JPH11174249A - Polyamide acid varnish for optical waveguide and production of optical waveguide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the production of defects such as voids when a polyimide is used as a material for an optical waveguide by using a specified polymide acid varnish. SOLUTION: This polyamide acid varnish for an optical wceguide contains a polyamide acid having an atomic group expressed by the formula and having the weight average mol.wt. (Mw) of 160000 to 250000. In the formula, Ar<1> and Ar<2> are each independently bivalent aromatic groups or bivalent aromatic groups having substituents, R<1> , R<2> and R<3> are each independently hydrogen or univalent org. groups, Y is hydrogen or univalent functional group, and (n) is an integer of 2 to 10. As for Ar<1> , Ar<2> , they are each phenydiyl, naphthalenediyl, biphenyldiyl, or their substituted groups or their position isomers. As for R<1> , R<2> and R<3> , not only hydrogen atoms but satd. hydrocarbon groups such as methyl, ethyl, propyl and butyl groups can be used and they may have substitutents.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyamic acid varnish for an optical waveguide and a method for producing the optical waveguide.

[0002]

2. Description of the Related Art Conventionally, as an optical waveguide in an optoelectronic IC, LiNbO ₃ , LiTaO ₃ , PL
Inorganic materials such as ZT and Sr ₂ Nb ₂ O ₇ are used.
However, these materials have deliquescence, low destruction thresholds,
Furthermore, the response speed is slow due to the high dielectric constant, and the applicable frequency band is limited. Organic polymer materials are generally superior to inorganic materials in that they do not have deliquescence and have a high destruction threshold.However, they generally have no orientation, and as they are, optical switches and devices that use the electro-optical effect can be used. It cannot be used as a material for a modulation element or the like.

For an organic polymer material having no orientation,
A method of applying a DC electric field while heating to orient, that is, a method of expressing an electro-optical effect by poling (orientation) processing is known and used. Is lost,
There are problems such as the disappearance of the electro-optic effect. A major organic polymer material that has been conventionally studied is polymethyl methacrylate.

Polyimide has heat resistance to temperatures of 250 ° C. or higher and is resistant to various organic solvents. Therefore, polyimide has an interlayer insulating film and a surface protective film of a semiconductor device requiring a high-temperature manufacturing process. Widely used for bonding materials, circuit forming substrates, and the like. In addition, polyimide containing fluorine has a low dielectric constant and an improved light transmittance in addition to the above-mentioned characteristics. Therefore, a light-transmitting material for a substrate of an arithmetic processing unit for high-speed signal processing or an optical device (Japanese Patent Laid-Open No. 3-72528). Gazette).

In recent years, research and development of active optical waveguide materials having an optical switching function and an optical modulation function by combining a polyimide and a nonlinear material have also attracted attention. Furthermore, it has been reported that polyimide having a non-linear dye has high heat resistance after the dipole of the non-linear dye in the polymer is oriented by an electric field (J. Chem. Soc., Chem. Commun., 2711-).
2712, 1994).

[0006]

When an optical waveguide is produced, a polyimide film is formed by using a polyamic acid (which is a precursor of polyimide) in an organic solvent because polyimide is insoluble in most solvents. Melted polyamic acid varnish) is commonly used. That is, this is a method in which a polyamic acid varnish is applied on a substrate (for example, a silicon wafer) by spin coating or the like, the solvent is volatilized by a relatively low-temperature pre-curing process, and then the temperature is raised (imidation). At this time, there is a problem that voids are easily generated during the pre-curing process. When a void is generated, a defect occurs in the film, and light transmission is hindered at that portion. In addition, distortion and cracks are generated around the voids to increase optical transmission loss, thereby impairing the function as a waveguide. In addition, since the surface state becomes non-uniform, it causes an electric short circuit at the time of poling. These are problems specific to optical waveguides. An object of the present invention is to provide a method for manufacturing an optical waveguide which does not generate defects such as voids when polyimide is used as a material for an optical waveguide, and a polyamic acid varnish suitable for the method, thereby solving the above-mentioned problems.

[0007]

Means for Solving the Problems The present inventors apply a polyamic acid varnish onto a substrate such as a silicon wafer by spin coating or the like, and apply a varnish at a relatively low temperature in a pre-curing (semi-curing) process to evaporate the solvent. In the course of studying various methods that do not generate voids (hence, no voids after curing (curing)), the weight average molecular weight (Mw) of the polyamic acid varnish used is an important factor. It has been found that it is important to adjust the Mw to an optimum range by heating (also called cooking) in advance, and the present invention has been completed.

