Note: Descriptions are shown in the official language in which they were submitted.
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Description
SILICONE-HYDROGEL COMPOUND FOR SOFT
CONTACT LENS AND SOFT CONTACT LENS
PRODUCED USING THE COMPOUND
Technical Field
[1] The present invention relate to a silicone-hydrogel soft contact lens, and
more par-
ticularly, to a silicone-hydrogel composition for a soft contact lens
including
2-hydroxyethyl methacrylate and N,O-bis(trimethylsilyl)acrylamide as a
silicone
monomer, and a soft contact lens using the same.
Background Art
[2] Generally, a contact lens is classified into a hard lens having methyl
metacrylate
(MMA) as a basic material and a soft lens including 2-hydroxyethyl
methacrylate
(HEMA) as a basic material wherein the soft lens has been increasingly used
since it
provides relatively higher oxygen permeability and a water content rate. This
is
possible since HEMA includes a hydroxyl group, a representative hydrophilic
molecular structure, within a monomer and thus has a high water content rate
unlike
MMA (Refojo et., J. appl. Poly. Sci., 9:2425(1965)).
[3] Meanwhile, hydrogel refers to a cross-linking high molecule including much
moisture in equilibrium and has a lot of physiological applications including
medical
high molecule for a contact lens (Reference: US. Patent No. 4300820).
[4] Currently, hydrogel used for lenses includes mostly 2-hydroxyethyl
methacrylate as a
monomer which is mixed with a small amount of a cross-linking agent and man-
ufactured by a radical thermal polymerization. The lenses which are
manufactured by
the foregoing material have a water content rate of approximately 40% for
properties
of the material, are hydrophilic and soft to give a user less sense of a
foreign matter
and less pressure to the cornea when attached thereto. However, the lenses
have weak
mechanical strength and have a limited oxygen permeability of approximately
10Dk[10 "cm 2/sec] (rE 0 z mmHg)] and a limited wearing feeling, and protein
is
attached thereto if a user wears them for a long time (Wilson et al., Encyelo.
Of Chem.
Tech., 7:192(1976); and US patent No. 6096138).
[5] As known in the art, the wearing feeling of the lens is closely related to
the water
content rate, and various attempts have been made to raise the water content
rate.
Some of the attempts have been commercialized. Specifically, an advanced
product
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which has a water content rate of 80% and oxygen permeability of 40Dk[10 _"cm
z/sec]
(m~ 0 z mmHg)] with a water-soluble monomer such as N-vinyl-2-pyrrolidone
(NVP)
and N,N-dimethylacrylamide (DMA) has been developed. However, the soft contact
lens having the high water content rate easily dries and has a weak material
to lower
optical correction performance. A user may feel inconvenient when wearing and
removing the lens. Thus, the contact lens having the high water content rate
is mainly
used as a one day disposable lens and inappropriate for long term use (Refojo.
et al.,
Cont. & Intracular Lens Med. J., 1:36(1975)).
[6] Methacrylic high molecule which includes siloxane or fluorine and is used
to
manufacture RGP (rigid gas permeable) contact lens provides good wearing
feeling
and high oxygen permeability, and affects less to the cornea and is stable
even though
a hard material is used. Also, methacrylic high molecule triggers side effects
such as
corneal edema less than conventional polymethylmethacrylate (PMMA) does.
However, siloxane or fluorine high molecule is a representative hydrophobic
high
molecule and is not wet by tears when applying to a contact lens. As RGB
contact lens
is hard and has an inherent shape, it may trigger some side effects or
complications due
to cornea distortion or difficulty in tear circulation. Also, the RGB contact
lens has
weak strength and is difficult to be manufactured, which results in high
expenses and
is easy to be contaminated or damaged when being worn.
[7] To tackle problems of the contact lens that is widely used, a soft contact
lens
(silicone hydrogel soft contact lens) including hydrogel having good oxygen
per-
meability with silicone has been started to be manufactured. Such a contact
lens was
released in the market for the first time in 1998, sharply increasing market
share to ap-
proximately 150 million dollars in 2003 (Optician 2005).
[8] Silicone hydrogel is produced as a copolymer of a hydrophilic monomer such
as
HEMA and a silicone containing monomer. General silicone monomers are very hy-
drophobic and difficult to maintain visibility due to separation of a phase
when
polymerized with a hydrophilic monomer such as HEMA To overcome such problem,
a compatibilizer should be developed and used to improve compatibility between
hy-
drophilic and hydrophobic monomers. PBVC (poly [dimethysiloxy]di[silylbutanol]
bis[vinyl carbamate]), and a silicone macromer are used as a compatibilizer,
which
cost a lot of development expenses, and are difficult to manufacture lenses
since they
have a large molecular amount and high viscosity.
[9] Generally, silicone resin is hydrophobic and limitedly used in hydrogel
type lenses
since it lowers a water content rate. As a surface of the lenses is
hydrophobic, the
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surface should be oxygen plasma treated to be hydrophilic through a post
processing to
thereby prevent a problem in wearing the lenses. There arises a problem that
protein
adheres to the surface of the lenses.
[10] Silicone hydrogel has a low elongation due to a property of the material
and thus has
low shape restoration of a contact lens. With increased hydrophobic property
of the
surface of the lens due to silicone, epithelial tissue of the cornea and the
lenses are
compatible with each other, and the lenses adhere to the cornea.
Disclosure of Invention
Technical Problem
[11] Accordingly, it is an aspect of the present invention to improve oxygen
permeability
of a contact lens by polymeriang a hydrophobic silicone monomer with a
hydrophilic
monomer to make the monomer hydrophilic.
