U.S. patent application number 14/230298 was filed with the patent office on 2014-10-02 for coverlay for high-frequency circuit substrate.
This patent application is currently assigned to E I DU PONT DE NEMOURS AND COMPANY. The applicant listed for this patent is E I DU PONT DE NEMOURS AND COMPANY. Invention is credited to SHOTARO HIDAKA, TAKESHI INABA, HIDEAKI MACHIDA, SHINYA MURAKAMI, TAKESHI TANAKA.
Application Number | 20140295189 14/230298 |
Document ID | / |
Family ID | 49515261 |
Filed Date | 2014-10-02 |
United States Patent
Application |
20140295189 |
Kind Code |
A1 |
HIDAKA; SHOTARO ; et
al. |
October 2, 2014 |
COVERLAY FOR HIGH-FREQUENCY CIRCUIT SUBSTRATE
Abstract
To provide a coverlay for a high-frequency circuit substrate,
that uses polyimide film and fluororesin, has excellent mechanical
properties and heat resistance, and can increase workability during
the manufacture of high-frequency circuit substrates. Resolution
Means: The coverlay for a high-frequency circuit substrate
including a polyimide film and a fluororesin bonded together, and
an adhesive strength between the polyimide film layer and the
fluororesin layer being greater than 3.0 N/cm.
Inventors: |
HIDAKA; SHOTARO; (AICHI,
JP) ; TANAKA; TAKESHI; (CHUO-KU, JP) ;
MACHIDA; HIDEAKI; (CHUO-KU, JP) ; INABA; TAKESHI;
(OSAKA-FU, JP) ; MURAKAMI; SHINYA; (OSAKA-FU,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
E I DU PONT DE NEMOURS AND COMPANY |
Wilmington |
DE |
US |
|
|
Assignee: |
E I DU PONT DE NEMOURS AND
COMPANY
Wilmington
DE
|
Family ID: |
49515261 |
Appl. No.: |
14/230298 |
Filed: |
March 31, 2014 |
Current U.S.
Class: |
428/422 ;
428/421 |
Current CPC
Class: |
B65H 2515/32 20130101;
B32B 27/08 20130101; B65H 7/06 20130101; B65H 7/20 20130101; B65H
2553/51 20130101; B32B 2457/08 20130101; B65H 2404/143 20130101;
Y10T 428/3154 20150401; B65H 5/06 20130101; Y10T 428/31544
20150401; B41J 13/0027 20130101; B65H 5/062 20130101; B65H
2301/4474 20130101; B65H 2553/51 20130101; B65H 2220/02 20130101;
B65H 2220/02 20130101; B65H 2220/09 20130101; B65H 2220/01
20130101; B65H 2220/03 20130101; B65H 2220/09 20130101; B65H
2515/31 20130101; B32B 27/322 20130101; B32B 27/34 20130101; B65H
2515/31 20130101; B65H 2301/4474 20130101; B65H 2404/143 20130101;
B65H 2220/09 20130101; B65H 2301/4474 20130101; B65H 2515/32
20130101; H05K 1/036 20130101 |
Class at
Publication: |
428/422 ;
428/421 |
International
Class: |
H05K 1/03 20060101
H05K001/03; B32B 27/34 20060101 B32B027/34; B32B 27/32 20060101
B32B027/32; B32B 27/08 20060101 B32B027/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2013 |
JP |
2013-72750 |
Claims
1. A coverlay for a high-frequency circuit substrate, the coverlay
comprising a polyimide film and a fluororesin bonded together, and
an adhesive strength between the polyimide film layer and the
fluororesin layer being greater than 3.0 N/cm.
2. The coverlay as described in claim 1, wherein a thermal
shrinkage thereof at 260.degree. C. for 30 minutes is less than
.+-.0.1%.
3. The coverlay as described in claim 1 or 2, wherein the
fluororesin has a melting point of 200.degree. C. or less.
4. The coverlay as described in any one of claims 1 through 3,
wherein the fluororesin is a fluorine-containing ethylenic polymer,
and the fluorine-containing ethylenic polymer contains a carbonyl
group.
5. The coverlay as described in claim 4, wherein a quantity of
carbonyl groups contained in the fluorine-containing ethylenic
polymer totals 3 to 1000 groups per 1.times.10.sup.6 main-chain
carbon atoms.
6. The coverlay as described in any one of claims 1 through 3,
wherein the fluororesin is made up of fluorine-containing ethylenic
polymer that has at least one type selected from a group made up of
carbonate groups, carboxylic acid halide groups, and carboxylic
acid groups totaling 3 to 1000 groups per 1.times.10.sup.6
main-chain carbon atoms.
7. The coverlay as described in any one of claims 1 through 3,
wherein the fluororesin is one or more types of fluorine-containing
ethylenic monomer selected from a group made up of
tetrafluoroethylene, vinylidene fluoride, chlorotrifluoroethylene,
vinyl fluoride, hexafluoropropylene, hexafluoroisobutene, monomers
represented by the following formula (X):
CH.sub.2.dbd.CR.sup.1(CF.sub.2).sub.nR.sup.2 (X) (wherein R.sup.1
represents H or F, R.sup.2 represents H, F, or Cl, and n is a
positive integer in a range 1 to 10), and perfluoro(alkyl vinyl
ethers) having 2 to 10 carbon atoms, or a fluorine-containing
ethylenic polymer made by polymerizing the fluorine-containing
ethylenic monomer and an ethylenic monomer having 5 or fewer carbon
atoms.
8. The coverlay as described in any one of claims 1 through 3,
wherein the fluororesin is a copolymer made by polymerizing at
least the following (a), (b), and (c); (a) 20 to 90 mol % of
tetrafluoroethylene, (b) 10 to 80 mol % of ethylene, and (c) 1 to
70 mol % of a compound represented by the formula:
CF.sub.2.dbd.CFR.sup.3 (Y) (wherein R.sup.3 represents CF.sub.3 or
OR.sup.4, and R.sup.4 represents a perfluoroalkyl group having 1 to
5 carbon atoms).
9. The coverlay as described in any one of claims 1 through 8,
wherein the polyimide film is made up mainly of one or more
aromatic diamine components selected from a group made up of
paraphenylene diamine, 3,4'-diaminodiphenyl ether, and
4,4'-diaminodiphenyl ether, and one or more acid anhydride
components selected from a group made up of pyromellitic acid
dianhydride and 3,3',4,4'-biphenyl tetracarboxylic acid
dianhydride.
Description
BACKGROUND OF THE DISCLOSURE
[0001] The present invention pertains to a coverlay for a
high-frequency circuit substrate.
[0002] Printed wiring boards are used widely in electronic and
electrical equipment. Among them, flexible printed wiring boards
that can be bent are widely used in the bending parts of personal
computers, portable telephones, and the like, and in parts that
require bending, such as hard disks.
[0003] As substrates for such flexible printed wiring boards and
substrates for coverlays for protecting printed wiring boards,
normally various types of polyimide film are used in consideration
of such properties as heat resistance, dimensional stability,
flexibility, high bendability, and ease of making into a thin film,
and most coverlays are made of a combination of polyimide film and
adhesive.
[0004] With the growth in the volume of information being
transmitted in recent years, there is an increasing demand for
circuit substrates for high frequency applications. As the
frequency used for transmission increases, the increase in
frequency is also accompanied by more transmission loss. Because
circuits with high transmission loss are not practical, in order to
transmit information efficiently at high frequencies it is
necessary to reduce the transmission loss.
[0005] Transmission loss can be reduced by lowering the dielectric
constant of the substrate or coverlay, and because of this,
low-dielectric-constant substrates and coverlays are in demand.
Normally the dielectric constant of the polyimide film that is used
in the substrates and coverlays of flexible printed circuit boards
is 3.0 to 3.5, which is insufficient for a low-dielectric-constant
material.
[0006] So as a way to reduce the dielectric constant, methods have
been developed in which a fluororesin of low dielectric constant is
laminated between the copper and polyimide layer in the circuit
wires that are used in the substrate (the copper foil is etched on
the side of a copper-clad laminate (CCL)) (see Japanese Patent No.
2890747 and Japanese Patent No. 4917745 (Patent Documents 1 and
2)).
[0007] But in the process of manufacturing a circuit substrate
using the coverlay, if for example, kiss lamination is done by
aligning the positions of a copper-clad laminate and a coverlay, in
some cases, some time may be needed for the aligning in order to
prevent attachment misalignment, and further improvements in
manufacturing efficiency have been requested for industrial
implementation.
[0008] From such considerations, it has been desired that a
coverlay be developed that uses fluororesin, and has as a base
material a new polyimide film that is easy to process and is a low
dielectric constant material for use in high-frequency circuit
substrates. [0009] Patent Document 1: Japanese Patent No. 2890747
[0010] Patent Document 2: Japanese Patent No. 4917745
SUMMARY
[0011] An object of the present invention is to provide a coverlay
for a high-frequency circuit substrate that employs polyimide film
and fluororesin, has excellent mechanical properties and heat
resistance, and can improve workability during manufacture of a
high-frequency circuit substrate.
[0012] That is, the present invention pertains to the following
invention.
