Polymeric colorant and colored material for ocular lens using the colorant

A polymeric colorant represented by the following formula: EQU A.sub.1 --N.dbd.N--A.sub.2 --O--(CH.sub.2)n--X wherein, A.sub.1 represents an aryl group which may have a substituent group, A.sub.2 represents an arylene group which may have a substituent group, X represents one of an acryloyloxy group, a methacryloyloxy group, a vinylphenyl group, a vinylphenyloxy group, and a vinylphenylalkyloxy group whose alkyl portion has 1-5 carbon atoms, and n is an integer of 1-5, and a colored material for an ocular lens which uses the polymeric colorant is also disclosed.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a polymeric colorant suitably used for
 coloring ocular lenses such as a contact lens, an intraocular lens and an
 artificial cornea, and a colored material for forming the ocular lenses,
 which uses the polymeric colorant.
 2. Discussion of the Related Art
 There have been proposed various polymeric colorants for coloring a
 composition or material which is used for forming a colored product. In
 the field of manufacture of an ocular lens such as a contact lens or an
 intraocular lens, for instance, a lens composition or material
 (lens-forming composition) used for producing the ocular lens is
 copolymerized with a suitable polymeric colorant, to thereby provide a
 colored material from which the intended ocular lens is produced. The
 ocular lens formed of such a colored material is uniformly colored and
 exhibits a high degree of resistance to exposure to light and chemical
 substances without suffering from decoloring or a change in its color,
 which would be caused by separation or elution of the colorant from the
 colored material.
 JP-A-1-280464 discloses, as one example of the polymeric colorant for
 coloring the ocular lens, a polymeric colorant of azo-system or an
 azo-derived polymeric colorant wherein one of acryloyloxy,
 methacryloyloxy, vinyl, and aryl groups is substituted for at least one
 hydrogen atom of a naphthyl group which is bonded to an azo group. This
 polymeric colorant of the azo system is copolymerized with a vinyl
 monomer, to thereby provide a vinyl polymer from which the intended
 colored lens is produced.
 JP-A-1-299560 discloses a colored ocular lens material obtained by
 copolymerizing a suitably selected copolymerizable lens-forming monomer
 component, a polymeric UV absorbent including a suitable polymeric group,
 and a polymeric colorant including a polymeric group which is selected
 from the group consisting of an acryloyl group, a methacryloyl group, a
 vinyl group, an aryl group, and an isopropenyl group. This colored ocular
 lens material does not suffer from elution of the UV absorbent and the
 colorant, and exhibits excellent durability. The colorant used in this
 ocular lens material is a polymeric colorant of azo system, wherein the
 polymeric group suitably selected from among those described above is
 introduced into a phenyl group or a naphthyl group bonded to the azo
 group, via an ester bond or an amide bond.
 JP-A-8-503997 discloses a polymerizable yellow dye of azo system, wherein
 an unsaturated organic group having an ester structure or an amide
 structure is introduced into a phenyl group bonded to the azo group, via
 nitrogen or alkyl. This polymerizable yellow dye is polymerized with a
 lens-forming monomer component such as acrylate monomer or methacrylate
 monomer, to thereby provide a colored ocular lens material.
 In those polymeric colorants described above wherein the polymeric
 unsaturated group is introduced via an oxygen atom into the aromatic ring
 in the phenyl or naphthyl group bonded to the azo group, the unsaturated
 group is bonded or attached to the aromatic ring by the ester bond formed
 therebetween. The polymeric colorant in which the ester bond is directly
 attached to the aromatic ring as described above tends to suffer from easy
 hydrolysis, whereby the colorant is chemically unstable, making its
 handling difficult. Further, the original color tone of the colorant
 undesirably changes due to the introduction of the polymeric group. In
 this case, it is difficult to predict the color tone of the colorant in
 the end product.
 SUMMARY OF THE INVENTION
 It is therefore a first object of the present invention to provide a novel
 polymeric colorant which is less likely to suffer from separation or
 elution, and is chemically stable without suffering from denaturation as
 caused by hydrolysis, while maintaining the original color tone, in spite
 of introduction of a suitably selected polymeric group therein.
 It is a second object of the present invention to provide a colored ocular
 lens material having excellent characteristics, by using such a polymeric
 colorant.
