JPH10100533A - Ink jet paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet paper capable of holding stably ink on a surface of the paper by a method wherein in ink jet recording, permeation of an ink colorant into a surface of a medium is conveniently economically reduced, and a color area capable of reproducing an ink set is increased thereby. SOLUTION: A paper is composed of pulp fiber containing a pit (a wall pit). In order to deposit colorant in ink, the pit is filled with slightly soluble precipitated metal salt particles, the pit is sufficiently small to the extent that the particles can be mechanically held, and the ink jet paper is provided wherein the pit is sufficiently large to the extent that an ion from an ink medium of the ink used for ink jet recording can be transferred into the pit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to ink jet recording, and more particularly to ink jet paper in which the pulp fibers in the paper have been modified by the incorporation of slightly soluble precipitated metal salts.

[0002]

BACKGROUND OF THE INVENTION In thermal ink jet color printers, such as the printer commercially available from Hewlett-Packard Company (trademark: DeskJet), the color spectrum is obtained by mixing yellow, magenta, and cyan inks in various ratios. It has gained. The color spectrum obtained by mixing a set of color inks is called the color gamut of the ink set.
A color gamut is always a subset of the color spectrum that is theoretically applicable.

One reason that no theoretically applicable spectrum is obtained is that the strength of a particular ink in an ink set cannot be effectively increased above a certain level when it appears on a print medium. It is in. Therefore, it is not possible to create colors in the spectrum that require higher intensity of certain colorants than can be delivered to the print media. The total amount of colorant that can be delivered depends on many factors, including the concentration of the colorant in the ink and the deliverable amount of the ink. Typically, the concentration of the colorant in the ink cannot be arbitrarily increased to increase the concentration on paper without sacrificing other important ink formulation issues.

Another reason for reduced color gamut is that some of the ink colorants penetrate into the print media, especially when the media is paper. When this occurs, the apparent intensity of the colorant in the print area will be lower than expected based on the amount of colorant delivered to the surface of the print media. To mitigate this problem,
The purpose is to ensure that the colorant remains on the paper surface, in other words, to control the penetration of the colorant into the paper surface.

[0005] In the ink composition for ink jet, the ink is prepared by dispersing a dye or pigment in an ink medium.
For example, cyan ink contains a cyan dye dissolved in an ink medium. Dye molecules used in ink jet ink compositions are often in the form of dye salts consisting of the dye anion (cation) and a cation (cation) such as sodium. In the case of pigment-based colorants, the ink medium typically contains a charged dispersant.

[0006] Methods for controlling the penetration of colorants into the paper surface rely on interfering with the dispersibility of the medium after the ink has been applied to the paper. One way to stop the dispersion action of the medium is to evaporate the solvent of the ink. Alternatively, the penetration of the colorant into the paper surface may be reduced by extinguishing the dispersing power of the dispersant in the ink after the colorant has been applied. The method of extinguishing the action of the dispersant is one that produces an effect faster than the evaporation of the solvent and will more effectively reduce the penetration of the colorant into the paper surface.

US Pat. No. 4,694,302 entitled “Reactive Ink-Jet Printing” and assigned to the same assignee as the present application.
The specification discloses a printing method for improving the water fastness and print quality of the ink. In this patent,
The reactive species that chemically binds the dye in the ink to the paper substrate,
The ink is applied to the print media either before or after the ink is applied to the print media. However, this method requires two separate print heads to achieve improved print quality.

[0008] "Recording Medium for Ink-Jet Printin
g, "U.S. Pat. No. 4,740,420 and" Ink Jet
Recording Sheet Having a Bicomponent Cationic Rec
U.S. Pat. No. 4,554,181 entitled "Ording Surface" discloses a recording medium that has been modified by a surface treatment that includes a soluble metal salt to facilitate insolubilization of the colorant in the ink. , Complicated and expensive, suffering from commercialization, surface modification of the print media, and none of these methods particularly necessitates the need to reduce the penetration of colorants into the surface of the print media. No. Improving color gamut requires reduced penetration.

US Pat. No. 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 filler pigment. The additional treatment of the paper surface takes into account the absorption of the aqueous ink into the paper. This print medium is not designed to retain ink on the paper surface.

[0010]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to advantageously and economically reduce the penetration of a colorant into a medium surface, thereby increasing the color gamut at which an ink set can be regenerated. An object of the present invention is to provide an ink jet paper and an ink jet recording method capable of stably holding ink on a paper surface.

