Polyester film capacitor element

A film capacitor element produced from a metallized polyester film is described. In the metallized polyester film, the adhesion between a vapor-deposited metal layer and a polyester substrate is improved by providing a coating layer comprising a specific water soluble or water dispersible resin. The film capacitor produced by the use of the metallized polyester film has good moist heat resistance and long term stability in performance.

BACKGROUND OF THE INVENTION 
The present invention concerns a metallized polyester film capacitor. More 
in particular, the present invention relates to a metallized polyester 
film capacitor having excellent moist heat resistance made by the use of a 
film having an improved adhesion between a substrate film and a 
vapor-deposited metal. 
Since polyester films are excellent, for example, in mechanical property, 
heat resistance and electric property, they are generally used as elements 
fabricated by winding two polyester films which are vapor-deposited with a 
metal such as Al or Zn, or fabricated by laminating a plurality of such 
films and then cut into chips. With the progress in various kinds of 
electric devices and equipments in recent years, improvement for the 
characteristics of the polyester film capacitors has been intended. One of 
the requirements for the improvement of the characteristics is moisture 
resistance and heat stability for a long period of time. That is, the 
metallized polyester film has a drawback that the adhesion between the 
substrate film and the vapor-deposited metal, in particular, the adhesion 
under high temperature and high humidity atmosphere is poor to bring about 
a problem that if a capacitor is put under a high temperature and high 
humidity condition, moisture permeates through the interface between the 
substrate film and the vapor-deposited metal thereby changing the static 
capacitance of the capacitor with elapse of time. Accordingly, improvement 
has been demanded for moist heat resistance of the capacitor from a 
viewpoint of a long term stability. 
There have been disclosed a film capacitor having a vinylidene chloride 
coating layer in Japanese Patent Application Laid-Open (KOKAI) No. 
60-115214 and a film capacitor having a coating layer containing melamine 
and/or urea resin as the essential ingredient in Japanese Patent 
Application Laid-Open (KOKAI) No. 60-120511, respectively, as the 
capacitor of excellent moist heat resistance. 
However, even if the resin composition as disclosed in the above-mentioned 
publications is used, the performance of the capacitor can not be 
maintained sufficiently in a moist and high temperature circumstance. 
Further, along with remarkable development for various kinds of electronic 
equipments in recent years, demand for the long term reliability required 
for a capacitor, in particular, the long term moisture and heat stability 
of a capacitor performance has been increased further. 
SUMMARY OF THE INVENTION 
The feature of the present invention resides in a metallized polyester film 
capacitor element produced by winding or stacking a metallized polyester 
film or a plurality of the metallized polyester films, the metallized 
polyester film being produced by the following steps of: 
coating a coating solution containing a resin as the main ingredient at 
least on one surface of a polyester film to obtain a film having a coating 
layer at least on one surface of the film, the average center line surface 
roughness (Ra) of the coating layer being in the range from 0.005 to 0.5 
.mu.m; and 
vapor-depositing a metal on the surface of the coating layer to obtain the 
metallized polyester film.

DETAILED DESCRIPTION OF THE INVENTION 
The polyester for the polyester film in the present invention is a 
polyethylene terephthalate in which not less than 80% of the 
constitutional repeating unit is ethylene terephthalate, a polyethylene 
naphthalate in which not less than 80 mol % of the constitutional 
repeating unit is ethylene naphthalate or poly-1,4-cyclohexane dimethylene 
terephthalate in which not less than 80 mol % of the constitutional 
repeating unit is 1,4-cyclohexane dimethylene terephthalate. The intrinsic 
viscosity of the polyester is preferred to be in the range from 0.4 to 
1.2. 
As the copolymerizable component other than the components described above, 
there can be used, for example, a diol component such as diethylene 
glycol, propylene glycol, neopentyl glycol, polyethylene glycol or 
polytetramethylene glycol; a dicarboxylic acid component such as 
isophthalic acid, 2,6-naphthalane dicarboxylic acid, 
5-sodiumsulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid or 
an ester-forming derivative thereof and a hydroxy monocarboxylic acid such 
as hydroxy benzoic acid and an ester-forming derivative thereof. 
The polyester film in the present invention may include additive particles, 
deposited particles and other catalyst residues that form protrusions at 
the surface of the film in such an amount as not deteriorating the 
capacitor characteristic to be described later. Further, it may also 
contain, as additives other than the protrusion-forming agent, antistatic 
agent, stabilizer, lubricant, crosslinking agent, antiblocking agent, 
antioxidant, colorant, light shielding agent or UV absorber, as necessary, 
in such an amount as not deteriorating the capacitor characteristic. 
The coating layer in the present invention is obtained by coating a coating 
solution containing a water soluble or water dispersible resin as the main 
ingredient at least on one surface of a polyester film, and, subsequently 
stretching the resultant coated film at least in one direction of machine 
and transverse directions and heat-setting. The water soluble or water 
dispersible resin usable herein may properly be selected from polyester 
polyurethane, a resin mainly comprising a polyester type resin with a 
glass transition point (Tg) of not higher than 70.degree. C., a resin 
comprising a polyester component and an acryl component, and a resin 
containing a polyurethane or polyester and an epoxy compound. 
The polyester polyurethane usable in the present invention is prepared by 
reacting a polyester polyol and a polyisocyanate in accordance with a 
usual method. 
The polyester polyol is obtained by reacting a dicarboxylic acid and a 
glycol in accordance with a usual method. As the dicarboxylic acid 
component, there can be used, for example, an aromatic dicarboxylic acid 
such as terephthalic acid, isophthalic acid and 2,5-naphthalene 
dicarboxylic acid, aliphatic dicarboxylic acid such as adipic acid, 
azelaic acid and sebacic acid, hydroxycarboxylic acid such as 
hydroxybenzoic acid, or an ester-forming derivative thereof. As the glycol 
component, there can be used an aliphatic glycol such as ethylene glycol, 
1,4-butanediol, diethylene glycol and triethylene glycol, an alicyclic 
glycol such as 1,4-cyclohexane dimethanol, an aromatic diol such as 
p-xylenediol, or a poly(oxyalkylene) glycol such as polyethylene glycol, 
polypropylene glycol, polytetramethylene glycol. The saturated 
polyesterpolyol mentioned above has a linear structure but it may be 
formed into a branched polyesterpolyol by using tri or higher valent ester 
forming component. 
As the polyisocyanate compound, there can be mentioned, for example, 
hexamethylene diisocyanate, diphenylmethane diisocyanate, tolylene 
diisocyanate, isophorone diisocyanate, an adduct of tolylene diisocyanate 
with trimethylpropane and an adduct of hexamethylene diisocyanate with 
trimethylolethane. Among them, a polyester polyurethane coating agent 
obtained by using an aromatic diisocyanate such as isophorone diisocyanate 
and tolylene diisocyanate is particularly preferred since it is excellent 
in stretching follow-up property and the resultant coating is strong and 
excellent in the adhesion with a vapor-deposited metal layer. 
The polyester polyurethane usable in the present invention is preferably 
used as a coating agent using water as a medium in view of safety and 
sanitation but it may contain an organic solvent as a dispersion agent for 
a polyester polyurethane within the scope of the present invention. 
In a case of using water as the medium, the polyester polyurethane may be 
forcibly dispersed therein with the aid of a surface active agent, but the 
use of a self-dispersible type in which a hydrophilic nonionic group such 
as polyethers or a cationic group as described in Japanese Patent 
Publication (KOKOKU) No. 63-12890 is bonded to a polyester polyurethane is 
preferred and, the use of a self-dispersible type in which an anionic 
group is bonded to a polyester polyurethane as described in Angew. 
Makromol. Chem., 98, 133-165 (1981) is more preferred. 
The polyester polyurethane having the anionic group can be prepared by a 
method of using a compound having an anionic group as the polyurethane 
forming component such as a polyol, polyisocyanate compound and a chain 
extender, a method of reacting unreacted isocyanate group in the resultant 
polyester polyurethane with a compound having an anionic group or a method 
of reacting a group having an active hydrogen in polyester polyurethane 
with a specific compound. 
In the method of using the compound having the anionic group as the 
polyurethane forming component, it is possible to use, for example, a 
compound obtained by sulfonating an aromatic isocyanate compound, 
diaminocarboxylate and sulfuric ester salt of amino alcohols. 