 The above-indicated first object of the invention may be attained according
 to a first aspect of the invention, which provides a polymeric colorant
 represented by the following formula:
EQU A.sub.1 --N.dbd.N--A.sub.2 --O--(CH.sub.2)n--X
 wherein, A.sub.1 represents an aryl group which may have a substituent
 group, A.sub.2 represents an arylene group which may have a substituent
 group, X represents one of an acryloyloxy group, a methacryloyloxy group,
 a vinylphenyl group, a vinylphenyloxy group, and a vinylphenylalkyloxy
 group whose alkyl portion has 1-5 carbon atoms, and n is an integer of
 1-5.
 In the polymeric colorant obtained according to the above first aspect of
 the present invention, the colorant per se includes a suitable polymeric
 group (X). This colorant is chemically bonded to a composition or material
 for an intended product, to thereby provide a suitable colored material
 for forming the intended colored product. The colored material obtained by
 using the present polymeric colorant is free from discoloration which
 would arise from the elution of the colorant, even when the colored
 material is boiled or immersed in water or organic solvents. In the
 present polymeric colorant, the suitable polymeric group (X) is introduced
 into the aromatic ring (A.sub.2) which bonds to the azo group, via the
 "--O--(CH.sub.2).sub.n --" group, unlike the conventional colorants
 wherein the polymeric group is introduced via the ester bond. Accordingly,
 the present polymeric colorant is chemically stable without suffering from
 denaturation as caused by hydrolysis, assuring easy handling thereof. The
 colored material obtained by using the present polymeric colorant is
 capable of maintaining its color with high stability.
 In the present polymeric colorant wherein the suitable polymeric group (X)
 is introduced into the aromatic ring (A.sub.2) via the
 "--O--(CH.sub.2)n--" group, the original color tone which derives from the
 colorant moiety is not changed by the introduced polymeric group.
 Accordingly, the polymeric colorant in the end product can maintain the
 original color with high stability. In addition, the polymeric group which
 is introduced into the aromatic ring (A.sub.2) can be suitably and freely
 selected from among various polymeric groups.
 In a first preferred form of the above first aspect of the present
 invention, the aryl group is one of a phenyl group, a naphthyl group, a
 substituted phenyl group, and a substituted naphthyl group.
 In a second preferred form of the above first aspect of the present
 invention, the arylene group is a phenylene group which has at least one
 substituent group or a naphthylene group which has at least one
 substituent group. preferably, the above-indicated at least one
 substituent group is selected from a group consisting of a hydroxyl group,
 a linear alkyl group having 1-6 carbon atoms, and a branched alkyl group
 having 1-6 carbon atoms.
 The above-indicated second aspect of the present invention may be attained
 according to a second aspect of the present invention, which provides a
 colored material for an ocular lens, which is formed of a polymer obtained
 by copolymerizing at least one polymeric unsaturated monomer for the
 ocular lens and a polymeric colorant which is represented by the following
 formula:
EQU A.sub.1 --N.dbd.N--A.sub.2 --O--(CH.sub.2)n--X
 wherein, A.sub.1 represents an aryl group which may have a substituent
 group, A.sub.2 represents an arylene group which may have a substituent
 group, X represents one of an acryloyloxy group, a methacryloyloxy group,
 a vinylphenyl group, a vinylphenyloxy group, and a vinylphenylalkyloxy
 group whose alkyl portion has 1-5 carbon atoms, and n is an integer of
 1-5.
 In one preferred form of the above second aspect of the present invention,
 the polymeric colorant is used in an amount of 0.001-0.2 part by weight
 per 100 parts by weight of the above-indicated at least one unsaturated
 monomer for the ocular lens for copolymerization therewith.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
 In the present polymeric colorant represented by the above formula, A.sub.1
 is an aryl group which is a residue in the form of a monovalent
 substituent group, wherein one hydrogen atom is removed from the aromatic
 ring of the aromatic compound. In general, a phenyl group, a naphthyl
 group, a substituted phenyl group, or a substituted naphthyl group are
 used as the aryl group. A halogen atom such as chlorine, or a linear or a
 branched alkyl group having 1-6 carbon atoms such as methyl, ethyl or
 isopropyl may be substituted for the phenyl or naphthyl group.
 In the present polymeric colorant represented by the above formula, A.sub.2
 is an arylene group which is a residue in the form of a divalent
 substituent group, wherein two hydrogen atoms are removed from the
 aromatic ring of the aromatic compound. In general, a phenylene or a
 naphthylene group which includes at least one substituent group is used as
 the arylene group. The substituent group introduced into the phenylene or
 naphthylene group may be a hydroxyl group, or a linear or a branched alkyl
 group having 1-6 carbon atoms such as a methyl group or a tert-butyl
 group.
