EP1226959A2 - Porous ink-jet recording material - Google Patents

Abstract

An ink jet recording material with a support and at least one lower pigment-containing and one upper pigment-containing layer contains a pigment in the upper layer in two grain size fractions (A, B) and a grain size fraction (A) in a range from 10 to 100 nm and the other grain size fraction (B) is in a range of 1,000 and 3,000 nm and the pigment of the lower layer is different from that of the upper layer and its mean grain size is different from the mean grain sizes of the pigment of the upper layer.

Description

The invention relates to a recording material for the Inkjet printing process with a carrier and at least a lower pigment containing and an upper Layer containing pigment.

With the ink jet printing process (ink jet) tiny Ink droplets with the help of different, already several times techniques described on a recording material and taken up by this.

Different requirements are imposed on the recording material posed like high color density of the printed Dots, high ink absorption, short Drying time and associated sufficient smudge resistance, one that does not go beyond what is necessary Dye diffusion in the transverse direction of the printed Bleed, low mottle and high Water resistance. Other requirements, especially for photo-like prints, is an even print gloss and Surface gloss of the recording material.

Inkjet printing processes have been in the past few years become very important. The recording layers originally had a high proportion of one in water swelling binding agent, for example polyvinyl alcohol and gelatin. This binder was either on the base paper or one coated with polyolefin Substrate applied. Such materials have the advantage that they shine and very high color densities after the Have pressure. This also applies to systems based on of gelatin. A major disadvantage are the long ones Drying times so that when handling the prints surface quality is impaired can.

In recent years, the development has gone to so-called more mesoporous systems due to voids the ink in the applied layer during the Printing can absorb quickly and particularly suitable are for piezo type printheads. These recording materials generally contain a high Pigment content. The pigments have a size in the nanometer range, especially below the wavelength of the visible Lights on, are smaller than 400 nm, around one to ensure a shiny surface. These recording materials exhibit excellent image quality due to the good color fixation. You have one short drying time and problems with coalescence and Bleed do not occur. Such mesoporous systems respond but sensitive to exposure to light and Ozone. Silver salt photographs are lightfast over one Period of 15 to 20 years and ink jet images should be lightfast for at least as long.

Porous recording layers containing boehmite in U.S. Patents 4,879,155, 5,104,730, 5,264,275 and 5 275 867. EP 0 631 013 B1 describes a Boehmite, which is made on a porous silica layer an ink jet recording material is applied. Boehmite pigments, however, often show problems related to the lightfastness of magenta colors.

US 5 965 244 suggests the manufacture of a porous Marking layer the mixing of porous silica with colloidal silica. A wide distribution of the Particle sizes are preferred to the packing density of the particles enlarge and the ink movement causes due to the capillary action of the pores.

The invention has for its object a recording material for the ink jet printing process, that has a high gloss, high color density, light stability, has a large tonal range and high image resolution. The recording material is also intended to be a short Drying time, good water resistance and high ink absorption have.

These tasks are solved by an ink jet recording material with a carrier and at least one lower pigment containing and an upper pigment containing layer, wherein the pigment of the upper Layer exists in two grain size fractions (A, B) and a grain size fraction (A) in a range from 10 to 100 nm and the other grain size fraction (B) in one range of 1,000 and 3,000 nm and the pigment of lower layer is different from that of the upper one Layer and its average grain size is different from the average grain sizes of the pigment of the upper layer.

Such a pigment with clusters of grain sizes on two different places on the particle size scale referred to according to the invention as a bimodal pigment. The different Grain sizes can vary on the formation large secondary particles (agglomerates) one Pigments are based. You can also rely on a Part of the pigment as the primary particle and another part of the pigment is present as a secondary particle.

It has surprisingly been found that the invention Recording material is suitable for inks that Dyes included, and for pigmented inks. Thereby is a general purpose for a series given different printers. By the invention The two layers build up the ink liquid quickly absorbed by the lower layer, being the dyes or color pigments of the ink on the surface the upper layer. It is believed that by the pigments chosen according to the invention System of cross-linked pores formed in the upper layer becomes.

The one used according to the invention in the upper layer Pigment shows a distribution of particles in the range of 10 to 100 nm with an average particle size of 70 to 90 nm, particularly preferably 75 to 85 nm, and a further distribution in the range from 1,000 to 3,000 nm with an average particle size of 2,300 to 2,800 nm, especially preferably 2,400 to 2,600 nm. The upper layer is the layer on which the ink liquid passes through the Print head of the printer is applied.

