KR19980024075A - Method of passivating cationic dyes, anionic dyes and pigment dispersions using insoluble metal salts - Google Patents

Abstract

The present invention relates to a specially prepared ink-jet paper comprising fibers containing pores filled with metal salts slightly soluble by precipitation, such as a heated ink-jet color printer such as Hewlett-Packard Company's DeskJet® printer. It is about using. Ink-jet inks containing colorants, for example dyes or pigments and, if necessary, dispersions to disperse the colorants, are printed on specially prepared paper. The dispersing force of the dispersion can be reduced by the metal salt particles deposited in the holes contained in the ink-jet paper, whereby the colorant precipitates indirectly on the paper surface when printing the ink-jet ink on the ink-jet paper. In the case of dye-containing inks, the metal salt directly precipitates the dye. As a result, ink-jet color printers can produce high-quality color images in a reliable way in which color gamut and water resistance are improved and blurring between adjacently printed colors is reduced.

Description

Method of passivating cationic dyes, anionic dyes and pigment dispersions using insoluble metal salts

TECHNICAL FIELD The present invention relates to ink-jet printing, and more particularly to ink-jet printing paper wherein the pulp fibers are modified by filling a slightly soluble precipitated metal salt.

Commercially available heated ink-jet color printers, such as the DeskJet printers available from Hewlett-Packard Company, obtain a color spectrum by combining yellow, magenta and indigo inks at various ratios. The color spectrum obtained by combining the colored ink sets is referred to as the color gamut of the ink set. The color gamut is always part of the theoretically possible color spectrum.

One reason that theoretically possible spectra are not obtained is that the intensity of a particular ink in the ink set does not effectively grow beyond a certain degree when it appears on the printing medium. Thus, no color in the spectrum can be produced that requires a higher intensity than can be transferred to the printing medium. The total amount of colorant that can be transferred depends on many factors, including the colorant concentration of the ink and the movable volume of the ink. Typically, the colorant concentration of the ink cannot be arbitrarily increased to increase the strength on the paper without damaging other important aspects of the ink formulation.

Another reason for the reduced color gamut is that some ink colorants penetrate the paint medium, especially when the medium is paper. When this happens, the colorant appearance strength of the printed area is lower than expected based on the amount of colorant migrated to the printing medium surface. One way to alleviate this problem is to leave the colorant on the paper surface or, in other words, to suppress the penetration of the colorant into the paper surface.

In ink-jet ink compositions, the ink is formulated by dispersing the dye or pigment in the ink vehicle. For example, indigo inks include indigo dyes dissolved in an ink vehicle. Dye molecules used in ink-jet ink compositions are often in the form of dye salts, including dye anions and cations (eg sodium). In the case of pigment-containing colorants, the ink vehicle typically comprises a charged dispersion.

The method of inhibiting colorant penetration into the paper plane depends on the disturbance of the vehicle dispersion properties once the ink is applied to the paper. One way to stop vehicle dispersion is to evaporate the ink solvent. Alternatively, the penetration of the colorant into the paper surface can be reduced by breaking the dispersing force of the dispersion in the ink after applying the colorant. Dispersion action disruption, which acts faster than solvent evaporation, further reduces colorant penetration into the paper surface.

US Patent No. 4,694,302, entitled Reactive Ink-Jet Printing, issued to the same assignee as the present application, discloses a method of increasing the water-fastness and print quality of an ink. Doing. In this application, before or after the ink is applied to the printing medium, a reactive species that chemically connects the dye in the ink with the paper substrate is applied to the printing medium. However, this method requires two separate print heads to improve print quality.

US Patent No. 4,740,420, entitled Recording Medium for Ink-Jet Printing, and Ink Jet Recording Sheet Having a Bicomponent Cationic Recording Surface. U. S. Patent No. 4,554, 181, titled, discloses a recording medium modified by surface treatment containing soluble metal salts to promote insolubility of colorants in the ink. This method has the problem that the post-manufacturing and surface modification of the print medium is complex and expensive. In addition, this method does not require the need to reduce colorant penetration, especially into the printing medium side. Improvements in color gamut require reduced penetration.

U.S. Patent 5,126,010, entitled Ink-Jet Recording Sheet, discloses a recording sheet in which water-insoluble calcium carbonate is mixed into paper to act as a fill pigment. The paper side is further treated to allow the water-containing ink to be absorbed by the paper. This printing medium is not designed to hold the ink on the paper surface.

Therefore, there is still a need for an ink-jet printing method in which the color gamut that an ink set can reproduce is increased by conveniently and economically reducing the penetration of colorants into the medium surface.