 Examples of the polymeric colorant which is represented by the above
 formula include 2-phenylazo-4-(meth)acryloyloxyethoxy-6-tert-butylphenol,
 2-(4-methyl) phenylazo-4-(meth)acryloyloxyethoxy-6-tert-butylphenol,
 2-(3-methyl)phenylazo-4-(meth)acryloyloxyethoxy-6-tertbutylphenol,
 2-(4-chloro)phenylazo-4-(meth)acryloyloxyethoxy-6-tert-butylphenol,
 2-(2-chloro)phenylazo-4-(meth)acrylayloxyethoxy-6-tertbutylphenol,
 2-phenylazo-4-(meth)acryloyloxypropoxy-6-tert-butylphenol,
 2-(4-methyl)phenylazo-4-(meth)acryloyloxypropoxy-6-tert-butylphenol,
 2-(3-methyl)phenylazo-4-(meth)acryloyloxypropoxy-6-tertbutylphenol,
 2-(4-chloro)phenylazo-4-(meth)acryloyloxypropoxy-6-tert-butylphenol,
 2-(2-chloro)phenylazo-4-(meth)acryloyloxypropoxy-6-tertbutylphenol,
 2-phenylazo-4-(meth)acryloyloxybutoxy-6-tertbutylphenol,
 2-phenylazo-4-(meth)acryloyloxyethoxy-6-methylphenol,
 2-phenylazo-4-(meth)acryloyloxyethoxy-6-(2-methyl) butylphenol,
 2-(1-naphthylazo)-4-(meth)acryloyloxyethoxy-6-tert-butylphenol,
 2-(4-methyl-1-naphthylazo)-4-(meth)acryloyloxyethoxy-6-tert-butylphenol,
 2-(4-chloro-1-naphthylazo)-4-(meth)acryloyloxyethoxy-6-tertbutylphenol,
 2-(1-naphthylazo)-4-(meth)acryloyloxypropoxy-6-tert-butylphenol,
 2-(1-naphthylazo)-4-(meth)acryloyloxyethoxy-6-methylphenol,
 2-phenylazo-4-(4-vinyl) phenoxyethoxy-6-tert-butylphenol,
 1-phenylazo-4-(meth)acryloyloxyethoxy-2-naphthol,
 2-phenylazo-4-(4-vinyl)benzyloxy-6-tert-butylphenol, and
 2-phenylazo-4-(4-vinyl)benzyl-6-tert-butylphenol. In the above compounds,
 ". . . (meth)acryloyloxy . . . " is generic to the following two
 compounds: ". . . acryloyloxy . . . " and ". . . methacryloyloxy . . . ".
 The polymeric colorant described above can be easily produced by utilizing
 known reactions. For instance, the polymeric colorant represented by the
 above formula where X in the formula is one of acryloyloxy,
 methacryloyloxy, vinylphenyloxy, and vinylphenylalkyloxy groups, is
 obtained in the following manner. Initially, a phenol or a naphthol
 derivative (whose typical example is tert-butylhydroquinone) is
 hydroxyalkylated at its end by a hydroxyalkylation agent such as
 ethylenechlorohydrin, in water or a suitable organic solvent, to thereby
 provide a synthetic intermediate product A. In the meantime, an aromatic
 amine whose typical example is aniline is subjected to diazotization by
 using sodium nitrite, to thereby provide a diazonium salt. The obtained
 diazonium salt is coupled to the intermediate product A prepared as
 described above in the presence of alkali, so that a synthetic
 intermediate product B is obtained. This intermediate product B is
 subjected to a condensation reaction with (meth)acrylic chloride, or
 halogenated alkylstyrene (whose typical example is chloromethylstyrene),
 in the presence of metallic magnesium or an organic base such as
 triethylamine or 1,8-diazabicyclo[5,4,0]undecene-7 (DBU), in an organic
 solvent such as dehydrated methylene chloride, which solvent does not
 include a functional group such as a hydroxyl group or an amino group.
 Thus, the intended polymeric colorant is obtained.
