JP2008088287A - Optical polyimide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical polyimide useful for optical waveguide devices, etc., excellent in dimensional stability and having low coefficient of thermal expansion. <P>SOLUTION: The optical polyimide is obtained by reacting aromatic diamines each having a benzoazole skeleton with aromatic tetracarboxylic acids. The optical polyimide contains the benzoazole skeleton in a polyimide structure and has ≤35 ppm/°C coefficient of thermal expansion of polyimide. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical polyimide that can be used for an optical waveguide element having excellent dimensional stability and a low thermal expansion coefficient, an optical fiber, a lens, a substrate for an optical disk, and the like, and more particularly, an optical waveguide in an optoelectronic integrated circuit (OEIC) or an optoelectronic mixed mounting wiring board. The present invention relates to an optical polyimide excellent in properties that can be used as an optical material for a waveguide, and particularly has both a Fufu stability and a low thermal expansion coefficient. The present invention is used in polymer-based optical waveguides, such as peeling or warping due to the difference in thermal expansion coefficient between polyimide and silicon substrate, and deformation due to softening of polyimide at 320 ° C. or higher in Au—Sn solder, etc. It is related with the polyimide for optics which solved the subject of.

Conventionally, glass has been widely used as a transparent optical material. However, taking advantage of the excellent features such as molding processability, light weight, and impact resistance in recent years, optical components such as optical lenses, prisms, mirrors, optical disks, liquid crystal display sheets and films, and light guide plates of liquid crystal display devices are used. Transparent resin materials have come to be used. Typical examples thereof include polymethacrylic resin and polycarbonate resin.
In recent years, an attempt has been made to produce an optical fiber (waveguide) using a resin material.
Conventionally, inorganic optical waveguides in which a waveguide is produced using quartz or the like on a silicon or glass substrate are widely known. Inorganic waveguides have excellent properties such as low optical loss and high reliability, but they require high-temperature heating at the time of waveguide preparation, requiring special equipment for manufacturing and high manufacturing costs. In the case of mixed mounting with electronic parts, there is a problem that the degree of freedom of the manufacturing process is limited.

Many polymer-based optical waveguides using polymer materials have been recently proposed. Since it has properties such as transparency, heat resistance, and low hygroscopicity, many fluorine-containing polyimide resins have been proposed as polymer materials for optical waveguides (see Patent Documents 1 to 4).
As a polymer optical waveguide using a polymer material other than fluorinated polyimide, an optical waveguide using polymethyl methacrylate, polycarbonate, or the like has been proposed. The polymer material of polymethyl methacrylate is inexpensive and easy to process, but polymethyl methacrylate has a glass transition temperature (Tg) as low as about 100 ° C., so it is softened by heat during processing. There is also a problem that the refractive index cannot be controlled.
Although fluorinated polyimide has excellent transparency in the communication wavelength band (1.3 μm, 1.55 μm), its linear expansion coefficient is high, so if a waveguiding layer is formed on a silicon wafer or a synthetic quartz substrate, The substrate is often distorted or peeled off from the substrate.
Further, in order to provide a polymer optical waveguide having a core layer and a clad layer made of polyimide which does not cause curl (curvature) in the substrate and does not cause solvent cracks in the polyimide layer when multilayered, the polyimide is formed on the substrate. A core layer comprising a first polyimide obtained by polycondensation of 2,2′-dichloro-4,4 ′, 5,5′-biphenyltetracarboxylic dianhydride and an aromatic diamine and a cladding layer of 2, A second polyimide obtained by polycondensation of an aromatic tetracarboxylic dianhydride containing 2'-dichloro-4,4 ', 5,5'-biphenyltetracarboxylic dianhydride and an aromatic diamine; A provided polymer optical waveguide has been proposed (see Patent Document 5), but in a composite wiring board in which a fine conductor circuit and an optical waveguide are mixed, chlorine is dissociated and decomposed to form a poly Generated from De, often insulative poor great influence of the conductor circuit.
In addition, polybenzoazoles such as polybenzoxazole and polybenzothiazole have high heat resistance and have been studied for a long time as materials having high strength, high elastic modulus, and low thermal expansion. Due to these characteristics, development of a resin containing a benzoazole skeleton as a material for an optical waveguide has been advanced. Polybenzoxazole is obtained by polymerizing a bis (aminophenol) derivative and a dicarboxylic acid derivative to obtain a precursor polyhydroxyamide, and further dehydrating and ring-closing. By this method, a waveguide resin excellent in heat resistance and transparency was developed. However, since the precursor polyhydroxyamide has poor solubility and does not dissolve in a general-purpose organic solvent unless a flexible structure is introduced during polymerization, a resin having a low thermal expansion coefficient cannot be synthesized, warped, and peeled off. Could not solve the problem.

