Security liquid electrostatic ink composition

Patent metadata

Field	Value
Publication number	US-10591837-B2
Application number	US-201616066145-A
Country	US
Kind code	B2
Filing date	Mar 4, 2016
Priority date	Mar 4, 2016
Publication date	Mar 17, 2020
Grant date	Mar 17, 2020

Abstract

Described herein is a security LEP ink composition comprising an absorber, a resin; and a carrier liquid for printing a security image.

First claim

The invention claimed is:

1. A security liquid electrophotographic (LEP) ink composition comprising:
a first absorber;
a second absorber;
a resin; and
a carrier liquid,

wherein the LEP ink is colourless and transparent; wherein the first absorber and second absorber have absorption spectra in the infrared (IR) range; wherein the first absorber and second absorber have emission spectra in the IR range; wherein the first absorber and second absorber have different absorption spectra, different emission spectra, or both; wherein the LEP ink composition is detectable at an optical signal comprising a superposition of the absorption spectra of the first and second absorbers or a superposition of the emission spectra of the first and second absorbers; and wherein the first and second absorbers comprise an oxide, oxysulfide, sulfide, or combinations thereof.

2. An LEP ink composition according to claim 1 , wherein a ratio of the amount of first absorber to the amount of second absorber is selected such that the LEP ink composition is detectable at the optical signal.

3. An LEP ink composition according to claim 2 , wherein the ratio is from 1:4 to 4:1.

4. An LEP ink composition according to claim 1 , wherein the first and second absorbers comprise a compound selected from the group consisting of alkali metal oxides, alkali metal sulfides, alkali metal oxysulfides, alkaline earth metal oxides, alkaline earth metal sulfides, alkaline earth metal oxysulfides, transition metal oxides, transition metal sulfides, transition metal oxysulfides, rare earth oxides, rare earth sulfides, rare earth oxysulfides, silicon oxides, silicon sulfides, silicon oxysulfides, and combinations thereof.

5. An LEP ink composition according to claim 1 , wherein the first and second absorbers comprise a compound selected from the group consisting of yttrium oxysulfide, potassium sulfide, calcium sulfide, strontium sulfide, ytterbium oxysulfide, ytterbium oxide, lithium sulfide, gadolinium oxysulfide, niobium sulfide, and combinations thereof.

6. An LEP ink composition according to claim 1 , wherein the first absorber and second absorber are present in a total amount of 15 wt % to 50 wt % of the total solids in the LEP ink composition.

7. An LEP ink composition according to claim 1 , wherein the first absorber and second absorber have absorption spectra in the range of 820-980 nm and emission spectra in the range of 890-1040 nm.

8. A method for printing security information, the method comprising:
providing the LEP ink composition of claim 1 ; and
liquid electrophotographically printing the LEP ink composition onto a print substrate to provide a LEP image on the print substrate which is invisible to the human eye.

9. A method according to claim 8 , wherein a ratio of the amount of first absorber to the amount of second absorber is selected such that the LEP ink composition is detectable at the optical signal.

10. A method according to claim 8 , wherein the first and second absorbers comprise a compound selected from the group consisting of alkali metal oxides, alkali metal sulfides, alkali metal oxysulfides, alkaline earth metal oxides, alkaline earth metal sulfides, alkaline earth metal oxysulfides, transition metal oxides, transition metal sulfides, transition metal oxysulfides, rare earth oxides, rare earth sulfides, rare earth oxysulfides, silicon oxides, silicon sulfides, silicon oxysulfides, and combinations thereof.

11. A method according to claim 8 , wherein the first and second absorbers comprise a compound selected from the group consisting of yttrium oxysulfide, potassium sulfide, calcium sulfide, strontium sulfide, ytterbium oxysulfide, ytterbium oxide, lithium sulfide, gadolinium oxysulfide, niobium sulfide, and combinations thereof.

Assignees

• Hp Indigo Bv

Inventors

• Cohen Haim
• Grinwald Yaron
• Amir Gideon
• Avigdor Reut
• Kornilov Julia

Classifications

• G03G9/12

  in liquid developer mixtures · CPC title

• C09D11/52

  Electrically conductive inks · CPC title

• G03G9/135 Primary

  characterised by stabiliser or charge-controlling agents · CPC title

• B41M3/14

  Security printing {(securities B42D25/29)} · CPC title

• G03G9/122 Primary

  characterised by the colouring agents · CPC title