Non aqueous fluorescent dispersion ink

Abstract: Fluorescent Ink formulations have been conceived that result in inks having improved tack and flow properties so that problems relating to ink plugging with contemporary ink pads are reduced. Another advantage to the inks is that they have improved paper dust resistance, shelf life and flow properties. These inks are made of a coloring material having an organic non fluorescent pigment dispersed in a rosin ester and a solid solution of fluorescent dye in triazine paraformaldehyde aryl sulfonamide resin dispersed in an alkyd resin. The solvent system is preferably composed of non drying solvents such as emollients and higher molecular weight glycols.

Description: Many advances have been made recently in the field of printing. Great demands have been made upon printing systems and materials therefor in light of the need of faster printing, in conjunction with the computer age, and the seeking of lower toxicity to comply with governmental environmental regulations. In high speed printing, a problem has been encountered with paper dust which is generated during paper transport and the impact of a printing element on the paper. This is particularly true of printing on envelopes which are made of paper with loose fibers. One of the components of the printing system that has required extensive modification is the ink. In most printing applications, a pad or roller made of a porous material is supplied with ink for the purpose of transferring the ink to a printhead. The printing pad may be one which is self contained or one that is periodically supplied with ink from a reservoir. Problems in producing a satisfactory ink are compounded when one seeks to produce an ink that results in printing wherein the printed matter can be seen visually in ordinary light and can be seen having the same or a different color when exposed to ultraviolet light. These inks are known as fluorescent inks and are useful because of their ability to be detected by an optical device. Such inks have wide spread use in the mail handling field where devices, referred to as postage meters or franking machines, print an indicia upon mail pieces. The fluorescent ink yield the ability to determine the location of an indicia on a mail piece and discern the authenticity of postage. The problems in producing a satisfactory fluorescent ink are compounded because a plurality of dyes and pigments are required for achieving good color, fill in, edge acuity and the other qualities required from an ink. One of the major problems associated with inks is aging which results in printing that has a change in color and intensity with the passing of the time the ink is stored. An ink that overcomes the aging problem and shows low environmental sensitivity at high humidity and low and high temperature, low tackiness and flow properties, material compatibility and paper dust resistance would be advantageous. Another consideration is that the ink pad must function in an open environment without drying for at least six months; therefore, the ink solvents should be non volatile. We have found it possible to provide non aqueous, fluorescent dispersion ink formulations which are non toxic and have flow properties which substantially reduce the tendency of the ink to cause plugging in an inking pad. Ink pad life has a variability caused mainly by the inherent properties of the ink with which it is used. The inking pad may be assembled with two layers of foam, the first layer serving as an ink reservoir layer and the second layer serving as a metering layer which contacts the print head. Because of its high density and smaller pore size, the metering layer can act as a filter as a consequence of the ink concentrating at the interface of the two layers. As a result, plugging tends to occur. Of course, what is meant by plugging is the fact that particles of the ink are captured within the pores of the inking member which prevent the flow of ink. It has been found that the plugging onset can be delayed with the ink formulations of the instant invention because of decreased dissolved