JP 09-021920 A Japanese Patent Laid-Open No. 11-147955 Japanese Patent Laid-Open No. 06-208033 Japanese Patent Laid-Open No. 04-009807 JP-A-2005-350562 Republished WO2003-010223

  The present invention has been made against the background of such prior art problems. That is, an object of the present invention is to provide a heat-resistant optical polyimide resin having low thermal expansion and excellent dimensional stability by having a benzoazole skeleton in the polyimide skeleton.

６．芳香族ジアミン類が下記構造式［化４］又は［化５］のいずれか一種以上である前記１〜５いずれかに記載の光学用ポリイミド。
（式中のＸはＮ、ＹはＯ、Ｓ又はＮＨのいずれかを示す）

That is, this invention consists of the following structures.
1. An optical polyimide obtained by reacting an aromatic diamine and an aromatic tetracarboxylic acid, wherein the polyimide structure includes a benzoazole skeleton.
2. 2. The optical polyimide as described in 1 above, wherein the aromatic diamine is an aromatic diamine having a benzoazole skeleton.
3. The optical polyimide according to either 1 or 2 above, wherein the polyimide has a coefficient of thermal expansion of 35 ppm / ° C. or less.
4). The polyimide for optical use according to any one of 1 to 3, wherein the aromatic diamine having a benzoazole skeleton is 50 mol% or more of the total diamine.
5. The optical polyimide according to any one of 1 to 4, wherein the benzoazole skeleton is at least one of the following structural formulas (Chemical Formula 1), (Chemical Formula 2), and (Chemical Formula 3).
(Wherein X represents N, Y represents O, S or NH)

6). The optical polyimide according to any one of 1 to 5, wherein the aromatic diamine is at least one of the following structural formulas [Chemical Formula 4] and [Chemical Formula 5].
(Wherein X represents N, Y represents O, S or NH)

  The optical polyimide according to the present invention is a polyimide obtained by reacting an aromatic diamine and an aromatic tetracarboxylic acid, and has a benzoazole skeleton in the polyimide chain and has a thermal expansion coefficient of 35 ppm / ° C. or less. When the crack layer and core layer made of such polyimide are formed on these substrates because the thermal expansion coefficient is small and the difference between the linear expansion coefficients of the glass substrate and silicon substrate is small. However, the substrate is not curled and the substrate and the optical waveguide are not easily separated, and the conductor circuit and the optical waveguide are mixedly mounted. Dimensional stability and low thermal expansion with characteristics that do not cause malfunction due to softening of polyimide at 320 ° C or higher A polyimide which has both numbers, it is useful as an optical material, especially an optical waveguide.

  A polyimide obtained by reacting the aromatic diamine of the present invention with an aromatic tetracarboxylic acid, the aromatic diamine in a polyimide containing a benzoazole skeleton in the polyimide structure (diamine or amide-forming derivative, etc. Preferred examples of the aromatic diamine include the following compounds represented by chemical formulas 6 to 20, but are not limited thereto.

