EP1226959B2 - Porous ink-jet recording material - Google Patents

Abstract

An ink-jet recording material comprising a support material and at least a lower and an upper pigment-containing layer wherein the pigment of the upper layer is present in two particle size distributions (A, B) and one particle size distribution (A) is in the range of 10 to 100 nm and the other particle size distribution (B) is in the range of 1,000 to 3,000 nm, and wherein the pigment of the upper layer is different from the pigment of the lower layer and wherein the average particle size of the pigment of the upper layer is different from the average particle size of the pigment of the lower layer.

Description

The invention relates to a recording material for the inkjet printing process comprising a support and at least one lower pigment-containing and one upper pigment-containing layer.

In the ink-jet printing process (ink-jet), tiny ink droplets are applied to and recorded on a recording material by various techniques already described several times.

The recording material is subject to various requirements, such as high printed dot density, high ink receptivity, short drying time and adequate wiping resistance, underexceeded colorant diffusion (bleed), low mottle and high waterfastness , Other requirements, especially for photo-like prints, is a uniform print gloss and surface gloss of the recording material.

Inkjet printing processes have become very important in recent years. The recording layers originally had a high content of a water-swelling binding agent, for example, polyvinyl alcohol and gelatin. This binder was applied to either the base paper or a polyolefin coated substrate. Such materials have the advantage that they shine and have very high color densities after printing. This also applies to systems based on gelatin. A major drawback is the long drying times, which can lead to surface quality deterioration when handling the prints.

In recent years, the trend has been toward more mesoporous systems which, due to voids in the applied layer, can rapidly absorb the ink during printing and are particularly suitable for piezo-type printheads. These recording materials generally contain a high pigment content. The pigments have a size in the nanometer range, in particular below the wavelength of visible light, ie less than 400 nm, in order to ensure a glossy surface. These recording materials have excellent image quality due to good color fixation. They have a short drying time and problems with coalescence and bleed do not occur. However, such mesoporous systems are sensitive to exposure to light and ozone. Silver salt photographs are lightfast over a period of 15 to 20 years and inkjet images should be lightfast for at least as long.

Porous recording layers containing boehmite are disclosed in U.S. Pat U.S. Patents 4,879,155 . 5,104,730, 5,264,275 and 5,275,867 described. The EP 0 631 013 B1 describes a boehmite coated on a porous silica layer for producing an ink-jet recording material. However, boehmite pigments often present problems with the lightfastness of magenta inks.

The US 5,965,244 proposes mixing porous silica with colloidal silica to make a porous marking layer. A wide distribution of particle sizes is preferred in order to increase the packing density of the particles and to increase the ink movement caused by the capillary action of the pores.

EP-A-1016542 describes an ink jet recording material comprising a support and at least one lower pigment-containing and upper pigment-containing layer, wherein the upper layer pigment is silicic acid and is present in two coma fractions (a, b) and one grain size fraction (a) in a range of 1 to 10 and the other grain size fraction (b) is in a range of 10 and 100 nm, and the pigment of the lower layer is alumina having boehmite structure and its average grain size is 1 to 50 nm.

The invention has for its object to provide a recording material for the ink-jet printing process, which has a high gloss, high color density, light stability, large gamut and high image resolution. The recording material should also have a short drying time, good water resistance and high ink receptivity.

These objects are achieved by an ink jet recording material having a support and at least one lower pigment-containing and upper pigment-containing layer, wherein the upper layer pigment is present in two grain size fractions (A, B) and one grain size fraction (A) within a range of 10 to 100 nm and the other grain size fraction (B) is in a range of 1,000 to 3,000 nm and the pigment of the lower layer is different from that of the upper layer, the pigment of the upper layer being an alumina-based pigment predominantly amorphous and the pigment of the lower layer is a pigment based on silica and amorphous, and its average grain size is different from the mean grain sizes of the pigment of the upper layer.

Such a pigment with accumulations of grain sizes at two different points of the particle size scale is referred to as bimodal pigment according to the invention. The different particle sizes can be based on the formation of different sized secondary particles (agglomerates) of a pigment. They may also be based on having one part of the pigment as primary particles and another part of the pigment as secondary particles.

Surprisingly, it has been found that the novel recording material is suitable for inks containing dyes and for pigmented inks. This provides universal usability for a variety of printers. By the structure of the two layers according to the present invention, the ink liquid is quickly taken up by the lower layer, whereby the dyes or color pigments of the ink are fixed to the surface of the upper layer. It is believed that a system of crosslinked pores is formed in the upper layer by the pigments chosen according to the invention.