In the method of reacting the unreacted isocyanate group in the polyester 
polyurethane and the compound having the anionic group, it is possible to 
use, for example, bisulfite, aminosulfonic acid and its salts, 
aminocarboxylic acid and its salts, sulfuric acid ester of amino alcohols 
and its salts, hydroxyacetic acid and its salts. 
In the method of reacting the group having the active hydrogen in the 
polyester polyurethane and the specific compound, it is possible to use a 
3-membered to 7-membered cyclic compound having a group capable of forming 
a salt or a group capable of forming a salt after ring opening such as 
dicarboxylic anhydride, tetracarboxylic anhydride, sultone, lacton, 
epoxycarboxylic acid, epoxysulfonic acid, 2,4-dioxooxazolidine, isatoic 
anhydride, phoston, and carbyl sulfate. 
By using a compound having the anionic group as the polyester polyol, an 
anionic group can also be introduced into the polyester polyurethane. The 
polyester polyol having the anionic group is obtained by bonding a 
compound having a sulfonate group or a carboxylate group to a polyester 
polyol by means of copolymerization or graft. 
Anionic group of the polyester polyurethane is properly selected, for 
example, from sulfonic acid group carboxylic acid group, phosphoric acid 
group, and lithium salt, sodium salt, potassium salt or ammonium salt 
thereof. 
The amount of the anionic group in the polyester polyurethane is preferably 
from 0.05% by weight to 8% by weight. If the amount of the anionic group 
is less than 0.05% by weight, the water solubility or the water 
dispersibility of the polyester polyurethane is poor, whereas if the 
amount of the anionic group exceeds 8% by weight, water proofness of the 
primer layer after coating may be deteriorated or films may stick to each 
other by moisture absorption or the adhesion under high temperature and 
high humidity may be reduced. 
The polyester type resin as the water soluble or water dispersible resin 
usable in the present invention has a glass transition point (Tg) of not 
higher than 70.degree. C., preferably, 0.degree. to 60.degree. C. and, 
further preferably, 5.degree. to 50.degree. C. If Tg of the polyester type 
resin exceeds 70.degree. C., adhesion between a polyester film and the 
vapor-deposited metal may sometimes become poor. Further, if Tg of the 
polyester type resin is excessively low, films coated with a coating 
solution may stick to each other to reduce the operation efficiency. 
As examples of the components constituting the polyester type resin, the 
following polybasic carboxylic acids and polyhydroxy compounds can be 
mentioned. That is, as the polybasic carboxylic acid, there can be used 
terephthalic acid, isophthalic acid, o-phthalic acid, phthalic acid, 
4,4'-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 
2,6-naphthalene dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 
2-potassium sulfoterephthalic acid, 5-sodium sulfoisophthalic acid, adipic 
acid, azetaic acid, sebacic acid, dodecane dicarboxylic acid, glutaric 
acid, succinic acid, trimellitic acid, trimesic acid, trimellitic 
anhydride, phthalic anhydride, p-hydroxybenzoic acid, trimellitic acid 
mono potassium salt or an ester-forming derivative thereof. As the 
polyhydroxy compound, there can be used ethylene glycol, 1,2-propylene 
glycol, 1,3-propylene glycol, 1,3-propanediol, 1,4-butanediol, 
1,6-hexanediol, 2-methyl-1,5-pentanediol, neopentyl glycol, 
1,4-cyclohexanedimethanol, p-xylylene glycol, an adduct of bisphenol A and 
ethylene glycol, diethylene glycol, triethylene glycol, polyethylene 
glycol, polypropylene glycol, polytetramethylene glycol, 
polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, 
trimethylolpropane, sodium dimethylolethylsulfonate and potassium 
dimethylolpropionate. 
The polyester type resin with the glass transition point within the 
above-mentioned range is synthesized by properly selecting one or more of 
the compounds described above and by means of an ordinary polycondensation 
method. 
The polyester type resin in the present invention may be used as a coating 
agent using an organic solvent as the medium but it is preferred to be 
used as a coating agent using water as a medium in view of safety and 
sanitation. In a case of using water as the medium, the polyester type 
resin may be forcibly dispersed by the aid of a surface active agent or 
the like. However, the use of a self-dispersible type having a hydrophilic 
nonionic group such as polyethers or cationic group such as quaternary 
ammonium salt is preferred, and, the use of a water soluble or water 
dispersible polyester type resin having an anionic group, is more 
preferred. 
The polyester having the anionic group is prepared by bonding a compound 
having the anionic group to a polyester by means of copolymerization or 
graft. The anionic group is properly selected from sulfonic acid group, 
carboxylic acid group, phosphoric acid group or their lithium salt, sodium 
salt, potassium salt or ammonium salt. 
The amount of the anionic group in the polyester type resin is preferably 
from 0.05% to 8% by weight. If the amount of the anionic group is less 
than 0.05% by weight, the water solubility or the water dispersibility of 
the polyester type resin is poor. On the other hand, if the amount of the 
anionic group exceeds 8% by weight, the water proofness of the primer 
layer after coating is deteriorated or the films may stick to each other 
by absorption of moisture or the adhesion under high temperature and high 
humidity is deteriorated. 
The resin comprising the polyester component and the acryl component as the 
water soluble or water dispersible resin usable in the present invention 
is a mixture of a polyester resin and an acrylic resin, or a resin having 
the polyester moiety and the acryl moiety in one molecule. 
The resin comprising the polyester component and the acryl component in the 
present invention includes, preferably, 
(1) a resin comprising (a) a mixture of a polyester type resin and acrylic 
resin and/or (b) a reaction product of a polymerizable compound having 
carbon-carbon unsaturated bond (acryl component) And a polyester type 
resin as the main ingredient, 
(2) a resin comprising (a) a polyester type resin and (b) a reaction 
product of a polymerizable compound having a carbon-carbon unsaturated 
bond (acryl component) and a polyester type resin as a main ingredient, or 
(3) a resin comprising (a) acrylic resin and (b) a reaction product of a 
polymerizable compound having carbon-carbon unsaturation double bond 
(acryl component) and a polyester type resin as the main ingredient. 
As the component constituting the polyester type resin in the present 
invention, the components referred to the previous description for the 
polyester type resin can be used. The polyester polyurethane in which the 
chain of the polyester polyols is extended by isocyanate can also be used. 
The acrylic resin usable in the present invention is preferably a resin 
comprising an alkyl acrylate or alkyl methacrylate as the main ingredient. 
The coating film-forming property, strength of the coating film and the 
blocking resistance can be improved by setting the sum for the components 
of the alkyl acrylate and alkyl methacrylate to not less than 50 mol %, 
more preferably, not greater than 60 mol %. As the substituent alkyl group 
for the alkyl acrylate and the alkyl methacrylate, there can be mentioned, 
for example, methyl group, ethyl group, n-propyl group, isopropyl group, 
n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, lauryl 
group, stearyl group and cyclohexyl group. 
As the copolymerizing component other than the main component described 
above, use of a vinyl monomer having a functional group is recommended for 
improving the adhesion of a substrate polyester film and vapor-deposited 
metal. As a preferred functional group, there can be mentioned, for 
example, carboxyl group or its salt, acid anhydride group, amide group, 
hydroxy group, epoxy group, amino group which may be substituted or its 
salt, alkylolamino group or its salt. Specific examples of such vinyl 
monomer are shown below. 
Carboxylic acid such as (meth)acrylic acid, itaconic acid, maleic acid, 
fumaric acid, crotonic acid and metal salts or ammonium salts thereof; a 
monoester of the carboxylic acid above with a monohydric alcohol; an 
adduct of hydroxyalkyl esters of .alpha.,.beta.-unsaturated carboxylic 
acid such as 
2-hydroxyethyl (meth)acrylate, 
2-hydroxypropyl (meth)acrylate, 
3-hydroxypropyl (meth)acrylate, 
2-hydroxybutyl (meth)acrylate, 
3-hydroxybutyl (meth)acrylate, 
4-hydroxybutyl (meth)acrylate, 
3-chloro-2-hydroxypropyl (meth)acrylate, 
di-2-hydroxyethyl fumarate, 
mono-2-hydroxyethyl monobutyl fumarate and polyethylene glycol 
monomethacrylate, with anhydride of a polybasic carboxylic acid such as 
maleic acid, succinic acid, phthalic acid, hexahydrophthalic acid, 
tetrahydrophthalic acid, benzenetricarboxylic acid, benzentetracarboxylic 
acid, tetrachlorophthalic acid and dodecylsuccinic acid; a compound having 
amide group or alkylolamine group such as (meth)acrylamide, 
N-methylmethacrylamide, methylol methacrylamide, ureide vinyl ether and 
ureide ethyl acrylate; a compound having amino group or alkylolamino group 
such as diethylaminoethyl vinyl ether, 
2-aminoethyl vinyl ether, 
3-aminopropyl vinyl ether, 
2-aminobutyl vinyl ether, 
dimethylaminoethyl methacrylate and 
dimethylaminoethyl vinyl ether; a quaternary ammonium salt prepared from 
the compound having amino group or alkylolamino group recited above and a 
halogenated alkyl, dimethyl sulfuric acid or sultone; hydroxyalkyl esters 
of .alpha.,.beta.-unsaturated carboxylic acid such as 
2-hydroxyethyl (meth)acrylate, 
2-hydroxypropyl (meth)acrylate, 
3-hydroxypropyl (meth)acrylate, 
4-hydroxybutyl (meth)acrylate, 
3-chloro-2-hydroxypropyl (meth)acrylate, 
di-2-hydroxyethyl fumarate, 
mono-2-hydroxyethyl-monobutyl fumarate and 
polyethylene glycol monomethacrylate; and a compound having an epoxy group 
such as glycidyl (meth)acrylate, (2-methyl)glycidyl (meth)acrylate and 
(meth)acrylglycidyl ether. 