That is, the present invention firstly provides the following general formula (I)

Embedded image Having a weight average molecular weight (Mw) of 1
Provided is a polyamic acid varnish for an optical waveguide, which comprises 60,000 or more and 250,000 or less polyamic acid.

In the formula (I), Ar ¹ and Ar ² each independently represent a divalent aromatic group or a divalent aromatic group having a substituent.
R ¹ , R ² and R ³ each independently represent hydrogen or a monovalent organic group, Y represents hydrogen or a monovalent functional group, and n represents 2 to 10 Indicates an integer.

Here, Ar ¹ and Ar ² are phenyldiyl, naphthalenediyl, biphenyldiyl, thiophendiyl, benzo [b] thiophendiyl, naphtho [2,3-b] thiophendiyl, thiaslendiyl,
Furandiyl, pyrandiyl, benzo [b] furandiyl, isobenzofurandiyl, chromendiyl, xanthendiyl, phenoxatindiyl, 2H-pyrrolediyl, pyrrolediyl, imidazolediyl, pyrazolediyl, pyridinediyl, pyrazinediyl, pyrimidinediyl, pyridazinediyl, indolizinediyl , Isoindolediyl, 3H-indolediyl, indolediyl, 1H-indazolediyl, purindiyl, 4H-quinolidindiyl, isoquinolindiyl, quinolindiyl, phthalazinediyl, naphthyridindiyl, quinoxalindiyl, quinazolindiyl, cinolinindiyl, pteridinediyl, 4aH-carbadiyl Zolidiyl, carbazolediyl, β-carbolinediyl, phenanthridindiyl, Kurijinjiiru, Perimijinjiiru, phenanthryl Ro phosphorus diyl, Fenajinjiiru,
Fenalsazindiyl, isothiazoldiyl, phenothiazinediyl, isoxazolediyl, furazanediyl, phenoxazinediyl, isochromandiyl, chromandiyl, pyrrolidinediyl, pyrrolindiyl, imidazolidindiyl, imidazolindiyl, pyrazolidindiyl, pyrazolindiyl, piperidindiyl , Piperazinediyl, indolinediyl, isoindolinediyl, quinuclidinediyl, morpholinediyl and the like, and their substituted or positional isomers.

As R ¹ , R ² and R ³ , in addition to a hydrogen atom, saturated hydrocarbon groups such as methyl, ethyl, propyl, butyl and pentyl, saturated cyclic hydrocarbon groups such as cyclopentyl and cyclohexyl, vinyl, allyl, Examples include unsaturated hydrocarbon groups such as cyclopentenyl, cyclohexenyl, benzyl, and triphenylmethyl; perfluoroalkyls such as trifluoromethyl, pentafluoroethyl, and heptafluoropropyl; and isomers thereof.

Y represents hydrogen, an alkylamino group, a dialkylamino group, an arylamino group, a diarylamino group, an alkylarylamino group, an alkyl group, an alkenyl group, an alkylsulfide group, an arylsulfide group, an alkyloxy group, In addition to electron donating groups such as an aryloxy group, a hydroxyl group and a thiol group, a nitro group,
There are a nitroso group, an alkynyl group, an acyl group, a formyl group, an aryl group, an alkylsulfoxide group, an arylsulfoxide group, an alkylsulfone group, an arylsulfone group, a halogen group, and the like, which may have a substituent.

The present invention also provides an optical waveguide manufactured through (a) a step of forming a polyamic acid layer on a substrate, (b) a step of precuring the polyamic acid, and (c) a step of curing. A varnish for minimizing the number of voids by examining the relationship between the "weight average molecular weight (Mw)" and the "number of voids generated during precuring" of the polyamic acid in advance.
The present invention relates to a polyamic acid varnish for an optical waveguide in which a range is determined, and the Mw of the polyamic acid used is adjusted to fall within the Mw range.

Further, the present invention provides a method of manufacturing an optical waveguide, comprising: (a) forming a polyamic acid layer on a substrate; (b) precuring the polyamic acid; and (c) curing. In the above, the relationship between “the weight average molecular weight (Mw)” and “the number of voids generated during pre-curing” for the polyamic acid to be used is determined in advance to determine the Mw range that minimizes the number of voids, The present invention also relates to a method for manufacturing an optical waveguide in which the Mw of an acid is adjusted to fall within the Mw range. In this specification, the term "polyamic acid" is used to mean, in addition to polyamic acid, a polyimide precursor in which polyamic acid is partially cyclized (polyimide).