The pigment used in the upper layer according to the invention shows a distribution of particles in the range of 10 to 100 nm with an average particle size of 70 to 90 nm, more preferably 75 to 85 nm, and a further distribution in the range of 1000 to 3000 nm with a average particle size of 2,300 to 2,800 nm, more preferably 2,400 to 2,600 nm. The top layer is the layer to which the ink fluid is applied through the printhead of the printer.

The particle size of the larger pigment particles of the upper layer is preferably about 20 to 30 times the particle size of the smaller pigment particles of the upper layer. Usually, large pigment particles cause a reduction in gloss. Surprisingly, however, it has been found that the gloss of the novel recording material is not impaired by the large pigment particles in the upper layer.

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

The pigment of the upper layer is a pigment based on alumina and predominantly amorphous.

The average particle size of the pigment particles of the lower layer is preferably 3 to 4 times the average particle size of the smaller particles of the upper layer. The grain size distribution of the lower layer pigment 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.

The lower layer pigment useful in the present invention is an amorphous silica based pigment. Such a pigment may be cationically modified.

The upper and lower layers contain a binder common in paper coating. The binder is preferably a water-soluble and / or water-dispersible polymer. Suitable binders are, for example, polyvinyl alcohol, fully or partially saponified, cationically modified polyvinyl alcohol, polyvinyl alcohol containing silyl groups, polyvinyl alcohol containing acetal groups, gelatin, polyvinylpyrrolidone, starch, hydroxyethyl starch, carboxymethylcellulose, polyethylene oxide, polyethylene glycol, styrene / butadiene latex and styrene / acrylate latex. The amount of the binder in the upper and lower layers is 5 to 35, preferably 10 to 30 wt.%, Based on the weight of the dried layer.

The top and bottom layers may contain conventional additives and auxiliaries for ink receiving layers such as surfactants, crosslinking agents and color fixing agents such as polyammonium compounds.

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

It has been found that a cross-linking agent layer between the lower and the upper layer avoids the decrease of the binder from the upper to the lower layer. The crosslinking agent layer thus has the function of a barrier layer for the binder. As a result, the recording material has a smoother surface, which contributes to the overall increase in gloss.

The crosslinking agent may also be added to the pigment / binder mixture used to form the upper and / or lower layer and may be applied in a mixture therewith to the support. The amount of the crosslinking agent in the layer may be 0.1 to 2.0% by weight, especially 0.2 to 1.5% by weight, based on the weight of the dried layer.

The lower layer may be formed directly on the carrier. The application thickness of the lower layer may be 10 to 60 μm, preferably 20 to 50 μm. The upper layer may be formed directly on the lower layer or on the crosslinking agent-containing layer. The application thickness of the upper layer may be 10 to 60 μm, preferably 20 to 50 μm.

Basically any base paper can be used as carrier material. Preference is given to surface-sized, calendered or non-calendered or heavily sized base papers. The paper may be acid or neutral sized. The base paper is said to have high dimensional stability and to be able to absorb the liquid contained in the ink without undulation. Papers with high dimensional stability from pulp mixtures of softwood pulps and eucalyptus pulps are particularly suitable. In that regard, the disclosure of the DE 196 02 793 B1 which describes a base paper for an ink-jet recording material. The base paper may contain other auxiliaries customary in the paper industry and additives such as dyes, optical brighteners or defoamers. The use of scrap pulp and reclaimed waste paper is also possible.

Particularly suitable as a carrier material is a paper coated on one or both sides with polyolefins, in particular with polyethylene. Also suitable is a paper coated with barium sulfate. Also plastic films, such as polyester or polyvinyl chloride, are suitable as a carrier. The basis weight of the carrier can be 80 be up to 300 g / m ² .

For the application of the layers, any well-known application and metering method can be used, such as roller application, engraving, nip method and Luftbürsten- or Rollrakeldosierung. Particularly preferred is the application by means of a cascade coating machine or a Schlitzgießers.

To adjust the curl behavior, antistatic and transportability in the printer, the back can be provided with a separate functional layer. Suitable backsheets are in the DE 43 08 274 A1 and DE 44 28 941 A1 described, the disclosure of which reference is made.

The following examples serve to further illustrate the invention.

Examples

The following tests were carried out using a neutral alkylketendimer and coated on both sides with polyethylene paper of a basis weight of 100 g / m ² as a carrier. The polyethylene is one of the type LDPE. The front-side coating further 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 prepare 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 resulting lower layer mixture was coated on the polyethylene-coated carrier with a slot caster and dried at 100 ° C for three minutes. The dry application weight was 18 g / m ² .