In addition to the compound as described above, it is also possible to use, 
in combination, (meth)acrylonitrile, styrene, butyl vinyl ether, mono- or 
dialkyl ester of maleic acid, mono- or dialkyl ester of fumaric acid, 
mono- or dialkyl ester of itaconic acid, methyl vinyl ketone, vinyl 
chloride, vinylidene chloride, vinyl acetate, vinyl pyridine, vinyl 
pyrrolidone, N-vinyl succinimide, N-vinyloxazolidone, silicone monomer 
such as vinyltrimethoxy silane, phosphorous atom-containing vinyl monomer 
such as 2-(meth)acryloyloxyethyl acid phosphate and a conjugated diene 
compound such as butadiene. 
A polymer having the acrylic unit such as a copolymer of polyester and 
polyacryl and a copolymer of silicone and polyacryl can be also used as 
the acrylic resin. 
The reaction between the compound having the carbon-carbon unsaturated bond 
and a polyester type resin is conducted by mixing a polyester type resin 
dispersed or dissolved in water or a solvent with a compound having 
carbon-carbon unsaturation bond, and using a polymerization initiator such 
as hydrogen peroxide, benzoyl peroxide, t-butyl peroxide, di-t-butyl 
peroxide, acetyl peroxide, azobisisobutyronitrile, cumene hydroperoxide, 
ammonium persulfate, potassium persulfate, 2,2-azobisaminomethane, 
2,2-azobisaminoethane, hydrogen chloride salt or sulfate salt thereof and 
ammonium ceric nitrate or a photopolymerization initiator such as 
2-hydroxy-2-methyl-1-phenylpropan-1-one and 
1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one. 
The blending ratio between the acrylic resin and the polyester type resin 
and the ratio of the polymerizable compound having the carbon-carbon 
unsaturation bond and the polyester type resin in the reaction product is 
such that the ratio of the polyester type resin is within a range, 
preferably from 5 to 95% by weight, more preferably, 10 to 85% by weight 
and, particularly preferably 20 to 80% by weight. If the ratio of the 
polyester type resin is less than 5% by weight, the adhesion to the 
polyester film or the strength of coating film may be deteriorated. On the 
other hand, if it exceeds 95% by weight, the effect of the acrylic resin 
and the compound having the carbon-carbon unsaturation bond cannot be 
expected so much and, when the film is wound into a roll, blocking is 
caused between the primer layer and the polyester film or between the 
primer layers to each other to cause practical problem. 
The coating agent containing the resin comprising the acrylic component and 
the polyester component in the present invention may be a coating agent 
using a solvent as the medium but it is preferably a coating agent using 
water as the medium in view of safety and sanitation. In a case of using 
water as the medium, the resin comprising the acrylic component and the 
polyester component may be compulsorily dispersed with the aid of a 
surface active agent or the like. However, the use of a self dispersion 
type resin having a hydrophilic nonionic group such as polyethers or a 
cationic group such as a quaternary ammonium salt group is preferred, and 
the use of a water soluble or water dispersible resin having an anionic 
group is more preferred. 
The water soluble or water dispersible resin having the anionic group is 
obtained by bonding a compound having an anionic group to the resin by 
means of copolymerization or graft. The anionic group can be properly 
selected from sulfonic acid group, carboxyl group, phosphoric acid group 
and lithium salt, sodium salt, potassium salt or ammonium salt thereof. 
The amount of the anionic group in the resin comprising polyester component 
and acryl component is preferably from 0.05% by weight to 8% by weight. If 
the amount of the anionic group is less than 0.05% the water solubility or 
water dispersibility of the resin is poor. On the other hand, if the 
amount of the anionic group exceeds 8% by weight, the water proofness of 
the primer layer after coating is deteriorated or films stick to each 
other by absorption of moisture to deteriorate the adhesion under high 
temperature and high humidity. 
The water soluble or water dispersible resin may further include those 
containing polyurethane or polyester and epoxy compound. The polyurethane 
is preferably a water soluble or water dispersible polyurethane having a 
carboxyl group or its salt on the side chain thereof. The preferred 
polyester is a water soluble or water dispersible polyester having a 
carboxyl group or its salt on the side chain thereof. The epoxy compound 
is preferred to have two or more epoxy group. 
The carboxyl group or its salt in the polyurethane or polyester 
(hereinafter simply referred to as the carboxyl group) is a hydrophilic 
functional group for improving the solubility or dispersibility to water 
and is a functional group capable of reacting with an epoxy group. 
The content of the carboxyl group in the polyurethane or polyester is 
preferably from 1 to 8% by weight. If the content of the carboxyl group is 
less than the above-mentioned range, the hydrophilic property of the 
polyurethane or the polyester becomes insufficient making it some time 
difficult to prepare the coating solution. On the other hand, if it is 
more than the above-mentioned range, the water proofness of the resultant 
coating film may some time be poor. 
The polyurethane may be prepared by reacting a polyhydroxy compound and a 
polyisocyanate compound in accordance with a usual method. 
As the polyhydroxy compound, there can be mentioned, for example, 
polyethylene glycol, polypropylene glycol, polyethylene-propylene glycol, 
polytetramethylene glycol, hexamethylene glycol, tetramethylene glycol, 
1,5-pentanediol, diethylene glycol, triethylene glycol, polycaprolactone, 
polyhexamethylene adipate, polyhexamethylene sebacate, polytetramethylene 
adipate, polytetramethylene sebacate, trimethylolpropane, 
trimethylolethane, pentaerythritol and glycerin. 
As the polyisocyanate compound, there can be mentioned, for example, 
hexamethylene diisocyanate, diphenylmethane diisocyanate, tolylene 
diisocyanate, isophorone diisocyanate, an adduct of tolylene diisocyanate 
with trimethylolpropane, and an adduct of hexamethylene diisocyanate with 
trimethylolethane. 
The carboxyl group can be introduced easily to the side chain of the 
polyurethane by a method, for example, of using a carboxyl 
group-containing polyhydroxy compound as one of starting polyhydroxy 
compounds or reacting a hydroxy group-containing carboxylic acid or an 
amino group-containing carboxylic acid to the unreacted isocyanate group 
in the polyurethane and then adding the reaction product in an aqueous 
alkaline solution for neutralization under a vigorous stirring. As the 
carboxyl group-containing polyhydroxy compound, there can be mentioned, 
for example, dimethylolpropionic acid, dimethylolacetic acid, 
dimethylolvaleric acid and bis(ethylene glycol) ester of trimellitic acid. 
As the hydroxy group-containing carboxylic acid, there can be mentioned, 
for example, 3-hydroxypropionic acid, .gamma.-hydroxybutyric acid, 
p-(2-hydroxyethyl)benzoic acid, malic acid or the like. As the amino 
group-containing carboxylic acid, there can be mentioned, for example, 
.beta.-aminopropionic acid, .gamma.-amino-butyric acid or p-aminobenzoic 
acid. 
As the polyester, either of saturated or unsaturated polyesters may be 
used. 