[0013] 1. A coverlay for a high-frequency circuit substrate, the
coverlay comprising a polyimide film and a fluororesin bonded
together, and an adhesive strength between the polyimide film layer
and the fluororesin layer being greater than 3.0 N.
[0014] 2. The coverlay according to 1 above, wherein a thermal
shrinkage thereof at 260.degree. C. for 30 minutes is less than
.+-.0.1%.
[0015] 3. The coverlay according to 1 or 2 above, wherein the
fluororesin has a melting point of 200.degree. C. or less.
[0016] 4. The coverlay according to any of 1 to 3 above, wherein
the fluororesin is a fluorine-containing ethylenic polymer, and the
fluorine-containing ethylenic polymer contains a carbonyl
group.
[0017] 5. The coverlay according to 4 above, wherein a quantity of
carbonyl groups contained in the fluorine-containing ethylenic
polymer totals 3 to 1000 groups per 1.times.10.sup.6 main-chain
carbon atoms.
[0018] 6. The coverlay according to any of 1 to 3 above, wherein
the fluororesin is made up of fluorine-containing ethylenic polymer
that has at least one type selected from a group made up of
carbonate groups, carboxylic acid halide groups, and carboxylic
acid groups totaling 3 to 1000 groups per 1.times.10.sup.6
main-chain carbon atoms.
[0019] 7. The coverlay according to any of 1 to 3 above, wherein
the fluororesin is one or more types of fluorine-containing
ethylenic monomer selected from a group made up of
tetrafluoroethylene, vinylidene fluoride, chlorotrifluoroethylene,
vinyl fluoride, hexafluoropropylene, hexafluoroisobutene, monomers
represented by the following formula (X):
CH.sub.2.dbd.CR.sup.1(CF.sub.2).sub.nR.sup.2 (X)
[0020] (wherein R.sup.1 represents H or F, R.sup.2 represents H, F,
or Cl, and n is a positive integer in the range of 1 to 10), and
perfluoro(alkyl vinyl ethers) having 2 to 10 carbon atoms, or a
fluorine-containing ethylenic polymer made by polymerizing the
fluorine-containing ethylenic monomer and an ethylenic monomer
having 5 or fewer carbon atoms.
[0021] 8. The coverlay according to any one of 1 to 3 above,
wherein the fluororesin is a copolymer made by polymerizing at
least the following (a), (b), and (c).
[0022] (a) 20 to 90 mol % of tetrafluoroethylene,
[0023] (b) 10 to 80 mol % of ethylene, and
[0024] (c) 1 to 70 mol % of a compound represented by the
formula:
CF.sub.2.dbd.CFR.sup.3 (Y)
[0025] (wherein R.sup.3 represents CF.sub.3 or OR.sup.4, and
R.sup.4 represents a perfluoroalkyl group having 1 to 5 carbon
atoms).
[0026] 9. The coverlay according to any of 1 to 8 above, wherein
the polyimide film is made up mainly of one or more aromatic
diamine components selected from a group made up of paraphenylene
diamine, 3,4'-diaminodiphenyl ether, and 4,4'-diaminodiphenyl
ether, and one or more acid anhydride components selected from a
group made up of pyromellitic acid dianhydride and
3,3',4,4'-biphenyl tetracarboxylic acid dianhydride.
[0027] The high-frequency circuit substrate coverlay of the present
invention is industrially useful because, with its excellent
mechanical properties and heat resistance, it enhances workability
during the manufacture of high-frequency circuit substrates. Also,
with a high-frequency circuit substrate that employs the coverlay
of the present invention, the low-dielectric-constant fluororesin
can be made so that the dielectric constant is low and the
transmission loss is kept in check.
BRIEF DESCRIPTION OF THE DRAWING
[0028] FIG. 1 shows the results of measuring the transmission
properties of circuits employing the coverlays of the working
examples and of the comparison examples.
DETAILED DESCRIPTION
[0029] The coverlay of the present invention for a high-frequency
circuit substrate is a coverlay that is made up of a polyimide film
and a fluorosein bonded together, and the adhesive strength between
the polyimide film layer and the fluororesin layer (initial
adhesive force) exceeds 3.0 N/cm.
[0030] In manufacturing the polyimide film that is used in this
coverlay, first, a polyamic acid solution is prepared by
polymerizing an aromatic diamine component and an acid anhydride
component in an organic solvent.
[0031] Specific examples of the aromatic diamine component include
paraphenylene diamine, metaphenylene diamine, benzidine,
paraxylilene diamine, 4,4'-diaminodiphenyl ether,
3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl methane,
4,4'-diaminodiphenyl sulfone, 3,3'-dimethyl-4,4'-diaminodiphenyl
methane, 1,5-diaminonaphthalene, 3,3'-dimethoxybentidine, 1,4-bis
(3 methyl-5 aminophenyl)benzene, and amidic derivatives thereof.
Among these, it is preferable for circuit substrate applications to
adjust the amounts of the diamines such as paraphenylene diamine,
3,4'-diaminodiphenyl ether, and the like, which are effective in
increasing the tensile strength of the film, so that the tensile
strength of the polyimide film that is ultimately obtained is 3.0
GPa or more. Of these aromatic diamines, paraphenylene diamine,
4,4'-diaminodiphenyl ether, and 3,4'-diaminodiphenyl ether are
preferable. These may be used either singly as one type, or with
two or more type thereof mixed together. If paraphenylene diamine
and 4,4'-diaminodiphenyl ether and/or 3,4'-diaminodiphenyl ether
are used together, there are no particular restrictions on their
blending ratio (mole ratio), but it is preferable that the ratio of
4,4'-diaminodiphenyl ether and/or 3,4'-diaminodiphenyl
ether:paraphenylene diamine=69:31 to 100:0 (except 0), and more
preferable that it be 70:30 to 90:10.
[0032] Specific examples of the acid anhydride component include
pyromellitic acid, 3,3',4,4'-biphenyl tetracarboxylic acid,
2,3',3,4'-biphenyl tetracarboxylic acid, 3,3',4,4'-benzophenone
tetracarboxylic acid, 2,3,6,7-naphthalene dicarboxylic acid,
2,2-bis(3,4-dicarboxylphenyl)ether,
pyridine-2,3,5,6-tetracarboxylic acid, and acid anhydrides of
amidic derivatives thereof and the like. Among these acid
anhydrides, pyromellitic acid, 3,3',4,4'-biphenyl tetracarboxylic
acid, 2,3',3,4'-biphenyl tetracarboxylic acid are preferable. These
may be used either singly as one type, or with two or more types
mixed together. As the mole ratio of the acid anhydride components,
if pyromellitic acid dianhydride and 3,3',4,4'-biphenyl
tetracarboxylic acid dianhydride are used together, there are no
particular restrictions on their blending ratio (mole ratio), but
it is preferable that the ratio of pyromellitic acid
dianhydride:3,3',4,4'-biphenyl tetracarboxylic acid dianhydride=0
(except 0):100 to 97:3, and more preferable that it be 30:70 to
95:5.
[0033] Examples of the polyimide film to be used in the coverlay of
the present invention preferably include mainly ones that are made
up of one or more aromatic diamine components selected from a group
made up of paraphenylene diamine, 3,4'-diaminodiphenyl ether, and
4,4'-diaminodiphenyl ether, and one or more acid anhydride
components selected from a group made up of pyromellitic acid
dianhydride and 3,3',4,4'-biphenyl tetracarboxylic acid
dianhydride.
[0034] As organic solvents that can be used for forming the
polyamic acid solution in the present invention, examples include
dimethyl sulfoxide, diethyl sulfoxide, and other sulfoxide
solvents; N,N-dimethyl form[amide], N,N-diethyl formamide, and
other formamide solvents; N,N-dimethyl acetoamide, N,N-diethyl
acetoamide, and other acetoamide solvents; N-methyl-2-pyrrolidone,
N-vinyl-2-pyrrolidone, and other pyrrolidone solvents; phenol, o-,
m-, or p-cresol, xylenol, phenol halide, catechol, and other phenol
solvents; or hexamethyl phosphoramide, .gamma.-butyrolactone, and
other aprotic polar solvents; it is desirable to use these either
singly or as a mixture of two or more types, and in addition,
aromatic hydrocarbons such as xylene or toluene may be used.
[0035] There are no particular restrictions on the polymerization
method; any well known method may be used, such as (1) a method of
polymerizing in which first the entire amount of the aromatic
diamine component is inserted into the solvent, and the acid
anhydride component is then added so that it becomes an amount
equivalent to the entire amount of the aromatic diamine
component.
[0036] (2) A method of polymerizing in which first the entire
amount of the acid anhydride component is inserted into the
solvent, then the aromatic diamine component is added so that it
becomes an amount equivalent to the acid anhydride component.
[0037] (3) A method of polymerizing in which a first aromatic
diamine component (a1) is inserted into the solvent, then a first
acid anhydride component (b1) is mixed at a ratio that becomes 95
to 105 mol % with respect to the reaction components for the time
needed for a reaction to occur, after which a second aromatic
diamine component (a2) is added, following which a second acid
anhydride component (b2) is added so that the entire aromatic
diamine component and the entire acid anhydride component become
roughly equivalent amounts.
