U.S. patent application number 11/451889 was filed with the patent office on 2006-10-19 for novel polymer compound, precursor for the same and thin film-forming method using the same polymer precursor.
Invention is credited to Takashi Kato.
Application Number | 20060235194 11/451889 |
Document ID | / |
Family ID | 27667385 |
Filed Date | 2006-10-19 |
United States Patent
Application |
20060235194 |
Kind Code |
A1 |
Kato; Takashi |
October 19, 2006 |
Novel polymer compound, precursor for the same and thin
film-forming method using the same polymer precursor
Abstract
Provided are polyimide and a thin film thereof which have a
three-dimensional structure and therefore are excellent in a
mechanical strength and a heat resistance as compared with those of
conventional linear polyimide. The polyimide is obtained from a
salt of multifunctional amine represented by Formula (1): ##STR1##
(wherein A represents a tetravalent organic group, and n represents
an integer of 0 to 3) and tetracarboxylic diester represented by
Formula (2): ##STR2## (wherein B represents a tetravalent organic
group having 1 to 20 carbon atoms, and R.sub.1 and R.sub.2 each
represent independently an alkyl group having 1 to 5 carbon
atoms).
Inventors: |
Kato; Takashi;
(Yokohama-Shi, JP) |
Correspondence
Address: |
J.C. Patents;Suite 250
4 Venture
Irvine
CA
92618
US
|
Family ID: |
27667385 |
Appl. No.: |
11/451889 |
Filed: |
June 12, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11207463 |
Aug 18, 2005 |
7087311 |
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11451889 |
Jun 12, 2006 |
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10283481 |
Oct 29, 2002 |
6949618 |
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11207463 |
Aug 18, 2005 |
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Current U.S.
Class: |
528/353 ;
528/170 |
Current CPC
Class: |
Y10T 428/31721 20150401;
C07C 2603/74 20170501; Y10T 428/31678 20150401; C08G 73/1007
20130101; Y10T 428/31681 20150401; C09J 179/08 20130101; C07C
211/50 20130101; Y10T 428/31504 20150401; C08G 73/10 20130101 |
Class at
Publication: |
528/353 ;
528/170 |
International
Class: |
C08G 73/00 20060101
C08G073/00; C08G 69/26 20060101 C08G069/26 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 26, 2001 |
JP |
2001-393985 |
Mar 22, 2002 |
JP |
2002-081230 |
Claims
1-21. (canceled)
22. A polyimide represented by Formula (4): ##STR15## (wherein A
represents a tetravalent organic group; B represents a tetravalent
organic group having 1 to 20 carbon atoms; and n represents an
integer of 0 to 3).
23. The polyimide as described in claim 22, wherein A in Formula
(4) is an adamantane skeleton.
24. (canceled)
25. The polyimide as described in claim 22, wherein B in Formula
(4) is a benzene ring or a biphenyl ring.
26. The polyimide as described in any of claim 23, wherein B in
Formula (4) is a benzene ring or a biphenyl ring.
27. (canceled)
28. A polyimide having the three-dimensional structure represented
by Formula (3): ##STR16##
29-30. (canceled)
31. A polyimide represented by Formula (5): ##STR17##
32-41. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the priority benefit of Japan
applications serial no. 2001-393985, filed Dec. 26, 2001, and
2002-081230, filed Mar. 22, 2002.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a novel polyimide having a
rigid three-dimensional structure. Further, it relates to a novel
polyimide precursor making it possible to produce the polyimide of
the present invention and the thin film thereof by a simple method
which is not likely to cause gelation, and a solution thereof.
[0004] The polyimide thin film of the present invention is used as
a layer insulating film for integrated circuits (LSI) in
microelectronics and an aligning film for liquid crystal
displays.
[0005] 2. Description of the Related Art
[0006] In recent years, fineness and high speed of LSI using copper
wires are desired. A dielectric constant of a layer insulating film
has to be reduced in order to meet them, and development thereof is
actively carried out at present, which results in successive
publication of the new materials. In the greater part thereof, a
dielectric constant thereof is reduced by making use of a
dielectric constant (1.0) of the air to introduce a hole into a
material. However, simple dispersion of holes in the structure has
brought about the problem that an increase in the hole rate results
in a reduction in the mechanical strength.