[0011]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that an ink medium for dissolving or dispersing an ink colorant in pits (pits, cell pores) of pulp fibers. The present inventors have found that by conveniently supplying a metal salt that stops the dispersing action of the ink, the penetration of the ink colorant into the print medium (paper) is substantially reduced, and the present invention has been achieved. That is, the above object can be achieved by the following configurations. (1) An inkjet paper having an improved color gamut and its retention in inkjet recording, comprising pulp fibers containing pits, wherein the pits are filled with particles of slightly soluble precipitated metal salt, and the pits are An ink-jet paper characterized in that it is small enough to hold particles mechanically and large enough to allow ions from the ink medium of the ink used for the ink-jet recording to enter the pits.

The use of the ink jet paper of the present invention, which incorporates a slightly soluble precipitated metal salt to precipitate the colorant on the paper surface, improves color gamut and retention, reduces colorant penetration, In addition, bleeding between adjacently printed colorants is reduced.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ink jet color printer, and more particularly to a DeskJe printer of Hewlett-Packard Company.
It is directed to methods and papers for using a thermal ink jet color printer, such as a printer. With the paper, the ink jet color printer induces the precipitation of the colorant of the ink jet ink, thereby increasing the color gamut and color retention of the printed ink jet ink and producing high quality images with reduced penetration and bleeding. It can be created. In particular, the paper contains metal salts settled in pits in the fibers of the paper pulp before the paper sheet is made. The metal salt causes precipitation of the colorant in the inkjet ink by eliminating the dispersing or dissolving ability of the ink medium. This dispersing ability results from the interaction of the dye with the ink medium of the dye-based ink and from the interaction of the dispersant molecules and / or the pigment when the colorant is pigment-based. If the dispersing ability of the ink medium or pigment molecules disappears upon interaction with the metal salt, the ink medium can no longer dissolve the colorant, and the colorant will precipitate. The precipitation reaction occurs more rapidly than penetration into the paper, so that the colorant substantially remains on the paper surface. The resulting print color is extremely water-resistant, since any component that can substantially dissolve the colorant in water is no longer present. The print color is more resistant to water than its base paper.

The size of the pits in the paper pulp fiber plays an important role in trapping the settled salt as it sinks into the pits, but perhaps more critically, softwood pulp (softwood) is used in the papermaking process. Wood pulp). Pit size, or physical properties, depend on the type of wood used in the pulp and not on the pulp process.
The type used for softwood, or blotter paper (described below), is that the hardwood contains vessel elements and the pits are sedimentary substances because the vessel elements have an open-ended structure. And hardwood (hardwood). The softwood tracheids and parenchyma are not open-ended and thus contain pits that can contain sedimented salt. Therefore, softwood is desirable in the practice of the present invention.

[0015] The metal salt must be sufficiently insoluble in water so that it is not removed during processing of the paper pulp fiber, and must be sufficiently soluble to produce free ions that react with the ink medium or dispersant molecules. The metal salts are believed to consist of various slightly soluble metal salts with low solubility product constants. Preferably, the metal salts used in the practice of the present invention will have a solubility product of less than about 5 x ^10-5 .

Cations suitably used as inorganic salts include, but are not limited to, alkaline earth metals of Group 2A of the Periodic Table (eg, magnesium, barium and calcium). Metal salts that may be effective in the practice of the present invention are magnesi-um oxalyte, calcium sulfate, calcium tartrate, barium oxalate, and barium fluoride. Preferably, magnesium is used as a cation in the practice of the present invention. Anions suitably used as inorganic salts include, but are not limited to,
There are sulfates, carbonates and oxalates. The most preferred anion associated with magnesium is carbonate.

The performance of the color and black ink sets of the DeskJet 850C and DeskJet 500C inkjet printers, when printed on the above-described paper of the present invention,
It will be improved. Table 1 shows Hewlett-Packard part numbers for these ink sets. In addition, a Canon BJC® 600 ink set was tested; results related to penetration were similar to those seen with the Hewlett-Packard ink. Table 1 also lists Canon part numbers.

[0018]

[Table 1]

The purity of all components is that employed in normal industrial practice in papermaking. All concentrations are expressed in weight percent unless otherwise specified. The paper may include, in addition to metal salts, components such as those found in the paper industry.
The wood pulp used in the present invention is ordinary paper pulp as prepared by bleached wood pulp. Wood pulp can also be combined with other types of pulp provided that the pit size in the pulp fibers is in the proper range.

[0020]

[Table 2]

[0021] The concentration of the metal salt in the paper may range from 5 to 15 wt%, and preferably ranges from about 7 to 12 wt%. The weight percentage of calcium carbonate is determined with a thermogravimetric analyzer (TGA, Perkin Elmer TGA7). In the case of TGA, the paper is ashed and the resulting material is assumed to be magnesium oxide, a mineral form of magnesium carbonate. Its weight percent is calculated using MgCO ₃ using stoichiometry.
Is converted to grams.