(12] Also, it is another aspect of the present invention to provide a silicone
hydrogel
composition for a soft contact lens which includes water properly by adding N-
vinyl-2-pynolidone (NVP>99%: Aldrich) or N,N-dimethylacrylamide (DMA,
Aldrich), provides good optical transmission without a compatibilizer, and
does not
have a problem to be worn even without an additional surface treatment, and a
soft
contact lens using the same.
Technical Solution
[13] The foregoing and/or other aspects of the present invention can be
achieved by
providing a silicone hydrogel composition for a soft contact lens which
comprises
2-hydroxycthyl mcthacrylatc and silicone N,O-bis(trimcthylsilyl)acrylamide)
monomer represented by a following chemical formula 1.
[14] [Chemical Formula 11
[15] H2C = CH
C -- 0 - Si(CH3)3
11
N
(H3C)3Si Z
[16] According to another aspect of the present invention, a content of
N,O-bis(trimethylsilyl)acrylamide) in the composition is 10 wt% and below.
[17] According to another aspect of the present invention, the composition
comprises
ethylene gl)ool dimethacrylate.
[18] According to another aspect of the present invention, a content of
N,O-bis(trimethylsilyl)acrylamide in the composition is 10 wt% and below, and
a
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content of ethylene glycol dimethacrylate is 05 wt% and below.
[19] According to another aspect of the present invention, the composition
comprises
divinyl benzene.
[20] According to another aspect of the present invention, a content of
N,O-bis(trimethylsilyl)acrylamide in the composition is 10 wt% and below, and
a
content of divinyl benzene is 04 wt% and below.
[21] According to another aspect of the present invention, the composition
comprises one
of N-vinyl-2-pyrrolidone and N,N-dimethylacrylamide.
[22] According to another aspect of the present invention, a content of
N,O-bis(trimethylsilyl)acrylamide) is 5 wt% and below, a content of ethylene
glycol
dimethacrylate is 04 to 07 wt% and below and a content of N-vinyl-2-
pyrrolidone is
45 wt% and below.
[23] According to another aspect of the present invention, the composition
comprises N-
vinyl-2-pyrrolidone.
[24] According to another aspect of the present invention, a content of
N,O-bis(trimethylsilyl)acrylamide is 5 wt% and below, a content of divinyl
benzene is
03 to 05 wt% and below and a content of N-vinyl-2-pyrrolidone is 35 wt% and
below.
[25] According to another aspect of the present invention, the composition
comprises
N,N-dimethylacrylamide.
[26] According to another aspect of the present invention, a content of
N,O-bis(trimethylsilyl)acrylamide is 5 wt% and below, a content of ethylene
glycol
dimethacrylate is 04 wt% and below and a content of N,N-dimethylacrylamide is
40
wt% and below.
[27] According to another aspect of the present invention, the composition
comprises
N,N-dimethylacrylamide.
[28] According to another aspect of the present invention, a content of
N,O-bis(trimethylsilyl)acrylamide is 5 wt% and below, a content of divinyl
benzene is
04 wt% and below and a content of N,N-dimethylacrylamide is 30 wt% and below.
[29] The foregoing and/or other aspects of the present invention can be
achieved by
providing a soft contact lens which is manufactured by the composition.
Advantageous Effects
[30] As described above, silicone hydrogel composition for a soft contact lens
and a soft
contact lens using the same according to the present invention provides a
contact lens
which is directly attached to the eye to correct myopia, hypermetropia and
astigmatism
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and adjust eyesight. The silicone hydrogel soft contact lens according to the
present
invention has hydrophilic property and high water content of 40 to 70%, high
oxygen
permeability of 50 to 100DK, good elongation of 200 to 400% and good optical
transmission, secures healthy eyes, minimizes a sense of a foreign matter, a
sense of
dryness and pressure of the cornea to make a user feel comfortable. Also, the
contact
lens reduces rates of corneal edema or other illnesses.
[31] Further, the silicone hydrogel soft contact lens according to the present
invention
provides advantages of both oxygen permeable hard lens (RGP lens) having good
oxygen permeability and a soft contact lens providing good wearing feeling to
be
wearable for consecutive two weeks to one month and tackle the problem of an
existing lens being attached and detached every day.
[321 Additional aspects and advantages of the general inventive concept will
be set forth
in part in the description which follows and, in part, will be obvious from
the de-
scription, or may be learned by practice of the general inventive concept.
Best Mode for Carrying Out the Invention
[331 The present invention relates to a copolymer which is made by mixing
2-hydroxyethyl methacrylate (BISOMER HEMA ULTRA made by Cognis), a hy-
drophilic monomer as a main material, N,O-bis(trimethylsilyl)acrylamide (self
synthesis) as a silicone monomer to improve oxygen permeability, N-
vinyl-2-pyrrolidone (NVP>99%, made by Aldrich) or N,N-dimethylacrylamide (DMA
made by Aldrich) water soluble monomer to raise hydrophilic property and
ethylene
glycol dimethacrylate (EGDMA>98%, made by Aldrich) or divinyl benzene (DVB>
80%, made by Aldrich) as a cross-linking agent in small amounts and then by a
thermal polymerization of 2,5-dimethyl-2,5-di(2-ethylhexanoyl peroxy)hexane)
as a
radical initiator. A copolymer is a long molecular structure in which small
units called
monomers are repeatedly linked to each other and includes a chemical linkage
(three-dimensional structure) of those monomers.
[34] The contact lens was not particularly surface treated as it had a water
content rate of
40 to 70% and was very hydrophilic. Here, a compatibilizer was not used. The
contact
lens is not weak and thus wearable for two weeks even though it has a high
water
content rate.
[35] Oxygen permeability was high, 50- 100Dk ([10"(crn/sec)(m$ OZ mmHg)], and
had no
side effects, provided comfortable feeling and caused no problem for long term
wear
according to many clinical tests.