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The polyamic acid used in the above-mentioned method for producing an optical waveguide can be obtained by reacting tetracarboxylic dianhydride with a diamine in an organic solvent in an equimolar or almost equimolar manner. . Here, as the tetracarboxylic dianhydride, for example, 2,2-bis
(3,4-dicarboxyphenyl) hexafluoropropane dianhydride, 1,2,4,5-benzenetetracarboxylic dianhydride, 3-trifluoromethyl-1,2,4,5
-Benzenetetracarboxylic dianhydride, 3,6-bis (trifluoromethylmethyl) -1,2,4,5-benzenetetracarboxylic dianhydride, 3,6-difluoro-
1,2,4,5-benzenetetracarboxylic dianhydride,
2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-tetrafluoro-2,3,6,7
-Naphthalenetetracarboxylic dianhydride, 2,3,6
7-tetrafluoro-1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride Anhydrous,

Bis (3,4-dicarboxyphenyl) dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, (3,4-dicarboxyphenyl) ketone dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis [(3,4-dicarboxyphenyl) dimethylsilyl] ether dianhydride, 2,2
-Bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenyl)
-1,1,3,3-tetrafluoropropane dianhydride,
1,4-bis (3,4-dicarboxyphenyl) benzene dianhydride,

2,2-bis [4- (3,4-dicarboxyphenyloxy) phenyl] dodecane dianhydride;
2-bis [4- (3,4-dicarboxyphenyloxy) phenyl] tridecane dianhydride, 1,4-bis (3,4-dicarboxyphenyloxy) benzene dianhydride, 2,3,5,6 -Tetrafluoro-1,4-bis (3,4-dicarboxy-2,5,6-trifluorophenyloxy) benzene dianhydride, bis (3,4-dicarboxy) cyclohexyl dianhydride, bis (1 , 2-dicarboxyethyl) dianhydride, alkandio-bis (trimellitic anhydride) and the like. These acid dianhydrides may be used as a mixture of two or more kinds. The alkanediol bis (trimellitic anhydride) preferably has 2 to 12 carbon atoms.

For use in optical applications, those obtained by replacing hydrogen (preferably all hydrogen) by fluorine or deuterium are preferable because of their small optical transmission loss.

Examples of the diamine that can be used include:
4,4′-diamino-2,2′-dimethylbiphenyl,
4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl, 4,4'-diamino-2,2'-difluorobiphenyl, 4,4'-diamino-3,3'-
Dimethylbiphenyl, 4,4'-diamino-3,3'-
Bis (trifluoromethyl) biphenyl, 4,4'-diamino-3,3'-difluorobiphenyl, 4,4'-
Diamino-2,2'-dihydroxybiphenyl, 4,
4'-diamino-3,3'-dihydroxybiphenyl,
4,4′-diamino-2,2 ′, 3,3 ′, 5,5 ′,
6,6′-octafluorobiphenyl,

Bis (4-diaminophenyl) ether,
Bis (4-diaminophenyl) thioether, bis (4
-Diaminophenyl) sulfone, bis (4-diaminophenyl) methane, bis (3-diaminophenyl) ether, bis (3-diaminophenyl) thioether, bis (3-diaminophenyl) sulfone, bis (3- Diaminophenyl) methane, 2,2-bis (4-diaminophenyl) propane, 2,2-bis (4-diaminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2- Bis (3-diaminophenyl) -1,1,
1,3,3,3-hexafluoropropane, 2,2-bis [(4-diaminophenyloxy) methyl] propane, 2,2-bis [4- (4-diaminophenyloxy) phenyl] propane, 2, 2-bis [4- (3-diaminophenyloxy) phenyl] propane,

Bis [1,2,5,6-tetrafluoro-
4- (4-diaminophenyloxy) phenyl], 2,
2-bis (4-diaminophenyloxy) phenyl-
1,1,1,3,3,3-hexafluoropropane,
2,2-bis (3-diaminophenyloxy) phenyl-1,1,1,3,3,3-hexafluoropropane,
2,2-bis (4-diamino-2-trifluoromethylphenyloxy) phenyl-1,1,1,3,3,3-
Hexafluoropropane, alkanediol [bis (4
-Aminophenyl) ether], and alkandioles [bis (3-aminophenyl) ether].
These diamines may be used as a mixture of two or more kinds. Also, the diamine may be the corresponding diisocyanate. Alkane diols have an alkane carbon number of 2
It is preferably from 12 to 12.