In the present invention, one or more diamines exemplified below may be used in combination. Preferably, it is less than 50 mol% of all diamines (including diamine and amide bond derivatives), or less than 30 mol%, and more preferably less than 20 mol%.
Examples of such diamines include 5-amino-2- (p-aminophenyl) benzoxazole, 6-amino-2- (p-aminophenyl) benzoxazole, and 5-amino-2- (m-aminophenyl) benzo Oxazole, 6-amino-2- (m-aminophenyl) benzoxazole, 4,4′-bis (3-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (3 -Aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (3 -Aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, m-phenylenediamine , O-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 2,6-diaminonaphthalene, 1,4-diaminonaphthalene, 1,8-diaminonaphthalene, 2,7-diaminonaphthalene ,

  3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfoxide, 3,4′-diaminodiphenyl sulfoxide 4,4′-diaminodiphenyl sulfoxide, 3,3′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminobenzophenone, 3,4′- Diaminobenzophenone, 4,4′-diaminobenzophenone, 3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, bis [4- (4-aminophenoxy) phenyl] methane, 1 , 1-Bi [4- (4-aminophenoxy) phenyl] ethane, 1,2-bis [4- (4-aminophenoxy) phenyl] ethane, 1,1-bis [4- (4-aminophenoxy) phenyl] propane, 1 , 2-bis [4- (4-aminophenoxy) phenyl] propane, 1,3-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl ]propane,

  1,1-bis [4- (4-aminophenoxy) phenyl] butane, 1,3-bis [4- (4-aminophenoxy) phenyl] butane, 1,4-bis [4- (4-aminophenoxy) Phenyl] butane, 2,2-bis [4- (4-aminophenoxy) phenyl] butane, 2,3-bis [4- (4-aminophenoxy) phenyl] butane, 2- [4- (4-aminophenoxy) Phenyl] -2- [4- (4-aminophenoxy) -3-methylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) -3-methylphenyl] propane, 2- [4- ( 4-aminophenoxy) phenyl] -2- [4- (4-aminophenoxy) -3,5-dimethylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) -3,5-dimethylphen Le] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane,

  1,4-bis (3-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) ) Biphenyl, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfoxide, bis [4- ( 4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 1,3-bis [4- (4-aminophenoxy) ) Benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (3 Aminophenoxy) benzoyl] benzene, 4,4′-bis [(3-aminophenoxy) benzoyl] benzene, 1,1-bis [4- (3-aminophenoxy) phenyl] propane, 1,3-bis [4- (3-aminophenoxy) phenyl] propane, 3,4'-diaminodiphenyl sulfide,

  2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, bis [4- (3-aminophenoxy) phenyl] methane, 1,1 -Bis [4- (3-aminophenoxy) phenyl] ethane, 1,2-bis [4- (3-aminophenoxy) phenyl] ethane, bis [4- (3-aminophenoxy) phenyl] sulfoxide, 4,4 '-Bis [3- (4-aminophenoxy) benzoyl] diphenyl ether, 4,4'-bis [3- (3-aminophenoxy) benzoyl] diphenyl ether, 4,4'-bis [4- (4-amino-α) , Α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] diphenylsulfone, bis 4- {4- (4-aminophenoxy) phenoxy} phenyl] sulfone, 1,4-bis [4- (4-aminophenoxy) phenoxy-α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) phenoxy-α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-trifluoromethylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3 -Bis [4- (4-amino-6-fluorophenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-methylphenoxy) -α, α-dimethylbenzyl Benzene, 1,3-bis [4- (4-amino-6-cyanophenoxy) -α, α-dimethylbenzyl] benzene,

3,3′-diamino-4,4′-diphenoxybenzophenone, 4,4′-diamino-5,5′-diphenoxybenzophenone, 3,4′-diamino-4,5′-diphenoxybenzophenone, 3, 3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4'-diamino-5'-phenoxybenzophenone, 3,3 '-Diamino-4,4'-dibiphenoxybenzophenone, 4,4'-diamino-5,5'-dibiphenoxybenzophenone, 3,4'-diamino-4,5'-dibiphenoxybenzophenone, 3,3'- Diamino-4-biphenoxybenzophenone, 4,4′-diamino-5-biphenoxybenzophenone, 3,4′-diamino-4-bipheno Cibenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone, 1,3-bis (3-amino-4-phenoxybenzoyl) benzene, 1,4-bis (3-amino-4-phenoxybenzoyl) benzene 1,3-bis (4-amino-5-phenoxybenzoyl) benzene, 1,4-bis (4-amino-5-phenoxybenzoyl) benzene, 1,3-bis (3-amino-4-biphenoxybenzoyl) ) Benzene, 1,4-bis (3-amino-4-biphenoxybenzoyl) benzene, 1,3-bis (4-amino-5-biphenoxybenzoyl) benzene, 1,4-bis (4-amino-5) -Biphenoxybenzoyl) benzene, 2,6-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzonitrile and Some or all of the hydrogen atoms on the aromatic ring in the aromatic diamine are fluorine atoms, some or all of the hydrogen atoms of the alkyl group or alkoxyl group having 1 to 3 carbon atoms, cyano group, or alkyl group or alkoxyl group are fluorine. An aromatic diamine substituted with a fluorinated alkyl group having 1 to 3 carbon atoms substituted with an atom or an alkoxyl group is exemplified.
The aromatic tetracarboxylic acids that can be preferably used as the aromatic tetracarboxylic acids (including tetracarboxylic acids, dianhydrides, amide-bonded derivatives, etc.) used in the present invention are specifically shown in Chemical formulas 21 to 25 below. Examples include, but are not limited to, compounds.