[361 The weak property of silicone hydrogel contact lens was improved and the
result is
* Trade-mark
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as follows.
[371 Elongation was 200 to 400%, young modulus was 50 to 65 g/nni, tensile
strength was
80 to 110 g/mnf and toughness was 120 to 145 glmul, which are very good for a
contact
lens.
Mode for the Invention
[38]
[391 ExemglaLy embodiment 1
[40] Polymerization of N,O-bis(trimethylsilyl(xrylamide) and 2-hydroxyethyl
methacrylate
[41] The amount of N,O-bis(trimethylsilyl)acrylamide is increased from lOg to
90g by
adding I Og each, and the amount of 2-hydroxyethyl methacrylate is decreased
from
90g to l Og by redoing l Og each to make a mixture. An initiator, 2,5-dimethyl
2,5-di(2-ethylhexanoylperoxy)hexane of 01g to Ig is dissolved to polymerize
the
mixture at 110 C for 30 minutes.
[42] As a result, it was polymerized when the initiator of 02g (02 wt%) and
above was
used, regardless of the amount, but the initiator was not involved in
transparency
(compatibility). The mixture was cured by N,O-bis(trimethylsilyl)arylamide of
lOg
(10 wt%) and above, but had lower compatibility and became opaque milk color.
The
more N,O-bis(trimethylsilyl)xrylamide is used, the lower curability becomes.
Thus,
the polymer became soft.
[431 Preferably, an initiator of 02g (02 wt%) is used for polymerization. As
N,O-bis(trimethylsilyl)xrylamide has high degree of crosslink, the mixture is
aired
without a cross-linking agent. Compatibility (transparency) was good with
2-hydroxyethyl methacrylate and N,O-bis(trimethylsilyl)acrylamide monomer of
lOg
(10 wt%).
[44] Exemolay embodiment 2
[45] Polymerization of N,O-bis(trimethylsilyl)acrylamide and N-vinyl-2-
pyrrolidone
[46] The amount of N,O-bis(trimethylsilyl)acrylamide is increased from lOg to
90g by
adding IOg each, and the amount of N-vinyl-2-pyrrolidone is decreased from 90g
to
l Og by reducing lOg each to make a mixture. An initiator, 2,5-dimethyl
2,5-di(2-ethylhexanoylperoxy)hexane, of 01g to ig is dissolved to polymerize
the
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mixture at 110 C for 30 minutes.
[47] As a result, the mixture was not cured regardless of the amount of the
initiator. The
more N,O-bis(trimethylsilyl)acrylamide was used, the lower curability became.
Thus,
the mixture is not cured even when polymerized, and is sticky like an
adhesive.
[48] In the present polymerization, even though N,O-
bis(trimethylsilyl)acrylamide and a
water soluble monomer, N-vinyl-2-pyrrolidone, are polymerized, the polymer was
not
cured. Thus, the mixture was not applicable for a lens and requires a cross-
linking
agent to be cured.
[49] Exemplary embodiment 3
[50] Polymerization of N,O-bis(trimethylsilyl)acrylamide, 2-hydroxyethyl
methacrylate
and ethylene glycol dimethacrylate
[51] The amount of N,O-bis(trimethylsilyl)acrylamide is increased from lOg to
90g by
adding 5g each, and the amount of 2-hydroxyethyl methacrylate is decreased
from 90g
to lOg by redtring 5g each to make a mixture added with a cross-linking agent,
ethylene glycol dimethacrylate, of Olg to 1g. An initiator, 2,5-dimethyl
2,5-di(2-ethylhexanoylperoxy)hexane of 02g is dissolved to polymerize the
mixture at
110 C for 30 minutes.
[52] As a result, with increase in ethylene glycol dimethacrylate,
transparency
(compatibility) and curability improved but elongation became weaker. A
polymer was
obtained to be applicable to a lens by using ethylene glycol dimethacrylate of
05g (05
wt% and below). The polymer was cured by using N,O-
bis(trimethylsilyl)acrylamide
of 20 wt% and below and became transparent, but water absorption was not good
after
hydration for N,O-bis(trimethylsilyl)acrylamide of 10 wt% to 20 wt% and below.
The
polymer was transparently cured for 20 wt% and above, but became opaque and
easily
broken after hydration.
[53] In the present polymerization, use of the cross-linking agent, ethylene
glycol
dimethacrylate, improved degree of cross link and transparency (compatibility)
and
raised curability of the polymer and strength. It can be known that ethylene
glycol
dimethacrylate of 05 wt% is suitable for a lens.
[54] If N,O-bis(trimethylsilyl)acrylamide of 10 wt% and below, 2-hydroxyethyl
methacrylate of 90 wt% and above and a cross-linking agent, ethylene glycol
dimethacrylate, of 05 wt% and below are polymerized, compatibility improved
and
the polymer was transparently cured and had good hydration, which is
applicable for a
flexible lens to some extent.
[55] Exemplary embodiment 4
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[56] Polymerization of N,O-bis(trimethylsilyl)acrylamide, 2-hydroxyethyl
methacrylate
and divinyl benzene
[57] The amount of N,O-bis(trimethylsilyl)acrylamide is increased from lOg to
90g by
adding 5g each, and the amount of 2-hydroxyethyl methacrylate is decreased
from 90g
to 5g by reducing 5g each to make a mixture added with a cross-linking agent,
divinyl
benzene, of Dig to 1g. An initiator, 2,5-dimethyl
2,5-di(2-ethylhexanoylperoxy)hexane of 02g is dissolved to polymerize the
mixture at
110 C for 30 minutes.
[58] As a result, with increase in divinyl benzene, transparency
(compatibility) and
curability improved but elongation became weaker. A polymer was obtained to be
applicable to a lens by using divinyl benzene of 04g (04 wt%) and below. The
polymer was cured by using N,O-bis(trimethylsilyl)acrylamide of 20 wt% and
below
and became transparent, but water absorption was not good after hydration for
10 wt%
to 20 wt% and below. The hydration of the polymer was good for 10 wt% and
below.
