Rubber-padded frames of eye spectacles and method for preparing same

The invention proposes a novel method for providing a covering pad member of silicone rubber to a frame of spectacles on the portions coming into contact with the human body of the wearer of the spectacles, such as the side pieces and the nose pads. According to the inventive method, a shaped member of the silicone rubber having dimensions somewhat smaller than the portion to be covered therewith is first swelled with an orgnosilicon compound having volatility, inserted to the portion, e.g. sidepiece, and then dried by evaporation of the organosilicon compound as the swelling agent whereby the member shrinks to fit the portion of the frame tightly. Organosilicon compounds, e.g. hexamethyldisiloxane, are recommended owing to the physiological inertness to human body as well as owing to the absence of aggressiveness to the plastic part used in the frames of spectacles causing no damage to the beautiful appearance of the frame even in an inadvertent contact.

BACKGROUND OF THE INVENTION 
The present invention relates to an improved rubber-padded frame of eye 
spectacles or, more particularly, to a frame of spectacles padded with 
members of a silicone rubber on portions where the frame is in contact 
with the human body of the wearer and a method for preparing the same. 
When spectacles are worn by a wearer, the frame of the spectacles is 
usually hung on the ears of the wearer by the sidepieces and, in the same 
time, it is supported by the upper portion of the nose at the nose pads of 
the frame. Accordingly, much of optician's skill is required not only in 
the optics of the glasses per se but also in fitting the frame to the 
wearer's face because otherwise the wearer feels a great deal of 
unpleasantness or uncomfortableness in continued wearing of the 
spectacles. For example, too tight fitting of the frame to the wearer's 
face sometimes causes pains in his ears and nose while too loose fitting 
is undesirable because the spectacles often slide down out of the proper 
position, especially, with perspiration in hot weathers. 
Thus, not only opticians but also wearers of spectacles encounter difficult 
problems in obtaining comfortable feeling in wearing spectacles. 
An attempt to solve such a problem is to provide the frame with padding 
members of rubber on the portions where the frame comes into contact with 
the body of the wearer. That is, the frame is provided with covering pads 
made of a rubbery material on the nose pads and the sidepieces where the 
frame comes into contact with the nose and the ears of the wearer, 
respectively. One of the difficulties in providing such covering pads on 
the nose pads and the sidepieces of a frame of spectacles is that the nose 
pads and the sidepieces of a frame have usually very irregular forms so 
that good fitting of the rubber covering is hardly obtained with the nose 
pads or sidepieces as the substrates. For example, many of the sidepieces 
have a larger width at the end portions thereof than at the middle 
portions so that mere insertion of a plain rubber tube to the side piece 
cannot give a good result when a tightly covering rubber layer is desired 
on the sidepiece in consideration of the appearance of the frame. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a frame of 
spectacles having rubber pads on the portions thereof coming into contact 
with the body of the wearer without adverse effect on the appearance of 
the frame. 
Another object of the invention is to provide an improved frame of 
spectacles having covering pads of a silicone rubber on the nose pads and 
the sidepieces tightly fitting thereto. 
Further object of the invention is to provide a novel method for providing 
such covering pads of a silicone rubber on the nose pads and sidepieces of 
a frame of spectacles. 
According to the invention, a shaped member of a silicone rubber having 
dimensions somewhat smaller than the dimensions of the nose pad or 
sidepiece of the frame to be covered with the covering pads is first 
swollen with a swelling agent, then inserted to the nose pad or the 
sidepiece to cover it and finally subjected to evaporation of the swelling 
agent so as that the silicone rubber member is dried and shrunk to tightly 
fit the nose bad or the sidepiece. 
In particular, there is recommended the use of a low molecular weight 
organosilicon compound as the swelling agent.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
It is of course that the form of the shaped member of a silicone rubber 
depends on whether the member is used to cover a nose pad or a side piece 
of a frame of spectacles. Thus, a bag-like shaped member is suitable for 
covering a nose pad of a frame while a sidepiece of a frame is most 
conveniently covered with a tubular shaped member with an open end or 
closed end. At any rate, the shaped member of a silicone rubber is shaped 
to have dimensions somewhat smaller than the dimensions of the nose pad or 
sidepiece to be covered therewith so as that tight fitting is obtained. 