[0038] (4) A method of polymerizing in which a first acid anhydride
component (b1) is inserted into the solvent, then a first aromatic
diamine component (a1) is mixed at a ratio that becomes 95 to 105
mol % with respect to the reaction components for the time needed
for a reaction to occur, after which a second acid anhydride
component (b2) is added, following which a second aromatic diamine
component (a2) is added so that the entire aromatic diamine
component and the entire acid anhydride component become roughly
equivalent amounts.
[0039] (5) A method wherein, in a solvent, a polyamic acid solution
(A) is prepared by causing reactions such that one or the other of
the first aromatic diamide component and an acid anhydride
component is in excess, and in a separate solvent, a polyamic acid
solution (B) is prepared by causing reactions so that one or the
other of the second aromatic diamine component and an acid
anhydride component is in excess, and then the polyamic acid
solutions (A) and (B) thereby obtained are mixed together and the
polymerization is completed. If when preparing the polyamic acid
solution (A), the aromatic diamine component is in excess, then
with the polyamic acid solution (B) the acid anhydride component is
made in excess, or when with the polyamic acid solution (A), the
acid anhydride component is in excess, then the aromatic diamine
component is made in excess with the polyamic acid solution (B).
The polyamic acid solutions (A) and (B) are mixed together, and an
adjustment is made so that the total aromatic diamine component and
acid anhydride component to be used in these reactions are of
roughly equivalent amounts.
[0040] Also, the polymerization methods are not limited thereto,
and one may also use any other well known method.
[0041] The polyamic acid solution that is thus obtained normally
contains a solid portion of 5 to 40 wt %, and preferably 10 to 30
wt %. Moreover, its viscosity is normally 10 to 10,000 Pas as
measured by a Brookfield viscometer, and is preferably 300 to 5,000
Pas for sake of stable liquid feeding. It is acceptable for the
polyamic acid in an organic solvent solution to be partially
imidized.
[0042] Next, the method for manufacturing the polyimide film of the
present invention, which employs the above polyamic acid solution,
is described.
[0043] Examples as methods for making the polyimide film include a
method in which the polyimide film is obtained by casting the
polyamic acid solution in film form and then thermally removing
rings and the solvent, and a method in which the polyimide film is
obtained by mixing a ring removal catalyst and dehydrating agent
into the polyamic acid solution to chemically remove rings and make
a gel film, which is then heated to remove the solvent.
[0044] The polyamic acid solution may contain a ring removal
catalyst (imidization catalyst), dehydrating agent, gelling
delaying agent, and the like.
[0045] Specific examples of the ring removal catalysts to be used
in the present invention include trimethyl amine, triethylene
diamine, and other aliphatic tertiary amines; dimethyl aniline and
other aliphatic tertiary amines; and isoquinoline, pyridine, beta
picoline, and other heterocyclic tertiary amines, and the like, but
heterocyclic tertiary amines are preferable. These may be used
either singly as one type or as a mixture of two or more types.
[0046] Specific examples of the dehydrating agents to be used in
the present invention include acetic anhydride, propionic
anhydride, butyric anhydride, and other aliphatic carboxylic
anhydrides, and benzoic anhydride and other aromatic carboxylic
anhydrides, and the like, but acetic anhydride and/or benzoic
anhydride are preferable.
[0047] As a method for manufacturing polyimide film from a polyamic
acid solvent, examples include a method in which a polyamic acid
solution that is made to contain the ring removal catalyst and the
dehydrating agent is made to flow from a slitted nozzle onto a
support body and is molded into a film form, imidization on the
support body is allowed to proceed partway, a gel film that can
support itself is made, then it is peeled off from the support
body, is heated, dried, and imidized, and is heat-treated.
[0048] The "support body" is a metal rotating drum or endless belt,
and its temperature is controlled by a liquid or gas heat transfer
medium and/or an electric heater or other radiant heat.
[0049] The gel film is heated normally to 30 to 200.degree. C., and
preferably to 40 to 150.degree. C. by being heated by the support
body and/or by being heated by hot air, an electric heater, or
another heat source, thereby causing ring closure reactions, and by
drying the volatile component, such as the organic solvent, that is
set free, the film acquires the ability to support itself, and is
peeled away from the support body.
[0050] The gel film that is peeled from the support body may as
necessary undergo a stretching extension treatment in the running
direction while regulating the running speed by a rotating roll.
The extension magnification (MDX) in the mechanical conveyance
direction and the extension magnification (TDX) in the direction
perpendicular to the mechanical conveyance direction are
implemented at 1.01 to 1.9-times, and preferably at 1.05 to
1.6-times.
[0051] The film dried in the drying zone is heated from 15 seconds
to 10 minutes by hot air, an infrared heater, or the like. Next, it
is heat-treated for 15 seconds to 20 minutes at a temperature of
250 to 500.degree. C. by hot air and/or an electric heater, or the
like.
[0052] Also, the running speed is adjusted to adjust the thickness
of the polyimide film, and the thickness of the polyimide film is
normally about 2 to 250 .mu.m, and preferably about 2 to 100 .mu.m.
Thicknesses thinner or thicker are undesirable because that would
significantly degrade the manufacturability of the film.
[0053] As the polyimide film to be used in the present invention,
commercially available products may be used. There are no
particular restrictions on the commercially available products, and
examples include Capton EN types (for example, 50EN-S (brand name,
made by Dupont-Toray Co., Ltd.), 100EN (brand name, made by
Dupont-Toray Co., Ltd.), and the like), Capton H types (for
example, Capton 100H (brand name, made by Dupont-Toray Co., Ltd.),
etc.), and the like.
[0054] The polyimide film in the present invention may include a
plasticizer or other resin, or the like to the extent that doing so
does not detract from the purpose of the present invention.
[0055] For the plasticizers, there are no particular restrictions,
and examples include hexylene glycol, glycerin, .beta.-naphthol,
dibenzyl phenol, octyl cresol, bisphenol A, and other bisphenol
compounds; p-hydroxyoctyl benzoate, p-hydroxy benzoic acid-2-ethyl
hexyl, p-hydroxy benzoic acid peptyl, p-hydroxy benzoic acid
ethylene oxide and/or propylene oxide adducts,
.epsilon.-caprolactone, phosphoric acid ester compounds of phenols,
N-methyl benzene sulfonamide, N-ethyl benzene sulfonamide, N-butyl
benzene sulfoneamide, toluene sulfonamide, N-ethyl toluene
sulfonamide, N-cyclohexyl toluene sulfonamide, and the like.
[0056] As the other resins to be blended into the polyimide, those
having superior compatibility are preferable, and examples include
ester and/or carboxylic acid modified olefin resin, acrylic resin
(in particular, acrylic resin that has a glutarimide group),
ionomer resin, polyester resin, phenoxy resin,
ethylene-propolyene-diene copolymer, polyphenylene oxide, and the
like.
[0057] The polyimide film in the present invention may include
colorants and various types of additives, insofar as this would not
detract from the purpose of the present invention. As the
additives, examples include antistatic agents, flame retardants,
heat stabilizers, ultraviolet ray absorbents, lubricants, mold
release agents, crystal nucleus agents, reinforcing agents
(fillers), and the like. Also, the surface of the polyimide film
may be coated with ink, and the like.
[0058] There are no particular restrictions on the fluororesin that
is used in the coverlay of the present invention, but a
fluorine-containing ethylenic polymer is preferable. In the
fluorine-containing ethylenic polymer in the present invention, a
carbonyl group or a functional group that contains a carbonyl group
is joined to the fluorine-containing ethylenic polymer chain.
[0059] The "carbonyl group" means a functional group having
--C(.dbd.O)-- that can basically react with the imide groups or
amino groups in the polyimide film. Specifically examples include
carbonates, carboxylic acid halides, aldehydes, ketones, carboxylic
acid, esters, acid anhydrides, isocyanate groups, and the like.
There are no particular restrictions on the carbonyl group, but
preferable for ease of introduction and high reactivity with the
polyamide resin are carbonate groups, carboxylic acid halide
groups, carboxylic acid groups, ester groups, and acid anhydride
groups, and more preferable are carbonate groups and carboxylic
acid halide groups.
[0060] The number of carbonyl groups in the fluorine-containing
ethylenic polymer in the present invention can be suitably selected
according to differences in the types of materials that are
laminated together, the shape, the purpose of the adhesion, the
application, the adhesive force that is required, the mode of
polymerization, and the method of adhesion, and the like, but it is
preferable that the number of carbonyl groups total 3 to 1000
groups per 1.times.10.sup.6 carbon atoms in the main chain. If the
number of the carbonyl groups per 1.times.10.sup.6 carbon atoms in
the main chain is less than 3, sometimes there will not be
sufficient adhesive force. Moreover, if it is greater than 1000,
sometimes the adhesive force will be reduced due to chemical
changes of the carbonyl groups during the adhesion operation. More
preferable is 3 to 500, even more preferable is 3 to 300, and
particularly preferable is 5 to 150. Also, the amount of carbonyl
groups in the fluorine-containing ethylenic polymer can be measured
by infrared absorption spectrum analysis.
