Patent Application
20070003348
1. Field of Invention
The present invention relates printer ribbons and print ribbon inks.
2. Related Art
Line matrix and other types of impact printing systems utilize print ribbons to transfer images, such as letters and characters, onto media or paper. The print ribbons hold ink so that hammers striking the print ribbon transfer corresponding ink images to the paper. However, print ribbons have a finite life, as continued impact of the hammers may wear down the ribbon fabrics so that it no longer can effectively retain ink or even wear a hole through the ribbon. Also, the ink may have a tendency to oxidize and dry out once it is in the print ribbon. This could cause the decrease of ribbon shelf life, and the result is the inefficient use of the inked ribbon. The costs are therefore increased due to the need for replacing or re-inking the ink ribbons more frequently.
Current printer ribbons are formed from different materials and fabrics of different thicknesses. The type of ribbon depends on various factors, such as price and intended use. Also, different ribbons have different types of inks and ink contents for optimal performance. For example, if too much ink is placed on a thin ribbon, the ink may smear on the paper. However, the same amount of ink may be ideal with a thicker, more absorbent ribbon fabric material. Thus, there are many factors in determining an optimal ribbon and the type and amount of ink to use for the ribbon.
Therefore, there is a need for a line matrix printer ribbon that overcomes the performance disadvantages discussed above.
According to one aspect of the invention, a print ribbon uses a 5-mil 230 threads per square inch fabric constructed with 70 denier warp (yarn) and 70 denier filling (yarn). The thickness can range from 5.0 to 5.7 mil and the threads per square inch can range from 210 to 250 in one embodiment. Such a thick ribbon can withstand the high forces delivered by the impact printing mechanism, resulting in a longer-lasting ribbon. In one embodiment, the fabric is textured, thereby enabling the ribbon to hold more ink and provide extended character yield, i.e., longer ribbon life.
According to another embodiment, printer ink of approximately 18% to 20% (e.g., 19%) concentration [(weight of inked ribbon minus weight of un-inked ribbon)/(weight of inked ribbon)], such as in the printer ribbon of the present invention. At this concentration, initial density performance and initial barcode print quality are both optimized. Furthermore, using this concentration with the ribbon of the present invention, the ink load is higher than with conventional generic fiber ribbons.
In one embodiment, the pigment content, such as carbon black, is between 0% and 15%, and the ink is mixed with a liquid pigment for easier manufacturing. In another embodiment, the pigment content is around 2.5%, e.g., weight percentage of carbon black in the ink.
The printer ribbon and/or ink of the present invention provides numerous performance advantages, such as increased life, higher ink retention, good print quality, less ink migration to print mechanisms, less print dot smearing, long shelf life, better printout light fastness, and improved fabric ink ability.
Embodiments of the present invention and their advantages are best understood by referring to the detailed description that follows.
It should be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the figures.
According to one embodiment of the present invention, a print ribbon is approximately 5-mil thick (e.g., 5.0 mil to 5.7 mil) and made of a fabric of 70 denier warp (yarn) and 70 denier filling (yarn) (70/70 denier), where denier is a unit of weight for describing the size of filament yarn. For example, the lower the number, the lighter (or finer) the yarn, and the higher the number, the heavier (or thicker) the yarn. In particular, denier is one unit of measure for the linear mass density of fibers. Denier is defined as the mass in grams per 9000 meters. An example of a denier is 1 denier equals 1 gram per 9000 meters equals 0.05 grams per 450 meters.
The print ribbon contains approximately 210 to 250 (e.g., 230) threads per square inch in one embodiment. The print ribbon construction enables it to withstand the high force delivered by the impact printing mechanism.
In another embodiment, the 70/70 denier fabric is textured, where textured styles use a flat warp and a textured filling. Texturizing is the process of crimping the individual filaments to provide increased interstices in which ink can reside.
According to another aspect of the invention, the print ribbon uses specific inks and concentrations. In one embodiment, the ink has a high concentration of oil-based color dye chemicals, such as mainly blue, purple, orange, and/or other dyes to blend with the nigrosine to increase the ink color strength. The result is longer printing yield and darker image tone.
Ink oxidation, which reduces shelf life, is caused by the reaction between unsaturated fatty acid moieties (e.g., Oleic acid) and oxygen. The rate of oxidation of these fatty acids increases with the degree of un-saturation, i.e., more available reactive sites. The combination of high dye concentration and adequate ink manufacturing process greatly reduces the total amount of the un-saturated fatty acids, resulting in less oxidation and longer shelf life.
The ink shows a Newtonian behavior throughout the operational inking range (e.g., 5 to 15 rpm). Newtonian fluid represents that the viscosity of the fluid remains constant as the shear rate is varied, i.e., the ink has better ink ability. Optimal ribbon ink concentration helps to eliminate ink smearing and free flowing without sacrificing ribbon life performance.
Pigment in oil-based inks serves several functional purposes. Pigment is typically added to the ink in solid form, carbon black powder, or liquid form, which the carbon black has been pre-mixed in an oil suspension, so-called dispersion. Dispersing the carbon black particulates in ink requires high shear energy. This typically is done by a ball milling process. Therefore, carbon black liquid dispersions are used to achieve the good results without applying high shear energy during the ink-making process.
An ideal dispersion of carbon black would be the condition in which all agglomerates are broken down into primary aggregates, where each primary aggregate is separated from every other aggregate and completely covered by vehicle. Primary aggregates are the characteristic units of carbon black and are not broken down further under normal dispersion conditions. In this stage, each separated primary aggregate must adsorb sufficient vehicle to cover its surface completely thus stabilizing the dispersion. A well-prepared carbon black dispersion and lower pigment content will help to prevent re-agglomeration or settling. However, the minimum loading levels of pigments are needed in order to achieve reasonable opacity and IR readability at very thin printed thickness.