The particle size of the larger pigment particles of the upper one Layer is preferably about 20 to 30 times that Particle size of the smaller pigment particles of the upper one Layer. Usually cause large pigment particles a reduction in gloss. But it was surprising found that the gloss of the recording material of the invention through the large pigment particles in the upper layer is not affected.

The quantitative ratio of the pigment particles of fraction A to the pigment particles of fraction B is preferably 8: 1 to 20: 1, particularly preferably 10: 1 to 15: 1.

Pigments of the upper layer suitable according to the invention are, for example, aluminum oxide, aluminum hydroxide, Alumina hydrate, silica, barium sulfate and titanium dioxide. The pigment of the top layer is particularly preferred a pigment based on aluminum oxide and predominantly amorphous.

The average particle size of the pigment particles of the lower one Layer is preferably 3 to 4 times that average particle size of the smaller particles of the upper one Layer. The grain size distribution of the pigment of the lower one Layer is preferably in the range of 150 to 1,000 nm with an average particle size of 240 to 350 nm, preferably 260 to 290 nm.

Pigments of the lower layer suitable according to the invention are, for example, aluminum oxide, aluminum hydroxide, Alumina hydrate, silica, barium sulfate and titanium dioxide. Particularly preferred pigment of the lower layer is a pigment based on amorphous silicon dioxide. Such a pigment can be modified cationically his.

The top and bottom layers contain one in the paper coating shop usual binder. The binder is preferably a water-soluble and / or water-dispersible Polymer. Suitable binders are, for example Polyvinyl alcohol, completely or partially saponified, cationically modified polyvinyl alcohol, silyl groups containing polyvinyl alcohol, containing acetal groups Polyvinyl alcohol, gelatin, polyvinyl pyrrolidone, Starch, hydroxyethyl starch, carboxymethyl cellulose, Polyethylene oxide, polyethylene glycol, styrene / butadiene latex and styrene / acrylate latex. The amount of binder in the top and bottom layers are 5 each to 35, preferably 10 to 30 wt.%, Based on the weight the dried layer.

The top and bottom layers can be used for ink receiving layers Contain usual additives and auxiliaries such as surfactants, crosslinking agents and color fixing agents such as polyammonium compounds.

According to a further preferred embodiment of the invention, a layer containing crosslinking agent is formed between the upper and the lower layer. Suitable crosslinking agents are, for example, epichlorohydrin, boric acid, boric acid salts, boron oxides, 3-glycidoxypropyltimethoxysilane, titanium (IV) diisopropoxydis (acetylacetonate), titanium (IV) (triethanol) aminate) isopropoxide, glyoxal and chromium alum. The application quantity can be 0.25 to 0.5 g / m ² .

It was found that through a crosslinking agent layer the sinking between the lower and upper layers of the binder from the top to the bottom layer is avoided. The crosslinking agent layer thus has the function of a barrier layer for the binder. Thereby the recording material has a smoother surface, which contributes to increasing the gloss overall.

The crosslinking agent can also be the pigment / binder mixture, that for the formation of the upper and / or lower Layer is used, added and mixed with this be applied to the carrier. The amount of Crosslinking agent in the layer can contain 0.1 to 2.0% by weight, in particular 0.2 to 1.5% by weight, based on the weight the dried layer.

The lower layer can be formed directly on the carrier his. The thickness of the lower layer can be 10 to 60 microns, preferably 20 to 50 microns. The upper Layer can be directly on the bottom layer or on the Crosslinking agent-containing layer can be formed. The thickness of the top layer can be 10 to 60 µm, preferably 20 to 50 microns.

In principle, any base paper can be used as a carrier material be used. Surface-sized, calendered or non-calendered or heavily glued Base papers. The paper can be acid or neutral sized his. The base paper is said to have high dimensional stability have and should be able to contain the contained in the ink Liquid without absorbing waves. papers with high dimensional stability from pulp mixtures from Softwood pulps and eucalyptus pulps are special suitable. In this respect, the revelation of the DE 196 02 793 B1, which is a base paper for a Ink jet recording material describes. The raw paper can contain other auxiliary materials that are common in the paper industry and additives such as dyes, optical brighteners or defoamers included. The use of reject pulp and refurbished waste paper is possible.

A paper that is coated on one or both sides with polyolefins, in particular with polyethylene, is particularly suitable as a carrier material. A paper coated with barium sulfate is also suitable. Plastic films, for example made of polyester or polyvinyl chloride, are also suitable as supports. The basis weight of the carrier can be 80 to 300 g / m ² .

Any, general, can be used to apply the layers known application and dosing processes used are like roller application, engraving, nipping and Air brush or roller doctor metering. Particularly preferred is the application with the help of a cascade coating system or a slot caster.