[0007] In order to solve this problem, it is tried in several cases
to allow a mechanical strength and a low dielectric constant to
stand together by controlling a size of the holes and a form of the
material at a nanometer level. For example, disclosed in Shingaku
Technical Report, SDM2000-194 (2001) is the proposal that a
limiting low dielectric constant and a high strength can be
achieved by regularly forming nanoholes of a molecular level
between structural units of a three-dimensional organic polymer
having a pseudo-diamond structure.
[0008] Further, polyimide comprising tetraminoadamantane and
benzenetetracarboxylic acid is disclosed in Japanese Patent
Laid-Open No. 332543/2001, but polyimides having the other
structures are not disclosed at all.
[0009] The most general method for producing a polyimide thin film
is a method in which diamine and tetracarboxylic dianhydride are
subjected to polycondensation reaction in a solvent to prepare a
polyamic acid solution and in which it is then dehydrated by
heating or a chemical method to form an imide ring. However, when
the above method is applied to multifunctional amino compounds
higher than triamine, a three-dimensional cross-linking structure
is formed by polyaddition reaction, and a solvent is taken
thereinto to cause gelation. A gel has the defects that it is an
insoluble swollen substance and uneasy to handle and that it is
very difficult to form a molded matter such as a thin film.
[0010] A vapor deposition polymerization method is introduced as a
polyimide synthetic method using no solvent in Salon et al.,
Journal of Vacuum Science and Technology 1986, vol. A4, p. 369, but
an expensive vapor deposition apparatus is needed for this vapor
deposition method, and it is not necessarily a simple and
industrial method.
SUMMARY OF THE INVENTION
[0011] An object of the present invention is to provide a precursor
for readily producing polyimide without causing gelation in the
middle of synthesis even if using a multifunctional amino compound
as a monomer.
[0012] Further, it is to provide a novel polyimide having a
three-dimensional structure using a solution of such precursor and
a thin film thereof.
[0013] The present inventors have repeated intensive researches
from a viewpoint of preventing gelation by carrying out
polymerization on a non-solvent condition. As a result thereof,
they have found that a novel polyimide having a three-dimensional
structure can readily be synthesized without causing gelation by
using diester of tetracarboxylic acid in place of tetracarboxylic
dianhydride having a high reactivity, that is, using a salt of
multifunctional amine and diester of tetracarboxylic acid as a
precursor, and thus they have come to complete the present
invention.
[0014] That is, the polyimide of the present invention is
characterized by applying a multifunctional amine-tetracarboxylic
acid diester salt solution which is a precursor thereof on a
substrate, evaporating the solvent at a relatively low temperature
and then further subjecting the thin film precursor remaining on
the substrate to heat treatment to thereby turn it into imide by
dehydration and dealcohol reactions.
[0015] The present invention comprises the following structures.
(1) A salt of a multifunctional amine represented by Formula (1):
##STR3## (wherein A represents a tetravalent organic group, and n
represents an integer of 0 to 3) and tetracarboxylic diester
represented by Formula (2): ##STR4## (wherein B represents a
tetravalent organic group having 1 to 20 carbon atoms, and R.sub.1
and R.sub.2 each represent independently an alkyl group having 1 to
5 carbon atoms). (2) The salt of multifunctional amine and
tetracarboxylic diester as described in the item (1), wherein A in
Formula (1) is an adamantane skeleton. (3) The salt of
multifunctional amine and tetracarboxylic diester as described in
the item (1), wherein A in Formula (1) is a diamantane skeleton.