[0061] Therefore if the fluorine-containing ethylenic polymer of
the present invention for example is one that has carbonate groups
and/or carboxylic acid halide groups, if it has carbonate groups,
it is preferable that the number of carbonate groups be 3 to 1000
per 1.times.10.sup.6 carbon atoms in the main chain, and if the
fluorine-containing ethylenic polymer of the present invention has
carboxylic acid halide groups, it is preferable that the number of
carboxylic acid halide groups be 3 to 1000 per 1.times.10.sup.6
carbon atoms in the main chain. If the fluorine-containing
ethylenic polymer of the present invention has both carbonate
groups and carboxylic acid halide groups, it is preferable that the
total number of carbonate groups and carboxylic acid halide groups
be 3 to 1000 per 1.times.10.sup.6 carbon atoms in the main chain.
If the number of the carbonate groups and/or carboxylic acid halide
groups is less than 3 per 1.times.10.sup.6 carbon atoms in the main
chain, sometimes there will not be sufficient adhesive force.
Moreover, if it is greater than 1000, sometimes, due to chemical
changes of the carbonate groups or carboxylic acid halide groups
during the adhesion operation, the production of gas coming from
the adhesive interface will have an adverse effect, and the
adhesive force will be reduced. From the standpoint of heat
resistance and resistance to chemicals, it is more preferable that
it be 3 to 500, even more preferable that it be 3 to 300, and
particularly preferable that it be 5 to 150. Also, if carboxylic
acid halide groups, which have excellent reactivity with polyamide
resin, are present in the fluorine-containing ethylenic polymer in
a quantity of 10 or more, and more preferably 20 or more per
1.times.10.sup.6 carbon atoms in the main chain, then even if the
quantity contained in the total of carbonyl groups is less than 150
per 1.times.10.sup.6 carbon atoms in the main chain, excellent
adhesion can be obtained with a layer (A) made up of polyamide
resin.
[0062] The carbonate group in the fluorine-containing ethylenic
polymer in the present invention is generally a group that has a
--OC(.dbd.O)O-- bond; specifically, it is one with a structure of
an --OC(.dbd.O)O--R group (where R is an organic group (for
example, a C.sub.1 to C.sub.20 alkyl group (and preferably a
C.sub.1 to C.sub.10 alkyl group), a C.sub.2 to C.sub.20 alkyl group
having an ether bond, or the like) or a group VII element). As
carbonate groups, preferable examples include
--OC(.dbd.O)OCH.sub.3, --OC(.dbd.O)OC.sub.3H.sub.7,
--OC(.dbd.O)OC.sub.8H.sub.17,
--OC(.dbd.O)OCH.sub.2CH.sub.2CH.sub.2OCH.sub.2CH.sub.3, and the
like.
[0063] The carboxylic acid halide group in the fluorine-containing
ethylenic polymer in the present invention is specifically one of a
--COY structure (where Y is a halogen element), and examples
include --COF and --COCl.
[0064] A fluorine-containing ethylenic polymer that has these
carbonyl groups can itself retain the excellent properties of a
fluorine-containing resin, and can confer them to the laminate
after formation, with no diminution in such excellent properties
that a fluorine-containing resin has.
[0065] The fluorine-containing ethylenic polymer in the present
invention includes carbonyl groups in its polymer chain, but there
are no particular restrictions on how the carbonyl groups are
contained in the polymer chain; for example a carbonyl group or a
functional group that contains a carbonyl group may be joined to
the end of the polymer chain or to a side chain. Among them, those
that have a carbonyl group on the end of the polymer chain are
preferable, because they do not significantly reduce heat
resistance, mechanical properties, or resistance to chemicals, or
because they are beneficial from a productivity and cost
perspective. Here, a mode that is preferable, because it is very
easy to introduce and because it is also easy to control the
quantity introduced, is the method in which either carbonyl groups
are included such as peroxy carbonate or peroxy ester, or the
carbonyl groups are introduced to the ends of the polymer chain
using a polymerization initiator that has a functional group that
can be changed into a carbonyl group. Also, in the present
invention, a carbonyl group that originates in a peroxide means a
carbonyl group that is introduced directly or indirectly from a
functional group that is included in the peroxide.
[0066] Also, in the fluorine-containing ethylenic polymer in the
present invention, even if a fluorine-containing ethylenic polymer
that does not contain carbonyl groups is present, it suffices that
as an overall polymer, it have a number of carbonyl groups in the
above range as a total per 1.times.10.sup.6 carbon atoms in the
main chain.
[0067] In the present invention, the type and structure of the
fluorine-containing ethylenic polymer can be suitably selected
according to the purpose, the application, and the method of use,
but here it is preferable that its melting point be 160 to
270.degree. C. With such a polymer, this is advantageous especially
if the lamination is done by a heating, melting, sticking-together
process, because, in particular, sufficient adhesiveness can be
obtained between the carbonyl groups and the other material, and a
strong adhesive force with the other material can be obtained. From
the perspective of enabling lamination to an organic material of
relatively low heat resistance, the melting point is more
preferably 250.degree. C. or less, even more preferably 230.degree.
C. or less, and particularly preferably 200.degree. C. or less. For
the melting point, using a Seiko model DSC device (made by Seiko
Electronics Co.), the melting peak was recorded when the
temperature was increased at a rate of 10.degree. C./min, and the
temperature corresponding to the maximum value was taken as the
melting point (Tm).
[0068] With regard to the molecular weight of the
fluorine-containing ethylenic polymer in the present invention, it
is preferable that it be in a range in which the polymer can be
formed below the thermal breakdown temperature and that the
resulting formed body be able to exhibit the excellent mechanical
properties that are characteristic of the fluorine-containing
ethylenic polymer. Specifically, taking the melt flow rate (MFR) as
an index of the molecular weight, it is preferable that the MFR be
0.5 to 100 g/10 min at any temperature in the range of about 230 to
350.degree. C., which is the general molding temperature range for
fluororesin. For the MFR, using a melt indexer (made by Toyo Seiki
Seisaku-Sho, Ltd.), measurements were taken at unit intervals
(10-minute intervals) of the weight (g) of the polymer flowing out
of a 2 mm diameter nozzle having a length of 8 mm under a load of 5
kg at various temperatures.
[0069] The structure of the fluorine-containing ethylenic polymer
chain is in general a homopolymer chain or copolymer chain that has
repeated units that are derived from at least one type of
fluorine-containing ethylenic monomer, and it may be a polymer
chain made up of either a fluorine-containing ethylenic monomer
only, or made by polymerizing a fluorine-containing ethylenic
monomer with an ethylenic monomer that does not have any fluorine
atoms.
[0070] The fluorine-containing ethylenic monomer is an olefinic
unsaturated monomer that has fluorine atoms, and specific examples
include tetrafluoroethylene, vinylidene fluoride,
chlorotrifluoroethylene, vinyl fluoride, hexafluoropropylene,
hexafluoroisobutene, monomers represented by the formula (X):
CH.sub.2.dbd.CR.sup.1(CF.sub.2).sub.nR.sup.2 (X)
(wherein R.sup.1 represents H or F, R.sup.2 represents H, F, or Cl,
and n is a positive integer in the range 1 to 10), and
perfluoro(alkyl vinyl ethers) having 2 to 10 carbon atoms, and the
like.
[0071] The above ethylenic monomer that does not have any fluorine
atoms is preferably selected from ethylenic monomers having 5 or
fewer carbon atoms, in order not to reduce the heat resistance, and
the like. Specific examples include ethylene, propylene, 1-butene,
2-butene, vinyl chloride, vinylidene chloride, and the like.
[0072] If a fluorine-containing ethylenic monomer and an ethylenic
monomer that does not have any fluorine atoms are used, the
composition of the monomers may have a weight ratio such that the
fluorine-containing ethylenic monomer is 10 mol % or more to less
than 100 mol % (for example, 30 mol % or more to less than 100 mol
%), and the ethylenic monomer that does not have any fluorine atoms
is greater than 0 mol % to no greater than 90 mol % (for example,
greater than 0 mol % to no greater than 70 mol %).
[0073] In the fluorine-containing ethylenic polymer in the present
invention, the melting point or glass transition point of the
polymer can be adjusted by selecting the type, combination,
composition ratio, and other properties of the fluorine-containing
ethylenic monomer and the ethylenic monomer that does not have any
fluorine atoms.
[0074] As the fluorine-containing ethylenic polymer in the present
invention, preferable for heat resistance and resistance to
chemicals is a fluorine-containing ethylenic polymer that contains
a carbonyl group in which a tetrafluoroethylene unit is an
essential component, and preferable for formability and workability
is a fluorine-containing ethylenic copolymer that contains a
carbonyl group in which a vinylidene fluoride unit is an essential
component.
