JP2000198844A - Polyimide for optical substrate and polyimide substrate for optical - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide optimized for performance required for an optical substrate, an inexpensive polyimide, and an inexpensive and high-performance optical polyimide substrate using those polyimides. SOLUTION: A polyimide for an optical substrate having a glass transition temperature of 300 ° C. or more and a thermal expansion coefficient of 60 ppm or more, and an optical polyimide substrate manufactured using the polyimide for an optical substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyimide for an optical substrate and a polyimide substrate for an optical substrate.

[0002]

2. Description of the Related Art With the practical use of optical communication systems by the development of low-loss optical fibers, development of various optical communication components has been desired. It is also desired to establish an optical wiring technology for mounting these optical components at a high density, particularly an optical waveguide technology.

Generally, optical waveguide materials are required to have conditions such as low optical loss, easy production of the optical waveguide, control of the refractive index difference between the core and the clad, and excellent heat resistance. Quartz-based materials have been most studied so far as optical waveguide materials. Quartz has a very good light transmittance as demonstrated in an optical fiber. Therefore, even when used as an optical waveguide, a low optical loss of 0.1 dB / cm or less is achieved at a wavelength of 1.3 μm. However, there are manufacturing problems such as a long time required for the production of the optical waveguide, a high temperature during the production, and difficulty in increasing the area.

On the other hand, a plastic optical material such as polymethyl methacrylate has the advantages that an optical waveguide can be formed at a low temperature and can be expected to be inexpensive, but has the disadvantage that it is inferior in heat resistance and moisture resistance. . Polyimide has the highest heat resistance among plastics, but the conventional polyimide has a problem in that it has poor light transmittance.

Accordingly, the present inventors have studied polyimide optical materials having excellent light transmittance. The present inventors have disclosed a fluorinated polyimide excellent in light transmittance in JP-A-3-72528. Further, Japanese Patent Application Laid-Open No. 4-8734 discloses that copolymerization of this fluorinated polyimide makes it possible to control the refractive index necessary for forming an optical waveguide, for example. Optical waveguides using this fluorinated polyimide are disclosed in JP-A-4-9807 and JP-A-4-23.
5505 and 4-235506. As described above, a plastic optical waveguide excellent in heat resistance is realized by using polyimide excellent in light transmittance.

However, polyimide optical waveguides have some problems. For example, polyimide has excellent heat resistance, but has a surface on which aromatic rings in the chemical structure are easily oriented. This means that birefringence easily occurs when viewed as an optical material. The birefringence itself is a desirable characteristic as an optical material in some cases, and an undesirable characteristic in some cases. The same can be said when viewed as a material for an optical waveguide. For example, if it is desired to guide the light while preserving the plane of polarization of linearly polarized light, it is better to have birefringence, but if it is desired to guide non-polarized light, it is better not to have birefringence. It is expected that the birefringence can be controlled in any way.

The inventors of the present invention have studied so far that the low birefringence polyimide film has a low birefringence by matching the coefficient of thermal expansion of the substrate with the coefficient of thermal expansion of the polyimide, that is, by using a polyimide substrate as the substrate. It has been found that a polyimide film can be realized.
608. However, at present, there is no optical polyimide substrate or any polyimide manufactured or sold as an optical polyimide substrate. The reason is that it is not clear what kind of polyimide is best for the optical substrate, and it is expensive to manufacture an optical polyimide substrate using fluorinated polyimide, which is an optical waveguide material. This is probably because there is a problem.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polyimide having an optimized performance required for an optical substrate, an inexpensive polyimide, and an inexpensive and high-performance optical polyimide substrate using these polyimides. With the goal.

[0009]

Means for Solving the Problems In order to achieve the above object, the present inventors examined the relationship between the chemical structure and properties of polyimide for an optical substrate, and the relationship between the polyimide production raw material and the properties and cost of polyimide. Thus, the present invention has been achieved.

In summary, the polyimide for an optical substrate according to the first invention of the present invention has a glass transition temperature of 300 ° C.
And the thermal expansion coefficient is 60 ppm or more. The polyimide for an optical substrate of the second invention of the present invention is that at least one of the polyimide produced from diamine and acid dianhydride is a polyimide produced from diamine and acid dianhydride containing no fluorine. Features. An optical polyimide substrate according to a third aspect of the present invention is manufactured using the polyimide for an optical substrate according to the first or second aspect.