As part of the diamine, silicon diamine may be used. 1,3 as silicon diamine
-Bis (3-aminopropyl) -1,1,1-tetraphenyldisiloxane, 1,3-bis (3-aminopropyl) -1,1,1-tetramethyldisiloxane, 1,3
-Bis (4-aminobutyl) -1,1,1-tetramethyldisiloxane and the like. For use in optical applications, hydrogen (preferably all hydrogen) replaced with fluorine or deuterium is preferred because of its small optical transmission loss.

As the polyamic acid in the production method of the present invention, a polyamic acid containing plural kinds of polyamic acids may be used.

As the polyamic acid, a polyamic acid to which a nonlinear optical dye is bonded can be used. The production of polyamic acid to which a non-linear dye is bound is performed by using a tetracarboxylic dianhydride having an atomic group of a non-linear optical dye in the molecule as a raw material tetracarboxylic dianhydride or a non-linear in the molecule as a raw material diamine This can be performed by using a diamine having an atomic group of an optical dye.

As the diamine having an atomic group of a nonlinear optical dye in the molecule, for example, the following general formula (II)

Embedded image And a polyamic acid having an atomic group represented by the general formula (II) can be synthesized by using this diamine.
Here, in the formula (II), Ar ¹ , Ar ² , R ¹ , R ² , R ³ ,
Y and n have the same meanings as in formula (I),
Ar ³ is a trivalent aromatic group or a trivalent aromatic group having a substituent, and the type of the aromatic ring is the same as that of Ar ¹ and Ar ² . As the nonlinear optical dye, various other known nonlinear optical dyes can be used.

In the present invention, the "number of voids generated during pre-curing" means that a polyamic acid layer is formed on a substrate and heated to such an extent that the solvent volatilizes (for example, treatment on a hot plate at 100 ° C. for 2 minutes). After that, observe and count with the naked eye. In the naked eye observation, a void having a diameter of about 0.05 mm or more can be recognized. The “weight average molecular weight (Mw)” of the polyamic acid is determined by gel filtration chromatography (G
PC).

Solvents for the polyamic acid production reaction include amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidinone, diethyl ether, tetrahydrofuran, dioxane, diglyme and the like. Ether solvents, benzene,
Aromatic solvents such as toluene and xylene, and mixtures thereof can be used, and among them, amide solvents and ether solvents are preferable. The temperature of the production reaction is 80 ° C. or less,
Preferably it is 0-50 degreeC. As the reaction proceeds, the viscosity of the reaction solution gradually increases, and polyamic acid is generated.
The molecular weight of the polyamic acid can be appropriately adjusted by selecting the reaction conditions such as the reaction temperature, the reaction time, and the amount of the substrate (raw material) used.

The polyamic acid having an atomic group represented by the general formula (I) contained in the polyamic acid varnish for an optical waveguide of the present invention may be a polyamic acid containing a plurality of types of polyamic acids or a copolymer. Two types of polyamic acids, for example, a first polyamic acid in which a non-linear optical dye is pendantly bonded to a polymer and a second polyamic acid containing no non-linear optical dye (weight average of the two types of polyamic acid mixture) And a mixture having a molecular weight of preferably more than 250,000) and heating (also referred to as a cooking process) until the weight average molecular weight falls within an optimum range.

Solvents that can be used for the above mixing and heating include amide solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidinone, diethyl ether, tetrahydrofuran, dioxane, and the like. Ether solvents such as diglyme, benzene,
Aromatic solvents such as toluene and xylene, and mixed solvents thereof, among which amide solvents and ether solvents are preferable. The heating temperature is preferably 30 ° C. or higher, where the amide bond cleavage / recombination reaction is likely to occur. In the above-mentioned heating, it is preferable to mix the polyamic acids of different structural units so as to exist as uniformly as possible in the system.

When the polyamic acid having the atomic group represented by the general formula (I) is out of the range of 160,000 to 250,000, the weight average molecular weight (Mw) is coated on a substrate by spin coating or the like. When the solvent is volatilized by pre-cure, voids are easily generated. Further, the degree of dispersion of the polyamic acid is preferably 4 or less.

