Coating compositions for plastic substrates

Details Coating compositions for plastic substrates Coating compositions for plastic substrates

2002-07-03

2003-11-11

Lipman, Bernard (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S241000, C526S279000

Reexamination Certificate

active

06646080

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to radiation curable compositions, to coatings formed by curing these compositions, and to articles comprising such coatings. An aspect of the invention concerns the use of the present compositions to form protective coatings on substrates including for example display monitors (like flat screen computer and/or television monitors such as those utilizing technology discussed in, for example, U.S. Pat. Nos. 6,091,184 and 6,087,730 which are both hereby incorporated by reference), optical discs, touch screens, smart cards and the like.
BACKGROUND OF THE INVENTION
There is great interest in the development of plastic substrates for, for instance, LCD (liquid crystal display) and OLED (organic light emitting diode) display applications. Plastic substrates are light and tough, and comparatively easy to shape. However, plastics are typically relatively soft and, thus, there is the need to deposit a protective layer on the exposed surface of the plastic. Such protective layers are preferably relatively hard (to provide, e.g., scratch resistance) yet also substantially flexible. In addition, such layers should adhere well to the surface they are coated on.
SUMMARY OF THE INVENTION
The present invention provides compositions that, after cure, adhere well to plastic substrates and provide a flexible material having a hard, scratch resistant surface. The compositions comprise
(i) metal oxide particles; and
(ii) a poly(meth)acrylate compound.
In one embodiment, the compositions are used to coat substrates for use in display applications.
DESCRIPTION OF THE INVENTION
It is to be understood that the term polynorbornene herein refers to a polymer wherein at least 10 wt %, relative to the total weight of the polymer, results from the polymerization of norbornene monomers, more preferably at least 50 wt %, even more preferably at least 80 wt %, and most preferably at least 95 wt % results from the polymerization of norbornene monomers. Polynorborene may be a random copolymer, a block copolymer, a homopolymer or a polymer resulting from three or more monomers. Examples of polynorbornenes are, for instance, described in U.S. Pat. Nos. 5,468,819; 5,569,730; 5,571,881; 5,677,405; 5,741,869; and RE 34,638; which six patents are hereby incorporated in their entirety by reference. “(Meth)acrylate” refers in this application to “acrylate and/or methacrylate”.
The present invention includes compositions for coating a plastic substrate, wherein the compositions comprise a component (A) comprised of a metal oxide bonded to an organic compound, wherein the organic compound has
(i) a radiation curable group; and
(ii) a group represented by the following formula (1)
wherein
X represents an amine (NH), oxygen (O), or sulfur (S) radical; and
Y represents an oxygen (O) or sulfur (S) radical.
Suitable examples of the component comprised of a metal oxide bonded to an organic compound are, for instance, set forth in U.S. Pat. No. 6,160,067 to Eriyama et al., which is hereby incorporated in its entirety by reference. Preferably, the metal oxide comprises at least one metal selected from the group consisting of silicon, aluminum, zirconium, titanium, zinc, germanium, indium, tin, antimony, and cerium. The organic group preferably comprises a radiation-curable group that is ethylenically unsaturated, for instance a (meth)acrylate group, preferably an acrylate group.
There are no specific limitations to the method for preparing the crosslinkable particles (A). Methods for preparing the particles are disclosed in, for instance, WO 00/47666, which is hereby incorporated in its entirety by reference. A method of reacting the above-mentioned specific organic compound and oxide particles can be given as an example:
Oxide particles (A
1
) are known to have moisture on the surface of particles as adsorption water under usual storage conditions. In addition, components which react with a silanol group-forming compound such as a hydroxide, hydrate, or the like are presumed to be present at least on the surface of the oxide particles. Therefore, the crosslinkable particles (A) can be produced by mixing the silanol group-forming compound and oxide particles (A
1
), and heating the mixture while stirring. It is preferable that the reaction be carried out in the presence of water to efficiently bind the silanol group-forming site possessed by the specific organic compound (A
2
) and the oxide particle (A
1
). However, water is not required when the specific organic compound (A
2
) and (optionally) compound (A
3
) possess silanol groups. Therefore, the crosslinkable particles (A) can be prepared for example by a method which includes at least the operation to blend the oxide particles (A
1
), the specific organic compound (A
2
) and (optionally) compound (A
3
).
The crosslinkable particles may be prepared, for example, by a two step process. The first step involving hydrolyzing the compound (A
2
) and bonding the hydrolyzed compound to oxide particles (A
1
). And a second step of hydrolyzing the compound (A
3
) and bonding the particles obtained in the first step to the hydrolyzed compound obtained from compound (A
3
). Hydrolysis may be omitted, when the compound (A
2
) and compound (A
3
) are not silanol group-forming compounds, but silanol group-containing compounds.
First Step
The first step comprises reacting a mixture of oxide particles (A
1
) and a solvent or oxide particles (A
1
) dispersed in a solvent with the compound (A
2
) to bond oxide particles (A
1
) and the compound (A
2
) (such bonded particles may be hereinafter referred to as “intermediate particles”). Specifically, the oxide particles (A
1
), the compound (A
2
), and water are blended under the following conditions to produce the intermediate particles.
Here, p-methoxyphenol for example, may be added as a thermal polymerization inhibitor. The same solvent as used as a dispersion medium for the solvent dispersion sol of the oxide particles (A
1
) can be used as a solvent.
The temperature for the reaction may be between the temperature at which the solutes do not precipitates and the boiling point of the solvent, with the preferable temperature range being from 0 to 150° C.
There are no specific restrictions to the manner of stirring inasmuch as the mixture can be homogeneously mixed.
A reaction time within which the reaction is sufficiently completed, for example, from 5 minutes to 24 hours, and preferably from one hour to 8 hours, can be applied.
Second Step
The second step comprises reacting the intermediate particles produced in the first step and the compound (A
3
), thereby obtaining crosslinkable particles in which the intermediate particles are bonded with the compound (A
3
). Specifically, the intermediate particles, the compound (A
3
), and water are mixed under the following conditions to produce crosslinkable particles.
The temperature for the reaction may be between the temperature at which the solutes do not precipitates and the boiling point of the solvent, with the preferable temperature range being from 0 to 150° C.
There are no specific restrictions to the manner of stirring inasmuch as the mixture can be homogeneously mixed.
A reaction time within which the reaction is sufficiently completed, for example, from 5 minutes to 24 hours, and preferably from one hour to 8 hours, can be applied.
The crosslinkable particles can be obtained by bonding the oxide particles (A
1
), compound (A
2
), and compound (A
3
) through first and second steps in this manner.
As mentioned above, it is desirable to produce the crosslinkable particles by first treating with the compound (A
2
), followed by a treatment with the compound (A
3
).
Taking the case using silica particles as the oxide particles (A
1
) as an example, both impaired storage stability and inferior coating surfaces are associated with dispersion stability of the crosslinkable particles in the composition. Because the compound (A
2
) is relatively bulky, the treatment only with the compound (A
2
) cannot completely restrain the silanol group on

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