MXPA97007412A - Ink container for printer by it jet - Google Patents

Abstract

The present invention relates to a printer ink cartridge containing a non-felted crosslinked foam having from about 25 to 45 pores per cm (65 to about 110 pores per inch) and a compression ratio of from about 1.5 to about 6.

Description

INK CONTAINER FOR INK JET PRINTER Technical Field The present invention relates to ink cartridges that are used in inkjet printers. Particularly, it refers to containers that contain and feed the ink in those cartridges during the printing process. BACKGROUND OF THE INVENTION Ink jet heads (or ink jet cartridges) are well known in the art. They provide the means by which an ink jet printer contains and doses the appropriate amount of ink, when needed, to ensure a clear, stain-free print. Such cartridges usually consist of an energy generating portion that forms droplets of ink and an ink tank that supplies ink to the energy generating portion. Generally, in such ink cartridges, the ink is absorbed and held in place by a compressed porous material and enclosed in an ink tank. The ink contained by the porous material is ejected by the capillary force of a nozzle as required in the ejection portion of ink from the head by ink jet. Polyurethane foams are the best container materials known for use in inkjet cartridges. US Pat. No. 4,306,245 to Kasugayama et al., Issued December 15, 1981, discloses a specific use range of the ink absorbing material in an ink jet recording apparatus. In addition, United States Patent 4,790,409 to Deaver, issued December 13, 1989, and United States Patent 4,824,887 to Aycock et al., Issued April 25, 1989 teaches the manufacture of a commercial foam in a size suitable for use in a cartridge, as well as a process to rinse the non-volatile matter contained in that material. The presence of non-volatile materials (also known as non-volatile residues, or NVR) in the foam container can cause significant problems in the printing process. Typically, the foam used for the ink supply in an ink jet cartridge contains nonvolatile residue levels in the range of from about 0.5% to more than 3% by weight of the foam. This residue consists of low molecular weight urethanes resulting from the chain termination during the formation of the foam and the degradation of the urethane linkages during the manufacture of the foam, as well as remnants of the surfactant used as an ingredient in the foam formulation. During the use of the printer, such residues can be deposited on the plate containing the nozzles, causing obstruction and other operational faults. A typical ink container of the prior art could comprise a polyether urethane foam, having a pore size of 70 pores per inch (ppi), which are crosslinked to obtain open cells. Then, the material is felted by applying heat and compression in order to provide the foam with its containment and ink dosing capabilities by reducing its volume to between 1/3 and 1/6 of the non-felted volume. After this, the felted foam is cut into individual pieces to be placed in the ink container. However, the felting process also results in high levels of unwanted, non-volatile residues in the foam. It is possible to clean the non-volatile residues of the foam, but this adds expensive and extra steps to the manufacturing process. An example of such a procedure is found in Heffernan US Pat. No. 4,824,487, issued April 25, 1989, which discloses a specific solvent process for removing foam residues. Another way to minimize non-volatile waste is disclosed in the co-pending, commonly assigned application, US Series No.