Hereinafter, the present invention will be described in more detail.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One of the limitations of the polyimide for an optical substrate of the present invention is that the glass transition temperature is 300 ° C. or higher. The polyimide for an optical substrate is used to produce a polyimide substrate for an optical element, and it is assumed that a polyimide film is usually formed on the polyimide substrate for an optical element. Therefore, for that purpose, it is necessary to withstand the temperature of the thermal imidization of the polyamic acid to the polyimide.

The imidization is said to occur between 120 ° C. and 200 ° C., although it varies depending on the type of polyamic acid, and curing is usually performed at a temperature of 300 ° C. or more in view of the stability of the polyimide film. Therefore, the polyimide substrate for optical needs to withstand curing at 300 ° C. Withstanding the curing at 300 ° C. means that the polyimide does not thermally decompose at 300 ° C., and has a glass transition temperature of 30 ° C.
That is, 0 ° C. or more is required. On the other hand, the reason why the lower limit is limited and the upper limit is not limited is that no matter how high the glass transition temperature is, it is not directly related to the present invention.

The glass transition temperature described in the present invention refers to physical properties measured by thermomechanical analysis.
For reference, the equipment used and the measurement conditions in the present invention are as follows.

Apparatus used: TM-70 manufactured by Vacuum Riko Co., Ltd.
00.

Measurement conditions: Measurement sample: width 5 mm × length 15 mm × thickness 15 to 20 μm Tensile load: 3 g Atmosphere: Nitrogen atmosphere Heating rate 5 ° C./min.

As another limitation, the coefficient of thermal expansion is 6
Although the content is set to 0 ppm or more, the reason will be described.
A polyimide optical waveguide is assumed as a main optical component manufactured on the optical polyimide substrate of the present invention. For polyimide optical waveguides, fluorinated polyimides have low birefringence among fluorinated polyimides in order to avoid polarization dependence of the waveguides from the viewpoint of light transmission. Is also considered to be used. The fluorinated polyimide for an optical waveguide currently used is 2,2-bis (3,4-dicarboxyphenyl).
Hexafluoropropane dianhydride (hereinafter abbreviated as 6FDA) and 2,2'-bis (trifluoromethyl) -4,
4'-diaminobiphenyl (hereinafter abbreviated as TFDB)
Fluorinated polyimide (hereinafter 6FDA / T)
FDB), fluorinated polyimide (hereinafter abbreviated as 6FDA / ODA) produced from 6FDA and 4,4'-diaminodiphenyl ether (hereinafter abbreviated as ODA), and a copolymer of 6FDA with TFDB and ODA. is there.

The thermal expansion coefficient of 6FDA / TFDB is 82 ppm, and that of 6FDA / ODA is 61 ppm.
Therefore, if an optical polyimide substrate is prepared using an optical substrate polyimide having a similar coefficient of thermal expansion as these,
It can be expected that the polarization dependence of a polyimide optical waveguide fabricated on an optical polyimide substrate is very small. For this reason, the thermal expansion coefficient of the polyimide for optical substrates is 60
It was limited to ppm or more. On the other hand, the reason for limiting the lower limit and not limiting the upper limit is that if 100 ppm of a polyimide for an optical substrate is realized, copolymerization, 60 ppm to 100 ppm of a polyimide up to 100 ppm can be sufficiently realized by existing techniques by a method such as blending. is there.

The coefficient of thermal expansion described in the present invention is a physical property measured by thermomechanical analysis and has a temperature range of 5
Average coefficient of thermal expansion from 0 to 300 ° C., measured for the second time (usually called second run). For reference, the equipment used and the measurement conditions in the present invention are as follows.

Apparatus used: TM-70 manufactured by Vacuum Riko Co., Ltd.
00.

Measurement conditions: Measurement sample: width 5 mm × length 15 mm × thickness 15 to 20 μm Tensile load: 3 g Atmosphere: Nitrogen atmosphere Heating rate 5 ° C./min.

The polyimide for an optical substrate of the present invention has a glass transition temperature of 300 ° C. or higher and a thermal expansion coefficient of 60 p.
All polyimides above pm can be used. For example, there are polyimides, polyimide copolymers, and polyimide mixtures produced from the following tetracarboxylic acids or derivatives thereof and diamines, which have a glass transition temperature of 300 ° C. or more and a thermal expansion coefficient of 60 ppm or more.

Examples of the tetracarboxylic acid and its derivatives such as acid anhydrides, acid chlorides and esterified compounds are as follows. Here, an example of tetracarboxylic acid will be given.