For 20 wt% and above, the polymer was cured transparently, but became opaque
and
easily broken after hydration.
[59] In the present polymerization, use of the cross-linking agent, divinyl
benzene,
improved degree of cross link and transparency (compatibility) and raised
curability of
the polymer and strength. It can be known that divinyl benzene of 04 wt% and
below
is suitable for a lens.
[do] If N, O-bis (trimethylsilyl) acrylamide of 10 wt% and below, 2-
hydroxyethyl
methacrylate of 90 wt% and above and a cross-linking agent, divinyl benzene,
of 04
wt% and below are polymerized, compatibility improves and thus a polymer which
is
elongated and has good transparency and water absorption can be made.
[61] Compared to the exemplary embodiment 3, use of divinyl benzene is better
for com-
patibility (transparency) than ethylene glycol dimethacrylate.
[62] Exemplary embodiment 5
[63] Polymerization of N,O-bis(trimethylsilyl)acrylamide, 2-hydroxyethyl
methacrylate,
N-vinyl-2-pyrrolidone and ethylene glycol dimethacrylate
[64] The polymerization is performed by adjusting a water content rate of the
polymer
according to the exemplary embodiment 3 to improve hydrophilic property and by
adding a water soluble monomer, N-vinyl-2-pyrrolidone, to check polymerization
between the materials.
[65] The amount of N,O-bis(trimethylsilyl)acrylamide is increased from 5 wt%
to 50 wt%
by adding 5 wt% each, the amount of 2-hydroxyethyl methacrylate is decreased
from
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90 wt% by reducing 5 wt% each, and N-vinyl-2-pyrrolidone is increased from 5
wt%
by adding 5 wt% each to make a mixture added with a cross-linking agent,
ethylene
glycol dimethacrylate, of 01 wt% to 1 wt%. An initiator, 2,5-dimethyl
2,5-di(2-ethylhexanoylperoxy)hexane of 02 wt% is dissolved to polymerize the
mixture at 110 C for 30 minutes.
[66] As a result, with the cross-linking agent, ethylene glycol
dimethacrylate, of 1 wt%,
the polymer was cured by using N,O-bis(trimethylsilyl)acrylamide of 5 wt% to
10
wt%, 2-hydroxyethyl methacrylate of 50 wt% and below and N-vinyl-2-pyrrolidone
of
40 wt% and above are polymerized to be cured transparently. However, the
polymer
was easily broken, and lost elongation and was easily torn after hydration.
With the
cross-linking agent of 04 wt% to 09 wt%, the polymer was cured by using
N,O-bis(trimethylsilyl)acrylamide of 5 wt% and below, 2-hydroxyethyl
methacrylate
of 5 wt% to 90 wt% and below and N-vinyl-2-pyrrolidone of 5 wt% to 40 wt% and
below are polymerized to be cured transparently. Particularly, the polymer
using the
cross-linking agent of 04 wt% to 07 wt% had good water absorption and
elongation
after hydration.
[67] If the amount of N-vinyl-2-pyrrolidone increases, a water content rate
rises and com-
patibility between materials improves to thereby raise transparency.
Compatibility was
good with N-vinyl-2-pyrrolidone of 45 wt% and below, and a transparent polymer
was
obtained. Here, the water content rate was 38% to 55%. With N-vinyl-2-
pyrrolidone of
45 wt% and above, a polymer having high water content rate of 55% and above
was
obtained.
[68] In the present polymerization, use of N,O-bis(trimethylsilyl)acrylamide
of 5 wt% and
below results in a polymer having good transparency, elongation and water
absorption
to be suitable for a lens.
[69] Use of the cross-linking agent, ethylene glycol dimethacrylate, raised a
degree of
cross link, improved transparency (compatibility) and curability of the
polymer to
make it strong. Elongation of the lens was lowered after hydration. Use of
ethylene
glycol dimethacrylate of 04 wt% to 07 wt% is appropriate for a lens.
[70] Increased use of N-vinyl-2-pyrrolidone improves compatibility between
materials
and transparency, but increases a water content rate and lowers elongation and
tensile
strength of the polymer. If N-vinyl-2-pyrrolidone of 45 wt% and below is used,
a
polymer having a water content rate of 38 wt% to 55 wt% is created to
appropriate for
a lens since it has good elongation and wettability.
[71] Exemplary embodiment 6
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[72] Polymerization of N,O-bis(trimethylsilyl)acrylamide, 2-hydroxyethyl
methacrylate,
N-vinyl-2-pyrrolidone and divinyl benzene
[73] The polymerization is performed by adjusting a water content rate of the
polymer
awording to the exemplary embodiment 4 to improve hydrophilic property and by
adding a water soluble monomer, N-vinyl-2-pyrrolidone, to check polymerization
between the materials and by using divinyl benzene to be compared with
ethylene
glycol dimethacrylate as the cross-linking agent woording to the exemplary
embodiment 5.
[74] The amount of N,O-bis(trimethylsilyl)acrylamide is increased from 5 wt%
to 50 wt%
by adding 5 wt% each, the amount of 2-hydroxyethyl methacrylate is decreased
from
90 wt% by reducing 5 wt% each, and N-vinyl-2-pyrrolidone is increased from 5
wt%
by adding 5 wt% each to make a mixture added with a cross-linking agent,
divinyl
benzene, of 01 wt% to 1 wt%. An initiator, 2,5-dimethyl
2,5-di(2-ethylhexanoylperoxy)hexane of 02 wt% is dissolved to polymerize the
mixture at 110 C for 30 minutes.