In general, inks are primarily composed of vehicle, colorants, and supplementary additives. The function of the vehicle, which can be a fatty acid such as an oleic acid, is to act as a carrier and as a binder to affix the colorants and pigments to the printed surface. The nature of the vehicle may determine in large measure the tack and flow characterization including viscosity. Colorants include pigment and dyes, such as carbon black. Pigments are finely divided solid materials that give ink color and opacity or transparency. Dyes are soluble in the material they are used in and are commonly used in line matrix printer inks. Supplementary additives make up only few percent of total inks, but may have tremendous effects of the performance of the ink such as anti-oxidant, waxes, surfactants, and resins. Supplementary additives in the way of dyes can be such as induline, azine, methyl violet, or nigrosine, or other dyes which can adjust viscosity and flow properties.
Basically, the manufacture of inks is known and is essentially just a mixing process. Beforehand, a vehicle with dyes (e.g., dye oleate), pigment dispersion, and additives have to be prepared separately. The vehicle or carrier can include, for example, organic acids such as aliphatic carboxylic acids such as lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, adipic acid, citric acid and ascorbic acid; aromatic carboxylic acids such as benzoic acid, salicylic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthoic acid, gallic acid and tannic acid; and sulfonic acids such as dodecyl sulfonic acid and alkylbenzenesulfonic acid.
Dispersion of pigments into vehicles may use mixing and milling techniques. In some cases, pigments can be purchased or manufactured in a liquid suspension form which makes the ink manufacturing process much easier. Various oily substances can also be used as the dissolution medium for the dye or the dispersion medium for pigment. Examples of the oily substances include among others: vegetable oils such as rapeseed oil, castor oil and soybean oil; animal oils such as beef foot oil; higher fatty acids such as isostearic acid and oleic acid and mixtures thereof.
In one embodiment, the 70/70 denier print ribbon, with textured fabric and 230-thread count, uses an ink concentration of approximately 19%, resulting in an ink load of approximately 0.46 grams per yardage. The ink concentration can range from 18% to 20%, and the ink load can range from 0.44 to 0.49 grams per yardage in different embodiments. Different ink concentrations were used to measure Macbeth density as a function of the number of characters printed and barcode print quality (ANSI Grade) as a function of number of labels printed.
As seen in
As sees from Table 1, at optimal ink concentrations, the 70/70 denier textured ribbon has the highest ink load at 0.46 (grams per yardage), as compared with 0.39 for a generic 5-mil ribbon and 0.35 for a generic 4-mil ribbon.
Ink viscosity, in one embodiment, is between 2000 centipoises (cps) and 3400 cps. Viscosity for an ink is a measure of the ink's thickness. Low viscosity printer ink loses shear strength at high temperatures even when disposed on a carrier such as a printer ink ribbon. Within impact printing applications such as those using an ink ribbon, this can result in ink smearing and ink migration, which lowers the print quality. On the other hand, the viscosity of an ink that performs well at elevated temperatures becomes excessively high as to its viscosity at lower temperatures. Excessively high ink viscosity exhibits other printing problems. The problems can include increased difficulty of the inking process, poor transfer into and out of the printer ribbon, resistance to pumping through small tubing, and a very slow transfer through foam materials. Table 2 below shows how low and high ink viscosity affects, in general, various ink or print parameters.
Viscosity can be adjusted in various ways as each ingredient contributes to the final viscosity. In addition to the vehicle or carrier, other ingredients can be added which can further adjust the viscosity. Examples of viscosity-adjusting agents include among others mineral oils, such as motor oil, and synthetic oils, such as olefin-polymerized oil (e.g. ethylene hydrocarbon oil, butylene hydrocarbon oil, and the like), diester oils (e.g. dioctyl phthalate, dioctyl sebacate, di(1-ethylpropyl) sebacate, dioctyl azelate, dioctyl adipate, and the like), and silicone oils (e.g. linear dimethyl polysiloxane having a low viscosity, and the like). Mixtures of two or more kinds can also be used.
In one embodiment, color strength or absorbance is between approximately 1.5 to 2.0.
The solution is prepared with 0.1 grams of ink diluted by 50-ml mixture of methanol and chloroform and then a 2-mil mixture is further diluted by 50-mil methanol. Samples are scanned by spectro-photometers. As seen, the ink color strength is higher (1.853) for the 70/70 denier ribbon than for other conventional ribbons.
In one embodiment, the pigment content of the ink is approximately 0% to 15%. Such a low pigment ink has advantages over high pigment inks. Newtonian fluid flow represents that the fluid's viscosity remains constant as the shear rate is varied. In general, the operation rotation speed of the ribbon inking machine is around 5 to 15 rpm. Non-Newtonian fluid will cause inking difficulty for variations of rotation speed during the inking process. High viscosity, high dye concentration, and low pigment ink has better ink ability (Newtonian fluid), less pigment content (no pigment settling problem), and still meets IR requirements (minimum 35 labels per yardage).
Thus, the inks can be made in a conventional manner by thoroughly mixing together the ingredients in any convenient manner known to those skilled in the art. The resulting mixture can be adjusted for the desired viscosity as described herein and applied to the ribbon to the desired fabric thickness in any convenient manner.
Having thus described embodiments of the present invention, persons skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the invention.
The present invention claims priority to U.S. Provisional Application Ser. No. 60/692,195, filed Jun. 17, 2005, and which is incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60692195 | Jun 2005 | US |
