Glass fiber base material for print wiring substrate

A glass fiber base material for print wiring substrate is disclosed, comprising a fluorescent whitening agent attached to the surface of a sheet made of glass fibers such as woven fabrics, non-woven fabrics and paper. The glass fiber base material has excellent ultraviolet light-shielding properties and, hence, is very useful in production of super LSI.

FIELD OF THE INVENTION 
The present invention relates to a glass fiber sheet-like base material for 
use in production of glass fiber-reinforced laminated plates for print 
wiring substrate. More particularly, the present invention is intended to 
provide a glass fiber base material in which a fluorescent whitening agent 
is attached to the surface of a constituent glass fiber. 
BACKGROUND OF THE INVENTION 
As a substrate for print wiring/ laminated plates produced by impregnating 
a fiber sheet (e.g., woven fabrics, non-woven fabrics or paper of glass 
fiber) as a reinforcing material with a thermosetting synthetic resin 
(e.g., epoxy resins or polyimide resins) to produce a prepreg, laminating 
a plurality of prepregs as produced above, placing a metal foil on each of 
the both surfaces of the laminate, and then hot pressing the assembly are 
widely use. 
A circuit wiring is formed on the metal foil on each of the both surfaces 
of the substrate by the photoresist method, and a solder resist cured 
pattern is further provided thereon by the photoresist method to produce a 
print wiring plate. 
As the solder resist, ultraviolet light-curable resists (e.g., acrylic 
compound-modified epoxy resins having excellent physical properties) are 
used. In order to obtain a resist cured pattern by irradiating the both 
surfaces with an ultraviolet light at the same time, it is required that 
the above-described glass fiber-reinforced synthetic resin substrate 
itself does not transmit therethrough an ultraviolet light. In order to 
obtain a glass fiber-reinforced laminated plate which shields an 
ultraviolet light, a method in which an organic ultraviolet light absorber 
is compounded into an impregnating resin varnish in the production of 
prepregs for glass fiber sheet (cf. JP-A-62-37822) and a method in which 
fine particles of titanium oxide are attached to a glass fiber sheet (cf. 
JP-A-62-28241) have been proposed. The term "JP-A" as used herein means an 
"unexamined published Japanese patent application". 
In the method for obtaining ultraviolet light-shielding substrates, means 
for compounding an ultraviolet light absorber into a resin varnish for 
production of prepregs involves problems that satisfactory ultraviolet 
light-shielding properties are difficult to obtain even if a relatively 
large amount of the ultraviolet light absorber is compounded, curing 
properties of the varnish are readily reduced, and that the substrate is 
colored yellow. The method in which fine particles of titanium oxide are 
attached to the glass fiber sheet directly or after adding to a silane 
coupling emulsion involves problems that uniform dispersion stability of 
fine particles of titanium oxide is difficult to maintain and that since 
attachment of fine particles of titanium oxide often becomes uneven, it is 
necessary to attach the fine particles of titanium oxide in an amount more 
than the necessary amount for imparting the ultraviolet light-shielding 
properties, leading to whitening of the substrate. 
SUMMARY OF THE INVENTION 
The present invention is intended to overcome the above-described problems 
of the conventional means by attaching a fluorescent whitening agent to a 
glass fiber base material for print wiring substrate and provide a 
substrate having good ultraviolet light-shielding properties. 
That is, an object of present invention is to provide a glass fiber base 
material for print wiring substrate, comprising a fluorescent whitening 
agent attached to the surface of a glass fiber sheet, e.g., woven fabrics, 
non-woven fabrics or paper. 
DETAILED DESCRIPTION OF THE INVENTION 
As the fluorescent whitening agent, various compounds are commercially 
available as an agent for treating fibers or plastics to exhibit a 
whitening effect by shielding an energy of ultraviolet light of from 340 
to 400 nm and emitting a purplish blue light of from 400 to 500 nm. 
For example, bis(triazinylamino)stilbenedisulfonic acid-, coumarin-, 
pyrazoline-, naphthalamide-, bisbenzoxazolyl-, and bisstyrylbiphenyl-based 
whitening agents are generally used in the form of an aqueous solution or 
aqueous emulsion, and these materials can be utilized in the present 
invention. 
The glass fiber sheet is usually subjected to desizing, dipping in a 
solution of the fluorescent whitening agent, squeezing, drying, and then 
processing with a surface treating agent to produce a substrate for 
production of a print wiring substrate. 
As the surface treating agent, known coupling agents such as vinyltriethoxy 
silane and epoxy silane are chosen depending on the type of the resin for 
prepregs and usually used in such an amount that the amount attached is 
from 0.05 to 0.2%. 
Though it is most preferred that the treatment with the solution of 
fluorescent whitening agent is achieved before processing with the surface 
treating agent, it may be carried out after processing with the surface 
treating agent, or it may be carried out by adding the fluorescent 
whitening agent to the solution of surface treating agent. Adding the 
fluorescent whitening agent to the resin varnish for prepregs, however, is 
unsuitable because it is readily dissolved in a dissolving developing 
solution at the time of forming a wiring circuit by the photoresist 
method, leading to a reduction in ultraviolet light-shielding properties. 
The amount of the fluorescent whitening agent attached to the glass fiber 
sheet is usually not more than 0.5%. Depending on the number of laminated 
sheets, a 99% or more ultraviolet light-shielding effect can be obtained. 
No special effect can be obtained even if the amount is increased to more 
than 1%. 
The glass fiber base material of the present invention has a fluorescent 
whitening agent uniformly attached to the surface of the constituent glass 
fiber. Therefore, in the print wiring substrate obtained by laminating a 
plurality of prepregs produced using this base material, the ultraviolet 
light projected from one surface is converted into a fluorescent light and 
almost completely prevented from reaching the other surface. 
In the base material to which the fluorescent whitening agent has been 
attached, coloration is not substantially observed and, therefore, such is 
suitable when the substrate is transluscent or arbitrarily colored.