[0075] Preferable specific examples of the fluorine-containing
ethylenic polymer in the present invention include
fluorine-containing ethylenic copolymers (I) to (V) that contain a
carbonyl group in which the fluorine-containing ethylenic polymer
is essentially made by polymerizing the following monomers:
(I) a copolymer made by polymerizing at least tetrafluoroethylene
and ethylene, (II) a copolymer made by polymerizing at least
tetrafluoroethylene and a compound represented by the formula
(Y):
CF.sub.2.dbd.CFR.sup.3 (Y)
(wherein R.sup.3 represents CF.sub.3 or OR.sup.4, and R.sup.4
represents a perfluoroalkyl group having 1 to 5 carbon atoms),
(III) a copolymer made by polymerizing at least vinylidene
fluoride, (IV) a copolymer made by polymerizing at least (a), (b),
and (c) below, (a) tetrafluoroethylene 20 to 90 mol % (b) ethylene
10 to 80 mol % (c) 1 to 70% of a compound expressed by
CF.sub.2.dbd.CFR.sup.3 (Y)
(where R.sup.3 has the same meaning as above), and (v) a copolymer
made by polymerizing at least (d), (e), and (f) below. (d)
vinylidene fluoride 15 to 60 mol % (e) tetrafluoroethylene 35 to 80
mol % (f) hexafluoropropylene 5 to 30 mol % Other known monomers
may be added to these specific examples, including the above
monomers, insofar as they do not interfere with the effects of the
present invention.
[0076] Each of these examples of a fluorine-containing ethylenic
polymer that contains a carbonyl group is preferable especially in
that it has excellent heat resistance.
[0077] Examples of the copolymer (I) include polymer-chain carbonyl
group-containing copolymers that, with respect to the monomers as a
whole excluding monomers that have a carbonyl group (if it has a
functional group that has a carbonyl group on a side chain), are
made up of 20 to 90 mol % tetrafluoroethylene units (for example,
20 to 60 mol %), 10 to 80 mol % ethylene units (for example, 20 to
60 mol %), and 0 to 70 mol % of other monomers that can be
copolymerized therewith.
[0078] As other monomers that can be copolymerized, examples
include hexafluoropropylene, chlorotrifluoroethylene, and monomers
represented by the formula (X):
CH.sub.2.dbd.CR.sup.1(CF.sub.2).sub.nR.sup.2 (X)
(wherein R.sup.1 represents H or F, R.sup.2 represents H, F, or Cl,
and n is a positive integer in the range 1 to 10), and
perfluoro(alkyl vinyl ethers) having 2 to 10 carbon atoms, and
normally these are used as a single types or as two or more types
together.
[0079] As the copolymer (I), the following can be suitably listed
in that they maintain excellent performance in a
tetrafluoroethylene/ethylene copolymer, they can be made to have a
relatively low melting point as well, and they can exhibit maximum
adhesion with other materials.
(I-1) Polymer-chain carbonyl group-containing copolymers made up of
62 to 82 mol % tetrafluoroethylene units, 20 to 38 mol % ethylene
units, and 0 to 10 mol % of other monomer units, (I-2)
Polymer-chain carbonyl group-containing copolymers made up of 20 to
80 mol % tetrafluoroethylene units, 10 to 80 mol % ethylene units,
0 to 30 mol % hexafluoropropylene units, and 0 to 10 mol % of other
monomer units.
[0080] Suitable examples of the copolymer (II) include the
following.
(II-1) Polymer-chain carbonyl group-containing copolymers made up
of 65 to 95 mol % (preferably, 75 to 95 mol %) tetrafluoroethylene
units and 5 to 35 mol % (preferably, 5 to 25 mol %)
hexafluoropropylene units, (II-2) polymer-chain carbonyl
group-containing copolymers made up of 70 to 97 mol %
tetrafluoroethylene units and 3 to 30 mol % CF.sub.2.dbd.CFOR.sup.4
(where R.sup.4 is a perfluoroalkyl group having 1 to 5 carbon
atoms) units, (II-3) and a polymer-chain copolymer having carbonyl
groups that is made up of tetrafluoroethylene units,
hexafluoropropylene units, and CF.sub.2.dbd.CFOR.sup.4 (where
R.sup.4 is as above) units, wherein the total of the
hexafluoropropylene units and the CF.sub.2.dbd.CFOR.sup.4 units is
5 to 30 mol %.
[0081] The (II-1) to (II-3) above are also perfluoro copolymers,
and even among fluorine-containing polymers, they are the most
excellent in heat resistance, electrical insulation performance,
and other properties.
[0082] As the copolymer (III), examples include polymer-chain
carbonyl group-containing copolymers that, with respect to the
monomer total excluding the monomers that have a carbonyl group (if
they have a carbonyl group-containing functional group in a side
chain), are made up of 15 to 99 mol % vinylidene fluoride units, 0
to 80 mol % tetrafluoroethylene units, and 0 to 30 mol % of either
one or more types of hexafluoropropylene or chlorotrifluoroethylene
units. As specific examples of the copolymer (III), the following
can be suitably listed.
(III-1) Polymer-chain carbonyl group-containing copolymers made up
of 30 to 99 mol % vinylidene fluoride units and 1 to 70 mol %
tetrafluoroethylene units, (III-2) polymer-chain carbonyl
group-containing copolymers made up of 60 to 90 mol % vinylidene
fluoride units, 0 to 30 mol % tetrafluoroethylene units, and 1 to
20 mol % chlorotrifluoroethylene units, (III-3) polymer-chain
carbonyl group-containing copolymers made up of 60 to 99 mol %
vinylidene fluoride units, 0 to 30 mol % tetrafluoroethylene units,
and 5 to 30 mol % hexafluoropropylene units, (III-4) polymer-chain
carbonyl group-containing copolymers made up of 15 to 60 mol %
vinylidene fluoride units, 35 to 80 mol % tetrafluoroethylene
units, and 5 to 30 mol % hexafluoropropylene units.
[0083] There are no particular restrictions on how to manufacture
the fluorine-containing ethylenic polymer in the present invention.
The fluorine-containing ethylenic polymer of the present invention
can be manufactured by taking an ethylenic monomer that has a
carbonyl group and copolymerizing it with a fluorine-containing
and/or ethylenic monomer of a type and blend that fits the desired
fluorine-containing polymer. As the ethylenic monomer that has a
carbonyl group, preferable examples include fluorine-containing
monomers, such as perfluoroacrylic acid (fluoride), 1-fluoroacrylic
acid (fluoride), acrylic acid fluoride, 1-trifluoromethacrylic acid
(fluoride), perfluorobutenic acid, and the like; and monomers that
do not include fluorine, such as acrylic acid, methacrylic acid,
acrylic acid chloride, vinylene carbonate, itaconic acid,
citraconic acid, and the like.
[0084] On the other hand, various methods can be adopted for
obtaining fluorine-containing ethylenic polymer that has a carbonyl
group at the end of the polymer molecule, but the method of using
peroxide, in particular peroxycarbonate or peroxy ester, as a
polymerization initiator can be preferably adopted for its economy
and for quality considerations such as heat resistance and
resistance to chemicals. With this method, a carbonyl group
originating in a peroxide (for example, a carbonate group that
originates in a peroxide carbonate; an ester group that originates
in a peroxy ester; or a carboxylic acid halide group or carboxylic
acid group that is obtained by modifying these functional groups)
can be introduced at the end of a polymer chain. Among these
polymerization initiators, it is more preferable if peroxide
carbonate is used, because the polymerization temperature can be
made low and because the initiation reactions are not accompanied
by side reactions.
[0085] As the peroxycarbonates, we can suitably list, for example,
compounds that are represented by the following formulas (1) to
(4):
##STR00001##
(wherein R and R.sup.a represent a straight-chain or branched
monovalent saturated hydrocarbon group having 1 to 15 carbon atoms,
or a straight-chain or branched monovalent hydrocarbon group having
1 to 15 carbon atoms that contains an alkoxy group on the end, and
R.sup.b represents a straight-chain or branched divalent saturated
hydrocarbon group having 1 to 15 carbon atoms, or a straight-chain
or branched divalent hydrocarbon group having 1 to 15 atoms that
contains an alkoxy group on the end). Particularly preferable are
diisopropyl peroxycarbonate, di-n-propyl peroxydicarbonate, t-butyl
peroxyisopropyl carbonate, bis(4-t-butyl
cyclohexyl)peroxydicarbonate, di-2-ethyl hexylperoxydicarbonate,
and the like.
[0086] The amount of peroxycarbonate, peroxy ester, or other
initiators that is used varies depending on the type (composition,
and the like), molecular weight, and polymerization conditions of
the desired polymer and the type of initiator that will be used,
but normally it is preferable that it be 0.05 to 20 parts by
weight, and in particular 0.1 to 10 parts by weight, per 100 parts
by weight of the polymer that is obtained by the
polymerization.
[0087] As the polymerization method, for industrial purposes,
suspension polymerization using a fluorine solvent, in an aqueous
medium using peroxycarbonate, or the like as the polymerization
initiator, is preferable, but other polymerization methods may also
be adopted, such as, for example, solution polymerization, emulsion
polymerization, bulk polymerization, and the like. In suspension
polymerization, a fluorine solvent may be used in addition to
water. As the fluorine solvent used in suspension polymerization,
one can use, for example, hydrofluorochloroalkanes (for example,
CH.sub.3CClF.sub.2, CH.sub.3CCl.sub.2F, CF.sub.3CF.sub.2CCl.sub.2H,
CF.sub.2CICF.sub.2CFHCl), chlorofluoroalkanes (for example,
CF.sub.2CICFClCF.sub.2CF.sub.3, CF.sub.3CFClCFClCF.sub.3), and
perfluoroalkanes (for example, perfluorocyclobutane,
CF.sub.3CF.sub.2CF.sub.2CF.sub.3,
CF.sub.3CF.sub.2CF.sub.2CF.sub.2CF.sub.3,
CF.sub.3CF.sub.2CF.sub.2CF.sub.2CF.sub.2CF.sub.3), and
perfluoroalkanes are preferable. There are no particular
restrictions on the amount of fluorine solvent that is used, but in
the case of suspension polymerization, for suspendability and
economy it is preferable to use 10 to 100 wt % with respect to the
aqueous medium.