No. 438,585, filed May 18, 1995, which discloses a method for felting open cell foams under conditions of reduced humidity in order to provide minimized waste of low volatile materials. Although these methods are effective in achieving their proposed purposeIt would be useful to be able to minimize non-volatile waste without having to add additional manufacturing steps or process controls. Of course, one might consider the use of non-felted foams in the ink container since it is the felting process that forms the bulk of the non-volatile waste. However, such non-felted foams tend to be too large to fit in conventional ink containers and have insufficient back pressure to effectively contain the ink. This is especially true with low viscosity inks (ie, those having a viscosity of less than about 2 centipoise). The net result is a phenomenon called runoff where the ink drips from the ink container during the printing process, causing stains and dirt on the printing apparatus. Accordingly, the purpose of the present invention is to provide foam containers for use in inkjet printer cartridges that minimize the presence of non-volatile residues while providing sufficient ink feed to the printer to print effectively without allowing runoff from ink. It has been found that this objective can be achieved by using as an ink container a cross-linked non-felted foam having a relatively small pore size (i.e., a relatively large number of pores per inch) and which is compressed at a compression ratio. specify In addition, since it eliminates the stages of felting and cleaning of waste, the present invention fulfills this objective in a very cost-effective manner. US Patent 2,961,710 to Stark, issued November 29, 1960, describes a process for producing expanded urethane foam materials, used as filters. The materials produced are cross-linked open cell foams; Non-volatile waste does not seem to be an article considered in this process. U.S. Patent 3,978,855 to McRae et al., Issued September 7, 1976, discloses a surgical bandage of open cell polyurethane foam made by compression (low heat) of one side of the foam to form small pores and then Apply a wetting agent (surfactant) to that face. United States Patent 4,454,248 to Pollock et al., Issued June 12, 1984, discloses a strong, non-elastic foam having macroscopic cells. When producing these foams, a partially solidified cellular resin softens and compresses causing the cell walls to break, forming an open cell structure. The foam is then expanded again and given its final solidification. A filler material, such as natural gas carbon black, can be added to the foam prior to the final solidification stage. US Patent Re.32, 032, to Pettingell, issued November 19, 1985, discloses a method for densifying open cell polyurethane (ie, felting) foams. In this process, hot air circulates through the foam, which is then compressed through rollers and cooled immediately. U.S. Patent 5,025,271 to Baker et al., Issued June 18, 1991, discloses thermal, conventional, inkjet print cartridges, which include a foam material such as an ink container. U.S. Patent 5,104,908 to Allred et al., Issued April 14, 1992, discloses a partially solidified polychloroprene foam that can be formed into complicated shapes for use in printing. A felting process is used to provide the final solidification to these foams. U.S. Patent 5,182,579 to Haruta et al., Issued January 26, 1993, discloses an ink tank enclosing an absorbent member for use in an inkjet printer. The patent specifically defines the required ratio between the compression ratio and the pore size of the foam. The patent teaches that compression can be achieved by felting, but can also be achieved by compressing the foam in the cartridge. The patent states that the foam should have a pore size of no more than 60 ppi and, in fact, the teachings deviate from foams having smaller pore sizes (i.e., larger pore densities). US Patent Application Serial No. 08 / 635,795 to Harshbarger and Suthar, filed April 22, 1996, discloses ink cartridges using non-felted foams, specially adapted to act as containers for high viscosity (pigmented) inks. The use of compressed foams in the cartridge is not exposed.

SUMMARY OF THE INVENTION The present invention relates to printer ink cartridges containing a non-felted crosslinked foam having from about 65 to about 110 pores per inch (preferably from about 88 to about 98 pores per inch) and a compensation ratio from about 1.5 to about 6.5, preferably from about 2 to about 4. Preferred foams for use in the present invention are urethane foams, particularly polyether polyurethane foams. The foams contain very low levels (e.g., less than about 1.5%) of non-volatile residues. Since the foam does not fellate and, in addition, only 50% (by weight) of the foam in the ink container is used at most (when compared to conventional ink cartridges), the non-volatile waste content is reduced in 50% or more on a weight basis or to an equivalent of 0.75% compared to a felted foam (basis adjusted to weight). All percentages and proportions described herein are "Xen weight" unless otherwise specified.

DETAILED DESCRIPTION OF THE INVENTION Ink cartridges are well known in the field of printers. For example, they are described in detail in U.S. Patent 5,182,579 to Haruta et al., Issued January 26, 1993, and U.S. Patent 5,025,271 to Baker et al., Issued June 18, 1991, both incorporated herein. for reference. The portion of the cartridge to which the present invention relates is the ink tank and particularly the ink container in the ink tank. This portion of the cartridge contains the ink before it conforms to droplets and is ejected onto the page in the proper pattern during the printing process. The container actually contains the ink but doing so requires a very careful balance. If the force that holds the ink in the container is too large, the ink will not be fed and the print either does not occur or is too light. If the force that holds the ink is not large enough, the ink will squeeze out of the container, staining the printer and shortening the life of the printer cartridge. Generally, in the prior art, the material used in the formation of the ink container (ink absorbing members) is a crosslinked felted foam.