Silicone rubbers are particularly preferred to the other kinds of synthetic 
or natural rubbers because (1) a silicone rubber can have a hardness 
ranging in a wide range so that the hardness of the silicone rubber can be 
selected to just comply with the wearer's preference, (2) the surface of 
silicone rubbers is less slippery on the human skin when wet with sweat 
than the other kinds of rubbers and good feeling is obtained in wearing, 
(3) silicone rubbers are generally physiologically inert and safe from 
skin irritation or contact dermatitis even in continued contact with human 
skin, and (4) transparent silicone rubbers are readily obtained so that 
the appearance of the frame is not affected adversely. 
The thickness of the shaped member of the silicone rubber is not 
particularly limitative but it is preferably in the range from 0.1 to 5 mm 
or, more preferably, from 0.3 to 2 mm so as that a sufficient padding 
effect is obtained. The hardness of the silicone rubber is also of some 
importance in order to give comfortable feeling to the wearer. The 
hardness should be in the range from 15 to 90 or, preferably, 30 to 70 by 
the JIS scale. 
The next step is swelling of the silicone rubber shaped member with a 
suitable swelling agent. Numbers of organic solvents are known as a 
swelling agent for silicone rubbers but preferred swelling agents in this 
case should have adequate volatility so as that rapid drying and shrinkage 
of the member after insertion to the nose pad or sidepiece can be ensured. 
The organic solvents suitable as a swelling agent for silicone rubbers are 
exemplified by aromatic hydrocarbon solvents such as benzene, toluene and 
xylene and halogenated hydrocarbons such as carbon tetrachloride, 
trichloroethylene, perchloroethylene and the like. The swelling agent has 
a boiling point, preferably, in the range from 20.degree. to 200.degree. 
C. as a measure of the volatility. 
The silicone rubber shaped member becomes readily swollen when it is dipped 
in the swelling agent at room temperature for a time of, for example, 3 
minutes or longer to reach a swelling equilibrium. When the swelling ratio 
at the swelling eauilibrium is too large, the ratio can be adjusted by use 
of a swelling agent which is a mixture of the above named swelling 
solvents and a non-swelling solvent in an appropriate proportion. It is 
recommended that the equilibrium swelling ratio is in the range from 105 
to 600% by weight. This is because too small swelling ratios lead to a 
difficulty in inserting the shaped member to the nose pad or sidepiece or 
loose fitting after drying and shrinkage while too large swelling ratios 
are undesirable due to the excessively long time taken for drying and 
shrinkage after insertion of the member to the substrate. 
The above named aromatic hydrocarbon solvents and halogenated hydrocarbon 
solvents are quite satisfactory in so far as the swelling and drying 
performance is concerned. However, they are undesirable in several points. 
For example, these solvents are aggressive to the materials usually used 
in the frames of spectacles. It is very conventional that at least part of 
the frames are formed of a plastic material such as cellulosic plastics 
which are readily attacked by the above named solvents causing whitening 
on the surface. Therefore, the silicone rubber shaped member swollen with 
these solvents must be kept away from the parts of plastics other than the 
nose pads or sidepieces to be covered therewith. Otherwise the beautiful 
appearance of the frames is greatly reduced. 
In addition, the above named solvents are more or less toxic to the human 
body so that their use is undesirable, especially, when a large volume of 
the solvent is to be handled. 
In view of the above problems in the use of the conventional solvents for 
swelling the silicone rubber shaped members, the inventors have conducted 
extensive investigations to obtain a swelling solvent suitable for the 
purpose with no adverse effect on the plastic material of the frame as 
well as with no problem on the human health. 
The above investigations have arrived at a discovery that certain kinds of 
low molecular weight organosilicon compounds are the most suitable as a 
swelling agent of the silicone rubber shaped members as a covering pad of 
frames of spectacles. They are not only physiologically inert to human 
body but also not aggressive to the materials of which the frame is 
formed. In addition, the swellability and volatility can be adjusted as 
desired by properly choosing the compounds or by using a mixture of two or 
more of organosilicon compounds having different swellability and 
volatility. 
