U.S. patent application number 12/290523 was filed with the patent office on 2009-05-28 for novel polyimide copolymer and metal laminate using the same.
This patent application is currently assigned to NIPPON MEKTRON LIMITED. Invention is credited to Jenq-Tain Lin, Min Zuo.
Application Number | 20090133907 12/290523 |
Document ID | / |
Family ID | 31949541 |
Filed Date | 2009-05-28 |
United States Patent
Application |
20090133907 |
Kind Code |
A1 |
Zuo; Min ; et al. |
May 28, 2009 |
Novel polyimide copolymer and metal laminate using the same
Abstract
A novel polyimide copolymer, which is a copolymer comprising two
kinds of tetracarboxylic acid dianhydrides consisting of (A)
isopropylidene-bis(4-phenyleneoxy-4-phthalic acid) dianhydride and
(B) 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, and one
kind of a diamine consisting of (C)
6-amino-2-(p-aminophenyl)benzimidazole, or two or three kinds of
diamines consisting of component (C) and (D) at least one kind of
diamines consisting of bis(4-amino-phenyl)ether (D.sub.1) and
phenylenediamine (D.sub.2), and a metal laminate manufactured by
laminating said polyimide copolymer to a metallic foil. The metal
laminate comprising the novel polyimide copolymer as a layer on the
metallic foil has a low curling susceptibility to cause curling,
twisting, warping, etc. against temperature changes due to a low
coefficient of linear thermal expansion of the polyimide copolymer,
and also has satisfactory adhesiveness and thermal dimensional
stability and a low water absorbability, and thus can be used as a
suitable for a flexible, finely printed circuit board requiring a
high dimensional stability.
Inventors: |
Zuo; Min; (Ibaraki, JP)
; Lin; Jenq-Tain; (Ibaraki, JP) |
Correspondence
Address: |
BUTZEL LONG;IP DOCKETING DEPT
350 SOUTH MAIN STREET, SUITE 300
ANN ARBOR
MI
48104
US
|
Assignee: |
NIPPON MEKTRON LIMITED
Tokyo
JP
|
Family ID: |
31949541 |
Appl. No.: |
12/290523 |
Filed: |
October 31, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10815164 |
Mar 31, 2004 |
7459216 |
|
|
12290523 |
|
|
|
|
Current U.S.
Class: |
174/254 ;
528/353 |
Current CPC
Class: |
H05K 1/0346 20130101;
Y10T 428/31721 20150401; C08G 73/1085 20130101; B32B 15/08
20130101; Y10T 428/31681 20150401; B32B 27/34 20130101; Y10T
428/31692 20150401; C08G 73/1042 20130101 |
Class at
Publication: |
174/254 ;
528/353 |
International
Class: |
H05K 1/00 20060101
H05K001/00; C08G 69/26 20060101 C08G069/26 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 20, 2002 |
JP |
2002-239145 |
Nov 11, 2002 |
JP |
2002-326599 |
Claims
1. A novel polyimide copolymer, which is a copolymer comprising two
kinds of tetracarboxylic acid dianhydrides consisting of (A)
isopropylidenebis(4-phenyleneoxy-4-phthalic acid) dianhydride and
(B) 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, and (C)
6-amino-2-(p-aminophenyl)-benzimidazole.
2. A novel polyimide copolymer according to claim 1, wherein the
copolymer has a film formability.
3. A novel polyimide copolymer according to claim 1, wherein the
two kinds of tetracarboxylic acid dianhydrides are used in a
proportion of component (A) to component (B) of 10-80 mol. % to
90-20 mol. %.
4. (canceled)
5. (canceled)
6. A flexible printed circuit board which comprises a metal
laminate manufactured by laminating a layer of a novel polyimide
copolymer according to claim 3 to a metallic foil.
7-17. (canceled)
Description
RELATED APPLICATIONS
[0001] The present application is a divisional application of U.S.
patent application Ser. No. 10/815,164, filed Mar. 31, 2004, which
in turn is a 35 U.S.C. .sctn.371 national stage filing of
International Patent Application No. PCT/JP2003/08484, filed Jul.
3, 2003, to which priority is claimed under 35 U.S.C. .sctn.120 and
through which priority is claimed under 35 U.S.C. .sctn.119 to
Japanese Priority Patent Application Nos. 2002-239145, filed Aug.
