Incremental printing of symbolic information – Ink jet – Fluid or fluid source handling means
Reexamination Certificate
2000-01-28
2003-11-04
Nguyen, Judy (Department: 2853)
Incremental printing of symbolic information
Ink jet
Fluid or fluid source handling means
C347S096000, C106S031130
Reexamination Certificate
active
06641257
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This application relates to the field of inks and more particularly to the field of inks for ink jet printers.
2. Description of Related Art
Ink jet printing is a form of printing where very fine stable liquid droplets are discharged from an orifice and deposited onto a substrate. Use of three or more colored inks enables the user to produce full color images, text, or graphics. The ink jet printing industry is growing in parallel with the explosive development of other computer technology. Ink jet printers provide low cost, low maintenance, high speed, and high color printing quality for a wide variety of applications, from industrial labeling to office printing. However, although ink jet printing is used in more and more applications, problems with fading of the printed image when exposed to light continue plague the technology.
The printed colorants used in many ink jet inks fade when exposed to electromagnetic radiation in range of 290 nm to 1200 nm, a range present in sunlight and artificial light. This fading degrades image quality, and in many applications, such color fading is unacceptable. Accordingly, for an ink jet printer to be useful for a range of printing applications, ink jet inks and media are needed that are less susceptible to fading.
Ink colorants undergo photodecomposition via a number of oxidation and reduction mechanisms including but not limited to: electron ejection from the colorant, reaction with ground state or excited singlet state oxygen, and electron or hydrogen abstraction to form radical intermediates. While direct bond cleavage can occur, the spectral energies involved suggest that this is not a primary mechanism of photolysis of the colorants.
Which of the aforementioned mechanisms contribute to a colorant's photodecomposition depends on many factors. First, the chemical properties of the chosen colorant are critical to its lightfastness. Generally, a more chemically stable colorant fades less upon exposure to sunlight or artificial light. Most colorants are believed to be extremely resistant to photolysis in vacuo. This belief emphasizes the relationship of the chemical environment of the printed colorant to its lightfastness.
The substrate on which the printed ink is deposited is a part of the colorant's chemical environment, and thus can have a significant effect on lightfastness of the print. For example, cotton, rayon, and polyesters, commonly used in paper and other substrates, contain carbonyl groups. Carbonyl groups absorb light of wavelengths greater than 300 nm, such as are present in sunlight. The excitation of carbonyl groups can lead to reactive species capable of causing colorant fading. The physical characteristics of the substrate can also affect the printed colorant's environment. The nature of the substrate may determine, in part, how much of the colorant is held on the surface. The porosity of the substrate can also affect the penetration of moisture and gases into the colorant.
The components of the ink can also have an effect on the colorant's chemical environment, and can thus play a role in the lightfastness of the final print. The ink's humectants, pH buffers, biocides, other additives, and even colorless photodecomposed products can catalyze the photodecomposition of the printed colorant. Likewise, the components of other inks, including the colorant(s), that mix with the ink on the substrate can contribute to the fading of the print. A notable example of catalytic fading is found in phthalocyanine dyes that catalyze the fading of certain magenta dyes. For this reason, printed blacks made by combining cyan, magenta, and yellow inks tend to fade to green, and printed blues made with cyan and magenta tend to fade to cyan.
Other various environmental factors can also affect the fading rates of printed colors. These include but are not limited to temperature, humidity, and pollutants/gaseous reactants such as O
2
, S
2
, and NO
2
. Also of great importance to fading rate is the spectral distribution of the radiation incident on the printed colorant.
All of the factors that affect colorant fading are interdependent to varying degrees, so it is difficult to develop an ink suitable for all general substrates or a substrate suitable for all general ink jet inks. One mechanism that has been shown to provide general protection against most mechanisms of photodegradation is aggregation of the colorant molecules. The aggregation of colorant molecules tends to reduce catalytic fading by reducing the surface area of the colorant per unit of mass that is subject to oxygen and light exposure. This point is clearly demonstrated with pigmented colorants. However, pigmented colorants tend to clog the small orifices used in ink jet printers.
Accordingly, there is a need to identify light-stable dyes suitable for ink jet printing that can be used independently or in combination and be resistant to color fading under typical environmental conditions.
SUMMARY OF THE INVENTION
The present invention provides a set of aqueous ink jet inks with improved lightfastness.
It is an object of the invention to provide an ink jet ink set with improved lightfastness suitable for thermal, piezo, or continuous ink jet printing which comprises an aqueous vehicle, a colorant, a light stabilizer to protect the colorant in the ink during exposure to light, and optionally a humectant and/or a biocide.
It is an object of the present invention to provide a combination of an ink jet ink with improved lightfastness and a substrate that reinforces the lightfastness of the ink jet ink.
It is an object of the invention to provide a combination of an ink jet ink with a printing medium that is substantially carbonyl-free.
It is an object of the invention to provide an ink jet ink set substantially stable to light or UV radiation.
Thus, in one aspect, the systems and methods described herein relate to an ink suitable for ink jet printing, comprising an aqueous vehicle, a dye having an excitation energy, and a stabilizer capable of absorbing energy of wavelengths similar to the excitation energy of the dye. In certain embodiments, the dye is substantially lightfast. In certain embodiments, the dye is a phthalocyanine dye. In certain embodiments, the dye is an azo dye. In certain embodiments, the ink includes two magenta dyes, of which one dye includes a copper complex.
In certain embodiments, the ink further includes a biocide, whereby the dye is substantially lightfast in the presence of the biocide. The biocide may be selected from 1,2-benzisothiazolin-3-one, 2-methyl-4,5-trimethylene-4-isothiazolin-3-one, 1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane, and 6-acetoxy-2,4-dimethyl-1,3-dioxane.
In certain embodiments, the ink further includes a humectant, whereby fading of the dye is not promoted in the presence of the humectant. The humectant may be selected from glycerin, propylene glycol, ethylene glycol, 1,5-pentanediol, di(ethylene glycol), poly(ethylene glycol)-200, poly(propylene glycol)-425, di(propylene glycol), propylene glycol, triethylene glycol, poly(ethylene glycol)-300, 2-pyrrolidone, thiodiglycol, dimethyl imidazolidinone, glycerin, acetamide, urea, N-methyl urea, N-allyl urea, ethoxylated glycerin, sorbitol, ethoxylated glucose, dimethoxyethane, diethoxyethane, ethyleneglycol diacetate, and glycinamide hydrochloride. In certain embodiments, the dye is a yellow dye and the ink is substantially free of N-methylpyrrolidone.
In certain embodiments, the ink further includes a surfactant, and wherein the dye is substantially lightfast in the presence of the surfactant. The surfactant may be selected from non-ionic surfactants, sodium decyl diphenyl oxide disulfonate, alkyloxypolyethyleneoxyethanol, and polyoxypropylene methyl diethyl ammonium chloride.
In certain embodiments, the ink includes a yellow dye and at least one light stabilizer selected from 2,2′-dihydroxy-4,4′-dimenthoxybenzophenone-5,5′-bis(sodium sulfonate), 5-benzoyl-4-hydroxy-2-methoxybenzenesul
Andreottola Michael
Doll Paul
Shi Fengying
Wnek Walter
American Ink Jet Corporation
DeVaul William
Nguyen Judy
Shah Manish
LandOfFree
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