Flame-retardant liquid photosensitive resin composition

Disclosed is a flame-retardant liquid photosensitive resin composition consisting essentially of PA1 (a) a (meth)acrylate obtained by the reaction of a compound having two or more epoxy groups in the molecule with (meth)acryalic acid and a dibasic acid or its anhydride, the (meth)acrylate having an average acid value of 4 to 150 and a number average molecular weight of 300 to 5,000; PA1 (b) a monomer having at least one (meth)acryloxyloxy group and containing not less than 20% by weight of bromine; PA1 (c) a monomer having two or more (meth)acryloxyloxy groups in the molecule; PA1 (d) a monomer having one (meth)acryloyloxy group in the molecule; PA1 (e) at least one inorganic filler; and PA1 (f) at least one photopolymerization catalyst selected from the group consisting of photo-initiators and photosensitizers, wherein the content of bromine in the total composition is in the range of 0.5 to 28% by weight. This flame-retardant liquid photosensitive resin composition has excellent homogeneity and alkali developability, yields a cured coating film having good adhesion, solvent resistance, thermal resistance, electrical insulating properties and flame retardancy, and is suitable for use as a solder resist in the fabrication of printed circuit boards.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
This invention relates to flame-retardant liquid photosensitive resin 
compositions which have pattern-forming properties and can be used as 
solder resists (or solder masks) in the fabrication of printed circuit 
boards. 
(2) Description of the Prior Art 
Conventionally, a solder resist (or solder mask) is widely used in the 
fabrication of printed circuit boards in order to form a permanent 
protective coating for printed circuit boards. Such a solder resist is 
used for the purpose of preventing the formation of a solder bridge during 
soldering and of ensuring the protection of the conductive parts against 
corrosion and the retention of their electrical insulation during use. 
Solder resists used under severe conditions, unlike etching resists, must 
have the following performance characteristics: 
(a) Retention of adhesion during soaking in solder (at 240.degree. to 
280.degree. C.). 
(b) Permanent retention of adhesion. 
(c) Excellent resistance to solvents and chemicals. 
(d) Retention of good electrical insulating properties under high-humidity 
conditions. 
(e) Flame retardance. 
In order to meet these requirements, it has been conventional and common 
practice to form a solder resist by screen printing of a thermosetting ink 
or a photocurable ink. However, the increasing miniaturization of printed 
circuits has created a demand for solder resists having large coating 
thickness and high precision, and it is the existing state of the art that 
the screen printing method for the formation of a solder resist is no 
longer satisfactory from the viewpoint of precision and coating thickness. 
The formation of solder resists by the development technique has been 
proposed as a means for responding to this miniaturization or printed 
circuits. According to the development technique, a pattern is formed by 
applying a liquid photosensitive resin composition, or laminating a 
photosensitive film, to a printed circuit board, exposing the coating film 
to active radiation through, for example, a photomask to cure only desired 
portions thereof, and then washing the coating film with a developer to 
remove any uncured portions thereof. This technique makes it possible to 
form a solder resist pattern having large coating thickness and high 
precision. 
According to the manner in which the coating film to be cured is formed, 
solder resists for use in the development technique can be classified into 
three types: dry film type, solvent evaporation type and solventless 
liquid type (see Japanese Patent Laid-Open Nos. 52703/'77 and 15733/'76). 
Among them, solder resists of the dry film type have the disadvantage 
that, in order to cause the solder resist to adhere closely to an uneven 
surface having a circuit formed thereon, a special process such as heat 
lamination under reduced pressure is required (see Japanese Patent 
Laid-Open No. 52703/'77) and that, notwithstanding the use of such a 
process, perfect adhesion is not always ensured. In contrast, solder 
resists of the solvent evaporation type can exhibit good adhesion to an 
uneven surface having a circuit formed thereon. However, they have the 
disadvantage that, after the application of a liquid photosensitive resin 
composition, the resulting coating film must be dried in an 
explosion-proof dryer or similar equipment so as to evaporate the solvent. 
Accordingly, there is a great need to develop an improved photosensitive 
resin composition of the solventless liquid type for use as a solder 
resist. 
On the other hand, liquid photosensitive resin compositions can also be 
classified according to the type of developer used. That is, they include 
ones using an organic solvent such as 1,1,1-trichloroethane and ones using 
a dilute aqueous alkaline solution. Since the use of an organic solvent 
involves problems concerning the pollution of the working environment and 
the disposal of waste liquid, development with a dilute aqueous alkaline 
solution is highly desirable. It is known that these problems can be 
solved by use of compositions containing a carboxyl-modified epoxy 
(meth)acrylate as an alkali developability imparting agent (see Japanese 
Patent Laid-Open Nos. 204252/'87, 204253/'87 and 205113/87). However, 
these compositions do not have a sufficient degree of flame retardancy. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a flame-retardant 
liquid photosensitive resin composition having excellent homogeneity and 
alkali developability, yielding a cured coating film having good adhesion, 
solvent resistance, thermal resistance and electrical insulating 
properties, and exhibiting excellent flame retardancy. 
It is another object of the present invention to provide a flame-retardant 
liquid photosensitive resin composition having excellent performance, 
especially when used as a solder resist in the fabrication of printed 
circuit boards. 
According to the present invention, there is provided a flame-retardant 
liquid photosensitive resin composition consisting essentially of 
(a) 10 to 55% by weight of a (meth)acrylate obtained by the reaction of a 
compound having two or more epoxy groups in the molecule with 
(meth)acrylic acid and a dibasic acid or its anhydride, the (meth)acrylate 
having an average acid value of 4 to 150 and a number average molecular 
weight of 300 to 5,000; 
(b) 3 to 35% by weight of a monomer having at least one (meth)acryloyloxy 
group and containing not less than 20% by weight of bromine; 
(c) 10 to 55% by weight of a monomer having two or more (meth)acryloyloxy 
groups in the molecule, exclusive of components (a) and (b); 
(d) 5 to 50% by weight of a monomer having one (meth)acryloyloxy group in 
the molecule, exclusive of components (a) and (b); 
(e) 2 to 35% by weight of at least and 
(f) 0.05 to 20% by weight of at least one photopolymerization catalyst 
selected from the group consisting of photo-initiators and 
photosensitizers, 
wherein the content of bromine in the total composition is in the range of 
0.5 to 28% by weight. 