The pit size of the pulp fiber is about 1
It can be in the range of ５０50 microns, with a preferred average size of about 15-30 microns.

In a preferred embodiment, the paper is about 8
The dried paper pulp present at 3.3 wt% contains about 5.9 wt% magnesium carbonate settled in about 15-30 micron pits and also contains the ingredients listed in Table 2. The paper is printed using any of the inks described above.

[0024]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only this embodiment. The results for all examples and comparative examples are listed at the end of the description of the examples.

Example 1 The paper prepared in this example is referred to as in-situ filled paper (paper in situ, ie, a pulp filled with filler). The paper of the present invention was prepared by immersing blotter paper to modify the pulp rather than using non-dried pulp. The blotters were used because they had not been subjected to any kind of chemical treatment. The blotter used was obtained from James River; its type was Blotting Verigood 19 "x24" -160M
Basis 80, 411-01-11. 500 ml of 4 blotters
In saturated magnesium sulfate solution overnight. Excess solution was removed from the soak modified pulp. The pulp fibers were kept moist with the magnesium sulfate solution. The fibers are then placed in 500 ml of saturated sodium carbonate and mixed with Hamilton
Beated at high speed for 5 minutes using a Beach blender. Remove the fiber from the sodium sulfate solution and adjust the pH of the washing water
Was washed until neutral. The fibers were placed on a screen and the paper was sheeted. Place the wax paper on the fiber,
The screen was rolled on a 10 pound roller to remove excess water. The sheet was then dried at 105 ° C. until all the water had evaporated.

The amount of magnesium carbonate in the paper was 9 wt%, calculated by the gravimetric method. This in situ paper is
Printing was performed using ink from a non BJC 600, DeskJet 850C and DeskJet 500C inkjet printer, and then the penetration depth of the ink was measured (Table 3, heading MgCO
₃ (in situ)). The penetration depth was measured by taking a cross section of the print medium and measuring the penetration depth of the ink. Samples were made by embedding the samples in epoxy and mounting microtome sections on microscope glass. The penetration depth was measured from the micrograph and the appropriate transformation was applied to get the actual penetration depth of the ink.

A micrograph of a cross section of the paper showed a layer of ink overlying the surface, thus illustrating the expected colorant immobilization and anti-penetration conditions. Penetration tests performed on the inks showed low (improved) penetration with the dyes of the 500 series printer and the dye-based color inks of the DeskJet 850C printer (see Table 3). Microscopic observation of the paper indicated that the fibers of the paper were relatively long. The pit is
They seemed to be physically different than paper pits made from hardwood (hardwood). Further emphasizing the difference is that hardwood has fewer sites where sediments settle and remain. The main softwood (softwood) structures are tracheids and parenchymal cells, both of which contain encapsulated pits inside the cell wall to capture sedimented salts. But,
Hardwoods also contain certain vascular elements as main components. As mentioned above, the vascular element is open-ended, allowing sedimented material to escape during the pulp washing process. The pit size in both cases may range from about 1 to 50 microns.

To test the stability of the ink, the paper was printed using a Hewlett-Packard DeskJet 850C printer. After soaking and stirring the paper for 3 days, the paper was recycled using the fibers using the method described above. The recycled paper was blue, indicating that the ink was retained on the fibers during the recycling process. Also, the recorded sheet was placed in water, but after almost one month its deep rich color was still retained.

The color gamut indicates the saturation state, hue, and whiteness of a specific color. Here, a high color gamut was qualitatively measured by an observer comparing conventional paper to a magnesium carbonate filled handsheet. Optical density values were obtained using a Macbeth RD 913 with a 2 mm aperture. The precipitated magnesium carbonate sheet of this example is DeskJet 85
Hewlett-Packard Prem loaded into 0C printer
Performed better than all other samples except ium® inkjet paper. Other metal salts of the present invention were similarly tested. In DeskJet 560C and 500C printers, the precipitated magnesium carbonate followed HP Premium Inkjet paper in optical density for cyan, yellow, and black. The calcium carbonate settled sheet worked well for magenta. For the Canon BJC 600 printer, the precipitated magnesium carbonate is Eu for all colors.
reka! Optical densities higher than 35 (described below) resulted.

Comparative Example 1 To make a conventional filled paper, magnesium carbonate was mixed with the fiber. The fibers were placed on a screen and the paper was sheeted. Wax paper was placed on the fibers and the screen was rolled with a 10 pound roller to remove excess water. The sheet was then dried at 105 ° C. until all the water had evaporated. Magnesium carbonate was found to be 2 wt% in conventionally treated sheets. In the in situ paper method, the metal salts settle into the fibers, whereas in conventionally treated sheets, the metal salts are incorporated into the pulp, resulting in mechanical entrapment between the pulp fibers. In the case of settling material,
Salt is trapped within the cell walls of the fiber.

