JPH1112465A - Polyamic acid solution, polyimide film and method for controlling characteristics of polyimide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide film having light transmittance, refractive index controllability, thermal expansion coefficient controllability and low birefringence required for an optical material. SOLUTION: In a polyimide film containing silicon dioxide fine particles and polyimide as a main component, the particle size of the silicon dioxide fine particles is 0.5 to 50 nm.
A polyimide film containing silicon dioxide fine particles, characterized in that:

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel polyimide material, and more particularly to a polyimide material that can be used for optical applications and its property control.

[0002]

2. Description of the Related Art Polyimide is a polymer material having excellent heat resistance and is used as an interlayer insulating film such as an LSI and an electronic material such as a flexible printed circuit board. It is important for electronic materials to be compatible with the semiconductor process and to be able to withstand the soldering process. Therefore, heat resistance is an essential property. It can be said that application to electronic materials is an application destination in which the performance of polyimide having excellent heat resistance is exhibited.

[0003] With the development of optical communication systems, demands for optical materials as well as electronic materials have become apparent. For example, the fabrication of an optical waveguide that is essential for the construction of optical components requires compatibility with semiconductor processes, and since the optical wiring and electrical wiring are manufactured on the same substrate, the optical waveguide also requires solder heat resistance. Is done. Conventional polymer optical materials include polymethyl methacrylate, polycarbonate, and polystyrene, but do not have heat resistance to withstand the soldering process. In that respect, polyimide is excellent in heat resistance, and can be expected as an optical material.

When polyimide is used as an optical material, various performances are required for the polyimide. In particular, light transmittance, refractive index controllability, thermal expansion coefficient controllability, and low birefringence are extremely important as an optical material. It is a characteristic. Light transmission is particularly important when polyimide is used as the light propagation medium. The refractive index controllability is important for coupling and confinement of light. The thermal expansion coefficient controllability is important for solving problems due to stress generated due to a difference in thermal expansion coefficient between the substrate and the substrate, such as substrate warpage and adhesion reliability. Furthermore, low birefringence is important so as not to cause polarization dependence of optical components.

In general, polyimide has a brown color peculiar to polyimide and is inferior in light transmittance. The biggest reason why it has not been used in optical applications is that it has poor light transmittance. Some reports have recently begun on the improvement of the light transmittance of polyimides, such as SAMPE JO
On page 28 of URNAL JULY / AUGUST 1985, an example of polyimide having excellent light transmittance is reported. The present inventors have disclosed a fluorinated polyimide excellent in light transmittance in JP-A-3-72528. Regarding the refractive index controllability, the present inventors have realized in Japanese Patent Application Laid-Open No. 4-8734 by copolymerizing two kinds of fluorinated polyimides and adjusting the fluorine content. Japanese Patent Application Laid-Open No. 6-51146 discloses that the refractive index can be controlled by irradiating a fluorinated polyimide with an electron beam and controlling the amount of irradiation. Matsuura et al. Reported in Macromolecules, Vol. 26, pp. 419-423, published in 1993, that the thermal expansion coefficient can be controlled by copolymerizing a polyimide with a low thermal expansion coefficient and a polyimide with a high thermal expansion coefficient. ing. Regarding low birefringence, Kosho and co-workers disclose a polyimide having a relatively small birefringence in the 44th volume 316 pages of the proceedings of the 44th Annual Meeting of the Society of Polymer Science, Japan. As described above, the light transmittance, the refractive index controllability, the thermal expansion coefficient controllability, and the low birefringence required when using polyimide as an optical material are realized by several methods.

[0006] However, the conventional methods also have problems such as changing the chemical structure of the polyimide itself, performing copolymerization, irradiating an electron beam, and the like, which can be applied only to a specific polyimide, or requires a complicated process. is there. If these properties can be added by a simple method using an existing polyimide, it is expected that the range of application to optical applications will be dramatically expanded.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method for imparting the light transmittance, refractive index controllability, thermal expansion coefficient controllability, and low birefringence required for an optical polyimide to a polyimide by a simple method. The purpose is to provide a material therefor.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object. As a result, by blending fine particles of silicon dioxide having a controlled particle size with polyimide, transparency was not impaired. The inventors have found that it is possible to control the refractive index, control the coefficient of thermal expansion, and reduce birefringence, and have completed the present invention.

That is, the first invention of the present invention is a polyamic acid solution containing silicon dioxide fine particles, wherein the particle size of the silicon dioxide fine particles in the polyamic acid solution containing silicon dioxide fine particles and silicon dioxide fine particles containing polyamic acid as a main component is reduced. It is 0.5 to 50 nm.

The second invention of the present invention is the polyamic acid solution containing silicon dioxide fine particles according to the first aspect, wherein the polyamic acid solution is a fluorinated polyamic acid solution.