As the dicarboxylic acid component for the saturated polyester, there can 
be used, for example, an aromatic dicarboxylic acid such as terephthalic 
acid, isophthalic acid and 2,5-naphthalene dicarboxylic acid; an aliphatic 
dicarboxylic acid such as adipic acid, azelaic acid and sebacic acid; a 
hydroxycarboxylic acid such as hydroxybenzoic acid; and ester forming 
derivatives thereof. As the glycol component, there can be used, for 
example, an aliphatic glycol such as ethylene glycol, 1,4-butanediol, 
diethylene glycol and triethylene glycol; an alicyclic glycol such as 
1,4-cyclohexane dimethanol, an aromatic diol such as p-xylenediol, and a 
poly(oxyalkylene) glycol such as polyethylene glycol, polypropylene glycol 
and polytetramethylene glycol. 
The saturated polyester described above has a linear structure but it may 
be formed into a branched polyester by using a tri- or higher valent ester 
forming component. 
On the other hand, as the unsaturated polyester, there can be mentioned, 
for example, the followings. 
(1) An unsaturated polyester having a copolymerizable unsaturated group in 
the polymer chain obtained by reacting a starting compound containing a 
copolymerizable unsaturated group with other starting compound as 
disclosed in Japanese Patent Publication (KOKOKU) No. 45-2201, 46-2050, 
44-7134, Japanese Patent Application Laid-Open (KOKAI) No. 48-78233 and 
50-58123. 
(2) An unsaturated polyester obtained, as disclosed in Japanese Patent 
Publication (KOKOKU) No. 49-47916 and 50-6223, by preparing a saturated 
polyester, and subsequently adding to the saturated polyester a vinyl 
monomer, for example as shown below, having a functional group reactive 
with a functional group such as a hydroxy group or carboxyl group in the 
saturated polyester: 
(a) a compound having an epoxy group and a vinyl group such as glycidyl 
(meth)acrylate, 
(b) a compound having an alkoxysilanol group and an vinyl group such as 
vinylmethoxy silane and (meth)acryloxyethyl trimethoxysilane, 
(c) a compound having an acid anhydride group and a vinyl group such as 
maleic anhydride and tetrahydrophthalic anhydride, 
(d) a compound having an isocyanate group and a vinyl group such as an 
equimolar adduct of 2-hydroxypropyl (meth)acrylate and hexamethylene 
diisocyanate. 
The carboxyl group can be easily introduced to the side chain of the 
saturated or unsaturated polyester described above, for example, by a 
method of reacting a dioxane compound having a carboxylic group with the 
polyester as disclosed in Japanese Patent Laid-Open (KOKAI) No. 61-228030, 
a method of radical graft of an unsaturated carboxylic acid to the 
polyester as disclosed in Japanese Patent Laid-Open (KOKAI) No. 62-225510, 
a method of reacting the polyester and a halogenoacetic acid to introduce 
a carboxylic group on the aromatic ring as disclosed in Japanese Patent 
Laid-Open (KOKAI) No. 62-225527 or a method of reacting the polyester and 
a polybasic carboxylic anhydride as disclosed in Japanese Patent Laid-Open 
(KOKAI) No. 62-240318. 
The pair ion to the carboxylic group in the polyurethane and the polyester 
in the present invention is preferably a monovalent ion. In particular, a 
hydrogen ion or an amine type onium ion containing ammonium ion is 
preferred. 
The epoxy compound crosslinks with the polyurethane or polyester having the 
carboxyl group on the side chain to enhance the adhesion with the 
vapor-deposited thin metal layer. As the epoxy compound having two or more 
groups, there can be mentioned, for example, the following aliphatic epoxy 
compounds (a)-(k). 
##STR1## 
The blending ratio of the epoxy compound is preferably from 1 to 40% by 
weight, more preferably, from 2 to 30% by weight based on the polyurethane 
or polyester described above. If the ratio of the epoxy compound is less 
than 1% by weight, the effect for improving the water resistant adhesion 
can not be attained sufficiently. On the other hand, if the ratio of the 
epoxy compound is larger than 40% by weight, reduction is caused in the 
water resistant adhesion, which is assumed to due to the remaining 
unreacted epoxy compound. 
The coating solution containing the polyurethane or polyester and the epoxy 
compound having two or more epoxy groups may also contain, for example, 
tertiary amine (including guanidine, biguanide and imidazole containing a 
tertiary amino group), boron complex salt, Lewis acid, inorganic acid, 
short chain amide, dihydrazide or titanate ester as a catalyst, in order 
to improve the reactivity of the epoxy group. 
The content of the water soluble or water dispersible resin in the coating 
solution is preferably from 20 to 100% by weight. 
The coating solution in the present invention may contain methylol or 
alkylol urea compounds, melamine compounds, guanamine compounds, 
acrylamide compounds or polyamide compounds, epoxy compound, azylidine 
compound, block polyisocyanate, silane coupling agent, titanium coupling 
agent, zirco-aluminate coupling agent, vinyl compound reactive by heat, 
peroxide or light and photosensitive resin as a crosslinking agent for the 
improvement of the stickiness (blocking), water proofness, solvent 
resistance and mechanical strength of the coating layer. Further, it may 
contain silica, silica sol, alumina, alumina sol, zirconium sol, kaolin, 
talc, calcium carbonate, titanium oxide, barium salt, carbon black, 
molybdenum sulfide or antimony oxide sol in such an amount as to provide 
the coating layer with a surface roughness within a range described later 
as inorganic fine particles for the improvement of the stickiness and 
slipping property. 
Further, the coating solution may contain, as required, defoaming agent, 
coating improver, viscosity improver, antistatic agent, organic lubricant, 
organic polymer particle, antioxidant, UV-ray absorber, foaming agent, 
dye, pigment or the like. Further, the coating solution may contain, in 
addition to the water soluble or water dispersible resin, a different kind 
of polymer such as polyurethane, polyester, acryl resin or vinyl resin for 
the improvement of the characteristics of the coating solution or coating 
layer. 
The medium for the coating solution may include water and a mixed solvent 
of water and an organic solvent, and water is preferred in view of safety 
and sanitation. The organic solvent may include methanol, ethanol, 
isopropyl alcohol, n-butanol, ethylene glycol, propylene glycol, methyl 
cellosolve, ethyl cellosolve, n-butyl cellosolve, dioxane, 
tetrahydrofuran, ethyl acetate, methyl ethyl ketone and 
n-methylpyrrolidone. 
As the method of coating the above-mentioned coating solution on the 
polyester film, there can be mentioned a method of coating a coating 
solution to an unstretched polyester film and then successively or 
simultaneously biaxially stretching the coated film; a method of coating 
the coating solution to a monoaxially stretched polyester film and then 
stretching the coated film in the direction perpendicular to the previous 
monoaxial stretching direction; a method of stretching the biaxially 
stretched film having the coating layer again; or a method of coating a 
coating solution to a biaxially stretched polyester film and then further 
stretching the coated film in the transverse and/or machine direction, by 
using a reverse roll coater, a gravure coater, a load coater, an air 
doctor coater or other coating devices as shown in "Coating System", 
written by Yuji Harazaki, published from Maki Shoten in 1979. 
The stretching step is conducted at a temperature, preferably of 60.degree. 
to 130.degree. C. and the stretching ratio is at least 4 times, 
preferably, 6 to 20 times as expressed by the area ratio. The stretched 
film is subjected to a heat treatment at 150.degree. to 250.degree. C. 
Further, it is preferred to subject to relaxation by 0.2 to 20% in the 
machine direction and the transverse direction in the highest temperature 
zone for the heat treatment and/or cleaning zone at the exit of the heat 
treatment. 
In particular, it is preferred to use such a method of coating a coating 
solution to a polyester film monoaxially stretched by 2 to 6 times at 
60.degree.-130.degree. C. by a roll stretching process and, with or 
without appropriate drying, stretching the coated polyester film by 2 to 6 
times in the direction perpendicular to the previous stretching direction 
at 80.degree. to 130.degree. C. and then subjecting to a heat treatment at 
150.degree. to 250.degree. C. for 1 to 600 sec. 
According to this method, it is possible to dry the coating layer at the 
same time with stretching as well as reduce the thickness of the coating 
layer in accordance with the stretching ratio, so that a film suitable to 
the polyester film substrate can be manufactured at a relatively reduced 
cost. 
The coating solution may be applied either only one surface or both 
surfaces of the polyester film. In a case of single-surface coating, a 
different kind of coating layer may be formed on the opposite surface, as 
required, to provide other characteristics to the polyester film. Further, 
for improving the coating property and the adhesion of the coating agent 
to the film, a chemical treatment or electric discharging treatment may be 
applied to the film prior to the coating. Further, for improving the 
adhesion, coating property or the like of the biaxially stretched 
polyester film to the coating layer, an electric discharge treatment may 
be applied to the coating layer after forming the coating layer. 