20, 2002 and 2002-326599, filed Nov. 11, 2002
TECHNICAL FIELD
[0002] The present invention relates to a novel polyimide copolymer
and a metal laminate using the same, and more particularly to a
novel polyimide copolymer capable of suitably using as a film for a
flexible printed circuit board and a metal laminate using the
same.
BACKGROUND ART
[0003] Most of substrates for flexible printed circuit boards, etc.
have been so far manufactured by bonding a metallic foil and an
aromatic polyimide film with an adhesive such as epoxy resin,
polyurethane resin, etc. However, the flexible printed circuit
boards manufactured with such an adhesive have problems such as
adhesive peeling due to successive thermal compression bonding
hysteresis or due to exposure to elevated temperatures in the
soldering step, or smear generation in the drilling step owing to
an adhesive, and further have such drawbacks as curling, twisting,
warping, etc. of the substrates after cooling, causing trouble
particularly to form a fine pattern.
[0004] These problems owe their origin to differences in
coefficient of linear thermal expansion between a conductor and an
insulating material, and thus it has been proposed to improve the
heat resistance of the adhesive. Basically, omission of the
adhesive layer can solve not only the problems due to the adhesive
layer, but can also save the labor of bonding the adhesive to the
polyimide film.
[0005] From such a viewpoint, a metal laminate has been formed in
some cases by directly coating a metallic conductor with polyamic
acid as a polyimide precursor copolymer, followed by heating to
effect polyimidization. It is known that the metal laminate thus
obtained has a poor dimensional stability and suffers from
curling.
[0006] To overcome these drawbacks, JP-B-5-22399, JP-B-6-93537,
JP-B-7-39161, etc. disclose metal laminates with distinguished
dimensional stability, adhesiveness, flatness after etching,
reduction in curling, etc., manufactured by forming a plurality
layers of a polyimide resin layer having low thermal expansion and
other polyimide resin layers on a conductor, where two or three
kinds of polyimide precursor copolymers must be used, the
individual copolymer solutions must be applied one by one to the
conductor to form an insulation multilayer, and a ratio in
thickness of the resulting individual polyimide layers must be
specified, inevitably complicating the manufacture of the metal
laminate thereby.
[0007] The present applicant has already proposed a metal laminate
where one kind of polyimide copolymer layer is directly laminated
to a metallic conductor (WO 01/29136). The polyimide copolymer used
therein is a copolymer of
isopropylidenebis(4-phenyleneoxy-4-phthalic acid) dianhydride and
6-amino-2-(p-aminophenyl)benzimidazole. The polyimide copolymer
obtained by polycondensation of these monomer components has a high
adhesive strength by itself and can give a metal laminate with a
satisfactory peel strength even if laminated directly to a metallic
foil without interposing an adhesive layer therebetween, and also
has a good solder heat resistance, but originally the polyimide
copolymer has not been intended to lower the coefficient of linear
thermal expansion or percent heat shrinkage or improvement of
curling resistance.
DISCLOSURE OF THE INVENTION
[0008] An object of the present invention is to provide a polyimide
copolymer capable of giving a flexible printed circuit board with
satisfactory adhesive strength and dimensional stability in a metal
laminate comprising one kind of polyimide copolymer layer formed on
the metallic conductor, by lowering the coefficient of linear
thermal expansion or percent heat shrinkage of the polyimide
copolymer or approaching the coefficient of linear thermal
expansion or percent heat shrinkage of the polyimide copolymer to
that of the conductor, thereby effectively suppressing curling,
twisting, warping, etc. of the metal laminate even if subjected to
heat hysteresis, and also to provide a metal laminate using the
same.
