Plastic lenses and primer composition used for coating the same

Details Plastic lenses and primer composition used for coating the same Plastic lenses and primer composition used for coating the same

1999-01-22

2002-08-27

Copenheaver, Blaine (Department: 1773)

Stock material or miscellaneous articles

Composite

Of polyamidoester

C428S423100, C428S423300, C428S425500, C528S073000, C528S083000, C523S457000, C523S460000

Reexamination Certificate

active

06440568

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a plastic lens and a primer composition for coating the same.
BACKGROUND ART
A plastic lens has a silicon-based or other hard-coating or ultraviolet light-cured film on the surface thereof because it easily receives a scratch. An anti-reflection film may be further formed on the plastic lens by vapor-depositing an inorganic material to suppress reflection on the surface of the plastic lens. Such a lens has defects in that its impact resistance is low and is cracked in a falling ball impact test (FDA standards of USA).
To solve this problem, there is known a technology for forming a primer layer of an urethane resin between a lens substrate and a hard coat.
JP-A 5-25299 discloses a process for producing a plastic lens that comprises coating a primer coating comprising a blocked polyisocyanate blocked with &bgr;-diketone and a polyol as main components, on the surface of a plastic lens substrate; curing it by heating to form a primer layer of a thermosetting polyurethane; forming a hard layer; and forming a single-layer or multi-layer anti-reflection film on the surface of the hard layer by vapor-depositing an inorganic material.
JP-B 7-62722 discloses a plastic lens which is produced by laminating a primer layer having a thickness of 0.01 to 30 &mgr;m, which is formed by coating and heating a polyurethane resin solution obtained from diisocyanate and at least one diol selected from the group consisting of alkylene glycol, polyalkylene glycol, poly(alkyleneadipate), poly-&egr;-caprolactones, polybutadienes, poly(alkylenecarbonate) and silicone polyol), a silicon-based resin cured layer, and a single-layer or multi-layer anti-reflection film formed by vapor depositing an inorganic material, in this order on a plastic lens made mainly from a terpolymer of diethylene glycol bisallyl carbonate, diallyl phthalate and benzyl methacrylate.
The above prior arts involve the following problems.
(1) Although spectacle lenses are used in temperate districts of 30° C. and even in cold districts of 0° C., an urethane primer prepared from a polyester polyol comprising adipic acid as a main component in particular is inferior in impact resistance at high temperatures, and may not achieve sufficient impact resistance in some cases.
(2) Of lenses having a high refractive index (HI lenses), there is a lens having low impact resistance. A lens having higher impact resistance is demanded.
It is therefore an object of the present invention to provide a plastic lens having high impact resistance, in spite of having an anti-reflection film, in various environments and a primer for the plastic lens.
It is another object of the present invention to provide a plastic HI lens having effective impact resistance and a primer for the plastic lens.
Other objects and advantages of the present invention will become apparent from the following description.
DISCLOSURE OF THE INVENTION
According to the present invention, firstly, the above objects and advantages of the present invention can be attained by a plastic lens comprising a plastic lens substrate and a polyurethane layer formed on at least one side of the substrate, particularly preferably on a concave surface side, characterized in that the polyurethane layer is a cured product of a primer (to be referred to as “primer-cured layer” hereinafter) comprising a polyester polyol which contains, as an acid component, isophthalic acid in an amount of at least 50 mol % based on the total of all acid components and other dicarboxylic acid in an amount of 50 molt or less based on the total of all acid components and a polyisocyanate as main components.
A description is first given of the primer-cured layer.
(a) Primer-cured Layer
An urethane resin comprising a polyester polyol containing isophthalic acid as a main component has higher impact resistance at a wide temperature range experienced in a daily life than a conventional urethane resin comprising a polyester polyol containing adipic acid as a main component. Particularly, the impact resistance of the former does not degrade at high temperatures. The urethane resin provides an HI lens substrate which is slightly inferior in impact resistance, with sufficiently high impact resistance for practical use.
The primer that forms the primer-cured layer in the present invention comprises a polyester polyol and a polyisocyanate as main components.
(1) Polyester Polyol
The polyester polyol is a polyester which comprises isophthalic acid in an amount of at least 50 mol % of the total of all acid components and other dicarboxylic acid in an amount of 50 mol % or less based on the total of all acid components, and which has a hydroxyl group at terminals of the molecule.
Illustrative examples of the other dicarboxylic acid which is to be contained in an amount of 50 mol % or less include phthalic acid, terephthalic acid, phthalic anhydride, hydrogenated phthalic acid, fumaric acid, dimerized linoleic acid, maleic acid and saturated aliphatic dicarboxylic acids having 4 to 8 carbon atoms. They may be used alone or in combination of two or more.
As the hydroxyl compound may be used a compound which is widely used for the synthesis of a polyester polyol, as exemplified by compounds represented by the following general formula (1):
wherein X
1
is —CH
2
CH
2
O— or
X
2
is —OCH
2
CH
2
— or
and p and q are independently an integer of 1 to 3, and the following general formula (2):
wherein Z
1
and Z
2
are independently an organic group having one OH group and comprising a carbon atom, hydrogen atom and oxygen atom, and r and t are independently 0 or 1.
Illustrative examples of the polyol include diols such as ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, butanediol, hexanediol, nonanediol, methyl pentanediol, neopentyl glycol and an adduct of bisphenol A with ethylene oxide or with propylene oxide; and polyols having three or more hydroxyl groups such as trimethylol propane, glycerin, trimethylol ethane and pentaerythritol.
Typical examples of the compound represented by the above formula (1) are a bromide of an adduct of bisphenol A with ethylene oxide or propylene oxide, and typical examples of the compound represented by the above formula (2) are 4,4′-thiobisbenzenethiol and 4,4′-thiobisbenzylthiol.
The above hydroxyl compounds may be used alone or in combination of two or more.
(2) Polyisocyanate
As the polyisocyanate may be used any of a polyisocyanate having a saturated aliphatic skeleton and one having an aromatic ring skeleton. These polyisocyanates may be used in the form of a monomer, isocyanurate, allophanate, burette, carbodiimide, adduct, modified product or prepolymer.
Illustrative examples of the polyisocyanate having a saturated aliphatic skeleton include hexamethylene diisocyanate, 1,3,3-trimethyl hexamethylene diisocyanate, isophorone diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, hydrogenated xylylene diisocyanate and hydrogenated diphenylmethane diisocyanate.
Illustrative examples of the polyisocyanate having an aromatic ring skeleton include xylylene diisocyanate, tetramethylxylylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate and tetramethylxylylene diisocyanate.
(3) Blocking Agent
The isocyanate group (—N═C═O) of the polyisocyanate may be blocked by a blocking agent.
Illustrative examples of the blocking agent include &bgr;-diketone, diethyl malonate, dimethyl malonate, acetoxime, methyl ethyl ketoxime, butanone oxime, acetylacetone, 2,4-hexanedione, 3,5-heptanedione and caprolactam.
In the present invention, when the polyisocyanate is hexamethylene diisocyanate, it is in the form of an isocyanurate of hexamethylene diisocyanate and the isocyanate group thereof is preferably blocked by at least one compound selected from the group consisting of &bgr;-diketone, diethyl malonate, dimethyl malonate, acetoxime and butanone oxime.
Similarly, when the polyisocyanate is xylylene diisocyanate or teteramethylxylylene diisocyanat

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