As used herein, the terms "(meth)acrylate", "(meth)acryloyloxy" and 
"(meth)acrylic acid" mean methacrylate and/or acrylate, methacryloyloxy 
and/or acryloyloxy, and methacrylic acid and/or acrylic acid, 
respectively. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The flame-retardant liquid photosensitive resin composition of the present 
invention contains 10 to 55% by weight of a (meth)acrylate (a) obtained by 
the reaction of a compound having two or more epoxy groups in the molecule 
with (meth)acrylic acid and a dibasic acid (inclusive of its anhydride) 
and having an acid value of 4 to 150 and a number average molecular weight 
of 300 to 5,000, which will hereinafter be referred to as a 
carboxyl-modified epoxy (meth)acrylate. The term "carboxyl-modified epoxy 
(meth)acrylate" as used herein denotes compounds obtained by the addition 
of (meth)acrylic acid to the epoxy groups present in a multi-functional 
epoxy compound or epoxy resin selected, for example, from bisphenol 
A-epichlorohydrin resins, epoxy-novolak resins, alicyclic epoxy resins, 
aliphatic epoxy resins, heterocylic epoxy resins, glycidyl ester type 
resins and other resins as described in "Engineering Plastics" (published 
by Kagaku Kogyo Nipposha on Mar. 15, 1983), followed by the addition of a 
dibasic acid anhydride (such as maleic anhydride or succinic anhydride) to 
the remaining hydroxyl groups; or compounds obtained by the reaction of a 
multifunctional epoxy compound or epoxy resin with (meth)acrylic acid and 
a dibasic acid, and thus characterized by containing carboxyl groups in 
the molecule. Specific examples of such compounds include a compound 
obtained by the reaction of a bisphenol A-epichlorohydrin epoxy resin with 
acrylic acid and the subsequent addition of maleic anhydride (molar ratio 
of epoxy group/acrylic acid/maleic anhydride=1/1/0.1) and a compound 
obtained by the reaction of a phenolic novolak epoxy resin with acrylic 
acid, methacrylic acid and succinic acid (molar ratio of epoxy 
group/acrylic acid/methacrylic acid/succinic acid=1/0.7/0.1/0.2). 
In the carboxyl-modified epoxy (meth)acrylate (a), all molecules need not 
have carboxyl groups, but some molecules having no carboxyl group may 
remain. Accordingly, there may be used a compound synthesized under such 
conditions as to leave some molecules unmodified with carboxyl groups, or 
a mixture of a carboxyl-modified compound and an unmodified compound. 
The carboxyl-modified epoxy (meth)acrylate (a) should have an average acid 
value of 4 to 150. If the average acid value is less than 4, the resulting 
composition will have such poor washability with alkali that, after 
curing, the uncured portions of the composition cannot be thoroughly 
washed off. On the other hand, if the average acid value is greater than 
150, the cured coating film will be so hygroscopic that it cannot retain 
good electrical insulating properties under high-humidity conditions. From 
the viewpoint of electrical insulating properties, the preferred range of 
the average acid value is from 5 to 100. 
Moreover, the carboxyl-modified epoxy (meth)acrylate (a) should have a 
number average molecular weight of 300 to 5,000, preferably 400 to 3,000. 
If the number average molecular weight is greater than 5,000, the 
resulting composition will have unduly high viscosity and, therefore, 
exhibit poor alkali developability and poor miscibility with other 
monomers and oligomers. 
The carboxyl-modified epoxy (meth)acrylate (a) should be used in an amount 
10 to 55% by weight, preferably 15 to 50% by weight, based on the total 
amount of the composition. If its amount used is less than 10% by weight, 
the resulting composition will have low resolution and give a cured 
coating film having poor adhesion to metallic surfaces. On the other hand, 
if it is greater than 55% by weight, the resulting composition will show a 
reduction in electrical insulating properties under high-humidity 
conditions. 
Conventionally, the addition of a linear polymer containing carboxyl groups 
has been widely used as a means for imparting full alkali developability 
to a photosensitive resin composition of the full alkali developing type. 
However, the addition of a carboxyl-containing linear polymer to a liquid 
photosensitive resin composition for use as a solder resist would pose the 
following two serious problems One is that, since such a linear polymer 
cannot form a cross-linked structure, the cured coating film will show a 
decrease in solvent resistance. The other is that a special reactive 
diluent capable of dissolving this carboxyl-containing linear polymer must 
be used to prepare the photosensitive resin composition in the form of a 
homogeneous solution, and this reactive diluent tends to reduce the 
electrical insulating properties of the composition. 
In the present invention, these problems have been solved by using a 
specific carboxyl-modified epoxy (meth)acrylate (a) in place of the 
aforesaid linear polymer. Specifically, when the resulting composition is 
cured by active radiation, the carboxyl-modified epoxy (meth)acrylate (a) 
is incorporated in the cross-linked structure and, therefore, can impart 
excellent solvent resistance to the cured coating film. Moreover, the 
carboxyl-modified epoxy (meth)acrylate (a) has a lower molecular weight 
than the aforesaid linear polymer and can be readily mixed with 
cross-linking monomers usually used in combination. This allows greater 
latitude in monomer composition and makes it possible to achieve excellent 
properties such as electrical insulating properties. 
The flame-retardant liquid photosensitive resin composition of the present 
invention also contains 3 to 35% by weight of a monomer (b) having at last 
one (meth)acryloyloxy group and containing not less than 20% by weight of 
bromine in the molecule (hereinafter abbreviated as the bromine-containing 
(meth)acrylate (b)). Specific examples of the bromine-containing 
(meth)acrylate (b) include 2,4,6-tribromophenyl (meth)acrylate, 
2,4,6-tribromophenoxyethyl (meth)acrylate, 2,4,6-tribromophenoxydiethoxy 
(meth)acrylate, 2,4,6-tribromophenoxytriethoxy (meth)acrylate, 
tetrabromobisphenol A mono(meth)acrylate, tetrabromobisphenol A 
di(meth)acrylate, tetrabromobiphenol A diethoxy mono(meth)acrylate, 
tetrabromobisphenol A diethoxy di(meth)acrylate, tetrabromobipshenol A 
bis(tetraethoxy(meth)acrylate), 2,4,6-tribromophenoxytetraethoxy 
(meth)acrylate and 3-(2,4,6-tribromophenoxy)-2-hydroxypropyl 
(meth)acrylate. 