[0009] The object of the present invention can be attained by a
novel polyimide copolymer, which is a copolymer comprising two
kinds of tetracarboxylic acid dianhydrides consisting of (A)
isopropylidenebis(4-phenyleneoxy-4-phthalic acid) dianhydride and
(B) 3,3',4,4'-biphenyl-tetracarboxylic acid dianhydride, and one
kind of a diamine consisting of (C)
6-amino-2-(p-aminophenyl)benzimidazole or two or three kinds of
diamines consisting of said component (C) and (D) at least one kind
of diamines consisting of bis(4-aminophenyl)ether (D1) and
phenylenediamine (D2), and also by a metal laminate comprising a
metallic foil and a layer of said polyimide copolymers laminated
thereto. The present novel polyimide copolymer is film-formable
[0010] Tetracarboxylic acid dianhydrides for use in the synthesis
of the present novel polyimide copolymer are two kinds of acid
dianhydrides consisting of (A)
isopropylidenebis(4-phenylene-oxy-4-phthalic acid) dianhydride as
shown below:
##STR00001##
and (B) 3,3',4,4'-biphenyltetracarboxylic acid dianhydride as shown
below:
##STR00002##
[0011] Component (A) and component (B) are used in a proportion of
component (A) to component (B) of 10-80% by mole, preferably 20-60%
by mole to 90-20% by mole, preferably 80-40% by mole. When a
proportion of component (A) is more than 80% by mole, curling will
be pronounced in the stage of forming a metal laminate, together
with an increased coefficient of linear thermal expansion and also
with increased percent heat shrinkage. Whereas when a proportion of
component (A) is less than 10% by mole, the resulting film will
become not only brittle, but also the adhesive strength will be no
more observable in the metal laminate.
[0012] Other kinds of tetracarboxylic acid dianhydrides can be used
together within such a range as not to deteriorate the object of
the present invention.
Diamine for use in forming a polyimide copolymer upon reaction with
these two kinds of tetracarboxylic acid dianhydrides is (C)
6-amino-2-(p-aminophenyl)benzimidazole as shown below:
##STR00003##
[0013] The above mentioned diamine compound (C) can be used
together with (D) at least one of bis(4-aminophenyl)ether (D1) and
phenylenediamine, for example, p-phenylenediamine (D.sub.2) as
shown below:
##STR00004##
[0014] When bis(4-aminophenyl)ether (Dj) is used as diamine
compound (D), a proportion of component (D.sub.1) to component (C)
is not more than 40% by mole, preferably 30-10% by mole, to not
less than 60% by mole, preferably 70-90% by mole. When a proportion
of component (D.sub.1) to component (C) is more than 40% by mole,
curling will be pronounced in the stage of forming a metal
laminate, together with an increased coefficient of linear thermal
expansion.
[0015] When phenylenediamine (D.sub.2) is used as diamine compound
(D), a proportion of component (D.sub.2) to component (C) is not
more than 80% by mole, preferably 70-50% by mole to not less than
20% by mole, preferably 30-50% by mole. When a proportion of
component (D.sub.2) to component (C)
is more than 80% by mole, curling will be pronounced in the stage
of forming a metal laminate.
[0016] When bis(4-aminophenyl)ether (D.sub.1) and phenylenediamine
(D.sub.2) are used together as diamine compounds (D), a proportion
of sum total of components (D.sub.1) and (D.sub.2) to component (C)
is generally not more than 75% by mole to not less than 25% by
mole, though dependent on a proportion of diamine compound (Dj) to
diamine compound (D.sub.2), and component (C) and component (D) can
be used in such a molar ratio as not to cause curling in the stage
of forming a metal laminate.
[0017] Other kinds of diamine compounds can be used together in
such a range as not to deteriorate the object of the present
invention.
[0018] Reaction of tetracarboxylic acid dianhydrides with
diamine(s) is carried out preferably in a N-methyl-2-pyrrolidone
solvent, but can be carried out also in a polar solvent such as
dimethylformamide, dimethyl-acetamide, m-cresol, etc. Actually,
diamine (mixture) or its solution in a polar solvent is dropwise
added to a solution in a polar solvent of tetracarboxylic acid
dianhydride mixture at about 0.degree.-about 60.degree. C., and
then subjected to reaction at about 0.degree.-about 60.degree. C.
for about 0.5-about 5 hours to form polyamic acid as a polyimide
precursor copolymer.
[0019] The polyamic acid solution in a polar solvent is applied to
a metallic foil, typically a copper foil, and after removal of the
solvent by drying, polyimidization reaction is carried out by
heating. To promote dehydration cyclization reaction for the
polyimidization, the polyamic acid-applied metallic foil is passed
through a drying oven heated to a temperature of about
150.degree.-about 450.degree. C., preferably about 200.degree.