The polyamide acid varnish for an optical waveguide of the present invention is used for an optical waveguide such as a Mach-Zehnder type waveguide. Therefore, a manufacturing process of the Mach-Zehnder waveguide will be described with reference to FIG. Forming an aluminum-based metal film 102a on the surface of the silicon wafer 101 (a) (b),
After a resist 103 is applied to this surface, exposed and developed for patterning (c), the metal film 102a is etched and the resist is peeled off to form a lower electrode 102 (d). A polyamic acid (P ₁ ) solution is applied to the surface of the wafer 101 by spin coating or the like so as to cover the lower electrode 102, and is cured by heating to form a polyimide layer 104a (e). A resist is applied to the surface of the polyimide layer 104a, exposed in a predetermined pattern, and developed (f). Then, the polyimide layer 104a is etched, the resist is peeled off, and a portion corresponding to the core pattern of the Mach-Zehnder waveguide is formed. To form a lower cladding layer 104b having a concave portion (g).

Next, another type of polyamic acid (P ₂ ) solution is spin-coated on the surface of the lower cladding layer 104b so as to cover the concave portion, and is heated and cured to form a polyimide layer 10b.
After the formation of 6a (h), the surface of the polyimide layer 106a is ground until the lower cladding layer 104b is exposed.
Thereby, the core 106 of the core pattern of the Mach-Zehnder waveguide is formed (i). The polyamic acid (P ₁ ) solution is spin-coated and heat-cured so as to cover the core 106 to form an upper clad layer, which is integrated with the already formed lower clad layer 104b (j). As a result, the surface of the core 106 is
Covered with 4. An aluminum-based metal film 107a is formed on the surface of the cladding layer 104 (k), a resist 103 is applied to the surface, and is exposed and developed to be patterned (l).
Etching the metal film 107a, removing the resist,
The upper electrode 107 is formed (m). The surface of the cladding layer is covered with a resin so as to cover the upper electrode 107 to form a cover coat layer 108 (n).

After polling the obtained wafer,
After spin-coating the protective film layer, curing by heating, dicing, and peeling off the protective film, a Mach-Zehnder waveguide switch is obtained. Waveguides are typically 5 to 15 microns wide
m, height 1-4 μm, pattern interval 2-3
It is about μm.

[0034]

The present invention will be described below with reference to examples. Synthesis Example 1 Synthesis of First Polyamic Acid (1) In a 50 ml four-necked flask, the following formula (III) was added.

[0035]

Embedded image

The nonlinear optical dye-based diamine 50 represented by
0 mg (0.83 mmol) was weighed and dissolved in 5.25 ml of diglyme in a nitrogen stream. Then, at 0 ° C., the following formula (IV)

[0037]

Embedded image

2,2-bis (3,4-dicarboxyphenyl) -hexafluoropropane dianhydride 3
69 mg (1.0 equivalent) was added, and the mixture was stirred at 0 ° C. for 2 hours, then at room temperature for 4 hours, and stirred with polyamic acid varnish (1st
Polyamic acid: and A _1. ).

Synthesis Example 2 Synthesis of First Polyamic Acid (2) Synthesis Example 1 except that the reaction temperature and time were changed to 6 hours at room temperature.
Similarly performed as polyamic acid varnish: was obtained (first polyamic acid and A _2.).

Synthesis Example 3 Synthesis of First Polyamic Acid (3) The same procedure as in Synthesis Example 1 was carried out except that the reaction temperature and the time were set at 40 ° C. for 6 hours, and a polyamic acid varnish (first polyamic acid: A ₃ ).

Synthesis Example 4 Synthesis of First Polyamic Acid (4) The procedure of Synthesis Example 1 was repeated except that the reaction temperature and time were changed to 50 ° C. for 6 hours, and a polyamic acid varnish (first polyamic acid: A ₄ ).

Synthesis Example 5 Synthesis of second polyamic acid 46.60 g of 4,4′-diaminodiphenyl ether
(0.23 mol) in a nitrogen atmosphere.
-Dissolved in 850 g of dimethylacetamide. 2,2-
Bis (3,4-dicarboxyphenyl) -hexafluoropropane dianhydride 103.40 g (0.23 mol)
Was added and stirred at room temperature for 6 hours to obtain a polyamic acid varnish (second polyamic acid: B).

