to 3.0 dB in the case of the flexible waveguide with the transparent protective film, while it was almost unchanged at 1.6 dB in the case of the flexible waveguide with the ultraviolet absorbing layer. As is clear from the above results, the flexible polymer optical waveguide with the ultraviolet absorbing layer has an effect of remarkably improving the deterioration of the waveguide characteristics due to the irradiation of ultraviolet rays, as compared with the conventional flexible polymer optical waveguide device with the transparent protective film.

[0019]

As described above, the polymer optical waveguide film having flexibility according to the present invention sufficiently maintains the optical waveguide characteristics before the substrate is peeled off. There was an effect of remarkably improving the deterioration of the waveguide characteristics due to the irradiation.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a method for producing an intermediate product according to the present invention.

FIG. 2 is a conceptual diagram of a polymer optical waveguide with an ultraviolet absorbing layer according to the present invention.

[Explanation of symbols]

1: substrate, 2: copper sputtering film, 3: lower cladding layer, 4: core layer, 5: upper cladding layer, 6: ultraviolet absorbing layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Ryoyuki Yoshimura 3-20-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Saburo Imamura 3-20 Nishishinjuku, Shinjuku-ku, Tokyo No. 2 Nippon Telegraph and Telephone Corporation

Claims (1)

[Claims] 1. A polymer optical waveguide film comprising only a polymer and having at least a core and an upper clad and a lower clad having a lower refractive index than the core, wherein ultraviolet light is absorbed on the upper part of the upper clad and the lower part of the lower clad. A polymer optical waveguide film having a layer.