[75] As a result, with the cross-linking agent, divinyl benzene, of 1 wt%,
N,O-bis(trimethylsilyl)acrylamide of 5 wt% to 10 wt%, 2-hydroxyethyl
methacrylate
of 50 wt% to 90 wt% and below and N-vinyl-2-pyrrolidone of 10 wt% and above
are
polymerized to be cured transparently. However, the polymer was easily broken,
and
lost elongation and was easily torn after hydration. With the cross-linking
agent of 04
wt% to 09 wt%, N,O-bis(trimethylsilyl)acrylamide of 5 wt% and below,
2-hydroxyethyl methacrylate of 5 wt% to 90 wt% and below and N-
vinyl-2-pyrrolidone of 5 wt% to 40 wt% and below are polymerized to be cured
transparently. Particularly, the polymer using the cross-linking agent of 04
wt% to 07
wt% had good water absorption and elongation after hydration.
[76] Increased use of N-vinyl-2-pyrrolidone improves compatibility between
materials
and transparency. If N-vinyl-2-pyrrolidone of 35 wt% and below is used,
compatibility
was good and a transparent polymer was obtained. Here, a water content rate
was 38%
to 55%. If N-vinyl-2-pyrrolidone of 35 wt% and above is used, a polymer having
high
water content rate of 55% and above was obtained.
[77] In the present polymerization, use of N,O-bis(trimethylsilyl)acrylamide
of 5% and
below results in a polymer having good transparency, elongation and water
absorption
to be suitable for a lens.
[78] Use of the cross-linking agent, divinyl benzene, further improves
transparency
(compatibility) with higher degree of cross link than ethylene glycol
dimethacrylate
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according to the exemplary embodiment 5 and raises curability of the polymer
to make
it strong. Elongation of the lens was lowered after hydration. The size of the
polymer
was smaller than that using ethylene glycol dimethacrylate. Use of divinyl
benzene of
03 wt% to 05 wt% improves transparency and elongation of the polymer which is
ap-
propriate for a lens.
[79] Increased use of N-vinyl-2-pyrrolidone improves compatibility between
materials
and transparency, but lowers elongation and tensile strength of the polymer
due to
increase in a water content rate. If N-vinyl-2-pyrrolidone of 35 wt% and below
is used,
a polymer has a water content rate of 38% to 55%, and provides good
transparency and
elongation to be appropriate for a lens.
[80] Exemplary embodiment 7
[81] Polymerization of N,O-bis(trimethylsilyl)acrylamide, 2-hydroxyethyl
methacrylate,
N,N-dimethylacrylamide and ethylene glycol dimethacrylate
[82] The polymerization is performed by adjusting a water content rate of the
polymer
according to the exemplary embodiment 3 to improve hydrophilic property and by
adding another water soluble monomer, N,N-dimethylacrylamide to check poly-
merization between the materials.
[83] N,O-bis(trimethylsilyl)acrylamide of 5wt% and below axording to the
result from
the exemplary embodiment 5 is used, the amount of 2-hydroxyethyl methacrylate
is
decreased from 90 wt% by reducing 5 wt% each, and the amount of
N,N-dimethylacrylamide is increased from 5 wt% by adding 5 wt% each to make a
mixture added with a cross-linking agent, ethylene glycol dimethacrylate, of
04 wt%.
An initiator, 2,5-dimethyl 2,5-di(2-ethylhexanoylperoxy)hexane of 02 wt% is
dissolved to polymerize the mixture at 110 C for 30 minutes.
[84] As a result, N,N-dimethylacrylamide of 40 wt% and above was compatible
with
N,O-bis(trimethylsilyl)acrylamide of 5 wt% and became cured to generate a
transparent polymer. A water content rate was 55% and above with a very high
expansion rate. Increased use of N,N-dimethylacrylamide raised the water
content rate
and expansion rate, and improved compatibility between the materials and
transparency.
[85] In the present polymerization, use of N,O-bis(trimethylsilyl)acrylamide
of 5% and
below results in a polymer having good transparency, elongation and water
absorption
to be suitable for a lens.
[86] Increased use of N,N-dimethylacrylamide improved compatibility between
the
materials and transparency, but triggered a very high expansion rate due to
increase in
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the water content rate and lowered elongation and tensile strength of the
polymer. If
N,N-dimethylacrylamide of 40 wt% and above and 70 wt% and below is used, a
polymer provides good transparency, water content rate and elongation to be ap-
propriate for a lens.
[87] Exemplary embodiment 8
[88] Polymerization of N,O-bis(trimethylsilyl)acrylamide, 2-hydroxyethyl
methacrylate,
N,N-dimethylacrylamide and divinyl benzene
[89] The polymerization is performed by adjusting a water content rate of the
polymer
according to the exemplary embodiment 4 to improve hydrophilic property, to
check
polymerization suitability between materials and to compare with the cross-
linking
agent, ethylene glycol dimethacrylate, according to the exemplary embodiment
7.
[90] N,O-bis(trimethylsilyl)acrylamide of 5wt% and below according to the
result from
the exemplary embodiment 5 is used, the amount of 2-hydroxyethyl methacrylate
is
decreased from 90 wt% by reducing 5 wt% each, and the amount of
N,N-dimethylacrylamide is increased from 5 wt% by adding 5 wt% each to make a
mixture added with a cross-linking agent, divinyl benzene, of 04 wt%. An
initiator,
2,5-dimethyl 2,5-di(2-ethylhexanoylperoxy)hexane of 02 wt% is dissolved to
polymerize the mixture at 110 C for 30 minutes.