 The polymeric colorant which is represented by the above formula where X in
 the formula is a vinylphenyl group or a vinylphenylalkyl residue, is
 obtained in the following manner. Initially, the aromatic amine whose
 typical example is aniline is subjected to the diazotization by using
 sodium nitrite, to thereby provide the diazonium salt. The obtained
 diazonium salt is coupled to the phenol or naphthol derivative (whose
 typical example is tert-butylhydroquinone), in the presence of alkali, so
 that a synthetic intermediate product C is obtained. This intermediate
 product C is subjected to the condensation reaction with the halogenated
 alkylstyrene (whose typical example is chloromethylstyrene), in the
 presence of metallic magnesium or an organic base such as DBU, in an
 organic solvent such as dehydrated methylene chloride, which solvent does
 not include a polyfunctional group such as a hydroxyl or an amino group.
 Thus, the intended polymeric colorant is obtained.
 In producing the intended colored material for the ocular lens by using the
 polymeric colorant prepared as described above, the polymeric colorant is
 added to and mixed with a suitable polymeric lens-forming composition.
 Then, the mixture is copolymerized to provide the colored material for the
 ocular lens. The lens-forming composition to be copolymerized with the
 polymeric colorant is suitably selected from among known monomers having
 at least one polymeric unsaturated bond. Examples of the monomer include:
 (meth)acrylates such as alkyl (meth)acrylate, siloxanyl (meth)acrylate,
 fuluoroaklyl (meth)acrylate, hydroxyalkyl (meth)acrylate, phenoxyalkyl
 (meth)acrylate, phenylalkyl (meth)acrylate, polyethyleneglycol
 (meth)acrylate and polyhydric alcohol (meth)acrylate, derivatives of
 styrene; and N-vinyllactam. As needed, a polyfunctional monomer such as
 ethyleneglycol di(meth)acrylate or diethyleneglycol di(meth)acrylate is
 added as a cross-linking agent. Other examples of the monomer are
 described in detail in laid-open publication JP-A-1-280464 of Japanese
 Patent Application which was filed by the assignee of the present
 invention. In the present invention, the monomers disclosed in the
 publication and other monomers known in the art are suitably used.
 In producing the intended colored ocular lens material by copolymerizing
 the above-indicated lens-forming composition and the polymeric colorant,
 the polymeric colorant is used in an amount of 0.001-0.2 part by weight
 per 100 parts by weight of the lens-forming composition. If the amount of
 the polymeric colorant is smaller than the lower limit of 0.001 part by
 weight, the lens material to be obtained is not sufficiently colored. On
 the other hand, if the amount of the polymeric colorant exceeds the upper
 limit of 0.2 part by weight, the obtained lens material is excessively
 colored (having an excessively high color tone), giving rise to problems
 in practical use. For instance, the excessively colored lens material does
 not permit sufficient transmission of the visible rays therethrough.
 The mixture of the polymeric colorant and the lens-forming composition is
 polymerized according to any known methods. For instance, the mixture to
 which a radical polymerization initiator has been added as needed is
 gradually heated from the room temperature to about 130.degree. C., so
 that the mixture is polymerized to provide the intended colored ocular
 lens material. Alternatively, the mixture is polymerized by exposure to an
 electromagnetic radiation such as microwave, ultraviolet radiation, or
 .gamma. ray. The polymerization of the mixture may be effected according
 to a bulk polymerization method or a solution polymerization method using
 a solvent The mixture may be heat-polymerized with its temperature raised
 in steps. Other known polymerization methods may be suitably employed in
 the present invention.
 As the radical polymerization initiator, azobisisobutyronitrile,
 azobisdimethylvaleronitrile, benzoylperoxide, tert-butylhydroperoxide, and
 cumenehydroperoxide may be used, for instance. At least one suitably
 selected radical polymerization initiator is added to the mixture of the
 polymeric colorant and the lens-forming composition. The radical
 polymerization initiator is included in the mixture generally in an amount
 of 001-1 part by weight per 100 parts by weight of the mixture.
 The ocular lens such as the contact lens or intraocular lens may be
 produced according to any methods known in the art. For instance, the
 mixture of the polymeric colorant and the lens-forming composition is
 polymerized in a suitable mold or container, to thereby provide a
 bar-shaped, block-shaped, or plate-shaped blank (polymer). The obtained
 polymer blank is subjected to machining operations such as cutting and
 grinding, whereby the ocular lens having a desired configuration is
 produced. Alternatively, the mixture is polymerized in a mold whose
 profile follows that of the intended ocular lens. The obtained polymerized
 product is subjected to machining operations, as needed, so as to provide
 the intended ocular lens. In producing the intraocular lens which is to be
 inserted within the eye, a support member(s) of the intraocular lens,
 which holds the lens body in position within the eye, may be prepared
 separately from the lens body to be obtained from the polymerized product,
 and later fixed to the lens body. Alternatively, the support member(s) may
 be formed integrally with the lens body upon polymerization of the mixture
 in a mold cavity.