According to the present invention, there is provided a printing method that substantially reduces ink colorant penetration into a printing medium (paper) by conveniently supplying metal salts into the pulp fiber apertures, wherein the metal salts are characterized in that the dispersing action of the ink vehicle Dissolve or discontinue use. Specifically, the ink-jet printing method includes the following steps:

(a) an ink comprising pulp fibers containing pores filled with slightly soluble precipitated metal salt particles (small enough to mechanically retain the particles, but large enough to transport ions in the ink vehicle into the holes) Providing a jet paper;

(b) one or more colorants that can be precipitated by slightly soluble precipitated metal salt particles in the ink-jet paper when (1) ink-jet ink is printed on the ink-jet paper, and (2) the colorant contains a pigment Providing at least one ink-jet ink comprising, in one case, a vehicle that contains one or more dispersions or, if the colorant contains a dye, dissolves the colorant without the dispersion; And

(c) depositing the colorant on the ink-jet paper surface by printing the ink-jet ink on the ink-jet paper surface, thereby improving color gamut and retention and reducing penetration and bleeding of the colorant.

According to the present invention, there is also provided an ink-jet paper having improved color gamut and retention in ink jet-printing, which includes pulp fibers containing pores therein. The hole is filled with precipitated metal salt particles that are slightly soluble, and the hole is small enough to hold the particles mechanically and large enough to transfer ions from the ink vehicle to the hole.

Using ink-jet paper incorporating a slightly soluble precipitated metal salt that precipitates the colorant onto the paper surface improves the color gamut and retention and reduces colorant penetration and smearing between adjacently printed colorants.

The invention described herein relates to a method and paper for use in an ink-jet color printer, in particular a heated ink-jet printer such as a Hewlett-Packard DeskJet printer. The paper allows ink-jet color printers to produce high quality spirituality by inducing colorant precipitation in ink-jet inks, thereby increasing color gamut and color preservation and reducing penetration and bleeding of printed ink-jet inks. Specifically, before placing the paper sheet underneath, the paper contains a metal salt precipitated in the pores of the paper pulp fibers. Metal salts cause colorant precipitation in ink-jet inks by destroying the dispersing or dissolving power of the ink vehicle. This dispersing force arises from the interaction of the dye in the ink vehicle and the dye-containing ink, and from the dispersion molecule / pigment interaction when the colorant contains a pigment. If the dispersing force of the ink vehicle or pigment molecule is destroyed by interaction with the metal salt, the colorant precipitates because the ink vehicle can no longer dissolve the colorant. Precipitation reactions occur faster than penetration into paper, so the colorant remains substantially on the paper surface. The resulting printed color is extremely water resistant since there are no longer any components that can substantially dissolve the colorant in water. The printed color has improved water resistance than the original paper.

The pore size in the paper pulp fibers plays an important role in capturing the salts once precipitated salts precipitate in the pores, but it will be more important to use softwood pulp during the papermaking process. The pore size, which is a physical property, depends on the type of wood used in the pulp, and not on the pulp processing process. Softwood, the type used for blotting paper (described below), differs from hardwood because the water pipe element contained in the hardwood consists of an open end structure so that the hole in the water pipe element cannot contain sediment material. The softwood conduits and tissues are not open ends and have holes that may contain precipitated salts. Therefore, softwood is preferred in the practice of the present invention.

The metal salt must be sufficiently soluble to not be removed during processing of the pulp fibers into paper, and must be soluble enough to provide free ions that can interact with the ink vehicle or dispersion molecules. It is contemplated that the metal salts may contain various slightly soluble metal salts with low solubility product constants. Preferably the metal salts used in the practice of the present invention have a solubility product of less than about 5 × 10 ⁻⁵ .

Cations suitably used as inorganic salts include, but are not limited to, alkaline earth metals (eg, magnesium, barium or calcium) of the Periodic Table 2A group. Metal salts that may be effective in practicing the present invention are magnesium oxylate, calcium sulfate, calcium tartarate, barium oxylate and barium fluoride. Preferably magnesium is used as the cation in the practice of the present invention. Anions suitably used as metal salts include, but are not limited to, sulfates, carbonates and oxylates. The most preferred anion with respect to magnesium is carbonate.

When printing on the paper described in the present invention, it is expected that the performance of the color and black ink sets of the DeskJet 850C and DeskJet 500C ink-jet printers will be improved. The Hewlett-Packard part number for this ink set is shown in Table 1 below. In addition, the Canon BJC 600 ink set was also tested and the results in terms of penetration were similar to those found in Hewlett-Packard inks. Canon part numbers are also listed in Table 1 below.

TABLE 1

The purity of all ingredients is such that they are used in commercially available products for the papermaking process. All concentrations are expressed in weight percent unless otherwise indicated.