[91] As a result, N,N-dimethylacrylamide of 30 wt% and above was compatible
with
N,O-bis(trimethylsilyl)acrylamide of 5 wt% and became cured to generate a
transparent polymer. A water content rate was 55% and above with a very high
expansion rate. Increased use of N,N-dimethylacrylamide raised the water
content rate
and expansion rate, and improved compatibility between the materials and
transparency.
[92] In the present polymerization, use of N,O-bis(trimethylsilyl)acrylamide
of 5% and
below results in a polymer having good transparency, elongation and water
absorption
to be suitable for a lens.
[93] Increased use of N,N-dimethylacrylamide improved compatibility between
the
materials and transparency, but triggered a very high expansion rate due to
increase in
the water content rate and lowered elongation and tensile strength of the
polymer. If
N,N-dimethylacrylamide of 30 wt% and above and 70 wt% and below is used, a
polymer provides good transparency, water content rate and elongation to be ap-
propriate for a lens.
[94] Compared to the exemplary embodiment 7, use of the cross-linking agent,
divinyl
benzene, improved compatibility (transparency) of the polymer more than
ethylene
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13
glycol dimethacrylate does, but decreased elongation and had a smaller
diameter.
[95] Exemplary embodiment 9
[96] Polymerization of N,O-bis(trimethylsilyl)acrylamide, 2-hydroxyethyl
methacrylate,
N,N-dimethylacrylamide, N-vinyl-2-pyrrolidone and ethylene glycol
dimethacrylate
[97] The polymerization is performed by adjusting a water content rate of the
polymer
according to the exemplary embodiment 4 to improve hydrophilic property and to
check polymerization suitability between two materials of N,N-
dimethylacrylamide
and N-vinyl-2-pyrrolidone as water soluble monomers.
[98] N,O-bis(trimethylsilyl)acrylamide of 5 wt% and below according to the
result from
the exemplary embodiment 7 is used, 2-hydroxyethyl methacrylate of 60wt% is
used
and N,N-dimethylacrylamide and N-vinyl-2-pyrrolidone are changed properly
within
40 wt% to make a mixture added with a cross-linking agent, ethylene glycol
dimethacrylate, of 04 wt%. An initiator, 2,5-dimethyl
2,5-di(2-ethylhexanoylperoxy)hexane of 02 wt% is dissolved to polymerize the
mixture at 110 C for 30 minutes.
[99] As a result, regardless of changes in N,N-dimethylacrylamide and N-
vinyl-2-pyrrolidone, the mixture had good compatibility and generated a
transparent
polymer when cured, but it changed into a milk color by absorbing water.
[100] In the present polymerization, the mixture had good compatibility and
generated a
transparent polymer when cured, but it changed into a milk color by hydration,
regardless of changes in N,N-dimethylacrylamide and N-vinyl-2-pyrrolidone.
Thus,
the polymer may not be used for a lens, and one of N,N-dimethylacrylamide and
N-
vinyl-2-pyrrolidone should be selected to use the polymer for a lens.
[101] Exemplary embodiment 10
[102] Polymerization of N,O-bis(trimethylsilyl)acrylamide, 2-hydroxyethyl
methacrylate,
N-vinyl-2-pyrrolidone, N,N-dimethylacrylamide and divinyl benzene
[103] The polymerization is performed by adjusting a water content rate of the
polymer
according to the exemplary embodiment 5 to check polymerization suitability
between
two materials of N,N-dimethylacrylamide and N-vinyl-2-pyrrolidone.
[104] With the result from the exemplary embodiment 8,
N,O-bis(trimethylsilyl)acrylamide of 5 wt% and 2-hydroxyethyl methacrylate of
60
wt% are used and N,N-diemthylacrylamide and N-vinyl-2-pyrrolidone are changed
properly within 40 wt% to make a mixture added with a cross-linking agent,
divinyl
benzene, of 04 wt%. An initiator, 2,5-dimethyl 2,5-di(2-
ethylhexanoylperoxy)hexane
of 02 wt% is dissolved to polymerize the mixture at 110 C for 30 minutes.
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[105] As a result, regardless of changes in N,N-dimethylacrylamide and N-
vinyl-2-pyrrolidone, the mixture had good compatibility and generated a
transparent
polymer when cured, but it changed into a milk color by absorbing water.
[106] The polymerization according to the present embodiment has the same
result as that
according to the exemplary embodiment 9. The mixture had good Compatibility
and
generated a transparent polymer when cured, but it changed into a milk color
by
hydration, regardless of changes in N,N-dimethylacrylamide and N-
vinyl-2-pyrrolidone. Thus, the polymer may not be used for a lens, and one of
N,N-dimethylacrylamide and N-vinyl-2-pyrrolidone should be selected to use the
polymer for a lens.
[107] That is, the polymerization according to the present embodiment has the
same result
as that according to the exemplary embodiment 9.
[108] Exemplary embodiments 11 to 16 and Comparative embodiment 1
[109] Based on the results from the exemplary embodiments, a wording to
exemplary em-
bodiments 11 to 16, a soft contact lens was made by mixing 2-hydroxyethyl
methacrylate, N,O-bis(trimethylsilyl)acrylamide and divinyl benzene (or
ethylene
glycol dimethaerylate), and N-vinyl-2-pyrrolidone or N,N-dimethylacrylamide.
According to a comparative embodiment 1, a contact lens was made by mixing
2-hydroxyethyl methacrylate, divinyl benzene as a cross-linking agent and
2,5-dimethyl-2,5-di(2-ethylhexanoyl peroxy)hexane) as an initiator to thereby
compare
properties such as a water content rate, elongation rate, tensile strength and
oxygen
permeability.