C.-about 400.degree. C., to form a metal laminate substantially
free from the solvent. The polar solvent used in the synthesis
reaction of polyimide precursor copolymer can be used as a polar
solvent for the polyanaic acid as such. N-methyl-2-pyrrolidone is a
preferable polar solvent.
[0020] As a result of reaction between tetracarboxylic acid
dianhydride (A) and diamine (C), a polyimide copolymer with the
following repeat unit can be obtained:
##STR00005##
[0021] As a result of the reaction between the tetracarboxylic acid
dianhydride (B) and the diamine (C), a polyimide copolymer with the
following repeat unit can be obtained in addition to the
above-mentioned repeat unit:
##STR00006##
[0022] When diamine (D.sub.1) is used together with diamine (C), a
polyimide copolymer with the following repeat units can be obtained
by reaction with the tetracarboxylic acid dianhydrides (A) and
(B):
##STR00007##
When diamine (D.sub.2) is used together with diamine (C), a
polyimide copolymer with the following repeat units can be obtained
by reaction with the tetracarboxylic acid dianhydrides (A) and
(B):
##STR00008##
[0023] Polyimide copolymers having said repeat units are insoluble
in various solvents and thus their molecular weights or viscosities
cannot be determined or the ranges thereof cannot be specified, but
it is certain that these polyimide copolymers have molecular
weights necessary for enabling film formation. In the stage of
polyamic acids which are deemed to be in a form of polyimide
precursor copolymers, it is possible to determine a viscosity of a
reaction mixture solution at a given concentration of solid
matters, but the viscosity is of variable nature, e.g. dependent on
reaction time, etc.
[0024] Polyimide copolymer obtained by polycondensation of
isopropylidene-bis(4-phenyleneoxy-4-phthalic acid) dianhydride and
6-amino-2-(p-amino-phenyl)benzimidazole, as disclosed in the
afore-mentioned WO 01/29136, is soluble by itself in a solvent such
as dimethyl formamide, dimethyl acetamide, N-methyl-2-pyrrolidone,
m-cresol, etc., and when a solution of such a copolymer is applied
to a metallic foil, a metal laminate with a satisfactory peel
strength can be obtained.
[0025] On the other hand, the present polyimide copolymer obtained
by using isopropylidenebis(4-phenyleneoxy-4-phthalic acid)
dianhydride and 3,3',4,4'-biphenyltetracarboxylic acid dianhydride
as acid dianhydrides to be polycondensated with
6-amino-2-(p-aminophenyl)benzimidazole is insoluble in various
solvents, as mentioned above, and a metal laminate obtained by
laminating the present polyimide copolymer to a metallic foil has a
distinguished curling resistance and an improved coefficient of
linear thermal expansion or percent heat shrinkage.
[0026] A polyimide copolymer film having a thickness of about
5-about 50 .mu.m with good mechanical strength and thermal
dimensional stability can be also obtained by removing the metallic
foil from the thus formed metal laminate.
BEST MODES FOR CARRYING OUT THE INVENTION
[0027] The present invention Will be described below, referring to
Examples.
Example 1
[0028] A solution containing 520.1 g (1.0 mole) of (A)
isopropylidenebis(4-phenyleneoxy-4-phthalic acid) dianhydride and
294.0 g (1.0 mole) of (B) 3,3',4,4'-biphenyltetracarboxylic acid
dianhydride in 7,150 ml of N-methyl-2-pyrrolidone was charged into
a four-necked flask having a capacity of 10 L and provided with a
stirrer in a nitrogen gas-flushed atmosphere, and then 448.0 g (2.0
moles) of (C) 6-amino-2-(p-aminophenyl)-benzimidazole was charged
thereto, while keeping the temperature not higher than 60.degree.
C. The resulting mixture was stirred at room temperature for three
hours to obtain 8,245 g of a varnish-state polyimide precursor
copolymer solution (viscosity at 25.degree. C.: 7,900 cps;
concentration of solid matters: 15 wt. %).
[0029] The above-mentioned polyimide precursor copolymer solution
was applied to a roughened surface of rolled electrolytic copper
foil (product of Furukawa Electric Co., Ltd.; thickness 10 .mu.m)
with a coat thickness of 18 .mu.m using a reverse type roll coater,
and then the solvent was continuously removed therefrom through a
hot air drying oven at 120.degree. C., followed by heat treatment
by elevating the temperature up to 400.degree. C. over 10 minutes
to form a 12.5 .mu.m-thick polyimide layer on the copper foil.