The organosilicon compounds suitable for the purpose are organosilane 
compounds or organopolysiloxane compounds represented by the general 
formula 
EQU R.sup.1.sub.a Y.sub.b SiO.sub.4-a-b/2, (I) 
where R.sup.1 is a hydrogen atom or a substituted or unsubstituted 
monovalent hydrocarbon group, Y is a hydroxy group or a hydrolyzable 
group, a is a positive number not exceeding 4 and b is zero or a positive 
number not exceeding 4 with the proviso that a+b is a positive number not 
exceeding 4. When a+b is equal to 4, the compound is an organosilane 
represented by the general formula R.sup.1.sub.a SiY.sub.4-a while the 
compound is an organopolysiloxane when a+b is smaller than 4. The 
organosilicon compound should desirably have a boiling point in the range 
from 20.degree. to 200.degree. C. because a compound having a too low 
boiling point is difficult to handle and no sufficient swelling ratio is 
obtained while an organosilicon compound having a boiling point higher 
than 200.degree. C. is undesirable due to the low velocity of vaporization 
when the swollen silicone rubber is to be dried. 
In the above given general formula (I), R.sup.1 is exemplified by alkyl 
groups such as methyl, ethyl and propyl groups, preferably, methyl group, 
aryl groups such as phenyl and tolyl groups, preferably, phenyl group, and 
alkenyl groups such as vinyl and allyl groups, preferably, vinyl group. 
Those groups derived from the above named hydrocarbon groups by the 
substitution of halogen atoms or other substituent groups for part or all 
of the hydrogen atoms in the hydrocarbon groups are also suitable. 
The group Y in the general formula (I) is a hydroxy group or a hydrolyzable 
group exemplified by alkoxy groups such as methoxy, ethoxy and propoxy 
groups, acyloxy groups such as acetoxy and propoxy groups, amino group and 
substituted amino groups, aminoxy group and substituted aminoxy groups, 
ketoxime groups, amido groups and alkenyloxy groups. However, such a 
hydroxy or hydrolyzable group is not essential in the organosilicon 
compounds. 
Several of the examples of the above defined organosilicon compounds are as 
follows: tetramethylsilane; trimethylethylsilane; trimethylvinylsilane; 
trimethyl perfluoropropylsilane; trimethylmethoxysilane; 
trimethylethoxysilane; dimethyldimethoxysilane; vinyl trimethoxysilane; 
trimethyl silanol; perfluoropropyl trimethoxysilane and a silacyclo 
compound expressed by the formula 
##STR1## 
as the examples of the organosilane compounds and hexamethyldisiloxane; 
1,1,3,3-tetramethyldisiloxane; 1,3-dimethyldisiloxane; 
1,1,1,3,3-pentamethyldisiloxane; 
1,1,3,3-tetramethyl-1,3-divinyldisiloxane; octamethyltrisiloxane; 
1,3,5-trimethylcyclotrisiloxane; octamethylcyclotetrasiloxane and 
1,3,5,7-tetramethylcyclotetrasiloxane as the examples of the 
organopolysiloxane compounds. 
In addition, several kinds of silalkylene compounds and silazane compounds 
are also used as a kind of substituted alkylcontaining organosilane 
compounds or substituted amino-containing organosilane compounds. Examples 
of these compounds are bis(trimethylsilyl) methane and 
hexamethyldisilazane. 
Among the above named organosilicon compounds, the most preferred is 
hexamethyldisiloxane owing to its adequate swelling performance and 
moderate vaporization velocity with a boiling point of about 100.degree. 
C. along with its inexpensiveness. It is, however, optional to use a 
mixture of two kinds or more of the organosilicon compounds, if desired, 
with an object of controlling the swelling and drying performance. It is 
further optional that the organosilicon compounds is admixed or diluted 
with an organic solvent miscible therewith according to need to increase 
or decrease the swelling ratio of the silicone rubber shaped members. 