The thickness of the coating layer is preferably within a range from 0.01 
to 5 .mu.m and, more preferably, within a range from 0.02 to 1 .mu.m. The 
thickness of the coating layer is preferred to be reduced also in view of 
the demand for reducing the size of the capacitor. However, if the 
thickness of the coating layer is less than 0.01 .mu.m, it is difficult to 
obtain a uniform coating layer and, accordingly, coating unevenness tends 
to be caused to the product which is not undesirable. 
The thickness of the polyester film as the substrate is preferably in a 
range from 0.5 to 30 .mu.m, more preferably from 0.8 to 15 .mu.m. The 
thickness of the polyester film is preferred to be thinner in view of the 
demand for reducing the size of the capacitor. However, an extremely 
thinner polyester film is not preferred due to poor workability and poor 
handling property. 
In the coating layer formed as described above, the contact angle of water 
droplet is preferably not less than 60.degree.. If the contact angle of 
droplet is less than 60.degree., the water resistant adhesion with the 
vapor-deposited metal film is sometimes insufficient. Accordingly, the 
amount of the hydrophilic group, the amount of the emulsifier and the 
amount of the hydrophilic compound in the coating agent is preferred to be 
so selected that the contact angle of water droplet against the coating 
layer may be not less than 60.degree.. 
Further, it is necessary that the average center line surface roughness 
(Ra) at the surface of the coating layer is within a range from 0.005 to 
0.5 .mu.m, preferably, within a range from 0.02 to 0.3 .mu.m. If Ra is 
less than 0.005 .mu.m, the slipping property film is insufficient to 
worsen the operability. On the other hand, if Ra exceeds 0.5 .mu.m, the 
surface is too roughened to deteriorate the dielectric strength. Further, 
it is neither preferred also in view of the demand for the increase of the 
capacitance and reduction of the size of the capacitor. 
In the present invention, as the metal to be vapor deposited, there can be 
mentioned aluminum, palladium, zinc, nickel, silver, copper, gold, indium, 
tin, stainless steel, chromium and titanium, and most preferred metal is 
aluminum. The metal mentioned above also includes metal oxides. The 
thickness of the vapor-deposited metal film or layer is preferably within 
a range from 10 to 5000 .ANG.. 
Vapor deposition is generally conducted by vacuum vapor deposition but it 
may be applied by a method such as electroplating or sputtering. 
The vapor-deposited layer may be formed on one surface or on both surfaces 
of the polyester film, and surface treatment or film coating treatment 
with other resin to the vapor-deposited metal layer may be applied. 
Two metallized polyester films obtained in this way are stacked and wound 
or a plurality of the films are stacked to prepare a capacitor element and 
then applied, for example, with hot press, taping, metallikon, voltage 
treatment, sealing at both end faces, attaching of lead wires in 
accordance with the customary manner to fabricate a capacitor. 
The present invention will now be described more specifically by way of 
examples but the invention is not restricted only to the following 
examples unless it goes beyond the scope of the present invention. 
Evaluation methods used in the examples are shown below. 
(1) Average Center line surface roughness (Ra) 
Ra was determined as below by using a surface roughness meter (SE-3F) 
manufactured by Kosaka Kenkyusho Co. A portion of a reference length L 
(2.5 mm) was sampled out from a cross sectional curve of a coated film 
along the direction of the center line. The curve was expressed as the 
roughness curve y=f(x) by assuming the center line of the sampling part as 
x-axis and the direction perpendicular to x-axis as y-axis. The value 
calculated from the following formula was represented by .mu.m as the 
average surface roughness of the film. The average center line surface 
roughness was obtained by determining ten cross sectional curves from the 
surface of the coated film and expressing by an average value of center 
line surface roughnesses for the sampled portions determined from the 
cross sectional curves. The radius of the feeler was 2 .mu.m, the load was 
30 mg and the cut off values was 0.8 mm. 
##EQU1## 
(2) Contact angle of water droplet 
A contact angle against the surface of a coating layer at a temperature of 
23.degree. C. and a humidity of 50% RH with distilled water was measured 
by using a contact angle gauge (CA-DT-A type, manufactured by Kyowa Kaimen 
Kagaku Co.). The contact angle was measured for three specimens each on 
two points in right and left part, that is, six points in total and an 
average value was determined as the contact angle. 
The diameter of a water droplet was set to 2 mm and the value one min after 
the dropping was read. 
(3) Evaluation for Adhesion 
After laminating a polyester film of a thickness identical with that of a 
substrate polyester film to the surface of a vapor-deposited thin metal 
layer of a metallized film by means of a usual dry lamination method, 
aging treatment was applied. The resultant laminate was shaped into a 
rectangular form of 15 mm width and immersed in a hot water at 50.degree. 
to 55.degree. C. for 30 min (boiling treatment). 
The end of the specimen applied with the boiling treatment was partially 
peeled, and the specimen was further subjected to T-peeling at a speed of 
100 mm/min by using a peeling tester to measure the load required to peel 
off. The T-peeling was further carried out applying water on the peeling 
portion. The evaluation standard for adhesion was as shown below. 
______________________________________ 
o: 100 g &lt; peeling load 
.DELTA.: 10 g .ltoreq. peeling load .ltoreq. 100 g 
x: peeling load .ltoreq. 10 g 
______________________________________ 
(4) Dielectric strength 
Measurement was conducted in accordance with JIS (Japanese Industrial 
Standard) C-2319 
The voltage was increased at a rate of 100 V/sec in an atmosphere at a 
temperature of 23.degree. C. and a humidity of 50% RH by using a 10 kV DC 
dielectric strength tester, and voltage at which the metallized film was 
broken to cause short-circuit was read. 
(5) Change of the static capacitance 
A capacitor was left in an atmosphere at a temperature of 60.degree. C. and 
a humidity of 95% RH for 1000 hours and the change was determined as the 
rate of change in static capacitance based on the initial static 
capacitance as a reference value. 
(6) Glass transition point (Tg) 
Measurement was made by using a differential scanning calorimeter SSC580 
DSC20 type manufactured by Seiko Denshi Kogyo Co. The measuring conditions 
of DSC were as shown below. Namely, 10 mg of a previously frozen-dry 
specimen was set to the DSC device, heated to a temperature of 200.degree. 
C. at a rate of 10.degree. C./min, quenched by liquid nitrogen and then 
heated again to a range from -50.degree. C. to 200.degree. C. at a rate of 
10.degree. C./min and the glass transition point was measured. The glass 
transition point was detected when the DSC curve was bent by the change of 
the specific heat and the base line was moved in parallel. A crossing 
point between a tangential line for the base line at a temperature lower 
than the bending point and a tangential line at a point of the bent 
portion with the greatest gradient is defined as the starting point for 
the bending and the temperature at the starting point was determined as 
the glass transition point. 
(7) Blocking resistance 
A surface of a coating layer of a polyester film and another polyester film 
with no coating layer were stacked to each other and pressing was applied 
at a temperature of 40.degree. C., a relative humidity of 80% RH and under 
a load of 10 kg/cm.sup.2 for 20 hours. The specimen after the 
above-mentioned treatment was visually evaluated based on the following 
standards for the judgment. 
o: no blocking at all 
.DELTA.: partial blocking 
.times.: blocking for not less than 50% portion 
EXAMPLE 1 
100 parts of dimethyl terephthalate, 70 parts of ethylene glycol and 0.11 
parts of calcium acetate monohydrate were charged in a reactor and heated 
to an elevated temperature while distilling off methanol to conduct ester 
interchange reaction. The temperature was elevated to 230.degree. C. in 
about 4 hours after starting the reaction to substantially complete the 
ester interchange reaction. 
Subsequently, a solution prepared by dissolving 0.065 parts of triethyl 
phosphite and 0.30 parts of triethyl phosphate in ethylene glycol was 
added to the reaction mixture, to which 0.04 parts of antimony trioxide 
was added and the temperature was elevated to 238.degree. C. in 10 min. 
Then, polycondensation reaction was conducted by a customary method to 
obtain a polyethylene terephthalate (A) with an intrinsic viscosity of 
0.66 after 4 hours. 
The polyester contained 0.23% by weight of deposited particles containing 
elemental calcium and elemental phosphorous by 6.4% and 6.5% by weight 
respectively. The average particle size was 1.2 .mu.m. 