In order to keep the composition homogeneous during storage at low 
temperatures and yield a cured coating film having good thermal resistance 
under severe conditions, it is preferable to use a compound of the general 
formula 
##STR1## 
where R.sup.1 is a hydrogen atom or a methyl group, and A is 
##STR2## 
in which n is a whole number of 1 to 3. 
The bromine-containing (meth)acrylate (b) containing not less than 20% by 
weight of bromine in the molecule should be used in an amount of 3 to 35% 
by weight based on the total amount of the composition, and the content of 
bromine in the total composition should be in the range of 0.5 to 28% by 
weight and preferably 1 to 20% by weight. If the amount of bromine 
compound (b) used is less than 3% by weight or the bromine content is 0.5% 
by weight, the resulting composition will not have a sufficient degree of 
flame retardancy. On the other hand, if the amount of bromine compound (b) 
is greater than 35% by weight or the bromine content is greater than 28% 
by weight, the cured coating film will show a reduction in adhesion and 
thermal resistance. 
Use of the bromine-containing (meth)acrylate (b) containing not less than 
20% by weight of bromine makes it possible to produce a flame-retardant 
liquid photosensitive resin composition having excellent homogeneity and 
alkali developability, yielding a cured coating film having good adhesion, 
solvent resistance, thermal resistance and electrical insulating 
properties, and exhibiting excellent flame retardancy. 
If a different bromine compound, such as decabromobiphenyl ether that is 
known to be a flame retarder for plastics, is used in combination with the 
other components of the present invention and the resulting composition is 
applied to a copper surface, a slight amount of decabromobiphenyl ether 
will be adsorbed to and remain on the copper surface even after it has 
been sprayed and washed with a 1% aqueous solution of sodium carbonate. If 
tetrabromobisphenol A is used in combination with the other components of 
the present invention, the cured coating film may peel off when soaked in 
molten solder at 260.degree. C. This seems to be due to the unreacted 
tetrabromobisphenol A which remains in the cured coating film and, when 
heated at 260.degree. C., migrates to the copper surface to reduce the 
adhesion thereof. 
The reason why the combination of the carboxyl-modified (meth)acrylate (a) 
and the bromine-containing (meth)acrylate (b) brings about the 
above-described excellent performance has not been understood fully. 
However, it is believed that the bromine-containing (meth)acrylate (b) is 
uniformly dissolved in the liquid composition prior to curing, and curing 
by ultraviolet radiation causes the bromine-containing (meth)acrylate (b), 
together with carboxyl-modified epoxy (meth)acrylate (a), to be 
incorporated in the cross-linked network, thus producing a more powerful 
flame-retarding effect without exerting any adverse influence on the 
properties of the cured coating film. 
The flame-retardant liquid photosensitive resin composition of the present 
invention also contains 10 to 55% by weight of a monomer (c) having two or 
more (meth)acryloyloxy groups in the molecule (hereinafter referred to as 
a cross-linking monomer), exclusive of the compounds used as components 
(a) and (b). This crosslinking monomer (c) is used to improve the 
properties required for use as a solder resist, such as the curing rate of 
the composition and the scratch resistance, solvent resistance and 
electrical insulating properties of the cured coating film. 
Specific examples of the cross-linking monomer (c) include 1,4-butanediol 
di(meth)acrylate, 1,6-hexamethylene glycol di(meth)acrylate, neopentyl 
glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, 
pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, 
dipentaerythritol hexa(meth)acrylate, triethylene glycol di(meth)acrylate, 
urethane acrylates (such as Viscoat #812, #813, #823 and #851, 
manufactured by Osaka Organic Chemical Industry Co., Ltd.) and urethane 
methacrylates. These compounds may be used alone or in admixture of two or 
more. 
This cross-linking monomer (c) should be used in an amount of 10 to 55% by 
weight, preferably 10 to 50% by weight, based on the total amount of the 
composition. If its amount used is less than 10% by weight, the resulting 
composition will have poor solvent resistance and show a reduction in 
electrical insulating properties under high-humidity conditions. On the 
other hand, if its amount used is greater than 55% by weight, the 
resulting composition will have poor alkali developability and poor 
adhesion to metallic surfaces. 
Moreover, 50% by weight or more, particularly 60% by weight or more of the 
cross-linking monomer (c) should preferably comprise a monomer containing 
ester linkages not associated with acrylate and/or methacryalte and having 
a number average molecular weight of 200 to 800 and a number average 
molecular weight per polymerizable double bond of 100 to 250. 
By having a moderate molecular weight and a moderate molecular weight per 
double bond, the aforesaid cross-linking monomer containing ester linkages 
can impart an adequate cross-linking density to the cured coating film and 
thereby improve the solvent resistance and adhesion of the cured coating 
film at the same time. Moreover, by containing ester linkages not 
associated with (meth)acrylate in the molecule, the aforesaid 
cross-linking monomer can improve especially the adhesion and thermal 
resistance of the cured coating film and thus enables the resulting 
composition to retain high electrical insulating properties under 
high-humidity conditions. Specific examples of the above-defined compound 
include neopentyl glycol hydroxypivalate diacrylate [molecular weight=312; 
molecular weight per polymerizable double bond=156], neopentyl glycol 
hydroxypivalate dimethacrylate [molecular weight=340; molecular weight per 
polymerizable double bond=170], a co-condensation product of succinic 
acid/trimethylolethane/acrylic acid (molar ratio=1/2/4) average molecular 
weight=600; molecular weight per polymerizable double bond=150], a 
co-condensation product of adipic acid/trimethylolpropane/acrylic acid 
(molar ratio=1/2/4) [average- molecular weight=680; molecular weight per 
polymerizable double bond=170], and various oligoester (meth)acrylates 
manufactured by Toagosei Chemical Industry Co., Ltd., such as Aronix 
M-6100 [average molecular weight=450; molecular weight per polymerizable 
double bond=225 ), Aronix M-6250 [average molecular weight=450; molecular 
weight per polymerizable double bond=225], Aronix M-6500 [average 
molecular weight=446; molecular weight per polymerizable double bond=223], 
Aronix M-7100 [average molecular weight=565; molecular weight per 
polymerizable double bond=188], Aronix M-8030 average molecular 
weight=393, molecular weight per polymerizable double bond=119], Aronix 
M-8060 average molecular weight=489; molecular weight per polymerizable 
double bond=136], Aronix M-8100 average molecular weight=618; molecular 
weight per polymerizable double bond=155] and Aronix M-6300 average 
molecular weight=478; molecular weight per polymerizable double bond=239]. 