[0088] There are no particular restrictions on the polymerization
temperature; 0 to 100.degree. C. is acceptable. The polymerization
pressure is appropriately set according to the type, amount, and
vapor pressure of the solvent that is used, and the polymerization
temperature and other polymerization conditions, but 0 to 9.8 MPaG
is acceptable.
[0089] Also, to adjust the molecular weight, any well known chain
transfer agent may be used. As chain transfer agents, one may use,
for example, a hydrocarbon such as isopentane, n-pentane, n-hexane,
cyclohexane, and the like; an alcohol such as methanol, ethanol,
and the like; or a hydrocarbon halide such as carbon tetrachloride,
chloroform, methylene chloride, methyl chloride, and the like.
Also, the quantity of end carbonate groups or ester groups it
contains can be controlled by adjusting the polymerization
conditions, and can be controlled by the amount of peroxycarbonate
or peroxy ester that is used, the amount of chain transfer that is
used, the polymerization temperature, and the like.
[0090] Various methods can be adopted to obtain a
fluorine-containing ethylenic polymer that has a carboxylic acid
halide group or a carboxylic acid group at the end of the polymer
molecule; for example, one can obtain it by heating, and causing
thermal breakdown (decarboxylation) of a fluorine-containing
ethylenic polymer that has at its end the aforementioned carbonate
group or ester group. The heating temperature varies depending on
the type of carbonate group or ester group and on the type of
fluorine-containing ethylenic polymer, but normally it is
270.degree. C. or more, preferably 280.degree. C. or more, and
particularly preferably 300.degree. C. or more. Also, it is
preferable that the heating temperature be below the thermal
breakdown temperature of the parts of the fluorine-containing
ethylenic polymer other than the carbonate groups or ester groups;
specifically, 400.degree. C. or less is preferable, and 350.degree.
C. or less is more preferable.
[0091] A white powder of the resulting fluorine-containing
ethylenic polymer or cut pieces of its molten extruded pellets were
compression-formed at room temperature and made into a uniform film
of thickness 0.05 to 0.2 mm. By infrared spectrum absorption
analysis of this film, the peak originating in the carbonyl group
of the carbonate group (--OC(.dbd.O)O--) appeared at an absorption
wavelength of 1809 cm.sup.-1 (v.sub.c-o), and its absorbance at the
v.sub.c-o peak was measured. The number (N) of carbonate groups per
1.times.10.sup.6 main-chain carbon atoms was computed by the
following formula (5).
N=500 AW/.di-elect cons.df (5)
A: absorbance at the v.sub.c-o peak of the carbonate group
(--OC(.dbd.O)O--) .di-elect cons.s: mole absorbance coefficient
(lcm.sup.-1mol.sup.-1) of the v.sub.c-o peak of the carbonate group
(--OC(.dbd.O)O--). From model compounds, epsilon was set to
.di-elect cons.=170. W: average molecular weight of the monomer as
computed from the monomer composition d: density of the film
(g/cm.sup.3) f: thickness of the film (mm) Also, in the infrared
absorption spectrum analysis, scanning was done 40 times using a
Perkin-Elmer FTIR spectrometer 1760.times.(made by Perkin-Elmer
Co.). The resulting IR spectrum was used to automatically determine
the baseline using Perkin-Elmer Spectrum for Windows (registered
trademark) Ver. 1.4, and the absorbance of the peak at 1809
cm.sup.-1 was measured. Also, the film thickness was measured with
a micrometer.
Measurement Method for the Number of Carboxylic Acid Fluoride
Groups
[0092] In the same way as with the above measurement method for the
number of carbonate groups, by infrared spectrum analysis of the
resulting film, the peak originating in the carbonyl group of the
carboxylic acid fluoride group (--C(.dbd.O)F) appeared at an
absorption wavelength of 1880 cm.sup.-1 (v.sub.c-o), and the
absorbance thereof at the v.sub.c-o peak was measured. The number
of carboxylic acid fluoride groups was measured in the same way as
in the above measurement method for the number of carbonate groups
using the above formula (5), except that from model compounds. the
mole absorbance coefficient (lcm.sup.-1mol.sup.-1) of the v.sub.c-o
peak of the carboxylic acid fluoride group was set to .di-elect
cons.=600.
Measurement Method for the Number of Other Carbonyl Groups
[0093] In the same way as with the above measurement method for the
number of carbonate groups, infrared spectrum analysis of the
resulting film can be used to measure the number of other carbonyl
groups that can basically react with amide groups, amino groups,
and other functional groups in a polyamide resin such as carboxylic
acid groups, ester groups, acid anhydride groups, and the like.
Here, except for setting the mole absorbance coefficient
(lcm.sup.-1mol.sup.-1) of the v.sub.c-o peak originating in these
carbonyl groups to .di-elect cons.=530, the number of other
carbonyl groups was measured in the same way as in the above
measurement method for the number of carbonate groups using the
above formula (5).
Measurement Method for the Composition of the Fluorine-Containing
Ethylenic Polymer
[0094] Measurements were made by .sup.19F-NMR analysis.
[0095] It is preferable that the fluorine-containing ethylenic
polymer in the present invention be used singly, so as not to
detract from the adhesiveness, heat resistance, resistance to
chemicals, and other properties that it has itself, but insofar as
its performance is not degraded, it may according to purpose and
application be blended with various well known fillers such as
inorganic powder, glass fiber, carbon fiber, metal compounds,
carbon, or the like. Moreover, besides fillers, one may also mix in
other additives as desired, such as pigments and ultraviolet ray
absorbents. Besides additives, one may also blend in other
fluororesins or thermoplastic resins, thermoplastic and other
resins, synthetic rubber, and the like, thereby making it possible
to improve the mechanical properties, improve the weather
resistance, add decorative designs, prevent static electricity,
improve the moldability, and the like.
[0096] As a result of combining the above polyimide film with the
above fluororesins, the coverlay of the present invention has
excellent thermal shrinkage and plenty of adhesive strength. The
coverlay of the present invention at the least is formed by
laminating the fluororesin to the polyimide film in an adhesive
state. Various manufacturing methods can be applied to the
manufacture of the coverlay, including a manufacturing method of
forming, one after another or by extrusion together, the
constituent layers that include the polyimide film and the
fluororesin, a manufacturing method of thermocompression bonding of
a molded body; and a manufacturing method of taking either the
polyimide film or the fluororesin as a molded body that is coated
with a precursor or molten version of the other resin, and is
allowed to flow along to make a resin composition; and a good
adhesive state is formed between the constituent layers, which
include the polyimide film and the fluororesin. In this
manufacturing, one may use any well known molding machine that is
normally used for thermoplastic resin, such as an injection molding
machine, a compression molding, a flow molding machine, or an
extrusion molding machine.
[0097] The forming conditions vary with the carbonyl group,
especially the type of carbonate group, and with the type of
fluorine-containing ethylenic polymer, but with extrusion or flow
molding it is appropriate to heat the cylinder to a temperature of
200.degree. C. or more. It is preferable that the heating
temperature be set to no greater than a temperature that will
suppress foaming or other bad effects caused by the thermal
breakdown of the fluorine-containing ethylenic polymer itself;
specifically, 400.degree. C. or less is preferable, and 350.degree.
C. or less is more preferable.
[0098] There are no particular restrictions on the manufacturing
method through thermocompression bonding, and examples include the
methods of vacuum pressing, lamination (the hot laminate method,
and the like), and coating. Also, the fluorine-containing resin
layer may include lamination and coating on either one side or both
sides of the polyimide film.
[0099] With a vacuum press, a coverlay is obtained by, for example,
thermocompressing together the polyimide resin and the fluororesin
at the prescribed temperature and pressure using a well known
vacuum press machine. To make the processing simple, it is
preferable when doing this that the press temperature be in the
range of 100 to 250.degree. C. Annealing may be done following the
pressing, and it is preferable that the annealing temperature be in
the range of 100 to 250.degree. C.
[0100] With the hot laminate method, on which there are no
particular restrictions, a coverlay is obtained by using two
heatable rollers whose distance between them can be adjusted as
desired, layering film of two or more types between the rollers,
and pressing them together while applying heat and pressure. If
necessary, heat treatment can be done continuously immediately
after the laminating is done. In the heat treatment, it is
preferable that the temperature be no less than the glass
transition point (Tg) of the fluororesin and no greater than its
melting point +50.degree. C., because this allows the
pressing-together force to be increased. A temperature below Tg is
undesirable because then the desired bonding force cannot be
obtained, and a temperature above the melting point+50.degree. C.
is undesirable because then the fluororesin begins to break down,
lowering the bonding force. There are no particular restrictions on
the heating time; it can be set suitably as necessary. There are no
particular restrictions on the equipment, as long as it does not
hamper the effects of the present invention.