In addition to the metal salts, the paper may include components that can be found in commercial paper making. Wood pulp used in the present invention is a general pulp for paper making, such as wood pulp produced by bleaching. It is also possible to combine wood pulp with other pulp sources, provided that the pore size of the pulp fibers is in a suitable range.

TABLE 2 Weight% of Commercial Paper Components

The metal salt concentration in the paper may range from 5 to 15% by weight, preferably from about 7 to 12% by weight. The weight percent of magnesium carbonate can be measured with a thermogravimetric analyzer (TGA; Perkin Elmer TGA7). If TGA is used, the paper is made of ash and the resulting material is assumed to be magnesium oxide, the mineral form of magnesium carbonate. Weight percent is converted to g of MgCO ₃ using stoichiometry.

The pore size in the pulp fibers may range from about 1 to 50 microns, with a preferred average size of about 15 to 30 microns.

In a preferred embodiment, it contains about 5.9% by weight magnesium carbonate and the components listed in Table II, wherein the magnet carbonate is present in about 83.3% precipitated in about 15 to 30 microns of pores of dried paper pulp. Paper is printed using one of the inks described above.

EXAMPLE

Example Description Next, the results of all Examples and Comparative Examples are included.

Example 1

The paper produced in this example is referred to as loaded paper according to the present invention. The paper of the present invention was prepared by immersing the blotter paper rather than using non-dried pulp to regenerate the pulp to carry out the examples. The use of blotter paper is because they do not require chemical treatment. The blotter paper used is from the James River, in the form of Blotting Verigood 19 x 24-160 M Basis 80, 411-01-11. Four blotter papers were immersed in 500 ml of saturated magnesium sulfate solution overnight. Excess solution was removed from the soaked and regenerated pulp. The pulp fibers are wetted with magnesium sulfate solution. These fibers were then placed in 500 ml of saturated sodium carbonate and decomposed at high speed for 5 minutes using a Hamilton Beach blender. The fibers were removed from the sodium sulfate solution and washed until the pH of the wash water was neutral. The paper was placed on the sheet by fixing the fibers on the screen. Paraffin paper was placed on the fibers and the screen was rolled using a 10 lb mill to remove excess water. The sheet was then dried at 105 ° C. to evaporate all water.

The amount of magnesium carbonate present in the paper was found to be 9% by weight by weight.

According to the present invention, paper was printed using ink from Canon BJC 600, DeskJet 850C and DeskJet 500C ink-jet printers, and then the penetration depth of the ink was measured (see Table 3, title MgCO ₃ (invention)). The penetration depth was measured by taking the cross section of the printed medium and measuring the penetration depth of the ink. The sample was prepared by fixing the sample to epoxy and placing a microtome slice on the microscope glass. The penetration depth was measured from the micrographs and converted appropriately to obtain the actual penetration depth of the ink.

The cross-sectional micrograph of the paper shows the ink layer for coating the surface, thus explaining the fixation and prevention of penetration of the colorant as expected. Penetration tests conducted on inks showed reduced penetration (ie, improvement) for the dyes of the 500 series printers and the dye-containing color ink set of the DeskJet 850C printer (see Table 3). Microscopic examination of this paper indicated that the fibers of the paper were relatively long. The holes appeared physically different when compared to the holes of paper made from hardwood. To further highlight the difference, the hardwood contains even smaller amounts of sites where any precipitate remains loaded. The main softwood structures are conduits and tissue cells, both contain sealed pores in the cell wall to capture precipitated salts. Hardwood, however, also contains the water element as a main component. The water tube element is open end as described above so that the material precipitated during the pulp cleaning process leaks out. In both cases the pore size can range from about 1 to 50 microns.

To test the ink stability, paper was printed using a Hewlett-Packard DeskJet 850C printer. After the paper was immersed and stirred for 3 days, the fibers were used to regenerate the paper according to the method. The recycled paper was blue, indicating that ink remained on the fibers during the regeneration process. The printed sheets were also in water, but preserved a deep and rich color almost a month later.

The color gamut represents the saturation, hue and lightness of a particular color. Here, the observer qualitatively measured the increased color gamut by comparing the conventional paper with the magnesium carbonate-loaded hand sheet. Optical density values were obtained using Macbeth RD 913 with 2 mm holes. The precipitated magnesium carbonate sheet of this example had better performance than all other samples with the exception of Hewlett-Packard Premium Inkjet Paper on the DeskJet 850C printer. Other metal salts of the present invention were also tested. For DeskJet 560C and 500C printers, precipitated magnesium carbonate followed HP Premium Inkjet paper at optical densities for indigo, yellow and black. The sheet on which calcium carbonate was precipitated was suitable for magenta. The magnesium carbonate precipitated on the Canon BJC 600 printer produced higher optical density than Eureka! 35 (described below) for all colors.