The time taken for swelling and the equilibrium swelling ratio of the 
silicone rubber shaped members are largely dependent on the kind of the 
swelling agent and the grade of the silicone rubber or, particularly, on 
the degree of crosslinking of the silicone rubber. As a general measure, 
however, 24 hours of dipping at room temperature is sufficient in most 
cases to obtain equilibrium swelling to give an equilibrium swelling ratio 
by weight of 105 to 500% for the organosilicon compounds. Further, the 
time taken for complete evaporation of the swollen silicone rubber shaped 
member also depends largely on the kind of the swelling agent to be 
evaporated but a silicone rubber member swollen with hexamethyldisiloxane 
is completely dry within about 10 minutes when exposed to open air. 
It is further noteworthy that a silicone rubber member once swollen with an 
organosilicon compound regains its original dimensions and mechanical 
properties when it is completely dried. In this connection, several 
experiments were undertaken to demonstrate the reversibility of the 
dimensions and mechanical properties of silicone rubber members by 
swelling and drying. 
Thus, tubular specimens of a cured silicone rubber were prepared by cutting 
a continuous length silicone rubber tube having an inner diameter of 1.20 
cm obtained by extrusion molding of a silicone rubber stock (KT 120R, a 
product by Shin-Etsu Chemical Co., Japan). The individual tubular 
specimens had a length of 2.50 to 2.51 cm and a weight of 2.03 to 2.04 
grams. The tubular specimens were each dipped in an organosilicon compound 
given in Table 1 below at 20.degree. C. for 24 hours and the dimensions 
and the weight of each specimen were recorded. Thereafter, the swollen 
specimens were exposed to open air at 20.degree. C. for 3 hours to be 
completely dry and the dimensions and the weight were again determined. 
The results are summarized in Table 1. 
TABLE 1 
__________________________________________________________________________ 
As swollen After drying 
Inner Inner 
Length, 
diame- 
Weight, 
Length, 
diame- 
Weight, 
Swelling agent 
cm ter, cm 
g cm ter, cm 
g 
__________________________________________________________________________ 
Trimethylvinylsilane 
3.78 1.81 
5.51 2.51 1.20 
2.04 
Trimethylmethoxysilane 
3.86 1.85 
6.20 2.50 1.20 
2.03 
Dimethyldimethoxysilane 
3.79 1.81 
6.29 2.51 1.20 
2.04 
Vinyltrimethoxysilane 
3.52 1.69 
4.70 2.51 1.20 
2.04 
Hexamethyldisiloxane 
3.74 1.80 
5.83 2.50 1.20 
2.03 
1,3,5-Trimethylcyclo- 
3.75 1.79 
6.83 2.52 1.21 
2.06 
trisiloxane 
Bis(trimethylsilyl)- 
3.71 1.78 
5.48 2.50 1.20 
2.03 
methane 
Hexamethyldisilazane 
3.81 1.83 
6.03 2.53 1.21 
2.08 
__________________________________________________________________________ 
Further, a cured silicone rubber sheet having a thickness of 2 mm prepared 
with a silicone rubber stock (KE 556, a product by Shin-Etsu Chemical Co., 
Japan) was cut into dumbell-shaped test specimens of No. 2 as specified in 
JIS K 6301 and the test specimens were subjected to swelling by dipping in 
hexamethyldisiloxane or trimethylmethoxysilane at room temperature for 72 
hours. The thus swollen test specimens were then exposed to open air at 
20.degree. C. for 3 hours to complete dryness and the mechanical strengths 
of the dried specimens were determined to give the results set out in 
Table 2 below together with the data for the specimens before swelling. 
TABLE 2 
______________________________________ 
Elongation Tensile 
Hardness at break, strength, 
Swelling agent 
(JIS) % kg/cm.sup.2 
______________________________________ 
No swelling 54 370 85 
Hexamethyldisiloxane 
54 375 84 
Trimethylmethoxysilane 
54 395 86 
______________________________________ 
Thus, it is self-evident that, when the sidepieces or nose pads of a frame 
of spectacles are covered with a tubular or bag-like shaped member of 
cured silicone rubber swollen with the above specified organosilicon 
compound and then dried, The silicone rubber member shrinks to fit the 
sidepiece or nose pad so tightly that cannot be expected by mere insertion 
of a dry silicone rubber member to the sidepiece or nose pad to give a 
padding comfortable to the wearer of the spectacles even by continued 
wearing with no adverse effect on the beautiful appearance of the frame.