これらの芳香族テトラカルボン酸二無水物は単独で用いてもよいし、二種以上を併用してもよい。
本発明においては、全テトラカルボン酸類の３０モル％未満であれば下記に例示される非芳香族のテトラカルボン酸二無水物類を一種又は二種以上、併用しても構わない。

These aromatic tetracarboxylic dianhydrides may be used alone or in combination of two or more.
In the present invention, one or two or more non-aromatic tetracarboxylic dianhydrides exemplified below may be used in combination as long as they are less than 30 mol% of the total tetracarboxylic acids.

  Examples of such tetracarboxylic acid anhydrides include butane-1,2,3,4-tetracarboxylic dianhydride, pentane-1,2,4,5-tetracarboxylic dianhydride, and cyclobutanetetracarboxylic acid. Acid dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride, cyclohex-1-ene-2,3 5,6-tetracarboxylic dianhydride, 3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohexane-3 -(1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride 1-ethylcyclohexane -(1,2), 3,4-tetracarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1,3-dipropylcyclohexane- 1- (2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ′, 4′-tetracarboxylic dianhydride,

Bicyclo [2.2.1] heptane-2,3,5,6-tetracarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1 , 3-Dipropylcyclohexane-1- (2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ′, 4′-tetracarboxylic dianhydride, bicyclo [2.2.1] Heptane-2,3,5,6-tetracarboxylic dianhydride, bicyclo [2.2.2] octane-2,3,5,6-tetracarboxylic dianhydride, bicyclo [2.2.2] Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride and the like. These tetracarboxylic dianhydrides may be used alone or in combination of two or more.

For example, the solvent used when polymerizing an aromatic diamine and an aromatic tetracarboxylic dianhydride to obtain a polyamic acid is particularly suitable if it can dissolve both the raw material monomer and the polyamic acid to be produced. Although not limited, polar organic solvents are preferred, such as N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, dimethyl Examples thereof include sulfoxide, hexamethylphosphoric amide, ethyl cellosolve acetate, diethylene glycol dimethyl ether, sulfolane, and halogenated phenols. These solvents can be used alone or in combination. The amount of the solvent used may be an amount sufficient to dissolve the monomer as a raw material. As a specific amount used, the mass of the monomer in the solution in which the monomer is dissolved is usually 5 to 40% by mass, The amount is preferably 10 to 30% by mass.
The polyimide in the present invention comprises an aromatic tetracarboxylic dianhydride having a benzoazole skeleton and / or an aromatic diamine having a benzoazole skeleton and an aromatic tetracarboxylic dianhydride or aromatic diamine having no benzoazole skeleton. It is not particularly limited as long as it is a polyimide obtained by reacting, but preferably, an aromatic diamine having a benzoazole skeleton and an aromatic tetracarboxylic dianhydride having no benzoazole skeleton are reacted. It is a polyimide obtained, more preferably a polyimide obtained by reacting an aromatic diamine having a skeleton of [Chemical Formula 3] and an aromatic tetracarboxylic dianhydride having no benzoazole skeleton, and in particular, 5-amino 2- (4-Aminophenyl) benzoxazole [Chem. 6] It is desirable to use a Min. In the present invention, mixing other resin with the polyimide does not exclude this unless the dimensional stability and low thermal expansion coefficient of the present invention are impaired, but 50 mass in the resin mixed with the polyimide of the present invention. % Or more is preferable.