[110] The oxygen permeability is a flow rate of oxygen transmitting a unit
area of a Contact
lens material in a unit thickness, awording to a unit pressure change. The
method of
measuring the oxygen permeability is as follows.
[111] A Dry a sample to be measured and a tool at the maximum.
[112] B. Mount a lens on a lower tool, and fix the lower tool by O-rings and
then cover it
with an upper tool by four screws not to leak gas.
[113] C. Make bubbles by soapy water of approximately 10% in an indicator.
[114] D. Connect a gas container with each line and operate a gas pressure
sensor.
[115] E Purge each part with gas to be measured, for about two hours.
[116] F. Record time when the bubbles from the indicator started moving and
the envi-
ronmental factors at that time, and check and record the status at
predetermined time
intervals.
[117] G. Calculate by using a formula.
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[118] The formula is as follows.
[119] V" cm 3 (S'P )
area of sample x time taken for reference scale to rise cm2-see - 1
Pv P"v"
T T,
[120] Here, P, V and T refer to the status of the environment where the
experiment is
carried out. P' and T' refer to STP status and V is a value calculated
according to the
STP status.
[121] cin3 (STP)' CIn
Permeability (DID) 2 -
APressure cm,sec=CmHa
[122] Here, f is an average thickness of the sample, Pressure has a value
indicated by the
pressure sensor. The value of the formula 1P is substituted for the formula 20
to
calculate permeability (DK).
[123] The water content rate is calculated commonly by dry-weight-basis
representing
moisture weight ratio to a dry weight of the sample as percent, but also by
wet-
weight-basis representing containing moisture ratio to a total weight
including
moisture as percent. However, there are made many definitions related to the
water
content rate such as "relative water content rate in saturated water content
rate" or
"equilibrium water content rate by relative humidity of surrounding air".
Recently,
volume water content rate representing containing moisture volume ratio to a
total
volume of the sample is also used in some cases.
[124] The moisture content of the contact lens is measured by using wet-weight-
basis.
[125] The measuring method is as follows.
[126] A Hydrate the lens sufficiently (for about 24 hours and more).
[127] B. Remove water from the lens with a deer skin and measure a weight (M
).
[128] C. Dry the lens from an oven for at least 20 minutes and above (the
point of time
where the weight is not changed any more).
[129] D. Measure the weight of the dried lens (M ).
z
[130] E Measure the weight of at least ten sample lenses according to the
processes of A to
D and determine an average value as a water content rate.
[131] The formula is as follows.
[132] -1I, ~1 1
W Cfter con tear ate = ' h 10Q
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[133] Exemplary embodiment 11: Manufacturing of contact lens 1:
[134] 2-hydroxyethyl methacrylate, N,O-bis(trimethylsilyl)acrylamide, N-
vinyl-2-pyrrolidone and divinyl benzene (or ethylene glycol dimethacrylate)
[135] A mixture of 2-hydroxyethyl methacrylate of 643 wt% and above, N-
vinyl-2-pyrrolidone of 30 wt% and below, N,O-bis(trimethylsilyl)acrylamide of
5 wt%
and below, and divinyl benzene of 05 wt% and above (or ethylene glycol
dimethacrylate of 06 wt% and above) as a cross-linking agent is added with
dissolved
2,5-dimethyl-2,5-di(2-ethylhexanoyl peroxy)hexane) of 02 wt% and above as an
initiator. The mixture was then injected to a mold manufactured with
polypropylene
(Casting Mold) and polymerized at 110 C for 30 minutes to be cured. Then, the
lens
was separated from the mold to check compatibility (transparency). The lens
was
transparent, and the water content rate and the status were measured after
hydration.
[136] Exemplary embodiment 12: Manufacturing of contact lens 2:
[137] 2-hydroxyethyl methacrylate, N,O-bis(trimethylsilyl)acrylamide, N-
vinyl-2-pyrrolidone and divinyl benzene (or ethylene glycol dimethacrylate)
[138] A mixture of 2-hydroxyethyl methacrylate of 835 wt% and above, N-
vinyl-2-pyrrolidone of 15 wt% and below, N,O-bis(trimethylsilyl)acrylamide of
1 wt%
and below, and divinyl benzene of 03 wt% and above (or ethylene glycol
dimethacrylate of 04 wt% and above) as a cross-linking agent is added with
dissolved
2,5-dimethyl-2,5-di(2-ethylhexanoyl peroxy)hexane) of 02 wt% and above as an
initiator. A lens was manufactured the same as that w rding to the exemplary
embodiment 11 to evaluate properties.
[139] Exemplary embodiment 13: Manufacturing of contact lens 3:
[140] 2-hydroxyethyl methacrylate, N,O-bis(trimethylsilyl)acrylamide, N-
vinyl-2-pyrrolidone and divinyl benzene (or ethylene glycol dimethacrylate)
[141] A mixture of 2-hydroxyethyl methacrylate of 71.4 wt% and above, N-
vinyl-2-pyrrolidone of 25 wt% and below, N,O-bis(trimethylsilyl)acrylamide of
3 wt%
and below, and divinyl benzene of 04 wt% and above (or ethylene glycol
dimethacrylate of 05 wt% and above) as a cross-linking agent is added with
dissolved
2,5-dimethyl-2,5-di(2-ethylhexanoyl peroxy)hexane) of 02 wt% and above as an
initiator. A lens was manufactured the same as that w rding to the exemplary
embodiment 11 to evaluate properties.