To prepare the composition for the top layer, alumina, 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 composition for the top layer was applied to the previously coated support with a slot caster and then dried at 100 ° C for four minutes. The dry application weight was 20 g / m ² .

In the following Table 1, the information on the composition of the layers are summarized. <u> Table 1 </ u> component Lower class upper layer Silicic acid ave. 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 weight percentages. They relate to the dry weight of the layer.

Example 2

The upper and lower layers have the same composition as in Example 1 except that the upper layer does not contain boric acid. Instead, a 5% boric acid solution was applied to the support coated with the lower layer as an intermediate coat in order to obtain a coating with an application thickness of 0.4 g / m ² . The application of the upper layer with the composition known from Example 1 to the intermediate crosslinking agent layer took place after wet-on-wet coating.

Comparative Example 1 (V1)

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

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

The alumina used here is not a so-called bimodal alumina with particle size accumulations at two different sizes but a monodispersed alumina.

Comparative Example 2 (V2)

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

In the following Table 1, the information on the composition of the layers are summarized. <u> Table 2 </ u> ingredients Lower class upper layer V1 V2 V1 V2 Silica, avg. Particle size 250 nm 71 - - - Alumina, avg. Particle size 165 nm - - 87.3 - Alumina, avg. Particle size 1560 nm - 85.7 - - Aluminum oxide Example 1 - - - 89.7 Polyvinyl alcohol, saponification degree 88 mol% 28.5 14.3 12.4 9.3 boric acid 0.5 - 0.3 1.0

The values in the table are weight percentages. They relate to the dry weight of the layer.

exams

The resulting recording materials were tested for color density, gloss and print gloss, absorbency, water resistance and light resistance.

Color Density - The color density was measured with an X-Rite Densitometer Type 428 on the colors cyan, magenta, yellow and black. The basis of the tests are color prints of different printer types. The higher the value for a particular color, the better the color density.

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

Absorbency - The absorbency was made with the standard Cobb ₆₀ test using demineralized water.

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

Light fastness - The printed samples were placed for 24 hours 3000i Weatherometer at 30 ° C and a relative humidity of 60% in an ATLAS. The color bleaching evaluation was done 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. <u> Table 3 </ u> - Determination of color density of color blocks and water resistance Printer Epson 740 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 Printer HP970cxi color density example 1 Example 2 Comparative Example 1 Comparative Example 2 black 1.81 1.88 1.19 1.49 cyan 1, 29 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 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 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 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 trade standard 1.72 7.27 0.94 5.18 4.47 14,60 5.78 39.96 2.31 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 Shine (20 °) 12.9 12.9 13.5 2.3

Claims (7)

1. An ink-jet recording material comprising a support material and at least a lower pigment containing layer and an upper pigment containing layer characterized in that the pigment of the upper layer is present in two particle size distributions (A,B) and particle size distribution (A) is in the range of 10 to 100 nm and the other particle size distribution (B) is in the range of 1,000 to 3,000 nm and the pigment of the lower layer is different from the pigment of the upper layer and the pigment of the upper layer is based on alumina and is mainly amorphous and the pigment of the lower layer is based on silica and is amorphous and the average particle size of the pigment of the lower layer is different from the average particle size of the pigment of the upper layer.
2. An ink-jet recording material according to claim 1 characterized in that the weight ratio of the particle size distribution A:B is 8:1 to 20:1, in particular 10:1 to 15:1.
3. An ink-jet recording material according to one of claims 1 or 2, characterized in that the particle size distribution of the pigment of the lower layer is in the range of 150 to 1,000 nm.
4. An ink-jet recording material according to claim 1, characterized in that the pigment of the lower layer is cationically modified.
5. An ink-jet recording material according to one of claims 1 to 4, characterized in that between the lower and the upper layer a cross-linking agent containing layer is provided.
6. An ink-jet recording material according to one of claims 1 to 5, characterized in that the cross-linking agent is selected from the group consisting of epichlorohydrin, boric acid, boric acid salts, boron oxides, 3-glycidyloxypropyltrimethoxysilane, titanium(IV) diisopropoxydbis(acetylacetonat), titanium (IV) (triethanol)aminato)isoproxyd, glyoxal and chromalum.
7. An ink-jet recording material according to one of claims 1 to 6, characterized in that the support material is a polyolefin coated paper.