resin concentration, thereby decreasing the viscosity, even though the size of the pigments can vary from 0.1 µm to 0.5 µm. Plugging onset also is delayed through stabilization of the pigment dispersion by the macromolecules present in the alkyds of the fluorescent pigments and in the rosin esters used in the predispersed non fluorescent pigments. The ink formulation of the instant invention is based on combinations of organic non fluorescent pigments dispersed in a rosin ester and a solid solution of fluorescent dyes in triazine toluene sulfonamide/formaldehyde resin dispersed in an alkyd resin varnish of linseed oil alkyd resin. The resulting visual colour of these inks can be red, blue, green or black. It has been found that these ink formulations reduce the effects of paper dust accumulations because the solvents of the instant ink formulations are non drying on the printing elements and maintains printing elements in a wet state. This wet state causes the flushing of elements resulting in paper dust being carried away. Lower concentrations of dissolved resin produces a lower tack ink which results in less paper dust attraction in the ink. According to the present invention, there is provided a non aqueous, fluorescent dispersion ink composition, comprising: a) 40 to 90 wt % of a non aqueous continuous phase of emollient solvent selected from stearyl polyoxypropylene ether, polyoxypropylene (10) cetyl ether, castor oil, soya bean oil and oleic acid, b) 1 to 10 wt % non fluorescent organic pigment having a size of 0.2 to 0.4 µm dispersed in rosin ester, and c) 5 to 30 wt % organic fluorescent pigment having an average particle size of 0.1 to 0.5 µm made of solid solution of fluorescent dye in triazine toluene sulfonamide/formaldehyde resin dispersed in an alkyd resin varnish of linseed oil alkyd resin. Preferably, the non aqueous continuous phase further includes 0.1 to 4 wt % of a surface tension modifier. Preferably, the non aqueous phase includes 0.1 to 4 wt % fumed silica with grafted polysiloxane groups. Preferably, the organic non-fluorescent pigment is flushed in non-ionic surfactants having an HLB of 4 to 13. Preferably, the non aqueous phase includes 1 to 8 wt % nonyl phenoxy polyoxyethylene alcohol and may further include 5 to 30 wt % polypropylene glycol. Preferably, the non aqueous phase is selected from a mixture of 10 to 30 wt % polypropylene glycol and 70 to 90 wt % stearyl polyoxypropylene ether, and a mixture of 10 to 30 wt % polypropylene glycol and 70 to 90 wt % polyoxypropylene (10) cetyl ether; polyoxypropylene stearyl ether being the emollient solvent. Preferably, the non aqueous phase includes trace to 10 wt % linseed oil alkyd resin and may also include 0.2 to 1 wt % coupling agent. The ink formulations of the instant invention have low environmental sensitivity due to small variation of the viscosity in the operating temperature range of 5 to 45°C and the low hygroscopicity of the solvents. The present invention provides for the inclusion of an emollient solvent in the ink formulation. Use of this type of solvent has been found to be compatible with the pigments used to produce the ink, provides low toxicity, ease of fabrication of the ink, is inert to materials in the inking system and provides a non-drying ink. Another advantage to the inclusion of an emollient solvent is that it is non-volatile and consequently results in the inking pad not drying. Various preferred features and embodiments of the present invention will now be described by way of non-limiting example. The formulations of the instant invention provide inks with improved print quality, are inert to materials used in a printer such as inker foams and rubber, have low tack, good shelf life stability, and good flow through porous foam materials. It has been found that the inks of the instant invention have an acceptable shelf life. The aged samples show no settling after two weeks of accelerated testing. The aging of the inks by temperature shock shows no settling for the inks during two weeks of accelerated testing that simulated one year of aging by varying the temperature