A third invention of the present invention is a polyimide film containing silicon dioxide fine particles, wherein the particle size of the silicon dioxide fine particles is 0.5%. ５０50 nm.

[0012] A fourth invention of the present invention is the polyimide film containing silicon dioxide fine particles according to claim 3, wherein
The polyimide is a fluorinated polyimide.

The fifth invention of the present invention relates to a method for controlling the refractive index of a polyimide film, wherein silicon dioxide fine particles having a particle size of 0.5 to 50 nm are blended in the polyimide film, and the blending amount is adjusted. The refractive index is controlled by adjusting the refractive index.

The sixth invention of the present invention is a method for controlling the coefficient of thermal expansion of a polyimide film, wherein silicon dioxide fine particles having a particle size of 0.5 to 50 nm are blended in the polyimide film, and the blending amount is adjusted. To control the coefficient of thermal expansion.

A seventh invention of the present invention relates to a method for reducing birefringence of a polyimide film, comprising reducing the birefringence by blending silicon dioxide fine particles having a particle size of 0.5 to 50 nm into the polyimide film. It is characterized by.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail.

The polyamic acid and polyimide used in the present invention include, for example, polyamic acid and polyimide produced from the following tetracarboxylic acid or its derivative and diamine. In addition, copolymers and mixtures of these polyamic acids and polyimides can also be used.

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, 2,3,3 ′,
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'-tetracarboxydiphenyl sulfone, 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-dicarboxyphenoxy) phenyl] propane, butanetetracarboxylic acid, cyclopentanetetracarboxylic acid, 2,2-bis [4-
(3,4-dicarboxyphenoxy) phenyl] hexafluoropropane, bis [(trifluoromethyl) dicarboxyphenoxy] biphenyl, bis [(trifluoromethyl) dicarboxyphenoxy] bici (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-biscarboxytrifluorophenoxy) octafluorobiphenyl and the like.

Among these tetracarboxylic acids, there are 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane and 1,4-bis (3,4-dicarboxytrifluorophenoxy) having a fluorine substituent. Tetrafluorobenzene, (trifluoromethyl) pyromellitic acid, di (trifluoromethyl) pyromellitic acid, difluoropyromellitic acid, and the like are preferable, and 2,2-bis (3,4-dicarboxyphenyl) hexafluoro is more preferable. Propane and 1,4-bis (3,4-dicarboxytrifluorophenoxy) tetrafluorobenzene.

Examples of the diamine include the following. 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, 2,2'-bis (trifluoromethoxy)-
4,4'-diaminobiphenyl, octafluorobenzidine, 3,3'-bis (trifluoromethyl) -4,
4'-diaminobiphenyl, 3,3'-bis (trifluoromethoxy) -4,4'-diaminobiphenyl, 4,
4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 2,2-bis (p-aminophenyl) propane, 3,3'-dimethyl-4,4'-diaminodiphenylether 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'-diaminodiphenyl 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,
2,2-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, Bis {[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 these diamines, 2,2'-bis (trifluoromethyl)-having a fluorine substituent
4,4'-diaminobiphenyl, bis (2,3,5,6
-Tetrafluoro-4-aminophenyl) ether,
2,2-bis (p-aminophenyl) hexafluoropropane, 1,3-diaminotetrafluorobenzene,
2,2'-bis (trifluoromethoxy) -4,4'-
Diaminobiphenyl, bis (2,3,5,6-tetrafluoro-4-aminophenyl) ether and the like are preferable,
More preferred are 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl and bis (2,3,5,6-tetrafluoro-4-aminophenyl) ether.

Among the above-mentioned polyamic acids and polyimides obtained from tetracarboxylic acids and diamines, those obtained from tetracarboxylic acids having a fluorine substituent and diamines having a fluorine substituent, ie, those contained in the repeating structural unit, are used. So-called fluorinated polyamic acids and fluorinated polyimides containing a fluorine substituent are preferred from the viewpoint of moisture resistance. It is also preferable from the viewpoint of light transmittance, but is particularly preferable from the viewpoint of light transmittance in an optical communication wavelength region having a wavelength of 1.0 to 1.7 μm.

The silicon dioxide fine particles used in the present invention are:
It is preferable that the particle size is small in order to prevent scattering of light and to have high light transmittance. It is considered that the range of 0.5 to 50 nm, particularly the range of 5 to 50 nm is practically preferable considering the dispersibility of the fine particles. The particle size here means a particle size determined using the Bet method, which is generally known as a method for estimating the particle size of particles.

