Optical device having EO polymer core and specially-polymerized clad

Abstract

An optical device including a core layer that includes an EO polymer, and clad layers that are disposed on and beneath the core layer, in which a polymer polymerized in a composition containing a reactive ionic liquid is used in the clad layers.

Claims

1. An optical device comprising: a core layer that includes an EO polymer; and clad layers that are disposed on and beneath the core layer, wherein a polymer polymerized in a composition containing a reactive ionic liquid is used in the clad layers.

2. The optical device according to claim 1, wherein the reactive ionic liquid is a material having a reactive group that is polymerizable with a basic skeleton resin.

3. The optical device according to claim 1, wherein the reactive ionic liquid is a material represented by Chemical Formula 1, here, an anion X.sup. is any of [N(SO.sub.2CF.sub.3).sub.2].sup., [PF.sub.6].sup., [BF.sub.4].sup., Cl.sup., and Br.sup., and, R, R, R, and R are hydrogen atoms or alkyl groups having 1 to 10 carbon atoms that are identical to or different from one another ##STR00003##

4. The optical device according to claim 1, further comprising: a blocking layer that blocks migration of ions included in the reactive ionic liquid between the core layer and the clad layer.

5. The optical device according to claim 4, wherein the blocking layer is formed of any of SiO.sub.2 and Al.sub.2O.sub.3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross-sectional view showing a scheme of an optical device of the related art.

(2) FIG. 2 is a cross-sectional view showing an example of an optical device of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(3) Hereinafter, an optical device of the present invention will be described in detail using preferred examples. The optical device of the present invention is an optical device in which, as shown in FIG. 1, clad layers are disposed on and beneath a core layer and the core layer includes an EO polymer, in which a polymer polymerized in a composition containing a reactive ionic liquid is used in the clad layers.

(4) As the EO polymer, PMMA-DR1 in which PMMA is used as a basic skeleton resin and, as an EO molecule, Disperse Red1 is polymerized into a side chain of the basic skeleton resin can be preferably used. In addition, heat resistance can be improved by increasing a glass transition temperature Tg of the EO polymer. In this case, Tg can be increased by imparting a cage-type molecule such as an adamantyl group to the side chain of the basic skeleton resin or forming a main skeleton resin in a network structure.

(5) A characteristic of the optical device of the present invention is that a material that is used in the clad layers is, unlike a coating liquid obtained by mixing alkoxide acrylate, alkoxy silane, and a polymerization initiator, not cationic radial polymerization. Specifically, the material is a polymerization reaction by a Co complex for which a reactive ionic liquid is used. Therefore, there is no case where the polymerization initiator remains in the clad layers.

(6) For the clad layers, a polymer of the reactive ionic liquid as shown in Chemical Formula 1 and an acrylic resin is used. The reactive ionic liquid is a material having a reactive group that can be polymerized with the basic skeleton resin.

(7) ##STR00002##

(8) An anion X.sup. in Chemical Formula 1 is any of [N(SO.sub.2CF.sub.3).sub.2].sup., [PF.sub.6].sup., [BF.sub.4].sup., Cl.sup., and Br.sup.. Particularly, the diffusion of anions in the clad layers acts as a cause for the intrusion of anions into an EO polymer in the core layer. Therefore, bulky [N(SO.sub.2CF.sub.3).sub.2].sup. is more preferred since the diffusion thereof is suppressed.

(9) R, R, R, and R in Chemical Formula 1 are hydrogen atoms or alkyl groups having 1 to 10 carbon atoms that are identical to or different from one another. R, R, and R are more preferably hydrogen atoms, and R is more preferably a hydrogen atom or a methyl group.

(10) Furthermore, in order to suppress the intrusion of anions in the clad layers into the core layer, a blocking layer that blocks the migration of ions included in the reactive ionic liquid is preferably provided between the core layer and the clad layer as shown in FIG. 2.

(11) As the blocking layer, any of SiO.sub.2 and Al.sub.2O.sub.3 can be preferably used.

(12) In a method described below, four types of clads were produced, and a test that evaluated characteristics was carried out.

Example 1

(13) A liquid mixture was prepared by blending 1.5 wt % of a reaction-type ionic liquid IL-MA2 manufactured by Kyoeisha Chemical Co., Ltd., 28.5 wt % of UV-1700B manufactured by The Nippon Synthetic Chemical Industry Co., Ltd., 1.5 wt % of IRGACURE 127 manufactured by BASF, 15 wt % of methanol, 15 wt % of methyl isobutyl ketone, 3 wt % of butyl carbitol, and 35.5 wt % of normal butanol. The liquid mixture was applied by spin coating, dried on a hot plate at 100 C., and cured by radiating ultraviolet rays for one minute using a 300 W UV radiator, thereby forming a clad layer. As a result of measuring the clad layer as a single body, the volume resistance at room temperature was 410.sup.13 cm, and the volume resistances at 120 C., 150 C., and 180 C. were 310.sup.13 cm, 210.sup.13 cm, and 110.sup.13 cm respectively.