On the other hand, a polyethylene terephthalate (B) containing 1.0% by 
weight of calcium carbonate with an average particle size of 1.6 .mu.m was 
prepared. Namely, after conducting an ester interchange reaction in the 
same manner as in the preparation for the polyester (A), 0.036 parts of 
phosphoric acid and 0.04 parts of antimony trioxide were added, to which a 
predetermined amount of calcium carbonate was added and polycondensation 
reaction was conducted by a customary method. A polyester (B) with an 
intrinsic viscosity of 0.65 was obtained after 4 hours. 
Subsequently, after blending 90 parts of the polyester (A) and 10 parts of 
the polyester (B), they were extruded into a sheet from an extruder at 
290.degree. C. and then quenched to obtain an amorphous sheet. After 
stretching the resultant sheet at 95.degree. C. in the machine direction 
by 4.2 times, a coating solution comprising 80 parts (weight for solid 
content, here and hereinafter) of a polyester polyurethane having 
isophorone diisocyanate (trade name Hydran AP-40, manufactured by 
Dainippon Ink Chemical Industry Co.) and 20 parts of a water dispersible 
polyester (trade name: Polyester WR-961, manufactured by Nippon Gosei 
Kagaku Kogyo Co.) and using water as a medium was coated on one surface of 
the film. Then the coated film was stretched at 110.degree. C. in the 
transverse direction by 3.9 times and then subjected to a heat treatment 
at 230.degree. C. to obtain a biaxially stretched polyester film with the 
thickness of the coating layer of 0.04 .mu.m and the thickness of the 
polyester film substrate of 2.2 .mu.m. 
The contact angle of water droplet against the coating layer was 63.degree. 
and the average center line surface roughness (Ra) was 0.020 .mu.m. 
Aluminum was vapor deposited to a thickness of 450 .ANG. on the coating 
surface of the resultant film by using a resistance heating type 
metallizing apparatus under a pressure in the vacuum chamber of lower than 
10.sup.-4 Torr. 
The resultant vapor-deposited film had an excellent adhesion in the 
adhesion evaluation test. 
Two vapor-deposited films were stacked and wound and attached with 
electrodes to prepare a film capacitor of 0.1 .mu.F capacitance. 
As shown in Table 1, the resultant metallized film capacitor was excellent 
in dielectric strength characteristic, with less change in the static 
capacitance and excellent in the moist heat resistance. 
Results of experiments and comparative experiments described later are also 
shown collectively in Table 1. 
Comparative Example 1 
A metallized polyester film capacitor was prepared in the same procedures 
as those in Example 1 except for not coating a coating solution as used in 
Example 1. 
The resultant capacitor was inferior with respect to the moist heat 
resistance characteristic as compared with Example 1. 
EXAMPLE 2 
A polyester polyol comprising 664 parts of terephthalic acid, 631 parts of 
isophthalic acid, 472 parts of 1,4-butanediol and 447 parts of neopentyl 
glycol was obtained, to which 321 parts of adipic acid and 268 parts of 
dimethylolpropylenic acid were added to obtain a polyester polyol (C) 
having pendant carboxyl groups. 
A polyester polyurethane (D) was prepared by adding 160 parts of tolylene 
diisocyanate to 1880 parts of the polyester polyol (C). 
A metallized polyester film was obtained in the same procedures as those in 
Example 1 except for blending 80 parts by weight of the polyester 
polyurethane (D) as described above instead of Hydran AP-40 in Example 1. 
Comparative Example 2 
A metallized polyester film was obtained in the same procedures as those in 
Example 1 except for coating a coating solution comprising 70 parts of a 
surface active agent--forced-emulsion type polyurethane aqueous dispersion 
(trade name Superflex 4000, manufactured by Daiichi Kogyo Seiyaku Co.), 10 
parts of polyoxyethylene nonyl phenyl ether and 20 parts of the Polyester 
WR-961 manufactured by Nippon Gosei Kagaku Kogyo Co. and using water as 
the medium on one surface of the film. 
In the coating layer of Comparative Example 2, the contact angle of water 
droplet against the coating layer was as low as 57.degree. due to the 
surface active agent and the adhesion between the polyester film and 
vapor-deposited metal layer was also poor. 
A capacitor obtained in the same procedures as those in Example 1 by using 
the metallized polyester film was poor in the moist heat resistance 
characteristic. 
EXAMPLE 3 
A polyethylene terephthalate containing 0.1 parts of silica with an average 
particle size of 0.1 .mu.m was extruded into a sheet through an extruder 
at a temperature of 290.degree. C. and quenched to obtain an amorphous 
sheet. After stretching the resultant sheet in the machine direction by 
4.2 times, a coating solution comprising 80 parts of AP-40, 15 parts of 
WR-961 and 5 parts of silica sol with an average particle size of 0.06 
.mu.m and using water as a medium was coated and, subsequently, a 
metallized polyester film capacitor was obtained in the same procedures as 
those in Example 1. 
Comparative Example 3 
A polyester film was obtained in the same procedures as those in Example 3 
excepting for not coating the coating solution as used in Example 3. 
The film had an average center line surface roughness of 0.002 .mu.m and 
the winding operability was poor because of poor slipping property and 
could not be served to practical use. 
TABLE 1 
__________________________________________________________________________ 
Vapor- 
Capacitor 
Substrate film 
deposited Rate of 
Con- film Dielectric 
change in 
Coating 
Ra tact Adhe- 
strength 
capacitance 
layer 
(.mu.m) 
angle 
sion (kV/.mu.m) 
(%) 
__________________________________________________________________________ 
Example 1 
Provided 
0.020 
63.degree. 
o 0.56 0.9 
Comparative 
Not 0.021 
66.degree. 
x 0.55 3.8 
Example 1 
provided 
Example 2 
Provided 
0.021 
63.degree. 
o 0.56 0.8 
Comparative 
Provided 
0.025 
56.degree. 
x 0.55 3.2 
Example 2 
Example 3 
Provided 
0.025 
62.degree. 
o 0.60 1.0 
Comparative 
Not 0.002 
66.degree. 
x -- -- 
Example 3 
provided 
__________________________________________________________________________ 
EXAMPLE 4 
100 parts of dimethyl terephthalate, 70 parts of ethylene glycol and 0.11 
parts of calcium acetate monohydrate were charged in a reactor and heated 
to an elevated temperature while distilling off methanol to conduct ester 
interchange reaction. The temperature was elevated to 230.degree. C. in 
about 4 hours after starting the reaction to substantially complete the 
ester interchange reaction. Subsequently, 0.065 parts of triethyl 
phosphite and 0.30 parts of triethyl phosphate were added to the reaction 
mixture, to which 0.04 parts of antimony trioxide was further added and 
polycondensation reaction was conducted to obtain a polyester (A) with an 
intrinsic viscosity of 0.66 after 4 hours. 
A polyester (B) containing 1.0% by weight of calcium carbonate with an 
average particle size of 1.6 .mu.m was obtained in the same procedures as 
those in the preparation of the polyester (A) except for adding the 
calcium carbonate. 
On the other hand, 100 parts of dimethyl isophthalate, 15 parts of dimethyl 
sebacate, 6 parts of sodium dimethyl-5-sulfoisophthalate, 80 parts of 
ethylene glycol and 0.041 parts of manganese acetate tetrahydrate were 
heated to an elevated temperature while distilling off methanol to conduct 
ester interchange reaction. The temperature was elevated to 230.degree. C. 
in 4 hours after starting the reaction to substantially complete the ester 
interchange reaction. Then, 0.005 parts of phosphoric acid was added to 
the reaction mixture, to which 0.04 parts of antimony trioxide was further 
added and a polycondensation reaction was conducted to obtain a 
copolyester (E) with an intrinsic viscosity of 0.50 after 4 hours. The 
glass transition point of the resultant copolyester (E) was 38.degree. C. 
180 parts of water was added under vigorous stirring to a solution 
comprising 20 parts of the copolyester (E) dissolved in 80 parts of 
tetrahydrofuran to obtain an aqueous dispersion of copolyester (E). 