(4) A precursor of polyimide characterized by using the salt as
described in any of the items (1) to (3). (5) A polyimide precursor
solution, wherein the polyimide precursor as described in the above
item (4) is dissolved in an organic solvent. (6) A polyimide thin
film obtained by applying the polyimide precursor solution as
described in the item (5) on a substrate, evaporating the solvent
to form a film and then heating and baking it. (7) The polyimide
thin film as described in the item (6) comprising polyimide having
a three-dimensional structure represented by Formula (3): ##STR5##
(8) A layer insulating film using the polyimide thin film as
described in any of the items (6) to (7). (9) A polyimide
represented by Formula (4): ##STR6## (wherein A represents a
tetravalent organic group; B represents a tetravalent organic group
having 1 to 20 carbon atoms; and n represents an integer of 0 to
3). (10) The polyimide as described in the item (9), wherein A in
Formula (4) is an adamantane skeleton. (11) The polyimide as
described in the item (9), wherein A in Formula (4) is a diamantane
skeleton. (12) The polyimide as described in any of the items (9)
to (11), wherein B in Formula (4) is a benzene ring or a biphenyl
ring. (13) A polyimide having the three-dimensional structure
represented by Formula (3) as described in the item (7). (14) A
polyimide represented by Formula (5): ##STR7## (15) An electric
fixing apparatus characterized by using the polyimide as described
in any of the items (9) to (14) as a layer insulating film.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is an IR spectrum of
1,3,5,7-tetrakis(4-aminophenyl)adamantane synthesized in [1] of
Example 1.
[0017] FIG. 2 is an IR spectrum of polyimide synthesized in Example
1.
[0018] FIG. 3 is an IR spectrum of polyimide synthesized in Example
2.
DETAILED DESCRIPTION OF THE PREFERED EMBODIMENTS
[0019] The polyimide of the present invention is obtained from a
solution of a salt of multifunctional amine and tetracarboxylic
acid diester which is a precursor of the polyimide of the present
invention. For example, a multifunctional amine and tetracarboxylic
acid diester may be blended in an organic solvent. A reaction
example thereof shall be shown below: ##STR8##
[0020] A bond of this salt is weaker than a covalent bond of
polyamic acid, and therefore a strong cross-linking network
structure can not be formed in a solution. Accordingly, the
solution is not likely at all to be gelatinized.
[0021] The polyimide precursor solution thus obtained is applied in
the form of a vanish on a substrate such as a glass plate, a copper
plate, an aluminum plate or a silicone wafer, and then the
substrate is heated at a temperature lower than a boiling point of
the solvent for short time to evaporate the solvent. Thereafter,
the filmy precursor remaining on the substrate is heated and baked
at 200 to 450.degree. C., whereby an amide bond is formed by
dehydration reaction from the salt. When using multifunctional
amine, gelation is ought to take place at this stage, but the
solvent which is indispensable for gelation has already been almost
evaporated, so that gelation is no longer caused. A reaction
example thereof shall be shown below: ##STR9##
[0022] When heating is further continued, an intramolecular
dealcohol reaction takes place between the amide bond and an
adjacent carboxylic acid ester (alkoxycarbonyl group), and finally
an imide ring is formed. A reaction example thereof shall be shown
below: ##STR10##
[0023] In the polyimide and the precursor thereof according to the
present invention, the compound used as the multifunctional amino
compound is a tetraamine derivative represented by Formula (1). A
in the formula shall not specifically be restricted as long as it
is a tetravalent organic group.
[0024] A in the tetraamine derivative represented by Formula (1) is
the same as A in the polyimide represented by Formula (4) which is
derived from this. However, in the case of the mixture, the
composition ratio thereof itself is not necessarily the same
because of a difference in the reactivity.
[0025] The organic group which can be used for the polyimide and
the precursor thereof according to the present invention is not
specifically restricted in elements and is a part of a structure
constituting the organic compound, and the specific structure has a
skeleton structure shown below: ##STR11##
[0026] Among them, the organic group which can be used for the
polyimide and the precursor thereof according to the present
invention is preferably the following structures which can have a
regular tetrahedron, more preferably an adamantane skeleton, a
diamantane skeleton and a quaternary carbon atom. ##STR12##
[0027] In the polyimide precursor according to the present
invention and the solution thereof, the tetracarboxylic diester
represented by Formula (2) can readily be synthesized by a
conventional organic synthetic method. That is, most preferred is a
method which is widely used at present in synthesis of polyimide,
in which tetracarboxylic dianhydride is subjected to ring opening
with excess alcohol. In this case, it is not problematic at all to
use suitable solvents other than alcohol and add a base component
such as pyridine as an acylation catalyst. Also, two kinds of the
intended structure are present in a certain case depending on the
mode of the reaction, and they may be used in the form of a mixture
without isolating. Further, mixed tetracarboxylic diester obtained
by reaction using two or more kinds of alcohols may be used.