Although it will not specifically limit if it is 35 ppm / degrees C or less as a coefficient of thermal expansion of the polyimide in this invention, Preferably it is 30 ppm / degrees C or less, More preferably, it is 20 ppm / degrees C or less, More preferably, 15 ppm / degrees C or less is desirable. . When the coefficient of thermal expansion exceeds 35 ppm / ° C., distortion occurs between the polyimide and the substrate, and there is a high possibility that warping and peeling occur due to this distortion.
The measurement of the thermal expansion coefficient in the present invention is performed as follows.
About the polyimide resin (film) to be measured, the stretch rate / temperature at intervals of 30 ° C. to 40 ° C., 40 ° C. to 50 ° C.,. The average value of all measured values from 50 ° C. to 200 ° C. was calculated as the coefficient of thermal expansion (CTE).
Device name: TMA4000S manufactured by MAC Science
Sample length; 10mm
Sample width: 2 mm
Temperature rise start temperature: 25 ° C
Temperature rising end temperature: 400 ° C
Temperature increase rate: 5 ° C / min
Atmosphere: Argon

The polyimide resin in the present invention is not particularly limited as long as it is used for optical purposes, but is particularly preferably used as a resin for optical waveguides.
By using the polyimide of the present invention, it can withstand a high temperature of 300 ° C. in an IC manufacturing process, has a low thermal expansion coefficient, excellent dimensional stability, low stress, excellent durability, and is physically stable. It is possible to obtain a polymer-based optical waveguide that can be packed with a density and is inexpensive to manufacture.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples. In addition, the evaluation method of the physical property in the following examples is as follows.

1. Reduced viscosity of polyamic acid and polyimide (ηsp / C)
A solution dissolved in N-methyl-2-pyrrolidone so that the polymer concentration was 0.2 g / dl was measured at 25 ° C. with an Ubbelohde type viscosity tube.
(When the solvent used for preparing the polyamic acid solution was N, N-dimethylacetamide, the polymer was dissolved and measured using N, N-dimethylacetamide.)
2. The thickness of the polyimide film The thickness was measured using a micrometer (Millitron 1254D manufactured by Fine Reef).

3. Birefringence measurement The polyimide resin layer (film) to be measured was placed on a glass substrate, the refractive indexes nTE and nTM in the TE and TM directions were measured under the following conditions, and the birefringence Δn = nTE−nTM was calculated.
Device name; Metriccon prism coupler model 2010
Measurement wavelength: 633 nm
Mode; Dual Film

4). Propagation loss measurement Using an optional function of a prism coupler model 2010 manufactured by Metricon, measurement was performed by a scattering detection method. The scattering detection method uses an optical fiber as a probe, moves the tip approaching the waveguide while keeping the angle and the distance from the waveguide constant, and plots logP against L to calculate the propagation loss. It is a measuring method.
Device name; Metriccon prism coupler model 2010
Measurement wavelength: 633 nm
Measuring distance: 5cm

5. Glass transition point measurement About the polyimide resin layer (film) of a measuring object, the glass transition point (Tg) was measured on condition of the following. For the glass transition point referred to here, the Inflection temperature in the analysis of the step-like curve was calculated.
Device name: DSC2920 manufactured by TA Instruments
Sample amount: 10 ± 0.5mg
Temperature rise start temperature; Room temperature Temperature rise end temperature; 450 ° C
Temperature rising rate: 10 ° C / min
Atmosphere: Argon In addition, the polyimide having a rigid primary structure sometimes had no glass transition point detected by the DSC measurement. In that case, the inflection point in the above average thermal expansion coefficient measurement was taken as the glass transition point. If there was no inflection point up to 400 ° C, the glass transition point was determined to be 400 ° C or higher.

