JPH0841324A - Composition for active optical waveguide, production of active optical waveguide therefrom and active optical waveguide - Google Patents

Abstract

PURPOSE:To provide a composition for an active optical waveguide excellent in heat resistance and the ability to process optical signals such as optical switching or optical modulation, a process for producing an active optical waveguide therefrom and an active optical waveguide. CONSTITUTION:This composition is one comprising a fluoropolyamic acid and an electrooptical material, wherein the electrooptical material is a compound represented by the formula (wherein R<1> is hydrogen, cyano, phenyl, amino, alkoxy, acylamino, alkylthio, alkyl, alkoxycarbonyl, carbamoyl or a heterocyclic group; R<3> and R<4>, which are independent of each other, are the same groups as defined in R<1> or may be combined with each other to form a ring; not all of R<1>, R<2> and R<4> are hydrogen atoms; and R<2> is hydrogen, alkyl or acyl).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for active optical waveguide, a method for producing an active optical waveguide using the same, and an active optical waveguide.

[0002]

2. Description of the Related Art Optoelectronic ICs (OEI)
The optical waveguide in C) is conventionally made of LiNbO ₃ , L
Inorganic materials such as iTaO ₃ , PLZT, Sr ₂ Nb ₂ O ₇ are used. However, these materials have a problem that the response speed is slow due to deliquescent property, low threshold value for destruction, and high dielectric constant, which limits the applicable frequency band. On the other hand, organic polymer materials are generally superior to inorganic materials in that they have no deliquescent property and have a high threshold value for destruction, but such polymer materials generally have no orientation, and as-is It cannot be used as a material for optical switches and modulators that utilize the optical effect. In general, a polymer material having no orientation is applied with a DC electric field while being heated to orient, that is, a method of expressing an electro-optical effect by a poling treatment is used. As a result, the orientation is lost and the electro-optic effect is lost, which is a serious problem. Conventionally, polymethylmethacrylate (PMMA), etc., has been vigorously studied as a polymer-based optical waveguide material, but the glass transition temperature (Tg) is as low as about 150 ° C, and poling is performed at a temperature of 200 ° C or higher required during OEIC manufacturing. However, there is a problem that the orientation generated by the above is completely lost.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art as described above, and is excellent in heat resistance and electro-optical effect and for an active optical waveguide applicable to a wide frequency band. The present invention provides a composition, a method for producing an active optical waveguide using the composition, and an active optical waveguide.

[0004]

The present invention is a composition for an active optical waveguide containing a fluorinated polyamic acid and an electro-optical material, wherein the electro-optical material has the general formula (I).

[Chemical 6] (In the formula, R ¹ represents a hydrogen atom, a cyano group, a phenyl group, an amino group, an alkoxy group, an acylamino group, an alkylthio group, an alkyl group, an alkoxycarbonyl group, a carbamoyl group or a heterocyclic group, and R ³ and R ⁴ are each independently represent an atom group and R ¹ similar to that of the group or R ³ and R ⁴ constitute a ring formed by connecting, never all R ^1, R ³ and R ⁴ are hydrogen atom, R ² is a compound represented by a hydrogen atom, an alkyl group or an acyl group), and relates to a composition for active optical waveguide.

Further, according to the present invention, the method for producing an active optical waveguide is characterized in that the fluorinated polyamic acid in the composition for active optical waveguide is imide ring-closed to give a fluorinated polyimide, and the electro-optical material is oriented. Regarding

The present invention also relates to an active optical waveguide manufactured by the method for manufacturing an active optical waveguide described above.