Allowed to be contained therein are triester and tetraester which
are obtained by further esterification of the resulting diester by
excess alcohol. In this case, tetraester neither forms a salt nor
inhibits salt formation of other carboxylic acids, and therefore it
may be contained.
[0028] The formula of this reaction and the specific example
thereof using pyromellitic anhydride are shown below: ##STR13##
[0029] These tetracarboxylic dianhydrides which are raw materials
for diesters can be considered according to the compound
represented by Formula (2). That is, B in Formula (2) shall not
specifically be restricted as long as it is a tetravalent organic
group having 1 to 20 carbon atoms. Specific examples thereof
include pyromellitic dianhydride, 3,3'4,4'-biphenyltetracarboxylic
dianhydride, 2,2'3,3'-biphenyltetracarboxylic dianhydride,
2,3,3',4'-biphenyltetracarboxylic dianhydride,
3,3'4,4'-benzophenonetetracarboxylic dianhydride,
2,3,3',4'-benzophenonetetracarboxylic dianhydride,
2,3,3',4'-benzophenonetetracarboxylic dianhydride,
2,2'3,3'-benzophenonetetracarboxylic dianhydride,
bis(3,4-dicarboxyphenyl)ether dianhydride,
bis(3,4-dicarboxyphenyl)sulfone dianhydride,
1,2,5,6-naphthalenetetracarboxylic dianhydride,
2,3,6,7-naphthalenetetracarboxylic dianhydride,
bis(dicarboxyphenyl)methane dianhydride, cyclobutanetetracarboxylic
dianhydride, cyclopentanetetracarboxylic dianhydride,
cyclohexanetetracarboxylic dianhydride,
dicyclohexanetetracarboxylic dianhydride,
dicyclopentanetetracarboxylic dianhydride,
bis(dicarboxycyclohexl)ether dianhydride,
bis(dicarboxycyclohexl)sulfone dianhydride,
bis(dicarboxycyclohexl)methane dianhydride and
4,4'-(hexafluoroisopropylidene)diphthalic dianhydride.
[0030] Among them, preferred are pyromellitic dianhydride,
3,3'4,4'-biphenyltetracarboxylic dianhydride,
3,3'4,4'-benzophenonetetracarboxylic dianhydride,
bis(3,4-dicarboxyphenyl)ether dianhydride,
cyclobutanetetracarboxylic dianhydride and
4,4'-(hexafluoroisopropylidene)diphthalic dianhydride. Those
containing isomers are included in these compounds, and they may be
isomer mixtures. Further, two or more kinds of the compounds may be
used in combination.
[0031] B in polyimidetetracarboxylic dianhydride represented by
Formula (2) is the same as B in the polyimide represented by
Formula (4) which is derived from this. However, in the case of the
mixture, the composition ratio thereof itself is not necessarily
the same because of a difference in the reactivity.
[0032] For example, when tetracarboxylic dianhydride is
pyromellitic dianhydride, B in Formula (2) and Formula (4) is a
benzene ring. Further, when it is 3,3'4,4'-biphenyltetracarboxylic
dianhydride, B in Formula (2) and Formula (4) is a biphenyl
ring.
[0033] Further, when multifunctional amine having an adamantane
skeleton and pyromellitic dianhydride are used as the raw
materials, polyimide represented by Formula (3) is obtained, and
when multifunctional amine having an adamantane skeleton and
3,3'4,4'-biphenyltetracarboxylic dianhydride are used as the raw
materials, polyimide represented by Formula (5) is obtained.