[0101] The adhesive strength between the polyimide layer and the
fluororesin layer of the coverlay before the copper-clad laminate
is attached is preferably more than 3.0 N/cm, more preferably at
least 5.0 N/cm, and even more preferably at least 8.0 N/cm; this is
for sake of improving the precision in the positioning of the
copper-clad laminate and coverlay and raising the operational
efficiency. There are no particular restrictions on the upper limit
for the adhesive strength.
[0102] Although there are no particular restrictions on the
thickness of the polyimide layer in the coverlay of the present
invention, because this thickness affects the bonding force of the
coverlay's polyimide layer and fluororesin layer, it is preferably
about 0.01 to 2.0 times the thickness of the fluororesin layer,
more preferably about 0.05 to 1.0 times, and even more preferably
about 0.1 to 0.9 times. A thickness of the polyimide layer that
exceeds a factor of 2.0 is undesirable because, although it
improves the rigidity and dimensional stability for the substrate,
it increases the dielectric constant. Moreover, if it is less than
a factor of 0.01, the rigidity of the polyimide layer will
decrease, the coefficient of linear expansion will tend to
increase, and the rigidity and dimensional stability as a substrate
will decrease.
[0103] The thermal shrinkage of the coverlay of the present
invention as measured at 260.degree. C. at 30 minutes is normally
less than .+-.0.1%, preferably less than .+-.0.08%, and more
preferably less than .+-.0.06%.
[0104] A high-frequency circuit substrate can be manufactured by
affixing the coverlay of the present invention to a copper-clad
laminate. There are no particular restrictions on how to make the
copper-clad laminate; it may be manufactured by any well known
method. Also, the copper-clad laminate may have either a one-sided
structure or a two-sided structure.
[0105] As manufacturing methods for the copper-clad laminate to be
affixed to the coverlay of the present invention, examples include
a three-layer CCL in which a base-material film and copper foil are
laminated together with an intervening adhesive, a method in which
a copper layer is formed by making use of vapor deposition onto the
base-material film along with sputtering and electroplating, a
so-called cast-type two-layer CCL (COC) in which a polyimide layer
is cast and formed on copper foil, and the copper layer is formed
using electroless plating on the base-material film.
[0106] As the base-material film, examples include polyimide film
and LCP film for use with high-frequency circuits. In addition, as
the adhesive layer, examples include epoxy, acrylic, or polyimide
adhesives, as well as fluororesins, and the like. Commercially
available products may be used for the adhesive. As commercially
available products, there are no particular restrictions, and
examples include the LF Series (of acrylic adhesives) of Pyralux
(made by Dupont Co., Ltd.), and the like. Preferable modes among
these are copper-clad laminates that make use of LCP film, and
copper-clad laminates in which the laminate is made with the
fluororesin between the base-material film and the copper foil.
[0107] As the polyimide film to be used for the copper-clad
laminate, ones similar to the above polyimide film for the coverlay
can be cited, and their composition may be either the same as or
different from the polyimide film for the coverlay.
[0108] There are no particular restrictions on the fluororesin to
be used in the copper-clad laminate; any well known fluororesin may
be used, including commercially available products. As such
commercially available products, examples include Toyoflon F, FE,
FL, FR, and FV (brand names; made by Toray Advanced Film Co.,
Ltd.), and the like.
[0109] There are no particular restrictions on the thickness of the
polyimide layer in the copper-clad laminate (the layer including
the adhesive, if a polyimide adhesive is used), but a thickness
0.01 to 2.0 times the thickness of the fluororesin layer is
preferable, about 0.05 to 1.0 times is more preferable, and about
0.1 to 0.9 times is even more preferable. A thickness of the
polyimide layer that exceeds 2.0 times the thickness of the
fluororesin layer is undesirable because although the rigidity and
dimensional stability as a copper-clad laminate will improve, the
dielectric constant will increase. Moreover, if it is less than a
factor of 0.01, the rigidity of the polyimide layer will decrease,
the coefficient of linear expansion will tend to increase, and the
rigidity and dimensional stability as a copper-clad laminate will
decrease.
[0110] A wiring-processed copper-clad laminate is obtained by
etching the copper-clad laminate. There are no particular
restrictions on how the etching is to be done, and any well known
method may be used.
[0111] In manufacturing a high-frequency circuit substrate,
laminating is done in such a way that the fluororesin side of the
coverlay comes into contact with the circuit of the copper-clad
laminate, and the coverlay and the copper-clad laminate are held
temporarily in place.
[0112] There are no particular restrictions on the step by which
the copper-clad laminate and the coverlay are held temporarily in
place, and any well known method may be used; examples include a
method in which the copper-clad laminate and the coverlay are
aligned in position, kiss lamination is done, then as necessary,
quick-pressing is done to produce lamination at about 150 to
200.degree. C., a method in which the copper-clad laminate and the
coverlay are aligned in position, and multi-stage pressing is done,
and the like. There are no particular restrictions on the maximum
temperature in the step for temporarily holding in place, as long
as it is lower than the melting point of the fluororesin that is to
be used in the coverlay, but to obtain sufficient adhesive strength
by subsequent annealing, it is appropriate that it be in the range
of 100 to 250.degree. C. There are no particular restrictions on
the treatment time for the step of temporarily holding in
place.
[0113] There are no particular restrictions on the manufacture of a
high-frequency circuit substrate, but following the step of
temporarily holding in place, it is preferable to execute a step in
which the copper-clad laminate to which the coverlay is attached is
annealed.
[0114] There are no particular restrictions on the maximum heating
temperature in the annealing step, but for good adhesive strength
of the resulting high-frequency circuit substrate, it is preferable
to set it to a temperature within the range from 150.degree. C. to
350.degree. C. at a temperature that is higher than the maximum
temperature in the step for temporarily holding in place, and it is
preferable that the temperature difference be at least 20.degree.
C. Moreover, in the annealing step, it is preferable that it be
done by free tension between 150.degree. C. and 350.degree. C. Free
tension has the advantage of simplifying the treatment steps, and
with regard to the annealing temperature, from 200.degree. C. to
280.degree. C. is more preferable, and from 205.degree. C. to
275.degree. C. is even more preferable. There are no particular
restrictions on the annealing time.
[0115] The annealing increases the bonding force based on the
adhesive force of the fluororesin layer, and results in a
high-frequency circuit substrate that has practical adhesive
strength (peel strength). To ensure performance as a coverlay, the
adhesive strength after annealing of the resulting high-frequency
circuit substrate preferably is a value that exceeds 8 N/cm, and
more preferably is at least 10 N/cm. It is even more preferable
that it be at least 14 N/cm. The adhesive strength in the present
invention is the value that was measured by the method described
below in the working examples.
[0116] A high-frequency circuit substrate can be manufactured by
laminating together the coverlay of the present invention and a
copper-clad laminate that has been wiring processed. Making the
thickness of the polyimide film and the thickness of the
fluororesin so that they have the above-specified ratio not only
further improves the electrical and mechanical properties but also
ensures excellent dimensional stability, further repressing the
occurrence of curling, twisting, warping, and the like even if one
carries out etching for circuit formation of the copper layer, and
various heating steps in the steps following circuit formation.
WORKING EXAMPLES
[0117] Next, the present invention is described in greater
specificity, citing working examples, but the present invention is
not restricted by the working examples thereof, and many
modifications can be made by a person who has the usual knowledge
in this field, within the technical concept of the present
invention.
[0118] The following is a description of the methods for measuring
the various properties in the present invention.
(1) Peel Strength
[0119] A sample was cut into a strip 10 mm wide, and the peel
strength (unit: N/cm) was measured in a 90.degree. C. [sic; 90
degrees] pulling test (pulling speed: 50 mm/min, measurement
length: 20 mm, measurement range: 5.0 to 20.0 mm) using the
Autograph AG-IS universal tensile testing device made by Shimadzu
Ltd.
(2) Thermal Shrinkage
[0120] A sample of size 190 mm.times.200 mm was cut, and its
dimensions before heat treatment were measured with the CNC image
processing device system NEXIVVM-250 made by Nikon Co., Ltd. Then
the sample was put into an oven set to 260.degree. C. and heat
treated for 30 minutes. The sample after heat treatment was
moisture-adjusted for 12 hours or more at a constant temperature
and high humidity. The sample after moisture adjustment was
measured for its dimensions in the same way as before the heat
treatment, and the rate of change in the dimensions before and
after the heat treatment was shown as a percentage.
(3) Transmission Loss
[0121] The high-frequency transmission characteristics from 1 to 40
GHz were measured using a prober device for substrate measurement
made by Cascade Microtech.
Synthesis Example 1
[0122] Pyromellitic acid dianhydride (molecular weight
218.12)/3,3',4,4'-biphenyl tetracarboxylic acid dianhydride
(molecular weight 294.22)/4,4'-diaminodiphenyl ether (molecular
weight 200.24)/paraphenylene diamine (molecular weight 108.14) was
prepared at mole ratio of 95/5/85/15, and was made into a 20 wt %
solution in DMAc (N,N-dimethyl acetoamide) and polymerized, and a
3500-poise polyamic acid solution was obtained.
