CA1059748A - Fluorescent ink for automatic identification - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A fluorescent printing ink for non-impact type application, especially used for coding purposes, in which the fluid ink composition is formulated of an organic solvent base containing 0.005 to 2.0% by weight fluorescent dye, up to 60% by weight resinous binder, up to 5% by weight of an organic brightener, and 0.1 to 3.0% by weight organic phosphor, and which also includes an evaporation retardant in an amount within the range of 2 to 30% by weight and an alkali metal thiocyanate in an amount up to 2% by weight, and in which the ingredients are all dissolved in the organic solvent.

Description

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S P E C I F I C A T I 0 N ~ ~

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This invention relates to a fluorescent printing ink which can be applied in sufficient intensity by a non-impact type printer to enable use of electronic equipment ;
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capable of reading light reflected or emitted from the printed image in the visual wave length range.
Heretofore such fluorescent lnk compositions for identification of coding have been applied to an item by an impact type printer, using a ribbon having a wax coating con-taining a fluorescent material. The applied image was read -for identification by an electronic scanner having a sensitiv~
ity to light in the wave length range from 500 nanometers (nm~
to above 700 nm. The reader has a maximum sensitivity at 630 to 640 nm with sensitivity of 50% of maximum between 520 and 700 nm. The fluorescent image printed by the impact type of ;
printer has an emission which peaks at about 525 nm. While this level is outside the range for maximum efficiency o~ tbe reader, the deficiency can be made up by the volume of coat-ing capable of being applied by impact printing for coding identification.
Attempts have heretofore been made to develop a fluorescent ink composition having an intensity at least equiv-alent to impact printed coding but such attempts have not led ~; to success because of the insufficient amount of material deposited by non-impact printing and because of interferences or absorptions introduced by the substrate.
Thus it is an object of this invention to produce a fluorescent ink composition which can be applied by a non-impact type printer and read or deciphered by an electronic ~-reader operating within the range previously described; in 3 which the ink composition is characterized by an intensity ~

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which is higher than heretofore believed possible; in which the emission of the image printed with the fluorescent ink composition is displaced to a peak at 580 nm wave lengths, and in which the ink can be applied by a "Video Jet" Printer with increased effective intensity.
According to the present invention, there is provided a fluorescent ink composition for non-impact type application in the form of a solution comprising an organic solvent carrier in which the essential non-solvent components of the ink composition, which are dissolved in the organic solvent carrier, consist essentially of solvent soluble organic phosphor, solvent soluble organic brightener, solvent soluble fluorescent dye components, and solvent soluble organic binder which does not interfere with the fluorescence of the fluorescent dye, the essential components being present in amounts within the range of 0.1 to 3% by weight of the organic phosphor, 0 to 5% by weight of the organic brightener, up to 60%
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by weight of the resinous binder and 0.005 to 2.0% by weight of the ;~
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fluorescent dye.
In another aspect, the present invention, provides a method ~ -of cooling or printing with a fluorescent dye comprising a non-impact ; -~
application of a fluid ink composition as defined above.
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The invention will hereafter be described with reference to a fluorescent printing ink adapted for use in printing or coding with a jet type~printer. It will be understood, however, that the printing inks embodying the features of this invention can be used for printing or coding on suitable substrates by other non-impact type printing, or other imaging devices and equipment, such as electrostatic printing, flex- ~ -~
ographic printing, or gravure printing.
~or a description of a jet printer and its me~hod of operation in use, reference can be made to a Technical Report No. 1722-1 of the Stanford University Electronics Research Laboratory, dated March 196~ and entitled "High ~requency Oscillograph With Electrostatically Deflected Ink Jets".