The flame-retardant liquid photosensitive resin composition of the present 
invention also contains 5 to 50% by weight of a monomer (d) having one 
(meth)acryloyloxy group in the molecule (hereinafter referred to as a 
monofunctional (methacrylate), exclusive of the compounds used as 
components (a) and (b). This monofunctional (meth)acrylate (d) not only 
dilutes the aforesaid carboxyl-modified epoxy (meth)acrylate (a) to reduce 
the viscosity of the composition, but also takes part in its cure by 
active radiation to impart flexibility to the cured coating film and 
thereby improve the adhesion of the coating film to the substrate. 
Specific examples of the monofunctional (meth)acrylate (d) include 
acrylates and methacrylates such as tetrahydrofurfuryl (meth)acrylate, 
ethoxyethoxyethyl (meth)acrylate, 2-methoxyethyl (meth)acryalte, benzyl 
(meth)acrylate, cyclohexyl (meth)acryalte, dicyclopentadienyloxyethyl 
(meth)acrylate, methyltriethylene glcyol (meth)acrylate and lauryl 
(meth)acrylate. 
The monofunctional (meth)acryalte (d) should be used in an amount of 5 to 
50% by weight, preferably 10 to 50% by weight, based on the total amount 
of the composition. If its amount used is less than 5% by weight, the 
adhesion of the cured coating film will be reduced, while if it is greater 
than 50% by weight, its solvent resistance will be decreased. 
Moreover, in view of the performance requirements of a liquid 
photosensitive resin composition for use as a solder resist, including 
good adhesion to metallic surfaces, high hardness, good adhesion at high 
temperatures, high solvent resistance, good electrical insulating 
properties under high-humidity conditions, little odor development and 
little irritation to the skin, 50% by weight or more of the 
bromine-containing (meth)acrylate (b) should preferably comprise a 
compound of the general formula 
##STR3## 
where R.sup.2 is a hydrogen atom or a methyl group, B is 
##STR4## 
in which n is a whole number of 1 to 3, and Ar is a phenyl group which may 
have an alkyl group of not more than 12 carbon atoms. 
The compounds within the scope of the general formula (II) are 
characterized by the fact that the presence of a phenoxy group raises 
their boiling points (resulting in little odor development and little 
irritation to the skin) and their appropriate degree of polarity improves 
the adhesion of the cured coating film to metallic surfaces (at ordinary 
and elevated temperatures) without reducing its electrical insulating 
properties under high-humidity conditions. Moreover, these compounds have 
relatively short side chains in spite of their high molecular weights and, 
therefore, do not decrease the solvent resistance or hardness of the cured 
coating film. 
Specific examples of the compounds represented by the general formula (II) 
include phenoxyethyl (meth)acrylate, phenoxyethyloxyethyl (meth)acrylate, 
phenoxytetraethylene glycol (meth)acryalte, p-nonylphenoxyethyl 
(meth)acrylate and 3-phenoxy-2-hydroxypropyl (meth)acrylate. 
The flame-retardant liquid photosensitive resin composition of the present 
invention also contains 2 to 35% by weight of at least one inorganic 
filler (e). Usable inorganic fillers include extender pigments, antimony 
compounds as auxiliary flame retarders, silica materials as thickeners, 
and the like. 
Extender pigments may be used not only to improve the strength of the cured 
coating film, but also to moderate its polymerization shrinkage and 
thereby improve its adhesion to the substrate. Specific examples of usable 
extender pigments include calcium carbonate, talc and mica. Among others, 
plate-like particles of talc or mica or needle-like particles of talc are 
highly effective in improving the adhesion of the coating film. These 
extender pigments may be used without any treatment or in a form 
surface-treated or surface-coated with an inorganic material and/or an 
organic material. 
In view of the strength, adhesion and resolution of the coating film, such 
an extender pigment should be used in an amount of 2 to 35% by weight, 
preferably 5 to 30% by weight, based on the total amount of the 
composition. 
Antimony compounds may be used as a part of the inorganic filler (e). 
Antimony compounds can impart a higher degree of flame retardancy to the 
composition and, moreover, can reduce the amount of bromine compound (b) 
used. Specific examples of usable antimony compounds include antimony 
trioxide and antimony pentoxide (tetrahydrate). From the viewpoint of 
uniform dispersibility in the composition and transmissivity to 
ultraviolet radiation at wavelengths of 300 to 400 nm, it is preferable to 
use an antimony compound having an average particle diameter of not 
greater than 0.1 .mu.m. Such an antimony compound should preferably be 
used in an amount of 0.2 to 4% by weight based on the total amount of the 
composition. 
In order to improve the viscosity, thixotropy and coating properties of the 
composition, thickeners such as amorphous silica may be used as a part of 
the inorganic filler (e). As the amorphous silica, there may be used 
various commercial products including Aerosil (manufactured by Nippon 
Aerosil K.K.), Cab-O-Sil (manufactured by Cabot Inc.), Syloid 
(manufactured by Fuji-Devison Co., Ltd.) and Nipsil (manufactured by 
Nippon Silica Industrial Co., Ltd.). In addition, silica products having 
hydrophilic surfaces and silica products surface-treated to be hydrophobic 
(such as Nipsil SS-50X and Cab-O-Sil T720) may also be used. Such a 
thickener should be used in an amount of 0 to 25% by weight based on the 
total amount of the composition. 
The inorganic filler (e) should be used in an amount of 2 to 35% by weight, 
preferably 3 to 35% by weight, based on the total amount of the 
composition. If its amount used is less than 2% by weight, the resulting 
composition will have poor coating properties and poor adhesion at 
elevated temperatures. If it is greater than 35% by weight, the resulting 
composition will have shortcomings from the viewpoint of electrical 
insulating properties and developability. 