(Trifluoromethyl) pyromellitic acid,
Di (trifluoromethyl) pyromellitic acid, di (heptafluoropropyl) pyromellitic acid, pentafluoroethylpyromellitic acid, bis {3,5-di (trifluoromethyl) phenoxy} pyromellitic acid, 3,4,3 ′,
4'-biphenyltetracarboxylic acid, 3,3 ', 4
4'-tetracarboxydiphenyl ether, 2,
3 ', 3,4'-tetracarboxydiphenyl ether, 3,3', 4,4'-benzophenonetetracarboxylic acid, 2,3,6,7-tetracarboxynaphthalene,
1,4,5,7-tetracarboxynaphthalene, 1,
4,5,6-tetracarboxynaphthalene, 3,3 ′,
4,4'-tetracarboxydiphenylmethane, 3,
3 ', 4,4'-tetracarboxydiphenylsulfone, 2,2-bis (3,4-dicarboxyphenyl) propane, 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane, 5,5 '-Bis (trifluoromethyl) -3,3', 4,4'-tetracarboxybiphenyl, 2,2 ', 5,5'-tetrakis (trifluoromethyl) -3,3', 4,4'- Tetracarboxybiphenyl, 5,5'-bis (trifluoromethyl) -3,3 ', 4,4'-tetracarboxydiphenyl ether, 5,5'-bis (trifluoromethyl)-
3,3 ', 4,4'-tetracarboxybenzophenone, bis {(trifluoromethyl) dicarboxyphenoxy} benzene, bis {(trifluoromethyl) dicarboxyphenoxy} (trifluoromethyl) benzene,
Bis (dicarboxyphenoxy) (trifluoromethyl) benzene, bis (dicarboxyphenoxy) bis (trifluoromethyl) benzene, bis (dicarboxyphenoxy) tetrakis (trifluoromethyl) benzene, 3,4,9,10-tetra Carboxyperylene,
2,2-bis {4- (3,4-dicarboxydiphenoxy) phenyl} propane, butanetetracarboxylic acid, cyclopentanetetracarboxylic acid, 2,2-bis {4-
(3,4-dicarboxyphenoxy) phenyl {hexafluoropropane, bis (trifluoromethyl) dicarboxyphenoxy} biphenyl, bis {(trifluoromethyl) dicarboxyphenoxy} bis (trifluoromethyl) biphenyl, bis} ( Trifluoromethyl)
Dicarboxyphenoxy diphenyl ether, bis (dicarboxyphenoxy) bis (trifluoromethyl) biphenyl, bis (3,4-dicarboxyphenyl) dimethylsilane, 1,3-bis (3,4-dicarboxyphenyl) tetramethyldi Siloxane, difluoropyromellitic acid, 1,4-bis (3,4-dicarboxytrifluorophenoxy) tetrafluorobenzene,
1,4-bis (3,4-dicarboxytrifluorophenoxy) octafluorobiphenyl and the like.