Then, after blending 90 parts of the polyester (A) and 10 parts of the 
polyester (B), they were melt-extruded at 290.degree. C. into an amorphous 
sheet, stretched in the machine direction at 90.degree. C. by 4.2 times 
and then the aqueous dispersion of the copolyester (E) was coated on one 
surface of the film, which was then stretched in the transverse direction 
at 110.degree. C. by 3.9 times and subjected to a heat treatment at 
230.degree. C. to obtain a biaxially stretched polyester film with a 
thickness of the coating layer of 0.04 .mu.m and the thickness of the 
substrate polyester film of 4 .mu.m. The contact angle of water droplet 
against the coating layer was 63.degree. and the average central line 
surface roughness (Ra) was 0.20 .mu.m. Aluminum was vapor deposited to a 
thickness of 450 .ANG. on the coating surface of the resultant film by 
using a resistance heating type metallizing apparatus under a pressure in 
a vacuum chamber of not higher than 10.sup.-4. 
The resultant vapor-deposited film had an excellent adhesion in the 
evaluation for the adhesion. Two vapor deposited films were stacked and 
wound and applied with electrodes to form a film capacitor of 0.1 .mu.F. 
As shown in Table 2, the resultant metallized film capacitor was excellent 
in dielectric strength characteristics, with less change in the static 
capacitance and excellent in the moist heat resistance characteristics. 
Comparative Example 4 
A metallized polyester film capacitor was obtained in the same procedures 
as those in Example 4 except for not coating the coating solution as used 
in Example 4. 
EXAMPLE 5 
A metallized polyester film capacitor was obtained in the same manner as in 
Example 4 except for coating an aqueous dispersion of the copolyester (F) 
comprising 100 parts of dimethyl terephthalate, 20 parts of sodium 
dimethyl-5-sulfoisophthalate and 80 parts of ethylene glycol instead of 
the aqueous dispersion of the copolyester (E) in Example 4. 
Comparative Example 5 
A metallized polyester film capacitor was obtained in the same procedures 
as those in Example 4 except for coating an aqueous dispersion of the 
copolyester (G) comprising 100 parts of dimethyl terephthalate, 20 parts 
of sodium dimethyl-5-sulfoisophthalate and 80 parts of cyclohexane 
dimethanol instead of the aqueous dispersion of the copolyester (E) in 
Example 4. 
EXAMPLE 6 
After blending 90 parts of the polyester (A) and 10 parts of the polyester 
(B), they were melt-extruded into an amorphous sheet at 290.degree. C., 
stretched in the machine direction at 90.degree. C. by 4.2 times, then 
stretched in the transverse direction at 110.degree. C. by 3.9 times and 
subjected to a heat treatment at 230.degree. C. to obtain a biaxially 
stretched polyester film with a thickness of 4 .mu.m. A coating solution 
of 90 parts of TP-236 (Tg: 60.degree. C.) which was a copolyester 
manufactured by Nippon Gosei Co. and 10 parts of Coronate which was a 
polyisocyanate manufactured by Nippon Polyurethane Co. in a mixed solvent 
comprising methyl ethyl ketone and toluene was coated on the substrate 
polyester film. The thickness of the coating layer after drying was 0.1 
.mu.m. 
From the resultant polyester film, a metallized polyester film capacitor 
was obtained in the same procedures as those in Example 4. 
EXAMPLE 7 
A metallized polyester film capacitor was obtained in the same procedures 
as those in Example 6 except for using a coating solution blended with 
SP-131 (Tg: -20.degree. C.) which was a copolyester manufactured by Nippon 
Gosei Co. in place of TP-236 used in Example 6. 
The resultant metallized polyester film capacitor had satisfactory moist 
heat resistance but the polyester film having the above-mentioned coating 
layer was slightly insufficient in the slipping property. 
Comparative Example 6 
After melt-extruding a polyethylene terephthalate containing 0.1 parts of 
silica with an average particle size of 0.1 .mu.m into an amorphous sheet 
at 290.degree. C., it was stretched in the machine direction at 90.degree. 
C. by 4.2 times and then an aqueous dispersion of the copolyester (E) was 
coated on one surface of the film. Then a polyester film was obtained in 
the same procedures as those in Example 4. The average center line surface 
roughness of the film was 0.002 .mu.m and since the slipping property was 
poor, the winding operability was poor and the film could not be served 
practical use. 
EXAMPLE 8 
A polyester film having a coating layer was obtained in the same procedures 
as those in Comparative Example 6, excepting for using a coating solution 
comprising 95 parts of an aqueous dispersion of the copolyester (E) and 5 
parts of an aqueous dispersion of silica sol with an average particle size 
of 0.06 .mu.m instead of the aqueous dispersion of the copolyester (E) in 
Comparative Example 6. 
By using the polyester film thus obtained, a metallized polyester film 
capacitor was obtained in the same procedures as those in Example 4. 
TABLE 2 
__________________________________________________________________________ 
Charac- 
Surface teristics 
Characteristics 
characteristics 
of vapor 
of capacitor 
Tg of 
of coating 
deposi- Rate of 
coating 
layer tion Dielectric 
change in 
agent 
Ra Contact 
Adhe- 
strength 
capacitance 
(.degree.C.) 
(.mu.m) 
angle 
sion (kV/.mu.m) 
(%) 
__________________________________________________________________________ 
Example 4 
38 0.020 
62.degree. 
o 0.56 0.9 
Comparative 
-- 0.020 
66.degree. 
x 0.55 -12.0 
Example 4 
Example 5 
41 0.021 
57.degree. 
.DELTA. 
0.56 -2.9 
Comparative 
80 0.025 
57.degree. 
x 0.55 -10.9 
Example 5 
Example 6 
60 0.020 
64.degree. 
o 0.55 0.5 
Example 7 
-20 0.018 
64.degree. 
o 0.54 0.8 
Comparative 
38 0.002 
62.degree. 
-- -- -- 
Example 6 
Example 8 
38 0.025 
61.degree. 
o 0.60 0.6 
__________________________________________________________________________ 
EXAMPLE 9 
100 parts of dimethyl terephthalate, 70 parts of ethylene glycol and 0.11 
parts of calcium acetate monohydrate were charged in a reactor and heated 
to an elevated temperature while distilling off methanol to conduct ester 
interchange reaction. The temperature was elevated to 230.degree. C. in 
about 4 hours after starting the reaction to substantially complete the 
ester interchange reaction. Subsequently, 0.065 parts of triethyl 
phosphite, 0.30 parts of triethyl phosphate were added to the reaction 
mixture, to which 0.04 parts of antimony trioxide was further added and 
polycondensation reaction was conducted to obtain a polyester (A1) with an 
intrinsic viscosity of 0.66 after 4 hours. 
A polyester (A2) containing 1.0% by weight of calcium carbonate with an 
average particle size of 1.6 .mu.m was obtained in the same manner as the 
preparation for the polyester (A), excepting for adding the calcium 
carbonate. 
On the other hand, 20 parts of dimethyl terephthalate, 80 parts of dimethyl 
isophthalate, 25 parts of dimethyl sebacate, 6 parts of sodium 
dimetyl-5-sulfoisophthalate, 80 parts of ethylene glycol and 0.041 parts 
of manganese acetate tetrahydrate were heated to an elevated temperature 
while distilling off methanol to conduct ester interchange reaction. The 
temperature was elevated to 230.degree. C. in 4 hours after the starting 
the reaction to substantially complete the ester interchange reaction. 
Subsequently, 0.005 parts of phosphoric acid was added to the reaction 
mixture, to which 0.04 parts of antimony trioxide was further added to 
conduct polycondensation reaction and a copolyester with an intrinsic 
viscosity of 0.50 was obtained after 4 hours. After adding 180 parts of 
water under high speed stirring to a solution of 20 parts of the resultant 
copolyester in 80 parts of tetrahydrofuran, tetrahydrofuran was removed by 
evaporation under heating to obtain an aqueous dispersion of a copolyester 
(A3). 
On the other hand, 51 parts of ethyl acrylate, 40 parts of methyl 
methacrylate, 9 parts of methacrylic acid, 0.5 parts of dodecyl mercaptan 
and 0.25 parts of sodium lauryl sulfate dissolved in one part of water 
were homogeneously mixed by a blender to obtain a monomer emulsion. The 
monomer emulsion and 0.8 parts of ammonium persulfate dissolved in 1.5 
parts of water were separately dropped into 187 parts of water at a 
temperature of 75.degree. C. to conduct reaction, while maintaining the 
reaction temperature at 75.degree. to 85.degree. C. After the dropping was 
over, an aqueous 28% ammonia was added therein to adjust the pH to 7.5 
while maintaining the temperature at 80.degree. C. for further 3 min, and 
aged for 30 min to obtain a polyacrylic aqueous dispersion (B1). 