The average molecular weights of the above polyamic acids A ₁ , A ₂ , A ₃ , A ₄ and B were as follows. In Table 1, M
w is the weight average molecular weight, Mn is the number average molecular weight, Mw / Mn
Indicates the degree of dispersion. The molecular weight is a value determined by a method using gel permeation chromatography (in terms of polystyrene).

[0044]

Table 1 Physical properties of polyamic acid ポ リ ア ミ ド Polyamic acid Mw (million) Mn (million) Mw / Mn─────────────────────────────A ₁ 19.2 6.2 3.12 A ₂ 17.7 5.7 _{3.09 A 3 12.9 5.1 2.58 A 4} 7.5 3.6 2.08 B 45.1 12.9 3.48 ━━━━━━━━━━━━━━━ ━━━━━━━━━━━━━━

Example 1 1. To 965 ml of the polyamic acid varnish (first polyamic acid: A ₁ ) obtained in Synthesis Example _1, 1.35 g of the polyamic acid varnish (second polyamic acid: B) obtained in Synthesis Example 5 was added, and the mixture was added at room temperature. After stirring for 2 hours, Mw = 20.
The mixture was stirred until 30,000 (the dispersity at this time was 2.77). The reaction product was filtered under pressure using a filter (φ = 0.22 μm) to obtain a polyamic acid varnish.

No. 2. To 965 ml of the polyamic acid varnish (first polyamic acid: A ₂ ) obtained in Synthesis Example 2, 1.35 g of the polyamic acid varnish (second polyamic acid: B) obtained in Synthesis Example 5 was added, and the mixture was added at room temperature. After stirring for 2 hours, Mw = 21.
The mixture was stirred until it reached 30,000 (the dispersity at this time was 2.95). The reaction product was filtered under pressure using a filter (φ = 0.22 μm) to obtain a polyamic acid varnish.

No. 3. To 965 ml of the polyamic acid varnish (first polyamic acid: A ₃ ) obtained in Synthesis Example 3, 1.35 g of the polyamic acid varnish (second polyamic acid: B) obtained in Synthesis Example 5 was added, and the mixture was added at room temperature. After stirring for 2 hours, Mw = 21.
The mixture was stirred until it reached 0,000 (the dispersity at this time was 2.95). The reaction product was filtered under pressure using a filter (φ = 0.22 μm) to obtain a polyamic acid varnish.

No. 4. To 965 ml of the polyamic acid varnish (first polyamic acid: A ₄ ) obtained in Synthesis Example 4, 1.35 g of the polyamic acid varnish (second polyamic acid: B) obtained in Synthesis Example 5 was added, and the mixture was added at room temperature. After stirring for 2 hours, Mw = 19.
The mixture was stirred until it reached 40,000 (the dispersity at this time was 3.18). The reaction product was filtered under pressure using a filter (φ = 0.22 μm) to obtain a polyamic acid varnish.

No. 5. To 965 ml of the polyamic acid varnish (first polyamic acid: A ₂ ) obtained in Synthesis Example 2, 1.35 g of the polyamic acid varnish (second polyamic acid: B) obtained in Synthesis Example 5 was added, and the mixture was added at room temperature. After stirring for 2 hours, Mw = 27.
The mixture was stirred until it reached 20,000 (the dispersity at this time was 3.34). The reaction product was filtered under pressure using a filter (φ = 0.22 μm) to obtain a polyamic acid varnish.

No. 6. To 965 ml of the polyamic acid varnish (first polyamic acid: A ₃ ) obtained in Synthesis Example 3, 1.35 g of the polyamic acid varnish (second polyamic acid: B) obtained in Synthesis Example 5 was added, and the mixture was added at room temperature. After stirring for 2 hours, Mw = 27.
The mixture was stirred until 50,000 (the dispersity at this time was 3.37). The reaction product was filtered under pressure using a filter (φ = 0.22 μm) to obtain a polyamic acid varnish.

No. 7. To 965 ml of the polyamic acid varnish (first polyamic acid: A ₄ ) obtained in Synthesis Example 4, 1.35 g of the polyamic acid varnish (second polyamic acid: B) obtained in Synthesis Example 5 was added, and the mixture was added at room temperature. After stirring for 2 hours, Mw = 29.
The mixture was stirred until it reached 0,000 (the dispersity at this time was 3.97). The reaction product was filtered under pressure using a filter (φ = 0.22 μm) to obtain a polyamic acid varnish.