For setting the curl behavior, antistatic and the back of the printer can be transported in the printer be provided with a separate functional layer. suitable Back layers are in the DE 43 08 274 A1 and DE 44 28 941 A1 described on their Disclosure is referred.

The following examples are provided for further explanation the invention.

Examples

For the following tests, paper with a basis weight of 100 g / m ^2, neutral glue with alkyl ketene dimer and coated on both sides with polyethylene, was used as a support. The polyethylene is of the LDPE type. The front coating also contains 0.95% by weight of an optical brightener, 10% by weight of titanium dioxide, 4% by weight of lubricant and 10.8% by weight, based in each case on the mass of the layer, of a pigment concentrate of 10% ultramarine and 90% LDPE.

example 1

To produce the lower layer, silica, polyvinyl alcohol and boric acid were mixed, heated to 40 ° C. and stirred for 30 minutes. Based on the mass of the mixture obtained, 0.05% by weight of Triton X100 was added and the preparation was adjusted to a solids content of 15%. The resultant mixture for the lower layer was slit-coated on the polyethylene-coated support and dried at 100 ° C for three minutes. The dry application weight was 18 g / m ² .

To produce the mass for the upper layer, aluminum oxide, polyvinyl alcohol and boric acid were mixed and heated to 40 ° C. The mixture was stirred for 30 minutes and adjusted to a solids content of 20%. The mass for the upper layer was applied to the previously coated support with a slot coaster and then dried at 100 ° C. for four minutes. The dry application weight was 20 g / m ² .

The following table 1 summarizes the information on the composition of the layers. component Lower class upper layer Average silica Particle size 250 nm 71.0 - Alumina middle Particle size 80 nm (A), 2500 nm (B) ratio A: B = 15: 1 - 86.6 Polyvinyl alcohol saponification degree 88 mol% 28.5 12.4 boric acid 0.5 1.0

The values in the table are percentages by weight. she refer to the dry weight of the layer.

Example 2

The upper and lower layers have the same composition as in Example 1, with the difference that the upper layer contains no boric acid. Instead, a 5% boric acid solution was applied as an intermediate coat to the support coated with the lower layer in order to obtain a coat with an application thickness of 0.4 g / m ² . The upper layer with the composition known from Example 1 was applied to the crosslinking agent intermediate layer after the wet-on-wet coating.

Comparative Example 1 (V1)

The lower layer of Comparative Example 1 has the identical composition as in Example 1. she is applied in the same layer thickness.

To produce the upper layer, aluminum oxide with an average particle size of 160 to 170 nm, polyvinyl alcohol and boric acid were mixed and heated to 40.degree. The mixture was stirred for 30 minutes. The resulting mixture was applied to the previously coated support and then dried at 100 ° C for four minutes. The dry application weight was 20 g / m ² .

The aluminum oxide used here is not a so-called bimodal alumina with particle size clusters at two different places on the size scale monodisperse alumina.

Comparative Example 2 (V2)

Aluminum oxide with an average particle size of 1.56 µm, polyvinyl alcohol and boric acid were mixed and heated to 40 ° C. The mixture was stirred for 30 minutes and 0.05% Triton X100 was added. The resulting mixture for the lower layer was applied to the polyethylene-coated support and dried at 100 ° C for three minutes. The dry application weight was 18 g / m ² .

The following table 1 summarizes the information on the composition of the layers. ingredients Lower class upper layer V1 V2 V1 V2 Silica, average Particle size 250 nm 71 - - - Alumina, average Particle size 165 nm - - 87.3 - Alumina, average Particle size 1560 nm - 85.7 - - Aluminum oxide example 1 - - - 89.7 Polyvinyl alcohol, degree of saponification 88 mol% 28.5 14.3 12.4 9.3 boric acid 0.5 - 0.3 1.0

The values in the table are percentages by weight. she refer to the dry weight of the layer.

exams

The recording materials obtained were examined on color density, gloss and print gloss, absorbency, Water resistance and light resistance.

Color Density - Color density was measured using an X-Rite Densitometer Type 428 on the colors cyan, magenta, yellow and black. The tests are based on color prints from various printer types. The higher the value for a certain color, the better the color density.

Gloss - The gloss was measured with a gloss meter from Dr. Lange GmbH measured according to DIN 67530 at an angle of 60 °. The measurement was carried out on the unprinted recording sheet.

Printing gloss - The printing gloss was measured with a gloss meter from Dr. Lange GmbH measured according to DIN 67530 at angles of 20 ° and 60 °. The measurement was made on a part of the recording sheet printed in black.

Absorbance - Absorbance was done with the standard Cobb ₆₀ test using demineralized water.