The present invention will be described in detail below. The fluorinated polyamic acid used in the present invention is a polyamic acid having a fluoro group, a fluoroalkyl group, etc., and can be produced under the same conditions as in the production of ordinary polyamic acid, and generally N-methyl-2-pyrrolidone is used. , N, N-dimethylacetamide, N, N-dimethylformamide and the like, in a polar organic solvent, at least one of which is substituted with a fluoro group or a fluoroalkyl group, and a tetracarboxylic acid or a derivative thereof is reacted. be able to. Examples of the diamine substituted with a fluoro group, a fluoroalkyl group or the like include 3-fluoro-1,2-phenylenediamine, 4-fluoro-1,2-phenylenediamine,
3,4-difluoro-1,2-phenylenediamine, 3
-Fluoro-1,3-phenylenediamine, 4-fluoro-1,3-phenylenediamine, 3,4-difluoro-1,3-phenylenediamine, 3-fluoro-1,4
-Phenylenediamine, 4-fluoro-1,4-phenylenediamine, 3,4-difluoro-1,4-phenylenediamine, 3-trifluoromethyl-1,2-phenylenediamine, 4-trifluoromethyl-1,2 -Phenylenediamine, 3-trifluoromethyl-1,3-phenylenediamine, 4-trifluoromethyl-1,3-
Phenylenediamine, 3-trifluoromethyl-1,4
-Phenylenediamine, 4-trifluoromethyl-1,
4-Phenylenediamine, 2,2 '-(bistrifluoromethyl) -4,4'-diaminobiphenyl, 2,2'
-Difluoro-4,4'-diaminobiphenyl and the like.

The tetracarboxylic acid substituted with a fluoro group, a fluoroalkyl group or the like, or an acid anhydride, an acid chloride or an ester compound as a derivative thereof is, for example, 1-
Fluoropyromellitic acid, 1,4-difluoropyromellitic acid, 1-trifluoromethylpyromellitic acid, 2,
2-bis (2,3-dicarboxyphenyl) -hexafluoropropane, 1,4-bis (3,4-dicarboxytrifluorophenoxy) tetrafluorobenzene,
2,2'-difluoro-3,3 ', 4,4'-biphenyltetracarboxylic acid, 2,2'-bis (trifluoromethyl) -3,3', 4,4'-biphenyltetracarboxylic acid and these Acid anhydrides, acid chlorides, ester compounds, and the like. It should be noted that diamines or tetracarboxylic acids and their derivatives which are not substituted with fluoro groups, fluoroalkyl groups and the like other than the above may be used within the range not impairing the object of the present invention.

The fluorinated polyamic acid in the present invention is
From the viewpoint of electro-optical effect, heat resistance, etc., when the imide ring-closes to give a fluorinated polyimide, the refractive index is 1.4 to 1.9.
(589 nm), a dielectric constant of 2.6 to 3.5 (1 MHz) and a glass transition temperature (Tg) of 300 ° C. or higher are preferable.

The fluorinated polyamic acid in the present invention is
From the viewpoint of electro-optic effect, heat resistance, etc., formula (II-1)

[Chemical 7] A repeating unit represented by the formula (II-2)

Embedded image Of at least one repeating unit represented by the formula (III-
1)

[Chemical 9] A repeating unit represented by the formula (III-2)

[Chemical 10] A fluorinated polyamic acid having at least one repeating unit represented by

The above formula (II-
To provide the repeating unit represented by 1) or the repeating unit represented by the formula (II-2), for example, 2,2 ′-(bistrifluoromethyl) -4,4 ′ as a diamine
-Diaminobiphenyl may be used, and pyromellitic acid anhydride may be used as the tetracarboxylic acid anhydride.

[0012] The above formula (III-
To provide the repeating unit represented by 1) or the repeating unit represented by the above formula (III-2), for example, 2,2 ′-(bistrifluoromethyl) -4, as a diamine,
4,2'-bis (trifluoromethyl)-as a tetracarboxylic acid anhydride using 4'-diaminobiphenyl
3,3 ', 4,4'-biphenyltetracarboxylic acid anhydride may be used.

The refractive index of the fluorinated polyimide obtained by subjecting the fluorinated polyamic acid in the present invention to imide ring closure can be easily adjusted by appropriately selecting the type and amount of the diamine or tetracarboxylic acid and its derivative to be used. can do. For example, when the content of the repeating unit represented by the formula (II-1) or the repeating unit represented by the formula (II-2) in the fluorinated polyamic acid is increased, the refractive index of the obtained fluorinated polyimide is increased. Can be increased. On the other hand, when the content of the repeating unit represented by the formula (III-1) or the repeating unit represented by the formula (III-2) in the fluorinated polyamic acid is increased, the refractive index of the obtained fluorinated polyimide is increased. Can be reduced.

