Compositions – Inorganic luminescent compositions with organic...
Reexamination Certificate
2001-08-06
2004-04-06
Anthony, Joseph D. (Department: 1714)
Compositions
Inorganic luminescent compositions with organic...
C252S30140R, C252S301330, C252S301350, C524S436000, C524S403000, C524S437000, C524S432000, C524S435000, C528S196000, C528S198000, C528S200000
Reexamination Certificate
active
06716368
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to transparent or translucent thermoplastic compositions comprising a thermoplastic polycarbonate resin and a phosphorescent compound with an aluminate matrix expressed by MAl
2
O
4
in which M is at least one metal element selected from calcium, strontium and barium. The thermoplastic compositions can comprise besides the polycarbonate resin other polymers. The compositions of the invention are particularly suitable for injection molding processes. The invention also relates to objects obtained by injection molding of the compositions according to the invention.
Phosphorescent compounds with an aluminate matrix are well known. U.S. Pat. No. 5,424,006 describes this type of phosphors and refers to the possibility to mix them into a plastic material. The particle size of the described phosphors is such that they pass a sieve mesh 100 i.e. that they have a particle size below about 150 micrometer.
U.S. Pat. No. 5,607,621 describes phosphorescent synthetic resin materials comprising about 5 to about 20% by weight of similar aluminate based phosphors and a synthetic resin. Many synthetic resins are mentioned by way of example. The particle size of the pigment for the compositions of U.S. Pat. No. 5,607,621 is chosen as follows: synthetic resin compositions for injection molding should have a phosphorescent pigment with an average particle size of 15 to 25 micrometer, synthetic resin compositions suitable for extrusion molding should comprise a phosphorescent compound with an average particle size of 10 to 20 micrometer. The phosphorescent compound in compositions for monofilament extrusion molding should have an average particle size of 1 to 10 micrometer.
U.S. Pat. No. 5,976,411 describes molded, extruded or formed phosphorescent plastic articles made out of a plastic composition comprising a thermoplastic or a thermosetting resin, about 1% to about 50% by weight of a phosphorescent phosphor pigment and about 0.001% to about 20% by weight of a laser energy absorbing additive. Polycarbonate has been mentioned as one of the many suitable resins. U.S. Pat. No. 5,976,411 describes aluminate based phosphors with various particle sizes such as a particle size of “20±5 micrometer to greater than 100 micrometer” or particles that pass through a mesh 200 sieve, which approximately corresponds to a size of below 75 micrometer. U.S. Pat. No. 5,976,411 gives an example of a composition comprising polycarbonate and 5% by weight of a phosphor with unknown particle size.
JP-A-12-034 414 describes semitransparent light-storing resins which contain in total 1-4% by weight of a light storing pigment. The content of light-storing pigment particles with a size of 20 micrometer or higher should be in the range of 1-4% by weight and the content of light storing pigment particles with a size of lower than 20 micrometer should be in the range of 1% by weight or lower. Strontium aluminates are used in the examples of this Japanese patent application. According to JP-A-12-034 414 it was common to use pigments with a very wide range of particle sizes varying from several tens micrometers to hundreds of micrometers and an average particle size of about 10-20 micrometer. JP-A-12-034 414 seeks to improve the balance of relative density of residual luminescence and the light transmission of the known compositions by using pigments with above described particle size. Upon incorporation of the pigments of JP2000-34414 in a polycarbonate resin the favorable physical properties of the polycarbonate get lost. The aluminate particles are very bard and cause wear of the screws in injection molding machinery. The wear is so strong that graying of the composition processed with the screw may result.
SUMMARY OF THE INVENTION
It has now be found that upon incorporating phosphorescent pigments of a specific particle size in polycarbonates it is possible to combine the phosphorescent properties while maintaining the favorable physical properties of the polycarbonate. It has also become possible to obtain less graying of the composition of the invention when processed with the screws of injection molding machines. The invention deals with transparent or translucent thermoplastic compositions comprising a thermoplastic polycarbonate resin and a phosphorescent compound with an aluminate matrix expressed by MAl
2
O
4
in which M is at least one metal element selected from calcium, strontium and barium, wherein the phosphor is present in a quantity of 0.1 to 2.0% by weight with respect to the quantity of polycarbonate resin and possesses a median particle size of less than 10 micrometer. The more preferred quantity of the phosphor is 0.1 to 1.0% by weight.
In a more preferred embodiment of the invention, the phosphor has a median particle size of below 5.0 micrometer and a maximum particle diameter of 10 micrometer.
It is possible to use aluminate phosphors which have been doped with Europium.
It is also possible to use aluminate phosphors which have been doped with Europium and at least one co-dopant like Dysprosium.
Objects formed by injection molding of the transparent or translucent thermoplastic composition of any of the compositions of the invention also form part of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The transparent or translucent compositions of the invention should comprise at least:
A. a thermoplastic polycarbonate and
B a phosphorescent phosphor with an aluminate matrix as defined in the claims.
The compositions of the invention may further comprise one or more other polymers, agents to improve the impact strength, usual additives to the extent that they do not interfere with the desired optical and aesthetic effects obtained by the incorporation of the phosphorescent pigment.
Polycarbonates.
As used herein, the term “polycarbonate ” includes polymers having structural units of the formula (I):
in which at least about 60 percent of the total number of R
1
groups are aromatic organic radicals and the balance thereof are aliphatic, alicyclic, or aromatic radicals. Preferably, R
1
is an aromatic organic radical and, more preferably, a radical of the formula (II):
—A
1
—Y
1
—A
2
— (II)
wherein each of A
1
and A
2
is a monocyclic divalent aryl radical and Y
1
is a bridging radical having zero, one, or two atoms which separate A
1
from A
2
. In an exemplary embodiment, one atom separates A
1
from A
2
. Illustrative, non-limiting examples of radicals of this type are —O—, —S—, —S(O)—, —S(O
2
)—, —C(O)—, methylene, cyclohexylmethylene, 2-[2,2,1]-bicycloheptylidene, ethylidene, isopropylidene, neopentylidene, cyclohexylidene, cyclopentadecylidene, cyclododecylidene, adamantylidene, and the like. In another embodiment, zero atoms separate A
1
from A
2
, with an illustrative example being biphenol (OH-benzene-benzene-OH). The bridging radical Y
1
can be a hydrocarbon group or a saturated hydrocarbon group such as methylene, cyclohexylidene or isopropylidene.
Polycarbonates can be produced by the reaction of dihydroxy compounds in which only one atom separates A
1
and A
2
. As used herein, the term “dihydroxy compound” includes, for example, bisphenol compounds having general formula (III) as follows:
wherein R
a
and R
b
each independently represent hydrogen, a halogen atom, or a monovalent hydrocarbon group; p and q are each independently integers from 0 to 4; and X
a
represents one of the groups of formula (IV):
wherein R
c
and R
d
each independently represent a hydrogen atom or a monovalent linear or cyclic hydrocarbon group, and R
e
is a divalent hydrocarbon group.
Some illustrative, non-limiting examples of suitable dihydroxy compounds include dihydric phenols and the dihydroxy-substituted aromatic hydrocarbons such as those disclosed by name or formula (generic or specific) in U.S. Pat. No. 4,217,438,. A nonexclusive list of specific examples of the types of bisphenol compounds that may be represented by formula (III) includes the following: 1,1-bis(4-hydroxyphenyl) methane; 1,1-bis(4-hydroxyphenyl) ethane; 2
Brown Michael W.
Peak Steven R.
Schottland Philippe
Anthony Joseph D.
General Electric Company
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