between 70°C to -20°C, every four hours of the working day. The dual inker foam described above that is used for making the print pad in high speed flat bed systems is made of a polychloroprene foam bottom layer. The top layer is made of polyethylene sintered foam. The rubber used in the print head is made of polybutadiene acrylonitrile rubber, which is plasticized with dibutyl phthalate. The solvents used in the instant ink formulations are inert to all these materials. The print head should be usable for ten million prints, or ten years, and the pad materials should be compatible with the inks for six months and non drying in an open environment. The non aqueous pigment dispersion used in the ink formulation is stabilized by using easily dispersible non fluorescent organic pigments predispersed in a rosin ester carrier. The rosin ester dispersants are preferable because of the wide range of compatibility with solvents and resins. The non-fluorescent pigments also can be predispersed in a non-ionic surfactant such as oleyl alcohol ethoxylate and the like. Preferably, the non-ionic surfactant has an HLB (hydrophilic lipophilic balance) value from 4-13. In one embodiment, the non fluorescent pigments are mixed with red fluorescent pigments in order to obtain red fluorescent inks. The solvent system makes up 40 to 90 wt % of the formulation and is of the emollient solvent type. The solvent system can be composed of 95 to 99 wt % polyoxypropylene stearyl ether (an emollient solvent) and 1 to 5wt% of other additives such as nonyl phenoxy polyoxyethylene alcohol. All percentages in this disclosure and the accompanying claims are in weight percent, Other solvents that can be used are castor oil, polyoxypropylene (10) cetyl ether, soya bean oil, oleic acid or mixtures of solvents such as 70 wt % stearyl polyoxypropylene ether and 30 wt % polypropylene glycol. The pigment dispersion can be further stabilized with 0.2 to 1 wt % of a coupling agent such as neoalkoxy titanate and 1 to 5 wt % emulsifiers such as nonyl phenoxy polyethoxylated alcohols, which emulsifiers have an HLB value from 2 to 16. The inks of the formulation may have visual red and non red colour of acceptable purity, such as blue, black and green and red fluorescence that yields a high signal. The solvent system is inert to the materials used in the printer, such as inker foams, print elements, pumps, tubing, print pads, and the like. The formulation of the instant invention involves unique color combinations based on mixtures of pigments such as the phthalocyanines and red fluorescent organic pigments and results in strong non red colors with high purity and a red fluorescent portion with high fluorescent signal. The selection of the phthalocyanines is based also on their dichroic properties. They reflect highly in the red region of the spectrum where the transmitted color is much greener. Non fluorescent organic pigments such as phthalocyanines are used in different forms such as powder or chips or predispersed pigments in rosin esters, pigments flushed with added rosin ester and soy bean oil or pigments flushed with non-ionic surfactants such as oleyl alcohol ethoxylates, the non-ionic surfactants representing 6 to 10 wt % of the formulation. The organic fluorescent pigments are solid solutions of fluorescent dyes in friable organic resins of triazine toluene sulfonamide/formaldehyde resin dispersed in an alkyd resin varnish of linseed oil alkyd resin. For example, organic resins such as triazine para formaldehyde and aryl sulfanomide which are dispersed in drying type alkyd vehicles of linseed oil alkyd and alkyd varnish manufactured and available from Lawter Company. The average particle size of the pigments, non fluorescent and fluorescent, is between 0.2 and 0.4 µm for at least 98 wt % of the non fluorescent and between 0.1 to 0.5 µm for at least 98 wt % of the fluorescent pigments. Because of the larger size of the pigments, the collision probability followed by quenching is less probable than in a molecular solution. This results in the ability to achieve blue visual color with red