- 2 -~j lOS9748 The basic imaging technique in jet printing involves the use o one or more ink jet assemblies connected to a pressurized source of ink. Each jet includes a very small orifice, usually having a diameter of the order of about 0.0024 inch which is electromagnetically energized by magneto-restrictive or piezoelectric means to emit a contlnuous stream of uniform droplets of ink at a rate of the order of 33 to 75 kilohertz.
The stream of droplets is directed onto the surface of a moving web of paper and is controlled to form printed characters in response to video signals derived from an electronic character generator and in response to `
an electrostatic deflection system.
Such jet type printers have since become well known to the trade and are commercially available from many sources.
In the early work relating to jet printing, use was made of various types of commercial fountain pen inks. However, generally available inks were unsuitable for use in jet printing because they . ; :
frequently contained solids which operated to clog the very small orifice ~ ~ ~
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of the ink jet. -~
Commercially available jet printing inks also have the tendency to tip dry when left in the ink jet over short periods of time with the result that the dried ink tended to clog the orifices and prevent flow of ink therethrough on resumption of operation of the jet printer. This deficiency has been overcome by the formulation of the ink composition with suitable evaporation retarder.
The invention will hereinafter be described in greater detail by reference to the following examples which are given by way of illustration, but not by way o limitation:
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Ex. 1 Ex. 2 Ex. 3 F,x. 4 Gener~l ~7ectric Oryanic Pho~phor 118-15-3 1.3 1.3 1.3 1.3 ¦' Day-Glo Bri ghtener ~M-35 (1% dye iIl solution~ 15.6 15.6 15.6 15.6 Day-Glo* Strong Yellow Soluble Toner 122-7081 11.2 10.1 10.7 -Day-Glo* Strong Red Soluble Toner 122-7G82 - 1~1 .5 11.2 Potassium Tlliocyanate 2.0 2.0 2.0 2.0 ' ' ' ' ~cetone 43.0 43.0 43.0 ~13.0 , 10 Ethylene Glycol Mono ¦ Ethyl Ether 26.9 26.9 26.9 26.9 ~ -- Effecti~e emission with `
present readers 100% 144% 151% 110%

The values given in the for~ulations are in percent by weight. The values for effective emission are for the . .
~ 15 image printed with the ink compositions represented by the .
- examples. ~ -In the abov7 formulations, the Day-Glo Strong Yellow~
Soluble Toner 122-7081 and th.e Day-Glo Strong Red Solub:le Toner 122-7082 are fluorescent pi~ments manufactured ~y Lawter Chem- ~
20 ~ ~1cals, Inc. or ~orthbrook~ Illlnois, in accordance with the ~ ~ ' -formulations and procedures described in the D'Alelio et al Reissue Patent ~o. 25,8450 Such toners embody the fluorescent dye co~,ponent dissolved in resinous material formed by co-condensation of benzoguanamir.e-formaldehyde with an aryl -sulfonamide-formaldehyde. The toner ls crushed and ground to a particle si~e o 1 to 2 microns for use as a pigment i~ the manufacture of daylight fluorescent coating compositions. ~-Strong Yellow 122-7081 is formulated of a yellow fluorescent dye dissolved in the -esi~ous matrix with a maximum emission pea'k of 525 to 532 nm wavelength. Strong Red 122-7082 is * Trade Mark .

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formulated of a red fluorescent dye dissolved in the resin matrix with a maximum emission peak of 575 to 595 nm wave~
length.
In the practice of this invention~ the resinous matrix dissolves in the acetone solvent to function as a binder component in the ink composition while the fluorescent dye component remains dissolved in the solution of the modi- -~
fied sulfonamide resin in the organic solvent.
It will be appreciated that, instead of combining the resin and dye to form a pigment for formulation into the printing ink composition of the invention, the resinous binder component and a soluble fluorescent dye may be introduced as separate components fo~~ solution in the organic solvent vehicle although it is preferred to formulate the ink composition of the fluorescent dye component and the resinous binder combined in the form of a pigment of the type described, since the desired ratio, distribution, and size of the materials are easier to control and to maintain.
Instead of using a modified toluene sulfonamide resinous component as the binder, use can be made of other organic solvent soluble high molecular weight or polymeric resinous materials as the binder component introduced separate ;~
and apart from or in combination with the fluorescent dye.
Such other binder components may be represented by methyl cel-lulose, ethyl cellulose, acrylic or methacrylic or other Cl to C5 alkyl acrylic polymer~, alcohol soluble butyrates, poly-amide resins and shellac.
As the fluorescent dye component use can be made of such organic soluble fluorescent dyes as xylene Red B ~2,4 di-sulfo benzoic acid), Rhodamine 6 GD~ (ethyl ester of m-mono-. , 105974~3 .