(Example 1)
In a dry nitrogen atmosphere, 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride (10 mmol, 4.442 g) and 5-amino-2- (4-aminophenyl) benzoxazole [Chem. 6] (10 mmol, 2.253 g) was dissolved in m-cresol to give a 10% by weight solution. After stirring this at room temperature for 3 hours, isoquinoline is added as a catalyst, stirred at 200 ° C. for 3 hours under a nitrogen stream, and cooled to room temperature to obtain a highly viscous solution. When this polyimide solution was reprecipitated in methanol, a light yellow fibrous polymer was obtained. The obtained polymer was washed with methanol and dried. The polymer obtained had a reduced viscosity of 1.2. The polymer is dissolved in N-methyl-2-pyrrolidone to form a 10% by mass solution, coated on a clean silicon substrate, and heated in a dry nitrogen atmosphere at 120 ° C. for 15 minutes and at 250 ° C. for 1 hour. A 14.3 μm polyimide film was obtained. The film was peeled off from the silicon substrate, and the coefficient of thermal expansion was measured to find 31.7 ppm / ° C. Further, this film had a birefringence of Δn = 0.0823 (nTE = 1.6544, nTM = 1.5631) and a propagation loss of 1.7 dB / cm. The glass transition point could not be detected by DSC, and no inflection point was found in the TMA measurement, so the glass transition point was determined to be 400 ° C. or higher.

(Example 2)
2,2′-diphenyl-3,4,3 ′, 4′-tetracarboxylic anhydride (10 mmol, 2.942 g) and 5-amino-2- (4-aminophenyl) benzoxazole in a dry nitrogen atmosphere (10 mmol, 2.253 g) was dissolved in dimethylacetamide to give a 10% by mass solution. When this is stirred at room temperature for 96 hours in a nitrogen atmosphere, a highly viscous solution is obtained. The reduced viscosity of the obtained solution was 0.44. The polymer solution was applied on a clean silicon substrate and heated in a dry nitrogen atmosphere at 120 ° C. for 15 minutes and at 350 ° C. for 1 hour to obtain a polyimide film having a thickness of 13.0 μm. The film was peeled from the silicon substrate, and the coefficient of thermal expansion was measured to find 8.1 ppm / ° C. Further, this film had a birefringence of Δn = 0.602 (nTE = 1.8765, nTM = 1.6163) and a propagation loss of 4.9 dB / cm. The glass transition point could not be detected by DSC, and no inflection point was found in the TMA measurement, so the glass transition point was determined to be 400 ° C. or higher.

(Example 3)
In a dry nitrogen atmosphere, pyromellitic anhydride (10 mmol, 2.181 g) and 5-amino-2- (4-aminophenyl) benzoxazole (10 mmol, 2.253 g) were dissolved in dimethylacetamide, and 10% by mass. Solution. When this is stirred at room temperature for 24 hours in a nitrogen atmosphere, a highly viscous solution is obtained. The resulting solution had a reduced viscosity of 3.1. The polymer solution was applied onto a clean silicon substrate and heated in a dry nitrogen atmosphere at 120 ° C. for 15 minutes and 350 ° C. for 1 hour to obtain a 9.4 μm thick polyimide film. The film was peeled from the silicon substrate, and the coefficient of thermal expansion was measured to find 0.8 ppm / ° C. Further, this film had a birefringence of Δn = 0.2524 (nTE = 1.8471, nTM = 1.5947) and a propagation loss of 5.2 dB / cm. The glass transition point could not be detected by DSC, and no inflection point was found in the TMA measurement, so the glass transition point was determined to be 400 ° C. or higher.

Example 4
In a dry nitrogen atmosphere, 3,4,3 ′, 4′-benzophenonetetracarboxylic anhydride (10 mmol, 3.222 g) and 5-amino-2- (4-aminophenyl) benzoxazole (10 mmol, 2.253 g) ) Was dissolved in dimethylacetamide to give a 10% by mass solution. When this is stirred at room temperature for 24 hours in a nitrogen atmosphere, a highly viscous solution is obtained. The resulting solution had a reduced viscosity of 2.5. The polymer solution was applied on a clean silicon substrate and heated in a dry nitrogen atmosphere at 120 ° C. for 15 minutes and at 350 ° C. for 1 hour to obtain a polyimide film having a thickness of 20.6 μm. The film was peeled from the silicon substrate, and the coefficient of thermal expansion was measured to find 23.7 ppm / ° C. Further, this film had a birefringence of Δn = 0.320 (nTE = 1.8417, nTM = 1.6097) and a propagation loss of 3.0 dB / cm. The glass transition point could not be detected by DSC, and no inflection point was found in the TMA measurement, so the glass transition point was determined to be 400 ° C. or higher.