Then, after blending 90 parts of the polyester (A1) and 10 parts of the 
polyester (A2), they were melt-extruded into an amorphous sheet at 
290.degree. C., stretched in the machine direction at 90.degree. C. by 4.2 
times. A coating agent comprising 80 parts of the aqueous dispersion of 
the copolyester (A3) and 20 parts of the polyacrylic aqueous dispersion 
(B1) was coated on one surface of the film and, subsequently, stretched in 
the transverse direction by 3.9 times at 110.degree. C. and subjected to a 
heat treatment at 230.degree. C. to obtain a biaxially stretched polyester 
film with the thickness of a coating layer of 0.04 .mu.m and the thickness 
of the substrate polyester film of 4 .mu.m. 
The resultant film had a contact angle of water droplet against the coating 
layer of 63.degree. and the average center line surface roughness (Ra) of 
0.020 .mu.m. 
Aluminum was vapor deposited to a thickness of 450 .ANG. on the coating 
surface of the resultant film by using a resistance heating type 
metallizing apparatus under a pressure in a vacuum chamber of not higher 
than 10.sup.-4 Torr. 
The resultant vapor deposited film had an excellent adhesion in the 
evaluation test for the adhesion. 
Two vapor-deposited films were stacked to each other and wound, and 
attached with electrodes to manufacture a film capacitor of 0.1 .mu.F 
capacitance. 
As shown in Table 3, the resultant metallized film capacitor was excellent 
in dielectric strength characteristics, with less change of the static 
capacitance and excellent in the moist heat resistance characteristics. 
EXAMPLE 10 
An aqueous dispersion of a polyester comprising 50 mol % of terephthalic 
acid, 40 mol % of isophthalic acid and 10 mol % of disodium 
sulfoisophthalate as the dicarboxylic acid component and 67 mol % of 
ethylene glycol and 33 mol % of diethylene glycol as the glycol component 
was sufficiently displaced with nitrogen gas, and was dissolved acrylamide 
thereinto. To the mixture, ammonium cerium nitrate was further added as a 
polymerization initiator and stirred under a nitrogen atmosphere to obtain 
an aqueous dispersion of the reaction product (C1) at a ratio of 70 parts 
of polyester and 30 parts of polyacryl amide. 
A metallized polyester film capacitor was prepared in the same procedures 
as those in Example 9, except for coating 100 parts of the aqueous 
dispersion (C1) instead of the coating solution used in Example 9. 
EXAMPLES 11 TO 13 
Metallized polyester film capacitors were obtained in the same procedures 
as those in Example 9, except for using a coating solution of a blend 
composition shown in Table 3 instead of the coating solution used in 
Example 9. 
Comparative Example 7 
A metallized polyester film capacitor was obtained in the same procedures 
as those in Example 9, except for using no coating solution. The resultant 
capacitor was poor in the moist heat resistant characteristics as compared 
with Example 9. 
Comparative Example 8 
A polyester film having a coating layer was obtained in the same procedures 
as those in Example 9, except for coating 100 parts of the copolyester 
aqueous dispersion (A3) instead of the coating solution used in Example 9. 
The resultant polyester film partially caused blocking and was poor in the 
operability. 
EXAMPLE 14 
A metallized polyester film capacitor was obtained in the same procedures 
as those in Example 9, except for blending 80 parts of an aqueous 
dispersion (A4) of a copolyester comprising 100 parts of dimethyl 
terephthalate, 25 parts of sodium dimetyl-5-sulfoisophthalate and 80 parts 
of ethylene glycol into a coating solution instead of the copolyester 
aqueous dispersion (A3) used in Example 9. 
Comparative Example 9 
A polyethylene terephthalate containing 0.1 parts of silica with an average 
particle size of 0.1 .mu.m was melt-extruded at 290.degree. C. into an 
amorphous sheet, stretched in the machine direction by 4.2 times at 
90.degree. C. A coating solution comprising 80 parts of the copolyester 
aqueous dispersion (A3) and 20 parts of the polyacrylic aqueous dispersion 
(B1) was coated on one surface of the film and then a polyester film was 
obtained in the same procedures as those in Example 9. The film had an 
average center line surface roughness of 0.002 .mu.m and since the 
slipping property was poor, the winding operability was poor and could not 
be served for practical use. 
EXAMPLE 15 
A polyester film having a coating layer thereon was obtained in the same 
procedures as those in Comparative Example 9, except for using a coating 
solution comprising 75 parts of the copolyester aqueous dispersion (A3), 
20 parts of the polyacrylic aqueous dispersion (B1) and 5 parts of an 
aqueous dispersion of silica sol with an average particle size of 0.06 
.mu.m (S1) instead of the coating solution used in Comparative Example 9. 
By using the polyester film thus obtained, a metallized polyester film 
capacitor was obtained in the same procedures as those in Example 9. 
The obtained results are collectively shown in the following Tables 3 and 
4. 
TABLE 3 
______________________________________ 
Composition of 
Characteristics 
coating of coating layer 
solution Ra Contact Blocking 
A3/A4/B1/C1/S1 
(.mu.m) angle resistance 
______________________________________ 
Example 9 80/0/20/0/0 0.020 63.degree. 
o 
Example 10 
0/0/0/100/0 0.021 63.degree. 
o 
Example 11 
60/0/20/20/0 
0.021 62.degree. 
o 
Example 12 
60/0/0/40/0 0.023 62.degree. 
o 
Example 13 
0/0/20/80/0 0.021 62.degree. 
o 
Example 14 
0/80/20/0/0 0.020 57.degree. 
o 
Example 15 
75/0/20/0/5 0.025 61.degree. 
o 
Comparative 
0/0/0/0/0 0.020 66.degree. 
o 
Example 7 
Comparative 
100/0/0/0/0 0.023 62.degree. 
.DELTA. 
Example 8 
Comparative 
80/0/20/0/0 0.002 62.degree. 
o 
Example 9 
______________________________________ 
TABLE 4 
______________________________________ 
Characteristics of 
capacitor 
Adhesion of 
Dielectric Rate of 
vapor-deposited 
strength change in 
layer (kV/.mu.m) capacitance 
______________________________________ 
Example 9 o 0.57 0.9 
Example 10 
o 0.56 0.9 
Example 11 
o 0.56 0.7 
Example 12 
o 0.56 0.9 
Example 13 
o 0.56 0.8 
Example 14 
o 0.55 -2.8 
Example 15 
o 0.60 0.6 
Comparative 
x 0.55 -15.0 
Example 7 
Comparative 
o 0.55 0.9 
Example 8 
Comparative 
-- -- -- 
Example 9 
______________________________________ 
EXAMPLE 16 
A polyethylene terephthalate with an intrinsic viscosity of 0.62 was 
extruded from an extruder at a temperature of 280.degree. to 300.degree. 
C. and cast on a cooling drum while using an electrostatic contact method 
to obtain an amorphous polyester sheet with a thickness of about 150 
.mu.m. 
After stretching the above-mentioned sheet in the machine direction by 3.5 
times at 95.degree. C., a coating solution comprising 80 parts of a water 
dispersible polyurethane having carboxyl groups (trade name: Hydran AP-40, 
manufactured by Dainippon Ink Kagaku Kogyo Co.), 20 parts of triethylene 
glycol diglycidyl ether and water as the medium was coated on both 
surfaces of the film. The coated film was further stretched in the 
transverse direction by 3.5 times at 110.degree. C. and then subjected to 
a heat treatment at 230.degree. C., to obtain a biaxially stretched 
polyester film with the thickness of the coating layer of 0.1 .mu.m and 
the thickness of the substrate polyester film of 12 .mu.m. The contact 
angle of water droplet against the coating layer was 63.degree.. 
Aluminum was vapor deposited to a thickness of 450 .ANG. on one surface of 
the above-mentioned film by using a resistance heating type metallizing 
apparatus under a pressure in a vacuum chamber of not higher than 
10.sup.-4 Torr. 
The resultant vapor-deposited film showed excellent adhesion as shown in 
Table 5. 
Comparative Example 10 
A metallized polyester film was obtained in the same procedures as those in 
Example 16, except for not coating the coating solution used in Example 
16. 
The resultant film was poor in the adhesion between the vapor-deposited 
metal layer and the polyester substrate film as compared with Example 16. 
TABLE 5 
______________________________________ 
Adhesion [g/15 mm width] 
No boiling With boiling 
treatment treatment 
Not With Not With Con- 
applying 
applying applying applying 
tact 
water water water water angle 
______________________________________ 
Example 16 
310 185 200 180 63.degree. 
Comparative 
90 10 30 0 -- 
Example 10 
______________________________________