Waterfastness - To test waterfastness, the color density of a printout was determined and the recording sheet was then immersed in a water bath with water at 25 ° C for 1 minute. The sheet was dried, then the color density was determined visually, ie graded from 1 (very good) to 5, and the difference in color density was determined before and after the treatment with water.

Lightfastness - The printed samples were placed in an ATLAS 3000i Weatherometer for 24 hours at 30 ° C and 60% relative humidity. The color fading was assessed according to the CIE L * a * b * system for each color before and after the treatment described above. The CIE L * a * b * values were recorded with an X-Rite Color Swatchbook.

The results of the tests are summarized in Tables 3 to 8. Determination of the color density of color blocks and the water resistance Epson 740 printer color density example 1 Example 2 Comparative Example 1 Comparative Example 2 black 2.32 2.42 1.71 2.10 cyan 2.39 2.50 1.60 1.92 magenta 1.79 1.88 1.18 1.42 yellow 1.29 1.32 1.06 1.08 Total color density 7.79 8.12 5.55 6.52 Water resistance (1 min) 1.5 1 4 5 Determination of the color density of color blocks HP970cxi printer color density example 1 Example 2 Comparative Example 1 Comparative Example 2 black 1.81 1.88 1.14 1.49 cyan 1.24 1.24 1.12 1.19 magenta 1.99 1.99 1.28 1.76 yellow 1.25 1.24 0.86 1.11 Total color density 6.29 6.35 4.40 5.55 Determination of the color density of color blocks Canon BJC8200 printer color density example 1 Example 2 Comparative Example 1 Comparative Example 2 black 2.11 2.15 1.5 1.85 cyan 2.33 2.31 1.55 1.93 magenta 1.66 1.68 1.21 1.48 yellow 0.89 0.88 0.85 0.86 Total color density 6.99 7.02 5.11 6.12 Print gloss measurement color block black printer example 1 Example 2 Comparative Example 1 Comparative Example 2 Epson 740 45.2 44.7 42.7 16.2 HP970cxi 44.1 43.1 46.0 18.4 Canon 8200 40.2 39.6 44.2 15.2 ΔE of color blocks after 24 hours of light exposure sample K C M Y B G R total substratum example 1 0.20 3.14 0.17 0.93 1.09 5.82 4.09 15.44 3.01 Comparative Example 2 1.24 4.12 5.61 10.47 6.74 12,99 12.76 53.93 5.38 Konica QP trading standard 1.72 7.27 0.94 5.18 4.47 14,60 5.78 39.96 2.31 Water absorption and gloss measurement example 1 Example 2 Comparative Example 1 Comparative Example 2 Cobb ₆₀ (g / m ² ) 36 45 31 48 Gloss (60 °) 34.0 34.1 39.6 15.0 Gloss (20 °) 12.9 12.9 13.5 2.3

Claims (9)

Ink jet recording material with a support and at least one lower pigment-containing and one upper pigment-containing layer, characterized in that the pigment of the upper layer is present in two grain size fractions (A, B) and a grain size fraction (A) in a range from 10 to 100 nm and the other grain size fraction (B) is in a range of 1,000 and 3,000 nm and the pigment of the lower layer is different from that of the upper layer and its mean grain size is different from the mean grain sizes of the pigment of the upper layer. Ink jet recording material according to Claim 1, characterized in that the quantitative ratio of the grain size fractions A to B is 8: 1 to 20: 1, in particular 10: 1 to 15: 1. Ink jet recording material according to claim 1 or 2, characterized in that the pigment of the upper layer is a pigment based on aluminum oxide and predominantly amorphous. Ink jet recording material according to one of Claims 1 to 3, characterized in that the grain size distribution of the pigment of the lower layer is in the range from 150 to 1,000 nm. Ink jet recording material according to claim 4, characterized in that the pigment of the lower layer is a pigment based on silicon dioxide and amorphous. Ink jet recording material according to claim 5, characterized in that the pigment of the lower layer is cationically modified. Ink jet recording material according to one of Claims 1 to 6, characterized in that a layer containing crosslinking agent is formed between the upper and the lower layer. Ink jet recording material according to one of claims 1 to 7, characterized in that the crosslinking agent is selected from the group consisting of epichlorohydrin, boric acid, boric acid salts, boron oxides, 3-glycidoxypropyltimethoxysilane, titanium (IV) diisopropoxydis (acetylacetonate) titanium (IV) ( triethanol) -aminate) isopropoxide, glyoxal and chrome alum. Ink jet recording material according to one of claims 1 to 8, characterized in that the carrier is a paper coated with polyolefin.