fluorescence. Dispersed pigments can be diluted with a mixture of solvents composed of: polyoxypropylene stearyl ether 15-60 wt %, low molecular weight polypropylene glycol 5 to 30 wt %, polyoxyethylene oleyl ether 5 to 20 wt %, and optionally emulsifiers such as nonyi phenoxypolyoxy ethylene alcohol with a hydrophilic lipophilic balance (HLB) from 4 to 13, 1 to 8 wt %, and optionally a coupling agent for the dispersion stabilization such as titanate polyalkoxy complex (neopentyl diallyl) oxy, tri (dioctyl) pyro-phosphatotitanate, 0.3 to 0.5 wt %. Another component that may be included as an additive to the ink formulations is fumed silica with grafted polysiloxane groups. This additive controls the thixotropy of the ink, reduces surface tension and flattens the variation of the viscosity at different temperatures. At the same time, it reduces the hygroscopicity of the ink. The present invention provides a new class of inks that are compatible with and inert to the polymeric materials used in contemporary printers. Examples of such inks are as follows: General Composition Ingredients Weight Percent 1. Non fluorescent organic pigments (≈ 33 wt %) predispersed in a rosin ester vehicle (≈ 67 wt %) and, optionally pigments, flushed in a non ionic surfactant such as oleylpolyoxy ethylene ether and fatty acid ester C12 to C14: 1-10% Example of non fluorescent organic pigments are: a) C.I. Pigment Blue 15.1 and Blue 15.3 b) RED LAKE C (Pigment Red 53:1) c) Pigment Red C.I.#144 d) PERMANENT RED 2B (Pigment Red 48 CI 144) e) LITHOL RED (Pigment Red 49:1) f) Pigment Red 52:1 g) Pigment Yellow C.I. #110 h) Pigment Brown C.I. #23 i) Pigment Green C.I. #7 j) Pigment Black C.I. #7 2. Fluorescent pigments made of solid solutions of fluorescent dyes (≈ 20 wt %) in triazine aryl sulfonamide/paraformaldehyde resin dispersed in linseed oil alkyd or in other alkyd varnish (≈ 80 wt %) 5.0 to 30% Examples of Fluorescent dyes are: a) solvent Red 49 b) C.I. Basic Red 1 c) C.I. Basic Violet 11.1 d) ALBERTA YELLOW e) POTOMAC YELLOW 3. Non aqueous continuous phase 40 to 90% Emollient solvent: a) polyoxypropylene stearyl ether or b) polyoxypropylene (10) cetyl ether c) Oleic acid d) Castor oil e) Soy bean oil f) a mixture of 10 to 30 wt % polypropylene glycol and 70 to 90 wt % stearyl polyoxypropylene ether or 70 to 90 wt % polyoxypropylene (10) cetyl ether 4. Low polarity emulsifier (optional) nonylphenoxypolyoxyethylene alcohol HLB value 2-4.9 traces to 5% 5. Moderate polarity emulsifier(optional) with HLB value 11-16 1.0 to 5.0% 6. Surtace tension modifier (optional) 0.1 to 4.0% a) silicon glycol b) fumed silica with grafted polysiloxane groups 7. Coupling Agent (optional) titanate neoalkoxy 0.2 to 1% 8. Linseed oil alkyd trace to 10% It will be appreciated that the above are given by way of example only and one skilled in the art will recognize that other components having similar properties can be used in the practice of the invention. Example I Manufacturer wt% Pigment Blue in rosin ester Microlith Blue 4 GT Ciba Geigy 4.0 Fluorescent pigment D-536 Lawter Int. 20 Arlamol (RTM) E ICI 76 Properties Fluorescence of drawdown 35 PMU Hunter colour parameters L, 49.2 a, -5.1 b, -25.2 Viscosity at 500 sec-1 is 209 cp (x10 -3 Pa.s). The ASTM D-1309 test for settling shows a rating of 8 (perfect dispersion with no settling). Example II Red Ink - Red Fluorescence Ingredient Manufacturer wt% Pigment Red 52.1 (20 wt %) flushed in AMEROXOL (RTM) 0E5 (Oleylalcoholethoxylate) (80 wt %) Penn Color 2.0 Red Fluorescent Pigment D-536 Lawter Intl. 18.0 Solid solution of Basic Red 1 in triazine paraformaldehyde aryl sulfonamide MICROLITH (RTM) RED BRT (Pigment red C.I. 144 Predispersed in rosin ester) Ciba Geigy 1.0 MICROLITH (RTM) BROWN (Pigment brown C.I. 123) Ciba Geigy 0.5 MICROLITH (RTM) YELLOW (Pigment Yellow C.I. 110) Ciba Geigy 0.5 BLAZE ORANGE (pigment consisting of a aminoformaldehyde/sulphonamide resin and Basic violet 11:1, Basic Red 1, Alkyd resin and hydrocarbon oils) DayGlo 4.0 Igepal CO - 210 GAF 2.0 " CO 530 GAF 2.0 LICA (RTM) 38 (titanium IV neoalkanolato, tris (diisooctyl) pyrophosphate) Kenrich 0.6 