The following are examples of the diamine. m-phenylenediamine, 2,4-diaminotoluene, 2,4-diaminoxylene, 2,4-diaminodulene, 4- (1H, 1H, 11H-eicosafluoroundecanooxy) -1,3-diaminobenzene, 4-
(1H, 1H-perfluoro-1-butanoxy) -1,
3-diaminobenzene, 4- (1H, 1H-perfluoro-1-heptanoxy) -1,3-diaminobenzene,
4- (1H, 1H-perfluoro-1-octanoxy)
-1,3-diaminobenzene, 4-pentafluorophenoxy-1,3-diaminobenzene, 4- (2,3
5,6-tetrafluorophenoxy) -1,3-diaminobenzene, 4- (4-fluorophenoxy) -1,3
-Diaminobenzene, 4- (1H, 1H, 2H, 2H-
Perfluoro-1-hexanoxy) -1,3-diaminobenzene, 4- (1H, 1H, 2H, 2H-perfluoro-1-dodecanoxy) -1,3-diaminobenzene,
p-phenylenediamine, 2,5-diaminotoluene,
2,3,5,6-tetramethyl-p-phenylenediamine, 2,5-diaminobenzotrifluoride, bis (trifluoromethyl) phenylenediamine, diaminotetra (trifluoromethyl) benzene, diamino (pentafluoroethyl) benzene , 2,5-diamino (perfluorohexyl) benzene, 2,5-diamino (perfluorobutyl) benzene, benzidine, 2,2'-
Dimethylbenzidine, 3,3'-dimethylbenzidine,
3,3'-dimethoxybenzidine, 2,2'-dimethoxybenzidine, 3,3 ', 5,5'-tetramethylbenzidine, 3,3'-diacetylbenzidine, 2,2'-
Bis (trifluoromethyl) -4,4'-diaminobiphenyl, octafluorobenzidine, 3,3'-bis (trifluoromethyl) -4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl ether, 4,4 ′
-Diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 2,2-bis (p-aminophenyl)
Propane, 3,3'-dimethyl-4,4'-diaminodiphenyl ether, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 1,2-bis (anilino) ethane, 2,2-bis (p- Aminophenyl) hexafluoropropane, 1,3-bis (anilino) hexafluoropropane, 1,4-bis (anilino) octafluorobutane, 1,5-bis (anilino) decafluoropentane, 1,7-bis (anilino ) Tetradecafluoroheptane, 2,2'-bis (trifluoromethyl) -4,
4'-diaminodiphenyl ether, 3,3'-bis (trifluoromethyl) -4,4'-diaminodiphenyl ether, 3,3 ', 5,5'-tetrakis (trifluoromethyl) -4,4'-diaminophenyl Ether, 3,3'-bis (trifluoromethyl) -4,4 '
-Diaminobenzophenone, 4,4 "-diamino-p
-Terphenyl, 1,4-bis (p-aminophenyl)
Benzene, p-bis (4-amino-2-trifluoromethylphenoxy) benzene, bis (aminophenoxy)
Bis (trifluoromethyl) benzene, bis (aminophenoxy) tetrakis (trifluoromethyl) benzene, 4,4 ″ ″-diamino-p-quarterphenyl, 4,4′-bis (p-aminophenoxy) biphenyl, , 2-bis {4- (p-aminophenoxy) phenyl} propane, 4,4'-bis (3-aminophenoxyphenyl) diphenylsulfone, 2,2-bis {4-
(4-aminophenoxy) phenyl} hexafluoropropane, 2,2-bis {4- (3-aminophenoxy)
Phenyl {hexafluoropropane, 2,2-bis} 4
-(2-aminophenoxy) phenyl} hexafluoropropane, 2,2-bis {4- (4-aminophenoxy) -3,5-dimethylphenyl} hexafluoropropane, 2,2-bis {4- (4- Aminophenoxy)-
3,5-ditrifluoromethylphenyl @ hexafluoropropane, 4,4'-bis (4-amino-2-trifluoromethylphenoxy) biphenyl, 4,4'-bis (4-amino-3-trifluoromethylphenoxy) ) Biphenyl, 4,4'-bis (4-amino-2-trifluoromethylphenoxy) diphenylsulfone, 4,4 '
-Bis (3-amino-5-trifluoromethylphenoxy) diphenylsulfone, 2,2-bis {4- (4-amino-3-trifluoromethylphenoxy) phenyl}
Hexafluoropropane, bis {(trifluoromethyl) aminophenoxy} biphenyl, bis [{(trifluoromethyl) aminophenoxy} phenyl] hexafluoropropane, diaminoanthraquinone, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, Screw
[{2- (aminophenoxy) phenyl} hexafluoroisopropyl] benzene, bis (2,3,5,6-tetrafluoro-4-aminophenyl) ether, bis (2,3,5,6-tetrafluoro-4) -Aminophenyl) sulfide, 1,3-bis (3-aminopropyl)
Tetramethyldisiloxane, 1,4-bis (3-aminopropyldimethylsilyl) benzene, bis (4-aminophenyl) diethylsilane, 1,3-diaminotetrafluorobenzene, 1,4-diaminotetrafluorobenzene, 4, 4'-bis (tetrafluoroaminophenoxy) octafluorobiphenyl and the like.

Among the above-mentioned polyimides, fluorinated polyimides are more preferable from the viewpoint of moisture resistance. On the other hand, fluorinated polyimides are expensive as raw materials such as fluorinated diamines, fluorinated tetracarboxylic acids or their dielectrics. For,
From the viewpoint of suppressing the production cost, a fluorinated polyimide produced from a combination of raw materials in which at least one of the raw materials does not contain fluorine is more preferable.

For the production of polyimide, a usual polyimide production method can be applied. That is, a diamine and an acid dianhydride are polymerized in a polar solvent to produce a polyamic acid solution, which is then subjected to heat imidization or chemical imidization to obtain a polyimide. Further, a vacuum vapor deposition polymerization method using no solvent may be used.