ethylclmine phenolphthalein hydrochloride)~ Azosol Yellow 6 GF
(4 amino '~8 llaphthol 2',~' dimethyl phenJl imide), Brilliant Sulfoflavine FFA (3 sulfo 4 amino 1,8 na~hthol 4` methyl phenyl imide sodium salt), Rhoda~ine ~X ~meta-diethyl amino phenol-phthalein hydrochloride). In the above examples, the Day-Glo YellOW Soluble Toner e~bodies Azosol Yellow 6 GF as the dye component and the Day-Glo Strong Red Soluble Toner embodies xylene Red B and Rhoda~ine sx as toner.
When calculated on the basis of the pigment formed of the resinous matrix with dissolved fluorescent dye componen~
the pigment concentration of the ink composition may comprise up to 50% by weight of the ink composition, such as up to 30% -by weight of the Day-Glo Strong Yellow Soluble Toner 122-7081 and up to 30% by weight of the Day-Glo Strong Red Soluble Toner 122-7082, andlpreferably from 5-15% by weight of the pigment, such as from 8.0 to 12.5% by weight of the Day-Glo 122-7081 Yellow and 0.2 to 3.0% by welght o the Day-Glo~
122-7082 Red.
The conce~tration of the~fluorescent dye in the~
printing ink composition can be varied over a fairly wide limit,;~
depending somewhat upon the pariicular dye component present~ -and the binder component employed in combination therewith. Th~
dasired fluorescence can be;developed when the fluorescent dye ~ component is present in an amount of at least 0.005% by weight up to an amount of about 2.0% by weight, and preferably in an amount within the range of 0.05 to 1.5% by weight. The desired ..
dye concentration can be incorporated by way of pigments of the type descri~ed, when the pigment is fonmulated to contain 0.1 to 5% by weignt of the dyé component with the remainder calcu-3 lated as binder solids.* Tr~de Mark :

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As the organic solvent, use should be made of highly volatile organic solvents in which the binder and the fluores~
cent dye components are soluble. Por example, instead of acetone forrnulated in Examples 1-4, use can be made of alcohols -~
such as ethyl alcohol, isopropyl alcohol, propyl alcohol and the like Cl to C5 alcohols; acetate such as ethyl acetate, iso-propyl acetate, butyl acetate and the like ethers or esters;
glycols, glycol ethers, glycol ethyl acetate; ketones such as methyl ethyl ketone, methyl isobutyl ketone; chlorinated solvents such as methyl chloride, ethyl chloride, and the like.
The amount of organic solvent component will depend somewhat upon the type of resinous binder and others of the ingredients used in the ink composition. It is desirable to make use of an amount of solvent sufficient to provide for a viscosity ;
within the range of l to 20 centipoises and preferably 1.5 to 10 centipoises. In general, the amount of solvent component employed in the ink composition will range from 30-80% by weight, and preferably 39-70% by weight.
A noticeable effect is obtained when use is made of an organic phosphor present in an amount of as little as 0.1%
by weight and up to about 3% by weight. More than 3% by weight can be employed but corresponding increase in the amount of emission is not experienced sufficient to warrant the increase in the amount of phosphor. In fact, some interferences are ~ ;
noticed which reduces the amount of light emission when such increased concentrations of phosphor are employed. Organic phosphors which may be used in the practice of this invention are high intensity fluorescent dyes or pigments characterized by very short rise and decay times and can be excited over a ; 3 wide range of wave lengths which include 254-365 nm.
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~.epresentative of such organic phosphors are heterocyclic phenols and alimido derivatives of benzothiozol. These mater~
ials have various peak emission wave lengths but it is prefer~
red to make use of such organic phosphor materials which have ~ -peak emission in the area of 500-535.
Organic phosphors suitable for use in the practice of this invention are marketed by the General Electric Company under the trade names set forth in the following tabulation w~ich also lists the essential characteristics of the phos- -phors.