In the present invention, the diamine, tetracarboxylic acid or its derivative is not only used alone but
A plurality of diamines, tetracarboxylic acids or their derivatives can be used in combination. In that case, it is preferable that the total number of moles of a plurality or single diamine and the total number of moles of a plurality or single tetracarboxylic acid or its derivative are equal or almost equal. In the solution of the fluorinated polyamic acid obtained by the reaction of the diamine and the tetracarboxylic acid or its derivative, the solid content concentration of the solution is preferably 5 to 40% by weight, particularly 10 to 25% by weight. Further, when the solid content of the fluorinated polyamic acid is 15% by weight, the rotational viscosity (20 ° C.) of the n-methyl-2-pyrrolidone solution is 2000 to 8000.
It is preferably mPa · s, 4000 to 6000 mPa · s
Is more preferable.

The fluorinated polyimide of the present invention has the following formula (II) from the viewpoint of electro-optical effect, heat resistance and the like.

[Chemical 11] And a repeating unit represented by the following formula (III)

[Chemical 12] A fluorinated polyimide having a repeating unit represented by

The electro-optical material in the present invention has the general formula (I) from the viewpoint of heat resistance and electro-optical effect.

[Chemical 13] (In the formula, R ¹ represents a hydrogen atom, a cyano group, a phenyl group, an amino group, an alkoxy group, an acylamino group, an alkylthio group, an alkyl group, an alkoxycarbonyl group, a carbamoyl group or a heterocyclic group, and R ³ and R ⁴ are each independently represent an atom group and R ¹ similar to that of the group or R ³ and R ⁴ constitute a ring formed by connecting, never all R ^1, R ³ and R ⁴ are hydrogen atom, R ² represents a hydrogen atom, an alkyl group or an acyl group).

Examples of the compound represented by the general formula (I) include the following compounds.

[0018]

Embedded image

[0019]

[Chemical 15]

[0020]

Embedded image

The imidazole ring of the compound represented by the general formula (III) is generally synthesized from amidine having R ¹ and bromacetophenone having R ³ and R ⁴ (for example, Chemische Berichte 34 537). , Chemische
Berichte 29 2097). Other synthetic methods include Chemi
sche Berichte 38 1531, Chemische Berichte 35 2630,
Annalen der Chemie 600 95-108, Annalen der Chemie
663, Synthesis 1978 6, Journal of Chemical Societ
y 1957 4225 etc. are known. The benzimidazole ring is generally synthesized by a dehydration reaction between an o-phenylenediamine derivative and a carboxylic acid derivative.
When R ² is an alkyl group or an acyl group, it can be easily synthesized by reacting imidazole with the corresponding alkyl halide or acid chloride in the presence of a base, or by selecting a raw material for ring formation.

The composition for active optical waveguide of the present invention is
For example, it can be easily produced by adding an electro-optical material to a polar organic solvent solution of fluorinated polyamic acid and mixing them by stirring or the like. At this time, the amount of the electro-optical material used is preferably in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the fluorinated polyamic acid, and is preferably 0.1.
The amount is more preferably 5 to 5 parts by weight, and particularly preferably 0.5 to 3 parts by weight. If the amount used is too small or too large, electro-optical properties, other optical properties, mechanical properties, stability, workability, etc. tend to be poor. The composition for active optical waveguide of the present invention includes a polymer other than fluorinated polyamic acid (for example, polyamic acid containing no fluorine atom, liquid crystalline polymer such as liquid crystal polyester), pinhole inhibitor, leveling agent, plasticizer. An additive such as an adhesion improver can be included.

The active optical waveguide of the present invention will be described. The active optical waveguide of the present invention is used, for example, in optical matrix switches, modulators, optical polarizers, optical isolators, and the like. The basic form of the optical matrix switch and modulator is shown in FIG. In forming the optical waveguide, a general film forming method, for example, a spin coating method, a dipping method, a doctor blade method, a wire bar method, a roller method, a spray method or the like can be used. The core material and the clad material of the optical waveguide may be selected so that the difference between the wavelength of light and the refractive index suitable for the intended use.