Example 2
[0030] In Example 1, the amount of component (A) was changed to
260.0 g (0.5 moles), that of component (B) to 441.0 g (1.5 moles)
and that of N-methyl-2-pyrrolidone to 6,510 ml, respectively, and
7,572 g of a varnish-state polyimide precursor copolymer solution
(8,200 cps; 15 wt. %) was obtained. A polyimide-laminated copper
foil was manufactured from the thus obtained polyimide precursor
copolymer solution in the same manner as in Example 1.
Example 3
[0031] In Example 2, the amount of N-methyl-2-pyrrolidone was
changed to 6,520 ml and that of component (C) to 403.2 g (1.8
moles), respectively, while 40.0 g (0.2 moles) of (D.sub.1)
bis(4-aminophenyl)ether was additional used. 7,470 g of a
varnish-state polyimide precursor copolymer solution (5,500 cps; 15
wt. %) was obtained. A polyimide-laminated copper foil was
manufactured from the thus obtained polyimide precursor copolymer
solution in the same manner as in Example 1.
Example 4
[0032] In Example 3, the amount of N-methyl-2-pyrrolidone was
changed to 6,200 ml, that of component (C) to 313.6 g (1.4 moles)
and that of component (D.sub.1) to 80.0 g (0.6 moles),
respectively. 7,221 g of a varnish-state polyimide precursor
copolymer solution (3,800 cps; 15 wt. %) was obtained. A
polyimide-laminated copper foil was manufactured from the thus
obtained polyimide precursor copolymer solution in the same manner
as in Example 1.
[0033] The copper foil/polyimide laminates obtained in the
foregoing Examples and polyimide films obtained by removing the
copper foils from the laminates by etching were subjected to
determination of the following items.
[0034] Glass transition temperature (Tg): Loss elastic modulus E''
in terms of Pa unit was obtained from dynamic viscoelasticity
determined by a dynamic viscoelasticity analyzer DMe 7e made by
Parkin Elmer Co., Ltd. and maximum E'' was made "Tg"
[0035] Coefficient of linear thermal expansion
(100.degree.-200.degree. C.) (CTE): A film sample obtained from a
laminate, 10 cm.times.10 cm, by etching, and stress relaxed by
heating to 400.degree. C. was fixed to a TMA tester and subjected
to determination in a tensile mode under such conditions as load: 2
g, sample length: 20 mm and temperature elevation rate: 10.degree.
C./min
[0036] Adhesive strength: A laminate, 1 cm.times.10 cm, was
subjected to determination according to JIS C-6481
[0037] Tensile strength and elongation at break: A film obtained
from a laminate, 10 cm.times.20 cm, by etching was subjected to
determination according to ASTM D-882-83 Water absorbability: A
film obtained from a laminate, 11 cm.times.11 cm, by etching was
dried at 150.degree. C. for 60 minutes (dry weight W1) and then
dipped in distilled water at 23.degree. C. for 24 hours
(after-dipping weight W.sub.2), then determined as a change in
weight by the equation of (W.sub.2-W.sub.1)/W.sub.1.times.100
[0038] Percent shrinkage after etching: Percent dimensional changes
in MD direction and TD direction before and after etching were
determined according to JIS C-6481
[0039] Percent heat shrinkage: A film obtained from a laminate, 10
cm.times.20 cm, by etching was subjected to heat treatment in a hot
air oven at 150.degree. C. for 30 minutes to determine percent
dimensional changes in MD direction and TD direction before and
after the heat treatment
[0040] Curling: A laminate, 5 cm.times.5 cm, was gently placed on a
horizontal flat base to bring the laminate into a concave state
thereon, and the state was visually observed without applying any
particular external force thereto
[0041] Results of determination and observation are shown in the
following Table 1.
TABLE-US-00001 TABLE 1 Determination/observation item Ex. 1 Ex. 2
Ex. 3 Ex. 4 Tg (.degree. C.) 306 323 318 301 CTE (ppm/.degree. C.)