[142] Exemplary embodiment 14: Manufacturing of contact lens 4:
[143] 2-hydroxyethyl methacrylate, N,O-bis(trimethylsilyl)acrylamide, N-
vinyl-2-pyrrolidone and divinyl benzene (or ethylene glycol dimethacrylate)
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17
[144] A mixture of 2-hydroxyethyl methacrylate of 643 wt% and below, N-
vinyl-2-pyrrolidone of 30 wt% and above, N,O-bis(trimethylsilyl)acrylamide of
5 wt%
and below, and divinyl benzene of 05 wt% and above (or ethylene glycol
dimethacrylate of 06 wt% and above) as a cross-linking agent is added with
dissolved
2,5-dimethyl-2,5-di(2-ethylhexanoyl peroxy)hexane) of 02 wt% and above as an
initiator. A lens was manufactured the same as that according to the exemplary
embodiment 11 to evaluate properties.
[145] Exemplary embodiment 15: Manufacturing of contact lens 5:
[146] 2-hydroxyethyl methacrylate, N,O-bis(trimethylsilyl)acrylamide, N-
vinyl-2-pyrrolidone and divinyl benzene (or ethylene glycol dimethacrylate)
[147] A mixture of 2-hydroxyethyl methacrylate of 65.4 wt% and below, N-
vinyl-2-pyrrolidone of 30 wt% and above, N,O-bis(trimethylsilyl)acrylamide of
4 wt%
and below, and divinyl benzene of 04 wt% and above (or ethylene glycol
dimethacrylate of 05 wt% and above) as a cross-linking agent is added with
dissolved
2,5-dimethyl-2,5-di(2-ethylhexanoyl peroxy)hexane) of 02 wt% and above as an
initiator. A lens was manufactured the same as that according to the exemplary
embodiment 11 to evaluate properties.
[148] Exemplary embodiment 16: Manufacturing of contact lens 5:
[149] 2-hydroxyethyl methacrylate, N,O-bis(trimethylsilyl)acrylamide,
N,N-dimethylacrylamide and divinyl benzene (or ethylene glycol dimethacrylate)
[150] A mixture of 2-hydroxyethyl methacrylate of 66.4 wt% and below,
N,N-dimethylacrylamide of 30 wt% and above, N,O-bis(trimethylsilyl)acrylamide
of
03g, and divinyl benzene of 04 wt% and above (or ethylene glycol
dimethacrylate of
05 wt% and above) as a cross-linking agent is added with dissolved
2,5-dimethyl-2,5-di(2-ethylhexanoyl peroxy)hexane) of 02 wt% and above as an
initiator. A lens was manufactured the same as that according to the exemplary
embodiment 11 to evaluate properties.
[151] Comparative embodiment 1: Manufacturing of contact lens
[152] A mixture of 2-hydroxyethyl methacrylate of 9g and divinyl benzene of lg
as a
cross-linking agent which are commonly used is added with dissolved
2,5-dimethyl-2,5-di(2-ethylhexanoyl peroxy)hexane) of (fig as an initiator.
The
mixture was then injected to a mold manufactured with polypropylene (Casting
Mold)
and polymerized at 110 C for 30 minutes to be cured. Then, the lens was
separated
from the mold to check a water content rate. According to the checking result,
the lens
had low water content rate of 38% and oxygen permeability of 10 to 20Dk[10 -
"(cm' /
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18
sec)(m~ 0 mmHg)].
2
[153] Table 1
[Table 1]
[Table ]
Exemp.e Exemp.e Exemp.e Exemp.e Exemp.e Exemp.e Comp.e
mbodi.1 mbodi.1 mbodi.1 mbodi. 1 mbodi. 1 mbodi. 1 mbodi.
1 2 3 4 5 6
2-hydroxyethyl 642% 83.4% 71.3% 642% 65.3% 69% and 99.4%
methacrylate and and and and and above
above above above above above
N,O-bis(trimet 5% and 1% and 3% and 5% and 4% and 03% -
hylsilyl)acryla below below below below below and
mide below
N-vinyl-2-pyrr 30% and 15% and 25% and 30% and 30% and - -
olidone below below below below below
N,N-dimethyla - - - - - 30% and -
crylamide below
Divinyl 05% 03% 04% 05% 04% 04% 10%
benzene(or and and and and and and
ethyleneglycol above above above above above above
dimeth (or 06% (or 04% (or 05% (or 06% (or 05% (or 05%
acrylate) and and and and and and
above) above) above) above) above) above)
2,5-dimethyl-2, 02% 02% 02% 02% 02% 02% 02%
5-di(2-ethyLhe and and and and and and and
xanoylperoxy)h above above above above above above above
exane
[154] The properties of the contact lens which was manufactured with the
foregoing
content according to the exemplary embodiments and comparative embodiment are
as
follows.
[155] Table 2
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[Table 21
[Table I
Exemp.em Exemp.e Exemp.e Exemp.e Exemp.e Exemp.e Comp.e
bodi.ll mbodi.l mbodi.l mbodi.l mbodi.l mbodi.l mbodi.
2 3 4 5 6
Water content 40 to 50 40 to 50 40 to 50 50 to 70 50 to 70 50 to 70 38
rate (%)
Elongation 200 to 250 to 300 to 250 to 300 to 300 to
rate (%) 300 300 350 350 350 400
Tensile 80 to 100 90 to 90 to 80 to 80 to 90 to
strength 110 110 100 100 100
(g/mrn3)
Oxygen per- 70 to 90 50 to 70 a) to 80 80 to 65 to 85 70 to 90 10 to 20
meability 100
(DK)
11561 As shown in Table 2, the exemplary embodiments according to the present
invention
are hydrophilic, and have high water content rate of 40 to 70% and high oxygen
per-
meability of 50 to 90Dk[ 10 "(an 2/sec)(m2 0 z mmHg)[, which are far better
than those
according to the comparative embodiment.
11571 The scope of the claims should not be limited by the preferred
embodiments set
forth in the examples, but should be given the broadest interpretation
consistent
with the description as a whole.