In the active optical waveguide of the present invention, the composition for active optical waveguide is spin-coated on, for example, a silicon substrate and heat-treated under a nitrogen atmosphere to imidize the fluorinated polyamic acid in the composition for active optical waveguide. It can be formed by ring closure to give a fluorinated polyimide and orienting the electro-optic material. For example, manufacturing of a directional coupler type optical switch, which is one mode of the active optical waveguide, will be described with reference to FIG. 1 is a substrate, 2 is a lower electrode, 3 is a lower clad layer, 4 is a core layer, 5 is an aluminum layer, 6 is a resist layer, 7 is an upper clad layer, 8
Means the upper electrode. A lower electrode 2 of aluminum or the like is formed on a substrate of silicon or the like by a vapor deposition method, a sputtering method, or the like, and then has a smaller refractive index than the core layer 4 made of the active optical waveguide composition of the present invention. A lower clad layer 3 composed of fluorinated polyimide, which is one of the two essential components in the composition for active optical waveguide, is formed. A core layer 4 is obtained by applying the active optical waveguide composition of the present invention (containing an electro-optical material and a fluorinated polyamic acid as essential constituents) to a predetermined thickness and heating and curing the composition. Next, after applying the aluminum layer 5 by a vapor deposition method or the like, resist coating, pre-baking, exposure, development and after-baking are performed to obtain a patterned resist layer 6. After aluminum which is not protected by the resist layer 6 is removed by wet etching, the polyimide layer of the core layer 4 which is not protected by the aluminum layer 5 is removed by dry etching. The remaining aluminum layer 6 is removed by wet etching, and an upper clad layer 7 is formed thereon by using the polyimide used for forming the lower clad layer 3. Finally, an upper electrode 8 is formed on a predetermined core layer 4 through a mask pattern by a vapor deposition method, a sputtering method, or the like to obtain a directional coupler type optical switch.

To orient the electro-optical material contained in the core layer in the active optical waveguide, poling treatment or the like may be performed. For example, it is possible to orient the electro-optical material at the same time while heating while applying an electric field to perform imidization by imide ring closure. Examples of the method of applying the electric field include a method of providing an electrode and a method of charging the surface by corona discharge. The strength of the electric field is 10 ⁵ V / cm
And more preferably 10 ⁶ V / cm or more. It is also possible to orient the electro-optical material by applying an electric field to this and heating it to a temperature of Tg or higher after imidizing by imide ring closure to give a final structure of fluorinated polyimide. Waveguide is usually 10 μm
It is formed with a width of ˜15 μm and a height of 3 μm to 4 μm, and the pattern interval is about 2 μm to 3 μm.

In the present invention, the fluorinated polyimide having the highest heat resistance among plastics is used for either or both of the core layer and the clad layer of the optical waveguide.
In addition, the general formula (I), which is an electro-optical material having excellent heat resistance,
The compound represented by is contained in the fluorinated polyimide.

[0027]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples.

Preparation Example 1 Synthesis of (Compound 1) 15 g of 4-aminosalicylic acid and 11 g of o-phenylenediamine were dissolved in 150 ml of dioxane to prepare N, N'-.
20 g of dicyclohexylcarbodiimide was added dropwise and reacted at room temperature for 4 hours. After removing the urea, remove the solvent,
After heating at 120 ° C. for 1 hour, purification (yield 10
g). The whole amount was dissolved in 100 ml of acetonitrile, 7 g of benzoyl chloride was added, the mixture was refluxed for 3 hours, and then the reaction liquid was cooled to obtain 13 g of the desired crystal (compound 1). The NMR and FD-MAS spectra of this compound were measured to confirm the structure.

Production Example 2 Synthesis of (Compound 6) 10.25 g of p-nitrobenzamidine was suspended in 50 ml of dimethylformamide, and bromoacetophenone 3.1 was added.
When 1 g was added, heat was generated and a reddish brown solution was formed. After allowing this solution to cool, water was added and the precipitated solid was collected by filtration to give the desired product ((Compound 6), melting point 231 ° C.) 2.2
7 g were obtained. In addition, NMR and FD-MA of this compound
The S spectrum was measured to confirm the structure.