The present invention is described in greater detail with reference to the 
following Example as one embodiment of the process of production. In the 
Example all percents (%) are by weight. 
EXAMPLE 
(1) As the glass fiber sheet base material, a desized glass fiber fabric 
(produced by Nitto Boseki Co., Ltd., WEA-18w, basis weight: 212 
g/cm.sup.2) was used. 
(2) As the fluorescent whitening agent, an aqueous solution of 
Illuminarl.RTM. BBS (a stilbene-based fluorescent whitening agent produced 
by Showa Chemical Co., Ltd.) and an aqueous emulsion of Uvitex.RTM. EBF (a 
benzoxazolyl-based fluorescent whitening agent produced by Ciba-Geigy AG) 
were prepared in a concentration of 0.05%, 0.1%, 0.5% and 1.0%, 
respectively. 
(3) Each of the glass fiber sheet base materials as prepared in (1) was 
dipped in each of the eight types of fluorescent whitening agent solutions 
as prepared in (2) with a pickup of 30% and then dried upon heating to 
obtain eight types of products in each of which the fluorescent whitening 
agent was attached uniformly to the surface of the constituent glass fiber 
sheet. 
(4) Each of the products as prepared in (3) was dipped in a 0.1% aqueous 
acetic acid solution containing 0.8% of a silane coupling agent (Epoxy 
Silane.RTM.A- 187 produced by Nippon Unicar Co., Ltd.) with a pickup of 
30% and then dried upon heating. Furthermore, it was impregnated with an 
epoxy resin varnish according to the following G-10 formulation to an 
extent of 70% and preliminarily dried to obtain a prepreg. Three prepregs 
were laminated and molded by the usual method to obtain eight types of 
test laminated plates. 
Epoxy Resin Varnish 
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Epikote .RTM. 1001 (an epoxy resin 
100 parts by weight 
produced by Shell 
Chemical Co., Ltd.) 
Dicyandiamide 2 parts by weight 
Benzyldimethylamine 
0.2 part by weight 
Methyl oxitol about 100 parts by weight 
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As a comparative example, the glass fiber sheet as prepared in (1) was 
subjected to the treatment in (4) with the silane coupling agent and then 
with the epoxy resin varnish to prepare prepregs, three of which prepregs 
were molded to produce a test laminated plate. 
The above-prepared eight types of laminated plates using the glass fiber 
material of the present invention and the comparative laminated plate were 
measured for 365 nm-ultraviolet light transmittance (% T) by the use of a 
B 100A type lamp, a UVX 36 type sensor, and a UVX radio meter, all of 
which are produced by UVP Co. The results were tabulated below. 
______________________________________ 
Fluorescent Whitening Agent 
Illuminarl .RTM. 
Uvitex .RTM. 
Concentration of Solution 
BBS EBF 
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0.05% 4.89% T 4.18% T 
0.1% 2.76 2.01 
0.5 0.79 0.38 
1.0 0.48 0.19 
0 27.3 
(Comparative Example) 
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As can be seen from the foregoing results, it is apparent that the 
laminated plate using the glass fiber base material of the present 
invention has excellent ultraviolet light-shielding properties, and its 
color tone is translucent, which is substantially the same as that of the 
Comparative Example. 
In accordance with the present invention, a glass fiber sheet-like base 
material having excellent ultraviolet light-shielding effects can be 
easily and economically produced utilizing an ultraviolet light conversion 
action of a fluorescent whitening agent which has hitherto been used to 
increase the degree of whiteness. With a laminate substrate produced using 
the glass fiber sheet-like base material, the formation of cured patterns 
of the both surfaces of a solder resist at the time of production of a 
print wiring plate can be efficiently carried out by irradiation the both 
surfaces with an ultraviolet light at the same time. The invention greatly 
contributes to an increase in efficiency in production of a print wiring 
plate for super LSI. 
While the invention has been described in detail and with reference to 
specific embodiments thereof, it will be apparent to one skilled in the 
art that various changes and modifications can be made therein without 
departing from the spirit and scope thereof.