32 17 23 32 Adhesive strength (Kg/cm) 1.80 1.92 1.85 1.90 Tensile
strength (MPa) 164 244 237 240 Elongation at break (%) 46 36 47 66
Water absorbability (%) 2.98 3.36 3.05 2.27 Percent shrinkage after
etching MD direction (%) -0.05 0.099 0.067 -0.054 TD direction (%)
-0.118 0.061 0.048 -0.084 Percent heat shrinkage MD direction (%)
-0.165 0.121 0.037 -0.086 TD direction (%) -0.181 0.05 0.013 -0.107
Curling Laminate flat flat flat flat
Comparative Example 1
[0042] In Example 1, the amount of component (B) was changed to
588.0 g (2.0 moles) and that of N-methyl-2-pyrrolidone to 5,870 ml,
respectively, without using component (A). 6,699 g of a
varnish-state polyimide precursor copolymer solution (6,450 cps; 15
wt. %) was obtained. A polyimide-laminated copper foil was
manufactured from the thus obtained polyimide precursor copolymer
solution in the same manner as in Example 1.
Comparative Example 2
[0043] In Example 1, the amount of component (A) was changed to
936.0 g (1.8 moles), that of component (B) to 58.8 g (0.2 moles)
and that of N-methyl-2-pyrrolidone to 8,170 ml, respectively. 9,234
g of a varnish-state polyimide precursor copolymer solution (2,500
cps; 15 wt. %) was obtained. A polyimide-laminated copper foil was
manufactured from the thus obtained polyimide precursor copolymer
solution in the same manner as in Example 1.
Comparative Example 3
[0044] In Example 3, the amount of N-methyl-2-pyrrolidone was
changed to 6,400 ml, that of component (C) to 224.0 g (1.0 mole)
and that of component (Dj) to 200.0 g (1.0 mole), respectively.
7,375 g of a varnish-state polyimide precursor copolymer solution
(2,700 cps; 15 wt. %) was obtained. A polyimide-laminated copper
foil was manufactured from the thus obtained polyimide precursor
copolymer solution in the same manner as in Example 1.
Comparative Example 4
[0045] In Example 3, the amount of N-methyl-2-pyrrolidone was
changed to 6,270 ml, that of component (C) to 44.8 g (0.2 moles)
and that of component (D.sub.1) to 360.0 g (1.8 moles),
respectively. 6,981 g of a varnish-state polyimide precursor
copolymer solution (7,900 cps; 15 wt. %) was obtained. A
polyimide-laminated copper foil was manufactured from the thus
obtained polyimide precursor copolymer solution in the same manner
as in Example 1.
[0046] The copper foil/polyimide laminates obtained in the
foregoing Comparative Examples and polyimide films obtained by
removing the copper foils from the laminates by etching were
subjected to the same determination and observation as in Examples
1 to 4. Results of determination and observation are shown in the
following Table 2. In Comparative Example 1, the film after etching
was so brittle that determination of "percent shrinkage after
etching" and "percent heat shrinkage" could not be determined.
TABLE-US-00002 TABLE 2 Comp. Comp. Comp. Comp.
Determination/observation item Ex. 1 Ex. 2 Ex. 3 Ex. 4 Tg (.degree.
C.) 341 301 276 266 CTE (ppm/.degree. C.) 6.5 48 39 47 Adhesive
strength (Kg/cm) 0.5 -- -- -- Tensile strength (MPa) 329 133 191
185 Elongation at break (%) 20 60 62 80 Water absorbability (%)
3.75 2.61 1.93 1.20 Percent shrinkage after etching MD direction
(%) -- -0.163 -0.136 -0.285 TD direction (%) -- -0.228 -0.242
-0.270 Percent heat shrinkage MD direction (%) -- -0.404 -0.237
-0.401 TD direction (%) -- -0.411 -0.346 -0.495 Curling Laminate
large large large
Example 5
[0047] A solution containing 208.0 g (0.4 moles) of (A)
isopropylidenebis(4-phenyleneoxy-4-phthalic acid) dianhydride and
470.4 g (1.6 moles) of (B) 3,3',4,4'-biphenyltetracarboxylic acid
dianhydride in 5,460 ml of N-methyl-2-pyrrolidone was charged into
a four-necked flask having a capacity of 10 L and provided with a
stirrer in a nitrogen gas-flushed atmosphere, and a mixture
consisting of 134.4 g (0.6 moles) of (C)
6-amino-2-(p-aminophenyl)benzimidazole and 152.2 g (1.4 moles) of
(D.sub.2) p-phenylene-diamine was added thereto, while keeping the
temperature not higher than 30.degree. C. Then, the resulting
mixture was stirred at room temperature for three hours to obtain
6,420 g of a polyimide precursor copolymer solution (concentration
of solid matters: 15 wt. %; viscosity at 25.degree. C.: 2,150 cps).