[0034] In the polyimide according to the present invention, a
solvent used in preparing a solution of the multifunctional
amine-tetracarboxylic diester salt which is the precursor shall not
specifically be restricted as long as it can dissolve the raw
materials and the salt, but solvents having a markedly high boiling
point are not suited. To be specific, preferred are
N-methyl-2-pyrrolidone, formamide, N,N-dimethylformamide,
N,N-dimethylacetamide, N,N-dimethylimidazolidinoe,
dimethylsulfoxide, hexamethylphosphoric acid triamide, dioxane,
tetrahydrofuran, sulfolane and .gamma.-butyrolactone, and more
preferred are N-methyl-2-pyrrolidone, N,N-dimethylformamide and
N,N-dimethylacetamide. These solvents may be used alone or in a
mixture of a plurality thereof.
[0035] In producing the polyimide according to the present
invention, the multifunctional amine-tetracarboxylic diester salt
which is the precursor can be used for producing a thin film in the
form of a solution dissolved in the solvent used in preparing the
solution. That is, the multifunctional amine-tetracarboxylic
diester salt does not have to be particularly isolated and
refined.
[0036] Further, the other solvents having a low surface tension may
be used in combination, if necessary, for the purpose of improving
the coating characteristic. To be specific, capable of being given
are alkyl lactate, 3-methyl-3-methoxybutanol, tetralin, isophorone,
ethylene glycol monoalkyl ethers (ethylene glycol monobutyl ether
and the like), diethylene glycol monoalkyl ethers (diethylene
glycol monoethyl ether and the like), ethylene glycol monoalkyl or
phenyl acetate, triethylene glycol monoalkyl ether, propylene
glycol monoalkyl ether (propylene glycol monobutyl ether and the
like), dialkyl malonate (diethyl malonate and the like),
cyclohexanone and cyclopentanone. These solvents are poor solvents
in many cases while the foregoing solvents are good solvents.
Accordingly, they are added preferably in such an amount that the
dissolved components are not deposited.
[0037] A method usually used can be used as a method for applying
the precursor solution dissolved in these solvents on a substrate
on which a layer insulating film is formed. For example, a spinner
method, a printing method, a dipping method and a dropping method
can be used.
[0038] In heat treatment required for drying the solvent after
applying this solution, the same method as methods used in
conventional layer insulating films can be carried out. For
example, an oven, a hot plate and an infrared furnace can be used.
After applying the solution, the solvent is vaporized at a
relatively low temperature, and then heat treatment is preferably
carried out at a temperature of 200 to 450.degree. C., preferably
300 to 400.degree. C. In this case, heating is carried out more
preferably on a condition of nitrogen atmosphere or reduced
pressure. Heating time is varied depending on the substrate, and it
is preferably 30 to 180 minutes, more preferably about 60 to 120
minutes.
EXAMPLES
[0039] The present invention shall be explained below in further
details with reference to examples, but the present invention shall
by no means be restricted by these examples.
[0040] The physical properties of the compounds obtained in the
examples were measured by the following methods.
Infrared Absorption Spectrum (IR):
[0041] Measured at room temperature by a KBr method by means of
model FT/IR-7000 manufactured by Nippon Bunko Co., Ltd.
Proton NMR Spectrum (.sup.1H-NMR):
[0042] Measured at room temperature by means of EX-90A manufactured
by Nippon Electron Co., Ltd. at 90 MHz using DMSO-d.sub.6 as a
solvent and tetramethylsilane as an internal standard
substance.
Example 1
[1] Synthesis of 1,3,5,7-tetrakis(4-aminophenyl)adamantane
[0043] 1,3,5,7-Tetrakis(4-aminophenyl)adamantane (compound 3) was
synthesized by a method described in Laychart et al.,
Macromolecules, vol. 27, p. 7024 (1994), which was shown in a
reaction equation described later.
[0044] Detailed explanations shall be given below by every step.
##STR14##
[1]-(1) Synthesis of 1,3,5,7-tetraphenyladamantane (compound 1)
[0045] A three neck flask of one liter equipped with a
nitrogen-introducing tube, a cooling tube and a stirrer was charged
with 30.0 g (0.14 mol) of 1-bromoadamantane and 38.2 g (0.28 mole)
of t-butyl bromide, and they were dissolved in 300 ml of benzene
and stirred at 0.degree. C. Anhydrous aluminum chloride 1.6 g
(0.012 mole) divided into four portions was added to this solution
in the form of a solid. The reaction solution was stirred for one
hour after returned to room temperature, and then it was heated and
refluxed for further one hour.