Synthesis Example 2
[0123] Pyromellitic acid dianhydride (molecular weight
218.12)/4,4'-diaminodiphenyl ether (molecular weight 200.24) was
prepared at a mole ratio of 100/100, and was made into a 20 wt %
solution in DMAc (N,N-dimethyl acetoamide) and polymerized, and a
3500-poise polyamic acid solution was obtained.
Synthesis Example 3
[0124] A 380-liter quantity of distilled water was put into an
autoclave, and after carrying out nitrogen replacement
sufficiently, it was charged with 75 kg
1-fluoro-1,1-dichloroethane, 155 kg hexafluoropropylene, and 0.5 kg
perfluoro(1,1,5-trihydro-1-pentene), and the interior of the system
was kept at 35.degree. C. at a stirring speed of 200 rpm. Next,
tetrafluoroethylene was pressurized to 0.7 MPa, and subsequently
ethylene was pressured to 1.0 MPa, then 2.4 kg di-n-propyl
peroxydicarbonate was inserted, and polymerization was initiated.
Because the pressure within the system decreases as the
polymerization proceeds, the pressure within the system was kept to
1.0 Mpa by continuously supplying a mixed gas made of
tetrafluoroethylene/ethylene/hexafluoropropylene=40.5/44.5/15.0 mol
%. Then, for the perfluoro(1,1,5-trihydro-1-pentene) as well, a
total quantity of 1.5 kg was charged, and stirring was continued
for 20 hours. Then, after the pressure was released and the system
returned to atmospheric pressure, the reaction products were washed
with water and dried, producing 200 kg of powder
(fluorine-containing ethylenic polymer F-A). The analysis results
thereof are presented in Table 1.
Synthesis Example 4
[0125] In the same way as in Synthesis Example 3,
fluorine-containing ethylenic polymer F--B was obtained in the
blends shown in Table 1. The analysis results thereof are presented
in Table 1.
Synthesis Example 5
[0126] A 9.5 kg quantity of powder of the fluorine-containing
ethylenic polymer F--B obtained in Synthesis Example 4, 700 g of
28% aqueous ammonia, and 10 liter of distilled water were charged
into an autoclave, the system was heated while stirring, and kept
at 80.degree. C., and the stirring was continued for 7 hours. Then
the content was water-washed and dried, yielding 9.2 kg of powder
(fluorine-containing ethylenic polymer F--C). By carrying out such
treatment, the active functional groups contained in the resin
(carbonate groups and carboxylic acid fluoride groups) were
transformed into amide groups that are stable both chemically and
thermally. Also, it was confirmed by infrared spectrum analysis
that this transformation proceeded quantitatively. The analysis
results of the resin after treatment are presented in Table 2.
Also, no carbonyl groups except carbonate groups and carboxylic
acid fluoride groups were found in the fluorine-containing
ethylenic polymer (F-A) shown in Synthesis Example 3. In Table 1,
TFE represents tetrafluoroethylene, Et represents ethylene, HFP
represents hexafluoropropylene, and HF-Pa represent
perfluoro(1,1,5-trihydro-1-pentene).
TABLE-US-00001 TABLE 1 Quantity (number) per 10.sup.6 carbon
Fluoro- atoms in main resin chain (fluorine- Monomer composition
carboxylic MFR containing (mol %) acid Melting (g/10 min) ethylenic
HF- carbonate fluoride point (measured polymer TFE Et HFP Pa groups
groups (.degree. C.) temperature) SE 3 F-A 40.8 44.8 13.9 0.5 300 3
162.5 2.6 (230.degree. C.) SE 4 F-B 46.2 43.8 9.5 0.5 255 5 194.3
8.9 (230.degree. C.) SE 5 F-C 46.1 43.8 9.5 0.5 not detected not
detected 193.5 9.8 (230.degree. C.) SE = Synthesis example
Working Example 1
(1) Preparation of the Polyimide Film
[0127] Acetic anhydride (molecular weight 102.09) and
.beta.-picoline were mixed in the polyamic acid solution obtained
in Synthesis Example 1 at respective ratios of 17 wt % and 17 wt %
with respect to the polyamic acid solution, and stirred. The
resulting mixture was cast by a T-shaped slit die onto a rotating
stainless steel drum at 75.degree. C., and after the mixture was
allowed to flow and extend for 30 seconds, the resulting gel film
was stretched 1.2-fold in the running direction while being heated
for 5 minutes at 100.degree. C. Next, both ends in the width
direction were gripped, and the film was stretched 1.3-fold in the
width direction while heating for 2 minutes at 270.degree. C.,
after which it was heated for 5 minutes at 380.degree. C.,
producing a polyimide film with a thickness of 12.5 .mu.m.
(2) Preparation of the Fluororesin Film
[0128] The fluorine-containing ethylenic polymer polymerized in
Synthesis Example 3 was pelletized using a 65-mm-diameter
short-axis extruding machine with a temperature setting of
230.degree. C. to 280.degree. C., then it was made into a film
using a 50-mm-diameter short-axis extruding machine equipped with a
T-die and having a temperature setting of 230.degree. C. to
280.degree. C., thereby producing a fluororesin film with a
thickness of 25 .mu.m.
(3) Preparation of the Coverlay
[0129] Using the polyimide film obtained in (1) above and the
fluororesin film obtained in (2) above, a coverlay was made by the
vacuum press method. Specifically, the polyimide film and the
fluororesin film were laid atop each other and then pressed for 90
seconds at 120.degree. C. and 30 kN with a vacuum press machine,
after which an electric furnace set to 180.degree. C. was used to
heat the material for 20 minutes with free tension, thereby
producing a coverlay film. The above-described properties were then
measured for the resulting coverlay, and the results are shown in
Table 2.
Working Example 2
[0130] A coverlay was made in the same way as in Working Example 1,
with the exception that instead of the polyimide film obtained in
(1) of Working Example 1, a polyimide film made in the same way as
in (1) of Working Example 1 using the polyamic acid solution
obtained in Synthesis Example 2 was used, and instead of the
fluorine-containing ethylenic polymer (F-A) obtained in Synthesis
Example 3, the fluorine-containing ethylenic polymer (F--B)
obtained in Synthesis Example 4 was used. Each of the
above-described properties was measured, and the results are
presented in Table 2.
Comparison Example 1
[0131] A coverlay was made using the same method as the preparation
method of (3) in Working Example 1 and using the polyimide film
obtained in (1) of Working Example 1 and the fluorine-containing
ethylenic polymer (F--C) obtained in Synthesis Example 5.
TABLE-US-00002 TABLE 2 Working Working Comparison Item Unit Example
1 Example 2 Example 1 Peel strength [N/cm] 3.1 3.6 0.1 or less
Thermal [%] 0.05 0.09 0.18 shrinkage
(In the table, each coverlay peel strength denotes the adhesive
strength between the polyimide film layer and the fluororesin
layer.)
[0132] In Comparison Example 1, it took time to align the positions
of the copper-clad laminate and the coverlay, which is not suitable
for industrial implementation. Moreover, it was learned that, as
shown in Table 2, in Comparison Example 1, sufficient bonding force
is not obtained, which makes it unsuitable industrially. On the
other hand, with the coverlay of the present invention, the
workability was excellent, and the thermal shrinkage was less than
.+-.0.1%.
Preparation 1
[0133] A two-sided CCL was fabricated by using an epoxy adhesive to
attach an 18 .mu.m copper foil to the polyimide film obtained in
(1) of Working Example 1.
Working Example 3
[0134] A coverlay was fabricated by the method shown in (3) of
Working Example 1, using polyimide film (thickness: 12.5 .mu.m)
obtained in the same way as in (1) of Working Example 1 and the
fluorine-containing ethylenic polymer (F--B) obtained in Synthesis
Example 4.
Comparison Example 2
[0135] A coverlay was fabricated by using a bar coater to coat one
side of a polyimide film (thickness: 12.5 .mu.m) obtained in the
same way as in (1) of Working Example 1 with epoxy adhesive to a
thickness of 25 .mu.m, heat-drying it for 5 minutes at 150 degrees
[sic; degrees Celsius], performing B staging, and then bonding the
separate film to the resin composition surface with a
laminator.
Test Example
Transmission Properties
[0136] Using the CCL fabricated in Working Example 1, etching was
done to produce the desired wiring, and using the etched CCL and
the coverlay of Working Example 3 or the coverlay of Comparison
Example 2, a circuit was fabricated, and the transmission
properties thereof were measured. The measurement results are shown
in FIG. 1.
[0137] As described above, when the coverlay of the present
invention was used, a high-frequency circuit substrate was obtained
that exhibits superior workability when manufacturing
high-frequency circuit substrates, and that has excellent
mechanical properties and heat resistance. Moreover, as shown in
FIG. 1, the coverlay of the present invention also has better
properties than a conventional coverlay, including transmission
properties.
INDUSTRIAL POTENTIAL
[0138] The coverlay of the present invention requires no
high-temperature pressing beforehand, and by low-temperature
pressing and subsequent heating with free tension, one can obtain a
FPC [flexible printed circuit] that has excellent high-frequency
properties, dimensional stability, and wiring precision. Also,
because it has a low dielectric constant, the high-frequency
circuit substrate of the present invention can keep transmission
loss in check.
* * * * *