The resulting polyimide precursor varnish was continuously applied
to the roughened surface of a rolled electrolytic copper foil
(thickness: 10 .mu.m; a product made by the Furukawa Electric Co.,
Ltd.) with a coat thickness of 18 .mu.m using a reverse type roll
coater, and then the solvent was continuously removed therefrom
through a hot air drying oven at 120.degree. C., followed by heat
treatment for polyimidization by elevating the temperature up to
400.degree. C. over 10 minutes to obtain a copper foil/polyimide
laminate with a 12.5 .mu.m-thick polyimide layer and without any
curling.
Example 6
[0048] In Example 5, the amount of N-methyl-2-pyrrolidone was
changed to 5,730 ml, that of component (C) to 224.0 g (1.0 mole)
and that of component (D.sub.2) to 108.0 g (1.0 mole),
respectively. 6,736 g of a polyimide precursor copolymer solution
(concentration of solid matters: 15 wt. %; viscosity: 1,850 cps)
was obtained. A curling-free copper foil/polyimide laminate was
also manufactured from the thus obtained polyimide precursor
varnish in the same manner as in Example 5.
Example 7
[0049] In Example 5, the amount of component (A) was changed to
260.0 g (0.5 moles), that of component (B) to 441.0 g (1.5 moles),
that of N-methyl-2-pyrrolidone to 5,720 ml, that of component (C)
to 179.2 g (0.8 moles) and that of component (D.sub.2) to 129.2 g
(1.2 moles), respectively. 6,723 g of a polyimide precursor
copolymer solution (concentration of solid matters: 15 wt. %;
viscosity: 2,180 cps) was obtained. A curling-free copper
foil/polyimide laminate was also manufactured from the thus
obtained polyimide precursor varnish in the same manner as in
Example 5.
Example 8
[0050] In Example 5, the amount of component (A) was changed to
260.0 g (0.5 moles), that of component (B) to 441.0 g (1.5 moles),
that of N-methyl-2-pyrrolidone to 5,850 ml, that of component (C)
to 224.0 g (1.0 mole) and that of component (D.sub.2) to 108.0 g
(1.0 mole), respectively. 6,880 g of a polyimide precursor
copolymer solution (concentration of solid matters: 15 wt. %;
viscosity: 2,300 cps) was obtained. A curling-free copper
foil/polyimide laminate was also manufactured from the thus
obtained polyimide precursor varnish in the same manner as in
Example 5.
Example 9
[0051] A solution containing 156.0 g (0.3 moles) of (A)
isopropylidenebis(4-phenyleneoxy-4-phthalic acid) dianhydride and
500.0 g (1.7 moles) of (B) 3,3',4,4'-biphenyltetracarboxylic acid
dianhydride in 5,800 ml of N-methyl-2-pyrrolidone was charged into
a four-necked flask having a capacity of 10 L and provided with a
stirrer in a nitrogen gas-flushed atmosphere, and a mixture
consisting of 180.0 g (0.8 moles) of (C)
6-amino-2-(p-aminophenyl)benzimidazole, 120.0 g (0.6 moles) of
(D.sub.1) bis(4-aminophenyl)ether and 64.0 g (0.6 moles) of
(D.sub.2) p-phenylenediamine was added thereto, while keeping the
temperature not higher than 30.degree. C. The mixture was stirred
at room temperature for three hours to obtain 6,800 g of a
polyimide precursor copolymer solution (concentration of solid
matters: 15 wt. %; viscosity at 25.degree. C.: 5,500 cps). A
curling-free copper foil/polyimide laminate was also manufactured
from the thus obtained polyimide precursor varnish in the same
manner as in Example 5.