[0046] After finishing the reaction, the reaction solution was
poured into excess diluted hydrochloric acid cooled with ice and
left standing for one hour. A deposited solid substance was
filtered and dried under reduced pressure. This solid substance was
put into a three neck flask of one liter equipped with a cooling
tube and a stirrer and suspended in 500 ml of chloroform, and it
was stirred for one hour under refluxing. The suspension was
quickly filtered while it was hot to obtain 3.0 g (yield: 70%) of
the intended compound of a white insoluble solid matter. This
compound was used for a subsequent reaction without being refined
any more.
[1]-(2) Synthesis of 1,3,5,7-tetrakis(4-iodophenyl)adamantane
(compound 2)
[0047] Put into a mortar were 120.0 g (0.045 mole) of the compound
synthesized in [1]-(1) described above and 23.0 g (0.090 mole) of
iodine, and they were sufficiently crushed and blended with a
pestle. The resulting pink powder was put into an Erlenmeyer flask
of 500 ml, and 200 ml of chloroform was added thereto, followed by
stirring the solution at room temperature under nitrogen flow.
Added thereto was 39.0 g (0.090 mole) of
[bis(trifluoroacetoxy)iodo]benzene, and the solution was stirred
for 4 hours.
[0048] The reaction solution was filtered, and the resulting solid
matter was suspended in 300 ml of chloroform and stirred for one
hour under refluxing. The solution was filtered while it was hot to
remove the insoluble raw materials. The whole filtrates were put
together and washed twice with a 5% sodium thiosulfate solution and
twice with refined water. After the organic layer was dried on
anhydrous magnesium sulfate, the desiccant was filtered off, and
the solvent was distilled off under reduced pressure. A crude
crystal thus obtained was recrystallized from chloroform to obtain
226.3 g (yield: 62%) of the intended compound of a colorless needle
crystal.
[1]-(3) Synthesis of 1,3,5,7-tetrakis(4-aminophenyl)adamantane
(compound 3)
[0049] A three neck flask of 300 ml equipped with a cooling tube, a
stirrer and a mantle heater was charged with 5.0 g (5.30 mmole) of
the compound synthesized in [1]-(2) described above, 3.9 g (21.2
mmole) of potassium phthalimide and 4.20 g (20.2 mmole) of copper
iodide, and they were dissolved in 100 ml of N,N-dimethylacetamide
(hereinafter referred to as DMAc) and refluxed for 12 hours under
nitrogen flow by heating. After finishing the reaction, the
solution temperature was returned to room temperature, and the
solution was thrown into an excess 5 weight % sulfuric acid aqueous
solution to filter a deposited solid matter. Further, the solid
matter was sufficiently washed with dichloromethane, and the
filtrate was extracted twice with dichloromethane. The organic
layer was washed twice with refined water and dried on anhydrous
magnesium sulfate. Then, the desiccant was filtered off, and the
solvent was distilled off under reduced pressure. A yellow crude
crystal thus obtained was recrystallized from a
methanol/dichloromethane mixed=4/1 mixed solution to obtain 4.30 g
(yield: 79%) of a tetraphthalimide compound of a white crystal.
[0050] Subsequently, a three neck flask of 300 ml equipped with a
cooling tube and a stirrer was charged with 3.50 g (3.43 mmole) of
the tetraphthalimide compound and 100 ml of ethanol, and the
solution was stirred at room temperature under nitrogen flow. Added
thereto was 10 g of hydrazine hydrate, and the solution was heated
and refluxed for 4 hours. The reaction solution was thrown into
excess water to filter a deposited solid matter. After drying the
solid matter under reduced pressure, it was dissolved in excess hot
chloroform, and the solution was quickly filtered while it was hot
to remove insoluble phthalhydrazide. The filtrate was concentrated
under reduced pressure, and the resulting solid matter was washed
with methanol to obtain 1.50 g (yield: 87%) of
1,3,5,7-tetrakis(4-aminophenyl)adamantane (compound 3) of the
intended compound.
[0051] IR and NMR spectra of this compound were consistent with the
literature values. The IR spectrum is shown in FIG. 1.