TITANATE and LICA (RTM) 09 Emollient Solvent Arlamol (RTM) E ICI 44.4 Polypropylene Glycol pluracol (RTM) P-410 BASF 24.53 Fumed Silica (CABOSIL (RTM) TS-720 grafted siloxanes on fumed silica) Cabot chemical 0.47 Properties for Example II Fluorescence of drawdown 160PMU Color, Hunter parameters L=61.16 a=48.58 b=20.89 Viscosity at 15°C at 500 sec -1 462cps (x10 -3 Pa.s) " 25°C " " " " 258cps (x10 -3 Pa.s) " 45°C " " " " 96cps (x10 -3 Pa.s) Average particle size diameter 0.3µm Shelf life by ASTM procedure D-1309 Rating 10 Water absorption at 29'C, 95 wt % RH after 23 hrs gr% 1.07 wt% Yield stress 1-1.4 Pa Plastic viscosity .210 cp (x10 -3 Pa.s) Number of prints obtained by continuous printing without decrease in print intensity 500K Example III Blue Ink - Red Fluorescence Ingredient Manufacturer wt% Red Fluorescent Pigment D536 Lawter 16 PHTHALOCYANINE BLUE/0E2 (Pigment Blue 15.1 and Pigment Blue 15.2) Penn Color 4 Microlith (RTM) Blue 4GT Cibe Geigy 2 Polypropylene Glycol (Pluracol (RTM) P410) BASF 25 Nonyl phenoxy polyoxyethylene alcohol Ciba Geigy 4 Igepal CO 210 & C0530 (nonylphenoxypolyoxyethylene ethanol) 2 LICA (RTM) 38 TITANATE (titanium IV neoalkanolato, tris (diisooctyl) pyrophosphate) coupling agent Kenrich 0.3 Emollient Solvent Arlamol (RTM) E ICI 44 Linseed Oil Alkyd Lawter 4.7 Total 100.0% The above embodiments have been given by way of illustration only, and other embodiments of the instant invention will be apparent to those skilled in the art from consideration of the detailed description.

Claims: A non aqueous, fluorescent dispersion ink composition, comprising: a) 40 to 90 wt % of a non aqueous continuous phase of emollient solvent selected from stearyl polyoxypropylene ether, polyoxypropylene (10) cetyl ether, castor oil, soya bean oil and oleic acid, b) 1 to 10 wt % non fluorescent organic pigment having a size of 0.2 to 0.4 µm dispersed in rosin ester, and c) 5 to 30 wt % organic fluorescent pigment having an average particle size of 0.1 to 0.5 µm made of solid solution of fluorescent dye in triazine toluene sulfonamide/formaldehyde resin dispersed in an alkyd resin varnish of linseed oil alkyd resin. The non aqueous, fluorescent dispersion ink composition according to claim 1 wherein the non aqueous continuous phase further includes 0.1 to 4 wt %, based upon the whole ink composition, of a surface tension modifier. The non aqueous, fluorescent dispersion ink composition according to claim 2 wherein the surface tension modifier is fumed silica with grafted polysiloxane groups. The non aqueous, fluorescent ink composition according to any preceding claim wherein the non-fluorescent organic pigment is flushed in non-ionic surfactants having an HLB of 4 to 13. The non aqueous, fluorescent ink composition according to any preceding claim wherein the non aqueous phase includes 1 to 8 wt %, based upon the whole ink composition, of nonyl phenoxy polyoxyethylene alcohol. The non aqueous, fluorescent dispersion ink composition according to claim 5 wherein the non aqueous phase further includes 5 to 30 wt %, based upon the whole ink composition, of polypropylene glycol. The non aqueous, fluorescent dispersion ink according to claim 6 wherein the non aqueous phase is selected from a mixture of 10 to 30 wt % polypropylene glycol and 70 to 90 wt % stearyl polyoxypropylene ether, and a mixture of 10 to 30 wt % polypropylene glycol and 70 to 90 wt % polyoxypropylene (10) cetyl ether. The non aqueous, fluorescent dispersion ink composition according to any preceding claim wherein the stearyl polyoxypropylene ether is the emollient solvent. The non aqueous, fluorescent dispersion ink composition according to any preceding claim wherein the non aqueous continuous phase includes trace to 10 wt % based upon the whole ink composition, of linseed oil alkyd resin. The non aqueous, fluorescent dispersion ink composition according to any preceding claim further including 0.2 to 1 wt % coupling agent.

Inventors: AUSLANDER JUDITH D, AUSLANDER, JUDITH D.
Applicants: PITNEY BOWES INC, PITNEY BOWES INC.
Application year: 1993
Main classification: C09D11
IPC codes: C09D11