No. 8. To 965 ml of the polyamic acid varnish (first polyamic acid: A ₄ ) obtained in Synthesis Example 4, 1.35 g of the polyamic acid varnish (second polyamic acid: B) obtained in Synthesis Example 5 was added, and the mixture was added at room temperature. After stirring for 2 hours, Mw = 14.
The mixture was stirred until 90,000 (the degree of dispersion at this time was 2.52). The reaction product was filtered under pressure using a filter (φ = 0.22 μm) to obtain a polyamic acid varnish.

Evaluation Test No. 9 cm ^{2 of the} polyamic acid varnish obtained in 1 to 8
Was spin-coated (at 1000 rpm for 30 seconds) on a silicon wafer and precured on a hot plate at 100 ° C. for 2 minutes. Table 2 shows the results of measuring the number of voids (number per 1 cm ² ) of the obtained film. Table 2 shows that for the polyamic acids used, the M
The w range indicates 160,000 to 250,000.

[0054]

Table 2 Evaluation test results 結果 Polyamide varnish <Mw> Number of voids ( (Number per 1 cm ² ) Ｎｏ No. 1 <203,000> 0.10 No. 1 2 <213,000> 0.00 No. 3 <210,000> 0.22 No. 3 4 <194,000> 0.22 No. 4 5 <272,000> 3.35 No. 5 6 <275,000> 4.45 No. 6 7 <2900,000> 1.37 No. 8 <149,000> 1.09 ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

[0055]

According to the present invention, the polyamide acid varnish for an optical waveguide is formed on a substrate such as a silicon wafer and is preliminarily cured, so that there is little danger of generating voids and a polyimide film having a small transmission loss can be formed. . for that reason,
An optical waveguide manufactured using the above-mentioned polyamide acid varnish for an optical waveguide has high reliability. According to the manufacturing method of claims 3 to 7, a void-free optical waveguide can be manufactured.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a manufacturing process of a Mach-Zehnder optical waveguide.

[Explanation of symbols]

101: silicon wafer 102: lower electrode 102a: metal film 103: resist 104, 104a: polyimide layer 104b: lower cladding layer 105: resist 106: core pattern 106a: polyimide layer 107: upper electrode 107a: metal film 108: cover coat layer

Claims (6)

[Claims] (1) The following general formula (I): [In the formula (I), Ar ¹ and Ar ² each independently represent a divalent aromatic group or a divalent aromatic group having a substituent, and R ¹ , R ² and R ³ each represent Independently represents hydrogen or a monovalent organic group, Y represents hydrogen or a monovalent functional group, and n represents an integer of 2 to 10. And a weight average molecular weight (Mw) of 160,000 or more and 250,000 or less. 2. A polyamide used for an optical waveguide manufactured through (a) a step of forming a layer of polyamic acid on a substrate, (b) a step of precuring the polyamic acid, and (c) a step of curing. An acid varnish,
Regarding the polyamic acid, its weight average molecular weight (M
w) vs. the number of voids generated during pre-curing to determine the Mw range in which the number of voids is minimized, and to adjust the Mw of the polyamic acid to be used within the Mw range. Polyamic acid varnish. 3. A method of manufacturing an optical waveguide, comprising: (a) forming a polyamic acid layer on a substrate; (b) precuring the polyamic acid; and (c) curing. The relationship between "weight average molecular weight (Mw)" and "the number of voids generated during pre-curing" of the polyamic acid to be used is examined to determine the Mw range for minimizing the number of voids, and the Mw of the polyamic acid to be used is determined.
A method for manufacturing an optical waveguide, wherein w is adjusted to fall within the Mw range. 4. The method according to claim 2, wherein the polyamic acid used is a polyamic acid containing a plurality of types of polyamic acids. 5. The method according to claim 2, wherein the polyamic acid used is a polyamic acid to which a nonlinear optical dye is bonded. 6. The non-linear optical dye is represented by the following general formula (I): [In the formula (I), Ar ¹ and Ar ² each independently represent a divalent aromatic group or a divalent aromatic group having a substituent, and R ¹ , R ² and R ³ each independently represent Y represents hydrogen or a monovalent organic group, Y represents hydrogen or a monovalent functional group, and n represents an integer of 2 to 10. The method according to claim 4, which is a dye having an atomic group represented by the formula: 6. The method according to claim 2, wherein the adjusting means is heating.
Manufacturing method.