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HM-35 is a fluorescent brightener, containing 1% by weight dye component in solution and which emits in the ultra-violet to blue visible light range (below 500 nm). While emission thereof is not in the detector area, it adds to the .
cascading effect in the total fluorescent ink formulation Other organic solvent soluble brighteners which may be used :
are listed in the following tabulation: .

Peak Peak Emission Emission : .
C.I.No. of Com~ination : ~
' Fluorescent Brightener % at .: ~ :
j 10 - BrightenerBrightener Source nm _ 525-530 nm : :

¦ : Calco~luor*~BT158 Cyanamid 465 100 - Calcofluor*A2RT 159 Cyanamid 440 : 40 ; :
Blancophos*SV25 GAF 440 ~- 40 .
Tinopa~ GS 47 Geigv 460 60 Leucophor*BSW30 Sandoz 450 :50 Paper ~Yhite*SP 102 DuPont : 440 40 .: ~ ~
Paper White*BP28 DuPont 440 40 ~ ~ : :
o Brlghtener ~ 20;~

.The amount of brightenèr employed .is limited by its~ ~ ~;
solubility in the solvent system. Generally~ when present,~the~ ~ ::
: brightener component is employed in the ink composition in an ~ .
amount up to~5% by weight and preferably in an amount within. ~
20 the range of 0.1% to~2% by weight.~ :: :-; The ethylene glycol monoethyl ether functions in the~ .
ink composition as an evaporation retarâant which operates to:
~ minimize drying of the ink composltion and thereby ellminate ~ ~ :
:the problem raised by various jet inks which are caused by dry-25 ing of the ink in the tip of the nozzle to clog the nozzle and .
prevent proper usage thereof. Representative of other evapor-ation retardants whlch can be used are aliphatic polyols, and preferably alkylene glycols in which the alkylene group pre-ferably contains 2-6 carbon atoms, as represented by ethylene glycol~ propylene glycol, bulylene glycol, hexylene glycol, * Trade Mark .
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including the polyalkylene glycols as represented by diethylene g]ycol, dipropylene glycol, trie'chylene glycol, tripropylene glycol, tetraet~lylene glycol. It is possible to employ com- ' mercially available polyalkylene glycols, such as Carbowax*200 ~ ~
5 ' or Carbowax*400, which are polyethylene glycols having average '~ ;
molecular weights of about 200 and 400~ respectively. In general, it is preferred, when using polyalkylene glycols, to use those materials having an average molecular weight less ';;
than 600 since higher molecular weight polyalkylene glycols frequently serve to undesirably increase the ViScOs1ty of the ; ink composition.
As the evaporation retardant, use can also be made ' ' ;~
of alkyl ether derivatives of the foregoing polyols but in higher concentration because of their higher rate o~ evapora-tion. Preferred glycol ethers are the alkyl ethers of alkylene glycols in which the alkyl group contains 1-6 carbon atoms ~ ;
(e.g. methyl, ethyl~ propyl, butyl, etc.) and the alkylené
group contains 2-6 carbon atoms.~ Representative of ~he fore~
going glycol ether$~are~ethylene glycol methyl ether~'~e~hyle~e ~;~
20 ~ glycol ethyl e her~'ethylene glycoi butyl ether~ ethylene ' ' ' ; glycol hexyl ether, diethylene glycol methyl ether, diethylene ~ ..
: glycol ethyl ether, diethylene glycol but~l ether~ propylene ~ glycol methyl ether, dipropylene glycol methyl ether~ tri-'~ propylene glycol methyl ether, ethoxy triglycol (triethylene ~'~
. ~ - .
25 glycol ethyl ether)~ methoxy triglycol (triethylene glycol :
methyl ether), etc. Mixtures of the orego1ng g1yco~s and ' glycol esters can be used and frequently are preferred. Other materials which find excellent U52 as evaporation retardants in the ink compositions of this inven~ion are certain plasti-3 cizers such as the phthalate, sebacate, citrate and adipate' * Trade Mark - ~ .
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_ f ~ ; _ - _ 1~5979L8 esters, and rosin esters such as marketed by Hercules under the trade name EIercoly~ D and Petrex*SS.
The total amount of the evaporation retardant em-:: .ployed in the composition of the invention can be varied with~
in wide limits depending on the viscosity and rate of : -:
evaporation, as ~iscussed above. As will be appreciated by :~
those skilled in the art, the amount depends somewhat on the molecular weight of the glycol and/or glycol ether employed. . .
In general, the glycols constitute from 2-30% by weight of the composition. The glycol ethers may range from 5-40% by weight, and when use is made of a plasticizer or phthalate~ adipate, citrate and the like ester, the amount may vary from 1~23% by weight. ~ -~ The potassium thiocyanate has materlal effect on the ;~ :~
: 15 ~resistivity in ohms-cm of the ink composition. -This can be. :~
demonstrated by the experiment in which the amount of potassium;~
thiocyanate was varied from 0 to 2% by.weight in the: ink form~ .
: ulation of Example 3, with:the following results~
: %:by weight potassium thiocyanate:: 0%::.~ .5% 1.5%~ 2.0% ~ :: . :
20` Re9istivity ohm-cm ~ ~ ~ 6300 1300 5a0 390~ .
Suitable~substrates capable of being coded or printed ~ ~ ~
with ink-compositions:representative of-the practice of this ~ : .
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invention~ and by non-impact type printing processes~ ancl to which the applied ink can adhere when dry to provide ~the de-sired fluorescent response for reading by conventional readers, include plastic films of polyolefin, metal foils, polymer . .
coated cellophane, polyvinylidene chloride films, metal sur- .