Comparative Example 1

Typically to prepare a loaded paper, magnesium carbonate was mixed with the fibers. The paper was placed on the sheet by fixing the fibers on the screen. Paraffin paper was placed on the fibers and the screen was rolled on a 10 lb rolling mill to remove excess water. The sheet was then dried at 105 ° C. to evaporate all water. Magnesium carbonate was found to be 2% by weight in conventionally treated sheets. In the process of the present invention, metal salts are precipitated on the fiber walls, whereas in conventionally treated sheets the metal salts are mixed with the pulp and mechanically trapped between the pulp fibers. In the case of precipitated material, the salt is confined within the cell walls of the fibers.

Typically loaded paper was printed using ink from Canon BJC 600, DeskJet 850C and DeskJet 500C ink-jet printers. Optical density values were measured and listed in Table 4 under the conventional MgCO ₃ heading.

Comparative Example 2

The above method was carried out on the paper treated in the present invention to produce a flat paper, but no salt solution was treated. As noted above, the blotter paper was dispersed in pulp, then deposited on the screen and dried.

Flat paper was printed using ink from Canon BJC 600, DeskJet 850C, and DeskJet 500C ink-jet printers. The optical density values were measured and listed in Table 4 under the heading of paper.

Comparative Example 3

Two commercial papers were used as controls. These papers were named Eureka! 35 brand paper (James River Corporation) and Hewlett-Packard Premium Inkjet Paper Part No. HP 51634Y. These papers were printed using ink from Canon BJC 600, DeskJet 850C, and DeskJet 500C printers, and then the penetration depth of the ink was measured. Penetration depths are listed in Table 3 under the headings Eureka! (James River) and HP Premium Ink-Jet Paper, respectively. Measure the optical density value to measure the Eureka! And HP Premium Inkjet Title.

[Table 3a] Penetration Data

It is anticipated that the methods of causing the precipitation of colorants in inks using the slightly soluble precipitated metal salts disclosed herein on paper may find commercial use in ink-jet color printers, in particular heated ink-jet printers.

Thus, a method is disclosed in which a slightly soluble precipitated metal salt is used in paper to cause precipitation of colorants in the ink used for heated ink-jet color printing. It will be readily apparent to one skilled in the art that various changes and modifications can be made to the specific features without departing from the scope of the invention, which such changes and modifications are deemed to be within the scope of the invention as defined by the appended claims. do.

Claims (8)

A pulp fiber filled with slightly soluble precipitated metal salt particles and small enough to mechanically retain the particles and containing pores large enough to allow ions in the vehicle of the ink used for ink-jet printing to migrate; Ink-jet paper with improved color gamut and retention of ink-jet printing. The method of claim 1, Ink-jet paper, wherein the particles comprise at least one cation and at least one anion, and a metal salt having a solubility product of less than about 5 × 10 ⁻⁵ . The method of claim 2, Ink-jet paper, wherein said at least one cation is selected from the group consisting of magnesium, barium and calcium, and said at least one anion is selected from the group consisting of sulfate, carbonate and hydroxide. The method of claim 3, wherein An ink-jet paper, wherein said slightly soluble metal salt is selected from the group consisting of magnesium carbonate, magnesium hydroxide, calcium carbonate, calcium sulfate, calcium hydroxide, barium sulfate, barium hydroxide and barium carbonate. The method of claim 1, Ink-jet paper, wherein the slightly soluble precipitated metal salt has a concentration in the paper in the range of about 5-15% by weight. The method of claim 1, Ink-jet paper having a pore size in the range of about 1 to 50 microns and having a substantially closed end. The method of claim 1, Ink-jet paper, wherein the particles consist essentially of magnesium carbonate present in about 5 to about 15 weight percent, and the apertures range in size from about 1 to about 50 microns. (a) providing an ink-jet paper according to claim 1; (b) (1) one or more colorants, and (2) (iii) if said colorant contains a pigment, one or more dispersions having a dispersing force capable of dispersing one or more colorants in the vehicle, or (ii) If the colorant contains a dye, it comprises a vehicle that dissolves the colorant without dispersion, wherein (3) slightly soluble precipitated metal salt particles in the ink-jet paper when printing the ink-jet ink on the ink-jet paper. Providing at least one ink-jet ink, by which the colorant may be precipitated; And (c) printing ink-jet ink on the ink-jet paper surface to precipitate one or more colorants on the ink-jet paper surface, thereby improving color gamut and retention and reducing penetration and bleeding of the one or more colorants. , How to improve color gamut and retention in ink-jet printing.