Example 2

(14) Components were blended in the same manner as in Example 1 except for the fact that 6 wt % of the reaction-type ionic liquid IL-MA2 manufactured by Kyoeisha Chemical Co., Ltd. and 24 wt % of UV-1700B manufactured by The Nippon Synthetic Chemical Industry Co., Ltd. were blended. As a result of measuring a clad layer produced using this liquid mixture as a single body, the volume resistance at room temperature was 210.sup.13 cm, and the volume resistances at 120 C., 150 C., and 180 C. were 110.sup.13 cm, 510.sup.12 cm, and 310.sup.12 cm respectively.

Comparative Example 1

(15) Components were blended in the same manner as in Example 1 except for the fact that the reaction-type ionic liquid was not blended, and 30 wt % of UV-1700B manufactured by The Nippon Synthetic Chemical Industry Co., Ltd. was blended. As a result of measuring a clad layer produced using this liquid mixture as a single body, the volume resistance at room temperature was 110.sup.15 cm, and the volume resistances at 120 C., 150 C., and 180 C. were 810.sup.14 cm, 610.sup.14 cm, and 410.sup.14 cm respectively.

Comparative Example 2

(16) A liquid mixture was prepared by blending 20 wt % of acrylsilane KBM-503 manufactured by Shin-Etsu Chemical Co., Ltd., 10 wt % of tetramethylsilane manufactured by Kanto Chemical Co., Inc., 1.5 wt % of IRGACURE 127 manufactured by BASF, 15 wt % of methanol, 15 wt % of methanol, 15 wt % of methyl isobutyl ketone, 3 wt % of butyl carbitol, and 35.5 wt % of normal butanol and stirred at 60 C. for one hour. As a result of measuring a clad layer produced using this liquid mixture as a single body, the volume resistance at room temperature was 110.sup.14 cm, and the volume resistances at 120 C., 150 C., and 180 C. were 310.sup.13 cm, 210.sup.13 cm, and 110.sup.13 cm respectively.

(17) (Testing method) Lower clad layers were formed using individual clad materials on silicon substrates on which gold electrodes (lower electrodes) had been formed by vacuum deposition, EO polymers having different glass transition temperatures of 120 C., 150 C., and 180 C. were applied and dried, and upper clads were formed by lamination using individual materials in the same manner as the lower clads. Gold electrodes were partially provided on the laminate film substrates in the same manner as the lower electrodes, thereby producing test specimens in which gold electrodes were not placed on parts other than the above-described gold electrode-provided parts.

(18) Table 1 shows the evaluation results of characteristics such as surface cracks, electrode peeling, and polling regarding a variety of the test specimens. The test specimens were heated up to the same temperatures as the respective glass transition temperatures of the EO polymers, and the surfaces and the peeling statuses of the gold electrodes were evaluated. In a case where there are cracks on the surface, the case of 10 or more cracks per four-inch wafer is expressed as X, and the case of 50 cracks or more or a state in which cracks reach the EO polymer layer is expressed as XXX. In a case where electrode peeling occurs, a case where electrode peeling occurs at 10 or more places in a four-inch wafer is expressed as X, and a case where the percent defective of a waveguide pattern is 10% or more is expressed as XXX.

(19) TABLE-US-00001 TABLE 1 120 C. 150 C. 180 C. Surface Electrode Surface Electrode Surface Electrode cracks peeling Polling cracks peeling Polling cracks peeling Polling Example 1 No No No Example 2 No No No Comparative No x No x No x Example 1 Comparative No x Yes xxx Yes xxx Example 2 x xxx

(20) Regarding the evaluation of the polling treatment, optical devices were produced and evaluated using the following method. A lower electrode was formed on a Si substrate, and the above-described clad layer was formed as a lower clad. A groove that served as a waveguide was formed by photolithography and dry etching. After that, an EO polymer solution was applied by spin coating and dried, thereby forming an EO polymer layer. After that, an upper clad layer was formed on the lower clad layer in the same manner, an electrode was provided on the upper clad layer, and a polling treatment was carried out by heating the laminate up to near the glass transition temperature of the EO polymer and applying a direct-current high voltage. After that, a polling electrode was processed, and a signal electrode was formed, thereby producing an optical device. Regarding the effect of the polling, optical devices having an optical modulation intensity after the polling are expressed as O, and optical devices having no optical modulation intensity are expressed as X. indicates that the optical device is not uniformly polled.

(21) As shown in Table 1, it was confirmed that, in the clads for which the reactive ionic liquid was used, no disadvantages were caused regarding surface cracks, electrode peeling, and polling.

(22) As described above, according to the present invention, it is possible to provide an optical device in which the polling of a core layer is appropriately carried out and the generation of cracks in clad layers is suppressed.