The flame-retardant liquid photosensitive resin composition of the present 
invention also contains 0.05 to 20% by weight of at least one 
photopolymerization catalyst (f) selected from the group consisting of 
photo-initiators and photosensitizers. The photopolymerization catalyst 
can be any compound that produces a radical on exposure to active 
radiation such as ultraviolet or visible radiation and thereby initiates 
the polymerization reaction. Specific examples of usable 
photopolymerization catalysts include 2-ethylanthraquinone, 
1,4-naphthoquinone, benzoin ethyl ether, benzoin propyl ether, 
benzophenone, 4,4'-bis(dialkylamino)benzophenones, benzyl dimethyl ketal, 
4'-isoipropyl-2-hydroxy-2-methylpropiophenone, 
2-hydroxy-2-methylpropiophenone and 
2-methyl-(4-methylthio)phenyl-2-morpholino-1-propane. These 
photopotopolymerization catalysts may be used alone or in admixture of two 
or more. 
From the viewpoint of the curing rate of the composition and properties of 
the cured coating film, the photopolymerization catalyst should be used in 
an amount of 0.05 to 20% by weight, preferably 0.1 to 10% by weight, based 
on the total amount of the composition. 
In addition to components (a) to (f), the flame-retardant liquid 
photosensitive resin composition of the present invention may further 
contain various conventional additives such as thermal polymerization 
inhibitors, colorants (i.e., pigments and dyes) and antifoaming agents, 
according to the intended purpose. 
Thermal polymerization inhibitors may be used in order to prevent the 
photosensitive resin composition from being thermally cured prior to 
photocuring. Specific examples of usable thermal polymerization inhibitors 
include p-methoxyphenol, hydroquinone, p-benzoquinone, tert-butylcatecol, 
pyrogallol, naphthylamine and phenothiazine. In view of their influence on 
photocurability and other factors, thermal polymerization inhibitors 
should preferably be used in an amount of not greater than 3% by weight, 
more preferably not greater than 1% by weight, based on the total amount 
of the composition. 
For example, if it is desired to give a green color to the composition, 
usable pigments include chlorinated phthalocyanine green (P. Gr. 7) and 
chlorobrominated phthalocyanine green (P. Gr. 36), and usable dyes include 
Sumiplast Green G (manufactured by Sumitomo Chemical Industries Co., 
Ltd.). 
Usable antifoaming agents include various antifoaming agents such as 
silicone type and non-silicone type ones. 
The liquid photosensitive resin composition of the present invention may 
have any viscosity that renders the composition substantially flowable at 
ordinary temperatures. However, from the viewpoint of handling properties 
(in particular, coating properties), the composition should have a 
viscosity of 1,000 to 100,000 cps, more preferably 2,000 to 80,000 cps, as 
measured at 25.degree. C. with a Brookfield type viscometer. 
The liquid photosensitive resin composition of the present invention may be 
used according to any of various well-known methods. It is most common to 
form a cured coating film according to a method involving the steps of 
application, exposure and alkali development. 
The method of application can be any of various well-known methods. For 
example, there may be employed the "direct application method" in which 
the liquid photosensitive resin composition is directly applied to a 
printed circuit board with an applicator (such as a Baker type applicator 
or a bar coater) or through a silk screen; the "indirect application 
method" in which the liquid photosensitive resin composition is applied to 
the surface of a transparent film or sheet or an artwork, and the latter 
is placed on a printed circuit board in such a way that the liquid 
photosensitive resin composition layer comes into contact with the printed 
circuit board; and the "double-side application method" in which the 
liquid photosensitive resin composition is applied to the surface of a 
printed circuit board and the surface of a transparent film or sheet or an 
artwork, which are laid on top of each other in such a way that the liquid 
photosensitive resin composition layers come into contact with each other. 
The method of exposure can be any of various well-known methods. For 
example, this can be accomplished by irradiating the liquid photosensitive 
resin composition layer with active radiation (such as visible or 
ultraviolet radiation) through a photomask. In this case, the liquid 
photosensitive resin composition layer may be in direct contact with the 
photomask or in indirect contact with the photomask through a transparent 
film, sheet or the like. Alternatively, the liquid photosensitive resin 
composition layer may be separated from the photomask by a thin layer of 
gas. 
Development can be carried out according to any of various well-known 
developing methods for photosensitive resin compositions of the alkali 
developing type. 
Furthermore, in order to obtain a more completely cured coating film, the 
alkali development may be followed by after-treatment with active 
radiation and/or heat. 
The liquid photosensitive resin composition of the present invention is not 
only useful as a solder resist, but also suitable for use in a wide 
variety of applications such as letterpress printing and the like.

The present invention is further illustrated by the following examples. 
EXAMPLE 1 
A liquid photosensitive resin composition (with a bromine content of 3.2%) 
was prepared by mixing the following ingredients and kneading the mixture 
on a three-roll mill: 
______________________________________ 
Reaction product of bisphenol A 
30 g 
diglycidyl ether/acrylic acid/maleic 
anhydride (molar ratio of epoxy 
group/acrylic acid/maleic anhydride = 
1/1/0.25; average molecular weight = 
400; acid value = 50) 
Tetrabromibisphenol A diethoxy 
7.5 g 
diacrylate (bromine content = 43.2%) 
Neopentyl glycol diacrylate 
20.9 g 
Dicyclopentadienyl oxyethylacrylate 
15 g 
Talc (Talc SK, manufactured by Tsuchiya 
15 g 
Kaolin Co., Ltd.) 
Antimony trioxide (average particle 
0.4 g 
diameter = 0.02 .mu.m) 
Silica (Nipsil SS 50X, manufactured by 
8 g 
Nippon Silica Industrial Co., Ltd.) 
Benzyl dimethyl ketal 1 g 
Chlorinated copper phthalocyanine 
0.1 g 
p-Methoxyphenol 0.1 g 
Antifoaming agent (Silicone Oil SH-200, 
2 g 
manufactured by Toray Silicone Co., Ltd.) 
______________________________________ 
EXAMPLE 2 
A liquid photosensitive resin composition (with a bromine content of 4.2%) 
was prepared by mixing the same ingredients as used in Example 1, except 
that the tetrabromobisphenol A diethoxy diacrylate was replaced by the 
same amount of 2,4,6-tribromophenoxy ethyl acrylate, and kneading the 
mixture on a three-roll mill. 