Preparation Example 3 Synthesis of (Compound 7) 6.75 g of o-aminoacetophenone was dissolved in 60 ml of acetonitrile, 5 ml of pyridine was added, benzoyl chloride was added dropwise with stirring, and the mixture was left for 3 hours, and the solvent was distilled off under reduced pressure. After removal, water and ethyl acetate were added for extraction, the organic layer was dried over anhydrous magnesium sulfate, and the solvent was evaporated. Alcohol was precipitated to obtain 9.6 g of white crystals of o-benzamido bromoacetophenone. The bromoacetophenone of Production Example 2 was synthesized as described above.
Benzamide bromoacetophenone was reacted in the same manner as in Production Example 2 except that it was replaced with 4.97 g, and recrystallized from alcohol to give the desired product ((compound 7), melting point: 250 ° C. or higher).
3.65 g was obtained. The NMR and FD of this compound
-MAS spectrum was measured to confirm the structure.

Example 1 1 part by weight of (Compound 1) as an electro-optical material produced in Production Example 1 and fluorinated polyamic acid OPI-
N-added 15 parts by weight of 1005 (trade name of Hitachi Chemical Co., Ltd.)
A solution of the composition for active optical waveguide obtained by dissolving it in 200 parts by weight of methylpyrrolidone (NMP) was spun on a quartz glass having a semi-transparent aluminum electrode with a thickness of 100 nm and a rotation speed of 20.
Spin coating was performed at 00 rpm to form a 2 μm film. NMP
To remove the solvent, soft baking was performed under vacuum at 120 ° C. for 6 hours, and then a 100 nm-thick semitransparent aluminum electrode was formed on the film to prepare a sandwich type sample. While applying a voltage of 400 V between the electrodes, the sample was heated to 250 ° C. (poling temperature) at a heating rate of 2 ° C./min,
Further, the sample was held at the same temperature for 1 hour while applying a voltage of 400V, then cooled to room temperature while applying a voltage of 400V, and the active optical waveguide test sample (here, the core layer 4 portion in FIG. The corresponding core part was included, and the clad part was not included.

The thermal stability of the active optical waveguide test sample was examined by using the measuring apparatus shown in FIG.
This device is an electro-optical constant measuring device, and the measuring method is CCTe.
ng and HTMan, Appl. Phys. Lett. 56 (18) 1734 (1990). The measuring device shown in FIG. 3 is configured as follows. The light from the He-Ne laser 9 is passed through the polarizer 10 to be linearly polarized light, and then the sample 11 tilted so that the angle formed by the normal axis of the sample 11 and the beam axis is θ is transmitted, and the Babinet is used. Detecting with a detector (photodiode) 14 through a Soleil compensator 12 and an analyzer 13. The detected light intensity is used as a voltage, and the DC voltmeter 16 and the lock-in amplifier 15 are used.
Is measured at. The angle of the transmission axis of the analyzer when measuring is
The analyzer is set to rotate so that the difference between the maximum value and the minimum value of the DC voltage measured by the DC voltmeter 16 is 1/2. When an oscillator 17 applies a frequency of 1 kHz and an AC voltage of 10 V to the sample 11, the output signal is also modulated at 1 kHz by the electro-optic effect. At this time, the AC component is measured by the lock-in amplifier 15 and the DC component is measured by the DC voltmeter 16. When the measured voltages at the lock-in amplifier 15 and the DC voltmeter 16 are defined as V _m and V, respectively, the electro-optical constant r
₃₃ is calculated from the following formula (1).

[Equation 1] The refractive index n was measured with an Abbe refractometer. Thermal stability is determined by electro-optic constant r ₃₃ (0) and temperature of 15 after poling.
The electro-optical constant r ₃₃ (T) of the sample after standing in a constant temperature bath of 0 ° C. for 250 hours was measured, and the retention was calculated from the above r ₃₃ (0) and r ₃₃ (T) by using the following formula (2). Evaluation was made from the rate d (T), and the results are shown in Table 1.