As a method of blending the polyamic acid solution or the polyimide solution of the silicon dioxide fine particles, a method of blending a solution in which the silicon dioxide fine particles are dispersed in a solvent dissolving the polyamic acid or the polyimide into the polyamic acid solution or the polyimide solution can be used. . For example, an organosilica sol manufactured by Nissan Chemical Industries, Ltd. can be used. Further, a method in which silicon dioxide fine particles are directly blended with a polyamic acid solution or a polyimide solution using a ball mill or the like can also be used.

The compounding amount of the silicon dioxide fine particles may be freely changed depending on the intended value of the refractive index or the coefficient of thermal expansion.
The upper limit is 5 considering the mechanical strength of the polyimide film.
It is considered to be about 0 wt%, and at least 1 wt% is necessary from the viewpoint of characteristic control.

To prepare a film from the polyamic acid solution or the polyimide solution containing the silicon dioxide fine particles prepared as described above, the same method as in a usual method for preparing a polyimide film may be used. For example, it can be manufactured by the following method. A polyamic acid solution or a polyimide solution is applied to a uniform thickness on a substrate such as silicon by a spin coating method, a dipping method, or the like. Thereafter, heating is performed to evaporate the solvent. When a polyamic acid solution is used, heating required for imidization is further performed.

In order to control the refractive index of the polyimide film containing the silicon dioxide fine particles, the amount of the silicon dioxide fine particles may be adjusted, and to control the coefficient of thermal expansion, the amount of the silicon dioxide fine particles may be similarly controlled. Can be adjusted.

[0029]

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.

Example 1 An Erlenmeyer flask was charged with 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (hereinafter referred to as 6FD).
A) (abbreviated as A) 88.8 g (0.2 mlo) and 2,2 ′
-Bis (trifluoromethyl) -4,4'-diaminobiphenyl (hereinafter abbreviated as TFDB) 64.0 g (0.
2 mol) and 1000 g of N, N-dimethylacetamide (hereinafter abbreviated as DMAc). This mixture was stirred under a nitrogen atmosphere at room temperature for 3 days to a concentration of about 15 wt.
% Polyamic acid solution (hereinafter abbreviated as 6FDA / TFDB polyamic acid solution).

In a glass container having a capacity of 100 ml, 8.52 g of the obtained 6FDA / TFDB polyamic acid solution,
1.53 g of a silicon dioxide fine particle dispersion solution (organic silica sol DMAc-ST, manufactured by Nissan Chemical Industries, Ltd.) in which 20 wt% of silicon dioxide fine particles having a particle size of 10 to 20 nm are dispersed in DMAc is added, and the mixture is stirred at room temperature for 24 hours to be colorless. A polyamic acid solution containing transparent silicon dioxide fine particles was obtained.

Next, the polyamic acid solution containing the silicon dioxide fine particles was dropped on a silicon substrate provided with an oxide film, and a film having a uniform thickness was formed by a spin coating method. Subsequently, this was placed in an oven at 70 ° C. for 2 hours, at 160 ° C. for 1 hour, at 250 ° C.
For 30 minutes at 350 ° C. for 1 hour to perform imidization,
A polyimide film containing silicon dioxide fine particles having a thickness of about 13 μm was obtained. This polyimide film contains 20 wt% of silicon dioxide fine particles.

Table 1 shows the measurement results of the light transmittance, the refractive index, and the coefficient of thermal expansion of the obtained polyimide film containing 20 wt% of silicon dioxide fine particles.

Example 2 A polyamic acid solution containing fine particles of silicon dioxide was prepared so that the content of fine particles of silicon dioxide in the polyimide film containing fine particles of silicon dioxide was 10 wt%, and a polyimide film containing fine particles of silicon dioxide was prepared in the same manner as in Example 1. Obtained.

Table 1 shows the measurement results of the light transmittance, refractive index, and coefficient of thermal expansion of the obtained polyimide film containing 10 wt% of silicon dioxide fine particles.

Example 3 A polyamic acid solution containing fine particles of silicon dioxide was prepared so that the content of fine particles of silicon dioxide in the polyimide film containing fine particles of silicon dioxide was 5 wt%, and a polyimide film containing fine particles of silicon dioxide was prepared in the same manner as in Example 1. Obtained.

Table 1 shows the measurement results of the light transmittance, refractive index, and coefficient of thermal expansion of the obtained polyimide film containing 5 wt% of silicon dioxide fine particles.

Examples 4 to 6 Except that the particle size of the silicon dioxide fine particles was 30 to 40 nm, and the compounding amount was 20 wt% (Example 4), 10 wt% (Example 5) and 5 wt% (Example 6). In the same manner as in Example 1, a polyimide film containing silicon dioxide fine particles was obtained.

Table 1 shows the measurement results of the light transmittance, the refractive index, and the coefficient of thermal expansion of the obtained silicon dioxide-containing polyimide film.

Comparative Example 1 A polyimide film containing no silicon dioxide fine particles was obtained from the 6FDA / TFDB polyamic acid solution prepared in Example 1.