 To further clarify the concept of the present invention, some examples of
 the invention will be described. It is to be understood that the invention
 is not limited to the details of the illustrated examples, but may be
 embodied with various changes, modifications and improvements, which may
 occur to those skilled in the art without departing from the scope of the
 invention defined in the attached claims.
 EXAMPLES
 Example 1
 &lt;Preparation of 2-phenylazo-4-(2-hydroxy)ethoxy-6-tertbutylphenol&gt;
 Initially, the diazotization of 9.30 g (0.10 mol) of aniline was effected
 in a known manner. Next, into a four-neck flask whose capacity is one
 liter and which is equipped with a stirrer, a dropping funnel, a
 thermometer and a cock, there were introduced 100 ml of ethanol, 21.04 g
 (0.10 mol) of 4-(2'-hydroxy)ethoxy-2-tert-butylphenol, and 100 ml of 10%
 aqueous solution of sodium hydroxide. The diazotized aniline was added
 dropwise for 30 minutes into the reaction solution in the flask prepared
 as described above. After the dropping was completed, the reaction mixture
 was stirred for 30 minutes. Then, the reaction mixture was filtered to
 collect a solid substance. After this solid substance was dissolved in
 methylene chloride, it was washed with water three times. Subsequently,
 the solvent was removed from the substance, to thereby provide a crude
 crystal. Then, the obtained crude crystal was recrystallized with
 methanol, whereby 15.90 g of reddish needle crystal was obtained. This
 needle crystal was subjected to an IR analysis by using "FT/IR-8300"
 available from JAPAN SPECTROSCOPIC Co., LTD., Japan. The IR analysis
 revealed that the crystal was the intended substance, i,e.,
 2-phenylazo-4-(2-hydroxy)ethoxy-6-tert-butylphenol. The infrared radiation
 absorption spectrum of this substance obtained by the IR analysis is shown
 in the graph of FIG. 1.
 Example 2
 &lt;Preparation of 2-phenylazo-4-methacryloyloxyethoxy-6-tert-butylphenol&gt;
 Into a 500 ml-three-neck flask equipped with a stirrer, a dropping funnel
 with a calcium chloride-filled tube, and a thermometer, there were
 introduced 300 ml of methylene chloride, 6.28 g of
 2-phenylazo-4-(2-hydroxy)ethoxy-6-tert-butylphenol prepared in the above
 Example 1, and 2.02 g (0.02 mol) of triethylamine. 2.30 g (0.022 mol) of
 chloride methacrylate which had been diluted with 15 ml of methylene
 chloride was added dropwise for 30 minutes into the reaction solution in
 the flask prepared as described above at a temperature of not higher than
 3.degree. C. After the reaction mixture was stirred overnight, it was
 washed with water three times, and the solvent was removed from the
 reaction mixture at a reduced pressure, whereby a reddish solid substance
 was obtained. 7.37 g of the obtained reddish solid substance was isolated
 by column chromatography. From the second fraction developed by methylene
 chloride, 5.60 g of crude crystal of
 2-phenylazo-4-methacryloyloxyethoxy-6-tert-butylphenol was obtained.