However, as discussed above, the felting process results in too high a level of non-volatile residues for effective use of the printer. The present invention solves this problem by providing an ink container that effectively contains the ink and dispenses it at the proper speed but, since it is not felted, does not include high levels of non-volatile residues. In the present invention, any open cell foam material conventionally used in ink containers can be used. Urethane foams and formaldehyde foams are preferred materials, polyether polyurethane foams being particularly preferred. An example of a foam that can be used in the present invention is that commercially available from Foamex, Eddystone, Pennsylvania and is a cross-linked, non-felted, polyether polyurethane foam having a pore size of about 93 ppi. The ink absorbing member is preferably made of polyurethane foam of the polyether type in the form of a porous, elastic, polymeric material having continuous foam cells. The ink absorbing member can be prepared by conducting the reaction of, for example, polyether polyols and toluene diisocyanate as starting materials together with an additive such as a silicon based surfactant and catalysts, according to conventional processes , thereby forming the cell reaction product having the desired porosity and density. The resulting foam is then crosslinked (i.e., an explosion of gas is used to extinguish the cell faces) by making an open cell foam. The foam can then be cut into the desired shape and size for use in the present invention. There may be impurities, such as unreacted starting materials, in the foam produced; These can be partially removed by rinsthe foam with organic polar solvents that are not able to react with the absorbent material. However, since the foam is not subject to a feltstep, the level of non-volatile residues in the foam material is relatively low and does not normally require a separate removal step for the purpose of beused in the present invention. The ink-absorbmaterials used in the present invention generally have low levels of non-volatile residues, typically not greater than about 1.5% non-volatile residues, and preferably not greater than about 1.0% non-volatile residues. The amount and identity of the surfactant used in the synthesis reaction, as well as the level of water used and the type and degree of mechanical mixused, affect the pore size and density of the finished foam product. In this way, the reaction conditions can be manipulated, as they are recognized by one of ordinary skill in the art, to form a foam havoptimized conditions for use in the present invention. In contrast to the ink container materials used in the prior art, the foams used in the present invention contain a relatively high pore density (ie, a relatively small pore size). Conventional thinkwas that such small pore diameter, high pore density foams would provide a level of capillary action that would be high enough to contain the ink tightly and not feed the ink effectively to the printhead. See, for example, U.S. Patent 5,182,579 to Haruta et al., Issued January 26, 1993, which states that the pore density in the foams of an ink container should not be greater than 60 ppi and preferably are significantly less than that (that is, 35-40 ppi). It has surprisy been found that high pore densities, when used in a foam hava specifically defined compression ratio, provide sufficient capillary action to prevent the ink from runnoff although they do not provide so much capillary action for the Ink is not fed effectively into the printhead. The foams used in the present invention have a pore density of from about 65 to about 110 pores per inch (ppi), preferably from about 75 to about 102 ppi, more preferably from about 84 to about 102 ppi, more preferably from about 88. to about 98 ppi, and more preferably about 93 ppi. Preferred foams have a pore density of more than about 90 ppi and up to about 98 ppi. If the pore density of the foam is too low, it provides insufficient back pressure and ink runoff occurs. If the pore density is too high, the foam provides too much back pressure and there is insufficient ink feed Of course, the foams must be molded so that the size of the cells is essentially uniform throughout the foam material so that the ink feed is uniform at all points in the container. The densities of the foams themselves generally range from about .015 to about .040 g / cm.sup.3, preferably from about .026 to about .038 g / cm.sup.3. The piece of foam used for the container is cut larger than the size of the ink tank in the body of the cartridge in which it is enclosed. As a result, the act of placthe foam on the body of the cartridge acts to compress the foam. When it is in place, the foam container must fill the ink tank and the cartridge body completely and without corrugation or channel otherwise, the flow of the ink out of the container will not be uniform. One method to define the compression of the ink container is the compression ratio (R) which is the ratio of the apparent volume of the foam before compression (Vi) and the apparent volume of the foam after compression (V2). The compression ratio (R) is, therefore, equal to V? / V2. When used in the present invention, the materials of the foam container must have a compression ratio in the cartridge body of from about 1.5 to about 6.5, preferably from about 2.0 to about 4.0, more preferably from about 2.4 to about 3.6. When structuring the ink cartridges of the present invention, the viscosity and surface tension of the ink to be used must be taken into consideration. The viscosity of ink used in inkjet printers typically ranges from about 1 cps to about 5 cps. Inks based on dyes tend to be less viscous than pigment inks. Colored inks tend to be less viscous than black ink. The viscosity of the color ink is typically in the range of from about 1.1 cps to about 2.5 cps and the viscosity of the black ink is typically from about 1.3 cps to about 4.5 cps. The inks typically have a surface tension of between about 30 and about 65 dynes / cm, with the color inks ranging from about 30 to about 45 dynes / cm and the black inks being from about 45 to about 65 dynes / cm. . The surface tension and viscosity of the ink to be used can have an effect on the optimum pore size and the compression ratio to be used in the foam container with that ink. For example, an ink having a higher viscosity does not need to be held by the container so tightly, which means that the optimum foam material for the container can have a larger pore size or less compression. Conversely, a less viscous ink may require more tight containment by the ink container in order to prevent runoff and the optimum foam material will be structured to provide such containment. The optimum characteristics of the foam container material for use with ink of a particular viscosity can be readily determined by one of ordinary skill in the art. As a general guideline, the ink tanks in the cartridge bodies of the ink jet printer typically have a volume in the range of from about 15 cm3 for color inks to about 60 cm3 for monochrome inks. However, these sizes can vary widely depending on the particular application involved and are limited only by the design of the printer. The dimensions of the foam container material used with black inks are typically in the range of about 160 cm3, preferably about 64 x 42 x 59 mm. The size of the foam container material used with color inks is typically in the range of about 55 cm3, preferably about 22 x 42 x 59 mm. The present invention is particularly useful for inks based on dyeing (although it can be used - Í l ¬ with any type of ink), especially those that have viscosities below about 1.5 centipoise. It is especially surprising that non-felted foams can contain such low viscosity inks effectively. The following examples attempt to illustrate the ink containers of the present invention, including how to make and use them. These examples are intended to be illustrative only and are not intended to limit the scope of the invention in any way. EXAMPLE 1 For a black ink having a viscosity of about 1.3 centipoise at 25 ° C and a surface tension of about 50 dynes / cm, the following pore sizes and compression ratios, as the foam (polyether polyurethane foam) is placed in the container, provide a cartridge that prints satisfactorily, does not exhibit run-off or overflow and provides an acceptable print life . Pore size = 88 - 98 ppi, non-felted foam density = .026 - .038 g / cm3 foam size / volume = 64 x 42 x 59 mm = 159 cm3 container size / volume = 51 x 38 x 33 mm = 64 cm3 compression ratio = 2.48 (159/64) EXAMPLE 2 For a color ink having a viscosity of approximately 1.1 centipoise at 25 ° C and a surface tension of approximately 35 dynes / cm, the following pore sizes and compression ratios, as the foam (polyether polyurethane foam) is placed in the container, provide a cartridge that prints satisfactorily, does not exhibit runoff or overflow and provides an acceptable print life. Pore size = 88 - 98 ppi, non-felted foam density = 1.6 - 2.4 lbs / ft3 (.026 - .038 g / cm3) foam size / volume = 22 x 42 x 59 mm = 55 cm3 size / container volume = 10 x 38 x 48 mm = 18 cm3 compression ratio = 3.1 (55/18) EXAMPLE 3 For a black ink having a viscosity of about 4.5 centipoise at 25 ° C and a surface tension of about 55 dynes / cm, the following pore sizes and compression ratios, as the foam (polyether polyurethane foam) is placed in the container, provide a cartridge that prints satisfactorily, does not exhibit run-off or overflow and provides a life of printing acceptable. Pore size = 65 - 80 ppi, non-felted foam density = (.026 - .038 g / cm3) foam size / volume = 64 x 42 x 59 mm = 159 cm3 container size / volume = 51 x 38 x 33 mm = 64 cm3 compression ratio = 2.48 (159/64)