Comparative Example 5
[0052] In Example 5, the amount of component (B) was changed to
588.0 g (2.0 moles), that of N-methyl-2-pyrrolidone to 5,260 ml,
that of component (C) to 134.4 g (0.6 moles) and that of component
(D.sub.2) to 86.4 g (0.8 moles), respectively, without using
component (A). 120.0 g (0.6 moles) of bis(4-aminophenyl)ether was
further used. 6,182 g of a polyimide precursor copolymer solution
(concentration of solid matters: 15 wt. %; viscosity: 3,200 cps)
was obtained. A copper foil/polyimide laminate was also
manufactured from the thus obtained polyimide precursor varnish in
the same manner as in Example 5.
Comparative Example 6
[0053] In Example 5, the amount of N-methyl-2-pyrrolidone was
changed to 5,060 ml and that of component (D.sub.2) to 216.0 g (2.0
moles), respectively, without using component (C). 5,963 g of a
polyimide precursor copolymer solution (concentration of solid
matters: 15 wt. %; viscosity: 1,000 cps) was obtained. A copper
foil/polyimide laminate was also manufactured from the thus
obtained polyimide precursor varnish in the same manner as in
Example 5.
[0054] The copper foil/polyimide laminates obtained in the
foregoing Examples 5 to 9 and Comparative Example 5 and polyimide
films obtained by removing the copper foils from the laminates by
etching were subjected to the same determination and observation as
in Examples 1 to 4. Determination of elastic modulus and evaluation
of curling were carried out in the following manner:
[0055] Elastic modulus: Films obtained from laminates, 10
cm.times.20 cm, by etching were subjected to determination
according to ASTM D-882-83
[0056] Curling: Laminates, 5 cm.times.5 cm, films obtained
therefrom by etching and the same films subjected to heat treatment
at 150.degree. C. for one hour, were gently placed on a horizontal
flat base to bring them into a concave state thereon, and the state
was visually observed without applying any external force
thereto
[0057] Results of determination and observation are shown in the
following Table 3. In Comparative Example 6, the film obtained by
etching was broken, so that other items than adhesive strength (0.3
Kg/cm) could not be determined, and curling of the laminate itself
was observed.
TABLE-US-00003 Comp. Determination/observation item Ex. 5 Ex. 6 Ex.
7 Ex. 8 Ex. 9 Ex. 5 Tg (.degree. C.) 312 330 311 321 304 329 CTE
(ppm/.degree. C.) 21 19 23 23 25 18 Adhesive strength (Kg/cm) 1.2
1.5 1.1 1.2 1.0 1.2 Elastic modulus (GPa) 4.8 3.8 4.2 3.9 4.2 4.1
Tensile strength (MPa) 256 204 202 193 198 239 Elongation at break
(%) 47 30 38 32 48 42 Water absorbability (%) 2.3 3.0 2.3 2.8 2.1
3.0 Percent shrinkage after etching MD direction (%) 0.049 0.085
0.023 0.043 -0.013 0.069 TD direction (%) 0.060 0.109 0.035 0.049
-0.011 0.076 Percent heat shrinkage MD direction (%) 0.039 0.081
-0.022 0.016 -0.084 0.083 TD direction (%) 0.058 0.110 -0.019 0.035
-0.062 0.090 Curling Laminate flat flat flat flat flat a little
curled Film obtained by etching flat flat flat flat flat a little
curled Heat-treated film flat flat flat flat flat pencil state
NOTE) "Pencil state" means such a state that the film is curled and
shrinked into a bar-like form
INDUSTRIAL UTILITY
[0058] A metal laminate manufactured by laminating the present
novel polyimide copolymer to a metallic foil has a low curling
susceptibility to cause curling, twisting, warping, etc. against
temperature changes due to a low coefficient of linear thermal
expansion of the polyimide copolymer, and also has satisfactory
adhesiveness and thermal dimensional stability and a low water
absorbability, and thus can be used as a suitable for a flexible,
finely printed circuit board requiring a high dimensional
stability.
[0059] Furthermore, in the manufacture of a metal laminate by
laminating a polyimide copolymer layer directly to a metallic foil
without interposing an adhesive layer therebetween, it is not
necessary to form a plurality of polyimide copolymer layers as in
the prior art. In the present invention, a metal laminate with
desired properties can be manufactured by a simple method, i.e. by
forming a single polyimide copolymer layer on a metallic foil.
* * * * *