 Subsequently, the thus obtained crude crystal was recrystallized with
 methanol, so that 4.04 g of a reddish needle crystal was obtained. This
 needle crystal was subjected to the IR analysis by using "FT/IR-8300"
 available from JAPAN SPECTROSCOPIC CO., LTD., Japan, and an NMR analysis
 by using "Gemi 2000/400BB" at 400 MHz, available from Varian, U.S.A. The
 analyses revealed that the needle crystal was the intended substance,
 i.e., 2-phenylazo-4-methacryloyloxyethoxy-6-tert-butylphenol. The infrared
 absorption spectrum of the substance obtained by the IR analysis is shown
 in the graph of FIG. 2, while the result of the NMR analysis (.sup.1
 H-nuclear magnetic resonance spectrum) is as follows:
 .sup.1 H-NMR (400 MHz, CDCl.sub.3), .delta.1.45[9H, s, --C(CH.sub.3).sub.3
 ], .delta.1.97(3H, s, --CH.sub.3), .delta.4.28(2H, t, --CH.sub.2 --),
 .delta.4.53(2H, t, --CH.sub.2 --), .delta.5.60(1H, s, =CH),
 .delta.6.17(1H, s, .dbd.CH), .delta.7.00.about.7.90(7H, m, benzene ring)
 Example 3
 &lt;Preparation of the colored ocular lens material specimen No. 1&gt;
 Initially, 0.02 part by weight of
 2-phenylazo-4-methacryloyloxyethoxy-6-tert-butylphenol prepared in the
 above Example 2, 97 parts by weight of methyl methacrylate, 3 parts by
 weight of ethyleneglycol dimethacrylate, 0.18 part by weight of
 2-[2'-hydroxy-5'-(2"-methacryloyloxyethoxy)-3'-tert-butylphenyl]-5-methyl-
 2H-benzotriazole, and 0.05 part by weight of azobisisobutyronitrile were
 mixed and dissolved together. The thus obtained mixture was introduced
 into a silicone-coated test tube made of a glass material. The test tube
 was heated from 35.degree. C. to 130.degree. C., with the opening of the
 test tube being plugged. Thus, the mixture in the test tube was
 polymerized into a polymer by a bulk polymerization method. The thus
 obtained polymer was subjected to a cutting operation and a surface
 grinding operation, to thereby provide three plates with different
 thickness values of 0.2 mm, 0.5 mm, and 1.0 mm, respectively. For each of
 the plates, the spectral transmittance at 360-800 nm was measured by using
 an auto-recording spectrophotometer ("UV-3100" available from SHIMAZU
 SEISAKUSHO, CO., LTD., Japan). The result of the measurement is shown in
 the graph of FIG. 3. The appearance of each of the three plates was
 visually inspected. The visual inspection revealed that all of the three
 plates were reddish yellow.
 Example 4
 &lt;Preparation of the colored ocular lens material specimen No. 2&gt;
 Initially, 0.013 part by weight of
 2-phenylazo-4-methacryloyloxyethoxy-6-tert-butylphenol prepared in the
 above Example 2, and 100 parts by weight of 2-hydroxyethylmethacrylate,
 0.2 part by weight of ethyleneglycol dimethacrylate, 0.25 part by weight
 of
 2-[2'-hydroxy-5'-(2"-methacryloyloxyethoxy)-3'-tert-butylphenyl]-5-methyl-
 2H-benzotriazole, and 0.1 part by weight of
 2,2'-azobis(2,4-dimethylvaleronitrile) were mixed and dissolved together.
 The thus obtained mixture was introduced into a silicone-coated test tube
 made of a glass material. The test tube was heated from 35.degree. C. to
 80.degree. C., with the opening of the test tube being plugged. Thus, the
 mixture in the test tube was polymerized into a polymer by a bulk
 polymerization method. The thus obtained polymer was subjected to a
 cutting operation and a surface grinding operation, to thereby provide a
 plate having a thickness value of 0.5 mm. The appearance of the plate was
 reddish yellow.
 Thereafter, the thus obtained plate was immersed in a physiological salt
 solution or saline for 16 hours, and boiled therein for two hours. The
 boiled plate was measured of its spectral transmittance at 360-800 nm in a
 manner similar to that in the above Example 3. The result is shown in the
 graph of FIG. 4. This plate was further boiled for 48 hours, and similarly
 measured of its spectral transmittance. The result is shown in the graph
 of FIG. 5. On the basis of the spectrum data after 2-hour boiling and
 after the additional 48-hour boiling, a chrominance, namely, a color
 difference between the two data was calculated according to a method as
 specified in JIS-Z-8730. The chrominance .DELTA.E*ab was 0.51.
 As is apparent from the explanation of the above Examples, the colored
 ocular lens materials which were obtained by including the polymeric
 colorant according to the present invention assume reddish yellow, and
 have a color tone suitable for practical use. It is to be understood from
 the results of the graphs of FIGS. 4 and 5 that the spectral transmittance
 of the ocular lens material (specimen No. 2) remains unchanged after the
 additional boiling operation. This indicates that the present polymeric
 colorant does not eluate or separate from the ocular lens material.
 Further, the polymeric colorant does not suffer from hydrolysis, and
 assures sufficiently high safety to the eye.