[Equation 2]

Examples 2 to 5 (Compound 1) used in Example 1 and polyamic acid O
Instead of PI-1005, the electro-optical material and fluorinated polyamic acid (made by Hitachi Chemical Co., Ltd.) shown in Table 1 were used.
An active optical waveguide test sample was prepared in the same manner as in Example 1, and the retention rate d (T) of electro-optical characteristics was evaluated.
The results are shown in Table 1.

Comparative Example 1 In place of (Compound 1) and fluorinated polyamic acid OPI-1005 used in Example 1, 4- [N] shown in Table 1 was used.
-Ethyl-N- (2-hydroxyethyl)]-amino-
Example 1 except that 4'-nitroazobenzene (Disperse Red 1) and polymethylmethacrylate (PMMA) solution (12% by weight) were used and the polling temperature was 150 ° C.
A sample for active optical waveguide test was prepared in the same manner as described above, and the retention rate d (T) of electro-optical characteristics was evaluated. The results are shown in Table 1. The electro-optical properties disappeared by 75% only by heating to 100 ° C.

[0035]

[Table 1]

[0036]

The composition for active optical waveguide of the present invention gives an optically excellent transparent film. The active optical waveguide produced by using the composition for active optical waveguide of the present invention is very stable thermally and is suitable for producing electro-optical elements such as optical switches and modulators. By using the fluorinated polyimide having excellent heat resistance and the compound represented by the general formula (I), the thermal stability required when producing an optical waveguide is improved. Furthermore, the spin coating method has an advantage that a large-area optical waveguide can be easily manufactured, and the cost of the optical waveguide can be reduced.

[Brief description of drawings]

FIG. 1 is a basic form of an optical matrix switch and a modulator.

FIG. 2 is an explanatory diagram of an active optical waveguide manufacturing process.

FIG. 3 is an explanatory diagram of an electro-optical constant measuring device used in Examples and Comparative Examples.

[Explanation of symbols]

 1 Substrate 2 Lower Electrode 3 Lower Cladding Layer 4 Core Layer 5 Aluminum Layer 6 Resist Layer 7 Upper Cladding Layer 8 Upper Electrode 9 He-Ne Laser 10 Polarizer 11 Sample 12 Habine-Soleil Compensator 13 Analyzer 14 Detector 15 Lock-in Amplifier 16 DC voltmeter 17 Oscillator

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Claims (5)

[Claims] 1. A composition for an active optical waveguide, comprising a fluorinated polyamic acid and an electro-optical material, wherein the electro-optical material has the general formula (I): (In the formula, R ¹ represents a hydrogen atom, a cyano group, a phenyl group, an amino group, an alkoxy group, an acylamino group, an alkylthio group, an alkyl group, an alkoxycarbonyl group, a carbamoyl group or a heterocyclic group, and R ³ and R ⁴ are each independently represent an atom group and R ¹ similar to that of the group or R ³ and R ⁴ constitute a ring formed by connecting, never all R ^1, R ³ and R ⁴ are hydrogen atom, R ² is a compound represented by a hydrogen atom, an alkyl group or an acyl group) and is a composition for active optical waveguide. 2. When the fluorinated polyamic acid is imide-closed to form a fluorinated polyimide, the refractive index is 1.4 to
1.9 (589 nm), dielectric constant 2.6-3.5 (1 MH
The composition for active optical waveguides according to claim 1, wherein z) and the glass transition temperature (Tg) are 300 ° C or higher. 3. The fluorinated polyamic acid has the formula (II-1): The repeating unit represented by the formula and the formula (II-2): Of at least one repeating unit represented by the formula (III-
1) [Chemical 4] A repeating unit represented by the formula and formula (III-2): The composition for active optical waveguides according to claim 1 or 2, which is a fluorinated polyamic acid having at least one repeating unit represented by: 4. The active optical waveguide characterized in that the fluorinated polyamic acid in the composition for active optical waveguide according to claim 1, 2 or 3 is imide ring-closed to give a fluorinated polyimide to orient an electro-optical material. Waveguide manufacturing method. 5. An active optical waveguide manufactured by the method for manufacturing an active optical waveguide according to claim 4.