EXAMPLES 3-10 AND COMATIVE EXAMPLES 1-5 
Various compositions were prepared by mixing the following ingredients and 
kneading the mixture on a three-roll mill: 
______________________________________ 
Reaction product of bisphenol A 
a g 
diglycidyl ether/acrylic acid/maleic 
anhydride (molar ratio of epoxy group/ 
acrylic acid/maleic anhydride = 1/1/0.25; 
average molecular weight = 400; acid value = 
50) 
Bromine compound b g 
Neopentyl glycol hydroxypivalate 
c g 
diacrylate 
Phenoxyethyl acryalte d g 
Talc (Talc SK, manufactured by 
e' g 
Tuchiya Kaolin Co., Ltd.) 
Antimony trioxide (average particle 
e" g 
diameter = 0.02 .mu.m) 
Silica (Aerosil #200, manufactured by 
e'" g 
Nippon Aerosil K. K.) 
Benzyl dimethyl ketal 1 g 
Chlorinated copper phthalocyanine 
0.1 g 
p-Methoxyphenol 0.1 g 
Antifoaming agent (Colloid #640, 
2 g 
manufactured by Americal Colloid lnc.) 
______________________________________ 
The values for a to e"' are given in Table 1 below. 
TABLE 1 
__________________________________________________________________________ 
Example Comparative Example 
Example No. 
3 4 5 6 7 8 9 10 1 2 3 4 5 
__________________________________________________________________________ 
a 32 32 32 30 25 32 32 32 32 32 20 32 32 
Type of bromine 
(1) 
(1) 
(1) 
(1) 
(1) 
(2) 
(3) 
(4) 
-- (1) 
(1) 
(5) 
(6) 
compound 
b 7.5 
7.5 
3 25 3 7.5 
7.5 
7.5 
0 1.5 
40 7.5 
7.5 
c 22.9 
22.9 
22.9 
12.4 
16 22.9 
22.9 
22.9 
22.9 
22.9 
12.4 
22.9 
22.9 
d 15 15 19.5 
11.2 
23.6 
15 15 15 22.5 
21 11.2 
15 15 
e' 15 15.4 
15 13.8 
28 15 15 15 15 15 8.8 
15 15 
e" 0.4 
0 0.4 
0.4 
0.2 
0.4 
0.4 
0.4 
0.4 
0.4 
0.4 
0.4 
0.4 
e'" 4 4 4 4 1 4 4 4 4 4 4 4 4 
Bromine content 
4.2 
4.2 
1.7 
14.0 
1.7 
3.5 
4.7 
3.2 
0 0.8 
22.4 
6.3 
4.2 
of composition (%) 
__________________________________________________________________________ 
(1) 2,4,6Tribromophenoxyethyl acrylate (bromine content = 55.9%) 
(2) 2,4,6Tribromophenoxytriethoxy acrylate (bromine content = 46.4%) 
(3) 2,4,6Tribromophenyl acrylate (bromine content = 62.3%) 
(4) 2,4,6Tribromophenoxytetraethoxy acrylate (bromine content = 42.8%) 
(5) Decabromobiphenyl ether (bromine content = 83.3%) 
(6) Tetrabromobisphenol A (bromine content = 58.8%) 
EXAMPLE 11 
A liquid photosensitive resin composition (with a bromine content of 4.1%) 
was prepared by mixing the following ingredients and kneading the mixture 
on a three-roll mill: 
______________________________________ 
Reaction product of bisphenol A diglycidyl 
16 g 
ether/acrylic acid/maleic anhydride 
(molar ratio of epoxy group/acrylic acid/ 
maleic anhydride = 1/1/0.13; average 
molecular weight = 400; acid value = 25) 
2,4,6-Tribromophenoxyethyl methacrylate 
7.5 g 
(bromine content = 54.1%) 
Co-condensation product of succinic 
15 g 
acid/trimethylolethane/acrylic acid 
(molar ratio = 1/2/4) (average molecular 
weight = 680; molecular weight per 
polymerizable double bond = 150) 
3-Phenoxy-2-hydroxypropyl acrylate 
39.2 g 
Talc 12 g 
Antimony pentoxide tetrahydrate 
3 g 
Silica 4 g 
Benzyl dimethyl ketal 1 g 
Chlorobrominated copper phthalocyanine 
0.2 g 
p-Methoxyphenol 0.1 g 
Antifoaming agent 2 g 
______________________________________ 
In this and the following examples, the talc comprised Talc SK, 
manufactured by Tsuchiya Kaolin Co., Ltd.; the silica comprised Aerosil 
#200, manufactured by Nippon Aerosil K.K.; and the antifoaming agent 
comprised Colloid #640, manufactured by Colloid International Inc. 
