Red and red-orange afterglow phosphors

Claim 2

A red or red-orange afterglow phosphor comprising: an alkaline earth chalcogenide host and europium and thulium activators, said phosphor producing a long lasting red or red-orange afterglow in the range of about 620 to about 550 nm after being charged with visible light in the range of about 400 to about 550 nm without the need for infrared stimulation.

Claim 3

The phosphor of Claim 1, wherein the host is represented by the formula comprising M:X wherein M is selected from the group consisting of magnesium, calcium, strontium, barium and mixtures thereof and X is selected from the group consisting of sulfur selenium and mixtures or solid solutions thereof.

Claim 4

The phosphor of Claim 1, wherein the host is selected from the group consisting of calcium sulfide, strontium sulfide, strontium selenide, calcium selenide and mixtures or solid solutions thereof (e.g. a solid solution between calcium sulphide and strontium sulphide).

Claim 5

The phosphor of Claim 1, wherein the europium and thulium activators are present as oxides, sulfates, carbonates, nitrates, halides or mixtures thereof.

Claim 6

The phosphor of any preceding claim, wherein the activator is selected from the group consisting of europium sulfate, europium oxide, thulium sulfate and thulium oxide.

Claim 7

The phosphor of any preceding claim, containing a flux selected from the group consisting of an alkali, alkaline earth, or ammonium halide, sulfate, carbonate, phosphate and mixtures thereof as residue or otherwise.

Claim 8

The phosphor of Ciaim 6, wherein the flux is seiected from the group consisting of calcium fluoride, strontium sulfate, lithium fluoride, ammonium fluoride, calcium sulfate and mixtures thereof.

Claim 9

The phosphor of Ciaim 6, wherein the flux is seiected from the group consisting of calcium fluoride, strontium sulfate, lithium fluoride, ammonium fluoride, calcium sulfate and mixtures thereof.

Claim 10

The phosphor of Claim 6 or 7, wherein the flux is present in the reaction mixture in an amount of from about 2 to about 50 percent by weight, based on the weight of the host.

Claim 11

The phosphor of Claim 6 or 7, wherein the flux is present in the reaction mixture in an amount of from about 5 to 30 percent by weight, based on the weight of the host.

Claim 12

The phosphor of any preceding claim, wherein the amount of the europium and thulium are each several hundred to about several thousand parts per million based on the moles of host.

Claim 13

The phosphor of any preceding claim, wherein said phosphor has an emission between about 620 and about 650 nm.

Claim 14

The phosphor of any preceding claim, wherein the molar ratio of the europium to the thulium activators is in the range of from about 2:1 to about 1:100.

Claim 15

A red afterglow phosphor comprising: a calcium sulfide host and europium and thulium activators.

Claim 16

A red afterglow phosphor comprising: a calcium sulfide host and europium and thulium activators.

Claim 17

A red afterglow phosphor prepared from a reaction mixture comprising: calcium sulfide host; europium in an amount of about 200 parts per million (0.020 a/o) based on the moles of host; and thulium in an amount of 170 parts per million (0.017 a/o) based on the moles of host; and calcium fluoride in an amount of about 9 percent by weight based on the weight of the host.

Claim 18

A red afterglow phosphor prepared from a reaction mixture comprising: calcium sulfide host; europium in an amount of about 200 parts per million (0.020 a/o) based on the moles of host; and thulium in an amount of 170 parts per million (0.017 a/o) based on the moles of host; and calcium fluoride in an amount of about 9 percent by weight based on the weight of the host.

Claim 19

A red-orange afterglow phosphor prepared from a reaction mixture comprising: strontium sulfide; europium in an amount of about 200 parts per million (.02 a/o) based on the moles of host and thulium in an amount of about 165 parts per million based on the moles of host; and 9 weight percent calcium fluoride and about 9 weight percent strontium sulfate based on the weight of the host.

Claim 20

A red-orange afterglow phosphor prepared from a reaction mixture comprising: strontium sulfide; europium in an amount of about 200 parts per million (.02 a/o) based on the moles of host and thulium in an amount of about 165 parts per million based on the moles of host; and 9 weight percent calcium fluoride and about 9 weight percent strontium sulfate based on the weight of the host.

Claim 23

The method of Claim 16, wherein said mixture is introduced into an alpha-alumina crucible having a loose fitting cap and placed into a heating chamber.

Claim 24

The method of Claim 16 or 17, wherein said heating chamber is a tube furnace and wherein said tube furnace is purged with an inert gas selected from the group consisting of nitrogen, helium, argon and mixtures thereof, said inert gas being introduced in an amount of about 1 to 20 volumes, based on one volume in the heating chamber.

Claim 25

The method of Claim 16, 17 or 18, wherein any of the following conditions apply to the heating step: (a) said mixture is heated to about 800 to about 1200°C; (b) said mixture is heated to about 900 to 1050°C; (c) said mixture is heated at a rate of about 2 to 100 degrees per minute; (d) said mixture is heated at a rate of about 5 degrees per minute; (e) the mixture is maintained at the selected elevated temperature for from 15 minutes to several hours; (f) said purge gas is introduced during the heating of the reaction mixture, during the period the reaction mixture is maintained at the selected elevated temperature and during the cooling period; (g) the mixture is maintained at the elevated temperature for about one hour; (h) the phosphor is ground into fine particles; (i) the ground particles are heated to a temperature below their melting temperature so that dislocations present in the crystal structure may be relieved.

Claim 28

The method of Claim 20, wherein a purge gas is introduced into said heating chamber.

Claim 29

A composition comprising (a) a phosphor as claimed in any of Claims 1 to 14 or made by the method of any of Claims 16 to 21 and (b) any of the following a solvent; a resin or plastics material; a green phosphor; an organic fluorescent dye

Claim 30

A red or red-orange afterglow article comprising a substrate in or on which is a red or red-orange afterglow phosphor according to any of Claims 1 to 15 or made by the method of any of Claims 16 to 21.

Claim 31

The article of Claim 23 wherein, said substrate is of plastics.

Claim 32

The article of Claim 23, wherein said plastics is methyl methacrylate.

Claim 33

An afterglow phosphor composition comprising: a physical mixture of a phosphor comprised of zinc sulfide activated with copper and displaying a green phophorescence and a phosphor as claimed in any of Claims 1 to 15 or made by the method of any of Claims 16 to 21.