Claims (1)

NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and therefore the property described in the following claims is claimed as property. 1. A printer ink cartridge containing a non-felted crosslinked foam having from about 65 to about 110 pores per inch and a compression ratio of from about 1.5 to about 6.5. 2. The ink cartridge according to the claim 1, characterized in that the foam is selected from urethane foams and formaldehyde foams. 3. The ink cartridge according to the claim 2, characterized in that the foam contains no more than about 1.5% non-volatile residues. 4. The ink cartridge according to the claim 3, characterized in that it is molded for use with an ink having a viscosity of about 1 cps to about 5 cps. 5. The ink cartridge according to the claim 4, characterized in that the foams have from about 84 to about 102 pores per inch. The ink cartridge according to claim 5, characterized in that the foam fills the body of the ink tank of the cartridge completely without corrugation or grooving. 7. The ink cartridge according to the claim 6, characterized in that the foam has a compression ratio of from about 2.0 to about 4.0. 8. The ink cartridge according to the claim 7, characterized in that the foam contains no more than about 1.0% non-volatile residues. 9. The ink cartridge according to the claim 7, characterized in that the foam has from about 88 to about 98 pores per inch. The ink cartridge according to claim 9, characterized in that the foam is a polyether polyurethane foam. The ink cartridge according to claim 10, characterized in that the foam has a density of from about .015 to about .040 g / cm3. The ink cartridge according to claim 1, characterized in that the foam has from about 88 to about 98 pores per inch. The ink cartridge according to claim 1, characterized in that the foam is a polyether polyurethane foam. The ink cartridge according to claim 1, characterized in that the foam has a density of from about .015 to about .040 g / cm3. 15. The ink cartridge according to claim 1, characterized in that it additionally comprises a dye-based ink that is releasably contained within said non-felted foam. 16. The ink cartridge according to claim 14, characterized in that said ink has a viscosity of less than about

1.5 centipoise.