EXAMPLE 12 
A liquid photosensitive resin composition (with a bromine content of 3.8%) 
was prepared by mixing the following ingredients and kneading the mixture 
on a three-roll mill: 
______________________________________ 
Reaction product of bisphenol A diglycidyl 
48 g 
ether/acrylic acid/maleic anhydride 
(molar ratio of epoxy group/acrylic acid/ 
maleic anhydride = 1/1/0.4; average molecular 
weight = 500; acid value = 80) 
2,4,6-Tribromophenoxydiethoxy acrylate 
7.5 g 
(bromine content = 50.7%) 
Neopentyl glycol hydroxypivalate 
11.9 g 
diacrylate 
Phenoxydiethoxy acrylate 10 g 
Talc 15 g 
Antimony trioxide (average particle 
0.4 g 
diameter = 0.02 .mu.m) 
Silica 4 g 
Benzyl dimethyl ketal 1 g 
Chlorinated copper phthalicyanine 
0.1 g 
p-Methoxyphenol 0.1 g 
Antifoaming agent 2 g 
______________________________________ 
EXAMPLE 13 
A liquid photosensitive resin composition (with a bromine content of 3.5%) 
was prepared by mixing the following ingredients and kneading the mixture 
on a three-roll mill: 
______________________________________ 
Reaction product of phenolic novolak type 
32 g 
epoxy resin/acrylic acid/succinic anhydride 
(molar ratio of epoxy group/acrylic 
acid/succinic anhydride = 1/1/0.3; average 
molecular weight = 1,100; acid value = 74) 
2,4,6-Tribromophenoxytriethoxy acrylate 
7.5 g 
(bromine content = 46.4%) 
Aronix M-6100 (average molecular weight = 
44.9 g 
450; molecular weight per polymerizable 
double bond = 125) 
Phenoxyethyl acrylate 6 g 
Talc 5 g 
Antimony trioxide (average particle 
0.4 g 
diameter = 0.02 .mu.m) 
Silica 1 g 
Benzyl dimethyl ketal 1 g 
Chlorinated copper phthalocyanine 
0.1 g 
p-Methoxyphenol 0.1 g 
Antifoaming agent 2 g 
______________________________________ 
EXAMPLE 14 
A liquid photosensitive resin composition (with a bromine content of 3.9%) 
was prepared by mixing the following ingredients and kneading the mixture 
on a three-roll mill: 
______________________________________ 
Reaction product of bisphenol A diglycidyl 
20 g 
ether/acrylic acid/maleic anhydride 
(molar ratio of epoxy group/acrylic acid/ 
maleic anhydride = 1/1/0.5; average 
molecular weight = 500; acid value = 110) 
3-(2,4,6-Tribromophenoxy)-2-hydroxypropyl 
7.5 g 
acrylate (bromine content = 52.3%) 
Neopentyl glycol hydroxypivalate 
30.9 g 
diacrylate 
Phenoxyethyl acrylate 20 g 
Talc 15 g 
Antimony trioxide (average particle 
0.4 g 
diameter = 0.02 .mu.m) 
Silica 4 g 
Benzyl dimethyl ketal 1 g 
Sumiplast Green G (manufactured by 
0.1 g 
Sumitomo Chemical Industries Co., Ltd.) 
p-Methoxyphenol 0.1 g 
Antifoaming agent 1 g 
The performance of the compositions obtained in the foregoing examples and 
comparative examples was evaluated according to the following procedures. 
The results thus obtained are shown in Table 2. 
(1) Preparation of a coating ready for curing 
A copper-clad laminate (ELC4708, manufactured by Sumitomo Bakelite Co., 
Ltd.) was cut into 10 cm.times.15 cm pieces, which were pretreated by 
abrasion, washing and dewatering. Using a Baker type applicator, the 
pretreated pieces of copper-clad laminate were each coated with a liquid 
photosensitive resin composition prepared under various conditions to a 
thickness of 100 .mu.m. Each of the coating films so formed was then 
covered with a polyester film 25 .mu.m thick to obtain a coating ready for 
curing. (The term "coating ready for curing" as used wherein means a 
coating film formed as described above and then covered with a polyester 
film.) 
(2) Determination of optimum primary exposure conditions and evaluation of 
developability 
(2-1) Primary exposure 
On a coating ready for curing were placed a negative film 120 .mu.m thick 
(STOUFFER Resolution Guide #1-T, manufactured by Stouffer Graphic Arts 
Equipment Co.) and then a Pyrex.RTM. glass plate 3 mm thick. Then, the 
coating was exposed to radiation from a 100 W high pressure mercury lamp 
(UH-100, manufactured by Ushio Inc.) located 15 cm above the coating. The 
exposure time was varied from 10 to 180 seconds. The magnitude of the 
exposure energy was measured by means of a UVR-365 tester (manufactured by 
Tokyo Optical Co., Ltd.). 
(2-2) Development 
The 25 .mu.m thick polyester film was stripped from the coating film after 
undergoing the primary exposure. Then, the coating film was subjected to 
spray development under the following conditions: 
______________________________________ 
Developer: 1% aqueous solution of sodium 
carbonate (40.degree. C.). 
Nozzle: JUP-03 [manufacture by H, Ikeuchi 
& Co., Ltd.] (1.5 Kg/cm.sup.2, 2.6 
liters/min.). 
Distance from 
15 cm. 
nozzle: 
Time: 30 seconds. 
______________________________________ 
Thereafter, the coating film was washed with running water, dewatered by a 
stream of air, and then dried at 70.degree. c. for 5 minutes. 
(2-3) Postcuring 
After completion of the development, the coating film was photocured and 
heat-treated under the following conditions, and then allowed to cool to 
room temperature: 
(A) Photocuring 
______________________________________ 
Light source: 
5 kW high pressure mercury vapor lamp 
(H-500 UVA, manufactured by Mitsubishi 
Electric Corp.). 
Distance: 20 cm. 
Speed of 0.9 m/min. 
passage: 
______________________________________ 
(B) 
Heat treatment (after postcuring), 
Heat-treating conditions: 160.degree. C. 10 min. 
(2-4) Determination of optimum primary exposure energy 
By comparing the coating films obtained at varying primary exposure times, 
the exposure energy (in mJ/cm.sup.2) required to obtain a coating film 
reproducing the patterns of the aforesaid Resolution Guide most exactly 
was determined. 
(2-5) Evaluation of developability 
The developability of the composition was evaluated by observing the 
surface of the sample developed at the optimum primary exposure energy 
under a microscope (30.times. magnification). 
______________________________________ 
.circleincircle.. . . 
No residual resinous material was present 
in the unexposed areas. 
X . . . Residual resinous material was present in 
the unexposed areas. 
______________________________________ 
(3) Evaluation of properties of a cured coating film 
(3-1) Primary exposure 
On a coating ready for curing were placed a polyester film 120 .mu.m thick 
and then a Pyrex.RTM. glass plate 3 mm thick. Then, the coating was 
exposed to radiation from a 100W high pressure mercury vapor lamp (UH-100, 
manufactured by Ushio Inc.) located 15 cm above the coating, for a period 
of time corresponding to the optimum primary exposure energy. 
(3-2) Development 
The coating film was developed in the same manner as described in (2-2). 
(3-3) Postcuring 
The coating film was postcured in the same manner as described in (2-3). 
(3-4) Evaluation of thermal resistance 
The postcured coating film, together with the substrate, was soaked in 
molten solder at 260.degree. C. for either 10 or 20 seconds. After 
removal, the state of the coating film was examined and evaluated. 
______________________________________ 
.circleincircle.. . . 