faces~ wooden surfaces, glass surfaces, paper and the like.

Having described the basic concepts of this inven- -:

!. 3 tion~ the following defines the range of the components making .. : .

* Trade Mark ~" -1~3597a~

up the non-volatiles of the inX composition embodying the ;
features of this invention.

Broad range Narrow range - % by weiqht % by weiqht Organic phosphor 0.1 - 3.0 1.0 - 1.5 ;
Organic brightener 0 - 5 .01 - 2.0 Resinous binder up to 60 8 - 15 :: ~
Fluorescent dye 0.005 - 2.0 0.005 - 2.0 It will be understood that changes may be made in the details of formulation and operation without departing from the i ~ .
spirit of the invention, especially as defined in the following claims.

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Claims (7)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A fluorescent ink composition for non-impact type application in the form of a solution comprising an organic solvent carrier in which the essential non-solvent components of the ink composition, which are dissolved in the organic solvent carrier, consist essentially of (1) solvent soluble organic phosphor, (2) solvent soluble organic brightener, (3) solvent soluble fluorescent dye components, and (4) solvent soluble organic binder which does not interfere with the fluorescence of the fluorescent dye, the essential components being present in amounts within the range of 0.1 to 3% by weight of the organic phosphor, 0 to 5% by weight of the organic brightener, up to 60% by weight of the resinous binder and 0.005 to 2.0%
by weight of the fluorescent dye.

2. A fluorescent ink composition according to claim 1 in which the essential components are present in amounts within the range of 1.0 to 1.5% by weight of the organic phosphor, 0.1 to 2% by weight of the organic brightener, 8 to 15% by weight of the resinous binder, and 0.005 to 2.0% by weight of the fluorescent dye.

3. A fluorescent ink composition according to claim 1 in which the fluorescent dye component comprises 8.0 to 12.5% by weight of the Yellow fluorescent dye, and 0.2 to 3.0% by weight of the Red fluorescent dye, both of which are dissolved in the binder component formed of an amide aldehyde - aryl sulfonamide resin.

4. A fluorescent ink composition according to claim 1 which includes an evaporation retardant in an amount within the range of 2 to 30% by weight of the ink composition.

5. A fluorescent ink composition according to claim 1 in which the binder is an amide aldehyde - aryl sulfonamide resin.

6. A fluorescent ink composition according to claim 1 which includes an alkali metal thiocyanate in an amount within the range of 0 to 2% by weight.

7. The method of coding or printing with a fluorescent dye comprising a non-impact application of a fluid ink composition as claimed in claim 1.