Light transmittance of the obtained polyimide film,
Table 1 shows the measurement results of the refractive index and the coefficient of thermal expansion.

Comparative Example 2 A polyimide film containing 20% by weight of silicon dioxide fine particles was obtained in the same manner as in Example 1, except that silicon dioxide fine particles having a particle size of 70 to 100 nm were used.

Light transmittance of the obtained polyimide film,
Table 1 shows the measurement results of the refractive index.

Comparative Example 3 A polyimide film containing 20% by weight of silicon dioxide fine particles was obtained in the same manner as in Example 1 except that silicon dioxide fine particles having a particle diameter of 500 nm were used. This film hardly transmitted light, and the refractive index could not be measured.

[0045]

[Table 1]

The particle size is a value determined by using the Bet method. The compounding amount is the weight% of the fine particles in the polyimide film. The refractive index is wavelength 1 measured by the prism coupler method.
It is a value at 320 nm. The refractive index TE is the refractive index in the direction in which the electric field vector of the incident polarization is parallel to the substrate surface, and the refractive index TM is the refractive index in the direction perpendicular to the polarization plane. Birefringence is the difference between the refractive index TE and the refractive index TM. The light transmittance was measured at a wavelength of 500 using a spectrophotometer.
It is a value in nm. The coefficient of thermal expansion was measured using a thermomechanical analyzer and expressed as an average coefficient of thermal expansion from 50 ° C to 300 ° C.

The following is clear from Table 1.

(1) The particle size of the silicon dioxide fine particles is 15 to
The polyimide film blended with 20 nm has the same light transmittance as the one not blended with silicon dioxide fine particles, whereas the polyimide film blended with a particle size of 70 nm or more has remarkable light transmittance. Bad.

(2) The refractive index can be controlled without impairing the light transmittance of the polyimide film by changing the amount of the silicon dioxide fine particles having a particle size of 15 to 20 nm.

(3) Birefringence can be reduced without changing the light transmittance of the polyimide film by changing the amount of the silicon dioxide fine particles having a particle size of 15 to 20 nm.

(4) The thermal expansion coefficient can be controlled without changing the light transmittance of the polyimide film by changing the amount of the silicon dioxide fine particles having a particle size of 15 to 20 nm.

[0052]

As described above, the polyimide film prepared by using the polyamic acid solution containing silicon dioxide fine particles of the present invention can control the refractive index without impairing the light transmittance by adjusting the content of the silicon dioxide fine particles. And the coefficient of thermal expansion can be controlled. The effect of reducing birefringence is also remarkable.

When the polyimide film of the present invention is used as an optical component such as an optical waveguide, it is possible to control the refractive index and the coefficient of thermal expansion of these optical components by utilizing these characteristics, and of course, to simplify these components. There is an advantage that it can be manufactured.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G02B 1/04 G02B 1/04 5/30 5/30 (72) Inventor Toru Maruno 3-9-1, Nishishinjuku, Shinjuku-ku, Tokyo No. Nippon Telegraph and Telephone Corporation (72) Inventor Noriyoshi Yamada 1-3-1 Gotenyama, Musashino-shi, Tokyo NTT Advanced Technology Corporation

Claims (7)

[Claims] In a polyamic acid solution containing silicon dioxide fine particles and polyamic acid as a main component, the particle size of the silicon dioxide fine particles is 0.5 to 50 nm.
A polyamic acid solution containing silicon dioxide fine particles, characterized in that: 2. The polyamic acid solution containing fine silicon dioxide particles according to claim 1, wherein the polyamic acid solution is a fluorinated polyamic acid solution. 3. A polyimide film containing silicon dioxide fine particles and polyimide containing silicon dioxide fine particles as a main component, wherein the particle size of the silicon dioxide fine particles is 0.5 to 50 nm.
A polyimide film containing silicon dioxide fine particles, characterized in that: 4. The polyimide film containing silicon dioxide fine particles according to claim 3, wherein the polyimide is a fluorinated polyimide. 5. The polyimide film having a particle size of 0.5 to 0.5.
A method for controlling the refractive index of a polyimide film, comprising mixing fine particles of silicon dioxide having a thickness of 50 nm and adjusting the amount thereof to control the refractive index. 6. The polyimide film having a particle size of 0.5 to 0.5.
A method for controlling the coefficient of thermal expansion of a polyimide film, comprising mixing fine particles of silicon dioxide having a thickness of 50 nm and adjusting the amount of the compound to control the coefficient of thermal expansion. 7. The polyimide film having a particle size of 0.5 to 0.5.
A method for reducing birefringence of a polyimide film, comprising mixing silicon dioxide fine particles having a thickness of 50 nm to reduce birefringence.