Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
1. _ Field_of the Invention
This invention relates to a method for distinctly
ànd durably printing minute letters or symbols on the
` 15 surfaco of a soft contact lens.
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~'~!, 2~ Description of the Prior Art
~; Soft contact lenses made from a hydrophilic thermo-
plastic resin ha~e been developed recently. They are better
than hard contact lenses in the good wear feeling and the
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`20 -considerable long time wearability given from the first
'` wearing day. Therefore, soft contact lenses have been
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- replacing hard contact lenses. Many companies have produced
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various kinds of contact lenses of their own. But, these
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contact lenses are so similar on~ another in the shape that
even specialists of the maker can hardly differentiate their
own product from others. Wearers can hardly tell between the
left one and right one of a pair, and between the front and
back of a lens, especially a thin lens, because soft contact
lenses are so soft that the front is easily turned over to
the back and vice versa. Therefore, lt is considered to be
very significant for the sake of overcoming above said problems
to mark on the surface of soft contact lenses. However, soft
contact lenses easily get wet because of their hydrophilic
property, so that there has been heretofore no effective
method for distinctly and durably printing such minute letters
or symbols as being printed on a marginal area of the surface
of soft contact lens.
SUMMAP~Y OF THE INVENTION
It is an object of the present invention to provide a
method for distinctly and durably printing minute letters or
symbols on the surface of soft contact lenses.
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In one particular aspect the present invention provides
a method of printing soft contact lenses with identifying
- ind~cia, comprising the steps of:
~-. (a) causing the soft contact lens to swell by immersion
i in a swelling agent selected from the group consisting of
water and hydrophilic solvents;
(b) wiping the surface oE the soft contact lens in at
~, least the area to be printed to remove excess swelling
agent;
; (c) stamping the prepared surface of the soft contact
lens with identifying indicia comprised of an aqueous solution
or paste of a light resistlve coloring composition hardenable
by ultraviolet radiation; and
(d) hardening said composition by application of
ultraviolet radiation.
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DETAII.ED DESCRIPTION OF THE PREFERR~D EMBODIMENTS
The light sensiti~e coloring composition of this
invention includes all of known composition which contains
a coloring component and is hardened by the photo polymeriza-
tion reaction caused by irradiation of ultraviolet ray, andalso may include even unknown compositions which con~ain
` a coloring componen~ and are hardened by the photo polymeriza-
tion reaction.
The following examples are presented in order to
` 10 illustrate the practice of the method of this invention.
Powdered light sensitive dye composition (Product of
Toppan Printing Co., Ltd.) is dissolved in water in an amount
` of 5 - 30 wt.%. Ethylene glycol, glycerine, polyvinyl alcohol ~-
or polyvinyl pyrrolidone is preferably added thereto in an ~ -
amount of 5 - 20 wt.~, because the addition can prevent
vaporization of water from the solution, so that the solution
can be available for a long period of time. Thus prepared
solution is soaked into a porous rubber stamp graved with
necessary letters or symbols. The stamp is wiped to remove
` 20 excessive solution from the surface, and then impressed
evenly to the surface of a soft contact lens. The soft
contact lens to be stamped is taken out of the isotonic -
.,sodium chloride solution, and wiped to remove the solution
from the surface, and placed on a table to be stamped.
; 25 One stamping is kept for several seconds. I`hus, successive
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stampings are feasible dozens of time without any spread of
the solution on the surface of lens. The workability is
very good. The stamped soft contact lens is irradiated
- with ultraviolet ray by a ultraviolet lamp, so that the
solution adhered on the surface by the stamping is color
developed and becomes insoluble. The one beca~lle insoluble
~` is no longer dissolved and spread around on the surface by
the following boiling in water or chemical treatments thereof,
- so that the minute letters or symbols printed on the surface ~ ~.
-~ 10 of the soft contact lens are kept permanently as it is. ;
- Another method is cited whlch comprises using one
of UV inks by the use of an intaglio transfer press. An
intagll~o plate made of~c~opper or glass on which the letters
or symbols are engraved i5 covered wlth~the~UV ink paste
~ and is.squeezed by a spatula to remain~the UV lnk paste only
in the engraved part of the plate, Then~ the remained UV
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ink pas~te is transferred to the conical transfer made of
- a~sillcone resin or gelatin in the intaglio transfer press.
The~conical transfer is impressed~onto the surface of the
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`! 20 soft contact lens~from whlch water is wiped out in order to
transfer the ink of the~letters or symbols to the surface of
~ the~soft~contact lens.~The resul-tlng lens is then subjected
`~ to irradlation of ultrav~lolet~ ray~to make the UV ink insoluble. ;
~The~stamping may be carried out on the soft contac~
lens in dry state. But in this case, the ink is adhered ;~
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only onto the superficies of soft contact lens. However,
; soft contact lenses are used in the swelling state with water.
~-i Accordingly, the print carried out in the dry state may be
peelled off because of the strain due to the swelling with
water, and the letters or symbols printed may be deformed
in the swelling state. Therefore, stamping is preferably
; carried out in the state of swelling, because the ink will -
be able to penetrate inside the lens to some extent, so that
`~ the letters or symbols printed are made more stable. One ~ ~ -
method for bringing to the swelling state is that the lens
is once removed from the isotonic sodium chloride solution
- into a distilled water or ethanol in order to increase the
- swelling degree thereof temporalily, and~then is printed.
Preferable prlnting position is 1 - 2 mm inside from
- 15 the edge of the convex surface of the lens, because no
- ;influence is yielded~to eye sight and wear feeling of the
wearer by the printing and no print can be visible by viewers.
According to the method of this invention, minute
f letters or symbols which can represent necessary characte-
; 20 rlstics, for example, name of manufacturer, vairous kinds
of dimension such as base-curve, diameter, diopters, or
production lot number, front side and back side etc. can
be distinctly and durably pTinted on soft contact lenses.
It is clear that such lenses are by far more convenient
~3 25 than prior lenses with no print of those letters or symbols.
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