Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2000-08-25
2003-01-07
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S174000, C522S090000, C522S096000, C522S150000, C522S151000, C522S152000, C522S167000, C522S176000
Reexamination Certificate
active
06503961
ABSTRACT:
The present invention relates to an active energy beam-curable adhesive composition capable of bonding various base materials by irradiation with active energy beams such as electron beams and ultraviolet rays. The composition of the present invention is preferably used for bonding thin layer adherends such as plastic films or plastic sheets. Further, it is preferably used for manufacturing various optical films or sheets to be used in liquid crystal display elements and the like. Thus, it can advantageously be used in these technical fields.
Conventionally, in a laminating method in which bonding is achieved between thin layer adherends such as plastic films or sheets, or between a thin layer adherend such as a plastic film or sheet and another thin layer adherend made from a different material, there has been principally employed a dry laminating method in which a solvent type adhesive composition including an ethylene-vinyl acetate copolymer or a polyurethane polymer is coated on a first thin layer adherend, and dried, and a second thin layer adherend is then compression bonded thereto by means of a nip roller or the like.
The adhesive composition used in this method generally contains a large amount of solvent for uniforming the coated amount of the composition. For this reason, the solvent evaporates in large amounts during drying, presenting the problems of toxicity, working safety and environmental pollution. Further, the adhesive composition also causes a problem that peeling occurs between thin film adherends in a post-processing step conducted immediately after bonding the thin layer adherends together, such as in a heat sealing step for ensuring the bonding of the resulting laminated film, and in a ruling step for engraving grooves.
A solventless adhesive composition has been examined as an adhesive composition for solving these problems.
As a solventless adhesive composition, a two-part adhesive composition or an adhesive composition curable by active energy beams such as ultraviolet rays and electron beams has been widely used.
As a two-part adhesive composition, there has been prevalently used a so-called polyurethane adhesive composition including a polymer having a hydroxyl group at the terminal as a base agent, and a polyisocyanate compound having an isocyanate group at the terminal as a curing agent. However, the composition has a deficiency that too much time is required for curing. For this reason, there have occurred problems in terms of production such that the post-processing steps such as a ruling step cannot be started immediately after bonding the thin layer adherends.
In contrast, the active energy beam-curable adhesive composition is excellent in productivity because of its high curing speed, and hence has received attention in recent years.
On the other hand, liquid crystal display apparatuses have been widely used as display devices such as compact televisions, portable personal computers, portable telephones, and word processors, including simple display apparatuses in digital watches and various electric appliances as a matter of course. In recent years, the active energy beam-curable adhesive has also come into use in bonding of various optical films used in the liquid crystal display devices.
The adhesive composition to be used in the optical film has been required to have such a performance as to be capable of holding its adhesive force under extreme conditions of high temperatures and high humidities.
However, while most of conventional active energy beam-curable adhesives have been excellent in initial adhesive strength, they may show a reduction in adhesive strength after long-duration use under high temperature or high humidity conditions, resulting in peeling, or whitening due to moisture absorption.
The present inventors have already proposed a composition including urethane (meth)acrylate and imide (meth)acrylate with a specific structure as a composition applicable for various uses, including use as an adhesive (Japanese Laid-Open (Kokai) Patent Publication No. Hei 10-36462).
The composition has been more excellent in adhesion under high temperature and high humidity conditions as compared with conventional active energy beam-curable adhesive composition when used as an adhesive for manufacturing an optical film, but has not reached the practical level.
In view of the foregoing problems, the present inventors have intensively studied and it is therefore an object of the present invention to provide an active energy beam-curable adhesive composition excellent in adhesion under high temperature and high humidity conditions, and at a practicable level.
As a result of various studies, the present inventors have found that an active energy beam-curable adhesive composition which comprises a specific urethane (meth)acrylate and a compound having a specific cyclic imide group is excellent in adhesion under either condition of high temperature or high humidity and at a practicable level, and have completed the present invention.
Below, the present invention will be described in details.
It is noted that, in this specification, acrylate and/or methacrylate is referred to as (meth)acrylate, an acryloyl group and/or a methacryloyl group is referred to as a (meth)acryloyl group, and acrylic acid and/or methacrylic acid is referred to as (meth)acrylic acid.
1. (A) Urethane (meth)acrylate Derived from Polyester Polyol or Polycarbonate Polyol
The component (A) in the present invention is urethane (meth)acrylate derived from polyester polyol or polycarbonate polyol. The urethane (meth)acrylate provides a particularly excellent adhesive strength under high humidities.
As the component (A), both of the oligomer and polymer are usable, and the one having a weight-average molecular weight of 500 to 30,000 is preferred. It is noted in the present invention that the weight-average molecular weight is defined as a polystyrene-converted value of the molecular weight determined by gel permeation chromatography.
Examples of urethane (meth)acrylate include a compound obtained by allowing the reaction product of polyester polyol or polycarbonate polyol and organic polyisocyanate to react with (meth)acrylate containing hydroxyl group.
Examples of polycarbonate polyol include the reaction product between low molecular weight polyol (described later), polyether polyol (described later) and/or bisphenol such as bisphenol A, and ethylene carbonate and carboxylic acid dialkyl ester such as carboxylic acid dibutyl ester. Examples of polyester polyol include the esterification reaction product between low molecular weight polyol (described later) and/or polyether polyol (described later) and each acid component of dibasic acid such as adipic acid, succinic acid, phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, or terephtalic acid, or anhydrides thereof.
Here, examples of the low molecular weight polyol include ethylene glycol, propylene glycol, 1,6-hexanediol, cyclohexane dimethanol, and 3-methyl-1,5-pentanediol. Examples of polyether polyol include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, and diol of a block or randompolymer such as polyethylene polypropoxy block polymer diol.
Examples of the organic polyisocyanate include tolylene diisocyanate, 1,6-hexane diisocyanate, 4,4′-diphenylmethane diisocyanate, polymethylene polyphenylisocyanate, 1,6-hexane diisocyanate trimer, hydrogenated tolylene diisocyanate, hydrogenated 4,4′-diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, paraphenylene diisocyanate, tolylene diisocyanate dimer, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate adduct, 4,4′-dicyclohexylmethane diisocyanate, trimethylolpropane tris(tolylene diisocyanate) adduct, and isophorone diisocyanate.
Examples of the hydroxyl group-containing (meth)acrylate include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxypentyl (meth)acrylate, hydr
Igarashi Ichiro
Mizutani Kunihiko
Okazaki Eiichi
Fitch Even Tabin & Flannery
McClendon Sanza
Toagosei Co. Ltd.
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