No change was observed after soaking for 20 
seconds. 
.circle. . . . 
No change was observed after soaking for 
10 seconds, but blistering, peeling and/or 
cracking were noted after soaking for 20 
seconds. 
X . . . Blistering, peeling and/or cracking are 
noted after soaking for 10 seconds. 
______________________________________ 
(3-5) Evaluation of adhesion 
The adhesion of the postcured coating film was evaluated according to the 
first method for crosscut adhesion testing described in JIS-D-0202. 
(Crosscuts were made at intervals of 2 mm.) 
______________________________________ 
.circleincircle.. . . 
The area of the lost portions was less than 
5% of the total square area. 
.circle. . . . 
The area of the lost portions was less than 
10% of the total square area. 
X . . . The area of the lost portions was not less 
than 10% of the total square area. 
______________________________________ 
(3-6) Evaluation of solvent resistance 
The postcured coating film, together with the substrate, was soaked in 
trichloroethane and dichloromethane at 25.degree. C. for 10 minutes each. 
After removal, the state of the coating film was examined and evaluated. 
______________________________________ 
.circleincircle.. . . 
No change was observed after soaking in 
trichloroethane or after soaking in 
dichloromethane. 
.circle. . . . 
Blistering, peeling and/or dissolution were 
noted after soaking in trichloroethane or 
after soaking in dichloromethane. 
X . . . Blistering, peeling and/or dissolution were 
noted both after soaking in trichloroethane 
and after soaking in dichloromethane. 
______________________________________ 
(3-7) Measurement of volume resistivity (evaluation electrical insulating 
properties) 
The postcured coating film was kept for 100 hours in an environment having 
a temperature of 50.degree. C. and a relative humidity of 90%. Thereafter, 
using a Model SM-10E Ultrahigh Insulation Resistance Tester (manufactured 
by Toa Electronics Ltd.), the volume resistivity of the coating film was 
measured after a voltage of 500 V was applied for 1 minute. 
(4) Evaluation of flame retardancy 
Using a copper-clad glass-epoxy laminate (Sumilite ELC-4756, manufactured 
by Sumitomo Bakelite Co., Ltd.) having a thickness of 1.6 mm, the copper 
layers were removed from both sides thereof by etching with an aqueous 
solution of ferric chloride. On both sides of the etched substrate, a 
cured coating film 100 .mu.m thick was formed according to the procedures 
described in (1), (3-1), (3-2) and (3-3). Then, ten test pieces measuring 
127 mm.times.12.7 mm were cut out of the coated substrate. Of these ten 
test pieces, five were allowed to stand at a temperature of 23.degree. C. 
and a relative humidity of 50% for 48 hours or more, and the other five 
were heat-treated at 125.degree. C. for 24 hours and then cooled in a 
desiccator containing anhydrous calcium chloride for 4 to 5 hours. These 
test pieces were tested for flame retardancy according to the "UL-94 V-0" 
method of Underwriters' Laboratories, Inc., and the maximum burning time 
(in seconds) and the average burning time (in seconds) were recorded. 
(5) Homogeneity of the liquid composition 
The resulting liquid photosensitive resin composition was stored in the 
dark at both 23.degree. C. and 0.degree. C. for 2 hours and then examined 
for homogeneity. 
______________________________________ 
.circleincircle.. . . 
No change was observed. 
.circle. . . . 
precipitate was formed, but the composition 
could be made homogeneous by remixing at 
23.degree. C. 
X . . . A precipitate was formed, and the composition 
could no longer be made homogeneous by 
remixing at 23.degree. C. 
______________________________________ 
TABLE 2 
__________________________________________________________________________ 
Example 
Example No. 
1 2 3 4 5 6 7 8 9 10 11 12 13 14 
__________________________________________________________________________ 
Optimum primary 
120 
120 
120 
120 
120 
130 
110 
120 
120 
120 
130 
130 
130 
130 
exposure energy 
(mJ/cm.sup.2) 
Developability 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
Thermal resistance 
.circle. 
.circle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
Adhesion .circle. 
.circle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
Solvent resistance 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
Volume resistivity 
4.2 
3.9 
2.8 
2.8 
2.9 
2.6 
1.8 
2.9 
3.3 
2.7 
3.1 
2.0 
1.9 
1.8 
(.OMEGA. = 10.sup.13) 
Flame 
Maximum 
7.0 
6.9 
3.8 
5.9 
5.0 
3.8 
4.8 
4.1 
8.7 
7.2 
4.1 
4.3 
4.8 
4.2 
retard- 
burning 
ancy 
time (sec.) 
Average 
1.5 
1.4 
0.9 
1.2 
1.1 
0.8 
1.1 
1.0 
1.5 
1.6 
1.0 
1.1 
1.2 
1.0 
burning 
time (sec.) 
UL-94 grade 
V0 V0 V0 V0 V0 V0 V0 V0 V0 V0 V0 V0 V0 V0 
Homogeneity of 
.circle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
liquid composition 
__________________________________________________________________________ 
Comparative Example 
Example No. 
1 2 3 4 5 
__________________________________________________________________________ 
Optimum primary 
120 
120 
120 
120 
120 
exposure energy 
(mJ/cm.sup.2) 
Developability 
.circleincircle. 
.circleincircle. 
.circleincircle. 
X .circleincircle. 
Thermal resistance 
.circleincircle. 
.circleincircle. 
X .circleincircle. 
X 
Adhesion .circleincircle. 
.circleincircle. 
.circle. 
.circleincircle. 
.circle. 
Solvent resistance 
.circleincircle. 
.circleincircle. 
.circle. 
.circleincircle. 
.circleincircle. 
Volume resistivity 
3.0 
2.9 
2.0 
2.0 
2.6 
(.OMEGA. = 10.sup.13) 
Flame 
Maximum 
25.1 
18.1 
3.9 
11.1 
10.1 
retard- 
burning 
ancy 
time (sec.) 
Average 
4.3 
4.0 
0.8 
3.6 
4.6 
burning 
time (sec.) 
UL-94 grade 
V1 V1 V0 V1 V1 
Homogeneity of 
.circleincircle. 
.circleincircle. 
.circle. 
.circle. 
.circleincircle. 
liquid composition 
__________________________________________________________________________