(Example 5)
In a dry nitrogen atmosphere, 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride (10 mmol, 4.442 g) and 5-amino-2- (4-aminophenyl) benzoxazole [Chem. 6] (5 mmol, 1.127 g) and 2,2′-bis (trifluoromethyl) benzidine (5 mmol, 1.601 g) were dissolved in m-cresol to obtain a 10 mass% solution. After stirring this at room temperature for 3 hours, isoquinoline is added as a catalyst, stirred at 200 ° C. for 3 hours under a nitrogen stream, and cooled to room temperature to obtain a highly viscous solution. When this polyimide solution was reprecipitated in methanol, a light yellow fibrous polymer was obtained. The obtained polymer was washed with methanol and dried. The polymer obtained had a reduced viscosity of 1.4. The polymer is dissolved in N-methyl-2-pyrrolidone to form a 10% by mass solution, coated on a clean silicon substrate, and heated in a dry nitrogen atmosphere at 120 ° C. for 15 minutes and at 250 ° C. for 1 hour. A 17.6 μm polyimide film was obtained. This film was peeled off from the silicon substrate, and the coefficient of thermal expansion was measured. As a result, it was 34.1 ppm / ° C. Further, this film had a birefringence of Δn = 0.0639 (nTE = 1.994, nTM = 1.5355) and a propagation loss of 0.8 dB / cm. The glass transition point could not be detected by DSC, and no inflection point was found in the TMA measurement, so the glass transition point was determined to be 400 ° C. or higher.

(Comparative Example 1)
In a dry nitrogen atmosphere, diphenylsulfone-3,4,3 ′, 4′-tetracarboxylic dianhydride (3.58 g) and 4,4′-diaminodiphenyl ether (2.00 g) were dissolved in m-cresol. A 10% by mass solution was obtained. After stirring this at room temperature for 3 hours, isoquinoline is added as a catalyst, stirred at 200 ° C. for 3 hours under a nitrogen stream, and cooled to room temperature to obtain a highly viscous solution. When this polyimide solution was reprecipitated in methanol, a yellow fibrous polymer was obtained. After drying the polymer, a polyimide film having a film thickness of 20.8 μm was obtained in the same manner as in Example 1. The coefficient of thermal expansion was measured and found to be 64.5 ppm / ° C. and the glass transition point was 280 ° C. On the other hand, the birefringence was Δn = 0.0072 (nTE = 1.6692, nTM = 1.620), and the propagation loss was 2.0 dB / cm.

(Comparative Example 2)
In a dry nitrogen atmosphere, 4,4 ′-(2,2′-hexafluoroisopropylidene) diphthalic acid dianhydride (4.442 g) and p-phenylenediamine (1.081 g) were dissolved in m-cresol. A 10% by mass solution was obtained. After stirring this at room temperature for 3 hours, isoquinoline is added as a catalyst, stirred at 200 ° C. for 3 hours under a nitrogen stream, and cooled to room temperature to obtain a highly viscous solution. When this polyimide solution was reprecipitated in methanol, a yellow fibrous polymer was obtained. After drying the polymer, a polyimide film having a film thickness of 14.2 μm was obtained in the same manner as in Example 1. The coefficient of thermal expansion was measured to find that it was 41.3 ppm / ° C., the glass transition point could not be detected by DSC, and the TMA measurement also changed. Since no inflection point was seen, the glass transition point was determined to be 400 ° C. or higher. On the other hand, the birefringence was Δn = 0.0481 (nTE = 1.5935, nTM = 1.5454), and the propagation loss was 1.2 dB / cm.