[0052] A chemical shift of .sup.1H-NMR was .delta. 1.83 (s, 12H),
4.80 (s, 8H), 6.53 (d, 8H), 7.04 to 7.19 (m, 8H).
[2] Production of Multifunctional Amine-Tetracarboxylic Diester
Salt Solution
[0053] A sample bottle was charged with 0.5007 g (1.0 mmol) of
1,3,5,7-tetrakis(4-aminophenyl)adamantane (in Formula (1), A=an
adamantyl group, and n=1) obtained by synthesis in [1] described
above, and it was dissolved in 10.1 g of DMAc at room
temperature.
[0054] Added to this solution was 0.6205 g (2.0 mmol) of diethyl
pyromellitate (in Formula (2), B=a benzene ring, and
R.sub.1=R.sub.2=ethyl), and it was stirred at room temperature
until it became a homogeneous solution. After stirred for about one
hour, the solution was filtered through a membrane filter of 0.2
.mu.m to obtain a brown polyimide precursor solution.
[3] Production of Polyimide (Thin Film)
[0055] The polyimide precursor solution obtained in [2] described
above was applied as a coating solution on a glass substrate by a
spinner method and heated on a hot plate of 150.degree. C. for one
minute. The solvent was almost vaporized, and a brown filmy residue
was obtained. Immediately, it was put in an oven and baked at
400.degree. C. for one hour. A part of the resulting thin film was
peeled off and measured for an IR spectrum by a KBr method to
confirm absorptions showing formation of an imidocarbonyl group in
the vicinities of 1780 cm.sup.-1 and 1720 cm.sup.-1,
polypyromellitimide in the vicinities of 1375 cm.sup.-1 and 720
cm.sup.-1. The absorption showing formation of this
polypyromellitimide was consistent with that described in
Industrial Chemical Magazine, 69, 1069 (1966).
[0056] This IR spectrum is shown in FIG. 2. It is apparent from
this result that the polyimide of the present invention having a
three-dimensional structure was formed without causing gelation
during synthesis by using the polyimide precursor of the present
invention and the solution thereof.
Example 2
[0057] A brown polyimide precursor solution was obtained according
to Example 1, and then a thin film was formed, except that 0.7728 g
(2.0 mmol) of diethyl 3,3',4,4'-biphenyltetracarboxylate (in
Formula (2), B=a biphenylene group, and R.sub.1=R.sub.2=ethyl) was
used as tetracarboxylic acid diester and that 11.5 g of DMAc was
used.
[0058] This IR spectrum is shown in FIG. 3. It is apparent from
this result that the polyimide of the present invention having a
three-dimensional structure was formed without causing gelation
during synthesis by using the polyimide precursor of the present
invention and the solution thereof.
Comparative Example 1
[0059] A sample bottle was charged with 0.5007 g (1.0 mmol) of
1,3,5,7-tetrakis(4-aminophenyl)adamantane, and it was dissolved in
8.34 g of DMAc at room temperature. Pyromellitic dianhydride 0.4362
g (2.0 mmol) was added little by little to this solution in the
form of a solid matter to find that a gelatinized insoluble matter
was gradually deposited and that finally, the whole part of the
reaction solution was covered with a swollen gel.
[0060] The resulting substance was a gel and therefore could not be
coated.
Effects of the Invention
[0061] The polyimide of the present invention and the thin film
thereof have a three-dimensional structure and therefore are
excellent in a mechanical strength and a heat resistance as
compared with those of conventional linear polyimide, so that it is
useful as a functional thin film such as a layer insulating film
and a liquid crystal aligning film.
[0062] Further, the polyimide precursor of the present invention is
not likely to cause gelation if a multifunctional amino compound is
used, and it is so useful that polyimide having a three-dimensional
structure and a thin film thereof can readily be produced.
[0063] Further, the polyimide of the present invention can be used
for producing a thin film as it contains a solvent used in
producing a solution of a multifunctional amine-tetracarboxylic
diester salt which is the precursor. That is, the multifunctional
amine-tetracarboxylic diester salt does not have to be isolated and
refined, so that it is effective as well from an industrial point
of view.
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