Conventionally filled paper is applied to a Canon BJC 60
0, printed using ink from DeskJet 850C and DeskJet 500C inkjet printers. The optical density values were measured and found in Table 4 and indicated as MgCO ₃ conventional.

[Comparative Example 2] The same procedure as in the above-described in-situ treated paper was carried out except that no treatment with a salt solution was carried out to produce plain paper. The blotter was dispersed into pulp and then deposited on a screen and dried as described above. The obtained plain paper is Canon BJC 600, DeskJet 8
Printed using ink from 50C and DeskJet 500C inkjet printers. The optical density values were measured and are shown in Table 4 under the heading Blotter Paper.

Comparative Example 3 Two kinds of commercially available papers were used as controls. These papers are Eureka! 35 (R) paper (James River Corporation) and HP Premiu
m (R) Inkjet Paper Part Number HP 51634Y. Use these papers on a Canon BJC 600, Desk
Printing was performed using ink from a Jet 850C and DeskJet 500C inkjet printer, and then the penetration depth of the ink was measured. The penetration depth, heading Eure, respectively
ka! (James River) and HP Premium Inkjet Paper are listed in Table 3. Measure the optical density value and head it, respectively, Eureka! And Table 4 as HP Premium Ink Jet
Are listed.

[0034]

[Table 3]

[0035]

[Table 4]

Thus, a method has been disclosed in which a slightly soluble precipitated metal salt is used in paper to cause precipitation of a colorant in a thermal ink jet color recording ink. Various changes and modifications of the obvious nature may be made without departing from the spirit of the invention; all such changes and modifications are considered to fall within the scope of the invention as defined in the appended claims. It will be readily understood by those skilled in the art. Hereinafter, each embodiment of the present invention will be generally described as follows.

1) An ink-jet paper having improved color gamut and retention in ink-jet recording, comprising pulp fibers containing pits, wherein the pits are filled with particles of slightly soluble precipitated metal salt, and the pits are: Ink jet paper characterized in that it is small enough to hold the particles mechanically and large enough to allow ions from the ink medium of the ink used in the ink jet recording to enter the pits.

2) wherein said particles comprise a metal salt consisting of at least one cation and at least one anion, and wherein said salt has a solubility product of less than about 5 x 10 ^-5. 2. The ink-jet paper according to 1. 3) The at least one cation is selected from the group consisting of magnesium, barium, and calcium, and the at least one anion is selected from the group consisting of sulfate, carbonate, and hydroxide. The inkjet paper according to 2) above.

4) The 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 inkjet paper according to the above 3), which is characterized in that: 5) The slightly soluble precipitated metal salt has a concentration in the paper in the range of about 5 to 15 wt%.
2. The ink-jet paper according to 1.

6) The size of the pit is about 1 to 50
The inkjet paper according to the above 1), wherein the inkjet paper has a closed-end structure within a range of microns. 7) The method according to 1), wherein the particles substantially comprise magnesium carbonate present at about 5 to about 15 wt%, and wherein the pits have a size in the range of about 1 to about 50 microns. Inkjet paper as described.

8) A method for improving color gamut and retention in ink jet recording, comprising: (a) the step of preparing the ink jet paper of 1) above; (b) (1) at least one colorant; Or (i) the medium contains at least one dispersant capable of dispersing the at least one colorant in the medium when the colorant is pigment-based. Or (ii) the medium comprises a medium that dissolves the colorant without a dispersant when the colorant is dye-based, and (3) and prints the inkjet ink on the inkjet paper. At this time, by the particles of the slightly soluble precipitated metal salt in the inkjet paper,
Producing at least one ink jet ink characterized by being able to precipitate the colorant; and (c) printing the ink jet ink on a surface of the ink jet paper, thereby forming the ink jet paper. Depositing said at least one colorant on a surface, thereby improving color gamut and retention and reducing penetration and bleeding of said at least one colorant.

[0042]

As described above, the present invention relates to an ink jet paper in which a slightly soluble precipitated metal salt is introduced into pits of pulp to precipitate a colorant on the paper surface. In addition, it is possible to provide an ink-jet paper in which the colorant is improved, the penetration of the colorant is reduced, and the bleeding between the colorants printed adjacently is reduced, which greatly contributes to the industry.

Claims (1)

[Claims] An ink-jet paper having improved color gamut and its retention in ink-jet recording, comprising pulp fibers containing pits, wherein said pits are filled with particles of slightly soluble precipitated metal salt, and said pits are An ink-jet paper characterized in that it is small enough to hold the particles mechanically and large enough to allow ions from an ink medium of the ink used for the ink-jet recording to enter the pits.