In the production of an optical polyimide substrate, a polyamide acid solution or, if the polyimide is soluble in a solvent, a polyimide solution is used, and the polyimide substrate can be produced by a casting method or the like. A method of molding polyimide powder at high temperature and high pressure can also be applied. That is, an existing technique for manufacturing a substrate using a polymer material can be applied.

If the surface of the manufactured optical substrate is not smooth, it is better to perform surface polishing. The surface smoothness is preferably 100 nm or less in average surface roughness, preferably 50 nm or less.

[0030]

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

The refractive index in this embodiment is a value at a wavelength of 1320 nm measured by the prism coupler method. Note that TE
The direction is a direction in which the electric field vector of the incident polarization is parallel to the substrate surface, and the TM direction is a direction in which the plane of polarization is perpendicular to the direction. The birefringence was indicated by the absolute value of the value obtained by subtracting the refractive index in the TM direction from the refractive index in the TE direction.

<Example 1> 6FDA8 was placed in an Erlenmeyer flask.
8.8 g (0.2 mol) and TFDB 64.0 g (0.
2 mol) and N, N-dimethylacetamide 1000
g was added. This mixture was stirred under a nitrogen atmosphere at room temperature for 3 days to obtain a polyamic acid solution having a concentration of about 13 wt% (hereinafter referred to as 6 wt.
FDA / TFDB polyamic acid solution). This 6FDA / TFDB polyamic acid solution was formed into a film by a casting method and then heated and cured to obtain a 15 μm thick film and a 150 μm thick substrate (6FDA / TFDB substrate). The coefficient of thermal expansion of this film was 82 ppm, and the glass transition temperature was 325 ° C.

On this 6FDA / TFDB substrate, 6FDA
/ TFDB polyamic acid solution is spin-coated in an oven at 70 ° C. for 2 hours, 160 ° C. for 1 hour, 250 ° C.
For 30 minutes at 300 ° C. for 1 hour to perform imidization,
A polyimide film having a thickness of 10 μm was obtained. The refractive index of this polyimide film in the TE direction was 1.525, the refractive index in the TM direction was 1.525, and the birefringence was 0.000.

<Example 2> 64.4 g (0.2 mol) of benzophenonetetracarboxylic dianhydride (hereinafter abbreviated as BTDA) and 64.0 g of TFDB were placed in an Erlenmeyer flask.
(0.2 mol) and N, N-dimethylacetamide 1
000 g were added. This mixture was stirred at room temperature under a nitrogen atmosphere for 3 days to obtain a polyamic acid solution having a concentration of about 11 wt% (hereinafter abbreviated as BTDA / TFDB polyamic acid solution). The BTDA / TFDB polyamic acid solution was formed into a film by a casting method and then heated and cured to obtain a film having a thickness of 15 μm and a substrate having a thickness of 150 μm (BTDA / TFDB substrate). The coefficient of thermal expansion of this film is 75 ppm
The glass transition temperature was 305 ° C.

6FDA on the BTDA / TFDB substrate
/ TFDB polyamic acid solution is spin-coated in an oven at 70 ° C. for 2 hours, 160 ° C. for 1 hour, 250 ° C.
For 30 minutes at 300 ° C. for 1 hour to perform imidization,
A polyimide film having a thickness of 10 μm was obtained. The refractive index in the TE direction of this polyimide film was 1.525, the refractive index in the TM direction was 1.524, and the birefringence was 0.001.

Example 3 6FDA8 was placed in an Erlenmeyer flask.
8.8 g (0.2 mol) and ODA 40.0 g (0.2
mol) and 1000 g of N, N-dimethylacetamide
Was added. This mixture was stirred under a nitrogen atmosphere at room temperature for 3 days to obtain a polyamic acid solution having a concentration of about 11 wt% (hereinafter referred to as 6F).
DA / ODA polyamic acid solution). This 6FDA / ODA polyamic acid solution is formed into a film by a casting method and then heated and cured to form a film having a thickness of 15 μm and a thickness of 15 μm.
A 0 μm substrate (6FDA / ODA substrate) was obtained. The coefficient of thermal expansion of this film was 61 ppm, and the glass transition temperature was 302 ° C.