(Comparative Example 3)
In a dry nitrogen atmosphere, pyromellitic anhydride (2.181 g) and 1,3-bis (4-aminophenoxy) benzene (2.923 g) were dissolved in dimethylacetamide to give a 12% by mass solution. When this is stirred at room temperature for 24 hours in a nitrogen atmosphere, a highly viscous solution is obtained. Using this polyamic acid solution, a polyimide film having a film thickness of 15.2 μm was obtained in the same manner as in Example 2, and the thermal expansion coefficient was measured. As a result, it was 51.4 ppm / ° C. and the glass transition point was 330 ° C. On the other hand, the birefringence was Δn = 0.1307 (nTE = 1.7380, nTM = 1.6073), and the propagation loss was 2.8 dB / cm.

(Comparative Example 4)
In a dry nitrogen atmosphere, 3,4,3 ′, 4′-benzophenonetetracarboxylic anhydride (10 mmol, 3.222 g) and 4,4′-diaminodiphenyl ether (2.00 g) were dissolved in dimethylacetamide, 12 A mass% solution was obtained. When this is stirred at room temperature for 24 hours in a nitrogen atmosphere, a highly viscous solution is obtained. Using this polyamic acid solution, a polyimide film having a film thickness of 23.0 μm was obtained in the same manner as in Example 2, and the thermal expansion coefficient was measured. As a result, it was 47.8 ppm / ° C. and the glass transition point was 305 ° C. On the other hand, the birefringence was Δn = 0.124 (nTE = 1.6876, nTM = 1.6752), and the propagation loss was 2.4 dB / cm.

(Comparative Example 5)
In a dry nitrogen atmosphere, 4,4 ′-(2,2′-hexafluoroisopropylidene) diphthalic dianhydride (4.442 g) and 2,2′-bis (trifluoromethyl) benzidine (1.281 g) ) Was dissolved in m-cresol to give a 10% by mass solution. After stirring this at room temperature for 3 hours, isoquinoline is added as a catalyst, stirred at 200 ° C. for 3 hours under a nitrogen stream, and cooled to room temperature to obtain a highly viscous solution. When this polyimide solution was reprecipitated in methanol, a yellow fibrous polymer was obtained. After drying the polymer, a polyimide film having a film thickness of 5.0 μm was obtained in the same manner as in Example 1. The coefficient of thermal expansion was measured and found to be 48.0 ppm / ° C. and the glass transition point was 380 ° C. On the other hand, the birefringence was Δn = 0.0455 (nTE = 1.5534, nTM = 1.580), and the propagation loss was 0.3 dB / cm.

Since the optical polyimide of the present invention has a small coefficient of thermal expansion and a small difference from the coefficient of thermal expansion of a glass substrate or silicon substrate, a clad layer or a core layer made of such polyimide is formed on these substrates. However, the substrate does not curl and the substrate and the optical waveguide are not easily separated, and the conductor circuit and the optical waveguide are mixedly mounted. It is a polyimide that combines dimensional stability, low thermal expansion coefficient, heat resistance, light transmission characteristics, and insulation sustainability, with characteristics that do not cause deformation and malfunction due to softening of the polyimide at 320 ° C. or higher. It is useful for optical materials, particularly optical waveguides.
Semiconductor mounting technology can be used as it is for optical waveguide fabrication, and it is possible to produce highly reliable optical waveguides with little misalignment and warpage at low cost, and is expected to make a significant contribution to the industry. .

Claims (6)

An optical polyimide obtained by reacting an aromatic diamine and an aromatic tetracarboxylic acid, wherein the polyimide structure includes a benzoazole skeleton. The optical polyimide according to claim 1, wherein the aromatic diamine is an aromatic diamine having a benzoazole skeleton.   The optical polyimide according to claim 1, wherein the polyimide has a coefficient of thermal expansion of 35 ppm / ° C. or less. 4. The optical polyimide according to claim 1, wherein the aromatic diamine having a benzoazole skeleton is 50 mol% or more of the total diamine. 5. The optical polyimide according to claim 1, wherein the benzoazole skeleton is at least one of the following structural formulas [Chemical Formula 1], [Chemical Formula 2], and [Chemical Formula 3].
(Wherein X represents N, Y represents O, S or NH)

The optical polyimide according to any one of claims 1 to 5, wherein the aromatic diamine is at least one of the following structural formulas [Chemical Formula 4] and [Chemical Formula 5].
(Wherein X represents N, Y represents O, S or NH)