On this 6FDA / ODA board, 6FDA /
After spin-coating the ODA polyamic acid solution in an oven at 70 ° C. for 2 hours, 160 ° C. for 1 hour, and 250 ° C. for 3 hours.
The mixture was heated for 0 minute at 300 ° C. for 1 hour to perform imidization, thereby obtaining a polyimide film having a thickness of 10 μm. T of this polyimide film
The refractive index in the E direction is 1.569, and the refractive index in the TM direction is 1.69.
569, birefringence was 0.000.

Comparative Example 1 Pyromellitic dianhydride (hereinafter abbreviated as PMDA) 43.6 g in an Erlenmeyer flask
(0.2 mol) and ODA 40.0 g (0.2 mol)
And 1000 g of N, N-dimethylacetamide. The mixture was stirred at room temperature under a nitrogen atmosphere for 3 days,
A polyamic acid solution having a concentration of about 11 wt% (hereinafter referred to as PMDA /
(Abbreviated as ODA polyamic acid solution). This PM
A DA / ODA polyamic acid solution is formed into a film by a casting method, and then heated and cured to form a film having a thickness of 15 μm and a thickness of 150 μm.
(PMDA / ODA substrate) was obtained. The coefficient of thermal expansion of this film is 35 ppm, and the glass transition temperature is 400
400 ° C cannot be clarified by measurement up to
It is considered above.

On this PMDA / ODA board, 6FDA /
After spin-coating the ODA polyamic acid solution in an oven at 70 ° C. for 2 hours, 160 ° C. for 1 hour, and 250 ° C. for 3 hours.
The mixture was heated for 0 minute at 300 ° C. for 1 hour to perform imidization, thereby obtaining a polyimide film having a thickness of 10 μm. T of this polyimide film
The refractive index in the E direction is 1.523, and the refractive index in the TM direction is 1.23.
519, birefringence was 0.004.

[0040]

As described above, according to the present invention, the glass transition temperature is 300 ° C. or higher and the coefficient of thermal expansion is 60
The birefringence is smaller than that of the polyimide film produced on the polyimide substrate having a coefficient of thermal expansion of 60 ppm or less. When an optical waveguide is manufactured by using the same, there is an effect that a polyimide optical waveguide having small polarization dependence can be manufactured. The glass transition temperature is 300 ° C. or higher, and the thermal expansion coefficient is 60 ppm.
There is an advantage that an inexpensive optical polyimide substrate can be manufactured by using an optical substrate polyimide manufactured from a diamine containing no fluorine and an acid dianhydride at least one of the above-described optical substrate polyimides. .

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigekuni Sasaki 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Japan Telegraph and Telephone Corporation (72) Inventor Tohru Matsuura 1-3-1 Gotenyama, Musashino City, Tokyo No. NTT Advanced Technology Co., Ltd. (72) Inventor Fumio Yamamoto 1-3-1 Gotenyama, Musashino-shi, Tokyo, Japan Inside NTT Advanced Technology Co., Ltd. (72) Inventor Nagahiro Moroi 2805 Imafukunakadai, Kawagoe-shi, Saitama Prefecture, Japan Chemical Research Laboratory (72) Inventor Kazuhiko Kazuhiko Maeda 2805, Imafukunakadai, Kawagoe-shi, Saitama Prefecture, Japan Chemical Research Laboratory (72) Inventor Kentaro Tsutsumi 2805, Imafukunakadai, Kawagoe-shi, Saitama F-term (Central Glass Co., Ltd.) ) 2H047 QA05 TA00 4J043 PA02 PA19 PC155 PC156 QB15 QB26 RA35 SA06 SA44 SA56 SB01 TA22 TA48 TB01 UA032 UA121 UA122 UA131 UA132 UA141 UA142 UA151 UA152 UB UB UB 191 UB 012 UB 012 UB 191 UB401 UB402 VA011 VA012 VA021 VA022 VA031 VA032 VA041 VA042 VA051 VA052 VA081 VA082 XA16 XB33 YA06 ZA35 ZA52 ZB21

Claims (3)

[Claims] 1. A polyimide for an optical substrate, which has a glass transition temperature of 300 ° C. or more and a thermal expansion coefficient of 60 ppm or more. 2. The polyimide according to claim 1, which is produced from a diamine and an acid dianhydride, wherein at least one of the polyimides is produced from a fluorine-free diamine and an acid dianhydride. 4. The polyimide for an optical substrate according to item 1. 3. An optical polyimide substrate manufactured using the polyimide for an optical substrate according to claim 1.